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101.
Photocyclisation of 3-alkoxy-6-chloro-2-(3-methylthiophen-2-yl)-4H-chromen-4-ones in methanol with pyrex filtered UV-light lead to the formation of tetracyclic compounds through intramolecular γ-hydrogen abstraction. The methyl group on the thiophenyl ring does not interfere in the photocyclisation although it does effect the product formation. 相似文献
102.
Jang DP Kim I Chang SY Min HK Arora K Marsh MP Hwang SC Kimble CJ Bennet KE Lee KH 《The Analyst》2012,137(6):1428-1435
Although fast-scan cyclic voltammetry (FSCV) has contributed to important advances in neuroscience research, the technique is encumbered by significant analytical challenges. Confounding factors such as pH change and transient effects at the microelectrode surface make it difficult to discern the analytes represented by complex voltammograms. Here we introduce paired-pulse voltammetry (PPV), that mitigates the confounding factors and simplifies the analytical task. PPV consists of a selected binary waveform with a specific time gap between each of its two comprising pulses, such that each binary wave is repeated, while holding the electrode at a negative potential between the waves. This allows two simultaneous yet very different voltammograms (primary and secondary) to be obtained, each corresponding to the two pulses in the binary waveform. PPV was evaluated in the flow cell to characterize three different analytes, (dopamine, adenosine, and pH changes). The peak oxidation current decreased by approximately 50%, 80%, and 4% for dopamine, adenosine, and pH, in the secondary voltammogram compared with the primary voltammogram, respectively. Thus, the influence of pH changes could be virtually eliminated using the difference between the primary and secondary voltammograms in the PPV technique, which discriminates analytes on the basis of their adsorption characteristics to the carbon fiber electrode. These results demonstrate that PPV can be effectively used for differentiating complex analytes. 相似文献
103.
104.
Renu Chadha Poonam Arora Swati Bhandari Dharam Vir Singh Jain 《Journal of inclusion phenomena and macrocyclic chemistry》2012,72(3-4):275-287
The present work describes the effect of PVP on the complexation efficiency of cyclodextrins towards efavirenz, a poorly soluble antiretroviral agent imparting irritating sensation to buccal cavity. The phase solubility study indicates 1:1 stoichiometry for binary and ternary systems. DSC and XRPD revealed complete inclusion only in the lyophilized systems. The ternary systems were autoclaved before being lyophilized for the best results. Proton NMR suggests that the chlorobenzene part of benzoxazinone ring of the drug is involved in inclusion and was confirmed by 2D-COESY. The thermodynamic parameters, indicative of complexation efficiency were calculated calorimetrically by determining the interaction enthalpy of efavirenz with cyclodextrins in the presence and absence of PVP. The value of stability constants increased in the order β-CD?<?HP-β-CD?<?M-β-CD and is still higher in the presence of PVP illustrating the facilitation of the inclusion. Molar enthalpy of interaction of autoclaved solid formulation determined calorimetrically indicated stronger interaction for efavirenz:M-βCD-PVP system (?12.20?kJ/mol) which showed highest solubility and dissolution rate. The in vitro measurement of permeability showed a ten fold increase in the flux for the autoclaved formulation containing efavirenz-M-β-CD-PVP. In conclusion, encapsulation by cyclodextrins increases the solubility and suppresses the oral irritation of efavirenz. PVP further increases the complexation efficiency and decreases the bulk of cyclodextrins. 相似文献
105.
In Alzheimer's disease, copper binds to amyloid beta (Aβ) peptide and generates oxidative stress. The coordination of histidine (His) residues to Cu(2+) is still uncertain. We studied Cu(2+) binding to Aβ1-16 peptide using the diethyl pyrocarbonate (DEPC) assay and mass spectrometry. Our results show that only one His is involved in Cu(2+) coordination, which is identified as His6 using mass spectral studies. Novel nickel displacement studies have further supported the proposal that the Cu(2+) binding site of Aβ1-16 peptide resembles the ATCUN motif of human serum albumin. 相似文献
106.
The theory of Tuncay and Corapcioglu (Transp Porous Media 23:237–258, 1996a) has been employed to investigate the possibility
of plane wave propagation in a fractured porous medium containing two immiscible fluids. Solid phase of the porous medium
is assumed to be linearly elastic, isotropic and the fractures are assumed to be distributed isotropically throughout the
medium. It has been shown that there can exist four compressional waves and one rotational wave. The phase speeds of these
waves are found to be affected by the presence of fractures, in general. Of the four compressional waves, one arises due to
the presence of fractures in the medium and the remaining three are those encountered by Tuncay and Corapcioglu (J Appl Mech
64:313–319, 1997). Reflection and transmission phenomena at a plane interface between a uniform elastic half-space and a fractured
porous half-space containing two immiscible fluids, are analyzed due to incidence of plane longitudinal/transverse wave from
uniform elastic half-space. Variation of modulus of amplitude and energy ratios with the angle of incidence are computed numerically
by taking the elastic half-space as granite and the fractured porous half-space as sandstone material containing non-viscous
wetting and non-wetting fluid phases. The results obtained in case of porous half-space with fractures, are compared graphically
with those in case of porous half-space without fractures. It is found that the presence of fractures in the porous half-space
do affect the reflection/transmission of waves, which is responsible for raising the reflection and lowering the transmission
coefficients. 相似文献
107.
Sham M. Sondhi Nidhi Singhal Rajeshwar P. Verma Sudershan K. Arora Rakesh Shukla Ram Raghubir 《Monatshefte für Chemie / Chemical Monthly》2000,131(5):501-509
Summary. Upon condensation with 4-isothiocyanato-4-methyl-2-pentanone, 2,3-diaminonaphthalene and N-aminoethyladenosine gave in good
yields substituted pyrimidonaphthoimidazole and imidazopyrimidine thione. Refluxing pyrimidobenzthiazole with methanol H2SO4 at pH∼1 resulted in S-methyl pyrimidobenzthiazole in moderate yield. Pyrimidobenzimidazole derivatives could be reacted to S-alkylated
and N-acylated derivatives by refluxing with ethyl bromoacetate in the presence of anhydrous potassium carbonate in THF and by heating in an acetic acid/acetic anhydride mixture. Heating of pyrimidobenzimidazole with 75% aqueous H2SO4 on a water bath ended up in a rearranged product. All compounds gave correct 1H NMR, IR, and HR mass spectra. Results of antiinflammatory, analgesic, and anticancer activity screening of the new compounds
are described.
Received October 29, 1999. Accepted (revised) January 13, 2000 相似文献
108.
Efforts have been successful to crystallize the electroceramic compound of cadmium tartrate through silica hydrogel. Analysis of thermograms reveals decomposition of the crystals to take place within the temperature range 65 to 442°C in air atmosphere. Some important characteristic data, i.e., valance electron plasma energy, Penn gap, Fermi energy, interionic distance, electronic polarizability have been obtained. The DC conductivity of the crystal typically lies between the conductivities of metal and insulator and we derived several pertinent parameters such as hopping energy, hopping distance, coulomb gap, etc. The micromechanical indentation of the crystal shows nonlinear variation of the impact microhardness as a function of the applied load. The estimation of fracture toughness, fragility coefficient and yield strength has too been made for the synthesized crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
109.
Flow of fluid through packed bed of porous particles is modelled with the help of Peclet number (Pe) and Biot number (Bi). Packed bed is divided into three zones, flowing liquor, intrapore solute present in pores of particles and solute adsorbed on particle surface. Langmuir isotherm is used to describe the relationship between intrapore solute concentration and concentration of solute adsorbed on particle surface, whereas the bulk fluid concentration and the intrapore solute concentration are related by linear adsorption isotherm. Model predicted values are also compared with the experimental values. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
110.
Lal Sohan Arora Sanjiv Kumar Vinod Rani Shikha Jagdeva Geetanjali 《Journal of Thermal Analysis and Calorimetry》2021,143(4):3267-3274
Journal of Thermal Analysis and Calorimetry - The different concentrations of chitosan were applied on cotton fabrics using glutaraldehyde as a cross-linking agent. The fabric samples were... 相似文献