3,746 research outputs found
Combined analysis of KamLAND and Borexino neutrino signals from Th and U decays in the Earth's interior
The KamLAND and Borexino experiments have detected electron antineutrinos
produced in the decay chains of natural thorium and uranium (Th and U
geoneutrinos). We analyze the energy spectra of current geoneutrino data in
combination with solar and long-baseline reactor neutrino data, with
marginalized three-neutrino oscillation parameters. We consider the case with
unconstrained Th and U event rates in KamLAND and Borexino, as well as cases
with fewer degrees of freedom, as obtained by successively assuming for both
experiments a common Th/U ratio, a common scaling of Th+U event rates, and a
chondritic Th/U value. In combination, KamLAND and Borexino can reject the null
hypothesis (no geoneutrino signal) at 5 sigma. Interesting bounds or
indications emerge on the Th+U geoneutrino rates and on the Th/U ratio, in
broad agreement with typical Earth model expectations. Conversely, the results
disfavor the hypothesis of a georeactor in the Earth's core, if its power
exceeds a few TW. The interplay of KamLAND and Borexino geoneutrino data is
highlighted.Comment: 12 pages, including 6 figure
Geoneutrinos and reactor antineutrinos at SNO+
In the heart of the Creighton Mine near Sudbury (Canada), the SNO+ detector
is foreseen to observe almost in equal proportion electron antineutrinos
produced by U and Th in the Earth and by nuclear reactors. SNO+ will be the
first long baseline experiment to measure a reactor signal dominated by CANDU
cores (55\% of the total reactor signal), which generally burn natural
uranium. Approximately 18\% of the total geoneutrino signal is generated by the
U and Th present in the rocks of the Huronian Supergroup-Sudbury Basin: the
60\% uncertainty on the signal produced by this lithologic unit plays a crucial
role on the discrimination power on the mantle signal as well as on the
geoneutrino spectral shape reconstruction, which can in principle provide a
direct measurement of the Th/U ratio in the Earth.Comment: 7 pages including 2 figures and 1 table, in XIV International
Conference on Topics in Astroparticle and Underground Physics (TAUP 2015) IOP
Publishing , published on Journal of Physics: Conference Series 718 (2016)
06200
Euclid at Threescore Years and Ten: The Twilight of Environmental and Land-Use Regulation?
Life, Liberty, and Whose Property lecture given by Loren A. Smith, Chief Judge, United States Court of Federal Claims.
Is this the Twilight of Land Use Controls? lecture given by Charles M. Haar, Professor of Law at Harvard University Law.
Capture and Counteraction: Self-Help and Environmental Zealots lecture given by James E. Krier, Earl Warren Delano Professor of Law, University of Michigan.
Ecology and Aesthetics: Our Future and the Making of Things lecture given by William A. McDonough, Dean and Elson Professor, University of Virginia School of Architecture
Effects of prosodically modulated sub-phonetic variation on lexical competition
Eye movements were monitored as participants followed spoken instructions to manipulate one of four objects pictured on a computer screen. Target words occurred in utterance-medial (e.g., Put the cap next to the square) or utterance-final position (e.g., Now click on the cap). Displays consisted of the target picture (e.g., a cap), a monosyllabic competitor picture (e.g., a cat), a polysyllabic competitor picture (e.g., a captain) and a distractor (e.g., a beaker). The relative proportion of fixations to the two types of competitor pictures changed as a function of the position of the target word in the utterance, demonstrating that lexical competition is modulated by prosodically conditioned phonetic variation
Teleology and Realism in Leibniz's Philosophy of Science
This paper argues for an interpretation of Leibniz’s claim that physics requires both mechanical and teleological principles as a view regarding the interpretation of physical theories. Granting that Leibniz’s fundamental ontology remains non-physical, or mentalistic, it argues that teleological principles nevertheless ground a realist commitment about mechanical descriptions of phenomena. The empirical results of the new sciences, according to Leibniz, have genuine truth conditions: there is a fact of the matter about the regularities observed in experience. Taking this stance, however, requires bringing non-empirical reasons to bear upon mechanical causal claims. This paper first evaluates extant interpretations of Leibniz’s thesis that there are two realms in physics as describing parallel, self-sufficient sets of laws. It then examines Leibniz’s use of teleological principles to interpret scientific results in the context of his interventions in debates in seventeenth-century kinematic theory, and in the teaching of Copernicanism. Leibniz’s use of the principle of continuity and the principle of simplicity, for instance, reveal an underlying commitment to the truth-aptness, or approximate truth-aptness, of the new natural sciences. The paper concludes with a brief remark on the relation between metaphysics, theology, and physics in Leibniz
Studies of MCP-PMTs in the miniTimeCube neutrino detector
This report highlights two different types of cross-talk in the
photodetectors of the miniTimeCube neutrino experiment. The miniTimeCube
detector has 24 -anode Photonis MCP-PMTs Planacon XP85012,
totalling 1536 individual pixels viewing the 2-liter cube of plastic
scintillator
Imaging the Earth's Interior: the Angular Distribution of Terrestrial Neutrinos
Decays of radionuclides throughout the Earth's interior produce geothermal
heat, but also are a source of antineutrinos. The (angle-integrated)
geoneutrino flux places an integral constraint on the terrestrial radionuclide
distribution. In this paper, we calculate the angular distribution of
geoneutrinos, which opens a window on the differential radionuclide
distribution. We develop the general formalism for the neutrino angular
distribution, and we present the inverse transformation which recovers the
terrestrial radioisotope distribution given a measurement of the neutrino
angular distribution. Thus, geoneutrinos not only allow a means to image the
Earth's interior, but offering a direct measure of the radioactive Earth, both
(1) revealing the Earth's inner structure as probed by radionuclides, and (2)
allowing for a complete determination of the radioactive heat generation as a
function of radius. We present the geoneutrino angular distribution for the
favored Earth model which has been used to calculate geoneutrino flux. In this
model the neutrino generation is dominated by decays in the Earth's mantle and
crust; this leads to a very ``peripheral'' angular distribution, in which 2/3
of the neutrinos come from angles > 60 degrees away from the downward vertical.
We note the possibility of that the Earth's core contains potassium; different
geophysical predictions lead to strongly varying, and hence distinguishable,
central intensities (< 30 degrees from the downward vertical). Other
uncertainties in the models, and prospects for observation of the geoneutrino
angular distribution, are briefly discussed. We conclude by urging the
development and construction of antineutrino experiments with angular
sensitivity. (Abstract abridged.)Comment: 25 pages, RevTeX, 7 figures. Comments welcom
Bacterial Death Results from Mutations Made in Translocation Peptide of Leucyl-tRNA Synthetase
The family of aminoacyl-tRNA synthetases (aaRSs) ensures the fidelity of translation through providing a pool of correctly aminoacylated tRNA products that become incorporated by the ribosome. Leucyl-tRNA synthetase (LeuRS) has two functionally separate domains, one is the aminoacylation domain and the other is the CP1 editing domain. LeuRS can aminoacylate noncognate amino acids, therefore it relies on the CP1 editing domain to hydrolyze misaminoacylated tRNA products before they are released from the enzyme. The LeuRS enzyme must undergo a structural transition state in its reaction cycle in order to translocate the 3\u27 acceptor stem of tRNA 30 Ã… from the aminoacylation active site to the CP1 domain hydrolytic active site. The translocation event is difficult to study, but we believe that we have generated mutations within LeuRS that alter the translocation event of tRNA. The mutations that we have generated lead to bacterial death in Escherichia coli (E. coli). Circular dichorism experiments indicate that our mutations do not significantly alter the secondary structure of LeuRS. In vitro biochemical studies demonstrate that these mutations reduce the rates of aminoacylation and hydrolysis, while also displaying misaminoacylation activity. We attribute these biochemical findings to the resulting bacterial death that is caused by these mutation
Bacterial Death Results from Mutations Made in Translocation Peptide of Leucyl-tRNA Synthetase
The family of aminoacyl-tRNA synthetases (aaRSs) ensures the fidelity of translation through providing a pool of correctly aminoacylated tRNA products that become incorporated by the ribosome. Leucyl-tRNA synthetase (LeuRS) has two functionally separate domains, one is the aminoacylation domain and the other is the CP1 editing domain. LeuRS can aminoacylate noncognate amino acids, therefore it relies on the CP1 editing domain to hydrolyze misaminoacylated tRNA products before they are released from the enzyme. The LeuRS enzyme must undergo a structural transition state in its reaction cycle in order to translocate the 3\u27 acceptor stem of tRNA 30 Ã… from the aminoacylation active site to the CP1 domain hydrolytic active site. The translocation event is difficult to study, but we believe that we have generated mutations within LeuRS that alter the translocation event of tRNA. The mutations that we have generated lead to bacterial death in Escherichia coli (E. coli). Circular dichorism experiments indicate that our mutations do not significantly alter the secondary structure of LeuRS. In vitro biochemical studies demonstrate that these mutations reduce the rates of aminoacylation and hydrolysis, while also displaying misaminoacylation activity. We attribute these biochemical findings to the resulting bacterial death that is caused by these mutation
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