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At least 19 recordsLinked to original sources
PubMed1989

In re Schmidt.

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Civil Rights↗
PubMed2002

Passive dissolution of hydrogen gas into groundwater using hollow-fiber membranes.

A new hollow-fiber membrane remediation system has recently been developed to passively supply groundwater with dissolved hydrogen (H2) to stimulate the biodegradation of chlorinated solvents. Understanding the mass transfer behavior of membranes under conditions of creeping flow is critical for the design of such systems. Therefore, the objectives of this research were to evaluate the gas transfer behavior of hollow-fiber membranes under conditions typical of groundwater flow and to assess the effect of membrane configuration on gas transfer performance. Membrane gas transfer was evaluated using laboratory-scale glass columns operated at low flow velocities (8.6-12,973 cm/d). H2 was supplied to the inside of the membrane fibers while water flowed on the outside and normal to the fibers (i.e. cross-flow). Membrane configuration (single fiber and fabric) and membrane spacing for the fabric modules did not affect gas transfer performance. Therefore, the results from all of the experiments were combined to obtain the following dimensionless Sherwood number (Sh) correlation expressed as a function of Reynolds number (Re) and Schmidt number (Sc): Sh = 0.824Re(0.39)Sc(0.33) (0.0004<Re<0.6). This correlation is useful for predicting the rate of transfer of any gas from clean membranes to flowing water at low Re. This correlation provides a basis for estimating the membrane surface area requirements for groundwater remediation as illustrated by a simple example.

Biodegradation, Environmental↗
PubMed1999

Application of Traditional and Phylogenetically Based Comparative Methods to Test for a Trade-off in Bacterial Growth Rate at Low versus High Substrate Concentration.

Abstract It is often hypothesized that those organisms that are superior competitors for sparse resources fare poorly in competition for abundant resources, and vice versa. If there is indeed such a systematic trade-off, then this has important implications for the choice of bacterial strains in bioremediation and other applications. We studied seven bacterial strains that can grow on either 2,4-dichlorophenoxyacetate (2,4-D) or succinate as a sole source of carbon. Growth rates were measured on each substrate at both low (5 µg/ml) and high (500 µg/ml) concentrations. We used two different methods to test the significance of correlations among growth rates, a traditional method that treats each strain as an independent observation and a newer method that takes into account phylogenetic relationships between strains, thereby avoiding spurious correlations caused by a lack of statistical independence of strains. In both 2,4-D and succinate, we observed significant positive correlations between growth rates measured at high and low substrate concentrations by the traditional comparative method. No significant correlations were detected after adjusting for the phylogenetic relationships among the strains. In neither case did we observe the negative correlation expected from a trade-off between growth rates at high and low substrate levels.http://link.springer-ny.com/link/service/journals/00248/bibs/38n3p191.html</hea

Journal Article↗
PubMed2006

Transport and uptake of MTBE and ethanol vapors in a human upper airway model.

Potential human exposure to vapors of methyl tertiary-butyl ether (MTBE) and ethanol is of increasing concern because these materials are widely used as gasoline additives. In this study we analyzed numerically the transport and deposition of MTBE and ethanol vapors in a model of the human upper respiratory airway, consisting of an oral airway and the first four generations of the tracheobronchial tree. Airflow characteristics and mass transfer processes were analyzed at different inspiratory flow conditions using a three-dimensional computational fluid and particle dynamics method. The deposition data were analyzed in terms of regional deposition fractions (DF = regional uptake/mouth concentration) and deposition enhancement factors (DEF = local DF/average DF) at local micro surface areas. Results show that DF in the entire upper airway model is 21.9%, 12.4%, and 6.9% for MTBE and 67.5%, 51.5%, and 38.5% for ethanol at a flow rate of 15, 30, and 60 L/min, respectively. Of the total DF, 65-70% is deposited in the oral airway for both vapors. Deposition is localized at various sites within the upper airway structure, with a maximum DEF of 1.5 for MTBE and 7.8 for ethanol. Local deposition patterns did not change with inhalation conditions, but DF and the maximum DEF increased with diffusivity, solubility, and the degree of airway wall absorption of vapors, as shown by a greater deposition of ethanol than MTBE. The vapor deposition efficiency as expressed by the dimensionless mass transfer coefficient correlated well with a product of Reynolds (Re) and Schmidt (Sc) numbers. In conclusion, MTBE and ethanol vapors deposit substantially in the upper airway structure with a marked enhancement of dose at local sites, and the deposition dose may be reasonably estimated by a functional relationship with dimensionless fluid flow and diffusion parameters.

Absorption↗
PubMedDate not supplied

Dissolution of azathioprine from tablets in forced laminar flow of liquid.

The dissolution of azathioprine from tablets was investigated in a column apparatus with forced laminar liquid flow. The experiments showed that auxiliary ingredients and hydrodynamic factors affected the diffusion coefficient and solubility of the active principle and the density and viscosity of eluates from dissolution cell. For laminar flows changes in these physico-chemical parameters are described by a dimensionless equation (Formula: see text), where Sh--Sherwood number, Sc--Schmidt number, Re--Reynolds number, (Formula: see text)--grain dispersion in disintegrated tablet mass.

Azathioprine↗
PubMed1997

Measurements of airway dimensions and calculation of mass transfer characteristics of the human oral passage.

This paper presents measurements of the geometric shape, perimeter, and cross-sectional area of the human oral passage (from oral entrance to midtrachea) and relates them through dimensionless parameters to the depositional mass transfer of ultrafine particles. Studies were performed in two identical replicate oral passage models, one of which was cut orthogonal to the airflow direction into 3 mm elements for measurement, the other used intact for experimental measurements of ultrafine aerosol deposition. Dimensional data were combined with deposition measurements in two sections of the oral passage (the horizontal oral cavity and the vertical laryngeal-tracheal airway) to calculate the dimensionless mass transfer Sherwood number (Sh). Mass transfer theory suggests that Sh should be expressible as a function of the Reynolds number (Re) and the Schmidt number (Sc). For inhalation and exhalation through the oral cavity (O-C), an empirical relationship was obtained for flow rates from 7.5-30.0 1 min-1: Sh = 15.3 Re0.812 Sc-0.986 An empirical relationship was likewise obtained for the laryngeal-tracheal (L-T) region over the same range of flow rates: Sh = 25.9 Re0.861 Sc-1.37 These relationships were compared to heat transfer in the human upper airways through the well-known analogy between heat and mass transfer. The Reynolds number dependence for both the O-C and L-T relationships was in good agreement with that for heat transfer. The mass transfer coefficients were compared to extrathoracic uptake of gases and vapors and showed similar flow rate dependence. For gases and vapors that conform to the zero concentration boundary condition, the empirical relationships are applicable when diffusion coefficients are taken into consideration.

Absorption↗
PubMed1998

Re: Saving face.

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Hair Removal↗
PubMed1985

[Persistence of antibodies against hepatitis B surface antigens after vaccination against hepatitis B].

In 195 patients vaccinated against hepatitis B the course of anti-HBs concentration was followed over 4 years. Persistence of anti-HBs proved to be dependent on the level of anti-HBs concentration after basal immunization: in 14 subjects with a maximal anti-HBs level between 10 and 100 IU/l the level had dropped to less than 10 IU/l (considered to be the lowest prophylactic concentration), while 7 were anti-HBs negative. Of those who had 101-1000 IU/l after initial immunization 49% had anti-HBs levels under 10 IU/l after 4 years, while 18% were negative. Among subjects with concentrations 1001-10 000 IU/l after the third immunization only 7% had values below 10 IU/l after 4 years, 4.2% were negative. All those who, after the third immunization, had had anti-HBs levels above 10 000 IU/l, 4 years later still had anti-HBs levels of more than 100 IU/l (mean 581 IU/l). Quantitative anti-HBs determination after triple vaccination against hepatitis B thus makes it possible to predict the duration of protection and to determine the timing of re-vaccination.

Adult↗
PubMed1985

[Electrocardiogram in acute anterior wall infarct after restoration of the blood supply].

Changes in QRS complexes and ST-T segments were measured in 70 patients after acute anterior-wall myocardial infarction. Intracoronary streptokinase infusion was undertaken in the acute phase in 58 patients, 12 other patients treated conventionally without infusion serving as controls. Precordial ECG mapping employed 48 unipolar precordial leads. If recanalization of an occluded coronary artery was achieved, there was a significant rise in R amplitude (sum of R-wave amplitudes in the 48 leads) from 12.4 +/- 10.9 to 16.2 +/- 11.2 mV, within a period of up to four months after the acute stage. If thrombolysis failed or only conventional treatment had been practised, there was no rise in R-wave amplitude. Renewed occlusion of a vessel previously re-opened by streptokinase infusion produced a reduction in R-wave amplitude from 14.0 +/- 13.0 to 9.8 +/- 11.0 mV. The S-T segment elevation regressed immediately after recanalization of the coronary artery. The S-T segments were iso-electric after four months. Re-occlusion caused renewed S-T segment elevation up to monophasic form. Precordial ECG mapping is thus well suited for serial controls after various re-perfusion measures.

Electrocardiography↗
PubMed1972

Mass transfer from gas bubbles to impinging flow of biological fluids with chemical reaction.

The rates of mass transfer from a gas bubble to an impinging flow of a biological fluid such as whole blood and plasma are investigated analytically and experimentally. Gases commonly found dissolved in body fluids are included. Consideration is given to the effects of the chemical reaction between the dissolved gas and the liquid on the rate of mass transfer. Through the application of boundary layer theory the over-all transfer is found to be Sh/(Re)(1/2) = 0.845 Sc(1/3) in the absence of chemical reaction, and Sh/(Re) (1/2) = F' (0) in the presence of chemical reaction, where Sh, Re, and Sc are the Sherwood, Reynolds, and Schmidt numbers, respectively, and F' (0) is a function of Sc and the dimensionless reaction rate constant. Analytical results are also obtained for the bubble lifetime and the bubble radius-time history. These results, which are not incompatible with experimental results, can be applied to predict the dissolution of the entrapped gas emboli in the circulatory system of the human body.

Biochemistry↗