Anisotropic fiber with a depressed-cladding profile

Anisotropic fibers of the depressed-cladding type are analyzed by employing an iterative perturbation technique in a simple and straightforward way. An analytic expression is obtained for calculating the leaky-mode losses of an anisotropic depressed-cladding fiber. Numerical results show that such fibers possess much higher losses than those predicted earlier for a step-index model and hence are more advantageous for use in achieving singlepolarization, single-mode operation.

Influence of passive smoking on admissions for respiratory illness in early childhood

An association was sought between passive smoking and inpatient admissions for respiratory illness in 1058 children born between 1 June and 31 December 1981 and living in the neighborhoods of Nan-Jing Western Road and Yan-An Western Road in Jing-An District, Shanghai. The admission rate for first episodes of respiratory illness was positively correlated with the total daily cigarette consumption of family members during the children's first 18 months of life. The relative risk of developing a first episode of respiratory illness was 1.80 for children living in families including people who smoked 10 or more cigarettes a day compared with those living in non-smoking families. Multiple logistic regression analysis showed that the effect of passive smoking on inpatient admission for respiratory illness was independent of the child's birth weight, type of feeding, father's education, size of the home, and chronic respiratory disease among adults in the family. The adjusted odds ratios compared with the non-smoking group were 1.17 in families smoking 1.9 cigarettes daily and 1.89 in families smoking 10 or more cigarettes daily. These data suggest that exposure to household cigarette smoke of children in early life increases the risk of severe respiratory illness.

Co-operativity and enzymatic activity in polymer-activated enzymes. A one-dimensional piggy-back binding model and its application to the DNA-dependent ATPase of DNA gyrase

The binding of a ligand to a one-dimensional lattice in the presence of a second ("rider") ligand, which binds only to the first ligand (piggy-back binding), is studied. A model derived from this study is used to analyze the effects of co-operativity on the reaction rates of enzymes activated by polymeric cofactors that provide multiple binding sites for the enzyme. It is found that in the presence of strong co-operativity, the steady-state reaction rates of polymer-activated enzymes can be very different from the Michaelis-Menten paradigm. By adjusting the co-operativity parameters and the binding constants of the ligands, the model can generate apparent auto-catalytic enhancement by substrates at low substrate concentrations and apparent substrate inhibition at high substrate concentrations. The model is shown to be able to explain the differences in the rates of ATP hydrolysis by DNA gyrase in the presence of long versus short DNA molecules and in the presence of long DNA molecules at different gyrase to DNA ratios.

Free jejunal grafts for reconstruction of pharynx and cervical esophagus

Reconstruction of the pharynx and cervical esophagus continues to pose a challenge to the surgeon. Over the last 2 years the free jejunal graft with microvascular anastomosis has been used to reconstruct pharyngoesophageal defects in ten consecutive cases with failure in only one case, because of a malfunctioning microscope and a temporary pharyngocutaneous fistula. Eight procedures were performed for reconstruction of a pharyngoesophageal defect after an extensive excision of hypopharyngeal carcinoma, one for pharyngoesophageal defect due to cervical trauma in an accident, and another for corrosive atresia. In seven of these cases the unaffected larynx or normal part of the larynx was simultaneously preserved and reconstructed with laryngeal function restored totally in four cases and partially in three cases. The techniques of both pharyngoesophageal and laryngeal reconstruction are presented. In our experience this is a relatively safe and reliable single-staged procedure that provides easier and earlier rehabilitation compared to other methods of reconstruction. Furthermore, the majority of patients may have their larynges rehabilitated simultaneously.

Thermal effects of laser and electrical discharge on cardiovascular tissue: implications for coronary artery recanalization and endocardial ablation

To determine the thermal responses of cardiovascular tissues to laser and electrical ablation, and to characterize the effects of different superfusing media and temperatures on target tissue temperatures and resulting extent of tissue injury, 184 laser and 15 electrical discharges were delivered to segments of human and canine aorta and canine ventricular endocardium. Tissue temperatures were measured 2 mm from the point of contact of laser fiber tip and tissue. When superfusing media consisted of whole blood or plasma at room temperature, a standard 40 J laser discharge caused peak arterial temperatures to rise 29.2 +/- 1.6 degrees C and 30 +/- 1.4 degrees C, respectively; however, tissue cooling was significantly slower in blood than in plasma. When saline solution was superfused, tissue temperatures rose by 11.4 +/- 2.2 degrees C, and tissue cooling occurred significantly faster than with either plasma or blood. The dimensions of the resulting aortic lesions were larger when blood (1.69 +/- 0.26 mm) was superfused than when plasma (1.39 +/- 0.04 mm) or saline (0.77 +/- 0.13 mm) was superfused (p less than 0.0001). Similar findings were observed with ventricular endocardium using blood or saline as the superfusing medium. In arterial tissue, superfusion with cold blood or saline solution resulted in lower peak temperature elevations (22 +/- 3.8 degrees C and 13.5 +/- 1.3 degrees C, respectively) and faster tissue cooling after laser discharge. Corresponding aortic lesion sizes were significantly smaller (1.4 +/- 0.03 and 0.5 +/- 0.02 mm, respectively) than when blood or saline medium was superfused at room temperature (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of passive smoking on children's pulmonary function in Shanghai

We report the findings of a cross-sectional study of the relationship between passive smoking and pulmonary function of children in Shanghai, People's Republic of China. The 571 study subjects included 303 males and 268 females, ranging in age from 8 to 16 years, from a primary school and a secondary school at Xu-Hui District. Lung function tests were performed at the schools, and questionnaires were completed by parents. The father's cigarette smoking status during child's lifetime was linearly related to a decrease in the per cent predicted values of FEV1.0, MMEF and FEF 62.5-87.5% in total subjects; in school-girls, father's smoking status accounted for 0.5 per cent, 1.2 per cent, and 1.6 per cent of the total variation, respectively; the trend was less marked in boys. Other environmental factors considered in this study, i.e., educational level of the father, the use of coal or gas for cooking, the presence of patients with chronic respiratory diseases in the family, etc., did not seem to have any important role on the children's pulmonary function.