Use of capillary gas chromatography with negative ion-chemical ionization mass spectrometry for the determination of perfluorocarbon tracers in the atmosphere.

A sensitive and selective technique for the quantitative measurement of atmospheric perfluorocarbon trace species at the sub part per quadrillion (10(-15)) levels is presented. The method utilizes advances in adsorbent enrichment techniques coupled with benchtop capillary gas chromatography and negative ion-chemical ionization mass spectrometry. The development and enhancement of sampling technology for tracer experiments is described, and the results from background measurements and a preliminary field experiment are presented. The overall precision of the analytical method with respect to the preferred tracer for these atmospheric transport studies, perfluoromethylcyclohexane, was +/-1.7%. The background concentrations of perfluorodimethylcyclobutane, perfluoromethylcyclopentane, and perfluoromethylcyclohexane at a remote coastal location (Mace Head, Ireland, 53 degrees N, 10 degrees W) were found to be 2.5 (+/-0.4), 6.8 (+/-1.0), and 5.2 fL L(-1) (+/-1.3), respectively. Background concentrations within an urban conurbation (Bristol, U.K.) were slightly greater at 3.0 (+/-1.5), 8.1 (+/-1.8), and 6.3 fL L(-1) (+/-1.1), respectively.

Reticulography: a simple and sensitive technique for mapping misorientations in single crystals.

Interposition of a fine-scale X-ray absorbing mesh between a Laue-diffracting crystal specimen and the photographic plate recording its topographic image splits the diffracted beam into an array of individually identifiable microbeam elements. Direction differences between the microbeams in the array, which are twice the orientation differences between the crystal elements reflecting them, are measured by recording the array at two or more mesh-to-photoplate distances. Maps of misorientation vectors over the crystal lattice planes under examination can be derived from these array images by visual or digital electronic metrological procedures. Applications to two specimens widely different in diffracting properties are described. Angular size of the X-ray source is the principal instrumental factor setting misorientation detection limits, and was less than 1 arc second in this work.

Applications of synchrotron radiation to defect characterization and pendellösung fringe-spacing measurement in a natural diamond.

A small polished rectangular block of natural diamond unusually free from impurity zoning was examined by birefringence and synchrotron X-ray topography to map internal defects and assess effects of some accidental mechanical damage. ;Orthogonal-view' projection topographs facilitated comparisons between optical and X-ray images. Speedy and precise positioning of crystal sections cut in synchrotron X-ray section topographic studies was aided by radiographic and fluoroscopic procedures, which are described. Several X-ray reflection and refraction phenomena are illustrated, including high-contrast refraction images of crystal edges, chipping and crack outcrops. It was demonstrated that by combining optical and X-ray goniometry it was possible to record Pendellösung fringe systems employing precisely selected X-ray wavelengths in well defined crystal volumes. Valuable gain in fringe visibility resulted from the use of pure sigma-mode polarized synchrotron radiation. Absolute values of the diamond 004 structure factor were derived from five fringe systems measured, the findings (in upward order) being 11.7, 11.7, 12.0, 12.5, 12.6. Their scatter greatly exceeds the uncertainty in the measurement procedure (believed to be within +/-1%) and is attributed to different strain distributions within the five volumes sampled.

Some characteristics of endoscopic and radiological systems used in elaboration of the diagnosis of velopharyngeal incompetence.

The characteristics of rigid and flexible endoscopes have been studied with reference to their suitability for nasal pharyngoscopy in the assessment of velopharyngeal incompetence taking into account a number of fallacies which are known to exist. It is concluded that the ability to achieve correct positioning of the rigid endoscope and the wide angle field of view of the 70 degrees Storz-Hopkins nasopharyngoscope, in particular, made it the best single instrument at present available for this work despite the greater ease of introduction of the flexible endoscopes. The characteristics of the information obtained by radiological examination were studied and in comparison with endoscopic information it was concluded that endoscopic information was more reliable for qualitative and radiological for quantitative analysis. The systems were considered to be mutually complementary and simultaneous examination with, preferably, synchronous recording provided the advantages of optimal placement of the endoscope and the possibility of measurement of the velopharyngeal isthmus.

Operating microscope eyepiece heaters.

Precipitation of water vapour from expired air on to exposed eyepiece lenses of operating microscopes can seriously interfere with the surgeon's view. By warming these optical surfaces to temperatures well above the dew point of expired air this problem is eliminated. A pair of small heaters were designed to clamp over the eyepiece tubes of a standard operating microscope and their effectivity assessed.

An optoelectronic slide identifier.

An inexpensive optoelectronic slide identifier that uses binary code is described. It can be attached to most automatic projectors and provides for automatic indexing of up to two-hundred and fifty-five different coded slides, while each slide is being projectd.

Resuscitation teaching room in a district general hospital: concept and practice.

Practical training in cardiopulmonary resuscitation presents a problem because of the shortage of teacher time and the many potential trainees. A resuscitation teaching room in district general hospital has been established, equipped with training mannikins and models, together with wall diagrams and cassette recordings. The arrangement enables many trainees to gain training in small groups with minimal demand on teachers. Experience with the room in use has suggested that the concept may have an application in many district general hospitals and possibly also in large industrial concerns.

A dual viewing attachment with the hand-held ophthalmoscope.

A flexible dual viewing attachment for a hand-held ophthalmoscope permits rapid and effective instruction of undergraduate medical students in the ophthalmoscopic technique.

The technique of recording nasal pharyngoscopy.

Nasal pharyngoscopy is a relatively simple and most informative technique requiring a small amount of very portable equipment. Recording the observations objectively is of considerable clinical and research value, but will require a two-man team, one of whom must be thoroughly versed in audio-visual communication techniques and apparatus. The equipment is more expensive and although it can be transported is probably best used at a routine site.