Application of complex reaction kinetic models in thermal analysis

The complexity of the phenomena which arise during the heating of the various substances seldom can be described by a single reaction kinetic equation. As a consequence, sophisticated models with several unknown parameters have to be developed. The determination of the unknown parameters and the validation of the models requires the simultaneous evaluation of whole series of experiments. We can accept a model and its parameters if, and only if we get a reasonable fit to several experiments carried out at different experimental conditions. In the field of the thermal analysis the method of least squares alone seldom can select abest model or abest set of parameter values. Nevertheless, the careful evaluation of the experiments may help in the discerning between various chemical or physical assumptions by the quality of the corresponding fit between the experimental and the simulated date. The problem is illustrated by the thermal de-composition of cellulose under various experimental conditions.This research program was funded by the National Science Foundation (grant INT 8914934), the US Hungarian Science and Technology Joint Fund (grants 90b-22 and 93b-375), the Hungarian National Research Fund (OTKA, grant 3077/91) and the Coral Industries Endowment.     

Every Moufang loop of odd order with nontrivial commutant has nontrivial center

We get a partial result for Phillips’ problem: does there exist a Moufang loop of odd order with trivial nucleus? First we show that a Moufang loop Q of odd order with nontrivial commutant has nontrivial nucleus, then, by using this result, we prove that the existence of a nontrivial commutant implies the existence of a nontrivial center in Q. Introducing the notion of commutantly nilpotence, we get that the commutantly nilpotence is equivalent to the centrally nilpotence for the Moufang loops of odd order.     

Bioleaching of Nickel and Cobalt from Lateritic Chromite Overburden Using the Culture Filtrate of Aspergillus niger

Extraction of metals (Ni, Co) from chromite overburden of Sukinda mines of Orissa, India, with the culture filtrate of Aspergillus niger was studied. Results showed that the amounts of metals leached varied directly with reaction temperature and period of fermentation. The culture filtrate was analyzed for citric and oxalic acids, and contained only oxalic acid—the concentration of which increased with time. Although this acid played the major role in leaching of metals, other unidentified metabolites present in the culture filtrate influenced the dissolution of the metals significantly. Maximum recovery of metals from raw and roasted ore samples was achieved at 80 °C with the 21-day culture filtrate containing the highest amount of oxalic acid. Under identical experimental conditions, much higher amounts of the metals were leached from roasted ore. Microstructures of the ore particles were studied by scanning electron microscopy and transmission electron microscopy; the bonding behaviors of metal compounds were identified by Fourier transform infrared spectroscopy which showed that the metals were leached after chelation with oxalic acid.     

Microstructure characterization of titanium dioxide nanodispersions and thin films for dye-sensitized solar cell devices

This article reports on the microstructure characterization of titanium dioxide nanodispersions and thin films made thereof for dye-sensitized solar cell devices. Structure–property relationships have been investigated mainly using electron microscopy to assess how microstructure (crystalline structure, defects) and morphological (e.g. heterogeneities, inclusions, voids) features in the electron transport element of the solar cell device correlate with electrical performance, namely, short-circuit photocurrent density (J_sc). This work shows that for a nanodispersion synthesized in the laboratory different electrical performances are measurable depending on the thin film forming process, more specifically, heat-sintering at 450 °C or pressure-sintering at 500 bar. For the heat-sintered device J_sc is about 7.3 mA/cm² whereas for the pressure-sintered one this value is much lower, this difference being attributed to the existence of inclusions in the titanium dioxide matrix, which are spatially isolated from the rest of the electron transport element thereby limiting the charge transport process by promoting their premature recombination. PACS 68.37.Lp; 73.61.Le; 81.40.-z; 84.60.Jt     

Left conjugacy closed loops of nilpotency class two

Every LCC loop Q with Inn Q abelian is nilpotent class two. A loop Q of nilpotency class two is LCC ? L(x, y) = L(y, x) for all x, y ∈ Q ? ?/Z(Mlt Q) is abelian ? [x, y, z] = [x,z,y] for all x, y, z ∈ Q ? [x, y, z] = [xy, z][x, z]^?1 for all x, y, z ∈ Q. All nilpotent LCC loops of order p² are described, and some of their multiplication groups are computed.     

Some results on supersolvability of finite groups

We get new characterizations of finite supersolvable groups based on the structure of the generalized Fitting subgroup. Then we extend our results to the saturated formations containing the class of all supersolvable groups. Authors’ addresses: M. Asaad, Department of Mathematics, Faculty of Science, Cairo University, Giza, Egypt; Piroska Cs?rg?, Department of Algebra and Number Theory, E?tv?s University, Pázmány Péter sétány 1/c, H-1117 Budapest, Hungary     

Novel calorimetric investigation of different degenerative disorders of the human hyaline cartilage

The purpose of this investigation was to further elucidate calorimetric properties of cartilage samples from femoral head necrosis and osteoarthritis from live surgeries. The natural course of this disease is one of steady progression with eventual collapse of the femoral head, followed by secondary osteoarthritis in the hip joint. All samples showed a clear denaturation peak on the calorimetric curve. Cartilage obtained from necrotic femoral head required the lowest amount of energy for decomposition. The use differential scanning calorimetry as part of thermal analysis was a reliable method for differentiating.     

Beiträge zur Chemie des Thalliums und Arsens

Zusammenfassung Verfasser untersuchten die Änderungen des Oxydationszustandes des Thalliums und Arsens in konz. Schwefelsäure und in Schwefelsäurehydraten. Es wurde festgestellt, daß Thallium(I) keine Veränderung erfährt, Thallram(III) jedoch quantitativ zu Thallium(I) reduziert wird. Während der Reduktion bildet sich Sauerstoffgas. Arsen(III) und Arsen(V) unterliegen bei ähnlichen Bedingungen weder einer Oxydation noch einer Reduktion.Diese Eigenschaften der beiden Elemente ermöglichen es, das Thallium nach Zerstörung bzw. Behandlung der Probe mit einem Gemisch aus konz. Schwefelsäure und Wasserstoffperoxyd auch in Gegenwart großer Arsenmengen direkt, ohne vorangehende Trennung zu bestimmen. Die Titrationen wurden mit KBrO₃-Lösung durchgeführt, als Indikator diente p-Äthoxychrysoidin.

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Summary A study has ben made of the changes in the oxidation state of thallium and arsenic in concentrated sulfuric acid and in hydrates of sulfuric acid. It was found that thallium(I) undergoes no change, whereas thallium (III) is reduced quantitatively to thallium(I). Oxygen gas is produced during the reduction. Under similar conditions, arsenic(III) and arsenic(V) exhibit neither an oxidation or a reduction.These properties of the two elements make possible a direct determination of thallium, even in the presence of considerable amounts of arsenic, and without a preliminary separation. The sample must be treated with a mixture of concentrated sulfuric acid and hydrogen peroxide. The titrations were made with KBrO₃ solution;p-ethoxychrysoidine serves as indicator.

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Résumé Les auteurs étudient les changements d'état d'oxydation du thallium et de l'arsenie dans l'acide sulfurique concentré et dans l'acide sulfurique hydraté. On a établi que le thallium-I ne subit pas d'altération, cependant que le thallium-III est réduit quantitativement en thallium-I. Pendant la réduction il se forme de l'oxygène. Dans les mêmes conditions, l'arsenic-III et l'arsenic-V ne subissent ni oxydation ni réduction.Ces propriétés des deux éléments rendent possible le dosage direct du thallium après décomposition ou traitement de l'essai par un mélange d'acide sulfurique concentré et d'eau oxygénée, même en présence de grandes quantités d'arsenic, sans séparation préalable. Les titrages ont été réalisés avec une solution de bromate de potassium en utilisant lap-éthoxychrysoïdine comme indicateur.

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Gewidmet zur 100. Wiederkehr des Geburtstages vonFriedrich Emich.     

On Centrally and Nuclearly Nilpotent Moufang Loops

Let Q be a finite Moufang loop with nucleus N(Q) and associator subloop 𝒜(Q). First we prove if the factor loop over the nucleus Q/N has nontrivial center, then the center of Q is nontrivial too. By using this result we prove that the centrally nilpotence of Q/N(Q) implies the centrally nilpotence of 𝒜(Q), and we show that, for the centrally nilpotence of a finite Moufang loop, the centrally nilpotence of Q/N(Q) and Q/𝒜(Q) is a necessary and sufficient condition. Finally, as a corollary we give a necessary and sufficient condition for the equivalence of centrally and nuclearly nilpotence of finite Moufang loops, namely, the centrally nilpotence of Q/𝒜(Q).