1H-NMR of the amidation of syndiotactic poly(methacrylic acid) with carbodiimide

Summary The reaction of syndiotactic poly(methacrylic acid) with dicyclohexylcarbodiimide in the presence of benzylamine yields syndiotactic methacrylic acid-methacryloyl-N-benzylamide copolymers. A limiting conversion to amide of about 62% and a tendency of alternation for the monomer units is observed by¹H-NMR. The amidation is accompanied by the formation of a smaller amount of cyclic imide as a side reaction. The imide portion can also be transformed into amide by a consecutive hydrolysis step.     

In vitro incorporation of acetate-1-14C into the phospholipids of rabbit and human endometria

Endometria from nonpregnant and 6-day pregnant rabbits and from humans in the proliferative and secretory phases were incubated with 1-¹⁴C-acetate.¹⁴CO₂ was collected, and subsequently the amounts, specific radioactivities, and in some cases the fatty acid compositions of the isolated phospholipids were determined. Phosphatidyl choline was the phospholipid present in highest amount in endometria from both nonpregnant and pregnant rabbits, and in human endometria; this phospholipid also showed the highest degree of incorporation of¹⁴C-acetate. Pregnancy in the rabbit seemed to decrease the incorporation of¹⁴C-acetate into most of the endometrial phospholipid classes. In humans, the incorporation of acetate into phosphatidyl choline and phosphatidyl ethanolamine was lower in the secretory than the proliferative endometria. Of the fatty acids, linoleic acid in phosphatidyl choline and phosphatidyl ethanolamine of the rabbit endometria showed a significant relative increase during pregnancy and palmitoleic acid showed a decrease. This investigation was supported by a grant from the Ford Foundation.     

Ionic conductivity of polymer gels deriving from alkali metal ionic liquids and negatively charged polyelectrolytes

We have prepared polymer gel electrolytes with alkali metal ionic liquids (AMILs) that inherently contain alkali metal ions. The AMIL consisted of sulfate anion, imidazolium cation, and alkali metal cation. AMILs were mixed directly with poly(3-sulfopropyl acrylate) lithium salt or poly(2-acrylamido-2-methylpropanesulfonic acid) lithium salt to form polymer gels. The ionic conductivity of these gels decreased with increasing polymer fraction, as in general ionic liquid/polymer mixed systems. At low polymer concentrations, these gels displayed excellent ionic conductivity of 10⁻⁴ to 10⁻³ S cm⁻¹ at room temperature. Gelation was found to cause little change in the diffusion coefficient of the ionic liquid, as measured by pulse-field-gradient NMR. These data strongly suggest that the lithium cation migrates in successive pathways provided by the ionic liquids.     

Volatile compounds on the surface and within Iberian dry-cured loin

The profile of volatile compounds from external and internal areas of Iberian dry-cured loin was studied by headspace solid-phase microextraction. Higher levels of 16 volatile compounds (hexane, decane, 3-methylbutanal, several sulphur compounds and some aromatic hydrocarbons) were detected in the outer part of the loins. These differences could be owing to several factors, such as greater exposure to oxygen and dehydration conditions in the surface of the product, which favour oxidation reactions and Strecker degradation of amino acids. Moreover, the addition of spices on the surface and the proximity of a mould layer growing on the surface of the product could also contribute to the higher levels of these compounds on the external layer. However, other sulphur compounds coming from spices showed similar levels on the surface and within the loins. This different behaviour could be a consequence of different diffusion rates depending on the features of the compound and the matrix.     

Characterization of the mechanism of interaction in ibuprofen-Eudragit RL100 coevaporates

The present study is a preliminary exploration of the affinity between a carboxylic model drug, the nonsteroidal antiinflammatory agent ibuprofen (IBU) and Eudragit RL100 (RL) polymer. Due to the presence of a variable amount of quaternary ammonium groups in this matrix, physical and chemical interaction with the carboxylic drug can occur, which reinforces its scant mechanical dispersion in the polymer network and can ultimately affect its release profile in vitro and in vivo. To study these aspects, IBU was mixed at increasing weight ratios and in different chemical forms (free acid, sodium salt, and n-butyl ester), to investigate further the role of the carboxylic group in the interaction with the RL polymer. Therefore, IBU-RL solid dispersions (coevaporates) were obtained and fully characterized in the solid state through spectroscopic, calorimetric, and x-ray diffractometric analyses. The in vitro release pattern of the drug, in the different chemical states, was studied for the coevaporates, compared with drug-RL physical mixtures, along with drug adsorption profiles from aqueous solutions on the surface of the polymer granules.     

Phytotoxicity and heavy metals speciation of stabilised sewage sludges

The presence of heavy metals in the sludges produced in wastewater treatment restricts plants growth and hence their use for agricultural purposes. This study looks at different types of sludges (aerobic, anaerobic, unstabilised and sludge from a waste stabilisation pond) and compares the distribution of the heavy metals that they contain according to the treatment that they have undergone. The sewage sludges were subjected to chemical characterisation and phytotoxicity testing (in absence of substrate) to provide a preliminary assessment of their suitability for land application. In addition, the total quantity of metals (Cd, Cr, Cu, Ca, K, Fe, Mg, Ni, Na, Pb and Zn) was determined. The Community Bureau of Reference (BCR) method for heavy metal speciation was followed. It was confirmed that the total concentration of heavy metals did not exceed the limits set out by European legislation and that the stabilisation treatment undergone by the sludges strongly influenced the heavy metal distribution and the phases to which they were associated. The sludge extracts did not exert any significant adverse effect on the relative seed germination (RSG) of barley (Hordeum vulgare L.) or cress (Lepidium sativum L.), although the reduction in germination index (GI) indicates that some characteristics existed did have an adverse effect on root growth.     

Study of condition-dependent decomposition reactions; Part I. The thermal behaviour and decomposition of 2-nitrobenzoyl chloride

The risks associated with batch processing in the manufacture of chemicals and pharmaceuticals via highly exothermic reactions are of special interest due to the possibility of runaway reactions. o-Nitrated benzoyl chlorides are intermediates in the production of agrochemicals and are produced via the reaction of o-nitrated carboxylic acids with thionyl chloride in a solvent mixture. ortho-Nitrated acyl chlorides have exploded violently on attempted distillation on numerous occasions. An inadequate investigation of the process prior to large-scale operation is the most likely cause. Here we present preliminary results of studies on the decomposition of 2-nitrobenzoyl chloride. This study has revealed that the decomposition reaction is strongly condition dependent. The heating rate of the sample plays a preponderant role in the course of the decomposition reaction. That renders the interpretation of differential scanning calorimetry (DSC) or adiabatic calorimetry measurements, which are routinely used to assess the thermochemistry and safety of the large-scale reactions, problematic. Following this on-going study, we report here key features of the system that have been identified.     

Morphological evaluation of bioartificial hydrogels as potential tissue engineering scaffolds

Poly(vinyl alcohol) hydrogels prepared by freeze-thawing procedure represent synthetic systems widely investigated as non-biodegradable scaffolds for tissue regeneration. In order to improve the biocompatibility properties of pure poly(vinyl alcohol) (PVA) hydrogels, blends of PVA with different biological macromolecules, such hyaluronic acid, dextran, and gelatin were prepared and used to produce bioartificial hydrogels. The porosity characteristics of these hydrogels were investigated by scanning electron microscopy and mercury intrusion porosimetry. The morphology of bioartificial hydrogels was evaluated and compared with that of pure PVA hydrogels. In particular the effect exerted by each biological component on pore size and distribution was investigated. The obtained results indicate that when a natural macromolecule is added to PVA the internal structure of the material changes. A small amount of biopolymer induces the structural elements of PVA matrix to take on a well evident lamellar appearance and an apparent preferential orientation. Comparing the results of SEM and mercury intrusion porosimetry it was concluded that hydrogels containing 20% of biological component have the most regular structure and at the same time the lowest total porosity. On the contrary samples with the highest content of natural polymer (40%) show the less regular structure and the highest total porosity.     

Influence of air abrasion preparation on microleakage in glass ionomer cement restorations

The aim of this study was to assess microleakage in class V cavities prepared by air abrasion or high-speed dental bur and restored with different glass ionomer cements. Sixty bovine incisors were equally divided into 6 groups: I, II and III (preparation by high-speed) and IV, V and VI (preparation by air abrasion). Groups I and IV were restored with Fuji IX; groups II and V with Ketac Molar; and groups III and VI with Vitremer. After 24 h (37 °C), specimens were thermocycled, isolated with nail varnish, immersed in a 0.2% Rhodamine B solution for 24 hours, sectioned longitudinally and analyzed for microleakage using an optical microscope connected to a digital camera and a computer. The images were digitized and a software allowed the quantitative evaluation of microleakage in millimeters. Data were analyzed by Wilcoxon and Kruskal-Wallis tests. It was observed that there were significant differences (p ≤ 0.05) between incisal (enamel) and cervical (dentine/cementum) margins, mainly for Ketac Molar; there was no difference (p ≥ 0.05) between preparation methods, except for group II (high-speed/Ketac Molar) that showed higher infiltration; regarding the materials, Ketac Molar demonstrated the highest microleakage values (p ≤ 0.05), and only Vitremer sealed completely both margins of restorations. It was concluded that air abrasion preparation did not influence microleakage in class V restorations with the employed glass ionomer cements.