PHOTODYNAMIC DAMAGE AND ITS REPAIR IN Vibrio cholerae

Abstract— Repair of photodynamic damage induced by acriflavine and visible light has been examined in three strains of Vibrio cholerae differing in their capabilities to repair ultraviolet (UV) light induced DN A damage. Excision repair deficient wild type cells of strain 154 are more sensitive to photodynamic treatment compared to repair proficient cells of strain 569B. However, no difference in their capabilities to repair of damage following photodynamic treatment can be detected. No single-strand breaks in the irradiated cell DNA are observed when the cell survival is more than 10%. Single-strand breaks observed at cell survival less than 5% are not dark repairable even in excision repair proficient wild type cells. Repair of membrane damage can partially account for the recovery observed at low doses. In contrast, radiation-sensitive mutant 569B_s cells which lack both excision and medium-dependent dark repair for UV-lesions are most efficient in repairing damage induced by photodynamic treatment.     

Condensed cyclic and bridged-ring systems. VII. Acid-catalysed cyclisation of methyl substituted benzylcyclohexanols. Factors influencing the nature of cyclisation products

The gross structures of the cyclised products from the acid-catalysed cyclisations of 2-benzyl-1, 3-dimethylcyclohexanol (6) and 1-benzyl-3, 5-dimethylcyclohexanol (11) revealing the influence of the structure of the benzylcyclohexanol derivative, and of the cyclisation reagent, have been evaluated. Polyphosphoric acid and aluminium chloride catalysed cyclisations of (6) result in the formation of predominantly 1, 4a-dimethyl-1, 2, 3, 4, 4a, 9a-hexahydrofluorene (7) and 4, 9-dimethyl-7, 8-benzobicyclo [3.3.1] non-7-ene (9) respectively. Under the same conditions, (11) produced cyclised products consisting mostly the benzobicyclo [3.3.1] non-7-ene derivative (12), characterised through 1,3-dimethyl-7,8-benzobicyclo [3.3.1] non-6-oxo-7-ene (14) by oxidation with chromium trioxide. Phosphorus pentoxide induced cyclisation of (6), followed by oxidation gave a mixture of the bridged-ring ketone (10) and the 9-oxohydrofluorene (8) in a ratio ofca. 3 : 2, whereas 2-benzyl-5-methylcyclohexanol (19) resulted in mostly 2-methyl-7,8-benzobicyclo [3.3.1] non-6-oxo-7-ene (19).     

Large magnetic field effect on back electron transfer from uncharged radical to its cationic partner in anionic micelle

The magnetic field effect (MFE) on the radical pair (RP) generated by photoexcitation of the acetyl derivative of phenyl pyrylium ion (APP⁺) in the presence of biphenyl, an electron donor, has been investigated. The escape yield at 3.5 T is more than ten times the zero-field value. The MFE reaches near-saturation twice, once at fields of the order of 10mT and again at about 3.5 T. The low-field variation of the MFE conforms to the pattern expected for the isotropic HFC mechanism, and the high-field variation to that expected for the relaxation mechanism. In this particular system two types of radical pair are generated, one by electron transfer from the donor to the acceptor and another by H-abstraction from the micelle. The MFEs on the two types of ³RP have been compared.     

Efficient and selective enzymatic acylation reaction: separation of furanosyl and pyranosyl nucleosides

Candida antarctica lipase-B (CAL-B) immobilized on lewatite selectively acylated the primary hydroxyl group of the furanosyl nucleoside in a mixture of 1-(alpha-D-arabinofuranosyl)thymine and 1-(alpha-D-arabinopyranosyl)thymine. This selective biocatalytic acylation of furanosyl nucleoside has enabled us an easy separation of arabinofuranosyl thymine from an inseparable mixture with arabinopyranosyl thymine. The primary hydroxyl selective acylation methodology of arabinonucleoside has also been successfully used for the separation of 1-(beta-D-xylofuranosyl)thymine and 1-(beta-D-xylopyranosyl)thymine from a mixture of the two, which demonstrate the generality of the enzymatic methodology for separation of furanosyl and pyranosyl nucleosides.     

Gravimetric determination of beryllium with acetoacetanilide

Summary An organic reagent viz. acetoacetanilide has been found out which precipitates beryllium quantitiatively aboveph 5.5. The complex, Be(C₁₂H₁₀O₂N)₂, containing 2.49% Be can be weighed directly after drying. Beryllium can be precipitated from solutions containing aluminium and iron by masking these foreign elements with EDTA. A method has also been described for the determination of beryllium content in beryl.

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Zusammenfassung Beryllium kann oberhalbph 5,5 mit Acetoacetanilid quantitativ gefällt werden. Der gebildete Komplex, Be(C₁₀H₁₀O₂N)₂, der 2,49% Be enthält, kann gleich nach dem Trocknen gewogen werden. Die Gegenwart von Aluminium und Eisen stört nicht, wenn äDTA als Maskierungsmittel zugegeben wird. Die Bestimmung von Beryllium in Beryll wird ebenfalls beschrieben.

     

A standby system with two types of repair persons

A continuously monitored one‐unit system, backed by an identical standby unit, is perfectly repaired by an in‐house repair person, if achievable within a random or deterministic patience time (DPT), or else by a visiting expert, who repairs one or all failed units before leaving. We study four models in terms of the limiting availability and limiting profit per unit time, using semi‐Markov processes, when all distributions are exponential. We show that a DPT is preferable to a random patience time, and we characterize conditions under which the expert should repair multiple failed units (rather than only one failed unit) during each visit. We also extend the method when life‐ and repair times are non‐exponential. Copyright © 2009 John Wiley & Sons, Ltd.     

Fabrication of microfluidic mixers and artificial vasculatures using a high-brightness diode-pumped Nd:YAG laser direct write method

This paper describes a direct write laser technology, which is fast and flexible, for fabricating multiple-level microfluidic channels. A high brightness diode-pumped Nd-YAG laser with slab geometry was used for its excellent beam quality. Channels with flat walls and staggered herringbone ridges on the floor have been successfully fabricated and their ability to perform passive mixing of liquid is discussed. Also, a multi-width multi-depth microchannel has been fabricated to generate biomimetic vasculatures whose channel diameters change according to Murray's law, which states that the cube of the radius of a parent vessel equals the sum of the cubes of the radii of the daughters. The multi-depth architecture allows for flow patterns to resemble physiological vascular systems with lower overall resistance and more uniform flow velocities throughout the network compared to planar patterning techniques which generate uniformly thin channels. The ability to directly fabricate multiple level structures using relatively straightforward laser technology enhances our ability to rapidly prototype complex lab-on-a-chip systems and to develop physiological microfluidic structures for tissue engineering and investigations in biomedical fluidics problems.     

Separation of titanium, iron and aluminium on a chelating resin with benzoylphenylhydroxylamine group and application to bauxite and clay

Summary A chelating polystyrene based resin containing N-benzoyl-N-phenylhydroxylamine has been sythesized by two methods and characterized. Conditions for quantitative separation of Ti(IV), Fe(III) and Al(III) on the resin have been studied. A method has been developed for the determination of these three metal ions in bauxite or clay samples after their separation on the resin with recoveries of 98.5–99.5% for different metal ions. The maximum sorption values are observed at pH 1, 2.5 and 2.5 for Ti(IV), Fe(III) and Al(III), respectively, which are recovered by successive elution with 1 mol/l H₂SO₄, 2 mol/l HCl and 4 mol/l H₂SO₄ in the above order.