280 research outputs found
Na I and H absorption features in the atmosphere of MASCARA-2b/KELT-20b
We have used the HARPS-North high resolution spectrograph (=115
000) at TNG to observe one transit of the highly irradiated planet
MASCARA-2b/KELT-20b. Using only one transit observation, we are able to clearly
resolve the spectral features of the atomic sodium (Na I) doublet and the
H line in its atmosphere, measuring absorption depths of
0.170.03 and 0.590.08 for a 0.75 passband,
respectively. These absorptions are corroborated with the transmission measured
from their respective transmission light curves, which show a large
Rossiter-McLaughlin effect. In case of H, this absorption corresponds
to an effective radius of =1.200.04. While the S/N of the
final transmission spectrum is not sufficient to adjust different temperature
profiles to the lines, we find that higher temperatures than the equilibrium
are needed to explain the lines contrast. Particularly, we find that the Na I
lines core require a temperature of T=4210180K and that H requires
T=4330520K. MASCARA-2b, like other planets orbiting A-type stars, receives
a large amount of UV energy from its host star. This energy excites the atomic
hydrogen and produces H absorption, leading to the expansion and
abrasion of the atmosphere. The study of other Balmer lines in the transmission
spectrum would allow the determination of the atmospheric temperature profile
and the calculation of the lifetime of the atmosphere. In the case of
MASCARA-2b, residual features are observed in the H and H lines,
but they are not statistically significant. More transit observations are
needed to confirm our findings in Na I and H, and to build up enough
S/N to explore the presence of H and H planetary absorptions.Comment: 14 pages, 12 figure
Structural basis for distinctive recognition of fibrinogen γC peptide by the platelet integrin αIIbβ3
Hemostasis and thrombosis (blood clotting) involve fibrinogen binding to integrin αIIbβ3 on platelets, resulting in platelet aggregation. αvβ3 binds fibrinogen via an Arg-Asp-Gly (RGD) motif in fibrinogen's α subunit. αIIbβ3 also binds to fibrinogen; however, it does so via an unstructured RGD-lacking C-terminal region of the γ subunit (γC peptide). These distinct modes of fibrinogen binding enable αIIbβ3 and αvβ3 to function cooperatively in hemostasis. In this study, crystal structures reveal the integrin αIIbβ3–γC peptide interface, and, for comparison, integrin αIIbβ3 bound to a lamprey γC primordial RGD motif. Compared with RGD, the GAKQAGDV motif in γC adopts a different backbone configuration and binds over a more extended region. The integrin metal ion–dependent adhesion site (MIDAS) Mg2+ ion binds the γC Asp side chain. The adjacent to MIDAS (ADMIDAS) Ca2+ ion binds the γC C terminus, revealing a contribution for ADMIDAS in ligand binding. Structural data from this natively disordered γC peptide enhances our understanding of the involvement of γC peptide and integrin αIIbβ3 in hemostasis and thrombosis
bRing: An observatory dedicated to monitoring the Pictoris b Hill sphere transit
Aims. We describe the design and first light observations from the
Pictoris b Ring ("bRing") project. The primary goal is to detect photometric
variability from the young star Pictoris due to circumplanetary
material surrounding the directly imaged young extrasolar gas giant planet
\bpb. Methods. Over a nine month period centred on September 2017, the Hill
sphere of the planet will cross in front of the star, providing a unique
opportunity to directly probe the circumplanetary environment of a directly
imaged planet through photometric and spectroscopic variations. We have built
and installed the first of two bRing monitoring stations (one in South Africa
and the other in Australia) that will measure the flux of Pictoris,
with a photometric precision of over 5 minutes. Each station uses two
wide field cameras to cover the declination of the star at all elevations.
Detection of photometric fluctuations will trigger spectroscopic observations
with large aperture telescopes in order to determine the gas and dust
composition in a system at the end of the planet-forming era. Results. The
first three months of operation demonstrate that bRing can obtain better than
0.5\% photometry on Pictoris in five minutes and is sensitive to
nightly trends enabling the detection of any transiting material within the
Hill sphere of the exoplanet
MASCARA-2 b: A hot Jupiter transiting the A-star HD185603
In this paper we present MASCARA-2 b, a hot Jupiter transiting the
A2 star HD 185603. Since early 2015, MASCARA has taken more than 1.6 million
flux measurements of the star, corresponding to a total of almost 3000 hours of
observations, revealing a periodic dimming in the flux with a depth of .
Photometric follow-up observations were performed with the NITES and IAC80
telescopes and spectroscopic measurements were obtained with the Hertzsprung
SONG telescope. We find MASCARA-2 b orbits HD 185603 with a period of
at a distance of , has a radius of and place a
upper limit on the mass of . HD 185603 is a
rapidly rotating early-type star with an effective temperature of
and a mass and radius of
, , respectively. Contrary
to most other hot Jupiters transiting early-type stars, the projected planet
orbital axis and stellar spin axis are found to be aligned with . The brightness of the host star and the high equilibrium
temperature, , of MASCARA-2 b make it a suitable target for
atmospheric studies from the ground and space. Of particular interest is the
detection of TiO, which has recently been detected in the similarly hot planets
WASP-33 b and WASP-19 b.Comment: 8 pages, 4 figures, Accepted for publication in A&
Data calibration for the MASCARA and bRing instruments
Aims: MASCARA and bRing are photometric surveys designed to detect
variability caused by exoplanets in stars with . Such variability
signals are typically small and require an accurate calibration algorithm,
tailored to the survey, in order to be detected. This paper presents the
methods developed to calibrate the raw photometry of the MASCARA and bRing
stations and characterizes the performance of the methods and instruments.
Methods: For the primary calibration a modified version of the coarse
decorrelation algorithm is used, which corrects for the extinction due to the
earth's atmosphere, the camera transmission, and intrapixel variations.
Residual trends are removed from the light curves of individual stars using
empirical secondary calibration methods. In order to optimize these methods, as
well as characterize the performance of the instruments, transit signals were
injected in the data. Results: After optimal calibration an RMS scatter of 10
mmag at is achieved in the light curves. By injecting transit
signals with periods between one and five days in the MASCARA data obtained by
the La Palma station over the course of one year, we demonstrate that MASCARA
La Palma is able to recover 84.0, 60.5 and 20.7% of signals with depths of 2, 1
and 0.5% respectively, with a strong dependency on the observed declination,
recovering 65.4% of all transit signals at versus 35.8% at
. Using the full three years of data obtained by MASCARA La
Palma to date, similar recovery rates are extended to periods up to ten days.
We derive a preliminary occurrence rate for hot Jupiters around A-stars of , knowing that many hot Jupiters are still overlooked. In the era of
TESS, MASCARA and bRing will provide an interesting synergy for finding
long-period ( days) transiting gas-giant planets around the brightest
stars.Comment: 18 pages, 17 figures, accepted for publication in A&
Optical and mechanical properties of cocona chips as affected by the drying process
[EN] The effect of the application of a pre-osmotic treatment to obtain hot air dried cocona(Solanum sessiliofurum Dunal) chips was studied. The drying kinetics and the optical andmechanical properties of cocona chips obtained by the combined method of osmotic dehy-dration and hot air drying (OD + HAD) and by only hot air drying (HAD) were compared.Samples were dried by hot air at 60◦C. For the combined method, they were pre-dried toa moisture content of 75 gwater/100 g, immersed in a 55◦Brix sucrose solution at 25◦C for48 min. The pre-osmodehydration applied did not influence the subsequent hot air dryingkinetics, resulting in a final product with 0.055 ± 0.005 gwater/gcocona.The optical properties ofOD + HAD chips were more favorable, exhibiting a smaller color change with respect to thefresh fruit (±15 units) than the HAD samples (±23 units). On the other hand, the OD + HADchips presented more fracture peaks than HAD ones, this related with a structure with ahigher degree of crispness, a very desirable property for a chip product.The authors thank the Universidad Politecnica de Valencia for the financial support given throughout the Project ADSIDEO-COOPERACION 2010 "Adaptacion de procesos de secado para favorecer la comercializacion de super frutas de origen colombiano".Agudelo Sterling, CM.; Igual Ramo, M.; Talens Oliag, P.; Martínez Navarrete, N. (2015). Optical and mechanical properties of cocona chips as affected by the drying process. Food and Bioproducts Processing. 95:192-199. doi:10.1016/j.fbp.2015.05.009S1921999
An unusually large gaseous transit in a debris disc
We present the detection of an unusually large transient gas absorption in several ionized species in the debris disc star HD 37306 using high-resolution optical spectra. We have been analysing a large sample of debris discs searching for circumstellar gas absorptions aiming to determine the frequency of gas in debris discs. HD 37306 stood out showing remarkably broad absorptions superimposed on to several photospheric Ca II, Fe II, and Ti II lines. The observed absorptions, unlike typical exocometary transits, lasted for at least eight days. Here, we analyse simultaneous spectroscopic and photometric data of the event and evaluate different scenarios that might explain the observed features. We conclude that the most likely scenario might be an exocometary break-up releasing a significant amount of gas close to the star, producing an occulting `ring'/`torus' shape
Physicochemical properties and structural characteristics of whole grain Oryza sativa L. with different treatments
[EN] Physicochemical properties and structural characteristics of whole rice flours with different treatments
(soaking, germination and extrusion cooking) were studied. Water solubility, water absorption, crystallinity,
adsorption isotherms (BET and GAB models), and glass transition temperature of the samples were determined.
Water solubility and water absorption were enhanced by extrusion cooking process (3.17 4.98 vs.
24.1 53.76 g/100 g and 2.77 3.05 vs. 4.46 7.04 ml/g, respectively), but crystallinity was decreased (30 33 vs.
4 16%). Adsorption isotherms showed that extruded samples exhibited higher equilibrium moisture content
as compared with their corresponding non-extruded samples (5.0 19.2 vs. 4.0 16.1 g water/g solids). There
were no changes in glass transition temperature values in the studied moisture range (3.8 16 g/100 g). These
results allow the correct use of whole rice flours with different treatments in foods and also contributed to the
knowledge of stabilization of the productsThe author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was partially financed by ANPCYT (PICT 1105) and ERASMUS MUNDUS ACTION 2 ARCOIRIS Fellowship.Albarracin, M.; Talens Oliag, P.; Martínez Navarrete, N.; González, RJ.; Drago, SR. (2016). Physicochemical properties and structural characteristics of whole grain Oryza sativa L. with different treatments. Food Science and Technology International. 22(4):1-10. doi:10.1177/1082013215600078S110224Albarracín, M., José González, R., & Drago, S. R. (2015). Soaking and extrusion effects on physicochemical parameters, phytic acid, nutrient content and mineral bio-accessibility of whole rice grain. International Journal of Food Sciences and Nutrition, 66(2), 210-215. doi:10.3109/09637486.2014.986070Björck, I., & Asp, N.-G. (1983). The effects of extrusion cooking on nutritional value — A literature review. Journal of Food Engineering, 2(4), 281-308. doi:10.1016/0260-8774(83)90016-xBrunauer, S., Deming, L. S., Deming, W. E., & Teller, E. (1940). On a Theory of the van der Waals Adsorption of Gases. Journal of the American Chemical Society, 62(7), 1723-1732. doi:10.1021/ja01864a025Donkor, O. N., Stojanovska, L., Ginn, P., Ashton, J., & Vasiljevic, T. (2012). Germinated grains – Sources of bioactive compounds. Food Chemistry, 135(3), 950-959. doi:10.1016/j.foodchem.2012.05.058Gonzalez, R. J., De Greef, D. M., Torres, R. L., Borras, F. S., & Robutti, J. (2004). Effects of endosperm hardness and extrusion temperature on properties of products obtained with grits from two commercial maize cultivars. LWT - Food Science and Technology, 37(2), 193-198. doi:10.1016/j.lwt.2003.07.004Gonzalez, R., Drago, S., Torres, R., & De Greef, D. (2013). Extrusion Cooking of Cereal-Based Products. Contemporary Food Engineering. doi:10.1201/b15246-13González, R. J., Pastor Cavada, E., Vioque Peña, J., Torres, R. L., De Greef, D. M., & Drago, S. R. (2013). Extrusion Conditions and Amylose Content Affect Physicochemical Properties of Extrudates Obtained from Brown Rice Grains. International Journal of Food Science, 2013, 1-8. doi:10.1155/2013/584148Herawat, H., Kusnandar, F., Adawiyah, D. R., Budijanto, S., & Rahman, M. S. (2014). Thermal characteristics and state diagram of extruded instant artificial rice. Thermochimica Acta, 593, 50-57. doi:10.1016/j.tca.2014.08.017Jones, J. M., & Engleson, J. (2010). Whole Grains: Benefits and Challenges. Annual Review of Food Science and Technology, 1(1), 19-40. doi:10.1146/annurev.food.112408.132746Kim, H. Y., Hwang, I. G., Kim, T. M., Woo, K. S., Park, D. S., Kim, J. H., … Jeong, H. S. (2012). Chemical and functional components in different parts of rough rice (Oryza sativa L.) before and after germination. Food Chemistry, 134(1), 288-293. doi:10.1016/j.foodchem.2012.02.138Lowry, R. R., & Tinsley, I. J. (1976). Rapid colorimetric determination of free fatty acids. Journal of the American Oil Chemists’ Society, 53(7), 470-472. doi:10.1007/bf02636814Matveev, Y. (2000). The plasticizing effect of water on proteins, polysaccharides and their mixtures. Glassy state of biopolymers, food and seeds. Food Hydrocolloids, 14(5), 425-437. doi:10.1016/s0268-005x(00)00020-5Perdon, A., Siebenmorgen, T. J., & Mauromoustakos, A. (2000). Glassy State Transition and Rice Drying: Development of a Brown Rice State Diagram. Cereal Chemistry Journal, 77(6), 708-713. doi:10.1094/cchem.2000.77.6.708ROOS, Y., & KAREL, M. (1991). Plasticizing Effect of Water on Thermal Behavior and Crystallization of Amorphous Food Models. Journal of Food Science, 56(1), 38-43. doi:10.1111/j.1365-2621.1991.tb07970.xRuiz-Ruiz, J., Martínez-Ayala, A., Drago, S., González, R., Betancur-Ancona, D., & Chel-Guerrero, L. (2008). Extrusion of a hard-to-cook bean (Phaseolus vulgaris L.) and quality protein maize (Zea mays L.) flour blend. LWT - Food Science and Technology, 41(10), 1799-1807. doi:10.1016/j.lwt.2008.01.005SIU, G. M., & DRAPER, H. H. (1978). A SURVEY OF THE MALONALDEHYDE CONTENT OF RETAIL MEATS AND FISH. Journal of Food Science, 43(4), 1147-1149. doi:10.1111/j.1365-2621.1978.tb15256.xSun, Z., Yang, W., Siebenmorgen, T., Stelwagen, A., & Cnossen, A. (2002). Thermomechanical Transitions of Rice Kernels. Cereal Chemistry Journal, 79(3), 349-353. doi:10.1094/cchem.2002.79.3.349Timmermann, E. O. (2003). Multilayer sorption parameters: BET or GAB values? Colloids and Surfaces A: Physicochemical and Engineering Aspects, 220(1-3), 235-260. doi:10.1016/s0927-7757(03)00059-1Tovar, J., Bjoerck, I. M., & Asp, N. G. (1990). Starch content and .alpha.-amylolysis rate in precooked legume flours. Journal of Agricultural and Food Chemistry, 38(9), 1818-1823. doi:10.1021/jf00099a00
- …