Infrared focal plane array with a built-in stationary Fourier-transform spectrometer: basic concepts

A novel configuration of stationary Fourier transform infrared (FTIR) spectrometer is presented. Contrary to classic configurations, the interferometer is directly integrated in the focal plane array (FPA) during its process of fabrication. A first, to the best of our knowledge, demonstration of the spectrometric function has been achieved departing from a well-known structure of an HgCdTe photodetector. We show that the obtained FTIR-FPA can be described by intrinsic parameters such as an optical path difference and a so-called spectrometric efficiency. First experimental results are presented.     

Equidistribution of Heegner points and the partition function

Let p(n) denote the number of partitions of a positive integer n. In this paper we study the asymptotic growth of p(n) using the equidistribution of Galois orbits of Heegner points on the modular curve X ₀(6). We obtain a new asymptotic formula for p(n) with an effective error term which is O(n^-(\frac12+d)){O(n^{-(\frac{1}{2}+\delta)})} for some δ > 0. We then use this asymptotic formula to sharpen the classical bounds of Hardy and Ramanujan, Rademacher, and Lehmer on the error term in Rademacher’s exact formula for p(n).     

Quinquevalent tungsten as a reducing agent in potentiometric titrations

Qmnquevalcnt tungsten prepared by the electrolytic reduction of tungstate in ION HC1 is sufficiently stable when kept in strong acid solutions under COg to be used as an effective reducing agent in potcntiometric titrations. It can be accurately standardised with dichromate. The formal redox potentials of the $\text{W}{}^{\mathrm{+6}}\text{W}{}^{\mathrm{+5}}$ system as determined at different acidities indicate that quinquevalent tungsten is more reducing than the corresponding molybdenum compound.Quinquevalent tungsten can be applied successfully as a volumetric reagent in the potentiometric titration of ferric iron in 8-ioN HC1 or in a mixture of HCl and H3PO4 0.5.N each and of cupric copper in 8N HCl at 80° C. It can also be applied for the estimation of iodate, provided that the latter is used as the titrant.     

Polymerization of formic acid under high pressure

We report Raman, infrared, and x-ray diffraction (XRD) measurements, along with ab initio calculations on formic acid (FA) under pressure up to 50 GPa. We find an infinite chain Pna2(1) structure to be a high-pressure phase at room temperature. Our data indicate the symmetrization and a partially covalent character of the intrachain hydrogen bonds above approximately 20 GPa. Raman spectra and XRD patterns indicate a loss of long-range order at pressures above 40 GPa, with a large hysteresis upon decompression. We attribute this behavior to a three-dimensional polymerization of FA.     

Acid-Base properties of ethylenediamineamminenitro complexes of tetravalent platinum

Russian Chemical Bulletin -     

Poly(ethylene sulfide). III. Oxidative degradation

Injection-molded poly(ethylene sulfide) containing polyamines and zinc salts as thermal stabilizers has excellent physical properties at room temperature, but discolors rapidly on air aging at 150°C, with embrittlement and general deterioration of properties. Degradative breakdown under these conditions is preponderantly thermo-oxidative in nature. The site of the polymer's thermo-oxidative instability was sought in oxidation experiments involving the resin as well as model compounds for the polymer's organic structure. Identification studies were carried out on the oxidation products of 3,6-dithiaoctane (a model compound). Rate of oxygen consumption by the model compound was measured by a pressure-bomb technique and by a volumetric method. Oxidation of the model compound was found to proceed indefinitely as long as the supply of oxygen was replenished. Rate of oxidation was nonaccelerating and independent of oxygen pressure within the range 1.7–3 atm O₂. The gaseous products of the oxidation of unstabilized (no polyamine) resin were found to be identical to the products from the oxidation of the model compound. A mechanism has been proposed taking into account the products isolated and identified, and the nonaccelerating nature of the oxidation. The poly(ethylene sulfide) structure is able to decompose hydroperoxides via formation of sulfoxides, preventing the acceleration of the oxidation reaction. While effecting this radical deactivation, the polymer chains are cleaved, with a resultant loss in molecular weight and physical properties. Some success has been met in the use of inorganic or metallo-organic additives as antioxidants. Among these are dithiocarbamate salts and selenocyanates. The effectiveness of these compounds has been demonstrated in the polymer, and a suggested rationale for stabilization is given.     

Early chemistry in hot and dense nitromethane: molecular dynamics simulations

We report density functional molecular dynamic simulations to determine the early chemical events of hot (T=3000 K) and dense (rho=1.97 g/cm(3), V/V(0)=0.68) nitromethane (CH(3)NO(2)). The first step in the decomposition process is an intermolecular proton abstraction mechanism that leads to the formation of CH(3)NO(2)H(+) and the aci ion H(2)CNO(2) (-). This event is also confirmed to occur in a fast annealing simulation to a final temperature of 4000 K at rho=2.20 g/cm(3). An intramolecular hydrogen transfer that transforms nitromethane into the aci acid form, CH(2)NO(2)H, accompanies this event. To our knowledge, this is the first confirmation of chemical reactivity with bond selectivity for an energetic material near the Chapman-Jouget state of the fully reacted material. We also report the decomposition mechanism followed up to the formation of H(2)O as the first stable product. We note that similarities in the global features of reactants, intermediates, and products of the reacting fluid seem to indicate a threshold for similar chemistry in the range of high densities and temperatures reported herein.     

Reaction of vinylpyridines with oxazoles

Depending on the structure, the reaction of the hydrochlorides of 2- and 4-vinylpyridines and 2-methyl-5-vinylpyridine with oxazoles leads to the synthesis of dipyridyls with or without a hydroxy group. It is shown that the regiospecificity of the reaction can be predicted on the basis of quantum-chemical calculations with the aid of the concepts of MO perturbation theory.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1255–1262, September, 1980.     

Thermal Effects Associated with the Incorporation of Transition Metal Catalysts Inside Alumino-silicate Supports

Kaolinic and bentonitic-clays are selected to prepare transition metals, iron, cobalt and nickel catalysts. The metals are incorporated into two supports through new impregnation technique. The original clays and the prepared catalysts were subjected to different techniques. The crystallite size (X-ray diffraction analysis) increases from iron to cobalt then to nickel upon heating and the increase for bentonitic-catalysts is higher than that for kaolinic-ones. Infrared spectra show the appearance of bands signifying the presence of iron, cobalt and nickel bonded to OH group constituting the silica-silica tetrahedral sheets inside the clay structure. The enthalpy (ΔH) andentropy (ΔS) values (differential scanning calorimetric) are lower for bentonitic-catalysts than for kaolinic-catalysts. Thus, the incorporation of the metal hydroxide in the interlamella of the silicate-silicate bentonite clay structure facilitates the interaction between the unpaired electrons on the adjacent atoms and the support which enables the prepared catalysts to be more active for catalytic conversion. This revised version was published online in July 2006 with corrections to the Cover Date.     

Numerical analysis of heat and mass transfer in a compact finned tubes air heat exchanger under dehumidification conditions

A simulation model of a fin-and-tube heat exchanger is presented. The effect of the relative humidity, air speed, fin base temperature, and inlet air temperature on the estimation of the overall heat-transfer coefficient and fin efficiency under wet conditions is also investigated. This model considers a non-uniform airflow velocity as well as a variable sensible heat transfer coefficient.