Teflon Foil Research Articles

Effects of doxorubicin on maturation of human monocytes in adherent and non-adherent cultures

Purified human monocytes were cultured for 2 h, 88 h, and 10 days in plastic tubes (adherent) and for 10 days in Teflon foil bags (non-adherent). Monocytes were incubated with doxorubicin by two short-term exposures (750 or 1500 ng/ml) for 1 h or by continuous exposure (75 ng/ml). Maturation was monitored by measuring the intracellular activity of three metabolic enzymes and two acid hydrolases. Expression of receptors for the Fc moiety of immunoglobulin G (FcRI, FcRII, FcRIII), CD14, and HLA-DR was assayed by indirect immunofluorescence with monoclonal antibodies. In the presence of doxorubicin, the adherent capacity, the yield, and the enzyme activities reflecting growth and intermediary metabolism were similar to the control groups. However, doxorubicin reduced the expression of FcRI (32–45%), FcRII (10–26%), CD14 (20–37%), and HLA-DR (25–34%) on the monocyte-derived macrophages. Expression of FcRIII was not detectable after 10 days of culture.

Acoustic emission proves its worth in nuclear plants : Pollock, A.A.; Carlyle, J.M.; Ternowchek, S.J. Nuclear engineering international, vol. 33, no. 405, pp. 52–53 (Apr. 1988)

An approach to analyze delamination in a circular composite beam specimen loaded in bending is presented. First, an experimental investigation of the interlaminar fracture behavior of unidirectional glass fiber reinforced polyester under mixed mode (I/II, opening + sliding) loading conditions was performed. For this purpose, the ring-fracture-test was used. The test was derived from a modified unidirectional glass fiber reinforced polyester ring specimen, which originally was used for investigation of the interlaminar tensile strength. The ring-shaped fracture-test specimens were produced by filament-winding technology. The ring specimen contains a tangential starter-delamination crack, being initiated from a strip of Teflon foil, which was added during the winding process. A radial cut was made in each ring at the opposite side of the starter crack, realizing a kind of horseshoe specimen. During the test, this specimen was subjected to opening forces. The crack propagated along the fibers (in circumferential direction) in a symmetrical manner with respect to the starter foil. A linear-elastic fracture-mechanics model is applied to interpret the crack-mechanical data recorded during the ring-test. The value of the interlaminar fracture energy is considered as a function of the length of the propagating circular crack. The total strain-energy release rate is decomposed into opening (mode I) and shearing (mode II) components. The mode partitioning shows that the ring-fracture-test gives variable mixed mode (I/II) ratios. The obtained values of the strain-energy release rate are compared with finite-element analysis results. It is found that the ring-fracture-test represents a new and useful approach for investigating the mixed mode (I/II) fracture behavior of unidirectional glass fiber reinforced polyester.

Polarization currents and switching in undoped poly-p-phenylene sulfide

Charging and discharging electrical currents have been measured at room temperature in undoped PPS, with bimetalized aluminum electrodes. Sample thickness and area around 1 mm and 2.4 cm 2 respectively. Two regimes are observed. In the low voltage one the currents seems to result from the processes: dipolar polar i zation, and conduction caused by negative (electron) charge injection. From the transients we barely deduced the negative carrier mobility to be of the order of 10 −6cm 2/Vsec. These conclusions could be reached analysing the results obtained when one side metalized 25 μm thick teflon foil makes contact with an one side metalized PPS sample, allowing the formation of Maxwell-Wagner polarization. Both polarities were used in this study. A switching is observed for fields higher than 4×10 4V/cm and the current shows a large initial spike lasting a few seconds at this threshold, and less for higher fields, after which a steady state is reached. We have interpreted this behavior by an abrupt increase of free carriers at the threshold voltage. In this view, the current decreases because the bulk delivers more current than the contact may supply, forming a positive depletion layer. At more higher voltages the contact current increases faster and a space charge limit regime is observed.

Sample handling and storage for the quantitative analysis of volatile compounds in blood: the determination of toluene by headspace gas chromatography.

The problems associated with the handling and storage of blood samples for the analysis of toluene in toxicological casework using headspace gas chromatography have been investigated. Significant losses of toluene and the internal standard, ethylbenzene, from solution may be observed during handling. Toluene may be lost into the headspace above the blood in a storage container while such headspaces can also be detrimental, leading to the formation of n-hexanal, a possible interference with the assay. Large differences in the stability of toluene were seen for blood samples in different types of storage container. Storage containers in which the sample was only in contact with glass, teflon, or aluminum foil were most satisfactory. It is recommended that blood samples should be stored in appropriate containers with minimum headspace under cold conditions (4 degrees C). Transfers of blood should also be made at cold temperatures. The applicability of these guidelines to the analysis of other volatile compounds is discussed.

Track radiography of heavy-ion induced sputtering

To study heavy-ion induced sputter phenomena, several glasses of different chemical composition were irradiated with 56Fe +-ions in the energy of 70.5–100 keV at the GSI-UNILAC, Darmstadt. A sensitive particle track technique was employed to measure differential sputter yields and the angular distribution of sputtered atoms in 2π-geometry. This techniques utilizes U, Th, Li and B contained in the target matrix as tracer elements. The sputtered target atoms are collected on a cone-shaped catcher (Makrofol polycarbonate or Teflon foil) and the target atoms are recorded via ( n, f) and ( n, ƒ) reactions as particle-track radiographs of the catcher on mica or CA 80-15 cellulose nitrate detectors. The cone shape of the catcher foils allows one to scan the sputtering process in 2π-geometry in a single irradiation experiment. The detection sensitivity for sputtered atoms is estimated to be <5×10 11 target atoms cm −2 in the case phosphate glass containing 0.06% 235U and <10 13 target atoms cm -2 in the case Li 2B 4O 7 glass. Angular distributions for U-phosphate and Li 2B 4O 7 glass sputtered by 100 keV 56Fe +-ions are presented.

Bilayer Lipid Membranes

AbstractThin lipid membranes formed across an aperture in a teflon foil are frequently used as model systems to simulate the hydrophobic diffusion barrier of biological membranes. These membranes have a thickness of about twice the length of a lipid molecule (bilayer membranes) and are prepared either by a spontaneous transition of a thick lamella made from a solution of lipids in a hydrocarbon [1] or by a direct “addition” of two monomolecular lipid layers on the two water surfaces separated by the teflon foil [2]. The aqueous phases on both sides of these planar membranes are easily accessible by electrodes which may serve to study the electrical properties of the membranes. The whole system allows the application of steady state electrical methods as well as that of fast relaxation methods. The latter include the voltage jump‐current relaxation technique [3,6], the charge pulse method [4,5] as well as the temperature jump method [6]. These kinetic techniques have been used throughout recent years to investigate ion transport phenomena across bilayer lipid membranes.Unmodified lipid membranes have been found to represent high energy barriers for the movement of inorganic cations and anions. A simple equivalent electrical circuit of the membrane consists of a parallel arrangement of the membrane resistance RM and the membrane capacitance CM (typical values: RM = 106‐108μcm2, CM = 0.3‐0.8μF/cm2). A refined version composed of three of such elements (one for the hydrocarbonlike membrane interior, the two others for the polar membrane‐water interfaces) has been suggested on the basis of a.c. measurements [7]. These measurements were, however, confined to the rather small band width of 0.1‐100 Hz. A different possibility of testing such a circuit is to make use of the voltage jump method. The induced current relaxation may be measured with a time resolution of at least 1 μs and very high sensitivity by using signal averaging techniques. For the three element circuit described above the relaxation should consist of two exponential terms. At least five different relaxation times were, however, necessary to obtain a sufficiently good fit to the experimental data [8.9]. This finding indicates that even the refined equivalent circuit is insufficient for a phenomenological description of the high frequency behaviour of bilayer lipid membranes. The complex current relaxation may be interpreted on the basis of cooperative dielectric relaxation phenomena associated with the dipoles of the polar head groups of the lipid molecules.

Enzyme assays at the single cell level using a new type of microfluorimeter.

A direct method for the microfluorimetric determination of NADPH2 and 4-methylumbelliferon in the sub-picomole range is described. By means of an inverted fluorescence microscope with epi-illumination it has been possible to measure low concentrations of these fluorophores in volumes down to 17 nl. The aqueous microvolumes to be measured are suspended in oil to prevent evaporation. Since the droplets are sunk on thin teflon foil, to attain a spherical form, they can be measured in a reproducible way. The excitation of the microdroplet takes place from below through the teflon foil, while the fluorescence emission follows the same route back to a photomultiplier. The possibilities of this method are illustrated with the biochemical measurements of glucose-6-phosphate dehydrogenase (G6PD) activity in single fibroblasts. It was possible to distinguish between normal and G6PD deficient cells on a single cell level. The microfluorimetric measurement of lysosomal enzymes with 4-methylumbelliferyl substrates is discussed.

Preparation of highly pure potassium hydroxide by zone melting

The method of preparing highly pure potassium hydroxide by zone melting of its monohydrate in a Teflon foil has been worked out. The . effect of conditions, such as the rate of zone travel, width of molten zone, and number of zone passes on the distribution of impurities has been investigated. Zone refined KOH.H2 0 contained at most 106 % of heavy metals, at most 10% of Fe, Ca, Mg, and less than 104 % of pol-, F-, C -, sol-, and 0'05% of CO~-,