Physical characterization of laser interaction and shock generation in laser shock processing: coupled theoretical-experimental analysis

Laser Shock Processing is developing as a key technology for the improvement of surface mechanical and corrosion resistance properties of metals due to its ability to introduce intense compressive residual stresses fields into high elastic limit materials by means of an intense laser driven shock wave generated by laser with intensities exceeding the 109 W/cm2 threshold, pulse energies in the range of 1 Joule and interaction times in the range of several ns. However, because of the relatively difficult-to-describe physics of shock wave formation in plasma following laser-matter interaction in solid state, only limited knowledge is available in the way of full comprehension and predictive assessment of the characteristic physical processes and material transformations with a specific consideration of real material properties. In the present paper, an account of the physical issues dominating the development of LSP processes from a moderately high intensity laser-matter interaction point of view is presented along with the theoretical and computational methods developed by the authors for their predictive assessment and new experimental contrast results obtained at laboratory scale.

Physical characterization of laser interaction and shock generation in laser processing: coupled theoretical-experimental analysis

Outline: • Introduction • Fundamental Physics of the Laser-Plasma Interaction in Laser Shock Processing • Theoretical/Computational Model Description • Some Results. Analysis of Interaction Parameters • Experimental Validation. Diagnosis Setup • Discussion and Outlook

Multistability, chaos, and random signal generation in semiconductor superlattices

Peer reviewed

Field theory in superfluid 3He: What are the lessons for particle physics, gravity, and high-temperature superconductivity?

There are several classes of homogeneous Fermi systems that are characterized by the topology of the energy spectrum of fermionic quasiparticles: (i) gapless systems with a Fermi surface, (ii) systems with a gap in their spectrum, (iii) gapless systems with topologically stable point nodes (Fermi points), and (iv) gapless systems with topologically unstable lines of nodes (Fermi lines). Superfluid 3He-A and electroweak vacuum belong to the universality class 3. The fermionic quasiparticles (particles) in this class are chiral: they are left-handed or right-handed. The collective bosonic modes of systems of class 3 are the effective gauge and gravitational fields. The great advantage of superfluid 3He-A is that we can perform experiments by using this condensed matter and thereby simulate many phenomena in high energy physics, including axial anomaly, baryoproduction, and magnetogenesis. 3He-A textures induce a nontrivial effective metrics of the space, where the free quasiparticles move along geodesics. With 3He-A one can simulate event horizons, Hawking radiation, rotating vacuum, etc. High-temperature superconductors are believed to belong to class 4. They have gapless fermionic quasiparticles with a “relativistic” spectrum close to gap nodes, which allows application of ideas developed for superfluid 3He-A.

Predicting crossover generation in DNA shuffling

We introduce a quantitative framework for assessing the generation of crossovers in DNA shuffling experiments. The approach uses free energy calculations and complete sequence information to model the annealing process. Statistics obtained for the annealing events then are combined with a reassembly algorithm to infer crossover allocation in the reassembled sequences. The fraction of reassembled sequences containing zero, one, two, or more crossovers and the probability that a given nucleotide position in a reassembled sequence is the site of a crossover event are estimated. Comparisons of the predictions against experimental data for five example systems demonstrate good agreement despite the fact that no adjustable parameters are used. An in silico case study of a set of 12 subtilases examines the effect of fragmentation length, annealing temperature, sequence identity and number of shuffled sequences on the number, type, and distribution of crossovers. A computational verification of crossover aggregation in regions of near-perfect sequence identity and the presence of synergistic reassembly in family DNA shuffling is obtained.

Role of cortical N-methyl-D-aspartate receptors in auditory sensory memory and mismatch negativity generation: implications for schizophrenia.

Working memory refers to the ability of the brain to store and manipulate information over brief time periods, ranging from seconds to minutes. As opposed to long-term memory, which is critically dependent upon hippocampal processing, critical substrates for working memory are distributed in a modality-specific fashion throughout cortex. N-methyl-D-aspartate (NMDA) receptors play a crucial role in the initiation of long-term memory. Neurochemical mechanisms underlying the transient memory storage required for working memory, however, remain obscure. Auditory sensory memory, which refers to the ability of the brain to retain transient representations of the physical features (e.g., pitch) of simple auditory stimuli for periods of up to approximately 30 sec, represents one of the simplest components of the brain working memory system. Functioning of the auditory sensory memory system is indexed by the generation of a well-defined event-related potential, termed mismatch negativity (MMN). MMN can thus be used as an objective index of auditory sensory memory functioning and a probe for investigating underlying neurochemical mechanisms. Monkeys generate cortical activity in response to deviant stimuli that closely resembles human MMN. This study uses a combination of intracortical recording and pharmacological micromanipulations in awake monkeys to demonstrate that both competitive and noncompetitive NMDA antagonists block the generation of MMN without affecting prior obligatory activity in primary auditory cortex. These findings suggest that, on a neurophysiological level, MMN represents selective current flow through open, unblocked NMDA channels. Furthermore, they suggest a crucial role of cortical NMDA receptors in the assessment of stimulus familiarity/unfamiliarity, which is a key process underlying working memory performance.

Nonuniformity of the constitutive law parameters for shear rupture and quasistatic nucleation to dynamic rupture: a physical model of earthquake generation processes.

Based on the recent high-resolution laboratory experiments on propagating shear rupture, the constitutive law that governs shear rupture processes is discussed in view of the physical principles and constraints, and a specific constitutive law is proposed for shear rupture. It is demonstrated that nonuniform distributions of the constitutive law parameters on the fault are necessary for creating the nucleation process, which consists of two phases: (i) a stable, quasistatic phase, and (ii) the subsequent accelerating phase. Physical models of the breakdown zone and the nucleation zone are presented for shear rupture in the brittle regime. The constitutive law for shear rupture explicitly includes a scaling parameter Dc that enables one to give a common interpretation to both small scale rupture in the laboratory and large scale rupture as earthquake source in the Earth. Both the breakdown zone size Xc and the nucleation zone size L are prescribed and scaled by Dc, which in turn is prescribed by a characteristic length lambda c representing geometrical irregularities of the fault. The models presented here make it possible to understand the earthquake generation process from nucleation to unstable, dynamic rupture propagation in terms of physics. Since the nucleation process itself is an immediate earthquake precursor, deep understanding of the nucleation process in terms of physics is crucial for the short-term (or immediate) earthquake prediction.

(Table 1) Chemical composition of interstitial waters from the area of gas hydrate generation, Sea of Okhotsk

Distributions of halogens (Cl, Br and I) in interstitial waters from sediments containing methane hydrate and in water of the hydrate itself are presented. High concentrations of halogens do not occur in interstitial waters from sediments that contain gas hydrates. The main reason for their low concentrations is the poverty of organic matter in sediments.

Reconstruction of SN1987a event

IMB (Irvine, Michigan, Brookline), a collaboration between the University of Michigan, the University of California at Irvine, and the U.S. Department of Energy, was an experiment designed to determine the ultimate stability of matter. Using data from the PMT hits (bl003799) the neutrino interaction point and direction in the detector are shown (long purple line). The produced position (short purple line) is also shown along with its cherenkov cone hitting the walls of the detector (yellow squares).

Artificial event

IMB (Irvine, Michigan, Brookline), a collaboration between the University of Michigan, the University of California at Irvine, and the U.S. Department of Energy, was an experiment designed to determine the ultimate stability of matter. Computer display of PMT [photomultiplier tubes] hits from simulated event based on neutrino interatction seen in Gargamelle bubble chamber.

Artificial event

IMB (Irvine, Michigan, Brookline), a collaboration between the University of Michigan, the University of California at Irvine, and the U.S. Department of Energy, was an experiment designed to determine the ultimate stability of matter. Computer display of simulated proton decay info (...) mode

Artificial event

IMB (Irvine, Michigan, Brookline), a collaboration between the University of Michigan, the University of California at Irvine, and the U.S. Department of Energy, was an experiment designed to determine the ultimate stability of matter. Computer display of simulated event based on Gargamelle (...) event produced by neutrino interaction.

Event no. 143

IMB (Irvine, Michigan, Brookline), a collaboration between the University of Michigan, the University of California at Irvine, and the U.S. Department of Energy, was an experiment designed to determine the ultimate stability of matter. One of nine interesting events from the IMB detector in its first 204 live days of running. Similar to proton decay but rejected.

Event no. 225

IMB (Irvine, Michigan, Brookline), a collaboration between the University of Michigan, the University of California at Irvine, and the U.S. Department of Energy, was an experiment designed to determine the ultimate stability of matter. One of nine interesting events from the IMB detector in its first 204 live days of running. Similar to proton decay but rejected.

Event no. 299

IMB (Irvine, Michigan, Brookline), a collaboration between the University of Michigan, the University of California at Irvine, and the U.S. Department of Energy, was an experiment designed to determine the ultimate stability of matter. One of nine interesting events from the IMB detector in its first 204 live days of running. Similar to proton decay but rejected.