7,387 research outputs found
Isotropic magnetometry with simultaneous excitation of orientation and alignment CPT resonances
Atomic magnetometers have very high absolute precision and sensitivity to
magnetic fields but suffer from a fundamental problem: the vectorial or
tensorial interaction of light with atoms leads to "dead zones", certain
orientations of magnetic field where the magnetometer loses its sensitivity. We
demonstrate a simple polarization modulation scheme that simultaneously creates
coherent population trapping (CPT) in orientation and alignment, thereby
eliminating dead zones. Using Rb in a 10 Torr buffer gas cell we measure
narrow, high-contrast CPT transparency peaks in all orientations and also show
absence of systematic effects associated with non-linear Zeeman splitting.Comment: 4 pages, 4 figure
Comparison of techniques for identification of peripheral vestibular nystagmus.
To determine the best clinical method for identifying peripheral vestibular nystagmus, by comparing eye movement examination with optic fixation, and with fixation removed using Frenzel's glasses, infra-red video-Frenzel's goggles or an ophthalmoscope, with results of electronystagmography
Filling some black holes: modeling the connection between urbanization, infrastructure, and global service intensity
This empirical article combines insights from previous research on the level of knowledge-intensive service in metropolitan areas with the aim to develop an understanding of the spatial structure of the global service economy. We use a stepwise regression model with the Globalization and World Cities research network's measure of globalized service provisioning as the dependent variable and a range of variables focusing on population, infrastructure, urban primacy, and national regulation as independent variables. The discussion of the results focuses on model parameters as well as the meaning of outliers and is used to explore some avenues for future research
To Sleep, Perchance to Dream: Acute and Chronic Sleep Deprivation in Acute Care Surgeons
Background
Acute and chronic sleep deprivation are significantly associated with depressive symptoms and felt to be contributors to the development of burnout. In-house call (IHC) inherently includes frequent periods of disrupted sleep and is common amongst acute care surgeons (ACS). The relationship between IHC and sleep deprivation (SD) amongst ACS has not been previously studied. The goal of this study was to determine prevalence and patterns of SD in ACS.
Study
Design: A prospective study of ACS with IHC responsibilities from two Level I trauma centers was performed. Participants wore a sleep tracking device continuously over a 3-month period. Data collected included age, gender, schedule of IHC, hours and pattern of each sleep stage (light, slow wave (SWS), and REM), and total hours of sleep. Sleep patterns were analyzed for each night excluding IHC and categorized as normal (N), acute sleep deprivation (ASD), or chronic sleep deprivation (CSD).
Results
1421 nights were recorded amongst 17 ACS. (35.3% female; ages 37-65, mean 45.5 years). Excluding IHC, average amount of sleep was 6.54 hours with 64.8% of sleep patterns categorized as ASD or CSD. Average amount of sleep was significantly higher on post-call day 1 (6.96 hours, p=0.0016), but decreased significantly on post-call day 2 (6.33 hours, p=0.0006). Sleep patterns with ASD and CSD peaked on post-call day 2, and returned to baseline on post-call day 3 (p=0.046).
Conclusion
Sleep patterns consistent with ASD and CSD are common amongst ACS and worsen on post-call day 2. Baseline sleep patterns were not recovered until post-call day 3. Future study is needed to identify factors which impact physiologic recovery after IHC and further elucidate the relationship between SD and burnout
A New View on Worst-Case to Average-Case Reductions for NP Problems
We study the result by Bogdanov and Trevisan (FOCS, 2003), who show that
under reasonable assumptions, there is no non-adaptive worst-case to
average-case reduction that bases the average-case hardness of an NP-problem on
the worst-case complexity of an NP-complete problem. We replace the hiding and
the heavy samples protocol in [BT03] by employing the histogram verification
protocol of Haitner, Mahmoody and Xiao (CCC, 2010), which proves to be very
useful in this context. Once the histogram is verified, our hiding protocol is
directly public-coin, whereas the intuition behind the original protocol
inherently relies on private coins
Bubbles and jackets: new scaling bounds in topological group field theories
We use a reformulation of topological group field theories in 3 and 4
dimensions in terms of variables associated to vertices, in 3d, and edges, in
4d, to obtain new scaling bounds for their Feynman amplitudes. In both 3 and 4
dimensions, we obtain a bubble bound proving the suppression of singular
topologies with respect to the first terms in the perturbative expansion (in
the cut-off). We also prove a new, stronger jacket bound than the one currently
available in the literature. We expect these results to be relevant for other
tensorial field theories of this type, as well as for group field theory models
for 4d quantum gravity.Comment: v2: Minor modifications to match published versio
TCT-667 Aortic Valve Intervention In Octogenarians In The “TAVI-Era”: Analysis Of The UK National Adult Cardiac Surgery Audit Registry And The UK Transcatheter Aortic Valve Implantation (TAVI) Registry between 2006 and 2012
Modelling of bismuth segregation in InAsBi/InAs superlattices: Determination of the exchange energies
InAsBi dilute alloys are potential new candidates for the improvement of infrared optoelectronic devices such as photodetectors or lasers. In this work, InAsBi/InAs superlattices (SLs)with Bi contents ranging between 1 and 3% were grown by molecular beam epitaxy with different Bi fluxes and growth temperatures to analyze Bi segregation by cross sectional transmission electron microscopy techniques. Bi segregation profiles have been described layer-by-layer using a three-layer fluid exchange mechanism, extracting the values of the As/Bi exchange energies (E 1 , 1.26 ± 0.01 eV and E 2 , 1.36 ± 0.02 eV). A relationship to calculate the activation energies for exchange from the binding energies in III–V alloys is proposed, which would allow predicting them for other hitherto unknown compounds
A categorification of Morelli's theorem
We prove a theorem relating torus-equivariant coherent sheaves on toric
varieties to polyhedrally-constructible sheaves on a vector space. At the level
of K-theory, the theorem recovers Morelli's description of the K-theory of a
smooth projective toric variety. Specifically, let be a proper toric
variety of dimension and let M_\bR = \mathrm{Lie}(T_\bR^\vee)\cong \bR^n
be the Lie algebra of the compact dual (real) torus T_\bR^\vee\cong U(1)^n.
Then there is a corresponding conical Lagrangian \Lambda \subset T^*M_\bR and
an equivalence of triangulated dg categories \Perf_T(X) \cong
\Sh_{cc}(M_\bR;\Lambda), where \Perf_T(X) is the triangulated dg category of
perfect complexes of torus-equivariant coherent sheaves on and
\Sh_{cc}(M_\bR;\Lambda) is the triangulated dg category of complex of sheaves
on M_\bR with compactly supported, constructible cohomology whose singular
support lies in . This equivalence is monoidal---it intertwines the
tensor product of coherent sheaves on with the convolution product of
constructible sheaves on M_\bR.Comment: 20 pages. This is a strengthened version of the first half of
arXiv:0811.1228v3, with new results; the second half becomes
arXiv:0811.1228v
Electrostatic Interactions of Asymmetrically Charged Membranes
We predict the nature (attractive or repulsive) and range (exponentially
screened or long-range power law) of the electrostatic interactions of
oppositely charged and planar plates as a function of the salt concentration
and surface charge densities (whose absolute magnitudes are not necessarily
equal). An analytical expression for the crossover between attractive and
repulsive pressure is obtained as a function of the salt concentration. This
condition reduces to the high-salt limit of Parsegian and Gingell where the
interaction is exponentially screened and to the zero salt limit of Lau and
Pincus in which the important length scales are the inter-plate separation and
the Gouy-Chapman length. In the regime of low salt and high surface charges we
predict - for any ratio of the charges on the surfaces - that the attractive
pressure is long-ranged as a function of the spacing. The attractive pressure
is related to the decrease in counter-ion concentration as the inter-plate
distance is decreased. Our theory predicts several scaling regimes with
different scaling expressions for the pressure as function of salinity and
surface charge densities. The pressure predictions can be related to surface
force experiments of oppositely charged surfaces that are prepared by coating
one of the mica surfaces with an oppositely charged polyelectrolyte
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