221 research outputs found
Transition from oil & gas drilling fluids to geothermal drilling fluids
The harsh downhole conditions encountered in geothermal wells, specifically the high temperatures (HT) together with the toughness of the rock found in many geothermal formations, makes the drilling operation challenging. Drilling in such environments requires specialised drilling fluid formulations that have high thermal stability, good rheological properties, excellent lubricity and low formation damage. Given the wealth of experience in drilling wells in the oil industry, it is tempting to assume that the design of geothermal drilling fluids would be straightforward. However, is this the case? In this literature review, we have attempted to answer the question: “to what degree can developments in oil and gas drilling fluids be transferred to drilling fluids for geothermal wells?” To keep the scope of the review manageable, we have focused on two key aspects of drilling fluid design: rate of penetration (ROP) and HT fluid stability (and maintenance of the desired rheological properties of the fluid at high temperatures). The review has allowed the identification of gaps in both fundamental understanding and in existing technology. Rate of penetration is improved using low viscosity and low-density fluids, and we recommend that foams and aphron systems should be investigated to achieve this (depending on the application pressure). It should be noted, however, that such systems to date have only been studied at relatively low temperatures and the challenge of increasing the thermal stability of the formulation components needs to be addressed. Highly thermally stable polymer systems exist but these are both expensive and not widely available. A systematic study of the impact of copolymer molecular architecture on hydrolytic thermal stability is recommended. A promising solution to both maintaining good rheological properties at high temperature and providing fluid loss control is the use of particulates, especially those in the nano-size range. Additionally, nanocomposite systems show promise in this area and should be investigated. Particle stabilized foams and aphrons are a particularly interesting solution and we recommend that these are studied. It is also recommended to investigate the effect of drilling fluid on long term geothermal well performance
CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS
Context. CARMENES is a stabilised, high-resolution, double-channel
spectrograph at the 3.5 m Calar Alto telescope. It is optimally designed for
radial-velocity surveys of M dwarfs with potentially habitable Earth-mass
planets. Aims. We prepare a list of the brightest, single M dwarfs in each
spectral subtype observable from the northern hemisphere, from which we will
select the best planet-hunting targets for CARMENES. Methods. In this first
paper on the preparation of our input catalogue, we compiled a large amount of
public data and collected low-resolution optical spectroscopy with CAFOS at the
2.2 m Calar Alto telescope for 753 stars. We derived accurate spectral types
using a dense grid of standard stars, a double least-squares minimisation
technique, and 31 spectral indices previously defined by other authors.
Additionally, we quantified surface gravity, metallicity, and chromospheric
activity for all the stars in our sample. Results. We calculated spectral types
for all 753 stars, of which 305 are new and 448 are revised. We measured
pseudo-equivalent widths of Halpha for all the stars in our sample, concluded
that chromospheric activity does not affect spectral typing from our indices,
and tabulated 49 stars that had been reported to be young stars in open
clusters, moving groups, and stellar associations. Of the 753 stars, two are
new subdwarf candidates, three are T Tauri stars, 25 are giants, 44 are K
dwarfs, and 679 are M dwarfs. Many of the 261 investigated dwarfs in the range
M4.0-8.0 V are among the brightest stars known in their spectral subtype.
Conclusions. This collection of low-resolution spectroscopic data serves as a
candidate target list for the CARMENES survey and can be highly valuable for
other radial-velocity surveys of M dwarfs and for studies of cool dwarfs in the
solar neighbourhood.Comment: A&A, in pres
A Search for FeH in Hot-Jupiter Atmospheres with High-Dispersion Spectroscopy
Most of the molecules detected thus far in exoplanet atmospheres, such as
water and CO, are present for a large range of pressures and temperatures. In
contrast, metal hydrides exist in much more specific regimes of parameter
space, and so can be used as probes of atmospheric conditions. Iron hydride
(FeH) is a dominant source of opacity in low-mass stars and brown dwarfs, and
evidence for its existence in exoplanets has recently been observed at low
resolution. We performed a systematic search of archival CARMENES near-infrared
data for signatures of FeH during transits of 12 exoplanets. These planets span
a large range of equilibrium temperatures (600
4000K) and surface gravities (2.5 3.5). We
did not find a statistically significant FeH signal in any of the atmospheres,
but obtained potential low-confidence signals (SNR3) in two planets,
WASP-33b and MASCARA-2b. Previous modeling of exoplanet atmospheres indicate
that the highest volume mixing ratios (VMRs) of 10 to 10 are
expected for temperatures between 1800 and 3000K and log . The two
planets for which we find low-confidence signals are in the regime where strong
FeH absorption is expected. We performed injection and recovery tests for each
planet and determined that FeH would be detected in every planet for VMRs , and could be detected in some planets for VMRs as low as 10.
Additional observations are necessary to conclusively detect FeH and assess its
role in the temperature structures of hot Jupiter atmospheres.Comment: Accepted to AAS journal
A search for He I airglow emission from the hot Jupiter tau Boo b
The helium absorption line at 10830 {\AA}, originating from the metastable
triplet state 2S, has been suggested as an excellent probe for the extended
atmospheres of hot Jupiters and their hydrodynamic escape processes, and has
recently been detected in the transmission spectra of a handful of planets. The
isotropic re-emission will lead to helium airglow that may be observable at
other orbital phases. The goal of this paper is to investigate the
detectability of He I emission at 10830 {\AA} in the atmospheres of exoplanets
using high-resolution spectroscopy, providing insights into the properties of
the upper atmospheres of close-in gas giants. We estimated the expected
strength of He I emission in hot Jupiters based on their transmission signal.
We searched for the He I 10830 {\AA} emission feature in tau Boo b in three
nights of high-resolution spectra taken by CARMENES at the 3.5m Calar Alto
telescope. The spectra from each night were corrected for telluric absorption,
sky emission lines, and stellar features, and were shifted to the planetary
rest frame to search for the emission. The He I emission is not detected in tau
Boo b, reaching a 5 sigma contrast limit of 410 for emission
line widths above 20 km/s. This is roughly a factor of 8 above the expected
level of emission (assuming a typical He I transit absorption of 1% for hot
Jupiters). This suggests that targeting the He I emission with well-designed
observations using upcoming instruments such as VLT/CRIRES+ and E-ELT/HIRES is
possible.Comment: Accepted for publication in A&A; 9 pages, 9 figure
O humor em manuais escolares de matemática
O humor tem larga presença na vida das pessoas, combinando elementos afetivos e cognitivos com o intuito de bem-dispor. Para além dos contextos de lazer, o humor tem também sido utilizado em contextos associados ao trabalho, nomeadamente nas escolas, colocado ao serviço do ensino. Sendo os manuais escolares um recurso muito utilizado pelos professores, particularmente pelos de Matemática, pareceu-nos pertinente: (i) averiguar a utilização do humor em manuais escolares de Matemática; e (ii) descrever o humor utilizado nos manuais, discutindo o seu enquadramento didático. Para isso, submetemos a análise de conteúdo quatro manuais escolares de Matemática (dos 4.º e 5.º anos de escolaridade) com larga difusão nacional. Os resultados revelam que o humor, tanto no texto como na ilustração, não tem praticamente expressão nos manuais. Ainda assim, todos os manuais valorizam, ao nível da ilustração, situações de boa disposição, apresentando, recorrentemente, pessoas a rir.Humor has a wide presence in people's lives, combining affective and cognitive elements with the intention of well-being. In addition to the leisure contexts, humor has also been used in contexts associated with work, namely schools, placed at the service of teaching. Since school textbooks are a resource widely used by teachers, particularly those of mathematics, it seems pertinent to us: (I) to access the usage of humor in Mathematics school textbooks; and (ii) describe the humor used in textbooks and discuss their didactic framework. For this, we submitted, to content analysis, four textbooks of Mathematics (of the 4th and 5th grades) with wide national diffusion. The results reveal that humor, both in the text and in the illustration, has practically no expression in the textbooks. Even so, all textbooks value, at the illustration level, light-hearted situations, presenting repeatedly, people laughing.info:eu-repo/semantics/publishedVersio
Morte súbita e angina vasoespástica
Variant angina is defined by chest pain occurring at rest associated with transitory ST segment elevation on ECG, and is caused by a spasm of a coronary artery. Frequently, variant angina is associated with atherosclerotic coronary obstruction and patients with normal coronary arteries are rare. Patients with variant angina and normal coronary arteries have good prognosis, and the development of ventricular arrhythmias or sudden death is rare. The authors present two cases of sudden cardiac death in patients with variant angina and normal coronary arteries
Detection of He I \AA{} absorption on HD 189733 b with CARMENES high-resolution transmission spectroscopy
We present three transit observations of HD 189733 b obtained with the
high-resolution spectrograph CARMENES at Calar Alto. A strong absorption signal
is detected in the near-infrared He I triplet at 10830 \AA{} in all three
transits. During mid-transit, the mean absorption level is %
measured in a 10 km s range at a net blueshift of km
s (10829.84--10830.57 \AA{}). The absorption signal exhibits radial
velocities of km s and km s during
ingress and egress, respectively; measured in the planetary rest frame. We show
that stellar activity related pseudo-signals interfere with the planetary
atmospheric absorption signal. They could contribute as much as 80% of the
observed signal and might also affect the radial velocity signature, but
pseudo-signals are very unlikely to explain the entire signal. The observed
line ratio between the two unresolved and the third line of the He I triplet is
, which strongly deviates from the value expected for an optically
thin atmospheres. When interpreted in terms of absorption in the planetary
atmosphere, this favors a compact helium atmosphere with an extent of only 0.2
planetary radii and a substantial column density on the order of cm. The observed radial velocities can be understood either in
terms of atmospheric circulation with equatorial superrotation or as a sign of
an asymmetric atmospheric component of evaporating material. We detect no clear
signature of ongoing evaporation, like pre- or post-transit absorption, which
could indicate material beyond the planetary Roche lobe, or radial velocities
in excess of the escape velocity. These findings do not contradict planetary
evaporation, but only show that the detected helium absorption in HD 189733 b
does not trace the atmospheric layers that show pronounced escape signatures.Comment: 13 pages, 12 figures, accepted for publication in A&
Efficacy of conventional treatment with composite resin and atraumatic restorative treatment in posterior primary teeth: study protocol for a randomised controlled trial
Introduction Despite the widespread acceptance of
conventional treatment using composite resin in primary
teeth, there is limited evidence that this approach is the
best option in paediatric clinics. Atraumatic restorative
treatment (ART) using high-viscosity glass ionomer
cement has gradually become more popular because it
performs well in clinical studies, is easy to handle and
is patient friendly. Therefore, the aim of this randomised
clinical trial study is to compare the restoration longevity
of conventional treatment using composite resin with that
of ART in posterior primary teeth. As secondary outcomes,
cost-efficacy and patient self-reported discomfort will also
be tested.
Methods and analysis Children aged 3–6 years
presenting with at least one occlusal and/or occlusalproximal cavity will be randomly assigned to one of
two groups according to the dental treatment: ART
(experimental group) or composite resin restoration
(control group). The dental treatment will be performed
at a dental care trailer located in an educational complex
in Barueri/SP, Brazil. The unit of randomisation will be the
child. A sample size of 240 teeth with occlusal cavities
and 188 teeth with occlusal-proximal cavities has been
calculated. The primary outcome will be restoration
longevity, which will be clinically assessed after 6, 12,
18 and 24 months by two examiners. The duration of the
dental treatment and the cost of all materials used will
be considered when estimating the cost-efficacy of each
treatment. Individual discomfort will be measured after
each dental procedure using the Facial Scale of WongBaker.
Ethics and dissemination This clinical trial was
approved by the local ethics committee from the
Faculty of Dentistry of the University of São Paulo
(registration no. 1.556.018). Participants will be
included after their legal guardians have signed an
informed consent form containing detailed information
about the research
Interobserver agreement in dysplasia grading: toward an enhanced gold standard for clinical pathology trials
Objective: Interobserver agreement in the context of oral epithelial dysplasia (OED) grading has been notoriously unreliable and can impose barriers for developing new molecular markers and diagnostic technologies. This paper aimed to report the details of a 3-stage histopathology review and adjudication process with the goal of achieving a consensus histopathologic diagnosis of each biopsy. Study Design: Two adjacent serial histologic sections of oral lesions from 846 patients were independently scored by 2 different pathologists from a pool of 4. In instances where the original 2 pathologists disagreed, a third, independent adjudicating pathologist conducted a review of both sections. If a majority agreement was not achieved, the third stage involved a face-to-face consensus review. Results: Individual pathologist pair κ values ranged from 0.251 to 0.706 (fair-good) before the 3-stage review process. During the initial review phase, the 2 pathologists agreed on a diagnosis for 69.9% of the cases. After the adjudication review by a third pathologist, an additional 22.8% of cases were given a consensus diagnosis (agreement of 2 out of 3 pathologists). After the face-to-face review, the remaining 7.3% of cases had a consensus diagnosis. Conclusions: The use of the defined protocol resulted in a substantial increase (30%) in diagnostic agreement and has the potential to improve the level of agreement for establishing gold standards for studies based on histopathologic diagnosis
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