3 research outputs found
Radio Science Investigation on a Mercury Orbiter Mission
We review the results from {\it Mariner 10} regarding Mercury's gravity field
and the results from radar ranging regarding topography. We discuss the
implications of improving these results, including a determination of the polar
component, as well as the opportunity to perform relativistic gravity tests
with a future {\it Mercury Orbiter}. With a spacecraft placed in orbit with
periherm at 400 km altitude, apherm at 16,800 km, period 13.45 hr and latitude
of periherm at +30 deg, one can expect a significant improvement in our
knowledge of Mercury's gravity field and geophysical properties. The 2000 Plus
mission that evolved during the European Space Agency (ESA) {\it Mercury
Orbiter} assessment study can provide a global gravity field complete through
the 25th degree and order in spherical harmonics. If after completion of the
main mission, the periherm could be lowered to 200 km altitude, the gravity
field could be extended to 50th degree and order. We discuss the possibility
that a search for a Hermean ionosphere could be performed during the mission
phases featuring Earth occultations.
Because of its relatively large eccentricity and close proximity to the Sun,
Mercury's orbital motion provides one of the best solar-system tests of general
relativity. Consequently, we emphasize the number of feasible relativistic
gravity tests that can be performed within the context of the parameterized
post-Newtonian formalism - a useful framework for testing modern gravitational
theories. We pointed out that current results on relativistic precession of
Mercury's perihelion are uncertain by 0.5 %, and we discuss the expected
improvement using {\it Mercury Orbiter}. We discuss the importance of {\it
Mercury Orbiter} for setting limits on a possible time variation in theComment: 23 pages, LaTeX, no figure
Anion-Accelerated Palladium-Catalyzed Intramolecular Coupling of Phenols with Aryl Halides
1q21.1 distal copy number variants are associated with cerebral and cognitive alterations in humans.
Low-frequency 1q21.1 distal deletion and duplication copy number variant (CNV) carriers are predisposed to multiple neurodevelopmental disorders, including schizophrenia, autism and intellectual disability. Human carriers display a high prevalence of micro- and macrocephaly in deletion and duplication carriers, respectively. The underlying brain structural diversity remains largely unknown. We systematically called CNVs in 38 cohorts from the large-scale ENIGMA-CNV collaboration and the UK Biobank and identified 28 1q21.1 distal deletion and 22 duplication carriers and 37,088 non-carriers (48% male) derived from 15 distinct magnetic resonance imaging scanner sites. With standardized methods, we compared subcortical and cortical brain measures (all) and cognitive performance (UK Biobank only) between carrier groups also testing for mediation of brain structure on cognition. We identified positive dosage effects of copy number on intracranial volume (ICV) and total cortical surface area, with the largest effects in frontal and cingulate cortices, and negative dosage effects on caudate and hippocampal volumes. The carriers displayed distinct cognitive deficit profiles in cognitive tasks from the UK Biobank with intermediate decreases in duplication carriers and somewhat larger in deletion carriers-the latter potentially mediated by ICV or cortical surface area. These results shed light on pathobiological mechanisms of neurodevelopmental disorders, by demonstrating gene dose effect on specific brain structures and effect on cognitive function