Removing and stabilizing as in acid mine water

Arsenic is often present in a variety of forms in sulfide mineral deposits and can become a soluble constituent of mine drainage due to oxidation reactions taking place in mine workings and waste deposits. Its removal from solution must be carried out to meet water-quality discharge criteria, and it must be fixed in a solid form that is environmentally stable. The preferred form of arsenic for disposal is as a basic ferric arsenate, FeAsO₄·xFe(OH)₃, which can be readily produced by coprecipitation with iron in a high-density sludge process. High-density sludge plants are simple to operate and can be designed to meet stringent water-quality specifications and produce stable sludges over long periods of continuous operation. For more information, contact R.W. Lawrence, Simons Perú, S.A., Aramburú 166, Piso 5, Miraflores, Lima 18, Perú; telephone 51-1-221-3130; fax 51-1-221-3143; e-mail rwlawrence@ibm.net.     

A study of the prevalence and enumeration of Salmonella enterica in cattle and on carcasses during processing

Salmonella prevalence and counts were estimated for samples from the oral cavity, hide, rumen, and feces of 100 cattle at slaughter and from the pre- and postchill carcasses of these cattle. Samples were collected from 25 consecutively slaughtered cattle from each of four unrelated groups slaughtered at a single abattoir on different days. Ten additional fecal samples from each group were collected from their respective abattoir holding pens prior to slaughter. The prevalence of Salmonella was estimated using automated immunomagnetic separation, and the counts were estimated using a combination of most probable number (MPN) and automated immunomagnetic separation. A total of 606 samples were collected with Salmonella isolated from 157 (26%), including 29% of oral cavities, 68% of hides, 16% of feces collected after evisceration, 25% of rumen samples, 2% of prechill carcasses, 3% of postchill carcasses, and 48% of feces collected from holding pens. The prevalence and count of Salmonella varied between the different groups of animals tested. The highest count obtained was from a rumen sample (1.1 x 10(4) MPN/g). Other counts were generally low, with a maximum count in feces collected after evisceration and in the abattoir holding pens of 93 and 23 MPN/g, respectively. The highest count on hides, in oral cavities, and on carcasses was 4.8 MPN/cm2, 23 MPN/g, and 0.31 MPN/cm2, respectively. Even though Salmonella was present on the hides and in the rumen and feces of at least one animal from each group of cattle, the processing of animals at this abattoir resulted in few contaminated carcasses, and when contamination occurred, Salmonella was detected at low numbers.     

An explicit finite element model to study the influence of rake angle and friction during orthogonal metal cutting

A fundamental understanding of the tribology aspects of machining processes is essential for increasing the dimensional accuracy and surface integrity of finished products. To this end, the present investigation simulates an orthogonal metal cutting using an explicit finite element code, LS-DYNA. In the simulations, a rigid cutting tool of variable rake angle was moved at different velocities against an aluminum workpiece. A damage material model was utilized for the workpiece to capture the chip separation behavior and the simultaneous breakage of the chip into multiple fragments. The friction factor at the cutting tool–workpiece interface was varied through a contact model to predict cutting forces and dynamic chip formation. Overall, the results showed that the explicit finite element is a powerful tool for simulating metal cutting and discontinuous chip formation. The separation of the chip from the workpiece was accurately predicted. Numerical results found that rake angle and friction factor have a significantly influence on the discontinuous chip formation process, chip morphology, chip size, and cutting forces when compared to the cutting velocity during metal cutting. The model was validated against the experimental and numerical results obtained in the literature, and a good agreement with the current numerical results was found.     

Quantitative validation of the discrete element method using an annular shear cell

The discrete element method (DEM) is often used as the “gold standard” for comparison to continuum-level theories and/or coarse-grained models of granular material flows due to its derivation from first-principal constructs, like contact mechanics. Despite its prevalence, the method is most often validated against experiment in only qualitative ways - comparison of mixing rates, gross features of concentration profiles, etc. - for exactly the reason it has found its popularity; detailed experimental measurements are difficult and often expensive. In this paper, we outline work aimed at using detailed, particle-level experimental measurements to quantitatively validate DEM simulations. Specifically, we examine the flow in a horizontally-aligned annular shear cell. Measurements are performed using digital particle tracking velocimetry (DPTV) so that the velocity, granular temperature, and solids fractions profiles may be extracted. Computationally, we attempt to match the experimental measurements as closely as possible and study the impact of a variety of contact mechanics-inspired force laws as well as perform sensitivity analysis on device and particle geometry and material properties employed.     

Cloning of a phosphatidic acid-preferring phospholipase A1 from bovine testis

We report the molecular cloning and expression of a phosphatidic acid-preferring phospholipase A1 from bovine testis. The open reading frame encoded an 875-amino acid protein with a calculated molecular mass of 97,576 daltons and a pI of 5.61. The sequence included a region similar to a lipase consensus sequence containing the putative active site serine and also included a potential, coiled-coil-forming region. Expression of the open reading frame in COS1 cells resulted in a 20-44-fold increase in phosphatidic acid phospholipase A1 activity over that of control cells. Mutation of the putative active site serine (amino acid 540) demonstrated that it was essential for this increase in enzyme activity. Northern blot analysis revealed at least five different messages with the highest overall message levels in mature testis, but detectable message in all tissues examined. Two possible alternately spliced regions in the open reading frame also were identified. Finally, a search of the data base identified six related proteins: a potential counterpart of the phospholipase A1 in Caenorhabditis elegans, two putative lipases in yeast, and three proteins separately encoded by the Drosophila retinal degeneration B gene and its mouse and human homologues.     

Interactions of Acanthamoeba profilin with actin and nucleotides bound to actin

Three methods, fluorescence anisotropy of rhodamine-labeled profilin, intrinsic fluorescence and nucleotide exchange, give the same affinity, Kd = 0.1 microM, for Acanthamoeba profilins binding amoeba actin monomers with bound Mg-ATP. Replacement of serine 38 with cysteine created a unique site where labeling with rhodamine did not alter the affinity of profilin for actin. The affinity for rabbit skeletal muscle actin is about 4-fold lower. The affinity for both actins is 5-8-fold lower with ADP bound to actin rather than ATP. Pyrenyliodoacetamide labeling of cysteine 374 of muscle actin reduces the affinity for profilin 10-fold. The affinity of profilin for nucleotide-free actin is approximately 3-fold higher than for Mg-ATP-actin and approximately 24-fold higher than for Mg-ADP-actin. As a result, profilin binding reduces the affinity of actin 3-fold for Mg-ATP and 24-fold for Mg-ADP. Mg-ATP dissociates 8 times faster from actin-profilin than from actin and binds actin-profilin 3 times faster than actin. Mg-ADP dissociates 14 times faster from actin-profilin than from actin and binds actin-profilin half as fast as actin. Thus, profilin promotes the exchange of ADP for ATP. These properties allow profilin to bind a high proportion of unpolymerized ATP-actin in the cell, suppressing spontaneous nucleation but allowing free barbed ends to elongate at more than 500 subunits/second.     

Cloning and analysis of the human complement factor H gene promoter

The compound WR 238605 is a primaquine analog being developed by the U.S. Army as an antimalarial drug. Currently, there is no established treatment for Plasmodium vivax parasitemias that are not cured by chloroquine. This study tested WR 238605, chloroquine, and their combinations against a chloroquine-resistant strain of P. vivax (AMRU 1) in Aotus monkeys. A total dose of 3 mg/kg of WR 238605 given at a dosage of 1 mg/kg/day for three days cleared patent parasites in all eight monkeys but recrudescence of parasitemia occurred 15-25 days after initiation of treatment. A total dose of 9 mg/kg of WR 238605 over a three-day period cured all three monkeys of their infections. A total dose of 30 mg/kg of chloroquine did not clear patent infections in three monkeys, whereas a total dose of 60 mg/kg generally (two of three) cleared patent parasitemia but did not cure. Whereas total doses of 30 mg/kg of chloroquine or 3 mg/kg of WR 238605 given alone failed to cure, both drugs given in combination at these dosages cured two of three infections. These results indicate that WR 238605 may be an alternative treatment for chloroquine-resistant vivax malaria.     

Evaluating gonadosomatic index as an estimator of reproductive condition in the invasive round goby, Neogobius melanostomus

Using gonadosomatic index cut-off scores has become a standard protocol for selecting reproductive fish in studies on the reproductive biology of round goby, Neogobius melanostomus, a significant invader of the Laurentian Great Lakes, but the validity of this practice has not been validated with histological staging. The goal of the current study was to evaluate the effectiveness of using gonadosomatic index (GSI) cut-off scores to classify reproductive status in male and female round goby by documenting associations between GSI, sex steroids, and gonad development. Gonadal stage was determined in both sexes using hematoxylin and eosin histology. Plasma 11-ketotestosterone and testosterone were measured in males, and testosterone and 17β-estradiol were measured in females. Gonadosomatic index cut-off scores were effective in selecting spawning capable individuals at higher GSI values, but GSI values were limited in the ability to make further distinctions of gonadal stage and missed many spawning capable females. In females, testosterone levels were highest during vitellogenic growth and declined prior to ovulation. 17β-estradiol displayed a similar, but non-statistically significant pattern. Males with developing testes had higher levels of 11-ketotestosterone —but not testosterone —than reproductively immature males, although levels of these androgens were overall positively correlated in males. The findings indicate that the conventional GSI cut-off scores (1% in males, 8% in females) accurately assign spawning capable condition in both sexes; however, they may also exclude some spawning capable females with lower GSIs.     

Song of the burbot: Under-ice acoustic signaling by a freshwater gadoid fish

Burbot (Lota lota) are northern freshwater gadoid fish that spawn under ice-cover, making their reproductive behavior largely unknown to science. Some members of the cod family vocalize as part of their mating system. These calls are produced by rapidly contracting drumming muscles on their swim bladders. Burbot also possess drumming muscles, like their marine counterparts, which may enable them to vocalize. To assess the potential for burbot to make calls, pre-spawning adult burbot were collected and placed in a large under-ice enclosure in Great Slave Lake, Northwest Territories, Canada, along with a recorder that monitored low frequency sound over their spawning period. The recorded acoustic data revealed that burbot called coincident with the onset of their spawning period and that the call signatures were stereotypical of swim bladder generated vocalizations made by other gadoid fishes. Burbot showed a wide repertoire of calls, from slow knocks to fast buzzing, similar to the closely related haddock (Melanogrammus aeglefinus). Although never-before documented, calling by fish under ice-cover is likely an important part of the mating system of under-ice spawning gadoids because light limitation would reduce the usefulness of visual cues. These under-ice communications may be affected by anthropogenic noise from increasing resource development in northern regions.     

Detection of alpha thalassaemia in Negro infants

A prospective study of 2191 Negro infants in Jamaica showed that approximately 7% of them had detectable levels of Hb Bart's (gamma 4) in the neonatal period. The red cell indices, globin chain biosynthesis and restriction endonuclease mapping of DNA from these infants were used to determine the significance of Hb Bart's at birth. The results indicate that the genotypes alpha alpha/alpha alpha, -- alpha/alpha alpha and -- alpha/ -- alpha are associated with 0%, 0.1-2%, and greater than 2% Hb Bart's respectively. Although trace amounts of Hb Bart's may be associated with the genotype -- alpha/alpha alpha this is not always the case and therefore haemoglobin analysis in the neonatal period cannot be used to diagnose this genotype with any certainty.