Passive Janus Particles Are Self-propelled in Active Nematics

While active systems possess notable potential to form the foundation of new classes of autonomous materials, designing systems that can extract functional work from active surroundings has proven challenging. In this work, we extend these efforts to the realm of designed active liquid crystal/colloidal composites. We propose suspending colloidal particles with Janus anchoring conditions in an active nematic medium. These passive Janus particles become effectively self-propelled once immersed into an active nematic bath. The self-propulsion of passive Janus particles arises from the effective +1/2 topological charge their surface enforces on the surrounding active fluid. We analytically study their dynamics and the orientational dependence on the position of a companion −1/2 defect. We predict that at sufficiently small activity, the colloid and companion defect remain bound to each other, with the defect strongly orienting the colloid to propel either parallel or perpendicular to the nematic. At sufficiently high activity, we predict an unbinding of the colloid/defect pair. This work demonstrates how suspending engineered colloids in active liquid crystals may present a path to extracting activity to drive functionality.

Mortality in Different Mountain Sports Activities Primarily Practiced in the Winter Season—A Narrative Review

Annually, millions of people engage in mountain sports activities all over the world. These activities are associated with health benefits, but concurrently with a risk for injury and death. Knowledge on death rates is considered important for the categorization of high-risk sports in literature and for the development of effective preventive measures. The death risk has been reported to vary across different mountain sports primarily practiced in the summer season. To complete the spectrum, the aim of the present review is to compare mortality rates across different mountain sports activities primarily practiced in winter. A comprehensive literature search was performed on the death risk (mortality) during such activities, i.e., alpine (downhill) skiing, snowboarding, cross-country skiing, ski touring, and sledging. With the exception of ski touring (4.4 deaths per 1 million exposure days), the mortality risk was low across different winter sports, with small activity-specific variation (0.3–0.8 deaths per 1 million exposure days). Traumatic (e.g., falls) and non-traumatic (e.g., cardiac death) incidents and avalanche burial in ski tourers were the predominant causes of death. Preventive measures include the improvement of sport-specific skills and fitness, the use of protective gear, well-targeted and intensive training programs concerning avalanche hazards, and sports-medical counseling for elderly and those with pre-existing diseases.

INFLUENCE OF THE LECTIN LACTOBACILLUS DELBRUECKII ssp. BULGARICUS ON ACTIVITY OF THE PROCESS OF PHAGOCYTOSIS

The effect of Lactobacillus delbrueckii ssp. bulgaricus on the activity of macrophages — peritoneal (PMP) and alveolar (AMP), isolated from the body of white mice at 1, 3, 5, 7 days after the introduction of lectin, in the process of phagocytosis of bacteria Staphylococcus aureus 209-P. In the course of the studies, it was shown that by 6 hours the activity of PMP and AMP isolated within 24 hours after lectin administration had increased by 3.4 and 2.9 times. The PMP and AMP, isolated from the mice for 3 days, showed the greatest activity after 6 hours of incubation with bacterial cells in 1.6 and 2 times in comparison with the control. On day 5, PMP and AMP showed the greatest activity by 6 hours in the process of phagocytosis compared with the control, respectively, in 2.2 and 2.4 times. At day 7, only AMP had the highest activity after 30 minutes of incubation with bacteria 1.5 times in comparison with the control in the process of phagocytosis in vitro by S. aureus 209-P. With respect to PMP, no changes were observed compared to the control. The analysis of the obtained data showed that the activity of macrophages isolated from the organism of mice injected with lectin on days 1, 3, 5 significantly differed from the control values at the final stages of the phagocytosis process of S. aureus 209-P. It can be assumed that the lectin interacting with the surface structures of PMP and AMP on the 1st, 3rd, 5th day of the experiment promotes a more short-term process of adhesion of bacterial cells in phagocytosis. To evaluate the specificity of lectin interaction with receptor structures of macrophages, experiments were conducted with a protein that did not have lectin properties-bovine serum albumin-BSA and lectin blocked by specific carbohydrates. It was shown that the phagocytic activity of macrophages in the presence of BSA was similar to control and did not differ significantly from it. BSA did not influence the completion of bacterial phagocytosis by macrophages. When studying the interaction of lectin blocked by specific carbohydrates on the phagocytic activity of macrophages, there was a slight increase in phagocytic activity against PMP, after 6 hours of phagocytosis and a slight decrease after 0.5 hours, 1 hour and 24 hours of phagocytosis. For AMP, the lectin blocked by a mixture of carbohydrates was similar to the control values. The results obtained made it possible to speak of the specific binding of lectin L. delbrueckii ssp. bulgaricus with surface AMP receptors. However, with respect to PMP, a small activity of macrophages in the process of phagocytosis was observed, which indicates the specific and non-specific binding of lectin L. delbrueckii ssp. bulgaricus with surface TMF receptors. It can be assumed that, at the molecular level, L. delbrueckii ssp. bulgaricus, in addition to a specific interaction with the receptor structures of PMP, can participate in a variety of nonspecific reactions. Thus, the lectin L. delbrueckii ssp. bulgaricus increased the adhesive ability of macrophages of mice, significantly influenced the completeness of the phagocytosis process of bacterial cells. A specific interaction of L. delbrueckii ssp bulgaricus with surface AMP receptors, both specific and non-specific interactions were observed with respect to PMP.

A bibliometric assessment of energy research in South Africa

The results of an effort to identify the performance of energy and fuels research in South Africa during the most recent period (2003–2013) are reported. Bibliometric approaches have been employed in order to assess the field of energy research. Energy research was identified to be improving over time, albeit from a small basis. The field appears to equally emphasise fossil and renewable energy research. Similarly, universities were identified to be producing a subcritical number of energy articles in comparison with international organisations. The relatively small activity in the energy field appears to affect the international collaboration of the field, which is well below the national average. International comparisons in terms of articles per GWH of electricity produced and articles per million population show that South Africa should increase substantially its effort in the field in order to be comparable with other countries.

IMPROVED MECHANICAL PROPERTY OF ELECTRODEPOSITED NANOCRYSTALLINE NICKEL-COBALT ALLOY

A bulk and dense nc Ni -24.7% Co with an average grain size of 15nm was fabricated by a direct current electrodeposition. This Ni -24.7% Co exhibits very high tensile strength of 1813MPa to 2232MPa with relatively good tensile ductility of 6.0%~9.6% under tensile test over a wide strain rate range of 0.417s-1 ~ 1.35×10-5s-1. The combination of high strength and good ductility should be attributed to the increased strain hardening ability induced by the addition of alloying Co element. The interaction of dislocation and grain boundaries is the rate-controlling deformation mechanism controlled in the Ni -24.7% Co based on its high strain rate sensitivity of 0.029 and small activity volume of ~14b3.

Subcellular localization and properties of mouse adrenal C19-steroid 5β-reductase

The localization and some characteristics of mouse adrenal C19-steroid 5 β-reductase were determined by the incubation of subcellular fractions of mouse adrenal tissue with [7 α-3H]androst-4-ene-3,17-dione. This enzyme was present only in the soluble fraction and was NADPH-dependent, although a small activity in the presence of NADH was also detected. The soluble fraction also contained 3α-, 3β- and a small amount of 17 β-hydroxy steroid dehydrogenase. These and other steroid-metabolizing enzymes present in the remaining subcelluar fractions are also described briefly. To measure 5 β-androstane-3,17-dione production by the mouse adrenal soluble fraction, all 5 β products first had to be oxidized to 5 β-androstane-3,17-dione, and the recovery of radio-activity between the substrate androst-4-ene-3,17-dione and product 5 β-androstane-3,17-dione of 96.1 +/-3.2% validated this technique. C19-steroid 5 β-reductase has a pH optimum of 6.5 and at low substrate concentrations the Km and Vmax. for 5 β reduction of [7 α-3H]androst-4-ene-ene-3,17-dione was 2.22 times 10(-6) ±0.48 times 10(-6) M and 450+/- 53 pmol/min per mg of protein respectively. At high substrate concentration, inhibition of the reaction occurred, which was shown to be due to increasing product concentration.