Ultraviolet properties of individual hot stars in globular cluster cores. 1: NGC 1904 (M 79)

As part of an observing program using the International Ultraviolet Explorer (IUE) satellite to investigate the ultraviolet properties of stars found within the cores of galactic globular clusters with blue horizontal branches (HBs), we obtained three spectra of the cluster NGC 1904 (M 79). All three were long integration-time, short-wavelength (SWP) spectra obtained at the so called 'center of light' and all three showed evidence of sources within the IUE large aperture (21.4 in. by 10 in.). In this paper we shall describe the analysis of these spectra and present evidence that the UV sources represent individual hot stars in the post-HB stage of evolution

Lasset uns Menschen machen: Der biotechnische Fortschritt zwischen Manipulation und Therapie

Es wird ein Überblick über die gegenwärtigen gentechnischen Möglichkeiten und Gefahren gegeben. Am Beispiel der Präimplantationsdiagnostik wird gegenüber anthropotechnischen Positionen die zentrale soziale Dimension von Zeugung, Schwangerschaft und Geburt unterstrichen. Hintergrund der unterschiedlichen Einstellungen zum biotechnischen Fortschritt sind gegensätzliche ethische Grundpositionen, vor allem des Utilitarismus, wie er etwa von Singer zum Ausdruck gebracht wird, und der christlichen Sozialethik. Zur Rationalisierung der Entscheidungsfindung wird ein öffentliches Diskursverfahren als Instrument sozialer Kontrolle des technologischen Fortschritts vorgeschlagen.The following text represents the actual possibilities and the controversial points of the genetical progress. Particularly the preimplantationdiagnosis (PID) will be discussed under the social perspective of conception, pregnancy and birth. The different positions in the context of biotechnological progress culminate in the confrontation of utilitarianism (P. Singer) on the one and Christian social ethics on the other side. To come to a fair balance between the different positions it is for the political institutions urgent, to start a public discussion-program as an instrument of public social control

A New Framework for Network Disruption

Traditional network disruption approaches focus on disconnecting or lengthening paths in the network. We present a new framework for network disruption that attempts to reroute flow through critical vertices via vertex deletion, under the assumption that this will render those vertices vulnerable to future attacks. We define the load on a critical vertex to be the number of paths in the network that must flow through the vertex. We present graph-theoretic and computational techniques to maximize this load, firstly by removing either a single vertex from the network, secondly by removing a subset of vertices.Comment: Submitted for peer review on September 13, 201

Taming the Invisible Monster: System Parameter Constraints for Epsilon Aurigae from the Far-Ultraviolet to the Mid-Infrared

We have assembled new Spitzer Space Telescope Infrared Array Camera observations of the mysterious binary star Epsilon Aurigae, along with archival far-ultraviolet to mid-infrared data, to form an unprecedented spectral energy distribution spanning three orders of magnitude in wavelength from 0.1 microns to 100 microns. The observed spectral energy distribution can be reproduced using a three component model consisting of a 2.2+0.9/-0.8 Msun F type post-asymptotic giant branch star, and a 5.9+/-0.8 Msun B5+/-1 type main sequence star that is surrounded by a geometrically thick, but partially transparent, disk of gas and dust. At the nominal HIPPARCOS parallax distance of 625 pc, the model normalization yields a radius of 135+/-5 Rsun for the F star, consistent with published interferometric observations. The dusty disk is constrained to be viewed at an inclination of i > 87 deg, and has effective temperature of 550+/-50 K with an outer radius of 3.8 AU and a thickness of 0.95 AU. The dust content of the disk must be largely confined to grains larger than ~10 microns in order to produce the observed gray optical-infrared eclipses and the lack of broad dust emission features in the archival Spitzer mid-infrared spectra. The total mass of the disk, even considering a potential gaseous contribution in addition to the dust that produces the observed infrared excess, is << 1 Msun. We discuss evolutionary scenarios for this system that could lead to the current status of the stellar components and suggests possibilities for its future evolution, as well as potential observational tests of our model.Comment: 13 pages, 3 figures. Accepted for publication in The Astrophysical Journal

A small cichlid species flock from the Upper Miocene (9--10 MYA) of Central Kenya

Fossil cichlids from East Africa offer unique insights into the evolutionary history and ancient diversity of the family on the African continent. Here we present three fossil species of the extinct haplotilapiine cichlid †Baringochromis gen. nov. from the upper Miocene of the palaeolake Waril in Central Kenya, based on the analysis of a total of 78 articulated skeletons. †Baringochromis senutae sp. nov., †B. sonyii sp. nov. and †B. tallamae sp. nov. are superficially similar, but differ from each other in oral-tooth dentition and morphometric characters related to the head, dorsal fin base and body depth. These findings indicate that they represent an ancient small species flock. Possible modern analogues of palaeolake Waril and its species flock are discussed. The three species of †Baringochromis may have begun to subdivide their initial habitat by trophic differentiation. Possible sources of food could have been plant remains and insects, as their fossilized remains are known from the same place where †Baringochromis was found

Forschung für eine naturgerechte Landwirtschaft

Eine Wende hin zu einer naturgerechten Landwirtschaft setzt voraus, dass auch in der Agrarforschung neue Akzente gesetzt werden. Eine Denkschrift* bringt auf den Punkt, was sich in Forschung, Lehre und Ausbildung ändern muss. Die Langfassung dieser Denkschrift, die in diesem Beitrag zusammengefasst wird, kann beim Bundesamt für Naturschutz, Konstantinstr. 110, D-53179 Bonn, Tel. 0228 - 8491 0, Fax - 8491 200, E-Mail [email protected], bezogen oder im Internet unter www.bfn.de/10/ eingesehen und unterzeichnet werden

2D Monte-Carlo Radiative transfer modeling of the disk shaped secondary of Epsilon Aurigae

We present two dimensional Monte-Carlo radiative transfer models for the disk of the eclipsing binary $\epsilon$ Aur by fitting its spectral energy distribution from optical to the far-IR wavelengths. We also report new observations of $\epsilon$ Aur made by AKARI in its five mid and far-IR photometric bands and were used to construct our SED. The disk is optically thick and has flared disk geometry containing gas and dust with a gas to dust mass ratio of 100. We have taken the primary of the binary to be a F0Iae-type post-AGB star and the disk is heated by a B5V hot star with a temperature of 15,000 K at the center of the disk. We take the radius of the disk to be 3.8 AU for our models as constrained from the IR interferometric imaging observations of the eclipsing disk. Our models imply that the disk contains grains which are much bigger than the ISM grains (grain sizes 10$\mu$ to 100$\mu$). The grain chemistry of the disk is carbonaceous and our models show that silicate and ISM dust chemistry do not reproduce the slope of the observed SED in the mid-IR to far-IR regions. This implies that the formation of the disk shaped secondary in $\epsilon$ Aur system could be the result of accretion of matter and or mass transfer from the primary which is now a F0Iae post-AGB star. It is not a proto-planetary disk. The disk is seen nearly edge on with an inclination angle larger than 85$^{o}$. We propose from our radiative transfer modeling that the disk is not solid and have a void of 2AU radius at the center within which no grains are present making the region nearly transparent. The disk is not massive, its mass is derived to be less than 0.005M$_{\odot}$.Comment: 27 pages, 5 figures, 2 table

Benchmarking Of Risk Management Methods With Regard to Variations As A Source Of Risk

When developing new systems, there is always some kind of reference to existing systems. Various approaches aim at describing qualitatively different characteristics of such connections, often depicted as some form of variation. Among other things, this is done with regard to innovation potential and development risk. In this paper, we investigate the extent to which established methods of risk management refer to modelling approaches for variations by means as mentionend above. After a litertaure search 11 methods and method clusters are analyzed more in detail within a method benchmark

New haplochromine cichlid from the upper Miocene (9-10 MYA) of Central Kenya

Background: The diversification process known as the Lake Tanganyika Radiation has given rise to the most speciose clade of African cichlids. Almost all cichlid species found in the lakes Tanganyika, Malawi and Victoria, comprising a total of 12-16 tribes, belong to this clade. Strikingly, all the species in the latter two lakes are members of the tribe Haplochromini, whose origin remains unclear. The 'out of Tanganyika' hypothesis argues that the Haplochromini emerged simultaneously with other cichlid tribes and lineages in Lake Tanganyika, presumably about 5-6 million years ago (MYA), and that their presence in the lakes Malawi and Victoria and elsewhere in Africa today is due to later migrations. In contrast, the 'melting pot Tanganyika hypothesis' postulates that Haplochromini emerged in Africa prior to the formation of Lake Tanganyika, and that their divergence could have begun about 17 MYA. Haplochromine fossils could potentially resolve this debate, but such fossils are extremely rare. Results: Here we present a new fossil haplochromine from the upper Miocene site Waril (9-10 million years) in Central Kenya. Comparative morphology, supported by Micro-CT imaging, reveals that it bears a unique combination of characters relating to dentition, cranial bones, caudal skeleton and meristic traits. Its most prominent feature is the presence of exclusively unicuspid teeth, with canines in the outer tooth row. †Warilochromis unicuspidatus gen. et sp. nov. shares this combination of characters solely with members of the Haplochromini and its lacrimal morphology indicates a possible relation to the riverine genus Pseudocrenilabrus. Due to its fang-like dentition and non-fusiform body, †W. unicuspidatus gen. et sp. nov. might have employed either a sit-and-pursue or sit-and-wait hunting strategy, which has not been reported for any other fossil haplochromine cichlid. Conclusions: The age of the fossil (9-10 MYA) is incompatible with the 'out of Tanganyika' hypothesis, which postulates that the divergence of the Haplochromini began only 5-6 MYA. The presence of this fossil in an upper Miocene palaeolake in the Central Kenya Rift, as well as its predatory lifestyle, indicate that Haplochromini were already an important component of freshwater drainages in East Africa at that time