Mechanism of thermally activated c-axis dissipation in layered High-Tc_c superconductors at high fields

We propose a simple model which explains experimental behavior of $c$-axis resistivity in layered High-T$_c$ superconductors at high fields in a limited temperature range. It is generally accepted that the in-plane dissipation at low temperatures is caused by small concentration of mobile pancake vortices whose diffusive motion is thermally activated. We demonstrate that in such situation a finite conductivity appears also in $c$-direction due to the phase slips between the planes caused by the mobile pancakes. The model gives universal relation between the components of conductivity which is in good agreement with experimental data.Comment: RevTeX, 4 pages, 2 Postscript figure

Crystal structure of an aminoglycoside 6′-N-acetyltransferase: defining the GCN5-related N-acetyltransferase superfamily fold

AbstractBackground: The predominant mechanism of antibiotic resistance employed by pathogenic bacteria against the clinically used aminoglycosides is chemical modification of the drug. The detoxification reactions are catalyzed by enzymes that promote either the phosphorylation, adenylation or acetylation of aminoglycosides. Structural studies of these aminoglycoside-modifying enzymes may assist in the development of therapeutic agents that could circumvent antibiotic resistance. In addition, such studies may shed light on the development of antibiotic resistance and the evolution of different enzyme classes.Results: The crystal structure of the aminoglycoside-modifying enzyme aminoglycoside 6′-N-acetyltransferase type Ii (AAC(6′)-Ii) in complex with the cofactor acetyl coenzyme A has been determined at 2.7 Å resolution. The structure establishes that this acetyltransferase belongs to the GCN5-related N-acetyltransferase superfamily, which includes such enzymes as the histone acetyltransferases GCN5 and Hat1.Conclusions: Comparison of the AAC(6′)-Ii structure with the crystal structures of two other members of this superfamily, Serratia marcescens aminoglycoside 3-N-acetyltransferase and yeast histone acetyltransferase Hat1, reveals that of the 84 residues that are structurally similar, only three are conserved and none can be implicated as catalytic residues. Despite the negligible sequence identity, functional studies show that AAC(6′)-Ii possesses protein acetylation activity. Thus, AAC(6′)-Ii is both a structural and functional homolog of the GCN5-related histone acetyltransferases

Structure of the GDP-Pi complex of Gly203→Ala G(iα1): a mimic of the ternary product complex of Galpha-catalyzed GTP hydrolysis

Background: G proteins play a vital role in transmembrane signalling events. In their inactive form G proteins exist as heterotrimers consisting of an α subunit, complexed with GDP and a dimer of βγ subunits. Upon stimulation by receptors, G protein α subunits exchange GDP for GTP and dissociate from βγ. Thus activated, α subunits stimulate or inhibit downstream effectors. The duration of the activated state corresponds to the single turnover rate of GTP hydrolysis, which is typically in the range of seconds. In G(iα1), the Gly203→Ala mutation reduces the affinity of the substrate for Mg2+, inhibits a key conformational step that occurs upon GTP binding and consequently inhibits the release of βγ subunits from the GTP complex. The structure of the Gly203→Ala mutant of G(iα1) (G203AG(iα1)) bound to the slowly hydrolyzing analog of GTP (GTPγS) has been determined in order to elucidate the structural changes that take place during hydrolysis. Results: We have determined the three dimensional structure of a Gly203→Ala mutant of G(iα1) at 2.6 Å resolution. Although crystals were grown in the presence of GTPγS and Mg2+, the catalytic site contains a molecule of GDP and a phosphate ion, but no Mg2+. The phosphate ion is bound to a site near that occupied by the γ-phosphate of GTPγS in the activated wild-type α subunit. A region of the protein, termed the Switch II helix, twists and bends to adopt a conformation that is radically different from that observed in other G(iα1) subunit complexes. Conclusions: Under the conditions of crystallization, the Gly203→Ala mutation appears to stabilize a conformation that may be similar, although perhaps not identical, to the transient ternary product complex of G(iα1)-catalyzed GTP hydrolysis. The rearrangement of the Switch II helix avoids a potential static conflict caused by the mutation. However, it appears that dissociation of the γ-phosphate from the pentacoordinate intermediate also requires a conformational change in Switch II. Thus, a conformational rearrangement of the Switch II helix may be required in Gα-catalyzed GTP hydrolysis

Synthesis of Chitosan-Lignin using Mannich Reaction and Its Characterization

Senyawa lignin dan kitosan merupakan biopolimer melimpah yang berada di alam. Akan tetapi aspek penggunaan dari biopolimer ini masih sangat minim dan hanya menjadi limbah di lingkungan. Sintesis lignin-kitosan dengan reaksi Mannich ini bisa menjadi salah satu alternatif untuk dapat menggunakan limbah tersebut hingga menjadi bahan yang berguna ke depannya. Kitosan yang digunakan merupakan kitosan komersil dengan %DD (persen deasetilisasi) sebesar 71,57%.  Karakterisasi yang digunakan ialah FTIR serta TGA. Keberhasilan sintesis lignin-kitosan ditandai dengan munculnya peak pada spektrum FTIR pada bilangan gelombang 3300 – 3500 cm-1. Analisis TGA digunakan untuk mengetahui sifat degradasi termal dari senyawa lignin-kitosan yang diduga dapat menjadi senyawa biopolimer baru.   Kata kunci: Kitosan, Lignin, Reaksi MannichLignin and chitosan compounds are abundant biopolymers that occur in nature. However, the use aspect of this biopolymer is still very minimal and only becomes waste in the environment. The synthesis of lignin-chitosan using the Mannich reaction can be an alternative to be able to use this waste to become useful material in the future. The chitosan used was commercial chitosan with% DD (percent deacetylation) of 71.57%. The characterization used is FTIR and TGA. The success of lignin-chitosan synthesis is indicated by the appearance of peaks in the FTIR spectrum at wavenumbers 3300 - 3500 cm-1. TGA analysis is used to determine the thermal degradation properties of lignin-chitosan compounds which are thought to be new biopolymer compounds.   Keywords: Chitosan, Lignin, Mannich Reactio

Structure of the first C\u3csub\u3e2\u3c/sub\u3e domain of synaptotagmin I: A Novel CA(2+)/Phospholipid-Binding Fold

C2 domains are regulatory sequence motifs that occur widely in nature. Synaptotagmin I, a synaptic vesicle protein involved in the Ca2+ regulation of exocytosis, contains two C2 domains, the first of which acts as a Ca2+ sensor. We now describe the three-dimensional structure of this C2 domain at 1.9 Å resolution in both the Ca2+-bound and Ca2+-free forms. The C2 polypeptide forms an eight-stranded β sandwich constructed around a conserved four-stranded motif designated as a C2 key. Ca2+ binds in a cup-shaped depression between two polypeptide loops located at the N- and C-termini of the C2-key motif

Organic-inorganic hybrid solution-processed H2-evolving photocathodes

Here we report for the first time an H2-evolving photocathode fabricated by a solution-processed organic inorganic hybrid composed of CdSe and P3HT. The CdSe:P3HT (10:1 (w/w)) hybrid bulk heterojunction treated with 1,2-ethanedithiol (EDT) showed efficient water reduction and hydrogen generation. A photocurrent of -1.24 mA/cm(2) at 0 V versus reversible hydrogen electrode (V-RHE), EQE of 15%, and an unprecedented V-oc of 0.85 V-RHE under illumination of AM1.5G (100 mW/cm(2)) in mild electrolyte were observed. Time-resolved photoluminescence (TRPL), internal quantum efficiency (IQE), and transient photocurrent measurements were carried out to clarify the carrier dynamics of the hybrids. The exciton lifetime of CdSe was reduced by one order of magnitude in the hybrid blend, which is a sign of the fast charge separation upon illumination. By comparing the current magnitude of the solid-state devices and water-splitting devices made with identical active layers, we found that the interfaces of the water-splitting devices limit the device performance. The electron/hole transport properties investigated by comparing IQE spectra upon front- and back-side illumination evidenced balanced electron/hole transport. The Faradaic efficiency is 80-100% for the hybrid photocathodes with Pt catalysts and similar to 70% for the one without Pt catalysts

Vortices in a Thin Film Superconductor with a Spherical Geometry

We report results from Monte Carlo simulations of a thin film superconductor in a spherical geometry within the lowest Landau level approximation. We observe the absence of a phase transition to a low temperature vortex solid phase with these boundary conditions; the system remains in the vortex liquid phase for all accessible temperatures. The correlation lengths are measured for phase coherence and density modulation. Both lengths display identical temperature dependences, with an asymptotic scaling form consistent with a continuous zero temperature transition. This contrasts with the first order freezing transition which is seen in the alternative quasi-periodic boundary conditions. The high temperature perturbation theory and the ground states of the spherical system suggest that the thermodynamic limit of the spherical geometry is the same as that on the flat plane. We discuss the advantages and drawbacks of simulations with different geometries, and compare with current experimental conclusions. The effect of having a large scale inhomogeneity in the applied field is also considered.Comment: This replacment contains substantial revisions: the new article is twice as long with new and different results on the thermodynamic limit on the sphere plus a full discussion on the alternative boundary conditions used in simulations in the LLL approximation. 19 pages, 12 encapsulated PostScript figures, 1 JPEG figure, uses RevTeX (with epsf

Receiving visits in prison and aggressive and contraband misconduct among Dutch prisoners

Criminal Justice: Legitimacy, accountability, and effectivit

Receiving Visits and the Relative Timing of Inmates’ Infractions: Investigations into how Inmates’ Behavior Change Before and After Visits in Dutch Prisons

ObjectivesThis study tests the relative timing of inmate infractions in the weeks before and after a visit.MethodOur sample is a cohort of 823 male inmates who participated in the Dutch Prison Visitation Study (DPVS) (2017) and had visitation and misconduct data. Using two-level random effects logistic regression models, we examined week-to-week associations between infractions and prison visits, including visits from partners, family, friends, and official visitors.ResultsThe probability of an infraction is comparable to average levels in anticipation of visits, increases up to 18 percent in the weeks immediately following visits, and then returns to baseline levels. This pattern is found for contraband infractions, but no effects were found for aggressive infractions. Strongest effects were found for family and official visits. When inmates are visited frequently, the risk of infractions postvisit is similar to average levels.ConclusionsThe findings show that visits can have harmful effects on inmate infractions. These effects seem to stem from increases in contraband infractions. More research is needed to further understand the mechanism behind visits’ effects.Criminal Justice: Legitimacy, accountability, and effectivit

Symptomatology of carbamazepine- and oxcarbazepine-induced hyponatremia in people with epilepsy

OBJECTIVE: To ascertain whether adverse effects experienced by people taking carbamazepine or oxcarbazepine could be attributed to carbamazepine- or oxcarbazepine-induced hyponatremia (COIH). METHODS: We performed an observational study, collecting data between 2017 and 2019 on serum sodium levels and adverse effects retrospectively in people with epilepsy while receiving treatment with either carbamazepine (CBZ) or oxcarbazepine (OXC). We defined hyponatremia as sodium level ≤134 mEq/L and severe hyponatremia as sodium level ≤128 mEq/L. Adverse effects experienced were compared between groups of individuals with and without hyponatremia. RESULTS: A total of 1370 people using CBZ or OXC were identified, of whom 410 had at least one episode of hyponatremia. We checked for symptoms related to the use of CBZ and OXC in 710 people (410 with and 300 without hyponatremia) and found relevant information in 688. Adverse effects occurred in 65% of people with hyponatremia compared to 21% with normal sodium levels (odds ratio [OR] 7.5, P ≤ .001) and in 83% of people with severe hyponatremia compared to 55% in those with mild hyponatremia (P ≤ .001). Significant predictors of adverse effects were the drug (OXC vs CBZ), and the number of concomitant anti-seizure medications. Dizziness (28% vs 6%), tiredness (22% vs 7%), instability (19% vs 3%), and diplopia (16% vs 4%) were reported more often in the hyponatremia group than in patients with normal levels. SIGNIFICANCE: People with COIH had a 7-fold increased risk of developing adverse effects during treatment. Clinicians should consider ascertainment of sodium levels in patients taking CBZ and OXC and act upon findings