In this Letter, we report on the successful fabrication of low loss, high refractive index contrast waveguides via ion migration upon femtosecond laser writing in phosphate glass. Waveguides were produced in two different phosphate glass compositions with high and low La 2 O 3 content. In the La-rich glass, a large refractive index increase in the guiding region was observed due to the incoming migration of La accompanied by the out-diffusion of K. The much smaller refractive index change in the La-less glass is caused by rearrangements of the glass structure. These results confirm the feasibility of adapting the glass composition for enabling the laser writing of high refractive index contrast structures via spatially selective modification of the glass composition. The origin of the refractive index modification caused by femtosecond (fs) laser irradiation in phosphate glasses has been investigated by several research groups. In such reports, mostly commercial glass from Kigre, Inc. (QX and MM2) and Schott AG (IOG) are used [1][2][3][4][5]. Most of these glasses were developed for telecommunication research and industry as base materials for waveguide fabrication by Ag-Na ion exchange [6][7][8]. With the advent of fs-laser-inscription techniques, demand for new glasses grew even higher due to the ability of fast prototyping and fabrication of complex 3D custom components [5]. Still, little effort was made to optimize the glass composition for this new technique. Due to the versatility of fs-laser writing, many problems were surmounted by adjusting the processing conditions to produce excellent results in various glasses [1,5]. However, there is little doubt that glass composition is a key parameter for further optimizing fs-laser-written optical devices. Among various commercial phosphate glass compositions, we have identified and isolated a set of glass with and without La 2 O 3 to demonstrate the importance of optimizing the glass matrix composition for fs-laser writing. We show that the presence of La 2 O 3 enables us to achieve a large positive refractive index contrast (RIC) in the written structures. The responsible mechanism is identified as the migration of La to form a region of increased refractive index accompanied by out-diffusion of K. The compositional changes unambiguously correlate to positive and negative refractive index modifications. Indeed, the refractive index changes observed via La migration are far beyond what can be attributed to changes in the glass structure.In the present work, we have investigated in detail the role of La 2 O 3 in the photo-inscription mechanisms in phosphate glasses. The addition of La 2 O 3 to P 2 O 5 -Al 2 O 3 glasses is known to increase the refractive index of the glass [9,10] as well as to improve its thermal, mechanical, and optical properties. We have used two different QX special melt phosphate glass samples from Kigre, Inc., both doped with 2 wt. % Er and 4 wt. % Yb (QX was introduced as a laser glass capable of withstanding high thermal loading and shoc...

The effects of fat (7.0, 14.0 and 20.0%), starch (0, 5 and 10%) and egg white (0, 1.5 and 3%) on the microstructure and texture of bologna sausages were examined. As levels of fat and starch increased, the microstructure exhibited increasing numbers of holes (P<0.05), smaller in size (P<0.05) and similar (P>0.05) in shape. No clear relationship was found between addition of egg white and these morphological variations. Low‐fat sausage (7.0%) was less hard and chewy (P<0.05) than high‐fat (20.0%) sausage; likewise, a direct relationship was found between starch and egg white content and hardness and chewiness of the bologna.

The binding of 0-methyl and fluorodeoxy derivatives of methyl P-lactoside to the Ricinus communis toxin (RCA60) and agglutinin (RCA120) was studied in order to determine the donor/acceptor relationships of the hydrogen bonds between the hydroxyl groups of methyl &lactoside and the binding sites of the lectins. Free energy contributions of the hydrogen bonds at each position have been estimated from these data and from those previously reported for the monodeoxy derivatives Analysis of the results indicates that both the C-3' and C-4' hydroxyl groups act as hydrogen-bond donors to charged groups of both RCA60 and RCA120. The C-6' and probably also the C-2' hydroxyl groups participate both as donors and as acceptors of two hydrogen bonds with neutral groups of the lectins. And finally, the C-6 hydroxyl group possibly acts as a donor of a weak hydrogen bond to a neutral group in RCA60, but not in RCA120. The results provide a molecular basis to explain some features of the binding specificity of the lectins. Comparison of RCAGO binding data with the recently refined X-ray crystal structure of the RCA60-lactose complex shows similarities but also some discrepancies that can be attributed to the marked influence of the pH on the carbohydrate -lectin interaction.Carbohydrate-protein interactions have attracted considerable attention in view of their central role in a large number of key events of cell biology. In consequence, there is a growing interest in the understanding of the molecular basis for specificity and affinity in these interactions. X-ray crystallographic studies of several carbohydrate-protein complexes have shown that hydrogen bonds together with van der Waals contacts and stacking interactions are the dominant forces that stabilize the complexes [l -31. Because hydrogen bonds are highly directional, they ensure the correct fit of the ligand and confer stereospecificity to the binding. They also provide a stable solvation shell for the bound sugars. In addition, hydrogen bond strength is high enough to stabilize the complexes but low enough to allow rapid ligand dissociation. All these features make hydrogen bonding the primary interaction in protein-carbohydrate complex formation.Binding studies with selected deoxy, 0-methyl and fluorodeoxy sugar derivatives have been used to probe the involvement of hydrogen bonding in carbohydrate -protein interactions [4-111. The use of fluorodeoxy derivatives is particularly interesting since the electronegative fluorine cannot act as a hydrogen-bond donor but it can be a hydrogenbond acceptor, albeit weakly [6,12]. In addition, the replace- ment of a hydroxyl group by fluorine is more sterically conservative than substitution by hydrogen or a methoxy group. On the other hand, binding studies with mono-0-methyl derivatives provides information on the flexibility of the combining site to steric demands for complexation [lo]. Analysis of the bindmg data of such as derivatives compared with available refined X-ray crystal structure data on the carbohydrate-protein ...

Sintering of ZnO pressed powder under Ar flow at temperatures between 1250 and 1300 • C leads to the formation of elongated microstructures and nanostructures, with different morphologies, on the sample surface. Rods and needles with cross-sectional dimensions ranging from tens of nanometres to several tens of microns and up to hundreds of microns in length are obtained. In an advanced stage of growth, nanoneedles are frequently arranged in bundles, forming the walls of tubes with different cross-sectional dimensions. In addition, microcombs and microfeathers consisting of well oriented nanoneedles are observed. Cathodoluminescence (CL) in the scanning electron microscope (SEM) has been used to characterize the structures grown. The formation of the elongated structures causes spectral changes, in particular an enhancement of the green-orange luminescence. High CL emission from the internal surface of the tubes has been observed.

Sintering of a ZnO–SnO2 mixture under argon flow leads to the growth of microrods on the sample surface, which are formed by oriented stacks of nanoplates. Energy dispersive spectroscopy and cathodoluminescence (CL) in the scanning electron microscope show that the stacks of nanoplates consist of Sn doped ZnO. The stacks of nanoplates have well defined orientations relative to the growth axis of the rod. The formation of the nanoplates, which is not observed when undoped ZnO is used in the same process, is attributed to the stresses generated by the presence of Sn atoms in the rods.