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Biomedical subjects

W J Weber

Publications and source records attributed to W J Weber.

At least 19 recordsLinked to original sources
PubMed2005

Molecular dynamic simulation of disorder induced amorphization in pyrochlore.

The defect accumulation mechanism of amorphization has been studied for the La2Zr2O7 pyrochlore by means of classical molecular dynamic simulations. Present calculations show that the accumulation of cation Frenkel pairs is the main driving parameter for the amorphization process, while the oxygen atoms simply rearrange around cations. Under Frenkel pair accumulation, the structure follows the pyrochlore-fluorite-amorphous sequence. Present results consequently provide atomic-level interpretation to previous experimental irradiation observations of the two-step phase transition.

Journal Article↗
PubMed2005

Growth hormone response to growth hormone releasing hormone in calves that differ in genetic merit for milk yield.

Holstein heifer, steer, and bull calves from control (CL) and select (SL) lines of cows that differed by more than 4000 kg of milk during a 305-d lactation (SL > CL) were used to determine growth hormone (GH) response to 5 doses of GH releasing hormone (GHRH) and how this response was affected by gender, period (age), and genetic merit for milk yield. Doses (0, 2.5, 5, 10, and 20 microg/100 kg of BW) of a GHRH analog were assigned randomly to each heifer (4 CL, 4 SL), steer (4 CL, 4 SL), and bull (3 CL, 3 SL) calf and administered on consecutive days at approximately 3, 6, and 10 mo of age (periods; P1, P2, and P3). Jugular blood samples (n = 15) collected between -30 and 240 min relative to GHRH administration were used to quantify area under the GH response curve (AUC) after subtracting mean prechallenge GH concentrations. Estimates of maximum response (Rmax) and sensitivity (ED50) to GHRH were obtained from the hyperbolic dose response curves (AUC vs. dose). Data were analyzed for effects of dose, line, period, gender, and their interactions with period as the repeated effect. Prechallenge GH concentrations were not affected by genetic line, gender, or period. The AUC was not affected by line, but decreased with period and increased with GHRH dose. The Rmax did not differ between lines or among genders, but decreased with period. The ED50 did not differ between lines or among periods, but heifers were more sensitive to GHRH than steers or bulls. Although GH response to GHRH has been identified as a potential indicator of genetic merit, it did not differ between these substantially different genetic lines.

Aging↗
PubMed2005

Effects of week of lactation and genetic selection for milk yield on milk fatty acid composition in Holstein cows.

Control (CL) and select line (SL) dairy cows (n = 22) managed identically but differing in milk yield (>4100 kg/305 d) were used to determine differences in milk fatty acid profile as lactation progressed. Milk yield was recorded daily and milk samples were collected during wk 1, 4, 8, 12, and 16 postpartum for milk composition analysis. Milk samples from wk 1, 8, and 16 were also analyzed for fatty acid composition. Select-line cows produced more milk (44.4 vs. 31.2 kg/d) and milk components than CL cows during the 16-wk period. There was no difference in rate of milk yield increase, but peak milk yield for SL cows was greater and occurred later in lactation. There were no differences in milk SCC or milk fat, protein, or lactose content. Selection for milk yield did not affect the content of most individual milk fatty acids; however, compared with CL, SL cows had a reduced Delta(9)-desaturase system and tended to produce milk with lower monounsaturated fatty acid content. Selection for milk yield did not affect milk fatty acid origin but the percentage of de novo fatty acids increased and preformed fatty acids decreased as lactation progressed. Milk fat trans-11 18:1 and cis-9,trans-11 conjugated linoleic acid increased with progressing lactation (10.7 vs. 14.1 and 3.1 vs. 5.4 mg/g, or 31 and 76%, respectively) and were correlated strongly among wk 1, 8, and 16 of lactation. Temporal changes in the Delta(9)-desaturase system occurred during lactation but these changes were not correlated with milk fat cis-9,trans-11 conjugated linoleic acid content. Results indicate prolonged genetic selection for milk yield had little effect on milk fatty acid composition, but milk fatty acid profiles varied markedly by week of lactation.

Animals↗
PubMed2003

Achieving geodetic motion for LISA test masses: ground testing results.

The low-frequency resolution of space-based gravitational wave observatories such as LISA (Laser Interferometry Space Antenna) hinges on the orbital purity of a free-falling reference test mass inside a satellite shield. We present here a torsion pendulum study of the forces that will disturb an orbiting test mass inside a LISA capacitive position sensor. The pendulum, with a measured torque noise floor below 10 fN m/square root of Hz from 0.6 to 10 mHz, has allowed placement of an upper limit on sensor force noise contributions, measurement of the sensor electrostatic stiffness at the 5% level, and detection and compensation of stray dc electrostatic biases at the millivolt level.

Journal Article↗
PubMed2003

Demonstration of a role for insulin in the regulation of leptin in lactating dairy cows.

In lactating dairy cows, the onset of negative net energy balance (EB) at parturition causes a reduction in plasma leptin and is also associated with increased concentration of growth hormone (GH) and decreased concentration of insulin. These observations raise the possibility that opposite changes in plasma insulin and GH are partly responsible for reduced plasma leptin. To test this hypothesis, we first examined the effects of undernutrition without the confounding influence of parturition by using late lactating dairy cows fed 120% of their nutrient requirements or restricted to 33% of maintenance requirements. Plasma leptin was reduced within 24 h of feed restriction, and was associated with increased plasma GH and decreased plasma insulin. Complete food deprivation for 48 h caused similar changes in the plasma concentration of leptin. To determine if an elevation in GH is responsible for the fall in plasma leptin, dairy cows were treated with excipient or bovine somatotropin in early lactation or in late lactation. Growth hormone treatment had no significant effect on plasma leptin irrespective of stage of lactation. Finally, the effects of insulin were studied by performing euglycemic hyperinsulinemic clamps in mid-lactating dairy cows. After 96 h of hyperinsulinemia, plasma leptin was increased significantly. These data indicate that insulin regulates plasma leptin in lactating dairy cows. They also suggest that, in undernourished lactating dairy cows, reduced plasma insulin could account for a portion of the decline in plasma leptin but that elevated plasma GH is unlikely to have a major effect.

Animal Nutritional Physiological Phenomena↗
PubMed2002

Effects of selection for milk yield on growth hormone response to growth hormone releasing factor in growing Holstein calves.

Bull and heifer calves (n = 81) from genetic lines of Holstein cows that differed by more than 4000 kg milk/305-d lactation were used to determine effects of selection for milk yield on growth hormone (GH) response to a GH releasing factor (GRF) analog. Calves received GRF (4 microg/100 kg BW) on 10, 56, 140, 196, 252, and 364 +/- 3 d of age. Jugular blood samples (n = 15) were obtained from -30 to 120 min relative to GRF administration. Area under the GH response curve (0 to 60 min, AUC60) was quantified after subtracting mean prechallenge GH concentrations. Data were analyzed for effects of line, age, gender, and their interactions with PROC MIXED of SAS for repeated measures and incorporated the spatial power law for unequally spaced data with age as the repeated effect. Means were considered different when P < 0.05. Prechallenge GH concentrations did not differ between lines, were greater in bulls than heifers (4.6 vs. 3.7 ng/ml), and decreased with age. The AUC60 decreased with age but did not differ between lines. Heifers responded more to GRF than bulls (1550 vs. 1336 ng x min/ml). Peak GH concentration decreased with age and was less in bulls than heifers (54.7 vs. 62.1 ng/ml) but did not differ between lines. Although plasma GH has been identified as an inheritable trait, we conclude the GH variables measured in this study were not useful in predicting genetic merit of calves from these substantially different lines of cows.

Aging↗
PubMed2002

Distributed optimal technology networks: a concept and strategy for potable water sustainability.

Viable strategies for ensuring adequate supplies of potable water are essential to long-term societal sustainability. The steadily increasing necessity for multiple reuse of water in urban societies is even now taxing our technical and financial abilities to meet ongoing needs for water suitable for human consumption. As a consequence, the current practice of treating the entire water demands of urban communities to the increasingly stringent standards required for drinking water is becoming an unsustainable practice, and thus a questionable strategy for planning and development of urban water systems. An innovative technology-based concept for implementation of a more sustainable strategy and practice for potable water is developed here. The concept is predicated on the inherent advantages of flexibility and responsiveness associated with decentralization of complex functions and operations. Specifically, it calls for strategic dispersal of flexible advanced treatment and control technologies throughout urban water transport and storage networks. This is in direct contradistinction to current strategies and practices of centralized and inflexible monolithic facilities. By integrating use-related satellite systems with critical components of existing systems and infrastructures, the concept can enable and facilitate optimal cost-effective applications of highly sophisticated advanced treatment and on-line monitoring and control technologies to in-place infrastructures in a holistic and sustainable manner.

Cities↗
PubMed2001

Mass transfer effects on microbial uptake of naphthalene from complex NAPLs.

The bioavailability of naphthalene present as a component of a complex nonaqueous phase liquid(NAPL) comprised by nine aromatic compounds was investigated. Specifically, the effects of naphthalene mass transfer from the NAPL to the aqueous phase on rates of its microbial degradation were examined. The investigations were conducted using a pure culture, ATCC 17484, and a mixed culture of naphthalene-degrading bacteria, the former having been implicated previously in the direct uptake of sorbed naphthalene. The studies were conducted in mass-transfer-limited, segregated-phase reactors(SPRs) in which both the NAPL and aqueous phases were internally well-mixed. A 30-day active biodegradation period was preceded and followed by a 5-7-day period devoid of bioactivity, during which time the rates and extents of mass transfer of components from the NAPL to the aqueous phase were quantified. The NAPL-phase naphthalene mass depletion profiles during biodegradation were compared to those predicted by assuming maximum mass depletion under mass-transfer-limited conditions using both pre- and post-biodegradation dissolution rate and equilibrium parameters. The observed mass depletion rates were high during the initial stages of biodegradation but decreased significantly in later stages. Throughout biodegradation, even in the initial rapid stage, mass depletion rates never exceeded maximum predicted rates based on pre-biodegradation mass transfer parameters. Reduced depletion rates in the later stages appear to relate to mass transfer hindrance caused by formation of biofilms at the NAPL-water interface.

Bacteria↗
PubMed2001

A distributed reactivity model for sorption by soils and sediments 13. Simulated diagenesis of natural sediment organic matter and its impact on sorption/desorption equilibria.

Subcritical water treatment was used to effect rapid compositional and functional changes to peat organic matter that mimic those of the natural diagenesis process. Elemental, solid state 13C NMR, FTIR, and calorimetry analyses all indicated that the organic matter of the artificially aged peat was chemically similar to that of geologically mature coal kerogens. This paper extends the work of the previous paper in this series, which investigated the effects of subcritical water treatment of humic topsoil on subsequent phenanthrene sorption and desorption equilibria. As opposed to the previous study, however, changes in sorptive reactivity herein were unequivocally related to changes in organic matter rather than other soil constituents, and organic matter functional changes due to the simulated diagenesis were more accurately characterized. Phenanthrene sorption capacity and isotherm nonlinearity both increased with increasing degrees of artificial aging, supporting the viewpoint that hydrophobic organic contaminant sorption equilibrium properties can be directly related to the degree of diagenesis of geosorbent organic matter. In addition, this work investigated effects of subcritical water treatment of a geologically mature, kerogen-containing shale sample. In contrast to the peat, the functional characteristics of the shale were unchanged by this treatment, and subsequent phenanthrene sorption equilibria were altered far less.

Adsorption↗
PubMed2001

A distributed reactivity model for sorption by soils and sediments. 14. Characterization and modeling of phenanthrene desorption rates.

Rates and extents of phenanthrene desorption were studied for more than 250 days as functions of sorbent type, initial loading level, and aging. Apparent first-order desorption rate constants for the slowly desorbing fraction were found to (i) range from 0.00086 to 0.148 days-1 for geosorbents that contain geologically mature kerogen and less rigid humic-type soil organic matter, respectively, (ii) decrease by as much as an order of magnitude with decreasing initial sorbed solid-phase phenanthrene concentration, (iii) decrease by a factor of 2 with increasing aging time for a humic topsoil but remain unaffected by aging time beyond 3 months for a shale, and (iv) be 1-2 orders of magnitude lower than rate constants for the rapidly desorbing phenanthrene fractions for any given contaminated sample. Six models were used to fit the desorption rate data. Biphasic diffusion and biphasic first-order models with three fitting parameters possess broad utility and are potentially useful in a variety of environmental applications. Disadvantages of a five-parameter triphasic first-order desorption model, a two-parameter gamma-function model, and a one- or two-parameter pore diffusion model are also discussed.

Adsorption↗
PubMed2001

Evaluation of shale and organoclays as sorbent additives for low-permeability soil containment barriers.

A natural shale and four synthetic organoclays were compared as potential sorbent additives to containment barriers at hazardous waste sites. Trimethylphenyl ammonium bentonite (TMPA-bent) was shown in batch experiments to have the greatest sorption capacities for 1,2,4-trichlorobenzene, trichloroethylene, and methyl isobutyl ketone, followed by the shale and a commercial organoclay. Sorption capacities were lowest for hexadecyltrimethyl ammonium bentonite (HDTMA-bent) and hexadecyl pyridinium bentonite (HDP-bent). Operative sorption mechanisms for the organoclays depended on the size of the organic modifier, i.e., uptake by the TMPA-bent occurred via adsorption onto mineral surfaces, while that for the HDTMA-bent and HDP-bent took place by absorption into organic phases formed by their long hydrocarbon tails. The shale was found to be by far the most cost-effective sorbent, an important factor for large scale applications. Solids concentration effects (i.e., higher apparent sorption capacities at lower experimental sorbent concentrations) were exhibited by HDTMA-bent and HDP-bent. This can be attributed to aggregation of sorbent particles as a result of interactions among their hydrocarbon chains. Solids effects were observed to decline and eventually disappear as sorbent concentrations were increased. Such effects must be considered in applying batch sorption results to flow-through systems.

Adsorption↗
PubMed2001

Rapid prediction of long-term rates of contaminant desorption from soils and sediments.

A method using heated and superheated (subcritical) water is described for rapid prediction of long-term desorption rates from contaminated geosorbents. Rates of contaminant release are measured at temperatures between 75 and 150 degrees C using a dynamic water desorption technique. The subcritical desorption rate data are then modeled to calculate apparent activation energies, and these activation energies are used to predict desorption behaviors at any desired ambient temperature. Predictions of long-term release rates based on this methodology were found to correlate well with experimental 25 degrees C desorption data measured over periods of up to 640 days, even though the 25 degrees C desorption rates were observed to vary by up to 2 orders of magnitude for different geosorbent types and initial solid phase contaminant loading levels. Desorption profiles measured under elevated temperature and pressure conditions closely matched those at 25 degrees C and ambient pressure, but the time scales associated with the high-temperature measurements were up to 3 orders of magnitude lower. The subcritical water technique rapidly estimates rates of desorption-resistant contaminant release as well as those for more labile substances. The practical implications of the methodology are significant because desorption observed under field conditions and ambient temperatures typically proceeds over periods of months or years, while the high temperature experiments used for prediction of such field desorption phenomena can be completed within periods of only hours or days.

Hot Temperature↗
PubMed2001

Contaminant interactions with geosorbent organic matter: insights drawn from polymer sciences.

This is a state-of-science review of interrelationships between the sorption/desorption behaviors and chemical structures of natural organic matter (NOM) matrices associated with soils, sediments and aquifer materials. It identifies similarities between these behavior-property interrelationships for natural geosorbents and those for synthetic organic polymers. It then invokes, with appropriate restrictions and modifications, several structure-function relationships that have been developed for synthetic polymers to explain the behavior of NOM matrices with respect to the sorption and desorption of hydrophobic organic contaminants (HOCs). Previous research regarding HOC sorption and desorption by different types of NOM and by synthetic polymers is summarized, and research requirements for further refinement of the NOM-polymer analogy are examined. The discussion focuses on structural and compositional heterogeneities that exist at the particle and aggregate scale, a scale at which homogeneity is commonly, and often improperly, assumed in the development of contaminant fate and transport models.

Adsorption↗
PubMed1998

Mass transfer effects on microbial uptake of naphthalene from complex NAPLs.

The bioavailability of naphthalene present as a component of a complex nonaqueous phase liquid (NAPL) comprised by nine aromatic compounds was investigated. Specifically, the effects of naphthalene mass transfer from the NAPL to the aqueous phase on rates of its microbial degradation were examined. The investigations were conducted using a pure culture, ATCC 17484, and a mixed culture of naphthalene-degrading bacteria, the former having been implicated previously in the direct uptake of sorbed naphthalene. The studies were conducted in mass-transfer-limited, segregated-phase reactors (SPRs) in which both the NAPL and aqueous phases were internally well-mixed. A 30-day active biodegradation period was preceded and followed by a 5-7-day period devoid of bioactivity, during which time the rates and extents of mass transfer of components from the NAPL to the aqueous phase were quantified. The NAPL-phase naphthalene mass depletion profiles during biodegradation were compared to those predicted by assuming maximum mass depletion under mass-transfer-limited conditions using both pre- and post-biodegradation dissolution rate and equilibrium parameters. The observed mass depletion rates were high during the initial stages of biodegradation but decreased significantly in later stages. Throughout biodegradation, even in the initial rapid stage, mass depletion rates never exceeded maximum predicted rates based on pre-biodegradation mass transfer parameters. Reduced depletion rates in the later stages appear to relate to mass transfer hindrance caused by formation of biofilms at the NAPL-water interface.

Bacteria↗
PubMed1997

A mere exposure effect for transformed three-dimensional objects: effects of reflection, size, or color changes on affect and recognition.

If the mere exposure effect is based on implicit memory, recognition and affect judgments should be dissociated by experimental variables in the same manner as other explicit and implicit measures. Consistent with results from recognition and picture naming or object decision priming tasks (e.g., Biederman & E.E. Cooper, 1991, 1992; L.A. Cooper, Schacter, Ballesteros, & Moore, 1992), the present research showed that recognition memory but not affective preference was impaired by reflection or size transformations of three-dimensional objects between study and test. Stimulus color transformations had no effect on either measure. These results indicate that representations that support recognition memory code spatial information about an object's left-right orientation and size, whereas representations that underlie affective preference do not. Insensitivity to surface feature changes that do not alter object form appears to be a general characteristic of implicit memory measures, including the affective preference task.

Analysis of Variance↗
PubMed1985

Comparison of the healing of prescrotal urethrotomy incisions in the dog: sutured versus nonsutured.

Comparison was made of the healing of sutured prescrotal urethral incisions (12 dogs) with that of nonsutured incisions (6 dogs). Comparison was also made of the healing of 5-0 polyglactin 910-sutured urethral incisions (6 dogs) with that of 5-0 polydioxanone-sutured incisions (6 dogs). Three dogs from each treatment group were euthanatized 3 weeks and 6 weeks after the surgical procedure. Surgical sites were examined grossly, and urethral circumference measurements were taken at 3 locations (surgical site, 1 cm cranially, and 1 cm caudally). Transverse sections of the surgical sites were prepared and examined by light microscopy. Hemorrhage occurred postoperatively in dogs in which the incisions were not sutured. The surgical sites from the 6 dogs in which incisions healed by second intention had more fibrosis and less inflammation than did those that were sutured. There was little difference between incisions sutured with polyglactin 910 and those sutured with polydioxanone suture material. Postoperative urethral stricture formation did not occur in any of the dogs.

Animals↗