Strain Enhanced Functionality in a Bottom‐Up Approach Enabled 3D Super‐Nanocomposites

The ability to control nanoparticle size, concentration, and distribution in epitaxial nanocomposite films has been a formidable challenge in the synthesis of nanostructured composite materials. Here, a novel 3D super‐nanocomposite (3D‐sNC) architecture is successfully demonstrated by integrating superlattice and vertically aligned nanocomposite structures. In the 3D‐sNC architecture, the feature size and distribution of the nanocylinders such as the height/lateral dimension and the vertical/lateral spacing of nanocylinders can be precisely controlled. The microstructure parameters such as nanocylinder height and spacing modulated interfacial area control the lattice strain, which further tunes the magnetotransport property. These results demonstrate that 3D‐sNC is a simple and yet effective architecture to achieve controlled functionalities via the precise control of nanocylinder size, spacing, concentration, and distribution. Such a 3D‐sNC structure can be used to design advanced nanostructures with desired physical properties for a variety of material systems.     

Development of biphenyl monomers and associated crosslinked polymers with intramolecular pi-pi interactions

Monomers containing biphenyl moieties were employed to create two sets of covalently crosslinked polymers that displayed noncovalent interactions in their 3-dimensional network. The biphenyls (precursors) used were 2-phenylphenol, 4-phenylphenol and 4,4′-dihydroxybiphenyl, and their acrylated forms were synthesized and named as 2-phenylphenolmonoacrylate, 4-phenylphenolmonoacrylate, and 4,4′-dihydroxybiphenyldiacrylate, respectively. These were characterized by differential scanning calorimetry, nuclear magnetic resonance, and Fourier transform infrared spectroscopy to confirm the successful acrylation reaction. Polymers were synthesized via free radical polymerization reactions with varying crosslinker contents, and their network properties were characterized using swelling studies and compressive modulus tests. Interestingly, swelling studies did not show the expected decreasing swelling ratio with increasing crosslinker content, while compression testing indicated the expected trend of increasing modulus with increasing crosslinking density. The unexpected swelling results are hypothesized to result from the intramolecular interactions between the biphenyl side groups that result in noncovalent crosslinks.     

Temperature responsive hydrogel with reactive nanoparticles

The application of temperature responsive hydrogels with ion‐exchange domain for nanoscale catalytic reactions is an emerging and attractive area because of the combination of individual unique features: temperature responsive tunability by the polymer domain and the high catalytic reactivity of the nanomaterial. Here, we report the entrapment and/or direct synthesis of reactive Fe and Fe/Pd nanoparticles (about 40–70 nm) in a temperature responsive hydrogel network (N‐isopropylacrylamide (NIPAAm), and NIPAAm—PAA). These nanoparticles are stabilized in the hydrogel network and the dechlorination (using trichloroethylene, TCE, as a model compound) reactivity in water is enhanced and controllable in the temperature range of 30–34°C involving polymer domain transitions at lower critical solution temperature (LCST) from hydrophilic to collapsed hydrophobic state. Water fraction modulation of the network and the enhancement of pollutant partitioning by the thermally responsive polymers play an important role in the catalytic activity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Investigation of natural convection induced outer side heat transfer rate of coiled-tube heat exchangers

Natural convection induced heat transfer has been studied over the outer surface of helically coiled-tube heat exchangers. Several different geometrical configurations (curvature ratio δ ε [0.035, 0.082]) and a wide range of flow parameters (60 <= T_tank <= 90, T_in = 19 and 60 <= T_in <= 90, T_tank = 20, 4000 <= Re <= 45000) have been examined to broaden the validity of the results gained from this research. A fluid-to-fluid boundary condition has been applied in the numerical calculations to create the most realistic flow configurations. Validity of the numerical calculations has been tested by experiments available in the open literature. Calculated results of the inner side heat transfer rate have also been compared to existing empirical formulas and experimental results to test the validity of the numerical computation in an independent way from the outer side validation of common helical tube heat exchangers. Water has been chosen to the working fluid inside and outside of the coiled tube (3 < Pr < 7). Outer side heat transfer rate along the helical tube axis has been investigated to get information about the performance of the heat transport process at different location of the helical tube. It was found that the outer side heat transfer rate is slightly dependent on the inner flow rate of any helical tube in case of increasing temperature differences between the tank working fluid temperature and the coil inlet temperature. A stable thermal boundary layer has been found along the axial direction of the tube.In addition to this the qualitative behavior of the peripherally averaged Nusselt number versus the axial location along the helical tube function is strongly dependent on the direction of the heat flow (from the tube to the storage tank and the reversed direction). Inner side heat transfer rate of helical coils have also been investigated in case of fluid-to-fluid boundary conditions and the calculation results have been compared with different prediction formulas published in the last couples of decades.     

Renal transplantation for end-stage renal disease due to paroxysmal nocturnal haemoglobinuria

Bacillus subtilis 168 is unable to grow on xylose and galactose as sole carbon sources, owing to the lack of specific transporters. We show that they are imported into the cell by the activity of AraE, an arabinose transporter whose synthesis is induced by L-arabinose.     

How to include the dependency of the R/sub DS(on/) of power MOSFETson the instantaneous value of the drain current into the calculation ofthe conduction losses of high-frequency three-phase PWM inverters

In this paper, the conduction losses of power MOSFETs are calculated analytically for application in three-phase voltage DC-link pulsewidth modulation (PWM) power converter systems. Contrary to a conventional calculation, the dependency of the turn-on behavior on the drain current is considered in terms of a quadratic approximation. The derived relationships are represented graphically; they can be included directly into the dimensioning of the power transistors     

The use of gas chemistry to evaluate boiling processes and initial steam fractions in geothermal reservoirs with an example from the olkaria field, Kenya

A method has been developed to evaluate boiling processes in the producing aquifer of “high-enthalpy” geothermal wells using data on the concentrations of CO₂, H₂S and H₂ in steam discharged. The extent to which water and steam are separated in the producing aquifer is evaluated as well as the amount of enhanced evaporation due to heat flow from the rock to the boiling water. Further, the initial steam fraction in the reservoir fluid is calculated. Results are presented for the Olkaria geothermal field, Kenya, to demonstrate the use of our method. They show that the initial steam fraction in the reservoir is very small: up to 0.25% of the mass, or about 10% by volume. Segregation of water and steam in the producing aquifers is rather extensive for some of the wells. Thus, water which has boiled and yielded steam into wells amounts to more than two times the mass of the fluid discharged from the well. The larger part of the exploited steam ( ) is generated by flow of heat from the rock to the boiling water.