Role of the officer in Air Force Public Relations

Thesis (M.S.)--Boston Universit

The role of prostaglandin and antioxidant availability in recovery from forearm ischemia-reperfusion injury in humans

This article is made available through the Brunel Open Access Publishing Fund. It is shared under the Creative Commons License Attribution-Noncommercial No Derivative 3.0 (CCBY NCND). Copyright @ Lippincott Williams & Wilkins.Background: Endothelial dysfunction, manifesting as attenuated flow-mediated dilation (FMD), is clinically important. Antioxidants may prevent this dysfunction; however, the acute effects of oral administration in humans are unknown. Low flow-mediated constriction (L-FMC), a further parameter of endothelial health, is largely unstudied and the mechanisms for this response unclear. Methods: Twelve healthy participants (five women and seven men) completed three test conditions: control; antioxidant cocktail (α-lipoic acid, vitamins C and E); and prostaglandin inhibitor ingestion (ibuprofen). Ultrasound measurements of brachial artery responses were assessed throughout 5 min of forearm ischemia and 3 min after. Subsequently, an ischemia–reperfusion injury was induced by a 20-min upper arm occlusion. Further, vascular function protocols were completed at 15, 30, and 45 min of recovery. Results: Endothelial dysfunction was evident in all conditions. FMD was attenuated at 15 min after ischemia–reperfusion injury (Pre: 6.24 ± 0.58%; Post15: 0.24 ± 0.75%; mean ± SD, P  0.05). The magnitude of L-FMC was augmented at 15 min (Pre: 1.44 ± 0.27%; Post15: 3.75 ± 1.73%; P < 0.05) and recovered by 45 min. Ibuprofen administration produced the largest constrictive response (Pre: −1.13 ± 1.71%; Post15: −5.57 ± 3.82%; time × condition interaction: P < 0.05). Conclusion: Results demonstrate ischemia–reperfusion injury causes endothelial dysfunction and acute oral antioxidant supplementation fails to reduce its magnitude. Our results also suggest that a lack of shear stress during occlusion combined with suppression of prostaglandin synthesis magnifies L-FMC, possibly due to augmented endothelin-1 expression.Society of Biolog

Exhumation history of eastern Ladakh revealed by Ar-40/Ar-39 and fission-track ages: the Indus River-Tso Morari transect, NW Himalaya

Fission-track and Ar-40/Ar-39 ages place time constraints on the exhumation of the North Himalayan nappe stack, the Indus Suture Zone and Molasse, and the Transhimalayan Batholith in eastern Ladakh (NW India). Results from this and previous studies on a north-south transect passing near Tso Morari Lake suggest that the SW-directed North Himalayan nappe stack (comprising the Mata, Tetraogal and Tso Morari nappes) was emplaced and metamorphosed by c. 50-45 Ma, and exhumed to moderately shallow depths (c. 10 km) by c. 45-40 Ma. From the mid-Eocene to the present, exhumation continued at a steady and slow rate except for the root zone of the Tso Morari nappe, which cooled faster than the rest of the nappe stack. Rapid cooling occurred at c. 20 Ma and is linked to brittle deformation along the normal Ribil-Zildat Fault concomitant with extrusion of the Crystalline nappe in the south. Data from the Indus Molasse suggest that sediments were still being deposited during the Miocene

Modelling the light-curves of objects tidally disrupted by a black hole

Tidal disruption by massive black holes is a phenomenon, during which a large part of gravitational energy can be released on a very short time-scale. The time-scales and energies involved during X-ray and IR flares observed in Galactic centre suggest that they may be related to tidal disruption events. Furthermore, aftermath of a tidal disruption of a star by super-massive black hole has been observed in some galaxies, e.g. RX J1242.6-1119A. All these discoveries increased the demand for tools for tidal disruption study in curved space-time. Here we summarise our study of general relativistic effects on tidal deformation of stars and compact objects.Comment: 2 pages, to appear in the proceedings of the JENAM 2008, Symposium 7: "Grand Challenges in Computational Astrophysics

Staticity Theorem for Higher Dimensional Generalized Einstein-Maxwell System

We derive formulas for variations of mass, angular momentum and canonical energy in Einstein (n-2)-gauge form field theory by means of the ADM formalism. Considering the initial data for the manifold with an interior boundary which has the topology of (n-2)-sphere we obtained the generalized first law of black hole thermodynamics. Supposing that a black hole evevt horizon comprisesw a bifurcation Killing horizon with a bifurcate surface we find that the solution is static in the exterior world, when the Killing timelike vector field is normal to the horizon and has vanishing electric or magnetic fields on static slices.Comment: 10 pages, REVTEX, to published in Phys.Rev. D1

Linearized self-forces for branes

We compute the regularized force density and renormalized action due to fields of external origin coupled to a brane of arbitrary dimension in a spacetime of any dimension. Specifically, we consider forces generated by gravitational, dilatonic and generalized antisymmetric form-fields. The force density is regularized using a recently developed gradient operator. For the case of a Nambu--Goto brane, we show that the regularization leads to a renormalization of the tension, which is seen to be the same in both approaches. We discuss the specific couplings which lead to cancellation of the self-force in this case.Comment: 15 page

Experimental study of ion heating and acceleration during magnetic reconnection

Ion heating and acceleration has been studied in the well-characterized reconnection layer of the Magnetic Reconnection Experiment [M. Yamada , Phys. Plasmas 4, 1936 (1997)]. Ion temperature in the layer rises substantially during null-helicity reconnection in which reconnecting field lines are anti-parallel. The plasma outflow is sub-Alfvenic due to a downstream back pressure. An ion energy balance calculation based on the data and including classical viscous heating indicates that ions are heated largely via nonclassical mechanisms. The T-i rise is much smaller during co-helicity reconnection in which field lines reconnect obliquely. This is consistent with a slower reconnection rate and a smaller resistivity enhancement over the Spitzer value. These observations show that nonclassical dissipation mechanisms can play an important role both in heating the ions and in facilitating the reconnection process

Cosmic Vortons and Particle Physics Constraints

We investigate the cosmological consequences of particle physics theories that admit stable loops of superconducting cosmic string - {\it vortons}. General symmetry breaking schemes are considered, in which strings are formed at one energy scale and subsequently become superconducting in a secondary phase transition at what may be a considerably lower energy scale. We estimate the abundances of the ensuing vortons, and thereby derive constraints on the relevant particle physics models from cosmological observations. These constraints significantly restrict the category of admissible Grand Unified theories, but are quite compatible with recently proposed effects whereby superconducting strings may have been formed close to the electroweak phase transition.Comment: 33 pages, 2 figures, RevTe

Effect of atomic scale plasticity on hydrogen diffusion in iron: Quantum mechanically informed and on-the-fly kinetic Monte Carlo simulations

We present an off-lattice, on-the-fly kinetic Monte Carlo (KMC) model for simulating stress-assisted diffusion and trapping of hydrogen by crystalline defects in iron. Given an embedded atom (EAM) potential as input, energy barriers for diffusion are ascertained on the fly from the local environments of H atoms. To reduce computational cost, on-the-fly calculations are supplemented with precomputed strain-dependent energy barriers in defect-free parts of the crystal. These precomputed barriers, obtained with high-accuracy density functional theory calculations, are used to ascertain the veracity of the EAM barriers and correct them when necessary. Examples of bulk diffusion in crystals containing a screw dipole and vacancies are presented. Effective diffusivities obtained from KMC simulations are found to be in good agreement with theory. Our model provides an avenue for simulating the interaction of hydrogen with cracks, dislocations, grain boundaries, and other lattice defects, over extended time scales, albeit at atomistic length scales