bluuebunny/crossref_metadata_2025 huggingface dataset:
An Apparatus for the Measurement of Alpha-Particle Range and Relative Stopping Power of Gases
Authors: Colby M. Y. , Hatfield T. N.
Published: February 2005

A description is given of an apparatus which has been developed for measuring the extrapolated range of alpha-particles in gases by the method of specific ionization. The improved apparatus is designed after the Curie-Naidu apparatus but increases the specific ionization current about one hundredfold without increasing the thickness of the alpha-particle source.
The Interval Selector: A Device for Measuring Time Distribution of Pulses
Authors: Roberts Arthur
Published: February 2005

An apparatus called an interval selector is described. In conjunction with two scaling circuits the apparatus records the total number of pulses in a distribution and also the number of intervals between pulses less than any arbitrary value τ. The range of τ in the instrument described is from 10−4 to 0.3 second. The application of the interval selector to the testing of particle-counting apparatus is described.
A Simple Photoelectric Turbidimeter
Authors: Silverman Shirleigh
Published: February 2005

A simple rugged photoelectric turbidimeter is described. The instrument is intended primarily for use with very clear liquids, and is suitable for such problems as counting micellar organisms in aqueous solutions, intensity measurements of fluorescent solutions, white blood or bacterial counts. A typical working curve is shown.
Studies of the Mechanical Properties of Substances of High Molecular Weight I. A Photoelastic Method for Study of Transverse Vibrations in Gels
Authors: Ferry John D.
Published: February 2005

The wave-lengths of transverse vibrations in gels are measured at various frequencies by observing the strain double refraction stroboscopically. Use of a Babinet compensator inclined at a small angle to the plane of polarization of the incident light detects very small amounts of double refraction. From the velocity of propagation of the vibrations, the modulus of rigidity is calculated; values ranging from 300 to 13,000 dynes/cm2 have been determined.
A Circuit for Testing Current Transformers
Authors: Walker Eric A.
Published: February 2005

A circuit is described for measuring the ratio and phase angle of current transformers. By using two standard resistances and a high impedance amplifier or vacuum tube voltmeter the use of mutual inductances or the necessity of comparisons is avoided. The method is applicable to potential and power transformers.
A Simplified Correction Factor for Equi-Inclination Weissenberg Patterns
Authors: Warren B. E. , Fankuchen I.
Published: February 2005

The correction for the Lorentz-polarization-rotation factor for equi-inclination Weissenberg patterns is given in a simple form in terms of the Lorentz-polarization factor for the corresponding equator spot.
A Vacuum-Tight Sliding Seal
Authors: Wilson Robert R.
Published: February 2005

The operation and construction of a vacuum-tight sliding seal by means of which unlimited translational and rotational motion in vacuum can be obtained is described. The seal is made by an appropriately distorted rubber gasket, and a table has been prepared which gives the dimensions of the gaskets to be used for various sizes of sliding rods.
An Approximate Analytic Expression of the Ballistic Sensitivity Curve and Its Application to Rapid Measurement
Authors: de Gerszonowicz D. Maggiolo , Gerszonowicz S.
Published: February 2005

The authors propose an approximate formula Sq=Sq0R/(R+mRc) to represent the variation of the ballistic sensitivity in terms of the resistance of the galvanometer circuit; its accuracy and application are discussed.
``Magic Eye'' Ionization Gauge
Authors: Ridenour Louis N.
Published: February 2005

An ionization vacuum gauge control and indicating circuit is described. It has the following features: (1) No meters whatever are required; the plate current of the gauge tube is indicated by a 6E5 tube, both during normal operation and during the outgassing operation. (2) The grid current in the gauge tube is held constant at any desired value, regardless of changes in line voltage, gas pressure, or the nature of gas in the vacuum system. (3) Outgassing of the grid of the gauge tube may be done by throwing one switch. (4) The grid current is controlled automatically during outgassing. (5) Any type of tube may be used as gauge tube proper, without changes in the control and indicating circuit. A note on leak testing with the ionization gauge is added.
A Regulated Battery-Operated High Voltage Supply
Authors: Barry J. Griffiths
Published: February 2005

A portable, battery-operated high voltage supply has been developed that is capable of furnishing 100 microamperes or more at voltages up to about 2000 volts with sufficient constancy of voltage for making accurate Geiger counter measurements. For stratosphere balloon use, few batteries are required other than the usual plate and bias supplies and the additional current drain on these is small. The outfit may also be used with other portable cosmic-ray apparatus, as well as radium finders and radioactivity meters.
A Light Weight, High Voltage Supply for Geiger Counters
Authors: Neher H. V. , Pickering W. H.
Published: February 2005

A light weight, high voltage supply for Geiger counters is described. Its total weight, including batteries to operate it for approximately 6 hours, is 650 grams. The power input including the rectifying tube is 0.3 watt. The output can be varied from several hundred to about 2000 volts, and varies linearly with the voltage of the supply battery. Random fluctuations are of the order of 1 percent. A simple circuit for regulating the voltage is also given.
An Electro-Optic Pressure Indicator
Authors: Robertson A. F.
Published: February 2005

The author describes improvements on a diaphragm type of engine pressure indicator. The indicator takes advantage of the fact that a polished metal diaphragm forming part of the combustion chamber wall will be deflected in the form of a spherical mirror when there is a pressure difference across it. Since the radius of the mirror is inversely proportional to the change of pressure, the intensity of a beam of light reflected from this diaphragm will vary with the pressure. By measuring the changes of intensity of the reflected light beam an indication of the change of engine pressure is obtained. A special direct-current amplifier has been constructed which makes possible the use of the indicator at any engine speed. Charts are included which may be used to determine when operation of the indicator is closely linear.
A Laboratory High Vacuum Furnace
Authors: Ehret William F. , Gurinsky David H.
Published: February 2005

The authors have reported the details of construction and operation of a carbon tube resistance furnace which operates in high vacuum (10−3 to 10−5 mm) or special atmospheres. The furnace has the following advantages: relatively low cost, compactness, and rapid heating. Melts of 25 grams are made at 1550° in 6 minutes. Larger melts and higher temperatures should be easily attainable. When operated under vacuum the furnace produces melts that are practically gas- and carbon-free. A marked freedom from the usual difficulty of maintaining vacuum has been achieved by using the base of the furnace as an electrode, thus reducing the number of entrance ports, and by using vacuum rubber-tape to seal flexible connections.
A Galitzin-Type Gravity Meter
Authors: Welch George I.
Published: February 2005

The general requirements involved in the design of a gravity meter are outlined. The construction and characteristics of a gravity meter developed by the author are discussed. The probable error of a single reading of the instrument when used in the field is 0.06 milligal.
Combination Vacuum Tube Switch for Double-Trace Cathode-Ray Oscillograph, Audio-Amplifier and Mixer
Authors: Hughes Harold K. , Koch Richard F.
Published: February 2005

Two circuits are described which act as medium-speed, single-pole, double-throw switches to connect two independent voltages to the input of a single-beam cathode-ray oscillograph. In each, a square wave is applied to the cathodes of two high-mu pentodes, biasing them beyond cut-off on alternate half-cycles. The independent inputs go to the control grids and the output is taken from the common plate connection. The circuits differ in the means of generating the square wave. In one, a high voltage transformer connects to the plates of two diodes which are run at reduced heater current in order to secure voltage saturation. In the other, a transformer swings the grids of two high transconductance, sharp cut-off television amplifier pentodes, overloading the grids on positive peaks and cutting off the plate current on negative peaks. The relative merits of the two circuits are discussed. A complete bibliography is included. A simple mechanical switch serves to change the circuit into either a two-stage, audiofrequency amplifier or into an electronic mixer.
An Electronic Switch and Square Wave Oscillator
Authors: Cosby J. R. , Lampson C. W.
Published: February 2005

An electronic switch and square wave generator for laboratory use are described. Complete instruction for construction and adjustment are included as well as diagram, parts list, voltage data and a few suggested uses. The device is entirely self-contained and employs some of the latest types of vacuum tubes.
An Electronic Switch for the Simultaneous Observation of Two Waves with the Cathode-Ray Oscillograph
Authors: Reich Herbert J.
Published: February 2005

This paper describes an electronic switch for use with the cathode-ray oscillograph in the simultaneous observation of two waves. The circuit differs from similar ones described previously in that it uses a high vacuum tube trigger circuit in place of thyratrons as the switching element.
A Motor Driven Ionization Spectrometer
Authors: Jefferson M. E. , Hendricks S. B.
Published: February 2005

An ionization spectrometer for intensity measurements is described. The coaxial rotation of chamber and crystal is accomplished on precision ball bearings in place of the usual conical bearing. The scales of the instrument are projected for ease in operation. A simple ``manual'' recorder is included.
Some Characteristics of Hollow-Cathode Discharge Tubes
Authors: Van Voorhis C. C. , Shenstone A. G.
Published: February 2005

A study has been made of the characteristic effects of the inert gas, and of variations in the dimensions of the cathode, on the minimum pressure at which the Schuler discharge may be started and maintained. Partially closing the open end of the cathode was found to have a very beneficial effect. An interesting example of rotating anode spots, observed incidentally, is also described.
A Recording Sensitive Differential Manometer
Authors: Hurst William
Published: February 2005

A sensitive differential manometer used in the recording of small differential pressures is described. This instrument responds to pressure differences as small as 0.00003 cm of mercury and as rapid as 80 cycles per second. The moving element is a rectangular glass mirror 0.010 inch thick and approximately 0.060 inch×0.080 inch, supported on a glass shaft 0.007 inch in diameter. Motion is supplied by a thin rubber diaphragm approximately 0.003 inch thick. Included in recordings made with the aid of this instrument are wave forms originating in the human neck and finger, also pressure changes in a glass cell enclosing a tracheal breathing insect.
A Quantity Type Rotor for the Ultracentrifuge
Authors: Masket A. Victor
Published: February 2005

An improved design for fixed angle quantity type rotors is presented in which the holes are drilled at 10° to the axis of rotation and the Lusteroid tubes containing the centrifugate are individually sealed by means of tapered plugs. The advantages of this design are (a) increased capacity for a given diameter rotor, (b) prevention of tube collapse at all speeds and (c) more efficient concentration of materials in solution. Some charts illustrating differential sedimentation and concentration of proteins are given.
A Timer For Spark Breakdown Studies
Authors: Cobine J. D. , Easton E. C.
Published: February 2005

As an aid in the study of the time lag of spark breakdown, devices have been constructed to apply a rectangular voltage wave and to measure its length which is from one to 5000 microseconds in duration. Oscillograms of switching transients and test-gap voltages in this investigation indicate that many previous investigators have been deceived in assuming a rectangular wave of applied voltage, and that others may have introduced errors by assuming the gap voltage to be influenced by reflections. It is possible to apply an essentially rectangular voltage by (1) maintaining the spark which closes the circuit through the applying switch before the contacts meet mechanically, and (2) by making the test-gap circuit aperiodic. The length of the applied voltage wave is determined by a vacuum tube circuit designed to pass a constant current output as long as the bias to the first tube exceeds a predetermined value. The output current is passed through a ballistic galvanometer whose reading is a measure of the time during which the gap voltage remains above the datum level. A thyratron circuit has been arranged to supply the timer with rectangular waves for the purpose of calibration. Cathode-ray oscillograms showing errors of 5 percent to 10 percent indicate that the accuracy of the apparatus is sufficient for most breakdown studies.
Use of Corona Gaps in High Voltage Work
Authors: Van Atta L. C. , Nowak W. B.
Published: February 2005

The several applications of corona gaps to high voltage work require current-voltage curves having somewhat different shapes. Data are presented to show how the characteristic curve of a corona gap depends upon polarity, gap length, electrode shape, and combined linear resistance. The selection of the proper corona gaps for various applications is discussed.
A Monochromatic Source of Mercury Resonance Radiation
Authors: Thomas Lloyd B.
Published: February 2005

The strong absorption and subsequent re-emission of mercury resonance radiation in mercury vapor has been utilized in the construction of a highly monochromatic and moderately intense source of λ2537. The construction and performance of the lamp are described and a rough analysis shows the line half-breadth to be about twenty percent greater than the ideal Doppler half-breadth at room temperature.
Production of Liquid Helium by the Kapitza Method
Authors: Lane C. T.
Published: February 2005

A description of the design and operation of the low temperature laboratory recently built at Yale University is given. The equipment consists of a Kapitza type helium liquefier and associated helium gas storage and circulation systems. The design and performance of the expansion engine of the liquefier is discussed and those details most important to successful operation are stressed. The size and arrangement of the heat exchanger coils are next discussed and a table of tube sizes given. The lay-out of the helium distribution and purifying system is given including a description of the type and performance of the compressor and vacuum pumps. Finally figures are given on the over-all efficiency of the plant, including the starting up time, the amount of liquid air consumed and the hourly rate of production of liquid helium.
Automatic Speed Control for the Air-Driven Ultracentrifuge
Authors: Rothen Alexandre
Published: February 2005

A speed control for the air-driven ultracentrifuge based on a stroboscopic principle is described. The pressure of the air driving the centrifuge is automatically decreased or increased according as the centrifuge tends to accelerate or decelerate. The speed of the centrifuge can be maintained constant within less than one revolution a second.
Electrical Bombardment of Biological Materials II. An Electron Tube for the Production of Homogeneous Beams of Cathode Rays from Ten to One Hundred Kilovolts
Authors: Morningstar O. , Evans R. D. , Haskins C. P.
Published: February 2005

An apparatus is described for irradiation of biological and chemical materials in vacuum with electron beams of intensities varying between 10−6 and 10−10 coulomb per square centimeter and of energies ranging between 10 and 100 kv. The beam can be easily adjusted and scanned for homogeneity. Through an arrangement of stops, a large number of targets can be conveniently irradiated in a relatively short period.
An Integrator for Small Currents
Authors: Watt Bob E.
Published: February 2005

A current integrator employing a neon bulb has been used; it is found to require no correction of any kind, and to be independent of power supply fluctuations. The lowest current for which the integrator can be considered reliable is 0.05 microampere. Currents up to 30 microamperes have been integrated properly, and it is believed that currents up to 200 microamperes could be integrated by a similar circuit.
An Adjustable Infra-Red Absorption Cell for Liquids
Authors: Barr E. S.
Published: February 2005

The use of foil or mica washers to regulate absorption cell thicknesses renders difficult the rapid preparation of thin films of liquids of a determined thickness. The device described here regulates cell thickness by means of a micrometer screw and wedge arrangement. Films of non-volatile liquids are readily prepared to within 1 micron, up to about 200 microns, without estimation.
Automatic Integration of Linear Second-Order Differential Equations by Means of Punched Card Machines
Authors: Feinstein Lillian , Schwarzschild Martin
Published: February 2005

It is shown how punched card machines can be used for solving ordinary linear differential equations of the second order.
The Production of High Rotational Speed
Authors: MacHattie L. E.
Published: February 2005

Small steel rotors have been suspended by an axial magnetic suspension using inductance control to effect vertical stabilization. They have been spun in vacuum by means of a rotating magnetic field having a frequency of the order of 100 kilocycles. Rod rotors tended to precess in the absence of horizontal damping. This was remedied by placing a copper block just above the upper end of the rod. A tapered length of drill rod ⅞″ long (max. diam. 316′′) reached 36,000 r.p.s. before bending double due to the effect of centrifugal force. Steel balls have the advantage of no precession; however, on starting to spin they soon built up a circular orbital motion of increasing amplitude. A damping needle situated outside the vacuum system and immersed in oil was found to eliminate this motion satisfactorily. A 332′′ diam. ball has been spun to 110,000 r.p.s. This corresponds to a centripetal acceleration at the periphery of 58×106 gravity. The rate of free deceleration at 106,000 r.p.s. was about 1 percent per hour. Rotational speed was measured by observing the rotor in stroboscopic light whose frequency could be matched with the speed of the rotor.
An All Electric Integrator for Solving Differential Equations
Authors: Varney Robert N.
Published: February 2005

Four basic devices are required for an integrator of differential equations. These are (1) integrating units themselves, (2) coupling devices for interlocking the various integrators and multipliers, (3) multiplier units, (4) generators of functional coefficients entering into differential equations. These devices and their applications to various types of problems are given. Results of an entirely completed machine are not available, but preliminary results show the device to be good to half a percent and potentially in some cases to nearly a tenth of a percent. The electric coupling used renders the machine very free from mechanical difficulties and also reduces the cost enormously. A machine capable of attacking many theoretical problems might cost as little as $5000.
A Method of Minimizing Supercooling and Its Application in the Determination of Freezing Points from Dielectric Constant Measurements
Authors: Shaw Thomas M.
Published: February 2005

The determination of the freezing points of water in colloidal systems from dielectric constant measurements is shown to be unsatisfactory when supercooling occurs. A method is described for minimizing supercooling, which makes possible accurate determinations of the freezing point. Data showing the freezing points obtained for a Barnes soil at various moisture contents are included.
Two Bridge-Controlled Thyratron Thermostats
Authors: Bancroft Dennison
Published: February 2005

Two circuits for the regulation of temperature by means of a bridge-controlled thyratron are described. The first utilizes a resistance thermometer; the second controls through changes in the resistance of the furnace winding. Improved stability is achieved by adequate filtering of the voltage applied to the control grid of the thyratron. The circuits are so designed that extreme overload in control voltage never causes erratic behavior; thus when the thermostatic bridge is set for a new temperature, unstable operation does not occur, and control is established smoothly and promptly.
The Electrical Capacitance Diaphragm Manometer
Authors: Lilly John C.
Published: February 2005

A new type of diaphragm manometer for direct pressure measurements in the arterial blood stream and in other fluid systems is described using a radiofrequency, crystal-controlled oscillator and a pressure-sensitive condenser in the pick-up unit. The potential drop due to the plate current of the oscillator tube flowing through a resistor is amplified, and is observed and photographed by means of a cathode-ray tube. Sensitivity control is obtained by the use of an inverse feed-back network in the amplifier. The range of sensitivity is from a maximum of one mm Hg per inch of cathode-ray tube spot deflection to any desired minimum. The approximate cut-off frequency of the manometer is 580 c.p.s. when used with a number 20 needle, 475 c.p.s. with a number 22 needle and 205 c.p.s. with a number 26 needle, each one inch long. These values are higher than those of previous diaphragm manometers with the same size liquid system and the same size needle. Sample records of the arterial pressure are presented.
Rotating Bubble Method for the Determination of Surface and Interfacial Tensions
Authors: Vonnegut Bernard
Published: February 2005

A new method for the measurement of surface and interfacial tensions is suggested. The two phases to be investigated are placed in a closed container which is rotated at a known speed about a horizontal axis. Under the influence of the forces of rotation and of surface tension the lighter phase will take the equilibrium shape of an elongated bubble along the axis of rotation. If the length of the bubble is made large compared to the radius, the shape of the bubble can be closely approximated by a circular cylinder with hemispherical ends. For the case of a long bubble expressions are derived for the surface tension as a function of the bubble dimensions and for the shape of the bubble end.
The Oximeter, an Instrument for Measuring Continuously the Oxygen Saturation of Arterial Blood in Man
Authors: Millikan G. A.
Published: February 2005

The oxygen saturation of arterial blood in man can be measured continuously in situ by means of bichromatic photoelectric colorimetry of the intact fully flushed ear. The accuracy of the device as determined by gas analysis of arterial blood samples is from 3 to 8 percent. The entire optical and photoelectric system, comprising a miniature lamp bulb, two color filters, and two selenium barrier-layer photo-cells, weighs 30 grams, and slips over the shell of the ear. One of the color filters transmits a wave-length band which is equally absorbed by oxy- and reduced hemoglobin, thus providing a means of measuring the amount of total hemoglobin in the optical path, independent of its degree of oxygen saturation. The other color is very differently absorbed by the two hemoglobin forms. Several direct reading forms of the instrument are discussed.
Use of the Mechanical Multiharmonograph for Graphing Types of Functions and for Solution of Pairs of Non-Linear Simultaneous Equations
Authors: Brown S. Leroy , Wheeler Lisle L.
Published: February 2005

Mechanical means are described whereby types of equations may be graphically represented and non-linear simultaneous equations may be solved. The procedure requires, in each case, that the equation be changed to a trigonometric form by polar transformation. Graphs are shown to illustrate the processes involved.
A Continuous Electronic Pulse-Rate Indicator and Recorder
Authors: Schwarzschild M. M. , Shelesnyak M. C.
Published: February 2005

A circuit is described which is operated by the cardiac action current impulses in which the reading of a meter is a nearly linear function of the pulse rate. The impulses are amplified and applied to a trigger tube which sets off a gas discharge tube discharging a condenser at each beat. The charge transferred at each beat is independent of the shape of the action current wave within wide limits. The meter, shunted by a large smoothing condenser, reads the average current and is calibrated in beats per minute. The instrument may be connected to any suitable type of recording millivolt meter to obtain a continuous record of rate. The device may be used for indicating or recording the rates of any quasi-periodic phenomenon, in the range of frequency from 20 to 400 per minute, if at each period an electrical impulse of the order of 1 mv can be provided.
A Monochromator Using a Large Water Prism
Authors: Cannon C. V. , Rice O. K.
Published: February 2005

An inexpensive monochromator, capable of giving high intensity in the near ultraviolet, is described. Its distinguishing feature is a large water prism with quartz sides. This prism has an internal reflection so that the beam always comes through it at minimum deviation, and gives straight undistorted spectral lines at the exit slit.
The Infra-Red Prism Spectrograph as a Precision Instrument
Authors: Oetjen R. A. , Kao Chao-Lan , Randall H. M.
Published: February 2005

An investigation of the working conditions of an infra-red spectrometer of the recording type has resulted in techniques of operation which have increased the precision of the measurements attainable and has permitted an appraisal of the magnitudes of the variations in the resulting data which may still be expected. Included in this study is the remeasurement of the fine structure of certain of the absorption bands of CO2, NH3, and H2O. Measured with a grating instrument whose resolution was made to equal that of the prism instrument in each case, these data give 150 sharp absorption lines between 5μ and 15μ suitable for an empirical calibration of great accuracy.
An Improved Source for the Lyman Continuum in the Vacuum Ultraviolet
Authors: Worley R. Edwin
Published: February 2005

An improved design of Lyman discharge tube, a well-known high intensity source of continuous radiation, is described. The usual mechanical difficulties are largely avoided by use of a replaceable quartz capillary held in permanent alignment by a metal clip, and of a fin-type electrode that effectively prevents clogging of the spectrograph slit even for widths as narrow as 0.02 mm. Some features of the operation of the source are discussed.
Stress Analysis and Design of High Speed Angle Centrifuges
Authors: Pickels E. G.
Published: February 2005

A detailed graphical method for determining mechanical stresses in high speed angle centrifuges is explained and equations convenient for obtaining approximate values are presented. Various points of design are discussed, and stresses have been determined for several typical rotors to serve as guides for the designer. Theoretical considerations indicate that a properly designed rotor having a diameter of 20 cm and accommodating several hundred cubic centimeters of fluid can operate at speeds up to 50,000 r.p.m. for thousands of runs.
Electronic Differentiation
Authors: Schmitt Otto H. , Tolles Walter E.
Published: February 2005

Electronic circuits are described which, over a wide range of frequency and wave form, generate output voltages accurately proportional at every instant to the time derivative of their input potentials. Three basic circuits are described which provide successively increasing accuracy of differentiation with attendant increases in complexity of construction and delicacy of adjustment. Criteria are provided for choosing between the circuits for particular applications.
A Method of Recording Low Intensity Flashes of Light
Authors: Butt Charles , Alexander Robert S.
Published: February 2005

A circuit is described for recording the low intensity flashes of light of luminous animals, with examples of its application to the firefly flash. Between an alternating current source and a high gain a.c. amplifier, a photo-cell bridge circuit is introduced which is capable of blocking the a.c. signal when the photo-cells are dark. Light falling on the photo-cells allows the a.c. signal to pass the bridge, the output of the bridge being amplified and recorded photographically by the use of the cathode-ray oscilloscope.
Analytical Cell for the Ultracentrifuge
Authors: Rosenfeld Morris
Published: February 2005

An analytical cell has been designed for the angle type quantity rotor of the air-driven ultracentrifuge. Sieve-like partitions covered with filter paper separate the cell into two or three compartments from which fractions can be removed for chemical analysis or for bioassay. Fourteen tubes each containing 4.5 cc of solution can be run simultaneously. Equations have been derived for the calculation of sedimentation constants from the analytical data.
Photoelectric Colorimeter for Rapid Reactions
Authors: Chance Britton
Published: February 2005

A differential photoelectric colorimeter has been built for the high speed measurement of small absorption changes in enzyme substrate reactions. Under the conditions of the experiments, the total differential change of light intensity was approximately 0.2 percent and a photoelectric resolution of approximately 1.7×104 was achieved, giving an accuracy of 3 percent. The time resolution of the system was at least 0.01 second and a complete kinetic curve was obtained with as little as 0.5 cc of peroxidase solution of 1×10−6 molar hematin iron.
Membrane Interferometer Manometer
Authors: Tobias Julian M.
Published: February 2005

A sensitive indicator of pressure change has been constructed which utilizes a thin organic film as one of a pair of interferometer reflectors. Displacement of the film with respect to a fixed glass plate results in a shift of interference fringes. The film, being very thin, is extremely sensitive to pressure changes.
Some Operating Characteristics of the Wilson Cloud Chamber
Authors: Hazen Wayne E.
Published: February 2005

The following characteristics of cloud-chamber behavior were studied: (a) the dependence of minimum pressure on expansion time, (b) the ion threshold expansion ratio as a function of expansion time, (c) the sensitive time and its dependence on the percent expansion, (d) the rate of pressure rise after completion of a fast expansion, and (e) the rate of drop growth in N2, H2, and He with vapor from 95 percent C2H5OH or a liquid mixture of one part H2O to three parts C2H5OH. The experiments were performed with large cloud chambers (30-cm diameter and 10- to 30-cm depth) filled, in most cases, with N2 as the permanent gas and with the vapor from a 1 : 3 liquid mixture of H2O and C2H5OH. (a) The minimum pressure is found to be proportional to the square root of the expansion time. (b) The ion threshold expansion ratio increases linearly with expansion time. (c) The sensitive time increases with expansion ratio, reaches a maximum when the general background becomes appreciable, and approaches zero for higher expansion ratios. (d) The initial pressure rise after completion of an expansion is proportional to the square root of the time. (e) The surface area of a drop increases linearly with time in all cases. The temperature of a drop calculated from the rate of growth and from thermal constants is much lower for H2 and He than for N2. The results in (a), (b), (c), and (d) agree with results predicted by Williams' equations or equations obtained from similar considerations. The results for the rate of growth in (e) are in reasonable accord with values calculated from the diffusion equation.
The Preparation of Silver Chloride Films
Authors: Fugassi Paul , McKinney D. S.
Published: February 2005

Transparent, plastic films of silver chloride can be obtained by rolling fused silver chloride. Such films show high transmission for infra-red radiation and can be used as windows for infra-red absorption cells.
Multiple Electrode High Voltage Arc for Spectrographic Analysis
Authors: Owsley W. D. , McReynolds R. C.
Published: February 2005

An apparatus is described which provides arcing facilities for twelve samples without the necessity of removing the electrodes. The lower electrodes rotate during arcing. All controls for selecting the electrode pairs and for vertical and horizontal adjustment are insulated and are located outside a safety cage which must be completely closed before application of the high voltage is possible. Contamination is prevented by adequate ventilation.
A Permanent Magnet β-Ray Spectrograph
Authors: Plesset E. H. , Harnwell G. P. , Seidl F. G. P.
Published: February 2005

The method of design followed in the construction of a permanent magnet containing 450 pounds of red dot Alnico and having a total mass of about 3000 pounds is reviewed. The magnet can produce fields which are permanent and highly homogeneous and of any magnitude up to about 3000 oersteds in a gap 8′′×16′′×1916′′. The moderate cost and excellent performance of the installation indicate that such magnets should be useful for numerous applications. A photographic type spectrograph is described, which is suitable for the study of internally converted electrons. To render quantitative comparisons of electron intensities feasible, the photographic action of β-rays has been investigated. Examination of β-spectra emitted by naturally radioactive elements indicates that the performance of the spectrograph is quite satisfactory.
The Phosphorescence Microscope
Authors: Harvey E. Newton , Chase Aurin M.
Published: February 2005

Four different methods of microscope observation of the phosphorescence of minute structures in cells or cell products, or microcrystals, both organic and inorganic, are described. The material must be dry or nearly so and the illumination short ultraviolet such as occurs in condenser discharges in air or in mercury, or the iron arc. Observations on various types of material, including tooth sections, are described. Some protein particles, notably casein, must be rayed a short time before they become markedly phosphorescent and they lose this property quickly on standing in the dark.
A 20-Million Electron-Volt Betatron or Induction Accelerator
Authors: Kerst D. W.
Published: February 2005

The details of construction of an improved induction accelerator which gives electrons 20-million electron-volts energy are described. The accelerator has a 19-inch diameter pole face and weighs approximately 3.5 tons. The x-ray output as measured in a thick wall ionization chamber is 16 r.p.m. at one meter. The most important improvement incorporated in this accelerator is the electromagnetic expansion of the equilibrium orbit which can be timed to send the electrons against the target at any desired energy up to 20 million electron volts. The accelerator is now in use at the University of Illinois.
A Variable Ratio-Arm Conductivity Bridge
Authors: Luder W. F.
Published: February 2005

A shielded conductivity bridge employing direct balance to ground and variable ratio arms is described. The bridge as a whole is probably capable of an accuracy of about 0.01 percent over a range of one million ohms with greater flexibility than that of the customary fixed ratio-arm conductivity bridge. The range may be extended to ten million ohms with only slight loss in precision. By using the two extra ratios provided in the ground arms the resistance of all solvents except those of lowest dielectric constant may be measured to a few percent on the same bridge.
Behavior of a Balanced D.C. Amplifier
Authors: Spencer Roy C. , Schulz LeRoy
Published: February 2005

A study of the Barth balanced circuit employing the FP-54 electrometer tube disclosed several new properties of the circuit. (1) The value of the filament current at which a balance is obtained usually shifts when the potential of the control grid is changed, thus throwing the circuit out of balance. This shift may be eliminated by suitable adjustments of the circuit resistances. (2) A balance usually exists at two or more values of the filament current, and these may be moved together by adjusting the circuit resistances so as to form a broad plateau. (3) Tubes with low plate current were difficult to balance until after their plate current was increased by ``flashing.'' The new balance, necessitating changes in circuit resistances, resulted in an increased range of balance.
The Use of Stroboscopic Patterns in the Determination of Speeds of Rotation
Authors: MacInnes D. A.
Published: February 2005

The use of stroboscopic patterns for fixing and measuring rotational speeds is discussed. Patterns having as many as nine bands may be utilized. The patterns occur in a definite recurring sequence, according to a simple numerical relation. Most of the speeds intermediate to those at which patterns are stationary may be obtained by correcting for the precession or recession of the patterns.
Methods and Instruments for the Selective Irradiation of Chromatin
Authors: Zamenhof Stephen
Published: February 2005

Methods and instruments to produce minute spots of ultraviolet light to realize selective irradiation of chromatin in living cells are discussed theoretically and checked experimentally. Two methods were developed: (1) lens method (focusing of ultraviolet light by means of quartz or fluorite lens), and (2) screen method (screening of ultraviolet light by means of a screen with minute opening). While the diffraction phenomena restrict the lower limit of the size of the irradiated spot, yet a spot as minute as 0.2μ in diameter with the lens method, and 1μ in diameter with the screen method, is obtainable. Biological material suitable for experimentation (certain protozoa, spermatozoa) is discussed briefly.
A Cold Cathode X-Ray Diffraction Tube
Authors: Chesley Frank G.
Published: February 2005

The design and construction details for making a cold cathode x-ray diffraction tube are included. A metal bellows incorporated in the cathode assembly permits adjustment of the cathode-target distance. Vertical fins provide adequate cooling without forced draft and a simple target sealing assembly permits rapid interchange of targets.
Construction of Monochromator Cams for Recording Spectrophotometers
Authors: Moran J. M.
Published: February 2005

Procedures are described which permit the use of an optical filter with sharp absorption bands to supplement emission line data in the laying out of a wave-length cam for a recording spectrophotometer. The range 355 to 1200 mμ is covered in order to fulfill the need for obtaining spectrophotometric data in the photographic infra-red region as well as that of the visual. Emphasis has been placed primarily on the requirement of securing a reproducible calibration among several instruments.
Stable Self-Quenching Geiger-Müller Counters Containing Organo-Metallic Compounds
Authors: Keston Albert S.
Published: February 2005

Stable self-quenching counters may be prepared by filling counter tubes with tetramethyl lead vapor at about 2 cm pressure. The counters are characterized by wide usable voltage ranges and show wide voltage ranges where the count is practically independent of voltage.
The Interference Spherometer
Authors: Speyer Edward
Published: February 2005

The substitution of Newton rings for mechanical contact permits (a) locating the setting reliably within ±0.0002 mm and (b) elimination of errors due to weight of lens since the optical setting can be achieved before mechanical contact. Guild's original instrument is described; also a new model recently constructed.
An X-Ray Tube Using an Electron Gun
Authors: McCue J. J. G.
Published: February 2005

By using an electron gun, one can effect a great reduction in the contamination of the target by material evaporated from the filament, and can prevent space charge from limiting the target currents available at low voltages. An arrangement which has proved satisfactory is described.
Heat Capacity of Fine Wires
Authors: Kurrelmeyer Bernhard , Mais Walter H. , Green Edward H.
Published: February 2005

A wire enclosed in an evacuated tube is placed in one arm of a Wheatstone bridge and brought to the temperature at which its heat capacity is to be determined. With the bridge balanced, galvanometer key closed, and battery key opened, a charged condenser is connected across the battery terminals of the bridge. The heat capacity is evaluated from the resulting ballistic deflection. In an alternative procedure, the bridge is initially unbalanced so that discharge of the condenser gives zero deflection. The method has been tested on pure platinum in the neighborhood of room temperature. The over-all accuracy is estimated at ½ percent. The internal consistency is much better. A table is given of the authors' results together with the best previous measurements.
Ring Method for Measuring Elastic Moduli
Authors: King Allen
Published: February 2005

The theory of the ring method for measuring shear moduli of wire specimens is developed. The resonant frequency fs for oscillations at right angles to the plane of the loop is related to the shear modulus n and Young's modulus E by the equation Bν(ν+7)=2{(2π2/3)(ν2+2ν+9)+5ν2+46ν+17},in which ν = 2n/E and B=E(a/r)4/2π(1−h)mfs2·a is the radius of the wire, r is the radius of the loop, m is the mass per unit length of the specimen, and h is a small gap correction term. Measurements of shear moduli on the same wire samples of Cu and Mo by the torsion pendulum and ring methods check within the experimental errors.
A Volumetric Respirometer for Aquatic Animals
Authors: Scholander P. F. , Haugaard Niels , Irving Laurence
Published: February 2005

A closed circuit respirometer is described which circulates a given volume of water through the chamber containing the fish and equilibrates the water with a small volume of air. As oxygen is consumed by the fish, its removal from the air space is indicated manometrically, and is compensated for by measuring in oxygen from a syringe. Continuous, direct measurements can be made at any intervals and for many hours. The instrument described was used for cunners weighing from 30–70 grams and for toadfish weighing 300 grams, with oxygen consumption from 1 to 12 milliliters per hour. It showed accurately the use of 110 milliliter oxygen per hour.
An Improved Current Integrator
Authors: Blair J. Morris
Published: February 2005

An improved integrator circuit for measuring the ion beam current used in nuclear research is described. A condenser is allowed to be charged and upon reaching a definite potential is discharged through a thyratron tube. This action is brought about at the proper point by a trip circuit composed of two pentode tubes. The potential between the thyratron cathode and the trip circuit is accurately controlled by a voltage regulator network. The action of the circuit proves to be quite linear over a wide range of currents and rates of operation.
Geiger-Mueller Counter Pulse Size
Authors: Miller Carlton W.
Published: February 2005

A description is presented of the equipment for the measurement of the pulse size from Geiger-Mueller counters, and the results are given for the gas mixtures 90 percent He 10 percent H2, 90 percent Ne 10 percent H2, 90 percent A 10 percent H2, 100 percent H2, and 90 percent A 10 percent O2 for pressures from 2 to 30 cm of mercury, and for a mixture of 9.7 cm of argon and 1.2 cm of ethyl alcohol.
A Method for Removing Microscopic Fog from Photographic Plates
Authors: Liebermann L. N. , Barschall H. H.
Published: February 2005

A method is described for removing the microscopic fog found in commercial photographic emulsions. The removal of the fog makes a greater number of emulsions available for recording tracks of nuclear particles. An example of this application is shown in photomicrographs of the tracks of polonium alpha-particles in treated and untreated lantern slide plates.
An Experimental Mass Spectrometer
Authors: Coggeshall N. D. , Jordan E. B.
Published: February 2005

A mass spectrometer, designed for investigating different source arrangements with great ease, has been completed. It is an all metal, sector-shaped magnetic field type, constructed so that it may be disassembled, repaired, or modified without altering its focusing properties in any way. An important feature of the design is a removable ion source unit. A new source arrangement, investigated with this instrument, is discussed.
An Electrical Transducer Circuit for Use with Capacity Pick-Up Devices
Authors: Potter E. V.
Published: February 2005

An electrical circuit suitable for converting changes in capacity into changes in a rectified electrical current has been developed by the Bureau of Mines and has been used in seismic work as well as other studies in which mechanical vibrations are involved. The circuit employs two radio-frequency oscillators and a rectifier and can be operated from batteries or 110-volt, 60-cycle alternating current. Sensitivities up to 2 ma per micro-microfarads change in capacity and a current range of 5 to 40 ma can be obtained with 25L6 oscillator tubes. This transducer circuit has the following advantages: Its sensitivity, current range, and the shape of the current capacity curve can be readily changed. It is simple to operate. It can be used to study vibrations or capacity changes having frequencies from 0 to over 200 kc per second. Its sensitivity depends on absolute changes in capacity rather than the relative change in total capacity. It has low background noise level. It is free from interference by local magnetic and electrostatic fields without requiring shielding, except when such fields are close to the operating frequency of the two oscillators.
A Versatile Oil-Testing Cell of Novel Design
Authors: Hazen Thomas
Published: February 2005

An inexpensive oil-testing cell for use in routine determinations of the electrical properties of insulating oils, liquid dielectrics, plasticizers, etc., is described. The cell consists of two concentric cylindrical electrodes designed to fit snugly inside a standard-sized test tube. The electrodes are insulated from each other by a standard type ceramic stand-off insulator fitted with banana plugs. The cell is assembled by plugging in the inner electrode. Satisfactory electrical measurements with cells of this type have been made over wide temperature and frequency ranges.
An Electronic Circuit to Control Intensity and Timing of Power for Spot Welding
Authors: Nottingham Wayne B.
Published: February 2005

A welder control is described which can deliver currents as high as 200 amperes R.M.S. for any predetermined time from a fraction of a half-cycle of the 60-cycle power supply to 60 half-cycles. At any specified timing, the intensity may be controlled continuously from zero to its maximum value. The operation of the control depends on the co-ordinated application of two electronic circuits which individually or together have many other uses. The one circuit is a regenerative d.c. amplifier which serves as a controlled square wave generator and the other is a ``biased multivibrator.'' The operation of these circuits is described in considerable detail so that they may be adapted to the solution of other electronic control problems. The construction of pool-type mercury rectifiers and the life tests on these are also presented.