110 research outputs found
Crystal structure of [Fe(L<sup>1</sup>)<sub>2</sub>](ClO<sub>4</sub>)<sub>2</sub>.H<sub>2</sub>O having Fe<sup>II</sup>N<sub>6</sub> coordination [L<sup>1</sup>= 2,6- bis(pyrazol-1-ylmethyl)pyridine]
No full text973-975The structure
of the compound [Fe(L1)2](ClO4)2.H2O
(1)[L1= 2,6-
bis(pyrazol-1-ylmethyl)pyridine]
has been determined by X-ray crystallography at ≈130 K. Temperature-dependent magnetic
susceptibility and Mossbauer spectral studies reveal that the iron atom in 1 is
in the high-spin state at room temperature and in the low-spin state at low
temperature, whereas in [Fe(L2)2](ClO4)2.H2O
(2) and [Fe(L3)2](ClO4)2.H2O
(3) [L2 = 2,6-bis(3,5-
dimethylpyrazole-1-ylmethyl)pyridine
and L3 = 2-(pyrazol-1-ylmethyl)-
6-(3,5-dimethylpyrazol-1-ylmethyl)pyridine)
the iron atom is in the high-spin state at both the temperatures [Mahapatra S,
Mukherjee R, Polyhedron 12 (1993) 1603]. The metal-ligand bond distances
in 1 have been compared with those of 3, determined at ≈173 K
[Mahapatra S, Butcher R J, Mukherjee, R,
J chem Soc,
Dalton Trans (1993)
3723]. The Fe-Npyridine and Fe-Npyrazole
bond
distances in 1 are shorter by ~0.23 Å and ~0.14 Å,respectively, than
those for the high-spin complex 3, revealing its low-spin character. Moreover,
a noticeable variation of the N-Fe-N angles, leading to a more regular shape of
the FeIIN6 octahedron in 1, is observed
Rise of Red Terror: The Ethics and Effectiveness of Maoist Violence in India
No full textThe University Archives has determined that this item is of continuing value to OSU's history.The media can be accessed here: http://streaming.osu.edu/knowledgebank/mershon10/043010.mp4Sangeeta Mahapatra is a Fulbright-Nehru Doctoral and Professional Research Fellow. As a visiting scholar at the Mershon Center for International Security Studies, she is currently working on a comparative study of counterterrorism strategies of India, Israel and the United States. As Mahapatra argues, the core of counterterrorism is capability. While states may set for themselves certain goals, how far they are able to deliver on them determines the strengths and weaknesses of their counterterrorism strategy. The aim of the study is to expand the scope of counterterrorism decision-making by studying how the three countries use their political, legal, civilian and economic structures to deal with an outlier event. The question is not about expending a lot of resources on a "high risk-low probability" threat but about responding to it in timely, cost-efficient and effective manner. Mahapatra is the author of Pacification of the Irreconcilable: The Israeli-Palestinian Conflict (Kolkata, 2005) and Miasma: A Collection of Short Stories (Chowringhee Prakashini Press, Kolkata, 1999). She has also published various journal articles including "Economic Globalization: Understanding the Process beyond the Politics," in Globalization in India: New Frontiers, Emerging Challenges, ed. by Swapan Kumar Pramanick and Ramanuj Ganguly (Prentice Hall of India, 2009) and "Human Rights in Pakistan: A Heuristic of Hope and Despair," in Human Rights in South Asia, ed. by Joseph Benjamin (Nagpur University, 2009).Ohio State University. Mershon Center for International Security Studie
Velocity-Dependent Dark Matter Annihilation from Simulations, and 3D Modeling of the Interstellar Medium of the Milky Way
No full textThis dissertation is composed of two main research topics: velocity-dependent dark matter (DM) annihilation from simulations, and 3D modeling of the interstellar medium of the Milky Way (MW). The former has been my focus of research for the last four years, and has resulted in the three papers discussed in this dissertation. We have performed numerical calculations of J -factors using hydrodynamical simulations of galaxies from the Auriga and APOSTLE simulations. My first project involves calculations of velocity-dependent line-of-sight J -factors for the smooth DM halo component of MW-like galaxies. We also determine that the DM relative velocity distribution can be modeled using a Maxwell-Boltzmann distribution. My second project includes the velocity-dependent annihilation radiation from DM substructure, or subhalos, within the Auriga simulations. My third project focuses on the velocity-dependent DM annihilation from dwarf spheroidal (dSph) analogues within the APOSTLE simulations. In my fourth project, we are currently working to extend this research to examine the velocity-dependent J -factors of the Andromeda galaxy (M31). We hope to compare these J -factors to the extended ��-ray emission detected from M31. Another project that I am working on involves creating a 3D model of the interstellar radiation field (ISRF) of the MW. We plan for this model to include large-scale structures, such as spiral arms and the bar, as well as details of the stellar and dust distribution in the MW. My contribution to the project is a 3D completeness model of OB stars in Gaia DR3
Spinal dysraphism controversies: AIIMS experiences and contribution
No full textA large series of split cord malformation (SCM). Over the last 22 years, we have operated more than 1500 patients of SD, of which over 450 are (SCM), and 300 are with various lipomatus malformations. About 55% type II and 45% type I SCM. A separate sub-classification of type I SCM (a,b,c and d), is presented which alter the surgical approach and influence the results. Overall improvement following surgery in patients with SCM was observed in 94%. Fifty percent patients improved and 44% remained stable. However, deterioration was noticed in 6%, mostly with composite type of SCM. A paradigm for management of SCM is provided taking into consideration also the author′s large experience
Synthesis, spectroscopy and electrochemistry of ruthenium(II) complexes of tridentate pyridylpyrazole ligands. Predominance of electronic over steric effects
No full textThe preparations and properties of bis complexes of ruthenium(II) containing various combinations of the tridentate ligands 2,6-bis(pyrazol-1-ylmethyl)pyridine (L1) and di- and tetra-methyl substituted derivatives (L2 and L3) are described. The absorption spectral properties of the complexes are thoroughly analysed. Full assignments have been made for the 1H NMR spectra of two representative complexes in CD3CN and the origins of the co-ordination-induced shifts are discussed. Cyclic voltammetric experiments (MeCN solutions) reveal reversible one-electron RuIII-RuII redox couples in the potential range 1.00-1.06 V vs. saturated calomel electrode (SCE). The occurrence of ligand-based irreversible reductions at low potentials (Ep,c values lie in the range: -1.90 to -2.20 V vs. SCE) reveals that these pyrazole-rich ligands are very poor p acceptors. The formal potentials of the RuIII-RuII couples decrease (by ca. 8 mV per methyl group) as the number of methyl groups in the ligands are increased. The decreased potential step size for [RuL(L')]2+(L,L'= L1-L3) relative to those observed for non-sterically hindered ruthenium(II) complexes reveals that in the present system steric effects due to 3-Me substituent(s) contribute to the observed effect but that electronic factors predominate over steric effects
Consequences of electronic/steric effects on monochelate and bischelate manganese(II) (S =5/2 ) complexes using pyridinylpyrazole ligands. Synthesis and electrochemistry
No full textA group of three high-spin manganese(II) bis-chelates were synthesized using tridentate 2,6-bis(pyrazol-l-ylmethyl)pyridine and its methyl substituted derivatives. The complexes were isolated as crystalline diperchlorate salts. Two five-coordinate mono-chelates with two chlorides as co-ligands were also synthesized. All the complexes were characterized using conventional physico-chemical techniques. Nucleophilic halide displacement reactions in water on the dichloro complexes afforded aqua complexes. When examined by cyclic voltammetry each complex displays an irreversible MnIII/MnII couple. The trends in the anodic peak potentials are rationalized on the basis of electronic/steric effects of the methyl groups present near the donor site
Geodetic network design for InSAR: Application to ground deformation monitoring
No full textFor the past two decades, interferometric synthetic aperture radar (InSAR) has been used to monitor ground deformation with subcentimetric precision from space. But the applicability of this technique is limited in regions with a low density of naturally-occurring phase-coherent radar targets, e.g. vegetated nonurbanized areas. Third-party end-users of InSAR survey results cannot, in a systematic way, determine a priori whether these coherent targets have adequate spatial distribution to estimate the parameters of their interest. Additionally, InSAR deformation estimates are referred to a local datum, meaning that the technique is sensitive only to the relative deformation occurring within the SAR images. This makes it difficult to compare these estimates with those from other techniques, e.g. historical levelling data or changes in the sea level. Here we propose the design of a geodetic network for InSAR, aimed at densifying the naturally-occurring measurement network and converting from a local datum to a global one. A practical solution for improving spatial sampling is to deploy coherent target devices such as corner reflectors or transponders on ground, tailored to the specific monitoring application under consideration. The proposed method (1) provides a generic description of any deformation phenomenon; (2) determines whether the naturally-occurring InSAR measurements are adequate in terms of user-defined criteria; (3) finds the minimum number of additional devices to be deployed (if required); and (4) finds their optimal ground locations. It digests, as inputs, any prior knowledge of the deformation signal, the expected locations and quality of the existing coherent targets, and the quality of the deployed devices. The method is based on comparing different covariance matrices of the final parameters of interest with a criterion matrix (i.e., the ideal desired covariance matrix) using a predefined metric. The resulting measurement network is optimized with respect to precision, reliability and economic criteria; this is demonstrated via synthetic examples and a case of subsidence in the Netherlands. As a basis for the choice and number of deployed devices, we evaluate the measurement precision of compact active transponders and demonstrate their viability as alternatives to passive corner reflectors through three field experiments, using different satellite data and geodetic validation techniques. Transponders are shown to be usable for subcentimetre-precision geodetic applications, while improving upon the drawbacks of corner reflectors in terms of size, shape, weight and conspicuousness. For transforming the spatially-relative InSAR deformation estimates (local datum) to a standard terrestrial reference frame (global datum), we introduce a new concept involving the collocation of transponders with Global Navigation Satellite System (GNSS) measurements. The displacement of such a transponder is consequently determined in the standard reference frame used by GNSS, eliminating the need for any assumptions on reference-point stability in applications where the InSAR deformation estimates are compared with results from other techniques. The considerations, results and practical lessons learnt at several permanent GNSS stations in the Netherlands are described.Geoscience and Remote SensingCivil Engineering and Geoscience
New triply bridged diiron(III) complexes with [Fe<SUB>2</SUB>(μ-O)(μ-X)<SUB>2</SUB>]<SUP>2+</SUP> cores [X = MeCO<SUB>2</SUB>, PhCO<SUB>2</SUB> or (PhO)<SUB>2</SUB>PO<SUB>2</SUB>]
No full textA group of three diiron(III) complexes having [Fe2(μ-O)(μ-X)2]2+ cores (X = benzoate, acetate or diphenyl phosphate) has been synthesised with the use of unsymmetrical facially capping tridentate ligands (L1 and L2), where L1 and L2 are [2-(2-pyridyl)ethyl](2-pyridylmethyl)amine and methyl[2-(2-pyridyl)ethyl](2-pyridylmethyl)amine respectively. The lability of the bridging acetate groups in [Fe(μ-O)(μ-MeCO2)2L22]2+ has been demonstrated by exchange with diphenyl phosphate and deuterioacetate as revealed by UV/VIS and 1H NMR studies. These complexes exhibit infrared, electronic and Mossbauer spectral features very similar to those of μ-oxo-diiron(III) proteins as well as of μ-oxo-bis(μ-carboxylato) or μ-oxo-bis(μ-phosphato)diiron(III) complexes. The inequivalence in the chelate rings around each iron(III) might have caused the asymmetry in these compounds which is reflected in their distinctively strong antiferromagnetic coupling (J=-127, -125 and -108 cm-1 for the benzoate-, acetate- and phosphate-bridged complexes respectively)
Consequences of incremental steric crowding at the Fe<SUP>II</SUP>N<SUB>6</SUB>(S=2) co-ordination sphere. Synthesis, spectra and electrochemistry
No full textThe effect of methyl substituents adjacent to donor atoms on the complexing properties of a novel family of tridentate (N3) heterocyclic ligands has been explored. In the course of this investigation a new group of high-spin iron(II) complexes has been synthesised. The characterization in solution of FeIIN6 co-ordination has been done on the basis of paramagnetically shifted 1H NMR spectroscopy. Increased steric crowding progressively decreases the values of 10 Dq for these ligands with iron(II) and nickel(II) in the grossly octahedral complexes. The iron(II) complexes also display metal-to-ligand charge-transfer (m.l.c.t.) transition at ca. 360 nm. Cyclic voltammetric studies (MeCN solutions) reveal reversible one-electron FeIII-FeII redox couples at high potentials [1.06-1.22 V vs. saturated calomel electrode (SCE)]. The electrochemical experiments further corroborate the fact that in the present system steric effects due to 3-Me substituent(s) predominate over the electronic contributions of the 5-Me substituent
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