Thermal and cardiovascular strain imposed by motorcycle protective clothing under Australian summer conditions

Motorcycle protective clothing can be uncomfortably hot during summer, and this experiment was designed to evaluate the physiological significance of that burden. Twelve males participated in four, 90-min trials (cycling 30 W) across three environments (25, 30, 35 °C [all 40% relative humidity]). Clothing was modified between full and minimal injury protection. Both ensembles were tested at 25 °C, with only the more protective ensemble investigated at 30 and 35 °C. At 35 °C, auditory canal temperature rose at 0.02 °C min^?1 (SD 0.005), deviating from all other trials (p < 0.05). The thresholds for moderate (>38.5 °C) and profound hyperthermia (>40.0 °C) were predicted to occur within 105 min (SD 20.6) and 180 min (SD 33.0), respectively. Profound hyperthermia might eventuate in ~10 h at 30 °C, but should not occur at 25 °C. These outcomes demonstrate a need to enhance the heat dissipation capabilities of motorcycle clothing designed for summer use in hot climates, but without compromising impact protection.

Practitioner’s Summary:

Motorcycle protective clothing can be uncomfortably hot during summer. This experiment was designed to evaluate the physiological significance of this burden across climatic states. In the heat, moderate (>38.5 °C) and profound hyperthermia (>40.0 °C) were predicted to occur within 105 and 180 min, respectively.     

Optimal neuronal tuning for finite stimulus spaces

The efficiency of neuronal encoding in sensory and motor systems has been proposed as a first principle governing response properties within the central nervous system. We present a continuation of a theoretical study presented by Zhang and Sejnowski, where the influence of neuronal tuning properties on encoding accuracy is analyzed using information theory. When a finite stimulus space is considered, we show that the encoding accuracy improves with narrow tuning for one- and two-dimensional stimuli. For three dimensions and higher, there is an optimal tuning width.     

Hydration of tricalcium germanate

The hydration characteristics of tricalcium germanate were examined. Kinetics of tricalcium germanate hydration, and hydration product morphologies and compositions were determined at 5 °C intervals between 5 and 70 °C. Complete hydration was rapidly achieved, X-ray diffraction indicated that tricalcium germanate reacted completely within 2 h at all the temperatures investigated. However, a constant value for an Arrhenius activation energy could not be determined. At hydration temperatures above 45 °C a small heat peak, which preceded the main calorimetric peak, appeared in the calorimetric curves. Calcium hydroxide was rarely observed by SEM for hydration at temperatures below 45 °C. Dense regions of calcium hydroxide were readily observed for hydration above this temperature. In contrast to the hydration of tricalcium silicate, an induction period was not observed nor was an extended period of diffusionally controlled reaction. Calcium germanate hydrate was fibrous with the fibre thickness exhibiting a temperature dependence. Hydration product compositions were determined by thermal gravimetry. Expressing the composition of calcium germanate hydrate as (CaO)_3–x GeO₂·nH₂O, the value of 3–x decreases from 1.68 to 1.59 with increasing temperature from 5–70 °C. The values obtained forn varied inconsistently between 2.4 and 3.3. The unit cell of the calcium germanate hydrate was determined to be monoclinic. Cell parameters werea=1.851,b=1.147,c=0.531 nm and =98.10 °.     

The time required for recovery from mixing stress in young bulls and the prevention of dark cutting beef

Two trials were conducted in which a total of twenty-eight Friesian bulls (12 months old) were slaughtered 0, 1, 2, 4, 7, 9 or 10 days after they had been mixed with unfamiliar animals overnight. The resulting behavioural interactions and associated physical activity led to large rises in plasma creatine phosphokinase (CPK) activity and free fatty acid (FFA) concentration and a decrease in plasma lactate. In the second trial the relative number of interactions engaged in by each animal was estimated. Bulls which exhibited the most interactions had the highest levels of plasma CPK and FFA after mixing. Liver and muscle glycogen were depleted by mixing. Animals killed on days 0 and 1 after mixing had low concentrations of liver glycogen compared with animals allowed longer to recover. Concentrations of glycogen in the M. longissimus dorsi (LD) had recovered by day 4 and in the M. psoas by day 2. Muscle glycogen concentrations were reflected in the ultimate pH (pHu) of the meat. All animals killed immediately after mixing produced carcasses with pHu>6. in the LD. By the second day of recovery muscle glycogen stores had been repleted sufficiently so that all animals had muscles with pHu<6. However, the LD from these animals was still very slightly darker than those killed after 7 or more days of recovery although this was probably not commercially significant. It was concluded that, if young bulls from separate rearing groups are mixed before slaughter, either on the farm or during lairage, then they require resting with food for at least 48 h before being killed to ensure that no carcasses are produced with high pHu in the musculature.