Hollow-core photonic crystal fibres have excited interest as potential ultra-low loss telecommunications fibres because light propagates mainly in air instead of solid glass. We propose that the ultimate limit to the attenuation of such fibres is determined by surface roughness due to frozenin capillary waves. This is confirmed by measurements of the surface roughness in a HC-PCF, the angular distribution of the power scattered out of the core, and the wavelength dependence of the minimum loss of fibres drawn to different scales.

We describe a hollow-core photonic bandgap fiber designed for use in the 850 nm wavelength region. The fiber has a minimum attenuation of 180dB/km at 847nm wavelength. The low-loss mode has a quasi- Gaussian intensity profile. The group-velocity dispersion of this mode passes through zero around 830nm, and is anomalous for longer wavelengths. The polarization beat length varies from 4 mm to 13 mm across the band gap. We expect this fiber to be useful for delivery of high-energy ultrashort optical pulses.

Although there is unanimity of opinion that the nephrotic syndrome is characterized by proteinuria, hypoproteinemia, edema and hyperlipemia, there is considerably less agreement as to the mechanisms which result in these findings. It is now generally held that the proteinuria found in this disease is related directly to the renal lesion (1) and is not attributable to the excretion of abnormal plasma proteins (2). The cause of the severe hypoproteinemia in this disease, however, is a more controversial subject. The association of proteinuria and hypoproteinemia as cause and effect has been postulated by a number of investigators (1-4) and the occasionally prodigious amounts of plasma protein excreted by children with the nephrotic syndrome makes the relationship attractive. This concept, however, is not universally accepted (5), and it has long been suggested that the degree of hypoproteinemia may not depend upon the severity of proteinuria alone (6).This study was undertaken in an effort to determine the factors responsible for hypoproteinemia in children with the nephrotic syndrome. Since the concentration of a given plasma protein in the circulation is dependent upon its rate of synthesis, its rate of loss from the body whether by catabolism or excretion or both, and its distribution within the body, an attempt was made to estimate these quantities for albumin, y-globulin and iron-binding globulin during various stages of this disease. METHODSPatients: Six children with the nephrotic syndrome were selected for study. The pertinent medical data are summarized in Table I These children were fully ambulatory throughout the study, which took place during the summer months. No evidence of infection was observed in these children during the course of the investigation.Method of study: Each of the six patients was first given radio-iodinated albumin and, when the radiation in urine and plasma had fallen to background level, radioiodinated y-globulin was injected. After the latter, when background level was again attained in urine and plasma, three of the children were given radio-iodinated iron-binding globulin. The proteins were injected intravenously; the specific activities of these protein preparations were such that no more than 1 mg. of iodoalbumin, 0.5 mg. of iodinated y-globulin or 0.2 mg. of iodinated iron-binding globulin was injected per patient. The maximum radiation employed in any given injection was 1.5 microcuries per kilogram body weight. Beginning 24 hours prior to the administration of radio-iodinated albumin and continuing throughout the period of study, the children were given 10 drops of Lugol's solution three times a day.Radio-iodinated plasma proteins: Each lot of radioiodinated plasma protein used in this study was tested for free and loosely bound radio-iodide by dialysis, by precipitation of protein in 10 per cent trichloracetic acid in the presence of suitable carrier protein, and by precipitation of specific protein in the zone of antibody excess with specific rabbit antiserum (7). Contro...

We report what we believe is the first example of efficient rocking filter formation in polarization-maintaining photonic crystal fiber. Very high coupling efficiencies (as much as -23.5-dB suppression of the input polarization) and loss of < 0.02 dB were achieved for fibers as short as 11 mm. The filters, which we prepared by periodic mechanical twisting and heating with a scanned CO2 laser beam, are highly compact, and they are expected to be temperature stable.

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