Vapors

The sensing of chemicals and biochemical molecules using several porous silicon optical microsensors, based both on single-layer interferometers and resonant-cavity-enhanced microstructures, is reported. The operation of both families of sensors is based on the variation of the average refractive index of the porous silicon region, due to the interaction with chemical substances either in vapor or liquid state, which results in marked shifts of the device reflectivity spectra. The well established single-layer configuration has been used to test a new chemical approach based on Si-C bonds for covalent immobilization of biological molecules, as probe, in a stable way on the porous silicon surface. Preliminary results on complementary oligonucleotide recognition, based on this technique, are also presented and discussed. Porous silicon optical microcavities, based on multilayered resonating structures, have been used to detect chemical substances and, in particular, flammable and toxic organic solvents, and some hydrocarbons. The results put in evidence the high sensitivity, the reusability, and the low response time of the resonant-cavity-enhanced sensing technique. The possibility of operating at room temperature, of remote interrogation, and the absence of electrical contacts are further advantages characterizing the sensing technique.

An experimental investigation is presented concerning the boiling of water at atmospheric pressure on a single copper surface in which the spatial distribution of active nucleation sites was investigated at different levels of heat flux and subcooling. The results obtained ...

Alcohol abuse causes dramatic neuroadaptations in the brain, which contribute to tolerance, dependence, and behavioral modifications. Previous proteomic studies in human alcoholics and animal models have identified candidate alcoholism-related proteins. However, recent evidences suggest that alcohol dependence is caused by changes in co-regulation that are invisible to single protein-based analysis. Here, we analyze global proteomics data to integrate differential expression, co-expression networks, and gene annotations to unveil key neurobiological rearrangements associated with the transition to alcohol dependence modeled by a Chronic Intermittent Ethanol (CIE), two-bottle choice (2BC) paradigm. We analyzed cerebral cortices (CTX) and midbrains (MB) from male C57BL/6J mice subjected to a CIE, 2BC paradigm, which induces heavy drinking and represents one of the best available animal models for alcohol dependence and relapse drinking. CIE induced significant changes in protein levels in dependent mice compared with their non-dependent controls. Multiple protein isoforms showed region-specific differential regulation as a result of post-translational modifications. Our integrative analysis identified modules of co-expressed proteins that were highly correlated with CIE treatment. We found that modules most related to the effects of CIE treatment coordinate molecular imbalances in endocytic- and energy-related pathways, with specific proteins involved, such as dynamin-1. The qRT-PCR experiments validated both differential and co-expression analyses, and the correspondence among our data and previous genomic and proteomic studies in humans and rodents substantiates our findings. The changes identified above may play a key role in the escalation of ethanol consumption associated with dependence. Our approach to alcohol addiction will advance knowledge of brain remodeling mechanisms and adaptive changes in response to drug abuse, contribute to understanding of organizational principles of CTX and MB proteomes, and define potential new molecular targets for treating alcohol addiction. The integrative analysis employed here highlight the advantages of systems approaches in studying the neurobiology of alcohol addiction.

Measurements of nucleation site density, n/A, have been obtained for forced convection boiling of refrigerant R113 in a horizontal 25 × 25 mm i.d. square transparent test section with a nichrome heating strip. It has been found that the behavior of the nucleation site density is significantly different from that found in pool boiling. The mean vapor velocity, heat flux, and system pressure appear to exert a strong parametric influence. It is demonstrated that although the nucleation site density is dependent on the critical cavity radius, rc, it is not sufficient for correlating n/A.

In this work subcooled film boiling on a horizontal disc was studied analytically/numerically. Linearized stability analysis of a vapor film underlying a pool of heavier liquid was performed in three-dimensional, cylindrical coordinates. From the analysis the dominant wavelength and configuration of vapor releasing nodes was identified. Complete numerical simulation of the nonlinearly evolving interface have been carried out in axisymmetric coordinates. Finite difference method was used to simultaneously solve the equations governing conservation of mass, momentum, and energy in the vapor and liquid phases. The equations for the two phases were coupled through the matching of normal and tangential stresses and continuity of mass and energy at the interface. Second order projection method was employed for decoupling velocities from pressure. Numerical grid generation method was utilized to construct a grid system which was aligned with the interface. From the simulations the shape of...

This study concerns pressure drop of adiabatic water liquid-vapor two-phase flow across an array of 1950 staggered square micropin-fins having a 200×200 μm cross section by 670 μm height. The ratios of longitudinal pitch and transverse pitch to pin-fin equivalent diameter are equal to 2. An inline immersion heater upstream of the micropin-fin test module was employed to produce liquid-vapor two-phase mixture, which flowed across the micropin-fin array. The test module was well insulated to maintain adiabatic condition. Four maximum mass velocities of 184 kg/m2 s, 235 kg/m2 s, 337 kg/m2 s, and 391 kg/m2 s, and a range of vapor qualities for each maximum mass velocity were tested. Measured pressure drop increases drastically with increasing vapor quality. Nine existing two-phase pressure drop models and correlations were assessed. The Lockhart–Martinelli correlation for laminar liquid-laminar vapor combination in conjunction with a single-phase friction factor correlation proposed for...

The flow of a uniform stream of pure saturated vapour past a cold, semi-infinite vertical plate is examined. The formulation incorporates the limits of both pure forcedconvection and pure body-force-convection laminar film condensation. Detailed asymptotic and exact numerical solutions are obtained and comparisons drawn with approximate methods and experimental results reported in the literature.

Vapor phase lubrication (VPL) is an emerging technology that is currently targeted for application in limited life, expendable engines. It has the potential to cut 90 percent of the cost and weight of the lubrication system, when compared to a conventional liquid lubricated system. VPL, is effective at much higher temperatures than conventional liquid lubrication (600°C versus 200°C), so considerably less cooling for the bearing is required, to the extent that the bearing materials often dictate the maximum upper temperature for its use. The hot no. 8 bearing and the cold no. 1 bearing of the T63 engine were used to evaluate the applicability of this technology to the expendable engine environment. The no. 8 bearing was a custom made hybrid with T15 steel races, silicon nitride balls, and a carbon–carbon composite cage; it was run for 10.7 h at a race temperature of 450°C at full power, without incident. Prior to engine tests, a bearing rig test of the no. 8 bearing demonstrated an ...

Nonlinear thin film rupture has been analyzed by investigating the stability of films under the influence of a nonuniform electrostatic field to finite amplitude disturbances. The dynamics of the liquid film is formulated using the Navier-Stokes equations including a body force term due to van der Waals attractions. The effect of the electric field is included in the analysis only in the boundary condition at the liquid vapor interface. The governing equation was solved by finite difference method as part of an initial value problem for spatial periodic boundary conditions. The electric field stabilizes the film and increases the time to rupture when a long wavelength perturbation is introduced.

A boiling liquid, expanding vapor explosion (BLEVE) occurs when a pressure vessel containing a superheated liquid undergoes a catastrophic failure, resulting in a violent vaporization of the liquid. The exposure of a pressure vessel to a fire is a classic scenario that can result in a BLEVE. The thermomechanical exergy of a pressure vessel’s contents provides — by definition — an upper bound on the work that can be performed by the system during the explosion. By fixing the values of ambient pressure and temperature (i.e., the dead state), exergy can be interpreted as another thermodynamic property. This rigorous and unambiguous definition makes it ideal to estimate the maximum energy of explosions. The numerical value of exergy depends on the definition of the dead state. In this paper we examine the effect of different definitions for the dead state on the explosion energy value. We consider two applications of this method: the contribution of the vapor head-space to the explosive...