Pinched tube flow reactor: Hydrodynamics and suitability for exothermic multiphase reactions

A novel tubular flow reactor where a straight tube is modified by pinching it periodically at a fixed pitch and at different angles is presented. Pinched tubes (straight tube as well as helical coils) with different pitch and angles between successive pinching are studied. This work reports a detailed hydrodynamic study involving single and two‐phase flow. Mixing experiments showed that having an angle of 90° between successive pinchs achieves the shortest mixing length when compared to lower angles. Pressure recovery along with sequence of high and low shear zones and change of flow direction imposed better mixing. Residence time distribution studies showed that higher number of pinch sections decreases the extent of dispersion, yet it deviates from plug flow. The performance is evaluated by carrying a homogeneous and two‐phase aromatic nitration and also liquid‐liquid extraction. Pinched tube presents an economical option as a flow reactor for conducting exothermic reactions. © 2016 American Institute of Chemical Engineers AIChE J, 63: 358–365, 2017     

Substrate Selection Influences Molecular Recognition in a Screen for Lymphoid Tyrosine Phosphatase Inhibitors

Assay design is an important variable that influences the outcome of an inhibitor screen. Here, we have investigated the hypothesis that protein tyrosine phosphatase inhibitors with improved biological activity could be identified from a screen by using a biologically relevant peptide substrate, rather than traditional phosphotyrosine mimetic substrates. A 2000‐member library of drugs and drug‐like compounds was screened for inhibitors of lymphoid tyrosine phosphatase (LYP) by using both a peptide substrate (Ac‐ARLIEDNE‐pCAP‐TAREG‐NH₂, peptide 1) and a small‐molecule phosphotyrosine mimetic substrate (difluoromethyl umbelliferyl phosphate, DiFMUP). The results demonstrate that compounds that inhibited enzyme activity on the peptide substrate had greater biological activity than compounds that only inhibited enzyme activity on DiFMUP. Finally, epigallocatechin‐3,5‐digallate was identified as the most potent inhibitor of lymphoid tyrosine phosphatase activity to date, with an IC₅₀ of 50 nM and significant activity in T‐cells. Molecular docking simulations provided a first model for binding of this potent inhibitor to LYP; this will constitute the platform for ongoing lead optimization efforts.     

Thiuram Disulfides as Pseudo‐irreversible Inhibitors of Lymphoid Tyrosine Phosphatase

We screened a small library of thiuram disulfides for inhibition of lymphoid tyrosine phosphatase (LYP) activity. The parent thiuram disulfide, disulfiram, inhibited LYP activity in vitro and in Jurkat T cells, whereas diethyldithiocarbamate failed to inhibit LYP at the concentrations tested. Compound 13 , an N‐(2‐thioxothiazolidin‐4‐one) analogue, was found to be the most potent LYP inhibitor in this series, with an IC₅₀ value of 3 μM . Compound 13 inhibits LYP pseudo‐irreversibly, as evidenced by the time‐dependence of inhibition, with a K_i value of 1.1 μM and a k_inact value of 0.004 s^?1. The inhibition of LYP by compound 13 could not be reversed significantly by incubation with glutathione or by prolonged dialysis, but could be partially reversed by incubation with dithiothreitol. Compound 13 also inhibited LYP activity in Jurkat T cells.     

Exceptionally High Dielectric Constant in Ceramic Pr2CuO4

The pristine layered cuprate Pr₂CuO₄ samples of >95% density were fabricated as thin disks. The samples, analyzed by X‐ray diffraction and Scanning electron microscopy, showed clean T′‐type phase with Rietveld refined lattice parameters a = b = 3.95805(±5) Å and c = 12.2262(±5) Å. The measured dielectric properties of the Pr₂CuO₄ ceramics, in the temperature range ?100°C–150°C and frequencies (ν) 0.1 Hz–1 MHz, showed extremely high ε_r′ > 10⁴ (above ?30°C), and dissipation (tan δ = ε_r′′/ε_r′) between 0.1 and 5 (for 500 Hz ≤ ν ≤ 1 MHz, and ?100 ≤ T ≤ 150°C). The ac conductivity of Pr₂CuO₄ ceramics ranged between 10^?6 and 10^?3 Scm^?1 for the measured frequencies and temperatures, and showed frequency‐dependent double power law behavior akin to a modified Jonscher's power law.     

Thermal and mechanical properties of polyisobutylene‐based thermoplastic polyurethanes

We investigated thermal and mechanical properties of thermoplastic polyurethanes (TPUs) with the soft segment comprising of both polyisobutylene (PIB) and poly(tetramethylene)oxide (PTMO) diols. Thermal analysis reveals that the hard segment in all the TPUs investigated is completely amorphous. Significant mixing between the hard and soft segments was also observed. By adjusting the ratio between the hard and soft segments, the mechanical properties of these TPUs were tuned over a wide range, which are comparable to conventional polyether‐based TPUs. Constant stress creep and cyclic stress hysteresis analysis suggested a strong dependence of permanent deformation on hard segment content. The melt viscosity correlation with shear rate and shear stress follows a typical non‐Newtonian behavior, showing decrease in shear viscosity with increase in shear rate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 891‐897, 2013     

Synthesis,characterization and application of Azadirachta indica juss (neem oil) fatty amides (AIJFA) based polyurethanes coatings: A renewable novel approach

Number of diethanol amides has been developed by scientist using various vegetable oils and not from neem seed oil. Most of the research work on neem seed oil has explored its applications in pharmaceutical and pesticides fields. This paper representing new area of application of neem seed oil for polymeric resin, in which we attempted to synthesize the neem seed oil based poly(urethane fatty amides) by reaction of neem oil fatty amide (AIJFA) with trimer of isophorone diisocyanate (IPDI). Spectral study of AIJFA was carried out by using FT-IR and ¹H NMR techniques. Molecular weight of AIJFA was determined by gel permeation chromatography (GPC). Fatty acid composition of neem seed oil was obtained by gas chromatographic method. The coatings applied on mild steel plates were evaluated by determining coating properties, chemical and corrosion resistances. TGA study of coatings showed higher thermal stability to AIJFA based PU coatings compared to normal urethane and alkyd coatings.     

C-3 Substituted Lawsonemonoximates of Holmium(III): Synthesis, Characterization, and Antimicrobial Activity

A series of five new metal complexes of Ho(III) with C-3 substituted derivatives of lawsonemonexime (2-hydroxy-1,4-naphthalenediene-1-oxime) were synthesized. The compounds were characterized by melting point, elemental analysis, IR spectroscopy and magnetic susceptibility. The antimicrobial activity of the compounds were determined by disk diffusion method and broth micro-dilution techniques using Mueller Hinton medium against the following organisms: S. aureus ATCC 6538P, Klebsiella pneumoniae, NCTC 418, Pseudomonas aeruginosa ATCC 27833, Salmonella typhimurium ATCC 23564, E. coli U 1777, E. coli HB101, Proteus morganii NCIM 2860, Providencia stuartii NCIM 2799 and Acinetobacter baumannii U 24. The chelates of Ho(III) with lawsonemonoxime and Ho(III) with 3-bromolawsonemonoxime showed a variable antimicrobial activity against all organisms tested except Pseudomonas and Klebsiella spp. S. aureus was found more sensitive to all ligands and chelates tested; but the MIC values of chelates were considerably less; thus having more antimicrobial effect.     

Blends of polypropylene and ethylene octene comonomer with conducting fillers: Influence of state of dispersion of conducting fillers on electrical conductivity

Blends of polypropylene/ethylene octene comonomer (PP/EOC) with conducting fillers viz., carbon black (CB) and multiwall carbon nanotubes (MWNT) were prepared using melt mixing technique with varying filler concentration and blend compositions. Thermo gravimetric analysis studies indicated that presence of filler enhanced the thermal stability of PP/EOC blends. Morphological analysis revealed the formation of matrix‐dispersed droplet and co‐continuous type of morphology depending on the blend compositions. Significant reduction in droplet size and finer ligament thickness in co‐continuous structure were observed in the blends with filler due to compatibilization action. Fillers were found to be aggregated in the EOC phase irrespective of blends compositions and could be related to the affinity of the fillers toward EOC phase. The electrical conductivity of PP/EOC blends with CB and MWNT was found to be highest for 80/20 composition and decreased as EOC content increased. The percolation threshold of CB was between 10 and 15 wt% for the 80/20 and 70/30 blends whereas it was 15–20 wt% for blends with EOC content higher than 30 wt%. The percolation threshold was 2–3 wt% MWNT for PP/EOC blends. This was attributed to the aggregated filler network preferentially in the EOC phase. The melt‐rheological behavior of PP/EOC blends was significantly influenced in presence of both the fillers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

A miniature disk electrostatic aerosol classifier (mini-disk EAC) for personal nanoparticle sizers

We have developed a miniature disk electrostatic aerosol classifier (mini-disk EAC) for use in electrical mobility-based personal nanoparticle instrumentation for measurement of personal exposures to nanoaerosols. The prototype consists of two parallel disk electrodes separated by an electrically insulating spacer, to create the particle classification zone. The aerosol enters and exits the classification zone along the bottom disk electrode. An additional, particle-free sheath flow is used to improve the measurement resolution. The transmission measurement of the mini-disk EAC for DMA-classified particles shows that particle losses due to diffusion and electrical image forces were low. The particle penetration at 10 nm diameter (the designed lower size limit for the classifier) was 67% when the prototype was operated at the aerosol and sheath flow rates of 0.5 and 1.0 l min^?1, respectively. The performance of the mini-disk EAC was experimentally characterized using the particle cutoff curves that describe their penetration through the classifier as a function of applied voltage across the two disk electrodes. Based on the measurement of particle penetration at different aerosol and sheath flows, it was found that the aerosol and sheath flow rates of 0.5 and 1.5 l min^?1 were optimal for classifier operation. Finally, a semi-empirical model was also developed to describe the transfer function of the mini-disk EAC for non-diffusive particles.     

Biodiesel production from mixtures of canola oil and used cooking oil

Used cooking oil (UCO) was mixed with canola oil at various ratios in order to make use of used cooking oil for production of biodiesel and also lower the cost of biodiesel production. Methyl and ethyl esters were prepared by means of KOH-catalyzed transesterification from the mixtures of both the oils. Water content, acid value and viscosity of most esters met ASTM standard except for ethyl esters prepared from used cooking oil. Canola oil content of at least 60% in the used cooking oil/canola oil feedstock is required in order to produce ethyl ester satisfying ASTM specifications. Although ethanolysis was proved to be more challenging, ethyl esters showed reduced crystallization temperature (−45.0 to −54.4 °C) as compared to methyl esters (−35.3 to −43.0 °C). A somewhat better low-temperature property of ester was observed at higher used cooking oil to canola oil ratio in spite of similar fatty acid compositions of both oils.