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11.
Surfactants have been employed in high-performance liquid chromatography (HPLC) for the separation of ionic and non-ionic compounds. We have developed a method employing a reversed-phase column and a mobile phase containing a surfactant, hexadecyltrimethylammonium hydroxide (HDTMA+OH-), for the separation of several inositol phosphate positional isomers. Various parameters were studied for their effect on the chromatographic capacity factor (k'). They included the concentration of HDTMA+OH-, the pH of the bulk micellar suspension and the addition of inorganic salts to the mobile phase. Resolution of the inositol monophosphates was controlled by a mixed mechanism, where the predominant elements were electrostatic forces and the formation of micelles. The elution of the inositol polyphosphate isomers was obtained by increasing the amount of a non-polar solvent, in agreement with an ion-pairing process. This method represents an alternative to ion-exchange HPLC. If offers a practical advantage when detection of radiolabeled samples by in-line radioactive flow detectors is required, because low-quenching solvents with good miscibility with scintillant fluids are employed. The analysis of various chromatographic conditions, the system reproducibility and its application to the analysis of biological samples are described. 相似文献
12.
D. Alde R. Bellazzini F. G. Binon M. Boutemeur A. Brez C. Bricman S. V. Donskov M. Gouanère A. V. Inyakin V. A. Kachanov G. V. Khaustov E. A. Knapp A. V. Kulik A. A. Lednev M. M. Massai L. Massonnet J. P. Peigneux Yu. D. Prokoshkin S. A. Sadovsky V. D. Samoylenko P. M. Shagin A. V. Shtannikov A. V. Singovsky J. P. Stroot V. P. Sugonyaev M. R. Torquati 《Zeitschrift fur Physik C Particles and Fields》1989,43(4):541-547
The exculsive production of π0, η, and η′ mesons in π+ N central collisions has been studied with 300 GeV incident pions. The experiment has been performed at the CERN SPS. The gammas from decaying mesons were detected in the hodoscope multiphoton spectrometer GAMS-4000. The measured differential cross sections show a plateau in the longitudinal momentum interval 0.1F<0.3. 相似文献
13.
In this paper we study the existence of maximizers for two families of interpolation inequalities, namely a generalized Gagliardo–Nirenberg inequality and a new inequality involving the Riesz energy. Two basic tools in our argument are a generalization of Lieb’s Translation Lemma and a Riesz energy version of the Brézis–Lieb lemma. 相似文献
14.
F Steglich J Arndt O Stockert S Friedemann M Brando C Klingner C Krellner C Geibel S Wirth S Kirchner Q Si 《J Phys Condens Matter》2012,24(29):294201
Both CeCu2Si2 and YbRh2Si2 crystallize in the tetragonal ThCr2Si2 crystal structure. Recent neutron-scattering results on normal-state CeCu2Si2 reveal a slowing down of the quasielastic response which complies with the scaling expected for a quantum critical point (QCP) of itinerant, i.e., three-dimensional spin-density-wave (SDW), type. This interpretation is in full agreement with the non-Fermi-liquid behavior observed in transport and thermodynamic measurements. The momentum dependence of the magnetic excitation spectrum reveals two branches of an overdamped dispersive mode whose coupling to the heavy charge carriers is strongly retarded. These overdamped spin fluctuations are considered to be the driving force for superconductivity in CeCu2Si2 (Tc = 600 mK). The weak antiferromagnet YbRh2Si2 (TN = 70 mK) exhibits a magnetic-field-induced QCP at BN = 0.06 T (B⊥c). There is no indication of superconductivity down to T = 10 mK. The magnetic QCP appears to concur with a breakdown of the Kondo effect. Doping-induced variations of the average unit-cell volume result in a detachment of the magnetic and electronic instabilities. A comparison of the properties of these isostructural compounds suggests that 3D SDW QCPs are favorable for unconventional superconductivity. The question whether a Kondo-breakdown QCP may also give rise to superconductivity, however, remains to be clarified. 相似文献
15.
Jacopo Bellazzini Claudio Bonanno Gaetano Siciliano 《Mediterranean Journal of Mathematics》2009,6(3):347-366
We study the existence of vortices of the Klein-Gordon-Maxwell equations in the two dimensional case. In particular we find
sufficient conditions for the existence of vortices in the magneto-static case, i.e. when the electric potential f = 0{\phi = 0}. This result, due to the lack of suitable embedding theorems for the vector potential A is achieved with the help of a penalization method. 相似文献
16.
Subham Majumdar EV Sampathkumaran St Berger M Della Mea H Michor E Bauer M Brando J Hemberger A Loidl 《Pramana》2002,58(5-6):777-782
Recently, the solid solution Ce2Au1−
x
Co
xSi3 has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo
effect. Here we report high pressure electrical resistivity of Ce2AuSi3, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these
alloys. High pressure resistivity behavior is consistent with the proposal that Ce2AuSi3 lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which
are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions
before attaining non-magnetism for the Co end member. 相似文献
17.
Mycobacterium tuberculosis, the causative agent of tuberculosis, is one of the most effective human pathogens. The mycobacterial cell envelope contains
lipoglycans, and of particular interest is lipoarabinomannan (LAM), one of the most potent mycobacterial immunomodulatory
molecules. The importance of lipoarabinomannan (LAM) in the immunopathogenesis of tuberculosis has incited structural studies
on this molecule to (1) establish a precise structural model of the molecule and (2) decipher the structure/function relationships.
In recent years, we have focused on the two domains essential for LAM biologic activities: the mannosyl-phosphatidyl-myo-inositol anchor and the caps. We review here the recent procedures developed for the structural analysis of these domains. 相似文献
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20.
J. Sichelschmidt M. Paraskevopoulos M. Brando R. Wehn D. Ivannikov F. Mayr K. Pucher J. Hemberger A. Pimenov H.-A. Krug von Nidda P. Lunkenheimer V.Yu. Ivanov A.A. Mukhin A.M. Balbashov A. Loidl 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(1):7-17
The charge-ordered perovskite Pr0.65Ca0.28Sr0.07MnO3 was investigated by means of magnetic susceptibility, specific heat, dielectric and optical spectroscopy and electron-spin
resonance techniques. Under moderate magnetic fields, the charge order melts yielding colossal magnetoresistance effects with
changes of the resistivity over eleven orders of magnitude. The optical conductivity is studied from audio frequencies far
into the visible spectral regime. Below the phonon modes hopping conductivity is detected. Beyond the phonon modes the optical
conductivity is explained by polaronic excitations out of a bound state. ESR techniques yield detailed informations on the
(H,T ) phase diagram and reveal a broadening of the linewidth which can be modeled in terms of activated polaron hopping.
Received 9 August 2000 相似文献