A supersymmetric model for triggering Supernova Ia in isolated white dwarfs

We propose a model for supernovae Ia explosions based on a phase transition to a supersymmetric state which becomes the active trigger for the deflagration starting the explosion in an isolated sub-Chandrasekhar white dwarf star. With two free parameters we fit the rate and several properties of type Ia supernovae and address the gap in the supermassive black hole mass distribution. One parameter is a critical density fit to about $3 \cdot 10^7$ g/cc while the other has the units of a space time volume and is found to be of order $0.05\,$ Gyr $R_E^3$ where $R_E$ is the earth radius. The model involves a phase transition to an exact supersymmetry in a small core of a dense star.Comment: 20 pages, 5 figures, expanded version to be published in Physical Review

Automatic Dti-based Parcellation Of The Corpus Callosum Through The Watershed Transform

Introduction: Parcellation of the corpus callosum (CC) in the midsagittal cross-section of the brain is of utmost importance for the study of diffusion properties within this structure. The complexity of this operation comes from the absence of macroscopic anatomical landmarks to help in dividing the CC into different callosal areas. In this paper we propose a completely automatic method for CC parcellation using diffusion tensor imaging (DTI). Methods: A dataset of 15 diffusion MRI volumes from normal subjects was used. For each subject, the midsagital slice was automatically detected based on the Fractional Anisotropy (FA) map. Then, segmentation of the CC in the midsgital slice was performed using the hierarchical watershed transform over a weighted FA-map. Finally, parcellation of the CC was obtained through the application of the watershed transform from chosen markers. Results: Parcellation results obtained were consistent for fourteen of the fifteen subjects tested. Results were similar to the ones obtained from tractography-based methods. Tractography confirmed that the cortical regions associated with each obtained CC region were consistent with the literature. Conclusions: A completely automatic DTI-based parcellation method for the CC was designed and presented. It is not based on tractography, which makes it fast and computationally inexpensive. While most of the existing methods for parcellation of the CC determine an average behavior for the subjects based on population studies, the proposed method reflects the diffusion properties specific for each subject. Parcellation boundaries are found based on the diffusion properties within each individual CC, which makes it more reliable and less affected by differences in size and shape among subjects.302132143Aboitiz, F., Scheibel, A.B., Fisher, R.S., Zaidel, E., Fiber composition of the human corpus callosum (1992) Brain Research, 598 (1-2), pp. 143-153. , http://dx.doi.org/10.1016/0006-8993(92)90178-CBasser, P.J., Pierpaoli, C., Microstructural and physiological features of tissues elucidated by quantitative-diffusion-tensor MRI (1996) Journal of Magnetic Resonance, Series B, 111 (3), pp. 209-219. , http://dx.doi.org/10.1006/jmrb.1996.0086Basser, P.J., Mattiello, J., LeBihan, D., MR diffusion tensor spectroscopy and imaging (1994) Biophysical Journal, 66 (1), pp. 259-267. , http://dx.doi.org/10.1016/S0006-3495(94)80775-1Beucher, S., Lantuéjoul, C., (1979) Use of watersheds in contour detection, , In: International Workshop on Image Processing: Proceedings of the International Workshop on Image Processing: Real-time Edge and Motion Detection/EstimationRennes, FranceBeucher, S., Meyer, F., (1992) The morphological approach to segmentation: The Watershed Transformation, pp. 433-481. , Mathematical Morphology in Image Processing (CRC Press)Biegon, A., Eberling, J.L., Richardson, B.C., Roos, M.S., Wong, S.T., Reed, B.R., Jagust, W.J., Human corpus callosum in aging and alzheimer's disease: A magnetic resonance imaging study (1994) Neurobiology of Aging, 15 (4), pp. 393-397. , http://dx.doi.org/10.1016/0197-4580(94)90070-1Chepuri, N.B., Yen, Y.F., Burdette, J.H., Li, H., Moody, D.M., Maldjian, J.A., Diffusion anisotropy in the corpus callosum (2002) American journal of Neuroradiology, 23 (5), pp. 803-808. , PMid: 12006281DeLacoste-Utamsing, C., Holloway, R., Sexual dimorphism in the human corpus callosum (1982) Science, 216 (4553), pp. 1431-1432. , http://dx.doi.org/10.1126/science.7089533Digabel, H., Lantuéjoul, C., Iterative algorithms, pp. 85-99. , In: European Symposium Quantitative Analysis of Microstructures in Material Science, Biology and Medicine: Proceedings of the 2nd European Symposium Quantitative Analysis of Microstructures in Material Science, Biology and Medicine1978Dougherty, R.F., Ben-Shachar, M., Bammer, R., Brewer, A.A., Wandell, B.A., Functional organization of human occipital-callosal fiber tracts (2005) Proceedings of the National Academy of Sciences of the United States of America, 102 (20), pp. 7350-7355. , http://dx.doi.org/10.1073/pnas.0500003102, PMid: 15883384 PMCid: PMC1129102Duara, R., Kushch, A., Gross-Glenn, K., Barker, W.W., Jallad, B., Pascal, S., Loewenstein, D.A., Lubs, H., Neuroanatomic differences between dyslexic and normal readers on magnetic resonance imaging scans (1991) Archives of Neurology, 48 (4), pp. 410-416. , http://dx.doi.org/10.1001/archneur.1991.00530160078018, PMid: 2012516Falcão, A.X., Stolfi, J., Lotufo, R.A., The image foresting transform: Theory, algorithms, and applications (2004) IEEE Transactions on Pattern Analysis and Machine Intelligence, 26 (1), pp. 19-29. , http://dx.doi.org/10.1109/TPAMI.2004.1261076, PMid: 15382683Freitas, P., Rittner, L., Appenzeller, S., Lotufo, R.A., Watershed-based segmentation of the midsagittal section of the corpus callosum in diffusion MRI IEEE Computer Society, pp. 274-280. , In: Graphics, Patterns and Images, Conference on: Proceedings of the 24th Conference on Graphics, Patterns and Images2011Grimaud, M., A new measure of contrast: The dynamics (1992) Image Algebra and Morphological Image Processing III, 1769, pp. 292-305. , http://dx.doi.org/10.1117/12.60650Habib, M., Gayraud, D., Oliva, A., Regis, J., Salamon, G., Khalil, R., Effects of handedness and sex on the morphology of the corpus callosum: A study with brain magnetic resonance imaging (1991) Brain and Cognition, 16 (1), pp. 41-61. , http://dx.doi.org/10.1016/0278-2626(91)90084-LHampel, H., Teipel, S.J., Alexander, G.E., Horwitz, B., Teichberg, D., Schapiro, M.B., Rapoport, S.I., Corpus callosum atrophy is a possible indicator of region-and cell type-specific neuronal degeneration in Alzheimer disease: A magnetic resonance imaging analysis (1998) Archives of Neurology, 55 (2), pp. 193-198. , http://dx.doi.org/10.1001/archneur.55.2.193, PMid: 9482361Hofer, S., Frahm, J., Topography of the human corpus callosum revisited-comprehensive fiber tractography using diffusion tensor magnetic resonance imaging (2006) NeuroImage, 32 (3), pp. 989-994. , http://dx.doi.org/10.1016/j.neuroimage.2006.05.044, PMid: 16854598Huang, H., Zhang, J., Jiang, H., Wakana, S., Poetscher, L., Miller, M.I., van Zijl, P.C., Mori, S., DTI tractography based parcellation of white matter: Application to the mid-sagittal morphology of corpus callosum (2005) NeuroImage, 26 (1), pp. 195-205. , http://dx.doi.org/10.1016/j.neuroimage.2005.01.019, PMid: 15862219Johnson, S.C., Farnworth, T., Pinkston, J.B., Bigler, E.D., Blatter, D.D., Corpus callosum surface area across the human adult life span: Effect of age and gender (1994) Brain Research Bulletin, 35 (4), pp. 373-377. , http://dx.doi.org/10.1016/0361-9230(94)90116-3Körbes, A., Lotufo, R.A., Analysis of the watershed algorithms based on the Breadth-First and Depth-First exploring methods (2009) IEEE Computer Society, pp. 133-140. , http://dx.doi.org/10.1109/SIBGRAPI.2009.43, In: Computer Graphics and Image Processing, Brazilian Symposium on: Proceedings of the 22th Brazilian Symposium on Computer Graphics and Image Processing2009Rio de Janeiro, BrazilLarsen, J.P., Höien, T., Odegaard, H., Magnetic resonance imaging of the corpus callosum in developmental dyslexia (1992) Cognitive Neuropsychology, 9 (2), pp. 123-134. , http://dx.doi.org/10.1080/02643299208252055Lotufo, R.A., Falcão, A.X., The ordered queue and the optimality of the watershed approaches Kluwer Academic Publishersv, pp. 341-350. , http://dx.doi.org/10.1007/0-306-47025-X_37, In: Mathematical Morphology and its Applications to Image and Signal Processing: Proceedings of the 5th International Symposium on Mathematical Morphology and its Applications to Image and Signal Processing2000, 18Mori, S., Crain, B.J., Chacko, V.P., van Zijl, P.C.M., Three-dimensional tracking of axonal projections in the brain by magnetic resonance imaging (1999) Annals of Neurology, 45 (2), pp. 265-269. , http://dx.doi.org/10.1002/1531-8249(199902)45:2265::AID-ANA213.0.CO;2-3Narr, K.L., Thompson, P.M., Sharma, T., Moussal, J., Cannestra, A.F., Toga, A.W., Mapping morphology of the corpus callosum in schizophrenia (2000) Cerebral cortex (New York, NY, 1991), 10 (1), pp. 40-49. , http://dx.doi.org/10.1093/cercor/10.1.40Narr, K.L., Cannon, T.D., Woods, R.P., Thompson, P.M., Kim, S., Asunction, D., van Erp, T.G., Toga, A.W., Genetic Contributions to Altered Callosal Morphology in Schizophrenia The Journal of Neuroscience, 22 (9), pp. 3720-3729. , PMid: 11978848O'Dwyer, L., Lamberton, F., Bokde, A.L.W., Ewers, M., Faluyi, Y.O., Tanner, C., Mazoyer, B., Hampel, H., Multiple indices of diffusion identifies white matter damage in mild cognitive impairment and Alzheimer's disease (2011) PLoS one, 6 (6), pp. e21745. , http://dx.doi.org/10.1371/journal.pone.0021745, PMid: 21738785 PMCid: PMC3128090Oh, J.S., Suk Park, K., Chan Song, I., Ju Kim, S., Hwang, J., Chung, A., Kyoon Lyoo, I., Fractional anisotropy-based divisions of midsagittal corpus callosum (2005) Neuroreport, 16 (4), pp. 317-320. , http://dx.doi.org/10.1097/00001756-200503150-00002Park, H.J., Kim, J.J., Lee, S.K., Seok, J.H., Chun, J., Kim, D.I., Lee, J.D., Corpus callosal connection mapping using cortical gray matter parcellation and DT-MRI (2008) Human Brain Mapping, 29 (5), pp. 503-516. , http://dx.doi.org/10.1002/hbm.20314, PMid: 17133394Park, J.S., Yoon, U., Kwak, K.C., Seo, S.W., Kim, S.I., Na, D.L., Lee, J.M., The relationships between extent and microstructural properties of the midsagittal corpus callosum in human brain (2011) NeuroImage, 56 (1), pp. 174-184. , http://dx.doi.org/10.1016/j.neuroimage.2011.01.065, PMid: 21281715Rajapakse, J.C., Giedd, J.N., Rumsey, J.M., Vaituzis, A.C., Hamburger, S.D., Rapoport, J.L., Regional MRI measurements of the corpus callosum: A methodological and developmental study (1996) Brain and Development, 18 (5), pp. 379-388. , http://dx.doi.org/10.1016/0387-7604(96)00034-4Rumsey, J.M., Casanova, M., Mannheim, G.B., Patronas, N., De Vaughn, N., Hamburger, S.D., Aquino, T., Corpus callosum morphology, as measured with MRI, in dyslexic men Biological Psychiatry, 39 (9), pp. 769-775. , http://dx.doi.org/10.1016/0006-3223(95)00225-1Rosas, H.D., Lee, S.Y., Bender, A.C., Zaleta, A.K., Vangel, M., Yu, P., Fischl, B., Hersch, S.M., Altered white matter microstructure in the corpus callosum in Huntington's disease: Implications for cortical disconnection (2010) NeuroImage, 49 (4), pp. 2995-3004. , http://dx.doi.org/10.1016/j.neuroimage.2009.10.015, PMid: 19850138 PMCid: PMC3725957Thompson, P.M., Narr, K.L., Blanton, R.E., Toga, A.W., Mapping structural alterations of the corpus callosum during brain development and degeneration (2003) Proceedings of the NATO ASI on the corpus callosum, pp. 93-130Von Plessen, K., Lundervold, A., Duta, N., Heiervang, E., Klauschen, F., Smievoll, A.I., Ersland, L., Hugdahl, K., Less developed corpus callosum in dyslexic subjects-a structural MRI study (2002) Neuropsychologia, 40 (7), pp. 1035-1044. , http://dx.doi.org/10.1016/S0028-3932(01)00143-9Wahl, M., Lauterbach-Soon, B., Hattingen, E., Jung, P., Singer, O., Volz, S., Klein, J.C., Ziemann, U., Human motor corpus callosum: Topography, somatotopy, and link between microstructure and function (2007) Journal of Neuroscience, 27 (45), pp. 12132-12138. , http://dx.doi.org/10.1523/JNEUROSCI.2320-07.2007, PMid: 17989279Witelson, S.F., Hand and sex differences in the isthmus and genu of the human corpus callosum. A postmortem morphological study (1989) Brain, 112 (PART 3), pp. 799-835. , http://dx.doi.org/10.1093/brain/112.3.799, PMid: 2731030Witelson, S.F., Goldsmith, C.H., The relationship of hand preference to anatomy of the corpus callosum in men (1991) Brain Research, 545 (1-2), pp. 175-182. , http://dx.doi.org/10.1016/0006-8993(91)91284-

9286 Stars: An Agglomeration of Stellar Polarization Catalogs

This is a revision. The revisions are minor. The new version of the catalog should be used in preference to the old. The most serious error in the older version was that $\theta_diff$ was incorrect, being sometimes far too large, for Reiz and Franco entries; the correct values are all zero for that reference. We present an agglomeration of stellar polarization catalogs with results for 9286 stars. We have endeavored to eliminate errors, provide accurate (arcsecond) positions, sensibly weight multiple observations of the same star, and provide reasonable distances. This catalog is included as an ASCII file (catalog.txt) in the source of this submission.Comment: The most serious error in the older version was that $\theta_diff$ was incorrect, being sometimes far too large, for Reiz and Franco entries; the correct values are all zero for that reference. 11 pages, no figures. Accepted for Astronomical Journal. Catalog also available as an ASCII file by anonymous FTP from ftp://vermi.berkeley.edu/pub/polcat/p14.ou

Beliefs and Self-Efficacy of Parents of Young Children with Hearing Loss

The purpose of this study was to learn more about the beliefs and self-efficacy of parents of young children with hearing loss. Seventy-two parents completed the Scale of Parental Involvement and Self-Efficacy - Revised (SPISE-R), which queries parents about their child’s hearing device use and their perceptions of their own beliefs, knowledge, confidence, and actions pertaining to supporting their child’s auditory access and spoken language development. Two beliefs were identified that related to parents’ action scores and one belief was identified that related to children’s hearing device use. Knowledge and confidence scores were significantly correlated with action scores and children’s hearing device use, whereas only confidence scores were related to scores on a measure of children’s spoken language abilities. Results indicate the SPISE-R is a promising tool for use in early intervention to better understand parents’ strengths and needs pertaining to supporting their young child’s auditory access and spoken language development

A Census of the Chamaeleon I Star-Forming Region

Optical spectroscopy has been obtained for 179 objects that have been previously identified as possible members of the cluster, that lack either accurate spectral types or clear evidence of membership, and that are optically visible (I<18). I have used these spectroscopic data and all other available constraints to evaluate the spectral classifications and membership status of a total sample of 288 candidate members of Chamaeleon I that have appeared in published studies of the cluster. The latest census of Chamaeleon I now contains 158 members, 8 of which are later than M6 and thus are likely to be brown dwarfs. I find that many of the objects identified as members of Chamaeleon I in recent surveys are actually field stars. Meanwhile, 7 of 9 candidates discovered by Carpenter and coworkers are confirmed as members, one of which is the coolest known member of Chamaeleon I at a spectral type of M8 (~0.03 M_sun). I have estimated extinctions, luminosities, and effective temperatures for the members and used these data to construct an H-R diagram for the cluster. Chamaeleon I has a median age of ~2 Myr according to evolutionary models, and hence is similar in age to IC 348 and is slightly older than Taurus (~1 Myr). The measurement of an IMF for Chamaeleon I from this census is not possible because of the disparate methods with which the known members were originally selected, and must await an unbiased, magnitude-limited survey of the cluster.Comment: 59 pages, 22 figure

Common-Path Interference and Zener Tunneling in Bilayer Graphene p-n Junctions

Interference and tunneling are two signature quantum effects that are often perceived as the yin and yang of quantum mechanics: particle simultaneously propagating along several distinct classical paths versus particle penetrating through a classically inaccessible region via a single least-action path. Here we demonstrate that the Dirac quasiparticles in graphene provide a dramatic departure from this paradigm. We show that Zener tunneling in gapped bilayer graphene (BLG), which governs transport through p-n heterojunctions, exhibits common-path interference that takes place under the tunnel barrier. Due to a symmetry peculiar to the BLG bandstructure, interfering tunneling paths form `conjugate pairs', giving rise to high-contrast oscillations in transmission as a function of the gate-tunable bandgap and other control parameters of the junction. The common-path interference is solely due to forward-propagating waves; in contrast to Fabry-Perot-type interference in resonant tunneling structures it does not rely on multiple backscattering. The oscillations manifest themselves in the junction I-V characteristic as N-shaped branches with negative differential conductivity, enabling new high-speed active-circuit devices with architectures which are not available in electronic semiconductor devices.Comment: 7 pgs, 5 fg

The First VLT FORS1 spectra of Lyman-break candidates in the HDF-S and AXAF Deep Field

We report on low-resolution multi-object spectroscopy of 30 faint targets (R \~ 24-25) in the HDF-S and AXAF deep field obtained with the VLT Focal Reducer/low dispersion Spectrograph (FORS1). Eight high-redshift galaxies with 2.75< z < 4 have been identified. The spectroscopic redshifts are in good agreement with the photometric ones with a dispersion $\sigma_z = 0.07$ at z<2 and $\sigma_z = 0.16$ at z>2. The inferred star formation rates of the individual objects are moderate, ranging from a few to a few tens solar masses per year. Five out of the eight high-z objects do not show prominent emission lines. One object has a spectrum typical of an AGN. In the AXAF field two relatively close pairs of galaxies have been identified, with separations of 8.7 and 3.1 proper Mpc and mean redshifts of 3.11 and 3.93, respectively.Comment: 5 pages Latex, with 2 PostScript figures. Astronomy and Astrophysics, in pres

Spectral line profiles changed by dust scattering in heavily obscured young stellar objects

It is known that scattering of radiation by circumstellar dust can strongly change the line profiles in stellar spectra. This hampers the analysis of spectral lines originating in the emitting regions of heavily obscured young stars. To calculate the line profile of the scattered radiation, we suggest to use the approximation of remote scattering particles. This approximation assumes that the scattering dust grains are at a distance from the star that is much larger than the characteristic size of the emitting region. Using this method, we calculated the line profiles of several simple models. They show the H alpha line profiles of Herbig AeBe stars in the presence and absence of motionless or moving dust

Superlattice properties of carbon nanotubes in a transverse electric field

Electron motion in a (n,1) carbon nanotube is shown to correspond to a de Broglie wave propagating along a helical line on the nanotube wall. This helical motion leads to periodicity of the electron potential energy in the presence of an electric field normal to the nanotube axis. The period of this potential is proportional to the nanotube radius and is greater than the interatomic distance in the nanotube. As a result, the behavior of an electron in a (n,1) nanotube subject to a transverse electric field is similar to that in a semiconductor superlattice. In particular, Bragg scattering of electrons from the long-range periodic potential results in the opening of gaps in the energy spectrum of the nanotube. Modification of the bandstructure is shown to be significant for experimentally attainable electric fields, which raises the possibility of applying this effect to novel nanoelectronic devices.Comment: 7 pages, 3 figure