The Butcher--Oemler effect at z~0.35: a change in perspective

The present paper focuses on the much debated Butcher-Oemler effect: the increase with redshift of the fraction of blue galaxies in clusters. Considering a representative cluster sample made of seven group/clusters at z~0.35, we have measured the blue fraction from the cluster core to the cluster outskirts and the field mainly using wide field CTIO images. This sample represents a random selection of a volume complete x-ray selected cluster sample, selected so that there is no physical connection with the studied quantity (blue fraction), to minimize observational biases. In order to statistically assess the significance of the Butcher-Oemler effect, we introduce the tools of Bayesian inference. Furthermore, we modified the blue fraction definition in order to take into account the reduced age of the universe at higher redshifts, because we should no longer attempt to reject an unphysical universe in which the age of the Universe does depend on redshift, whereas the age of its content does not. We measured the blue fraction from the cluster center to the field and we find that the cluster affects the properties of the galaxies up to two virial radii at z~0.35. Data suggest that during the last 3 Gyrs no evolution of the blue fraction, from the cluster core to the field value, is seen beyond the one needed to account for the varying age with redshift of the Universe and of its content. The agreement of the radial profiles of the blue fraction at z=0 and z~0.35 implies that the pattern infall did not change over the last 3 Gyr, or, at least, its variation has no observational effect on the studied quantity.Comment: MNRAS, in pres

De la cartografía de la vegetación a la cartografía ecológica

Fil: Quintana, Victor G.

El papel del lenguaje en la vida individual y social.

Sin resumenCommunication in the sense of ideas transmission is non-existing. Ideas are untransferable. Language facilitates the interchange of ideas by its very nature, insofar as being an arbitrary sign and in virtue of its three dimensions: the syntactical, the semantie and the pragmatic. The decoding of language on the recipient is an act of sense creation: material sense, figurative, formal and real (universal or particular, collective or distributive, etc. ). Ihe role of language, then, is to stimulate the receiver so that he can begin to create sense. Didáctica, 8, 197-225. Servicio de Publicaciones UCM. Madrid. 1996 198 Guillermo Quintan

Blocked algorithms for the reduction to Hessenberg-triangular form revisited

We present two variants of Moler and Stewart's algorithm for reducing a matrix pair to Hessenberg-triangular (HT) form with increased data locality in the access to the matrices. In one of these variants, a careful reorganization and accumulation of Givens rotations enables the use of efficient level 3 BLAS. Experimental results on four different architectures, representative of current high performance processors, compare the performances of the new variants with those of the implementation of Moler and Stewart's algorithm in subroutine DGGHRD from LAPACK, Dackland and Kågström's two-stage algorithm for the HT form, and a modified version of the latter which requires considerably less flop

Fruit Bruising in Solo Papaya: Quality Ripening and Disinfestation

Carica papaya L. cv. Solo fruit were taken off different points in a commercial postharvest handling system to determine where in the handling chain mechanical injury occurred and what caused it. "Green islands" (GI) apparently induced by mechanical injury were seen in all fruit and the occurrence increased as fruit moved through the handling system. This type of injury was only seen in fruit taken from the sides but not in fruit taken from the center of the field bins. To duplicate the GI seen in fruit from the handling system, fruit at different stages of ripeness (5 to 50% yellow) were dropped from different heights (0 to 100 cm) onto a smooth steel plate. Injury seen did not resemble the GI seen in fruit from the handling system. Fruit (10 to 15% yellow) were then dropped on different grades of sandpaper (220 mesh to 36 mesh) from a height of 10 cm. GI similar to those seen on fruit from the handling system were observed in fruit dropped on all grades of sandpaper. Fruit dropped on fine sandpaper had a higher severity of GI than those dropped on coarse sandpaper. A lesser severity of GI was seen in 40 to 50% yellow fruit dropped onto 150 mesh sandpaper from a height of 10 cm compared to greener fruit. These results suggest that abrasion damage was more important than impact damage in Solo papaya fruit. Respiration rate and ethylene production did not significantly increase when fruit were dropped onto a smooth steel plate or sandpaper from a height of 10 cm. Similar results were seen even when the number of drops were increased to eight. Washing off the latex did not affect the severity of GI. Heating fruit at 48°C for ~ 6 hours or until fruit core temperature (FCT) reached 47.5°C aggravated the severity of GI. Delaying the time of heating from the time of dropping did not significantly lower the severity of GI, except for fruit heated 24 hours after dropping. Heating also resulted in fruit that had a rubbery texture. Waxing fruit alleviated the severity of GI and it did not matter whether waxing was done before or after the heat treatment

Prevalence of thoracic vertebral malformations in french bulldogs, pugs and english bulldogs with and without associated neurological deficits

Congenital vertebral malformations are common incidental findings in small breed dogs. This retrospective observational study evaluated the type and prevalence of thoracic vertebral malformations in 171 neurologically normal and 10 neurologically abnormal screw-tailed brachycephalic dogs. Neurologically normal dogs underwent CT for reasons unrelated to spinal disease, while affected dogs underwent MRI. Imaging studies were reviewed and vertebral malformations including hemivertebrae, block vertebrae, transitional vertebrae, and spina bifida were documented. The group of clinically normal dogs consisted of 62 French bulldogs, 68 Pugs and 41 English bulldogs. The group of affected dogs consisted of one French bulldog and nine Pugs. Overall, 80.7% of neurologically normal animals were affected by at least one vertebral malformation. There was a significant influence of breed, with thoracic vertebral malformations occurring more often in neurologically normal French bulldogs (P < 0.0001) and English bulldogs (P = 0.002). Compared to other breeds, hemivertebrae occurred more often in neurologically normal French bulldogs (93.5%; P < 0.0001 vs. Pugs; P = 0.004 vs. English bulldogs) and less often in neurologically normal Pugs (17.6%; P = 0.004 vs. English bulldogs). Neurologically normal Pugs were more often diagnosed with transitional vertebrae and spina bifida compared to other breeds (P < 0.0001 for both malformations). Of Pugs included in the study, 4.7% were diagnosed with clinically relevant thoracic vertebral malformations. When compared to the general veterinary hospital population, this was significantly more than the other two breeds (P = 0.006). This study indicates that thoracic vertebral malformations occur commonly in neurologically normal screw-tailed brachycephalic dogs. While hemivertebrae are often interpreted as incidental diagnostic findings, they appear to be of greater clinical importance in Pugs compared to other screw-tailed brachycephalic breeds