371 research outputs found
Observation of a quenched moment of inertia in a rotating strongly interacting Fermi gas
We make a model-independent measurement of the moment of inertia of a
rotating, expanding strongly-interacting Fermi gas. Quenching of the moment of
inertia is observed for energies both below and above the superfluid
transition. This shows that a strongly interacting Fermi gas with angular
momentum can support irrotational flow in both the superfluid and collisional
normal fluid regimes.Comment: 4 pages 5 figure
Measurement of the Entropy and Critical Temperature of a Strongly Interacting Fermi Gas
We report a model-independent measurement of the entropy, energy, and
critical temperature of a degenerate, strongly interacting Fermi gas of atoms.
The total energy is determined from the mean square cloud size in the strongly
interacting regime, where the gas exhibits universal behavior. The entropy is
measured by sweeping a bias magnetic field to adiabatically tune the gas from
the strongly interacting regime to a weakly interacting regime, where the
entropy is known from the cloud size after the sweep. The dependence of the
entropy on the total energy quantitatively tests predictions of the
finite-temperature thermodynamics.Comment: 16 pages, 3 figure
Observation of Anomalous Spin Segregation in a Trapped Fermi Gas
We report the observation of spin segregation, i.e., separation of spin
density profiles, in a trapped ultracold Fermi gas of Li with a
magnetically tunable scattering length close to zero. The roles of the spin
components are inverted when the sign of the scattering length is reversed. The
observed density profiles are in qualitative agreement with the spin-wave
theory applied previously to explain spin segregation in a Bose gas, but
disagree in amplitude by two orders of magnitude. The observed atomic density
profiles are far from equilibrium, yet they persist for 5 seconds in a
trap with an axial frequency of 150 Hz. We attribute this long
lifetime to Fermi statistics: The scattering amplitude is nonzero only for
atoms in opposite states, and vanishes for atoms in the same state. By
measuring the magnetic field at which spin segregation ceases, we precisely
determine the zero crossing in the scattering length of Li as
G.Comment: 4 pages, 3 figure
Effects of Ortet Genotype and Western Spruce Budworm Defoliation on Foliar Nutrients in Douglas-fir Clones
UNDA Forest service Research and DevelopmentNorth Arizona UniversityProceedings : IUFRO Kanazawa 2003 "Forest Insect Population Dynamics and Host Influences"., Scedule:14-19 September 2003, Vemue: Kanazawa Citymonde Hotel, Kanazawa, Japan, Joint metting of IUFRO working groups : 7.01.02 Tree resistance to Insects | 7.03.06 Integrated management of forset defoloating insects | 7.03.07 Population dynamics of forest insects, Sponsored by: IUFRO-J | Ishikawa Prefecture | Kanazawa City | 21st-COE Program of Kanazawa University, Editors: Kamata, Naoto | Liebhold, Nadrew M. | Quiring, Dan T. | Clancy, Karen M
First results on Martian carbon monoxide from Herschel/HIFI observations
We report on the initial analysis of Herschel/HIFI carbon monoxide (CO)
observations of the Martian atmosphere performed between 11 and 16 April 2010.
We selected the (7-6) rotational transitions of the isotopes ^{13}CO at 771 GHz
and C^{18}O at 768 GHz in order to retrieve the mean vertical profile of
temperature and the mean volume mixing ratio of carbon monoxide. The derived
temperature profile agrees within less than 5 K with general circulation model
(GCM) predictions up to an altitude of 45 km, however, show about 12-15 K lower
values at 60 km. The CO mixing ratio was determined as 980 \pm 150 ppm, in
agreement with the 900 ppm derived from Herschel/SPIRE observations in November
2009.Comment: Accepted for publication in Astronomy and Astrophysics (special issue
on HIFI first results); minor changes to match published versio
Room Temperature Optically and Magnetically Active Edges in Phosphorene Nanoribbons
Nanoribbons - nanometer wide strips of a two-dimensional material - are a
unique system in condensed matter physics. They combine the exotic electronic
structures of low-dimensional materials with an enhanced number of exposed
edges, where phenomena including ultralong spin coherence times, quantum
confinement and topologically protected states can emerge. An exciting prospect
for this new material concept is the potential for both a tunable
semiconducting electronic structure and magnetism along the nanoribbon edge.
This combination of magnetism and semiconducting properties is the first step
in unlocking spin-based electronics such as non-volatile transistors, a route
to low-energy computing, and has thus far typically only been observed in doped
semiconductor systems and/or at low temperatures. Here, we report the magnetic
and semiconducting properties of phosphorene nanoribbons (PNRs). Static (SQUID)
and dynamic (EPR) magnetization probes demonstrate that at room temperature,
films of PNRs exhibit macroscopic magnetic properties, arising from their edge,
with internal fields of ~ 250 to 800 mT. In solution, a giant magnetic
anisotropy enables the alignment of PNRs at modest sub-1T fields. By leveraging
this alignment effect, we discover that upon photoexcitation, energy is rapidly
funneled to a dark-exciton state that is localized to the magnetic edge and
coupled to a symmetry-forbidden edge phonon mode. Our results establish PNRs as
a unique candidate system for studying the interplay of magnetism and
semiconducting ground states at room temperature and provide a stepping-stone
towards using low-dimensional nanomaterials in quantum electronics.Comment: 18 pages, 4 figure
Production of Magnetic Arsenic–Phosphorus Alloy Nanoribbons with Small Band Gaps and High Hole Conductivities
Quasi-1D nanoribbons provide a unique route to diversifying the properties of their parent 2D nanomaterial, introducing lateral quantum confinement and an abundance of edge sites. Here, a new family of nanomaterials is opened with the creation of arsenic–phosphorus alloy nanoribbons (AsPNRs). By ionically etching the layered crystal black arsenic–phosphorus using lithium electride followed by dissolution in amidic solvents, solutions of AsPNRs are formed. The ribbons are typically few-layered, several micrometers long with widths tens of nanometers across, and both highly flexible and crystalline. The AsPNRs are highly electrically conducting above 130 K due to their small band gap (ca. 0.035 eV), paramagnetic in nature, and have high hole mobilities, as measured with the first generation of AsP devices, directly highlighting their properties and utility in electronic devices such as near-infrared detectors, quantum computing, and charge carrier layers in solar cells
Socioeconomic differentials in the immediate mortality effects of the national Irish smoking ban
This article has been made available through the Brunel Open Access Publishing Fund.Background: Consistent evidence has demonstrated that smoking ban policies save lives, but impacts on health inequalities are uncertain as few studies have assessed post-ban effects by socioeconomic status (SES) and findings have been inconsistent. The aim of this study was to assess the effects of the national Irish smoking ban on ischemic heart disease (IHD), stroke, and chronic obstructive pulmonary disease (COPD) mortality by discrete and composite SES indicators to determine impacts on inequalities. Methods: Census data were used to assign frequencies of structural and material SES indicators to 34 local authorities across Ireland with a 2000–2010 study period. Discrete indicators were jointly analysed through principal component analysis to generate a composite index, with sensitivity analyses conducted by varying the included indicators. Poisson regression with interrupted time-series analysis was conducted to examine monthly age and gender-standardised mortality rates in the Irish population, ages ≥35 years, stratified by tertiles of SES indicators. All models were adjusted for time trend, season, influenza, and smoking prevalence. Results: Post-ban mortality reductions by structural SES indicators were concentrated in the most deprived tertile for all causes of death, while reductions by material SES indicators were more equitable across SES tertiles. The composite indices mirrored the results of the discrete indicators, demonstrating that post-ban mortality decreases were either greater or similar in the most deprived when compared to the least deprived for all causes of death. Conclusions: Overall findings indicated that the national Irish smoking ban reduced inequalities in smoking-related mortality. Due to the higher rates of smoking-related mortality in the most deprived group, even equitable reductions across SES tertiles resulted in decreases in inequalities. The choice of SES indicator was influential in the measurement of effects, underscoring that a differentiated analytical approach aided in understanding the complexities in which structural and material factors influence mortality
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