1,161 research outputs found

    Microscopic dynamics and relaxation processes in liquid Hydrogen Fluoride

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    Inelastic x-ray scattering and Brillouin light scattering measurements of the dynamic structure factor of liquid hydrogen fluoride have been performed in the temperature rangeT=214Ă·283K T=214\div 283 K. The data, analysed using a viscoelastic model with a two timescale memory function, show a positive dispersion of the sound velocity c(Q)c(Q) between the low frequency value c0(Q)c_0(Q) and the high frequency value c∞α(Q)c_{\infty \alpha}(Q). This finding confirms the existence of a structural (α\alpha) relaxation directly related to the dynamical organization of the hydrogen bonds network of the system. The activation energy EaE_a of the process has been extracted by the analysis of the temperature behavior of the relaxation time τα(T)\tau_\alpha(T) that follows an Arrhenius law. The obtained value for EaE_a, when compared with that observed in another hydrogen bond liquid as water, suggests that the main parameter governing the α\alpha-relaxation process is the number of the hydrogen bonds per molecule.Comment: 9 pages and 12 figure

    Elastic constant dishomogeneity and Q2Q^2 dependence of the broadening of the dynamical structure factor in disordered systems

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    We propose an explanation for the quadratic dependence on the momentum QQ, of the broadening of the acoustic excitation peak recently found in the study of the dynamic structure factor of many real and simulated glasses. We ascribe the observed Q2Q^2 law to the spatial fluctuations of the local wavelength of the collective vibrational modes, in turn produced by the dishomegeneity of the inter-particle elastic constants. This explanation is analitically shown to hold for 1-dimensional disordered chains and satisfatorily numerically tested in both 1 and 3 dimensions.Comment: 4 pages, RevTeX, 5 postscript figure

    Evidence of two viscous relaxation processes in the collective dynamics of liquid lithium

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    New inelastic X-ray scattering experiments have been performed on liquid lithium in a wide wavevector range. With respect to the previous measurements, the instrumental resolution, improved up to 1.5 meV, allows to accurately investigate the dynamical processes determining the observed shape of the the dynamic structure factor, S(Q,ω)S(Q,\omega). A detailed analysis of the lineshapes shows the co-existence of relaxation processes with both a slow and a fast characteristic timescales, and therefore that pictures of the relaxation mechanisms based on a simple viscoelastic model must be abandoned.Comment: 5 pages, 4 .PS figure

    Could Dietary Goals and Climate Change Mitigation Be Achieved Through Optimized Diet? The Experience of Modeling the National Food Consumption Data in Italy

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    Objective: The aim of this study is to define a healthy and sustainable diet model with low GHGE, fulfilling dietary requirements, and considering current Italian food consumption patterns. Design: A duly designed database was developed, linking food nutritional composition and GHGE based on 921 food items consumed in Italy according to the last national food consumption survey (INRAN-SCAI 2005–2006). Linear programming was used to develop new diet plans separately for males and females, aged 18–60 years (n = 2,098 subjects), in order to minimize GHGE. The program is based on dietary goals and acceptability constraints as well as on 13 nutrient requirement constraints aiming to reach a healthy and acceptable diet for the Italian population. Results: Diet optimization resulted in a nutritionally adequate pattern minimizing GHGE values (4.0 vs. 1.9 kg CO2e/day for males and 3.2 vs. 1.6 kg CO2e/day for females). In both sexes, the nutrient intake of the optimized diet was at the established lower bound for cholesterol and calcium and at the established upper bound for free sugar and fiber. In males, intake of zinc was at the established lower bound whereas iron was at the established upper bound. Consumption of red meat and fruit and vegetables was at the established lower and upper bound, respectively, in both males and females. Despite the decrease in meat consumption, especially red meat, in the optimized diet with respect to the observed diet, levels of iron intake in females increased by 10% (10.3 vs. 11.3 mg/day) but remained below the adequate intake established in Italian national DRIs. Conclusions: An attainable healthy dietary pattern was developed that would lead to the reduction of GHGE by 48% for males and by 50% for females with respect to current food consumption in the Italian adult population. Health-promoting dietary patterns can substantially contribute to achieve related Sustainable Development Goals

    Resistance to adverse conditions and characterization of Cladosporium species from marine and terrestrial Antarctic samples

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    Abstract Microbial adaptations to extreme environments can lead to biotechnological applications. This study aimed to evaluate the resistance of Antarctic Cladosporium to adverse conditions (temperature, salinity, UV radiation, and nutrients) and refine their taxonomy. Sequencing and phylogenetic analysis using ITS-act markers resulted in a more accurate taxonomic identification, revealing the presence of five different species, belonging to the complexes C. cladosporioides and C. sphaerospermum. The growth at different temperatures indicates that the soil isolates LAMAI 564 and 1800 (phylogenetically closely related) and LAMAI 2541 are psychrophilic, while the other isolates are psychrotolerant. The fungi isolated from the saline samples LAMAI 595, 616, and 1369 showed better growth results at higher salinity (15%). The fungi most resistant to UV radiation were isolated from terrestrial and marine samples (LAMAI 595, 616, 1800, and 564). LAMAI 595 and 616 (phylogenetically closely related and isolated from the same kind of sample) showed the capacity of nutritional versatility, growing well in both rich and poor-nutrient media. The fungus LAMAI 595 was the most promising for biotechnological application, exceeding the other isolates in the harsh conditions studied. The resistance of the Antarctic Cladosporium to adverse conditions opens new perspectives in the field of applied microbiology of extremophiles

    Crystal-like high frequency phonons in the amorphous phases of solid water

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    The high frequency dynamics of low- (LDA) and high-density amorphous-ice (HDA) and of cubic ice (I_c) has been measured by inelastic X-ray Scattering (IXS) in the 1-15 nm^{-1} momentum transfer (Q) range. Sharp phonon-like excitations are observed, and the longitudinal acoustic branch is identified up to Q = 8nm^{-1} in LDA and I_c and up to 5nm^{-1} in HDA. The narrow width of these excitations is in sharp contrast with the broad features observed in all amorphous systems studied so far. The "crystal-like" behavior of amorphous ices, therefore, implies a considerable reduction in the number of decay channels available to sound-like excitations which is assimilated to low local disorder.Comment: 4 pages, 3 figure

    A measles virus-based vaccine induces robust chikungunya virus-specific CD4<sup>+</sup> T-cell responses in a phase II clinical trial

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    Chikungunya virus (CHIKV) is an alphavirus transmitted by mosquitos that causes a debilitating disease characterized by fever and long-lasting polyarthralgia. To date, no vaccine has been licensed, but multiple vaccine candidates are under evaluation in clinical trials. One of these vaccines is based on a measles virus vector encoding for the CHIKV structural genes C, E3, E2, 6K, and E1 (MV-CHIK), which proved safe in phase I and II clinical trials and elicited CHIKV-specific antibody responses in adult measles seropositive vaccine recipients. Here, we predicted T-cell epitopes in the CHIKV structural genes and investigated whether MV-CHIK vaccination induced CHIKV-specific CD4+ and/or CD8+ T-cell responses. Immune-dominant regions containing multiple epitopes in silico predicted to bind to HLA class II molecules were found for four of the five structural proteins, while no such regions were predicted for HLA class I. Experimentally, CHIKV-specific CD4+ T-cells were detected in six out of twelve participants after a single MV-CHIK vaccination and more robust responses were found 4 weeks after two vaccinations (ten out of twelve participants). T-cells were mainly directed against the three large structural proteins C, E2 and E1. Next, we sorted and expanded CHIKV-specific T cell clones (TCC) and identified human CHIKV T-cell epitopes by deconvolution. Interestingly, eight out of nine CD4+ TCC recognized an epitope in accordance with the in silico prediction. CHIKV-specific CD8+ T-cells induced by MV-CHIK vaccination were inconsistently detected. Our data show that the MV-CHIK vector vaccine induced a functional transgene-specific CD4+ T cell response which, together with the evidence of neutralizing antibodies as correlate of protection for CHIKV, makes MV-CHIK a promising vaccine candidate in the prevention of chikungunya.</p

    Vibrational spectrum of topologically disordered systems

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    The topological nature of the disorder of glasses and supercooled liquids strongly affects their high-frequency dynamics. In order to understand its main features, we analytically studied a simple topologically disordered model, where the particles oscillate around randomly distributed centers, interacting through a generic pair potential. We present results of a resummation of the perturbative expansion in the inverse particle density for the dynamic structure factor and density of states. This gives accurate results for the range of densities found in real systems.Comment: Completely rewritten version, accepted in Physical Review Letter

    Instantaneous Normal Mode Analysis of Supercooled Water

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    We use the instantaneous normal mode approach to provide a description of the local curvature of the potential energy surface of a model for water. We focus on the region of the phase diagram in which the dynamics may be described by the mode-coupling theory. We find, surprisingly, that the diffusion constant depends mainly on the fraction of directions in configuration space connecting different local minima, supporting the conjecture that the dynamics are controlled by the geometric properties of configuration space. Furthermore, we find an unexpected relation between the number of basins accessed in equilibrium and the connectivity between them.Comment: 5 pages, 4 figure
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