Forests comprise the greatest storage of carbon on land, provide fuel for millions, are the habitat for most terrestrial biodiversity, and are critical to the economies of many countries. Yet changes in the extent and dynamics of forests are inherently difficult to detect and quantify. Remote sensing technologies may facilitate the measurement of some key forest properties which, when combined with other information contained in various computer models, may allow for the quantification of critical forest functions. This book explores how remote sensing and computer modeling can be combined to estimate changes in the carbon storage, or productivity, of forests - from the level of the leaf to the level of the globe. Land managers, researchers, policy makers and students will all find stimulating discussions among an international set of experts at the cutting edge of the interface between science, technology and management.

The development of an effective method of drilling oil and gas wells to depths of 3-5 km and more is a complex problem of great practical interest. "Deep Hole Drilling With Explosives" is a distinctive and very interesting work of the engineer A. P. Ostrovskii, who more than twenty years ago, by his original suggestions, made a start in investigating the field of so-called non-bit processes of shattering rocks when drilling holes, a.nd, with his co-workers, developed a fundamentally new explosive method of drilling deep holes. This book discusses the new trend in worldwide a.pplication of explosives in technology and the national economy; it presents considerable experimental material on the effect of explosions in solid media, material that is not only interesting to specialists in mining but also to physicists. Many phenomena discussed by the author and cited in the book still await explanation, but the fact that these phenomena have been already subjected to experimental study undoubtedly adds to our knowledge of one of the most meagerly investigated areas of the science of explosions-concerning the shattering effect of explo sions on solid media. July 29, 1960 Professor M. A. Sadovskii Corresponding Member of the Academy of Sciences of the USSR 1 INTRODUCTION Together with the perfection of turbine drilling and the introduction of electrical drills in the USSR, new methods have been developed for shattering rock and drilling deep oil and gas wells without the use of a bit."

This volume offers an introduction into the technology programs and international projects of reusable orbital transport systems. Besides the technological requirements, meteorological and air chemical aspects in regard to the environmental compatibility of future transport systems are the most important topics. The aim of the symposium was to investigate the classical disciplines and methods of aeronautics and astro- nautics in connection with meteorological and air chemical methods and models. For this purpose an attempt was made to identify technological optimization parameters in respect to the air chemical environmental compatibility of future orbital transport systems.

There is no shortage of general books on the subject of acid rain, or of symposium proceedings reviewing work ranging from atmospheric chemistry and deposition processes to freshwater acidification and effects on vegetation. In contrast, the collection of papers from this Workshop is focussed on a much smaller subject, the processes of acid deposition at high altitude sites. Interest in deposition at high elevation sites comes largely from observed vertical gradients in the degree of forest damage at sites in the Federal Republic of Germany and the eastern United States. These gradients show that damage to Norway spruce and fir increases with altitude at sites in Bavaria and the Black Forest, and that Red spruce are declining at high elevation sites in the Appalachian Mountains. With the large scale of scientific interest in forest decline, cany research groups, during the last five years, have been examining atmospheric chemistry, deposition processes, and effects on vegetation and soils at upland sites. In particular there have been many recent studies of cloud and precipitation chemistry, which show much larger concentrations of all ions in cloud water than in rain or snow. These studies have also shown that processes of wet and dry deposition and also the chemistry of the air at hill tops are modified strongly by orographic effects.

The subject of this volume is the observation and modelling of the gravity wave field in the atmosphere. The focus is on the question of how to include the effects of small-scale gravity waves in sophisticated global climate models.
The book comprises 26 chapters, including contributions from distinguished experts in observation and theory, along with results from studies of gravity wave parameterization within comprehensive climate models.

CEOS was established under the auspices of the Economic Summit of Industrialized Nations in 1984 in response to a recommendation from a panel of experts in remote sensing within the Working Group on Growth, Technology and Employment (CEOS, 2009). The panel recognized the collective value of the world's Earth remote sensing capabilities and the advantages that would be gained by the coordination of civil Earth observing satellite missions. By cooperating in mission planning and the development of compatible data products, applications, services and policies, the national space programs would maximize the bene?ts of their individual inve- ments and be able to better address the environmental challenges of the entire international community. CEOS was to serve as the focal point for this inter- tional coordination and to provide the forum for the change of policy and technical information. The members of CEOS are governmental organizations that are international or national in nature and are responsible for a civil space-borne Earth observation program that is currently in operation or in an advanced stage of system devel- ment. CEOS also has established Associate Members that are similar governmental organizations with a civil space-segment activity in an early stage of system dev- opment or those with a signi?cant ground-segment activity that supports CEOS objectives. Associate Members may also be existing satellite coordination group and scienti?c or governmental bodies that are international in nature and have a signi?cant programmatic activity that likewise is aligned with the goals of CEOS.

Year by year the Earth sciences grow more diverse, with an inevitable increase in the degree to which rampant specialization isolates the practitioners of an ever larger number of subfields. An increasing emphasis on sophisticated mathematics, physics and chemistry as well as the use of advanced technology have set up barriers often impenetrable to the uninitiated. Ironically, the potential value of many specialities for other, often non-contiguous ones has also increased. What is at the present time quiet, unseen work in a remote corner of our discipline, may tomorrow enhance, even revitalize some entirely different area. The rising flood of research reports has drastically cut the time we have available for free reading. The enormous proliferation of journals expressly aimed at small, select audiences has raised the threshold of access to a large part of the literature so much that many of us are unable to cross it. This, most would agree, is not only unfortunate but downright dangerous, limiting by sheer bulk of paper or difficulty of compre hension, the flow of information across the Earth sciences because, after all it is just one earth that we all study, and cross fertilization is the key to progress. If one knows where to obtain much needed data or inspiration, no effort is too great. It is when we remain unaware of its existence (perhaps even in the office next door) that stagnation soon sets in.

In this volume, the Camnission of the Eurc.pean camunities presents the proceedissJs of the secood Eurc.pean Synpositun en the physioo-chemical behaviour of atIoospheric pollutants. '!bese Symposia are organized in intervals of about t'110 years wi thin the framework of a Concerted Action in this area, which is part of the CCIIlIlIll1ities' research progranure in the environmental field. '!be Eurc.pean CCIIlIlIll1ities co-operate in this area wi th Eurc.pean Non-Member States under an agreement within the frame'llOrk of coor (~ration Scientifique et Technique). This Jlgreement (COOT Project 61a bis) has been signed by the European Communities, Austria, Switzerland, Sweden and Yugoslavia. 'lbe scc.pe of the Concerted Actien is to co-onHnate all research in the area executed in the participatissJ countries and to collect and dissemi- nate the results. The research inventory established comprises 165 individual projects~ regular meetings of 5 WorkissJ Parties permit close contacts amossJst the scientists involved. 'lbe Eurc.pean Syrrposia should pennit fran time to time an overall review of the progress. 'lbe first Symposium held in October 1979 *) permitted to review the state of progress at the beginning of the Concerted Actien. The second Symposium gives now an overview of the important achievements durissJ the past two years. These are evident already fran the number of contri- butions which increased from 45 in 1979 to 74 in 1981. The results collected durissJ this per iod permi tted the presentation of a number of important review papers.

GKSS SCHOOL OF ENVIRONMENTAL RESEARCH The National Research Laboratory GKSS (member of the Hermann von Helmholtz-Association of German Reserach Centres) located in Geesthacht, near Hamburg, is engaged in environmental research. The main interest of the research center focuses on regional climatology and climate dynamics, interdecadal variations in the state of the Baltic and North Sea and related estuaries, and the flow ofheavy metals, nutrients, and other materials in river catchments to the coastal zones. This research aims at-developing an under standing ofchanges in the environment, both as a result ofinternal (natural) dynamics and as a result of anthropogenic interference. In an effort to dis seminate the results of these research activities, as well as to initiate a broad discussion among senior scientists in the field, and younger colleagues from all areas of the globe, the Institutes of Hydrophysics and Atmospheric Physics at GKSS have instituted the GKSS School of Environmental Research. Appliedenvironmental research has always containedanelement ofaware ness ofthe societal implications and boundary conditions associated with en vironmental concerns. Consequently, the School of Environmental Research adheres to the philosophy that all discussion regarding environmental change should incorporate a social component. This necessity has been well acknowl edged and is apparent by the incorporation ofsocial scientists into the series of lectures. Senior scientists from Europe and North America were invited to give lectures to "students" from all parts of the globe."

by Julius S6lnes An Advanced Study Institute on engineering seismology and earthquake engineering was held in Izrrir, 'rurkey July 2-13, 1973 under the auspices of the Scientific Affairs Division of NATO. The Institute was organized by an organizing committee headed by the two scientific directors and with representation by the Turkish National Science Foundation, Turkish National Committee for Earthquake Engineering, the Middle East Technical University and the Aegean University. 93 scientists and engineers of 18 countries took part in the work of the Institute which comprised 10 working days with lectures, discussions and panel meetings. The main lecture topics of the Institute were covered in five main sections: 1. Generic causes of earthquakes. 2. Ground motion and foundation response. 3. Earthquake response of structures and design consi derations. 4. Codes and regulations; implementation. 5. Earthquake hazards and emergency planning. Upon completion of each section, general discussion and short presentations by several of the participants took place and summary statements were offered by the main lecturers. The atmosphere of the meetings was in- VI formal and cordial thus giving rise to many unorthodox and newly conceived ideas."

In regard to global change, emphasis is generally placed on the increase in global temperature, but large changes in the distribution of precipitation are also likely to occur. Such changes have been redorded in the past by paleoclimatological studies or in the field of climatology. Different approaches to monitoring and forecasting the evolution of climate-scale precipitation are reviewed by paleoclimatologists, hydrologists, satellite meteorologists, and climate modellers.

consequences of broken symmetry -here parity-is studied. In this model, turbulence is dominated by a hierarchy of helical (corkscrew) structures. The authors stress the unique features of such pseudo-scalar cascades as well as the extreme nature of the resulting (intermittent) fluctuations. Intermittent turbulent cascades was also the theme of a paper by us in which we show that universality classes exist for continuous cascades (in which an infinite number of cascade steps occur over a finite range of scales). This result is the multiplicative analogue of the familiar central limit theorem for the addition of random variables. Finally, an interesting paper by Pasmanter investigates the scaling associated with anomolous diffusion in a chaotic tidal basin model involving a small number of degrees of freedom. Although the statistical literature is replete with techniques for dealing with those random processes characterized by both exponentially decaying (non-scaling) autocorrelations and exponentially decaying probability distributions, there is a real paucity of literature appropriate for geophysical fields exhibiting either scaling over wide ranges (e. g. algebraic autocorrelations) or extreme fluctuations (e. g. algebraic probabilities, divergence of high order statistical moments). In fact, about the only relevant technique that is regularly used -fourier analysis (energy spectra) -permits only an estimate of a single (power law) exponent. If the fields were mono-fractal (characterized by a single fractal dimension) this would be sufficient, however their generally multifractal character calls for the development of new techniques.

The VDI Commission on Air Pollution Prevention - in cooperation with the German Meteorological Society - presents in this book the proceedings of the first International Symposium on "Environmental Meteorology", held in Wurzburg (West Germany) from 29 September to 1 October 1987. The primary goal was to get together scientists, experts of the meteorological services, specialists of environmental boards, and consulting engineers of the European countries. An equally important objective was to provide a bench mark document in the resulting proceedings publication. The 1987 symposium shall start a series of symposia on all fields of environmental meteorology to be held once in three or four years in one of the European countries. We are full of hope to come to an intense cooperation with the national meteorological and environmental societies in the countries with this concern. We like to express our sincere appreciation to the authors for their efforts and attention to the quality shown herein. The credit must be extended to the session Chairmen and to the advisory committee for the selection of the papers. We think the book contributes substantially to a better understanding of meteorology being the link between emission and deposition of atmospheric pollutants.

According to my latest model for the last glacial maximum (LGM) (Grosswald 1988), the Arctic continental margin of Eurasia was glaciated by the Eurasian ice sheet, which consisted of three interconnected ice domes --the Scandinavian, Kara, and East Siberian. The Kara Sea glacier was largely a marine ice dome grounded on the sea's continental shelf. The ice dome discharged its ice in all directions, northward into the deep Arctic Basin, southward and westward onto the mainland of west-central North Siberia, the northern Russian Plain, and over the Barents shelf into the Norwegian-Greenland Sea On the Barents shelf, the Kara ice dome merged with the Scandinavian ice dome. In the Arctic Basin the discharged ice floated and eventually coalesced with the floating glacier ice of the North-American provenance giving rise to the Central-Arctic ice shelf. Along its southern margin, the Kara ice dome impounded the northward flowing rivers, causing the formation of large proglaciallakes and their integration into a transcontinental meltwater drainage system. Despite the constant increase in corroborating evidence, the concept of a Kara ice dome is still considered debatable, and the ice dome itself problematic. As a result, a paleogeographic uncertainty takes place, which is aggravated by the fact that a great deal of existing knowledge, no matter how broadly accepted, is based on ambiguous interpretations of the data, most of which are published in Russian and, therefore, not easily available to western scientists.

This volume contains progress papers in atmospheric ozone research which were presen- ted at the Ouadrennial Ozone symposium held in Greece from 3 to 7 September, 1984. These pa- pers are grouped in nine chapters corresponding to the nine sessions of the symposium. The Editors proVide the following summary of the highlights for each chapter; this summary has been prepared after consulting the papers submitted for publication as well as session summa- ries kindly provided by the following session chairmen: R. Bojkov, H. DOtsch, P. Fabian, J. Hai- gh, I. Isaksen, L. Kaplan, K. KOnzi, J. London, H. Mantis, C. Mateer, A. Matthews, G. Megie and J. Russell. Chapter 1 entitled: Chemical -radiative -dynamical model calculations includes results from recent developments in modeling techniques. The chapter begins with the results from a two -dimensional model using isentropic coordinates. With prescribed diabatic heating rates and a judicious choice of eddy diffusion coefficients this method can produce realistic fields of several stratospheric species. Three dimensional model simulations come next which demon- strate ozone transport by the stationary and transient components of the flow and emphasize the role of wave transport of ozone during a sudden stratospheric warming. The problem of chemical model validation is addressed in several different approaches.

The Dawn of Massively Parallel Processing in Meteorology presents collected papers of the third workshop on this topic held at the European Centre of Medium-Range Weather Forecasts (ECMWF). It provides an insight into the state of the art in using parallel processors operationally, and allows extrapolation to other time-critical applications. It also documents the advent of massively parallel systems to cope with these applications.

Ten years have passed since the last symposium on "Rock Deformation" was held in Los Angeles. The intervening period has seen striking advances in X-ray and experimental structural petrology. The Symposium of the Working Group on X-Ray and Experimental Structural Petrology, held at the invitation of the Deutsche Forschungsgemeinschaft on 17 and 18 February, 1969, in the Mineralogy Institute of the Technische Hochschule Darmstadt, was intended to display the progress made in this field. A meeting on the same had been held in 1968 at the Mineralogy Institute of the Technische Hochschule Aachen. The outcome of many years of effort has been the development of new, automated in- struments for the X-ray processing of specimens. The X-ray and optical data so obtained are processed by computer to give complete texture diagrams; it is also possible to rotate the coordinates, and to make an indirect determination of data which have not been measured. In experimental structural petrology, the temperature and pressure dependence of the translational system has been studied in minerals from various types of rock formation which had not previously been investigated, and deductions were made concerning certain mineral parageneses. The original contributions on field findings were conceived and executed so as to point up the possible links with experimental work on structural petrology. They determine for a given mineral facies the pressure and temperature ranges to be applied in experimen- tal studies of deformation in single crystals and in rocks.

In their approach to Earth dynamics the authors consider the fundamentals of "Jacobi Dynamics" (1987, Reidel) for two reasons. First, because satellite observations have proved that the Earth does not stay in hydrostatic equilibrium, which is the physical basis of today's treatment of geodynamics. And secondly, because satellite data have revealed a relationship between gravitational moments and the potential of the Earth's outer force field (potential energy), which is the basis of "Jacobi Dynamics." This has also enabled the authors to come back to the derivation of the classical virial theorem and, after introducing the volumetric forces and moments, to obtain a generalized virial theorem in the form of Jacobi's equation. Thus a physical explanation and rigorous solution was found for the famous Jacobi's equation, where the measure of the matter interaction is the energy.
The main dynamical effects which become understandable by that solution can be summarized as follows:
" "the kinetic energy of oscillation of the interacting particles which explains the physical meaning and nature of the gravitation forces;
" "separation of the shell's rotation of a self-gravitating body with respect to the mass density;
difference in angular velocities of the shell rotation;
" "continuity in changing the potential of the outer gravitational force field together withchanges in density distributionof the interacting masses (volumetric center of masses);
" "the nature of the precession of the Earth, the Moon and satellites; the nature of the rotating body's magnetic field and the generation of the planet's electromagnetic field.As a final result, the creation of the bodies in the Solar System having different orbits was discussed. This result is based on the discovery that all the averaged orbital velocities of the bodies in the Solar System and the Sun itself are equal to the first cosmic velocities of their proto-parents during the evolution of their redistributed mass density.
Audience
The work is a logical continuation of the book "Jacobi Dynamics" and is intended for researchers, teachers and students engaged in theoretical and experimental research in various branches of astronomy (astrophysics, celestial mechanics and stellar dynamics and radiophysics), geophysics (physics and dynamics of the Earth's body, atmosphere and oceans), planetology and cosmogony, and for students of celestial, statistical, quantum and relativistic mechanics and hydrodynamics.

Most industrial and natural materials exhibit a macroscopic behaviour which results from the existence of microscale inhomogeneities. The influence of such inhomogeneities is commonly modelled using probabilistic methods. Most of the approaches to the evaluation of the safety of structures according to probabilistic criteria are somewhat scattered, however, and it is time to present such material in a coherent and up-to-date form. Probabilities and Materials undertakes this task, and also defines the great tasks that must be tackled in coming years. For engineers and researchers dealing with materials, geotechnics, solid mechanics, soil mechanics, statistics and stochastic processes. The expository nature of the book means that no prior knowledge of statistics or probability is required of the reader. The book can thus serve as an excellent introduction to the nature of applied statistics and stochastic modelling.

Structural clay products have had a place in the history of civilization like bread and cloth. Probably because the industry has been so commonplace in the lives of people, 1ittle has been written about it; even the history of its development is sketchy. There is no other book quite like this in publication at present, and it is prompted now because much general scientific knowledge can be, and is, applied to the manufacture of structural clay products. This book is an attempt to bring together in one place the basic sciences that can be useful in all of the processes and experiences of the clayworker. This volume was written primarily as a text to be used in courses for third and fourth year college students; however, there will be a broader interest in it by industrial foremen, engineers, architects, and scientists employed in the manu facture, research and use of structural clay products. It will also be a source of general information for those interested in entering the field. The treatment of the basic principles of clay products manufacturing and use is so general that even those interested in refractories, whitewares, and pottery may find many parts useful to them."

Le rassemblement sur la zone industrielle de FOS-BERRE d'une densite importante de mesures meteorologiques et physioo-chimiques, per- met de proposer, dans Ie cadre de notre action COST 61 a bis, l'utilisa- tion de ces mesures pour initialiser et verifier divers types de modeles. L'objectif initial de cette campagne est l'intercomparaison d'instruments de teledetection. II s'agit d'une des campagnes effectuees periodiquement, en des sites differents a l'initiative des Communautes europeennes. Ces campagnes comportent deux phases: la premiere est l'inter- calibration des instruments au m@me point, et la seconde est l'estimation des flux de polluants sur la zone etudiee. Effectuee en general a l'aide de moyens mobiles de teledetec- tion, cette estimation ne peut @tre assuree que si lion connatt Ie champ de vent et Ie profil vertical de temperature (et, bien sOr, les caracte- ristiques des sources polluantes). L'Etablissement d'Etudes et de Recherches Meteorologiques de la Meteorologie Nationale (EERM) et Ie Service Etudes et Recherches de l'E- lectricite de France (EDF) sollicites pour fournir l'assistance meteoro- logique correspondante, ont propose, du fait de la presence de moyens im- portants sur Ie site, une campagne mesometeorologique. Ce deuxieme objec- tif a permis d'obtenir des donnees tres completes, que les modelisateurs europeens devraient pouvoir utiliser. II - Aspects meteorologigues, reconstitution des champs Le site de FOS-BERRE se caracterise par sa geographie tourmen- tee: presence de la mer, de l'Etang de Berre et de reliefs. Toutefois, Ie mecanisme engendrant les fortes pollutions reste en gros Ie m@me que sur site homogene.

The outflow of heat from the earth's interior, the terrestrial heat flow, and the temperature field at depth are determined by deep-seated tectonic processes. The knowledge of the re gional heat flow pattern is thus very important in geophysics and provides a useful tool for studying crustal and litho spheric structure and understanding the nature of their evo lution. In order to use the results of heat flow measurements for regional studies and/or to correlate the observed surface geothermal activity with other geophysical or geological fea tures, a map showing the surface distribution of heat flow is necessary. Since 1963, when the first comprehensive listing of all available heat flow data appeared (Lee, 1963), several at tempts have been made to up-date the list, to classify all the data and to interpret them with respect to tectonics, deep structure and to use them for constructing surface heat flow maps. The first listing was subsequently revised by Lee and Uyeda (1965); numerous new data which were published there after were included in successive catalogs compiled by Simmons and Horai (1968) and then again by Jessop et al. (1976). The map showing the surface heat flow pattern may also be of great value for practical purposes, in view of the recent world-wide search for applicable sources of geothermal energy."

This volume includes revised versions of most of the presentations made at the International Conference "Understanding the Earth Sys tem: Compartments, Processes and Interactions" held on November 24-26, 1999 in Bonn. The Conference was organized by the German National Committee on Global Change Research as part of the Bonn Science Festival 1999-2000. The Bonn Science Festival (Wissen schaftsfestival Region Bonn) was organized and funded by sfg Strukturforderungsgesellschaft Bonn/Rhein-Siegl Ahrweiler mbH. The generous support for organizing the conference and printing this volume by sfg is gratefully acknowledged. Additional financial and organizational support for separate workshop sessions and publica tions have also been provided by the German Federal Ministry for Science and Research, BMBF and Germany's major research funding agency, Deutsche Forschungsgemeinschaft. The editors wish to gratefully acknowledge the help, advice and especially patience of many individuals who have contributed to this volume. The contributions are intended to document the debate on crucial issues of the emerging concept of earth system science and to stimulate the necessary scientific discussion. While every effort has been made on the part of the editors to ensure consistency in termi nology, style and methods of quotation, the variety of contributors has inevitably resulted in certain discrepancies. E. EHLERS Bonn, February 2001 T. KRAFFT Contents Part I Panorama: The Earth System: Analysis from Science and the Humanities Chapter 1 Understanding the Earth System - From Global Change Research to Earth System Science . . . . . . . 3 E. EHLERS and T. KRAFFT Chapter 2 Earth System Analysis and Management. . . . . . . . . . . . .. . . . 17 . . .

Although a considerable amount of information concerning the applications for arc plasmas in the materials sciences is available, it is contained in literally thousands of separate manuals, technical notes, textbooks, and government and industrial reports. Each source generally deals with only one specific application or, at best, a narrow range of utilization. This book was developed to provide a comprehensive and up-to-date compilation of information in the technology of arc plasma utilization. The book is divided into two general categories: flame spraying and materials evaluation. In the flame spraying section a comprehensive review of the plasma spraying process is presented. The design and operation of plasma spraying equipment are described. Included are a description of the nature of a plasma, and the design and operation of plasma generators, powder feed systems and accessory control equip ment. The general process procedures, and associated process variables are de scribed. Particular emphasis is given to the particle heating process and the mechanisms for adherence and cohesion of coatings. Competitive flame spraying equipment is also detailed (combustion process, detonation and electric arc) and compared with the plasma spray process. A discussion and compilation of flame sprayed ceramic and metal materials, their properties and applications are also included."

This book describes and analyses various aspects of Israeli climate. This work also elucidates how both man and nature adjust to various climates. The first part (Chapters 1-9) deals with the meteorological and climatological network stations, the history of climate research in Israel, analysis of the local climate by season, and a discussion of the climate variables their spatial and temporal distribution. The second part (Chapters 10-14) of this work is devoted to a survey of applied climatology. This part presents information on weather forecasting, rainfall enhancement, air quality monitoring, and various climatological aspects of planning. There is no sharp division between theoretical and applied climatology topics. Moreover, though various sections seem exclusively theoretical, they also include important applications for various real life situations (such as rainfall intensities (Section 5. 3), frost, frost damage (Section 6. 2. 4), degree-days (Section 6. 2. 5) and heat stress (Section 6. 2. 6). Professionals and university students of geography and earth science, meteorology and climatology, even high school students majoring in geography will be able to use this book as a basic reference work. Researchers in atmospheric science can also use this work as an important source of reference. Students of agriculture will also gain theoretical and practical insights. Even architects and engineers will gain another perspective in their fields.