428 research outputs found
Delayed presentation of traumatic aortocaval fistula: A report of two cases and a review of the associated compensatory hemodynamic and structural changes
Chronic aortocaval fistula (ACF) is a rare complication of gunshot wounds to the abdomen. Herein we report two cases of traumatic ACF: one asymptomatic and the other presenting with congestive heart failure (CHF) 20 and 30 years, respectively, after their initial injury. The recent onset of CHF, the presence of a continuous abdominal bruit, and, in the second patient, a history of penetrating trauma suggested the diagnosis of ACF. The diagnosis was confirmed by computed tomography scanning in both patients. Surgical repair of the ACF in the symptomatic patient resulted in resolution of the CHF and reversed the dilatation of the aorta and inferior vena cava. The asymptomatic patient was lost to follow-up. CHF in a young male patient with a history of penetrating abdominal trauma should alert the surgeon to this rare complication
First-Order Definability of Trees and Sparse Random Graphs
This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Let D(G) be the smallest quantifier depth of a first-order formula which is true for a graph G but false for any other non-isomorphic graph. This can be viewed as a measure for the descriptive complexity of G in first-order logic.
We show that almost surely , where G is a random tree of order n or the giant component of a random graph with constant c<1. These results rely on computing the maximum of D(T) for a tree T of order n and maximum degree l, so we study this problem as well.Peer Reviewe
Simulated Responses of the West African Monsoon and Zonal-Mean Tropical Precipitation to Early Holocene Orbital Forcing
This study seeks to improve our mechanistic understanding of how the insolation changes associated with orbital forcing impact the West African monsoon and zonal‐mean tropical precipitation. We impose early Holocene orbital parameters in simulations with the Geophysical Fluid Dynamics Laboratory AM2.1 atmospheric general circulation model, either with fixed sea surface temperatures, a 50‐m thermodynamic slab ocean, or coupled to a dynamic ocean (CM2.1). In all cases, West African Monsoon rainfall expands northward, but the summer zonal‐mean Intertropical Convergence Zone does not—there is drying near 10°N, and in the slab ocean experiment a southward shift of rainfall. This contradicts expectations from the conventional energetic framework for the Intertropical Convergence Zone location, given anomalous southward energy fluxes in the deep tropics. These anomalous energy fluxes are not accomplished by a stronger Hadley circulation; instead, they arise from an increase in total gross moist stability in the northern tropics
Simulated Responses of the West African Monsoon and Zonal-Mean Tropical Precipitation to Early Holocene Orbital Forcing
This study seeks to improve our mechanistic understanding of how the insolation changes associated with orbital forcing impact the West African monsoon and zonal‐mean tropical precipitation. We impose early Holocene orbital parameters in simulations with the Geophysical Fluid Dynamics Laboratory AM2.1 atmospheric general circulation model, either with fixed sea surface temperatures, a 50‐m thermodynamic slab ocean, or coupled to a dynamic ocean (CM2.1). In all cases, West African Monsoon rainfall expands northward, but the summer zonal‐mean Intertropical Convergence Zone does not—there is drying near 10°N, and in the slab ocean experiment a southward shift of rainfall. This contradicts expectations from the conventional energetic framework for the Intertropical Convergence Zone location, given anomalous southward energy fluxes in the deep tropics. These anomalous energy fluxes are not accomplished by a stronger Hadley circulation; instead, they arise from an increase in total gross moist stability in the northern tropics
Saturn in hot water: viscous evolution of the Enceladus torus
The detection of outgassing water vapor from Enceladus is one of the great
breakthroughs of the Cassini mission. The fate of this water once ionized has
been widely studied; here we investigate the effects of purely neutral-neutral
interactions within the Enceladus torus. We find that, thanks in part to the
polar nature of the water molecule, a cold (~180 K) neutral torus would undergo
rapid viscous heating and spread to the extent of the observed hydroxyl cloud,
before plasma effects become important. We investigate the physics behind the
spreading of the torus, paying particular attention to the competition between
heating and rotational line cooling. A steady-state torus model is constructed,
and it is demonstrated that the torus will be observable in the millimeter band
with the upcoming Herschel satellite. The relative strength of rotational lines
could be used to distinguish between physical models for the neutral cloud.Comment: submitted to Icarus updated: references fixe
Diversity of gut microflora is required for the generation of B cell with regulatory properties in a skin graft model
B cells have been reported to promote graft rejection through alloantibody production. However, there is growing evidence that B cells can contribute to the maintenance of tolerance. Here, we used a mouse model of MHC-class I mismatched skin transplantation to investigate the contribution of B cells to graft survival. We demonstrate that adoptive transfer of B cells prolongs skin graft survival but only when the B cells were isolated from mice housed in low sterility "conventional" (CV) facilities and not from mice housed in pathogen free facilities (SPF). However, prolongation of skin graft survival was lost when B cells were isolated from IL-10 deficient mice housed in CV facilities. The suppressive function of B cells isolated from mice housed in CV facilities correlated with an anti-inflammatory environment and with the presence of a different gut microflora compared to mice maintained in SPF facilities. Treatment of mice in the CV facility with antibiotics abrogated the regulatory capacity of B cells. Finally, we identified transitional B cells isolated from CV facilities as possessing the regulatory function. These findings demonstrate that B cells, and in particular transitional B cells, can promote prolongation of graft survival, a function dependent on licensing by gut microflora
Cassini UVIS Observations of the Io Plasma Torus. IV. Modeling Temporal and Azimuthal Variability
In this fourth paper in a series, we present a model of the remarkable
temporal and azimuthal variability of the Io plasma torus observed during the
Cassini encounter with Jupiter. Over a period of three months, the Cassini
Ultraviolet Imaging Spectrograph (UVIS) observed a dramatic variation in the
average torus composition. Superimposed on this long-term variation, is a
10.07-hour periodicity caused by an azimuthal variation in plasma composition
subcorotating relative to System III longitude. Quite surprisingly, the
amplitude of the azimuthal variation appears to be modulated at the beat
frequency between the System III period and the observed 10.07-hour period.
Previously, we have successfully modeled the months-long compositional change
by supposing a factor of three increase in the amount of material supplied to
Io's extended neutral clouds. Here, we extend our torus chemistry model to
include an azimuthal dimension. We postulate the existence of two azimuthal
variations in the number of super-thermal electrons in the torus: a primary
variation that subcorotates with a period of 10.07 hours and a secondary
variation that remains fixed in System III longitude. Using these two hot
electron variations, our model can reproduce the observed temporal and
azimuthal variations observed by Cassini UVIS.Comment: Revised 24 August 2007 Accepted by Icarus, 50 pages, 2 Tables, 8
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Development of a wireless displacement measurement system using acceleration responses
Displacement measurements are useful information for various engineering applications such as structural health monitoring (SHM), earthquake engineering and system identification. Most existing displacement measurement methods are costly, labor-intensive, and have difficulties particularly when applying to full-scale civil structures because the methods require stationary reference points. Indirect estimation methods converting acceleration to displacement can be a good alternative as acceleration transducers are generally cost-effective, easy to install, and have low noise. However, the application of acceleration-based methods to full-scale civil structures such as long span bridges is challenging due to the need to install cables to connect the sensors to a base station. This article proposes a low-cost wireless displacement measurement system using acceleration. Developed with smart sensors that are low-cost, wireless, and capable of on-board computation, the wireless displacement measurement system has significant potential to impact many applications that need displacement information at multiple locations of a structure. The system implements an FIR-filter type displacement estimation algorithm that can remove low frequency drifts typically caused by numerical integration of discrete acceleration signals. To verify the accuracy and feasibility of the proposed system, laboratory tests are carried out using a shaking table and on a three storey shear building model, experimentally confirming the effectiveness of the proposed system.open3
Audible Image Description as an Accommodation in Statewide Assessments for Students with Visual and Print Disabilities.
Introduction:Although image description has been identified as an accommodation for presentations conducted in the classroom, only a few U.S. states have approved it for use in high-stakes assessments. This study examined the use of audible image description as an assessment accommodation for students with visual and print disabilities by investigating student comprehension under multiple conditions. Methods: Students in three western states in grades three through eight who had visual (n= 117) or print (n= 178) disabilities participated in an abbreviated test constructed of retired assessment questions in English language arts, mathematics, and science, that were aligned with each state's instructional standards, under conditions with and without standardized description of graphic images. The study used a within-subjects block design to collect and compare comprehension data under conditions where audible image description was both used and not used in an abbreviated test. Results: Results indicated that students who read braille were more likely to
respond correctly under the audible image description condition, and students
with visual and print disabilities who used print were equally likely to respond
correctly regardless of condition. Discussion: Braille readers were more likely to
obtain a correct answer when audible image description accompanied the question.
Audible image description did not affect the likelihood of a correct response
from students with print disabilities or students with visual disabilities who read
print. Implications for practitioners: Audible image description is an accommodation
that may help braille readers perform better on tests. Although the
Partnership for Assessment of Readiness for College and Careers (PARCC) and
Smarter Balanced consortia are taking steps to include image (or picture) descriptions
in their assessment accommodations, teachers may want to develop a standard method for describing images and familiarize their braille readers to the strategy by
including it in instruction and in classroom tests. Readers are referred to the National
Center on Accessible Media’s online guidelines for image description
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