Non-stationary dynamo & magnetospheric accretion processes of the classical T Tauri star V2129 Oph

We report here the first results of a multi-wavelength campaign focussing on magnetospheric accretion processes of the classical TTauri star (cTTS) V2129Oph. In this paper, we present spectropolarimetric observations collected in 2009 July with ESPaDOnS at the Canada-France-Hawaii Telescope (CFHT). Circularly polarised Zeeman signatures are clearly detected, both in photospheric absorption and accretion-powered emission lines, from time-series of which we reconstruct new maps of the magnetic field, photospheric brightness and accretion-powered emission at the surface of V2129Oph using our newest tomographic imaging tool - to be compared with those derived from our old 2005 June data set, reanalyzed in the exact same way. We find that in 2009 July, V2129Oph hosts octupolar & dipolar field components of about 2.1 & 0.9kG respectively, both tilted by about 20deg with respect to the rotation axis; we conclude that the large-scale magnetic topology changed significantly since 2005 June (when the octupole and dipole components were about 1.5 and 3 times weaker respectively), demonstrating that the field of V2129Oph is generated by a non-stationary dynamo. We also show that V2129Oph features a dark photospheric spot and a localised area of accretion-powered emission, both close to the main surface magnetic region (hosting fields of up to about 4kG in 2009 July). We finally obtain that the surface shear of V2129Oph is about half as strong as solar. From the fluxes of accretion-powered emission lines, we estimate that the observed average logarithmic accretion rate (in Msun/yr) at the surface of V2129Oph is -9.2+-0.3 at both epochs, peaking at -9.0 at magnetic maximum. It implies in particular that the radius at which the magnetic field of V2129Oph truncates the inner accretion disc is 0.93x and 0.50x the corotation radius in 2009 July and 2005 June respectively.Comment: MNRAS in press - 16 pages, 9 figure

Magnetic fields and accretion flows on the classical T Tauri star V2129 Oph

From observations collected with the ESPaDOnS spectropolarimeter, we report the discovery of magnetic fields at the surface of the mildly accreting classical T Tauri star V2129 Oph. Zeeman signatures are detected, both in photospheric lines and in the emission lines formed at the base of the accretion funnels linking the disc to the protostar, and monitored over the whole rotation cycle of V2129 Oph. We observe that rotational modulation dominates the temporal variations of both unpolarized and circularly polarized line profiles. We reconstruct the large-scale magnetic topology at the surface of V2129 Oph from both sets of Zeeman signatures simultaneously. We find it to be rather complex, with a dominant octupolar component and a weak dipole of strengths 1.2 and 0.35 kG, respectively, both slightly tilted with respect to the rotation axis. The large-scale field is anchored in a pair of 2-kG unipolar radial field spots located at high latitudes and coinciding with cool dark polar spots at photospheric level. This large-scale field geometry is unusually complex compared to those of non-accreting cool active subgiants with moderate rotation rates. As an illustration, we provide a first attempt at modelling the magnetospheric topology and accretion funnels of V2129 Oph using field extrapolation. We find that the magnetosphere of V2129 Oph must extend to about 7R* to ensure that the footpoints of accretion funnels coincide with the high-latitude accretion spots on the stellar surface. It suggests that the stellar magnetic field succeeds in coupling to the accretion disc as far out as the corotation radius, and could possibly explain the slow rotation of V2129 Oph. The magnetospheric geometry we derive produces X-ray coronal fluxes typical of those observed in cTTSs.Comment: MNRAS, in press (18 pages, 17 figures

Rapidly rotating second-generation progenitors for the blue hook stars of {\omega} Cen

Horizontal Branch stars belong to an advanced stage in the evolution of the oldest stellar galactic population, occurring either as field halo stars or grouped in globular clusters. The discovery of multiple populations in these clusters, that were previously believed to have single populations gave rise to the currently accepted theory that the hottest horizontal branch members (the blue hook stars, which had late helium-core flash ignition, followed by deep mixing) are the progeny of a helium-rich "second generation" of stars. It is not known why such a supposedly rare event (a late flash followed by mixing) is so common that the blue hook of {\omega} Cen contains \sim 30% of horizontal branch stars 10 , or why the blue hook luminosity range in this massive cluster cannot be reproduced by models. Here we report that the presence of helium core masses up to \sim 0.04 solar masses larger than the core mass resulting from evolution is required to solve the luminosity range problem. We model this by taking into account the dispersion in rotation rates achieved by the progenitors, whose premain sequence accretion disc suffered an early disruption in the dense environment of the cluster's central regions where second-generation stars form. Rotation may also account for frequent late-flash-mixing events in massive globular clusters.Comment: 44 pages, 8 figures, 2 tables in Nature, online june 22, 201

Radio Emission from Ultra-Cool Dwarfs

The 2001 discovery of radio emission from ultra-cool dwarfs (UCDs), the very low-mass stars and brown dwarfs with spectral types of ~M7 and later, revealed that these objects can generate and dissipate powerful magnetic fields. Radio observations provide unparalleled insight into UCD magnetism: detections extend to brown dwarfs with temperatures <1000 K, where no other observational probes are effective. The data reveal that UCDs can generate strong (kG) fields, sometimes with a stable dipolar structure; that they can produce and retain nonthermal plasmas with electron acceleration extending to MeV energies; and that they can drive auroral current systems resulting in significant atmospheric energy deposition and powerful, coherent radio bursts. Still to be understood are the underlying dynamo processes, the precise means by which particles are accelerated around these objects, the observed diversity of magnetic phenomenologies, and how all of these factors change as the mass of the central object approaches that of Jupiter. The answers to these questions are doubly important because UCDs are both potential exoplanet hosts, as in the TRAPPIST-1 system, and analogues of extrasolar giant planets themselves.Comment: 19 pages; submitted chapter to the Handbook of Exoplanets, eds. Hans J. Deeg and Juan Antonio Belmonte (Springer-Verlag

Circumstellar disks and planets. Science cases for next-generation optical/infrared long-baseline interferometers

We present a review of the interplay between the evolution of circumstellar disks and the formation of planets, both from the perspective of theoretical models and dedicated observations. Based on this, we identify and discuss fundamental questions concerning the formation and evolution of circumstellar disks and planets which can be addressed in the near future with optical and infrared long-baseline interferometers. Furthermore, the importance of complementary observations with long-baseline (sub)millimeter interferometers and high-sensitivity infrared observatories is outlined.Comment: 83 pages; Accepted for publication in "Astronomy and Astrophysics Review"; The final publication is available at http://www.springerlink.co

The role of a probiotics mixture in the treatment of childhood constipation: a pilot study

<p>Abstract</p> <p>Background</p> <p>Inconsistent data exist about the efficacy of probiotics in the treatment of constipation. Several studies in adults with constipation showed positive effects of probiotics on constipation. Inconsistent data exist regarding the effect of a single probiotic strain in constipated children. The aim of this pilot study was to determine the effect of a mixture of probiotics containing bifidobacteria and lactobacilli in the treatment of childhood constipation.</p> <p>Methods</p> <p>Children aged 4–16 years with constipation as defined by the Rome III criteria were eligible for the study. During a 4 week period, children received a daily mix of 4 × 10⁹colony forming units of a probiotic mixture (<it>Ecologic</it>^®<it>Relief</it>) containing Bifidobacteria (B.) bifidum, B. infantis, B. longum, Lactobacilli (L.) casei, L. plantarum and L. rhamnosus. Primary outcome measures were frequency of bowel movements (BMs) per week and stool consistency. Secondary outcome measures were number of faecal incontinence episodes per week, abdominal pain and side effects.</p> <p>Results</p> <p>Twenty children, 50% male, median age 8 (range 4–16) were included.</p> <p>The frequency of BMs per week increased from 2.0 (1.0–5.0) to 4.2 (0.0–16.0) in week 2 (p = 0.10) and 3.8 (2.1–7.0) in week 4 (p = 0.13). In 12 children presenting with <3 BMs/week, BMs per week increased significantly from 1.0 (0.0–2.0) to 3.0 (0.0–7.0) in week 2 (p = 0.01) and 3.0 (0.0–10.0) in week 4 (p = 0.01). The stool consistency was reported as hard in 7 children at baseline, in 4 children at week 2 (p = 0.23) and in 6 children after 4 weeks of treatment (p = 1.00). A significant decrease in number of faecal incontinence episodes per week was found in the entire group: 4.0 (0.0–35.0) to 1.5 (0.0–14.0) in week 2 (p = 0.01) and 0.3 (0.0–7.0) in week 4 (p = 0.001). The presence of abdominal pain decreased significantly from 45% to 25% in week 2 (p = 0.04) and 20% at week 4 (p = 0.006). No side effects were reported.</p> <p>Conclusion</p> <p>This pilot study shows that a mixture of probiotics, has positive effects on symptoms of constipation. To confirm these findings, a large randomised placebo controlled trial is required.</p

Plant-made polio type 3 stabilized VLPs—a candidate synthetic polio vaccine

Poliovirus (PV) is the causative agent of poliomyelitis, a crippling human disease known since antiquity. PV occurs in two distinct antigenic forms, D and C, of which only the D form elicits a robust neutralizing response. Developing a synthetically produced stabilized viruslike particle (sVLP)-based vaccine with D antigenicity, without the drawbacks of current vaccines, will be a major step towards the final eradication of poliovirus. Such a sVLP would retain the native antigenic conformation and the repetitive structure of the original virus particle, but lack infectious genomic material. In this study, we report the production of synthetically stabilized PV VLPs in plants. Mice carrying the gene for the human PV receptor are protected from wild-type PV when immunized with the plant-made PV sVLPs. Structural analysis of the stabilized mutant at 3.6 Å resolution by cryo-electron microscopy and single particle reconstruction reveals a structure almost indistinguishable from wild-type PV3

Incidence and Risk Factors for Hepatocellular Carcinoma in Texas Latinos: Implications for Prevention Research

Hepatocellular carcinoma (HCC) is increasing in the U.S. despite a decline in cancer overall. Latinos have higher rates of HCC than the general population according to the Surveillance, Epidemiology, and End Results (SEER) Program. Not included in SEER, Texas Latinos make up one-fifth of the U.S. Latino population. To determine whether HCC incidence differs among U.S. and Texas Latinos, this descriptive study compares HCC incidence from 1995 through 2006 among three Latino populations: U.S. SEER, Texas overall and a South Texas subset. To identify lines of prevention research, we compare prevalence of known HCC risk factors among these Latino groups.Data were collected from the U.S. SEER Program, Texas Cancer Registry and Texas Department of State Health Services (TDSHS). Annual age-specific and age-adjusted HCC incidence rates, annual percent changes (APCs) and 95% confidence intervals were calculated as well as prevalence of obesity, diabetes, heavy alcohol use and cigarette smoking.Of the three Latino groups compared, South Texas Latinos had the highest age-adjusted HCC incidence rates and SEER Latinos had the lowest (10.6/100,000 (10.1-11.1) and 7.5/100,000 (7.2-7.7), respectively). HCC incidence significantly increased over time (APCs>0) among Latinos in all three geographic groups. Between 1995 and 2006, there was an increase in obesity among all three populations, and obesity was highest among South Texas Latinos. Diabetes increased among U.S. Latinos, and Latino women in South Texas had significantly higher diabetes prevalence than U.S. Latino women. Cigarette smoking and heavy alcohol use were similar among groups.The incidence of HCC among Latinos in South Texas is higher than elsewhere in the United States. Higher rates of HCC among Texas and South Texas Latinos may be associated with greater prevalence of obesity and diabetes, risk factors for HCC that are amenable to intervention

Short-term follow-up of chagasic patients after benznidazole treatment using multiple serological markers

<p>Abstract</p> <p>Background</p> <p>Conventional serological tests, using total soluble proteins or a cocktail of recombinant proteins from <it>T. cruzi </it>as antigens, are highly sensitive for Chagas disease diagnosis. This type of tests, however, does not seem to be reliable tools for short- and medium-term monitoring of the evolution of patients after antiparasitic treatment. The aim of the present study was to search for immunological markers that could be altered in the sera from Chagas disease patients after benznidazole treatment, and therefore have a potential predictive diagnostic value.</p> <p>Methods</p> <p>We analyzed the reactivity of sera from chagasic patients during different clinical phases of the disease against a series of immunodominant antigens, known as KMP11, PFR2, HSP70 and Tgp63. The reactivity of the sera from 46 adult Chronic Chagas disease patients living in a non-endemic country without vector transmission of <it>T. cruzi </it>(15 patients in the indeterminate stage, 16 in the cardiomiopathy stage and 16 in the digestive stage) and 22 control sera from non-infected subjects was analyzed. We also analyzed the response dynamics of sera from those patients who had been treated with benznidazole.</p> <p>Results</p> <p>Regardless of the stage of the sickness, the sera from chagasic patients reacted against KMP11, HSP70, PFR2 and Tgp63 recombinant proteins with statistical significance relative to the reactivity against the same antigens by the sera from healthy donors, patients with autoimmune diseases or patients suffering from tuberculosis, leprosy or malaria. Shortly after benznidazole treatment, a statistically significant decrease in reactivity against KMP11, HSP70 and PFR2 was observed (six or nine month). It was also observed that, following benznidazole treatment, the differential reactivity against these antigens co-relates with the clinical status of the patients.</p> <p>Conclusions</p> <p>The recombinant antigens KMP11, PFR2, Tgp63 and HSP70 are recognized by Chagas disease patients' sera at any clinical stage of the disease. Shortly after benznidazole treatment, a drop in reactivity against three of these antigens is produced in an antigen-specific manner. Most likely, analysis of the reactivity against these recombinant antigens may be useful for monitoring the effectiveness of benznidazole treatment.</p

Initiation of V(D)J Recombination by Dβ-Associated Recombination Signal Sequences: A Critical Control Point in TCRβ Gene Assembly

T cell receptor (TCR) β gene assembly by V(D)J recombination proceeds via successive Dβ-to-Jβ and Vβ-to-DJβ rearrangements. This two-step process is enforced by a constraint, termed beyond (B)12/23, which prohibits direct Vβ-to-Jβ rearrangements. However the B12/23 restriction does not explain the order of TCRβ assembly for which the regulation remains an unresolved issue. The initiation of V(D)J recombination consists of the introduction of single-strand DNA nicks at recombination signal sequences (RSSs) containing a 12 base-pairs spacer. An RSS containing a 23 base-pairs spacer is then captured to form a 12/23 RSSs synapse leading to coupled DNA cleavage. Herein, we probed RSS nicks at the TCRβ locus and found that nicks were only detectable at Dβ-associated RSSs. This pattern implies that Dβ 12RSS and, unexpectedly, Dβ 23RSS initiate V(D)J recombination and capture their respective Vβ or Jβ RSS partner. Using both in vitro and in vivo assays, we further demonstrate that the Dβ1 23RSS impedes cleavage at the adjacent Dβ1 12RSS and consequently Vβ-to-Dβ1 rearrangement first requires the Dβ1 23RSS excision. Altogether, our results provide the molecular explanation to the B12/23 constraint and also uncover a ‘Dβ1 23RSS-mediated’ restriction operating beyond chromatin accessibility, which directs Dβ1 ordered rearrangements