Inertial navigation/calibration/precise time and frequency capabilities

The Aerospace Guidance and Metrology Center was conceived in 1959 to be the US Air Force Inertial Navigation and Metrology Center. This paper will show the mission capabilities of the Inertial Navigation Maintenance Center and the Air Force Measurement and Standards Laboratory. Highlighted will be the precise time and frequency program developed by AGMC to support Air Force precise time and frequency requirements worldwide. A description of the past, present, and future precise time and frequency activities will be presented

The Cosmic Censor Forbids Naked Topology

For any asymptotically flat spacetime with a suitable causal structure obeying (a weak form of) Penrose's cosmic censorship conjecture and satisfying conditions guaranteeing focusing of complete null geodesics, we prove that active topological censorship holds. We do not assume global hyperbolicity, and therefore make no use of Cauchy surfaces and their topology. Instead, we replace this with two underlying assumptions concerning the causal structure: that no compact set can signal to arbitrarily small neighbourhoods of spatial infinity (``$i^0$-avoidance''), and that no future incomplete null geodesic is visible from future null infinity. We show that these and the focusing condition together imply that the domain of outer communications is simply connected. Furthermore, we prove lemmas which have as a consequence that if a future incomplete null geodesic were visible from infinity, then given our $i^0$-avoidance assumption, it would also be visible from points of spacetime that can communicate with infinity, and so would signify a true naked singularity.Comment: To appear in CQG, this improved version contains minor revisions to incorporate referee's suggestions. Two revised references. Plain TeX, 12 page

Semiconductor technology program: Progress briefs

Measurement technology for semiconductor materials, process control, and devices, is discussed. Silicon and silicon based devices are emphasized. Highlighted activities include semiinsulating GaAs characterization, an automatic scanning spectroscopic ellipsometer, linewidth measurement and coherence, bandgap narrowing effects in silicon, the evaluation of electrical linewidth uniformity, and arsenicomplanted profiles in silicon

Strongly-Coupled Quarks and Colorful Black Holes

We use the AdS/CFT correspondence to study the behavior of strongly-coupled quarks in a black hole background. The supergravity background consists of a six-dimensional Schwarzschild-black string AdS soliton, for which the bulk horizon extends from the AdS boundary down to an infra-red floor. By going to higher energy scales, the regime of validity of the classical supergravity background can be extended closer to the singularity than might be expected from the four-dimensional perspective. Small black holes potentially created by the Large Hadron Collider could typically carry color charges inherited from their parton progenitors. The dynamics of quarks near such a black hole depends on the curved spacetime geometry as well as the strong interaction with the color-charged black hole. We study the resulting behavior of quarks and compute the rate at which a quark rotating around the black hole loses energy. We also investigate how the interaction between a quark and an antiquark is altered by the presence of the black hole, which results in a screening length.Comment: Proceedings of the DPF-2011 Conference, 8 pages, 5 figures, added reference

Evidence for a parsec scale X-ray jet from the accreting neutron star Circinus X-1

We analyzed the zero-order image of a 50 ks Chandra gratings observation of Circinus X-1, taken in 2005 during the source's low-flux state. Circinus X-1 is an accreting neutron star that exhibits ultra-relativistic arcsecond-scale radio jets and diffuse arcminute-scale radio jets and lobes. The image shows a clear excess along the general direction of the north-western counter-jet, coincident with the radio emission, suggesting that it originates either in the jet itself or in the shock the jet is driving into its environment. This makes Circinus X-1 the first neutron star for which an extended X-ray jet has been detected. The kinetic jet power we infer is significantly larger than the minimum power required for the jet to inflate the large scale radio nebula.Comment: Added journal reference, corrected on reference and typo in labels for Fig. 1; 5 pages, 3 figures, ApJ Letter, in pres

Correlated radial velocity and X-ray variations in HD 154791/4U 1700+24

We present evidence for approximately 400-d variations in the radial velocity of HD 154791 (V934 Her), the suggested optical counterpart of 4U 1700+24. The variations are correlated with the previously reported approximately 400 d variations in the X-ray flux of 4U 1700+24, which supports the association of these two objects, as well as the identification of this system as the second known X-ray binary in which a neutron star accretes from the wind of a red giant. The HD 154791 radial velocity variations can be fit with an eccentric orbit with period 404 +/- 3 d, amplitude K=0.75 +/- 0.12 km/s and eccentricity e=0.26 +/- 0.15. There are also indications of variations on longer time scales >~ 2000 d. We have re-examined all available ASM data following an unusually large X-ray outburst in 1997-98, and confirm that the 1-d averaged 2-10 keV X-ray flux from 4U 1700+24 is modulated with a period of 400 +/- 20 d. The mean profile of the persistent X-ray variations was approximately sinusoidal, with an amplitude of 0.108 +/- 0.012 ASM count/s (corresponding to 31% rms). The epoch of X-ray maximum was approximately 40 d after the time of periastron according to the eccentric orbital fit. If the 400 d oscillations from HD 154791/4U 1700+24 are due to orbital motion, then the system parameters are probably close to those of the only other neutron-star symbiotic-like binary, GX 1+4. We discuss the similarities and differences between these two systems.Comment: 6 pages, 2 figures; accepted by Ap

Corrosive wear behaviour of various stainless steel alloys and a Stellite 6 weld cladding

This study has comprised an investigation the corrosive wear behaviour of UNS S31600, a low hardness (280Hv) UNS S42000, a high hardness (480Hv) UNS S42000 and a single layer Stellite 6 (UNS R30006) weld cladding on a low alloy carbon steel (UNS G43400). Erosion-corrosion testing was conducted using a submerged jet of 3.5% NaCl aqueous solution with spherical silica sand particles. The sand concentration was 2.4g/l, the velocity of the jet was 18m/s and the testing temperature range was 16°C-27°C. Both normal incidence (90°) and low angle (20°) tests were performed. Mass losses, wear scar depths and a volumetric analysis technique were used to assess the damage in the direct impinged zone (DIZ) and the outer area (OA) of the specimens. For all materials, it was found that mass loss was higher at 20° tests than that of 90°. However, when comparing wear scar depths the opposite trend was found. The results are discussed in terms of comparative material behaviour, the influence of material hardness and the corrosive wear mechanisms in different regions formed during slurry jet impingement

Accumulation and fate of nano- and micro-plastics and associated contaminants in organisms

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Following a decade of research on the environmental impacts of microplastics, a knowledge gap remains on the processes by which micro and nanoplastics pass across biological barriers, enter cells and are subject to biological mechanisms. Here we summarize available literature on the accumulation of microplastics and their associated contaminants in a variety of organisms including humans. Most data on the accumulation of microplastics in both field and lab studies are for marine invertebrates. Microplastics accumulation data for insects, birds, marine mammals and sea turtles are scarce due to methodological issues. There is no conclusive evidence for the mode of accumulation of microplastics in either mammals or humans. The mechanism of chemical partitioning, role of contaminants associated with plastics, and mode of action of both nano- and micro-plastics and associated chemicals in a range of organisms and associated compartments/tissues also requires further research.Natural Environment Research Council (NERC)Queensland Department of Healt

The reactions and ashes of thermonuclear explosions on neutron stars

This paper reports on the detailed rp-process reaction flow on an accreting neutron star and the resulting ashes of a type I X-ray burst. It is obtained by coupling a 298 isotope reaction network to a self-consistent one-dimensional model calculation with a constant accretion rate of dM/dt=1.0e17g/s (0.09 Eddington).Comment: 4 pages, 2 figures, submitted to the INPC2004 proceeding