Potential of scrap tire rubber as lightweight aggregate in flowable fill.

Flowable fill is a self-leveling and self-compacting material that is rapidly gaining acceptance and application in construction, particularly in transportation and utility earthworks. When mixed with concrete sand, standard flowable fill produces a mass density ranging from 1.8 to 2.3 g/cm(3) (115-145 pcf). Scrap tires can be granulated to produce crumb rubber, which has a granular texture and ranges in size from very fine powder to coarse sand-sized particles. Due to its low specific gravity, crumb rubber can be considered a lightweight aggregate. This paper describes an experimental study on replacing sand with crumb rubber in flowable fill to produce a lightweight material. To assess the technical feasibility of using crumb rubber, the fluid- and hardened-state properties of nine flowable fill mixtures were measured. Mixture proportions were varied to investigate the effects of water-to-cement ratio and crumb rubber content on fill properties. Experimental results indicate that crumb rubber can be successfully used to produce a lightweight flowable fill (1.2-1.6 g/cm(3) [73-98 pcf]) with excavatable 28-day compressive strengths ranging from 269 to 1194 kPa (39-173 psi). Using a lightweight fill reduces the applied stress on underlying soils, thereby reducing the potential for bearing capacity failure and minimizing soil settlement. Based on these results, a crumb rubber-based flowable fill can be used in a substantial number of construction applications, such as bridge abutment fills, trench fills, and foundation support fills.

A novel psychophysical procedure for bitter taste assessment in rats.

A persistent problem with attempts to examine bitter taste mechanisms has been the lack of adequate behavioral methodology providing data which parallels that obtained from physiological investigations. We developed a brief contact procedure to assess the ability of rats to detect the presence of a weak bitter compound dissolved in a strong sucrose solution. Male Fischer 344 rats were trained to drink immediately to multiple 10-s presentations of acetaminophen (2, 8, 32, 128 mM), chlorpheniramine maleate (1, 3, 9, 27 mM) L-tryptophan (13.5, 27, 54, 108 mM), pseudoephedrine hydrochloride (1, 4, 16, 64 mM) and quinine hydrochloride (0.008, 0.04, 0.2, 1.0 mM) dissolved in 0.8 M sucrose. The number of licks to sucrose and water were also measured. A microcomputer controlled stimulus presentations and measured the animal's licks of each solution during each 10-s presentation. The responses to the bitter+sucrose mixture were significantly decreased at most concentrations with increasing levels of the bitter component. This was true for all five bitter-tasting compounds, but over different concentration ranges relatively unique to each compound. The present study is the first to characterize the sensory effects of acetaminophen, pseudoephedrine, and chlorpheniramine maleate, all purported to taste bitter to humans. These results demonstrate rats' acute ability to discriminate by taste not only the presence but the concentration of a dilute bitter compound dissolved in a strong sucrose solution.

Towards an assessment of the influence of climate on wet acidic deposition in Europe.

The EMEP precipitation composition network is used to examine relationships between non-marine SO4(2-), NO3-, NH4+, H+ concentrations and precipitation amount and a local zonal pressure index (an index of the atmospheric circulation). The pattern of the relationships changes across Europe with the zonal pressure gradient explaining more of the variance in ion concentrations in the west, and precipitation amount explaining relatively more of the variance in the east. There is some predictive capability for precipitation composition in the zonal pressure gradient for restricted regions in Europe; R2 values are up to 40% on a daily basis but in some seasons/months attain >60%. The zonal pressure gradient is an index which appears to include pertinent information on transport and wet removal. Preliminary analysis indicates that this approach can be useful in assessing the contributions of changing atmospheric circulation to time-trends of wet acidic deposition in an area stretching from the UK over the North Sea to Denmark. The zonal pressure gradient is known to have varied on time-scales of decades, and the simple index may be one appropriate approach to assessing future deposition patterns from future climate projections.

Rapid healing of diabetic foot ulcers with meticulous blood glucose control.

Fifteen diabetic patients, with neuropathic food ulcers refractory to conventional treatment, were found to be poorly balanced and were put on meticulous regimens; some on continuous subcutaneous insulin infusion and others on split mixed doses. Once diabetes was controlled, the wound healed rapidly in 11 of the patients within 4 to 13 weeks. In 4 patients amputation was necessary. The outcome was better in patients with good peripheral pulses. We suggest that tight control of diabetes promotes healing of diabetic foot lesions.

A thyrotropin radioimmunoassay kit evaluated vs two reference assays.

We evaluated a double-antibody radioimmunoassay kit for thyrotropin that includes calibrators prepared in a matrix of human serum and involves overnight nonequilibrium. Results were compared with those from two reference assays for thyrotropin. The range of within-assay CVs for the kit for thyrotropin values between 0.9 and 2.4 milli-int. units/L was 2.2 to 5.3%, that for between-assay CVs was 8.3 to 30%. The estimated minimum detectable concentration of thyrotropin was 0.6 milli-int. unit/L. We saw no cross reactivity with human choriogonadotropin by any of 48 sera from pregnant women. The original lot of serum specified as thyrotropin-free contained small but measurable amounts of thyrotropin; a second lot did not. Clinical data generated with the kit and the reference assays correlated well and were consistent with the clinical status of various categories of patients.

Rapid healing of diabetic foot ulcers with continuous subcutaneous insulin infusion.

Two patients with inadequately controlled diabetes mellitus had chronic foot ulcers that were refractory to repeated attempts with conventional treatment. In both patients, complete healing of the foot lesions occurred six to eight weeks after continuous subcutaneous insulin infusion was instituted and blood sugar levels had become normal. This suggests that good control of diabetes, as obtainable with continuous subcutaneous insulin infusion, stimulates healing of foot ulcers. Possible reasons for this finding are reviewed.

Dihydropteridine reductase activity of adult, fetal and neoplastic tissues.

Optimal conditions for the assay of dihydropteridine reductase in crude tissue extracts have been developed. Among adult rat tissues, liver and kidney had the highest activity followed by thymus, lung, cerebellum and cerebrum. Fetal tissues and neoplasms exhibit lower activities than the cognate adult tissues. In both liver and kidney the developmental upsurge of dihydropteridine reductase, which produces the cofactor necessary for the hydroxylation of aromatic amino acids, begins earlier than does that of phenylalanine hydroxylase. In human liver and lung also, the dihydropteridine reductase activity doubles between midgestation and adult life. The undifferentiated enzymic composition of neoplasms is reflected by the lower dihydropteridine reductase content of pulmonary tumors than of nonneoplastic human lung.

Absorption of L-methionine from the human small intestine.

Absorption of L-methionine was measured in all parts of the human small intestine using transintestinal intubation and perfusion. In four normal subjects, adsorption was higher in the proximal than in the distal intestine. In two patients with nontropical sprue in relapse, there was a proximal zone of low absorption with higher absorption distally. In all parts of the small intestine, absorption showed rate-limiting kinetics as methionine concentration was increased. In normal subjects, the proximal K(m) (Michaelis constant) was more than 3 times higher than the distal, which suggests a difference in transport mechanisms between the two segments.