Hyperelliptic functions and geodesic equations

A method for solving geodesic equations in Schwarzschild–de Sitter space–times and higher dimensional Schwarzschild space–times is presented. The solutions are derived from Jacobi's inversion problem on a Riemann surface of genus 2 restricted to the set of zeros of the theta function, which is called a theta–divisor. In its final form, the solutions are given in terms of derivatives of Kleinian sigma functions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Gadolinium doped Ceria nanocrystals synthesized from mesoporous silica

Highly crystalline and thermally stable gadolinium doped ceria (GDC) particles have been synthesized by hard template route for the first time. This oxide is being recognized as an intermediate temperature (500–700 °C) electrolyte material for applications in solid-oxide fuel cells. The GDC particles show high crystallinity and nanometric size (2.83 ± 0.05 nm in diameter) and Raman analyses confirm the formation of the solid solution instead of a CeO₂ and Gd₂O₃ mixture. EDX and EELS studies indicate a stoichiometry coherent with the Gd_0.2Ce_0.8O_1.9 phase. The synthesized nanometric powder is expected to be used in solid oxide fuel cells as well as in the catalytic treatment of automobile exhaust fumes.

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Graphical abstract

     

Voice Change in Seasonal Allergic Rhinitis

Voice problems are seldom reported in pollen allergy, although the allergic reaction involves the entire airways. The objective of this study was to investigate voice dysfunction during the pollen season in patients with allergic rhinitis. Thirty patients with verified birch pollen allergy and 30 controls were investigated twice, during the pollen season and outside the pollen season. Both times they scored respiratory and voice symptoms, the latter with the validated questionnaire Voice Handicap Index (VHI), and performed standardized voice recordings. These recordings were analyzed in a controlled manner by a professional voice therapist. During the allergy season, patients reported more respiratory and voice symptoms compared with controls. Those with blinded scored voice dysfunction scored their voice quality during springtime as 31 mm (95% confidence interval [CI] 20-42 mm), compared with 13 mm (95% CI 6-21 mm for participants without voice dysfunction (P<0.01). Furthermore, the group with experienced voice dysfunction scored significantly higher on the VHI in the functional and physical domains and in the total VHI score. Although voice problems during the pollen season are rarely discussed, in allergic rhinitis the larynx may also be involved. These findings support that some patients experience voice change, an experience which can be objectively confirmed.     

Protein Backbone N Relaxation Rates as a Tool for the Diagnosis of Structure Quality

In the work reported herein we define a structure validation factor that depends on protein backbone ¹⁵N relaxation rates. This is an alternative method to the previously defined quality factors derived from anisotropic chemical shifts or residual dipolar couplings. We have used the structure dependence of ¹⁵N relaxation rates of anisotropically tumbling proteins to calculate this structure diagnosis factor and have used it to demonstrate the improvement of protein structures refined with residual dipolar couplings.     

Improving boron isotope ratio measurement precision with quadrupole inductively coupled plasma-mass spectrometry

A method was developed to improve the precision of inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) for the determination of boron isotope ratios (¹¹B/¹⁰B) in various environmental materials including seawater. This approach is based on the common analyte internal standardization (CAIS) chemometric algorithm. The sample solution obtained after digestion is spiked with lithium, and both ⁷Li/⁶Li and ¹¹B/¹⁰B values are measured using long-counting periods (20 min). The CAIS algorithm corrects the measured ¹¹B/¹⁰B values for (a) statistical fluctuations resulting from short-term noise; (b) drift in ¹¹B-to-¹⁰B ratio as a result of long-term deviation in instrumental parameters likely to occur during long counting times; (c) change in ¹¹B-to-¹⁰B ratio caused by variation in matrix elements concentrations; and (d) drift in mass bias correction factor. Comparing boron isotopic ratios in seawater measured by conventional and the new isotope ratio methods validates the procedure. A synthetic isotopic mixture of boron SRM 951 and enriched ¹⁰B SRM 952 also was examined. The CAIS method provided a measured boron isotopic ratio precision of 0.05% R.S.D. while eliminating 5.1% matrix concentration error and 0.25% instrumental drift error.     

Characterization of a high-productivity recombinant strain of Zymomonas mobilis for ethanol production from glucose/xylose mixtures

The fermentation characteristics of a recombinant strain of Zymomonas mobilis ZM4(pZB5) capable of converting both glucose and xylose to ethanol have been further investigated. Previous studies have shown that the strain ZM4(pZB5) was capable of converting a mixture o 65 g/L of glucose and 65 g/L of xylose to 62 g/L of ethanol in 48 h with an overall yield of 0.46 g/g. Higher sugar concentrations (e.g., 75/75 g/L) resulted in incomplete xylose utilization (80 h). In the present study, further kinetic evaluations at high sugar levels are reported. Acetate inhibition studies and evaluation of temperature and pH effects indicated increased maximum specific uptake rates of glucose and xylose under stressed conditions with increased metabolic uncoupling. A high-productivity system was developed that involved a membrane bioreactor with cell recycling. At sugar concentrations of approx 50/50 g/L of glucose/xylose, an ethanol concentration of 50 g/L, an ethanol productivity of approx 5 g/(L·h), and a yield (Y _p/s) of 0.50 g/g were achieved. Decreases in cell viability were found in this system after attainment of an initial steady state (40–60 h); a slow bleed of concentrated cells may be required to overcome this problem.     

The influence of hemicellulose on fibril aggregation of kraft pulp fibres as revealed by FE-SEM and CP/MAS 13C-NMR

Three Norway spruce pulps were produced using different kraft pulping methods, in order to obtain large differences in cellulose and hemicellulose proportions at a similar lignin content. The hemicellulose content in the three pulps varied between 10% and 22%. The aim of the study was to evaluate the influence of cellulose and hemicellulose on fibre ultrastructure and correlate this with the differences observed in the mechanical properties between the pulps. The ultrastructure of the pulp fibres were studied using Field Emission Scanning Electron Microscopy (FE-SEM) and Solid-State Cross Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance (CP/MAS ¹³C-NMR) in combination with spectral fitting. CP/MAS ¹³C-NMR measured the average bulk properties of the pulp fibres, while FE-SEM allowed for observations on the ultrastructure of fibre surfaces. The ultrastructure of the fibres varied with varying hemicellulose content. The pulp with a high hemicellulose content had a porous surface structure. In fibres with a low hemicellulose content, the fibril aggregates (macrofibrils) formed a much more compact surface structure. With CP/MAS ¹³C-NMR this change was reflected by an increase in average fibril aggregate width with decreasing hemicellulose content. Results from FE-SEM and CP/MAS ¹³C-NMR correlated well. The changes recorded in ultrastructure may explain the very different mechanical properties reported previously for pulps with different hemicellulose content.     

Elucidation of the function of two glycosyltransferase genes (lanGT1 and lanGT4) involved in landomycin biosynthesis and generation of new oligosaccharide antibiotics

BACKGROUND: The genetic engineering of antibiotic-producing Streptomyces strains is an approach that became a successful methodology in developing new natural polyketide derivatives. Glycosyltransferases are important biosynthetic enzymes that link sugar moieties to aglycones, which often derive from polyketides. Biological activity is frequently generated along with this process. Here we report the use of glycosyltransferase genes isolated from the landomycin biosynthetic gene cluster to create hybrid landomycin/urdamycin oligosaccharide antibiotics. RESULTS: Production of several novel urdamycin derivatives by a mutant of Streptomyces fradiae Tü2717 has been achieved in a combinatorial biosynthetic approach using glycosyltransferase genes from the landomycin producer Streptomyces cyanogenus S136. For the generation of gene cassettes useful for combinatorial biosynthesis experiments new vectors named pMUNI, pMUNII and pMUNIII were constructed. These vectors facilitate the construction of gene combinations taking advantage of the compatible MunI and EcoRI restriction sites. CONCLUSIONS: The high-yielding production of novel oligosaccharide antibiotics using glycosyltransferase gene cassettes generated in a very convenient way proves that glycosyltransferases can be flexible towards the alcohol substrate. In addition, our results indicate that LanGT1 from S. cyanogenus S136 is a D-olivosyltransferase, whereas LanGT4 is a L-rhodinosyltransferase.     

UV spectrophotometry and nonaqueous determination of terbinafine hydrochloride in dosage forms.

An ultraviolet spectrophotometric and a nonaqueous volumetric method for determining terbinafine hydrochloride (TH) in pharmaceutical formulations are presented. The UV spectrophotometric procedure was developed for assay of TH in raw materials, tablets, and creams. The method was tested for linearity (0.8-2.8 micrograms/mL, r = 0.9997), recovery (102.00% for creams and 99.90% for tablets) and precision (101.3%, CV = 0.96%, n = 9, for creams; 100.25%, CV = 1.08%, n = 9, for tablets). The volumetric method involves titration of TH with 0.05M perchloric acid with crystal violet as indicator. This method was used for quantitative determination of TH in raw materials and tablets. Mean recovery and precision were, respectively, 100.41 and 101.18% (CV = 1.64%, n = 9) for TH tablets. There were no significant differences between the proposed methods and a previously described high-performance liquid chromatographic method. The UV spectrophotometric and titrimetric methods are potentially useful for a routine laboratory because of their simplicity, rapidity, and accuracy.