A rectangular radio pulse propagation in a selectively absorbing medium

A pulse with rectangular envelope propagation, in which carrier frequency is close to the medium spectral absorption line’s one frequency, is considered. It is shown that when the signal carrier frequency is shifted relative to the spectral line centre, the primary interference and the response signal can lead to the total signal significant oscillations over time.

The Role of National Farmers Helps Line in Agricultural Information Dissemination Among Crop Farmers in Nigeria: A Case Study of Farmers Help Line Centre, NAERLS ABU Zaria

The study examined the role of national farmers helpline in agricultural information dissemination among crop farmers in Nigeria, with the specific objectives to identify the various sources of information on agricultural practices available to the farmers and identify the various information disseminated to the farmers from the National Farmers Helpline. One Thousand farmers were randomly selected from the farmers who frequently call the Helpline Centre from the database of NAERLS across the six geo-political zones of Nigeria; to source the required information. Some of the crop farmers were contacted through phone calls, SMS, and social media platforms like Facebook and WhatsApp while some were through administration of questionnaires and face to face discussion. Data sourced were subjected to descriptive statistics such as frequency distribution and percentage for analysis and were presented in tables and charts. The findings reveal that the Farmers Help Line Centre, NEARLS supply farmers around the country with all the necessary information on cultural practices, access to improved seed varieties, fertilizer and application, pest and disease management practices, weed management practices, marketing strategies, post-harvest activities, management of farm tools and machineries and also information on Government policies on agriculture. It is recommended that stakeholders of National Farmers Help Line ensure the sustainability of its services by including other Nigerian languages to have a larger coverage and not limiting spoken languages to only the major Nigerian languages (English, Yoruba, Hausa, Igbo and Nigerian pidgin); and also extend their services to West African countries and other parts of the globe at large. Key words: Agriculture, information, dissemination and crop farmers

Evolution of atmospheric escape in close-in giant planets and their associated Ly α and H α transit predictions

ABSTRACT Strong atmospheric escape has been detected in several close-in exoplanets. As these planets consist mostly of hydrogen, observations in hydrogen lines, such as Ly α and H α, are powerful diagnostics of escape. Here, we simulate the evolution of atmospheric escape of close-in giant planets and calculate their associated Ly α and H α transits. We use a 1D hydrodynamic escape model to compute physical properties of the atmosphere and a ray tracing technique to simulate spectroscopic transits. We consider giant (0.3 and 1 Mjup) planets orbiting a solar-like star at 0.045 au, evolving from 10 to 5000 Myr. We find that younger giants show higher rates of escape, owing to a favourable combination of higher irradiation fluxes and weaker gravities. Less massive planets show higher escape rates (1010–1013 g s−1) than those more massive (109–1012 g s−1) over their evolution. We estimate that the 1-Mjup planet would lose at most 1 per cent of its initial mass due to escape, while the 0.3-Mjup planet, could lose up to 20 per cent. This supports the idea that the Neptunian desert has been formed due to significant mass-loss in low-gravity planets. At younger ages, we find that the mid-transit Ly α line is saturated at line centre, while H α exhibits transit depths of at most 3–4 per cent in excess of their geometric transit. While at older ages, Ly α absorption is still significant (and possibly saturated for the lower mass planet), the H α absorption nearly disappears. This is because the extended atmosphere of neutral hydrogen becomes predominantly in the ground state after ∼1.2 Gyr.

The recognition and modelling of a backbone and its deformity

In this article the authors present a method for the backbone recognition and modelling. The process of recognition combines some classical techniques (Hough transformation, GVF snakes) with some new (authors present a method for initial curvature detection, which they call the Falling Ball method). The result enables us to identify high-quality features of the spine and to detect the major deformities of backbone: the intercrestal line, centre sacral vertical line, C7 plumbline; as well as angles: proximal thoracic curve, main thoracic curve, thoracolumbar/lumbar. These features are used for measure in adolescent idiopathic scoliosis, especially in the case of treatment. Input data are just radiographic images, meet in everyday practice.

Observing convection in stellar atmospheres

Convection occurs in the visible photospheric layers of most stars having Te less than about 10000 K, and in some hotter stars. The solar granulation pattern is a symptom of this, as is the non-zero microturbulent velocity often required in abundance analysis to make both weak and strong lines yield the same abundance.In very sharp-lined stars, the presence of a non-thermal velocity field in the visible stellar atmosphere leads to several other effects which may be detected in spectral line profiles. These include radial velocities that vary systematically with equivalent width, distortions of the line profile as compared to a profile computed with a Voigt profile and rotational broadening (“macroturbulence”), and asymmetries with respect to the line centre (“bisector curvature”).Detection and interpretation of these effects, with the goal of obtaining empirical information about a velocity field present in the visible layers, requires comparison with calculated synthetic spectra which incorporate model velocity fields. Thus, this review will summarize some of the observational clues concerning photospheric velocity fields, as well as modelling aimed at interpreting these data.

Wind Inhomogeneities in [WC] Central Stars: From Late-to Early-Type Nuclei

In Grosdidier et al. (2000, 2001), wind fluctuations were described for five [WC 8–10] stars. In this poster we present new results discussing the case of the hotter subtype [WO 4] (Grosdidier & Acker 2002). Specifically, we concentrate on the CIVλλ5801/12 emission-line variability observed for NGC 1501 and NGC 6751 (see also Acker & Durand, these proceedings). Main results: NGC 1501: The OVλ5590 and CIVλλ5801/12 emission lines as well as the CIV/CIII complex around 5690Å are variable at the 1% level. The amplitudes of the variations range from about 5% (OV), up to 7% (CIV) of the adjacent continuum flux. The HeIλ5876 is also found to be variable; NGC 6751: For this star, significant variability at the 1% level is detected for the CIVλλ5801/12 emission line only. Note that the variations are quite huge since they span 6–10% of the adjacent continuum flux. Small variations are seen around the line centre but they are essentially located in the red and blue wings of the line, the latter showing the largest level of variability. Generally, the amplitudes of the variations in [WO 4] central stars range up to 10% of the adjacent continuum flux, over timescales of hours, or days. This result is essentially the same than that found for [WC]-late type stars. We expect strong, hydrogen-deficient [WC] winds to be extreme examples for central stars of PN, so that any fine structure found in [WC] winds may apply to all winds of central stars of PN, much as one is finding now that weak, massive O-star winds also show the same fine structure as massive WR winds. The consequences of clumping in hot-star winds are manifold, including substantial constraints on the effective mass-loss rates, and their possible impact on the surrounding nebula itself (Acker et al. 2002). On the whole, the winds of all [WC] central stars are significantly stochastically variable on relatively short time-scales. This supports a turbulent origin.

Molecular Hydrogen in the Lagoon: H2 Line Emission from Messier 8

The 2.12 μm v = 1−0 S(1) line of molecular hydrogen has been imaged in the Hourglass region of M8. The line is emitted from a roughly bipolar region, centred around the O7 star Herschel 36. The peak H2 1−0 S(1) line intensity is 8.2 × 10−15 erg s−1 cm−2arcsec−2. The line centre emission velocity varies from −25 kms−1 in the SE lobe to +45 kms−1 in the NW lobe. The distribution is similar to that of the CO J = 3−2 line. The H2 line appears to be shock-excited when a bipolar outflow from Herschel 36 interacts with the ambient molecular cloud. The total luminosity of all H2 lines is estimated to be ˜16 L⊙ and the mass of the hot molecular gas ˜9 × 10−4 M⊙ (without any correction for extinction).