576 research outputs found
STRATIGRAPHIC DISTRIBUTION AND PALEOENVIRONMENTAL IMPLICATIONS OF PEDOGENIC FEATURES AND TRACE FOSSILS FROM THE LOWER PERMIAN OF KANSAS
ABSTRACT Paleosols in the Lower Permian (Asselian-Sakmarian) Council Grove Group from western Kansas, USA, contain numerous pedogenic features, including carbonate nodules (caliche), redoximorphic coloration, rhizoliths, and trace fossils, which can be used to reconstruct the paleoenvironmental and paleoclimatic conditions during the interval of soil formation. Due to the paleogeographic setting of the Hugoton Basin, 5th-order cycles recorded in distant Council Grove Group outcrops are condensed in the study area into cumulic paleosols that contain pedogenic features signifying both wet and dry climates. Wet/dry cycles are interpreted to be the product of eustatically driven climate change, as well as seasonal changes related to monsoonal weather variability. Statistical analyses of the distribution of pedogenic features indicate a change from drier to wetter conditions over the upper Council Grove Group interval. Detailed study of trace fossils revealed unique morphologies that warrant the erection of a new ichnospecies, proposed here as Naktodemasis krausi. These assemblages are the oldest known occurrence of the genus Naktodemasis. Trace fossils were interpreted as the burrows of soil dwelling insects or insect larvae that colonized semiarid coastal plain environments during periods of subaerial exposure, creating topography and reducing accommodation, thereby preventing the formation of discrete 5th-order lithologic cycles. In order to provide further evidence for the origin of trace fossils, neoichnological experiments were conducted to compare ancient burrows to those of modern fossorial insects. Experimental results showed that the burrows of modern coleopterans belonging to the masked chafer beetles (Cyclocephala sp.) are convincing analogs for Permian trace fossils, and provide some general constraints on moisture tolerances for potential Permian tracemakers. The presence of these traces in Permian sediments, therefore, indicate that soil moisture levels during sea-level lowstands were high enough to support sustained populations of similar organisms. This study also conclusively demonstrates that burrows of this type could be constructed in subaerial settings, and documents the unique burrowing mechanism of the masked chafer beetle
Table of Contents and Prologue
Editorial board, Table of contents, and Prologue, an introduction to volume 1
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DETERMINATION OF CORROSION INHIBITOR CRITERIA FOR TYPE III/IIIA TANKS DURING SALT DISSOLUTION OPERATIONS INTERIM REPORT
Preparation of high level waste for vitrification involves in part the dissolution of salt cake from the carbon steel storage tanks. During dissolution, a point is reached in which the corrosion inhibitors, hydroxide and nitrite, are diluted below established guidelines, and nitrate stress corrosion cracking (SCC) is possible. Because the addition of inhibitors may be counterproductive to process efficiency and waste minimization, corrosion testing was initiated to revisit and possibly revise the guidelines for inhibitor limits. The bases for the work summarized in this status report are results from previously-completed phases of study. In the first two phases of study, several reduced-inhibitor levels were tested in HLW simulants with nitrate concentrations ranging from 4.5 M to 8.5 M. The first two phases of work determined, among other things, the reduced-inhibitor levels and solution chemistries in which heat-treated and non-heat-treated A537 carbon steel is susceptible to SCC, crevice corrosion, and pitting. The work covered in this current task both builds on and verifies the conclusions of the previous work. The current work involves testing of low levels of inhibitors in HLW simulants with 5.5 M to 8.5 M nitrate concentrations. Stressed U-bend specimens, both polarized and non-polarized, were tested. Non-polarized U-bend testing is ongoing, with the U-bends currently in test for 100 days. The purpose of the testing is to determine SCC susceptibility in the vapor space (VS) and liquid air interface (LAI) regions of the HLW tanks under conditions expected during salt dissolution, and also to verify previous accelerated testing. The simulated wastes being tested have nitrate concentrations of 5.5 M and 8.5 M and inhibitor levels of 0.01 M/0.01 M hydroxide/nitrite and 0.1 M/ 0.1 M hydroxide/nitrite. The open circuit potential measurements being monitored and the corrosion morphology of the U-bends are in agreement with results and observations of previous phases of work. No SCC has occurred in the first 100 days of testing. The LAI specimens experienced minor corrosion at the liquid line with corrosion products visible on the weld material and in the heat-affected zones on either side of the welds. The VS specimens are more evenly and slightly more corroded. Polarized U-bend testing is complete after approximately 80 days of testing. No SCC occurred, but the results are inconclusive due to a competing, unexpected galvanic corrosion mechanism that interfered in the last 50 days of testing. No cracking was indicated during the first month. The tests will be repeated in order to satisfy the original objective which was to determine the effect of grinding HLW tank welds and heat treating the tanks had on corrosion. Both the non-polarized and polarized U-bend tests will continue. Additionally, cyclic polarization (CP) testing will be performed to examine the effects of surface oxides on corrosion and the differences in corrosion susceptibility between welded and un-welded areas
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Observation of associated production of a boson with a meson in the~forward region
A search for associated production of a boson with an open charm meson is
presented using a data sample, corresponding to an integrated luminosity of
of proton--proton collisions at a centre-of-mass energy
of 7\,TeV, collected by the LHCb experiment. %% Seven candidate events for
associated production of a boson with a meson and four candidate
events for a boson with a meson are observed with a combined
significance of 5.1standard deviations. The production cross-sections in the
forward region are measured to be where the first uncertainty is statistical and the
second systematic.Comment: 18 pages, 2 figure
Measurements of the , , meson and baryon lifetimes
Measurements of -hadron lifetimes are reported using collision data,
corresponding to an integrated luminosity of 1.0fb, collected by the
LHCb detector at a centre-of-mass energy of Tev. Using the exclusive decays
, , ,
and the average decay
times in these modes are measured to be = 0.004 0.003 ps, =
0.006 0.004 ps, = 0.013
0.005 ps, = 0.027
0.006 ps and = 0.011
0.005 ps, where the first uncertainty is statistical and the second is
systematic. These represent the most precise lifetime measurements in these
decay modes. In addition, ratios of these lifetimes, and the ratio of the
decay-width difference, , to the average width, , in
the system, , are
reported. All quantities are found to be consistent with Standard Model
expectations.Comment: 28 pages, 4 figures. Updated reference
First observation and amplitude analysis of the decay
The decay is observed in a data sample
corresponding to of collision data recorded by the LHCb
experiment during 2011 and 2012. Its branching fraction is measured to be
where the uncertainties are statistical, systematic and from
the branching fraction of the normalisation channel , respectively. An amplitude analysis of the resonant
structure of the decay is used to measure the
contributions from quasi-two-body ,
, and
decays, as well as from nonresonant sources. The
resonance is determined to have spin~1.Comment: 39 pages, 10 figures, submitted to Phys. Rev. D. Updated following
erratum 10.1103/PhysRevD.93.11990
Differential branching fraction and angular analysis of decays
The differential branching fraction of the rare decay is measured as a function of , the
square of the dimuon invariant mass. The analysis is performed using
proton-proton collision data, corresponding to an integrated luminosity of 3.0
\mbox{ fb}^{-1}, collected by the LHCb experiment. Evidence of signal is
observed in the region below the square of the mass. Integrating
over 15 < q^{2} < 20 \mbox{ GeV}^2/c^4 the branching fraction is measured as
d\mathcal{B}(\Lambda^{0}_{b} \rightarrow \Lambda \mu^+\mu^-)/dq^2 = (1.18 ^{+
0.09} _{-0.08} \pm 0.03 \pm 0.27) \times 10^{-7} ( \mbox{GeV}^{2}/c^{4})^{-1},
where the uncertainties are statistical, systematic and due to the
normalisation mode, , respectively.
In the intervals where the signal is observed, angular distributions are
studied and the forward-backward asymmetries in the dimuon ()
and hadron () systems are measured for the first time. In the
range 15 < q^2 < 20 \mbox{ GeV}^2/c^4 they are found to be A^{l}_{\rm FB} =
-0.05 \pm 0.09 \mbox{ (stat)} \pm 0.03 \mbox{ (syst)} and A^{h}_{\rm FB} =
-0.29 \pm 0.07 \mbox{ (stat)} \pm 0.03 \mbox{ (syst)}.Comment: 27 pages, 10 figures, Erratum adde
Observation of the decay
The first observation of the decay is reported. The
study is based on a sample of proton-proton collisions corresponding to
of integrated luminosity collected with the LHCb detector. The
significance of the signal is standard deviations. The branching fraction
is measured to be , where the third uncertainty comes from the
branching fraction that is used as a normalisation.
In addition, the charge asymmetries of and
, which are control channels, are measured to be and , respectively. All results are consistent with
theoretical expectations
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