Brushes of flexible, semiflexible and rodlike diblock polyampholytes: Molecular dynamics simulation and scaling analysis

Planar brushes of flexible, semiflexible and rodlike diblock polyampholytes are studied using molecular dynamics simulations and scaling analysis in a wide range of the grafting density. Simulations show linear dependence of the average thickness on the grafting density for all the brushes regardless of their different equilibrium conformations and different flexibility of anchored chains. Slopes of fitted lines to the average thickness of the brushes of semiflexible and rodlike polyampholytes versus the grafting density are approximately the same and differ considerably from that of the brush of flexible chains. The average thickness of the brush of diblock polyampholytes is also obtained as a function of the grafting density using a simple scaling analysis which is in good agreement with the results of our simulations.Comment: 5 Figure

Constraints on scalar-tensor theories from observations

We study the dynamical description of scalar-tensor gravity by performing the best-fit analysis for two cases of exponential and power-law form of the potential and scalar field function coupled to the curvature. The models are then tested against observational data. The results show that in both scenarios the Universe undergoes an acceleration expansion period and the geometrical equivalent of dark energy is associated with a time-dependent equation of state.Comment: 16 pages, 32 figure

Interacting Cosmic Fluids in Brans-Dicke Cosmology

We provide a detailed description for power-law scaling FRW cosmological models in Brans-Dicke theory dominated by two interacting fluid components during the expansion of the universe.Comment: 13 pages, 8 figure

Suspended liquid particle disturbance on laser-induced blast wave and low density distribution

The impurity effect of suspended liquid particles on the laser-induced gas breakdown was experimentally investigated in quiescent gas. The focus of this study is the investigation of the influence of the impurities on the shock wave structure as well as the low density distribution. A 532 nm Nd:YAG laser beam with an 188 mJ/pulse was focused on the chamber filled with suspended liquid particles 0.9 ± 0.63 μm in diameter. Several shock waves are generated by multiple gas breakdowns along the beam path in the breakdown with particles. Four types of shock wave structures can be observed: (1) the dual blast waves with a similar shock radius, (2) the dual blast waves with a large shock radius at the lower breakdown, (3) the dual blast waves with a large shock radius at the upper breakdown, and (4) the triple blast waves. The independent blast waves interact with each other and enhance the shock strength behind the shock front in the lateral direction. The triple blast waves lead to the strongest shock wave in all cases. The shock wave front that propagates toward the opposite laser focal spot impinges on one another, and thereafter a transmitted shock wave (TSW) appears. The TSW interacts with the low density core called a kernel; the kernel then longitudinally expands quickly due to a Richtmyer-Meshkov-like instability. The laser-particle interaction causes an increase in the kernel volume which is approximately five times as large as that in the gas breakdown without particles. In addition, the laser-particle interaction can improve the laser energy efficiency

Reaction Kinetics Analysis of Urethane Polymerization to Gelation

A chemical reaction analysis of a thermosetting, urethane resin formulated from a triol and a diisocyanate is reported. Population density distributions of oligomeric molecules, monomer concentration, the cumulative molar concentration of intramolecular bonds, the resin\u27s average molecular weights, and extent of reaction were determined as a function of time. Rate expressions for intermolecular reactions were first order with respect to the concentration of each reactant and were proportional to the functionality of their respective chemical moieties. Rate expressions for intramolecular reactions were first order with respect to the concentration of the reactant and were proportional to the functionality of the limiting chemical moiety on the reactant. The initial ratio of the chemical equivalents and effects of dilution were incorporated into numerical simulations. Stanford and Stepto\u27s experimental data were analyzed. Gel points and the concentration of intramolecular bonds were correlated as a function of conversion. Intramolecular reaction rate expressions derived with the aid of Gaussian chain statistics require the molar concentrations of all chemical isomers of a specified chemical composition. The present reaction rate expression allows chemical isomers to be lumped into a single population density distribution variable, substantially reducing the dimensions of the simulation. Numerical results demonstrate that the simplified rate expression is an excellent

QED Corrections to Planck's Radiation Law and Photon Thermodynamics

Leading corrections to Planck's formula and photon thermodynamics arising from the pair-mediated photon-photon interaction are calculated. This interaction is attractive and causes an increase in occupation number for all modes. Possible consequences, including the role of the cosmic photon gas in structure formation, are considered.Comment: 15 pages, Revtex 3.

Exact dynamics of interacting qubits in a thermal environment: Results beyond the weak coupling limit

We demonstrate an exact mapping of a class of models of two interacting qubits in thermal reservoirs to two separate spin-bath problems. Based on this mapping, exact numerical simulations of the qubits dynamics can be performed, beyond the weak system-bath coupling limit. Given the time evolution of the system, we study, in a numerically exact way, the dynamics of entanglement between pair of qubits immersed in boson thermal baths, showing a rich phenomenology, including an intermediate oscillatory behavior, the entanglement sudden birth, sudden death, and revival. We find that stationary entanglement develops between the qubits due to their coupling to a thermal environment, unlike the isolated qubits case in which the entanglement oscillates. We also show that the occurrence of entanglement sudden death in this model depends on the portion of the zero and double excitation states in the subsystem initial state. In the long-time limit, analytic expressions are presented at weak system-bath coupling, for a range of relevant qubit parameters

Unscreened water-diversion pipes pose an entrainment risk to the threatened green sturgeon, Acipenser medirostris.

Over 3,300 unscreened agricultural water diversion pipes line the levees and riverbanks of the Sacramento River (California) watershed, where the threatened Southern Distinct Population Segment of green sturgeon, Acipenser medirostris, spawn. The number of sturgeon drawn into (entrained) and killed by these pipes is greatly unknown. We examined avoidance behaviors and entrainment susceptibility of juvenile green sturgeon (35±0.6 cm mean fork length) to entrainment in a large (>500-kl) outdoor flume with a 0.46-m-diameter water-diversion pipe. Fish entrainment was generally high (range: 26-61%), likely due to a lack of avoidance behavior prior to entering inescapable inflow conditions. We estimated that up to 52% of green sturgeon could be entrained after passing within 1.5 m of an active water-diversion pipe three times. These data suggest that green sturgeon are vulnerable to unscreened water-diversion pipes, and that additional research is needed to determine the potential impacts of entrainment mortality on declining sturgeon populations. Data under various hydraulic conditions also suggest that entrainment-related mortality could be decreased by extracting water at lower diversion rates over longer periods of time, balancing agricultural needs with green sturgeon conservation