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排序方式: 共有560条查询结果,搜索用时 31 毫秒
31.
The temperature‐ and electric field‐dependent dielectric relaxation and polarisation of a new chiral swallow tailed antiferroelectric liquid crystal, i.e. 1‐ethylpropyl (S)‐2‐{6‐[4‐(4′‐decyloxyphenyl)benzoyloxy]‐2‐naphthyl}propionate (abbreviated as EP10PBNP), were investigated. The electric field‐induced dielectric loss spectra of EP10PBNP revealed electroclinic and anomalous dielectric behaviour in the chiral smectic A (SmA*)–chiral antiferroelectric smectic C (SmCA*) pre‐transitional regime. From an analysis of thermal hysteresis of the dielectric constant, electric field‐induced polarisation and dielectric loss spectra, the appearance of a ferrielectric‐like mesophase is observed followed by an unstable SmCA* phase in the SmA*–SmCA* pre‐transitional regime. 相似文献
32.
Kommuri Shekarrao Partha Pratim KaishapShyamalee Gogoi Sanjib Gogoi Romesh C. Boruah 《Tetrahedron letters》2014
A facile method for the synthesis of steroidal D-ring fused pyrazolo[1,5-a]pyrimidines through a microwave mediated reaction between steroidal β-bromovinyl aldehydes and pyrazoloamines using palladium(II) catalyst has been described. 相似文献
33.
Partha Pratim Kaishap Kommuri ShekarraoPallabi Saikia Sanjib Gogoi Romesh C. Boruah 《Tetrahedron letters》2014
The preparation of steroid/nonsteroid fused benzo[b][1,4]thiazepines and 2-arylsubstituted benzo[b][1,4]thiazepines is described from Pd(OAc)2 catalyzed reaction of steroidal/nonsteroidal β-halovinyl aldehydes and 2-aminothiophenols in DMF under heating condition. 相似文献
34.
Biswajit Acharya Partha Sarathi Guru 《Journal of Dispersion Science and Technology》2014,35(10):1492-1501
Tween-80–n–butanol–diesel–water microemulsion systems with various surfactant:cosurfactant (S:C) ratio have been reported as a class of alternative diesel fuel from their phase behavior, clouding phenomena, conductivity, turbidity, and inflammation studies. Temperature induced clouding of microemulsion containing 2% brine at an S:C ratio of 1:1 from a suitable turbid zone has been examined to see the stability of the diesel–water microemulsion systems. Regression models have been proposed to understand the impact of various components of the microemulsion on their cloud point (CP) values. Conductivity of the microemulsions at various S:C ratio increases with the volume of brine having two cut points depicting the presence of three microheterogenous phases within the system, whereas turbidity shows a linear increase. Dye-probed investigation of water-rich and oil-rich zones of the microemulsions indicates the involvement of a dynamic mass transfer process within the various zones. The intensities of flames produced during burning of the microemulsions with various O:E:W weight percentages selected from the isotropic regions of the phase diagrams have been estimated using MATLAB image processing method and the impacts of various components on the fuel use of the microemulsions have been analyzed. 相似文献
35.
S. Kumar S. U. Kasar R. K. Bajpai C. P. Kaushik R. Guin S. K. Das B. S. Tomar 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(1):45-49
Kinetics of sorption of Pu(IV) by smectite-rich clay has been studied at varying metal ion concentrations. Different concentrations were achieved using different isotopes of Pu, namely, 239Pu, 238Pu and 237Pu. 237Pu was produced by alpha induced reaction on 235U, followed by radiochemical separation of Pu from irradiated U3O8 target. The concentrations used are above and below the solubility of Pu(IV) under neutral pH conditions, thereby, indicating the mechanism of sorption reactions of Pu(IV) in typical laboratory experiments and field level observations. Kinetics of Pu(IV) at 10?13 M concentration was found to be fast whereas at higher metal concentration the rate is governed by a slow step, indicating the role of formation of Pu(IV) polymeric species at the sorbent surface. 相似文献
36.
Modification of Extended Open Frameworks with Fluorescent Tags for Sensing Explosives: Competition between Size Selectivity and Electron Deficiency
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Bappaditya Gole Dr. Arun Kumar Bar Prof. Partha Sarathi Mukherjee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(8):2276-2291
Three new electron‐rich metal–organic frameworks ( MOF‐1 – MOF‐3 ) have been synthesized by employing ligands bearing aromatic tags. The key role of the chosen aromatic tags is to enhance the π‐electron density of the luminescent MOFs. Single‐crystal X‐ray structures have revealed that these MOFs form three‐dimensional porous networks with the aromatic tags projecting inwardly into the pores. These highly luminescent electron‐rich MOFs have been successfully utilized for the detection of explosive nitroaromatic compounds (NACs) on the basis of fluorescence quenching. Although all of the prepared MOFs can serve as sensors for NACs, MOF‐1 and MOF‐2 exhibit superior sensitivity towards 4‐nitrotoluene (4‐NT) and 2,4‐dinitrotoluene (DNT) compared to 2,4,6‐trinitrotoluene (TNT) and 1,3,5‐trinitrobenzene (TNB). MOF‐3 , on the other hand, shows an order of sensitivity in accordance with the electron deficiencies of the substrates. To understand such anomalous behavior, we have thoroughly analyzed both the steady‐state and time‐resolved fluorescence quenching associated with these interactions. Determination of static Stern–Volmer constants (KS) as well as collisional constants (KC) has revealed that MOF‐1 and MOF‐2 have higher KS values with 4‐NT than with TNT, whereas for MOF‐3 the reverse order is observed. This apparently anomalous phenomenon was well corroborated by theoretical calculations. Moreover, recyclability and sensitivity studies have revealed that these MOFs can be reused several times and that their sensitivities towards TNT solution are at the parts per billion (ppb) level. 相似文献
37.
Daniel L. Obrzut Prakash M. Adekkanattu Jyothi Thundimadathil Jing Liu Delphine R. Dubois James A. Guin 《Reaction Kinetics and Catalysis Letters》2003,80(1):113-121
SAPO-34 silicoaluminophosphate molecular sieve produces large amounts of methane at elevated temperatures in the methanol
to olefins (MTO) process. This significantly reduces the lower olefins selectivity a key factor in determining the commercial
viability of this catalyst. Impregnation of the SAPO-34 molecular sieve with metal ions such as K, Cs, Pt, Ag and Ce was found
to reduce the amount of methane significantly at higher temperatures thereby increasing the lower olefins selectivity. This
observed effect is less apparent at lower temperatures where the amount of methane formed is generally low.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
38.
39.
Assuming confinement and chiral symmetry breaking, we have calculated constituent quark masses from phenomenological q potentials by using a BCS-like gap equation. 相似文献
40.
Alexander McKillop Alan Henderson Partha S. Ray Carmen Avendano Encarnacion G. Molinero 《Tetrahedron letters》1982,23(33):3357-3360
Ethyl carboethoxyformimidate is shown to be a versatile reagent for the synthesis of a variety of mono- and bicyclic heterocyclic systems. 相似文献