Electron transport through multilevel quantum dot

Quantum transport properties through some multilevel quantum dots sandwiched between two metallic contacts are investigated by the use of Green's function technique. Here we do parametric calculations, based on the tight-binding model, to study the transport properties through such bridge systems. The electron transport properties are significantly influenced by (a) number of quantized energy levels in the dots, (b) dot-to-electrode coupling strength, (c) location of the equilibrium Fermi energy $E_F$ and (d) surface disorder. In the limit of weak-coupling, the conductance ($g$) shows sharp resonant peaks associated with the quantized energy levels in the dots, while, they get substantial broadening in the strong-coupling limit. The behavior of the electron transfer through these systems becomes much more clearly visible from our study of current-voltage ($I$-$V$) characteristics. In this context we also describe the noise power of current fluctuations ($S$) and determine the Fano factor ($F$) which provides an important information about the electron correlation among the charge carriers. Finally, we explore a novel transport phenomenon by studying the surface disorder effect in which the current amplitude increases with the increase of the surface disorder strength in the strong disorder regime, while, the amplitude decreases in the limit of weak disorder. Such an anomalous behavior is completely opposite to that of bulk disordered system where the current amplitude always decreases with the disorder strength. It is also observed that the current amplitude strongly depends on the system size which reveals the finite quantum size effect.Comment: 12 pages, 7 figure

Design and stability study of a paediatric oral solution of methotrexate 2mg/ml

Oral paediatric forms development by pharmaceutical industry is still insufficient. The present study was performed to propose an adapted and pleasant formulation of liquid oral formulation of MTX. The solution is composed of injectable methotrexate, water, Ora Sweet(®) and sodium bicarbonate. After 120 days storage, pH remained stable at about 8 in all formulations, insuring no risk of MTX precipitation. MTX content in solution formulation, determined by high performance liquid chromatography measurements, remained in the specifications of >90% of the initial concentration when stored at 4 and 25°C. Forced degradation of MTX by heat and acidic conditions allowed formation and detection of degradation products by the analytical method. Microbial study of the preparation shows that the solution remains in the specifications during all the storage, or after one sample each week during one month, eventually indicating the microbial properties are not affected by patient use. To conclude, we here propose a new MTX liquid formulation stable for at least 120 days

Low temperature heat capacity of Fe_{1-x}Ga_{x} alloys with large magneostriction

The low temperature heat capacity C_{p} of Fe_{1-x}Ga_{x} alloys with large magnetostriction has been investigated. The data were analyzed in the standard way using electron ($\gamma T$) and phonon ($\beta T^{3}$) contributions. The Debye temperature $\Theta_{D}$ decreases approximately linearly with increasing Ga concentration, consistent with previous resonant ultrasound measurements and measured phonon dispersion curves. Calculations of $\Theta_{D}$ from lattice dynamical models and from measured elastic constants C_{11}, C_{12} and C_{44} are in agreement with the measured data. The linear coefficient of electronic specific heat $\gamma$ remains relatively constant as the Ga concentration increases, despite the fact that the magnetoelastic coupling increases. Band structure calculations show that this is due to the compensation of majority and minority spin states at the Fermi level.Comment: 14 pages, 6 figure

Early Hospital Discharge of Older Adults Admitted to the Emergency Department: Effect of Different Types of Recommendations Made by a Mobile Geriatric Team

International audienc

The cosmic microwave background radiation temperature at z = 3.025 toward QSO 0347--3819

From the analysis of the CII fine-structure population ratio in the damped Ly_alpha system at z = 3.025 toward the quasar Q0347--3819 we derive an upper bound of 14.6 (+/- 0.2) K on the cosmic microwave background temperature regardless the presence of other different excitation mechanisms. The analysis of the ground state rotational level populations of H_2 detected in the system reveals a Galactic-type UV radiation field ruling out UV pumping as an important excitation mechanism for CII. The low dust content estimated from the Cr/Zn ratio indicates that the IR dust emission can also be neglected. When the collisional excitation is considered, we measure a temperature for the cosmic background radiation of T = 12.1 (+1.7, -3.2) K. The results are in agreement with the T = 10.968 (+/-) 0.004 K predicted by the hot Big Bang cosmology at z = 3.025.Comment: Accepte

The Conserved nhaAR Operon Is Drastically Divergent between B2 and Non-B2 Escherichia coli and Is Involved in Extra-Intestinal Virulence

The Escherichia coli species is divided in phylogenetic groups that differ in their virulence and commensal distribution. Strains belonging to the B2 group are involved in extra-intestinal pathologies but also appear to be more prevalent as commensals among human occidental populations. To investigate the genetic specificities of B2 sub-group, we used 128 sequenced genomes and identified genes of the core genome that showed marked difference between B2 and non-B2 genomes. We focused on the gene and its surrounding region with the strongest divergence between B2 and non-B2, the antiporter gene nhaA. This gene is part of the nhaAR operon, which is in the core genome but flanked by mobile regions, and is involved in growth at high pH and high sodium concentrations. Consistently, we found that a panel of non-B2 strains grew faster than B2 at high pH and high sodium concentrations. However, we could not identify differences in expression of the nhaAR operon using fluorescence reporter plasmids. Furthermore, the operon deletion had no differential impact between B2 and non-B2 strains, and did not result in a fitness modification in a murine model of gut colonization. Nevertheless, sequence analysis and experiments in a murine model of septicemia revealed that recombination in nhaA among B2 strains was observed in strains with low virulence. Finally, nhaA and nhaAR operon deletions drastically decreased virulence in one B2 strain. This effect of nhaAR deletion appeared to be stronger than deletion of all pathogenicity islands. Thus, a population genetic approach allowed us to identify an operon in the core genome without strong effect in commensalism but with an important role in extra-intestinal virulence, a landmark of the B2 strains

Association of Depressive Symptoms with Recurrent Falls: A Cross-Sectional Elderly Population Based Study and a Systematic Review

Background: Screening of depressive symptoms is recommended in recurrent fallers. Compared to the 30-item and 15-item Geriatric Depression Scales (GDS), the 4-item GDS is easier to administer and quicker to perform. The association between abnormal 4-item GDS score and recurrent falls has not yet been examined. In addition, while depressive symptoms-related gait instability is well known, the association with recurrent falls has been few studied. Objective: 1) To examine the association between abnormal 4-item GDS score and recurrent falls in community-dwelling older adults using original data from health examination centers (HEC) of French health insurance of Lyon, and 2) to perform a systematic review of studies that examined the association of depressive symptoms with recurrent falls among older adults. Methods: Firstly, based on a cross-sectional design, 2,594 community-dwellers (mean age 72.1 +/- 5.4years; 49.8% women) were recruited in HEC of Lyon, France. The 4-item GDS score (abnormal if score >= 1) and recurrent falls (i.e., 2 or more falls in the past year) were used as main outcomes. Secondly, a systematic English and French Medline literature search was conducted on May 28, 2012 with no limit of date using the following Medical Subject Heading (MeSH) terms "Aged OR aged, 80 and over", "Accidental falls", "Depressive disorder" and "Reccurence". The search also included the reference lists of the retrieved articles. Results: A total of 19.0% (n=494) participants were recurrent fillers in the cross-sectional study. Abnormal 4-item GDS score was more prevalent among recurrent fallers compared to non-recurrent fallers (44.7% versus 25.0%, with P<0.001), and was significantly associated with recurrent falls (Odd ratio (OR)=1.82 with P<0.001 for full model; OR=1.86 with P<0.001 for stepwise backward model). In addition to the current study, the systematic review found only four other studies on this topic, three of them examining the association of depressive symptoms with recurrent falls using 30-item or 15-item GDS. All studies showed a significant association of depressive symptoms with recurrent falls. Conclusions: The current cross-sectional study shows an association between abnormal 4-item GDS score and recurrent falls. This association of depressive symptoms with recurrent falls was confirmed by the systematic review. Based on these results, we suggest that recurrent falls risk assessment should involve a systematic screening of depressive symptoms using the 4-item GDS

Mobile Geriatric Team Advice: Effect on Length of Hospital Stay in Older Adults

International audienc