Search

The undoped and Cr doping ZnS nanostructures have been synthesized using the solvothermal methods. X-ray diffraction measurements indicate that undoped and Cr doping ZnS nanosheet exhibit a wurtzite structure. The nanosheets have rule morphologies, with a thickness of approximately 30–80 nm, a width of 150–300 nm, and a length of 170–470 nm. The results of component analysis indicated that the sample contained Cd, S and Cr. The optical characteristic of undoped ZnS nanosheet is investigated using UV-Visible spectroscopy. From the magnetic research, it can be observed that undoped ZnS nanosheet displays diamagnetism at room temperature, while Cr doping ZnS nanosheet displays ferromagnetism. Spontaneous magnetization ($M_s$Ms) of Cr doping ZnS nanosheet (Cr = 8.35at%) is roughly 8.961 (10−3emu/g), and coercivity ($H_c$Hc) is roughly 90.554Oe. Ferromagnetism of Cr-doping ZnS nanosheet may be induced by the dual exchange mechanism principle. [ABSTRACT FROM AUTHOR]

This paper presents a compact dual-band reconfigurable antenna. This antenna covers the Long-Term Evolution (LTE) bands 1.9 GHz, 2.4 GHz, and 3 GHz. The reconfigurability was achieved with two PIN-diodes which provided four switching states. Both frequency and radiation characteristics have consistent results. The antenna gain was evaluated at every switching state. Results from the simulation and measurements have good agreement. [ABSTRACT FROM AUTHOR]

In this study, the effect of Cr content on microstructure, mechanical properties and corrosion behaviour of Ti6Al4V alloy produced by selective laser melting (SLM) was investigated. The microstructure exhibited that α' martensite and β phase are obtained in SLM processed Ti6Al4V alloy and Ti6Al4V-Cr system alloys. The increment of Cr content results in the increment of β phase amount. The effect of Cr on the compressive strength and plastic deformation of Ti6Al4V alloy was evaluated by a compression test. The results indicate that the Ti6Al4V+5Cr alloy has a higher compressive strength and superior plastic deformation than that of the SLM processed Ti6Al4V alloy under optimum printing parameters. Meanwhile, the Ti6Al4V+8Cr alloy possesses the best plastic deformation and corrosion resistance. The Ti6Al4V-Cr system alloys, due to the combination of good mechanical properties and corrosion resistant, can be potentially applied in automotive, naval architecture and offshore facility manufacturing. [ABSTRACT FROM AUTHOR]

In the present study, an attempt has been made to utilise spent alumina catalyst (SAC) and carbonised eggshell (CAES) in the fabrication of AA5052-based composite material. Cr was also added to further enhance the tensile strength, hardness and corrosion resistance of the material. Results showed that by adding 4.5% SAC, 4.5% CAES and 1.5% Cr in aluminium alloy, mechanical properties such as tensile strength, hardness and compressive strength enhanced significantly. Tensile strength, hardness and compressive strength increased by about 11.98%, 37.22% and 23.06%, respectively, concerning the base material. However, the toughness and ductility of composite have been reduced. Microstructure results of Al/4.5% SAC/4.5% CAES/1.5% Cr composite showed uniform. Corrosion weight loss and thermal expansion behaviour of composite have been also investigated to observe the SAC, CAES and Cr addition effect in the aluminium alloy. [ABSTRACT FROM AUTHOR]

Chrome-tanned leather shavings (CTLS) are a type of solid waste generated from the leather industry. In this study, the pyrolysis experiment of CTLS was conducted in a high-temperature tubular furnace reactor at different temperatures. The results showed that the pyrolysis temperature highly affected the product yields. The tar generated from the CTLS pyrolysis presented a wide distribution of pyrolytic compounds, and nitrogenated derivatives were the major group. The scanning electronic microscopy (SEM) investigation showed that a continuous structure of irregular but rather uniformly distributed interconnected pores of the chars. Cr was found to exist in the char as its reduced state (Cr3+). This study provided basic data for the determination of pyrolysis temperatures of CTLS targeting different products. [ABSTRACT FROM AUTHOR]

The present study investigated the phytoremediation of simulated wastewater, mimicking wastewater generated by industrial processes containing significant amounts of toxic heavy metal ions. The wetland plant Ludwigia stolonifera was used to study its efficiency in the removal of the three toxic metals Pb, Cd and Cr. Survivability of the plant has been studied in solutions at different concentrations of three metals separately or as a mixture, and the accumulation of these toxic metals for a prolonged period has been evaluated. The plant performed very successful in eliminating Cd, Cr and Pb as single metals of up to 65%, 97% and 99%, respectively, within four days. In addition, the trend of metal uptake revealed negligible dependence on different masses of plant and on various pH-values. L. stolonifera has high potential in eliminating various toxic pollutants from aquatic environments. [ABSTRACT FROM AUTHOR]

Nimonic C-263 superalloy offers a wide range of outstanding properties, namely, high-temperature resistance, high specific strength, high thermal fatigue, and hot corrosion resistance. The concern of the present study is mainly focused on the effect of wire electrical discharge machining (WEDM) process parameters namely, spark energy, spark frequency, and peak current on surface roughness, average cutting rate, and surface integrity aspects of Nimonic C-263 superalloy by using one-parameter-at-a-time (OPAT) approach. Surface roughness and average cutting rate were showing the increasing trend with the spark energy and peak current and reverse trend with the spark frequency. Surface integrity aspects of Nimonic C-263 such as surface topography, surface morphology, recast layer thickness, elemental composition, and phase analysis have been also considered in this study. Scanning electron microscope (SEM) micrograph of the machined surface shows the presence of micro-voids, discharge craters, micro-globules, and droplets of molten material. A recast layer of minimum thickness, with less transfer of foreign atoms (Mo, C, and O) from dielectric fluid and molybdenum wire, has been formed at lower spark energy compared to higher spark energy. The various compounds of Ni, Fe, Al, and Ti such as Fe1.2Ni0.8, Fe1.5Ni0.5, Co0.06Fe0.94, and Alo.29Ni0.27Ti0.44 were formed on the machined surface identified through analysis of XRD peaks. [ABSTRACT FROM AUTHOR]

Microbial transformation of sulfate minerals plays an important role in controlling the behavior of heavy metals in mining areas. Here, the anaerobic reduction of Cr (VI)-loaded schwertmannite by Shewanella oneidensis MR-1 (S. oneidensis MR-1) was investigated. The release of ferrous iron (Fe(II)) to the solution demonstrated the microbial reduction of structural Fe(III) from the schwertmannite to Fe(II). The concentration of Cr in solution decreased in all treatments, indicating that no Cr was released to the solution during this bio-reduction process of schwertmannite. The incorporation of chromate into the mineral structure of schwertmannite increased the microbial stability of the mineral, retarding the formation of secondary phases during bio-reduction process. Analysis of the XRD, SEM and fourier transform infrared spectroscopy (FT-IR) results further showed that goethite formed after 3 or 7 days with a lower content (0.22% or 0.37%) of Cr in schwertmannite, while no secondary mineral was observed with a higher concentration of Cr (0.6 wt%) incorporated in schwertmannite until 22 days. These results imply that microbial reduction of Cr(VI)-loaded schwertmannite does not lead to the release of Cr to the solution, and the microbial stability of schwertmannite will be increased by the incorporation of chromate. [ABSTRACT FROM AUTHOR]

The microstructure of high-temperature metals such as Ti, Ni, and Cr can be modified using ceramic nanoparticles to form metal matrix nanocomposites (MMNCs). Such materials are generally prepared via powder metallurgy routes. In this study, 25 wt% SiCnpand Al2O3npwere separately ball milled as a reinforcement of Ti, Cr, and Ni matrices to investigate their effects on the phase formation and morphology of the MMNCs. The x-ray diffraction (XRD), scanning electron microscopy (SEM), and field emission scanning electron microscopy (FESEM) results indicated that the alumina–metal system could not be thermodynamically stable in a high-energy ball mill, while the SiC reinforcement could be retained and milled with the metals even after 24 h. It was further observed that the distribution of nanoparticles was not affected by the type of metal, ceramic, and milling time. Finally, it was determined that the nanoparticles significantly reduced the average particle size of composite powders. [ABSTRACT FROM PUBLISHER]

Background: Various uses of metals in industries, including the domestic sphere, agriculture, medicine and technology, have led to their wide distribution in the environment. These result in raising concerns over their potential effects on human health and the environment. Because of their high degree of toxicity, Cd, Cr and Pb are some of the priority metals that are of public health significance. The levels of Cd, Cr, Pb and Ni were measured in Parkinson's disease (PD) patients.Methods: Blood samples were collected from 40 patients and 40 healthy controls, and stored at −80 °C until assayed. Atomic absorption spectrophotometry was used to determine the levels of metals.Results: The level of Pb was significantly decreased in patients than in controls. However, the difference in the level of Ni between patients and controls failed to reach significance. Cr was not detectable in patients, but it was measurable in 12 controls (controls = 0.056–2.397 µg/ml). Similarly, Cd was not detectable in patients, but it was measurable in all the controls (controls = 0.004–1.268 µg/ml). Pb was the only metal that was found in all study participants (PD = 0.012–2.758 µg/ml and controls = 0.779–9.840 µg/ml). Ni could be measured only in six patients and in all the controls (PD = 0.154–0.754 µg/ml and controls = 0.034–1.691 µg/ml).Conclusion: Patients exhibited significantly decreased levels of Pb than in controls. However, Cd, Cr and Ni were too low to be measured among the patients. This indicates that these metals might play a probable role in PD. [ABSTRACT FROM PUBLISHER]

According to the experimental researches of dynamic friction polishing (DFP) technology, high density and hardness W–Mo–Cr alloy with strong graphitization ability of diamond can achieve a high material removal rate of diamond. In the preparation process of polishing plate, mechanical alloying (MA) method is used to synthetize pre-alloying powders by means of fierce mechanical action and supersaturated solid state reaction performed by high-energy ball milling. The effect and progress of MA are directly affected by the process parameters of ball milling. This article mainly summarizes the microstructural changes of W–Mo–Cr pre-alloying powders varying with milling time and process control agent (PCA) content, and their function mechanisms and potential causes are discussed. The reasonable process parameters of ball milling are optimized by single-factor experiments. The results show that under the conditions of 300 rpm rotation speed, 60 h milling time, and 10% PCA content, the surface activities, compositional uniformity, and grain refinement level of powders are heightened. The preparation of excellent pre-alloying powders provides early technical guarantee for the study of high density tungsten-based alloy used for DFP diamond. [ABSTRACT FROM AUTHOR]

Molten carbonate has high energy potential, which can be used as a source of energy in industrial applications. In this study, the anode of a molten carbonate fuel cell is synthesized and characterized. Three different types of anode materials for molten carbonate are synthesized using tape-casting method. These materials are nickel, nickels–chrome tape including 5% chrome, and nickels–chrome tape including 10% chrome. After that, all anodes were plated with alumina by an impregnation method. Surface areas of these different anodes and their porosities were determined. It was observed that plating with alumina improved the surface areas of molten carbonate fuel cell anodes. [ABSTRACT FROM PUBLISHER]

The use of tannery sludge in arid soils could be promising due to the high content of organic carbon and nitrogen. However, tannery waste also contains high amounts of Cr and salts that could leach into drainage water in response to rainfall. In order to study the effects of two tannery wastes as organic fertilizers on two types of semi-arid soils, simulated rainfall experiments were carried out. Soils collected from under and outside a mesquite tree canopy were amended with fleshing waste and/or tannery sludge and incubated 0 to 6 months prior to being subjected to simulated rainfall. The parameters measured were: infiltration, runoff, soil and Cr losses, and NH4+-N and NO3−-N released after a rainfall event. Results showed that fleshing waste added to soils from outside the canopy tree was the most effective treatment for decreasing runoff, soil losses, and Cr, NH4+-N and NO3−-N loss in runoff and infiltration, in general. However, the same treatment had the opposite results for soil under the canopy. These results indicate that the types of waste and soil must be taken into consideration when attempting to improve physical and chemical characteristics of semi-arid soils. Thus, the use of tannery waste represents a potential hazard, not only causing soil erosion but also Cr contamination in adjacent sites and aquifers. [ABSTRACT FROM AUTHOR]

CrN monolayers along with CrN/SiC and CrN/diamond-like carbon (DLC) duplex layers were deposited by arc plasma acceleration on 4340 steel substrates. The layers exhibit a dense microstructure with a low density of surface defects and macroparticles. The tribological properties were evaluated with dry ball-on-disk sliding tests against an alumina counterface at room temperature. The CrN monolayer exhibits a coefficient of friction, µ = 0.28 ± 0.02, while CrN/SiC and CrN/DLC duplex layers both demonstrate much lower µ = 0.07 ± 0.01. The wear rates of the coatings were very low and measured as 0.53, 0.73, and 0.79 µm3/Nm, respectively, for CrN, CrN/DLC, and CrN/SiC. Corrosion resistance was evaluated in both cyclical environmental testing as well as quantitatively via electrochemical impedance spectroscopy. The corrosion resistance in both cases is compared to standard electroless Ni and electroplated Cr coatings. The highest level of corrosion resistance was observed for the CrN monolayer and CrN/SiC duplex layer. Both exhibit improved corrosion resistance over electroless Ni and electroplated Cr coatings. This high level of corrosion resistance is remarkable for physical vapor deposited thin nitride layers. The arc plasma acceleration deposited materials show great promise for applications in which a combination of low friction, wear resistance, and corrosion resistance are required. [ABSTRACT FROM AUTHOR]

As a low-cost treatment technology for effluent, the constructed wetlands can be applied to remove the heavy metals from wastewater.Leersia hexandraSwartz is a metal-accumulating hygrophyte with great potential to remove heavy metal from water. In this study, two pilot-scale constructed wetlands planted withL. hexandra(CWL) were set up in greenhouse to treat electroplating wastewater containing Cr, Cu and Ni. The treatment performance of CWL under different hydraulic loading rates (HLR) and initial metal concentrations were also evaluated. The results showed that CWL significantly reduced the concentrations of Cr, Cu and Ni in wastewater by 84.4%, 97.1% and 94.3%, respectively. High HLR decreased the removal efficiencies of Cr, Cu and Ni; however, the heavy metal concentrations in effluent met Emission Standard of Pollutants for Electroplating in China (ESPE) at HLR less than 0.3 m3/m2d. For the influent of 5 mg/L Cr, 10 mg/L Cu and 8 mg/L Ni, effluent concentrations were below maximum allowable concentrations in ESPE, indicating that the removal of Cr, Cu and Ni by CWL was feasible at considerably high influent metal concentrations. Mass balance showed that the primary sink for the retention of contaminants within the constructed wetland system was the sediment, which accounted for 59.5%, 83.5%, and 73.9% of the Cr, Cu and Ni, respectively. The data from the pilot wetlands support the view that CWL could be used to successfully remove Cr, Cu and Ni from electroplating wastewater. [ABSTRACT FROM PUBLISHER]

This research paper deals with Static Random Access Memory (SRAM) design opportunities for low power consumption. Initially, four leakage current components are reviewed. Subsequently, some leakage current reduction techniques are discussed for a 6T SRAM cell. Based upon the configurations, a double fingered latch is analyzed and compared with a single finger latch that exhibits significant reduction in sub threshold leakage current. In this paper, the reduction of sub threshold leakage currents are demonstrated up to 12160 nA for 64K byte memory. [ABSTRACT FROM AUTHOR]

Vanadium phosphorus oxide (VPO) catalysts synthesized via hydrothermal method were introduced with some different dopants, Cr, Ni, Fe, and Mn during the preparation of the precursors, VOHPO4 · 0.5H2O. All modified precursors were subsequently transformed under reaction conditions to give the active phase, (VO)2P2O7. Several techniques were used to characterize the physicochemical properties of the catalysts, such as X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), H2-temperature programmed reduction (TPR), laser Raman spectroscopy (LRS), and chemical analysis. The catalytic performance of the catalysts for selective oxidation of n-butane to maleic anhydride has been carried out by using a fixed bed microreactor (673 K, gas hourly space velocity [GHSV] = 2,400 hr-1). The results show that the addition of dopants into the VPO catalysts increased the surface area of the catalysts and induced the formation of V5+ phases as shown in XRD and LRS spectra that promoted the catalytic performance. A further water reflux treatment to all the precursors gave catalysts with only (VO)2P2O7 phase. However, the activity and selectivity of these catalysts were reduced markedly. [ABSTRACT FROM AUTHOR]

Phytoremediation is an emerging technology where specially selected and engineered metal-accumulating plants are used for bioremediation. This study was undertaken to evaluate the potential of Amaranthus dubius for phytoremediation of chromium (Cr), mercury (Hg), arsenic (As), lead (Pb), copper (Cu) and nickel (Ni). Locally gathered soil and plants of A. dubius were investigated for the metals from a regularly cultivated area, a landfill site and a waste water treatment site. Metals were extracted from the samples using microwave-digestion and analyzed using Inductively Coupled Plasma-Mass Spectroscopy. The mode of phytoremediation, effect of the metals on the plants, ability of the plant to extract metals from soil (Bioconcentration Factor) and the ability of the plants to move the metals to the aerial parts of the plants (Translocation Factor) were evaluated. The survey of the three sites showed that soils were heavily contaminated with Cr, Hg, Cu and Ni. These levels were far above acceptable standards set for soils and above the standards set for the Recommended Dietary Allowance. Specimens of A. dubius from the three sites showed that they could tolerate Hg, sequester it from the soil, and translocate it to the shoots. Cr could only be removed from the soil and stored in the roots, with limited amounts translocated to the aerial parts. Pb, As, Ni, and Cu have some degree of transportability from the soil to the roots but not to aerial parts. The ability of A. dubius to be considered for phytoremediation has to be viewed with caution because translocation of the metals to the aerial parts of the plant is limited. [ABSTRACT FROM AUTHOR]

A pot experiment was set up in 1999 for examining the effect of sewage sludge loads on soils and plants. Four soils were used. Soils can be classified as the following: Őrbottyan, calcareous sandy soil; Nagyhorcsok, calcareous silty soil; Gyongyos, acidic silty soil; and Nyirlugos, acidic sandy soil. Applied sewage sludge loads were 0, 2.5, 5, 10, and 20 g sludge DM/kg air-dry soil. From the soil samples, total recoverable [cc. nitric acid (HNO3) + hydrogen peroxide (H2O2) digestion], extractable [0.5 M ammonium acetate + 0.02 M ethylenediaminetetraacetic acid (EDTA)-extractable], and the mobile [1 M ammonium nitrate (NH4NO3)-extractable] elemental concentrations were measured. There was an increase in all of three fractions after sewage sludge application for both cadmium (Cd) and chromium (Cr); the extent of changes was varied. To quantify the Cd and Cr response to sewage sludge loads, sewage sludge loads vs. elemental concentration functions were plotted, and the slope of these functions means sensitivity of soils in the given fraction. After examining the sensitivity of four soils in the three fractions for elements investigated, it can be stated that the most sensitive fraction was the total recoverable fraction. The ammonium acetate + EDTA-extractable fraction has the second greatest sensitivity, whereas NH4NO3 extraction was a good indicator for treatments only on sandy soils. However, the strongest correlation was found between mobile Cd and Cr and the plant element uptake. So there is an obvious contradiction: the fraction that is less sensitive to sewage sludge treatments has the strongest correlation with plant uptake. [ABSTRACT FROM AUTHOR]

Heavy metals present in electronic components may leach upon disposal and therefore pose significant environmental hazards. The potential leaching of Pb, Cd, Cr and Ag from PC cathode ray tubes, printed circuit boards (PCBs), PC mice, TV remote controls, and mobile phones was assessed. After controlled crushing, each component was extracted using the Toxicity Characteristic Leaching Procedure (TCLP), EPA Method 1312 (SPLP), NEN 7371 (Dutch Environmental Agency), and DIN S4 (Germany). The TCLP consistently leached the greatest amounts of Pb from all components. The SPLP, NEN 7371 and DIN S4 extracted relatively small amounts of metals compared with the TCLP and were not considered effective as leaching tests for e-waste. The smallest size fraction (< 2 mm) of CRT glass and PCBs leached significantly (p < 0.05) highest Pb via the TCLP. A modified TCLP removed 50.9% more extractable Pb compared with the conventional procedure. [ABSTRACT FROM AUTHOR]

Abstract: The industrial activity areas, rivers, and water sources in neighboring areas are influenced by wastewater of manufacturers. Utilizing water influenced by wastewater increased heavy metals in soils and plants. In 2004, to investigate the effects of wastewater on cadmium (Cd), nickel (Ni), chromium (Cr), and lead (Pb) content in soil and plants, wastewaters of three manufactures (chrome chemical, wood and paper, and textiles) were examined. At harvest time roots, whole shoots (rice, spinach, clover, grass), and rice grain in industrial wastewater-influenced areas and uninfluenced areas were sampled. Soil samples were also taken (0-15, 15-30 cm). Results indicated that when wastewater was discharged into the river water, the concentrations of Cd, Ni, Cr, and Pb increased in river water. Application of river water influenced by industrial wastewater for irrigation of rice and another plants enhanced, the amounts of available Cd, Ni, Cr and Pb in soil. In subsurface horizons (15-30 cm), the concentrations of heavy metals were more than in the surface horizon (0-15 cm). With increasing cation exchange capacity in the soil, the amount of available Cr increased. When the calcium carbonate content in soils was raised, the available Cd and Pb increased in the soil, but Ni and Cr decreased. Meanwhile, organic matter enhanced the concentrations of heavy metals in soil. Accumulations of heavy metals were higher in the roots of rice (control and treatment) than in shoot and rice grain. Cadmium accumulation in rice root was three times that in whole shoot, and grain was two times more than control. The concentrations of Ni, Cr, and Pb in root, whole shoot, and grain of rice were two times higher in industrial wastewater-treated areas. The concentrations of heavy metals in root and whole shoot of spinach, clover, and grass in industrial wastewater area increased about 100%, but not to a toxic level. Cadmium translocated more than other heavy metals from soil to root, whole shoot, and grain of rice, and whole shoot of spinach, clover, and grass. [ABSTRACT FROM AUTHOR]

The graft copolymerization of acrylic acid (AA) onto styrene butadiene rubber (SBR) was carried out in toluene at 80°C using benzoyl peroxide (BPO) as initiator. The synthesized styrene butadiene rubber-g-acrylic acid (SBR-g-AA) was characterized with Raman IR spectroscopy. A study was conducted on the use of SBR-g-AA for improving the homogeneity of styrene butadiene rubber/chloroprene rubber (SBR/CR) blend. The SBR-g-AA was incorporated into SBR/CR blend with different blend ratios. The homogeneity of such blends was examined with scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and determination of the dielectric properties. The scanning electron micrographs illustrate improvement of the morphology of SBR/CR rubber blend as a result of the incorporation of SBR-g-AA onto that blend. Also, the dielectric constant (permittivity) and the dielectric loss plots versus the SBR/CR blend ratio show straight lines upon incorporation SBR-g-AA, indicating and confirming the homogeneity of that blend. Physico-mechanical properties of the blend vulcanizates, in presence and absence of SBR-g-AA, were determined, and their thermal stability was evaluated after accelerated thermal aging. The results reveal that SBR/CR (25/75) blend possesses the best thermal stability. Swelling behavior in toluene, in motor oil, and in brake fluid of the blend vulcanizates was also assessed. [ABSTRACT FROM AUTHOR]

The bioavailability of heavy metals, and thus their possible harmful impact on ecosystems and humans, depends on metal partitioning. This study describes the chemical partitioning of iron, manganese, zinc and chromium, because the potential effect of soil contamination is better assessed through the knowledge of the forms in which a given metal is present rather than the use of its total concentration. In four soil types representative of mountain soils in the Iberian and Pyrenean ranges in Aragón, a total of 16 selected sites have been sampled and five subsamples were taken in each site to create a composite sample. The 4 heavy metals have been extracted by the sequential extraction procedure of Tessier et al. (1979) and analyzed by emission atomic spectrometry of solid state (ICP OES). Little Fe, Mn and Zn ( [ABSTRACT FROM AUTHOR]

This study investigates the precipitation of Fe containing intermetallic compounds in A413 aluminium alloy in the Cr- and Co-modified conditions. The Fe content varied from 0.5 to 2.5 wt-%. For each amount of Fe, different levels of Cr and Co were added to identify the optimum Fe:Cr and Fe:Co ratios to eliminate the β-phase and obtain microstructures containing well distributed fine intermetallic α-phase in dendritic or Chinese script morphology. It was found that the addition of Cr and Co changes the morphology of Fe rich intermetallic compounds from the harmful plate like β-phase to a less damaging morphology. The critical ratios were Fe:Cr=3.0 and Fe:Co=1.0 approximately. In addition, it was noted that the addition of Cr or Co promotes the formation of primary Si. The results suggest that the presence and the form of all precipitates (both Fe rich and primary Si) seem to be strongly related to the presence of bifilms (doubled over oxide films) suspended in the liquid alloy. [ABSTRACT FROM AUTHOR]

A technologically feasible process called bioleaching was used to remove Cr from tannery sludge with Acidithiobacilli TS6 bacteria in this study. The buffering capacity of tannery sludge and municipal sewage sludge were compared. The effects of initial sulfuric acid addition on bioleaching process and influences of recycle rate of acidified bioleached sludge on subsequent bioleaching reaction were examined. The quantities of initial sulfuric acid addition ranged from 0 to 0.185 ml g-1 dry sludge. Recycle rate(Vbioleached/Vtotal) was controlled at 1/3, 1/2, 3/5 and 2/3. We found that tannery sludge had a higher buffering capacity than sewage sludge. The results showed that there was an increase in the rates of pH reduction and Cr solubilization with the increase of initial sulfuric acid addition. The suitable quantity of sulfuric acid addition was 0.185 ml g-1 dry sludge at the beginning of the first bioleaching process. After 10 days of bioleaching, pH reached 1.5 and almost 100% of Cr could be leached in this case. Besides, an evidently dividing point pH 2.0 was found to be the threshold value for considerable Cr solubilization during the leaching reaction. Recycle experiments confirmed that the application of the method by recycling acidified sludge to launch subsequent bioleaching is feasible. The optimal recycle rate of acidified sludge for consecutive leaching of Cr from tannery sludge is 2/3. [ABSTRACT FROM AUTHOR]

Non-Hodgkin's lymphoma is an AIDS-defining disease. The impact of HAART on the epidemiology and prognosis is debated controversially. A retrospective analysis has been performed in order to determine the influence of HAART. We collected data of 214 cases of AIDS-related Lymphoma (ARL) treated at our centre from January 1984 until May 2003 and analysed them using the Kaplan-Meier-, log rank- and Cox proportional hazard-model. The incidence of ARL increased between 1991 and 1994 up to a peak of 14.83 per 1000 patient years. In the subsequent periods from 1995 onwards however, it decreased to 3.7 in 1000 patient years. The incidence of AIDS-related primary CNS lymphomas (PCNSL) took a comparable, yet more pronounced development. Using the univariate Kaplan-Meier analysis prolonged survival was significantly associated with the achievement of a complete remission as well as with a favourable virological response to HAART. No significant differences could be shown for the use of protease inhibitors as well as for virological response being achieved before the diagnosis of NHL. When using the Cox model, complete remission overrides viral response and thus remained the only independent prognostic factor. Classical prognostic factors (CD4 count, prior Kaposi Sarcoma, extranodal manifestation, staging and histological subtype of NHL) were no longer significant for HAART patients in the multivariate analysis. These results illustrate the requirement for new prospective studies in order to determine the best options and ideal timing of coadministering chemotherapy and the type of HAART. Furthermore this study demonstrates that HAART decreases the incidence of ARL, and that achievement of a complete remission in patients suffering from ARL is--according to the multivariate analysis--the single most important prognostically relevant factor with respect to the time of survival. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL), thermally stimulated luminescence (TSL), and photosensitivity of SrTiO3 and Cd2Nb2O7 crystals with Mn4+ and Cr3+ spectroscopic probes, respectively, were studied. Manganese doping of SrTiO3 results in structured luminescence of Mn4+ consisting of narrow zero-phonon (ZPL) R-line (²E → 4A2) and vibrational sidebands. It is suggested that unusually large temperature shift of ZPL is caused mainly by the contribution of the lowest TO soft optical branch into interaction of emitting center with a lattice. The PL spectrum of Cd2Nb2O7:Cr3+ consists of four narrow emission lines accompanied by vibrational sidebands. Emission lines are attributed to the zero-phonon transitions ²E → 4A2 of two kinds of octahedral coordinated Cr3+ centers. The change in activation energies of PL thermal quenching at Tc = 196 K is tentatively explained by a change of the adiabatic potential of the Cr3+ centers at the ferroelectric phase transition of Cd2Nb2O7 at Tc. The low-temperature photosensitivity of both materials is attributed to the photoinduced change of charge state of manganese and chromium centers. [ABSTRACT FROM AUTHOR]

Dielectric permittivity ℇ′ and a "dielectric-related" temperature shift of the R -emission line ( 2 E → 4 A 2 ) of the Cr 3+ impurity centres were studied in SrTiO 3 (STO), Sr 0.99 Mg 0.01 TiO 3 (SMT) and SrTi 0.99 Mg 0.01 O 3 (STM) ceramics. In STO, ℇ increases on cooling revealing a weak dispersion in the 100 Hz-1 MHz region at low temperatures. SMT shows nearly the same behaviour. In STM the low-frequency permittivity reveals a wide maximum at ∼36 K with pronounced relaxation-type dispersion. However, in the THz region no ℇ′ ( T ) anomaly was found in all the materials under study. All the compositions studied--STO, SMT and STM demonstrate large "dielectric-related" temperature shift of Cr 3+ R -emission line but this shift seems to be associated not only with TO 1 soft mode but also with the relaxation process. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate L-asparaginase activity in relation to some soil physical and chemical properties and to assess the effects of Cr, Cd, and Pb on the enzyme activity. L-asparaginase activity was significantly correlated with organic carbon (r = 0.867, P < 0.001), total nitrogen (r = 0.784, P < 0.001) and biological index of nitrogen availability (r = 0.816, P < 0.001), whereas it was not correlated with sand, silt, and clay contents. L-asparaginase activity was negatively correlated with electrical conductivity of saturation paste extracts (r = -0.59, P < 0.01) and sodium adsorption ratio (r = -0.58, P < 0.01). Multiple stepwise regression revealed that 80.4% of L-asparaginase activity variation was due to organic carbon and sodium adsorption ratio. Cd and Pb inhibited soil L-asparaginase to a similar extent (by 23%), and did so to a greater extent than did Cr (13.5%). [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) spectra and thermoluminescence (TSL) of Cr doped Cd 2 Nb 2 O 7 were investigated for the first time. The 12 - 300 K and 350 - 900 nm temperature-spectral regions were inspected. It was found that PL spectrum consists of four narrow emission lines centered at 737.7, 737.1, 736.7, and 736.5 nm accompanied by vibrational sidebands with excitation bands at 650, 500, and 370 nm ( T = 12 K). Emission lines are attributed to the zero-phonon transitions 2 E → 4 A 2 of two kinds of octahedral coordinated Cr 3+ centers, which substitute Nb, with local charge compensating oxygen vacancy and with non-local compensation. TSL revealed temperature maxima of intensity at 98 and 183 K. Activation energies of PL quenching at T < T c = 196 K and for T > 196 K appeared to be 122 meV and 216 meV, respectively. This effect is tentatively explained by the change of the adiabatic potential of the Cr 3+ centers upon a ferroelectric phase transition of CNO at T c . [ABSTRACT FROM AUTHOR]

The concurrent effect of NaCl salinity and heavy metals [cadmium (Cd), chromium (Cr) and nickel (Ni)] on growth, sodium (Na), and heavy metal accumulation was assessed in four salt tolerant plant species. These were: barley (Hordeum vulgare L.), purslane (Portulaca oleracea L.), Inula crithmoides L., and Plantago coronopus L., all of which have documented potential for use in saline agriculture. Plants were grown in perlite and irrigated with salinized and non-salinized nutrient solutions (9 dS m-1 and 18 dS m-1) containing 2 ppm Cd, 4 ppm Cr, 10 ppm Ni, and a non-metal control. Salinity, Cd, and Ni caused a significant decrease in the dry biomass accumulation of P. oleracea, but had no effects on other plant species. Sodium accumulation was highest in P. coronopus and I. crithmoides, indicating pronounced halophytic properties. The presence of heavy metals reduced Na accumulation in H. vulgare and P. oleracea, but had no effect on P. coronopus and I. crithmoides, indicating that the Na-heavy metal interaction is plant-specific. Metal accumulation in the four plant species was generally enhanced by the 9 dS m-1 treatment, but not by the 18 dS m-1 treatment. This could indicate the presence of an ionic exclusion mechanism operating at high salinity levels that would operate indiscriminately on Na as well as on Cd, Cr, and Ni [ABSTRACT FROM AUTHOR]