On neutrino and antineutrino scattering by electrons,and by partons

Assuming a non-derivative point interaction, and Born approximation, there are some simple relations between neutrino and antineutrino scattering on electrons or partons. They have been observed already, for some special cases, in the results of explicit calculations. Here they are obtained from simple general considerations.     

Measurement of Very Fast Exchange Rates of Individual Amide Protons in Proteins by NMR Spectroscopy

NMR spectroscopy is a pivotal technique to measure hydrogen exchange rates in proteins. However, currently available NMR methods to measure backbone exchange are limited to rates of up to a few per second. To raise this limit, we have developed an approach that is capable of measuring proton exchange rates up to approximately 10⁴ s⁻¹. Our method relies on the detection of signal loss due to the decorrelation of antiphase operators 2N_xH_z by exchange events that occur during a series of pi pulses on the ¹⁵N channel. In practice, signal attenuation was monitored in a series of 2D H(CACO)N spectra, recorded with varying pi-pulse spacing, and the exchange rate was obtained by numerical fitting to the evolution of the density matrix. The method was applied to the small calcium-binding protein Calbindin D_9k, where exchange rates up to 600 s⁻¹ were measured for amides, where no signal was detectable in ¹⁵N−¹H HSQC spectra. A temperature variation study allowed us to determine apparent activation energies in the range 47–69 kJ mol⁻¹ for these fast exchanging amide protons, consistent with hydroxide-catalyzed exchange.     

Heat of fusion and excess thermodynamic functions of organic eutectics

Phase diagrams and heats of fusion of some organic eutectics have been studied. An empirical equation is proposed for the determination of heats of fusion of eutectics. Excess thermodynamic functions such as h^E, S^E and g^E have been calculated. The heats of fusion of various organic eutectics have been compared with values obtained from the mixture law. The results have been explained on the basis of the fact that clusters are formed during melting. The cluster formation tendency is greater in systems in which hydroxyl groups are present.     

Uptake mechanism of oppositely charged fluorescent nanoparticles in HeLa cells

The endocytotic mechanisms involved in the uptake of charged polystyrene nanoparticles into HeLa cells were investigated. Uptake experiments were done in the presence or absence of drugs known to inhibit various factors in endocytosis. Independent of the particle charge, endocytosis is highly dependent on dynamin, F-actin, and tyrosine-specific protein kinases, which suggests a dynamin-dependent and lipid raft-dependent mechanism. However, cholesterol depletion did not hinder particle uptake. Regarding positively charged particles, macropinocytosis, the microtubule network, and cyclooxygenases are also involved. The clathrin-dependent pathway plays a minor role.     

DEVELOPMENT OF A CATALYST FOR SOLUTION OF POLY(VINYL ALCOHOL) IN NON-AQUEOUS MEDIUM

Chloro ethane dimethyl sulfoxide,C_2H_5Cl·DMSO(ECI·DMSO)was prepared by interaction of acrylic acid with conc.Hydrochloric acid in dimethyl sulfoxide(DMSO)and subsequent decarboxylation with H_2O_2 solution.The formation of the compound was confirmed by spectral and analytical methods;the molecular weight was determined by cryoscopic method.The solubility of poly(vinyl alcohol)(PVA)in different solvents or mixed solvents at 40℃,50℃and 60℃temperature in the presence of 0.01% of EC1·-DMSO was determined.It...     

Nanoparticle MALDI-TOF mass spectrometry without fragmentation: Au25(SCH2CH2Ph)18 and mixed monolayer Au25(SCH2CH2Ph)(18-x)(L)(x)

Intact molecular ions of the organothiolate-protected nanoparticle Au25(SCH2CH2Ph)18, including their isotopic resolution, can be observed at 7391 Da as 1- and 1+ ions in negative and positive mode, respectively, by MALDI-TOF mass spectrometry when using a tactic of threshold laser pulse intensities and trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) as matrix. Previous MALDI-TOF studies of Au nanoparticles using other matrices have encountered extensive fragmentation of nanoparticle as well as thiolate ligands. Absence of fragmentation enables precise determination of the distribution of mixed monolayer compositions on nanoparticles prepared by ligand exchange reactions and by synthesis using thiol mixtures. Reaction conditions producing mixed monolayers containing only one or a small number of usefully functional ligands can be readily identified. At increased laser pulse intensity, the first fragmentation step(s) for the Au25(SCH 2CH2Ph)18 nanoparticle results in losses of AuL units and, in particular, loss of Au4(SCH2CH2Ph)4.     

Electrospray ionization mass spectrometry of uniform and mixed monolayer nanoparticles: Au25[S(CH2)2Ph]18 and Au25[S(CH2)2Ph]18-x(SR)x

New approaches to electrospray ionization mass spectrometry (ESI-MS)-with exact compositional assignments-of small (Au25) nanoparticles with uniform and mixed protecting organothiolate monolayers are described. The results expand the scope of analysis and reveal a rich chemistry of ionization behavior. ESI-MS of solutions of phenylethanethiolate monolayer-protected gold clusters (MPCs), Au25(SC2Ph)18, containing alkali metal acetate salts (MOAc) produce spectra in which, for Na+, K+, Rb+, and Cs+ acetates, the dominant species are MAu25(SC2Ph)182+ and M2Au25(SC2Ph)182+. Li+ acetates caused ligand loss. This method was extended to the analysis of Au25 MPCs with mixed monolayers, where thiophenolate (-SPh), hexanethiolate (-SC6), or biotinylated (-S-PEG-biotin) ligands had been introduced by ligand exchange. In negative-mode ESI-MS, no added reagents were needed in order to observe Au25(SC2Ph)18- and to analyze mixed monolayer Au25 MPCs prepared by ligand exchange with 4-mercaptobenzoic acid, HSPhCOOH, which gave spectra through deprotonation of the carboxylic acids. Adducts of tetraoctylammonium (Oct4N+) with -SPhCOO- sites were also observed. Mass spectrometry is the only method that has demonstrated capacity for measuring the exact distribution of ligand-exchange products. The possible origins of the different Au25 core charges (1-, 0, 1+, 2+) observed during electrospray ionization are discussed.     

An equation of state and non-linear parameter from sound velocity measurements for liquid alkali metals

In the present paper, an equation of state has been obtained in case of liquid alkali metals like Na, K, Rb and Cs from sound velocity measurements. The theory developed gives very good agreement for both the sound velocity and the volume as a function of pressure at different temperatures in these liquid alkali metals. Further, the variation of non-linear parameter,B / A, as a function of pressure and temperature is also studied.