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131.
Filter cake formation is important in groundwater and oil wells where drilling contains suspended mud particles. The accumulation of these mud particles on the borehole wall creates a pressure drop in the well. Furthermore, the migration of colloidal particles into adjacent porous rock could damage the formation and cause productivity decline. In this study, numerical solutions for pore liquid pressure variation across the cake with variable total stress and associated porosity variation are obtained. Mass equations for captured and suspended particles are averaged along the mud cake thickness, taking into account conditions on the cake surface and at the filter septum. The variability of total stress in soil consolidations problem is considered to determine the pore liquid pressure along the mud cake thickness. Then, the relation between porosity and pressure is studied to determine the mud cake porosity. Experimental data obtained by various researchers is used to compare and test the validity of numerical solutions to develop guidelines for model applications. Results show that the pore liquid pressure increases with the decrease of membrane impedance value (i.e. less pervious membrane). Also, the pressure profile has a cubic function of dimensionless cake thickness. The conclusions from the sensitivity analysis conducted in this study agree with earlier conclusions. 相似文献
132.
John W. CranMarie E. Krafft Kimberly A. SeibertThomas F.N. Haxell James A. WrightChitaru Hirosawa Khalil A. Abboud 《Tetrahedron》2011,67(51):9922-9943
From the initial development of a homologous Morita-Baylis-Hillman reaction utilizing epoxides as electrophiles, the method was expanded to enable the exclusively organocatalyzed intramolecular allylation of enones and to develop the intramolecular MBH-type alkylation of activated alkenes. We successfully utilized both enones and unsaturated thioesters as the activated alkene component. This work, carried out using stoichiometric amounts of the trialkylphosphine, gave an array of functionalized five- and six-membered carbocycles in high yields. With the cycloalkylation of enones and thioesters, conditions that allowed the use of substoichometric amounts of the phosphine catalyst were developed. As a result both five- and six-membered rings can be formed efficiently with little to no loss in yield upon comparison to yields obtained when stoichiometric amounts of trialkylphosphines were employed. We isolated, for the first time, an MBH-type intermediate exhibiting unprecedented trans geometry of the phosphonium salt and acyl group. 相似文献
133.
Park J Lang K Abboud KA Hong S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(7):2236-2245
A series of novel bis-urea-functionalized (salen)Co complexes has been developed. The complexes were designed to form self-assembled structures in solution through intermolecular urea-urea hydrogen-bonding interactions. These bis-urea (salen)Co catalysts resulted in rate acceleration (up to 13 times) in the hydrolytic kinetic resolution (HKR) of rac-epichlorohydrin in THF by facilitating cooperative activation, compared to the monomeric catalyst. In addition, one of the bis-urea (salen)Co(III) catalyst efficiently resolves various terminal epoxides even under solvent-free conditions by requiring much shorter reaction time at low catalyst loading (0.03-0.05 mol %). A series of kinetic/mechanistic studies demonstrated that the self-association of two (salen)Co units through urea-urea hydrogen bonds was responsible for the observed rate acceleration. The self-assembly study with the bis-urea (salen)Co by FTIR spectroscopy and with the corresponding (salen)Ni complex by (1)H NMR spectroscopy showed that intermolecular hydrogen-bonding interactions exist between the bis-urea scaffolds in THF. This result demonstrates that self-assembly approach by using non-covalent interactions can be an alternative and useful strategy toward the efficient HKR catalysis. 相似文献
134.
A hybrid ion mobility-mass spectrometer (IM-MS) incorporating a variable-temperature (80–400 K) drift tube is presented. The
instrument utilizes an electron ionization (EI) source for fundamental small molecule studies. Ions are transferred to the
IM-MS analyzer stages through a quadrupole, which can operate in either broad transmission or mass-selective mode. Ion beam
modulation for the ion mobility experiment is accomplished by an electronic shutter gate. The variable-temperature ion mobility
spectrometer consists of a 30.2 cm uniform field drift tube enclosed within a thermal envelope. Subambient temperatures down
to 80 K are achievable through cryogenic cooling with liquid nitrogen, while elevated temperatures can be accessed through
resistive heating of the envelope. Mobility separated ions are mass analyzed by an orthogonal time-of-flight (TOF) mass spectrometer.
This report describes the technological considerations for operating the instrument at variable temperature, and preliminary
results are presented for IM-MS analysis of several small mass ions. Specifically, mobility separations of benzene fragment
ions generated by EI are used to illustrate significantly improved (greater than 50%) ion mobility resolution at low temperatures
resulting from decreased diffusional broadening. Preliminary results on the separation of long-lived electronic states of
Ti+ formed by EI of TiCl4 and hydration reactions of Ti+ with residual water are presented. 相似文献
135.
Wyche TP Hou Y Braun D Cohen HC Xiong MP Bugni TS 《The Journal of organic chemistry》2011,76(16):6542-6547
A marine Verrucosispora sp. isolated from the sponge Chondrilla caribensis f. caribensis was found to produce thiocoraline, a potent cytotoxic compound. Five new analogs of thiocoraline were isolated and represent the first analogs of thiocoraline. 22'-Deoxythiocoraline (2), thiochondrilline C (5), and 12'-sulfoxythiocoraline (6) demonstrated significant cytotoxicity against the A549 human cancer cell line with EC(50) values of 0.13, 2.86, and 1.26 μM, respectively. The analogs provide insight into the SAR and biosynthesis of thiocoraline. The DP4 probability method was used to analyze ab initio NMR calculations to confirm stereochemical assignments. 相似文献
136.
Schnaars DD Batista ER Gaunt AJ Hayton TW May I Reilly SD Scott BL Wu G 《Chemical communications (Cambridge, England)》2011,47(27):7647-7649
Syntheses and characterization of UCl(2)((Ar)acnac)(2), UI(2)((Ar)acnac)(2), and PuI(2)((Ar)acnac)(2) are reported ((Ar)acnac denotes a bis-phenyl β-ketoiminate ligand where Ar = 3,5-(t)Bu(2)C(6)H(3)). Structural analyses and computations show significant metal-ligand orbital interaction differences in U(IV) vs. Pu(IV) bonding. 相似文献
137.
Santos CM Tria MC Vergara RA Ahmed F Advincula RC Rodrigues DF 《Chemical communications (Cambridge, England)》2011,47(31):8892-8894
The first report on the fabrication and application of a nanocomposite containing poly-N-vinyl carbazole (PVK) polymer and graphene oxide (GO) as an antimicrobial film was demonstrated. The antimicrobial film was 90% more effective in preventing bacterial colonization relative to the unmodified surface. More importantly, the nanocomposite thin film showed higher bacterial toxicity than pure GO-modified surface. 相似文献
138.
Sharma SK May PS Jones MB Lense S Hardcastle KI MacBeth CE 《Chemical communications (Cambridge, England)》2011,47(6):1827-1829
The ligand bis(2-isobutyrylamidophenyl)amine has been prepared and used to stabilize both mononuclear and dinuclear cobalt(II) complexes. The nuclearity of the cobalt product is regulated by the deprotonation state of the ligand. Both complexes catalytically oxidize triphenylphosphine to triphenylphosphine oxide in the presence of O(2). 相似文献
139.
Elias Abboud 《Israel Journal of Mathematics》1987,59(3):272-282
A finite groupG is calledQ-admissible if there exists a finite dimensional central division algebra overQ, containing a maximal subfield which is a Galois extension ofQ with Galois group isomorphic toG. It is proved thatS
5
−
, one of the two nontrivial central extensions ofS
5 byZ/2Z, isQ-admissible. As a consequence of that result and previous results of Sonn and Stern, every finite Sylow-metacyclic group,
havingA
5 as a composition factor, isQ-admissible.
This paper is part of a M.Sc. thesis written at the Technion — Israel Institute of Technology, under the supervision of Professor
J. Sonn, whom the author wishes to thank for his valuable guidance. 相似文献
140.
The blue organic dye, 2,6-dichloroindophenol (DCIP), was immobilized on PEGylated Merrifield resin after a chlorination step followed by a nucleophilic substitution reaction, using microwave-assisted methodology. The final product was a blue pigmented resin that can be reversibly reduced by ascorbic acid and changes color from blue to light yellow. Structural elucidation of this immobilized indicator was confirmed through FTIR and elemental analyses. 相似文献