Suitability of lyocell fiber for pillow fillings

The choice of a comfortable pillow is essential for good sleep. The filling material for pillows should be bulky, resilient and comfortable. For reasons of price, availability and resilience, polyester is the most commonly used filling material. Its drawbacks, however, lie in poor moisture management and a lack of biodegradability. This is the first study of the physical and microclimate properties of pillows with carded filling containing lyocell fiber. Pillow samples were manufactured on an industrial production line. Their carded fillings were rolled and comprised either 30% or 50% lyocell, blended with polyester (virgin and recycled), high elastic triexta and biodegradable polylactide fibers. In simulated sleeping conditions, using a thermal sweating manikin, it was proven that pillows with fillings made of 50% lyocell blended with polyester demonstrated an enhanced microclimate through much better moisture management than pillows with fillings made from pure polyester. It was also found, under use and care conditions, that lyocell affected the sensorial properties of pillows. Pillow form stability and height regain correlated with lyocell’s linear density. A higher lyocell content (50%) improved the form-keeping characteristics of pillows after repeated washing and drying. The type of lyocell used had only a minor effect on the compression resilience of the filling and perception of pillow firmness. The evaluators perceived higher pillows as firmer. The developed new methods for the evaluation of pillow quality and the results of this study can be of practical relevance in the bedding industry, where the reduction of non-biodegradable raw material is strategically important.

Effects of simulated weightlessness on thermal sweating of human body: An experimental study

Thermal sweating is the thermoregulatory activity of the human body in hot and warm environments, which is critical to the human thermal comfort and health. The sweating of a human body in a real weightlessness environment has seldom been researched, and simulated weightlessness has usually been conducted under comfortable environments. In order to study the sweating of the human body under weightlessness, a 7-day −6° head down bed rest experiment was carried out on six male subjects lying on their backs to simulate the physiological changes that occur under a weightless environment. The skin microcurrents of the subjects were recorded to evaluate sweating under a range of environments. The results showed that sweating was more significant in the torso and head areas than on the arms and lower body. The whole body sweat rates of subjects were lower than those before the simulated weightlessness experiment. However, the threshold air temperature for the onset of sweating under simulated weightlessness was higher than that before the simulation. This was possibly due to the raising of thermoregulatory set-point temperature of the body. Findings have shown that the sweating behaviour and thermal response of a male human body in a weightless environment could be different to those in the terrestrial condition.

Brain stem representation of thermal and psychogenic sweating in humans

Functional MRI was used to identify regions in the human brain stem activated during thermal and psychogenic sweating. Two groups of healthy participants aged 34.4 ± 10.2 and 35.3 ± 11.8 years (both groups comprising 1 woman and 10 men) were either heated by a water-perfused tube suit or subjected to a Stroop test, while they lay supine with their head in a 3-T MRI scanner. Sweating events were recorded as electrodermal responses (increases in AC conductance) from the palmar surfaces of fingers. Each experimental session consisted of two 7.9-min runs, during which a mean of 7.3 ± 2.1 and 10.2 ± 2.5 irregular sweating events occurred during psychogenic (Stroop test) and thermal sweating, respectively. The electrodermal waveform was used as the regressor in each subject and run to identify brain stem clusters with significantly correlated blood oxygen level-dependent signals in the group mean data. Clusters of significant activation were found with both psychogenic and thermal sweating, but a voxelwise comparison revealed no brain stem cluster whose signal differed significantly between the two conditions. Bilaterally symmetric regions that were activated by both psychogenic and thermal sweating were identified in the rostral lateral midbrain and in the rostral lateral medulla. The latter site, between the facial nuclei and pyramidal tracts, corresponds to a neuron group found to drive sweating in animals. These studies have identified the brain stem regions that are activated with sweating in humans and indicate that common descending pathways may mediate both thermal and psychogenic sweating.