The peeling of flexible probabilistic fasteners

Probabilistic fasteners are attachment devices consisting of two elements each of which is covered by an array of outgrowths or protuberances which interact or interlock with those on the opposing surface to form a bond which can be made and detached many times. A number of peel tests are described in which the behaviour of such bonds, specifically those formed by Velcro® hooks and loops and Dual Lock®, has been explored. The value of the specific energy of detachment of such mechanically latched systems can be related to the geometry and material properties of the individual fixing elements. Similar arguments can be applied, both qualitatively and quantitatively, to some natural systems such as the spines on some cacti.     

Effect of sodium and potassium sulphates on zinc electrowinning

In order to evaluate the intrinsic effect of high concentrations of sodium and potassium sulphates in zinc electrowinning solutions, measurements of coulombic efficiency were carried out under mass transfer-controlled conditions in synthetic solutions of very high purity. A solution composition of 1 mol dm^–3 ZnSO₄+1.5 mol dm^–3 H₂SO₄ was employed with and without additions of 0.5 mol dm^–3 Na₂SO₄ and/or 0.25 mol dm^–3 K₂SO₄. With temperature and current density similar to plant practice (37° C, 650 A m^–2) and electrode rotation rates of 10 and 45 s^–1, the coulombic efficiency for three successive batch tests (200 mg zinc) increased by an average of 1.2% (from an average of 96.0%) for additions of 0.5 mol dm^–3 Na₂SO₄+0.25 mol dm^–3 K₂SO₄. The results were evaluated in terms of available theories, solution purity and predicted changes in solution composition (zinc and hydrogen ion activities) and physical properties following additions of Na₂SO₄/K₂SO₄. It was concluded that in the plant situation the increase in coulombic efficiency would probably be offset by an increase in cell voltage of about 2%, the net effect on power efficiency being a decrease of about 1%. The zinc deposit morphology and preferred orientation were also studied. The addition of sodium and/or potassium sulphate to the solution resulted in rougher, darker zinc deposits, a slight grain refining effect, and a change from random to predominantly basal (002), (004) crystal orientation (at 45 s^–1).     

Effectiveness of a participatory ergonomics intervention in improving communication and psychosocial exposures

A participatory ergonomics programme was implemented in an automotive parts manufacturing factory in which an ergonomics change team was formed, composed of members from management, the organized labour union and the research team. It was hypothesized that the participatory nature of this change process would result in enhanced worker perceptions of workplace communication dynamics, decision latitude and influence, which in conjunction with anticipated mechanical exposure reductions would lead to reduced worker pain severity. Utilizing a sister plant in the corporation as a referent group, a quasi-experimental design was employed with a longitudinal, repeat questionnaire approach to document pre-post intervention changes. Nine participatory activities (psychosocial interventions) were implemented as part of the process. Communication dynamics regarding ergonomics were significantly enhanced at the intervention plant compared to the referent plant. However, there were no significantly different changes in worker perceptions of decision latitude or influence between the two plants, nor did pain severity change. Possible explanations for these results include limited intervention intensity, context and co-intervention differences between the two plants, high plant turnover reducing the statistical power of the study and lack of sensitivity and specificity in the psychosocial measures used. Further research should include the development of psychosocial tools more specific to participatory ergonomic interventions and the assessment of the extent of change in psychosocial factors that might be associated with improvements in pain.     

Quantitative determination of the mineral-matter content of coal by a radiofrequency -oxidation technique

The development of a low-temperature (≈150 °C) radiofrequency-oxidation technique as a routine laboratory method for the quantitative determination of the mineral-matter content of coal is described. The main advantage of the method over air-oxidation (370 °C) and acid-extraction methods is that isolation of the unaltered mineral matter permits a more accurate expression of coal analyses on a dry mineral-matter-free basis. Comparison with the air-oxidation method has demonstrated the superiority of the radiofrequency-oxidation method for retention of carbonate and sulphide minerals; reproducibility is generally similar. The radiofrequency-oxidation method yields higher results for the percentage of mineral matter than the air-oxidation method. The differences between the combined water contents of the mineral-matter samples prepared by the two methods indicate that the air-oxidation method partly dehydrates clay minerals and that the radiofrequency-oxidation method produces results closer to the true mineral-matter contents. Other advantages — independence of extra analytical determinations, lower elapsed time and labour costs, applicability to a wider range of coals — are detailed in the Conclusions.     

Computer Automation in Chemistry

The digital computer is a common instrument in many laboratories; it is no longer necessary to describe its operating characteristics in detail. However, it is not yet generally used in an entirely satisfactory manner nor are its full capabilities understood and exploited in laboratory automation. Some of the more pressing issues to be understood and resolved are opti-minal trade-offs between hardware and software, dedicated computer automation versus automation via time-shared systems, single-processor time-shared systems versus multiprocessor hierarchical time-shared systems, and the development of a real-time high-level control language.     

Effects of diet on the lipid composition of Echinostoma caproni (Trematoda) in ICR mice

High-performance thin-layer chromatography (HPTLC) was used to determine neutral lipids and phospholipids in the intestinal trematode Echinostoma caproni from experimentally infected ICR mice fed a high-fat diet (hen's egg yolk) as compared with worms from mice fed a standard laboratory diet. Worms were removed from the hosts at 2, 3, and 4 weeks postinfection (p.i.). Analysis by TLC-densitometry showed significantly greater amounts of triacylglycerols and free sterols at 2, 3, and 4 weeks p.i. in worms from mice on the high-fat diet as compared with worms from mice on the standard laboratory diet. Significantly greater amounts of phosphatidylcholine and phosphatidylethanolamine were found in worms from mice on the high-fat diet as compared with worms from those on the standard diet at 2 weeks p.i. but not at 3 and 4 weeks p.i. The results of this study suggest that the host diet influences the lipid content of E. caproni adults.     

Decreased epinephrine responses to hypoglycemia during sleep

BACKGROUND: In patients with type I diabetes mellitus, hypoglycemia occurs commonly during sleep and is frequently asymptomatic. This raises the question of whether sleep is associated with reduced counterregulatory-hormone responses to hypoglycemia. METHODS: We studied the counterregulatory-hormone responses to insulin-induced hypoglycemia in eight adolescent patients with type I diabetes and six age-matched normal subjects when they were awake during the day, asleep at night, and awake at night. In each study, the plasma glucose concentration was stabilized for 60 minutes at approximately 100 mg per deciliter (5.6 mmol per liter) and then reduced to 50 mg per deciliter (2.8 mmol per liter) and maintained at that concentration for 40 minutes. Plasma free insulin, epinephrine, norepinephrine, cortisol, and growth hormone were measured frequently during each study. Sleep was monitored by polysomnography. RESULTS: The plasma glucose and free insulin concentrations were similar in both groups during all studies. During the studies when the subjects were asleep, no one was awakened during the hypoglycemic phase, but during the final 30 minutes of the studies when the subjects were awake both the patients with diabetes and the normal subjects had symptoms of hypoglycemia. In the patients with diabetes, plasma epinephrine responses to hypoglycemia were blunted when they were asleep (mean [+/-SE] peak plasma epinephrine concentration, 70+/-14 pg per milliliter [382+/-76 pmol per liter]; P=0.3 for the comparison with base line), as compared with when they were awake during the day or night (238+/-39 pg per milliliter [1299+/-213 pmol per liter] P=0.004 for the comparison with base line, and 296+/-60 pg per milliliter [1616+/-327 pmol per liter], P=0.004, respectively). The patients' plasma norepinephrine responses were also reduced during sleep, whereas their plasma cortisol concentrations did not increase and their plasma growth hormone concentrations increased slightly. The patterns of counterregulatory-hormone responses in the normal subjects were similar. CONCLUSIONS: Sleep impairs counterregulatory-hormone responses to hypoglycemia in patients with diabetes and normal subjects.