Development of Broad Band VCO at Ka-Band

A broad band VCO has been developed at Ka-band for FMCW Radar applications. To achieve a wide range of frequency variation, VCO has been designed in series configuration. Design steps have been presented. VCO exhibits a tuning range of 600 MHz with the power output of 50 mw, when the controlled varactor voltage varies from 7.5 volts to 15 volts. Frequency drift with temperature has been contained within 30 MHz using a proportionally controlled DC heater module over the temperature range of 0°C to +55°C. Phase Noise of the oscillator measured at the mid and extreme frequencies is about -70 dBc/kHz at 10 kHz away from the carrier. The experimental circuit and measured performance is also presented.     

Growth and electrical characterization of L‐arginine added KDP and ADP single crystals

Potassium dihydrogen orthophosphate (KDP) and ammonium dihydrogen orthophosphate (ADP) single crystals added with L‐arginine have been grown by the solution methods. DC and AC electrical measurements were carried out at various temperatures along both a‐ and c‐ directions. Results indicate an increase of the electrical parameters with the increase of temperature which can be attributed mainly to the increase of thermally generated hydrogen bond vacancies (L. defects). Also, the present study indicates that L‐arginine addition leads to reduction of electrical parameters of KDP and ADP single crystals which can be attributed mainly to the decrease of L‐defects due to creation of additional hydrogen bonds by the impurity in random directions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On Lie nilpotent modular group algebras

Let K be a field of characteristic p>0 and let KG be the group algebra of an arbitrary group G over K. It is known that if KG is Lie nilpotent, then its lower as well as upper Lie nilpotency index is at least p+1. The group algebras KG for which these indices are p+1 or 2p or 3p?1 or 4p?2 have already been determined. In this paper, we classify the group algebras KG for which the upper Lie nilpotency index is 5p?3, 6p?4 or 7p?5.     

Compounds of imidazoles with ruthenium(III) chloride

Summary Reaction of ruthenium(III) chloride with imidazole(Im) and different substituted imidazoles,viz. N-methylimidazole (N-MeIm), 2-methylimidazole(2-MeIm), 4-methylimidazole (4-MeIm),N-vinylimidazole(N-VIm), 2-methyl- 1-vinyl-imidazole(2-Me-1-VIm), 1,2-dimethylimidazole(1,2-Me,Im), 2-ethylimidazole(2-EtIm) and 2-ethyl-4(5)-methylimidazole (2-Et-4(5)-MeIm] yield products of the types [Ru₂L₄Cl₆] · 2 H₂O (L = N-VIm or 4-MeIm), [Ru₂L₄Cl₆] · 4 H₂O (L = Im or 2-Et-4(5)-MeIm), [Ru₂L ³ (H₂O)Cl₆] (L =N-MeIm or 2-MeIm), [Ru₂L ² (H₂O)₂Cl₆] (L = 1,2-Me₂Im or 4-MeIm), [Ru(2-Me-1-VIm)₃Cl₃] · H₂O and [Ru(2-EtIm)₃(H₂O)Cl₂]. These compounds were characterised by elemental analyses, conductometric measurements, i.r. and electronic spectral analyses. Magnetic moments range from 1.01 to 1.9 B.M. The e.s.r. spectra and g values of some of the compounds are indicative of high distortion.     

The spectrophotometric determination of nitrite in water with 8-quinolinol

The method is based on the formation of a purple azoxine dye by coupling diazotized p-nitroaniline with 8-quinolinol. Beer's law is obeyed at 550 nm in the range 2–28 μg NO₂^- per 25 ml. The molar absorptivity and Sandell sensitivity are 3.88 × 10⁴ l mol^-1 cm^-1 and 0.0012 μg cm^-2, respectively.     

PHYTOCHROME-MEDIATED RAPID CHANGES IN THE LEVEL OF PHOSPHOINOSITIDES IN ETIOLATED LEAVES OF Zea mays

The role of the active form of phytochrome in Zea mays on the polyphosphoinositide cycle was studied. As little as 15 s of red irradiation of etiolated leaves immediately increased the level of phosphatidylinositol bisphosphate (PIP₂) 3–6-fold compared to unirradiated leaves. The elevated level of PIP₂ decreased with longer red irradiations up to 5 min, but remained higher than in unirradiated leaves. The level of PIP₂ decreased if red irradiation was followed by far-red irradiation. Far-red alone had no effect. Levels of phosphatidylinositol phosphate (PIP) and phosphatidylinositol did not change significantly. Since red irradiation significantly changed PIP, but not PIP, photocontrol appears to be at the PIP kinase and phospholipase level. In related studies of the effect of light on phospholipids, 5 min of red irradiation induced significant decreases in phosphatidylcholine and phosphatidylethanola-mine.     

Polymeric complexes of bivalent transition metal ions with 2-hydroxy-1-naphthaldehyde oxaldihydrazone and 2-hydroxy-1-naphthaldehyde malondihydrazone

Summary Polymeric complexes prepared by solid-solution reactions, from 2-hydroxy-1-naphthaldehyde oxaldihydrazone (HNODH) and 2-hydroxy-1-naphthaldehyde malondihydrazone (HNMDH), had the empirical composition M(L-2H)·nH₂O where M=Fe^II, Mn^II, Co^II, Ni^II, Cu^II, Zn^II, Cd^II and Hg^II; L=HNODH, HNMDH andn=0,1, 2. The complexes, which are intensely coloured and insoluble in common organic solvents, were characterized by elemental analysis, magnetic susceptibility, electronic and i.r. spectral data. The absence of anions indicates that the ligands which bind the metal ions from the hydroxyl and the imino groups have been deprotonated.     

Radical Chain Breaking Bis(ortho-organoselenium) Substituted Phenolic Antioxidants

The presence of a chalcogen atom at the ortho-position of phenols enhances their radical chain-breaking activity. Here, a copper(I)-catalyzed reaction of 2,6-dibromo- and 2,6-diiodophenols with diorganodiselenides has been studied for the introduction of two organoselenium substituents at both ortho-positions of the phenolic radical chain-breaking antioxidants, which afforded 2,6-diorganoseleno-substituted phenols in 80–92% yields having electron-donating CH₃, and electron-withdrawing CN and CHO functionalities. Additionally, 2,6-diiodophenols with electron-withdrawing CHO and CN groups also afforded novel 5,5′-selenobis(4-hydroxy-3-(phenylselanyl)benzaldehyde) and 5,5′-selenobis(4-hydroxy-3-(phenylselanyl)benzonitrile) consisting of three selenium and two phenolic moieties along with 2,6-diorganoseleno-substituted phenols has been synthesized. The electron-withdrawing CHO group has been reduced by sodium borohydride to the electron-donating alcohol CH₂OH group, which is desirable for efficient radical quenching activity of phenols. The developed copper-catalyzed reaction conditions enable the installation of two-arylselenium group ortho to phenolic radical chain-breaking antioxidants, which may not be possible by conventional organolithium-bromine exchange methods due to the sluggish reactivity of trianions (dicarba and phenoxide anion), which are generated by the reaction of organolithium with 2,6-dibromophenols, with diorganodiselenides. The antioxidant activities of the synthesized bis and tris selenophenols have been accessed by DPPH, thiol peroxides, and singlet oxygen quenching assay. The radical quenching antioxidant activity has been studied for the synthesized compounds by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The bis-selenophenols show comparable radical deactivating activity, while tris seleno-bisphenols show higher radical deactivating activity than α-tocopherol. Furthermore, the tris seleno-bisphenol shows comparable peroxide decomposing activity with ebselen molecules.     

Aqueous spray-drying synthesis of alluaudite Na2+2xFe2−x(SO4)3 sodium insertion material: studies of electrochemical activity,thermodynamic stability,and humidity-induced phase transition

Journal of Solid State Electrochemistry - In pursuit of high-energy density sodium insertion materials, polyanionic frameworks can be designed with tuneable high-voltage operation stemming from...