Polarization Gradient Study of Interstellar Medium Turbulence Using The Canadian Galactic Plane Survey

We have investigated the magneto-ionic turbulence in the interstellar medium through spatial gradients of the complex radio polarization vector in the Canadian Galactic Plane Survey (CGPS). The CGPS data cover 1300 square-degrees, over the range ${53^{\circ}}\leq{\ell}\leq{192^{\circ}}$, ${-3^{\circ}}\leq{b}\leq{5^{\circ}}$ with an extension to ${b}={17.5^{\circ}}$ in the range ${101^{\circ}}\leq{\ell}\leq{116^{\circ}}$, and arcminute resolution at 1420 MHz. Previous studies found a correlation between the skewness and kurtosis of the polarization gradient and the Mach number of the turbulence, or assumed this correlation to deduce the Mach number of an observed turbulent region. We present polarization gradient images of the entire CGPS dataset, and analyze the dependence of these images on angular resolution. The polarization gradients are filamentary, and the length of these filaments is largest towards the Galactic anti-center, and smallest towards the inner Galaxy. This may imply that small-scale turbulence is stronger in the inner Galaxy, or that we observe more distant features at low Galactic longitudes. For every resolution studied, the skewness of the polarization gradient is influenced by the edges of bright polarization gradient regions, which are not related to the turbulence revealed by the polarization gradients. We also find that the skewness of the polarization gradient is sensitive to the size of the box used to calculate the skewness, but insensitive to Galactic longitude, implying that the skewness only probes the number and magnitude of the inhomogeneities within the box. We conclude that the skewness and kurtosis of the polarization gradient are not ideal statistics for probing natural magneto-ionic turbulence.Comment: 21 pages, 15 figures, accepted by Ap

Advanced Diagnostics for the Study of Linearly Polarized Emission. II: Application to Diffuse Interstellar Radio Synchrotron Emission

Diagnostics of polarized emission provide us with valuable information on the Galactic magnetic field and the state of turbulence in the interstellar medium, which cannot be obtained from synchrotron intensity alone. In Paper I (Herron et al. 2017b), we derived polarization diagnostics that are rotationally and translationally invariant in the $Q$-$U$ plane, similar to the polarization gradient. In this paper, we apply these diagnostics to simulations of ideal magnetohydrodynamic turbulence that have a range of sonic and Alfv\'enic Mach numbers. We generate synthetic images of Stokes $Q$ and $U$ for these simulations, for the cases where the turbulence is illuminated from behind by uniform polarized emission, and where the polarized emission originates from within the turbulent volume. From these simulated images we calculate the polarization diagnostics derived in Paper I, for different lines of sight relative to the mean magnetic field, and for a range of frequencies. For all of our simulations, we find that the polarization gradient is very similar to the generalized polarization gradient, and that both trace spatial variations in the magnetoionic medium for the case where emission originates within the turbulent volume, provided that the medium is not supersonic. We propose a method for distinguishing the cases of emission coming from behind or within a turbulent, Faraday rotating medium, and a method to partly map the rotation measure of the observed region. We also speculate on statistics of these diagnostics that may allow us to constrain the physical properties of an observed turbulent region.Comment: 34 pages, 25 figures, accepted for publication in Ap

First Temperature Observations with the USU Very Large Rayleigh Lidar: An Examination of Mesopause Temperatures

As the impetus for extended observational measurements throughout the middle atmosphere has increased1 , the limits of previous instrumentation need to be pushed. The Rayleigh lidar group at the Atmospheric Lidar Observatory (ALO) at Utah State University has pushed such limits on existing Rayleigh scatter lidar technology and, through major upgrades to the previous lidar system, has been able to gather temperature measurements in the upper mesosphere and lower thermosphere from approximately 70P109 km. A data campaign with the new system was conducted around the annual temperature minimum, centered on late June 2012, in this region. The temperatures from this campaign show a considerable night to night variation as well as evidence of wave activity on several nights

Scaffold attachment factor B1 (SAFB1) heterozygosity does not influence Wnt-1 or DMBA-induced tumorigenesis

<p>Abstract</p> <p>Background</p> <p>Scaffold Attachment Factor B1 (SAFB1) is a multifunctional protein which has been implicated in breast cancer previously. We recently generated SAFB1 knockout mice (SAFB1^-/-), but pleiotropic phenotypes including high lethality, dwarfism associated with low IGF-I levels, and infertility and subfertility in male and female mice, respectively, do not allow for straightforward tumorigenesis studies in these mice. Therefore, we asked whether SAFB1 heterozygosity would influence tumor development and progression in MMTV-Wnt-1 oncomice or DMBA induced tumorigenicity, in a manner consistent with haploinsufficiency of the remaining allele.</p> <p>Methods</p> <p>We crossed female SAFB1^+/-(C57B6/129) mice with male MMTV-Wnt-1 (C57B6/SJL) mice to obtain SAFB1^+/+/Wnt-1, SAFB1^+/-/Wnt-1, and SAFB1^+/-mice. For the chemical induced tumorigenesis study we treated 8 weeks old SAFB1^+/-and SAFB^+/+BALB/c mice with 1 mg DMBA once per week for 6 weeks. Animals were monitored for tumor incidence and tumor growth. Tumors were characterized by performing H&E, and by staining for markers of proliferation and apoptosis.</p> <p>Results</p> <p>We did not detect significant differences in tumor incidence and growth between SAFB1^+/+/Wnt-1 and SAFB1^+/-/Wnt-1 mice, and between DMBA-treated SAFB1^+/+and SAFB1^+/-mice. Histological evaluation of tumors showed that SAFB1 heterozygosity did not lead to changes in proliferation or apoptosis. There were, however, significant differences in the distribution of tumor histologies with an increase in papillary and cribriform tumors, and a decrease in squamous tumors in the SAFB1^+/-/Wnt-1 compared to the SAFB1^+/+/Wnt-1 tumors. Of note, DMBA treatment resulted in shortened survival of SAFB1^+/-mice compared to their wildtype littermates, however this trend did not reach statistical significance.</p> <p>Conclusion</p> <p>Our data show that SAFB1 heterozygosity does not influence Wnt-1 or DMBA-induced mammary tumorigenesis.</p

Comparative mitochondrial genomics of snakes: extraordinary substitution rate dynamics and functionality of the duplicate control region

<p>Abstract</p> <p>Background</p> <p>The mitochondrial genomes of snakes are characterized by an overall evolutionary rate that appears to be one of the most accelerated among vertebrates. They also possess other unusual features, including short tRNAs and other genes, and a duplicated control region that has been stably maintained since it originated more than 70 million years ago. Here, we provide a detailed analysis of evolutionary dynamics in snake mitochondrial genomes to better understand the basis of these extreme characteristics, and to explore the relationship between mitochondrial genome molecular evolution, genome architecture, and molecular function. We sequenced complete mitochondrial genomes from Slowinski's corn snake (<it>Pantherophis slowinskii</it>) and two cottonmouths (<it>Agkistrodon piscivorus</it>) to complement previously existing mitochondrial genomes, and to provide an improved comparative view of how genome architecture affects molecular evolution at contrasting levels of divergence.</p> <p>Results</p> <p>We present a Bayesian genetic approach that suggests that the duplicated control region can function as an additional origin of heavy strand replication. The two control regions also appear to have different intra-specific versus inter-specific evolutionary dynamics that may be associated with complex modes of concerted evolution. We find that different genomic regions have experienced substantial accelerated evolution along early branches in snakes, with different genes having experienced dramatic accelerations along specific branches. Some of these accelerations appear to coincide with, or subsequent to, the shortening of various mitochondrial genes and the duplication of the control region and flanking tRNAs.</p> <p>Conclusion</p> <p>Fluctuations in the strength and pattern of selection during snake evolution have had widely varying gene-specific effects on substitution rates, and these rate accelerations may have been functionally related to unusual changes in genomic architecture. The among-lineage and among-gene variation in rate dynamics observed in snakes is the most extreme thus far observed in animal genomes, and provides an important study system for further evaluating the biochemical and physiological basis of evolutionary pressures in vertebrate mitochondria.</p

Amyloid-β nanotubes are associated with prion protein-dependent synaptotoxicity

Growing evidence suggests water-soluble, non-fibrillar forms of amyloid-β protein (Aβ) have important roles in Alzheimer's disease with toxicities mimicked by synthetic Aβ1-42. However, no defined toxic structures acting via specific receptors have been identified and roles of proposed receptors, such as prion protein (PrP), remain controversial. Here we quantify binding to PrP of Aβ1-42 after different durations of aggregation. We show PrP-binding and PrP-dependent inhibition of long-term potentiation (LTP) correlate with the presence of protofibrils. Globular oligomers bind less avidly to PrP and do not inhibit LTP, whereas fibrils inhibit LTP in a PrP-independent manner. That only certain transient Aβ assemblies cause PrP-dependent toxicity explains conflicting reports regarding the involvement of PrP in Aβ-induced impairments. We show that these protofibrils contain a defined nanotubular structure with a previously unidentified triple helical conformation. Blocking the formation of Aβ nanotubes or their interaction with PrP might have a role in treatment of Alzheimer's disease

EPS architecture analysis for future highpower missions

The space tug can represent a valid solution to provide transportation capabilities for future space missions. In particular, the tug can be effectively adopted for different applications such as electric orbit raising for commercial satellites and cargo transfer to resupply space infrastructures. The adoption of high-power electric propulsion is a fundamental enabler for these mission scenarios, owing to its advantages in terms of long lifetime, high performance and operational flexibility. However, further investigation should be performed in order to optimize the design of the space tug considering different architecture alternatives. We defined two sets of thruster operative points for a more representative comparison of EPS architecture cases. In particular, we analyzed three aspects: the adoption of a cluster of thrusters vs the monolithic approach; the implementation of a direct drive power supply vs the traditional power processing unit; the selection of krypton propellant vs xenon. The design of the space tug is performed with MAGNETO tool, a software developed in a collaboration between SITAEL and Politecnico di Torino in the framework of an ESA GSTP project. The results are compared by means of the analytical hierarchy process to identify the optimal design solution for the spacecraft design

Synthesis of CdS and CdSe nanocrystallites using a novel single-molecule precursors approach

The synthesis of CdS and CdSe nanocrystallites using the thermolysis of several dithioor diselenocarbamato complexes of cadmium in trioctylphosphine oxide (TOPO) is reported. The nanodispersed materials obtained show quantum size effects in their optical spectra and exhibit near band-edge luminescence. The influence of experimental parameters on the properties of the nanocrystallites is discussed. HRTEM images of these materials show well-defined, crystalline nanosized particles. Standard size fractionation procedures can be performed in order to narrow the size dispersion of the samples. The TOPO-capped CdS and CdSe nanocrystallites and simple organic bridging ligands, such as 2,2¢-bipyrimidine, are used as the starting materials for the preparation of novel nanocomposites. The optical properties shown by these new nanocomposites are compared with those of the starting nanodispersed materials

Survey of Photochemical and Rate Data for Twenty‐eight Reactions of Interest in Atmospheric Chemistry

Photochemical and rate data have been evaluated for 28 gas phase reactions of interest for the chemistry of the stratosphere. The results are presented on data sheets, one per reaction. For each reaction, the available data are summarized. Where possible there is given a preferred value for the rate constant or, for the photochemical reactions, preferred values for primary quantum yields and optical absorption coefficients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87745/2/267_1.pd