The influence of factors other than pollution on the value of Shannon's diversity index for benthic macro-invertebrates in streams

The effects of six factors on the value of Shannon's diversity index are examined using data collected from the River Cynon, a polluted river in South Wales. Four of these are shown to influence the value of Shannon's diversity index, and it is recommended that these be taken into consideration when interpreting and comparing index values.     

Evaluation of a program to teach phonemic awareness to young children: A 1-year follow-up.

A follow-up of a study evaluating a program to teach young children about phonemic structure is reported. In the original study (B. Byrne and R. Fielding-Barnsley; see record 1992-10755-001), preschoolers were trained with the program for 12 wks and gained in phonemic awareness and knowledge of the alphabetic principle as compared with a control group. The children were retested at the end of kindergarten on phonemic awareness, word identification, decoding, and spelling. Children who entered school with advanced levels of phonemic awareness scored significantly higher on each of the measures. Alphabetic knowledge predicted literacy development, but phonemic awareness accounted for significant additional variance in decoding and spelling. Verbal intelligence did not influence reading and spelling performance. Other parts of the data led to the conclusion that some aspects of phonemic awareness may be a consequence of literacy instruction rather than a cause. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Silicon Nitride Oxidation Based on Oxynitride Interlayers with Graded Stoichiometry

The oxidation kinetics of Si₃N₄ were modeled by describing the simultaneous diffusion and reaction of interstitial oxygen that is believed to occur inside of the silicon oxynitride interlayer. The oxynitride was assumed to have a variable composition, and oxidation was described as a reaction where interstitial oxygen is incorporated into the network structure of the oxynitride and nitrogen is removed. It was assumed that both the diffusion coefficient and the solubility of interstitial oxygen decrease as the nitrogen content of the network structure increases. The results accurately describe both the formation of an oxynitride layer during oxidation, and the relatively slow oxidation kinetics of Si₃N₄ (compared to Si and SiC).     

Hertzian Contact Response of Tailored Silicon Nitride Multilayers

The nature and degree of damage accumulation beneath Hertzian contacts in silicon nitride-based laminates are studied. Specimens with alternating homogeneous and heterogeneous layers are fabricated by a tape-casting route, with strong interlayer bonding. Homogeneous material consisting of relatively pure fine-grain silicon nitride is used as the overlayers. Heterogeneous material containing 10 to 30 wt% boron nitride platelets in a silicon nitride matrix, with weak platelet/matrix interphase boundaries, forms the underlayers. Contact tests with spherical indenters are used to monitor the stress-strain response of the laminates and to investigate the damage modes within the individual layers. The heterogeneous layer exhibits a distinctive "softening" in the stress-strain curve, indicating a quasi-plasticity in the silicon nitride associated with local microfailures at the platelet/matrix interfaces. In contrast to the welldefined cone cracks that develop within the tensile zone outside the contact area in bulk homogeneous silicon nitride, the damage in the laminates is widely distributed within the shear-compression zone below the contact. Fractures form incompletely in the homogeneous layers, as downward-propagating partial cone cracks and upwardpropagating stable cracks. Comparatively extensive, diffuse microscopic damage occurs in the heterogeneous layers, culminating in a macroscopic failure that traverses these layers at higher loads. A strong synergism between the interlayer damage modes is apparent. Implications concerning the design of composite laminates for improved damage tolerance, with retention of strength and wear resistance, are considered.     

Millimeter wave narrowband optical fiber links using externalcavity semiconductor lasers

We present the theoretical analysis and the experimental implementation of a narrowband millimeter wave optical fiber communication system using an external cavity semiconductor laser. We derive analytic expressions and present experimental data for the modulation response, relative intensity noise, carrier-to-noise ratio, and harmonic distortion for a semiconductor laser in an external cavity operating as a transmitter in the millimeter wave frequency range. We present a system implementation of this capable of transmitting 40-Mbt/s digital data at a 35-GHz subcarrier frequency with bit-error rates below 10^-9 over a 6.3-km-long optical fiber link     

The training of cognitive therapists: What have we learned from treatment manuals?

Discusses 3 key aspects of selection and training of cognitive therapists: relationship building factors, case conceptualization, and therapeutic techniques. A recommended sequence of training is provided, and general issues for psychotherapy trainers are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Unix System and Software Reusability

The Unix system contains a variety of facilities that enhance the reuse of software. These vary from the utterly conventional, such as function libraries, to basic architectural mechanisms, such as the Unix pipe. The Unix pipe, which makes whole programs building blocks of larger computational structures, has been the primary reason for the development of a literature of useful, but specialized programs-programs that would be too costly to write in a conventional programming language such as C. It has led to high levels of program reuse both by the nature of its operation and through its effect on programming conventions (e.g., programs structured as simple filters). Another facility enhancing reuse on Unix is the on-line C source code for Unix system programs. This has led to a shared style of programming in which existing programs are used as models for new programs, allowing the reuse of ideas, algorithms and source code. Finally, the Unix system contains many other reuse enhancing facilities, such as generic facilities for screen management (curses and termcap) and program generators (lex and yacc).