Convective envelopes in rotating OB stars

We study the effects of rotation on the outer convective zones of massive stars. We examine the effects of rotation on the thermal gradient and on the Solberg--Hoiland term by analytical developments and by numerical models. Writing the criterion for convection in rotating envelopes, we show that the effects of rotation on the thermal gradient are much larger and of opposite sign to the effect of the Solberg-Hoiland criterion. On the whole, rotation favors convection in stellar envelopes at the equator and to a smaller extent at the poles. In a rotating 20 Msun star at 94% of the critical angular velocity, there are two convective envelopes, with the bigger one having a thickness of 13.2% of the equatorial radius. In the non-rotating model, the corresponding convective zone has a thickness of only 4.6% of the radius. The occurrence of outer convection in massive stars has many consequences.Comment: 4 pages, 3 figures, accepted by Astronomy and Astrophysic

Solar Resonant Diffusion Waves as a Driver of Terrestrial Climate Change

A theory is described based on resonant thermal diffusion waves in the sun that appears to explain many details of the paleotemperature record for the last 5.3 million years. These include the observed periodicities, the relative strengths of each observed cycle, and the sudden emergence in time for the 100 thousand year cycle. Other prior work suggesting a link between terrestrial paleoclimate and solar luminosity variations has not provided any specific mechanism. The particular mechanism described here has been demonstrated empirically, although not previously invoked in the solar context. The theory also lacks most of the problems associated with Milankovitch cycles.Comment: in press with The Journal of Atmospheric and Solr Terrestrial Physic

Identification of factors affecting the outcome of transanal advancement flap repair for high transsphincteric fistulas

A fistula is defined as an abnormal communication between two epithelium lined surfaces. Perianal fistulas are abnormal communications between the anal canal and the perianal skin. Perianal fistulas have been treated since ancient times. Probably the first to describe the diagnosis and treatment of anal fistula was Sushruta around 600 BC. Around 430 BC, Hippocrates (460-370 BC) described perianal fistulas in more detail. It is remarkable that some of his guidelines carry worldwide popularity up to today. The estimated incidence of perianal fistulas varies between 0.86 and 2.32 per 10,000/year. There is a male predominance with a reported male-to-female-ratio varying from 2:1 to 5:1 2. The maximum incidence is between the third and fifth decades of life . Perianal fistulas account for a substantial discomfort and morbidity to the patient and although many fistulas are easily recognized and treated, others can be complex and difficult to treat

Identification of epithelialization in high transsphincteric fistulas

textabstractBackground At present, transanal advancement flap repair (TAFR) is the treatment of choice for transsphincteric fistulas passing through the upper and middle third of the external anal sphincter. It has been suggested that epithelialization of the fistula tract contributes to the failure of the treatment. The aim of this study was to assess the prevalence of epithelialization of the fistula tract and to study its effect on the outcome of TAFR and TAFR combined with ligation of the intersphincteric fistula tract (LIFT). Methods Forty-four patients with a high transsphincteric fistula of cryptoglandular origin underwent TAFR. Nine of these patients underwent a combined procedure of TAFR with LIFT. In all patients the fistula tract was excised from the external opening up to the outer border of the external anal sphincter. In patients undergoing TAFR combined with LIFT an additional central part of the intersphincteric fistula tract was excised. A total of 53 specimens were submitted. Histopathological examination of the specimens was carried out by a pathologist, blinded for clinical data. Results Epithelialization of the distal and intersphincteric fistula tract was observed in only 25 and 22% of fistulas, respectively. There was no difference in outcome between fistulas with or without epithelialization. Conclusions Epithelialization of high transsphincteric fistulas is rare and does not affect the outcome of TAFR and TAFR combined with LIFT

Evolution of low-mass metal-free stars including effects of diffusion and external pollution

We investigate the evolution of low-mass metal-free Population III stars. Emphasis is laid upon the question of internal and external sources for CNO-elements, which - if present in sufficient amounts in the hydrogen-burning regions - lead to a strong modification of the stars' evolutionary behavior. For the production of carbon due to nuclear processes inside the stars, we use an extended nuclear network, demonstrating that hot pp-chains do not suffice to produce enough carbon or are less effective than the triple3-alpha-process. As an external source of CNO-elements we test the efficiency of pollution by a nearby massive star combined with particle diffusion. For all cases investigated, the additional metals fail to reach nuclear burning regions before deep convection on the Red Giant Branch obliterates the previous evolution. The surface abundance history of the polluted Pop III stars is presented. The possibilities to discriminate between a Pop II and a polluted Pop III field star are also discussed.Comment: Accepted for publication in Ap

Seton drainage prior to transanal advancement flap repair: useful or not?

Introduction: Transanal advancement flap repair (TAFR) provides a useful tool in the treatment of high transsphincteric fistulas. Recent studies indicate that TAFR fails in one out of three patients. Until now, no definite predictive factor for failure has been identified. Although some authors have reported that preoperative seton drainage might improve the outcome of TAFR, this could not be confirmed by others. We conducted the present study to assess the influence of preoperative seton drainage on the outcome of TAFR in a relatively large series. Methods: Between December 1992 and June 2008, a consecutive series of 278 patients [M/F = 179:99, median age 46 years (range, 19-73 years)] with cryptoglandular, transsphincteric fistula, passing through the upper or middle third of the external anal sphincter underwent TAFR. Patients were recruited from the colorectal units of two university hospitals (Erasmus Medical Center, Rotterdam, n = 211; and Leiden University Medical Center, Leiden, n = 67). Baseline characteristics did not differ between the two clinics. Sixty-eight of these patients underwent preoperative seton drainage for at least 2 months and until the day of the flap repair. Results: Median healing time was 2.2 months. In patients without preoperative seton drainage, the healing rate was 63%, whereas the healing rate was 67% in patients who underwent preoperative seton drainage. This difference was not statistically significant. No differences in healing rates were found between the series from Leiden and Rotterdam. Conclusion: Preoperative seton drainage does not improve the outcome of TAFR

Shock-heating of stellar envelopes: A possible common mechanism at the origin of explosions and eruptions in massive stars

Observations of transient phenomena in the Universe reveal a spectrum of mass-ejection properties associated with massive stars, covering from Type II/Ib/Ic core-collapse supernovae (SNe) to giant eruptions of Luminous Blue Variables (LBV) and optical transients. Here, we hypothesize that a fraction of these phenomena may have an explosive origin, the distinguishing ingredient being the ratio of the prompt energy release E_dep to the envelope binding energy E_binding. Using one-dimensional one-group radiation hydrodynamics and a set of 10-25Msun, massive-star models, we explore the dynamical response of a stellar envelope subject to a strong, sudden, and deeply-rooted energy release. Following energy deposition, a shock systematically forms, crosses the progenitor envelope on a day timescale, and breaks-out with a signal of hour-to-days duration and a 10^5-10^11 Lsun luminosity. For E_dep > E_binding, full envelope ejection results with a SN-like bolometric luminosity and kinetic energy, modulations being commensurate to the energy deposited and echoing the diversity of Type II-Plateau SNe. For E_dep ~ E_binding, partial envelope ejection results with a small expansion speed, and a more modest but year-long luminosity plateau, reminiscent of LBV eruptions or so-called SN impostors. For E_dep < E_binding, we obtain a "puffed-up" star, secularly relaxing back to thermal equilibrium. In parallel with gravitational collapse and Type II SNe, we argue that the thermonuclear combustion of merely a few 0.01Msun of C/O could power a wide range of explosions/eruptions in loosely-bound massive stars, as those in the 8-12Msun range, or in more massive ones owing to their proximity to the Eddington limit and/or critical rotation.Comment: 20 pages, 16 figures, 2 tables; accepted to MNRA