Facile Exfoliation of Single‐Crystalline Copper Alkylphosphates to Single‐Layer Nanosheets and Enhanced Supercapacitance

Manipulation of low‐dimensional solids through soft chemical routes is an elegant way to realize newer materials. A new family of single‐crystalline transition‐metal layered organophosphates, with about 185 000 metal phosphate layers in a single crystal, can be exfoliated to a single‐layer nanosheet by a facile and rapid solvent assisted method. This exfoliation aids the formation of high‐surface‐area pyrophosphates with enhanced supercapacitance.     

Implications of spectral hole burning on the manipulation of spatial Goos–Hänchen shift in an atomic cell

We present a new scheme to report on Goos–Hänchen (GH) shift experienced by the Gaussian light beam interacting with an optical cavity filled with four-level sodium atomic medium in the spectral hole burning region with and without Doppler broadening effect. Theoretical atomic density-matrix formalism is employed to obtain the susceptibility of atomic medium while the stationary-phase-theory is used to compute the GH shift in the reflected and transmitted probe beams subjected to control fields. A steep normal slope of dispersion is observed with a maximum and zero probability of transmission and reflection coefficients, respectively, at the regions of the spectral holes burning. In the normal dispersion spectrum at the region of spectral hole burning, positive and negative GH shift is observed, respectively, in the transmitted and reflected light beams. However, at anomalous dispersive regions negative GH shift in the transmission beam and positive GH shift in the reflection beam is observed. The reflection and transmission coefficients as well as the spatial GH shift are the functions of probe detuning, collective phase of control fields, beam incident angle and inverse Doppler broadening effect in the spectral hole burning region. The position and number of spectral holes also depend on the same spectral parametrs as stated above. The study is expected to be useful for optoelectronic devices and optical-clocking applications.     

粘结剂对形貌各异的石墨负极电化学性能的影响

As an important component in electrodes, the choice of an appropriate binder is significant when fabricating lithium-ion batteries (LIBs) with good cycle stability and rate capability, which are used in numerous applications, especially portable electronics and eco-friendly electric vehicles (EVs). Semi-crystalline poly(vinylidene fluoride) (PVDF), which is a traditional and widely used binder, cannot efficiently accommodate the volume changes observed in the anode during the charge-discharge process while binding all the components in the electrode together, which results in increased internal cell resistance, detachment of the electrode components, and capacity fading. Herein, we have investigated a highly polar and elastomeric polyacrylonitrile-butadiene (NBR) rubber for use as a binder in LIBs, which can accommodate graphite particles of different shapes compared to semi-crystalline PVDF. Prior to our electrochemical tests, NBR was analyzed using thermogravimetric analysis (TGA) and X-ray diffraction (XRD), showing good thermal stability and an amorphous morphology. NBR is more conformable to irregular surfaces, which results in the formation of a homogeneous passivation layer on both spherical and flaky graphite particles to effectively suppress any electrolyte side reactions, further allowing more uniform and fast Li ion diffusion at the electrolyte/electrolyte interface. As a result, the electrochemical performance of both spherical and flaky shape graphite electrodes was significantly improved in terms of their first cycle Coulombic efficiency (CE) and cycle stability. With comparative specific capacity, the first cycle CE of the NBR-based spherical and flaky graphite electrodes were 87.0% and 85.5%, compared to 85.3% and 82.6% observed for their corresponding PVDF-based electrodes, respectively. After 1000 discharge-charge cycles at 1C, the capacity retention of the NBR-based graphite electrodes was significantly higher than that of PVDF-based electrodes. This was attributed to the good stability of the solid electrolyte interphase (SEI) formed on the graphite electrodes and the high stretching ability of the elastomeric NBR binder, which help to accommodate the repeated volume fluctuation of graphite observed during long-term charge-discharge cycling. Electrochemical impedance spectroscopy (EIS) and microscopic analysis (SEM and TEM) were carried out to investigate the formation and evolution of the SEI layers formed on the spherical and flaky graphite electrodes. The results show that thin, homogeneous, and stable SEI layers are formed on the surface of both spherical and flaky graphite electrodes prepared using the NBR binder. When compared to the PVDF-based graphite electrodes, the graphite electrodes constructed using NBR showed decreased resistance in the SEI layer and faster charge transfer, thus enhancing the electrode kinetics for Li ion intercalation/deintercalation. Our study shows that the electrochemical performance of spherical and flaky graphite electrodes prepared using the NBR binder is significantly improved, demonstrating that NBR is a promising binder for these electrodes in LIBs.     

Tetracyclic triterpenoids from the leaves of Azadirachta indica and their insecticidal activities

A new tetranortriterpenoid, meliatetraolenone [24,25,26,27-tetranor-apotirucalla-(apoeupha)-6alpha-O-methyl, 7alpha-senecioyl(7-deacetyl)-11alpha,12alpha,21,23-tetrahydroxy-21,23-epoxy-2,14,20(22)-trien-1,16-dione] (1) was isolated from the methanolic extract of fresh leaves of Azadirachta indica along with the known compound odoratone (3) which was hitherto unreported from this source. Their structures have been elucidated by spectral studies including 2D NMR. The insecticidal activities of 1 as well as those of odoratone (3) are reported. 1 and odoratone both showed mortality on fourth instar larvae of mosquitoes (Anopheles stephensi) with LC(50) values of 16 and 154 ppm, respectively.     

Comparison of urinary iodide determination in female thyroid patients by two techniques

Iodine deficiency affects a substantial portion of the world’s population, provoking severe health problems as well as important economic losses to the region in which this condition is found. In present study, evaluated the levels of urinary iodide (UI) and thyroid hormone status in female hypothyroid patients (HPs) and control subjects of same age group 16–30 years. The UI in HPs was measured by means of a Potentiometric method after microwave-assisted acid digestion, and compared the results with those obtained by the Sandell-Kolthoff method. The validity and accuracy was checked by using certified reference materials. The significantly lower concentration of iodide in the urine samples of the female goiter patients were observed as compared to control/referents subjects (p < 0.001). Serum thyroid status thyroid stimulating hormone, free triiodothyronine and free thyroxin were significantly lower in female patients as compared to control females (p < 0.003). The proposed method was relatively rapid, precise, accurate, efficient, as well as cost effective by using inexpensive equipment.     

Sulfated Triterpenes from Lemon Balm

The hydroalcoholic (EtOH/H₂O) extract of matured leaf margins of lemon balm (Melissa officinalis L.) afforded a new 3,23‐disulfate of 2α,3β‐23,29‐tetrahydroxyolean‐12‐en‐28‐oic acid 28‐O‐β‐D ‐glucopyranoside ( 1 ) and a new 23‐monosulfate of 2α,23‐dihydroxyurs‐12‐en‐28‐oic acid 3‐O‐β‐D ‐glucopyranoside ( 2 ), along with six known compounds, i.e., 23‐monosulfate of 2α,3β,19α,23‐tetrahydroxyurs‐12‐ene‐28‐oic acid 28‐O‐β‐D ‐glucopyranoside ( 3 ), 3,5,6‐trihydroxydehydro‐α‐ionol 9‐O‐β‐D ‐glucopyranoside ( 4 ), quadranoside III ( 5 ), rosmarinic acid ( 6 ), caffeic acid ( 7 ), and luteolin ( 8 ). All the isolated compounds were evaluated for their antioxidant, antimicrobial, antimalarial, and cytotoxic activities. Only rosmarinic acid exhibited substantial antioxidant and antimicrobial activities, whereas sulfated terpenes showed considerably lower or no antimicrobial activity.     

Evaluation of radon induced lung cancer risk in occupants of the old and new dwellings of the Dera Ismail Khan City,Pakistan

In order to carry out indoor radon measurement in new and old buildings of the Dera Ismail Khan city, CR-39 based radon detectors were installed in bed rooms and sitting rooms/TV lounges in 25 (each) old and new houses and were exposed to indoor radon for 90 days. After processing, mean weighted average indoor radon concentrations in old and new houses were found to be 275 ± 33 and 86 ± 18 Bq m^?3 whereas mean annual effective doses expected to be received by the occupants were 6.86 ± 0.79 and 2.1 ± 0.43 mSv year^?1, respectively. From the measured weighted average indoor radon concentration, excess relative risk factor was calculated using the risk model of BEIR VI for the age group of 35 and 55 years. Average excess lung cancer risk was found to be 1.63 ± 0.19 and 1.35 ± 0.16 and 0.5 ± 0.10 and 0.4 ± 0.08 for old and new houses, respectively.     

Exploring the Transition of Human α-Synuclein from Native to the Fibrillar State: Insights into the Pathogenesis of Parkinson’s Disease

The etiology of Parkinson’s disease involves the interplay between the environmental and genetic factors. Here in this study human α-synuclein upon exposure to 100 μM pendimethalin for 12 h in vitro passes through a partially folded state which proceeds to the aggregated state and terminally ends in the fibrillar phase. Variations in the ANS fluorescence intensities led to the detection of intermediate and aggregated states at 6 and 10 h respectively. Far-UV CD analysis depicted significant α-helical content for intermediate state at 6 h in presence of 100 μM pendimethalin. Further increasing the incubation time to 12 h resulted in a predominant β-sheet content which was confirmed to be fibrillar by TEM. Turbidity, Rayleigh scattering analysis, Congo red assay and ThT measurements supported the TEM data i.e. the formation of fibrillar structure of human α-synuclein upon 12 h incubation. Thus, our observation could suggest a possible underlying molecular basis for Parkinson’s disease.

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Graphical Abstract Schematic elucidation of the factors involved in the fibrillation of α-Synuclein during Parkinson’s pathogenesis.

     

Photodetachment Spectrum of Hydrogen Negative Ion Near a Partially Reflecting Spherical Surface

Photodetachment of negative ions near surfaces is of great interest in view of its fundamental significance and technological applications. We reinvestigate the dynamics of photoelectrons in H^? photodetachment near a partially reflecting spherical surface by the semiclassical closed-orbit theory. Reflection parameter R and curvature K is used to observe inelastic and spherical effects of the surface, respectively. The classical action is evaluated from the photodetached electron trajectories incident normally at the surface, arising simultaneously from the source and its image. The derived analytical formula of photodetachment cross section correctly recovers the results of reflective spherical surface published recently based on theoretical imaging method.     

Assessing the issue of instability due to Michael adduct formation in novel chemical entities possessing a carbon-carbon double bond during early drug development--applicability of common laboratory analytical protocols

The discovery of small-molecule novel chemical entities (NCEs) is often a complex play between appropriate structural requirements and optimization of the desired efficacy, safety and pharmacokinetic properties. One of the typical structural variants such as having an active carbon-carbon double bond (alpha, beta-unsaturated carbonyl group) in xenobiotics may lead to stability issues. Such functionalities are extremely reactive, paving way to nucleophilic attack by endogenously occurring and ubiquitous nucleophiles like thiols. While it is easy to make a unilateral decision to not pursue the development of xenobiotics with such functionalities, we question the wisdom of such a decision. In this report, we present in vitro methodologies with appropriate examples to illustrate the ease of assessing the reactivity of the xenobiotics containing double bonds with a known nucleophile. The protocols involve simple reaction procedures followed by measurements using standard laboratory equipments (UV spectrophotometer, HPLC and LC-MS). Our data suggests that not all xenobiotics with carbon-carbon double bonds readily form a Michael's adduct product with glutathione. Hence, the criterion for dropping discovery compounds because of alpha,beta-unsaturated double bonds needs to be reconsidered. Copyright (c) 2008 John Wiley & Sons, Ltd.