Advances in local area optical data communication systems.

This paper reviews optical fibre technology for local area optical communications systems. Technologies used in local systems include single and multimode fibre, single and multimode lasers, optical modulators, photodetectors, wavelength division multiplexing, multilevel modulation formats, electronic packet switching, electronic equalization and error correction. These methods have enabled the local area optical link data rate to increase from 0.1 Gb s-1 in 1990 to nearly a Tb s-1 in 2019. The challenges to increasing link data rates further, while reducing the transmitted power per bit, at reduced cost are discussed. Potential technical solutions and newly proposed methods which might address these challenges are highlighted.

Experimental demonstration of optical data links using a hybrid CAP/QAM modulation scheme.

The first known experimental demonstrations of a 10 Gb/s hybrid CAP-2/QAM-2 and a 20 Gb/s hybrid CAP-4/QAM-4 transmitter/receiver-based optical data link are performed. Successful transmission over 4.3 km of standard single-mode fiber (SMF) is achieved, with a link power penalty ∼0.4 dBo for CAP-2/QAM-2 and ∼1.5 dBo for CAP-4/QAM-4 at BER=10(-9).

Gigabit NRZ, CAP and optical OFDM systems over POF links using LEDs.

Simulations have been performed to compare the system capacity and power dissipation of NRZ, CAP-64 and 64-QAM-OFDM systems over FEC enhanced POF links using LEDs, for both unidirectional and bidirectional transmission. It is shown that CAP-64 outperforms NRZ and 64-QAM-OFDM in terms of system capacity and supports a record high 3.5 Gb/s bidirectional and 2.1 Gb/s unidirectional transmissions over 50 m POF. The CAP-64 transceiver consumes similar power compared with NRZ whilst the 64-QAM-OFDM transceiver consumes about twice as much.

Thermal dye measurements of extravascular lung water in critically ill patients. Intravascular Starling forces and extravascular lung water in the adult respiratory distress syndrome.

To assess the concurrent influence on extravascular lung water (EVLW) content of the intravascular Starling forces, the pulmonary capillary wedge pressure (PCWP), and the colloid osmotic pressure (COP), we measured EVLW by the thermal green dye technique in 174 patients with and without radiographically defined pulmonary edema; in the former group, patients with cardiac (CPE) and noncardiac (NCPE) causes of pulmonary edema were compared (study A). In 119 patients, EVLW was again measured one to three days later (study B). Patients with CPE demonstrated a significantly lower EVLW (9.3 +/- 3.9 ml/kg) (mean +/- SD) than patients with NCPE (14.5 +/- 4.9 ml/kg; p less than 0.05), despite a higher mean PCWP in the former group (20 +/- 7 mm Hg) than in the latter (12 +/- 6 mm Hg; p less than 0.05). In patients potentially with only a hydrostatic cause of pulmonary edema in study A, regression analysis demonstrated the following: EVLW = 3.2 + 0.30 PCWP (r2 = 0.38; p less than 0.005); and in patients with NCPE, EVLW = 10.9 + 0.304 PCWP (r2 = 0.17; p less than 0.01). In study B the change (delta) in EVLW between the two studies was described as follows: delta EVLW = 0.25 + 0.173 delta PCWP (p less than 0.01) + 0.663 group NCPE (p, not significant) + 0.236 group NCPE X delta PCWP (p less than 0.01). This latter equation indicated that the EVLW content manifested a greater change with concurrent alterations in the PCWP in patients with NCPE than was found in patients with only a hydrostatic influence to EVLW formation. Therefore, NCPE is characterized by a greater measurable thermal green dye EVLW than is observed in CPE at any given PCWP, and the PCWP synergistically influences EVLW accumulation in both CPE and NCPE.

Assisted ventilation in patients with preexisting cardiopulmonary disease. The effect on systemic oxygen consumption, oxygen transport, and tissue perfusion variables.

We have evaluated systemic oxygen consumption (VO2), systemic oxygen transport, and tissue perfusion variables in 30 patients with preexisting cardiac and underlying pulmonary disease during continuous positive-pressure ventilation and positive end-expiratory pressure [PEEP], during intermittent mandatory ventilation (IMV and PEEP), and during spontaneous ventilation (continuous positive airway pressure [CPAP]), with end-expiratory pressure held constant during all ventilatory modes. Using radionuclide angiography together with invasive determinations of pressure and flow, we also measured left and right ventricular ejection fractions and calculated the end-systolic (ESVI) and end-diastolic (EDVI) volume indices of both ventricles. We found that oxygen transport was significantly greater during CPAP (583 +/- 172 ml/min/M2)(mean +/- SD) than during either IMV and PEEP (543 +/- 151 ml/min/sq; p less than 0.01) or CPPV and PEEP (526 +/- 159 ml/min/M2; p less than 0.01); however, we found no significant change in systemic VO2 with conversion from CPPV and PEEP to CPAP. The increase in oxygen transport was related to a greater cardiac index and, more specifically, to a higher heart rate during CPAP (CPAP, 106 +/- 16 beats per minute; CPPV and PEEP, 97 +/- 14 beats per minute) (p less than 0.01). Enhanced oxygen transport during CPAP was also associated with an increase in mixed venous oxygenation and a decrease in arterial lactate. Although neither the mean left ventricular EDVI nor ESVI changed from CPPV and PEEP to CPAP, the mean pulmonary capillary wedge pressure increased (CPPV and PEEP, 12 +/- 5 mm Hg; CPAP, 14 +/- 7 mm Hg) (p less than 0.01), suggesting the possibility of a decrease in left ventricular compliance with the spontaneous ventilatory mode. This study suggests that in the absence of ventilatory failure, spontaneous ventilation provides for better systemic oxygen transport and overall tissue perfusion than either controlled ventilation or IMV; however, this benefit of enhanced oxygen delivery with spontaneous ventilation may potentially be offset by a decrease in left ventricular compliance.

Aeromonas-associated diarrhea in children.

In a 27-month prospective study, Aeromonas spp. were isolated from 7.3% of children with diarrhea and from 2.2% of controls. In 32 patients with diarrhea, ranging in age from 1 to 27 months old, Aeromonas spp. were the only potential bacterial enteropathogens isolated. Principal symptoms of Aeromonas-associated diarrhea were vomiting, fever and bloody stools. Diarrhea was often self-limiting and lasted for 10 days or less in 90% of patients. No secondary spread of diarrhea among close contacts was observed and no clear-cut seasonal patterns of Aeromonas isolation were found. Aeromonas caviae was the most frequently isolated species in fecal samples of patients (24 of 29 isolates) as well as controls (5 of 7 isolates). Cholera toxin cross-reactive cytotoxic enterotoxin was produced by a vast majority of Aeromonas isolates, as compared to a non-cholera toxin cross-reactive cytotonic enterotoxin. In addition no significant correlation was observed between severity of the diarrheal disease and different Aeromonas or the quantity of enterotoxins produced. In our geographic area Aeromonas spp., and A. caviae in particular, seem to be an important and frequent cause of diarrhea in young children.

Infantile cortical hyperostosis and facial nerve palsy.

Facial nerve palsy was diagnosed in a 13-month-old child with infantile cortical hyperostosis. Facial palsy preceded the roentgenographic evidence of mandibular hyperostosis but there was concurrent evidence of hyperostosis of multiple other bones. This case exemplifies the importance of maintaining a high index of suspicion for infantile cortical hyperostosis in infants and children presenting with facial swelling and facial nerve palsy.

Large outbreak of food poisoning caused by Salmonella typhimurium definitive type 49 in mayonnaise.

An investigation was conducted to determine the vehicle of infection of an outbreak of food poisoning in a large metropolitan building early in 1988. A questionnaire was distributed to 700 people who had eaten in the building during the week of the outbreak, and attack rates for specific food were calculated. Food and stool samples, environmental samples, and eggs and environmental swabs from the egg suppliers were examined microbiologically. Altogether 474 questionnaires were returned, 120 people reporting gastrointestinal illness. The illness was significantly associated with foods containing mayonnaise. Salmonella typhimurium definitive type 49 was isolated from 76 of the 84 stool samples containing salmonella and from five of the eight samples taken from the chicken house of the main egg supplier. Mayonnaise was probably the vehicle of infection, which was caused by S typhimurium definitive type 49.

Effect of psychotropic drugs on aggression in a prison setting.

The authors, working in a maximum security correctional institution, had noted an apparent increase in acts of aggression by inmates when these inmates were on psychotropic drugs. A retrospective study was therefore carried out to attempt to correlete and prove or disprove this hypothesis. It was found that violent, aggressive incidents occurred significantly more frequently in Inmates who were on psychotropic medication than when these inmates were not on psychotropic drugs. Of these, antianxiety agents (diazepam in 81 percent of the cases), appeared to be most implicated, with 3.6 times as many acts of aggression occurring when inmates were on these drugs. For the other classes of psychotropic medication the aggressive incident rate was double the rate of those on no psychotropic medication.

Computed tomography in the evaluation of liver disease in cystic fibrosis patients.

The results of a study of cystic fibrosis patients with liver disease using computed tomography are reported. The findings are described, and a discussion of their significance and place in patient investigation is offered.

Gas chromatographic determination of fatty acids and sterols in orange juice.

A gas chromatographic (GC) method has been developed for the simultaneous quantitation of fatty acids and sterols in orange juice, using a bonded phase fused silica capillary column of intermediate polarity, splitless automatic injection, and flame ionization detection. Sample preparation has been simplified by using 1 g C-18 adsorbent in a disposable minicolumn to extract 2 mL orange juice. Methylation of fatty acids and silylation of the sterols were carried out in the eluted extract (low polarity lipid fraction). The method precision was 7%; recoveries ranged from 83 to 113%. The precision of the injection technique was 2%. Seven major fatty acids and 5 sterols in orange juice were quantitated by the GC method and identified by GC/mass spectrometry. Quantitative data for several orange juice samples indicated that the levels of the compounds of interest were in the 1.3-72.0 mg/L range. The results demonstrate that bonded phase fused silica capillary GC has great versatility and potential for the quantitative determination of fatty acids and sterols.

Right and left ventricular performance in acute hypoxemic respiratory failure.

We examined biventricular performance on two occasions in 28 patients with acute hypoxemic respiratory failure (ARF), using a combination of invasively determined pressures and flows as well as radionuclide scintigraphy to measure the right and left ventricular ejection fractions (RVEF and LVEF, respectively). From the EF and concurrently measured thermodilution stroke volumes, we calculated right and left ventricular end-diastolic and end-systolic volume indices (EDVI and ESVI, respectively). Regression analysis demonstrated that changes (delta) in global right ventricular function (RVEF) were inversely correlated with concurrent changes in the mean pulmonary arterial pressure (MPAP): delta RVEF = 0.015-0.015 delta MPAP (r2 = 0.60; p less than .005), while an increase in right ventricular preload (RVEDVI) was positively correlated with changes in MPAP: delta RVEDVI = 2.68 +/- 6.27 delta MPAP (r2 = 0.46; p less than .005). Global left ventricular function (LVEF) was related to changes in systemic pressures as well as to right-sided events: delta LVEF = -0.01-0.0015(delta RVESVI) + 0.001(delta BP systolic)-0.42(CVP/RVEDVI) (r2 = 0.35; p less than .01). These data confirm the significant influence of right ventricular afterload on RVEF in ARF patients and an apparent interrelationship between altered right ventricular systolic function and global left ventricular performance.

HIV testing: changing trends at a clinic for sexually transmitted diseases in London.

Trends in human immunodeficiency virus (HIV) counselling and antibody testing at a London clinic for sexually transmitted diseases showed substantial changes over a 12 month period. From around 100 a month in the summer of 1986 the numbers of people attending rose substantially to 276 in October 1986 and 475 in November at the time of the campaign in the popular press. They rose further still, to 700, at the time of AIDS (acquired immune deficiency syndrome) week in March 1987. In April they fell to the levels seen six months previously. Apart from this increase in overall numbers the proportions of women and heterosexual men who were seen increased.