900 research outputs found
Live–virtual–constructive simulation for testing and evaluation of air combat tactics, techniques, and procedures, Part 1: assessment framework
Harvest Demographics of Temperate-breeding Canada Geese in South Dakota, 1967–1995
In South Dakota, breeding giant Canada geese (Branta canadensis maxima) have increased substantially, and harvest management strategies have been implemented to maximize hunting opportunity (e.g., special early-September seasons) on local, as well as molt-migrant giant Canada geese (B. c. interior) while still protecting lesser abundant Arcticbreeding Canada geese and cackling geese (e.g., B. hutchinsii, B. minima). Information on important parameters, such as survival and recovery rates, are generally lacking for giant Canada geese in the northern Great Plains. Patterns in Canada goose band recoveries can provide insight into the distribution, chronology, and harvest pressures to which a given goose population segment is exposed. We studied spatial and temporal recovery patterns of molting Canada geese during annual banding efforts in South Dakota between 1967 and 1995. Recovery rates (% ± SE) for Canada geese increased over time in both western South Dakota (0.034 ± 0.005 [1967 to 1976], 0.056 ± 0.009 [1977 to 1986]) and eastern (0.026 ± 0.002 [1967 to 1978], 0.058 ± 0.003 [1987 to 1995]) South Dakota. Although recovery rates for Canada geese west of the Missouri River (WR) and east of the Missouri River (ER) were relatively similar, recovery distribution and harvest chronology indicate spatial and temporal differences for geese banded in these 2 geographic regions. Overall, Canada geese banded in South Dakota were recovered in 23 states and 5 Canadian provinces, and recovery distribution varied relative to banding region. Distribution of recoveries suggests a south-southwesterly movement for WR-banded geese compared to a south-southeasterly movement for ERbanded geese. For WR-banded geese, 40 to 52% and 30 to 34% of direct and indirect recoveries, respectively, occurred in December. In contrast, for ER-banded geese, 19 to 38% and 15 to 19% of direct and indirect recoveries, respectively, occurred in December. Waterfowl managers need to consider that recovery rates and harvest chronology of banded giant Canada geese may vary geographically within a state or province. Refinement of harvest management strategies at multiple spatial scales may be required
Transition from ion-coupled to electron-only reconnection: Basic physics and implications for plasma turbulence
Using kinetic particle-in-cell (PIC) simulations, we simulate reconnection
conditions appropriate for the magnetosheath and solar wind, i.e., plasma beta
(ratio of gas pressure to magnetic pressure) greater than 1 and low magnetic
shear (strong guide field). Changing the simulation domain size, we find that
the ion response varies greatly. For reconnecting regions with scales
comparable to the ion Larmor radius, the ions do not respond to the
reconnection dynamics leading to ''electron-only'' reconnection with very large
quasi-steady reconnection rates. The transition to more traditional
''ion-coupled'' reconnection is gradual as the reconnection domain size
increases, with the ions becoming frozen-in in the exhaust when the magnetic
island width in the normal direction reaches many ion inertial lengths. During
this transition, the quasi-steady reconnection rate decreases until the ions
are fully coupled, ultimately reaching an asymptotic value. The scaling of the
ion outflow velocity with exhaust width during this electron-only to
ion-coupled transition is found to be consistent with a theoretical model of a
newly reconnected field line. In order to have a fully frozen-in ion exhaust
with ion flows comparable to the reconnection Alfv\'en speed, an exhaust width
of at least several ion inertial lengths is needed. In turbulent systems with
reconnection occurring between magnetic bubbles associated with fluctuations,
using geometric arguments we estimate that fully ion-coupled reconnection
requires magnetic bubble length scales of at least several tens of ion inertial
lengths
Simulating open quantum systems: from many-body interactions to stabilizer pumping
In a recent experiment, Barreiro et al. demonstrated the fundamental building
blocks of an open-system quantum simulator with trapped ions [Nature 470, 486
(2011)]. Using up to five ions, single- and multi-qubit entangling gate
operations were combined with optical pumping in stroboscopic sequences. This
enabled the implementation of both coherent many-body dynamics as well as
dissipative processes by controlling the coupling of the system to an
artificial, suitably tailored environment. This engineering was illustrated by
the dissipative preparation of entangled two- and four-qubit states, the
simulation of coherent four-body spin interactions and the quantum
non-demolition measurement of a multi-qubit stabilizer operator. In the present
paper, we present the theoretical framework of this gate-based ("digital")
simulation approach for open-system dynamics with trapped ions. In addition, we
discuss how within this simulation approach minimal instances of spin models of
interest in the context of topological quantum computing and condensed matter
physics can be realized in state-of-the-art linear ion-trap quantum computing
architectures. We outline concrete simulation schemes for Kitaev's toric code
Hamiltonian and a recently suggested color code model. The presented simulation
protocols can be adapted to scalable and two-dimensional ion-trap
architectures, which are currently under development.Comment: 27 pages, 9 figures, submitted to NJP Focus on Topological Quantum
Computatio
Asymptomatic anterior shoulder dislocation of 24-year duration
A 73-year-old woman presented with a very long-standing anterior dislocation of her right shoulder. She had no pain, mild impairment of active shoulder motion and clinical features suggesting no tear of the rotator cuff. CT 3D reconstructions showed a newly formed glenoid cavity below the coracoid process. This case indicates that an anterior shoulder dislocation lasting even decades may be compatible with an almost normal shoulder function
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Schizophrenia-risk variant rs6994992 in the neuregulin-1 gene on brain developmental trajectories in typically developing children
The neuregulin-1 (NRG1) gene is one of the best-validated risk genes for schizophrenia, and psychotic and bipolar disorders. The rs6994992 variant in the NRG1 promoter (SNP8NRG243177) is associated with altered frontal and temporal brain macrostructures and/or altered white matter density and integrity in schizophrenic adults, as well as healthy adults and neonates. However, the ages when these changes begin and whether neuroimaging phenotypes are associated with cognitive performance are not fully understood. Therefore, we investigated the association of the rs6994992 variant on developmental trajectories of brain macro- and microstructures, and their relationship with cognitive performance. A total of 972 healthy children aged 3–20 years had the genotype available for the NRG1-rs6994992 variant, and were evaluated with magnetic resonance imaging (MRI) and neuropsychological tests. Age-by-NRG1-rs6994992 interactions and genotype effects were assessed using a general additive model regression methodology, covaried for scanner type, socioeconomic status, sex and genetic ancestry factors. Compared with the C-carriers, children with the TT-risk-alleles had subtle microscopic and macroscopic changes in brain development that emerge or reverse during adolescence, a period when many psychiatric disorders are manifested. TT-children at late adolescence showed a lower age-dependent forniceal volume and lower fractional anisotropy; however, both measures were associated with better episodic memory performance. To our knowledge, we provide the first multimodal imaging evidence that genetic variation in NRG1 is associated with age-related changes on brain development during typical childhood and adolescence, and delineated the altered patterns of development in multiple brain regions in children with the T-risk allele(s)
3D Magnetic Reconnection with a spatially confined X-line extent -- Implications for Dipolarizing Flux Bundles and the Dawn-Dusk Asymmetry
Using 3D particle-in-cell (PIC) simulations, we study magnetic reconnection
with the x-line being spatially confined in the current direction. We include
thick current layers to prevent reconnection at two ends of a thin current
sheet that has a thickness on an ion inertial (di) scale. The reconnection rate
and outflow speed drop significantly when the extent of the thin current sheet
in the current direction is < O(10 di). When the thin current sheet extent is
long enough, we find it consists of two distinct regions; an inactive region
(on the ion-drifting side) exists adjacent to the active region where
reconnection proceeds normally as in a 2D case. The extent of this inactive
region is ~ O(10 di), and it suppresses reconnection when the thin current
sheet extent is comparable or shorter. The time-scale of current sheet thinning
toward fast reconnection can be translated into the spatial-scale of this
inactive region; because electron drifts inside the ion diffusion region
transport the reconnected magnetic flux, that drives outflows and furthers the
current sheet thinning, away from this region. This is a consequence of the
Hall effect in 3D. While this inactive region may explain the shortest possible
azimuthal extent of dipolarizing flux bundles at Earth, it may also explain the
dawn-dusk asymmetry observed at the magnetotail of Mercury, that has a global
dawn-dusk extent much shorter than that of Earth.Comment: 9 pages, 9 figures, submitted to JGR on 01/23/201
Magnetospheric Multiscale observations of magnetic reconnection associated with Kelvin-Helmholtz waves
The four Magnetospheric Multiscale (MMS) spacecraft recorded the first direct evidence of reconnection exhausts associated with Kelvin-Helmholtz (KH) waves at the duskside magnetopause on 8 September 2015 which allows for local mass and energy transport across the flank magnetopause. Pressure anisotropy-weighted Walén analyses confirmed in-plane exhausts across 22 of 42 KH-related trailing magnetopause current sheets (CSs). Twenty-one jets were observed by all spacecraft, with small variations in ion velocity, along the same sunward or antisunward direction with nearly equal probability. One exhaust was only observed by the MMS-1,2 pair, while MMS-3,4 traversed a narrow CS (1.5 ion inertial length) in the vicinity of an electron diffusion region. The exhausts were locally 2-D planar in nature as MMS-1,2 observed almost identical signatures separated along the guide-field. Asymmetric magnetic and electric Hall fields are reported in agreement with a strong guide-field and a weak plasma density asymmetry across the magnetopause CS
Fiducial marker placement with electromagnetic navigation bronchoscopy: a subgroup analysis of the prospective, multicenter NAVIGATE study
Fiducial markers (FMs) help direct stereotactic body radiation therapy (SBRT) and localization for surgical resection in lung cancer management. We report the safety, accuracy, and practice patterns of FM placement utilizing electromagnetic navigation bronchoscopy (ENB).
Methods:
NAVIGATE is a global, prospective, multicenter, observational cohort study of ENB using the superDimension™ navigation system. This prospectively collected subgroup analysis presents the patient demographics, procedural characteristics, and 1-month outcomes in patients undergoing ENB-guided FM placement. Follow up through 24 months is ongoing.
Results:
Two-hundred fifty-eight patients from 21 centers in the United States were included. General anesthesia was used in 68.2%. Lesion location was confirmed by radial endobronchial ultrasound in 34.5% of procedures. The median ENB procedure time was 31.0 min. Concurrent lung lesion biopsy was conducted in 82.6% (213/258) of patients. A mean of 2.2 ± 1.7 FMs (median 1.0 FMs) were placed per patient and 99.2% were accurately positioned based on subjective operator assessment. Follow-up imaging showed that 94.1% (239/254) of markers remained in place. The procedure-related pneumothorax rate was 5.4% (14/258) overall and 3.1% (8/258) grade ⩾ 2 based on the Common Terminology Criteria for Adverse Events scale. The procedure-related grade ⩾ 4 respiratory failure rate was 1.6% (4/258). There were no bronchopulmonary hemorrhages.
Conclusion:
ENB is an accurate and versatile tool to place FMs for SBRT and localization for surgical resection with low complication rates. The ability to perform a biopsy safely in the same procedure can also increase efficiency. The impact of practice pattern variations on therapeutic effectiveness requires further study
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