Theoretical study of a membrane reactor for the water gas shift reaction under nonisothermal conditions

A simulation of a membrane reactor for the water gas shift reaction is carried out by means of a 1D pseudo‐homogeneous nonisothermal mathematical model. The composite membrane consists of a dense layer of Pd (selective to H₂) supported over a porous ceramic layer. The effect of temperature, overall heat‐transfer coefficient, and mode of operation on the membrane reactor performance and stability are analyzed, and the results obtained are compared with those corresponding to a reactor with no hydrogen permeation. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Computational Study of the Lipase‐Mediated Desymmetrisation of 2‐Substituted‐Propane‐1,3‐Diamines

The enantioselectivity displayed by the lipase from Pseudomonas cepacia towards a wide range of prochiral 2‐substituted‐propane‐1,3‐diamines was studied by means of molecular dynamics simulations (MDS). In all cases the enzyme allows the recovery of the corresponding amino carbamates of R configuration. However, the enantioselectivity is only synthetically useful if no ortho substituent is present and the aromatic ring is directly bonded to the 2‐carbon of the 1,3‐diamine core. Analysis of the MDS trajectories revealed that the homologation of 2‐aryl substituents by means of a methylene group lowers enantioselectivity by alleviating the conformational tension of the slow‐reacting orientations due to unfavourable intramolecular contacts between the ortho carbons of the aryl group and the nucleophilic nitrogen, as well as between the chiral carbon and the oxyanion. Additionally, the relative solvent accessible surfaces of the atoms of the aryl ring nicely correlate with the effect of the location of the substituent on enantioselectivity.     

Preparation and characterization of silicate nanofilms doped with europium β-diketonate complexes

Films consisting of Eu³⁺ β-diketonate complexes were deposited onto glassy substrates by means of the spin- and dip-coating techniques, using different ion/ligand ratios. Absorption spectroscopy in the infrared region revealed the typical stretching bands of the SiOSi and SiOH bonds of the inorganic matrix as well as bands relative to the CO and CH symmetric vibration of β-diketone (dibenzoylmethane). The films displayed UV-visible absorption band at 350 nm, attributed to the organic ligand. Luminescence properties were studied by photoluminescence spectroscopy. Upon ligand excitation, the emission spectra exhibited the characteristic bands of the Eu³⁺ ion corresponding to the transition from the excited state ⁵D₀ to the ground state ⁷F_J. Scanning electron microscopy confirmed the formation of a film with average thickness ranging from 80 to 100 nm. The sol-gel process and the deposition techniques resulted in the effective formation of nanofilms, which opens up perspectives for their application in photonics.     

Selenium,iodine, ω-3 PUFA and natural antioxidant from Melissa officinalis L.: A combination of components from healthier dry fermented sausages formulation

A new formulation of dry fermented sausage, including ingredients that improve the nutritional and health benefits of this type of product is presented. Se yeast (2 g/kg), iodized salt (26 g/kg), linseed:algae (3:2) emulsion (62.5 g/kg), and lyophilized water extract of Melissa officinalis L. as a source of natural antioxidants (686 mg/kg), yielded dry fermented sausages with technological and sensory properties similar to traditional ones.     

Identification of key odor volatile compounds in the essential oil of nine peach accessions

BACKGROUND: Volatile compounds, together with sugars and acids, are the main chemical species determining the characteristic aroma and flavor of food. In peach, more than 100 volatiles have been identified. RESULTS: The essential oil of six peach and three nectarine accessions used in Italian breeding programs was obtained by steam distillation, and the volatiles were investigated. A total of 47 known volatiles, two unidentified compounds and nine hydrocarbons were identified, including 12 aldehydes, six alcohols, three acids, three esters, six terpenes, two phenylalanine derivates, two C₁₃ norisoprenoids, one ketone (C₉) and 10 lactones. A wide variation in the number of volatiles and in their concentration was observed among the nine accessions. Twenty‐one compounds presented odor activity values (OAVs) higher than 1 in at least one of the accessions and were therefore putatively considered as key odorants in the peach volatile composition. CONCLUSION: This study reports the identification, quantification and potency, based on the OAVs, of the most important volatile compounds, along with fruit quality characteristics, of nine different peach/nectarine accessions and will help future peach volatile breeding programs for the selection of odor‐rich accessions to be used in the development of new improved cultivars. Copyright © 2010 Society of Chemical Industry     

Myosin heavy chain fibre types and fibre sizes in nuliparous and primiparous ovariectomized Iberian sows: Interaction with two alternative rearing systems during the fattening period

To investigate the effects of the reproductive background (nuliparous/primiparous) on skeletal muscle phenotype and their interaction with two alternative finishing systems (indoors/outdoors) in Iberian sows, 32 contemporary piglets were assigned to four different groups: indoors-nuliparous, indoors-primiparous, outdoors-nuliparous and outdoors-primiparous. Nuliparous sows were ovariectomized at 4 months of age, whereas primiparous were castrated at 14 months of age, after their first lactation. Indoors sows were fattened (2 months prior to slaughter) intensively, whereas outdoors sows were finished in an extensive land with natural resources. Muscle samples (semimembranosus, gluteobiceps) were analyzed for myosin fibre types and fibre sizes. Sows finished out-of-doors had more type I and IIA fibres and smaller fibres than indoor-fattened pigs. Primiparous reared indoors had a significantly lower IIX:IIB fibre ratio and showed a clear tendency for having larger fibres than nuliparous reared indoors. Reproductive background effect interacted with rearing condition effect inducing relevant muscular adaptations. Thus, the influence of reproductive background on muscle characteristics was not significant in sows reared out-of-doors but highly significant in sows finished intensively. This interaction resulted in muscular traits less favourable for meat quality in primiparous vs. nuliparous reared indoors.     

Computational studies of the primary phototransduction event in visual rhodopsin

This Account addresses recent advances in the elucidation of the detailed molecular rearrangements due to the primary photochemical event in rhodopsin, a prototypical G-protein-coupled receptor (GPCR) responsible for the signal transmission cascade in the vertebrate vision process. The reviewed studies provide fundamental insight on long-standing problems regarding the assembly and function of the individual residues and bound water molecules that form the rhodopsin active site, a center that catalyzes the 11-cis/all-trans isomerization of the retinyl chromophore in the primary step of the phototransduction mechanism. Emphasis is placed on the authors' recent computational studies, based on state-of-the-art quantum mechanics/molecular mechanics (QM/MM) hybrid methods, addressing the structural refinement of the retinyl chromophore binding site in high-resolution X-ray structures of bovine visual rhodopsin, the energy storage mechanism, and the molecular origin of spectroscopic changes due to the primary photochemical event.     

Visual Disfunction due to the Selective Effect of Glutamate Agonists on Retinal Cells

One of the causes of nervous system degeneration is an excess of glutamate released upon several diseases. Glutamate analogs, like N-methyl-DL-aspartate (NMDA) and kainic acid (KA), have been shown to induce experimental retinal neurotoxicity. Previous results have shown that NMDA/KA neurotoxicity induces significant changes in the full field electroretinogram response, a thinning on the inner retinal layers, and retinal ganglion cell death. However, not all types of retinal neurons experience the same degree of injury in response to the excitotoxic stimulus. The goal of the present work is to address the effect of intraocular injection of different doses of NMDA/KA on the structure and function of several types of retinal cells and their functionality. To globally analyze the effect of glutamate receptor activation in the retina after the intraocular injection of excitotoxic agents, a combination of histological, electrophysiological, and functional tools has been employed to assess the changes in the retinal structure and function. Retinal excitotoxicity caused by the intraocular injection of a mixture of NMDA/KA causes a harmful effect characterized by a great loss of bipolar, amacrine, and retinal ganglion cells, as well as the degeneration of the inner retina. This process leads to a loss of retinal cell functionality characterized by an impairment of light sensitivity and visual acuity, with a strong effect on the retinal OFF pathway. The structural and functional injury suffered by the retina suggests the importance of the glutamate receptors expressed by different types of retinal cells. The effect of glutamate agonists on the OFF pathway represents one of the main findings of the study, as the evaluation of the retinal lesions caused by excitotoxicity could be specifically explored using tests that evaluate the OFF pathway.     

α-particle emission probabilities in the decay of U

²³⁵U decays by α-particle emission to ²³¹Th. The decay scheme of this nuclide is very complex, with more than 20 alpha branches. Recommended values for P_α of this nuclide are based on measurements carried out in 1975. This work presents the results of new measurements made with Si detectors and sources of enriched uranium in the frame of the EUROMET 591 cooperation project. The use of improved measurement techniques and numerical analysis of spectra allowed a new set of P_α values for 13 lines with improved uncertainties to be obtained.     

Morphology and water affinity of superabsorbent hydrogels composed of methacrylated cashew gum and acrylamide with good mechanical properties

This paper comprises the characterization of superabsorbent hydrogels based on methacrylated cashew gum (CGMA) co-polymerized with acrylamide (AAm) by measuring of the water uptake, water retention capacity in dependence of time, morphological and mechanical properties. The morphological features of hydrogels were evidenced by SEM images. Stress measurements of hydrogels as a function of temperature were considered as being the necessary force for compressing the hydrogels at 1 mm deformation. Stress-strain modeling was used to obtain the compressive elastic modulus and apparent cross-linking density of superabsorbent hydrogels. Hydrolyzed CGMA-co-AAm hydrogels showed highly water absorbing. Another remarkably feature of these hydrogels is the efficiency in the water retaining that was caused by increasing in CGMA content. Higher temperature leads to an enhancement in the stress values of superabsorbent hydrogels because the large content of water that penetrates into superabsorbent hydrogels and expands their polymer network. The increase in the amount of CGMA and AAm were accompanied by an increasing on the apparent cross-linking density of hydrogels. This contributed to increase their elastic modulus, which is inherent to a more rigid structure.