Enhancement of electrokinetic remediation of hyper-Cr(VI) contaminated clay by zero-valent iron

This paper investigated the effectiveness of incorporating zero-valent iron (ZVI) into electrokinetic (EK) to remediate hyper-Cr(VI) contaminated clay (2497 mg/kg). A ZVI wall was installed in the center of the soil specimen and was filled with 1:1 (w/w) ratio of granular ZVI and sand. Results show that transport of H(+) is greatly retarded by the strong opposite migration of anionic chromate ions, whereupon a revered electroosmosis flow (EO) was resulted and alkaline zone across the specimen was developed promoting the release of Cr(VI) from the clay. Chromium removal was characterized by high Cr(VI) concentration occurred in the anolyte and the presence of Cr(III) precipitates in the catholyte. The Cr(VI) reduction efficiencies for the process without ZVI wall were 68.1 and 79.2% for 1 and 2V/cm, respectively. As ZVI wall was installed, the corresponding reduction efficiencies increased to 85.8 and 92.5%. The costs for energy and ZVI utilized in this process are US$ 41.0 and 57.5 per cubic meter for the system with electric gradient of 1 and 2V/cm, respectively. The role of ZVI wall effectively reducing Cr(VI) contamination and the operation simultaneous collection of Cr(VI) from the electrode reservoirs are two major advantages of this process.     

Study of the EDM performance to produce a stable process and surface modification

In this work, the effect of pulse current and pulse duration in die-sinking electrical discharge machining (EDM) on the machining characteristics of Ti-6Al-4V alloy is studied. The EDM characteristics, including the electrode wear ratio (EWR), the material removal rate (MRR), and the surface roughness (SR), are used to measure the effect of machining. An increase in the intensity of the pulse current from 2.5 to 5 A produces a slow increase in EWR, MRR, and SR. An increase in the intensity of the pulse current from 5 to 7 A produces a rapid increase in EWR, MRR, and SR. Control charts are basic and powerful tools for controlling statistical processes and are widely used to monitor manufacturing processes and ensure good EDM quality. EWR, MRR, and SR are normal distributions, and the regression curves for the data are straight lines. All of the data points vary randomly around the centerline, which follows the Shewhart criteria and shows that the EDM process and product performance are under control and stable over time. After EDM, the surface exhibits an irregular fused structure, with pinholes, micro voids, globule debris, and many damaged surfaces. Oxygen plasma etching and surface modification after EDM reduce these surface defects, so finer and flatter surfaces can be achieved. Moreover, fatigue life can be enhanced.     

A novel algal toxicity testing technique for assessing the toxicity of both metallic and organic toxicants

This study presents a closed-system algal toxicity test technique that is capable of detecting the effects of both organic and metallic toxicants. Toxicity testing was conducted by transferring adequate amounts of algal suspension, dilution water (with culture growth medium), and toxicants into 300-mL BOD bottles. The BOD bottles were completely filled up with no head-space left. The initial cell density and the exposure time were 15,000 cells/mL and 48 h, respectively. The performance of the above test method was evaluated using three heavy metals and six organic toxicants based on three different test endpoints, i.e., dissolved oxygen production, algal growth rate, and cell density. The proposed test revealed excellent test sensitivity and reproducibility. Currently, none of the existing algal toxicity test protocols is adequate for assessing the toxicity of organic chemicals. The closed-system algal toxicity tests developed by previous researchers also may not be ideal because the enlarged headspace and/or enriched bicarbonate buffer may result in either underestimations of the exposure concentrations or insensitive responses to both heavy metals and organic toxicants. Compared to the aforementioned algal toxicity test methods, the proposed technique in the present study has a more general applicability under conditions such as effluent samples containing both metals and organic toxicants or samples with unknown compositions.     

Voronoi-based relay placement scheme for wireless sensor networks

Energy consumption is a crucially important issue in battery-driven wireless sensor networks (WSNs). In most sensor networks, the sensors near the data collector (i.e. the sink) become drained more quickly than those elsewhere in the network since they are required to relay all of the data collected in the network to the sink. Therefore more balanced data paths to the sink should be established in order to extend the lifetime of the sensor network. Accordingly, a novel relay deployment scheme for WSNs based on the Voronoi diagram is proposed. The proposed scheme is applicable to both two-dimensional and three-dimensional network topologies and establishes effective routing paths that balance the traffic load within the sensor network and alleviate the burden on the sensors around the sink. Simulation results indicate that the number of relays deployed in the proposed scheme is similar to that deployed in the predetermined location scheme and is significantly less than that deployed in the minimum set cover scheme. Furthermore, the lifetime of the sensor network containing relay nodes deployed using the current scheme is longer than that achieved using either the predetermined location scheme or the minimum set cover scheme.     

Kinetics and Microstructural Evolution of Heterogeneous Transformation of θ-Alumina to α-Alumina

Ultrafine (<0.1 μm) high-purity θ-Al₂O₃ powder containing 3–17.5 mol%α-Al₂O₃ seeds was used to investigate the kinetics and microstructural evolution of the θ-Al₂O₃ to α-Al₂O₃ transformation. The transformation and densification of the powder that occurred in sequence from 960° to 1100°C were characterized by quantitative X-ray diffractometry, dilatometry, mercury intrusion porosimetry, and transmission and scanning electron microscopy. The relative bulk density and the fraction of α phase increased with annealing temperature and holding time, but the crystal size of the α phase remained ∼50 nm in all cases at the transformation stage (≤1020°C). The activation energy and the time exponent of the θ to α transformation were 650 ± 50 kJ/mol and 1.5, respectively. The results implied the transformation occurred at the interface via structure rearrangement caused by the diffusion of oxygen ions in the Al₂O₃ lattice. A completely transformed α matrix of uniform porosity was the result of appropriate annealing processes (1020°C for 10 h) that considerably enhanced densification and reduced grain growth in the sintering stage. The Al₂O₃ sample sintered at 1490°C for 1 h had a density of 99.4% of the theoretical density and average grain size of 1.67 μm.     

The effect of carbon coating thickness on the capacity of LiFePO4/C composite cathodes

Two types of carbon source and precursor mixing pellets were employed simultaneously to prepare the LiFePO₄/C composite materials: Type I using the LiFePO₄ precursor with 20 wt.% polystyrene (PS) as a primary carbon source, and Type II using the LiFePO₄ precursor with 50 wt.% malonic acid as a secondary carbon vapor source. During final sintering, a Type I pellet was placed down-stream and Type II precursor pellet(s) was(were) placed upstream next to a Type I precursor pellet in a quartz-tube furnace. The carbon-coated product of the sintered Type I precursor pellet was obtained by using both PS and malonic acid as carbon sources. When two Type II pellets were used as a carbon vapor source (defined as Product-2), a more uniform film between 4 and 8 nm was formed, as shown in the TEM images. In the absence of a secondary carbon source (defined as Product-0), the discharge capacity of Product-0 was 137 mAh g⁻¹ with 100 cycles at a 0.2C-rate, but Product-2 demonstrated a high capacity of 151 mAh g⁻¹ with 400 cycles. Our results indicate that electrochemical properties of LiFePO₄ are correlated to the amount of carbon and its coating thickness and uniformity.     

Carbon and nitrogen isotopic compositions of particulate organic matter and biogeochemical processes in the eutrophic Danshuei Estuary in northern Taiwan

The Danshuei Estuary is distinctive for the relatively short residence time (1-2 d) of its estuarine water and the very high concentration of ammonia, which is the dominant species of dissolved inorganic nitrogen in the estuary, except near the river mouth. These characteristics make the dynamics of nitrogen cycling distinctively different from previously studied estuaries and result in unusual isotopic compositions of particulate nitrogen (PN). The delta(15)N(PN) values ranging from -16.4 per thousand to 3.8 per thousand lie in the lower end of nitrogen isotopic compositions (-16.4 to +18.7 per thousand) of suspended particulate matter observed in estuaries, while the delta(13)C values of particulate organic carbon (POC) and the C/N (organic carbon to nitrogen) ratios showed rather normal ranges from -25.5 per thousand to -19.0 per thousand and from 6.0 to 11.3, respectively. There were three major types of particulate organic matter (POM) in the estuary: natural terrigenous materials consisting mainly of soils and bedrock-derived sediments, anthropogenic wastes and autochthonous materials from the aquatic system. During the typhoon induced flood period in August 2000, the flux-weighted mean of delta(13)C(POC) values was -24.4 per thousand, that of delta(15)N(PN) values was +2.3 per thousand and that of C/N ratio was 9.3. During non-typhoon periods, the concentration-weighted mean was -23.6 per thousand for delta(13)C(POC), -2.6 per thousand for delta(15)N(PN) and 8.0 for C/N ratio. From the distribution of delta(15)N(PN) values of highly polluted estuarine waters, we identified the waste-dominated samples and calculated their mean properties: delta(13)C(POC) value of -23.6+/-0.7 per thousand, delta(15)N(PN) value of -3.0+/-0.1 per thousand and C/N ratio of 8.0+/-1.4. Using a three end-member mixing model based on delta(15)N(PN) values and C/N ratios, we calculated contributions of the three major allochthonous sources of POC, namely, wastes, soils and bedrock-derived sediments, to the estuary. Their contributions were, respectively, 83%, 12% and 5% under non-typhoon conditions, and 9%, 63% and 28% under typhoon conditions. The autochthonous POM had the most varied isotopic compositions, encompassing the full ranges of delta(13)C(POC) (-25.5 to -19.1 per thousand), delta(15)N(PN) (-16.4-3.8 per thousand) and C/N ratio (6.0-11.3). The heavy end of the carbon isotopic composition reflected the typical marine condition and the lower end the estuarine condition, which probably had elevated concentrations of dissolved inorganic carbon with low delta(13)C values due to input from decomposition of organic matter. The lack of isotopically heavy PN, as found in larger estuaries, was attributed to isotopically light starting materials, namely, anthropogenic wastes, the slow phytoplankton growth within the estuary and the rather short residence time; the latter two factors made (15)N enrichment during ammonia consumption very limited. The most isotopically light PN likely originated from phytoplankton incorporating (15)N-depleted nitrate near the river mouth, where ammonia inhibition of nitrate uptake probably stopped.     

Outage and coverage considerations for microcellular mobile radiosystems in a shadowed-Rician/shadowed-Nakagami environment

This paper presents outage analysis and the associated reuse distance and service area estimations for microcellular mobile radio systems that operate in a shadowed-Rician/shadowed-Nakagami (1960) fading environment. Outages caused either by the minimum carrier-to-interference ratio (CIR) requirement alone or by the CIR plus the minimum signal strength [or, equivalently, carrier-to-noise ratio (CNR)] requirements are considered. The desired signal is assumed to suffer from Rician fading while the interference signals from cochannel cells experience Nakagami fading. The interferers may have identical or different statistics. In addition, the local mean strength of the desired and interference signals may fluctuate due to shadowing     

The Role of E-Cadherin and microRNA on FAK Inhibitor Response in Malignant Pleural Mesothelioma (MPM)

Malignant pleural mesothelioma (MPM) is an aggressive malignancy with limited effective treatment options. Focal adhesion kinase (FAK) inhibitors have been shown to efficiently suppress MPM cell growth initially, with limited utility in the current clinical setting. In this study, we utilised a large collection of MPM cell lines and MPM tissue samples to study the role of E-cadherin (CDH1) and microRNA on the efficacy of FAK inhibitors in MPM. The immunohistochemistry (IHC) results showed that the majority of MPM FFPE samples exhibited either the absence of, or very low, E-cadherin protein expression in MPM tissue. We showed that MPM cells with high CDH1 mRNA levels exhibited resistance to the FAK inhibitor PND-1186. In summary, MPM cells that did not express CDH1 mRNA were sensitive to PND-1186, and MPM cells that retained CDH1 mRNA were resistant. A cell cycle analysis showed that PND-1186 induced cell cycle disruption by inducing the G2/M arrest of MPM cells. A protein−protein interaction study showed that EGFR is linked to the FAK pathway, and a target scan of the microRNAs revealed that microRNAs (miR-17, miR221, miR-222, miR137, and miR148) interact with EGFR 3′UTR. Transfection of MPM cells with these microRNAs sensitised the CHD1-expressing FAK-inhibitor-resistant MPM cells to the FAK inhibitor.     

超声抛光变幅杆动态分析及其优化

超声抛光方法是解决模具内腔抛光这一模具加工瓶颈的有效手段之一,而超声变幅杆的性能对于超声加工来讲至关重要。本文根据变幅杆理论设计方法设计了适用于自动超声抛光设备的变幅杆,并使用有限元技术对四种类型的变幅杆进行了模态分析和谐响应分析,然后以稳定性最好的圆锥形变幅杆为基础进行了优化设计,得到了稳定性较好且放大系数较大的综合性能优良的变幅杆。