15n-1h nmr relaxation: Topics by WorldWideScience.org

Two dimensional NMR and NMR relaxation studies of coal structure

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 ...

3

Dynamic NMR effects in breast cancer dynamic-contrast-enhanced MRI

This report covers the progress made on the title project for the project period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups that determine the reactivity of coals. Special attention is being paid to methods that are compatible with the very high magic angle sample spinning rates needed for operation at the high magnetic field strengths available today. Polarization inversion methods utilizing the difference in heat capacities of small groups of spins are particularly promising. Methods combining proton-proton spin diffusion with [sup 13]C CPMAS readout are being developed to determine the connectivity of functional groups in coals in a high sensitivity relay type of experiment. Additional work is aimed at delineating the role of methyl group rotation in the proton NMR relaxation behavior of coals.

1992-11-25

4

Contrast factors in nuclear magnetic resonance imaging

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

2008-11-18

5

Isotope labeling strategies for NMR studies of RNA

In Nuclear Magnetic Resonance (NMR) imaging, contrast is dependent on the emission of radiofrequency waves by atomic nuclei, balanced by several parameters. The high information content of NMR images is due to the multiplicity of its parameters. However, this advantage introduces a difficulty in the interpretation of the contrast. There are three contrast parameters for each tissue: hydrogen nuclei density; relaxation time T1; relaxation time T2. Contrast may be enhanced towards any of these parameters by increasing the emission of radiowaves by atomic nuclei using particular pulse sequences.

1985-01-01

6

Magnetic resonanse imaging in otorhinolaryngology. With special reference to the influence of factors upon NMR parameters and differential diagnosis of otorhinolaryngic lesions

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 ...

2010-01-15

7

Two dimensional NMR and NMR relaxation studies of coal structure. Progress report, July 1, 1992--September 30, 1992

MRI diagnosis for malignant tumors are made possible by direct comparison to the results obtained by the brain and it seems possible to differentiate malignant tumors from other benign lesions. Cystic lesions, and mycotic sinusitis sometimes resemble malignant tumors in MR Image. In the present report, we investigated the relationships between the biochemical contents of cystic lesions and NMR-parameters to clarify why some inflammatory lesions appeared similar to malignant tumors in MRI. The variation of relaxation time depends upon the amount of protein in the cystic contents and the amount of glucose affects the relaxation time. We conclude that NMR-parameters are useful for the differential diagnosis of malignant tumors, cystic lesions and mycositic sinusitis by using the multiple variation analysis.

1987-07-01

8

Modulation of proton NMR free induction decay by spin diffusion

This report covers the progress made on the title project for the project period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups that determine the reactivity of coals. Special attention is being paid to methods that are compatible with the very high magic angle sample spinning rates needed for operation at the high magnetic field strengths available today. Polarization inversion methods utilizing the difference in heat capacities of small groups of spins are particularly promising. Methods combining proton-proton spin diffusion with {sup 13}C CPMAS readout are being developed to determine the connectivity of functional groups in coals in a high sensitivity relay type of experiment. Additional work is aimed at delineating the role of methyl group rotation in the proton NMR relaxation behavior of coals.

1992-11-25

9

NMR study of one-dimensional ionic conductor with hollandite-type structure (IV) Rb-priderite

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.

1982-02-01

10

Imazalil-cyclomaltoheptaose (beta-cyclodextrin) inclusion complex: preparation by supercritical carbon dioxide and 13C CPMAS and 1H NMR characterization.

Conduction properties of Rb"+ ion in Rb-Al-priderite and K"+ ion and Rb"+ ion in (K,Rb)-Al-priderite, were investigated by NMR using "2"7Al in the framework as a probe. Size effect was observed remarkably in the activation energies. Frequency dependence of T_1 in Rb-Al-priderite at a low temperature indicates that the relaxation behavior of "2"7Al in Rb-Al-priderite can be described by the continuum model. Barrier height distributions and 'attempt frequencies' in both samples obtained by a curve-fitting method are discussed in comparison with those of K-Al-priderite. (orig.).

1985-08-18

11

Model for ionic hopping in Li/sub 3/N

An inclusion complex between imazalil (IMZ), a selected fungicide, and cyclomaltoheptaose (beta-cyclodextrin, betaCD) was obtained using supercritical fluid carbon dioxide. The best preparation conditions were determined, and the inclusion complex was investigated by means of 1H NMR spectroscopy in aqueous solution and 13C CPMAS NMR spectroscopy in the solid state. Information on the geometry of the betaCD/IMZ complex was obtained from ROESY spectroscopy, while the dynamics of the inclusion complex in the kilohertz range was obtained from the proton spin-lattice relaxation times in the rotating frame, T(1rho) (1H). PMID:14553984

2003-10-10

12

Molecular dynamic study of different regions of Angelin Pedra (Himenolobium paetrum) wood by low field NMR

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.

1980-08-01

13

High Magnetic Field NMR Studies of LiVGe$_2$O$_6$, a quasi 1-D Spin $S = 1$ System

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, ...

2005-11-06

14

Mesodynamics in the SARS nucleocapsid measured by NMR field cycling

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 ...

2001-01-01

15

Theory of NMR multiple echoes in solid hydrogen

Protein motions on all timescales faster than molecular tumbling are encoded in the spectral density. The dissection of complex protein dynamics is typically performed using relaxation rates determined at high and ultra-high field. Here we expand this range of the spectral density to low fields through field cycling using the nucleocapsid protein of the SARS coronavirus as a model system. The field-cycling approach enables site-specific measurements of R{sub 1} at low fields with the sensitivity and resolution of a high-field magnet. These data, together with high-field relaxation and heteronuclear NOE, provide evidence for correlated rigid-body motions of the entire {beta}-hairpin, and corresponding motions of adjacent loops with a time constant of 0.8 ns (mesodynamics). MD simulations substantiate these findings and provide direct verification of the time scale and collective nature of these motions.

2009-09-15

16

Polymers and paper as packaging materials of irradiated food

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.

1995-11-01

17

/sup 109/Ag NMR spectra of aqueous silver ions coordinated with nitroxide radical. Silver-TANOL complex and TANOL as a doping agent

Effects of #gamma#-irradiation on synthetic polymers and paper used as packaging materials for irradiated food have been studied by NMR. Polystyrene, polybutadiene and some copolymers were studied before and after the #gamma#-irradiation treatment and in the presence or absence of antioxidants and stabilisers. In the absence of additives, the effect of #gamma#-irradiation on polystyrene is negligible even irradiating at high doses. In turn, the role of antioxidants and stabilisers is crucial in polybutadiene and butadiene-containing copolymers. Wood pulp paper was also studied by NMR. Preliminary measurements on #gamma#-irradiated wood pulp sheets show a shortening in the T_2 relaxation time component due to the bound water, i.e. some of the bound water is lost. (author)

2000-03-01

18

Moderately heavy, heavy-fermion compound YbPd_2Si_2 at low temperatures

The effects of TANOL radical have been examined on chemical shifts and relaxation rates of /sup 109/Ag NMR in aqueous solution of silver salts. The silver ion in aqueous solution is found to coordinate with TANOL radical. A small amount of TANOL is added as a doping agent(0.020M), since /sup 109/Ag signals are obtained for (1.0M) silver ion within 30 minutes. The /sup 109/Ag chemical shifts of silver salt in aqueous solutions were found within the range of 0 to -1000 ppm relative to that of 1.0M AgNo/sub 3/.

1982-09-01

19

Moderately heavy, heavy-fermion compound YbPd sub 2 Si sub 2 at low temperatures

The available experimental data on the specific heat, magnetic susceptibility, magnetization, valence, NMR Knight shift and relaxation rate, and the quadrupolar moment of YbPd_2Si_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_2Si_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-T properties. These three doublets should have a splitting of the order of the Kondo temperature, i.e., about 100 K. A simple ...

20

Solid-state NMR on polymers and quantum computing NMR

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., ...

1992-07-01

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21

Use of lanthanide shift reagents with [sup 31]P FT-NMR spectroscopy to analyze concentrated lake-water samples

No abstract prepared.

2005-07-01

22

Studies of the involvement of metal ions with several medicinal agents

Several lanthanide shift reagents (LSR) were synthesized from praseodymium, europium, dysprosium, and terbium using ethylenediaminetetraacetic acid, trans-1,2-diaminocyclohexane-N,N,N[prime],N[prime]-tetraacetic acid, and diethylenetriaminepentaacetic acid for the purpose of separating overlapping [sup 31]P FT-NMR spectral signals of dissolved organic phosphorus compounds present in concentrated lake-water samples. The extent of change in signal position and line width of several known phosphorus compounds dissolved in pure water was examined as a function of solution pH and the molar ratio of LSR to phosphorus. Praseodymium ethylenediaminetetraacetate (PrEDTA) was determined to be the most effective LSR. Concentrated lake-water samples mixed with PrEDTA were examined with [sup 31]P FT-NMR. The use of PrEDTA provided separation of overlapping signals, indicated that phosphorus compounds were becoming isolated from the solution environment ...

1994-08-01

23

Positioning of the Alzheimer A{beta}(1-40) peptide in SDS micelles using NMR and paramagnetic probes

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.

1985-01-01

24

NMR study of Ba2"+ ion motion in one-dimensional ionic conductor with hollandite-type structure

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 ...

2007-09-15

25

Gd-25 DTPA-MAb, a potential NMR contrast agent for MRI in the xenografted nude mouse: preliminary studies

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 ...

26

Clinical trial of NMR-CT, (4). Clinical evaluation of hybrid image

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.

1988-01-01

27

Nuclear magnetic resonance imaging of the abnormal live rat and correlations with tissue characteristics

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 ...

1985-01-01

28

NMR studies of the partially disordered state in a triangular antiferromagnet UNi_4B

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.

1981-10-01

29

Contribution to the experimental study of the polarized liquid helium-3; Contributions a l'etude experimentale de l'helium-3 liquide polarise

A triangular antiferromagnet UNi_4B experiences a partially disordered state, in which two-thirds of U 5f moments order in a vertex-like structure and one-third of U 5f moments remain paramagnetic. Magnetization and NMR measurements of UNi_4B have been performed to study the dynamical properties of U magnetic moments in the partially disordered state. The value of the effective moment above T_N derived from the fitting of the Curie-Weiss law suggests a significant crystal field splitting and the Kondo effect. The Weiss temperature was also estimated to be -28 K, which suggests that the exchange interaction is antiferromagnetic. Furthermore, the exchange interaction estimated from the relaxation rate T_1"-"1 above 50 K is 18 K, which is close to the Weiss temperature. These results suggest that the dominant interactions between U moments are antiferromagnetic in the basal plane. The relaxation rate T_1"-"1 decreases abruptly ...

2007-04-11

30

Vacancy ordering and oxygen dynamics in oxide ion conducting La1-xSrxGa1-xMgxO3-x ceramics: 71Ga, 25Mg and 17O NMR

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 ...

1999-07-15

31

Mound Facility activities in chemical and physical research: July--December 1977. [Kr-Xe and Kr-Ar diffusion; Ne-Ar thermal diffusion

The oxygen vacancies distribution in the rigid lattice and the thermally activated motion of oxygen atoms are studied in La1-xSrxGa1-xMgxO3-x (x=0.00; 0.05; 0.10; 0.15 and 0.20) compounds. For that 71Ga, 25Mg and 17O NMR was performed from 100 K up to 670 K, and ion conductivity measurements were carried out up to 1273 K. The comparison of the electric field gradients at the Ga- and Mg-sites evidences that oxygen vacancies appear exclusively near gallium cations as a species trapped below room temperature in local clusters, GaO5/2-#square#-GaO5/2. These clusters decay at higher temperature into mobile constituents of the structural octahedra Ga(O5/6#square#1/6)6/2. At the same time, the nearest octahedral oxygen environment of magnesium cations persists at different doping levels. The case of two adjacent vacant anion sites is found highly unlikely within the studied doping range. The thermally activated oxygen motion starts to develop above room temperature as is ...

2011-01-01

32

Solid-state NMR Techniques for Chemistry Research

Isotope separation of Ar, C, /sup 3/He, Kr, Ne, O, and Xe isotopes is reported. TiFeH/sub x/, TiCoH/sub x/, TiCuH/sub x/, and VH/sub x/ were studied using NMR (proton relaxation times). VD/sub x/ and VT/sub x/ were synthesized. The problem of calculating the valence state of Pu is discussed. A series solution to the plutonium (N,H) characteristic equation is suggested. Shipments of /sup 231/Pa, /sup 230/Th, and /sup 229/Th are reported. Separation and processing of /sup 234/U are also reported. Theoretical methods were developed to calculate temperature distributions as functions of water flow rate in liquid thermal diffusion columns. Diffusion coefficients were measured from 300 to 1200/sup 0/K for Kr-Xe and Kr-Ar. New thermal diffusion factors are submitted for Ne-Ar.

1978-05-01

33

NMR spectroscopy study of serum lipids from HIV patients

No abstract prepared.

2000-09-01

34

KAIS Resistive NMR-CT and Its Clinical Application

Short communication.

1996-12-31

35

KoreaScience (Korea)

Full Text Available

1985-01-01

36

Studies of weak hcp "3He-"4He solution decomposition and magnetic properties of decomposed samples

Structure and magnetic properties of the UNi_1_0_-_xFe_xSi_2 system and "2"9Si nuclear magnetic resonance in UNi_1_0Si_2

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 ...

37

Validation of the GROMOS force-field parameter set 45A3 against nuclear magnetic resonance data of hen egg lysozyme

Structure and magnetic properties of UNi_1_0_-_xFe_xSi_2 intermetallics and "2"9Si nuclear magnetic resonance (NMR) in UNi_1_0Si_2 are investigated in a wide temperature range. Solid solutions in the exactly single-phase tetragonal form, ThMn_1_2 type, exist for x<2. The Ni and Fe atoms occupy the 8(f), 8(i) and 8(j) positions statistically, whereas the U atoms occupy the 2(a) and the Si atoms the 8(j) sites. The lattice parameters roughly follow Vegard's law. The magnetic susceptibility does not exhibit Curie-Weiss behaviour and, at about 630 K, an anomaly in the temperature dependence is observed. At low temperature, other anomalies are observed at 32 K and 45 K, for x=0.5 and 1.0 respectively. These low temperature anomalies are probably connected with magnetic ordering of a ferromagnetic character, whereas that at 630 K might result from the superparamagnetic state of Ni. Two "2"9Si NMR lines in UNi"1"0Si"2 were observed with the Knight ...

1993-09-01

38

Design and Construction of a Versatile Dual Volume Heteronuclear Double Resonance Microcoil NMR Probe

The quality of molecular dynamics (MD) simulations of proteins depends critically on the biomolecular force field that is used. Such force fields are defined by force-field parameter sets, which are generally determined and improved through calibration of properties of small molecules against experimental or theoretical data. By application to large molecules such as proteins, a new force-field parameter set can be validated. We report two 3.5 ns molecular dynamics simulations of hen egg white lysozyme in water applying the widely used GROMOS force-field parameter set 43A1 and a new set 45A3. The two MD ensembles are evaluated against NMR spectroscopic data NOE atom-atom distance bounds, {sup 3}J{sub NH{alpha}} and {sup 3}J{sub {alpha}}{sub {beta}} coupling constants, and {sup 1}5N relaxation data. It is shown that the two sets reproduce structural properties about equally well. The 45A3 ensemble fulfills the atom-atom distance bounds derived ...

2004-12-15

39

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

2009-04-01

40

Tips for Living with Scleroderma

High resolution of NMR spectroscopic data of biosamples are a rich source of information on the metabolic response to physiological variation or pathological events. There are many advantages...Full Text Available

2010-01-01

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41

Reveal the Level of Anxiety in Patients With Crohn's Disease Receiving Adalimumab (Relax)

... relaxation and a sense of well-being. Warm whirlpool baths, molten paraffin application to the hands and ...

42

{sup 13}C-NMR signal enhancement by using parahydrogen induced polarization (PGIP) and appropriate pulse sequences

Severe Crohn's Disease; Anxiety

2011-09-01

43

QCCM - Center for NMR Quantum Information Processing

No abstract prepared.

2009-07-01

44

NMR-based Enantiodifferentiation of Chiral trans-2-Phenylcyclopropane Derivatives Using a Chiral Lanthanide Shift Reagent

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

2011-02-16

45

KoreaScience (Korea)

Full Text Available

2011-06-01

46

NMR assignment of the cAMP-binding domain A of the PKA regulatory subunit

Carbon-13 NMR analysis of shale oil and shale oil derived jet fuels

No abstract prepared.

2006-12-15

47

Investigation of lithium niobate nonstoichiometric monocrystals by the NMR method

No Abstract Available

1981-01-01

48

Biochemical monitoring of black raspberry (Rubus coreanus Miquel) fruits according to maturation stage by ^1H NMR using multiple solvent systems

The paper studies the effect of crystal structure of LiNbO_3 monocrystals on NMR spectra of "7 Li and "9"3 Nb. Models of defect structure are analyzed via comparison of NMR experimental spectra and gradients of electrical field predicted on the basis of the calculations on "7 Li and "9"3 Nb nuclei using the relevant model. It is shown that no one of the main models of lithium niobate defect structure explains the peculiarities of NMR spectra. Conclusions are made about the independence of the reasons of occurrence of NMR additions lines "7 Li and "9"3 Nb, as well as, about links of "9"3 Nb NMR weak additional lines with the ranges of a different crystalline phase that may form while growing. 18 refs., 2 figs., 3 tabs.

49

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 ...

2011-01-01

50

Water Molecule Contributions to Proton Spin-Lattice Relaxation in Rotationally Immobilized Proteins

Two-site exchange revisited: a new method for extracting exchange parameters in biological systems.

Spin-lattice relaxation rates of protein and water protons in dry and hydrated immobilized bovine serum albumin were measured in the range of ¹H Larmor frequency from 10 kHz to 30...Full Text Available

2009-07-01

51

Near Infrared-Fluorescent and Magnetic Resonance Imaging Molecular Probe with High T1 Relaxivity for In Vivo Multimodal Imaging

A new analysis is presented which links real volume fractions, relaxation rates, and intracompartmental exchange rates directly with apparent volume fractions and relaxation rates obtained from biexponential...Full Text Available

1989-02-01

52

A possible role of decreased relaxation mediated by beta-adrenoceptors in bladder outlet obstruction by benign prostatic hyperplasia.

A new gadolinium chelating NIR fluorescent molecular probe increases T₁ relaxivity of water protons, facilitating combined optical and magnetic resonance imaging.

2010-06-07

53

Identification of triterpene saponine separated from Potentilla erecta (L.) rhizome on the base of {sup 13}C NMR spectra analysis; Identyfikacjie saponin triterpenowych wyizolowanych z klacza Potentilla Erecta (L.) na podstawie analizy {sup 13}C - NMR

1. To explore mechanisms of urinary obstruction in benign prostatic hyperplasia (BPH), the features of contraction and relaxation in human hyperplastic and non-hyperplastic (control) prostatic tissues...Full Text Available

1992-11-01

54

Fluorine-19 NMR Chemical Shift Probes Molecular Binding to Lipid Membranes

No abstract prepared

1995-12-31

55

Flip-flop sequence for restoring Zeeman order in the laboratory reference frame

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

2008-05-22

56

Massage Therapy

Medline Plus

... Massage therapy can help the body release certain chemicals. These chemicals help us relax, improve blood circulation and get ...

57

Sc"4"5 NMR of scandium(3) salt aqueous solutions

... spin-lattice relaxation angular momentum electronic circuits magnetic

58

Influence of resonant US on H-NMR at application of magnetic nanoparticles

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

59

Evaluation of the total oil and oleic acid contents in peanut seeds by low field NMR

2010 [1 p.] Germany Repp, Felix El-Miladi, Nouri Hoehl, Christian Jahanbakhsh,

2010-03-21

60

Stress relaxation in Mg-Al-Alloys AZ31 reinforced by ceramic form

... PHYSICAL AND ANALYTICAL CHEMISTRY calibration standards diagrams

2010-08-04

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

61

Phonon relaxation and internal friction in heterogeneous systems based on poly(vinyl chloride)

Stress relaxation was studied at 408 K on AZ31 reinforced by ceramic foam produced by in situ foaming of filler loaded preceramic polymer melt. Reinforcement causes significant enhancement of the resistance against stress relaxation compared to AZ91. It is correlated with hardening by the ceramic skeleton as well as ceramic particles formed in the AZ31-matrix. (orig.)

2003-07-01

62

British Library Electronic Table of Contents (United Kingdom)

Phonon relaxation and internal friction in kaolin-and bentonite-filled PVC composites are studied. By varying the temperature and/or content of the ultrafine mineral filler in the PVC, one can control the contribution from phonon viscosity, damping force, and the effect of viscosity into the energy dissipation of ultrasonic oscillations in the MHz frequency interval. The dynamic character of the measurements makes it possible to differentiate between relaxation phenomena in the composites and to suggest methods for their controlled changes.

2010-01-01

63

Unilateral NMR, 13C CPMAS NMR spectroscopy and micro-analytical techniques for studying the materials and state of conservation of an ancient Egyptian wooden sarcophagus

British Library Electronic Table of Contents (United Kingdom)

A multi-technique approach was employed to study a decorated Egyptian wooden sarcophagus (XXV?XXVI dynasty, Third Intermediate Period), belonging to the Museo del Vicino Oriente of the Sapienza University of Rome. Portable non-invasive unilateral NMR was applied to evaluate the conservation state of the sarcophagus. Moreover, using unilateral NMR, a non-invasive analytical protocol was established to detect the presence of organic substances on the surface and/or embedded in the wooden matrix. This protocol allowed for an educated sampling campaign aimed at further investigating the state of degradation of the wood and the presence of organic substances by 13C cross polarization magic angle spinning (CPMAS) NMR spectroscopy. The composition of the painted layer was analysed by optical micr...

2011-01-01

64

All-atom molecular dynamics simulations using orientational constraints from anisotropic NMR samples

British Library Electronic Table of Contents (United Kingdom)

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...

2007-01-01

65

All-atom molecular dynamics simulations using orientational constraints from anisotropic NMR samples

All-atom molecular dynamics simulations using orientational constraints from anisotropic NMR samples

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, ...

2007-03-03

66

All-atom molecular dynamics simulations using orientational constraints from anisotropic NMR samples

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, ...

2007-05-15

67

A microscale protein NMR sample screening pipeline

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, ...

2007-05-01

68

Spin-Lattice Relaxation in Metal-Organic Platinum; 3, Complexes

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 ...

2010-01-01

69

Relaxation oscillation of amplified spontaneous radiation pulse emitted from a single-mirror Cu/CuBr laser

The dynamics of spin-lattice relaxation (slr) of metal-organic Pt(II) compounds is studied. Often, such systems are characterized by pronounced zero-field splittings (zfs) of the lowest-lying triplets. Previous expressions for the Orbach slr process do not allow to treat such splitting patterns properly. We discuss the behavior of a modified Orbach expression for a model system and present results of a fit of the temperature dependence of the spin-lattice relaxation rate of Pt(2-thpy)$_2$ based on the modified expression.

1999-01-01

70

The fluorescence properties and NMR analysis of protopine and allocryptopine

The relaxation oscillation of the amplified spontaneous radiation pulses emitted from a single-mirror Cu/CuBr laser has been observed for the first time and the experimental characteristics of the relaxation oscillation were obtained. In addition, the spatial and temporal distributions of the light pulse intensity of the amplified spontaneous radiation were also measured and found to be comparatively and uniform. The spatial coherence of the amplified spontaneous radiation was found to be better than that of the laser with the same lasant.

1985-10-01

71

NMR use in structural determination of natural products from Brazilian northeast plants; Uso de RMN na determinacao estrutural de produtos naturais de plantas nordestinas

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.

2011-07-01

72

NMR at earth's magnetic field using para-hydrogen induced polarization

This work has carried out a molecular structure characterization of two Brazilian plants, Harpalyce brasiliana Benth and Bredemeyera floribunda Wild, using {sup 1} H and {sup 13} C NMR spectroscopy. NMR spectra were presented and analysed, then several structures have been proposed based on spectral data, and finally the structural determination was done 3 refs., 4 figs., 1 tab.

1995-12-31

73

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.

2011-01-01

74

Study of the authenticity of Maytenus ilicifolia by measuring T1 from 1H nuclear magnetic relaxation in a vast array of frequencies

Plane-wave-basis pseudopotential calculations of the surface relaxations of Ti(0001) and Zr(0001)

Portuguese 2010 p. 137-138 Brazil Preto, Monica S. de Moura Tavares,

2010-08-04

75

Influence of the strain-relaxation induced defect creation on the leakage current of embedded Si{sub 1-x}Ge{sub x} source/drain junctions

The relaxations of the Ti(0001) and Zr(0001) surfaces are studied using the plane-wave-basis pseudopotential method within the local-density approximation. We find that the first interlayer spacings of Ti(0001) and Zr(0001) are contracted with respect to the bulk spacings by 6.8% and 6.1%, respectively. Such large relaxations for the close-packed surfaces of Ti and Zr are in good agreement with recent linear-augmented-plane-wave calculations. In addition, we predict a weak vibrational effect on the surface relaxation of Zr(0001) by considering the free energy in the quasiharmonic approximation. This result can be attributed to a very strong bonding between the first- and second-layer Zr atoms as a consequence of the bond-order endash bond-length correlation. copyright 1997 The American Physical Society.

76

Idiopathic (primary) achalasia

The purpose of this paper is to evaluate the role of the strain-relaxation processes on the leakage current of embedded SiGe S/D junctions. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics were measured to further investigate the relaxation degree of embedded SiGe S/D junctions in the regime where partial relaxation by misfits dislocations is assumed, yielding a reduction of the leakage current density. Further, the impact of the ion implantation-related defects on the electrical performance is discussed. The analysis is complemented with structural characterization based on High Resolution Transmission Electron Microscopy (HRTEM) and Nomarski microscopy. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

2009-08-15

77

Use of {sup 13} C in solid state NMR for characterization of commercial thermoplastic polyurethanes; Caracterizacao de poliuretanos termoplasticos comerciais por RMN de carbono-13 no estado solido

Idiopathic achalasia is a primary esophageal motor disorder characterized by esophageal aperistalsis and abnormal lower esophageal sphincter (LES) relaxation in response to deglutition. It is a rare...Full Text Available

78

Use of "1"3 C in solid state NMR for characterization of commercial thermoplastic polyurethanes

No abstract prepared.

2000-07-01

79

The Product Operator Formalism: A Physical and Graphical Interpretation

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

2000-08-02

80

NMR-Spectroscopy for Nontargeted Screening and Simultaneous Quantification of Health-Relevant Compounds in Foods: The Example of Melamine

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

2010-03-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

81

NMR characterization of composition and fiber size parameters of the sugarcane Eva/bagasse composites

The recent melamine crisis in China has pointed out a serious deficiency...Full Text Available

2009-08-26

82

Effects of polyvinylpyrrolidinone addition on thermoplastic polymers by using solid state "1"3 C NMR

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

1998-11-26

83

Copper deficiency alters the neurochemical profile of developing rat brain

Portuguese 1998 p. 47 Brazil Silva, Edemilson P. Universidade Federal,

1998-08-13

84

Biological effects and physical safety aspects of NMR imaging and in vivo spectroscopy

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

2009-06-01

85

Analysis of 'espinheira-santa' (Maytenus aquifolium) infusion by RP_3_0-HPLC-NMR

An assessment is made of the biological effects and physical hazards of static and time-varying fields associated with the NMR devices that are being used for clinical imaging and in vivo spectroscopy. A summary is given of the current state of knowledge concerning the mechanisms of interaction and the bioeffects of these fields. Additional topics that are discussed include: (1) physical effects on pacemakers and metallic implants such as aneurysm clips, (2) human health studies related to the effects of exposure to nonionizing electromagnetic radiation, and (3) extant guidelines for limiting exposure of patients and medical personnel to the fields produced by NMR devices. On the basis of information available at the present time, it is concluded that the fields associated with the current generation of NMR devices do not pose a significant health risk in themselves. However, rigorous guidelines must be followed to avoid ...

1985-08-01

86

"1H-NMR analysis of reaction mixture of lauric acid with monoethanolamine utilizing in situ reaction with trichloroacetyl isocyanate

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

1999-05-25

87

Structural relaxation and crystallization in the Fe-Cr-Si-B and Fe-Cu-Cr-Si-B amorphous alloys

Page 1. ANALYSIS OF REACTION MIXTURE OF LAURIC ACID WITH MONO-

1984-06-18

88

Isotherme Weerstandsmetingen Aan FE40 NI40 B20 en PD80 SI20 (Isothermal Resistivity Measurements on FE40NI40B20 and PD80SI20).

Structural relaxation, crystallization and optimisation processes in soft magnetic amorphous alloys based on iron are examined by applying different experimental techniques: X-ray diffraction analysis, high-resolution electron microscopy, measurements of magnetic and electric properties (permeability, after-effect resistivity). The presented results are discussed in terms of annealing out of microvoids, formation of nanocrystalline phase and changes of effective magnetostriction constant. (author)

2001-09-23

89

Influence of relaxation phenomena in liquid phase on magnetic anisotropy of metallic glasses

Resistivity measurements were performed on Fe40 Ni40 B20 and Pd80 Si20 in order to improve the understanding of structural relaxation in amorphous metals. A model describing structural relaxation as a combination of chemical short range ordering (CSRO) an...

1986-01-01

90

Influence of microwaves on the order parameter relaxation time of superconducting aluminium

It if first shown, that the effective field of uniaxial magnetic anisotropy of Fe-Cr-P-C and Fe-Ni-B-Si system amorphous alloys is reduced with an increase of the source melt isothermal exposure time. The behaviour noted is conditioned by microcoherence and relaxation processes in the nonequilibrium liquid phase after crystal-liquid phase transition.

1996-12-01

91

Quantitative ³¹P NMR Spectroscopy and ¹H MRI Measurements of Bone Mineral and Matrix Density Differentiate Metabolic Bone Diseases in Rat Models

Experimentally it is found that at constant temperature the order-parameter relaxation time, tausub(..delta..), decreases with increasing power of the microwaves, coupled into a superconducting strip. If the same increase in critical current, that corresponds with a given power of the microwaves, is obtained by lowering the temperature, the decrease in tausub(..delta..) is smaller. This reflects the fact that quasiparticles are removed more efficiently from the gap edge by microwaves than by lowering the temperature in equilibrium. A modified time-dependent Ginzburg-Landau equation is shown to describe these results adequately.

1982-04-01

92

NMR study of aluminium chloride and lithium tetrachloroaluminate solutions in a mixed solvent of thionylchloride-methylacetate

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

2010-06-01

93

Metabolomics in Lung Inflammation: A High Resolution ¹H NMR Study of Mice Exposed to Silica Dust

Lithium tetrachloroaluminate solutions in thionylchloride, methylacetate and their mixtures are studied by "7Li and "2"7Al NMR. It is found that introduction of methylacetate in the LiAlCl_4-SOCl_2 system results in a change of lithium tetrachloroaluminate formation constant. In the ternary system, Li"+ is solvated by methyl-acetate after complete destruction of tetrachloroaluminate anion. Refs. 9, figs. 2.

94

Interactions of myristic acid with bovine serum albumin: a 13C NMR study.

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

2008-01-01

95

31P NMR study of improvement in oxidative phosphorylation by vitamins K3 and C in a patient with a defect in electron transport at complex III in skeletal muscle.

Interactions of myristic acid with bovine serum albumin were studied by 13C NMR spectroscopy at 50.3 MHz using 90% isotopically substituted [1-13C]-, [3-13C]-, and [14-13C]myristic acids, either individually...Full Text Available

1984-06-01

96

³¹P NMR Observations on the Effect of the External pH on the Intracellular pH Values in Plant Cell Suspension Cultures ¹

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

1984-06-01

97

Modeling of the relaxation kinetics of metastable tensile strained Si:C alloys

³¹P nuclear magnetic resonance (NMR) spectroscopy was used to monitor the response of oil palm (Elaeis guineensis) and carrot (Daucus carota) cell suspensions...Full Text Available

1990-06-01

98

Kinetic studies of preactivated derivatives of cyclophosphamide by "3"1P NMR spectroscopy

In order to enhance the performance of CMOS transistors, embedded epitaxial layers of Si:C can be used. In the present work, Si:C layers with Carbon contents up to 1.9 at-% and in-situ Phosphorus doping up to 4 x 10{sup 20}At/cm{sup 3} have been investigated. Due to the low solubility of Carbon in Silicon (0.0004 at.-% at the melting point), all layers considered in this work are metastable and tend to relax. Since it is crucial to the application to retain the strain of those layers, the responsible mechanisms must be understood. The relaxation during thermal treatment was studied by high resolution X-ray diffraction and was found to behave differently, depending on Carbon content and Phosphorus doping concentration. In this work, we propose a relaxation mechanism based on a kick-out reaction of substitutional Carbon which is accelerated by Phosphorus content through transient enhanced diffusion. We simulate the time ...

2010-07-01

99

Vibrational relaxation of a triatomic molecular impurity: D{sub 2}O in vitreous As{sub 2}S{sub 3}

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 ...

100

Menstrual variation of breast volume and T{sub 2} relaxation times in cyclical mastalgia

Measurements of the relaxation of the D{sub 2}O stretch mode in vitreous As{sub 2}S{sub 3} are presented. Because the bending mode of the molecule offers an intra-molecular decay channel for the stretch mode, the decay scheme of the D{sub 2}O molecule is more complex than that of diatomic molecules. The asymmetric stretch mode of D{sub 2}O has a frequency of 2680 cm{sup -1}. To study the relaxation of this mode we applied a pump-probe technique, using intense psec; pulses of the Stanford Free Electron Laser. Due to the small cross-section of the vibrational mode, successful efforts were made to improve the signal to noise ratio by using a laser stabilization system and a tightly focused beam to increase the intensity, by averaging the signal with a kHz repetition rate and by using samples with an optimized D{sub 2}O concentration. A rapid relaxation rate on the order of 5 x 10{sup 9} sec{sup -1} at low temperature is found ...

1995-12-31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

101

Time-resolved triple-axis spectroscopy - a new method for real-time neutron scattering

Purpose: Hormonal activity causes breast volume to change during the menstrual cycle. One possible cause of this volume change is thought to be due to water retention or oedema within the tissues. We used magnetic resonance imaging (MRI) to study the variation in breast volume and {sup 1}H Magnetic Resonance Spectroscopy (MRS) to measure T{sub 2} relaxation times which are known to increase with increasing tissue water content. We hypothesised that an increase in breast volume will elevate T{sub 2} relaxation due to the presence of an increased water content within the breast. T{sub 2} Relaxation time and volume were studied in fifteen control subjects and in a cohort of eight patients with cyclical mastalgia in order to determine whether changes in breast volume and T{sub 2} relaxation times differed in controls and patients during menses, ovulation and premenses. Method: Breast volume was determined ...

2008-02-15

102

Study of oxygen diffusion in YBaCuO by isothermal internal friction. Etude par frottement interieur isotherme de la diffusion de l'oxygene dans YBaCuO

A new method for kinetic experiments with neutrons is described. This method combines the conventional triple-axis neutron spectroscopy with relaxation-type experiments. Whereas the former method yields information about the microscopic dynamics of solids, the latter provides macroscopic relaxation times. The combination of both methods allows to determine the microscopic mechanism of relaxation processes. The time-resolved triple-axis spectroscopy is limited to reversible processes and to time scales from 10"-"3 to 10"4 s. Typical applications are the kinetics of phase transformations (structural and dynamical changes), kinetics of domain distributions, kinetics of (spinodal) decomposition, reversible solid state reactions, time-dependent occupation of phonon states or phonon lifetimes. (orig.).

1990-04-01

103

Spin dynamics in Ho{sub 2}Ru{sub 2}O{sub 7}

The elastic behaviour of YBaCuO specimens has been studied by very low-frequency isothermal internal-friction measurements. A relaxation peak is observed which is attributed to oxygen atom jumps, between A(1/2 0 0) and B(0 1/2 0) sites, in the CuO planes of the orthorhombic phase. A limit relaxation time {tau}{sub 0}, 2.6 {center dot} 10{sup -15}s, and an activation energy, 1.3eV, have been obtained from the shift of the maximum damping frequency observed when the measurement temperature is changed. The proposed values for the limit relaxation time and the activation energy are in good agreement with those previously proposed in the literature.

1992-02-07

104

Spin dynamics in Ho_2Ru_2O_7

The spin relaxation processes within the pyrochlore Ho{sub 2}Ru{sub 2}O{sub 7} have been investigated by neutron scattering and bulk property techniques. A single-ion process, that is thermally activated, dominates the spin-spin relaxation spectrum above 2 K. Assuming Arrhenius behaviour, we found an activation energy {delta} = (329 {+-} 6) K and characteristic relaxation time {tau}{sub 0} (5.2 {+-} 0.3) x 10{sup -12} s in the paramagnetic state, akin to those found in the spin ice, Ho{sub 2}Ti{sub 2}O{sub 7}. Atlow temperature (T<95 K) the activation energy lowers and below 20 K the entropy and ac susceptibility are similar to that observed in other spin ice compounds within a 10 kOe field.

2005-11-09

105

Mechanical properties of Cu-Ni-Be system alloys

The spin relaxation processes within the pyrochlore Ho_2Ru_2O_7 have been investigated by neutron scattering and bulk property techniques. A single-ion process, that is thermally activated, dominates the spin-spin relaxation spectrum above 2 K. Assuming Arrhenius behaviour, we found an activation energy #DELTA# = (329 #+-# 6) K and characteristic relaxation time #tau#_0 (5.2 #+-# 0.3) x 10"-"1"2 s in the paramagnetic state, akin to those found in the spin ice, Ho_2Ti_2O_7. Atlow temperature (T<95 K) the activation energy lowers and below 20 K the entropy and ac susceptibility are similar to that observed in other spin ice compounds within a 10 kOe field.

2005-11-09

106

Measurement of the relaxation time of hot electrons in laser-solid interaction at relativistic laser intensities

The effects of addition of 0.17wt%Zr, 0.1wt%Mg and 0.1wt%Co on the mechanical properties of a Cu-1.2wt%Ni-0.2wt%Be alloy have been investigated. Adding Zr, Co or Mg to the Cu-Ni-Be alloy brings about the improvement in strength and stress relaxation property. The Zr, Co or Mg addition decreases the inter-precipitate spacing of #gamma#'' precipitates, resulting in the increase in strength. The higher resistance to the stress relaxation of the Zr- or Co-added alloy is attributed to the lower density of mobile dislocations. The improvement of stress relaxation property by the Mg addition is explained by the viscous glide motion of dislocations dragging Mg atoms, in addition to the lower density of mobile dislocations.

2010-07-01

107

Internal friction of amorphous Pd/sub 80/ Si/sub 20/ metal doped with hydrogen isotopes

The authors have measured the relaxation time of hot electrons in short pulse laser-solid interactions using a picosecond time-resolved x-ray spectrometer and a time-integrated electron spectrometer. Employing laser intensities of 10{sup 17}, 10{sup 18}, and 10{sup 19} W/cm{sup 2}, they find increased laser coupling to hot electrons as the laser intensity becomes relativistic and thermalization of hot electrons at timescales on the order of 10 ps at all laser intensities. They propose a simple model based on collisional coupling and plasma expansion to describe the rapid relaxation of hot electrons. The agreement between the resulting K{sub {alpha}} time-history from this model with the experiments is best at highest laser intensity and less satisfactory at the two lower laser intensities.

2006-08-22

108

Injection control and thermally stimulated current in ionic polarized polymer based light emitting diode

Internal friction of amorphous Pd/sub 80/Si/sub 20/ metal doped with hydrogen or deuterium was measured with a specially designed apparatus using amorphous metal sheet as a part of the electric oscillating circuit. Two peaks in Q/sup -1/ curve are observed. Applying the peak shift method to the first Snoek-like peak, we can determine the relaxation time from which the microdiffusion coefficient can be calculated. The obtained microdiffusion coefficient is about 10/sup -14/ m/sup 2//s at 200 K, being comparable with the macrodiffusion coefficient obtained from the releasing method. It can, however, not elucidate the hydrogen isotopic effect on the peak temperature of Q/sup -1/ curve, the activation energy for relaxation and the relaxation time from the present work because of the broadness of obtained Q/sup -1/ curve.

1983-02-01

109

Generation and relaxation of microstrains in GaN nanocrystals under extreme pressures

An effective method of enhancing charge injection and electroluminescence efficiency of polymer-based light emitting diode is introduced. Spin-coated films of poly (N-vinylcarbazole) blended with electron-transport material (Bu-PBD), laser dye (Coumarin6), and the typical supporting electrolyte (tetraethylammonium perchlorate; TEAP) were examined and it was found that the injection current and luminance of the light emitting diode doped with TEAP were enhanced dramatically after heat-treatment at 80 deg. C and appropriate biasing in an external electric field of 1.5x10"8 V/m at this temperature. The thermally stimulated current (TSC) was also measured to investigate the relaxation process of ionic space charges in the films. The relaxation times of ionic polarization were found to be related to the cation size of the electrolyte. And the relaxation time becomes long enough by the use of TEAP doping.

2003-08-22

110

Behavior of Stress-Relaxation phenomena in Zr-1.1Nb-0.05Cu

Nanocrystalline powders of GaN with grain sizes ranging from 2 to 30 nm were examined under high external pressures by in situ diffraction techniques in a diamond anvil cell at DESY (HASYLAB, Station F3). The experiments on densification of pure powders under high pressure were performed without a pressure medium. The mechanism of generation and relaxation of internal strains and their distribution in nanoparticles was deduced from Bragg reflections recorded in situ under high pressures at room temperature. The microstrain was calculated from the full-width at half-maximum (FWHM) values of the Bragg lines. It was found that microstrains in GaN crystallites are generated and subsequently relaxed by two mechanisms: generation of stacking faults and change of the size and shape of the grains occurring under external stress. (author)

2001-09-23

111

An in situ observation of the growth kinetics and stress relaxation Pd sub 2 Si thin films on Si(111)

Zirconium alloys have anisotropic mechanical properties depending on their physical orientations and are widely used as nuclear materials such as cladding tube material. An operation condition of the nuclear reactor requires a high creep resistance, because it is subjected to long period operations, high temperature and high pressure. Generally, it takes a few days or months to do the creep experiment, so it is difficult to get a data in short period. However, there is a way to predict a creep property by using the stress-relaxation in the short term. These studies realized the stress-relaxation through a compressive test of HANA-6 (Zr-1.1Nb-0.05Cu) alloy that was developed by KAERI (Korea Atomic Energy Research Institute), and then predicted the creep property

2010-10-01

112

An efficient computational method for a stochastic dynamic lot-sizing problem under service-level constraints

The growth of the Pd{sub 2}Si thin fllms on Si(111) substrates has been monitored by an {ital in} {ital situ} x-ray diffraction technique in vacuum and in helium atmosphere from 160 to 250 {degree}C. A familiar parabolic growth rate was found, confirming the diffusion-controlled film growth process. The activation energies were found to be 1.34 and 1.37 eV for the measurements performed in vacuum and helium environment, respectively. Stress relaxation in the growing Pd{sub 2}Si fllm was observed when the reaction temperature exceeds 200 {degree}C. The relaxed films showed a higher degree of texture as evidenced by the rocking curve measurements.

1990-04-15

113

British Library Electronic Table of Contents (United Kingdom)

We provide an efficient computational approach to solve the mixed integer programming (MIP) model developed by Tarim and Kingsman [8] for solving a stochastic lot-sizing problem with service level constraints under the static-dynamic uncertainty strategy. The effectiveness of the proposed method hinges on three novelties: (i) the proposed relaxation is computationally efficient and provides an optimal solution most of the time, (ii) if the relaxation produces an infeasible solution, then this solution yields a tight lower bound for the optimal cost, and (iii) it can be modified easily to obtain a feasible solution, which yields an upper bound. In case of infeasibility, the relaxation approach is implemented at each node of the search tree in a branch-and-bound procedure to efficiently sear...

2011-01-01

114

An in situ observation of the growth kinetics and stress relaxation Pd sub 2 Si thin films on Si(111)

Use of lanthanide shift reagents together with silver trifluoroacetate for quantitative analysis of mixtures of aromatic hydrocarbons

The growth of the Pd{sub 2}Si thin fllms on Si(111) substrates has been monitored by an {ital in} {ital situ} x-ray diffraction technique in vacuum and in helium atmosphere from 160 to 250 {degree}C. A familiar parabolic growth rate was found, confirming the diffusion-controlled film growth process. The activation energies were found to be 1.34 and 1.37 eV for the measurements performed in vacuum and helium environment, respectively. Stress relaxation in the growing Pd{sub 2}Si fllm was observed when the reaction temperature exceeds 200 {degree}C. The relaxed films showed a higher degree of texture as evidenced by the rocking curve measurements.

1990-04-15

115

Uniform and Residue-specific {sup 15}N-labeling of Proteins on a Highly Deuterated Background

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.

1980-01-01

116

Silica Polyamine Composites: New Supramolecular Materials for Cation and Anion Recovery and Remediation

A general method for stable-isotope labeling of large proteins is introduced and applied for studies of the E. coli GroE chaperone proteins by solution NMR. In addition to enabling the residue-specific {sup 15}N-labeling of proteins on a highly deuterated background, it is also an efficient approach for uniform labeling. The method meets the requirements of high-level deuteration, minimal cross-labeling and high protein yield, which are crucial for NMR studies of structures with sizes above 150 kDa. The results obtained with the new protocol are compared to other strategies for protein labeling, and evaluated with regard to the influence of external factors on the resulting isotope labeling patterns. Applications with the GroE system show that these strategies are efficient tools for studies of structure, dynamics and intermolecular interactions in large supramolecular complexes, when combined with TROSY- and CRINEPT-based experimental ...

2004-07-15

117

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...

2006-01-01

118

Magic-angle-spinning NMR studies of acid sites in zeolite H-ZSM-5

High-resolution NMR on /sup 29/Si nuclei in acidic zeolites

{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.

1991-01-01

119

Uridine adenosine tetraphosphate induces contraction and relaxation in rat aorta

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.

1986-12-01

120

Structural, electronic and energetic properties of silicon carbon alloys

Uridine adenosine tetraphosphate (Up₄A) has been recently reported as an endothelium-derived vasoconstrictor and plasma levels of this dinucleotide are increased in juvenile hypertensive...Full Text Available

2008-01-01

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121

Relaxant effects of hexosamines on isolated small human placental arteries

We studied the influence of alloying on the structural and electronic properties of the unrelaxed and relaxed Si_1_-_yC_y random alloys by means of ab initio theoretical calculations using two methods: (i) a supercell approach in connection with the plane-wave pseudopotential method; (ii) the full-potential augmented plane-wave plus local orbitals (APW+lo) method. The first method is used to obtain the relaxed atomic structure. The relaxed atomic positions obtained by pseudopotential calculations were used to calculate the band structure via the second method. The local density approximation was used for the exchange and correlation energy density functional. We investigated the lattice parameters and band gap energies. We found that a quite smaller gap appears in the neighborhood of y=0.03125 concentration of C atoms. The band gap shows a large anomalous bowing and is strongly composition dependent. The electron densities ...

2007-01-15

122

DEFF Research Database (Denmark)

Wharton's jelly contains large amounts of hyaluronic acid, and glucosamine is an important constituent of this macromolecule. In order to evaluate the placental vascular effects of this aminosugar, small chorionic and stem villous arteries were dissected from placental specimens obtained at normal term vaginal deliveries (n = 15). Ring preparations were mounted in organ baths, and isometric wall tensions were measured. Glucosamine and its epimer galactosamine (5 X 10(-4) to 10(-2) M) produced marked relaxation of contractions induced by PGF2 alpha (10(-5) M) in both chorionic and stem villous arteries. The effect was unchanged after pretreatment with atropin, propranolol and indomethacin. The relaxant effect of the neutral sugar mannose was less pronounced compared with that of the hexosamines. Total tissue concentrations of placental hexosamines have been reported within the range needed to produce placental vascular ...

1987-01-01

123

Metallic seals offer improved resilience

Mechanism of Catch Force: Tethering of Thick and Thin Filaments by Twitchin

Metallic O-ring or Helicoflex seals can prevent relaxation and provide greater resilience than composite seals, helping to keep joints leaktight. Their characteristics and applications in the nuclear industry are outlined. (Author).

124

Induction of autolysis in nongrowing Escherichia coli.

Catch is a mechanical state occurring in some invertebrate smooth muscles characterized by high force maintenance and resistance to stretch during extremely slow relaxation. During catch, intracellular...Full Text Available

2010-01-01

125

Effect of #gamma#-irradiation on relaxation properties of sealants on organosilicon rubber base

Unless relaxation of the stringent response is achieved, all nongrowing bacteria rapidly develop resistance to autolysis induced by a variety of agents, including all classes of cell wall synthesis...Full Text Available

1986-09-01

126

Dendroaspis natriuretic peptide is the most potent natriuretic peptide to cause relaxation of lower esophageal sphincter

The dielectrical properties of organosilicon sealants have been studied in the wide range of temperatures in the low and radio frequencies range. The effect of thermal treatment and #gamma#-irradiation on these properties is discussed.

127

British Library Electronic Table of Contents (United Kingdom)

Atrial natriuretic peptide (ANP) causes relaxation in the opossum lower esophageal sphincter. The effects of dendroaspis natriuretic peptide (DNP) and other natriuretic peptides in the lower esophageal sphincter were not known. We measured the relaxation of transverse strips from the guinea pig lower esophageal sphincter caused by DNP, ANP, brain natriuretic peptide (BNP), C-type natriuretic peptide (CNP), and a natriuretic peptide receptor-C agonist des[Gln^1^8, Ser^1^9, Gly^2^0, Leu^2^1, Gly^2^2]ANP(4-23) amide (cANF(4-23)) in vitro. In resting strips of the guinea pig lower esophageal sphincter DNP and BNP caused marked relaxations. Furthermore, in both sarafotoxin S6c and carbachol-contracted lower esophageal sphincter strips, DNP caused marked and BNP caused moderate, concentration-de...

2011-01-01

128

Defect modelling

Coping with Test Pain, Discomfort, and Anxiety

Calculations, drawing principally on developments at AERE Harwell, of the relaxation about lattice defects are reviewed with emphasis on the techniques required for such calculations. The principles of defect modelling are outlined and various programs developed for defect simulations are discussed. Particular calculations for metals, ionic crystals and oxides, are considered. (UK).

1980-03-01

129

Control of wrist position and muscle relaxation by shifting spatial frames of reference for motoneuronal recruitment: possible involvement of corticospinal pathways

... Search Help? Coping with Test Pain, Discomfort, and Anxiety Introduction | Be Prepared | Know Your Tests | Relax | Conclusion ... though they may feel some embarrassment, discomfort, or anxiety at the outset. If undergoing medical tests makes ...

130

Bimodal MR-PET agent for quantitative pH imaging

It has previously been established that muscles become active in response to deviations from a threshold (referent) position of the body or its segments, and that intentional motor actions result from...Full Text Available

2010-05-01

131

ALTERATION OF THE PKC-MEDIATED SIGNALING PATHWAY FOR SMOOTH MUSCLE CONTRACTION IN OBSTRUCTION-INDUCED HYPERTROPHY OF THE URINARY BLADDER

Activatable or “smart” magnetic resonance contrast agents have relaxivities that depend on environmental factors such as pH or enzymatic activity, but the MR signal depends on...Full Text Available

2010-03-22

132

Structure of human insulin monomer in water/acetonitrile solution

Normal urinary bladder function requires contraction and relaxation of the detrusor smooth muscle (DSM). The DSM undergoes compensatory hypertrophy in response to partial bladder outlet obstruction...Full Text Available

2009-07-01

133

Strategies for the uses of lanthanide NMR shift probes in the determination of protein structure in solutio. Application to the EF calcium binding site of carp parvalbumin.

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 ...

2008-01-15

134

Solid-state ¹³C NMR spectroscopy of a ¹³C carbonyl-labeled polypeptide

The homologous sequences observed for many calcium binding proteins such as parvalbumin, troponin C, the myosin light chains, and calmodulin has lead to the hypothesis that these proteins have homologous...Full Text Available

1980-10-01

135

Non-contiguous regions of Z-DNA in a DNA dodecamer.

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

1992-06-01

136

Multivariate analysis of {sup 1}H NMR spectral data of Brazilian wines from the Sao Francisco region (Pernambuco); Analise multivariada dos dados espectrais de RMN de {sup 1}H dos vinhos elaborados no submedio Sao Francisco

The conformation of the self-complimentary DNA dodecamer d(br5CGbr5CGAATTbr5CGbr5CG) has been investigated in a variety of salt and solvent conditions by one and two-dimensional 1H NMR. In low salt...Full Text Available

1989-10-11

137

Long-lived states to sustain hyperpolarized magnetization

No abstract prepared.

2008-07-01

138

Insertion of a Bulky Rhodium Complex into a DNA Cytosine-Cytosine Mismatch: An NMR Solution Study

Major breakthroughs have recently been reported that can help overcome two inherent drawbacks of NMR: the lack of sensitivity and the limited memory of longitudinal magnetization. Dynamic nuclear polarization...Full Text Available

2009-11-03

139

Hydroxylation of 3-Nitrotyrosine and Its Derivatives by Gamma Irradiation

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

2007-10-10

140

HCN polymers characterized by solid state NMR: Chains and sheets formed in the neat liquid

... the hydroxyl group with the benzene ring. The molar extinction coefficients for the various species at their respective absorption ... Glya Recorded by 1H-NMR Spectroscopy TABLE 2 Molar Extinction Coeff...

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141

Ensemble quantum computing by NMR?spectroscopy

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

2009-04-07

142

Different distribution of fluorinated anesthetics and nonanesthetics in model membrane: a 19F NMR study.

A quantum computer (QC) can operate in parallel on all its possible inputs at once, but the amount of information that can be extracted from the result is limited by the phenomenon of wave function...Full Text Available

1997-03-04

143

Antioxidant activity and {sup 1}H and {sup 13}C NMR data of isocatalpanol and a derivative of tecomaquinone of Lippia sidoides; Atividade antioxidante e dados RMN {sup 1}H e {sup 13}C do isocatalpanol e um derivado da tecomaquinona de Lippia sidoides

Despite their structural resemblance, a pair of cyclic halogenated compounds, 1-chloro-1,2,2-trifluorocyclobutane (F3) and 1,2-dichlorohexafluorocyclobutane (F6), exhibit completely different anesthetic...Full Text Available

1997-04-01

144

¹³C-NMR Assessment of the Pattern of Organic Matter Transformation during Domestic Wastewater Treatment by Autothermal Aerobic Digestion (ATAD)

No abstract prepared.

2005-07-01

145

¹H-NMR-Based Metabolomic Profiling of CSF in Early Amyotrophic Lateral Sclerosis

The pattern of biodegradation and the chemical changes occurring in the macromolecular fraction of domestic sludge during autothermal thermophilic aerobic digestion (ATAD) was monitored and characterised...Full Text Available

2009-08-01

146

Study of vibrational relaxation in the active medium of a CO/sub 2/-laser by the phase-absorption method

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

147

Semantic network array processor and its applications to image understanding

The authors attemps to confirm a modification of the phase-absprotion method applicable to the study of the decay rate of energy stored in the upper level in the active medium of a CO/sub 2/-laser. The essence of the method is described. Relationships are determined which allow one to obtain the unknown parameters of the experimentally measured phase shift. The work exeprimentally shows the possibility of studying vibratioanl relaxation in the active medium of a CO/sub 2/-laser by the phase-absorption method using both ordinary and isotope-substitued molecules.

1986-09-01

148

Relaxation oscillations and diffusion chaos in the Belousov reaction

The problems in computer vision range from edge detection and segmentation at the lowest level to the problem of cognition at the highest level. This correspondence describes the organization and operation of a semantic network array processor (SNAP) as applicable to high level computer vision problems. The architecture consists of an array of identical cells each containing a content addressable memory, microprogram control, and a communication unit. The applications discussed in this paper are the two general techniques, discrete relaxation and dynamic programming. While the discrete relaxation is discussed with reference to scene labeling and edge interpretation, the dynamic programming is tuned for stereo.

1987-01-01

149

British Library Electronic Table of Contents (United Kingdom)

Asymptotic and numerical analysis of relaxation self-oscillations in a three-dimensional system of Volterra ordinary differential equations that models the well-known Belousov reaction is carried out. A numerical study of the corresponding distributed model-the parabolic system obtained from the original system of ordinary differential equations with the diffusive terms taken into account subject to the zero Neumann boundary conditions at the endpoints of a finite interval is attempted. It is shown that, when the diffusion coefficients are proportionally decreased while the other parameters remain intact, the distributed model exhibits the diffusion chaos phenomenon; that is, chaotic attractors of arbitrarily high dimension emerge.

2011-01-01

150

On the mechanism of the nonmonotonic relaxation processes in the metallic melts

Grain boundary dissociation by the emission of stacking faults

The numerical analysis of the experimental data on viscosity change by time in the period after fast heating and crystal-liquid phase transition for the copper nonequilibrium melts and the Fe_7_0Cr_1_0P_1_3C_7 glass-forming melt near their melting temperatures is accomplished through the method of correlation functions and the Rytov-Dimentberg criterion. The observed dependences have nonmonotonic oscillating character but they do not relate to auto-oscillations. The proposed theoretical model of the properties oscillations origination by relaxation in the nonequilibrium liquids explains them as manifestation of noise-induced transitions in the metastable area near the critical temperatures (melting, structural transitions)

2000-01-01

151

Dynamics of the Edge Transport Barrier at Plasma Biasing on the Castor Tokamak

A range of <110> symmetric tilt grain boundaries (GBs) are investigated in several fcc metals with simulations and high resolution electron microscopy. Boundaries with tilt angles between 50.5{degree} and 109.5{degree} dissociate into two boundaries 0.6 to 1.1 nm apart. The dissociation takes place by the emission of stacking faults from one boundary that are terminated by Shockley partials at a second boundary. This is a general mode of GB relaxation for low stacking fault energy metals. The reasons for the occurrence of this relaxation mode are discussed using the theory of GB dislocations.

1995-05-01

152

Accelerated aging of EPDM and butyl elastomers

A clear and reproducible transition to a regime with an improved particle confinement is routinely observed on the CASTOR tokamak, if the biasing electrode is inserted deep enough into the plasma (r/a?0.5) and biased up to +250 V. The steepening of the radial profiles of the plasma density and potential demonstrate the formation of a transport barrier just inside the last closed flux surface. Fast relaxations of the edge plasma parameters, with a frequency of about 10 kHz, are observed when the average radial electric field within the barrier prevails values of about 20 kV/m. A detailed analysis of the spatial-temporal behaviour of these relaxations is presented.

2006-01-01

153

[Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts

This study was composed of three parts: a post cure study to optimize final properties of an ethylene-propylene-diene (EPDM) formulation, an accelerated aging study to compare the stress relaxation behavior of a butyl and an EPDM elastomer under compression, and a cursory evaluation of a new 70 Shore A EPDM. The optimum postcure for the EPDM was found to be 2 to 4 hours at 182{degrees}C in a vacuum. The EPDM was also shown to have superior aging characteristics compared to the butyl and is recommended for use instead of the butyl material. The physical properties for new 70 Shore A EPDM are satisfactory, and the stress relaxation behavior was only slightly inferior to the other EPDM.

1996-06-01

154

NMR analysis of the structure of synaptobrevin and of its interaction with syntaxin

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.

1993-01-01

155

A preliminary design for a one GHz NMR spectrometer magnet

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.

1999-07-15

156

Solid state NMR, basic theory and recent progress for quadrupole nuclei with half-integer spin

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.

1993-09-20

157

Experimental study of lipiodol ultra-fluid. On its signal intensity in MR imaging

This review describes the basic theory and some recently developed techniques for the study of quadrupole nuclei with half integer spins in powder materials. The latter is connected to the introduction of the double rotation (DOR) by A. Samoson et al. (1) and to the introduction of the multiple quantum magic-angle spinning (MQ MAS) technique by L. Frydman et. al. (2). For integer spins, especially the solid-state deuterium magnetic resonance, we refer to the review of G.L. Hoatson and R.L. Vold: ''"2H-NMR Spectroscopy of Solids and Liquid Crystals'' (3). For single crystals we refer to O. Kanert and M. Mehring: ''Static quadrupole effects in disordered cubic solids''(4) and we would like also to mention the ''classic'' review of M.H. Cohen and F. Reif: ''Quadrupole effects in NMR studies of solids'' (5). Some more recent reviews in the field under study are D. Freude and J. Haase ''Quadrupole effects in solid-state NMR'' ...

1998-12-01

158

Some computer simulations of semiconductor thin film growth and strain relaxation in a unified atomistic and kinetic model

Lipiodol Ultra-Fluid (Lipiodol) is widely applied in the transcatheter arterial embolization (TAE). We studied signal intensity, the T1 relaxation time and the T2 relaxation time of Lipiodol itself using Siemens Magnetom H15-2 T (1.5 Tesla) and Magnetom M10 (1.0 Tesla). Lipiodol showed higher signal intensity than saline solution on the T1-weighted images (short TR, short TE technique in spin echo method). On the T2-weighted images (long TR, long TE technique in spin echo method), Lipiodol showed lower signal intensity than saline solution. The T1 relaxation time of Lipiodol, measured at 1.0 T, was 201 msec and 218 msec at 1.5 T. The T2 relaxation time of Lipiodol, measured at 1.0 T, was 127 msec; and 167 msec at 1.5 T. The signal intensity of Lipiodol at 1.0 T was higher than the intensity at 1.5 T. Shorter T1 relaxation time of Lipiodol at 1.0 T is probably responsible for the ...

1988-11-01

159

Relaxation and corrosion resistance of alloy 800 used for steam generator tubes of ship borne boilers

An overview is provided of an evolving atomistic and kinetic model of semiconductor growth that unifies the main features of strain relaxation in low and high lattice misfit heteroepitaxy. The model reveals a kinetic pathway for dislocation formation during growth with little or no energy cost at low misfits, thus providing a way out of the longstanding dilemma of too high dislocation nucleation energies predicted by classical theories of the equilibrium behavior of a fixed number of particles at low misfits. The essential kinetic process underlying the model are identified on the basis of comparison of the predictions of kinetic Monte-Carlo simulations of growth with real-time or in-situ data obtained in such experiments as reflection high-energy electron diffraction (RHEED) and scanning probe microscopy (SPM). Relative significance of these atomistic kinetic processes is shown to naturally lead to strain relaxation via defect initiation at ...

1996-12-31

160

Lattice relaxation around impurity atoms in semiconductors - arsenic in silicon - a comparison between experiment and theory

The INCO ``INCOLOY 800`` trademark groups the Fe-Cr-Ni alloys containing 30 to 35% nickel, 19 to 23% chromium, 0,15 to 0,60% aluminium, 0,15 to 0,60% titanium and less than 0,10% carbon contents, used as construction materials for condenser and heat exchanger tubes. In parallel with water chemistry control and studies aimed at reducing the residual stresses resulting from tube expansion, studies have been conducted to a better understanding of this alloy, its metallurgy and its corrosion behaviour under accurately defined fabrication and heat treatment conditions. The purpose of this paper is to present the results of a behaviour study of INDRET alloy 800 concerning isothermal relaxation and effects of the said relaxation heat treatments on alloy microstructure studied with a transmission electron-chemical method to determine the sensitiveness to intergranular corrosion, and by electrochemistry in pressurized hot water. (authors). 4 figs., 5 ...

1994-12-31

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161

Silica Polyamine Composites: New Supramolecular Materials for Cation and Anion Recovery and Remediation

We have measured the lattice relaxation around As in Si at a homogeneous As concentration of 4x10"1"8 cm"-"3 by EXAFS spectroscopy. From the absorption spectra, distances up to the 4th shell could be extracted. A sizeable misfit due to an increased distance is only observed for the 1st shell. Complementing our experimental work we have performed ab initio calculations based on the density functional theory with the WIEN97 package which uses the linearised augmented plane wave method and with the FHI96md program which uses first-principles pseudo-potentials and a plane wave basis set to investigate the size dependence of the super-cells constructed around one substitutional As atom. The calculations yielded good agreement with our EXAFS experiment so that the determined relaxations can be used as a solid basis for further interpretations of derived parameters such as hyperfine interaction parameters in defect complexes.

2003-01-01

162

NMR study on the formation mechanism of #beta#-SiAlON from zeolite by nitridation using ammonia gas

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 resonances than the linear polymers poly(allylamine) (PAA) and poly(vinylamine) (PVA). These results are understood in terms of the low energy ...

2006-03-01

163

Monitoring of the insecticide trichlorfon by phosphorus-31 nuclear magnetic resonance ({sup 31}P NMR) spectroscopy

#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)

2008-09-01

164

Crystalline O,O'-di-sec-butyl and O,O'-diethyl dithiophosphate platinum(II) complexes: Synthesis, 13C and 31P CP/MAS NMR, single crystal X-ray diffraction studies and thermal behaviour

Trichlorfon is an organophosphorus insecticide, which is extensively being used for protection of fruit crops. Trichlorfon is a thermal labile compound, which cannot be easily determined by gas chromatography (GC) and has no suitable group for sensitive detection by high performance liquid chromatography (HPLC). In this study, a {sup 31}P nuclear magnetic resonance ({sup 31}P NMR) has been described for monitoring of trichlorfon without any separation step. The quantitative works of {sup 31}P NMR spectroscopy has been performed in the presence of an internal standard (hexamethylphosphoramide). Limit of detection (LOD) for this method has been found to be 55 mg L{sup -1}, without any sample preparation, and the linear working range was 150-5500 mg L{sup -1}. Relative standard deviation (R.S.D.%) of the method for three replicates within and between days was obtained {<=}9%. The average recovery efficiency was approximately 99-112%. This ...

2006-08-25

165

British Library Electronic Table of Contents (United Kingdom)

Crystalline bis(O,O'-di-sec-butyldithiophosphato)platinum(II) was prepared and studied by means of 13C, 31P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the platinum(II) compound is comprised of one centrosymmetric mononuclear molecule [Pt{S2P(O-sec-C4H9)2}2], in which the dithiophosphate groups display structural equivalence in both 31P NMR and XRD data. A pair of the dithiophosphate ligands exhibit the same S,S'-bidentate chelating structural function and form two planar four-membered chelate rings, [PtS2P], in this molecule. The planar configuration of the [PtS4] chromophore in structure 1 is governed by the dsp2-hybrid state of platinum(II). The structural states of the dithiophosphate groups in two different samples of complex 1 (one crystallised from...

2011-01-01

166

Consolidated silica glass from nanoparticles

Acidity of H-Y zeolites: Role of extralattice aluminum

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 ...

2008-09-01

167

Transverse-field Formula Not Shown SR and magnetic disorder in Formula Not Shown

The nature of extralattice aluminum and its effect on acidity in zeolites was studied. A series of zeolites (some commercial), dealuminated by various methods, were obtained having Si/Al ratios between 1.5 and 20. These were characterized using volumetric sorption, XRD, AA, NMR, and reaction studies. Samples dealuminated using ammonium hexafluorosilicate were found to contain little or no extralattice aluminum. In contrast, steam-dealuminated zeolites had large amounts of extralattice aluminum. In some cases a significant portion of the extralattice aluminum was unobservable by [sup 27]Al NMR, suggesting the existence of an aluminum species of low symmetry. Proton NMR indicated that all the protons were associated with the lattice aluminum atoms. Depending on the preparation history, different groups of H-Y zeolites exhibited different maxima in catalytic activity as a function of aluminum content. The maxima in catalytic ...

1993-02-01

168

British Library Electronic Table of Contents (United Kingdom)

We have carried out transverse-field ( Formula Not Shown ) Formula Not Shown SR experiments in Formula Not Shown for temperatures from 300 down to 2.2K. The muon-decay asymmetry can be fit to a stretched exponential relaxation function: Formula Not Shown . The exponent Formula Not Shown for Formula Not Shown , but drops continuously below this temperature (being Formula Not Shown for Formula Not Shown and reaching Formula Not Shown near 2K). The characteristic relaxation rate Formula Not Shown grows six-fold in the experimental temperature range (from Formula Not Shown for Formula Not Shown to Formula Not Shown for Formula Not Shown ). Independently of theoretical models, the behavior of these parameters is consistent with strong magnetic disorder. Although the magnetic susceptibility of F...

2008-01-01

169

The significance of local hard zones on the outside of pipeline girth welds: Further studies

Dissipative dynamics of circuit-QED in the mesoscopic regime

The NACE MR-01-75 standard imposes a restriction of 22HRC maximum for regions of a pipeline girth weld that are not in direct contact with H[sub 2]S containing environments. TWI have demonstrated in an earlier project for the Pipeline Research Committee (PRC) that it may be permissible to relax this maximum hardness requirement. Such a relaxation, which already exists in the BS4515: 1984 standard, offers potential benefits when applied to the capping pass and heat affected zone of a pipeline girth weld. This report presents additional data to supplement that obtained in a previous PRC project conducted at TWI. Further pipe materials with differing pipe wall thicknesses have been welded, exposed to an internal H[sub 2]S containing environment and examined for sulphide stress corrosion cracking.

1991-10-01

170

Control area performance improvement by extended security constrained economic dispatch

We investigate the behavior of a circuit QED device when the resonator is initially populated with a mesoscopic coherent field. The strong coupling between the cavity and the qubit produces an entangled state involving mesoscopic quasi-pointer states with respect to cavity dissipation. The overlap of the associated field components results in collapse and revivals for the Rabi oscillation. Although qubit relaxation and dephasing do not preserve these states, a simple analytical description of the dissipative dynamics of the circuit QED device including cavity relaxation as well as qubit dissipation is obtained from the Monte-Carlo approach. Explicit predictions for the spontaneous and induced Rabi oscillation signals are derived and sucessfully compared with exact calculations. We show that these interesting effects could be observed with a 10 photon field in forthcoming circuit QED experiments.

2007-01-01

171

Alignment of nematic liquid crystals on mixed Langmuir-Blodgett mono-layers

An algorithm for solving the extended security constrained economic dispatch (ESCED) problem with real-time economic dispatch grade speed and reliability is presented. The ESCED problem is formulated by adding regulating margin and ramp rate constraints to the network security constrained economic dispatch problem previously solved by the CEDC algorithm. Starting with Newton`s method to optimize the Lagrangian, the ESCED is developed by superimposing on Newton`s method eight major components called Tracking Start Initialization, Hessian Pre-Elimination, Implicit Dual Variable Calculations, Regulating Margin Sensitivity Coefficient Calculations, Traumatic Event Evaluation, Constraint Relaxation, Implicit Ramp Rate Constraint Implementation, and Relaxed Incremental Cost Calculations. Test results are also presented.

1997-02-01

172

Patagonicosides B and C, two antifungal sulfated triterpene glycosides from the sea cucumber Psolus patagonicus.

Mono-layers of stearic and behenic acids and mixtures of them in different proportions, deposited with the Langmuir-Blodgett technique, were used to study the alignment and the alignment dynamics in nematic liquid crystal cells. A relaxation process from a splay-bend flow induced metastable orientation to the homeotropic one occurs. The lifetime of the metastable state was found to depend on the mono-layer composition. The transition between the homeotropic and the conical anchoring was found to be irreversible in the case of the mixed aligning mono-layers: on cooling from the isotropic phase a quasi-planar nematic state (schlieren texture) appears. It is stable in a range of a few degrees below the clearing point and, on decreasing the temperature, relaxes to the homeotropic state in form of expanding domains.

1998-01-01

173

Investigation of the electronic structure of base adducts derived from tris(#eta#"5-cyclopentadienyl)-lanthanide(III) and related compound types

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

2011-03-01

174

Evaluation of gels obtained from acetylation of chitosan in heterogeneous medium

The purpose of this work is the elucidation of the f"n electronic structure of neutral mono base adducts derived from tris(#eta#"5-cyclopentadienyl)-lanthanide(III) (Cp_2Ln). The available data on related compounds like bis adducts and anionic mono adducts of the same moiety was also analyzed. The first aim was to derive the experimental crystal field splitting pattern from optical, magnetooptical and magnetochemical measurements and to reproduce it using an empirical Hamiltonian operator. The eigenvalues and eigenvectors obtained in this manner were used for a quantitative interpretation of the magnetochemical, EPR- and NMR-spectroscopic properties. For the latter subject it was necessary to develop an own procedure for the NMR analysis of paramagnetic compounds. This method is based on factor analysis and as demonstrated in the second part of this work, is clearly superior to all previous procedures. (orig.).

175

Endophytic fungus Trichothecium roseum LZ93 antagonizing pathogenic fungi in vitro and its secondary metabolites

Chitosan was acetylated during 2, 5 and 10 h and physical gels were obtained at different polymer concentrations in N,N-dimethylacetamide containing 5% of LiCl. Acetylation was confirmed by infrared spectroscopy and "1"3C NMR, and degrees of acetylation in the range of 0.82-0.91 were determined by NMR. The O-acetylation degree (0.12-0.15) was exclusively determined by a volumetric method. Rheological studies showed that the storage modulus values were smaller for the more acetylated samples and increased with the temperature and the polymer concentration. All the gels presented storage modulus superior to loss modulus, evidencing more elastic than viscous characteristics. The results obtained in this work suggest a gelation process based on a balance between O and N-acetylation and intermolecular bonds. (author)

176

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...

2010-01-01

177

Effects of molecular mobility on high resolution solid state NMR spectra: model systems

Cationic cyclization of purified natural rubber in latex form with a trimethylsilyl triflate as a novel catalyst

It is the intention of this paper to point to some of the problems due to molecular motion and to suggest a few solutions to those problems. A few examples will be presented of model systems which demonstrate the effects of motion on the NMR spectroscopy and a very qualitative example of severe spectral distortion in fulvic acids will be shown. In the following discussions we will use concepts derived from the oft repeated thermodynamic picture shown in figure 1. When dealing with a homogeneous, pure compound this picture is sufficient but in a heterogeneous mixture, it is likely that there will be different compounds and different domains all with slightly different versions of figure 1 with poor thermodynamic contact between them. Thus optimal conditions for cross polarization in one domain may be totally inappropriate for another. 59 refs., 10 figs.

1986-01-01

178

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....

2007-01-01

179

Asymmetric Hydrogenation with Highly Active IndolPhos-Rh Catalysts: Kinetics and Reaction Mechanism

British Library Electronic Table of Contents (United Kingdom)

The mechanism of the IndolPhos-Rh-catalyzed asymmetric hydrogenation of prochiral olefins has been investigated by means of X-ray crystal structure determination, kinetic measurements, high-pressure NMR spectroscopy, and DFT calculations. The mechanistic study indicates that the reaction follows an unsaturate/dihydride mechanism according to Michaelis-Menten kinetics. A large value of KM (KM=5.01+-0.16 M) is obtained, which indicates that the Rh-solvate complex is the catalyst resting state, which has been observed by high-pressure NMR spectroscopy. DFT calculations on the substrate-catalyst complexes, which are undetectable by experimental means, suggest that the major substrate-catalyst complex leads to the product. Such a mechanism is in accordance with previous studies on the mechanism...

2010-01-01

180

A non-uniformly sampled 4D HCC(CO)NH-TOCSY experiment processed using maximum entropy for rapid protein sidechain assignment

Why the negative corona current in air decreases?

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.

2010-05-01

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181

Relationship between microstructural evolution and low cycle fatigue behaviour at 550/sup 0/C of alloy 800 grade 2

The time dependence of negative corona current I, called by Gagarin like 'relaxing of CV-characteristics', is a observed phenomena. The observed phenomena was explained by two theoretical models considering the ion-molecule and chemical reactions in the negative corona discharges in air, especially the ozone production. In the presented paper the discrepancies of above mentioned models, re-examination the earlier experimental data and presumptions used in models in a light the latest experimentally confirmed facts are discussed.

1996-08-01

182

On the theory of transient enhanced diffusion in boron-implanted silicon

In this study, deformation modes and precipitations have been characterized in test pieces made of alloy 800, grade 2 hyper-hardened state and age-conditioned for 3000 h at 550/sup 0/C, used for steam generator tubes of the Super Phenix Reactor, after continuous fatigue and fatigue-relaxation tests in the oligocyclic range. This microstructural study has provided an interpretation of the fatigue behaviour of the material.

1989-01-01

183

On the theory of transient enhanced diffusion in boron-implanted silicon

Transient enhanced diffusion in boron-implanted silicon is interpreted as being due to the fact that during rapid thermal annealing a relaxation process takes place, associated with quasi-chemical reactions including defects. A simple analytical model makes it possible to describe the annealing mechanism on a microscopic scale in terms of reaction-diffusion processes. The measured dependences of the boron diffusion coefficient of the enhanced diffusion on time, temperature and implantation energy are satisfactorily explained. (author).

1991-01-01

184

Nuclear magnetic resonance and the question of 5f electron localization in the actinides

Transient enhanced diffusion in boron-implanted silicon is interpreted as being due to the fact that during rapid thermal annealing a relaxation process takes place, associated with quasi-chemical reactions including defects. A simple analytical model makes it possible to describe the annealing mechanism on a microscopic scale in terms of reaction-diffusion processes. The measured dependences of the boron diffusion coefficient of the enhanced diffusion on time, temperature and implantation energy are satisfactorily explained. (author).

185

Nuclear magnetic resonance and the question of 5F electron localization in the actinides

Nuclear magnetic resonance results are presented for a number of NaCl-type compounds and cubic Laves-phase type compounds of uranium, neptunium, and plutonium. Special emphasis is placed on the Knight shift and spin-lattice relaxation time measurements and their interpretation in terms of localized or itinerant pictures of the 5f electrons. (author).

186

Molecular dynamics simulation of nanoctrystalline nickel: structure and mechanical properties

Nuclear magnetic resonance results are presented for a number of NaCl-type compounds and cubic Laves-phase type compounds of uranium, neptunium, and plutonium. Special emphasis is placed on the Knight shift and spin-lattice relaxation time measurements and their interpretation in terms of localized or itinerant pictures of the 5Line integral electrons.

1976-01-01

187

Metastability and dynamics of the shock-induced phase transition in iron

Molecular dynamics computer simulations of a dense nanocrystalline Nickel sample are performed on the parallel Cray T3 (EPFL-Lausanne). The sample contains 50 grains with an average size of 3 nm. By perturbing the relaxed configuration elastic and plastic properties are studied. (author) 1 fig., 1 ref.

1996-10-01

188

Layerwise reaction at a buried interface

The shock-induced {alpha}(bcc){r_arrow}{var_epsilon}(hcp) transition in iron begins at 13 GPa on the Hugoniot. In the two-phase region above 13 GPa, the Hugoniot lies well above the equilibrium surface defined by G{sub {alpha}}=G{sub {var_epsilon}}, with G the Gibbs free energy. Also, the phase transition relaxation time {tau} is uncertain, with estimates ranging from {lt}50 ns to {approx}180 ns. Here we present an extensive study of these important aspects, metastability and dynamics, of the {alpha}-{var_epsilon} transition in iron. Our primary theoretical tools are (a) accurate theoretically based free energies for {alpha} and {var_epsilon} phases of iron and (b) accurate calculations of the wave evolution following planar impacts. We define metastable surfaces for forward and reverse transitions by the condition that the thermodynamic driving force G{sub {alpha}}{minus}G{sub {var_epsilon}} is just balanced by an opposing force resulting from elastic stresses, ...

1997-02-01

189

Influence of electric-field is on luminescence of ZnSe

X-ray diffraction was used to monitor the {ital in} {ital situ} reaction of Pd deposited on Si(111) at room temperature. An ordered silicide forms spontaneously beneath a poorly ordered overlayer. It is commensurate and strained at low coverage, but relaxes to an unstrained state above a critical thickness of 18 A. During both phases of growth sustained intensity oscillations are seen that correspond to a layerwise consumption of the substrate at the buried interface.

1992-10-26

190

Contribution of surface rayleigh waves to the heat capacity of poly(vinyl chloride)

The results of experimental researches of photoluminescence and X-ray luminescence in crystal ZnSe are presented at the different values of tension of electric-field to samples. Observed, that the electric field changes both intensity of stationary luminescence and form of bars in the spectrums of luminescence. At the saliatory change of difference of potentials on the electrodes of crystal in luminescence there are of long duration relaxation processes character of which substantially depends on the type of excitation of standard.

191

British Library Electronic Table of Contents (United Kingdom)

The method of surface acoustic waves is employed to determine the frequency and temperature dependences of the molar heat capacity of poly(vinyl chloride) on the contribution of Rayleigh local components of the longitudinal and transverse vibrations of structural units of the polymer. The calculated and experimental data are compared in terms of their dependence on the relaxation state of the system.

2009-01-01

192

Room temperature synthesis of tri-, tetrasubstituted imidazoles and bis-analogues by mercaptopropylsilica (MPS) in aqueous methanol: application to the synthesis of the drug trifenagrel

British Library Electronic Table of Contents (United Kingdom)

The heterogeneous solid catalyst, mercaptopropylsilica (MPS), has been prepared by a modified procedure in water and its structure confirmed by solid state carbon-13 CP-MAS NMR spectrum. This catalyst has been efficiently utilized for the synthesis of a wide variety of tri-, tetrasubstituted imidazoles and their bis-analogues at room temperature. The protocol was further explored for the synthesis of the drug trifenagrel.

2010-01-01

193

Reactivity of aliphatic amines toward platinum(II) complexes

Quantum molecular dynamics and molecular interactions studied by NMR and INS[Nuclear magnetic resonance; Proton tunnelling; Hydrogen bond

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.

1994-08-31

194

Quality control in Nuclear Magnetic Resonance Imaging. Indications et strategies pour le controle de qualite en IRM

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 spectroscopic ...

2002-07-01

195

Physical basis of the effect of hemoglobin on the "3"1P NMR chemical shifts of various phosphoryl compounds

In this article, the authors recall the factors apt to influence image quality in NMR Imaging and present the european works that have been developed in MRIQA to set 5 quality assurance tests: EUROSPIN 1 to 5.

1993-01-01

196

Phospholamban and its Phosphorylated Form Interact Differently with Lipid Bilayers: A ³¹P, ²H and ¹³C Solid-State NMR Spectroscopic Study

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 ...

197

Molecules with polymerizable ligands as precursors to porous doped materials

Phospholamban (PLB) is a 52-amino acid integral membrane protein that helps to regulate the flow of Ca²⁺ ions in cardiac muscle cells. Recent structural studies on the PLB pentamer...Full Text Available

2006-11-07

198

Medium-chain fatty acid binding to albumin and transfer to phospholipid bilayers.

Titanium and aluminum alkoxide derivatives with polymerizable ligands such as 2-(methacryloyloxy)ethylacetoacetate (HAAEMA), oleic acid and geraniol (HOGE) have been obtained. The various compounds have been characterized by FT-IR and NMR {sup 1}H. Copolymerization with styrene and divinylbenzene affords porous doped organic materials which have been characterized by scanning electron microscopy (SEM), elemental analysis, density measurements.

1996-12-31

199

Measurement of the susceptibility of solid "3He along the melting curve from 20 mK down to the nuclear ordering temperature

Temperature-dependent (5-42 degrees C) 13C NMR spectra of albumin complexes with 90% isotopically substituted [1-13C]decanoic acids (3 mol of fatty acid per mol of albumin) showed a single peak at greater...Full Text Available

1989-04-01

200

Measurement of the Self-Diffusion Coefficient of Water as a Function of Position in Wheat Grain Using Nuclear Magnetic Resonance Imaging

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.).

1977-02-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

201

Fatty acid distribution in systems modeling the normal and diabetic human circulation. A 13C nuclear magnetic resonance study.

A pulsed field gradient spin echo sequence has been incorporated in a nuclear magnetic resonance (NMR) imaging experiment to provide an image contrast dependent on local molecular self-diffusion. The...Full Text Available

1988-01-01

202

Effect of steric hindrance on carbon dioxide absorption into new amine solutions. Thermodynamic and spectroscopic verification through solubility and NMR analysis

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

1991-04-01

203

Characterization of polymers for microcellular foams

Aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), a sterically hindered amine, was examined as a potential CO{sub 2} absorbent and compared with the most commonly used absorbent, monoethanolamine (MEA) solution, through equilibrium solubility measurements and {sup 13}C NMR spectroscopic analyses. The solubilities of CO{sub 2} in aqueous 10 mass % AHPD solutions were higher than those in aqueous 10 mass% MEA solutions above 4 kPa at 298.15 K, but lower below 4 kPa. The solubility difference between these two solutions increased with the CO{sub 2} partial pressures above the crossover pressure. Equilibrated CO{sub 2}-MEA-H{sub 2}O and CO{sub 2}-AHPD-H{sub 2} solutions at various CO{sub 2} partial pressures ranging from 0.01 to 3000 kPa were analyzed by {sup 13}C NMR spectroscopy. AHPD contains more hydroxyl groups than nonhindered MEA, and hence the chemical shifts in its {sup 13}C NMR spectra were strongly ...

2003-04-15

204

Calculation of the knight shift in the system CaCdsub(1-x)Tlsub(x) by using relativistic APW wave functions

We have measured, by {sup 1}H and {sup 13}C nuclear magnetic resonance (NMR), the percent deuteration, the tacticity and the purity of several polymers and one solvent used in the preparation of microcellular foams. The percent deuteration was measured for polystyrene, polyacrylonitrile and polyethylene. The tacticities of polystyrene and polyacrylonitrile were determined. The purity and degradation products of polyacrylonitrile and maleic anhydride were examined. This report documents the experimental procedures and results of these measurements.

1992-03-01

205

Besarhanamides A and B from the marine cyanobacterium Lyngbya majuscula

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 ...

206

British Library Electronic Table of Contents (United Kingdom)

Besarhanamides A (1) and B (2) are fatty acid amides purified from the marine cyanobacterium, Lyngbya majuscula, collected from Pulau Hantu, Singapore. The structure determination of these secondary metabolites was carried out using extensive 2D NMR spectral data as well as chemical manipulations including the Marfey's method. In addition, besarhanamide A exhibited moderate toxicity with LD50 at 13mM in the brine shrimp toxicity bioassay.

2008-01-01

207

Solution conformations of CaCl sub 2 and Ca(NO sub 3 ) sub 2 complexes of chiral tetramethyl 18-crown-6 macrocycles: A 1D and 2D sup 1 H and sup 13 C NMR investigation

X-ray absorption spectroscopy, EELS, and full-potential augmented plane wave study of the electronic structure of Ti_2AlC, Ti_2AlN, Nb_2AlC, and (Ti_0_._5Nb_0_._5)_2AlC

One- and two-dimensional NMR techniques have been used to investigate the solution structures of (2S,6S,11S,15S)-2,6,11,15-tetramethyl-1,4,7,10,13,16-hexaoxacyclooctadecane (I) and (2R,3R,11R,12R)-2,3,11,12-tetramethyl-1,4,7,10,13,16-hexaoxyacyclooctadecane (II) macrocycle complexes of CaCl{sub 2} and Ca(NO{sub 3}){sub 2} in CDCl{sub 3}. Previous chiroptical studies of these and similar crown complexes by circularly polarized luminescence (CPL), total luminescence (TL), and circular dichroism (CD) spectroscopy have shown that the macrocycle asymmetric carbons in these complexes constrain the ring such that the sense of the ring twist in the S chiral ring complexes is opposite to that in the R chiral ring complexes. These studies have also shown that there is an added chirality element in the di- and trivalent (alkaline earth and lanthanide metal, respectively) nitrate complexes of I and II associated with the twist of the nitrate anions relative to one another as ...

1989-10-04

208

Viscoplasticity of elastomeric materials: experimental facts and constitutive modelling

The structural parameters of various Haegg phases (H or M_n_+_1AX_n phases) are studied experimentally by x-ray and electron spectroscopies, x-ray diffraction, and ab initio full potential as well as full mutiple scattering theoretical calculations. Experimentally it was found that the structure of all ternary compounds analyzed herein are relaxed. The values of the lattice parameters and relaxations obtained from ab initio calculations are in excellent agreement with those deduced from the analysis of the experimental data. The bonding scheme has been analyzed and the charge transfer between constituting atoms determined. It is demonstrated that the strength and electrical transport properties in these materials are principally governed by the metallic planes. For the solid solution (Ti_0_._5Nb_0_._5)_2AlC, the most salient result is that the basal planes are corrugated, which could explain the solid solution scattering observed in this H ...

2005-01-01

209

Ultrafast carrier dynamics of InGaAsN and InGaAs single quantum wells

A characteristic of filled elastomers is their ability to undergo very large deformations without damaging their internal structure. The material behaviour is mainly elastic, however, elastomers show hysteresis effects leading to damping properties, which are quite important as regards their applications in various fields of mechanical engineering.A series of experiments (tension, torsion and combinations of both) was carried out on cylindrical bars made of a carbon-black filled rubber mixture. In addition to a pronounced nonlinear rate-dependence, relaxation and viscosity properties are observed as being influenced by the process histories.The behaviour of elastomeric materials is modelled on the basis of a free energy function and evolution equations for additional internal variables. Incorporating or disregarding the very small rate-independent hysteresis, the constitutive modelling may be classified under viscoplasticity or viscoelasticity. The constitutive ...

2001-03-01

210

T{sub 1} and T{sub 2} relaxivities of succimer-coated MFe{sub 2}{sup 3+}O{sub 4} (M=Mn{sup 2+}, Fe{sup 2+} and Co{sup 2+}) inverse spinel ferrites for potential use as phase-contrast agents in medical MRI

Striking differences in differential reflectance and carrier relaxation in In0.4Ga0.6As and In0.4Ga0.6As0.98N0.02 single quantum wells (SQWs) were studied using ultrafast time-resolved photoreflectance. Even with extremely thin SQW of only 60 A within 3000 A wide GaAs confining layers, negative and positive differential reflectance was observed for the excitation photon energy far above the bandgaps at 820 and 880 nm for both samples. Due to absorption by the GaAs confining layer, the peak differential reflectance pumped at 820 nm is an order of magnitude larger than that pumped at 880 nm; and it is larger for InGaAs SQWs than for InGaAsN SQWs. The shorter carrier lifetimes of these samples result from carrier-carrier scattering as pumped at both wavelengths. The longer carrier lifetime as pumped at 880 nm is due to hot phonon decay in InGaAs but may be due to stimulated emission in InGaAsN. The results reveal that the carrier dynamics is strongly affected by N ...

2008-04-21

211

Time-resolved resonance and linewidth of an ultrafast switched GaAs/AlAs microcavity

Superparamagnetic MFe{sub 2}{sup 3+}O{sub 4} (M=Mn{sup 2+}, Fe{sup 2+} and Co{sup 2+}) inverse spinel ferrite (ISF) nanoparticles with narrow size distribution having average diameters of 6-8 nm were synthesized by a diol reduction of organic metals and the surface was modified to be hydrophilic by coating with succimer. Magnetic resonance imaging (MRI) contrast enhancement by dipolar coupling defined interactions between the synthesized ISFs and protons in the bulk water was investigated with initial susceptibility, magnetization and anisotropy of the succimer-coated ISFs. The relaxivity ratios, r{sub 2}/r{sub 1}, for MnFe{sub 2}O{sub 4}, Fe{sub 3}O{sub 4} and CoFe{sub 2}O{sub 4} were measured to be 12.2, 23.1 and 62.3, respectively, which demonstrate the potential usefulness of these magnetic nanoparticles as T{sub 2} contrast agents for MRI.

2009-12-15

212

The effect of swimming exercise on spontaneous ventricular defibrillation and ventricular fibrillation threshold in the isolated perfused rat heart.

We explore a planar GaAs/AlAs photonic microcavity using pump-probe spectroscopy. Free carriers are excited in the GaAs with short pump pulses. The time-resolved reflectivity is spectrally resolved short probe pulses. We show experimentally that the cavity resonance and its width depend on the dynamic refractive index of both the lambda-slab and the lambda/4 GaAs mirrors. We clearly observe a double exponential relaxation of both the the cavity resonance and its width, which is due to the different recombination timescales in the lambda-slab and the mirrors. In particular, the relaxation time due to the GaAs mirrors approaches the photon storage time of the cavity, a regime for which nonlinear effects have been predicted. The strongly non-single exponential behavior of the resonance and the width is in excellent agreement to a transfer-matrix model taking into account two recombination times. The change in width leads to a change in ...

2009-01-01

213

T1 and T2 relaxivities of succimer-coated MFe23+O4 (M=Mn2+, Fe2+ and Co2+) inverse spinel ferrites for potential use as phase-contrast agents in medical MRI

Effects of swimming exercise training on left ventricular contraction and relaxation, the incidence of spontaneous defibrillation and the ventricular fibrillation threshold were studied in the isolated, perfused rat heart. The heart/body weight ratio was 4.8 +/- 0.4 x 10(-3) in swimmers compared with 3.9 +/- 0.6 x 10(-3) in sedentary controls (p less than 0.0005). The spontaneous heart rate was lower in isolated hearts of trained animals (222 +/- 18 bpm compared with 244 +/- 28, p less than 0.05). Left ventricular systolic pressure was higher in trained hearts and the rate of ventricular relaxation enhanced (p less than 0.05). The ventricular fibrillation threshold was 7.2 +/- 5.2 and 10.8 +/- 6.1 mamp in hearts of swimmers and controls, respectively, the difference not being significant. The incidence of spontaneous defibrillation was not significantly different between the two groups. It is concluded that, while swimming induces cardiac ...

1990-12-01

214

Strain dependence of Si-Ge interdiffusion in epitaxial Si/Si{sub 1-y}Ge{sub y}/Si heterostructures on relaxed Si{sub 1-x}Ge{sub x} substrates

Superparamagnetic MFe23+O4 (M=Mn2+, Fe2+ and Co2+) inverse spinel ferrite (ISF) nanoparticles with narrow size distribution having average diameters of 6-8 nm were synthesized by a diol reduction of organic metals and the surface was modified to be hydrophilic by coating with succimer. Magnetic resonance imaging (MRI) contrast enhancement by dipolar coupling defined interactions between the synthesized ISFs and protons in the bulk water was investigated with initial susceptibility, magnetization and anisotropy of the succimer-coated ISFs. The relaxivity ratios, r2/r1, for MnFe2O4, Fe3O4 and CoFe2O4 were measured to be 12.2, 23.1 and 62.3, respectively, which demonstrate the potential usefulness of these magnetic nanoparticles as T2 contrast agents for MRI.

2009-12-01

215

Spin-lattice relaxation in A-15 type intermetallic compounds

The strain dependence of Si-Ge interdiffusion in epitaxial Si/Si{sub 1-y}Ge{sub y}/Si heterostructures on relaxed Si{sub 1-x}Ge{sub x} substrates has been studied using secondary ion mass spectrometry, Raman spectroscopy, and simulations. At 800 and 880 deg. C, significantly enhanced Si-Ge interdiffusion is observed in Si/Si{sub 1-y}Ge{sub y}/Si heterostructures (y=0.56, 0.45, and 0.3) with Si{sub 1-y}Ge{sub y} layers under compressive strain of -1%, compared to those under no strain. In contrast, tensile strain of 1% in Si{sub 0.70}Ge{sub 0.30} layer has no observable effect on interdiffusion in Si/Si{sub 0.70}Ge{sub 0.30}/Si heterostructures. These results are relevant to the device and process design of high mobility dual channel and heterostructure-on-insulator metal oxide semiconductor field effect transistors.

2006-01-02

216

Spin-lattice relaxation in A-15 type intermetallic compounds

The temperature dependence of T/sub 1/ spin-lattice relaxation time on /sup 51/V, /sup 69/Ga, /sup 71/Ga and Knight shift on /sup 51/V and /sup 29/Si nuclei in polycrystalline V/sub 3/Si, V/sub 3/Ga, V/sub 3/Ge and in the monocrystal V/sub 3/Si in normal state is investigated. For V/sub 3/Si and V/sub 3/Ga a rapid growth (T/sub 1/T)/sup -1/ is observed with temperature decrease while for V/sub 3/Ge the maximum (T/sub 1/T)/sup -1/ at T approximately equal to 60 K has been found. The temperature dependence peculiarities have been discussed on the basis of theoretical models available and zone structure calculations for A-15 compounds. The T/sub 1/ anisotropy and possibility of its experimental discovery are considered. Anisotropic contribution in (T/sub 1/T)/sup -1/ and contributions of d states of different symmetries into the electron state density at the Fermi level are estimated for V/sub 3/Si from T/sub 1/ measurements.

1981-04-01

217

Self-Interacting Dark Matter Halos and the Gravothermal Catastrophe

The temperature dependence of T_1 spin-lattice relaxation time on "5"1V, "6"9Ga, "7"1Ga and Knight shift on "5"1V and "2"9Si nuclei in polycrystalline V_3Si, V_3Ga, V_3Ge and in the monocrystal V_3Si in normal state is investigated. For V_3Si and V_3Ga a rapid growth (T_1T)"-"1 is observed with temperature decrease while for V_3Ge the maximum (T_1T)"-"1 at T approximately equal to 60 K has been found. The temperature dependence peculiarities have been discussed on the basis of theoretical models available and zone structure calculations for A-15 compounds. The T_1 anisotropy and possibility of its experimental discovery are considered. Anisotropic contribution in (T_1T)"-"1 and contributions of d states of different symmetries into the electron state density at the Fermi level are estimated for V_3Si from T_1 measurements.

218

Proton spin lattice relaxation studies in lithium ammonium sulfate LiNH_4SO_4

We study the evolution of an isolated, spherical halo of self-interacting dark matter (SIDM) in the gravothermal fluid formalism. We show that the thermal relaxation time, $t_r$, of a SIDM halo with a central density and velocity dispersion of a typical dwarf galaxy is significantly shorter than its age. We find a self-similar solution for the evolution of a SIDM halo in the limit where the mean free path between collisions, $\\lambda$, is everywhere longer than the gravitational scale height, $H$. Typical halos formed in this long mean free path regime relax to a quasistationary gravothermal density profile characterized by a nearly homogeneous core and a power-law halo where $\\rho \\propto r^{-2.19}$. We solve the more general time-dependent problem and show that the contracting core evolves to sufficiently high density that $\\lambda$ inevitably becomes smaller than $H$ in the innermost region. The core undergoes secular collapse to a ...

2002-01-01

219

On the orbital evolution and growth of protoplanets embedded in a gaseous disc

Lithium ammonium sulfate (LAS) undergoes a phase transition at Tsub(c1) = 459.5deg K from a paraelectric phase (phase 1) to a ferroelectric phase (phase II) and again at Tsub(c2) = 283deg K to a polar ferroelastic phase (phase III). Proton spin lattice relaxation investigations in the temperature range 480-77deg K at 10 MHz show discontinuous changes in Tsub(1) at the transition temperatures, indicating first order phase transitions. The absence of the slow motion region (#omega#sub(not)tausub(not)>>1) shows that the ammonium ions are reorienting fast enough to keep the resonance absorption line narrow down to liquid nitrogen temperatures. The possibility of a second minimum and a low activation energy, Esub(a) = 2.659 kcal/mole, in phase III suggest the possibility of tunnelling of the protons at low temperatures. The nature of the transitions have been discussed in the light of the available literature. The unusually high activation energy, Esub(a) = 17.845 ...

1978-12-31

220

We present a new computation of the linear tidal interaction of a protoplanetary core with a thin gaseous disc in which it is fully embedded. For the first time a discussion of the orbital evolution of cores with eccentricity (e) significantly larger than the gas-disc scale height to radius ratio (H/r) is given. We find that the direction of orbital migration reverses for e>1.1H/r. This occurs as a result of the orbital crossing of resonances in the disc that do not overlap the orbit when the eccentricity is very small. Simple expressions giving approximate fits to the eccentricity damping rate and the orbital migration rate are presented. We go on to calculate the rate of increase of the mean eccentricity for a system of protoplanetary cores due to dynamical relaxation. By equating the eccentricity damping time-scale with the dynamical relaxation time-scale we deduce that an equilibrium between eccentricity damping and excitation through ...

1999-01-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

221

Magnetism in "3He

MR imaging of experimental intramuscular hemorrhage at 0. 02 T; Contrast enhancement with Gd-DOTA

The nuclear magnetic susceptibility, #chi#, of "3He is seen to nearly obey a pure Curie Law, #chi# = C/T, over the temperature range 0.5 mK < T < 2 K when contained in the 20#ALPHA#, multiply connected pores of Vycor glass at low external pressure. Raising the external pressure to 5 bar (1 bar 100 kPa) causes the susceptibility to obey the Curie-Weiss law, #chi# = C' /T - #THETA# whose #THETA# = 0.3 mK. The longitudinal relaxation time, T_1, varies monotonically with T between 17 and 90 ms at both pressures. At 5 bar, the transverse relaxation time T_2*, is nearly temperature independent (about 600 #mu#s) above 2 mK. Below 2 mK, T_2* drops precipitously. Preliminary measurements indicate that the magnetism is produced by atoms that can flow through the pores of the Vycor glass. (10 refs., fig.).

1986-10-01

222

Kinetics of the stress induced phase transition in quartz by real-time neutron scattering

Intramuscular hermorrhage was induced by injecting autologous blood into the paraspinal muscle of 8 rabbits. In order to evaluate the time-dependent changes of hemorrhage observed on MRI, the animals were imaged at different stages of blood resolution at 0.02 tesla (T), and control examined with ultrasound using a 7.5 MHz linear transducer. Six inversion recovery sequences (TR=1 000 ms. TE=30 ms, and TI=18, 48, 148, 201, 302, and 398 ms) were used for the invivo calculation of T1 relaxation times. IR 1 000 (398)/30 imaging was performed before and after the Gd-DOTA administration. The hemorrhage was evident on MR images throughout the study, especially on the T2 weighted (SE 1 000/100) images. MRI showed the healing lesion longer than ultrasound. The T1 relaxation time increased during the time of resolution. Lesions on days 4 to 7 enhanced in intensity after the injection of Gd-DOTA. (orig.).

1990-09-01

223

Gas electrode reactions in molten carbonate media. Pt. 2. Oxygen reduction kinetics on conductive oxide electrodes in (Li+K)CO/sub 3/ eutectic at 650/sup 0/C

Complete text of publication follows. The stability regime of the incommensurate phase of quartz is influenced by uniaxial stress. Hence, the phase transition can be induced under isothermal conditions by the application of external mechanical forces. Using real-time neutron scattering the time evolution of structural changes is investigated id detail during stress variations. The time dependent behaviour of the satellite reflection is compared with that one of the fundamental Bragg reflection which - via primary extinction - gives information about the perfection of the crystal. On increasing stress the perfection of the lattice is destroyed immediately while the modulated structure is built up with a delay of about 1 s. Decreasing the stress leads to a reverse behaviour. Moreover, there is evidence that under periodical load residual non-relaxed strain fields survive leading to a different temperature dependence as compared to static conditions. This finding is ...

1999-09-01

224

First-principles calculations of the stability and local structure of #alpha#-sialon ceramics on the line Si_3N_4- 1/2 Ca_3N_2:3AlN

The electrode kinetics for oxygen reduction on conducting metal oxides, including lithiated NiO (formed in situ) and Sb-doped SnO/sub 2/, have been investigated. Kinetic measurements were carried out by using ac impedance and coulostatic relaxation methods. The ac behavior on the oxide electrodes was analyzed on the basis of a modified Randles-Ershler type equivalent circuit which takes into account the effect of non-faradaic components due to the semiconducting oxide films. The kinetic parameters (the charge transfer resistance and Warburg coefficient) and the interfacial parameters (the double layer capacity, film capacity and film resistance) were obtained by a least squares curve fitting method under P/sub O2//P/sub CO2/=0.9/0.1 atmosphere. The exchange current density was found to be 10 to 20 mA cm/sup -2/ at the oxide electrodes, assuming n=2. The coulostatic relaxation experiments supported the magnitude of the i/sub o/ values.

1986-01-01

225

Electronic structure and proton spin-lattice relaxation in PdH

The atomic structures of calcium sialons Ca_xSi_1_2_-_mAl_mN_1_6 (m = 0.5, 1, 2, 4) with the #alpha#- or #beta#-Si_3N_4-type structure were calculated, using the ab initio DFT approach, including relaxations of both lattice parameters and positions of the atoms. For all m values the #alpha#-Si_3N_4-type structure has a lower energy than the #beta#-type. For m = 1, 2 and 4 the #alpha#-type structure is also stable against decomposition into the metal nitrides, in agreement with experimental data. For m = 0.5 stability becomes uncertain. Al ions prefer positions close to Ca. Rather strong structural relaxations occur around the Ca ion.

2004-04-28

226

Effects of the insertion of a thick sp"2 buffer layer on the adhesion of cBN-rich film

We report a detailed augmented-plane-wave energy-band study and wave-function analysis of stoichiometric PdH which shows that, even though the Fermi surface of PdH is qualitatively similar to that of silver, the simple ''proton model'' is not valid. Instead, the screening of the proton in PdH is found to be larger than in an isolated H atom due, in part, to the formation of a H-Pd bonding band below the bottom of the d-band complex. This result, which is in qualitative agreement with Switendick's earlier calculation, is confirmed by ultraviolet photoemission experiments. A partial density-of-states (DOS) analysis in the energy range spanned by the six valence and conduction bands reveals the quantitative details of the bonding mechanism between the Pd and H constituents. At the Fermi energy, the high Pd d to H s DOS ratio approx. 10.3 is found to be far higher than expected in silver, despite the fact that the Fermi-surface geometry is similar. The field-induced conduction-electron ...

227

Effects of chronic treatment with honokiol in spontaneously hypertensive rats.

A method was proposed and examined to deposit thick cubic boron nitride (cBN)-rich layer of good adhesion to silicon substrate. The method combined (i) the insertion of a thick sp"2 buffer layer, and (ii) the use of an appropriate assist ion beam energy for the growth of the cBN-rich top layer. The sp"2-bonded boron nitride buffer layer was deposited under irradiation of ions with energies in the range of 200-360 eV. The buffer layer was found to contain curled graphitic basal planes, and so was supposed to be relatively deformable, and facilitate the relaxation of stresses in the cBN-rich top layer. The ion assist introduced during the growth of the cBN-rich layer was supposed to both create and annihilate defects, and so resulted in the generation and relaxation of internal stresses. Results showed that the insertion of a 492 nm sp"2 buffer layer, and the use of a beam energy of 450 eV for assisting the growth of the top layer can produce a ...

2004-05-01

228

Diffusion-accomodated rigid-body translations along grain boundaries in nanostructured materials

The present study was performed to evaluate the antihypertensive effects of honokiol in vivo in spontaneously hypertensive rats (SHR). The effects of honokiol were investigated by determination of the blood pressure, vascular reactivity, oxidative parameters, and histologic change in the aorta. Long-term administration of honokiol (400 mg/kg/d) to SHR decreased systolic blood pressure significantly. Honokiol (200, 400 mg/kg/d) enhanced the aortic relaxation in response to acetylcholine after 49-d treatment, but had no significant effects on the relaxation to sodium nitroprusside. The oral administration of honokiol significantly increased the plasma level of NO(2(-))/NO(3(-)), but decreased the level of malondialdehyde in liver of SHR compared with the control vehicle. In addition, SHR administered honokiol showed significant reductions in the elastin bands and media thickness in the aorta. These results suggest that chronic treatment with ...

2010-01-01

229

Benzyl carbamyl analogue of lignocaine: vasodepressor mechanism of action.

A model for the structural relaxation of grain boundaries (GBs) in nanostructured materials (NSMs) by diffusion-accommodated rigid body translations along GBs is proposed. The model is based on the results of recent computer simulations that have demonstrated that the GBs in NSMs retain a high-energy structure with random translational states due to severe geometrical constraints applied from neighboring grains (J. Appl. Phys. 78 (1995) 847; Scripta Metall. Mater. 33 (1995) 1245). The shear stresses within a GB caused by non-optimized rigid-body translations (RBTs) can be accommodated by diffusive flow of atoms along a GB. This mechanism is particularly important for low-angle and vicinal GBs, the energy of which noticeably depends on the rigid body translations. At moderate and high temperatures the model yields relaxation times that are very short and therefore GBs in NSMs can attain an equilibrium structure with optimized rigid body ...

2003-10-25

230

A critical review of behavioural treatments for chronic benign pain other than headache.

1. The benzyl carbamyl analogue of lignocaine [2-(diethylaminoacetamido)-3-carbamyl-4-methyl-5-benzylpyrrole] at an intravenous dose of 4 mg/kg caused a blood pressure decrease of 54 mmHg. 2. A greater hypotensive effect was observed in hypertensive compared to normotensive animals. Anaesthesia magnified the vasodepressor effect in both groups. 3. The analogue did not possess centrally-mediated effects on blood pressure but exerted its hypotensive effect via a peripheral mechanism. 4. The analogue produced a relaxant effect on intestinal and vascular smooth muscle while exerting minimal effects on muscarinic, sympathetic, or ganglionic nicotinic receptors. 5. The analogue exhibited less cardiac depressant action on left ventricular rate (dp/dt) and force of contraction than lignocaine. 6. Lethal effects for the analogue were first observed at 16 mg/kg following intravenous administration and at 500 mg/kg following intraperitoneal administration. 7. In conclusion, ...

231

Tertiary structure prediction of C-peptide of ribonuclease A by multicanonical algorithm

Studies of the effectiveness of operant, relaxation, cognitive, and multimodal behavioural approaches to the treatment of chronic benign pain other than headache were evaluated. In general, the quality of the studies was poor, and most investigations lacked appropriate and adequate control conditions, outcome measures, and/or follow-ups. While outcome reports for all four behavioural treatments have been mainly positive, few data were found which conclusively demonstrate that any of the approaches are effective or that they are the treatment of choice. The data do, however, imply that behavioural approaches may help patients lead more normal and productive lives. Specifically, the literature suggests that: (1) the operant method leads to increased activity levels and decreased pain and drug intake, (2) the relaxation approach results in decreased EMG levels and some pain reductions, (3) the cognitive techniques are speculative at this time, and ...

1982-11-01

232

Synthesis, characterization and antitumor activity study of some cyclometalated organoplatinum(II) complexes containing aromatic N-donor ligands

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 ...

1998-01-01

233

British Library Electronic Table of Contents (United Kingdom)

A general approach has been designed to synthesize some mononuclear and binuclear cyclometalated platinum(II) complexes, containing aromatic N-donor ligands with the presence of one Cl- trans to carbon. In this way, cyclometalated platinum(II) complex [Pt(C^N)Cl(dmso)], 1, C^N = N(1),C(2prime)-chelated, deprotonated 2-phenylpyridine and dmso = dimethylsulfoxide, was used as a precursor to react with imidazole derivatives (1-methylimidazole, 2a, imidazole, 2b,), monodentate pyridine derivatives (4-methylpyridine, 2c, pyridine, 2d,) and bidentate pyridine derivative (4,4prime-bipyridine, 3 and 4,). Synthesized complexes were fully characterized by using multinuclear NMR spectroscopy (1H, 13C{1H} and 195Pt), correlation NMR spectroscopy (1H-1H COSY, 13C{1H}-1H Heteronuclear Multiple Quantum C...

2011-01-01

234

Synthesis of Poly (D L-lactide-co-dl-3,6 dimethyl-morpholine, 2,5 - dione)

Structural studies of the O-antigenic polysaccharide from Escherichia coli O177

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.

2001-09-01

235

British Library Electronic Table of Contents (United Kingdom)

The structure of the O-antigen polysaccharide (PS) from Escherichia coli O177 has been determined. Component analysis together with 1H and 13C NMR spectroscopy experiments was used to determine the structure. Inter-residue correlations were determined by 1H,13C-heteronuclear multiple-bond correlation and 1H,1H-NOESY experiments. PS is composed of tetrasaccharide repeating units with the following structure: 2)-a-l-Rhap-(13)-a-l-FucpNAc-(13)-a-l-FucpNAc-(13)-b-d-GlcpNAc-(1 An a-l-Rhap residue is suggested to be present at the terminal part of the polysaccharide, which on average is composed of 20 repeating units, since the 1H and 13C chemical shifts of an a-linked rhamnopyranosyl group could be assigned by a combination of 2D NMR spectra. Consequently, the biological repeating unit has a 3-...

2011-01-01

236

Stereospecific ligands and their complexes. Part VII. Synthesis, characterization and in vitro antitumoral activity of platinum(II) complexes with O,Oprime-dialkyl esters of (S,S)-ethylenediamine-N,Nprime-di-2-(4-methyl)pentanoic acid

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...

2011-01-01

237

Recognition and Detoxification of the Insecticide DDT by Drosophila melanogaster Glutathione S-Transferase D1

Pressure effect of the /sup 1/H NMR spectra of organic compounds in the presence of lanthanide shift reagents. A formally associative process characterized by volume expansion

GSTD1 is one of several insect glutathione S-transferases capable of metabolizing the insecticide DDT. Here we use crystallography and NMR to elucidate the binding of DDT and glutathione to GSTD1. The crystal structure of Drosophila melanogaster GSTD1 has been determined to 1.1 {angstrom} resolution, which reveals that the enzyme adopts the canonical GST fold but with a partially occluded active site caused by the packing of a C-terminal helix against one wall of the binding site for substrates. This helix would need to unwind or be displaced to enable catalysis. When the C-terminal helix is removed from the model of the crystal structure, DDT can be computationally docked into the active site in an orientation favoring catalysis. Two-dimensional {sup 1}H,{sup 15}N heteronuclear single-quantum coherence NMR experiments of GSTD1 indicate that conformational changes occur upon glutathione and DDT binding and the residues that broaden upon DDT ...

2010-06-14

238

Pozzolanic behaviour of compound-activated red mud-coal gangue mixture

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 ...

1987-11-11

239

Pozzolanic behaviour of compound-activated red mud-coal gangue mixture

The pozzolanic behaviour of compound-activated red mud-coal gangue has been investigated through TG, DTA, XRD, FTIR and {sup 27}Al 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 Ca{sub 3}Al{sub 2}O{sub 6} center dot xH{sub 2}O. From TG analysis results, it is thought that the high amount of Ca(OH){sub 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. {sup 27}Al MAS NMR proved to be an effective technique to obtain valuable ...

2011-03-15

240

Novel recombinant insulin analogue with flexible C-terminus in B chain. NMR structure of biosynthetic engineered A22^G-B31^K-B32^R human insulin monomer in water/acetonitrile solution

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 ...

2011-03-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

241

British Library Electronic Table of Contents (United Kingdom)

A tertiary structure of recombinant A22^G-B31^K-B32^R-human insulin monomer (insulin GKR) has been characterized by ^1H, ^1^3C NMR at natural isotopic abundance using NOESY, TOCSY, ^1H/^1^3C-GHSQC, and ^1H/^1^3C-GHSQC-TOCSY spectra. Translational diffusion studies indicate the monomer structure in water/acetonitrile (65/35vol.%). CSI analysis confirms existence of secondary structure motifs present in human insulin standard (HIS). Both techniques allow to establish that in this solvent recombinant insulin GKR exists as a monomer. Starting from structures calculated by the program CYANA, two different refinement protocols used molecular dynamics simulated annealing with the program AMBER; in vacuum (AMBER_VC), and including a generalized Born solvent model (AMBER_GB). From these calculation...

2011-01-01

242

NMR in highly correlated superconductors

In vivo phosphorylation of histones H1 and H5 in calf thymus and chicken erythrocytes as studied by /sup 31/P nuclear magnetic resonance spectroscopy

Results of our systematic NMR study in high T_c cuprates are reviewed. The antiferromagnetic spin fluctuations (AFSF) decrease in the order of La_1_._8_5Sr_0_._1_5CuO_4. YBa_2Cu_3O_7 and Tl_2Ba_2CuO_6_+_y. 1/T_1 of "6"3Cu in the CuO_2 plane in the normal state follows essentially a Curie-Weiss law at high temperature and T_1T = const. law at low temperature. The temperature dependence of 1/T_1 and the Knight shift together with their impurity effect in the superconducting state strongly suggest d-wave pairing implying the AFSF to be responsible for the occurrence of superconductivity. From the NQR frequency measurement the density of Cu 3d and O 2p holes decreases and increases, respectively, in the order of La, Y and Tl compounds, which is consistent with the change of AFSF. The relation between T_c and #nu#_Q, and their pressure dependence suggest that there exists and optimum value of the ratio of Cu 3d and O 2p hole density to give a maximum in T_c. (orig.).

1992-08-01

243

Effect of external pH on the cytoplasmic and vacuolar pHs in Mung bean root-tip cells. A T P nuclear magnetic resonance study

The /sup 31/P NMR method was first applied to characterize in vivo phosphorylation of H1 and H5 in calf thymus and chicken erythrocytes as well as in vitro phosphorylation of H1 and H5 by cAMP-dependent protein kinase. The amino acid residues phosphorylated in vivo in the histones were exclusively serine residues, and the mole fraction of phosphoserine was estimated to be 0.34 and 0.27 per molecule of calf thymus H1 and chicken erythrocyte H5, respectively. Interestingly, chicken erythrocyte H1 was not phosphorylated in vivo. Three H1 subtypes from calf thymus H1 varied in the /sup 31/P NMR spectra, and the bisected fragments of calf thymus H1 and chicken erythrocyte H5 exhibited characteristic spectral patterns, indicating that there are considerable diversities of the degree of phosphorylation and phosphorylation sites in very-lysine-rich histones. Furthermore, it was found that the microenvironment of phosphoserine residues phosphorylated in ...

1987-08-01

244

Effect of external pH on the cytoplasmic and vacuolar pHs in Mung bean root-tip cells

The effect of the external pH on the intracellular pH in mung bean (Vigna mungo (L.) Hepper) root-tip cells was investigated with the T P nuclear magnetic resonance (NMR) method. The T P 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.

1984-12-01

245

Constituents of fruit pulp of Maytenus salicifolia and complete 1D/2D NMR data of 3?-hydroxy-D:B-friedo-olean-5-ene

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).

246

British Library Electronic Table of Contents (United Kingdom)

A mixture of long-chain hydrocarbons constituted by nonacosane (29C, 7.5%), hentriacontane (31C, 48.3%), and tritriacontane (33C, 30.1%), the ester 1?-acetyloxymethylpentacosa-20?-enyl 10-hydroxydecanoate (2), ?-amyrin (3), friedelin (4), and lupeol (5), and 3?-hydroxy-D:B-friedo-olean-5-ene (6) were identified as constituents of fruits of Maytenus salicifolia Reissek (Celastraceae). The structural formula and the stereochemistry of compound 6 were established by the data obtained through 1H and 13C NMR spectroscopy, including DEPT-135 and 2D (HMQC, HMBC, and NOESY) experiments. By analysis of the spectral data, it was possible to correct seven chemical shift assignments of compound 6, which were erroneous attributed and published in the scientific literature.

2010-01-01

247

Characterization of proton exchange membrane materials for fuel cells by solid state nuclear magnetic resonance

Aluminum siting in mordenite and dealumination mechanism

Solid-state nuclear magnetic resonance (NMR) has been used to explore the nanometer-scale structure of Nafion, the widely used fuel cell membrane, and its composites. We have shown that solid-state NMR can characterize chemical structure and composition, domain size and morphology, internuclear distances, molecular dynamics, etc. The newly-developed water channel model of Nafion has been confirmed, and important characteristic length-scales established. Nafion-based organic and inorganic composites with special properties have also been characterized and their structures elucidated. The morphology of Nafion varies with hydration level, and is reflected in the changes in surface-to-volume (S/V) ratio of the polymer obtained by small-angle X-ray scattering (SAXS). The S/V ratios of different Nafion models have been evaluated numerically. It has been found that only the water channel model gives the measured S/V ratios in the normal hydration ...

2010-03-15

248

Trapping of neutral atoms with resonant microwave radiation

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 ...

1986-10-09

249

The elastic plastic behaviour of a 1/2% Cr Mo V steam turbine steel during high strain thermal fatigue

We duscuss a resonant microwave trap for neutral atoms. Because of the long spontaneous radiation time this trap is remarkably different from the optical trap. It also has advantages over static magnetic traps that trap the excited spin state of the lowest electronic level, in that atoms predominantly in the spin ground state can be trapped. We analyze the relaxation-ejection lifetime of atoms in such a trap using the formalism of dressed atomic states. Results are appliedi to atomic hydrogen and the possibility of Bose-Einstein condensation is considered.

1989-05-15

250

The 2s{sup 1}2p{sup 4} autodetachment resonance in the C{sup -} negative ion

High strain fatigue problem in steam turbine. Cyclic stress strain hysteresis loops and stress relaxation behaviour in 16 h dwell period tests. Variation of stress and strain during tests under nominally strain controlled conditions. Definition of test conditions and of criteria for crack initiation and failure. Comparison of reverse bend and push pull failure data. (orig.) 891 RW/orig. 892 RKD.

251

Randomization of heavily damaged regions in annealed low energy Ge{sup +}-implanted (0 0 1)Si

The calculations of the photodetachment cross section for the C{sup -} negative ion has been performed within the newly-developed many-body theory method, the RPAE interchannel interaction and dynamic relaxation and polarization corrections being included. The 2s{sup 1}2p{sup 4} shape resonance is shifted to a higher photon energy and broadens as compared to the resonance parameters determined earlier within the RPAE, which is consistent with the experimental evidence and the recent R-matrix calculations. (orig.) 18 refs.

1998-08-10

252

Randomization of heavily damaged regions in annealed low energy Ge"+-implanted (0 0 1)Si

Apparent growth of amorphous layers during low temperature annealing was observed in low energy Ge{sup +}-implanted (0 0 1)Si by high-resolution transmission electron microscopy. The occurrence of abnormal growth is due to the randomization of heavily damaged regions beneath the original amorphous/crystalline interfaces. The randomization process is attributed to the strain, incurred by the presence of a high density of large Ge atoms in the heavily damaged Si substrate, relaxation to lower the free energy of the systems. The randomization upon annealing may be fruitfully applied to minimize the transient enhanced diffusion in shallow junction formation.

2004-01-15

253

Photoluminescence and cathodoluminescence properties of Tb3+ activated Sr3AlO4F emitting-color tunable phosphor

Apparent growth of amorphous layers during low temperature annealing was observed in low energy Ge"+-implanted (0 0 1)Si by high-resolution transmission electron microscopy. The occurrence of abnormal growth is due to the randomization of heavily damaged regions beneath the original amorphous/crystalline interfaces. The randomization process is attributed to the strain, incurred by the presence of a high density of large Ge atoms in the heavily damaged Si substrate, relaxation to lower the free energy of the systems. The randomization upon annealing may be fruitfully applied to minimize the transient enhanced diffusion in shallow junction formation.

2004-01-01

254

British Library Electronic Table of Contents (United Kingdom)

Tb3+-activated Sr3AlO4F phosphors were synthesized by a high-temperature solid-state reaction method. The investigation of photoluminescence and cathodoluminescence indicates that these phosphors can be effectively excited by ultraviolet light and low-voltage electron beam. The phosphors exhibit a tunable-green emission. The luminescence behaviors are explained by the site occupancy of Tb3+ ions in the host crystal and the cross-relaxation of 5D3 to 5D4 state.

2011-01-01

255

Photoluminescence and cathodoluminescence properties of Tb3+ activated Sr3AlO4F emitting-color tunable phosphor

Nuclear quadrupole resonance of "9"3Nb in intermetallic compounds with A-15 crystal strucutre

Tb3+-activated Sr3AlO4F phosphors were synthesized by a high-temperature solid-state reaction method. The investigation of photoluminescence and cathodoluminescence indicates that these phosphors can be effectively excited by ultraviolet light and low-voltage electron beam. The phosphors exhibit a tunable-green emission. The luminescence behaviors are explained by the site occupancy of Tb3+ ions in the host crystal and the cross-relaxation of 5D3 to 5D4 state.

2011-03-01

256

Negative charges in liquid hydrogen and deuterium

The impulse method has been used to study "9"3Nb (nuclear quadrupole resonance (NQR) parameters quadrupole connection constant, spin-lattice and spin-spin relaxation times) in binary intermetallic compounds of Nb_3X (x=Al, Ga, Ge, Sn, Pt, Os, Ir, Sb) and in some ternary phases on the basis of the Nb_3Al compound. The discussion on experimental data obtained is carried out in approximation of a tight connection for d-electrons.

1981-02-01

257

Inner-shell excitation of intrinsic luminescence and resonantly excited X-ray fluorescence at Be 1s edge in oriented BeO crystals

The temperature and pressure dependence of the mobilities of negative charges injected into liquid hydrogen and deuterium have been measured. The authors propose the existence of two types of charge carriers in liquid parahydrogen. One is a bubble with an electron inside while the other has higher mobility. Relaxation of the current through liquid hydrogen was observed. It is suggested that in liquid and solid hydrogen under {beta}-irradiation neutral complexes are created which can trap the negative charges and have a lifetime of about 10 hours. 6 refs., 5 figs.

1992-11-01

258

Implantation of single-impurity Fe and its magnetic coupling in Er studied by TDPAD

The results of studies of the time-resolved luminescence of self-trapped excitons (STE) with different multiplicity as well as the X-ray emission in oriented BeO crystals under excitation in the vicinity of the 1 s Be photoabsorption edge are presented. The branching of the electronic excitations relaxation depends strongly on the crystal orientation after the inner-shell excitation. The common features between the processes of the STE luminescence and resonantly excited X-ray fluorescence have been discussed.

2007-05-21

259

Electromagnetic wiggler technology development at the Lawrence Livermore National Laboratory

Single Fe impurities were implanted in an Er single crystal and found to occupy both substitutional and interstitial sites, below a temperature of 200 K. The local susceptibility of Fe on both sites follows a Curie-Weiss law and exhibits a positive local Curie constant, indicating an antiferromagnetic coupling between the Fe and the surrounding Er moments. The corresponding nuclear spin relaxation rates follow a Korringa law as a function of temperature, confirming the dominance of local magnetism and the formation of local moments on each of the sites occupied by Fe.

2004-05-01

260

Electromagnetic wiggler technology development at the Lawrence Livermore National Laboratory

As a part of the program at the Lawrence Livermore National Laboratory (LLNL) in induction-linac free-electron laser (IFEL) research, the authors are conducting a variety of activities addressing the unique requirements imposed on IFEL wiggler systems. They are actively developing improved DC iron-core electromagnetic wiggler designs to attain higher peak fields, greater tunability, and lower random error levels. They are pursuing specialized control systems, such as magnetic-field and beam-position controllers, which can relax requirements on the wiggler itself. They are also pursuing basic studies to establish the effect of radiation on permanent magnets.

1988-03-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

261

ESR studies on reactivity of HO{sub 2} radicals in polycrystalline ice: non-monotonic changes of disproportionation rate in the temperature range 100-200 K

As a part of the program at the Lawrence Livermore National Laboratory (LLNL) in induction-linac free-electron laser (IFEL) research, we are conducting a variety of activities addressing the unique requirements imposed on IFEL wiggler systems. We are actively developing improved dc iron-core electromagnetic wiggler designs to attain higher peak fields, greater tunability, and lower random error levels. We are pursuing specialized control systems, such as magnetic-field and beam-position controllers, which can relax requirements on the wiggler itself. We are also pursuing basic studies to establish the effect of radiation on permanent magnets.

1987-01-01

262

A correlation between electrochemical parameters and stress corrosion cracking of alloy 600 in high temperature caustic solution

The kinetics of HO{sub 2} radicals in UV-irradiated frozen dilute solutions of H{sub 2}O{sub 2} were followed by the ESR technique. Radical disproportionations at the irradiation temperature were found to be adequately described in terms of dispersive kinetics by a second-order equal-concentration kinetic equation with rate parameters changing non-monotonically in the temperature range 100-200 K. These changes are thought to occur due to well separated structural relaxation regions of polycrystalline ice in the above temperature range. (author).

1994-11-01

263

Synthesis and characterization of nickel(II), chromium(III), cobalt(II), copper(II), zinc(II), and cadmium(II) complexes with isatin- isonicotinoylhydrazone

The properties of the passive films formed on Alloy 600 at different applied potentials in 10% NaOH solution at 315 .deg. C was studied using in situ AC impedance and polarization measurements. The results were correlated with the stress corrosion cracking (SCC) behavior obtained from the C-ring tests in the same conditions. The change of the semiconductive property and the peak of relaxation time were observed at 0.2 V where the SCC rate showed a maximum. These results were also consistent with the prediction parameter for SCC obtained from fast and slow polarization scans.

2001-10-01

264

Syntheses of all singly labeled (/sup 15/N)adenines: mass spectral fragmentation of adenine

A few metal complexes of isatin-isonicotinoylhydrazone with Ni(II), Cr(III), Co(II), Cu(II), Zn(II) and Cd(II) have been prepared and characterized on the basis of elemental analyses, infrared and electronic spectra as well as "1H NMR spectra, conductivity and magnetic measurements. In view of the results obtained, it has been found that two molecules of isatin-isonicotinoylhydrazone are chelated to the central metal ion as bis-uninegative ONO tridentate ligand forming non-electrolytic octahedral metal complexes. (author)

1997-03-01

265

Syntheses and phosphorus-31 NMR studies of five-coordinate platinum(II) complexes of tris(2-(diphenylphosphino)ethyl)phosphine and monodentate phosphorus ligands

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.

1981-07-01

266

Radiation induced synthesis of low molecular weight of PTFE and their crosslinking in acetone medium

The first preparation and characterization of the platinum (II) complexes containing five phosphorus ligands are reported herein. The complexes are represented by the formulae (Pt(PP/sub 3/)(P(OR)/sub 3/)Cl/sub 2/, where R = Me or Et, and (Pt(PP/sub 3/)(PEt/sub 3/))Cl/sub 2/. The /sup 31/P spectra of the complexes are presented. 10 references, 2 tables.

1987-12-02

267

Osmoregulation in methanogens. Progress report, May 15, 1991--January 15, 1993

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)

2007-09-03

268

Osmoregulation in methanogens

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.

1993-01-01

269

Orthophosphoric acid interactions with ultrastable zeolite Y: Infrared and NMR studies

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.

1993-01-01

270

Nuclear magnetic resonance on oriented XVTa and XXTa

Zeolite Y is the active component of most commercial cracking catalysts. Interaction of H[sub 3]PO[sub 4] with extraframework aluminum of ultra-stable zeolite (USY) leads to the formation of different types of aluminum phosphates, while there is no indication of the formation of SAPO zeotype structures. The total acidity of USY slightly decreases upon the H[sub 3]PO[sub 4] treatment, while the maximum in the distribution of acid strength is shifted to milder acidities. Dealumination of the zeolite and creation of POH sites associated with AIPO[sub 4] are responsible for the modifications observed. 37 refs., 8 figs., 3 tabs.

1994-01-01

271

Nuclear magnetic moments of "1"7"5Ta and "1"7"7Ta

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.

1984-08-01

272

Mechanism of the metal-mediated carbalkoxylation of vinyl electrophiles. 2. Preparation, molecular structure, and reductive couplings of {sigma}-alkoxycarbonyl {sigma}-vinyl platinum(II) complexes

"1"7"5Ta and "1"7"7Ta nuclei as dilute impurities in Fe were oriented at low temperatures. Using the technique of NMR/ON the magnetic moments have been measured: "+#mu#("1"7"5Ta, 7/2"+,"+=2.270(45) #mu# sub(N) and "+#mu#("1"7"5Ta, 7/2"+)"+=2.250(45) #mu# sub(N). These values are discussed in the framework of the rotational model. (author).

273

Effect of Cl substituent in the aromatic tetracycline ring on its reactivity with solvated electrons

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.

1992-03-01

274

Design of intelligent nucleobases and DNA HOMO mapping.

Decomposition yields of tetracycline hydrochloride (TC.HCl) and chlorotetracycline hydrochloride (ClTC.HCl) in methanol solution saturated with Ar or N/sub 2/O were determined. Rate constants of the reaction esub(s)/sup -/ with some antibiotics were obtained. It was demonstrated by /sup 1/H NMR that the radical formed by degradation of 7-C-Cl group is recombined with the H atoms leading to ClTC.HCl being converted into tetracycline hydrochloride (TC.HCl).

1984-09-18

275

Continuous coal hydrogenation; processes and products, annual report July 1981 to June 1982

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

2002-01-01

276

Chemical constituents of Galianthe brasiliensis (Spreng.) E.L.Cabral and Bacigalupo (Rubiaceae)

The first stage of the continuous coal hydrogenation unit has been used to test a number of coals with different processing strategies. This work has shown that conversion increases with product recycle, however after the second pass the increase is small but operability of the reactor is considerably improved. A kinetic model for the aromatic saturation of the recycle solvent in the second stage has been developed and will be used in the selection of conditions for oil upgrading processes. New insights into the structural composition of coal derived materials have been made due to the refinement of chromatographic or solubility separation analyses into routine operations and the development of a new technique in NMR spectroscopy.

1982-01-01

277

/sup 18/O isotope effect in carbon-13 nuclear magnetic resonance spectroscopy. Part 8. Oxygen exchange of 2,4,6-trimethylpyrylium cation

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)

278

Properties of cubic boron nitride films with buffer layer control for stress relaxation using ion-beam-assisted deposition

The rate of the oxygen-exchange reaction in an aqueous solution of a heterocyclic oxygen compound, 2,4,6-trimethylpyrylium perchlorate, was quantitated. The /sup 18/O isotope effect in /sup 13/C NMR spectroscopy affords a direct, continuous, and relatively simple analysis of the reaction and was used to obtain data on the incorporation of /sup 18/O from solvent H/sub 2//sup 18/O into the pyrylium salt. Due to the low solubility of this salt in aqueous solutions, 2,4,6-trimethyl(2-/sup 13/C)pyrylium perchlorate and 2,4,6-trimethyl(2,6-/sup 13/C/sub 2/)pyrylium perchlorate were synthesized to facilitate the acquisition of the data on an NTC-200 spectrometer operating at 50.31 MHz. Upon incorporation of /sup 18/O into the pyrylium salt, the /sup 13/C NMR signal of the directly bonded carbon atom is shifted upfield 0.038 ppm. A /sup 13/C isotope effect is also detected in the doubly /sup 13/C-enriched pyrylium salt where the /sup 13/C ...

1984-12-12

279

Photophysical properties of new psoralen derivatives: psoralens linked to adenine through polymethylene chains

Significant ion irradiation during film growth is required for the formation of cubic boron nitride (cBN) films. Meanwhile, a huge level of intrinsic stress possibly induced by the ion bombardment has been frequently reported to result in cracking and/or lack of adhesion of deposited cBN films. The present work has been performed to investigate the interfacial and/or the buffer layer structures with better matching to the cBN film by relaxation of the film stress using ion-beam-assisted deposition (IBAD). Boron nitride films have been synthesized on Si(100) wafer and tungsten carbide (WC) substrates by depositing boron vapor under simultaneous bombardment with nitrogen ions and nitrogen-argon mixture ions in the energy range of 0.5-10 keV. Cubic BN films with enhanced tribological properties have been explored by inserting a BN layer with various B/N compositions as a controlled buffer at the interface. Significant relaxation of the film stress ...

1999-09-01

280

Origins of residual stress in Mo and Ta films: The role of impurities, microstructural evolution, and phase transformations

The model compounds, 8-methoxypsoralen-CH_2O(CH_2)_n-adenine (MOPCH_2OC_nAd, n=2,3,5,6,8, and 10) in which 5 position of 8-methoxypsoralen (8-MOP) is linked by various lengths of polymethylene bridge to N"9 of adenine. UV absorption spectra are identical with the sum of MOPCH_2OC3 and adenine absorption spectra. Solvent effect on the UV absorption and fluorescence emission spectra indicate that the lowest excited singlet state is the (#pi##->##pi#"*) state. The spectral characteristics of the fluorescence of MOPCH_2OC_nAd are strongly dependent upon the nature of the solvents. The fluorescence emission spectra in aprotic solvents are broad and structrueless due to the excimer formation through the folded conformation accelerated by hydrophobic #pi#-#pi# stacking interaction. Increasing polarity of the protic solvents leads to higher population of unfolded conformation stabilized through favorable solvation and H-bonding, and consequently to an increase in the fluorescence intensity, ...

2002-10-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

281

Estimation of hydrogen bondings in coal utilizing FTir and differential scanning calorimetry (DSC); FTir to DSC wo mochiita sekitannai suiso ketsugo no teiryoteki hyoka no kokoromi

Both the sign and magnitude of residual stress can vary with the thickness of sputter deposited films. The origins of this behavior are not well understood. In this work, the authors consider the correlation between the residual stress behavior and the depth dependence of impurities in thin (2.5 nm--150 nm) sputtered Mo and Ta films. They also consider the effects of phase transformations and microstructural changes on the stress behavior. Films were deposited onto Si substrates with native oxide. The residual stress observed in the Mo films varied from highly compressive at 2.5 nm film thickness to {approximately}0 at 10 nm thickness. Ta films also exhibited a high compressive stress, which relaxed from highly compressive to tensile between 10 nm and 50 nm film thickness. Impurities in the films may originate from the sputtering targets, the background gases, and the substrate surfaces. Auger Electron Spectroscopy (AES) results showed the presence of O and C ...

1997-05-01

282

Closure relations for the multi-species Euler system. Construction and study of relaxation schemes for the multi-species and multi-components Euler systems; Relations de fermeture pour le systeme des equations d'Euler multi-especes. Construction et etude de schemas de relaxation en multi-especes et en multi-constituants

With an objective to know coal condensation structure which has influence on coal conversion reaction, an attempt was made on quantitative evaluation of hydrogen bonding in coal. Using as test samples the VDC made from Taiheiyo coal swollen by tetralin and vacuum-dried, and its pyrolyzed char, DSC measurement and Fourier transform infrared spectroscopy (FT) were performed. An FT spectrum comparison revealed that the VDC swollen at 220{degree}C has the hydrogen bonding relaxed partly from the original coal. However, since the change is in a huge coal molecular structure restraining space, it has stopped at relaxation of the bonding energy without causing separation as far as free radicals. On the other hand, the DSC curve shows that the VDC has slower endothermic velocity than the original coal. In other words, the difference in heat absorption amounts in both materials is equivalent to the difference of enthalpy ({Delta} H) of both materials, ...

1996-10-28

283

Acid/base and hydrogen bonding effects on the proton-coupled electron transfer of quinones and hydroquinones in acetonitrile: Mechanistic investigation by voltammetry, "1H NMR and computation

After having recalled the formal convergence of the semi-classical multi-species Boltzmann equations toward the multi-species Euler system (i.e. mixture of gases having the same velocity), we generalize to this system the closure relations proposed by B. Despres and by F. Lagoutiere for the multi-components Euler system (i.e. mixture of non miscible fluids having the same velocity). Then, we extend the energy relaxation schemes proposed by F. Coquel and by B. Perthame for the numerical resolution of the mono-species Euler system to the multi-species isothermal Euler system and to the multi-components isobar-isothermal Euler system. This allows to obtain a class of entropic schemes under a CFL criteria. In the multi-components case, this class of entropic schemes is perhaps a way for the treatment of interface problems and, then, for the treatment of the numerical mixture area by using a Lagrange + projection scheme. Nevertheless, we have to find a good projection ...

2001-07-01

284

Transition-metal dimers and physical limits on magnetic anisotropy

This report seeks to address the role of hydrogen bonding with Bronsted acids and bases in proton-coupled electron transfer (PCET) as it pertains to concerted or stepwise pathways of quinone (Q) and hydroquinone (QH_2) electrochemistry. This study was performed using a series of techniques that included cyclic voltammetry (CV), digital simulations, computational chemistry and "1H NMR. Hydrogen bonding was inferred by a decrease in diffusion coefficient (D) values measured using a pulsed gradient echo- (PGE-) "1H NMR technique. Changes of 40.8% and 37.9% in D values were only noted after the addition of two equivalents of acetate to 1,4-hydroquinone (1,4-QH_2) and catechol (1,2-QH_2), respectively. In contrast, the D values for the addition of selected amines (pyridine, N,N-diisopropylethylamine and triethylamine) changed only 3.2% on average. Quantum mechanical calculations were conducted to determine the pK_a of all quinoid species to serve as ...

2010-09-01

285

British Library Electronic Table of Contents (United Kingdom)

Recent advances in nanoscience have raised interest in the minimum bit size required for classical information storage. This bit size is determined by the necessity for bistability with suppressed quantum tunnelling and energy barriers that exceed ambient temperatures. In the case of magnetic information storage, much attention has centred on molecular magnets with bits consisting of about 100 atoms, magnetic uniaxial anisotropy energy barriers of about 50?K and very slow relaxation at low temperatures. Here, we draw attention to the remarkable magnetic properties of some transition-metal dimers, which have energy barriers approaching 500?K with only two atoms. The spin dynamics of these ultrasmall nanomagnets is strongly affected by a Berry phase, which arises from quasi-degen...

2007-01-01

286

Transient Fluid Dynamics of the Quark-Gluon Plasma According to AdS/CFT

Thermal noise as a spectroscopic tool to determine transport properties

We prove, using the AdS/CFT correspondence, that the long wavelength dynamics of the shear stress tensor in a strongly coupled N=4 SYM plasma is not described by the relaxation-type, fluid dynamical equations proposed by Israel and Stewart: the coarse grained dynamics will necessarily contain a second-order comoving derivative of the shear stress tensor. We argue that this should be true for any strongly-coupled gauge theory with a gravity dual. If the QGP formed in heavy ion collisions can indeed be described in terms of a (yet unknown) theory of gravity in higher dimensions, the equations of motion used in hydrodynamical simulations of the QGP must necessarily include second order comoving derivatives of the shear stress tensor.

2011-01-01

287

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...

2009-01-01

288

Temperature, moisture, and strain rate effects on the compressive mechanical behavior of Nylon 6/6

Superconducting-like behaviour of the layered Chalcogenides CuS and CuSe below 40 K

Material test results are presented for the mechanical behavior of Nylon 66 in compression. Static compression modes include direct compression, stress relaxation and creep. Dynamic direct compression results are included. Tests are performed at atmospheric pressure; strain rates range from 10/sup /minus/4/sec to 10/sup 2/sec; temperatures are 20, 65, 110, 150 and 200/degree/C; moisture levels are 0% (dry), 2% and 6% (saturated); true strains to /minus/0.25 are imposed. Our empirical Temperature-Moisture equivalence of 14/degree/C per 1% moisture is discussed with respect to the /open quotes/free volume/close quotes/ concept.

1988-04-01

289

British Library Electronic Table of Contents (United Kingdom)

The investigation of strongly sintered ''quasi molten'' CuS and CuSe chalcogenides shows that they exhibit a sharp diamagnetic transition and a resistivity drop around 40 K. The reminiscence of such high temperature superconductivity features, never observed to date for these phases, is strongly supported by two chemical characteristics: bidimensionality of the structure and mixed valency of copper. The absence of zero resistance suggests that the internal chemical pressure in the samples has a key role in the existence of superconductivity: the S-S or Se-Se interlayer distances are very sensitive to the pressure, so that the critical distance for the percolation can be reached in the core of the samples, but not at the vicinity of the surface, where relaxation may appear.

2011-01-01

290

Structural analysis of a binary metallic glass model. I. - The Pd/sub 80/Si/sub 20/ alloy

Spontaneous resistance fluctuations and their evolution near the threshold in o-TaS_3 below the liquid-nitrogen temperature

In the first paper of this series devoted to a structural analysis of a binary metallic glass model, we study a Pd/sub 80/Si/sub 20/ sample obtained by numerical relaxation. We discuss the reproducibility of the method and make a comparison with the experimental interference functions. Then we undertake a microscopic structural analysis from several point of view: we first study the number of neighbours of each type for each type of atoms; secondly, we analyse the structure by means of the radical plane method; at last, we show that it is possible to generalize the five fundamental characteristic units introduced by Bernal, so that we can define the environment of any Si atom without any ambiguity. All these methods reveal a certain tendency towards a prismatic environment for the metalloids.

1985-02-01

291

Spectroscopic properties of the f-elements in compounds and solutions. [79 references

It is found that below 80 K o-TaS_3 demonstrates spontaneous resistance fluctuations growing when the temperature is decreasing. The average relaxation time, #tau#_0, obtained from the noise spectra demonstrates activated behavior, #tau#_0 #propor to# exp(W/T), W #approx# 1300 K for 50 < or #approx# T < or #approx# 70 K. In the vicinity of the threshold the average frequency of the fluctuations, f_0, grows with increasing the voltage, revealing onset of the Froehlich current. log(f_0) is found to be proportional to the increase of conductivity. We conclude that the main source of the resistance fluctuations are thermally-assisted jumps of dislocations of the charge-density waves. (orig.).

1993-06-01

292

Small heat shock protein 20 (HspB6) in cardiac hypertrophy and failure

In this systematic examination of some of the spectroscopic properties of the f-elements we deal with both the trivalent lanthanides and actinides. We summarize the present status of our energy level calculations in single crystal matrices and in aqueous solution, and compare the predicted crystal-field structure in certain low-symmetry sites with that observed. Some interesting new structural insights are thereby gained. The state eigenvectors from these calculations are then used in part in reassessing and interpreting the intensities of transitions in aqueous solution via the Judd-Ofelt theory. The parameters of this theory derived from fitting experimental data are compared with those computed from model considerations. Finally, we discuss some recent contributions to the interpretation of excited state relaxation processes in aqueous solution. 79 references, 23 figures, 17 tables.

1982-01-01

293

British Library Electronic Table of Contents (United Kingdom)

Hsp20, referred to as HspB6, is constitutively expressed in various tissues. Specifically, HspB6 is most highly expressed in different types of muscle including vascular, airway, colonic, bladder, and uterine smooth muscle; cardiac muscle; and skeletal muscle. It can be phosphorylated at Ser-16 by both cAMP- and cGMP-dependent protein kinases (PKA/PKG). Recently, Hsp20 and its phosphorylation have been implicated in multiple physiological and pathophysiological processes including smooth muscle relaxation, platelet aggregation, exercise training, myocardial infarction, atherosclerosis, insulin resistance and Alzheimer's disease. In the heart, key advances have been made in elucidating the significance of Hsp20 in contractile function and cardioprotection over the last decade. This mini-rev...

2011-01-01

294

Shear rigidity of spread stearic acid monolayers on water

Polarised neutron reflectometry study of Co/CoO exchange-biased multilayers

The effect of Al/sup 3 +/, Fe/sup 3 +/, Ca/sup 2 +/, and Mg/sup 2 +/ ions and of pH on the two-dimensional shear modulus of stearic acid spread on a water substrate was determined. A large shear modulus was displayed by the films when the subphase contained Al/sup 3 +/ and Fe/sup 3 +/ ions at the self-buffered pH. With Fe/sup 2 +/ dissolved in the subphase, the film displayed a viscous relaxation when strained but no residual stress was observed. No effect was observed with the Ca/sup 2 +/ or Mg/sup 2 +/. Reducing the pH value in the subphase with the trivalent ions caused the shear modulus to disappear. The observations are interpreted in terms of hydrogen bonding.

1981-09-15

295

Phylogeography of rabies virus isolated from dogs in Brazil between 1985 and 2006

We have investigated via SQUID magnetometry and polarised neutron reflectivity the exchange-bias effect in CoO/Co sputtered multilayers. In particular, we studied the magnetisation reversal and the time relaxation of the exchange-bias field close to the coercive field H{sub c1}. Neutron intensities of all four cross sections (I++, I+-, I-+, I-) were recorded at the position of the first multilayer Bragg peak while scanning the magnetic field. From such scans we infer that the magnetisation reversal for the ascending as well as for the descending branch of the magnetic hysteresis occurs not by in-plane rotation but through domain-wall movements. The exchange-bias field, H{sub EB}, is strongly affected by thermal fluctuations. H{sub EB} decreases, following an exponential decay function with a half-life time of about 580 s at T=240 K. (orig.)

2002-07-01

296

British Library Electronic Table of Contents (United Kingdom)

To establish the phylogeographic relationships in rabies viruses in Brazil, we studied a dataset retrieved from GenBank consisting of 71 genetic sequences from the coding region of the N gene of rabies viruses isolated in dogs over a period of 22?years. The Bayesian Markov chain Monte Carlo method available in the BEAST package was used with the GTR+G+?4 evolutionary model in conjunction with the relaxed uncorrelated lognormal molecular clock model and an exponential growth tree prior. A discrete phylogeographic diffusion model was also analyzed using a standard continuous-time Markov chain viewed with Google Earth to provide a spatial projection of the diffusion of genetic lineages based on their phylogeographic relationships. The topology of the time and substitution phylogenetic trees a...

2011-01-01

297

Nuclear magnetic resonance study of La_3X compounds and related phases

Non-standard antineutrino interactions at Daya Bay

Normal state nuclear magnetic resonance studies of the La_3In, La_3Tl compounds have been made in order to investigate the origin of the large temperature-dependent magnetic susceptibility. It is possible to analyse the different contributions to the susceptibility using Knight-shift and relaxation time T_1 measurements of In"1"1"5 and Tl"2"0"5 nuclei. The exchange enhancement of the spin-susceptibility chisub(pd) is of the same order as that found in A-15 compounds and the strong temperature-dependence of chi(T) is attributed to the presence of a peak in the electronic density of states near the Fermi level. The variation of the Knight-shift in the ternary alloys La_3Xsub(1-y)Xsub(y)sup(') is analogous to that observed in the corresponding La_3X phases, on the other hand the Knight-shift in the carbides La_3XC is temperature independent. (author).

298

New pulse sequence for simultaneous T1, T2, and RHO determination in whole-body proton MR imaging

We study the prospects of pinning down the effects of non-standard antineutrino interactions in the source and in the detector at the Daya Bay neutrino facility. It is well known that if the non-standard interactions in the detection process are of the same type as those in the production, their net effect can be subsumed into a mere shift in the measured value of the leptonic mixing angle theta_13. Relaxing this assumption, the ratio of the antineutrino spectra measured by the Daya Bay far and near detectors is distorted in a characteristic way, and good fits based on the standard oscillation hypothesis are no longer viable. We show that, under certain conditions, three years of Daya Bay running can be sufficient to provide a clear hint of non-standard neutrino physics.

2011-01-01

299

Magnetic properties of ErPd_2Si_2 from magnetization Moessbauer and neutron diffraction measurements

A newly developed method to support tissue characterization in routine MR imaging is presented. It represents a compromise between the practical requirements of clinical routine (short measurement time, multisection imaging) and the necessary accuracy of the relaxation parameter evaluation. The sequence employed is a modification of the PHAPS technique and works with two excitation pulses. It allows the simultaneous acquisition of all measurement data for the subsequent T1, T2, and rho evaluations. T1 is determined with a specially designed computation formula based on four signal ratios. A multiexponential T2 analysis is performed with use of 28 echoes. From these parameters, relative proton density can be computed.

300

Loading of wellbores with explosives

Magnetization, neutron diffraction and "1"6"6Er Moessbauer measurements on ErPd_2Si_2 are reported. Below 4.8 K ErPd_2Si_2 orders AF with complex modulated magnetic structures, where the Er moments are aligned along the c-axis. At 1.5 K a squared structure with #mu#_E_r #approx# 7.8(1)#mu#_B is found while a saturation Er moment of 8.2(2)#mu#_B is inferred from the hyperfine field data. The temperature dependence of the Moessbauer spectra in the paramagnetic region is explained in the framework of a relaxation model implying excited crystal field levels. Its analysis is used to estimate the B"m_n CEF parameters. (orig.).

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

301

Junction conditions in General Relativity with spin sources

Bags of explosive are loaded rapidly into deep wellbores by suspending a rigid positioning tube partway into the wellbore, and loading the bags into the tube, the bags being prevented from dropping through the open bottom end of the tube by a cord attached to the lowermost bag and secured at the upper end of the tube when the tube-suspending cable is in tension by a cordsecuring/releasing means, E.G., a pivotable bar having a hook on one end. When the bag-laden tube is lowered to the bottom of the wellbore, or to a column of bags previously placed therein, the tension on the cable is relaxed and the cord is released, allowing the positioning tube thereafter to be raised to the surface for re-use, leaving the cord and bags in the wellbore. Freedom of the bag-supporting cord to move with respect to the positioning tube when the latter is raised to the surface is assured by threading the cord through plastic tubing mounted to the wall of the positioning tube and ...

1983-04-26

302

Investigations for judging the working behaviour of components made of alloy 800 and alloy 617 under creep stress. Untersuchungen zur Beurteilung des Betriebsverhaltens kriechbeanspruchter Bauteile aus Alloy 800 und Alloy 617

The junction conditions for General Relativity in the presence of domain walls with intrinsic spin are derived in three and higher dimensions. A stress tensor and a spin current can be defined just by requiring the existence of a well defined volume element instead of an induced metric, so as to allow for generic torsion sources. In general, when the torsion is localized on the domain wall, it is necessary to relax the continuity of the tangential components of the vielbein. In fact it is found that the spin current is proportional to the jump in the vielbein and the stress-energy tensor is proportional to the jump in the spin connection. The consistency of the junction conditions implies a constraint between the direction of flow of energy and the orientation of the spin. As an application, we derive the circularly symmetric solutions for both the rotating string with tension and the spinning dust string in three dimensions. The rotating string with tension ...

2006-01-01

303

Investigations for judging the working behaviour of components made of alloy 800 and alloy 617 under creep stress

The program introduced here for determining and describing the multi-axial creep of pipes is based, on the one hand, on the results of the nuclear process heat prototype plant material program and, on the other hand, on the possible load conditions which arise for evaluating accidents or extreme working situations. The basis of a theoretical description of multi-axial creep is the invariant theory in which both the von Mises configuration change hypothesis and the Norton creep law are included. Combined tension and torsion are also considered in detail, the superimposition of cyclic stresses in the tensile threshold area is discussed and cases of partial relaxation are explained. Experimental results for the discussed loads are introduced, which have led to satisfactory agreement between theory and experiment. (orig./MM).

1987-01-01

304

Internal strain and texture evolution during deformation twinning in magnesium

The program introduced here for determining and describing the multi-axial creep of pipes is based, on the one hand, on the results of the nuclear process heat prototype plant material program and, on the other hand, on the possible load conditions which arise for evaluating accidents or extreme working situations. The basis of a theoretical description of multi-axial creep is the invariant theory in which both the von Mises configuration change hypothesis and the Norton creep law are included. Combined tension and torsion are also considered in detail, the superimposition of cyclic stresses in the tensile threshold area is discussed and cases of partial relaxation are explained. Experimental results for the discussed loads are introduced, which have led to satisfactory agreement between theory and experiment. (orig./MM).

1987-11-27

305

Impact properties of low alloy TRIP steels; Teigokin TRIP ko no shogeki tokusei

The development of a twinned microstructure in hexagonal close-packed rolled magnesium compressed in the in-plane direction has been monitored in situ with neutron diffraction. The continuous conversion of the parent to daughter microstructure is tracked through the variation of diffraction peak intensities corresponding to each. Approximately 80% of the parent microstructure twins by 8% compression. Elastic lattice strain measurements indicate that the stress in the newly formed twins (daughters) is relaxed relative to the stress field in the surrounding matrix. However, since the daughters are in a plastically 'hard' deformation orientation, they quickly accumulate elastic strain as surrounding grains deform plastically. Polycrystal modeling of the deformation process provides insight about the crystallographic deformation mechanism involved.

2005-06-15

306

Hybrid Camera Surveillance System Using Robust Human Detection

The impact properties of high-strength low alloy TRIP steels such as 'TRIP-aided dual-phase steel' and 'TRIP-aided bainitic steel' associated with the transformation-induced plasticity (TRIP) of retained austenite were investigated for some applications to the automotive impact members. The TRIP steels possessed far higher impact absorbed value and lower ductile-brittle transition temperature than the conventional ferrite-martensite and ferrite-pearlite steels. The stress relaxation resulting from the strain-induced transformation of retained austenite islands or films improved the impact properties in terms of suppressing void and/or crack initiation and these propagation. The best impact properties were completed in the steel composing of uniform fine bainitic lath structure and a large amount of stable interlath retained austenite films. (author)

2000-08-01

307

How Much Does the Midline Incision Add to Urethral Diameter After Tubularized Incised Plate Urethroplasty? An Experimental Animal Study

We propose a novel surveillance system that uses hybrid camera network. The system contains a panorama camera and PTZ cameras to take the wide range images and face images at high enough resolution for identification tasks. The robust human detection methods include robust background subtraction method (RRC), skin color segmentation and face tracking method. First, the system detects persons from a panorama image, and then the detailed face images are obtained with the PTZ cameras. The PTZ cameras can track the faces using the four directional features and the relaxation matching. In addition, the system has automatic camera position calibration feature. Thus, the user can use the system without any troublesome settings.

2007-01-01

308

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PurposeWe objectively quantified the gain in urethral diameter and the effect of stenting after tubularized incised plate urethroplasty in a rabbit hypospadias model. Materials and MethodsWe created a hypospadias model in 12 New Zealand white male rabbits by excising the ventral urethra. A 3 cm tattoo line was made longitudinally in the dorsal urethral plate midline. Two weeks later a 2 cm relaxing incision was made in the middle part of the tattooed line. The stretched incision width between the tattooed edges was measured, followed by urethral plate tubularization. Six rabbits were stented and 6 were nonstented. Two weeks later the animals were sacrificed and the distance separating the tattoo was measured at the midpoint of the tattooed line. Transverse sections at this point were exami...

2011-01-01

309

High-temperature property data: Ferrous alloys

Furnace for rapid change of temperature for neutron diffraction

In this book over 250 alloys are organized by AISI number into 10 major sections: Irons, Carbon Steels, Alloy Steels, Low Alloy Constructional Steels, Ultra High Strength Steels, Tool Steels, Maraging Steels, Wrought Stainless Steels, Heat Resistnat Casting Alloys, and Iron Based Rought Superalloys. Each alloy record lists the designation, specifications, UNS number, composition, product forms and a comment on the high-temperature properties and applications. Referenced data is then given for physical properties such as density, specific heat, thermal conductivity, thermal expansion, electrical conductivity, Poisson's ratio, moduli of elasticity and rigidity, etc. Mechanical properties follow, and include tensile properties, shearing and bearing properties, impact properties, creep, stress rupture and stress relaxation and fatigue properties. The last part of the alloy record gives other effects of temperature, such as hot hardness, corrosion, and growth.

1987-01-01

310

Formation of pentagonal Cu nano wires

A new furnace for neutron diffraction experiments is capable of heating and cooling a sample very rapidly. The rapid heating is done by two circular infrared lamps placed over and under a sample, whose radiation is roughly focused on the sample by a reflector. The rapid cooling is done by high-pressure gas blows against the sample from two circular nozzles which are also placed over and under the sample. This system enables us to obtain the heating rate of over 1000"0C/min and cooling rate of -500"0C/min for an alloy of 10 mm diameter and 30 mm length. The performance is sufficient to carry out some kinetics measurements in real-time neutron diffraction by the use of a position-sensitive detector. This kind of experiment is demonstrated by the observation of the relaxation process of order--disorder transitions in CuZn and Ni_3Mn alloys.

311

Dynamical Quasi-Stationary States in a system with long-range forces

The development of nano/molecular devices will require atomic-sized electrical contacts or nano metric conductors for wiring. As metal nano wires exhibit quantized conductance at room temperature, quantum transport effects will play an important role in the practical implementation of nano devices. As copper is currently used as interconnecting metal in standard microelectronics, the characterization of Cu nano wire properties deserves special attention. In this work, we show a detailed study of structural and electronic properties of atomic-sized Cu wires. In particular, we have established a complete correlation between the conductance and the structure by associating real-time atomic resolution transmission electron microscopy imaging with molecular dynamic simulations, conductance measurements and conductance calculations. Our study has revealed the structural relaxation of Cu wires forming a pentagonal atomic arrangement along the [110] direction that allows a ...

2004-07-01

312

Drift-kink instability induced by beam ions in field-reversed configurations

The Hamiltonian Mean Field model describes a system of N fully-coupled particles showing a second-order phase transition as a function of the energy. The dynamics of the model presents interesting features in a small energy region below the critical point. In particular, when the particles are prepared in a ``water bag'' initial state, the relaxation to equilibrium is very slow. In the transient time the system lives in a dynamical quasi-stationary state and exhibits anomalous (enhanced) diffusion and L\\'evy walks. In this paper we study temperature and velocity distribution of the quasi-stationary state and we show that the lifetime of such a state increases with N. In particular when the $N\\to \\infty$ limit is taken before the $t \\to \\infty$ limit, the results obtained are different from the expected canonical predictions. This scenario seems to confirm a recent conjecture proposed by C.Tsallis.

2001-01-01

313

Dielectric properties of sols of silver nanoparticles capped by alkyl carboxylate ligands

The drift-kink instability in field-reversed configurations with a beam component is investigated by means of a three-dimensional particle simulation. The unstable mode with the toroidal mode number n=4 grows with the rate {gamma} {approx} 0.1 - 1.0{omega}{sub ci} for a strong beam current and deforms the plasma profile along the beam orbit in the vicinity of the field-null line. This mode is nonlinearly saturated as a result of the relaxation of current profile. Both the saturation level and the growth rate tend to increase as the ratio of the beam current to the plasma current I{sub b}/I{sub p} increases. It is also found that there is a threshold value of the beam velocity {upsilon}{sub b} {approx} {upsilon}{sub Ti} (ion thermal velocity) for the excitation of the instability. (author)

1999-04-01

314

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Sols of silver nanoparticles in toluene were studied by broadband dielectric spectroscopy (10?3?105 Hz). The frequency dependences of the specific alternating current (ac) conductivity and the complex electric modulus were used to estimate the temperature/frequency intervals of long- and short-range charge transfer occurs, respectively. A considerable increase (by more than 30 ?C) in the Vogel temperature T 0 and the glass transition temperature T g in sols compared with the pure solvent was found. It can be hypothesized that these cooperative effects reflect the initial stage of the superlattice formation. Although the dielectric characteristics of sols are generally controlled by the conductivity relaxation, the dielectric response was observed in the high-frequency range (1?103 Hz) at l...

2011-01-01

315

Dielectric abnormities in BaTi_0_._9(Ni_1_/_2W_1_/_2)_0_._1O_3 giant dielectric constant ceramics

Dependence of the evolution of the cavity radiation of a coherently pumped correlated emission laser on dephasing and phase fluctuation

BaTi_0_._9(Ni_1_/_2W_1_/_2)_0_._1O_3 ceramics were fabricated and their dielectric properties were investigated. With the sintering temperature increasing from 1250 to 1280 deg. C, the grain size abruptly increases from 1-2 to 20-40 #mu#m, accompanying significant changes in dielectric response. The samples with larger grains exhibit giant dielectric constant characteristics, which are considered to be mainly attributed to the domain boundary effect. The activation energies of the dielectric relaxation E_r_e_l_a_x=0.325 eV reveal the existence of microdomains in larger grains. The ac conductivity results also give the evidence of the domain boundary effect in the present ceramics.

2007-07-30

316

Computational study of non-stationary cluster size distribution and rate of nucleation in case of pre-existing clusters

Analysis of the dynamics of the cavity radiation of a coherently pumped correlated emission laser is presented. The phase fluctuation and dephasing are found to affect the time evolution of the two-mode squeezing and intensity of the cavity radiation significantly. The intensity and degree of the two-mode squeezing increase at early stages of the process with time, but this trend changes rapidly afterwards. It is also shown that they increase with phase fluctuation and dephasing in the strong driving limit, however the situation appears to be opposite in the weak driving limit. This essentially suggests that the phase fluctuation and dephasing weaken the coherence induced by a strong driving mechanism so that the spontaneous emission gets a chance. The other important aspect of the phase fluctuation, in this regard, is the relaxation of the time at which the maximum squeezing is manifested as well as the time in which the radiation remains in a squeezed state.

2010-01-01

317

Collisionless driven reconnection in an open system

The dynamics of a cluster-type system formed by constant total number of molecules, M, is studied when clusters change their sizes by nearest-size transitions (the Szilard model) with time-dependent boundary conditions and non-zero initial cluster size distribution. We compare these results to those reported previously, when non-stationary cluster size distribution was considered under the condition that only monomers are present in the system at the initial moment t=0, and describe the effect of arbitrary pre-existing clusters on the time evolution of the interacting clusters with different sizes, n. The average group size problem is also solved, and the process of relaxation in the system is studied. authors)

318

Chemistry between crosslinks affects the properties of peptide hydrogels

Particle simulation studies of collisionless driven reconnection in an open system are presented. Collisionless reconnection evolves in two steps in accordance with the formation of two current layers, i.e., an ion current layer in the early ion phase and an electron current layer in the late electron phase. After the electron current layer is formed inside the ion current layer, the system relaxes gradually to a steady state when convergent plasma flow is driven by an external electric field with a narrow input window. On the other hand, when the convergent plasma flow is driven from the wide input window, magnetic reconnection takes place in an intermittent manner, due to the frequent formation of magnetic islands in the vicinity of neutral sheet. (author)

2000-06-01

319

British Library Electronic Table of Contents (United Kingdom)

Protein hydrogels were prepared by substituting ovalbumin with different concentrations of ethyl vinyl sulfone (EVS) or acrylic acid (AA) and crosslinking with divinyl sulfone (DVS). Fourier transform-infrared (FT-IR) spectroscopic studies confirmed the addition of EVS, AA, and DVS onto the protein. Swelling was assessed as a function of pH in the range of 2.5 to 9.4 and ionic strength. The elastic modulus of the gels was determined in shear and compression. Stress relaxation was assessed in compression. The substituent highly affected swelling and modulus with both hydrogels displaying non-Gaussian behavior in the range of hydrogel environments studied. Acrylic acid substituted ovalbumin exhibited a decreasing modulus with increasing swelling behaving as a polyelectrolyte with low added s...

2011-01-01

320

Chemical isomeric effects on propanol glassy structures

Chemical isomeric effects on propanol glassy structures

We have studied the structure of both propanol isomers in their glassy and crystalline states by neutron diffraction. The glass-transition temperatures of 1- and 2-propanol are about 98 and 115 K, respectively and, surprisingly, even larger differences are observed for the melting temperatures of the stable crystals, which are 148 and 185 K, respectively. Their supercooled liquid phases show rather different relaxation spectra, 1-propanol manifesting strong deviations from Debye behavior, whereas 2-propanol shows a far weaker effect. We discuss the spectra obtained for the static structure factor and the static pair correlation function D(r). There is a noticeable difference in the position of the first sharp diffraction peak, which clearly indicates a density change, well correlated with the period of the intermolecular oscillations shown by D(r). (orig.)

2002-07-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

321

Calculation of the hyperfine constants of the V sub (K) center in CaF_2, SrF_2 e BaF_2

We have studied the structure of both propanol isomers in their glassy and crystalline states by neutron diffraction. The glass-transition temperatures of 1- and 2-propanol are about 98 and 115 K, respectively and, surprisingly, even larger differences are observed for the melting temperatures of the stable crystals, which are 148 and 185 K, respectively. Their supercooled liquid phases show rather different relaxation spectra, 1-propanol manifesting strong deviations from Debye behavior, whereas 2-propanol shows a far weaker effect. We discuss the spectra obtained for the static structure factor and the static pair correlation function D(r). There is a noticeable difference in the position of the first sharp diffraction peak, which clearly indicates a density change, well correlated with the period of the intermolecular oscillations shown by D(r). (orig.)

322

Broad-linewidth laser absorption measurements of oxygen between 211 and 235nm at high temperatures

The magnetic hyperfine constants of the V sub(K) center in CaF_2, SrF_2 and BaF_2 have been calculated, assuming a phenomenological model, based on the F"-_2 'central molecule', to describe the wave function of the defect. The introduction of covalence with the ions neighboring the 'central molecule', has shown that this is a better description for the defect than a simple 'central molecule' model. It was also shown that the results for the hyperfine constants are strongly dependent on the relaxations of these neighboring ions, which have been determined by fitting the experimental data. The present results are compared with other previous calculations where similar and different methods have been used. A better description for the wave function of the defect is suggested. (author).

2004-06-02

323

British Library Electronic Table of Contents (United Kingdom)

Absorption coefficient data are presented for molecular oxygen at temperatures between 1100 and 2000K and discrete wavelengths between 211 and 235nm. Measurements were made behind reflected shock waves using broad-linewidth ultraviolet laser radiation generated from a frequency-quadrupled, tunable, pulsed Ti:Sapphire laser. Test mixtures consisting of 15% O"2, 15% He and balance Ar were used to minimize the influence of vibrational relaxation on the reflected shock temperature. The experimental results are in good agreement with theoretical calculations and confirm that discrete features from the Schumann-Runge system dominate between 211 and 235nm at temperatures higher than 1100K.

2011-01-01

324

Beyond Acid Suppression: New Pharmacologic Approaches for Treatment of GERD

British Library Electronic Table of Contents (United Kingdom)

Proton pump inhibitors are highly successful in treating gastroesophageal reflux disease, but a significant proportion of patients have persistent symptoms from weakly or nonacidic reflux. Transient lower esophageal sphincter relaxation (TLESR) represents the dominant mechanism of gastroesophageal reflux and has therefore become the most intensely investigated therapeutic target. The triggering of TLESR involve the vagal pathways and the ?-aminobutyric type B (GABA(B)) and metabotropic glutamate type 5 (mGluR5) receptors. Baclofen is a GABA(B) receptor agonist that is effective in inhibiting TLESR and reducing the number of reflux episodes, but is associated with significant central nervous system (CNS) side effects. The newer GABA(B) agonists, such as AZD9343 and AZD3355, and mGluR5 antag...

2010-01-01

325

Anomalous properties of the local dynamics in polymer glasses

Analysis of the mechanical properties of metal-ceramic interfaces using the four-point bending test: application to dental metal-ceramic couples (Pd-Ag, Pd-Au)

The emergence of nanoscience has increased the importance of experiments able to probe the very local structure of materials, especially for disordered and heterogeneous systems. This is technologically important; for example, the nanoscale structure of glassy polymers has a direct correlation with their macroscopic physical properties. We have discovered how a local, high frequency dynamic process can be used to monitor and even predict macroscopic behavior in glassy polymers. Polyvinylethylenes vitrified by different chemical and thermodynamic pathways exhibit different densities in the glassy state. We find that the rate and amplitude of a high frequency relaxation mode (the Johari-Goldstein process involving local motion of segments of the chain backbone) can either correlate or anti-correlate with the density. This implies that neither the unoccupied (free) volume nor the configurational entropy governs the local dynamics in any general sense. Rather it is the ...

2008-01-01

326

Analysis of possibilities of concentrating mine operation in deep coal mines on the example of the Halemba mine

Different semi precious alloys (Pd-Ag, Pd-Au) have been studied after thermal oxidation treatments to analyze the mechanical improvement of the interface between the metal and the ceramic. Using the four point bending test, the authors have analyzed the different steps corresponding to the mechanical evolution of the bi-material : cracking energy on the surface, relaxation energy after first cracking, propagation energy of cracks at the interface zone. It has been shown that some alloys only have a high resistance to the interface cracking and the role played by the interface reactions to improve this property. (orig.).

1993-06-01

327

A unified framework for biological evolution and stochastic quantization

Discusses longwall mining in the Halemba mine with mining depth to 1,000 m and coal seams prone to rock bursts. Since 1985 the Halemba mine has been characterized by the highest rock burst hazards in Poland. Rock burst hazards are associated with large mining depth, complicated geology, rock strata structure, natural rock burst hazards, high coal output of longwall faces and high advance rate. Methods for rock burst forecasting (test borehole drilling, measuring volume of cuttings from each test borehole, acoustic monitoring, etc.) and methods for rock burst control (stress relaxation by shock blasting) are analyzed. Effects of face advance rate on degree of rock burst hazard and stress concentration in a coal ribside are investigated. The increase achieved in longwall advance and coal production is pointed out.

1992-12-31

328

ent-Rosane and abietane diterpenoids as cancer chemopreventive agents

We investigate the profound relation between the equations of biological evolution and quantum mechanics by writing a biologically inspired equation for the stochastic dynamics of an ensemble of particles. Interesting behavior is observed which is related to a new type of stochastic quantization. We find that the probability distribution of the ensemble of particles can be decomposed into eigenfunctions associated to a discrete spectrum of eigenvalues. In absence of interactions between the particles, the out-of-equilibrium dynamics asymptotically relaxes towards the fundamental state. This phenomenon can be related with the Fisher theorem in biology. On the contrary, in presence of scattering processes the evolution reaches a steady state in which the distribution of the ensemble of particles is characterized by a Bose-Einstein statistics. In order to show a concrete example of this stochastic quantization we have solved explicitly the case in which the potential ...

2010-01-01

329

British Library Electronic Table of Contents (United Kingdom)

Two ent-rosane- (cuzcol, 1 and 6-dehydroxycuzcol, 2) and a abietatriene- (salvadoriol, 3) type diterpenoids have been isolated from Maytenus cuzcoina and Crossopetalum uragoga, respectively, along with five known diterpene compounds (4-8). Their stereostructures have been elucidated on the basis of spectroscopic analysis, including 1D and 2D NMR techniques, and computational data. The absolute configuration of cuzcol was determined by application of Riguera ester procedure. This is the first instance of isolation of ent-rosane diterpenoids from species of the Celastraceae. The isolated diterpenes were found to be potent anti-tumour-promoter agents, and carnosol (7) also showed a remarkable chemopreventive effect in an in vivo two-stage carcinogenesis model.

2011-01-01

330

The use of domestic microwave oven in experimental classes of organic chemistry: salicylaldehyde nitration; O uso de aparelhos de micro-ondas domesticos em aulas experimentais de quimica organica: nitracao de salicilaldeido

Synthesis, Herbicidal Activities and Comparative Molecular Field Analysis Study of Some Novel Triazolinone Derivatives

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)

2010-07-01

331

British Library Electronic Table of Contents (United Kingdom)

A series of novel triazolinones were synthesized and their structures were characterized by 1H NMR, elemental analysis and single-crystal X-ray diffraction analysis. The herbicidal activities were evaluated against Echinochloa crusgalli (L.) Beauv., Digitaria adscendens, Brassica napus and Amaranthus retroflexus. The herbicidal activity data indicated that the title compounds had higher activities with substituted benzyl group moieties than with other groups such as sulfonyl, alkyl, etc. To further investigate the structure-activity relationship, comparative molecular field analysis was performed on the basis of herbicidal activity data. Both the steric and electronic field distributions of comparative molecular field analysis are in good agreement in this work. The results showed that a b...

2009-01-01

332

Structure and antimicrobial activity relationship of quaternary N-alkyl chitosan derivatives against some plant pathogens

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...

2010-01-01

333

Solvothermal Synthesis of a New Photochromic Azo Polymer and its Self-assembly Behavior

British Library Electronic Table of Contents (United Kingdom)

An amphiphilic azobenzene diblock copolymer {2-[4-(4-methoxy phenyl azo)phenoxy]hexyl acrylate co-acrylic acid} was synthesized via reversible addition-fragmentation chain transfer polymerization in a hydrothermal reactor. The products were characterized by 1H-NMR, DSC, GPC and UV-Vis spectroscopy. Different self-assembly behaviors of this amphiphilic diblock copolymer in different organic solvent with different water content were investigated. In THF/H2O solution, the diblock copolymer self-assembled into spheres and the spheres would then change to vesicles with smaller size by increasing the volume of H2O. However, in DMSO/H2O solution, the sizes and morphologies of the self-assembled spheres would not change significantly with an enhanced amount of H2O. Photochromic behaviors of the am...

2010-01-01

334

Preparation and characterization of a novel polymeric based solid-solid phase change heat storage material

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.

1997-10-01

335

Premnalatifolin A, a novel dimeric diterpene from Premna latifolia Roxb

Here we reported a two-step procedure for preparing a novel polymeric based solid-solid phase change heat storage material. Firstly, a copolymer monomer containing a polyethylene glycol monomethyl ether (MPEG) phase change unit and a vinyl unit was synthesized via the modification of hydrogen group of MPEG. Secondly, by copolymerization of the copolymer monomer and phenyl ethylene, a novel polymeric based solid-solid phase change heat storage material was prepared. The composition, structure and properties of the novel polymeric based solid-solid phase change material were characterized by IR, "1H NMR, DSC, WAXD, and POM, respectively. The results show that the novel polymeric based solid-solid phase change material possesses of excellent crystal properties and high phase change enthalpy.

2009-06-01

336

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.

2011-01-01

337

Preliminary studies on the chemical characterization and antioxidant properties of acidic polysaccharides from Sargassum fusiforme

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...

2008-01-01

338

Polyester and multiwalled carbon nanotube composites: characterization, electrical conductivity and antibacterial activity

British Library Electronic Table of Contents (United Kingdom)

Abstract Poly(butylene terephthalate) (PBT) composites containing multiwalled carbon nanotubes (MWCNTs) were prepared using a melt-blending process and used to examine the effects on the composite structure and properties of replacing PBT with acrylic acid-grafted PBT (PBT-g-AA). PBT-g-AA and multihydroxyl-functionalized MWCNTs (MWCNTs-OH) were used to improve the compatibility and dispersibility of the MWCNTs within the PBT matrix. The composites were characterized morphologically using transmission electron microscopy, and chemically using Fourier transform infrared, solid-state 13C NMR and UV-visible absorption spectroscopy. The antibacterial and electrical conductivity properties of the composites were also evaluated. MWCNTs or MWCNTs-OH enhanced the antibacterial activity and electric...

2011-01-01

339

Palladium polypyridyl complexes: synthesis, characterization, DNA interaction and biological activity on Leishmania (L.) mexicana

Oxidation of polycaprolactone to induce compatibility with other degradable polyesters

This paper describes the search for new potential chemotherapeutic agents based on transition metal complexes with planar ligands. In this study, palladium polypyridyl complexes were synthesized and characterized by elemental analysis, NMR, UV-VIS and IR spectroscopies. The interaction of the complexes with DNA was also investigated by spectroscopic methods. All metal-to-ligand charge transfer (MLCT) bands of the palladium polypyridyl complexes exhibited hypochromism and red shift in the presence of DNA. The binding constant and viscosity data suggested that the complexes [PdCl{sub 2}(phen)] and [PdCl{sub 2}(phendiamine)] interact with DNA by electrostatic forces. Additionally, these complexes induced an important leishmanistatic effect on L. (L.) mexicana promastigotes at the final concentration of 10 {mu}mol L{sup -1} in 48 h. (author)

2008-07-01

340

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...

2007-01-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

341

Nuclear magnetic resonance on oriented "1"7"5Ta and "1"7"7Ta

Neutron powder diffraction and solid-state deuterium NMR studies of Ca{sub 2}RuD{sub 6} and the stability of transition metal hexahydride salts

"1"7"5Ta and "1"7"7Ta nuclei were oriented at low temperature as dilute impurities in Fe. The magnetic hyperfine splitting frequencies #nu#="+#mu#B sub(HF)/Ih"+ of the "1"7"5Ta and "1"7"7Ta 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 "1"8"1Ta in Fe, the magneticmoments have been deduced: "+#mu#("1"7"5Ta, 7/2"+)"+=2.270(45) and "+#mu#("1"7"7Ta, 7/2"+)"+=2.250(45)#mu# sub(N). These values of the magnetic moments are discussed in the framework of the rotational model. (author).

342

Neutron powder diffraction and solid-state deuterium NMR studies of Ca2RuD6 and the stability of transition metal hexahydride salts

The crystal structure of Ca{sub 2}RuD{sub 6} has been determined by neutron powder diffraction: space group Fm3m, K{sub 2}PtCl{sub 6} 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 340 K and 50 K. The deuterium nuclear quadrupole coupling constant, 54.7 kHz, leads to an ionic character of the Ru-D bond of 76%. The known trends in the behaviour of A{sub 2}MH{sub 6} salts are interpreted in terms of the ionization energies of the cation and the central metal atom.

2008-07-28

343

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.

2008-01-01

344

In situ ligand exchange of thiol-capped CuInS2/ZnS quantum dots at growth stage without affecting luminescent characteristics

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.

2011-01-01

345

Hydrocracking of Arabian mix asphaltenes in the presence of modified red mud

Heteropolyanion-based ionic hybrid solid: A green bulk-type catalyst for hydroxylation of benzene with hydrogen peroxide

Asphaltenes precipitated from an Arabian Mix vacuum residue were hydrocracked in a batch autoclave at 435 and 460{degree}C for 5-90 min. Experiments without catalyst, with modified red mud and with an industrial Co Mo/Al{sub 2}O{sub 3} catalyst were compared. The products were fractionated into gas, naphtha, oil, asphaltenes and coke. Feed asphaltenes and several product fractions were characterised by elemental analysis, by average molecular mass and by {sup 1}H n.m.r. Due to the hydrogenation activity, both catalysts caused - with similar efficiency - the decrease of coke formation and the increase of quantity and quality of oil. 21 refs., 9 figs., 5 tabs.

1996-11-01

346

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...

2011-01-01

347

Fullerene-Derivatized Amino Acids: Synthesis, Characterization, Antioxidant Properties, and Solid-Phase Peptide Synthesis

British Library Electronic Table of Contents (United Kingdom)

A series of [60]fullerene-substituted phenylalanine (Baa) and lysine derivatives have been prepared by the condensation of 1,2-(4prime-oxocyclohexano)fullerene with the appropriately protected (4-amino)phenylalanine and lysine, respectively. Conversion of the imine to the corresponding amine is achieved by di-acid catalyzed hydroboration. The reduction of the imine is not accompanied by hydroboration of the fullerene cage. The [70]fullerene phenylalanine derivative has also been prepared as have the di-amino acid derivatives. The compounds were characterized by MALDI-TOF mass spectrometry, UV/Vis spectroscopy, and cyclic voltammetry. 1H and 13C NMR spectroscopy allowed the observation of diastereomers. Fullerene-substituted peptides may be synthesized on relatively large scale by solid-pha...

2007-01-01

348

Flavonols and an oxychromonol from Piliostigma reticulatum

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,-...

2008-01-01

349

Five naturally bioactive molecules including two rhamnopyranoside derivatives isolated from the Streptomyces sp. strain TN58

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.

2009-01-01

350

Control of biofilm formation in marine environment using some N{sub 2}O{sub 2} donor Schiff bases

Complexation of nitrogen and sulphur donor Schiff's base ligand to Cr(III) and Ni(II) metal ions: Synthesis, spectroscopic and antipathogenic studies

The adhesion of microorganisms onto materials surface mediated by extracellular polymeric substances (EPS) lead to an important modification of the metal-solution interface. The requirement of modern civilization with the heightened sense of environmental responsibilities and quality of life can be met by using some eco-friendly microbiocides with different spectra of activity. Some N{sub 2}O{sub 2} donor Schiff base compounds were synthesized and characterized by IR, NMR and ESR spectroscopy. These compounds were found effective in controlling the growth of biofilm of E. coli, Pseudomonas fluorescens and Thiobacillus thiooxidans on copper surface. The optimum concentration of these compounds are in the range of 1--10 ppm. Various electrochemical, microbiological and surface-analytical techniques were used to monitor the biofilm in the presence of microbiocides.

1997-08-01

351

British Library Electronic Table of Contents (United Kingdom)

2,6-Diacetyl pyridine based ligand was synthesized by the reaction of 2,6-diacetyl pyridine with thiocarbohydrazide in presence of acetic acid. The coordination compounds with Cr(III) and Ni(II) metal ions having [Cr(L)X]X2 and [Ni(L)X]X compositions (where L=ligand and X=NO3^-, Cl^- and CH3COO^-) were synthesized and characterized by physicochemical and spectral studies. The studies like elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, UV-Vis, NMR, mass and EPR reveal that the complexes are octahedral. The compounds were examined against the pathogenic fungal and bacterial strains like Alternaria brassicae, Aspergillus niger, Fusarium oxysporum, Xanthomonas compestris and Pseudomonas aeruginosa. A. niger causes the diseases Apergillosis and Oto...

2011-01-01

352

Chemical constituents of Galianthe brasiliensis (Spreng.) E.L.Cabral and Bacigalupo (Rubiaceae); Constituintes quimicos de Galianthe brasiliensis (Rubiaceae)

Chemical constituents and anti-inflammatory and antioxidant activities evaluation of the leaves extracts of Chomelia obtusa Cham. and Schltdl. (Rubiaceae)

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)

2006-05-15

353

Antibacterial iridoid glucosides from Eremostachys laciniata

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)

354

British Library Electronic Table of Contents (United Kingdom)

Eremostachys laciniata (L) Bunge (family: Lamiaceae alt. Labiatae; subfamily: Lamioideae) is one of the 15 endemic Iranian herbs of the genus Eremostachys. A decoction of the roots and flowers of E. laciniata has traditionally been taken orally for the treatment of allergies, headache and liver diseases. Three antibacterial iridoid glucosides, phloyoside I (1), phlomiol (2) and pulchelloside I (3) have been isolated from the rhizomes of this plant. The structures of these compounds were elucidated unequivocally by a series of 1D and 2D NMR analyses. The antibacterial activity and brine shrimp toxicity of these compounds were assessed using the resazurin microtitre assay and the brine shrimp lethality assay, respectively. All three iridoid glycosides 1-3 exhibited from low to moderate level...

2009-01-01

355

A nontoxic antitumour compound from the leaves of Bauhinia scandens characterized as 1-O-alkyl glycerol by gas-liquid chromatography and evaluation of its antitumour property by Brine Shrimp bioassay

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...

2008-01-01

356

A new vanadium Schiff base complex as catalyst for oxidation of alcohols

British Library Electronic Table of Contents (United Kingdom)

The monoanionic bidentate Schiff base, N-(phenolyl)-benzaldimine (HL), has been employed to synthesize a new vanadium(IV) complex of general composition [VO(L)2] (where L = O, N donor of Schiff base). The ligand and complex have been fully characterized by elemental analyses, molar conductance data, FT-IR, 1H- and 13C-NMR, and UV-Vis spectroscopies. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted by this complex catalyst using Oxone as oxidant under biphasic reaction conditions (CH2Cl2/H2O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature.

2010-01-01

357

Vibrational population dynamics in liquids and glasses: IR pump-probe experiments from 10 K to 300 K

Raman spectroscopic studies of liquid phase ordering and dynamics for solutions of ME6N liquid crystal: the approach to simple molecule behavior at high dilutions.

The temperature dependent vibrational relaxation of the CO stretching mode of Rhodium dicarbonyl acetylacetonate (Rh(CO){sub 2}(acac)) and tungsten hexacarbonyl (W(CO){sub 6}) in dibutylphthalate (DBP) and 2-methylpentane (2-MP) were measured with IR pump and probe (P-P) experiments. The experiments were performed with {approximately}1.5 ps pulses generated by the Stanford superconducting accelerator pumped free electron laser (FEL). Measurements were performed on the Rh(CO){sub 2}(acac) CO asymmetric stretching mode at {lambda} = 4.98{mu}m from 10 K to 300 K. Both the parallel and magic angle probe polarizations decay curves are biexponential over the entire temperature range. The slow component (ranging from 40 ps at 300 K to 55 ps at 10K) is attributed to the population relaxations. For the fast component (ranging from 4-5 ps at 300 K to 13-15 ps at 10K), we propose a mechanism of spectral diffusion, in contrast to the previously proposed ...

1995-12-31

358

Natural circulation reactor design safety analysis

We have measured the Raman isotropic profiles of the ?(C?N) band at 2235 cm(-1) for five solutions of ME6N (4-cyanophenyl-4'-hexylbenzoate) liquid crystal dissolved in CCl(4) in the range from x = 0.12 to 0.007 (x, mole fraction of ME6N) and then obtained the corresponding vibrational correlation functions, C(v)(t), by time Fourier transformation. The increase with dilution of the dephasing times ?(v) complies with the behavior of the nonmonotonic concentration dependence predicted by the fluctuation concentration model for this concentration range (x Rothschild, which, being based on the assumption that the environmental modulation is described by a stretched exponential decay e(-(t/?(0))(?)), is more appropriate for the interpretation of the vibrational correlation function arising from a distribution of relaxation processes caused, as in the present case, by the persistence of pseudonematic domains. With dilution the dispersion parameter ? and the average ...

2010-11-11

359

Electronic and geometric structure of transition-metal nanoclusters

This thesis study covers both global performance and local phenomena analyses focusing on natural circulation reactor design safety. Four important topics are included: the global SBWR design safety assessment, important local phenomena investigation, steady and transient natural circulation process study, and two-phase instability analysis. The conceptual design of the SBWR-200 is introduced in this thesis and the global performance of a natural circulation reactor is then assessed using PUMA integral test data and RELAP5 simulations. A safety assessment methodology is developed to evaluate the PUMA integral test data extrapolation and code scalability. The RELAP5 code simulation capability in low-pressure low-flow conditions is also validated. The study shows that the code is capable of predicting the global accident scenario in natural circulation reactors with reasonable accuracy, while failing to reproduce some safety related local phenomena. The natural circulation process is ...

2001-01-01

360

Dynamic mechanical and molecular weight measurements on polymer bonded explosives from thermally accelerated aging tests. III. Kraton block copolymer binder and plasticizers

A massively-parallel ab initio computer code, which uses Gaussian bases, pseudopotentials, and the local density approximation, permits the study of transition-metal systems with literally hundreds of atoms. We present total energies and relaxed geometries for Ru, Pd, and Ag clusters with N = 55, 135, and 140 atoms; we also used the DMOL code to study 13-atom Pd and Cu clusters, with and without hydrogen. The N = 55 and 135 clusters were chosen because of simultaneous cubo-octahedral (fcc) and icosahedral (icos) sub-shell closings, and we find icos geometries are preferred. Remarkably large compressions of the central atoms are observed for the icos structures (up to 6% compared with bulk interatomic spacings), while small core compressions ({approx} 1 %) are found for the fcc geometry. In contrast, large surface compressive relaxations are found for the fcc clusters ({approx} 2-3% in average nearest neighbor spacing), while the icos surface ...

1996-08-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

361

Dielectric dispersion study of Mn-doped PLZT (8/65/35)

The dynamic mechanical properties and molecular weight distribution of two experimental polymer bonded explosives, X-0287 and X-0298, maintained at 23, 60, and 74/sup 0/C for 3 years were examined. X-0287 is 97% 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane explosive, 1.8% Kraton G-1650, and 1.2% B/sup 2/ was 170. X-0298 is 97.4% explosive, 1.4% Kraton G-1650, and 1.2% Cenco Hi-vac oil. The relaxation associated with the Kraton rubber block glass transition is observed in both X-0287 and X-0298. In the unaged X-0298 it occurs at -59/sup 0/C and in the aged explosive at 50/sup 0/C. This is caused by migration of the oil plasticizer out of the explosive. In X-0287 the Kraton rubber block T/sub g/ is weak and broad due to the presence of the wax plasticizer. X-0287 has a second broad relaxation associated with the melting of the wax from 10 to 65/sup 0/C. The molecular weight of the Kraton binder decreased with increasing accelerated aging ...

1981-01-01

362

Development of MHD generator channel walls, 1

Mn-modified Pb0.92La0.08(Zr0.65Ti0.35)O3 (PLZT) was prepared chemically by a coprecipitate method using their respective nitrate salts and isopropoxides. Differential thermal analysis (DTA) and X-ray analysis clearly show the formation of PLZT single rhombohedral phase for samples calcined beyond 750 C. Uniform grain distribution was observed from scanning electron microscopic (SEM) studies and grain size was found to increase with Mn doping up to x=0.08 and then decreased. Dielectric measurement shows the decrease in peak transition temperature (TC) with Mn doping up to x=0.12 and then increase along with a sharp rise in dielectric maxima. A diffuse dielectric dispersion is observed in all the compositions. A detailed dispersion study was carried out using the Vogel-Fulcher empirical relation, a universal relaxation law and the Havriliak-Negami function. The Vogel-Fulcher relation fitting parameters of activation energy and freezing temperature were found to ...

2009-07-01

363

A density functional study of atomic hydrogen and oxygen chemisorption on the relaxed (0001) surface of double hexagonal close packed americium

Experimental results of compatibility tests on ceramics-metal bonded structures performed under high heat flux conditions in splash test apparatus are reported. Emphasis is placed on results of the channel wall design and its critical operating conditions under MHD environment. The module design of one cold type and three semihot type insulators have been tested. These materials were Al_2O_3, Al_2MgO_4, LaAlO_4, MgO and Sialon ceramics. The methods of cold type ceramics-metal bonding structure were studied on Al_2O_3 and Spinel spray coating technology. The refractory metallizing and ceramics-metal graded structure manufactured by HIP technologies were applied to bonding between the MgO or LaAlO_4 and metallic cooling system. The Sialon non-bonding structure was tested with mechanical supported cooling system by shrinc fitting method. The results indicated that the bonding structures made of the MgO(MG-S) with Copper and Fe-Ni Alloy relaxation layers and MgO(MG-NC) ...

364

{alpha}- and {beta}-Cyclodextrin [2]rotaxanes with (diethylenetriamine)platinum(II) stoppers

Ab initio total energy calculations within the framework of density functional theory have been performed for atomic hydrogen and oxygen chemisorption on the (0001) surface of double hexagonal packed (dhcp) americium using a full-potential all-electron linearized augmented plane wave plus local orbitals method. Chemisorption energies were optimized with respect to the distance of the adatom from the relaxed surface for three adsorption sites, namely top, bridge, and hollow hcp sites, the ad-layer structure corresponding to the coverage of a 0.25 monolayer in all cases. Chemisorption energies were computed at the scalar-relativistic level (no spin-orbit coupling NSOC) and at the fully relativistic level (with spin-orbit coupling SOC). The two-fold bridge adsorption site was found to be the most stable site for O at both the NSOC and SOC theoretical levels with chemisorption energies of 8.204 eV and 8.368 eV respectively, while the three-fold hollow hcp adsorption ...

2008-02-01

365

Temperature-induced fusion of small unilamellar vesicles formed from saturated long-chain lecithins and diheptanoylphosphatidylcholine

A series of dinuclear platinum(II) complexes, [(dien)Pt(NH{sub 2}(CH{sub 2}){sub n}NH{sub 2})Pt(dien)]Cl{sub 4} (dien = diethylenetriamine, n = 8, 9, 10, and 12) and their corresponding [2]rotaxanes with {alpha}-cyclodextrin ({alpha}-CD), [(dien)Pt{l_brace}NH{sub 2}(CH{sub 2}){sub n}NH{sub 2}{center_dot}{alpha}-CD{r_brace}Pt(dien)]Cl{sub 4}, have been synthesized and characterized by {sup 1}H, {sup 13}C, and {sup 195}Pt NMR spectroscopy and electrospray mass spectrometry. The rotaxanes were prepared by reacting the {l_brace}NH{sub 2}(CH{sub 2}){sub n}NH{sub 2}{center_dot}{alpha}-CD{r_brace} pseudorotaxanes with [Pt(dien)]Cl, to stopper the included linear {alpha},{omega}-diaminoalkane chains with the inert Pt(II) end groups. The kinetics of the self-assembly and dissociation of the {beta}-CD rotaxane, [(dien)Pt{l_brace}NH{sub 2}(CH{sub 2}){sub 10}NH{sub 2}{center_dot}{beta}-CD{r_brace}Pt(dien)]{sup 4+}, were investigated by using {sup 1}H NMR ...

2005-12-15

366

Supramolecular selectivity of [60]-fullerene among equivalently photoactive porphyrins

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 ...

1989-10-03

367

Solid-state NMR and XRD study of #alpha#-SiAlON powders prepared by combustion synthesis

The photophysical investigation of different para-substituted tetraphenylporphyrins (TP), viz., meso-tetra(4'-hydroxyphenyl)-21H-23H-porphyrin(1),meso-tetrakis (4'-hex-5-enyloxyphenyl)-21H-23H-porphyrin(2), meso-tetrakis(4'-oct-7-enyloxyphenyl)-21H-23H-porphyrin(3) and meso-tetrakis(4'-undecyloxyphenyl)-21H-23H-porphyrin (4) revealed that except for quantum yield (#phi#) the para-substitution has little effect on any other photophysical properties like lifetime, excitation, emission wavelength, etc. The host-guest type interactions of these tetraarylporphyrins (TP 1-4), with [60]-fullerene (F) have been studied with "1H NMR and fluorescence spectrometric techniques in carbon tetrachloride medium. Fluorescence studies revealed that the Q band of the TPs was sufficiently quenched upon addition of F. All the fullerene/porphyrin systems were found to produce stable complexes with 1:1 stoichiometry. Binding constants (K) of all the fullerene/porphyrin complexes have ...

2010-10-01

368

Simple Methods for Determining Relative Stereochemistry of Kainoid Amino Acids by (1)H NMR Chemical Shifts.

"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 ...

2007-07-31

369

Quantum-chemical simulation of 1H NMR spectra. 2. Comparison of DFT-based procedures for computing proton-proton coupling constants in organic molecules.

The kainoid amino acids are biologically important compounds because they show remarkable neuroexcitatory and excitotoxic activities. For exhibiting potent activity, the stereochemical relationship of the substituents on the pyrrolidine ring is crucial. We found simple methods for determining the relative stereochemistry of these compounds on the basis of the (1)H NMR chemical shifts of H-2 and H-4 in D(2)O solution. The signals of H-2 appear at fields higher than 4.2 ppm when the compounds have 2,3-trans stereochemistry whereas, in the 2,3-cis compounds, they appear lower than 4.2 ppm, irrespective of the C-4 substituent. This criterion holds when the solution is in the range of pD 3-8. Moreover, when an epimeric pair at C-2 is available and the spectra are recorded at the same or nearly equal pD, the H-2 chemical shift of the 2,3-trans isomer is higher than that of the corresponding 2,3-cis isomer. Similarly, the relative stereochemistry between C-3 and C-4 can ...

1996-07-12

370

Platinum(II) complexes as spectroscopic probes for biomolecules

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 ...

2011-05-16

371

Onium ions. 34. The methoxydiazonium ion: preparation, /sup 1/H, /sup 13/C, and /sup 15/N NMR and IR structural studies, theoretical calculations, and reaction with aromatics. Attempted preparation and the intermediacy of the hydroxydiazonium ion

The use of platinum(II) complexes as tags and probes for biomolecules is indeed advantageous for their reactivities can be selective for certain purposes through an interplay of mild reaction conditions and of the ligands bound to the platinum. The use of {sup 195}Pt NMR as a method of detecting platinum and its interactions with biomolecules was carried out with the simplest model of platinum(II) tagging to proteins. Variable-temperature {sup 195}Pt NMR spectroscopy proved useful in studying the stereodynamics of complex thioethers like methionine. The complex, Pt(trpy)Cl{sup +}, with its chromophore has a greater potential for probing proteins. It is a noninvasive and selective tag for histidine and cysteine residues on the surface of cytochrome c at pH 5. The protein derivatives obtained are separable, and the tags are easily quantitated and differentiated through the metal-to-ligand charge transfer bands which are sensitive to the ...

1990-09-21

372

Nuclear magnetic resonance spectroscopy in biomedicine. Course organized by the Istituto Superiore di Sanita`. Marciana Marina (Isola d`Elba), September 18-23, 1995; Spettroscopia di risonanza magnetica nucleare in biomedicina. Corso organizzato dall`Istituto Superiore di Sanita`. Marciana Marina (Isola d`Elba), 18-23 settembre 1995

Nitrous oxide is methylated with CH/sub 3/F ..-->.. SbF/sub 5/F/sub 2/ or with CH/sub 3/O/sup +/SOClF in SO/sub 2/ClF to give the stable methoxydiazonium ion CH/sub 3/ON/sub 2//sup +/ (1), which was characterized by NMR (/sup 15/N, /sup 13/C, /sup 1/H) and FT IR spectroscopic studies. It is stable below -30 /sup 0/C, above which it decomposes, regenerating N/sub 2/O. When reacted with aromatics, such as toluene, 1 gives only methylation products and no methoxy derivatives are formed. Spectroscopic and chemical data indicate that the mesomeric form CH/sub 3/O-N=N/sup +/ is a significant contributor to the overall structure of 1. Consideration of computed charge distribution (4-31 G with full geometry optimization and 4-31 G*) also supports this conclusion. Independent generation of 1 was also studied by solvolysis of methylazoxy triflate and diazotization of methoxylamine with NO/sup +/BF/sub 4//sup -/. Preparation of the elusive hydroxydiazonium ion HON/sub ...

1986-04-16

373

NMR of a synthetic peptide spanning the triphosphate binding site of adenosine 5'-triphosphate in actin

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 condizioni imposto dalla ...

1997-12-01

374

Isoelectric focusing purity criteria and "1H NMR detectable spectroscopic heterogeneity in the major isolated monomer hemoglobins from Glycera dibranchiata

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 ...

1987-03-10

375

General fundamentals of radiological diagnostics. Specific diagnostic radiology: Throat, mediastinum, diaphragm, mammary gland, infant thorax. 7. rev. ed.

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 ...

376

/sup 15/N NMR spectra of pentaamminerhodium(III) complexes

The fundamentals and the technical application methods of the imaging procedures are discussed in detail with regard to their application in medicine. The development of the X-ray contrast media has led to a better tolerance and a significant reduction of risks. Problems relating to radiation protection and radiation exposure are discussed critically. The general point gives an overview of the radiological examination methods and is meant to deepen the understanding of the special techniques and their rationally determined application. The following special part deals with diagnosing of organs in the region of the neck and the thorax. The general basis is the conventional radiological examination. The great increase in information achieved by means of the new imaging methods becomes clear if we look at the diagnostics of the soft tissue of the neck. Computerized tomography and NMR imaging open the view at the fine structures of the mediastinum. Mammography is an ...

377

Velocity measurement of wake behind flat plate simulating BWR fuel spacer

A series of pentaamminerhodium(III) complexes, Rh(NH/sub 3/)/sub 5/Z/sup n+/, has been prepared with 80% enrichment in /sup 15/N (Z = H/sub 2/O, OH/sup /minus//, Cl/sup /minus//, Br/sup /minus//, I/sup /minus//, NH/sub 3/, /minus/ONO/sup /minus//, /minus/NO/sub 2//sup /minus//, /minus/NCS/sup /minus//, /minus/SCN/sup /minus//, /minus/NCO/sup /minus//, CN/sup /minus//). The /sup 1/H-decoupled /sup 15/N NMR spectra show two doublets (from coupling to /sup 103/Rh) with approximate intensity ratio 4:1. /delta//sub N/ and /sup 1/J(rh-N) are sensitive to Z, especially for the unique amine trans to Z. Good correlations exist between /delta//sub N/ in this series of /delta//sub N/ in this series and /delta//sub N/ in the corresponding cobalt(III) complexes Co(NH/sub 3/)/sub 5/Z/sup n+/ and platinum(II) complexes Pt(NH/sub 3/)/sub 3/Z/sup m+/, J(Rh-N) trans to Z also correlates well with H(Pt-N) trans to Z in the platinum series. 16 refs., 2 figs., 1 tab.

1988-11-30

378

Time-lapse slip variation associated with a medium-size earthquake revealed by "repeating" micro-earthquakes: the 1999 Xiuyan, Liaoning, MS = 5.4 earthquake

Velocity field behind a flat plate, placed near the wall in a narrow channel as a simulant of a BWR fuel spacer, was measured by using a hot wire anemometer. It was found that not only the positions where the dead water region behind flat plate disappeared but also the locations where the velocity relaxation completed were almost independent of the width of the clearance, although the local average velocity and velocity fluctuation immediately downstream the flat plate were affected by the difference in the clearance. The transverse flow diversions in the channel cross section were evaluated from the shape of the average velocity profile. The decrease of local flow rate near the channel wall, which may causes the drift flow behind a flat plate, was encouraged as the drag of clearance increased. Attempts have been made to measure spanwise velocity in the narrow channel. A spanwise velocity that occurred due to flow diversion was observed and its magnitude reached ...

2004-10-04

379

Three-dimensional simulation study of compact toroid plasmoid injection into magnetized plasmas

We obtained the time-lapse cumulative slip before and after the 29 November 1999, Xiuyan, Liaoning, China, Ms = 5.4 earthquake by using "repeating events" defined by waveform cross-correlation. We used the seismic waveform data from the Liaoning Regional Seismograph Network from June 1999 to December 2006. Two "multiplets" located near the seismogenic fault of the 1999 Xiuyan earthquake and the 4 February 1975, Haicheng Ms = 7.3 earthquake, respectively, were investigated. For the "multiplet" that occurred before and after the 1999 Xiuyan earthquake, apparent pre-shock accelerating-like slip behavior, clear immediate-post-seismic change, and relaxation-like post-seismic change can be observed. As a comparison, for the "multiplet" near the 1975 Haicheng earthquake which occurred a quarter century ago, the cumulative slip appears linear with a much smaller slip rate.

2011-07-01

380

The challenges in building Sasol Two and Three in South Africa

Three-dimensional dynamics of a compact toroid (CT) plasmoid, which is injected into a magnetized target plasma region is investigated by using magnetohydrodynamic (MHD) numerical simulations. It is found that the process of the CT penetration into this region is much more complicated than what has been analyzed so far by using a conducting sphere (CS) model. The injected CT suffers from a tilting instability, which grows with the similar time scale as the CT penetration. The instability is accompanied by magnetic reconnection between the CT magnetic field and the target magnetic field, which disrupts the magnetic configuration of the CT. Magnetic reconnection plays a role to supply the high density plasma initially confined in the CT magnetic field into the target region. Also, the penetration depth of the CT high density plasma is examined. It is shown to be shorter than that estimated from the CS model. The CT high density plasma is decelerated mainly by the Lorentz force of the ...

1999-04-01

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381

Stress-assisted crystallisation in anodic titania

In 1980, Congress passed the energy security act which created the United States Synthetic Fuels Corporation. This entity was created to serve as a catalyst for the development of synthetic fuels projects by the private sector. Then what happened. Increased exploration in the United States stimulated by relaxation of price controls on oil produced an increase in reserves of these resources. Fuel conservation, combined with a reduced energy demand caused by a recession, significantly reduced our overall energy consumption and curtailed our imports of foreign crude oil. All of these factors combined have reduced the enthusiasm to invest in synthetic fuels plants, in spite of the fact that the difference between surplus and shortage is frighteningly thin. South Africa, compared to the U.S., is a small country. The Sasol Two and Sasol Three projects are equivalent to a U.S. investment of $400 billion, on a country size-by-size basis. It's hard to believe that ...

1983-12-01

382

Spectral dependence of absorption photoinduced in a Bi{sub 12}TiO{sub 20} crystal by 532-nm laser pulses

Research highlights: ? Correlations between microstructure and internal stress during Ti anodising are established. ? Large internal compressive stresses are accumulated in the film during anodising upto 12 V. ?A transition from compressive to tensile stress is observed when the cell voltage exceeds 12 V. ? At 40 V, the oxide films consist of two regions with different compositions and microstructures. Crystallisation of amorphous to anatase TiO2 contributes to the compressive stress relaxation. - Abstract: The relationship between the microstructural and internal stress evolution during Ti anodising is discussed. Samples anodised galvanostatically to 12 V and 40 V, corresponding to different stages of the internal stress evolution, were examined by in-plane and cross-section transmission electron microscopy. Electron diffraction patterns have been complemented with stoichiometry data obtained from energy loss near edge structure spectra. The sample anodised to 40 ...

2011-04-01

383

Solid-state amorphization of a quenched high-pressure GaSb phase studied by real-time neutron diffraction: evolution of the crystalline phase

The spectral dependences of absorption photoinduced in a pure bismuth titanium oxide crystal by 532-nm laser pulses are studied. It is shown that optical absorption in the crystal in the range from 492 to 840 nm increases with increasing exposure. The photoinduced absorption relaxes in the dark for more than 60 hours. A model of photoinduced absorption is proposed which assumes the population of two trap centres with the normal energy distribution law for the concentrations of electrons photoexcited from donors to the conduction band. This model well describes the spectral dependences of photoinduced absorption by using the average ionisation energies of the traps E{sub 1} = 1.60 eV and E{sub 2} = 2.57 eV. The model is used to estimate the increase in the photorefractive sensitivity of a bismuth titanium oxide crystal in the near IR region, which was earlier observed after exposing the crystal to visible radiation. It is predicted that the speed of response of ...

2007-11-30

384

Solid-state amorphization of a quenched high-pressure GaSb phase studied by real-time neutron diffraction: evolution of the crystalline phase

The amorphization of a quenched sample of the GaSb-II high-pressure phase was studied at ambient pressure by real-time neutron diffraction in the course of the sample heating from 100 K to room temperature at a rate of 0.4 K min{sup -1}. The transformation to the amorphous state begins at 140 K and is completed near room temperature. The {beta}-Sn type structure was shown to represent only the mean lattice of the high-pressure GaSb-II phase. The superstructure of this phase widely varied with temperature and is caused by the ordered displacement of atoms. The temperature range of the metastable crystalline phase relaxation is divided into three intervals according to the temperature dependence of the tetragonality ratio (c/a). At the boundaries of these temperature intervals, i.e. temperatures T = 170 and 230 K, two second-order phase transitions are observed. Anomalous heat and volumetric effects were observed earlier by means of calorimetry and dilatometry in the ...

2009-01-28

385

Plasma membrane as the target site of cholic acid analogs.

The amorphization of a quenched sample of the GaSb-II high-pressure phase was studied at ambient pressure by real-time neutron diffraction in the course of the sample heating from 100 K to room temperature at a rate of 0.4 K min-1. The transformation to the amorphous state begins at 140 K and is completed near room temperature. The ?-Sn type structure was shown to represent only the mean lattice of the high-pressure GaSb-II phase. The superstructure of this phase widely varied with temperature and is caused by the ordered displacement of atoms. The temperature range of the metastable crystalline phase relaxation is divided into three intervals according to the temperature dependence of the tetragonality ratio (c/a). At the boundaries of these temperature intervals, i.e. temperatures T = 170 and 230 K, two second-order phase transitions are observed. Anomalous heat and volumetric effects were observed earlier by means of calorimetry and dilatometry in the same ...

2009-01-28

386

Photoconductive ultraviolet detectors based on ZnO films

Although the mechanism is unknown, Calculus Bovis and its active components, cholic acid analogs (CAAs), have been used in China to treat a wide range of diseases. Based on the previous finding that the potency of CAA is strongly dependent on the intrinsic surface activity, this paper aimed to investigate the role of the plasma membrane in the pharmacological activity of CAAs. First, CAAs (0.1 mM) caused a surface activity-dependent depression on ATPase activity in the cell membrane extract, but it had no effects on other cellular extracts, suggesting an indispensable role of the membrane environment for pharmacological activity. Second, CAAs lowered the membrane fluidity of cultured Caco-2 cells with the same rank-order of potency sequence. Third, the hypothesis that any functional protein located on the membrane is influenced by changes in cellular membrane fluidity was supported by: ileal contraction that was induced by acetylcholine and mediated by the muscarinic receptor ...

2011-08-03

387

Photoconductive ultraviolet detectors based on ZnO films

Properties of photoconductive ultraviolet detectors fabricated on ZnO films were presented. Highly c-axis oriented ZnO films were grown on glass substrates by pulsed laser deposition. Ultraviolet photodetectors were fabricated based on metal-semiconductor-metal planar structures. The photoresponsivity and the quantum efficiency are much higher in the ultraviolet range than in the visible range, and the peak values are around 360 nm. Photocurrent transients show that the detector has a large photocurrent with the peak value of 2.8 mA, and a slow photoresponse with a rise time of 5 min and a decay time of 7 min. The response curve of the detector is fitted well with exponential curve. The large photocurrent should result from the both effects of the accumulation of conduction electrons and the decrease of the barrier height between crystallites. The relaxation time constant {tau} obtained from the curve fitting represents the time accumulation during the process. The ...

2006-12-15

388

New polysaccharide-based polymer electrolytes; Nouveaux electrolytes polymeres a base de polysaccharides

Properties of photoconductive ultraviolet detectors fabricated on ZnO films were presented. Highly c-axis oriented ZnO films were grown on glass substrates by pulsed laser deposition. Ultraviolet photodetectors were fabricated based on metal-semiconductor-metal planar structures. The photoresponsivity and the quantum efficiency are much higher in the ultraviolet range than in the visible range, and the peak values are around 360 nm. Photocurrent transients show that the detector has a large photocurrent with the peak value of 2.8 mA, and a slow photoresponse with a rise time of 5 min and a decay time of 7 min. The response curve of the detector is fitted well with exponential curve. The large photocurrent should result from the both effects of the accumulation of conduction electrons and the decrease of the barrier height between crystallites. The relaxation time constant #tau# obtained from the curve fitting represents the time accumulation during the process. The ...

2006-12-15

389

Negotiated settlements with a cost of service backstop: The consequences for depreciation

Polysaccharides like cellulose and chitosan are known for their filmic properties. This paper concerns the synthesis and the study of chitosan-based polymer electrolytes. A preliminary work concerns the study of glucosamine reactivity. The poly-condensation of chitosan ethers (obtained by reaction with ethylene oxide or propylene oxide) with bifunctional and monofunctional oligo-ethers leads to the formation of thin lattices (10 {mu}m) having excellent mechanical properties. The presence of grafted polyether chains along the polysaccharide skeleton allows to modify the vitreous transition temperature and the molecular disorder of the system. Two type of polymer electrolytes have been synthesized: electrolytes carrying a dissolved alkaline metal salt and ionomers. The analysis of their thermal, dynamical mechanical, nuclear magnetic relaxation, electrical, and electrochemical properties shows that this new class of polymer electrolytes has the same performances as ...

1996-12-31

390

Nanocontact heteroepitaxy of thin GaSb and AlGaSb films on Si substrates using ultrahigh-density nanodot seeds.

The movement from traditional regulatory hearings to negotiated settlements represents both a departure from cost of service regulation and a relaxation of regulatory oversight. Under negotiation parties are able to renegotiate inclusions in their cost of service while simultaneously creating a profit margin for the regulated firm where none existed under the cost of service outcome of a traditional hearing. This paper constructs a model to illustrate the existence of positive gains to pipeline and shipper from the re-allocation of expenses through time in the regulated pipeline services market in Canada. Behaviour consistent with the model is observable in anecdotal and econometric evidence gathered from the library of the National Energy Board of Canada, responsible for pipeline toll regulation in Canada. Empirical investigation by into settlement procedures in the Florida electricity market reveals similar findings; however, this analysis represents the first ...

2011-03-01

391

Minimal Curvature Trajectories: Riemannian Geometry Concepts for Model Reduction in Chemical Kinetics

A film of GaSb grown epitaxially on a Si substrate is a direct transition semiconductor useful for application as a light source in Si photonics and channel material in next-generation field effect transistors because its energy bandgap is close to the optical fibre communication wavelength and it possesses high carrier mobility. Here, we report a novel method for heteroepitaxial growth of high-quality GaSb/Si films, despite having a lattice mismatch as large as ? 12%, using elastically strain-relaxed GaSb nanodots with ultrahigh density as seed crystals for film growth. The nanodot seed crystals were grown epitaxially by restricted contact with the Si substrate through nanowindows in an ultrathin SiO(2) film on the Si substrate. A light-emitting diode containing GaSb/Si films with a thickness of ? 90 nm fabricated by this method operated at room temperature. The growth method was also used to fabricate AlGaSb films of high quality. Our method provides a new avenue ...

2011-05-17

392

Method of unilateral relaxation of a stressed rock mass intended to protect development workings

In dissipative ordinary differential equation systems different time scales cause anisotropic phase volume contraction along solution trajectories. Model reduction methods exploit this for simplifying chemical kinetics via a time scale separation into fast and slow modes. The aim is to approximate the system dynamics with a dimension-reduced model after eliminating the fast modes by enslaving them to the slow ones via computation of a slow attracting manifold. We present a novel method for computing approximations of such manifolds using trajectory-based optimization. We discuss Riemannian geometry concepts as a basis for suitable optimization criteria characterizing trajectories near slow attracting manifolds and thus provide insight into fundamental geometric properties of multiple time scale chemical kinetics. The optimization criteria correspond to a suitable mathematical formulation of "minimal relaxation" of chemical forces along reaction trajectories under ...

2009-01-01

393

Magnetic resonance imaging in multiple sclerosis. Imagerie nouvelle par resonance magnetique nucleaire au cours de la sclerose en plaques

Introduces three designs of development working protection recommended for immediate roof, basic roof and a coal seam of 1.5-2 m, 2.5-4 m and 0.7-1.1 m thickness respectively. The first design of roof control includes a dummy road with breaker props (cutting-off support) and pack, and reinforced concrete props. The second pattern comprises a breaking gate, two rows of cutting-off timber support, up to 10 m long pack and wood chocks. According to the third pattern a breaking road was executed 5.7-6 m away from the face end with breaker props at both its sides. Two rows of pack chocks were added to the dip. Advantages and drawbacks of the three patterns are pointed out. Stress distribution in rock is shown. Position of roof and support before and after roof settling is shown. The cost of the three methods is analyzed. Recommendations useful in application of the method are provided.

1991-06-01

394

Latest technologies for process control in hot rolling mill; Netsukanatsuen miru ni okeru saishin no purosesu seigyo gijutsu

Magnetic resonance imaging (MRI) has rapidly attained a major position among the examinations used in the diagnostic approach of multiple sclerosis because it is highly sensitive in demonstrating lesions. However, these lesional images may have several meanings, and there is the problem of distinguishing between oedema, which is said to reflect recent lesions, and gliosis which is thought to betray old lesions. The intrinsic MRI parameters studied (i.e. relaxation times) are unable to make this distinction, whereas it is provided by paramagnetic contrast media such as gadolinium. There is no correlation between the changes observed at MRI and the severity of the disease. Another problem is the accuracy of lesion localization, since visualization is predominantly macroscopic. This raises several questions about the demonstration of correlations between clinical signs and site of the lesion(s). At the moment, several teams of neuroradiologists are trying to find the ...

1991-09-15

395

Intracranial tuberculoma: MR imaging

The most recently developed control technologies in a hot strip mill are described. Preview AGC has been developed with a preview control synthesis. It controls roll gaps by using the previous information of disturbances. The disturbances which are concerned are derived from the rolling force, the roll gap and the thickness of a previous stand. The thickness accuracy and the availability of mill have been improved by this technology. An on-line roll grinding (ORG) system with an on-line roll profile meter (OPM) has been developed for the purpose of achieving schedule-free rolling. The ORG smooths the worn and roughed surface of a work roll and OPM can measure the profile of a revolving roll without contact. The data obtained by the OPM are given as feedback information to the ORG. As a result, grinding accuracy has been improved and rolling restriction on width has been relaxed widely. (author)

1999-12-01

396

Hydrogen synthesis via combustion of fuel-rich natural gas/air mixtures at elevated pressure

MR studies of 6 patients with intracranial tuberculoma are reviewed. All patients also underwent CT scans which showed hypo- or isodense lesions with abnormal enhancement following contrast administration. MR showed lesions with prolongation of the T1 relaxation time in every case. On the T2-weighted sequences, the signal properties of the tuberculoma varied according to the stage of evolution of the lesion. Incipient tuberculomas appeared as scattered areas of hypointensity surrounded by edema. Mature tuberculomas were composed of a dark necrotic center surrounded by an isointense capsule which was, in turn, surrounded by edema. In one patient, the center of the lesion was hyperintense probably because of liquefaction and pus formation (tuberculous abscess). While both, CT and MR, were equally sensitive in visualizing the intracranial tuberculoma in every patient, MR was slightly superior in demonstrating the extent of the lesion, especially for brainstem ...

1988-11-01

397

High resolution electron microscopy and computer simulation studies of the atomic structure of tilt boundaries in TiO{sub 2}

Combustion of extremely fuel-rich ({phi}=4) methane/air mixtures at elevated pressures is investigated as a potential means to generate molecular hydrogen by non-catalytic partial oxidation. This system is investigated both computationally and experimentally. The computations use a perfectly-stirred reactor model and an explicit methane cool-flame mechanism to investigate the effects of reactor parameters on reaction time and product composition. Under adiabatic conditions, such mixtures are predicted to autoignite at low temperatures {approx}700 K for pressures exceeding 8.5 atm. Above 15 atm, conversion to products is complete in roughly 1 s. The dependence of reaction time and hydrogen yield is investigated as a function of inlet temperature, system pressure, and flame equivalence ratio. Actual product yields are measured in a tube reactor facility, and many of the predictions of the model, including long relaxation times to chemical equilibrium and temperatures ...

2005-07-01

398

Glass Transition Behaviors of Ethylene Glycol-Water Solutions Confined within Nano-Pores of Silica Gel

The atomic structure of [001] tilt grain boundaries of {Sigma}5 (210), {Sigma}5 (310), {Sigma}13 (320) and {Sigma}17 (410) in TiO{sub 2}(rutile) were studied using high resolution electron microscopy and computer simulation. Regularly separated small steps (1/2 [120] high) and big steps (3/2 [120] high) which contain secondary dislocations were found in the (210) boundary as a result of deviation from the exact {Sigma}5 misorientation and (210) symmetric plane. Similar steps were also found in (310) and (320) boundaries. Flat segments between the steps were found to have very accurate misorientation of the {sigma}`s and a nearly symmetric boundary plane. Their rigid body translation, volume expansion and relaxed structures were determined by comparing HRTEM images with computer calculated structures and simulated images. An irregular core structure was found in the (410) boundary when its misorientation deviated 2{degree} from the exact {Sigma}17 misorientation.

1995-09-01

399

Flash pyrolysis of coal-solvent slurry prepared from the oxidized coal and the coal dissolved in solvent; Ichibu yokaishita sanka kaishitsutan slurry no jinsoku netsubunkai

Enthalpy relaxation properties of the ethylene glycol (EG) aqueous solutions confined within silica-gel void spaces of 1.1 nm in the average void thickness and 6, 12 and 52 nm in their average diameters were examined by an adiabatic calorimetry to understand the glass transition behavior of the solutions and the rearrangement processes of the molecules. The glass transition temperature Tg of EG was found to decrease with adding the water molecules which are mobile under the condition lacking in the full hydrogen-bond network. Meanwhile, the Tg in the water-rich region showed a rise towards pure water; after a phase separation in a 25 mol% (x = 0.25) EG solution, the Tg was 160 K which was higher than that derived by extrapolating the composition dependence to pure water. The Tg = 160 K is the same as observed in the pure water confined within 1.1 nm voids; this indicates the validity of the interpretation that the glass transition at 160 K of the confined water ...

2008-02-01

400

Electron spin resonance investigation of Mn^{2+} ions and their dynamics in manganese doped SrTiO_3

In order to develop a high-efficiency coal pyrolysis method, flash pyrolysis was experimented on slurry prepared by using liquid-phase oxidation reformed coal and a methanol-based solvent mixture. Australian Morwell coal was used for the experiment. The oxidized coal, into which carboxyl groups have been introduced, has the condensation structure relaxed largely, and becomes highly fluid slurry by means of the solvent. Char production can be suppressed by making the oxidation-pretreated coal into slurry, resulting in drastically improved pyrolytic conversion. The slurry was divided into dissolved solution, dried substance, extracted residue, and residual slurry, which were pyrolized independently. The dissolved solution showed very high conversion. Improvement in the conversion is contributed by separating the dissolved substances (coal macromolecules) at molecular levels, coagulating the molecules, suppressing cross-link formation, and reducing molecular weight of ...

1996-10-28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

401

Distribution of activation energies for impurity hopping in amorphous metals

Using electron spin resonance, lattice position and dynamic properties of Mn2+ ions were studied in 0.5 and 2 % manganese doped SrTiO3 ceramics prepared by conventional mixed oxide method. The measurements showed that Mn2+ ions substitute preferably up to 97 % for Sr if the ceramics is prepared with a deficit of Sr ions. Motional narrowing of the Mn2+ ESR spectrum was observed when temperature increases from 120 K to 240-250 K that was explained as a manifestation of off-center position of this ion at the Sr site. From the analysis of the ESR spectra the activation energy Ea = 86 mV and frequency factor 1/?0 ? (2-10)x10^(-14) 1/s for jumping of the impurity between symmetrical off-center positions were determined. Both values are in agreement with those derived previously from dielectric relaxation. This proves the origin of dielectric anomalies in SrTiO3:Mn as those produced by the reorientation dynamics of Mn2+ dipoles.

2007-01-01

402

Direct observation of radial distribution change during tensile deformation of metallic glass by high energy X-ray diffraction method

The distribution of activation energies ..delta.. for classical over-the-barrier hopping is computed for a model amorphous metal. The spread in ..delta.. is determined by the variation in equilibrium-site and saddle-point sizes for the assumed model of dense random packing (DRP) of soft spheres. The size distribution is related to the radial distribution function in a manner which reproduces recent numerical results for the interstitials in DRP models. Size (distance) variation in general is related to energy variation by the form of the potential energy V(r). We show, however, that the distribution of equilibrium-site energies can be related directly to the impurity-induced lattice expansion and bulk modulus without detailed knowledge of V(r). The form of V(r) is necessary for the saddle-point distribution, and we estimate this using simple analytic expressions which fit the observed lattice expansion and impurity (hydrogen) vibrational frequency. The effects of a hard core plus ...

1983-02-15

403

Determination of Inter-Phase Line Tension in Langmuir Films

The purpose of this research is to investigate the micro-mechanism of deformation behavior of metallic glasses. We report the results of direct observations of short-range and medium-range structural change during tensile deformation of metallic glasses by high energy X-ray diffraction method. Cu50Zr50 and Ni30Zr70 metallic glass samples in the ribbon shape (1.5 mm width and 25 ?m) were made by using rapid quenching method. Tensile deformation added to the sample was made by using special equipment adopted for measuring the high energy X-ray diffraction. The peaks in pair distribution function g(r) for Cu50Zr50 and N30iZr70 metallic glasses move zigzag into front and into rear during tensile deformation. These results of direct observation on atomic distribution change for Cu50Zr50 and Ni30Zr70 metallic glass ribbons during tensile deformation suggest that the micro-relaxations occur.

2009-08-26

404

DNA alterations photosensitized by tetracycline and some of its derivatives

A Langmuir film is a molecularly thin film on the surface of a fluid; we study the evolution of a Langmuir film with two co-existing fluid phases driven by an inter-phase line tension and damped by the viscous drag of the underlying subfluid. Experimentally, we study an 8CB Langmuir film via digitally-imaged Brewster Angle Microscopy (BAM) in a four-roll mill setup which applies a transient strain and images the response. When a compact domain is stretched by the imposed strain, it first assumes a bola shape with two tear-drop shaped reservoirs connected by a thin tether which then slowly relaxes to a circular domain which minimizes the interfacial energy of the system. We process the digital images of the experiment to extract the domain shapes. We then use one of these shapes as an initial condition for the numerical solution of a boundary-integral model of the underlying hydrodynamics and compare the subsequent images of the experiment to the numerical ...

2007-01-01

405

Cost reduced inspection concept of PE/XLPE medium voltage cables; Kostensparende Zustandsanalyse an PE-/VPE-isolierten Mittelspannungskabeln

Bacteriophage M13 mp10 DNA were irradiated with near-UV light in the presence of tetracycline derivatives and primed with synthetic oligonucleotide to be used for DNA synthesis using Escherichia coli DNA polymerase. Chain terminations were observed by denaturing polyacrylamide gel electrophoresis and mapped precisely. All the synthesis stops occurred before or at the level of guanine residues, showing that the photoreaction mediated by tetracycline derivatives led to a preferential alteration of guanine residues. These lesions were demonstrated to be induced in DNA through a pathway involving singlet oxygen. Tetracycline derivatives also photoinduced the breakage of the DNA sugar-phosphate backbone monitored by the conversion of supercoiled phi X174 DNA to a relaxed form. This lesion was shown to be initiated by hydroxyl radicals. The production of this free radical has been confirmed by electron paramagnetic resonance (EPR) spin trapping experiments using ...

1986-06-01

406

Consolidation settlement analysis of pile foundations; Kui kiso no atsumitsu chinka kaiseki

The microelectronic cable diagnosis is a substantial tool to determine destruction free the residual strength and the lifetime of laid PE/XLPE medium voltage cables. Fundamentals of the ageing diagnosis and a cost reduced inspection concept are the `Isothermal-Relaxation-Current` Analysis and the Neuro-Fuzzy evaluation software. These new tools are able to determine the ageing status of the investigated cable without any references. The authors also show that the test breakdown during the assessment of the ageing status of criterial systems can be reduced by this approach. The cable diagnosis equipment KDA is also useful for the steering of investment as well as for preventive maintenance. (orig.) [Deutsch] Die zerstoerungsfreie dielektrische Kabeldiagnostik kann heute einen wesentlichen Beitrag zur Bestimmung der Restfestigkeit und der Restlebensdauer eines PE/VPE-isolierten Mittelspannungskabels leisten. Basis der Alterungsdiagnose und des Konzeptes zur ...

1997-12-15

407

CoSi_2 nanostructures by writing FIB ion beam synthesis

Deformation of the ground can be considered as a sum of volume deformation and shear deformation. At circumferential ground of pile axis, simple shear type of shear deformation becomes main factor of settlement. As shear forces with reverse direction are overlapped at parallel face for pile around face of the ground between the piles, the shear deformation is relaxed. At deeper place from top of the pile, volume deformation becomes larger and component of shear deformation approaches to a pure shear type. In case of the land surface loading type consolidation settlement calculation, a method adopting one dimensional consolidation calculating method using only vertical component within stress obtained by elasticity theory even when investigating multi dimensionally is used widely. In Japanese design standards, the method calculating the consolidation settlement by presuming imaginary loading face for land surface is widely adopted. In case of abrasion pile, the ...

1997-02-01

408

Assembly of Linear Nano-Chains from Iron Oxide Nanospheres with Asymmetric Surface Chemistry

A mass separated focused ion beam (FIB) is a very useful tool to fabricate nanostructures by writing implantation within an ion beam synthesis process. In these investigations the IMSA-OrsayPhysics FIB, equipped with a Co_3_6Nd_6_4 alloy liquid metal ion source, was applied. Si(100) and (111) wafers were implanted with 60 keV Co"+"+ ions in the dose range of 2 . 10"1"6 to 2 . 10"1"7 cm"-"2. Implantation parameters were investigated, like pixel dwell time, relaxation time (time between two cycles), dose rate as well as the pixel overlapping factor. The subsequent annealing was done in a two step process, namely 600 deg. C for 60 min and 1000 deg. C for 30 min in a N_2 ambient. The results obtained by SEM investigations in terms of continuous nanowire structures following the direction and interrupted CoSi_2 pattern in the direction show a clear dependence on the time scale as well as the scanning mode of the irradiation. Structure sizes as small as 10 nm are ...

2006-07-01

409

An investigation of the isothermal creep response of Al-based composites by neutron diffraction

Besides the multifunctionality, another equally important aspect of nanoparticles is their engineerability to control the geometrical and chemical properties during fabrication. In this work, we exploited this aspect to define asymmetric surface chemistry of an iron oxide nanosphere by controlling the topology of ligand expression on its surface resulting in a particle with two faces, one displaying only amines and the other only thiols. Specifically, amine-functionalized iron oxide nanospheres were attached on a solid support via a crosslinker containing a disulfide bridge. Liberation of the nanosphere using thiolytic cleavage created thiols on the portion of the particle's surface that interacted with the solid support. Employing a solid-phase strategy and a step-by-step addition of particles, the two unique faces on the same nanosphere served as fittings to assemble them into linear nano-chains. Assembly of chains with various lengths and aspect ratios was controlled by the size and ...

2011-01-06

410

Ammonia adsorption on the C_3_0B_1_5N_1_5 heterofullerene: DFT study of nuclear magnetic shielding and electric field gradient tensors of N and B nuclei

Discontinuously reinforced aluminium-based composites containing particulate or whisker SiC reinforcements at different volume fractions, were produced via a powder-route. Isothermal creep tests have been carried out at 270, 300 and 320 C. During these tests axial and transverse strains were monitored using a non-contacting laser scanning extensometer arrangement. At the same time neutron diffraction has been used to measure the elastic phase strain evolution with composite creep deformation. It was found that after the initial loading the phase strains remained essentially constant during primary and secondary creep. This indicates that the initial matrix/reinforcement inelastic misfits remain largely unchanged, probably due to the setting up of a dynamic equilibrium between misfit generation and stress relaxation. For each system, the neutron data has been combined with Eshelby modelling to obtain a measure of the load transfer. It was found that while the ...

2000-05-31

411

A structural and corrosion study of triethoxysilyl and perfluorooctyl functionalized polyhedral silsesquioxane nanocomposite films on AA 2024 alloy

Ammonia adsorption on the external surface of C_3_0B_1_5N_1_5 heterofullerene was studied using density functional calculations. Three models of the ammonia-attached C_3_0B_1_5N_1_5 together with the perfect model were optimized at the B3LYP/6-31G"* level. The optimization process reveals that dramatic influences occurred for the geometrical structure of C_3_0B_1_5N_1_5 after ammonia adsorption; the B atom relaxes outwardly and consequently the heterofullerene distorts from the spherical form in the adsorption sites. The chemical shielding (CS) tensors and nuclear quadrupole coupling constants of B and N nuclei were calculated at the B3LYP/6-311G"*"* level. Our calculations reveal that the B atom is chemically bonded to NH_3 molecule. The B atom in the NH_3-attached form has the largest chemical shielding isotropic (CSI) value among the other boron nuclei. The C_Q parameters of B nuclei at the interaction sites are significantly decreased after ammonia adsorption.

2011-04-01

412

A 3-parameter critical power model.

A tri-functional polyhedral oligomeric silsesquioxane (POSS) based silane precursor R_xR_yR_z(SiO_3_/_2)_n (x + y + z = n = 6, 8, 10, ...) bearing 3-(N-(3-triethoxysilylpropyl)ureido)propyl, isooctyl and perfluoropropyl groups was synthesized and investigated as corrosion protective coating for AA 2024 alloy. Infrared reflection-absorption (IR RA) combined with X-ray photoelectron spectroscopy and atomic force microscopy provided information about partial self-assembling of coatings having a fluorine enriched upper layer with a low surface energy (#gamma#"t"o"t = 12.37 mN/m). The structural changes that accompanied corrosion produced under chronocoulometrical conditions were assessed from ex-situ IR RA spectra. A new band at 1690-1700 cm"-"1 appeared above the corrosion potential, and was assigned to the formation of amidonium ions and consequent relaxation of urea-urea associations.

2010-03-01

413

Water-soluble cis-[(NHC)PdBr2(TPPTS)] catalysts and their applications in Suzuki-Miyaura coupling of aryl chlorides

The critical power test is a well-established procedure that provides estimates of two important parameters characterizing work performance; anaerobic work capacity (AWC) and critical power (CP). The concept proscribes a hyperbolic relationship between power output (P) and time to exhaustion (t), given by (P - CP)t = AWC. Since evidence now exists that the procedure overestimates CP and underestimates AWC, this study was undertaken to investigate the effect of relaxing the requirement that the time asymptote necessarily be at zero. Using data from a previous study, it is shown that in so doing, (1) a time asymptote significantly less than zero is obtained, (2) significantly smaller estimates of CP and larger estimates of AWC are obtained, (3) a third parameter is introduced that theoretically represents maximal instantaneous power, (4) it implies that the maximal power that could be developed at any instant is proportional to the amount of AWC remaining at that ...

1996-04-01

414

British Library Electronic Table of Contents (United Kingdom)

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.

2011-01-01

415

The synthesis of (1',3'- sup 3 H)4-(4'-azido-5',6',7',8'-tetrahydro-5',5',8',8'-tetramethyl -2'-anthracenyl)benzoic acid as a probe of the retinoic acid receptor

The effect of oxide additives on the synthesis and sintering of x-Sialon

The synthesis of (1',3'-{sup 3}H)4-(4'-azido-5',6',7',8'-tetrahydro-5'5'8',8'-tetramethyl-2'-anthracenyl)benzoic acid is described. This retinoid was designed as a photoaffinity probe of the receptor sites of cellular retinoic acid-binding protein and the nuclear retinoic acid receptor protein. The ({sup 3}H)azidoretinoid was prepared from 1,2,3,4-tetrahydro-1,1,4,4-tetra-methyl-7-(4-methylphenyl)-5-nitroanthracene in five steps in 15% yield (89% radiochemical purity by HPLC). {sup 1}H and {sup 3}H NMR was used to confirm the sites of {sup 3}H substitution on the ring. (author).

1990-01-01

416

Synthesis, solid and solution studies of paraquat dichloride calixarene complexes. Molecular modelling

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

1998-09-28

417

Synthesis, characterization and evaluation of antibacterial activity of some thiazolo[3,2-b][1,2,4]triazole incorporating diphenylsulfone moieties

The interaction of the herbicide paraquat dichloride (P Q, substrate) with p-tert-butylcalix arenas (L, receptor) was investigated in both the solution and solid states. The isolated paraquat calixarene complexes were characterised by UV-visible, 1H NMR, ESI-Ms, Luminescence and IR spectroscopies and elemental analysis. The stoichiometry of complexes 1 and 2 was 1:1 (1 herbicide: 1 calixarene) and both revealed a biexponential luminescence decay with lifetimes depending on the size and the conformational particularity of the calixarenes. Molecular modelling suggested that both calixarenes interact with the herbicide through cation-? interaction. P Q in included in the p-tert butylcalix a rene cavity, a situation favoured by its pinched conformation in polar solvent while it is partially included in the p-tert butylcalix a rene cavity because of its in-out cone conformation. The theoretical results, in particular using Mopac procedures, were in agreement with the ...

418

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...

2009-01-01

419

Synthesis, characterization and biological evaluation of mononuclear Co(II), Ni(II), Cu(II) and Pd(II) complexes with new N2O2 Schiff base ligands.

Synthesis of alkylated deoxyno irimycin and 1,5-dideoxy-1,5-iminoxylitol analogues: : Polar side-chain modification, sulfonium and selenonium heteroatom variants, conformational analysis, and evaluation as glycosidase inhibitors

New tetradentate N(2)O(2) donor Schiff bases and their mononuclear Co(II), Ni(II), Cu(II), and Pd(II) complexes were synthesized and characterized extensively by IR, (1)H-, (13)C-NMR, mass, ESR, conductivity measurements, elemental and thermal analysis. Specifically the magnetic and electronic spectral measurements demonstrate the octahedral structures of cobalt(II), nickel(II) complexes and square planar geometries of copper(II), palladium(II) complexes. All the ligands and complexes were screened for their in vitro antibacterial activity against two gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) and two gram-negative bacteria (Escherichia coli, Klebsiella pneumonia). In this study, Pd(II) complexes exhibited potent antibacterial activity against B. subtilis, S. aureus whereas other metal complexes also exerted good activity towards all tested strains even than standard drugs streptomycin and ampicillin. PMID:21297294

2011-02-01

420

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 ...

2004-01-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

421

Synthesis of (diamine)platinum(II) and (diamine)platinum(IV) complexes of isopropylidenmalonate ligand and their interaction with guanosine-5'-monophosphate

Synthesis and characterization of diastereomeric (substituted iminodiacetato)(1,2-diaminocyclohexane)platinum(II) complexes

A series of (diamine)isopropylidenmalonatoplatinum(II) complexes and the oxidation products, (diamine)Pt(OOC){sub 2}C=C(CH{sub 3}){sub 2}(X){sub 2}, (diamine=ethylenediamine(en), 1,2-diaminopropan(dap), N-methylethylenediamine(men); X=OH, OCOCH{sub 3}, OCOCF{sub 3}), have been prepared, and their interaction with guanosine-5'-monophosphate (5'-GMP) have been examined by means of {sup 1}H NMR spectroscopy. The present platinum(II) complexes have shown to interact with 5'-GMP through N7 coordination in two consecutive steps in a similar way as with cisplatin, but no interaction between the present platinum(IV) complexes and 5'-GMP was observed. However, in the presence of ascorbic acid, the platinum(IV) complexes have been found to interest with 5'-GMP with the reation rate depending on their reduction rate.

1998-10-01

422

Syntheses, characterizations and structures of NO donor Schiff base ligands and nickel(II) and copper(II) complexes

Novel complexes of the type (Pt(DACH)(N-R-iminodiacetate)), wherein DACH represents (R,S)- and (R,R)-1,2 diaminocyclohexane and R represents /minus/Me, /minus/EtOH, and /minus/CH/sub 2/Ph groups, have been prepared, purified, and characterized by spectroscopic techniques (/sup 1/H, /sup 13/C, and /sup 195/Pt NMR;MS(FAB);IR) and by the measurement of selected physical properties (pH, pK/sub a/, conductivity, and molecular weights). The data are consistent with the formation of two diastereomeric complexes in unequal proportions in which the N-R-iminodiacetate ligand appears to be bonded as a pseudofacial tridentate chelate. One are of the ligand forms a stable five-membered-ring O,N-chelate while the other arm appears to be involved in ion-pair formation (zwitterion-like) involving the carboxylate anion and the formally positive Pt(II) central metal atom. It has been demonstrated indirectly that an active impurity was present in predictably inactive bulk complexes ...

1988-11-16

423

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.

2011-01-01

424

Studies of initial stage in coal liquefaction. Effect of decomposition of oxygen-functional groups on coal liquefaction; Ekika hanno no shoki katei ni kansuru kenkyu. 3. Gansanso kannoki no bunkai kyodo to ekika hanno eno eikyo

Structure determination and investigation on cytotoxicity of potassium dichlorido(l-prolinato)platinate(II) versus chlorido(dimethyl sulfoxide)(l-prolinato)platinum(II) complex -In vitro antitumor deactivation by Cl^-/dmso ligand exchange

Pretreatment of brown coal in oil was conducted using 1-methyl naphthalene or mixture of tetralin and 1-methyl naphthalene as solvent at temperatures ranging from 300 to 430{degree}C under nitrogen atmosphere. Effects of the solvent properties on the structural change of oxygen-functional groups (OFG) and coal liquefaction were investigated by means of quantitative analysis of OFG and solid state {sup 13}C-NMR measurement. When hydrogen transfer from solvent was insufficient, it was suggested that brown coal molecules loose their hydrogen to be aromatized. While, at lower temperatures ranging from 300 to 350{degree}C, hydrogen contained in brown coal molecules was consumed for the stabilization of pyrolytic radicals, and the deterioration of liquefaction was not observed. When hydrogen transfer from solvent was insufficient at higher temperatures above 400{degree}C in nitrogen atmosphere during pretreatment in oil, crosslinking like benzofuran type was formed by ...

1996-10-28

425

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.

2011-01-01

426

Structural Change Accompanying Crystallization in the Lithium Ion Conductive Li{sub 2}S-SiS{sub 2}-Li{sub 3}PO{sub 4} Oxysulfide Glasses

Structural Change Accompanying Crystallization in the Lithium Ion Conductive Li[sub 2]S-SiS[sub 2]-Li[sub 3]PO[sub 4] Oxysulfide Glasses

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)

1999-02-01

427

Si3C2-rings: from a nonconjugated trisilacyclopentadiene to an aromatic trisilacyclopentadienide and cyclic disilenide.

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)

1999-02-01

428

Review of progress in quantitative NDE. Abstracts

1,2,3-Trisilacyclopenta-1,4-diene 2, featuring three skeletal Si atoms in the five-membered ring, was synthesized by the thermolysis of the 1,2,3-trisilabicyclo[1.1.0]butane derivative 1 at 130 degrees C in the presence of hex-3-yne. Possessing the properties of nonconjugated cyclopentadiene, 2 readily underwent reduction with KC(8), which was followed by treatment with LiBr to form the lithium salt of 1,2,3-trisilacyclopentadienide 3(-)*[Li(+)(thf)], from which the ketone-coordinated derivative 3(-)*[Li(+)(O=C(t)Bu(2))] was prepared. Both 3(-)*[Li(+)(L)] (L = thf, O=C(t)Bu(2)) are classified as novel 6pi-electron aromatic systems based on their characteristic X-ray crystal and NMR spectral data. Addition of 12-crown-4 to 3(-)*[Li(+)(thf)] resulted in the unexpected formation of 4(-)*[Li(+)(12-crown-4)(2)], featuring the unprecedented cyclic disilenide ion 4(-). PMID:19378994

2009-05-13

429

Research on development of adsorbent for separating and collecting light element isotopes

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 ...

1986-01-01

430

Radiolytic stabilization of poly(methyl methacrylate) using commercial additives; Estabilizacao radiolitica do poli(metacrilato de metila) usando aditivos comerciais

Lithium isotopes are used as the raw material of tritium which is the fuel for fusion power generation and the material for fusion reactors, accordingly those are indispensable for future nuclear fusion power generation. As for boron isotopes, the neutron absorption corss section is very large, therefore, they are used for shielding neutrons and controlling fast neutron reactors. In order to further develop the utilization of nuclear power, it is important to develop the technology for separating and refining light element isotopes in large amount. In fiscal year 1995, the relation of the ion sieve characteristics of inorganic ion exchanger and the behavior of lithium isotope separation was examined. The behavior of forming boron complex of polyol amine was examined by B-11 NMR. These experiments and the results are reported. It was shown to be feasible that lithium is adsorbed from seawater, and isotopes are concentrated. Titanium phosphate and its heat treated ...

431

Potential anti fungal agents. Synthesis and activity of 2-alkylthiopyridine-4-carbothioamides

Poly(methyl methacrylate), PMMA, Acrigel, a Brazilian polymer, is used in the manufacture of medical supplies sterelizable by ionizing radiation. However, when PMMA is gamma-irradiated it undergoes main chain scissions, which promote molecular degradation causing reduction in its mechanical properties. Therefore, radiolytic of PMMA is important for it to become commercially radiosterizable. In this work some commercial additives, originally used in photo-and thermo-oxidate stabilization of polymers, were tested. Only two additives, type HALS (Hindered Amine Light Stabilizer), denoted Scavenger, showed a good protective quality. The investigation of radiation-induced main scissions was carried out by viscosimetric method. The most effective additive, added to the polymer system at 0.3 w/w%, promotes a great molecular radioprotection of 93%. That means a reduction of G-value (scissions/100 eV) from 0.611 to 0.053. In addition, the glassy transition temperature (T{sub g}) of PMMA (no ...

2000-04-01

432

Physics through the 1990s: scientific interfaces and technological applications

A series of 2-alkylthiopyrine-4-carbothioamides were synthesized, and their anti-fungal potency was tested. The chemical structures were proved by infrared spectroscopy (IR) and {sup 1}H nuclear magnetic resonance ({sup 1}H-NMR) data and by elemental analysis. The minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) assessment were used for the estimation of potential activity in vitro. The study comprising 21 clinical isolates of fungi showed that two compounds exhibited fair inhibitory activity against some yeasts and dermatophytes. Selective fungistatic activity against non-dermatophytes (MIC = 3.12-25.0 {mu}g/mL) was found also in another compound. None of the above compounds showed inhibitory activity against non-dermatophyte filamentous fungi. Microbiological activity of 2-alkylthiopyridine-4-carbothioamides appears to be mainly related to hydrophobicity of alkyl in position 2. (authors). 10 refs., 8 tabs.

1996-05-01

433

Photochemically and Pharmacological studies of Maytenus Frosskaoliana

The volume examines the scientific interfaces and technological applications of physics. Twelve areas are dealt with: biological physics--biophysics, the brain, and theoretical biology; the physics-chemistry interface--instrumentation, surfaces, neutron and synchrotron radiation, polymers, organic electronic materials; materials science; geophysics--tectonics, the atmosphere and oceans, planets, drilling and seismic exploration, and remote sensing; computational physics--complex systems and applications in basic research; mathematics--field theory and chaos; microelectronics--integrated circuits, miniaturization, future trends; optical information technologies--fiber optics and photonics; instrumentation; physics applications to energy needs and the environment; national security--devices, weapons, and arms control; medical physics--radiology, ultrasonics, NMR, and photonics. An executive summary and many chapters contain recommendations regarding funding, ...

1986-01-01

434

Phospholipid asymmetry in large unilamellar vesicles induced by transmembrane pH gradients

Column chromatography of the petroleum ether and chloroformic extracts of Maytenus Forsskaoliana afforded four compounds: friedilin1, B-amyrin 2, B-sitosterol 3 and betulin 4. The structure of these compounds were established on bases of spectral (IR,MS,H and C-NMR)as well as physical data. Antimicrobial activity for extracts indicated weak potency (200ug/ml) while betulin4 showed a pronounced activity (MIC and MBC 20ug/ml).The cytotoxic activity of beutalin4 significantly indicated promising activity (IC50 40ug/ml) on both HeLa and Hep-2 cells. The pharmacological activity of diferent extracts showed sedative effect, slowing respiration, dose -dependent decrease in the arterial blood pressure by 40.1mm Hg (at adose 200mg /kg),decrease in the heart rate 67.3% (at a dose 50mg /kg)and decrease in the body temperature by 4.2C after 2 hrs (at a dose 200mg /kg). (author)

435

Palladium(II) and platinum(II) saccharinate complexes containing pyridine and 3-acetylpyridine: Synthesis, crystal structures, fluorescence and thermal properties

The influence of membrane pH gradients on the transbilayer distribution of some common phospholipids has been investigated. The authors demonstrate that the transbilayer equilibrium of the acidic phospholipids egg phosphatidylglycerol (EPG) and egg phosphatidic acid (EPA) can be manipulated by membrane proton gradients, whereas phosphatidylethanolamine, a zwitterionic phospholipid, remains equally distributed between the inner and outer monolayers of large unilamellar vesicles (LUVs). Asymmetry of EPG is examined in detail and demonstrated by employing three independent techniques: ion-exchange chromatography, {sup 13}C NMR, and periodic acid oxidation of the (exterior) EPG headgroup. In the absence of a transmembrane pH gradient ({Delta}pH) EPG is equally distributed between the outer and inner monolayers of LuVs. When vesicles composed of either egg phosphatidylcholine (EPC) or DOPC together with 5 mol % EPG are prepared with a transmembrane {Delta}pH. EPG ...

1989-05-16

436

British Library Electronic Table of Contents (United Kingdom)

New palladium(II) and platinum(II) complexes of saccharinate (sac), trans-[Pd(py)"2(sac)"2] (1), cis-[Pt(py)"2(sac)"2] (2), trans-[Pd(3-acpy)"2(sac)"2] (3) and cis-[Pt(3-acpy)"2(sac)"2] (4) (py=pyridine and 3-acpy=3-acetylpyridine) have been synthesized. Elemental analysis, UV-Vis, IR, NMR and TG/DTA characterizations have been carried out. The structures of 1-4 were determined by X-ray diffraction. The palladium(II) and platinum(II) ions are coordinated by two N-bonded sac ligands, and two nitrogen atoms of py or 3-acpy, forming a distorted square-planar geometry. The palladium(II) complexes (1 and 3) are trans isomers, while the platinum(II) complexes (2 and 4) are cis isomers. The mononuclear species in the solid state are connected by weak intermolecular C-H...O hydrogen bonds, C-H...@...

2011-01-01

437

Oil shale, tar sand, coal research, advanced exploratory process technology jointly sponsored research

Nuclear magnetic resonance spectroscopy in the structure elucidation and biosynthesis of natural products

Accomplishments for the quarter are presented for the following areas of research: oil shale, tar sand, coal, advanced exploratory process technology, and jointly sponsored research. Oil shale research includes; oil shale process studies, environmental base studies for oil shale, and miscellaneous basic concept studies. Tar sand research covers process development. Coal research includes; underground coal gasification, coal combustion, integrated coal processing concepts, and solid waste management. Advanced exploratory process technology includes; advanced process concepts, advanced mitigation concepts, and oil and gas technology. Jointly sponsored research includes: organic and inorganic hazardous waste stabilization; development and validation of a standard test method for sequential batch extraction fluid; operation and evaluation of the CO[sub 2] HUFF-N-PUFF Process; fly ash binder for unsurfaced road aggregates; solid state NMR analysis of Mesa Verde Group, ...

1992-01-01

438

Novel platinum(II) complexes of long chain aliphatic diamine ligands with oxalato as the leaving group: Comparative cytotoxic activity relative to chloride precursors

Examination of a chloroform extract of Dracaena loureiri Gagnep (Agavaceae), a Thia medicinal plant possessing antibacterial activity, has led to the isolation of fifteen flavenoids. The biogenic relationships among these flavenoids isolated were briefly discussed. Definition of the skeleton and the unambiguous assignment of all of the protons of the isolates was achieved through extensive 2D-homonuclear chemical shift correlation, nuclear Overhauser effect (NOE) difference spectroscopy and 2D-NOE experiments. The {sup 1}H and {sup 13}C NMR spectra of staurosporine, a potent biologically active agent from Streptomyces staurosporeus, were unambiguously assigned by using 2D homonuclear chemical shift correlation, NOE, {sup 1}H-detected heteronuclear multiple-quantum coherence via direct coupling and via multiple-bond coupling for resonance assignments of protonated and nonprotonated carbons, respectively. S. Staurosporeus was found to utilize endogenous and exogenous ...

1988-01-01

439

New Lactone and Xanthone Derivatives Produced by a Mangrove Endophytic Fungus Phoma sp. SK3RW1M from the South China Sea

Platinum complexes play an important role in the development of anticancer drugs. Their cytotoxicity can be influenced by the nature of the leaving ligands, due to the hydrolysis reaction that occurs prior to the binding of the platinum complex to DNA. Also, non-leaving groups such as lipophilic diamines may affect cellular uptake. In this work, we describe the synthesis of platinum(II) complexes having oxalato and long chain aliphatic N-alkyl ethylenediamines as ligands. The products were characterized by elemental analyses, infrared spectroscopy and {sup 1}H, {sup 13}C and {sup 195}Pt NMR spectroscopy. Biological activity was assessed against tumor cell lines (A{sub 549}, B16-F1, B16-F10, MDA-MB-231) and non-tumor cell lines (BHK-21 and CHO). The length of the carbon chain affects the cytotoxicity and the oxalato complexes were less cytotoxic than the respective chloride-containing analogues. (author)

2010-07-01

440

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.

2010-01-01

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

441

NMR studies of Borrelia burgdorferi OspA, a 28 kDa protein containing a single-layer #beta#-sheet

Methimazole complexes of platinum(II): Synthesis, characterization and redox behavior

The crystal structure of outer surface protein A (OspA) from Borrelia burgdorferi contains a single-layer #beta#-sheet connecting the N- and C-terminal globular domains. The central #beta#-sheet consists largely of polar amino acids and it is solvent-exposed on both faces, which so far appears to be unique among known protein structures. We have accomplished nearly complete backbone H, C and N and C";/H"#beta# assignments of OspA (28 kDa) using standard triple resonance techniques without perdeuteration. This was made possible by recording spectra at a high temperature (45 "oC ). The chemical shift index and "1"5N T_1/T_2 ratios show that both the secondary structure and the global conformation of OspA in solution are similar to the crystal structure, suggesting that the unique central #beta#-sheet is fairly rigid.

1998-05-01

442

British Library Electronic Table of Contents (United Kingdom)

A variety of platinum(II) complexes of methimazole (2-mercapto-1-methylimidazole; HImS=neutral form and ImS=thiolate form), coordinated in both thione and thiolate forms, have been isolated by reacting methimazole with [PtCl(terpy)]Cl (terpy=2,2prime:6prime,2Prime terpyridine), [PtCl2(bipy)] (bipy=bipyridine), [PtCl2(o-phen)] (o-phen=o-phenanthroline), [PtCl2(CH3CN)2] and [PtCl2(COD)] (COD=1,5-cyclooctadiene). These complexes were characterized by electronic absorption, IR and NMR (1H, 13C, 195Pt) spectroscopies. Molecular structure of [Pt(bipy)(HImS)2]Cl23H2O (3a3H2O) has been established by single crystal X-ray crystallography. Platinum thiolate complex, [Pt(ImS)2(HImS)2] (5), could be obtained by treatment of [Pt(HImS)4]Cl2 with sodium methoxide in methanol. The solution of 5 in organic...

2011-01-01

443

Metal coordination and selectivity with oxine ligands bound to silica polyamine composites

British Library Electronic Table of Contents (United Kingdom)

A series of oxine ligands, 5-X, 8 OH C9H6N (X = H, Cl, SO3H) have been covalently bound to a silica gel polyamine composite made from a silanized amorphous silica xerogel and poly(allylamine) (BP-1) by the Mannich reaction. The resulting modified composites WP-4(X = H), CB-1(X = Cl), and SB-1(X = SO3H) were characterized by elemental analysis, FTIR, and solid state CPMAS-13C-NMR. Using the analytical data before and after the ligand modification, the ligand loading could be estimated and in combination with metal ion capacities a metal to ligand ratio could be obtained. The composites WP-4 and CB-1 both showed ratios of approximately 1 : 1 while the sulfonate modified composite, SB-1, showed a metal to ligand ratio of 1 : 2. This is tentatively interpreted in terms of a zwitterionic oxine ...

2010-01-01

444

Measurement of in-situ stress in salt and rock using NQR techniques

Luminescent property and catalytic activity of Ru(II) carbonyl complexes containing N, O donor of 2-hydroxy-1-naphthylideneimines

A discussion of how stress and strain affect the quantities which can be measured in an NQR experiment shows that, for stresses of the magnitude to be expected at depths up to about 10,000 feet, quadrupole coupling constants will fall in the range of 1 to 10 kHz for both the sodium and chloride ions in NaCl. The most promising system involves pulsed nuclear double resonance detection; and alterative is to observe the quadrupolar splitting of the NMR signal. Choices to be made in the measurement and mapping techniques are discussed. The well-known perturbation of the homogenous stress field in the neighborhood of a borehole is shown to be advantageous from the point of view of obtaining directional information on the stress. Construction and operation of a borehole stress sensor are considered. The NQR technique seems feasible for measuring the magnitude and direction of underground stress with a resolution of about 25 psi, or 2.5% at 1000 psi. Downhole ...

1980-12-01

445

British Library Electronic Table of Contents (United Kingdom)

The reaction of the chelating ligands (obtained by the condensation of 2-hydroxy-1-naphthaldehyde with various primary amines) with [RuHCl(CO)(EPh3)2(B)] (where E=P; B=PPh3, py or pip: E=As; B=AsPh3) in benzene afforded new stable ruthenium(II) carbonyl complexes of the general formula [Ru(Cl)(CO)(EPh3)(B)(L)] (L=anion of bidentate Schiff bases). The structure of the new complexes was investigated using elemental analyses, spectral (FT-IR, UV-vis and 1H NMR) and electrochemical studies and is found to be octahedral. All the metal complexes exhibit characteristic MLCT absorption and luminescence bands in the visible region. The luminescence efficiency of the ruthenium(II) complexes was explained based on the ligand environment around the metal ion. These complexes catalyze oxidation of prim...

2007-01-01

446

Kinetic study of the epoxidation of 1-octene with hydrogen peroxide catalyzed by platinum(II) complexes. Evidence of the involvement of two metal species in the oxygen-transfer step

Interaction of cis-diamminediaquoplatinum(II) with adenosylcobalamin and alkylcobalamins

A detailed kinetic study of the epoxidation of 1-octene with hydrogen peroxide catalyzed by Pt(II) complexes is reported. The two systems analyzed were (diphoe)Pt(CF/sub 3/)(OH)/1-octene/H/sub 2/O/sub 2//THF and ((diphoe)Pt(CF/sub 3/)(CH/sub 2/Cl/sub 2/))BF/sub 4//1-octene/H/sub 2/O/sub 2//H/sub 2/O/CH/sub 2/Cl/sub 2/. Rate data were determined with GLC from epoxide formed vs time plots. Evidence for many of the organometallic intermediates and the individual steps involved was gained from IR studies, /sup 19/F NMR studies, and especially designed experiments including studies of the acidity effect. In both cases the kinetic analysis suggests a mechanism in which the actual oxidant is a PtOOH species that interacts with a Pt-olefin complex in the oxygen-transfer step (second-order dependence on platinum). 29 references, 12 figures, 3 tables.

1988-06-01

447

Heats of formation of gas phase organosulfur molecules, radicals and ions measured by PEPICO, and application of /sup 17/O and /sup 33/S NMR spectroscopy to structure determinations of organosulfur compounds. Progress report, June 1, 1983-April 15, 1984

The interaction of cis-diamminediaquoplatinum(II) nitrate with adenosylcobalamin and a series of alkylcobalamins was studied by carbon-13 nuclear magnetic resonance spectroscopy and by electronic spectroscopy. With these cobalamins cis-(Pt(NH/sub 3/)/sub 2/(OH/sub 2/)/sub 2/)/sup 2 +/ forms adducts in which N(3) of the 5,6-methylbenzimidazole moiety is co-ordinated to platinum(II) rather than to cobalt(III) of the corrin. The chemical shifts of the 5'-methylene carbon of adenosylcobalamin-platinum adduct and of the Co-methyl carbon of the methylcobalamin-platinum adduct are characteristic of these cobalamins in the base-off form. Furthermore, these cobalamin-platinum complexes have visible spectra identical to those of the cobalamins in acidic solution. The /sup 13/C NMR spectrum of the adenosylcobalamin-platinum complex suggests the presence of a second adduct in which platinum(II) complexes are co-ordinated to both the N(3) of the ...

1980-01-01

448

Cytotoxic Naphtho--pyrones from the Mangrove Endophytic Fungus Aspergillus tubingensis (GX1-5E)

A number of fragment ion onsets from the photoionization of CH/sub 3/SCCSCH/sub 3/ and CH/sub 3/SSSCH/sub 3/ have been measured. In addition, our experiment has been converted to a molecular beam source which will increase the precision of our measurements. Exhaustive oxidation of the divalent sulfur to sulfonic acids serves to quench the effects of quadrupolar broadening and thereby allowing for quantitative evaluation of structurally similar sulfonic acids. W/sub 1/2/ are reduced to < 25 Hz at 19 MHz (57,500 Gauss). Electronegative substituents shield the /sup 33/S nucleus perhaps imploying more efficient 2p-3d..pi.. backbonding between sulfur and oxygen. ..cap alpha..-Hetero substituents of sulfonyl groups do not influence the shift of the /sup 33/S to a dramatic extent. The exception is the dianion of thiosulfate compared to the dianion of sulfate. Lanthanide shift reagents, (Eu(fod)/sub 3/), are potentially useful in distinguishing sulfonyl /sup 17/O shifts from those of ...

1984-01-01

449

British Library Electronic Table of Contents (United Kingdom)

Abstract Four new dimeric naphtho--pyrones, named rubasperone D (1), rubasperone E (2), rubasperone F (3), and its atropisomer rubasperone G (4), together with four known monomeric naphtho--pyrones, TMC 256 A1 (5), rubrofusarin B (6), fonsecin (7), and flavasperone (8), were isolated from the mangrove endophytic fungus Aspergillus tubingensis (GX1-5E) cultivated in solid rice medium. Their structures were elucidated by spectroscopic methods, including IR, 1D- and 2D-NMR, and MS. In the in vitro cytotoxicity assays, 5 displayed inhibitory activities against tumor cell lines of MCF-7, MDA-MB-435, Hep3B, Huh7, SNB19, and U87-MG with IC50 values between 19.92 and 47.98-M. Compounds 1, 6, and 8 also showed mild cytotoxic activity.

2011-01-01

450

Cyclopalladated 2-phenyldihydrooxazole complexes with ethylenediamine, 2,2?-bipyridine, and bridging acetate ligands

British Library Electronic Table of Contents (United Kingdom)

The 1H NMR, electronic absorption, and luminescence spectra, as well as voltammograms of the reduction and oxidation of the complexes [Pd(C?N)(N?N)]ClO4 and [Pd(C?N)(?-OOCCH3)]2 [where (C?N)? is deprotonated 2-phenyl-4,5-dihydro-1,3-oxazole, and N?N is ethylenediamine or 2,2?-bipyridine (bpy)] were compared. Magnetic nonequivalence of protons in the dihydrooxazole ring and upfield shift of the corresponding signals were observed as a result of anisotropic effect of the ring current in palladated phenyl substituents in the [Pd(C?N)(?-OOCCH3)]2 complex having a C 2 symmetry. One-electron reduction wave of [Pd(C?N)bpy]+ was assigned to ligand-centered electron transfer to the ?* orbital of 2,2?-bipyridine, and two oxidation waves of [Pd(C?N)(?-OOCCH3)]2 were attributed to successive one-elect...

2011-01-01

451

Chemical modification of soybean oil for lubricant

Characterization of nanosized Tb-MCM-41 synthesized by the sol-gel-assisted self-assembly method

This paper presents a series of structural modifications of soybean oils for lubricant. The reaction was monitored and products were confirmed by NMR and FTIR. The structural modification is carried out in four stages, (1) synthesis of soybean oil isooctyl ester from soybean oil; (2) synthesis of epoxy-soybean oil isooctyl ester from soybean oil isooctyl ester; (3) synthesis of hydroxylated products from epoxy soybean oil isooctyl ester with fatty acid; (4) esterification of the hydroxylated product with anhydride. Rheological behaviour of the products was measured. Pour points of the products (3) were observed as low as -24 C (lauric acid) and -15 C (isooctanoic acid) respectively. When the hydroxyl groups in the products were esterified with and acid anhydride, the pour points were became higher, which were -21 C (lauric acid) and -6 C (isooctanoic acid) without pour point depressant, and -27 C (lauric acid) and -24 C (isooctanoic acid) with 1% of pour point ...

2008-07-01

452

Atlas and toolbook of MR mammography; Lehratlas der MR-Mammographie

The nanosized luminescent Tb-MCM-41 (1:10) is synthesized by means of sol-gel-assisted self-assembly under basic conditions at room temperature. The results of "2"9Si-MAS NMR and XRD prove that Tb"3"+ doped Si-O framework. The HRTEM image shows that the regular uniform particles with a diameter of 10 nm possess ultralarge pore with diameter 2.0 nm, which is consistent with the result of N_2 adsorption. The BET surface area and porosity of Tb-MCM-41 (1:10) are 1127 m"2/g and 0.84 cm"3/g, respectively. The patterns of selected-area electron diffraction and XRD of Tb-MCM-41 (1:10) show an Fm3m space group in the cubic. FT-IR results show that the peaks near 970 cm"-"1 are assigned to the deformation vibration of silanol group. The as-products are calcined at 800 deg. C and the mesoporous materials possess enormous specific areas and large porosity, it shows that the mesoporous materials are ultrastable.

2003-10-06

453

Aging mechanism of Sulfonated poly(aryl ether ketone) (sPAEK) in an hydroperoxide solution and in fuel cell

This richly illustrated toolbook and atlas contains information on all aspects of nmr diagnostic imaging of benign or malignant neoplasms of female and male mammary glands. It offers pinpointed guidance and insight for vocational training and continuing training of radiology assistants, students and medical radiologists. (orig./AJ) [German] Die MRT als hochaufloesendes und schaedigungsfreies Diagnostikum gewinnt gerade in der emotional stark besetzten Mammadiagnostik zunehmend an Bedeutung. Dennoch beherrschen nur wenige Zentren im deutschsprachigen Raum diese Technik, die - eine hohe Reproduzierbarkeit bei fehlender Belastung fuer die Patientin bietet, - invasive Karzinome bereits ab einer Groesse von 5 mm mit hoher Zuverlaessigkeit ausschliessen kann und - gerade bei widerspruechlichen Befunden zwischen klinischer Untersuchung, Roentgenmammographie und perkutaner Biopsie eine wesentliche Entscheidungshilfe bieten kann. Aus einem der fuehrenden Zentren in der ...

2000-07-01

454

A joint computational and experimental study of a novel dioxomolybdenum(VI) complex bearing chiral N,N-dimethyllactamide ligand

Ex situ and in situ fuel cell degradation of a sPAEK membrane were investigated. Post-mortem analyses of the aged membrane and of the degradation products eluted in water were carried out by NMR, IR, SEC and EDX. Ex situ agings were performed in a low concentration H{sub 2}O{sub 2} solution (0.07%) without any metallic catalyst. We exemplify that ex situ accelerated aging tests in such hydrogen peroxide solution are relevant to the chemical degradation in fuel cell. We have shown that a 500 h fuel cell test at moderate temperature (60 C) induces significant modifications on the macromolecules such as a 40% molecular weight reduction. Degradation appears heterogeneous and limited to the cathode side. The model compound approach developed in the previous article (Perrot et al.) has allowed the identification of the aging path in fuel cell. Phenolic and carboxylic acid chain ends have been identified as the main products resulting from polymer chain scissions. The ex ...

2010-01-15

455

British Library Electronic Table of Contents (United Kingdom)

A new cis-dioxomolybdenum complex MoO2(DMLA)2 (DMLA=N,N-dimethyllactamide) has been synthesized and characterized by X-ray crystallography, H NMR and IR spectroscopies and electronic structure calculations at DFT/B3LYP level. This compound (chemical formula C10H20MoO6N2) crystallizes in the orthorhombic space group P212121 with Z=4, a=6.9357(2)?, b=11.8761(4)?, c=17.7251(5), V=1460.00(8)?3 and renders a slightly distorted octahedral structure with two long Mo-O bonds (2.253(3)? and 2.257(3)?) trans to each of the MoO groups and with two short Mo-O bonds of 1.942(3)4? cis to them. The MoO bond length are 1.715(3) and 1.704(3)?). Each lactamide ligand is bidentate; they are coordinated in their deprotonated form with the carbonyl oxygen occupy...

2011-01-01

456

A fluorescent aminolipid from a green photosynthetic bacterium

DISSIPATION AND EXTRA LIGHT IN GALACTIC NUCLEI. II. 'CUSP' ELLIPTICALS

A preliminary chemical characterization is presented of phosphate-free aminolipids isolation from Chlorobium limicola f. thiosulfatophilum. The lipid contains no phosphorus, glycerol, sugar, ornithine, or lysine. Ultraviolet absorption and fluorescence spectra indicate that the amino moiety of the lipid is an aromatic heterocyclic compound. Infrared spectra indicate that the lipid is a secondary or tertiary amide, and gas chromatograhic analysis of the hydrolyzed lipid shows that for each 1100 g of lipid, 1 mol of myristic acid (C/sub 14:0/) is linked in an amide bond. Acid hydrolysis of the lipid yields two fluorescent substances, A (ninhydrine positive) and B (negative), in addition to myristic acid. Proton nuclear magnetic resonance (NMR) studies indicate that substance A contains a butyl groups attached to a conjugated ring carbon, two equivalent ethyl groups attached to one or two nitrogen atoms, and two downfield protons (8.4 ppm), perhaps attached to a ring ...

1983-04-12

457

Heterodifunctional ligands derived from monooxidized Bis(phosphino)amines. Synthesis and transition metal (Molybdenum(0), Tungsten(0), Rhodium(I), Palladium(II), and Platinum(II)) complexes of (Diphenylphosphino)(diphenylphosphinothioyl)- and (Diphenylphosphino) (diphenylphosphinoselenoyl)phenylamine, Ph[sub 2]PN(Ph)P(E)PH[sub 2] (E = S, Se). Crystal and molecular structure of the Pt(II) Complex [Cl[sub 2]P[ovr tPPh[sub 2]N(Ph)P(S)]Ph[sub 2

We study the origin and properties of 'extra' or 'excess' central light in the surface brightness profiles of cusp or power-law elliptical galaxies. Dissipational mergers give rise to two-component profiles: an outer profile established by violent relaxation acting on stars already present in the progenitor galaxies prior to the final stages of the merger, and an inner stellar population comprising the extra light, formed in a compact central starburst. By combining a large set of hydrodynamical simulations with data that span a broad range of profiles at various masses, we show that observed cusp ellipticals appear consistent with the predicted 'extra light' structure, and we use our simulations to motivate a two-component description of the observations that allows us to examine how the properties and mass of this component scale with, e.g., the mass, gas content, and other properties of the galaxies. We show how to robustly separate the physically meaningful ...

2009-03-01

458

Coordination of U"4"+ in the complex U(P_2W_1_7O_6_1)"1"6"-_2 in solid state and in aqueous solution

Bis(diphenylphosphino)phenylamine can be selectivity oxidized by S or Se in toluene or hexane solvents to the monooxidized thioyl or selenoyl products Ph[sub 2]PN(PH)PPh[sub 2]=E, (E = S, Se). These compounds act as bidentate chelate ligands toward metal complexes forming (CO)[sub 4]M(LL) (M = Mo, W), CO(Cl)Rh(LL), and Cl[sub 2]M(LL), (M = Pt, Pd) where (LL) is the thioyl or selenoyl derivative of the aminobis(phosphine). IR and NMR data are given for all complexes. The carbonyl infrared stretching frequencies show that the chelates form with the phosphine cis to any CO which is present. The [sup 31]P NMR of all complexes of two doublets except for the Rh complexes wherein the Rh spin also couples to phosphorous to produce two doublets of doublets. The [sup 2]J[sub PP] values range from 56 to 112 Hz. [sup 1]J[sub PSe] coupling provide valuable assistance for the assignment of the phosphorus resonances which range widely from 55 to 126 ppm for ...

1993-12-08

459

Antimalarial activity of selected Sudanese medicinal plants with emphasis to Maytenus senegalensis

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 actinide and enables ...

1996-09-01

460

MRI evaluation and image processing in gel dosimetry. A study of selected MRI properties and image processing in 3D gel dosimetry

The aim of the present study is to identify and characterize the antimalrial agents from traitional Sudanese medicinal plants. 49 plants parts representing 26 species from 15 families were extracted and screened for their in vitro antimalrial activity using P. falciparum strain 3D7 which is chloroquine sensitive and Dd2 strain which is chloroquine resistant and pyrimethamine sensitive.The plant species investigated exhibited diverse botanical families. They includes Annonaceae, Aristolochiaceae, Asteraceae, Balantiaceae, Caesalpiniceae, Celasteraceae, Cucurbitaceae, Fabaceae, Graminae, Meliaceae, Myrtaceae, Polygonaceae, Rubiaceae, Rutaceae, and simaroubaceae. The evaluation of these plants for their antimalarial activity and their effect on lymphocyte proliferation was carried out. 57 extracts were tested on the chloroquine sensitive strain (3D7). Where 34 extracts (59%) exhibited significant activity against 3D7 with IC_5_0 values #100 #mu# g/ml), where as Sonochous cornatus, ...

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

461

Zinc-blende--wurtzite polytypism in semiconductors

Gel dosimetry is a new dosimetry method applied in radiation therapy. Gel dosimeters consist of a radiation sensitive gel, which can integrate absorbed doses from several radiation sources or beams. The dose to the gel can be evaluated by magnetic resonance imaging (MRI), a procedure that is the focus of the present thesis. A robust tool for the evaluation of the nonuniformity in MRI has been developed, the Deviation Image method. Unlike previously presented methods, the Deviation Image method includes all nonuniformity variations across a phantom surface and is insensitive to stochastic noise. Methods for the estimation of stochastic noise were analyzed in terms of sensitivity to nonuniformities. A method that averages the stochastic noise level over five regions over the phantom surface, and a method that assesses the stochastic noise level from the background, were found to be the methods of choice. Pronounced MR image nonuniformity variation with repetition and T1 ...

2001-03-01

462

Thermodynamics of complexation of aqueous 18-crown-6 with potassium ion: apparent molar volumes and apparent molar heat capacities of aqueous 18-crown-6 and of the (18-crown-6 + potassium chloride) complex at temperatures (278.15 to 393.15) K, at molalities (0.02 to 0.3) mol . kg"-"1, and at the pressure 0.35 MPa

The zinc-blende (ZB) and wurtzite (W) structures are the most common crystal forms of binary octet semiconductors. In this work we have developed a simple scaling that systematizes the {ital T}=0 energy difference {Delta}{ital E}{sub W{minus}ZB} between W and ZB for all simple binary semiconductors. We have first calculated the energy difference {Delta}{ital E}{sub W{minus}ZB}{sup LDF}({ital AB}) for AlN, GaN, InN, AlP, AlAs, GaP, GaAs, ZnS, ZnSe, ZnTe, CdS, C, and Si using a numerically precise implementation of the first-principles local-density formalism (LDF), including structural relaxations. We then find a {ital linear} scaling between {Delta}{ital E}{sub W{minus}ZB}{sup LDF}({ital AB}) and an atomistic orbital-radii coordinate {ital {tilde R}}({ital A},{ital B}) that depends only on the properties of the free atoms {ital A} and {ital B} making up the binary compound {ital AB}. Unlike classical structural coordinates (electronegativity, atomic sizes, electron ...

1992-10-15

463

Spin freezing in the re-entrant spin glass FeNiMn close to the frustration limit

We have measured the densities at temperatures T = (278.15 to 363.15) K and heat capacities at T = (278.15 to 393.15) K of aqueous solutions of 18-crown-6 and of (18-crown-6 + KCl) at molalities m = (0.02 to 0.3) mol . kg"-"1 and at the pressure 0.35 MPa. We have calculated apparent molar volumes V_#phi# and apparent molar heat capacities C_p_,_#phi# for 18-crown-6(aq), and we have applied Young's Rule and have accounted for chemical speciation and relaxation effects to resolve V_#phi# and C_p_,_#phi# for the (18-crown-6: K"+,Cl"-)(aq) complex in the mixture. We have also calculated estimates of the change in volume #DELTA#_rV_m, the change in heat capacity #DELTA#_rC_p_,_m, the change in enthalpy #DELTA#_rH_m, and the equilibrium quotient log Q for formation of the complex at T = (278.15 to 393.15) K and m = (0 to 0.3) mol . kg"-"1.

2004-12-01

464

Semiconductor-metal transition of pyrite FeS_2 under high pressure by full-potential linearized-augmented plane wave calculations

In the invar alloy (Fe{sub 0.65}Ni{sub 0.35}){sub 1-} {sub x} Mn {sub x} we measured the magnetic form factor s(Q) and the intermediate scattering function s(Q,t) for a sample close to the critical Mn concentration (x {sub c}=0.139), at which the sample turns to a re-entrant spin glass phase. The aim was to check whether the magnetic behaviour would approach the Q-independent relaxation behaviour of a classical spin glass when x=x {sub c}. The experiment showed a quite similar spin freezing as for a more ferromagnetic sample with x=0.113. The intermediate scattering function and the form factor were determined by paramagnetic NSE. The normalized scattering function S(Q,t)=s(Q,t)/s(Q)=exp[(-{gamma}t) {sup n}] was fitted by stretched exponential decay. As a function of temperature T<200 K the inverse time constant {gamma} showed the change of more than four orders of magnitude from frozen spin glass (T=60 K to T=100 K), where the ferromagnetic phase occurred. ...

2007-07-15

465

Revisit to the helicity and the generalized self-organization theory

The effects of hydrostatic pressure on the electronic band structure of the semiconductor mineral iron pyrite FeS_2 have been investigated theoretically by an ab initio full-potential linearized-augmented plane wave (FPLAPW) method within a local approximation (LDA/GGA) to the density functional theory. The calculations predict that at a pressure of 94.1 GPa the indirect band gap of pyrite FeS_2 vanishes and the material becomes a metal. This is due to the presence of the S-S and Fe-S bonds, which provide novel energy band distortions in the process of attaining the metallic state. Analysis indicates that, under increasing high pressure, the conduction bands (3p_z of sulfur and 3d_x_"2_-_y_"2+3d_x_y of iron) intrude downwards into the valence bands, which are predominantly 3d in nature. At normal pressure, the lattice constant, the bulk modulus, sulfur position parameter u, S-S bond length, and the indirect band gap of pyrite FeS_2 are calculated using a fully ...

2006-10-11

466

Preparation and electrochemical investigation of Li{sub 2}CoPO{sub 4}F cathode material for lithium-ion batteries

It is clarified that the so-caned 'helicity conservation law' is never the conservation equation of the helicity K itself', but is merely 'the time change rate equation of K', which is passively and resultantly determined by the mutually independent volume and surface integral terms. It is shown that since the total helicity K can never be conserved in the real experimental systems, the conjecture of the total helicity invariance is not physically available to real magnetized plasmas in an exact sense. The well-known relaxation theory by Dr. J. B. Taylor is clarified to be neither the variational principle nor the energy principle, but be merely a mathematical calculation, using the variational calculus in order to find the minimum magnetic energy solution from the set of solutions having the same value of K. With the use of auto-correlations for physical quantities, it is presented that a novel basic formulation of an ...

2000-09-01

467

Polymers in mechanical systems; structure-property requirements

In this paper, we report the electrochemical characteristics of a novel cathode material, Li{sub 2}CoPO{sub 4}F, prepared by solid-state reactions. The solid-state reaction mechanism involved in synthesizing the Li{sub 2}CoPO{sub 4}F also is analyzed in this paper. When cycled between 2.0 V and 5.0 V during cyclic voltammetry measurements, the Li{sub 2}CoPO{sub 4}F samples present one, fully reversible anodic reaction at 4.81 V. When cycled between 2.0 V and 5.5 V, peaks occurring at 4.81 V and 5.12 V in the first anodic scan evolved to one broad oxidative, mound-like pattern in subsequent cycles. Correspondingly, the X-ray diffraction (XRD) pattern of the Li{sub 2}CoPO{sub 4}F electrode discharged from 5.5 V to 2.0 V is slightly different from the patterns exhibited by a fresh sample and the sample discharged from 5.0 V to 2.0 V. This difference may correspond to a structural relaxation that appears above 5 V. In the constant current cycling measurements, the ...

2011-02-15

468

On the analysis and evaluation of enhanced creep behavior of LMFBR structure

This project has been concerned with the understanding of certain key physical and physical chemical properties of polymeric systems which are related to their use as working substances in mechanochemical systems. Since the crystal-liquid phase transition is involved in the process of interest, attention has been focused on this transition and on the properties of semi-crystalline polymers. Two kinds of behavior and properties have been studied in this program. One of these is concerned with melting-crystallization under an applied external force. Here the primary matters of concern are the equilibrium melting temperature-stress relations and the associated problem of crystallization kinetics under an applied external stress. The other area of study involves mechanical properties, with particular emphasis on the influence of the morphological and structural variables which describe the semi-crystalline state. We have taken advantage in this work of concurrent research in our laboratory ...

1983-01-01

469

Molecular-beam/surface-science apparatus for state-resolved chemisorption studies using pulsed-laser preparation

High temperature structures of LMR experience inelastic deformation such as plasticity and creep due to high temperature operating temperature of 530{approx}550 .deg. C. The generated creep strains are connected with the stress relaxations, redistributions and/or progressive deformations. The superposition of primary and secondary stresses may lead to enhanced creep deformations. The term 'creep ratchetting' refer to the phenomenon where enhanced creep occurs with plasticity ratcheting. The interchange of elastoplastic and creep strains is important for its understanding. Since creep ratcheting is highly nonlinear structural behavior, it is required to secure the proper analysis technique to evaluate inelastic strain due to enhanced creep. In this project, the simplified evaluation method for enhanced creep using core stress concept was investigated and the enhanced creep of pipe subjected to sustained axial tensile loading and transient thermal ...

2003-03-01

470

Magnetic properties of laminated perovskite-like ferroelectromagnetics

We describe a new apparatus that combines pulsed laser excitation in a molecular beam with surface-science methods for preparation of clean single-crystal surfaces and detection of adsorbates to enable state-selected studies of gas-surface reaction dynamics. Reactant molecules are prepared in specific vibrationally excited states via overtone pumping using tunable, narrow-band laser radiation. The collision-free environment of the molecular beam prevents relaxation of the prepared molecules before impact on the target surface and enables complete control over the collision energy and incidence angle. Chemisorption products are detected after a given deposition time by Auger electron spectroscopy. To achieve sufficient beam flux of state-selected reactant molecules for product detection by standard surface-science techniques, we use a high-intensity, short-pulse molecular-beam source matched to the low duty cycle of the pulsed lasers used in our experiments. We ...

2003-09-01

471

MRI of normal fetal brain development

Magnetic properties of layer ferromagnets against the thickness are investigated. Two new compounds served for studies: Bisub(6)Tisub(2)Nbsub(0,5)Fesub(2,5)Osub(18) and Bi_7Ti_3Fe_3O_2_1. The Moessbauer effect and the magnetic susceptibility measurements were applied in the experiment. The Faraday method was used in magnetic measurements in fields from 1 to 9,5 kOe. The results of Moessbauer measurements show that temperature dependence of the spectra is typical for compounds with superparamagnetic properties. The magnetic fields Hsub(n) on Fe"5"7 nuclei in Bisub(6)Tisub(2)Nbsub(0,5)Fesub(2,5)Osub(18) and Bi_7Ti_3Fe_3O_2_1 are similar and equal to 520+-10 kOe. Therefore it may be concluded that relaxation times of nuclear spins in these compounds are equal or close to each other. The lines of quadrupole splitting appear in spectra together at 20 K. The results of magnetic measurements show that the Curie-Weiss law is satisfied in the range of high temperatures for ...

1975-01-01

472

Liquid-metal flow in a sharp elbow in a uniform transverse magnetic field

Normal fetal brain maturation can be studied by in vivo magnetic resonance imaging (MRI) from the 18th gestational week (GW) to term, and relies primarily on T2-weighted and diffusion-weighted (DW) sequences. These maturational changes must be interpreted with a knowledge of the histological background and the temporal course of the respective developmental steps. In addition, MR presentation of developing and transient structures must be considered. Signal changes associated with maturational processes can mainly be ascribed to the following changes in tissue composition and organization, which occur at the histological level: (1) a decrease in water content and increasing cell-density can be recognized as a shortening of T1- and T2-relaxation times, leading to increased T1-weighted and decreased T2-weighted intensity, respectively; (2) the arrangement of microanatomical structures to create a symmetrical or asymmetrical environment, leading to structural ...

2006-02-01

473

Light charged particles and intermediate mass fragments from the reactions 486, 550, 640, and 730 MeV [sup 86]Kr + [sup 63]Cu

In the self-cooling blankets of the Tokamak fusion reactor, a liquid metal, namely liquid lithium, is pumped through a system of ducts to transfer heat and capture neutrons. One of the blanket designs proposed in Argonne National Laboratory's Blanket Comparison and Selection study uses a combination of poloidal and toroidal ducts in order to maximize heat transfer while minimizing net pressure drop. In the design, the poloidal and toroidal ducts meet at sharp, abrupt corners. They were modelled as two identical, straight, semi-infinite, thin-walled, rectangular ducts with 45{degree} miters and joined at a 90{degree} angle in the plane of a strong, uniform magnetic field. While in the toroidal containment vessel (i.e. the blanket), the liquid lithium is subjected to a large electromagnetic body force due to the presence of a strong magnetic field. This body force so dominates the flow as to make the inertial and viscous forces negligible everywhere, except in thin boundary or ...

1989-01-01

474

High resolution electron microscopy of interfaces in fcc materials

A study has been made of the reaction [sup 86]Kr + [sup 63]Cu at incident energies of 486, 550, 640, and 730 MeV. Measurements include cross sections, angular distributions, and energy spectra for light charged particles ([sup 1,2,3]H and [sup 4]He), intermediate mass fragments (IMF) (4 [le] Z [le] 17), and heavy fragments (Z [ge] 18). Coincidences between light charged particles and between particles and fragments have been measured to obtain cross sections, energy spectra, and angular distributions. Statistical model analysis of the energy spectra for [sup 1]H and [sup 4]He detected in coincidence with the fragments has allowed estimation of [sup 1]H and [sup 4]He multiplicities associated with the evaporation residues, fragments, and composite nuclei prior to scission. A comparison of cross sections, energy spectra, angular distributions, and particle multiplicities for these matched entrance channels has provided the means for a detailed test of the Bohr Independence Hypothesis. ...

1992-01-01

475

Ground and excited state absorption of Ni{sup 2+} ions in MgAl{sub 2}O{sub 4}: Crystal field analysis

Modern high-resolution electron microscopy (HREM) instruments, which are capable of a point-to-point resolution of better than 0.2 nm, have allowed atomic-scale observations of a variety of internal interfaces. The application of the HREM technique to fcc model systems for the purpose of addressing a number of interface issues will be examined in this paper. Atomic structure observations for heterophase interfaces of metal/metal and metal/metal-oxide systems as well as HREM studies of grain boundaries in NiO and Au will be discussed with emphasis on generic structural features and the role of the interface plane. Comparisons between observed interface structures and atomistic computer modeling results have shown agreements for some interfaces, as well as certain differences in others. A number of structural features are common to both metal and oxide grain boundaries, as well as certain heterophase boundaries. Of particular importance in close-packed solids appears to be the tendency ...

1990-08-01

476

Effects of chronic swimming training on cardiac sarcolemmal function and composition.

The exchange charge model (ECM) of crystal field is utilized to provide the theoretical explanation of the ground state absorption and the excited state absorption observed for the octahedrally coordinated Ni{sup 2+} ions in the spinel MgAl{sub 2}O{sub 4}. The ECM enables modeling of the crystal field parameters (CFPs) for the impurity ions based on the crystal structure data of the host lattice. To ensure the reliability of the CFPs, the convergence of the CFP values with the increasing number of the coordination spheres taken into account in the ECM calculations is considered. The trigonal CFPs B{sub 2}{sup 0},B{sub 4}{sup 0}andB{sub 4}{sup -3} determined by the ECM, together with the appropriate Racah parameters B and C, serve as input to two crystal field analysis computer packages, which compute the energy level schemes within the whole 3d{sup 8} configuration. The cubic approximation utilizing only one CFP Dq is also discussed. Basic features of the ground and excited state ...

2007-04-25

477

Design and performance of radioisotope space power systems based on OSC multitube AMTEC converter designs

Cardiac contractile function is dependent on the integrity and function of the sarcolemmal membrane. Swimming exercise training is known to increase cardiac contractile performance. The purpose of the present study was to examine whether a swimming exercise program would alter sarcolemmal enzyme activity, ion flux, and composition in rat hearts. After approximately 11 wk of exercise training, cardiac myosin and actomyosin Ca2+-adenosinetriphosphatase (ATPase) activity was significantly higher in exercised rat hearts than in sedentary control rat hearts. Glycogen content was increased in plantaris and gastrocnemius muscles from exercised animals as was succinic dehydrogenase activity in gastrocnemius muscle of exercised rats in comparison to sedentary rat preparations. Sarcolemmal vesicles were isolated from hearts of exercise-trained and control rats. Sarcolemmal Na+-K+-ATPase and K+-p-nitrophenylphosphatase activities, Na+-Ca2+ exchange, and passive Ca2+ binding did not differ between ...

1989-04-01

478

Chemical solution deposition of ferroelectric lead lanthanum zirconate titanate films on base-metal foils.

This paper extends the analytical procedure described in another paper in these proceedings to analyze a variety of compact and light-weight OSC-designed radioisotope-heated generators. Those generators employed General Purpose Heat Source (GPHS) modules and a converter containing sixteen AMTEC cells of OSC`s revised five-tube design with enhanced cell wall reflectivity described in a companion paper in these proceedings. OSC found that the performance of the generator is primarily a function of the thermal insulation between the outside of the generator`s 16 cells and the inside of its wall. After examining a variety of insulation options, it was found that the generator`s performance is optimized by employing a hybrid insulation system, in which the space between the cells is filled with fibrous Min-K insulation, and the generator walls are lined with tapered (i.e., graded-length) multifoil insulation. The OSC design results in a very compact generator, with eight AMTEC cells on each ...

1997-12-31

479

Appearance of normal brain maturation on 1.5-T MR images

Development of electronic devices with better performance and smaller size requires the passive components to be embedded within a printed wire board (PWB). The 'film-on-foil' approach is the most viable method for embedding these components within a PWB. We have deposited high-permittivity ferroelectric lead lanthanum zirconate titanate (Pb{sub 0.92}La{sub 0.08}Zr{sub 0.52}Ti{sub 0.48}O{sub x}, PLZT 8/52/48) films on base metal foils by chemical solution deposition. These prefabricated capacitor sheets can be embedded into PWBs for power electronic applications. To eliminate the parasitic effect caused by the formation of a low-permittivity interfacial oxide, a conductive buffer layer of lanthanum nickel oxide (LNO) was applied by chemical solution deposition on nickel foil before the deposition of PLZT. With a {approx} 0.7-{micro}m-thick ferroelectric PLZT film grown on LNO-buffered nickel foil, we measured capacitance densities of 1.5 {micro}F/cm{sup 2}, breakdown ...

2009-01-01

480

Analysis and design of an ultra-high-temperature, hydrogen-fueled MHD generator as an open cycle power supply

To investigate the pattern of normal white-matter maturation as demonstrated by high-field-strength MR imaging, 82 normal infants were examined using a 1.5-T unit with spin-echo T1-weighted and T2-weighted pulse sequences. The infants ranged in age from 4 days to 2 years. The scans were assessed for qualitative changes of white matter relative to gray matter and correlated with the patient's age in 14 anatomic areas of the brain. The MR images showed that changes of brain maturation occur in an orderly manner, commencing in the brain stem and progressing to the cerebellum and the cerebrum. Changes from brain myelination were seen earlier on T1-weighted images than on T2-weighted images, possibly because of T1 shortening by the components of the developing myelin sheaths. The later changes on the T2-weighted images correlated best with the development of myelination, as demonstrated by histochemical methods. T1-weighted images were most useful to monitor normal brain development in the ...

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

481

An investigation of Newton-Krylov algorithms for solving incompressible and low Mach number compressible fluid flow and heat transfer problems using finite volume discretization

The theoretical analysis of a partially-ionized hydrogen gas flow (gas temperatures of approximately 10,000 to 20,000 K) through a particular class of magnetohydrodynamic (MHD) generators and the preliminary design of these MHD generators as open cycle, electric power supplies are performed. Analysis of the gas flow through these ultra-high temperature MHD generators requires a coupled gas dynamics/radiative heat transfer solution. Gas dynamics are modeled by a set of quasi-one-dimensional, nonlinear differential equations which account for friction, convective and radiative heat transfer and the interaction between the ionized gas and applied magnetic field. Radiative heat transfer is modeled using non-gray, absorbing-emitting two- and three-dimensional P-1 approximations which permit an arbitrary variation of the spectral absorption coefficient with frequency. Gas dynamics and radiative heat transfer are coupled through the energy equation, and through the temperature-and ...

1990-01-01

482

Accident analysis in research reactors

Fully coupled, Newton-Krylov algorithms are investigated for solving strongly coupled, nonlinear systems of partial differential equations arising in the field of computational fluid dynamics. Primitive variable forms of the steady incompressible and compressible Navier-Stokes and energy equations that describe the flow of a laminar Newtonian fluid in two-dimensions are specifically considered. Numerical solutions are obtained by first integrating over discrete finite volumes that compose the computational mesh. The resulting system of nonlinear algebraic equations are linearized using Newton`s method. Preconditioned Krylov subspace based iterative algorithms then solve these linear systems on each Newton iteration. Selected Krylov algorithms include the Arnoldi-based Generalized Minimal RESidual (GMRES) algorithm, and the Lanczos-based Conjugate Gradients Squared (CGS), Bi-CGSTAB, and Transpose-Free Quasi-Minimal Residual (TFQMR) algorithms. Both Incomplete Lower-Upper (ILU) ...

1995-10-01

483

ATP-dependent partitioning of the DNA template into supercoiled domains by Escherichia coli UvrAB

Full text: Full text: The incomplete understanding of the complex mechanisms connected with the interaction between thermal-hydraulic and neutron kinetics still challenges the design and the operation of nuclear reactors and imposes the adoption of conservatism in the evaluation of safety limits. The recent availability of powerful computer and computational techniques together with the continuing increase in operational experience suggests the revisiting of those areas and the identification of design/operation requirements that can be relaxed. So far, almost all of the safety analyses of research reactors have been performed using conservative computational tools such as channel codes but, nowadays, the application of Best-Estimate (BE) methods constitutes a real necessity. The global aim of the current work is an attempt to apply the best-estimate system thermal-hydraulic code Relap5. For this purpose, the generic IAEA research reactor Benchmark problem is ...

2006-10-15

484

A phenomenological finite element model of stereolithography processing

The helicase action of the Escherichia coli UvrAB complex on a covalently closed circular DNA template was monitored using bacterial DNA topoisomerase I, which specifically removes negative supercoils. In the presence of E. coli DNA topoisomerase I and ATP, the UvrAB complex gradually introduced positive supercoils into the input relaxed plasmid DNA template. Positive supercoils were not produced when E. coli DNA topoisomerase I was replaced by eukaryotic DNA topoisomerase I or when both E. coli and eukaryotic DNA topoisomerases I were added simultaneously. These results suggest that like other DNA helix-tracking processes, the ATP-dependent action of the UvrAM complex on duplex DNA simultaneously generates both positive and negative supercoils, which are not constrained by protein binding but are torsionally strained. The supercoiling activity of UvrAB on UV-damaged DNA was also studied using UV-damaged plasmid DNA and a mutant UvrA protein that lacks the 40 ...

485

A pain management program for chronic cancer-treatment-related pain: a preliminary study.

In the stereolithography process, three dimensional parts are built layer by layer using a laser to selectively cure slices of a photocurable resin, one on top of another. As the laser spot passes over the surface of the resin, the ensuing chemical reaction causes the resin to shrink and stiffen during solidification. When laser paths cross or when new layers are cured on top of existing layers, residual stresses are generated as the cure shrinkage of the freshly gelled resin is constrained by the adjoining previously-cured material. These internal stresses can cause curling in the compliant material. A capability for performing finite element analyses of the stereolithography process has been developed. Although no attempt has been made to incorporate all the physics of the process, a numerical platform suitable for such development has been established. A methodology and code architecture have been structured to allow finite elements to be birthed (activated) according to a ...

1996-03-01

486

Yeast allosteric chorismate mutase is locked in the activated state by a single amino acid substitution

A large proportion of patients may develop chronic pain following cancer treatments such as surgery, radiotherapy, or chemotherapy. These patients can experience significant levels of physical and psychological morbidity. Our aim was to investigate a cognitive-behavioral pain management program (PMP) for cancer patients with chronic treatment-related pain. Thirteen patients (1 man, 12 women; mean age 52 yrs) completed the study, 9 of whom had a history of breast cancer and had received extensive medical treatment, including surgery. A combination of physical and psychological techniques were adapted from previous work in chronic benign pain and implemented by two therapists. Interventions included education, relaxation, exercise training, and goal setting. A variety of outcomes were examined to assess general fitness, psychological distress, coping success, activities of daily living, and pain report. The median number of interventions by each therapist was 10 (4 ...

2006-02-01

487

Synthesis and spectral properties of diethyl organylchalcogenoalkyl(alkyl)malonates, RX(CH/sub 2/)/sub n/CR'(COOC/sub 2/H/sub 5/)/sub 2/, and 5-alkyl-5-(organylchalcogenoalkyl)barbiturates, RX(CH/sub 2/)/sub n/C(R')CONHC(Y)NHCO (X = Se, Te)

Chorismate mutase, a branch-point enzyme in the aromatic amino acid pathway of Saccharomyces cerevisiae, and also a mutant chorismate mutase with a single amino acid substitution in the C-terminal part of the protein have been purified approximately 20-fold and 64-fold from overproducing strains, respectively. The wild-type enzyme is activated by tryptophan and subject to feedback inhibition by tyrosine, whereas the mutant enzyme does not respond to activation by tryptophan nor inhibition by tyrosine. Both enzymes are dimers consisting of two identical subunits of M_r 30,000, each one capable of binding one substrate and one activator molecule. Each subunit of the wild-type enzyme also binds one inhibitor molecule, whereas the mutant enzyme lost this ability. The enzyme reaction was observed by "1H NMR and shows a direct and irreversible conversion of chorismate to prephenate without the accumulation of any enzyme-free intermediates. The kinetic data of the ...

488

Synthesis and radiolabelling of cysteine derivatives and pharmacological behaviour of their "9"9"mTc complexes

Barbiturates substituted at the 5-position with organyltelluroalkyl or organylselenoalkyl groups were prepared by ring annulation of appropriately substituted diethyl malonates with urea or thiourea. The substituted diethyl malonates (phenyltellurobutyl(ethyl), i-propyltelluropropyl(ethyl), i-propyltelluropropyl(allyl), i-propyselenopropyl(ethyl), and phenylselenohexyl(methyl)) were prepared in 55-91% yield by reaction of diethyl omega-bromoalkyl(alkyl)malonates with organyltellurolates or selenolates (RXNa; X = Se, Te) in ethanol/benzene. The following barbiturates were obtained in 28-84% yield: phenyltellurobutyl(ethyl), m.p. 100/sup 0/C; i-propyltelluropropyl(ethyl), m.p. 119/sup 0/C; i-propylselenopropyl(ethyl), m.p. 137/sup 0/C; phenyl-selenohexyl(methyl), m.p. 124/sup 0/C. The 5-substituted thiobarbiturates i-propyltelluropropyl(ethyl)-(m.p. 75/sup 0/C) and i-propylselenopropyl(ethyl)thiobarbiturate (m.p. 83/sup 0/C) were isolated in 32 and 20% yield, respectively. The ...

1983-01-01

489

Structure and electronic studies of defects in amorphous silicon. Final report, March 1980-February 1981

Full text: HMPAO, a butane monoxime derivative of propylene amine and ECD, ethyl cysteinate dimer, are currently being used as brain imaging agents. In an effort to develop new radiopharmaceuticals for imaging brain, we have synthesized amine and imine derivatives of ethyl cysteinate with butane monoxime, optimized labelling procedure with "9"9"mTc and studied the in vivo behaviour of their "9"9"mTc complexes. Imine derivative of ethyl cysteinate with butane monoxime was synthesized by refluxing equimolar amounts of butane monoxime and ethyl cystinate in dry benzene for 3 hours. The product was purified over silica with 10% ethyl acetate in chloroform as eluent. Amine derivative was prepared by reducing the imine derivative with sodium borohydride. The ligands were characterized by NMR spectroscopy and were found to be pure. The ligands were labelled with "9"9"mTc using stannous chloride as reducing agent. The complexes were characterized by paper chromatography, ...

1998-09-01

490

Structural Investigations of Silica Polyamine Composites: Surface Coverage, Metal Ion Coordination, and Ligand Modification

Basic research of the structure and electronic properties of a-Si:H is reported with particular emphasis on the role of defects. The main findings are as follows: (1) low defect density material can be deposited at a high rate using SiH/sub 4/ diluted in He or Ne. Using Ar or Kr results in a high defect density and columnar material; (2) an electrical bias during deposition modifies the band gap, hydrogen concentration and structure; (3) the clustering of hydrogen in the regions between the columns is confirmed; (4) hydrogen diffusion is observed by NMR; (5) the oxidation of an a-Si:H surface results in approx. 3 x 10/sup 11/ cm/sup -2/ dangling bonds at the interface; (6) auger recombination of photoexcited carriers is a significant non-radiative mechanism at low temperatures; (7) non-radiative recombination by diffusion and capture at dangling bonds is observed at temperatures above 50 to 100/sup 0/K; (8) the defect density in doped and compensated a-Si:H is ...

1981-08-01

491

Structural Investigations of Silica Polyamine Composites: Surface Coverage, Metal Ion Coordination, and Ligand Modification

Silanization of the silica gel surface in the synthesis of silica gel polyamine composites uses (chloropropyl)-trichlorosilane (CPTCS). It is possible to substitute a molar fraction of reagent CPTCS with methyltrichlorosilane (MTCS), creating a mixed silane surface layer. Two types of silica gels were modified with a series of MTCS:CPTCS molar ratios. Solid-state CP/MAS 29Si and 13C NMR spectroscopies were used to evaluate the surface silane composition. Surface silane coverage was markedly improved for the resulting gels. When polyamines were grafted to the resultant MTCS:CPTCS silane layers, it was shown that the decrease in the number of propyl attachments to the polyamine resulted in increased quantities of ''free amines''. Optimum MTCS:CPTCS ratios were determined for three polyamines grafted onto one silica gel. A substantial free amine increase was observed for poly(allylamine) (PAA). Metal uptake studies show increases in ...

2006-09-13

492

Radiation testing of organic ion exchange resins

Silanization of the silica gel surface in the synthesis of silica gel polyamine composites uses (chloropropyl)-trichlorosilane (CPTCS). It is possible to substitute a molar fraction of reagent CPTCS with methyltrichlorosilane (MTCS), creating a mixed silane surface layer. Two types of silica gels were modified with a series of MTCS:CPTCS molar ratios. Solid-state CP/MAS 29Si and 13C NMR spectroscopies were used to evaluate the surface silane composition. Surface silane coverage was markedly improved for the resulting gels. When polyamines were grafted to the resultant MTCS:CPTCS silane layers, it was shown that the decrease in the number of propyl attachments to the polyamine resulted in increased quantities of ''free amines''. Optimum MTCS:CPTCS ratios were determined for three polyamines grafted onto one silica gel. A substantial free amine increase was observed for poly(allylamine) (PAA). Metal uptake studies show increases in ...

2006-09-13

493

Purification and characterization of (-)(/sup 125/I)hydroxyphenylisopropyladenosine, an adenosine R-site agonist radioligand and theoretical analysis of mixed stereoisomer radioligand binding

A number of ion exchange materials are being evaluated as part of the Tank Waste Remediation System (TWRS) Pacific Northwest Laboratory (PNL) Pretreatment Project for the removal of {sup 137}Cs from aqueous tank wastes. Two of these materials are organic resins; a phenol-formaldehyde resin (Duolite CS-100) produced by Rohm and Haas Co. (Philadelphia, Pennsylvania) and a resorcinol-formaldehyde (RF) resin produced by Boulder Scientific Co. (Mead, Colorado). One of the key parameters in the assessment of the organic based ion exchange materials is its useful lifetime in the radioactive and chemical environment that will be encountered during waste processing. The focus of the work presented in this report is the radiation stability of the CS-100 and the RF resins. The scope of the testing included one test with a sample of the CS-100 resin and testing of two batches of the RF resin (BSC-187 and BSC-210). Samples of the exchangers were irradiated with a {sup 60}Co source to a total ...

1995-09-01

494

Mechanistic studies of ethylene biosynthesis in higher plants

(-)-N6-(R-4-Hydroxyphenylisopropyl)adenosine (HPIA) was iodinated with NaI and trace /sup 125/I. Mono- and diiodinated reaction products and the starting material were separated by high pressure liquid chromatography and the structures of the reaction products were verified by NMR. (-)-N6-(R-Phenylisopropyl)adenosine (PIA), IHPIA, and I2HPIA decreased rat atrial contractility with ED50 values of 24, 28, and 33 nM, respectively. The contractile effects of these compounds were competitively blocked by theophylline (KI . 7.9 microM), but were not affected by adenosine deaminase. IHPIA also inhibited (-)isoproterenol-stimulated cyclic AMP accumulation in adipocytes with an ED50 (10 nM) and to an extent (83%) nearly identical to PIA. (/sup 125/I)HPIA prepared using carrier-free /sup 125/I bound to adenosine receptors on membranes from rat cerebral cortex, adipocyte ghosts, and heart ventricles. Binding was inhibited stereospecifically by PIA and by other adenosine ...

1984-11-01

495

Ionising radiation effects on food packaging

Ethylene is a plant hormone that elicits a wide variety of responses in plant tissue. Among these responses are the hastening of abscission, ripening and senescence. In 1979 it was discovered that 1-amino-1-cyclopropane carboxylic acid is the immediate biosynthetic precursor to ethylene. Given the obvious economic significance of ethylene production the authors concentrated their studies on the conversion of ACC to ethylene. They delved into mechanistic aspects of ACC oxidation and they studied potential inhibitors of ethylene forming enzyme (EFE). They synthesized various analogs of ACC and found that EFE shows good stereodiscrimination among alkyl substituted ACC analogs with the 1R, 2S stereoisomer being processed nine times faster than the 1S, 2R isomer in the MeACC series. They also synthesized 2-cyclopropyl ACC which is a good competitive inhibitor of EFE. This compound also causes time dependent loss of EFE activity leading us to believe it is an irreversible inhibitor of ...

1986-01-01

496

Formation of silk fibroin nanoparticles in water-miscible organic solvent and their characterization

The main aim of any food irradiation treatment is to guarantee the best safe quality of the products, reducing the spreading risk ("cross-contamination") for several food-associated diseases. Actually, over 40 countries provide clearances for the treatment of about 45 different types of foodstuffs. EU has to homogenise the situation within the associated States. With the European directive 1999/2/EC Italy, as other EU countries, already has brought into force their regulations to comply. The current Italian regulation on irradiation treatment of foodstuffs is referred since 1996 as follows: a) potatoes, onions and garlic; b) spices, herbs and condiments microbial. The new (April 2001) Italian law allows the possibility to ask for special permission of treatment for other foodstuff which is possible to treat in other E.U. countries. Large majority of foods are submitted to irradiation treatment after they have been packaged. In Dutch cases the study of radiation effects on the package ...

2001-10-22

497

Effects of low-temperature catalytic pretreatments on coal structure and reactivity in liquefaction

When Silk fibre derived from Bombyx mori, a native biopolymer, was dissolved in highly concentrated neutral salts such as CaCl{sub 2}, the regenerated liquid silk, a gradually degraded peptide mixture of silk fibroin, could be obtained. The silk fibroin nanoparticles were prepared rapidly from the liquid silk by using water-miscible protonic and polar aprotonic organic solvents. The nanoparticles are insoluble but well dispersed and stable in aqueous solution and are globular particles with a range of 35-125 nm in diameter by means of TEM, SEM, AFM and laser sizer. Over one half of the {epsilon}-amino groups exist around the protein nanoparticles by using a trinitrobenzenesulfonic acid (TNBS) method. Raman spectra shows the tyrosine residues on the surface of the globules are more exposed than those on native silk fibers. The crystalline polymorph and conformation transition of the silk nanoparticles from random-coil and {alpha}-helix form (Silk I) into anti-parallel {beta}-sheet form ...

2007-10-15

498

Crystal and solution structures of an odorant-binding protein from the southern house mosquito complexed with an oviposition pheromone

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 sulfide catalyst. We also performed a ...

1992-08-01

499