4,293 research outputs found
Earth resources-regional transfer activity contracts review
A regional transfer activity contracts review held by the Earth Resources Office was summarized. Contracts in the earth resources field primarily directed toward applications of satellite data and technology in solution of state and regional problems were reviewed. A summary of the progress of each contract was given in order to share experiences of researchers across a seven state region. The region included Missouri, Kentucky, Tennessee, Mississippi, Alabama, Georgia, and North Carolina. Research in several earth science disciplines included forestry, limnology, water resources, land use, geology, and mathematical modeling. The use of computers for establishment of information retrieval systems was also emphasized
The kinetic temperature in a damped Lyman-alpha absorption system in Q2206-199 - an example of the warm neutral medium
By comparing the widths of absorption lines from OI, SiII and FeII in the
redshift z=2.076 single-component damped Lyman alpha absorption system in the
spectrum of Q2206-199 we establish that these absorption lines arise in Warm
Neutral Medium gas at ~12000 +/- 3000K. This is consistent with thermal
equilibrium model estimates of ~ 8000K for the Warm Neutral Medium in galaxies,
but not with the presence of a significant cold component. It is also
consistent with, but not required by, the absence of CII* fine structure
absorption in this system. Some possible implications concerning abundance
estimates in narrow-line WNM absorbers are discussed.Comment: 9 pages, 3 figures. MNRAS accepte
Bang-bang control of fullerene qubits using ultra-fast phase gates
Quantum mechanics permits an entity, such as an atom, to exist in a
superposition of multiple states simultaneously. Quantum information processing
(QIP) harnesses this profound phenomenon to manipulate information in radically
new ways. A fundamental challenge in all QIP technologies is the corruption of
superposition in a quantum bit (qubit) through interaction with its
environment. Quantum bang-bang control provides a solution by repeatedly
applying `kicks' to a qubit, thus disrupting an environmental interaction.
However, the speed and precision required for the kick operations has presented
an obstacle to experimental realization. Here we demonstrate a phase gate of
unprecedented speed on a nuclear spin qubit in a fullerene molecule (N@C60),
and use it to bang-bang decouple the qubit from a strong environmental
interaction. We can thus trap the qubit in closed cycles on the Bloch sphere,
or lock it in a given state for an arbitrary period. Our procedure uses
operations on a second qubit, an electron spin, in order to generate an
arbitrary phase on the nuclear qubit. We anticipate the approach will be vital
for QIP technologies, especially at the molecular scale where other strategies,
such as electrode switching, are unfeasible
Mid- to Far-Infrared spectroscopy of Sharpless 171
We have collected one-dimensional raster-scan observations of the active
star-forming region Sharpless 171 (S171), a typical HII region-molecular cloud
complex, with the three spectrometers (LWS, SWS, and PHT-S) on board ISO. We
have detected 8 far-infrared fine-structure lines, [OIII] 52um, [NIII] 57um,
[OI] 63um, [OIII] 88um, [NII] 122um, [OI] 146um, [CII] 158um, and [SiII] 35um
together with the far-infrared continuum and the H2 pure rotation transition
(J=5-3) line at 9.66um. The physical properties of each of the three phases
detected, highly-ionized, lowly-ionized and neutral, are investigated through
the far-infrared line and continuum emission. Toward the molecular region,
strong [OI] 146um emission was observed and the [OI] 63um to 146um line ratio
was found to be too small (about 5) compared to the values predicted by current
photodissociation region (PDR) models. We examine possible mechanisms to
account for the small line ratio and conclude that the absorption of the [OI]
63um and the [CII] 158um emission by overlapping PDRs along the line of sight
can account for the observations and that the [OI] 146um emission is the best
diagnostic line for PDRs. We propose a method to estimate the effect of
overlapping clouds using the far-infrared continuum intensity and derive the
physical properties of the PDR. The [SiII] 35um emission is quite strong at
almost all the observed positions. The correlation with [NII] 122um suggests
that the [SiII] emission originates mostly from the ionized gas. The [SiII]
35um to [NII] 122um ratio indicates that silicon of 30% of the solar abundance
must be in the diffuse ionized gas, suggesting that efficient dust destruction
is undergoing in the ionized region.Comment: 15 pages with 15 figures, accepted in Astronomy & Astrophysic
Scoping Potential Routes to UK Civil Unrest via the Food System: Results of a Structured Expert Elicitation
We report the results of a structured expert elicitation to identify the most likely types of potential food system disruption scenarios for the UK, focusing on routes to civil unrest. We take a backcasting approach by defining as an end-point a societal event in which 1 in 2000 people have been injured in the UK, which 40% of experts rated as âPossible (20â50%)â, âMore likely than not (50â80%)â or âVery likely (>80%)â over the coming decade. Over a timeframe of 50 years, this increased to 80% of experts. The experts considered two food system scenarios and ranked their plausibility of contributing to the given societal scenario. For a timescale of 10 years, the majority identified a food distribution problem as the most likely. Over a timescale of 50 years, the experts were more evenly split between the two scenarios, but over half thought the most likely route to civil unrest would be a lack of total food in the UK. However, the experts stressed that the various causes of food system disruption are interconnected and can create cascading risks, highlighting the importance of a systems approach. We encourage food system stakeholders to use these results in their risk planning and recommend future work to support prevention, preparedness, response and recovery planning
Chern-Simons Invariants of Torus Links
We compute the vacuum expectation values of torus knot operators in
Chern-Simons theory, and we obtain explicit formulae for all classical gauge
groups and for arbitrary representations. We reproduce a known formula for the
HOMFLY invariants of torus links and we obtain an analogous formula for
Kauffman invariants. We also derive a formula for cable knots. We use our
results to test a recently proposed conjecture that relates HOMFLY and Kauffman
invariants.Comment: 20 pages, 5 figures; v2: minor changes, version submitted to AHP. The
final publication is available at
http://www.springerlink.com/content/a2614232873l76h6
The effect of COVID19 public health restrictions on the health of people with musculoskeletal conditions and symptoms : the CONTAIN study
Funding This work was supported by Versus Arthritis [Grant Number: 20748] and the British Society for Rheumatology. The funding for the original studies included were from Versus Arthritis (MAmMOTH) and the British Society for Rheumatology (BSRBR-AS and BSR-PsA). Daniel Whibley is supported by a Versus Arthritis Foundation Fellowship [Grant Number 21742] Acknowledgements We are grateful to help from staff at the National Ankylosing Spondylitis Society and specifically to patient partners Lynne Laidlaw (for help with designing questionnaire) and Susan Davis (for commenting on the manuscript). The authors do not report any conflicts of interest. GJM conceived the idea for the study and all authors were involved in the detailed planning. MH, KK, EM-B and MB were responsible for obtaining ethics and research governance approvals. MB undertook the analysis which was independently verified by GTJ. GJM, with input from MB, drafted the manuscript, and all authors contributed important intellectual content via written comments. We thank Linda Dean for comments on the manuscript. Data Availability Statement The data within the article which relate to the collection of BSR register data are owned by the BSR â access to these data are subject to application being made to the BSR: Registers (rheumatology.org.uk) . For other data in the article, application can be made for access to the data by contacting the corresponding author.Peer reviewedPublisher PD
Prospects for precision measurements of atomic helium using direct frequency comb spectroscopy
We analyze several possibilities for precisely measuring electronic
transitions in atomic helium by the direct use of phase-stabilized femtosecond
frequency combs. Because the comb is self-calibrating and can be shifted into
the ultraviolet spectral region via harmonic generation, it offers the prospect
of greatly improved accuracy for UV and far-UV transitions. To take advantage
of this accuracy an ultracold helium sample is needed. For measurements of the
triplet spectrum a magneto-optical trap (MOT) can be used to cool and trap
metastable 2^3S state atoms. We analyze schemes for measuring the two-photon
interval, and for resonant two-photon excitation to high
Rydberg states, . We also analyze experiments on the
singlet-state spectrum. To accomplish this we propose schemes for producing and
trapping ultracold helium in the 1^1S or 2^1S state via intercombination
transitions. A particularly intriguing scenario is the possibility of measuring
the transition with extremely high accuracy by use of
two-photon excitation in a magic wavelength trap that operates identically for
both states. We predict a ``triple magic wavelength'' at 412 nm that could
facilitate numerous experiments on trapped helium atoms, because here the
polarizabilities of the 1^1S, 2^1S and 2^3S states are all similar, small, and
positive.Comment: Shortened slightly and reformatted for Eur. Phys. J.
The neutral gas extent of galaxies as derived from weak intervening CaII absorbers
(Abridged) We present a systematic study of weak intervening CaII absorbers
at low redshift (z<0.5), based on the analysis of archival high resolution
(R>45,000) optical spectra of 304 quasars and active galactic nuclei observed
with VLT/UVES. Along a total redshift path of Dz~100 we detected 23 intervening
CaII absorbers in both the CaII H & K lines, with rest frame equivalent widths
W_r,3934=15-799 mA and column densities log N(CaII)=11.25-13.04. We obtain a
bias corrected number density of weak intervening CaII absorbers of
dN/dz=0.117+-0.044 at z=0.35 for absorbers with log N(CaII)>11.65. This is ~2.6
times the value obtained for damped Lyman alpha absorbers (DLAs) at low
redshift. From ionization modeling we conclude that intervening CaII absorption
with log N(CaII)>11.5 arises in optically thick neutral gas in DLAs, sub-DLAs
and Lyman limit systems (LLS) at HI column densities of log N(HI)>17.4. The
relatively large cross section of these absorbers together with the frequent
detection of CaII absorption in high velocity clouds (HVCs) in the halo of the
Milky Way suggests that a considerable fraction of the intervening CaII systems
trace dusty neutral gas structures in the halos and circumgalactic environment
of galaxies (i.e., they are HVC analogs). Considering all galaxies with
luminosities L>0.05L* we calculate that the characteristic radial extent of
(partly) neutral gas clouds with log N(HI)>17.4 around low-redshift galaxies is
R_HVC ~ 55 kpc.Comment: 20 pages, 15 figures; A&A, in press; this revision contains several
changes that improve clarity of presentation reflecting the suggestions made
by the refere
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