Electrophoresis for the analysis of heparin purity and quality

The adulteration of raw heparin with oversulfated chondroitin sulfate (OSCS) in 2007-2008 produced a global crisis resulting in extensive revisions to the pharmacopeia monographs and prompting the FDA to recommend the development of additional methods for the analysis of heparin purity. As a consequence, a wide variety of innovative analytical approaches have been developed for the quality assurance and purity of unfractionated and low-molecular-weight heparins. This review discusses recent developments in electrophoresis techniques available for the sensitive separation, detection, and partial structural characterization of heparin contaminants. In particular, this review summarizes recent publications on heparin quality and related impurity analysis using electrophoretic separations such as capillary electrophoresis (CE) of intact polysaccharides and hexosamines derived from their acidic hydrolysis, and polyacrylamide gel electrophoresis (PAGE) for the separation of heparin samples without and in the presence of its relatively specific depolymerization process with nitrous acid treatment.     

Iridium-catalyzed alternative of the Meinwald rearrangement

A novel and easy to handle procedure for the regioselective rearrangement of epoxides has been developed, based on an iridium catalyst.     

Polynomial time approximation schemes and parameterized complexity

In this paper, we study the relationship between the approximability and the parameterized complexity of NP optimization problems. We introduce a notion of polynomial fixed-parameter tractability and prove that, under a very general constraint, an NP optimization problem has a fully polynomial time approximation scheme if and only if the problem is polynomial fixed-parameter tractable. By enforcing a constraint of planarity on the W-hierarchy studied in parameterized complexity theory, we obtain a class of NP optimization problems, the planar W-hierarchy, and prove that all problems in this class have efficient polynomial time approximation schemes (EPTAS). The planar W-hierarchy seems to contain most of the known EPTAS problems, and is significantly different from the class introduced by Khanna and Motwani in their efforts in characterizing optimization problems with polynomial time approximation schemes.     

新型固态荧光增强的萘酰亚胺衍生物的合成与发光行为

萘酰亚胺及其衍生物由于其独特的光物理性质、光稳定性和电子接受能力而广泛应用于荧光传感器、光电材料等领域。本文设计并合成了一种新型固态荧光增强的萘酰亚胺衍生物,其结构经¹H NMR、 ¹³C NMR、 MS和IR表征,并研究了该化合物的固态和溶液发光行为。结果表明：该化合物不仅在稀溶液中表现出可调谐的可见光发射,而且表现出固态荧光增强,这种行为与ACQ和AIE发色团明显不同。     

Synthesis and vibrational circular dichroism of enantiopure chiral oxorhenium(V) complexes containing the hydrotris(1-pyrazolyl)borate ligand

The infrared and vibrational circular dichroism (VCD) spectra of six chiral oxorhenium(V) complexes, bearing a hydrotris(1-pyrazolyl)borate (Tp) ligand, have been investigated. These complexes are promising candidates for observation of parity violation (symmetry breaking due to the weak nuclear force). New chiral oxorhenium complexes have been synthesized, namely, [TpReO(eta2-O(CH3)CH2CH2O-O,O)] (4a and 4b) diastereomers and [TpReO(eta2-N(CH3)CH2CH2O-N,O)] (5) and [TpReO(eta2-N(tBu)CH2CH2O-N,O)] (6) enantiomers. All compounds could be obtained in enantiomerically pure form by using either column chromatography or HPLC over chiral columns. VCD spectroscopy of these compounds and of [TpReO(eta2-N(CH3)CH(CH3)CH(Ph)O-N,O)] (2) and [TpReO(eta2-N(CH2)3CHCO2-N,O)] (3) (with chiral bidentate ligands derived, respectively, from ephedrine and proline) were studied. This allowed the absolute configuration determination of all compounds together with their conformational analysis, by comparing calculated and experimental spectra. This is the first VCD study of rhenium complexes which further demonstrates the applicability of VCD spectroscopy in determining the chirality of inorganic complexes.     

Ultrafast laser assisted fabrication of ZnO nanorod arrays for photon detection applications

Orderly aligned ZnO nanorod arrays were grown by the ultrafast laser assisted ablation deposition method. These nanorod arrays were further used to make efficient p-n heterojunction photodetector arrays, which have the potential to have nanoscale spatial resolution for imaging, unique incident polarization discrimination capability, and much improved quantum efficiency as well as detection sensitivity. Both front- and back-illumination photodetection schemes were demonstrated by growing those ZnO nanorod arrays on p-type silicon and p-type Zn_0.9Mg_0.1O-coated Al₂O₃ (0 0 0 1) substrates, respectively. Typical diode rectification behavior and photosensitivity were observed in both designs through I-V and photocurrent measurements.     

A linear viscoelastic model for solid polyethylene

Stress relaxation tests have been carried out on a blue, pipe grade PE 80 medium density polyethylene (BP Chemicals), to provide thermo-viscoelastic rheology for use in calculating thermal stresses in pipe production. Stresses up to 4 MPa were used, with strains up to about 2%, in tests at temperatures from 23° to 90°C. Within this range a linear viscoelastic model was applicable, provided the initial ramp strain rate was less than 7×10^–5 s^–1. The stress relaxation data was fitted directly by a model incorporating an elastic response to volumetric strains, and a generalised linear solid model, consisting of two Maxwell elements and a purely elastic element in parallel, for deviatoric strains. Arrhenius type temperature dependence of relaxation times and shear moduli is found, and within experimental accuracy the temperature dependence of all these model parameters is the same. As a consequence, and provided that the duration of the strain ramp is sufficiently short relative to relaxation times, the model leads to time-temperature superposition of the relaxation moduli, using the same shift factor on both the response magnitude and time axes.     

Memetic techniques for examination timetabling

In this paper, we investigate the effectiveness of combining the main components of the memetic algorithms (MAs) on the quality of solutions produced for Uncapacitated Examination Timetabling Problem (UETP). These components are recombination, randomness, and neighbourhood structures. The Harmony Search Algorithm (HSA), which is a variation of MA, is used to perform different combinations of these components. It has three main components: Memory Consideration using the recombination, Random Consideration using the randomness and Pitch Adjustment using the neighbourhood structures (or local search). The combinations among MA components are evaluated using 17 different scenarios each of which reflects a combination of one, two or three components. The results show that the system that combines the three components (recombination, randomness, and neighbourhood structures) provides the best results. Furthermore, the best results obtained from the convergence scenarios were compared with 22 other methods that used a de facto dataset defined by Carter et al. (in Journal of the Operational Research Society 74:373–383, 1996) for UETP. The results exceed those produced by the previous methods in 2 out of 12 datasets.