Abundances determined using Si II and Si III in B-type stars: evidence for stratification

It is becoming clear that determination of the abundance of Si using lines of Si II and Si III can lead to quite discordant results in mid to late B-type stars. The difference between the Si abundances derived from the two ion states can exceed one dex in some cases. We have carried out a study intended to clarify which kinds of B stars exhibit this discrepancy, to try to identify regularities in the phenomenon, and to explore possible explanations such as abundance stratification by comparing models to observed spectra. We used spectra from the ESPaDOnS spectropolarimeter and FEROS spectrograph, supplemented with spectra from the ESO and ELODIE archives, of magnetic Bp, HgMn, and normal B-type stars ranging in effective temperature from about 10500 to 15000 K. Using these spectra, we derived abundances using the spectrum synthesis program ZEEMAN which can take into account the influence of magnetic fields. For each star, accurate abundances of Si II, Si III, Ti, Cr, and Fe were derived. All magnetic Bp stars in our sample show a discordance between the derived abundances of the first and second ions of silicon, with the latter being between 0.6 - 1.7 dex higher. The same behaviour is observed in the non-magnetic stars but to a much smaller extent: Si III is enhanced by between 0.3 - 0.8 dex compared to Si II.We do not detect the discrepancy in three stars, HD 22136 (normal), HD 57608 (HgMn) and HD 27295 (HgMn); these are the only stars in our sample for which the microturbulence parameter is significantly different from zero, and which therefore probably have convection occurring in their atmospheres. We find that vertical stratification of silicon in the atmospheres of B-type stars may provide an explanation of this phenomenon, but our detailed stratification models do not completely explain the discrepancies, which may, in part, be due to non-LTE effects.Comment: 9 pages, 2 figures, accepted for publication in A&

Bounds on solutions of the rotating, stratified, incompressible, non-hydrostatic, three-dimensional Boussinesq equations

We study the three-dimensional, incompressible, non-hydrostatic Boussinesq fluid equations, which are applicable to the dynamics of the oceans and atmosphere. These equations describe the interplay between velocity and buoyancy in a rotating frame. A hierarchy of dynamical variables is introduced whose members $\Omega_{m}(t)$ ($1 \leq m < \infty$) are made up from the respective sum of the $L^{2m}$-norms of vorticity and the density gradient. Each $\Omega_{m}(t)$ has a lower bound in terms of the inverse Rossby number, $Ro^{-1}$, that turns out to be crucial to the argument. For convenience, the $\Omega_{m}$ are also scaled into a new set of variables $D_{m}(t)$. By assuming the existence and uniqueness of solutions, conditional upper bounds are found on the $D_{m}(t)$ in terms of $Ro^{-1}$ and the Reynolds number $Re$. These upper bounds vary across bands in the $\{D_{1},\,D_{m}\}$ phase plane. The boundaries of these bands depend subtly upon $Ro^{-1}$, $Re$, and the inverse Froude number $Fr^{-1}$. For example, solutions in the lower band conditionally live in an absorbing ball in which the maximum value of $\Omega_{1}$ deviates from $Re^{3/4}$ as a function of $Ro^{-1},\,Re$ and $Fr^{-1}$.Comment: 24 pages, 3 figures and 1 tabl

Persistence pays off: Paying Attention to What the LSTM Gating Mechanism Persists

Language Models (LMs) are important components in several Natural Language Processing systems. Recurrent Neural Network LMs composed of LSTM units, especially those augmented with an external memory, have achieved state-of-the-art results. However, these models still struggle to process long sequences which are more likely to contain long-distance dependencies because of information fading and a bias towards more recent information. In this paper we demonstrate an effective mechanism for retrieving information in a memory augmented LSTM LM based on attending to information in memory in proportion to the number of timesteps the LSTM gating mechanism persisted the information

Saddam Hussein is “dangerous to the extreme”: The ethics of professional commentary on public figures

People are intrinsically interested in the personalities of public figures such as the celebrities they follow, political leaders, and citizens at the center of newsworthy events. The goal of the present article is to examine the key issues that surround ethical commentary on public figures by psychologists, psychiatrists, and other mental health professionals. Public commentaries carry with them a host of issues from representing a given discipline such as psychology well, to potentially harming an individual who is discussed, to furthering public education about personality and mental health issues. For this reason such commentary deserves special consideration as to when and how it is appropriate to carry out

\u3ci\u3eArhyssus Hirtus\u3c/i\u3e (Hemiptera: Heteroptera: Rhopalidae) in Minnesota: The Inland Occurrence of an East Coast Species

Arhyssus hirtus (Hemiptera: Heteroptera: Rhopalidae), is reported from the Cedar Creek Natural History Area, a Long-Term Ecological Research site, outside of Minneapolis, Minnesota where over 4000 species of arthropods have been collected. This species has previously been known only from a narrow zone along the sandy edges of the Atlantic Ocean (Maryland, Massachusetts, New Jersey and New York). The species is known on Hudsonia tomentosa at these ocean sites, but other hosts may be involved at Cedar Creek. This small species of Arhyssus occurs in both micropterous and macropterous forms, unusual for this genus. Thus far, only micropterous forms have been collected at the Minnesota site

Science on View

Book review of "Envisioning Science: The Design and Craft of the Science Image," by Felice Frankel, MIT Press, 2002

A Winning Hand: A Proposal for an International Regulatory Schema with Respect to the Growing Online Gambling Dilemma in the United States

While a multitude of Internet enterprises folded in the 1990s, online gambling websites not only have held strong, but appear to be ready to increase the stakes. No business relating to the Internet currently generates more revenue than online gambling, and that trend does not look like it will change soon. While many Americans desire to participate in this form of cyber-gambling, the current legality of their ability to do so remains vague. For the most part, an American\u27s ability to gamble currently resides under the purview of state law and a hodgepodge of antiquated federal wire acts. The nature of the Internet, however, mandates that any scheme, regulatory or prohibitory, be constructed in the international arena. For various reasons, there have been efforts by members of Congress to create strong prohibitory legislation specifically targeting Internet gambling. The Author analyzes not only whether a domestic prohibition schema is the best model to implement, but also whether such a model could even be truly effective. The Author further shows that an international regulatory model can provide a legitimate method of control while allowing individual countries to maintain discretion over the form of online gambling they allow to their citizens. At the same time, this international regulatory schema would still provide a valid international enforcement net against offenders. Under this regulatory schema, problem gamblers can be protected while still preserving the opportunity for other patrons to get lucky and hit it big