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Articles 1 - 26 of 26
Full-Text Articles in Physical Sciences and Mathematics
Reply (To "Comment On 'The Absolute Scattering Cross Section At50 Mhz Of Equatorial Electrojet Irregularities' By Farley Et Al." By N. D'Angelo), D. T. Farley, Bela G. Fejer
Reply (To "Comment On 'The Absolute Scattering Cross Section At50 Mhz Of Equatorial Electrojet Irregularities' By Farley Et Al." By N. D'Angelo), D. T. Farley, Bela G. Fejer
Bela G. Fejer
No abstract provided.
Centers Of Polymer Research; Polymer Science In Tokyo, Japan, Part I: Central Area, Otto Vogl, A. Nakajima
Centers Of Polymer Research; Polymer Science In Tokyo, Japan, Part I: Central Area, Otto Vogl, A. Nakajima
Otto Vogl
No abstract provided.
The Absolute Scattering Cross Section At 50 Mhz Ofequatorial Electrojet Irregularities, D. T. Farley, H. M. Ierkic, Bela G. Fejer
The Absolute Scattering Cross Section At 50 Mhz Ofequatorial Electrojet Irregularities, D. T. Farley, H. M. Ierkic, Bela G. Fejer
Bela G. Fejer
We have made carefully calibrated radar scattering measurements by using the large 50-MHz Jicamarca antenna. Typical results from the altitudes of maximum echo power for the vertically directed beam are σradar ∼1–2 × 10−10 m−1 for strong daytime electrojet conditions with type 1 irregularities present, with values a factor of 10 or so smaller during moderate conditions when only type 2 are observed. These cross sections, which are very large in comparison with those for incoherent scatter (σradar ≃5 × 10−18 m−1 for an electron density of 1011 m−3), are not nearly large enough, however, to cause pseudo-absorption events on …
Exactly Soluble Ising Models On Hierarchical Lattices, Miron Kaufman, Robert B. Griffiths
Exactly Soluble Ising Models On Hierarchical Lattices, Miron Kaufman, Robert B. Griffiths
Miron Kaufman
Certain approximate renormalization-group recursion relations are exact for Ising models on special hierarchical lattices, as noted by Berker and Ostlund. These lattice models provide numerous examples of phase coexistence and critical points at finite temperatures, including cases of continuously varying critical exponents and phase transitions without phase coexistence. The lattices are, typically, quite inhomogeneous and may possess several inequivalent limits as infinite lattices.
Effects Of Three Vesicular-Arbuscular Mycorrhizal Fungi On Sweetgum Seedlings From Nine Mother Trees, Richard C. Schultz, Paul P. Kormanik, William C. Bryan
Effects Of Three Vesicular-Arbuscular Mycorrhizal Fungi On Sweetgum Seedlings From Nine Mother Trees, Richard C. Schultz, Paul P. Kormanik, William C. Bryan
Richard C. Schultz
Soil in microplots was infested with three vesicular-arbuscular (VA) symbionts then sown with seed of half-sib progeny from nine sweetgum mother trees. The VA treatments were Glomus fasciculatus, Glomus spp. (a mixture containing both Glomus mosseae and Glomus etunicatus), or a VA mixture of several fungi from the genera Glomus and Gigaspora. Before the seed was sown, all plots had calcium standardized and received an application of commercial fertilizer. During the growing season, NH4NO3 was applied to all plots in equal portions. Mycorrhizal seedlings with G. fasciculatus were slightly but not significantly larger in both height and root-collar diameter than …
Relative Stability Of Multiple Bonds To Silicon: An Ab Initio Study Of C2sih4 Isomers, Mark S. Gordon, Robert D. Koob
Relative Stability Of Multiple Bonds To Silicon: An Ab Initio Study Of C2sih4 Isomers, Mark S. Gordon, Robert D. Koob
Mark S. Gordon
Ab initio (6-31G*/ /3-21G) SCF calculations have been carried out on 15 isomers with the chemical formula C2SiH4• The isomers include structures with formal double and triple bonds to silicon, as well as carbenes and silylenes, so a direct comparison of these types of species is possible. The isomerization energies provide an opportunity to consider the relative strengths of analogous bonds to carbon and silicon. With the appropriate isodesmic reactions, the stabilizing or destabilizing effects of substituents and strain in three-membered rings both may be investigated.
Structure And Stability Of A Silicon-Carbon Triple Bond, Mark S. Gordon, John A. Pople
Structure And Stability Of A Silicon-Carbon Triple Bond, Mark S. Gordon, John A. Pople
Mark S. Gordon
The stability of the carbon-silicon triple bond in silaethyne is investigated via an analysis of its isomerization to silylidene and through a study of its hydrogenation energy relative to acetylene and silaethylene. It is found that silaethyne is rather unstable in a thermodynamic sense. However, while SCF calculations predict this species to rearrange to its more stable isomer with no barrier, the introduction of perturbation corrections suggests the existence of a small barrier separating the two isomers.
Direct Nmr Observation Of Rotational Freeze-Out In The Smectic C-Phase, Demetri J. Photinos, Philip J. Bos, Mary E. Neubert, J. William Doane
Direct Nmr Observation Of Rotational Freeze-Out In The Smectic C-Phase, Demetri J. Photinos, Philip J. Bos, Mary E. Neubert, J. William Doane
Philip J. Bos
We report here a simple and direct observation that the molecular long axis is not, on the average, a rotation axis for the entire molecule in the smectic C phase (rotational freeze-out). This observation is made in the compound 4-n-heptyl-d15-oxybenzoic acid-d1 where experiment clearly shows that the principal axes of the time-averaged deuterium quadrupole interactions at specific sites of the hydrocarbon chain are not all parallel, demonstrating that they do not share a common axis of rotation.
Interferometer Studies Of Equatorial Fregion Irregularities And Drifts, E. Kudeki, Bela G. Fejer, D. T. Farley, H. M. Ierkic
Interferometer Studies Of Equatorial Fregion Irregularities And Drifts, E. Kudeki, Bela G. Fejer, D. T. Farley, H. M. Ierkic
Bela G. Fejer
A radar interferometer technique developed at Jicamarca, Peru and first used to study electrojet irregularities has now been used successfully to study plasma turbulence in the equatorial F region. Our first results have shown that the most ‘turbulent’ echoes appear to come from a region that extends for tens of kilometers in altitude but for only a kilometer or less in the east-west direction. This slab may very well be the wall of a depleted region, a plasma ‘bubble’. Sometimes the irregularities can be tracked as they move eastward or westward. Velocity profiles for the evening period obtained in this …
Three-Component Model And Tricritical Points: A Renormalization-Group Study., Miron Kaufman, Robert B. Griffiths, Julia M. Yeomans, Michael E. Fisher
Three-Component Model And Tricritical Points: A Renormalization-Group Study., Miron Kaufman, Robert B. Griffiths, Julia M. Yeomans, Michael E. Fisher
Miron Kaufman
The global phase diagram for a three-component lattice gas or spin-one Ising model with general single-site and nearest-neighbor "ferromagnetic" interactions is worked out for twodimensional lattices using a Migdal-Kadanoff recursion relation. It differs in important qualitative respects from the corresponding mean-field phase diagram. The set of fixed points and flows provides the characteristic'phase diagrams of the three-state Potts multicritical point and the ordinary (n =1) tricritical point in a complete set of symmetry-breaking fields. The latter is associated, in this renormalization-group scheme, with seven distinct critical fixed points, a number which is surprisingly large.
Radar Interferometry: A New Technique For Studyingplasma Turbulence In The Ionosphere, D. T. Farley, H. M. Ierkic, Bela G. Fejer
Radar Interferometry: A New Technique For Studyingplasma Turbulence In The Ionosphere, D. T. Farley, H. M. Ierkic, Bela G. Fejer
Bela G. Fejer
A new radar interferometer technique has been developed and used successfully at the Jicamarca Radio Observatory in Peru to study the strong nighttime plasma turbulence in the equatorial electrojet. The technique represents a major step forward in radar probing of turbulent irregularities such as (but not limited to) those in the electrojet. In many situations it provides far more information than previous Doppler measurements. We form the cross spectrum of the backscattered signals received from approximately overhead on two antennas, separated in this case along an east-west baseline, as well as the individual power spectra. From the phase of the …
Acute Headaches; Presenting Symptoms And Diagnostic Rules To Identify Patients With Tension And Migraine Headache , Paula Diehr
Acute Headaches; Presenting Symptoms And Diagnostic Rules To Identify Patients With Tension And Migraine Headache , Paula Diehr
Paula Diehr
Headache is the ninth most common cause of physician visits, but data on acute headaches have not been collected in a standardized manner and have not been analyzed in a multivariate fashion. We report on 726 patients presenting with acute headaches, which were diagnosed as tension (38%), migraine (25%), no diagnosis (30%), and other (6%). The prevalence of 32 signs and symptoms is shown for each group. Four of these findings were significant predictors of tension headache, and 19 were significant predictors of migraine headache (p<.05). Several diagnostic rules are developed which classify nearly 90% of the headaches correctly, using only three to seven of the findings. On a new set of patients the classification was correct over 80% of the time. It is suggested that most acute headaches could be diagnosed over the telephone or by midlevel providers, which would provide substantial cost savings.
A Survey Of Water Flow In Drainage Ditches And Streams In South Central Minnesota, Clay L. Pierce, Bill Thompson
A Survey Of Water Flow In Drainage Ditches And Streams In South Central Minnesota, Clay L. Pierce, Bill Thompson
Clay L. Pierce
Discharge was monitored on 13 agricultural drainage ditches and 4 small rivers in south central Minnesota. Derived data were categorized by response to hydrologic events and stream order. Stream order was found to be the most reliable predictor of hydrologic event response. Peak flows in drainage ditches were found to correspond to peak flows in rivers.
Expansion Approach To Photodissociation Dynamics. I. Theory, Kazuo Takatsuka, Mark S. Gordon
Expansion Approach To Photodissociation Dynamics. I. Theory, Kazuo Takatsuka, Mark S. Gordon
Mark S. Gordon
We propose a new formulation for a photodissociation process to which an expansional (or algebraic) quantum‐variation‐method of scattering is applicable. By solving a ’’full collision’’ problem which describes a multichannel process on the repulsive surface, the photodissociation scheme takes account of interchannel coupling from the outset. Our expression for the amplitude of the partial linewidth is similar to that of the ’’half‐collision’’ approximation of Jortner e t a l. The present formalism differs in that the scattering wave functions take acount of interchannel coupling exactly. As a result, only on‐the‐energy‐shell contributions appear in the partial linewidth.
Expansion Approach To Photodissociation Dynamics. Ii. Correction Formula For Linewidth And Numerical Examples For Hcn, Kazuo Takatsuka, Mark S. Gordon
Expansion Approach To Photodissociation Dynamics. Ii. Correction Formula For Linewidth And Numerical Examples For Hcn, Kazuo Takatsuka, Mark S. Gordon
Mark S. Gordon
A correction formula for energy disposal and linewidth of photodissociation dynamics is proposed. This formula was derived from an identity similar to the Kato identity of the scattering theory. Thanks to the correction formula the resultant linewidth turns out to be more accurate and stable even when a relatively poor basis set is used. Numerical examples for assumed direct dissociation of HCN, DCN, and TCN and for the predissociation of HCN and DCN are presented.
A Quantitative Test Of Unimolecular Rate Theory In The Multi‐Photon Dissociation Of Cf2Cfcl, John C. Stephenson, Stephen E. Bialkowski, David S. King, Everet Thiele, James Stone, Myron F. Goodman
A Quantitative Test Of Unimolecular Rate Theory In The Multi‐Photon Dissociation Of Cf2Cfcl, John C. Stephenson, Stephen E. Bialkowski, David S. King, Everet Thiele, James Stone, Myron F. Goodman
Stephen E. Bialkowski
We have measured the distribution of total energy in reaction products for the CO2 laser‐induced MPD: CF2CFCl→CF2+CFC1. From a separate study of MPD rates as a function of laser intensity and inert buffer gas pressure, reliable estimates of the radiative pumping rates are known for this reaction. These results, when analyzed together, allow us to extract a unimolecular A factor from the MPD data. The determined value A = 3×1016 sec−1 agrees well with estimates based on independent thermal data.
F-Region East-Westdrifts At Jicamarca, Bela G. Fejer, D. T. Farley, C. A. Gonzales, R. F. Woodman, C. Calderson
F-Region East-Westdrifts At Jicamarca, Bela G. Fejer, D. T. Farley, C. A. Gonzales, R. F. Woodman, C. Calderson
Bela G. Fejer
F region east-west drifts have been measured at Jicamarca for almost 10 years, using incoherent scatter. The drifts are westward during the day and eastward at night. The daytime drift velocities are about 50 m/s and change very little with season or solar cycle. The evening reversal occurs at about 1600 local time throughout the solar cycle. The maximum nighttime eastward drifts are about 105 and 130 m/s during solar minimum and maximum, respectively. The daytime and nighttime drifts show very litle variation with magnetic activity. These Jicamarca incoherent scatter results (especially the reversal times) differ appreciably from results obtained …
Centers Of Polymer Research; Polymer Science In Kyoto, Japan, Otto Vogl, A. Nakajima
Centers Of Polymer Research; Polymer Science In Kyoto, Japan, Otto Vogl, A. Nakajima
Otto Vogl
No abstract provided.
Synoptic Climatology Of The Western United States In Relation To Climatic Fluctuations During The Twentieth Century, R. G. Barry, G. Kiladis, Raymond S. Bradley
Synoptic Climatology Of The Western United States In Relation To Climatic Fluctuations During The Twentieth Century, R. G. Barry, G. Kiladis, Raymond S. Bradley
Raymond S Bradley
An objectively derived catalogue of daily pressure patterns for 11199-1974 has been prepared for the western United States. The temperature and precipitation characteristics of the major types are described and a more detailed analysis for Colorado in extreme cold and warm months shows that the sign of the anomalies for each type is generally consistent with expectation hased Oil the prohable airflow patterns. A regression analysis of type frequencies versus temperature and precipitation anomalies for 1899--1970 at stations east and west of the Continental Divide in the Rocky Mountain states shows that useful explanation of variance is obtained only for …
Structure-Factor Measurements In 4he At Saturated Vapor Pressure For 1.38<~T<~4.24 K, Robert Hallock, H. N. Robkoff
Structure-Factor Measurements In 4he At Saturated Vapor Pressure For 1.38<~T<~4.24 K, Robert Hallock, H. N. Robkoff
Robert Hallock
We present the results of measurements of the liquid structure factor, S(k), for liquid 4He at saturated vapor pressure at seven temperatures between 1.38 and 4.24 K over the momentum-transfer range k<~5.1 Å-1. The results are compared with previous measurements carried out by both x-ray and neutron scattering techniques. Comparison with recent theoretical work emphasizes the importance of higher-order correlations and more realistic potentials in the description of the liquid. Measurements in the vicinity of the λ transition document a loss in spatial order as the liquid is cooled through Tλ.
Phase Separation In 3he-4he Mixture Films, Robert Hallock, F. M. Ellis, M. D. Miller, R. A. Guyer
Phase Separation In 3he-4he Mixture Films, Robert Hallock, F. M. Ellis, M. D. Miller, R. A. Guyer
Robert Hallock
We report detailed observations of the propagation of third sound in 3He-4He mixture films as a function of temperature and 3He concentration. The data are consistent with a simple model for the film and we conclude that thin 3He-4He mixture films exhibit nearly complete phase separation.
Areal Distribution, Thickness, Mass, Volume, And Grain Size Of Air-Fall Ash From The Six Major Eruptions Of 1980, Andrei M. Sarna-Wojcicki, Susan Shipley, Richard B. Waitt Jr., Daniel Dzurisin, Spencer H. Wood
Areal Distribution, Thickness, Mass, Volume, And Grain Size Of Air-Fall Ash From The Six Major Eruptions Of 1980, Andrei M. Sarna-Wojcicki, Susan Shipley, Richard B. Waitt Jr., Daniel Dzurisin, Spencer H. Wood
Spencer H. Wood
The airborne-ash plume front from the Mount St. Helens eruption of May 18 advanced rapidly to the northeast at an average velocity of about 250 km/hr during the first 13 min after eruption. It then traveled to the east-northeast within a high-velocity wind layer at altitudes of 10-13 km at an average velocity of about 100 km/hr over the first 1,000 km. Beyond about 60 km, the thickest ash fall was east of the volcano in Washington, northern Idaho, and western Montana. A distal thickness maximum near Ritzville, Wash., is due to a combination of factors: (1) crude sorting within …
Effects Of N2h4 On The Transition Temperature In The Anisotropic Superconductor Tase3, K. Yamaya, T. H. Geballe, Juana Vivó Acrivos, J. Code
Effects Of N2h4 On The Transition Temperature In The Anisotropic Superconductor Tase3, K. Yamaya, T. H. Geballe, Juana Vivó Acrivos, J. Code
Juana Vivó Acrivos
No abstract provided.
Mott G-Ratios In Rbx(Nh3)1-X And Oxidation State Of Rubidium Compounds From Xas, Juana Vivó Acrivos, K. Hathaway, A. Robertson, M. P. Klein, A. Thompson
Mott G-Ratios In Rbx(Nh3)1-X And Oxidation State Of Rubidium Compounds From Xas, Juana Vivó Acrivos, K. Hathaway, A. Robertson, M. P. Klein, A. Thompson
Juana Vivó Acrivos
The x-ray absorption spectra (XAS) of Rb metal, Rh,("JH,J, ,, 2H-NbSe2Rb111x and RbBr near the Rb K-edge have been used to ascertain that the oxidation state V of rubidium dissolved in ammonia and intt:rcalated in the layer compound is in the range 0 < V < I. Theobservededge shifts with temperature for semimctals are explainedin terms of the population of band states, and the ratio of the density states near the mobility edge over that calculated for a free electron model, i.e. the Mott ratio g, is ascertained using a semiempirical relation developed for the x-ray absorbance from Is levels to empty states ncar the mobility edge.
Conduction Band Symmetry In Ta Chalcogenides From Ta L Edge X-Ray Absorption Spectroscopy (Xas), Juana Vivó Acrivos, S.S. P. Parkin, J. Code, J. Reynolds, K. Hathaway, H. Kurasaki, E. Marseglia
Conduction Band Symmetry In Ta Chalcogenides From Ta L Edge X-Ray Absorption Spectroscopy (Xas), Juana Vivó Acrivos, S.S. P. Parkin, J. Code, J. Reynolds, K. Hathaway, H. Kurasaki, E. Marseglia
Juana Vivó Acrivos
No abstract provided.
Limits Of Certain Sequences Associated With Cylinder Functions, William F. Trench
Limits Of Certain Sequences Associated With Cylinder Functions, William F. Trench
William F. Trench
No abstract provided.