Bulk free radical polymerizations of methyl methacrylateunder non-isothermal conditions and with intermediate additionof initiator: Experiments and modeling

Experimental data on the monomer conversion, x_m, and the weight average molecular weight, M_w, have been generated under several isothermal and non-isothermal conditions for the polymerization of methyl methacrylate in a rheometer-reactor assembly. The non-isothermal results, in particular, can be used to provide more stringent tests of kinetic models than isothermal data alone. A simple empirical model has been used to describe this system that accounts for the gel (Trommsdorff) and glass effects. The model involves only x_m and the temperature, and is quite general. The model parameters are tuned using only three sets of isothermal data. Good agreement is found between the experimental results and model predictions for a whole variety of experimental conditions, including non-isothermal operation and with intermediate addition of initiator. Because of its generality, this model is quite suitable for use for on-line optimizing control as well as for describing industrial reactors.     

A Qualitative Review on Tunnel Field Effect Transistor- Operation,Advances, and Applications

Silicon - Tunnel Field Effect Transistor (TFET) has become one of the promising devices to be part of Integrated circuits as the technology advances to the nanoscale. A TFET has many advantages...     

Identification of the Trail Pheromone of the Pavement Ant Tetramorium immigrans (Hymenoptera: Formicidae)

Journal of Chemical Ecology - Four species of Tetramorium pavement ants are known to guide foraging activities of nestmates via trail pheromones secreted from the poison gland of worker ants, but...     

1-[2-(1-Cyclobutylpiperidin-4-yloxy)-6,7-dihydro-4H-thiazolo[5,4-c]pyridin-5-yl]propan-1-one: a Histamine H3 Receptor Inverse Agonist with Efficacy in Animal Models of Cognition

A series of chemical optimizations, which was guided by in vitro affinity at histamine H₃ receptor (H₃R), modulation of lipophilicity, ADME properties and preclinical efficacy resulted in the identification of 1-[2-(1-cyclobutylpiperidin-4-yloxy)-6,7-dihydro-4H-thiazolo[5,4-c]pyridin-5-yl]propan-1-one ( 45 e ) as a potent and selective (K_i=4.0 nM) H₃R inverse agonist. Dipsogenia induced by (R)-α-methylhistamine was dose dependently antagonized by 45 e , confirming its functional antagonism at H₃R. It is devoid of hERG and phospholipidosis issues. Compound 45 e has adequate oral exposures and favorable half-life in both rats and dogs. It has demonstrated high receptor occupancy (ED₈₀=0.22 mg/kg) and robust efficacy in object recognition task and, dose dependently increased acetylcholine levels in brain. The sub-therapeutic doses of 45 e in combination with donepezil significantly increased acetylcholine levels. The potent affinity, selectivity, in vivo efficacy and drug like properties together with safety, warrant for further development of this molecule for potential treatment of cognitive disorders associated with Alzheimer's disease.     

Electrical and Dielectric Properties of Non-magnetic Al<Superscript>3+</Superscript> Substituted Ni–Zn Nano Ferrites for High Frequency Applications

The effect of Al substitution on electrical and dielectric parameters of Ni–Zn ferrite has been discussed in the present work. The phase identification, surface morphology was studied using X-ray diffractometer (XRD), scanning electron microscope (SEM), respectively. The XRD patterns confirm the single-phase formation of these ferrites. With Al³⁺, substitution lattice parameter decreases due to smaller Al³⁺ ions replacing Fe³⁺ ions. The average grain size obtained from SEM results are in the range of 390–27 nm. The DC resistivity was observed to increase with increasing Al³⁺ ions concentration due to the unavailability of Fe³⁺ ions. Dielectric constant (\(\upvarepsilon ^{\prime }\)) and dielectric loss tangent (tan δ) have been studied as a function of frequency (1 kHz–10 MHz) and temperature (50–300 °C). The observed results are explained on the basis of interfacial polarization as predicted by Maxwell and Wagner.     

Effect of Sintering Temperature on Thermoelectric Properties of p‐Bi2Te3 Alloys Produced by Gas Atomization

In this research, p‐type Bi₂Te₃–75% Sb₂Te₃ thermoelectric alloy powders were produced by gas atomization and subsequently sintered by hot pressing at different temperatures. The grain growth of the hot‐pressed samples was observed with increasing sintering temperature from 380°C to 460°C. The compressive strength increased with increasing hot‐pressing temperature due to the high relative density of bulk samples obtained at high temperatures. The effect of sintering temperature on thermoelectric (TE) properties was studied. The maximum power factor 3.48 mW/mK² was obtained for the sample hot pressed at 420°C due to the resulting high electrical conductivity and enhanced Seebeck coefficient values.     

Effect of Milling Time on the Microstructure and Thermoelectric Properties of P‐type TAGS‐90 Alloys by HEM and SPS

In this study, p‐type TAGS‐90 powders were fabricated using high‐energy milling (HEM), subsequently sintered by spark plasma sintering (SPS). And then, the effects of milling time on the microstructure, mechanical, and thermoelectric properties were investigated. The powders were quickly decreased to fine particles of ~1 μm in size and uniformly agglomerated with the increasing of milling time. XRD results indicated that all milled powders and SPSed samples showed single GeTe phase. Also, EDX results showed almost no contamination and exact composition after milling. The maximum figure of merit, ZT = 1.08, was obtained for 30‐min‐milled sample at 723 K.     

Enantiospecific Synthesis and Cytotoxicity Evaluation of Oximidine II Analogues

Analogues of the anticancer natural product oximidine II were prepared and evaluated for cytotoxicity. One analogue of oximidine II that carries a C15 allylic amide side chain as well as two analogues with C15 vinyl sulfone side chains were found to lack cytotoxicity against the cancer cell line SK‐Mel‐5, thereby confirming the necessity of the C15 enamide side chain of oximidine II for cytotoxicity. Four analogues, designed by comparative molecular similarity index analysis (CoMSIA), that feature a less complex macrolactone scaffold were prepared and tested. The two analogues carrying a C15 vinyl sulfone group and the two analogues with a C15 oximidine II enamide side chain showed weak cytotoxicity against the SK‐Mel‐5 cell line and other cell lines, indicating that the designed simplified macrocycles cannot replace the oximidine II macrocycle.     

Influence of Undercooling and Nd4Ba2Cu2O10 Content on the Growth Rate of Large-Grain Bulk Nd-Ba-Cu-O Superconductor

The dependence of growth rate on isothermal undercooling and composition has been investigated for Nd-Ba-Cu-O single grains containing various amounts of nonsuperconducting Nd₄Ba₂Cu₂O₁₀ (Nd-422) phase inclusions and fabricated under a 1% O₂ in N₂ atmosphere using a top seeded melt growth technique. The growth rate along the crystallographic c -direction is observed to exceed that along the a / b direction at all undercooling temperatures and exhibits a maximum for a Nd-422 content of ∼10 mol%. The samples have been examined by optical microscopy and the results interpreted within an established planar solidification model.     

Removal of toxic metal Cr(VI) from aqueous solutions using sawdust as adsorbent: Equilibrium, kinetics and regeneration studies

In the present study, a low-cost adsorbent is developed from the naturally and abundantly available sawdust which is biodegradable. The removal capacity of Cr(VI) from aqueous solutions and from the synthetically prepared industrial effluent of electroplating and tannery industries is obtained. The batch experiments are carried out to investigate the effect of the significant process parameters such as initial pH, change in pH during adsorption, contact time, adsorbent amount, and the initial Cr(VI) concentration. The maximum adsorption of Cr(VI) on sawdust is obtained at an initial pH value of 1. The value of pH increases with increase in contact time and initial Cr(VI) concentration. The equilibrium data for the adsorption of Cr(VI) on sawdust is tested with various adsorption isotherm models such as Langmuir, Freundlich, Redlich–Peterson, Koble–Corrigan, Tempkin, Dubinin–Radushkevich and Generalized equation. The Langmuir isotherm model is found to be the most suitable one for the Cr(VI) adsorption using sawdust and the maximum adsorption capacity obtained is 41.5 mg g⁻¹ at a pH value of 1. The adsorption process follows the second-order kinetics and the corresponding rate constants are obtained. Desorption of Cr(VI) from sawdust using acid and base treatment exhibited a higher desorption efficiency by more than 95%. A feasible solution is proposed, for the disposal of the contaminant (acid and base solutions) containing high concentration of Cr(VI) obtained during the desorption process. The interference of other ions which are generally present in the electroplating and tannery industrial effluent streams on the Cr(VI) removal is investigated.