Bio-optical properties in waters influenced by the Mississippi River during low flow conditions

Spatial and temporal patterns of bio-optical properties were studied in the Northern Gulf of Mexico during cruises in April and October of 2000, a year during which the discharge volume from the Mississippi River was unusually low. Highly variable surface Chl a concentrations (0.1 to 17 mg m⁻³) and colored dissolved organic matter (CDOM) absorption (0.07 to 1.1 m⁻¹ at 412 nm) were observed in the study region that generally decreased with increasing salinity waters, being highest nearshore and decreasing at offshore stations. The optical properties of absorption, scattering, and diffuse attenuation coefficients reflected these distributions with phytoplankton particles and CDOM contributing to most of the spatial, vertical, and seasonal variability. The diffuse attenuation coefficient K_d(λ) and spectral remote sensing reflectance R_rs(λ) were linear functions of absorption and backscattering coefficients a(λ) and b_b(λ) through the downward average cosine μ_d and the ratio of variables f/Q at the SeaWiFS wavebands for waters with widely varying bio-optical conditions. Although various R_rs(λ) ratio combinations showed high correlation with surface Chl a concentrations and CDOM absorption at 412 nm, power law equations derived using the R_rs(490)/R_rs(555) and R_rs(510)/R_rs(555) ratios provided the best retrievals of Chl a concentrations and CDOM absorption from SeaWiFS reflectance data.     

Thermal and electronic properties of Bi1 − xSbx alloys

Polycrystalline Bi_1 ? xSb_x (x = 0.10, 0.12 and 0.15) semiconducting alloys were synthesized by mechanical alloying in order to achieve homogeneous thermoelectric materials with improved mechanical strength. The homogeneity of the powder samples were repeatedly checked by X-ray diffraction and scanning electron microscopy to standardize the milling conditions. The best possible homogenized material was developed with the milling conditions of BPR 30:1, ball diameter 30 mm, 400 rpm and milling time of 15 h. The electrical resistivity, thermoelectric power and thermal conductivity were measured in the temperature range 300–500 K. It was found through these experiments that the composition with x = 0.12 behaved in a normal semiconducting way, whereas the other two compositions (x = 0.10 and 0.15) showed degenerate semiconductor behaviour. These features have been qualitatively explained from the band structure and interband scattering mechanisms.     

Bio-optical properties and ocean color algorithms for coastal waters influenced by the Mississippi River during a cold front

During the passage of a cold front in March 2002, bio-optical properties examined in coastal waters impacted by the Mississippi River indicated that westward advective flows and increasing river discharge containing high concentrations of nonalgal particles contributed significantly to surface optical variability. A comparison of seasonal data from three cruises indicated spectral models of absorption and scattering to be generally consistent with other coastal environments, while their parameterization in terms of chlorophyll (Chl) alpha concentration showed seasonal variability. The exponential slope of the colored dissolved organic matter (CDOM) averaged 0.0161+/-0.00054 nm(-1) and nonalgal absorption averaged 0.011 nm(-1) with deviations from general trends observed due to anomalous water properties. Although the phytoplankton specific absorption coefficients varied over a wide range [0.02 to 0.1 m2 (mg Chl)(-1) at 443 nm] being higher in offshore surface waters, values of phytoplankton absorption spectra at the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) wave bands were highly correlated to modeled values. Particulate scattering characteristics were similar to observations for other coastal waters, while backscattering ratios were on average lower in phytoplankton-dominated surface waters (0.011+/-0.003) and higher in low Chl near-bottom waters (0.0191+/-0.0045). Average percent differences in remote sensing reflectance Rrs derived from modeled and in-water radiometric measurements were highest in the blue wave bands (52%) and at locations with more stratified water columns. SeaWiFS estimates of Chl and CDOM absorption derived using regional empirical algorithms were highly correlated to in situ data.     

Nanoscale surface modifications to control capillary flow characteristics in PMMA microfluidic devices

Polymethylmethacrylate (PMMA) microfluidic devices have been fabricated using a hot embossing technique to incorporate micro-pillar features on the bottom wall of the device which when combined with either a plasma treatment or the coating of a diamond-like carbon (DLC) film presents a range of surface modification profiles. Experimental results presented in detail the surface modifications in the form of distinct changes in the static water contact angle across a range from 44.3 to 81.2 when compared to pristine PMMA surfaces. Additionally, capillary flow of water (dyed to aid visualization) through the microfluidic devices was recorded and analyzed to provide comparison data between filling time of a microfluidic chamber and surface modification characteristics, including the effects of surface energy and surface roughness on the microfluidic flow. We have experimentally demonstrated that fluid flow and thus filling time for the microfluidic device was significantly faster for the device with surface modifications that resulted in a lower static contact angle, and also that the incorporation of micro-pillars into a fluidic device increases the filling time when compared to comparative devices.     

Effect of pH, NaCl content, and temperature on growth and survival of Arcobacter spp

Growth and survival of six human isolates of the pathogenic Arcobacter spp. in the presence of selected environmental factors were studied. Four strains of Arcobacter butzleri and two strains of Arcobacter cryaerophilus were exposed to pH levels of 3.5 to 8.0. Most strains grew between pH 5.5 and 8.0, with optimal growth of most A. butzleri and A. cryaerophilus strains at pH 6.0 to 7.0 and 7.0 to 7.5, respectively. The 24-h optimal growth range in the presence of NaCl was 0.5 to 1.0% for A. cryaerophilus. However, after 96 h, the optimum was between 0.5 and 2.0% NaCl. The optimum range for growth of A. butzleri strains was 0.09 to 0.5% NaCl after 96 h. The upper growth limits were 3.5 and 3.0% NaCl for A. butzleri and A. cryaerophilus, respectively. Survival at 25 degrees C in up to 5% NaCl was noted for A. butzleri 3556 and 3539 and A. cryaerophilus 3256. Decimal reduction times (D-values) at pH 7.3 in phosphate-buffered saline for three A. butzleri strains were 0.07 to 0.12 min at 60 degrees C, 0.38 to 0.76 min at 55 degrees C, and 5.12 to 5.81 min at 50 degrees C. At pH 5.5, decreased thermotolerance was observed, with D-values of 0.03 to 0.11 min at 60 degrees C, 0.30 to 0.42 min at 55 degrees C, and 1.97 to 4.42 min at 50 degrees C. Calculated z-values ranged from 5.20 to 6.28 degrees C. D-values of a three-strain mixture of A. butzleri in raw ground pork were 18.51 min at 50 degrees C and 2.18 min at 55 degrees C. Mild heat (50 degress C) followed by cold shock (4 or 8 degrees C exposure) had a synergistic lethal effect, reducing more cells than with an individual 50 degrees C treatment or with cold shock temperatures of 12 or 16 degrees C.     

Stagnation flow and heat transfer in a zonal magnetic field

Summary The problem stated in the title is studied for small values of the diffusivity ratio and the magnetic force coefficient , the magnetic field being of internal origin. Uniformly valid expansions are derived for the velocity and magnetic fields in the fluid. It is found that as 1, the viscous layer is brought to rest and the current in the layer is uniform and normal to the wall.The heat transfer is next calculated at a uniformly heated wall on the assumption of small temperature variations. It is deduced that when log(^–1) approaches a certain value depending on the wall temperature etc., the thermal boundary layer separates at the stagnation point and, if dissipation is neglected, along the whole wall.     

Lower limb ischaemia-reperfusion injury alters gastrointestinal structure and function

BACKGROUND: It has been suggested that bowel permeability is altered following abdominal aortic aneurysm surgery. The effect of ischaemia-reperfusion injury to the lower limb on the morphological structure, neutrophil infiltration and permeability of the bowel was investigated. METHODS: Histological assessment of the bowel was undertaken in five groups of Wistar rats: control, 3 h of bilateral hind limb ischaemia and 3 h of bilateral hind limb ischaemia followed by 1, 2 or 3 h of reperfusion. Using an everted gut sac model and 14C-labelled polyethylene glycol, the effect of ischaemia-reperfusion on small bowel permeability was studied. RESULTS: The small bowel showed a significant decrease in mucosal thickness, villus height and crypt depth in animals subjected to ischaemia followed by 2-hr reperfusion (mean(s.e.m.) 420(15), 217(9) and 163(6) microns respectively) compared with controls (481(11), 245(6) and 195(6) microns) (P < 0.05). Neutrophil count within the lamina propria was similar in the different groups. A significant increase in mean(s.e.m.) 14C-labelled polyethylene glycol translocation was detected in animals subjected to ischaemia-reperfusion compared with controls (760(40) versus 560(27) c.p.m. per ml per h) (P < 0.05). CONCLUSION: These data suggest that reperfusion of acutely ischaemic extremities produces structural and functional changes in the small intestine, although these changes are not associated with increased neutrophil infiltration within the bowel wall.     

Tension control: dancer rolls or load cells

The authors attempt to answer the question of whether the use load cells or dancer roll regulation systems in modern-day paper machinery. A computer model based on an existing off-machine coater that has both systems integrated is used as the basis for this research. The two systems are analyzed, considering the stability of the system and its dynamic response. Practical results based on measurements made on site are included     

Effectiveness of two cooking systems in destroying Escherichia coli O157:H7 and Listeria monocytogenes in ground beef patties

A rapid, high-temperature double-sided grilling-broiling (DGB) system was compared to a single-sided broiling (SSB) system for cooking of foodservice ground beef patties to reduce microbial numbers and maintain textural quality. Patties (110 g) containing either Escherichia coli O157:H7 or Listeria monocytogenes (10(6-7) CFU/g) were cooked to target internal temperatures of 60 or 68 degrees C on each cooking system and immediately removed from the grills without the additional holding time at 60 or 68 degrees C that is recommended for foodservice cooking of ground beef patties. Actual final internal temperature attained, position on the grill, degree of doneness, cooking time, after-cook weight, texture characteristics, and bacterial counts of the patties were monitored. The DGB reduced E. coli O157:H7 and L. monocytogenes populations in ground beef patties by 5.7 log10 and 5.4 log10 CFU/g, respectively, when cooked to a target temperature of 60 degrees C (actual final internal temperature of 71.2 degrees C) and by 6.1 log10 and 5.6 log10 CFU/g, respectively, when cooked to a target temperature of 68 degrees C (actual final internal temperature of 75.8 degree C). The SSB reduced E. coli O157:H7 and L. monocytogenes populations by 1.3 log10 and 1.8 log10 CFU/g, respectively, when cooked to a target temperature of 60 degrees C (actual final internal temperature of 62.7 degrees C) and by 2.9 log10 and 3.6 log10 CFU/g, respectively, when cooked to a target temperature of 68 degrees C (actual final internal temperature of 69.3 degrees C). The DGB system effected a higher, more rapid temperature increase in patties cooked to either target temperature compared to the SSB system. This higher temperature was more effective in destroying pathogens in beef patties. Texture analyses determined that patties cooked on the DGB system had significantly higher values for springiness, adhesiveness, and product height as compared to the SSB system, and patties cooked on either system had significantly higher hardness, gumminess, chewiness, and product height values at the target temperature of 68 degrees C as compared to 60 degrees C.     

Oncogene expression in carotid body tumors

BACKGROUND: The genetic etiology of carotid body tumors is suggested by the familial occurrence of the neoplasm. Environmental influences are also implied by the fact that the tumor is more common in those living at high altitudes. However, the development of sporadic tumors occurring at sea level, which account for the majority of cases, remains unknown. METHODS: The clinical and pathologic features of 13 carotid body tumors excised in 13 patients were reviewed. Two patients had bilateral tumors, one with a strong family history, and two patients had recurrent carotid body tumors. All tumors were benign except for one that had local lymph gland metastases. All patients were followed up for a period ranging from 1 to 17 years. Each tumor was examined for the oncoproteins c-myc, bcl-2 c-erbB-2, c-erbB-3 and c-jun and for the proliferating cell nuclear antigen (PCNA) by immunohistochemistry. RESULTS: c-myc immunoreactivity was observed in all tumors and, in 12 of 13 cases, was present in more than 10% of tumor cells, bcl-2 immunoreactivity was found in 11 cases with 6 tumors exhibiting more than 10% immunopositive cells, c-jun expression was found in 5 cases with 3 tumors containing more than 10% immunopositive cells. Only two tumors were positive for c-erb-B2 immunoreactivity with a cytoplasmic staining pattern. One tumor was positive for c-erb-B3. CONCLUSIONS: The oncogenes c-myc, bcl-2 and c-jun, are abnormally expressed in some carotid body tumors. Their expression may contribute to the genesis of carotid body tumors.