3,060 research outputs found
Simultaneous Identification of the Diffusion Coefficient and the Potential for the Schr\"odinger Operator with only one Observation
This article is devoted to prove a stability result for two independent
coefficients for a Schr\"odinger operator in an unbounded strip. The result is
obtained with only one observation on an unbounded subset of the boundary and
the data of the solution at a fixed time on the whole domain
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Studying the impact of biomass burning aerosol radiative and climate effects on the Amazon rainforest productivity with an Earth system model
Diffuse light conditions can increase the efficiency of photosynthesis and carbon uptake by vegetation canopies. The diffuse fraction of photosynthetically active radiation (PAR) can be affected by either a change in the atmospheric aerosol burden and/or a change in cloudiness. During the dry season, a hotspot of biomass burning on the edges of the Amazon rainforest emits a complex mixture of aerosols and their precursors and climate-active trace gases (e.g. CO2, CH4, NOx). This creates potential for significant interactions between chemistry, aerosol, cloud, radiation and the biosphere across the Amazon region. The combined effects of biomass burning on the terrestrial carbon cycle for the present day are potentially large, yet poorly quantified. Here, we quantify such effects using the Met Office Hadley Centre Earth system model HadGEM2-ES, which provides a fully coupled framework with interactive aerosol, radiative transfer, dynamic vegetation, atmospheric chemistry and biogenic volatile organic compound emission components. Results show that for present day, defined as year 2000 climate, the overall net impact of biomass burning aerosols is to increase net primary productivity (NPP) by +80 to +105 TgC yr−1, or 1.9 % to 2.7 %, over the central Amazon Basin on annual mean. For the first time we show that this enhancement is the net result of multiple competing effects: an increase in diffuse light which stimulates photosynthetic activity in the shaded part of the canopy (+65 to +110 TgC yr−1), a reduction in the total amount of radiation (−52 to −105 TgC yr−1) which reduces photosynthesis and feedback from climate adjustments in response to the aerosol forcing which increases the efficiency of biochemical processes (+67 to +100 TgC yr−1). These results illustrate that despite a modest direct aerosol effect (the sum of the first two counteracting mechanisms), the overall net impact of biomass burning aerosols on vegetation is sizeable when indirect climate feedbacks are considered. We demonstrate that capturing the net impact of aerosols on vegetation should be assessed considering the system-wide behaviour
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Modeling esophageal protection from radiofrequency ablation via a cooling device: an analysis of the effects of ablation power and heart wall dimensions.
BACKGROUND: Esophageal thermal injury can occur after radiofrequency (RF) ablation in the left atrium to treat atrial fibrillation. Existing methods to prevent esophageal injury have various limitations in deployment and uncertainty in efficacy. A new esophageal heat transfer device currently available for whole-body cooling or warming may offer an additional option to prevent esophageal injury. We sought to develop a mathematical model of this process to guide further studies and clinical investigations and compare results to real-world clinical data. RESULTS: The model predicts that the esophageal cooling device, even with body-temperature water flow (37 °C) provides a reduction in esophageal thermal injury compared to the case of the non-protected esophagus, with a non-linear direct relationship between lesion depth and the cooling water temperature. Ablation power and cooling water temperature have a significant influence on the peak temperature and the esophageal lesion depth, but even at high RF power up to 50 W, over durations up to 20 s, the cooling device can reduce thermal impact on the esophagus. The model concurs with recent clinical data showing an 83% reduction in transmural thermal injury when using typical operating parameters. CONCLUSIONS: An esophageal cooling device appears effective for esophageal protection during atrial fibrillation, with model output supporting clinical data. Analysis of the impact of ablation power and heart wall dimensions suggests that cooling water temperature can be adjusted for specific ablation parameters to assure the desired myocardial tissue ablation while keeping the esophagus protected
A Graph-Based Modeling Framework for Tracing Hydrological Pollutant Transport in Surface Waters
Anthropogenic pollution of hydrological systems affects diverse communities
and ecosystems around the world. Data analytics and modeling tools play a key
role in fighting this challenge, as they can help identify key sources as well
as trace transport and quantify impact within complex hydrological systems.
Several tools exist for simulating and tracing pollutant transport throughout
surface waters using detailed physical models; these tools are powerful, but
can be computationally intensive, require significant amounts of data to be
developed, and require expert knowledge for their use (ultimately limiting
application scope). In this work, we present a graph modeling framework --
which we call -- for understanding pollutant transport and
fate across waterbodies, rivers, and watersheds. This framework uses a
simplified representation of hydrological systems that can be constructed based
purely on open-source data (National Hydrography Dataset and Watershed Boundary
Dataset). The graph representation provides an flexible intuitive approach for
capturing connectivity and for identifying upstream pollutant sources and for
tracing downstream impacts within small and large hydrological systems.
Moreover, the graph representation can facilitate the use of advanced
algorithms and tools of graph theory, topology, optimization, and machine
learning to aid data analytics and decision-making. We demonstrate the
capabilities of our framework by using case studies in the State of Wisconsin;
here, we aim to identify upstream nutrient pollutant sources that arise from
agricultural practices and trace downstream impacts to waterbodies, rivers, and
streams. Our tool ultimately seeks to help stakeholders design effective
pollution prevention/mitigation practices and evaluate how surface waters
respond to such practices.Comment: 39 pages, 9 figures updated format, updated github link, updated
agricultural land in figures/analysis; methods/overall results remain
unchange
Vegetation distribution and terrestrial carbon cycle in a carbon cycle configuration of JULES4.6 with new plant functional types
This is the final version. Available on open access from EGU via the DOI in this recordDynamic global vegetation models (DGVMs) are used for studying historical and future changes to vegetation and the terrestrial carbon cycle. JULES (the Joint UK Land Environment Simulator) represents the land surface in the Hadley Centre climate models and in the UK Earth System Model. Recently the number of plant functional types (PFTs) in JULES was expanded from five to nine to better represent functional diversity in global ecosystems. Here we introduce a more mechanistic representation of vegetation dynamics in TRIFFID, the dynamic vegetation component of JULES, which allows for any number of PFTs to compete based solely on their height; therefore, the previous hardwired dominance hierarchy is removed. With the new set of nine PFTs, JULES is able to more accurately reproduce global vegetation distribution compared to the former five PFT version. Improvements include the coverage of trees within tropical and boreal forests and a reduction in shrubs, the latter of which dominated at high latitudes. We show that JULES is able to realistically represent several aspects of the global carbon (C) cycle. The simulated gross primary productivity (GPP) is within the range of observations, but simulated net primary productivity (NPP) is slightly too high. GPP in JULES from 1982 to 2011 is 133PgCyrg'1, compared to observation-based estimates (over the same time period) between 1238 and 150-175PgCyrg'1. NPP from 2000 to 2013 is 72PgCyrg'1, compared to satellite-derived NPP of 55PgCyrg'1 over the same period and independent estimates of 56.214.3PgCyrg'1. The simulated carbon stored in vegetation is 542PgC, compared to an observation-based range of 400-600PgC. Soil carbon is much lower (1422PgC) than estimates from measurements ( > 2400PgC), with large underestimations of soil carbon in the tropical and boreal forests. We also examined some aspects of the historical terrestrial carbon sink as simulated by JULES. Between the 1900s and 2000s, increased atmospheric carbon dioxide levels enhanced vegetation productivity and litter inputs into the soils, while land use change removed vegetation and reduced soil carbon. The result is a simulated increase in soil carbon of 57PgC but a decrease in vegetation carbon of 98PgC. The total simulated loss of soil and vegetation carbon due to land use change is 138PgC from 1900 to 2009, compared to a recent observationally constrained estimate of 15550PgC from 1901 to 2012. The simulated land carbon sink is 2.01.0PgCyrg'1 from 2000 to 2009, in close agreement with estimates from the IPCC and Global Carbon Project.The authors acknowledge support from the
Natural Environment Research Council (NERC) Joint Weather
and Climate Research Programme through grant numbers
NE/K016016/1 (Anna B. Harper) and NEC05816 (Lina M. Mercado).
NERC support was also provided to Lina M. Mercado
through the UK Earth System Modelling project (UKESM,
grant NE/N017951/1). Anna B. Harper also acknowledges support
from her EPSRC Fellowship (EP/N030141/1) and the EU
H2020 project CRESCENDO (GA641816). The EU project FP7
LUC4C (GA603542) provided support for Stephen Sitch and
Pierre Friedlingstein. The Met Office authors were supported
by the Joint UK BEIS/Defra Met Office Hadley Centre Climate
Programme (GA01101)
Habitability: CAMELOT 4
During 1988 to 1989 the NASA/USRA Advanced Design Program sponsored research and design efforts aimed at developing habitability criteria and at defining a habitability concept as a useful tool in understanding and evaluating dwellings for prolonged stays in extraterrestrial space. The Circulating Auto sufficient Mars-Earth Luxurious Orbital Transport (CAMELOT) was studied as a case in which the students would try to enhance the quality of life of the inhabitants by applying architectural design methodology. The study proposed 14 habitability criteria considered necessary to fulfill the defined habitability concept, which is that state of equilibrium that results from the interaction between components of the Individual Architecture Mission Complex, which allows a person to sustain physiological homeostatis, adequate performance, and acceptable social relationships. Architecture, design development, refinements and revisions to improve the quality of life, new insights on artificial gravity, form and constitution problems, and the final design concept are covered
Technical note: A simple theoretical model framework to describe plant stomatal “sluggishness” in response to elevated ozone concentrations
Elevated levels of tropospheric ozone, O3, cause damage to terrestrial vegetation, affecting leaf stomatal functioning and reducing photosynthesis. Climatic impacts under future raised atmospheric greenhouse gas (GHG) concentrations will also impact on the net primary productivity (NPP) of vegetation, which might for instance alter viability of some crops. Together, ozone damage and climate change may adjust the current ability of terrestrial vegetation to offset a significant fraction of carbon dioxide (CO2) emissions. Climate impacts on the land surface are well studied, but arguably large-scale modelling of raised surface level O3 effects is less advanced. To date most models representing ozone damage use either O3 concentration or, more recently, flux-uptake-related reduction of stomatal opening, estimating suppressed land–atmosphere water and CO2 fluxes. However there is evidence that, for some species, O3 damage can also cause an inertial “sluggishness” of stomatal response to changing surface meteorological conditions. In some circumstances (e.g. droughts), this loss of stomata control can cause them to be more open than without ozone interference. To both aid model development and provide empiricists with a system on to which measurements can be mapped, we present a parameter-sparse framework specifically designed to capture sluggishness. This contains a single time-delay parameter τO3, characterizing the timescale for stomata to catch up with the level of opening they would have without damage. The larger the value of this parameter, the more sluggish the modelled stomatal response. Through variation of τO3, we find it is possible to have qualitatively similar responses to factorial experiments with and without raised O3, when comparing to reported measurement time series presented in the literature. This low-parameter approach lends itself to the inclusion of ozone-induced inertial effects being incorporated in the terrestrial vegetation component of Earth system models (ESMs)
Heterologous expression of AtNPR1 gene in olive for increasing fungal tolerance
The NPR1 gene encodes a key component of SAR signaling mediated by salicylic acid (SA). After a pathogen infection, the accumulation of SA releases NPR1 monomers in the cytosol that are translocated to the nucleus, activating the expression of pathogenesis-related (PR) genes. Overexpression of NPR1 has conferred resistance to fungal, viral and bacterial pathogens in several plant species. The aim of this research was to generate transgenic olive plants expressing the gene AtNPR1 from Arabidopsis thaliana to obtain material resistant to fungal pathogens. Three transgenic lines expressing AtNPR1 gene under the control of the constitutive promoter CaMV35S were obtained following the protocol of Torreblanca et al. (2010), using an embryogenic line derived from a seed of cv. Picual. Level of AtNPR1 expression in transgenic calli varied greatly among the different lines, being higher in the line NPR1-780. The elicitation of embryogenic calli in liquid medium with AS did not increase endochitinase activity, a PR protein. However, jasmonic acid induced a transient increase in chitinase activity after 24 h of treatment in all the lines, being the increment higher in transgenic NPR1 than in control. After maturation and germination of transgenic somatic embryos, plants were micropropagated and acclimated to ex vitro conditions. The expression of AtNPR1 did not alter the growth of transgenic plants neither in vitro nor in the greenhouse. Experiments are in progress to determine the resistance of transgenic AtNPR1 plants to V. dalihae and R. necatrix.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.
Research projects: Plan Nacional AGL2014-52518-C2-1-R; AGL2017-83368-C2-1-R and Junta de Andalucía P11-AGR799
SURVIVAL ANALYSIS FOR THE RISK OF DEVELOPING HEART ATTACK
Heart disease is the leading cause of death among Filipinos, accounting for 1 out of every 5 deaths in the past year. Each year, 170,000 Filipinos die from cardiovascular diseases, up from 85,000 more than 20 y ago. This paper aims to estimate the risk of developing Heart Attack using Survival Analysis. The data were obtained from the records of Quirino Memorial Medical Center with a total of 447 observations. The data includes the time t (patient's age), gender of the patient, covariates such as lifestyle (smoking and drinking alcohol); health conditions (Hypertension, Diabetes, High-density Lipoprotein (HDL) and Low-density Lipoprotein (LDL) level); and family history of Cardiovascular Disease, and the event of interest which is the occurrence of heart attack. The researchers applied two main statistical treatments in examining the data: (1) Cox Regression in formulating a model to estimate the risk of heart attack based on the given covariates; (2) Kaplan-Meier Estimates in calculating the probability of each patient to survive in accordance to their gender depending on the covariates the patients have. Results showed that females have more risks of developing heart attack than males for patients with hypertension, with diabetes, with a family history of CVD, and those who are smoking. However, for patients who are alcoholic, men are more prone to the risk of heart attack than women. The results were obtained with the help of SPSS
El ensayo de solubilidad diferencial como método de caracterización de la estructura fina de las fibras químicas
La solubilidad diferencial es un ensayo físico-químico para la caracterización de la estructura fina de las fibras de poliéster, poliamida, acrílicas y fibras químicas de celulosa. En esta publicación se describe esta técnica, así como la influencia de las variables del ensayo. También se interpreta la curva de solubilidad diferencial vs. temperatura del ensayo. Por último, se citan ejemplos de campos de aplicación de este ensayo a diferentes grupos de sustratos de las mencionadas fibras
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