Fertilization of Crops with Feedlot Wastes on the Texas High Plains.

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Overview of C/C-SiC Composite Development for the Orion Launch Abort System

Past and present efforts by the authors to further understanding of the ceramic matrix composite (CMC) material used in the valve components of the Orion Launch Abort System (LAS) Attitude Control Motor (ACM) will be presented. The LAS is designed to quickly lift the Orion Crew Exploration Vehicle (CEV) away from its launch vehicle in emergency abort scenarios. The ACM is a solid rocket motor which utilizes eight throttleable nozzles to maintain proper orientation of the CEV during abort operations. Launch abort systems have not been available for use by NASA on manned launches since the last Apollo ]Saturn launch in 1975. The CMC material, carbon-carbon/silicon-carbide (C/C-SiC), is manufactured by Fiber Materials, Inc. and consists of a rigid 4-directional carbon-fiber tow weave reinforced with a mixed carbon plus SiC matrix. Several valve and full system (8-valve) static motor tests have been conducted by the motor vendor. The culmination of these tests was the successful flight test of the Orion LAS Pad Abort One (PA ]1) vehicle on May 6, 2010. Due to the fast pace of the LAS development program, NASA Marshall Space Flight Center assisted the LAS community by performing a series of material and component evaluations using fired hardware from valve and full ]system development motor tests, and from the PA-1 flight ACM motor. Information will be presented on the structure of the C/C-SiC material, as well as the efficacy of various non ]destructive evaluation (NDE) techniques, including but not limited to: radiography, computed tomography, nanofocus computed tomography, and X-ray transmission microscopy. Examinations of the microstructure of the material via scanning electron microscopy and energy dispersive spectroscopy will also be discussed. The findings resulting from the subject effort are assisting the LAS Project in risk assessments and in possible modifications to the final ACM operational design

Hand ischemia associated with elbow trauma in children

ObjectivesPrevious observational studies suggest that children with hand ischemia following elbow trauma can be safely observed if Doppler signals are present in the wrist arteries (pink pulseless hand, PPH). Nonoperative management of PPH is predicated on the assumption that PPH results from local arterial spasm, but the mechanism of arterial compromise has not been investigated. We hypothesized that PPH signifies a brachial artery injury that requires surgical repair.MethodsRetrospective review of operations performed on children with hand ischemia following elbow trauma at a level I trauma center pediatric hospital.ResultsBetween 2003 and 2010, 12 children (seven males, mean age 7.4 years) underwent brachial artery exploration for hand ischemia following elbow trauma (11 supracondylar fractures, one elbow dislocation) due to falls (n = 10) or motor vehicle crashes (n = 2). At presentation, three subjects had normal radial pulses, eight subjects had Doppler signals but no palpable pulses, and one had weak Doppler flow with advanced hand ischemia. Six of the nine subjects without palpable pulses also had neurosensory changes. All 12 subjects underwent brachial artery exploration either initially (n = 2) or following orthopedic fixation (n = 10) due to persistent pulselessness. At operation, eight of 12 patients (67%) had focal brachial artery thrombosis due to intimal flaps, and four had brachial artery and median nerve entrapment within the pinned fracture site. At discharge, all 12 subjects had palpable radial pulses, but three with entrapment had dense median nerve deficits. One of the three subjects with dense neurologic deficit had complete recovery of neurologic function at ten months. The other two subjects had residual median nerve deficits with partial recovery at 5 and 6 months follow-up, respectively. No patient developed Volkman's contracture.ConclusionsBrachial artery injuries should be anticipated in children with hand ischemia associated with elbow trauma. Neurovascular entrapment at the fracture site is a possible complication of orthopedic fixation. Absence of palpable wrist pulses after orthopedic fixation should prompt immediate brachial artery exploration. PPH should not be considered a consequence of arterial spasm in these patients

Accuracy and utility of three-dimensional contrast-enhanced magnetic resonance angiography in planning carotid stenting

BackgroundContrast-enhanced magnetic resonance angiography (CE-MRA) is a proven diagnostic tool for the evaluation of carotid stenosis; however, its utility in planning carotid artery stenting (CAS) has not been addressed. This study assessed the accuracy of three-dimensional CE-MRA as a noninvasive screening tool, compared with digital subtraction angiography (DSA), for evaluating carotid and arch morphology before CAS.MethodsIn a series of 96 CAS procedures during a 2-year period, CE-MRAs and DSAs with complete visualization from the aortic arch to the intracranial circulation were obtained before CAS in 60 patients. Four additional patients, initially considered potential candidates for CAS, were also evaluated with CE-MRA and DSA. The two-by-two table method, receiver operating characteristic curve, and Bland-Altman analyses were used to characterize the ability of CE-MRA to discriminate carotid and arch anatomy, suitability for CAS, and degree of carotid stenosis.ResultsThe sensitivity and specificity of CE-MRA were, respectively, 100% and 100% to determine CAS suitability, 87% and 100% to define aortic arch type, 93% and 100% to determine severe carotid tortuosity, and 75% and 98% to detect ulcerated plaques. CE-MRA had 87% sensitivity and 100% specificity for the detection of carotid stenosis ≥80%. The accuracy of CE MRA to determine optimal imaging angles and stent and embolic protection device sizes was >90%. The operative technique for CAS was altered because of the findings of preoperative CE-MRA in 22 procedures (38%). The most frequent change in the operative plan was the use of the telescoping technique in 11 cases (18%). CAS was aborted in four patients (5%) due to unfavorable anatomy identified on CE-MRA, including prohibitive internal carotid artery tortuosity (n = 1), long string sign of the internal carotid artery (n = 2), and concomitant intracranial disease (n = 1). Among patients considered suitable for CAS by CE-MRA, technical success was 100%, and the 30-day stroke/death rate was 1.6%.ConclusionsContrast-enhanced magnetic resonance angiography of the arch and carotid arteries is accurate in determining suitability for CAS and may alter the operative technique. Certain anatomic contraindications for CAS may be detected without DSA. Although CE-MRA is less accurate to estimate the degree of stenosis, it can accurately predict imaging angles, and stent and embolic protection device size, which may facilitate safe and expeditious CAS

Defining the type of surgeon volume that influences the outcomes for open abdominal aortic aneurysm repair

ObjectivePrior studies have reported improved clinical outcomes with higher surgeon volume, which is assumed to be a product of the surgeon's experience with the index operation. We hypothesized that composite surgeon volume is an important determinant of outcome. We tested this hypothesis by comparing the impact of operation-specific surgeon volume versus composite surgeon volume on surgical outcomes, using open abdominal aortic aneurysm (AAA) repair as the index operation.MethodsThe Nationwide Inpatient Sample was analyzed to identify patients undergoing open AAA repairs for 2000 to 2008. Surgeons were stratified into deciles based on annual volume of open AAA repairs (“operation-specific volume”) and overall volume of open vascular operations (“composite volume”). Composite volume was defined by the sum of several open vascular operations: carotid endarterectomy, aortobifemoral bypass, femoral-popliteal bypass, and femoral-tibial bypass. Multiple logistic regression analyses were used to examine the relationship between surgeon volume and in-hospital mortality for open AAA repair, adjusting for both patient and hospital characteristics.ResultsBetween 2000 and 2008, an estimated 111,533 (95% confidence interval [CI], 102,296-121,232) elective open AAA repairs were performed nationwide by 6,857 surgeons. The crude in-hospital mortality rate over the study period was 6.1% (95% CI, 5.6%-6.5%). The mean number of open AAA repairs performed annually was 2.4 operations per surgeon. The mean composite volume was 5.3 operations annually. As expected, in-hospital mortality for open AAA repair decreased with increasing volume of open AAA repairs performed by a surgeon. Mortality rates for the lowest and highest deciles of surgeon volume were 10.2% and 4.5%, respectively (P < .0001). A similar pattern was observed for composite surgeon volume, as the mortality rates for the lowest and highest deciles of composite volume were 9.8% and 4.8%, respectively (P < .0001). After adjusting for patient and hospital characteristics, increasing composite surgeon volume remained a significant predictor of lower in-hospital mortality for open AAA repair (odds ratio, 0.994; 95% CI, .992-.996; P < .0001), whereas increasing volume of AAA repairs per surgeon did not predict in-hospital deaths.ConclusionsThe current study suggests that composite surgeon volume—not operation-specific volume—is a key determinant of in-hospital mortality for open AAA repair. This finding needs to be considered for future credentialing of surgeons

Ethical and methodological issues in engaging young people living in poverty with participatory research methods

This paper discusses the methodological and ethical issues arising from a project that focused on conducting a qualitative study using participatory techniques with children and young people living in disadvantage. The main aim of the study was to explore the impact of poverty on children and young people's access to public and private services. The paper is based on the author's perspective of the first stage of the fieldwork from the project. It discusses the ethical implications of involving children and young people in the research process, in particular issues relating to access and recruitment, the role of young people's advisory groups, use of visual data and collection of data in young people's homes. The paper also identifies some strategies for addressing the difficulties encountered in relation to each of these aspects and it considers the benefits of adopting participatory methods when conducting research with children and young people

Fragment reattachment, reproductive status, and health indicators of the invasive colonial tunicate Didemnum vexillum with implications for dispersal

This manuscript is not subject to U.S. copyright. The definitive version was published in Biological Invasions 14 (2012): 2133-2140, doi:10.1007/s10530-012-0219-8.The invasive colonial tunicate Didemnum vexillum is now widespread in coastal and offshore waters of New England, USA. D. vexillum can inflict ecological and economic damage through biofouling and habitat modification. Natural and anthropogenic processes that fragment colonies of D. vexillum may be accelerating the spread of this invader. Reattachment success and fragment viability were confirmed in the laboratory after four weeks of suspension in experimental aquaria. The shape of suspended D. vexillum fragments progressed from flattened to globular spheres and then flattened again after reattachment to the substrate. Reproductive activity, confirmed by the presence of eggs and larvae, was observed for fragments suspended up to three weeks suggesting that D. vexillum is capable of reproducing while in a fragmented, suspended state. An index of colony health was used to monitor change in D. vexillum health while in suspension. Overall, colony health declined with time in suspension although colonies that appeared dead (black and gray in overall color) still contained a substantial number of healthy live zooids. These results suggest that activities that cause fragmentation can significantly facilitate the spread of D. vexillum. Coastal managers should consider reducing or eliminating, when practical, activities that return fragmented colonies of D. vexillum to the water. In-water cleaning of biofouling and dredging are likely expediting the spread of this invasive species unless biofouling can be contained and removed from the water.This research was funded by the NOAA Aquatic Invasive Species Program