Adsorption characteristics of Cu(II) and Pb(II) onto expanded perlite from aqueous solution

The adsorption characteristics of Cu(II) and Pb(II) onto expanded perlite (EP) from aqueous solution were investigated with respect to the changes in pH of solution, adsorbent dosage, contact time and temperature of solution. For the adsorption of both metal ions, the Langmuir isotherm model fitted to equilibrium data better than the Freundlich isotherm model. Using the Langmuir model equation, the monolayer adsorption capacity of EP was found to be 8.62 and 13.39 mg/g for Cu(II) and Pb(II) ions, respectively. Dubinin-Radushkevich (D-R) isotherm model was also applied to the equilibrium data and the mean free energies of adsorption were found as 10.82 kJ/mol for Cu(II) and 9.12 kJ/mol for Pb(II) indicating that the adsorption of both metal ions onto EP was taken place by chemical ion-exchange. Thermodynamic functions, the change of free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) of adsorption were also calculated for each metal ions. These parameters showed that the adsorption of Cu(II) and Pb(II) ions onto EP was feasible, spontaneous and exothermic at 20-50 degrees C. Experimental data were also evaluated in terms of kinetic characteristics of adsorption and it was found that adsorption process for both metal ions followed well pseudo-second-order kinetics.     

Synthesis,characterization and electrorheological properties of poly(o‐toluidine)/Zn conducting composites

In this study, the synthesis, characterization, and electrorheological (ER) properties of poly(o‐toluidine)/Zn, (POT/Zn), composites were investigated. Syntheses of the composites were carried out by a chemical method using ammonium persulfate, (NH₄)₂S₂O₈, (APS), as a free radical initiator. The composites were characterized by Fourier transform infrared (FTIR) spectroscopy, electrical conductivity, magnetic susceptibility, particle size measurements, and scanning electron microscopy (SEM). A series of Zn‐containing composites were prepared (0.8–7.6% by mass), and their conductivities were measured to be within the range of 1.7 × 10^?3–5.0 × 10^?2 Scm^?1. Magnetic properties of POT/Zn composites were analyzed by Gouy scale measurements; it was found that their conducting mechanisms are bipolaron. A series of particle size (13, 17, 18, 26, 83 μm) were prepared by ground milling the crude POT/Zn composites. Colloidal suspensions of POT/Zn composites were prepared in silicone oil (SO), at a series of concentrations (10–30%, m/m), and sedimentation stabilities were measured at 25°C. ER measurements showed that the POT/Zn/SO suspension system was ER active. Thus, the effects of solid particle concentration, shear rate, electric field strength, addition of polar promoters, and temperature (25–125°C) onto ER activities of suspensions were investigated. The ER activity of suspensions was increased with increasing particle concentration and electric field strength and decreasing shear rate and showing a non‐Newtonian flow behavior. τ = 1.1 kPa shear stress was reached for POT/Zn (4.1 wt %, Zn) composite under E = 2.0 kV, c = 15 (%, m/m), , and T = 25°C conditions. It was found that the ER activity was slightly decreased with increasing temperature. Further, the addition of polar promoters had no promoting effect on the ER activity of the suspensions and POT/Zn/SO system was classified as dry ER materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1058–1065, 2007     

Achieving global environmental benefits through local development of clean energy? The case of small hilly hydel in India

Energy and development are closely intertwined. Yet, increasing fossil fuel-based energy consumption contributes significantly to environmental problems both locally and globally. This article explores the interlinkages between local livelihood and environmental benefits from the provision of energy to remote rural households through small hydropower development. The analysis is based on research carried out around a large development project designed to assist the Government of India in the optimum utilization of small hydropower resources in the Himalayan and sub-Himalayan regions. There are about 100,000 villages in India that are not connected to electricity supply, many of them in the hilly regions with ample hydropower potential. The project aimed to demonstrate the utility of and options for providing electricity to such villages through clean mini-hydro. The article addresses the nature of the impacts of the demonstration small hydel schemes on the local communities, to what extent they translate into environmental benefits both locally and globally, and the perceptions and participation of the local communities in these small hydro schemes. The study explores the impacts of the schemes on financial capital, natural capital, social capital, physical capital, human capital, and gender equity in the local communities. It further provides a discussion on the links between local and global environmental benefits. Overall, it is found that the schemes’ impacts both on the local communities and the environment are mostly marginally positive or neutral, although achieving clearly demonstrable benefits would require major upscaling of the effort involving broader changes than possible under this project. Furthermore, it is argued that some of the assumptions behind the project design were faulty. Involvement of the local communities and direct livelihood benefits to them are essential for the long-term sustainability of the small hydro schemes. The discussion and conclusions are intended to provide guidance to programmes and projects that aim to promote environmentally sound energy in the rural areas of developing countries.     

Provably secure hybrid key agreement protocols in cluster-based wireless ad hoc networks

Wireless ad hoc networks support rapid on-demand and adaptive communication among the nodes due to their self-configurable and autonomous nature and lack of fixed infrastructure. Security is a crucial factor for such systems. Since ad hoc networks rely on the collaboration principle, the issue of key distribution and efficient group key management in such networks represents two of the most important problems. We describe hybrid solutions to the problem of key distribution and key management by reflecting ad hoc networks in a topology composed of a set of clusters. To date no security proofs exist for these types of protocols. We present two dynamically efficient schemes. We show that both our hybrid schemes are provably secure in the standard model under Decision Diffie–Hellman (DDH) assumption. The proposed protocols avoid the use of a trusted third party (TTP) or a central authority, eliminating a single point of attack. We analyse the complexity of the schemes and differentiate between the two approaches based on performance in a wireless setting. In comparison with the existing cluster-based hybrid key agreement protocols, our proposed approaches individually provide better performance in terms of both communication and computation, handle dynamic events efficiently, and are supported by sound security analysis in formal security models under standard cryptographic assumptions.     

Nano-hydroxyapatite reinforced AZ31 magnesium alloy by friction stir processing: a solid state processing for biodegradable metal matrix composites

Friction stir processing (FSP) was successfully adopted to fabricate nano-hydroxyapatite (nHA) reinforced AZ31 magnesium alloy composite as well as to achieve fine grain structure. The combined effect of grain refinement and the presence of embedded nHA particles on enhancing the biomineralization and controlling the degradation of magnesium were studied. Grain refinement from 56 to ~4 and 2 μm was observed at the stir zones of FSP AZ31 and AZ31–nHA composite respectively. The immersion studies in super saturated simulated body fluid (SBF 5×) for 24 h suggest that the increased wettability due to fine grain structure and nHA particles present in the AZ31–nHA composite initiated heterogeneous nucleation which favored the early nucleation and growth of calcium-phosphate mineral phase. The nHA particles as nucleation sites initiated rapid biomineralization in the composite. After 72 h of immersion the degradation due to localized pitting was observed to be reduced by enhanced biomineralization in both the FSPed AZ31 and the composite. Also, best corrosion behavior was observed for the composite before and after immersion test. MTT assay using rat skeletal muscle (L6) cells showed negligible toxicity for all the processed and unprocessed samples. However, cell adhesion was observed to be more on the composite due to the small grain size and incorporated nHA.     

Treatment of Escherichia coli O157:H7 inoculated alfalfa seeds and sprouts with electrolyzed oxidizing water

Electrolyzed oxidizing water is a relatively new concept that has been utilized in agriculture, livestock management, medical sterilization, and food sanitation. Electrolyzed oxidizing (EO) water generated by passing sodium chloride solution through an EO water generator was used to treat alfalfa seeds and sprouts inoculated with a five-strain cocktail of nalidixic acid resistant Escherichia coli O157:H7. EO water had a pH of 2.6, an oxidation-reduction potential of 1150 mV and about 50 ppm free chlorine. The percentage reduction in bacterial load was determined for reaction times of 2, 4, 8, 16, 32, and 64 min. Mechanical agitation was done while treating the seeds at different time intervals to increase the effectiveness of the treatment. Since E. coli O157:H7 was released due to soaking during treatment, the initial counts on seeds and sprouts were determined by soaking the contaminated seeds/sprouts in 0.1% peptone water for a period equivalent to treatment time. The samples were then pummeled in 0.1% peptone water and spread plated on tryptic soy agar with 5 microg/ml of nalidixic acid (TSAN). Results showed that there were reductions between 38.2% and 97.1% (0.22-1.56 log(10) CFU/g) in the bacterial load of treated seeds. The reductions for sprouts were between 91.1% and 99.8% (1.05-2.72 log(10) CFU/g). An increase in treatment time increased the percentage reduction of E. coli O157:H7. However, germination of the treated seeds reduced from 92% to 49% as amperage to make EO water and soaking time increased. EO water did not cause any visible damage to the sprouts.     

Desorption of hydrophobic compounds from laboratory-spiked sediments measured by Tenax absorbent and matrix solid-phase microextraction

Tenax extraction and matrix solid-phase microextraction (matrix-SPME) were used to study desorption of hydrophobic contaminants (HOC) from sediments. 14C-labeled hexachlorobiphenyl, DDE, permethrin, chlorpyrifos, and phenanthrene were individually spiked into sediments differing in physical characteristics. Sequestration of the HOCs into sediment was observed for all compounds, and desorption was described by rapid, slow, and very slow rates. The freely dissolved HOC concentration in the sediment porewater was estimated by matrix-SPME, and serial sampling was used to ensure equilibrium was achieved among sediment, porewater and matrix-SPME fiber. Differences in partitioning of the HOCs between sediment and porewater for the different sediments were reduced by replacing the HOC concentration in sediment with the rapidly desorbing fraction. The significantly lower porewater concentration determined from matrix-SPME, than predicted from equilibrium partitioning theory (EPT), showed that only a small fraction of sediment HOCs were available for equilibrium and the predictability of EPT can be improved with the consideration of sequestration in sediment. A good correlation was noted between sediment concentration in the rapidly desorbing fraction measured by Tenax extraction, and SPME fiber concentration as determined by matrix-SPME. Thus, the two methods both tracked the readily desorbed contaminant equally well though Tenax extraction measures the accessible pool, and matrix-SPME measures the chemical activity of the HOCs.     

The registered dietitian in primary care: the Hamilton experience.

The Hamilton Health Service Organization Nutrition Program integrates nine registered dietitians (RDs) into the offices of 80 family physicians (FPs) at 50 sites in Hamilton, Ontario. The program is based on a shared care model, in which FPs and RDs work collaboratively to provide nutrition services aimed at prevention, treatment, and management of nutrition-related problems. In addition to their clinical role, dietitians in the program are involved in health promotion, disease prevention and early intervention strategies, interdisciplinary collaboration, building links with community services, and research. The RDs' specialized knowledge, skills, and experience allow them to provide a wide range of services that complement and augment those of the FP. This model is consistent with Canadian health care reform recommendations and offers significant benefits for both health care providers and consumers.