离子色谱法测定大蒜中的糖

为了解大蒜多糖中单糖的组成,在AminoPac PA10(2×250mm)离子色谱分离柱上用10.0mM NaOH溶液作为流动相,以Au为工作电极,Ag/AgCl为参比电极的脉冲安培检测器,分离检测了大蒜多糖水解产生的单糖成分及含量.实验结果表明,大蒜多糖中阿拉伯糖、甘露醇、葡萄糖和果糖的相对含量分别为0.22%、6.43%、0.14%和93.20%.该方法具有灵敏度和精密度高、分离效果好及样品不需要衍生化处理的优点,适合大蒜样品中单糖或大蒜多糖水解后单糖的分析.     

Error compensation of four and five buckets wavefront extraction algorithms in phase-shifting interferometer

The phase-shifting method is all along an important wavefront extraction technique in the interferometer. Moreover, to require almost real-time measurement an algorithm with a small number of grabbed buckets is very helpful to the phase-shifting interferometer. Therefore, those algorithms within five buckets are very practical and are given more attention. In the paper, popular phase shifting algorithms within five buckets are compared and new four and five buckets algorithms are developed to compensate for two dominate error sources which are linear phase shift deviation and detector nonlinearity. Numerical simulations and wavefront extraction experiment verify that the proposed compensation algorithms are insensitive to linear phase shift deviation and detector nonlinearity compared with classical four and five bucket algorithm.     

The detection and estimation of the change point in a disccrete-time stochastic system

A piecewise-constant process containing a single jump is observed under noise in the context of discrete time. The conditional density and maximum a posteriori (MAP) estimator of the jump time as well as the Bayes detector of the jump itself are determined using the powerful measure transformation approach. The Bayes detector provides a convenient sequential detection rule for practical on-line implementation. An asymptotic result for the distribution of the MAP estimator's estimation error and the corresponding convergence rate are derived. This result provides a reference measure of optimal performance for jump-time estimators in discrete-time stochastic systems that does not depend on the jump time's prior distribution     

Stability Indicating Hplc Method for the Determination of Sparfloxacin (Spar)

ABSTRACT

A rapid, sensitive and stability indicating method for the determination of sparfloxacin (SPAR) by RP - HPLC has been developed on a Merck RP - Select B (5 μm; 12.5 cm x 4.0 mm) column using a mobile phase of water: acetonitrile: triethylamine (80 : 20 : 0.2 v/v) pH of which was adjusted to 2.6 with orthrophosphoric acid. The flow rate was 1 ml / min. and the detection was carried out at 304 nm using Waters 486 variable wavelength detector. The retention time for SPAR was 7.2 min. Linearity range was from 8 - 1000 ppm. The method showed good precision and accuracy when applied to two brands of tablets containing SPAR. In alkaline media SPAR is stable where as it undergoes degradation in acidic and oxidising conditions generating different degradation products the nature of which is required to be established. The proposed method nicely separates the degraded products from SPAR and hence can be used as stability indicating method for the assay of SPAR.     

Extremely high-frequency piezoelectroacoustic transducer based on BN-tube/SiC-whiskers rope

Innovative idea of piezoelectric electroacoustic transducer in extremely high-frequency terahertz range on the basis of BN-tube/SiC-whiskers rope is suggested and substantiated. Unlike an acoustic spectrum of solid rectangular pins and films used so far in ultrasonic pulsers and receivers, in the acoustic spectrum of circular hollow nanotubes, the peculiar squash E_2g and the subsequent E_ng modes of starlike chain belonging to a gallery of whispering acoustic modes was shown by ab initio RHF/6-31G calculations to exist in the Raman spectra. Inherent important feature of these standing vibrations is their weak attenuation and high frequency, which, as depended on the nanotube diameter, fall in the range of about 1 GHz–1 THz. Hypersound was suggested to be excited by resonant microwaves using the piezoelectric properties of BN heteropolar nanotubes and then to transmit it into a sample by high modulus encapsulated SiC-whiskers. Such BN-tube/SiC-whiskers of 100–800 nm in diameter and with 20 aspect ratio were synthesized by carbothermal and CVD techniques. Cactus-like arrays of SiC nanowhiskers were synthesized by CVD technique. A sketch of the hypersound generator/detector, with the piezoelectroacoustical transducer on the basis of the BN-tube/SiC-whisker assembly serving as hypersonic antenna, was advanced.     

Analysis of trace components in gases by gas chromatography

Summary Relationships are derived describing how the detection limit of a chromatographic system depends on the minimum detectable limit of the detector and the chromatographic parameters such as column length, efficiency, carrier gas flow rate and the capacity factor. Performance data of detectors developed in the last 25 years at the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences are given and a few selected application examples are listed. These include trace analysis by preconcentration and by direct analysis and the utilization of multidimensional gas chromatography with two columns, two detectors, a 12-port valve, and a catalytic conversion reactor.     

Emergence of a Lanthanide Chalcogenide as an Ideal Scintillator for a Flexible X-ray Detector

The development of high-performance X-ray detectors requires scintillators with fast decay time, high light yield, stability, and X-ray absorption capacity, which are difficult to achieve in a single material. Here, we present the first example of a lanthanide chalcogenide of LaCsSiS₄ : 1 % Ce³⁺ that simultaneously integrates multiple desirable properties for an ideal scintillator. LaCsSiS₄ : 1 % Ce³⁺ demonstrates a remarkably low detection limit of 43.13 nGy_air s⁻¹ and a high photoluminescence quantum yield of 98.24 %, resulting in a high light yield of 50480±1441 photons/MeV. Notably, LaCsSiS₄ : 1 % Ce³⁺ exhibits a fast decay time of only 29.35±0.16 ns, making it one of the fastest scintillators among all lanthanide-based inorganic scintillators. Furthermore, this material shows robust radiation and moisture resistance, endowing it with suitability for chemical processing under solution conditions. To demonstrate the X-ray imaging capacity of LaCsSiS₄ : 1 % Ce³⁺, we fabricated a flexible X-ray detector that achieved a high spatial resolution of 8.2 lp mm⁻¹. This work highlights the potential of lanthanide chalcogenide as a promising candidate for high-performance scintillators.     

Rationale and principle of an instrument measuring lung deposited nanoparticle surface area

The risk of nanoparticles by inhalation for human health is still being debated but some evidences of risk on specific properties of particles <100 nm diameter exist. One of the nanoparticle parameters discussed by toxicologists is their surface area concentration as a relevant property for e.g. causing inflammation. Concentrations of these small particles (~ <100 nm) are currently not measured, since the mass concentrations of these small particles are normally low despite large surface area concentrations. Airborne particles will always be polydisperse and show a size distribution. Size is normally described by an equivalent diameter to include deviations in properties from ideal spherical particles. Here only nanoparticles below a certain size to be defined are of interest. Total concentration measures are determined by integration over the size range of interest. The ideal instrument should measure the particles according to the size weighting of the wanted quantity. Besides for the geometric surface area the wanted response function can be derived for the lung deposited surface area in the alveolar region. This can be obtained by weighting the geometric surface area as a function of particle size with the deposition efficiency for the alveolar region for e.g. a reference worker for work place exposure determination. The investigation of the performance of an Electrical Aerosol Detector (EAD) for nearly spherical particles showed that its response function is close to the lung deposited surface areas in different regions of the human respiratory system. By changing the ion trap voltage an even better agreement has been achieved. By determining the size dependent response of the instrument as a function of ion trap voltage the operating parameters can be optimized to give the smallest error possible. Since the concept of the instrument is based on spherical particles and idealized lung deposition curves have been used, in all other cases errors will occur, which still have to be defined. A method is now available which allows in principle the determination of the total deposited surface area in different regions of the lung in real time. It can easily be changed from one deposited region to another by varying the ion trap voltage. It has the potential to become a routine measurement technique for area measurements and personal control in e.g. work place environments.     

Detector and trigger challenge for supersymmetrical dark matter scenarios at the international linear collider

Two supersymmetrical (SUSY) dark matter scenarios are discussed to illustrate how challenging it is to detect and trigger these events out of standard model background events at a future international linear collider (ILC).      

A novel method for detecting and counting overlapping tracks in SSNTD by image processing techniques

Overlapping object detection and counting is a challenge in image processing. A new method for detecting and counting overlapping circles is presented in this paper. This method is based on pattern recognition and feature extraction using “neighborhood values“ in an object image by implementation of image processing techniques. The junction points are detected by assignment of a value for each pixel in an image. As is shown, the neighborhood values for junction points are larger than the values for other points. This distinction of neighborhood values is the main feature which can be utilized to identify the junction points and to count the overlapping tracks. This method can be used for recognizing and counting charged particle tracks, blood cells and also cancer cells. The method is called “Track Counting based on Neighborhood Values” and is symbolized by “TCNV”.