Internal structure and occurrence of accretionary lapilli — a case study at Laacher See Volcano

Accretionary lapilli are common in fine-grained pyroclastic flow and surge deposits and related co-ignimbrite/co-surge ash layers of Laacher See volcano. Two morphologically different types are distin-guished: (1) Rim-type lapilli are composed of a coarse-grained core surrounded by a fine-grained rim. Rims are internally graded or made up of several layers of alternating fine and very-fine grained ash. (2) Core-type lapilli lack fine-grained rims. Field relationships, internal, and grain-size characteristics are specific to accretionary lapilli from different types of tephra deposits. Accretionary lapilli may therefore be a helpful tool to infer the origin of tephra of different origin. In co-ignimbrite ashfall, accretionary lapilli are generally concentrated at the base, whereas pyroclastic flow and surge deposits contain lapilli in the upper parts of individual, thin-bedded layers. Rim-type lapilli are found in pyroclastic flow and surge deposits up to 4 km from the source. Core-type lapilli occur at greater distances or are associated with vesiculated tuffs where they are within 1 km from the vent. Accretionary lapilli from co-ignimbrite/co-surge ash show open framework textures and edge-to-face contacts of individual ash particles. Vesicularity is generally low but the overall porosity of 40% to 50% results in an average density of 1200 kg/m³. Accretionary lapilli in pyroclastic flow and surge deposits are more densely packed and platy particles are often in face-to-face contacts. Vesicularity of those from pyroclastic flow deposits is significantly higher; the overall porosity is about 30% to 40% and the average density 1600 kg/m³. Grain-size analyses show that the accretionary lapilli in co-ignimbrite/co-surge ashfall deposits are the most fine-grained with a median (Md) of 20 to 30 m and a maximum grain size of 250 to 350 m. Accretionary lapilli from pyroclastic flow deposits have intermediate Md-values of 30 to 50 m and a maximum grain size of 350 to 500 m. Those of surge deposits are the coarsest grained with Md-values of 30 to >63 m and a maximum grain size up to 2 mm.     

On the efficiency with which aerosol particles of radius larger than 0.1 μm are collected by simple ice crystal plates

A theoretical model is presented which allows computing the efficiency with which aerosol particles of radius 0.1r10 m are collected by simple ice crystal plates of radius 50a _c 640 m in air of various relative humidities, temperatures and pressures. Particle capture due to thermophoresis, diffusiophoresis and inertial impaction are considered. It is shown that the capture efficiency of an ice crystal in considerably affected by phoretic effects in the range 0.1r1 m. For aerosol particles ofr>1 m the efficiency is strongly controlled by the flow field around the crystal and the density of the aerosol material. Trajectory analysis also predicts that aerosol particles are preferentially captured by the ice crystal rim. Our theoretica results are found to agree satisfactorily with the laboratory studies presently available. Comparison shows that for the same pressure, temperature and relative humidity of the ambient air ice crystal plates are better aerosol particle scavengers than water drops.     

Rotatory vibration of a thick spherical shell of isotropic non-homogeneous elastic material

Summary Rotatory vibrations of a thick spherical shell of isotropic non-homogeneous material with rigidity and density given by (i) = ₀ r ^-2 withQ =Q ₀ r ^-2 e ^2mr and (ii) = ₀ r ^m with =Q ₀ r ⁿ have been discussed and the frequency equation is derived with numerical enumeration of frequency in each case.     

Hazard evaluation of lead effects using marine protozoan communities

Protozoan communities developed in laboratory microecosystems were used to evaluate the toxic effects of lead ion. The lead was added as lead acetate in different concentrations (50 g · l^–1, 20 g · l^–1, 10 g · l^–1 and 1 g · l^–1). The protozoans were taxonomically identified and classified into functional groups according to their common nutritional type. The population dynamics of protozoa has been studied. In the control the most frequent groups were bacterivore-detritivores and photosynthetics (more than 75% of abundance). Noticeable lead effects were observed after 24 hours of exposure to metal in all fractions. In general, the lead caused reductions in the number taxa, in total protozoan abundance and in protozoan biomass. The diversity values decreased in more than two nep respect to control in the different fractions. At the end of assay, the protozoan communities structure was simplified in the fractions with lead and some species of little flagellates were dominant. The information provided by this microecosystems of protozoan community was more complex than the one provided by single-species bioassays. Community protozoan bioassays may give more information about the toxic effects to compare with actual ecosystems.     

Scientific objectives of the Solar Mesosphere Explorer mission

The 1981–82 Solar Mesosphere Explorer (SME) mission is described. The SME experiment will provide a comprehensive study of mesospheric ozone and the processes which form and destroy it. Five instruments will be carried on the spinning spacecraft to measure the ozone density and its altitude distribution from 30 to 80 km, monitor the incoming solar ultraviolet radiation, and measure other atmospheric constituent which affect ozone. The polar-orbiting spacecraft will be placed into a 3pm-3 am Sun-synchronous orbit. The atmospheric measurements will scan the Earth's limb and measure: (1) the mesospheric and stratospheric ozone density distribution by inversion of Rayleigh-scattered ultraviolet limb radiance, and the thermal emission from ozone at 9.6 m; (2) the water vapor density distribution by inversion of thermal emission at 6.3 m; (3) the ozone photolysis rate by inversion of the O₂(¹g) 1.27 m limb radiance; (4) the temperature profile by a combination of narrow-band and wide-band measurements of the 15 m thermal emission by CO₂; and, (5) theNO₂ density distribution by inversion of Rayleighscattered limb radiance at 0.439 m. The solar ultraviolet monitor will measure both the 0.2–0.31 m spectral region and the Lyman-alpha (0.1216 m) contribution to the solar irradiance. This combination of measurements will provide a rigorous test of the photochemical equilibrium theory of the mesospheric oxygen-hydrogen system, will determine what changes occur in the ozone distribution as a result of changes in the incoming solar radiation, and will detect changes that may occur as a result of meteorological disturbances.     

Effects of temperature and sliding rate on frictional strength of granite

Layers of artificial granite gouge have been deformed on saw-cut granite surfaces inclined 30° to the sample axes. Samples were deformed at a constant confining pressure of 250 MPa and temperatures of 22 to 845°C. The velocity dependence of the steady-state coefficient of friction (^ss) was determined by comparing sliding strengths at different sliding rates. The results of these measurements are consistent with those reported bySolberg andByerlee (1984) at room temperature andStesky (1975) between 300 and 400°C. Stesky found that the slip-rate dependence of (^ss) increased above 400°C. In the present study, however, the velocity dependence of (^ss) was nearly independent of temperature.     

Examen de quelques formules pour la predetermination de l'epaisseur du glacier a l'occasion de sondages recents

Summary Thirty years ago, when no easy and efficient process of sounding could reveal them the true depth of a glacier,C. Somigliana tried to help the glaciologist with a formula giving them the maximal thickness of any transverse section. Requisites were: breadth, maximal velocity, slope and coefficient of internal friction to be known. Commanding condition: no gliding of the ice on the glacier-bed. Numerous recent soundings of Swiss ice-streams did afford the opportunity of verifying the pertinency of the formula. Therefore the writer selected sixteen of the most reliable soundings and reckoned the values of the coefficient of viscosity . The results have been deceptive: if however the mean value of differs not much from 10¹⁴ CGS usually accepted (afterLagally), the divergencies are very great, extending from less than the half to almost the double (The same is been shown for the recent formulae ofHaefeli andKoechlin). Therefore no secure number can be derived for the required depth. The condition of no gliding is mostly not realized and the are therefore lessened. If however the real value of for the ice can ever be ascertained it will be possible to reckon the velocity of the up to now unmeasured gliding of the ice on the bed.     

On the propagation of wave from a cylindrical cavity

Summary This paper discusses the disturbance produced in an infinite layer of non-homogeneous elastic material characterised by =0 ⁿ and =0ⁿ(n>0) where and are the density and shear modulus respectively of the material, due to periodic torsional force applied on the wall of a cylindrical hole in the layer. The variation of the displacement component with the radius vector is shown graphically and compared with the corresponding homogeneous case.     

The effects of sliding velocity on the frictional and physical properties of heated fault gouge

The frictional properties of a crushed granite gouge and of gouges rich in montmorillonite, illite, and serpentine minerals have been investigated at temperatures as high as 600°C, confining pressures as high as 2.5 kbar, a pore pressure of 30 bar, and sliding velocities of 4.8 and 4.8×10^–2 m/sec. The gouges showed nearly identical strength behaviors at the two sliding velocities; all four gouges, however, showed a greater tendency to stick-slip movement and somewhat higher stress drops in the experiments at 4.8×10^–2 m/sec. Varying the sliding velocity also had an effect on the mineral assemblages and deformation textures developed in the heated gouges. The principal mineralogical difference was that at 400°C and 1 kbar confining pressure a serpentine breakdown reaction occurred in the experiments at 4.8×10^–2 m/sec but not in those at 4.8 m/sec. The textures developed in the gouge layers were in part functions of the gouge type and the temperature, but changes in the sliding velocity affected, among other features, the degree of mineral deformation and the orientation of some fractures.     

Infrared absorption spectra of atmospheric dust over an interior desert basin

Summary Based on the qualitative microspectrophotometric analysis of 287 atmospheric dust samples taken within the surface boundary layer over south central New Mexico, U.S.A. from May 1966 through October 1967, a representative infrared absorption spectrum from 4000 to 250 cm^–1 (2.5 to 40 m) is presented. The strongest absorption band is centered at 1027 cm^–1 (9,7 m), within the 1250 to 770 cm^–1 (8 to 13 m) atmospheric window, and is silicate induced. Two other strong broad absorption bands are the carbonate band at 1425 cm^–1 (7.0 m) and the silicate band at 468 cm^–1 (21.4 m). Temporal variations in the absorption spectra of the dust are observed primarily in the varying relative intensities of the 1027 and 1425 cm^–1 (9.7 and 7.0 m) absorption bands and in the occasional enhancement of the 1027 cm^–1 (9.7 m) band caused by sulfates in the dust. This study indicates that there is a close similarity between the absorption spectra of the atmospheric dust and the spectra of the small particle fraction of area soils, and between the representative dust spectrum and a spectrum of a synthetic mixture (by weight) of 80% silicates, 16% carbonates, and 4% nitrates.     

The oceans as source of cloud-forming nuclei

Summary The number and size of salt particles produced by the bursting of air bubbles in sea water has been measured. Bubbles of diameters varying between 1/2 and 2 mm each produced about 300 nuclei the sizes of which, under the electron microscope, were mainly between 0.1 and 0.5 diameter. They appeared to consist mainly of sodium chloride, the smallest ones containing only 10^–15 g of salt.These results, together with measurements of the size distribution of salt nuclei collected over the oceans in areas of spray formation, indicate that the total concentrations of salt nuclei over the oceans in winds of up to 15 m sec^–1 probably do not exceed 100 cm^–3. The corresponding rate of production of salt nuclei at the sea surface is estimated to be 1000 cm^–2 sec^–1. It is therefore inferred that sea spray contributes perhaps only one-fifth of the nuclei involved in cloud formation, the majority being the products of combustion, either natural or man-made.     

Contributions of H2S to the atmospheric sulfur cycle

H₂S is a most important biogenic sulfur compound with regard to the atmospheric sulfur cycle. Our present knowledge of the spatial and temporal distribution of this trace gas is rather incomplete owing to unreliable analytical methods. Therefore, a new method for the analysis of H₂S in the g-range was applied. This paper deals with the results of ground- and aircraft measurements of H₂S in unpolluted air over swamps and tidal flats. Based on the measured vertical distributions a removal coefficient of 2.3×10^–5 sec^–1 and an average lifetime of 12 hours were calculated. Some conclusions of the contribution of H₂S to the atmospheric sulfur budget are added.     

An approximate computation of infrared radiative fluxes in a cloudy atmosphere

A two-stream approximation is applied to the equation of infrared (IR) radiative transfer in order to compute the detailed structure of fluxes and cooling/heating rates in inhomogeneous, cloudy atmospheres. The spectrum between 4 and 400 m is split into 50 bands, and absorption of water vapour, uniformly mixed gases, ozone, water vapour polymers and water droplets are taken into account. Allowance is made for scattering by water droplets in the atmospheric window region (8–12.8 m) where the delta function approximation is used. The backward scattering coefficient is calculated from the asymmetry parameter by means of a new simple formula. The model is compared to other radiative transfer schemes and some applications are presented.     

On sea-salt nuclei in the atmosphere

Summary The residues of cloud droplets collected at the summit of a mountain were examined with an electron microscope and their materials were identified with the aid of micro-electron-diffraction method. About 30% of nuclei of cloud droplets larger than 5 in radius were mainly composed of sodium chloride and their masses were 10^–1210^–13 gr. We also found salt particles in snow crystals. Some discussions are made about the process of the capture of these particles by snow crystals.     

Propagation of surface waves on a nonhomogenous spherically aeolotropic shell

Summary This paper studies the propagation of Surface Waves on a spherically aeolotropic shell surrounded by vacuum. The elastic constantsc _ij and density of the material of the shell are assumed to be of the form _ij r ^l and _o r ^m respectively, where _{ij o} are constants andl, m are any integers.     

Rayleigh waves in an inhomogeneous medium

Summary Dispersion in Rayleigh waves is discussed for semi-infinite media with = ₁(1 ± cos s z) and = ₁(1 ± cosh s z), being the rigidity of the medium. A few workers tried with the above Fourier type of model but failed to find the dispersive nature. Because they neglected s due to the complexity of the calculation they arrived at a non dispersive frequency equation. This difficulty is removed in this paper and a dispersive frequency equation is obtained which shows both direct and inverse dispersion. The second model leads to non-convergent solution forz but shows many interesting results which are also discussed.     

On spectral extinction of solar radiation within a tropical atmospheric boundary layer

Helicopter measurements of solar irradiance and meteorological data within the atmospheric boundary-layer were made in Lagos during February 1979. Filter samples of aerosols were collected both during flight in February 1979 and at ground level in December 1978. Profile data on spectral aerosol optical depth were obtained and, from these, the aerosol extinction coefficient at two wavelengths (0.5 and 0.88 m) were calculated. Precipitable water was low and was contained mainly within the 750 m layer above ground, suggesting the establishment of a deep unstable boundary layer. Calculated channel energy depletions by aerosols show that, within the first 750 m of the surface, the 0·88 m might be more efficient at attenuating solar energy than 0·5 m. The lagoon (maritime) aerosol sample indicated a more monodisperse size-distribution than the dusty harmattan aerosol sample.     

Organic compounds in aerosol samples

In 1975, aerosols were collected with high-volume-samplers and impactors on the west coast of Ireland. The ether extractable organic material (EEOM) was separated into three main fractions: bases (B), acids (A), and neutral compounds (N). Each fraction is a very complex mixture of numerous species. Detailed investigations were carried out on these three main fractions. The individual species were determined quantitatively by gas chromatography. Qualitative identification was done by combined GC-MS.The concentration of total particulate matter (TPM) was in the range of 10 g/m³ (STP) air and the concentration of EEOM was 1 g/m³. The relative composition of the EEOM with regard to the main fractions A, B, and N was N>A>B — the same as in previous measurements. Particles with radii <1 m were investigated separately and showed an enrichment in organic matter.A comparison of individual species from several sample locations is now possible for then-paraffins C₁₀ to C₂₈. The concentrations of all thesen-paraffins are below 10 ng/m³, with no overall obvious preference for specific compounds and no obvious dependence on particle size above or below 1 m radius.A preliminary survey does not show any characteristic differences in the relative composition of the organic constituents of clean air aerosols from different sampling localities. The relative composition with regard to the three main fractions is rather uniform in clean air samples and in samples from polluted regions.     

Size distribution of airborne magnetic ‘back spherules’ in the 1–5 μ range

Summary Airborne particulate matter was sampled at Mt. Cimone, Italy, to determine the size distribution of black spherules in the 1–5 diameter range. The magnetic fraction of airborne particulate matter was separated by forcing air through a strong magnetic sampling device, where ferromagnetic particles accumulated on microscope slides.Sizes of the black spherules were determined by counting under a microscope. Samples were dissolved and analyzed for iron content. Distribution was found to be in agreement with that of deep-sea sediment and satellite high atmosphere samples. The rate of terrestrial accretion of cosmic matter composed of black spherules appears to be approximately 10^–15 g cm^–2 sec^–1.     

Large-scale structure of the magnetic field in the outer heliosphere

Summary Magnetic field structures at great distances from the Sun have been analyzed qualitatively for a simple vacuum reconnection model of the interplanetary and interstellar magnetic field. In dependence on the mutual orientation of the main solar dipole _s and the local interstellar fieldB ₀ , either an open or closed configuration of the large-scale field is formed. For(_s B ₀ )>0, the field lines are represented by a system of magnetic lines open towards interstellar space. In the case of(_s B ₀ )<0 there exist two zero-points and a separating surface below the heliopause separating the open lines of the interstellar field from the closed lines of the interplanetary field. The magnetic field configuration is characterized by a certain asymmetry, which is considered for(_s B ₀ )=0.