Rapidly tunable optical add-drop multiplexer utilising relaxed beam splitters

A polarisation-independent four-port electro-optic tunable filter in the 1530 nm wavelength regime utilising non-polarising relaxed beam splitters and strain-induced polarisation converters on LiNbO₃ with 16 nm tuning range and 46 ns tuning speed is reported.     

A quantitative evaluation of the glomerular capillary endothelium in rat and human kidneys: Utilization of vascular perfusion,freeze-cracking of tissue,and scanning electron microscopy

Modern morphological investigation requires the use of a variety of technological approaches and the employment of rigorous morphometric analysis for an adequate evaluation of the structural and ultrastructural features of a tissue or organ. The introduction of the technique of freeze-cracking of tissue to expose new surfaces has made it possible to quantitate the normal surface characteristics of the glomerular capillaries of the mammalian kidney. This report describes the techniques used for the preparation and quantitative assessment of normal glomerular endothelial morphology. The techniques of in vivo and in vitro vascular perfusion of kidneys as a method of fixation and the freeze-cracking of tissue are outlined in detail. In addition, a morphometric analysis of the endothelial surface characteristics are described and values are reported for the control rat and human kidneys from transplant donors.     

Narrowband Bragg reflectors in Ti:LiNbO3 optical waveguides

Bragg grating reflectors etched in amorphous silicon overlay films have been integrated with Ti:LiNbO3 optical waveguides to obtain a narrow (0.05 nm) reflectance spectrum with a > 20 dB dip in the transmittance spectrum. These results were realized at a wavelength of 1542.7 nm for TE polarization on an x-cut, y-propagating substrate with gratings etched to a depth of approximately 93 nm in a 105 nm thick silicon film over a length of 12.5 mm. The reflectance in the channel waveguides is found to be strongly dependent on the depth of the etched grating. The effect of the Bragg waveguide loss factor on the transmittance and reflectance spectra is investigated by using a model for contradirectional coupling that includes an attenuation coefficient. The values for coupling constants kappa and amplitude attenuation constants alpha of samples etched for different time durations to control the grating depths are obtained from the model through the use of the depth of the dips in the transmittance spectra and the spectral widths of the reflectance peaks. It is concluded that the corrugated Si overlay film increases the insertion loss by approximately 2.7 dB, and the loss is not significantly affected by the grating depth.     

Characterization of Ti:LiNbO3 deep waveguides diffused in dry and wet oxygen ambient

The diffusivity of thicker than usual Ti films into LiNbO3 to create deep waveguides has been investigated as a function of crystal orientation and diffusion ambient for temperatures ranging from 1050 to 1100 degrees C. The diffusion parameters for substrates diffused in water vapor environment are always larger than ones diffused in dry ambient. Differences in the diffusion coefficient for the extraordinary mode as high as 90, 66, and 84% are measured for X-, Y-, and Z-cut crystals, respectively. Smaller but noticeable differences are detected for the ordinary mode. Similar enhancing effects of the water vapor are also obtained for the surface-index change. Severe rough surface finish and surface contouring, revealing an etchedlike appearance, are observed on Z-cut substrates diffused in wet atmosphere. In general, substrates diffused in dry O2 produced relatively smoother surfaces. No outdiffused modes are excited in Z-cut substrates when diffused in dry oxygen ambient for long times at high temperatures.     

Enhancement of Alkaline Protease Activity and Stability via Covalent Immobilization onto Hollow Core-Mesoporous Shell Silica Nanospheres

The stability and reusability of soluble enzymes are of major concerns, which limit their industrial applications. Herein, alkaline protease from Bacillus sp. NPST-AK15 was immobilized onto hollow core-mesoporous shell silica (HCMSS) nanospheres. Subsequently, the properties of immobilized proteases were evaluated. Non-, ethane- and amino-functionalized HCMSS nanospheres were synthesized and characterized. NPST-AK15 was immobilized onto the synthesized nano-supports by physical and covalent immobilization approaches. However, protease immobilization by covalent attachment onto the activated HCMSS–NH₂ nanospheres showed highest immobilization yield (75.6%) and loading capacity (88.1 μg protein/mg carrier) and was applied in the further studies. In comparison to free enzyme, the covalently immobilized protease exhibited a slight shift in the optimal pH from 10.5 to 11.0, respectively. The optimum temperature for catalytic activity of both free and immobilized enzyme was seen at 60 °C. However, while the free enzyme was completely inactivated when treated at 60 °C for 1 h the immobilized enzyme still retained 63.6% of its initial activity. The immobilized protease showed higher V_max, k_cat and k_cat/K_m, than soluble enzyme by 1.6-, 1.6- and 2.4-fold, respectively. In addition, the immobilized protease affinity to the substrate increased by about 1.5-fold. Furthermore, the enzyme stability in various organic solvents was significantly enhanced upon immobilization. Interestingly, the immobilized enzyme exhibited much higher stability in several commercial detergents including OMO, Tide, Ariel, Bonux and Xra by up to 5.2-fold. Finally, the immobilized protease maintained significant catalytic efficiency for twelve consecutive reaction cycles. These results suggest the effectiveness of the developed nanobiocatalyst as a candidate for detergent formulation and peptide synthesis in non-aqueous media.     

Treatment of Goodpasture syndrome with cyclophosphamide, prednisone and plasma exchange transfusions

Repeated plasm exchanges were performed in a 44-year-old man with Goodpasture syndrome, also treated with cyclophosphamide and prednisone. Improvement was observed within 3 weeks of starting the protocol, and by the 76th week, endogenous creatinine clearance had increased from 30 to 56 ml/min/1.73 M2 and serum albumin from 2.7 to 3.7 g/dl. Prior treatment with immunosuppressive drugs had not significantly influenced circulating antibody levels. But sustained suppression of antibody was achieved after the plasma exchanges were begun, suggesting that physical removal of circulating antibody combined with antiproliferative drug treatment may be a useful way to control undesirable humoral immune responses.     

Systemic consequences of acid-base disorders

It is apparent that disturbances in acid-base equilibrium, particularly in the direction of acidosis, interfere with the normal physiologic function of a number of organs. While the effect on each organ system may not be severe, and while adequate compensatory mechanisms may come into play, cummulative involvement of a number of organs, especially when the changes are acute or left untreated, may prove fatal.     

Fabry-Perot intensity modulator with integrated Bragg reflectors in Ti:LiNbO/sub 3/

A Fabry-Perot electro-optic intensity modulator in Ti:LiNbO/sub 3/ utilising surface integrated Bragg reflectors is demonstrated. A modulation depth of 96% at 1542 nm wavelength is obtained, with a voltage-length product value which is a factor of 4.4 smaller than for a polarisation intensity modulator of the same switching voltage.     

Interferometric polarization-independent modulator in LiTaO3

Polarization-independent Mach-Zehnder modulators that utilize the off-diagonal r₅₁ electrooptic coefficient are produced in LiTaO₃. The waveguides are formed by Zn vapor diffusion. Extinction values of 85% at 0.633-μm wavelength are demonstrated for both transverse electric and transverse magnetic polarization using a single control voltage and thermal tuning. The relatively large voltage-length product values (VL⩾15 V-cm) attained in these devices are attributed to a weak overlap between optical and electrical field profiles. Electrode alignment and dielectric loading are critical factors for the optimization of device operation