Solid-state photoelectrochemical device based on poly(3-hexylthiophene) and an ion conducting polymer electrolyte, amorphous poly(ethylene oxide) complexed with I3/I redox couple

The photoelectrochemical properties of a solid-state photoelectrochemical cell (PEC) based on poly(3-hexylthiophene), P3HT, and an ion-conducting polymer electrolyte, amorphous poly(ethylene oxide), POMOE, complexed with I₃⁻/I⁻ redox couple has been constructed and studied. The current–voltage characteristics in the dark and under white light illumination, transient photocurrent and photovoltage studies, photocurrent action spectra for front and back side illuminations and an open-circuit voltage and short-circuit current dependence on light intensity have been studied. An open-circuit voltage of 130 mV and a short-circuit current of 0.47 μA cm⁻² were obtained at light intensity of 100 mW/cm². IPCE% of 0.024% for front side illumination (ITO/PEDOT) and IPCE% of 0.003% for backside illumination (ITO/P3HT) were obtained.     

Early prostate cancer detection and potential for surgical cure in men with poorly differentiated tumors

Postgastrectomy osteopenia is observed generally in humans. Fructooligosaccharides increase the absorption of calcium from the large intestine of healthy rats. Thus, we have examined whether they stimulate calcium absorption and prevent osteopenia in rats following total gastrectomy. Rats were subjected to either a sham surgical operation or Billoth II gastrectomy. Seven rats from each surgical treatment group were fed a control diet, and another seven rats of each treatment group were fed a diet containing fructooligosaccharides (75 g/kg diet) for 4 wk. For 5 d each week, feces were collected, and the calcium and phosphorus contents were measured for calculation of the absorption of these minerals. At the end of the experiment, the rats were killed and bones were collected. The net calcium absorption, calcium content and bone mineral density of the femur and tibia in gastrectomized rats fed the control diet were significantly less than those in sham-operated rats fed control diet. The net calcium absorption in rats fed the fructooligosaccharides diet was greater than that in rats fed control diet. Moreover, dietary fructooligosaccharides prevented the decrease in the calcium content and bone mineral density in gastrectomized rats. Dietary fructooligosaccharides enhanced calcium absorption and prevented the changes indicative of postgastrectomy osteopenia such as decreases in bone calcium content and bone mineral density in gastrectomized rats.     

Lean Construction: From Theory to Implementation

This article compares the techniques developed for lean construction with those developed for lean manufacturing. Lean manufacturing and lean construction techniques share many common elements despite the obvious differences in their assembly environments and processes. Manufacturing plants and construction sites are different in many ways that might explain why lean production theories and practices do not fully fit the construction industry. Though many lean construction tools and elements are still in an embryonic state, lean construction techniques are gaining popularity because they can affect the bottom line of projects. Additionally, this paper presents a study of a construction project in which specific lean construction elements were tested. Each technique was evaluated in terms of its impact on the performance of the project. Based on the findings of the study, a new “lean assessment tool” is proposed to quantify the results of lean implementations. The assessment tool evaluates six lean construction elements: last planner, increased visualization, huddle meetings, first-run studies, five S’s, and fail safe for quality. This paper provides a simple and comprehensive approach that is transferable to any construction project.     

SHAPE GENERALIZED ISOTHERMAL EFFECTIVENESS FACTOR FOR FIRST-ORDER KINETICS

A generalized effectiveness factor equation (Eq. (32)), in terms of modified Bessel functions, is derived for a catalyst pellet of arbitrary shape. The derivation is based on utilizing an appropriate one-dimensional approximation for the Laplacian in an arbitrary shaped body subjected to a uniform external concentration field. The comparison of the result with the available expressions for various geometries is highly satisfactory. It unifies the expressions for the three fundamental shapes, viz., infinite slab, infinite cylinder and sphere, and also compares very well with the exact solutions for finite shapes over the entire range of the Thiele modulus.     

Accumulation and depuration of polychlorinated biphenyls from field-collected sediment in three freshwater organisms

As laboratory-based bioaccumulation methods are standardized and expanded to include other test species, kinetic studies assessing the major classes of contaminants with these species are needed to adequately select the standard duration for bioaccumulation tests. In the present study we measured the uptake (28-d exposure) of polychlorinated biphenyls (PCBs; total and selected congeners) from field-contaminated sediment in the oligochaete Lumbriculus variegatus, mayfly nymph Hexagenia spp., and fathead minnow Pimephales promelas. Depuration (25 d) of PCBs was measured in organisms that had been transferred to clean sediment after the 28-d exposure. Uptake and elimination of PCBs was rapid in L. variegatus and Hexagenia spp. Tissue residues reached steady-state concentrations within 28 d; elimination rates and biota-sediment accumulation factors (BSAFs) of the PCB congeners were not correlated with K(OW). Uptake and elimination rates of PCBs were slower in P. promelas, and it is not clear whether steady-state was reached in fish tissues. Elimination rates of the PCB congeners significantly decreased with increasing K(OW) in fish. The appropriateness of a 28-d exposure for measuring steady-state concentrations in tissue of the invertebrates was confirmed, but further study is required for fish.     

Inulin mixed esters crosslinked with 2-ethyl-hexyl-acrylate and their promotion as bio-based materials

New inulin-based materials were obtained by graft-copolymerization of inulin (poly-β(1 → 2)-fructoside) with 2-ethyl-hexyl acrylate. Inulin mixed esters were first synthesized by acylation using methacryloyl and palmitoyl chlorides. Further, these esters were copolymerized with 2-ethyl-hexyl acrylate in order to obtain bio-based crosslinked materials that could be used as commodity plastics and that would have biodegradable properties. The obtained products were characterized using FT-IR and ¹H NMR spectroscopies, thermogravimetry; differential scanning calorimetry, and activation energy for the degradation processes (using Kissinger method) was calculated. These biomaterials were also subjected to density measurement, tensile and torsion tests to evaluate their mechanical properties.     

Study of the Catalytic Activity–Semiconductive Properties Relationship For BaTiO<Subscript>3</Subscript> and PbTiO<Subscript>3</Subscript> Perovskites,Catalysts for Methane Combustion

Abstract  

The electrical conductivity of barium and lead perovskites used as catalysts for the total oxidation of methane, has been measured under nitrogen, methane–nitrogen mixture, air and methane–air mixture (reaction mixture) at the catalytic reaction temperature. The two compounds appeared to be p-type semiconductors under air with positive holes as the main charge carriers but became n-type when contacted with methane–nitrogen mixture. Their conductivities differ by 1.5 orders of magnitude as n-type semiconductors and by three orders of magnitude when being p-type semiconductors. These results explained the difference in the catalytic activity encountered on the two solids. The alkane activation was proposed to be related in both cases to the p-type semiconducting properties of the solids, likely through hydrogen abstraction by a surface O⁻ species, forming a CH₃^• radical. The overall reaction mechanism on both perovskites can be assimilated to a Mars and van Krevelen mechanism.     

Graft copolymerization studies. III. Methyl methacrylate onto polypropylene and polyethylene terephthalate

The tert‐butoxy radical‐facilitated grafting of methyl methacrylate (MMA) onto commercial polypropylene (PP) pellets and fiber was investigated in heterogeneous conditions similar to practical systems. Free‐radical grafting of several other monomers onto PP fiber was also investigated. Also, preliminary data from the grafting of MMA onto poly(ethylene terephthalate) pellets is presented. The PP‐graft‐PMMA residues were detected by solid‐state ¹³C‐NMR and photoacoustic IR spectroscopy. There was a good correlation between the degree of grafting (DG) determined from these spectroscopic techniques and the results from gravimetric methods. A maximum grafting efficiency of over 50% was found, whereas DG (20%) remained constant at various PP pellet, initiator, and monomer concentrations. However, at relatively low PP fiber concentrations, the DG was 27%; the increase was most likely due to the greater surface area of the fiber. There was also a reduction in DG (14%) at relatively low initiator concentrations. The reaction conditions were altered to favor grafting by the addition of more polymer substrate. When the ratio of tert‐butoxy radicals to PP was decreased, more of the substrate remained unmodified, and empirical calculations showed the formation of grafts with up to 40 monomer units. At high initiator concentrations, calculations showed that the graft residues were 1–2 units long. Therefore, variation of the polymer, initiator, and monomer concentrations was shown to have a significant effect on grafting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 898–915, 2002     

Controlling carbon microporosity: the structure of carbons obtained from different phenolic resin precursors

Carbons were prepared from resins synthesised using the phenolic precursors phenol, para methylphenol, para ethylphenol, para n-propylphenol, para isopropylphenol and 3,5-dimethylphenol. Loss of phenolic OH from these materials was followed using solid-state nuclear magnetic resonance. The surface areas of the carbons were determined using N₂ and CO₂ adsorption. No significant differences in the loss of phenolic OH were observed. Under the same carbonisation conditions, the para alkyl phenols gave carbons with wide micropores, while the phenol and 3,5-dimethylphenol gave carbons with narrow micropores. Grinding the cured resins prior to carbonisation was found to significantly increase the surface area of the carbons obtained, with the microporous surface area increasing rapidly with a fall in particle size, without a significant increase in burn-off. Higher carbonisation temperatures widened the micropore size distribution, as shown by fitting the CO₂ adsorption isotherm with the Dubinin-Astakhov equation. The ability to change the carbon micropore structure obtained from a simple, well defined precursor, has many potential applications in carbon molecular sieves, catalyst supports and the investigation of adsorption processes.