Sodium citrate: A universal reducing agent for reduction / decoration of graphene oxide with au nanoparticles

A facile method is proposed for the synthesis of reduced graphene oxide nanosheets (RGONS) and Au nanoparticle-reduced graphene oxide nanosheet (Au-RGONS) hybrid materials, using graphene oxide (GO) as precursor and sodium citrate as reductant and stabilizer. The resulting RGONS and Au-RGONS hybrid materials were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy, transmission electron microscopy, and X-ray diffraction. It was found that the RGONS and Au-RGONS hybrid materials formed stable colloidal dispersions through hydrogen bonds between the residual oxygen-containing functionalities on the surface of RGONS and the hydroxyl/carboxyl groups of sodium citrate. The electrochemical responses of RGONS and Au-RGONS hybrid material-modified glassy carbon electrodes (GCE) to three kinds of biomolecules were investigated, and all of them showed a remarkable increase in electrochemical performance relative to a bare GCE.      

Hooked on a feeling: Rumination about positive and negative emotion in inter-episode bipolar disorder.

Rumination has been consistently implicated in the onset and maintenance of depression. Less work has examined rumination in the context of bipolar disorder, especially rumination about positive emotion. The present study examined rumination about negative and positive emotion in interepisode bipolar disorder (BD; n = 39) and healthy controls (CTL; n = 34). Trait rumination about positive and negative emotion, as well as experiential and physiological responses to a rumination induction, was measured. Illness course was also assessed for the BD group. Results indicated that the BD group reported greater trait rumination about positive and negative emotion compared with the CTL group, though no group differences emerged during the rumination induction. For the BD group, trait rumination about positive and negative emotion, as well as increased cardiovascular arousal (i.e., heart rate), was associated with greater lifetime depression frequency; trait rumination about positive emotion was associated with greater lifetime mania frequency. These findings suggest that interepisode BD is associated with greater rumination about positive and negative emotion, which in turn is associated with illness course. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Field Effect Transistors for Terahertz Detection and Emission

Resonant frequencies of the two-dimensional plasma in field effect transistors (FETs) increase with the reduction of the channel dimensions and can reach the Terahertz (THz) range. Nonlinear properties of the plasma/electron gas in the transistor channel can be used for the rectification and detection of THz radiation. The excitation of plasma waves by sub-THz and THz radiation was demonstrated for short gate transistors at cryogenic temperatures. At room temperature plasma oscillations are usually overdamped, but the FETs can still operate as efficient broadband rectifiers/detectors in the THz range. We present a few recent experimental results on THz detection by FETs showing some new ways of improvement of FETs for THz imaging at room temperature as well as the new physical phenomena like detection in quantizing magnetic fields. We also demonstrate THz emission properties of GaN based FETs.     

Performance evaluation of gas chromatography-atmospheric pressure chemical ionization-time-of-flight mass spectrometry for metabolic fingerprinting and profiling

Gas chromatography-atmospheric-pressure chemical ionization-time-of-flight mass spectrometry (GC-APCI-TOFMS) was compared to GC × GC-electron ionization (EI)-TOFMS, GC-EI-TOFMS, GC-chemical ionization (CI)-quadrupole mass spectrometry (qMS), and GC-EI-qMS in terms of reproducibility, dynamic range, limit of detection, and quantification using a mix of 43 metabolites and 12 stable isotope-labeled standards. Lower limits of quantification for GC-APCI-TOFMS ranged between 0.06 and 7.81 μM, and relative standard deviations for calibration replicates were between 0.4% and 8.7%. For all compounds and techniques, except in four cases, R(2) values were above 0.99. Regarding limits of quantification, GC-APCI-TOFMS was inferior to only GC × GC-EI-TOFMS, but outperformed all other techniques tested. GC-APCI-TOFMS was further applied to the metabolic fingerprinting of two Escherichia coli strains. Of 45 features that differed significantly (false discovery rate < 0.05) between the strains, 25 metabolites were identified through highly accurate and reproducible (Δm ± SD below 5 mDa over m/z 190-722) mass measurements. Starting from the quasimolecular ion, six additional metabolites were identified that had not been found in a previous study using GC × GC-EI-TOFMS and an EI mass spectral library for identification purposes. Silylation adducts formed in the APCI source assisted the identification of unknown compounds, as their formation is structure-dependent and is not observed for compounds lacking a carboxylic group.     

Excess dietary iodine differentially affects thyroid gene expression in diabetes, thyroiditis-prone versus -resistant BioBreeding (BB) rats

Scope : To identify genes involved in the susceptibility to iodine‐induced autoimmune thyroiditis. Methods and results : Diabetes, thyroiditis‐prone (BBdp) and ‐resistant (BBc) rats were fed either a control or a high‐iodine diet for 9 wk. Excess iodine intake increased the incidence of insulitis and thyroiditis in BBdp rats. BBdp rats fed the high‐iodine diet that did not develop thyroiditis had higher mRNA levels of Fabp4, Cidec, perilipin, Pparγ and Slc36a2 than BBdp rats fed the control diet and BBc rats fed either the control or the high‐iodine diet. BBdp rats fed the high‐iodine diet that did develop thyroiditis had higher mRNA levels of Cidec, Icam1, Ifitm1, and Slpi than BBdp rats fed the control diet and BBc rats fed either the control or the high‐iodine diet. BBdp rats that did develop thyroiditis had lower mRNA levels of Fabp4, perilipin and Slc36a2 but higher mRNA levels of Icam1, Ifitm1 and Slpi than BBdp that did not develop thyroiditis. Excess dietary iodine also increased the protein levels of Fabp4, Cidec and perilipin in BBdp rats. Conclusion : Differential expression of thyroid genes in BBdp versus BBc rats caused by excess dietary iodine may be implicated in autoimmune thyroiditis and insulitis pathogenesis.     

Specific features of Eu^3＋ and Tb^3＋ magnetooptics in gadolinium-gallium garnet （Gd3Ga5O12）

We reported magnetooptical properties of Eu3+(4f(6)) and Tb3+(4f(8)) in single crystals of Gd3Ga5O12 (GGG), Y3Ga5O12 (YGG), and Eu3+(4f(6)) in Eu3Ga5O12 (EuGG) for both ions occupying sites of D2 symmetry in the garnet structure. Absorption, luminescence, and magnetic circular polarization of luminescence (MCPL) spectra of Tb3+ in GGG and YGG and absorption and magnetic circular dichroism (MCD) of Eu3+ in EuGG were studied. The data were obtained at 85 K and room temperature (RT). Magnetic susceptibility of Eu3+ in EuGG was also measured between 85 K and RT. The magnetooptical and magnetic susceptibility data were modeled using the wavefunctions of the crystal-field split energy (Stark) levels of Eu3+ and Tb3+ occupying D2 sites in the same garnets. The results reported gave a precise determination of these Stark level assignments and confirmed the symmetry labels (irreducible representations) of the closely-spaced Stark levels (quasi-doublets) found in the 5D1 (Eu3+) and 5D4 (Tb3+) multiplets. Ultraviolet (UV) excitation (<300 nm) of the 6PJ and 6IJ states of Gd3+ in the doped GGG crystals led to emission from 5D4 (Tb3+) and 5D1 and 5D0 (Eu3+) through radiationless energy transfer to the 4f(n-1)5d band of Tb3+ and to UV quintet states of Eu3+. The temperature-dependent emission line shapes and line shifts of the magnetooptical transitions excited by UV radiation suggested a novel way to explore energy transfer mechanisms in this rare-earth doped garnet system.     

Stainless steel patterning by combination of micro-patterning and driven strain produced by plasma assisted nitriding

Plasma-assisted nitriding treatments on austenitic stainless steel at low temperature produce the so called “expanded austenite”. The expansion of the nitrided layer that occurs from the initial surface of the substrate in a direction perpendicular to the surface is used here as a mean to produce patterned surfaces by selective nitrogen diffusion through masks. Using grids, a network of well defined square dots can be obtained. In this communication, the results of nitriding treatments on austenitic stainless steel substrates previously covered by a patterned silicon oxide layer are presented. The interactions mechanisms at the interface between fixed silicon oxide mask with several different shapes (circular and square dots) and the expanded austenite are also described. The role of nitrogen diffusion, consistent with the experimental conditions and the mask characteristics, is shown to be very important. Depending on the size of the dots, it leads to a simple uniform mask deformation or to a significant mask deformation with strong distortions at the edges. This phenomenon is noted as a toroidal-shell shape distortion. Optical cross-section seems to prove that it is only the result of the vertical force due to the austenite expansion induced by nitrogen diffusion just under the mask edges.     

Deciphering the Epigenetic Alphabet Involved in Transgenerational Stress Memory in Crops

Although epigenetic modifications have been intensely investigated over the last decade due to their role in crop adaptation to rapid climate change, it is unclear which epigenetic changes are heritable and therefore transmitted to their progeny. The identification of epigenetic marks that are transmitted to the next generations is of primary importance for their use in breeding and for the development of new cultivars with a broad-spectrum of tolerance/resistance to abiotic and biotic stresses. In this review, we discuss general aspects of plant responses to environmental stresses and provide an overview of recent findings on the role of transgenerational epigenetic modifications in crops. In addition, we take the opportunity to describe the aims of EPI-CATCH, an international COST action consortium composed by researchers from 28 countries. The aim of this COST action launched in 2020 is: (1) to define standardized pipelines and methods used in the study of epigenetic mechanisms in plants, (2) update, share, and exchange findings in epigenetic responses to environmental stresses in plants, (3) develop new concepts and frontiers in plant epigenetics and epigenomics, (4) enhance dissemination, communication, and transfer of knowledge in plant epigenetics and epigenomics.     

Tailoring a stabilized variant of hydroxynitrile lyase from Arabidopsis thaliana

The R-selective hydroxynitrile lyase from Arabidopsis thaliana (AtHNL) cannot be applied for stereoselective cyanohydrin syntheses in aqueous media because of its limited stability at pH<5, which is required in order to suppress the uncatalyzed racemic cyanohydrin formation. To stabilize AtHNL we designed a surface-modified variant incorporating 11 changes in the amino acids on the protein surface. Comparative characterization of the variant and the wild-type enzyme showed a broadened pH optimum towards the acidic range, along with enhancement of activity by up to twofold and significantly increased pH- and thermostabilities. The effect can most probably be explained by a shift of the isoelectic point from pH 5.1 to 4.8. Application of the variant for the synthesis of (R)-cyanohydrins in an aqueous/organic two-phase system at pH 4.5 demonstrated the high stereoselectivity and robustness of the variant relative to the wild-type enzyme, which is immediately inactivated under these conditions.     

Mercury distribution in tropical soil profiles related to origin of mercury and soil processes

The aim of the study is to improve our understanding of the vertical and lateral variations in the mercury content [Hg] of tropical soils. In addition to the distance to anthropogenic sources of Hg, the most frequently evoked determining factor is the abundance of Hg-bearing phases. Soil processes (weathering, mass or water transfer) determine the abundance of carrier phases. We assume that soil processes also have a direct impact on the distribution of Hg and that the impact is different according to the lithogenic or atmospheric origin of this element. We compare two types of soil (oxisol and ultisol) in the French Guiana forest, at localities a few tens of metres apart and exhibiting very different Hg contents. We show that vertical profiles of [Hg] are strongly related to the variations of [Hg(atmospheric)], whereas [Hg(lithogenic)] varies little. The penetration of Hg(atmospheric) from the surface deposits is favoured down to a depth of 3 m in the oxisol and limited to the upper horizons of the ultisol because of contrasted hydraulic conductivity between the two soils. Hg is primarily of lithogenic origin in the alteritic horizons of the ultisol. The relative accumulation of Hg(lithogenic) during the progressive weathering of parental material is limited near the soil surface by the disequilibrium of secondary minerals. Remobilization of Hg(atmospheric) or Hg(lithogenic) stored in the soil is a function of the chemical or particulate erosion of Hg-bearing phases, particularly active in the upper horizons of the ultisol, where lateral flow occurs during rain events. The correlations observed between the iron or clay contents and [Hg] can be caused by the affinity of Hg for these carrier phases, but may also reflect the weathering and the transfer processes which affect together the fate of Hg and the mineralogical and chemical composition of the soil.