Analytical far-field divergence angle of a truncated gaussian beam.

Approximate, but accurate, analytical expressions for the far-field divergence angle of a Gaussian beam normally incident on a circular aperture are derived. A first equation is obtained based on the concept of Gaussian transform, in which the Bessel function present in the far-field diffraction integral is approximated by a Gaussian function. Refining this approach yields another simple, practical closed-form formula with such a level of accuracy that we propose that it can be used as an exact reference. All approximations hold for any combination of Gaussian beam width and aperture radius.

Carcinoma arising within epiphrenic diverticula. A report of two cases and review of the literature.

Two patients with squamous cell carcinoma arising within an epiphrenic diverticulum are reported bringing the total reported in the English-language literature to fifteen. The majority of patients with carcinoma arising in an epiphrenic diverticulum are elderly males who have been symptomatic for years with a known diverticulum. This is the first report of multiple cases of carcinoma within an epiphrenic diverticulum from a single institution and the first report in a female patient. Similar to other reports, these two patients presented with several months of symptoms related to their esophageal diverticulum. It is important to entertain the diagnosis of esophageal carcinoma early in the evaluation of patients with signs and symptoms suggestive of epiphrenic diverticula as early intervention may be the only chance of cure.

Evaluation of the efficacy of an instructional programme in the self-management of patients with asthma.

The restrictions imposed on patients with asthma is problematic to them, in that their physical disability interferes with personal, interpersonal and/or professional goals. Twenty-three patients under the care of general practitioners were surveyed by interview in their homes, doctors' surgery or at work to determine their current control of selected variables related to their asthma: exercise, use of drugs and related factors. An instructional programme was offered to interested participants to assist in complying with their prescribed medication regimens and to tailor exercise to their tolerance levels. Findings showed that 18 patients experienced moderate to severe restrictions when troubled with asthma. Although over one-half of the patients exercised regularly for fitness, including seven with aerobic exercise, some chose sports they thought could provoke an asthmatic attack. Half took precautionary measures when exercising. All patients used bronchodilators to relieve their asthma, yet one-third did not keep their inhalers accessible. None of the most troubled 18 lived in a smoke-free environment, and one-third kept furry animals as pets. Recommendations are made for further study of the effects of instructional programme to improve compliance to a healthy lifestyle.

Variable angle, fixed position, beam alignment device.

We describe a general beam alignment device that allows variation of the angle of incidence while preserving the position of incidence on a sample.

Angular scanning mechanism for ellipsometers.

We describe the implementation of an elliptical mirror for variable angle, fixed position beam alignment in ellipsometers. The proposed configuration reduces mechanical complexity and allows for the determination of differential angular measurements of ellipsometric parameters.

Comparison of two methods for obtaining size distribution characteristics of particulate matter in large-volume parenterals.

The size distributions of the particulate matter present in six types of large-volume parenteral solutions, as determined by an automatic particle counter and a microscopic counting technique, were compared by plotting log N greater than D versus log D. The resulting data were analyzed individually and also as averages. The data showed a linear relationship between log N greater than D and log D over the 1-100-micron particle-size range, indicating that both methods determine a similar particle-size distribution. The data also indicated that the particle-size distributions were largely independent of the type of solution and obeyed a power law of the form N greater than D = N greater than 1DK. These observations suggest that the major source of contamination is air-borne dust particles, which fall into a solution randomly, and that it may be possible to monitor the smaller, more abundant particles with the automatic particle counter to obtain a rapid estimate of parenteral cleanliness. The automatic particle counter thus appears to be a viable alternative to the microscopic counting technique for assessing the particulate matter content of parenterals.

Parameter for assessing parenteral cleanliness based on particle-size distributions.

A new parameter for assessing the particulate matter content of large-volume parenteral solutions was developed and tested. Some problems and shortcomings associated with previously proposed standards are discussed, together with the potential advantages of employing the proposed parameter. Cleanliness factors were compared with another parameter and were less susceptible to changes resulting from the method of measurement utilized and the premeasurement conditions encountered by the solution. The use of these cleanliness factors in conjunction with an automatic particle counter is proposed as a worthwhile supplement to the USP-NF standard for monitoring the quality of large-volume parenteral solutions.

Effects of agitation on size distribution of particulate matter in large-volume parenterals.

The particle-size distributions of six types of large-volume parenterals subjected to different degrees of agitation were determined using an automatic particle counter. Data acquired from each solution, which had been maintained in a stored condition, subjected to agitation by inverting 20 times, and then mechanically shaken for 30 min, produced a linear relationship between log N greater than D and log D. Both the slope (K) and the number of particles per milliliter exceeding 1 micrometer in diameter (N greater than 1) exhibited a dependence on the degree of agitation. Their combined effect indicates that agitation by 20 hand inversions removed particulate matter from the surface of the container, which increased the total number of particles in solution (greater than 1 micrometer) but did not significantly alter the relative size distribution. Agitation for 30 min, however, disintegrated agglomerates and produced a particle-size distribution with a greatly increased number of particles whose diameters were less than 1 micrometer and a corresponding decrease in the number of particles exceeding 1 micrometer in diameter. The particle-size distribution of a parenteral solution determined by this in situ instrumental method was, therefore, dependent upon the degree of agitation to which the parenteral was subjected prior to examination.