Development of Discharge in a Saline Solution at Near-Threshold Voltages

The development of a discharge in a point?plane gap filled with a saline solution with a salt content of 3% was studied experimentally. The duration of the voltage pulse applied to the gap was about 2 ms. Data are presented on the formation dynamics of gas microcavities at near-threshold voltages at which gas-discharge plasma appears in some microcavities. The cavities are conglomerates of microbubbles with a typical size of ≈100 μm. At the threshold voltage (≈750 V), the active electrode is covered with a gas layer and the gap voltage is in fact applied to this layer, which leads to the development of discharges in individual microbubbles. In this case, the discharge operates in the form of short current pulses. The number of microcavities filled with plasma increases as the voltage grows above the threshold value. At the plasma boundary, new microbubbles are formed, in which discharges are ignited. As a result, the plasma front propagates from the active electrode into the gap with a characteristic velocity of 10³ cm/s.     

Triggering ubiquitination of a CDK inhibitor at origins of DNA replication

To ensure proper timing of the G1-S transition in the cell cycle, the cyclin E-Cdk2 complex, which is responsible for the initiation of DNA replication, is restrained by the p21(Cip1)/p27(Kip1)/p57(Kip2) family of CDK (cyclin-dependent kinase) inhibitors in humans and by the related p27(Xic1) protein in Xenopus. Activation of cyclin E-Cdk2 is linked to the ubiquitination of human p27(Kip1) or Xenopus p27(Xic1) by SCF (for Skp1-Cullin-F-box protein) ubiquitin ligases. For human p27(Kip1), ubiquitination requires direct phosphorylation by cyclin E-Cdk2. We show here that Xic1 ubiquitination does not require phosphorylation by cyclin E-Cdk2, but it does require nuclear accumulation of the Xic1-cyclin E-Cdk2 complex and recruitment of this complex to chromatin by the origin-recognition complex together with Cdc6 replication preinitiation factors; it also requires an activation step necessitating cyclin E-Cdk2-kinase and SCF ubiquitin-ligase activity, and additional factors associated with mini-chromosome maintenance proteins, including the inactivation of geminin. Components of the SCF ubiquitin-ligase complex, including Skp1 and Cul1, are also recruited to chromatin through cyclin E-Cdk2 and the preinitiation complex. Thus, activation of the cyclin E-Cdk2 kinase and ubiquitin-dependent destruction of its inhibitor are spatially constrained to the site of a properly assembled preinitiation complex.     

Stable Lithium Electrodeposition at Ultra‐High Current Densities Enabled by 3D PMF/Li Composite Anode

Lithium metal batteries (LMBs) are promising candidates for next‐generation energy storage due to their high energy densities on both weight and volume bases. However, LMBs usually undergo uncontrollable lithium deposition, unstable solid electrolyte interphase, and volume expansion, which easily lead to low Coulombic efficiency, poor cycling performance, and even safety hazards, hindering their practical applications for more than forty years. These issues can be further exacerbated if operated at high current densities. Here a stable lithium metal battery enabled by 3D porous poly‐melamine‐formaldehyde (PMF)/Li composite anode is reported. PMF with a large number of polar groups (amine and triazine) can effectively homogenize Li‐ion concentration when these ions approach to the anode surface and thus achieve uniform Li deposition. Moreover, the 3D structured anode can serve as a Li host to mitigate the volume change during Li stripping and plating process. Galvanostatic measurements demonstrate that the 3D composite electrode can achieve high‐lithium Coulombic efficiency of 94.7% at an ultrahigh current density of 10 mA cm^?2 after 50 cycles with low hysteresis and smooth voltage plateaus. When coupled with Li₄Ti₅O₁₂, half‐cells show enhanced rate capabilities and Coulombic efficiencies, opening great opportunities for high‐energy batteries.     

K+ and Cl− Conductance of Arabidopsis thaliana Plasma Membrane at Depolarized Voltages

The ion currents, activated by depolarizations, across the plasma membrane of Arabidopsis thaliana cultured cells were studied by means of the patch-clamp technique in the whole-cell configuration. The electrical conductance of the membrane could be shifted from a cation to an anion conducting state by changes in the [K⁺]: [Cl⁻] ratio in the external medium. For ratios between 1:1 and 1:5 the currents were due to K⁺ efflux and for a ratio of 1:10 to Cl⁻ influx. In the cation conducting state the permeability ratio of K⁺ over NH⁺₄ and the alkali metal ions was: K⁺ ≅ NH>Na⁺ ≅ Li⁺ >Cs⁺. In the anion conducting state the permeability of NO⁻₃ was the same as that of Cl⁻. These channels were activated by depolarizations in the range of physiological potentials (-70/-80mV) and, either by mediating the efflux of cations or the influx of anions, they could function to re-hyperpolarize the membrane potential after depolarizations due to the influx of cations or of solutes cotransported with protons and/or to the inhibition of electrogenic pumps.     

Storage Capacity and Cycling Stability in Ge Anodes: Relationship of Anode Structure and Cycling Rate

Operando X‐ray diffraction (XRD) and X‐ray absorption spectroscopy (XAS) studies of Ge anodes are carried out to understand the effect of cycling rate on Ge phase transformation during charge/discharge process and to relate that effect to capacity. It is discovered that the formation of crystalline Li₁₅Ge₄ (c‐Li₁₅Ge₄) during lithiation is suppressed beyond a certain cycling rate. A very stable and reversible high capacity of ≈1800 mAh g^?1 can be attained up to 100 cycles at a slow C‐rate of C/21 when there is complete conversion of Ge anode into c‐Li₁₅Ge₄. When the C‐rate is increased to ≈C/10, the lithiation reaction is more heterogeneous and a relatively high capacity of ≈1000 mAh g^?1 is achieved with poorer electrochemical reversibility. An increase in C‐rate to C/5 and higher reduces the capacity (≈500 mAh g^?1) due to an impeded transformation from amorphous Li_xGe to c‐Li₁₅Ge₄, and yet improves the electrochemical reversibility. A proposed mechanism is presented to explain the C‐rate dependent phase transformations and the relationship of these to capacity fading. The operando XRD and XAS results provide new insights into the relationship between structural changes in Ge and battery capacity, which are important for guiding better design of high‐capacity anodes.     

Uniform High Ionic Conducting Lithium Sulfide Protection Layer for Stable Lithium Metal Anode

Artificial solid‐electrolyte interphase (SEI) is one of the key approaches in addressing the low reversibility and dendritic growth problems of lithium metal anode, yet its current effect is still insufficient due to insufficient stability. Here, a new principle of “simultaneous high ionic conductivity and homogeneity” is proposed for stabilizing SEI and lithium metal anodes. Fabricated by a facile, environmentally friendly, and low‐cost lithium solid‐sulfur vapor reaction at elevated temperature, a designed lithium sulfide protective layer successfully maintains its protection function during cycling, which is confirmed by both simulations and experiments. Stable dendrite‐free cycling of lithium metal anode is realized even at a high areal capacity of 5 mAh cm^?2, and prototype Li–Li₄Ti₅O₁₂ cell with limited lithium also achieves 900 stable cycles. These findings give new insight into the ideal SEI composition and structure and provide new design strategies for stable lithium metal batteries.     

Mid-Infrared Study of Deoxyadenosine at High Pressures: Evidence of Phase Transitions

Abstract

Room temperature mid-infrared experiments between 500 and 1800 cm^?1 have been performed on crystalline deoxyadenosine as a function of pressure up to about 10 GPa. Discontinuities observed near 2 and 4 GPa indicate that two separate phase transitions occur at these pressures. Changes in the spectra suggest that both transitions involve a rearrangement of the pucker of the deoxyribose moiety. The wavenumbers of the vibrational modes shift to higher values with applied pressure. Our results for deoxyadenosine are compared to similar measurements on adenosine. Assignments for the observed modes are made on the basis of work published in the literature.     

Stability of helix-rich proteins at high concentrations

A number of techniques, including circular dichroism, FTIR, front face fluorescence, and UV absorption spectrophotometries, dynamic light scattering, and DSC, were used to directly measure the colloidal and conformational stability of proteins in highly concentrated solutions. Using bovine serum albumin (BSA), chicken egg white lysozyme, human hemoglobin A0, and bovine fibrinogen as model proteins, the thermal transition temperatures of proteins in dilute and concentrated solutions were compared. At 10 degrees C, no significant differences in both secondary and tertiary structures were detected for proteins at different concentrations. When temperature was introduced as a variable, however, hemoglobin and fibrinogen demonstrated higher transition midpoints (T(m)s) in concentrated rather than in dilute solutions (deltaT(m) approximately 2-10 degrees C). In contrast, lysozyme and BSA in concentrated solutions exhibit a lower T(m) than in dilute solutions (deltaT(m) approximately 2-20 degrees C). From these studies, it appears that a variety of factors determine the effect of high concentrations on the colloidal and conformational stability of a particular protein. While the prediction of excluded volume theory is that high concentrations should conformationally stabilize proteins, other factors such as pH, kinetics, protein dynamics, and intermolecular charge-charge effects may affect the overall stability of proteins at high concentrations under certain conditions.     

Efficient Organic Solar Cells with Extremely High Open‐Circuit Voltages and Low Voltage Losses by Suppressing Nonradiative Recombination Losses

One of the most important factors that limits the efficiencies of bulk‐heterojunction organic solar cells (OSCs) is the modest open‐circuit voltage (V_oc) due to their large voltage loss (V_loss) caused by significant nonradiative recombination loss. To boost the performance of OSCs toward their theoretical limit, developing high‐performance donor: acceptor systems featuring low V_loss with suppressed nonradiative recombination losses (<0.30 V) is desired. Herein, high performance OSCs based on a polymer donor benzodithiophene‐difluorobenzoxadiazole‐2‐decyltetradecyl (BDT‐ffBX‐DT) and perylenediimide‐based acceptors (PDI dimer with spirofluorene linker (SFPDI), PDI4, and PDI6) are reported which offer a high power conversion efficiency (PCE) of 7.5%, 56% external quantum efficiency associated with very high V_oc (>1.10 V) and low V_loss (<0.60 V). A high V_oc up to 1.23 V is achieved, which is among the highest values reported for OSCs with a PCE beyond 6%, to date. These attractive results are benefit from the suppressed nonradiative recombination voltage loss, which is as low as 0.20 V. This value is the lowest value for OSCs so far and is comparable to high performance crystalline silicon and perovskite solar cells. These results show that OSCs have the potential to achieve comparable V_oc and voltage loss as inorganic photovoltaic technologies.     

Molecular Dynamics Study on Protein and it's Water Structure at High Pressure

Abstract

We have performed NPT molecular dynamics simulations (Langevin Piston Method) on two types of solvated proteins-‘denaturation-unfavorable’ protein (insulin) and ‘denaturation-favorable protein’ (ribonuclease A) at high pressure (from 1 bar up to 20 kbar). The method is based on the extended system formalism introduced by Andersen, where the deterministic equations of motion for the piston degree of freedom are replaced by Langevin equation. We report the structural changes of proteins (ribonuclease A and insulin) and water molecules through radius of gyration, solvent accessible surface area, hydrogen bond pattern, and the topology of water clusters connected by the hydrogen bonded circular network. The solvent accessibility of ribonuclease A is mainly decreased by hydrophilic residues rather than hydrophobic residues under high pressure. From the results of hydrogen bond analysis, we have found that α-helix is more stable than β-sheet under high pressure. In addition, from the analysis of the water cluster, we have observed that for ribonuclease A, 5-membered ring structure is more favorable than 6-membered ring at higher pressure. However, for insulin, the ratio of 5 to 6-ring is constant over the pressure ranges for which we have performed MD simulation. This indicates that the water structure around insulin does not change under high pressure.     

Comparative Study of Pressure-Induced Germination of Bacillus subtilis Spores at Low and High Pressures

We have studied pressure-induced germination of Bacillus subtilis spores at moderate (100 MPa) and high (500 to 600 MPa) pressures. Although we found comparable germination efficiencies under both conditions by using heat sensitivity as a criterion for germination, the sensitivity of pressure-germinated spores to some other agents was found to depend on the pressure used. Spores germinated at 100 MPa were more sensitive to pressure (>200 MPa), UV light, and hydrogen peroxide than were those germinated at 600 MPa. Since small, acid-soluble proteins (SASPs) and dipicolinic acid (DPA) are known to be involved in spore resistance to UV light and hydrogen peroxide, we studied the fate of these compounds during pressure germination. DPA was released upon both low- and high-pressure germination, but SASP degradation, which normally accompanies nutrient-induced germination, occurred upon low-pressure germination but not upon high-pressure germination. These results adequately explain the UV and hydrogen peroxide resistance of spores germinated at 600 MPa. The resistance to pressure inactivation of 600-MPa-germinated spores could also, at least partly, be attributed to α/β-type SASPs, since mutants deficient in α/β-type SASPs were more sensitive to inactivation at 600 MPa. Further, germination at 100 MPa resulted in rapid ATP generation, as is the case in nutrient-induced germination, but no ATP was formed during germination at 600 MPa. These results suggest that spore germination can be initiated by low- and high-pressure treatments but is arrested at an early stage in the latter case. The implications for the use of high pressure as a preservation treatment are discussed.     

High Mitochondrial DNA Stability in B-Cell Chronic Lymphocytic Leukemia

Background

Chronic Lymphocytic Leukemia (CLL) leads to progressive accumulation of lymphocytes in the blood, bone marrow, and lymphatic tissues. Previous findings have suggested that the mtDNA could play an important role in CLL.

Methodology/Principal Findings

The mitochondrial DNA (mtDNA) control-region was analyzed in lymphocyte cell DNA extracts and compared with their granulocyte counterpart extract of 146 patients suffering from B-Cell CLL; B-CLL (all recruited from the Basque country). Major efforts were undertaken to rule out methodological artefacts that would render a high false positive rate for mtDNA instabilities and thus lead to erroneous interpretation of sequence instabilities. Only twenty instabilities were finally confirmed, most of them affecting the homopolymeric stretch located in the second hypervariable segment (HVS-II) around position 310, which is well known to constitute an extreme mutational hotspot of length polymorphism, as these mutations are frequently observed in the general human population. A critical revision of the findings in previous studies indicates a lack of proper methodological standards, which eventually led to an overinterpretation of the role of the mtDNA in CLL tumorigenesis.

Conclusions/Significance

Our results suggest that mtDNA instability is not the primary causal factor in B-CLL. A secondary role of mtDNA mutations cannot be fully ruled out under the hypothesis that the progressive accumulation of mtDNA instabilities could finally contribute to the tumoral process. Recommendations are given that would help to minimize erroneous interpretation of sequencing results in mtDNA studies in tumorigenesis.     

红汁乳菇色素稳定性的研究

本文对红汁乳菇色素的稳定性进行了系统研究 ,结果表明 :红汁乳菇色素紫外光谱最大吸收波长为 2 5 1nm ,且为单一吸收峰 ;在碱性条件下能稳定存在 ,在酸性条件下随酸度增大吸光度减小 ,颜色变浅 ,稳定性较差 ;对自然光比较敏感 ,耐热性差 ;色素对Fe3 + 较为敏感 ,而Na+ 、K+ 、Ca2 + 、Zn2 + 、Al3 + 、Mg2 + 、Cu2 + 对色素无不良影响 ;色素耐氧化、还原能力较好 ;加入淀粉会使色素增色 ,而葡萄糖、蔗糖、柠檬酸对色素影响甚微     

Triggering and modulation of apoptosis by oxidative stress

Cell survival requires multiple factors, including appropriate proportions of molecular oxygen and various antioxidants. Although most oxidative insults can be overcome by the cell's natural defenses, sustained perturbation of this balance may result in either apoptotic or necrotic cell death. Numerous, recent studies have shown that the mode of cell death that occurs depends on the severity of the insult. Oxidants and antioxidants can not only determine cell fate, but can also modulate the mode of cell death. Effects of oxidative stress on components of the apoptotic machinery may mediate this modulation. This review will address some of the current paradigms for oxidative stress and apoptosis, and discuss the potential mechanisms by which oxidants can modulate the apoptotic pathway.     

Nature of FeSe2/N‐C Anode for High Performance Potassium Ion Hybrid Capacitor

Potassium ion hybrid capacitors have great potential for large‐scale energy devices, because of the high power density and low cost. However, their practical applications are hindered by their low energy density, as well as electrolyte decomposition and collector corrosion at high potential in potassium bis(fluoro‐sulfonyl)imide‐based electrolyte. Therefore, anode materials with high capacity, a suitable voltage platform, and stability become a key factor. Here, N‐doping carbon‐coated FeSe₂ clusters are demonstrated as the anode material for a hybrid capacitor, delivering a reversible capacity of 295 mAh g^?1 at 100 mA g^?1 over 100 cycles and a high rate capability of 158 mAh g^?1 at 2000 mA g^?1 over 2000 cycles. Meanwhile, through density functional theory calculations, in situ X‐ray diffraction, and ex situ transmission electron microscopy, the evolution of FeSe₂ to Fe₃Se₄ for the electrochemical reaction mechanism is successfully revealed. The battery‐supercapacitor hybrid using commercial activated carbon as the cathode and FeSe₂/N‐C as the anode is obtained. It delivers a high energy density of 230 Wh kg^?1 and a power density of 920 W kg^?1 (the energy density and power density are calculated based on the total mass of active materials in the anode and cathode).     

Estimating the Sizes of Populations at High Risk for HIV: A Comparison Study

Objectives

Behavioral interventions are effective strategies for HIV/AIDS prevention and control. However, implementation of such strategies relies heavily on the accurate estimation of the high-risk population size. The multiplier method and generalized network scale-up method were recommended to estimate the population size of those at high risk for HIV by UNAIDS/WHO in 2003 and 2010, respectively. This study aims to assess and compare the two methods for estimating the size of populations at high risk for HIV, and to provide practical guidelines and suggestions for implementing the two methods.

Methods

Studies of the multiplier method used to estimate the population prevalence of men who have sex with men in China published between July 1, 2003 and July 1, 2013 were reviewed. The generalized network scale-up method was applied to estimate the population prevalence of men who have sex with men in the urban district of Taiyuan, China.

Results

The median of studies using the multiplier method to estimate the population prevalence of men who have sex with men in China was 4–8 times lower than the national level estimate. Meanwhile, the estimate of the generalized network scale-up method fell within the range of national level estimate.

Conclusions

When high-quality existing data are not readily available, the multiplier method frequently yields underestimated results. We thus suggest that the generalized network scale-up method is preferred when sampling frames for the general population and accurate demographic information are available.     

采用填充床阳极的甲醇生物燃料电池

燃料电池是将化学能转变为电能的装置,人们已经在无机物燃料电池方面取得了很大进展。现在以各种有机物为燃料的生物燃料电池受到了重视。自然界存在大量的微生物和酶,可以氧化各种有机物,因此在原理上可以构建许多采用天然原料为燃料的生物燃料电池。目前,生物燃料电池实用化的主要问题是所提供的电流密度低,通过使用介体可以提高电流密度,在这方面已经做了许多工作,本实验室也有类似的工