Enhanced chemical strengthening of feldspathic dental porcelain.

Previous studies on ion exchange of dental ceramics have shown that the biaxial flexural strength can be improved by exchanging potassium for sodium ions at temperatures below the strain point. The rubidium ion is bigger than the potassium ion and can also be considered as a candidate for replacing smaller ions, i.e.

Hydrogen in stishovite, with implications for mantle water content.

Stishovite, the highest pressure polymorph of silicon dioxide, may be an important mineral in some regions of the Earth's mantle. Fourier transform infrared spectroscopy has been used to determine the hydrogen content of synthetic stishovite. The concentration of hydrogen depends on the aluminum content of the sample and reaches a maximum of 549 +/- 23 hydrogen atoms per 10(6) silicon atoms for an Al(2)O(3) content of 1.

Positive and negative modulation of Jun action by thyroid hormone receptor at a unique AP1 site.

We have characterized the putative AP1 site in the backbone of pUC plasmids and found unique regulatory effects. The site, which mapped to a 19-bp region around nucleotide 37, conferred transcriptional activation by Jun or Jun/Fos that was boosted up to fivefold by unliganded thyroid hormone receptor (TR). Thyroid hormone changed potentiation of the Jun response by TR into repression.

Water sources for subduction zone volcanism: new experimental constraints.

Despite its acknowledged importance, the role of water in the genesis of subduction zone volcanism is poorly understood. Amphibole dehydration in subducting oceanic crust at a single pressure is assumed to generate the water required for melting, but experimental constraints on the reaction are limited, and little attention has been paid to reactions involving other hydrous minerals. Experiments on an oceanic basalt at pressure-temperature conditions relevant to subducting slabs demonstrate that amphibole dehydration is spread over a depth interval of at least 20 kilometers.

Export of north american ozone pollution to the north atlantic ocean.

Measurement of the levels of ozone and carbon monoxide (a tracer of anthropogenic pollution) at three surface sites on the Atlantic coast of Canada allow the estimation of the amount of ozone photochemically produced from anthropogenic precursors over North America and transported to the lower troposphere over the temperate North Atlantic Ocean. This amount is greater than that injected from the stratosphere, the primary natural source of ozone. This conclusion supports the contention that ozone derived from anthropogenic pollution has a hemisphere-wide effect at northern temperate latitudes.

RN/BSN distance learning through microwave.

Audio and video interactive electronic classroom systems are one way to increase access to baccalaureate programs for working nurses who do not reside near a degree-granting university. The authors describe the impact of this microwave television system on course implementation in a registered nurse/bachelor of science in nursing program. They also discuss the implications for course design, teaching strategies, class interaction, and student achievement.

Herbage allowance x yearling heifer phenotype interactions for the growth of Brahman-Hereford F1 first-calf females grazing humid pasture and semiarid rangeland.

Growth data were collected over 4 yr from 349 Brahman-Hereford F1, first-calf, lactating females that had been allotted as weanlings to either semiarid extensive rangeland (Uvalde) or humid improved Bermudagrass pasture (Overton) and to one of four herbage allowance levels at each location as yearlings. Heifers were wintered according to systems in local practice and maintained on allotted forage levels both as yearlings and during their first lactation. Heifers were bred to Braford bulls to calve as 2-yr-olds in January to March.

Delayed costs of suppressed pain.

The study demonstrates that the rebound effect of thought suppression (Wegner, 1989) has an analog in the experience of somatic discomfort. During a cold-pressor pain induction, 63 Ss were instructed either to concentrate on their room at home (distraction), to pay close attention to their hand sensations (monitoring), or to remove awareness of those sensations from mind (suppression). Two min of postpressor pain ratings showed that monitoring produced the most rapid recovery from the pain and that suppression produced the slowest.

Carotid endarterectomy for asymptomatic patients. Assessing results of a quantitative synthesis.

Carotid endarterectomy (CE) surgery for asymptomatic patients remains controversial despite hundreds of published studies and recent randomized trials. Safety and efficacy are assessed using a quantitative synthesis method derived from meta-analysis and a "critical multiplist" inference approach. In addition, multivariate analyses reveal that use of a surgical shunt could further improve CE outcomes.

Validating risk-adjusted mortality as an indicator for quality of care.

Risk-adjusted mortality is perhaps the most commonly referenced outcome indicator for assessments of hospital quality. While mortality rate possesses considerable intuitive appeal as a quality indicator, scientific evidence concerning its appropriateness for this purpose is mixed. In this paper, we use a computerized discharge database to model mortality risks for patients hospitalized for three different conditions: cardiac disease (ischemic heart disease, coronary artery disease, angina, and left ventricular aneurysm), acute myocardial infarction, and septicemia.

Forage availability x heifer phenotype interactions for Brahman-Hereford F1 yearling heifers grazing humid pasture and semiarid rangeland.

Yearling heifer growth data were obtained during 4 yr for 524 heifers allotted to either humid bermuda grass pastures (Overton) or semiarid rangeland (Uvalde). Each year, heifers were allotted on April 15 to four forage availability levels (400 to 2,800 kg of DM per 100 kg of BW at Uvalde and 80 to 260 kg of DM per 100 kg of BW at Overton) maintained by varying the stocking rate monthly until mid-October of each year. Forage availability and yearling heifer characteristics (weight, condition score, and height at hooks, taken on April 15) were treated as continuous variables in regression analyses.

Precision of blood cholesterol measurement and high blood cholesterol case-finding and treatment.

Imprecise blood cholesterol measurement can be expected to adversely affect large scale efforts to detect and treat high blood cholesterol. Using protocols specified by the National Cholesterol Education Program (NCEP), we used computer simulation techniques to quantify the effects of blood cholesterol measurement variability on misclassification rates, costs, effectiveness, and cost-effectiveness of high blood cholesterol case-finding and treatment. At the time of initial case-finding, increased measurement variability was associated with a moderate decrease in the proportions assigned to a treatment state and in the positive predictive value of such an assignment.

Safety from sharps.

Needlestick and sharps injuries are responsible for 35% of hospital injuries to staff. Despite this, there has been little effort in the past to reduce potential hazards. Nurses and other healthcare personnel must be made aware of the risks so that they can improve their practice.

Some physical properties of implant abutment luting cements.

The dislodging force, the compressive strength at 24 hours, and the film thickness of four resin composite luting cements (UDA, UDA with fluoride, Panavia OP, and DenMat) and a conventional glass-ionomer cement (Shofu Type I) were compared. The axial force necessary to dislodge each cemented 0 degree abutment from an internally threaded Steri-Oss implant (n = 5) was then determined using a mechanical testing machine. UDA with fluoride appears to be a significantly stronger luting agent for abutment cementation than is either UDA or DenMat (P less than .

Inhibition of DNA synthesis and decreased reproductive capacity in cattle maintained on semi-arid rangeland with Acacia species as a major component of available browse.

The ability of bovine lymphocytes to initiate in vitro blastogenesis in response to mitogen stimulation or to initiate DNA excision repair after treatment with a mutagen was evaluated as a function of the differing environmental conditions under which donor animals were maintained. Crossbred Brahman-Hereford F1 females were held on either a humid, coastal bermudagrass, improved pasture at Overton, TX, or in low or high grazing pressure herds on a semi-arid rangeland (Acacia-dominated shrubland) at Uvalde, Tx. Peripheral blood lymphocytes (PBL) from these animals were examined to determine their in vitro ability to engage in phytohemagglutinin (PHA)-stimulated blastogenesis and to initiate excision repair of DNA damage after exposure of the cells to the model polynuclear hydrocarbon carcinogen 7,8-dihydrodiol-9, 10-epoxy-benzo(a) pyrene (BPDE).

High social risk screening mechanisms: patient characteristics as predictors of social work utilization in the VA.

To facilitate timely access to social services in hospitals, high social risk (HSR) screening mechanisms have been implemented throughout the country. The purpose of these mechanisms is to identify patients upon admission who are most likely to need service. Because these screening mechanisms often identify patients who do not need service, this study determined how well the patient characteristics used as screening factors actually predicted service utilization.

RXR beta: a coregulator that enhances binding of retinoic acid, thyroid hormone, and vitamin D receptors to their cognate response elements.

The retinoic acid receptor (RAR) requires coregulators to bind effectively to response elements in target genes. A strategy of sequential screening of expression libraries with a retinoic acid response element and RAR identified a cDNA encoding a coregulator highly related to RXR alpha. This protein, termed RXR beta, forms heterodimers with RAR, preferentially increasing its DNA binding and transcriptional activity on promoters containing retinoic acid, but not thyroid hormone or vitamin D, response elements.

Effect of pre- and postweaning management system on the performance on Brahman crossbred feeder calves.

During a 3-yr period (1986 through 1988), 117 calves (57 steers and 60 heifers) from the same genetic base and reared under four distinct preweaning management systems were weaned in the fall and transported from Uvalde, TX to El Reno, OK (800 km). Weaning weight and transportation shrink varied more from year to year than among preweaning treatments. Postweaning performance was not affected by preweaning treatment.

The orientation and spacing of core DNA-binding motifs dictate selective transcriptional responses to three nuclear receptors.

Characterization of several thyroid hormone (T3), retinoic acid, and estrogen response elements has led to the identification of conserved DNA half-sites (core binding motifs). We present evidence that differences in both the relative orientation and spacing of these motifs within hormone response elements determine the distinct transcriptional responses of three members of the nuclear receptor superfamily. When separated by 3 bp, direct repeat, palindromic, and inverted palindromic arrangements of these motifs impart selective transcriptional responses to retinoic acid, estrogen, and T3 receptors, respectively.