382 research outputs found
Weak antilocalization and disorder-enhanced electron interactions in crystalline GeSbTe
Phase change materials can be reversibly switched between amorphous and
crystalline states and often show strong contrast in the optical and electrical
properties of these two phases. They are now in widespread use for optical data
storage, and their fast switching and a pronounced change of resistivity upon
crystallization are also very attractive for nonvolatile electronic data
storage. Nevertheless there are still several open questions regarding the
electronic states and charge transport in these compounds. In this work we
study electrical transport in thin metallic films of the disordered,
crystalline phase change material GeSbTe. We observe weak
antilocalization and disorder enhanced Coulomb interaction effects at low
temperatures, and separate the contributions of these two phenomena to the
temperature dependence of the resistivity, Hall effect, and magnetoresistance.
Strong spin-orbit scattering causes positive magnetoresistance at all
temperatures, and a careful analysis of the low-field magnetoresistance allows
us to extract the temperature dependent electron dephasing rate and study other
scattering phenomena. We find electron dephasing due to inelastic
electron-phonon scattering at higher temperatures, electron-electron scattering
dephasing at intermediate temperatures, and a crossover to weak temperature
dependence below 1 K
Cadmium influences the 5-fluorouracil cytotoxic effects on breast cancer cells
The aim of the research was to evaluate a heavy metal, cadmium (Cd), which was used to produce alterations in human breast cancer cell line MCF-7. Moreover, we analyzed both immunohistochemical and ultrastructural alterations induced by the antineoplastic drug, 5-fluorouracil (5-FU), after exposure to different concentrations of cd. Also, we compared the effects of these compounds on actin and tubulin cytoskeleton proteins. Under ultramicroscopic observation, control cells looked polymorphous with filopodia. In cells already treated with small concentrations of Cd, after brief times of incubation, we observed an intense metabolic activity with larger, clearer, and elongated mitochondria characterized by thin and numerous dilated cristae. 5-FU-treated cells showed cytotoxicity signs with presence of pore-like alterations in the cell membrane and evident degeneration of cytoplasm and cell nuclei. The addition of 5-FU (1.5 µM) to the cells treated with Cd (5 µM–20 µM) did not induce significant ultrastructural changes in comparison with cells treated only with Cd. In Cd+5FU-treated cells mitochondria with globular aspect and regular cristae indicated the active metabolic state. In cells treated only with Cd we observed alterations in actin distribution, while tubulin branched out throughout the cytoplasm. With the association of Cd+5FU, we observed less morphological alterations in both tubulin and actin cytoskeleton proteins. Although the mechanism remains unknown at present, our findings suggest that Cd prevents the cytotoxic effect of 5-FU on breast cancer cells. These preliminary results could have an important clinical application in patients with breast cancer
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Erratum to "Camillo Golgi and modern neuroscience" [Brain Res. Rev. 66/1-2 (2011) 1-4]
PIN92 Quality of Life Among Hiv Patients: Results from the Ianua Clinical Trial
OBJECTIVES To understand the relationship between socio-demographic variables, clinical factors, highly active anti-retroviral therapy (HAART) and health related quality of life (QoL) in HIV-infected individuals participants in the IANUA multicenter study.
METHODS Data relating to patients with HIV infection admitted to 3 infectious disease units in Genoa (Italy) between 2012 and 2014 are collected and analyzed. Univariate and multivariate association of demographic and clinical factors with QoL (computed using EQ-5D-3L) are examined. QoL determinants are assessed using a tobit model, while a logistic model is implemented in order to investigate the relation between specific patients characteristics and the likelihood of having higher QoL.
RESULTS Results of the empirical modeling suggest that being Italian and having a job are positively associate with QoL, whereas being a female, taking other drugs in addition to anti-retroviral drugs and being subsidisied are negatively related to QoL. Among clinical factors, CD4 cell count level cannot be considered as significant predictor of QoL, while higher QoL seem to be defined by single tablet regimens.
CONCLUSION The study investigates the major determinants of QoL among HIV patients and the results provide some informative tools useful to improve strategies aiming at maximizing QoL. As monitoring of QoL is nowadays a priority for clinicians, further work will be based on \u201cdynamic\u201d analysis comparing QoL at the initial time and QoL at 6-months follow up
Discovering electron transfer driven changes in chemical bonding in lead chalcogenides (PbX, where X = Te, Se, S, O)
Understanding the nature of chemical bonding in solids is crucial to
comprehend the physical and chemical properties of a given compound. To explore
changes in chemical bonding in lead chalcogenides (PbX, where X = Te, Se, S,
O), a combination of property-, bond breaking- and quantum-mechanical bonding
descriptors have been applied. The outcome of our explorations reveals an
electron transfer driven transition from metavalent bonding in PbX (X = Te, Se,
S) to iono-covalent bonding in beta-PbO. Metavalent bonding is characterized by
adjacent atoms being held together by sharing about a single electron and small
electron transfer (ET). The transition from metavalent to iono-covalent bonding
manifests itself in clear changes in these quantum-mechanical descriptors (ES
and ET), as well as in property-based descriptors (i.e. Born effective charge,
dielectric function, effective coordination number (ECON) and mode-specific
Grueneisen parameter, and in bond breaking descriptors (PME). Metavalent
bonding collapses, if significant charge localization occurs at the ion cores
(ET) and/or in the interatomic region (ES). Predominantly changing the degree
of electron transfer opens possibilities to tailor materials properties such as
the chemical bond and electronic polarizability, optical band gap and optical
interband transitions characterized by the imaginary part of the dielectric
function. Hence, the insights gained from this study highlight the
technological relevance of the concept of metavalent bonding and its potential
for materials design
Kondo Conductance in an Atomic Nanocontact from First Principles
The electrical conductance of atomic metal contacts represents a powerful
tool to detect nanomagnetism. Conductance reflects magnetism through anomalies
at zero bias -- generally with Fano lineshapes -- due to the Kondo screening of
the magnetic impurity bridging the contact. A full atomic-level understanding
of this nutshell many-body system is of the greatest importance, especially in
view of our increasing need to control nanocurrents by means of magnetism.
Disappointingly, zero bias conductance anomalies are not presently calculable
from atomistic scratch. In this Letter we demonstrate a working route
connecting approximately but quantitatively density functional theory (DFT) and
numerical renormalization group (NRG) approaches and leading to a
first-principles conductance calculation for a nanocontact, exemplified by a Ni
impurity in a Au nanowire. A Fano-like conductance lineshape is obtained
microscopically, and shown to be controlled by the impurity s-level position.
We also find a relationship between conductance anomaly and geometry, and
uncover the possibility of opposite antiferromagnetic and ferromagnetic Kondo
screening -- the latter exhibiting a totally different and unexplored zero bias
anomaly. The present matching method between DFT and NRG should permit the
quantitative understanding and exploration of this larger variety of Kondo
phenomena at more general magnetic nanocontacts.Comment: 11 pages, 3 figures. Supplementary materials under request at
[email protected]
IGLV3-21∗01 is an inherited risk factor for CLL through the acquisition of a single-point mutation enabling autonomous BCR signaling
© 2020 National Academy of Sciences. All rights reserved. The prognosis of chronic lymphocytic leukemia (CLL) depends on different markers, including cytogenetic aberrations, oncogenic mutations, and mutational status of the immunoglobulin (Ig) heavy-chain variable (IGHV) gene. The number of IGHV mutations distinguishes mutated (M) CLL with a markedly superior prognosis from unmutated (UM) CLL cases. In addition, B cell antigen receptor (BCR) stereotypes as defined by IGHV usage and complementaritydetermining regions (CDRs) classify ∼30% of CLL cases into prognostically important subsets. Subset 2 expresses a BCR with the combination of IGHV3-21-derived heavy chains (HCs) with IGLV3- 21-derived light chains (LCs), and is associated with an unfavorable prognosis. Importantly, the subset 2 LC carries a single-point mutation, termed R110, at the junction between the variable and constant LC regions. By analyzing 4 independent clinical cohorts through BCR sequencing and by immunophenotyping with antibodies specifically recognizing wild-type IGLV3-21 and R110-mutated IGLV3-21 (IGLV3-21R110), we show that IGLV3-21R110-expressing CLL represents a distinct subset with poor prognosis independent of IGHV mutations. Compared with other alleles, only IGLV3-21∗01 facilitates effective homotypic BCR-BCR interaction that results in autonomous, oncogenic BCR signaling after acquiring R110 as a single-point mutation. Presumably, this mutation acts as a standalone driver that transforms IGLV3-21∗01-expressing B cells to develop CLL. Thus, we propose to expand the conventional definition of CLL subset 2 to subset 2L by including all IGLV3-21R110-expressing CLL cases regardless of IGHV mutational status. Moreover, the generation ofmonoclonal antibodies recognizing IGLV3-21 or mutated IGLV3-21R110 facilitates the recognition of B cells carrying this mutation in CLL patients or healthy donors
Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
Quantum ESPRESSO is an integrated suite of computer codes for
electronic-structure calculations and materials modeling, based on
density-functional theory, plane waves, and pseudopotentials (norm-conserving,
ultrasoft, and projector-augmented wave). Quantum ESPRESSO stands for "opEn
Source Package for Research in Electronic Structure, Simulation, and
Optimization". It is freely available to researchers around the world under the
terms of the GNU General Public License. Quantum ESPRESSO builds upon
newly-restructured electronic-structure codes that have been developed and
tested by some of the original authors of novel electronic-structure algorithms
and applied in the last twenty years by some of the leading materials modeling
groups worldwide. Innovation and efficiency are still its main focus, with
special attention paid to massively-parallel architectures, and a great effort
being devoted to user friendliness. Quantum ESPRESSO is evolving towards a
distribution of independent and inter-operable codes in the spirit of an
open-source project, where researchers active in the field of
electronic-structure calculations are encouraged to participate in the project
by contributing their own codes or by implementing their own ideas into
existing codes.Comment: 36 pages, 5 figures, resubmitted to J.Phys.: Condens. Matte
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