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Results for “Laboratory Procedures”

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At least 145 records · Page 8Linked to original sources
PubMed1998

The National Acoustic Laboratories' procedure for selecting the saturation sound pressure level of hearing aids: experimental validation.

OBJECTIVE: The primary aim of this study is to evaluate the accuracy of a new procedure for selecting the saturation sound pressure level (SSPL) of hearing aids. Secondary aims are to investigate what limits the minimum SSPL that is acceptable to clients and whether the type of limiting (peak clipping or compression limiting) affects the SSPL required. DESIGN: The study comprised two experiments. In the first, subjects increased the SSPL of a laboratory master hearing aid until they experienced loudness discomfort and decreased it until the sound became less acceptable in some way. In the second study, subjects wore multi-memory programmable hearing aids in their own environments and reported which of the two programs, differing only in SSPL setting, provided the more acceptable sound quality and comfort. RESULTS: The theoretical procedure being investigated prescribed SSPLs that were within the acceptable range for 86% of the subjects in the laboratory study and for 63% of the subjects in the field experiment. On average, the theoretical predictions were neither too high nor too low. Incorporating individual measurements of loudness discomfort level into the prescription formula increased accuracy by such a small amount that it was not considered worthwhile. For a compression limiting hearing aid, the first thing that subjects noticed as SSPL was reduced was inadequate loudness. For the peak clipping hearing aid, however, both inadequate loudness and perception of distortion limited the acceptable SSPL range. CONCLUSION: The theoretical procedure provides a good initial prescription of three frequency average SSPL, but it is still essential to evaluate the fitting and, if necessary, fine tune the individual's hearing aid. Compression limiting hearing aids can have slightly lower SSPL settings than peak clipping hearing aids for the same acceptability.

Acoustic Stimulation↗
PubMed1998

Utilization of advanced metal-ceramic technology: clinical and laboratory procedures for a lower-fusing porcelain.

Metal-ceramic restorations remain the most widely accepted type of indirect restorative modality, and have been applied successfully for years. Recent advances in material science have resulted in the development of a new class of metal-ceramic materials that have been termed lower-fusing ceramics. Following proper procedures for preparation and metal framework design, these metal-ceramic porcelains achieve the aesthetics normally demonstrated by conventional all-ceramic restorations. This article provides an overview of the clinical and laboratory processes utilizing these materials and is illustrated by two case presentations.

Adult↗
PubMed1975

Laboratory procedures for the isolation of chlamydia trachomatis from the human genital tract.

The technique of isolating Chlamydia trachomatis from the human gential tract by centrifuging clinical specimens on to cell monolayers with subsequent incubation has been improved and simplified. Gentamicin in the media was found to be superior to streptomycin in reducing bacterial contamination of specimens. The infectivity of chlamydial suspensions of laboratory cultured material was significantly reduced by storage at +4 degrees C for more than 48 hours, and by immediate freezing to -70 degrees C. When compared with immediate processing of the specimens, freezing to -70 degrees C was found to reduce the isolation rate of C.trachomatis from men with non-gonococcal urethritis (NGU) by approximately 20%. McCoy cells pretreated with idoxuridine were compared with irradiated McCoy cells for the isolation of C. trachomatis from clinical specimens. There was no significant difference in sensitivity between the two systems, but the former is considerably simpler. The effect of the centrifugal force used for inoculating specimens on to the cell monolayers on the isolation rate of C. trachomatis was studied in groups of men with NGU. Maximal isolation rates were obtained with forces of about 3000 G, which were not significantly raised by further increasing the force used. It is suggested that the isolation of C. trachomatis from the genital tract is now well within the capacity of any laboratory equipped with simple cell culture facilities.

Cells, Cultured↗
PubMed2000

An evaluation of sampling and laboratory procedures for determination of heterotrophic plate counts in dental unit waterlines.

BACKGROUND: The high numbers of heterotrophic microorganisms that have been cultured from dental unit waterlines (DUWs) have raised concern that this water may exceed suggested limits for heterotrophic plate counts (HPCs). The main purpose of this investigation was to examine HPC variability in DUWs and to examine in detail the effect of laboratory processing of water samples on HPC values. METHODS: Water samples were collected from dental offices either at the beginning of or during the clinic day and were transported to the laboratory, where they were analyzed. RESULTS: Measuring HPC levels within an office would involve testing all units, because significant differences were found between units connected to the same municipal water supply. Within a unit, the average microbial count from high-speed lines was approximately twice the average count from air/water lines. The laboratory processing of water samples significantly affected the numbers of heterotrophic microorganisms that were recovered. Incubation temperature, time and media, as well as neutralization of residual chlorine, all had significant effects on the HPC values. However, no significant differences in microbial counts were found between samples plated with the spread plate method on R2A agar and those plated with the pour plate method with Plate Count Agar. CONCLUSIONS: Dental organizations have suggested target limits in terms of numbers of heterotrophic microorganisms recovered in water from dental units, but standards for laboratory handling must be established as well. A protocol for sample collection and laboratory handling is proposed.

Bacteriological Techniques↗
PubMed1995

A technique for separation of perfluorocarbons from blood used in cardiopulmonary bypass laboratory procedures.

Eliminating from physiologic circulation a significant amount of unnecessary perfluorocarbons (PFC) is advantageous since little is known about long-term effects of PFC in the circulatory system. The basic circuitry, cell-washer, mechanical manipulations, and overall concept revealed that a significant amount of PFC can be retrieved and estimated in volume and compared to initial volumes. A method of separating a certain PFC blood substitute from blood following laboratory cardiopulmonary bypass is described.

Animals↗
PubMed1978

Laboratory procedures for fitting removable partial denture frameworks.

A technique has been described for fitting a removable partial denture framework to the master cast prior to adapting it in the mouth. Emphasis should be placed on maintaining the original contour of the framework throughout the procedure. The amount of metal removed should be only that necessary to seat the casting on the master cast without abrading the stone. When finishing the tooth-contacting surfaces on the casting, very light pressure should be used to burnish the rough surfaces, not reduce them. If these steps are accomplished carefully in the laboratory, the dentist should be able to fit the framework in the mouth in a minimum of time (Fig. 7).

Dental Alloys↗
PubMed1986

Radiographic and clinical laboratory procedures.

Diseases of the oral cavity and related structures, either local or systemic, may have profound physical and emotional effects on a patient. In order to effectively manage these conditions, it is necessary that dentists have a basic understanding of diseases throughout the body. Such an obligation is tempered only by the extent to which diseases relate to the dental profession's anatomic field of responsibility or have clinical implications for office personnel, and the extent to which diseases require modification of dental therapy or alter the prognosis. A primary organic abnormality is typically reflected in the findings of radiographic, laboratory, and tissue studies. From the analysis of a large number of such profiles, certain patterns emerge that are sufficiently characteristic to suggest a specific diagnosis or groups of differential diagnoses for abnormalities that may prompt a request for urgent dental care.

Biopsy↗
PubMedDate not supplied

Laboratory procedures for cases of suspected infant botulism.

The recent development and evaluation of procedures for examination of fecal specimens for botulinal toxin and Clostridium botulinum have provided the means by which infant botulism can be recognized. The toxicity for mice of fecal extracts containing botulinal toxin can be neutralized with specific botulinal antitoxin. The presence of C. botulinum in the feces is detected by demonstrating the presence of botulinal toxin in enrichment culture supernatant by means of toxicity tests in mice. C. botulinum is isolated by streaking enrichment cultures on egg yolk agar and picking typical lipase-positive colonies. The experience of both the Center for Disease Control (CDC) Botulism Laboratory and other laboratories has been that botulinal toxin and C. botulinum are rarely, if ever, found in the feces of humans (infants or older people) not afflicted with botulism. Results of the examination in the CDC laboratory of specimens from 24 babies with infant botulism are given.

Animals↗
PubMed1985

[Rational hematologic diagnosis with reference to modern laboratory procedures].

The spectre of methods for the diagnostics and differentiation of haemolytic anaemias, particularly for the establishment of congenital, autoimmune haemolytic, drug-conditioned and other anaemias is treated. The clear delimitation of an iron deficiency from a disturbance of the iron distribution is advantageously to be achieved by iron staining of the bone marrow and by a determination of serum ferritin. The value of the diagnostic methods in megaloblastic anaemia is classified according to newer knowledge, in which case the vitamin-B12-absorption test and the serum level determination of vitamin B12 by no means range in the first place. Long-term culture results of haematopoietic stem cells are particularly evident in the aplastic syndrome of the bone marrow and further haematological diseases concerning the establishment of the intensiveness of proliferation. The classification of the acute leukemias demands conventional as well as cytochemical staining methods; recently, it is essentially improved using monoclonal antibodies. In leukemias cytogenetic investigations are more and more attracted to the estimation of the prognoses. In lymphogranulomatosis among others functional disturbances of the cellular immunity, in the group of the non-Hodgkin-lymphomas haematological, protein-analytic and immunological laboratory investigations are methods supporting the diagnosis. Altogether is to be established that the haematological diagnostics has become more and more perfect, in which case apart from new techniques old approved methods are still further used.

Anemia, Aplastic↗