2,036 research outputs found
Ab initio simulations of Cu binding sites in the N-terminal region of PrP
The prion protein (PrP) binds Cu2+ ions in the octarepeat domain of the
N-terminal tail up to full occupancy at pH=7.4. Recent experiments show that
the HGGG octarepeat subdomain is responsible for holding the metal bound in a
square planar coordination. By using first principle ab initio molecular
dynamics simulations of the Car-Parrinello type, the Cu coordination mode to
the binding sites of the PrP octarepeat region is investigated. Simulations are
carried out for a number of structured binding sites. Results for the complexes
Cu(HGGGW)+(wat), Cu(HGGG) and the 2[Cu(HGGG)] dimer are presented. While the
presence of a Trp residue and a H2O molecule does not seem to affect the nature
of the Cu coordination, high stability of the bond between Cu and the amide
Nitrogens of deprotonated Gly's is confirmed in the case of the Cu(HGGG)
system. For the more interesting 2[Cu(HGGG)] dimer a dynamically entangled
arrangement of the two monomers, with intertwined N-Cu bonds, emerges. This
observation is consistent with the highly packed structure seen in experiments
at full Cu occupancy.Comment: 4 pages, conference proceedin
LCA of Different Construction Choices for a Double-Track Railway Line for Sustainability Evaluations
The international commitment to achieve carbon neutrality in the next few decades has oriented human activities towards the preservation of natural and non-renewable resources. In this context, a great research effort has been devoted to the search for sustainable solutions for the infrastructure construction sector, based on a thorough assessment of the environmental impact (EI). In this regards, Life Cycle Assessment (LCA) is considered one of the main components of Environmental Impact Assessment (EIA) and, for a comprehensive analysis, all the costs incurred by stakeholders during the useful life of the infrastructure should also be taken into account, applying the Life Cycle Cost (LCC) methodology. So far, there is a lack of combined LCA and LCC analyses of railway projects to support a proper sustainable decision-making process at a project level. Therefore, this study aimed to contributed to this topic by determining the environmental effect and related costs of different planning and construction choices in terms of material and maintenance strategies. For this purpose, first, an LCA of typical railway infrastructures with a ballasted track was developed. The case study considered two different functional units of a double-track railway line: 1 km of embankment section and 1 km of a cut section, in straight alignment. After defining five alternative railway infrastructure scenarios with different materials (virgin or recycled material) and construction methods (e.g., lime stabilization), two different railway track maintenance approaches were analysed. SimaPro was used to analyse the case study, and the results were compared with those obtained using the PaLATE software, suitably adapted for use in the railway sector. Finally, a cost analysis was carried out using Life Cycle Cost (LCC) methodology for all the scenarios analysed. The results obtained in terms of EI and related costs of each scenario provide useful information, allowing a sustainable planning approach: as a general result, the initial construction phase always involves the larger part of the total environmental impact while the material production is the most polluting phase, reaching percentages always higher than 50% of the total
Reward-sensitive women overeat in a varied food environment, but only when hungry
In the current study we tried to elucidate the relationship between a personality trait, reward sensitivity, and an environmental variable; food variety. Based on scarce previous research we predicted that reward sensitivity would interact with variety in the food environment so that especially high reward sensitive individuals would be vulnerable to overeating in a varied food environment. It turned out that especially the high reward individuals did indeed overeat in a varied food environment. However, this was only the case for the highly reward sensitive individuals who experienced feelings of hunger. In other words, reward sensitivity does not affect food intake in varied food environments as long as feelings of hunger are not present. Future research should concentrate on identifying other factors that interact with the person and the environment to discourage reward-related overeating
Constraining Glueball Couplings
We set up a numerical S-matrix bootstrap problem to rigorously constrain
bound state couplings given by the residues of poles in elastic amplitudes. We
extract upper bounds on these couplings that follow purely from unitarity,
crossing symmetry, and the Roy equations within their proven domain of
validity. First we consider amplitudes with a single spin 0 or spin 2 bound
state, both with or without a self-coupling. Subsequently we investigate
amplitudes with the spectrum of bound states corresponding to the estimated
glueball masses of pure SU(3) Yang-Mills. In the latter case the 'glue-hedron',
the space of allowed couplings, provides a first-principles constraint for
future lattice estimates.Comment: 7 + 9 pages, 14 figure
Global Assessment of PA variability through concurrent Physics-based X-parameter and Electro-Magnetic simulations
The novel technique introduced in [1] is exploited to address a full variability analysis of a GaAs MMIC X-band power amplifier, including the statistical variations of several technological parameters, both in the active and passive components. The active device is modelled by means of X-parameters, directly extracted from physics-based analysis. A non-50 O X-Par model is used to take into account the input port mismatch with respect to the conventional 50 O reference. The scattering parameters of the passive structures are extracted from accurate electromagnetic simulations and then imported into the circuit simulator through data intercharge files (e.g. MDIF or CITIfile) as a function of the most important MMIC fabrication parameters, e.g. the thickness of the MIM capacitor dielectric layer. The analysis shows that more than 10% of output power variations can be ascribed to the concurrent MIM and doping variations in conventional GaAs MMIC technology
PA design and statistical analysis through X-par driven load-pull and EM simulations
Modeling the active device is a key step for the successful statistical analysis of power amplifiers: the nonlinear model must not only depend on the most relevant device fabrication parameters, but should also work accurately in source/load-pull analysis, since variations of the passive embedding network effectively act as a load-pull at the active device ports. We demonstrate that the X-parameter model extracted from physics-based nonlinear TCAD simulations is extremely accurate for load-pull analysis. The X-parameter model is coupled to electromagnetic simulations to assist the variability-aware design of a GaAs MMIC X-band power amplifier (PA): concurrent variations of the active device doping and of the capacitor dielectric layer thickness are considered as the main contributions to PA variability. Two possible output matching networks, with distributed or semi-lumped design, are compared: already for moderate doping variations the PA output power spread is dominated by the active device variability, while passive network variations are always the relevant contribution to PA efficiency
TCAD-based Dynamic Thermal X-parameters for PA Self-Heating Analysis
TCAD simulations are used to extract an accurate temperature-dependent X-parameter active device model, which describes it as instantaneously dependent on the junction temperature, and hence represents the ideal framework to analyze device self-heating. Once exported from TCAD into EDA tools, X-parameters are coupled to a dynamic thermal impedance, leading to a compact and efficient device black-box model, allowing for circuit-level analysis of thermal memory effects in microwave circuits, like Power Amplifiers (PAs), even in presence of complex modulated-signal excitation. In particular, we focus on the thermal analysis of a class-A PA at E-band based on a 54 nm Si FinFET. The accuracy of the temperature-dependent X-parameter model is demonstrated first by comparing circuit simulations with TCAD results in continuous wave. Then we extend the analysis to pulsed modulated operation, highlighting thermal dynamic effects as a function of the pulse period
Variability-aware MMIC design through multiphysics modelling
We present a novel multiphysics approach to the variability-aware modelling of MMIC stages, including technological variations in both the active devices and in the passive structures used to implement the matching networks. The models are based on accurate physical simulations via the TCAD numerical analysis of the active device, and electro-magnetic simulations of the passives. Black-box models are then extracted and implemented into circuit simulators, using parameter-dependent X-parameters and scattering matrix. In both cases, the link with the underlying technology is always retained. After model validation, we present the statistical analysis of an X-band GaAs power amplifier. We show that the stage is highly affected by process induced variability, with spreads up to 3 dB of output power, 1.5 dB of operative gain, and more than 10 percentage points of drain efficiency
RELAÇÃO Genética e Potencial de Virulência de Isolados de Escherichia Coli Enteroagregativa de Crianças de Comunidades Quilombolas
Escherichia coli enteroagregativa (EAEC) é um patotipo emergente responsável por diarreia aguda e persistente, caracterizado por marcante heterogeneidade quanto aos potenciais fatores de virulência entre os isolados. EAEC pode ser classificada em típica (tEAEC) e atípica (aEAEC) com base na presença do regulon AggR, sugerindo-se uma maior virulência para tEAEC, embora aEAEC esteja relacionada a surtos de diarreia. Tivemos como objetivo determinar a relação genética e o potencial de virulência in vivo de isolados de tEAEC e aEAEC de crianças de comunidades quilombolas. Para análise da heterogeneidade clonal, empregamos a técnica de eletroforese em campo pulsado (PFGE) após digestão com enzima de restrição XbaI em 73 amostras previamente caracterizadas quanto ao repertório de genes de virulência. A virulência de 20 amostras de EAEC (10 tEAEC e 10 aEAEC) além de cepas referência de tEAEC (EAEC 042), aEAEC (C1096) e E. coli não patogênica HB101 foi investigada em modelo de Galleria mellonella. Foi analisada a
sobrevivência das larvas após inoculação de 104 a 107 UFC/larva e determinada a carga bacteriana da hemolinfa após inoculação de 105 UFC/larva das cepas referência, em diferentes períodos após infecção. Além disso, avaliamos características fenotípicas de virulência de 10 amostras de EAEC, (produção de enzimas, sideróforos e de biofilme). Para análise epidemiológica a nível global, 10 isolados foram submetidos à tipagem molecular pela técnica de Multilocus Sequence Typing (MLST). Evidenciamos 58 pulsotipos distintos e sem relação com o perfil de genes de virulência e a comunidade de origem, para a maior parte das amostras. No modelo de G. mellonella, observamos que: (i) mortalidade das larvas foi dependente
da concentração inoculada de tEAEC e aEAEC; (ii) cepas e amostras de aEAEC
foram tão virulentas quanto de tEAEC, porém, a virulência média foi maior para as tEAEC; (iii) Não houve relação entre número de genes de virulência e a virulência no modelo; (iv) em contraposição às cepas EAEC 042 e EAEC C1096, a cepa E. coli HB101 não provoca melanização e é eliminada da hemolinfa com 2 horas após infecção. Em relação às características fenotípicas de virulência: (i) nenhuma amostra produziu fosfolipase, protease ou esterase; (ii) apenas uma amostra produziu hemolisina; (iii) todas as amostras analisadas produziram sideróforos; (iv) somente uma amostra não produziu biofilme. As 10 amostras analisadas pelo MLST pertencem a STs distintos e, portanto, representam diferentes linhagens evolutivas. Os STs: 443, 730, 1178, 1286 e 2481, detectados nas nossas amostras, não haviam sido descritos para EAEC até o momento. Em conclusão, os resultados obtidos demonstram uma alta heterogeneidade de EAEC nas comunidades quilombolas mesmo estas sendo semi-isoladas, visto que a maior parte das amostras não apresentou relação genotípica entre si. Além disso, novos STs foram observados em amostras de EAEC e ao contrário do que se sugere na literatura, pelo modelo de estudo, as aEAEC podem ser tão virulentas quanto as tEAEC
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