Spectroscopic observations of comet Kohoutek (1973f)

Coude spectrograms of comet Kohoutek obtained with the ESO 152-cm telescope in La Silla, Chile are discussed. Emission features of the C3, CH, and CO(+) molecules found in the blue region of the spectrum are considered along with measured emissions in the visual region of the spectrum. The observational and cometary data are given in tabular form

Observing facilities at the European Southern Observatory (ESO) in Chile for cometary observations

The (ESO) is located on the mountain La Silla (geographical coordinates: 4h42m55s10 west, -29 deg 15' 25".8 south, 2400 m elevation. The size of the telescopes ranges from a 40 cm Astrograph to the 3.6 m Richey-Chretien telescope. Future telescopes are discussed: a 2.2 m RC-Telescope which will be identical with the German 2.2 m telescope on Calor Alto in SE-Spain, and a 3.5 m telescope, the New Technology Telescope. In addition to these telescopes, a great number of auxiliary instrumentation are operational. Because ESO has to serve all requests of the visiting astronomers these instruments are designed for very different applications. The telescopes and auxiliary instruments that are especially suited for cometary observations are discussed. The dicussion is divided into three parts: photography, photometry-polarimetry and spectroscopy

Expression of MHC II genes

Innate and adaptive immunity are connected via antigen processing and presentation (APP), which results in the presentation of antigenic peptides to T cells in the complex with the major histocompatibility (MHC) determinants. MHC class II (MHC II) determinants present antigens to CD4+ T cells, which are the main regulators of the immune response. Their genes are transcribed from compact promoters that form first the MHC II enhanceosome, which contains DNA-bound activators and then the MHC II transcriptosome with the addition of the class II transactivator (CIITA). CIITA is the master regulator of MHC II transcription. It is expressed constitutively in dendritic cells (DC) and mature B cells and is inducible in most other cell types. Three isoforms of CIITA exist, depending on cell type and inducing signals. CIITA is regulated at the levels of transcription and post-translational modifications, which are still not very clear. Inappropriate immune responses are found in several diseases, including cancer and autoimmunity. Since CIITA regulates the expression of MHC II genes, it is involved directly in the regulation of the immune response. The knowledge of CIITA will facilitate the manipulation of the immune response and might contribute to the treatment of these diseases

Newly discovered halos and outer features around southern planetary nebulae

We have used the SuperCOSMOS H-alpha Survey to look for faint outer structures such as halos, ansae and jets around known planetary nebulae across 4000 square degrees of the southern Milky Way. Our search will contribute to a more accurate census of these features in the Galactic PN population. Candidate common-envelope PNe have also been identified on the basis of their microstructures. We also intend to determine more reliable distances for these PNe, which should allow a much better statistical basis for the post-AGB total mass budget. Our survey offers fresh scope to address this important issue.Comment: 2 pages, 1 figure. To be published in Planetary Nebulae: an Eye to the Future, Proceedings of IAU Symposium 283, held in Puerto de la Cruz, Tenerife, Spain, July 25-29 201

Optically Thick Radio Cores of Narrow-Waist Bipolar Nebulae

We report our search for optically thick radio cores in sixteen narrow-waist bipolar nebulae. Optically thick cores are a characteristic signature of collimated ionized winds. Eleven northern nebulae were observed with the Very Large Array (VLA) at 1.3 cm and 0.7 cm, and five southern nebulae were observed with the Australia Telescope Compact Array (ATCA) at 6 cm and 3.6 cm. Two northern objects, 19W32 and M 1-91, and three southern objects, He 2-25, He 2-84 and Mz 3, were found to exhibit a compact radio core with a rising spectrum consistent with an ionized jet. Such jets have been seen in M 2-9 and may be responsible for shaping bipolar structure in planetary nebulae.Comment: 29 pages, accepted for publication in Ap

Investigating the temporal trends in PAH, PCB and OCP concentrations in Hartbeespoort Dam, South Africa, using semipermeable membrane devices (SPMDs)

The seasonal variability of persistent organic pollutants in Hartbeespoort Dam, South Africa, was investigated using semipermeable membrane devices (SPMDs) as passive samplers. Freely dissolved waterborne  polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were sampled to investigate  seasonal changes in their concentrations. Exposure of the passive  samplers was done for 14 days at the same sampling site in each of the four seasons of the year, in 2011. The SPMD-derived analyte amounts  enabled the calculation of time-weighted averages of free dissolved  waterborne levels of the contaminants. Concentrations ranged from 30.0 ng·l-1 to 51.5 ng·l-1 for PAHs, 38 pg l-1 to 150 pg·l-1 for PCBs, 9.2 to 10.4 ng·l-1 for HCHs and 0.3 to 0.8 ng·l-1 for DDTs, respectively. It was also  noted that the winter season generally exhibited higher contaminant  concentrations for most compounds studied, which likely reflects the  seasonality of their atmospheric deposition. An attempt was also made to identify possible sources of PAH contaminants in the dam by examining PAH ratios. These diagnostic ratios were inclined towards pyrogenic sources of pollution, except for the winter season where both pyrogenic and  petrogenic sources likely contribute to the contamination pattern.Keywords: Hartbeespoort dam, persistent organic pollutants,  semipermeable membrane devices, water-dissolved concentrations, temporal trends

Microcystin-RR Like Toxin Identified in the Cyanobacterium Anabaena flos-aquae Strain CCAP 1403/13B Culture

Cyanobacteria abound in freshwaters in Ghana, including those used for the supply of drinking water. However, there have been no studies on their toxicity, the toxins they produce and their attending public health effects. As part of research activities to identify cyanobacteria and cyanotoxins associated with four reservoirs (Weija, Kpong, Owabi and Barekese), used for the production of drinking water in Ghana, Anabaena flos-aquae, a toxic cyanobacterium, was cultured in the laboratory with the objective of identifying potential cyanotoxins that may be associated with some of the cyanobacteria commonly found in Ghanaian waters. Cultures were kept in agrowth chamber with continuous illumination at 20 ìmol photon/m2/s and constant aeration at a temperature of 25 oC. High pressure liquid chromatography (HPLC) analysis of extract from the culture of Anabaena flos-aquae strain CCAP 1403/13B produced a toxin with a retention time similar to microcystin-RR external standard. The concentration of microcystin-RR quantified from Anabaena flos-aquae was 10.6 ìg/g DW. The biomass of lyophilized cells extracted was 52 mg. Anabaena flos-aquae is mainly known to produce neurotoxins, notably anatoxin-a and anatoxin-a(s). Anabaena and Microcystis were reported to be responsible for the lethal poisoning of over 2000 people in Bahia, Brazil through drinking water which resulted in the death of 88 children fromgastro-enteritis over a period of 42 days

An Observational Limit on the Dwarf Galaxy Population of the Local Group

We present the results of an all-sky, deep optical survey for faint Local Group dwarf galaxies. Candidate objects were selected from the second Palomar survey (POSS-II) and ESO/SRC survey plates and follow-up observations performed to determine whether they were indeed overlooked members of the Local Group. Only two galaxies (Antlia and Cetus) were discovered this way out of 206 candidates. Based on internal and external comparisons, we estimate that our visual survey is more than 77% complete for objects larger than one arc minute in size and with a surface brightness greater than an extremely faint limit over the 72% of the sky not obstructed by the Milky Way. Our limit of sensitivity cannot be calculated exactly, but is certainly fainter than 25 magnitudes per square arc second in R, probably 25.5 and possibly approaching 26. We conclude that there are at most one or two Local Group dwarf galaxies fitting our observational criteria still undiscovered in the clear part of the sky, and a roughly a dozen hidden behind the Milky Way. Our work places the "missing satellite problem" on a firm quantitative observational basis. We present detailed data on all our candidates, including surface brightness measurements.Comment: 58 pages in AJ manuscript format; some figures at slightly reduced quality; accepted by the Astronomical Journa

X-rays and Protostars in the Trifid Nebula

The Trifid Nebula is a young HII region recently rediscovered as a "pre-Orion" star forming region, containing protostars undergoing violent mass ejections visible in optical jets as seen in images from the Infrared Space Observatory and the Hubble Space Telescope. We report the first X-ray observations of the Trifid nebula using ROSAT and ASCA. The ROSAT image shows a dozen X-ray sources, with the brightest X-ray source being the O7 star, HD 164492, which provides most of the ionization in the nebula. We also identify 85 T Tauri star and young, massive star candidates from near-infrared colors using the JHKs color-color diagram from the Two Micron All Sky Survey (2MASS). Ten X-ray sources have counterpart near-infrared sources. The 2MASS stars and X-ray sources suggest there are potentially numerous protostars in the young HII region of the Trifid. ASCA moderate resolution spectroscopy of the brightest source shows hard emission up to 10 keV with a clearly detected Fe K line. The best model fit is a two-temperature (T = 1.2x10^6 K and 39x10^6 K) thermal model with additional warm absorbing media. The hotter component has an unusually high temperature for either an O star or an HII region; a typical Galactic HII region could not be the primary source for such hot temperature plasma and the Fe XXV line emission. We suggest that the hotter component originates in either the interaction of the wind with another object (a companion star or a dense region of the nebula) or from flares from deeply embedded young stars.Comment: Accepted in ApJ (Oct, 20 issue, 2001

Disks around Hot Stars in the Trifid Nebula

We report on mid-IR observations of the central region in the Trifid nebula, carried out with ISOCAM in several broad-band infrared filters and in the low resolution spectroscopic mode provided by the circular variable filter. Analysis of the emission indicates the presence of a hot dust component (500 to 1000 K) and a warm dust component at lower temperatures (150-200 K) around several members of the cluster exciting the HII region, and other stars undetected at optical wavelengths. Complementary VLA observations suggest that the mid-IR emission could arise from a dust cocoon or a circumstellar disk, evaporated under the ionization of the central source and the exciting star of the nebula. In several sources the $9.7\mu m$ silicate band is seen in emission. One young stellar source shows indications of crystalline silicates in the circumstellar dust.Comment: 4 pages with 1 figur