Use of the Nasicon/Na2SO4 couple in a solid state sensor for SOx (x=2,3)

The e.m.f. of a concentration cell for SO x (x=2,3)-O2 incorporating Nasicon as the main solid electrolyte has been measured in the temperature range 720 to 1080 K. The cell arrangement can be represented as,$$Pt, O'_2 + SO'_2 + SO'_3 \left| {Na_2 SO_4 \left\| {\left. {Nasicon} \right\|} \right.} \right.\left. {Na_2 SO_4 } \right|SO''_3 + SO''_2 + O''_2 , Pt$$ The Na2SO4 acts both as an auxiliary electrode, converting chemical potentials of SO x and O2 to equivalent sodium potentials, and as an electrolyte. The presence of Na2SO4 provides partial protection of Nasicon from chemical reaction with gas mixtures containing SO x . The open circuit e.m.f. of the cell is in close agreement with values given by the Nernst equation. For certain fixed inlet gas compositions of SO2+O2, the e.m.f. varies non-linearly with temperature. The intrinsic response time of the cell to step changes in gas composition is estimated to vary from sim2.0 ksec at 723K to sim 0.2 ksec at 1077K. The cell functions well for large differences in partial pressures of SO3(pPrimeSO 3/pprimeSO 3ap104) at the electrodes.

Vacuum emissivity meter for thermal emittance measurements of coatings

The problems in measuring thermal emittance by steady?state calorimetric technique have been analyzed. A few suggestions to make it more accurate, simple, and rapid have been discussed and results are presented.

Nationalism Circumscribed : Transnational Governance of Minority Rights in Post-Cold War Europe

For the past two centuries, nationalism has been among the most influential legitimizing principles of political organization. According to its simple definition, nationalism is a principle or a way of thinking and acting which holds that the world is divided into nations, and that national and political units should be congruent. Nationalism can thus be divided into two aspects: internal and external. Internally, the political units, i.e., states, should be made up of only one nation. Externally each nation-state should be sovereign. Transnational national governance of rights of national minorities violates both these principles. This study explores the formation, operation, and effectiveness of the European post-Cold War minorities system. The study identifies two basic approaches to minority rights: security and justice. These approaches have been used to legitimize international minority politics and they also inform the practice of transnational governance. The security approach is based on the recognition that the norm of national self-determination cannot be fulfilled in all relevant cases, and so minority rights are offered as a compensation to the dissatisfied national groups, reducing their aspiration to challenge the status quo. From the justice perspective, minority rights are justified as a compensatory strategy against discrimination caused by majority nation-building. The research concludes that the post-Cold War minorities system was justified on the basis of a particular version of the security approach, according to which only Eastern European minority situations are threatening because of the ethnic variant of nationalism that exists in that region. This security frame was essential in internationalising minority issues and justifying the swift development of norms and institutions to deal with these issues. However, from the justice perspective this approach is problematic, since it justified double standards in European minority politics. Even though majority nation-building is often detrimental to minorities also in Western Europe, Western countries can treat their minorities more or less however they choose. One of the main contributions of this thesis is the detailed investigation of the operation of the post-Cold War minorities system. For the first decade since its creation in the early 1990s, the system operated mainly through its security track, which is based on the field activities of the OSCE that are supported by the EU. The study shows how the effectiveness of this track was based on inter-organizational cooperation in which various transnational actors compensate for each other s weaknesses. After the enlargement of the EU and dissolution of the membership conditionality this track, which was limited to Eastern Europe from the start, has become increasingly ineffective. Since the EU enlargement, the focus minorities system has shifted more and more towards its legal track, which is based on the Framework Convention for the Protection of National Minorities (Council of Europe). The study presents in detail how a network of like-minded representatives of governments, international organizations, and independent experts was able strengthen the framework convention s (originally weak) monitoring system considerably. The development of the legal track allows for a more universal and consistent, justice-based approach to minority rights in contemporary Europe, but the nationalist principle of organization still severely hinders the materialization of this possibility.

Variational calculation for the spin-(1/2 Heisenberg antiferromagnet on a square lattice

The ground-state properties of the spin-(1/2 Heisenberg antiferromagnet on a square lattice are studied by using a simple variational wave function that interpolates continuously between the Néel state and short-range resonating-valence-bond states. Exact calculations of the variational energy for small systems show that the state with the lowest energy has long-range antiferromagnetic order. The staggered magnetization in this state is approximately 70% of its maximum possible value. The variational estimate of the ground-state energy is substantially lower than the value obtained for the nearest-neighbor resonating-valence-bond wave function.

Stereochemistry of peptides containing 1-aminocyclopentane carboxylic acid (Acc5). Solution and solid state conformations of Boc-Acc5-Acc5-NHMe.

The conformational analysis of a protected homodipeptide of 1-aminocyclopentanecarboxylic acid (Acc5) has been carried out. 1H-nmr studies establish a ?-turn conformation for Boc-Acc5-Acc5-NHMe in chloroform and dimethylsulfoxide solutions involving the methylamide NH in an intramolecular hydrogen bond. Supportive evidence for the formation of an intramolecular hydrogen bond is obtained from ir studies. X-ray diffraction studies reveal a type III ?-turn conformation in the solid state stabilized by a 4 ? 1 hydrogen bond between the Boc CO and methylamide NH groups. The ?,? values for both Acc5 residues are close to those expected for an ideal 310-helical conformation (?? ± 60°, ?? ±30°).

Conformations of the amino terminal tetrapeptide of emerimicins and antiamoebin in solution and in the solid state

The conformations of Boc-l-Phe-(AiB)3-OH (1) and Boc-l-Phe-(Aib)3-OMe (2) which correspond to the amino terminal sequence of the emerimicins and antiamoebins have been studied in solution using 270 MHz 1H n.m.r. In dimethyl sulphoxide solution both peptides show the presence of two strongly solvent shielded Aib NH groups, consistent with a consecutive β-turn conformation, involving the Aib(3) and Aib(4) NH groups in intramolecular 4 → I hydrogen bonds. This folded conformation is maintained for 2 in chloroform solution. Nuclear Overhauser effect studies provide evidence for a Type II Phe-Aib β-turn. An X-ray diffraction study of Boc-(d,l)-Phe-(Aib)3-OH establishes a single type III(III′) β-turn conformation with Aib(2)-Aib(3) as the corner residues. A single intramolecular 4 → I hydrogen bond between Phe(I) CO and Aib(4) NH groups is observed in the crystal. The solution conformation may incorporate a consecutive type II-III′ structure for the Phe(1)-Aib(2)-Aib(3) segment, with the initial type II β-turn being destabilized by intermolecular interactions in the solid state.

Crystallographic characterization of the conformation of the 1-aminocyclohexane-1-carboxylic acid residue in simple derivatives and peptides

The crystal structures of 1-aminocyclohexane-1-carboxylic acid (H-Acc6-OH) and six derivatives (including dipeptides) have been determined. The derivatives are Boc-Acc6-OH, Boc-(Acc6)2-OH, Boc-L-Met-Acc6-OMe, ClCH2CO-Acc6-OH, p-BrC6H4CO-Acc6-OH oxazolone, and the symmetrical anhydride from Z-Acc6-OH, [(Z-Acc6)2O]. The cyclohexane rings in all the structures adopt an almost perfect chair conformation. The amino group occupies the axial position in six structures; the free amino acid is the only example where the carbonyl group occupies an axial position. The values determined for the torsion angles about the N–Cα(φ) and Cα–CO (ψ) bonds correspond to folded, potentially helical conformations for the Acc6 residue.

Precise measurement of hyperfine structure in the 2P(1/2) state of Li-7 using saturated-absorption spectroscopy

We report a precise measurement of the hyperfine interval in the 2P(1/2) state of Li-7. The transition from the ground state (D-1 line) is accessed using a diode laser and the technique of saturated-absorption spectroscopy in hot Li vapor. The interval is measured by locking an acousto-optic modulator to the frequency difference between the two hyperfine peaks. The measured interval of 92.040(6) MHz is consistent with an earlier measurement reported by us using an atomic-beam spectrometer Das and Natarajan, J. Phys. B 41, 035001 (2008)]. The interval yields the magnetic dipole constant in the P-1/2 state as A = 46.047(3), which is discrepant from theoretical calculations by > 80 kHz.

Activity–Composition Relations in the Nickel Oxide–Magnesium Oxide System at 1300 K by the Solid-State Galvanic Cell Technique

The activity of NiO in NiO-MgO rock salt solid solution has been measured at 1300 K by employing a solid-state galvanic cell: Pt,Ni+ NiO||(CaO)ZrO2||Ni + (Nix,Mgl-x)O, Pt. A high-density tube of Zr02-15 mol% CaO has been used as the solid electrolyte for the emf measurements. The activities of the component oxides in the rock salt solid solution exhibit negative deviation from ideality at the temperature of investigation. The solid solution obeys regular solution behavior at 1300 K. The value of the regular solution parameter is found to be -12000 ((l000) J mol-1. The composition dependence of ΔGEx obtained in this study agrees reasonably well with the calorimetric data reported in the literature for NiO-MgO solid solution.

Inorganic Analogues of Graphene

The discovery of graphene has aroused great interest in the properties and phenomena exhibited by two-dimensional inorganic materials, especially when they comprise only a single, two or a few layers. Graphene-like MoS2 and WS2 have been prepared by chemical methods, and the materials have been characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques that include surface area measurements. A new layered material with the composition BCN possessing a few layers and a large surface area discovered recently exhibits a large uptake of CO2.

Convergence feedback and unstable low frequency oscillations in a simple coupled ocean‐atmosphere model

The role of convergence feedback on the stability of a coupled ocean‐atmosphere system is studied using model III of Hirst (1986). It is shown that the unstable coupled mode found by Hirst is greatly modified by the convergence feedback. If the convergence feedback strength exceeds a critical value, several new unstable intraseasonal modes are also introduced. These modes have very weak dependence on the wave number. These results may explain the behaviour of some coupled models and to some extent provide a mechanism for the observed aperiodicity of the El‐Nino and Southern Oscillation (ENSO) events.

Distribution of simple repetitive (TG/CA)n and (CT/AG)n sequences in human and rodent genomes

Sixteen million nucleotide sequence of genome of various organisms have been analysed to detect and study the extent of occurrence of simple repetitive sequences. Two sequence motifs (TG/CA)n and (CT/AG)n capable of adopting unusual DNA structures, left handed Z-conformation and triple-helical conformation respectively, are found to be abundant in rodent and human genomes, but almost completely absent in bacterial genome. (TG/CA)n and (CT/AG)n sequences are present mostly in the intron or 5'/3' flanking regions of the genes. The presence of such repeat motifs in genomic sequence of higher eukaryotes has been correlated with their possible functional significance in nucleosome organization, recombination and gene expression.

Geometrically simple linear weirs using circular quadrants

A detailed theoretical analysis of flow through a quadrant plate weir is made in the light of the generalized theory of proportional weirs, using a numerical optimization procedure. It is shown that the flow through the quadrant plate weir has a linear discharge-head relationship valid for certain ranges of head. It is shown that the weir is associated with a reference plane or datum from which all heads are reckoned.Further, it is shown that the measuring range of the quadrant plate weir can be considerably enhanced by extending the tangents to the quadrants at the terminals of the quadrant plate weir. The importance of this weir (when the datum of the weir lies below its crest) as an outlet weir for grit chambers is highlighted. Experiments show excellent agreement with the theory by giving a constant average coefficient of discharge.

Room-temperature gas sensors based on gallium nitride nanoparticles

Room-temperature sensing characteristics for H-2, ethanol, NH3, H2S and water have been investigated with thick-film sensors based on GaN nanoparticles, prepared by a simple chemical route. In general, GaN nanoparticles exhibit satisfactory sensor properties for these gases and vapors even at room temperature. The sensitivity for ethanol is found to be highest, the sensitivity and recovery times being smallest. Gas sensor properties of GaN seem to be related to intrinsic defects, which act as sorption sites for the gas molecules. (c) 2010 Elsevier Ltd. All rights reserved.

Photochromism of alkylisophthalaldehydes in the solid state: structure–reactivity correlations

The crystal and molecular structures of the photochromic compounds 2,5-dimethylisophthalaldehyde (I) and 5-isopropyl-2-methylisophthalaldehyde (II) have been determined by single crystal X-ray analyses. The intramolecular gamma-hydrogen abstraction process involved in the photoenolisation of I and II in the solid state has been rationalised in the light of relevant geometrical parameters.