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1.
Clusters of galaxies are excellent probes of cosmic structure and evolution. X-ray studies of clusters provide some of their
key parameters, viz., temperature of the hot intra-cluster gas, its metallicity, X-ray luminosity and surface brightness giving
mass distribution and mass-flow rate in the case of cooling flows. X-ray measurements for a large sample of clusters have
lead to estimates of the total gravitating mass in them, which can be compared to the virial masses derived from dynamical
considerations and gravitational lensing in some of them. X-ray derived total masses are consistent with masses obtained from
the other methods after the effects due to the presence of cooling flows are taken into account in the analyses. Estimated
virial masses, lack of evolution in X-ray properties, and detection of several very hot clusters at high redshifts indicate
a Universe with a low value (≤ 0.3) for the Ω parameter. 相似文献
2.
Adsorption kinetics of surfactant mixtures from micellar solutions as studied by maximum bubble pressure technique 总被引:1,自引:0,他引:1
Frese Ch Ruppert S Sugár M Schmidt-Lewerkühne H Wittern KP Fainerman VB Eggers R Miller R 《Journal of colloid and interface science》2003,267(2):475-482
The adsorption kinetics of micellar solutions of anionic/cationic SDS/DATB mixtures with mixing ratios of 10/1 and 10/2, respectively, are studied experimentally by means of the maximum bubble pressure method. For long adsorption times the adsorption of the highly surface-active anionic/cationic complex leads to a decrease of dynamic surface tension in comparison to the single SDS system. However, the situation is the reverse for short adsorption times where the dynamic surface tension is increased by addition of the cationic surfactant, although the overall concentration is increased. This unexpected behavior is explained by partial solubilization of free SDS molecules into micelles formed by SDS/DTAB complexes. With increasing overall concentration, when eventually the CMC of SDS is reached, the anionic/cationic complex itself is solubilized by SDS micelles. Finally, no complex micelles, which for their part can solubilize an excess of SDS molecules, are present. Hence, the dynamic properties of the solution are no longer influenced by the depletion of SDS molecules and the mixture tends to behave like a pure SDS solution. 相似文献
3.
Half life for the emission of exotic clusters like 8Be, 12C, 16O, 20Ne, 24Mg and 28Si are computed taking Coulomb and proximity potentials as interacting barrier and many of these are found well within the
present upper limit of measurement. These results lie very close to those values reported by Shanmugam et al using their cubic plus Yukawa plus exponential model (CYEM). It is found that 12C and 16O emissions from 116Ce and 16O from 118Ce are most favorable for measurement (T
1/2<1010 s). Lowest half life time for 16O emission from 116Ce stress the role of doubly magic 100Sn daughter in exotic decay. Geiger-Nuttall plots were studied for different clusters and are found to be linear. Inclusion
of proximity potential will not produce much deviation to linear nature of Geiger-Nuttall plots. It is observed that neutron
excess in the parent nuclei slow down the exotic decay process. These findings support the earlier observations of Gupta and
collaborators using their preformed cluster model (PCM). 相似文献
4.
Ccile Alberola Bernhard Blümich Detlef Emeis Klaus-Peter Wittern 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,290(1-3):247-255
The present work investigates the phase transitions of monoglyceride emulsifier systems and pearlescent effects in cosmetic creams using 13C-NMR spectroscopy and DSC. The four phases of monoglyceride emulsifier systems – the coagel, gel phase, liquid-crystalline lamellar phase, and cubic phase – can be characterized in creams at appropriate temperatures by NMR spectroscopy. The phase transition temperatures were determined by DSC. Cross polarization (13C-CP)-magic angle spinning (MAS) measurements confirmed that the formation of the coagel is responsible for the pearlescence of creams. It could be shown that the proportions of monoglyceryl laurate and monoglyceryl myristate in the emulsifier system influence the phase transitions and the intensity of the pearlescence of creams. Furthermore, the coagel forms directly from the liquid-crystalline lamellar phase without transition through the gel phase if the cream is at a temperature higher than that of gel phase formation. These insights into the monoglyceride-emulsifier system of creams make it possible to more closely study the pearlescent effect of the coagel. Especially, the amount of emulsifier system in the coagel can be quantified. It could be shown that for a typical pearlescent cream more than 27% of the emulsifier system must be found in the coagel in order for pearlescence to be detectable optically. Moreover, the increase in the intensity of pearlescence over time after fabrication of a cream correlated with the increase in the amount of emulsifier system in the coagel. This ripening process can take up to approximately 15 months. 相似文献
5.
Synthesis of Phenylnitrene Complexes with N-Trimethylsilylaniline. II. Characterization and Crystal Structure of the Rhenium(V) Complexes mer-[Re(NPh)Cl3(NH2Ph)(Ph3P)] and trans-[Re(NPh)(OMe)Cl2(Ph3P)2] Reaction of [ReOCl3(Ph3P)2] with N-trimethylsilylaniline yields mer-[Re(NPh)Cl3(Ph3P)2], which reacts under air with excess of N-trimethylsilylaniline to form [Re(NPh)Cl3 · (NH2Ph)(Ph3P)]. Crystallization from CH2Cl2/MeOH affords [Re(NPh)(OMe)Cl2(Ph3P)2] as an additional product. [Re(NPh)Cl3(NH2Ph)(Ph3P)] crystallizes in the monoclinic space group P21/n with a = 1 192.3(3); b = 1 918.9(3); c = 1 266.3(3) pm; β = 101.71(1)°; Z = 4. The rhenium atom has a distorted octahedral environment with the Cl atoms in meridional positions. The phenyl nitrene ligand is coordinated with an almost linear arrangement Re? N1? C40 = 166.8(6)° and with a bond distance Re?N = 170.5(6) pm. [Re(NPh)(OMe)Cl2(Ph3P)2] · 1/2CH2Cl2 crystallizes in the triclinic space group P1 : a = 1 103.1(4); b = 1 227.9(4); c = 1 711.3(5) pm; α = 70.48(3)°; β = 72.71(3)°; γ = 80.03(3)°; Z = 2. The rhenium atom exhibits a distorted octahedral coordination with the Cl atoms and the phosphine ligands in trans positions. As a consequence of the competition of the nitrene ligand and the trans-coordinated methoxy group the Re?;N bond length is slightly lengthened to 173.2(7) pm, while the Re? O bond length of 193.4(6) pm is short. The bond angles Re? N? C70 and Re? O? C80 are 173.3(7)° and 139.1(7)°, respectively. 相似文献
6.
The possibility of obtaining information about cluster structures in light nuclei from Coulomb break-up experiments is discussed. A few favorable cases are pointed out. A preliminary estimate of the break-up cross section of7Li into alpha particles and tritons and of7Be into alpha particles and3He in the field of a heavy target nucleus is given. The need for more experiments as well as more refined calculations is stressed. 相似文献
7.
Alberola C Dederichs T Emeis D Möller M Sokolowski T Wittern KP 《Journal of colloid and interface science》2007,307(2):500-508
The phase transitions of monoglyceride emulsifier systems and pearlescent effects in cosmetic creams are investigated using ultrasonic velocity measurements. The transitions between the different phases of monoglyceride emulsifier systems--the coagel, liquid-crystalline lamellar phase, and gel phase--are detected in creams by changes in the ultrasonic velocity with variation of the temperature. The phase transition temperatures correspond to DSC results. Furthermore, the slope of the ultrasound velocity curve correlates with the amount of bound water in the different phases. These insights into the ultrasonic velocity properties of the monoglyceride emulsifier system of creams make it possible to more closely study the pearlescent effect of the coagel. The temperature domain of the short time reversibility of the pearlescence as well as the back-formation time of the coagel can be determined with this method, which enable the optimization of the formulation of pearlescent creams. 相似文献
8.
Enthaler B Pruns JK Wessel S Rapp C Fischer M Wittern KP 《Analytical and bioanalytical chemistry》2012,402(3):1159-1167
Localization of endogenous and exogenous compounds directly in tissue sections is a challenging task in skin research. Matrix-assisted
laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is a powerful label-free technique that enables determination
of the distribution of a large range of biomolecules directly in tissue sections. Nevertheless, its application in this field
is limited in large part by the low adhesion of skin tissue sections to indium–tin oxide-coated (ITO) glass slides. For the
first time corona discharge (CD) treatment was used to modify the glass slide surface for improved adhesion. Localization
of endogenous cholesterol sulfate was performed directly in human skin tissue sections. A spatial resolution of approximately
30 μm was sufficient for assignment of mass signals to skin structure morphology. Furthermore, imaging of an exogenous model
compound, Nile red, was performed directly in skin tissue sections after ex-vivo penetration into porcine skin, enabling determination
of the pathway and depth of penetration. Finally, the ion density map of Nile red was compared with its high resolution fluorescence
micrograph. This work provides new insights into the application of MALDI–MSI in skin research. 相似文献
9.
Dr. Hans W. Wittern 《Zeitschrift für Physik A Hadrons and Nuclei》1969,229(3-5):420-431
Using refined clustermodel wave functions the Coulomb form factors for the elastic scattering of electrons as well as the formfactors for the inelastic scattering leading to the first and second excited states of7Li have been calculated. 相似文献
10.
Shashwati Sen DK Aswal Ajay Singh TV Chandrasekhar Rao KP Muthe JC Vyas LC Gupta SK Gupta VC Sahni 《Pramana》2002,58(5-6):867-870
The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties.
The upper critical field, irreversibility line and critical current density have been determined using magnetization data.
The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition.
The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation. 相似文献