Laminin β1a controls distinct steps during the establishment of digestive organ laterality

Visceral organs, including the liver and pancreas, adopt asymmetric positions to ensure proper function. Yet the molecular and cellular mechanisms controlling organ laterality are not well understood. We identified a mutation affecting zebrafish laminin β1a (lamb1a) that disrupts left-right asymmetry of the liver and pancreas. In these mutants, the liver spans the midline and the ventral pancreatic bud remains split into bilateral structures. We show that lamb1a regulates asymmetric left-right gene expression in the lateral plate mesoderm (LPM). In particular, lamb1a functions in Kupffer’s vesicle (KV), a ciliated organ analogous to the mouse node, to control the length and function of the KV cilia. Later during gut-looping stages, dynamic expression of Lamb1a is required for the bilayered organization and asymmetric migration of the LPM. Loss of Lamb1a function also results in aberrant protrusion of LPM cells into the gut. Collectively, our results provide cellular and molecular mechanisms by which extracellular matrix proteins regulate left-right organ morphogenesis

A search for spectral features in the XMM-Newton observation of UGC11763

This is an electronic version of an article published in Revista Mexicana de Astronomía y Astrofísica. Cardaci, M.V. et al. A search for spectral features in the XMM-Newton observation of UGC11763. Revista Mexicana de Astronomía y Astrofísica 32 (2008): 13

A comprehensive approach to analyzing the XMM-Newton data of Seyfert 1 galaxies

Aims. We seek a comprehensive analysis of all the information provided by the XMM-Newton satellite of the four Seyfert 1 galaxies ESO 359-G19, HE 1143-1810, CTS A08.12, and Mrk 110, including the UV range, to characterize the different components that are emitting and absorbing radiation in the vicinity of the active nucleus. Methods. The continuum emission was studied through the EPIC spectra by taking advantage of the spectral range of these cameras. The high-resolution RGS spectra were analyzed to characterize the absorbing and emission line features that arise in the spectra of the sources. All these data, complemented by information in the UV, are analyzed jointly in order to achieve a consistent characterization of the observed features in each object. Results. The continuum emission of the sources can be characterized either by a combination of a power law and a black body for the weakest objects or by two power law components for the brightest ones. The continuum is not absorbed by neutral or ionized material in the line of sight to any of these sources. In all of them we have identified a narrow Fe-Kα line at 6.4 keV. In ESO 359-G19 we also find an Fexxvi line at about 7 keV. In the soft X-rays band, we identify only one Ovii line in the spectra of HE 1143-1810 and CTS A08.12, and two Ovii-Heα triplets and a narrow Oviii-Lyα emission line in Mrk 110. Conclusions. Not detecting warm material in the line of sight to the low state objects is due to intrinsically weaker or absent absorption in the line of sight and not to a low signal-to-noise ratio in the data. Besides this, the absence of clear emission lines cannot be fully attributed to dilution of those lines by a strong continuum.Facultad de Ciencias Astronómicas y Geofísica

Characterization of the emitting and absorbing media around the nucleus of the active galaxy UGC 11763 using XMM-Newton data

Aims. The detailed analysis of all data taken by the XMM-Newton satellite of UGC11763 to characterize the different components that are emitting and absorbing radiation in the vicinity of the active nucleus. Methods. The continuum emission was studied through the EPIC spectra taking profit of the spectral range of these cameras. The high resolution RGS spectra were analyzed in order to characterize the absorbing features and the emission line features that arise in the spectra of this source. Results.A power law with a photon index Γ = 1.72+0.03-0.01 accounts for the continuum emission of this source in the hard X-rays from 10 down to 1 keV. At lower energies, a black body model with kT = 0.100 ± 0.003 keV provides a good description of the observed soft excess. The absorption signatures in the spectra of UGC 11763 are consistent with the presence of a two phase ionized material (logU = 1.65+0.07-0.08; 2.6 ± 0.1 and logNH = 21.2 ± 0.2; 21.51 ± 0.01 cm-2, respectively) in the line of sight. The physical conditions found are consistent with the two phases being in pressure equilibrium. The low ionization component is more ionized than typically found for warm absorbers in other Seyfert 1 galaxies. There are also signatures of some emission lines: Ovii Heα(r), Ovii Heα(f), a blend of the Neix Heα triplet and Fexviii at λ 17.5Å.Facultad de Ciencias Astronómicas y Geofísica

Characterization of the emitting and absorbing media around the nucleus of the active galaxy UGC 11763 using XMM-Newton data

Aims. The detailed analysis of all data taken by the XMM-Newton satellite of UGC11763 to characterize the different components that are emitting and absorbing radiation in the vicinity of the active nucleus. Methods. The continuum emission was studied through the EPIC spectra taking profit of the spectral range of these cameras. The high resolution RGS spectra were analyzed in order to characterize the absorbing features and the emission line features that arise in the spectra of this source. Results.A power law with a photon index Γ = 1.72+0.03-0.01 accounts for the continuum emission of this source in the hard X-rays from 10 down to 1 keV. At lower energies, a black body model with kT = 0.100 ± 0.003 keV provides a good description of the observed soft excess. The absorption signatures in the spectra of UGC 11763 are consistent with the presence of a two phase ionized material (logU = 1.65+0.07-0.08; 2.6 ± 0.1 and logNH = 21.2 ± 0.2; 21.51 ± 0.01 cm-2, respectively) in the line of sight. The physical conditions found are consistent with the two phases being in pressure equilibrium. The low ionization component is more ionized than typically found for warm absorbers in other Seyfert 1 galaxies. There are also signatures of some emission lines: Ovii Heα(r), Ovii Heα(f), a blend of the Neix Heα triplet and Fexviii at λ 17.5Å.Facultad de Ciencias Astronómicas y Geofísica

An XMM-Newton view of a small sample of Seyfert 1 Galaxies

We present a detailed analysis of all the X-ray data taken by the XMM-Newton satellite of a small sample of five Seyfert 1 galaxies: ESO 359-G19, HE 1143-1810, CTS A08.12, Mkn 110, and UGC 11763. Our aim is to characterize the different components of the material that print the absorption and emission features in the X-ray spectra of these objects. The continuum emission was studied through the EPIC spectra taking advantage of the spectral range of these cameras. The high resolution RGS spectra were analyzed in order to characterize the absorbing features and the emission line features that arise in the spectra of these sources.Facultad de Ciencias Astronómicas y Geofísica

An XMM-Newton view of a small sample of Seyfert 1 Galaxies

We present a detailed analysis of all the X-ray data taken by the XMM-Newton satellite of a small sample of five Seyfert 1 galaxies: ESO 359-G19, HE 1143-1810, CTS A08.12, Mkn 110, and UGC 11763. Our aim is to characterize the different components of the material that print the absorption and emission features in the X-ray spectra of these objects. The continuum emission was studied through the EPIC spectra taking advantage of the spectral range of these cameras. The high resolution RGS spectra were analyzed in order to characterize the absorbing features and the emission line features that arise in the spectra of these sources.Facultad de Ciencias Astronómicas y Geofísica

Spin injection through the depletion layer: a theory of spin-polarized p-n junctions and solar cells

A drift-diffusion model for spin-charge transport in spin-polarized {\it p-n} junctions is developed and solved numerically for a realistic set of material parameters based on GaAs. It is demonstrated that spin polarization can be injected through the depletion layer by both minority and majority carriers, making all-semiconductor devices such as spin-polarized solar cells and bipolar transistors feasible. Spin-polarized {\it p-n} junctions allow for spin-polarized current generation, spin amplification, voltage control of spin polarization, and a significant extension of spin diffusion range.Comment: 4 pages, 3 figure

A virtual intersubband spin-flip spin-orbit coupling induced spin relaxation in GaAs (110) quantum wells

A spin relaxation mechanism is proposed based on a second-order spin-flip intersubband spin-orbit coupling together with the spin-conserving scattering. The corresponding spin relaxation time is calculated via the Fermi golden rule. It is shown that this mechanism is important in symmetric GaAs (110) quantum wells with high impurity density. The dependences of the spin relaxation time on electron density, temperature and well width are studied with the underlying physics analyzed.Comment: 4+ pages, 4 figures, to be published in Solid Stat. Commu

Simultaneous direct measurement of the electrocaloric and dielectric dynamics of ferroelectrics with microsecond temporal resolution

A contactless technique for direct time-resolved measurements of the full dynamics of the adiabatic temperature change in electrocaloric materials is introduced. The infrared radiation emitted by the electrocaloric sample is sensitively detected with $\mu$s time resolution and mK temperature resolution. We present time-resolved measurements of the electrocaloric effect up to kHz frequencies of the driving electric field and down to small field strengths. The simultaneous recording of transients for applied electric field and induced polarization gives a comprehensive view on the correlation of electrocaloric and ferroelectric properties. The technique can further be applied to the continuous measurement of fatigue for $> 10^6$ electric field cycles.Comment: 12 pages, 11 figure