Disruption of a Red Giant Star by a Supermassive Black Hole and the Case of PS1-10jh

The development of a new generation of theoretical models for tidal disruptions is timely, as increasingly diverse events are being captured in surveys of the transient sky. Recently, Gezari et al. reported a discovery of a new class of tidal disruption events: the disruption of a helium-rich stellar core, thought to be a remnant of a red giant (RG) star. Motivated by this discovery and in anticipation of others, we consider tidal interaction of an RG star with a supermassive black hole (SMBH) which leads to the stripping of the stellar envelope and subsequent inspiral of the compact core toward the black hole. Once the stellar envelope is removed the inspiral of the core is driven by tidal heating as well as the emission of gravitational radiation until the core either falls into the SMBH or is tidally disrupted. In the case of tidal disruption candidate PS1-10jh we find that there is a set of orbital solutions at high eccentricities in which the tidally stripped hydrogen envelope is accreted by the SMBH before the helium core is disrupted. This places the RG core in a portion of parameter space where strong tidal heating can lift the degeneracy of the compact remnant and disrupt it before it reaches the tidal radius. We consider how this sequence of events explains the puzzling absence of the hydrogen emission lines from the spectrum of PS1-10jh and gives rise to its other observational features.Comment: Revised version accepted for publication in ApJ, 788, 99 (12 pages, 2 figures

Quine's Naturalized Epistemology

It is well known that modern epistemology is a discipline that was left as a legacy by the great French philosopher René Descartes, and it is generally believed that it is a typically philosophical discipline whose problems can be dealt with only by philosophical (speculative) means of inquiry. Recently, however, the idea of naturalization of epistemological inquiry has emerged, and one of its most prominent advocates was Quine. However, the question is to what extent, if at all, the proposal offered by Quine is tenable, as evidenced, apart from numerous criticisms, by significantly different interpretations regarding assumptions on which it should be based. Namely, three types of interpretations of Quine’s call for the reform of epistemological inquiry prevail in contemporary literature: behaviorist, which was largely advocated by Quine, but also coherentist and physicalist, which some of his interpreters argued for. However, while the first two of these options are in my opinion unacceptable because they are unable to provide the necessary autonomy for the epistemological context of inquiry, I will try to show that physicalism is also burdened with difficulties, albeit different ones, which make it an untenable position when it comes to epistemological inquiry. Nevertheless, even before I started writing, I thought that there were valuable insights in Quine’s proposal, and that we could learn important lessons from the failure of previous interpretations, both regarding the position that should be taken in its interpretation, and, closely related to this, the possibility of reforming epistemological inquiry in general. In other words, informed by the weaknesses of Quine’s proposal and its interpretations, I will argue that epistemological inquiry can ultimately be approached from one of two mutually incompatible theoretical positions: the traditional or Cartesian one, and the Kantian one. Given that, as noted above, Quine’s proposal was primarily a reaction to Cartesianism, I discuss the possibility of establishing the fundamental level of inquiry such as epistemological to which Quine had to aspire, but in a way that would enable the synthesis of his approach with Kant’s view, which is in my opinion the only genuine alternative to the traditional program. Although it implies taking a position that would be a kind of compromise and could not be attributed to Quine (which is why it is uncertain whether he would have supported this interpretation), I believe that, apart from preserving certain naturalistic elements, it is an interpretation that would ultimately satisfy most of the demands that Quine himself has set for epistemological inquiry

Successful Endoscopic Removal of a Swallowed Toothbrush: Case Report

Most ingested foreign bodies will pass uneventfully through the gastrointestinal tract. Nevertheless, long and rigid foreign bodies are associated with an increased risk of gastrointestinal impaction, perforation and bleeding. Moreover, there has been no case of spontaneous passage of a toothbrush reported. Therefore, the prompt removal of such ingested foreign objects is recommended before complications develop. This case report describes a case of an 18-year-old woman who accidentally swallowed her toothbrush. The toothbrush was successfully removed via flexible endoscopy using a polypectomy snare. A swallowed toothbrush is a special clinical challenge. Early endoscopic retrieval of the toothbrush is critical for reducing morbidity and mortality. In cases when endoscopic removal fails, a laparoscopic surgical approach may be an alternative

The State and Development Prospects of Goat Production in the World

Goats are the most popular animals in the world and goat meat and milk consumption are most widely distributed in the world. Goats are popular with small holders because of their efficient conversion of feed into edible and high-quality meat, milk and hide. Goats are also used as holistic tools for land vegetation management and fire fuel load control. With proper grazing management, goats can eliminate noxious weeds, restore native grasses and prevent fires through fuel load reduction. In the world the number of goats is increasing. However, when it comes to growing goats, the conditions prevailing today are fairly complex. Problems and prospects vary by region, which consequently have different cultural and economic implications. Both global and regional approaches to livestock farming are important from the economic aspect of developed and developing nations. Rapidly increasing goat populations in developing countries point to the goat assisting in solving some of the needs created by the rising human population. Goat farming in Europe also has a more positive outlook after nearly a century of a negative reputation. Dairy-goat farming is significant to the economies of the Mediterranean countries. Dairy goats produce about 15.2 million metric tons (MT) of milk, accounting for about 2% of the world total amount of milk produced by livestock species. The developing countries produce approximately 83% of the total amount. In Europe, goat breeding is strongly oriented towards milk production, with only 3% of the world goat population producing about 15% of the world’s goat milk, which is mostly used for cheese production. Goat meat is widely consumed in the developing countries. According to FAOSTAT (2008), total meat inventory is about 280 million MT. Goat meat represents only 2% of this total. The total amount of goat meat produced in 2008 was 4.9 million MT. The developing countries produced approximately 97% of this amount, reflecting the great importance of goat meat to feed millions of people in these countries. The top ten countries producing goat meat are all from Asia and Africa. China is a world leader in producing goat meat, accounting for 38% of the world total goat meat produced. Goat meat production has been increasing from 2.65 million MT in 1990 to 4.93 million MT in 2008

Quine's naturalized epistemology and skepticism

When it comes to Quine's position on the naturalization of epistemological inquiry, it is generally considered that as the first and most important step, that position implies the abandonment of Cartesianism and the skepticism it implies. However, here we will argue that such a diagnosis is inappropriate, and that, in principle at least, Quine's attitude towards skepticism, even of the Cartesian type, is much more flexible than is usually thought, and perhaps even than Quine himself thought. In this regard, we will try to show how Quine was actually the one who accepted what Barry Stroud called the 'conditional correctness of skepticism (Cartesianism)' and not the logical positivists, and that the main reason for this is that he recognized the autonomy of the discourse (‘epistemology’s meta-context’) established by Descartes

Electronic Structure of the Complex Hydride NaAlH4

Density functional calculations of the electronic structure of the complex hydride NaAlH4 and the reference systems NaH and AlH3 are reported. We find a substantially ionic electronic structure for NaAlH4, which emphasizes the importance of solid state effects in this material. The relaxed hydrogen positions in NaAlH4 are in good agreement with recent experiment. The electronic structure of AlH3 is also ionic. Implications for the binding of complex hydrides are discussed.Comment: 4 pages, 5 figure