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P F Renshaw J C Haselgrove L Bolinger B Chance J S Leigh 《Magnetic resonance imaging》1986,4(3):193-198
It has recently been demonstrated that NMR imaging can be used to record the distribution of lithium. We now report on the parameters pertinent to this imaging. Specifically, the relaxation of Li in aqueous solution, in agarose gel, and in vivo has been investigated. In the latter case, both the longitudinal and transverse relaxations were biexponential, consistent with the behavior expected for a spin 3/2 quadrupole relaxed nucleus. The overall relaxation rate was quite slow in vivo with T'1 = 3.5 sec and T'1 = 6.6 sec. 相似文献
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Vitalie Stavila Jae-Hyuk Her Wei Zhou Son-Jong Hwang Leigh Anna M. Ottley 《Journal of solid state chemistry》2010,183(5):1133-1140
Calcium borohydride can reversibly store up to 9.6 wt% hydrogen; however, the material displays poor cyclability, generally associated with the formation of stable intermediate species. In an effort to understand the role of such intermediates on the hydrogen storage properties of Ca(BH4)2, calcium dodecahydro-closo-dodecaborate was isolated and characterized by diffraction and spectroscopic techniques. The crystal structure of CaB12H12 was determined from powder XRD data and confirmed by DFT and neutron vibrational spectroscopy studies. Attempts to dehydrogenate/hydrogenate mixtures of CaB12H12 and CaH2 were made under conditions known to favor partial reversibility in calcium borohydride. However, up to 670 K no notable formation of Ca(BH4)2 (during hydrogenation) or CaB6 (during dehydrogenation) occurred. It was demonstrated that the stability of CaB12H12 can be significantly altered using CaH2 as a destabilizing agent to favor the hydrogen release. 相似文献
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Timothy J. Boyle Leigh Anna M. Ottley Todd M. Alam Mark A. Rodriguez Pin Yang Sarah K. Mcintyre 《Polyhedron》2010
The first study into the alcohol solvation of lanthanum halide [LaX3] derivatives as a means to lower the processing temperature for the production of the LaBr3 scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(μ-Br)(H2O)7](Br)2}2 (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H2O)7(MeOH)2](Br)3 (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH2, crystals of [Ca(MeOH)6](Br)2 (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr2.75·5.25(MeOH)]+0.25 [LaBr3.25·4.75(MeOH)]−0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr3 in MeOH forming the 8-coordinated [LaBr3(MeOH)5] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX3 derivatives were isolated as [(MeOH)4(Cl)2La(μ-Cl)]2 (6) and [La(MeOH)9](I)3·MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (139La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4–6 were slightly higher in comparison to their hydrated counterparts. 相似文献
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John R. Kucklick Michele M. Schantz Rebecca S. Pugh Barbara J. Porter Dianne L. Poster Paul R. Becker Teri K. Rowles Stefan Leigh Stephen A. Wise 《Analytical and bioanalytical chemistry》2010,397(2):423-432
The National Institute of Standards and Technology (NIST) has a diverse collection of control materials derived from marine
mammal blubber, fat, and serum. Standard Reference Material (SRM) 1945 Organics in Whale Blubber was recertified for polychlorinated
biphenyl (PCB) congeners, organochlorine pesticides, and polybrominated diphenyl ether (PBDE) congeners. SRM 1945 has also
been assigned mass fraction values for compounds not frequently determined in marine samples including toxaphene congeners,
coplanar PCBs, and methoxylated PBDE congeners which are natural products. NIST also has assigned mass fraction values, as
a result of interlaboratory comparison exercises, for PCB congeners, organochlorine pesticides, PBDE congeners, and fatty
acids in six homogenate materials produced from marine mammal blubber or serum. The materials are available from NIST upon
request; however, the supply is very limited for some of the materials. The materials include those obtained from pilot whale
blubber (Homogenates III and IV), Blainville’s beaked whale blubber (Homogenate VII), polar bear fat (Homogenate VI), and
California sea lion serum (Marine Mammal Control Material-1 Serum) and blubber (Homogenate V). 相似文献
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