bluuebunny/crossref_metadata_2025_split huggingface dataset:
InGaAs/GaAs quantum wells and quantum dots on GaAs(11n) substrates studied by photoreflectance spectroscopy
Authors: Rojas‐Ramirez J. S. , Yee‐Rendón C. M. , Cruz‐Hernandez E. , Contreras‐Guerrero R. , Vazquez‐Lopez C. , Melendez‐Lira M. , Lopez‐Lopez M. 
Published: February 2007

AbstractPseudomorphic InGaAs/GaAs quantum wells (QWs) and self‐assembled InAs quantum dots (QDs) were grown by molecular beam epitaxy (MBE) on GaAs(11n)A substrates. Photoreflectance spectroscopy was employed to investigate the transitions in the heterostructures. The transitions in QWs have two contributions, a blue shift due to the compressive strain, and a red shift due to the quantum confined Stark effect produced by the piezoelectric field. A traditional theoretical interpretation of the QWs transitions employing a simple well model with sharp interfaces shows discrepancies with the experimental results. In order to satisfactorily explain the transitions we proposed to include segregation effects of Indium at the wells interfaces. The matrix transfer method was implemented to numerically solve the Schrödinger equation taking into account In segregation effects by including an asymmetric potential well with a profile depending on the details of the In incorporation. With segregation effects included, the calculated transitions fit very well the PR spectra. On the other hand, the transitions in self‐assembled QDs were obtained by fitting the PR spectra employing a first derivative line‐shape function. For n = 2, 4, 5, two functions were required to fit the spectra. For n = 3 only one function was required, in agreement with the more uniform QDs size distribution observed by atomic force microscopy on GaAs(113)A. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic band structure of wurtzite InN around the fundamental gap in the presence of biaxial strain
Authors: Bhattacharyya Jayeeta , Ghosh Sandip 
Published: February 2007

AbstractWe present results of a theoretical study of the electronic band structure of wurtzite InN films under biaxial strain in the C ‐plane (0001) and in planes that correspond to non‐polar orientations such as the A ‐plane (11$ \bar 2 $0) and the M ‐plane (1$ \bar 1 $00). The calculations are performed under the k · p perturbation theory approach using the Bir–Pikus Hamiltonian. The results show that the fundamental bandgap of InN shifts by 30 meV (14 meV) for isotropic tensile (compressive) strain in the C ‐plane with out‐of‐plane contraction (dilation) of 0.2%. For films of non‐polar orientations, the c‐axis lies in the film plane and the strain is expected to be different between directions parallel and perpendicular to c. Such anisotropic strain give rise to valence band mixing which results in dramatic changes in the optical polarization properties as evidenced by the calculated oscillator strengths of the interband transitions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modulation spectroscopy of AlGaN/GaN heterostructures: The influence of electron–hole interaction
Authors: Goldhahn R. , Winzer A. T. , Dadgar A. , Krost A. , Weidemann O. , Eickhoff M. 
Published: February 2007

AbstractA detailed analysis of electroreflectance (ER) spectra for AlGaN/GaN heterostructures containing a two‐dimensional electron gas (2DEG) is presented. The properties of two samples with different Al‐content in the barrier layer are compared. Calculated field‐dependent dielectric functions (DF) for GaN and AlGaN which take into account electron–hole interaction (exciton effects) provide the basis for the modeling of the spectra. It is demonstrated that the Seraphin coefficients exhibit a strong spectral dependence around the gap which cannot be neglected in a fit of ER spectra. The use of the calculated DFs in a multi‐layer model allows to reproduce all peculiarities of experimental ER spectra for both, the GaN channel layer and the AlGaN barrier layer, despite the inhomogeneous field distribution. The determined AlGaN barrier field strengths are very close to the values obtained by applying the asymptotic formulation of the Franz–Keldysh effect. Finally, the polarization gradient at the AlGaN/GaN boundary is estimated from these field strengths. The gradient is slightly lower than theoretically predicted which confirms previous studies. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electroreflectance and photoreflectance spectra of tricolor III‐nitride detector structures
Authors: Drabinska Aneta , Korona K. P. , Pakula K. , Baranowski J. M. 
Published: February 2007

AbstractResults of photoreflectance and electroreflectance on tunable UV detector are presented. The active region of the detector consists of three layers: GaN, Al0.1Ga0.9N, and Al0.2Ga0.8N. Due to different spontaneous and piezoelectric polarization two‐dimensional electron gases with high electron concentration are formed at each interface. 2D electron gas may be depleted from particular interfaces by applied reverse bias to the Schottky diode. Therefore to the active region of the detector successive layers are enclosed. The photoreflectance spectra show that in “clean” structure low electric field is present in the active region of the detector and on both interfaces the 2D electron gases are present. In electroreflectance measurement with external electric field applied, there is possibility to observe the evolution of the electric field in these layers and the depletion of 2D electron gases from interfaces. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Antinociceptive and antiinflammatory activities of pine (Pinus densiflora) pollen extract
Authors: Choi Eun‐Mi 
Published: February 2007

AbstractThe study aimed to evaluate the antinociceptive and antiinflammatory activity of pine (Pinus densiflora) pollen in mice. The antinociceptive activity was determined using acetic acid‐induced abdominal constriction and formalin‐induced licking, and the hot plate test. Antiinflammatory effects were evaluated using carrageenan‐ and formalin‐induced paw edema, and arachidonic acid‐induced ear edema in mice. The ethanol extract of pine pollen (100 and 200 mg/kg, p.o.) produced a significant inhibition of both phases of the formalin pain test in mice, a reduction in mouse writhing induced by acetic acid and an elevation of the pain threshold in the hot plate test in mice. The pine pollen extract also produced a significant inhibition of carrageenan‐ and formalin‐induced paw edema as well as arachidonic acid‐induced ear edema in mice. The inhibitions were similar to those produced by aminopyrine and indomethacin, p.o. The different polyphenols found in pine pollen could account for the antinociceptive and antiinflammatory actions. The results obtained indicate that the extract possesses analgesic and antiinflammatory effects. Copyright © 2007 John Wiley & Sons, Ltd.
The evaluation of the coefficient of eddy diffusivity
Authors: Longley Richmond W. 
Published: February 2007

AbstractObservational data have been substituted into a modified form of the equation of heat transfer. By a statistical analysis of the resultant equations, values of the coefficient of eddy diffusivity for various stable lapse rates are obtained. It was found necessary in the analysis to define a “point of best fit,” and to derive the normal equations for obtaining this point.
Notes on upper air hygrometry–‐I calculation of the relative humidity from hair hygrometer readings during balloon ascents
Authors: Glückauf E. 
Published: February 2007

AbstractA method is described for calculating the relative humidity from the data obtainable from balloon hair hygrograph records under conditions in which the hair does not reach equilibrium with its surroundings. Based on and checked by means of laboratory measurements, the method gives consistent results if applied to the Dines meteorograph.
Dynamical control of atmospheric pressure
Authors: Priestley C. H. B. 
Published: February 2007

AbstractAny dynamical expression for the pressure tendency consists fundamentally of a number of potentially large terms. A mechanism of control is here put forward to explain the fact that the realised pressure tendency invariably emerges as a small residual of its much larger primary components.The field of flow determines the pressure change, but itself depends dynamically on the instantaneous pressuretendencyfield. It is this mutual interaction between the two fields which constitutes the brake or control on the mutability of the pressure field.The essential link is the path curvature. The mechanism of control in typical cases may thus be studied by replacing the true wind by the (suitably defined) gradient wind. A number of applications are made with the object of explaining the broad features of the translation of idealisd pressure systems and an indication is given of how the principle may be used to clarify some problems of development.
Notes on the theory of tropical cyclones
Authors: Sawyer J. S. 
Published: February 2007

AbstractThe conditions under which continued outward motion is possible in a circular vortex are investigated theoretically, and the results applied to the development of tropical cyclones, in order to give a possible explanation of the removal of air from the storm centre and the associated fall of pressure.The development of a storm by this mechanism is described and necessary conditions for such development are found to be:—(a) A lapse rate which will give rise to vertical instability and development of convection cloud. (b) A distribution of circulation at some level aloft such that anticyclonic circulation increases outward at a rate exceeding a certain value. (c) A distribution in the vertical of horizontal rotation such that cyclonic circulation decreases with height.The importance of horizontal turbulence in producing the calm “eye” of the storm is considered, and the relation between tropical cyclones and fronts is briefly discussed.
Notes on the measurement and estimation of atmospheric radiation
Authors: Robinson G. D. 
Published: February 2007

AbstractA series of measurements of the infra red emission of the atmosphere has been made at Kew Observatory with Dines and Linke‐Fuessner radiometers. Precautions necessary during the calibration and use of these instruments are discussed, the results obtained with them compared, and the accuracy of the measurements assessed.Computation of the atmospheric emission by Elsasser's method is discussed, and compared with the experimental results. It is suggested that the divergence found is due to over‐estimation of the emissivity of water vapour in the presence of carbon dioxide by Elsasser, together with the presence of a variable additional component of radiation of from 0 to 8 per cent of the total. Some comments are made on the possible origin of this radiation. A modification of the method of F. A. Brooks is used to derive values of water vapour emissivity from the measurements, and by combining these with the laboratory values of Elsasser and Brooks an emissivity curve is obtained which differs from that now generally accepted. This is used to compute the water vapour radiation, and the construction of an empirical radiation chart is described.Finally it is shown that the outward radiation of the ground may be obtained from the reading of an ordinary thermometer, and that by combining this with an estimate of atmospheric emission based on routine upper air data, the net infra red radiation of the surface may be estimated with an accuracy better than 15 per cent.
The significance of dynamic instability in atmospheric motions
Authors: Sawyer J. S. 
Published: February 2007

AbstractA discussion is given of the criterion for a special type of dynamic instability first derived by H. Solberg, viz. :—that the anti‐cyclonic wind shear along an isentropic surface should exceed the coriolis parameter. It is concluded that this criterion has no direct bearing on the formation of extratropical cyclones but it may be important in respect of the limit which it imposes on the wind shear to the south of the “jet stream”. Dynamic instability of this type may also be important in connection with the formation of tropical cyclones and certain features of frontal structure.
Evaporation over the British Isles
Authors: Penman H. L. 
Published: February 2007

AbstractTheoretical values of average annual evaporation from the British Isles are calculated from long‐term averages of air temperature, duration of sunshine, vapour pressure and wind speed for about 100 stations. Direct estimates of the same quantity are obtained from long‐term averages of annual rainfall and annual run‐off from about 40 catchment areas. The two kinds of estimate agree and are plotted on a map to show the geographical variation of evaporation. This shows an increase from 14 in. per annum in Scotland to 20 in. along the south coast.
The significance of vertical stability in synoptic development
Authors: Sumner E. J. 
Published: February 2007

AbstractThe connection between the development of depressions and anticyclones and the degree of vertical stability of the atmosphere is examined. It is concluded that in middle latitudes the damping due to stability is not important in the largest‐scale circulations of diameter greater than about 2,000 km, but has controlling significance for systems of diameter less than about 1,000 km. The difference in the rate of development between an ordinarily stable and a neutral atmosphere may be ten‐fold or more for the smaller systems. A very small degree of instability in depth will permit small‐scale cyclonic development to proceed rapidly.Furthermore, the damping effect of atmospheric stability is inversely proportional to the square of the Coriolis parameter. At 10° latitude, for example, the effect becomes dominant for all practical diameters, and it would appear difficult for cyclones or anticyclones of any reasonable size to develop significantly in low latitudes, with the exception of cyclones in a vertically unstable atmosphere.
Types and spells of weather around the year in the British Isles : Annual trends, seasonal structure of the year, singularities
Authors: Lamb H. H. 
Published: February 2007

AbstractFrom a classification of 50 years' daily weather maps (1898—1947) the outstandingly long spells of weather, lasting over 25 days, have been picked out. Frequency curves show the occurrences of these long spells on each day of the year and also the occurrences of each of the seven defined weather‐types individually. This leads to a suggested division of the year into five periods, to be considered as natural seasons, and appears to support the definition of more numerous shorter seasonal phases or episodes (singularities). Good correspondence is found with the long‐year daily or weekly mean figures of pressure, temperature, rainfall, sunshine, etc. The significance of these phenomena, their dependability as regards date and their secular persistence are discussed.
Recent work of the Thunderstorm Census Organisation
Authors: Morris Bower S. 
Published: February 2007

AbstractThe weakness of the definition of a day with a thunderstorm as any civil day on which thunder is heard at a station, and the great difficulty of interpreting data on such a basis, is illustrated. An example of a thunderstorm chart based on the daily areas of overhead thunderstorms drawn from a close network of recording stations is presented and is compared with the “thunder‐heard” results. A method of producing detailed period and average maps, published as County Thunderstorm Surveys, is shown. The similar charting of daily areas of lightning damage provides a convenient and reliable method of examining the distribution of storm severity, and has many practical applications.Analyses of thunderstorms on individual days by means of hourly isochrones, published as Daily Thunderstorm Charts, present new opportunities for detailed comparison with rainfall maps and with radio thunderstorm recordings.
The lag of temperature behind solar radiation
Authors: Prescott J. A. , Collins Joyce A. 
Published: February 2007

AbstractThe annual march of air and sea surface temperatures has been examined by harmonic analysis and characterised by mean and amplitude and first harmonic value of phase. The phase has been expressed as the lag of temperature behind solar radiation and the data so obtained have been transferred to two world maps. A more detailed map relating to air temperatures over the United States is also given.Coastal stations are late in phase and inland basins are earliest. Western margins of the continents show a substantially later phase than eastern margins. This is associated with a tendency towards a late phase in the sea surface temperatures of the eastern sections of the oceans.
Note on the seasonal variation of the meridional flux of angular momentum
Authors: Starr V. P. , White R. M. 
Published: February 2007

AbstractA marked seasonal variation of the poleward angular‐momentum flux for the northern hemisphere in the vicinity of 30°N. latitude is obtained from an analysis of upper‐wind soundings for a period of one year. The angular‐momentum flux appears to be about twice as great during the winter as during the summer. Indications of a mean meridional circulation of the strength and character necessary to provide a substantial flux of angular momentum are lacking. It is suggested that the horizontal eddy flux of angular momentum across 30°N. latitude is sufficient to account for the drain of this momentum in middle latitudes.
Sonic and advective disturbances
Authors: Scorer R. S. 
Published: February 2007

AbstractThis paper describes the role of sonic disturbances in redistributing the mass of the atmosphere when heating or cooling is applied to a part of it. It is shown that the effect, for meteorological purposes, of heating is a local reduction of density and surface pressure. The pressure field thus set up causes an advective disturbance which later modifies the field by transport of mass with the wind.It is concluded that no disturbance of meteorological significance ever travels from one place to another otherwise than by advection.
The calculation of a sea‐breeze circulation in terms of the differential heating across the coastline
Authors: Pearce R. P. 
Published: February 2007

AbstractA method is derived for calculating the velocity, temperature and pressure distributions of the sea‐breeze produced when an initially isothermal and static atmosphere is heated differentially across a long straight coastline. Heat is assumed to be distributed vertically from the land surface by convection currents; internal friction is included but surface drag is taken as zero. The motion is separated into two parts, a rotational non‐divergent component near the coast and a mainly irrotational large‐scale tidal motion transferring mass from land to sea. The former is considered first and a numerical method devised to enable the non‐linear equations to be solved. The solutions are given as a set of diagrams each showing values of velocity, temperature and pressure calculated over a network of points, and each referring to a particular time in the development of the motion. In Section 5 the tidal motion is considered and an analytical solution obtained since the equations can be linearized. The rotational solution represents the spread inland of a tongue of cold air; well inland the wind rises some hours after heating has started, and is accompanied by a fall in temperature. An upper return current occurs in all the diagrams as well as subsidence over the sea and upper cooling inland. The vertical temperature profiles show a sharpening of the discontinuity in lapse rate at the top of the convection layer produced by the vertical velocity component. Conditions for convective instability are found to be produced dynamically in a shallow layer of the upper return current. Comments are made on the formation of ‘heat lows’ and ‘cold highs’ over continents.
Synoptic evidence for a direct circulation about a jet stream
Authors: Lee R. 
Published: February 2007

AbstractThe examination of a uniformly‐sloping tropopause surface during the eastward progression of a jet‐stream maximum reveals that the observed perturbation of the tropopause can be interpreted in terms of the vertical branch of a direct circulation occurring above a jet stream in the entrance region. Indirect evidence is also obtained for the existence of a corresponding direct circulation below the jet stream.
Radar observations of showers suggesting a coalescence mechanism
Authors: Feteris P. J. , Mason B. J. 
Published: February 2007

AbstractRadar evidence suggesting the production of showers by the coalescence process is presented. On 13 days during the summer of 1955, 48 separate echoes were observed to originate below the −2°C level and 26 of these remained there during the whole life of the shower. These echoes, which were often associated with mixed formations of cumulus and stratocumulus cloud, sometimes extended above the 0°C level at their maximum state of development, but surpassed the −8°C level on only one occasion. Some of the limitations of using radar alone in this type of study are discussed.
A wind analysis for the northern Irish Sea
Authors: Reynolds G. 
Published: February 2007

AbstractThis paper presents frequency distributions of winds recorded at five stations in the northern Irish Sea, Holyhead, Point of Ayre, Liverpool (Bidston), Southport and Fleetwood, particular stress being laid on the strong or gale‐force winds. Figures are published which may be used for estimating the highest hourly wind speed and maximum gust to be expected in a given number of years. The direction and time of these extreme winds are discussed. The frequencies of winds of different speeds are tabulated; the frequncies of gales and winds in excess of 40 kt are examined in detail.The relationships between the direction and strength of the geostrophic, gradient and surface wind over the area have been closely examined. It is found that neigther the geostrophic nor the gradient winds can be used to provide quantitative estimates of the surface winds either in speed or direction, on specific occasions, nor in the surface wind at one station closely related to the surface wind at another.The variation of wind speed throughout the year is indicated.
The hydrogen content of atmospheric air at ground level
Authors: Glueckauf E. , Kitt G. P. 
Published: February 2007

AbstractA method is described for the separation and determination of hydrogen in air samples of approximately 200 litres N.T.P. by volume. The hydrogen is fractionally distilled from the bulk of the sample, oxidized to water by passing over heated copper oxide and finally condensed in a trap cooled in liquid oxygen. After freeing from the contaminating gases by pumping, the water is released from the trap and measured as vapour in a small calibrated volume.Although the accuracy of the method in its present form is not better than ± 10 per cent, the results seem to indicate that the hydrogen content of atmospheric air is a varying quantity.The average hydrogen content of air at ground level is 0.6 parts per million.