Mycosporine-like amino acids in the marine dinoflagellate Gyrodinium dorsum: induction by ultraviolet irradiation

Cultures of the marine dinoflagellate Gyrodinium dorsum have been exposed to polychromatic radiation (photosynthetically active radiation and UV) from a solar simulator for up to 72 h. Different irradiance spectra in the ultraviolet are produced by inserting cut-off filters between lamp and samples. The mycosporine-like amino acid (MAA) content and composition are investigated by spectroscopic and chromatographic analysis. The study reveals that G. dorsum contains a complex mixture of several aminocyclohexenimine-MAAs and one aminocyclohexenone-MAA. UV irradiation around 320 nm induces an increase in the concentration of all MAAs in the samples. In contrast, exposure to short-wavelength UV-B radiation results in decreased overall MAA production. Furthermore, there is a spectral shift in the absorption of the MAA mixture towards shorter wavelengths, indicating that short-wavelength UV-B induces an altered MAA composition. The amount of MAAs is normalized to the chlorophyll a concentration.     

Higher order symmetrizer and application to an unusual transport equation

We study a class of stationary transport equation with nonlocal low-order tems We obtain the existence and uniqueness of a solution in sobolev spaces     

Facility for preparation of gas mixture in muon catalyzed fusion experiments

A facility is described that allows safe handling of high tritium gas activity as dozens kilocuries in a regular laboratory environment. It is used to make and deliver into the target a mixture of specific isotopic composition with the contamination requirement of 10^-7 v.f. for Z>1 elements, and recover it upon completion of operation. With this facility, efforts have been accomplished to investigate into the muon catalyzed fusion on two targets – liquid tritium and high-pressure tritium types. Also, the operation range was 0.1–120 MPa for pressure and 20–800 K for temperature and the amount of tritium used was about 100 kCi. The facility showed reliability in operation without indications of radiation beyond the safety level. This revised version was published online in August 2006 with corrections to the Cover Date.     

求解复杂湍流的非线性涡黏性系数模型和代数应力模型

非线性涡黏性系数模型和代数应力模型联系了线性涡黏性系数湍流模型和完整的微分 雷诺应力模型.随着它们受到日益关注,其形式也越来越多样化.本篇综述的目的是对这些模 型加以总结并比较它们之间的共同点及不同之处,指出它们与完整微分雷诺应力模型之间的 关系,以及相对于线性涡黏性系数模型而言它们在预报流场上所具有的优势.     

Induction of mycosporine-like amino acids (MAAs) in cyanobacteria by solar ultraviolet-B radiation

Three filamentous and heterocystous N₂-fixing cyanobacteria, Anabaena sp., Nostoc commune and Scytonema sp. were tested for the presence of ultraviolet-absorbing mycosporine-like amino acids (MAAs) and their induction by solar ultraviolet-B (UV-B) radiation. High performance liquid chromatographic (HPLC) studies revealed the presence of only one type of MAAs in all three cyanobacteria, that was identified as shinorine, a bisubstituted MAA containing both glycine and serine groups having an absorption maximum at 334 nm and a retention time of around 2.8 min. There was a circadian induction in the synthesis of MAAs when the cultures were exposed to mid-latitude solar radiation (Playa Unión, Rawson, Chubut, Patagonia, Argentina) for 3 days, 4–6th February, 2000. Solar radiation was measured by an ELDONET (European Light Dosimeter Network) filter radiometer permanently installed on the roof of the Estación de Fotobiología Playa Unión (43°18′ S; 65°03′ W). The maximum irradiances were around 450–500, 45–50 and 1.0–1.2 W m⁻² for PAR (photosynthetic active radiation), UV-A (ultraviolet-A) and UV-B (ultraviolet-B), respectively. PAR and UV-A had no significant impact on MAA induction while UV-B induced the synthesis of shinorine in all three cyanobacteria. Shinorine was found to be induced mostly during the light period. During the dark period the concentration stayed almost constant. In addition to shinorine, another unidentified, water-soluble, brownish compound with an absorption maximum at 315 nm was found to be induced by UV-B only in Scytonema sp. and released into the medium. This substance was neither found in Anabaena sp. nor in Nostoc commune. Judging from the results, the studied cyanobacteria may protect themselves from deleterious short wavelength radiation by their ability to synthesize photoprotective compounds in response to UV-B radiation.     

12-Tungstosilicic Acid (12-TSA) as a Tungsten Precursor in Alcoholic Solution for Deposition of xWO3(1 − x)SiO2 Thin Films (x ≤ 0.7) Exhibiting Electrochromic Coloration Ability

The preparation of stable alcoholic solution of tungstosilicic acid and silicon alkoxide, which can be used for xWO3 (1 – x)SiO2 thin film deposition by dipping, is described. After thermal treatment at temperatures 440 to 500°C in nitrogen films with x higher than 0.6 exhibit electrochromic coloration ability. After coloring the film by H+ imtercalation (by contact with an indium wire trough a drop of aqueous solution of H2SO4) the luminous transmittance (illuminant D65, wavelength range from 380 to 780 nm, summation at 10 nm intervals) of glass coated with 90 nm thick xWO3(1 – x)SiO2 thin film decreases from 71.7 to 28.6% and the IR reflection increases to over 30%. At the same time the surface resistance decreases from a few M/ to about 400/. The thermal decomposition of tungstosilic acid embedded in alkoxy-hydroxy-oxy-silicon matrix is investigated with DTA, TGA, XRD and FTIR spectroscopy.     

The Stereostructure of Porphyra‐334: An Experimental and Calculational NMR Investigation. Evidence for an Efficient ‘Proton Sponge’

The mycosporine‐like amino acid (MAA) porphyra‐334 ( 1 ) is subjected to extensive ¹H‐ and ¹³C‐NMR analysis as well as to density‐functional‐theory (DFT) calculations. All ¹H‐ and ¹³C‐NMR signals of 1 are assigned, as well as the resonances of prochiral proton pairs. This is achieved by 500‐MHz standard COSY, HMQC, and HMBC experiments, as well as by one‐dimensional (DPFGSE‐NOE) and two‐dimensional (NOESY) NOE experiments. Diffusion measurements (DOSY) confirm that 1 is monomeric in D₂O solution. DFT Calculations yield ¹³C‐NMR chemical shifts which are in good agreement for species 6 which is the imino N‐protonated form of 1 . An exceptionally high proton affinity of 265.7 kcal/mol is calculated for 1 , indicating that 1 may behave as a very powerful ‘proton sponge’ of comparable strength as synthetic systems studied so far. Predictions of ¹³C‐NMR chemical shifts by the ‘NMRPredict’ software are in agreement with the DFT data. The absolute configuration at the ring stereogenic center of 1 is concluded to be (S) from NOE data as well as from similarities with the absolute configuration (S) found in mycosporine‐glycine 16 . This supports the assumption that 1 is biochemically derived from 3,3‐O‐didehydroquinic acid ( 17 ). The data obtained question the results recently published by a different research group claiming that the configuration at the imino moiety of 1 is (Z), rather than (E) as established by the here presented study.     

Collision induced dissociation of stored gold cluster ions

The stability of gold cluster ions Au _n ⁺ (2n23) has been investigated via collision induced dissociation in a Penning trap. Threshold energies and dissociation channels have been determined. The cluster stability exhibits a pronounced odd — even alternation: Clusters with an odd number of atoms,n, are more stable than the even-numbered ones. Enhanced stabilities are found for Au ₃ ⁺ , Au ₉ ⁺ , and Au ₁₉ ⁺ in accordance with the Clemenger-Nilsson and the deformed jellium model of delocalized valence electrons. Excited odd cluster ions withn15 predominantly decay by evaporation of dimers; all others decay by monomer evaporation. From the dissociation channels estimates of the binding energies are deduced.This publication comprises part of the thesis of St. Becker     

Wavelength dependence of mycosporine-like amino acid synthesis in Gyrodinium dorsum

The synthesis or accumulation of mycosporine-like amino acids (MAAs) is an important UV tolerance mechanism in aquatic organisms. To investigate the wavelength dependence of MAA synthesis in the marine dinoflagellate Gyrodinium dorsum, the organism was exposed to polychromatic radiation (PAR and UV) from a solar simulator for up to 72 h. Different irradiance spectra were produced by inserting various cut-off filters between lamp and samples. A polychromatic action spectrum for the synthesis of MAA synthesis was constructed. PAR and long wavelength UV-A radiation showed almost no effect while the most effective wavelength range was around 310 nm. Shorter wavelengths where less effective in the induction of MAA synthesis. Wavelengths below 300 nm damaged the organisms severely as indicated by a decrease in chlorophyll a absorption.