Authors:Buchi Reddy Vaddula, Swathi Yalla, and Michael A. Gonzalez
A simple and rapid one-step continuous-flow synthesis route has been developed for the preparation of chromene derivatives from the reaction of aromatic aldehydes, α-cyanomethylene compounds, and naphthols. In this contribution, a one-step continuous-flow protocol in a ThalesNano H-Cube Pro™ has been developed for the preparation of these chromene derivatives. This arises from the multicomponent one-step reaction of aromatic aldehydes, α-cyanomethylene compounds, and naphthols. This flow protocol was optimized in 2-methyltetrahydrofuran, which is a more environmentfriendly solvent. The faster residence times (<2 min) coupled with elevated pressure (∼25 bar) results in an efficient, safer, faster, and modular reaction. Results obtained illustrate that this base-catalyzed reaction affords the respective chromene derivative products in very high yields. The products can then be easily purified by recrystallization, if desired.
Authors:A. Zahia, F. Salhi, A. Pineau, and G. Moya
The results of isothermal calorimetric determination of the stored energy for 99.999% pure polycrystalline rolled silver are reported. The stored energy values were found to be linearly related to the recrystallization temperature. An explanation of this effect is given in terms of the specific heat difference between the rolled and annealed states.
DA-5018 is a new capsaicin derivative and has analgesic effect. The objective of this work was to investigate the existence
of polymorphs and pseudopolymorphs of DA-5018 and the transformation of crystal forms. Eight crystal forms of DA-5018 have
been isolated by recrystallization and characterized by powder X-ray diffractometry (PXRD), differential scanning calorimetry
(DSC), and thermogravimetric analysis (TG).
The PXRD and DSC patterns of the eight crystal forms were different respectively.
In the dissolution studies in simulated intestinal fluid at 37±0.5°C, the solubility of Form 2 was the highest. And the solubility
in water decreased in rank order: Form 2>Form 3>Form 1>Form 5>Form 7>Form 4>Form 6>Form 8.
Eight crystal forms were shown to have a good physical stability at room temperature for 60 days.
High hydrostatic pressure (HHP) has been investigated as an alternative to thermal processing for food preservation. HHP has
been known to affect high molecular weight polymers causing phase change. Starch is gelatinized at a pressure on the order
of 600–700 MPa, at 25 °C. Gelatinized starch recrystallizes during storage affecting the texture and shelf life of food products.
The effect of HHP processing on the crystallization of starches from different botanical origins during storage at 4 and 23 °C
was investigated. Crystallization kinetics of HHP treated wheat and corn starch gels were compared using DSC. The effect of
crystallization on structure was evaluated in terms of storage modulus. The rate of retrogradation depended on the storage
temperature (23 °C and 4 °C) and the botanical origin of the starch. The least crystallization was observed in HHP treated
wheat starch stored at 23 °C. The storage modulus increased with crystallization of starch.
Authors:Felicitász Velledits, János Csizmeg, and Anna Oravecz-Scheffer
The Little Plain Basin is one of the largest units in the Pannonian Basin System. Its continuation in Slovakia is called the Danube Basin. The Little Plain Basin is one of the most underexplored areas in Hungary. Based on archival geologic and geophysical data the lithostratigraphic composition of the area is controversial. The significance of the area is increased by the known Neogene and the supposed basement (Paleozoic and Mesozoic) hydrocarbon systems in Hungary and in Slovakia.
The purpose of this study is to identify the exact age, facies, geologic formations and possible source rocks of the Triassic section penetrated by the Gyõrszemere-2 well in the Little Plain Basin.
Based on new facies and paleontological results it can be stated that two Triassic sequences are identified in the well, separated by fault breccia. A carbonate sequence was deposited between the Induan and Early Anisian and above that a homogeneous recrystallized dolomite appears, the age of which is unknown.
The following formations were encountered, from base upward:
Arács Marl Fm. (3,249.5–3,030 m), silty marl with ooids, bivalves, gastropods and ostracode shells. Occasionally layers of angular quartz grains in large quantities appear. Postcladella kahlori and Spirobis phlyctaena indicates Induan (Early Triassic) age.
Köveskál Dolomite Fm. (3,030–2,790 m), rich in ooids and also containing anhydrite. The Glomospira and Glomospirella dominance indicates an age interval between Olenekian and earliest Anisian age.
Fault breccia (2,790–2,690 m) separating the Köveskál and overlying dolomites.
Upper dolomite (2,690–2,200 m): homogeneous, saccharoidal, and totally recrystallized. The age is unknown.
The low TOC values of the supposed source rock interval (marl between 3,249.5 and 3,030 m) indicate poor hydrocarbon potential.
A new method is presented to analyze the irreversible melting kinetics of polymer crystals with a temperature modulated differential
scanning calorimetry (TMDSC). The method is based on an expression of the apparent heat capacity,
. The present paper experimentally examines the irreversible melting of nylon 6 crystals on heating. The real and imaginary
parts of the apparent heat capacity showed a strong dependence on frequency and heating rate during the melting process. The
dependence and the Cole-Cole plot could be fitted by the frequency response function of Debye's type with a characteristic
time depending on heating rate. The characteristic time represents the time required for the melting of small crystallites
which form the aggregates of polymer crystals. The heating rate dependence of the characteristic time differentiates the superheating
dependence of the melting rate. Taking account of the relatively insensitive nature of crystallization to temperature modulation,
it is argued that the ‘reversing’ heat flow extrapolated to ω → 0 is related to the endothermic heat flow of melting and the
corresponding ‘non-reversing’ heat flow represents the exothermic heat flow of re-crystallization and re-organization. The
extrapolated ‘reversing’ and ‘non-reversing’ heat flow indicates the melting and re-crystallization and/or re-organization
of nylon 6 crystals at much lower temperature than the melting peak seen in the total heat flow.
Authors:Daniel Plano, Elena Lizarraga, Juan Antonio Palop, and Carmen Sanmartín
four types of thermal behavior for the series A and B:
• Behavior I Compounds that do not alter the thermal behavior after an initial fusion–recrystallization cycle ( Fig. 1 ). Under these conditions there is no evidence of polymorphic behavior. The
Authors:M. D. Baró, N. Clavaguera, S. Bordas, M. T. Clavaguera-Mora, and J. Casas-Vázquez
The kinetics of bulk crystallization of Se61.5Ge15 4Sb23.1 glasses was investigated from their thermal behaviour. In the thermal characterization of a glass the recrystallization temperature is highly dependent on both the rate of heating and the thermal history of the glass. Vitreous samples were prepared by quenching. From ratedependent curves it was found that the recrystallization process obeys first-order kinetics with an apparent activation enthalpy of 48±5 kcal/mole. Further analysis allows determination of both the activation enthalpy,H=90±4 kcal/mole, and the kinetic exponent of the Avrami equation,n=1.9±0.3.
Authors:R. Ceolin, V. Agafonov, A. Gonthier-Vassal, H. Szwarc, J. Cense, and Ph. Ladure
Flutamide usually crystallizes in the orthorhombic non-centrosymmetric space group Pna21 (from I) and melts atTfus=384 K with ΔfusH=30 kJ·mol−1. It may be obtained in the glassy state (Tg=272 K) by quenching the melt. Although evidence of polymorphism could not be obtained by means of crystallography, DSC studies
of the recrystallization process indicate that a metastable form (form II) occurs first and is transformed into the stable
form at room temperature. ΔH for the transition I→II (2.52 kJ·mol−1) is close to the difference in energy (about 2 kJ·mol−1) calculated for the two possible conformers of flutamide.
The kinetics of solute segregation to partial dislocations in a Cu–3.4 At.% Sb alloy was studied by using a phenomenological approach with differential scanning calorimetry and isothermal calorimetry. The material, severely deformed by repeated bending, presented an excess of dissociated edge dislocations with a dislocation density amounting to about 8.5·1014 m–2, calculated using a prior model of the authors, together with calorimetric recrystallization trace analysis. The kinetics was found to be ruled by two overlapping mechanisms: diffusion of solute atoms mostly through dislocation pipes in the initial and middle stages of the reaction process, acting together with bulk solute diffusion in these stages and later. Bulk solute diffusion increases as the reaction proceeds, as shown by the increasing values of apparent activation energy in the reaction. The exponent of the Mehl-Johnson-Avrami equation used in the phenomenological description was successfully fitted to a time—temperature-dependent function, increasing in agreement with the apparent activation energy behaviour, as may be expected.