196,502 research outputs found
Examples of threefolds with Kodaira dimension or
No full textWe construct three nonsingular threefolds X, X' and X''. X has Kodaira dimension =
\kappa(X)=1 and its m-canonical transformation \varphi_{|mK_X|} has the following property:
the minimum integer number m_0, such that the dimension of the image dim \varphi_{|mK_X|}(X) = \kappa(X)
= 1 for m \geq m_0, it is given by m_0=32. X' and X'' have Kodaira dimension \kappa(X')=\kappa(X'')=2
and their m-canonical transformations have the properties: dim \varphi_{|mK_{X'}|}(X') = \kappa(X') = 2
if and only if m \geq 12, dim \varphi_{|mK_{X''}|}(X'') = \kappa(X'') = 2 if and only if m = 9, 10
or m \geq 12
A threefold with and
No full textWe construct a nonsingular threefold X with q_1=q_2=p_g=0 and P_2=2 whose m-canonical transformation \varphi_{|mK_X|} has the following properties
1) \varphi_{|mK_X|} has the generic fiber of dimension \geq 1, for 2 \leq m \leq 5;
2) it is generically a tranformation 2 : 1, for 6 \leq m \leq 8 and m=10;
3) it is birational for m=9 and m \geq 11
Gaps in the birationality of pluricanonical transformations.
No full textWe construct a nonsingular threefold X of general
type as a desingularization of a double space of degree 10 in P^4, of
which an affine equation is
t^2+f_{10}(x,y,z)=0. X has the birational
invariants q_1=q_2=p_g=P_2=P_3=0,P_4=1 and its
m-canonical
transformation \varphi_{|mK_X|}, where K_X is a canonical divisor on X,
has fibers that are generically finite sets if and only if m \geq 16, and it
is birational if and only if m=23 or m \geq 27
Threefolds with Kodaira dimension 0 or 3
No full textUsing the theory of adjoints and pluricanonical adjoints, we construct three nonsingular threefolds, as desingularizations of degree six hypersurfaces in \P^4, having the irregularities q_1=q_2=0 and the following periodical sequences of plurigenera respectively
(p_g,P_2,P_3,...,P_m,...)=(0,0,1,0,0,1,...), (0,0,0,1,0,0,0,1,...), (0,0,0,0,1,0,0,0,0,1,...).
In the Appendix, starting from the second above-mentioned example, we construct a threefold of general type with q_1=q_2=0, p_g=1, P_2=2 whose m-canonical transformation is birational if and only if m \geq 11
Estrous cycle and ovulation time in native goats
No full textCONTENIDO
Editorial
González Stagnaro, Carlos
Morfología del tracto genital de los pequeños rumiantes
Morphology of the genital system of small ruminants
Nuñez M., Quiterio
Cambios ováricos durante el ciclo estrual en cabras criollas
Changes of the ovary during the estrous cycle of native goats
González Stagnaro, Carlos y Madrid Bury, Ninoska
Ciclo estrual y momento de ovulación en cabras criollas
Estrous cycle and ovulation time in native goats
González Stagnaro, Carlos y Madrid Bury, Ninoska
Neuroendocrinología de la reproducción en el caprino
Reproductive reuroendocrinology in goats
Chemineau, P. y Delgadillo, J. A.
Aspectos característicos de la fisiología de la oveja
Some aspects of the reproductive physiology of the ewes
López Sebastián, A.; Santiago Moreno, J.; De Bulnes, A.G. y García López, M.
Comportamiento reproductivo en ovinos tropicales
Reproductive performance in tropical sheep
De Cambellas, Josefina B.
Comportamiento reproductivo de la cabra en los trópicos
Reproductive performance of the goats in the tropics
García B., O. y García B., E.
Endocrinología de cabras criollas ovidectomizadas y mestizas en zonas semiáridas de Venezuela
Endocrine profiles of ovidectomized native and crossbred goats in semiarid zones of Venezuela
Leyva Ocariz, H.; Stabenfeldt, G. H.; Munro, C.; Arteaga, M.; Orduz, B.; Díaz, M. y Hernández, I.
Mensajes Institucionales99 - 112bimestralNivel analític
The impact of temporal aggregation of solid precipitation measurements on the correction for wind induced undercatch.
No full textSolid precipitation measurements are strongly affected by wind-induced errors, due to the aerodynamic response of catching type gauges. The snowflakes deviate from their undisturbed trajectories due to the alteration of the airflow field around the body of the gauge and the corresponding developed turbulence. The resulting effect consists in a certain degree of undercatch, which is a function of the undisturbed wind velocity.
Windshields have been developed to provide reference solid precipitation measurements in field test sites, e.g. the Double Fence Intercomparison Reference (DFIR), or employed in operational measurements with the aim of reducing the effect of the wind, such as the Single Alter shield (SA).
Various authors have studied wind-induced errors from different point of view (theoretical, numerical and experimental). The available data from CFD and field tests studies (Colli, 2015; Wolff,2 2015) lead to determine the Collection Efficiency (CE) of the gauges, which is a relation between the solid precipitation undercatch and the wind speed, and consequently the transfer function (TF) used to correct the wind-induced errors.
Since solid precipitation records, and the associated wind speed data, are commonly stored with a quite coarse resolution in time (60 or 30 minutes), we investigated the impact of the aggregation scale on the accuracy of snowfall data when corrected by using the transfer functions. From the WMO SPICE (Solid Precipitation Intercomparison Experiment) field campaign, we selected a number of snowfall events from the Marshall Field test site (Colorado, USA) during the winter seasons from 2013 to 2015. Three Geonor weighing gauges with different configurations (unshielded, Single Alter shielded and DFIR as the reference) recorded the snowfall rates. Both precipitation and wind speed data are quality controlled and provided with the time resolution of 1 minute.
The CE and the respective Transfer Function have been derived from the selected number of snowfall events. From the reference (DFIR) snowfall data and the wind speed values at the time resolution of 1 min, we derived synthetic sequences of wind affected snowfall rates using the derived CE curves at the coarser time resolution. The synthetic observations have been obtained both for the Unshielded and SA gauges.
Using the TF, the synthetic dataset has been corrected using different aggregation intervals (5, 15 and 30 minutes). It is observed that, by increasing the aggregation interval of both snow and wind data, the efficacy of the correction decreases, indicating that high resolution snowfall and wind measurements are essential to ensure high quality snowfall measurements
Is more competition better? Retail electricity prices and switching rates in the European Union.
No full textThe European Union (EU) promotes the liberalization of retail electricity markets to achieve lower prices, diversified offers, greater customer participation, and sustainable consumption behaviours. While retail competition has been a reality in most EU member states, most studies find that retail competition is suitable for large customers, but the evidence on small customers is inconclusive. We analyze data on electricity prices and switching rates in 27 EU member states and the UK from 2000 to 2019. We find that retail competition is associated with lower prices and that the effect of full liberalization is greater than that of partial liberalization
Calibration of non-catching type rain gauges: preliminary tests on an optical disdrometer
No full textThe last WMO Field Intercomparison on Precipitation Intensity highlights that non-catching type rain gauges show limited performance, in terms of precision and accuracy of the measurements, when compared to the traditional catching type rain gauges.
Moreover, the performance of these instruments differ significantly from each other, this fact suggests that the lack of a standardized calibration procedure leads to different behaviour in field measurements.
Building on these results and in order to understand the causes of this behaviour, the CIMO Lead Centre on Precipitation Intensity has developed a rain drop generator, able to reproduce drops with various diameters.
The Thies LPM disdrometer has been tested using the rain drop generator and the results are presented in terms of total number of droplets detected by the instrument, droplets per diameter class, total accumulation volume and measured rainfall intensity.
Preliminary results show that the disdrometer detects a larger number of droplets than those actually generated. Most of them are attributed by the instrument to the lower diameter class, and have a low impact in the total volume account or rainfall intensity estimation, but could affect the shape of the Drop Size Distribution (DSD) provided by the instrument. Moreover, in many cases it has been found that the disdrometer assigns most of the real droplets to the upper diameter class, therefore resulting in a significant overestimation of the rainfall amount and intensity.
These results, although still preliminary, reveal that a standardized and rigorous calibration procedure is needed for the non-catching type rain gauges to foster more reliable and comparable measurements
Velocity and concentration profiles of saline and turbidity currents flowing in a straight channel under quasi-uniform conditions
No full textWe present a series of detailed experimental observations of saline and turbidity currents flowing
in a straight channel. Experiments are performed by continuously feeding the channel with a dense mixture
until a quasi-steady configuration is obtained. The flume, 12 m long, is characterized by a concrete fixed bed
with a uniform slope of 0.005. Longitudinal velocity profiles are measured in ten cross sections, 1 m apart,
employing an ultrasound Doppler velocity profiler. We also measure the density of the mixture using a rake
of siphons sampling at different heights from the bottom in order to obtain the vertical density distributions in
a cross section where the flow already attained a quasi-uniform configuration. We performed 27 experiments
changing the flow discharge, the fractional excess density, the character of the current (saline or turbidity)
and the roughness of the bed in order to observe the consequences of these variations on the vertical velocity
profiles and on the overall characteristics of the flow. Dimensionless velocity profiles under quasi-uniform
flow conditions were obtained by scaling longitudinal velocity with its depth averaged value and the vertical
coordinate with the flow thickness. They turned out to be influenced by the Reynolds number of the flow, by the
relative bed roughness, and by the presence of sediment in suspension. Unexpectedly, the densimetric Froude
number of the current turned out to have no influence on the dimensionless velocity profiles
Assessing rainfall intensity calculation algorithms for tipping-bucket rain gauges at a field test site.
No full textFrom May to September 2013, a selected number of observed rain events has been selected in order to assess the effectiveness of the calculation algorithms employed to calculate the rainfall intensity (RI) for two tipping-bucket rain gauges (TBRs). For its accuracy and precision, a drop counter catching-type gauge has been selected as the working reference to perform comparisons with the two operational tipping-bucket rain gauges. The drop-counter field data have a time resolution of 10 s, while the actual time of tip is recorded for both TBRs; however, the time resolution employed for the calculation of the rainfall intensity is equal to 1 minute. Although the two TBRs have the same sensitivity of 0.1 mm, they are based on a different functioning system. One is a traditional TBR with a single bucket, while the other is characterized by two layers of buckets. The algorithm employed in the calculation of the rainfall intensity for both the TBRs is based on the assumption that the nominal volume of each bucket is uniformly distributed over the inter-tip period. In order to estimate the accuracy, a synthetic sequence of tip-times of an ideal TBR was derived from the drop-counter data for each selected event. The sensitivity of this ideal TBR is the same of the other two TBRs and equal to 0.1 mm. The performance of the two real TBRs were estimated from the direct comparison with the working reference. From the comparison between the real and the ideal TBRs, in terms of deviations from the average value, the effectiveness of the inter-tip algorithm is shown to be relevant up to mid-low values of rainfall intensity, while it decreases with further increasing the RI
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