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Shorter Wavelengths (shorter + wavelength)
Selected AbstractsPhotophysical and Photochemical Studies of PyridoxamineHELVETICA CHIMICA ACTA, Issue 10 2003Claudio Bueno The absorption and fluorescence emission of pyridoxamine were studied as function of pH and solvent properties. In the ground state, pyridoxamine exhibits different protonated forms in the range of pH,1.5,12. Fluorescence studies showed that the same species exist at the lowest singlet excited state but at different pH ranges. The phenol group is by ca. 8,units more acidic in the excited state than in the ground state. On the other hand, the pyridine N-atom is slightly more basic in the lowest excited state than in the ground state. Excitation spectra and emission decays in the pH range of 8,10 indicate the protonation of the pyridine N-atom by proton transfer from the amine group, in the ground and singlet excited states. Spectroscopic studies in different solvents showed that pyridoxamine in the ground or excited states exhibits intramolecular proton transfer from the pyridine N-atom to the phenol group, which is more favorable in solvents of low hydrogen-bonding capacity. The cationic form with the protonated phenolic group, which emits at shorter wavelength, is the dominant species in nonprotic solvents, but, in strong proton-donor solvents, both forms exist. The fluorescence spectra of these species exhibit blue shift in protic solvents. These shifts are well-correlated with the polarity and the H-donor ability of the solvent. [source] Reconstitution of Photosystem II Reaction Center with Cu-Chlorophyll aJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 11 2006Shuang Liu Abstract An isolated photosystem (PS) II reaction center (RC) with altered pigment content was obtained by chemical exchange of native chlorophyll a (Chl) with externally added Cu-Chl a (Cu-Chl). Pigment composition and spectroscopic properties of the RC exchanged with Cu-Chl were compared with native RC and RC treated with Chl in the same way. High-performance liquid chromatography analysis showed approximately 0.5 Cu-Chl per two pheophytin in the Cu-Chl-reconstituted RC preparation. Insertion of Cu-Chl resulted in a decrease in absorption at 670 nm and an increase at 660 nm, suggesting that the peripheral Chl may have been displaced. Fluorescence emission spectra of the Cu-Chl-reconstituted RC displayed a marked decrease in fluorescence yield and a blue shift of the band maximum, accompanied by the appearance of a broad peak at a shorter wavelength, indicating that energy transfer in the modified RC was disturbed by Cu-Chl, a quencher of the excited state. However, there were few differences in the circular dichroism (CD) spectra, suggesting that the arrangement of pigments and proteins responsible for the CD signal was not significantly affected. In addition, no obvious change in peptide components was found after the exchange procedure. (Managing editor: Ping He) [source] Continuously tunable S and C+L bands ultra wideband erbium-doped fiber ring laserLASER PHYSICS LETTERS, Issue 8 2009Q. Wang Abstract This paper presents an ultra wideband tunable silicabased erbium doped fiber ring laser (EDFRL) that can be continuously tuned in S and C+L bands from 1475 to 1619 nm. It is the first time that a fiber ring laser's tuning range reaches 144 nm using a standard silica-based C-band erbium-doped fiber as gain media. In the laser configuration two isolators are used in the fiber loop for suppressing the ASE in C-band and elevating the lasing gain in S-band. As a result the available lasing wavelength is extended toward the shorter wavelength of the gain bandwidth. The optimized erbium-doped fiber length, output coupling ratio and pumping laser power have been obtained through experimental study. This ring fiber laser has simple configuration, low threshold, flat laser spectral distribution and high signal-to-ASE-noise ratio. The laser will have many potential applications in fiber sensor wavelength interrogation, high-resolution spectroscopy and fiber optic communications. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Internal WWAN antenna for the clamshell mobile phone with various chassis shapesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010Kin-Lu Wong Abstract Stable performances of an internal WWAN antenna applied in the clamshell mobile phone with various chassis shapes are obtained. Six different states including five possible operating states and one closed state (idle condition) of the clamshell mobile phone, wherein the chassis shapes (main ground and upper ground) vary greatly, are studied. The WWAN antenna is mounted at the bottom of the main ground, and there are three connecting positions between the main ground and the upper ground. For each operating states, the upper ground is connected to the main ground at one of the three connecting positions. At each position, a band-stop circuit formed by two parallel LC chip elements is embedded, which is designed to excite a parallel resonance at around 900 MHz and hence leads to very high impedance seen into the upper ground in the 900 MHz band. This greatly decreases the excited surface currents on the upper ground, making the presence of the upper ground to have very small effects on the performances of the WWAN antenna mounted at the bottom of the main ground. At around 1900 MHz, owing to its shorter wavelength, the surface currents on the upper ground excited by the WWAN antenna on the main ground are small. Thus, over both the 900- and 1900-MHz bands, the various orientations of the upper ground to the main ground cause small effects on the WWAN antenna embedded therein. Details of the obtained results are presented. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2148,2154, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25413 [source] Effects of Three Characteristic Amino Acid Residues of Pharaonis Phoborhodopsin on the Absorption Maximum ,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2000Kazumi Shimono ABSTRACT Phoborhodopsin (pR or sensory rhodopsin II, sRII) or pharaonis phoborhodopsin (ppR or pharaonis sensory rhodopsin II, psRII) has a unique absorption maximum (,max) compared with three other archaeal rhodopsins: ,max of pR or ppR at ca 500 nm and others at 560,590 nm. Alignment of amino acid sequences revealed three sites characteristic of the shorter wavelength,absorbing pigments. The amino acids of these three sites are conserved completely among archaeal rhodopsins having longer ,max, and are different from those of pR or ppR. We replaced these amino acids of ppR with amino acids corresponding to those of bacteriorhodopsin, Val-108 to Met, Gly-130 to Ser and Thr-204 to Ala. The ,max of V108M mutant was 502 nm with a slight redshift. G130S and T204A mutants had ,max of 503 and 508 nm, respectively. Thus, each site contributes only a small effect to the color tuning. We then constructed three double mutants and one triple mutant. The opsin-shifts of these mutants suggest that Val-108 and Thr-204 or Gly-130 are synergistic, and that Gly-130 and Thr-204 work additively. Even in the triple mutant, the ,max was 515 nm, an opsin-shift only ca 30% of the shift value from 500 to 560 nm. This means that there is another yet unidentified factor responsible for the color tuning. [source] U-Pb Age Determination for Seven Standard Zircons using Inductively Coupled Plasma,Mass Spectrometry Coupled with Frequency Quintupled Nd-YAG (, = 213 nm) Laser Ablation System: Comparison with LA-ICP-MS Zircon Analyses with a NIST Glass Reference MaterialRESOURCE GEOLOGY, Issue 2 2008Yuji Orihashi Abstract This paper evaluates the analytical precision, accuracy and long-term reliability of the U-Pb age data obtained using inductively coupled plasma,mass spectrometry (ICP-MS) with a frequency quintupled Nd-YAG (, = 213nm) laser ablation system. The U-Pb age data for seven standard zircons of various ages, from 28 Ma to 2400 Ma (FCT, SL13, 91500, AS3, FC1, QGNG and PMA7) were obtained with an ablation pit size of 30 ,m diameter. For 207Pb/206Pb ratio measurement, the mean isotopic ratio obtained on National Institute of Standards and Technology (NIST) SRM610 over 4 months was 0.9105 ± 0.0014 (n = 280, 95% confidence), which agrees well with the published value of 0.9096. The time-profile of Pb/U ratios during single spot ablation showed no significant difference in shape from NIST SRM610 and 91500 zircon standards. These results encouraged the use of the glass standard as a calibration standard for the Pb/U ratio determination for zircons with shorter wavelength (, = 213 nm) laser ablation. But 206Pb/238U and 207Pb/235U ages obtained by this method for seven zircon standards are systematically younger than the published U-Pb ages obtained by both isotope dilution,thermal ionization mass spectrometry (ID-TIMS) and sensitive high-resolution ion-microprobe (SHRIMP). Greater discrepancies (3,4% younger ages) were found for the 206Pb/238U ages for SL13, AS3 and 91500 zircons. The origin of the differences could be heterogeneity in Pb/U ratio on SRM610 between the different disks, but a matrix effect accuracy either in the ICP ion source or in the ablation-transport processes of the sample aerosols cannot be neglected. When the 206Pb/238U (= 0.2302) newly defined in the present study is used, the measured 206Pb/238U and 207Pb/235U ages for the seven zircon standards are in good agreement with those from ID-TIMS and SHRIMP within ±2%. This suggests that SRM610 glass standard is suitable for ICP-MS with laser ablation sampling (LA-ICP-MS) zircon analysis, but it is necessary to determine the correction factor for 206Pb/238U by measuring several zircon standards in individual laboratories. [source] Copper(II),Girard's T complex as a promising anti-tumor agentAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2010A. M. A. El-Sokkary Abstract A copper(II) complex was evaluated for its anti-tumor activity. Firstly, electrophoretic studies were applied on the complex. These studies revealed the binding of the complex to calf thymus DNA, leading to a delay in electrophoretic mobility of the DNA molecule. Secondly, spectroscopic data pointed out that the ,max of DNA was shifted to a longer wavelength, which was accompanid by a hyperchromic shift. Moreover, the ,max of copper(II) complex was shifted to a shorter wavelength. The favorable reaction conditions between the DNA molecule and the copper(II) complex were studied. Thirdly, The effects of the ligand and the Cu(II) ion were tested separately on the DNA molecule by electrophoresis technique. Furthermore, the fluorescence quenching of DNA bound ethidium ion by Cu(II)-Girard's T complex was noticed. The IR spectral data of DNA before and after the reaction with the copper(II) complex indicated that the interaction takes place through the carbonyl group of DNA nucleobases. Finally, a significant increase in the mean survival of EAC (Ehrlich ascites carcinoma) tumor-bearing mice was observed when treated with the copper(II) complex. The tumor volume was also significantly reduced (p < 0.0001). Electrophoretic studies showed that the DNA pattern extracted from EAC cells of tumor-bearing mice was affected after treatment with the copper(II) complex. Flow cytometric studies showed that this complex may be taken into consideration in seeking novel anti-tumor agents. Copyright © 2010 John Wiley & Sons, Ltd. [source] Cyanide-Bridged Oligonuclear Complexes Containing Ni-CN-Cu and Pt-CN-Cu LinkagesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2003Marie-Louise Flay Abstract The central building blocks Ni(CN)42, and Pt(CN)42, can be combined with one, two or four CuIIL units (L = tren, Me6tren, tpa) to form di-, tri- and pentanuclear complexes with Ni-CN-Cu and Pt-CN-Cu linkages. Structure determinations of these and the side product [(tren)Cu,CN,Cu(tren)] (ClO4)2 reveal mostly linear M-C-N-Cu arrays and cis -, trans - and star-like arrangements of the CN-Cu units around the central Ni or Pt ions. The (CN) IR data for the bridging cyanides show a characteristic hypsochromic effect compared to the data for the free M(CN)42, complexes. The absorption bands in the visible spectra of the oligonuclear complexes are shifted to shorter wavelengths than those of the free LCuII -X complexes. The CuII/CuI redox steps in the cyclic voltammograms allow the conclusion that there is electronic communication between the external CuL units when they are arranged in a trans -orientation at PtII, but not NiII, centers. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Solution-Processible Phosphorescent Blue Dendrimers Based on Biphenyl-Dendrons and Fac -tris(phenyltriazolyl)iridium(III) Cores,ADVANCED FUNCTIONAL MATERIALS, Issue 19 2008Shih-Chun Lo Abstract Solution-processible saturated blue phosphorescence is an important goal for organic light-emitting diodes (OLEDs). Fac -tris(5-aryltriazolyl)iridium(III) complexes can emit blue phosphorescence at room temperature. Mono- and doubly dendronized fac -tris(1-methyl-5-phenyl-3- n -propyl-1H -[1,2,4]triazolyl)iridium(III) 1 and fac -tris{1-methyl-5-(4-fluorophenyl)-3- n -propyl-1H -[1,2,4]triazolyl}iridium(III) 4 with first generation biphenyl-based dendrons were prepared. The dendrimers emitted blue light at room temperature and could be solution processed to form thin films. The doubly dendronized 3 had a film photoluminescence quantum yield of 67% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.17, 0.33). OLEDs comprised of a neat film of dendrimer 3 and an electron transport layer achieved a brightness of 142,cd m,2 at 3.8,V with an external quantum efficiency of 7.9%, and CIE coordinates of (0.18, 0.35). Attachment of the fluorine atom to the emissive core had the effect of moving the luminescence to shorter wavelengths but also quenched the luminescence of the mono- and doubly dendronized dendrimers. [source] Synthesis and Optical Properties of Europium-Doped ZnS: Long-Lasting Phosphorescence from Aligned Nanowires,ADVANCED FUNCTIONAL MATERIALS, Issue 11 2005C. Cheng Abstract Quasi-aligned Eu2+ -doped wurtzite ZnS nanowires on Au-coated Si wafers have been successfully synthesized by a vapor deposition method under a weakly reducing atmosphere. Compared with the undoped counterpart, incorporation of the dopant gives a modulated composition and crystal structure, which leads to a preferred growth of the nanowires along the [010] direction and a high density of defects in the nanowire hosts. The ion doping causes intense fluorescence and persistent phosphorescence in ZnS nanowires. The dopant Eu2+ ions form an isoelectronic acceptor level and yield a high density of bound excitons, which contribute to the appearance of the radiative recombination emission of the bound excitons and resonant Raman scattering at higher pumping intensity. Co-dopant Cl, ions can serve not only as donors, producing a donor,acceptor pair transition with the Eu2+ acceptor level, but can also form trap levels together with other defects, capture the photoionization electrons of Eu2+, and yield long-lasting (about 4,min), green phosphorescence. With decreasing synthesis time, the existence of more surface states in the nanowires forms a higher density of trap centers and changes the crystal-field strength around Eu2+. As a result, not only have an enhanced Eu2+ 4f65d1,4f7 intra-ion transition and a prolonged afterglow time been more effectively observed (by decreasing the nanowires' diameters), but also the Eu2+ related emissions are shifted to shorter wavelengths. [source] Reversible Cluster Formation of Colloidal Nanospheres by Interparticle Photodimerization,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2004X. Yuan Abstract Crosslinked spherical nanoparticles based on trimethoxysilane monomers have been prepared by polycondensation in aqueous emulsion. These particles have been labeled chemically at their surface region with two different types of organic dye molecules (cinnamate, coumarin), which both are well known for their ability to undergo a reversible photodimerization if irradiated with light of a suitable wavelength. Upon irradiation of dilute solutions of these nanoparticles with UV light, the photodimerization of labels belonging to different colloidal nanoparticles caused the formation of large colloidal clusters consisting of chemically bound individual nanospheres. This process has been quantitatively investigated using light scattering and atomic force microscopy. Importantly, utilizing the reversibility of the photoreaction, the clusters could be broken up by irradiation of the sample with UV light of shorter wavelengths than the light used for their formation [source] Preen waxes do not protect carotenoid plumage from bleaching by sunlightIBIS, Issue 2 2008ADRIAN SURMACKI The plumage coloration of wild birds often changes during the breeding season. One of the possible reasons for this is that sunlight, and particularly ultraviolet (UV) wavelengths, degrades the pigments responsible for plumage coloration. It has been suggested that birds may apply preen wax to feathers to protect feathers from bleaching. This hypothesis is tested by exposing carotenoid-based breast feathers of Great Tits to ambient light, light filtered to exclude UV and darkness. Preen waxes were experimentally removed from feather samples and the effect of light on coloration of treatment and control feathers compared. Ambient light had an effect on feather colour but preen wax did not. Feathers exposed to sun gradually became less saturated and hues shifted towards shorter wavelengths. This was not apparent in control feathers kept in darkness. Feathers exposed to full-spectra sunlight faded more than those that were kept in light with UV wavelengths removed. There was a decrease in brightness of feathers in both experimental and control groups, which was assumed to be an effect of dirt accumulation. This experiment confirmed earlier suspicions regarding the detrimental effects of UV irradiation on carotenoid-based coloration of avian feathers but failed to show any protective function of preen waxes. The possible consequences of these mechanisms of colour change for birds with regard to mating strategies are discussed. [source] Theoretical studies on the electronic and optical properties of two new alternating fluorene/carbazole copolymersJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2005Li Yang Abstract Poly(fluorene)-type materials are widely used in polymer-based emitting devices. During operation there appears, however, an additional emission peak at around 2.3 eV, leading to both a color instability and reduced efficiency. The incorporation of the carbazole units has been proven to efficiently suppress the keto defect emission. In this contribution, we apply quantum-chemical techniques to investigate two series of alternating fluorene/carbazole oligomers and copolymers poly[2,7-(N-(2-methyl)-carbazole)- co - alt -2,7-m(9,9-dimethylfluorene)], namely, PFmCz (m = 1,2) and gain a detailed understanding of the influence of carbazole units on the electronic and optical properties of fluorene derivatives. The electronic properties of the neutral molecules, HOMO-LUMO gaps (,H-L), in addition to the positive and negative ions, are studied using B3LYP functional. The lowest excitation energies (Egs) and the maximal absorption wavelength ,abs of PFmCz (m = 1,2) are studied, employing the time-dependent density functional theory (TD-DFT). The properties of the two copolymers, such as ,H-L, Eg, IPs, and EAs were obtained by extrapolating those of the oligomers to the inverse chain length equal to zero (1/n = 0). The outcomes showed that the carbazole unit is a good electron-donating moiety for electronic materials, and the incorporation of carbazole into the polyfluorene (PF) backbone resulted in a broadened energy gap and a blue shift of both the absorption and photoluminescence emission peaks. Most importantly, the HOMO energies of PF1Cz and PF2Cz are both a higher average (0.4 eV) than polyfluorene (PF), which directly results in the decreasing of IPs of about 0.2 eV more than PF, indicating that the carbazole units have significantly improved the hole injection properties of the copolymers. In addition, the energy gap tends to broaden and the absorption and emission peaks are gradually blue-shifted to shorter wavelengths with an increase in the carbazole content in the copolymers. This is due to the interruption of the longer conjugation length of the backbone in the (F1Cz)n series. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 969,979, 2005 [source] Ultraviolet absorbance of the mucus of a tropical damselfish: effects of ontogeny, captivity and diseaseJOURNAL OF FISH BIOLOGY, Issue 6 2006J. P. Zamzow The ultraviolet (UV) absorbance of the mucus of a Great Barrier Reef damselfish Pomacentrus amboinensis was investigated with regard to ontogeny and time spent in captivity. The UV absorbance of P. amboinensis mucus increased with fish size and decreased with time spent in captivity. The wavelength of maximum absorbance of the mucus did not change with fish size, but shifted towards shorter wavelengths with increasing time spent in captivity. The UV absorbance of the mucus of fish with ,fin rot' was compared to that of similar healthy individuals, and a significant decrease in UV absorbance of unhealthy fish mucus was detected; no wavelength shifting occurred. Pomacentrus amboinensis appears to sequester mycosporine-like amino acids from the diet in order to protect epithelial tissues from UV damage, and decreases in UV absorbance in captive fish were probably due to insufficient dietary availability. [source] Determination of some hydroxybenzoic acids and catechins in white wine samples by liquid chromatography with luminescence detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2006Rafael Carlos Rodríguez-Díaz Abstract A liquid chromatographic method with luminescence detection for the determination of eight phenolic compounds is reported. The method involves postcolumn derivatization with terbium(III). This derivatization is based on the reaction between phenolics and terbium(III) to form luminescent chelates, which were determined at ,ex 295 and ,em 545 nm using the fluorescence mode. The long wavelength emission of lanthanide chelates can minimize interferences from background sample matrix, which usually emit at shorter wavelengths. Also, the chromatographic separation allows the individual determination of phenolics, which cannot be done using the direct measurement of the fluorescence of their corresponding terbium chelates. Dynamic ranges of the calibration graphs and detection limits, obtained with standard solutions of analytes were (,g/mL): gallic acid (0.9,40, 0.3), protocatechuic acid (0.05,7, 0.016), catechin (0.2,40, 0.07), vanillic acid (0.25,40, 0.08), p -hydroxybenzoic acid (0.8,40, 0.25), syringic acid (0.17,40, 0.05), epicatechin (0.3,40, 0.09) and salicylic acid (0.07,12, 0.02). The precision was established at two concentration levels of each analyte and expressed as the percentage of RSD with values ranging between 1.0 and 6.5%. The practical usefulness of the method was demonstrated by the analysis of white wine samples, which were diluted two-fold and directly injected into the chromatographic system. The recovery values obtained ranged between 93.3 and 108.0%. [source] Synthesis of CdSe quantum dots with luminescence in the violet region of the solar spectrumLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 1 2010Nisha Shukla Abstract We have designed a simple, one-step synthesis of CdSe quantum dots with photoluminescence frequencies ranging from the red through to the violet region of the solar spectrum. The photoluminescence peaks have FWHM of 30 nm indicating absorption over a narrow range of wavelengths. The effect of solvent type and solvent boiling point on the physical and photoluminescence properties of the quantum dots has been studied. High boiling point, non-polar solvents shift the photoluminescence peak to longer wavelengths and low boiling point, polar solvents shift the photoluminescence peak to shorter wavelengths. Copyright © 2009 John Wiley & Sons, Ltd. [source] Spectral reflectance-compositional properties of spinels and chromites: Implications for planetary remote sensing and geothermometryMETEORITICS & PLANETARY SCIENCE, Issue 4 2004Edward A. Cloutis These two groups of minerals are spectrally distinct, which relates largely to differences in the types of major cations present. Both exhibit a number of absorption features in the 0.3,26 ,m region that show systematic variations with composition and can be used to quantify or constrain certain compositional parameters, such as cation abundances, and site occupancies. For spinels, the best correlations exist between Fe2+ content and wavelength positions of the 0.46, 0.93, 2.8, Restrahelen, 12.3, 16.2, and 17.5 ,m absorption features, Al and Fe3+ content with the wavelength position of the 0.93 ,m absorption feature, and Cr content from the depth of the absorption band near 0.55 ,m. For chromites, the best correlations exist between Cr content and wavelength positions of the 0.49, 0.59, 2, 17.5, and 23 ,m absorption features, Fe2+ and Mg contents with the wavelength position of the 1.3 ,m absorption feature, and Al content with the wavelength position of the 2 ,m absorption feature. At shorter wavelengths, spinels and chromites are most readily distinguished by the wavelength position of the absorption band in the 2 ,m region (<2.1 ,m for spinels, >2.1 ,m for chromite), while at longer wavelengths, spectral differences are more pronounced. The importance of being able to derive compositional information for spinels and chromites from spectral analysis stems from the relationship between composition and petrogenetic conditions (pressure, temperature, oxygen fugacity) and the widespread presence of spinels and chromites in the inner solar system. When coupled with the ability to derive compositional information for mafic silicates from spectral analysis, this opens up the possibility of deriving petrogenetic information for remote spinel- and chromite-bearing targets from analysis of their reflectance spectra. [source] WR 143: a Wolf,Rayet binaryMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006Watson P. Varricatt ABSTRACT Near-infrared spectroscopy and photometry of the Wolf,Rayet star WR 143 (HD 195177) were obtained in the JHK photometric bands. High-resolution spectra observed in the J and H bands exhibit a narrow 1.083-,m He i line and the H i Pa, and Brackett series lines in emission superposed on the broad emission-line spectrum of the Wolf,Rayet star, giving strong indications of the presence of a companion. From the narrow emission lines observed, the companion is identified to be an early-type Be star. The photometric magnitudes exhibit variations in the JHK bands, which are probably due to the variability of the companion star. The flux density distribution is too steep for a Wolf,Rayet atmosphere. This is identified to be mainly due to the increasing contribution from the early-type companion star towards shorter wavelengths. [source] On the origin of the drifting subpulses in radio pulsarsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005G. Gogoberidze ABSTRACT We present a model for the main observational characteristics of the radio emission of pulsars with well-organized drifting subpulses. We propose that drifting subpulses result from the modulation of the radio emission mechanism due to long-wavelength drift waves in the magnetosphere. The drift waves are generated at shorter wavelengths, and their non-linear evolution favours accumulation in a specific azimuthal eigenmode with an integral number, m, of nodes encircling the magnetic pole. The electric field of the drift waves is along the magnetic field lines, and this modulates the distribution for particles and hence the radio emission mechanism. The ratio of the frequency of the eigenmode to the rotation frequency of the star is insensitive to the magnetic field strength and the period of rotation, and is of order unity. The period, P3, of the drifting subpulses is attributed to the mismatch between this frequency and the nearest harmonic of the rotation frequency of the star. [source] An Improved Algorithm for Satellite-derived UV Radiation,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2003Sigrid Wuttke ABSTRACT The improved algorithm surface irradiance derived from a range of satellite-based sensors (SIDES) is presented in this article. It calculates various types of surface UV intensities, such as biologically weighted or unweighted UV spectra, integrated doses or irradiance at specific wavelengths, using data from satellite instruments. These surface UV data are mainly useful for environmental impact or process studies where high accuracy or a high temporal resolution is required. In contrast to several previous studies, SIDES has been validated with spectral measurements. By this method an averaging of positive or negative deviations over the complete wavelength range is avoided. This is especially important for UV wavelengths around 300 nm where biological effectiveness is highest. The results of SIDES deviate less than 7% from ground-based observations for wavelengths between 295 and 400 nm. In contrast, the corresponding deviations of the joint research center algorithm escalate for shorter wavelengths, reaching 35% at 295 nm. This large deviation is due to an inaccurate interpolation procedure that has been detected by spectral analysis. Thus, spectral validation is demonstrated to be an appropriate tool to detect weaknesses in such an algorithm and provides information essential for improvement. [source] On Spectral Relaxation in Proteins,,§PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2000Joseph R. Lakowicz ABSTRACT During the past several years there has been debate about the origins of nonexponential intensity decays of intrinsic tryptophan (trp) fluorescence of proteins, especially for single tryptophan proteins (STP). In this review we summarize the data from diverse sources suggesting that time-dependent spectral relaxation is a ubiquitous feature of protein fluorescence. For most proteins, the observations from numerous laboratories have shown that for trp residues in proteins (1) the mean decay times increase with increasing observation wavelength; (2) decay associated spectra generally show longer decay times for the longer wavelength components; and (3) collisional quenching of proteins usually results in emission spectral shifts to shorter wavelengths. Additional evidence for spectral relaxation comes from the time-resolved emission spectra that usually shows time-dependent shifts to longer wavelengths. These overall observations are consistent with spectral relaxation in proteins occurring on a subnanosecond timescale. These results suggest that spectral relaxation is a significant if not dominant source of nonexponential decay in STP, and should be considered in any interpretation of nonexponential decay of intrinsic protein fluorescence. [source] Characterization of the common mode rejection ratio of amorphous silicon balanced photodiodePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010D. Caputo Abstract In this work we report on the detailed characterization of an amorphous silicon/amorphous silicon carbide balanced photodiode structure suitable for differential photocurrent measurements. The device is a three-terminal structure constituted by two series-connected amorphous silicon p-i-n photodiodes. Two terminals are used to bias the two photodiodes at the same reverse voltage by the readout electronics. The output signal is the current difference between the two diodes, measured at the third terminal with a transimpedance circuit. Several devices have been fabricated with different areas and geometries utilizing four mask-step process. The devices have been characterized by means of common mode rejection ratio (CMRR) measurements as a function of the radiation wavelength and intensity. The CMRR measured under white light illumination has been found to lie around 37 dB in the whole range of investigated radiation intensities. The decrease of the CMRR observed at shorter wavelengths has been ascribed to mismatches and inhomogeneities in the surface and in the p-type window layer of the two hemi-devices. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High-phasing-power lanthanide derivatives: taking advantage of ytterbium and lutetium for optimized anomalous diffraction experiments using synchrotron radiationACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2003É. Girard Ytterbium and lutetium are well suited for optimized anomalous diffraction experiments using synchrotron radiation. Therefore, two lanthanide complexes Yb-HPDO3A and Lu-HPDO3A have been produced that are similar to the Gd-HPDO3A complex already known to give good derivative crystals. Derivative crystals of hen egg-white lysozyme were obtained by co-crystallization using 100,mM solutions of each lanthanide complex. De novo phasing has been carried out using single-wavelength anomalous diffraction on data sets collected on each derivative crystal at the LIII absorption edge of the corresponding lanthanide ( = 28,e,). A third data set was collected on a Lu-HPDO3A derivative crystal at the Se,K absorption edge with = 10,e,. The structures were refined and compared with the known structure of the Gd-HPDO3A lysozyme derivative. The quality of the experimental electron-density maps allows easy model building. With LIII absorption edges at shorter wavelengths than the gadolinium absorption edge, lutetium and ytterbium, when chelated by a ligand such as HPDO3A, form lanthanide complexes that are especially interesting for synchrotron-radiation experiments in structural biology. [source] Diode laser photocoagulation of choroidal neovascularization associated with retinal pigment epithelial detachmentACTA OPHTHALMOLOGICA, Issue 1 2001Francisco Gomez-Ulla ABSTRACT. Aims/Background: Association of choroidal neovascularization with pigment epithelial detachment is not an uncommon feature. Since this condition usually has a poor visual outcome, new treatments should be developed. Methods: We studied the anatomical and visual results of 11 eyes with this association as a manifestation of an Exudative Age Related Macular Degeneration which were treated with diode laser photocoagulation guided by indocyanine green angiography. The average follow up time was 25.5 months (from 12 to 48 months). Results: Complete closure with complete resolution of the exudates and flattening of the detachment was observed in five eyes (45%). Visual acuity in the final examination improved or remained stable in 6 cases (55%). Conclusion: These results indicate that diode laser photocoagulation guided by indocyanine green angiography is at least as effective as conventional lasers with shorter wavelengths for treatment of vascularized pigment epithelial detachments in Age Related Macular Degeneration. [source] | |||||||||||||||||||