Model of single-electron decay from a strongly isolated quantum dot

Recent measurements of electron escape from a nonequilibrium charged quantum dot are interpreted within a two-dimensional (2D) separable model. The confining potential is derived from 3D self-consistent Poisson-Thomas-Fermi calculations. It is found that the sequence of decay lifetimes provides a sensitive test of the confining potential and its dependence on electron occupation

Theoretical study of elastic electron scattering off stable and exotic nuclei

Results for elastic electron scattering by nuclei, calculated with charge densities of Skyrme forces and covariant effective Lagrangians that accurately describe nuclear ground states, are compared against experiment in stable isotopes. Dirac partial-wave calculations are performed with an adapted version of the ELSEPA package. Motivated by the fact that studies of electron scattering off exotic nuclei are intended in future facilities in the commissioned GSI and RIKEN upgrades, we survey the theoretical predictions from neutron-deficient to neutron-rich isotopes in the tin and calcium isotopic chains. The charge densities of a covariant interaction that describes the low-energy electromagnetic structure of the nucleon within the Lagrangian of the theory are used to this end. The study is restricted to medium- and heavy-mass nuclei because the charge densities are computed in mean-field approach. Because the experimental analysis of scattering data commonly involves parameterized charge densities, as a surrogate exercise for the yet unexplored exotic nuclei, we fit our calculated mean-field densities with Helm model distributions. This procedure turns out to be helpful to study the neutron-number variation of the scattering observables and allows us to identify correlations of potential interest among some of these observables within the isotopic chains.

On the determination of the interface density of states in a-Si:H/a-SiC:H multilayers

This paper deals with the determination of the interface density of states in amorphous silicon-based multilayers. Photothermal deflection spectroscopy is used to characterize two series of aSi:H/aSi1-xCx:H multilayers, and a new approach in the treatment of experimental dada is used in order to obtain accurate results. From this approach, an upper limit of 10^10 cm-2 is determined for the interface density of states.

Rigorous characterization of oxygen vacancies in ionic oxides

Charged and neutral oxygen vacancies in the bulk and on perfect and defective surfaces of MgO are characterized as quantum-mechanical subsystems chemically bonded to the host lattice and containing most of the charge left by the removed oxygens. Attractors of the electron density appear inside the vacancy, a necessary condition for the existence of a subsystem according to the atoms in molecules theory. The analysis of the electron localization function also shows attractors at the vacancy sites, which are associated to a localization basin shared with the valence domain of the nearest oxygens. This polyatomic superanion exhibits chemical trends guided by the formal charge and the coordination of the vacancy. The topological approach is shown to be essential to understand and predict the nature and chemical reactivity of these objects. There is not a vacancy but a coreless pseudoanion that behaves as an activated host oxygen.

Valganciclovir in adult solid organ transplant recipients: pharmacokinetic and pharmacodynamic characteristics and clinical interpretation of plasma concentration measurements.

Valganciclovir and ganciclovir are widely used for the prevention of cytomegalovirus (CMV) infection in solid organ transplant recipients, with a major impact on patients' morbidity and mortality. Oral valganciclovir, the ester prodrug of ganciclovir, has been developed to enhance the oral bioavailability of ganciclovir. It crosses the gastrointestinal barrier through peptide transporters and is then hydrolysed into ganciclovir. This review aims to describe the current knowledge of the pharmacokinetic and pharmacodynamic characteristics of this agent, and to address the issue of therapeutic drug monitoring. Based on currently available literature, ganciclovir pharmacokinetics in adult solid organ transplant recipients receiving oral valganciclovir are characterized by bioavailability of 66 +/- 10% (mean +/- SD), a maximum plasma concentration of 3.1 +/- 0.8 mg/L after a dose of 450 mg and of 6.6 +/- 1.9 mg/L after a dose of 900 mg, a time to reach the maximum plasma concentration of 3.0 +/- 1.0 hours, area under the plasma concentration-time curve values of 29.1 +/- 5.3 mg.h/L and 51.9 +/- 18.3 mg.h/L (after 450 mg and 900 mg, respectively), apparent clearance of 12.4 +/- 3.8 L/h, an elimination half-life of 5.3 +/- 1.5 hours and an apparent terminal volume of distribution of 101 +/- 36 L. The apparent clearance is highly correlated with renal function, hence the dosage needs to be adjusted in proportion to the glomerular filtration rate. Unexplained interpatient variability is limited (18% in apparent clearance and 28% in the apparent central volume of distribution). There is no indication of erratic or limited absorption in given subgroups of patients; however, this may be of concern in patients with severe malabsorption. The in vitro pharmacodynamics of ganciclovir reveal a mean concentration producing 50% inhibition (IC(50)) among CMV clinical strains of 0.7 mg/L (range 0.2-1.9 mg/L). Systemic exposure of ganciclovir appears to be moderately correlated with clinical antiviral activity and haematotoxicity during CMV prophylaxis in high-risk transplant recipients. Low ganciclovir plasma concentrations have been associated with treatment failure and high concentrations with haematotoxicity and neurotoxicity, but no formal therapeutic or toxic ranges have been validated. The pharmacokinetic parameters of ganciclovir after valganciclovir administration (bioavailability, apparent clearance and volume of distribution) are fairly predictable in adult transplant patients, with little interpatient variability beyond the effect of renal function and bodyweight. Thus ganciclovir exposure can probably be controlled with sufficient accuracy by thorough valganciclovir dosage adjustment according to patient characteristics. In addition, the therapeutic margin of ganciclovir is loosely defined. The usefulness of systematic therapeutic drug monitoring in adult transplant patients therefore appears questionable; however, studies are still needed to extend knowledge to particular subgroups of patients or dosage regimens.

Advanced applications of scanning electron microscopy in geology

Nowadays Scanning Electron Microscopy (SEM) is a basic and fundamental tool in the study of geologic samples. The collision of a highlyaccelerated electron beam with the atoms of a solid sample results in theproduction of several radiation types than can be detected and analysed byspecific detectors, providing information of the chemistry and crystallography ofthe studied material. From this point of view, the chamber of a SEM can beconsidered as a laboratory where different experiments can be carried out. Theapplication of SEM to geology, especially in the fields of mineralogy andpetrology has been summarised by Reed (1996).The aim of this paper is to showsome recent applications in the characterization of geologic materials.

Biomedical and biological applications of scanning electron microscopy

This article summarizes the basic principles of scanning electron microscopy and the capabilities of the technique with different examples ofapplications in biomedical and biological research.

New diagnoses of dementia among older patients admitted to postacute care

Introduction : bien que la prévalence des syndromes démentiels soit élevée chez les personnes âgées hospitalisées et qu'une proportion non négligeable échappe au diagnostic, la littérature ne fournit que peu de données chez les patients admis en milieu de réadaptation post-aigu. L'objectif principal de ce travail était de déterminer la prévalence des démences, ainsi que la proportion de démences non diagnostiquées dans une population admise dans un centre de réadaptation gériatrique. Ensuite, nous nous sommes intéressés à identifier les caractéristiques des patients associées à une démence non-détectée. Méthode : nous avons utilisé les données de tous les patients âgés de 70 ans et plus admis durant 3 ans dans l'unité de réadaptation du service de gériatrie et réadaptation gériatrique, Centre Hospitalier Universitaire Vtudois, en excluant les patients décédés pendant l'hospitalisation. Lors de l'admission, des données sociodémographiques, médicales, ainsi que des données concernant le status fonctionnel et mental sont récoltées systématiquement. Par ailleurs, les dossiers des patients ont été examinés pour en extraire les informations quant aux performances cognitive (mini-Mental State Exam, MMSE) et au diagnostic de sortie. Résultats : un diagnostic de démence figurait dans la lettre de sortie de 425 des 1764 patients (24.1%), plus de la moitié présentant une démence de type Alzheimer. Pour 301 de ces 425 patients (70.8%), la démence avait été diagnostiquée durant le séjour de réadaptation. La proportion de démences non-détectées auparavant était plus élevée chez les patients provenant des services de chirurgie/orthopédie que de médecine interne (74.8% vs 65.8%, p=.42). Les patients non diagnostiqués comme déments étaient plus âgés, vivaient plus souvent seuls et avaient de meilleures performances fonctionnelles et cognitives que ceux chez qui le diagnostic avait été posé auparavant. Notamment, un tiers d'entre eux avait un score normal au MMSE. Une analyse multi-variée a mis en évidence deux facteurs prédisposant à la non-détection : l'âge (Odds Ratio (OR) : 2.4 pour le groupe d'âge 85 ans et plus par rapport aux plus jeunes, 96%CI : 1.5-4.0, p=.001) et le score au MMSE (OR : 5.9 lors d'un MMSE normal à l'admission, 96%CI : 2.7-12.7, p<.001) Conclusion et perspectives : cette étude montre qu'environ un quart des patients admis en réadaptation gériatrique souffre de démence, et que cette pathologie n'est pas reconnue chez les trois-quarts d'entre eux. Ces résultats soulignent la nécessité d'un dépistage systématique des troubles cognitifs chez les patients âgés. En effet, en l'absence de détection, ces patients ne peuvent bénéficier d'une prise en charge approprié, incluant non seulement des mesures médicales et pharmacologiques, mais surtout l'information du patient et des proches, dans le but de maintenir une qualité de vie acceptable du patient ainsi que de prévenir l'épuisement des proches et des.soignants. Cette étude incite aussi à être attentif aux signes évocateurs de troubles cognitifs lors de l'interprétation du test MMSE, car un score dans les limites de la norme ne permet pas d'exclure une démence.

Analytical interference of 4-hydroxy-3-methoxymethamphetamine with the measurement of plasma free normetanephrine by ultra-high pressure liquid chromatography-tandem mass spectrometry.

OBJECTIVES: The diagnosis of pheochromocytoma relies on the measurement of plasma free metanephrines assay whose reliability has been considerably improved by ultra-high pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). Here we report an analytical interference occurring between 4-hydroxy-3-methoxymethamphetamine (HMMA), a metabolite of 3,4-methylenedioxymethamphetamine (MDMA, "Ecstasy"), and normetanephrine (NMN) since they share a common pharmacophore resulting in the same product ion after fragmentation. DESIGN AND METHODS: Synthetic HMMA was spiked into plasma samples containing various concentrations of NMN and the intensity of the interference was determined by UPLC-MS/MS before and after improvement of the analytical method. RESULTS: Using a careful adjustment of chromatographic conditions including the change of the UPLC analytical column, we were able to distinguish both compounds. HMMA interference for NMN determination should be seriously considered since MDMA activates the sympathetic nervous system and if confounded with NMN may lead to false-positive tests when performing a differential diagnostic of pheochromocytoma.

Use of plasma Renin activity to monitor mineralocorticoid treatment in dogs with primary hypoadrenocorticism: desoxycorticosterone versus fludrocortisone.

BACKGROUND: Measurement of plasma renin activity (PRA) is the gold standard for monitoring mineralocorticoid treatment in humans with primary hypoadrenocorticism (PH). OBJECTIVES: To compare PRA in dogs with newly diagnosed PH, dogs with diseases mimicking PH, and healthy dogs, and evaluate measurement of PRA to monitor therapeutic effects in dogs with PH treated with different mineralocorticoids. ANIMALS: Eleven dogs with newly diagnosed PH (group 1), 10 dogs with diseases mimicking PH (group 2), 21 healthy dogs (group 3), 17 dogs with treated PH (group 4). METHODS: In group 1, PRA was measured before treatment and at different times after initiating treatment. In groups 2 and 3, PRA was measured at initial presentation only. In group 4, no baseline PRA was obtained but PRA was measured once or every 1-6 months during treatment. Mineralocorticoid treatment consisted of fludrocortisone acetate (FC) or desoxycorticosterone pivalate (DOCP). RESULTS: Plasma renin activity before treatment was increased in dogs with PH compared to normal dogs and dogs with diseases mimicking PH with median activity of 27, 0.8, and 1.0 ng/mL/h, respectively. In dogs with PH, PRA decreased and normalized with mineralocorticoid treatment using DOCP but not with FC. In dogs treated with DOCP, PRA was lower than in dogs treated with FC. Plasma sodium concentrations were higher and potassium concentrations were lower with DOCP treatment compared to FC treatment. CONCLUSION AND CLINICAL IMPORTANCE: Plasma renin activity is a reliable tool for monitoring mineralocorticoid treatment. DOCP treatment more effectively suppresses PRA compared to FC in dogs with PH.

High-throughput and sensitive quantitation of plasma catecholamines by ultraperformance liquid chromatography-tandem mass spectrometry using a solid phase microwell extraction plate.

Plasma catecholamines provide a reliable biomarker of sympathetic activity. The low circulating concentrations of catecholamines and analytical interferences require tedious sample preparation and long chromatographic runs to ensure their accurate quantification by HPLC with electrochemical detection. Published or commercially available methods relying on solid phase extraction technology lack sensitivity or require derivatization of catecholamine by hazardous reagents prior to tandem mass spectrometry (MS) analysis. Here, we manufactured a novel 96-well microplate device specifically designed to extract plasma catecholamines prior to their quantification by a new and highly sensitive ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. Processing time, which included sample purification on activated aluminum oxide and elution, is less than 1 h per 96-well microplate. The UPLC-MS/MS analysis run time is 2.0 min per sample. This UPLC-MS/MS method does not require a derivatization step, reduces the turnaround time by 10-fold compared to conventional methods used for routine application, and allows catecholamine quantification in reduced plasma sample volumes (50-250 μL, e.g., from children and mice).