3,119 research outputs found
Modeling of point defects annihilation in multilayered cu/nb composites under irradiation
This work focuses on a mathematical modeling of the response to irradiation of a multilayer composite material. Nonstationary balance equations are utilized to account for production, recombination, transport, and annihilation, or removal, of vacancies and interstitials at interfaces. Although the model developed has general validity, Cu/Nb multilayers are used as case study. Layer thickness, temperature, radiation intensity, and surface recombination coefficients were varied systematically to investigate their effect on point defect annihilation processes at interfaces. It is shown that point defect annihilation at interfaces mostly depends on point defect diffusion. The ability of interfaces to remove point defects can be described by a simple map constructed using only two dimensionless parameters, which provides a general tool to estimate the efficiency of vacancy and interstitial removal in multilayer composite materials
Self-healing ability assessment of irradiated multilayered composites: A continuum approach
Atomistic simulations have revealed an unconventional behavior of point defects at interfaces found in multilayer composites synthesized by physical vapor deposition but the observed mechanisms that involve point-defect annihilation are subject to time-scale limitations. So, a mathematical model that describes long-term evolution of point defects in such materials under irradiation is presented in this work. Firstly, the effect of interface point-defect trapping and recombination mechanisms on point-defect concentrations has been studied. In addition, the effect of interface self-interstitial atoms loading, which has been seen during collision cascades, and constitutional vacancies has been studied too. Two interface configurations have been considered between metals in a ÎČ-α-ÎČ three-layer system (αâŻ=âŻCu and ÎČâŻ=âŻNb, or V), KSmin and KS1. These interfaces correspond to ground-state and defect-free KS structures respectively. The respond to irradiation of the systems investigated here, Cu/Nb and Cu/V, depends on both, interface characteristics and bulk properties. Nonetheless, the influence of the properties of one metal in the point-defect evolution of the other metal is only effective if there are constitutional vacancies at the interface, i.e., for KSmin. Especial attention has been paid to the behavior of the same metal (Cu) when it is surrounded by diverse metals (Nb, or V) with the aim of comparing quantitatively our model predictions with experimental results reported elsewhere. The lower concentration of vacancies in Cu layer of Cu/Nb system at steady state is due to the low mobility of vacancies in niobium.European Social Fund, Operational Programme of Castilla y LeĂłn, and Junta de Castilla y LeĂłn, through the Ministry of Education, as well as by the European Union Framework Programme 7, Multiscale Modelling and Materials by Design of Interface-Controlled Radiation Damage in Crystalline Materials (RADINTERFACES) under grant agreement no. 26327
Can the development and autolysis of lactic acid bacteria influence the cheese volatile fraction? The case of Grana Padano
In this study, the relationship between the dynamics of the growth and lysis of lactic acid bacteria in Grana
Padano cheese and the formation of the volatile flavor compounds during cheese ripening was investigated.
The microbial dynamics of Grana Padano cheeses thatwere produced in two different dairies were followed during
ripening. The total and cultivable lactic microflora, community composition as determined by length heterogeneity-
PCR (LH-PCR), and extent of bacterial lysis using an intracellular enzymatic activity assaywere compared
among cheeses after 2, 6 and 13 months of ripening in two dairies.
The evolution of whole and lysed microbiota was different between the two dairies. In dairy 2, the number of
total cells was higher than that in dairy 1 in all samples, and the number of cells that lysed during ripening
was lower. In addition, at the beginning of ripening (2 months), the community structure of the cheese from
dairy 2 was more complex and was composed of starter lactic acid bacteria (Lactobacillus helveticus and Lactobacillus
delbrueckii) and NSLAB, possibly arising fromraw milk, including Lactobacillus rhamnosus/Lactobacillus casei
and Pediococcus acidilactici. On the other hand, the cheese from dairy 1 that ripened for 2 months was mainly
composed of the SLAB L. helveticus and L. delbrueckii. An evaluation of the free-DNA fraction through LH-PCR identified
those species that had a high degree of lysis. Data on the dynamics of bacterial growth and lysis were evaluated
with respect to the volatile profile and the organic acid content of the two cheeses after 13 months of
ripening, producing very different results. Cheese from dairy 1 showed a higher content of free fatty acids, particularly
those deriving from milk fat lipolysis, benzaldehyde and organic acids, such as pGlu and citric. In contrast,
cheese from dairy 2 had a greater amount of ketones, alcohols, hydrocarbons, acetic acid and propionic
acid. Based on these results, we can conclude that in the first cheese, the intracellular enzymes thatwere released
fromlysiswere mainly involved in aromaformation,whereas in the second cheese, the greater complexity of volatile
compounds may be associated with its more complex microbial composition caused from SLAB lysis and
NSLAB (mainly L. rhamnosus/L. casei) growth during ripening
Role of interface in multilayered composites under irradiation: A mathematical investigation
A continuum model of point-defects evolution during irradiation of a multilayer composite material is presented in this work. Nonstationary balance equations are used to describe production, recombination, transport, and annihilation, or removal, of vacancies and interstitials in a ÎČ-α-ÎČ three-layer system (α = Cu and ÎČ = Nb, V, or Ni). In addition, transport and trapping of point-defects at interfaces are taken into account. Numerical investigation on similarities and differences between Cu/Nb, Cu/V, and Cu/Ni systems is also performed. A general comparison of model results reveals that average vacancy concentration is typically higher than SIA one in both layers for all the systems investigated. This is a consequence of the higher diffusion rate of SIAs with respect to vacancies. Stationary state is reached without saturating interface point-defect traps by all systems but Cu/Ni for the case of SIAs. It can be also seen that Cu/Nb and Cu/V systems have a very similar behavior regarding point-defect temporal evolution in copper (layer α), while higher SIA concentration at steady state is shown therein by the Cu/Ni structure. Moreover, Cu/V system displays the lower stationary vacancy concentration in layer ÎČ.European Social Fund,
Operational Programme of Castilla y LeÂŽon, and Junta de
Castilla y LeÂŽon, through theMinistry of Education, as well as
by the EuropeanUnion Framework Programme 7,Multiscale
Modelling and Materials by Design of Interface-Controlled
Radiation Damage in Crystalline Materials (RADINTERFACES)
under Grant Agreement no. 26327
Forensic NMR metabolomics: one more arrow in the quiver
Introduction: NMR metabolomics is increasingly used in forensics, due to the possibility of investigating both endogenous metabolic profiles and exogenous molecules that may help to describe metabolic patterns and their modifications associated to specific conditions of forensic interest. Objectives: The aim of this work was to review the recent literature and depict the information provided by NMR metabolomics. Attention has been devoted to the identification of peculiar metabolic signatures and specific ante-mortem and post-mortem profiles or biomarkers related to different conditions of forensic concern, such as the identification of biological traces, the estimation of the time since death, and the exposure to drugs of abuse. Results and Conclusion: The results of the described studies highlight how forensics can benefit from NMR metabolomics by gaining additional information that may help to shed light in several forensic issues that still deserve to be further elucidated
Dense nanocrystalline W alloys: Enhancement of hardness and thermal stability by Al addition
Nanocrystalline W100-xAlx (x up to 20 at.%) powders obtained by mechanical alloying have been consolidated by spark plasma sintering (SPS). Alloying W with Al significantly improves the sinterability, allowing the fabrication of dense samples. The consolidation process keeps the nanocrystalline microstructure substantially unaffected, which contributes to the hardness of the final W-Al alloys. The room-temperature nano-and micro-hardness of dense W80Al20 alloy sintered at 1100 degrees C are as high as 18 and 14 GPa, respectively. These values are significantly higher than those previously reported for pure coarse-or submicron-grained W and may be ultimately ascribed to the grain boundary segregation of Al
Application of Recombined Milk to Produce Crescenza-Type Cheese in Laboratory-Scale Cheesemaking: Implications on Technology and Sensory Properties
Unexpected ovarian activity in premenopausal breast cancer survivors treated with exemestane and GnRH analogues
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New Constraints on the Future Evaporation of the Young Exoplanets in the V1298 Tau System
Transiting planets at young ages are key targets for improving our understanding of the evolution of exo-atmospheres. We present results of a new X-ray observation of V 1298 Tau with XMM-Newton, aimed to determine more accurately the high-energy irradiation of the four planets orbiting this pre-main-sequence star, and the possible variability due to magnetic activity on short and long timescales. Following the first measurements of planetary masses in the V 1298 Tau system, we revise early guesses of the current escape rates from the planetary atmospheres, employing our updated atmospheric evaporation models to predict the future evolution of the system. Contrary to previous expectations, we find that the two outer Jupiter-sized planets will not be affected by any evaporation on Gyr timescales, and the same occurs for the two smaller inner planets, unless their true masses are lower than ~40 Me. These results confirm that relatively massive planets can reach their final position in the mass-radius diagram very early in their evolutionary history
Endocrineâbased treatments in clinicallyârelevant subgroups of hormone receptorâpositive/HER2ânegative metastatic breast cancer: systematic review and metaâanalysis
A precise assessment of the efficacy of firstâ/secondâline endocrine therapies (ET) ± target therapies (TT) in clinicallyârelevant subgroups of hormone receptorâpositive (HR+)/HER2ânegative metastatic breast cancer (MBC) has not yet been conducted. To improve our current knowledge and support clinical decisionâmaking, we thus conducted a systematic literature search to identify all firstâ/secondâline phase II/III randomized clinical trials (RCT) of currently approved or most promising ET ± TT. Then, we performed a metaâanalysis to assess progressionâfree (PFS) and/or overall survival (OS) benefit in several clinicallyârelevant prespecified subgroups. Thirtyâfive RCT
were included (17,595 patients). Pooled results show significant reductions in the risk of relapse or death of 26â41% and 12â27%, respectively, depending on the clinical subgroup. Combination strategies proved to be more effective than singleâagent ET (PFS hazard ratio (HR) range for combinations: 0.60â0.65 vs. HR range for single agent ET: 0.59â1.37; OS HR range for combinations: 0.74â0.87 vs. HR range for single agent ET: 0.68â0.98), with CDK4/6âinhibitors(i) + ET being the most effective regimen. Single agent ET showed comparable efficacy with ET+TT combinations in nonvisceral (p = 0.63) and endocrine sensitive disease (p = 0.79), while mTORiâbased combinations
proved to be a valid therapeutic option in endocrineâresistant tumors, as well as PI3Ki + ET in PIK3CAâmutant tumors. These results strengthen international treatment guidelines and can aid therapeutic decisionâmaking
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