Metal matrix composites and Si3N4 ceramics are very attractive materials for various industry applications due to extremely high hardness and abrasive wear resistance. However because of these ...features they are problematic for the conventional turning process. The machining on a classic lathe still requires special polycrystalline diamond (PCD) or cubic boron nitride (CBN) cutting inserts which are very expensive. In the paper an experimental surface roughness analysis of laser assisted machining (LAM) for two tapes of hard-to-cut materials was presented. In LAM, the surface of work piece is heated directly by a laser beam in order to facilitate, the decohesion of material. Surface analysis concentrates on the influence of laser assisted machining on the surface quality of the silicon nitride ceramic Si3N4 and metal matrix composite (MMC). The effect of the laser assisted machining was compared to the conventional machining. The machining parameters influence on surface roughness parameters was also investigated. The 3D surface topographies were measured using optical surface profiler. The analysis of power spectrum density (PSD) roughness profile were analyzed.
Background: A need exists to determine whether college students engage in sufficient physical activity (PA) using objective methodology. Purpose: Accelerometry-based activity monitors were used to ...evaluate adherence to the U.S. Department of Health and Human Services' 2008 Physical Activity Guidelines for Americans. Methods: College students (N = 168) wore accelerometers for seven consecutive days. Results: The mean total minutes per day of moderate and vigorous PA were 53.9 minutes and 5.2 minutes, respectively, primarily via short intermittent bouts. When examining PA in bouts lasting the recommended minimum of 10 minutes, the average time spent per day in moderate and vigorous PA dropped to 12.5 minutes and 1.4 minutes, respectively. Thus, only 22.0% of the sample accumulated the recommended minimum of 150 minutes per week of sustained moderate-to-vigorous PA. Discussion: The findings suggest that college students intermittingly accumulate substantial moderate PA via lifestyle activities such as walking, but do not adhere to recommendations for prolonged moderate or vigorous PA. Translation to Health Education Practice: The results indicate that health education practitioners at the collegiate level should educate young adults about the increased efficiency and long-term health benefits of meeting PA recommendations by engaging in sustained moderate and vigorous activities.
This report of the BOOST2012 workshop presents the results of four working groups that studied key aspects of jet substructure. We discuss the potential of first-principle QCD calculations to yield a ...precise description of the substructure of jets and study the accuracy of state-of-the-art Monte Carlo tools. Limitations of the experiments’ ability to resolve substructure are evaluated, with a focus on the impact of additional (pile-up) proton proton collisions on jet substructure performance in future LHC operating scenarios. A final section summarizes the lessons learnt from jet substructure analyses in searches for new physics in the production of boosted top quarks.
Over the past decade, a large number of jet substructure observables have been proposed in the literature, and explored at the LHC experiments. Such observables attempt to utilize the internal ...structure of jets in order to distinguish those initiated by quarks, gluons, or by boosted heavy objects, such as top quarks and
W
bosons. This report, originating from and motivated by the BOOST2013 workshop, presents original particle-level studies that aim to improve our understanding of the relationships between jet substructure observables, their complementarity, and their dependence on the underlying jet properties, particularly the jet radius and jet transverse momentum. This is explored in the context of quark/gluon discrimination, boosted
W
boson tagging and boosted top quark tagging.
Catalytic reactivity of Si–H bond of di-, trisiloxanes with allyl chloride in the presence of platinum catalyst has been examined. Hydrosilylation process competes with hydrogen substitution by ...chlorine and/or propenyl group. The effect of the reaction conditions on the yield and selectivity of the number of products has been discussed.
Catalytic reactivity of Si–H bond of di-, trisiloxanes with allyl chloride in the presence of platinum catalyst has been examined. Hydrosilylation process competes with hydrogen substitution by chlorine and/or propenyl group. The effect of the reaction conditions as well as structure of siloxane on the yield and selectivity of the number of products has been discussed. Several consecutive-competitive processes have been identified. The results obtained can be helpful in the study of the catalytic hydropolysiloxanes reactions with allyl derivatives–systems of great practical importance, to produce commercial functionalized silicones.
Anthocyanins belong to the flavonoid family and are ubiquitous in plants, especially in flower petals and fruit peels. We established that anthocyanins isolated from fruits of
Aronia melanocarpa ...markedly inhibited the mutagenic activity of benzo(
a)pyrene and 2-amino fluorene in the Ames test. In the Sister Chromatid Exchanges (SCEs) test with human blood-derived lymphocytes cultured in vitro, a significant decrease of SCEs frequency induced by benzo(
a)pyrene was observed in the presence of anthocyanins. In the case of mitomycin C the effect of anthocyanins on SCEs frequency was smaller but still noticeable. Anthocyanins markedly inhibited the generation and release of superoxide radicals by human grartulocytes. The results suggest that the antimutagenic influence of anthocyanins is exerted mainly by their free-radicals scavenging action as well as by the inhibition of enzymes activating promutagens and converting mutagens to the DNA-reacting derivatives. These preliminary data seem to be important in the aspect of a possible antimutagenic and anticarcinogenic potency of anthocyanins commonly present in fruits and vegetables.
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