Synthesis of A<Subscript>2</Subscript>B<Subscript>2</Subscript> miktoarm star copolymers from a new heterobifunctional initiator by combination of ROP and ATRP

Abstract  

A new heterobifunctional initiator, 2,3-bis(2-bromo-2-methylpropionyloxy) succinic acid, was synthesized and used in preparation of A₂B₂ miktoarm star copolymers, (polystyrene)₂(poly(ε-caprolactone))₂, by combination of atom transfer radical polymerization (ATRP) and Controlled ring-opening polymerization (ROP). The structures of products were confirmed by the ¹H NMR, ¹³C NMR, FT–IR, elemental analysis, differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). GPC traces show that the obtained polymers have a relatively narrow molecular weight distribution. The compositions of resulting miktoarm star copolymers were very close to theoretical.     

Effect of alternative C2 carbon sources on the growth, lipid, and γ-linolenic acid production of spirulina (Arthrospira platensis)

The influence of different organic carbon sources (glucose, ethanol, and acetic acid) at different concentrations (0.1, 0.5, and 1.0 g/L for batch and 1.0, 2.0, and 3.0 g/L for fed-batch) were studied in the mixotrophic production (using both light and carbon source) of γ-linolenic acid (GLnA) by spirulina (Arthrospira platensis). The obtained spirulina was analyzed in terms of biomass, lipid, and GLnA production. In the batch media, increasing the concentrations of glucose, ethanol, and acetic acid led to an increase in the biomass, lipid, and GLnA production. However, carbon sources at concentrations greater than 1.0 g/L in fed-batch media appeared to have no significant effects on the above parameters. It was also demonstrated that biomass, lipid, and GLnA production using ethanol and acetic acid could be as good as those achieved with the classic glucose-based culture media.     

Use of sourdough to reduce phytic acid and improve zinc bioavailability of a traditional flat bread (sangak) from Iran

In this study, effects of 8 different sourdough starters prepared with Saccharomyces cerevisiae, Lactobacillus plantarum, L. acidophilus, and Leuconostoc mesenteroides were investigated on the phytic acid level and mole ratio of phytic acid to zinc in a traditional Iranian bread (sangak). Different sourdough preparations were made and incubated at 30°C for 16 h and added to the dough at 10, 20, and 30% replacement levels. Use of sourdough resulted in a decrease in phytic acid level (also in a decrease in the phytic acid to zinc mole ratio) and corresponding increase in zinc bioavailability index when compared to the commercial sangak bread. The lowest phytic acid concentration and highest zinc bioavailability index were achieved when S. cerevisiae, L. plantarum, and Leu. mesenteroides were used at 30.0% dough replacement with sourdough. This study provides awareness about the negative impacts of higher phytic acid level in the breads, which is particularly the case for sangak bread, and also provides a solution for such issue.     

Ultra low voltage, high performance operational transconductance amplifier and its application in a tunable Gm-C filter

This paper presents an ultra low voltage, high performance Operational Transconductance Amplifier (OTA) and its application to implement a tunable Gm-C filter. The proposed OTA uses a 0.5 V single supply and consumes 60 μw. Employing special CMFF and CMFB circuits has improved CMRR to 138 dB in DC. Using bulk driven input stage results in higher linearity such that by applying a 500 mv_p-p sine wave input signal at 2 MHz frequency in unity gain closed loop configuration, third harmonic distortion for output voltage is −46 dB and becomes −42.4 dB in open loop state for 820 mv_p-p output voltage at 2 MHz. DC gain of the OTA is 47 dB and its unity gain bandwidth is 17.8 MHz with 20 pF capacitance load due to both deliberately optimized design and special frequency compensation technique. The OTA has been used to realize a wide tunable Gm-C low-pass filter whose cutoff frequency is tunable from 1.4 to 6 MHz. Proposed OTA and filter have been simulated in 0.18 μm TSMC CMOS technology with Hspice. Monte Carlo and temperature dependent simulation results are included to forecast the mismatch and temperature effects after fabrication process.     

Pomegranate seed oil as a functional ingredient in beverages

Pomegranate seeds are by‐products of pomegranate juice industry. Since the seeds contain valuable oil that has nutritional and medicinal properties, they can be useful for food applications (especially in juice and beverage industries) as a functional agent. In this study, the possibility of producing a stable pomegranate‐seed‐oil‐in‐water emulsion to be used as a base formula for a new functional beverage was investigated. The influence of gum Arabic (GA) concentration (10.0, 12.5, and 15.0%, w/w) with a constant oil phase content (6.0% w/w) on the turbidity loss rate, emulsion stability index, and droplet size distribution was investigated. Turbidity loss rate was inversely proportional to the GA concentration for all the formulations studied here. Compared to other emulsions, emulsion with 15.0% w/w GA did not show a discernible cream layer during 42 days of storage. Emulsion with 15.0% w/w GA indicated the smallest polydispersity index during this period. The results of this study showed that it was possible to produce a relatively stable pomegranate‐seed‐oil‐in‐water emulsion for use as a functional agent in beverages.     

Synthesis of high surface area nanocrystalline MgO by pluronic P123 triblock copolymer surfactant

Nanocrystalline magnesium oxide with high surface area was prepared by a simple precipitation method using pluronic P123 triblock copolymer (Poly(ethylene glycol)-block, Poly(propylene glycol)-block, Poly(ethylene glycol)) as surfactant. The prepared samples were characterized by X-ray Diffraction (XRD), N₂ adsorption (BET), Fourier transform infrared spectroscopy (FTIR), Thermal, differential thermal gravimetric and differential thermal analyses (TG/DTG/DTA) and Scanning electron microscopy (SEM). The obtained results revealed that the addition of surfactant is effective to prepare magnesium oxide with high surface area and affects the morphology of the prepared samples. The results showed that the magnesium oxide calcined at different temperatures ranging from 600 to 800 °C possessed a high surface area in the range of 133.9–78.1 m² g^?1. In addition, the magnesium oxide prepared with the addition of surfactant showed a narrower pore size distribution compared to the sample prepared without the addition of a surfactant.     

Effect of Different Substrate Pre-Treatments on the Resistance of Aluminum Joints to Moist Environments

The goal of this work was to evaluate and compare the performance of different surface pre-treatments applied to aluminium single lap joints exposed to warm moisture. Four different processes were considered: 1) degreasing-roughening; 2) degreasing-roughening and phosphoric acid anodising; 3) degreasing-roughening and conditioning with Picklex®20 (a water-based product for metal surface preparation); 4) degreasing-roughening and phosphoric acid anodising and contaminating the adherend surface with CaCl₂ to accelerate the tests.

After each pre-treatment, lap-shear specimens were prepared with the open face technique. The half-joints were exposed to warm moisture (50°C, 100% RH) for times up to 4 weeks, then they were completed and subjected to mechanical testing.

The results show that anodising yields the best durability, as strength remained practically constant over time; all the other groups of specimens exhibited progressive reduction in strength and wider scatter of the results. A large role is played by interfacial damage of the adherends, since, under increasing exposure time, failure tends to occur as separation at the adhesive-metal interface. The strength decreased dramatically also for the anodised specimens when the surface was contaminated, which evidences the role of the interfacial damage. The interpretation is supported also by scanning electronic microscopy observation and energy-dispersive X-ray analysis.     

High temperature water gas shift reaction over promoted iron based catalysts prepared by pyrolysis method

In this work the effects of different promoters (Cr, Al, Mn, Ce, Ni, Co and Cu) on the structural and catalytic properties of Nanocrystalline iron based catalysts for high temperature water gas shift reaction were investigated. The catalysts were prepared in active phase (Fe₃O₄) via a facile direct synthesis routs without any additive and characterized using X-ray diffraction (XRD), N₂ adsorption (BET), temperature-programmed reduction (TPR), transmission and scanning electron microscopies (TEM,SEM) techniques. The obtained results indicated that synergic effect of Mn and Ni promoters can lead to obtain a Cr-free catalyst with high activity. In addition, the effect of Ni content on the structural and catalytic properties of the Fe–Mn–Ni catalysts was investigated. It was found that Fe–Mn–Ni catalyst with Fe/Mn = 10 and Fe/Ni = 5 weight ratios showed the highest catalytic activity among the prepared catalysts and possessed a stable catalytic performance without any decrease during 10 h time on stream. Moreover, the effect of GHSV and steam/gas ratio on the catalytic performance of this catalyst was investigated.     

VAD Based on Kernel Smoothed Function of EGARCH Models

An algorithm for a voice activity detector (VAD) is proposed. It is based on the exponential generalized autoregressive conditional heteroscedasticity (EGARCH) filter for generalized hyperbolic (GH), Gaussian random variables, adaptive threshold values and autocorrelation coefficients. EGARCH models are a new variation of GARCH models used especially in economic time series. A speech signal is assumed to have a GH because GH has heavier tails than the Gaussian distribution (GD) covering other heavy tailed distributions like hyperbolic, skewed $t$ , variance gamma (VG), inverse Gaussian (NIG), Cauchy, Student’s $t$ and Laplace distributions. The distribution of noise signal is assumed to be uncorrelated (white noise), but in general, that is not necessary. In the proposed method, heteroscedasticity is modeled by EGARCH. A kernel smoothed function of conditional variances and autocorrelations generate the soft detection vector. Finally, hard detection is the result of comparing the soft detection vector with an adaptive threshold value. The simulation results show that the proposed VAD is able to operate down to $-5$  dB.     

Analytical modeling of grinding wheel loading phenomena

Wheel surface condition plays an important role in the grinding operation. Grinding wheel loading, meaning chip accumulation in the space between grains, leads to deteriorating wheel cutting ability and causes excessive force and temperature. This paper presents an analytical model of wheel loading phenomena as a function of cutting parameters, wheel structure, and material properties. The model is based on the adhesion of workpiece material to abrasive grain surface. It is validated by experimental results from grinding nickel-based superalloy with cubic boron nitride vitrified wheel. This model considers wheel specifications including abrasive grains size and the number of cutting edges. Cutting parameters and process temperature are the other determinant factors. On the basis of this model and empirical results, the effects of the various process parameters are presented.