Simultaneous Decay Research Articles

Inflation from a tachyon fluid?

Motivated by recent works of Sen [hep-th/0203211, hep-th/0203265] and Gibbons [hep-th/0204008], we study the evolution of a flat and homogeneous universe dominated by tachyon matter. In particular, we analyze the necessary conditions for inflation in the early roll of a single tachyon field. Comparison with string theory reveals that the potential is too steep to explain the fluctuations in the CMBR. We suggest a scenario based on the simultaneous decay of many branes and comment on the issue of reheating of the universe after tachyon rolling.

Transient absorption and photovoltage study of‘ self-assembled bacteriorhodopsin/polycation multilayer films

A series of organized (PDAC/PM) n (poly(diallyldimethylammonium chloride)/purple membrane) multilayer films were prepared by alternate adsorptions of positively charged PDAC polyelectrolyte and negatively charged purple membrane (PM). The kinetics of the photocycle of bacteriorhodopsin (bR) in PM was studied by flash photolysis and transient photovoltage methods. Although the orientation of the adsorbed bR depends on the pH of the PM suspension, the kinetics of the photo-induced reaction cycle in dehydrated films is independent of the deposition pH. In dry (PDAC/PM) n films the decay of the M intermediate to the initial bR state is multiexponential and delayed to several minutes for both orientations. A simultaneous two-exponential decay in millisecond time domain was observed at red wavelengths. The source of the red-shifted absorption is suggested to be the C 610 intermediate of the cis photocycle of bR.

Electrochemical impedance spectroscopy as a probe for wet chemical silicon oxide characterization

The kinetics of the chemical growth of silicon oxide in H2O2-containing ammonia solutions and its break-up by dilute ammonia solutions was investigated using electrochemical techniques and more specifically electrochemical impedance spectroscopy. The recording of the open circuit potential (OCP), complemented by successive impedance diagrams, demonstrates clearly the build-up of a silicon oxide passivating layer when hydrophobic Si surfaces are immersed in NH3+H2O2 solutions. The thickening of the chemical oxide coating mainly results in the decrease of the capacitance value together with the enhancement of the ohmic surface resistance. On the other hand, pure ammonia dilute solutions lead to the progressive destruction of this hydrophilic passivating surface oxide, which is revealed by the simultaneous decay of the real component of the impedance. Finally, we observed the break-up of the passive layer, characterized by a sudden drop of the OCP to a value quite identical to that obtained with a bare Si surface. This process resulted in a dramatic corrosion of the substrate surface.

Analysis of internal transport barrier heat diffusivity from heat pulsepropagation induced by an ITB event in JT-60U reverseshear plasmas

Internal transport barrier (ITB) formation in the positive shear zone ofreverse shear (RS) plasmas in the JT-60U tokamak is described as a series ofITB events, which are abrupt in time and widein space variations of heat diffusivity, observed as the simultaneous rise and decay of the electrontemperature Te in two zones. A new source of heat pulse propagation(HPP) is found in RS plasmas. HPP is created by an ITB event. For the last ITBevent described in the present paper, the region of strong(~20 keV s-1) Te rise is initially well localized(~4 cm) in space. Later, a slow diffusive broadening of the risingTe perturbation is seen. Outward HPP is analysed in the region with~8 cm width fully located in the positive shear space zone. Values ofthe electron dynamic heat diffusivity as low as ~0.1 m2 s-1 arefound. A similar low value of the ion dynamic heat diffusivity (close to theneoclassical value) is obtained for ion HPP. An important consequence of HPPanalysis is the absence of electron and ion `heat pinch' in the ITB region.

Decay of a Resonance in 18Ne by the Simultaneous Emission of Two Protons.

Radioactive ion beams of 17F were used to study several resonance states in 18Ne. Clear evidence for simultaneous two-proton emission from the 6.15 MeV state (Jpi = 1(-)) in 18Ne has been observed with the reaction 17F+1H. Because of limited angular coverage, the data did not differentiate between the two possible mechanisms of simultaneous decay, diproton (2He) emission or direct three-body decay. The two-proton partial width was found to be 21+/-3 eV assuming 2He emission and 57+/-6 eV assuming three-body decay. The total width of the 1(-) state was measured to be 50+/-5 keV. Several additional resonances that decay by single proton emission were also studied.

Theoretical feasibility study of new high-efficiency continuous-wave lasers operating at electron transitions in the spectral regions from near ir to uv on the basis of unconventional mechanisms of forming the active gaseous media

This paper is a review of the results of theoretical studies related to the search for new mechanisms, which are not yet completely understood and have not been implemented so far, of forming the active laser media that offer the prospect of development of high-efficiency continuous-wave (cw) laser operating at electron transitions (in atoms or molecules) in a wide range of wavelengths (from near IR to UV). The main attention is paid to unconventional mechanisms of forming the population inversion of lasing-active levels. These mechanisms involve the intramultiplet (due to collisions with heavy particles) or ionization-induced (due to collisions with electrons) deactivation of the lowest lasing-active atomic level; the population of the upper lasing-active level as a result of three-body electron-ion recombination induced by the presence of alkali impurity, with simultaneous intramultiplet decay of the lower level; the mechanism ensuring the lasing transitions between repulsing terms of the involved molecules; and the exchange of vibrational-electronic excitation (for example, exchange of two vibrational quanta of an excited hydrogen molecule for a single electronic quantum of the iodine atom).

Metastability in Josephson transmission lines

Thermal activation and macroscopic quantum tunneling in current-biased discrete Josephson transmission lines are studied theoretically. The degrees of freedom under consideration are the phases across the junctions which are coupled to each other via the inductances of the system. The resistively shunted junctions that we investigate constitute a system of N interacting degrees of freedom with an overdamped dynamics. We calculate the decay rate within exponential accuracy as a function of temperature and current. Slightly below the critical current, the decay from the metastable state occurs via a unique (rigid) saddle-point solution of the Euclidean action describing the simultaneous decay of the phases in all the junctions. When the current is reduced, a crossover to a regime takes place, where the decay occurs via an elastic saddle-point solution and the phases across the junctions leave the metastable state one after another. This leads to an increased decay rate compared with the rigid case both in the thermal and the quantum regime. The rigid-to-elastic crossover can be sharp or smooth analogous to first- or second-order phase transitions, respectively. The various regimes are summarized in a current-temperature decay diagram.

Vibronic state specific predissociation rates from excited electronic states

It is shown that predissociation can be perceived as a primary process due to the continuum part of a Morse oscillator potential. In the model proposed here internal conversion to the ground state is thus not necessarily the primary process of a consecutive dissociation but may be a simultaneous decay. As a consequence, dissociation rates should show strong variations from specific (ro-) vibrational states of the first excited electronic states that are similar to those known from “pure” internal conversion rates. This behaviour is demonstrated by calculating predissociation rates for the \(\) process. Especially the out-of-plane modes seem to play an extraordinary role in the excess energy behaviour of the predissociation rate. At lower excess energies, rates from single vibronic levels with out-of-plane mode characteristics may show an increase by several orders of magnitude.

Breakup density in spectator fragmentation

Proton–proton correlations and correlations of protons, deuterons and tritons with α particles from spectator decays following 197 Au + 197 Au collisions at 1000 MeV per nucleon have been measured with two highly efficient detector hodoscopes. The constructed correlation functions, interpreted within the approximation of a simultaneous volume decay, indicate a moderate expansion and low breakup densities, similar to assumptions made in statistical multifragmentation models.

The 12C(p, p′3α) Breakup Reaction Induced by 14, 18 and 26 MeV Protons

Double-differential cross sections (DDXs) of emitted protons and αs particles were measured for proton-induced reactions on 12C at 14, 18 and 26MeV in order to investigate the 12C(p, p′3α) breakup reaction. The experimental DDXs were analyzed on the assumption that the (p, p′3α) reaction proceeds through two major processes, a three-body simultaneous breakup (3BSB) process (i.e., p+12C→p+α+8Be*2094Mev) and sequential decay processes from unstable nuclei produced by (p, p′) and (p, α) reactions (i.e., 12C, 9B, 8Be and 5Li). Partial cross sections for the various reaction channels were extracted from the measured DDXs by a least squares method with two fitting functions: a three-body phase distribution function for the 3BSB process and a Breit-Wigner function for the transition to a discrete level in the first step of the sequential decay process. The result showed that the 12C(p, p′3α) reaction took place predominantly via nearly isotropic particle emission in the 3BSB process, and emission of protons and α particles with low energies was explained well by the sequential decay via 12C* and 9Bg.s Experimental (p, p) and (p, p′) scattering cross sections at 26 MeV were reproduced well by the coupled-channels calculation with the soft-rotator model. The experimental DDXs were compared with a Monte Carlo calculation based on the SCINFUL/DDX code and the latest intermediate energy nuclear data evaluation library LA150.

Anatomical Study of the Decay Caused by the White-Rot Fungus Trametes Trogii (Aphyllophorales) in Wood of Salix and Populus

Different stages of decay caused in vitro by Trametes trogii in Salix sp. and Populus sp. wood are described. Anatomical features are reported in three stages of this process. Decay progressed in a different pattern in both species studied. In Populus sp. T. trogii caused a combination of selective delignification and simultaneous decay within the same substrate. In advanced stages wood blocks exhibited large empty holes and a spongy structure. In Salix sp. a simultaneous white-rot decay took place. Only vessels remained and the residual white-rotted wood developed a stringy appearance.

An analytically based model for the simultaneous leaching-chain decay of radionuclides from contaminated ground surface soil layers.

This paper describes an analytically based method for modeling the time-dependent radionuclide areal densities of contaminated soil surface layers when the soil experiences simultaneous leaching, surface erosion and chain radioactive decay. The model is used to predict time-dependent radionuclide areal densities in a volcanic ash blanket contaminated with spent nuclear fuel particles for the purpose of assessing the risks of radiation exposure from an extrusive volcanic event near a proposed high-level waste repository at Yucca Mountain. The method uses general analytical solutions (an expansion of the Bateman equations) for calculating serial decay, including non-radioactive decay loss terms, in order to calculate time-dependent radionuclide areal densities in the ash blanket. In the presented example, 43 "key" radionuclides are tracked and their concentrations in the blanket are displayed for a 10,000-y time period following the volcanic event. Although the analysis presented herein is for modeling contaminated volcanic ash blankets, the model would work equally well for modeling time-dependent radionuclide contamination of land surfaces in, for example, site decommissioning. It is suggested that the general solutions for serial decay (with non-radioactive decay loss terms) can also be used to model the release of radionuclides from the waste packages under anticipated repository conditions.

Statistical nature of nuclear multifragmentation

A recent analysis of multifragmentation data in terms of an elementary binary decay appears to imply that the decay is sequential and from a thermalized source. This last feature would imply a lack of sensitivity to dynamical effects, at least in this multifragmentation data. We discuss this analysis using a simultaneous statistical multifragmentation model (SMM), which assumes decay from a thermalized source, and also employing a molecular dynamics model (MDM). The elementary binary decay analysis of the SMM predictions yields results which are qualitatively similar to those of the data. The differences are shown to stem from superposition of processes associated with very different impact parameters. Thus the data are not inconsistent with simultaneous decay. The MDM calculations, on the other hand, disagree with the data. We suggest, however, that more reliable dynamical calculations are needed before accepting an absence of dynamical effects in these data.

Evaluation of Neutron Cross Sections of Carbon-12 for Energies up to 80MeV

We have evaluated the cross sections of 12C for neutrons up to 80MeV, paying more attention to the intermediate energy range above 20MeV. For energies below 20MeV, the evaluated data of JENDL-3.2 were adopted with some modifications. In the energy range above 20MeV, total cross section and its covariance matrix were evaluated using a generalized least-squares method with available experimental data. The spherical optical model was used to evaluate reaction and elastic scattering cross sections. Inelastic scattering to the first 2+ state was calculated based on the DWBA. The optical potentials used in these calculations were obtained by means of the microscopic folding model based on the Jeukenne-Lejeune-Mahaux theory. Double-differential emission cross sections for neutron, proton, deuteron, triton, 3He, alpha-particle and other heavier products were calculated using the Monte-Carlo method by which three-body simultaneous breakup process and two-body sequential decay process were taken into account in n+12C multibody breakup reactions. Kerma factors calculated from the evaluated cross sections were also compared with measurements and other evaluations.

The daily changing pattern of hydrogen peroxide in new zealand surface waters

AbstractConcentrations of hydrogen peroxide (H2O2) were measured during daytime every 2 h at several depths in a catena of lakes of different trophic states including oligotrophic lakes Selfe and Oxbow, eutrophic Lake Hayes, dystrophic Lake Hochstetter, and a hypertrophic oxidation pond. The daily patterns of H2O2 of the various lakes can be explained firstly by the turnover regime of H2O2 which results out of simultaneous biological or chemical decay and formation yield (ratio of H2O2 formed per UV radiation dose) and secondly by internal transport. As in dystrophic, eutrophic, and hypertrophic lakes with high turnover, H2O2 is formed near the surface and the decay is rapid over the entire water column, a H2O2 pattern with sharp temporal and vertical gradients develops. In contrast, oligotrophic lakes allow deeper penetration of UV radiation, thus H2O2 is formed over greater depths. Further, the (biological) decay is slower than in lakes of higher trophic state leading to less sharp gradients within the daily H2O2 pattern. Input of H2O2 by wet deposition can contribute considerably to the increase of H2O2 in lakes, whereas dry deposition and groundwater flow do not.

Correction for Amino Acid Loss during Acid Hydrolysis of a Purified Protein

Hydrolyzing a protein in acid for a single hydrolysis interval, normally 24 h, will lead to inaccurate estimates of the amino acid composition of that protein due to an effect of the time of hydrolysis on peptide bond cleavage and amino acid degradation. The simultaneous yield and decay of amino acids during the hydrolysis of a protein can be described by a compartmental model with parameters for the hydrolysis and loss rates specific to each amino acid in a protein. The amino acid composition of the protein prior to hydrolysis can be determined by nonlinear regression of data derived from multiple hydrolysis intervals. In the present study egg-white lysozyme was hydrolyzed in 6MHCl using 18 hydrolysis intervals (range, 2–141 h) using the conventional duplicate hydrolyses/interval system. Hydrolysis and loss rates were determined for each amino acid. Increasing the number of hydrolysis intervals prior to the maximum point on the hydrolysis curve, and including an hydrolysis interval greater than 100 h increased the accuracy with which the hydrolysis and loss rates were estimated. Most of the amino acids underwent some degree of loss during hydrolysis. Of particular note was the loss rate for cysteic acid, which was greater than that found for serine which is commonly regarded as an acid-labile amino acid. The determined amino acid composition of the protein, based on the nonlinear regression of the data from four different series of hydrolysis intervals, was compared with the known amino acid composition (sequencing). Using the routine duplicate sampling system, a nonlinear regression including 10 hydrolysis intervals (2, 6, 10, 14, 18, 22, 26, 30, 60, and 141 h) resulted in a mean amino acid recovery of 100% (range, 94–110%) and provided an acceptable compromise between accuracy and the cost of analysis.

Photoacoustic diagnostics of fast photochemical and photobiological processes. Analysis of inverse problem solution

Photoacoustic (PA) diagnostics is a time-resolved experimental technique that measures transient photoinduced volume changes on the nano- and microsecond time-scales. The technique has been used to study the energetics and dynamics of chemical and biochemical reactions initiated by absorption of light. The dynamics of the volume changes and associated relaxation processes can be restored from PA-waveforms by solving an ill-posed problem of deconvolution. For the systems with known relaxation kinetics scheme this problem is usually solved by an iterative approximation algorithm. In complex photoactive systems (e.g. photosynthetic samples), where information about kinetics of fast photoinduced volume changes is not available, an algorithm of direct deconvolution must be used. The implementation of one of the linear deconvolution algorithms (Tikhonov's α-regularization) for the PA-diagnostics is therefore considered. The problem of the optimal choice of experimental set-up, and restoration algorithm is analyzed by a numerical simulation. It is shown that the quality of PA-diagnostic experiment is mainly determined by a transfer function converting the relaxation spectrum to the spectrum of output electric signal. The analytical expressions to calculate this function (so called PA-filter) are presented. The performance of two widely used schemes of PA-diagnostics are then directly compared. The time-resolution of the PA-diagnostics in analysis of simultaneous bi-exponential decay is evaluated, and the relationship between the resolving power and parameters of the experimental set-up (signal-to-noise ratio, sampling rate, shape of the PA-filter) is found. The advantage of front face irradiation scheme with piezopolymer film detector for time-resolved measurements is demonstrated.

A convenient method for experimental determination of yields and isomeric ratios in photonuclear reactions measured by the activation technique

A generalized exact formula is derived for a determination of the experimental isomeric ratio in any incident particle activation. For the particular case, when the activity of the ground state results from the simultaneous decay of both states and can be conveniently measured, the appropriate modification of this formula is evaluated and applied to six photonuclear reactions induced by 43 MeV bremsstrahlung. The experimental isomeric yield ratios of (γ, 3n) 110m,gIn; (γ, p) (γ, pn), (γ, 2n2p) 117m,gIn; (γ, n) 164m,gHo and (γ, 3n) 162m,gHo are deduced.

Statistical and sequential breakup of 24Mg in peripheral reactions at intermediate energies

The fragmentation of the projectile 24Mg, excited in peripheral collisions on 197Au and 12C targets, has been investigated at 25A MeV and 35A MeV with a large scintillator detector array. Projectile breakup events were selected in the off-line analysis, by requiring that the total detected charge in one event be equal to that of the projectile. The projectile-like nucleus (PLN) excitation energies have been reconstructed and compared to results at 50A MeV and 70A MeV. The branching ratios of 2-, 4-, 5-, and 6-fold decays show a linear dependence, characteristic of statistical decay. Global variable analysis in terms of relative angles was applied to the six-alpha exit channel and the corresponding data have been compared to theoretical calculations based on simultaneous and sequential binary decay. The latter have been divided into sequential fission and sequential evaporation decays. The data has been found to be consistent with a sequential evaporation decay mechanism for a wide range of the intermediate-energy domain.

Effects of Incubation Time and Temperature on In Vitro Selective Delignification of Silver Leaf Oak by Ganoderma colossum

The effects of incubation time and temperature on the ability of isolates of the chlamydosporic and thermophilic fungus Ganoderma colossum (Fr.) C. F. Baker to cause selective delignification of Quercus hypoleucoides A. Camus were evaluated by standard in vitro agar block tests. Chemical and scanning electron microscopy studies of decayed wood were used to determine the extent of selective delignification or simultaneous decay caused by each fungal isolate. At 35 deg C, the percent weight loss increased from 6.1% after 4 weeks to a maximum of 32.5 to 33.0% after 16 and 20 weeks of incubation. The average percent Klason lignin-chlorite holocellulose ratios (PKL/CHC) decreased from 0.35 in the control wood block to 0.22 in wood blocks incubated for 12 weeks; this indicated selective delignification. The average PKL/CHC increased for the 16- and 20-week incubation periods, indicating greater removal of polysaccharides during longer incubation periods. In temperature studies, the percent weight loss after 12 weeks was 26 to 27% between 30 and 40 deg C and less than 16% for the 25 and 45 deg C treatments. The average PKL/CHC ranged from 0.18 to 0.16 between 35 and 40 deg C, whereas they were 0.23 and 0.31 for the 25 and 45 deg C treatments, respectively. Scanning electron microscopy confirmed an optimum temperature range near 35 to 40 deg C and incubation times of 8 to 12 weeks for selective delignification. Under these conditions, ray parenchyma, fiber tracheids, and vessels were devoid of middle lamella; pit regions of cells were visible with significantly enlarged apertures; and individual cells were separated and clearly delimited. Extensive delignification of wood occurred throughout the wood blocks evaluated. Incubation times longer than 12 weeks resulted in greater degradation of wood cell walls and thus in greater removal of the polysaccharide component of the wood. For incubation times of 4 weeks or a temperature of 25 deg C, limited to no degradation of cells was observed. At 45 deg C, walls of fiber tracheids were eroded and ray parenchymal cells were extensively degraded, indicating that simultaneous degradation of cell walls occurred. Thus, the incubation temperature influenced the type of decay by G. colossum observed on oak wood blocks: extensive selective delignification at 35 to 40 deg C after more than 8 weeks of incubation or simultaneous decay at 45 deg C with 14% weight loss after 12 weeks of incubation. Isolates of G. colossum may prove useful in studies on mechanisms of delignification and biotechnological applications (e.g., biopulping) of lignin-degrading fungi.