On cosmic-ray cut-off terminology

Summary The study of cosmic-ray access to locations within the geomagnetic field has evolved over the past fifty years. Cosmic-ray cut-off terminology, originally developed to describe particle access and cut-off rigidities, has not evolved with the scientific advances in the field, and misunderstandings and misapplications of historical work have occurred. This paper is an attempt to remedy this situation by clarifying the areas in which changes have occurred and by providing a cross reference between the historical terms and those terms now in use for innovative cosmic-ray studies which are underway in several laboratories.     

Partial-wave analysis of the (KKK) system in the reaction K−p→K−K−K+p at 10 and 16 GeV/c

The reaction K^?p→K^?K^?K⁺p is shown to have properties similar to those of the diffractive reaction K^?p→K^?π^?π⁺p. This is true, at least in first approximation, for (a) the energy dependence of the cross sections, (b) the shape of the three meson spectra and (c) the differential cross sections dσ/dt_pp which have the same slope for the same mass of the three-meson system. Furthermore, the partial-wave composition of the (KKK) system is similar to that of the (Kππ) system, both systems being produced mostly in unnatural spin-parity states by natural parity exchange. In the KKK system, the J^P = 1⁺ state with S-wave decay into Kø(1020) is dominant, (72 ± 11) % of all events with (KKK) masses below 2 GeV.     

Nonlinear wave-packet interferometry and molecular state reconstruction in a vibrating and rotating diatomic molecule

We formulate two-color nonlinear wave-packet interferometry (WPI) for application to a diatomic molecule in the gas phase and show that this form of heterodyne-detected multidimensional electronic spectroscopy will permit the reconstruction of photoinduced rovibrational wave packets from experimental data. Using two phase-locked pulse pairs, each resonant with a different electronic transition, nonlinear WPI detects the quadrilinear interference contributions to the population of an excited electronic state. Combining measurements taken with different phase-locking angles isolates various quadrilinear interference terms. One such term gives the complex overlap between a propagated one-pulse target wave packet and a variable three-pulse reference wave packet. The two-dimensional interferogram in the time domain specifies the complex-valued overlap of the given target state with a collection of variable reference states. An inversion procedure based on singular-value decomposition enables reconstruction of the target wave packet from the interferogram without prior detailed characterization of the nuclear Hamiltonian under which the target propagates. With numerically calculated nonlinear WPI signals subject to Gaussian noise, we demonstrate the reconstruction of a rovibrational wave packet launched from the A state and propagated in the E state of Li2.     

Molecular state reconstruction by nonlinear wave packet interferometry

We show that time- and phase-resolved two-color nonlinear wave packet interferometry can be used to reconstruct the probability amplitude of an optically prepared molecular wave packet without prior knowledge of the underlying potential surface. We analyze state reconstruction in pure- and mixed-state model systems excited by shaped laser pulses and propose nonlinear wave packet interferometry as a tool for identifying optimized wave packets in coherent control experiments.     

An impact parameter description of single and double diffraction dissociation

An s-channel impact parameter model of inelastic diffraction dissociation is constructed which describes quantitatively the momentum transfer distributions of both pion and nucleon induced reactions. It is stressed that the impact parameter profile is peripheral and is approximately the same for all helicity amplitudes. From the fits to the data, the concept of a universal limiting strength (ULS) for each amplitude is deduced and its consequence for other diffractive processes, and the approximate TCHC hypothesis are discussed. Finally, detailed predictions are presented the momentum transfer distributions in the double diffraction process NN → (Nπ)(Nπ), and compared with a simple t-channel picture of diffraction dissociation.     

Combinatorial Library Based Engineering of Candida antarctica Lipase A for Enantioselective Transacylation of sec‐Alcohols in Organic Solvent

A method for determining lipase enantioselectivity in the transacylation of sec‐alcohols in organic solvent was developed. The method was applied to a model library of Candida antarctica lipase A (CalA) variants for improved enantioselectivity (E values) in the kinetic resolution of 1‐phenylethanol in isooctane. A focused combinatorial gene library simultaneously targeting seven positions in the enzyme active site was designed. Enzyme variants were immobilized on nickel‐coated 96‐well microtiter plates through a histidine tag (His₆‐tag), screened for transacylation of 1‐phenylethanol in isooctane, and analyzed by GC. The highest enantioselectivity was shown by the double mutant Y93L/L367I. This enzyme variant gave an E value of 100 (R), which is a dramatic improvement on the wild‐type CalA (E=3). This variant also showed high to excellent enantioselectivity for other secondary alcohols tested.     

Role of the ubiquitin proteasome system in Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder. Although a subject of intense research, the etiology of PD remains poorly understood. Recently, several lines of evidence have implicated an intimate link between aberrations in the ubiquitin proteasome system (UPS) and PD pathogenesis. Derangements of the UPS, which normally functions as a type of protein degradation machinery, lead to alterations in protein homeostasis that could conceivably promote the toxic accumulation of proteins detrimental to neuronal survival. Not surprisingly, various cellular and animal models of PD that are based on direct disruption of UPS function reproduce the most prominent features of PD. Although persuasive, new developments in the past few years have in fact raised serious questions about the link between the UPS and PD. Here I review current thoughts and controversies about their relationship and discuss whether strategies aimed at mitigating UPS dysfunction could represent rational ways to intervene in the disease. Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com).     

Optimum Redundancy with Equipment that Operates and Idles

Despite their widespread exclusion from the literature on reliability and replacement, many items of equipment are subject to failures to idle as well as failures to operate. For such equipment a new optimisation problem arises at the stage of systems design in terms of the optimal use of redundancy to maximise expected systems life. The models hitherto used as the basis for the solution of this optimization problem ignore the dependence that should exist for the solutions upon the operating and idling requirements to which the system is to be exposed. In this paper a simple model for equipment subject to such opposite failure modes is constructed which takes explicit account of the proportion of time the equipment is in use. The implications of this new model for the selection of an optimum redundancy configuration are illustrated for the case where four identical items of equipment are available.     

A comparison of πππ, Kππ, πKKKK system produced in the reactions meson +p→3 mesons + p

A comparison is made of the low-mass three-meson systems (πππ), (Kππ), $\text{(π}\text{K}\text{K}\text{)}$ and $\text{(}\text{K}\text{K}\text{K}\text{)}$ diffractively produced in the reaction meson + proton → three mesons + proton. Several striking similarities and a few important differences are observed: (i) the reactions are consistent with the assumption that the three mesons decay entirely into a 0^? meson and a 0⁺, 1^? or 2⁺ resonance; (ii) the three-meson mass spectra have a peak ≈ 250 MeV above the effective threshold M_eff of the dominant decay mode and then fall off approximately as (mass)^?3;(iii) the average spin 〈J〉 = 0.55 + 1.1 Q_eff, where Q_eff = M - M_eff; (iv) the average orbital angular momentum 〈l〉 increases according to 〈l〉 = 0.75 Q_eff; (v) the three-meson states are produced dominantly in unnatural spin-parity states and no evidence for their being resonant is found; (vi) the only natural spin-parity states found are the well-established 2⁺ resonances A₂ and K¹ (1420); they have similar properties to the non-resonant unnatural parity states except for a dip at t = 0 in the dσ/dt distributions; (vii) both the unnatural and natural spin-parity states are produced mostly by an exchange of natural parity; (viii) there is evidence for two types of production mechanism with different polarization properties, one approximately conserving helicity in the t-channel and the other in the s-channel.