bluuebunny/crossref_metadata_2025 huggingface dataset:
Persistence of topographic controls on the spatial distribution of snow in rugged mountain terrain, Colorado, United States
Authors: Erickson Tyler A. , Williams Mark W. , Winstral Adam
Published: April 2005

We model the spatial distribution of snow depth across a wind‐dominated alpine basin using a geostatistical approach with a complex variable mean. Snow depth surveys were conducted at maximum accumulation from 1997 through 2003 in the 2.3 km2 Green Lakes Valley watershed in Colorado. We model snow depth as a random function that can be decomposed into a deterministic trend and a stochastic residual. Three snow depth trends were considered, differing in how they model the effect of terrain parameters on snow depth. The terrain parameters considered were elevation, slope, potential radiation, an index of wind sheltering, and an index of wind drifting. When nonlinear interactions between the terrain parameters were included and a multiyear data set was analyzed, all five terrain parameters were found to be statistically significant in predicting snow depth, yet only potential radiation and the index of wind sheltering were found to be statistically significant for all individual years. Of the five terrain parameters considered, the index of wind sheltering was found to have the greatest effect on predicted snow depth. The methodology presented in this paper allows for the characterization of the spatial correlation of model residuals for a variable mean model, incorporates the spatial correlation into the optimization of the deterministic trend, and produces smooth estimate maps that may extrapolate above and below measured values.
Dynamic carbon dioxide exchange through snowpack by wind‐driven mass transfer in a conifer‐broadleaf mixed forest in northernmost Japan
Authors: Takagi Kentaro , Nomura Mutsumi , Ashiya Daitaro , Takahashi Hiroyuki , Sasa Kaichiro , Fujinuma Yasumi , Shibata Hideaki , Akibayashi Yukio , Koike Takayoshi
Published: April 2005

CO2 efflux in the period of snow cover can be a large carbon source in the yearly carbon budget of snowy ecosystems. However, the behavior of CO2 in snowpacks and the mechanisms of the snow surface efflux are still unclear. We performed continuous (half‐hourly) midwinter measurements of CO2 concentrations in a conifer‐broadleaf mixed forest snowpack, and found that concentrations in the snowpack fluctuated significantly as wind speeds varied. The snow surface efflux was evaluated as the sum of the CO2 storage change in the snowpack and the CO2 input from the soil to the snowpack, taking into account the mixing due to airflow. The median value over 52 days (49 mmol m−2 d−1) was almost the same as the daily net ecosystem exchange rate in this forest (50 mmol m−2 d−1) estimated by the eddy covariance technique and the storage‐change flux in the air column. These values are clearly larger than the value we estimated using Fick's law of diffusion. These results show that airflow can be a dominant cause of mixing within snowpacks in midwinter. In addition, in the soil pores under the snowpack, the CO2 concentration was primarily related to air temperature, implying that soil respiration responds directly to air temperature, not to soil temperature, even beneath a 1‐m‐thick snowpack. We infer that the air temperature affected the root activity of trees through their trunks and that the variation in root respiration strongly affected the CO2 concentration fluctuation in soil under the snowpack.
Intrabasin comparison of surface radiocarbon levels in the Indian Ocean between coral records and three‐dimensional global ocean models
Authors: Grumet Nancy S. , Duffy Philip B. , Wickett Michael E. , Caldeira Ken , Dunbar Robert B.
Published: April 2005

Oceanic uptake and transport of bomb‐produced radiocarbon is used as a diagnostic in global ocean models to test parameterizations of mixing and air‐sea gas exchange between the ocean and atmosphere. A model's ability to simulate bomb‐produced 14C is also a good indicator of its ability to predict uptake of anthropogenic CO2. We have conducted a model‐data comparison of surface radiocarbon time series from coral records from the coasts of Kenya and Sumatra and a suite of dynamical three‐dimensional ocean models that were included in the second phase of the Ocean Carbon‐Cycle Model Intercomparison Project. The coral records comprise the first intrabasin record of surface water Δ14C variability in the equatorial Indian Ocean and provide an independent evaluation of model performance. Differing treatments of lateral subgrid scale mixing in different models appear to be less important than other, unknown factors in explaining differences in results between the models. Those models that include a dynamic vertical mixing scheme appear to be more capable of matching observed coral radiocarbon time series. However, among models with the same parameterization of lateral subgrid scale mixing, there is a large degree of variation, suggesting that at both sites, factors such as resolution, topography, physical forcing and horizontal advection are more important than mixing parameterization in explaining intermodel differences. None of the models reproduce the time lag in the rate of bomb 14C response between the Kenya and Sumatra coral sites. Future efforts are needed to improve model simulation of radiocarbon in surface waters in the equatorial Indian Ocean.
Impacts of future land cover changes on atmospheric CO2 and climate
Authors: Sitch Stephen , Brovkin Victor , von Bloh Werner , van Vuuren Detlef , Eickhout Bas , Ganopolski Andrey
Published: April 2005

Climate‐carbon cycle model CLIMBER2‐LPJ is run with consistent fields of future fossil fuel CO2 emissions and geographically explicit land cover changes for four Special Report on Emissions Scenarios (SRES) scenarios, A1B, A2, B1, and B2. By 2100, increases in global mean temperatures range between 1.7°C (B1) and 2.7°C (A2) relative to the present day. Biogeochemical warming associated with future tropical land conversion is larger than its corresponding biogeophysical cooling effect in A2, and amplifies biogeophysical warming associated with Northern Hemisphere land abandonment in B1. In 2100, simulated atmospheric CO2 ranged from 592 ppm (B1) to 957 ppm (A2). Future CO2 concentrations simulated with the model are higher than previously reported for the same SRES emission scenarios, indicating the effect of future CO2 emission scenarios and land cover changes may hitherto be underestimated. The maximum contribution of land cover changes to future atmospheric CO2 among the four SRES scenarios represents a modest 127 ppm, or 22% in relative terms, with the remainder attributed to fossil fuel CO2 emissions.
Direct and indirect effects of experimental warming on ecosystem carbon processes in a tallgrass prairie
Authors: Wan Shiqiang , Hui Dafeng , Wallace Linda , Luo Yiqi
Published: April 2005

This study was conducted to examine direct and indirect impacts of global warming on carbon processes in a tallgrass prairie in the U.S. Great Plains. Infrared radiators were used to simulate global warming, and clipping was used to mimic hay mowing. Experimental warming caused significant increases in green biomass in spring and autumn and total biomass in summer on most of the measuring dates. Green aboveground biomass showed positive linear correlations with soil temperature in spring and autumn whereas total aboveground biomass in summer was negatively correlated with soil temperature. Experimental warming also affected aboveground biomass indirectly by extending the length of growing season and changing soil nitrogen process. Elevated temperature tended to increase net nitrogen mineralization in the first year but decrease it in the second year, which could be attributable to stimulated plant growth and belowground carbon allocation and consequently enhanced microbial nitrogen immobilization. Warming‐induced changes in soil respiration were proportional to those of total aboveground biomass. Clipping significantly reduced aboveground biomass and increased root biomass, but had no effect on net nitrogen mineralization and annual mean soil respiration. The proportional changes in soil respiration to those of aboveground biomass indicate warming‐stimulated ecosystem carbon uptake could be weakened by increased carbon release through soil respiration.
Laboratory investigations into the electromagnetic properties of magnetite/silica mixtures as Martian soil simulants
Authors: Pettinelli E. , Vannaroni G. , Cereti A. , Pisani A. R. , Paolucci F. , Del Vento D. , Dolfi D. , Riccioli S. , Bella F.
Published: April 2005

In this paper a set of frequency domain (500 Hz to 1 MHz) experimental data on electrical and magnetic parameters of magnetite/silica mixtures as Martian soil simulants is presented. Complex permittivity was obtained by measuring the magnitude and phase of the electrical impedance of a capacitive cell filled with the tested material. Complex magnetic permeability was obtained by measuring the impedance of a toroid fully embedded in the mixtures. Both the permittivity and magnetic permeability exhibited an appreciable increase with the magnetite volume fraction and a complex behavior with grain size and origin. Furthermore, to assess the possibility of extending the data acquired at 1 MHz to higher frequencies (tens to hundreds of MHz), some comparisons were made between these data and Time Domain Reflectometry measurements. Finally, the attenuation versus magnetite volume fraction and frequency (in a band consistent with the MARSIS and SHARAD sounders) was computed for various types of magnetite/silica mixtures. The results indicate that in a dry soil which contains a significant fraction of magnetic material both the wave velocity and the attenuation are a combination of different factors, including the dimension, shape, and origin of the magnetic material.
Magnetotelluric measurements in SW Iberia: New data for the Variscan crustal structures
Authors: Almeida Eugénio , Monteiro Santos F. , Mateus António , Heise Wiebke , Pous Jaume
Published: April 2005

Thirty new MT soundings were carried out in SW Iberia allowing the investigation of the lateral continuity of some major structures and lithological features that are believed to control decisively the deep architecture of the Ossa Morena Zone belts. Results of the two‐dimensional inversion of the data reveal high‐conductivity zones in the middle‐lower crust, interpreted as the signal of a granulitic basement with grain‐boundary interconnected films of graphite. The resistive features, located preferentially in the upper‐middle crust, are ascribable to igneous complexes of variable age.
Tumour necrosis factor α‐induced adipose‐related protein (TIARP): co‐localization with caveolin‐1
Authors: Chambaut‐Guérin Anne‐Marie , Pairault Jacques
Published: April 2005

We previously identified TIARP (TNFα‐induced adipose‐related protein, where TNFα stands for tumour necrosis factor α), a novel plasma‐membrane protein that is induced during 3T3‐L1 preadipocytes differentiation by TNFα. Whereas the biological function of TIARP is currently unknown, its protein sequence is reminiscent of transporter protein and/or NAD(P)/NAD(P)H‐dependent oxidoreductase activities. We hypothesized that TIARP could be associated with the 3T3‐L1 adipocyte plasma‐membrane caveolae domains that contain many proteins involved in cellular trafficking and signalling processes. Studies by confocal microscopy showed that TIARP and caveolin‐1, a major protein of caveolae, co‐localized as patches at the plasma membrane. Immunoblot analysis of cell extracts indicated that TIARP was completely detergent‐extractible from membranes, whereas caveolin‐1 was present as both detergent‐extractible and ‐insoluble pools. Since TIARP is compartmentalized with caveolin‐1 within caveolae domains, we suggest this protein to be part of a signalling complex in association with caveolin‐1 and regulatory proteins.
Stem‐cell‐driven regeneration of synovial joints
Authors: Mao Jeremy J.
Published: April 2005

Mammalian skeletal motion is made possible by synovial joints. Widespread suffering from arthritis and joint injuries has motivated recent effort to regenerate a stem‐cell‐driven synovial joint condyle implantable in total joint replacement. A single adult stem cell lineage, mesenchymal stem cells, differentiate to form all components of a synovial joint. Whereas localized joint lesions may be repaired by either cell‐based or cell‐free approaches, regeneration of the entire articular condyle of the synovial joint is unattainable without tissue‐forming cells. A series of experiments are presented here to describe our initial attempts to regenerate a synovial joint condyle in the shape and dimensions of a human mandibular condyle, with both cartilaginous and osseous components derived from a single population of rat mesenchymal stem cells. Upcoming challenges are along several intertwining fronts including structural integrity, tissue maturation, mechanical strength and host integration. The synovial joint condyle may turn out to be one of the first ‘human body parts’ or organs truly regeneratable by stem‐cell‐derived approaches. Current approaches to regenerate the synovial joint condyle from stem‐cell‐derived multiple cell lineages may also offer clues for engineering complex organs such as the kidney or liver.
Abnormalities in cardiac baroreceptor sensitivity in acute ischaemic stroke patients are related to aortic stiffness
Authors: EVESON David J. , ROBINSON Thompson G. , SHAH Nainal S. , PANERAI Ronney B. , PAUL Sanjoy K. , POTTER John F.
Published: April 2005

Cardiac BRS (baroreceptor reflex sensitivity) is impaired following ischaemic stroke and predicts the risk of subsequent long-term death and disability. Impaired cardiac BRS may be due to impaired central processing of baroreceptor information following stroke or reduced baroreceptor activity due to increased large artery stiffness. We evaluated the relationship between large (aortic) artery stiffness and cardiac BRS during the acute phase of ischaemic stroke and in comparison with a group of stroke-free control subjects. Thirty-one ischaemic stroke patients were studied within 48 h of onset and again on day 14, along with 26 control subjects free of cerebrovascular disease. Cardiac BRS (determined by spectral analyses) and arterial stiffness estimated by PWVcf (carotid–femoral pulse wave velocity) using applanation tonometry were obtained. At baseline, cardiac BRS was lower in the stroke compared with the control group (4.3±2.3 compared with 6.5±4.2 ms/mmHg; P<0.05). Cardiac BRS values were correlated with PWVcf at <48 h (r=−0.51, P<0.01) and on day 14 (r=−0.54, P<0.01), but not in the control group (r=−0.27, P=not significant). In quantile regression models, taking into account the effect of all cardiovascular variables, cardiac BRS was independently related to PWVcf at baseline and on day 14 in the stroke patients, but stroke was not related to cardiac BRS level when other cardiovascular variables were considered. Wall stiffness of the arterial vessels involved in the baroreflex arc may account for, at least in part, the reduced cardiac BRS observed in acute stroke patients.
Folic acid treatment increases homocysteine remethylation and methionine transmethylation in healthy subjects
Authors: STAM Frank , SMULDERS Yvo M. , van GULDENER Coen , JAKOBS Cornelis , STEHOUWER Coen D. A. , de MEER Kees
Published: April 2005

Folic acid treatment decreases plasma total homocysteine concentrations in healthy subjects, but the effects on homocysteine metabolism are unknown. In the present study, we investigated the effect of 3 weeks of oral treatment with 5 mg of folic acid on one-carbon flux rates in 12 healthy subjects, using in vivo stable isotope methods. In addition, we determined the effect of folic acid on blood concentrations of amino acids which may have regulatory roles in homocysteine metabolism, i.e. homocysteine, AdoMet (S-adenosylmethionine), AdoHcy (S-adenosylhomocysteine), serine and glycine. Primed, continuous infusions with [2H3-methyl-1-13C]methionine were used to determine flux rates of methionine transmethylation, homocysteine remethylation and homocysteine trans-sulphuration. Metabolic homocysteine clearance was defined as the ratio of trans-sulphuration and plasma homocysteine level. Folic acid treatment increased the homocysteine remethylation rate by 59% [95% CI (confidence interval), 13–97%; P=0.02] and methionine transmethylation rate by 20% (95% CI, 3–41%; P=0.03). Plasma total homocysteine concentration (−18%; 95% CI, −28 to −9%; P<0.01) and the serine/glycine ratio (−20%; 95% CI, −63 to −6%; P<0.01) decreased significantly, and the AdoMet/AdoHcy ratio (11%; 95% CI, 1–20%; P=0.02) increased significantly. Changes in one-carbon flux rates did not correlate significantly with changes in plasma concentration of these amino acids. In conclusion, folic acid treatment lowered plasma homocysteine concentration and increased whole-body remethylation and transmethylation flux in healthy subjects.
Analysis of human neurological disorders using mutagenesis in the mouse
Authors: OLIVER Peter L. , DAVIES Kay E.
Published: April 2005

The mouse continues to play a vital role in the deciphering of mammalian gene function and the modelling of human neurological disease. Advances in gene targeting technologies have facilitated the efficiency of generating new mouse mutants, although this valuable resource has rapidly expanded in recent years due to a number of major random mutagenesis programmes. The phenotype-driven mutagenesis screen at the MRC Mammalian Genetics Unit has generated a significant number of mice with potential neurological defects, and our aim has been to characterize selected mutants on a pathological and molecular level. Four lines are discussed, one displaying late-onset ataxia caused by Purkinje cell loss and an allelic series of three tremor mutants suffering from hypomyelination of the peripheral nerve. Molecular analysis of the causative mutation in each case has provided new insights into functional aspects of the mutated proteins, illustrating the power of mutagenesis screens to generate both novel and clinically relevant disease models.
Thermionic Emission from Oxide Cathodes: Retarding and Accelerating Fields
Authors: Hung C. S.
Published: April 2005

An experimental investigation of the thermionic emission from oxide-coated cathodes is presented in which the applied voltage range extends from the retarding potential region through zero field and up to an average accelerating field of 50,000 volts per cm. The retarding potential range yields information concerning the energy distribution of the electrons emitted, and indicates an excellent agreement between theory and experiment for high retarding fields. Near zero field, cathode inhomogeneity or patch effect may be responsible for the deviations found. Consideration is given to the influence of a possible reflection effect, but theoretical calculation indicates that with the large area cathode used, the simultaneous reflection at the emitter and the collector surfaces so alter the observed current voltage relationship, that the existence or non-existence of a reflection effect cannot be determined by the experiment. Results shown in the accelerating field region up to 50,000 volts per cm are accounted for on the bases of two assumptions which are (1) patch effect for small accelerating fields and (2), the intensification of the field at sharp points expected in view of the inherent roughness of the cathodes studied. The deviation of the experimental results from those predicted by the Schottky mirror image theory is explained over the whole range of observation by these two assumptions.
Augmented Flames in Half-Open Tubes
Authors: Evans Marjorie W. , Scheer Milton D. , Schoen Louis J. , Miller Emmy L.
Published: April 2005

High velocity flames in half-open tubes produced by placing a grid augmenter in the path of an advancing flame are described. High speed schlieren motion pictures and instantaneous pressure measurements are used to study flame structure and accompanying flow in the tube. It is found that the grid augmenter causes a mixing of burning and unburned gases, resulting in an increase in reaction surface. As a result the total amount of reaction per unit time per unit volume is increased, thus leading to the observed high velocities.
Static Magnetic Storage and Delay Line
Authors: Wang An , Woo Way Dong
Published: April 2005

Magnetic cores with a rectangular hysteresis loop are used in a storage system which requires no mechanical motion and is permanent. The binary digit ``1'' is stored as a positive residual flux, and the binary digit ``0'' as a residual flux in the opposite direction. When a negative probing field is applied to the core, a large voltage is induced in another winding if the digit stored has been a ``1,'' and very small voltage if it has been a ``0.'' The induced voltage in the former case is large enough to magnetize another core of identical construction. Binary digits can thus be transferred from one core into another. Many cores are arranged in tandem to form an information delay line. Binary digits can be advanced along the line step by step. The present upper limit of the speed of propagation is about 35,000 digits per second, and there is no lower limit.
Interference of Growing Spherical Precipitate Particles
Authors: Wert C. , Zener C.
Published: April 2005

The exact theory of the rate of growth of spherical precipitate particles has previously been developed for the initial stage where the individual precipitate particles do not interfere with one another. In the present paper this theory is carried one stage further to include their mutual interference. It is found that in the particular case of a very dilute solution this interference may be accounted for in a relatively simple manner. The applicability of the theory has been tested by new observations upon the precipitation of carbon from α-iron. Good agreement is found up to 95 percent completion of precipitation.
Turbulence in Apparatus for Measurement of Streaming Double Refraction
Authors: Jerrard H. G.
Published: April 2005

The different apparatus used by some thirty investigators, who have induced double refraction in a liquid contained in the annular gap between two concentric cylinders, are examined with particular reference to the onset of turbulence. In the case where the outer cylinder alone rotates, curves are given which easily enable the critical gradients corresponding to the dimensions of the apparatus used to be found. The results of the examination are so tabulated that present and future workers in this field can quickly decide on the significance of the measurements obtained by any of the investigators. An explanation is put forward of the surprising fact that with either the inner or outer cylinder rotating measurements of double refraction apparently show no very sharp break between regions of laminar and turbulent flow. The value of making simultaneous measurements of streaming double refraction and viscosity is pointed out and the advantages of using an apparatus with rotating outer and stationary inner cylinder are briefly summarized. Mention is made of optical design.
Effective Stress and Effective Strain in Relation to Stress Theories of Plasticity
Authors: White G. N. , Drucker D. C.
Published: April 2005

The correlation of experimental data and the proper description of the state and history of deformation of work-hardening materials has received much attention. An often desired objective is the plotting of a variable involving stress alone, a so-called effective stress, against a variable depending on the instantaneous strain or the history of strain, effective strain. Quantities such as maximum or octahedral shearing stress and strain or better an integrated effective strain increment have been employed. Also, simple effective stress definitions have been given for anisotropic as well as isotropic metals by Dorn, by Jackson, Smith, Lankford, and by previous investigators.

It is shown that the stress-strain relations of a recent theory of plasticity provide a very convenient means of defining and studying effective stress and effective strain. The strong theoretical and practical limitations of such concepts are indicated and the calculation of specific plastic work is discussed for both isotropic and anisotropic metals.

One of the major objectives of the paper is to stimulate critical experimental examination of as yet unproved assumptions in the theory of plasticity and in the correlation of experimental data.
Single Wave-Length X-Rays for Powder Diffraction
Authors: Frevel L. K. , North P. P.
Published: April 2005

WL α radiation filtered through a Cu–Zn foil is essentially monochromatic and has the advantage over filtered CuKα or MoKα radiation in that the WLα1 line is approximately ten times as intense as the WLα2 line. Moreover the comparatively wide Δλ-spread (WLα2−WLα1) results in very sharp powder lines at those Bragg angles where the CuKα doublet or MoKα doublet is unresolved.
Graphical Representation of Particle Trajectories in a Moving Reference System
Authors: Garbuny M.
Published: April 2005

A graphical method is derived for the analysis of microwave electron tubes, ion accelerators etc., which refers particle positions and velocities to a moving reference system. If the forces are dependent on time only, the trajectories are transformed into straight lines. For inhomogeneous fields an approximation procedure applies. To demonstrate the capabilities of this method a brief treatment of the transit time phenomena in cavity triodes is outlined.
Some Observations on the Epitaxy of Sodium Chloride on Silver
Authors: Johnson G. W.
Published: April 2005

An experimental study was made of the orienting effects of silver on sodium chloride crystallized from solution. Pronounced epitaxy was observed in the following cases: (1) On oriented films of silver with (100) and also with (111) planes parallel to the surface; and (2) on polycrystalline high purity silver sheet.
Determination of Residual Stresses of Quenching Origin in Solid and Concentric Hollow Cylinders from Interferometric Observations
Authors: Sáenz A. W.
Published: April 2005

A theoretical procedure for the determination of the stresses of quenching origin in solid and concentric hollow cylinders has been derived. The method relies on interferometric data and the assumptions discussed in Section I, whose validity for the technically important case of glass is supported by a number of experimental investigations.

The results should be of interest for the analysis of stresses in quenched glass cylinders, so great in magnitude that the usual cutting techniques are precluded, because of the explosive characteristics of highly stressed objects of this material.
Single Crystal Copper Surfaces
Authors: Rhodin T. N.
Published: April 2005

Some surface structure characteristics of a metal single crystal are considered and the conclusions are applied to the preparation of single crystal plates of copper. A successful preparation is described as well as suitable methods for evaluating the effectiveness of the preparation. Using physical microadsorption isotherms of nitrogen at 78.1°K, electron diffraction, and x-ray diffraction methods, the conclusion is tentatively asserted that the surfaces are essentially planar on a molecular scale, and that the surface atoms are arranged in an approximately undistorted lattice.
High Frequency Impedance of Low Pressure Gaseous Diodes
Authors: Yeh Chai , Chaffee E. L.
Published: April 2005

A simple theory of the lagging effect of the positive ions in neutralizing the space charge near the cathode of a gaseous diode is developed. By means of bridge measurement up to a frequency of 350 or 1000 kc per second, depending upon the type of tube used, the theory is checked experimentally in terms of the high frequency impedance of the diodes. Several constants of interest, such as the transit time and the lifetime of a positive ion, its effectiveness in neutralizing space charge, etc., can be deduced from the theoretical and experimental investigations.
A Kerr Cell Camera and Flash Illumination Unit for Ballistic Photography
Authors: Quinn H. F. , McKay W. B. , Bouroue O. J.
Published: April 2005

This paper describes an experimental model of a combination Kerr cell camera and flash illumination unit designed specifically for the photography of projectiles under conditions of strong ambient illumination. Specific cases wherein such conditions are found are considered and the applicability of the Kerr cell as a secondary protecting shutter is described. A description is given of a pulse forming network—pulse transformer circuit designed to apply an operating voltage pulse to a Kerr cell of thirty-six (36) kilovolts amplitude and one point nine (1.9) microseconds duration. Limitations inherent in the present equipment are considered together with proposals for overcoming these defects in future models. Typical results are presented, including (a) a picture taken with the unit showing a twenty-millimeter shot at the time of emergence from the muzzle of a gun, and (b) a picture of a thirty-seven millimeter shot taken shortly after penetration of a metal target plate.
End-Cooling of Power Tube Filaments
Authors: Clark John W. , Neuber Ralph E.
Published: April 2005

The differential equation defining the relation between temperature and distance in that portion of a vacuum tube filament which is cooled by both conduction and radiation is formulated. This equation has been solved by numerical integration; the results are presented as a set of universal curves in a form convenient for use in vacuum tube design. The calculations agree well with some experimental measurements which were made to verify the theory.
On the Endurance Limit of a Round Bar with Longitudinal Grooves
Authors: Ōkubo H.
Published: April 2005

In a previous paper, we reached a consideration that the endurance limit of a material should be determined by the amount of the mean stress in a certain area around a point, instead of the stress at the point, and the extent of the area is determined for several kind of metals, by using the results of tension-compression fatigue tests.

In this paper, the extent of area where the mean value of stress to be taken, is determined for a mild steel in another way, viz., by a torsion fatigue test, and we reached the conclusion that the extent of area chiefly depends on the kind of metal and independent of the course of the experiment.
The Magnetic Field of a Plane Circular Loop
Authors: Bartberger C. L.
Published: April 2005

The axial and radial components of the magnetic field of a plane circular loop are expressed in terms of cylindrical coordinates. The expressions involve two integrals which are related to certain of the complete elliptic integrals. Tables of values of these integrals are presented. Interpolation in these tables facilitates rapid calculation of the field components.
Effect of Coating Composition of Oxide-Coated Cathodes on Electron Emission
Authors: Widell E. G. , Hellar R. A.
Published: April 2005

Investigation of oxide-coated cathodes has been made to determine the effect on electron emission of varying the proportions of emitting oxides. The results show that maximum electron emission under saturation conditions is obtained from a solid solution containing strontium oxide (SrO) and barium oxide (BaO) in an approximate molecular ratio of 7 to 3.

These results also indicate that maximum size of the co-precipitated alkaline-earth carbonate particle occurs at the same molecular ratio as that giving maximum electron emission from the oxides.

When the saturation emission obtained with a square-wave voltage pulse was measured, the current pulse as observed on a synchroscope was also a square wave and showed no measurable decay characteristic for a pulse duration time of 10 microseconds.
A Small Electron Microscope
Authors: Reisner John H. , Dornfeld Edmund G.
Published: April 2005

A new electron microscope of greatly simplified design has been constructed. The instrument has a resolution of 100 Angstroms, yet is small enough to be mounted on a desk or laboratory table. Magnetic lenses are energized by permanent magnets. An accelerating voltage of 50 kilovolts is varied over a narrow range to provide means of focus. Images may be photographed on 2×2 plates. Plates may be changed in a minute, and specimens in fifteen seconds. Direct magnifications of 1500, 3000 and 6000 are possible depending on pole pieces used. Photographic images may be enlarged up to ten times. The instrument is free of x-radiation and completely interlocked and provided with shorting devices for protection from high voltage.
Hypersonic Research Facilities at the Ames Aeronautical Laboratory
Authors: Stevens Victor I.
Published: April 2005

Two wind tunnels recently completed at the Ames Laboratory of the NACA—the 10- by 14-in. supersonic wind tunnel and the supersonic free-flight wind tunnel—are capable of providing test Mach numbers well in excess of 5. Since at this time such facilities are relatively uncommon, this paper is primarily devoted to a description of these wind tunnels and their associated equipment.

The treatment of the 10- by 14-in. supersonic wind tunnel is concerned for the most part with the design and operation of the nozzle and diffuser which provides Mach numbers of 3.5 to about 8. Some mention is also made of the pressure measuring and flow visualization equipment. In the case of the supersonic freeflight wind tunnel high test Mach numbers are obtained by firing models at high speed into an oncoming supersonic air stream. Consequently the main emphasis is placed upon the launching techniques, the available range of test conditions, and the methods of obtaining data.
The Application of Rate-Process Theory to Glass. II. Viscosity
Authors: Hodgdon F. B. , Stuart D. A.
Published: April 2005

In previous efforts to derive an equation for the temperature-viscosity relation of glass it has been assumed, tacitly or otherwise, that glass is a simple liquid. Since glass is not a simple liquid, it is necessary to find a model that will, in its reaction to applied stresses, have the same characteristics as a specimen of glass. By the use of Eyring's rate-process theory, such a model is proposed and several equations relating viscosity to time and to temperature are derived. The equations include an equation that relates the viscosity of any glass specimen to time, one which defines the rate of removal of internal strain, and an equation which relates the viscosity of a specimen an infinite time after beginning of a test to the temperature of the test. This final viscosity is the viscosity usually reported in the literature. It is found that the parameters in the equation reduced to infinite time can be calculated from the chemical composition of the glass and the viscosity of any given glass can be predicted at any temperature over a very wide range. Curves and tables are included to show the agreement of experiment and theoretical values.
Gas Evolution in Liquids and Cavitation
Authors: Schweitzer P. H. , Szebehely V. G.
Published: April 2005

Nine heavy lubricating oils, four light lubricating oils, three aircraft engine fuels, one diesel fuel, and distilled water were tested for their air solubility and for the rate of solution and evolution of air when equilibrium is disturbed. The technique consisted of shaking of a container partly filled with liquid and taking accurate pressure measurements of the air above the liquid. Since air in solution exerts no pressure, the variation of pressure during and after the agitation furnished information on the amount of air that went into or came out of solution and their time rates. The solution was considered to have reached equilibrium when further shaking no longer changed the air content of the liquid.

A wide variation exists in the solubility constants and rates, but the rate of evolution was always found to be proportional to the supersaturation, and the rate of solution to the undersaturation, under otherwise similar conditions. At room temperature the air solubility constant for distilled water is 1.84 percent, for a gasoline approximately 20 percent, and for (light and heavy) lubricating oils approximately 10 percent. The ``half-life'' for evolution on the other hand was 3.86 sec. for distilled water, 0.13–0.24 sec. for gasoline, 3.6–7.6 sec. for light, and 11.6–51.4 sec. for heavy lubricating oils.

The investigation gave some insight into the phenomenon of cavitation which is still largely shrouded in mystery.
On the Theory of Dislocations
Authors: Bogdanoff John Lee
Published: April 2005

If, in a multiply-connected elastic solid, discontinuities are permitted across a stationary barrier in either the strain or its first derivatives or both, dislocations of a more general type than encountered in classical theory are possible. A number of these more general dislocations have been obtained for states of plane and anti-plane strain in a hollow right circular cylinder when the surface of discontinuity is a single stationary plane barrier. Some of the dislocations found possess the characteristic that although the strain is continuous across the barrier the displacement discontinuity is not one which would be possible in a rigid body. Examination of the conditions for the uniqueness of solution of the boundary value problems of elasticity reveals that when dislocations of the more general type are admitted appropriate data must be given at each point on the specified barrier in addition to the usual information.
A Relationship between Resistance and Temperature of Thermistors
Authors: Bosson G. , Gutmann F. , Simmons L. M.
Published: April 2005

The equation logR=A+B/(T+θ) for the resistance R of a thermistor at T°K is proposed. Least square analyses of the most precise resistance-temperature data available for three different thermistor materials show that the equation is a considerable improvement over its predecessors; the standard relative errors of fit are 0.4 percent, 0.17 percent, and 0.91 percent.
Techniques for Measuring the Dynamic Characteristics of a Low Pressure Discharge
Authors: Barnes Bentley T. , Eros Stephen
Published: April 2005

The dynamic characteristics of a discharge can be determined by making square-wave changes of arc current. This is done by putting the discharge tube in the plate circuit of a group of pentodes connected in parallel and supplied with a square-wave signal superimposed on a d.c. bias.

Probes operated at constant current are very useful in recording the characteristics of a modulated discharge. For measuring electron temperature (Te), two identical probes are centered about points having the same space potential. If the probes are operated at different fixed currents on the straight line part of the probe characteristic, the voltage between them is proportional to Te. Longitudinal voltage gradient or radial potential differences may be recorded by use of identical probes operated at the same current.

A probe operated at a suitable current will follow roughly the variations in space potential of the adjacent region of the discharge. Another probe made sufficiently negative with respect to such a probe will collect only positive ions. A probe made 0–10 volts positive with respect to the constant-current one gives records from which electron concentrations can be computed. In this case, a bias connection without current flow is obtained by use of a cathode-follower with two stages of direct-coupled amplification.

The oscillograph amplifier used for dynamic probe records must be either a differential one or one with ungrounded power supply. In the latter case, the stray capacitance is many times larger; but fairly reliable records can be obtained if the arc current is 0.1 ampere or more, and if the time constant for the decay of the transient effects being measured is at least 10 microseconds. The oscilloscope amplifier and any preamplifier used for recording spectral intensities should be direct-coupled.
Precision Determination of the Lattice Constants of Zinc Oxide
Authors: Heller R. B. , McGannon J. , Weber A. H.
Published: April 2005

A total of 350 back-reflection ZnO powder x-ray diffraction lines on 25 photographic films have been measured and analysed by the Cohen analytical least squares extrapolation method to yield a=(3.2495±0.00002)A, c=(5.2069±0.00011)A; where the stated errors are the probable errors. The statistical reliability of the results is emphasized.

In the measurement of the Debye-Scherrer ring radii the accuracy obtained with a metric scale and indicator (employing no optical lens system) and with a dividing engine equipped with a microscope are compared and the former simpler method is found more reliable. It is concluded that the use of precision measuring instruments for observing diffraction ring radii are unnecessary and even undesirable apparently because the magnifying power of the optical system of precision micrometers leads to uncertainties in settings on photographic lines.
The Virtual Mass of a Sphere Entering Water Vertically
Authors: May Albert , Woodhull Jean C.
Published: April 2005

The manner in which a sphere behaves when it enters the water from air depends on the rate at which energy is taken from it, and most of this energy is utilized in setting water into motion. The virtual mass is a partial measure of this motion. An investigation of virtual mass for spheres shortly after vertical water entry is described. The spheres used had specific gravities between 1.06 and 16.77 and impact velocities ranged from 21 to 103 ft./sec. The value of the virtual-mass coefficient was found to be much smaller than had previously been estimated, an average value of 0.08 being obtained. The method used recognizes the dependence of CD on sphere speed and depth, and makes comparisons only where these parameters have the same value.
Quantum Limits of the Electrostatic Image Force Theory
Authors: Sachs R. G. , Dexter D. L.
Published: April 2005

The quantum mechanical problem of the interaction of a charged macroscopic body with a metal surface is treated by means of the variation method. The resulting expression for the interaction energy is the same as that obtained by the classical image force method except for three correction terms. These corrections are caused by the change in kinetic energy associated with the concentration of the electrons on the surface of the metal, the reduction in the electron-electron interaction energy in the metal resulting from the anti-symmetrization of the wave function and the effect of the finite thickness of the surface charge. It is found that these terms are negligible except for distances between the charged body and metal surface such that surface structure effects are important.
Vibrational Relaxation Times in Gases
Authors: Griffith Wayland
Published: April 2005

Relaxation times for seventeen gases have been measured using a steady flow method, the velocity field being found numerically by Southwell's Relaxation Method. Where a comparison is possible the results are found to be in good agreement with sound dispersion data. The present state of knowledge about relaxation effects is discussed and a few instances of their possible appearance are cited.
Numerical Determination of Fundamental Modes
Authors: Flanders Donald A. , Shortley George
Published: April 2005

A convenient and practical method of numerical determination of the fundamental eigenfunction and eigenvalue in a class of linear eigenvalue problems has been developed and applied in two and three dimensions. The method is based on use of a network and of difference equations, but departs from previous methods in that it is not iterative. Rather, a polynomial operator is applied to a trial function just once, to accomplish a determinable degree of reduction in all eigenfunctions other than the fundamental that are contained in the trial function. In the case of the diffusion equation, the polynomial operator is a Tschebyscheff polynomial of a simple averaging operator. It is shown that this operator, when of degree m, is ``better'' than any other polynomial operator of this degree and much ``better'' than m iterations of a simple averaging operator—``better'' in the sense of accomplishing to a greater degree the elimination of all unwanted eigenfunctions. Techniques for the use of computing equipment for application of the polynomial operator are discussed. By orthogonalization, the method can be applied to modes other than the fundamental.
Determination of Eigenvalues Using a Generalized Laplace Transform
Authors: Friedman Morris D.
Published: April 2005

The classical eigenvalue problems of mathematical physics are solved by means of a Laplace Transform extended, not over the interval (0, ∞) but over the interval of interest for the differential equation. The method is applied to the Hermite, Laguerre and Bessel equations and to the equation for the hypergeometric polynomials which include the Legendre, Tschebyscheff, and Jacobi polynomials as special cases.
The Current Build-Up in a Planar Diode
Authors: Gamble Edward H.
Published: April 2005

A theoretical study has been made of the initial electron flow when a signal voltage V(t) is applied across an idealized planar diode. The analysis is based upon three fundamental postulates: Poisson's equation, Newton's equation, and the continuity equation. This quasi-stationary study includes both the growth and motion of the space-charge cloud of electrons across the interelectrode space and the transient build-up of the current in the external circuit. The analytical forms and numerical plots of the current build-up under space-charge-limited and temperature-limited operation are compared for various ``large'' and ``small'' signal voltages.
Depolymerization by Ultrasonic Irradiation: The Role of Cavitation
Authors: Weissler Alfred
Published: April 2005

Contrary to current belief, cavitation has been found responsible for the depolymerizing effect of intense ultrasonic waves. This was demonstrated by irradiating two portions of a 1 percent polystyrene solution in toluene under conditions identical except for the following. The first portion was given no special prior treatment, showed many cavitation bubbles during irradiation, and decreased in molecular weight (as measured by the intrinsic viscosity) to about one-tenth of the initial value. The second portion was given a preliminary treatment of degassing by boiling under vacuum, showed no cavitation bubbles during the irradiation, and underwent no appreciable change in molecular weight.

Similar experiments with solutions of hydroxyethyl cellulose in water showed that, in this case also, cavitation is necessary for depolymerization. The opposite conclusion of earlier investigators is attributed to their inadequate method for eliminating cavitation.

Oxidants known to be produced by ultrasonic waves in solutions containing dissolved oxygen or nitrogen cannot be responsible for the degradation, because substantially the same amount of depolymerization occurs even when helium is the only gas present.
Steady-State Internal Temperature Rise in Magnet Coil Windings
Authors: Emmerich Claude L.
Published: April 2005

The temperature distribution in an electric coil winding is determined by solving the differential equations which apply to the system approximately. The maximum and average temperature rises are given for several types of windings. A distinction is made between small and large temperature rise; the treatment of the former neglects local changes in resistivity and thermal conductivity caused by the increase in temperature. A correction factor is computed to obtain the actual temperature rise from the much simpler calculations for the maximum temperature rise which would occur if the resistance were independent of temperature. It is found that non-uniform windings, wound of several different wire sizes to minimize the resistance, exhibit the same temperature rise characteristics as conventional uniform windings of zero curvature.