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Biomedical subjects

D M Clarkson

Publications and source records attributed to D M Clarkson.

16 recordsLinked to original sources
PubMed2003

Dual channel light pulse exposure timer.

An instrument has been developed for routine measurement of pulse durations of lasers and pulsed light sources. A four digit light emitting diode (LED) count display is used with a range of selectable clock rates in five decades from 1 MHz to 100 Hz with a longest time duration corresponding to 99.99 s. The performance of the system was verified using a Schmidt trigger test circuit to drive an LED where the time of the drive pulse was compared to that indicated by the timer unit and where also silicon photodiodes of different detector areas were used to verify device measurement accuracy.A buffered output channel allows inspection by an oscilloscope to verify output pulse characteristics. This can be especially relevant to verify performance characteristics of a given laser/pulsed light system and to establish definitive assessments for eye safety based on relevant standards.

Electronics↗
PubMed2002

Accuracy estimations of testing of infusion devices using weighing balances.

The role of gravimetric balances in the evaluation of infusion devices is considered from a perspective of accuracy for such evaluations and the actual physical and interface characteristics of such balances as specialist measurement devices. In particular, the dynamic properties of weighing balances are discussed in relation to observations of variation of response times and stability settings. This work has identified characteristics, which may influence flow measurement techniques as defined by measurement protocols adopted by relevant standards and those developed independently. While a dominant error is introduced due to balance resolution error, consideration of timing errors associated with data capture is also essential.

Calibration↗
PubMed1993

New ultraviolet monitoring technology.

There is a growing awareness of the hazards of ultraviolet (UV) radiation to the health of the community and to our environment's integrity. There is a need for monitoring this hazard. Until recently, UV radiation sensors tended to be relatively expensive. However, as a result of the introduction of mass-produced GaAs photodiodes in the late 1980s, UV radiation now can be measured more accurately, cost-effectively and conveniently. A new, low-cost sensor is available with a wavelength tailored to the skin's erythmal response without additional complex circuitry or filter elements; it can be used in a variety of settings.

Hawaii↗
PubMed1992

Lasers in dentistry.

Lasers, which are constantly evolving, can be customized to meet dental requirements and could become a very useful tool for dental practitioners. The article provides an introduction to the instruments, which includes a description of how they work and discusses their applications in dentistry.

Dental Caries↗
PubMed1988

Flexible software for the processing of obstetric ultrasound scan and related information.

Software has been developed whose main function is to relate obstetric ultrasound scan data to patient details at delivery. Up to four separate scan measurements can be recorded for each ultrasound investigation. Data on up to six such scanning sessions can be stored in a separate computer record for each patient. Up to four gestational tables can be configured by the user and stored on disc for each scan measurement. Flexible selection of computer records is possible on a broad range of criteria. Summary information such as Apgar score and birth weight distribution and the deviation from predicted delivery dates in half week intervals and also discrete days for each relevant set of maturity estimations can be generated. The software, written in Microsoft BASIC (GWBASIC and quickBASIC) can be run on a broad range of 16 bit microcomputers.

Delivery, Obstetric↗
PubMed1982

Microcomputer system in an accident unit.

A microcomputer-based records system has been developed for use in the accident unit of a district general hospital. Patient details are entered directly at the reception desk and the computer generates a casualty card that is updated after the patient has been seen by the doctor, who determines the diagnosis to be recorded and specifies the injury coding. Information is stored on floppy discs, each holding the details of 3400 patients. The computer is used to produce a daily log-book of attendances, including revisits. The stored data may be examined and analysed for both administrative and medical purposes. The work load can be rapidly analysed according to various options that include the nature, type, and site of injuries. The system was introduced in December 1980. Location within the unit allows control over its operation, and many of the limitations of a manual system have been overcome.

Computers↗
PubMed1982

A microcomputer system for the collection and analysis of antibiotic sensitivity test data.

A microcomputer system for the routine collection and analysis of microbiological data is described. A digitising tablet is used as a method of data input. A series of analysis programmes was developed to allow investigation of the distribution of organisms in relation to the type of specimen in which they occur, the origin of the specimen and also to examine their associated sensitivity patterns. In this instance a Commodore PET was used, though other microcomputers could be similarly employed with equal facility.

Anti-Bacterial Agents↗
PubMed1980

Failure of propranolol and metoprolol to alter ventilatory responses to carbon dioxide and exercise.

Neither propranolol (80 mg) nor metoprolol (100 mg) give orally to eight normal subjects altered mean ventilatory responses to carbon dioxide or to moderate graded exercise. Incremental doses of the drugs to totals of 320 mg propranolol and 400 mg metoprolol also did not effect these ventilatory responses. Both drugs markedly decreased the heart rate response to exercise. Neither propranolol nor metoprolol are likely to cause CO2 retention by an effect on the ventilatory responses to inhaled carbon dioxide or to exercise.

Adult↗
PubMed1978

Effects of ultrasonication of the rabbit lens in situ as evaluated by analysis of crystallin composition.

Ultrasonication and aspiration is a recently developed method of lens extraction. We have attempted todetermine whether extraction by this procedure is total or partial and, if so, whether certain regions or components are preferentially removed, and also whether the contents of the lens are physico-chemically modified by the process of extraction. The water-soluble and urea-soluble protein fractions from the ultrasonicated lenses and the contra-lateral intact lenses of six rabbits were analysed by isoelectric focusing. Differences are found in the crystallin content which indicate that extraction is frequently non-representative and that beta- and gamma- crystallins are modified by the process.

Animals↗
PubMed1976

Lens extraction with ultrasound. Experiments in rabbits.

The extraction of the rabbit lens is described using a 25 G irrigating needle and a 22 G aspirating needle; at the latter's bevelled tip lens fragmentation occurs due to the longitudinal ultrasonic vibrations generated there--an 'acoustic horn' causes the tip to vibrate with large amplitudes. The use of small needles allows considerable manoeuvrability in the anterior chamber and usually eliminates the need for corneal suturing. Push-pull coupled syringes equate the volume of irrigation with that of aspiration. This procedure makes possible lens extraction through an aperture in the anterior capsule of the rabbit's lens and a similar machine is being constructed for trial on human cataract.

Animals↗
PubMed1975

Ultrasonic cataract extraction with acoustic horn.

An ultrasonic lens-disintegrations system is added to the aspiration side of an irrigation-aspiration system. It incorporates an acoustic horn of which one part is a stainless steel cone 4 cm long with a 1 cm diameter base. From the apex of the cone projects the other part, viz. a 22 gauge needle, which is inserted into the anterior chamber at the limbus temporally (left eye) and which carries aspirated lens fragments with saline out into a duct drilled 2 cm into the cone along its axis. At that point the duct turns at right-angles to leave the cone; a polythene tube connects the duct with the aspiration syringe. A vibration generator (sandwich transducer) initiates ultrasonic vibrations which the needle-cone combination magnifies about 100-fold at the tip of the needle. Saline input to and output from the anterior chamber are maintained exactly equal (and simultaneous) by means of a 'push-pull' system of twin reciprocating hand-driven 30 ml. syringes (Fig. 7). Saline input is through a 25 gauge needle at the limbus at 6 o'clock (left eye).

Amplifiers, Electronic↗
PubMedDate not supplied

Hazards of non coherent light sources as determined by the framework of IEC TR-60825-9.

An overview is provided of the scope and application of IEC TR 60825-9 in determination of hazards of non coherent optical radiation sources. Specific areas reviewed in detail include those relating to hazards of ultraviolet radiation, retinal thermal hazard and blue light photochemical hazard. The effect of spectral temperature on relative risk relating to retinal thermal hazard and blue light photochemical hazard are outlined. Assessment of risk factors of these hazards was determined using a range of measurement devices including spectral radiometer, broad band power meter and a locally developed device for determination of pulse profile of pulsed light sources.

Eye↗
PubMedDate not supplied

The role of measurement of pulse duration and pulse profile for lasers and intense pulsed light sources.

Details of the use of an instrument designed to measure pulse duration and pulse profile of lasers and intense pulsed light sources are described. The unit has been found to provide clarification of pulse timing characteristics of lasers where observed characteristics were at variance with system specification. Also, the unit was found to determine output pulse characteristics of intense pulsed light (IPL) sources where definition of such pulse profiles is typically absent in supplied technical descriptions and where pulse profiles are usually more complex than that of laser systems. These measurements have allowed more accurate determination of safety criteria for the use of such systems.

Lasers↗
PubMedDate not supplied

A review of technology and safety aspects of erbium lasers in dentistry.

This article reviews aspects of the probable mechanisms used by erbium dental lasers for cutting dentine and enamel, describes key issues of the risk of temperature elevation and speed of cutting relative to conventional techniques and looks at issues concerned with the safety of lasers.

Dental Instruments↗