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At least 145 records · Page 8Linked to original sources
PubMed1979

[Materials testing demonstration of the suitability of a viscous plastic silicone elastomer for long-term functional impressions].

Comparative laboratory tests with elastomers as well as clinical trials showed that the visco-elastic silicone elastomer "Stefanat zähplastisch" (manufacturer: VEB Arzneimittelwerk Dresden, Leipziger Arzneimittelwerk) is suited for long-term dynamic impression. It is necessary to use a special, exactly dosed cross-linking agent and to apply the reactive material carefully.

Clinical Trials as Topic↗
PubMed1981

Analytical and biological analyses of test materials from the synthetic fuel technologies. III. Use of sephadex LH-20 gel chromatography technique for the bioassay of crude synthetic fuels.

To determine the health effects associated with newly emerging energy technologies, we have subjected a group of synthetic fuels to mutagenicity evaluation, using the Ames Salmonella assay. Coupling of chemical fractionation to the mutagenicity assays was necessary. Fractions obtained by use of Sephadex LH-20 gel chromatography on crude-coal-derived oils and shale oil were tested for mutagenicity with strain TA98 (with Aroclor S9 mix). Mutagenicity results obtained with synthetic fuels were compared with those from a mixture of natural petroleum crude oils. Merits of the Sephadex LH-20 separation technique and precautions in interpreting experimental results are discussed.

Chromatography, Gel↗
PubMed1985

Aluminium in Finn chambers reacts with cobalt and nickel salts in patch test materials.

Aluminium has a greater affinity for electrons than cobalt and nickel. Therefore, cobalt and nickel ions would be expected to exchange with metallic aluminium in Finn chambers. This theory has been proven to be valid, as shown in 2 series of experiments: first, cobalt and nickel salt solutions (0.25 M) etch a metallic aluminium surface; secondly, aluminium Finn chambers kept in 10(-3) M nickel salt solutions significantly reduce the concentration of dissolved nickel. Dichromate solutions do not etch an aluminium metal surface significantly. Petrolatum, which is routinely used as vehicle in standard patch tests, probably protects the aluminium of Finn chambers from the interaction of cobalt and nickel salts. The interaction may have significance in tests with solutions.

Aluminum↗
PubMed1981

Analytical and biological analysis of test materials from the synthetic fuel technologies.

Nitrogen-containing organic compounds from environmental sources are receiving increasing attention because of uniquely active mutagens which have been found in this class (Chrisp et al., 1978; Nagao and Sugimura, 1978: Guerin et al., 1980) Differences in mutagenic activities among the various organo-nitrogen compounds, i.e., pyrrole types, pyridine types and aniline types, have been noted consistently. Furthermore, differences among homologs of a particular compound type are often striking. Information in this paper engages the question of chemical structure/biological activity relationships. Activity data for several N-heterocyclic, nitro-, amino- (primary, secondary and tertiary), and amino-N-heterocyclic aromatic compounds are presented. The number of fused rings and the substituent type affect the mutagenic activities greatly. The trends observed are discussed generally with reference to molecular structural features.

Cyclic N-Oxides↗
PubMed1992

Auditory-visual word identification test materials: computer application with children.

The purpose of this investigation was to obtain performance data from normal-hearing children using the written word portion of existing auditory-visual word identification materials, for example, the Picture Identification Task (Wilson and Antablin, 1980). The response foils, consisting of four written words (target and alternative words) were entered into computer memory so that responses were made by pointing to a computer monitor. Subjects were 24 fourth graders with normal hearing who repeated auditory-stimulus words in noise in oral conditions, and pointed to written words representing the stimulus words in pointing conditions. Mean percent correct performance scores were higher in the pointing conditions than in the oral conditions, reflecting closed- versus open-set tasks. The results indicated that the written word portion of the Picture Identification Task can be utilized to assess the word identification performance of children who read at a fourth grade level or above.

Audiovisual Aids↗
PubMed1987

Biological tissue simulation and standard testing material for MRI.

The polyacrylamide gel is proposed here as a phantom material for NMR imaging. This substance has electrical and NMR relaxation characteristics very similar to those of biological tissues. The thermal and time stabilities also make this material a convenient standard for MRI.

Acrylic Resins↗
PubMed2005

Quantitative shear wave magnetic resonance elastography: comparison to a dynamic shear material test.

Magnetic resonance elastography (MRE), a phase contrast MRI technique, images the propagation of applied mechanical waves in tissue, allowing shear stiffness to be quantified in vivo. This MRE technique has been validated with static mechanical compression tests. Dynamic mechanical analysis (DMA) may be a more appropriate comparison to MRE because it directly measures the shear modulus dynamically, while compression tests convert the measured elastic modulus to shear modulus with an assumed Poisson ratio. This study compared the shear stiffness estimated with various MRE inversion algorithms (i.e., manual calculation, local frequency estimate, phase gradient, direct inversion, and matched filter) to the dynamic mechanical test. The shear stiffness of five agarose gels with concentrations ranging from 1.5 to 3.5% were measured using MRE and DMA. The phase gradient inversion algorithm overestimated the shear modulus at higher concentrations (i.e., 3-3.5% agar), while the results from the other techniques correlated well with the dynamic mechanical test.

Agar↗
PubMed1986

Anisotropic tensile viscoelastic properties of vascular graft materials tested at low strain rates.

Mechanical matching of vascular grafts and host vessels has been suggested to be important in determining graft patency rates. In this context, we have examined the anisotropic viscoelastic properties of natural vessels and some synthetic replacements using low strain rate tensile testing of circumferential and longitudinal strips. The canine iliac artery and iliac vein were compared with 6 mm diameter woven and knitted Dacron grafts, expanded polytetrafluoroethylene (PTFE) grafts, and helically constructed prototype polyurethane grafts at wrap angles of 45, 60 and 75 degrees. A thick-walled pressure vessel analysis was used to approximate physiological stress levels, and SEM was used to correlate anisotropic properties with graft wall structure.

Animals↗
PubMed2000

Reduction of intra- and interlaboratory variation in CD34+ stem cell enumeration using stable test material, standard protocols and targeted training. DK34 Task Force of the European Working Group of Clinical Cell Analysis (EWGCCA).

The European Working Group on Clinical Cell Analysis (EWGCCA) has, in preparation for a multicentre peripheral blood stem cell clinical trial, developed a single-platform flow cytometric protocol for the enumeration of CD34+ stem cells. Using this protocol, stabilized blood and targeted training, the EWGCCA have attempted to standardize CD34+ stem cell enumeration across 24 clinical sites. Results were directly compared with participants in the UK National External Quality Assessment Scheme (NEQAS) for CD34+ Stem Cell Quantification that analysed the same specimens using non-standardized methods. Two bead-counting systems, Flow-Count and TruCount, were also evaluated by the EWGCCA participants during trials 2 and 3. Using Flow-Count, the intralaboratory coefficient of variation (CV) was </= 5% in 39% of the laboratories (trial 1), increasing to 65% by trial 3. Interlaboratory variation was reduced from 23.3% (trial 1) to 10.8% in trial 3. In trial 2, 70% of laboratories achieved an intralaboratory CV </= 5% using TruCount, increasing to 74% for trial 3; the interlaboratory CV was reduced from 23.4% to 9.5%. Comparative analysis of the EWGCCA and the UK NEQAS cohorts revealed that EWGCCA laboratories, using the standardized approach, had lower interlaboratory variation. Thus, the use of a common standardized protocol and targeted training significantly reduced intra- and interlaboratory CD34+ cell count variation.

Antigens, CD34↗