Influence of acetylene on methane-air explosion characteristics in a confined chamber.

To study the impact of acetylene on methane explosions, the safe operation of coal mines should be ensured. In this paper, a 20 L spherical tank was used to study the explosive characteristics of acetylene-methane-air mixture. In addition, the GRI-Mech3.0 mechanism was used to study the chemical kinetic mechanism for the mixed gas, and the effect of adding acetylene on the sensitivity of methane and the yield of free radicals was analysed. The results show that acetylene can expand the scope for methane explosion, lower the lower explosion limit, and increase the risk of explosion. Acetylene increases the maximum explosion pressure, laminar combustion rate and maximum pressure rise rate for the methane-air mixture while shortening the combustion time. Three combustion modes for the acetylene-methane-air mixture were determined: methane-dominated, transitional and acetylene-dominated combustion modes. Chemical kinetic analysis for the mixed gas shows that as the volume fraction of acetylene increases, the generation rate for key free radicals (H*, O* and OH*) gradually increases, thereby increasing the intensity of the explosive reaction. The results from this research will help formulate measures to prevent coal mine explosion accidents.

Adaptation to exercise-induced stress is not dependent on cardiomyocyte α1A-adrenergic receptors.

The 'fight or flight' response to physiological stress involves sympathetic nervous system activation, catecholamine release and adrenergic receptor stimulation. In the heart, this induces positive inotropy, previously attributed to the ß1-adrenergic receptor subtype. However, the role of the α1A-adrenergic receptor, which has been suggested to be protective in cardiac pathology, has not been investigated in the setting of physiological stress. To explore this, we developed a tamoxifen-inducible, cardiomyocyte-specific α1A-adrenergic receptor knock-down mouse model, challenged mice to four weeks of endurance swim training and assessed cardiac outcomes. With 4-OH tamoxifen treatment, expression of the α1A-adrenergic receptor was knocked down by 80-89%, without any compensatory changes in the expression of other adrenergic receptors, or changes to baseline cardiac structure and function. Swim training caused eccentric hypertrophy, regardless of genotype, demonstrated by an increase in heart weight/tibia length ratio (30% and 22% in vehicle- and tamoxifen-treated animals, respectively) and an increase in left ventricular end diastolic volume (30% and 24% in vehicle- and tamoxifen-treated animals, respectively) without any change in the wall thickness/chamber radius ratio. Consistent with physiological hypertrophy, there was no increase in fetal gene program (Myh7, Nppa, Nppb or Acta1) expression. In response to exercise-induced volume overload, stroke volume (39% and 30% in vehicle- and tamoxifen-treated animals, respectively), cardiac output/tibia length ratio (41% in vehicle-treated animals) and stroke work (61% and 33% in vehicle- and tamoxifen-treated animals, respectively) increased, regardless of genotype. These findings demonstrate that cardiomyocyte α1A-adrenergic receptors are not necessary for cardiac adaptation to endurance exercise stress and their acute ablation is not deleterious.

Rapid selection of environmentally friendly layered alkaline-earth metal phosphates as solid lubricants using crystallographic data.

Lubricating technologies are essential for saving energy and identifying effective, environmentally friendly layered materials that meet the demands of solid lubricants is an important direction. Herein, we probed the relationships between load-carrying capacity and crystal structure. The results showed that increasing the sliding resistance of interlayers using corrugated layers increased the load-carrying capacity of layered solid lubricants. This finding expands on the traditional lubrication mechanism of layered materials. Following the rules, rapid selection of layered potassium magnesium and calcium phosphates (K-LMP and K-LCP) as effective solid lubricants was achieved using crystallographic data and strict filtering criteria. In order to prepare materials suitable for lubrication, the synthesis of K-LMP and K-LCP was optimised. These materials could be utilised in the food, textile or marine machinery industries in the future. The developed method could successfully guide the synthesis of application-oriented materials.