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91.
We have determined the temperature dependence of σ1 of 129Xe in oxygen gas. These results were obtained by measurement of the resonance frequency of 129Xe in gas samples of known densities in Xe and O2. The shift of the resonance frequency due to Xe-Xe interactions has been measured in pure Xe gas samples with improved precision. This allows the determination of σ1(Xe-O2) by subtracting out the known effect of Xe-Xe interactions in mixed Xe-O2 samples. σ1(Xe-O2) values are reported here for the temperature range 220 to 440 K. The values of σ1(Xe-O2) are adequately described by the polynomial function in p.p.m. amagat-1 σ1(Xe-O2) = - 1·061 + 3·64 × 10-3τ - 2·19 × 10-5τ2 + 9·58 × 10-8τ3 - 2·08 × 10-10τ4, where τ = (T - 300 K). It is found that the temperature dependence of σ1(Xe-O2) can be interpreted in terms of a contact interaction between Xe and the paramagnetic O2 molecule. 相似文献
92.
Ronald Richard Martin Steven Naftel Sheila Macfie Keith Jones Andrew Nelson 《Applied Physics A: Materials Science & Processing》2013,111(1):23-29
Synchrotron micro-X-ray Fluorescence has been used to map the metal distribution in selected bone fragments representative of remains associated with the Franklin expedition. In addition, laser ablation mass spectroscopy using a 25 μm diameter circular spot was employed to compare the Pb isotope distributions in small regions within the bone fragments. The X-ray Fluorescence mapping shows Pb to be widely distributed in the bone while the Pb isotope ratios obtained by laser ablation within small areas representative of bone with different Pb exchange rates do not show statistically significant differences. These results are inconsistent with the hypothesis that faulty solder seals in tinned meat were the principle source of Pb in the remains of the expedition personnel. 相似文献
93.
Sheila C. Araujo Fernanda S. Sousa Thais A. Costa-Silva Andre G. Tempone Joo Henrique G. Lago Kathia M. Honorio 《Molecules (Basel, Switzerland)》2021,26(14)
In the present study, the phytochemical study of the n-hexane extract from flowers of Nectandra leucantha (Lauraceae) afforded six known neolignans (1–6) as well as one new metabolite (7), which were characterized by analysis of NMR, IR, UV, and ESI-HRMS data. The new compound 7 exhibited potent activity against the clinically relevant intracellular forms of T. cruzi (amastigotes), with an IC50 value of 4.3 μM and no observed mammalian cytotoxicity in fibroblasts (CC50 > 200 μM). Based on the results obtained and our previous antitrypanosomal data of 50 natural and semi-synthetic related neolignans, 2D and 3D molecular modeling techniques were employed to help the design of new neolignan-based compounds with higher activity. The results obtained from the models were important to understand the main structural features related to the biological response of the neolignans and to aid in the design of new neolignan-based compounds with better biological activity. Therefore, the results acquired from phytochemical, biological, and in silico studies showed that the integration of experimental and computational techniques consists of a powerful tool for the discovery of new prototypes for development of new drugs to treat CD. 相似文献
94.
Pandey S Ali M Kamath G Pandey S Baker SN Baker GA 《Analytical and bioanalytical chemistry》2012,403(8):2361-2366
Acridine orange (AO) was used as a fluorescent probe molecule to study the encapsulation of an alkylimidazolium cation from a water-soluble ionic liquid (IL) within two cavitand species, p-tetranitrocalix[4]arene (1) and calix[4]resorcinarene (2), both in alkaline aqueous media. The addition of IL to the preformed [1·AO] adduct resulted in significantly increased fluorescence due to the expulsion of AO from the inclusion complex to the aqueous phase by competitive recognition of the 1-alkyl-3-methylimidazolium cation ([C(n)mim](+), n = 4 and 6) by 1. Conversely, the fluorescence signal dropped upon the addition of IL to the [2·AO] host-guest complex due to unfavorable binding between [C(n)mim](+) and 2. The formation of these postulated adducts is corroborated using ab initio calculations, which also provide evidence for the location of [bmim](+) at the lower external rim of [2·AO], providing an explanation for the observed luminescence quenching in the latter case. These results point to a number of different paths for exploration, ranging from the fluorescence monitoring of IL contamination in groundwater to the "daisy chaining" of macrocyles toward supramolecular ionic networks. They also broadly encourage the exploration of ILs in host-guest-based optical and mass spectrometric sensory systems. 相似文献
95.
Rauner Marion S. Niessner Helmut Odd Steen Pope Andrew Neville Karen O’Riordan Sheila Sasse Lisa Tomic Kristina 《Central European Journal of Operations Research》2018,26(2):485-530
Central European Journal of Operations Research - Mankind has faced a huge increase in severe natural and man-made disasters worldwide in the last few years. Emergency responders on a strategic,... 相似文献
96.
Michael Campbell Gang Zheng Peter A. Wallace A. Sheila Holmes-Smith 《Optical Review》1997,4(1):A114-A116
A new distributed stress sensor, based on a birefringent fiber Sagnac ring configuration and frequency modulation continuous wave technology, has been investigated. The two forward-coupled mode beams in the Sagnac ring, induced by an applied stress at any given point along the fiber length, produce a beat frequency which can be analysed to determine, simultaneously, the magnitude and position of the stress. The system has a reasonable spatial resolution of 1 m in a dynamic sensing range of 50 m. 相似文献
97.
The Rayleigh-Sommerfeld diffraction theory is used to derive expressions for (1) the spectral irradiance on the surface of
a hemisphere covering the aperture and (2) the spectral radiant intensity. For a uniform, noncoherent source-aperture, both
calculations predict a cosθ angular variation, as is known to be the case of Lambertian sources. A cosine-fourth dependence of the spectral irradiance
on a plane parallel to the aperture plane is also indicated. 相似文献
98.
Reaction of (5, X = H, Cl, Br) with methyl lithium in ether in the presence alkenes leads to cyclopropanes, e g.(6), apparently derived by trapping of an intermediate carbene (4); in the case of (5, X = Br), the precursor of the carbene, a cyclopropene (1, X=Y=Cl, Z=Me), may be trapped by addition of bromine at ?90°C. 相似文献
99.
Charles F. Beam Howard L. Hall Ann M. Huff Rebecca C. Tummons Sheila A. O'Grady 《Journal of heterocyclic chemistry》1984,21(6):1897-1899
C(α),N-Carboalkoxyhydrazones were metalated with an excess of lithium diisopropylamide (LDA), and the resulting dianions were condensed with methyl iodide, an unsubstituted ketone, a benzoate ester, salicylates, a benzoylacetate, or ethyl chloroformate. 相似文献
100.
V. A. Job S. B. Kartha G. Krishnamurty Sheila Gopal 《Analytical and bioanalytical chemistry》1974,269(1):26-28
The fluoride content of aqueous and organic Purex process solutions can be determined with good reproducibility and accuracy. The method includes a distillation separation of fluoride and its subsequent electrometric determination using a fluoride-selective electrode. The analytical range covers 5 to 500 μg of fluoride per aliquot and the concentration limit is 5×10?5 M (1 ppm). Complexing cations like Al(III), Zr(IV), La(III), and U(VI) do not interfere. 相似文献