Calibrating the uptake kinetics of semipermeable membrane devices in water: impact of hydrodynamics

The use of lipid-containing semipermeable membrane devices (SPMDs) is becoming commonplace, but the potential effects of environmental variables affecting the accumulation of contaminants into SPMDs had not been characterized sufficiently, yet. To characterize the effect of hydrodynamic conditions on the contaminant uptake kinetics, accumulation of pentachlorobenzene, hexachlorobenzene, and hexachlorocyclohexane isomers from water into SPMD was studied at various water flow rates. The accumulation kinetics of hydrophobic compounds (log Kow > 4) are governed by the aqueous boundary layer in linear flow velocity range from 0.06 to 0.28 cm s(-1) and sensitive to slight changes in flow rate. The effect of flow velocity on the exchange kinetics increases with increasing hydrophobicity. Under faster, but still laminar flow conditions (0.28-1.14 cm s(-1)), the sensitivity to changes in flow decreases to a nonsignificant level for the substances under consideration. The results of this study confirm that the use of the laboratory-derived calibration data for estimation of analyte concentrations in the ambient environment is limited unless flow-sensitive performance reference compounds are used.     

Calibration and quantification of fast intracellular motion (FIM) in living cells using correlation analysis

Video rate confocal laser scanning microscopy at the highest spatial and temporal resolution of backscattered light (BSL) imaging allowed for regular observation of fast intracellular motion (FIM) first revealed in living neoplastic cells. However, the absence of an objective evaluation has hampered further study of the mechanisms and biological significance of FIM. Particularly, a quantification of apparent differences in velocities that would complement and improve the current demonstration of FIM by color coding using the combination of red-green-blue (RGB) images had been missing. Standard methods of tracking or pattern recognition could not be applied because of the fuzzy nature of images of FIM. A search for a suitable method led to correlation analysis. It was calibrated on Brownian motion and a known type of motion, such as cell marginal ruffling, compared with FIM. Results approved its explanatory potential. Therefore, several crucial incidences of FIM could be analyzed. Apart from an argument against viewing FIM as a manifestation of simple Brownian motion, the correlation analysis of FIM in the adjacent peripheries of a rat fibroblast and a K4 rat sarcoma cell confirmed the notion of higher and uneven distribution of velocity of FIM in a tumor cell so far shown in color-coded images only. This result and other yet unpublished observations indicate that the velocity and topology of FIM can also contribute to a biological distinction between neoplastic and normal cells. Regular application of the correlation analysis should further expand the study of FIM for its mechanisms and predictive value. Such an approach should be thoroughly examined for a contribution to the knowledge of cancer cells.     

DATA CLUSTERING USING A REORGANIZING NEURAL NETWORK

A new approach, designed for clustering of arbitrary distributed patterns, is presented. This study is concerned with the use of a self-organizing neural network as a frame for data clustering. The nearest network nodes in feature space are treated as prototypes, assigned to the corresponding cluster. The rules for dead-node shifting and simple adjustment of coordinates of the active nodes are introduced. The performance of the proposed self-organizing neural network is examined on the benchmark synthetic and the real-world problem.     

Estimation of the number of trays for natural gas triethylene glycol dehydration column

The paper deals with the tray-to-tray method for determining the required number of trays in columns with intensive entrainment of liquid when the operating line of the “dry working regime” is not straight and with a small concentration of diffusing component in gas. Presented calculations show that the number of transfer units for gas and liquid should be calculated using the AIChE method accompanied with longitudinal mixing according to Gilbert properly transformed for case of diffusion through stagnant film. The suggested method can be applied for TEG dehydration absorbers-columns for dehydration of natural gas using triethylene glycol with system factor SF = 0.5.     

Environmental upregulation of the atrial natriuretic peptide gene in the living fossil, Limulus polyphemus

Northern blot analysis revealed that atrial natriuretic peptide (ANP) gene expression occurs in heart, hematocytes and gills of the invertebrate Limulus polyphemus, the horseshoe crab. In low salinity and on land ANP prohormone messenger RNA in Limulus' heart was 32-fold less compared to that in a vertebrate heart (i.e., rat, Rattus norvegicus). ANP gene expression doubled (P < 0.05) in Limulus' heart and gills with change from land and low salinity to medium salinity and osmolality. ANP gene expression was 10-fold higher in Limulus' gills in seawater (i.e., high salinity). The products of this ANP gene expression (i.e., ANP, long acting natriuretic peptide, vessel dilator and kaliuretic peptide) were released and increased in the circulation, i.e., hemolymph, of Limulus proportional to the increase in salinity and osmolality (P = <0.01). These results suggest that modification of ANP gene expression enables animals to adapt to freshwater, seawater, and land.     

Monoclonal antibody for the demonstration by ELISA of antibodies to protein p24 of enzootic bovine leukosis virus in individual and pooled blood serum and milk samples

A sensitive and specific ELISA for the demonstration of antibodies to the protein p24 of enzootic bovine leukosis virus (EBVL) using a 'capture' monoclonal antibody to this protein (MAb p24) was developed. The method is sensitive enough to detect the international reference serum E4/10 in pooled blood serum samples collected from up to 50 cows, or, if a 10-fold concentrate of milk whey is tested, in samples of bulk milk collected from up to 400 cows. The application of MAb p24 has considerably increased not only the sensitivity, but also the specificity of ELISA. Moreover it is possible to differentiate reliably between positive and 'false positive' reagents by testing a suspicious sample in a pair of wells of which one is coated with MAb p24 alone and the other with the complex MAb p24 + EBLV antigen and the subsequent calculation of 'specific absorbance'. This method, showing the highest sensitivity of detection of antibodies to EBLV p24 described so far, can become an effective tool on the sanitation of infected herds as well as in checks of the EBL-free status. A diagnostic kit suitable for commercial manufacture has been devised.     

High performance AlyGa1−yAs-GaAs-lrxGa1−xAs quantum well lasers defined by silicon-oxygen impurity-induced layer disordering

In these experiments impurity-induced layer disordering (IILD) utilizing chemical reduction of SiO₂ by Al (from Al_0.8Ga_0.2As) is employed to generate Si and O to effect layer disordering. The SiO₂-Al_0.8Ga_0.2As reaction is studied with respect to annealing ambient. By controlling the extent of disordering via As₄ overpressure, closely spaced (∼1μm) Si-O IILD buried heterostructure lasers can be optically coupled or uncoupled. Direct observation of O incorporation into the buried layers is shown using secondary ion mass spectroscopy (SIMS). The thermal stability of separate-confinement Al_yGa_1−yAs-GaAs-In_xGa_1−xAs quantum well heterostructure (QWH) laser crystals is investigated using SIMS, transmission electron microscopy (TEM), and photoluminescence (PL) measurements. The data show that the thermal stability of a strained-layer In_0.1Ga_0.9As quantum well (QW) is strongly dependent upon: (1) the layer thickness and heterointerfaces of the Al_yGa_1−yAs-GaAs waveguide layers located directly above and below the QW, (2) the type of surface encapsulant employed, and (3) the annealing ambient. Narrow single-stripe (<2μm) lasers fabricated via Si-O diffusion and layer disordering exhibit low threshold currents (I_th ∼ 4 mA) and differential quantum efficiencies,η, of 22% per facet under continuous (cw) room-temperature operation.