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Search Results: 1 - 10 of 209993 matches for " Nadia L. Scampoli "
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Fishing the Molecular Bases of Treacher Collins Syndrome
Andrea M. J. Weiner, Nadia L. Scampoli, Nora B. Calcaterra
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029574
Abstract: Treacher Collins syndrome (TCS) is an autosomal dominant disorder of craniofacial development, and mutations in the TCOF1 gene are responsible for over 90% of TCS cases. The knowledge about the molecular mechanisms responsible for this syndrome is relatively scant, probably due to the difficulty of reproducing the pathology in experimental animals. Zebrafish is an emerging model for human disease studies, and we therefore assessed it as a model for studying TCS. We identified in silico the putative zebrafish TCOF1 ortholog and cloned the corresponding cDNA. The derived polypeptide shares the main structural domains found in mammals and amphibians. Tcof1 expression is restricted to the anterior-most regions of zebrafish developing embryos, similar to what happens in mouse embryos. Tcof1 loss-of-function resulted in fish showing phenotypes similar to those observed in TCS patients, and enabled a further characterization of the mechanisms underlying craniofacial malformation. Besides, we initiated the identification of potential molecular targets of treacle in zebrafish. We found that Tcof1 loss-of-function led to a decrease in the expression of cellular proliferation and craniofacial development. Together, results presented here strongly suggest that it is possible to achieve fish with TCS-like phenotype by knocking down the expression of the TCOF1 ortholog in zebrafish. This experimental condition may facilitate the study of the disease etiology during embryonic development.
H_2 emission arises outside photodissociation regions in ultra-luminous infrared galaxies
Nadia L. Zakamska
Physics , 2010, DOI: 10.1038/nature09037
Abstract: Ultra-luminous infrared galaxies are among the most luminous objects in the local universe and are thought to be powered by intense star formation. It has been shown that in these objects the rotational spectral lines of molecular hydrogen observed at mid-infrared wavelengths are not affected by dust obscuration, leaving unresolved the source of excitation of this emission. Here I report an analysis of archival Spitzer Space Telescope data on ultra-luminous infrared galaxies and demonstrate that star formation regions are buried inside optically thick clouds of gas and dust, so that dust obscuration affects star-formation indicators but not molecular hydrogen. I thereby establish that the emission of H_2 is not co-spatial with the buried starburst activity and originates outside the obscured regions. This is rather surprising in light of the standard view that H_2 emission is directly associated with star-formation activity. Instead, I propose that H_2 emission in these objects traces shocks in the surrounding material, which are in turn excited by interactions with nearby galaxies, and that powerful large-scale shocks cooling by means of H_2 emission may be much more common than previously thought. In the early universe, a boost in H_2 emission by this process may speed up the cooling of matter as it collapsed to form the first stars and galaxies and would make these first structures more readily observable.
Theory of Special Relativity
Nadia L. Zakamska
Physics , 2015,
Abstract: Special Relativity is taught to physics sophomores at Johns Hopkins University in a series of eight lectures. Lecture 1 covers the principle of relativity and the derivation of the Lorentz transform. Lecture 2 covers length contraction and time dilation. Lecture 3 covers Minkowski diagrams, simultaneous events and causally connected events, as well as velocity transforms. Lecture 4 covers energy and momentum of particles and introduces 4-vectors. Lecture 5 covers energy and momentum of photons and collision problems. Lecture 6 covers Doppler effect and aberration. Lecture 7 covers relativistic dynamics. Optional Lecture 8 covers field transforms. The main purpose of these notes is to introduce 4-vectors and the matrix notation and to demonstrate their use in solving standard problems in Special Relativity. The pre-requisites for the class are calculus-based Classical Mechanics and Electricity & Magnetism, and Linear Algebra is highly recommended.
Models of Galaxy Clusters with Thermal Conduction
Nadia L. Zakamska,Ramesh Narayan
Physics , 2002, DOI: 10.1086/344641
Abstract: We present a simple model of hot gas in galaxy clusters, assuming hydrostatic equilibrium and energy balance between radiative cooling and thermal conduction. For five clusters, A1795, A1835, A2199, A2390 and RXJ1347.5-1145, the model gives a good description of the observed radial profiles of electron density and temperature, provided we take the thermal conductivity $\kappa$ to be about 30% of the Spitzer conductivity. Since the required $\kappa$ is consistent with the recent theoretical estimate of Narayan & Medvedev (2001) for a turbulent magnetized plasma, we consider a conduction-based equilibrium model to be viable for these clusters. We further show that the hot gas is thermally stable because of the presence of conduction. For five other clusters, A2052, A2597, Hydra A, Ser 159-03 and 3C295, the model requires unphysically large values of $\kappa$ to fit the data. These clusters must have some additional source of heat, most likely an active galactic nucleus since all the clusters have strong radio galaxies at their centers. We suggest that thermal conduction, though not dominant in these clusters, may nevertheless play a significant role by preventing the gas from becoming thermally unstable.
Advocacy and Policy Change in the Multilevel System of the European Union: A Case Study within Health Policy  [PDF]
Nadia Carboni
Open Journal of Political Science (OJPS) , 2012, DOI: 10.4236/ojps.2012.23005
Abstract: Health policy is basically Member States’ competence. However, the European Union has recently raised a number of key questions facing both (pharmaceutical) industries and public health interests. By applying the Advocacy Coalition Framework, the paper sheds light on policy change within the European multilevel system. The analysis is based on a case-study strategy. Two processes in the pharmaceutical policy are taken into account: the “Pharma Forum” and the “Pharma Package”. They both concern “information to patient”—a controversial policy issue at the crossroad of competing pressures.
Quasar feedback and the origin of radio emission in radio-quiet quasars
Nadia L. Zakamska,Jenny E. Greene
Physics , 2014, DOI: 10.1093/mnras/stu842
Abstract: We conduct kinematic analysis of the SDSS spectra of 568 obscured luminous quasars, with the emphasis on the kinematic structure of the [OIII]5007 emission line. [OIII] emission tends to show blueshifts and blue excess, which indicates that at least part of the narrow-line gas is undergoing an organized outflow. The velocity width containing 90% of line power ranges from 370 to 4780 km/sec, suggesting outflow velocities up to 2000 km/sec. The velocity width of the [OIII] emission is positively correlated with the radio luminosity among the radio-quiet quasars. We propose that radio emission in radio-quiet quasars is due to relativistic particles accelerated in the shocks within the quasar-driven outflows; star formation in quasar hosts is insufficient to explain the observed radio emission. The median radio luminosity of the sample of nu L_nu[1.4GHz] = 10^40 erg/sec suggests a median kinetic luminosity of the quasar-driven wind of L_wind=3x10^44 erg/sec, or about 4% of the estimated median bolometric luminosity L_bol=8x10^45 erg/sec. Furthermore, the velocity width of [OIII] is positively correlated with mid-infrared luminosity, which suggests that outflows are ultimately driven by the radiative output of the quasar. As the outflow velocity increases, some emission lines characteristic of shocks in quasi-neutral medium increase as well, which we take as further evidence of quasar-driven winds propagating into the interstellar medium of the host galaxy. None of the kinematic components show correlations with the stellar velocity dispersions of the host galaxies, so there is no evidence that any of the gas in the narrow-line region of quasars is in dynamical equilibrium with the host galaxy. Quasar feedback appears to operate above the threshold luminosity of L_bol=3x10^45 erg/sec.
Warm molecular hydrogen in outflows from Ultraluminous Infrared Galaxies
Matthew J. Hill,Nadia L. Zakamska
Physics , 2013, DOI: 10.1093/mnras/stu123
Abstract: Ultraluminous infrared galaxies (ULIRGs) show on average three times more emission in the rotational transitions of molecular hydrogen than expected based on their star formation rates. Using Spitzer archival data we investigate the origin of excess warm H_2 emission in 115 ULIRGs of the IRAS 1 Jy sample. We find a strong correlation between H_2 and [FeII] line luminosities, suggesting that excess H_2 is produced in shocks propagating within neutral or partially ionized medium. This view is supported by the correlations between H_2 and optical line ratios diagnostic of such shocks. The galaxies powered by star formation and those powered by active nuclei follow the same relationship between H_2 and [FeII], with emission line width being the major difference between these classes (about 500 and 1000 km/sec, respectively). We conclude that excess H_2 emission is produced as the supernovae and active nuclei drive outflows into the neutral interstellar medium of the ULIRGs. A weak positive correlation between H_2 and the length of the tidal tails indicates that these outflows are more likely to be encountered in more advanced mergers, but there is no evidence for excess H_2 produced as a result of the collision shocks during the final coalescence.
Estimates of MM type for the multivariate linear model
Nadia L. Kudraszow,Ricardo A. Maronna
Statistics , 2010, DOI: 10.1016/j.jmva.2011.04.011
Abstract: We propose a class of robust estimates for multivariate linear models. Based on the approach of MM estimation (Yohai 1987), we estimate the regression coefficients and the covariance matrix of the errors simultaneously. These estimates have both high breakdown point and high asymptotic efficiency under Gaussian errors. We prove consistency and asymptotic normality assuming errors with an elliptical distribution. We describe an iterative algorithm for the numerical calculation of these estimates. The advantages of the proposed estimates over their competitors are demonstrated through both simulated and real data.
Detection of drechslera avenae in oat seeds
Fitopatologia Brasileira , 2001, DOI: 10.1590/S0100-41582001000400010
Abstract: the fungus drechslera avenae, the causal agent of helminthosporium leaf spot on oats (avena sativa), survives as mycelium in crop residues and in infected seeds. in trials carried out in the laboratory, ten methods were evaluated for their efficiency to detect d. avenae in oat seeds. in each experiment, groups of two or three methods were compared to a standard protocol, in which seeds were placed in petri dishes containing the reis selective medium and incubated at 25±2 °c for ten days. data were submitted to analysis of variation and the means of the methods were compared using the dunnett test at the 5% significance level. overall, the highest levels of seed infection by d. avenae were observed on oat seeds plated in the osmotic, the oat-agar and the reis media, or on seeds subjected to heat treatment previous to incubation in malt-agar. therefore, these methods should be recommended for detection of d. avenae in oat seed testing.
Detection of drechslera avenae in oat seeds
Fitopatologia Brasileira , 2001,
Abstract: The fungus Drechslera avenae, the causal agent of Helminthosporium leaf spot on oats (Avena sativa), survives as mycelium in crop residues and in infected seeds. In trials carried out in the laboratory, ten methods were evaluated for their efficiency to detect D. avenae in oat seeds. In each experiment, groups of two or three methods were compared to a standard protocol, in which seeds were placed in Petri dishes containing the Reis selective medium and incubated at 25±2 °C for ten days. Data were submitted to analysis of variation and the means of the methods were compared using the Dunnett test at the 5% significance level. Overall, the highest levels of seed infection by D. avenae were observed on oat seeds plated in the osmotic, the oat-agar and the Reis media, or on seeds subjected to heat treatment previous to incubation in malt-agar. Therefore, these methods should be recommended for detection of D. avenae in oat seed testing.
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