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181.
S Biswas R Chakraborti R Cowsik N Durgaprasad P J Kajarekar R K Singh M N Vahia J S Yadav N Dutt J N Goswami D Lal H S Mazumdar D V Subhedar M K Padmanabhan 《Pramana》1986,27(1-2):89-104
The measurements of the ionization states, composition, energy spectra and spatial distribution of heavy ions of helium to
iron of energies 10–100 MeV/amu in the anomalous cosmic rays are of major importance in understanding their origin which is
unknown at present.Anuradha (IONS) cosmic ray experiment in Spacelab-3 was designed to determine the above properties in near earth space and this had
a highly successful flight and operations aboard the shuttle Challenger at an orbital altitude of 352 km during 29 April to
6 May 1985. The instrument employs solid state nuclear track detectors (CR-39) of high sensitivity and large collecting area
of about 800 cm2 and determines the arrival time information of particles with active elements. Experimental methods, flight operations and
preliminary results are briefly described. Initial results indicate that relatively high fluxes of low energy cosmic ray α-particles,
oxygen group and heavier ions were obtained. The flight period corresponded to that of quiet Sun and the level of solar activity
was close to solar minimum. It is estimated that about 10,000 events of low energy cosmic ray alpha particles with time annotation
are recorded in the detector together with similar number of events of oxygen and heavier ions of low energy cosmic rays.
The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion. 相似文献
182.
183.
Frdric Tronc Mitchell A. Winnik Bansi Lal Kaul Jean‐Christophe Graciet 《Journal of polymer science. Part A, Polymer chemistry》2004,42(8):1999-2009
We describe the synthesis of several different polycarbonate particles by miniemulsion polymerization. The monomers were allylmethyl carbonate (AlMeC), di(ethylene glycol) bisallylcarbonate (DBAC), and 4‐vinyl‐1,3‐dioxan‐2‐one [vinyl ethylene carbonate (VEC)]. For these polymerizations, higher monomer conversions were obtained with oil‐soluble initiators (azobisisobutyronitrile and benzoyl peroxide) than with a water‐soluble initiator (potassium persulfate). Benzoyl peroxide was particularly effective in yielding particles with a narrow size distribution. Although increasing amounts of a surfactant (sodium dodecyl sulfate) led to smaller particles, the choice of the monomer was the major determinant. For example, in polymerization reactions carried out at 85 °C with benzoyl peroxide as the initiator and with otherwise identical recipes, we obtained particle sizes of 181 nm with AlMeC, 296 nm with VEC, and 203 nm with DBAC. Fluorescent particles were synthesized with comonomers based on the benzothioxanthene nucleus. Because the dyes had poor solubility in the monomers, it was necessary to include typically 20 wt % bromobenzene or dichlorobenzene based on the monomer in the miniemulsion reaction mixture. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1999–2009, 2004 相似文献
184.
Adamovich MI Aggarwal MM Alexandrov YA Andreeva NP Anzon ZV Arora R Avetyan FA Badyal SK Bhalla KB Bhasin A Bhatia VS Bogdanov VG Bubnov VI Burnett TH Cai X Chasnikov IY Chernova LP Chernyavsky MM Eligbaeva GZ Eremenko LE Gaitinov AS Ganssauge ER Garpman S Gerassimov SG Grote J Gulamov KG Gupta SK Gupta VK Heckman HH Huang H Jakobsson B Judek B Just L Kachroo S Kalyachkina GS Kanygina EK Karabova M Kaul GL Kitroo S Kharlamov SP Krasnov SA Kulikova S Kumar V Lal P Larionova VG Lepetan VN Liu LS 《Physical review letters》1992,69(5):745-748
185.
186.
187.
Huang QR Dubin PL Lal J Moorefield CN Newkome GR 《Langmuir : the ACS journal of surfaces and colloids》2005,21(7):2737-2742
Small-angle neutron scattering was used to characterize the solution behavior of charged carboxylic acid terminated "cascade" dendrimers (Z-Cascade/methane [4]/3-oxo-6-oxa-2-azaheptylidyne/3-oxo-2-azaheptylidyne/propanoic acids) of third (G3) and fifth (G5) generations as a function of dendrimer concentration, pH, and ionic strength. An increase in dendrimer concentration leads to a single broad peak in the scattering profile arising from interdendrimer interaction. The dissociation of terminal carboxylate groups also gives rise to an interdendrimer interaction peak, which could be suppressed by the addition of excess salt. The results of contrast matching measurements indicate the accumulation of an excess concentration of tetramethylammonium counterions around the surface of these highly charged particles, and the thickness of these counterions lies somewhere between 4 and 6 A. This conclusion is consistent with our previous potentiometric titration (Zhang, H.; et al. J. Phys. Chem. B 1997, 101, 3494) and capillary electrophoresis (Huang, Q. R.; et al. J. Phys. Chem. B 2000, 104, 898) data. 相似文献
188.
Summary The kinetics and mechanism of exchange of HPDTA in [Fe2HPDTA(OH)2] with cyanide ion (HPDTA=2-hydroxytrimethylenediaminetetraacetic acid) was investigated spectrophotometrically by monitoring the peak at 395 nm (
max of [Fe(CN)5OH]3– at pH=11.0±0.02,I=0.25m (NaClO4) at ±0.1°C).Three distinct observable stages were identified; the first is the formation of [Fe(CN)5OH]3–, the second the formation of [Fe(CN)6]3– from it and the third the reduction of [Fe(CN)6]3– to [Fe(CN)6]4– by HPDTA4– released in the first stage.The first stage follows first-order kinetics in [Fe2HPDTA(OH)2] and second-order in [CN–] over a wide range of [CN–], but becomes zero order at [CN–]<5×10–2
m. We suggest a cyanide-independent dissociation of [Fe2HPDTA)(OH)2] into [FeHPDTA(OH)] and [Fe(OH)]2+ at low cyanide concentrations and a cyanide-assisted rapid dissociation of [Fe2HPDTA(OH)2] to [FeHPDTA(OH)(CN)]3– and [Fe(OH)]2+ at higher cyanide concentrations. The excess of cyanide reacts further with [FeHPDTA(OH)(CN)]3– finally to form [Fe(CN)5OH]3–.The reverse reaction between [Fe(CN)5OH]3– and HPDTA4– is first-order in [Fe(CN)5OH]3– and HPDTA4–, and exhibits inverse first-order dependence on cyanide concentration.A six-step mechanism is proposed for the first stage of reaction, with the fifth step as rate determining. 相似文献
189.
Vijayan K Discher DE Lal J Janmey P Goulian M 《The journal of physical chemistry. B》2005,109(30):14356-14364
Alamethicin is a well-studied channel-forming peptide that has a prototypical amphipathic helix structure. It permeabilizes both microbial and mammalian cell membranes, causing loss of membrane polarization and leakage of endogenous contents. Antimicrobial peptide-lipid systems have been studied quite extensively and have led to significant advancements in membrane biophysics. These studies have been performed on lipid bilayers that are generally charged or zwitterionic and restricted to a thickness range of 3-5 nm. Bilayers of amphiphilic diblock copolymers are a relatively new class of membranes that can have significantly different physicochemical properties compared with those of lipid membranes. In particular, they can be made uncharged, nonzwitterionic, and much thicker than their lipid counterparts. In an effort to extend studies of membrane-protein interactions to these synthetic membranes, we have characterized the interactions of alamethicin and several other membrane-active peptides with diblock copolymer bilayers. We find that although alamethicin is too small to span the bilayer, the peptide interacts with, and ruptures, thick polymer membranes. 相似文献
190.
Summary Complexes of bidentate 3-amino-5-()-pyridyl-1,2,4-triazole (L1) and 3-amino-5-()-pyridyl-1, 2, 4-triazole (L2) of composition [ML1Cl2·H2O], [ML2Cl2·H2O], [ML
3
2/1
Cl2] and [ML
3
2/2
Cl2] [M=CoII, NiII, CuII, M=ZnII] have been prepared and characterized by elemental analyses, i.r., u.v./visible, e.s.r. spectra, magnetic moments and molar conductances. 相似文献