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Ahmadābād, India

Pandya B.M.,Cu Shah Science College | Haider S.A.,Physical Research Laboratory
Planetary and Space Science | Year: 2012

We have analyzed 1500 electron density profiles obtained from radio occultation experiment onboard Mars Global Surveyor to study the physical characteristics of meteoric plasma layers over Mars during the months of JanuaryJune, 2005. It is found that 65 electron density profiles were strongly perturbed with peak densities ∼0.51.4×10 10 m -3 at altitude between 80 km and 105 km probably due to ablation of meteoroids and subsequent ionization of meteoric atoms. These profiles are used to estimate Total Electron Content (TEC) in the lower atmosphere of Mars. Our analysis suggests that meteoroids ablation caused enhancements in TEC by a factor of ∼1.53.0. We also report that maximum TEC were observed on 21 January and 23 May, 2005, when comets 2007 PL42 and 4015 Wilson-Harrington intersected the orbit of Mars from a close distance 1.49 AU and 1.17 AU, respectively. TEC were increased by a factor of ∼57 on these days. This is a significant increase in TEC, which might be associated with the meteor showers that were produced when Mars crossed the dust stream left along the orbit of these comets. © 2011 Elsevier Ltd. All rights reserved.


Prajapati H.R.,Cu Shah Science College | Doshi A.V.,Mvm Science And Home Science College
Der Pharma Chemica | Year: 2011

New homologous series with -COO- and -N=N- as central group have been synthesized by the treatment of 4-n-alkoxy benzoyl chloride with 2-Hydroxy -naphthyl - 1 - azo - 4' - nitro benzene. All the homologues of the series are enantiotropically nematogenic without exhibition of smectic mesophase. The texture of nematic mesophase is of threaded type. Well known odd-even effect is clearly observed in the nematic isotropic transition curve. Thermal stabilities and liquid crystalline properties are compared with other structurally identical homologous series. Transition temperatures are observed through hot stage polarizing microscope. Analytical data support the structure of molecules.


Prajapati H.R.,Cu Shah Science College | Doshi A.V.,Saurashtra University
Molecular Crystals and Liquid Crystals | Year: 2015

Novel homologous series 4-(4′-n-alkoxy benzoyloxy) napthyl azo 2″ - nitro benzenes, consisted of eleven members of a series. All the eleven members (methoxy to tetradecyloxy) homologs are only enantiotropically nematogenic without exhibition of any smectogenic character. Transition temperatures and the textures are determined by an optical polarizing microscopy equipped with a heating stage. Textures of a nematic phase are threaded or schlieren. Analytical and spectral data supported the molecular structure of homologs. Transition curves viz., solid-nematic and nematic-isotropic showing phase behavior of the mesophase in a phase diagram behave in normal manner. Odd-even effect and alternation of transition temperatures are exhibited by N-I transition curve. N-I thermal stability is 129.7°C and Nematic mesophase vary from 12 to 64°C. Thus, novel series is entirely nematogenic and middle ordered melting type. Mesomorphic behavior of a novel series are compared with the structurally similar homologous series. Copyright © 2015 Taylor & Francis Group, LLC.


Haider S.A.,Physical Research Laboratory | Pandya B.M.,Cu Shah Science College | Molina-Cuberos G.J.,University of Murcia
Journal of Geophysical Research: Space Physics | Year: 2013

We report that radio science (RS) experiment onboard Mars Express (MEX) has observed three plasma layers in the nighttime ionosphere of Mars at altitudes ∼80-100 km, ∼120 km, and ∼160 km, which are reproduced by model calculation due to impact of meteoroid, solar wind proton, and electron, respectively. The densities of 21 ions (Mg+, Fe+, Si +, MgO+, MgCO2 +, MgO 2 +, MgN2 +, FeO+, FeO 2 +, FeN2 +, FeCO2 +, SiO+, SiCO2 +, SiN 2 +, SiO2 +, CO2 +, N2 +, O+, O2 +, CO+, and NO+) have been computed between altitude 50 km and 200 km. The model shows that all atmospheric ions (CO 2 +, N2 +, O+, CO +, O2 +, and NO+) are produced above 100 km due to solar wind electron and proton impact ionizations. The metallic ions are formed between 50 km and 100 km due to ablation of micrometeoroids. It is found that mass ∼3.0 × 10-4 g of incoming meteoroid is sufficient for meteor ablation and its characteristic flux ∼4.0 × 10-15 cm-2s-1 could produce the nighttime metallic layer observed by MEX. The calculated electron densities are also compared with the occultation measurements made by Mars 4/5 in the nighttime ionosphere of Mars. Key Points First observation made by MEX in the night time of Mars The model shows that all atmospheric ions are produced in the upper ionosphere The metallic ions are formed between 50 km and 100 km ©2013. American Geophysical Union. All Rights Reserved.


Makwana N.G.,Rc Technical Institute | Prajapati H.R.,Cu Shah Science College | Doshi A.V.,Saurashtra University
Molecular Crystals and Liquid Crystals | Year: 2015

A novel azoester homologous series of liquid crystals consisting of 12 members is majorly nematogenic without the exhibition of smectic mesomorphism, except for the hexadecyloxy derivative. The methoxy and ethoxy members are monotropically nematic and the rest of the homologs are enantiotropically nematogenic. Transition temperatures and mesophase morphology were determined on an optical polarizing microscope equipped with a heating stage. The textures of the nematic mesophase are threaded or Schlieren in type. Infra red, 1H NMR, mass spectral data, and elemental analysis data confirm the molecular structures of the novel homologs. The mesophase length varies from 00 to 72°C and the average thermal stability for the nematic phase is 133.5°C. Liquid crystal properties vary from homolog to homolog in present novel series. The liquid crystal behavior of the presently investigated novel series is compared with structurally similar known series. The transition curves (Cr-N/Cr-I and N-I/I-N) behave in a normal manner. The N-I/I-N transition curve exhibit an odd-even effect. The series is majorly nematogenic without exhibition of smectogenic character. Only the C16 homolog is nonmesogenic. © 2015 Taylor & Francis Group, LLC.

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