1,116 research outputs found
Comparing Models for Early Warning Systems of Neglected Tropical Diseases
Early Warning Systems (EWS) are management tools to predict the occurrence of epidemics. They are based on the dependence of a given infectious disease on environmental variables. Although several neglected tropical diseases are sensitive to the effect of climate, our ability to predict their dynamics has been barely studied. In this paper, we use several models to determine if the relationship between cases and climatic variability is robust—that is, not simply an artifact of model choice. We propose that EWS should be based on results from several models that are to be compared in terms of their ability to predict future number of cases. We use a specific metric for this comparison known as the predictive R2, which measures the accuracy of the predictions. For example, an R2 of 1 indicates perfect accuracy for predictions that perfectly match observed cases. For cutaneous leishmaniasis, R2 values range from 72% to77%, well above predictions using mean seasonal values (64%). We emphasize that predictability should be evaluated with observations that have not been used to fit the model. Finally, we argue that EWS should incorporate climatic variables that are known to have a consistent relationship with the number of observed cases
Midday measurements of leaf water potential and stomatal conductance are highly correlated with daily water use of Thompson Seedless grapevines
A study was conducted to determine the relationship between midday measurements of vine water status and daily water use of grapevines measured with a weighing lysimeter. Water applications to the vines were terminated on August 24th for 9 days and again on September 14th for 22 days. Daily water use of the vines in the lysimeter (ETLYS) was approximately 40 L vine−1 (5.3 mm) prior to turning the pump off, and it decreased to 22.3 L vine−1 by September 2nd. Pre-dawn leaf water potential (ΨPD) and midday Ψl on August 24th were −0.075 and −0.76 MPa, respectively, with midday Ψl decreasing to −1.28 MPa on September 2nd. Leaf g s decreased from ~500 to ~200 mmol m−2 s−1 during the two dry-down periods. Midday measurements of g s and Ψl were significantly correlated with one another (r = 0.96) and both with ETLYS/ETo (r = ~0.9). The decreases in Ψl, g s, and ETLYS/ETo in this study were also a linear function of the decrease in volumetric soil water content. The results indicate that even modest water stress can greatly reduce grapevine water use and that short-term measures of vine water status taken at midday are a reflection of daily grapevine water us
Heat and water stress induce unique transcriptional signatures of heat-shock proteins and transcription factors in grapevine
Grapevine is an extremely important crop worldwide.
In southern Europe, post-flowering phases of the growth
cycle can occur under high temperatures, excessive light, and
drought conditions at soil and/or atmospheric level. In this
study, we subjected greenhouse grown grapevine, variety
Aragonez, to two individual abiotic stresses, water deficit stress
(WDS), and heat stress (HS). The adaptation of plants to stress
is a complex response triggered by cascades of molecular
networks involved in stress perception, signal transduction,
and the expression of specific stress-related genes and metabolites.
Approaches such as array-based transcript profiling allow
assessing the expression of thousands of genes in control
and stress tissues. Using microarrays, we analyzed the leaf
transcriptomic profile of the grapevine plants. Photosynthesis
measurements verified that the plants were significantly affected
by the stresses applied. Leaf gene expression was obtained
using a high-throughput transcriptomic grapevine array, the
23K custom-made Affymetrix Vitis GeneChip. We identified
1,594 genes as differentially expressed between control and
treatments and grouped them into ten major functional categories
using MapMan software. The transcriptome of Aragonez
was more significantly affected by HS when compared with
WDS. The number of genes coding for heat-shock proteins and
transcription factors expressed solely in response to HS suggesting
their expression as unique signatures of HS. However, a cross-talk between the response pathways to both stresses was
observed at the level of AP2/ERF transcription factors
Brain iron accumulation in unexplained fetal and infant death victims with smoker mothers-The possible involvement of maternal methemoglobinemia
<p>Abstract</p> <p>Background</p> <p>Iron is involved in important vital functions as an essential component of the oxygen-transporting heme mechanism. In this study we aimed to evaluate whether oxidative metabolites from maternal cigarette smoke could affect iron homeostasis in the brain of victims of sudden unexplained fetal and infant death, maybe through the induction of maternal hemoglobin damage, such as in case of methemoglobinemia.</p> <p>Methods</p> <p>Histochemical investigations by Prussian blue reaction were made on brain nonheme ferric iron deposits, gaining detailed data on their localization in the brainstem and cerebellum of victims of sudden death and controls. The Gless and Marsland's modification of Bielschowsky's was used to identify neuronal cell bodies and neurofilaments.</p> <p>Results</p> <p>Our approach highlighted accumulations of blue granulations, indicative of iron positive reactions, in the brainstem and cerebellum of 33% of victims of sudden death and in none of the control group. The modified Bielschowsky's method confirmed that the cells with iron accumulations were neuronal cells.</p> <p>Conclusions</p> <p>We propose that the free iron deposition in the brain of sudden fetal and infant death victims could be a catabolic product of maternal methemoglobinemia, a biomarker of oxidative stress likely due to nicotine absorption.</p
Cold gas accretion in galaxies
Evidence for the accretion of cold gas in galaxies has been rapidly
accumulating in the past years. HI observations of galaxies and their
environment have brought to light new facts and phenomena which are evidence of
ongoing or recent accretion:
1) A large number of galaxies are accompanied by gas-rich dwarfs or are
surrounded by HI cloud complexes, tails and filaments. It may be regarded as
direct evidence of cold gas accretion in the local universe. It is probably the
same kind of phenomenon of material infall as the stellar streams observed in
the halos of our galaxy and M31. 2) Considerable amounts of extra-planar HI
have been found in nearby spiral galaxies. While a large fraction of this gas
is produced by galactic fountains, it is likely that a part of it is of
extragalactic origin. 3) Spirals are known to have extended and warped outer
layers of HI. It is not clear how these have formed, and how and for how long
the warps can be sustained. Gas infall has been proposed as the origin. 4) The
majority of galactic disks are lopsided in their morphology as well as in their
kinematics. Also here recent accretion has been advocated as a possible cause.
In our view, accretion takes place both through the arrival and merging of
gas-rich satellites and through gas infall from the intergalactic medium (IGM).
The infall may have observable effects on the disk such as bursts of star
formation and lopsidedness. We infer a mean ``visible'' accretion rate of cold
gas in galaxies of at least 0.2 Msol/yr. In order to reach the accretion rates
needed to sustain the observed star formation (~1 Msol/yr), additional infall
of large amounts of gas from the IGM seems to be required.Comment: To appear in Astronomy & Astrophysics Reviews. 34 pages.
Full-resolution version available at
http://www.astron.nl/~oosterlo/accretionRevie
State–Space Forecasting of Schistosoma haematobium Time-Series in Niono, Mali
Adequate forecasting and early warning systems are based upon observations of human behavior, population, disease time-series, climate, environment, and/or a combination thereof, whichever option best compromises among realism, feasibility, robustness, and parsimony. Fully automatic and user-friendly state–space forecasting frameworks, incorporating myriad options (e.g., expert opinion, univariate, multivariate, and spatial-temporal), could considerably enhance disease control and hazard mitigation efforts in regions where vulnerability to neglected tropical diseases is pervasive and statistical expertise is scarce. The operational simplicity, generality, and flexibility of state–space frameworks, encapsulating multiple methods, could conveniently allow for 1) unsupervised model selection without disease-specific methodological tailoring, 2) on-line adaptation to disease time-series fluctuations, and 3) automatic switches between distinct forecasting methods as new time-series perturbations dictate. In this investigation, a univariate state–space framework with the aforementioned properties was successfully applied to the Schistosoma haematobium time-series for the district of Niono, Mali, to automatically generate contemporaneous on-line forecasts and hence, providing a basis for local re-organization and strengthening public health programs in this and potentially other Sahelian districts
Direct block scheduling technology : analysis of avidity.
This study is focused on Direct Block Scheduling testing (Direct Multi-Period
Scheduling methodology) which schedules mine production considering the correct
discount factor of each mining block, resulting in the final pit. Each block is analyzed
individually in order to define the best target period. This methodology presents an
improvement of the classical methodology derived from Lerchs-Grossmann?s initial
proposition improved by Whittle. This paper presents the differences between these
methodologies, specially focused on the algorithms? avidity. Avidity is classically defined
by the voracious search algorithms, whereupon some of the most famous greedy
algorithms are Branch and Bound, Brutal Force and Randomized. Strategies based on
heuristics can accentuate the voracity of the optimizer system. The applied algorithm
use simulated annealing combined with Tabu Search. The most avid algorithm can
select the most profitable blocks in early periods, leading to higher present value in the
first periods of mine operation. The application of discount factors to blocks on the
Lerchs-Grossmann?s final pit has an accentuated effect with time, and this effect may
make blocks scheduled for the end of the mine life unfeasible, representing a trend to
a decrease in reported reserves
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