4,991 research outputs found
On the Unruh effect in de Sitter space
We give an interpretation of the temperature in de Sitter universe in terms
of a dynamical Unruh effect associated with the Hubble sphere. As with the
quantum noise perceived by a uniformly accelerated observer in static
space-times, observers endowed with a proper motion can in principle detect the
effect. In particular, we study a "Kodama observer" as a two-field Unruh
detector for which we show the effect is approximately thermal. We also
estimate the back-reaction of the emitted radiation and find trajectories
associated with the Kodama vector fields are stable.Comment: 8 pages; corrected typos; sections structure revise
African trypanosomiasis in travelers returning to the United Kingdom.
Two returning safari tourists with African trypanosomiasis were admitted to the Hospital for Tropical Diseases, London, in a 3-day period, compared with six cases in the previous 14 years. We describe the clinical features, diagnosis, and problems encountered in accessing appropriate therapy, and discuss the potential for emergence of this disease in increasingly adventurous international travelers
A Reflective Analysis of Image Processing Operations on Kato-Katz Images for the Pathological Diagnosis of Neglected Tropical Diseases
This paper gives an insight into the interdisciplinary work that has been carried out to diagnose some of the neglected tropical diseases, in particular micro-parasitic diseases, using image processing operations. The infections from micro-parasites are collectively called Helminthiasis. The Kato-Katz method is a slide scanning technique commonly used for the qualitative and semi-quantitative diagnosis of helminthiasis. This paper explains the image analysis and processing of Kato-katz images to extract meaningful information and convert the qualitative features of the images to quantitative data and thereby effectively diagnose the disease. This is the preliminary stage of a pioneering work done in the field of neglected tropical disease diagnosis and would be beneficial for thousands of people including children in the endemic region
Temperature and pressure gas geoindicators at the Solfatara fumaroles (Campi Flegrei)
Long time series of fluid pressure and temperature within a hydrothermal
system feeding the Solfatara fumaroles are investigated here, on the basis
of the chemical equilibria within the CO2-H2O-H2-CO gas system. The
Pisciarelli fumarole external to Solfatara crater shows an annual cycle of
CO contents that indicates the occurrence of shallow secondary processes
that mask the deep signals. In contrast, the Bocca Grande and Bocca Nova
fumaroles located inside Solfatara crater do not show evidence of
secondary processes, and their compositional variations are linked to the
temperature–pressure changes within the hydrothermal system. The
agreement between geochemical signals and the ground movements of the
area (bradyseismic phenomena) suggests a direct relationship between the
pressurization process and the ground uplift. Since 2007, the gas
geoindicators have indicated pressurization of the system, which is most
probably caused by the arrival of deep gases with high CO2 contents in
the shallow parts of the hydrothermal system. This pressurization process
causes critical conditions in the hydrothermal system, as highlighted by
the increase in the fumarole temperature, the opening of new vents, and
the localized seismic activity. If the pressurization process continues with
time, it is not possible to rule out the occurrence of phreatic explosions
Single Event Effects in the Pixel readout chip for BTeV
In future experiments the readout electronics for pixel detectors is required
to be resistant to a very high radiation level. In this paper we report on
irradiation tests performed on several preFPIX2 prototype pixel readout chips
for the BTeV experiment exposed to a 200 MeV proton beam. The prototype chips
have been implemented in commercial 0.25 um CMOS processes following radiation
tolerant design rules. The results show that this ASIC design tolerates a large
total radiation dose, and that radiation induced Single Event Effects occur at
a manageable level.Comment: 15 pages, 6 Postscript figure
Soil CO2 emissions at Furnas volcano (São Miguel Island, Azores archipelago) - volcano monitoring perspectives, geomorphologic studies and land-use planning application
Carbon dioxide (CO2) diffuse degassing structures (DDS) at Furnas Volcano (São
Miguel Island, Azores) are mostly associated with the main fumarolic fields, evidence
that CO2 soil degassing is the surface expression of rising steam from the hydrothermal
system. Locations with anomalous CO2 flux are mainly controlled by tectonic structures
oriented WNW-ESE and NW-SE and by the geomorphology of the volcano, as
evidenced by several DDS located in depressed areas associated with crater margins.
Hydrothermal soil CO2 emissions in Furnas volcano are estimated to be ~ 968 t d-1.
Discrimination between biogenic and hydrothermal CO2 was determined using a
1
statistical approach and the carbon isotope composition of the CO2 efflux. Different
sampling densities were used to evaluate uncertainty in the estimation of the total CO2
flux, and showed that a low density of points may not be adequate to quantify soil
emanations from a relatively small DDS. Thermal energy release associated to diffuse
degassing at Furnas caldera is about 118 MW (from an area of ~ 4.8 km2) based on the
H2O/CO2 ratio in fumarolic gas. The DDS affect also Furnas and Ribeira Quente
villages, which are located inside the caldera and in the south flank of the volcano,
respectively. At these sites, 58% and 98% of the houses are built over hydrothermal
CO2 emanations, and the populations are at risk due to potential high concentrations of
CO2 accumulating inside the dwellings.
Keywords: Soil diffuse degassing; soil CO2 flux; emission rates; Azores archipelago
Improving monitoring techniques by exploiting TerraSAR-X data: an application to Campi Flegrei (Naples, Italy)
Geodetic monitoring of the Neapolitan Volcanic District, including the Campi Flegrei caldera on the west of the
city of Naples (Italy), is carried out via an integration between ground based networks and space-borne DInSAR
techniques, exploiting the SAR sensors onboard ERS1-2 and ENVISAT satellites. This allowed, for instance, to
follow the time evolution of the small uplift events which took place in 2000 and 2005-2006. Unfortunately, the
use of the ENVISAT C-band could result sometimes in no information when dealing with very low deformation
rates, as in the 2005-2006 case, when only continuous ground stations were able to detect the very beginning of
the uplift event.
To overcome this problem, from December 2009 we decided to use an high resolution SAR sensor operating in
the X band, i.e. TerraSAR-X from DLR.
TerraSAR-X High Resolution Spotlight scenes covering the main part of the Campi Flegrei caldera and centred on
the Solfatara crater were used for a DInSAR analysis, using the GENESIS DLR’s software. The first two scenes
(Dec. 15 and 26) were acquired with a temporal baseline of only one repetition cycle (11 days) and formed an
interferogram with a very small perpendicular baseline (16.5 m).
Apart from some minor atmospheric effects, the interferogram shows a small but clear deformation signal in the
Pisciarelli area, close to the east side of the Solfatara crater. The ellipse shaped uplift area extends approximately
30 meters in E-W and 20 meters in N-S directions and the maximum deformation is up to 10 mm in the centre of
the uplifted area.
The availability of a new scene (06/01/2010) allowed three possible combinations.
The deformation event highlighted by this analysis is consistent with geochemical observations carried out in
Pisciarelli by INGV-OV.
Pisciarelli area is seat of a fumarolic field systematically monitored in the frame of the volcanic surveillance of
the Campi Flegrei caldera. Two field surveys highlighted that, during the period of SAR images acquisition, a
new and strong fumarolic vent appeared in the centre of the uplifted area. In fact the vent, firstly observed on
Dec. 21, was absent on Dec. 16. The two independent observations, field surveys and SAR data, suggest that the
opening of the fumarolic vent was preceded by the pressurization of a small part of the fumarolic field highlighted
by the documented uplift. The correlation between the dynamics of the fumarolic field and the deformation
signal is confirmed by the fact that in the 26/12/2009-06/01/2010 interferogram the deformation signal is no more
detectable.
Finally, this case proves the high potentiality of TerraSAR-X High Resolution Spotlight data in monitoring
volcanic activity with a resolution suitable for detecting also minor, but possibly dangerous, changes of the
systems, as it could be in the early recognition of the signals generated by impending phreatic eruptions.
TerraSAR-X High Resolution Spotlight acquisitions will continue every cycle and PS-InSAR and SBAS algorithms
will be applied to carefully monitor any further changes in the activity of the Campi Flegrei volcanic system
Long time-series of chemical and isotopic compositions of Vesuvius fumaroles: evidence for deep and shallow processes
Long time-series of chemical and isotopic compositions of Vesuvius
fumaroles were acquired in the framework of the volcanic surveillance in
the 1998-2010 period. These allow the identification of processes that
occur at shallow levels in the hydrothermal system, and variations that are
induced by deep changes in volcanic activity. Partial condensation
processes of fumarolic water under near-discharge conditions can explain
the annual 18O and deuterium variabilities that are observed at Vesuvius
fumaroles. Significant variations in the chemical compositions of
fumaroles occurred over the 1999-2002 period, which accompanied the
seismic crisis of autumn 1999, when Vesuvius was affected by the most
energetic earthquakes of its last quiescence period. A continuous increase
in the relative concentrations of CO2 and He and a general decrease in the
CH4 concentrations are interpreted as the consequence of an increment in
the relative amount of magmatic fluids in the hydrothermal system. Gas
equilibria support this hypothesis, showing a PCO2 peak that culminated in
2002, increasing from values of ~40 bar in 1998 to ~55-60 bar in 2001-
2002. We propose that the seismic crisis of 1999 marked the arrival of the
magmatic fluids into the hydrothermal system, which caused the observed
geochemical variations that started in 1999 and culminated in 2002
Search for new phenomena in high-mass diphoton final states using 37 fb(-1) of proton-proton collisions collected at root(s) = 13 TeV with the ATLAS detector
Searches for new phenomena in high-mass diphoton final states with the
ATLAS experiment at the LHC are presented. The analysis is based on pp
collision data corresponding to an integrated luminosity of 36.7 fb(-1)
at a centre-of-mass energy root s = 13 TeV recorded in 2015 and 2016.
Searches are performed for resonances with spin 0, as predicted by
theories with an extended Higgs sector, and for resonances with spin 2,
using a warped extra-dimension model as a benchmark model, as well as
for non-resonant signals, assuming a large extra-dimension scenario. No
significant deviation from the Standard Model is observed. Upper limits
are placed on the production cross section times branching ratio to two
photons as a function of the resonance mass. In addition, lower limits
are set on the ultraviolet cutoff scale in the large extra-dimensions
model. (C) 2017 The Author(s). Published by Elsevier B.V
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