Capillary Surfaces Research Articles

The augmented skeleton method for parametrized surfaces of liquid drops

A numerical method for parametrized capillary surfaces with prescribed volume is presented. The walls of the container to which the liquid is confined are assumed to be planar, or more generally ruled surfaces.

Capillary zone electrophoresis–mass spectrometry with electrospray ionization of peptides and proteins

AbstractCapillary zone electrophoresis (CZE) coupled with an on‐line mass spectrometric (MS) detection system by an atmospheric pressure electrospray ionization (ESI) interface has been used successfully for Separations of peptide and protein mixtures. For CZE‐MS, ESI produces multiply charged molecular ions and thus allows mas spectrometers with a limited mass‐to‐charge range to analyze proteins having molecular weights greater than 100,000. Various pH buffer systems have been investigated, including buffer systems in which pH > pI (isoelectric point of analytes) and pH « pI are designed to reduce protein adsorption onto silica capillary surfaces and thus improve separation efficiencies. More than 125,000 theoretical plates have been obtained from a CZE‐MS separation of less than 1 pmol per component of leucine enkephalin and horse heart myoglobin. CZE‐MS of other large peptides and proteins are demonstrated.

Instability of certain capillary surfaces

A family of capillary surface configurations, shown in an earlier paper to be unstable for sufficiently small Bond numberB, is here shown to be unstable also forB sufficiently large. Numerical evaluations indicate that it is unstable for allB. Some numerical calculations of the corresponding container shapes are included.

Moon Surfaces, and Boundary Behaviour of Capillary Surfaces for Perfect Wetting and Non-Wetting

Moon Surfaces, and Boundary Behaviour of Capillary Surfaces for Perfect Wetting and Non-Wetting

Human platelets attenuate oxidant injury in isolated rabbit lungs.

Because platelets contain active antioxidant systems, the capacity of platelets to attenuate oxidant lung injury was investigated. Purine and xanthine oxidase were infused into isolated perfused rabbit lungs (IPL) to generate H2O2, thereby causing increased membrane permeability edema. The coinfusion of washed human platelets (1.20 +/- 0.07 x 10(10) cells) attenuated the degree of edema formation as measured by lung weight gain and lung lavage albumin concentration. Electron microscopy of lung preparations demonstrated platelet adherence to capillary endothelial luminal surfaces of oxidant-injured lungs, but there was no evidence of vascular plugging with platelet macroaggregates. The platelet glutathione redox cycle or platelet catalase were inhibited before infusion of platelets into the IPL with purine and xanthine oxidase. Inhibition of the glutathione redox cycle with 1,3-bis(2-chloroethyl)-1-nitrosourea, 1-chloro-2,4-dinitrobenzene, or buthionine sulfoximine prevented platelet attenuation of lung injury. Inactivation of platelet catalase with 3-amino-1,2,4-triazole, however, did not significantly reduce the platelet-induced lung protection. We conclude that the platelet glutathione redox cycle plays a major role in reducing enzymatically generated toxic O2 metabolites and attenuating lung injury.

Lipid transport function of lipoproteins in blood plasma.

Fatty acid and cholesterol transport in plasma lipoproteins evolved in the context of an open circulatory system in which lipoprotein particles are secreted directly into the blood and have ready access to cells in various tissues. In higher vertebrates with closed capillary beds, hydrolysis of triglycerides at capillary surfaces is required for efficient uptake of their component fatty acids into cells. Likewise, hydrolysis of cellular triglycerides in cells of adipose tissue precedes mobilization of the fatty acids and permits large amounts to be transported in the blood. However, in all Metazoa lipoproteins are secreted primarily from cells adjacent to an open microvascular bed. Uptake of lipoprotein particles as such into cells occurs in invertebrates and vertebrates alike, facilitated by binding to high-affinity receptors on cell surfaces. In vertebrates, a concentration gradient created between cholesterol in cells and lipoproteins by a cholesterol-esterifying enzyme that acts on lipoproteins promotes movement of cholesterol into the plasma compartment. Thus the strategies to transport poorly soluble lipids include enzymatic reactions at cell surfaces and in blood plasma as well as the processes of exocytosis and endocytosis.

Control of electroosmosis in coated quartz capillaries

Analytical particle microelectrophoresis was used to evaluate the effectiveness of various coatings for control of the electroosmotic fluid flow that hinders electrophoretic processes. Mobilities of 2-μm-diameter glass and polystyrene latex spheres, exhibiting both negative and zero effective surface charge, were measured in 2-mm-diameter quartz capillaries filled with NaCl solutions within the pH range of 3.5 to 7.8. Covalent coating of capillary inner surfaces with poly(ethylene glycol) caused a reduction in the degree of electroosmotic flow which was related to the poly(ethylene glycol) molecular weight. Poly(ethylene glycol) coatings of 5000 molecular weight, or higher, greatly reduced electroosmosis within the selected pH range, were stable for long periods of time, and appeared to be more effective than dextran, methylcellulose, or silane coatings. Because of these characteristics, poly(ethylene glycol) coatings should be of considerable use for improving various electrophoretic processes as well as in the production of standard particles exhibiting controlled electrophoretic mobilities.

On existence criteria for capillary free surfaces without gravity

On existence criteria for capillary free surfaces without gravity

Regularity of capillary surfaces over domains with corners: borderline case

Regularity of capillary surfaces over domains with corners: borderline case

Deactivation of small diameter fused silica capillary columns with organosilicon hydrides

AbstractSmall diameter fused silica capillary columns (50–75 μm i.d.) were deactivated at relatively low temperatures (250–300°C) with a mixture of polymethylhydrosiloxanes and several lowmolecular‐weight organosilicon hydrides. Reproducible surface deactivations of highest quality were achieved with the polymethylhydrosiloxane (PMHS) reagent. Deactivations performed with PMHS via dynamic coating with neat or diluted reagent were evaluated by gas chromatography. Deactivations achieved with organosiloxane mono‐, tri‐, and tetrahydrides were also evaluated and compared. Low‐molecular‐weight organosilicon hydride deactivations were less time consuming and required lower head pressures for filling and coating columns with the reagent. Critical surface tensions of capillary surfaces modified with PMHS and the low‐molecular‐weight organosilicon hydrides gave support to the dehydrocondensation reaction between silica surface silanols and silyhydride bonds of the reagents. Slopes from Zisman plots indicated that coverage of the surface ranged from highest for the polymer (PMHS) to lowest for the monomers (TMS and PMDS). Efficiency measurements showed the influence that surface modification had on the uniformity and stability of the coated capillary columns. Well‐deactivated capillary columns permitted the chromatography of polar solutes using supercritical carbon dioxide as mobile phase.

On Capillary Free Surfaces without Gravity

The non-parametric capillary problem in the absence of gravity can be replaced by a Dirichlet problem for a quasilmnear equation of mixed type by introducing a stream function. We prove a maximum principle for an expression depending on the gradient of the stream function and, furthermore, regularity properties of C^1(\bar {\Omega} -solutions in domains \Omega with corners.

Capillary surfaces over obstacles

We consider the usual capillarity problem with the additional requirement that the capillary surface lies above some obstacle. This involves a variational inequality instead of a boundary value problem. We prove existence of a solution to the variational inequality and study the boundary regularity. In particular, global C 11 -regularity is shown for a wider class of variational inequalities with conormal boundary condition.

Lung fixation by airway instillation: effects on capillary hematocrit.

Instillation of glutaraldehyde into the airways of collapsed lungs is a widely used fixation procedure for analysis of pulmonary structure-function relations. In order to better define the effect of this fixation method on the pulmonary microvasculature, a morphometric analysis was made in rat lungs fixed under different conditions. In one group of animals the lungs were allowed to collapse; then the circulation was suddenly interrupted with a sling placed in the coronary sulcus before instillation of the fixative. In a second group the same procedure was carried out with the exception that the lungs were kept inflated at the time of circulatory arrest. In third group the standard technique was used, i.e., the collapsed lungs were instilled before circulatory arrest. The results show that important parameters of alveolar and septal dimensions, and in particular the capillary surfaces and volumes, are alike regardless of the procedure of fixation. However, in lungs fixed by the standard technique a higher capillary hematocrit (approximately 33%) and a decreased harmonic mean thickness of the plasma barrier were found. This artificial hemoconcentration in the microvasculature resulted in a substantial morphometric overestimate of the diffusing capacity of the lung.

Capillary surfaces in negative gravitational fields

where lc (nonnegative) is the capillarity constant and flEL~163 is the cosine of the contact angle between the surface and the cylinder walls. We made the physical assumption that there is no contribution to the energy from the top of the tube, i.e. that the liquid 'wets ' the obstacle ~k. For convenience of notation we reverse the coordinate system such that ~ becomes the bot tom of the tube and the gravitational field is upwards directed. Because of the bad term K v 2 dx (0.2) 2

A subsidiary variational problem and existence criteria for capillary surfaces.

Article A subsidiary variational problem and existence criteria for capillary surfaces. was published on January 1, 1984 in the journal Journal für die reine und angewandte Mathematik (volume 1984, issue 353).

Role of surface groups in affecting the chromatographic performance of certain types of fused-silica glass capillary columns : II. Deactivation by esterification with alcohols and deactivation with specially prepared high-molecular-weight stationary phases

Silanol groups present on fused-silica glass capillary column surfaces were readily esterified in the presence of alcohols to form stable, inert, organophilic and hydrophobic alkoxy linkages, which were then easily wetted by a variety of non-polar stationary phases. Such gas chromatographic capillary columns exhibited well deactivated surfaces, good thermal stability and high column efficiencies. Preliminary studies showed that a new series of appropriately designed and custom-synthesized non-polar and highly polar stationary phases that contain varying degrees of phenyl (up to 50%) or cyanopropyl (up to 98%) substitution, when applied in a single step, efficiently wetted and deactivated the surfaces of fused-silica glass. Then, on exposure to appropriate free-radical generators, these vinyl-containing polymers were readily cross-linked. The characteristics of such columns are considered to be very close to ideal.

On singularities of capillary surfaces in the absence of gravity

We study numerical solutions to the equation of capillary surfaces in trapezoidal domains in the absence of gravity when the boundary contact angle declines from 90° to some critical value. We also discuss a result on the behavior of solutions in more general domains that confirms numerical calculations.

Convexity of capillary surfaces in the outer space

Convexity of capillary surfaces in the outer space

Characterization of glass, quartz, and fused silica capillary column surfaces from contact-angle measurements

This paper describes the systematic characterization of glass and the newly introduced fused silica and quartz capillary columns from surface wettability measurements. Common gas chromatographic stationary phases were used in capillary-rise measurements at temperatures up to 300°C. By construction of Zisman plots and using the Cassie equation, the relative surface concentrations of wettable and non-wettable groups were determined. By application of the Fowkes equation, the dispersion force component of the surface energy was investigated. The influence of various surface treatments such as leaching, silylation, and polymeric film formation are discussed. Wettability measurements were also used to evaluate the thermostability of various treated surfaces and to compare the surface properties of glass, quartz, and fused silica. The wettability of the surfaces with selected stationary phases as a function of temperature is also discussed.

Analytical and computational studies of capillary free surfaces

Analytical and computational studies of capillary free surfaces