Experiments and analyses of a new type optical system for computed radiography

A new high-performance laser scanning system is designed. In this system, a scanning arm consisting of a pentagonal prism and a scanning object lens is used to replace the traditional Fθ lens, and a circular imaging plate transmission mechanism is specially designed in order to meet the requirement of the scanning arm. At the same time, the stimulation fluorescence can be obtained by the scanning arm. Some main factors that influence the spatial resolution and the performance of the laser scanner system are analyzed, and the analysis results are presented, which is helpful for further optimization design of the system. Experimental results indicate that the images obtained by the system have good visual effects and can meet the requirements of industrial inspection.     

Improving the precision of fluorescence lifetime measurement using a streak camera

Streak camera has high temporal resolution and high sensitivity, and is a powerful tool in biomedical study to measure fluorescence lifetime and perform fluorescence lifetime imaging. However, nonuniformity of the gain in the streak tube and nonlinearity of the sweeping speed limit the precision of fluorescence lifetime measurement, particularly when fluorescence lifetimes are short. We have constructed a two-photon excitation fluorescence lifetime measurement system that is based on a synchroscan streak camera and have developed accordingly a method to correct the effect of gain nonuniformity and nonlinearity of sweeping speed on the measurement precision. A continuous-wave laser of high stability is used to calibrate the gain of the streak camera, and a Fabry-Perot etalon is used to calibrate the nonlinearity of the sweeping speed. Fitting algorithms are used to correct the gain of the streak camera and nonlinearity of the sweeping speed respectively, which significantly improves the measurement precision of the system, as characterized through the fluorescence lifetime of the short-lived fluorescence dye, Rose Bengal. Experimental results show that the measurement fluctuation of the lifetime has been improved from more than 10% to 2% after correcting the effects of gain nonuniformity and sweeping speed nonlinearity.     

A new cerebroside from fruits of Ailanthus altissima Swingle

A new cerebroside and three known cycloartan triterpenes were isolated from fruits of Ailanthus altissima Swingle. Their structures were identified as 1-O-beta-D-glucopyranosyl-(2S, 3R, 4E, 9E)-2-(2'R-hydroxyhexadecenoy)-4, 9-octadecadiene-1, 3-diol (1), 9, 19-cyclolanost-23 (Z)-ene-3beta, 25-diol (2), cycloart-25-ene-3beta, 24R-diol (3), and cycloart-25-ene-3beta, 24S-diol (4) by means of chemical and spectroscopic analysis. Compounds 2, 3, and 4 were isolated from genus Ailanthus for the first time. The analgesic activity of 1 was also evaluated.     

A new anthraquinone from Galium verum L

A new anthraquinone (4) and three known anthraquinones (1-3) were isolated from Galium verum L. Their structures were identified as 1,3-dihydroxy-2-methylanthraquinone (1), physcion (2), 2-hydroxy-1,3-dimethoxyanthraquinone (3), 2,5-dihydroxy-1,3-dimethoxyanthraquinone (4) by means of chemical and spectroscopic analysis. Compound 2 was isolated from the genus Galium for the first time. In addition, compound 4 was assayed for antimicrobial activity in vitro.     

On the spectral radius of trees with fixed diameter

Let T_{(n, d)} be the set of trees on n vertices with diameter d. In this paper, the first spectral radii of trees in the set T_{(n, d)} (3 ? d ? n − 4) are characterized.     

Advances in methods and algorithms in a modern quantum chemistry program package

Advances in theory and algorithms for electronic structure calculations must be incorporated into program packages to enable them to become routinely used by the broader chemical community. This work reviews advances made over the past five years or so that constitute the major improvements contained in a new release of the Q-Chem quantum chemistry package, together with illustrative timings and applications. Specific developments discussed include fast methods for density functional theory calculations, linear scaling evaluation of energies, NMR chemical shifts and electric properties, fast auxiliary basis function methods for correlated energies and gradients, equation-of-motion coupled cluster methods for ground and excited states, geminal wavefunctions, embedding methods and techniques for exploring potential energy surfaces.     

Preparation and characterization of poly(N-isopropylacrylamide)-modified poly(2-hydroxyethyl acrylate) hydrogels by interpenetrating polymer networks for sustained drug release

In order to investigate the influence of hydrophobic moieties formed by poly(N-isopropylacrylamide) (PNIPAm) in a hydrogel matrix on the release behavior of the hydrogel, a series of poly(N-isopropylacrylamide) (PNIPAm)-modified poly(2-hydroxyethyl acrylate-co-2-hydroxyethyl 2-hydroxyethyl methacrylate) (P(HEA-co-HEMA)) via interpenetrating polymer networks (IPNs) were prepared by a sequential UV solution polymerization. Interestingly, it was found that P(HEA-co-HEMA)/PNIPAm IPN indicated a single glass transition temperature (T(g)) and the T(g)s of the IPNs increased with an increase in the PNIPAm component. This phenomenon may be attributed to hydrogen bonding between the two polymer networks, but the hydrogen bonding exerts less influence on the swelling behavior of the IPNs, due to the fact that IPNs can respond to changes in temperature like PNIPAm. Using 2-[(diphenylmethyl)sulphiny]acetamide (modafinil, MOD) and p-hydroxybenzoic acid (HBA) as model drug compounds, the release behavior of the IPNs was studied at body temperature, and it was found that the presence of PNIPAm could retard drug release regardless of the solubility of the drugs. Release profiles of HBA from the IPNs and their component samples as a function of time at 37 degrees C.     

Fluorescence quenching method for the determination of sodium carboxymethyl cellulose with acridine yellow or acridine orange

In near neutral to weak basic media, sodium carboxymethyl cellulose (NaCMC) will dissociate to become a macro polymeric anion, which can react with acridine yellow (AY) or acridine orange (AO) to form an ion-association complex resulting in fluorescence quenching of the acridine dyes. The maximum fluorescence quenching wavelength is 505 nm (lambda(ex)=440 nm) for AY system and 530 nm (lambda(ex)=493 nm) for AO system, respectively. The fluorescence quenching values (DeltaF) are directly proportional to the concentrations of NaCMC and the linear ranges are 20.0-4000 microg/L for AY system and 20.0-7000 microg/L for AO system, separately. This method has high sensitivity and the detection limits for NaCMC are 58.0 microg/L (AY system) and 157.2 microg/L (AO system). The effects of coexistent substance have been investigated, and the results show that this method has a relatively good selectivity. A fluorescence quenching method for the determination of NaCMC based on the ion-association reactions of CMC polymeric anion with a basic acridine dye was developed. The method is sensitive, simple and fast.     

"Click" synthesis of small molecule probes for activity-based fingerprinting of matrix metalloproteases

By using "Click Chemistry", we achieved the facile synthesis of various affinity-based hydroxamate probes that enable generation of activity-based fingerprints of a variety of metalloproteases, including matrix metalloproteases (MMPs), in proteomics experiments.     

UV-visible spectroscopic study of the salicyladehyde benzoylhydrazone and its cobalt complexes

Salicyladehyde benzoylhydrazone (SBH) has three groups suitable for forming coordination bond with transition metal. The UV-vis absorption spectra of SBH and its Co(II) complexes in various media were studied by using the deconvolution method. It is found that the structure of complex in solution is different from those in solid crystals. The nature of complexes in solution depends on acidity of the phenolic proton of SBH and on the medium. In neutral or slightly acid medium, the SBH is a non-charged bidentate ligand. And the "free" hydroxyl group on the SBH molecule makes it possible to form hydrogen bonds in solution. In basic medium, the SBH is a mono, negatively charged tridentates ligand.