Health aspects of the curing of synthetic rubbers.
A commonly used tread rubber formulation was cured in the laboratory under conditions simulating vulcanization in the Bag-O-Matic press. Volatile emissions were collected on charcoal and analyzed by combined GC-mass spectrometry. The compounds identified were either contaminants present in the raw material or reaction products. Some of these compounds were also identified in charcoal tube samples collected in the atmosphere of the industrial operations. Estimates based on the loss of weight of rubber during curing were used to predict airborne concentrations and compared to the concentrations actually found. The literature of the toxicity of raw materials and effluents was reviewed, and no acute or chronic toxicological effects would be anticipated. Information concerning potential carcinogenicity was not available and could not be evaluated. (+info)
Flake density of steam-processed sorghum grain alters performance and sites of digestibility by growing-finishing steers.
The effect of several flake densities (FD) of steam-processed sorghum grain on performance, and site and extent of nutrient digestibilities by steers fed growing and finishing diets was determined. The effectiveness of common laboratory methods of starch availability (enzymatic hydrolysis or gelatinization) to provide target specifications for quality control of steam-flaked grains was also measured. In vitro starch availability of the processed grains increased (P < .05) linearly in response to decreased FD. Flake density was more highly correlated with enzymatic measures than with percentage gelatinization (R2 = .87 to .93 vs .36). Using 140 crossbred beef steers (181 kg initial weight), feedlot performance was determined for 112 d with a growing diet (50% grain), followed by 119 d with a finishing diet (78% grain). Each FD treatment (412, 360, 309, and 257 g/L or 32, 28, 24, and 20 lb/bu) was randomly assigned to five pens of seven steers each. Intake of DM by steers decreased linearly (P < .05) as FD decreased (7 and 13%, respectively, for growing and finishing diets). Decreasing FD reduced linearly (P < .05) ADG in the finishing phase and for the entire 231-d trial. With the growing diet only, feed efficiency and estimated diet NEm and NEg responses to decreasing FD were curvilinear (P < .05), with the 360 g/L (28 lb/bu) flake being most efficient. Electrical energy requirements for processing increased linearly (P < .05) as FD decreased. Using four multi-cannulated crossbred steers (275 kg), starch digestibility increased linearly (P < .05) in the rumen (82 to 91%) and total tract (98.2 to 99.2%) as FD decreased. Digestibilities within the small (74%) and large intestines (62%) were not altered by FD. Decreasing FD increased (P < .05) total CP digestibility, but did not consistently alter fiber digestibility or DE content of the diets. In conclusion, enzymatic laboratory methods to evaluate starch availability in processed grains can be used satisfactorily to establish FD criteria for quality control of the steam-flaking process. The greatest improvements in efficiency, estimated diet NE, and starch and protein digestibilities usually occurred when FD was decreased from 412 to 360 g/L (32 to 28 lb/bu). Based on these measures and processing costs, the optimal FD was 360 g/L (28 lb/bu). (+info)
Sorghum grain flake density and source of roughage in feedlot cattle diets.
Feedlot performance was studied in a 262-d trial using 126 crossbred beef steers (182 kg initial BW) to determine whether source of dietary roughage influences performance and carcass characteristics by steers fed growing (112 d) and finishing (150 d) diets with various flake densities (FD) of steam-processed sorghum grain. A 3 x 3 arrangement of treatments (two pens of seven steers each) was used, with dietary roughages being chopped alfalfa hay or 50:50 mixtures (equal NDF basis) of cotton-seed hulls or chopped wheat straw with alfalfa hay; sorghum grain was steam-flaked to densities of 386, 322, and 257 g/L (SF30, SF25, and SF20, reflecting bushel weight in pounds). The effects of these same FD on nutrient digestibilities were determined in three experiments with 24 crossbred steers fed finishing diets containing each of the roughage sources. No interactions between FD and roughage type were detected in any performance or carcass measurements (P > .10). Intake of DM decreased linearly (P < .05) in response to decreased FD. Daily rate and efficiency of gain were not altered (P >.10) by FD. Decreasing FD decreased linearly (P < .05) dressing percentage and fat thickness, but not other carcass measurements. Dietary roughage did not affect (P >.10) daily gains or carcass measurements, but DM intake was lower and feed efficiencies were superior (P < .05) when alfalfa hay was the sole source of roughage. Cottonseed hulls and wheat straw were relatively less valuable in the low roughage finishing diets than in higher roughage growing diets. Digestibilities of starch increased linearly as FD was decreased (P = .02) when steers were fed diets containing wheat straw, but not for alfalfa hay or cottonseed hull diets. Digestibilities of DM did not vary with changes in FD; however, changes in CP, NDF, and ADF digestibilities due to FD seemed to differ among experiments. In conclusion, performance and carcass measurement responses by growing-finishing steers to differences in sorghum grain FD were not related to source of dietary roughage, but diets with alfalfa hay as the only source of roughage were most efficient. Decreasing FD of sorghum grain below 386 g/L (30 lb/bu) was not advantageous in improving performance or carcass merit by growing-finishing steers. (+info)
Autoclaves and their dangers and safety in laboratories.
Using a laboratory downward displacement vertical autoclave with the help of thermocouples recorded on a 12 point multichannel strip recorder, the risk of failing to sterilize laboratory discard buckets has been demonstrated. The use of proper temperature and time controls can prevent this risk. A load in a bucket with perforated sides is more easily sterilized than in a solid bucket. Wire baskets, where appropriate, facilitate the sterilizing practice. The addition of water to a bucket does not reduce the time of heating up. It is desirable that sealed bottles of media should not be sterilized in simple downward displacement autoclaves, but if used, strict monitoring of temperatures and times is essential both in the heating up stage and especially in the cooling stage. The temperatures in bottles are slow to rise and very slow to fall. Bottles at high temperature 80-105 degrees C. or over have a high internal pressure which can allow the bottles to explode when subjected to thermal shock if removed too early. It is suggested that all laboratory autoclaves should have a load temperature simulator or similar device to control the temperature of the load during the cycle automatically. For the sterilization of fluid media, it is suggested that, in addition to a simulator there should be accelerated cooling to reduce damage to the media and, what is more important, to rapidly bring down the temperature and thus the internal pressure in the bottles to a safe level. The opening of the sterilizer door or lid should be automatically controlled by the load temperature simulator. (+info)
The effect of autoclave resterilisation on polyester vascular grafts.
OBJECTIVES: polyester grafts are expensive, single-use items. Some manufacturers of uncoated, woven grafts include instructions for autoclave resterilisation to be performed at the surgeon's own request. Others warn against such manipulation. Theoretically, the glass transition point of polyester at 70-80 degrees C and the possible acceleration of hydrolysis suggest that autoclave resterilisation at 135 degrees C might be a problem. MATERIALS AND METHODS: a DeBakey Soft Woven Dacron Vascular Prosthesis (Bard) and a Woven Double Velour Dacron Graft (Meadox) were autoclave-resterilised 0 to 20 times, having been weighed before and after sterilisation. Tactile testing was performed. Mechanical properties were examined by probe puncture and single-filament testing, the surface was examined by scanning electron microscopy and the degree of hydrolysis by infra-red spectroscopy. RESULTS: tactile testing revealed a change of feeling with increasing cycles of resterilisation. Investigation of weight, textile strength, single-filament strength, electron microscopy of the surface and infra-red spectroscopy showed no change of the material. CONCLUSIONS: changes felt are presumably a surface phenomenon, not measurably affecting strength or chemistry of material after autoclave resterilisation. We therefore feel that it is safe to use once-autoclave-resterilised surplus uncoated polyester grafts, provided that sterility is guaranteed. (+info)
Possible remediation of dioxin-polluted soil by steam distillation.
2,7-Dichlorodibenzo-p-dioxin (DCDD) was found to evaporate easily with water vapor from a heated solution. Steam distillation was also effective for the removal of DCDD from DCDD-applied soil; its concentration (250 microg/50g soil) in the original soil decreased to less than 5% after steam distillation for only 20 min. Actual dioxin-polluted soil in Tokorozawa City was partially decontaminated using the same method. These results suggest that steam distillation could be a new remedial method for soils contaminated with persistent environmental pollutants, such as dioxins and polychlorinated biphenyls. (+info)
The hottest thing in remediation.
Scientists and engineers are exploring a new way to decontaminate toxic waste sites by literally turning up the heat on pollutants. The method heats the ground using electricity or steam, which mobilizes the contaminants so they can either be extracted from the ground and destroyed or actually destroyed in place. Among the targets for this method are pollutants such as creosote, solvents, and gasoline. These in situ thermal technologies also offer the benefit of reaching contaminants not previously amenable to cleanup, such as those found beneath structures and below the water table. (+info)
Flaking corn: processing mechanics, quality standards, and impacts on energy availability and performance of feedlot cattle.
Based on performance of feedlot cattle, steam flaking increases the value of corn by 18%, considerably more than is suggested by tabular values. Tabular values underestimate the energy availability of flaked corn by failing to account for digestibility of the nonstarch OM that is increased by flaking by the same magnitude (10%) as starch. Correcting for improvement in digestibility of nonstarch OM increases the NEg value of steam-flaked corn to 1.70 Mcal/kg, a value very close to values calculated from cattle performance trials. Digestibility of starch from corn grain is limited by the protein matrix that encapsulates starch granules, and by the compact nature of the starch itself. Disruption of the protein matrix (by shear forces on hot grain during flaking) is the first limiting step toward optimizing starch digestion. Five critical production factors influence the quality of steam-flaked corn: steam chest temperature, steaming time, roll corrugation, roll gap, and roll tension. For optimal shear, it is important that rolls be hot and that kernels be hot when flaked. Steam chests should be designed to allow a steaming time of at least 30 min at maximum roller mill capacity producing a flake of 0.31 kg/L (24 lb/bushel). As little as 5% moisture uptake during steaming appears adequate. The rate of flaking and distribution of kernels across the rolls also are critical. Quality standards for steam-flaked corn include measurements of flake thickness, flake density, starch solubility, and enzyme reactivity. Flake density, the most common quality standard, closely associated with starch solubility (r2 = 0.87) and enzyme reactivity (r2 = 0.79), still explains only 63% of the variability in percentage fecal starch and 52% of the variability in starch digestibility. Direct determination of fecal starch can explain 91% of the variability in starch digestion. The NEg value of corn can be predicted from fecal starch: NEg= 1.78 - 0.0184FS. Starch digestion is a Kappa Curve function of hot flake density, reaching a maximum at a flake density of approximately 0.31 kg/L. Flaking to a density of less than 0.31 kg/L, though increasing starch solubility, may reduce DMI, increase variability of weight gain among animals within a pen, and predispose cattle to acidosis and bloat without increasing starch digestion. We recommend that the steam-flaking process be optimized on the basis of fecal starch analysis. (+info)