X-ray analysis at 150?K, synthesis and theoretical calculations of 1-naphthaleneacrylic acid

The X-ray structure, synthesis, theoretical calculation and IR spectra of 1-naphthaleneacrylic acid are reported. The titled compound crystallizes in the monoclinic C 2/c space group with unit cell parameters: a = 14.556(3), b = 5.1332(10), c = 26.832(5) ?, β = 97.02(3)°, V = 1989.8(7) ?³, Z = 8 and form typical centrosymmetric hydrogen-bonded dimers. Theoretical calculations of 1-naphthylacrylic acid isolated molecule and hydrogen-bonded dimer have been carried out using density functional theory at the B3LYP level. For optimized structures the vibrational spectra have been then calculated and compared with experimental IR spectrum. The assignment and characterization of theoretical vibrational spectra were based on the potential energy distribution analysis. This comparison has shown that the theoretical spectrum for the dimer structure is in good agreement with the experimental one. Structural comparisons with naphthalene, and with some substituted 2-propenoic acids have shown influence of the substituent on conformation of the naphthalene ring or 2-propenoic moiety.     

Plasma-Electrospinning Hybrid Process and Plasma Pretreatment to Improve Adhesive Properties of Nanofibers on Fabric Surface

Electrospun nanofiber mats are inherently weak, and hence they are often deposited on mechanically-strong substrates such as porous woven fabrics that can provide good structural support without altering the nanofiber characteristics. One major challenge of this approach is to ensure good adhesion of nanofiber mats onto the substrates and to achieve satisfactory durability of nanofiber mats against flexion and abrasion during practical use. In this work, Nylon 6 nanofibers were deposited on plasma-pretreated woven fabric substrates through a new plasma-electrospinning hybrid process with the objective of improving adhesion between nanofibers and fabric substrates. The as-prepared Nylon 6 nanofiber-deposited woven fabrics were evaluated for adhesion strength and durability of nanofiber mats by carrying out peel strength and flex resistance tests. The test results showed significant improvement in the adhesion of nanofiber mats on woven fabric substrates. The nanofiber-deposited woven fabrics also exhibited good resistance to damage under repetitive flexion. X-Ray photoelectron spectroscopy and water contact angle analyses were conducted to study the plasma effect on the nanofibers and substrate fabric, and the results suggested that both the plasma pretreatment and plasma-electrospinning hybrid process introduced radicals, increased oxygen contents, and led to the formation of active chemical sites on the nanofiber and substrate surfaces. These active sites helped in creating crosslinking bonds between substrate fabric and electrospun nanofibers, which in turn increased the adhesion properties. The work demonstrates that the plasma-electrospinning hybrid process of nanofiber mats is a promising method to prepare durable functional materials.     

GC-MS analysis of aroma of Medemia argun (mama-n-khanen or mama-n-xanin), an ancient Egyptian fruit palm

The fruits of the edible and medicinal Egyptian palm, Medemia argun, were collected from Aswan in Egypt and the essential oil (EO) from fruits and headspace (HS) of the seeds and fleshy mesocarps were analyzed by GC and GC-MS. Results obtained by GC-MS analysis indicated a high variability in the oil and in the headspace from seeds and mesocarps. Sesquiterpene derivatives were the main group of volatiles in the EO from fruits and in the HS from seeds (45.0 and 64.0%, respectively), while oxygenated hydrocarbon derivatives were the main constituents in the HS obtained from fleshy mesocarps (96.5%). The different chemical composition of the headspace obtained from the seeds and mesocarps of M. argun can be correlated with the different roles that the different constituents play in the prevention of dehydration of the fruits in the desert region from where the plant was collected.     

Mass transfer limitation in thermogravimetry of biomass gasification

In order to determine the intrinsic reactivity behavior from thermogravimetry studies, the experimental conditions should be such that the reactions are not mass transfer limited. Biomass char usually has a higher reactivity than coal chars. Therefore, mass transfer limitations may be more problematic when studying biomass char reactivity. Chemical reaction kinetics and mass transfer processes present in thermogravimetry are used for modeling the overall reaction rate for spruce bark CO₂ gasification. Thermogravimetric experiments are carried out between 700 and 900 °C, and the CO₂ concentration is varied between 10 and 90 vol%. The intrinsic activation energy is found to be 120 kJ mol^?1. The transition temperature between regimes I and II is here defined when the fraction apparent to true activation energy equals 0.75. Higher external mass transfer (e.g., by decreasing the diffusion path through the crucible’s freeboard), decreasing the sample amounts, and higher CO₂ partial pressures for the Langmuir–Hinshelwood reaction type increase the transition temperature. The results show that the transition temperature between regimes I and II conditions is approx. 1,030 °C for 90 vol% CO₂.     

Reduction of Phenyl-Substituted Pyridinium Methoiodides with Sodium Borohydride. Formation of Amine-Borane Complexes in Water

Reduction of phenyl-substituted pyridinium methoiodides with sodium borohydride in water afforded besides the desired tetrahydropyridines substantial amounts of amine-borane complexes. Reduction in methanol afforded tetrahydropyridines in high yield, with almost no amine-boranes formed.     

Beiträge zur Chemie der Silicium-Schwefel-Verbindungen. 46 [1]. 29Si-NMR-chemische Verschiebungen von Trialkoxysilylthioderivaten der Permethylpolysilane

Contributions to the Chemistry of Silicon-Sulphur Compounds. 46. ²⁹Si-N.M.R. Chemical Shifts of Trialkoxysilylthio Derivatives of Permethylpolysilanes ²⁹Si-N.M.R. chemical shifts of trialkoxysilythio derivatives of permethylpolysilanes of the two series: α, ω-(RO)₃SiS(SiMe₂)_nSSi(OR)₃, n = 2, 3, 4, 6 and 1-(RO)₃SiS(SiMe₂)_nMe, n = 2, 4; R = i-Pr, t-Bu and also ³¹C-NMR shifts are given. The relationship of ²⁹Si-NMR chemical shift from the netto charge at the silicon atom q(Si) which value has been corrected according to the Sandorfy C quantum-chemical model is discussed. The greater reduction of the electron density at silicon in compounds with Si? X bond (X = S, P, Cl) has been explained by a conjugation of the lone of sulphur with the Si? X bonding pair.     

Die Struktur des Pentaphenyldisilans

Structure of Pentaphenyldisilane For the first time Pentaphenyldisilane was prepared by Gilman and Goodman. It is produced by the reaction of Ph₃SiLi with Ph₂ClSiH. The crystal structure presents an ideally staggered conformation. The distance d(Si? Si) = 235.7 pm corresponds to a normal single bond length. This emphasizes the complete relief of the central Si? Si bond by the insertion of only one hydrogen atom.     

Biosilica from sea water diatoms algae—electrochemical impedance spectroscopy study

Here, we report on an electrochemical impedance study of silica of organic origin as an active electrode material. The electrode material obtained from carbonized marine biomass containing nanoporous diatoms has been characterised by means of XRD, IR, SEM and EIS. Different kinds of crystallographic phases of silica as a result of thermal treatment have been found. The electrode is electrochemically stable during subsequent cyclic voltammetry measurements taken in the potential range from 0.005 up to 3.0 V vs. Li/Li⁺. The material has been found to exhibit high charge capacitance of 521 mAh g⁻¹ being cycled at a rate C/20 with capacity retention of about 97%. Electrochemical impedance spectroscopy performed at an equilibrated potential E = 0.1 V in the temperature range 288–294 K discloses low charge transfer resistivity and low diffusional impedance.

     

Application of Microwave Energy to Cleavage of Sulfur Bonds in the S8Ring in the Simplest Amide Solvents

Microwave energy has been employed for cleavage of sulfur bonds in the S₈ring. Cleavage of S–S bonds was carried out in extraction of elemental sulfur in simple amide solvents. Due to the use of microwave energy and the polarity of amides, up to, 100 times lower concentration of a nucleophilic reducer, such as azide or nitrite, may be used to cleave the sulfur bonds. The time needed for cleavage of sulfur bonds at sulfur concentration higher than 0.1 mg S/100 mg solvent was reduced from hours to minutes. This cleavage was quantitative when carried out in a Teflon container in a microwave oven with continuous or pulsed heating. UV spectra show from which value of absorption there will be a sulfur sol at different sulfur concentrations. This allows us to adjust the microwave exposure power and time to avoid sulfur sol formation and not destroy the sample.     

Comparative PIV and LDA studies of Newtonian and non-Newtonian flows in an agitated tank

The paper presents results of an experimental study of the fluid velocity field in a stirred tank equipped with a Prochem Maxflo T (PMT) type impeller which was rotating at a constant frequency of N = 4.1 or 8.2 s^?1 inducing transitional (Re = 499 or 1307) or turbulent (Re = 2.43 × 10⁴) flow of the fluid. The experiments were performed for a Newtonian fluid (water) and a non-Newtonian fluid (0.2 wt% aqueous solution of carboxymethyl cellulose, CMC) exhibiting mild viscoelastic properties. Measurements were carried out using laser light scattering on tracer particles which follow the flow (2-D PIV). For both the water and the CMC solution one primary and two secondary circulation loops were observed within the fluid volume; however, the secondary loops were characterized by much lower intensity. The applied PMT-type impeller produced in the Newtonian fluid an axial primary flow, whilst in the non-Newtonian fluid the flow was more radial. The results obtained in the form of the local mean velocity components were in satisfactory agreement with the literature data from LDA. Distribution of the shear rate in the studied system was also analyzed. For the non-Newtonian fluid an area was computed where the elastic force dominates over the viscous one. The area was nearly matching the region occupied by the primary circulation loop.