Determination of Thermophysical Properties for Polymer Films using Conduction Analysis of Laser Heating

Determination of the thermophysical properties of thin film materials is important for modeling and optimizing laser microvia drilling of organic substrates in microelectronics applications. Techniques to measure the density, thermal conductivity, thermal diffusivity, thermal decomposition point, and specific ablation heat of thin polymer films are described. An experimental apparatus was set up for laser heating of the sample. To measure the thermal diffusivity, an analytic heat transfer model is developed. One-dimensional heat conduction is assumed due to the small thickness of the film compared to the radius of the laser beam. The value of thermal diffusivity is obtained by fitting the experimental data to the theory. The specific ablation heat is obtained by measuring the mass loss during laser ablation. The experimental apparatus and the property determination methodology can also be applied to thin samples of other materials.     

Virtue ethics, multiculturalism, and the paradox of cultural dialogue.

Comments on the article by Fowers and Davidov, "The virtue of multiculturalism: Personal transformation, character and openess to the other," (see record 2006-11202-002). Fowers and Davidov offered a virtue-based approach to understanding and fostering multiculturalism in psychology. Fowers and Davidov argued that multiculturalism fulfills the classical components of being a virtue, being a worthy goal that requires the wise use of consistent and worthwhile goods. They concluded that the virtue of multiculturalism and its correlate, openness, provide a sound basis for transformative cultural dialogue. It appears that Fowers and Davidov may be caught in what Meiland (1980) has called "The Paradox of Cognitive Relativism." I would argue that the problem, rather than being a faulty argument on their part, is the intrinsic incoherence of an ethic of multiculturalism, which insists that we respect a diversity of cultural backgrounds, and yet insists. The virtue model of ethics is relevant to our cultural concerns as psychologists but certainly does not resolve them. Instead, because it is soundly based in the idea of personal character, its value lies in bringing to light the very dilemmas involving human similarity and difference that have troubled psychologists since the inception of the field. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gramicidin Ion Channel-Based Biosensors: Construction, Stochastic Dynamical Models, and Statistical Detection Algorithms

This paper deals with the experimental construction, stochastic modeling, and statistical signal processing of a novel, artificially constructed biosensor comprised of biological ion channels. Such nanoscale biosensors have been built by incorporating dimeric gramicidin A (bis-gA) ion channels into bilayer membranes of giant unilamellar liposomes, and then excising small patches of the membrane loaded with ion channels. We present a stochastic model for the response of the biosensor and present statistical model validation tests to verify the adequacy of the model. We show that in the presence of specific target molecules, the statistics of the gating mechanisms of the gA channels are altered. By capturing the change in real time, we devise a maximum-likelihood detector to detect the presence of target molecules. To test the sensitivity of this model, we conducted patch-clamp experiments with two compounds known to inhibit conduction of the gA channels. We found experimentally that the real-time detection algorithm was able to accurately identify the addition of the compounds even when the alterations in the patch-clamp recordings were very small. This algorithm provides the sensitive detection system for ongoing development of lipid-based nanosensors.     

A physics‐based model of DC and microwave characteristics of GaN/AlGaN HEMTs

A physics‐based model of AlGaN/GaN High Electron Mobility Transistor (HEMT) is developed for the analysis of DC and microwave characteristics. Large‐ and small‐signal parameters are calculated for a given device dimensions and operating conditions. Spontaneous and piezoelectric polarizations at the heterointerface and finite effective width of the 2DEG gas have been incorporated in the analysis. The model predicts a maximum drain current of 523 mA/mm and transconductance of 138 mS/mm for a 1 μm × 75 μm device, which are in agreement with the experimental data. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Degradation Kinetics and Storage Stability of Vacuum Spray-Dried Micro Wet-Milled Orange Juice (<Emphasis Type="Italic">Citrus unshiu</Emphasis>) Powder

The aim of this work was to evaluate the degradation kinetics and stability of micro wet milled orange juice powders obtained by vacuum spray drying, using maltodextrin as a carrier agent. Powders were produced with four combinations of orange juice solids/maltodextrin solids 60:40, 50:50, 40:60, and 30:70 by weight. Ascorbic acid degradation, color, and antioxidant activity of powders were evaluated throughout 90 days. Powders were stored at 10, 25, and 35 °C and relative humidity of 33%. Temperature and storage time negatively influenced the stability of ascorbic acid and color, whereas antioxidant activity increased at the beginning of storage at a higher temperature then decreased slightly after 60 days. For stability study, powders were stored at different water activities (0.11 to 0.84) in order to determine the plasticizing effects of water on glass transition temperature. Both water activity and glass transition temperature were used to predict the critical conditions for storage. Vacuum spray dried powder produced with a ratio of 30:70 (orange juice solids/maltodextrin solids) was considered as the most stable, since it showed highest critical water activity (a_w?=?0.61) and lowest moisture content (0.11 g water/g of dry solid) among the four powders. Vacuum spray drying using superheated steam as the heating medium was proven to be an effective way of producing orange juice powders with minimum loss of nutrients.     

Multiple shear step approach to determine the rotational viscosity of asphalt emulsions and its correlation with water content of original and diluted emulsions

Viscosity determination of thixotropic emulsions with good repeatability has always been a major challenge. Currently, Saybolt Furol viscometer (SFV) is used to determine the viscosity of the emulsion, but the main drawback of the SFV is that it cannot simulate the behaviour of emulsion under different shear rate. Rotational viscometer (RV) can measure viscosity at different shear rates. Due to the thixotropic behaviour of the emulsions, getting repeatable results by following the hot binder specification is a problematic task. In this study, a new multiple shear step approach is used to determine the viscosity of the emulsified asphalt using RV. Three low viscous (SS-1, SS-1H and SS-1L) and two high viscous (CRS-2 and CRS-2P) emulsions were used in this study. Shear stress is gradually stepped up to different levels after certain time interval to determine the viscosity. In this manner, emulsion undergoes a known shear state and each reading is preceded by a certain repeatable shear history. It was observed that with the progression of time and simultaneous increase in shear rate, the viscosity results are much more stable and repeatable with less than 5% coefficient of variance. The final specifications proposed are 220–730 and 5–90 cP at 50 rpm and 30 °C for high and low viscous emulsions, respectively, which are based on 98% probability. Viscosity measured by this approach also showed strong correlation with water content (R² > 0.94). The correlation between viscosity and water content is even stronger after dilution. With different dilution water content, viscosity of CRS-2 and CRS-2P exhibited R² values of 0.97 and 0.98, respectively.     

Oral Secretions Affect HIPVs Induced by Generalist (<Emphasis Type="Italic">Mythimna loreyi</Emphasis>) and Specialist (<Emphasis Type="Italic">Parnara guttata</Emphasis>) Herbivores in Rice

Plants synthesize variable mixtures of herbivore-induced plant volatiles (HIPVs) as part of their evolutionary conserved defense. To elucidate the impact of chewing herbivores with different level of adaptation on HIPV profiles in rice, we measured HIPVs released from rice seedlings challenged by either the generalist herbivore Mythimna loreyi (MYL) or the specialist Parnara guttata (PAG). Both herbivores markedly elicited the emission of HIPVs, mainly on the second and third days after attack compared to control plants. In addition, side-by-side HIPV comparisons using MYL and PAG caterpillars revealed that generalist feeding induced comparably more HIPVs relative to specialist, particularly on day two as highlighted by multivariate analysis (PLS-DA) of emitted HIPVs, and further confirmed in mimicked herbivory experiments. Here, mechanically wounded plants treated with water (WW) released more VOCs than untreated controls, and on top of this, oral secretions (OS) from both herbivores showed differential effects on volatile emissions from the wounded plants. Similar to actual herbivory, MYL OS promoted higher amounts of HIPVs relative to PAG OS, thus supporting disparate induction of rice indirect defenses in response to generalist and specialist herbivores, which could be due to the differential composition of their OS. (196 words).     

Flow and heat transfer of two immiscible fluids in double-layer optical fiber coating

The coatings of optical fibers are generally characterized by a multi-layer coating structure. In this work, the mathematical modeling of two immiscible non-Newtonian fluids for optical fiber coating inside a straight annular die is developed in the form of a nonlinear differential equation with nonhomogeneous boundary conditions. Two non-Newtonian fluids, namely power law and Phan-Thien–Tanner fluids, are used in the primary and secondary coating dies, respectively. An exact solution is obtained for velocity fields and temperature distributions for the primary and secondary coating resins. The thickness of coated fiber optics is also calculated for both layers. The effect of different emerging parameters on the solution is discussed and sketched.     

Patterning of worm-like soft polydimethylsiloxane structures using a TiO2 nanotubular array

Patterned polydimethylsiloxane (PDMS) is an important structure for soft lithography. Various materials have been deployed as mold for patterning PDMS. Anodized nanotubular array has been sought after as cost-effective alternative for textured silicon. An array of TiO₂ nanotubes with characteristic diameter ≈140 nm and the length of ≈1.5 microns, created by anodic oxidation of a titanium substrate, was used here as a template for soft PDMS molding. The optimal molding process was developed by a combination of silanization, use of solvent, application of a vacuum, and hydraulic pressing. The silanization was confirmed by Fourier transform infrared spectroscopy and contact angle measurements while the PDMS structure was examined by scanning electron microscope and energy dispersive X-ray spectroscopy. Hydraulic pressing significantly improved the infiltration of PDMS into the pores of nanotubular array resulting in formation of PDMS nanobumps after separation of the polymer from the template. Complete infiltration of PDMS precursor into the cavity of nanotubes was observed on the hydraulic-pressed sample without toluene impurities. The hydraulic-pressed samples exhibited higher adhesion strength than nonpressed ones. The adhesive strength was measured by a simple experimental arrangement, in which the PDMS layer was stuck on a vertical glass surface followed by pulling it downwards.     

The influences of thermal stratification and flow interaction on the enhanced natural convective heat transfer at low temperatures

This paper applies the modified heat transfer correlation: Nu/Nu_iso = f(S) to horizontal cylinders immersed in the thermally stratified vapour over boiling liquid nitrogen. Correlation of the heat transfer data confirms that the thermal stratification parameter, S is the appropriate parameter to account for the observed heat transfer enhancement.When the data are compared with the theory for natural convection in an extensive environment with a linear thermal stratification, it is found that heat transfer in the cryogenic vapour columns is significantly enhanced. This enhancement appears to arise from a secondary flow circulation inducecd by the interaction of the flow field around the heated cylinder with the primary flow of the cold vapour column. The influence of this flow interaction upon the heat transfer has been studied by varying the cylinder and vapour column diameters. The data have been analysed and correlated with the empirical relation:

$\text{Nu}\text{Nu}{}_{\mathrm{iso}}\text{=0.80}{}^{0.5}\text{(}\text{D}\text{W}\text{)}{}^{-0.4}$

All the results on enhanced convective heat transfer obtained at Southampton are reported and the conditions under which heat transfer enhancement takes place are discussed.