Photovisual light curve and photometric elements of the eclipsing nucleus of the planetary nebula Abell 63

The firstV-photoelectric light curve (on theUBV system) of the eclipsing variable UU Sagittae (constituting the central star of a faint planetary nebula Abell 63) was obtained in 1979 with the 74 in. reflector at the Kottamia station of Helwan Observatory in Egypt, and analysed for the photometric elements of the system. Some of the geometrical elements obtained by us differ significantly from those previously deduced by Bondet al. (1978) from theirB-light curve secured in 1976; but there is no reason to suspect from this that any physical change has taken place in the system between 1976 and 1979.The most significant feature of the light curve of UU Sge (in both colours) is the large amplitude of the reflection effect exhibited between minima, as well as the fact that the secondary minimum appears to be almost wholly due to an eclipse of reflected light. This, combined with the depths of the alternate minima observed in both colours, leads us to conclude that the effective temperature of the O-type component is probably not much higher than 30 000 K, while that of the secondary component is not less than 6000 K (corresponding to a subgiant of spectral class close to G0).     

On the behaviour of the hydrogen Lyman series in flares

The Lyman spectrum of hydrogen has been computed for a number of flare models, characterized by the column density of hydrogen atoms in the ground state (N ₁), the electron density (n _e) and the electron temperature (T _e). Broadening by the thermal Doppler effect and by Stark effect has been accounted for. The source functions for the individual lines of the series have been derived from non-LTE calculations of the excitation in hydrogen flares. The aim of the investigation is to evaluate the use of the intensities in between two successive Lyman lines for a determination of the value for N ₁, which is a physical parameter of the flare for which only indirect determinations are available. Whilst in principle this method could give reliable results, its practical application meets with difficulties which hardly can be overcome. Therefore, one probably has to base the N ₁ determination on the highest line resolvable in the spectrum.     

Highlights of the Flare Build-up Study

Years of preparation within the framework of the Flare Build-up Study culminated with intensive observations of solar flares during the Solar Maximum Year (1979–1981). Scientists operating several spacecraft and roughly 70 ground-based observatories participated in an internationally coordinated effort to observe flares with higher spatial, spectral, and temporal resolution over a wider range of wavelengths than heretofore. The FBS stimulated important advances in theories of magnetic reconnection and the growth of plasma instabilities under preflare circumstances. A series of international FBS workshops facilitated data exchanges and collaborative studies for interpreting and synthesizing the wealth of new information about flares. The FBS ended officially at the Symposium on Synopsis of the Solar Maximum Analysis held 2–5 July, 1986 at the COSPAR meeting in Toulouse, France. Here we summarize highlights of its progress towards an understanding of the storage and release of preflare energy.     

A new spatial prediction model and its application to wind records

Summary Contour maps of any meteorological variable cannot give radius or area of influences around the measurement station by considering the records at surrounding sites. The main purpose of this paper is to propose a trigonometric point cumulative semivariogram (TPCSV) concept for deciding on a spatial dependence function and then its use for regional prediction. The TPCSV provides a unique opportunity for the establishment of a regional objective prediction method whereby the radius of influence helps to predict wind velocity at any site by using the weighted averages. The spatial correlations and weightings are obtained through the TPCSV provided that the distance between two sites is known. If the slope of TPCSV is greater than 80° after some distance, then beyond this distance the regional correlation is considered as negligible. The implementation of the proposed methodology is presented for 68 wind velocity measurement stations in Turkey. The proposed method yields the least prediction error compared with other objective methodologies. It is seen that areas of influence at Central Anatolia are generally bigger than coastal areas of Turkey.     

Zinc, Lead and Cadmium Content in Meadow Plants and Mosses Along the M3 Motorway (Hungary)

The heavy metal content was investigated in meadow plants located in a cultivated area and situated along the M3 motorway (Hungary). In addition to the meadow plants used as passive bioindicators, active bioindicators were also exposed to examine the accumulation rate of air pollutants. Tortula ruralis (Hedw.) Geartn. ssp. ruralis was applied to monitor the status of the environment. Meadow plant samples were collected at distances of 5, 10, 25, 50 and 100 m from the motorway and moss samples were exposed at the same distances. The zinc, lead and cadmium content of meadow plants and moss samples were analysed by ICP spectrophotometry. It was found that the zinc, lead and cadmium contents of the meadow plants decreased as the distance increased from the motorway. There was a significant difference even between values measured at the distances of 5 m and 10 m. The heavy metal contents in the moss samples exceeded those of the meadow plants. The heavy metal content in moss samples decreased with distance from the motorway. On comparing the data with Hungarian standards, it was found that measured values did not exceed the maximum allowed concentration levels.     

Arsenic Speciation in Lichens and in Coarse and Fine Airborne Particulate Matter by HPLC–UV–HG–AFS

A three-step sequential extraction procedure with Milli-Q, CaCl₂ and H₃PO₄ was applied for extraction of arsenic species in lichen transplants and airborne particulate matter (fine and coarse fractions). The samples used in this work were collected in 1994–1995 near coal-fired power plants. Both transplant lichens and airborne particulate matter were submitted to the same environment simultaneously. Arsenic species identification and quantification was performed by HPLC–UV–HG–AFS. Inorganic forms of arsenic (arsenite and arsenate) were present in significant amounts in most of the samples. Only in lichens also organic forms of arsenic (monomethyl arsonic acid and dimethyl arsinic acid) were identified which may indicate biotransformation of inorganic arsenic.     

OH defects in cassiterite

Summary Two infrared (IR) spectral types are discerned in cassiterites with OH defect concentrations ranging from several wt. ppm H₂O in synthetic melt-grown samples up to 0.017wt.% in natural samples of hydrothermal origin. Spectrum type I is characterised by one sharp band centred at 3255cm^–1, type II spectra reveal an additional band group centred around 3340cm^–1, which is clearly correlated with the presence of Ti. Both OH band groups are strongly polarised with maximum absorption perpendicular to the c-axis. Type I spectra prevail in nearly colourless samples, type II spectra typically occur in light to dark brown cassiterites, bearing essentially higher amounts of minor elements, especially Ti, Nb, Ta, W, Zr, and Fe. The total amount of water is not significantly correlated with the minor element content. It is concluded that different OH concentrations reflect different water activities prevalent during the formation of cassiterite crystals in different geological environments.     

Analysis of Wedge Stability Using Different Methods

Summary The stability problem of a rock slope containing a wedge resting on two intersecting discontinuities is of great interest in rock slope engineering. It is a statistically indeterminate problem with two extra unknowns according to the force (stress) equilibrium analysis. The widely used limit equilibrium methods in practice assume that the directions of the shear forces acting on the two discontinuities are parallel to their line of intersection. The validity of this assumption, however, has not been verified theoretically. This paper presents a general limit equilibrium method that determines the directions of the shear forces by using Pans Maximum principle and an upper bound method that applies the classic upper bound theorem of limit analysis to avoid making extra assumptions. The formulations of the two methods are derived. A non-symmetric wedge and a symmetric wedge are analyzed using the two derived methods. To further explore the influence on stability due to the direction of the shear force acting on the two discontinuities, three-dimensional finite-element analyses are also conducted. The results are compared and discussed.