Impact tests of low-alloy martensitic-bainitic steel AB2 showed that the scale of dynamic deformation and the fracture mechanism change in a threshold manner. The change in the mechanism and scale of ...fracture is triggered by the resonant excitation of large-scale structural elements of the material (grain conglomerates) due to plastic flow oscillations. In this case, the grain-boundary mechanism of dynamic fracture is replaced by a transcrystalline one. Beyond the strain rate threshold, mesoscopic elementary carriers of dynamic deformation are divided into two groups: low-velocity and high-velocity. Accordingly, the velocity distribution of mesoparticles shows two humps. The velocity spread of mesoparticles sharply increases under these conditions, while the mass velocity defect (change in the shock wave amplitude) becomes negative. The latter fact indicates the local acceleration of mesoparticles in discrete regions of the target (the so-called shooting of mesoparticles in the shock wave direction). Transcrystalline cracks are randomly distributed throughout the specimen and have a random orientation.
We have performed the most comprehensive resonance-model fit of π−π−π+ states using the results of our previously published partial-wave analysis (PWA) of a large data set of diffractive-dissociation ...events from the reaction π−+p→π−π−π++precoil with a 190 GeV/c pion beam. The PWA results, which were obtained in 100 bins of three-pion mass, 0.5<m3π<2.5 GeV/c2, and simultaneously in 11 bins of the reduced four-momentum transfer squared, 0.1<t′<1.0 (GeV/c)2, are subjected to a resonance-model fit using Breit-Wigner amplitudes to simultaneously describe a subset of 14 selected waves using 11 isovector light-meson states with JPC=0−+, 1++, 2++, 2−+, 4++, and spin-exotic 1−+ quantum numbers. The model contains the well-known resonances π(1800), a1(1260), a2(1320), π2(1670), π2(1880), and a4(2040). In addition, it includes the disputed π1(1600), the excited states a1(1640), a2(1700), and π2(2005), as well as the resonancelike a1(1420). We measure the resonance parameters mass and width of these objects by combining the information from the PWA results obtained in the 11 t′ bins. We extract the relative branching fractions of the ρ(770)π and f2(1270)π decays of a2(1320) and a4(2040), where the former one is measured for the first time. In a novel approach, we extract the t′ dependence of the intensity of the resonances and of their phases. The t′ dependence of the intensities of most resonances differs distinctly from the t′ dependence of the nonresonant components. For the first time, we determine the t′ dependence of the phases of the production amplitudes and confirm that the production mechanism of the Pomeron exchange is common to all resonances. We have performed extensive systematic studies on the model dependence and correlations of the measured physical parameters.
To study the processes of multiscale structure formation far from thermodynamic equilibrium, a series of experiments concerning impact loading of aluminum alloy targets has been carried out by ...nanosecond pulses initiated by a propelling device and a pulsed electron beam. In both cases, large-scale structures of the mesoscopic level have been revealed in the near-contact region of shock loading, the sizes of which decrease with increasing target thickness, while the target material becomes homogeneous. Transition to a homogeneous structure in aluminum 1565 occurs at a target thickness of 2.2 mm with simultaneous change in the macroscopic response (spall strength) of the material for impact loading.
Among the species of the genus
Crotalaria
L.,
Crotalaria juncea
is the only cover crop cultivated for its fiber. The quality of the latter depends on the nutritional conditions, accumulation of ...biophilic elements in the biomass, and synthesis of proteinogenic amino acids. Thus, the purpose of this study was a qualitative and quantitative assessment of the green harvest at the active flowering stage, before the bean formation phase, when the entire biochemical cycle of the plant is reconfigured, and the biochemical indicators are maximum. The plants were grown for 140 days (from April 22 to September 9, 2023) in protected soil conditions. The experimental design consisted of two units of 50 plants each: in the first (control) unit, plants were grown in a soil mixture without any additives; in the second one, they were treated three times during the growing season with an organic suspension of humic acids (1000 ppm) obtained from sapropel (Pskov oblast, UDHSS) by applying it when watering at the root. The soil substrate in both cases was typical chernozem (Kamennaya Steppe Nature Reserve, Voronezh oblast, 51°01′41.6″ N, 40°43′39.3″ E) with a 20% addition of volcanic zeolite. Over the course of every 14 days, morphometric trends of the crop growth (height and dry biomass) were systematically recorded with the removal of five cultivars from each unit of options. After 140 days, the remaining five replicates per option were subjected to biochemical analysis by inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography (HPLC) using the 7500 and LC 1200 devices (Agilent Technologies, United States) according to the manufacturer’s method. Treatment with UDHSS increased productivity and shoot height by 51.1% and 11.3%, respectively. The microelement concentration order in the dry biomass was as follows: Na > K > Ca > S > P > Mg in the control option and Na > K > Ca > Mg > P > S in the UDHSS option, while the microelement export was observed as Fe > Mn > Zn > Ba > B > Cu > Mo and Fe > Mn > B > Zn > Ba > Cu > Mo. In total, the increase was more evident in the microelement accumulation due to a twofold increase in the concentration of iron ions. As for amino acids, L-lysine, L-glycine, L-glutamine, and L-tyrosine became higher. The first three are structural components of biological tissues indirectly indicative of an increase in the fiber strength of the plant culture.
Threshold modes of multiscale dynamic deformation were identified for 1561 aluminum alloy by conducting two series of impact tests in the velocity range of 250–750 m/s: under uniaxial deformation and ...with high-speed penetration of elongated impactors. It was found that the scale of deformation changes at the same strain rate in the spall fracture zone under uniaxial deformation and on the lateral cavity face during impactor penetration. The scale changes due to resonant interaction between oscillations of plastic flow and structural elements of the deformed material. A constitutive equation was derived for multiscale dynamic deformation, and a transport equation was obtained to describe energy exchange between the scale levels. The transition of dynamic deformation to a larger scale level was shown to reduce the resistance to the high-speed penetration of elongated impactors.
Four brittle materials are subjected to shock tests: gabbrodiabase, two modifications of cast iron, fused quartz, and beryllium. An interferometer is used to locally probe a free surface in order to ...calculate its velocity, thereby determining the criterion of the initial stage of brittle fracture of all materials tested—the formation of horizontal steps at the forefront of a compression pulse, which indicate the presence of local sources of fracture of the material. It is determined that the brittle material resists the shock compression as long as it has the reversible transfer of momentum and energy of the processes occurring at meso- and macrolevels.
To identify threshold structuring regimes, two series of tests of 1565 aluminum alloy were conducted in the speed range of 250–750 m/s: impact tests under uniaxial deformation and penetration of ...impactors. Comparison of the results of both series of tests enables the separation of the drag in the interaction of an elongated impactor with a target from the friction resistance with its side part. The structuring scale changes twice on the lateral surface of the cavity—at speeds of 400 and 623.3 m/s—and the second structuring threshold almost coincides with the same threshold under loading under uniaxial deformation.
We have searched for exclusive production of exotic charmonia in the reaction μ+N→μ+(J/ψπ+π−)π±N′ using COMPASS data collected with incoming muons of 160 GeV/c and 200 GeV/c momentum. In the J/ψπ+π− ...mass distribution we observe a signal with a statistical significance of 4.1 σ. Its mass and width are consistent with those of the X(3872). The shape of the π+π− mass distribution from the observed decay into J/ψπ+π− shows disagreement with previous observations for X(3872). The observed signal may be interpreted as a possible evidence of a new charmonium state. It could be associated with a neutral partner of X(3872) with C=−1 predicted by a tetraquark model. The product of cross section and branching fraction of the decay of the observed state into J/ψπ+π− is determined to be 71±28(stat)±39(syst) pb.
The COMPASS Collaboration experiment recently discovered a new isovector resonancelike signal with axial-vector quantum numbers, the a1( 1420 ) , decaying to f0( 980 ) π . With a mass too close to ...and a width smaller than the axial-vector ground state a1( 1260 ) , it was immediately interpreted as a new light exotic meson, similar to the X , Y , Z states in the hidden-charm sector. We show that a resonancelike signal fully matching the experimental data is produced by the decay of the a1( 1260 ) resonance into K∗( → K π ) ¯ K and subsequent rescattering through a triangle singularity into the coupled f0( 980 ) π channel. The amplitude for this process is calculated using a new approach based on dispersion relations. The triangle-singularity model is fitted to the partial-wave data of the COMPASS experiment. Despite having fewer parameters, this fit shows a slightly better quality than the one using a resonance hypothesis and thus eliminates the need for an additional resonance in order to describe the data. We thereby demonstrate for the first time in the light-meson sector that a resonancelike structure in the experimental data can be described by rescattering through a triangle singularity, providing evidence for a genuine three-body effect.
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