Basic Difference Between Brain and Computer: Integration of Asynchronous Processes Implemented as Hardware Model of the Retina

There exists a common view that the brain acts like a Turing machine: The machine reads information from an infinite tape (sensory data) and, on the basis of the machine's state and information from the tape, an action (decision) is made. The main problem with this model lies in how to synchronize a large number of tapes in an adaptive way so that the machine is able to accomplish tasks such as object classification. We propose that such mechanisms exist already in the eye. A popular view is that the retina, typically associated with high gain and adaptation for light processing, is actually performing local preprocessing by means of its center-surround receptive field. We would like to show another property of the retina: The ability to integrate many independent processes. We believe that this integration is implemented by synchronization of neuronal oscillations. In this paper, we present a model of the retina consisting of a series of coupled oscillators which can synchronize on several scales. Synchronization is an analog process which is converted into a digital spike train in the output of the retina. We have developed a hardware implementation of this model, which enables us to carry out rapid simulation of multineuron oscillatory dynamics. We show that the properties of the spike trains in our model are similar to those found in vivo in the cat retina     

The Pediatric Bowel Management Clinic: initial results of a multidisciplinary approach to functional constipation in children

The multifactorial nature of functional constipation in children suggests that a multidisciplinary management approach may be effective. The authors tested this hypothesis in a newly created pediatric Bowel Management Clinic (BMC). Detailed data were collected prospectively on all patients seen in the clinic over the first 16 months. Both quantitative and qualitative analyses were performed to describe the index population and to demonstrate the impact of the intervention. Satisfaction with care in the clinic was measured using the Measure of Processes of Care tool, then compared with a normative sample. One hundred fourteen patients, all previously treated unsuccessfully for constipation, were referred to a team comprised of a physician, nurse practitioner, nurse educator, dietitian, and psychosocial nurse specialist. The mean age was 5.4 years with equal gender distribution. Between the first and last visits recorded, several variables including stool consistency and frequency, soiling frequency, abdominal pain, rectal pain, and rectal bleeding all showed statistically significant (P < .05) improvement. Qualitative data analysis showed the significant psychosocial impact of constipation on patients and their families. In the Measures of Processes of Care questionnaire, scores for the BMC were higher than normal on all scales except in provision of information. A multidisciplinary approach to functional constipation leads to both patient and parent satisfaction and significant short-term improvement. Further studies will examine the long-term impact of the clinic.     

Process mineralogy of gold: Gold from telluride-bearing ores

Petrographic and microanalytical studies of gold in gold-silver telluride deposits show that it occurs as “visible gold” extracted by cyanidation, and as visible gold and “invisible gold” that are unamenable to cyanidation. Two gold-bearing tellurides, calaverite and buckhornite, are considerably less amenable to cyanidation in comparison to Au-Ag tellurides. Secondary ion mass spectroscopy and recent developments in dynamic analysis of proton-induced x-ray emission demonstrate that Au occurs as nanoparticles and is structurally bound in As-, Ag-, and Te-rich pyrite and that an antithetic relationship can also exist between Au and As in pyrite. For more information, contact P.G. Spry, Iowa State University, Department of Geological and Atmospheric Sciences, Ames, Iowa 50011-3212; (515) 294-9637; fax (515) 294-6049; e-mail pgspry@iastate.edu.     

Mixed tenure communities as a policy instrument for educational outcomes in a deprived urban context?

This article considers mixed community strategies, enacted through planning and regeneration policies, as a policy approach to the improvement of educational outcomes in schools. Analysis is undertaken of educational outcomes across secondary schools in Glasgow. The level of owner occupation in the catchment is positively associated with both examination results at S4 and positive destinations post-school, particularly at the more deprived end of the school spectrum. The results suggest that tenure mix may be both directly and indirectly related to school performance, with neighbourhood context effects not being entirely mediated through the school context.     

Cross-sectional TEM and KOH-Etch Studies of Extended Defects in 3C-SiC <Emphasis Type="Italic">p</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">n</Emphasis> Junction Diodes Grown on 4H-SiC Mesas

This article presents cross-sectional transmission electron microscopy and molten-potassium hydroxide etching studies of (111) 3C-SiC diodes which we previously reported to be free of forward-voltage drift despite abundant electroluminescent linear features presumed to be defects. Our results show that the majority of linear features are stacking faults lying in inclined {111} planes. Additionally, high densities of isolated etch pits (10⁶–10⁸ cm⁻²) are observed in 3C films grown on stepped 4H mesas, while 3C films nucleated on step-free 4H mesas exhibited orders of magnitude fewer etch pits and stacking faults. Defect formation mechanisms whose impetuses are steps on the 4H-SiC pregrowth mesa are discussed.     

Survey of home hemodialysis patients and nursing staff regarding vascular access use and care

Vascular access infections are of concern to hemodialysis patients and nurses. Best demonstrated practices (BDPs) have not been developed for home hemodialysis (HHD) access use, but there have been generally accepted practices (GAPs) endorsed by dialysis professionals. We developed a survey to gather information about training provided and actual practices of HHD patients using the NxStage System One HHD machine. We used GAP to assess training used by nurses to teach HHD access care and then assess actual practice (adherence) by HHD patients. We also assessed training and adherence where GAPs do not exist. We received a 43% response rate from patients and 76% response from nurses representing 19 randomly selected HHD training centers. We found that nurses were not uniformly instructing HHD patients according to GAP, patients were not performing access cannulation according to GAP, nor were they adherent to their training procedures. Identification of signs and symptoms of infection was commonly trained appropriately, but we observed a reluctance to report some signs and symptoms of infection by patients. Of particular concern, when aggregating all steps surveyed, not a single nurse or patient reported training or performing all steps in accordance with GAP. We also identified practices for which there are no GAPs that require further study and may or may not impact outcomes such as infection. Further research is needed to develop strategies to implement and expand GAP, measure outcomes, and ultimately develop BDP for HHD to improve infectious complications.     

Stop, look, listen, and think? What young children really do when crossing the road.

This study sought to provide basic information about children's behaviour in realistic traffic situations. Most literature in this area has focused on children's knowledge about road safety or has assessed their behaviour in simulated traffic environments. However, until more is known about what children actually do in traffic environments, our ability to identify the important elements for inclusion in educational programmes remains limited. Fifty-six children, aged 5-6 years, took part in a 'treasure trail' activity in which they were confronted with two road crossings, one at a T-junction with a moving car and the other between parked cars. Children's performance was videotaped and coded for relevant behaviours such as stopping at the kerb, looking for traffic, direction of gaze, and style of crossing (i.e. walking vs. running). Results revealed that performance was extremely poor. Sixty percent of the children failed to stop before proceeding from the kerb onto the road. Looking for oncoming traffic was exhibited by no more than 41% of the sample, dropping to as low as 7% in some instances. When looking did occur, it was initially as likely to be in the inappropriate direction (i.e. to the left) as in the appropriate direction (i.e. to the right). Consideration of individual performance revealed the existence of individual differences within the sample; such differences were relatively stable across the two road crossings. These findings, based on controlled naturalistic tasks and detailed observational methods, build on earlier studies that are generally able to provide only estimated rates of children's behaviour.     

Stable Electrical Operation of 6H–SiC JFETs and ICs for Thousands of Hours at 500 $^{circ}hbox{C}$

The fabrication and testing of the first semiconductor transistors and small-scale integrated circuits (ICs) to achieve up to 3000 h of stable electrical operation at 500degC in air ambient is reported. These devices are based on an epitaxial 6H-SiC junction field-effect transistor process that successfully integrated high-temperature ohmic contacts, dielectric passivation, and ceramic packaging. Important device and circuit parameters exhibited less than 10% of change over the course of the 500degC operational testing. These results establish a new technology foundation for realizing durable 500degC ICs for combustion-engine sensing and control, deep-well drilling, and other harsh-environment applications.