The MuCap experiment at the Paul Scherrer Institute has measured the rate Λ(S) of muon capture from the singlet state of the muonic hydrogen atom to a precision of 1%. A muon beam was stopped in a ...time projection chamber filled with 10-bar, ultrapure hydrogen gas. Cylindrical wire chambers and a segmented scintillator barrel detected electrons from muon decay. Λ(S) is determined from the difference between the μ(-) disappearance rate in hydrogen and the free muon decay rate. The result is based on the analysis of 1.2 × 10(10) μ(-) decays, from which we extract the capture rate Λ(S) = (714.9 ± 5.4(stat) ± 5.1(syst)) s(-1) and derive the proton's pseudoscalar coupling g(P)(q(0)(2) = -0.88 m(μ)(2)) = 8.06 ± 0.55.
Advancing phenology is one of the most visible effects of climate change on plant communities, and has been especially pronounced in temperature-limited tundra ecosystems. However, phenological ...responses have been shown to differ greatly between species, with some species shifting phenology more than others. We analysed a database of 42,689 tundra plant phenological observations to show that warmer temperatures are leading to a contraction of community-level flowering seasons in tundra ecosystems due to a greater advancement in the flowering times of late-flowering species than early-flowering species. Shorter flowering seasons with a changing climate have the potential to alter trophic interactions in tundra ecosystems. Interestingly, these findings differ from those of warmer ecosystems, where early-flowering species have been found to be more sensitive to temperature change, suggesting that community-level phenological responses to warming can vary greatly between biomes.
Rapid climate warming is altering Arctic and alpine tundra ecosystem structure and function, including shifts in plant phenology. While the advancement of green up and flowering are well-documented, ...it remains unclear whether all phenophases, particularly those later in the season, will shift in unison or respond divergently to warming. Here, we present the largest synthesis to our knowledge of experimental warming effects on tundra plant phenology from the International Tundra Experiment. We examine the effect of warming on a suite of season-wide plant phenophases. Results challenge the expectation that all phenophases will advance in unison to warming. Instead, we find that experimental warming caused: (1) larger phenological shifts in reproductive versus vegetative phenophases and (2) advanced reproductive phenophases and green up but delayed leaf senescence which translated to a lengthening of the growing season by approximately 3%. Patterns were consistent across sites, plant species and over time. The advancement of reproductive seasons and lengthening of growing seasons may have significant consequences for trophic interactions and ecosystem function across the tundra.
The TixZr1-xC solid solutions were synthesized by electro-thermal explosion under pressure in the (Ti + Zr + C) blends mechanically activated in hexane (MA-ETE). The effect of mechanical activation ...(MA) duration on reaction blend characteristics, ETE parameters, phase composition, and microstructure formation in solid solutions was investigated. At MA, the Ti + Zr blend deforms metal crystal lattices for 20 min, complete amorphization occurs for 40 min, and the carbide grains form a cubic structure for 90 min. The single-phase Zr0.50Ti0.50C solid solution with a grain size of 3–5 μm and a submicron composite with a grain size of 0.1–0.2 μm containing the Ti0.86Zr0.14C and Zr0.74Ti0.26C solid solutions were synthesized in a one-stage process for the first time without any additional thermotreatment. The influence of mechanical activation on diffusional mass transfer of reactants, structure, and phase formation is discussed.
The rate of nuclear muon capture by the proton has been measured using a new technique based on a time projection chamber operating in ultraclean, deuterium-depleted hydrogen gas, which is key to ...avoiding uncertainties from muonic molecule formation. The capture rate from the hyperfine singlet ground state of the microp atom was obtained from the difference between the micro(-) disappearance rate in hydrogen and the world average for the micro(+) decay rate, yielding Lambda(S)=725.0+/-17.4 s(-1), from which the induced pseudoscalar coupling of the nucleon, g(P)(q(2)=-0.88m(2)(micro))=7.3+/-1.1, is extracted.
Ultra-high-temperature TiC–ZrC composites with submicron structure were synthesized by electro-thermal explosion (ETE) under pressure. The precursors for synthesis were prepared from a mixture ...containing Ti, Zr, and carbon black powders by high energy ball milling in hexane. The influence of mechanical activation (MA) on the metal crystalline structure was studied. It was shown that the phase composition of the precursor depends on MA duration. The partial amorphization of metal particles occurred after 40 min of MA; while after 90 min, the amorphization was completed. In the last case, carbide phase crystallites with a cubic structure were formed. It was shown that the composite synthesized from precursor activated for 40 min contains Zr
0.50
Ti
0.50
C single-phase solid solution with a grain size of 3–5 μm, while the composite synthesized from precursor activated for 90 min consists of Zr
0.14
Ti
0.86
C and Zr
0.74
Ti
0.26
C phases with a grain size of about 0.2 μm. The Vickers hardness of composites with a residual porosity of no more than 10% was found to be in the range from 11.3 to 18.53 GPa.
The work scrutinizes the main directions of improving conventional methods of arc, plasma and electroslag welding and cladding that are based on the algorithms of adaptive pulsed control of energetic ...parameters of the process. The deliverables demonstrate that the adaptive pulsed technologies feature a range of undeniable advantages against conventional methods that implement a strictly specified program for changing main energetic parameters of the process. The treatise justifies the main principles of adaptive technologies that ensure stability of heat and mass transfer and production of permanent joints of demanded quality under various disturbances affecting the system: power source, arc, weld pool, product.
The paper presents the investigation results of the heat and mass transfer kinetics during shielded metal arc welding (SMAW). It is shown that instability of the electrode melting and metal transfer ...to the molten pool is mostly caused by a system of forces acting on the metal droplet at the continuous electrode tip. Experiments show that the process instability and spatter of the electrode metal depend on the energy parameters of the SMAW mode. At the same time, the SMAW technology can be significantly improved through the implementation of the energy parameter control by the adaptive pulsed-arc welding method.
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