Excitation of the fundamental and low-order modes of optical fiber waveguides with gaussian beams. 2: offset beams

The excitation efficiencies of the dominant and low-order modes in an optical fiber are theoretically determined for an incident Gaussian beam that is offset with respect to the fiber axis. The excitation efficiencies are shown to be strongly influenced by both the numerical aperture of the fiber and the wavefront curvature of the incident beam.

Haemagglutination inhibition assay of the common determinants and subspecificities of Australia antigen

Antigenic determinants of Australia antigen (AuAg) may be determined by haemagglutination inhibition with ease and high sensitivity. The reaction depends on the inhibitory effect of the test antigen-positive sample on the agglutination by specific antibody of glutaraldehyde-fixed sheep erythrocytes which have been tanned and coated with AuAg of different specificities. The standard monospecific antibody reactants are directed against one or other of the common antigens, a and Re, or against the subtypic determinants, d, y, w and r. Because it is more sensitive than conventional immunodiffusion or electrosyneresis, and more convenient than radio-immunoassay, haemagglutination inhibition is most suited to large-scale determinations of AuAg subtypes in samples of relatively low antigenic activity.

Excitation of fundamental and low-order modes of optical fiber waveguides by gaussian beams. 1: tilted beams

The optimum condition for coupling energy into an optical fiber waveguide is theoretically computed for an incident beam with a Gaussian intensity distribution and a curved wavefront. The dependence of the modal excitation efficiencies on the tilt angle of the incident beam and on the refractive index difference of core and cladding is discussed. Numerical results show that maximum efficiency for the HE(11) mode can be achieved when the beam radius is chosen to be approximately 0.65 times the core radius. Excitation efficiencies of low-order modes, HE(1m) (m >/= 2) approach 80% at their cutoff when the beam size is suitably larger than the core diameter.

Sodium chloride, urea, and water transport in the thin ascending limb of Henle. Generation of osmotic gradients by passive diffusion of solutes

Studies were designed to examine whether the thin ascending limb of Henle (tALH) decreases its luminal solute concentration by an active or a passive transport process. In all experiments isolated segments of rabbit tALH were perfused in vitro. When tubules were perfused with solutions identical to the bath, active transport of NaCl was excluded by the following: (a) osmolality of the collected fluid remained unchanged and the same as the bath. (b) net water reabsorption could not be demonstrated, and (c) transtubular potential difference was zero. Isotopic permeability coefficients (x 10(-5) cm s-1) were calculated from the disappearance rate of the respective isotope added to the perfusate. These values indicate that tALH is moderately permeable to [14C]urea (6.97 +/- 1.95) while having a higher permeability to 22Na (25.5 +/- 1.8) and [not readable: see text]Cl (117 +/- 9.1) than any other segment similarly studied. The influx (bath-to-lumen) isotopic permeabilities were not statistically different from the above efflux permeabilities. Osmotic water permeability was immeasurably small. When tALH were perfused with a 600 mosmol/liter solution predominantly of NaCl against a 600 mosmol/liter bath in which 50% of osmolality was NaCl and 50% urea (to simulate in vivo papillary interstitium), the collected fluid osmolality was decreased significantly below that of the bath (300 mosmol/liter/mm of tubule). The decrease in osmolality was due to greater efflux of NaCl as compared to influx of urea. We conclude that active transport of salt by the tALH was not detected by the experimental protocol of the current studies, and that the unique membrane characteristics of tALH allows for generation of osmotic gradients (lumen less concentrated than adjacent surroundings) on purely passive mechanisms when perfused with isosmolal salt solutions in a bath with appropriate salt and urea concentrations. These findings are consistent with the passive counter-current model previously proposed from this laboratory.

Antigenicity of Reduced and Alkylated Australia Antigen

The association of Australia antigen (AuAg)2 with human type B hepatitis has been fully established. It has been reported that AuAg, which contains 6.5 M% of cysteine (1), completely lost the ability to react with humoral anti-Au antibodies after reduction and alkylation (2). Recently, Vyas et al. (3) have further reported that the reduced and alkylated AuAg could induce a delayed-type hypersensitivity response in guinea pigs but did not raise humoral antibody, suggesting the significance of the disulfide-bond dependent conformation in stimulating the humoral antibody response.

We have found, however, that a part of the antigenic reactivity of AuAg was relatively resistant to reduction and alkylation, although most of it was sensitive to this procedure. This unexpected finding prompted us to study in detail the hitherto recognized antigenic determinants of AuAg—a, d, y, w and r3—with respect to their susceptibility to the conformational changes induced by this chemical modification.