Saving farmland,a Canadian program

This paper deals primarily with the steps followed by the Ontario government to save farmland. The development of policy responses to preserve Ontario farmland are not of long-standing duration. Although the Urban Development in Rural Areas (UDIRA) policy announced in 1966, could have led to greater provincial supervision no action was undertaken in the form of direct controls or guidelines until ten years later. In 1976 the government published documents which were to lead to the establishment of Food Land Guidelines. The Guidelines have been effective in preserving farm land but since they have been operative for such a short time it is probably too early to make a definitive statement. The results of hearings with respect to the urbanization of prime tender fruit land in Niagara have shown the Guidelines to be effective in setting boundaries between urban and agricultural uses. Further proof of the durability of the Guidelines in maintaining land in agriculture is evidenced by the low resale rate of farm related lots to non-farm uses.     

Behavior of the geodynamo during reversal: A phenomenological model

The solar isotopic composition of Sm is decomposed into s, r andp components. The anomaly pattern discovered [1] in EK1-04 Allende inclusion can be presented as a fractionation of the average s-pattern from the average r-pattern. This representation requires a fractionation of 0.029% (amu)^?1 and either (1) a 0.42% deficiency of s relative to r and a 0.15% deficiency of p relative to r, or (2) a 0.42% excess of r relative to s and a 0.27% excess of p relative to s. The nature of this anomaly suggests a systematic physical fractionation of r, s and p nuclei from each other in the initial condition leading to EK1-04. A neighboring supernova injection would not be expected to produce this anomaly.     

The med-dead sea project — A vision or reality?

The dramatic proposal to link the Mediterranean Sea to the Dead Sea by a canal or tunnel, for the purpose of power generation, is currently being investigated in Israel. This paper examines the various route alignments which have been advocated and suggests that the two Southern routes present the potentially greatest advantages. These are then discussed at greater detail, and attention directed to outlining the range of possible economic advantages as well as potential ecological impacts.     

The Sierra Club and the Law of the Sea

The office of International Environmental affairs of the Sierra Club is focusing its attention on a number of issues, identified at the UN Stockholm conference last year as significant. One of these is the Law of the Sea. This article is an abbreviated version of a preliminary paper prepared for a Working Party or Task Force that is examining the issues and attempting to produce an integrated view of all the issues.     

显微CT的锥束重建技术

显微CT技术一直是Iowa大学CT/显微CT实验室研究的焦点。这篇文章报告了我们在锥束显微CT方面最近取得的一些进展。我们利用Feklkamp类算法了多X光源和检测器偏置条件下的近拟图象重建；解释了Grangeat精确重构框架下的图象伪影。最后重点介绍了最近有关一般分块迭代Landweber格式的收敛性结果；给出了模拟和实验结果，探讨了进—步的研究方向。     

Dynamical System Analysis and Forecasting of Deformation Produced by an Earthquake Fault

— We present a method of constructing low-dimensional nonlinear models describing the main dynamical features of a discrete 2-D cellular fault zone, with many degrees of freedom, embedded in a 3-D elastic solid. A given fault system is characterized by a set of parameters that describe the dynamics, rheology, property disorder, and fault geometry. Depending on the location in the system parameter space, we show that the coarse dynamics of the fault can be confined to an attractor whose dimension is significantly smaller than the space in which the dynamics takes place. Our strategy of system reduction is to search for a few coherent structures that dominate the dynamics and to capture the interaction between these coherent structures. The identification of the basic interacting structures is obtained by applying the Proper Orthogonal Decomposition (POD) to the surface deformation fields that accompany strike-slip faulting accumulated over equal time intervals. We use a feed-forward artificial neural network (ANN) architecture for the identification of the system dynamics projected onto the subspace (model space) spanned by the most energetic coherent structures. The ANN is trained using a standard back-propagation algorithm to predict (map) the values of the observed model state at a future time, given the observed model state at the present time. This ANN provides an approximate, large-scale, dynamical model for the fault. The map can be evaluated once to provide a short-term predictions or iterated to obtain a prediction for the long-term fault dynamics.     

Shallow seismic reflection profiles and geological structure in the Benton Hills, southeast Missouri

During late May and early June of 1993, we conducted two shallow, high-resolution seismic reflection surveys (Mini-Sosie method) across the southern escarpment of the Benton Hills segment of Crowleys Ridge. The reflection profiles imaged numerous post-late Cretaceous faults and folds. We believe these faults may represent a significant earthquake source zone.

The stratigraphy of the Benton Hills consists of a thin, less than about 130 m, sequence of mostly unconsolidated Cretaceous, Tertiary and Quaternary sediments which uncomfortably overlie a much thicker section of Paleozoic carbonate rocks. The survey did not resolve reflectors within the upper 75–100 ms of two-way travel time (about 60–100 m), which would include all of the Tertiary and Quaternary and most of the Cretaceous. However, the Paleozoic-Cretaceous unconformity (Pz) produced an excellent reflection, and locally a shallower reflector within the Cretaceous (K) was resolved. No coherent reflections below about 200 ms of two-way travel time were identified.

Numerous faults and folds, which clearly offset the Paleozoic-Cretaceous unconformity reflector, were imaged on both seismic reflection profiles. Many structures imaged by the reflection data are coincident with the surface mapped locations of faults within the Cretaceous and Tertiary succession. Two locations show important structures that are clearly complex fault zones. The English Hill fault zone, striking N30°–35°E, is present along Line 1 and is important because earlier workers indicated it has Pleistocene Loess faulted against Eocene sands. The Commerce fault zone striking N50°E, overlies a major regional basement geophysical lineament, and is present on both seismic lines at the southern margin of the escarpment.

The fault zones imaged by these surveys are 30 km from the area of intense microseismicity in the New Madrid seismic zone (NMSZ). If these are northeast and north-northeast oriented fault zones like those at Thebes Gap they are favorably oriented in the modern stress field to be reactivated as right-lateral strike slip faults. Currently, earthquake hazards assessments are most dependent upon historical seismicity, and there are little geological data available to evaluate the earthquake potential of fault zones outside of the NMSZ. We anticipate that future studies will provide evidence that seismicity has migrated between fault zones well beyond the middle Mississippi Valley. The potential earthquake hazards represented by faults outside the NMSZ may be significant.     

Platinum group metals in common plants of northern forests: developments in analytical methods, and the application of biogeochemistry to exploration strategies

All platinum-group metals (PGM) in ashed plant tissues, from an area of platinum mineralization in Saskatchewan, have been measured by neutron activation analysis of a NiS fire assay bead. Concentrations of up to 1350 ppb (ng/g) Pd, 880 ppb Pt, 49 ppb Rh, 37 ppb Ru, 24 ppb Ir, and 15 ppb Os occur in ashed twigs of black spruce (Picea mariana), indicating that the ratios of PGM uptake are about the same as those occurring in the bedrock. Plants growing on drift-covered diabase, known to have about 100 ppb PGM, contain up to 77 ppb Pt in ash, demonstrating the potential value of biogeochemical methods in helping to delineate platiniferous zones. Twigs of black spruce, jack pine, and labrador tea appear to be the optimum sample media in this environment.A rapid multi-element neutron activation analysis by direct irradiation of tissue permits measurement of 0.05 ppb Ir in dry material, or 2 ppb Ir in ashed samples. In view of the normally very low concentrations of Ir in plants, any detectable Ir probably indicates enrichment of PGM in the substrate.Comparison of several wet-chemical analytical methods indicates that the optimum (cost-effective) technique for detecting 1–2 ppb Pt, Pd, or Rh in 2-g samples of ash is by Te co-precipitation (following fusion and dissolution), and analysis by ICP-MS with sample introduction by electrothermal vaporization. However, care must be taken to ensure complete dissolution of all PGMs in the ash.     

The microcomputer in geochemical exploration

A microcomputer system can be a powerful interpretive tool in the hands of the explorationist, particularly for his geochemical surveys. Data entry and plotting of site parameters and/or trace-element values on 18 cm × 26 cm maps, on site, can be carried out at reasonable cost with available technology. Plotting characteristics of some microcomputer systems are the equal to those of mainframes.All geochemical data, even for surveys of 38 elements with up to four sample media, can be displayed by a large plotter as ten single-element plots (18 cm × 26 cm) on each of four mapsheets. Plotting 2000 points for ten elements requires five hours and can be scheduled for overnight operation. Elements showing meaningful variations can be replotted subsequently at large scales using character and/or symbol formats. Examples of geochemical plots are given for soil- and stream-sediment surveys and for drill-core lithogeochemical studies.The microcomputer can calculate statistics; however, large numbers of such calculations are slow. Transfer of data to a mainframe computer allows access to fast, sophisticated statistical software. The mainframe can also provide high-quality laser-printed paper copy and can be used for fail-safe archiving.