Single Micropore Research Articles

Electrical fingerprinting, 3D profiling and detection of tumor cells with solid-state micropores

Solid-state micropores can provide direct information of ex vivo or in vitro cell populations. Micropores are used to detect and discriminate cancer cells based on the translocation behavior through micropores. The approach provides rapid detection of cell types based on their size and mechano-physical properties like elasticity, viscosity and stiffness. Use of a single micropore device enables detection of tumor cells from whole blood efficiently, at 70% CTC detection efficiency. The CTCs show characteristic electrical signals which easily distinguish these from other cell types. The approach provides a gentle and inexpensive instrument that can be used for specific blood analysis in a lab-on-a-chip setting. The device does not require any preprocessing of the blood sample, particles/beads attachment, surface functionalization or fluorescent tags and provides quantitative and objective detection of cancer cells.

Equilibrium adsorption of a cyclopentane—benzene vapor mixture on active carbon

The data on adsorption of cyclopentane, benzene, and their mixture on active carbon were analyzed by the statistical thermodynamic model. A method to describe the state of a binary mixture in single micropores was offered. A substantial negative deviation from Raoult's law predicted by the concept of an ideal adsorption solution is a consequence of a decrease in the excessive Helmholtz energy brought about by progressive filling when values of the excessive energy are positive over a wide range of adsorption. The excessive values found for the entropy and internal energy of a mixture of molecules in a single micropore are negative due to the heterogeneity of the adsorption field. The approach suggested adequately describes the experimental data and can be used for the determination of differential heats of adsorption.

Equilibrium adsorption of an oxygen-nitrogen mixture on zeolite NaX

Dependences of the Helmholtz energy, entropy, and internal energy in single micropores on the total number of guest molecules and the oxygen to nitrogen ratio were found by analysis of experimental data on adsorption of the binary oxygen-nitrogen mixture on zeolite NaX using the statistical model. A substantially non-ideal character of the adsorption phase, which exhibits negative deviations from Raout's law, can result from heterogeneity of the adsorption field inside single cavities.

Counter-Diffusion of Isotopically Labeled Trichloroethylene in Silica Gel and Geosorbent Micropores: Model Development

A new model was developed to determine if reduced uptake rates observed during isotope exchange experiments could plausibly be attributed to sterically hindered counter-diffusion in one-dimensional micropores. During exchange experiments, hydrogenated trichloroethylene ({sup 1}HTCE) was displaced with deuterated TCE (DTCE) in the slow-desorbing sites of a silica gel, a groundwater sediment, and a clay and silt fraction. To describe this process, the model accounts for co- and counter-diffusion of TCE isotopes in one-dimensional micropores, where each micropore type is defined by a single codiffusion rate constant and a single counter-diffusion rate constant. For silica gel, isotope exchange was simulated in a single micropore type. For geosorbents, isotope exchange was simulated in a distribution of micropore types characterized by a {gamma} distribution of diffusion rate constants. Simulation results indicate that (1) the proposed model accounts for the mechanisms controlling isotope exchange in the silica gel and the groundwater sediment and (2) the rate of counter-diffusion is up to 6 times slower than the rate of codiffusion. This suggests that steric hindrance between counter-diffusing sorbates can significantly affect mass transfer and, consequently, the transport of chemical mixtures in the subsurface.

Contribution of a Repulsive Potential in a Micropore Volume Filling. A Surface of Micropore Walls

In the case of narrow micropores, a volume filling of the single micropore and a two-dimensional condensation on its walls occur at the same condensation pressure, and the local adsorption behavior may be modeled by the condensation approximation. Proceeding from (i) the accepted model of carbon heterogeneity, (ii) the theory of adsorption on homogeneous surfaces considering lateral interactions, and (iii) the 10−4 potential function, the correlation between a micropore filling pressure, p, and a micropore reduced half-width, d/r0, is derived. This approach provides a correct description of equilibrium data in a range of p/ps ≈ 5 × 10-7 to 0.2 at 293 K and leads to reasonable distribution functions of micropore sizes and adsorption energies. The model contains a specific prediction that there is a minimum filling pressure, pmin, that corresponds to the maximum adsorption energy at d/r0 = 1 and determines the lower boundary of the micropore volume filling. For benzene adsorption at 293 and 423 K, the pmin/ps values are equal to 7.36 × 10-8 and 1.15 × 10-5, respectively. When p < pmin, only a submonolayer adsorption occurs on a micropore surface. The expression for the calculation of a micropore surface is derived, and the underlying assumption is discussed.

Physical Adsorption in Micropores: A Condensation Approximation Approach

An approach to adsorption in micropores is developed on the basis of the condensation approximation method. In the case of micropores with half-width less than 0.8 nm, a volume filling of the single micropore and a two-dimensional (2D) condensation on its walls occur at the same critical pressure, pc. From this point of view, the statistical mechanical theories of adsorption on homogeneous surfaces considering lateral interactions may be taken to be a starting point to the description of physical adsorption in micropores. The increased well depth, ε*, in micropores causes the 2D condensation on their surface to occur at a smaller pc compared with a nonporous surface. As a consequence, the overall adsorption isotherm is determined by the distribution of micropore walls over adsorption energies resulting from a random distribution of micropore widths, d. Proceeding from a model of heterogeneity and the normal distribution of micropore widths, the log-normal distributions of micropore volumes over ε* and pc are obtained, and an occupied adsorption volume as a function of outer pressures is found. This approach has been successfully applied to seven benzene adsorption isotherms on four species of active carbons. It provides a correct description of equilibrium data in a wide temperature range, leads to reasonable distribution function of ε* and d, and gives values of an average micropore size that are close to the experimental one.

Micropore Volume Filling. A Condensation Approximation Approach as a Foundation to the Dubinin−Astakhov Equation

A volume filling of a single micropore and a two-dimensional (2D) condensation on its walls occur at the same critical pressure, and the local adsorption behavior may be modeled by the condensation approximation. This phenomenon underlies the approach to the micropore volume filling based on the condensation approximation (VFCA) and the Dubinin-Astakhov (DA) equation. The DA equation follows from the VFCA approach, being an approximate form to the general relationship. The physical meanings of the exponent, n, and the characteristic energy, E, with respect to the surface heterogeneity, are given. As a whole, n is determined only by the standard deviation of the micropore widths: the less the heterogeneity, the larger n, approaching to infinity for the homogeneous carbon. The characteristic energy depends on the average micropore sizes and its standard deviation. In the case of the DA equation with n = 2 or n = 3, standard deviations are equal to 0.4915 or 0.3493, respectively, and E depends only upon an average micropore size or upon a related adsorption potential. For the individual micropore, E determines the critical pressure of a 2D condensation. In the case of water adsorption on active carbons, the base heterogeneity due to variation in the pore widths, as perceived by water molecules, is negligible. Hence, water adsorption may be considered to be an extension of a 2D-condensation into practically homogeneous micropore volumes. It is shown that empirical relationships for calculating of average micropore sizes and an applicability of the DA equation to the adsorption on nonporous surfaces may be also explained in the framework of the VFCA approach.

Tremelloid haustorial cells with haustorial filaments and potential host range of Tremella mesenterica

Zugmaier, W. &amp; Oberwinkler, F. 1995. Tremelloid haustorial cells with haustorial and potential host ranges of Tremella mesenterica. ‐ Nord. J. Bot. 15: 207–213. Copenhagen. ISSN 0107–055X.In vitro and in vivo haustorial cells of Tremella mesenterica, consisting of a subglobose basal part with one or more thread‐like haustorial filaments, were examined using light and electron microscopy. The haustorial cells developed from clamp connections of hyphal septa or intercalarily. Mostly such haustorial cells were monokaryotic, but in a few cases also dikaryotic haustorial cells were observed. In vitro, the host range of Tremella mesenterica was tested with the corticiaceous homobasidiomycetes Peniophora erikssonii, P. quercina and Phanerochaete eremea. The in vitro interaction of Tremella mesenterica with all these fungi was principally the same as in vivo with Peniophora laeta. A single micropore connected the cytoplasm of the haustorial filament with that of the respective host cell. The pore domain at the host side was delimited by curved ER cisternae only in Peniophora quercina, but not in Peniophora erikssonii and Phanerochaete cremea.

Mycoparasitism of Some Tremella Species

The parasitic interaction of Tremella mesenterica, T. encephala and T. mycophaga was studied by light and electron microscopy. The host range of T. mesenterica was tested with Peniophora laeta, Peniophora incarnata, Phlebia radiata, Schizopora paradoxa, Stereum hirsutum and Diatrype stigma. It was demonstrated that T. mesenterica is, at least in vivo, a mycoparasite of the corticiaceous homobasidiomycete Peniophora laeta. Specialized interactive cells of T. mesenterica, T. encephala and T. mycophaga, designated as tremelloid haustorial cells with haustorial filaments, penetrated the cell walls of their respective hosts. A single micropore connected the cytoplasm of the haustorial filament with that of the host cell. The pore membrane appears to be continuous with the plasmalemma of both cells. In older interaction structures, the micropore was often overgrown on the host side by secondary wall formation. In vitro such micropores were present in the interaction of T. mesenterica with Peniophora laeta, P. incarnata and Phlebia radiata but could not be found in the interaction of T. mesenterica with Schizopora paradoxa, Stereum hirsutum and Diatrype stigma. However, only in Peniophora laeta and P. incarnata was the pore domain delimited by a more or less circular arrangement of ER cisternae. Wall thickening may be responsible for the nonmicropore interaction.

Measurement of human red blood cell deformability using a single micropore on a thin Si/sub 3/N/sub 4/ film

The filtration method for the evaluation of the RBC deformability has been further refined to simulate the deformations encountered in the recticuloendothelial system (in particular the spleen), a recognized site of aged and sickled cells removal. The core of the developed measuring system is a very thin (0.4 micron thick) filter that consists of single micropore (diameters down to 1 micron) on a Si3N4 film which has been constructed using silicon microfabrication techniques. Individual RBC's deformability is quantified measuring the cell pore passage time. From one blood sample 200 passage times are analyzed by a computer, displaying mean and median values as deformability indexes, and class and cumulative histograms for studying the passage times distribution. In this paper the effectiveness of the developed system as a routine clinical evaluation tool is demonstrated by studying several factors that are known to affect the RBC deformability, such as temperature, addition of diamide and glutaraldehyde, and blood storage conditions. In addition, it is experimentally demonstrated that the human RBC can traverse a pore with a diameter as small as 1 micron when the pore length is very short, thus broadening the experimental conditions under which the RBC deformability (fluidity) can be studied.

Direct cytoplasm-cytoplasm connection: an unusual host-parasite interaction of the tremelloid mycoparasiteTetragoniomyces uliginosus

The cellular interaction ofTetragoniomyces uliginosus andRhizoctonia sp. was restudied by transmission electron microscopy. During the first stages of interaction a body of medium electron density is visible at the center of the haustorial apex in close association with the plasmalemma. A single micropore is produced between the haustorial filament and the host cell. Cytoplasmic connection via the pore always occurred. The pore membrane is continuous with the plasmalemma of both cells. The protoplasts of both the haustorium and the host cell fuse via the micropore. An electron transparent to dense body occlude the pore. Among basidiomycetes, direct connection between the parasite and host protoplasts represents a hitherto unknown type of parasitic interaction.

Fine structure of the endogenous stages of Eimeria labbeana. I. The first generation merozoites.

The fine structure of the 1st generation merozoites of Eimeria labbeana from the ileal mucosa of artificially infected pigeons (Columba livia) was investigated and described. The 1st generation merozoites which appeared between 36-48 hr after infection averaged 4.4 times 2.1 mum in size. The 3-membraned pellicle was irregular in texture and harbored a single micropore, and many micropore-like invaginations. Closely apposed to the inner pellicular membrane were seen 22 microtubules, each 22-25 nm in diameter. An apical vesicle, 50 nm in diameter, seen at the anterior extremity, was connected with the common duct of the micronemes. The conoid consisted of 9 spiral elements, each 30 times 25 nm. The paired organelle (rhoptries) varied in length (1.4-2.2 mum), and the ductules (23 nm diameter) were composed of 2 inner tubules, each 6 nm in diameter. A unit membrane enveloped the partially alveolar and differentially osmiophilic interior of the bulbous regions of the rhoptries. The "rod-like structure" was found to be tubular and represented the common duct of the micronemes.

Micro- and macroheterogeneities of SAS-1 alloy

1. Physical heterogeneity in SAS-1 alloy was established and studied. 2. It is shown that the single micropores and nest- and band-like micropore colonies found in the alloy have a technological origin and form during the extrusion and sintering of alloy sections. It is only single pores less than 40μ in size that may occasionally be produced also during the machining of alloy specimens, as a result of large silicon grains being pulled out of the specimen surfaces. 3. Macro- and microscopical volumes of the alloy were found to exhibit a heterogeneity of chemical composition. 4. The results of the investigation lead to the conclusion that, by reducing the particle size of alloy powder to be extruded, using narrow particle size fractions, protecting the powder against contamination, and employing degassing during melting, extrusion, and sintering, it should be possible significantly to decrease the physicochemical micro- and macroheterogeneities of SAS-1 alloy and, hence, improve its physicomechanical properties.