bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving Quality Control and Workflow Management in High- Throughput Single-Nucleotide Polymorphism Genotyping Environments
Authors: Teuber Markus , Koch W. Andreas , Manaster Carl , Wächter Stefan , Hampe Jochen , Schreiber Stefan
Published: February 2005

Single-nucleotide polymorphism (SNP) genotyping is a fundamental tool in the rapidly growing area of complex diseases and pharmacogenomics. SNP patterns that correlate with disease or response to treatment, respectively, are identified using bioinformatic techniques. We present an integrated laboratory information and management system (LIMS) for our high-throughput TaqMan™-based SNP genotyping platform. Three new client tools (ProjectManager, AssayManager, OrderTool) for our LIMS improve quality control and workflow management. The programs support organizing multiple genotyping experiments as projects, managing reagents with barcodes, and automation of assay ordering. The tools are freely available at our homepage.
Diurnal variations in the hygroscopic growth cycles of ambient aerosol populations
Authors: Santarpia Joshua L. , Gasparini Roberto , Li Runjun , Collins Don R.
Published: February 2005

During August and September of 2002, a relative humidity (RH) scanning tandem differential mobility analyzer system was used to measure the deliquescence/crystallization properties of ambient aerosol populations in southeast Texas. During August, sampling was conducted at a rural site on the Texas A&M campus in College Station, and in September, sampling was conducted at an urban site near the Houston ship channel. Measurements from both sites indicate that there are cyclical changes in the composition of the soluble fraction of the aerosol, which are not strongly linked to the local aerosol source. The observations show that as temperature increases and RH decreases, the hysteresis loop describing the RH dependence of aerosol hygroscopic growth collapses. On the basis of results from other studies that have shown the dominant ions present in aerosols in this region to be ammonium and sulfate, it is proposed that this collapse is due to a decrease in the ammonium to sulfate ratio in the aerosol particles, which coincides with increasing temperature and decreasing RH. This cyclical change in aerosol acidity may influence secondary organic aerosol production and may exaggerate the impact of the aerosol on human health. The compositional changes also result in a daily cycle in crystallization RH that is in phase with that of the ambient RH, which reduces the probability that hygroscopic particles will crystallize in the afternoon when the ambient RH is a minimum.
Some Characteristics of a Gridded Parallel-Plate Ionization Chamber
Authors: Herwig Lloyd O. , Miller Glenn H. , Utterback Nyle G.
Published: February 2005

Studies have been made of effects encountered in the use of a gridded parallel-plate ion chamber for energy measurements. These effects are: gas multiplication about the grid structure, capture of electrons by the grid, and variation of saturation characteristics between various gases and gas mixtures. Curves relating to these are presented for He, Ne, A, Kr, N2, He+3% CO2, A+3% CO2, and A+5% N2. It is found that the field conditions necessary to prevent electron capture by the grid may be correlated with electron lateral diffusion. Anomalies in connection with the behavior of argon-carbon dioxide mixtures are pointed out, and several possible explanations for these are discussed.
Continuously Variable Mercury Delay Line Equipment for the Measurement of Short Time Intervals
Authors: Sheer C. , Zinn A. , Hartmann N.
Published: February 2005

This paper describes an equipment for the precision measurement of short time intervals as defined by two successive electrical pulses. It features two identically constructed mercury ultrasonic delay lines, one in each of two channels. These lines are precision built and extensible in length by approximately 10%. The measurement is made by first adjusting the lines for equal delay, feeding the pulses into the two channels, respectively, and then noting the extension of the line receiving the prior pulse which is required to bring the two output pulses into coincidence. A continuous range of measurement of 0 to 40 μsec is available, and the upper limit can be extended as desired by inserting fixed delays in one channel externally. Aside from the continuously variable feature, the instrument is characterized by relatively high precision capabilities, ease of measurement, versatility, and reliability of operation.
High Resolution Automatic Beta Spectrometer
Authors: Birkhoff Robert D. , Smith Arthur W. , Hubbell Harry H. , Cheka Joseph S.
Published: February 2005

A homogeneous magnetic field beta spectrometer and its completely automatic control system are described. Momentum resolution is such that a monoenergetic line has a full width at half maximum intensity of 0.22%. The instrument was used to analyze the conversion line spectrum of the 411-kev gamma ray from Hg198. The data give for the conversion ratios K:L:M:N values of 1:0.361:0.100:0.027; and for (LI+LII): LIII, the value 5.9.
Micromachining with Virtual Electrodes
Authors: Uhlir A.
Published: February 2005

Minute holes have been drilled in germanium, molybdenum, iron, copper, silver, and tungsten carbide by a new technique for machining by electrolytic etching. The flow of current is localized by a nonconducting partition in the electrolyte. The partition may be a glass tube drawn down to a tip as small as one micron diam. A variety of shapes can be produced by moving the tip with respect to the work. Holes 20 microns in diameter and 1 mm deep have been drilled; shallow grooves 2 microns wide have been made. Localized plating has also been accomplished with the technique.
Dynamic Deflection Transducer Utilizing Photoconductive Sensors
Authors: Papirno Ralph , Gerard George
Published: February 2005

A deflection transducer for dynamic studies in which the movable element has negligible inertia is described. The sensing element utilizes a light beam incident upon a photoconductive cell which is modulated by a suitably gridded film strip attached to the specimen at the desired location. The output of the photoconductive cell circuit is a varying voltage signal applied directly to a cathode ray oscilloscope. A calibration scheme is described and the results of tests are given. The data indicate agreement within 2% over the entire calibrated range of deflections.
Fast Counting System for High-Energy Particle Measurements
Authors: Madey Richard
Published: February 2005

A fast coincidence counting system for high-energy particle measurements combines a scintillation counter pulse-shaping circuit and a crystal diode coincidence circuit. The system is simple and reliable. Both the resolution time of the system and the double pulse separation time of the individual counters can be as short as three millimicroseconds, with essentially one hundred percent detection efficiency.
Operation of Proportional Counters at High Temperatures
Authors: Moljk A. , Drever R. W. P. , Curran S. C.
Published: February 2005

The operation of proportional counters at temperatures up to 900°C has been investigated and it is shown that the factors determining the maximum working temperature are thermal emission of electrons from the cathode, and the conductivity of heated insulating materials. Several types of proportional tubes are discussed and the advantages of counters with external cathodes are pointed out. Pulse spectra from quartz and glass counters containing K-capture A37 sources indicate satisfactory operation at temperatures of 810°C in the case of quartz and 450°C in the case of glass.
High-Pressure Diffusion Cloud-Chamber System
Authors: Schluter R. A. , Wright S. C.
Published: February 2005

The high-pressure diffusion cloud-chamber system in use at the University of Chicago is described. The chamber is characterized by (1) 30 atmospheres of hydrogen operating pressure, (2) a sensitive volume 16 inches in diameter and 2½ to 3 inches deep, (3) a quite uniform and accurately known magnetic field of 12 600 gauss, and (4) unit assembly in which the magnet pole is an integral part of the chamber. Pictures are analyzed by a three-dimensional reprojection system designed to eliminate optical distortion. Devices for rapid and accurate measurement of several different types of events are described.
Measurement of Curvature, Length, and Spatial Direction of Cloud-Chamber Tracks
Authors: Dicks J. B. , Hopkins J. I.
Published: February 2005

This method of obtaining information from stereoptic pictures of events in cloud chambers holds several advantages over methods currently in use. It permits the measurement of tracks which make large angles with the plane of the chamber. The equipment required is simple to construct. Errors involved in the measurements are small. About ten minutes are required to measure the energy and angular direction of a helical track. A disadvantage of this method is that the operator must have some experience in order to work effectively.
High Transmission Coincidence Spectrometer with Good Resolution
Authors: Gerholm T. R.
Published: February 2005

An electron-electron coincidence spectrometer is described. Magnetic lenses are used for the energy selection in each channel, and the coincidence counting efficiency is increased by using long lens spectrometers. At an effective transmission of 3%, relative half-widths of 1.3% (source diameter 0.2 cm) and 3.1% (source diameter 0.5 cm) were obtained. ``Triangular field'' focusing, introduced here, gives a favorable high luminosity in spite of small dimensions, distance between source and detector being only 25 cm in each half of the instrument. The focusing properties of this field form are discussed. Anthracene crystals cemented onto Lucite light guides serve as detectors, and it is shown that the light transmission efficiency of the guides can be considerably improved by machining them to a certain profile theoretically corresponding to 100% light collection. In practice efficiencies of 70−60% are obtained for Lucite light guides between 10 cm and 20 cm. The performance of the instrument is illustrated by some results obtained with coincidence measurements on the electron spectrum of Pb200.
Ionization in a Mass Spectrometer by Monoenergetic Electrons
Authors: Fox R. E. , Hickam W. M. , Grove D. J. , Kjeldaas T.
Published: February 2005

Over the last few years, a method has been developed for obtaining ionization probability curves with essentially monoenergetic electrons. A retarding potential is applied to the electron beam to yield an energy distribution with a sharp low-energy limit. By varying the retarding potential slightly, a new low-energy limit of the distribution can be selected. The difference in the ionization produced in the two cases is ionization by those electrons with a small energy spread selected from the original distribution. By pulsing the electrons and ions, it is possible to eliminate the adverse effect of the ion-drawout field on the electron energy. With this retarding potential difference (RPD) method, a detailed analysis of ionization probability curves is possible. A full description of this method is given in this paper with a discussion of its advantages and limitations. The mass spectrometer used in this series of studies is described, particular attention being given to a description of the ion source. The various electrodes of the electron beam slit system are described in terms of their influence on the electron energy, and on the shapes of ionization probability curves.
Rotary Device for Producing a Stream of Uniform Drops
Authors: Rayner A. C. , Haliburton Wm.
Published: February 2005

A rotary device was developed to produce uniform drops of liquids in the diameter range of 50 to 700 microns. A horizontally rotating blade detaches drops in a steady stream of regular trajectory, from a stabilized liquid mass fed under constant head through a stationary capillary. Its operation is described, and performance characteristics with oil and aqueous test solutions are given. Drop size is calculated from the mass of drops emitted in a given interval at a known generation frequency. Variation in size of individual drops, electrostatic effects, and some uses for the machine are noted.
Absolute Measurement of Cyclotron Beam Currents for Radiation-Chemical Studies
Authors: Schuler Robert H. , Allen Augustine O.
Published: February 2005

Characteristics are described for the collection of cyclotron beams in a conducting medium separated from the accelerator by an insulating window. The measured current can be interpreted in terms of an absolute beam current if charge displacement within the insulator is taken into account. Collection of the beam in this manner is particularly advantageous in a region external to the cyclotron magnetic field where stray currents due to air ionization and secondary electron emission are pronounced. A comparison is made between particle energies determined by the charge-input method and by calorimetry. A simplified arrangement for particle range determination is described.
Precision Seconds Pulse Timing System
Authors: Taylor R. Dean , Kilpatrick John E.
Published: February 2005

A timing system is described which provides sharp, one-millisecond, electric pulses at one-second intervals. These pulses are used to actuate a trigger circuit which is used to control one or more relays. The accuracy of the time scale can easily be checked against radio station WWV. Auxiliary apparatus can be controlled for time intervals of any even number of seconds. The accuracy of this interval can be determined to better than one millisecond. This system has proved to be particularly useful in calorimetry.
Improved Alpha Air Proportional Counter
Authors: Lynch Frank J. , Baumgardner James B.
Published: February 2005

The limitations of alpha counters using air in the proportional amplification region were investigated with a view toward a better design that would provide improved performance and reliability. A new detector is described which incorporates a shielded guard-ring insulator assembly that provides freedom from insulator failure at high humidities. It is believed that spurious pulses also arise from the effect of humidity on the conductivity of foreign particles adhering to the anode wires. Reducing the relative humidity (rh) by the use of a small heater which maintains the detector 20°F above room temperature prevents this type of failure and provides reliable operation at 98% rh. The associated amplifier and discriminator were designed to detect the slow components of the ionization pulses associated with the transit time of negative oxygen ions. The resulting efficiency is 39% of the total disintegrations, with a plateau of over 150 volts having a slope of less than 4% per 100 volts.
C14 Dating with a Methane Proportional Counter
Authors: Burke W. H. , Meinschein W. G.
Published: February 2005

Apparatus and procedures for conversion of sample carbon to carbon dioxide, quantitative hydrogenation of carbon dioxide to methane, and radiocarbon assay of the methane are described. Two sizes of counters are used. At the operating pressure of two atmospheres, the larger size contains 0.85 g of carbon and the smaller 0.22 g. If the sample and background are both counted for 24 hours in a 0.85-g counter, a sample 34 000 years old (26 000 years old in the 0.22-g counter) gives a C14 count equal to twice its standard statistical error. If desired, this method can readily be adapted to larger samples with a consequent increase in the maximum measurable age.
Third-Order Aberration and Focusing with Sector-Shaped Magnetic Fields
Authors: Dempsey Daniel F.
Published: February 2005

A divergent beam of monoenergetic charged particles can be refocused by a homogeneous magnetic field whose sharply defined boundaries are straight lines or circles. The transverse aberration of order α3 at the image point is evaluated and a general third-order focusing condition is given. Design equations for third-order instruments are obtained and the results presented graphically. Many third-order focusing designs follow, both symmetrical and asymmetrical.
Time-of-Flight Mass Spectrometer with Improved Resolution
Authors: Wiley W. C. , McLaren I. H.
Published: February 2005

A new type of ion gun is described which greatly improves the resolution of a nonmagnetic time-of-flight mass spectrometer. The focusing action of this gun is discussed and analyzed mathematically. The validity of the analysis and the practicability of the gun are demonstrated by the spectra obtained. The spectrometer is capable of measuring the relative abundance of adjacent masses well beyond 100 amu.
Fast Neutron Coincidence Spectrometer. II
Authors: Chagnon Paul R. , Owen George E. , Madansky Leon
Published: February 2005

A fast neutron coincidence spectrometer utilizing stilbene scintillators is described. The principle of the spectrometer is based upon the pulse-height analysis of the recoil protons resulting from a 45 degree scattering of the incident neutron beam. This is achieved by requiring the scattered neutron to be recorded in a secondary ring of ten stilbene scintillators. With delays corresponding to a fixed time of flight, a coincidence between the primary and secondary crystals gates the primary pulse. At 4 Mev the efficiency is of the order of 10−4 per incident neutron, and the pulse-height distribution has a width at half-maximum of 17%. The corresponding energy width is 10%. The time-of-flight characteristic is used to reject gamma rays. Limitations caused by accidentals and pulse-height resolution are discussed.
Three-Terminal Dielectric Cell with a Floating Micrometer Electrode
Authors: Work Richard N.
Published: February 2005

A description is given of a three-terminal cell for dielectric measurements on polymeric materials over a wide temperature range. Use is made of a lightly spring-loaded, floating electrode to maintain good electrical contact with the specimen when it expands or contracts thermally. A differential-capacitor, built into the movable electrode, is used with a simple detector circuit to indicate the position of the electrode with respect to its micrometer-driven carriage. Simultaneous measurements can be made of cell capacitance and electrode separation. The latter can be determined with a precision of better than 10−4 inch. Provision is made to confine the specimen when it softens at temperatures above its glass-transition temperature. The cell has been operated successfully at frequencies between 20 cps and 1 Mc and at temperatures between 20 and 200°C.
New Multichannel Recording Time-Delay Analyzer
Authors: Koontz P. G. , Johnstone C. W. , Keepin G. R. , Gallagher J. D.
Published: February 2005

A new time-delay analyzer encompassing a wide flexible time base is described. Time channels of 0.001, 0.01, 0.1, 1, and 10 sec width are provided; these may be combined in progressive sequence or used individually for essentially an infinite number of channels. Provision is made for either photographic or electric recording. Data obtained with the new analyzer agree with a conventional ten-channel time-delay analyzer over the limited range of the latter. A simple procedure is given for checking correct operation of the system.
Betatron Oscillations in the Synchrotron
Authors: Hammer C. L. , Pidd R. W. , Terwilliger K. M.
Published: February 2005

Betatron oscillations in the University of Michigan synchrotron have been investigated by exciting these oscillations with a transverse electric field. The results indicate that the betatron oscillation is composed of a group of component frequencies which are separated by the frequency of synchrotron phase oscillation. The suggested explanation of the observed splitting is the modulation of the betatron oscillation frequency by the synchroton oscillations.
Technique for Measuring Small Differences in Surface Tension
Authors: Young Niels O.
Published: February 2005

Small differences in surface tension have been measured by a new method. The method makes use of a horizontal capillary tube, which may, for example, have a temperature gradient along its axis. The velocity of a small sample within the capillary may then be measured, or brought to zero by tilting the tube. As a check, the temperature coefficient of surface tension of benzene and n-decane was measured to within 2 percent of previously published values. The method seems to be particularly adapted to the investigation of small samples.
New Absolute Manometer for Vapor Pressures in the Micron Range
Authors: Ernsberger F. M. , Pitman H. W.
Published: February 2005

An absolute manometer is described which provides a means of measuring vapor pressures in the range 0.5 to 20 microns with a precision and accuracy of better than one percent. Construction and use of the manometer is described in detail and an analysis of the possible sources of error is given. The vapor pressure of mercury has been determined and is presented to give an example of the performance of the manometer.
Method for the Prompt Destruction of the Electron Beam in a Synchrotron. I
Authors: Hammer C. L. , Bureau A. J.
Published: February 2005

By passing current through coils wrapped around a section of the vacuum chamber of a synchrotron it is possible to change the fall-off index of a part of the guide field while leaving the remaining guide field unaltered. This technique is used on the Iowa State College 70-Mev synchrotron, and complete beam destruction is found experimentally to occur in less than 0.08 microseconds. The build-up of the radial oscillation is analyzed, and it is estimated that complete destruction of the beam is accomplished in approximately 10 revolutions or 0.06 μsec. The analysis also shows that this technique can be a valuable aid in the extraction of an electron beam from a synchrotron or betatron.
Multichannel Recording Apparatus for Physiological Studies
Authors: Scher Allen M. , Young Allan C. , Malmgren Arthur L.
Published: February 2005

Apparatus used in a study of the pathway of the excitation of the heart is described. The multipolar electrode consists of fifteen fine (50-μ) tungsten wires staggered at 1.0 or ½-mm intervals along a central shaft. Details of its construction are included. The electrode is used in conjunction with a sixteen-channel oscilloscope which permits recording from all terminals simultaneously. One channel is used for a time reference potential and one for a conventional electrocardiographic lead. A continuously variable circuit triggers the sweep. The delay is triggered by one heartbeat so that the depolarization of the heart during the next beat appears on the oscilloscope. Time signals are fed into all channels from a single oscillator. Circuit and schematic diagrams and experimental results are presented.
Apparatus for Measuring Resistivity and Hall Coefficient of Semiconductors
Authors: Dauphinee T. M. , Mooser E.
Published: February 2005

An apparatus for measuring resistivity and Hall coefficient of semiconductors is described. Using a new type of measuring circuit, it combines the best features of both ac and dc apparatus. Thus, on the one hand, errors due to thermal emf's and the Ettingshausen effect are eliminated while, on the other hand, the one necessary balance is still made on a simple dc potentiometer with a dc galvanometer as null indicator. Contact and lead resistances do not affect the readings. Results of resistance and Hall coefficient measurements on a germanium specimen are given as an indication of performance.
Liquid Nitrogen Generator
Authors: Collins S. C.
Published: February 2005

A low-pressure laboratory liquefier having a capacity of 45 to 50 liters per hour is described. A combination of old and new features makes possible continuous operation without an attendant. Impurities such as water, carbon dioxide, and oil are eliminated automatically by reversing exchangers. The liquid nitrogen product flows directly from the rectifier to a large external storage vessel. The net power requirement is approximately 50 kilowatts.
Automatic Drift Compensation in dc Amplifiers
Authors: Cederbaum I. , Balaban P.
Published: February 2005

The application of an automatic circuit for the periodical compensation of drift in dc amplifiers is described. The circuit consists principally of a relay and memory condenser and is analogous to that described by Offner [Rev. Sci. Instr. 25, 579 (1954)]. The difference is mainly in the application. Whereas Offner used the circuit to restore the balance in differential amplifiers, here it is applied to the drift compensation of an unbalanced straightforward or feedback dc amplifier.
High-Speed Rotating Cylinder for Rarefied Gas Dynamics Research
Authors: Maslach G. J. , Frisch J.
Published: February 2005

Recent interest in slip-flow phenomenon as applied to high-altitude supersonic flight problems has revived experimental activity aimed at determining slip-flow boundary conditions and evaluating empirical reflection and accommodation coefficients. A unique rotating cylinder apparatus has been designed and constructed for studies involving rarefied gas-surface interactions over a wide range of flow characteristics extending from continuum conditions to the free molecular flow region. In addition to the above studies the equipment can be used to generate a shear flow field essential to the development of instrumentation necessary for the measurement of rarefied gas flow boundary layers and other nonuniform flow conditions. The flow requirements and design considerations which govern the geometry of the system, the choice of vacuum pumping equipment, vacuum instrumentation, and the controlled speed centrifuge drive mechanism are discussed. The remotely controlled floating torsion balance system is described and the mechanical precision of the entire equipment is indicated.
Proton Recoil Fast-Neutron Spectrometer. Part I. Principles
Authors: Gossick B. R.
Published: February 2005

A general equation for calculating the neutron energy spectrum from proton recoil counting data is derived. This equation is optimized subject to a constant total error to determine the most favorable experimental conditions. Feasible accuracy is illustrated by presenting a family of curves of the counting time (required for one point of a spectrum) plotted against total error with source intensity as a parameter. The calculations apply only to a ``good geometry'' experiment with a point source.
Gamma-Ray Scintillation Spectrometer with Logarithmic Pulse-Height Response
Authors: Maeder D.
Published: February 2005

Practical use of scintillation spectrometers is unnecessarily complicated by the strong predominance of small pulses encountered especially in measuring complex spectra. The difficulties arising from this general trend can be reduced by deforming the pulse spectra before recording them in a conventional linear pulse-height analyzer. A discussion of energy dispersion obtained with different types of deformation shows that a logarithmic transformation not only multiplies the counting rates of the original spectrum with a factor proportional to energy, but at the same time increases the energy band which can be resolved with a given number of counting channels. The reduction of counting rate extremes obtained by such a transformation permits attainment of higher total counting speeds with given multichannel equipment (assuming equal scaling factors in all channels); on the other hand, it facilitates accurate intensity measurements using photographic recording techniques. An electronic circuit is described, which accepts input pulses having a sharp rise (<1 μsec) and produces, 30 μsec later, a dc voltage in linear relationship with log [input pulse height]. The 100-v range of the output voltage is adjustable to cover pulse-height ratios from 1:2 up to 1:50. Gray-wedge spectrograms of the γ rays from Ra taken with the usual linear and with the new logarithmic circuit are presented. Theoretical calculations, as well as measurements with various calibration sources show that the photopeak counting efficiency of a NaI spectrometer becomes nearly constant over a wide energy range when the logarithmic energy transformation is introduced.
Photometric Determination of Ionization of Cloud-Chamber Tracks
Authors: Björnerud E. K.
Published: February 2005

A photoelectric method for measuring the specific ionization of tracks on cloud-chamber photographs is described. An important feature of the method is the use of a comparison track of known ionization in the same part of the chamber. A microphotometer slit is made to scan the track perpendicular to its direction, and a tracing of the transmission of the track relative to the background transmission is obtained. A parameter relating the transmission of the track in question to the transmission of the comparison track is obtained directly from the tracings. Identified π-μ decays are used to establish a calibration curve, and the method is applied to various unknown tracks. The error of measurement is of the order of 10%. A theoretical treatment of the problem is carried out to show the effects of various physical parameters not easily ascertained experimentally.
Automatic Instrument for Electron Scattering Measurements
Authors: Marton L. , Simpson J. Arol , McCraw T. F.
Published: February 2005

An instrument capable of automatically recording the distribution in energy and angle of electrons scattered from solids is described. The energy range of the primary electrons is 10 to 50 kev. On a two-second cycle the instrument obtains and records an energy loss spectrum at a fixed angle, advances in angle, and repeats. The instrument will distinguish energy peaks less than 20 volts apart at 20 kev and angular details less than 10−3 radian apart.
Tracer-Type Instrument for Changing Scales in Two Mutually Perpendicular Directions
Authors: Freudenstein F. , Calcaterra P.
Published: February 2005

An instrument using linkages is described by means of which curves can be redrawn to different scales. The scale size in each of two mutually perpendicular directions can be varied independently and continuously within a certain range. In operation one point of the instrument traces the original curve while a second point on the instrument traces the changed curve. The scale change can be varied between a 2:1 reduction and a 20:1 magnification. The size of the changed curve is not less than 8½×11 in. and can be as large as 11×22 in. depending on the setting, the instrument itself measuring not less than 40×60 in.
Compensated Precision High-Voltage Attenuator
Authors: Cottingham J. G.
Published: February 2005

A high-voltage divider consisting of twelve 2.5 megohm units enclosed by metal spinnings is modified to have good frequency response up to 200 kc. This is done by compensating for the capacity of the spinnings to ground by introducing an appropriate capacity from the spinnings to the high-voltage source.
Apparatus for the Measurement of the Internal Friction of Metals in Transverse Vibration
Authors: Berry B. S.
Published: February 2005

Apparatus incorporating a specially designed piezoelectric pickup serving in turn as an exciter and detector is described for the measurement of the internal friction of vertically suspended specimens vibrating transversely in vacuo in the free-free mode. Measurements have been made by the free-decay method in the frequency range 5 cy/sec-2 kc/sec, and at maximum strain-amplitudes of 10−4−5×10−7. The method of frequency variation by loading with weights has been applied successfully to the fundamental vibration. Methods of investigating external energy losses are described, and results presented to show that the total external loss is small, rarely exceeding 5% of the observed internal friction.
Fast Trigger Circuit
Authors: Davidon William C. , Frank Richard B.
Published: February 2005

A trigger circuit has been developed using a 6BQ7A receiving tube with a recovery time of approximately 1.5×10−7 second and an input sensitivity of 0.17 volt. The circuit and test results are described.
Diffracted-Beam Monochromatization Techniques in X-Ray Diffractometry
Authors: Lang A. R.
Published: February 2005

Four techniques using curved-crystal focusing monochromators are described: combinations of a reflection specimen and reflection monochromator, a reflection specimen and transmission monochromator, a transmission specimen and reflection monochromator, and a transmission specimen and transmission monochromator. The first technique allows recording of diffraction patterns due to Kα1 radiation only, and elimination of Compton-scattered radiation (except at low angles). The second technique provides a back-reflection diffractometer for measurements at Bragg angles up to 90°. The third technique can be applied to weakly absorbing specimens when a strictly monochromatic diffraction pattern is required. Various aspects of the focusing geometry are analyzed.
Torsion Balance for a Single Microscopic Magnetic Particle
Authors: Yu S. P. , Morrish A. H.
Published: February 2005

The construction and principle of operation of a new type of quartz fiber torsion balance are described. The quartz suspension fiber used can be as small as 0.5-μ diameter. This enables magnetic measurements to be made on an individual microscopic magnetic particle of about 1-μ diameter.
Calculation of Heat Flow in a Medium the Conductivity of which Varies with Temperature
Authors: Garwin Richard L.
Published: February 2005

It is shown that the heat flow in a single homogeneous medium of thermal conductivity σ(T), between boundaries at temperatures T2 and T1 is the same as that for the same geometry in a medium of unit thermal conductivity and boundary ``thermal potentials'' Σ(T2) and Σ(T1), where Σ(T)=∫0Tσ(T′)dT′. Some applications are given, as well as a short table of Σ(T) for common cryogenic temperatures and materials.
Application of a Statistical Correlation Function for Determining Daughter Half-Lives in the Range 10−4 to 10−1 Second
Authors: Petroff Michael D. , Doggett Wesley O.
Published: February 2005

Discussed herein is the application of a statistical correlation method [Goldanski and Podgoretski, Doklady Akad. Nauk. S.S.S.R. 100, 237 (1955)] to the determination of the lifetime of an activity in equilibrium with a long-lived parent activity. It is shown that this method has a definite advantage over delayed-coincidence methods when the lifetime to be measured is of the order of 10−4 sec or longer. An electronic apparatus designed to perform the operations required by the statistical correlation method is described. This equipment has been used for a new determination, 0.293±0.020×10−3 sec, for the half-life of Y88m.
Absolute Low Speed Anemometer
Authors: Walker R. E. , Westenberg A. A.
Published: February 2005

An absolute anemometer suitable for measurements in gases under a wide variety of conditions is described. The instrument, based on an idea first used by Kovasznay, utilizes the temperature fluctuations in the wake of a sinusoidally heated fine wire as tracer. A second hot-wire detects the fluctuations, and the phase change between two successive positions of this wire can be used to determine the free stream velocity. The technique is shown to have good spatial resolution and an accuracy better than 2% in the velocity range 40–400 cm/sec. Sources of error and various experimental conditions are discussed in detail.
``Twin'' Scintillation Fast Neutron Detector
Authors: Berlman I. B. , Marinelli L. D.
Published: February 2005

Two organic scintillating solutions, containing the same total number of electrons, but differing by more than a fourfold in the total number of hydrogen atoms, are used to detect neutrons in the presence of a gamma-ray background. By suitable adjustments of their luminescence their pulse-height spectra can be made to coincide in the presence of gamma radiation; hence by subtracting the spectrum of one solution from that of the other it is possible to obtain the pulse-height spectrum due to the excess of proton recoils in the latter. Although refinements in the interpretation of its response must wait for basic information on the luminescent efficiency of both protons and electrons of various energy, this detector is simple to build, stable in time, isotropic in response, and suitable to evaluate radiation hazards in the presence of mixed radiations. Typical responses to gamma radiation, D-D, and D-T neutrons are presented.
Heat of Water Vaporization as a Chemical Calibration Standard for Solution Calorimetry
Authors: Ray James D.
Published: February 2005

A simple method for calibration of calorimeters used in solution calorimetry has been devised. The heat of vaporization of water is taken as a chemical standard for this process and shown to be unaffected by the speed and pressure employed in pumping it out of the evaporator described.
Simple Aid to Infrared Intensity Measurements
Authors: Arends C. B. , Eggers D. F.
Published: February 2005

A device is described for the simple, accurate determination of infrared absorption intensity directly from spectral curves. Variations in incident energy and stray light will not introduce errors. Comparison with the conventional method on some bands of isotopic carbon dioxide shows the same integrated intensity, but a great saving in time by this device.
Apparatus for the Production of Large Water Drops
Authors: Magarvey R. H. , Taylor B. W.
Published: February 2005

Drop generators are described for the production of streams of drops the equivalent diameters of which are between 0.5 and 20 mm. These generators are based on the principle of the interrupted jet described by Lord Rayleigh. An assessment is made of the advantages and disadvantages of drop production based on this principle, and data given showing a high degree of uniformity of drop size. Accurate size control and determination are discussed relative to the execution of experiments designed to measure the physical properties of drops during free fall. In order to study the instability and breakup of large drops, reasonably well-formed drops are produced with equivalent diameters that are extremely difficult to produce by any other method. The behavior of large drops during free fall is concerned with theories of drop size distribution in natural rain.
Accurate Method for Measurement of Microwave Attenuation
Authors: Fulford J. A. , Blackwell J. H.
Published: February 2005

An accurate method for the measurement of microwave attenuation has been developed in which the change in microwave power fed to a thermistor is compared with an equal amount of low-frequency (1 kc) power supplied to the same thermistor through a precision attenuator pad.

The method is a modification and refinement of one originally suggested by Montgomery but employs two thermistors in the measuring circuit, an arrangement resulting in improved accuracy and stability.
Controlled Capillary Gas Leak
Authors: Smither R. K.
Published: February 2005

A relatively simple adjustable capillary leak is described in which the gas flow is controlled by regulating the temperature of the gas in the capillary. This capillary leak contains no moving parts and can be controlled from a distance. The actual controlled flow is compared with the theoretical predictions, and a calibration curve is shown.
Magnetostrictive Electricity in Strain Gauges
Authors: Vigness Irwin
Published: February 2005

Ferromagnetic wires, that have been suitably conditioned, generate electrical potentials when subjected to changes in elastic strain. Conditioning the wires involves alignment of the circumferential component of the magnetic field, due to domains, in a preferred direction. This is accomplished by the magnetic field associated with a current passed through the wire. A disturbance which changes this established circumferential field causes a potential to appear between the ends of the wire.
Hot Wire Liquid-Level Indicator
Authors: Maimoni Arturo
Published: February 2005

The theory of the method of measurement of liquid level by measurement of the resistance of a heated wire is developed, and it is applied to the design of a liquid-nitrogen-level indicator having a power dissipation of 3.4 mw/in. of length and a deviation from linearity in the calibration of less than 0.1 in. over its working length of 2.0 in. The apparatus should be applicable to the measurement of level of low viscosity liquids and its sensitivity is limited only by the temperature coefficient of resistance of the heated wire.
Microdensitometer for Photographic Research
Authors: Altman Joseph H. , Stultz Keith F.
Published: February 2005

A recording microdensitometer is described that has a resolving power of 800 lines/mm when the scanning aperture is 1 μ wide and 200 μ long. The response is linear in density to 3.0 for the same aperture. By narrowing the aperture to 0.1 μ, the resolving power can be increased to 1800 lines/mm. The record is made either on chart paper with rectangular coordinates, on punched cards, or on both.
Cryostat for Spectrophotometric Measurements
Authors: Jones Thomas O. , Willard John E.
Published: February 2005

A cryostat is described which will maintain optical cells at any temperature from −190°C to 0°C while they are being scanned in a recording spectrophotometer. Liquid air is used as the refrigerant and the temperature is adjusted by means of an electrical resistance heater. Fogging of the optical system is avoided by circulation of the dry refrigerant vapors and by window heaters.
Frequency-Sensitive Switching Circuit
Authors: Earnshaw J. B.
Published: February 2005

A frequency-sensitive switching circuit is described which automatically selects between two ranges of an otherwise conventional frequency meter by switching the leak resistor of the integrating circuit. The basis of the unit is a diode pump integrator operated as a nonlinear device to obtain maximum sensitivity. The sensitivity is such that the ``on-off'' backlash of the switching relay corresponds to less than 1% of the switching frequency.
Rotating Electrometer for Comparative Work Function Measurements
Authors: Kolm H. H.
Published: February 2005

An apparatus for measuring work functions by the Kelvin method is described in which the customary vibrating motion is replaced by rotary motion. A set of three coplanar samples is mounted on a turntable which rotates below a set of three stationary samples. This arrangement permits simultaneous observation of three electrode pairs in all permutations and provides ready access to the sample surfaces for purposes of treatment, illumination, inspection, etc., without the necessity for repositioning. The rigid structure also permits the application of electrostatic fields between electrodes, which is difficult in a vibrating system. Measurements can be made in high vacuum by driving the turntable inductively with coils located outside the glass envelope. The instrument has a sensitivity of ±1 millivolt.
Linear Theory of Betatron Oscillations in Sectorial Cyclotrons
Authors: Teng Lee C.
Published: February 2005

In a sectorial cyclotron the ``force functions'' and the frequencies of the linearized normal and axial betatron oscillations are given as power series in the inverse-square of the number of sectors. The coefficients in these series are expressed either in terms of parameters characterizing the magnetic field or in terms of those specifying the family of equilibrium orbits. The first-order terms agree with those in existing approximate expressions. Among other features of the higher order terms, they show that it is possible to design magnetic fields with momentum compactions varying over wide ranges and frequencies of betatron oscillations remaining constant. Together with a scheme proposed earlier of transferring ions continually between circular accelerators, this opens the possibility of accelerating ions continually in several stages of constant-frequency sectorial cyclotrons to multi-Bev energies. This method of analysis can also be applied to the study of nonlinear betatron oscillations.
Measurement of Short Carrier Lifetimes
Authors: Wertheim G. K. , Augustyniak W. M.
Published: February 2005

Semiconductor carrier lifetimes as short as 10−8 sec may be obtained from the decay of bombardment conductivity following pulsed excitation by high energy (700 kev) electrons from a Van de Graaff accelerator. Bombardment damage of the sample is minimized by the use of short pulses (2×10−8 or 3×10−4 sec) and a low repetition rate (15 or 30 pulses per sec). Modification of a standard accelerator for these measurements is discussed in some detail and some typical results are presented.
Effect of an Axial Cavity on the Temperature History of a Surface Heated Slab
Authors: Masters Joseph I. , Stein Seymour
Published: February 2005

A theoretical study is made of the surface temperature of a front heated slab in the presence of small holes drilled to within a fraction of a centimeter of the heated surface. In addition, equations and calculations are presented which yield an estimate of the error incurred when the surface temperature is measured by a transducer located at the end of such a hole.

In the absence of a practical exact solution to the problem, the method of attack chosen here leads to an upper bound on the additional surface temperature or hot spot caused by a cavity. The upper bound is justified because it is a close upper bound and, for cavity dimensions in the range of interest, the resulting hot spot is quite small. It is shown, for instance, that a ½-mm hole drilled to within 1 mm of the exposed surface will cause a time variant surface hot spot that is no more than 1.5% of the surface temperature. If the hole depth is reduced to ½ mm, then the hot spot is less than 5.5% of the surface temperature.

An additional finding is that the magnitude of the hot spot is nearly independent of the temporal shape of the surface heat pulse for a large variance in the latter.
Compound Ion-Resonance Mass Spectrometer
Authors: Robinson Charles F.
Published: February 2005

A new mass spectrometer, which constitutes essentially a low-resolution 180° instrument and a cyclotron in series, is proposed. The instrument appears to have substantial merits in freedom from space charge, discrimination, and gas scattering, in signal available, and in the possibility of differential pumping, while retaining the important features that the fine resolution depends only on the instrument parameters and the e/m of the ion involved.
Calibration of Current Integrators for Small Beam Currents
Authors: Royden Herbert N. , Caldwell David O.
Published: February 2005

The current-time method of calibrating beam current integrators has been extended to give reliable calibrations for small currents when used with a feedback electrometer. The method described has given calibrations with absolute standard errors ranging from 0.2% at 10−10 amp to 0.3% at 10−11 amp. The equipment needed, including a precision 100-megohm resistance, is described, and some experimental difficulties in making calibrations for small currents are discussed.
Thermistor Temperature Control
Authors: Malmberg Paul R. , Matland Carl G.
Published: February 2005

A temperature controller using small bead thermistors as temperature sensing elements has been developed. The controller has an over-all range of +20 to +300°C, or −60 to +190°C, using 51A2 or 32A12 thermistors, respectively, in an ac bridge. Extension of the operating temperature range to other limits is possible using other sensing elements. Linear proportional action is achieved with power relay output by comparing the amplified and rectified bridge signal with a stable and linear sawtooth wave form. This comparison controls the fractional ``on'' time of the power relay during a periodic ``on-off'' cycle. The controller offers stable control under all conditions of unbalance, and is stable to 0.1°C or better over an eight-day period.