3,163 research outputs found
Brevity, Speed, and Deference: An Account from the Williams Chambers
One of the leading books on administrative law advocates judicial review for âsound governance.âReviewing the book while sitting on the D.C. Circuit, Judge Williams posited that, even if âjudges are smarter than agency heads, or have more time on their hands, or have cleverer clerks,â the proper institutional role requires more deference. Divining âsound governanceâ is not for courts. The Judge concluded by quoting Miltonâs poem about the role of the blind: âThey also serve who only stand and waite.
Measuring Arbitrary Physical Properties in Analog Quantum Simulation
A central challenge in analog quantum simulation is to characterize desirable
physical properties of quantum states produced in experiments. However, in
conventional approaches, the extraction of arbitrary information requires
performing measurements in many different bases, which necessitates a high
level of control that present-day quantum devices may not have. Here, we
propose and analyze a scalable protocol that leverages the ergodic nature of
generic quantum dynamics, enabling the efficient extraction of many physical
properties. The protocol does not require sophisticated controls and can be
generically implemented in analog quantum simulation platforms today. Our
protocol involves introducing ancillary degrees of freedom in a predetermined
state to a system of interest, quenching the joint system under Hamiltonian
dynamics native to the particular experimental platform, and then measuring
globally in a single, fixed basis. We show that arbitrary information of the
original quantum state is contained within such measurement data, and can be
extracted using a classical data-processing procedure. We numerically
demonstrate our approach with a number of examples, including the measurements
of entanglement entropy, many-body Chern number, and various superconducting
orders in systems of neutral atom arrays, bosonic and fermionic particles on
optical lattices, respectively, only assuming existing technological
capabilities. Our protocol excitingly promises to overcome limited
controllability and, thus, enhance the versatility and utility of near-term
quantum technologies
Neuropsychological Decline Stratifies Dementia Risk in Cognitively Unimpaired and Impaired Older Adults
ObjectiveValidation and widespread use of markers indicating decline in serial neuropsychological exams has remained elusive despite potential value in prognostic and treatment decision-making. This study aimed to operationalize neuropsychological decline, termed âneuropsychological (NP) decline,â in older adults followed over 12 months in order to aid in the stratification of dementia risk along the cognitively unimpaired-to-mild cognitive impairment (MCI) spectrum.MethodsA prospective cohort study utilized 6,794 older adults from the National Alzheimerâs Coordinating Center (NACC) database with a baseline diagnosis of normal cognition, impaired without MCI or with MCI. Operationalization of NP decline over 12-month follow-up used regression-based norms developed in a robustly normal reference sample. The extent to which each participantâs 12-month follow-up score deviated from norm-referenced expectations was quantified and standardized to an NP decline z-score. Cox regression evaluated whether the NP decline metric predicted future dementia.ResultsParticipantâs NP decline scores predicted future all-cause dementia in the total sample, Ï2 = 110.71, hazard ratio (HR) = 1.989, p < 0.001, and in the subset diagnosed with normal cognition, Ï2 = 40.84, HR = 2.006, p < 0.001, impaired without MCI diagnosis, Ï2 = 14.89, HR = 2.465, p < 0.001, and impaired with MCI diagnosis, Ï2 = 55.78, HR = 1.916, p < 0.001.ConclusionOperationalizing NP decline over 12 months with a regression-based norming method allows for further stratification of dementia risk along the cognitively unimpaired-to-MCI spectrum. The use of NP decline as an adjunctive marker of risk beyond standard cognitive diagnostic practices may aid in prognosis and clinical decision-making
Cohomology of quantum groups: An analog of Kostant's Theorem
We prove the analog of Kostant's Theorem on Lie algebra cohomology in the
context of quantum groups. We prove that Kostant's cohomology formula holds for
quantum groups at a generic parameter , recovering an earlier result of
Malikov in the case where the underlying semisimple Lie algebra . We also show that Kostant's formula holds when is
specialized to an -th root of unity for odd (where is
the Coxeter number of ) when the highest weight of the
coefficient module lies in the lowest alcove. This can be regarded as an
extension of results of Friedlander-Parshall and Polo-Tilouine on the
cohomology of Lie algebras of reductive algebraic groups in prime
characteristic.Comment: 12 page
Understanding atom probe's analytical performance for iron oxides using correlation histograms and ab initio calculations
Field evaporation from ionic or covalently bonded materials often leads to
the emission of molecular ions. The metastability of these molecular ions,
particularly under the influence of the intense electrostatic field (1010
Vm-1), makes them prone to dissociation with or without an exchange of energy
amongst them. These processes can affect the analytical performance of atom
probe tomography (APT). For instance, neutral species formed through
dissociation may not be detected at all or with a time of flight no longer
related to their mass, causing their loss from the analysis. Here, we evaluated
the changes in the measured composition of FeO, Fe2O3 and Fe3O4 across a wide
range of analysis conditions. Possible dissociation reactions are predicted by
density-functional theory (DFT) calculations considering the spin states of the
molecules. The energetically favoured reactions are traced on to the multi-hit
ion correlation histograms, to confirm their existence within experiments,
using an automated Python-based routine. The detected reactions are carefully
analysed to reflect upon the influence of these neutrals from dissociation
reactions on the performance of APT for analysing iron oxides
Asymptomatic stenosis in the cervical and thoracic spines of patients with symptomatic lumbar stenosis
Study DesignâRetrospective study. ObjectiveâStudies on age-related degenerative changes causing concurrent stenoses in the cervical, thoracic, and lumbar spines (triple stenosis) are rare in the literature. Our objectives were to determine: (1) the incidence of asymptomatic radiologic cervical and thoracic stenosis in elderly patients with symptomatic lumbar stenosis, (2) the incidence of concurrent radiologic spinal stenosis in the cervical and thoracic spines, and (3) the radiologic features of cervical stenosis that might predict concurrent thoracic stenosis. MethodsâWhole-spine T2 sagittal magnetic resonance images of patients older than 80 and diagnosed with lumbar spinal stenosis between January 2003 and January 2012 were evaluated retrospectively. We included patients with asymptomatic spondylotic cervical and thoracic stenosis. We measured the anteroposterior diameters of the vertebral body, bony spinal canal, and spinal cord, along with the Pavlov ratio and anterior or posterior epidural stenosis at the level of the disk for each cervical and thoracic level. We compared the radiologic parameters between the subgroups of cervical stenosis with and without thoracic stenosis. ResultsâAmong the 460 patients with lumbar stenosis, 110 (23.9%) had concurrent radiologic cervical stenosis and 112 (24.3%) had concurrent radiologic thoracic stenosis. Fifty-six patients (12.1%) had combined radiologic cervical and thoracic stenosis in addition to their symptomatic lumbar stenosis (triple stenosis). Anterior epidural stenosis at C7âT1 was associated with a high prevalence of thoracic stenosis. ConclusionsâIt appears that asymptomatic radiologic cervical and thoracic stenosis is common in elderly patients with symptomatic lumbar stenosis
A millimeter-wave kinetic inductance detector camera for long-range imaging through optical obscurants
Millimeter-wave imaging provides a promising option for long-range target detection through optical obscurants such as fog, which often occur in marine environments. Given this motivation, we are currently developing a 150 GHz polarization-sensitive imager using a relatively new type of superconducting pair-breaking detector, the kinetic inductance detector (KID). This imager will be paired with a 1.5 m telescope to obtain an angular resolution of 0.09° over a 3.5° field of view using 3,840 KIDs. We have fully characterized a prototype KID array, which shows excellent performance with noise strongly limited by the irreducible fluctuations from the ambient temperature background. Full-scale KID arrays are now being fabricated and characterized for a planned demonstration in a maritime environment later this year
SuperMassive Black Holes in Bulges
We present spatially extended gas kinematics at parsec-scale resolution for
the nuclear regions of four nearby disk galaxies, and model them as rotation of
a gas disk in the joint potential of the stellar bulge and a putative central
black hole. The targets were selected from a larger set of long-slit spectra
obtained with the Hubble Space Telescope as part of the Survey of Nearby Nuclei
with STIS (SUNNS). They represents the 4 galaxies (of 24) that display
symmetric gas velocity curves consistent with a rotating disk. We derive the
stellar mass distribution from the STIS acquisition images adopting the stellar
mass-to-light ratio normalized so as to match ground-based velocity dispersion
measurements over a large aperture. Subsequently, we constrain the mass of a
putative black hole by matching the gas rotation curve, following two distinct
approaches. In the most general case we explore all the possible disk
orientations, alternatively we constrain the gas disk orientation from the
dust-lane morphology at similar radii. In the latter case the kinematic data
indicate the presence of a central black hole for three of the four objects,
with masses of 10^7 - 10^8 solar masses, representing up to 0.025 % of the host
bulge mass. For one object (NGC2787) the kinematic data alone provide clear
evidence for the presence of a central black hole even without external
constraints on the disk orientation. These results illustrate directly the need
to determine black-hole masses by differing methods for a large number of
objects, demonstrate that the variance in black hole/bulge mass is much larger
than previously claimed, and reinforce the recent finding that the black-hole
mass is tightly correlated with the bulge stellar velocity dispersion.Comment: 26 pages, 11 Postscript figures, accepted for publication on Ap
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