Biodegradable polymers: A review about biodegradation and its implications and applications

Plastic waste pollution is a global environmental problem that could be solved by biodegradable materials. In addition, its biodegradability has been important for medical applications. In this way, the biodegradability performance has been investigated for different materials under diversified environmental conditions. In this context, this review shows the main up-to-date biodegradable polymers (from renewable sources and fossil-based), their structure and properties, and their biodegradability characteristics. Also, this review shows the effect of polymer properties and environmental conditions on biodegradability, methods of biodegradability and toxicity determination, modification processes to enhance biodegradability, and main applications of biodegradable polymers for agriculture, medical, and packaging. Finally, this review presents a discussion of the implications of biodegradation on the environment, the current context, and future perspectives of plastic biodegradation.     

An experimental study of the dissemination of Titanium and Zirconium in the body

Metallic implants can generate and release titanium oxide (TiO₂) and zirconium oxide (ZrO₂) to the tissues. These products can accumulate locally or disseminate systemically. The aim of the present study was to assess the distribution of TiO₂ and ZrO₂ administered intraperitoneally to rats. We used male Wistar rats of approximately 100 g body weight throughout the study. An intraperitoneal injection of a suspension of TiO₂ or ZrO₂ (16, 1600 and 16×10³ mg/kg body weight) was administered. The animals were killed at 5–10 months post-administration by ether overdose. Samples of peritoneum, liver, kidney, lung and spleen were taken, fixed in formalin and routine processed for embedding in paraffin. One set of sections was stained with hematoxylin and eosin and another set was prepared unstained. The presence of titanium in the tissues was detected by X-ray diffraction crystallography. The histological analysis revealed the presence of abundant intracellular aggregates of metallic particles of Ti and Zr in peritoneum, liver, lung and spleen. The crystallographic study revealed the presence of anatasa. The dissemination of metallic particles from orthopedic or odontological implants would not be restricted to a local phenomenon. The particles also target vital organs. The distribution of these deposits over lengthy periods deserves meticulous attention given the clinical relevance of this phenomenon.     

Acculturation: A psychometric perspective.

A review of recent research indicates that the measurement of individual acculturation is not only a legitimate area of investigation but can also meet conventional criteria of reliability and validity. Furthermore, particularly within the framework of a full measurement model, psychometric methods have the potential to contribute to a better understanding of complex issues such as the identification and cross-cultural equivalence of the cultural variable as an antecedent of behavior. Recent developments in the quantification of acculturation along multiple dimensions suggest that this approach is more promising than arbitrary cultural group or generational typologies. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Testing linguistic minorities.

Suggests that psychological and educational testing of members of linguistic minority groups should take into account the diverse social, political, and economic realities currently facing these groups. These realities are moderated by educational opportunities, which in turn are closely linked to various forms of standardized testing. Key conceptual and operational issues underlying concern about this situation are described. Conceptual issues include bilingualism, acculturation, and the "emic–etic" distinction, particularly as the latter applies to the cross-cultural generalizability of cognitive constructs. Operational issues include assessment of language dominance, test translation and development, and the examiner variable. The author appeals for concern with and sensitivity to individual differences in sociocultural and linguistic characteristics. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A non-linear AC spectrometry study of the electrodeposition of Cu from acidic sulphate solutions in the presence of PEG

Non-linear Alternated-Current (AC) spectrometry has been recently proposed [Bozzini and Sgura, Math. Prob. Eng. (in press)] as an approach able to yield basically the same results as AC impedance spectroscopy, but with a remarkably higher statistical confidence. In particular, quantitative parameter estimation problems commonly found in the analysis of AC impedance data carried out with the available methods [Sgura and Bozzini, J. Non-Lin. Mech. 40 (2005) 557], can be remarkably reduced. This paper reports the first example of the experimental implementation of the method, as applied to Cu electrodeposition from a sulphate solution containing polyethyleneglycol, a system relevant to semiconductor fabrication, previously investigated by electrochemical and spectroelectrochemical methods in our group [Bozzini et al. J. Appl. Electrochem. (in press), Bozzini et al. J. Appl. Electrochem. 36 (2006) 87].     

Theoretical model to estimate the thermal performance of an evaporative wind tower placed in an open space

A theoretical model to evaluate the thermal performance of an evaporative wind tower installed in open spaces with hot and dry climates has been developed. It was based on the laws of conservation of mass and energy and used TRNSYS as a simulation tool. Evaporative wind towers produce an adiabatic cooling which has been modelled taking into account all the heat and mass exchanges between the airflow and the injected water, and also considering the processes of radiation, convection and conduction. The system analyzed has a special design based on an existing installation placed in Madrid, which is composed of sixteen evaporative wind towers with one fan and six nozzles on the top of each one. A first validation of this theoretical model was done by comparing calculated results obtained through numerical simulation with experimental data. These last data were previously registered in a campaign carried out during the summer 2008 to evaluate the thermal behaviour of the system. To contrast both results, the same initial assumptions in fan and water operation as well as environmental conditions were considered. The comparison between them during the period of 18th to 20th July 2008, show an average temperature drop of 6.5 °C and an average increase of relative humidity of 27%. These values present a high correlation, up to 0.79, between experimental and calculated wet bulb depression. The average cooling power achieved by this system varies from 13 to 16 kW, with maximum peaks around 20 kW. So this theoretical model could be used for future energy estimations of wind towers design with similar constructive characteristics.     

Polar compounds dominate in vitro effects of sediment extracts

Sediment extracts from three polluted sites of the river Elbe basin were fractionated using a novel online fractionation procedure. Resulting fractions were screened for mutagenic, aryl hydrocarbon receptor (AhR)-mediated, transthyretin (TTR)-binding, and estrogenic activities and their potency to inhibit gap junctional intercellular communication (GJIC) to compare toxicity patterns and identify priority fractions. Additionally, more than 200 compounds and compound classes were identified using GC-MS/MS, LC-MS/MS, and HPLC-DAD methods. For all investigated end points, major activities were found in polar fractions, which are defined here as fractions containing dominantly compounds with at least one polar functional group. Nonpolar PAH fractions contributed to mutagenic and AhR-mediated activities while inhibition of GJIC and estrogenic and TTR-binding activities were exclusively observed in the polar fractions. Known mutagens in polar fractions included nitro- and dinitro-PAHs, azaarenes, and keto-PAHs, while parent and monomethylated PAHs such as benzo[a]pyrene and benzofluoranthenes were identified in nonpolar fractions. Additionally, for one sample, high AhR-mediated activities were determined in one fraction characterized by PCDD/Fs, PCBs, and PCNs. Estrone, 17β-estradiol, 9H-benz[de]anthracen-7-one, and 4-nonylphenol were identified as possible estrogenic and TTR-binding compounds. Thus, not only nonpolar compounds such as PAHs, PCBs, and PCDD/Fs but also the less characterized and investigated more polar substances should be considered as potent mutagenic, estrogenic, AhR-inducing, TTR-binding, and GJIC-inhibiting components for future studies.     

Energy sector in Ecuador: Current status

This paper describes the current energy sector in Ecuador, its present structure, the oil industry, subsidies, and renewable energy, focusing on the evolution and reform of the electricity sector. Currently, 86% of the primary energy originates from nonrenewable sources. In 2005, the gross electricity generation was 15 127 GWh (45.5% hydropower, 43.11% thermal, and 11.39% imported). Ecuador is the fifth largest oil producer in South America but lacks sufficient oil refining capacity. Reserves of natural gas (NG) are small, and most of NG is produced from oil fields without energy recovery. Several projects are underway to increase the utilization of NG and renewable energies to meet Ecuador commitments to the Kyoto Protocol.     

Biodistribution of titanium dioxide from biologic compartments

The layer of titanium dioxide (TiO(2)) of the implant is chronically exposed to the internal electrolyte milieu in the peri-implant biological compartment. Corrosion results from electrochemical attack and ensuing gradual degradation of the metallic materials and is thus of biological interest when these biomaterials are employed in clinical implantology. Herein we evaluated and compared the chronic effect and the biodistribution of TiO(2) administered subcutaneously or intraperitoneally. We propose that the compartmentalization of titanium in the area of subcutaneous injection would reproduce the biological compartment of the implant and its microenvironment from which metal ions could be released and migrate systemically. Potential TiO(2) deposits were identified and characterized in skin, liver and lung by histological and EDX analyses. After both treatments, the skin, liver, and lungs exhibited histological evidence of TiO(2) deposits. In order to characterize in situ macrophage-like cells, tissue sections were immunohistochemically stained for CD68. Tissue specimens from all organs assayed showed positive staining for anti-macrophage monoclonal antibody CD68 (PGM1). Despite the compartmentalization of titanium within nodular areas in rats treated subcutaneously, systemic migration occurred. We concluded that systemic migration of TiO(2) occurred regardless of the administration route.     

Biomonitorization of cadmium, chromium, manganese, nickel and lead in whole blood, urine, axillary hair and saliva in an occupationally exposed population

Heavy metal contamination from occupational origin is a cause for concern because of its potential accumulation in the environment and in living organisms leading to long term toxic effects. This study was aimed to assess Cd, Cr, Mn, Ni and Pb levels in whole blood, urine, axillary hair and saliva from 178 individuals with occupational exposure to heavy metals. Levels of metal compounds were determined by atomic absorption spectrometry. We collected information on occupation, lifestyle habits and food intake by questionnaire. Multiple linear regression analyses for metal ion concentration in whole blood, urine, axillary hair and saliva were adjusted for age, gender, smoking and alcohol consumption, lifetime workplace exposure, residence area and food habits. Overall, blood and urine median concentrations found for the five metals analyzed do not exceed biological exposure indexes, so that they are very similar to a non-occupationally exposed population. Toxicokinetic differences may account for the lack of correlations found for metal levels in hair and saliva with those in blood or urine. For those heavy metals showing higher median levels in blood with respect to hair (Cd, Mn and Pb) indicating lesser hair incorporation from blood, the lifetime working experience was inversely correlated with their hair levels. The longer the lifetime working experience in industrial environments, the higher the Mn and Ni concentration in saliva. Axillary hair and saliva may be used as additional and/or alternative samples to blood or urine for biomonitoring hair Mn, and saliva Ni in subjects with occupational exposure.