A plausible energy source and structure for quasi-stellar objects

If a collision of two large, massive, fast gas clouds occurs, their kinetic energy is converted to radiation in a pair of shock fronts at their interface. The resulting structure is described, and the relevance of this as a radiation source for quasi-stellar objects is considered

On the He(plus) triplet line intensities

The theoretical calculations of helium triplet line strengths, including collisional enhancement, are compared to astronomical observations. Both are plotted on an I(10830)/I(5876) vs I(5876)/I(4471) plane. It appears that the theory of helium triplet line strengths agrees with present observations, and that the question of an additional depopulation mechanism for the 2 3S population is probably predicted correctly within 30%

The high-excitation planetary nebulae: NGC 3918 and IC 2448

International Ultraviolet Exploration observations of NGC 3918 and IC 2448 are presented. Combining these observations with data in the optical range and computed model structure, the chemical composition for these objects is derived. For NGC 3918 log C = -3.02, log N = -3.61 and log 0 = -3.22; while for IC 2448 log C = -3.44, log N = -81 and log 0 = 3.54

The warm interstellar medium around the Cygnus Loop

Observations of the oxygen lines [OII]3729 and [OIII]5007 in the medium immediately beyond the Cygnus Loop supernova remnant were carried out with the scanning Fabry-P\'erot spectrophotometer ESOP. Both lines were detected in three different directions - east, northeast and southwest - and up to a distance of 15 pc from the shock front. The ionized medium is in the immediate vicinity of the remnant, as evinced by the smooth brightening of both lines as the adiabatic shock transition (defined by the X-ray perimeter) is crossed. These lines are usually brighter around the Cygnus Loop than in the general background in directions where the galactic latitude is above 5 degrees. There is also marginal (but significant) evidence that the degree of ionization is somewhat larger around the Cygnus Loop. We conclude that the energy necessary to ionize this large bubble of gas could have been supplied by an O8 or O9 type progenitor or the particles heated by the expanding shock front. The second possibility, though highly atractive, would have to be assessed by extensive modelling.Comment: 18 pages, 8 figures, ApJ 512 in pres

Recombination spectrum and reddening in NGC 1068

Measurements of the emission-line intensities of NGC 1068 have been made over the wavelength range extending from λ_(rest) = 1216 Å to 1.875 μm. The data, plus other available emission-line data, can be explained in terms of a simple model where the emission lines are formed in an H II region, and the line ratios are consistent with those predicted by standard radiative recombination theory and reddening corresponding to E_(B-v) = 0.4 mag. The continuum flux is seen to consist of a galaxy component plus a nonstellar component which dominates the observed flux in the ultraviolet. The observed ultraviolet continuum does not show an absorption dip caused by the interstellar 2200 A feature nor does it contain enough energy to power the observed infrared flux

Are anthropogenic factors affecting nesting habitat of sea turtles? The case of Kanzul beach, Riviera Maya-Tulum (Mexico)

Marine coast modification and human pressure affects many species, including sea turtles. In order to study nine anthropogenic impacts that might affect nesting selection of females, incubation and hatching survival of loggerhead (Caretta caretta) and green turtle (Chelonia mydas), building structures were identified along a 5.2 km beach in Kanzul (Mexico). A high number of hotels and houses (88; 818 rooms), with an average density of 16.6 buildings per kilometer were found. These buildings form a barrier which prevents reaching the beach from inland, resulting in habitat fragmentation. Main pressures were detected during nesting selection (14.19% of turtle nesting attempts interrupted), and low impact were found during incubation (0.77%) and hatching (4.7%). There were three impacts defined as high: beach furniture that blocks out the movement of hatchlings or females, direct pressure by tourists, and artificial beachfront lighting that can potentially mislead hatchlings or females. High impacted areas showed lowest values in nesting selection and hatching success. Based on our results, we suggest management strategies to need to be implemented to reduce human pressure and to avoid nesting habitat loss of loggerhead and green turtle in Kanzul, Mexico

DESARROLLO DE UNA TÉCNICA DE PCR PARA DETECTAR VIRUS MAEDI-VISNA (VMV) LIBRE E INTEGRADO EN CÉLULAS Y APLICACIÓN AL ESTUDIO DE LA INFECCIÓN CALOSTRAL EN CORDEROS

A PCR test was developed to detect cell-free and cell-integrated maedi-visna virus (MVV), its degree of agreement with an LTR-PCR and an antibody ELISA of proven efficacy was analysed in colostrum samples and all three tests were employed to investigate colostral MVV infection in lambs. Primers were designed from gag gene sequences homologous in the six MVV sequences presently in GenBank, and amplify a 744bp frag- ment. 856 assays were carried out including 283 with the new gag-PCR and a good correlation was observed between the presence of cell-free and -integrated MVV. This is novel and questions the relative role of the two viral forms in MVV infection. Instead, the correlation between PCR and ELISA results was only moderate and provided further evidence that MVV detection may fail in infected animals. The PCRs detected MVV in colostrum ingested by most lambs that later tested seropositive at 10 months-old and additionally, the gag-PCR and to a lesser extent the LTR-PCR, detected MVV in colostrum taken by lambs seronegative at 10 months-old most likely because they ingested less colostrum. As well as providing further evidence of the positive association between MVV infection and volume of MVV-containing colostrum ingested, this result suggest that the gag-PCR developed is more sensitive than the LTR-PCR used in this study.Se desarrolló una técnica de PCR para detectar virus maedi-visna (VMV) libre e integrado en células, se estudio su concordancia con una PCR-LTR y un ELISA de anticuerpos de probada eficacia en muestras de calostro de ovejas infectadas y se emplearon los tres ensayos para investigar la infección calostral por VMV en corderos. Los cebadores se diseñaron en una región conservada en las seis secuencias de VMV disponibles en GenBank y amplifican un producto de 744 pares de bases (pb). Se realizaron 856 ensayos incluidos 283 con la gag, e independientemente de la PCR empleada se observó una buena correlación entre la presencia de virus libre e integrado y esto es novedoso y plantea la importancia relativa de ambas formas víricas en la infección por VMV. En cambio, la concordancia entre las PCRs y el ELISA fue solo moderada y se corroboró que a menudo no se detecta VMV en animales seropositivos. Las PCRs detectaron VMV en la mayoría de calostros ingeridos por corderos que posteriormente a los 10 meses de edad fueron seropositivos y además la gag y en menor medida la LTR, también en algunos calostros de corderos que fueron seronegativos, probablemente porque tomaron menos cantidad de calostro que los seropositivos. Además de aportar mas evidencia de la asociación positiva entre la infección por VMV y el volumen de calostro con VMV ingerido, este resultado sugiere que la gag es más sensible que la LTR en esta matriz