Kinetics and mechanism of acid and base hydrolysis ofcis-chloro-(benzotriazole)bis(ethylenediamine)cobalt(III) andcis-chloro-(N-methylbenzotriazole)bis(ethylenediamine)cobalt(III) cations

Summary The kinetics of acid hydrolysis ofcis-[CoCl(btzH)(en)₂]²⁺ andcis-[CoCl(btzMe)(en)₂]²⁺ complexes (where btzH = benzotriazole, btzMe =N-methylbenzotriazole and en = ethylenediamine) have been investigated in HClO₄ at ionic strength 1 = 0.25 mol dm^–3 in the 30–40° range. In the 1.0 x 10^–1 to 1.0 X 10^–3 mol dm^–3 acid strength range, the rate of aquation of the [CoCl(btzH)(en)₂]²⁺ cation follows the relationship:-d ln[complex]/dt = k₁ + k₂K_NH[^H+]^–1, where k₁ and k₂ are aquation rate constants of the acid independent and acid dependent steps respectively, and K_NH is the acid dissociation constant of the coordinated benzotriazole.cis-[CoCl(btzMe)-(en)₂]²⁺ undergoes acid independent hydrolysis presumably due to the absence of a labile N-H proton. The base hydrolysis could be followed for thecis-[CoCl(btzMe)(en)₂]²⁺ complex only by measuring hydrolysis rates at 0°.     

Epitaxial morphologies of polyoxymethylene. I. Electron microscopy

Epitaxial crystallization of polyoxymethylene (POM) from 0.5% iodobenzene solution has been attempted between 150 and 165°C on 11 different substrates having surface energies ranging from 136 to 1240 ergs/cm². Included in this series are several substrates such as CaF₂, SrF₂, BaF₂, graphite, mica, and silicon which had not been previously tested as substrates for POM epitaxy. The fluorite series materials are not good substrates for the epitaxial crystallization of POM from solution. In contrast, both rodlike and fold-plane epitaxial morphologies have been found on the (001) surfaces of NaCl, NaF, and mica. A possible mechanism for the formation of fold-plane epitaxy is discussed which involves solution nucleation followed by adsorption and growth of the nuclei on the substrate. It is suggested that variations observed in nucleation density of rodlike epitaxial crystals from substrate to substrate are a result of differences in degree of preferential solvent adsorption. Substrates having higher surface energies should tend to adsorb solvent more strongly and thus inhibit profuse nucleation of polymer crystals on the surface.     

Fluctuation and relaxation properties of pulled fronts: A scenario for nonstandard kardar-parisi-zhang scaling

We argue that while fluctuating fronts propagating into an unstable state should be in the standard Kardar-Parisi-Zhang (KPZ) universality class when they are pushed, they should not when they are pulled: The 1/t velocity relaxation of deterministic pulled fronts makes it unlikely that the KPZ equation is their proper effective long-wavelength low-frequency theory. Simulations in 2D confirm the proposed scenario, and yield exponents beta approximately 0.29+/-0.01, zeta approximately 0.40+/-0.02 for fluctuating pulled fronts, instead of the (1+1)D KPZ values beta = 1/3, zeta = 1/2. Our value of beta is consistent with an earlier result of Riordan et al., and with a recent conjecture that the exponents are the (2+1)D KPZ values.     

Molecular structure calculations applied to solid state polymer physics: Part II

The ultimate reaction of a material to an external action involves geometrical rearrangements of the constituent atoms to disperse or accept the external action. These geometric rearrangements persist, on a time scale, from completely and instantaneously reversible (a dissipated structural fluctuation) to a permanent deformation (a nonreversible phase transition).     

Comparative view of the various dielectric functions based on the moment sum-rule approach

The density response function obtained by solving the equation of motion for the double time retarded commutator of the classical density fluctuation operators is expanded for large ω and the coefficients are compared with those from the large ω expansion of the density response function in the effective mean field theory. It is found that the expression for the local field correction is the same as obtained by Pathak and Vashishta following a calculation of the third frequency moment using the spectral form of the density response function. In this paper a comparative study of the various dielectric functions derived on the moment conserving scheme is presented and the results are analysed.     

Determining the dispersions of the fifth- and seventh-order nonlinear optical susceptibilities of a poly(4-BCMU) film through electroabsorption spectroscopy

The dispersions of the fifth- and seventh-order nonlinear optical susceptibilities, chi((5))(113333) and chi((7))(11333333) , respectively, of a polydiacetylene film, poly(4-BCMU), are determined through electroabsorption spectroscopy. To our knowledge this is the first time that a spectrum of seventh-order nonlinear optical susceptibility has been obtained by means of electro-optic measurements.     

Studies of Coupled Anharmonic Oscillator Problem Using Coherent States and Path Integral Approaches

The present review is devoted to the study of the problem of coupled anharmonic oscillators. A perturbative solution is obtained for the system of an undamped and the damped coupled anharmonic oscillators in the coherent state representation. The solution does not contain the vicious secular terms and shows, explicitly, the anharmonic effects of a coupled system. In order to derive the perturbative solution of a damped coupled system a new frame of time, called quasi time τ, has been exploited. The large quantum number behaviour of coupled anharmonic oscillators has been derived using the path integral method.     

Biocomputational Assessment of Natural Compounds as a Potent Inhibitor to Quorum Sensors in Ralstonia solanacearum

Ralstonia solanacearum is among the most damaging bacterial phytopathogens with a wide number of hosts and a broad geographic distribution worldwide. The pathway of phenotype conversion (Phc) is operated by quorum-sensing signals and modulated through the (R)-methyl 3-hydroxypalmitate (3-OH PAME) in R. solanacearum. However, the molecular structures of the Phc pathway components are not yet established, and the structural consequences of 3-OH PAME on quorum sensing are not well studied. In this study, 3D structures of quorum-sensing proteins of the Phc pathway (PhcA and PhcR) were computationally modeled, followed by the virtual screening of the natural compounds library against the predicted active site residues of PhcA and PhcR proteins that could be employed in limiting signaling through 3-OH PAME. Two of the best scoring common ligands ZINC000014762512 and ZINC000011865192 for PhcA and PhcR were further analyzed utilizing orbital energies such as HOMO and LUMO, followed by molecular dynamics simulations of the complexes for 100 ns to determine the ligands binding stability. The findings indicate that ZINC000014762512 and ZINC000011865192 may be capable of inhibiting both PhcA and PhcR. We believe that, after further validation, these compounds may have the potential to disrupt bacterial quorum sensing and thus control this devastating phytopathogenic bacterial pathogen.     

Study on South African Indigenous Teas—Antioxidant Potential,Nutritional Content,and Hypoxia-Induced Cyclooxygenase Inhibition on U87 MG Cell Line

Background: This study comparatively assessed seven indigenous traditional tea plants on several attributes that included antioxidant, nutritional, caffeine contents, and cyclooxygenase activity. Methodology: Nutritional content of all tea plants were determined for energy, fat, carbohydrates, total sugars, dietary fiber and amino acids. Antioxidant potential and the antioxidant potentiating secondary metabolites were also measured and compared. Further, we investigated the tea plants for any role they would have on cyclooxygenase (COX) activity on cobalt chloride (CoCl₂) induced human glioma cell lines (U87MG). Results: The tea plants were found non-cytotoxic at concentrations tested against the human Chang liver and HeK 293 kidney cells and were found to be naturally caffeine free. The lowest and highest extraction yield among the tea plants was 7.1% for B. saligna and 15.48% for L. scaberrimma respectively. On average, the flavonol content was 12 to 8 QE/g, ORAC 800 µmol TE/g, TEAC 150 µmol TE/g, FRAP 155 µmol AAE/g, polyphenols 40 mg GAE/g, flavanols 0.35 mg CE/g, flavonols 12 mg QE/g and total flavonoid content (TFC) 180 µg QE/mg. The COX activity has been found to be inhibited by a dose-dependent manner by L. scaberrimma, B. saligna and L. javanica. Conclusion: The results further support competitive value of tea plants and need for improved and further development.     

Impact Assessment of Electroplating in the Leaching of Harmful Metals from Utensils

Electroplating is a widely used technique in the manufacturing of utensils for household and commercial use. This process involves the deposition of a metal coating onto a base material, such as steel or brass, to improve the aesthetics, durability, and corrosion resistance of the utensil. Several studies have investigated the migration of heavy metals from utensils, but there is a lack of research specifically focused on the impact of electroplating on this phenomenon. Therefore, this research article aims to assess the impact of electroplating by analyzing the migration of heavy metals from such utensils. The objective of this research is to assess the impact of electroplating on the migration of heavy metals from utensils. The research also aims to evaluate the impact of coating thickness. Stainless-steel and brass utensils (Plate, Tumbler, and Bowl) are purchased. The samples are analyzed as per standard test methods based on inductively coupled plasma mass spectrometry (ICP-MS) techniques. Leaching stimulant is used for extraction process. Testing is performed in an ISO/IEC 17025: 2017 accredited laboratory. The experiments reveal that the electroplating process decreased the migration of lead from the utensils. These findings highlight the need for stricter regulations and standards to ensure the safety of electroplated utensils.