The Sperm-Class Analyser was validated for assessing morphometric parameters of the head and midpiece of unwashed and washed human ejaculated spermatozoa from volunteers providing a wide range of semen quality. A higher proportion of sperm could be assessed (86% fresh semen and 75% washed sperm) if Hemacolor staining was used rather than DiffQuik (80 and 73%) or Papanicolaou (78 and 68%). Different stains employed different fixatives and the area, length, width and perimeter of the sperm head was significantly larger for washed sperm stained by Hemacolor and DiffQuik. Acrosomal area ranged from 48 to 51% of the sperm head area and this percentage was larger for washed sperm stained with DiffQuik. Sperm at the end of the slide, distant from the initial semen droplet, were larger in area and perimeter than those at that site or in the middle. The high precision and reproducibility of the equipment required assessing only 50 sperm on the slide. Far greater variation was found in head width, relative acrosomal area and midpiece width between different slides prepared from the same ejaculate, highlighting the inherent variability within the ejaculate and smear preparation, and requiring more than one slide to be assessed.
20Droughts are among the most important natural disasters, particularly in the arid and 21 semiarid regions of the world. Proper management of droughts requires knowledge of the 22 expected frequency of specific low magnitude precipitation totals for a variety of durations. 23Probabilistic approaches have often been used to estimate the average recurrence period of 24 a given drought event. However, probabilistic model fitting by conventional methods, such 25 as product moment or maximum likelihood in areas with low availability of long records 26 often produces highly unreliable estimates. Recognizing the need for adequate estimates of 27 return periods of severe droughts in the arid and semiarid region of Chile, a regional 28 frequency analysis method based on L-moments (RFA-LM) was used for estimating and 29 mapping drought frequency. Some adaptations to the existing procedures for forming 30 homogeneous regions were found necessary. In addition, a new 3-parameter distribution, 31 the Gaucho, which is a special case of the 4-parameter Kappa distribution, was introduced, 32 and the analysis procedure was improved by the developments of two new software tools 33 named L-RAP, to perform the RFA-LM analysis, and L-MAP, to map the resulting drought 34 maps. Eight homogeneous sub-regions were delineated using the Gaucho distribution and 35 used to construct return period maps for drought events with 80% and 40% precipitation of 36 the normal. The study confirms the importance of a sub-regional homogeneity test, and the 37 usefulness of the Gaucho distribution. The RFA-LM showed that droughts with a 40% 38 precipitation of the normal have return periods that range from four years at the northern 39 arid boundary of the study area to 22 years at the southern sub-humid boundary. The results 40 demonstrate the need for different thresholds for declaring a drought than those currently in 41 use for drought characterization in north-central Chile. 42 43
This paper provides evidence on the degree and patterns of intergenerational income and educational mobility in urban
Resumen
Este paper proporciona evidencia sobre el grado y los patrones de movilidad intergeneracional del ingreso y la educación en zonas urbanas de Chile. Encontramos elasticidades intergeneracionales del ingreso en el Gran Santiago
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