On the heating of source of the Orion KL hot core

We present images of the J=10-9 rotational lines of HC3N in the vibrationally excited levels 1v7, 1v6 and 1v5 of the hot core (HC) in Orion KL. The images show that the spatial distribution and the size emission from the 1v7 and 1v5 levels are different. While the J=10-9 1v7 line has a size of 4''x 6'' and peaks 1.1'' NE of the 3 mm continuum peak, the J=10--9 1v5 line emission is unresolved (<3'') and peaks 1.3'' south of the 3 mm peak. This is a clear indication that the HC is composed of condensations with very different temperatures (170 K for the 1v7 peak and $>230$ K for the 1v5 peak). The temperature derived from the 1v7 and 1v5 lines increases with the projected distance to the suspected main heating source I. Projection effects along the line of sight could explain the temperature gradient as produced by source I. However, the large luminosity required for source I, >5 10^5 Lsolar, to explain the 1v5 line suggests that external heating by this source may not dominate the heating of the HC. Simple model calculations of the vibrationally excited emission indicate that the HC can be internally heated by a source with a luminosity of 10^5 Lsolar, located 1.2'' SW of the 1v5 line peak (1.8'' south of source I). We also report the first detection of high-velocity gas from vibrationally excited HC3N emission. Based on excitation arguments we conclude that the main heating source is also driving the molecular outflow. We speculate that all the data presented in this letter and the IR images are consistent with a young massive protostar embedded in an edge-on disk.Comment: 13 pages, 3 figures, To be published in Ap.J. Letter

The role of low-mass star clusters in massive star formation. The Orion Case

To distinguish between the different theories proposed to explain massive star formation, it is crucial to establish the distribution, the extinction, and the density of low-mass stars in massive star-forming regions. We analyze deep X-ray observations of the Orion massive star-forming region using the Chandra Orion Ultradeep Project (COUP) catalog. We studied the stellar distribution as a function of extinction, with cells of 0.03 pc x 0.03 pc, the typical size of protostellar cores. We derived stellar density maps and calculated cluster stellar densities. We found that low-mass stars cluster toward the three massive star-forming regions: the Trapezium Cluster (TC), the Orion Hot Core (OHC), and OMC1-S. We derived low-mass stellar densities of 10^{5} stars pc^{-3} in the TC and OMC1-S, and of 10^{6} stars pc^{-3} in the OHC. The close association between the low-mass star clusters with massive star cradles supports the role of these clusters in the formation of massive stars. The X-ray observations show for the first time in the TC that low-mass stars with intermediate extinction are clustered toward the position of the most massive star, which is surrounded by a ring of non-extincted low-mass stars. This 'envelope-core' structure is also supported by infrared and optical observations. Our analysis suggests that at least two basic ingredients are needed in massive star formation: the presence of dense gas and a cluster of low-mass stars. The scenario that better explains our findings assumes high fragmentation in the parental core, accretion at subcore scales that forms a low-mass stellar cluster, and subsequent competitive accretion. Finally, although coalescence does not seem a common mechanism for building up massive stars, we show that a single stellar merger may have occurred in the evolution of the OHC cluster, favored by the presence of disks, binaries, and gas accretion.Comment: 17 pages, 11 figures, 3 Tables. Accepted for publication in A&

ORAL CYCLOSPORINE AS AN ALTERNATIVE FOR INITIAL STANDARD PROPHYLAXIS IN ALLOGENEIC STEM CELL TRANSPLANTATION WHEN INTRAVENOUS FORMULATION IS UNAVAILABLE

Objective: The objective of the study was to compare the incidence of acute graft versus host disease (aGVHD) between oral and intravenous (IV) initial standard cyclosporine A (CsA) prophylaxis in a tertiary care center in Mexico.Methods: A total of 117 consecutive patients who underwent allogeneic hematopoietic stem cell transplantations (HSCT) were retrospectively analyzed. GVHD prophylaxis consisted of CsA and methotrexate (MTX). CsA was administered IV, until 2005, when it was withdrawn from the market, and CsA was administered orally.Results: Most of the patients were male (55%), with a median age of 33 years (range, 15–63). 92 patients (79%) received CsA orally, and 25 (22%) intravenously. There were no significant differences in CsA concentrations during weeks 1, 2, 3, and 4 between the oral and IV group. From the entire cohort, 1 patient (4%) from the IV group and 16 (17%) from the oral group developed aGVHD, respectively. Sex, gender disparity, and HSCT source were statistically associated with aGVHD in the multivariate analysis.Conclusions: Using oral instead of IV CsA for aGVHD prophylaxis is feasible and could be financially efficient; nonetheless, our results showed a higher incidence of aGVHD in the oral group; however, our study has limitations and further prospective studies including a larger cohort are encouraged

Wigner Crystal State for the Edge Electrons in the Quantum Hall Effect at Filling ν=2\nu = 2

The electronic excitations at the edges of a Hall bar not much wider than a few magnetic lengths are studied theoretically at filling $\nu = 2$. Both mean-field theory and Luttinger liquid theory techniques are employed for the case of a null Zeeman energy splitting. The first calculation yields a stable spin-density wave state along the bar, while the second one predicts dominant Wigner-crystal correlations along the edges of the bar. We propose an antiferromagnetic Wigner-crystal groundstate for the edge electrons that reconciles the two results. A net Zeeman splitting is found to produce canting of the antiferromagnetic order.Comment: 22 pgs. of PLAIN TeX, 1 fig. in postscript, published versio

The Neurological Traces of Look-Alike Avatars

We designed an observational study where participants (n = 17) were exposed to pictures and look-alike avatars pictures of themselves, a familiar friend or an unfamiliar person. By measuring participants’ brain activity with electroencephalography (EEG), we found face-recognition event related potentials (ERPs) in the visual cortex, around 200–250 ms, to be prominent for the different familiarity levels. A less positive component was found for self-recognized pictures (P200) than pictures of others, showing similar effects in both real faces and look-alike avatars. A rapid adaptation in the same component was found when comparing the neural processing of avatar faces vs. real faces, as if avatars in general were assimilated as real face representations over time. ERP results also showed that in the case of the self-avatar, the P200 component correlated with more complex conscious encodings of self-representation, i.e., the difference in voltage in the P200 between the self-avatar and the self-picture was reduced in participants that felt the avatar looked like them. This study is put into context within the literature of self-recognition and face recognition in the visual cortex. Additionally, the implications of these results on look-alike avatars are discussed both for future virtual reality (VR) and neuroscience studies

ArlCDE form the archaeal switch complex

Cells require a sensory system and a motility structure to achieve directed movement. Bacteria and archaea both possess rotating filamentous motility structures that work in concert with the sensory chemotaxis system. This allows microorganisms to move along chemical gradients. The central response regulator protein CheY can bind to the motor of the motility structure, the flagellum in bacteria and the archaellum in archaea. Both motility structures have a fundamentally different protein composition and structural organization. Yet, both systems receive input from the chemotaxis system. We applied a fluorescent microscopy approach in the model euryarchaeon Haloferax volcanii, and shed light on the sequence order in which signals are transferred from the chemotaxis system to the archaellum. Our findings indicate that the euryarchaeal specific ArlCDE are part of the archaellum motor and that they directly receive input from the chemotaxis system via the adaptor protein CheF. Hence, ArlCDE are an important feature of the archaellum of euryarchaea, are essential for signal transduction during chemotaxis and represent the archaeal switch complex

Growth Phase Dependent Cell Shape of Haloarcula

Several haloarchaea are reported to be pleomorphic, while others exhibit remarkable shapes, such as squares. Recently, Haloferax volcanii was found to alter its morphology during growth. Cells are motile rods in early exponential phase, and immotile plates in stationary phase. It is unknown if this growth phase dependent cell shape alteration is a specific feature of Hfx. volcanii, or conserved amongst haloarchaea. Here, we studied the cell shape and motility of two haloarchaea species Haloarcula hispanica and Haloarcula californiae. With a combination of light and electron microscopy, we observed that both strains undergo a growth phase dependent morphological development, albeit in a slightly different fashion as Hfx. volcanii. For both Haloarcula strains, the cell size is changing throughout growth. Cell shape seems to be related with motility, as highly motile cells on semi-solid agar plates are predominantly rod-shaped. We conclude that the growth phase dependent cell morphology alteration might be a common feature amongst haloarchaea, and that cell shape is generally linked with a motile life style. The conservation of this phenomenon underscores the importance of studies of the molecular mechanisms regulating cell shape in archaea

Growth Phase Dependent Cell Shape of Haloarcula

Several haloarchaea are reported to be pleomorphic, while others exhibit remarkable shapes, such as squares. Recently, Haloferax volcanii was found to alter its morphology during growth. Cells are motile rods in early exponential phase, and immotile plates in stationary phase. It is unknown if this growth phase dependent cell shape alteration is a specific feature of Hfx. volcanii, or conserved amongst haloarchaea. Here, we studied the cell shape and motility of two haloarchaea species Haloarcula hispanica and Haloarcula californiae. With a combination of light and electron microscopy, we observed that both strains undergo a growth phase dependent morphological development, albeit in a slightly different fashion as Hfx. volcanii. For both Haloarcula strains, the cell size is changing throughout growth. Cell shape seems to be related with motility, as highly motile cells on semi-solid agar plates are predominantly rod-shaped. We conclude that the growth phase dependent cell morphology alteration might be a common feature amongst haloarchaea, and that cell shape is generally linked with a motile life style. The conservation of this phenomenon underscores the importance of studies of the molecular mechanisms regulating cell shape in archaea