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Increasing occurrence of extreme heat waves poses serious risks to human society and ecosystems. Past studies generally examined the changes in heat wave characteristics at individual stations or grid points; however, a heat wave typically appears as a regional event being continuous in time and space. Using an objective identification technique for distinguishing regional extreme events and a metric for measuring regional heat wave magnitude (i.e., an integrated index that accounts for heat wave intensity, duration, and spatial extent), this study revealed an approximate doubling in both the frequency and the magnitude of regional heat wave events observed over 1960–2018 in China. The identified top three regional heat wave events occurred in the summers of 2013, 2017, and 2003, respectively. Fine-resolution multimodel climate projections suggest that China will experience regional heat wave events with magnitude exceeding the 2013 heat event on a regular basis by 2030 under a business-as-usual scenario (RCP8.5). Compared to a 2 °C warming level, 1.5 °C warming could halve the expected occurrence of future severe regional heat wave events with magnitude similar to or slightly greater than the record-breaking one in 2013.

Climate extremes, as recurring events, are the result of natural climate variability (including phenomena such as El Nino), which can have significant local and regional impacts on the society and the environment. These events are typically related to unusually high or low temperature, prolonged dry or wet conditions, heavy precipitation, or extreme winds. Recently, there has been considerable debate about the possible consequences of warming of the atmosphere for terrestrial ecosystems and societies, particularly related to changes in frequency, intensity, spatial extent, and duration of climate extremes over most land areas. This chapter provides an overview of the state of knowledge concerning the science of climate variability and climate extremes, emphasizing both present and past climate conditions and the projected changes over the 21st century. Science-based information based on robust findings and relevant uncertainties on changing extremes can provide useful information for sectorial planning, disaster risk prevention, and overall reduction of societal vulnerability related to climate and weather extremes.

Background Motor mapping with navigated transcranial magnetic stimulation (nTMS) requires defining a “hotspot”, a stimulation site consistently producing the highest-amplitude motor-evoked potentials (MEPs). The exact location of the hotspot is difficult to determine, and the spatial extent of high-amplitude MEPs usually remains undefined due to MEP variability and the spread of the TMS-induced electric field (E-field). Therefore, here we aim to define the hotspot as a sub-region of a motor map. New method We analyzed MEP amplitude distributions in motor mappings of 30 healthy subjects in two orthogonal directions on the motor cortex. Based on the widths of these distributions, the hotspot extent was estimated as an elliptic area. In addition, E-field distributions induced by motor map edge stimulations were simulated for ten subjects, and the E-field attenuation was analyzed to obtain another estimate for hotspot extent. Results The median MEP-based hotspot area was 13 mm2 (95% confidence interval (CI) = [10, 18] mm2). The mean E-field-based hotspot area was 26 mm2 (95% CI = [13, 38] mm2). Comparison with existing methods In contrast to the conventional hotspot, the new definition considers its spatial extent, indicating the most easily excited area where subsequent nTMS stimuli should be targeted for maximal response. The E-field-based hotspot provides an estimate for the extent of cortical structures where the E-field is close to its maximum. Conclusions The nTMS hotspot should be considered as an area rather than a single qualitatively defined spot due to MEP variability and E-field spread.

Odorants can reach olfactory receptor neurons (ORNs) by two routes: orthonasally, when volatiles enter the nasal cavity during inhalation/sniffing; and retronasally, when food volatiles released in the mouth pass into the nasal cavity during exhalation/eating. Previous work in humans has shown that orthonasal and retronasal delivery of the same odorant can evoke distinct perceptions and patterns of neural responses. Each delivery route is known to influence specific responses across the glomerular sheet of the dorsal parts of the olfactory bulb (OB), but spatial distributions across the entire glomerular sheet throughout the whole OB remain largely unexplored. We used functional MRI (fMRI) to measure and compare activations across the entire glomerular sheet in rat OB resulting from both orthonasal and retronasal stimulations of the same odors. We observed reproducible fMRI activation maps of the whole OB during both orthonasal and retronasal stimuli. However, retronasal stimuli required double the orthonasal odor concentration for similar response amplitudes in the OB. Regardless, both the magnitude and spatial extent of activity were larger during orthonasal versus retronasal stimuli for the same odor. Orthonasal and retronasal response patterns show overlap as well as some route-specific dominance. Orthonasal maps were dominant in dorsal-medial regions, whereas retronasal maps were dominant in caudal and lateral regions. These different whole OB encodings likely underlie differences in odor perception between these biologically important routes for odorants among mammals. These results establish the relationships between orthonasal and retronasal odor representations in the rat OB.

Hazards from drought events has made it of utmost importance for scientist to concentrate on the establishment of a dependable early warning systems that will enable stakeholders to effectively cope with the probable effect of this climatic phenomenon. Drought assessment in the northern region of Nigeria (NRN) was conducted majorly using a self-calibrated Palmer's Drought Severity Index (sc-PDSI). Between 1981 and 2015, the number of drought episodes identified ranged from 5 to 18. The most severe drought episodes took place from 1998 to 2001, next to it was between 2006 and 2008. The power spectral analysis of sc-PDSI timeseries identified periodicities ranging between 3 and 18 years. The spatial extent of extreme drought episodes shows that, the peak coverage area (10%) occurred at multiple times (August 1987, 2001, 2002 and 2009), most of which is in the 21st century. sc-PDSI reveals the long-term hydrological drought of River Niger indicated at Baro gauging station about 12 months before the low flow occurred. There is a need for policymakers to make adequate preparation by drawing out appropriate mitigation plans using established drought indices before future drought events occur. Keywords: Drought, sc-PDSI, Relative frequency, Agroecological zones, Spatial extent, Nigeria

Due to the penetration capacity of synthetic aperture radar (SAR) data through clouds and hazy atmospheric circumstances like fog, smog, light rain, mist etc., it has ability to continuous observation of flood events for producing accurate, rapid and cost effective flood mapping. A study using time series RADARSAT SAR images in flood water detection, monitoring of spatial extent and propagation of flood inundation were described and analysed in this paper. The SAR images were first calibrated, geometrically corrected and filtered. Afterward, threshold method was applied to extract the inundated areas from the SAR images. In threshold method, density slicing technique was used to separate the open water and non-water (land) areas from the images. Later, to delineate the actual flooded area, permanent water bodies (e.g. river, lake, ponds etc.) were subtracted from the open water. Flood maps were super-imposed and analysed to find out the nature of spatial extent, duration of flood and to show how flooding spread through time. This study illustrates that the SAR data along with GIS can be used effectively for flood water mapping, monitoring and analysing the propagation of flood water in a flood prone area. Therefore, the findings of this study will help to take initiative to reduce the flood hazard impact and increase the flexibility in the process of flood management. Keywords: SAR data, GIS, Flood mapping, Flood extent, Flood duration

Semiconductor nanocrystals (NCs) represent an important class of building blocks materials for next-generation solution-processed optoelectronic devices. The ability to control the shape and thus the spatial extent of electron and hole-wave functions enables new opportunities for materials design and performance enhancement of NC-based devices. For example, rod-shaped CdSe NCs have shown improved power conversion efficiency compared to their spherical counterpart in photovoltaic devices. Over the past three decades, the synthetic control over semiconductor NCs has grown in sophistication, and has now reached a stage where a rich variety of morphologies has been demonstrated, including many convex and concave polyhedral shapes, branched (e.g., tetrapods), and cage-like morphologies. In this chapter, we provide a survey of different families of colloidal semiconductor NCs, with an emphasis on key principles underlying synthetic control.

SummaryDespite the increasing use of optogenetics in vivo, the effects of direct light exposure to brain tissue are understudied. Of particular concern is the potential for heat induced by prolonged optical stimulation. We demonstrate that high-intensity light, delivered through an optical fiber, is capable of elevating firing rate locally, even in the absence of opsin expression. Predicting the severity and spatial extent of any temperature increase during optogenetic stimulation is therefore of considerable importance. Here, we describe a realistic model that simulates light and heat propagation during optogenetic experiments. We validated the model by comparing predicted and measured temperature changes in vivo. We further demonstrate the utility of this model by comparing predictions for various wavelengths of light and fiber sizes, as well as testing methods for reducing heat effects on neural targets in vivo.

Recent studies suggest that wave motions of the tectorial membrane (TM) play a critical role in determining the frequency selectivity of hearing. However, frequency tuning is also thought to be limited by viscous loss in subtectorial fluid. Here, we analyze effects of this loss and other cochlear loads on TM traveling waves. Using a viscoelastic model, we demonstrate that hair bundle stiffness has little effect on TM traveling waves calculated with physiological parameters, that the limbal attachment can cause small (, National Institutes of Health (U.S.) (Grant R01-DC00238), National Science Foundation (U.S.) (Grant 1122374)

Asian dust storm (ADS) events have raised concerns regarding their adverse impact on human health. Whether ADS events can result in the heterogeneity of health impacts on children across space and time has not been studied. The goal of this study is to examine the spatial vulnerability impact of ADS events on children's respiratory health geographically and to analyze any patterns related to ADS episodes. From 1998 to 2007, data from both preschool children's and schoolchildren's daily respiratory clinic visits, gathered from patients located in 41 districts of Taipei City and New Taipei City, are analyzed in a Bayesian spatiotemporal model in order to investigate the interaction between spatial effects and ADS episodes. When adjusting for the temporal effect, air pollutants, and temperature, the spatial pattern explicitly varies during defined study periods: non-ADS periods, ADS periods, and post-ADS periods. Compared to non-ADS periods, the relative rate of children's respiratory clinic visits significantly reduced 0.74 to 0.99 times in most districts during ADS periods, while the relative rate rose from 1.01 to 1.11 times in more than half of districts during post-ADS periods, especially in schoolchildren. This spatial vulnerability denotes that the significantly increased relative rate of respiratory clinic visits during post-ADS periods is primarily located in highly urbanized areas for both children's populations. Hence, the results of this study suggest that schoolchildren are particularly more vulnerable to the health impacts of ADS exposure in terms of higher excessive risks over a larger spatial extent than preschool children, especially during post-ADS periods. Keywords: Asian dust storm, Air pollution, Children's respiratory clinic visits, Spatial vulnerability, Spatiotemporal analysis

In this chapter I will review evidence showing that the processing of numerical information is closely linked to the processing and representation of spatial information. This general phenomenon will be analyzed under the hypothesis that there are two dissociable components: on the one hand, numbers can be associated to different spatial extents depending on their magnitude; on the other hand, numbers can be associated to different spatial positions depending on their order. I will present studies showing that newborns, preverbal infants, children, and adults spontaneously associate different numbers to corresponding spatial extents, and that from very early in development, numbers are associated to different spatial positions along a spatial axis whose orientation is closely linked to inborn spatial asymmetries. The studies presented will be discussed under the assumption that mature forms of number–space mappings derive from these two numerical–spatial components.

Droughts are widespread natural hazards and are reported to have killed more lives than all the other natural hazards combined over the past century. Repeated droughts can advance an area into desertification, severely impact on ecosystems, and cause many other tangible and intangible damages. Droughts can be characterized quantitatively for their spatial extent, intensity, and duration using various drought indices. In this chapter we focus on the assessment of various aspects of hydrology-related droughts and show that a process-based hydrological model has a lot to offer for drought assessment. To illustrate this we present a case study on the Limpopo river basin in Southern Africa. By comparing different types of droughts, we also highlight that various types of droughts need to be analyzed to understand the comprehensive nature of drought impacts.

When deciding which security line at the airport might be the quickest, do we rely on the number of people in each of the lines or the non-numerical sources of information such as the physical lengths of the lines? Do the mind and brain isolate number from other magnitudes such as spatial extent, or are different magnitudes processed in integrated form? Many researchers argue for differentiation between representations of numerical and non-numerical magnitude. One prevalent view is that numerical representations engage the approximate number system (ANS), which is specific to the processing of discrete numerical magnitude. In this chapter, I outline the evidence consistent with a general magnitude system, which encompasses numerical and non-numerical magnitudes such as spatial extent (length, area, etc.) and duration. Beyond highlighting a common analog format for representing different magnitudes, this system emphasizes shared neural mechanisms in the frontoparietal cortex and overlapping representational content. In support of this model, I describe findings from human infants, children, and adults showing cognitive interactions between different representations of magnitudes and transfer of representational precision across magnitudes following training. These effects are described in the context of simple (nonverbal) discrimination tasks as well as in relation to mathematical competence. Emerging work showing that, starting early in development, the precision of both nonverbal numerical and non-numerical magnitude representations predict mathematical competence, including arithmetic and geometry, suggests an important role for a general magnitude system in learning relatively formal math concepts and computations. A general magnitude system better accommodates evidence for relations between representations of numerical and non-numerical magnitudes than does the alternative ANS model.

This chapter presents results from comprehensive tsunami forensic field surveys conducted by the authors immediately following three major tsunami events: 2004 Indian Ocean (Indonesia and Thailand), 2010 Chile, and 2011 Tohoku, Japan. Coastal and inland nonengineered structures located in coastal communities suffered extreme damage, many of which were completely destroyed. The Japan event also resulted in heavy damage to engineering structures. These reconnaissance field investigations were conducted within 4 weeks after the tsunamis hit the above affected areas. While tsunami surveys typically focus on determining the spatial extent of the coastal flooding, these three surveys focused on investigating the behavior of structures impacted by extreme loading due to inland flooding generated by the tsunamis. Therefore, a comprehensive review and analysis of the damage induced by the tsunamis on a variety of structures with various functions (industrial, residential, and community uses) and characteristics (geometry, type of construction material, etc.) is presented herein. In addition, this chapter also presents a concise comparison between the types of tsunami damage observed during these surveys.

Currently, coastal protection potential of ecosystems is estimated primarily as a function of its spatial extent and type. The degree to which coastal protection depends on aspects of biodiversity within these ecosystems is, however, less explored. Here, we provide a short summary of classical coastal protection strategies and the current state of knowledge of nature-based shoreline protection, and then discuss relevant biodiversity theory and the few studies that have investigated how species identity affects shoreline protection. This chapter provides the first attempt to identify the aspects of biodiversity that are likely to be important in enhancing coastal protection efforts.

Among the most fundamental of mental capacities is the ability to represent magnitude information such as physical size, numerosity, and duration. Accumulating evidence suggests that such cues are processed as part of a general magnitude system with shared more versus less representational structure. Here we review recent research with young children and preverbal infants suggesting that this system is operational from early in human life and may be far more general than currently believed. We present data suggesting that from early in development the representation of magnitude extends across modality (e.g., vision and audition) and beyond the “big three” dimensions of spatial extent, number, and time. We also speculate about particular properties of the general magnitude system, including the potentially special role of space in grounding magnitude information.

This chapter focuses on spatio-temporal extents and describes some of the basic kinds of spatio-temporal extents that are commonly found. It examines the space-time patterns that different kinds of spatio-temporal extents exhibit. The most important relationship between spatio-temporal extents is that of one being part of another. This is called aggregation when the whole is the sum of the parts. An aggregation is a relationship where one spatio-temporal extent is a part of another such that the whole is the sum of the parts. This key relationship is also examined in the chapter. Sometimes, the whole is more than the sum of its parts. The parts compose something that has emergent properties that result from the way that the parts are arranged. This is called composition. A composition is an aggregation where the parts are arranged in such a way that the whole is more than the sum of the parts. Finally, there is the case where the part is the full spatial extent for a period in the; that is, the part is a state of the whole. This is termed temporal composition. A spatio-temporal extent may be part of one or more other spatio-temporal extents.

Random field theory is used in the statistical analysis of statistical parametric maps (SPMs) whenever there is a spatial component to the inference. Most important is the question of detecting an effect or activation at an unknown spatial location. Very often we do not know in advance where to look for an effect, and we are interested in searching the whole brain, or part of it. This chapter presents special statistical problems related to the problem of multiple comparisons, or multiple tests. Two methods have been proposed, the first based on the maximum of the T or F statistic, the second based on the spatial extent of the region where these statistics exceed some threshold value. Both involve results from random field theory (Adler, 1981) .

Publisher Summary This chapter reviews three specific elements that constitute the notion of a scale—cartographic scale, sampling frequency, and spatial extent— and highlights the way in which 3D visualization may be used to explore these elements. These elements are shown to affect both the measurements of spatial phenomena, as well the way in which such phenomena can be represented in a visualization environment. Visual techniques that highlight these scale dependencies are considered. In particular, the rendering heuristic of mipmapping is suggested as a way of allowing intelligent surface generalization techniques to be rendered and explored in real-time in a dynamic 3D visual environment. Cartographic scale (the ratio between a referent's size and its representation's size), level of detail (resolution or sampling frequency), and spatial extent all affect the measurements and observations that are taken from a phenomenon. By taking advantage of the heuristics designed to improve the efficiency of 3D surface rendering, the scale dependent measures in a dynamic 3D environment can be explicitly mapped. This offers new opportunities to create environments in which scale dependencies can be explored.

Publisher Summary Regional mapping is an essential component to determining the suitability of potential sites for geological storage of CO 2 . Within the Weyburn Project, regional mapping established the distribution of primary seals and the lateral continuity of reservoir equivalent strata, and provided the basis for studying the bounding conditions affecting the long-term storage of CO 2 . The resulting stratigraphic framework was used to develop a high-resolution hydrostratigraphy needed in investigating the fluid-flow regime around the Weyburn reservoir. In addition, isopach and structure maps and the relationships among different strata levels were used to assess and identify processes such as salt dissolution, erosion and tectonism, and their potential impact on the storage site. Whereas none of these processes has been observed to have compromised the Weyburn reservoir, they have affected potential reservoir strata elsewhere in the larger study region. The stratigraphic data in combination with other geoscience information helped to constrain the spatial extent of the System Model used in risk and performance assessment.

This chapter reviews some of the recent literature on glaciation in Greece and presents new data on the age of the glacial deposits on the southern flanks of Mount Tymphi in Northwest Greece. The chapter presents radiometric (uranium-series) ages obtained for glacial sediments in Greece and discusses the wider implications of this new chronostratigraphic framework. Recent work has shown that the mountains of Greece contain evidence for multiple phases of ice build up and decay during the Middle and Late Pleistocene. However, there is still a need for detailed field mapping in many areas to establish the precise spatial extent and style of glacial activity in the Greek mountains. The morphological and sedimentological evidence for glaciation is less extensive and less preserved in Central and Southern Greece. At present, the only glaciated terrain in Greece where detailed field-based mapping and lithostratigraphic assessment have been carried out is on Mount Olympus and the surrounding piedmont zone. However, the absence of a reliable and internally consistent chronology for this work limits its value as a source of palaeoclimatic information and prevents detailed comparison with data from Mount Tymphi and with the long pollen sequences in Greece and other records of proxy climate.

Publisher Summary This chapter reviews the current status of equations of state for fluids and fluid mixtures in the critical region. Critical phenomena in fluids have been the subject of many theoretical and experimental studies during the past thirty years. The most striking result of these studies has been the discovery of critical-point universality: the microscopic structure of fluids becomes unimportant near a critical point. Moreover, the principle of critical-point universality has been extended to near-critical binary mixtures (isomorphism approach). These discoveries make it possible to develop universal equations of state for fluids in the critical region and enable us to look into the problem of formulating global equations of state for dense fluids and fluid mixtures from an entirely new point of view. The principle of critical-point universality finds its physical origin in the phenomenon that long-range fluctuations of the order parameter (density in one-component fluids or/and concentration in fluid mixtures) dominate in the critical region and that the range of these fluctuations becomes much larger than any other microscopic scale. The spatial extent of these critical fluctuations is determined by a correlation length ξ, which diverges at the critical point. Therefore, the behavior of the thermodynamic properties becomes singular at the critical point. The mathematical nature of the asymptotic, singular, critical behavior is now well understood: it can be characterized by scaling laws with universal critical exponents.

Publisher Summary This chapter discusses the impact of spatial scales on the chemical–physical parameters which differ from the scale of impacts on ecological parameters based on life-history features of the affected organisms. It examines the spatial relationships among various physical/chemical and biological variables used to measure the spatial extent of impacts caused by an industrial outfall in a coastal marine habitat. It presents ideas as to which attributes of species are most likely to lead to broad-scale population changes as a result of a localized disturbance. Knowledge of which species characteristics lead to dispersed effects may not allow dispersed impacts to be detected in most situations. Details of oceanographic transport and larval behavior under different transport regimes are critical to the accurate prediction of where dispersed impacts will most likely occur. Complementary information on sources and sinks of population replenishment can aid in predicting where and how much change can be expected from a given local impact. Such information may require the use of modem techniques in molecular biology and in the analyses of stable isotopes to develop genetic and environmental markers for distinguishing source and sink populations.

Publisher Summary The receptive field of a cat visual cortical cell should not be considered as a fixed entity but more as a dynamic field of integration and association. The central core of the receptive field can be profoundly reorganized at least during development and most probably during selective phases of learning under the control of activity-dependent mechanisms. Adaptive changes in visual responses are thought to reflect long-lasting potentiation and/or depression of synaptic efficacies. During sensory processing, reconfiguration of synaptic weights may be achieved on a much faster time scale and linked to nonlinear properties of the postsynaptic membrane, as well as that of recruited networks. Association of information available in the central part of the receptive field (RF) and of input coming from the reputed unresponsive regions surrounding it, or arising simultaneously from different parts of the visual field, might be suppressive in certain cases and capable of boosting hidden responses in other cases, depending on the global stimulus configuration. It is found that that the spatial extent of cortical receptive fields could vary on at least two distinct time scales. The faster one, compatible with recognition processes, would depend on the kinetics of inactivation of specific conductance and the recent history of the postsynaptic membrane potential.

Publisher Summary This chapter focuses on the highway pollutant monitoring. Many analytical methods provide adequate levels of specificity and precision for undertaking both mono- and multi-element analyses. The frequency of sampling, averaging time and the total duration and spatial extent of the monitoring programme are considered. The chapter discusses the sampling and analysis systems. Pollutants are deposited from the atmosphere to solid and aqueous surfaces by wet and dry deposition. The heterogeneous nature of dust and soil increases the problem of obtaining a representative sample. The parameters of importance with particulate pollution are mass, size and chemical composition. Analysis can be performed either on bulk samples or by summing the properties of a large number of single particles. The chapter discusses the techniques appropriate for each pollutant. The ideal analytical technique for undertaking environmental elemental analysis must offer: (1) qualitative, semi-quantitative and quantitative analysis, (2) high degree of specificity, (3) very low detection limits, (4) simple sample preparation, (5) simple interference-free spectra, (6) high throughput and low cost per determination, and (7) unattended batch-mode operation.

Publisher Summary This chapter discusses time as a variable in behavior analysis. Behavior takes place in time and has temporal dimensions. As an independent variable, time is an essential property of the environments within which behavior occurs. As a dependent variable, it includes not only response durations but also the distribution of responses in time. Each stimulus dimension has intrinsic properties, and those of the temporal dimension differ in important ways from those of other stimulus dimensions such as wavelength, intensity, and spatial extent. The molecular properties of behavior involve the properties of individual stimuli and responses. The processes of discrimination and differentiation are molar as they are aspects of populations of stimuli and responses observed over extended periods of time. If the search for behavior mediating timing were successful, the outcome might be regarded as relevant to the organism's temporal receptor.

We consider here a structural model for amorphous metals in which disorder is created by limiting the spatial extent of structural operations which generate structural units (triangular prisms) and define the correlation between such units. This description is exemplified by some results obtained for Ni 80 B 20 from a computer-built model generated by simple chemical twinning. Emphasis is placed on the main characteristics of this model: effects of frustration and concentration fluctuations as sources of disorder, the correlation length between units, and a classification scheme for amorphous structures.

Publisher Summary This chapter describes the spatial patterns of phytoplankton and its primary production as determined by the shipboard program conducted between 1974 and 1982. From the available shipboard productivity data and from the analysis of available satellite color imagery of the spatial extent of the highly productive regions, it can be estimated that an average of 11.5 metric tons of carbon are annually fixed in the waters overlying the shelf and slope off Washington. The distribution of phytoplankton and its productivity in the waters overlying the Washington shelf and slope varies in space and time in response to the variability in the near-field and far-field physical forcing.

Publisher Summary In relating scalp-recorded event-related potentials (ERPs) to underlying brain activity on the one hand and psychological processes on the other, a key issue is the definition of ERP components. It is often assumed that the voltage peaks of scalp-recorded ERPs reflect distinct physiological processes within the brain, and that measuring the latency, amplitude and scalp distribution of each peak provides direct information on the timing, magnitude, and spatial extent of the intracranial neural processes that generated it. However, ERP peaks often represent composites of electrical activity arising from complex configurations of transmembrane current sources and sinks within more than one brain structure. The fusion of field potentials generated by different cellular elements within several concurrently active structures makes it difficult if not impossible to resolve the contribution of a particular structure or cellular group from the analysis of scalp recordings alone.

Publisher Summary Earthquakes, whether local or distant, are complex phenomena that can impose severe loadings on structures. They release large amounts of strain energy from limited volumes of the earth's crust in the form of seismic body and surface waves. The identification of seismic hazards connected with onshore and offshore resource development and facility sitings constitutes a primary task along many parts of the U.S. coastal zone. The risk ranges from nominal along the eastern seaboard to severe along the southern coast of Alaska. Countless projects have been, and many more will be, strongly affected by limitations imposed as a result of the apparent seismic risk. The economic and social impacts will be significant. The identification of seismic hazards in the coastal zone is uniquely challenging to the seismologist and structural engineer. The data is sparse and it is difficult and expensive to acquire; generally indirect methods of data gathering are required. Finally, the surface geology often consists of very recent, poorly lithified materials, whose spatial extent and physical characteristics under seismic shaking are poorly known.

Publisher Summary This chapter discusses the simplest of several possible corticospinal control systems—the localization in the cortical arm area of the baboon of colonies of pyramidal neurones, which project monosynaptically to sample motoneurones belonging to different muscle groups of the upper limb. Such colonies form significant functional groupings as the motor units to which they project are the ultimate elements in the organization of muscular contraction. The monosynaptic actions of the corticospinal discharges are recorded from the sampled motoneurones with intracellular microelectrodes. The cortico-motoneuronal colonies for motor units of different muscles overlap and they differ in their spatial extent and in the quantity of monosynaptic excitatory action they command on the test motoneurones. The colonies projecting to motoneurones controlling distal muscles tend to occupy smaller cortical areas and command larger monosynaptic actions; the colonies projecting to the motoneurones of proximal muscles tend to occupy larger areas, but command smaller monosynaptic actions.