1,173 research outputs found
Densidad de glandulas de Gossypol durante el desarrollo de botones florales de Gossypium hirsurtum L. y su relación con la resistencia a lepidopteros.
Forest growth dynamics of managed forests in the Southwestern Brazilian Amazon.
The objective of this work was to present the growth forest dynamics results obtained in two sites located in Acre and Amazonas states in the southwestern Brazilian Amazon.Abstracts of the XXV IUFRO World Congress
Twenty years monitoring growth dynamics of a logged tropical forest in Western Amazon.
Resumo - Foi conduzido um estudo sobre a dinâmica de crescimento em floresta localizada no Estado do Acre na Amazônia sul ocidental, onde uma área de 20 ha foi explorada para extração de madeira em 1992. O estudo foi baseado em parcelas permanentes (1 ha) estabelecidas dentro da área explorada e na floresta não manejada, imediatamente após o fim das operações florestais. Os parâmetros da dinâmica florestal foram analisados em termos da biomassa seca acima do solo (BAS). Durante o período do estudo três eventos climáticos extremos causaram um elevado impacto tanto nas áreas exploradas como nas não perturbadas por exploração, produzindo perdas de biomassa superiores às estimadas para a exploração. Vinte anos após a exploração, as taxas de ingresso e mortalidade foram semelhantes às esperadas em uma área de floresta não perturbada por exploração e a recuperação da BAS foi significativamente mais alta nas áreas cortadas. Quando praticado de forma adequada, o manejo de floresta pode promover uma recuperação da BAS mais rápida. Nós sugerimos que o manejo florestal pode ser considerado como uma alternativa para adaptação a eventos extremos de clima por meio da promoção de perturbações controladas que minimizem a mortalidade de árvores e a perda de biomassa
Detection of patients with functional dyspepsia using wavelet transform applied to their electrogastrogram
Cyrhetrenylaniline and new organometallic phenylimines derived from 4- and 5-nitrothiophene: Synthesis, characterization, X-Ray structures, electrochemistry and in vitro anti-T. brucei activity
A novel series of cyrhetrenyl (3a-4a) and ferrocenyl (3b-4b) Schiff bases were synthesized through a condensation reaction, between the known 4-ferrocenylaniline (2b) or the unreported 4-cyhretrenylaniline (2a) with 4- or 5-nitrothiophenecarboxaldehyde. The structure of 2a and the new Schiff bases have been elucidated using conventional spectroscopic techniques (FT-IR, 1H and 13C NMR), mass spectrometry, and single-crystal X-ray diffraction analysis of compounds 2a, 4a and 3b. Cyclic voltammetry of organometallic phenylimines derived from 5-nitrothiophene showed NO2 group reduction potentials (E1/2z 0.575 V) that were more anodic than those registered for their 4-nitro analogues (E1/2z 0.981 V). All organometallic imines were tested against the bloodstream form of Trypanosoma brucei. Evaluation indicated that the most active complexes are the 5-nitrothiophene derivatives, 4a, which were remarkably more active than nifurtimox. In addition, complex 4b resulted in less toxicity to host L6 cells than nifurtimox. The results revealed that the electronic effects of cyrhetrene and ferrocene are not an influential factor in E1/2 and anti-Trypanosoma brucei activity for these new imines, which is probably due to the non-coplanarity of the [(h5-C5H4)-C6H4-N=CH-(C4H2S)] system
Climate trends and glacier retreat in the Cordillera Blanca, Peru, revisited
The total glacial area of the Cordillera Blanca, Peru, has shrunk by more than 30% in the period of 1930 to the present with a marked glacier retreat also in the recent decades. The aim of this paper is to assess local air temperature and precipitation changes in the Cordillera Blanca and to discuss how these variables could have affected the observed glacier retreat between the 1980s and present. A unique data set from a large number of stations in the region of the Cordillera Blanca shows that after a strong air temperature rise of about 0.31 °C per decade between 1969 and 1998, a slowdown in the warming to about 0.13 °C per decade occurred for the 30 years from 1983 to 2012. Additionally, based on data from a long-term meteorological station, it was found that the freezing line altitude during precipitation days has probably not increased significantly in the last 30 years. We documented a cooling trend for maximum daily air temperatures and an increase in precipitation of about 60 mm/decade since the early 1980s. The strong increase in precipitation in the last 30 years probably did not balance the increase of temperature before the 1980s. It is suggested that recent changes in temperature and precipitation alone may not explain the glacial recession within the thirty years from the early 1980s to 2012. Glaciers in the Cordillera Blanca may be still reacting to the positive air temperature rise before 1980. Especially small and low-lying glaciers are characterised by a serious imbalance and may disappear in the near future
Periodontitis como factor de riesgo de enfermedades cardiovasculares
Las enfermedades cardiovasculares representan una de las principales causas de muerte en las sociedades desarrolladas. Estas enfermedades no sólo son importantes por la mortalidad que generan, sino por la gran cantidad de individuos afectados y en tratamiento que han de soportar los sistemas de salud de los distintos países. De ahí que la detección precoz de los factores de riesgo conducentes a desencadenar estas enfermedades haya sido vista como el mecanismo más eficaz para prevenirlas. En los últimos tiempos se viene relacionando de una manera más o menos directa a la patología periodontal con el padecimiento de enfermedades cardiovasculares. Este hecho podría tener una gran relevancia clínica y probablemente epidemiológica, debido a la considerable prevalencia actual de las enfermedades periodontales. En la presente revisión se analizan los factores clínicos y fisiopatológicos que dan soporte científico a esta asociación, llegándose a la conclusión de que hacen falta más estudios, para tener la evidencia de que dicha asociación, representa un factor de riesgo determinante para el padecimiento de las enfermedades cardiovasculares.
A Comprehensive View of the 2006 December 13 CME: From the Sun to Interplanetary Space
The biggest halo coronal mass ejection (CME) since the Halloween storm in
2003, which occurred on 2006 December 13, is studied in terms of its solar
source and heliospheric consequences. The CME is accompanied by an X3.4 flare,
EUV dimmings and coronal waves. It generated significant space weather effects
such as an interplanetary shock, radio bursts, major solar energetic particle
(SEP) events, and a magnetic cloud (MC) detected by a fleet of spacecraft
including STEREO, ACE, Wind and Ulysses. Reconstruction of the MC with the
Grad-Shafranov (GS) method yields an axis orientation oblique to the flare
ribbons. Observations of the SEP intensities and anisotropies show that the
particles can be trapped, deflected and reaccelerated by the large-scale
transient structures. The CME-driven shock is observed at both the Earth and
Ulysses when they are separated by 74 in latitude and 117
in longitude, the largest shock extent ever detected. The ejecta seems missed
at Ulysses. The shock arrival time at Ulysses is well predicted by an MHD model
which can propagate the 1 AU data outward. The CME/shock is tracked remarkably
well from the Sun all the way to Ulysses by coronagraph images, type II
frequency drift, in situ measurements and the MHD model. These results reveal a
technique which combines MHD propagation of the solar wind and type II
emissions to predict the shock arrival time at the Earth, a significant advance
for space weather forecasting especially when in situ data are available from
the Solar Orbiter and Sentinels.Comment: 26 pages, 10 figures. 2008, ApJ, in pres
Characterization of the HD 108236 system with CHEOPS and TESS Confirmation of a fifth transiting planet
Context. The HD 108236 system was first announced with the detection of four small planets based on TESS data. Shortly after, the transit of an additional planet with a period of 29.54 d was serendipitously detected by CHEOPS. In this way, HD 108236 (V = 9.2) became one of the brightest stars known to host five small transiting planets (Rp < 3 R⊕).
Aims. We characterize the planetary system by using all the data available from CHEOPS and TESS space missions. We use the flexible pointing capabilities of CHEOPS to follow up the transits of all the planets in the system, including the fifth transiting body.
Methods. After updating the host star parameters by using the results from Gaia eDR3, we analyzed 16 and 43 transits observed by CHEOPS and TESS, respectively, to derive the planets’ physical and orbital parameters. We carried out a timing analysis of the transits of each of the planets of HD 108236 to search for the presence of transit timing variations.
Results. We derived improved values for the radius and mass of the host star (R★ = 0.876 ± 0.007 R0 and M★ = 0.867-0.046+0.047M⊙). We confirm the presence of the fifth transiting planet f in a 29.54 d orbit. Thus, the HD 108236 system consists of five planets of Rb = 1.587±0.028, Rc = 2.122±0.025, Rd = 2.629 ± 0.031, Re = 3.008 ± 0.032, and Rf = 1.89 ± 0.04 [R⊕]. We refine the transit ephemeris for each planet and find no significant transit timing variations for planets c, d, and e. For planets b and f, instead, we measure significant deviations on their transit times (up to 22 and 28 min, respectively) with a non-negligible dispersion of 9.6 and 12.6 min in their time residuals.
Conclusions. We confirm the presence of planet f and find no significant evidence for a potential transiting planet in a 10.9 d orbital period, as previously suggested. Further monitoring of the transits, particularly for planets b and f, would confirm the presence of the observed transit time variations. HD 108236 thus becomes a key multi-planetary system for the study of formation and evolution processes. The reported precise results on the planetary radii – together with a profuse RV monitoring – will allow for an accurate characterization of the internal structure of these planets
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