Galileo internal electrostatic discharge program

The Galileo spacecraft which will orbit Jupiter in 1988 will encounter a very harsh environment of energetic electrons. These electrons will have sufficient energy to penetrate the spacecraft shielding, consequently depositing charges in the dielectric insulating materials or ungrounded conductors. The resulting electric field could exceed the breakdown strength of the insulating materials, producing discharges. The transients produced from these Internal Electrostatic Discharges (IESD) could, depending on their relative location, be coupled to nearby cables and circuits. These transients could change the state of logic circuits or degrade or even damage spacecraft components, consequently disrupting the operation of subsystems and systems of the Galileo spacecraft during its expected mission life. An extensive testing program was initiated for the purpose of understanding the potential threats associated with these IESD events. Data obtained from these tests were used to define design guidelines

Sequence of the mouse Q4 class I gene and characterization of the gene product

The Q4 class I gene has been shown to participate in gene conversion events within the mouse major histocompatibility complex. Its complete genomic nucleotide sequence has been determined. The 5' half of Q4 resembles H-2 genes more strongly than other Q genes. Its 3' end, in contrast, is Q-like and contains a translational stop signal in exon 5 which predicts a polypeptide with an incomplete membrane spanning segment. The presence of two inverted B1 repeats suggests that part of the Q4 gene may be mobile within the genome. Gene transfer experiments have shown that the Q4 gene encodes a ß2-microglobulin associated polypeptide of Mr 41 000. A similar protein was found in activated mouse spleen cells. The Q4 polypeptide was found to be secreted both by spleen cells and by transfected fibroblasts and was not detectable on the cell surface. Antibody binding and twodimensional gel electrophoresis indicate that the Q4 molecule is identical to a mouse class I polypeptide, Qb-1, which has been previously described

Prethermalization and thermalization in models with weak integrability breaking

We study the effects of integrability breaking perturbations on the non-equilibrium evolution of many-particle quantum systems. We focus on a class of spinless fermion models with weak interactions. We employ equation of motion techniques that can be viewed as generalizations of quantum Boltzmann equations. We benchmark our method against time dependent density matrix renormalization group computations and find it to be very accurate as long as interactions are weak. For small integrability breaking, we observe robust prethermalization plateaux for local observables on all accessible time scales. Increasing the strength of the integrability breaking term induces a "drift" away from the prethermalization plateaux towards thermal behaviour. We identify a time scale characterizing this cross-over.Comment: 9 pages, 4 figure

"Quasi-particle breakdown" in the quasi-one-dimensional Ising ferromagnet CoNb2_2O6_6

We present experimental and theoretical evidence that an interesting quantum many-body effect -- quasi-particle breakdown -- occurs in the quasi-one-dimensional spin-1/2 Ising-like ferromagnet CoNb$_2$O$_6$ in its paramagnetic phase at high transverse field as a result of explicit breaking of spin inversion symmetry. We propose a quantum spin Hamiltonian capturing the essential one-dimensional physics of CoNb$_2$O$_6$ and determine the exchange parameters of this model by fitting the calculated single particle dispersion to the one observed experimentally in applied transverse magnetic fields. We present high-resolution inelastic neutron scattering measurements of the single particle dispersion which observe "anomalous broadening" effects over a narrow energy range at intermediate energies. We propose that this effect originates from the decay of the one particle mode into two-particle states. This decay arises from (i) a finite overlap between the one-particle dispersion and the two-particle continuum in a narrow energy-momentum range and (ii) a small misalignment of the applied field away from the direction perpendicular to the Ising axis in the experiments, which allows for non-zero matrix elements for decay by breaking the $\mathbb{Z}_2$ spin inversion symmetry of the Hamiltonian.Comment: v1: 15 pages, 10 figures. v2: 16 pages, 10 figures, minor changes, as accepted to PR

The information-related behaviour of emerging artists and designers Inspiration and guidance for new practitioners

Purpose – This paper aims to report an empirical study of the information-related behaviour of emerging artists and designers. It also aims to add to understanding of the information behaviour of the group both as practising artists (a little understood category of information users), and also as “new practitioners”. Design/methodology/approach – A literature analysis is used to guide creation of an online questionnaire, eliciting both qualitative and quantitative data. A total of 78 practising artists participated, all having graduated in the seven years prior to the survey. Findings – The group have generally the same information practices as more established artists. They place reliance on internet and social networks, while also using traditional printed tools and libraries. Browsing is important, but not a predominant means of accessing information. Inspiration is found from a very diverse and idiosyncratic set of sources, often by serendipitous means. Their status as emergent practitioners means that their information behaviour is governed by cost factors, and by needs for career advice and interaction with peers. Research limitations/implications – The study group are a convenience sample, all having access to the internet. No observation or interviews were carried out. Practical implications – The results will provide guidance to academic and public librarians serving artist users, and to those providing career advice to them. It will also be valuable to those providing services to “new practitioners” in any field. Originality/value – This is one of a very few papers reporting empirical studies of the information behaviour of artists, and has the largest sample size of any such study. It is one of a very few papers considering the information needs and behaviour of new practitioners