Synthesis and characterization of semi‐interpenetrating networks based on poly(dimethylsiloxane) and poly(vinyl alcohol)

Semi‐interpenetrating networks (Semi‐IPNs) with different compositions were prepared from poly(dimethylsiloxane) (PDMS), tetraethylorthosilicate (TEOS), and poly(vinyl alcohol) (PVA) by the sol‐gel process in this study. The characterization of the PDMS/PVA semi‐IPN was carried out using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and swelling measurements. The presence of PVA domains dispersed in the PDMS network disrupted the network and allowed PDMS to crystallize, as observed by the crystallization and melting peaks in the DSC analyses. Because of the presence of hydrophilic (? OH) and hydrophobic (Si? (CH₃)₂) domains, there was an appropriate hydrophylic/hydrophobic balance in the semi‐IPNs prepared, which led to a maximum equilibrium water content of ～ 14 wt % without a loss in the ability to swell less polar solvents. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Breastfeeding, complimentary feeding practices and childhood malnutrition in the Bolivian Andes

Northern Potosi is one of the poorest parts of Bolivia with the highest indicators of rural poverty, malnutrition and food insecurity in the Bolivian Andes. The objective of this research was to characterize the levels of malnutrition and describe infant feeding practices in Potosi, Bolivia and use this information to develop an effective, gender sensitive and culturally relevant intervention encouraging good infant feeding practices. Standard methods were used to collect anthropometric data. Weight and height data were collected for 400 children under five years of age from 30 communities. In six of these communities, interviews and focus group discussions were conducted with 33 mothers and other families in addition to household observational data that were collected to describe infant feeding practices. Nearly 20% of children were underweight; stunting was widespread as well. 38% of mothers initiated breastfeeding 12 hours or more after birth. 39% of mothers initiated complementary feeding in the first three months following birth. The type of complementary food given to children was usually inadequate. With this research we could see that nutritional deficiencies often begin when the mother starts breastfeeding and when first introduced complementary feeding. Interventions aimed at improving maternal and child nutrition will require changes in parents' behavior, greater recognition and community support of the importance of child feeding, and the inclusion of strategies to reach young people, involve men, and make high quality nutrition promotion more widely available in the communities.     

Isolation and Phytotoxicity of Terpenes from <Emphasis Type=Italic>Tectona grandis</Emphasis>

A study was carried out on the allelopathic potential of four forest species, Tectona grandis, Aleurites fordii, Gliricidia sepium, and Maytenus buxifolia. The most active species, T. grandis, was selected to perform a phytochemical study. A new compound, abeograndinoic acid, was isolated, and elucidation of its structure showed that this compound has an unusual carbon skeleton. A further 21 known terpenoids—including 4 sesquiterpenoids, 8 diterpenes and 9 triterpenes—also were isolated. A biosynthetic scheme for the presence of the new compound is proposed. Bioactivity profiles that used etiolated wheat coleoptiles and phytotoxicity bioassays on the isolated compounds were conducted. The compounds that presented the highest phytotoxic activity are the diterpenes 9 (2-oxokovalenic acid) and 12 (19-hydroxyferruginol).     

SOLVENT EXTRACTION ENHANCED MICROFILTRATION OF STRONTIUM AND TECHNETIUM WITH DI-2-ETHYLHEXYLPHOSPHORIC ACID AND QUATERNARY AMMONIUM SALTS

ABSTRACT

Application of extractants in form of microphase (micelles or microdrops) separated from aqueous matrix by microfiltration, “solvent extraction enhanced microfiltration (SEEMF)” is closely related to micellar enhanced ultrafiltration (MEUF) technique.

Uptake of strontium from aqueous solutions with microphase di-2-ethylhexylphosphoric acid (DEHPA) and pertechnetate with quaternary ammoniumsalts (QAS): trioctylmethylammonium chloride, benzyldodecyl-dimethylammonium bromide, and n-(α-carbethoxypenthadecyl)trimetyl-ammonium chloride was investigated as a function of microphase concentration and composition, pH and salinity of aqueous phase. Recovery of microfiltration on cellulose acetate 200 nm filters reached 95% for strontium with 4×10^?3 M DEHPA and 99% for technetium with 10^?4 M trioctyl-methylammonium chloride. A substantial part of 88-99% retention of technetium with investigated quaternary ammonium salts on microfilter may be caused by the filter wetting or sorption phenomena.     

Fertilizer dynamics in different tillage and crop rotation systems in a Vertisol in Central Mexico

N-fertilization dynamics and agronomic practices on a Vertisol in central Mexico were evaluated under irrigated conditions: (1) wheat-maize rotation with conventional tillage (CT) and burning of residues (W-M/CT/B, regional control); (2) wheat-beans rotation with CT and incorporation of residues into the soil (W-P/CT/I); (3) wheat-maize rotation with CT and incorporation of residues into the soil (W-M/CT/I); (4) maize-beans rotation bi-annual with CT and incorporation of residues into the soil (M-P/CT/Bi); and (5) wheat-maize, no tillage (NT) and residues left on the soil surface as mulch (W-M/NT/S). ¹⁵N and acetylene inhibition techniques were used to estimate N fertilizer efficiency and losses (N₂ + N₂O). Treatments received 240, 60, and 300 kg N ha⁻¹ for spring maize, beans and winter wheat, as ammonium sulphate enriched with 5.468% atoms ¹⁵N excess. In the spring summer cycle, the fertilizer N recovery ranged from 27% for W-M/NT/S to 68% for M-P/CT/Bi. From the total N-fertilizer applied, only 3 to 9% remained in soil after harvest (W-M/NT/S and W-M/CT/I being the respective extremes). Unaccounted N-fertilizer ranged between 27 and 69%, the highest losses corresponding to W-M/NT/S treatment. Fertilizer N recovery in wheat varied from 19 to 37% (W-M/NT/S–W-M/CT/B). N-fertilizer remaining in soil was 14 to 24% (W-M/NT/S – W-M/CT/I). N₂ and N₂O emissions were higher in the no tillage system. Emissions ranged from 3 to 28 kg N ha⁻¹ for W-P/CT/I and W-M/NT/S, respectively. The best treatments were those in which residues were incorporated resulting in N immobilization in top soil (0–15 cm), small N gas losses, and higher soil organic matter, these treatments were W-P/CT/I, W-M/CT/I.     

Inguinal tumor as the first manifestation of a pancreatic pseudocyst

We report a case of pancreatic pseudocyst in alcoholic pancreatitis, that presented as a mass in the inguinal region. The mechanism of this peculiar clinical presentation was the dissemination of the content of the pseudocyst along the psoas muscle. We review the involvement of psoas muscle in pancreatic pathology, giving emphasis to reports of inguinal or thigh masses as initial manifestations.     

Full-term delivery following intracytoplasmic sperm injection with frozen-thawed immotile testicular spermatozoa

We present one of the very few deliveries occurring following intracytoplasmic sperm injection of thawed immotile testicular spermatozoa from a testicular biopsy of a man with bilateral congenital absence of the vas deferens. A first attempt in the 33 year old woman with fresh testicular biopsy extracted spermatozoa was unsuccessful. The supernumerary spermatozoa were cryopreserved for later use. After thawing, testicular spermatozoa were immotile. From 11 intact oocytes injected with frozen-thawed immotile testicular spermatozoa, a two pronuclear fertilization rate of 27% and a cleavage rate of 100% were obtained. A total of three embryos was transferred resulting in a singleton pregnancy and the birth of a normal female baby.     

Clinical assessment of olfactory dysfunction in Parkinson''s disease

The possibility of placing endosseous implants in the edentulous maxilla is frequently reduced by inadequate bone volume of the residual ridge. In totally edentulous maxillae with knife-edge conformation, insufficient thickness is frequently associated with insufficient height of the residual ridge in the posterior maxilla because of pneumatization of the maxillary sinuses. This surgical method combines grafting of the maxillary sinuses, onlay grafts on the buccal side of maxillary posterior segments, and sagittal osteotomy of the anterior maxilla with interpositional bone grafts. Five to six months after maxillary reconstruction, Br?nemark implants were placed and, after osseointegration occurred, implant-supported dental prostheses were fabricated. Three patients have been treated with this method and 22 implants have been placed. The mean follow-up after final prosthetic rehabilitation has been 16 months; survival rate has been 100%. Despite the small number of patients and the short follow-up, preliminary results have shown very promising results.     

Modelling a sequencing batch reactor to treat the supernatant from anaerobic digestion of the organic fraction of municipal solid waste

In this study, a lab‐scale sequencing batch reactor (SBR) has been tested to remove chemical oxygen demand (COD) and NH₄⁺‐N from the supernatant of anaerobic digestion of the organic fraction of municipal solid waste. This supernatant was characterized by a high ammonium concentration (1.1 g NH₄⁺‐N L^?1) and an important content of slowly biodegradable and/or recalcitrant COD (4.8 g total COD L^?1). Optimum SBR operating sequence was reached when working with 3 cycles per day, 30 °C, SRT 12 days and HRT 3 days. During the time sequence, two aerobic/anoxic steps were performed to avoid alkalinity restrictions. Oxygen supply and working pH range were controlled to promote the nitrification over nitrite. Under steady state conditions, COD and nitrogen removal efficiencies of more than 65% and 98%, respectively, were achieved. A closed intermittent‐flow respirometer was used to characterize and model the SBR performance. The activated sludge model ASM1 was modified to describe the biological nitrogen removal over nitrite, including the inhibition of nitrification by unionized ammonia and nitrous acid concentrations, the pH dependency of both autotrophic and heterotrophic biomass, pH calculation and the oxygen supply and stripping of CO₂ and NH₃. Once calibrated by respirometry, the proposed model showed very good agreement between experimental and simulated data. Copyright © 2007 Society of Chemical Industry