523 research outputs found
Water detection at the moon, Mars and comets with a combined neutron gamma ray instrument
Measuring the fluxes of thermal and epithermal neutrons at a planetary object in conjunction with gamma-ray spectroscopic observations will provide information about the chemical composition of the surface which is less model dependent than the gamma ray measurements by themselves. Researchers devised a passive neutron detector for this purpose. An experimental model was designed and built. Three variables provided the basis for a set of experiments: thickness of the Sm and B layers, the presence or absence of the ACS, and the position of the source relative to the PND's cylindrical axis. Experimental results are given
An X-ray measurement of Titan's atmospheric extent from its transit of the Crab Nebula
Saturn's largest satellite, Titan, transited the Crab Nebula on 5 January
2003. We observed this astronomical event with the {\it Chandra} X-ray
Observatory. An ``occultation shadow'' has clearly been detected and is found
to be larger than the diameter of Titan's solid surface. The difference gives a
thickness for Titan's atmosphere of 880 60 km. This is the first
measurement of Titan's atmospheric extent at X-ray wavelengths. The value
measured is consistent with or slightly larger than those estimated from
earlier Voyager observations at other wavelengths. We discuss the possibility
of temporal variations in the thickness of Titan's atmosphere.Comment: 14 pages, 5 figures, AASTeX preprint. Accepted for publication in the
Astrophysical Journa
Dissecting the polar dichotomy of the noncondensable gas enhancement on Mars using the NASA Ames Mars General Circulation Model
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95628/1/jgre2298.pd
Maternal and perinatal outcomes after bariatric surgery: a spanish multicenter study
The final publication is avaliable at Springer Link[Abstract] Background. Bariatric surgery (BS) has become more frequent among women of child-bearing age. Data regarding the underlying maternal and perinatal risks are scarce. The objective of this nationwide study is to evaluate maternal and perinatal outcomes after BS.
Methods. We performed a retrospective observational study of 168 pregnancies in 112 women who underwent BS in 10 tertiary hospitals in Spain over a 15-year period. Maternal and perinatal outcomes, including gestational diabetes mellitus (GDM), pregnancy-associated hypertensive disorders (PAHD), pre-term birth cesarean deliveries, small and large for gestational age births (SGA, LGA), still births, and neonatal deaths, were evaluated. Results were further compared according to the type of BS performed: restrictive techniques (vertical-banded gastroplasty, sleeve gastrectomy, and gastric banding), Roux-en-Y gastric bypass (RYGB), and biliopancreatic diversion (BPD).
Results. GDM occurred in five (3 %) pregnancies and there were no cases of PAHD. Women whose pregnancies occurred before 1 year after BS had a higher pre-gestational body mass index (BMI) than those who got pregnant 1 year after BS (34.6 ± 7.7 vs 30.4 ± 5.3 kg/m2, p = 0.007). In pregnancies occurring during the first year after BS, a higher rate of stillbirths was observed compared to pregnancies occurring after this period of time (35.5 vs 16.8 %, p = 0.03). Women who underwent BPD delivered a higher rate of SGA babies than women with RYGB or restrictive procedures (34.8, 12.7, and 8.3 %, respectively).
Conclusions. Pregnancy should be scheduled at least 1 year after BS. Malabsorptive procedures are associated to a higher rate of SGA births
Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV
The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8 TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum
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