Photoelastic channel optical waveguides in epitaxial GaAs layers

Photoelastic channel optical waveguides have been fabricated in GaAs epitaxial layers. These waveguides exhibit strong lateral confinement in a single region of their cross-section. They compare favourably with previously demonstrated integrated optical waveguide structures.     

New diffraction grating profiles in InP for DFB lasers and integrated optics

A bilevel processing technique has been used to obtain sub-micrometer-period InP diffraction gratings. Novel cross-sectional grating profiles with depths of up to 4000 ? have been obtained which should facilitate the fabrication of more efficient Bragg devices.     

Rupture mechanisms of elastomer–metal adhesive systems

This paper studies the influence of adverse conditions of stress and environment on a conventional industrial two-coat adhesive system for bonding filled elastomers to steel. Several test methods were used in order to produce rupture at the elastomer/adhesive interface, but even the most stringent stress distributions produced rupture in the elastomer under relatively rapid constant strain rate testing conditions. However, under fixed strains termed“static fatigue” below immediate rupture conditions, fracture occurred cohesively in the adhesive. This fracture originated in the elastomeric phase of the adhesive. Comparison of elastomer and adhesive creep curves show that the locus of failure depends only upon the ultimate properties of the phase in which fracture occurs. This becomes more complicated for propagation of the fracture because of the influence of rheological, thermodynamic, and morphologic aspects of the other constituents of the assembly. A third type of rupture, produced at the metal surface, was observed by testing under corrosive conditions such as saline solution. Throughout the study, original observations are confirmed for systems using different elastomers, adhesives, or metal surface coatings.     

Congenital dilatation of the bile ducts

Our experience with five cases of cystic dilatation of the extrahepatic bile ducts is reported and compared with the literature. The following conclusions have been reached: (1) The etiology of this anomaly is primarily congenital but may involve an acquired component. (2) Diagnosis should be suspected when any of the triad of abdominal pain, right upper quadrant mass, or jaundice is present. (3) The diagnosis can usually be made in infants based on the clinical picture and routine radiologic studies. (4) Retrograde cholangiopancreatography is a useful tool in making the diagnosis in older children and adults. (5) Roux-en-Y choledochocystojejunostomy is the procedure of choice for type I cysts, excision for type II, and choledochocystoduodenostomy for type III.     

Intermetallic compounds: Their past and promise

This review serves to call attention to intermetallic compounds as a class of materials of great practical importance in both ancient and modern times and as a fascinating topic of scientific inquiry. Exploration of the relevant metallurgical history illustrates the processes by which both ideas and practical developments evolve and emphasizes that some of the threads may be traced back very far in time. Three general conclusions are drawn from the review: a) The intrinsic properties of intermetallic compounds are truly unique and at present levels of understanding are not predictable from the fundamental parameters of the constituent atoms, b) Successful applications of intermetallics do not result from the mere knowledge of their composition, crystal structure, and intrinsic properties but require as well a skillful and understanding control of their processing, c) There is desirably and necessarily a strong interplay between science and technology in the development of the intermetallic field. The technological opportunity forecast by some unique property measurements stimulates further related scientific investigation. Conversely scientific advances, both those specific to intermetallics and those pertinent to metallurgy more generally, facilitate the rate of reduction to practice of empirical discoveries. Future trends seen in the further development of intermetallics are: greater appreciation and control of subgrain structure, investigation of compounds of metastable structure, study of compounds with complex chemistry, the use of intermetallics in composites, and new insights to be drawn from data compilations such as NMR and EDS.     

A comparison of three methods of group vocational counseling.

Superimposed a group discussion process over a typical vocational counseling process in which the primary focus was on test information, and over 2 atypical vocational counseling processes, one in which occupational information was primary and the other in which test information and occupational information were optional and randomly presented upon a group member's request. All Ss selected goals in the initial stages of counseling. 57 undergraduates were studied in 6 single-sex experimental groups and 2 control groups. Data from a levels-of-decision-making scale, the Edwards Personal Preference Schedule, and the Kuder Occupational Preference Inventory show that the atypical groups learned significantly more and retained longer than did both the typical and control groups. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multimillisecond timse delays with wrap-around surface-acoustic-wave delay lines

Time delays of up to 3 ms in passive systems, and up to 20 ms with the addition of loss compensation by means of internal surface-wave amplifiers, have been observed in wrap-around surface-wave delay lines constructed of Bi12GeO20 and operating in a recirculating mode at 52 MHz.     

Strain-induced optical waveguiding in GaAs epitaxial layers at 1.15 ?m

Transverse optical waveguide modes have been observed in GaAs Schottky-barrier electro-optic waveguide modulators with no electrical bias. This is attributed to the spatial variation of the dielectric constant generated by stresses originating in the metal Schottky-barrier stripe.     

Transmission of 10 Gbit/s directly modulated DFB signals over 200km standard fibre using mid-span spectral inversion

Dispersion compensation by mid-span spectral inversion has been used to achieve the transmission of 10 Gbit/s signals from a directly modulated DFB over 200 km dispersive fibre. The spectral inversion is provided by nondegenerate four-wave mixing in a semiconductor optical amplifier