2,969 research outputs found

    Is the growth of the child of a smoking mother influenced by the father's prenatal exposure to tobacco? A hypothesis generating longitudinal study

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    OBJECTIVES: Transgenerational effects of different environmental exposures are of major interest, with rodent experiments focusing on epigenetic mechanisms. Previously, we have shown that if the study mother is a non-smoker, there is increased mean birth weight, length and body mass index (BMI) in her sons if she herself had been exposed prenatally to her mother's smoking. The aim of this study was to determine whether the prenatal smoke exposure of either parent influenced the growth of the fetus of a smoking woman, and whether any effects were dependent on the fetal sex. DESIGN: Population-based prebirth cohort study. SETTING: Avon Longitudinal Study of Parents and Children. PARTICIPANTS: Participants were residents of a geographic area with expected date of delivery between April 1991 and December 1992. Among pregnancies of mothers who smoked during pregnancy, data were available concerning maternal and paternal prenatal exposures to their own mother smoking for 3502 and 2354, respectively. PRIMARY AND SECONDARY OUTCOME MEASURES: Birth weight, length, BMI and head circumference. RESULTS: After controlling for confounders, there were no associations with birth weight, length or BMI. There was a strong adjusted association of birth head circumference among boys whose fathers had been exposed prenatally (mean difference −0.35 cm; 95% CI −0.57 to −0.14; p=0.001). There was no such association with girls (interaction p=0.006). Similar associations were found when primiparae and multiparae were analysed separately. In order to determine whether this was reflected in child development, we examined the relationships with IQ; we found that the boys born to exposed fathers had lower IQ scores on average, and that this was particularly due to the verbal component (mean difference in verbal IQ −3.65 points; 95% CI −6.60 to −0.70). CONCLUSIONS: Head size differences concerning paternal fetal exposure to smoking were unexpected and, as such, should be regarded as hypothesis generating

    What drives modern protected area establishment in Australia?

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    Protected areas are a fundamental mechanism for ensuring the persistence of biodiversity. The strategic policy objectives set by governments for protected area land acquisition are strong determinants of biodiversity outcomes. An examination of these objectives is necessary to determine those most influential in designing protected area networks and understand why Australia's extinction rates exceed those elsewhere despite actively establishing protected areas over the past several decades. To examine spatio-temporal trends in policy objectives for protected areas, we evaluated the strategic priorities in Federal, State, and Territory policy documents across Australia between 1992 and 2019 using thematic analysis. We classified priorities into seven themes: adequacy, Indigenous and cultural values; representation of ecosystem and species types; threatened species and their habitat; social and recreational values; unique values and avoiding threatening processes. We found that the representation of ecosystem and species types was the most prevalent theme in policy documents, and the least common theme was social and recreational values. We posit several reasons for this trend and warn that emphasizing extent, in terms of area or representativeness, may diminish the effectiveness, efficiency, and impact for biodiversity outcomes. We found that policies were generally supportive of the strategic identification of particular species or communities that would quantifiably benefit from protection (referred to as avoided loss). Risked-based approaches to the establishment of protected areas are supported by modern conservation literature to enhance the protected area network's effectiveness. To maximize limited resources, we recommend that governments continue encouraging urgency to avoid species and habitat loss in their strategic priorities. This urgency should be accompanied by clear and consistent funding for on-the-ground actions which facilitate the socio-ecological outcomes that characterize modern protected area policy

    Spin-Orbit Coupling, Antilocalization, and Parallel Magnetic Fields in Quantum Dots

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    We investigate antilocalization due to spin-orbit coupling in ballistic GaAs quantum dots. Antilocalization that is prominent in large dots is suppressed in small dots, as anticipated theoretically. Parallel magnetic fields suppress both antilocalization and also, at larger fields, weak localization, consistent with random matrix theory results once orbital coupling of the parallel field is included. In situ control of spin-orbit coupling in dots is demonstrated as a gate-controlled crossover from weak localization to antilocalization.Comment: related papers at http://marcuslab.harvard.ed

    Inelastic semiclassical Coulomb scattering

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    We present a semiclassical S-matrix study of inelastic collinear electron-hydrogen scattering. A simple way to extract all necessary information from the deflection function alone without having to compute the stability matrix is described. This includes the determination of the relevant Maslov indices. Results of singlet and triplet cross sections for excitation and ionization are reported. The different levels of approximation -- classical, semiclassical, and uniform semiclassical -- are compared among each other and to the full quantum result.Comment: 9 figure

    Gate-Controlled Spin-Orbit Quantum Interference Effects in Lateral Transport

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    In situ control of spin-orbit coupling in coherent transport using a clean GaAs/AlGaAs 2DEG is realized, leading to a gate-tunable crossover from weak localization to antilocalization. The necessary theory of 2D magnetotransport in the presence of spin-orbit coupling beyond the diffusive approximation is developed and used to analyze experimental data. With this theory the Rashba contribution and linear and cubic Dresselhaus contributions to spin-orbit coupling are separately estimated, allowing the angular dependence of spin-orbit precession to be extracted at various gate voltages.Comment: related papers at http://marcuslab.harvard.ed

    Classical versus Quantum Structure of the Scattering Probability Matrix. Chaotic wave-guides

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    The purely classical counterpart of the Scattering Probability Matrix (SPM) Sn,m2\mid S_{n,m}\mid^2 of the quantum scattering matrix SS is defined for 2D quantum waveguides for an arbitrary number of propagating modes MM. We compare the quantum and classical structures of Sn,m2\mid S_{n,m}\mid^2 for a waveguide with generic Hamiltonian chaos. It is shown that even for a moderate number of channels, knowledge of the classical structure of the SPM allows us to predict the global structure of the quantum one and, hence, understand important quantum transport properties of waveguides in terms of purely classical dynamics. It is also shown that the SPM, being an intensity measure, can give additional dynamical information to that obtained by the Poincar\`{e} maps.Comment: 9 pages, 9 figure

    Scarring Effects on Tunneling in Chaotic Double-Well Potentials

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    The connection between scarring and tunneling in chaotic double-well potentials is studied in detail through the distribution of level splittings. The mean level splitting is found to have oscillations as a function of energy, as expected if scarring plays a role in determining the size of the splittings, and the spacing between peaks is observed to be periodic of period {2π2\pi\hbar} in action. Moreover, the size of the oscillations is directly correlated with the strength of scarring. These results are interpreted within the theoretical framework of Creagh and Whelan. The semiclassical limit and finite-{\hbar} effects are discussed, and connections are made with reaction rates and resonance widths in metastable wells.Comment: 22 pages, including 11 figure

    Geometry-dependent scattering through quantum billiards: Experiment and theory

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    We present experimental studies of the geometry-specific quantum scattering in microwave billiards of a given shape. We perform full quantum mechanical scattering calculations and find an excellent agreement with the experimental results. We also carry out the semiclassical calculations where the conductance is given as a sum of all classical trajectories between the leads, each of them carrying the quantum-mechanical phase. We unambiguously demonstrate that the characteristic frequencies of the oscillations in the transmission and reflection amplitudes are related to the length distribution of the classical trajectories between the leads, whereas the frequencies of the probabilities can be understood in terms of the length difference distribution in the pairs of classical trajectories. We also discuss the effect of non-classical "ghost" trajectories that include classically forbidden reflection off the lead mouths.Comment: 4 pages, 4 figure
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