Flexible Cord Research Articles

A Completion Item Teaching Machine for Routine Classroom Use

The current interest in teaching machines shows that psychology is recognizing its responsibility for applying learning theory to the practical problems of education. Every classroom teacher should by now have some awareness of the meaning of reinforcement and feedback. A number of ingenious but rather costly machines are becoming available for laboratory or special remedial purposes, but too little attention has been given to simple equipment and procedures suitable for regular classroom use. The punchboard makes possible inexpensive self-teaching use of the multiple choice item, and the model answer method has been shown to serve equally well for the essay test (Willey, 1958). Tests of these types can thus be scored easily item by item with consequent immediate knowledge of success or error. The writer has recently developed a device for similar scoring of completion items which he calls a teaching machine only for the reason that this has become the accepted general term for all such mechanical aids to self-instruction. (A new comprehensive term is needed.) The materials for this device are ( 1) a legal size manila mailing envelope, (2) a panel of 1/8 masonite slightly smaller than the envelope with one end rounded, so a sheet of paper will move around it, (3) a short length of flexible cord about l/s in diameter, and (4) a strip of acetate about 9 X 1% in. A mimeographed question and answer sheet is prepared in the following form:

On the motion of a simple pendulum

The vanishing of the tension in a simple pendulum supported by a flexible cord causes the particle to pass from the circular to a parabolic trajectory. The number and the nature of such transitions are related here to the value of the initial energy.

Umbilical cord casualties: A résumé with presentation of cases

Intrauterine life, sustained only by two small arteries and a tortuous vein coursing through a long flexible cord, hangs by a very delicate thread. That fetal fatalities occur so seldom from cord complications seems incredible. Gradually, however, it has become more apparent that cord abnormalities are frequently involved in Nature's plan for “survival of the fittest,” especially in view of Javert and Barton's12 findings in early and late abortions. They found 35 per cent of the available cords for study to be abnormal and inconsistent with life, with torsion occurring in 15.3 per cent, looping in 5.7 per cent, and knotting in 0.9 per cent. As pregnancy progresses the incidence of knotting apparently decreases, while the incidence of looping (and probably torsion) increases, if we are to refer to Lundgren and Boice's13 figure of 0.3 per cent for knotting and Atwood's1 figure of approximately 25 per cent for looping in the viable stages of pregnancy. These percentages probably reflect the fact that the more serious cord disorders kill the fetus in the early stages of pregnancy, leaving the lesser, though no less potentially dangerous, disorders until later gestation. It is these abnormalities which occur after viability has been reached with which we are concerned in this paper.Intrauterine death from cord abnormalities most frequently involves anoxia of the fetus. Clementson6 lists the general types of anoxia as anoxemic, histotoxic, cord obstruction, and anemic, the latter two being those in which cord complications may be directly involved. He further divides cord obstruction anoxia into the following causes: loops of cord about the fetus, prolapse of the cord, true knots, breech delivery with cord compression, and short cord. To this we might add torsion, new growths, and partial rupture of the cord with hematoma formation causing vascular obstruction. Anemic anoxia may be caused by complete laceration of the cord or its vessels with bleeding external to the cord's amniotic covering. Other sources of obstructive or anemic anoxia are so rare that their consideration is not warranted.It is the purpose of this paper to summarize briefly, in so far as is possible, the incidence, associated fetal mortality, influencing factors, and general considerations of cord anoxia; to present two additional cases; and to discuss methods by which our fetal salvage rate may be increased.

Kromayer method of corrective surgical planing of skin.

The recently published article by Kurtin1warrants some comments. It is unquestionably to his credit that he has reintroduced a method which was known for several decades and that he has modified the abrasion technic in that instead of using burrs he has made use of stainless wire brushes. It was Kromayer2who, 30 years ago, described this method, which consisted of the combination of freezing the skin with ethyl chloride, and the subsequent use of various-sized dental burrs mounted on a motor driven flexible cord (Fig. 1). This method became a recognized cosmetic procedure, and is known to most European3and to a good many American dermatologists. Its usefulness was proved in the treatment of some keloids, pigmented nevi, freckles, lentigines, tattoos, berloque dermatitis, and pitted scars. Kromayer also recommended this method in the treatment of the hyperpigmented borders of vitiligo. I have had extensive experience with

British Standard Specification for Cable Insulation

A 1946 edition of the well-known British Standard No. 7, the first edition of which appeared in 1904, and which deals with rubber-insulated cables and flexible cords for electric power and lighting, has recently been issued. The main specification, together with a supplement on the use of polyyinyl chloride compounds as an alternative to vulcanized rubber, is published as a single volume (B.S.7 ; 1946. British Standards Institution, Publications Department, 28 Victoria Street, London, S.W.I. 3s;. 6d., post paid) and an amendment, entitled “Transitory Relaxations”, is issued separately in the form of a leaflet (Ref. PD 540). War-time conditions hastened the introduction of polyvinyl chloride insulated cables, and this necessitated several modifications to the original specification. The 1946 edition, while retaining in substance all the usual features, makes allowance for the change-over to peace-time conditions. Some of the modifications referred to above are retained as permanent revisions to the specification, others are retained only temporarily, to be dropped eventually, while others have been entirely cancelled. The specification is divided into three sections : the first, of a general nature, defining terms, sizes, etc., used later in the specification ; the second, dealing with the construction of the different types of cables and cords ; and the third, with tests for thickness of insulation and sheath, voltage, insulation resistance, spark testing, tinning and armouring. The numerous tables with which the specification is provided make the publication an extremely useful one for all users and manufacturers of electrical cables and cords.

Fundamentals of Hearing-Aid Design

A HEARING AID is a miniature sound-amplifying system which is worn on the person in order to help overcome the handicap of impaired hearing. To be effective a hearing aid must be capable of amplifying those frequencies necessary for intelligibility of speech and reproducing them at a high-intensity level so as to make normal conversation audible to the person with impaired hearing. Modern hearing-aid amplifiers are of the vacuum-tube type, using small tubes designed specifically for them. A complete hearing aid consists of a microphone, a vacuum-tube amplifier, a receiver, and the necessary battery supply and connecting cords. Usually the microphone and amplifier unit are housed in a single case and the receiver and battery supply are connected to the amplifier by means of flexible cords. In order to determine the amount of amplification necessary, the type of frequency response needed, and the sound-pressure output required, it will be necessary to consider in some detail the different types of partial deafness and the characteristics of speech and hearing.

Fundamentals of hearing-aid design

A HEARING AID is a miniature sound-amplifying system which is worn on the person in order to help overcome the handicap of impaired hearing. To be effective a hearing aid must be capable of amplifying those frequencies necessary for intelligibility of speech and reproducing them at a high-intensity level so as to make normal conversation audible to the person with impaired hearing. Modern hearing-aid amplifiers are of the vacuum-tube type, using small tubes designed specifically for them. A complete hearing aid consists of a microphone, a vacuum-tube amplifier, a receiver, and the necessary battery supply and connecting cords. Usually the microphone and amplifier unit are housed in a single case and the receiver and battery supply are connected to the amplifier by means of flexible cords. In order to determine the amount of amplification necessary, the type of frequency response needed, and the sound-pressure output required, it will be necessary to consider in some detail the different types of partial deafness and the characteristics of speech and hearing.

The heating of domestic pendant lamp fittings and their connecting leads

This paper is an investigation of the temperature-rise of the rubber insulation of leads connected to pendant fittings using lamps up to 200 watts as now made for domestic use, and of methods for reducing existing values to safe limits. On account of the higher filament temperature of the gas-filled lamp than the vacuum lamp, and the presence of the gas in the bdlb, the temprature of the lamp cap and of the surface of the glass is much higher in the former case than in the latter. This causes the connecting leads to become unduly hot and their deterioration to be considerably accelerated. As a result, after a limited period of service there is a risk of short-circuit or burning of the flexible cord occurring adjacent to or within the holder. There is the further possibility of metallic holders becoming alive. Although these risks exist, it is by no means common for serious trouble to occur.Four general methods are available for mitigating these effects, viz.:—(i) By improving the heat-resisting properties of the rubber insulation.(ii) By replacing rubber by a material capable of withstanding, existing working temperatures.(iii) By modifying the design of fitting and lampholder so as to reduce the working temperature of the rubber to 50°C.(iv) By modifying the design of the lamp so as to reduce the working temperature of the rubber to 50°C.Methods (I) and (ii) have both been under consideration by the Cable Makers' Association, and as a result the E.R.A. has been advised, since the preparation of this paper, that in regard to method (i) it would be possible to supply an improved type of rubber-insulated flexible cord which would give satisfactory operation at 60°d C. for a reasonable life under reasonable usage; and, in respect to (ii), flexible cords of this description are available and are being used in dry situations. This paper is based on the 50° C. limit, but the modifications necessary to fittings, etc., so that a temperature of 60° C. will not be exceeded, will easily be seen from the test results given. Method (ii) is to some extent obligatory in the U.S.A. and Canada.This paper is restricted to methods (iii) and (iv), and it is shown that a satisfactory solution can invariably be obtained by a combination of them and, frequently, by method (iii) alone.Tests show that in nearly all domestic pendant lamp fittings up to 200 watts, the temperature-rise of the connecting lead at ⅝ in. from the terminal is in excess of the maximum permissible, viz 23–4 deg. C, and this temperature-rise is attained at points varying from 2½ in. to 9 in. from the terminal. At the terminal the value varies from 51 to 117.5 deg. C. for the fittngs tested. Theory and experiments show that the temperature-rise depends fundamentally on two factors, viz, the temperature of the source of the heat which is copducted fromthe lamp to the holder, and the temperature of the air surrqunding the holder, which in a large measure controls the dissipation of heat from the holder, surface. Other subsidiary factors are the thermal resistance in the heat path between the lamp and the holder, and the radiation emissivity of the holder.The lamps used for the tests conform to the British Standard Specification for Tungsten Filament Electric Lamps, No. 161, 1932.Investigational work has been extended to shop-window, office, and, factory lighting fittings, and will be the subject of a later report.

The Lapel Microphone and its Application to Public Address and Announcing Systems<!--<xref ref-type="other" rid="fn1-10.5594_J14754">*</xref>-->

Many speakers find it difficult to use the conventional type of microphone, because of the restrictions that it imposes upon their freedom of movement. A microphone, known as the lapel microphone, designed to be attached to the speaker's clothing, has been developed for overcoming these limitations. — The vibratory structure of the lapel microphone is designed to have low mass and stiffness, and to resonate at a comparatively high frequency. The resilient support of the diaphragm adds sufficient mechanical resistance to prevent the occurrence of a prominent peak in the response at the resonance frequency. Means are provided for reducing extraneous noise to a minimum. A part of the sound reaching the. microphone, due to body vibration, is rich in low frequencies and must be attenuated, otherwise the quality of transmission will be unnatural. This attenuation is accomplished in the coupling transformer, which, together with the apparatus required for suppressing clicks, for indicating when the circuit is in operation, etc., is mounted in a control cabinet. A flexible cord connects the microphone to this cabinet. — It is expected that the lapel microphone will find application in theaters, churches, convention halls, lecture and banquet rooms, and the like, where public address systems are now employed. It also can be applied in connection with other sound recording and reproducing equipment where the background noise, characteristic of carbon microphones, is not a limiting factor.

The Lapel Microphone

AT public meetings and at lectures, the microphone and loud speaker is often a great boon to both the speaker, who speaks practically in his natural voice, and to the audience, who hear him clearly. There are some, however, who forget that they are addressing a stationary microphone and move about freely, with the result that sometimes they can scarcely be heard. To get over this difficulty, the Bell Telephone Company has invented the lapel microphone, a description of which is given in its Record for January. The microphone is only about an inch in diameter and weighs one and one-half ounces. A thirty-foot length of flexible cord provides the connexion to the amplifier of the public address system. The diaphragm is made of thin aluminium in the shape of a cone of sufficient stiffness to cause it to vibrate as a unit throughout the required frequency range. A rubber covering for the microphone eliminates the disturbing noise which would otherwise result from rubbing against the speaker's clothing, or would be picked up through the clip which is provided for attaching it to the clothing. The best place to attach the clip is to the lapel of the speaker's coat. This device has been used very successfully in large auditoriums in America. It should prove useful to speakers who depend on gestures for effective delivery or who need to turn to explain lantern slides or use a blackboard.

BIPOLAR ELECTRODE FOR ELECTROCOAGULATION OF THE INFERIOR TURBINATE

The instrument to be described has been in use for about fifteen years. It consists of two terminal needles of spring brass wire, each 4 cm. in length, protruding from an insulated rubber handle. This measures 16 cm. in length. At the proximal end of the handle, flexible conductor cords lead from each wire and are attached to the proper terminals of the diathermy machine. The instrument is used for the reduction of hypertrophy of the mucous membranes of the inferior turbinate. The inferior turbinate is first anesthetized by means of pledgets of cotton moistened with a suitable anesthetic placed against the hypertrophied portion and left in place until anesthesia is complete, without the use of epinephrine. The needles of the electrode are now introduced into the submucous tissue by puncturing at the anterior portion of the hypertrophy and carrying the needles into the tissue parallel to the bone of

Rise and Fall of the Tides

IN NATURE of April 27, Mr. A. Mallock writes on rise and fall of the tides, and illustrates his views by three specific cases in which a constant amount of energy is continually concentrated into a diminishing mass. To quote briefly: A heavy flexible cord passes through a hole in a fixed horizontal plate. The part below the plate is given an initial oscillation and swings as a pendulum. The cord is then drawn upward through the hole. The part above the plate is stationary, and the energy it contained is transferred to the part still hanging free, the mass of which continually decreases. Hence the velocity of oscillation tends to become infinite when the length vanishes.

A Simple Arrangement for Platinizing Electrodes.

The accompanying figure shows a simple arrangement for the electrolytic deposition of platinum upon electrodes for hydrogen ion work.A battery of two dry cells, a, is connected in series to a commutator, d, by wires, b, and c. The commutator is connected to a single central anode, g, by wire e, and to the cathodes, h, by branching of the cable wire, f. The electrodes, g, and h, are loosely held in position by insertion through the holes of the flat cork, i, which is supported in the 100 cc. beaker, j, in such a way that the metal of the electrodes is immersed in the platinic chloride solution, k. The electrode, g, consists of a platinum foil connected to a short piece of platinum wire, which is in turn sealed into the 5 mm. glass tube. A single wire electrode would probably serve just as well here. The electrodes, h, were made by sealing 18 or 20 gauge platinum wire into pieces of 4 mm. Mett's tubing. The cable wire, f, is a piece of 16 strand electric wire such as is used in flexible extension cords. The...

A safe method for securing anaerobiosis with hydrogen. IX

In the course of some quantitative studies on the growth of anaerobes in various plant and animal products, one of the authors (C. C. D.) has, during the past year, employed 13 large anaerobic jars. They have been operated in accordance with the principles proposed by Laidlaw 1 and constructed according to the descriptions published by Mcintosh and Fildes.2 It is the purpose of this paper to enumerate briefly the various details and operations which have eliminated the danger of explosions. The arrangement of the equipment as used in this laboratory is shown in fig. 1. It will be seen from the illustration that the jar is not unlike that described by Brown.3 A few alterations in construction are indicated in the photograph and are briefly summarized as follows: (1) The wires conveying current to the heating coil are soldered4 to short pieces of Pyrex glass tubing, which are then cemented into a rubber stopper (A). This method of introducing the lead wires readily permits the use of multiple stranded copper wire (as ordinary, flexible electric light cord), minimizing the chance of breakage. The wires should be looped over and tied to the side of the glass tubes on the outside of the jar top to prevent any strain from occurring at the soldered joint. (2) A shield of asbestos sheet (B) is placed over the upper surface of the coil to prevent the heat from cracking the jar top. (3) Instead of mica as used by Mcintosh and Fildes, asbestos washers are placed at these points (C) to deflect the heat from the inner ends of the rubber stoppers. In several papers,5 it is emphasized that the anaerobic apparatus embodying the principle of Brown's jar produces excellent results, but

SIMPLE ELECTRIC ATTACHMENT FOR OPHTHALMOSCOPE

The electric ophthalmoscope is very much more convenient than the ordinary type—especially when the patient is in bed—but the cost is excessive in comparison with the convenience, from the point of view of the average physician. I have devised a very simple attachment for the usual form of instrument, which can easily be made for less than a dollar. The necessary materials are a piece of sheet brass as thick as a postcard, and about 6 inches square to allow for errors; a small electric light of the sort used in the familiar hand flash-light, together with its battery; a small mirror, and 3 feet of double flexible electric-wire cord. The tools required are the following: A pair of old shears; a small pair of pliers with quite narrow flat nose, and either a very thin small flat file or, much better, the use for half an hour of

ELECTRIC RECORDING PERIMETER.

Of the many perimeters which have been devised for recording the field of vision, the instrument devised by Dr. Malcolm M. McHardy, of London, has met with the most favor. It is an excellent instrument, and whatever its defects, they are to be found in all similar forms of apparatus in which the test object is moved by a flexible cord. The instrument here shown was devised with a view of correcting the faults which experience shows exist in the ordinary form of perimeter. Apart from the use of small electric lamps for the fixation spot and for the test object, it differs in important details of construction from the usual form of perimeter. The arc which ordinarily carries the movable test object is replaced by a steel tube, at the end of which are cog-wheels for rotating a metal arm carrying a small electric lamp. Motion is transmitted to

XXXVIII. On a simple method of illustrating the chief phenomena of wave-motion by means of flexible cords

XXXVIII. <i>On a simple method of illustrating the chief phenomena of wave-motion by means of flexible cords</i>

On a simple Method of Illustrating the chief Phenomena of Wave-Motion by means of Flexible Cords

On a simple Method of Illustrating the chief Phenomena of Wave-Motion by means of Flexible Cords

4. On Rhabdopleura, a New Genus of Polyzoa

Professor Allman described a new genus of Polyzoa, obtained by the Rev. A. M. Norman and Mr J. Gwyn Jeffreys, from deep-sea dredgings in Shetland.Its cœnœcium consists of a branched tube, partly adherent and partly free, the free portion forming tubes of egress, through which the polypides move in the acts of exsertion and retraction. In the walls of the adherent portion a rigid chitinous rod is developed along their attached side, and to this rod the polypides are connected from distance to distance each by a flexible cord or funiculus.

On the friction of fluids

The object of the author in this paper is to trace the relation subsisting between the different quantities of water discharged by orifices and tubes, and the retardations arising from the friction of the fluid. The results of the experiments hitherto made with a view of ascertaining the effects of the friction attending the mutual motion of solids and fluids, are exceedingly discordant, and therefore undeserving of confidence. Whether, for example, the retardation from friction be proportional to the surfaces, or to the velocities, are points by no means satisfactorily determined. The experiments of the author were designed to measure the retardations experienced by solids moving in fluids at rest; and of fluids moving over solids. For this purpose, he employed a cylinder of wood, about eleven inches in diameter and two feet in length, traversed by an iron axle, upon the upper part of which a small pulley was fixed. A fine flexible silken cord was wound round the pulley, at one end, and had a weight attached to the other end. A frame was provided, allowing the apparatus to slide up and down; and the cylinder to be immersed at various depths into the river Thames. When the velocities were small, the retardation was found to be nearly was the surface: but with great velocities it appears to have but little relation to the extent of the surface immersed. The resistances of iron discs and wooden globes revolving in water were found to be as the squares of the velocities.