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  • 122551.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Persson, J.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Intrinsic phase shift between a spin torque oscillator and an alternating current2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, nr 9, s. 09A510-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on a preferred phase shift Delta phi(0) between a spin torque oscillator (STO) and an alternating current (I-ac) injected at the intrinsic frequency (f(STO)) of the STO. In the in-plane (IP) precession mode the STO adjusts to a state where its resistance (or voltage) lags I-ac about a quarter of a wavelength [Delta phi(0)=(87-94)degrees]. In the IP mode Delta phi(0) increases somewhat with the direct current. As the precession changes into the out-of-plane (OOP) mode, Delta phi(0) jumps by about 180 degrees, i.e., the STO resistance now precedes I-ac about a quarter of a wavelength (Delta phi(0)=-86 degrees). At the IP/OOP boundary, the alternating current mixes the two oscillation modes and both periodic and chaotic oscillations are observed. As a consequence of mixing, subharmonic terms appear in the STO signal. The intrinsic Delta phi(0) will impact any circuit design based on STO technology and will, e.g., have direct consequences for phase locking in networks of serially connected STOs.

  • 122552.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Persson, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Bonetti, Stefano
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Tunable intrinsic phase of a spin torque oscillator2008Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, nr 9, s. 092505-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We show analytically why a spin torque oscillator (STO) locks to an alternating current (I-ac), having the same frequency as the STO, at a nontrivial, intrinsic, phase value Delta phi(0). We determine both the stability and the exact phase of the locked state and explain the recently observed phase jump by about 180 degrees at the in-plane-to-out-of-plane precession boundary. Delta phi(0) depends on the STO material parameters and is tunable through both the applied field and the dc current, which provides an additional control of the exact I-V phase in an STO driven radio frequency circuit.

  • 122553.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Persson, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Impact of Magnetoresistance and Anisotropy on Synchronized Spin Torque Oscillators2007Ingår i: 2007 7th IEEE Conference On Nanotechnology, Vol 1-3, 2007, s. 233-236Konferensbidrag (Refereegranskat)
    Abstract [en]

    Synchronization of pairs of serially connected Spin Torque Oscillators (STO) was studied using Landau-Lifshitz-Gilbert-Slonczewski magnetodynamic simulations. The impact of realistic process variations on STO synchronization was estimated by allowing for different in-plane anisotropy fields (H(k)) in the two STOs. We find that the synchronized state is extremely sensitive to STO process variations and can only sustain up to 4% H(k) variation. However, the addition of a small time delay dramatically improves the robustness of the synchronization and allows as much as 145% H(k) variation in the entire out-of-plane precession regime.

  • 122554.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Persson, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Tunable Intrinsic Phase Shift Between a Spin Torque Nano-Oscillator and an AC Current2007Ingår i: 2007 7th IEEE Conference On Nanotechnology, Vol 1-3, 2007, s. 229-232Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present magnetodynamic simulations, based on the Landau-Lifshitz-Gilbert-Slonczewski equations, of the interaction between a spin torque oscillator (STO) and an ac current (I(ac)). To avoide any extrinsic phase shift we inject the ac current at the intrinsic frequency (f(STO)) of the STO. We nevertheless find an unexpected intrinsic preferred phase shift Delta(phi 0) between the STO and I. In the in-plane precession mode (IP) the STO adjusts to a state where its resistance (or voltage) lags lac about a quarter of a wave length (Delta(phi 0)=87-94 degrees). In this regime Delta(phi 0) increases somewhat with the dc current. However, as the precession changes into the Out-Of-Plane (OOP) mode, Delta(phi 0) exhibits a dramatic jump by about 180 degrees, i.e. the STO resistance now precedes I(ac) about a quarter of a wave length (vertical bar Delta(phi 0)vertical bar=86 degrees). Delta(phi 0) can furthermore be tuned by changing one or more of the anisotropy field, the demagnetizing field or the applied field. At the IP/OOP boundary, the ac current mixes the two oscillation modes and both chaotic and periodic mixing is observed. We argue that the intrinsic Delta(phi 0) will impact any circuit design based on STO technology and will e.g. have direct consequences for phase locking in networks of serially connected STOs.

  • 122555.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Shin, Franklin G.
    Guan, Bo
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Capacitance Effect on Microwave Power Spectra of Spin-Torque Oscillator With Thermal Noise2009Ingår i: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 45, nr 6, s. 2773-2776Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A macro-spin simulation has been carried out to study the thermal stability of a spin-torque oscillator (STO) connected in parallel with a capacitance. To study the impact of realistic thermal fluctuation on an STO, a stochastic magnetic field vector is added into the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation. From the numerical solution, it is found that the addition of capacitance positively influences the thermal stability of the system, and can improve the quality factor of the microwave power spectrum even in the presence of thermal fluctuation. The results of I-V phase shift under different conditions suggest that there may exist an optimum capacitance for which the thermal stability of the system can be most enhanced.

  • 122556.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Tiberkevich, Vasil
    Consolo, Giancarlo
    Iacocca, Ezio
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Azzerboni, Bruno
    Slavin, Andrei
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Oscillatory transient regime in the forced dynamics of a nonlinear auto oscillator2010Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, nr 1, s. 012408-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate that the forced transient dynamics of a nonlinear (nonisochronous) auto-oscillator is qualitatively different from the dynamics of a quasilinear oscillator described by the classical Adler's model. If the normalized amplitude mu of the driving force exceeds a certain critical value mu(cr), the transition to the synchronized regime becomes oscillatory with a frequency proportional to proportional to root mu-mu(cr) and a synchronization time that is almost independent of mu. The discovered effect is illustrated on the example of a strongly nonlinear spin torque nano-oscillator (STNO) where the finite transient synchronization time can limit the possible range of STNO modulation frequencies.

  • 122557.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Zha, Chaolin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Bonetti, Stefano
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Persson, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Microwave generation of tilted-polarizer spin torque oscillator2009Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 105, nr 7, s. 07D116-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microwave frequency generation in a spin torque oscillator (STO) with a tilted fixed layer magnetization is studied using numerical simulation of the Landau-Lifshitz-Gilbert-Slonczewski equation. The dependence of the STO free layer precession frequency on drive current is determined as a function of fixed layer tilt angle. We find that zero-field STO operation is possible for almost all tilt angles, which allow for great freedom in choosing the detailed layer structure of the STO.

  • 122558.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Zha, Chaolin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Bonetti, Stefano
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Persson, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Spin-torque oscillator with tilted fixed layer magnetization2008Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, nr 26, s. 262508-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A spin-torque oscillator with a fixed layer magnetization tilted out of the film plane is capable of strong microwave signal generation in zero magnetic field. Through numerical simulations, we study the microwave signal generation as a function of drive current for two realistic tilt angles. The tilted magnetization of the fixed layer can be achieved by using a material with high out-of-plane magnetocrystalline anisotropy, such as L1(0) FePt.

  • 122559. Zhou, Yan
    et al.
    Zhang, Hong
    Liu, Yaowen
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Macrospin and micromagnetic studies of tilted polarizer spin-torque nano-oscillators2012Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, nr 6, s. 063903-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using nonlinear dynamical systems theory, we analytically studied a spin-torque device in which the magnetization of the polarizer (the fixed layer) is tilted at an arbitrary angle out of the thin-film plane. While the analytical theory can determine the major features of the system, macrospin simulations were employed to demonstrate the unique characteristics of the system, such as the hysteretic switching between bistable states. Material dependencies of the dynamic and static state diagrams were also studied in the framework of the macrospin model. Full-scale micromagnetics simulations were finally performed to reveal more subtle features of the dynamics of such tilted polarizer systems. Both the macrospin and micromagnetics simulations gave quantitatively the same results as our analytical theory.

  • 122560.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Perpendicular spin torque promotes synchronization of magnetic tunnel junction based spin torque oscillators2009Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, nr 11, s. 112503-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study how the perpendicular spin transfer torque term (b(j)), present in magnetic tunneling junctions (MTJs), affects the synchronization of serially connected MTJ-based spin torque oscillators (MTJ-STOs). We find that b(j) modifies the intrinsic preferred I-V phase shift in single MTJ-STO in such a way that serially connected MTJ-STOs synchronize much more readily without the need for additional circuitry to change the I-V phase. This result strongly suggests that synchronization of serially connected MTJ-STOs should be significantly more straightforward than the previously attempted serial synchronization of giant magnetoresistance based STOs (GMR-STOs).

  • 122561.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Sun, Jonathan Z
    Micromagnetic study of switching boundary of a ferromagnetic nanodeviceManuskript (preprint) (Övrigt vetenskapligt)
  • 122562.
    Zhou, Yan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Åkerman, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Sun, Jonathan Z.
    Micromagnetic study of switching boundary of a spin torque nanodevice2011Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, nr 10, s. 102501-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on a numerical study of the micromagnetic switching process of a nanostructured spin torque device. We show that incoherent spin waves can be excited over a wide range of current and field even at zero temperature. These large amplitude, incoherent, and nonzero k spin wave modes are shown to alter the switching phase boundary from that calculated within a macrospin model. The presence of telegraphic transitions between different spin wave modes may also contribute to the so-called back-hopping phenomenon where the switching probability varies nonmonotonically with increasing bias current.

  • 122563.
    Zhou, Yang
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    An Implementation and Evaluation of the Least-effort Approach of Crowd Simulation2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Crowd simulation serves as an important tool in architecture, where efficiency and safety could be improved with the knowledge of how large groups of people behave, and computer graphics as well as entertainment industry, where demands of animating large amounts of avatars exist. This project has implemented and evaluated an approach of crowd simulation based on the Principle of Least Effort, a fundamental rule of human behavior. The approach is capable of simulating thousands of agent in real time, and can be parallelized naturally to utilize the power of multiprocessor.

    The approach has been implemented using C++ and OpenMP. Results show that the approach generates smooth, collision-free, and visually plausible agent trajectories. To evaluate the approach in a quantitative manner, a set of metrics have been defined, and a set of test cases have been selected. By comparing the approach with RVO, a similar approach that does not consider the Principle of Least Effort, the evaluation shows that optimization based on the principle leads to agent trajectories that cost less effort and time. In further case studies, the approach has been proved to be able to generate a number of emergent phenomena verified in real crowd.

  • 122564.
    Zhou, Yang
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Comparison of Chinese Green Building Standard with Western Green Building standards2014Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    With rapid economic growth and urbanization in China, the Chinese building sector now accounted for a large amount of its energy usage and pollution. In order to minimize the environmental effect, the Ministry of Urban and Rural Development (MOHURD) has set a goal that 30% of all new constructed buildings will be green by 2020.

    This report reviews the Three Star System, the Chinese green building standard developed by the government agency MOHURD in order to promote and regulate green buildings in China. The study is done by comparing the Three Star System with two of its western equivalents, BREEAM and LEED. The technical manual of each standard is studied and compared, results from various researches within the area is also featured in the report.

    The finding of this report is that Three Star System is necessary to fulfill Chinas unique situation with a building sector that consist of high rates of new construction, although the standard is necessary it still need improvement in technical detail and user-friendliness to be at the same level as LEED and BREEAM. Some suggestion are proposed in the report for further development of the Three Star System 

  • 122565.
    Zhou, Yang
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Matematisk statistik.
    Modelling Swedish Inflation Using Market Data2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

     

    Denna studie är ett försök att modellera svensk inflation genom att använda ARIMA-modell och variationer av distributed lag modell med marknadsdata som förklarande variabler. Modellen är konstrukterad på underkomponents nivå av KPI och sedan aggregerad till KPI. Tre metoder prövas i denna studie. I första metoden modelleras underkomponenterna direkt med ARIMA-modeller. I andra metoden används distributed lag modell (DLM) på underkomponenter med signifikant korrelation till marknadsdata, residualen från DLM modelleras i sin tur med ARIMA-modeller. I den tredje metoden ersätter vi DLM med restricted finite distributed lag modell (RFDLM). Resultaten från studien visar att RFDLM är den bästa metoden att modellera inflationen och hade ett RMSE på 20 %. Detta jämfört med den naiva prognosen som hade en RMSE på 32 %. Däremot har RFDLM inte särskilt mycket praktiskt nytta i prognostisering av inflationen då man behöver marknadsdata för prognosperiod i förhand på grund att modellen använder sig av väldigt korta lagg. Däremot skulle modellen kunna ha nytta i scenario byggande med prognoser and antagande på marknadsdata som input.

  • 122566.
    Zhou, Yang
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Byggvetenskap, Betongbyggnad.
    Nonlinear analysis of reinforced concrete slab on partially softening ground: Ickelinjär analys av armerad betongplatta på delvis uppmjuknande grund2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Armerade betongplattor är en vanlig typ av fundament som ofta används för bostäder, kommersiella och industriella byggnader. De flesta av grundplattorna konstrueras direkt på marken utan andra strukturella medium emellan och vissa av plattorna påverkas därför av mjuknande undergrunder. En grundplatta är konstruerad för att överföra vertikala laster och överbrygga imperfektioner i marken, men stora sättningar i undergrunden kan förstöra plattans stödförhållanden och genom detta störa stabiliteten för överbyggnaderna.

    Syftet med projektet är att studera hur mjuknande undergrund och dess propagering påverkar en typisk betongplatta. Vidare används en approximativ analysmetod för att utvärdera tillståndet hos en platta på sådan mark. Ett praktiskt fall har studerats för att fånga det verkliga brottbeteendet hos en armerad betongplatta, vilket bygger på ett tidigare genomfört projekt. För det studerade fallet kan eventuell framtida gruvdrift nära ett höglager orsaka skadliga sättningar i undergrunden. Den förkastning som kan uppstå kan leda till uppmjukning av jordarna under fundamentet, vilket kan förvärras och orsaka kollaps av betongplattan under lagret. Två typer av brottscenarier studerades; uppmjuknande respektive full kollaps av undergrunden.

    Finita Element Metoden (FEM) användes för att analysera beteendet hos plattan och utvecklingen av fbrott och förskjutning i undergrunden. Ett kommersiellt FEM programpaket, Abaqus, användes som analytiskt verktyg, med en inbyggd plasticitets och skademodell (CDP) för att beskriva betongmaterialets egenskaper. Både linjärelastiska och icke-linjära materialegenskaper har använts i analyserna, för att simulera effekten av den mjukande undergrunnden. Ett stort antal modeller analyserades för att simulera skadepropageringen och fånga brottmoder i plattan genom olika skeden.

    Dragsprickor och vertikala deformationer uppstod i bägge de studerade scenariorna. Ett möjligt intern stabilitetsproblem hos lagret på grund av detta konstaterades också. Det olinjära beteendet hos betongplattan fångades fram tills allvarlig skada uppstod. Det visas att funktionen i bruksgränsstadiet hos den armerade betongplattan kan påverkas genom uppmjuknande undergrund, och att en mer realistisk beskrivning av möjliga brott här kunde erhållas genom den olinjära modellen, jämfört med tidigare elastiska analyser.

    Nyckelord:   Betongplatta , Icke-linjärt uppträdande, Finita Element Metoden (FEM), FE-modell, Abaqus, Plasticitets och skademodell för betong (CDP).

  • 122567.
    Zhou, Yang
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Numerical instability investigations for thin membranes2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Membrane structures are commonly used in many fields. The studies of these structures are of increasing interest. The projects in this thesis focus on the evaluations of equilibrium states for pressurized membranes under different problem settings, using finite element methods, and the corresponding instability behaviors.

    The first part of the current work discusses the instability behavior of a thin, planar, circular and initially horizontal membrane subjected to downwards or upwards fluid pressure. The membrane structures exhibit large deformations under pressure. The method for evaluating fluid pressure from gravity was developed in finite element context, and used in numerical simulations. Limit and bifurcation points have been detected for different loading parameters and conditions. The effects on instabilities of parameters, the initial states of the membrane, and the chosen mesh are discussed.

    The second part of the current work discusses instability behavior of a thin, spherical and closed membrane containing gas and fluid, when placed on a horizontal rigid and non-friction plane. A multi-parametric loading is described. By adding practically relevant controlling equations, different classes of equilibrium paths were followed using a generalized path following algorithm. Stability conclusions were made, according to the considered load parameters and the constraints. A generalized eigenvalue analysis was used to evaluate the stability behavior including the constraint effects. Fold line evaluations were performed to analyze the parametric dependence. A solution surface approach is used to visualize the mechanical response under this multi-parametric setting.

    The third part of the current work focuses on instability response of a truncated sphere, containing gas and fluid, and in contact with two vertical rigid and non-friction planes. Different penalty formulations were used and compared. The effects of contact implementations on instability behaviors were investigated. Bifurcation points induced by contacts have been observed. Multi-parametric problems were defined, and generalized paths were followed. The multi-parametric stability was evaluated using generalized eigenvalue analysis, based on the mass and total differential matrices. The effects of augmenting equations on bifurcation points and limit points are discussed.

    The fourth part of the current work analyses the instability response of a truncated sphere, completely filled with fluid, placed on a horizontal plane and spinning around the vertical axis. The loads from fluid pressure and the constraints, e.g., fluid volume, were formulated to generate a symmetric differential matrix. Several mesh patterns with different symmetries were used to simulate the model, and the obtained results are compared. Various problem settings were considered, and generalized paths were followed. The effects of symmetry aspects of the chosen meshes on instability behaviors are discussed, as are the effects of parameters.

  • 122568.
    Zhou, Yang
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Parametric stability analyses for fluid-loaded thin membranes2015Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Membrane structures are commonly used in many elds. The studies of thesestructures are of increasing interest. The two projects focus on the evaluations ofequilibrium states for uid-pressurized membranes under dierent loading conditions,and the corresponding instability behavior.The rst part of the current work discusses the instability behavior of a thin,planar, circular and initially horizontal membrane subjected to downwards or upwards uid pressure. The membrane structures exhibit large deformations under uid pressure. Various instability behaviors have been observed for dierent loadingparameters. Limit and bifurcation points have been detected for dierent loadingconditions. Dierent loading parameters have been used to interpret the instabilitybehavior. The eects on instability of parameters, the initial states of the membrane,and the chosen mesh have been discussed.The second part of the current work discusses instability behavior of a thin,spherical and closed membrane containing gas and uid placed on a horizontal rigidand non-friction plane. A multi-parametric loading has been described. By addingthe practically relevant controlling equations, the complex equilibrium paths werefollowed using the generalized path following algorithm, and the stability conclusionswere made dierently, according to the considered load parameters and theconstraints. A generalized eigenvalue analysis was used to evaluate the stabilitybehavior including the constraint eects. Fold line evaluations were performed toanalyze the parametric dependence of the instability behavior. A solution surfaceapproach was used to visualize the mechanical response under this multi-parametricsetting.

  • 122569.
    Zhou, Yang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Hussain, M.
    Guanglin, Kuang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Zhang, J.
    Tu, Yaoquan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Mechanistic insights into peptide and ligand binding of the ATAD2-bromodomain via atomistic simulations disclosing a role of induced fit and conformational selection2018Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, nr 36, s. 23222-23232Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ATAD2 has emerged as a promising bromodomain (BRD)-containing therapeutic drug target in multiple human cancers. However, recent druggability assessment studies predicted ATAD2's BRD as a target 'difficult to drug' because its binding pocket possesses structural features that are unfeasible for ligand binding. Here, by using all-atom molecular dynamics simulations and an advanced metadynamics method, we demonstrate a dynamic view of the binding pocket features which can hardly be obtained from the "static" crystal data. The most important features disclosed from our simulation data, include: (1) a distinct 'open-to-closed' conformational switch of the ZA loop region in the context of peptide or ligand binding, akin to the induced fit mechanism of molecular recognition, (2) a dynamic equilibrium of the BC loop "in" and "out" conformations, highlighting a role in the conformational selection mechanism for ligand binding, and (3) a new binding region identified distal to the histone-binding pocket that might have implications in bromodomain biology and in inhibitor development. Moreover, based on our simulation results, we propose a model for an "auto-regulatory" mechanism of ATAD2's BRD for histone binding. Overall, the results of this study will not only have implications in bromodomain biology but also provide a theoretical basis for the discovery of new ATAD2's BRD inhibitors.

  • 122570.
    Zhou, Yang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Nordmark, Arne
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Instability investigation for rotating thin spherical membrane2017Ingår i: International Journal of Non-Linear Mechanics, ISSN 0020-7462, E-ISSN 1878-5638, Vol. 97, s. 96-106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fluid-filled truncated spherical membrane fixed along its truncated edge to a horizontal, rigid and frictionless plane and spinning around a center axis was investigated. A two-parameter Mooney-Rivlin model was used to describe the material of the membrane. The truncated sphere was modeled in 3D using finite element meshes with different symmetry properties. A quadratic function was used for interpolating hydro-static pressure, giving a symmetric tangent stiffness matrix, thereby reproducing the conservative problem. Various problem settings were considered, related to the spinning, and different instability behaviors were observed. Multi-parametric problems were defined, generalized paths including primary and secondary paths were followed. Stability of the multi parametric problem was evaluated using generalized eigenvalue analysis based on the total differential matrix for the constrained problem. Numerical results showed that mesh symmetry affected the simulated stability behavior. Fold line evaluations showed the parametric effects on critical solutions.

  • 122571.
    Zhou, Yang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Instability investigation for rotating thin spherical membranesManuskript (preprint) (Övrigt vetenskapligt)
  • 122572.
    Zhou, Yang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Instability of thin circular membranes subjected to hydro-static loads2015Ingår i: International Journal of Non-Linear Mechanics, ISSN 0020-7462, E-ISSN 1878-5638, Vol. 76, s. 144-153Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Membrane structures subjected to hydrostatic load are prone to undergo large deformations and lose stability. This paper investigates different instability phenomena for a thin, circular and initially flat and horizontal membrane. The Mooney-Rivlin hyper-elastic model is used to provide the material description. An axisymmetric and a 3D model have been set up to show the large deformations and instability behavior with different parameter settings. Numerical examples show that the methods developed are capable to describe the deformation dependent loading conditions and the instability phenomena. The numerical simulations show fundamental differences in the response and instability behavior when the horizontal membrane is loaded from above or below. The parameters of fluids and membranes and the means for introducing the pressure are of essence for interpreting the instability behavior.

  • 122573.
    Zhou, Yang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Multi-parametric stability investigation for gas and uid pressurized thin membranesManuskript (preprint) (Övrigt vetenskapligt)
  • 122574.
    Zhou, Yang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Multi-parametric stability investigation for thin membranes with contactsManuskript (preprint) (Övrigt vetenskapligt)
  • 122575.
    Zhou, Yang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Multi-parametric stability investigation for thin spherical membranes filled with gas and fluid2016Ingår i: International Journal of Non-Linear Mechanics, ISSN 0020-7462, E-ISSN 1878-5638, Vol. 82, s. 37-48Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The instability behavior of spherical membranes completely or partially filled with fluid, also with internal gas over-pressure, placed on a friction-less rigid plane was investigated. The two-parameter Mooney-Rivlin model was used for material description. A third order penalty function was used to describe the rigid support. Different problem settings were considered, and different instability responses were observed. For the partially fluid-filled membrane, a multi-parametric problem was defined and analyzed. Augmenting equations were introduced to impose control constraints on variables chosen. These equations also affect the instability analysis. A generalized eigenvalue analysis was used for the stability conclusions. Numerical simulations showed that appropriate control constraints are of essence to interpret the instability conclusions. Fold line evaluations were performed to analyze the dependence of the instability behavior on the parameters. A solution surface algorithm was utilized to analyze and visualize the mechanical responses to multi-variable loading.

  • 122576.
    Zhou, Yang
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Nordmark, Arne
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Eriksson, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strukturmekanik.
    Multi-parametric stability investigation for thin spherical membranes with contacts2017Ingår i: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 131-132, s. 334-344Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The instability behavior for a thin truncated spherical membrane completely filled with fluid or containing both gas and fluid, fixed on a circular platform and in contact with two vertical planes was investigated. Different penalty functions for contacts, and symmetry aspects of the discretized model were studied, and gave effects on instability behavior. Stability conclusions for the multi-parametric problems were made using generalized eigenvalue analyses, showing limit points, bifurcation points and turning point. Contact conditions were shown to introduce bifurcations and secondary paths, dependent on the contact implementations and discretizations. Their effects on stability behaviors in connection with various controlling equations are discussed.

  • 122577. Zhou, Ye
    et al.
    Liedberg, Bo
    Gorochovceva, Natalij
    Makuska, Ricardas
    Dedinaite, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Chitosan-N-poly (ethylene oxide) brush polymers for reduced nonspecific protein adsorption2007Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 305, nr 1, s. 62-71Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The possibility of using a novel comb polymer consisting of a chitosan backbone with grafted 44 units long poly(ethylene oxide) side chains for reducing nonspecific protein adsorption to gold surfaces functionalized by COOH-terminated thiols has been explored. The comb polymer was attached to the surface in three different ways: by solution adsorption, covalent coupling, and microcontact printing. The protein repellant properties were tested by monitoring the adsorption of bovine serum albumin and fibrinogen employing surface plasmon resonance and imaging null ellipsometry. It was found that a significant reduction in protein adsorption is achieved as the comb polymer layer is sufficiently dense. For solution adsorption this was achieved by adsorption from high pH solutions. On the other hand, the best performance of the microcontact printed surfaces was obtained when the stamp was inked either at low or at high pH. For a given comb polymer layer thickness/poly(ethylene oxide) density, significant differences in protein repellant properties were observed between the different preparation methods, and it is suggested that a reduction in the mobility of the comb polymer layer generated by covalent attachment favors a reduced protein adsorption. (c) 2006 Elsevier Inc. All rights reserved.

  • 122578. Zhou, Ye
    et al.
    Tian, Yuan
    Wang, Keyou
    Ghandhari, Mehrdad
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    ROBUST OPTIMIZATION FOR AC-DC POWER FLOW BASED ON SECOND-ORDER CONE PROGRAMMING2017Ingår i: The Journal of Engineering, ISSN 1872-3284, E-ISSN 2051-3305Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents an adjustable robust optimization method for AC-DC optimal power flow (OPF) considering the uncertainty of renewable energy source (RESs). The optimal power flow of AC-DC system is modeled as a second-order cone (SOC) problem, and the affinely adjustable robust OPF (AAROPF) formulation is proposed. To apply AAROPF, the base-point generation is calculated and determined to match the power with forecasted RES output before the realization of the uncertainty. And once the uncertainty is revealed, generators reschedule its output through participation factors responding to the uncertain fluctuation of RES output to ensure a feasible solution for all realizations of RES output within a prescribed uncertainty set. Numerical results are obtained on a modified AC-DC IEEE 30-bus to minimize the expected operational cost. Results reveal a higher cost using AAROPF than the deterministic case, but it obtains a more robust solution with higher successful rates.

  • 122579. Zhou, Yi
    et al.
    Zhao, Xiaogang
    Zhao, Jianyu
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE).
    Chen, Du
    Research on Fire and Explosion Accidents of Oil Depots2016Ingår i: 3rd International Conference on Applied Engineering, AIDIC - associazione italiana di ingegneria chimica, 2016, Vol. 51, s. 163-168Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fire and explosion accidents occurred frequently in oil depots in China which lead to great casualties, severe environmental pollution and large economic losses. Case studies of 435 fire and explosion accidents of oil depots in China from 1951 to 2013 are reviewed in this paper. From the analysis of time scale, area, facilities & equipment, ignition sources, types of accident substances, and responsibility, the statistic results show that the most dangerous area is the loading and unloading operation area, and the most vulnerable facilities & equipment are the storage tanks. Meanwhile, the proportions of ignition sources are so evenly distributed that the prevention of fire and explosion should be equally concentrated to several impact factors. The vapor cloud explosion could be the most common accident type in oil depots, and the management responsibility dominates in all of the accident causes. According to data analysis, special lessons learned from these accidents are proposed, and the majority of fire and explosion accidents in oil depots would have been prevented or avoided if security management had been improved.

  • 122580. Zhou, Ying
    et al.
    Li, Xing
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Chen, Jue
    Yu, Fengtao
    Hua, Jianli
    The Effect of Pyridyl Nitrogen Atom Position in Pyrido-[3,4-b]pyrazines in Donor-Acceptor-pi-Acceptor Dyes on Absorption, Energy Levels, and Photovoltaic Performances of Dye-Sensitized Solar Cells2016Ingår i: ASIAN JOURNAL OF ORGANIC CHEMISTRY, ISSN 2193-5807, Vol. 5, nr 2, s. 293-300Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A donor-acceptor-pi-acceptor (D-A-pi-A)-type organic dye (DTN-1) incorporating a pyrido[3,4-b]pyrazine (PP) unit with the pyridyl N atom adjacent to the anchoring group has been synthesized for use in dye-sensitized solar cells (DSSCs). The maximum absorption wavelength of DTN-1 was clearly red-shifted compared with dye DT-1, based on PP unit with the pyridyl N atom adjacent to the donor group. However, this change of structure has a negative effect on photovoltaic performances, and devices made with DTN-1 only reached a power conversion efficiency of 6.10% under AM1.5G irradiation compared with 8.57% achieved by DT-1. Density functional theory calculations suggest that DTN-1 has a smaller oscillator strength, which is connected to its relatively low light-harvesting efficiency. In addition, the results of electrochemical impedance spectroscopy (EIS) reveal that charge recombination in DSSCs based on DTN-1 is more than that in the counterpart DT-1, thus leading to a lower open-circuit voltage (V-oc).

  • 122581. Zhou, Yong
    et al.
    Miao, Quan
    Sun, Yuping
    Gelmukhanov, Faris
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Wang, Chuan-Kui
    Solvent effect on dynamical TPA and optical limiting of BDMAS molecular media for nanosecond and femtosecond laser pulses2011Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 44, nr 3, s. 035103-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dynamical two-photon absorption (TPA) cross section as well as optical limiting of a 4,4'-bis(dimethylamino) stilbene (BDMAS) molecular medium for the nanosecond and femtosecond laser pulses is studied. This molecular medium can be described by a cascade three-level model in the visible light regime. Our numerical results show that the BDMAS molecular medium exhibits a strong optical limiting behaviour. The saturation TPA in the femtosecond time domain can be observed, and materials with larger nonlinear absorption cross sections would be much easier to saturate. Due to the contribution of the two-step TPA, the dynamical TPA cross section of BDMAS for nanosecond pulses is about three orders of magnitude larger than that for ultrashort femtosecond pulses. Special attention has been paid to the solvent effects on the optimal limiting performance. With an enhancement of the polarity of solvents, the dynamical optical limiting window becomes broader. In the origin of optical limiting, the dynamical TPA cross section of BDMAS decreases when the polarity of solvents increases, which is in good agreement with the experiment.

  • 122582. Zhou, Yongjin J.
    et al.
    Buijs, Nicolaas A.
    Zhu, Zhiwei
    Qin, Jiufu
    Siewers, Verena
    Nielsen, Jens
    KTH, Skolan för bioteknologi (BIO), Genteknologi.
    Production of fatty acid-derived oleochemicals and biofuels by synthetic yeast cell factories2016Ingår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, artikel-id 11709Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sustainable production of oleochemicals requires establishment of cell factory platform strains. The yeast Saccharomyces cerevisiae is an attractive cell factory as new strains can be rapidly implemented into existing infrastructures such as bioethanol production plants. Here we show high-level production of free fatty acids (FFAs) in a yeast cell factory, and the production of alkanes and fatty alcohols from its descendants. The engineered strain produces up to 10.4 gl(-1) of FFAs, which is the highest reported titre to date. Furthermore, through screening of specific pathway enzymes, endogenous alcohol dehydrogenases and aldehyde reductases, we reconstruct efficient pathways for conversion of fatty acids to alkanes (0.8 mgl(-1)) and fatty alcohols (1.5 gl(-1)), to our knowledge the highest titres reported in S. cerevisiae. This should facilitate the construction of yeast cell factories for production of fatty acids derived products and even aldehyde-derived chemicals of high value.

  • 122583.
    Zhou, You
    et al.
    Huazhong Univ Sci & Technol, Sch Opt & Elect Informat, Wuhan, Hubei, Peoples R China.;Huazhong Univ Sci & Technol, Wuhan Natl Lab Optoelect, Wuhan, Hubei, Peoples R China..
    Wu, Fei
    Huazhong Univ Sci & Technol, Wuhan Natl Lab Optoelect, Wuhan, Hubei, Peoples R China..
    Lu, Zhonghai
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik.
    He, Xubin
    Temple Univ, Dept Comp & Informat Sci, Philadelphia, PA 19122 USA..
    Huang, Ping
    Temple Univ, Dept Comp & Informat Sci, Philadelphia, PA 19122 USA..
    Xie, Changsheng
    Huazhong Univ Sci & Technol, Wuhan Natl Lab Optoelect, Wuhan, Hubei, Peoples R China..
    SCORE: A Novel Scheme to Efficiently Cache Overlong ECCs in NAND Flash Memory2019Ingår i: ACM Transactions on Architecture and Code Optimization (TACO), ISSN 1544-3566, E-ISSN 1544-3973, Vol. 15, nr 4, artikel-id 60Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Technology scaling and program/erase cycling result in an increasing bit error rate in NAND flash storage. Some solid state drives (SSDs) adopt overlong error correction codes (ECCs), whose redundancy size exceeds the spare area limit of flash pages, to protect user data for improved reliability and lifetime. However, the read performance is significantly degraded, because a logical data page and its ECC redundancy are stored in two flash pages. In this article, we find that caching ECCs has a large potential to reduce flash reads by achieving higher hit rates, compared to caching data. Then, we propose a novel scheme to efficiently cache overlong ECCs, called SCORE, to improve the SSD performance. Exceeding ECC redundancy (called ECC residues) of logically consecutive data pages are grouped into ECC pages. SCORE partitions RAM to cache both data pages and ECC pages in a workload-adaptive manner. Finally, we verify SCORE using extensive trace-driven simulations. The results show that SCORE obtains high ECC hit rates without sacrificing data hit rates, thus improving the read performance by an average of 22% under various workloads, compared to the state-of-the-art schemes.

  • 122584.
    Zhou, Yufeng
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Performance Evaluation of a Weighted Clustering Algorithm in NSPS Scenarios2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In national security and public safety (NSPS) scenarios, the concept of device-to-device (D2D) clustering allows user equipment (UEs) to dynamically form clusters and thereby allows for local communication with partial or no cellular network assistance. We propose and evaluate a clustering approach to solve this problem in this thesis report. One of the key components of clustering is the selection of so called cluster head (CH) nodes that are responsible for the formation of clusters and act as a synchronization and radio resource management information source. In this thesis work we propose a weighted CH selection algorithm that takes into account UE capability, mobility and other information and aims at balancing between energy efficiency, discovery rate and cluster formation time. Numerical results show that the clustering approach consumes more energy but it can achieve a much higher discovery rate and communication rate for the system. Simulation results indicate that the weighted clustering approach is a viable alternative in NSPS situations.

  • 122585.
    Zhou, Yukun
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Arkitektur, Stadsbyggnad.
    LANDSCAPE INTEGRATION IN URBAN CONTEXT: Landscape Regeneration of Slakthusområdet2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Taking as a starting point the theory and concept of Landscape Urbanism, this thesis project explores an alternative solution for the regeneration of old industrial areas using a case study: the design of Slakthusområdet in Stockholm. The project focuses on how to use landscape as a medium to transform Slakthusområdet into a sustainable, attractive, and people friendly area. And at the same time integrate it into a wider urban context. It covers two aspects: First, the integration of the site in the surrounding green network. Second, the regeneration of the green infrastructure inside of the site that could add ecological and social values to the site. 

  • 122586.
    Zhou, Yunyun
    et al.
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Baryshnikov, Gleb V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Bogdan Khmelnitsky Natl Univ, Dept Chem & Nanomat Sci, UA-18031 Cherkassy, Ukraine..
    Li, Xuping
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Zhu, Mingjie
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Ågren, Hans
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Zhu, Liangliang
    Fudan Univ, Dept Macromol Sci, State Key Lab Mol Engn Polymers, Shanghai 200433, Peoples R China..
    Anti-Kasha's Rule Emissive Switching Induced by Intermolecular H-Bonding2018Ingår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, nr 21, s. 8008-8016Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The exploration of emission pathways from high-excited states in organic luminogens has recently become prosperous owing to improved possibilities to study so-called anti-Kasha's rule emission with the potential of improving the luminescent quantum efficiency. However, emission pathway switching among different high-excited states has rarely been addressed through external control. We here present a rational design and synthesis of a novel azulene-based emitter to achieve a responsive control of its anti-Kasha's rule emissive switching. The emitter initially gives rise to an S-3-to-S-0 dominant emission as indicated by our experimental and theoretical studies. On this basis, it can be toggled into an S-2-to-S-0 dominant emission upon the H-bond formation between the triformyl groups and water molecules. Such a process, which originates from the H-bonding regulated distribution of excited state energy, is accompanied by a remarkable fluorescent color conversion and a significant improvement of the fluorescent quantum yield in the azulene family. Moreover, a reversible emissive switching in doped films was observed to depend on a solid-state H-bond tuning process with moisture sensitivity. These results may provide new insight for building advanced chemical systems for visualized sensing with high distinguishability.

  • 122587. Zhou, Yunyun
    et al.
    Zhuang, Yaping
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Yu, Lin
    Ding, Jiandong
    Zhu, Liangliang
    Selective Dual-Channel Imaging on Cyanostyryl-Modified Azulene Systems with Unimolecularly Tunable Visible-Near Infrared Luminescence2017Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, nr 32, s. 7642-7647Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although organic light-emitting molecules have received a growing attention and applicability in modern bioimaging science, the design and control of complex photoluminescent properties in unimolecularly selective imaging remains a challenging topic. Considering that tunable multipathway imaging can be advantagedly connected with treatment processes in therapy, the integration of an azulene and a cyanostyryl moiety into one skeleton is carried out for the generation of in situ stimuli-responsive luminescent materials, with the aim to achieve tunable and effective emissions in distinct channels through smart molecular design on a single-molecular platform. This strategy takes advantage of 1) the Z/E isomerization of the cyanostyryl unit that can vary the push-pull effect of the substitution on azulene, accompanied by altering absorption and emission of individual excited states, and 2) an optimized excited-state regulation for opening a near infrared emissive channel and making up for a controllable dual-pathway luminescent system together with the utilization of visible emission. As exemplified by a demonstration of manipulating the luminescence at the cell level, the materials exhibit a superior application potential for unimolecularly selective imaging, labeling and probing events.

  • 122588.
    Zhou, Yushan
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Impact of Surface Structures onDeposition and Erosion in a Tokamak2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Fusion är en potentiellt obegränsad och miljövänlig energikälla för det mänskliga samhället i framtiden. Det återstår emellertid vissa problem att lösa. Bland dem är deposition och erosion vid ytor som är i kontakt med plasmat kritiska. Deposition av bränsle och föroreningar ger potentiellt långsiktig ackumulation av bränsle (tritium) som kan ge upphov till säkerhetsproblem och försämra bränsleekonomin. Erosion av vakuumkärlets väggar i in fusionsanläggning alstrar förorenar plasmat och kan begränsa livstiden för väggkomponenter. Arbetet i denna avhandling fokuserar på deposition och erosion på ytor i JET-ILW-projektet, som består av volfram (eller volframbelagd kolfiberkomposit) i divertor och beryllium i limiter.

    För depositionsfrågorna användes mikroanalys för att observera hur deuterium och beryllium fördelas över ytorna efter plasmaexponering. Yttopografi erhölls från SEM, optisk mikroskopi och konfokal laserskanmikroskopi. Distributionskartor från IBA jämfördes med yttopografin. För att förklara experimentella resultat användes modellering av jontrajektorior, dels på verklig experimentell topografi, dels på förenklade modellytor. Micro IBA-resultat visar att deuterium och beryllium ansamlas i mikroskopiskt nedsänkta områden, t.ex. gropar och sprickor. Modelleringen visar att joners gyratation delvis kan förklara denna ojämna fördelning av deuterium och beryllium.

    För erosionsproblemet gjordes mätningar på markerplattor, konstruerade för att observera materialosion i JET. En ny metod införs för att erhålla erosionsdata, genom att kombinera mikro IBA och SEM-bild. Denna metod kan skilja på inflytande på IBA-resultat från skrovlighet, vilket är annars är ett problem IBA för på skrovlig yta. På samma sätt används mikroanalys för att förbättra tolkningen av analyser av deuterium som trängt in i en skiktad struktur.

  • 122589.
    Zhou, Yushan
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Bergsåker, Henric
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Bykov, Igor
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Paneta, C.
    Possnert, G.
    Micro ion beam analysis for the erosion of beryllium marker tiles in a tokamak limiter2019Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 450, s. 200-204Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Beryllium limiter marker tiles were exposed to plasma in the Joint European Torus to diagnose the erosion of main chamber wall materials. A limiter marker tile consists of a beryllium coating layer (7–9 μm) on the top of bulk beryllium, with a nickel interlayer (2–3 μm) between them. The thickness variation of the beryllium coating layer, after exposure to plasma, could indicate the erosion measured by ion beam analysis with backscattering spectrometry. However, interpretations from broad beam backscattering spectra were limited by the non-uniform surface structures. Therefore, micro-ion beam analysis (μ-IBA) with 3 MeV proton beam for Elastic backscattering spectrometry (EBS) and PIXE was used to scan samples. The spot size was in the range of 3–10 μm. Scanned areas were analysed with scanning electron microscopy (SEM) as well. Combining results from μ-IBA and SEM, we obtained local spectra from carefully chosen areas on which the surface structures were relatively uniform. Local spectra suggested that the scanned area (≈600 μm × 1200 μm) contained regions with serious erosion with only 2–3 μm coating beryllium left, regions with intact marker tile, and droplets with 90% beryllium. The nonuniform erosion, droplets mainly formed by beryllium, and the possible mixture of beryllium and nickel were the major reasons that confused interpretation from broad beam EBS.

  • 122590.
    Zhou, Yushan
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Bergsåker, Henric
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Bykov, Igor
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Possnert, G.
    Likonen, J.
    Pettersson, J.
    Koivuranta, S.
    Widdowson, A. M.
    Microanalysis of deposited layers in the inner divertor of JET with ITER-like wall2017Ingår i: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, s. 412-417Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In JET with ITER-like wall, beryllium eroded in the main chamber is transported to the divertor and deposited mainly at the horizontal surfaces of tiles 1 and 0 (high field gap closure, HFGC). These surfaces are tungsten coated carbon fibre composite (CFC). Surface sampleswere collected following the plasma operations in 2011-2012 and 2013-2014 respectively. The surfaces, as well as polished cross sections of the deposited layers at the surfaces have been studied with micro ion beam analysis methods (mu-IBA). Deposition of Beand other impurities, and retention of D is microscopically inhomogeneous. Impurities and trapped deuterium accumulate preferentially in cracks, pits and depressed regions, and at the sides of large pits in the substrate (e.g. arc tracks where the W coating has been removed). With careful overlaying of mu-NRA elemental maps with optical microscopy images, it is possible to separate surface roughness effects from depth profiles at microscopically flat surface regions.

  • 122591.
    Zhou, Yushan
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Bergsåker, Henric
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Modelling of effect from rough surface on deuterium and beryllium deposition on divertor targetManuskript (preprint) (Övrigt vetenskapligt)
  • 122592.
    Zhou, Yushan
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Bergsåker, Henric
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Possnert, G
    Likonen, J
    contributors, JET
    The effect of gyration on the deposition of beryllium and deuterium at rough surface on thedivertor tiles with ITER-like-wall in JET2019Ingår i: Nuclear Materials and Energy, E-ISSN 2352-1791Artikel i tidskrift (Refereegranskat)
  • 122593.
    Zhou, Yuye
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Romson, Joakim
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Emmer, Åsa
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    An antibody-free sample pretreatment method for osteopontin combined with MALDI-TOF MS/MS analysis2019Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 14, nr 3, artikel-id e0213405Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Osteopontin is an osteoblast-secreted protein with an aspartic acid-rich, highly phosphorylated, and glycosylated structure. Osteopontin can easily bind to integrins, tumor cells, extracellular matrix and calcium, and is related to bone diseases, various cancers, inflammation etc. Here, DEAE-Cibacron blue 3GA was used to extract recombinant osteopontin from human plasma, and to deplete abundant plasma proteins with an antibody-free method. Using selected buffer systems, osteopontin and human serum albumin could be bound to DEAE-Cibacron blue 3GA, while immunoglobulin G was excluded. The bound osteopontin could then be separated from albumin by using different sequential elution buffers. By this method, 1 μg/mL recombinant osteopontin could be separated from the major part of the most abundant proteins in human plasma. After trypsin digestion, the extracted osteopontin could be successfully detected and identified by MALDI-TOF MS/MS using the m/z 1854.898 peptide and its fragments.

  • 122594. Zhou, Z. -Q
    et al.
    Liu, X.
    Kedem, Yaron
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Cui, J. -M
    Li, Z. -F
    Hua, Y. -L
    Li, C. -F
    Guo, G. -C
    Experimental observation of anomalous trajectories of single photons2017Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 95, nr 4, artikel-id 042121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A century after its conception, quantum mechanics still hold surprises that contradict many "common sense" notions. The contradiction is especially sharp in case one consider trajectories of truly quantum objects such as single photons. From a classical point of view, trajectories are well defined for particles, but not for waves. The wave-particle duality forces a breakdown of this dichotomy and quantum mechanics resolves this in a remarkable way: Trajectories can be well defined, but they are utterly different from classical trajectories. Here, we give an operational definition to the trajectory of a single photon by introducing a technique to mark its path using its spectral composition. The method demonstrates that the frequency degree of freedom can be used as a bona fide quantum measurement device (meter). The analysis of a number of setups, using our operational definition, leads to anomalous trajectories which are noncontinuous and in some cases do not even connect the source of the photon to where it is detected. We carried out an experimental demonstration of these anomalous trajectories using a nested interferometer. We show that the two-state vector formalism provides a simple explanation for the results. © 2017 American Physical Society.

  • 122595.
    Zhou, Zhou
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Li, Xiaogai
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Kleiven, Svein
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Biomechanics of acute subdural hematoma in the elderly: A fluid-structure interaction study2019Ingår i: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042, Vol. 36, nr 13, s. 2099-2108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Acute subdural hematoma (ASDH) due to bridging vein (BV) rupture is a frequent and lethal head injury, especially in the elderly. Brain atrophy has been hypothesized to be a primary pathogenesis associated with the increased risk of ASDH in the elderly. Though decades of biomechanical endeavours have been made to elucidate the potential mechanisms, a thorough explanation for this hypothesis appears lacking. Thus, a recently improved finite element head model, in which the brain-skull interface was modelled using a fluid-structure interaction (FSI) approach with special treatment of the cerebrospinal fluid as arbitrary Lagrangian-Eulerian fluid formulation, is used to partially address this understanding gap. Models with various degrees of atrophied brains and thereby different subarachnoid thicknesses are generated and subsequently exposed to experimentally determined loadings known to cause ASDH or not. The results show significant increases in the cortical relative motion and BV strain in the atrophied brain, which consequently exacerbates the ASDH risk in the elderly. Results of this study are suggested to be considered while developing age-adapted protecting strategies for the elderly in the future.

  • 122596.
    Zhou, Zhou
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Li, Xiaogai
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Kleiven, Svein
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Fluid–structure interaction simulation of the brain–skull interface for acute subdural haematoma prediction2018Ingår i: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 18, nr 1, s. 155-173Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Traumatic brain injury is a leading cause of disability and mortality. Finite element-based head models are promising tools for enhanced head injury prediction, mitigation and prevention. The reliability of such models depends heavily on adequate representation of the brain–skull interaction. Nevertheless, the brain–skull interface has been largely simplified in previous three-dimensional head models without accounting for the fluid behaviour of the cerebrospinal fluid (CSF) and its mechanical interaction with the brain and skull. In this study, the brain–skull interface in a previously developed head model is modified as a fluid–structure interaction (FSI) approach, in which the CSF is treated on a moving mesh using an arbitrary Lagrangian–Eulerian multi-material formulation and the brain on a deformable mesh using a Lagrangian formulation. The modified model is validated against brain–skull relative displacement and intracranial pressure responses and subsequently imposed to an experimentally determined loading known to cause acute subdural haematoma (ASDH). Compared to the original model, the modified model achieves an improved validation performance in terms of brain–skull relative motion and is able to predict the occurrence of ASDH more accurately, indicating the superiority of the FSI approach for brain–skull interface modelling. The introduction of the FSI approach to represent the fluid behaviour of the CSF and its interaction with the brain and skull is crucial for more accurate head injury predictions.

  • 122597.
    Zhou, Zhou
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Li, Xiaogai
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Kleiven, Svein
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem, Neuronik.
    Shah, C.S.
    Hardy, W.N.
    A reanalysis of experimental brain strain data: implication for finite element head model validation2018Ingår i: Stapp Car Crash Journal, ISSN 1532-8546, Vol. 62, s. 293-318Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Relative motion between the brain and skull and brain deformation are biomechanics aspects associated with many types of traumatic brain injury (TBI). Thus far, there is only one experimental endeavor (Hardy et al., 2007) reported brain strain under loading conditions commensurate with levels that were capable of producing injury. Most of the existing finite element (FE) head models are validated against brain-skull relative motion and then used for TBI prediction based on strain metrics. However, the suitability of using a model validated against brain-skull relative motion for strain prediction remains to be determined. To partially address the deficiency of experimental brain deformation data, this study revisits the only existing dynamic experimental brain strain data and updates the original calculations, which reflect incremental strain changes. The brain strain is recomputed by imposing the measured motion of neutral density target (NDT) to the NDT triad model. The revised brain strain and the brain-skull relative motion data are then used to test the hypothesis that an FE head model validated against brainskull relative motion does not guarantee its accuracy in terms of brain strain prediction. To this end, responses of brain strain and brain-skull relative motion of a previously developed FE head model (Kleiven, 2007) are compared with available experimental data. CORrelation and Analysis (CORA) and Normalized Integral Square Error (NISE) are employed to evaluate model validation performance for both brain strain and brain-skull relative motion. Correlation analyses (Pearson coefficient) are conducted between average cluster peak strain and average cluster peak brain-skull relative motion, and also between brain strain validation scores and brain-skull relative motion validation scores. The results show no significant correlations, neither between experimentally acquired peaks nor between computationally determined validation scores. These findings indicate that a head model validated against brain-skull relative motion may not be sufficient to assure its strain prediction accuracy. It is suggested that a FE head model with intended use for strain prediction should be validated against the experimental brain deformation data and not just the brain-skull relative motion.

  • 122598. Zhou, Zude
    et al.
    Yao, Bitao
    Xu, Wenjun
    Wang, Lihui
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion, Produktionssystem.
    Condition monitoring towards energy-efficient manufacturing: a review2017Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 91, nr 9-12, s. 3395-3415Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Recently, sustainable development has obtained increasing attentions from governments, industry, and academia owing to the limited natural resources. In the area of energy consumption, manufacturing accounts for a major portion of the total energy usage in industry. There is a clear necessity for energy-efficient manufacturing by optimizing manufacturing activities. Condition monitoring is the technology that provides runtime information for optimization. This paper aims to provide a better understanding of past achievements and future trends of condition monitoring towards energy-efficient manufacturing. Since there are a variety of sensors and technologies that can be used for condition monitoring towards energy-efficient manufacturing, this paper divides manufacturing activities into three levels, namely unit process level, shop-floor level, and supply chain level, and summarizes and discusses the sensors and technologies required to enable energy-efficient manufacturing on each level. With the advancement of technology, condition monitoring shows the characteristic of intelligence. Intelligent sensors that can be applied to condition monitoring in energy-efficient manufacturing are also reviewed. This paper can be helpful to manufacturers who are willing to improve energy efficiency in own manufacturing practice.

  • 122599.
    Zhovtobriukh, Iurii
    et al.
    Stockholm Univ, FYSIKUM, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Pettersson, Lars G. M.
    Stockholm Univ, FYSIKUM, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden..
    X-ray absorption spectrum simulations of hexagonal ice2019Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, nr 3, artikel-id 034501Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We calibrate basis sets and performance of two theoretical approaches to compute X-ray absorption spectra (XAS) of condensed water by comparison to experiments on hexagonal ice Ih. We apply both the transition-potential half-core-hole approach and the complex polarization propagator using four different models of the crystal with increasing oxygen and proton disorder but find poor agreement with experiments. We note that there are large variations in experimental spectra depending on detection mode and how the ice samples were prepared, which leads us to critically investigate what structures were actually prepared and measured in each case. This is done by using a Monte Carlo-based fitting technique which fits the spectra based on a library of precomputed spectra and assigns weights to contributions from different model structures. These are then used to generate O-O and O-H radial distribution functions and tetrahedrality parameters associated with each of the measured spectra. We find that all spectra are associated with sharp peaks at the oxygen positions in the perfect lattice, but with significant disorder around these positions. We suggest that presently available XAS of hexagonal ice are not fully representative of the perfect crystalline lattice, but contain varying amounts of defects and possible contributions from low-density amorphous ice.

  • 122600. Zhow, Yongjin J.
    et al.
    Buijs, Nicolaas A.
    Zhu, Zhiwei
    Gomez, Diego Orol
    Boonsombuti, Akarin
    Siewers, Verena
    Nielsen, Jens
    KTH, Skolan för bioteknologi (BIO), Genteknologi. KTH, Centra, Science for Life Laboratory, SciLifeLab. Chalmers University of Technology, Sweden; Technical University of Denmark, Denmark.
    Harnessing Yeast Peroxisomes for Biosynthesis of Fatty-Acid-Derived Biofuels and Chemicals with Relieved Side-Pathway Competition2016Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, nr 47, s. 15368-15377Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Establishing efficient synthetic pathways for microbial production of biochemicals is often hampered by competing pathways and/or insufficient precursor supply. Compartmentalization in cellular organelles can isolate synthetic pathways from competing pathways, and provide a compact and suitable environment for biosynthesis. Peroxisomes are cellular organelles where fatty acids are degraded, a process that is inhibited under typical fermentation conditions making them an interesting workhouse for production of fatty-acid-derived molecules. Here, we show that targeting synthetic pathways to peroxisomes can increase the production of fatty-acid-derived fatty alcohols, alkanes and olefins up to 700%. In addition, we demonstrate that biosynthesis of these chemicals in the peroxisomes results in significantly decreased accumulation of byproducts formed by competing enzymes. We further demonstrate that production can be enhanced up to 3-fold by increasing the peroxisome population. The strategies described here could be used for production of other chemicals, especially acyl-CoA-derived molecules.

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