Simple Conceptual Model Research Articles

Body composition and susceptibility to type 2 diabetes: an evolutionary perspective.

Type 2 diabetes is rapidly increasing in prevalence worldwide, in concert with epidemics of obesity and sedentary behavior that are themselves tracking economic development. Within this broad pattern, susceptibility to diabetes varies substantially in association with ethnicity and nutritional exposures through the life-course. An evolutionary perspective may help understand why humans are so prone to this condition in modern environments, and why this risk is unequally distributed. A simple conceptual model treats diabetes risk as the function of two interacting traits, namely 'metabolic capacity' which promotes glucose homeostasis, and 'metabolic load' which challenges glucose homoeostasis. This conceptual model helps understand how long-term and more recent trends in body composition can be considered to have shaped variability in diabetes risk. Hominin evolution appears to have continued a broader trend evident in primates, towards lower levels of muscularity. In addition, hominins developed higher levels of body fatness, especially in females in relative terms. These traits most likely evolved as part of a broader reorganization of human life history traits in response to growing levels of ecological instability, enabling both survival during tough periods and reproduction during bountiful periods. Since the emergence of Homo sapiens, populations have diverged in body composition in association with geographical setting and local ecological stresses. These long-term trends in both metabolic capacity and adiposity help explain the overall susceptibility of humans to diabetes in ways that are similar to, and exacerbated by, the effects of nutritional exposures during the life-course.

Which impedance strategy is the most effective for cooperative object manipulation?

PurposeThe purpose of this paper is to present a comparison study of cooperative object manipulation control algorithms. To this end, a full comprehensive survey of the existing control algorithms in this field is presented.Design/methodology/approachCooperative manipulation occurs when manipulators are mechanically coupled to the object being manipulated, and the manipulators may not be treated as an isolated system. The most important and basic impedance control (IC) strategies for an assumed cooperative object manipulation task are the Augmented Object Model (AOM) control and the multiple impedance control (MIC) which are found based on the IC, where the former is designed based on the object movement, and the latter is designed based on the whole robot movement. Thus, the basis of these two algorithms are fully studied.FindingsThe results are fully analyzed, and it is practically verified that the MIC algorithm has the better performance. In fact, the results reveal that the MIC system could successfully perform the object manipulation task, as opposed to the AOM controller: for the same controller gains, the MIC strategy showed better performance than the AOM strategy. This means that because there is no control on the robot base with the AOM algorithm, the object manipulation task cannot be satisfactorily performed whenever the desired path is not within the robot work space. On the other hand, with the MIC algorithm, satisfactory object manipulation is achieved for a mobile robotic system in which the robot base, the manipulator endpoints and the manipulated object shall be moved.Practical implicationsA simple conceptual model for cooperative object manipulation is considered, and a suitable setup is designed for practical implementation of the two ICs.Originality/valueThe basis of these two aspects or these two algorithms is fully studied and compared which is the foundation of this paper. For this purpose, a case study is considered, in which a space free-flying robotic system, which contains two 2-degrees of freedom planar cooperative manipulators, is simulated to manipulate an object using the above control strategies. The system also includes a rotating antenna and camera as its third and fourth arm. Finally, a simple conceptual model for cooperative object manipulation is considered, and a suitable setup is designed for practical implementation of the two ICs.

Fuzzy tuning control approach to perform cooperative object manipulation by a rigid–flexible multibody robot

We study cooperative object manipulation control of rigid–flexible multibody systems in space. During such tasks, flexible members like solar panels may get vibrated. Which in turn may lead to some oscillatory disturbing forces on other subsystems and consequently produce errors in the motion of the end-effectors of the cooperative manipulating arms. Therefore, to design and develop capable model-based controllers for such complicated systems, deriving a dynamics model is required. However, due to practical limitations and real-time implementation, the system dynamics model should require low computations. So, first, to obtain a precise compact dynamics model, the rigid–flexible interactive dynamics modeling (RFIM) approach is briefly introduced. Using this approach, the system is virtually partitioned into two rigid and flexible portions, and a convenient model for control purposes is developed. Next, a fuzzy tuning manipulation control (FTMC) algorithm is developed for a simple conceptual model for cooperative object manipulation. In fact, a suitable setup is designed for practical implementation of this controller. After that, a wheeled mobile robot (WMR) system with flexible appendages is considered as a practical case that necessitates delicate force exertion by several end-effectors to move an object along a desired path. The WMR system contains two cooperative manipulators, appended with two flexible solar panels. To reveal the merits of the developed model-based controller, the maneuver is deliberately planned such that flexible modes of solar panels get stimulated due to arms motion. The obtained results show an effective performance of the proposed approach as will be discussed.

MSWEP: 3-hourly 0.25° global gridded precipitation (1979–2015) by merging gauge, satellite, and reanalysis data

Abstract. Current global precipitation (P) datasets do not take full advantage of the complementary nature of satellite and reanalysis data. Here, we present Multi-Source Weighted-Ensemble Precipitation (MSWEP) version 1.1, a global P dataset for the period 1979–2015 with a 3-hourly temporal and 0.25° spatial resolution, specifically designed for hydrological modeling. The design philosophy of MSWEP was to optimally merge the highest quality P data sources available as a function of timescale and location. The long-term mean of MSWEP was based on the CHPclim dataset but replaced with more accurate regional datasets where available. A correction for gauge under-catch and orographic effects was introduced by inferring catchment-average P from streamflow (Q) observations at 13 762 stations across the globe. The temporal variability of MSWEP was determined by weighted averaging of P anomalies from seven datasets; two based solely on interpolation of gauge observations (CPC Unified and GPCC), three on satellite remote sensing (CMORPH, GSMaP-MVK, and TMPA 3B42RT), and two on atmospheric model reanalysis (ERA-Interim and JRA-55). For each grid cell, the weight assigned to the gauge-based estimates was calculated from the gauge network density, while the weights assigned to the satellite- and reanalysis-based estimates were calculated from their comparative performance at the surrounding gauges. The quality of MSWEP was compared against four state-of-the-art gauge-adjusted P datasets (WFDEI-CRU, GPCP-1DD, TMPA 3B42, and CPC Unified) using independent P data from 125 FLUXNET tower stations around the globe. MSWEP obtained the highest daily correlation coefficient (R) among the five P datasets for 60.0 % of the stations and a median R of 0.67 vs. 0.44–0.59 for the other datasets. We further evaluated the performance of MSWEP using hydrological modeling for 9011 catchments (< 50 000 km2) across the globe. Specifically, we calibrated the simple conceptual hydrological model HBV (Hydrologiska Byråns Vattenbalansavdelning) against daily Q observations with P from each of the different datasets. For the 1058 sparsely gauged catchments, representative of 83.9 % of the global land surface (excluding Antarctica), MSWEP obtained a median calibration NSE of 0.52 vs. 0.29–0.39 for the other P datasets. MSWEP is available via http://www.gloh2o.org.

Deuterium retention and blistering in tungsten foils

To investigate deuterium retention and the onset of blistering, deuterium was implanted in cold rolled tungsten foils at fluences ranging from 3 ×1020 to 3 ×1022D/m2. Ion energies were 300eV and 2000eV in order to be below and above the tungsten theoretical damage energy threshold. While energy dependent phenomena were observed, blistering occurs regardless of ion energy. Both plastically and elastically deformed blisters were found, as manifest in before and after micrographs. The fraction of plastically deformed blisters did not saturate at the fluences used in these studies. However, the size of the largest blister that relaxed during TDS does saturate at ∼7µm. A simple conceptual model is presented, which proposes that the deuterium released from elastically deformed blisters appears at ∼600K in the thermal desorption spectra, which is consistent with large vacancy clusters.

Ecotone formation induced by the effects of tidal flooding: A conceptual model of the mud flat-coastal wetland ecosystem

The boundary between mud flat and coastal wetland ecosystems is highly productive and a haven of considerable biodiversity. It is also embedded in a highly dynamic environment and can be easily destabilised by environmental changes, invasive species, and human activity. Thus, understanding the processes which govern the formation of this ecotone is important both for conservation and economic reasons. In this study we introduce a simple conceptual model for this joint ecosystem, which demonstrates that the interaction between tidal flooding and habitat elevation is able to produce an ecotone with similar characteristics to that observed in empirical studies. In particular, the transition from mud flat to vegetated state is locally abrupt, occurring at a critical threshold elevation, but, on broader spatial scales can occur over a range of elevations determined by the variability in high tide water levels. Additionally, the model shows the potential for regime shifts, resulting from periods of unusual weather or the invasion of a fast growing, or flood resistant, species.

Factors Associated with Asthma ED Visit Rates among Medicaid-enrolled Children: A Structural Equation Modeling Approach.

BackgroundAsthma is one of the leading causes of emergency department visits and school absenteeism among school-aged children in the United States, but there is significant local-area variation in emergency department visit rates, as well as significant differences across racial-ethnic groups.AnalysisWe first calculated emergency department (ED) visit rates among Medicaid-enrolled children age 5–12 with asthma using a multi-state dataset. We then performed exploratory factor analysis using over 226 variables to assess whether they clustered around three county-level conceptual factors (socioeconomic status, healthcare capacity, and air quality) thought to be associated with variation in asthma ED visit rates. Measured variables (including ED visit rate as the outcome of interest) were then standardized and tested in a simple conceptual model through confirmatory factor analysis.ResultsCounty-level (contextual) variables did cluster around factors declared a priori in the conceptual model. Structural equation models connecting the ED visit rates to socioeconomic status, air quality, and healthcare system professional capacity factors (consistent with our conceptual framework) converged on a solution and achieved a reasonable goodness of fit on confirmatory factor analysis.ConclusionConfirmatory factor analysis offers an approach for quantitatively testing conceptual models of local-area variation and racial disparities in asthma-related emergency department use.

A functional overview of conservation biological control

Conservation biological control (CBC) is a sustainable approach to pest management that can contribute to a reduction in pesticide use as part of an Integrated Pest Management (IPM) strategy. CBC is based on the premise that countering habitat loss and environmental disturbance associated with intensive crop production will conserve natural enemies, thus contributing to pest suppression. The abundance and diversity of natural enemies increases in response to a variety of conservation measures, including plant and habitat diversification, a reduction in cropping intensity, and increased landscape complexity. However, the response of natural enemy populations to conservation measures is not consistent; often it fails to translate into pest suppression or improved crop yield, and is seldom utilised in commercial crop production settings. CBC is a complex strategy drawing on a number of ecological and behavioural processes, operating at multiple scales, and mediated by management actions that are, potentially, targeted at a wide range of pest organisms. Given this inherent complexity, it is not surprising that the scientific understanding of CBC is incomplete, or that the design and adoption of reliable CBC prescriptions have proved elusive. To tackle this, we consolidate existing knowledge of CBC using a simple conceptual model that organises the functional elements of CBC into a common, unifying framework. We identify and integrate the key biological processes affecting natural enemies and their biological control function across local and regional scales, and consider the interactions, interdependencies and constraints that determine the outcome of CBC strategies. Conservation measures are often effective in supporting natural enemy populations but their success cannot be guaranteed; the greatest limitation to the development of effective CBC is due to a failure to adequately direct biological control services to achieve suppression of the target pests. By considering the performance of these and other components of CBC within the context of an integrated system, we believe that the limiting factors can be identified, and removed, allowing effective CBC strategies to be implemented.

Earth evolution and dynamics—a tribute to Kevin Burke

Kevin Burke’s original and thought-provoking contributions have been published steadily for the past 60 years, and more than a decade ago he set out to resolve how plate tectonics and mantle plumes interact by proposing a simple conceptual model, which we will refer to as the Burkian Earth. On the Burkian Earth, mantle plumes take us from the deepest mantle to sub-lithospheric depths, where partial melting occurs, and to the surface, where hotspot lavas erupt today, and where large igneous provinces and kimberlites have erupted episodically in the past. The arrival of a plume head contributes to continental break-up and punctuates plate tectonics by creating and modifying plate boundaries. Conversely, plate tectonics makes an essential contribution to the mantle through subduction. Slabs restore mass to the lowermost mantle and are the triggering mechanism for plumes that rise from the margins of the two large-scale low shear-wave velocity structures in the lowermost mantle, which Burke christened TUZO and JASON. Situated just above the core–mantle boundary, beneath Africa and the Pacific, these are stable and antipodal thermochemical piles, which Burke reasons represent the immediate after-effect of the moon-forming event and the final magma ocean crystallization.

Self-rated health, multimorbidity and depression in Mexican older adults: Proposal and evaluation of a simple conceptual model.

Self-rated health is an individual and subjective conceptualization involving the intersection of biological, social and psychological factors. It provides an invaluable and unique evaluation of a person's general health status. To propose and evaluate a simple conceptual model to understand self-rated health and its relationship to multimorbidity, disability and depressive symptoms in Mexican older adults. We conducted a cross-sectional study based on a national representative sample of 8,874 adults of 60 years of age and older. Self-perception of a positive health status was determined according to a Likert-type scale based on the question: "What do you think is your current health status?" Intermediate variables included multimorbidity, disability and depressive symptoms, as well as dichotomous exogenous variables (sex, having a partner, participation in decision-making and poverty). The proposed conceptual model was validated using a general structural equation model with a logit link function for positive self-rated health. A direct association was found between multimorbidity and positive self-rated health (OR=0.48; 95% CI: 0.42-0.55), disability and positive self-rated health (OR=0.35; 95% CI: 0.30-0.40), depressive symptoms and positive self-rated health (OR=0.38; 95% CI: 0.34-0.43). The model also validated indirect associations between disability and depressive symptoms (OR=2.25; 95% CI: 2.01- 2.52), multimorbidity and depressive symptoms (OR=1.79; 95% CI: 1.61-2.00) and multimorbidity and disability (OR=1.98; 95% CI: 1.78-2.20). A parsimonious theoretical model was empirically evaluated, which enabled identifying direct and indirect associations with positive self-rated health.

Method for Visualizing Viscous Interaction in Hypersonic Low-Density Flows Using Electrical Discharge

The purpose of this study was to determine whether an electrical discharge method can be used to investigate separated flows around models tested in low-density, short-duration hypersonic facilities. To demonstrate the applicability of the proposed method, the visualization of the vortical structure around a circular cylinder placed perpendicular to a flat plate was attempted at a small Knudsen number, where methods commonly used for locating flow separations are ineffective. The density distribution of the flowfield was shown to be associated with the spatial distribution of the glow spectrum. The foci of the horseshoe vortices where the gas density was low enough appeared as dark regions in the visualization, especially in the viscous regime, allowing them to be easily located. In addition, this paper presents a simple conceptual model developed to describe the mechanism behind the present method.

River terraces and alluvial fans: The case for an integrated Quaternary fluvial archive

The fluvial archive literature is dominated by research on river terraces with appropriate mention of adjacent environments such as lakes. Despite modern sedimentary basins comprising a significant (>88%) volume of distributive fluvial systems, of which alluvial fans (>1 km, <30 km in scale) are a significant part, interaction with these environments tends to be neglected and discussed in separate literature. This paper examines the dynamic role of alluvial fans within the fluvial landscape and their interaction with river systems, highlighting the potential value of alluvial fans to the wider fluvial archive community. Published literature is used to examine both thematic and geographical based benefits of alluvial fan research that can assist understanding of Quaternary fluvial archives. 3 regional case studies are presented that illustrate the interaction between alluvial fan and river terrace archives at Quaternary time-scales at 3 different stages of landscape evolution. These are i) continuous mountain front alluvial fans interacting with a non incising but laterally eroding axial fluvial system; ii) alluvial fans which transition into fluvial terraces as sedimentary basins shift from net aggradation to net incision and iii) tributary-junction alluvial fans that develop predominantly within incising river valley systems. A simple conceptual model is proposed to summarise the dynamic role of alluvial fans within this landscape context. The alluvial fans act as potential ‘buffers’ between hillslopes and river terrace records under ‘top down’ climate-driven high sediment supply and alluvial fan aggradation, and ‘couplers’ during periods of less sediment (in relation to water) discharge and alluvial fan incision. These dynamics will change with the addition of ‘bottom up’ controls such as main river incision, which will typically enhance the coupling effect of both systems.

Revisiting the time scale and size of the Zanclean flood of the Mediterranean (5.33 Ma) from CFD simulations

The incision Zanclean Channel, which crosses the Strait of Gibraltar and the Alboran Sea, has been interpreted as the geological fingerprint of a cataclysmic stream of water which flowed from the Atlantic into a desiccated Mediterranean about 5.33MaBP. The mathematical support for this theory is provided by a simple conceptual model for hydrodynamics and erosion that, regardless of the initial conditions, leads to scenarios of catastrophic flooding (with water flows exceeding tens or hundreds of Sv which fill 90% of the Mediterranean in few months or few years). This paper revisits the incision model and carries out new numerical simulations of the Zanclean flood of the Mediterranean with a two-dimensional non-linear depth-averaged hydrodynamic model. The numerical output allows solving the equation for time. This way, it is possible to estimate the final incision and the involved time scales under different modelled scenarios. When lateral erosion is reformulated in terms of the causal processes instead of a questionable scaling law, initial conditions become relevant. Those involving narrow connecting channels can be discarded. A flooding scenario with an excavated channel of a few hundred meter depth can be achieved with the initial conditions of a wide sill covered by a water lamina. The threshold stress to initialize erosion must be surpassed in the very early stages of the flooding, which requires a catastrophic start up. Tectonics may have played a major role in it through strike–slip faulting.

A Simple Moisture Advection Model of Specific Humidity Change over Land in Response to SST Warming

Abstract A simple conceptual model of surface specific humidity change over land is described, based on the effect of increased moisture advection from the oceans in response to sea surface temperature (SST) warming. In this model, future q over land is determined by scaling the present-day pattern of land q by the fractional increase in the oceanic moisture source. Simple model estimates agree well with climate model projections of future (mean spatial correlation coefficient 0.87), so over both land and ocean can be viewed primarily as a thermodynamic process controlled by SST warming. Precipitation change is also affected by , and the new simple model can be included in a decomposition of tropical precipitation change, where it provides increased physical understanding of the processes that drive over land. Confidence in the thermodynamic part of extreme precipitation change over land is increased by this improved understanding, and this should scale approximately with Clausius–Clapeyron oceanic q increases under SST warming. Residuals of actual climate model from simple model estimates are often associated with regions of large circulation change, and can be thought of as the “dynamical” part of specific humidity change. The simple model is used to explore intermodel uncertainty in , and there are substantial contributions to uncertainty from both the thermodynamic (simple model) and dynamical (residual) terms. The largest cause of intermodel uncertainty within the thermodynamic term is uncertainty in the magnitude of global mean SST warming.

Agriculture, nutrition and the green revolution in Bangladesh

This paper explores agriculture and nutrition linkages in Bangladesh, a country that achieved rapid growth in rice productivity at a relatively late stage in Asia's Green Revolution, as well as unheralded progress against undernutrition. To do so, we first outline a simple conceptual model to identify the different impacts that productivity growth in a food staple(s) might have on child nutrition outcomes, with a particular focus on changes in diets at the household and child level. We then apply this framework to a descriptive overview of the evolution of Bangladesh's food system in recent decades. We show that this evolution is characterized rapid growth in yields and calorie availability, but relatively sluggish diversification in both food production and consumption, despite increasing reliance on imports for dietary diversification. Next, we create a multi-round district level panel that links changes in nutrition survey data with agricultural sample survey data over 1996–2011, a period in which rice yields rose by more than 70%. We then use this panel to more rigorously test for associations between yield growth and various anthropometric and child feeding indicators. Consistent with our descriptive evidence on dietary changes, we find that rice yields predict the earlier introduction of complementary foods to young children (most frequently rice) as well as increases in their weight-for-height, but no improvements in their dietary diversity or height-for-age. Since Bangladesh has one of the highest rates of child wasting in the world, these significant associations between yields and child weight gain are encouraging, but the lack of discernible effects on children's dietary diversity or linear growth is cause for concern. Indeed, it suggests that further nutritional impacts will require diversifying the Bangladeshi food basket through both supply and demand-side interventions.

Heterogeneity characteristics of flow and transport fields through rough-walled fractures

Due to the impact of rock surface roughness, fracture flow and transport fields are always heterogeneous with tortuous flow-lines. Typically as fracture apertures decrease, fracture flow tends to concentrate at preferential channels. Difficulty in studying fracture flow lies in the quantitative description of the evolution of preferential channels. In this study statistical measures are defined to capture the distributed characteristics of flow tortuosity and concentration. Tortuosity is defined as a ratio of flow-line length to some constant characteristic length of flow field, and the concentration is defined as spatial entropy of local parameters like local apertures, velocities or fluxes. Moreover, the spatial entropy production of local apertures is defined as the preferential channel maturity, which quantitatively indicates the evolution of preferential channels. Results suggest the tortuosity and spatial entropies of local flow field are all of significant positive relationships with preferential channel maturity. A similar positive relationship is found between solute transport contours’ tortuosity and preferential channel maturity as well, which suggests the preferential channels bring additional dispersion to solute transport. At last a simple conceptual model is discussed to show how fracture roughness and preferential channels affect the fracture flow and solute transport.

Conceptual models of forest dynamics in environmental education and management: keep it as simple as possible, but no simpler

Conceptual models of forest dynamics are powerful cognitive tools, which are indispensable for communicating ecological ideas and knowledge, and in developing strategic approaches and setting targets for forest conservation, restoration and sustainable management. Forest development through time is conventionally described as a directional, or “linear”, and predictable sequence of stages from “bare ground” to old forest representing the “climax-state”. However, this simple view is incompatible with the current knowledge and understanding of intrinsic variability of forest dynamics. Overly simple conceptual models of forest dynamics easily become transformed into biased mental models of how forests naturally develop and what kind of structures they display. To be able to communicate the essential features and diversity of forest dynamics, comprehensive conceptual models are needed. For this end, Kuuluvainen (2009) suggested a relatively simple conceptual model of forest dynamics, which separates three major modes of forest dynamics, and incorporates state changes and transitions between the forest dynamics modes depending on changes in disturbance regime. Conceptual models of forest dynamics should be comprehensive enough to incorporate both long-term directional change and short-term cyclic forest dynamics, as well as transitions from one dynamics mode to another depending on changes in the driving disturbance regime type. Models that capture such essential features of forest dynamics are indispensable for educational purposes, in setting reference conditions and in developing methods in forest conservation, restoration and ecosystem management.

An improved void-resistance model for abandoned coal mine gas reservoirs

Previous studies have shown that the gas pressure behaviour of some abandoned coal mines may be described with the aid of a simple conceptual model, the so called void-resistance model. In this study, an improved void-resistance model has been developed and validated using previously collected data. Two model parameters, i.e. an apparent source/sink pressure and a time constant, which control the gas pressure behaviour during recharge and under certain gas production conditions, are defined. It has been shown that the two parameters can be determined via linear regression through analysing the historical abandoned mine gas pressure data during recharge. The void-resistance model developed has been successfully applied to analyse the historical pressure data recorded at two abandoned coal mines in Europe.

Multi-component gas emission measurements of the active lava lake of Nyiragongo, DR Congo

Between 2007 and 2011 four measurement campaigns (June 2007, July 2010, June 2011, and December 2011) were carried out at the crater rim of Nyiragongo volcano, DR Congo. Nyiragongo is one of the most active volcanoes in Africa. The ground-based remote sensing technique Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), which uses scattered sunlight, the in-situ Multi-Component Gas Analyzer System (Multi-GAS) and alkaline impregnated filter were simultaneously applied during all field trips. The bromine monoxide to sulfur dioxide (BrO/SO2) and carbon dioxide to sulfur dioxide (CO2/SO2) molar ratios were determined, among other ratios. During the different field trips variations of the level of the lava lake up to several tens of meters were observed during intervals of the order of minutes up to days and also between the years. The measured gas ratios presented covariations with the lava lake level changes. BrO/SO2 ratios and CO2/SO2 ratios showed similar behavior. Annual CO2/SO2 and BrO/SO2 average values are generally positively correlated. In June 2011 increased BrO/SO2 as well as increased CO2/SO2 ratios have been observed before a sudden decrease of the lava lake.Overall the Cl/S ratio, determined by filter-pack sampling, shows an increasing trend with time, which is accompanied by a decreasing sulfur dioxide flux, the later measured nearly continuously by automated MAX-DOAS instruments since 2004.Mean gas emission fluxes of CO2, Cl and ‘minimum-BrO’ fluxes are calculated using their ratio to SO2. The first two show an increase with time, in contrast to the SO2 fluxes.A simple conceptual model is proposed which can explain in particular the June 2011 data, but as well our entire data set. The proposed model takes up the idea of convective magma cells inside the conduit and the possible temporary interruption of part of the cycling. We propose than two alternatives to explain the observed gas emission variation: 1. It is assumed that the diffuse and fumarolic degassing could have significant influence on measured gas composition. The measured gas composition might rather represent a gas mixture of plume, diffuse and fumarolic degassing than only representing the volcanic plume. 2. It is proposed that the interruption of the convection has taken place in the upper part of the conduit and deep degassing of CO2 and bromine initially continues while mixing already with gas emissions from an ageing source, which is characterized by an already diminishing sulfur content. These complex process but as well as the gas mixing of different sources, could explain general features of our dataset, but can unfortunately neither be confirmed nor disproven by the data available today.

Heat as a tracer for understanding transport processes in fractured media: Theory and field assessment from multiscale thermal push‐pull tracer tests

AbstractThe characterization and modeling of heat transfer in fractured media is particularly challenging as the existence of fractures at multiple scales induces highly localized flow patterns. From a theoretical and numerical analysis of heat transfer in simple conceptual models of fractured media, we show that flow channeling has a significant effect on the scaling of heat recovery in both space and time. The late time tailing of heat recovery under channeled flow is shown to diverge from the behavior expected for the classical parallel plate model and follow the scaling for a simple channel modeled as a tube. This scaling, which differs significantly from known scalings in mobile‐immobile systems, is of purely geometrical origin: late time heat transfer from the matrix to a channel corresponds dimensionally to a radial diffusion process, while heat transfer from the matrix to a plate may be considered as a one‐dimensional process. This phenomenon is also manifested on the spatial scaling of heat recovery as flow channeling affects the decay of the thermal breakthrough peak amplitude and the increase of the peak time with scale. These findings are supported by the results of a field experimental campaign performed on the fractured rock site of Ploemeur. The scaling of heat recovery in time and space, measured from thermal breakthrough curves measured through a series of push‐pull tests at different scales, shows a clear signature of flow channeling. The whole data set can thus be successfully represented by a multichannel model parametrized by the mean channel density and aperture. These findings, which bring new insights on the effect of flow channeling on heat transfer in fractured rocks, show how heat recovery in geothermal tests may be controlled by fracture geometry. In addition, this highlights the interest of thermal push‐pull tests as a complement to solute tracers tests to infer fracture aperture and geometry.