131 research outputs found
Realization of the farad from the dc quantum Hall effect with digitally-assisted impedance bridges
A new traceability chain for the derivation of the farad from dc quantum Hall
effect has been implemented at INRIM. Main components of the chain are two new
coaxial transformer bridges: a resistance ratio bridge, and a quadrature
bridge, both operating at 1541 Hz. The bridges are energized and controlled
with a polyphase direct-digital-synthesizer, which permits to achieve both main
and auxiliary equilibria in an automated way; the bridges and do not include
any variable inductive divider or variable impedance box. The relative
uncertainty in the realization of the farad, at the level of 1000 pF, is
estimated to be 64E-9. A first verification of the realization is given by a
comparison with the maintained national capacitance standard, where an
agreement between measurements within their relative combined uncertainty of
420E-9 is obtained.Comment: 15 pages, 11 figures, 3 table
Systematic study of the low-lying electric dipole strength in Sn isotopes and its astrophysical implications
The -ray strength functions (GSF) and nuclear level densities (NLD)
below the neutron threshold have been extracted for Sn
from particle- coincidence data with the Oslo method. The evolution of
bulk properties of the low-lying electric dipole response has been investigated
on the basis of the Oslo GSF data and results of a recent systematic study of
electric and magnetic dipole strengths in even-even Sn isotopes with
relativistic Coulomb excitation. The obtained GSFs reveal a resonance-like peak
on top of the tail of the isovector giant dipole resonance, centered at
8 MeV and exhausting 2\% of the classical Thomas-Reiche-Kuhn
(TRK) sum. In contrast to predictions of the relativistic quasiparticle
random-phase and time-blocking approximation calculations (RQRPA and RQTBA), no
monotonous increase in the total low-lying strength was observed in the
experimental data from Sn to Sn, demonstrating rather similar
strength distributions in these nuclei. The Oslo GSFs and NLDs were further
used as inputs to constrain the cross sections and Maxwellian-averaged cross
sections of reactions in the Sn isotopic chain using TALYS. The
obtained results agree well with other available experimental data and the
recommended values from the JINA REACLIB, BRUSLIB, and KADoNiS libraries.
Despite relatively small exhausted fractions of the TRK sum rule, the low-lying
electric dipole strength makes a noticeable impact on the radiative
neutron-capture cross sections in stable Sn isotopes. Moreover, the
experimental Oslo inputs for the SnSn
reactions were found to affect the production of Sb in the astrophysical
-process, providing new constraints on the uncertainties of the resulting
chemical abundances from multi-zone low-metallicity Asymptotic Giant Branch
stellar models.Comment: 27 pages, 14 pages. Submitted to Physical Review C journal on 13
November 202
New experimental constraint on the W()W cross section
In this work, we present new data on the W() cross
sections, utilizing a quasi-monochromatic photon beam produced at the NewSUBARU
synchrotron radiation facility. Further, we have extracted the nuclear level
density and -ray strength function of W from data on the
W()W reaction measured at the Oslo
Cyclotron Laboratory. Combining previous measurements on the
W() cross section with our new W()
and ()W data sets, we have deduced the
W -ray strength function in the range of MeV
and MeV.
Our data are used to extract the level density and -ray strength
functions needed as input to the nuclear-reaction code \textsf{TALYS},
providing an indirect, experimental constraint for the
W()W cross section and reaction rate. Compared to the
recommended Maxwellian-averaged cross section (MACS) in the KADoNiS-1.0 data
base, our results are on average lower for the relevant energy range keV, and we provide a smaller uncertainty for the MACS. The
theoretical values of Bao \textit{et al.} and the cross section experimentally
constrained on photoneutron data of Sonnabend \textit{et al.} are significantly
higher than our result. The lower value by Mohr \textit{et al.} is in very good
agreement with our deduced MACS. Our new results could have implications for
the -process and in particular the predicted -process production of
Os nuclei.Comment: 17 pages, 15 figures; to be submitted to Phys. Rev.
"Dangerous to Themselves and Others, and of Public Scandal": The Internment Procedure
Abstract
Through G.'s admission and medical files, this chapter illustrates internment laws and procedures, highlighting how Fascism pushed pre-existing legislation to its extreme consequences. In reconstructing internment's bureaucratic and legal practices, the chapter emphasises how the law could be bent to accommodate the regime's need to isolate those perceived as "different" and how psychiatry acquiesced in offering to "correct" individuals considered "non-conforming", "amoral", "immoral", "deviant", rebellious and, among them, homosexuals, in exchange for an increase of power and status
The stb Operon Balances the Requirements for Vegetative Stability and Conjugative Transfer of Plasmid R388
The conjugative plasmid R388 and a number of other plasmids carry an operon, stbABC, adjacent to the origin of conjugative transfer. We investigated the role of the stbA, stbB, and stbC genes. Deletion of stbA affected both conjugation and stability. It led to a 50-fold increase in R388 transfer frequency, as well as to high plasmid loss. In contrast, deletion of stbB abolished conjugation but provoked no change in plasmid stability. Deletion of stbC showed no effect, neither in conjugation nor in stability. Deletion of the entire stb operon had no effect on conjugation, which remained as in the wild-type plasmid, but led to a plasmid loss phenotype similar to that of the R388ÎstbA mutant. We concluded that StbA is required for plasmid stability and that StbA and StbB control conjugation. We next observed the intracellular positioning of R388 DNA molecules and showed that they localize as discrete foci evenly distributed in live Escherichia coli cells. Plasmid instability of the R388ÎÎstbA mutant correlated with aberrant localization of the plasmid DNA molecules as clusters, either at one cell pole, at both poles, or at the cell center. In contrast, plasmid molecules in the R388ÎÎstbB mutant were mostly excluded from the cell poles. Thus, results indicate that defects in both plasmid maintenance and transfer are a consequence of variations in the intracellular positioning of plasmid DNA. We propose that StbA and StbB constitute an atypical plasmid stabilization system that reconciles two modes of plasmid R388 physiology: a maintenance mode (replication and segregation) and a propagation mode (conjugation). The consequences of this novel concept in plasmid physiology will be discussed
Inter-Species Complementation of the Translocon Beta Subunit Requires Only Its Transmembrane Domain
In eukaryotes, proteins enter the secretory pathway through the translocon pore of the endoplasmic reticulum. This protein translocation channel is composed of three major subunits, called Sec61α, ÎČ and Îł in mammals. Unlike the other subunits, the ÎČ subunit is dispensable for translocation and cell viability in all organisms studied. Intriguingly, the knockout of the Sec61ÎČ encoding genes results in different phenotypes in different species. Nevertheless, the ÎČ subunit shows a high level of sequence homology across species, suggesting the conservation of a biological function that remains ill-defined. To address its cellular roles, we characterized the homolog of Sec61ÎČ in the fission yeast Schizosaccharomyces pombe (Sbh1p). Here, we show that the knockout of sbh1+ results in severe cold sensitivity, increased sensitivity to cell-wall stress, and reduced protein secretion at 23°C. Sec61ÎČ homologs from Saccharomyces cerevisiae and human complement the knockout of sbh1+ in S. pombe. As in S. cerevisiae, the transmembrane domain (TMD) of S. pombe Sec61ÎČ is sufficient to complement the phenotypes resulting from the knockout of the entire encoding gene. Remarkably, the TMD of Sec61ÎČ from S. cerevisiae and human also complement the gene knockouts in both yeasts. Together, these observations indicate that the TMD of Sec61ÎČ exerts a cellular function that is conserved across species
SalmoNet, an integrated network of ten Salmonella enterica strains reveals common and distinct pathways to host adaptation
Salmonella enterica is a prominent bacterial pathogen with implications on human and animal health. Salmonella serovars could be classified as gastro-intestinal or extra-intestinal. Genome-wide comparisons revealed that extra-intestinal strains are closer relatives of gastro-intestinal strains than to each other indicating a parallel evolution of this trait. Given the complexity of the differences, a systems-level comparison could reveal key mechanisms enabling extra-intestinal serovars to cause systemic infections. Accordingly, in this work, we introduce a unique resource, SalmoNet, which combines manual curation, high-throughput data and computational predictions to provide an integrated network for Salmonella at the metabolic, transcriptional regulatory and protein-protein interaction levels. SalmoNet provides the networks separately for five gastro-intestinal and five extra-intestinal strains. As a multi-layered, multi-strain database containing experimental data, SalmoNet is the first dedicated network resource for Salmonella. It comprehensively contains interactions between proteins encoded in Salmonella pathogenicity islands, as well as regulatory mechanisms of metabolic processes with the option to zoom-in and analyze the interactions at specific loci in more detail. Application of SalmoNet is not limited to strain comparisons as it also provides a Salmonella resource for biochemical network modeling, host-pathogen interaction studies, drug discovery, experimental validation of novel interactions, uncovering new pathological mechanisms from emergent properties and epidemiological studies. SalmoNet is available at http://salmonet.org
Reversal of the ÎdegP Phenotypes by a Novel rpoE Allele of Escherichia coli
RseA sequesters RpoE (ÏE) to the inner membrane of Escherichia coli when envelope stress is low. Elevated envelope stress triggers RseA cleavage by the sequential action of two membrane proteases, DegS and RseP, releasing ÏE to activate an envelope stress reducing pathway. Revertants of a ÎdegP ÎbamB strain, which fails to grow at 37°C due to high envelope stress, harbored mutations in the rseA and rpoE genes. Null and missense rseA mutations constitutively hyper-activated the ÏE regulon and significantly reduced the major outer membrane protein (OMP) levels. In contrast, a novel rpoE allele, rpoE3, resulting from the partial duplication of the rpoE gene, increased ÏE levels greater than that seen in the rseA mutant background but did not reduce OMP levels. A ÏE-dependent RybB::LacZ construct showed only a weak activation of the ÏE pathway by rpoE3. Despite this, rpoE3 fully reversed the growth and envelope vesiculation phenotypes of ÎdegP. Interestingly, rpoE3 also brought down the modestly activated Cpx envelope stress pathway in the ÎdegP strain to the wild type level, showing the complementary nature of the ÏE and Cpx pathways. Through employing a labile mutant periplasmic protein, AcrAL222Q, it was determined that the rpoE3 mutation overcomes the ÎdegP phenotypes, in part, by activating a ÏE-dependent proteolytic pathway. Our data suggest that a reduction in the OMP levels is not intrinsic to the ÏE-mediated mechanism of lowering envelope stress. They also suggest that under extreme envelope stress, a tight homeostasis loop between RseA and ÏE may partly be responsible for cell death, and this loop can be broken by mutations that either lower RseA activity or increase ÏE levels
Broken replication forks trigger heritable DNA breaks in the terminus of a circular chromosome
<p><u>(A) Circular map of the <i>E</i>. <i>coli</i> chromosome</u>: <i>oriC</i>, <i>dif</i> and <i>terD</i> to <i>terB</i> sites are indicated. Numbers refer to the chromosome coordinates (in kb) of MG1655. (<u>B) Linear map of the terminus region:</u> chromosome coordinates are shown increasing from left to right, as in the marker frequency panels (see Figure 1C for example), therefore in the opposite direction to the circular map. In addition to <i>dif</i> and <i>ter</i> sites, the positions of the <i>parS</i><sub>pMT1</sub> sites used for microscopy experiments are indicated. (<u>C) MFA analysis of terminus DNA loss in the <i>recB</i> mutant</u>: sequence read frequencies of exponential phase cells normalized to the total number of reads were calculated for each strain. Ratios of normalized reads in isogenic wild-type and <i>recB</i> mutant are plotted against chromosomal coordinates (in kb). The profile ratio of the terminus region is enlarged and the profile of the corresponding entire chromosomes is shown in inset. Original normalized profiles used to calculate ratios are shown in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007256#pgen.1007256.s005" target="_blank">S1 Fig</a>. The position of <i>dif</i> is indicated by a red arrow. The <i>ter</i> sites that arrest clockwise forks (<i>terC</i>, <i>terB</i>, green arrow) and counter-clockwise forks (<i>terA</i>, <i>terD</i>, blue arrow) are shown. <u>(D) Schematic representation of focus loss in the <i>recB</i> mutant:</u> Time-lapse microscopy experiments showed that loss of a focus in the <i>recB</i> mutant occurs concomitantly with cell division in one of two daughter cells, and that the cell that keeps the focus then generates a focus-less cell at each generation. The percentage of initial events was calculated as the percentage of cell divisions that generate a focus-less cell, not counting the following generations. In this schematic representation, two initial events occurred (generations #2 and #7) out of 9 generations, and focus loss at generation #2 is heritable. Panels shown in this figure were previously published in [<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1007256#pgen.1007256.ref019" target="_blank">19</a>] and are reproduced here to introduce the phenomenon.</p
Local Narrative-Making on Refugees: How the Interaction Between Journalists and Policy Networks Shapes the Media Frames
AbstractCity narratives are crucial in shaping public attitudes and perceptions, and in defining the viable policy options and cities' responses to hot issues, such as migration and asylum. Nevertheless, the literature on relations between media and political actors is scarce and often unable to account for the complex local mechanisms leading to the production of media frames. This chapter investigates two urban crises: the rapid increase of transit refugees at the Central Station of Milan, and refugees' illegal occupation of four buildings in the ex-MOI area (former Olympic village) in Turin. Both events started in 2013 and have been studied from their beginnings up to mid-2016 by using qualitative techniques and media frame analysis. By matching the media and policy analysis, the authors show the central role that the local institutions can play in shaping media narratives on migrants and how the cohesion of the policy networks strengthens their ability to affect the local media frames. The dynamics of local journalism also matter: the presence of reporters with specific expertise, a commitment to migration and stable engagement in the issue, as well as collaboration within and between newsrooms, namely the existence of a sort of local media community, contribute to the development of consistent narratives over time and the prevalence of humanitarian rather than security frames
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