Polarization induced water molecule dissociation below the first-order electronic-phase transition temperature

Hydrogen produced from the photocatalytic splitting of water is one of the reliable alternatives to replace the polluting fossil and the radioactive nuclear fuels. Here, we provide unequivocal evidence for the existence of blue- and red-shifting O-H covalent bonds within a single water molecule adsorbed on the MgO surface as a result of asymmetric displacement polarizabilities. The adsorbed H-O-H on MgO gives rise to one weaker H-O bond, while the other O-H covalent bond from the same adsorbed water molecule compensates this effect with a stronger bond. The weaker bond (nearest to the surface), the interlayer tunneling electrons and the silver substrate are shown to be the causes for the smallest dissociative activation energy on the MgO monolayer. The origin that is responsible to initiate the splitting mechanism is proven to be due to the changes in the polarizability of an adsorbed water molecule, which are further supported by the temperature-dependent static dielectric constant measurements for water below the first-order electronic-phase transition temperature.     

Weakly interacting particle systems on inhomogeneous random graphs

We consider weakly interacting diffusions on time varying random graphs. The system consists of a large number of nodes in which the state of each node is governed by a diffusion process that is influenced by the neighboring nodes. The collection of neighbors of a given node changes dynamically over time and is determined through a time evolving random graph process. A law of large numbers and a propagation of chaos result is established for a multi-type population setting where at each instant the interaction between nodes is given by an inhomogeneous random graph which may change over time. This result covers the setting in which the edge probabilities between any two nodes are allowed to decay to 0 as the size of the system grows. A central limit theorem is established for the single-type population case under stronger conditions on the edge probability function.     

The warm inflationary universe

In the past decade, the importance of dissipation and fluctuation to inflationary dynamics has been realized and has led to a new picture of inflation called warm inflation. Although these phenomena are common to condensed matter systems, for inflation models their importance has only recently started to be appreciated. The article describes the motivation for these phenomena during inflation and then examines their origins from first principles quantum field theory treatments of inflation models. Cosmology today is a data intensive field and this is driving theory to greater precision and predictability. This opens the possibility to consider tests for detecting observational signatures of dissipative processes, which will be discussed. In addition, it will be discussed how particle physics and cosmology are now working in tandem to push the boundaries of our knowledge about fundamental physics.     

Experimental measurements and numerical modeling of marginal burning in live chaparral fuel beds

An extensive experimental and numerical study was completed to analyze the marginal burning behavior of live chaparral shrub fuels that grow in the mountains of southern California. Laboratory fire spread experiments were carried out to determine the effects of wind, slope, moisture content, and fuel characteristics on marginal burning in fuel beds of common chaparral species. Four species (Manzanita sp., Ceanothus sp., Quercus sp., and Arctostaphylos sp.), two wind velocities (0 and 2 m/s), two fuel bed depths (20 and 40 cm), and three slope percents (0%, 40%, or 70%) were used. Oven-dry moisture content M of fine fuels (<6.25 mm diameter) ranged from 29% to 105%. Sixty-five of 115 fires successfully propagated the length (2.0 m) of the elevated fuel bed. A previously derived empirical marginal burning criterion was assessed, and a suitable modification was proposed for live chaparral fuels. Based on the experimental data, a stepwise logistic regression model was developed to predict the probability of successful fire spread. This procedure resulted in the selection of wind speed, slope percent, fuel loading, fuel moisture content, and relative humidity as the primary variables. It correctly classified 96% of 115 fires. Finally, a multidimensional numerical model for vegetation fire spread using a porous media sub-model was developed to simulate the laboratory fires. Results are used to analyze the internal heat transfer and combustion processes that determine fire spread success in shrub fuel bed.     

Z-scan studies on porphyrin derivative

Received: 10 January 1996 / Revised version: 15 June 1996     

The shape of an axisymmetric bubble in uniform motion

We consider in a frame fixed to a bubble translating with steady speedU, the inviscid, axisymmetric, irrotational motion of the liquid past it. If all speeds are normalized byU and lengths by {ie437-1}, whereT is the surface tension of the liquid-bubble interface, it can be shown that the unknown bubble shape and field depend on a single parameter {ie437-2} alone, where the pressures are the ones in the bubble and far away respectively. WhenΓ is very large the bubble is almost spherical in shape while for Γ<- Γ^* ≈ -0.315, bubbles whose exteriors are simply connected do not exist. We solve the non-linear, free boundary problem for the whole range Γ^* < Γ < ∞ by the use of an analytical representation for the bubble shape, a surface singularity method to compute potential flows and a generalized Newton’s method to continue inΓ. Apart from providing explicit representations for bubble shapes and detailed numerical values for the bubble parameters, we show that the classical linearized solution for largeΓ is a very good approximation, surprisingly, to as low values of Γ as 2. We also show that Miksiset al [1] is inaccurate over the whole range and in serious error for large and smallΓ. These have been corrected.     

Assessment of sandwich models for the prediction of sound transmission loss in unidirectional sandwich panels

The consistent higher-order approach and the two-parameter foundation formulation are used for the derivation of sound transmission loss in symmetric unidirectional (infinitely wide) sandwich panels with isotropic face sheets. In both models, transmission loss is calculated using decoupled equations representing symmetric and anti-symmetric motions of a sandwich panel. The closed-form expressions for impedances and transmission coefficient of a symmetric sandwich panel with an isotropic core are derived for the two-parameter foundation model. A comparison between the numerical predictions based on the two sandwich models and available experimental data shows that the consistent higher-order formulation can be used to predict the transmission loss in symmetric sandwich panels with both honeycomb and isotropic cores. For prediction of transmission loss of symmetric sandwich panels with an isotropic core, the two-parameter foundation model is more convenient, while the consistent higher-order approach is more accurate.     

Uhf to Ka band upconverter

A balanced upconverter circuit has been developed in planar transmission line configuration using NEC GaAs beam lead Schottky barrier diodes. RF power output of +1.6 dBm SSB is obtained at Ka-band when up converter is driven by +17 dBm IF and +20 dBm LO signal.     

Substitution of coordinated chlorides in cis-α and cis-β dichloro (triethylene tetramine) cobalt(III) chloride [Co(trien)Cl2]Cl by thiocyanate in aqueous medium

Substitution of coordinated chlorides in cis-α, and cis-β dichloro (triethylene tetramine) cobalt(III) chloride by thiocyanate was studied in aqueous medium in the pH range 3.8 to 4.0 at 25–26° C. Substitution, as in aquation, took place in two steps corresponding to the two chlorides, one step being faster than the other. Mechanisms have been discussed in the paper.