One-pot catalytic enantioselective domino nitro-michael/michael synthesis of cyclopentanes with four stereocenters

A highly enantioselective organocatalytic one-pot synthesis of nitro-, formyl-, and ester-functionalized cyclopentanes with four stereocenters is presented. The cyclopentanes were formed as a predominant diasteroisomer and isolated in high yields with 97-99 % ee.     

Über Halogenphenylester der Phosphorsäure

A simple method for preparing halogenphenylesters of phosphoric, phenylphosphonic and phosphorous acid from the respective acid chlorides and phenols in the presence of various nitrogen-containing catalysts is described. Contrary to other methods, these reactions give high yields, despite of steric hindrance.     

Measurements and automated mechanism generation modeling of OH production in photolytically initiated oxidation of the neopentyl radical

Production of OH in the reaction of the neopentyl radical with O2 has been measured by a laser photolysis/cw absorption method for various pressures and oxygen concentrations at 673, 700, and 725 K. The MIT Reaction Mechanism Generator (RMG) was used to automatically generate a model for this system, and the predicted OH concentration profiles are compared to present and literature experimental results. Several reactions significantly affect the OH profile. The experimental data provide useful constraints on the rate coefficient for the formally direct chemical activation reaction of neopentyl radical with O2 to form OH (CH3)3CCH2 + O2 --> OH + 3,3-dimethyloxetane (Rxn 1) At 673 K and 60 Torr, log k(1) (cm(3) molecule(-1) s(-1)) = -13.7 +/- 0.5. Absolute absorbance measurements on OH and I indicate that the branching ratio for R + O2 to OH is about 0.03 under these conditions. The data suggest that the ab initio neopentyl + O2 potential energy surface of Sun and Bozzelli is accurate to within 2 kcal mol(-1).     

Kinetics of the substitution of dehydroacetic acid in tris (dehydroacetato) Fe(III) complex by 8-hydroxyquinoline, di- and tetra-hydroxyquinone

The ligand substitution reactions of dehydroacetic acid (Hdha) in [Fe(dha)(3)] with second ligand such as 8-hydroxyquinoline (Hquin), 1,4-dihydroxyanthraquinone (H(2)dhaq) and 1,4,5,8-tetra-hydroxyanthraquinone (H(4)thaq) were investigated spectrophotometrically by in low polarity solvents like benzene, chloroform and dichloromethane. It is deduced that the substitution reaction takes place through one successive step. The reaction was performed at four different temperatures (5-25) degrees C, and it exhibits a first order dependence on the concentration of the starting complex. The observed rate constant depends on the concentration of both leaving and entering ligands. The evaluation of the kinetic data gives activation parameters which support an associative mechanism in the transition states and the higher rate of substitution of the dha in Fe(dha)(3) complex is due to entropy effect. The solid complexes were synthesized and characterized by elemental analysis, IR and UV-vis spectral techniques.     

Thermodynamic equilibrium for nitrogen species discharge: Comparison with global model

The equilibrium process of plasma nitrogen species by chemical kinetic reactions along various pressures is successfully investigated. The equilibrium process is required in industrial application to obtain the stable condition when heating up the material for having homogenous reaction. Nitrogen species densities is modeled by a continuity equation and extended Arrhenius form. These equations are used to integrate the change of density over the time. The integration is to acquire density and the reaction rate of each reaction where temperature and time dependence are imposed. A comparison is made with global model within pressure range of 1-100 mTorr and the temperature of electron is set to be higher than other nitrogen species. The results show that the chemical kinetic model only agrees for high pressure because of no power imposed; while the global model considers the external power along the pressure range then the electron and nitrogen species give highly quantity densities by factor of 3-5.     

Measurement of radionuclides and absorbed dose rates in soil samples of Peshawar,Pakistan, using gamma ray spectrometry

The analysis of gamma-emitting radionuclides in nature, i.e. ²²⁶Ra, ²³²Th, ⁴⁰K and ¹³⁷Cs, has been carried out in soil samples collected from Peshawar University Campus and surrounding areas using a high purity germanium detector coupled with a computer-based high-resolution multichannel analyser. The activity concentrations in soil ranged from 30.20±0.65 to 61.90±0.95, 50.10±0.54 to 102.80±1.04, 373.60±4.56 to 1082±11.38 and 9.50±0.11 to 46.60±0.42 Bq kg^?1 for ²²⁶Ra, ²³²Th, ⁴⁰K and ¹³⁷Cs, with a mean value of 45±7.70, 67±12.50, 878±180 and 19±9.20 Bq kg^?1, respectively. The radium equivalent activity, internal and external hazard indices have mean values of 203.40±29.40 Bq kg^?1, 0.56 and 0.68, respectively. The mean values of outdoor and indoor absorbed dose rates in air and the annual effective dose equivalents were found to be 106.50 and 128 nGy h^?1 and 0.19 and 0.54 mSv y^?1, respectively. In the present study, ⁴⁰K was the major radionuclide present in soil samples. The presence of ¹³⁷Cs indicates that this area also received some fallout from the nuclear accident of the Chernobyl power plant in 1986. The activity concentrations of radionuclides found in soil samples during the current investigation were nominal. Therefore, they are not associated with any potential source of health hazard to the public.     

Pyrazoles and Isoxazoles Based Sulfanilamide and Phenazone as Antimicrobial Agents: Synthesis and Biological Activity

New pyrazole and pyridine derivatives have been synthesized from sulfanilamide and phenazone via diazotization and coupling with a wide range of α-CH acids followed by heterocyclization with hydrazine derivative, hydroxylamine and cyanoacetamide. The antimicrobial tests of the products demonstrate high to moderate activity against Gram (?ve) bacteria and the tested fungi. No positive action of the products is observed against Gram (+ve) bacteria.

     

Tualang Honey: A Decade of Neurological Research

Tualang honey has been shown to protect against neurodegeneration, leading to improved memory/learning as well as mood. In addition, studies have also demonstrated its anti-inflammatory and antioxidant properties. However, a substantial part of this research lacks systematization, and there seems to be a tendency to start anew with every study. This review presents a decade of research on Tualang honey with a particular interest in the underlying mechanisms related to its effects on the central nervous system. A total of 28 original articles published between 2011 and 2020 addressing the central nervous system (CNS) effects of Tualang honey were analysed. We identified five main categories, namely nootropic, antinociceptive, stress-relieving, antidepressant, and anxiolytic effects of Tualang honey, and proposed the underlying mechanisms. The findings from this review may potentially be beneficial towards developing new therapeutic roles for Tualang honey and help in determining how best to benefit from this brain supplement.     

Effects of tip gap and amplitude of piezoelectric fans on the performance of heat sinks in microelectronic cooling

Piezoelectric fan is a promising option for cooling microelectronic devices owing to its unique features such as no electromagnetic noise, low power consumption and minimum space requirement. The recent interest is to integrate the piezoelectric fans (piezofans) with heat sink; this idea is widely accepted and researches are still underway. This article presents experimental analysis on the effects of tip gap (δ) and amplitude of piezofan vibration (α) on the heat transfer characteristics of finned heat sinks. Two heat sink configurations, namely A and B (with two and four fins respectively) each of which is arranged with three piezofans, are considered for the study. The transient temperature distributions for cases with and without piezofans are obtained for both the configurations, and compared. The heat transfer coefficient, thermal impedance, Nusselt number and Reynolds number are investigated as functions of δ and α. The effect of α on the fan effectiveness is also analyzed. It is observed that the configuration B has better cooling performance compared to A. Among the tested ranges of δ and α, the case with least tip gap (δ?=?0.03) and highest amplitude (α?=?5.29) is found to be the best; at this setting, the fan effectiveness is increased to almost 4?times compared to the case without piezofans.     

Performance of Rubberized and Hybrid Rubberized Concrete Structures under Static and Impact Load Conditions

In this study, rubberized concrete samples were prepared by partial substitution (5 %, 10 % and 20 % replacements by volume) of sand by waste crumb rubber, and tested under impact three-point bending load, as well as static load. Three types of specimens (size 50?×?100?×?500 mm) namely, plain concrete, rubberized concrete, and double layer concrete (with rubberized concrete top and plain concrete bottom) were loaded to failure in a drop-weight impact machine by subjecting to 20 N weight from a height of 300 mm, and another three similar specimens were used for the static load test. In both the tests, the load–displacement and fracture energy of each specimen were investigated. Finite-element simulations were also performed to study the dynamic behaviors of the samples, by using LUSAS V.14 software. It was noticed that, the impact tup, and inertial and bending loads increased with the increase in the percentage of sand replacement by crumb rubber. It was interesting to observe that these effects were more significant in the double layer specimen compared to the plain and rubberized concrete samples. The static peak bending load always decreased with increase of rubber in the mix. In general, the strength and energy absorbing capability of rubberized concrete was better under impact loading than under static loading. The simulated load against displacement behaviors of all the samples were validated by the experimental results.