1,869 research outputs found
r-Java 2.0: the nuclear physics
[Aims:] We present r-Java 2.0, a nucleosynthesis code for open use that
performs r-process calculations as well as a suite of other analysis tools.
[Methods:] Equipped with a straightforward graphical user interface, r-Java 2.0
is capable of; simulating nuclear statistical equilibrium (NSE), calculating
r-process abundances for a wide range of input parameters and astrophysical
environments, computing the mass fragmentation from neutron-induced fission as
well as the study of individual nucleosynthesis processes. [Results:] In this
paper we discuss enhancements made to this version of r-Java, paramount of
which is the ability to solve the full reaction network. The sophisticated
fission methodology incorporated into r-Java 2.0 which includes three fission
channels (beta-delayed, neutron-induced and spontaneous fission) as well as
computation of the mass fragmentation is compared to the upper limit on mass
fission approximation. The effects of including beta-delayed neutron emission
on r-process yield is studied. The role of coulomb interactions in NSE
abundances is shown to be significant, supporting previous findings. A
comparative analysis was undertaken during the development of r-Java 2.0
whereby we reproduced the results found in literature from three other
r-process codes. This code is capable of simulating the physical environment
of; the high-entropy wind around a proto-neutron star, the ejecta from a
neutron star merger or the relativistic ejecta from a quark nova. As well the
users of r-Java 2.0 are given the freedom to define a custom environment. This
software provides an even platform for comparison of different proposed
r-process sites and is available for download from the website of the
Quark-Nova Project: http://quarknova.ucalgary.ca/Comment: 26 pages, 18 figures, 1 tabl
DBEndo: a web-based endodontic case management tool
BACKGROUND: The success of endodontic treatment depends-among many other factors-on good documentation. Paper-based records are often difficult to read or incomplete and commercially available tools focus on billing. An electronic record captures the state of treatment at all times. Databases are a common tool in everyday life. RESULTS: Here, we present a database created for the Charite-Universitatsmedizin Berlin, Germany. Through consistent digital documentation, data analytics of patients, root canal anatomies, instrumentation techniques, efficacy of chemical disinfection, root filling techniques, and corresponding recall success rates, which needed extensive research before, are now easy to perform. Tables and even graphics and data analystics are only one click away and can be exported to other programs. CONCLUSIONS: DBEndo is a database to store and visualise internally, as well as to share endodontic cases online. For academic use we provide the database including all forms and some anonymous data for free at: http://dbendo.charite.de . Through easy import and export of the data, the system is open and flexible
Two different subunits of importin cooperate to recognize nuclear localization signals and bind them to the nuclear envelope
AbstractBackground: Selective protein import into the cell nucleus occurs in two steps: binding to the nuclear envelope, followed by energy-dependent transit through the nuclear pore complex. A 60 kD protein, importin, is essential for the first nuclear import step, and the small G protein Ran/TC4 is essential for the second. We have previously purified the 60 kD importin protein (importin 60) as a single polypeptide.Results We have identified importin 90, a 90 kD second subunit that dissociates from importin 60 during affinity chromatography on nickel (II)ânitrolotriacetic acidâSepharose, a technique that was originally used to purify importin 60. Partial amino-acid sequencing of Xenopus importin 90 allowed us to clone and sequence its human homologue; the amino-acid sequence of importin 90 is strikingly conserved between the two species. We have also identified a homologous budding yeast sequence from a database entry. Importin 90 potentiates the effects of importin 60 on nuclear protein import, indicating that the importin complex is the physiological unit responsible for import. To assess whether nuclear localization sequences are recognized by cytosolic receptor proteins, a biotin-tagged conjugate of nuclear localization signals linked to bovine serum albumin was allowed to form complexes with cytosolic proteins in Xenopus egg extracts; the complexes were then retrieved with streptavidinâagarose. The pattern of bound proteins was surprisingly simple and showed only two predominant bands: those of the importin complex. We also expressed the human homologue of importin 60, Rch1p, and found that it was able to replace its Xenopus counterpart in a functional assay. We discuss the relationship of importin 60 and importin 90 to other nuclear import factors.Conclusion Importin consists of a 60 and a 90 kD subunit. Together, they constitute a cytosolic receptor for nuclear localization signals that enables import substrates to bind to the nuclear envelope
Correlation of Microstructure and Properties of Cold Gas Sprayed INCONEL 718 Coatings
In the cold gas spray process, deposition of particles takes place through intensive plastic deformation upon impact in a solid state at temperatures well below their melting point. The high particle impact velocities and corresponding peening effects can lead to high compressive residual stresses in cold spray coatings. This can be advantageous with regard to mechanical properties as fatigue life and hence, cold spray is an ideal process for repair applications. In this study, INCONEL 718 particles were cold sprayed by using nitrogen as propellant gas. The deposited coatings with different thicknesses were characterized using electron microscopy techniques to study grain refinement and precipitates in the coating. In addition, depth-resolved residual stress measurements have been performed by the incremental hole drilling method. The residual stress depth profiles in the coatings indicate compressive residual stresses of several hundred MPa which are hardly influenced by the coating thickness. In addition, large compressive stress levels are found in surface- near regions of the substrate due to the grit blasting process. Furthermore, a post-heat treatment analysis was performed to investigate its influence on residual stresses and bonding strength. These findings are used to develop a consistent explanation of the dependence of strength values on thickness
Comparison of line-peak and line-scanning excitation in two-color laser-induced-fluorescence thermometry of OH
Two-line laser-induced-fluorescence (LIF) thermometry is commonly employed to generate instantaneous planar maps of temperature in unsteady flames. The use of line scanning to extract the ratio of integrated intensities is less common because it precludes instantaneous measurements. Recent advances in the energy output of high-speed, ultraviolet, optical parameter oscillators have made possible the rapid scanning of molecular rovibrational transitions and, hence, the potential to extract information on gas-phase temperatures. In the current study, two-line OH LIF thermometry is performed in a wellcalibrated reacting flow for the purpose of comparing the relative accuracy of various line-pair selections from the literature and quantifying the differences between peak-intensity and spectrally integrated line ratios. Investigated are the effects of collisional quenching, laser absorption, and the integration width for partial scanning of closely spaced lines on the measured temperatures. Data from excitation scans are compared with theoretical line shapes, and experimentally derived temperatures are compared with numerical predictions that were previously validated using coherent anti-StokesâRaman scattering. Ratios of four pairs of transitions in the A2ÎŁ+âX2Î (1,0) band of OH are collected in an atmospheric-pressure, near-adiabatic hydrogen-air flame over a wide range of equivalence ratiosâfrom 0.4 to 1.4. It is observed that measured temperatures based on the ratio of Q1(14)/Q1(5) transition lines result in the best accuracy and that line scanning improves the measurement accuracy by as much as threefold at lowequivalence- ratio, low-temperature conditions. These results provide a comprehensive analysis of the procedures required to ensure accurate two-line LIF measurements in reacting flows over a wide range of conditions
Generation of x-ray radiation in a storage ring by a superconductive cold-bore invacuum undulator
The first beam measurements with a cold-bore superconducting in-vacuum undulator in a storage ring are reported. Undulators are x-ray generators in light sources. The physical limitations of these devices limit the intensity and the brilliance of the x-ray beam. At present the undulators are made from permanent magnets. It was shown in earlier papers that at low electron beam intensities superconductive wires in the vacuum beam pipe can overcome the limitations inherent to permanent magnet undulators. It was argued that the use of these novel devices in light sources with high beam currents may be limited by the extreme anomalous skin effect regime in Cu at 4.2 K, which has so far undergone very little investigation, and the power deposited by the infrared part of the synchrotron radiation. The purpose of this paper is to present measurements of these effects at the synchrotron light source ANKA with stored currents up to 200 mA
Quark nova imprint in the extreme supernova explosion SN 2006gy
The extremely luminous supernova 2006gy (SN 2006gy) is among the most
energetic ever observed. The peak brightness was 100 times that of a typical
supernova and it spent an unheard of 250 days at magnitude -19 or brighter.
Efforts to describe SN 2006gy have pushed the boundaries of current supernova
theory. In this work we aspire to simultaneously reproduce the photometric and
spectroscopic observations of SN 2006gy using a quark nova model. This analysis
considers the supernova explosion of a massive star followed days later by the
quark nova detonation of a neutron star. We lay out a detailed model of the
interaction between the supernova envelope and the quark nova ejecta paying
special attention to a mixing region which forms at the inner edge of the
supernova envelope. This model is then fit to photometric and spectroscopic
observations of SN 2006gy. This QN model naturally describes several features
of SN 2006gy including the late stage light curve plateau, the broad H{\alpha}
line and the peculiar blue H{\alpha} absorption. We find that a progenitor mass
between 20Msun and 40Msun provides ample energy to power SN 2006gy in the
context of a QN.Comment: 15 pages, 9 figure
Secondary mineral formation associated with respiration of nontronite, NAu-1 by iron reducing bacteria
Experimental batch and miscible-flow cultures were studied in order to determine the mechanistic pathways of microbial Fe(III) respiration in ferruginous smectite clay, NAu-1. The primary purpose was to resolve if alteration of smectite and release of Fe precedes microbial respiration. Alteration of NAu-1, represented by the morphological and mineralogical changes, occurred regardless of the extent of microbial Fe(III) reduction in all of our experimental systems, including those that contained heat-killed bacteria and those in which O(2), rather than Fe(III), was the primary terminal electron acceptor. The solid alteration products observed under transmission electron microscopy included poorly crystalline smectite with diffuse electron diffraction signals, discrete grains of Fe-free amorphous aluminosilicate with increased Al/Si ratio, Fe-rich grains, and amorphous Si globules in the immediate vicinity of bacterial cells and extracellular polymeric substances. In reducing systems, Fe was also found as siderite. The small amount of Fe partitioned to the aqueous phase was primarily in the form of dissolved Fe(III) species even in the systems in which Fe(III) was the primary terminal electron acceptor for microbial respiration. From these observations, we conclude that microbial respiration of Fe(III) in our laboratory systems proceeded through the following: (1) alteration of NAu-1 and concurrent release of Fe(III) from the octahedral sheets of NAu-1; and (2) subsequent microbial respiration of Fe(III)
Impact of Hemlock Woolly Adelgid (Hemiptera: Adelgidae) Infestation on the Jasmonic Acid-Elicited Defenses of Tsuga canadensis (Pinales: Pinaceae)
Hemlock woolly adelgid is an invasive piercing-sucking insect in eastern North America, which upon infestation of its main host, eastern hemlock (âhemlockâ), improves attraction and performance of folivorous insects on hemlock. This increased performance may be mediated by hemlock woolly adelgid feeding causing antagonism between the the jasmonic acid and other hormone pathways. In a common garden experiments using hemlock woolly adelgid infestation and induction with methyl jasmonate (MeJA) and measures of secondary metabolite contents and defense-associated enzyme activities, we explored the impact of hemlock woolly adelgid feeding on the local and systemic induction of jasmonic acid (JA)-elicited defenses. We found that in local tissue hemlock woolly adelgid or MeJA exposure resulted in unique induced phenotypes, whereas the combined treatment resulted in an induced phenotype that was a mixture of the two individual treatments. We also found that if the plant was infested with hemlock woolly adelgid, the systemic response of the plant was dominated by hemlock woolly adelgid, regardless of whether MeJA was applied. Interestingly, in the absence of hemlock woolly adelgid, hemlock plants had a very weak systemic response to MeJA. We conclude that hemlock woolly adelgid infestation prevents systemic induction of JA-elicited defenses. Taken together, compromised local JA-elicited defenses combined with weak systemic induction could be major contributors to increased folivore performance on hemlock woolly adelgid-infested hemlock
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