Damage evolution in polymer due to exposure to high-pressure hydrogen gas

The use of hydrogen as a fuel is increasing exponentially, and the most economical way to store and transport hydrogen for fuel use is as a high-pressure gas. Polymers are widely used for hydrogen distribution and storage systems because they are chemically inert towards hydrogen. However, when exposed to high-pressure hydrogen, some hydrogen diffuses through polymers and occupies the preexisting cavities inside the material. Upon depressurization, the hydrogen trapped inside polymer cavities can cause blistering or cracking by expanding these cavities. A continuum mechanics–based deformation model was deployed to predict the stress distribution and damage propagation while the polymer undergoes depressurization after high-pressure hydrogen exposure. The effects of cavity size, cavity location, and pressure inside the cavity on damage initiation and evolution inside the polymer were studied. The stress and damage evolution in the presence of multiple cavities was also studied, because interaction among cavities alters the damage and stress field. It was found that all these factors significantly change the stress state in the polymer, resulting in different paths for damage propagation. The effect of adding carbon black filler particles and plasticizer on the damage was also studied. It was found that damage tolerance of the polymer increases drastically with the addition of carbon black fillers, but decreases with the addition of the plasticizer.     

Evidence for the presence of sodium- and potassium-dependent adenosine triphosphatase alpha1 and beta1 subunit isoforms and their probable role in blastocyst expansion in the preattachment horse conceptus

Two Caribbean hair sheep breeds, the St. Croix (SC) and Barbados Blackbelly (BB), are found in the United States, and the SC has led to the development of the Katahdin (K), a synthetic breed of hair sheep. These breeds have mature ewe BW ranging from 32 to 54 kg (for BB and SC) and from 55 to 73 kg (K). Hair sheep and hair sheep crosses have lower rectal temperatures and respiration rates than wool breeds and a lower DMI and water intake. There are indications of increased resistance to internal parasites in hair sheep. Although hair sheep are seasonal breeders under U.S. photoperiodic conditions, they tend to perform better under accelerated lambing systems than traditional wool breeds. Fertility, prolificacy, and lamb survival is high in BB and SC, but hair x wool crossbred ewes tend to have a higher level of fertility than hair and wool parent breeds. Ewe productivity is also higher in hair x wool crosses than in wool crosses, particularly when adjusted for ewe BW or under accelerated lambing systems. Hair sheep have a lower ADG and intake of high-energy diets, as well as a lower gain/feed ratio, than wool breeds. Growth rates tend to be higher in SC than in BB. Differences in carcass characteristics are inconsistent between hair and wool breeds. Production characteristics of hair sheep, particularly hair x wool crosses, make them suitable for low-input, sustainable production systems that do not require high growth rates and large carcasses. There is a need to preserve the existing U.S. hair sheep germplasm base in support of such systems.     

Granulation tissue polyposis associated with carcinoid tumours of the small intestine

We report two patients with ileal carcinoid tumours which were associated with polyps due to mucosal granulation tissue proliferation. In both cases the tumours had extensively infiltrated the small bowel wall and mesentery, and one had hepatic metastases. The mucosal surface of each specimen showed numerous, pale brown, sessile polyps which were restricted to the intestinal segment involved by carcinoid tumour, although not always closely related to neoplastic cells. The polyps were formed by the proliferation of capillaries, smooth muscle cells and myofibroblasts as demonstrated by immunohistochemistry and electronmicroscopy.     

Laser prostatectomy: initial experience and urodynamic follow-up

OBJECTIVES: An evolving technology for the treatment of bladder outlet obstruction due to benign prostatic hyperplasia (BPH) is the use of the side-firing neodymium: yttrium-aluminum-garnet (Nd:YAG) laser to achieve prostatic tissue ablation. The purpose of this study was to determine the short-term efficacy of this procedure in both an objective and subjective manner. METHODS: We examined this technique by carefully evaluating our first 25 men undergoing the procedure. Each patient was subjected to careful symptom score analysis using the American Urological Association symptom index and multichannel urodynamics, including pressure-flow studies both preoperatively and at 3 months postoperatively. RESULTS: At the 3-month follow-up, symptom scores improved from a preoperative mean of 11.4 to 7.2 and the mean maximum flow rate improved from 6.1 to 14.5 cc/s. These are both significant at P < 0.001. Statistically similar improvement was seen in detrusor pressure at opening and at maximum flow. Eighty percent of the men studied had at least a 50% reduction in symptom score and a 50% improvement in flow rate. CONCLUSIONS: We conclude that laser prostatectomy is a promising minimally invasive treatment for bladder outlet obstruction secondary to BPH and deserves further evaluation at longer terms of follow-up.     

Knowledge conceptualization tool

Knowledge acquisition is one of the most important and problematic aspects of developing knowledge-based systems. Many automated tools have been introduced in the past, however, manual techniques are still heavily used. Interviewing is one of the most commonly used manual techniques for a knowledge acquisition process, and few automated support tools exist to help knowledge engineers enhance their performance. The paper presents a knowledge conceptualization tool (KCT) in which the knowledge engineer can effectively retrieve, structure, and formalize knowledge components, so that the resulting knowledge base is accurate and complete. The KCT uses information retrieval technique to facilitate conceptualization, which is one of the human intensive activities of knowledge acquisition. Two information retrieval techniques employing best-match strategies are used: vector space model and probabilistic ranking principle model. A prototype of the KCT was implemented to demonstrate the concept. The results from KCT are compared with the outputs from a manual knowledge acquisition process in terms of amount of information retrieved and the process time spent. An analysis of the results shows that the process time to retrieve knowledge components (e.g., facts, rules, protocols, and uncertainty) of KCT is about half that of the manual process, and the number of knowledge components retrieved from knowledge acquisition activities is four times more than that retrieved through a manual process     

Combining beta-core fragment and total oestriol measurements to test for Down syndrome pregnancies

Recent articles by Cuckle et al., Canick et al., and Isozaki et al. have evaluated urine beta-core fragment as a screening test for Down syndrome in second-trimester pregnancies. They found over four-fold elevation of beta-core fragment levels in Down syndrome pregnancies, and between 62 and 88 per cent detection of this trisomy at a 5 per cent false-positive rate. Urine beta-core fragment may be a superior screening test for Down syndrome pregnancies. In the present study, urinary total oestriol has been evaluated as a marker to use in combination with beta-core fragment in screening for Down syndrome pregnancies. The two markers were evaluated separately in relation to the urine creatinine concentration. To amplify screening performance, we evaluated the ratio of beta-core fragment to total oestriol levels (creatinine-independent). beta-core fragment and total oestriol levels were determined (normalized to creatinine, ng/mg creatinine) in urine samples from 480 unaffected and 12 Down syndrome pregnancies, collected consecutively at a single prenatal diagnosis centre. The median beta-core fragment level in Down syndrome cases was 4.5 MOM. Fifty-eight per cent of Down syndrome cases had beta-core fragment levels exceeding the 95th centile of unaffected pregnancies. The median total oestriol level in Down syndrome cases was 0.33 MOM. Forty-two per cent of Down syndrome cases had total oestriol levels exceeding the 95th centile of unaffected pregnancies. We investigated the ratio of the two determinants (beta-core fragment, ng/ml divided by total oestriol, ng/ml) in our sample set. The median beta-core fragment:total oestriol ratio in Down syndrome cases was 13 MOM. Seventy-five per cent of Down syndrome cases had a ratio exceeding the 95th and the 99.5th centile of unaffected pregnancies. Total oestriol complements beta-core fragment in urine screening for Down syndrome pregnancies. A test measuring the ratio of the two urine determinants may be a significant improvement over current serum methods for detecting Down syndrome.