Characteristics investigation on heat transfer growth of sonochemically synthesized ZnO-DW based nanofluids inside square heat exchanger

Journal of Thermal Analysis and Calorimetry - In recent decades, the growth of heat transfer using nanomaterials in the conventional base fluid has caught the attention of researchers...     

Assessment of the Formant Frequencies in Normal and Laryngectomized Individuals Using Linear Predictive Coding

The objective of this study was to assess the difference in voice quality as defined by acoustical analysis using sustained vowel in laryngectomized patients in comparison with normal volunteers. This was designed as a retrospective single center cohort study. An adult tertiary referral unit formed the setting of this study. Fifty patients (40 males) who underwent total laryngectomy and 31 normal volunteers (18 male) participated. Group comparisons with the first three formant frequencies (F1, F2, and F3) using linear predictive coding (LPC) (Laryngograph Ltd, London, UK) was performed. The existence of any significant difference of F1, F2, and F3 between the two groups using the sustained vowel /i/ and the effects of other factors namely, tumor stage (T), chemoradiotherapy, pharyngectomy, cricothyroid myotomy, closure of pharyngoesophageal segment, and postoperative complication were analyzed. Formant frequencies F1, F2, and F3 were significantly different in male laryngectomees compared to controls: F1 (P<0.001, Mann-Whitney U test), F2 (P<0.001, Student's t test), and F3 (P=0.008, Student's t test). There was no significant difference between females in both groups for all three formant frequencies. Chemoradiotherapy and postoperative complications (pharyngocutaneous fistula) caused a significantly lower formant F1 in men, but showed little effect in F2 and F3. Laryngectomized males produced significantly higher formant frequencies, F1, F2, and F3, compared to normal volunteers, and this is consistent with literature. Chemoradiotherapy and postoperative complications significantly influenced the formant scores in the laryngectomee population. This study shows that robust and reliable data could be obtained using electroglottography and LPC in normal volunteers and laryngectomees using a sustained vowel.     

Stability studies of transition-metal linkage isomers using quantum mechanical methods. Groups 11 and 12 transition metals

Several hypotheses to elucidate the linkage isomer preference of the thiocyanate (SCN(-)) ion have been offered. For complexes with small coordination numbers (i.e., 1 and 2) and groups 11 (Cu-triad) and 12 (Zn-triad) metals, different levels of theory and a variety of basis sets have been employed to study linkage isomerism. Similar results are obtained for all density functionals tested, pure and hybrid. Overall, good agreement, vis-à-vis experimentally identified linkage isomers, is achieved for ab initio techniques, whereas semiempirical quantum mechanical methods show a bias toward S-ligated isomers. Despite the seeming ease for the a priori prediction of the most stable thiocyanate isomers using acid/base principles, this research highlights the sensitivity of quantitative calculations of transition-metal linkage isomerism to the choice of basis set and electron correlation, particularly with post-Hartree-Fock treatments.     

Evaluating the mobility of toxic metals in untreated industrial wastewater sludge using a BCR sequential extraction procedure and a leaching test

The distribution and speciation of toxic metals in industrial wastewater sludge (IWS) was investigated. In this work, the modified BCR three-stage sequential extraction procedure was applied to the fractionation of Cr Pb Ni, and Cd in untreated industrial wastewater sludge from industrial sites in Hyderabad (Pakistan). The extracts were analyzed using electrothermal atomic absorption spectrometry. The procedure was evaluated using a certified reference material for soil mixed with sewage sludge BCR 483. The results from the partitioning study indicate that more easily mobilized forms (acid exchangeable) of Cd were dominant. The oxidizable fraction was dominant for all four toxic metals. Metal recovery was good, with <4% difference between the total metal recovered through the extractant steps and the total metal determined after microwave digestion. Lixiviation tests (DIN 38414-S4) were used to evaluate the leaching of toxic species from IWS, and it was observed that levels of leachable toxic metals were low compared to the amount of metal extracted in the exchangeable fraction of the BCR protocol.     

Triosmium clusters derived from the reactions of thioureas with dodecacarbonyltriosmium: Crystal structures of [Os3(CO)11{η 1-SC(NMe2)2}], [Os3(CO)9(μ-OH)(μ-OMeOCO){η 1-SC(NMe2)2}] and [(μ-H)Os3(CO)9{μ 3-NHC(S)NH2}]

The reaction of [Os₃(CO)₁₂] with tetramethylthiourea in the presence of a methanolic solution of Me₃NO·2H₂O at 60° yields the compounds [Os₃(CO)₁₁{η ¹-SC(NMe₂)₂}] (1) in 56% yield and [Os₃(CO)₉(μ-OH)(μ-MeOCO){η ¹-SC(NMe₂)₂}] (2) in 10% yield in which the tetramethylthiourea ligand is coordinatedvia the sulfur atom at an equatorial position. Compound2 is a 50 e^? cluster with two metal-metal bonds and the hydroxy and methoxycarbonyl ligands bridging the open metal-metal edge. In contrast, the analogous reaction of [Os₃(CO)₁₂] with thiourea gives the compounts [(μ-H)Os₃(CO)₁₀{μ-NHC(S)NH₂}] (3) in 8% yield and [(μ-H)Os₃(CO)₉{₃-NHC(S)NH₂}] (4) in 30% yield. In3, the thioureato ligand bridges two osmium atomsvia the sulfur atom, whereas in4 in addition to the sulfur bridge, one of the nitrogen atoms of thioureato moiety bonds to the remaining osmium atom. The decacarbonyl compounds 3 can also be obtained in 50% yield from the reaction of [Os₃(CO)₁₀(MeCN)₂] with thiourea at ambient temperature. Compound3 converts to4 (65%) photochemically. Compound1 reacts with PPh₃ and acetonitrile at ambient temperature to give the simple substitution products [Os₃(CO)₁₁(PPh₃)] and [Os₃(CO)₁₁(MeCN)], respectively, while with pyridine, the oxidative addition product [(μ-H)Os₃(CO)₁₀(μ-NC₅H₄] is formed at 80°C. All the new compounds are characterized by IR,¹-H-NMR and elemental analysis together with the X-ray crystal structures of1,2 and4. Compound1 crystallizes in the triclinic space group P $P\bar 1$ with unit cell parametersa = 8.626(3) Å,b = 11.639(3) Å,c = 12.568(3_ Å,α = 84.67(2)°,β = 75.36(2)°,γ = 79.49(3)°,V = 1199(1) ų, andZ = 2. Least-squares refinement of 4585 reflections gave a final agreement factor ofR = 0.0766 (R _w = 0.0823). Compound2 crystallizes in the monoclinic space group P2_1/n with unit cell parametersa = 9.149(5) Å,b = 17.483(5) Å,c = 15.094(4) Å,β = 91.75(2)°,V = 2413(2) ų, andZ = 4. Least-squares refinement of 3632 reflections gave a final agreement factor ofR = 0.0603 (R _w = 0.0802). Compound4 crystallizes in the monoclinic space group C2/c with unit cell parametersa = 13.915(7) Å,b = 14.718(6) Å,c = 17.109(6) Å,β = 100.44(3)°,V = 3446(5) ų, andZ = 8. Least-squares refinement of 2910 reflections gave a final agreement factor ofR = 0.0763 (R _w = 0.0863).     

Speciation of arsenic in ground water samples: A comparative study of CE-UV, HG-AAS and LC-ICP-MS

The performance of capillary electrophoresis-ultraviolet detector (CE-UV), hydride generation-atomic absorption spectrometry (HG-AAS) and liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) have been compared for the speciation of arsenic (As) in groundwater samples. Two inorganic As species, arsenite (As^III), arsenate (As^V) and one organo species dimethyl arsenic acid (DMA) were mainly considered for this study as these are known to be predominant in water. Under optimal analytical conditions, limits of detection (LD) ranging from 0.10 (As^III, AsT) to 0.19 (DMA) μg/l for HG-AAS, 100 (As^III, DMA) to 500 (As^V) μg/l for CE-UV and 0.1 (DMA, MMA) to 0.2 (As^III, As^V) μg/l for LC-ICP-MS, allowed the determination of the above three species present in these samples. Results obtained by all the three methods are well correlated (r² = 0.996*** for total As) with the precision of <5% R.S.D. except CE-UV. The effect of interfering ions (e.g. Fe²⁺, Fe³⁺, SO₄²⁻ and Cl⁻) commonly found in ground water on separation and estimation of As species were studied and corrected for. Spike recovery was tested and found to be 80-110% at 0.5 μg/l As standard except CE-UV where only 50% of the analyte was recovered. Comparison of these results shows that LC-ICP-MS is the best choice for routine analysis of As species in ground water samples.     

Multifunctional mesoporous silica nanoparticles in poly(ethylene‐co‐vinyl acetate) for transparent heat retention films

Transparent inorganic‐polymer nanocomposite films are of tremendous current interest inemerging solar coverings including photovoltaic encapsulants and commercial greenhouse plastics, but suffer from significant radiative heat loss. This work provides a new and simple approach for controlling this heat loss by using mesoporous silica/quantum dot nanoparticles in poly(ethylene‐co‐vinyl acetate) (EVA) films. Mesoporous silica shells were grown on CdS‐ZnS quantum dot (QDs) cores using a reverse microemulsion technique, controlling the shell thickness. These mesoporous silica nanoparticles (MSNs) were then melt‐mixed with EVA pellets using a mini twin‐screw extruder and pressed into thin films of concentration variable controlled thickness. The results demonstrate that the experimental MSNs showed improved infrared and thermal wavebands retention in the EVA transparent films compared to commercial silica additives, even at lower concentrations. It was also found MSNs enhanced the quantum yield and photostability of the QDs, providing high visible light transmission and blocking of UV transmission of interest for next generation solar coatings. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 851–859     

Thermal evaluation of a heat pipe working with n-pentane-acetone and n-pentane-methanol binary mixtures

Journal of Thermal Analysis and Calorimetry - In the present study, a set of experiments were accomplished to appraise the thermal performance and heat transfer of n-pentane-acetone and...     

Covalently functionalized pentaethylene glycol-thermally treated graphene towards enhanced thermophysical and heat transfer characteristics

Journal of Thermal Analysis and Calorimetry - The current study outlined the use of synthesized, covalently functionalized pentaethylene glycol-thermally treated graphene (PEG-TGr). Miscible PEG...     

Analysis of a “3-(Naphthalen-1-ylimino)indolin-2-one” Compound and Its Antimicrobial Assessment Using Lipid-Based Self-Nanoemulsifying Formulations

In recent years, indole derivatives have acquired conspicuous significance due to their wide spectrum of biological activities—antibacterial, antiviral, and anticonvulsant. This compound is derived from naturally grown plants. Therefore, synthesis of a novel “3-(Naphthalen-1-ylimino)indolin-2-one” compound (2) and its analysis using UPLC systems along with antimicrobial assessment was the aim of the current study. Isatin was used as a parent drug for synthesizing compound (2). Liquid Chromatographic analysis was performed using a C18 BEH column (1.7 μm 2.1 × 50 mm) by UPLC systems. Degradation studies were carried out to see whether acid, base, thermal, and oxidizing agents had any impact on the synthesized molecule in stress conditions (100 °C). A lipid-based self-nanoemulsifying formulation was developed and selectivity, specificity, recovery, accuracy, and precision were measured as part of the UPLC system’s validation process. Antimicrobial studies were conducted using gram-positive and gram-negative bacteria. The standard samples were run with a concentration range of 5.0–100.0 μg/mL using the isocratic mobile phase comprising of methanol/water (70/30 %v/v) at 234 nm; good linearity (R² = 0.9998) was found. The lower limits of detection (LOD) and quantitation (LOQ) of the method were found to be 0.81 μg/mL and 2.5 μg/mL, respectively. The coefficients of variation were found to be less than 2%. The antimicrobial study suggests that compound (2) has a substantial growth effect against gram-negative bacteria. It was successfully synthesized and applied to measure the concentrations in lipid-based dosage form, along with potent antimicrobial activities.