11,765 research outputs found
Ultra-high-sensitivity two-dimensional bend sensor
A multicore fibre Fabry-Perot-based strain sensor interrogated with tandem interferometry for bend measurement is described. Curvature in two dimensions is obtained by measuring the difference in strain between three co-located low finesse Fabry-Perot interferometers formed in each core of the fibre by pairs of Bragg gratings. This sensor provides a responsivity enhancement of up to 30 times that of a previously reported fibre Bragg grating based sensor. Strain resolutions of 0.6 n epsilon/Hz(1/2) above 1 Hz are demonstrated, which corresponds to a curvature resolution of similar to 0.012 km(-1)/Hz(1/2)
Quantum Mechanics of Damped Systems II. Damping and Parabolic Potential Barrier
We investigate the resonant states for the parabolic potential barrier known
also as inverted or reversed oscillator. They correspond to the poles of
meromorphic continuation of the resolvent operator to the complex energy plane.
As a byproduct we establish an interesting relation between parabolic cylinder
functions (representing energy eigenfunctions of our system) and a class of
Gel'fand distributions used in our recent paper.Comment: 14 page
`Operational' Energy Conditions
I show that a quantized Klein-Gordon field in Minkowski space obeys an
`operational' weak energy condition: the energy of an isolated device
constructed to measure or trap the energy in a region, plus the energy it
measures or traps, cannot be negative. There are good reasons for thinking that
similar results hold locally for linear quantum fields in curved space-times. A
thought experiment to measure energy density is analyzed in some detail, and
the operational positivity is clearly manifested.
If operational energy conditions do hold for quantum fields, then the
negative energy densities predicted by theory have a will-o'-the-wisp
character: any local attempt to verify a total negative energy density will be
self-defeating on account of quantum measurement difficulties. Similarly,
attempts to drive exotic effects (wormholes, violations of the second law,
etc.) by such densities may be defeated by quantum measurement problems. As an
example, I show that certain attempts to violate the Cosmic Censorship
principle by negative energy densities are defeated.
These quantum measurement limitations are investigated in some detail, and
are shown to indicate that space-time cannot be adequately modeled classically
in negative energy density regimes.Comment: 18 pages, plain Tex, IOP macros. Expanded treatment of measurement
problems for space-time, with implications for Cosmic Censorship as an
example. Accepted by Classical and Quantum Gravit
Unitarity and the color confinement
We discuss how confinement property of QCD results in the rational
unitarization scheme and how unitarity saturation leads to appearance of a
hadron liquid phase at very high temperatures.Comment: 10 pages, no figire
Casimir force on a piston
We consider a massless scalar field obeying Dirichlet boundary conditions on
the walls of a two-dimensional L x b rectangular box, divided by a movable
partition (piston) into two compartments of dimensions a x b and (L-a) x b. We
compute the Casimir force on the piston in the limit L -> infinity. Regardless
of the value of a/b, the piston is attracted to the nearest end of the box.
Asymptotic expressions for the Casimir force on the piston are derived for a <<
b and a >> b.Comment: 10 pages, 1 figure. Final version, accepted for publication in Phys.
Rev.
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Memorandum of Understanding Between the United States Department of Energy and the State of Texas - Characterization of Oil and Gas Reservoir Heterogeneity
Ultimate recovery from Texas oil reservoirs at current technological and development levels is projected to be 36 percent of the oil in place. Thus, of the 165 billion barrels (Bbbl) of oil discovered statewide, 106 Bbbl will remain in existing reservoirs after recovery of proved reserves. This remaining resource is composed of residual oil (71 Bbbl) and mobile oil (35 Bbbl). The remaining mobile oil is conventionally recoverable but is prevented from migrating to the wellbore by intrareservoir seals or bounding surfaces.
Reservoir architecture, the internal fabric or structure of reservoirs, governs paths of fluid migration during oil and gas production. Reservoir architecture is, in turn, the product of the depositional and diagenetic processes responsible for the origin of the reservoir. If an understanding of the origin of the reservoir is developed, reservoir architecture, and therefore the paths of fluid migration, become predictable. Thus, with a greater understanding of the fabric of the reservoir and its inherent control on the paths of fluid flow, we can more efficiently design and implement advanced recovery strategies.Bureau of Economic Geolog
Greenstone belts: Their components and structure
Greenstone sucessions are defined as the nongranitoid component of granitoid-greenstone terrain and are linear to irregular in shape and where linear are termed belts. The chemical composition of greenstones is described. Also discussed are the continental environments of greenstone successions. The effects of contact with granitoids, geophysical properties, recumbent folds and late formation structures upon greenstones are examined. Large stratigraphy thicknesses are explained
Avian blood parasites in an endangered columbid: Leucocytozoon marchouxi in the Mauritian Pink Pigeon Columba mayeri
There is increasing evidence that pathogens can play a significant role in species decline. This study of a complete free-living species reveals a cost of blood parasitism to an endangered host, the Pink Pigeon Columba mayeri, endemic to Mauritius. We investigated the prevalence and effect of infection of the blood parasite, Leucocytozoon marchouxi, in the free-living Pink Pigeon population. Overall, L. marchouxi infection prevalence detected was 18·3%. Juveniles were more likely to be infected than older birds and there was geographical variation in infection prevalence. Survival of birds infected with L. marchouxi was lower than that of uninfected birds to 90 days post-sampling. This study suggests that while common haematozoa are well tolerated in healthy adults, these parasites may have greater pathogenic potential in susceptible juveniles. The study is unusual given its completeness of species sampling (96%) within a short time-period, the accurate host age data, and its focus on blood parasites in a threatened bird species. Species for which long-term life-history data are available for every individual serve as valuable models for dissecting the contribution of particular pathogens to species decline
The Continuum Limit and Integral Vacuum Charge
We investigate a commonly used formula which seems to give non-integral
vacuum charge in the continuum limit. We show that the limit is subtle and care
must be taken to get correct results.Comment: 5 pages. Submitted to JETP Letter
Detection of an atmosphere around the super-Earth 55 Cancri e
We report the analysis of two new spectroscopic observations of the
super-Earth 55 Cancri e, in the near infrared, obtained with the WFC3 camera
onboard the HST. 55 Cancri e orbits so close to its parent star, that
temperatures much higher than 2000 K are expected on its surface. Given the
brightness of 55 Cancri, the observations were obtained in scanning mode,
adopting a very long scanning length and a very high scanning speed. We use our
specialized pipeline to take into account systematics introduced by these
observational parameters when coupled with the geometrical distortions of the
instrument. We measure the transit depth per wavelength channel with an average
relative uncertainty of 22 ppm per visit and find modulations that depart from
a straight line model with a 6 confidence level. These results suggest
that 55 Cancri e is surrounded by an atmosphere, which is probably
hydrogen-rich. Our fully Bayesian spectral retrieval code, T-REx, has
identified HCN to be the most likely molecular candidate able to explain the
features at 1.42 and 1.54 m. While additional spectroscopic observations
in a broader wavelength range in the infrared will be needed to confirm the HCN
detection, we discuss here the implications of such result. Our chemical model,
developed with combustion specialists, indicates that relatively high mixing
ratios of HCN may be caused by a high C/O ratio. This result suggests this
super-Earth is a carbon-rich environment even more exotic than previously
thought.Comment: 10 pages, 10 figures, 4 tables, Accepted for publication in Ap
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