Kinetic study of stilbene synthesis with benzyltriphenylphosphonium bromide as phase transfer catalyst

Abstract

A kinetic study of the Wittig reaction for synthesizing stilbene is carried out by reacting benzaldehyde (C₆H₅CHO) with benzyltri‐phenylphosphonium bromide (BTPPB) in the NaOH(aq)/CH₂Cl₂(org) two‐phase reaction system. The rate of reaction depends on the agitation speed, the temperature and the concentrations of C₆H₅CHO, BTPPB, and NaOH. When the agitation speed is low, the reaction is highly affected by interface diffusion. The reactant rate constant, based on the S_N 2 substitution mechanism and the activation energy are also determined. It is found that the activation energy obtained from the present study (E_a =11.97 kcal/mole) is less than that of the previously documented data (E_a =12.984 kcal/mole) in which benzyltriphenylphosphonium chloride (BTPPC) was used as a phase transfer catalyst.     

Novel Stepped-Width Design Concept for Compact Multimode-Interference Couplers With Low Cross-Coupling Ratio

We show through detailed simulations that the length of conventionally designed multimode-interference couplers for low (<50%) cross-coupling ratios can be shortened significantly by replacing a segment that is 3/2-times the coupling length by a minimum-width design. For the 15% cross-coupling device, this stepped-width design results in 32% length reduction. With additional incorporation of adiabatic tapering, the length reduction can increase to over 44%. Shortening of the device makes it possible to fabricate ring resonators with larger free spectral range, significantly increases the 1-dB bandwidth for the total transmittance, and also helps to reduce the radiative loss     

Purification and detection of linamarin from cassava root cortex by high performance liquid chromatography

Linamarin, a cyanogenic glycoside in cassava (Manihot esculenta Crantz cv. KU-50) root cortex and parenchyma was extracted with different acids (HCl, H₂SO₄, H₃PO₄ or CH₃COOH) and detected by high performance liquid chromatography (HPLC). The highest linamarin was found in both tissues extracted with H₂SO₄. However, the concentration of linamarin in the extract of the root cortex was higher than that of the root parenchyma. Linamarin in crude extract of the root cortex using 0.25 M H₂SO₄ was purified by the second step HPLC with the yield of 91.54%. These extraction, detection and purification methods were useful to improve the purity of linamarin from cassava, especially the root cortex.     

A Microtransceiver for UHF Proximity Links Including Mars Surface-to-Orbit Applications

A low-volume low-mass low-power ultra-high-frequency radio transceiver for future planetary missions is described. The project targets a volume of less than 10 , mass of less than 50 grams, and power consumption of 50 mW on receive and 100 mW, 300 mW, or 3 W on transmit (for 10 mW, 100 mW, and 1 W output options). The transmitter design supports convolutionally coded binary phase-shift keying (BPSK), RC-BPSK, and quadrature phase-shift keying transmission from 1 to 256 kbps. Command/control instructions can be received at 2 or 8 kbps, with a sensitivity of better than 120 dBm. In addition to its low volume/mass/power features, temperature compensation to 100 C and radiation tolerance to 100 krad allow operation outside of thermally controlled, shielded enclosures, further reducing the mass and complexity of exploration vehicles. The design is described in a top-down format, beginning with system requirements and proceeding through digital modem algorithm development, discussion of the silicon-on-sapphire CMOS process used and elaboration of key blocks in the radio-frequency (RF) integrated circuit design. Techniques to address coupling between high-sensitivity RF and on-chip digital circuits are also presented, and test results are given for prototypes of all major functions. Although designed for the Martian environment, the transceiver is expected to be useful in other proximity links where a small low-power radio compatible with Prox-1 space-link protocols is desired.     

Enhancement of fermentative biohydrogen production from textile desizing wastewater via coagulation-pretreatment

A real textile desizing wastewater (TDW) was coagulation-pretreated to enhance its potential of biohydrogen production. Batch fermentation showed that the hydrogen production was efficiently enhanced (550 and 120% increments for hydrogen production rate and hydrogen yield, respectively) and the production performance was substrate-concentration dependent. A peak hydrogen production rate of 3.9 L/L-d and hydrogen yield of 1.52 mol/mol hexose were obtained while using coagulant GGEFloc-653 at a dosage of 1 g/L to pretreat TDW with the concentration of 15 g total sugar/L. The coagulation-pretreatment could have butyrate-type fermentation with high biohydrogen production and the removed some toxic materials that might drive the metabolic pathways to those not favoring biohydrogen production. Based on the data obtained, strategies to operate the coagulation and biohydogen fermentation are suggested. Moreover, fermentation effluent utilization such as for two-stage biogas production and further biohythane (a mixture of H₂ and CH₄) generation are also elucidated.     

Growth and Application of ZnO Nanostructures

Nanostructures are the building blocks of future nanodevices and thus methods for fabricating nanostructures of various materials in various forms are fundamentally important. Among those nanostructures ZnO has received much attention over the past few years due to the wide range of research by many different groups focused on different novel nanostructures with different properties. Although ZnO nanowires have been intensively studied, there are only a few methods that showed promising characteristics for practical applications. Without much effort, it can be grown in many different nanostructure forms, thus allowing various novel devices to be achieved. In this study, we intend to review those methods that enable nanostructure growth to be more controllable and feasible for applications. The methods for fabricating ZnO nanostructures are introduced in the first part. In the second part, the application of those nanostructures are mentioned and explained. Finally, the future realization of nanodevices is discussed.     

Plasticizer migration in bloodmeal‐based thermoplastics

Tri‐ethylene glycol (TEG) is an effective plasticizer for many protein‐based thermoplastics because of its low volatility, however, partial miscibility with the protein matrix may still lead to some phase separation. Spatial variation of TEG concentration in bloodmeal‐based thermoplastics as a result of processing was investigated using synchrotron‐based FT‐IR micro‐spectroscopy. Although TEG forms strong hydrogen bonding with proteins, for the protein to fold into β‐sheets bound plasticizer must be released. TEG can then migrate, pooling into localized areas, rich in plasticizer. Further heating causes further migration towards the edge of plasticized bloodmeal particles where the TEG may evaporate. Thermo‐gravimetric analysis confirmed that loss of TEG by evaporation may occur at 120°C, given enough time for diffusion. Efficient mixing combined with a short residence time at elevated temperature mean significant plasticizer loss is unlikely during processing. However, it does limit long‐term use at elevated temperatures. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39969.     

Influence of 4ZnO–B2O3 Addition on Dielectric Properties and Microstructures of Barium Strontium Titanate

This study investigates the effect of 4ZnO–B₂O₃ on the sintering behavior, dielectric properties, and microstructures of Ba_0.6Sr_0.4TiO₃ (BST) ceramics. These ceramics were sintered in air at temperatures ranging from 900°C to 1080°C. BST ceramics with 4ZnO–B₂O₃ addition can be sintered to a theoretical density higher than 95% at 1050°C. A secondary phase (Ba₂ZnTi₅O₁₃) is produced in the BST ceramics during 4ZnO–B₂O₃ addition. Compositional analysis using TEM-EDX of the BST ceramics with 3 wt% 4ZnO–B₂O₃ revealed that the Zn ion is generally located at the triple points. This result indicates that BaO, TiO₂, and ZnO form a liquid phase that acts as a secondary phase at the lower sintering temperatures. The amount of secondary phase was observed to increase as the amount of 4ZnO–B₂O₃ additives increased. In addition, the original Ba_0.6Sr_0.4TiO₃ phase was shifted to the Ba_0.5Sr_0.5TiO₃ phase by the addition of 3 wt% 4ZnO–B₂O₃ at 1050°C. The Ba_0.6Sr_0.4TiO₃ ceramic with 2 wt% 4ZnO–B₂O₃ sintered at 1050°C in air for 2 h exhibited dielectric properties of ɛ_r=1883 and dissipation loss=0.36%. Moreover, BST with 1 wt% 4ZnO–B₂O₃ addition sintered at 1080°C exhibits dielectric properties of ɛ_r=2330, dissipation loss=0.29%, and bulk density >95% of theoretical density.     

Integrated pretreatment with capacitive deionization for reverse osmosis reject recovery from water reclamation plant

Reverse osmosis (RO) reject recovery from the water reclamation process was demonstrated feasible using an integrated pretreatment scheme followed by the Capacitive Deionization (CDI) process. The RO reject had an average total dissolved solids (TDS) of 1276 ± 166 mg/L. Water recovery of 85% with water quality comparable with the RO feed was achieved. Pretreatments using biological activated carbon (BAC) and BAC–ultrafiltration (UF) attained total organic carbon (TOC) removal efficiencies of 23.5 ± 6.0% and 39.9 ± 9.0%, respectively. Organics removal of RO reject was attributed to simultaneous adsorption and biodegradation in the BAC pretreatment, while further biodegradation in the submerged UF membrane tank provided additional organics removal. Membrane and CDI fouling was reduced by pH adjustment of the pretreated RO reject to approximately 6.5, which prolonged the CDI operation time by at least two times. The CDI process was able to achieve more than 88 and 87% TDS and ion removals, respectively, while PO₄³⁻ and TOC removals were at 52–81% and 50–63%, respectively.