“Antiplasticization” in starch-glycerol films?

Calorimetric, mechanical, and thermomechanical properties have been measured on starch films with various glycerol/water contents. For calorimetric measurements, a continuous decrease in T_g was observed as glycerol increases from 0 to 25%. Mechanical properties exhibit a minimum of elongation at break for glycerol content ∼ 12%. In slightly hydrated starch films not containing another plasticizer, a β relaxation is detected by DMTA around −68°C. This relaxation is modified by the presence of glycerol, the α relaxation of which appears in the same temperature range. Results are discussed comparing with the well-known antiplasticization effect in synthetic polymers such as PVC and PC. The combination of the plasticizer α mode and the polymer β mode is considered. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1047–1053, 1997     

Analysis of the Parameters of the Mössbauer Spectra and the Spectra of Nuclear Quadrupole Resonance of the Superconducting Ceramic YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7</Subscript>

The parameters of the Mössbauer spectra on ⁶⁷Cu(⁶⁷Zn), ⁶⁷Ga(⁶⁷Zn) isotopes, and the data of nuclear quadrupole resonance on an ¹⁷O isotope are anlayzed, and the lattice gradient of the electric field for the crystal lattice YBa₂Cu₃O₇ is calculated. It is shown that these parameters correspond to the model when the hole is predominantly in the sublattice of the oxygen chain.     

Influence of the presence of bubbles on the parameters of crystal nucleation in the 26Li<Subscript>2</Subscript>O · 74SiO<Subscript>2</Subscript> glass

The crystal nucleation in the glass of composition (mol %) 26Li₂O · 74SiO₂ has been investigated in the cases of homogeneous and heterogeneous nucleation. Parameters of homogeneous nucleation, such as the stationary nucleation rate I _st, the time of nonstationary nucleation τ, and the crystal growth rate U, have been determined. The temperature dependences of these parameters have been constructed. The surface energy σ at the nucleus-glass melt interface has been determined, and its temperature dependence has been obtained. The surface energy σ has been evaluated using the graphical method for solving the transcendental equation derived by transforming the relationships for the stationary crystal nucleation rate and the time of nonstationary crystal nucleation. The critical nucleus sizes r* and the free energy of formation of the critical nucleus Φ* have been determined. The heterogeneous nucleation on bubbles specially produced in the glass has been studied. It has been demonstrated that the presence of bubbles in the initial glass does not affect the crystal growth rate and substantially changes the nonstationary nucleation rate. The largest contribution to the change in the nucleation rate is made by “active” bubbles (filled by water vapor) formed in the glasses synthesized with the use of hydrated silicon dioxide.     

“On Water” Direct and Site‐Selective Pd‐Catalysed C?H Arylation of (NH)‐Indoles

This communication describes the development of a versatile catalytic system based on palladium(II) acetate/bis(diphenylphosphino)methane [Pd(OAc)₂/dppm] that works “on water” giving site‐selective C H arylation of (NH)‐indoles without protecting or directing groups. Remarkably, the control of regioselectivity was achieved by small changes in the “extra‐catalytic” base/halide partners. These innovative methodologies allow a high‐yielding access to both C2 and C3‐arylindoles, as well as 2,3‐diarylindoles, and display high chemo/regioselectivities and structural versatility with regard to either indole or aryl moieties.     

The Symmetric and Topological Code of the Cluster Self-Assembly of the Crystal Structure of ε-Mg<Subscript>23</Subscript>Al<Subscript>30</Subscript> of K63 Nanoclusters

The geometrical and topological analysis of the crystal structure of intermetallide ε-Mg₂₃Al₃₀ (ToposPro program) with V = 3098.0 ų and space group R-3 is carried out. The symmetric and topological codes of the cluster self-assembly of the crystal structure are determined: primary chain S ₃ ¹ → microlayer S ₃ ² → microframework S ₃ ³ . A new type of nanocluster-precursor of the crystal structure, which is formed on the internal 13-atomic cluster, which represents a template and consists of two bound ridged rings Mg–Al–Mg–Al–Mg–Al with the central Mg atom, is discovered. A quasi-spherical deltahedron shell made from 50 atoms is formed on the template. The center of a K63 cluster occupies the position with the point symmetry 3? in the unit cell. There are six neighboring K63 clusters in the local environment of the K63 cluster in the layer. The basic 3D network, which characterizes the location of the gravity centers of the K63 clusters, corresponds to a hexagonal closely packed network (HCP, Mg type) with CN = 12. The localization of two Mg atoms in the pores of the framework is determined.     

Reductive amination of monoethanolamine in the presence of the NiCo/BPO<Subscript>4</Subscript> · γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst: Process optimization based on a mathematical model and calculation of the basic design parameters of the reactor

Based on experimental kinetic data for the reductive amination of monoethanolamine in the presence of the NiCo/BPO₄ · γ-Al₂O₃ catalyst, a mechanism of this process is suggested and the corresponding kinetic model is constructed. A mathematical model of the reactor process is developed, and this model is used to solve three process optimization problems. Optimal values of operating parameters are found, and these values are used in the calculation of basic dimensions of a commercial-scale reactor. The flexible process design suggested allows all of the three process variants corresponding to the three optimization problems to be carried out.     

Effect of the Nature of the Binder on the Formation Temperature of Glass-Ceramic Coatings Based on Si–B–ZrB<Subscript>2</Subscript> for Graphite Protection

This work is devoted to fabricating and studying the properties of coatings based on the Si–B–ZrB₂ systems used in graphite protection. The kinetics of the oxidation of graphite with coatings at different temperatures in air are investigated. The optimal conditions for the thermal treatment of the material with the coating are suggested.     

The Effect of Coating TiO<Subscript>2</Subscript> on the CO Oxidation of the Pt/γ-Alumina Catalysts

Abstract  

The effect of coating TiO₂ on the CO oxidation of the Pt/γ-alumina catalysts was observed through activity tests and surface characterization spectroscopy by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) experiments. XPS results evidenced the occurrence of different Pt²⁺ species and metallic Pt⁰ at the surface which suggest electron transfer of titanium (cation) to the platinum atom and the reduction of titanium (Ti⁴⁺ → Ti³⁺). FTIR analyses suggested oxygen spillover mechanism at the interface between titanium dioxide and platinum that may explain the catalytic activity of the platinum titania-supported catalysts. The apparent activation energy for the CO oxidation was 52.5 kJ/mol and similar for all catalysts. However, the frequency factor changed significantly, indicating interfacial phenomena caused by CO and oxygen adsorptions over TiO _x species and Al₂O₃ support with similar dispersions.     

Effect of the thermal treatment on the phase composition of the surface of coatings based on Si–B–ZrB<Subscript>2</Subscript> and modified with ZrO<Subscript>2</Subscript> fibers

Coatings on graphite that are stable to oxidation and based on the silicon–boron–zirconium boride composite containing from 5 to 50% of fibrous zirconium dioxide as a modifying dopant have been produced by the suspension–annealing method. A nonporous layer is formed at the zirconium dioxide content ranging from 5 to 15%, while a porous layer is formed at its 50% content. A glass-forming melt, as well as zirconium dioxide and silicate, is formed during thermal treatment as a result of the chemical reactions with the oxygen in air. The zirconium silicate content increases, along with the modifier’s concentration and temperature.     

Morphological and electrochemical properties of “polyelectrolyte multilayer films” made from polyaniline and ZnO nanoparticles: Deposition as films or as clusters?

Deposits made by the alternated deposition of polyaniline (PANI) and ZnO nanoparticles may offer interesting applications as nonvolatile memory devices owing to the specific properties of each constituent. The rectifying ratio of such devices may strongly depend on the PANI/ZnO interface and on the morphology of the (PANI/ZnO)_n or (PANI/ZnO)_n‐PANI films. In this article we show that even if the morphology of the PEI/PSS‐(PANI/ZnO)_n or of the PEI/PSS‐(PANI/ZnO)_n‐PANI films seems very heterogeneous on the basis of scanning electron micrographs, the deposits consist of clusters deposited on a continuous film. In addition, the deposits become impermeable to ferrocyanide anions after the deposition of n = 10 alternated deposition cycles, confirming the existence of a continuous and impermeable film below the observed clusters. Such deposits may find interesting properties as a nonvolatile memory device. POLYM. COMPOS. 34:1333–1341, 2013. © 2013 Society of Plastics Engineers     

Effects of Neutron Irradiation on the Current–Voltage Characteristics of SiO<Subscript>2</Subscript> Nanoparticles

Current–voltage characteristics of SiO₂ nanoparticles have been studied before and after neutron irradiation within 5 V steps in the voltage range of ??100 V to +?100 V at room temperature (RT). The angle of the current–voltage curve is changed appropriately for neutron irradiation periods. Simultaneously, it is seen that the amount of the current flowing through the environment increases proportionally to the irradiation period. Moreover, the mechanism of electrical conductivity appropriate to the obtained results is given in this work.     

Formation of the bubble structure in the 26Li<Subscript>2</Subscript>O · 74SiO<Subscript>2</Subscript> glass

The formation of a bubble structure in the glass of composition 26Li₂O · 74SiO₂ is investigated. The stable reproducible characteristics of the bubble structure are obtained, namely, dependences of the number of bubbles on the conditions of glass synthesis, i.e., the synthesis temperature, the synthesis time, and the type of initial reagents. It is shown that the number of bubbles decreases with an increase in the height of the sample (glass melt in the crucible), as well as with an increase in the synthesis temperature at a fixed synthesis time or with an increase in the synthesis time for each specific temperature. The bubble size distribution curves are obtained for all synthesis conditions. The reproducible bubble structure is determined for each layer of the glass sample, which is subsequently used in studying the kinetics of heterogeneous nucleation.     

The Use of the [H<Subscript>2</Subscript>O–CO<Subscript>2</Subscript>] Arbitrary Decomposition Assumption to Predict the Performance of Condensed High Explosives

The plate dent test is one of the simplest tools for fast determination of the detonation pressure. The test is based on the observation that the detonation pressure correlates with the depth of the dent produced by a detonating explosive on a metal witness plate. The present study is aimed at developing a model for estimating the dent depth, which is used not only to obtain the detonation pressure, but also to evaluate the brisance relative to a reference explosive. It is shown that the experimental dent depth values for CHNO and CHNOClF explosives can be successfully reproduced by a model based on few parameters, namely: loading density, number of moles of gaseous detonation products per gram of the explosive, and average molecular weight of the gaseous products, where the number of moles and the mean molecular weight of the gaseous products are calculated according to the [H₂O–CO₂] arbitrary decomposition assumption. Furthermore, the predicted values of the dent depth and the Kamlet–Jacobs method are used to estimate the detonation pressure for 37 explosives. The results show that the pressures obtained on the basis of the dent depth values are in better agreement with experimental/thermochemical code data than the predictions of the Kamlet–Jacobs method.     

Influence of CaO<Subscript>2</Subscript> additives on the properties of Fe–WB-based composite lining deposited by centrifugal SHS on the inner surface of steel pipe

Influence of calcium peroxide (CaO₂) additives on the characteristics and properties of composite coatings deposited by centrifugal SHS was investigated. Microstructure and composition of deposited coatings were characterized by SEM, EDX, XRD, and mechanical testing. The additives of CaO₂ and Al were found to markedly improve the properties of deposited composite coatings. Under optimized conditions, the deposited coatings exhibited rather smooth surface, good adhesive strength, and reasonable micro-hardness.     

Evidence of multi-component interaction in a V–Ce–HUSY catalyst: Is the cerium–EFAL interaction the key of vanadium trapping?

Cerium was introduced into a USY-based catalyst using three methodologies: precipitation, impregnation and ionic-exchange. The CeUSY catalysts were poisoned with vanadium and deactivated with steam at 1073 K. The catalysts were characterized by HRTEM-EDX, FTIR, BET, EPR, XPS and by the test of catalytic dehydration of 2-propanol. The results indicate that the presence of a V–Ce–EFAL multi-component interaction strongly affects the vanadium reduction and its migration, also inhibiting the cerium oxide sintering. HRTEM measurements with analysis of energy dispersive X-rays on the impregnated catalyst revealed a preferential V–Ce interaction in the extra framework aluminum (EFAL) domains. The FTIR results strongly support that this V–Ce–EFAL interaction occurs via hydroxyl groups. The impregnated catalysts showed greater vanadium tolerance than catalysts prepared by other methodologies of cerium introduction.     

A Glimpse at the Size of the Fetal Liver—Is It Connected with the Evolution of Gestational Diabetes?

Gestational diabetes mellitus (GDM) is defined as an impairment of glucose tolerance, manifested by hyperglycemia, which occurs at any stage of pregnancy. GDM is more common in the third trimester of pregnancy and usually disappears after birth. It was hypothesized that the glycemic status of the mother can modulate liver development and growth early during the pregnancy. The simplest modality to monitor the evolution of GDM employs noninvasive techniques. In this category, routinely obstetrical ultrasound (OUS) examinations (simple or 2D/3D) can be employed for specific fetal measurements, such as fetal liver length (FLL) or volume (FLV). FLL and FLV may emerge as possible predictors of GDM as they positively relate to the maternal glycated hemoglobin (HbA1c) levels and to the results of the oral glucose tolerance test. The aim of this review is to offer insight into the relationship between GDM and fetal nutritional status. Risk factors for GDM and the short- and long-term outcomes of GDM pregnancies are also discussed, as well as the significance of different dietary patterns. Moreover, the review aims to fill one gap in the literature, investigating whether fetal liver growth can be used as a predictor of GDM evolution. To conclude, although studies pointed out a connection between fetal indices and GDM as useful tools in the early detection of GDM (before 23 weeks of gestation), additional research is needed to properly manage GDM and offspring health.     

Reassessment of the Identity of the Blue Light Emitter in Copper‐Containing Pyrotechnic Flames – Is it really CuCl?

While it is commonly thought that the molecular species responsible for the emission of blue light in fireworks flames is CuCl, a review of the physicochemical data obtained on gaseous CuCl vapors indicates that the actual emitter is the trimer Cu₃Cl₃. The literature is reviewed with regard to this issue, and a few experiments which might resolve the question are proposed.     

Negative Effects of CO<Subscript>2</Subscript> in the Feed Stream on the Catalytic Performance of Precipitated Iron-Based Catalysts for Fischer–Tropsch Synthesis

Abstract  

Fischer–Tropsch synthesis was carried out over precipitated iron-based catalysts with different amounts of CO₂ in the feed stream while maintaining both total reaction pressure (1.5 MPa) and partial pressure of H₂ + CO (0.75 MPa) using an inert balance gas, N₂. The CO₂ in the feed stream decreased the rate of hydrocarbon formation, but it had no significant influence on the carbon number distribution of hydrocarbons. The CO₂ in the feed stream also suppressed CO₂ formation, decreasing both CO conversion and CO₂ selectivity. We attribute the decreased reaction rate to the partial competition in the adsorption behavior between CO and CO₂ as revealed in the temperature-programmed desorption.