967 research outputs found
Update on field use of the available drugs for the chemotherapy of human African trypanosomiasis
Despite the fact that eflornithine was considered as the safer drug to treat human African trypanosomiasis (HAT) and has been freely available since 2001, the difficulties in logistics and cost burden associated with this drug meant that the toxic melarsoprol remained the drug of choice. The World Health Organization responded to the situation by designing a medical kit containing all the materials needed to use eflornithine, and by implementing a training and drugs distribution programme which has allowed a transition to this much safer treatment. The introduction of the combination of nifurtimox and eflornithine (NECT) has accelerated the shift from melarsoprol to the best treatment available, due to reduced dosage and treatment time for eflornithine that has significantly lessened the cost and improved the burden of logistics encountered during treatment and distribution. The decrease in the use of more dangerous but cheaper melarsoprol has meant a rise in the per patient cost of treating HAT. Although NECT is cheaper than eflornithine monotherapy, an unexpected consequence has been a continuing rise in the per patient cost of treating HAT. The ethical decision of shifting to the best available treatment imposes a financial burden on HAT control programmes that might render long-term application unsustainable. These factors call for continuing research to provide new safer and more effective drugs that are simple to administer and cheaper when compared to current drug
Mixing and transport of water in a karst catchment: a case study from precipitation via seepage to the spring
One of the best-known and largest karst areas in Germany, the Blautopf Catchment, offers unique access to waters of the unsaturated zone through a large cave system. It was investigated with stable isotopes (<sup>18</sup>O/<sup>16</sup>O and D/H ratios expressed in permille = &permil;) in precipitation, seepage- and groundwater as tracers for water flow, mixing, and storage. The precipitation showed a distinct seasonality with &delta;<sup>18</sup>O values between &minus;2.9 and &minus;24.6&permil; during summer and winter, respectively. However, the isotope signals in seepage water in the caves as well as the discharge were almost completely buffered and ranged around an average &delta;<sup>18</sup>O value of &minus;10&permil;. This value was also close to the long-term average value of local precipitation, &minus;9.3&permil;. The homogeneous isotopic composition of the Blautopf Spring was unexpected, as its highly variable discharge (0.3 to 32 m<sup>3</sup> s<sup>&minus;1</sup>) is typical for a fast responsive karst system. These isotopic similarities could be explained by nearly complete mixing of the water already in the vadose zone. The data set therefore presents a case study to narrow down zones of mixing in karst catchments. It also confirms the minor role of the fast conduit system in the water balance of the Blautopf Catchment
Storage and transport in cave seepage- and groundwater in a South German karst system
International audienceWe investigated one of the best-known and second largest karst areas in Germany (Blautopf Catchment) that offers a unique access waters of the unsaturated zone through a large cave system. As tracers for water flow and storage we measured stable isotopes (18O/16O and D/H ratios) in precipitation, seepage- and groundwater. The precipitation showed a distinct seasonal cycle with ?18O values between ?2.6 and ?22.6? during summer and winter, respectively. However, the isotope signals in seepage water in the caves as well as the discharge were completely buffered and ranged around an average ?18O value of ?10?. This value also matched the long-term average of the precipitation. In addition, the homogeneous isotopic composition of the Blautopf Spring was against expectation for its highly variable discharge (0.3 to 32 m3 s?1) that is typical for a fast responsive karst system. We explain the isotopic similarity between cave seepage and the Blautopf Spring (as an integral signal for groundwater) by nearly complete mixing of the water already in the vadose zone. The latter can be divided into the compartments soil, epikarst and rock matrix that all have good storage capacities and also allow diffusive exchange of solutes between mobile and less mobile matrix water. The above approach revealed new aspects about turnover and flow paths of the infiltrated water and thus helps to constrain the risk by pollution to the groundwater
Multi-wavelength analysis of the field of the dark burst GRB 031220
We have collected and analyzed data taken in different spectral bands (from
X-ray to optical and infrared) of the field of GRB031220 and we present results
of such multiband observations. Comparison between images taken at different
epochs in the same filters did not reveal any strong variable source in the
field of this burst. X-ray analysis shows that only two of the seven Chandra
sources have a significant flux decrease and seem to be the most likely
afterglow candidates. Both sources do not show the typical values of the R-K
colour but they appear to be redder. However, only one source has an X-ray
decay index (1.3 +/- 0.1) that is typical for observed afterglows. We assume
that this source is the best afterglow candidate and we estimate a redshift of
1.90 +/- 0.30. Photometric analysis and redshift estimation for this object
suggest that this GRB can be classified as a Dark Burst and that the
obscuration is the result of dust extinction in the circum burst medium or
inside the host galaxy.Comment: 7 pages, 5 figures, accepted for publication on A&
The obscured hyper-energetic GRB 120624B hosted by a luminous compact galaxy at z = 2.20
Gamma-ray bursts are the most luminous explosions that we can witness in the
Universe. Studying the most extreme cases of these phenomena allows us to
constrain the limits for the progenitor models. In this Letter, we study the
prompt emission, afterglow, and host galaxy of GRB 120624B, one of the
brightest GRBs detected by Fermi, to derive the energetics of the event and
characterise the host galaxy in which it was produced. Following the
high-energy detection we conducted a multi-wavelength follow-up campaign,
including near-infrared imaging from HAWKI/VLT, optical from OSIRIS/GTC, X-ray
observations from the Chandra X-ray Observatory and at
sub-millimetre/millimetre wavelengths from SMA. Optical/nIR spectroscopy was
performed with X-shooter/VLT. We detect the X-ray and nIR afterglow of the
burst and determine a redshift of z = 2.1974 +/- 0.0002 through the
identification of emission lines of [OII], [OIII] and H-alpha from the host
galaxy of the GRB. This implies an energy release of Eiso = (3.0+/-0.2)x10^54
erg, amongst the most luminous ever detected. The observations of the afterglow
indicate high obscuration with AV > 1.5. The host galaxy is compact, with R1/2
< 1.6 kpc, but luminous, at L ~ 1.5 L* and has a star formation rate of 91 +/-
6 Msol/yr as derived from H-alpha. As other highly obscured GRBs, GRB 120624B
is hosted by a luminous galaxy, which we also proof to be compact, with a very
intense star formation. It is one of the most luminous host galaxies associated
with a GRB, showing that the host galaxies of long GRBs are not always blue
dwarf galaxies, as previously thought.Comment: 6 pages, 4 figures, 4 tables; accepted for publication in A&
Enhancement of the indistinguishability of single photon emitters coupled to photonic waveguides
One of the main steps towards large-scale quantum photonics consists of the
integration of single photon sources (SPS) with photonic integrated circuits
(PICs). For that purpose, the PICs should offer an efficient light coupling and
a high preservation of the indistinguishability of photons. Therefore,
optimization of the indistinguishability through waveguide design is especially
relevant. In this work we have developed an analytical model to calculate the
coupling and the indistinguishability of an ideal point-source quantum emitter
coupled to a photonic waveguide depending on source orientation and position.
The model has been numerically evaluated through finite-difference time-domain
(FDTD) simulations showing consistent results. The maximum coupling is achieved
when the emitter is embedded in the center of the waveguide but somewhat
surprisingly the maximum indistinguishability appears when the emitter is
placed at the edge of the waveguide where the electric field is stronger due to
the surface discontinuity
Growth of InP on GaAs (001) by hydrogen-assisted low-temperature solid-source molecular beam epitaxy
Direct heteroepitaxial growth of InP layers on GaAs (001) wafers has been performed by solid-source molecular beam epitaxy assisted by monoatomic hydrogen (H∗). The epitaxial growth has been carried out using a two-step method: for the initial stage of growth the temperature was as low as 200 °C and different doses of H∗ were used; after this, the growth proceeded without H∗ while the temperature was increased slowly with time. The incorporation of H∗ drastically increased the critical layer thickness observed by reflection high-energy electron diffraction; it also caused a slight increase in the luminescence at room temperature, while it also drastically changed the low-temperature luminescence related to the presence of stoichiometric defects. The samples were processed by rapid thermal annealing. The annealing improved the crystalline quality of the InP layers measured by high-resolution x-ray diffraction, but did not affect their luminescent behavior significantly
The host of the Type I SLSN 2017egm: A young, sub-solar metallicity environment in a massive spiral galaxy
Here we present an integral-field study of the massive, high-metallicity
spiral NGC 3191, the host of SN 2017egm, the closest SLSN Type I to date. We
use data from PMAS/CAHA and the public MaNGA survey to shed light on the
properties of the SLSN site and the origin of star-formation in this
non-starburst spiral galaxy. We map the physical properties different
\ion{H}{II} regions throughout the galaxy and characterize their stellar
populations using the STARLIGHT fitting code. Kinematical information allows to
study a possible interaction with its neighbouring galaxy as the origin of
recent star formation activity which could have caused the SLSN. NGC 3191 shows
intense star-formation in the western part with three large SF regions of low
metallicity. The central regions of the host have a higher metallicity, lower
specific star-formation rate and lower ionization. Modeling the stellar
populations gives a different picture: The SLSN region has two dominant stellar
populations with different ages, the youngest one with an age of 2-10 Myr and
lower metallicity, likely the population from which the SN progenitor
originated. Emission line kinematics of NGC 3191 show indications of
interaction with its neighbour MCG+08-19-017 at 45 kpc, which might be
responsible for the recent starburst. In fact, this galaxy pair has in total
hosted 4 SNe, 1988B (Type Ia), SN 2003ds (Type Ic in MCG+08-19-017), PTF10bgl
(SLSN-Type II) and 2017egm, underlying the enhanced SF in both galaxies due to
interaction. Our study shows that one has to be careful interpreting global
host and even gas properties without looking at the stellar population history
of the region. SLSNe seem to still be consistent with massive stars ( 20
M) requiring low () metallicity and those environments
can also occur in massive, late-type galaxies but not necessarily starbursts.Comment: Accepted for publication in A&A, 13 pages, 11 figures, 7 tables.
Abstract has been reduced to match arXiv form requirement
Searching for differences in Swift's intermediate GRBs
Gamma-ray bursts are usually classified through their high-energy emission
into short-duration and long-duration bursts, which presumably reflect two
different types of progenitors. However, it has been shown on statistical
grounds that a third, intermediate population is needed in this classification
scheme, although an extensive study of the properties of this class has so far
not been done. The large amount of follow-up studies generated during the Swift
era allows us to have a suficient sample to attempt a study of this third
population through the properties of their prompt emission and their
afterglows. Our study is focused on a sample of GRBs observed by Swift during
its first four years of operation. The sample contains those bursts with
measured redshift since this allows us to derive intrinsic properties.
Intermediate bursts are less energetic and have dimmer afterglows than long
GRBs, especially when considering the X-ray light curves, which are on average
one order of magnitude fainter than long bursts. There is a less significant
trend in the redshift distribution that places intermediate bursts closer than
long bursts. Except for this, intermediate bursts show similar properties to
long bursts. In particular, they follow the Epeak vs. Eiso correlation and
have, on average, positive spectral lags with a distribution similar to that of
long bursts. Like long GRBs, they normally have an associated supernova,
although some intermediate bursts have shown no supernova component. This study
shows that intermediate bursts are different from short bursts and, in spite of
sharing many properties with long bursts, there are some differences between
them as well. We suggest that the physical difference between intermediate and
long bursts could be that for the first the ejecta are thin shells while for
the latter they are thick shells.Comment: Accepted for publication in Astronomy and Astrophysics. 16 pages, 17
figures, 5 table
Padronização de perfil metabólico em bovinos tratados com ivermectina por meio da urina em ressonância magnética nuclear (RMN).
O controle de Rhipicephalus (Boophilus) microplus ocorre por meio de antiparasitários e a contaminação dos produtos de origem animal com resíduos é uma grande preocupação para os agentes de saúde pública e controle ambiental. Metabolômica e Metabonômica são duas ferramentas utilizadas no panorama da bioquímica moderna. Enquanto a primeira refere-se ao estudo sistemático dos níveis de metabólitos de um organismo, a última correlaciona as alterações destes níveis a estímulos externos, como doenças e mudanças alimentares. Neste trabalho, utilizou-se a Metabonômica para tentar estabelecer um padrão no perfil metabólico de animais tratados com ivermectina, por meio da RMN de alta resolução na Embrapa Instrumentação Agropecuária. Amostras de urina foram colhidas de 12 bezerras Holandesas da Embrapa Pecuária Sudeste, 0, 3 e 6 h pós tratamento com ivermectina 4% subcutânea (Master LP®, Ouro Fino), na dose de 1 mL/50 Kg e congeladas a -40°C para posterior análise
- …