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PubMed2004

Streaming current measurements in zirconia-coated capillaries.

The electroosmotic flow created in zirconia-modified capillaries has been previously investigated. In this paper, we compared the electroosmotic data set with streaming current measurements and we related all these data through zeta-potential. Streaming current measurements give an excellent indication on the direction and the value of the electroosmotic mobility of an electrolyte/capillary system for a large set of experimental conditions: 2 < pH < 12, 0 < ACN < 80 %, 10(-4) M < [SO(2- )4 ] < 4 x 10(-2) M. A good correlation between zeta-potential from streaming current measurements and zeta-potential from electroosmotic mobility measurements was observed (r2 = 0.95). However, the values obtained from streaming current were always slightly lower than the one calculated from electroosmotic mobility (slope = 0.86, sigma = 0.06). In zirconia-coated capillaries the zeta-potential can be tuned from -50 to +100 mV depending on the composition of the electrolyte.

Acetonitriles↗
PubMed2006

Electrophoresis of a spherical dispersion of polyelectrolytes in a salt-free solution.

The electrophoretic behavior of a spherical dispersion of polyelectrolytes of arbitrary concentration is analyzed theoretically under a salt-free condition, that is, the liquid phase contains only counterions which come from the dissociation of the functional groups of polyelectrolytes. We show that, in general, the surface potential of a polyelectrolyte increases nonlinearly with its surface charge. A linear relation exists between them, however, when the latter is sufficiently small; and the more dilute the concentration of polyelectrolytes, the broader the range in which they are linearly correlated. If the amount of surface charge is sufficiently large, counterion condensation occurs, and the rate of increase of surface potential as the amount of surface charge increases declined. Also, it leads to an inverse in the perturbed potential near the surface of a polyelectrolyte, and its mobility decreases accordingly. For a fixed amount of surface charge, the lower the concentration of polyelectrolytes and/or the lower the valence of counterions, the higher the surface potential. The qualitative behavior of the mobility of a polyelectrolyte as the amount of its surface charge varies is similar to that of its surface charge.

Journal Article↗
PubMed1994

Electroosmosis of polymer solutions in fused silica capillaries.

The classical von Smoluchowski equation predicts that the electroosmotic mobility generated by the wall zeta potential could be suppressed if the viscosity of the solution adjacent to the wall were extremely high. When performing runs in capillaries filled with polymer solutions (2% methyl cellulose solutions with viscosities of 25 cP), however, one consistently finds that the quenching of electroosmotic mobility is substantially less than predicted by the von Smoluchowski relationship. The electroosmotic flow is progressively suppressed with subsequent electrophoretic runs, suggesting a "dynamic coating" of the polymers onto the capillary wall. This progressive reduction of electroosmotic mobility tends to a plateau value which is still substantially higher than the value derived on the basis of the von Smoluchowski relationship. The following explanation is proposed: due to the very high shear rate in the electric double layer, the polymer molecules change their orientation and/or conformation, which lowers the fluid viscosity in this region. A scaling equation for electroosmotic mobility taking into account the non-Newtonian properties of polymer solutions is derived. It predicts electric field dependence of the electroosmotic mobility as the shear rate in the double layer is proportional to the electric field. Experimental measurements confirm the dependence of the electroosmotic mobility on the electric field.

Electromagnetic Fields↗
PubMed2000

Dynamic Mobility of Particles with Thick Double Layers in a Nondilute Suspension.

The dynamic mobility of a nondilute suspension of spherical particles is investigated in the case where the thickness of the electrical double layer around each particle is comparable to the particle radius. A formula is obtained for the O(&phi;) correction in a random suspension of particles with volume fraction &phi;, involving an integral over the dynamic mobility of a pair of spheres. This formula is then evaluated using both analytical approximations and numerical results previously obtained for the pair mobilities and valid for low surface potentials. The effect of double-layer thickness on the O(&phi;) coefficient is most pronounced at low frequencies, and lessens once the hydrodynamic penetration depth is smaller than the particle radius. Various approximations are considered that use the O(&phi;) result to predict the dynamic mobility in concentrated suspensions, and at high frequencies these approximations are shown to give results qualitatively different from those of recent cell models. Copyright 2000 Academic Press.

Journal Article↗
PubMed2001

Counterion Triple Layer in Solid/Solution Interface: Stirring and Temperature Effects on pH Measurements.

This paper reports on the pH glass electrode potential based on the double-capacitor theory and the discovery of a mobile counterion triple layer next to the double layer to explain the electrode potential changes caused by stirring and temperature increase. This mobile triple layer behaves like a rubberband, which may be loosened by stirring (or agitation) and temperature increase and tightened after stirring stops or temperature lowers. Stirring and temperature exert different effects on the potential of the pH and SCE electrodes via their different mechanisms. In contrast to the past, results reported here were obtained from experiments designed with the glass electrode and SCE in separate beakers connected with a conducting wire, so that one electrode could be stirred while keeping the other unstirred. There is a weak charge attraction between the double and triple layers, not a strong covalent bonding for complexation, so that the latter can be removed by stirring or temperature increase. In light of present results and the new concept, the Boltzmann equation has been modified to include the net charge density and the triple-layer potential. The counterion triple layer concept will have a tremendous impact on our understanding of the interface structure and properties, and stimulate further studies and applications of ion-selective electrodes. Copyright 2001 Academic Press.

Journal Article↗
PubMed2002

Density-modified displacement for DNAPL source zone remediation: density conversion and recovery in heterogeneous aquifer cells.

Low interfacial tension (IFT) displacement (mobilization) of nonaqueous phase liquids (NAPLs) offers potential as an efficient remediation technology for contaminated aquifer source zones. However, displacement of dense NAPLs (DNAPLs) is problematic due to the tendency for downward migration and redistribution of the mobilized DNAPL. To overcome this limitation, a density-modified displacement method (DMD) was developed, which couples in situ density conversion of DNAPLs via alcohol partitioning with low IFT NAPL displacement and recovery. The objective of this work was to evaluate the DMD method for two representative DNAPLs, chlorobenzene (CB) and trichloroethene (TCE). Laboratory-scale experiments were conducted in a two-dimensional (2-D) cell, configured to represent a heterogeneous unconfined aquifer system containing low permeability lenses. After release and redistribution of either CB- or TCE-NAPL, the 2-D aquifer cells were flushed with a 6% (wt) n-butanol aqueous solution to achieve DNAPL to light NAPL conversion, followed by a low IFT surfactant solution consisting of 4% (4:1) Aerosol MA/Aerosol OT + 20% n-butanol + 500 mg/L CaCl2. Visual observations and experimental measurements demonstrated that in situ density conversion and immiscible displacement of both CB and TCE were successful. Effluent NAPL densities ranged from 0.96 to 0.90 g/mL for CB and from 0.95 to 0.92 g/mL for TCE, while aqueous phase densities remained above 0.96 g/L. Density conversion of CB and TCE was achieved after flushing with 1.2 and 4.9 pore vol of 6% n-butanol solution, respectively. Recoveries of 90% CB and 85% TCE were realized after flushing with 1.2 pore vol of the low IFT surfactant solution, which was followed by a 1 pore vol posttreatment water flood. Surfactant and n-butanol recoveries ranged from 75 to 96% based on effluent concentration data. The observed minimal mobilization during the n-butanol density conversion preflood and near complete mobilization during the low IFT displacement flood were consistent with total trapping number calculations. The results reported herein demonstrate the potential efficiency of the DMD technology as a means of DNAPL source zone restoration.

Aerosols↗
PubMed2006

Enhanced aqueous solubilization of tetrachloroethylene by a rhamnolipid biosurfactant.

A rhamnolipid biosurfactant produced by Pseudomonas aeruginosa ATCC 9027 was isolated, purified and characterized in terms of its ability to mobilize and solubilize tetrachloroethylene (PCE) for potential use in surfactant-enhanced aquifer remediation (SEAR) applications. Using a drop volume method, the PCE-biosurfactant steady-state interfacial tension was determined and found to be ca. 10 mN/m which is not low enough to cause significant PCE nonaqueous phase liquid (NAPL) mobilization. It was observed that the biosurfactant partitioned significantly into PCE at aqueous concentrations higher than the critical micelle concentration (CMC). After accounting for rhamnolipid partitioning into the PCE phase, a weight solubilization ratio (WSR) of 1.2 g(PCE)/g(rhamnolipid) was determined and through this mechanism the biosurfactant significantly improved the apparent aqueous solubility of PCE.

Glycolipids↗
PubMed2001

Approximate Analytic Expression for the Electrophoretic Mobility of a Spherical Colloidal Particle.

An approximate analytic expression for the electrophoretic mobility of a spherical colloidal particle in a symmetrical electrolyte solution is obtained. This mobility expression, which is correct to the order of the third power of the zeta-potential of the particle, considerably improves Henry's mobility formula (Proc. R. Soc. London Ser. A 133, 106 (1931)) and has a much simpler form than similar mobility formulas expressed in powers of zeta derived by Overbeek (Kolloid-Beihefte 54, 287 (1943)) and by Booth (Proc. R. Soc. London Ser. A 203, 514 (1950)). Comparison with the exact computer calculation by O'Brien and White (J. Chem. Soc. Faraday Trans. 2 74, 1607 (1978)) shows that the obtained mobility formula is an excellent approximation, especially for small kappaa (where kappa is the Debye-Hückel parameter and a is theparticle radius) in which region no other simple analytic mobility formulas are available than Henry's formula, which is correct to order zeta and is applicable only for low zeta. Copyright 2001 Academic Press.

Journal Article↗
PubMed1998

Cooperative problem solving with personal mobile information tools in hospitals.

Health-care professionals have a broad range of needs for information and cooperation while working at different points of care (e.g., outpatient departments, wards, and functional units such as operating theaters). Patient-related data and medical knowledge have to be widely available to support high-quality patient care. Furthermore, due to the increased specialization of health-care professionals, efficient collaboration is required. Personal mobile information tools have a considerable potential to realize almost ubiquitous information and collaborative support. They enable to unite the functionality of conventional tools such as paper forms, dictating machines, and pagers into one tool. Moreover, they can extend the support already provided by clinical workstations. An approach is described for the integration of mobile information tools with heterogeneous hospital information systems. This approach includes identification of functions which should be provided on mobile tools. Major functions are the presentation of medical records and reports, electronic mailing to support interpersonal communication, and the provision of editors for structured clinical documentation. To realize those functions on mobile tools, we propose a document-based client-server architecture that enables mobile information tools to interoperate with existing computer-based application systems. Open application systems and powerful, partially wireless, hospital-wide networks are the prerequisites for the introduction of mobile information tools.

Decision Making, Computer-Assisted↗
PubMed1997

Requirement of gamma-carboxyglutamic acid residues for the biological activity of Gas6: contribution of endogenous Gas6 to the proliferation of vascular smooth muscle cells.

Gas6 (encoded by growth-arrest-specific gene 6) is a gamma-carboxyglutamic acid (Gla)-containing protein which is released from growth-arrested vascular smooth muscle cells (VSMCs) and potentiates VSMC proliferation induced by Ca2+-mobilizing growth factors, but not that induced by receptor tyrosine kinases. In this study we examined the importance of Gla residues for the biological activities of Gas6 and tried to assess the importance of endogenous Gas6 in VSMC proliferation. We demonstrated that Gla-deficient Gas6 lacked receptor-binding and growth-potentiating activities. Therefore the vitamin K-dependent modification of Gas6 appeared to be essential for its biological activities. Next we used warfarin, an inhibitor of vitamin K-dependent gamma-carboxylation, to estimate the contribution of endogenous Gas6 to VSMC proliferation. Warfarin markedly inhibited the thrombin-induced proliferation of VSMC without affecting the mRNA or protein expression of Gas6. Therefore the inhibition seems to be due to prevention of the vitamin K-dependent modification of Gas6. However, warfarin did not affect epidermal growth factor-induced proliferation. A neutralizing antibody against Gas6 gave a similar result, i.e. it inhibited thrombin-induced VSMC proliferation but not that induced by epidermal growth factor. These results indicate that endogenously produced Gas6 is very important for VSMC proliferation induced by Ca2+-mobilizing growth factors.

1-Carboxyglutamic Acid↗
PubMed2006

The Leishmania donovani complex: genotypes of five metabolic enzymes (ICD, ME, MPI, G6PDH, and FH), new targets for multilocus sequence typing.

Flagellates of the Leishmania donovani complex are causative agents of human cutaneous and visceral leishmaniasis. The complex is comprised of L. donovani, Leishmania infantum and Leishmania archibaldi, although the latter is not now considered to be a valid species. Morphological distinction of Leishmania species is impractical, so biochemical, immunological and DNA-based criteria were introduced. Multilocus enzyme electrophoresis (MLEE) is the present gold standard. We have sequenced the genes encoding five metabolic enzymes used for MLEE, both to resolve the DNA diversity underlying isoenzyme mobility differences and to explore the potential of these targets for higher resolution PCR-based multilocus sequence typing. The genes sequenced were isocitrate dehydrogenase, malic enzyme, mannose phosphate isomerase, glucose-6-phosphate dehydrogenase, and fumarate hydratase, for 17 strains of L. infantum, seven strains of L. donovani, and three strains of L. archibaldi. Protein mobilities predicted from amino acid sequences did not always accord precisely with reported MLEE profiles. A high number of heterozygous sites was detected. Heterozygosity was particularly frequent in some strains and indirectly supported the presence of genetic exchange in Leishmania. Phylogenetic analysis of a concatenated alignment based on a total of 263 kb protein-coding sequences showed strong correlation of genotype with geographical origin. Europe and Africa appear to represent independent evolutionary centres.

Animals↗
PubMed1998

Electrophoretic Mobility of a Sphere in a Spherical Cavity.

The electrophoretic behavior of a spherical particle in a spherical cavity is analyzed theoretically, taking the effect of double layer polarization into account. We show that for the case where the particle is positively charged and the cavity uncharged if the surface potential of particle is high, the variation of the mobility of the particle as a function of kappaa has a minimum, kappa and a being respectively the reciprocal Debye length and particle radius. This minimum does not appear if the effect of double layer polarization is neglected. The variation of the mobility as a function of kappaa has a minimum for a medium value of lambda (= particle radius/cavity radius); it becomes negligible if lambda is either small or large. In the case where the particle is uncharged and the cavity positively charged, if the surface potential is high, the variation of mobility as a function of kappaa has a maximum; if it is low, the mobility increases monotonically with kappaa. Here, the mobility is mainly determined by the drag force, rather than by the electric force, acting on the particle as in the case where the particle is positively charged and the cavity uncharged. If both the particle and the cavity are charged, the electrophoretic behavior of the particle can be deduced from the results of the above two cases. Copyright 1998 Academic Press.

Journal Article↗
PubMed2006

A small subsurface ion mobility spectrometer sensor for detecting environmental soil-gas contaminants.

A small subsurface ion mobility spectrometer (SS-IMS) was constructed and tested with several environmental contaminants to determine its potential for monitoring gaseous volatile organic compounds in the vadose zone. Trichloroethylene (TCE) and tetrachloroethylene (PCE) were detected and separated in IMS for the first time. Detection limits as low as 1 part per billion volume-to-volume (ppb(v)) were observed. Reduced mobility (K(0)) values were reported for 11 environmental contaminants. These data demonstrated the potential of ion mobility spectrometry as a viable technology for detecting and separating environmental soil-gas contaminants in the field, which may lead to a practical and simple approach for long-term monitoring of contaminated soils.

Environmental Monitoring↗
PubMed1998

Mobilization of lead from the skeleton during the postnatal period is larger than during pregnancy.

A cohort of 15 immigrant females to Australia and 7 native Australian controls were monitored on a monthly basis with high-precision lead isotopic methods during gestation and for 6 months after pregnancy to determine the extent of lead mobilization from the maternal skeleton. Quarterly environmental samples of house dust, drinking water, urban air, gasoline, and a 6-day duplicate diet were also measured. The geometric mean blood lead concentration for the immigrant females on arrival in Australia was 3.0 microg/dl (range: 1.9 to 20 microg/dl), and for the Australian controls was 3.1 gm/dl (range: 1.9 to 4.3 microg/dl). During gestation and after pregnancy, blood lead concentrations varied, with mean individual changes of -14% to 83%. For the immigrant subjects, the percentage change in blood lead concentration was significantly greater during the postpregnancy period than during the 2nd and 3rd trimesters (p < 0.001). Skeletal contribution to blood lead, based on the isotopic composition for the immigrant subjects, increased in an approximately linear manner during pregnancy. The mean increases for each individual during pregnancy varied from 26% to 99%. Skeletal lead contribution to blood lead was significantly greater (p < 0.001) during the postpregnancy period than during the 2nd and 3rd trimesters. The contribution of skeletal lead to blood lead during the postpregnancy period remained essentially constant at the increased level of lead mobilization, although the duration of breastfeeding varied from 1 week to more than 6 months. The increased contribution of skeletal lead to blood lead during the postpregnancy period is attributed to increased mobilization of lead from maternal skeletal stores during lactation. The increased contribution of skeletal lead both during pregnancy and in the postpregnancy period is consistent with increased bone resorption, and may be associated with an inadequate calcium intake observed in quarterly 6-day duplicate diets. Mobilization of skeletal lead stores represents a potentially important source of perinatal lead intake and accumulation in the developing fetus. Only two subjects consumed dietary supplements for calcium, and their mobilization of lead from the skeleton to the blood was the lowest of all the subjects. These two subjects' use of calcium supplements may have reduced mobilization of skeletal mineral stores to supply the calcium needs of pregnancy and lactation. Calcium supplementation may be an important means of limiting fetal exposure to lead.

Bone and Bones↗
PubMed1975

Noble metals: a toxicological appraisal of potential new environmental contaminants.

The public health benefits expected by reducing known hazardous emissions from mobile sources should not be compromised by increasing levels of other potentially hazardous unregulated emissions. Catalytic converters are going to be used to meet the statutory requirements on carbon monoxide and hydrocarbon emissions from light duty motor vehicles. Platinum and palladium metals are the catalytic materials to be used in these emission control devices. Preliminary experimental evidence and analysis of the impact of these control devices on the future use and demand for platinum indicates that this metal may appear at detectable levels in the environment by the end of this decade. At the present time, platinum and palladium are not present in the public environment and represent potentially new environmental contaminants as a consequence of use of this new abatement control technology. There is relatively little information available to adequately assess the potential health hazards that may be associated with exposure to these metals and their compounds. Analysis of the environmental problems and concerns associated with possible new environmental contaminants are discussed. Limited estimates are made on community exposure by use of a meteorological dispersion model. Biodegradation potential and attention is also given to the limited toxicological information available.

Air Pollutants↗
PubMed1992

[Population epidemiologic evaluation of the Hannover Mobile Rheumatoid Health Service].

The aim of the study was the evaluation of a potential selection process for patients with rheumatoid arthritis (RA) referred to the Mobile Service for Rheumatics in Hannover (MSRH). The MSRH is the only referral center for patients with inflammatory rheumatic diseases in Hannover. A comparison of the health status was made between 58 individuals with RA identified in a population study, and 103 RA patients from the MSRH. The following disease parameters were less favorable in the clinical group: duration of morning stiffness, functional capacity, number of swollen joints, rheumatoid factor, ESR, disease activity, and classical RA according to the Rome-criteria. Only 22% of the individuals with RA identified in the population study have been referred to the MSRH. These patients more frequently had definite or classical RA (statistically not significant: p = 0.17, p = 0.11, respectively). It was shown that the clinical group comprised more severe RA cases. Thus, data from such patients may not be generalized for the entire group of RA cases in the population.

Ambulatory Care Facilities↗
PubMed2026

Spiramycin fermentation residue-derived biochar regulates soil nutrient cycling, microbial communities, and antibiotic resistance gene dynamics.

Spiramycin fermentation residues (SFR) are hazardous wastes enriched with residual antibiotics, yet they can serve as potential feedstocks for resource recovery after appropriate treatment. In this study, SFR-derived biochar (SFR-BC) was produced by pyrolysis and applied to agricultural soil to evaluate its effects on soil properties, microbial communities, potential pathogenic bacteria, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs). A 60-day soil incubation experiment was conducted with one control and three SFR-BC application rates of 0.5%, 1.0%, and 2.0%. SFR-BC improved soil physicochemical properties, nutrient status, enzyme activities, and microbial alpha diversity. Metagenomic analysis showed that SFR-BC altered the abundance of functional genes associated with carbon and nitrogen cycling, indicating shifts in microbial functional potential. SFR-BC also changed bacterial co-occurrence patterns, with the high-dose treatment showing a more complex and highly connected network structure during incubation. In addition, high-dose SFR-BC reduced several potential pathogenic bacteria, including major plant pathogenic taxa. SFR-BC decreased soil ARG abundance by 9.38%-33.67% and MGE abundance by 6.49%-27.89% relative to the control, showing a dose-dependent reduction in antibiotic resistance-related genetic elements. Network and PLS-PM analyses further indicated that ARG variation was statistically associated with soil physicochemical properties, microbial diversity, potential bacterial hosts, and MGEs. Overall, these results suggest that SFR-BC can improve short-term soil nutrient status and reduce ARGs, MGEs, and several potential pathogenic taxa under controlled incubation conditions, providing useful evidence for the potential valorization of antibiotic fermentation residues through pyrolysis.

Charcoal↗
PubMed2004

Cellulose-based chromatography for cellooligosaccharide production.

The potential of using cellulose stationary phases for the chromatographic fractionation of cellooligosaccharide preparations has been explored. The impetus for the work is the current interest in using cellooligosaccharides as functional nondigestible oligosaccharides in foods. The conceptual studies illustrate the potential of using ethanol-water mobile phases in conjunction with cellulose stationary phases for cellooligosaccharide fractionation. Cellooligosaccharide solubility in ethanol-water mixtures and their elution order from cellulose-based columns using ethanol-water mobile phases were shown to be in line with their degree of polymerization (DP), with the higher DP cellooligosaccharides being less soluble and having longer retention times. The retention volume for all COS increased with increased temperature. Both microcrystalline and fibrous cellulose preparations were shown to work as chromatographic stationary phases. The application experiments demonstrate the potential of using cellulose stationary phases for the cleanup and fractionation of cellooligosaccharide mixtures generated via acid-catalyzed hydrolysis of cellulose.

Cellulose↗