Effect of complexation of oxidised corn starch with mineral elements on physicochemical properties

The objective of this study was to determine the effect of complexation of oxidised starch with mineral elements on its physicochemical properties. Corn starch was oxidised with sodium hypochlorite and, afterwards, modified with ions of potassium, magnesium and iron. Thus, native and modified starches were analysed for: contents of mineral elements, colour parameters (L*a*b*), water binding capacity and solubility in water at temperature of 60 and 80 °C. Thermodynamic characteristics of gelatinisation by DSC, molecular weight distribution by GPC, intrinsic viscosity and pasting properties by RVA were studied. The efficiency of incorporation of metal ions into oxidised corn starch was about 30%, 20% and 20% for potassium, magnesium and iron ions, respectively. The complexation with potassium ions caused the greatest changes in the molecular weight distribution and the intrinsic viscosity of starches and viscosity of starch pastes. Only modification of starch with iron ions affected the colour parameters of the starch. Incorporation of metal ions into starch resulted also in changes in its water binding capacity and solubility in water.     

Least-squares integration of one-dimensional codistributions with application to approximate feedback linearization

We study the problem of approximating one-dimensional nonintegrable codistributions by integrable ones and apply the resulting approximations to approximate feedback linearization of single-input systems. The approach derived in this paper allows a linearizable nonlinear system to be found that is close to the given system in a least-squares (L ₂) sense. A linearly controllable single-input affine nonlinear system is feedback linearizable if and only if its characteristic distribution is involutive (hence integrable) or, equivalently, any characteristic one-form (a one-form that annihilates the characteristic distribution) is integrable. We study the problem of finding (least-squares approximate) integrating factors that make a fixed characteristic one-form close to being exact in anL ₂ sense. A given one-form can be decomposed into exact and inexact parts using the Hodge decomposition. We derive an upper bound on the size of the inexact part of a scaled characteristic one-form and show that a least-squares integrating factor provides the minimum value for this upper bound. We also consider higher-order approximate integrating factors that scale a nonintegrable one-form in a way that the scaled form is closer to being integrable inL ₂ together with some derivatives and derive similar bounds for the inexact part. This allows a linearizable nonlinear system that is close to the given system in a least-squares (L ₂) sense together with some derivatives to be found. The Sobolev embedding techniques allow us to obtain an upper bound on the uniform (L _∞) distance between the nonlinear system and its linearizable approximation. This research was supported in part by NSF under Grant PYI ECS-9396296, by AFOSR under Grant AFOSR F49620-94-1-0183, and by a grant from the Hughes Aircraft Company.     

Influence of the tank shape on the electrostatic field generated by space charge

Contents The paper provides results of calculations of electric field for parallelepiped and ellipsoidal tanks. The calculations reported in the paper indicate that even at a relatively small volumetric density of charge (q=100 C/m³) the intensity of the electric field in the vapour/air mixture may exceed the critical value (3 MV/m), which may cause a spark discharge. They also show the maximum of the electric field intensity, the maximum potential and energy after the change in shape of the tank, while the volume of the stored liquid remains the same. The calculations of these quantities can be used as a basis for reduction or elimination of the electrostatic ignition hazard.

---

Einfluß der Behälterform auf das elektrostatische Feld infolge einer Raumladung

Übersicht Der Beitrag behandelt elektrische Felder in Behältern von der Form eines Parallelepipeds und eines Ellipsoids. Die Berechnungen zeigen, daß selbst bei relativ kleinen Werten der Raumladung (100 C/m³) die elektrische Feldstärke im Dampf-Luftgemisch den kritischen Wert (3 ÖMV/m) überschreiten und einen Durchschlag verursachen kann. Außerdem werden die Maxima der elektrischen Feldstärke, des Potentials und der Energie in Abhängigkeit der Behälterform angegeben unter der Voraussetzung, daß das Volumen der enthaltenen Flüssigkeit konstant bleibt. Die Rechenergebnisse lassen sich als Basis für die Verminderung oder Elimination der Gefahr von Überschlägen verwenden.

---

List of symbols A, B, C factors of the ellipsoidal tank - a, b, H length, width and height of the parallelepiped tank, respectively [m] - E electrical field strength [V/m] - h liquid height in the tank [m] - q volumetric charge density [C/m³] - R radius of the sphere [m] - V electric potential [V] - W _E electric field energy [J] - V volume of the tank - _r relative dielectric constant - _O absolute dielectric constant 8.854×10^–12 [As/Vm]     

Computer-Aided Search for 5-Arylideneimidazolone Anticancer Agents Able To Overcome ABCB1-Based Multidrug Resistance

ABCB1 modulation is an interesting strategy in the search for new anticancer agents that can overcome multidrug resistance (MDR). Hence, 17 new 5-arylideneimidazolones containing an amine moiety, as potential ABCB1 inhibitors, were designed, synthesized, and investigated. The series was tested in both parental (PAR) and multidrug-resistant (MDR) ABCB1-overexpressing T-lymphoma cancer cells using cytotoxicity assays. The ABCB1-modulating activity was examined in rhodamine 123 accumulation tests, followed by Pgp-Glo™ Assay to determine the influence of the most active compounds on ATPase activity. Lipophilic properties were assessed both, in silico and experimentally (RP-TLC). Pharmacophore-based molecular modelling toward ABCB1 modulation was performed. The studies allowed the identification of anticancer agents (p-fluorobenzylidene derivatives) more potent than doxorubicin, with highly selective action on MDR T-lymphoma cells (selectivity index >40). Most of the investigated compounds showed ABCB1-modulating action; in particular, two 5-benzyloxybenzylidene derivatives displayed activity nearly as strong as that of tariquidar.     

Effect of Ca2+ and Mg2+ ions on the sintering and spectroscopic properties of cr-doped yttrium aluminum garnet ceramics

In this work, we investigated the effects of Ca²⁺ and Mg²⁺ ions and annealing temperature on the spectroscopic parameters of chromium-doped yttrium aluminum garnet ceramics (Cr:YAG). Samples were obtained with either a separate or a simultaneous addition of calcium and magnesium oxides. To achieve this, aqueous suspensions were prepared using Y₂O₃, Al₂O₃, Cr₂O₃, MgO, and CaO high-purity powders as raw materials. The obtained suspensions were freeze-granulated, pressed into pellets, debinded, and subjected to reactive sintering in vacuum at 1715°C for 6 h. Each material was annealed in air with temperatures between 1300 and 1700°C. Samples were also compared to Cr:YAG ceramics with the addition of silica as a sintering aid. All the materials obtained were then exposed to 445 nm excitation, and emission spectra in the visible and infrared wavelengths were recorded. The results showed that the emission spectra of Cr:YAG ceramics varied according to the annealing conditions: as-sintered samples exhibited strong emissions of around 680 nm and, after air annealing, of around 1400 nm. This phenomenon is attributed to the Cr³⁺→Cr⁴⁺ transition. Samples doped solely with MgO exhibited the highest emission intensity in the infrared region. Thus, Mg²⁺ ions provided the best conversion efficiency of chromium ions.     

Investigation of some organic binders

These studies concern residues of the vacuum petroleum distillation of crude oil, used as binders for briquetting comminuted materials. The residues have been separated into the group components asphaltenes, resins, and oils. Chemical analyses of these components and calculations of some structural parameters by means of the Hazelwood and van Krevelen methods have been carried out on all these materials in order to indicate differences between the residues. The chemical constitutions of the binders examined do not differ basically but there are differences between some physical and rheological properties (viscosity, ductility), electrical properties (specific resistance, dielectric loss factor) and in molar refraction and in the carbon aromaticity (from volatile matter).     

Some aspects of the carbonization of vacuum distillation residue from crude oil

These studies concern the carbonization process of residues from vacuum distillation of crude oil. Some explanation aspects of the hypothetic reaction mechanism controlling the carbonization of high molecular weight components of crude oil are developed. On the basis of numerous experimental investigations, the thermal decomposition process can be divided into two stages, the first, from 670 to 790 K, in which the decomposition reactions take place and low and medium weight molecular compounds are emitted and the second stage, from above 790 K to 1000 K, in which cyclization, condensation and aromatization processes take place, and the degree of structural ordering in the solid products increases.     

Terahertz time domain spectroscopy of graphene and MXene polymer composites

The rising demand for faster and more efficient electronic devices forces electronics industry to shift toward terahertz frequencies. Therefore there is a growing need for efficient, lightweight, and easy to produce absorbing materials in the terahertz range for electromagnetic interference (EMI) shielding and related applications. This study presents a study on basic optical properties of two types polymer-based composites loaded with two-dimensional structures—graphene and MXene phases (Ti₂C). In said range, total EMI shielding efficiency (SE) and its components, the absorption coefficient (α ), refractive index, and complex dielectric function are investigated. The ratio of SE absorption component to reflection component (SE_ABS :SE_R ) of fabricated composites is equal or higher than 30:1 in over 80% of studied range. The fabricated composites exhibit low (<0.1) loss tangent in studied range. The addition of 1 wt% of graphene increases the composite α over 10-fold in respect to pure polymer–up to 60 cm⁻¹ for frequency higher than 2 THz.