This thesis is divided into two distinct parts, each containing a review of the relevant literature. In the first part, the packing of sands at a range of moisture contents was studied using both static loads and impacts provided by a Bruce compactor. Particle shape and particle size distribution were found to determine the maximum and minimum void ratio to which a sand would pack. With sand of greater than 45 Um in size, particle size was not found to exert a major effect on packing. Limitations to the concept of packability or ease of packing are discussed in detail. For narrowly graded sands, air-dry and nearly saturated sands were always foundto pack more closely than the same sand at any other moisture content. For a wide range of intermediate moisture contents, there was practically no effect of moisture content on packing.When saturated mixtures of sand with the addition of a small proportion of calcium-saturated kaolin were allowed to air-dry, they were found to pack to near their minimum void ratio without the aid of any externally applied force.In the second part, the strength of mixtures of sand with 0,0.5, 2 and 8 per cent kaolin was studied as a function of watertension and moisture content. Kaolin did not cause a large increase in strength until water tensions greater than 100 mbar. The concept of effective stress was extended by considering that the kaolin and water acted together within kaolin bridges which were observed to link sand grains up until air-entry occurred into the kaolin itself. In this way it was possible to explain the variation of strength of the mixtures over a range of water tensions from 20 mbar to 10 bar. The relevance of these results to the behaviour of soils and agricultural research is outlined.

No description available.

<p> The amplitude and spectral shape of shortwave radiation are used to retrieve aerosol and cloud properties from airborne and ground based measurements. By interacting with clouds and aerosols in the Earth's atmosphere, the wavelength-dependent radiation emitted by the sun is modified. This thesis presents the change in radiation due to absorption and scattering by clouds and aerosols, which result in distinct spectral signatures in shortwave radiation spectra. </p><p> The spectral signature in shortwave radiation due to aerosols is quantified by airborne measurements of irradiance above and below aerosol layers. This radiative effect is quantified by the relative forcing efficiency, which is used to compare the impact of aerosols from different air masses, locations, and time of day. The relative forcing efficiency is the net irradiance change due to the presence of aerosols normalized by aerosol optical thickness and incident irradiance. It is shown to vary by less than 20% per unit of midvisible aerosol optical thickness for aerosols sampled during 4 different experiments, except for highly absorbing aerosols near Mexico City. The similarity in relative forcing efficiency for these experiments, not expected a priori, suggests that this quantity is constrained for various types of aerosols with differing scattering and absorption characteristics even when surface albedo differs. To estimate the radiative effect of aerosols sampled in the Los Angeles basin during one of the experiments, where no concurrent measurements of optical thickness with spectral irradiance were available, a new iterative technique was devised to use aerosol optical thickness measurements from another airborne platform. </p><p> Cloud-transmitted zenith radiance spectra were measured from the ground in Boulder, Colorado. In these measurements, spectral signatures of cloud optical and microphysical properties were uncovered. The spectral signatures are the result of radiation that is transmitted through clouds, where ice or liquid water cloud particles modulate the radiation by absorbing and scattering incident light in a wavelength-dependent manner. Typically, the magnitudes of radiance at 2 wavelengths have been used to retrieve cloud properties, but by using wavelength-dependent features more sensitivity to cloud microphysical properties is obtained. This thesis presents a method to analyze wavelength-dependent signal, where spectral features such as slopes, curvatures, and shifts in locations of maxima and minima are parameterized. These spectral features found in normalized radiance are quantified by introducing 15 parameters. These 15 parameters form the basis of a new generalized retrieval obtaining cloud optical thickness (&tau;), effective radius (<i>r_e</i>), and thermodynamic phase (&phis;). When applied to a liquid water cloud case, this retrieval matched a measured transmittance spectrum with a smaller root mean square difference over the entire spectrum (3.1%) than two other methods (up to 6.4%). To quantify the retrieval over all possible combinations of &tau;, <i> r_e</i>, and &phis;, simulated measurements were used in conjunction with realistic measurement and model error characteristics. By combining these error characteristics within the GEneralized Nonlinear Retrieval Analysis (GENRA) a solution probability distributions can be built. The information of cloud properties contained within cloud-transmitted radiance is greater on average for liquid water clouds than for ice clouds. For all possible combinations of cloud properties, radiance transmitted through clouds with &tau;&lt;20 contain the most information on cloud properties, indicating that the 15 parameters have greatest sensitivity to cloud properties of optically thin clouds (&tau;&lt;20). Of the 15 parameters, only 10 are required to retrieve accurately &tau;, <i> r_e</i>, and &phis; for any cloud except for ice clouds with &tau;>25 and <i>r_e</i>>30 &mu;m. Using this retrieval, the correct thermodynamic phase is determined from transmittance with a probability greater than 99.4% for horizontally homogeneous clouds that contain either ice or liquid water cloud particles.</p>

A brief introduction to the theory of magnetism and magnetic domains is given which is followed by a review of X-ray topography techniques and an outline of the theory and contrast mechanisms necessary for the interpretation of the topographs. Results are presented on the perfection of flux grown rare-earth germanate crystals which clearly indicate the usefulness, to the crystal grower, of synchrotron X-ray topography for rapid routine assessment of a large number of crystals. The techniques of neutron topography are described and some of the more important results obtained are reviewed. Results obtained with neutron topography on the possible correlation between surface vicinal features and dislocations in holmium galium garnet are presented. These results, although not conclusive, provide further evidence of a probable correlation. Previous work reported on the antiferromagnetic KCoF(_3) is described with particular reference to the limited number of domain observations. Previous work on the motion of antiferromagnetic domain walls under an applied magnetic field has been extended by considering the case of the motion of these walls under an applied stress using both synchrotron X-ray topography and rocking curve measurements. The critical stress achieved was in reasonable agreement with that predicted from the magnetic field data. These results also confirm that data obtained in torque magnetometry and linear dichroism experiments may be explained by the motion of antiferromagnetic domain walls under stress. Work on the magnetic properties of terbium is reviewed, particularly work relating to measurements of magnetostriction. An X-ray technique for measuring the magnetostriction of high magnetostriction materials without resorting to absolute lattice parameters is described and the results obtained on using this technique to measure the magnetostriction of terbium are presented. These results are fitted to a two-ion interaction model. Work on the highly magnetostrictive Tb(_.27)Dy(_.73)FE(2) is described and results are presented on the observation of magnetic domains in this material in an applied magnetic field. Calculations of the domain wall energies and widths are presented which enabled the domain structure to be interpreted.

The last two decades have seen the publication of a large number of papers dealing with Palaeozoic acritarchs including many devoted to the description of Ordovician assemblages. It has become clear that, these microfossils have considerable potential for correlation and that they are frequently recovered From sequences otherwise devoid of fossil material. In Britain, acritarchs have been described in detail from the Cambrian (Potter 1974 M. S.); Tremadoc (Rasul 1971 M. S., 1974, 1977a, l977b) and from the Silurian (Lister 1966 M. S., 1970; Hill 1974 M. S.) Until the recent work of Booth (l979 M. S.) dealing with Arenig-Llanvirn assemblages, no detailed systematic investigation of British Ordovician acritarchs had been attempted. The primary objective of the present study is to provide a comprehensive description of acritarchs from the Middle and Upper Ordovician of Britain, with particular emphasis on the type-areas of the Llandeilo and Caradoc. In conjunction with the work of Booth it is hoped that this account will go some way towards providing a biostratigraphical framework which will facilitate the use of these microfossils for the purposes of correlation in the Ordovician.

No description available.

No description available.

<p> Thermal remote sensing is a powerful tool for measuring the spatial variability of evapotranspiration due to the cooling effect of vaporization. The residual method is a popular technique which calculates evapotranspiration by subtracting sensible heat from available energy. Estimating sensible heat requires aerodynamic surface temperature which is difficult to retrieve accurately. Methods such as SEBAL/METRIC correct for this problem by calibrating the relationship between sensible heat and retrieved surface temperature. Disadvantage of these calibrations are 1) user must manually identify extremely dry and wet pixels in image 2) each calibration is only applicable over limited spatial extent. Producing larger maps is operationally limited due to time required to manually calibrate multiple spatial extents over multiple days. This dissertation develops techniques which automatically detect dry and wet pixels. LANDSAT imagery is used because it resolves dry pixels. Calibrations using 1) only dry pixels and 2) including wet pixels are developed. Snapshots of retrieved evaporative fraction and actual evapotranspiration are compared to eddy covariance measurements for five study areas in Florida: 1) Big Cypress 2) Disney Wilderness 3) Everglades 4) near Gainesville, FL. 5) Kennedy Space Center. The sensitivity of evaporative fraction to temperature, available energy, roughness length and wind speed is tested. A technique for temporally interpolating evapotranspiration by fusing LANDSAT and MODIS is developed and tested.</p><p> The automated algorithm is successful at detecting wet and dry pixels (if they exist). Including wet pixels in calibration and assuming constant atmospheric conductance significantly improved results for all but Big Cypress and Gainesville. Evaporative fraction is not very sensitive to instantaneous available energy but it is sensitive to temperature when wet pixels are included because temperature is required for estimating wet pixel evapotranspiration. Data fusion techniques only slightly outperformed linear interpolation. Eddy covariance comparison and temporal interpolation produced acceptable bias error for most cases suggesting automated calibration and interpolation could be used to predict monthly or annual ET. Maps demonstrating spatial patterns of evapotranspiration at field scale were successfully produced, but only for limited spatial extents. A framework has been established for producing larger maps by creating a mosaic of smaller individual maps.</p>

The lateral distribution of muons of energy E(_u) >500 MeU in E.A.S. of median size 3.10(^5) particles at sea level and their correlation to the electron structure function (shower age parameter) has been investigated using a large flash tube chamber operated in conjunction with the Durham E.A.S. array. The lateral distribution seems to be not dependent on shower size, but for the more inclined and older showers it tends to be flatter. Old showers of a given size are found to contain a greater total number of muons than young showers of the same size. A measurement of the size spectrum has been performed in which the size and collecting area take into account the age parameter of a single shower. Except at very small and large shower sizes, the spectrum shows a close agreement with the spectrum obtained assuming all showers obey the Greisen average lateral structure function. A search for charged e/3 particles (quarks) close to the core of E.A.S. has been carried out using the flash tube chamber. In 511.2 hours running time, 2 low efficiency tracks have been observed but none fulfil all the criteria as a genuine quark candidate. A search for any preferred arrival direction of showers in galactic coordinates has been carried out, The results show an overall isotropic primary flux but in the galactic chart two anomalous regions (regions with an excess of events) are observed. Correlation of the regions with the known cosmic ray sources (supernova remnants, pulsars, quasars, X and y-ray sources) have been studied.

A method of transforming magnetic anomalies into pseudogravimetric anomalies which uses fast Fourier transforms and a method of interpreting gravity anomalies in three dimensions using a non-linear optimization technique which involves automatic end corrections are developed. These methods have been used to interpret the complicated aeromagnetic anomalies over the Mull, Skye and Blackstones Bank Tertiaryigneous centres of N.W. Scotland. One inch aeromagnetic maps over the complexes have been digitized at 1 km intervals covering 32 x 32 km2 (Mull and Blackstones Bank) or 64 x 64 km (Skye).The strongly magnetized rocks of the Mull complex extends in the preferred model to a depth of 2.1 km with normal magnetization of 6.7 A/m. This body is smaller in depth and a real extent than the gravity model of the complex. The magnetic model of the Skye complex consists of two strongly magnetized bodies of opposite polarity and a weakly magnetized region corresponding to the Red Hills granites. A reversely magnetized body of depth extent in the range 1.5km - 3.0km with a modelling magnetization of 4.9 A/m can be identified with the basic and ultrabasic rocks of the Cuillin centre. Normally magnetized body probably represents more weakly magnetized deep seated body which underlains the whole complex and extends to a modelled depth of 14 km with a modelling magnetization of 1.1 A/m. This composite model has approximately equal dimensions to the dense rocks of the gravity model. The main body of the Blackstones Bank magnetic model extends to a depth of 15 km with reverse magnetization of 0.93 A/m. A shallow normally magnetized body occurs within this to depth of the order of 1.0km - 5.0km with a magnetization in the range O.OA/m-2.47 A/m. The composite model has approximately equal dimensions to the gravity model. Intense negative anomalies over the lavas and over some intrusive rocks demonstrate the strong remanent magnetization of these rocks. The magnetic interpretations show that basic and ultrabasic rocks are strongly magnetized and large in volume and the granitic rocks are small in volume, shallow and weakly magnetized. Generally, the magnetic interpretations agree with previous gravity interpretations.