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José Gonzalo Rodríguez Alfonso de Pablo Julian Lopez de Lerma Aurea Perales 《Journal of chemical crystallography》1989,19(2):307-316
Methyl substituted 1,4-diacethoxynaphthalenes have been synthetized and analyzed by means of ultraviolet and1H-nmr. Positional effects of the methyl substitution on the spectroscopic parameters have been rationalized. 6,7-Dimethyl-1,4-diacethoxynaphthalene,V, has been analyzed by X-ray diffraction techniques. Crystals are monoclinic P21,a=8.816(1),b=26.676(7),c=6.189(1) Å,=103.9 (2) ° and four molecules in the unit cell. 相似文献
54.
Megan A. Whitefoot Diana Perales Dr. Matthias Zeller Prof. Dr. Suzanne C. Bart 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(72):18054-18057
Two Np(III) halides, NpI3(THF)4 and NpBr3(THF)4, have been prepared and isolated in high yields as described in this work. Starting with neptunia (NpO2), NpCl4(DME)2 was first generated in an updated, higher yielding synthesis than what was previously reported by using HCl/HF. This material was then reduced with KC8, followed by subsequent ligand exchange, to generate NpBr3(THF)4 and NpI3-(THF)4. Full characterization by single-crystal X-ray crystallography, 1H NMR spectroscopy and electronic absorption spectroscopy confirmed the molecular formulas and oxidation states. These trivalent materials are straightforward to synthesize and can be used as starting materials for non-aqueous Np(III) chemistry, obviating the need for rare and restricted Np metal and elemental halogens. 相似文献
55.
Luis F. Pacios Cristina Gómez‐Casado Leticia Tordesillas Arantxa Palacín Rosa Sánchez‐Monge Araceli Díaz‐Perales 《Journal of computational chemistry》2012,33(22):1831-1844
Plant nonspecific lipid transfer proteins (nsLTPs) bind a wide variety of lipids, which allows them to perform disparate functions. Recent reports on their multifunctionality in plant growth processes have posed new questions on the versatile binding abilities of these proteins. The lack of binding specificity has been customarily explained in qualitative terms on the basis of a supposed structural flexibility and nonspecificity of hydrophobic protein‐ligand interactions. We present here a computational study of protein‐ligand complexes formed between five nsLTPs and seven lipids bound in two different ways in every receptor protein. After optimizing geometries in molecular dynamics calculations, we computed Poisson‐Boltzmann electrostatic potentials, solvation energies, properties of the protein‐ligand interfaces, and estimates of binding free energies of the resulting complexes. Our results provide the first quantitative information on the ligand abilities of nsLTPs, shed new light into protein‐lipid interactions, and reveal new features which supplement commonly held assumptions on their lack of binding specificity. © 2012 Wiley Periodicals, Inc. 相似文献
56.
A comparison between two types of adsorbent tubes, the commonly used Tenax TA and a multi-sorbent bed (Carbotrap, Carbopack X, Carboxen 569) tube developed in our laboratory, has been done to evaluate their usefulness in the analysis of VOCs in ambient air. Duplicate indoor and outdoor samples of Tenax TA and multi-sorbent tubes of 10, 20, 40, 60 and 90 l were taken in Barcelona city (Spain) on July and October of 2009. Breakthrough values (defined as %VOCs found in the back tube) were determined for all sampling volumes connecting two sampling tubes in series. The analysis was performed by automatic thermal desorption (ATD) coupled with capillary gas chromatography (GC)/mass spectrometry detector (MSD). Significant differences between the concentrations obtained-from multi-sorbent bed and Tenax TA tubes are observed for the very volatile compounds (56 °C < boiling point < 100 °C and 4 kPa < vapour pressure (20 °C) < 47 kPa) (e.g. acetone, isopropanol, n-hexane) and for alcohols and chlorinated compounds (e.g. 1-butanol, carbon disulphide, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene), being the concentrations found higher in multi-sorbent bed than in Tenax TA tubes. On the other hand, mainly all compounds with boiling points higher than 100 °C (except α-pinene, chlorinated and polar compounds) do not show significant differences between the obtained multi-sorbent bed and Tenax TA tube concentrations. For the concentrations obtained (5 ppt to 100 ppb), Tenax TA present high breakthrough values (from 0 to 77%) for mainly all compounds and sampling volumes studied. On the other hand, multi-sorbent bed tubes do not exhibit important breakthrough values for these compounds, except the VVOCs ethanol (for all sampled volumes), and acetone, dichloromethane and isopropanol (for sampling volumes over 40 l). The concentration differences observed between Tenax TA and multi-sorbent bed tubes are directly related to the high breakthrough values determined for Tenax TA adsorbent. 相似文献
57.
Bose-Einstein condensation of metastable helium 总被引:5,自引:0,他引:5
Pereira Dos Santos F Léonard J Wang J Barrelet CJ Perales F Rasel E Unnikrishnan CS Leduc M Cohen-Tannoudji C 《Physical review letters》2001,86(16):3459-3462
We have observed a Bose-Einstein condensate in a dilute gas of 4He in the (3)2S(1) metastable state. We find a critical temperature of (4.7+/-0.5) microK and a typical number of atoms at the threshold of 8 x 10(6). The maximum number of atoms in our condensate is about 5 x 10(5). An approximate value for the scattering length a = (16+/-8) nm is measured. The mean elastic collision rate at threshold is then estimated to be about 2 x 10(4) s(-1), indicating that we are deeply in the hydrodynamic regime. The typical decay time of the condensate is 2 s, which places an upper bound on the rate constants for two-body and three-body inelastic collisions. 相似文献
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Toyoda H Trischuk W de Troconiz JF Truitt S Tseng J Turini N Ukegawa F Valls J Vejcik S Velev G Vidal R Vilar R Vologouev I Vucinic D Wagner RG Wagner RL Wahl J Wallace NB Walsh AM Wang C Wang CH Wang MJ Watanabe T Waters D Watts T Webb R 《Physical review letters》2000,84(10):2094-2099
We have reconstructed the radiative decays chi(b)(1P)-->Upsilon(1S)gamma and chi(b)(2P)-->Upsilon(1S)gamma in p&pmacr; collisions at sqrt[s] = 1.8 TeV, and measured the fraction of Upsilon(1S) mesons that originate from these decays. For Upsilon(1S) mesons with p(Upsilon)(T)>8.0 GeV/c, the fractions that come from chi(b)(1P) and chi(b)(2P) decays are [27.1+/-6.9(stat)+/-4. 4(syst)]% and [10.5+/-4.4(stat)+/-1.4(syst)]%, respectively. We have derived the fraction of directly produced Upsilon(1S) mesons to be [50.9+/-8.2(stat)+/-9.0(syst)]%. 相似文献
60.
Poolman HR Boersma DJ Harvey M Higinbotham DW Passchier I Six E Alarcon R van Amersfoort PW Bauer TS Boer Rookhuizen H van Den Brand JF van Buuren LD Bulten HJ Ent R Ferro-Luzzi M Geurts DG Heimberg P de Jager CW Klimin P Koop I Kroes F van Der Laan J Luijckx G Lysenko A Militsyn B Nesterenko I 《Physical review letters》2000,84(17):3855-3858
We report on first measurements with polarized electrons stored in a medium-energy ring and with a polarized internal target. Polarized electrons were injected at 442 MeV (653 MeV), and a partial (full) Siberian snake was employed to preserve the polarization. Longitudinal polarization at the interaction point and polarization lifetime of the stored electrons were determined with laser backscattering. Spin observables were measured for electrodisintegration of polarized 3He, with simultaneous detection of scattered electrons, protons, neutrons, deuterons, and 3He nuclei, over a large phase space. 相似文献