Matter waves in a gravitational field: An index of refraction for massive particles in general relativity

We consider the propagation of massive-particle de Broglie waves in a static, isotropic metric in general relativity. We demonstrate the existence of an index of refraction that governs the waves and that has all the properties of a classical index of refraction. We confirm our interpretation with a WKB solution of the general-relativistic Klein-Gordon equation. Finally, we make some observations on the significance of the optical action.Comment: 20 pages, latex, ps and pdf. To appear in Am.J.Phys September, 200

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Valproic acid determination by liquid chromatography coupled to mass spectrometry (LC–MS/MS) in whole blood for forensic purposes

Valproic acid (VPA) is a well-known drug prescribed as anti-epileptic. It has a narrow therapeutic range and shows great individual differences in pharmacodynamics and pharmacokinetics. Consequently, the therapeutical drug monitoring (TDM) in patient's plasma is of crucial importance. Liquid chromatography coupled to mass spectrometry (LC–MS/MS) has gained importance in TDM applications for its features of sensitivity, selectivity and rapidity. However, in case of VPA, the LC–MS/MS selectivity could be hampered by the lack of a sufficient number of multiple reaction monitoring (MRM) transitions describing the molecule. In fact, the product ion scan of deprotonated molecules of VPA does not produce any ion and thus most LC–MS/MS methods are based on the detection of the unique MRM transition m/z 143➔143. In this way, the advantages of selectivity in LC–MS cannot be effectively exploited. In the present method, stable analyte adducts were exploited for the determination of VPA in blood. An Acquity HSS C18 column and mobile phases consisting of 5-mM ammonium formate and acetonitrile both added 0.1% formic acid were used. Source worked in negative acquisition mode and parameters were optimized to increase the adduct (m/z 189) and dimer (m/z 287) stability, and their fragmentation were used to increase the selectivity of MRM detection. The method has been validated according to the toxicological forensic guidelines and successfully applied to 10 real blood samples. Finally, the present method showed suitable for the rapid LC–MS/MS detection of VPA in whole blood, demonstrating the possibility to increase specificity by exploiting stable in-source adducts. This should be considered of utmost importance in the case of forensic applications

Linear plasmon dispersion in single-wall carbon nanotubes and the collective excitation spectrum of graphene

We have measured a strictly linear pi-plasmon dispersion along the axis of individualized single wall carbon nanotubes, which is completely different from plasmon dispersions of graphite or bundled single wall carbon nanotubes. Comparative ab initio studies on graphene based systems allow us to reproduce the different dispersions. This suggests that individualized nanotubes provide viable experimental access to collective electronic excitations of graphene, and it validates the use of graphene to understand electronic excitations of carbon nanotubes. In particular, the calculations reveal that local field effects (LFE) cause a mixing of electronic transitions, including the 'Dirac cone', resulting in the observed linear dispersion

A case of fatal multidrug intoxication involving flualprazolam: distribution in body fluids and solid tissues

Purpose Designer benzodiazepines (DBZDs) increasingly emerged on the novel psychoactive substance (NPS) market in the last few years. They are usually sold as readily available alternatives to prescription benzodiazepines (BZDs) or added to counterfeit medicines. BZDs are generally considered relatively safe drugs due to the low risk of serious acute adverse effects in mono-intoxication, though e.g., alprazolam seems to display an elevated risk of respiratory depression. Here we report on a fatal intoxication involving the novel DBZD flualprazolam. Methods A complete postmortem examination was performed. General unknown screenings and analysis of drugs of abuse were performed on postmortem samples by immunoassay, gas chromatography–mass spectrometry and liquid chromatog- raphy–mass spectrometry. The standard addition method was employed to quantify flualprazolam in postmortem blood and tissues. Finally, a toxicological significance score (TSS) was assigned. Results Flualprazolam was detected in heart serum (25.4 ng/mL) and peripheral blood (21.9 ng/mL) as well as in urine, stomach contents, brain, liver and kidney (65.2–323 ng/g). The cause of death was deemed as central nervous system (CNS) and respiratory depression with agonal aspiration of stomach contents, in the setting of a multiple drug intake. Given the concentration levels of the co-consumed CNS depressants, the contribution of flualprazolam to the death was considered likely (TSS of 3). Conclusions Our results support that highly potent DBZDs like flualprazolam carry an elevated risk for unintended toxic- ity, especially in association with other CNS depressants. A multidisciplinary evaluation of fatalities remains mandatory, especially when pharmacological/toxicological data on intoxicating compounds are lacking. To our knowledge this is the first report of flualprazolam concentrations in solid tissues in human

Electrochemical synthesis of nano-cobalt hexacyanoferrate at a sol–gel-coated electrode templated with β-cyclodextrin

The paper describes the time-dependent evolution of the electrochemical deposition of cobalt hexacyanoferrate (CoHCFe) on graphite foil electrode modified with electrochemically formed sol–gel film doped with β-cyclodextrin to impart porosity. With short-time electrodeposition, cyclic voltammetry (CV) shows a single redox couple typical of nano-sized clusters of CoHCFe, while at longer deposition times the CV’s shape evolves to the classical form of a bulk compound in which there are present two redox couples. The electrode modified with β-cyclodextrin (CD) included in the sol–gel film has an active surface that corresponds to pores created by CD stacks normal to the surface. Hence, the electrochemical formation of CoHCFe starts in these conductive pores; only at long deposition times do the clusters overlap to form moieties with the voltammetric characteristics of bulk CoHCFe

Combination of intact, middle-up and bottom-up levels to characterize 7 therapeutic monoclonal antibodies by capillary electrophoresis – Mass spectrometry

Significant growth of biopharmaceuticals requires powerful analytical methods to better understand their structure by establishing a complete characterization. To this end, a combination of bottom-up, middle-up and intact molecule levels with a capillary electrophoresis-mass spectrometry coupling has been performed to have a comprehensive picture of monoclonal antibodies. In this study, 7 worldwide health authorities approved mAbs have been analyzed to get information about their charge heterogeneity, the identification of post translational modifications (PTMs), their location and relative quantitation. Intact mAbs isoforms have been partially separated in less than 12 minutes and enabled to have a global illustration of mAbs heterogeneity and high masses PTMs characterization notably major N-glycosylation forms. Particularly, 2X-glycosylated and 1X-glycosylated forms have been partially separated. To deepen characterize PTMs carried by the backbone structure, advanced investigations at a middle-up level have been performed. Limited IdeS proteolysis allowed to study independently Fc/2 and F(ab)’2 fragments. Following the same separation conditions, isoforms of these fragments have been separated and data interpretation allowed to disclose additional PTMs as K-clip, oxidations or deamidations. A second intermediate level has been examined by adding a reduction step to establish a more precise assessment of PTMs and isoforms from the F(ab)’2 fragment. This reduction step released the light chains from the Fd fragment to get only 25 kDa fragments to analyze. CE-ESI-MS coupling allowed to get more information particularly about low masses PTMs. The precise location and relative quantitation of each PTM has been investigated at the peptidic level induced by a tryptic digestion of the studied mAbs. The concordance of the results shows the efficiency of the CE-ESI-MS coupling to characterize mAbs and highlight the need of the multi-level combination to get a comprehensive characterization of biotherapeutics

Magnetic circular dichroism of x-ray absorption spectroscopy at rare-earth L2,3 edges in RE2Fe14B compounds (RE = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)

Magnetic circular dichroism (MCD) in the x-ray absorption spectroscopy (XAS) at the L2,3 edges for almost entire series of rare-earth (RE) elements in RE2Fe14B, is studied experimentally and theoretically. By a quantitative comparison of the complicated MCD spectral shapes, we find that (i) the 4f-5d intra-atomic exchange interaction not only induces the spin and orbital polarization of the 5d states, which is vital for the MCD spectra of the electric dipole transition from the 2p core states to the empty 5d conduction band, but also it accompanies a contraction of the radial part of the 5d wave function depending on its spin and orbital state, which results in the enhancement of the 2p-5d dipole matrix element, (ii) there are cases where the spin polarization of the 5d states due to the hybridization with the spin polarized 3d states of surrounding irons plays important roles, and (iii) the electric quadrupole transition from the 2p core states to the magnetic vale! nce 4f states is appreciable at the pre-edge region of the dipole spectrum. Especially, our results evidence that it is important to include the enhancement effect of the dipole matrix element in the correct interpretation of the MCD spectra at the RE L2,3 edges.Comment: 9 pages, 5 figures, 1 table, REVTe

Semiarid Grassland and Winter Cereals for Lamb Production in Northeast Patagonia, Argentina

In northeastern Patagonia where grain crops often led to harvest failure, low yields and a high drought risk, a lamb production system was established. On a 10 years old agriculture wheat cropping was interrupted in 1996, allowing re-vegetation through exclusion of grazing. Natural grassland recovered, prevailing the species Stipa tenuis, Piptochaetium napostaense, Stipa ambigua. Part of the plot was sown to wheat grass (Thinopyrum ponticum). In 1999, to improve sheep feeding, oat (Avena sativa) and barley (Hordeum vulgare) were sown for grazing during winter-spring season. In this system Corriedale sheep, Texel x australian Merino (TEMA) and Ile de France x Australian Merino (ILMA) crosses were tested. Fertility, prolificacy, lamb mortality and weaning were evaluated. No differences among genotypes (α= 0.05) were found. Weaned lamb weight per ewe was significantly higher in cross ewes (p\u3c 0.0035), while production efficiency showed no significant differences among genotypes (α= 0.05), because of the higher body live weight of the crosses (p\u3c 0.0001). Yields of 16.4; 19.4 and 20.2kg lamb hectare–1 for Corriedale, TEMA and ILMA respectively were calculated, which represent an increase of 18 and 23 %. These differences could become economically significant in the production system under study

A semi-classical field method for the equilibrium Bose gas and application to thermal vortices in two dimensions

We develop a semi-classical field method for the study of the weakly interacting Bose gas at finite temperature, which, contrarily to the usual classical field model, does not suffer from an ultraviolet cut-off dependence. We apply the method to the study of thermal vortices in spatially homogeneous, two-dimensional systems. We present numerical results for the vortex density and the vortex pair distribution function. Insight in the physics of the system is obtained by comparing the numerical results with the predictions of simple analytical models. In particular, we calculate the activation energy required to form a vortex pair at low temperature.Comment: 19 page