WAXS studies on block copolymers of ethylene and propylene

Wide-angle X-ray scattering from presumed block copolymers of polypropylene (PP) and ethylene-propylene copolymer (EPR), i.e., PP-EPR and PP-EPR-PP, synthesized by sequential polymerization with δ-TiCl₃? Et₂AlCl, was examined and compared with WAXS of mechanical blends and chain-transfer mixtures of PP and EPR with comparable compositions. The peak at 2θ = 20° for both the copolymers and the mixtures was attributed to the γ modification of PP in EPR. A strong variation in the ratio of diffraction intensities I₀₄₀/I₁₁₀ of PP in block copolymers and mixtures was explained in terms of crystallite growth in different directions. Analysis of the patterns and calculation of crystallinity, crystallite size, and lattice parameters led to the conclusion that block structure existed in the prepared copolymers.     

A climatology of solar erythema dose

Abstract —Semi-empirical formulas for the ultraviolet erythema dose derived in an earlier paper are used to deduce an ultraviolet photoclimatology. We calculate the climatology of daily erythema radiation doses for the northern hemisphere at 5d? latitude intervals. Similar dose calculations are also performed specifically for ten metropolitan areas. Effects of seasonal and geographic variations of ozone, turbidity, and cloudiness on the local erythema doses are also investigated. We present a simple approximate analytic formula for the annual erythema dose as a function of latitude, cloud cover, and ground albedo for use in connection with studies of the epidemiology of skin cancer. The implications of possible ozone depletion due to a future fleet of supersonic aircraft in the stratosphere are discussed. These calculations are made for a normal ozone thickness of 0.32 cm and for a 5, 10, 20, and 50 per cent ozone reduction.     

A study of solar erythema radiation doses

Abstract —Using semi-empirical analytic formulas for the transmitted and scattered ultraviolet spectral irradiance at the ground (Green, A. E. S., T. Sawada and E. P. Shettle, Photochem. Photobiol. 19 , 251–259, 1974), we calculate erythema dose rates and daily erythema doses. Results are illustrated graphically, and for the purpose of photobiological applications are given in terms of approximate analytic forms, with parameters presented in tabular form. The relative erythema data assembled by W. W. Coblentz and R. Stair (U.S. Bureau of Standards J. Res. 12 , 13–14, 1934), as fit by an analytic form, is taken as a standard spectrum in our calculations. Other forms of erythema spectra are also compared.     

The Antioxidant and Hypolipidemic Effects of Mesona Chinensis Benth Extracts

In this study, the antioxidant and hypolipidemic effects of Mesona Chinensis Benth (MCB) extracts were evaluated. Seven fractions (F0, F10, F20, F30, F40, F50 and MTF) were obtained from the MCB ethanol extracts. Compared to the commercial antioxidants (vitamin C), MTF and F30 exhibited higher antioxidant activities in the antiradical activity test and the FRAP assay. The half-inhibition concentration (IC50) for MTF and F30 were 5.323 µg/mL and 5.278 µg/mL, respectively. MTF at 200 µg/mL significantly decreased the accumulation of TG in oleic acid (OA)-induced HepG2 cells and reversed the inhibitory effect of Compound C on AMPK (MTF and F30 significantly increased the glucose utilization of insulin-induced HepG2 cells). In addition, the components of MTF were identified by HPLC-MS, which were caffeic acid, quercetin 3-O-galactoside, isoquercetin, astragalin, rosmarinic acid, aromadendrin-3-O-rutinoside, rosmarinic acid-3-O-glucoside and kaempferol-7-O-glucoside. Through statistical correlations by Simca P software, it was found that the main antioxidant and hypolipidemic components of MCB might be caffeic acid, kaempferol-7-O-glucoside, rosmarinic acid-3-O-glucoside and aromadendrin-3-O-rutinoside, which may play important roles in the AMPK pathway. MTF and F30 in MCB could be potential health products for the treatment of hyperlipidemia.     

Facile Synthesis of Porous Ag Crystals as SERS Sensor for Detection of Five Methamphetamine Analogs

Porous noble metal nanomaterials have attracted extensive attention due to their high specific surface area and surface plasmon resonance effect. However, it is difficult to form porous structures due to the high mobility and low reduction potential of noble metal precursors. In this article, we developed a facile method for preparing porous Ag with a controllable structure at room temperature. Two kinds of Ag crystals with different porous structures were successfully prepared by using AgCl cubes as sacrificial templates. Through the galvanic replacement reaction of Zn and AgCl, Ag crystals with a sponge-like porous structure were successfully prepared. Additionally, using NaBH₄ as the reducing agent, we prepared granular porous Ag cubes by optimizing the amount of reducing agent. Both the sponge-like and granular porous Ag cubes have clean and accessible surfaces. In addition, we used the prepared two porous Ag cubes as substrate materials for SERS detection of five kinds of methamphetamine analogs. The experimental results show that the enhancement effect of granular porous Ag is better than that of sponge-like porous Ag. Furthermore, we probed the hot spot distribution of granular porous Ag by Raman mapping. By using granular porous Ag as the substrate material, we have achieved trace detection of 5 kinds of methamphetamine analogs including Ephedrine, Amphetamine, N-Methyl-1-(benzofuran-5-yl)propan-2-amine (5-MAPB), N-Methyl-1-(4-methoxyphenyl)propan-2-amine (PMMA) and N-Methyl-1-(4-fluorophenyl)propan-2-amine (4-FMA). Furthermore, to achieve qualitative differentiation of analogs with similar structures we performed density functional theoretical (DFT) calculations on the Raman spectra of the above analogs. The DFT calculations provided the vibrational frequencies, Raman activities, and normal mode assignment for each analog, enabling the qualitative differentiation of the above analogs.     

Faraday-Michelson system for quantum cryptography

Quantum key distribution provides unconditional security for communication. Unfortunately, current experimental schemes are not suitable for long-distance fiber transmission because of phase drift or Rayleigh backscattering. In this Letter we present a unidirectional intrinsically stable scheme that is based on Michelson-Faraday interferometers, in which ordinary mirrors are replaced with 90 degree Faraday mirrors. With the scheme, a demonstration setup was built and excellent stability of interference fringe visibility was achieved over a fiber length of 175 km. Through a 125 km long commercial communication fiber cable between Beijing and Tianjin, the key exchange was performed with a quantum bit-error rate of less than 6%, which is to our knowledge the longest reported quantum key distribution experiment under field conditions.     

Use of the64Ni(36S,34,35Si)66,65Zn reactions to measure the masses of34Si and35Si

The ground-state masses of³⁵Si and³⁴Si have been measured using the reactions⁶⁴Ni(³⁶S,^35,34Si)^65,66Zn at a³⁶S beam energy of 198 MeV.^34,35Si¹⁴⁺ ions were analysed and identified in a QMG/2 magnetic spectrometer and gas-filled focal-plane detector. The experimental mass excess of³⁵Si was determined to be ?14.58± _0.12 ^0.07 MeV while that of³⁴Si was measured as ?19.961±0.034 MeV. A comparison is made with the results of mass model predictions.     

Line width analysis of a tunable optical filter based on free-space optics

The line width of a tunable optical filter based on free-space optics was analyzed. The relationship between the line width and the Gaussian beam waist was theoretically derived and experimentally verified. The experimental results meet the theoretical analysis well, which is beneficial for the design of a tunable optical filter based on free-space optics.     

Controllable synthesis of high aspect ratio Mg_2B_2O_5 nanowires and their applications in reinforced polyhydroxyalkanoate composites

Highly pure magnesium borate （Mg2B2O5） nanowires with an average diameter of - 30 nm, an average length of 15 μm, and a high aspect ratio of - 500 have been synthesized on a large scale via a two-step method. MgBO2（OH） nanowires with high aspect ratios were first prepared via a PVP-assisted hydrothermal technique. Using these nanowires as precursors, single crystalline Mg2B205 nanowires were synthesized by post-annealing treatment at a relatively low temperature of 700 ℃. The important effect of the MgBO2（OH）-Mg2B2O5 conversion process on the morphology of the Mg2B2O5 nanowires was investigated and it was indicated that the recrystallization process plays an important role in the protection of the one-dimensional （1D） nanostructure. Moreover, the rigidity and the toughness of the Mg2B2O5 nanowire- reinforced PHA composites were tremendously improved compared to those of the pure PHA. Our results demonstrate the effectiveness of Mg2B2O5 nanowires for reinforcement applications in polymer composites.