Formation of iron oxides in soils developed under natural fires and slash-and-burn based agriculture in a monsoonal climate (Chittagong Hill Tracts, Bangladesh)

Fire-induced mineral transformations have been investigated in composite mineral grains separated from the coarse sand fractions (400–2,000 μm) from Ultisols developed in the Chittagong Hill Tracts (Bangladesh). Magnetic and colour based separation (into light brown, dark red, and magnetic, dark red classes) were used to select the grains that were studied by Mössbauer spectroscopy. Aluminium substituted goethite (α-FeOOH) dominates the light brown particles. Fire transform the goethite into a poorly crystalline hematite (α-Fe₂O₃) dominating in the dark red particles. In the dark red, magnetic grains a recrystallized hematite dominates, but small amounts of maghemite (γ-Fe₂O₃) are also present. The latter is indicated by comparing the line intensities in spectra measurement with and without an external magnetic field.     

A forward scheme for backward SDEs

We introduce a forward scheme for simulating backward SDEs. Compared to existing schemes, ours avoids high order nestings of conditional expectations backwards in time. In this way the error, when approximating the conditional expectation, depending on the time partition, is significantly reduced. Besides this generic result, we present an implementable algorithm and prove its convergence. Finally, we demonstrate the strength of the new algorithm by solving a financial problem numerically.     

Binding of SO2 by Synthetic Substituted Apatites

The reaction of SO₂ with synthetic apatites was studied by TG, XRD and IR analyses at 400-1000°C. Due to an interaction of apatite with SO₂, destruction of apatite and formation of CaSO₄ and diphosphate up to 750°C takes place. The further calcination leads to the formation of β-Ca₃(PO₄)₂ and a part of the SO₂ bound is lost again. The amount of SO₂ bound with apatite at calcination depends on the substitution ((F^- ↔ OH^-, PO₄ ^3- ↔ CO₃ ^2-, Ca²⁺ ↔ Mg²⁺) in its structure. This revised version was published online in July 2006 with corrections to the Cover Date.     

Data structures for maintaining set partitions

Efficiently maintaining the partition induced by a set of features is an important problem in building decision‐tree classifiers. In order to identify a small set of discriminating features, we need the capability of efficiently adding and removing specific features and determining the effect of these changes on the induced classification or partition. In this paper we introduce a variety of randomized and deterministic data structures to support these operations on both general and geometrically induced set partitions. We give both Monte Carlo and Las Vegas data structures that realize near‐optimal time bounds and are practical to implement. We then provide a faster solution to this problem in the geometric setting. Finally, we present a data structure that efficiently estimates the number of partitions separating elements. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004     

The Z = 82 shell closure in neutron-deficient Pb isotopes

Recent mass measurements show a substantial weakening of the binding-energy difference δ_2p(Z, N) = E(Z - 2, N) - 2E(Z, N) + E(Z + 2, N) in the neutron-deficient Pb isotopes. As δ_2p is often attributed to the size of the proton magic gap, it might be speculated that reduction in δ_2p is related to a weakening of the spherical Z = 82 shell. We demonstrate that the observed trend is described quantitatively by self-consistent mean-field models in terms of deformed ground states of Hg and Po isotopes. Received: 25 October 2001 / Accepted: 28 February 2002     

Interactions of ammonium nitrate with different additives Thermodynamic analysis

In order to elucidate the influence of Ca and Mg carbonates with or without the presence of boron, manganese and copper compounds on the thermal stability of ammonium nitrate (AN), thermodynamic analysis of different reactions between AN and additives was carried out. Temperature dependency of Gibbs free energy changes ∆G _T and equilibrium composition of reaction products were calculated for a set of reactions using the HSC software. Main solid compounds that can form in the systems of AN and carbonates, were Ca(NO₃)₂ and Mg(NO₃)₂, Ca(OH)₂ and Mg(OH)₂, CaO₂ and MgO₂, CaO and MgO, and N-containing gaseous compounds NO, N₂O and NO₂. As a result of H₃BO₃, MnO₂ and CuSO₄ addition, the content of CuO, Cu₂O and MnO as solids and SO₂, SO₃ and HBO as gaseous reaction products reached the same level. Thereby, their equilibrium concentrations did not depend on the carbonate origin of CaCO₃, MgCO₃ or CaMg(CO₃)₂. Small amount of CuSO₄, H₃BO₃ or MnO₂ additive (0.01–0.05 mol) in the system, practically, did not influence the temperature dependencies of ∆G _T of the reactions between AN and CaCO₃ or CaMg(CO₃)₂. The influence of additives taken in the larger amount (0.5 mol) was evident and, depending on the additive and reaction, shifted their proceeding temperatures in either direction by more than 300–400 K.     

Extending $\mathcal{P}\mathcal{T}$ Symmetry from Heisenberg Algebra to E2 Algebra

The E2 algebra has three elements, J, u, and v, which satisfy the commutation relations [u,J]=iv, [v,J]=−iu, [u,v]=0. We can construct the Hamiltonian H=J ²+gu, where g is a real parameter, from these elements. This Hamiltonian is Hermitian and consequently it has real eigenvalues. However, we can also construct the PT\mathcal{P}\mathcal{T}-symmetric and non-Hermitian Hamiltonian H=J ²+igu, where again g is real. As in the case of PT\mathcal{P}\mathcal{T}-symmetric Hamiltonians constructed from the elements x and p of the Heisenberg algebra, there are two regions in parameter space for this PT\mathcal{P}\mathcal{T}-symmetric Hamiltonian, a region of unbroken PT\mathcal{P}\mathcal{T} symmetry in which all the eigenvalues are real and a region of broken PT\mathcal{P}\mathcal{T} symmetry in which some of the eigenvalues are complex. The two regions are separated by a critical value of g.     

Extension of the Application of Piers-Rubinsztajn Conditions to Produce Triarylamine Pendant Dimethylsiloxane Copolymers

Summary: In this paper we show how the strong organic Lewis acid catalyst, tris(pentafluorophenyl)borane (B(C₆F₅) or BCF), can be used to facilitate the functionalization of simple polymeric silicones with a triarylamine yielding a novel class of charge transporting materials. The reaction conditions we refer to as Piers-Rubinsztajn Conditions and we have previously shown such conditions to be suitable when using phenylated silicones as precursors. In this work we found they also work successfully for a silicone oligomer as well as cocopolymers of polymethylhydridosiloxane (PMHS) and polydimethylsiloxane (PDMS) and a PMHS homopolymer, all of which are highly abundent and available in industrial quanitities. The resulting material was either a waxy solid, viscous oil or a glass. An additional “finishing” step with anisole using the same chemistry was found necessary to prevent gelation of the copolymer and homopolymer of PMHS. Even after finishing a small fraction (<5%) of Si-H groups remained in the silicones. This nonetheless provides a rapid and mild method to synthesize functional silicones and tune their physical properties, using commonly available starting materials.     

Characterization of {111} planar defects induced in silicon by hydrogen plasma treatments

Microstructural characterization by transmission electron microscopy of the {111} planar defects induced in Si by treatment in hydrogen plasma is discussed. The {111} defects are analyzed by conventional (TEM) and high-resolution transmission electron microscopy (HRTEM). Quantitative image processing by the geometrical phase method is applied to the experimental high-resolution image of an edge-on oriented {111} defect to measure the local displacements and strain field around it. Using these data, a structural model of the defect is derived. The validity of the structural model is checked by high-resolution image simulation and comparison with experimental images.     

Boron Subphthalocyanine Polymers by Facile Coupling to Poly(acrylic acid‐ran‐styrene) Copolymers Synthesized by Nitroxide‐Mediated Polymerization and the Associated Problems with Autoinitiation

Boron subphthalocyanines (BsubPcs) are macrocyclic aromatic small molecules containing a chelated boron atom. BsubPcs have interesting optoelectronic and physical properties, justifying their use in various organic electronic devices such as organic solar cells and organic light‐emitting diodes. However, our group has only recently reported the first incorporation of a BsubPc moiety into a polymer using a two‐step post‐polymerization procedure. This communication outlines the use of acrylic acid as a method for obtaining carboxylic acid functional copolymers for the facile coupling to BsubPc post polymerization. In addition, the observations and the proposed mechanism of a side product unique to the copolymerization of acrylic acid and styrene due to autoinitiation are presented.