863 research outputs found
Application of Geo-Spatial Technology in Identifying Areas Vulnerable to Flooding in Ibadan Metropolis
This study makes use of the integrated approach of Remote Sensing and GIS techniques in flood management with the goal of identifying areas vulnerable to flood hazard in Ibadan Metropolis. Ibadan is the largest indigenous city in the continent of Africa and had experienced a lot of various severities of flood occurrences in the last fifty years. Topographic Map and Landsat TM image of 1993 and 2000 respectively were processed, scanned, digitized, interpolated, classified and overlaid using ILWIS 3.3 academic and ARC GIS 9.2 software modules to generate classified land cover map, Digital Terrain Map (DTM), Triangulated Irregular Network (TIN) and flood vulnerability map of the study area respectively. The results obtained shows that, areas lying along the banks of River Ona and River Ogunpa are most vulnerable to flood hazards with the vulnerability decreasing towards the northern part of the city, much of the area is built up with improper planning and this gives rise to high vulnerability to flash flood hazards. The Odo Ona, Idi Isin, Eleyele, Olopometa and Molete areas are the most vulnerable to flood threat. The incessant violation of land use plan, unchecked population growth, old nature of the structures and poor materials used in the construction of the houses make the areas vulnerable to flood hazard. In reducing the vulnerability of these areas from flood there is need for improved land use planning, removal of structures from River Ona and Ogunpa flood plains around the city, intensify environmental education to the residents and enhance the active participation of government agencies in the continual generation of flood vulnerability maps of urban centres. Keywords: Flood, Vulnerability, DEM, GIS, Remote Sensing, TIN
Age-dependent differences in human brain activity using a face- and location-matching task: An fMRI study
Purpose: To evaluate the differences of cortical activation patterns in young and elderly healthy subjects for object and spatial visual processing using a face- and location-matching task. Materials and Methods: We performed a face- and a location-matching task in 15 young (mean age: 28 +/- 9 years) and 19 elderly (mean age: 71 +/- 6 years) subjects. Each experiment consisted of 7 blocks alternating between activation and control condition. For face matching, the subjects had to indicate whether two displayed faces were identical or different. For location matching, the subjects had to press a button whenever two objects had an identical position. For control condition, we used a perception task with abstract images. Functional imaging was performed on a 1.5-tesla scanner using an EPI sequence. Results: In the face-matching task, the young subjects showed bilateral (right 1 left) activation in the occipito-temporal pathway (occipital gyrus, inferior and middle temporal gyrus). Predominantly right hemispheric activations were found in the fusiform gyrus, the right dorsolateral prefrontal cortex (inferior and middle frontal gyrus) and the superior parietal gyrus. In the elderly subjects, the activated areas in the right fronto-lateral cortex increased. An additional activated area could be found in the medial frontal gyrus (right > left). In the location-matching task, young subjects presented increased bilateral (right > left) activation in the superior parietal lobe and precuneus compared with face matching. The activations in the occipito-temporal pathway, in the right fronto-lateral cortex and the fusiform gyrus were similar to the activations found in the face-matching task. In the elderly subjects, we detected similar activation patterns compared to the young subjects with additional activations in the medial frontal gyrus. Conclusion: Activation patterns for object-based and spatial visual processing were established in the young and elderly healthy subjects. Differences between the elderly and young subjects could be evaluated, especially by using a face-matching task. Copyright (c) 2007 S. Karger AG, Basel
An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 1: new molecules, metabolism, fate, and transport
With the exponential number of published data on neonicotinoids and fipronil during the last decade, an updated review of literature has been conducted in three parts. The present part focuses on gaps of knowledge that have been addressed after publication of the Worldwide Integrated Assessment (WIA) on systemic insecticides in 2015. More specifically, new data on the mode of action and metabolism of neonicotinoids and fipronil, and their toxicity to invertebrates and vertebrates, were obtained. We included the newly detected synergistic effects and/or interactions of these systemic insecticides with other insecticides, fungicides, herbicides, adjuvants, honeybee viruses, and parasites of honeybees. New studies have also investigated the contamination of all environmental compartments (air and dust, soil, water, sediments, and plants) as well as bees and apicultural products, food and beverages, and the exposure of invertebrates and vertebrates to such contaminants. Finally, we review new publications on remediation of neonicotinoids and fipronil, especially in water systems. Conclusions of the previous WIA in 2015 are reinforced; neonicotinoids and fipronil represent a major threat worldwide for biodiversity, ecosystems, and all the services the latter provide
A Self-Programmable Interface for WSN Applications
Numerous applications of Wireless Sensor Networks (WSN) involve monitoring physical and chemical parameters in large regions, thus needing a large number of sensor nodes. In order to reduce the cost of these nodes, it is usual to use low-cost analogue sensors followed by a programmable electronic interface capable of adapting every sensor output to the port requirements of the microcontroller embedded in the sensing node. The goal of the present work is the design and test of a low-voltage plug&play programmable sensor-to-microcontroller interface able to self-configure its operation when adapting the output of different sensors, achieving an optimum reading performance for every sensor. The proposed interface, which includes both electronic and software elements, is shown in Figure 1a. By properly programming the interface electronics, the system can be used to conditioning active and passive sensors, enabling plug&play to be easily integrated in a WSN node and taking advantage of the full span of the connected device. It provides a value of the measured parameter coded as the frequency of a signal compatible with the logic levels of the master microcontroller. Experimental test results to validate its performance are given for a resistive humidity sensor (Figure 1b) and other low-cost sensors. By properly managing the interface electronics, the average power consumption in a measurement process of the conditioning electronics remains low
Profitability and Stock Price Volatility of Nigerian Listed Manufacturing Companies
The crux of this study was to examine the impact of profitability on stock price volatility using earnings yield, return on total asset, dividend yield and dividends per share as proxies for profitability. This study adopted Ex-post facto design. The population of this study consisted of manufacturing companies listed on the Nigerian Stock Exchange (NSE) from which five companies were selected. We found that overall; the profitability proxies combined have significant effect on stock price volatility of the sampled companies. Each of the models revealed that earnings yield, dividend yield and dividends per share have a significant relationship with stock price volatility. It was also observed that return on total assets has no significant relationship with stock price volatility. The study concluded that all variables put together show a positive significant impact on stock price volatility with the most impact from dividend yield and dividends per share. Hence, recommendations were made in the light that investors should invest in companies with well-defined ownership structure and managers should adopt a dividend policy beneficial to shareholders. Keywords: Profitability, Stock Price Volatility, Earnings Yield, Return on Total Assets, Dividend Yield and Dividends per Share
The First Science Results from SPHERE: Disproving the Predicted Brown Dwarf around V471 Tau
Variations of eclipse arrival times have recently been detected in several
post common envelope binaries consisting of a white dwarf and a main sequence
companion star. The generally favoured explanation for these timing variations
is the gravitational pull of one or more circumbinary substellar objects
periodically moving the center of mass of the host binary. Using the new
extreme-AO instrument SPHERE, we image the prototype eclipsing post-common
envelope binary V471 Tau in search of the brown dwarf that is believed to be
responsible for variations in its eclipse arrival times. We report that an
unprecedented contrast of 12.1 magnitudes in the H band at a separation of 260
mas was achieved, but resulted in a non-detection. This implies that there is
no brown dwarf present in the system unless it is three magnitudes fainter than
predicted by evolutionary track models, and provides damaging evidence against
the circumbinary interpretation of eclipse timing variations. In the case of
V471 Tau, a more consistent explanation is offered with the Applegate
mechanism, in which these variations are prescribed to changes in the
quadrupole moment within the main-sequence sta
The Gaia-ESO Survey: dynamics of ionized and neutral gas in the Lagoon nebula (M8)
We present a spectroscopic study of the dynamics of the ionized and neutral
gas throughout the Lagoon nebula (M8), using VLT/FLAMES data from the Gaia-ESO
Survey. We explore the connections between the nebular gas and the stellar
population of the associated star cluster NGC6530. We characterize through
spectral fitting emission lines of H-alpha, [N II] and [S II] doublets, [O
III], and absorption lines of sodium D doublet, using data from the
FLAMES/Giraffe and UVES spectrographs, on more than 1000 sightlines towards the
entire face of the Lagoon nebula. Gas temperatures are derived from line-width
comparisons, densities from the [S II] doublet ratio, and ionization parameter
from H-alpha/[N II] ratio. Although doubly-peaked emission profiles are rarely
found, line asymmetries often imply multiple velocity components along the line
of sight. This is especially true for the sodium absorption, and for the [O
III] lines. Spatial maps for density and ionization are derived, and compared
to other known properties of the nebula and of its massive stars 9 Sgr,
Herschel 36 and HD 165052 which are confirmed to provide most of the ionizing
flux. The detailed velocity fields across the nebula show several expanding
shells, related to the cluster NGC6530, the O stars 9 Sgr and Herschel 36, and
the massive protostar M8East-IR. The origins of kinematical expansion and
ionization of the NGC6530 shell appear to be different. We are able to put
constrains on the line-of-sight (relative or absolute) distances between some
of these objects and the molecular cloud. The large obscuring band running
through the middle of the nebula is being compressed by both sides, which might
explain its enhanced density. We also find an unexplained large-scale velocity
gradient across the entire nebula. At larger distances, the transition from
ionized to neutral gas is studied using the sodium lines.Comment: 26 pages, 31 figures, accepted on Astronomy and Astrophysics journa
Is there really a debris disc around ?
The presence of a debris disc around the Gyr-old solar-type star
was suggested by the infrared
excess detection. Follow-up observations with /PACS revealed
a double-lobed feature, that displayed asymmetries both in brightness and
position. Therefore, the disc was thought to be edge-on and significantly
eccentric. Here we present ALMA/ACA observations in Band 6 and 7 which
unambiguously reveal that these lobes show no common proper motion with
. In these observations, no flux has been detected
around that exceeds the levels. We
conclude that surface brightness upper limits of a debris disc around
are at 1.3 mm, and
at 870 microns. Our results overall demonstrate
the capability of the ALMA/ACA to follow-up observations of
debris discs and clarify the effects of background confusion.Comment: 6 pages, 2 figures, 2 table
OTS44: Disk and accretion at the planetary border
We discover that the very low-mass brown dwarf OTS44 (M9.5, ~12 M_Jup) has
significant accretion and a substantial disk, which demonstrates that the
processes that accompany canonical star formation occur down to a central mass
of a few Jupiter masses. We discover in VLT/SINFONI spectra that OTS44 has
strong, broad, and variable Paschen beta emission that is evidence for active
accretion at the planetary border. We also detect strong Halpha emission of
OTS44 in a literature spectrum and determine an Halpha EW (-141 A) that is
indicative of active accretion. Both the Pa beta and Halpha emission lines have
broad profiles with wings extending to velocities of about +/-200 km/s. We
determine the mass accretion rate of OTS44 based on Halpha to 7.6x10^{-12}
Msun/yr, which shows that OTS44 has a relatively high mass-accretion rate
considering its small central mass. This mass rate is nevertheless consistent
with the general decreasing trend found for stars of several solar masses down
to brown dwarfs. Furthermore, we determine the properties of the disk
surrounding OTS44 through radiative transfer modeling of flux measurement from
the optical to the far-IR (Herschel) by applying a Bayesian analysis. We find
that OTS44 has a highly flared disk (beta >1.2) with a mass of 9.1x10^{-5}
M_Sun, i.e. about 0.1 M_Jup or 30 M_Earth. We show that the ratio of
disk-to-central-mass of about 10^{-2} found for objects between 0.03 Msun and
14 Msun is also valid for OTS44 at a mass of ~0.01 M_Sun. Our observations are
in line with an isolated star-like mode of the formation of brown dwarfs down
to 0.01 M_Sun.Comment: Accepted for publication in Astronomy and Astrophysics Lette
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