Whistler instability in a semi-relativistic bi-Maxwellian plasma

Employing linearized Vlasov–Maxwell system of equations, the whistler instability is discussed for a semi-relativistic bi-Maxwellian distribution. The dispersion relations are analyzed analytically along with the graphical representation and the estimates of the growth rate and instability threshold condition are also presented in the limiting cases i.e., _ξ±=(ω?Ω)/_k∥vt‖?1${\xi }_{\pm }=(\omega ?\Omega )/k_{\parallel }{v}_{t_{\Vert }}?1$ (resonant case) and _ξ±?1${\xi }_{\pm }?1$ (non-resonant case). Further for field free case i.e., _B0=0$B_0=0$, the growth rates for Weibel instability in a semi-relativistic bi-Maxwellian plasma are presented for both the limiting cases.     

Synthesis and characterization of palladium(II) complexes of thioureas. X-ray structures of [Pd( N , N ′-dimethylthiourea)4]Cl2?·?2H2O and [Pd(tetramethylthiourea)4]Cl2

Palladium(II) complexes of thiones having the general formula [Pd(L)₄]Cl₂, where L = thiourea (Tu), methylthiourea (Metu), N,N′-dimethylthiourea (Dmtu), and tetramethylthiourea (Tmtu) were prepared by reacting K₂[PdCl₄] with the corresponding thiones. The complexes have been characterized by elemental analysis, IR and NMR spectroscopy, and two of these, [Pd(Dmtu)₄]Cl₂ · 2H₂O (1) and [Pd(Tmtu)₄]Cl₂ (2), by X-ray crystallography. An upfield shift in the >C=S resonance of thiones in ¹³C NMR and downfield shift in N–H resonance in ¹H NMR are consistent in showing sulfur coordination with palladium(II). The crystal structures of the complexes show a square-planar coordination environment around the Pd(II) ions with the average cis and trans S–Pd–S bond angles of 89.64° and 173.48°, respectively. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. An erratum to this article can be found at     

A new synthesis of 2′,3′-dideoxycytidine

A new synthesis of 2′,3′-dideoxycytidine is described and the utility of this synthesis to prepare larger quantities of said nucleoside is shown.     

Thermoreversible gels of polyacrylonitrile

Polyacrylonitrile (PAN) is soluble at room temperature in some ionic aqueous media and in many polar organic liquids such as dimethyl sulfoxide, but the polymer will not crystallize from these solvents. It is known, however, that PAN will from single crystals from dilute propylene carbonate (PC) solutions. It was found that on cooling concentrated PAN-PC solutions, thermoreversible gels were formed. The gels showed x-ray diffraction peaks and calorimetry indicated first-order dissolution endotherms and crystallization exotherms. Thus, on cooling, crystallization of the polymer from this solvent was identified as the cause for gelation of concentrated solutions. © 1992 John Wiley & Sons, Inc.     

All Modules Have Flat Covers

In this paper we give two different proofs that the flat coverconjecture is true: that is, every module has a flat cover.The two proofs are of completely different nature, and, we hope,will have different applications. The first of the two proofs(due to the third author) is essentially an application of thework of P. Eklof and J. Trlifaj (work which is more set-theoretic).The second proof (due to the first two authors) is more direct,and has a model-theoretic flavour.     

P-N compounds. 25. Phosphaminimides. 1. Synthesis and bioevaluation of a derivative of tetrahydro-2H-1,3,4,2-oxadiazaphosphorinium inner salt

2-Phenoxy-4,4-dimethyltetrahydro-2H-1,3,4,2-oxadiazaphosphorinium 2-oxide inner salt, the first known cyclic phosphaminimide, was synthesized by dehydroiodination of its hydrazinium salt. The corresponding 2-phenyl derivative was unstable and not isolated. The 2-phenoxy and 2-phenylphosphorinium iodides and their precursors produced weak inhibition of sympathetic ganglionic transmission. The phosphaminimide caused a slight potentiation and was also found to be less toxic than its corresponding hydrazinium iodide precusor.     

Synthesis,characterization and DFT aspects of some oxovanadium(IV) and manganese(II) complexes involving dehydroacetic acid and β-diketones

Six new mixed-ligand oxovanadium(IV) and manganese(II) complexes of the general composition [VO(dhaH)(L¹H)(L²)] and [Mn(dhaH)(L¹H)(L²)], where dhaH=dehydroacetic acid, L¹H=β-ketoenolates viz., acetoacetanilide (aaaH), o-acetoacetotoluidide (o-aatdH), o-acetoacetanisidide (o-aansH) and L²=benzimidazole (bzl), 3-methyl-1phenyl-2pyrazoline-5one (mphp), 2-aminobenzimidazole (abzl) or 2-aminobenzathiozole (abtz) have been synthesized. The resultant complexes were characterized on the basis of elemental analysis, molar conductance, magnetic measurements, mass spectrometry, thermogravimetric analysis, infrared and electron spin resonance studies. The thermal decomposition processes of one representative of the complexes are discussed and the order of reaction (n), the activation energies (E_a), the pre-exponential factor (A), have been calculated from thermogravimetric (TG) and differential thermogravimetric (DTG) curves. Gaussian 09 software package was used to carry out theoretical computation using density functional theory (DFT) methods with Becke3-Lee-Yang-Parr (B3LYP) hybrid exchange-correlation functional and the standard LANL2 MB basis set. Based on combined experimental-theoretical characterization, a suitable octahedral structure has been proposed for this class of complexes.     

Sensitive and selective ion chromatographic method for the determination of trace beryllium in water samples

A selective and sensitive ion chromatographic method has been developed for the determination of beryllium in a number of water samples at low-μg/l concentrations. The separation was performed on a 250×4.0 mm I.D. iminodiacetic acid functionalised silica gel column. Chromatographed Be(II) was detected using visible detection at 590 nm following post-column reaction with chrome azurol S (CAS). The optimum separation and derivatisation conditions were studied in detail. The optimum eluent conditions were found to be 0.4 M KNO₃, adjusted to pH 2.5 using HNO₃, with optimum post-column detection being achieved using a solution containing 0.26 mM CAS, 2% Triton X-100, 50 mM 2-(N-morpholino)ethanesulfonic acid, pH 6.0. Under the above conditions, the concentration detection limit for Be(II) was found to be 3 μg/l in a standard solution and 4 μg/l in a typical tap water sample, using a 250 μl injection. The method was linear over the investigated range of 10 μg/l to 10 mg/l and highly reproducible. The method was successfully applied to a number of water samples of varying matrix complexity, including simulated seawater, and also to a natural freshwater certified reference material NIST 1640.     

Indole as a reagent for nitrite in aqueous solution

A fairly selective and sensitive spectrophotometric method for the trace determination of nitrite in aqueous solution is described. The titled ion reacts with indole in acidic medium to form a soluble pink-red product, which is measured at 530 nm. Maximum absorbance is achieved in 10 min and remains constant for about 45 min. This method is applicable to water samples containing 0–2 μg/ml with a relative error of 0.0 to–0.8%, and relative standard deviation of 0.3–0.8%, depending on the concentration level. The optimum reaction conditions affecting and related to the color reaction and interferences due to foreign ions have been studied.     

Photometric determination of iron (III)

A sensitive colored reaction of tiron with iron (III) is described. It is based on a complex formation between tiron and iron (III) in basic medium. The method is suitable to determine 0.4–10 ppm of iron (III) with a relative standard deviation of 0.45–1.4% depending on the concentration level, molar absorptivity of 5.7 × 10³ liter mol⁻¹ cm⁻¹, and Sandell sensitivity index of 0.0098 μg/cm².Because of being simple and rapid, this method can certainly be used in routine analysis.