709 research outputs found
Atmospheric Propagation
Reviewed here is the current state of knowledge with respect to each basic mechanism of sound propagation in the atmosphere and how each mechanism changes the spectral or temporal characteristics of the sound received at a distance from the source. Some of the basic processes affecting sound wave propagation which are present in any situation are discussed. They are geometrical spreading, molecular absorption, and turbulent scattering. In geometrical spreading, sound levels decrease with increasing distance from the source; there is no frequency dependence. In molecular absorption, sound energy is converted into heat as the sound wave propagates through the air; there is a strong dependence on frequency. In turbulent scattering, local variations in wind velocity and temperature induce fluctuations in phase and amplitude of the sound waves as they propagate through an inhomogeneous medium; there is a moderate dependence on frequency
Identification of plasmids in a Salmonella Typhimurium septicemic isolate without the classical 95 kb virulence plasmid
In this study, we report the characterization of plasmids from a Salmonella Typhimurium strain isolated from a septicemic pig. This isolate did not possess the classical 95 kb plasmid associated with virulence, but contained several low molecular weight plasmids
Transcutaneous measurement of volume blood flow
Blood flow velocity measurements, using Doppler velocimeter, are described. The ability to measure blood velocity using ultrasound is derived from the Doppler effect; the change in frequency which occurs when sound is reflected or transmitted from a moving target. When ultrasound of the appropriate frequency is transmitted through a moving blood stream, the blood cells act as point scatterers of ultrasonic energy. If this scattered ultrasonic energy is detected, it is found to be shifted in frequency according to the velocity of the blood cells, nu, the frequency of the incident sound, f sub o, the speed of sound in the medium, c, and the angle between the sound beam and the velocity vector, o. The relation describing this effect is known as the Doppler equation. Delta f = 2 f sub o x nu x cos alpha/c. The theoretical and experimental methods are evaluated
Quantifying Resonant Structure in NGC 6946 from Two-dimensional Kinematics
We study the two-dimensional kinematics of the H-alpha-emitting gas in the
nearby barred Scd galaxy, NGC 6946, in order to determine the pattern speed of
the primary m=2 perturbation mode. The pattern speed is a crucial parameter for
constraining the internal dynamics, estimating the impact velocities of the
gravitational perturbation at the resonance radii, and to set up an
evolutionary scenario for NGC 6946. Our data allows us to derive the best
fitting kinematic position angle and the geometry of the underlying gaseous
disk, which we use to derive the pattern speed using the Tremaine-Weinberg
method. We find a main pattern speed Omega_p=22 km/s/kpc, but our data clearly
reveal the presence of an additional pattern speed Omega_p=47 km/s/kpc in a
zone within 1.25 kpc of the nucleus. Using the epicyclic approximation, we
deduce the location of the resonance radii and confirm that inside the outer
Inner Lindblad Resonance radius of the main oval, a primary bar has formed
rotating at more than twice the outer pattern speed. We further confirm that a
nuclear bar has formed inside the Inner Lindblad Resonance radius of the
primary bar, coinciding with the inner Inner Lindblad Resonance radius of the
large-scale m=2 mode oval.Comment: Accepted for publication in ApJ Letter
Identification of putative virulence attributes using suppression subtractive hybridization using Salmonella Typhimurium isolates from septicemic and healthy pigs
In this study, we used the suppression subtractive hybridization (SSH) method to identify DNA restriction fragments present in a Salmonella Typhimurium isolate from septicemic pig but absent in a S. Typhimurium isolate recovered from a healthy animal at slaughter. Thirteen different clone inserts were identified and 5 clones had similarities with sequences with predicted functions. Two fragments showed similarities with genes found on plasmids. The putative functions are those of a DNA restriction subunit of a type III restriction and modification system for one clone and a replication protein for the other one. Three fragments showed similarities with genes found on the chromosome. The putative genes are pgtA, stbD and emrB. Seven fragments have unknown function. One plasmid of the septicemic isolate used in the SSH was characterized as it was present in another septicemic isolate that lacked the classical virulence plasmid. It contained several genes of unknown function that will need further investigation to assess their putative role in virulence
Experience of primary care among homeless individuals with mental health conditions
The delivery of primary care to homeless individuals with mental health conditions presents unique challenges. To inform healthcare improvement, we studied predictors of favorable primary care experience among homeless persons with mental health conditions treated at sites that varied in degree of homeless-specific service tailoring. This was a multi-site, survey-based comparison of primary care experiences at three mainstream primary care clinics of the Veterans Administration (VA), one homeless-tailored VA clinic, and one tailored non-VA healthcare program. Persons who accessed primary care service two or more times from July 2008 through June 2010 (N = 366) were randomly sampled. Predictor variables included patient and organization characteristics suggested by the patient perception model developed by Sofaer and Firminger (2005), with an emphasis on mental health. The primary care experience was assessed with the Primary Care Quality-Homeless (PCQ-H) questionnaire, a validated survey instrument. Multiple regression identified predictors of positive experiences (i.e. higher PCQ-H total score). Significant predictors of a positive experience included a site offering tailored service design, perceived choice among providers, and currently domiciled status. There was an interaction effect between site and severe psychiatric symptoms. For persons with severe psychiatric symptoms, a homeless-tailored service design was significantly associated with a more favorable primary care experience. For persons without severe psychiatric symptoms, this difference was not significant. This study supports the importance of tailored healthcare delivery designed for homeless persons' needs, with such services potentially holding special relevance for persons with mental health conditions. To improve patient experience among the homeless, organizations may want to deliver services that are tailored to homelessness and offer a choice of providers
Innovative approach for transcriptomic analysis of obligate intracellular pathogen: selective capture of transcribed sequences of Ehrlichia ruminantium
<p>Abstract</p> <p>Background</p> <p>Whole genome transcriptomic analysis is a powerful approach to elucidate the molecular mechanisms controlling the pathogenesis of obligate intracellular bacteria. However, the major hurdle resides in the low quantity of prokaryotic mRNAs extracted from host cells. Our model <it>Ehrlichia ruminantium (ER</it>), the causative agent of heartwater, is transmitted by tick <it>Amblyomma variegatum</it>. This bacterium affects wild and domestic ruminants and is present in Sub-Saharan Africa and the Caribbean islands. Because of its strictly intracellular location, which constitutes a limitation for its extensive study, the molecular mechanisms involved in its pathogenicity are still poorly understood.</p> <p>Results</p> <p>We successfully adapted the SCOTS method (Selective Capture of Transcribed Sequences) on the model Rickettsiales <it>ER </it>to capture mRNAs. Southern Blots and RT-PCR revealed an enrichment of <it>ER</it>'s cDNAs and a diminution of ribosomal contaminants after three rounds of capture. qRT-PCR and whole-genome <it>ER </it>microarrays hybridizations demonstrated that SCOTS method introduced only a limited bias on gene expression. Indeed, we confirmed the differential gene expression between poorly and highly expressed genes before and after SCOTS captures. The comparative gene expression obtained from <it>ER </it>microarrays data, on samples before and after SCOTS at 96 hpi was significantly correlated (R<sup>2 </sup>= 0.7). Moreover, SCOTS method is crucial for microarrays analysis of <it>ER</it>, especially for early time points post-infection. There was low detection of transcripts for untreated samples whereas 24% and 70.7% were revealed for SCOTS samples at 24 and 96 hpi respectively.</p> <p>Conclusions</p> <p>We conclude that this SCOTS method has a key importance for the transcriptomic analysis of <it>ER </it>and can be potentially used for other Rickettsiales. This study constitutes the first step for further gene expression analyses that will lead to a better understanding of both <it>ER </it>pathogenicity and the adaptation of obligate intracellular bacteria to their environment.</p
Validation of Model-Based Prognostics for Pneumatic Valves in a Cryogenic Fueling Demonstration Testbed
Because valves control many critical operations, they are prime candidates for deployment of prognostic algorithms. But, similar to the situation with most other components, examples of failures experienced in the field are hard to come by. This lack of data impacts the ability to test and validate prognostic algorithms. A solution sometimes employed to overcome this shortcoming is to perform run to failure experiments in a lab. However, the mean time to failure of valves is typically very high (possibly lasting decades), preventing evaluation within a reasonable time frame. Therefore, a mechanism to observe development of fault signatures considerably faster is sought. Described here is a testbed that addresses these issues by allowing the physical injection of leakage faults (which are the most common fault mode) into pneumatic valves. What makes this testbed stand out is the ability to modulate the magnitude of the fault almost arbitrarily fast. With that, the performance of end-of-life estimation algorithms can be tested. Further, the testbed is mobile and can be connected to valves in the field. This mobility helps to bring the overall process of prognostic algorithm development for this valve a step closer to validation. The paper illustrates the development of a model-based prognostic approach that uses data from the testbed for partial validation
Novel Insights Regarding the Operational Characteristics and Teleological Purpose of the Renal Na+-K+-Cl2 Cotransporter (NKCC2s) Splice Variants
The absorptive Na+-K+-Cl− cotransporter (NKCC2) is a polytopic protein that forms homooligomeric complexes in the apical membrane of the thick ascending loop of Henle (TAL). It occurs in at least four splice variants (called B, A, F, and AF) that are identical to one another except for a short region in the membrane-associated domain. Although each of these variants exhibits unique functional properties and distributions along the TAL, their teleological purpose and structural organization remain poorly defined. In the current work, we provide additional insight in these regards by showing in mouse that the administration of either furosemide or an H2O-rich diet, which are predicted to alter NKCC2 expression in the TAL, exerts differential effects on mRNA levels for the variants, increasing those of A (furosemide) but decreasing those of F and AF (furosemide or H2O). Based on a yeast two-hybrid mapping analysis, we also show that the formation of homooligomeric complexes is mediated by two self-interacting domains in the COOH terminus (residues 671 to 816 and 910 to 1098), and that these complexes could probably include more than one type of variant. Taken together, the data reported here suggest that A, F, and AF each play unique roles that are adapted to specific physiological needs, and that the accomplishment of such roles is coordinated through the splicing machinery as well as complex NKCC2–NKCC2 interactions
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