Quantification of Pulmonary Arterial Wall Distensibility Using Parameters Extracted from Volumetric Micro-CT Images

Stiffening, or loss of distensibility, of arterial vessel walls is among the manifestations of a number of vascular diseases including pulmonary arterial hypertension. We are attempting to quantify the mechanical properties of vessel walls of the pulmonary arterial tree using parameters derived from high-resolution volumetric x-ray CT images of rat lungs. The pulmonary arterial trees of the excised lungs are filled with a contrast agent. The lungs are imaged with arterial pressures spanning the physiological range. Vessel segment diameters are measured from the inlet to the periphery, and distensibilities calculated from diameters as a function of pressure. The method shows promise as an adjunct to other morphometric techniques such as histology and corrosion casting. It possesses the advantages of being nondestructive, characterizing the vascular structures while the lungs are imaged rapidly and in a near-physiological state, and providing the ability to associate mechanical properties with vessel location in the intact tree hierarchy

SPECT Imaging of Pulmonary Blood Flow in a Rat

Small animal imaging is experiencing rapid development due to its importance in providing high-throughput phenotypic data for functional genomics studies. We have developed a single photon emission computed tomography (SPECT) system to image the pulmonary perfusion distribution in the rat. A standard gamma camera, equipped with a pinhole collimator, was used to acquire SPECT projection images at 40 sec/view of the rat thorax following injection of Tc99m labeled albumin that accumulated in the rat\u27s lungs. A voxel-driven, ordered-subset expectation maximization reconstruction was implemented. Following SPECT imaging, the rat was imaged using micro-CT with Feldkamp conebeam reconstruction. The two reconstructed image volumes were fused to provide a structure/function image of the rat thorax. Reconstruction accuracy and performance were evaluated using numerical simulations and actual imaging of an experimental phantom consisting of Tc99m filled chambers with known diameters and count rates. Full-width half-maximum diameter measurement errors decreased with increasing chamber diameter, ranging from \u3c 6% down to 0.1%. Errors in the ratio of count rate estimates between tubes were also diameter dependent but still relatively small. This preliminary study suggests that SPECT will be useful for imaging and quantifying the pulmonary blood flow distribution and the distribution of Tc99m labeled ligands in the lungs of small laboratory animals

Micro-CT Image-Derived Metrics Quantify Arterial Wall Distensibility Reduction in a Rat Model of Pulmonary Hypertension

We developed methods to quantify arterial structural and mechanical properties in excised rat lungs and applied them to investigate the distensibility decrease accompanying chronic hypoxia-induced pulmonary hypertension. Lungs of control and hypertensive (three weeks 11% O2) animals were excised and a contrast agent introduced before micro-CT imaging with a special purpose scanner. For each lung, four 3D image data sets were obtained, each at a different intra-arterial contrast agent pressure. Vessel segment diameters and lengths were measured at all levels in the arterial tree hierarchy, and these data used to generate features sensitive to distensibility changes. Results indicate that measurements obtained from 3D micro-CT images can be used to quantify vessel biomechanical properties in this rat model of pulmonary hypertension and that distensibility is reduced by exposure to chronic hypoxia. Mechanical properties can be assessed in a localized fashion and quantified in a spatially-resolved way or as a single parameter describing the tree as a whole. Micro-CT is a nondestructive way to rapidly assess structural and mechanical properties of arteries in small animal organs maintained in a physiological state. Quantitative features measured by this method may provide valuable insights into the mechanisms causing the elevated pressures in pulmonary hypertension of differing etiologies and should become increasingly valuable tools in the study of complex phenotypes in small-animal models of important diseases such as hypertension

A biogeochemical analysis of the Pocono till barrens and adjacent hardwood forest underlain by Wisconsinan and Illinoian till in northeastern Pennsylvania

We assessed soil and vegetation nutrient capital in the landscape mosaic of till barrens and hardwood forests on the Pocono Plateau in northeastern Pennsylvania. These shrublands, which contain an unusual abundance of rare species, occur primarily on Illinoian-aged glacial till, though some patches grow on Wisconsinan till. We hypothesized that barrens soil and vegetation contain smaller quantities of nutrients than forest soil and vegetation, and under the same vegetation, Illinoian till soils have a smaller nutrient content than Wisconsinan till soils. We measured pH, total C and N, and exchangeable Ca, Mg, K, and Al content of the soils and determined C, N, Ca, Mg, K, and P content of the vegetation. Litter and soil organic matter in the barrens have a higher C/N ratio than the forest. The Illinoian barrens Oa horizon is thicker and contains a greater quantity of exchangeable mineral nutrients than the other Oa horizons. Differences in vegetation nutrient capital strongly mirror differences in biomass. Our results show no strong association of parent material with soil or vegetation nutrient capital. Instead, they suggest that plant community characteristics, not soil nutrient availability, shape the landscape pattern of barrens and forest, particularly plant-driven positive feedbacks primarily involving fire frequency

The reduced Ostrovsky equation : integrability and breaking

Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Massachusetts Institute of Technology for personal use, not for redistribution. The definitive version was published in Studies in Applied Mathematics 129 (2012): 414–436, doi:10.1111/j.1467-9590.2012.00560.x.The reduced Ostrovsky equation is a modi cation of the Korteweg-de Vries equation, in which the usual linear dispersive term with a third-order deriva- tive is replaced by a linear non-local integral term, which represents the e ect of background rotation. This equation is integrable provided a certain curvature constraint is satis ed. We demonstrate, through theoretical analysis and numeri- cal simulations, that when this curvature constraint is not satisfi ed at the initial time, then wave breaking inevitably occurs.KRH was supported by grant N00014-09-10227 from the Offi ce of Naval Research

Effects of Sulfates in Water on Performance of Cow-Calf Pairs

Past data from our laboratory showed water sulfate levels of 3,000 ppm reduced performance and health of growing steers during the summer. This experiment, conducted at the South Dakota State University Cottonwood Research Station, evaluated the effects of high sulfate water on cow and calf performance, milk production, and cow reproduction. Ninety-six crossbred, lactating cows (ages 2-13; average calving date of May 1) and their calves were assigned, after stratifying by age, weight, and previous winter management, to one of six pastures (16 cows/pasture) from June 3 to August 26, 2003. Pastures were randomly assigned to one of two water sulfate levels (three pastures/level). Treatments were low sulfate water (LS; average 388 ± 17 ppm sulfates) or high sulfate water (HS; average 2,608 ± 408 ppm sulfates). The HS water was created by adding sodium sulfate to the LS water. Cow 12-hour milk production was estimated by the weigh-suckle-weigh method at the initiation of the trial and again on July 2 and July 29. Initial milk production estimates were used to adjust the July 2 and July 29 estimates, which represented an average of 64 and 91 days into lactation, respectively. Cows on LS gained 15 lb and cows on HS lost 36 lb during the experiment (P = 0.04). Cows on HS tended to loose more (P = 0.10) body condition than LS (-0.27 and -0.48 for LS and HS, respectively). Twelve-hour milk production did not differ on July 2 (P = 0.33; 10.6 and 9.5 lb for LS and HS, respectively) or July 29 (P = 0.48; 11.9 and 11.0 lb for LS and HS, respectively). Calf ADG did not differ (P = 0.71) between treatments. Pregnancy rates (55-d breeding season) were 98% and 94% for the LS and HS treatments, respectively (P = 0.36). Sulfate levels averaging 2,608 ppm in the drinking water of cow-calf pairs during the summer increased cow weight loss and condition loss but did not reduce calf performance or reproduction compared to sulfate levels averaging 388 ppm

Public Price Reporting, Marketing Channel Selection, and Price Discovery: The Perspective of Cow/Calf Producers in the Dakotas

Cow/calf producers operating in the Dakotas were surveyed on their price discovery strategies, marketing channel preferences, and their perceptions of how regime change in the public price reporting system for fed cattle affected the beef industry in general and the cow/calf industry in particular. Survey results indicate cow/calf producers consider local institutions (auction barns, etc.) to be more reliable for price discovery than regional or national institutions (futures market, USDA public price reports, satellite auctions, etc.). The auction barn marketing channel is the preferred channel for marketing cattle and is considered the most reliable source of market information by producers. Dakota cow/calf producers perceive livestock mandatory price reporting as benefiting the beef industry in general, but consider public price reports to be less reliable than local sources of market information.beef supply chain, cow-calf marketing, marketing channel, price discovery, public price reporting, Livestock Production/Industries,

The Effect of Early vs. Normal Calf Weaning on Feedlot Performance and Herd Management: A Cross-Discipline Case Study

A study of early vs. normal weaning of calves concludes that early weaning improves feedlot production efficiency, reducing per day and per pound feedlot production costs. Early weaned steers finished higher thus feedlot profitability was not affected. Early weaning has a positive affect on cow health and pasture utilization rates.Livestock Production/Industries,