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See detailThermal conductivity enhancement of graphene nanoplatelet/epoxy composites - Covalent functionalization with nitrene chemistry for reducing the interfacial thermal resistance
Depaifve, Sébastien Fabian L UL

Doctoral thesis (2020)

Polymer composites with high thermal conductivity are in strong demand for efficient thermal management in many modern applications such as electronics, batteries, aerospace structural materials, LED ... [more ▼]

Polymer composites with high thermal conductivity are in strong demand for efficient thermal management in many modern applications such as electronics, batteries, aerospace structural materials, LED lightings, etc. Nanocarbon fillers have recently attracted a lot of interest due to their extremely high intrinsic thermal conductivity. Nevertheless, the effective thermal conductivity achieved with nanocarbon-polymer composites is below the expectations. In particular, at low fillers loading due to the large interfacial thermal resistance at the nanocarbon-polymer interface. Covalent functionalization of nanocarbons has been suggested to reduce the interfacial thermal resistance in nanocarbon-polymer composites. However, large scale covalent functionalization of nanocarbons is usually achieved with harsh oxidizing conditions, causing a dramatic decrease of the intrinsic thermal conductivity of the nanocarbon fillers. In this thesis, we developed and optimized a non-disruptive covalent functionalization for graphene nanoplatelets (GNP), based on nitrene chemistry. We achieved unprecedented functionalization yields. The fillers functionalized by nitrene chemistry produced a significant thermal conductivity enhancement (TCE) compared to pristine and oxidized fillers. However, increasing the chain length or introducing heteroatoms in the functional chain afforded reduced performances. In parallel, we developed an innovative combination of SEM and µCT analyses to afford an unprecedented description of nanocarbon-polymer composites. This allowed us to elucidate the contradictory results, reported in the literature, on the influence of the aggregation level and the geometrical parameters of the fillers on the TCE. In this thesis we propose a novel and detailed description of the parameters responsible of TCE in GNP-epoxy composites. Moreover, we demonstrate that covalent functionalization of GNP by nitrene chemistry reduces the interfacial thermal resistance in epoxy composites and improves the thermal conductivity. [less ▲]

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See detailThermal Conversion of Solid Fuels
Peters, Bernhard UL

Book published by WIT Press (2003)

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See detailThermal Glass Transition Beyond the Vogel-Fulcher-Tammann Behavior for Glass Forming Diglycidylether of Bisphenol A
Krüger, Jan-Kristian UL; Britz, Th; Baller, Jörg UL et al

in Physical Review Letters (2002), 89

For the low molecular weight fragile liquid diglycidyl ether of bisphenol A we report, based on Brillouin and dielectric spectroscopy, on a thermal glass transition where the relaxation time of the α ... [more ▼]

For the low molecular weight fragile liquid diglycidyl ether of bisphenol A we report, based on Brillouin and dielectric spectroscopy, on a thermal glass transition where the relaxation time of the α process does not go to infinity. Instead, the structural α relaxation disappears spontaneously at the transition point. That discontinuity in relaxation time coincides with a kink in the longitudinal hypersonic velocity and determines unambiguously the transition from the liquid to the glassy state. [less ▲]

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See detailThermal Model of a Solar Hybrid Module as the Heat Source for a CO2 Heat Pump
Rullof, Johannes UL; Lambers, Klaus Jürgen; Blieske, Ulf et al

in Proceedings of 2017 International Energy and Sustainability Conference (IESC 2016) (2017)

In recent years, the possibility of combining photovoltaics (PV) and solar thermal collectors into one solar hybrid module (PVT-module) has been increasingly investigated. PVT-modules produce thermal and ... [more ▼]

In recent years, the possibility of combining photovoltaics (PV) and solar thermal collectors into one solar hybrid module (PVT-module) has been increasingly investigated. PVT-modules produce thermal and electrical energy at the same time. Since the efficiency of a photovoltaic module decreases with increasing temperature, the temperature of the heat transfer media is often limited to about 30 °C and the PVT-module is combined with a heat pump, which increases the temperature on the “warm side”. A common approach is to integrate the PVT-module directly as an evaporator in a heat pump system (PVT-direct). This paper presents a thermal model of a PVT-direct module as the heat source for a R744/CO2 heat pump. Due to the combined effect of flow channel patterns, solar radia-tion, the ambient conditions and possible condensation and frost formation, heat transfer and thermal distribution conditions of the PVT-direct evaporator are inevitably com-plicated to determine. The proposed thermal model of this hybrid solar module that has CO2 direct evaporation in microchannels will be used to simulate the behavior of the module under different climatic operating conditions. Fur-thermore, it will quantify all energy inputs and/or losses as well as their influence on the total energy supplied by the PVT-module. This will be used to investigate the overall CO2-PVT heat pump system performance in prospective simulations. [less ▲]

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See detailThermal monitoring of facades by UAV: applications for building rehabilitation
Gonzalez-Rodrigo, Beatriz; Tendero-Caballero, Ricardo; Garcia-De-Viedma, Maria et al

in Dyna (2016), 91(5), 571--577

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See detailThermal sensitivity during rest and exercise: a sex comparison
Gerrett, Nicola; Ouzzahra, Yacine UL; Coleby, Samantha et al

in European Journal of Applied Physiology (2014)

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See detailThermal sensitivity to warmth during rest and exercise: a sex comparison
Gerrett, Nicola; Ouzzahra, Yacine UL; Coleby, S et al

in European Journal of Applied Physiology (2014)

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See detailThermionic Field Emission in p-Barrier enhanced InP/InGaAs/InP HEMTs
Schimpf, K.; Horstmann, M.; Hardtdegen, H. et al

in Electronics Letters (1996), 32(1996), 2132-2133

A model for thermionic field emission in p-barrier enhanced InP HEMTs is presented indicating that a reduction in the gate leakage of those devices is related to an increase in effective barrier thickness ... [more ▼]

A model for thermionic field emission in p-barrier enhanced InP HEMTs is presented indicating that a reduction in the gate leakage of those devices is related to an increase in effective barrier thickness. Good agreement between this model and our experimental data is obtained. [less ▲]

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See detailThermochemical and kinetic aspects of the sulfurization of Cu–Sb and Cu–Bi thin films
Colombara, Diego UL; Peter, Laurence M.; Rogers, Keith D. et al

in Journal of Solid State Chemistry (2011)

CuSbS2 and Cu3BiS3 are being investigated as part of a search for new absorber materials for photovoltaic devices. Thin films of these chalcogenides were produced by conversion of stacked and co ... [more ▼]

CuSbS2 and Cu3BiS3 are being investigated as part of a search for new absorber materials for photovoltaic devices. Thin films of these chalcogenides were produced by conversion of stacked and co-electroplated metal precursor layers in the presence of elemental sulfur vapour. Ex-situ XRD and SEM/EDS analyses of the processed samples were employed to study the reaction sequence with the aim of achieving compact layer morphologies. A new “Time-Temperature-Reaction” (TTR) diagram and modified Pilling–Bedworth coefficients have been introduced for the description and interpretation of the reaction kinetics. For equal processing times, the minimum temperature required for CuSbS2 to appear is substantially lower than for Cu3BiS3, suggesting that interdiffusion across the interfaces between the binary sulfides is a key step in the formation of the ternary compounds. The effects of the heating rate and sulfur partial pressure on the phase evolution as well as the potential losses of Sb and Bi during the processes have been investigated experimentally and the results related to the equilibrium pressure diagrams obtained via thermochemical computation. [less ▲]

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See detailThermodynamic Aspects of the Synthesis of Thin-Film Materials for Solar Cells
Scragg, Jonathan J.; Dale, Phillip UL; Colombara, Diego UL et al

in Chemphyschem : A European Journal of Chemical Physics and Physical Chemistry (2012), 13(12), 30353046

A simple and useful thermodynamic approach to the prediction of reactions taking place during thermal treatment of layers of multinary semiconductor compounds on different substrates has been developed ... [more ▼]

A simple and useful thermodynamic approach to the prediction of reactions taking place during thermal treatment of layers of multinary semiconductor compounds on different substrates has been developed. The method, which uses the extensive information for the possible binary compounds to assess the stability of multinary phases, is illustrated with the examples of Cu(In,Ga)Se2 and Cu2ZnSnSe4 as well as other less-studied ternary and quaternary semiconductors that have the potential for use as absorbers in photovoltaic devices. [less ▲]

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See detailThermodynamic Characterisation of Carbohydrate-Active Enzymes
Ebenhoeh, Oliver; Skupin, Alexander UL; Kartal, Oender et al

in Experimental Standard Conditions of Enzyme Characterisation, Ruedesheim 12-16 2011 (2011)

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See detailThermodynamic cycles with active matter
Ekeh, Timothy; Cates, Michael E.; Fodor, Etienne UL

in PHYSICAL REVIEW E (2020), 102(1),

Active matter constantly dissipates energy to power the self-propulsion of its microscopic constituents. This opens the door to designing innovative cyclic engines without any equilibrium equivalent. We ... [more ▼]

Active matter constantly dissipates energy to power the self-propulsion of its microscopic constituents. This opens the door to designing innovative cyclic engines without any equilibrium equivalent. We offer a consistent thermodynamic framework to characterize and optimize the performances of such cycles. Based on a minimal model, we put forward a protocol which extracts work by controlling only the properties of the confining walls at boundaries, and we rationalize the transitions between optimal cycles. We show that the corresponding power and efficiency are generally proportional, so that they reach their maximum values at the same cycle time in contrast with thermal cycles, and we provide a generic relation constraining the fluctuations of the power. [less ▲]

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See detailThermodynamic Description of Polymorphism in Q- and N-Rich Peptide Aggregates Revealed by Atomistic Simulation
Berryman, Josh UL; Radford, Sheena E.; Harris, Sarah A.

in Biophysical Journal (2009), 97(1), 1-11

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See detailThermodynamic efficiency in dissipative chemistry
Penocchio, Emanuele UL; Rao, Riccardo; Esposito, Massimiliano UL

in Nature Communications (2019), 10(1), 1-5

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See detailThermodynamically consistent coarse graining of biocatalysts beyond Michaelis–Menten
Wachtel, Artur UL; Rao, Riccardo UL; Esposito, Massimiliano UL

in New Journal of Physics (2018), 20(4), 042002

Starting from the detailed catalytic mechanism of a biocatalyst we provide a coarse-graining procedure which, by construction, is thermodynamically consistent. This procedure provides stoichiometries ... [more ▼]

Starting from the detailed catalytic mechanism of a biocatalyst we provide a coarse-graining procedure which, by construction, is thermodynamically consistent. This procedure provides stoichiometries, reaction fluxes (rate laws), and reaction forces (Gibbs energies of reaction) for the coarse-grained level. It can treat active transporters and molecular machines, and thus extends the applicability of ideas that originated in enzyme kinetics. Our results lay the foundations for systematic studies of the thermodynamics of large-scale biochemical reaction networks. Moreover, we identify the conditions under which a relation between one-way fluxes and forces holds at the coarse-grained level as it holds at the detailed level. In doing so, we clarify the speculations and broad claims made in the literature about such a general flux–force relation. As a further consequence we show that, in contrast to common belief, the second law of thermodynamics does not require the currents and the forces of biochemical reaction networks to be always aligned. [less ▲]

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See detailThermodynamically constrained averaging theory for cancer growth modelling
Albrecht, Marco UL; Sciumè, Giuseppe; Lucarelli, Philippe UL et al

in IFAC-PapersOnLine (2016), 49(26), 289-294

In Systems Biology, network models are often used to describe intracellular mechanisms at the cellular level. The obtained results are difficult to translate into three-dimensional biological systems of ... [more ▼]

In Systems Biology, network models are often used to describe intracellular mechanisms at the cellular level. The obtained results are difficult to translate into three-dimensional biological systems of higher order. The multiplicity and time dependency of cellular system boundaries, mechanical phenomena and spatial concentration gradients affect the intercellular relations and communication of biochemical networks. These environmental effects can be integrated with our promising cancer modelling environment, that is based on thermodynamically constrained averaging theory (TCAT). Especially, the TCAT parameter viscosity can be used as critical player in tumour evolution. Strong cell-cell contacts and a high degree of differentiation make cancer cells viscous and support compact tumour growth with high tumour cell density and accompanied displacement of the extracellular material. In contrast, dedifferentiation and losing of cell-cell contacts make cancer cells more fluid and lead to an infiltrating tumour growth behaviour without resistance due to the ECM. The fast expanding tumour front of the invasive type consumes oxygen and the limited oxygen availability behind the invasive front results automatically in a much smaller average tumour cell density in the tumour core. The proposed modelling technique is most suitable for tumour growth phenomena in stiff tissues like skin or bone with high content of extracellular matrix. [less ▲]

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See detailThermodynamics and Aggregation Kinetics of Lysozyme-Derived Peptides
Hakami Zanjani, Ali Asghar UL

Doctoral thesis (2019)

When multiple similar protein or peptide chains form non-covalent aggregates, this is termed 'amyloid'. Many serious progressive diseases such as Alzheimer's and Parkinson's are related to undesirable ... [more ▼]

When multiple similar protein or peptide chains form non-covalent aggregates, this is termed 'amyloid'. Many serious progressive diseases such as Alzheimer's and Parkinson's are related to undesirable amyloid aggregation. From a positive perspective, functional amyloids have applications as robust and versatile biomaterials in nature, nanotechnology, and biomedicine. To probe the properties of the amyloid aggregation process in terms of the structure of molecules and the microscopic interactions between them, molecular simulation methods such as molecular dynamics (MD) and Monte Carlo (MC) can be used. These tools are especially valuable to illustrate short length and time scales not easily accessible for systems in solution via current experimental techniques. In this work the thermodynamics and aggregation kinetics of the ILQINS hexapeptide are studied. ILQINS is a biological material derived from hen's egg-white lysozyme. Two ILQINS homologues, IFQINS and TFQINS are compared to ILQINS and some of the complex physics which leads to the increased amyloidogenicity of these species, which is not expected from first-order consideration of amino acid properties, is discussed. The IFQINS hexapeptide is of particular interest as the human homologue of ILQINS. Solution X-ray and X-ray crystallography are compared to simulation, verifying that at least two metastable polymorphic structures exist for this system which are substantially different at the atomistic scale, and illustrating the physics driving kinetic competition between polymorphs. [less ▲]

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See detailThermodynamics of a Physical Model Implementing a Maxwell Demon
Strasberg, Philipp; Schaller, Gernot; Brandes, Tobias et al

in Physical Review Letters (2013), 110(4)(040601(5)), 040601-1

We present a physical implementation of a Maxwell demon which consists of a conventional single electron transistor (SET) capacitively coupled to another quantum dot detecting its state. Altogether, the ... [more ▼]

We present a physical implementation of a Maxwell demon which consists of a conventional single electron transistor (SET) capacitively coupled to another quantum dot detecting its state. Altogether, the system is described by stochastic thermodynamics. We identify the regime where the energetics of the SET is not affected by the detection, but where its coarse-grained entropy production is shown to contain a new contribution compared to the isolated SET. This additional contribution can be identified as the information flow generated by the ‘‘Maxwell demon’’ feedback in an idealized limit. [less ▲]

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See detailThermodynamics of a stochastic twin elevator
Kumar, Niraj; Van den Broeck, Christian; Esposito, Massimiliano UL et al

in Physical Review E (2011), 84(5),

We study the nonequilibrium thermodynamics of a single particle with two available energy levels, in contact with a classical (Maxwell-Boltzmann) or quantum (Bose-Einstein) heat bath. The particle can ... [more ▼]

We study the nonequilibrium thermodynamics of a single particle with two available energy levels, in contact with a classical (Maxwell-Boltzmann) or quantum (Bose-Einstein) heat bath. The particle can undergo transitions between the levels via thermal activation or deactivation. The energy levels are alternately raised at a given rate regardless of occupation by the particle, maintaining a fixed energy gap equal to ε between them. We explicitly calculate the work, heat, and entropy production rates. The efficiency in both the classical and the quantum case goes to a limit between 100 and 50% that depends on the relative rates of particle transitions and level elevation. In the classical problem we explicitly find the large deviation functions for heat, work, and internal energy. [less ▲]

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