The effects of space radiation on a chemically modified graphite-epoxy composite material

The effects of the space environment on the engineering properties and chemistry of a chemically modified T300/934 graphite-epoxy composite system are characterized. The material was subjected to 1.0 x 10 to the 10th power rads of 1.0 MeV electron irradiation under vacuum to simulate 30 years in geosynchronous earth orbit. Monotonic tension tests were performed at room temperature (75 F/24 C) and elevated temperature (250 F/121 C) on 4-ply unidirectional laminates. From these tests, inplane engineering and strength properties (E sub 1, E sub 2, Nu sub 12, G sub 12, X sub T, Y sub T) were determined. Cyclic tests were also performed to characterize energy dissipation changes due to irradiation and elevated temperature. Large diameter graphite fibers were tested to determine the effects of radiation on their stiffness and strength. No significant changes were observed. Dynamic-mechanical analysis demonstrated that the glass transition temperature was reduced by 50 F(28 C) after irradiation. Thermomechanical analysis showed the occurrence of volatile products generated upon heating of the irradiated material. The chemical modification of the epoxy did not aid in producing a material which was more radiation resistant than the standard T300/934 graphite-epoxy system. Irradiation was found to cause crosslinking and chain scission in the polymer. The latter produced low molecular weight products which plasticize the material at elevated temperatures and cause apparent material stiffening at low stresses at room temperature

Phases of granular segregation in a binary mixture

We present results from an extensive experimental investigation into granular segregation of a shallow binary mixture in which particles are driven by frictional interactions with the surface of a vibrating horizontal tray. Three distinct phases of the mixture are established viz; binary gas (unsegregated), segregation liquid and segregation crystal. Their ranges of existence are mapped out as a function of the system's primary control parameters using a number of measures based on Voronoi tessellation. We study the associated transitions and show that segregation can be suppressed is the total filling fraction of the granular layer, $C$, is decreased below a critical value, $C_{c}$, or if the dimensionless acceleration of the driving, $\gamma$, is increased above a value $\gamma_{c}$.Comment: 12 pages, 12 figures, submitted to Phys. Rev.

Looking beyond the physical management of patients with head and neck cancer

Cancers of the head and neck region often leave patients with conspicuous defects, as well as limitations in physical and psycho-social functions. Rehabilitation is challenging and can never fully restore the anatomical, physiological, or functional characteristics that have been lost. Ideally newly diagnosed cancer patients should be managed by a multidisciplinary team of specialists from various allied fields who will be able to educate them and help them decide on the most appropriate and suitable treatment options. Patients must understand the processes, be of possible side effects and comprehend the limitations aware of rehabilitation. At the same time, clinicians may need to consider issues of distributive justice when deciding which patients will receive which resources, especially in financially limited institutions and countries. The biggest challenge to us as clinicians as well as community members is to try and treat all patients holistically and to address both their physical and psychosocial needs. This requires a fervent commitment to action, and that we all stand together and help each other through difficult times

Spatial nonlocal pair correlations in a repulsive 1D Bose gas

We analytically calculate the spatial nonlocal pair correlation function for an interacting uniform 1D Bose gas at finite temperature and propose an experimental method to measure nonlocal correlations. Our results span six different physical realms, including the weakly and strongly interacting regimes. We show explicitly that the characteristic correlation lengths are given by one of four length scales: the thermal de Broglie wavelength, the mean interparticle separation, the healing length, or the phase coherence length. In all regimes, we identify the profound role of interactions and find that under certain conditions the pair correlation may develop a global maximum at a finite interparticle separation due to the competition between repulsive interactions and thermal effects.Comment: Final published version, modified titl

Efficient and Selective Carbon-Carbon Coupling on Coke-Resistant PdAu Single-Atom Alloys

We demonstrate that PdAu single-atom alloy model catalysts offer a heterogeneous route to selective Würtz-type C–C coupling. Specifically, when methyl iodide is exposed to an otherwise unreactive Au(111) surface, single Pd atoms in the surface layer promote C–I dissociation and C–C coupling, leading to the selective formation of ethane

Persistent punishment : users views of short prison sentences

Semi-structured interviews were conducted of 22 prisoners to gather information about the characteristic features of short prison sentences. Themes raised in comments included: the frequency and quality of sentences, addiction, family, and penal legitimacy. Most of the participants had extensive experience of prison, and the effects of this played out across sentences and years, accumulating and amplifying impacts. And, despite expressions of guilt and remorse, most participants saw their sentence as unjust, and mainly a reaction to offending history. We conclude by suggesting the need for research to shift focus from evaluating individual penal interventions towards more holistic and narrative accounts that cut across sentences

Low temperature expansion for the 3-d Ising Model

We compute the weak coupling expansion for the energy of the three dimensional Ising model through 48 excited bonds. We also compute the magnetization through 40 excited bonds. This was achieved via a recursive enumeration of states of fixed energy on a set of finite lattices. We use a linear combination of lattices with a generalization of helical boundary conditions to eliminate finite volume effects.Comment: 10 pages, IASSNS-HEP-92/42, BNL-4767