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The research has involved the characterization of catalyst acidity, [sup 2]D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

Science.gov (United States)

Two new triterpene glycosides, patagonicosides B and C (2 and 3, resp.), together with the known patagonicoside A (1), have been isolated from the EtOH extract of the sea cucumber Psolus patagonicus. The structures of the new compounds were established on the basis of extensive NMR spectroscopic analysis ((1)H- and (13)C-NMR, (1)H,(1)H-COSY, HMBC, HSQC, TOCSY, and NOESY), HR-ESI-MS data, and chemical transformations. Compounds 1-3 and their desulfated analogs showed antifungal activities against the phytopathogenic fungus Cladosporium cladosporoides in a dose-dependent fashion. PMID:21404430

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No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

The wavefunction of a particle extends into the classically forbidden barrier region of the potential energy surface. The consequence of this partial delocalisation is the phenomenon of quantum tunnelling, an effect which enables a particle to penetrate a potential barrier of magnitude greater than the energy of the particle. The tunnelling probability is an exponential function of the particle mass. The effect is therefore an important contribution to the behaviour of light atoms, in particular the proton. The hydrogen bond has long been appreciated to be an essential component of many biological and chemical systems, and the proton transfer reaction in the hydrogen bond is fundamental to many of these processes. The proton behaviour in the hydrogen bonds of benzoic acid, acetylacetone and calix-4-arene has been studied. A variety of techniques, both experimental and computational, were adopted for the study of the three hydrogen bonded systems. The complementary ...

British Library Electronic Table of Contents (United Kingdom)

Premnalatifolin A (1), a unique icetexane diterpene dimer was isolated from the stem-bark of Indian medicinal plant, Premna latifolia. Its structure and relative stereochemistry were elucidated on the basis of detailed spectroscopic analysis, including HRESIMS and 2D NMR (COSY, HSQC, HMBC, and NOESY) spectra. The compound has dimeric carbon skeleton composed of two icetexane skeletal diterpenes linked via ether bond. Further, premnalatifolin A (1) was also evaluated for its cytotoxicity against cancer cell lines (HT-29, A-431, MCF-7, Hep-G2, PC-3, A-549, B-16 F10, and ACHN), which displayed potent activity against HT-29 and MCF-7 cell lines with the IC50 values of 12.15 and 1.11mg/mL, respectively.

British Library Electronic Table of Contents (United Kingdom)

The leaf extract from the plant Piliostigma reticulatum was found to exhibit antimicrobial activity against some bacteria and fungi such as Staphylococcus aureus (NCTC 6571), Escherichia coli (NCTC 10418), Bacillus subtilis (NCTC 8236), Proteus vulgaris (NCTC 4175), Aspergillus niger (ATCC 10578) and Candida albicans (ATCC 10231). Upon investigation of the chemical constituents present in the leaf extract, a total of seven compounds were isolated and their structures were unambiguously established by spectroscopic methods including HR-MS and NMR spectrometry. Four of the isolated compounds were novel, namely 6-C-methyl-2-p-hydroxyphenyloxychromonol (piliostigmol), 1, 6,8-di-C-methylquercetin-3,3prime,7-trimethyl ether, 2, 6,8-di-C-methylquercetin-3,3prime-dimethyl ether, 3 and 3prime,6,8,-...

International Nuclear Information System (INIS)

The phytochemical investigation of Chomelia obtusa leaves led to the isolation of four triterpenes (3-O-#beta#-D-quinovopyranosyl-28-O-#beta#-D-glycopyranosyl quinovic acid, 3-O-#beta#-D-quinovopyranosyl-28-O-#beta#-D-glycopyranosyl cincholic acid, and a mixture of ursolic and oleanolic acids), two flavonoids (3-O-#beta#-D-glycopyranosyl quercetin, 3-O-[#alpha#-L-rhamnopyranosyl-(1#->#6)-#beta#-D-galactopyranoside] quercetin), besides bornesitol and a mixture of 3,5- and 4,5-O-dicaffeoyl quinic acids. The structures of the isolated compounds were assigned on the basis of spectroscopic data, including two-dimensional NMR methods. The anti-inflammatory and antioxidant activities of the crude methanolic extract and of its fractions were evaluated. This is the first report on the chemical and biological investigation of the Chomelia genus. (author)

International Nuclear Information System (INIS)

Three major monomeric hemoglobins have been isolated from the erythrocytes of Glycera dibranchiata. Their importance to structure-function studies of heme proteins lies in the fact that they have been shown to possess an exceptional amino acid substitution. In these proteins, the E-7 position is occupied by leucine rather than the more common distal histidine. This substitution alters the polarity of the heme ligand binding environment compared to myoglobin. Due to this, the G. dibranchiata monomer hemoglobins are attracting much attention. However, until now no purity criterion has been developed. Here the authors demonstrate that, for all of the Glycera momomer hemoglobins, multiple line patterns are shown on high-voltage isoelectric focusing (IEF) gels. Most of these lines are shown to be a consequence of heme-related phenomena and can be understood on the basis of changes in oxidation and ligation state of the heme iron. The multiple line pattern does not indicate significant ...

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Short communication.

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New palladium(II) complexes (2), bearing NHC/TPPTS ligands, (NHC=benzimidazol-2-ylidene; TPPTS=triphenylphosphine-3,3',3''-trisulfonic acid trisodium salt) have been prepared and characterized by elemental analyses and spectroscopic methods. Their ability to catalyze the Suzuki-Miyaura reaction in neat water has been studied at 100^oC. Very high activities have been observed in the coupling of phenylboronic acid with aryl chlorides in the presence of 1% of the catalyst. We have compared the electronic properties of cis-[PdBr2(NHC)(TPPTS)] with the related complexes, [PdX2(NHC)]2 and [trans-PdBr2(NHC)(pdca)] (pdca=pyridine-2,6-dicarboxyic acid) (3) via three different techniques: cyclic voltammetry, thermogravimetric analysis and ^1^3C NMR spectroscopy.

British Library Electronic Table of Contents (United Kingdom)

A new lactone, 1,8-dihydroxy-10-methoxy-3-methyldibenzo[b,e]oxepine-6,11-dione (1), and two new xanthones, 1-hydroxy-8-(hydroxymethyl)-6-methoxy-3-methyl-9H-xanthen-9-one (2) and 1-hydroxy-8-(hydroxymethyl)-3-methoxy-6-methyl-9H-xanthen-9-one (3), were isolated from a mangrove endophytic fungus Phoma sp. SK3RW1M collected from the South China Sea. This is the first report on xanthone derivatives isolated as secondary metabolites from Phoma species. Their structures were elucidated by spectroscopic methods, mainly 1D- and 2D-NMR techniques, and the structure of compound 2 was confirmed by X-ray crystallography. Cytotoxicity assays showed that compounds 1-3 were inactive against KB and KBv200 cells.

Science.gov (United States)

Not Available

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Nuclear magnetic resonance is a powerful technique that can be used in a wide range of applications, such as the structural characterization of high molecular weight molecules, conformational studies on enzymes in solution, enzyme-substrate or DNA-protein interactions, monitoring of cell metabolism in vivo, and for diagnostic purposes, employing spectroscopic and imaging techniques. This course was organized in order to introduce the participants to the fundamentals of NMR spectroscopy, and offer practical advice on performing NMR experiments on cell systems, cell and tissue extracts and animal models. The main implications regarding human experiments were also discussed. Finally the quantification of information and the interpretation of data were considered with regard to the main nuclei observed. [Italiano] La risonanza magnetica nucleare e` una delle tecniche spettroscopiche che meglio risponde all`ampio spettro di ...

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Low-temperature catalytic pretreatment is a promising approach to the development of an improved liquefaction process- This work is a fundamental study on effects of pretreatments on coal structure and reactivity in liquefaction. The main objectives of this project are to study the coal structural changes induced by low-temperature catalytic and thermal pretreatments by using spectroscopic techniques; and to clarify the pretreatment-induced changes in reactivity or convertibility of coals in the subsequent liquefaction. This report describes the recent progress of our work. Substantial progress has been made in the spectroscopic characterization of structure and pretreatment-liquefaction reactions of a Montana subbituminous Coal (DECS-9), and thermochemical analysis of three mw and reacted bituminous coals. Temperature programmed liquefaction has been performed on three low-rank coals both in the presence and absence of dispersed molybdenum ...

UK PubMed Central (United Kingdom)

Improved NMR detection of mass limited samples can be obtained by taking advantage of the mass sensitivity of microcoil NMR, while throughput issues can be addressed using multiple, parallel...Full Text Available

International Nuclear Information System (INIS)

The aim of this work is to understand the reasons for the selectivity shown in the complexation by unsaturated heteropolyanions (HPA) of actinides (An) which are oxidized to the number +IV. Different studies have been carried out, both in solution and in solid state, on P_2W_1_7O_6_1"1"0"- and its complexes with Zn"2"+, UO_2"2"+, Ce"4"+, Th"4"+ and U"4"+ to characterize the nature of the complexation site offered to the cation. Among the actinides(IV), the U"4"+ ion has been selected due to its singular spectroscopic and magnetic properties. An initial series of studies, in solution, using NMR"3"1P has thus enabled us to characterize these complexes and to compare them to those formed with the complexing agent PW_1_1O_3_9"8"-. This body of data allows to identify an identical complexation site for both ligands. An analysis of the NMR"3"1P spectrum of U(P_2W_1_7O_6_1)_2"1"6"- has shown a plane of symmetry passing through the ...

Science.gov (United States)

... decoherence. Descriptors : *QUANTUM COMPUTING, NUCLEAR MAGNETIC RESONANCE, JOSEPHSON JUNCTIONS. Subject ...

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

New platinum(II) complexes with asymmetrically substituted chiral diamine ligands A{sub 2}PtX{sub 2}, (A{sub 2}=NH{sub 2}CH(CH{sub 3})CH{sub 2}NH(c-C{sub 5}H{sub 9}) (apcpa), NH{sub 2}CH(CH{sub 3})CH{sub 2}NH(c-C{sub 6}H{sub 11}) (apcha); X{sub 2}=2Cl, isopropylidenmalonate (IPM), 1,1'-cyclobutandicarboxylate (CBDCA) have been synthesized and characterized by means of elemental analyses, infrared and NMR spectroscopies, and X-ray crystallography. The crystal structures of (S-apcha)Pt[CBDCA]{center_dot}3H{sub 2}O (orthorhombic, P2{sub 1}2{sub 1}2(No. 18), a=6.926(3), b=15.243(3), c=19.319(4) A, V=2039.5(10) A{sup 3}, Z=4, R=0.072) and (S-apcha)Pt[IPM]{center_dot}2.5H{sub 2}O (monoclinic, P2/c(No. 13), a=9.882(1), b=18.502(1), c=22.056(1) A, V=4032.8(5) A{sup 3}, Z=8, R=0.093) exhibit that the platinum atoms achieve a typical square planar arrangement with two nitrogen atoms in cis position and with the chiral center retained. The ...

International Nuclear Information System (INIS)

A single round of Edman degradation was employed to remove the NH_2-terminal valine from isolated #alpha# chains of human hemoglobin. Reconstitution of normal #beta# chains with truncated or substituted #alpha# chains was used to form truncated (des-Val"1-#alpha#1) and substituted ([[1-"1"3C]Gly"1]#alpha#1) tetrameric hemoglobin analogs. Structural homology of the analogs with untreated native hemoglobin was established by using several spectroscopic and physical methods. Functional studies indicate that the reconstituted tetrameric protein containing des-Val"1-#alpha# chains has a higher affinity for oxygen, is less influenced by chloride ions or 2,3-biphosphoglycerate, and shows lower cooperativity than native hemoglobin. These results confirm the key functional role of the #alpha#-chain NH_2 terminus in mediating cooperative oxygen binding across the dimer interface. The NH_2-terminal pK/sub 1/2/ value was determined for the ["1"3C]glycine-substituted analog to ...

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No abstract prepared.

British Library Electronic Table of Contents (United Kingdom)

Nuclear magnetic resonance (NMR) techniques coupled with multivariate data analysis were used to conduct monitoring of biochemical changes of black raspberry fruits at different stages of maturation and under various extraction and NMR dissolution solvent conditions: extraction with 50% methanol and D"2O as an NMR dissolution solvent, extraction with 50% methanol and 50% methanol-d"4 as an NMR dissolution solvent, and extraction with 100% ethyl acetate and 100% methanol-d"4 as an NMR dissolution solvent. Partial least-squares discriminant analysis reliably distinguished black raspberry fruits according to the maturation stage, whereby the relative levels of various compounds such as amino acids, organic acids, sugars and phenolic compounds were compared using analysis of variance. Sucrose ...

UK PubMed Central (United Kingdom)

The binding of amphiphilic molecules to lipid bilayers is followed by ¹⁹F NMR using chemical shift and line shape differences between the solution and membrane-tethered states of...Full Text Available

International Nuclear Information System (INIS)

Russian (Jul 1974). USSR Buslaev, Yu.A. Petrosyants, SP Tarasov,

International Nuclear Information System (INIS)

... PHYSICAL AND ANALYTICAL CHEMISTRY calibration standards diagrams

International Nuclear Information System (INIS)

Development of evaluation technology of electrochemical reactions is very essential to understand chemical behavior of actinides and lanthanides in molten salt media in relation to the development of Pyrochemical process. The on-line electrochemical/spectroscopic measurement system is to produce electrochemical parameters and thermodynamic parameters of actinides and lanthanides in molten salts by using spectroscopic techniques such as UV-VIS absorption as well as electrochemical in-situ measurement techniques. The on-line electrochemical/spectroscopic measurement system can be applied to understand the chemical reactions and oxidation states of actinides and lanthanides in molten salts eventually for the Pyrochemical process

KoreaScience (Korea)

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International Nuclear Information System (INIS)

This work presents the spectroscopic results of the investigations of ancient pottery remains excavated in ancient Kremna (BURDUR-TURKEY). The micro-Raman and FT-IR spectroscopic studies of the pottery remains belonging to sixth century allowed us to identify the mineral composition. Some examples are described of the use of this technique in the field of art conservation and diagnostics, with regard to pigments, and some products of metal alteration.

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The known biological functions of RNA have expanded in recent years and now include gene regulation, maintenance of sub-cellular structure, and catalysis, in addition to propagation of genetic information. As for proteins, RNA function is tightly correlated with structure. Unlike proteins, structural information for larger, biologically functional RNAs is relatively limited. NMR signal degeneracy, relaxation problems, and a paucity of long-range {sup 1}H-{sup 1}H dipolar contacts have limited the utility of traditional NMR approaches. Selective isotope labeling, including nucleotide-specific and segmental labeling strategies, may provide the best opportunities for obtaining structural information by NMR. Here we review methods that have been developed for preparing and purifying isotopically labeled RNAs, as well as NMR strategies that have been employed for signal assignment and structure ...

International Nuclear Information System (INIS)

An attempt to determine lysozyme hydration by employing a proton nuclear magnetic resonance (NMR) spin-echo technique and to correlated such measurements with the 20 "0C sorption equilibrium data is made. Determinations of specific site hydration for lysozyme, as well as proton NMR transverse relaxation rates for five different types of water populations in the lysozyme-water system, are presented over the whole range of lysozyme concentrations. The proton spin-echo NMR results are consistent with a three-component analysis of the sorption isotherm up to 70% water content, above which two additional water populations are identified by 360-MHz proton NMR spin-echoes. On the basis of the proton NMR results, a major component (III) of the lysozyme sorption isotherm is assigned to the water trapped between lysozyem molecules, whose relaxation rate is increased by diffusion barriers. The ...

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Orientational constraints obtained from solid state NMR experiments on anisotropic samples are used here in molecular dynamics (MD) simulations for determining the structure and dynamics of several different membrane-bound molecules. The new MD technique is based on the inclusion of orientation dependent pseudo-forces in the COSMOS-NMR force field. These forces drive molecular rotations and re-orientations in the simulation, such that the motional time-averages of the tensorial NMR properties approach the experimentally measured parameters. The orientational-constraint-driven MD simulations are universally applicable to all NMR interaction tensors, such as chemical shifts, dipolar couplings and quadrupolar interactions. The strategy does not depend on the initial choice of coordinates, and is in principle suitable for any flexible molecule. To test the method on three systems of increasing complexity, ...

International Nuclear Information System (INIS)

As part of efforts to develop improved methods for NMR protein sample preparation and structure determination, the Northeast Structural Genomics Consortium (NESG) has implemented an NMR screening pipeline for protein target selection, construct optimization, and buffer optimization, incorporating efficient microscale NMR screening of proteins using a micro-cryoprobe. The process is feasible because the newest generation probe requires only small amounts of protein, typically 30-200 ?g in 8-35 ?l volume. Extensive automation has been made possible by the combination of database tools, mechanization of key process steps, and the use of a micro-cryoprobe that gives excellent data while requiring little optimization and manual setup. In this perspective, we describe the overall process used by the NESG for screening NMR samples as part of a sample optimization process, assessing optimal construct design and ...

International Nuclear Information System (INIS)

The fluorescence properties of protopine and allocryptopine in aqueous and organic environments are described for the first time. The fluorescence of alkaloids and their pH-dependent interconversion to cationic forms (transannular interaction) were studied using steady-state and time-resolved fluorescence techniques. For the analysis of tricyclic base and cis/trans tetracyclic cations of the alkaloids, NMR and X-ray crystallography were used. - Highlights: ? We describe fundamental fluorescence characteristics of alkaloids protopine and allocryptopine. ? We analyzed the pH-dependent transitions and cis/trans isomerization. ? These two alkaloids can be better distinguished by their fluorescence decay characteristics. ? The fluorescence parameters are related to the NMR and crystallographic structural data.

British Library Electronic Table of Contents (United Kingdom)

A method to achieve NMR of dilute samples in the earth's magnetic field by applying para-hydrogen induced polarization is presented. Maximum achievable polarization enhancements were calculated by numerically simulating the experiment and compared to the experimental results and to the thermal equilibrium in the earth's magnetic field. Simultaneous 19F and 1H NMR detection on a sub-milliliter sample of a fluorinated alkyne at millimolar concentration (1018 nuclear spins) was realized with just one single scan. A highly resolved spectrum with a signal/noise ratio higher than 50:1 was obtained without using an auxiliary magnet or any form of radio frequency shielding.

International Nuclear Information System (INIS)

Portuguese 2000 p. 117-118 Brazil Monteiro, Elisabeth EC Tavares,

UK PubMed Central (United Kingdom)

The product-operator formalism is the most commonly used tool for describing and designing multidimensional NMR experiments. In spite of its relative simplicity and sound theoretical underpinnings,...Full Text Available

International Nuclear Information System (INIS)

... Commission, Rio de Janeiro Rio de Janeiro, RJ (Brazil) 26-27 Nov 1998 1

UK PubMed Central (United Kingdom)

Copper deficiency is associated with impaired brain development and mitochondrial dysfunction. Perinatal copper deficiency was produced in Holtzman rats. In vivo proton NMR...Full Text Available

International Nuclear Information System (INIS)

Portuguese 1999 1 p. Brazil Vilegas, Wagner UNESP, Araraquara, SP

Energy Technology Data Exchange (ETDEWEB)

The fundamental product of tetracycline hydrochlorine gamma radiolysis was separated in its solid state. From the results of spectroscopic studies it has been established that it is des-N,N-dimethylaminotetracycline.

UK PubMed Central (United Kingdom)

An application that provides a flexible and easy to use interface to the GAMMA spectral simulation package is described that is targeted at investigations using in vivo MR spectroscopic methods....Full Text Available

UK PubMed Central (United Kingdom)

In this study, bone mineral density (BMD) of normal (CON), ovariectomized (OVX) and partially nephrectomized (NFR) rats was measured by ³¹P NMR spectroscopy; bone matrix density was...Full Text Available

UK PubMed Central (United Kingdom)

Here we report the first ¹H NMR metabolomics studies on excised lungs and bronchoalveolar lavage fluid (BALF) from mice exposed to crystalline silica. High resolution ¹H...Full Text Available

UK PubMed Central (United Kingdom)

The bioenergetic capacity of skeletal muscle in a 17-year-old patient with a severe defect in complex III of the electron transport chain has been examined by 31P NMR measurements of the molar ratio...Full Text Available

International Nuclear Information System (INIS)

Selected derivatives of cyclophosphamide (CP) metabolites were synthesized and the solution chemistry of each was studied by "3"1P nuclear magnetic resonance (NMR) spectroscopy under a standard set of reaction conditions at physiological pH (7.4) and temperature (37"0C). Complementary "2H and "1"3C NMR spectral data was obtained using isotopically ("2G and "1"3C) enriched CP metabolites. The CP derivatives were synthesized by the ozonolysis of substituted 3-butenyl phosphorodiamidates, and were isolated as analogues of either cis and trans 4-hydroperoxy-CP or aldophosphamide (AP). The relative ratios of the tautomeric species, 4-hydroxy-CP and AP, and their half-lives (T/sub 1/2/) were measured by "3"1P NMR spectroscopy. The influence of CP metabolites on perfused U-937 cells, a CP-sensitive human lymphoma, was observed by high resolution "3"1P NMR spectroscopy. In this manner, it was possible to ...

Energy Technology Data Exchange (ETDEWEB)

In embodiments, spectroscopic monitor monitors modulated light signals to detect low levels of contaminants and other compounds in the presence of background interference. The monitor uses a spectrometer that includes a transmissive modulator capable of causing different frequency ranges to move onto and off of the detector. The different ranges can include those with the desired signal and those selected to subtract background contributions from those with the desired signal. Embodiments of the system are particularly useful for monitoring metal concentrations in combustion effluent.

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A two-beam spectroscopy (TBS) system is evaluated theoretically and experimentally. This new spectroscopic technique uses correlations between components of emitted light separated by a small difference in angle of propagation. It is thus a non-perturbing plasma diagnostic which is shown to provide local (as opposed to line-of-sight averaged) information about fluctuations in the density of light sources within a plasma - information not obtainable by the usual spectroscopic methods. The present design is an improvement on earlier systems proposed in a thesis by Rostler.

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The shifts induced by equimolar mixture of typical lanthanide shift reagent such as 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octadionato europium with silver trifluoroacetate in /sup 1/H NMR spectra of aromatic hydrocarbons have been used for analytical purposes; the NMR determination of m- and p-xylenes in mixtures has been chosen as an example. The use has been made of the difference between induced shifts of methyl group signals in the /sup 1/H NMR spectra of m- and p-xylenes. The magnitude of induced shifts of methyl groups signal in m-xylene is always larger than that of p-isomer, irrespective of contents of m- and p-xylenes in mixture.

British Library Electronic Table of Contents (United Kingdom)

Summary: The surface coverage of amorphous silica gels used in the synthesis of silica polyamine composites has been investigated by 29Si NMR. By diluting the polyamine anchor silane, chloropropyl trichlorosilane, with methyl trichlorosilane it was found that surface coverage could be markedly improved for a range of amine polymers after grafting to the silica surface. The commensurate decrease in the number of anchor points and increase in the number of free amines results in an increase in metal capacity and/or an improvement in capture kinetics. Solid state CPMAS-13C NMR has been employed to investigate the structure and metal ion binding of a series of these composite materials. It is reported that the highly branched polymer, poly(ethyleneimine) (PEI) exhibits much broader 13C NMR res...

Science.gov (United States)

{sup 1}H, {sup 13}C, {sup 27}Al, and {sup 29}Si magic-angle-spinning (MAS) NMR was used to elucidate the nature of the catalytic activity of zeolite H-ZSM-5. {sup 1}H MAS NMR of sealed samples after mild hydrothermal dealumination shows that the enhanced activity for n-hexane cracking is not due to an enhanced Bronstead acidity. The concentrations of the various OH groups and aluminous species suggest that the reason for the enhanced catalytic activity is the interaction of the n-hexane molecule with a bridging hydroxyl group and with extra-framework aluminium species, which give rise to the enhanced activity, cannot be easily removed from their positions, and are therefore immobilized by the zeolitic framework.

Science.gov (United States)

The effect of treatment of Na-forms of zeolites with HCl solutions and of heat treatment of their NH/sub 4/-forms on the stability of aluminum-oxygen tetrahedra has been studied in this work by high-resolution NMR on /sup 29/Si nuclei, using the synthetic zeolites X, Y, and M (mordenite) as the objects of the study. The exchange capacity with respect to Na/sup +/ ions was determined by analyzing the equilibrium solutions after contact of the samples with 0.5 NH/sub 4/Cl solution on a flame photometer. The high-resolution /sup 29/Si NMR spectra of polycrystalline samples were recorded on an SKhR-200 spectrometer with a superconducting solenoid at a frequency of 39.75 MHz with ultrafast mechanical rotation (3 kHz) of the sample at the magic angle to the external magnetic field. The results obtained are given.

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Here we present evidence that in water/acetonitrile solvent detailed structural and dynamic information can be obtained for important proteins that are naturally present as oligomers under native conditions. An NMR-derived human insulin monomer structure in H{sub 2}O/CD{sub 3}CN, 65/35 vol%, pH 3.6 is presented and compared with the available X-ray structure of a monomer that forms part of a hexamer (Acta Crystallogr. 2003 Sec. D59, 474) and with NMR structures in water and organic cosolvent. Detailed analysis using PFGSE NMR, temperature-dependent NMR, dilution experiments and CSI proves that the structure is monomeric in the concentration and temperature ranges 0.1-3 mM and 10-30 deg. C, respectively. The presence of long-range interstrand NOEs, as found in the crystal structure of the monomer, provides the evidence for conservation of the tertiary structure. Starting from structures calculated by the ...

UK PubMed Central (United Kingdom)

High resolution structural elucidation of macromolecular structure by solid-state nuclear magnetic resonance requires the preparation of uniformly aligned samples that are isotopically labeled. In...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

UK PubMed Central (United Kingdom)

The bulky octahedral complex, Rh(bpy)₂chrysi³⁺ (chrysi = 5, 6- chrysenequinone diimine), binds single base mismatches in a DNA duplex with micromolar binding affinities...Full Text Available

UK PubMed Central (United Kingdom)

Hydrogen cyanide polymerizes readily under a variety of conditions and significant prebiotic roles have been suggested for these polymers due to the abundance of HCN in universe. However, the structures...Full Text Available

UK PubMed Central (United Kingdom)

The passage of a vascular-injected paramagnetic contrast reagent (CR) bolus through a region-of-interest affects tissue ¹H₂O relaxation and thus MR image intensity. For longitudinal...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

UK PubMed Central (United Kingdom)

BackgroundPathophysiological mechanisms involved in amyotrophic lateral sclerosis (ALS) are complex and none has identified reliable markers useful in routine patient evaluation....Full Text Available

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Synaptobrevin is a synaptic vesicle protein that has an essential role in exocytosis and forms the SNARE complex with syntaxin and SNAP-25. We have analyzed the structure of isolated synaptobrevin and its binary interaction with syntaxin using NMR spectroscopy. Our results demonstrate that isolated synaptobrevin is largely unfolded in solution. The entire SNARE motif of synaptobrevin is capable of interacting with the isolated C-terminal SNARE motif of syntaxin but only a few residues bind to the full-length cytoplasmic region of syntaxin. This result suggests an interaction between the N- and C-terminal regions of syntaxin that competes with core complex assembly.

International Nuclear Information System (INIS)

The authors have performed a preliminary design for a persistent GHz NMR magnet at 23.5 T and 1.8 K operating conditions. In this paper the authors shall address the issues of realistic conductor selection, the coil design, the magnetic and mechanical analysis of the coil, and the required field uniformity. In addition, they shall describe the GHz magnet cryostat with a practical 1.8 K J-T refrigerator system. Finally vibration isolation system and field shield design and its associated field harmonics will be analyzed.

UK PubMed Central (United Kingdom)

This paper discusses the fundamentals, applications, potential, limitations, and future perspectives of polarized light reflection techniques for the characterization of materials and related systems...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

We present photoelectric BVRI photometry for 16 T Tau and related stars in the Rho Oph dark cloud, as well as vidicon spectroscopic observations for nine stars. The color excesses of these stars favor circumstellar dust shells as the source of the observed infrared excesses.

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A novel approach to the Bragg curve spectroscopy is utilized to construct a charged particle detector which makes fragment elemental identification and energy measurement possible. The advantage of the construction includes good timing and spectroscopic properties with a very low energy threshold. ((orig.))

International Nuclear Information System (INIS)

For many centuries paper was the main material for recording cultural achievements all over the world. Paper is mostly made from cellulose with small amounts of organic and inorganic additives, which allow its identification and characterization and may also contribute to its degradation. Prior to 1850, paper was made entirely from rags, using hemp, flax and cotton fibres. After this period, due to the enormous increase in demand, wood pulp began to be commonly used as raw material, resulting in rapid degradation of paper. Spectroscopic techniques represent one of the most powerful tools to investigate the constituents of paper documents in order to establish its identification and its state of degradation. This review describes the application of selected spectroscopic techniques used for paper characterization and conservation. The spectroscopic techniques that have been used and will be reviewed include: ...

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The rare earth antimonates RE{sub 3}Sb{sub 5}O{sub 12} constitute an isostructural series, where the rare earth site symmetry is S{sub 4}. The spectroscopic properties of pure or doped compounds of this family are studied in order to derive their energy level schemes and to simulate them through the crystal field theory, by using the approximated D{sub 2d} potential. The paramagnetic susceptibilities are calculated with the derived wavefunctions and compared to experiment.

International Nuclear Information System (INIS)

The main features and advantages of a new low energy nuclear spectroscopic method, the in-beam spectroscopy are described. Results of in-beam spectroscopic experiments performed at the Institute of Nuclear Research (ATOMKI, Debrecen, Hungary) are summarized. Gamma spectra of in-beam produced odd-odd nuclei were measured, gamma-energies were determined. Measurement of gamma-gamma coincidences led to the construction of energy level schemes of the investigated nuclei. Internal conversion electron spectroscopy was used to determine the multipolarities of transitions. A few spectra and level schemes are presented to illustrate the review. Theoretical interpretation of experimental results are briefly summarized. (D.Gy.).

Energy Technology Data Exchange (ETDEWEB)

NMR and CD studies indicate that Mg/sup 2 +/ and Ca/sup 2 +/ are able to change the conformation of tetracycline in DMSO solution. This may affect the in vivo effect of tetracycline. Using /sup 23/Na NMR, the formation constant of NaLAS (LAS represents the anion of lasalocid A) was found to be 80 M/sup -1/ which is much smaller than that in less polar solvents. Spin-lattice relaxation measurements were made to study the binding sites of Gd/sup 3 +/ on Las in ChCl/sub 3/-DMF mixed solvent system. No intermediate conformation (between cyclic and open-chain) was found. LAS was found to be a good second-sphere ligand to inert transition-metal amines. NMR studies suggest that LAS is in cyclic conformation when bound to these metal amines. A new method for the synthesis of spin-labeled anticancer Pt(II) complexes was developed. It is very simple and gives high yield of pure spin-labeled Pt(II) complexes.

International Nuclear Information System (INIS)

#beta#-SiAlON was synthesized from a zeolite by NH_3 gas nitridation and its formation mechanism was investigated using X-ray diffraction and "2"9Si and "2"7Al NMR spectroscopy. It was revealed that most of the Si and Al atoms react to form #beta#-SiAlON via amorphous forms of Si-Al-O-N and O-SiAlON. Nitridation using NH_3 gas is an effective means of preventing mullite formation and promoting the introduction of nitrogen into aluminosilicate materials at lower temperatures than temperatures required by the carbothermal reduction nitridation process. Further, the NMR spectra showed that the siliceous part of the system changed into low z-value of Si_6_-_zAl_zO_zN_8_-_z (#beta#-SiAlON) and the incorporation of Al components into the #beta#-SiAlON was promoted in the later stages of the reaction. (author)

CERN Document Server

We report $^{7}$Li pulsed NMR measurements in polycrystalline and single crystal samples of the quasi one-dimensional S=1 antiferromagnet LiVGe$_2$O$_6$, whose AF transition temperature is $T_{\\text{N}}\\simeq 24.5$ K. The field ($B_0$) and temperature ($T$) ranges covered were 9-44.5 T and 1.7-300 K respectively. The measurements included NMR spectra, the spin-lattice relaxation rate ($T_1^{-1}$), and the spin-phase relaxation rate ($T_2^{-1}$), often as a function of the orientation of the field relative to the crystal axes. The spectra indicate an AF magnetic structure consistent with that obtained from neutron diffraction measurements, but with the moments aligned parallel to the c-axis. The spectra also provide the $T$-dependence of the AF order parameter and show that the transition is either second order or weakly first order. Both the spectra and the $T_1^{-1}$ data show that $B_0$ has at most a small effect on the alignment of the AF ...

International Nuclear Information System (INIS)

A dense silica glass was prepared by consolidating a highly dispersed silicic acid powder (particle size 1H magic-angle spinning (MAS) NMR confirmed an increase in hydroxyl groups in the sample prepared by SPS relative to that of the conventional SiO2 reference glass. Aside from the comparably high water content, we conclude from the similarity of the IR-reflectance and the 29Si MAS NMR spectra of the SPS sample and the corresponding spectra of the conventionally prepared silica glass, that the short- and medium-range order is virtually the same in both materials. Raman spectroscopy, however, suggests that the number of three- and four-membered rings is significantly smaller in the SPS sample compared to the conventionally prepared sample. Based on these results we conclude that it is possible to prepare glasses by compacting amorphous powders by the SPS process. The SPS process may therefore enable the preparation of glasses with compositions ...

International Nuclear Information System (INIS)

GaAs1-xPx p-n junction structures were grown on the epi-ready n-type GaAs(100) substrate by solid source MBE system for different phosphor compositions. To obtain the lattice-match sample structure was applied graded growth procedure. The structural and optical properties of the sample structures with different P concentration were investigated by using X-ray diffraction (XRD), spectroscopic ellipsometry (SE). In addition, The range of lattice parameters in the graded epilayer and phosphorous composition were determined from the HRXRD rocking curve simulation. We analyse dielectric function spectra of disordered GaAs1-xPx junction structures measured using spectroscopic ellipsometry at room temperature in the 0.6-4.7 eV photon energy region. The critical energy points such as band gap energy and spin-orbit-split energy of these structures were determined using SE data. It is detected that E0, E1 ,E2 energies of the GaAs1-xPx p-n junction ...

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We have examined the theory of NMR multiple echoes developed for solid {sup 3}He to determine whether multiple echoes could be observed in solid hydrogen. We were particularly interested in the possibility of testing for low frequency quantum tunneling motions in solid hydrogen by the observation of multiple echoes. We find that for easily accessible nuclear spin polarizations, P > 12%, multiple echoes would be observed for HD impurities in solid parahydrogen if motional narrowing is effective in increasing the HD nuclear spin-spin relaxation time T{sub 2} to the order of 1 msec. These values for T{sub 2}, which have been observed for HD impurity concentrations of the order of 1%, are larger than the calculated rigid lattice values and can be attributed to quantum tunneling at frequencies of the order of 1kHz.

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The effects of spin diffusion on the free induction decay (FID) of protons associated with the noncrystalline domains of two polymers, polyethylene and blended Nylon 66 (ZYTEL-408), have been examined using Goldman--Shen NMR pulse sequence ((1/2)..pi..x-t/sub 0/-(1/2)..pi..x-bar-tau-(1/2)..pi..x-t). At tau< or approx. =100 ..mu..s, the FID is drastically distorted from the exponential form while at longer tau(tau> or approx. =500 ..mu..s) an exponential FID is observed; but its transverse spin relaxation rate is smaller than that of the FID obtained after a single (1/2)..pi..x pulse and approaches this value at the limit of large tau. These findings are interpreted in terms of the theory of rapid spin diffusion. The spatial variation in the spin relaxation rate within the noncrystalline domain is inferred.

British Library Electronic Table of Contents (United Kingdom)

The endophytic fungus Trichothecium roseum LZ93 from Maytenus hookeri was found to antagonize other pathogenic fungi in vitro. To identify which compound contributed substantially to the antagonism, we fermented the strain and purified its fermentation products. Eleven compounds were obtained, including two trichothecenes, five rosenonolactones, two cardiotonic cyclodepsipeptides, and two sterols. Compound 11?-hydroxyrosenonolactone (1) was assigned according to 1D and 2D-NMR data for the first time. At the same time, the 1H and 13C-NMR assignments for 6?-hydroxyrosenonolactone (2) were revised. Of all of them, only trichothecin (6) showed strong antifungal activity. Based on our observations of the antagonistic activity and the other experimental results, we suggest that the antifungal co...

British Library Electronic Table of Contents (United Kingdom)

Cyclization of deproteinized natural rubber (DPNR) or purified natural rubber latex was effectively performed in latex phase by using trimethylsilyl-trifluoromethane sulfonate or trimethylsilyl triflate (TMSOTF) as a novel catalyst, which is still not reported in the case of natural rubber latex. Various cyclization conditions affecting the degree of cyclization were studied, such as dry rubber contents, temperature, TMSOTF concentrations, and time. The cyclized products were characterized by FTIR, Raman, 1H-, and 13C-NMR spectroscopies, as well as DSC and TGA. The degree of cyclization was estimated by 1H-NMR spectrum. It was found that the degree of cyclization in NR was a function of cyclization conditions. The thermal stability of cyclized DPNR increased with the degree of cyclization....

Science.gov (United States)

One of the stiffest challenges in structural studies of proteins using NMR is the assignment of sidechain resonances. Typically, a panel of lengthy 3D experiments are acquired in order to establish connectivities and resolve ambiguities due to overlap. We demonstrate that these experiments can be replaced by a single 4D experiment that is time-efficient, yields excellent resolution, and captures unique carbon-proton connectivity information. The approach is made practical by the use of non-uniform sampling in the three indirect time dimensions and maximum entropy reconstruction of the corresponding 3D frequency spectrum. This 4D method will facilitate automated resonance assignment procedures and it should be particularly beneficial for increasing throughput in NMR-based structural genomics initiatives.

British Library Electronic Table of Contents (United Kingdom)

The utilization of thermal fluctuations or Johnson/Nyquist noise as a spectroscopic method to determine transport properties in conductors or semiconductors is developed. The autocorrelation function is obtained from power spectral density measurements thus enabling electronic transport property calculation through the Green-Kubo formalism. This experimental approach is distinct from traditional numerical methods such as molecular dynamics simulations, which have been used to extract the autocorrelation function and directly related physics only. This work reports multi-transport property measurements consisting of the electronic relaxation time, resistivity, mobility, diffusion coefficient, electronic contribution to thermal conductivity and Lorenz number from experimental data. Double va...

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The luminescence spectra of trivalent europium ion embedded in various rare earth chromates were analysed. The spectroscopic data in most of chromates are in agreement with the structural determination but for some others the discrepancy between two methods is underlined. Energy level schemes were deducted from the experimental emission spectra and the crystal field simulation has been performed. The maximum splitting of the {sup 7}F{sub 1} manifold of the Eu{sup 3+} ion as a function of N{sub v}, the so-called crystal field strength parameter, is given. This allows us to classify the compounds according to their crystal field extent. (author) 11 refs, 8 figs, 2 tabs

International Nuclear Information System (INIS)

The spectroscopic properties of Pr"3"+ doping two lanthanum chlorotungstate hosts: the orthorhombic LaWO4Cl (1-1) and the hexagonal La3WO4Cl6 (3-1), as well as those of PrWO4Cl and Pr3wO613 have been investigated. The simulations of the energy level schemes are carried out within the crystal field theory frame. Each simulation involves 7 free ion parameters and 14 non-zero crystal field parameters (cfps), corresponding to the C_s point symmetry of the site occupied by the rare earth, in both structures.

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The feasibility of spectroscopic measurement of the velocity distribution of alpha particle using the ablation cloud of a lithium or boron pellet was tested in the DT experiment of TFTR. The measurement was performed using a 10-channel narrow-band filtered spectrometer in the wavelength covering the 3.5 MeV alpha particle Doppler broadening region of the He II 468.6 nm line and its vicinity. The spectra from a lithium pellet consists of the continuum bremsstrahlung background, lithium line emissions and possibly a 468.6 nm helium line. However, no clear evidence of alpha particles was observed, even when boron pellets were injected. (orig.) 4 refs.

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A first-principles quasiparticle approach to the electronic excitation energies in crystals and at surfaces is described. The quasiparticle energies are calculated within the GW approximation for comparison with photoemission and other spectroscopic experiments. Applications of the method to bulk semiconductors and the Si(111)2[times]l, Ge(111)2[times]l. and H/Si(III) surfaces are presented. In both cases, significant self-energy corrections arising from many-electron effects to the excitation energies are found. Using atomic positions from total energy minimization, the calculated excitation energies explain quantitatively the experimental spectra. This approach thus provides an ab initio means for analyzing and predicting results from spectroscopic probes.

International Nuclear Information System (INIS)

High-temperature LiCl-KCl molten salt medium provides an efficient way to produce the paramagnetic Eu(II) ion to be magnetically diluted into a diamagnetic host medium. Eu(II) was formed by a dissolution and an auto-reduction processes in a high-temperature LiCl-KCl eutectic melt at 723 K by using Eu_2O_3 as a starting material. By using EPR and luminescence spectroscopic method, we studied the nature of the magnetically isolated paramagnetic Eu(II) ion diluted in a LiCl-KCl medium. With the aid of these spectroscopic tools, it was found that stable Eu(II) species was formed spontaneously at 723 K under anaerobic conditions. EPR and luminescence spectroscopy provided detailed information regarding the nature of the europium ion in a molten salt.

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Pyrochemical processing of nuclear fuels using molten salts has attracted much attention because of its potential to be applied for a future spent nuclear fuel management. In the pyrochemical processing, there are a number of steps to electro-refine and electro-win each element of lanthanides and actinides, commonly called trans-uranic elements (TRU). In order to materialize the pyrochemical processing in the nuclear power plant environments, qualitatively and quantitatively monitoring of each elements is necessary. Thus, we have undertaken to develop an on-line observing system of the TRU in LiCl-KCl molten salt media by using electrochemical and spectroscopic methods. In this work, the electrochemical and spectroscopic behaviors of europium as a proxy material for TRU were investigated simultaneously in the LiCl-KCl molten salt.

British Library Electronic Table of Contents (United Kingdom)

It is assumed that protein fibrils manifested in amyloidosis result from an aggregation reaction involving small misfolded protein sequences being in an `oligomeric' or `prefibrillar' state. This review covers recent optical spectroscopic studies of amyloid protein misfolding, oligomerization and amyloid fibril growth. Although amyloid fibrils have been studied using established protein-characterization techniques throughout the years, their oligomeric precursor states require sensitive detection in real-time. Here, fluorescent staining is commonly performed using thioflavin T and other small fluorescent molecules such as 4-(dicyanovinyl)- julolidine and 1-amino-8-naphtalene sulphonate that have high affinity to hydrophobic patches. Thus, populated oligomeric intermediates and related `pre...

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Reaction kinetics for the displacement of 5-aminoquinoline (5-Aq) and diethyl sulfide (SEt{sub 2}) from cis-[PtPh{sub 2}(CO)(L)] (L = 5-Aq or SEt{sub 2}) by aliphatic amines was measured for a wide array of amines. Reaction products were characterized by IR and NMR spectroscopies and crystalk structures of selected products were reported. Steric effects on the substitutions were discussed.

International Nuclear Information System (INIS)

The marked difference between the intra- and extracellular "3"1P NMR chemical shifts of various phosphoryl compounds when added to a red cell suspension may be largely understood in terms of the effects of hemoglobin on the "3"1P NMR chemical shifts. The presence of [oxy- or (carbonmonoxy)-] hemoglobin inside the red cell causes the bulk magnetic susceptibility of the cell cytoplasm to be significantly less than that of the external solution. This difference is sufficient to account for the difference in the intra- and extracellular chemical shifts of the two phosphate esters trimethyl phosphate and triethyl phosphate. However, in the case of the compounds dimethyl methylphosphonate, diethyl methylphosphonate, and trimethylphosphine oxide as well as the hypophosphite, phenylphosphinate, and diphenylphosphinate ions, hemoglobin exerts an additional, much larger, effect, causing the "3"1P NMR resonances to shift to lower ...

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Analysis of published NMR relaxation data of /sup 6/Li and /sup 7/Li in Li/sub 3/N leads to a unique model fo Li/sup +/ hopping along the c-axis. It is one in which an ion goes directly from one Li(1) plane to another Li(1) plane by passing through the intermediate Li(2) plane.

International Nuclear Information System (INIS)

The susceptibility of solid "3He is deduced from multiple echoes observed in pulsed NMR experiments. It follows a Curie Weiss law at high temperature, increases faster than this law below 5 mK and drops abruptly around 1 mK. (Auth.).

UK PubMed Central (United Kingdom)

A nonperturbing 13C nuclear magnetic resonance (NMR) method was used to monitor the equilibrium distribution of carboxyl 13C-enriched fatty acids (FA) between distinct binding sites on human serum albumin,...Full Text Available

International Nuclear Information System (INIS)

For the intermetallic system CaCdsub(1-x)Tlsub(x), 0 <= x <= 1, the Knight shift Ksub(s) of the Cd-NMR and the Tl-NMR were calculated as a function of x, Ksub(s) = Ksub(s)(x). The theoretical investigations were performed on the basis of relativistic augmented-plane-wave (RAPW) band-structure calculations for the boundary phases CaCd and CaTl respectively, and by using the rigid band model for the ternary phases. The density of states and the matrix elements of the relativistic hyperfine operator for electron states at the Fermi surface were calculated in detail. The obtained values were compared with nonrelativistic calculations. The effect of using different exchange potentials was studied for Ksub(s)(Tl). For the Cd-NMR the relativistic effects enhance the nonrelativistic results by a factor of about 1.4. The theoretical value for the Knight shift is smaller than the experimental one by a factor of 1.13. The band ...

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Theoretical x-ray transition energies, lifetimes and partial multiplet fluorescence yields are presented for all spectroscopic terms of electron configurations with a single K-shell vacancy and varying number of electrons in the L-shell and M/sub 1/-subshell for multiply-ionized silicon. 9 tables.

International Nuclear Information System (INIS)

The 142Nd and 143Nd nucleus excited states have been studied using the "1"4"2","1"4"3Nd(p,p') and "1"4"0Ce(#alpha#,n)"1"4"3Nd reactions. The energy level schemes were determined as well as spectroscopic information about spin, parity and multipolarity of electromagnetic transitions. 54 refs, 25 figs, 9 tabs.

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By dissolution of iron (2) carbonate in rhenium acid iron (2) perrhenate of the Fe(ReO/sub 4/)/sub 2/x4H/sub 2/O composition is obtained. By the method of thermal analysis the limits of tetra-, dihydrate and anhydrous iron (2) perrhenate stability are revealed. By means of X ray phase and IR spectroscopic analysis methods modification of structure in the process of synthesized salt dehydration is shown.

UK PubMed Central (United Kingdom)

The alternative low-spin states of Fe³⁺ and Fe²⁺ cytochrome c induced by SDS or AOT/hexane reverse micelles exhibited the heme group in a less...Full Text Available

CERN Document Server

Dwarf galaxies are generally faint. To derive their age and metallicity distributions, it is critical to optimize the use of any collected photon. Koleva et al., using full spectrum fitting, have found strong population gradients in some dwarf elliptical galaxies. Here, we show that the population profiles derived with this method are consistent and more precise than those obtained with spectrophotometric indices. This allows studying fainter objects in less telescope time.

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Dithiolato-nickel complexes with multisulfur ligands derived from benzenehexathiolate have been synthesized. The properties of the monomeric and polymeric complexes have been characterized by ESR spectroscopic and magnetochemical data and by electrical conductivity measurements. The prepared complexes are paramagnetic and have characteristic absorptions between 800 and 1000 nm. (orig.).

International Nuclear Information System (INIS)

Evaluated spectroscopic data for all nuclei with mass number A = 216 are presented together with the relevant level schemes from radioactive decay and nuclear reaction studies. The experimental data are evaluated, inconsistencies and discrepancies are noted, and adopted values for level and #gamma#-ray energies, #gamma# intensities, as well as for other nuclear properties are given. The present evaluation supersedes the earlier one on A = 216 by A. Artna-Cohen (1997Ar04), published in Nuclear Data Sheets 80, 157 (1997).

Science.gov (United States)

An IR spectroscopic study of the reduction of copper-exchanged Linde Na-Y zeolite with hydrogen or carbon monoxide and oxidation with oxygen or oxygen-18 showed that copper(I) and AlO(+1) are formed during reduction, and that oxidation generates copper(II) ions but does not change the aluminum species. Trigonally coordinated aluminum was not detected.

CERN Document Server

We have performed multicanonical Monte Carlo simulations of C-peptide of ribonuclease A. It is known by CD and NMR experiments that this peptide has high alpha-helix content in aqueous solution and that the side-chain charges of residues Glu-2$^-$ and His-12$^+$ play an important role in the stability of the alpha-helix. In order to confirm these experimental implications, we have used two analogues of the peptide with charged and neutral side chains of Glu-2 and His-12. Two dielectric functions, distance-dependent and constant, are considered to study the effects of solvent contributions. All the simulations were started from random initial conformations. Various thermodynamic quantities such as average helicity as a function of residue number and average distance between two side chains as a function of temperature are calculated. The results are found to be in accord with the implications of CD and NMR experiments. The lowest-energy ...

International Nuclear Information System (INIS)

Polypeptides, copolymers of #alpha#-amino acids and #alpha#-hydroxy acids, could prove to be a valuable new class of synthetic biodegradable polymers. In this paper. steps in synthesis of poly (dl-lactide-co-3, 6-dimethylmorpholine-2,5-dione) from dl-lactide and dl-3,6-dimethylmorpholine-2,5-dione was explained. dl-Lactide was synthesized from lactic acid. In the reaction of 2-bromopropionyl chloride and dl-alanine, N-(2-bromopropionyl)-dl-alanine was prepared and this material was converted to its salt and finally this salt was converted to 3,6-dimethylmorpholine-2,5-dione in a sublime r. These two monomers, that is d l-lactide and dl-3,6-dimethylmorpholine-2,5-dione was polymerized by ring-opening polymerization. F T-IR, "1H NMR, "1"3C NMR Spectra were used for structure elucidation of all intermediate compounds and final product.

British Library Electronic Table of Contents (United Kingdom)

Platinum(II) complexes (1-4) with bidentate N,Nprime-ligands, O,Oprime-dialkyl esters (alkyl = ethyl, n-propyl, n-butyl and n-pentyl), of (S,S)-ethylenediamine-N,Nprime-di-2-(4-methyl)pentanoic acid were synthesized and characterized by IR, 1H NMR and 13C NMR spectroscopy and elemental analysis. DFT calculations were performed for the complexes and it was found that only one diastereoisomer could be formed. Cytotoxic activity of complexes 1-4 was determined against chronic lymphocytic leukemia cells (CLL) and compared to the activity of ligand precursors L12HCl-L42HCl and corresponding palladium(II) complexes, [PdCl2L] (L = L1-L4). The complexes were found to exhibit significantly higher antitumor activities than cisplatin on CLL cells. Cytotoxic effect of platinum(II) complexes on CLL cel...

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Following the successful application of hydrostatic pressure in mechanistic investigations of organic reactions, chemists have launched a vigorous effort to apply this tool to substitution reactions of coordination compounds. The authors began to study pressure effects in the NMR spectra of keton-lanthanide combination with the hope that the increase shifts anticipated might enhance the utility of the method, perhaps even expand its applicability to new classes of compounds. 5-Phenyl- and 5-tert-butyladamantan-2-one, piperidine, tetrahydrofuran, and cyclopentanol exhibited pressure-reduced lanthanide-induced shifts with Eu(fod)/sub 3/; Yb(fob)/sub 3/ and the shielding reagent Pr(fod)/sub 3/ showed the same effect with adamantanone. Solvent variations (CD/sub 2/Cl/sub 2/, CCl/sub 4/) caused minor changes in the magnitude of these shifts but did not reverse any. With the objective of learning whether these effects are due to a suppressed equilibrium population or to ...

International Nuclear Information System (INIS)

The pozzolanic behaviour of compound-activated red mud-coal gangue has been investigated through TG, DTA, XRD, FTIR and 27Al MAS NMR. From viewpoint of reaction kinetics, it is found that the pozzolanic reaction mechanism of the compound-activated red mud-coal gangue - lime system is clearly consistent with diffusion control up to 14 days, and the reaction rate constant calculated from Jander equation decreases with the increase of CaO addition in the system. The hydration products formed in the red mud-coal gangue - lime systems at ambient temperature are essentially aluminous C-S-H and Ca3Al2O6.xH2O. From TG analysis results, it is thought that the high amount of Ca(OH)2 in the pastes of studied system is not conducive to the continual increase of non-evaporable water content of the hydration products. Of particular interest, 27Al MAS NMR proved to be an effective technique to obtain valuable information of Al[4] in C-S-H and Al[6] in ...

International Nuclear Information System (INIS)

Ionic motion of a divalent cation, Ba"2"+, in a single crystal of Ba-Al-priderite was studied using "2"7Al as an NMR probe. Several pairs of satellite peaks due to electric quadrupole interaction were observed superposed on broad satellite tails on both sides of the main peak of "2"7Al. These peak pairs indicate the existence of some stable three-dimensional configurations of Ba"2"+ ions in the structure, and the broad shoulders show a random substitution of Al"3"+ for Ti"4"+ sites. The temperature dependence of the spin-lattice relaxation time T"*_l measured in the temperature range from 161 to 1176 K was analyzed by a curve fitting method on the assumption that there are two types of Ba"2"+ ions. An activation energy of 0.47 eV was obtained for the motion of Ba"2"+ ions which are easy to move, and a broad distribution of activation energies spread over a range from 0.95 to 2.45 eV was obtained for the motion of Ba"2"+ ions which form a three-dimensional honeycomb ...

International Nuclear Information System (INIS)

Angelin Pedra is a specie found in the north of Mato Grosso State in Brazil, where an expressive volume of waste of this wood is produced. An alternative to recycle this waste is to produce wood plastic composites. However, structural and chemical investigations are fundamental to generate information for this use. In the present work, low field NMR was used to determine the spin-lattice and spin-spin relaxation times with objective to investigate the molecular dynamic behavior of the alburnu and cerne regions of Angelin Pedra aiming at a potential use of this waste wood in polymeric composites. The results of the proton spin-lattice relaxation time (T1H) and the proton spin-spin relaxation time (T2H) showed at least three different mobility domains for both regions. Among the values, one was very flexible and other was rigid. Knowing that wood is a polymer composite basically constituted by cellulose, hemicellulose and lignin can attribute the smaller T1 value and ...

Energy Technology Data Exchange (ETDEWEB)

The available experimental data on the specific heat, magnetic susceptibility, magnetization, valence, NMR Knight shift and relaxation rate, and the quadrupolar moment of YbPd{sub 2}Si{sub 2} are examined within the framework of the single-ion Anderson model. Such an analysis has previously given excellent agreement between theory and experiment for numerous other light heavy-fermion compounds, where crystalline fields do not play a dominant role. For YbPd{sub 2}Si{sub 2}, substantial crystalline-field splittings make difficult a quantitative comparison with existing exact solutions of the Anderson model. Inconsistencies with the interpretation that a nearly degenerate ground quadruplet determines the low-temperature thermodynamics are pointed out. It is concluded that at least three of the four Kramers doublets participate in the low-{ital T} properties. These three doublets should have a splitting of the order of the Kondo temperature, i.e., about 100 K. A simple ...

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Monoclonal antibodies (MAbs) 19-9 and 73-3 specific for human colon adenocarcinoma were labelled with a high number of gadolinium atoms. Twenty five DTPA were chelated per MAb, with only slight loss of immunoreactivity. The NMR contrast agent Gd-25 DTPA-MAb 19-9 or 73-3 ((Gd) 17 mumole/kg, (MAb) 60 microM) was injected into nude mice bearing human colon adenocarcinoma (SW948). Tumors were removed 24 hr after injection and T1 was measured in vitro. T1 relaxation time varied according to MAb specificity against tumour targets; T1 decreased 20% for MAb 19-9 and MAb 73-3 with SW948 tumor. Imaging was performed with this model. Very good contrast was obtained 24 hr after Gd-25 DTPA-MAb injection.

International Nuclear Information System (INIS)

The effect of the external pH on the intracellular pH in mung bean (Vigna mungo (L.) Hepper) root-tip cells was investigated with the "3"1P nuclear magnetic resonance (NMR) method. The "3"1P NMR spectra showed three peaks caused by cytoplasmic G-6-P, cytoplasmic Psub(i) and vacuolar Psub(i). The cytoplasmic and vacuolar pHs could be determined by comparing the Psub(i) chemical shifts with the titration curve. When the external pH was changed over a range from pH 3 to 10, the cytoplasmic pH showed smaller changes than the vacuolar pH, suggesting that the former is regulated more strictly than the latter. The H"+-ATPase inhibitor, DCCD, caused the breakdown of the mechanism that regulates the intracellular pH. H"+-ATPase appears to have an important part in the regulation of the intracellular pH. (author).

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In our evaluation we utilized the Asahi Mark-J NMR-CT system, with a resistive vertical quadrupolar electromagnet (0.1 Tesla) and a proton resonance frequency of 4.5 MHz. Our main imaging methods are the inversion-recovery or IR, saturation-recovery, or SR, and calculated T/sub 1/. Difference, or D images, constructed by subtracting the data of the IR signal from that of the SR signal, have also been obtained in some cases. The system allows averaging of raw data. Hybrid images were constructed from two or more images to obtain clear definition of areas of interest. By using the hybrid image, several tissues of different relaxation times can be shown in the same image. Application in our study of the newly developed hybrid image indicates its importance in the detection and diagnosis of lesion, especially the detection of the differentiation of an edematous lesion from a tumor, and also abnormal fluid collection such as the pleural effusion or ascites. We hope that ...

Science.gov (United States)

The dealumination of mordenite by acidification (HCl, HNO/sub 3/) and by SiCl/sub 4/ and steaming treatments is followed by high-resolution magic-angle-spinning solid-state /sup 29/Si and /sup 27/Al NMR spectroscopy. The combined use of these techniques leads to the determination of the silicon-aluminum ordering. It is demonstrated that aluminum atoms preferentially occupy tetrahedral positions in the four-membered rings of the mordenite structure. In addition, a mechanism of dealumination can be inferred, consisting in removing the aluminum atoms two by two from the four-membered rings. It is also possible to compute the number of SiOH groups left in the unit cell after the progressive removal of aluminum atoms: four groups per extracted Al atom are generated in the beginning of dealumination and this number gradually decreases to two, suggesting that a structural reorganization must necessarily occur for substantial dealumination. These silanol groups are also ...

Science.gov (United States)

Syntheses of all five of the singly labeled (/sup 15/N)adenines are now provided. The presence or absence of two-bond /sup 15/N-/sup 1/H spin couplings in their /sup 1/H NMR spectra confirm the location of the isotope in each case. The fragmentation patterns in their mass spectra are indicative of the sequential losses of HCN units and of CH/sub 2/N/sub 2/ from adenine upon electron impact.

International Nuclear Information System (INIS)

Polytetrafluoroethylene was obtained by radiation induced polymerization of tetrafluoroethylene in acetone at 195 K. An average diameter of the products was very small compared with commercial one; it was about 0.3 micro-meters. The yield was reached to 100% with a dose of 4 kGy. The crystallinity of the products is decreasing with increasing dose. The products become amorphous, for higher irradiation doses. It was found that PTFE obtained by irradiation of TFE in acetone at 195 K has branching structure. This was demonstrated by means of "1"9F MAS NMR. (Author)

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Our major goal of our work has been to develop and use NMR techniques to study how methanogenic archaebacteria deal with osmotic stress with the hope of providing insights into increasing the salt tolerance of other cells. The project has three main sections: (i) in vivo studies of methanogens; (ii) use of [sup l3]C- and [sup l5]N- labeled potential precursors and in vitro analyses of specific label uptake for elucidation of osmolyte dynamics and biosynthetic pathways of osmolytes in these organisms, and isolation of key biosynthetic enzymes; and (iii) collaborative studies on identification of organic solutes in other methanogens.

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XVTa and XXTa nuclei were oriented at low temperature as dilute impurities in Fe. The magnetic hyperfine splitting frequencies = B sub(HF)/Ih of the XVTa and XXTa ground states have been measured to be 320.45(11) and 317.552(55) MHz by using the technique of NMR-ON. Taking the known hyperfine field of Y Ta in Fe, the magnetic moments have been deduced: ( XVTa, 7/2 ) =2.270(45) and ( XXTa, 7/2 ) =2.250(45) sub(N). These values of the magnetic moments are discussed in the framework of the rotational model.

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The authors continued their efforts in studying the mechanism of carbalkoxylation of {sigma}-vinyls bound to platinum(II). In this work, the focus was specifically on the reductive elimination of {alpha},{beta}-unsaturated carboxylic esters form the carbonylated, alkoylated intermediates. Crystal structures of the carbonylated (12) and alkoxylated (13) intermediates were reported. Kinetic and NMR studies indicate that reductive elimination proceeds via a preequilibration involving phosphine dissociation, followed by a rate-determining trans-cis isomerization. 35 refs., 3 figs., 5 tabs.

Science.gov (United States)

We have designed a new nucleobase, benzodeazaadenine (BDA) that has a stronger charge transport ability than guanine and is not destroyed during charge transport process. By incorporating this new nucleobase into DNA, we demonstrated a protocol for real DNA nano-wire that is far superior to natural DNA. We also demonstrated that the selectivity for the interaction of Mn(II) ion with guanine N7 in G runs is a HOMO-controlled process, and as a consequence, the selectivity for G-metal ion interactions obtained by 15N-NMR studies would directly reflect the HOMO distribution of G-containing sequences in B-DNA. PMID:12903077

International Nuclear Information System (INIS)

This paper describes the chemical constituents isolated from aerial parts of the plant Galianthe brasiliensis. From a methanol extract, the iridoid glycosides asperuloside, deacetylasperuloside, mixture of Z- and E-6-O-p-coumaroylscandoside methyl ester, the triterpene ursolic acid and the steroids stigmasterol, campesterol, b-sitosterol and 3-O-b-glucopyranosyl sitosterol were isolated. The structures of the natural products were identified on the basis of spectral data, including 2D NMR experiments. The antiproliferative properties of the crude methanolic extract were investigated against a series of nine human cancer cell lines. (author)

Energy Technology Data Exchange (ETDEWEB)

The low excitation energy spectroscopy of /sup 86/Sr, /sup 88/Sr, /sup 89/Sr, /sup 86/Rb, and /sup 87/Rb nuclear systems was studied via one-nucleon transfer reactions. The strontium isotopes, /sup 87/Sr and /sup 88/Sr, were used as targets in this study. Spectroscopic strengths were extracted from the measured transfer reaction cross sections and the distorted wave Born approximation (DWBA) analysis. Efforts have been made to accomplish a complete detection of spectroscopic strengths through the excitation energy region where levels can be resolved and identified. A shell model sum rule analysis is then made. Diagonal matrix elements for the effective two-nucleon interaction were deduced from empirical energy centroid. Matrix elements normalized by their empirical monopole energy was plotted against the semiclassical angle between two spins. They were compared with various analytical function forms of the effective two-nucleon interaction ...

CERN Document Server

We present a spectroscopic catalog of 70,841 visually inspected M dwarfs from the seventh data release of the Sloan Digital Sky Survey (SDSS). For each spectrum, we provide measurements of the spectral type, a number of molecular bandheads, and the H-alpha, H-beta, H-gamma, H-delta and Ca II K emission lines. In addition, we calculate the metallicity-sensitive parameter zeta and identify a relationship between zeta and the g-r and r-z colors of M dwarfs. We assess the precision of our spectral types (which were assigned by individual examination), review the bulk attributes of the sample, and examine the magnetic activity properties of M dwarfs, in particular those traced by the higher order Balmer transitions. Our catalog is cross-matched to Two Micron All Sky Survey (2MASS) infrared data, and contains photometric distances for each star. Lastly, we identify eight new late-type M dwarfs that are possibly within 25 pc of the Sun. Future studies will use these data ...

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The spectroscopic properties of Eu{sup 3+} doped into two lanthanum chlorotungstates matrices, namely LaWO{sub 4}Cl (1-1) and La{sub 3}WO{sub 6}Cl{sub 3}(3-1), are investigated. The fluorescence spectra of these compounds, recorded at room and liquid nitrogen temperatures, show that the lanthanide ion occupies only one site with the low symmetry, C{sub s}, in both cases. From the energy level schemes of the {sup 7}F{sub J} levels (J = 0, 1, 2, 3, 4, 5), two sets of crystal field parameters (cfp) are deduced, in a C{sub 2v} approximated point symmetry (i.e., 9 cfp), simulating the experimental data, correctly. Furthermore, for the 3-1 compound, the data is complete enough to extend the calculations to the real point group, C{sub s} (14 cfp).

Science.gov (United States)

Newly commercialized Fourier transform Raman spectroscopic instrumentation provides a simpler alternative for vibrational spectroscopic analysis. Instrument vendors currently design for laboratory use, but there are many potential process applications of these stable, easy to use instruments. Raman spectroscopy is highly suited to analysis of aqueous samples. Near infrared excitation minimized fluorescence interference and allows for remote operation via fiber optic probes. The Department of Energy has funded research at the Measurement and Control Center to establish the utility of this method for on-line composition analysis in distillation columns. Laboratory evaluation and instrument employs an air-cooled laser and a thermoelectrically cooled detector. The device is mounted on a three by foot cart for convenient location in control rooms. Current fiber optic extension cables allow for analysis in a cell thirty five meters from the ...

International Nuclear Information System (INIS)

The "2"0 "2"1 "2"2Ne("6Li, d)"2"4 "2"5 "2"6Mg reactions have been studied at a bombarding energy of 32 MeV. Alpha particle spectroscopic strengths have been extracted for several low-lying levels by a finite-range distorted wave analysis. These are compared with theoretical predictions. The agreement is good both for relative strengths to different levels within a nucleus and for ground-state strengths relative to the "1"6O("6Li, d) result. Strengths calculated using eigenfunctions determined in large shell-model computations agree well with pure symmetry SU(3) predictions. The "2"1Ne("6Li, d) angular distributions for transitions to the ground-state band of "2"5Mg are characterized by the lower of the two L-transfers allowed for populating each level. For the 3"+(5.24 MeV) unnatural parity level in "2"4Mg, a two-step calculation gives a better account of the data than does a compound nuclear calculation. (Auth.).

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NMR spectroscopy combined with paramagnetic relaxation agents was used to study the positioning of the 40-residue Alzheimer Amyloid {beta}-peptide A{beta}(1-40) in SDS micelles. 5-Doxyl stearic acid incorporated into the micelle or Mn{sup 2+} ions in the aqueous solvent were used to determine the position of the peptide relative to the micelle geometry. In SDS solvent, the two {alpha}-helices induced in A{beta}(1-40), comprising residues 15-24, and 29-35, respectively, are surrounded by flexible unstructured regions. NMR signals from these unstructured regions are strongly attenuated in the presence of Mn{sup 2+} showing that these regions are positioned mostly outside the micelle. The central helix (residues 15-24) is significantly affected by 5-doxyl stearic acid however somewhat less for residues 16, 20, 22 and 23. This {alpha}-helix therefore resides in the SDS headgroup region with the face with residues 16, 20, 22 and 23 directed away ...

Science.gov (United States)

Because of its high price, the extra virgin olive oil is frequently target for adulteration with lower quality oils. This paper presents an innovative optical technique capable of quantifying the adulteration of extra virgin olive oil caused by lowergrade olive oils. It relies on spectral fingerprinting the test liquid by means of diffuse-light absorption spectroscopy carried out by optical fiber technology in the wide 400-1700 nm spectral range. Then, a smart multivariate processing of spectroscopic data is applied for immediate prediction of adulterant concentration.

International Nuclear Information System (INIS)

We have performed molecular dynamics simulations of radiation damage in fused silica. In this study, we discuss the role of successive cascade overlap on the saturation and self-healing of oxygen vacancy defects in the amorphous fused silica network. Furthermore, we present findings on the topological changes in fused silica due to repeated energetic recoil atoms. These topological network modifications consistent with experimental Raman spectroscopic observation on neutron and ion irradiated fused silica are indicators of permanent densification that has also been observed experimentally.

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The fluorescence, absorption, infrared and Raman spectra of Sm/sub 3/Ga/sub 5/O/sub 12/ have been investigated. The energy-level schemes in the energy range 3000-16000 cm/sup -1/ have been determined. The number and symmetries of the Sm/sub 3/Ga/sub 5/O/sub 12/ crystal normal mode have been obtained by the molecular site group analysis and their comparison with the experiment has been made.

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Incorporation of TiO{sub 2}, into perfluoroionomer membrane by treatment with TiC1{sub 4}-methanol has been described. Platinum was used as an electrocatalyst. In order to make the system electronically as well as ionically conducting, the electrode was modified with polypyrrole (PPy). Photopolymerisation of pyrrole was accomplished by immersing TiO{sub 2}-Pt-NaF in pyrrole solution. UV-visible and FT-IR Spectroscopic studies were preformed with regards to the formation of the TiO{sub 2}, Pt and PPy within Nafion matrix. We report the construction and evaluation of this integrated system and establish the feasibility of hydrogen generation thereof. (Author)

International Nuclear Information System (INIS)

This report provides a summary of theoretical and experimental studies of actinide spectra in condensed phases. Much of the work was accomplished at Argonne National Laboratory, but references to related investigations by others are included. Spectroscopic studies of the trivlent actinides are emphasized, as is the use of energy level parameters, evaluated from experimental data, to investigate systematic trends in electronic structure and other properties. Some reference is made to correlations with atomic spectra, as well as with spectra of the (II), (IV), and higher valence states. 207 refs., 39 figs., 38 tabs.

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The performance of a high temperature ion source coupled to a helium gas-jet transport system for an efficient mass separation of neutron-rich alkaline earth and lanthanide isotopes is reported and the results of overall efficiency measurements using different cluster materials in the gas-jet are given. A fast, microprocessor controlled tape transport system for ..gamma..-spectroscopic studies on short-lived isotopes is described. Some results on the decay of 3.8sub(-s) /sup 152/Pr are presented.

International Nuclear Information System (INIS)

Discrepancies between the energy level schemes of "1"0"9Cd determined by radioactive decay studies and "1"1"0Cd(d, t) reaction studies were investigated by a new study of the "1"1"0Cd(d, t) reaction. Sixteen triton groups were found, J/sup pi/ assignments were made, and spectroscopic factors and fullnesses of single particle states were determined and compared with those for isotonic nuclei. The results remove or clarify all previous discrepancies.

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Evaluated spectroscopic data for all nuclei with mass number A = 177 and corresponding level schemes from radioactive decay and reaction studies are presented. Most of the new information since the previous evaluation of this mass chain consists of the decay of the recently discovered isotope [sup 177]Tm, and the level structure of [sup 177]Ir, [sup 177]Os, and [sup 177]Pt. The present evaluation supersedes the earlier one by Y. A. Ellis and B. Harmatz (75E107) published in Nuclear Data Sheets 16, 135 (1975).

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The aim of this textbook is to present a relatively simple treatise of the theoretical principles and working methods of photochemistry, key photochemical reactions and important practical applications to enable the reader (a basic knowledge of chemistry is assumed) to work independently is this field. In accordance with the broad scale of this subject, which cuts across numerous disciplines, the topics treated range from photochemical, photophysical and spectroscopical fundamentals, through associated work procedures and methods of evaluation and the various types of reactions to photochemical processes in nature and applied technology. The photochemical properties and reactions of organic and inorganic compounds (preferably coordination compounds) are discussed in each chapter.

International Nuclear Information System (INIS)

Glow discharge plasma nitriding of AISI 304 austenitic stainless steel has been carried out for different processing time under optimum discharge conditions established by spectroscopic analysis. The treated samples were analysed by X-ray diffraction (XRD) to explore the changes induced in the crystallographic structure. The XRD pattern confirmed the formation of an expanded austenite phase (#gamma#_N) owing to incorporation of nitrogen as an interstitial solid solution in the iron lattice. A Vickers microhardness tester was used to evaluate the surface hardness as a function of indentation depth (#mu#m). The results showed clear evidence of surface changes with substantial increase in surface hardness.

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The electron momentum density is measured applying positron annihilation and Compton spectroscopy in order to get information about electron wave functions. Compton spectroscopic measurements of Pd-Ag and Cu-Zn alloy systems are carried out taking into account crystal structure, mixability, and order state. Three-dimensional momentum densities of silicon are determined in order to get better information about its electronic structure. The momentum density and the spin density of ferromagnetic nickel are investigated using angular correlation curves.

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Intraionic spin-orbit--split multiplet levels have been observed by electronic Raman scattering in the intermediate-valence compound EuPd/sub 2/Si/sub 2/. From the temperature dependence of the Raman peak positions and widths the interconfigurational excitation energy E/sub x/ and an upper limit of the interconfigurational mixing width T/sub f/, respectively, have been obtained. This is the first spectroscopic support for the underlying assumptions of the ionic interconfigurational fluctuation model that has been proposed to describe intermediate valence.

British Library Electronic Table of Contents (United Kingdom)

We have measured the frequency-dependent dielectric function of semi-crystalline polybutylene terephthalate (PBT) in the terahertz region between 100?GHz and approximately 2.8?THz. A characteristic band is observed around 2.38?THz. The intensity of this band is a good indicator of the degree of crystallinity of the different samples. A potential assignment of this band is proposed, based on the comparison with spectroscopic data of the structurally very similar polyethylene terephtalate (PET). Furthermore, the frequency-dependent index of refraction of PBT reveals more insight about the morphology and different thermal history of the samples under investigation.

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This paper describes a novel Fourier transform infrared (FTIR) spectroscopic method that can be used to rapidly screen soil samples from potentially hazardous waste sites. Samples are heated in a thermal desorption unit and the resultant vapors are collected and analyzed in a long-path gas cell mounted in a FTIR. Laboratory analysis of a soil sample by FTIR takes approximately 10 minutes. This method has been developed to identify and quantify microgram concentrations of explosives in soil samples and is directly applicable to the detection of selected volatile organics, semivolatile organics, and pesticides.

International Nuclear Information System (INIS)

We measured differential cross sections and vector analyzing powers for the "4"8Ca(d,n)"4"9Sc reaction at 79 MeV. An overall energy resolution of about 325 keV was achieved, and data were extracted for states up to 3.4 MeV of excitation. Both distorted-wave Born approximation and Johnson-Soper adiabatic approximation calculations were performed; in general, the Johnson-Soper adiabatic approximation calculations provide a better description of the data, and yield reasonable spectroscopic factors.

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The use of microwave in chemistry has known benefits over conventional heating methods, e.g. reduced reaction times, chemical yield improvement and the possibility if reducing or eliminating the use of organic solvents. We describe herein a procedure for the nitration of salicylaldehyde in water using a domestic microwave oven, which can be used as an experiment in the undergraduate chemistry laboratory. The experiment involves safe and rapid preparation and identification of the position isomers by thin layer chromatography and {sup 1}H NMR, or by their melting points. (author)

British Library Electronic Table of Contents (United Kingdom)

In the present work, quaternary chitosans as water-soluble compounds were prepared based on three-step process. Schiff bases were firstly synthesized by the reaction between the amino groups of chitosan with aliphatic aldehydes followed by a reduction with sodium borohydride (NaBH4) to form N-(alkyl) chitosans. N,N,N-(dimethyl alkyl) chitosans were then obtained by a reaction of chitosan containing N-butyl, N-pentyl, N-hexyl, N-heptyl, and N-octyl substituents with methyl iodide. The compounds were characterized using IR and NMR spectroscopy. Subsequent experiments were conducted to test their antimicrobial activities against the most economic plant pathogenic bacteria of crown gall disease Agrobacterium tumefaciens, soft mold disease Erwinia carotovora, fungi of grey mold Botrytis cinerea...

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The relationship between microstructure and macro properties of different cementitious materials has been investigated. This study consists of the following tasks: using NMR and IR to better characterize the amorphous and poorly crystalline phases that occur in blended cements; characterizing the microstructure of the hydration products of modified Portland cement as a function of different percentages of pozzolan replacements by ESEM, SEM, and EDS; comparing the properties of blended cement pastes with a control group of normal Portland cements; and studying the engineering aspects of blended cement that are important for identifying and characterizing fundamental phenomena that are responsible for their durability. The overall influence of the nanoscale and microscale structure of blended and Portland cement on the properties of the resultant composite will be discussed.

British Library Electronic Table of Contents (United Kingdom)

In order to investigate the antioxidant properties of the polysaccharides from the brown alga Sargassum fusiforme, the crude polysaccharides from S. fusiforme (SFPS) were extracted in hot water, and the lipid peroxidation inhibition assay exhibited that SFPS possessed a potential antioxidant activity. Hence, two purely polymeric fractions, SFPS-1 and SFPS-2 were isolated by the column of DEAE (2-diethylaminoethanol)-Sepharose Fast Flow, with their molecular weights of 51.4 and 30.3 kDa determined by high performance gel permeation chromatography (HPGPC). They were preliminarily characterized using chemical analysis in combination of infrared (IR) and nuclear magnetic resonance (NMR) spectroscopies and found to contain large amounts of uronic acids and ?-glycosidical linkages. The antioxida...

British Library Electronic Table of Contents (United Kingdom)

Chemical modification of poly(?-caprolactone) PCL by oxidation with potassium permanganate in solution was investigated. According to the data obtained from Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance 1H NMR, after the oxidation reactions the PCL chains exhibited new functional groups (vinyl and hydroxyl) and possible intermolecular recombination, producing an oxidized-polycaprolactone (PCL-OX). Solution viscometry indicated that degradation also occurred during the oxidation reactions (30% drop in viscosity average molecular weight was detected). Differential scanning calorimetry (DSC) also indicated that PCL was chemically modified and degraded. The successive self-nucleation/annealing (SSA) treatment confirmed that a reduction (or interruption) in line...

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Nuclear magnetic resonance (NMR) images of live rats with sterile and pyogenic abscesses, hematomas, and various implanted and spontaneous neoplasms demonstrated good contrast differentiation between pathologic and surrounding normal tissues. This differentiation was maximal when both the T1 and T2 tissue relaxation times were used as criteria. Neoplasms have a broad range of T1 and T2 values and may be confused with abscesses or hematomas. Tissue rate constants (1/T1 and 1/T2) are mainly dependent on total water content, the exception being fat, which has a 1/T2 value much shorter than that expected on the basis of water content alone.

British Library Electronic Table of Contents (United Kingdom)

The crystal structure of Ca2RuD6 has been determined by neutron powder diffraction: space group Fm3m, K2PtCl6 structure, as found for other hexahydride salts of group 8 metals with alkaline earth or lanthanide counter ions. No structural phase transition was observed between 340K and 50K. The deuterium nuclear quadrupole coupling constant, 54.7kHz, leads to an ionic character of the Ru-D bond of 76%. The known trends in the behaviour of A2MH6 salts are interpreted in terms of the ionization energies of the cation and the central metal atom.

British Library Electronic Table of Contents (United Kingdom)

An aliphatic thiol ligand of CuInS2/ZnS core/shell quantum dots is replaced with a hydroxyl-terminated thiol ligand by utilizing `on-off state' of ligands during growth stage of the quantum dots. After the ligand-exchange, negligible differences were observed on both photoluminescence spectrum and luminescent quantum efficiency. The reason for the high retention of luminescent efficiency comes from no local agglomeration and no surface deterioration of QDs. It is also observed that 70% of initial ligands are exchanged by the replacing ligand, determined by FT-IR and 1H NMR. The proposed method provides the quantum dots with an excellent dispersibility in polar solvents, supported by identical luminescence decay characteristics of the QDs.

British Library Electronic Table of Contents (United Kingdom)

A novel heteropolyanion-based ionic hybrid was prepared by combining the divalent ionic liquid (IL) cation of 1,1'-(butane-1,4-diyl)-bis(3-methylimidazolium) with the Keggin-structured V-containing heteropolyanion, and characterized by ^1H NMR, FT-IR, ESI-MS, XRD, SEM, TG, BET surface area, melting point, and elemental analysis. Its catalytic activity was evaluated in the hydroxylation of benzene with aqueous H2O2, including the testing of the influence of organic cations, catalytic reusability and optimization of reaction conditions. This hybrid is characterized to be semi-amorphous nanoparticles with a IL-like composition. The hybrid catalyst leads to the liquid-solid biphasic reaction system for hydroxylation of benzene with H2O2, presenting such advantages as high catalytic activity, c...

British Library Electronic Table of Contents (United Kingdom)

Extraction of 25 L fermentation broth of the newly isolated Streptomyces sp. strain TN58 and various separation and purification steps led to the isolation of five bioactive metabolites, namely brevianamide F (C1), reported from a streptomycete for the first time, N?-acetyltryptamine (C2), thiazolidomycin (C3), and two rhamnopyranosides (C4 and C5). These two rhamnopyranosides were produced directly, without precursor addition. The chemical structure of these five active compounds was established on the basis of 1H, 13C/APT and 2D NMR spectra, ESI and EI-MS data, and by comparison with data from the literature. According to the biological studies, we show in this work that the compounds C1, C2, C4 and C5 possess antimicrobial activities.

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The paper describes the chemical constituents isolated from aerial parts of the plant Galianthe brasiliensis. From a methanol extract, the iridoid glycosides asperuloside, deacetylasperuloside, mixture of Z- and E-6-O-p-coumaroylscandoside methyl ester, the triterpene ursolic acid and the steroids stigmasterol, campesterol, b-sitosterol and 3-O-b-glucopyranosyl sitosterol were isolated. The structures of the natural products were identified on the basis of spectral data, including 2D NMR experiments. The antiproliferative properties of the crude methanolic extract were investigated against a series of nine human cancer cell lines. (author)

British Library Electronic Table of Contents (United Kingdom)

This is a report of extraction and identification of 1-O-alkyl glycerol present in the dried leaves of Bauhinia scandens. Fifty percent aqueous ethanolic extract of the plant at room temperature was fractionated over petroleum ether and diethyl ether. The diethyl ether soluble fraction showed positive bioactivity in Brine Shrimp bioassay. Isolation and purification of the active principle was subsequently done from diethyl ether fraction. The diethyl ether fraction was separated into acidic and neutral part. The acid free fraction was screened to be positive in Brine Shrimp bioassay. The NMR spectra (in CDCl3) indicated the probability of its lipoidal nature. The total lipid fraction was resolved into neutral, glyco, and phospho-lipids by column chromatography. Only the neutral fraction sh...

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In this work, we perform spectroscopic studies to characterize the energy transfer processes occurring in rare-earth doped lithium fluoride systems, aiming the optimization of the population inversion of these media. Yb{sup 3+} ion was used in order to probe the electron-phonon coupling in LiYF{sub 4}, LiGdF{sub 4} and LiLuF{sub 4} matrices. In these systems it was obtained the average phononenergy, the vibronic transition probability and Huang-Rhys coupling constant. These parameters are dependent on the crystal host and the LiLuF{sub 4} system presents excluded correlation effects, an electronic repulsion that weakens the vibronic coupling. The Tm:Ho:LiYF{sub 4} system was studied under diode laser pumping at 796 nm, aiming the 2 {mu}m emission optimization. The ideal conditions of concentration and laser power were determined favouring the latter emission. Upconversion processes of two photons were identified besides the energy transfer among ions. The dynamic ...

International Nuclear Information System (INIS)

In this study, the experimental and theoretical study on the structures and vibrations of 2 and 3-methylpiperidine are presented. The FT-IR spectra of molecules have been recorded between 4000-400 cm-1 region. The molecular geometry and vibrational frequencies of 2 and 3-methylpiperidine in the ground state have been calculated by using Density Functional method (B3LYP) with cc-pVQZ, 6-311++G(d,p) and 6-311G(d,p) as basis sets. The total energy distributions TED among the symmetry coordinates of the normal modes have computed for the the low energy structure of the molecule. Complete vibrational assingments have provided on the basis of the calculated TED values.

CERN Document Server

We present a HST/STIS spectroscopic and optical/radio imaging study of the Seyfert NGC 2110 aiming to measure the dynamics and understand the nature of the nuclear outflow in the galaxy. Previous HST studies have revealed the presence of a linear structure in the Narrow-Line Region (NLR) aligned with the radio jet. We show that this structure is strongly accelerated, probably by the jet, but is unlikely to be entrained in the jet flow. The ionisation properties of this structure are consistent with photoionisation of dusty, dense gas by the active nucleus. We present a plausible geometrical model for the NLR, bringing together various components of the nuclear environment of the galaxy. We highlight the importance of the circum-nuclear disc in determining the appearance of the emission line gas and the morphology of the jet. From the dynamics of the emission line gas, we place constraints on the accelerating mechanism of the outflow and discuss the relative ...

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Reactively sputtered tantalum nitride (Ta/sub 2/N) has been investigated as a diffusion barrier between Pd/sub 2/Si and aluminum and CoSi/sub 2/ and Al. Ta/sub 2/N is found to be an excellent matallurgical diffusion barrier for the two systems up to 555 /sup 0/C, with no intermixing observed in Rutherford backscattering and Auger electron spectroscopic studies. Schottky barrier devices n-Si/Pd/sub 2/Si/Ta/sub 2/N/Al were excellent and showed no deterioration after annealing at 500 /sup 0/C. However, similar devices with CoSi/sub 2/ contacts and Ta/sub 2/N barrier showed a creation of high contact resistance between the silicide and the as-deposited nitride.

CERN Document Server

The development of a replacement to the conventional film based X-ray imaging technique is required for many reasons. One possible route for this is the use of a large area film of a suitable semiconductor overlaid on an amorphous silicon readout array. A suitable semiconductor exists in cadmium telluride and its tertiary alloy cadmium zinc telluride. In this thesis the spectroscopic characteristics of commercially available CZT X- and gamma-radiation detectors are established. The electronic, optical, electro-optic, structural and compositional properties of these detectors are then investigated. The attained data is used to infer a greater understanding for the carrier transport in a CZT radiation detector following the interaction of a high energy photon. Following this a method used to fabricate large area films of CdTe on a commercial scale is described. This is cathodic electrodeposition from an aqueous electrolyte. The theory and experimental arrangement for ...

CERN Document Server

We study spectroscopically determined iron abundances of 642 solar-type stars to search for the signature of accreted iron-rich material. We find that the metallicity [Fe/H] of a subset of 466 main sequence stars, when plotted as a function of stellar mass, mimics the pattern seen in lithium abundances in open clusters. Using Monte Carlo models we find that, on average, these stars have accreted about 0.4 Earth masses of iron while on the main sequence. A much smaller sample of 19 stars in the Hertzsprung gap, which are slightly evolved and whose convection zones are significantly more massive, have lower average [Fe/H], and their metallicity shows no clear variation with stellar mass. These findings suggest that terrestrial-type material is common around solar type stars.

International Nuclear Information System (INIS)

We report here results of an application of single-nucleon stripping reactions at high energies (65 MeV/u) in inverse kinematics to obtain spectroscopic factors. From measurements of the partial cross-sections for ground and excited states in residual nuclei formed in one-proton stripping reactions, single particle orbits and occupancies of light nuclei have been studied in the s-d shell. Single proton stripping cross-sections of "2"5Al and "2"6","2"7","2"8P on a Be target have been measured using the S800 spectrograph and the NaI(Tl) array at the NSCL. These results indicate that this technique may provide a general tool for the intermediate energy range analogous to transfer (pick-up) reactions at low-energy.

International Nuclear Information System (INIS)

Judd-Ofelt parameters (?2 = 5.09?10-20, ?4 0.92?10-20, and ?6 = 0.63?10-20 cm2) and oscillator strengths of fundamental optical transitions involved in lasing at wavelength 1.54 ?m have been calculated for borosilicophosphate glass co-activated with Er3+ and Tb3+ ions based on experimental luminescence and absorption spectra and refractive indices. The results were used to determine the emission (6?10-23 cm2) and absorption (5?10-21 cm2) cross sections for lambda = 1.54 ?m and the gain cross section as a function of inverse population levels. (authors)

British Library Electronic Table of Contents (United Kingdom)

Upon addition of permanganate to a solution of tryptophan (Trp), yellow-brown color species appears within the time of mixing of tryptophan in absence and presence of cetyltrimethylammonium bromide (CTAB), which was stable for some days. Spectroscopic and kinetic evidences suggest the formation of water-soluble colloidal MnO2 as the most stable reduction product of MnO4-. Carbon dioxide and ammonia are not formed as the oxidation products. Carbon-carbon double bond of indole moiety of Trp is responsible for the fast reduction of permanganate. Cetyltrimethylammonium bromide catalyses the permanganate oxidation of Trp with a rate enhancement of ca. 200-fold. Sub- and postmicellar catalytic effect of CTAB ascribed to the association/incorporation/solubilization of both reactants (MnO4- and Tr...

International Nuclear Information System (INIS)

Nitriding of aluminium 2011 using a radio frequency plasma at higher power levels (500 and 700 W) and lower substrate temperature (500 deg. C) resulted in higher AlN/Al_2O_3 ratios than obtained at 100 W and 575 deg. C. AlN/Al_2O_3 ratios derived from X-ray photoelectron spectroscopic analysis (and corroborated by heavy ion elastic recoil time of flight spectrometry) for treatments preformed at 100 (575 deg. C), 500 (500 deg. C) and 700 W (500 deg. C) were 1.0, 1.5 and 3.3, respectively. Scanning electron microscopy revealed that plasma nitrided surfaces obtained at higher power levels exhibited much finer nodular morphology than obtained at 100 W.

International Nuclear Information System (INIS)

A review of the experimental work performed at the GASP array with the purpose of the identification and first spectroscopic measurements of the heaviest even-even N = Z and odd-A N = Z + 1 nuclei (mass larger than 80) is made. Systematic experiments in this mass region led to the first study of seven such nuclei: "8"8Ru, "8"1Zr, "8"5Mo, "8"9Ru, "9"1Rh, "9"3Pd, and "9"5Ag, and extensive data on many other nuclei in their neighborhood. The systematic evolution of the level structures in both even-even and odd-A nuclei, between N #approx# Z #approx# 40 and N #approx# Z #approx# 47 is briefly presented. The possibility that effects of the neutron-proton pairing have been observed, as well as the type of collectivity observed in this region are discussed. (author)

International Nuclear Information System (INIS)

Metal-organic chemical vapor deposition (MOCVD) made layers of strontium-bismuth-tantalate (SBT) were characterized by spectroscopic ellipsometry (SE) using the Adachi model [S. Adachi, Phys. Rev. B 35 (1987) 7454-7463]. The evaluated optical parameters were correlated with the physical and chemical behavior examined by X-ray diffraction (XRD). As a result, it was possible to fit the measured spectra with the Adachi model in a wide range covering the region of the band gap. The Adachi model provides electronic layer parameters like the transition energy E 0 and broadening ?. Our investigations established a correlation between XRD-determined average grain size and the electronic layer parameters.

International Nuclear Information System (INIS)

The chemical state of iron contained in several kinds of bauxite, which are utilized as a raw material in the aluminum industry in Japan, were investigated by Moessbauer spectroscopy. The main compounds of iron were identified from the results, which showed variations of the Moessbauer absorption spectra with calcination and measuring temperature. Although the absorption intensities of the spectra differed significantly, major species identified were paramagnetic or superparamagnetic #alpha#-Fe_2O_3 in all of these bauxite samples. The superparamagnetic #alpha#-Fe_2O_3 was found mainly in the gibbsite-type bauxite, but not in the boehmite/gibbsite-type or the boehmite-type bauxite. The Moessbauer absorption spectra of red mud and its calcined products were also given. (author).

British Library Electronic Table of Contents (United Kingdom)

Natural rubber (NR) and its derivatives as renewable and biodegradable materials have attracted considerable attention because of the serious pollution problems caused by synthetic materials and a shortage of resources. A new semi-interpenetrating polymer network (semi-IPN) based on epoxidised natural rubber and polyvinyl alcohol containing maleic acid as a crosslinking reagent was synthesized and characterized by FTIR, XRD, SEM, swelling ratio in both distilled water and toluene, and mechanical properties. The curing time and dose of maleic acid were varied from 10 to 60min, and from 10 to 60% (w/w), respectively. An IR spectroscopic study indicated the presence of an ester linkage at 1730cm-1 in maleic acid crosslinked with PVA in semi-IPN films. In addition, the crystalline content of P...

International Nuclear Information System (INIS)

Cavity ringdown spectroscopy (CRDS) with continuous-wave (cw) laser excitation has added high frequency resolution to the ability of CRDS being used for the absolute quantification of trace-level species present in many chemical processes. Cavity dithering technique has easily resolved the problem of resonant coupling of a cw laser light into a high-finesse cavity. The present study addresses the potential uncertainty involved in such cw-CRDS techniques incorporating the cavity mirror motion, i.e., the doppler frequency shift of a probe light inside the cavity. In the high-resolution spectroscopic work of megahertz-accuracy, even the influence of intracavity doppler effect may become significant.

Energy Technology Data Exchange (ETDEWEB)

The pronounced selectivity of near-threshold (p,..pi../sup -/) reactions for high-spin two-particle, one-hole states is exploited, in the first spectroscopic application of a (p,..pi..) reaction, to identify previously unknown 25/2/sup +/ and 21/2/sup +/ (g/sub 9/2/)/sup 3/ states in /sup 89/Zr. Relative cross sections for the two transitions are well reproduced by simple model calculations. The analyzing power for the 25/2/sup +/ state is markedly similar to previous (p/sub pol/,..pi../sup -/) results for two-particle one-hole stretched states in lighter nuclei.

British Library Electronic Table of Contents (United Kingdom)

This communication reports the formation of complex Langmuir monolayer at the air-water interface by charge transfer types of interaction with the water soluble N-cetyl Formula Not Shown -trimethyl ammonium bromide (CTAB) molecules doped with rosebengal (RB), with the stearic acid (SA) molecules of a preformed SA Langmuir monolayer. The reaction kinetics of the formation of RB-CTAB-SA complex monolayer was monitored by observing the increase in surface pressure with time while the barrier was kept fixed. Completion of interaction kinetics was confirmed by FTIR study. This complex Langmuir films at the air-water interface was transferred onto solid substrates at a desired surface pressure to form multilayered Langmuir-Blodgett films. Spectroscopic characterizations reveal some molecular lev...

International Nuclear Information System (INIS)

Absorption spectra of the visible I_2 band of I_2 complexes with Et_2O, Et_2S, and Et_2Se in heptane have been measured up to 3300 bar at 25"0C. The equilibrium constants and volume changes accompanying complex formation, the molar extinction coefficients and the absorption maxima have been estimated. The volume changes were found comparable with those estimated from the X-ray data of the I_2 complexes in the crystalline state. The enhancement of the molar extinction coefficient and the blue shift of the visible I_2 band with increasing pressure have been established. The results suggest a decrease in the bond distance between an n-donor and I_2, compared with the spectroscopic properties of the I_2 complex at 1 bar. The decrease has been estimated as 0.008 nm with increasing pressure up to 3300 bar. (author).

Energy Technology Data Exchange (ETDEWEB)

More than 2,500 Moessbauer spectroscopic studies on minerals have been published since 1960. These papers contain approximately 8,000 sets of Moessbauer mineral data on at least 400 different minerals. This information has been compiled into a database that includes isomer shifts, quadrupole splittings, and magnetic hyperfine interactions at room, liquid nitrogen, and liquid helium temperatures. The database provides a profile of the Moessbauer research performed to date on minerals, including type and locality of minerals investigated, significance of the studies and results, and location of the research facilities. The data and information are available both in printed and magnetic form.With the establishment of this resource, the Moessbauer Effect Data Center has begun a systematic evaluation of the Moessbauer mineral data. It is anticipated that this resource can be used for the identification of minerals as powder X-ray diffraction data is.

Energy Technology Data Exchange (ETDEWEB)

In the electrorefining step of the pyrochemical process, actinide ions dissolved in the LiCl-KCl eutectic salt are recovered as pure actinide metals at a cathode for a re-use as a nuclear fuel from the aspect of its nonproliferation of the nuclear fuel cycles. The lanthanide species dissolved in the LiCl-KCl eutectic salt play an important role in an effective metal purification during the electrorefining step, so it is necessary to understand the chemical and physical behaviors of lanthanides in molten salt. The in situ spectroscopic measurement system and studies according to temperature changes are essential for better understandable information. To our knowledge, the absorption studies of lanthanides at high temperatures have been reported before, but the fluorescence studies of those at high temperature are not reported yet. We will discuss here the fluorescence behaviors of lanthanides in LiCl-KCl molten salt medium according to a changing temperature.

International Nuclear Information System (INIS)

A conformational analysis of ethyl azidoformate (EAF) has been carried out by the MINDO/3 quantum-chemical method. It has been shown that EAF exists in the form of two conformers differing with respect to rotation around the C-N bond. Complete optimization of the geometry has been carried out for both conformers. It has been found that the transoid conformation is planar and that the cisoid conformation is nonplanar. The height of the rotation barrier is 15.4 kcal/mole. The optimal geometry of the transition state has been calculated. It has been noted that a significant role in the mechanism of the conformational transition is played by the inversion of a nitrogen, which facilitates the transition. The results of the calculation have been confirmed by IR-spectroscopic data.

CERN Document Server

The lowest-mass stars, brown dwarfs and extrasolar planets present challenges and opportunities for understanding dynamics and cloud formation processes in low-temperature atmospheres. For brown dwarfs, the formation, variation and rapid depletion of photospheric clouds in L- and T-type dwarfs, and spectroscopic evidence for non-equilibrium chemistry associated with vertical mixing, all point to a fundamental role for dynamics in vertical abundance distributions and cloud/grain formation cycles. For exoplanets, azimuthal heat variations and the detection of stratospheric and exospheric layers indicate multi-layered, asymmetric atmospheres that may also be time-variable (particularly for systems with highly elliptical orbits). Dust and clouds may also play an important role in the thermal energy balance of exoplanets through albedo effects. For all of these cases, 3D atmosphere models are becoming an increasingly essential tool for understanding spectral and ...

Energy Technology Data Exchange (ETDEWEB)

Composting of sawdust and paper mill sludge, using a 'Kneer' process reactor, was studied in an attempt to elaborate upon organic matter transformation during the process and to define parameters to measure the compost maturity level. Temperature, electron paramagnetic resonance data, ash and C, H, N and S contents, and a spectroscopic method using ultraviolet-visible (UV-VIS) for alkaline (pH = 8.5) and solid samples was used to study the maturity of the compost samples. These parameters were measured in 6 humic acids extracted from the compost samples during 29 days. The results of this work show that the 'Kneer' process is efficient in transforming ligno-celulitic residues in a short time (29 days), into an organic fertilizer material with application perspectives (author)

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Carbohydrate and nucleotide structural determination using modern spectroscopic techniques is dependent on our ability to label oligonucleotides and oligosaccharides with stable isotopes. Uniform Carbon 13 and Nitrogen 15 labeling of oligonucleotides is important to present-day efforts, which are focused on determining the structure of relatively small oligosaccharides and oligonucleotides, which form the elements of larger structures. Because of the relatively recent interest in three-dimensional structure, the development of techniques used to label them has lagged behind parallel techniques used to label peptides and proteins. Therefore, this group`s discussion focused primarily on problems faced today in obtaining oligonucleotides labeled uniformly with carbon 13 and nitrogen 15.

British Library Electronic Table of Contents (United Kingdom)

Abstract Jicama (Pachyrhizus erosus L.) is a root-based legume that has been cultivated in Mexico for centuries. Pectic polysaccharide from de-starched jicama pomace was extracted using an autoclave-assisted process and physicochemically characterized. The extracted polysaccharide (1.0 g L-1) was used for the formation of polyelectrolyte complexes (PECs) with water-soluble chitosan (WSCh; 0.5, 1.0 and 2.0 g L-1). The extraction yield of jicama pectic polysaccharide was 22.8 wt% (dry basis) and infrared spectroscopic analysis showed that it was methoxylated to a small degree. Thermogravimetric analysis indicated that this biopolymer was very stable, its weight loss being 51.2% after heating at 479 C. Anion-exchange chromatography showed it to have a wide and heterogeneous charge density. Th...

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The study of SO{sub 2} reduction in non-aqueous solvent can help to understand the functioning of Li/SO{sub 2} batteries and to find a simpler way for the synthesis of Li{sub 2}S{sub 2}O{sub 4} dithionite. This paper presents the results of electrochemical studies (cycle volt-amperometry in semi-infinite and thin film diffusion conditions, visible spectro-electrochemistry) and spectroscopic studies (UV, visible and RPE) performed on SO{sub 2} solutions. A mechanism of SO{sub 2} reduction is proposed and discussed. (J.S.) 18 refs.

Energy Technology Data Exchange (ETDEWEB)

Small unilamellar vesicles which form when gel-state long-chain phosphatidylcholines are mixed with micellar short-chain lecithins undergo an increase in size as the long-chain species melts to its liquid-crystalline form. Analysis of the vesicle population with quasi-elastic light scattering shows that the particle size increases from 90-A radius to greater than 5000-A radius. Resonance energy transfer experiments show total mixing of lipid probes with unlabeled vesicles only when the Tm of the long-chain phosphatidylcholine is exceeded. This implies that the large size change represents a fusion process. Aqueous compartments are also mixed during this transition. 31P NMR analysis of the vesicle mixtures above the phase transition shows a great degree of heterogeneity with large unilamellar particles coexisting with oligo- and multilamellar structures. Upon cooling the vesicles below the Tm, the original size distribution (e.g., small unilamellar vesicles) is ...

International Nuclear Information System (INIS)

The information is reported on the kinetics of decomposition of weak hcp "3He-"4He solutions with the starting "3He concentration 0.5#+-#0.1% and 1.20#+-#0.2% under the sample pressure 3.5 to 3.8 MPa before the decomposition. The NMR technique of the prompt control of the phase separation process is developed. To accelerate the metastable phase decomposition, the samples were thermally cycled at temperatures below 100 mK. Using the pulse NMR method, the magnetic susceptibility of "3He nuclei and the spin-lattice T_1 and spin-spin T_2 relaxation times were measured on three samples of the decomposed solid solutions with the starting "3He concentration 0.5% at the pressures 3.53, 3.71 and 3.78 MPa. Above 10 mK the Curie-Weiss constant was two to three times higher than the values typical of bulk bcc "3He of the corresponding density. Below 10 mK the magnetic susceptibility was observed to deviate from the Curie-Weiss law. One of the samples ...

International Nuclear Information System (INIS)

"2"7Al and "2"9Si solid-state NMR spectra and X-ray diffraction (XRD) patterns were obtained for #alpha#-SiAlON powders prepared by combustion synthesis, according to which the phase transformation and structure evolution of #alpha#-SiAlON were studied. It was found that in #alpha#-SiAlON "2"9Si chemical shift values (-48 < #delta# _S_i < -47) were close to those in #beta#-Si_3N_4 and #alpha#-Si_3N_4, indicating that Si atoms kept SiN_4 coordination to a large extent in #alpha#-SiAlON despite the presence of O atoms. Dissimilarly, "2"7Al chemical shift values in #alpha#-SiAlON deviated clearly from that corresponding to AlN_4 coordination (#delta# _A_l #approx# 112) and occurred in a range from #delta# _A_l 95.5 to 99.9, which should be assigned to tetrahedral AlO _xN_4_-_x (0 #<=# x #<=# 4) coordination. The broadening effect of AlO _xN_4_-_x peaks was noticed, which was suggested to induced by slight dispersion of #alpha#-SiAlON compositions. "2"7Al ...

Science.gov (United States)

The performance of 250 different computational protocols (combinations of density functionals, basis sets and methods) was assessed on a set of 165 well-established experimental (1)H-(1)H nuclear coupling constants (J(H-H)) from 65 molecules spanning a wide range of "chemical space". Thereby we found that, if one uses core-augmented basis sets and allows for linear scaling of the raw results, calculations of only the Fermi contact term yield more accurate predictions than calculations where all four terms that contribute to J(H-H) are evaluated. It turns out that B3LYP/6-31G(d,p)u+1s is the best (and, in addition, one of the most economical) of all tested methods, yielding predictions of J(H-H) with a root-mean-square deviation from experiment of less than 0.5 Hz for our test set. Another method that does similarly well, without the need for additional 1s basis functions, is B3LYP/cc-pVTZ, which is, however, ca. 8 times more "expensive" in terms of CPU time. A selection of the better ...

Energy Technology Data Exchange (ETDEWEB)

The amino acid residues 114-118 in actin were found to be implicated strongly in the binding of nucleotide, and as would be expected for such an important binding site, they are located in a completely conserved region of the actin sequence. A 19-residue peptide with the actin sequence 106-124 was synthesized in order to span the putative triphosphate binding site. Proton NMR spectra of the actin peptide 114-118 in the presence and absence of ATP indicated that Arg-116 and Lys-118 are particularly involved in binding ATP. A strong binding of ATP to the peptide 106-124 also was measured. Tripolyphosphate bound to the peptide 106-124 somewhat more weakly than ATP. Binding involved residues 115-118 and 121-124, indicating the presence of a reverse turn between these segments. Proton resonances were assigned by using two-dimensional double quantum correlated spectroscopy, one-dimensional spin decoupling techniques, one-dimensional nuclear Overhauser enhancement ...

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Spin-polarized liquid helium-3 is prepared by laser optical pumping in low magnetic field and at room temperature, prior to fast liquefaction of the polarized sample. The use of a new helium-3 cryostat enabled us to obtain liquid helium-3 with polarization rates up to 25 % at well-stabilized temperatures (around 0.5 K). We could thereby study the effect of nuclear polarization on liquid-vapour equilibrium, and particularly on the saturated vapour pressure. Very sensitive capacitive gauges were developed. We estimated (to first order in M{sup 2}) the expected effects when the polarization M is suddenly destroyed. These effects were experimentally observed in helium-3/helium-4 mixtures, in pure helium-3, only a transient increase in pressure has been recorded. We then describe in a third part a preliminary experiment which aimed at determining the longitudinal relaxation time T1 in mixtures. Relaxation on the walls is efficiently reduced by a cesium coating and T1s of order 20 minutes ...

Energy Technology Data Exchange (ETDEWEB)

The gas phase high resolution spectroscopic study of weakly bound clusters can provide the information necessary to develop an intermolecular potential energy surface. This surface can then be used to better understand condensed phases. In this work, a tunable far infrared laser spectrometer is used to study weakly bound dimers produced in the newly developed continuous planar supersonic jet expansion apparatus. The water dimer is an extensively studied hydrogen bonded dimer. It undergoes several tunneling motions which result in splittings and perturbations of the rovibrational energy levels. A review is presented of much of the experimental and theoretical work done on water dimer, including a description of the combined fit of all the high resolution spectroscopic results by Coudert and Hougen. Also included is a discussion of the measurement of the K = 1 lower {yields} K = 2 lower band performed using the tunable far infrared laser/planar ...

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Sulfur poisoning from engine fuel and lube is one of the most recognizable degradation mechanisms of a NOx adsorber catalyst system for diesel emission reduction. Even with the availability of 15 ppm sulfur diesel fuel, NOx adsorber will be deactivated without an effective sulfur management. Two general pathways are currently being explored for sulfur management: (1) the use of a disposable SOx trap that can be replaced or rejuvenated offline periodically, and (2) the use of diesel fuel injection in the exhaust and high temperature de-sulfation approach to remove the sulfur poisons to recover the NOx trapping efficiency. The major concern of the de-sulfation process is the many prolonged high temperature rich cycles that catalyst will encounter during its useful life. It is shown that NOx adsorber catalyst suffers some loss of its trapping capacity upon high temperature lean-rich exposure. With the use of a disposable SOx trap to remove large portion of the sulfur poisons from the ...

International Nuclear Information System (INIS)

Over the recent years the nuclear structure around the N = 50 shell closure, which is very pronounced in the strontium and zirconium isotopes, has been the subject of extensive experimental and theoretical work. On the proton side Z = 38 and Z = 40 provide fairly closed sub-shells. In the strontium isotopes the lg/sub 9/2/ neutron shell is closed at "8"8Sr, supplying relatively pure neutron-hole and neutron-particle states with large spectroscopic factors in "8"7Sr and "8"9Sr, as well as core-coupled states. The mass region is thus ideally suited to examine the transition from a correlated to an uncorrelated (chaotic?) excitational behavior. These two types are characterized e.g. by the density of excited states, the transition strengths, and the spectroscopic factors observed in transfer reactions. We conducted (n,#gamma#) and (d,p) reactions leading to /sup 87,88,89/Sr in addition to "8"8Sr(d,t)"8"7Sr and 24 keV neutron capture in "8"8Sr. The ...

International Nuclear Information System (INIS)

A wide variety of thin film coatings, deposited by different techniques and with potential applications in various important areas, have been characterised by the Phase Modulated Spectroscopic Ellipsometer, installed recently in the Spectroscopy Division, B.A.R.C. The Phase Modulated technique provides a faster and more accurate data acquisition process than the conventional ellipsometry. The measured Ellipsometry spectra are fitted with theoretical spectra generated assuming an appropriate model regarding the sample. The fittings have been done objectively by minimising the squared difference (#chi#"2) between the measured and calculated values of the ellipsometric parameters and thus accurate information have been derived regarding the thickness and optical constants (viz, the refractive index and extinction coefficient) of the different layers, the surface roughness and the inhomogeneities present in the layers. Measurements have been done on (i) ion-implanted ...

International Nuclear Information System (INIS)

The optical spectra of actinide ions in the compound AnCl_3 and doped into single crystal LaCl_3 were interpreted in terms of transitions within 5f"N configurations. Energy-level calculations were carried out using an effective operator Hamiltonian, the parameters of which were determined by fitting experimental data. Atomic and crystal-field matrices were diagonalized simultaneously assuming an approximate D_3_h site symmetry. The spectroscopic data were taken from the literature but in most cases supplemented by unpublished measurements in absorption and in fluorescence. Spectroscopic data for each ion were analyzed independently, then the model parameters were intercompared and in many cases adjusted such that in the final fitting process the principal interactions showed uniform trends in parameter values with increasing atomic number. Consistent with analyses of the spectra of lanthanide ions in both LaCl_3 and LaF_3, abrupt changes in ...

International Nuclear Information System (INIS)

The effect is reported of seven inorganic oxide additives on both the formation mechanism and the densification of X-Sialon prepared by a silicothermal process. The oxides were added to the starting mixture of halloysite clay, alumina and elemental silicon at a level of 1 wt% of the calculated final product, and fired in nitrogen at 1200-1500 deg C. The formation of X-Sialon was monitored by thermal analysis, powder XRD and 2"7"Al and "2"9Si solid state MAS NMR The effects of the additives are temperature dependent and influence the various stages of the reaction by differing degrees. The oxides which best promote the formation of crystalline X-Sialon (Y_2O_3, CaO and MgO) are also those which facilitate the conversion of initially-formed Si_3N_4 to SiO_2N_2 and SiO_3N units. Densification is most enhanced by Y_2O_3 CaO and CeO_2; MgO exerts its maximum effect on sintering at lower temperatures. Copyright (1998) Australasian Ceramic Society

British Library Electronic Table of Contents (United Kingdom)

A series of thiazolo[3,2-b][1,2,4]triazole incorporating diphenylsulfone moieties were synthesized starting from 5-[4-(4-X-phenylsulfonyl)phenyl]-4H-1,2,4-triazole-3-thioles 3a-c, X=H, Cl, Br. Thus, alkylation of 1,2,4-triazoles 3 with phenacyl bromide or 4-bromophenacyl bromide afforded S-substituted 1,2,4-triazoles 4, 5. These new intermediates 4 and 5, in the presence of H2SO4 (c), were cyclized to 2-[4-(4-X-phenylsulfonyl)phenyl]-6-(4-Y-phenyl)[1,3]thiazolo[3,2-b]-[1, 2,4]-triazoles 6, 7 (I) and not to isomeric thiazolo[2,3-c][1,2,4]-triazoles 6, 7 (II). The newly synthesized compounds were characterized by IR, 1H, 13C NMR and elemental analysis. MS spectra confirmed the formation of thiazolo[3,2-b][1,2,4]triazole 6, 7 (forms I) in detriment of [2,3-c] isomeric compounds (forms II). Th...

DEFF Research Database (Denmark)

The syntheses of N-alkylated deoxynojirimycin and 1,5-dideoxy-1,5-iminoxylitol derivatives having either a D- or an L-erythritol-3-sulfate functionalized N-substituent are reported. The alkylating agent used was a cyclic sulfate derivative, whereby selective attack of the nitrogen atom at the least hindered primary center afforded the desired ammonium salt. In aqueous solution, these salts were configurationally labile at the ammonium center. Sulfonium and/or selenonium analogues of the ammonium salts were prepared by analogous reactions. The chalcogen salts were obtained as mixtures of diastereomers, separable in some cases, differing only in the stereochemistry at the configurationally stable sulfur or selenium atoms. Proof of configuration and conformation of each compound was obtained by detailed NMR experiments. The compounds are six-membered ring analogues of salacinol, a known sulfonium-salt glucosidase inhibitor. Evaluation of the target compounds for ...

British Library Electronic Table of Contents (United Kingdom)

New Schiff base derivatives (L1 and L2) were prepared by the condensation of 2-hydroxy-3-methoxybenzaldehyde (o-vanillin) and 3-hydroxy-4-methoxybenzaldehyde (iso-vanillin) with 5-methylfurfurylamine. Two new complexes [Ni(L1)2] and [Cu(L1)2] have been synthesized with bidentate NO donor Schiff base ligand (L1). The Ni(II) and Cu(II) atoms in each complex are four coordinated in a square planar geometry. Schiff bases (L1 and L2) and complexes [Ni(L1)2] and [Cu(L1)2] were characterized by elemental analyses, FT-IR, UV-vis, mass and 1H, 13C NMR spectroscopies. The crystal structures of the ligand (L2) and complexes [Ni(L1)2] and [Cu(L1)2] have also been determined by using X-ray crystallographic technique.

British Library Electronic Table of Contents (United Kingdom)

Potassium dichlorido(l-prolinato)platinate(II), K[PtCl"2(l-pro"?"H)] (1), and chlorido(dimethyl sulfoxide)(l-prolinato)platinum(II), [PtCl(l-pro"?"H)(dmso)] (2), were synthesized by ligand substitution reactions. Both complexes were characterized by ^1H, ^1^3C, and ^1^9^5Pt NMR spectroscopy, elemental analysis, and HR-ESI-MS. The molecular structures of 1 and 2 were determined by single crystal X-ray diffraction, proving bidentate coordinated l-prolinato ligand and SP-4-4 configuration of 2a. With the help of DFT calculations stability of possible isomers of 1 and 2 was studied. A considerable difference in the in vitro cytotoxicity of 1 versus 2a (exchange of one chlorido ligand by dmso) against four human cancer cell lines was found.

Energy Technology Data Exchange (ETDEWEB)

The structural change of the (100-x)(0.6Li[sub 2]S[center dot]0.4SiS[sub 2])centre dotxLi[sub 3]PO[sub 4] oxysulfide glassesduring crystallization was analyzed by means of solid-state nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). The unique tetrahedral units of SiO[sub n]S[sub 4-n] (n=1,2,3) and PO[sub n]S[sub 4-n] (n=1,2,3) present in the glass samples vanished and the SiS[sub 4], PS[sub 4], SiO[sub 4] units increased with proceeding of the crystallization process. Nonbridging sulfur and oxygen atoms decreased while bridging oxygens and S[sup 2-] increased with proceeding of the crystallization process. Large structural difference between the glass and the corresponding crystallized sample explained the high stability against crystallization found in the oxysulfide glass with the composition of X=5. (author)

Energy Technology Data Exchange (ETDEWEB)

The meeting was arranged into the following sessions: introductory; advanced ceramics and ceramic composites; ceramic and metal matrix composites; electronic materials and devices; acoustoelasticity, stress, and texture; composites-porosity, strength, and UT propagation; process modeling and monitoring; thermal wave physics; material properties, composites, surfaces, and interfaces; acoustic emission; ferromagnetic materials; new sensors; NDE reliability assessment; elastic wave scattering and propagation; image analysis, data storage, and signal processing; UT transducers; weldments and bonded materials; eddy current models; unified life cycle engineering; x rays, CT, and NMR; eddy current probes and instruments; acoustic microscopy imaging, and reconstruction; signal processing, measurement techniques, and systems; NDE applications of artificial intelligence; crack behavior influenced by history; inversion procedures for UT and EC; process control and material ...

Energy Technology Data Exchange (ETDEWEB)