Helmet latching and attaching ring

A neck ring releasably secured to a pressurized garment carries an open-ended ring normally in the engagement position fitted into an annular groove and adapted to fit into a complementary annular groove formed in a helmet. Camming means formed on the inner surface at the end of the helmet engages the open-ended ring to retract the same and allow for one motion donning even when the garment is pressurized. A projection on the end of the split ring is engageable to physically retract the split ring

Hyperuniformity, quasi-long-range correlations, and void-space constraints in maximally random jammed particle packings. II. Anisotropy in particle shape

We extend the results from the first part of this series of two papers by examining hyperuniformity in heterogeneous media composed of impenetrable anisotropic inclusions. Specifically, we consider maximally random jammed packings of hard ellipses and superdisks and show that these systems both possess vanishing infinite-wavelength local-volume-fraction fluctuations and quasi-long-range pair correlations. Our results suggest a strong generalization of a conjecture by Torquato and Stillinger [Phys. Rev. E. 68, 041113 (2003)], namely that all strictly jammed saturated packings of hard particles, including those with size- and shape-distributions, are hyperuniform with signature quasi-long-range correlations. We show that our arguments concerning the constrained distribution of the void space in MRJ packings directly extend to hard ellipse and superdisk packings, thereby providing a direct structural explanation for the appearance of hyperuniformity and quasi-long-range correlations in these systems. Additionally, we examine general heterogeneous media with anisotropic inclusions and show for the first time that one can decorate a periodic point pattern to obtain a hard-particle system that is not hyperuniform with respect to local-volume-fraction fluctuations. This apparent discrepancy can also be rationalized by appealing to the irregular distribution of the void space arising from the anisotropic shapes of the particles. Our work suggests the intriguing possibility that the MRJ states of hard particles share certain universal features independent of the local properties of the packings, including the packing fraction and average contact number per particle.Comment: 29 pages, 9 figure

Black Holes and Naked Singularities in Low Energy Limit of String Gravity with Modulus Field

We show that the black hole solutions of the effective string theory action, where one-loop effects that couple the moduli to gravity via a Gauss-Bonnet term are taken into account, admit primary scalar hair. The requirement of absence of naked singularities imposes an upper bound on the scalar charges.Comment: more details are added and some misprint are correcte

Neural Networks for Modeling and Control of Particle Accelerators

We describe some of the challenges of particle accelerator control, highlight recent advances in neural network techniques, discuss some promising avenues for incorporating neural networks into particle accelerator control systems, and describe a neural network-based control system that is being developed for resonance control of an RF electron gun at the Fermilab Accelerator Science and Technology (FAST) facility, including initial experimental results from a benchmark controller.Comment: 21 p

Walking a Tightrope: Unaccompanied migrant young people, transitions and futures

With the collaboration of Praxis Community Projects and Shpresa Programme, a series of photography workshops were conducted with young people from different backgrounds who have gone through similar experiences of migration. Many of these people came to the UK on their own as children, without their family. Their images narrate the difficult and continuous journey they make, and the life changing transitions that this journey entailed. It is a journey without a clear point of departure or arrival - or a clear sense of direction – but which brings multiple transformations and transitions along the way. People have to negotiate completely different cultural, social and political environments and, most importantly, the constraints of an exclusionary asylum system that has profound effects on their everyday lives. These young people often live with the terrifying uncertainty of not knowing what will happen to them or whether they will be returned to the country from which they have fled

Industrial Applications of Auger Surface Analysis

Scanning Auger microscopy is distinguished by its unique combination of surface selectivity, high spatial resolution, ease of identifying elements and quantifying composition, and ability to distinguish between chemical states. This paper describes several applications of scanning Auger microscopy, emphasizing the range of industrial research activities: 1. Electronic Materials. Contamination in an integrated circuit processing facility was identified and procedures for its removal determined. Causes for the delamination of printed circuit board foils were identified. Superlattice films were characterized and the deposition process evaluated. 2. Tribology. Analysis of surfaces in lubricated sliding contact revealed the effects of con tact kinematics and of molybdenum antifriction additives. 3. Corrosion. Early growth stages of phosphate coatings were found to be associated with a thin phosphate layer, not visible in SEM, interspersed with larger crystals. A corrosion layer on stainless steel/aluminum bimetal trim was shown to contain calcium carbonate and silicate deposits consistent with its galvanic protection mechanism. 4. Catalysis. Oxidation studies of Pd/ Rh alloys revealed varying surface compositions as a function of heat treatment temperature. Several problems commonly encountered in Auger analysis are described and ways of minimizing or estimating their effects are discussed

A study of the phase transition in the usual statistical model for nuclear multifragmentation

We use a simplified model which is based on the same physics as inherent in most statistical models for nuclear multifragmentation. The simplified model allows exact calculations for thermodynamic properties of systems of large number of particles. This enables us to study a phase transition in the model. A first order phase transition can be tracked down. There are significant differences between this phase transition and some other well-known cases

Rare isotope production in statistical multifragmentation

Producing rare isotopes through statistical multifragmentation is investigated using the Mekjian method for exact solutions of the canonical ensemble. Both the initial fragmentation and the the sequential decay are modeled in such a way as to avoid Monte Carlo and thus provide yields for arbitrarily scarce fragments. The importance of sequential decay, exact particle-number conservation and the sensitivities to parameters such as density and temperature are explored. Recent measurements of isotope ratios from the fragmentation of different Sn isotopes are interpreted within this picture.Comment: 10 eps figure

Statistical properties of determinantal point processes in high-dimensional Euclidean spaces

The goal of this paper is to quantitatively describe some statistical properties of higher-dimensional determinantal point processes with a primary focus on the nearest-neighbor distribution functions. Toward this end, we express these functions as determinants of $N\times N$ matrices and then extrapolate to $N\to\infty$. This formulation allows for a quick and accurate numerical evaluation of these quantities for point processes in Euclidean spaces of dimension $d$. We also implement an algorithm due to Hough \emph{et. al.} \cite{hough2006dpa} for generating configurations of determinantal point processes in arbitrary Euclidean spaces, and we utilize this algorithm in conjunction with the aforementioned numerical results to characterize the statistical properties of what we call the Fermi-sphere point process for $d = 1$ to 4. This homogeneous, isotropic determinantal point process, discussed also in a companion paper \cite{ToScZa08}, is the high-dimensional generalization of the distribution of eigenvalues on the unit circle of a random matrix from the circular unitary ensemble (CUE). In addition to the nearest-neighbor probability distribution, we are able to calculate Voronoi cells and nearest-neighbor extrema statistics for the Fermi-sphere point process and discuss these as the dimension $d$ is varied. The results in this paper accompany and complement analytical properties of higher-dimensional determinantal point processes developed in \cite{ToScZa08}.Comment: 42 pages, 17 figure