Effect of transition metals on recovery from plasma of the growth-modulating tripeptide glycylhistidyllysine

Isolation and purification of growth-modulating peptides from biological sources is often accompanied by excessive losses of bioactive material. During the isolation of a growth-modulating tripeptide glycylhistidyllysine (GHL) from human plasma, copper and iron were found to co-isolate with the peptide. Studies with [3H]GHL demonstrated that these metals interfere at several steps of the procedure for the isolation of GHL from plasma (gel filtration chromatography, high-pressure silica-gel). Removal of these metals with an insoluble chelating resin (Cellex 100) enhanced recovery of [3H]GHL from plasma 8-fold. These results suggest that removal of transition metals may aid in the recovery of peptides which are difficult to isolate from biological sources.     

Reformulation of the close-coupled equations for the collision of two diatomic molecules

In the usual formulation of the close-coupled equations for the collision of two diatomic molecules, one assumes that the channel expansion forms an orthonormal set. This assumption can be invalid at small center-of-mass separations. We show how one can deal with this problem while solving the close-coupled equations.     

Finite amplitude,periodic motion of a body supported by arbitrary isotropic,elastic shear mountings

The undamped, finite amplitude, periodic motion of a load supported symmetrically by arbitrary isotropic, elastic shear mountings is investigated. Conditions on the shear response function sufficient to guarantee periodic motions for finite shearing with arbitrary initial data are provided. Some general results applicable for all simple shearing oscillators in the class are derived and illustrated graphically. The mechanical response of the general nonlinear shearing oscillator is compared with the response of a certain linear oscillator of comparable design. As consequence, certain static and dynamic aspects of the motion of an arbitrary nonlinear oscillator supported by shear springs are compared with those of a simple, linear oscillator for which the response is well-known and readily determined for the same initial data. The effect of a finite static shear deformation on the frequency equation for superimposed, small amplitude vibrations of the load is examined. The general analysis is applied to a class of hyperelastic biological tissues; and the frequency relation for finite amplitude oscillations of a load supported by soft tissue is derived. The finite amplitude oscillatory shearing of a general isotropic elastic continuum is described; and three universal relations connecting the stress and the oscillatory shearing deformation for every isotropic elastic material are presented.     

Thallium(I) as a Coordination Site Protection Agent: Preparation of an Isolable Zero‐Valent Nickel Tris‐Isocyanide

Blocking the pass: Low‐valent Ni centers readily bind Tl^I ions in a synthetically reversible fashion. The Tl units, in turn, serve as coordination site protection agents for Ni with respect to incoming Lewis basic ligands. This synthetic sequence allows for the isolation of a reactive zero‐valent Ni tris‐isocyanide complex.

     

Tuning pianos using reinforcement learning

The tuning system of a piano has remained relatively unchanged since the instrument’s inception. A piano’s tuning system has been designed to be both inexpensive to manufacture and to preserve the tension and thus pitch of each string over long periods of time. This tuning system requires such a high degree of skill to manipulate that only trained professionals are able to tune pianos. This paper presents a novel adjustable impact tuning hammer and a reinforcement learning control system that may allow piano owners to tune their own pianos in the future.     

Photoionization of highly charged ions using an ECR ion source and undulator radiation

Photoionization of Xe4+ to Xe7+ ions was studied by combining an electron cyclotron resonance ion source with synchrotron radiation. Multiconfiguration Dirac-Fock calculations were performed to interpret the data. Many autoionization lines were measured and identified, resulting from excitation of a 4d electron into nf and np orbitals followed by Auger decay of the excited states. Continuum photoionization is negligible for the higher members of the isonuclear series.     

Statistical and dynamical influences on electronic branching in reactions of ground- and excited-state alkaline earth atoms with molecular oxidants

We develop statistical predictions for the branching ratios into the various energetically allowed product electronic states in the reaction of Ca(4s4p³p) + O₂, CO₂, and N₂O as well as Ba(6s^{2 1}S) + N₂O. The statistical branching ratios, based solely on the total volume of translational phase space associated with each electronic channel, can be constrained to be consistent with the conservation of electronic spin and/or electronic adiabaticity. By making use of earlier formal work of Levine, Bernstein, and co-workers, it is further possible to incorporate available information on the internal energy distributions in the various product electronic channels. In the reactions of metastable calcium the experimentally determined branching ratios into electronically excited CaO products are larger than would be predicted by a purely statistical model, whereas the converse seems to be true for the oxidation of Ba(¹S) by N₂O. Also, the experimental branching ratios appear consistent with a dynamical model which allows surface crossings and changes in electronic multiplicity. These oxidation reactions are interpreted in terms of an electron-jump mechanism involving a single charged ion-pair intermediate.     

An exact solution to the classical,anisotropic Heisenberg model with long-range Kac interactions

A rigorous derivation is given for the “constant-magnetization” free energy density of the classical, anisotropic Heisenberg model with long-range Kac interactions. The derivation involves bounding arguments similar to those used for a classical fluid by Lebowitz and Penrose. The present work is carried out in a constant-magnetization ensemble. The free energy density is determined exactly under a quadruple-limiting process. The limits involved are a Lebowitz-Penrose type of triple-limiting process, followed by a final limit,x→ 0, wherex is a parameter which represents the range over which each component of the net spin density can vary. Explicit equations of state are determined for the special case of zero short-range interactions plus pure Kac-type long-range interactions.     

A constant-magnetization ensemble for the classical anisotropic Heisenberg model

A constant-magnetization ensemble is introduced in order to study classical, anisotropic Heisenberg systems. Existence, uniform convergence, and convexity properties are proved for an appropriate thermodynamic potential. The thermodynamic equivalence of this ensemble with the more common canonical ensemble is also established. In a subsequent paper, this formulation is used to obtain an exact statistical mechanical solution of classical Heisenberg systems with long-range Kac interactions.This research was carried out at The Department of Physics, Case Western Reserve University, Cleveland, Ohio, and was supported in part by the U.S. Atomic Energy Commission. This work is based on portions of a dissertation by K. M. submitted in partial fulfillment of the Ph.D. degree, Case Western Reserve University.