1,041 research outputs found
Ab initio GW many-body effects in graphene
We present an {\it ab initio} many-body GW calculation of the self-energy,
the quasiparticle band plot and the spectral functions in free-standing undoped
graphene. With respect to other approaches, we numerically take into account
the full ionic and electronic structure of real graphene and we introduce
electron-electron interaction and correlation effects from first principles.
Both non-hermitian and also dynamical components of the self-energy are fully
taken into account. With respect to DFT-LDA, the Fermi velocity is
substantially renormalized and raised by a 17%, in better agreement with
magnetotransport experiments. Furthermore, close to the Dirac point the linear
dispersion is modified by the presence of a kink, as observed in ARPES
experiments. Our calculations show that the kink is due to low-energy single-particle excitations and to the plasmon. Finally, the GW
self-energy does not open the band gap.Comment: 5 pages, 4 figures, 1 tabl
Synthetic cathinones related fatalities: an update
Synthetic cathinones, more commonly known as "bath salts", are synthetic drugs chemically related to cathinone, a psychostimulant found in the khat plant. They are the first most consumed products among new psychoactive substances, which cause psychostimulant and hallucinogenic effects determining a number of fatalities worldwide. In this paper, we have systematically reviewed cases of synthetic cathinones-related fatalities analytically confirmed, which have occurred in the last few years.OBJECTIVE: Synthetic cathinones,
more commonly known as “bath salts”, are synthetic
drugs chemically related to cathinone, a
psychostimulant found in the khat plant. They are
the first most consumed products among new
psychoactive substances, which cause psychostimulant
and hallucinogenic effects determining
a number of fatalities worldwide. In this paper, we
have systematically reviewed cases of synthetic
cathinones-related fatalities analytically confirmed,
which have occurred in the last few years.
MATERIALS AND METHODS: Relevant scientific
articles were identified in Medline, Cochrane
Central, Scopus, Web of Science and Institutional/
government websites up to November 2017
using the following keywords: synthetic cathinones,
mephedrone, methylenedioxypyrovalerone,
MDPV, methylone, ethylone, buthylone, fatal
intoxication, fatalities and death.
RESULTS: In total, 20 citations met the criteria
for inclusion, representing several fatal cases
with analytically confirmed synthetic cathinones
in biological sample/s of the deceased. The
death was attributed to hyperthermia, hypertension,
cardiac arrest and more in general to the
classic serotonin syndrome. Only rarely did the
concentration of the parent drug causing fatality
overcome the value of 1 mg/L in post-mortem
biological fluids.
CONCLUSIONS: Abuse of synthetic cathinones
still represents a serious public health issue.
Systematic clinical studies on both the animal
and human model are lacking; therefore, the
only available data are from the users who experience
the possible hazardous consequences.
Analytical methodologies for the identification
of parent compounds and eventual metabolites
both in ante-mortem and post-mortem cases
need to be developed and validated. Analytical
data should be shared through different communication
platforms with the aim of stopping this
serious health threat for drug users
Suitability of miRNA assessment in postmortem interval estimation
OBJECTIVE: The aim of this review was to explore recent pieces of evidence focused on the use of miRNAs for PMI estimation both in humans and animal experiments, with particular interest on the best miRNAs to use as reference/target markers in different tissues or biological fluids. MiRNAs are innovative biomarkers used in clinical and research field: they appear very attractive, being introduced in forensic research scenarios even for PMI estimation.MATERIALS AND METHODS: Data from PubMed and Scopus were analyzed from January 2013 to August 2020. Based on inclusion/exclusion criteria, high-quality articles have been selected to become the subject of this review.RESULTS: A total of 737 papers were found but, after titles/abstracts screening for inclusion criteria and a full-text careful selection, 33 papers were deeply studied. After the exclusion of 19 papers, 15 articles remained. Eight papers dealt with animals (mice/rats), two both with animals and humans (for method validation previously built), while 5 exclusively with humans. Myocardium (6/15) and brain (6/15) were the most studied tissues. respectively in mice/rats and humans. PMI considered was up to 7.5 days in mouse studies and less than 3 days in human models.CONCLUSIONS: Because of their significant stability in both early and long PMI, miRNAs are the cleverest reference markers to be used. Temperature and environmental conditions influence mostly mRNA, while miRNAs are less susceptible to them. The best miRNA to choose depends on its tissue specificity, i.e., miR-9 and miR-125 in brain or miR-1 and miR-133 in skeletal muscle/heart
Spectroscopic and microscopic analyses of Fe3O4/au nanoparticles obtained by laser ablation in water
Magneto-plasmonic nanoparticles constituted of gold and iron oxide were obtained in an aqueous environment by laser ablation of iron and gold targets in two successive steps. Gold nanoparticles are embedded in a mucilaginous matrix of iron oxide, which was identified as magnetite by both microscopic and spectroscopic analyses. The plasmonic properties of the obtained colloids, as well as their adsorption capability, were tested by surface-enhanced Raman scattering (SERS) spectroscopy using 2,2′-bipyridine as a probe molecule. DFT calculations allowed for obtaining information on the adsorption of the ligand molecules that strongly interact with positively charged surface active sites of the gold nanoparticles, thus providing efficient SERS enhancement. The presence of iron oxide gives the bimetallic colloid new possibilities of adsorption in addition to those inherent to gold nanoparticles, especially regarding organic pollutants and heavy metals, allowing to remove them from the aqueous environment by applying a magnetic field. Moreover, these nanoparticles, thanks to their low toxicity, are potentially useful not only in the field of sensors, but also for biomedical applications
Weathering Effects on Engineering Geological Properties of Trachydacitic Volcanic Rocks from the Monte Amiata (Southern Tuscany, Italy)
Variability in lithology and weathering degree affects physical and mechanical properties
of rocks. In this study, we investigated the relationships between weathering degree and engineering
geological properties of trachydacitic volcanic rocks from Monte Amiata (central Italy) by coupling
field and laboratory analyses. We collected in situ Schmidt hammer tests in the field. We evaluated
weathering quantifying the percentage of secondary minerals through thermal analysis in the
laboratory. We also determined dry density (rd), specific gravity of solids (Gs), porosity (n) and
two-dimensional (2D) porosity as resulted from scanning electron microscopy investigations. The
results of our study indicate a negative linear correlation between Schmidt hammer rebound values
and secondary mineral percentage. This correlation provides a tool to quantitatively estimate the
deterioration of rock uniaxial compressive strength (UCS) as weathering increases. Moreover, thermal
analysis turned out to be a quantitative and reproducible method to evaluate weathering degree of
magmatic rocks
Structural validation of a realistic wing structure: the RIBES test article
Several experimental test cases are available in literature to study and validate fluid structure interaction methods. They, however,
focus the attention mainly on replicating typical cruising aerodynamic conditions forcing the adoption of fully steel made models
able to operate with the high loads generated in high speed facilities. This translates in a complete loss of similitude with typical
realistic aeronautical wing structures configurations. To reverse this trend, and to better study the aerolastic mechanism from a structural point of view, an aeroelastic measurement campaign was carried within the EU RIBES project. A half wing model for wind tunnel tests was designed and manufactured replicating a typical metallic wing box structure, producing a database of loads, pressure, stress and deformation measurements. In this paper the design, manufacturing and validation activities performed within the RIBES project are described, with a focus on the structural behavior of the test article. All experimental data and numerical models are made freely available to the scientific community
Localization Capability of Cooperative Anti-Intruder Radar Systems
System aspects of an anti-intruder multistatic radar based on impulse radio ultrawideband (UWB) technology are addressed. The investigated system is composed of one transmitting node and at least three receiving nodes, positioned in the surveillance area with the aim of detecting and locating a human intruder (target) that moves inside the area. Such systems, referred to also as UWB radar sensor networks, must satisfy severe power constraints worldwide imposed by, for example, the Federal Communications Commission (FCC) and by the European Commission (EC) power spectral density masks. A single transmitter-receiver pair (bistatic radar) is considered at first. Given the available transmitted power and the capability of the receiving node to resolve the UWB pulses in the time domain, the surveillance area regions where the target is detectable, and those where it is not, are obtained. Moreover, the range estimation error for the transmitter-receiver pair is discussed. By employing this analysis, a multistatic system is then considered, composed of one transmitter and three or four cooperating receivers. For this multistatic system, the impact of the nodes location on area coverage, necessary transmitted power and localization uncertainty is studied, assuming a circular surveillance area. It is highlighted how area coverage and transmitted power, on one side, and localization uncertainty, on the other side, require opposite criteria of nodes placement. Consequently, the need for a system compromising between these factors is shown. Finally, a simple and effective criterion for placing the transmitter and the receivers is drawn
Two coupled feedback loops explain random mono-allelic Xist upregulation at the onset of X-chromosome inactivation
In female mammal s, dosage compensation for X-linked genes is ensured through random X-chromosome inactivation, which is initiated by mono-allelic up-regulation of Xist . We use mathematical modeling to identify the regulatory principles required to establish the mono-allelic and female-specific Xist expression pattern and test model predictions experimentally. A cis -acting positive feedback, which in mice is mediated by mutual repression of Xist and its antisense transcript Tsix , together with a trans -acting negative feedba ck are sufficient to explain mono-allelic Xist up-regulation. The model can reproduce data from several mutant, aneuploid and polyploid murine cell lines and explain s Xist expression patterns in other mammalian species. Furthermore, it predicts that transient , reversible bi-allelic Xist expression is not restricted to rabbits and humans but can also occur in mice, which we indeed confirm to occur in mouse embryos. Overall, our study provides a conceptual framework of the molecular mechanisms required to initiate random X-chromosome inactivation
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