Using radiotracer solutions of Hg (203Hg) and Os (185Os), techniques have been developed for sampling these elements presumably suitable for ion probe measurements. Mercury has been electrodeposited on the cross-sectional area (5 mm2) of an electrochemically pure Cu wire giving a recovery 25 to 30% at the tip. Similar efficiency is found for Hg distillate solutions. Osmium has been collected in a Ni–NiS bead after loading its thiourea complex solution on filter paper. The recovery in the bead is 80–90%. These methods should be of help for isotopic study of these elements by ion microprobe. The suitability of these samples for measurements remains unconfirmed. 相似文献
Diamagnetic susceptibilities of trimethyl(imino-oxy)silanes,Me3SiON CMeR, and dimethyldi(imino-oxy)silanes,Me2Si(ON CMeR)2, containing Si–O bonds are reported. M of these silicon compounds has been calculated theoretically from the method ofBaudet et al. and a good agreement has been obtained between the observed M values and the corresponding calculated values. Si in these compounds has been calculated graphically and the lower values have been explained on the basis of back-bonding to the silicon atom from the oxygen lone pair. 相似文献
A density-functional theory is presented to study the structure of polymers, having attractive interactions, confined between attractive surfaces. The theory treats the ideal-gas free-energy functional exactly and uses weighted density approximation for the hard-chain contribution to the excess free-energy functional. The bulk interactions of freely jointed hard spheres are obtained from generalized Flory equation of state and the attractive interactions are calculated using the direct correlation function obtained from the polymer reference interaction site model theory along with the mean spherical approximation closure. The theoretical predictions are found to be in quite good agreement with the Monte Carlo simulation results for varying densities, chain lengths, and different interaction potentials. The results confirm important implications of using different approximations for the hard-sphere and attractive interactions. 相似文献
A new molybdenum(VI) complex, Li2[Mo2O6(C2O4)] · 2 H2O (LMO), was prepared and characterized by chemical analysis and IR spectral studies. Its thermal decomposition was studied by using TG and DTA techniques. LMO loses its two moles of water between 75 and 170° to give the anhydrous product, which decomposes in three stages between 240 and 380°. The first two stages occur in the temperature ranges 240–280° and 280–305°, to give intermediates with the tentative compositions Li6[Mo6O19(C2O4)2] and Li6[Mo6O20(C2O4)], respectively. In the third stage, which extends up to 380°, Li6[Mo6O20(C2O4)] decomposes to give the end-product, Li2Mo2O7.
Zusammenfassung Ein neuer Molybdän(VI)-Komplex der Formel Li2[Mo2O6(C2O4)] · 2 H2O (LMO) wurde dargestellt und durch chemische Analyse und IR-spektroskopisch charakterisiert. Die thermische Zersetzung dieses Komplexes wurde mittels TG und DTA untersucht. LMO verliert die zwei Wassermoleküle zwischen 75 und 170° unter Bildung des wasserfreien Produktes, das zwischen 240 und 380° in drei Stufen zersetzt wird. Die in den Temperaturbereich von 240–280° und 280–305° verlaufenden ersten zwei Reaktionsschritte ergeben Intermediäre der tentativen Zusammensetzung Li6[Mo6O19(C2O4)2] bzw. Li6[Mo6O20(C2O4)]. In dem sich bis 380° erstreckenden dritten Reaktionsschritt wird Li6[Mo6O20(C2O4)] unter Bildung des Endproduktes Li2Mo2O7 zersetzt.
Using Lobatto nodes, one-step methods of order six and eight have been obtained for the second-order differential equation y″ = f(x, y), y(x0) = y0, y′(x0) = y′0. The methods are shown to be P-stable. If , then at each integration step a system of dimension 3s, 4s, respectively, has to be solved. The numerical results, for two problems, obtained by using these methods are given in the end. 相似文献
Suitably functionalized 3-carbomethoxy/cyano-2H-pyran-2-ones are excellent synthons for the synthesis of arenes and heteroarenes of therapeutic importance. The compounds 6-aryl-3-cyano-4-methylsulfanyl-2H-pyran-2-ones have been transformed into bridgedhead azolopyrimidines and imidazothiazines through thermal and base-induced ring transformation reactions with aminoazoles and imidazolidin-2-thiones, respectively. 相似文献
Tetrel bond, a weak noncovalent interaction between the σ-hole of a Group IV element (silicon in our case) and the cloud of an electronegative element (oxygen in our case) is the focus of this work. The percentage strengthening of tetrel bond has been investigated by optimizing 16 binary complexes of halogenated silane and water of general formula SiXnH4−n−H2O and 16 ternary complexes, of general formula NaX−SiXnH4−n−H2O, where X=F, Cl, Br and I and n=1, 2, 3 and 4 at various levels of theory defined within the formalism of density functional theory (DFT). With the addition of NaX, tetrel bond between Si and O in SiXnH4−n−H2O gets strengthened up to 49 %, owing to cooperativity effect exerted by hydrogen bonding between X and H in the ternary complex NaX−SiXnH4−n−H2O. In the series of complexes studied here, overall stabilization due to cooperativity lies between 10 kJ/mol to 170 kJ/mol. This large extent of reinforcement due to cooperativity has never been showcased before. The exceptional stabilization and reinforcement owe its genesis to the transformation of the ternary complex into a cluster orchestrated by the H-bonding in most of the cases and covalent bonding in few of the cases. 相似文献
The world is witnessing tumultuous times as major economic powers including the US, UK, Russia, India, and most of Europe continue to be in a state of lockdown. The worst-hit sectors due to this lockdown are sales, production (manufacturing), transport (aerospace and automotive) and tourism. Lockdowns became necessary as a preventive measure to avoid the spread of the contagious and infectious “Coronavirus Disease 2019” (COVID-19). This newly identified disease is caused by a new strain of the virus being referred to as Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS CoV-2; formerly called 2019-nCoV). We review the current medical and manufacturing response to COVID-19, including advances in instrumentation, sensing, use of lasers, fumigation chambers and development of novel tools such as lab-on-the-chip using combinatorial additive and subtractive manufacturing techniques and use of molecular modelling and molecular docking in drug and vaccine discovery. We also offer perspectives on future considerations on climate change, outsourced versus indigenous manufacturing, automation, and antimicrobial resistance. Overall, this paper attempts to identify key areas where manufacturing can be employed to address societal challenges such as COVID-19. 相似文献