1,883 research outputs found
Distributional extensions of Carollia castanea and Micronycteris minuta from Guatemala, Central America
Field expeditions in 2011 that inventoried the terrestrial vertebrate fauna of two wildlife protected areas in the tropical Caribbean of Guatemala have produced the first confirmed records of two bats for the country: the white-bellied big-eared bat, Micronycteris (Schizonycteris) minuta (Gervais 1856) and the Chesnut short-tailed bat Carollia castanea H. Allen, 1890, both of neotropical distribution and with their current northern limit at Lancetilla, Honduras. The record of M. minuta at Sierra de Caral, Guatemala extends the range of this species 137 km to the west, and the record of C. castanea at Cerro San Gil extends its range 147 km to the west
Conventional Space-Vector Modulation Techniques versus the Single-Phase Modulator for Multilevel Converters
Space-vector modulation is a well-suited technique
to be applied to multilevel converters and is an important
research focus in the last 25 years. Recently, a single-phase
multilevel modulator has been introduced showing its conceptual
simplicity and its very low computational cost. In this paper,
some of the most conventional multilevel space-vector modulation
techniques have been chosen to compare their results with those
obtained with single-phase multilevel modulators. The obtained
results demonstrate that the single-phase multilevel modulators
applied to each phase are equivalent with the chosen wellknown
multilevel space-vector modulation techniques. In this
way, single-phase multilevel modulators can be applied to a
converter with any number of levels and phases avoiding the
use of conceptually and mathematically complex space-vector
modulation strategies. Analytical calculations and experimental
results are shown validating the proposed concepts
Detection of a multi-shell planetary nebula around the hot subdwarf O-type star 2MASS J19310888+4324577
(Abridged) The origin of hot subdwarf O-type stars (sdOs) remains unclear
since their discovery in 1947. Among others, a post-Asymptotic Giant Branch
(post-AGB) origin is possible for a fraction of sdOs. We are involved in a
comprehensive ongoing study to search for and to analyze planetary nebulae
(PNe) around sdOs with the aim of establishing the fraction and properties of
sdOs with a post-AGB origin. We use deep Halpha and [OIII] images of sdOs to
detect nebular emission and intermediate resolution, long-slit optical
spectroscopy of the detected nebulae and their sdO central stars. These data
are complemented with other observations for further analysis of the detected
nebulae. We report the detection of an extremely faint, complex PN around 2MASS
J19310888+4324577 (2M1931+4324), a star classified as sdO in a binary system.
The PN shows a bipolar and an elliptical shell, whose major axes are oriented
perpendicular to each other, and high-excitation structures outside the two
shells. WISE archive images show faint, extended emission at 12 and 22 microns
in the inner nebular regions. The internal nebular kinematics is consistent
with a bipolar and a cylindrical/ellipsoidal shell, in both cases with the main
axis mainly perpendicular to the line of sight. The nebular spectrum only
exhibits Halpha, Hbeta and [OIII]4959,5007 emission lines, but suggests a very
low-excitation ([OIII]/Hbeta = 1.5), in strong contrast with the absence of
low-excitation emission lines. The spectrum of 2M1931+4324 presents narrow,
ionized helium absorptions that confirm the previous sdO classification and
suggest an effective temperature >= 60000 K. The binary nature of 2M1931+4324,
its association with a complex PN, and several properties of the system provide
strong support for the idea that binary central stars are a crucial ingredient
in the formation of complex PNe.Comment: 8 pages, 7 figures, accepted in Astronomy and Astrophysic
Effect of diet on live weight and egg weight of backyard hens during the rainy season
The objective was to determine the effect of diet on live weight (LW) and egg weight (EW) of backyard hens (BH) during the rainy season in the Bajío region of the state of Michoacán, Mexico. Seventeen municipalities were sampled, where 101 BH (six hens/municipality) were captured and weighed and 101 eggs (six eggs/municipality) were harvested and weighed. The crops of the captured hens were removed Post-sacrifice, the organic content/crop (OCC) was classified and weighed by components, to later perform chemical compositional analysis. Data were analysed using generalised linear models and the differences between municipalities were obtained by the method of least squares means. The weight of the OCC (36.4 ± 22.4 g) was affected by the municipality (P<0.001), but not by the LW of the BH (P>0.05). Commercial feed (8.1 ± 6.0 g), grains: maize and sorghum (13.9 ± 13.5 g) kitchen waste (1.5 ± 2.9 g), herbaceous (0.6 ± 0.9 g) and insects (0.3 ± 0.7 g) were found in the crop. According to the commercial feed (COF) component, two feeding systems (FS) were identified: traditional FS, without COF and nontraditional FS, with COF. The diets of both FS were similar (P>0.05) in nutritional composition and do not meet the nutritional requirements of the hens. The LW (1.567 ± 0.316 kg) and EW (51.3 ± 1.0 g) of the BH cannot be completely attributed to the diet consumed during the rainy season
Two-dimensional modulation technique with dc voltage control for single-phase two-cell cascaded converters
In this paper, a simple feed-forward modulation technique for single-phase two-cell multilevel cascaded converters is presented. All the possible switching states of the power converter are taken into account applying a two dimensional control region. The proposed technique uses the actual values of the DC-Link capacitor voltages to obtain output phase voltages and currents with low harmonic distortion with any dc voltage in the H-bridges of the cascaded converter. The possible switching sequences of the converter are studied and, depending on the actual dc voltage values, their desired values are achieved. Simulation results are shown in order validate the proposed technique working as a synchronous rectifier
New dental simulator for microsurgical training preliminary overview
Objective: To present a new simulator designed at the Minimally Invasive Surgery Centre (Cáceres) which offers an integral, effective and viable training system that can be used for learning microsurgical techniques. Study design: A square methacrylate block was used. Animal jaws were fixed to the sides by means of butterfly screws. This block also has a drainage tube to facilitate the escape of fluids. Results: Excellent results were obtained using this simulator in microsurgical suturing training in dental, Oral and Maxillofacial Surgery Conclusions: We believe that this simulator is an essential component in microsurgical training. It is an ethically and morally valid training method with which various suturing techniques can be practised before using live animals and before applying these to daily clinical practice
APOBEC3G mRNA expression in exposed seronegative and early stage HIV infected individuals decreases with removal of exposure and with disease progression
<p>Abstract</p> <p>Background</p> <p>APOBEC3G is an antiretroviral factor that acts by inducing G to A mutations. In this study, we examined the expression of APOBEC3G in uninfected HIV-1 exposed individuals at the time of their partner's diagnosis and one year later. We then compared this expression with that of infected individuals at different disease stages. APOBEC3G mRNA was measured in PBMCs from three groups: healthy controls with no known risk factor to HIV infection (n = 26), exposed uninfected individuals who had unprotected sex with their HIV+ partners for at least 3 months (n = 37), and HIV infected patients at various disease stages (n = 45), including 8 patients with low HIV viral loads < 10,000 copies/mL (LVL) for at least 3 years. Additionally, we obtained sequences from the env, gag, pol, nef, vif and the LTR of the patients' virus.</p> <p>Results</p> <p>Exposed uninfected individuals expressed higher APOBEC3G than healthy controls (3.86 vs. 1.69 relative expression units), and their expression significantly decreased after a year from the HIV diagnosis and subsequent treatment of their partners. Infected individuals showed a positive correlation (Rho = 0.57, p = 0.00006) of APOBEC3G expression with CD4+ T cell count, and a negative correlation with HIV viremia (Rho = -0.54, p = 0.00004). The percentage of G to A mutations had a positive correlation (Rho = 0.43, p = 0.0226) with APOBEC3G expression, and it was higher in LVL individuals than in the other patients (IQR 8.27 to 9.64 vs. 7.06 to 8.1, p = 0.0084). Out of 8 LVLs, 3 had hypermutations, and 4 had premature stop codons only in viral <it>vif</it>.</p> <p>Conclusion</p> <p>The results suggest that exposure to HIV may trigger APOBEC3G expression in PBMCs, in the absence of infection. Additionally, cessation of exposure or advanced disease is associated with decreased APOBEC3G expression.</p
Do the Historical Biogeography and Evolutionary History of the Digenean Margotrema spp. across Central Mexico Mirror Those of Their Freshwater Fish Hosts (Goodeinae)?
Host-parasite systems provide an ideal platform to study evolution at different levels, including codivergence in a historical biogeography context. In this study we aim to describe biogeographic and codivergent patterns and associated processes of the Goodeinae freshwater fish and their digenean parasite (Margotrema spp.) over the last 6.5 Ma (million years), identifying the main factors (host and/or hydrogeomorphology) that influenced the evolution of Margotrema. We obtained a species tree for Margotrema spp. using DNA sequence data from mitochondrial and nuclear molecular markers (COI and ITS1, respectively) and performed molecular dating to discern divergence events within the genus. The dispersal-extinction-cladogenesis (DEC) model was used to describe the historical biogeography of digeneans and applied to cophylogenetic analyses of Margotrema and their goodeine hosts. Our results showed that the evolutionary history of Margotrema has been shaped in close association with its geographic context, especially with the geological history of central Mexico during the Pleistocene. Host-specificity has been established at three levels of historical association: a) Species-Species, represented by Xenotaenia resolanae -M. resolanae exclusively found in the Cuzalapa River Basin; b) Species-Lineage, represented by Characodon audax-M. bravoae Lineage II, exclusive to the Upper and Middle Mezquital River Basin, and c) Tribe-Lineage, including two instances of historical associations among parasites and hosts at the taxonomical level of tribe, one represented by Ilyodontini-M. bravoae Lineage I (distributed across the Ayuquila and Balsas River Basins), and another comprised of Girardinichthyini/Chapalichthyini-M. bravoae Lineage III, found only in the Lerma River Basin. We show that the evolutionary history of the parasites is, on several occasions, in agreement with the phylogenetic and biogeographic history of their hosts. A series of biogeographic and host-parasite events explain the codivergence patterns observed, in which cospeciation and colonisation via host-switching and vicariant plus dispersal events are appreciated, at different times during the diversification history of both associates, particularly during the Pleistocene.Facultad de Ciencias Naturales y Muse
The participation of women in the Sports Department of the community of Madrid and the Madrid sports federations
Hasta no hace mucho tiempo, las mujeres se han visto relegadas a la esfera privada, es decir, al trabajo de la familia
y del hogar y, aunque en los últimos años se ha producido una incorporación paulatina a los distintos ámbitos de
la vida pública, todavía se observan diferencias importantes de participación entre la femenina y la masculina en
muchos de ellos. Con este artículo se pretende dar una visión general de lo que ocurre en un sector especifico del
mundo de la actividad física y del deporte, como es el de la gestión y dirección del deporte mediante el estudio de
las federaciones deportivas madrileñas y de la Dirección General de Deportes de la Comunidad de Madrid.
Los resultados demuestran que, aunque la situación está cambiando, los puestos la participación de las mujeres
dentro de la gestión de las federaciones es mínima, destacando el hecho, de que a mayor nivel de responsabilidad,
menor es la participación femenina
Evolution of the Agri-Food Chain Concept in the 21st Century: The Taro Case
Objective: To conceptualize the agri-food chain and analyze its evolution during the 21st century: The case of taro.
Design/methodology/approach: A systematic bibliography review was carried out in journals specialized in agri-food chains, value chains, logistics, and supply chains; these studies sustained qualitatively and based on a study case, the agri-food taro chain.
Results: Currently, the agri-food chains include processes such as the supply of inputs and necessary facilities, production, transformation, distribution, and commercialization, among other services. The study of agri-food chains has effects on globalization in a more demanding macroeconomic setting. The growing industrialization of products generates added value and provides a competitive advantage to the agents that integrate the chain. However, the agri-food malanga chain presents disadvantages in its production, distribution, and storage processes, due to the disintegration of its links.
Limitations of the study/implications: Scarce information exists on the malanga agri-food chain.
Findings/conclusions: The agri-food chain concept has had a continuous evolution. Its structure aims to benefit each one of the chain links; compromises are generated to produce based on need. The integration and experience gained allow the strengthening and importance assessment of each link, improving revenues. Also, agri-food chains´ incorporation makes them more sensitive to climate change, nutrition, and sustainability.Objective: To conceptualize the agri-food chain and analyze its evolution during the 21st century: The case of taro.
Design/methodology/approach: A systematic bibliography review was carried out in journals specialized in agri-food chains, value chains, logistics, and supply chains; these studies sustained qualitatively and based on a study case, the agri-food taro chain.
Results: Currently, the agri-food chains include processes such as the supply of inputs and necessary facilities, production, transformation, distribution, and commercialization, among other services. The study of agri-food chains has effects on globalization in a more demanding macroeconomic setting. The growing industrialization of products generates added value and provides a competitive advantage to the agents that integrate the chain. However, the agri-food malanga chain presents disadvantages in its production, distribution, and storage processes, due to the disintegration of its links.
Limitations of the study/implications: Scarce information exists on the malanga agri-food chain.
Findings/conclusions: The agri-food chain concept has had a continuous evolution. Its structure aims to benefit each one of the chain links; compromises are generated to produce based on need. The integration and experience gained allow the strengthening and importance assessment of each link, improving revenues. Also, agri-food chains´ incorporation makes them more sensitive to climate change, nutrition, and sustainability
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