Automated immunomagnetic separation and microarray detection of E. coli O157:H7 from poultry carcass rinse.

We describe the development and application of an electromagnetic flow cell and fluidics system for automated immunomagnetic separation (IMS) of Escherichia coli O157:H7 directly from poultry carcass rinse. We further describe the biochemical coupling of automated sample preparation with nucleic acid microarrays. Both the cell concentration system and microarray detection method did not require cell growth or enrichment from the poultry carcass rinse prior to IMS. Highly porous Ni foam was used to enhance the magnetic field gradient within the flow path, providing a mechanism for immobilizing immunomagnetic particles throughout the fluid rather than the tubing wall. A maximum of 32% recovery efficiency of non-pathogenic E. coli was achieved within the automated system with 6 s cell contact times using commercially available antibodies targeted against the O and K antigens. A 15-min protocol (from sample injection though elution) provided a cell recovery efficiency that was statistically similar to > I h batch captures. O157:H7 cells were reproducibly isolated directly from poultry carcass rinse with 39% recovery efficiency at 10(3) CFU ml(-1) inoculum. Direct plating of washed beads showed positive recovery of O157:H7 directly from poultry carcass rinse at an inoculum of 10 CFU ml(-1). Recovered beads were used for direct polymerase chain reaction (PCR) amplification and microarray detection, with a process-level detection limit (automated cell concentration though microarray detection) of < 10(3)CFU ml(-1) in poultry carcass rinse.     

Sublimation rate and the mass-transfer coefficient for snow sublimation

Sublimation of snow is a fundamental process that affects the crystal structure of snow, and is important for ice core interpretation, remote sensing, snow hydrology and chemical processes in snow. Prior investigations have inferred the sublimation rate from energy, isotopic, or mass-balance calculations using field data. Consequently, these studies were unable to control many of the environmental parameters which determine sublimation rate (e.g. temperature, relative humidity, snow microstructure). We present sublimation rate measurements on snow samples in the laboratory, where we have controlled many of these parameters simultaneously. Results show that the air stream exiting the snow sample is typically saturated under a wide range of sample temperature and air-flow rate, within measurement precision. This result supports theoretical work on single ice grains which found that there is no energy barrier to be overcome during sublimation, and suggests that snow sublimation is limited by vapor diffusion into pore spaces, rather than sublimation at crystal faces. Undersaturation may be possible in large pore spaces (i.e. surface- or depth-hoar layers) with relatively high air-flow rates. We use these data to place bounds on the mass-transfer coefficient for snow as a linear function of Reynolds number, and find that h_m = 0.566 Re + 0.075.     

On the bright side of the screen: Material-world interactions surrounding the socialization of outsiders to digital spaces

Internet technologies are generally characterized as deriving from Western mindsets—the assumptions, values, and beliefs that determine how individuals perceive, interpret, and communicate experience. For composition instructors, the Internet's Western accent raises concerns about how students who do not identify with IT's dominant discourse can find a voice that is their own and that also empowers them as participants in online spaces. Numerous studies have explored how outsiders adopt, transform, and resist Internet discourses; at the same time, few studies have used participant observation to explore offline interactions that support the socialization of newcomers and/or outsiders in the use of digital technologies. This essay extends existing research through reporting findings from a reflective, ethnographic study of material-world interactions surrounding the socialization of outsiders to digital spaces.     

Silver nanocolloids disrupt medaka embryogenesis through vital gene expressions

Silver nanomaterials are the major components of healthcare products largely because of their antimicrobial effects. However, their unintended toxicity to biological organisms and its mechanism are not well understood. Using medaka fish embryo model, the toxic effects and corresponding mechanisms of silver nanocolloids (SNC, particle size 3.8 ± 1.0-diameter nm) were investigated. SNC caused morphological changes in embryos including cardiovascular malformations, ischemia, underdeveloped central nervous system and eyes, and kyphosis at exposures of 0.5 mg/L. Interestingly, SNC were observed inside the eggs at a level of 786.1 ± 32.5 pg/mg egg weight, and TEM analysis showed that SNC adhered to the surface and inside of the chorion. Meanwhile, medaka oligo DNA microarray and qRT-PCR were used for gene expression analysis in the embryos exposed to 0.05 mg/L SNC for 48 h. As a result, expressions of six of the oxidative stress-, embryogenesis- and morphogenesis-related genes, ctsL, tpm1, rbp, mt, atp2a1, and hox6b6, were affected by the SNC exposure, and these genes' involvement in those malformations was implied. Thus, SNC could potentially cause malformations in the cardiovascular and central nervous systems in developing medaka embryo through SNC-induced differential expression of the genes related to oxidative stress, embryonic cellular proliferation, and morphological development.     

Effect of supplemental L-lysine-HCL and corn source on rumen fermentation and amino acid flow to the small intestine

Four lactating Jersey cows fitted with ruminal and duodenal cannulae were used in a 4 x 4 Latin square design trial to determine the effect of supplemental lysine in diets containing dry ground (GC) or steam-flaked (SFC, 360 g/L) corn on ruminal fermentation and amino acid (AA) flow to the duodenum. Supplemental L-lysine-HCL provided 10 g/d of additional Lys to the total mixed rations. There were no interactions between supplemental Lys and corn source. Supplemental Lys increased Lys intake, but did not alter nutrient intake and digestibility or N flow to the duodenum. Intake of dry matter (DM), organic matter (OM), and neutral detergent fiber (NDF) and ruminal digestibility of starch tended to be higher, whereas ruminal digestibility of DM, OM, acid detergent fiber, and NDF was lower for diets supplemented with SFC compared with GC. Whole-tract digestibility was similar for both corn supplements. Ruminal pH and molar proportions of volatile fatty acids were not affected by supplemental Lys or corn source; however, ruminal NH(3) concentrations were lowest when SFC was fed. Intake of N tended to be higher and the flow of total N and individual AA to the duodenum was higher for diets supplemented with SFC. There was a trend for increased flow of microbial N for diets supplemented with SFC. Supplemental L-lysine-HCL did not alter ruminal fermentation, flow of amino acid to the small intestine, or nutrient digestibility, but feeding SFC reduced ruminal fiber digestion and increased microbial protein synthesis and flow of amino acid to the duodenum.     

Scanning electron microscopy of vascular casts

Corrosion casts provide three dimensional replicas that can be examined readily by scanning electron microscopy (SEM). They are prepared by filling vascular networks with polymerizing plastic and then digesting away the tissue. As based on our studies of ocular vessels, this report describes the vascular anatomy, as well as the artifacts, that are encountered during SEM studies of such preparations.     

Graft copolymerization of methoxyacrylethyl phosphate onto expanded poly(tetrafluoroethylene) facial membranes

Expanded poly(tetrafluoroethylene) (ePTFE) membranes were modified by graft copolymerization with methoxyacrylethyl phosphate (MOEP) in methyl ethyl ketone (MEK) solutions at ambient temperature using gamma irradiation. The effect of monomer concentration (3–30%) was studied and the modified membranes were characterized by weight increase, x‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), contact angle measurements, and differential scanning calorimetry (DSC). Results show that the ePTFE membrane had a degree of crystallinity of 59% and that this did not significantly change after grafting indicating that grafting occurs in the amorphous regions. SEM images showed a globular surface morphology for the grafted membranes. XPS was used to evaluate the chemical structure of the graft copolymer and to determine the XPS grafting extent using the C‐F (ePTFE membrane) and the C‐C (MOEP graft copolymer) peaks. The graft yield as well as grafting extent was found to increase with increasing monomer concentration. Concomitantly, the contact angle was found to decrease with increasing monomer concentration. No direct correlation was found between XPS grafting extent and the advancing water contact angle illustrating that the former does not adequately give an indication of the copolymer surface coverage of the first molecular layer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Infilling of porous materials with various polymorphs of calcium carbonate by an electromigration technique

Recent interest in bio-inspired materials has led to the development of techniques that can be used to synthesize hierarchical structures with controlled morphology and mineralogy. One such technique investigated in this study consists of the use of electromigration and electrodeposition techniques to deposit mineral phases with controlled morphology and mineralogy by infilling a predefined porous templates. Here, the utility of precipitating various polymorphs of calcium carbonate in three-dimensional templates is demonstrated. Applied potentials and times were varied while scanning electron microscopy and X-ray diffraction were used to determine polymorph formed and its morphology. It was found that higher applied potentials and shorter operating times resulted in the formation of metastable polymorphs of calcium carbonate (e.g., vaterite) that infilled the porous media. Results provide insights for developing bio-inspired composite materials for various structural and medical applications, such as synthetic bone.     

Toughening cement-based materials through the control of interfacial bonding

Mortars are made from inherently brittle components: sand grains and hardened cement paste. Under normal circumstances, cracks will propagate rapidly through the cement matrix, bypassing the strong sand grains but fracturing some of the weakest. The approach of the work described in this paper was to modify the mortar in order to alter this process. These modifications produced tensile residual stresses between the matrix and the aggregate, which when released by an additional applied tensile stress produced microcracking, debonding of matrix from aggregate, a small expansion and increased toughness. This work demonstrates toughening in sand/Portland cement mortars modified with different expansive admixtures: sodium sulphate or dead-burnt lime. Additionally, mortars of sand/ASTM Type K cement were tested. In order to give additional insight into the toughening mechanism, spherical and angular aggregate have been used to ascertain the consequences of microcracking and aggregate-bridging. The role of aggregate-bridging, especially when related to fracture paths, is also discussed and suggests that the bond between the aggregate and the matrix has been found in some cases to control not only the crack path but consequently the apparent toughness.