4,265 research outputs found

    The Taking and Use of Records

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    Volume 1 Number 5, February, 1935 Describes the record taking process and the types of observational records the teachers at the Harriet Johnson Nursery School were taking. Includes excerpts of observations.https://educate.bankstreet.edu/sixty-nine-bank-street/1004/thumbnail.jp

    The Changing Telecommunications Industry

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    Telecommunications in today\u27s global society has undergone a dramatic transformation since the invention of the telephone. In the early years of telephony, a host of dedicated men and women endured tremendous hardships to pioneer the telephone. Bell, his wife Mabel, his two benefactors along with Thomas Watson and Theodore Vail fought to gain recognition of the instrument and establish its usefulness to society. Many great inventions came from by the Bell Laboratories, which forever sought a better way, encouraging the progress of civilization. Despite major setbacks caused by the government and regulation, the Bell system evolved into a very capable and customer-oriented entity. Even divestiture and the break up of the natural monopoly has served to open the doors of opportunity. New markets and services were created in an effort to meet the challenge of regulation and competition. The scope of possibilities afforded by the Information Age transcends the imagination. Today, data, voice and video transmissions coupled with increasingly popular computer networks, are eliminating cultural differences in a world of rapid change. Technological advancements occur continually, making the future of telephony and telecommunications difficult to project

    A cohort study of duplex Doppler examinations of the carotid artery in primary open angle glaucoma

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    Objectives To explore the possibility of pathological change in the common carotid artery at the bifurcation and in the internal carotid artery beyond the bifurcation which could contribute to a reduced diastolic pressure as observed in primary open angle glaucoma. Design Duplex ultrasonic examinations of carotid bifurcations were conducted on 80 patients. Carotid artery defects were allocated into three types: no demonstrable flow defects, internal carotid artery abnormalities and disease in the carotid bulb. Setting Bristol Royal Infirmary Vascular Laboratory. Participants Eighty patients (mean age 69.6 years) providing a total of 160 sides to the analysis. Main outcome measures An estimated central retinal artery pressure, intraocular pressure and field loss were recorded for each side measured. Results Doppler investigations revealed significant levels of pathological change in the internal carotid distinct from changes at the carotid bulb. The disease revealed in the internal carotid artery was significantly associated with intraocular pressure (p = 0.032), with an effect small to medium in magnitude. The Q2 measure, derived from mean arterial pressure and intraocular pressure, was also substantively associated with disease in the internal carotid artery. Both intraocular pressure and the Q2 measure effectively discriminated between groups, with field loss providing rather less discriminating capability. There was a strong trend towards a higher intraocular pressures and a greater visual field loss with internal carotid artery disease. Conclusions Pathological changes in the extra cranial carotid artery in primary open angle glaucoma exceed those in the arteries classified as normal. The presence of disease specifically in the internal carotid artery emphasised the need for a mechanism for the evaluation of the internal carotid apart from the carotid bulb. A basis for clarifying the presence of an ischaemic zone is proposed

    A systematic approach to atomicity decomposition in Event-B

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    Event-B is a state-based formal method that supports a refinement process in which an abstract model is elaborated towards an implementation in a step-wise manner. One weakness of Event-B is that control flow between events is typically modelled implicitly via variables and event guards. While this fits well with Event-B refinement, it can make models involving sequencing of events more difficult to specify and understand than if control flow was explicitly specified. New events may be introduced in Event-B refinement and these are often used to decompose the atomicity of an abstract event into a series of steps. A second weakness of Event-B is that there is no explicit link between such new events that represent a step in the decomposition of atomicity and the abstract event to which they contribute. To address these weaknesses, atomicity decomposition diagrams support the explicit modelling of control flow and refinement relationships for new events. In previous work,the atomicity decomposition approach has been evaluated manually in the development of two large case studies, a multi media protocol and a spacecraft sub-system. The evaluation results helped us to develop a systematic definition of the atomicity decomposition approach, and to develop a tool supporting the approach. In this paper we outline this systematic definition of the approach, the tool that supports it and evaluate the contribution that the tool makes

    Stacking Entropy of Hard Sphere Crystals

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    Classical hard spheres crystallize at equilibrium at high enough density. Crystals made up of stackings of 2-dimensional hexagonal close-packed layers (e.g. fcc, hcp, etc.) differ in entropy by only about 10−3kB10^{-3}k_B per sphere (all configurations are degenerate in energy). To readily resolve and study these small entropy differences, we have implemented two different multicanonical Monte Carlo algorithms that allow direct equilibration between crystals with different stacking sequences. Recent work had demonstrated that the fcc stacking has higher entropy than the hcp stacking. We have studied other stackings to demonstrate that the fcc stacking does indeed have the highest entropy of ALL possible stackings. The entropic interactions we could detect involve three, four and (although with less statistical certainty) five consecutive layers of spheres. These interlayer entropic interactions fall off in strength with increasing distance, as expected; this fall-off appears to be much slower near the melting density than at the maximum (close-packing) density. At maximum density the entropy difference between fcc and hcp stackings is 0.00115+/−0.00004kB0.00115 +/- 0.00004 k_B per sphere, which is roughly 30% higher than the same quantity measured near the melting transition.Comment: 15 page
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