Influence of simultaneous addition of MnO2 and CoO on properties of SnO2-based ceramics

This paper reports on a study of the: effect of replacing CoO by MnO2 on the sintering and electrical propel-ties of the 98.95% SnO2 + (1 - x)% CoO + x% MnO2 + 0.05% Ta2O5 system. All the samples were compacted into pellets and sintered at 1300 degrees C for 1 h, when they reached densities of about 98% of the theoretical density. An X-ray diffraction (XRD) analysis showed no other detectable phases other than SnO2. Current-voltage characterization indicated varistor behavior in the systems. The non-linear coefficient (alpha) and breakdown electric field (Eb) increased as the amount of MnO2 was increased. The results are explained in terms of an electric barrier modification, due to the presence of adsorbed negative oxygen species at the grain boundary inter face. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Aquatic macrophytes of Itaipu Reservoir, Brazil: Survey of species and ecological considerations

In a survey of the aquatic macrophytes of the Itaipu Reservoir, we identified 62 taxa in 25 families and 42 genera. The highest number taxa was observed for the emergent macrophytes (40 taxa). Reduced fluctuation in water level, increased light penetration, and sediment enrichment by nutrients and organic matter following the formation of the reservoir favored the appearance of a species-rich community of submerged macrophytes (23% of the taxa identified). The aquatic macrophytes were found mainly near the mouths of the main tributaries of the reservoir, in shallow area of depth less than 2 meters. In addition to the shallow depth, the greater nutrient input from the tributaries and relative protection from wind explained this distribution. Among the species found, Egeria najas merits mention for its occurrence in all localities sampled, with biomass values varying between 98 and 186 gDW/m2. Some potential nuisance species such as Eichhornia crassipes, Salvinia auriculata, and Pistia stratiotes also deserve attention, since they were also observed to be covering large areas of Itaipu Reservoir. © 1999, Paraná Institute of Technology Publication.

A revision of species diversity in the Neotropical genus Oreobates (Anura: Strabomantidae), with the description of three new species from the Amazonian slopes of the Andes

We revisit species diversity within Oreobates (Anura: Strabomantidae) by combining molecular phylogenetic analyses of the 16S rRNA amphibian barcode fragment with the study of the external morphology of living and preserved specimens. Molecular and morphological evidence support the existence of 23 species within Oreobates, and three additional candidate species (Oreobates sp. [Ca JF809995], Oreobates sp. [Ca EU368903], Oreobates cruralis [Ca EU192295]). We describe and name three new species from the Andean humid montane forests of Departamento Cusco, southern Peru: O. amarakaeri New Species from Rio Nusinuscato and Rio Mabe, at elevations ranging from 670 to 1000 m in the Andean foothills; O. machiguenga, new species, from Rio Kimbiri (1350 m), a small tributary of the Apurimac River, in the western versant of Cordillera Vilcabamba; and O. gemcare, new species, from the Kosnipata Valley at elevations ranging from 2400 to 2800 m. The three new species are readily distinguished from all other Oreobates by at least one qualitative morphological character. Three species are transferred to Oreobates from three genera of Strabomantidae: Hypodactylus lundbergi, Pristimantis crepitans, and Phrynopus ayacucho (for which the advertisement call, coloration in life, and male characteristics are described for first time). Oreobates simmonsi is transferred to the genus Lynchius. Hylodes verrucosus is considered a junior synonym of Hylodes philippi. In addition, H. philippi is removed from the synonymy of O. quixensis and considered a nomem dubium within Hypodactylus. The inclusion of Phrynopus ayacucho in Oreobates extends the ecological range of the genus to the cold Andean puna. Oreobates is thus distributed from the Amazonian lowlands in southern Colombia to northern Argentina, reaching the Brazilian Atlantic dry forests in eastern Brazil, across an altitudinal range from ca. 100 to 3850 m.

Numerical investigation of effects of addition of ethanol to gasoline on Laminar Flame Speed (LFS), autoignition, and wall quenching

Since the advent of automobiles, alcohol has been considered a possible engine fuel1,2. With the recent increased concern about the high price of crude oil due to fluctuating supply and demand and environmental issues, interest in alcohol based fuels has increased2,3. However, using pure alcohols or blends with conventional fuels in high percentages requires changes to the engine and fuel system design2. This leads to the need for a simple and accurate conventional fuels-alcohol blends combustion models that can be used in developing parametric burn rate and knock combustion models for designing more efficient Spark Ignited (SI) engines. To contribute to this understanding, numerical simulations were performed to obtain detailed characteristics of Gasoline-Ethanol blends with respect to Laminar Flame Speed (LFS), autoignition and Flame-Wall interactions. The one-dimensional premixed flame code CHEMKIN® was applied to simulate the burning velocity and autoignition characteristics using the freely propagating model and closed homogeneous reactor model respectively. Computational Fluid Dynamics (CFD) was used to obtain detailed flow, temperature, and species fields for Flame-wall interactions. A semi-detailed validated chemical kinetic model for a gasoline surrogate fuel developed by Andrae and Head4 was used for the study of LFS and Autoignition. For the quenching study, a skeletal chemical kinetic mechanism of gasoline surrogate, having 50 species and 174 reactions was used. The surrogate fuel was defined as a mixture of pure n-heptane, isooctane, and toluene. For LFS study, the ethanol volume fraction was varied from 0 to 85%, initial pressure from 4 to 8 bar, initial temperature from 300 to 900K, and dilution from 0 to 32%. Whereas for Autoignition study, the ethanol volume fraction was varied between 0 to 85%, initial pressure was varied between 20 to 60 bar, initial temperature was varied between 800 to 1200K, and the dilution was varied between 0 to 32% at equivalence ratios of 0.5, 1.0 and 1.5 to represent the in-cylinder conditions of a SI engine. For quenching study three Ethanol blends, namely E0, E25 and E85 are described in detail at an initial pressure of 8 atm and 17 atm. Initial wall temperature was taken to be 400 K. Quenching thicknesses and heat fluxes to the wall were computed. The laminar flame speed was found to increase with ethanol concentration and temperature but decrease with pressure and dilution. The autoignition time was found to increase with ethanol concentration at lower temperatures but was found to decrease marginally at higher temperatures. The autoignition time was also found to decrease with pressure and equivalence ratio but increase with dilution. The average quenching thickness was found to decrease with an increase in Ethanol concentration in the blend. Heat flux to the wall increased with increase in ethanol percentage in the blend and at higher initial pressures. Whereas the wall heat flux decreased with an increase in dilution. Unburned Hydrocarbon (UHC) and CO % was also found to decrease with ethanol concentration in the blend.

MECHANISMS OF SPECIES DIFFERENCES IN BRAIN ACETYLCHOLINESTERASE SENSITIVITY TO ORGANOPHOSPHATE INHIBITION

In vitro incubation of acetylcholinesterase from brain tissue of several species with organophosphate compounds indicated that the concentrations required to inhibit 50% of acetylcholinesterase activity (IC(,50)) differed from species to species for the same compound (Murphy, et al., 1968; Andersen, et al., 1972, 1977 and 1978).^ The hypothesis that non-specific binding proteins (Lauwerys and Murphy, 1969a,b) exerts a protective effect on acetylcholinesterase, and thus cause the differences observed in IC(,50) studies was tested by a ('3)H-DFP binding experiment. It was found that differences in the amount of non-specific binding protein cannot explain the observed differences observed in IC(,50) studies.^ An alternative hypothesis, that acetylcholinesterase from different species have different affinities for binding and/or different rates of phosphorylation by organophosphate insecticides was tested by determining the apparent affinity constant (k(,a)) and apparent rate of phosphorylation (k(,p)). Kinetic studies indicated that acetylcholinesterases from different species have different sensitivities to inhibition by organophosphate insecticides, and the differences are due to different affinities for binding and/or different rates of phosphorylation by the same organophosphate compound.^ Studies of the spontaneous reactivation of acetylcholinesterase after inhibition by organophosphate insecticides also indicated that acetylcholinesterases from different species have different rates and extents of spontaneous reactivation. This further substantiates the hypothesis that acetylcholinesterases from different species have different kinetic characteristics with respect to organophosphate insecticides inhibition.^ Eleven paraoxon analogs were synthesized for a quantitative structure-activity relationship study. It was found that the electron-withdrawing power ((sigma)) and hydrophobicity ((PARAGR)) of the substituent are important in determining the anti-cholinesterase activity of paraoxon analogs. Thus, predictions of species differences in acetylcholinesterase sensitivities to paraoxon analogs can be made if the physicochemical parameters ((sigma) and (PARAGR)) of the substituents are known.^ In another approach, i.e. enzyme modeling, the sensitivity of rat brain acetylcholinesterase to organophosphate insecticides was used as the independent variable to predict the sensitivities of acetylcholinesterases from other species to the same compound. Regression equations were derived for each species based on nineteen organophosphate insecticides studied. It was found, that in addition to paraoxon analogs, this method is also applicable to other organophosphate compounds with wide variations in structure. Thus, the sensitivities of acetylcholinesterases from other species can also be predicted from the sensitivity of rat brain acetylcholinesterase. ^

TABLE 2. - List of species of Garamaridea and Corophiidea collected in southern Tierra del Fuego

Species richness and faunistic affinities of gammaridean and corophiidean amphipods from southern Tierra del Fuego were studied. The material was collected with dredges and grabs at 7 locations (15 sampling stations) in a range of 5 to 35 m depth. A total of 61 species belonging to 20 families and 43 genera were identified. The genera Cephalophoxoides, Ceradocopsis and Photis are reported for the first time from the Magellan region and 3 species belonging to Atyhts, hchyrocerus and Photis appear to be new to science. Most of the species collected belong to Phoxocephalidae, whereas most individuals were contained in the Stenothoidae and Lysianassidae s.l. The analysis of the faunistic affinities showed that 16 species (39%) are endemic to the Magellan region, 9 species (22%) extend to the south, 5 species (12.2%) to the north and 5 other species (12.2%) to both the north and south. In addition, 6 species extend beyond the Magellan region as far as Oceania.

Apoptosis is induced in Chlamydia trachomatis infected HEp-2 cells by the addition of a combination innate immune activation compounds and the inhibitor wedelolactone

Problem: Innate immune activation of human cells, for some intracellular pathogens, is advantageous for vacuole morphology and pathogenic viability. It is unknown whether innate immune activation is advantageous to Chlamydia trachomatis viability. ----- ----- Method of study: Innate immune activation of HEp-2 cells during Chlamydia infection was conducted using lipopolysaccharide (LPS), polyI:C, and wedelolactone (innate immune inhibitor) to investigate the impact of these conditions on viability of Chlamydia. ----- ----- Results: The addition of LPS and polyI:C to stimulate activation of the two distinct innate immune pathways (nuclear factor kappa beta and interferon regulatory factor) had no impact on the viability of Chlamydia. However, when compounds targeting either pathway were added in combination with the specific innate immune inhibitor (wedelolactone) a major impact on Chlamydia viability was observed. This impact was found to be due to the induction of apoptosis of the HEp-2 cells under these conditions. ----- ----- Conclusion: This is the first time that induction of apoptosis has been reported in C. trachomatis-infected cells when treated with a combination of innate immune activators and wedelolactone.

A novel cyclization product from the polyphosphoric acid catalyzed addition of propanal to limonene

The polyphosphoric acid catalyzed addition of propanal to limonene yielded a novel bicyclic ether 2,2,6-trimethyl-4-ethyl-3-oxabicyclo[3.3.1]non-6-ene (I). The yield of (I) was significantly increased by carrying out the reaction under nitrogen rather than in air.

Does the addition of integrated cognitive behaviour therapy and motivational interviewing improve the outcomes of standard care for young people with comorbid depression and substance misuse?

Background: The high rates of comorbid depression and substance use in young people have been associated with a range of adverse outcomes. Yet, few treatment studies have been conducted with this population. Objective: To determine if the addition of Motivational Interviewing and Cognitive Behaviour Therapy (MI/CBT) to standard alcohol and other drug (AOD) care improves the outcomes of young people with comorbid depression and substance use. Participants and Setting: Participants comprised 88 young people with comorbid depression (Kessler 10 score of > 17) and substance use (mainly alcohol/cannabis) seeking treatment at two youth AOD services in Melbourne, Australia. Sixty young people received MI/CBT in addition to standard care (SC) and 28 received SC alone. Outcomes Measures: Primary outcome measures were depressive symptoms and drug and alcohol use in the past month. Assessments were conducted at baseline, 3 and 6 months follow up. Results and Conclusions: The addition of MI/CBT to SC was associated with a significantly greater rate of change in depression, cannabis use, motivation to change substance use and social contact in the first 3 months. However, those who received SC had achieved similar improvements on these variables by 6 months follow up. All young people achieved significant improvements in functioning and quality of life variables over time, regardless of the treatment group. No changes in alcohol or other drug use were found in either group. The delivery of MI/CBT in addition to standard AOD care may offer accelerated treatment gains in the short-term.

Increased charge transfer of Poly (ethylene oxide) based electrolyte by addition of small molecule and its application in dye-sensitized solar cells

A Poly (ethylene oxide) based polymer electrolyte impregnated with 2-Mercapto benzimidazole was comprehensively characterized by XRD, UV–visible spectroscopy, FTIR as well as electrochemical impedance spectroscopy. It was found that the crystallization of PEO was dramatically reduced and the ionic conductivity of the electrolyte was increased 4.5 fold by addition of 2-Mercapto benzimidazole. UV–visible and FTIR spectroscopes indicated the formation of charge transfer complex between 2-Mercapto benzimidazole and iodine of the electrolyte. Dye-sensitized solar cells with the polymer electrolytes were assembled. It was found that both the photocurrent density and photovoltage were enhanced with respect to the DSC without 2-Mercapto benzimidazole, leading to a 60% increase of the performance of the cell.

Addition of diazomethane to armchair single-walled carbon nanotubes and their reaction sequences : A computational study

The sidewall additions of diazomethane to (n, n), n = 3–10 armchair single-walled carbon nanotubes (SWCNTs) on two different orientations of C–C bonds have been studied using the ONIOM(B3LYP/6-31G(d):PM3) approach. The binding energies of SWCNTs complexes with CH2N2, CH2 and their transition-state structures were computed at the B3LYP/6-31G(d) level. The effects of diameters of armchair SWCNTs on their binding energies were studied. Relative reactivities of all the SWCNTs and their complexes based on their frontier orbital energies gaps are reported.

The formation of gold nanoparticles using hydroquinone as a reducing agent through a localized pH change upon addition of NaOH to a solution of HAuCl4

We demonstrate a rapid synthesis of gold nanoparticles using hydroquinone as a reducing agent under acidic conditions without the need for precursor seed particles. The nanoparticle formation process is facilitated by the addition of NaOH to a solution containing HAuCl4 and hydroquinone to locally change the pH; this enhances the reducing capability of hydroquinone to form gold nucleation centres, after which further growth of gold can take place through an autocatalytic mechanism. The stability of the nanoparticles is highly dependent on the initial solution pH, and both the concentration of added NaOH and hydroquinone present in solution. The gold nanoparticles were characterized by UV–visible spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy, dynamic light scattering, and zeta potential measurements. It was found that under optimal conditions that stable aqueous suspensions of 20 nm diameter nanoparticles can be achieved where benzoquinone, the oxidized product of hydroquinone, acts as a capping agent preventing nanoparticles aggregation.

Designing mixed species tree plantations for the tropics : balancing ecological attributes of species with landholder preferences in the Philippines

A mixed species reforestation program known as the Rainforestation Farming system was undertaken in the Philippines to develop forms of farm forestry more suitable for smallholders than the simple monocultural plantations commonly used then. In this study, we describe the subsequent changes in stand structure and floristic composition of these plantations in order to learn from the experience and develop improved prescriptions for reforestation systems likely to be attractive to smallholders. We investigated stands aged from 6 to 11 years old on three successive occasions over a 6 year period. We found the number of species originally present in the plots as trees >5 cm dbh decreased from an initial total of 76 species to 65 species at the end of study period. But, at the same time, some new species reached the size class threshold and were recruited into the canopy layer. There was a substantial decline in tree density from an estimated stocking of about 5000 trees per ha at the time of planting to 1380 trees per ha at the time of the first measurement; the density declined by a further 4.9% per year. Changes in composition and stand structure were indicated by a marked shift in the Importance Value Index of species. Over six years, shade-intolerant species became less important and the native shade-tolerant species (often Dipterocarps) increased in importance. Based on how the Rainforestation Farming plantations developed in these early years, we suggest that mixed-species plantations elsewhere in the humid tropics should be around 1000 trees per ha or less, that the proportion of fast growing (and hence early maturing) trees should be about 30–40% of this initial density and that any fruit tree component should only be planted on the plantation margin where more light and space are available for crowns to develop.

Greenhouse gas emissions from sub-tropical agricultural soils after addition of organic by-products

As the cost of mineral fertilisers increases globally, organic soil amendments (OAs) from agricultural sources are increasingly being used as substitutes for nitrogen. However, the impact of OAs on the production of greenhouse gases (CO2 and N2O) is not well understood. A 60-day laboratory incubation experiment was conducted to investigate the impacts of applying OAs (equivalent to 296 kg N ha−1 on average) on N2O and CO2 emissions and soil properties of clay and sandy loam soils from sugar cane production. The experiment included 6 treatments, one being an un-amended (UN) control with addition of five OAs being raw mill mud (MM), composted mill mud (CM), high N compost (HC), rice husk biochar (RB), and raw mill mud plus rice husk biochar (MB). These OAs were incubated at 60, 75 and 90% water-filled pore space (WFPS) at 25°C with urea (equivalent to 200 kg N ha−1) added to the soils thirty days after the incubation commenced. Results showed WFPS did not influence CO2 emissions over the 60 days but the magnitude of emissions as a proportion of C applied was RB < CM < MB < HC of the dry matter and C/N ratio of the OAs, WFPS, and the soil CEC. Application of RB reduced N2O emissions by as much as 42-64% depending on WFPS. The reductions in both CO2 and N2O emissions after application of RB were due to a reduced bioavailability of C and not immobilisation of N. These findings show that the effect of OAs on soil GHG emissions can vary substantially depending on their chemical properties. OAs with a high availability of labile C and N can lead to elevated emissions of CO2 and N2O, while rice husk biochar showed potential in reducing overall soil GHG emissions.