387 research outputs found
Some Derivatives of Tyrosine. Amino Acids. XXX
A new synthesis of DL-l-(p-hydroxyphenyl)- 2- aminobutan-3-one (la) is given. The optically active B-keto acid ester III and its racemic benzylidene derivative IV were prepared from L-tyrosine
Trapped ion emulation of electric dipole moment of neutral relativistic particles
The electric dipole moments of various neutral elementary particles, such as
neutron, neutrinos, certain hypothetical dark matter particles and others, are
predicted to exist by the standard model of high energy physics and various
extensions of it. However, the predicted values are beyond the present
experimental capabilities. We propose to simulate and emulate the electric
dipole moment of neutral relativistic particles and the ensuing effects in the
presence of electrostatic field by emulation of an extended Dirac equation in
ion traps
Slowly decaying classical fields, unitarity, and gauge invariance
In classical external gauge fields that fall off less fast than the inverse
of the evolution parameter (time) of the system the implementability of a
unitary perturbative scattering operator (-matrix) is not guaranteed,
although the field goes to zero. The importance of this point is exposed for
the counter-example of low-dimensionally expanding systems. The issues of gauge
invariance and of the interpretation of the evolution at intermediate times are
also intricately linked to that point.Comment: 8 pages, no figure
Investigation of an Aberrant Cell Voltage During the Filling of a Large Lithium Thionyl Chloride Cell
The investigation of an aberrant cell voltage during the filling of a large lithium thionyl chloride cell summary is at: an aberrant voltage trace was noted during the review of cell filling data; incident was traced to an interruption during filling; experimentation suggested oxidizable sites within the carbon electrode were responsible for the drop in voltage; the voltage anomaly could be reproduced by interrupting the filling of similar cells; and anomalous voltage dip was not due to a short
Transcranial Doppler in Smoking Relapse Prevention Strategy
Nicotine dependence is a progressive, chronic, relapsing disorder. Nicotine is the
principal and most potent psychopharmacologically active component of tobacco smoke.
Through activation of nicotine receptors in the central nervous system, nicotine can lead
to tolerance and dependence. Cessation of smoking is followed by severe pathophysiologic
withdrawal and by long-term craving. TCD measurement of cerebral blood flow
velocity (BFV) and nicotine dependence degree measured by Fragestrom questionnaire
was analyzed in relation to smoking relapse. This study includes 47 participants (25 females
and 22 males) included in Breathe Free Plan To Stop Smoking in Non Smoking
School in Zagreb.12 month following the end of treatment participants were divided in
three groups: continued abstinence, interrupted abstinence and non abstinence. High
nicotine dependence combined with TCD pathological finding significantly discriminated
successes and failures, suggesting that smokers with pathological TCD need specific
therapeutic approach with more social support, individualized coping skills and
cognitive restructuring. Measuring cerebral flow velocity by transcranial Doppler in
smokers showed the practical validity in prediction of smoking relaps
Spin dynamics in the Kapitza-Dirac effect
Electron spin dynamics in Kapitza-Dirac scattering from a standing laser wave
of high frequency and high intensity is studied. We develop a fully
relativistic quantum theory of the electron motion based on the time-dependent
Dirac equation. Distinct spin dynamics, with Rabi oscillations and complete
spin-flip transitions, is demonstrated for Kapitza-Dirac scattering involving
three photons in a parameter regime accessible to future high-power X-ray laser
sources. The Rabi frequency and, thus, the diffraction pattern is shown to
depend crucially on the spin degree of freedom
A structure-based proposal for the catalytic mechanism of the bacterial acid phosphatase AphA belonging to the DDDD superfamily of phosphohydrolases
The Escherichia coli gene aphA codes for a periplasmic acid phosphatase called AphA, belonging to class B bacterial phosphatases, which is part of the DDDD superfamily of phosphohydrolases. After our first report about its crystal structure, we have started a series of crystallographic studies aimed at understanding of the catalytic mechanism of the enzyme. Here, we report three crystal structures of the AphA enzyme in complex with the hydrolysis products of nucleoside monophosphate substrates and a fourth with a proposed intermediate analogue that appears to be covalently bound to the enzyme. Comparison with the native enzyme structure and with the available X-ray structures of different phosphatases provides clues about the enzyme chemistry and allows us to propose a catalytic mechanism for AphA, and to discuss it with respect to the mechanism of other bacterial and human phosphatases. (c) 2005 Elsevier Ltd. All rights reserved
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