Thermal study on decomposition of LiBH4 at non-isothermal and non-equilibrium conditions

Thermal decomposition measurements for lithium borohydride (LiBH₄) are performed at non-isothermal and non-equilibrium conditions by means of differential thermal analysis (DTA). A simplified alternative procedure is introduced for evaluating thermodynamic and kinetic parameters simultaneously using a single set of measurements. Rate constant (k) and enthalpy (ΔH = ?102.1 ± 0.7 kJ mol^?1 LiBH₄) are archived. Temperature dependence for activation energy (E _a) is found taking advantage of Guggenheim–Arrhenius method; the mean activation energy is $ \overline{E}_{a} $  93.9 ± 0.9 kJ mol^?1 LiBH₄ in the range of heating rate β 1–50 K min^?1.     

Three overlooked chemical approaches toward 3-naphthalimide amonafide N-derivatives

Three efficient strategies for derivatization of the anticancer drug candidate amonafide (Quinamed, originally AS1413) are described. Unprecedented reductive amination of aryl aldehydes, S_NAr, and addition–elimination reactions, while using readily available starting materials, give quick entry to potential libraries of novel 3-aryl, 3-benzyl N-derivatives of amonafide. The selective anticancer activity of this important DNA intercalation agent is expected to be enhanced by expanding the diversity of amonafide N-derivatives. The synthetic routes reported in this work are general and readily applicable.     

A Novel β-Glucosidase from Humicola insolens with High Potential for Untreated Waste Paper Conversion to Sugars

Humicola insolens produced a new β-glucosidase (BglHi2) under solid-state fermentation. The purified enzyme showed apparent molecular masses of 116 kDa (sodium dodecyl sulfate–polyacrylamide gel electrophoresis) and 404 kDa (gel-filtration), suggesting that it is a homotetramer. Mass spectrometry analysis showed amino acid sequence similarity with a β-glucosidase from Chaetomium thermophilum. Optima of pH and temperature were 5.0 and 65 °C, respectively, and the enzyme was stable for 60 min at 50 °C, maintaining 71 % residual activity after 60 min at 55 °C. BglHi2 hydrolyzed p-nitrophenyl-β-d-glucopyranoside and cellobiose. Cellobiose hydrolysis occurred with high apparent affinity (K _M?=?0.24?±?0.01 mmol L^?1) and catalytic efficiency (k _cat/K _M?=?1,304.92?±?53.32 L mmol^?1 s^?1). The activity was insensitive to Fe⁺³, Cr⁺², Mn⁺², Co⁺², and Ni²⁺, and 50–60 % residual activities were retained in the presence of Pb²⁺, Hg²⁺, and Cu²⁺. Mixtures of pure BglHi2 or H. insolens crude extract (CE) with crude extracts from Trichoderma reesei fully hydrolyzed Whatman no. 1 paper. Mixtures of H. insolens CE with T. reesei CE or Celluclast 1.5 L fully hydrolyzed untreated printed office paper, napkin, and magazine papers after 24–48 h, and untreated cardboard was hydrolyzed by a H. insolens CE/T. reesei CE mixture with 100 % glucose yield. Data revealed the good potential of BglHi2 for the hydrolysis of waste papers, promising feedstocks for cellulosic ethanol production.     

Transversality of stable and Nehari manifolds for a semilinear heat equation

It is well known that for the subcritical semilinear heat equation, negative initial energy is a sufficient condition for finite time blowup of the solution. We show that this is no longer true when the energy functional is replaced with the Nehari functional, thus answering negatively a question left open by Gazzola and Weth (2005). Our proof proceeds by showing that the local stable manifold of any non-zero steady state solution intersects the Nehari manifold transversally. As a consequence, there exist solutions converging to any given steady state, with initial Nehari energy either negative or positive.     

Dealloying of platinum-aluminum thin films: dynamics of pattern formation

The application of focused ion beam (FIB) nanotomography and Rutherford backscattering spectroscopy (RBS) to dealloyed platinum-aluminum thin films allows for an in-depth analysis of the dominating physical mechanisms of nanoporosity formation during the dealloying process. The porosity formation due to the dissolution of the less noble aluminum in the alloy is treated as result of a reaction-diffusion system. The RBS and FIB analysis yields that the porosity evolution has to be regarded as superposition of two independent processes, a linearly propagating diffusion front with a uniform speed and a slower dissolution process in regions which have already been passed by the diffusion front. The experimentally observed front evolution is captured by the Fisher-Kolmogorov-Petrovskii-Piskounov (FKPP). The slower dissolution is represented by a zero-order rate law which causes a gradual porosity in the thin film.     

Determination of the inclusion complex constant between oleuropein and cyclodextrins by complexation theory

Oleuropein (OLE) is a major phenolic compound of olive leaf (Olea europaea) and has many therapeutic properties associated with olive leaf extracts. This work concerns the determination of the inclusion complex constant between OLE and cyclodextrins (CDs), based on the competition of two guests for the CD cavity, one being a dye and the other OLE. The dye used was methylorange (MO) and pH 3 was selected, since MO molar absorptivity at 500 nm is at maximum in this condition. A solution of MO, OLE, and α-CD or β-CD, with citrate buffer was used for determining the absorbance values. From these data and by appropriate mathematical modeling, the equilibrium constant for the formation of OLE:CD complexes were obtained: for OLE:α-CD K = 1,352.4 L mol^?1 (R ² = 0.9975) and for OLE:β-CD K = 1,827.9 L mol^?1 (R ² = 0.9991). The results show that OLE has a greater affinity for β-CD than for α-CD and given the relatively high constants, OLE:CD complexes have potential for giving longer shelf lives for OLE medicinal and food additive preparations.     

Sulfuric Acid Adsorbed on Silica Gel. A Multipurpose Acid Catalyst

A series of acid catalyzed reactions like the dehydration of alcohols, conversion of ketones to 1,3-dioxolanes and their hydrolysis, α,β-unsaturated ketones to enol ethers, and alcohols to methyl-methoxyethyl ethers are performed efficiently in high yield with sulfuric acid adsorbed on silica gel as catalyst.     

Performance of fixed and fluidized bed reactors with immobilized enzyme

Applied Biochemistry and Biotechnology - Saccharification of α-amylase liquefied cassava starch was carried out at pH 4.5 and 45?C, in both fixed and fluidized bed reactors, using...     

Fluctuation-dissipation theorem and the dynamical renormalization group

The relation between a recently introduced dynamical real-space renormalization group and the fluctuation-dissipation theorem is discussed. An apparent incompatibility is pointed out and resolved.     

Solving a combinatorial problem with network flows

In this paper we present an algorithm based on network flow techniques which provides a solution for a combinatorial problem. Then, in order to provide all the solutions of this problem, we make use of an algorithm that given the bipartite graphG=(V ₁ ∪V ₂,E, w) outputs the enumeration of all bipartite matchings of given cardinalityv and costc.