Integrated polarization beam splitter with relaxed fabrication tolerances.

Polarization handling is a key requirement for the next generation of photonic integrated circuits (PICs). Integrated polarization beam splitters (PBS) are central elements for polarization management, but their use in PICs is hindered by poor fabrication tolerances. In this work we present a fully passive, highly fabrication tolerant polarization beam splitter, based on an asymmetrical Mach-Zehnder interferometer (MZI) with a Si/SiO(2) Periodic Layer Structure (PLS) on top of one of its arms. By engineering the birefringence of the PLS we are able to design the MZI arms so that sensitivities to the most critical fabrication errors are greatly reduced. Our PBS design tolerates waveguide width variations of 400nm maintaining a polarization extinction ratio better than 13dB in the complete C-Band.

Separation of functional subpopulations of murine and human lymphoid cells on colloidal silica density gradients. I. Preparation of the Ludox AM gradient material and characterization of separation capacities.

This report describes a unique modification of an isopycnic density gradient system utilizing as a separating menstrum colloidal silica (Ludox AM). The primary advantages of this preparation are: (1) It is chemically defined, allowing extremely reproducible cell separation employing different lots of material; (2) the physical parameters (pH, density, salt concentration) of the final gradient suspension can be manipulated over a wide range of values, allowing for the separation of many different biological materials; (3) it allows separation of very large numbers of lymphoid cells with greater than 95% recovery of applied cells; (4) separated cellular subpopulations can be easily washed free of silica and cellular function is retained. This paper is a report of the preparation and functional characteristics of the gradient material as it relates to the separation of very large numbers of lymphoid cell subpopulations in both mouse and man. Subpopulations of murine and human lymphocytes separated by this gradient material were assayed for IgM synthesis, T-cell mediated cytotoxicity, and lymphokine production.

Autosomal dominant mouse cataract (Lop-10). Consistent differences of expression in heterozygotes.

The clinical and histologic features are reported of an autosomal dominant mouse cataract that was first observed as a new mutation in a cross between BALB/cJ and AKR/J. In the homozygous state, the eyes were microphthalmic, and a dense white cataract was present when the eyes opened at day 12. Histologic changes were apparent from birth and as early as 18 days' gestation. Liquefaction started by day 4, and herniation of lens contents posteriorly was seen at day 11. Heterozygous mice had variable expression depending both on their genetic background and age. When the single gene was expressed fully, the cataract appeared as a fetal nuclear white opacity; partial expression gave a nuclear haze to snowflake nuclear opacities. Lop-10 appeared to be an excellent model for studying variable expression of a dominant gene.

Comparison of 24 versus 12 hours of ambulatory ECG monitoring.

In order to assess the additional information obtained from 24 hours compared to 12 hours of ambulatory ECG (electrocardiogram) recording, we analyzed 72 ambulatory ECG monitoring tapes in which arrhythmias were present. In all cases the second 12 hours included the entire period of sleep. Only 38 of 233 (16 percent) episodes of arrhythmias, frequent premature ventricular contractions (PVC's), two or more PVC's in a row, multiform PVC's, ventricular bigeminy, trigeminy, premature atrial contractions (PAC's), and supraventricular tachyarrhythmias occurred for the first time in the second 12-hour period. New ventricular arrhythmias were detected during the second 12-hour period in 13 percent of the arrhythmic episodes. Although sleep resulted in a marked decrease in PVC frequency in 63 percent of 30 recordings, with frequent PVC's while awake, 8 percent had a significant increase during sleep. In contrast, short runs of supraventricular tachyarrhythmias occurred during the second 12 hours in 48 percent of cases, 66 percent of these while asleep. These data suggest that a 24-hour ambulatory ECG tape recording be utilized initially to characterize the occurrence and frquency of the patients' ambulatory arrhythmias during awake and sleep periods. Thereafter, additional ECG recordings for monitoring antiarrhythmic drug therapy can be accomplished with a 12-hour recording in more than 80 percent of patients

Diode laser photocoagulation for prethreshold, posterior retinopathy of prematurity.

Nine infants with posterior retinopathy of prematurity were treated by using the diode laser through an indirect ophthalmoscopic delivery system. Treatment was commenced as soon as plus disease (defined as tortuosity and dilation of posterior vessels) developed. We defined posterior retinopathy of prematurity as retinopathy of prematurity located in zone 1 (the limits of zone 1 are defined as twice the disk-fovea distance in all directions from the optic disk, that is, an arc of 60 degrees centered on the optic disk) or the posterior one half of zone 2 (zone 2 extends from the edge of zone 1 peripherally to a point tangential to the nasal ora serrata and around to an area near the temporal anatomic equator). Disease regressed in all eyes. These results are encouraging and represent an improvement over the results obtained by allowing these eyes to reach threshold (threshold disease is defined as 5 or more contiguous or 8 total clock hours of neovascularization in zone 1 or 2 in the presence of plus disease) before intervention.

Histopathology of mitochondrial cytopathy and the Laurence-Moon-Biedl syndrome.

Clinical and histopathological studies of two patients with distinctly different inherited juvenile retinal dystrophies indicate that the ocular defect in mitochondrial cytopathy involves the underlying pigment epithelium, whereas in the Laurence-Moon-Biedl syndrome the photoreceptor cells are primarily affected.

Oral vitamin E supplements can prevent the retinopathy of abetalipoproteinaemia.

Six patients with abetalipoproteinaemia are described who received large doses of oral vitamin E for between 12 and 18 years in addition to a low fat diet and supplements of the other fat soluble vitamins. The progressive retinopathy observed in untreated abetalipoproteinaemia was substantially modified and most probably prevented by this therapy. Angioid streaks were noted in one patient. Treatment with vitamin A alone did not prevent or arrest the progression of the retinal lesion.

Gallbladder with ectopic gastric mucosa: ultrastructural analysis.

The clinical and pathological findings of two patients with ectopic gastric mucosa within the gallbladder are studied and compared with the findings recorded in the literature. A contrast between incidental and symptomatic ectopia was noted in these cases. Morphologically bountiful parietal cells were noted in our symptomatic case, while sparse parietal cells were found in our incidental case.

Eduard Jaeger's Test-Types (Schrift-Scalen) and the historical development of vision tests.

PURPOSE: Eduard Jaeger's original Test-Types were carefully evaluated: (1) to determine whether Jaeger had maintained a consistent standard, (2) to establish the correct Snellen equivalent for Jaeger's Test-Types, (3) to answer the question of why and how the standard was lost, and (4) to compare the visual angle of optotypes to lines of continuous text. METHODS: All original Viennese editions of Jaeger's Test-Types, as well as first generation United Kingdom (UK) and United States (US) versions, were evaluated. Data were collected objectively using a microruler with a 20X loupe and subjectively using a laser distance-measuring device. The data were analyzed using Microsoft Excel. All previous measurements of Jaeger's Test-Types, objective and subjective, collected over the past 133 years were compared to the current data and to each other. RESULTS: The correct Snellen equivalent of Jaeger's Test-Types was determined. The visual angle created from the measurement of the height of lowercase letters, without ascenders or descenders, provides an accurate method of assigning a visual angle of a line of continuous text. Comparing the typefaces used in printing first generation UK and US versions of Jaeger's Test-Types to the Viennese editions provided an explanation for the absence of a consistent standard for Jaeger's Test-Types today. CONCLUSIONS: All 10 versions of Jaeger's original Test-Types are virtually identical and established a gold standard for reading vision tests. Jaeger's standard was lost when his Test-Types were first printed in the UK and the US using local typefaces. The Jaeger standard has been re-established. Visual angles determined using continuous text are comparable to those obtained by using optotypes.

Ophthalmology services in the Magadan region of the Soviet Far East with special reference to diseases of the retina.

Ophthalmology Services were observed during the two week period July 4th through 16th, 1991 in Magadan in the Soviet Far East. The range of diabetic eye disease appears to be similar to that observed in the West. Major requirements for education (both patient and physician, stressing the importance of controlling blood glucose and its relationship to diabetic eye disease) and inexpensive reliable diagnostic and therapeutic equipment were identified. Substantial benefits can be achieved by supplementing the current medical infra-structure. Continued medical education through exchange of information remains a primary objective.

Giant peaked upright T waves in cerebrovascular accident.

Tall upright T waves, with a maximal T/QRS ratio (in lead V4) of 1.32, appeared in a 52-year-old patient after a cerebral haemorrhage which was confirmed at necropsy. Hyperkalaemia during life and endocardial or myocardial damage were not found.