Missing data are major concerns in epidemiological studies of the health effects of environmental air pollutants. This article presents an imputation-based method that is suitable for multivariate ...time series data, which uses the EM algorithm under the assumption of normal distribution. Different approaches are considered for filtering the temporal component. A simulation study was performed to assess validity and performance of proposed method in comparison with some frequently used methods. Simulations showed that when the amount of missing data was as low as 5%, the complete data analysis yielded satisfactory results regardless of the generating mechanism of the missing data, whereas the validity began to degenerate when the proportion of missing values exceeded 10%. The proposed imputation method exhibited good accuracy and precision in different settings with respect to the patterns of missing observations. Most of the imputations obtained valid results, even under missing not at random. The methods proposed in this study are implemented as a package called mtsdi for the statistical software system R.
•We propose a method for imputation of missing values in times series.•Simulations showed adequate goodness-of-fit.•The findings also suggest good accuracy and precision.•We implemented the method as an open source R library.
Despite recent advances in the development of detailed plant radiative transfer models, large-scale canopy models generally still rely on simplified one-dimensional (1-D) radiation models based on ...assumptions of horizontal homogeneity, including dynamic ecosystem models, crop models, and global circulation models. In an attempt to incorporate the effects of vegetation heterogeneity or “clumping” within these simple models, an empirical clumping factor, commonly denoted by the symbol Ω, is often used to effectively reduce the overall leaf area density and/or index value that is fed into the model. While the simplicity of this approach makes it attractive, Ω cannot in general be readily estimated for a particular canopy architecture and instead requires radiation interception data in order to invert for Ω. Numerous simplified geometric models have been previously proposed, but their inherent assumptions are difficult to evaluate due to the challenge of validating heterogeneous canopy models based on field data because of the high uncertainty in radiative flux measurements and geometric inputs. This work provides a critical review of the origin and theory of models for radiation interception in heterogeneous canopies and an objective comparison of their performance. Rather than evaluating their performance using field data, where uncertainty in the measured model inputs and outputs can be comparable to the uncertainty in the model itself, the models were evaluated by comparing against simulated data generated by a three-dimensional leaf-resolving model in which the exact inputs are known. A new model is proposed that generalizes existing theory and is shown to perform very well across a wide range of canopy types and ground cover fractions.
Bacterial infections in cirrhosis: Current treatment Miranda-Zazueta, Godolfino; León-Garduño, Luis A. Ponce de; Aguirre-Valadez, Jonathan ...
Annals of hepatology,
May-June 2020, 2020 May - Jun, 2020-05-00, 20200501, 2020-05-01, Letnik:
19, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Bacterial infections frequently cause decompensating events in cirrhotic patients and are also the most common factor identified for the development of acute-on-chronic liver failure (ACLF). The ...increase in the prevalence of infections caused by multidrug-resistant (MDR) microorganisms has resulted in the reduced effectiveness of empiric antimicrobial treatment. We conducted a PubMed search from the last 20 years using the Keywords cirrhosis; multidrug-resistant; infections; diagnosis; treatment; prophylaxis; monitoring; sepsis; nutrition and antibiotic resistant. We made a review about bacterial infections among cirrhotic patients; we mainly focus on the description of diagnostic tools; biomarkers; clinical scores for diagnosis and prognosis also; we made an analysis concerning the monitoring of cirrhotic patients with sepsis and finally made some recommendations about the treatment; prophylaxis and prevention.
Background and Aims
The interrelationship between alcohol consumption and depression is complex, and the direction of the association is unclear. We investigated whether alcohol consumption ...influences the risk of depression while accounting for this potential bidirectionality.
Methods
A total of 10 441 individuals participated in the PART study in 1998–2000, 8622 in 2001–2003, and 5228 in 2010. Participants answered questions on their alcohol consumption, symptoms of depression, childhood adversity, and sociodemographic, socioeconomic, psychosocial, and lifestyle factors. A total of 5087 participants provided repeated information on alcohol consumption. We used marginal structural models to analyze the association between alcohol consumption and depression while controlling for previous alcohol consumption and depressive symptoms and other time‐varying confounders.
Results
Non‐drinkers had a higher depression risk than light drinkers (≤7 drinks/week) (risk ratio: 1.7; 95% confidence interval 1.3–2.1). Consumers of seven–fourteen drinks/week had a depression risk similar to that of light drinkers. Hazardous drinking was associated with a higher risk of depression than non‐hazardous alcohol consumption (risk ratio: 1.8, 95% confidence interval: 1.4–2.4).
Conclusion
Light and moderate alcohol consumption and non‐hazardous drinking were associated with the lowest risk of subsequent depression after accounting for potential bidirectional effects. Hazardous drinking increased the risk of depression.
Soils contribute 15%–75% of total atmospheric nitrogen oxide (NOx) emissions in agricultural regions during the growing season. However, the impacts of cropland fertilizer management on spatially ...heterogeneous, temporally episodic NOx emission patterns are highly uncertain. We examine the effects of liquid slurry dairy manure application practices on soil NOx emissions in rainfed, corn‐soybean rotations during spring 2016 and 2017. Daily soil NOx emissions and weekly soil inorganic N measurements were performed in a randomized split–split plot design for 1–4 weeks following manure applications. NOx emissions and soil N with shallow‐disk injection and chisel‐disk manure incorporation methods were compared with unincorporated broadcast practices. Injected manure and chisel‐disk incorporation exhibited two–four times larger mean NOx emissions than those with unincorporated broadcast manure. Larger soil NOx emissions with manure incorporation practices were driven by the predominance of nitrification in these treatments with evidence of soil nitrate production. Soil NOx emission differences between treatments were detectable across order of magnitude changes in daily NOx emissions during two growing seasons. Larger soil NOx emissions associated with manure incorporation practices compared with unincorporated broadcast practices occur alongside larger N2O and smaller NH3 emissions, highlighting important air quality and climate impact tradeoffs for cropland manure fertilizer management choices.
Core Ideas
Soil NOx emissions were characterized following rainfed liquid dairy manure applications in the northeastern United States.
Soil NOx emissions with manure incorporation were two–four times larger than with unincorporated broadcast manure.
Larger soil NOx emissions with manure incorporation were associated with the predominance of nitrification.
Abstract During the last centuries, populations of marine megafauna—such as seabirds, turtles, and mammals—were intensively exploited. At present, other threats such as bycatch and pollution affect ...these species, which play key ecological roles in marine ecosystems as apex consumers and/or nutrient transporters. This study analyses the distribution of six megafaunal species (Chelonia mydas, Caretta caretta, Dermochelys coriacea, Thalassarche melanophris, Otaria flavescens, and Arctocephalus australis) coexisting in the Southwestern Atlantic to discuss their protection in terms of current management strategies in the region. Through the prediction of the species potential distributions and their relation to bathymetry, sea temperature and oceanographic fronts, key ecological areas are defined from a multi-taxa perspective. Information on the distribution of 70 individuals (18 sea turtles, 19 albatrosses, and 33 otariids) was obtained through satellite tracking conducted during 2007–2013 and analysed using a Geographic Information System and maximum entropy models. During the autumn–winter period, megafaunal species were distributed over the continental shelves of Argentina, Uruguay, and Brazil, mainly over the Argentine Exclusive Economic Zone and the Argentina-Uruguay Common Fishing Zone. Despite some differences, all megafaunal species seems to have similar environmental requirements during the autumn–winter period. Mostly waters shallower than 50 m were identified as key ecological areas, with the Río de la Plata as the habitat with the highest suitability for all the species. This area is highly productive and sustains the main coastal fisheries of Uruguay and Argentina, yet its role as a key ecological area for megafaunal species has been underestimated until now. This approach provides a basis to analyse the effect of anthropic activities on megafaunal species through risk maps and, ultimately, to generate knowledge to improve national and bi-national management plans between Argentina and Uruguay.
•A new 3D structure-resolving model was developed to predict grape berry temperature•Model validation used a new data set measuring berry temperature in four vineyards•Intermittent temperature ...increases from sun exposure were accurately reproduced•Modeled berry heat storage reduced errors by damping excessive fluctuations
Recent shifts in climatic patterns have influenced the frequency, timing, and severity of heat waves in many wine grape growing regions, which has introduced challenges for viticulturists. Growing the same varieties under these altered climatic conditions often requires mitigation strategies, but quantitative, generalized understanding of the impacts of such strategies can be difficult or time consuming to determine through field trials. This work developed and validated a detailed three-dimensional (3D) model of grape berry temperature that could fully resolve spatial and temporal heterogeneity in berry temperature, and ultimately predict the impacts of potential high berry temperature mitigation strategies such as the use of alternative trellis systems. A novel experimental data set was generated in which the temperature of exposed grape berry clusters was measured with thermocouples at four field sites with different trellis systems, topography, and climate. Experimental measurements indicated that the temperature of shaded berries closely followed the ambient air temperature, but intermittent periods of direct solar radiation could generate berry temperatures in excess of 10∘C above ambient. Validation results indicated that by accurately representing the 3D vine structure, the model was able to closely replicate rapid spatial and temporal fluctuations in berry temperature. Including berry heat storage in the model reduced the errors by dampening extreme temporal swings in berry temperature.
•Errors in Beer's law due to canopy heterogeneity and anisotropy were evaluated.•As plant spacing approached the canopy height, errors became significant.•Heterogeneity caused errors in daily light ...interception of up to 115%.•Errors due to anisotropy were usually small except for in the vineyard case.
Light interception in plant canopies is most commonly estimated using a simple one-dimensional turbid medium model (i.e., Beer's law). Inherent in this class of models are assumptions that vegetation is uniformly distributed in space (homogeneous) and in many cases that vegetation orientation is uniformly distributed (isotropic). It is known that these assumptions are violated in a wide range of canopies, as real canopies commonly have heterogeneity at multiple scales and almost always have highly anisotropic leaf angle distributions. However, it is not quantitatively known under what conditions these assumptions become problematic given the difficulty of robustly evaluating model results for a range of canopy architectures. In this study, assumptions of vegetation homogeneity and isotropy were evaluated under clear sky conditions for a range of virtually-generated crop canopies with the aid of a detailed three-dimensional, leaf-resolving radiation model. Results showed that Beer's law consistently over predicted light interception for all canopy configurations. For canopies where the plant spacing was comparable to the plant height, Beer's law performed poorly, and over predicted daily intercepted sunlight by up to ∼115%. For vegetation with a highly anisotropic leaf inclination distribution but a relatively isotropic leaf azimuth distribution, the assumption of canopy isotropy (i.e., G = 0.5) resulted in relatively small errors. However, if leaf elevation and azimuth were both highly anisotropic, the assumption of canopy isotropy could introduce significant errors depending on the orientation of the azimuthal anisotropy with respect to the sun's path.
•Reviews experimental data of the biochemistry of phagocytosis.•Presents a mechanistic model of the actin waves in frustrated phagocytosis and compares it to previous models of actin waves.•Performs ...a steady state and bifurcation analysis of the resulting differential equations.•Using simulation of the resulting differential equations makes several predictions that are testable in the lab.
Phagocytosis is a complex process by which phagocytes such as lymphocytes or macrophages engulf and destroy foreign bodies called pathogens in a tissue. The process is triggered by the detection of antibodies that trigger signaling mechanisms that control the changes of the cellular cytoskeleton needed for engulfment of the pathogen. A mathematical model of the entire process would be extremely complicated, because the signaling and cytoskeletal changes produce large mechanical deformations of the cell. Recent experiments have used a confinement technique that leads to a process called frustrated phagocytosis, in which the membrane does not deform, but rather, signaling triggers actin waves that propagate along the boundary of the cell. This eliminates the large-scale deformations and facilitates modeling of the wave dynamics. Herein we develop a model of the actin dynamics observed in frustrated phagocytosis and show that it can replicate the experimental observations. We identify the key components that control the actin waves and make a number of experimentally-testable predictions. In particular, we predict that diffusion coefficients of membrane-bound species must be larger behind the wavefront to replicate the internal structure of the waves. Our model is a first step toward a more complete model of phagocytosis, and provides insights into circular dorsal ruffles as well.
Five cattle Y-specific microsatellites, totalling six loci, were selected from a set of 44 markers and genotyped on 608 Bos taurus males belonging to 45 cattle populations from Europe and Africa. A ...total of 38 haplotypes were identified. Haplogroups (Y1 and Y2) previously defined using single nucleotide polymorphisms did not share haplotypes. Nine of the 27 Y2-haplotypes were only present in African cattle. Network and correspondence analyses showed that this African-specific subfamily clustered separately from the main Y2-subfamily and the Y1 haplotypes. Within-breed genetic variability was generally low, with most breeds (78%) showing haplotypes belonging to a single haplogroup. amova analysis showed that partitioning of genetic variation among breeds can be mainly explained by their geographical and haplogroup assignment. Between-breed genetic variability summarized via Principal Component Analysis allowed the identification of three principal components explaining 94.2% of the available information. Projection of principal components on geographical maps illustrated that cattle populations located in mainland Europe, the three European Peninsulas and Mediterranean Africa presented similar genetic variation, whereas those breeds from Atlantic Europe and British Islands (mainly carrying Y1 haplotypes) and those from Sub-Saharan Africa (belonging to Y2-haplogroup) showed genetic variation of a different origin. Our study confirmed the existence of two large Y-chromosome lineages (Y1 and Y2) in taurine cattle. However, Y-specific microsatellites increased analytical resolution and allowed at least two different Y2-haplotypic subfamilies to be distinguished, one of them restricted to the African continent.
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