4,034 research outputs found
Long-Term hydrological regime monitoring of a Mediterranean agro-ecological wetland using Landsat imagery: Correlation with the water renewal rate of a shallow lake
The Natural Park of Albufera (Valencia, Spain) is one of the Spanish Mediterranean wetlands where rice is cultivated intensively. The hydrology of the Albufera Lake, located in the center, combines natural contributions with complex human management. The aim of our study was to develop a new methodology to accurately detect the volume of flood water in complex natural environments which experience significant seasonal changes due to climate and agriculture. The study included 132 Landsat images, covering a 15-year period. The algorithm was adjusted using the NDWI index and simultaneous measurements of water levels in the rice fields. The NDVI index was applied to monitor the cultivated area during the summer. Lake inflows and residence times were also evaluated to quantify how the hydrodynamic of the lake is conditioned by the agricultural management. The algorithm developed is confirmed as a useful ecological tool to monitor the flood cycle of the wetland, being able to detect even the lowest water levels. The flood dynamics are consistent over the fifteen years, being in line with the rice cultivation cycle. Water renewal in Albufera lake is altered with respect to that expected according to the rainfall recorded in the study area, so an improvement in the water management of the hydrological basin is required to optimize the runoff during the rainiest months
Comparative evaluation of impedanciometry combined with chromogenic agars or RNA hybridization and real-time PCR methods for the detection of L. monocytogenes in dry-cured ham
Listeria monocytogenes is an important foodborne pathogen of particular relevance in “Ready To Eat” products. Food producers require rapid methods to detect L. monocytogenes, since the reference method (ISO 11290-1) is laborious, lengthy and costly. The aim of this study was to evaluate three alternative methods to detect L. monocytogenes in dry-cured ham following the ISO 16140-2:2016 standard: (A) impedance measurement followed by plating onto chromogenic agars; (B) impedance measurement followed by RNA hybridization, and (C) real-time PCR. Inclusivity and exclusivity were evaluated. The limits of detection 50 (LOD50) and the relative limits of detection (RLOD) were obtained by analysing dry-cured ham samples inoculated with L. monocytogenes at three different levels of contamination. The sensitivity study of alternative methods, as well as the relative specificity (SP), sensitivity (SE), and Kappa Cohen''s index were calculated analysing 93 samples of sliced dry-cured ham. The inclusivity and exclusivity tests of three methods showed no interference in pathogen detection. LOD50 were very low for the three methods evaluated (<1 cfu/25 g dry-cured ham). The RLOD values of the three alternative methods were below the acceptability limit established by ISO 16140. For methods A and C, good results were obtained in the sensitivity study, as well as in the SP and SE. However, method B showed poorer results in the sensitivity study, along with lower results for SP (99.7%) and SE (79.6%), due to the occurrence of false positives and negatives in samples with presence of other Listeria spp. Methods A and C were considered to be a thoroughly appropriate control tool for use in the meat industry to improve the detection of L. monocytogenes
Double-spending prevention for Bitcoin zero-confirmation transactions
Zero-confirmation transactions, i.e. transactions that have been broadcast but are still pending to be included in the blockchain, have gained attention in order to enable fast payments in Bitcoin, shortening the time for performing payments. Fast payments are desirable in certain scenarios, for instance, when buying in vending machines, fast food restaurants, or withdrawing from an ATM. Despite being quickly propagated through the network, zero-confirmation transactions are not protected against double-spending attacks, since the double-spending protection Bitcoin offers relies on the blockchain and, by definition, such transactions are not yet included in it. In this paper, we propose a double-spending prevention mechanism for Bitcoin zero-confirmation transactions. Our proposal is based on exploiting the flexibility of the Bitcoin scripting language together with a well-known vulnerability of the ECDSA signature scheme to discourage attackers from performing such an attack
Psychometric properties of the mindfulness in teaching scale among Spanish teachers
Mindfulness in the educational field provides several benefits. The assessment of mindfulness is a fundamental previous step for evidence-based interventions. Therefore, the present study aimed to adapt and validate the Mindfulness in Teaching Scale (MTS) among Spanish teachers. This scale comprises 14 items on two dimensions: intrapersonal and interpersonal. The sample comprised 398 teachers (31% males, 68% females) whose ages ranged from 25 to 69 years (M = 44.14; SD = 10.16). Once the scale was adapted in Spanish, we examined its psychometric properties. To do so, we conducted a Confirmatory Factor analysis (CFA), which supported the two-factor structure. As evidence for validity, the MTS scores correlated with perceived teaching self-efficacy. The reliability values using Cronbach’s alpha were good. This scale has adequate psychometric properties and is useful for assessing mindfulness among Spanish teachers. We discuss its implications for the education field
Toxicity of four Cuban botanical derivatives against two stored-products coleopteran pests: Poster
Plants are a source of substances for protection of stored products. The Cuban flora has not yet been fully studied as a source of pesticides for postharvest protection, partly due to its great diversity. The toxicity of four Cuban plant derivatives against Lasioderma serricorne (F.) and Sitophilus zeamais Motschulsky was investigated. The anti-insect activity of the powders and the essential oil from plants belonging to Asteraceae, Fabaceae and Piperaceae was tested. Mortality and emergence of adult insects and the repellent effect of products were evaluated. Two products derived from Piper aduncum subsp. ossanum, caused high mortality (81,6 and 100%), reduced emergence (27,9 and 0,4%) and exhibited strong repellent activity on L. serricorne. Against S. zeamais, treatments with the highest mortality values were stems of Lonchocarpus punctatus (72,4%), seeds and stems of Canavalia ensiformis (64,9 and 69,9%), and leaves of Tithonia diversifolia (67,2%). The progeny production of S. zeamais was inhibited by powders of L. punctatus stems (31,8%), C. ensiformis seeds (40,5%), leaves (43,7%) and stems (30,6%), and T. diversifolia leaves (38,7%). The stems of C. ensiformis, leaves of T. diversifolia and L. punctatus had the highest repellent effect. These products have potential for small-scale treatments of grains for protection against both insects, and P. aduncum subsp. ossanum-based products to control L. serricorne infestation in tobacco. Identification of local candidates to develop effective and safe pesticides offers new alternatives to the Cuban agriculture in the control of storage pests.Plants are a source of substances for protection of stored products. The Cuban flora has not yet been fully studied as a source of pesticides for postharvest protection, partly due to its great diversity. The toxicity of four Cuban plant derivatives against Lasioderma serricorne (F.) and Sitophilus zeamais Motschulsky was investigated. The anti-insect activity of the powders and the essential oil from plants belonging to Asteraceae, Fabaceae and Piperaceae was tested. Mortality and emergence of adult insects and the repellent effect of products were evaluated. Two products derived from Piper aduncum subsp. ossanum, caused high mortality (81,6 and 100%), reduced emergence (27,9 and 0,4%) and exhibited strong repellent activity on L. serricorne. Against S. zeamais, treatments with the highest mortality values were stems of Lonchocarpus punctatus (72,4%), seeds and stems of Canavalia ensiformis (64,9 and 69,9%), and leaves of Tithonia diversifolia (67,2%). The progeny production of S. zeamais was inhibited by powders of L. punctatus stems (31,8%), C. ensiformis seeds (40,5%), leaves (43,7%) and stems (30,6%), and T. diversifolia leaves (38,7%). The stems of C. ensiformis, leaves of T. diversifolia and L. punctatus had the highest repellent effect. These products have potential for small-scale treatments of grains for protection against both insects, and P. aduncum subsp. ossanum-based products to control L. serricorne infestation in tobacco. Identification of local candidates to develop effective and safe pesticides offers new alternatives to the Cuban agriculture in the control of storage pests
Spherically symmetric dissipative anisotropic fluids: A general study
The full set of equations governing the evolution of self--gravitating
spherically symmetric dissipative fluids with anisotropic stresses is deployed
and used to carry out a general study on the behaviour of such systems, in the
context of general relativity. Emphasis is given to the link between the Weyl
tensor, the shear tensor, the anisotropy of the pressure and the density
inhomogeneity. In particular we provide the general, necessary and sufficient,
condition for the vanishing of the spatial gradients of energy density, which
in turn suggests a possible definition of a gravitational arrow of time. Some
solutions are also exhibited to illustrate the discussion.Comment: 28 pages Latex. To appear in Phys.Rev.
Effect of Cutting Height on Tiller Population Density and Herbage Biomass of Buffel Grass
The aim of this trial was to investigate the effect of different cutting heights on tiller population density and herbage biomass of Buffel grass (Cenchrus ciliaris L) grown in miniature swards in a greenhouse. Four treatments with five replicates: five cm, ten cm, and 20 cm cutting height, and control (without cut) were randomly allocated. Intensity of defoliation affected the cumulative herbage harvested; the ten cm cutting height was greater (404.1 g DM m-2) than 5 cm (317.6 g DM m-2) and 20 cm (263.9 g DM m-2), respectively. Cumulative herbage harvested in the control, increased progressively until September; from then onwards tended to decrease. At the end of the trial, the highest tiller population density was found at five cm cutting height with 28 %, 48 % and 71 % more tillers than ten cm, 20 cm and control, respectively. Herbage mass at five cm and ten cm cutting height, were greater for tiller population density and herbage harvested than 20 cm and control (α\u3c 0.05)
Effects of transcranial static magnetic field stimulation over the left dorsolateral prefrontal cortex on random number generation
OBJECTIVE:
Focal application of transcranial static magnetic field stimulation (tSMS) is a neuromodulation technique, with predominantly inhibitory effects when applied to the motor, somatosensory or visual cortex. Whether this approach can also transiently interact with dorsolateral prefrontal cortex (DLPFC) function remains unclear. The suppression of habitual or competitive responses is one of the core executive functions linked to DLPFC function. This study aimed to assess the impact of tSMS on the prefrontal contributions to inhibitory control and response selection by means of a RNG task.
METHODS:
We applied 20 min of tSMS over the left DLPFC of healthy subjects, using a real/sham cross-over design, during performance of a RNG task. We used an index of randomness calculated with the measures of entropy and correlation to assess the impact of stimulation on DLPFC function.
RESULTS:
The randomness index of the sequences generated during the tSMS intervention was significantly higher compared to those produced in the sham condition.
CONCLUSIONS:
Our results indicate that application of tSMS transiently modulates specific functional brain networks in DLPFC, which indicate a potential use of tSMS for treatment of neuropsychiatric disorders.
SIGNIFICANCE:
This study provides evidence for the capacity of tSMS for modulating DLPFC function
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