Biodegradation of metal-EDTA complexes by an enriched microbial population

A mixed culture utilizing EDTA as the sole carbon source was isolated from a mixed inoculum of water from the River Mersey (United Kingdom) and sludge from an industrial effluent treatment plant. Fourteen component organisms were isolated from the culture, including representatives of the genera Methylobacterium, Variovorax, Enterobacter, Aureobacterium, and Bacillus. The mixed culture biodegraded metal-EDTA complexes slowly; the biodegradability was in the order Fe > Cu > Co > Ni > Cd. By incorporation of inorganic phosphate into the medium as a precipitant ligand, heavy metals were removed in parallel to EDTA degradation. The mixed culture also utilized a number of possible EDTA degradation intermediates as carbon sources.     

Materials characterization of the effect of mechanical bending on area array package interconnects

The mechanical integrity of solder joint interconnects in PWB assemblies with micro-BGA, chip scale, and land grid array packages is being questioned as the size and pitch decrease. Some consumer products manufacturers have mechanically reinforced fine pitch package interconnects with an adhesive underfill, and others are evaluating the need for underfill on a case-by-case basis. Three-point cyclic bend testing provides a useful tool for characterizing the expected mechanical cycling fatigue reliability of PWB assemblies. Cyclic bend testing is useful for characterizing bending issues in electronic assemblies such as repetitive keypad actuation in cell phone products. This paper presents the results of three-point bend testing of PWB assemblies with fine pitch packages. The solder joints on ceramic components performed better than a laminate interposer component in bend testing, because of the stiffening effect of the ceramic packaging materials. The methodology of materials analyses of the metallurgy of solder interconnects following mechanical bending and thermal cycle testing is described. The microstructure and fracture surfaces of solder joint failures in bend test samples differed significantly from thermal cycle test samples.     

Platinum-macrocycle co-catalysts for the electrochemical oxidation of methanol

Metal phthalocyanines (Fe, Co, Ni and Sn) and ruthenium tetramethylcyclam 14 and 15 were studied as cocatalysts for methanol oxidation on platinum supported catalysts. The formation of well defined monolayers of the adsorbed complexes was inferred from the Langmuirian form of the adsorption isotherms in solutions of macrocycles. The coverage at monolayer levels was low, e.g. 1.25 to 2.25×10¹³ molecules cm⁻² or 400 to 800 Ų molecule⁻¹. Enhancement for the methanol oxidation reaction was observed for Pt co-catalyzed with Sn phthalocyanine and Ru tetramethylcyclam. Ru tetramethylcyclam showed an enhancement for methanol oxidation on a per unit weight basis over pure Pt, approaching the activity of PtRu at lower potentials. Increasing the size of the nitrogen ring from 14 to 15 resulted in a lower redox potential and increase in the activity of methanol oxidation. The activity of Pt co-catalyzed with Ru TMC 15 decreased with time suggesting that the macrocycle was desorbing from the supported catalyst surface.     

Validity of specific subscales of the positive and negative symptom scales in older schizophrenia outpatients

The principal natural food colorants used in modern food manufacture are anthocyanins, betalains, carotenoids, chlorophylls, riboflavin and caramel. Carotenoids (carotenes and xanthophylls) occur naturally in some foods such as carrots, red tomatoes, butter, cheese, paprika, palm oil, corn kernels, marigold petals, annatto, and red salmon. Carotenoids (alpha- or beta-carotene and xanthophylls) are excellent antioxidants and inhibit some types of cancers. In the present study, we used the Salmonella typhimurium tester strain YG1024 in the plate-incorporation test to examine the antimutagenicity of xanthophylls extracted from Aztec Marigold (Tagetes erecta) on 1-nitropyrene (1-NP) mutagenicity. Further, we investigated the effect of lutein on DNA-repair system of tester strain YG1024, using a preincubation test. The possible mechanism of lutein on 1-NP mutagenicity was studied by comparing the absorption spectrum of lutein, 1-NP and lutein plus 1-NP. In a dose-response curve of 1-NP, the mutagenic potency was 4317 revertants/nmol, and the dose of 0.06 microgram of 1-NP/plate was chosen for the antimutagenicity studies. Lutein and xanthophylls from Aztec Marigold (pigments for poultry and human use) inhibited mutagenicity of 1-NP in a dose-dependent manner. Lutein and the pigments were not toxic to the bacteria at the concentrations tested (0.002, 0.02, 0.2, 2.0 and 10 micrograms/plate). The percentages of inhibition of 1-NP mutagenicity were 72%, 92% and 66.2% for lutein (10 micrograms/plate), pigment for poultry use (10 micrograms/plate) and pigment for human use (2 micrograms/plate), respectively. Lutein had no effect on the DNA-repair system of strain YG1024. A new peak was detected at 429 nm when lutein was added at 1-NP, and it was stable throughout the incubation time. The results suggest that the major mechanisms of lutein against 1-NP mutagenicity is the potential formation of a complex between lutein and 1-NP, which could limit the bioavailability of 1-NP.     

No-flow underfill flip chip assembly––an experimental and modeling analysis

In the flip-chip assembly process, no-flow underfill materials have a particular advantage over traditional underfill: the application and curing of the former can be undertaken before and during the reflow process. This advantage can be exploited to increase the flip-chip manufacturing throughput. However, adopting a no-flow underfill process may introduce reliability issues such as underfill entrapment, delamination at interfaces between underfill and other materials, and lower solder joint fatigue life. This paper presents an analysis on the assembly and the reliability of flip-chips with no-flow underfill. The methodology adopted in the work is a combination of experimental and computer-modeling methods. Two types of no-flow underfill materials have been used for the flip chips. The samples have been inspected with X-ray and scanning acoustic microscope inspection systems to find voids and other defects. Eleven samples for each type of underfill material have been subjected to thermal shock test and the number of cycles to failure for these flip chips have been found. In the computer modeling part of the work, a comprehensive parametric study has provided details on the relationship between the material properties and reliability, and on how underfill entrapment may affect the thermal–mechanical fatigue life of flip chips with no-flow underfill.     

X-ray tomography vizualization and mechanical modelling of swelling shale around the wellbore

A novel application of CT techniques to study the swelling of water-sensitive shale is described. X-ray tomography was used to study the swelling and swelling-induced fracturing of cylindrical samples of drained Pierre shale in contact with water-based mud placed in a central cylindrical borehole. Frequent CT images were taken over a 24-h period (allowing detection of subtle features during swelling), and used to generate quantitative maps of density, subtracted time lapse images, and three-dimensional reconstructions to map failure and fracture patterns.Two different situations were investigated. (1) When the water activity of the mud is greater than that of the shale, swelling and large deformation of the wellbore, driven by osmotic forces, are observed within a few minutes of mud injection, and continue at a decreasing rate throughout the test. Depending on the confinement conditions, two different fracture patterns are observed: (a) when the sample is not confined, fractures are mainly radial; and (b) when the sample is confined, fractures are mainly circular, with some well-developed slip lines around the borehole.As expected, no swelling is observed when the mud water activity is equal to that of the shale: thus, this type of wellbore failure can be avoided by adding sufficient salt to the mud.The pre-fracturing stresses induced within the core by the swelling process were simulated numerically, using a poroelastic model. The osmotic swelling pressure is treated as mechanically equivalent to pore pressure. The theoretical locations of failure agree with the CT observations, confirming that failure mode and extent depend on the confining conditions, and that osmotically induced failure can be understood on the basis of a simple mechanical model.