6,379 research outputs found
Carbon and oxygen isotope composition of carbonates from an L6 chondrite: Evidence for terrestrial weathering from the Holbrook meteorite
Terrestrial weathering in meteorites is an important process which alters pristine elemental and isotopic abundances. The Holbrook L6 chondrite fell in 1912. Material was recovered at the time of the fall, in 1931, and 1968. The weathering processes operating on the freshly fallen meteorite in a semi-arid region of northeastern Arizona have been studied after a ground residence of 19 and 56 years. It has been shown that a large portion of the carbonate material in 7 Antarctic ordinary chondrites either underwent extensive isotopic exchange with atmospheric CO2, or formed recently in the Antarctic environment. In fact it has been demonstrated that hydrated Mg-carbonates, nesquehonite and hydromagnesite, formed in less than 40 years on LEW 85320. In order to help further constrain the effects of terrestrial weathering in meteorites, the carbon and oxygen isotopes extracted from carbonates of three different samples of Holbrook L6: a fresh sample at the time of the fall in 1912, a specimen collected in 1931, and a third specimen collected at the same site in 1968
The Distribution of Redshifts in New Samples of Quasi-stellar Objects
Two new samples of QSOs have been constructed from recent surveys to test the
hypothesis that the redshift distribution of bright QSOs is periodic in
. The first of these comprises 57 different redshifts among all
known close pairs or multiple QSOs, with image separations 10\arcsec,
and the second consists of 39 QSOs selected through their X-ray emission and
their proximity to bright comparatively nearby active galaxies. The redshift
distributions of the samples are found to exhibit distinct peaks with a
periodic separation of in identical to that claimed
in earlier samples but now extended out to higher redshift peaks and 4.47, predicted by the formula but never seen before. The periodicity
is also seen in a third sample, the 78 QSOs of the 3C and 3CR catalogues. It is
present in these three datasets at an overall significance level -
, and appears not to be explicable by spectroscopic or similar
selection effects. Possible interpretations are briefly discussed.Comment: submitted for publication in the Astronomical Journal, 15 figure
Early pathways of maternal mentalization: Associations with child development in the FinnBrain birth cohort study
Parental mentalization refers to a parentsâ capacity and interest to consider the individual experience and mental state underlying the behaviors of the child. Higher mentalization is considered a key aspect for parental sensitivity in interaction, fostering childâs socioemotional and self-regulatory development. Yet, previous studies have not examined the dynamic pathways through which the maternal mentalization may develop, nor their effects on child development. Thus, in the current person-oriented studies, first, we identify distinct profiles and longitudinal trajectories of maternal mentalization from pregnancy to childâs 2 years of age. Second, we test how the profiles and trajectories associate with childrenâs internalizing and externalizing problems, socialâemotional competence and effortful control at the age of 2 years. Third, we examine how the profiles and trajectories associate with contextual demographic and child related. The substudy was part of the FinnBrain Birth Cohort and included families from general population (nâ=â2,687). Mothers reported their parental reflective functioning (PRF) at late pregnancy, 6 months and 2 years of childâs age. Both mothers (nâ=â1,437) and fathers (nâ=â715) reported the developmental child outcomes at the childâs age of 2 years. Latent Profile Analysis and Latent Transition Analysis were used to identify PRF profiles and trajectories. The results showed decreasing heterogeneity in PRF from pregnancy to childâs age of 6 months and 2 years (i.e., four, three and two latent classes, respectively). Most mothers progressed towards high PRF over time. Second, the profiles and trajectories depicting high PRF associated with child high socialâemotional competence at the age of 2 years, yet no clear positive effects were found on childâs problems and effortful control. The group of mixed PRF trajectories showed strongest association with childâs internalizing and externalizing problems. Finally, there were theoretically meaningful associations between the PRF trajectories and both the contextual (e.g., parity) and child related (e.g., infant temperament) factors. This was the first study to explore the early unfolding of maternal mentalization. The results are discussed in relation with the potential mechanisms accounting for child development and with the nature and limitations of self-reported parental mentalization
"Assisted cloning'' and "orthogonal-complementing" of an unknown state
We propose a protocol where one can exploit dual quantum and classical
channels to achieve perfect ``cloning'' and ``orthogonal-complementing'' of an
unknown state with a minimal assistance from a state preparer (without
revealing what the input state is). The first stage of the protocol requires
usual teleportation and in the second stage, the preparer disentangles the
left-over entangled states by a single particle measurement process and
communicates a number of classical bits (1-cbit per copy) to different parties
so that perfect copies and complement copies are produced. We discuss our
protocol for producing two copies and three copies (and complement copies)
using two and four particle entangled state and suggest how to generalise this
for N copies and complement copies using multiparticle entangled state.Comment: 7 pages, Latex, no figures, submitted to Phys. Rev. A. 1999(to be
accepted
Martian carbon dioxide: Clues from isotopes in SNC meteorites
Attempts to unravel the origin and evolution of the atmosphere and hydrosphere on Mars from isotopic data have been hampered by the impreciseness of the measurements made by the Viking Lander and by Earth-based telescopes. The SNC meteorites which are possibly pieces of the Martian surface offer a unique opportunity to obtain more precise estimates of the planet's volatile inventory and isotopic composition. Recently, we reported results on oxygen isotopes of water extracted by pyrolysis from samples of Shergotty, Zagami, Nakhla, Chassigny, Lafayette, and EETA-79001. Now we describe complementary results on the stable isotopic composition of carbon dioxide extracted simultaneously from those same samples. We will also report on C-14 abundances obtained by accelerator mass spectrometry (AMS) for some of these CO2 samples
Early pathways of maternal mentalization : Associations with child development in the FinnBrain birth cohort study
Parental mentalization refers to a parentsâ capacity and interest to consider the individual experience and mental state underlying the behaviors of the child. Higher mentalization is considered a key aspect for parental sensitivity in interaction, fostering childâs socioemotional and self-regulatory development. Yet, previous studies have not examined the dynamic pathways through which the maternal mentalization may develop, nor their effects on child development. Thus, in the current person-oriented study, first, we identify distinct profiles and longitudinal trajectories of maternal mentalization from pregnancy to childâs 2 years of age. Second, we test how the profiles and trajectories associate with childrenâs internalizing and externalizing problems, socialâemotional competence and effortful control at the age of 2 years. Third, we examine how the profiles and trajectories associate with contextual demographic and child related. The substudy was part of the FinnBrain Birth Cohort and included families from general population (n = 2,687). Mothers reported their parental reflective functioning (PRF) at late pregnancy, 6 months and 2 years of childâs age. Both mothers (n = 1,437) and fathers (n = 715) reported the developmental child outcomes at the childâs age of 2 years. Latent Profile Analysis and Latent Transition Analysis were used to identify PRF profiles and trajectories. The results showed decreasing heterogeneity in PRF from pregnancy to childâs age of 6 months and 2 years (i.e., four, three and two latent classes, respectively). Most mothers progressed towards high PRF over time. Second, the profiles and trajectories depicting high PRF associated with child high socialâemotional competence at the age of 2 years, yet no clear positive effects were found on childâs problems and effortful control. The group of mixed PRF trajectories showed strongest association with childâs internalizing and externalizing problems. Finally, there were theoretically meaningful associations between the PRF trajectories and both the contextual (e.g., parity) and child related (e.g., infant temperament) factors. This was the first study to explore the early unfolding of maternal mentalization. The results are discussed in relation with the potential mechanisms accounting for child development and with the nature and limitations of self-reported parental mentalization.publishedVersionPeer reviewe
Maximally localized Wannier functions in LaMnO3 within PBE+U, hybrid functionals, and partially self-consistent GW: an efficient route to construct ab-initio tight-binding parameters for e_g perovskites
Using the newly developed VASP2WANNIER90 interface we have constructed
maximally localized Wannier functions (MLWFs) for the e_g states of the
prototypical Jahn-Teller magnetic perovskite LaMnO3 at different levels of
approximation for the exchange-correlation kernel. These include conventional
density functional theory (DFT) with and without additional on-site Hubbard U
term, hybrid-DFT, and partially self-consistent GW. By suitably mapping the
MLWFs onto an effective e_g tight-binding (TB) Hamiltonian we have computed a
complete set of TB parameters which should serve as guidance for more elaborate
treatments of correlation effects in effective Hamiltonian-based approaches.
The method-dependent changes of the calculated TB parameters and their
interplay with the electron-electron (el-el) interaction term are discussed and
interpreted. We discuss two alternative model parameterizations: one in which
the effects of the el-el interaction are implicitly incorporated in the
otherwise "noninteracting" TB parameters, and a second where we include an
explicit mean-field el-el interaction term in the TB Hamiltonian. Both models
yield a set of tabulated TB parameters which provide the band dispersion in
excellent agreement with the underlying ab initio and MLWF bands.Comment: 30 pages, 7 figure
Suppression and Enhancement of Soliton Switching During Interaction in Periodically Twisted Birefringent Fiber
Soliton interaction in periodically twisted birefringent optical fibers has
been analysed analytically with refernce to soliton switching. For this purpose
we construct the exact general two-soliton solution of the associated coupled
system and investigate its asymptotic behaviour. Using the results of our
analytical approach we point out that the interaction can be used as a switch
to suppress or to enhance soliton switching dynamics, if one injects
multi-soliton as an input pulse in the periodically twisted birefringent fiber.Comment: 10 pages, 4 figures, Latex, submitted to Phys. Rev.
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