Catalytic residues are shared between two pseudosubunits of the dehydratase domain of the animal fatty acid synthase

Expression, characterization, and mutagenesis of a series of N-terminal fragments of an animal fatty acid synthase, containing the beta-ketoacyl synthase, acyl transferase, and dehydratase domains, demonstrate that the dehydratase domain consists of two pseudosubunits, derived from contiguous regions of the same polypeptide, in which a single active site is formed by the cooperation of the catalytic histidine 878 residue of the first pseudosubunit with aspartate 1032 of the second pseudosubunit. Mutagenesis and modeling studies revealed an essential role for glutamine 1036 in anchoring the position of the catalytic aspartate. These findings establish that sequence elements previously assigned to a central structural core region of the type I fatty acid synthases and some modular polyketide synthase counterparts play an essential catalytic role as part of the dehydratase domain.     

Model for cage formation in colloidal suspension of laponite

In this paper we investigate glass transition in aqueous suspension of synthetic hectorite clay, laponite. We believe that upon dispersing laponite clay in water, the system comprises of clusters (agglomerates) of laponite dispersed in the same. Subsequent osmotic swelling of these clusters leads to an increase in their volume fraction. We propose that this phenomenon is responsible for slowing down of the overall dynamics of the system. As clusters fill up the space, the system undergoes glass transition. Along with the mode coupling theory, the proposed mechanism rightly captures various characteristic features of the system in the ergodic regime as it approaches glass transition.     

Shock wave induced phase transition in \alpha-FePO_4

Shock wave induced response of the berlinite form of FePO has been investigated up to 8.5 GPa. The X-ray diffraction measurements on the shock recovered samples reveal transition to the mixture of an amorphous phase and an orthorhombic phase around 5 GPa. The proportion of the amorphous material in the recovered sample is found to decrease at higher pressure. The results are interpreted in terms of a three-level free energy diagram for the crystal to amorphous transitions. Received 26 May 1997 / Accepted 1 September 1997     

The reaction of activated RNA species with aqueous fluoride ion: a convenient synthesis of nucleotide 5′-phosphorofluoridates and a note on the mechanism

The chemistry of 5′-phosphorimidazolides of ribonucleosides is extended to include their reaction with alkali metal fluorides in aqueous solution. High yields of 5′-phosphorofluoridates are formed, especially with potassium fluoride, but no detectable oligomerization products were formed. A combination of HPLC, mass spectrometry, synthesis, kinetics, and NMR confirms the identities of the products. Judicious control of pH leads to higher yields in shorter reaction times. This new methodology contrasts favorably with other synthetic routes involving non-aqueous chemistry or aqueous chemistry with a nucleotide triphosphate.     

Quicksilver Solutions of a q‐Difference First Painlevé Equation

In this paper, we present new, unstable solutions, which we call quicksilver solutions, of a q‐difference Painlevé equation in the limit as the independent variable approaches infinity. The specific equation we consider in this paper is a discrete version of the first Painlevé equation (qP_I), whose phase space (space of initial values) is a rational surface of type . We describe four families of almost stationary behaviors, but focus on the most complicated case, which is the vanishing solution. We derive this solution's formal power series expansion, describe the growth of its coefficients, and show that, while the series is divergent, there exist true analytic solutions asymptotic to such a series in a certain q‐domain. The method, while demonstrated for qP_I, is also applicable to other q‐difference Painlevé equations.     

Reduction and second quantisation of generalised electromagnetic field for zero mass system

Reduction and second quantisation of generalised electromagnetic fields in the presence of massless spin-1/2 particles carrying both electric and magnetic charges have been carried out in terms of Lomont-Moses realisation of irreducible representations of Poincare group and the expression for field Hamiltonian has been derived.     

Quaternionic quantum mechanics is consistent with complex quantum mechanics

Quaternionic quantum mechanics is investigated in the light of the great success of complex quantum mechanics. It is shown that to reproduce the results of complex quantum mechanics, quaternionic quantum mechanics must contain complex quantum mechanics.     

Liquid level sensor using ultrasonic Lamb waves

This paper describes a novel, noninvasive method for measurement of liquid level in closed metal tanks that are under high pressure. It is based on the use of ultrasonic Lamb waves propagating along the tank wall. Contact with liquid substantially changes the characteristics of these waves and this can be used as an indicator of liquid presence. Theoretical analysis shows that the symmetric and antisymmetric Lamb wave modes, both fundamental and higher order, are sensitive to presence of the liquid. The optimal wave frequency depends on the thickness of the tank wall and wall material. A prototype level sensor based on this principle has been developed. It uses two pairs of wedge transducers to generate and detect Lamb waves propagating along the circumference of the gas tank. An operating frequency of 100 kHz is found to be optimal for use with tanks having a wall thickness of 30-50 mm. Prototype sensors developed under this program have been used successfully in oil fields in the far northern region of Russia.