Spinor algebra and null solutions of the wave equation

In this paper we exploit the ideas and formalisms of twistor theory, to show how, on Minkowski space, given a null solution of the wave equation, there are precisely two null directions in $\ker df$, at least one of which is a shear-free ray congruence

Twistor theory on a finite graph

We show how the description of a shear-free ray congruence in Minkowski space as an evolving family of semi-conformal mappings can naturally be formulated on a finite graph. For this, we introduce the notion of holomorphic function on a graph. On a regular coloured graph of degree three, we recover the space-time picture. In the spirit of twistor theory, where a light ray is the more fundamental object from which space-time points should be derived, the line graph, whose points are the edges of the original graph, should be considered as the basic object. The Penrose twistor correspondence is discussed in this context

Metal-oxide-metal point contact junction detectors

The detection mechanism(s) and design of a mechanically stable metal-oxide-metal point contact junction detector are considered. A prototype for a mechanically stable device has been constructed and tested. A technique has been developed which accurately predicts microwave video detector and heterodyne mixer SIM (semiconductor-insulator-metal) diode performance from low dc frequency volt-ampere curves. The difference in contact potential between the two metals and geometrically induced rectification constitute the detection mechanisms

A Writing Approach to High School Reading

Many of the problems which are endemic among middle school and senior high school youngsters who have difficulty in learning how to read effectively are overcome in writing workshops. Disabled readers at the secondary level often have a bad attitude toward reading. This attitude stems from their having developed bad self-images during their elementary school years, and these negative self-images are directly connected with their inability to perform at anticipated levels in the basic skills

Some Reasons for Oral Reading

Few would question the appropriateness of oral reading in the first and second grades. Most experts feel that reading aloud is a worthwhile activity in the earliest years of school because the students have not yet developed sufficient speed in silent reading to make silent reading a valuable enterprise for them. Lewis and Sisko (1963) caution, however, that from the time a child\u27s silent reading rate overtakes his rate of oral reading, usually during the second or third grade, too much oral reading has the adverse effect of slowing down the rate of silent reading and encouraging unnecessary lip movement, thoughtless word calling, and daydreaming on the parts of other pupils, who neither follow the printed text nor listen to the reader