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[en] We present a Fourier-transform spectroscopic technique for investigation of surfaces and interfaces based on IR-visible sum-frequency generation with femtosecond light pulses. The observed spectrum has a resolution that is independent of the input pulse characteristics. (c) 1999 Optical Society of America

[en] We demonstrate experimentally that visible-visible sum-frequency generation in the bulk of a chiral liquid is observable near electronic resonant transitions. Although the process is electric dipole allowed, it is rather weak because the orientational average over molecules effectively reduces the bulk chiral nonlinearity

[en] The species of Chromium(lll) and Chromium(Vl) in water samples were determined by flow injection on-line preconcentration and separation on two-microcolumn system-derivative flame atomic absorption spectrometry during a collaborative analysis for certification. The Chromium(lll) and Chromium(Vl) in water samples were retained on two micro columns with ion exchange resin and were eluted directly to nebulizers by 15% HNO₃ and 8% NH₄NO₃, respectively. The characteristic concentration ( at the sensitivity grade of 2 mV min^-1 for 1 min of preconcentration time ) for Chromium(lll) and Chromium(Vl) were 0.130 and 0.0985 μg 1^-1, in the order which were 332- and 431- fold better than those of FAAS, and 45-and 47-fold better than those of Fl-FAAS, respectively. The relative standard deviations were 3.27% and 3.66% with corresponding detection limits (3σ) of 0.244 and 0.235 μg 1^-1, respectively. The linear ranges of determinations for Chromium(lll) and Chromium(Vl) were 0 ∼100 μgm 1^-1 with correlation coefficients of 0.9984 to 0.9996. The satisfactory recovery of 94.4%∼106% for Chromium(lll) and Chromium(Vl) could be obtained from water samples

[en] Plant dehydrin (DHN) is a hydrophilic protein widely present in organisms, and it is accumulated when plants encounter adverse environments. Based on the sequence information of DHN family genes in Arabidopsis thaliana, 13 DHN genes were found in maize using the homology sequence alignment method, in which five DHN genes were located on chromosome 8. The maize DHN gene family can be classified into five branches by evolutionary analysis. The DHN proteins contain five subclasses which are Kn, SKn, KnS, YnSKn and FSKn. Analysis of cis-acting elements showed that the promoters of DHN gene family harbor cis-acting elements mainly responsive to stress and plant hormones. Tissue expression patterns revealed that almost all ZmDHN genes are expressed in the embryo and aleurone layer. DHN proteins were mainly distributed in the nucleus and cytoplasm by subcellular localization prediction. The present findings allow insight into understanding maize DHN family genes’ functions and facilitate the molecular breeding of ZmDHNs in coping with abiotic stress. (author)

[en] Hesperidin methyl chalcone (HMC) was a semisynthetic derivative of hesperidin, which owned antiviral and antimicrobial activities. Owing these properties, it can be applied in pharmaceutical industry. However low stability had become a barrier to its application. In order to overcome this problem, an inclusion complex of hesperidin methyl chalcone and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) were prepared by freeze-drying, using some analytical techniques to characterize the inclusion complex, including ultraviolet-visible spectroscopy (UV), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). The results of these analytical techniques indicated that the hesperidin methyl chalcone has been dispersed completely in the HP-beta-CD without a new compound formed, but entrapped inside the cavity of HP-beta-CD. (author)

[en] Optical nonlinearity of liquid crystals (LC) in the isotropic phase can be enhanced by 1 order of magnitude by dissolving 0.1% of anthraquinone dye in the LC. The enhancement decreases by ∼30% when the LC transforms into the nematic phase. The same guest-host effect also exists in non-LC liquids. It can be explained by a model based on the change of guest-host interaction induced by optical excitations of the dye. copyright 1996 The American Physical Society

[en] The first Chinese in-situ tritium release experiment is being carried out in the fission reactor SPRR-300 in the Southwest Institute of Nuclear Physics and Chemistry (SWINPC). Several runs of the experiment were conducted to study tritium generation and release behaviors from China-made γ -LiAlO₂ pellets. The effects of some key operational factors (temperature, sweep gas composition and flow rate) upon tritium release were studied. The results show that the equilibrium tritium release rate at different temperatures approached the tritium generation rate obtained from neutron calculations. The tritium concentration in the sweep gas decreased with increasing the flow rate. Addition of a small quantity of hydrogen greatly enhanced the release of tritium. It was also found that the tritium released in the sweep gas was mostly in the form of HT. However, when the generated tritium was not purged in time, the HTO fraction increased gradually. By using the inventory difference method, through the special run which lasted 72 hours, we determined the diffusion coefficient for tritium in γ-LiAlO₂. The obtained diffusivity and its activation energy were compared with those from other experiments. It was found that the value of Q was close to those from LILA and TTTEx experiments, but the value of D₀ was smaller. 8 refs., 5 figs., 4 tabs

[en] Purpose: Dose calculation software is thoroughly evaluated when it is commissioned; however, evaluation of periodic software updates is typically limited in scope due to staffing constraints and the need to quickly return the treatment planning system to clinical service. We developed a tool for quickly and comprehensively testing and documenting dose calculation software against measured data. Methods: A tool was developed using MatLab (The MathWorks, Natick, MA) for evaluation of dose calculation algorithms against measured data. Inputs to the tool are measured data, reference DICOM RT PLAN files describing the measurements, and dose calculations in DICOM format. The tool consists of a collection of extensible modules that can perform analysis of point dose, depth dose curves, and profiles using dose difference, distance-to-agreement, and the gamma-index. Each module generates a report subsection that is incorporated into a master template, which is converted to final form in portable document format (PDF). Results: After each change to the treatment planning system, a report can be generated in approximately 90 minutes. The tool has been in use for more than 5 years, spanning 5 versions of the eMC and 4 versions of the AAA. We have detected changes to the algorithms that affected clinical practice once during this period. Conclusion: Our tool provides an efficient method for quality assurance of dose calculation software, providing a complete set of tests for an update. Future work includes the addition of plan level tests, allowing incorporation of, for example, the TG-119 test suite for IMRT, and integration with the treatment planning system via an application programming interface. Integration with the planning system will permit fully-automated testing and reporting at scheduled intervals

[en] We have developed multi-channel signal acquisition with a coincidence digital circuit for a two-dimensional detector array of the small-angle neutron scattering spectrometer (SANS) of the Institute of Nuclear Physical Chemistry at the Chinese Academy of Engineering Physics. This paper discusses how to determine such factors as the coincidence time window and program dead time according to the characteristics of the detector signal and how to correct the timer to realize the data coincidence. The whole system can support up to 192 analog channels connected to a fast analog-to-digital converter, supporting speeds of 50 MSPS for each channel managed by a field-programmable gate array (FPGA). The internal clock of the FPGA is 50 MHz and the time accuracy is 20 ns. Preliminary experiments are carried out and the results are presented and discussed. The whole design can fully meet the needs of the spectrometer.