The impact of organic material on cloud and fog processes

Airborne surface-active organic substances can form adsorbed films at air-water and air-solid interfaces in the atmosphere. On the basis of considerable laboratory research, it has been suggested that these films can modify the microphysical processes of clouds and fog. The possible alterations of physical processes include retardation of the rate of growth and evaporation of water drops, passivation of cloud condensation nuclei, modification of drop coalescence efficiency, and the promotion of drop instability. The chemical structure of the film-forming compounds and the physical properties of the adsorbed films determine the degree to which the physical processes are modified. Upon consideration of the actual organic composition of the atmosphere, it was concluded that natural surface films will not greatly influence drop growth and evaporation. In addition, there is no definitive evidence from field experiments that other processes are influenced by natural organic films. The potential for useful weather modification through the intentional introduction of film-forming organic substances into the atmosphere was critically evaluated. Although numerous approaches have been suggested by laboratory studies, only the stabilization of airborne drops against evaporation has been unequivocally demonstrated in field experiments.     

An abundance model resource appraisal for some Canadian commodities

An abundance model resource appraisal has been undertaken for 10 mineral commodities in Canada: nickel, copper, zinc, lead, molybdenum, uranium, silver, gold, chromium, and tin. The purpose of the appraisal was to investigate the applicability of the model to the Canadian situation. Resource appraisals for the first 6 of the commodities studied have been published following deposit modeling studies. For many other commodities studied have been published following deposit modeling appraisals. The demonstration of the relevance of the abundance model to Canada would allow its application in such cases. The data presented in this paper indicate that the approximate relation, resource (short tons)=abundance (%)×10¹⁰. holds true for all commodities studied except chromium and tin. As the resources versus abundances relationship observed on a global scale is observable in Canada, it is concluded that Canada is a sufficiently large fraction (∼7%) of the earth's continental crust to represent a valid sample of that crust. Canada appears to be relatively well endowed with resources of copper, molybdenum, lead, and zinc, and poorly endowed with chromium and tin. It is proposed that the intersection of national boundaries with the boundaries of the world's metallogenic provinces is of greater importance than the intensity of past search, a feature that has been suggested in other studies. If these areas overlap, a nation may be self sufficient in a commodity: if they do not, the nation must import, or find a nationally available substitute. The sources of information used in the appraisal are outlined together with an analysis of the problems encounterea and the time requirements. This paper was presented at the International Geological Correlation Program (IGCP) Project 98: “Standards for Computer Applications in Resource Studies” held at Taita Hills Kenya, November 8–15, 1977.     

A case history of regional geoscience data integration and analysis for the purpose of mineral resource appraisal, kasmere lake area, Manitoba

The methods used to generate a unified cell structured data base for geological, mineral occurrence, geochemical, and three different types of geophysical data are reviewed. The extremes of both excess and paucity of data were encountered and procedures for data compression and interpolation between known values were required. In the latter case a weighted moving average was used to take advantage of knowledge of the regional geological structure in an informal kriging. Classical approaches based on training data sets were investigated and found to be wanting in the area due to the inadequate mineral occurrence data base. The few data cells containing mineral occurrences were known with certainty; however, many of the cells classified as non-mineral occurrence containing, due to the immature exploration history, probably contained mineral occurrences of equal or greater significance. This inadequacy in the mineral occurrence data base confounded formal statistical analysis. An empirical scoring approach was developed which draws on general exploration criteria. This methodology, based on the geochemical and geophysical data, was used to prepare an Athabasca type uranium deposit favorability index. The favorable areas are examined in terms of the known geology. Results show that the majority fell in areas that would also be considered favorable by geologic models for Athabasca type uranium deposits. This empirical approach, based on geochemical and geophysical interpretive procedures, may have particular potential in poorly explored areas lacking good training sets.Paper presented at the 10th Geochautauqua: Computer Applications in the Earth Sciences, 23–24 October 1981, Ottawa, Canada.     

A statistical analysis of the low-energy geosynchronous plasma environment—I. Electrons

There has been a long-standing lack of detailed statistical information on the low-energy (1-eV–100-keV) geosynchronous plasma environment. In this paper, data on the electron environment between ～30 eV and 80 keV were analyzed from a statistical standpoint. Specifically, ～50 days of 10-min averages of the first 4 moments of the distribution function from the University of California at San Diego low-energy plasma detectors on the ATS-5 and ATS-6 geosynchronous satellites were analyzed in terms of: occurrence frequency, local time variations, K_p variations and variations at a given local time following injection. The 4 moments were intercompared and simple expressions capable of simulating their relationships empirically derived. In conjunction with this analysis, the accuracy of the 4-moment representation was tested and, for the electrons, found to be of value in specifying the background electron environment at geosynchronous orbit.     

The effect of earthquake duration on the damage of structures

This paper presents a theoretical analysis of the effect of duration on the damage of structures subjected to earthquakes. The earthquake excitation is modelled by a non-stationary random process whose response spectrum is probabilistically consistent with a design response spectrum specified independently of the duration. Damage is assumed to accumulate with the cyclic application of large strains in the structural members. Two types of structure are examined: one representative of a steel structure and the other reprsentative of a reinforced concrete structure. The level of expected damage is found to be a strong function of both the ductility of the response and the duration of the excitation. Results are presented for systems with linear stiffness and a particular form of softening behaviour.     

The chi-square plot: a tool for multivariate outlier recognition

In large multi-element regional surveys statistically derived threshold levels of the form that define, for example, the top 2% of the data for each element as worthy of further investigation have led to the generation of inordinately large lists of geochemical samples for detailed study. This problem is compounded when a number of geological and secondary environments exists of sufficiently different character that separate thresholds should be estimated for each. Additionally, single-element thresholds for multi-element surveys can, in certain circumstances, lead to obviously out-of-character individuals not being recognized.Numerical approaches to the problem of anomaly recognition have commonly used a principal-component or regression analysis procedure as their basis. These, as indeed do all such approaches, have a common drawback in that the outliers being sought can distort the analysis being used to detect them. In addition, regression models have the further problem that there may be outliers in both the response and explanatory variables.A relatively simple approach would be to prepare a multivariate cumulative probability plot where each multi-element geochemical sample is represented as a single value. The resulting diagram would be interpreted much as a univariate probability plot where the presence of more than one straight-line segment is taken as evidence of multiple populations, and outliers as individuals or small groups are separated from the remaining data by gaps on the plot.Such a diagram may be prepared by plotting the rank-ordered values of the generalized or Mahalanobis distance, a multivariate distance measure, versus values of the chi-square statistic. This procedure is based on the covariance matrix of the data, a measure that underlies both principal-component and regression model approaches. In order to work effectively a statistically robust starting covariance matrix is essential.The procedure is described in detail with two examples, one a synthetic bivariate data set containing known outliers, and the other a small, well studied stream sediment data set from Norway extensively used in methodological comparison studies. The result of the procedure is to identify statistical outliers, which are candidates for interpretation as true geochemical anomalies, and to isolate a multi-element subset that is representative of the geochemical background.