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

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 ($S$-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