Network forming properties of various proteins adsorbed at the air/water interface in relation to foam stability

A series of proteins was studied with respect to their ability to form a network at the air/water interface and their suitability as foaming agents and foam stabilizers. Proteins were chosen with a range of structures from flexible to rigid/globular: beta-casein, beta-lactoglobulin, ovalbumin, and (soy) glycinin. Experiments were performed at neutral pH except for glycinin, which was studied at both pH 3 and pH 6.7. The adsorption process was followed with an automated drop tensiometer (ADT). Network forming properties were assessed in terms of surface dilational modulus (determined with the ADT), the critical falling film length (L(still)) and flow rate (Q(still)) below which a stagnant film exists (as measured with the overflowing cylinder technique), and the fracture stress and fracture strain measured in surface shear. It was found that glycinin (pH 3) can form an interfacial gel in a very short time, whereas beta-casein has very poor network-forming properties. Hardly any foam could be produced at the chosen conditions with glycinin (pH 6.7) and with ovalbumin, whereas beta-casein, beta-lactoglobulin, and glycinin (pH 3) were good foaming agents. It seems that adsorption and unfolding rate are most important for foam formation. Once the foam is formed, a rigid network might favor stabilizing the foam.     

Search for the scalar top quark in pp collisions at square root[s] = 1.8 TeV

We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of pp events corresponding to 108.3 pb(-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, t-->b chi+1 and t-->blnu, no evidence for signal is found. We derive cross-section limits as a function of stop ( t ), chargino ( chi+1), and sneutrino ( nu) masses.     

A generalized approach for the calculation and automation of potentiometric titrations Part 1. Acid-Base Titrations

Fast and accurate calculation procedures for pH and redox potentials are required for optimum control of automatic titrations. The procedure suggested is based on a three-dimensional titration curve V = f(pH, redox potential). All possible interactions between species in the solution, e.g., changes in activity coefficients and influences of redox potential on pH variations, are taken into account. The number of titrant additions can be reduced considerably without loss of precision, by using the fact that the pH of a protolyte or mixture of protolytes at some fraction titrated does not depend strongly on the actual concentration.     

Urea as the basic component in pyridine-free Karl Fischer reagent

A solution of urea, sulphur dioxide and sodium salicylate in methanol is proposed as the solvent in the Karl Fischer titration, with a separate iodine solution as titrant. Comparison of the performance of this solvent with that of some commercial reagents shows that it is has distinct advantages for use with amine samples.     

Systematical study of beta delayed proton emission energies

Graphs are given of the maximum proton energies in delayed proton emitters. This quantity, equal to the difference of the electron capture decay energy of the precursor and the separation energy of a proton in the daughter, has been calculated in a least squares adjustment of mass spectroscopic data and nuclear decay and reaction energies. The graphs would lead to expect a 950 keV lower maximum proton energy in⁷³Kr(?p)⁷²Se than has been reported from experiments. They can be used to predict new cases for further studies on this subject.     

The crystal and molecular structure of cyclopentadienyltin(II) chloride. The bonding of the cyclopentadienyl group in tin(II) compounds

The crystal and molecular structure of cyclopentadienyltin(II) chloride has been determined from three-dimensional X-ray data. The crystals are orthorhombic, space group Pc2₁n. The unit cell, of dimensions a = 5.711(5), b = 6.225(5), c = 17.24(2) Å, contains four molecules. The structure has been refined by full matrix least squares techniques to a final R value of 0.083 for 717 independent reflections. In the crystal unsymmetrical tin-chlorine bridges are present between the units of C₅H₅SnCl.It is suggested that in cyclopentadienyltin(II) compounds the cyclopentadienyl group occupies more than one coordination site as a result of the donation of π electron density from the cyclopentadienyl ring into an empty acceptor orbital of the tin atom having π symmetry.     

Characterization of laser-treated paper

Paper is one of the most important materials in cultural heritage given its extensive use as the data carrier for religious, artistic and scientific records. For both aesthetic and conservation reasons, cleaning of these materials is often needed. Current paper cleaning methods using conventional means are not always sufficient, e.g. for the local cleaning of paper in the vicinity of sensitive media. In this respect a ns-pulse laser provides a valuable tool for solving difficult cleaning problems. The influence of various laser wavelengths (355 nm, 532 nm, and 1064 nm) and the ageing status of modern paper test systems were studied. Colorimetric measurements, the determination of the average molecular mass of cellulose, and chemiluminescence analysis proved to be useful for the characterization of the laser-treated paper. Treatment with green laser light at =532 nm below the paper ablation threshold fluence gave the most promising results on pure papers, with no discolouration and no other visible alteration, nor detectable chemical changes. PACS 06.60.J; 78.60.Ps; 81.65.Cf     

Coding the principal character formula for affine Kac-Moody lie algebras

In this paper, an algorithm for computing the principal character for affine Lie algebras is discussed and presented. The principal characters discovered using this program are given and/or proven. Results include level 2 and 3 character formulas in and the sole existence of the Rogers-Ramanujan products in , , , , , , .     

Search for heavy particles decaying into electron-positron pairs in pp collisions

We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.