DFT model of hydrogen desorption from MgH2: The role of iron catalyst

Hydrogen desorption from hydride matrix is still an open field of research. Extensive, density functional theory based, ab-initio molecular dynamics simulations of MgH₂–Mg interface catches the atomic level structural mechanism leading to hydrogen desorption. The numerical model estimates the desorption temperature for an interface with Fe catalyst in excellent agreement with experimental results. Formation energies and the analysis of the structural data reveal the role played by the catalysts to lower the desorption temperature.     

On the Existence of Supersolid 4He Monolayer Films

Extensive Monte Carlo simulations of ⁴He monolayer films adsorbed on weak substrates have been carried out, aimed at ascertaining the possible occurrence of a quasi-two-dimensional supersolid phase. Only crystalline films not registered with underlying substrates are considered. Numerical results yield strong evidence that ⁴He will not form a supersolid film on any substrate strong enough to stabilize a crystalline layer. On weaker substrates, continuous growth of a liquid film takes place.     

Structural properties of hydrophilic polymeric chains bearing covalently-linked hydrophobic substituents: Exploring the effects of chain length, fractional loading and hydrophobic interaction strength with coarse grained potentials and Monte Carlo simulations

Chemical and physical properties of polymeric species in solution strongly depend on their structure, which can be modulated by covalently linking substituents of different solubility. In this work, the effect of changing the interaction strength and fractional loading of hydrophobic substituents on semi-flexible hydrophilic polymers of varying chain length is studied by means of Monte Carlo simulations and coarse grained model potentials. The latter are chosen in order to provide a more factual representation of a chain in diluted solution, introducing substituent flexibility and realistic torsional and bending potentials. Upon increasing the number and the interaction strength of the substituents, our results indicate a less steep rise of the chain gyration radius and “end to end” distance for the chain length than predicted for an unsubstituted polymer in an almost good solvent. Moreover, a “disordered to compact” structural transition appears. In parallel, the formation of hydrophobic nuclei and the consequent appearance of flexible polymer loops grafted to the semi-rigid cores is witnessed. The core formation resembles a nucleation phenomenon, where the change in the interaction between the substituents modulates the free energy surface for the aggregation process similarly to the change in chemical potential. Interestingly, it has been found that a single chain containing a sufficiently high number of interacting substituents may give rise to the formation of multiple cores, suggesting that the chain stiffness may play a role in defining the structure of the free energy minimum.     

Phase behavior of blends of poly(ethylene terephthalate) with liquid-crystalline polymers

Poly(ethylene terephthalate) (PET) was melt blended with several liquid-crystalline polymers (LCPs), both with and without Ti(OBu)₄ catalyst. The LCPs, referred to as VA, LC5, LC3, and SBH, respectively, were Vectra-A950, Rodrun LC-5000, Rodrun LC-3000, and a laboratory copolyester of sebacic acid (S), 4,4′-diacetoxybiphenyl (B), and 4-acetoxybenzoic acid (H). Their degree of aromaticity decreases in that order. The phase behavior and the morphology of the blends were studied by differential scanning calorimetry and scanning electron microscopy. All the LCPs retard the dynamic crystallization of PET. The lower the LCPs degree of aromaticity, the more pronounced was the effect. It was not possible to obtain any evidence of ester exchange reactions by the reactive blending of PET with VA. On the contrary, appreciable changes of phase behavior and morphology were observed under comparable conditions for the other blends. With LC5 and LC3, the transesterification process predominantly involved the ET-rich phase of those polymers. Extensive transesterification occurred between PET and SBH, as proven by the gradual formation of a quasi homogeneous material, with lowered temperatures and enthalpies of fusion and crystallization. For blends with more than 25% SBH, homogenization is followed by the segregation of a new, highly aromatic phase.     

Structural Features and Toxicity of α-Synuclein Oligomers Grown in the Presence of DOPAC

The interplay between α-synuclein and dopamine derivatives is associated with oxidative stress-dependent neurodegeneration in Parkinson’s disease (PD). The formation in the dopaminergic neurons of intraneuronal inclusions containing aggregates of α-synuclein is a typical hallmark of PD. Even though the biochemical events underlying the aberrant aggregation of α-synuclein are not completely understood, strong evidence correlates this process with the levels of dopamine metabolites. In vitro, 3,4-dihydroxyphenylacetaldehyde (DOPAL) and the other two metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylethanol (DOPET), share the property to inhibit the growth of mature amyloid fibrils of α-synuclein. Although this effect occurs with the formation of differently toxic products, the molecular basis of this inhibition is still unclear. Here, we provide information on the effect of DOPAC on the aggregation properties of α-synuclein and its ability to interact with membranes. DOPAC inhibits α-synuclein aggregation, stabilizing monomer and inducing the formation of dimers and trimers. DOPAC-induced oligomers did not undergo conformational transition in the presence of membranes, and penetrated the cell, where they triggered autophagic processes. Cellular assays showed that DOPAC reduced cytotoxicity and ROS production induced by α-synuclein aggregates. Our findings show that the early radicals resulting from DOPAC autoxidation produced covalent modifications of the protein, which were not by themselves a primary cause of either fibrillation or membrane binding inhibition. These findings are discussed in the light of the potential mechanism of DOPAC protection against the toxicity of α-synuclein aggregates to better understand protein and catecholamine biology and to eventually suggest a scaffold that can help in the design of candidate molecules able to interfere in α-synuclein aggregation.     

Long-term and collapse tests on a timber-concrete composite beam with glued-in connection

The paper reports the results of a comprehensive experimental test performed on a 6 m span timber-concrete composite beam with glued re-bar connection. The beam had first been subjected to sustained load in unsheltered outdoor conditions for 5 years. Eventually a ramp loading test up to failure was performed. The long-term test showed an increase in deflection mainly during the first two years, while the slip rose during the whole testing period. Thermo-hygrometric variations of environment caused an important fluctuation of all quantities on both yearly and daily scale. By comparing experimental and analytical results, it is highlighted that composite beams in outdoor conditions should be assigned to the 3rd service class according to the Eurocode 5 (EC5). Analytical predictions based on approximate formulae suggested by such regulation are found to be not conservative for the long-term behaviour and fairly accurate for the collapse behaviour. Since the simplified formulae proposed by the latest versions of the EC5-Parts 1.1 and 2 largely underestimate the actual connection stiffness and strength, it is recommended that realistic values of these properties, such as those obtained through push-out tests, be used when designing timber-concrete composite beams.     

Add-on mirtazapine enhances effects on cognition in schizophrenic patients under stabilized treatment with clozapine.

The development of therapeutic strategies for cognitive dysfunction remains one of the primary goals in the treatment of schizophrenia. The pharmacodynamic profile of mirtazapine, an antidepressant that enhances noradrenergic and serotonergic transmission, is based on a presynaptic α? antagonism and postsynaptic 5-HT? and 5-HT? antagonism. Mirtazapine shares some pharmacological similarities with that of clozapine. This 8-week open label trial aimed to discover whether the addition of 30 mg mirtazapine could potentiate the effects on cognition of an ongoing stabilized clozapine therapy in 15 persons who met the criteria for chronic schizophrenia in the Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; American Psychiatric Association, 2000). Mirtazapine adjunction was well tolerated and induced a significant improvement in cognitive performance, as measured by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS; Randolph, 1998) total score and by the subscales for immediate and delayed memory (p     

The Crossroads between Host Copper Metabolism and Influenza Infection

Three main approaches are used to combat severe viral respiratory infections. The first is preemptive vaccination that blocks infection. Weakened or dead viral particles, as well as genetic constructs carrying viral proteins or information about them, are used as an antigen. However, the viral genome is very evolutionary labile and changes continuously. Second, chemical agents are used during infection and inhibit the function of a number of viral proteins. However, these drugs lose their effectiveness because the virus can rapidly acquire resistance to them. The third is the search for points in the host metabolism the effect on which would suppress the replication of the virus but would not have a significant effect on the metabolism of the host. Here, we consider the possibility of using the copper metabolic system as a target to reduce the severity of influenza infection. This is facilitated by the fact that, in mammals, copper status can be rapidly reduced by silver nanoparticles and restored after their cancellation.     

The Influence of a Continuum Background on Carrier Relaxation in InAs/InGaAs Quantum Dot

We have investigated the ultra-fast carrier dynamics in Molecular Beam Epitaxy (MBE)-grown InAs/InGaAs/GaAs quantum dots (QDs) emitting at 1.3 μm by time resolved photoluminescence (TRPL) upconversion measurements with a time resolution of about 200 fs. Changing the detection energies in the spectral region from the energy of the quantum dots excitonic transition up to the barrier layer absorption edge, we have found that, under high excitation intensity, the intrinsic electronic states are populated mainly by carriers directly captured from the barrier.