Cryogenic crushing of polystyrene

Atactic and isotactic polystyrene powders were fractured with a ball mill at ?196°C. The molecular weight distributions at various milling times measured by GPC show an initial asymmetric broadening and then a gradual returning to the original narrow bell-shaped distribution. Analysis of molecular weight distributions suggests a preferential chain scission near the chain ends. X-ray diffraction spectra of isotactic polystyrene samples show that after 24 hr of milling, the semicrystalline polystyrene was completely transformed into an amorphous polymer. DSC thermogram of the milled isotactic polystyrene reveals several crystallization peaks preceding melting when the samples were heated.     

Development of cooling load temperature differential values for building envelopes in Thailand

Abstract

This article describes the development of cooling load temperature differential (CLTD) values for building envelopes made of materials commonly used in Thailand and using Bangkok weather data. The Bangkok design weather data are selected from 12 years of data collected by the meteorological department. Two sets of weather data for Bangkok are chosen. The first weather data set was selected based on dry bulb temperature of 0.4% annual cumulative frequency of occurrence. The second weather data set was selected based on dry bulb temperature of 0.4% hourly cumulative frequency of occurrence and solar radiation obtained from the ASHRAE mathematical model. The room parameters which have effects on thermal response, such as building envelope material, room decoration, and room conditions are investigated. 288 different room types for each exterior wall type and each roof type were checked. The values of amplitude and delay based on conduction weighting factors for a sinusoidal heat gain are analyzed. The distribution of the amplitude and delay of similar thermal response are grouped together and represented by a single point in the group. For each set of design weather data, 7 CLTD tables for exterior walls and 6 CLTD tables for roofs are developed.     

Deposition of tin oxide,iridium and iridium oxide films by metal-organic chemical vapor deposition for electrochemical wastewater treatment

In this research, the specific electrodes were prepared by metal-organic chemical vapor deposition (MOCVD) in a hot-wall CVD reactor with the presence of O₂ under reduced pressure. The Ir protective layer was deposited by using (Methylcyclopentadienyl) (1,5-cyclooctadiene) iridium (I), (MeCp)Ir(COD), as precursor. Tetraethyltin (TET) was used as precursor for the deposition of SnO₂ active layer. The optimum condition for Ir film deposition was at 300 °C, 125 of O₂/(MeCp)Ir(COD) molar ratio and 12 Torr of total pressure. While that of SnO₂ active layer was at 380 °C, 1200 of O₂/TET molar ratio and 15 Torr of total pressure. The prepared SnO₂/Ir/Ti electrodes were tested for anodic oxidation of organic pollutant in a simple three-electrode electrochemical reactor using oxalic acid as model solution. The electrochemical experiments indicate that more than 80% of organic pollutant was removed after 2.1 Ah/L of charge has been applied. The kinetic investigation gives a two-step process for organic pollutant degradation, the kinetic was zero-order and first-order with respect to TOC of model solution for high and low TOC concentrations, respectively.     

Hybrid transistor manipulation controlled by light within a PANDA microring resonator

In this paper, the novel type of transistor known as a hybrid transistor is proposed, in which all types of transistors can be formed by using a microring resonator called a PANDA microring resonator. In principle, such a transistor can be used to form for various transistor types by using the atom/molecule trapping tools, which is named by an optical tweezer, where in application all type of transistors, especially, molecule and photon transistors can be performed by using the trapping tools, which will be described in details.     

Cooperative diversity schemes for asynchronous wireless networks

We construct cooperative diversity coding schemes that mitigate the effects of symbol asynchronicity among network users. We do so by modifying, at the expense of implementation practicality, the signaling complexity of well behaved existing schemes. The modification allows the same good performance (DMT optimality) in the presence of synchronicity, and almost-surely permits full-diversity gains for any event of symbol asynchronicity. This work was in part carried out while Petros Elia was at the University of Southern California. This research is supported in part by NSF-ITR CCR-0326628.     

n-GaAlAs on p-GaAs heterostructure solar cells grown by molecular beam epitaxy

p-GaAs substrate was used as the starting material in molecular beam epitaxial growth. n-type GaAlAs for heterostructure and n-GaAs capping layer were then grown after a buffer layer deposition on the substrate. The n-GaAlAs on p-GaAs heterostructure solar cells, with active area of 13.25 mm² under 100 mW/cm² AM1 illumination light source, provide a typical output as follows: V_oc=0.73 V, I_sc=6 mA, FF=0.7 and η=23% (active area). Spectral response measurements from 500 to 850 nm reflects the window effect of GaAlAs and band edge of GaAs materials.     

Argon Plasma Treatment of Tapioca Starch Using a Semi-continuous Downer Reactor

To develop a novel modification process of tapioca starch using low-pressure argon plasma treatment in a large-scale production, a semi-continuous downer reactor was designed to provide a production rate of 0.1–0.5 kg per cycle. Physicochemical and rheological properties of plasma-treated starch were investigated in order to predict the phenomena occurred during the plasma treatment. Native tapioca starch (NTS) was plasma-treated for 1, 3, or 6 cycles, which were referred to as PTS-1, PTS-3, or PTS-6 samples, respectively. Plasma treatment of the NTS resulted in a significant decrease (P?<?0.05) in paste clarity and Rapid Visco Analyzer (RVA) breakdown viscosity, and an increase in gel strength of starch. The PTS-1 had the lowest paste clarity of 39.85 %T at 650 nm and breakdown viscosity of 29.71 Rapid Visco Unit (RVU), and the highest gel strength, e.g., G′?=?5.47ω ^0.32. With increasing the number of treatment cycles, i.e., the PTS-3 and PTS-6, the paste clarity and breakdown viscosity significantly increased (P?<?0.05), while the gel strength decreased. The Fourier transform infrared (FTIR) spectroscopy via relative areas of C–O–C peaks indicated that the PTS-1 had a significant increase (P?<?0.05) in the C–O–C cross-linked bonds compared to the NTS, but the effect of depolymerization could further suppress the cross-linking reaction when the number of treatment cycle was increased. Taking an advantage of a very short residence time (less than 0.3 s) in the plasma downer reactor, the semi-continuous process of starch modification could be developed for a commercial production of non-chemically modified starch with a relatively low degree of cross-linking.     

Chirped InGaAs quantum dot molecules for broadband applications

Lateral InGaAs quantum dot molecules (QDMs) formed by partial-cap and regrowth technique exhibit two ground-state (GS) peaks controllable via the thicknesses of InAs seed quantum dots (x), GaAs cap (y), and InAs regrowth (z). By adjusting x/y/z in a stacked QDM bilayer, the GS peaks from the two layers can be offset to straddle, stagger, or join up with each other, resulting in multi-GS or broadband spectra. A non-optimized QDM bilayer with a 170-meV full-width at half-maximum is demonstrated. The temperature dependencies of the emission peak energies and intensities from the chirped QDM bilayers are well explained by Varshni''s equation and thermal activation of carriers out of constituent quantum dots.     

Inside Cover: Cytotoxicities and Structure–Activity Relationships of Natural and Unnatural Lamellarins toward Cancer Cell Lines (ChemMedChem 3/2009)

The inside cover picture shows the structure of lamellarin N as a representative of cytotoxic marine lamellarin alkaloids, together with a potential molecular target, the topoisomerase I–DNA complex. Systematic SAR studies revealed the importance of the substituents for potent cytotoxicity. For more details, see the Full Paper by P. Ploypradith et al. on p. 457 ff.