Effects of lateral load and external twist on polarization-mode dispersion of spun and unspun fibers.

Using the coupled-mode theory, we have developed a theoretical model to analyze the effects of lateral load and external twist on polarization-mode dispersion (PMD) of spun and unspun fibers. Modeling results show that spun and unspun fibers have very different PMD responses to lateral load and external twist. Experimental results show good agreement with the theory.

Observation of a Raman-induced interpulse phase migration in the propagation of an ultrahigh-bit-rate coherent soliton train.

Coherent soliton packets generated in a passively mode-locked fiber laser are transmitted through 23km of dispersion-decreasing fiber. We observe a shift of the phase difference between solitons that is due to intrapulse Raman scattering. We attribute the stability in propagation of these trains to a trade-off between minimizing soliton-soliton interactions by reduction of the pulse width and minimizing this Raman-induced phase migration, which can force the solitons into a deleterious attractive phase relationship. We are thus able to demonstrate the propagation of 177-Gbit/s soliton packets over a distance of 123 soliton periods.

Spread of local anaesthetic solutions following sacral extradural (caudal) block: influence of posture.

Extradural sacral (caudal) block was performed in 17 cases (14 patients) of chronic low back pain. In each case 22 ml of a bupivacaine/methylprednisolone solution incorporating a radioopaque dye was injected over a 2-min period. Patients were randomly assigned to receive the injection in the horizontal position or with 15 degrees head-up or head-down tilt applied to the operating table. Results indicate that analgesia is usually more localised than spread of solution determined by x-ray evidence and that higher levels of analgesia are achieved in patients in the head-up position. Possible causes are the differing distribution characteristics of the constituents of the solution and the gravitational effects of posture on cerebrospinal fluid mechanics. Technical problems associated with obesity, congenital abnormalities, vascular uptake of solution, and delayed spread of the injectant due to adhesions are discussed.

Gall-bladder contraction and bile duct opacification in oral cholecystography--a comparison of different methods.

The effect of injection of a cholecystokinetic agent, Ceruletide, was compared with that of the fatty meal following a single dose of Biloptin, and Biloptin with Solubiloptin, in regard to efficiency of gall-bladder contraction, cystic and common bile duct visualisation and side effects. In terms of gall-bladder contraction and ductal delineation no advantage was found from giving Ceruletide or Solubiloptin. Gall-bladder contraction occurred more quickly after Ceruletide than after a fatty meal, with corresponding earlier duct delineation, although the gall bladder was completely emptied of contrast medium in a significant proportion of Ceruletide cases. The incidence of abdominal pain was significantly greater after Ceruletide than after a fatty meal. Because Ceruletide requires an intramuscular injection and has no significant advantage over the fatty meal in regard to gall-bladder contraction and ductal delineation, its use in cholecystography is unjustified. A morning dose of Solubiloptin following Biloptin the previous evening offers no advantage over the Biloptin and fatty meal regimen.

Analysis of the chest radiograph in Legionnaires' disease.

The serial chest radiographic findings of 10 patients with Legionnaires' disease seen in Liverpool during 1980 are described. A unilateral lobar pneumonia was the commonest initial finding. Every lobe was involved, with the lower lobes being the most common. Pleural effusion was present in 30% of the cases. A comparison is made with previously reported series both in the United States and in England. Though no single feature is pathognomonic, the radiographic pattern may aid in early diagnosis.

Further experience with glucagon enhanced cholangiography.

A series of infusion cholangiograms was obtained using a standard infusion technique of ioglycamide infused at a rate of 0.57 g min-1 over 30 min. Alternate patients were given either 1 or 2 mg of intravenous glucagon and a comparison of the cholangiograms obtained was then made. It has been shown that a dose of 1 mg of glucagon is equally as effective as 2 mg in improving visualisation of the biliary tract during infusion cholangiography. The possible mechanism of the extra opacification is discussed.

Device for extradural monitoring of intracranial pressure: technical note.

An ICP-monitoring device utilizing an extradural method is described. Clinical and laboratory use has shown it to be easily installed, safe, accurate, and reliable. It can be used with currently available transducers and monitoring equipment. It is hoped that this simple device will encourage the increased use of ICP monitoring.

The effect of glucagon on infusion cholangiography.

The study was undertaken to assess the effects of glucagon on biliary tract opacification during intravenous cholangiography. Two series of infusion cholangiograms were obtained at two investigating centres designated A and B. In series A, 41 patients had ioglycamide infusions at a rate of 0.2833 g min-1 over 1 h. In series B, 31 patients had ioglycamide infusions at a rate of 0.3886 g min-1 over 30 min. Radiographs were taken in both series, immediately at the end of the infusion, 10 min later and 30 min after the infusion. Two mg of intravenous glucagon was injected into alternate cases in both series A and B immediately after the first radiograph was taken at the completion of the ioglycamide infusion. Two observers in each series than assessed the radiographic opacification of the biliary system without prior knowledge of which patients had received the glucagon. Delineation of the biliary system was considered better in both series in those patients who received glucagon when compared with the controls. Gallbladder opacification was definitely increased in series A in those receiving glucagon, and a similar tendency was shown in series B. The amount of contrast in the upper intestine was increased in series A in the glucagon group, but not in series B. It is concluded that glucagon improves visualisation of the biliary tract, especially the gallbladder at infusion cholangiography.

Venous aortography--a forgotten technique.

A simple technique of venous aortography is described. Eleven patients were examined, 10 with suspected aortic aneurysms. The diagnosis was confirmed in six cases and the relationship of the aneurysm to the renal arteries shown in five of them. Three patients were shown to have a normal aorta. One patient with a suspected saddle embolus was shown to have a normal aorta and iliac arteries. There was one failure but there were no serious complications. The technique is a reliable and simple method of visualising arotic aneurysms, especially if subtraction prints are made.

Initial experiences with a formalised teaching programme in diagnostic radiology during the clinical undergraduate course.

The initial experiences of a four-week clinical undergraduate attachment in diagnostic radiology are described. The course is divided into (1) a series of prepared lecture programmes which cover aspects of diagnostic radiology in a systematic manner, (2) experience in hospital X-ray departments, observing special investigations and routine reporting, attending clinicoradiological conferences and receiving informal and formal tuition from radiologists, and (3) visits to specialised radiological and other imaging departments, namely ultrasound, nuclear medicine, neuroradiology and paediatrics. The aims of the courses are: (i) to provide a means of teaching clinical subjects and pathology in a dimension which crosses the tightly compartmentalised undergraduate curriculum; (ii) to instil basic principles of radiological interpretation, (iii) to teach undergraduates how to use the facilities of diagnostic imaging departments effectively and efficiently when they have qualified; (iv) to increase interest in the specialty, and insight into student opinion. There are difficulties involved in this large teaching commitment, for instance, understaffing, and the development of the course has been geared to counteracting these problems.

Post-traumatic skull radiographs. Time for a reappraisal.

504 patients who had skull radiographs for head injury are included in this study. Only 9 (1.9%) had demonstrable fractures. 129 (25%) of the patients reviewed were admitted to hospital. 93 of these were admitted for up to 24 hours, and 36 for a longer period, usually for conditions unrelated to the head trauma. All but 1 of the patients with a demonstrable skull fracture were admitted to hospital, and the radiographic findings initiated active medical intervention in 2 of these cases. There was no correlation between radiographic findings and the need for hospital admission, and little correlation between radiographic findings and the presenting signs and symptoms. It is, therefore, suggested that the indications for skull radiography in the management of head injuries require reappraisal.