Material forces in finite elasto-plasticity with continuously distributed dislocations

In this paper we propose a thermodynamically consistent model for elasto-plastic material with structural inhomogeneities such as dislocations, subjected to large deformations, in isothermal processes. The plastic measure of deformation is represented by a pair of plastic distortion, and plastic connection with non-zero torsion (in order to have the non-zero Burgers vector). The developments are focused on the balance equations (for material forces and for physical force system), derived from an appropriate principle of the virtual power formulated within the constitutive framework of finite elasto-plasticity and on constitutive restrictions imposed by the free energy imbalance. The presence of the material forces (microforce and microstress momentum) is a key point in the exposure, and viscoplastic (generally rate dependent) constitutive representation are derived.      

SPECTRAL METHODS FOR HISTORICAL PAPER ANALYSIS: COMPOSITION AND AGE APPROXIMATION

The research has been focusing on some connection between the chemical composition of the papers obtained by Fourier transform infrared (FTIR) spectroscopy and the nature of the fillers, determined by energy dispersion X-ray fluorescence (EDXRF) spectroscopy. The present paper corroborates the FTIR and EDXRF results obtained for some historical papers from books of the XIX-th and XX-th centuries, from private collections. These analytical results allowed a first approximation of technological paper composition and of the age determination of the samples. This analytical method can elaborate some properly methods for paper documents preservation, taking into account the aging and degradation processes of the historical paper.     

Study of diesel fuel desulfurization by adsorption

Removal of sulfur from diesel fuel by adsorption on a commercial activated carbon and 13X type zeolite was studied in a batch adsorber. Kinetic characterization of the adsorption process was performed applying Lagergren's pseudo-first order, pseudo-second order and intraparticle diffusion models using data collected during experiments carried out to determine the sulfur adsorption dependency on time. The experiments investigating adsorption efficiency regarding initial sulfur concentration were also performed and the results were fitted to Langmuir and Freundlich isotherms, respectively. Activated carbon Norit SXRO PLUS was found to have much better adsorption characteristics. The process of sulfur adsorption on the fore mentioned activated carbon was further studied by statistically analyzing data collected during experiments which were carried out according to three-factor two-level factorial design. Statistical analysis involved the calculation of effects of individual parameters and their interactions on sulfur adsorption and the development of statistical models of the process.     

Experimental investigation and optimization of carbohydrazide application using different alkalization agents on boilers All-Volatile treatment

This paper presents an experimental investigation of a carbohydrazide application on three Units with mixed metallurgy boilers water–steam cycles in the Power Plant of Ptolemais (Greece). The tests were performed using carbohydrazide as an oxygen scavenger and metal passivation agent, with the parallel application of different alkalization agents on All-Volatile regime, in order to find the most appropriate. The optimization of this carbohydrazide application concerns the adaptation of the final products dosage for the Units needs. The tests that were performed, the measurements, the analyses and other relevant data, the results evaluation and the conclusions, are presented. The results were obtained under real industrial conditions and may provide a general tool for developing the know-how of this kind of treatment.     

Synthesis and photoisomerization behavior of polyamide-phenyleneethynylenes bearing azobenzene moieties in the main chain

Polymer Bulletin - Novel azobenzene-containing optically active polyamide-phenyleneethynylenes, poly(2–3ap)–poly(2–3bm) were synthesized by the Sonogashira–Hagihara coupling...     

Synthesis and characterization of thermosensitive poly(N-isopropylacrylamide-co-hydroxyethylacrylamide) microgels as potential carriers for drug delivery

Thermoresponsive colloidal microgels were prepared by precipitation copolymerization of N-isopropylacrylamide (NIPAM) and N-hydroxyethylacrylamide (HEAM) with various concentrations of a cross-linker in the presence of an anionic surfactant, sodium dodecylsulphate (SDS). The volume phase transition temperature (VPTT) of the prepared microgels was studied by dynamic light scattering (DLS), ultraviolet–visible spectroscopy (UV–vis) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. In addition, atomic force microscopy (AFM) was used to characterize the polydispersity and morphology of the microgels. Results indicated that poly(NIPAM-co-HEAM) microgels are spherical and monodisperse. VPTTs of microgels determined by DLS and UV–vis methods are almost the same and very close to the human body temperature, presenting the microgels as candidates for biomedical application. The temperature at which the phase transition occurred is nearly independent of the cross-linking density, whereas the transition range is deeply influenced by temperature. Also, the SDS concentration was increased to decrease the average hydrodynamic size of the microgels, due to the electrostatic repulsion between the charged particles during the polymerization process. ¹H-NMR spectra of the microgels show a decrease in peak intensity with an increased temperature due to a reduction in molecular mobility of the polymer segments. Release rates of propranolol from microgels are deeply influenced by temperature; below the VPTT at 25 °C, the drug is rapidly released at a rate comparable to that of a free drug, whereas above the VPTT (37 and 42 °C), a fraction of the drug is mechanically expulsed in the first five min, followed by a prolonged release.     

Effects of zinc deficiency and castration on fatty acid composition and desaturation in rats

The effects of zinc deficiency and testosterone on fatty acid composition of plasma lipids and microsomes of liver, intestine and testes were studied. The activities of fatty acid desaturase (Δ6 and Δ5) in rat liver and testes were also measured. A significant decrease in the level of arachidonic acid was observed in plasma of normal rats fed the zinc-deficient diet. Castration significantly decreased arachidonic acid but increased 20∶3 fatty acid, which is negligible in normal rats. Testosterone and zinc administration restored arachidonic acid to normal values. Zinc deficiency does not significantly change the fatty acid profile in liver, but castration decreased both arachidonic and 22∶6 fatty acid. Intestinal mucosal microsomes showed that the predominant fatty acid in this tissue, palmitic acid, is independent of zinc status, whereas polyunsaturated fatty acids 18∶2 and 20∶4 were decreased by zinc-deficient diet or castration. Zinc deficiency sharply decreased 22∶5 fatty acid and to some extent, other polyunsaturated fatty acids in testis microsomes. These changes in fatty acids are in agreement with increased Δ9 desaturation and decreased Δ5 desaturase activity. In testes, both Δ6 and Δ5 desaturase activities are decreased in zinc deficiency. It appears that zinc influences the conversion of linoleic to arachidonic acid, whereas testosterone influences Δ6 desaturase activity. The data suggest that zinc deficiency may be one of the important factors in the causation of polyunsaturated fatty acid deficiency, which in turn, may induce serum hypertriglyceridemia.     

Synthesis and properties of amino acid-derived optically active photo-responsive polymers

Optically active azobenzenedicarboxylic acids were synthesized from l-alanine, and the polycondensation of the diacids with o-, m-, p-xylylenediols, 5-norbornene-2,3-endo,endo- and exo,exo-dimethanols, m-, p-xylylenediamines, and trans-1,4-cyclohexanediamine was carried in N,N-dimethylformamide. Polymers with weight-average molecular weights of 3,300–33,700 were obtained in 63%-quantitative yields. All the polymers reversibly isomerized the azobenzene units from trans to cis and vice versa upon UV- and visible-light irradiations. The polymers exhibited no evidence for the formation of a chiral secondary structure.     

Elasto-viscoplastic constitutive equations for rock-type materials (finite deformation)

In the present paper the elasto-viscoplastic frame indifferent constitutive equations for rock and rock-type materials are proposed within the frame-work of large deformations. The constitutive equations are written with respect to an arbitrary configuration at time t as reference configurations. Our model describe the dilatancy or compressibility and creep for rock-type materials as well as the existence of the irreversible part of strain even when the applied stresses are relatively small. Constitutive hypotheses are based on the experimental evidences which reveal the complex behaviour or rock-type materials. All the constitutive functions and moduli involved in the model can be determined from a complete set of experimental data.     

Gut Microbiome Changes in Gestational Diabetes

Gestational diabetes mellitus (GDM), one of the most common endocrine pathologies during pregnancy, is defined as any degree of glucose intolerance with onset or first discovery in the perinatal period. Physiological changes that occur in pregnant women can lead to inflammation, which promotes insulin resistance. In the general context of worldwide increasing obesity in young females of reproductive age, GDM follows the same ascending trend. Changes in the intestinal microbiome play a decisive role in obesity and the development of insulin resistance and chronic inflammation, especially in patients with type 2 diabetes mellitus (T2D). To date, various studies have also associated intestinal dysbiosis with metabolic changes in women with GDM. Although host metabolism in women with GDM has not been fully elucidated, it is of particular importance to analyze the available data and to discuss the actual knowledge regarding microbiome changes with potential impact on the health of pregnant women and newborns. We analyzed peer-reviewed journal articles available in online databases in order to summarize the most recent findings regarding how variations in diet and metabolic status of GDM patients can contribute to alteration of the gut microbiome, in the same way that changes of the gut microbiota can lead to GDM. The most frequently observed alteration in the microbiome of patients with GDM was either an increase of the Firmicutes phylum, respectively, or a decrease of the Bacteroidetes and Actinobacteria phyla. Gut dysbiosis was still present postpartum and can impact the development of the newborn, as shown in several studies. In the evolution of GDM, probiotic supplementation and regular physical activity have the strongest evidence of proper blood glucose control, favoring fetal development and a healthy outcome for the postpartum period. The current review aims to summarize and discuss the most recent findings regarding the correlation between GDM and dysbiosis, and current and future methods for prevention and treatment (lifestyle changes, pre- and probiotics administration). To conclude, by highlighting the role of the gut microbiota, one can change perspectives about the development and progression of GDM and open up new avenues for the development of innovative therapeutic targets in this disease.