2,534 research outputs found

    The Case Against Official Monolingualism: The Idiosyncrasies of Minority Language Rights In israel And The United States

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    Both Israel and the United States are multi-ethnic societies with a large percentage of linguistic minorities

    The Supreme Court and Libel

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    The Physical Structure of Protoplanetary Disks: the Serpens Cluster Compared with Other Regions

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    Spectral energy distributions are presented for 94 young stars surrounded by disks in the Serpens Molecular Cloud, based on photometry and Spitzer IRS spectra. Taking a distance to the cloud of 415 pc rather than 259 pc, the distribution of ages is shifted to lower values, in the 1-3 Myr range, with a tail up to 10 Myr. The mass distribution spans 0.2-1.2 Msun, with median mass of 0.7 Msun. The distribution of fractional disk luminosities in Serpens resembles that of the young Taurus Molecular Cloud, with most disks consistent with optically thick, passively irradiated disks in a variety of disk geometries (Ldisk/Lstar ~ 0.1). In contrast, the distributions for the older Upper Scorpius and Eta Chamaeleontis clusters are dominated by optically thin lower luminosity disks (Ldisk/Lstar ~ 0.02). This evolution in fractional disk luminosities is concurrent with that of disk fractions. The actively accreting and non-accreting stars (based on Ha data) in Serpens show very similar distributions in fractional disk luminosities, differing only in the brighter tail dominated by strongly accreting stars. In contrast with a sample of Herbig Ae/Be stars, the T Tauri stars in Serpens do not have a clear separation in fractional disk luminosities for different disk geometries: both flared and flat disks present wider, overlapping distributions. This result is consistent with previous suggestions of a faster evolution for disks around Herbig Ae/Be stars. Furthermore, the results for the mineralogy of the dust in the disk surface do not show any correlation to either stellar and disk characteristics or mean cluster age in the 1-10 Myr range probed here. A possible explanation for the lack of correlation is that the processes affecting the dust within disks have short timescales, happening repeatedly, making it difficult to distinguish long lasting evolutionary effects. [abridged]Comment: ApJ in pres

    Pregnancy Obstructs Involution Stage II of the Mammary Gland in Cows: General Biological Implications

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    *Background*
Repeated research findings over the last 4 decades show that involution of mammary glands in dairy cows did not regress to same extend as that noticed in other mammalian species.

*Methodology/Principal Findings*
We took an advantage of a rare event in the normal modern dairy farming: A cow that was false-positively identified as being pregnant was "dried up" (i.e., induced into involution) conventionally about 60 before her expected parturition. This cow was culled, and samples of her mammary gland tissue were examined for gross histology. In this study we demonstrate for the first time that modern dairy cow may undergo extensive obliteration of the lobular-alveolar structure, as expected in involution stage II. 

*Conclusions/Significance*
We conclude that lack of histological evidence for the appearance of involution stage II in the vast majority of modern cow's population is related to the peculiar modern dairy husbandry, in which dairy cows are induced into involution still pregnant. Because retardation of involution stage II in pregnant mammals is most likely a general physiological phenomena, it might occurs in other mammals, particularly in lactating humans. Thus, based on basic comparative physiology considerations, we suggest that concurrent lactation and pregnancy should be considered as an independent risk factor for breast cancer

    A submillimeter search for pre- and proto-brown dwarfs in Chamaeleon II

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    Context. Chamaeleon II molecular cloud is an active star forming region that offers an excellent opportunity for studying the formation of brown dwarfs in the southern hemisphere. Aims. Our aims are to identify a population of pre- and proto- brown dwarfs (5 sigma mass limit threshold of ~0.015 Msun) and provide information on the formation mechanisms of substellar objects. Methods. We performed high sensitivity observations at 870 microns using the LABOCA bolometer at the APEX telescope towards an active star forming region in Chamaeleon II. The data are complemented with an extensive multiwavelength catalogue of sources from the optical to the far-infrared to study the nature of the LABOCA detections. Results. We detect fifteen cores at 870 microns, and eleven of them show masses in the substellar regime. The most intense objects in the surveyed field correspond to the submillimeter counterparts of the well known young stellar objects DK Cha and IRAS 12500-7658. We identify a possible proto-brown dwarf candidate (ChaII-APEX-L) with IRAC emission at 3.6 and 4.5 microns. Conclusions. Our analysis indicates that most of the spatially resolved cores are transient, and that the point-like starless cores in the sub-stellar regime (with masses between 0.016 Msun and 0.066 Msun) could be pre-brown dwarfs cores gravitationally unstable if they have radii smaller than 220 AU to 907 AU (1.2" to 5" at 178 pc) respectively for different masses. ALMA observations will be the key to reveal the energetic state of these pre-brown dwarfs candidates.Comment: 11 pages, 6 figure

    A Herschel view of IC 1396 A: Unveiling the different sequences of star formation

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    The IC1396A globule in the young cluster Tr37, hosting many young stars and protostars, is assumed to be a site of triggered star formation. We mapped IC1396A with Herschel/PACS at 70 and 160 micron. The Herschel maps trace in great detail the very embedded protostellar objects and the structure of the cloud. PACS data reveal a previously unknown Class 0 object (IC1396A-PACS-1) located behind the ionization front. IC1396A-PACS-1 is not detectable with Spitzer, but shows marginal X-ray emission. The data also allowed to study three of the Class I intermediate-mass objects within the cloud. We derived approximate cloud temperatures to study the effect and potential interactions between the protostars and the cloud. The Class 0 object is associated with the densest and colder part of IC1396A. Heating in the cloud is dominated by the winds and radiation of the O6.5 star HD 206267 and, to a lesser extent, by the effects of the Herbig Ae star V 390 Cep. The surroundings of the Class I and Class II objects embedded in the cloud also appear warmer than the sourceless areas, although most of the low-mass objects cannot be individually extracted due to distance and beam dilution. The observations suggest that at least two episodes of star formation have occurred in IC1396A. One would have originated the known, ~1 Myr-old Class I and II objects in the cloud, and a new wave of star formation would have produced the Class 0 source at the tip of the brigth-rimmed cloud. From its location and properties, IC1396A-PACS-1 is consistent with triggering via radiative driven implosion (RDI) induced by HD 206267. The mechanisms behind the formation of the more evolved population of Class I/II/III objects in the cloud are uncertain. Heating of most of the remaining cloud by Class I/Class II objects and by HD 206267 itself may preclude further star formation in the region.Comment: Accepted by A&A, 9 pages, 5 figure
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