bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Models of Groundwater Flow and Transport
Authors: Holzbecher Ekkehard , Sorek Shaul 
Published: April 2006

Abstract
The article gives an introduction to numerical modeling of flow and transport problems and to software tools that are currently in use for modeling such phenomena. Details are explained on numerical approximations leading to different numerical models. Extensions for reactive transport are mentioned. Basic guidelines and criteria are given that should be taken into account by the modeler in order to improve the accuracy of results. Inverse modeling is presented as an advanced feature. Some examples of pre‐ and postprocessing, as implemented in several codes, are given, in addition to fundamental properties of solution methods. Finally, most common codes are listed with basic features and web‐sites.
Anthropogenic Land Subsidence
Authors: Gambolati Giuseppe , Teatini Pietro , Ferronato Massimiliano 
Published: April 2006

AbstractFluid removal from subsurface reservoirs, in the form of gas, oil, groundwater, geothermal water, and brine, produces a compaction of the depleted formations which migrates totally or partially to the ground surface thus inducing anthropogenic land subsidence. The paper presents: (i) a list of the major subsiding areas worldwide, (ii) a review of the mechanism which causes a measurable settlement above aquifer systems and gas/oil fields, (iii) a description of the currently available techniques to measure land subsidence and in situ rock compaction, (iv) a brief description of some mathematical models to predict the magnitude of subsidence, and (v) a description of a few remedial options that are available to control the event and mitigate the related environmental impact.
Energy Balance and Thermophysical Processes in Snowpacks
Authors: Lehning Michael 
Published: April 2006

Abstract

This contribution discusses heat and mass fluxes relating to snow. The first process treated is heat flux through snow. Snow can be described as a bulk material or as consisting of different phases. When a separate water vapor phase is considered, vertical mass flux due to vapor pressure differences can be treated. A significant amount of heat is transported along with the vapor fluxes because of the phase changes occurring when water molecules enter the vapor phase at one point and deposit back onto the ice matrix somewhere else. The vapor fluxes in snow also cause snow metamorphism changing the crystals' form and size. Equilibrium metamorphism dominates when weak, large‐scale temperature gradients exist, and water molecules are mainly rearranged locally by surface tension differences. Metamorphism is called
kinetic
when vertical vapor fluxes due to a large‐scale temperature gradient lead to a snow crystal re‐formation.

Mass‐ and energy fluxes in the snow cover are driven by surface exchange. The surface turbulent fluxes of sensible heat and moisture are derived from atmospheric surface layer similarity theory. The long‐wave radiation balance leads to a strong surface cooling especially during cold nights. Short‐wave radiation penetrates the snow cover and deposits energy at greater depths. Finally, the surface mass transport process of snow redistribution is treated with its subprocesses, saltation and suspension.
Role of Glaciers and Ice Sheets in Climate and the Global Water Cycle
Authors: Siegert Martin J 
Published: April 2006

AbstractGlaciers and ice sheets store nearly 70% of the world's freshwater and would raise sea level by around 70 m if they melted. They are, thus, an important component of the global water cycle. Their role in climate can be assessed through current responses to global warming and their influence on the environment during periods of glaciation. At the Last Glacial Maximum, ∼21 000 years ago, the glacial cover caused sea level to be 115 to 130 m lower than at present. The climate of Ice Age Earth was affected in many ways by ice sheets. First, the expansion of ice sheets caused huge changes to the surface albedo and, hence, the radiation budget of the planet. Second, the orography of North America and Eurasia was altered significantly by large ice sheets, which had implications for atmospheric flow. Third, as the ice sheets grew and decayed, the influx of freshwater to the oceans, and in particular the North Atlantic, affected the ocean circulation, which in turn affected climate. The result of this ice–ocean–atmosphere interaction was large‐scale short‐term oscillations in air temperatures, which have been recorded in Greenland ice cores. The ice and climate processes identified for the glacial cycle are relevant today. For example, the Greenland ice sheet is currently melting at its southern margin, and releasing freshwater to the North Atlantic. Importantly, global temperatures were a few degrees higher in the previous interglacial, and the Greenland ice sheet was about half its current size. As global warming continues, the response of the Greenland ice sheet could be to return to its Eemian configuration. Although far smaller in volume, glaciers respond much quicker to climate change than do ice sheets. In the last century, most have experienced decay, and the runoff generated has been estimated to account for at least 10% of the 15 to 20 cm of sea‐level rise measured (seeMass and Energy Balances of Glaciers and Ice Sheets,). In combination, glacier and ice‐sheet melting may send large quantities of water into the oceans, some of it rapidly. This could have serious implications for the climate of the North Atlantic and, through teleconnection, the world.
Permafrost Hydrology
Authors: Hinzman Larry D , Kane Douglas L , Woo Ming‐ko 
Published: April 2006

AbstractPermafrost is earth material that has temperature at or below 0°C for at least two consecutive summers. Above the permafrost is the active layer, a zone that freezes in winter and thaws in summer. Even though the principles governing water movement in permafrost areas are the same as those in more temperate regions, interactions of extremes in climate and the land surface characteristics render permafrost hydrology different from the hydrology of temperate latitudes. Ice‐rich permafrost prevents infiltration of rainfall or snowmelt water, often maintaining a moist to saturated active layer where the permafrost table is shallow. Most hydrologic activities are confined above ground or in the thin active layer, which supplies summer moisture to plants and for evaporative flux. Limited storage capacity of the thawed zone does not support extended baseflow in a stream, though the proportion of baseflow increases as the percentage of permafrost extent decreases. In areas where permafrost is discontinuous or where it has thawed substantially near the surface, local hydrology may display a marked different character as there are stronger exchanges between the surface water and the ground water system, or water may drain laterally resulting in drier surface conditions. Runoff paths range from interhummock cracks, soil pipes, water tracks to distinct channels; and permafrost affects the ground water and contaminant migration pathways. Understanding the interdependence of permafrost, hydrology, and ecosystems is critically important to enable accurate projections of future conditions in the high latitudes.
Global Water Budgets – Fundamental Theory and Mechanisms
Authors: Adam Schlosser C 
Published: April 2006

AbstractThe global water cycle represents the transport and transformation of water within the Earth system, and, in doing so, distributes freshwater over the Earth's surface. The cycling of water in the Earth's system employs water in all three of its phases: solid, liquid, and gaseous. In its coarsest and most conventional depiction, the Earth system's cycling of water is viewed as the continual displacement of water taken from the ocean, transported through the atmosphere, deposited over land, and ultimately fed back to the ocean. However, many processes and pathways are responsible for this global transit and cycling. Therefore, to monitor the global water cycle in the context of all of these key interactions with the global environment requires a comprehensive representation of the budgets and cycling of all phases of water storage. An analytic discussion is provided to elucidate the various mechanisms that contribute to the global transport of water within and between the Earth's atmosphere, land, and ocean systems
Short‐Term Predictions (Weather Forecasting Purposes)
Authors: Kallos George , Pytharoulis Ioannis 
Published: April 2006

Abstract
In recent years there is a growing need in hydrology for high‐resolution precipitation predictions. Accurate quantitative precipitation forecasts at various spatiotemporal scales can be made by the atmospheric numerical models that utilize sophisticated parameterization schemes to represent the various physical processes. Two soil parameterization schemes are presented here: a) the bucket model which is a simple single‐layer scheme and was the first one to be used in numerical models, and b) the multilayer Oregon State University scheme which is currently utilized in operational and research mode. A number of successful short‐term predictions of severe precipitation events are also presented. These predictions were produced by various full‐physics numerical models, such as the SKIRON/Eta modeling system, RAMS and the UKMO Unified model, under different forcing mechanisms. The performance of the models in representing the spatiotemporal variability of precipitation is mainly discussed. In general, the atmospheric numerical models exhibited a skill in providing accurate short‐term predictions of the spatiotemporal variability and severity of precipitation.
Water and Forests
Authors: Jewitt Graham 
Published: April 2006

Abstract
Years of research in various parts of the world has highlighted the interaction between forests and water. Forests impact on the hydrological cycle affecting processes such as interception, transpiration, infiltration, groundwater recharge, and runoff. These inevitably manifest themselves as impacts on the water resource, both positive and negative. In this article, the role of forests in the hydrological cycle is described, and the potential impacts for water resources are considered.
Land Use and Water Quality
Authors: Baker Andy 
Published: April 2006

Abstract
The literature investigating the relationship between land use and water quality is synthesized. It is demonstrated that although some general correlations between land use and water quality can be observed, in general the relationship is complex with correlations in individual watersheds likely to be site or regionally specific. Land cover measurements discussed include land use, land cover, ecotone, buffer strip, and indices of landscape metrics, whereas water quality issues include spatial and temporal sampling strategies and the use of nonconservative tracers. Examples of land use–water quality relationships are given for both the impacts of urbanization and the intensification of agriculture. A paucity of studies in developing countries and the need to advance models of land use–water quality relationships are highlighted.
Land Use and Water Resources under a Changing Climate
Authors: Giambelluca Thomas W 
Published: April 2006

Abstract

Water resources are becoming increasingly scarce because of the mounting demand for water associated with population growth and economic development. The availability of and need for water resources are strongly influenced by land use. Land use and land cover change can alter the regional hydrologic cycle by changing evapotranspiration (ET), runoff, soil moisture, and perhaps even precipitation, resulting in changes in water supply and demand. In addition to changes associated with land use, climate warming may significantly influence the global hydrological cycle, leading to a variety of regional hydrological changes. Higher atmospheric CO
2
levels and changing climate will influence land cover in various ways. Conversely, many types of land cover change disrupt the global carbon cycle, contributing to changes in atmospheric greenhouse gases. The drivers of climate and land cover change will be subject to complex feedbacks involving the hydrological cycle and water resources. Hence, it is important to consider the web of interacting factors affecting water resources in the context of climate and land use change. This article reviews the effects of land cover and land use change on water supply and demand, the predicted effects of global warming on water resources, the interaction between climate change and land cover change, and the combined effects of land use and climate change on water resources.
Hydromorphological Quality – A Policy Template for Channel Design in River Restoration
Authors: Large Andrew R G , Newson Malcolm D 
Published: April 2006

Abstract

The European Union's
Water Framework Directive
(
WFD
) is the most substantial piece of European water legislation to date and will have a profound effect on how water is managed in Europe over the next 25 years. The term “hydromorphological” was introduced by the WFD to describe the quality of water bodies in addition to physicochemical and ecological elements, and has rapidly become a prominent descriptor. Reference conditions are described as “having no or only very minor alterations” resulting from human activity yet, at the same time, there is considerable confusion as to how far back we have to go to approximate such conditions. A core uncertainty or ambiguity concerns the possible differences between structural definitions of a reference condition and those that relate to processes, or “functionality”. Whilst ecohydrology and hydroecology are clearly critical in the provision of a science foundation for the WFD, the introduction of hydromorphological quality as a measure of the condition of fresh waters requires new (or, at least, innovative) thinking.

A momentous challenge for those involved with the concept and realization of “good ecological quality” is to assess it, monitor it, and restore it within a basin‐wide strategy, considering also the element of land use and management. The potential role of fluvial geomorphology in understanding, assessing, monitoring, and restoring hydromorphological quality in river systems is stressed.
Land‐Atmosphere Models for Water and Energy Cycle Studies
Authors: Nijssen Bart , Bastidas Luis A 
Published: April 2006

Abstract
Land surface models simulate the temporal evolution of the energy and water balance at and near the land surface. These models can be used coupled to an atmospheric model, in which case feedbacks between the land surface and atmosphere are explicitly represented, or they can be used in a stand‐alone, uncoupled mode, in which case observed or simulated atmospheric conditions act as time‐varying boundary conditions. This article reviews the basic layout of land surface models, their history, and their uses, specifically in uncoupled simulations. In this context, the challenges of model performance evaluation and the role of model intercomparison projects are discussed. The article ends with a look toward the future and the next series of developments that land surface models are likely to undergo.
Use of Climate Information in Water Resources Management
Authors: Hartmann Holly C 
Published: April 2006

AbstractFailures in water resources management, evolving societal objectives, and advances in the scientific understanding of hydroclimatic systems have led to reassessment of techniques traditionally used in support of water resources management policies and practices. Climate information, encompassing a variety of timescales, is clearly useful for water resources management, yet remains underutilized. This article examines historical climate information provided by instrumental records and paleoclimatological indicators, and prognostications of future climate conditions provided by climate forecasts and assessments of climate change, and issues related to their use in water resources management. Two issues are of central importance: nonstationarity and uncertainty. The water resources community must accept that in many cases one of the fundamental assumptions underlying classical hydrology is simply incorrect. However, the water resources management community need not assess climate information and its use in isolation. Networks of researchers, including hydroclimatic and social scientists, are actively seeking more integrated involvement with the water resources management community, are adapting their research agenda and activities to address the needs of decision makers and stakeholders, and are committed to developing practical products and decision‐support tools.
Biochemical Processes/Kinetics
Authors: Voit Eberhard O. 
Published: April 2006

Abstract
Most biochemical processes are catalyzed by enzymes that facilitate the conversion of one type of metabolite into another. Enzymes are proteins whose activity the cells control rapidly through inhibitors, activators, or other modulators and, on a longer time scale, through altered gene expression. Kinetics addresses questions related to the dynamics of enzyme‐catalyzed reactions and of systems of such reactions. As this dynamic is nonlinear and therefore complex, it is presently difficult to analyze large systems in detail. The stoichiometric approach simplifies this complexity by formulating networks of reactions as linear equations, where all influxes into a metabolite pool are balanced against all effluxes from this pool. At the biologically important steady state, the analysis of stoichiometric systems becomes a matter of linear algebra. For smaller systems, enough kinetic information is available to formulate nonlinear models that account for the cell's various means of regulation. Traditionally, the reactions in such models have been based on representations like the kinetic rate law of Henri, Michaelis, and Menten. As these rate laws become cumbersome for systems of more than a few steps, new kinetic approaches use alternative representations, such as power‐law functions, which are manageable for realistically sized pathway systems.
Echocardiography
Authors: Jacobs Lawrence D. 
Published: April 2006

Abstract
Echocardiography is a powerful diagnostic imaging modality that uses the complex interaction of ultrasound waves with the heart and associated tissues to create images of these structures. Echocardiography's versatility comes mainly from the fact that it is able to simultaneously provide structural and physiologic data in real time, noninvasively, and without deleterious effects on biologic tissues.
A basic understanding of the physics of ultrasound and the manner in which ultrasound interacts with the body is crucial for understanding the strengths and weaknesses of echocardiography as a diagnostic tool. It is these basic principles of cardiac ultrasound that have been refined into the more complex and highly useful echocardiographic imaging modalities, such as Doppler, color Doppler, tissue Doppler, and harmonic imaging, which are commonly used in clinical cardiology today. Newer, cutting‐edge technologies, including contrast echocardiography, myocardial perfusion imaging, and real‐time 3‐D echocardiographic imaging have been developed and are just beginning to make their impact felt in clinical use.
As echocardiography is so versatile, with applications in the entire spectrum of cardiac disease, some consider it an extension of the physical examination. It is this clinical use, combined with a steady flow of new innovations and an excellent safety profile, that ensures that echocardiography will remain one of the most powerful and commonly performed diagnostic tests in medicine for the foreseeable future.
Human Motion Analysis
Authors: Morasso Pietro G. , Sanguineti Vittorio 
Published: April 2006

AbstractHuman motion analysis is addressed under three major headings: biomechanics, measurements, and motor control.The relevant biomechanical principles are subdivided into three main topics: (a) trajectory formation (including the principle of motor equivalence and the kinematic invariances), (b) kinematics (the Denavit–Hartenberg notation, direct and inverse kinematics), and (c) dynamics.The range of measurement techniques employed in human motion analysis is quite large. We categorize them in the following manner: (a) kinematic measurements (relative angular rotations, absolute angular orientation, position of body points with optical or magnetic techniques, accelerometry), (b) force measurements (wrist sensors and force platforms), (c) EMG measurements, and (d) stiffness measurements.Basic motor control principles are anlayzed in regard to three main issues: (a) the role of the mechanical properties of muscles, (b) the need of dynamic compensation with feedforward or feedback control mechanisms, and (c) the spatio‐temporal organization of locomotion patterns.
Lyapunov Exponents
Authors: Dingwell Jonathan B. 
Published: April 2006

AbstractThe analysis of potentially chaotic behavior in biological and biomedical phenomena has attracted increased attention in recent years. Chaotic systems exhibit a trademark “sensitive dependence on initial conditions” (SDIC), meaning that very small perturbations will cause the resulting trajectories to separate exponentially fast. Lyapunov exponents directly measure SDIC by quantifying the exponential rates at which neighboring orbits on an attractor diverge (or converge) as the system evolves in time. Dissipative deterministic systems that exhibit at least one positive Lyapunov exponent are by definition “chaotic.” Hence, Lyapunov exponents are considered one of the most useful diagnostic tools available for analyzing potentially chaotic dynamical systems. However, Lyapunov exponents are also notoriously difficult to estimate reliably from experimental data and one should always be very skeptical about accepting any claims of “chaos” based solely on findings of positive Lyapunov exponents alone. This article reviews the basic definitions of Lyapunov exponents and outlines several of the more widely disseminated algorithms available to estimate them from experimental time series data. Critical issues related to finding spurious exponents, analyzing noisy signals, and validating against surrogate data are reviewed. A brief discussion of how Lyapunov exponents have been applied to study a wide variety of biomedical and biological phenomena is also presented. Finally, some thoughts on appropriate interpretations of such findings and the future directions for using Lyapunov exponents to study potentially chaotic systems are presented.
Medical Devices: Regulations, Codes, and Standards
Authors: Munzner Robert 
Published: April 2006

Abstract
The approach that various countries have taken to regulate the marketing of medical devices differs, greatly as does their use of standards for medical devices. The United States has the most complex system because of its highly detailed legislation and the numerous amendments to that legislation. Whereas the European Community has adopted a method‐based certification of conformance to standards, the U.S. rules do not require conformance to standards. The complexity of the U.S. system is because of its evolution from a law that presumed medical devices being marketed before enactment of the law are reasonably safe and effective unless proven otherwise. Most new devices enter the U.S. market based on “substantial equivalence” to devices that are presently being marketed. Except for devices that have been exempted, the specifications of all devices entering the U.S. market are examined by the U.S. Food and Drug Administration.