An additivity model for unrestricted hartree-fock spin densities and charge densities in some fluoro-substituted naphthalene radical cations

An additivity model has been found to be adequate for predicting unrestricted Hartree-Fock spin densities and charge densities in various fluorinated napthalene radical cations.     

Synthesis of 1,3-disubstituted hydantoins as possible anticonvulsants

Seven newer 1,3-disubstituted hydantoins ( 17–23 ) were synthesized from 4-alkoxyanilines. The anticonvulsant activity of these substituted hydantoins and their precursor carbamides ( 10–16 ) was reflected by their ability to provide 28–80% and 30–70% protection, respectively, against pentylenetetrazol-induced convulsions in mice. In general, substituted hydantoins possessed greater anticonvulsant activity than their corresponding precursor carbamides.     

Valorization of industrial waste lignin via pyrolysis in the presence of additives: Formation,characterization, and application of fuel valued bio-oil and activated char

The annual production of over 50 million tonnes of industrial waste kraft lignin and scant utilization invites environmental concern. To explore the potential of simultaneously produced bio-oil and modified char (Activated char), lignin from industrial effluents was subjected to pyrolytic degradation at 380 °C using various additives, viz., H₃BO₃, ZnCl₂, and KOH yielding encouraging quantities of bio-oils besides substantial quantities of char. Quantitative and qualitative analyses of gaseous products (by GC-TCD) indicated a mixture of CO, CO₂, H₂, and methane, with some variation in volumetric composition suggesting potential for gaseous fuel/syngas. Gaseous products obtained in the presence of H₃BO₃ have the highest methane percentage. The bio-oils obtained in the presence of H₃BO₃, ZnCl₂, KOH, and only pure lignin under otherwise similar conditions were respectively 37%, 21%, 27%, and 11 wt%. In all cases, mainly bio-oils contain phenols, cyclic esters, and carboxylic acids, as indicated by GC-MS analysis. Elemental (C, H, O) Analyses of bio-oils obtained in the presence of (H₃BO₃, ZnCl₂, and KOH) indicated decreasing oxygen content compared to original lignin, suggesting their prima facie potential to lead to fuel additives/supplements. Similarly, the Char obtained in the presence of H₃BO₃, ZnCl₂, KOH, and only pure lignin were respectively, 40%, 53%, 48%, and 33 wt% with a high calorific value. Char obtained from KOH application demonstrated good uptake of Carbofuran (pesticide) from the aqueous solution. Less modified, cost-effective activated char was characterized using FTIR, TG-DTA, XRD, SEM, and BET-BJH, indicating 188.798 m²/g; this explores the role of KOH to form a microporous structure. Pseudo-second-order kinetics explain chemisorption to be dominant in the adsorption process. Thus, pyrolysis at selected temperatures/additives/and further treatments provides a much better way to utilize industrial waste lignin.     

High-temperature strain gages for use in sodium environments

High-temperature long-term static strain measurements have, for many years, been a problem to the experimental stress analyst. Strain gages operating in environments from 600–1000° F over extended periods of time have varying characteristics as to temperature compensation, gage-factor shifts and, also, drift. The weldable-type high-temperature gage offers a great deal of promise, considering the ease of application to nonlaboratory-type structures. In addition, the Microdot-type weldable gage offers additional protection against most environmental conditions. In the high-temperature range, the Microdot half bridge containing a platinum-tungsten alloy encased in magnesium oxide and protected by an outer shell of Inconel-X was evaluated. One of two major difficulties encountered with this gage is the silver-gold alloy used for brazing all of the connections that provide a sealed gage element. This alloy was a difficulty because the gages were to be used in a sodium environment which easily dissolves the silver-gold elements. The other difficulty is the highly individual characteristics of the gages. This paper describes two significant developments made in adapting this gage for use in sodium environments at high temperatures. These are:

1. 1.
   A calibrating technique whereby the bonded-gage characteristics of each gage can be obtained prior to actually bonding the gage to the structure under test     

Synthesis,spectral characterization,and evaluation of antimicrobial activity of O,O′-alkanediyl S-(N-phthalimidomethyl) dithiophosphates and zinc bis(O,O′-alkanediyl) dithiophosphates

The synthesis of novel dithiophosphate derivatives has been achieved. Two O,O′-alkanediyl S-(N-phthalimidomethyl) dithiophosphates and two Zinc bis(O,O′-alkanediyl) dithiophosphates are synthesized by an easy and facile chemical synthetic route. Zinc bis[O,O′-(2-methylpentane-2,4-diyl) dithiophosphate] L¹, Zinc bis[O,O′-(2-ethylhexane-1,3-diyl) dithiophosphate] L², O,O′-(2-methylpentane-2,4-diyl) S-(N-phthalimidomethyl) dithiophosphate L³ and O,O′-(2-ethylhexane-1,3-diyl) S-(N-phthalimidomethyl) dithiophosphate L⁴ are synthesized from the respective ammonium salts. Compounds L¹, L², L³, and L⁴ are characterized by (CHN) elemental analysis, ESI mass, FT-IR, ¹H, ¹³C, and ³¹P NMR techniques. The crystal structure of ammonium O,O′-(2-methylpentane-2,4-diyl) dithiophosphate is discussed. L¹, L², L³, and L⁴ were evaluated for antimicrobial activity. It was found that the phthalimide derivatives L³ and L⁴ showed much better antifungal potential against some species of fungus. The Zinc dithiophosphates L¹ and L² showed good antibacterial activity against Bacillus cereus and Escherichia coli.     

Determination of trace amounts of nitrogen in uranium based samples by ion chromatography (IC) without Kjeldahl distillation

A simple, sensitive and fast ion chromatographic (IC) method with suppressed conductivity detection is described for the determination of traces of nitrogen in uranium based fuel materials. Initially a method was developed to determine nitrogen as NH₄⁺ using cation exchange column after matrix separation by Kjeldahl distillation. The method was then improved by eliminating this distillation. Matrix separation after sample dissolution was done by hydrolyzing and filtering off the polyvalent cations. This had helped in reducing both the sample size and analysis time. Optimization of dissolution conditions for various kinds of uranium based samples was done to keep acid content minimum; a prerequisite chromatographic condition. The calibration plot for nitrogen was linear in the concentration range of 0.02-1 mg L⁻¹ with regression coefficient of 0.9999. The relative standard deviation (R.S.D.) obtained in this method (100 μL injected) was 3% and 2% in 9 replicates at nitrogen level of 28 and 55 ng g⁻¹, respectively. Detection limit based on S/N = 3 (100 μL injected) as well as three times of variation in blank value was 4 ng g⁻¹. The developed method was authenticated by comparison with certified uranium-alloy standard as well as with independent indophenol photometry method. The developed method was applied to uranium-alloy, uranium-metal, sintered UO₂ pellets and sintered UO₂ microspheres samples.     

Possible Topological Hall Effect in a Spin Gapless Semiconducting Mn2CoAl Heusler Compound

Topological Hall effect (THE), induced by the interaction of charge carriers with mesoscopic or microscopic noncoplanar spin structures, holds promising applications in the field of spintronics. In the present study, a giant THE of about 2 μΩ cm at room temperature is reported in a bulk spin gapless semiconducting Mn₂CoAl cubic Heusler compound. Temperature-dependent investigation of magneto-transport data reveals that the Mn₂CoAl has the large THE over a wide temperature range of 2–300 K. The alternating current (AC) susceptibility as a function of magnetic field exhibits a smooth and continuous response rather than any kink or anomaly, suggests that the observed THE in the Mn₂CoAl compound results from the interaction of charge carriers with the microscopic noncoplanar spin texture. The observed THE as a function of temperature follows the same behavior as the magnetocrystalline anisotropy (MCA) of the cubic Mn₂CoAl, indicating the competition of the MCA with ferromagnetic and antiferromagnetic exchange interactions as the origin of the noncoplanar spin texture and hence THE. Micromagnetic simulations further support the emergence of noncoplanar spin structure as a result of the competition between different energies.     

The onset of coulomb explosions in polyatomic molecules

With the development of high intensity femtosecond lasers, the ionisation and dissociation dynamics of molecules has become an area of considerable interest. Using the technique of femtosecond laser mass spectrometry (FLMS), the molecules carbon disulphide, pyrimidine, toluene, cyclohexanone and benzaldehyde are studied with pulse widths of 50 fs in the near infrared (IR) wavelength region (790 nm). Results are presented and contrasted for laser beam intensities around 10(15) and 10(16) W cm(-2). For the lower intensities, the mass spectra yield dominant singly charged parent ions. Additionally, the appearance of doubly charged parent ions is evident for carbon disulphide, toluene and benzaldehyde with envelopes of doubly charged satellite species existing in these local regions. Carbon disulphide also reveals a small triply charged component. Such atomic-like features are thought to be a strong fingerprint of FLMS at these intensities. However, upon increasing the laser intensity to approximately 10(16) W cm(-2), parent ion dominance decreases and the appearance of multiply charged atomic species occurs, particularly carbon. This phenomenon has been attributed to Coulomb explosions in which the fast absorption of many photons may produce transient highly ionised parent species which can subsequently blow apart. Copyright 1999 John Wiley & Sons, Ltd.     

Uniform molecular analysis using femtosecond laser mass spectrometry

The potential of femtosecond laser time-of-flight mass spectrometry (FLMS) for uniform quantitative analysis of molecules has been investigated. Various samples of molecular gases and vapours have been studied, using ultra-fast ( approximately 50 fs) laser pulses with very high intensity (up to 1.6 x 10(16) Wcm(-2)) for non-resonant multiphoton ionisation/tunnel ionisation. Some of these molecules have high ionisation potentials, requiring up to ten photons for non-resonant ionisation. The relative sensitivity factors (RSF) have been determined as a function of the laser intensity and it has been demonstrated that for molecules with very different masses and ionisation potentials, uniform ionisation has been achieved at the highest laser intensities. Quantitative laser mass spectrometry of molecules is therefore a distinct possibility. Copyright 1999 John Wiley & Sons, Ltd.