Anomalous Late Jurassic motion of the Pacific Plate with implications for true polar wander

True polar wander, or TPW, is the rotation of the entire mantle–crust system about an equatorial axis that results in a coherent velocity contribution for all lithospheric plates. One of the most recent candidate TPW events consists of a ∼30◦ rotation during Late Jurassic time (160–145 Ma). However, existing paleomagnetic documentation of this event derives exclusively from continents, which compose less than 50% of the Earth’s surface area and may not reflect motion of the entire mantle–crust system. Additional paleopositional information from the Pacific Basin would significantly enhance coverage of the Earth’s surface and allow more rigorous testing for the occurrence of TPW. We perform paleomagnetic analyses on core samples from Ocean Drilling Program (ODP) Site 801B, which were taken from the oldest available Pacific crust, to determine its paleolatitude during the Late Jurassic and Early Cretaceous (167–133 Ma). We find that the Pacific Plate underwent a steady southward drift of 0.49◦–0.74◦ My−1 except for an interval between Kimmeridgian and Tithonian time (157–147 Ma), during which it underwent northward motion at 1.45◦ ± 0.76◦ My−1 (1σ ). This trajectory indicates that the plates of the Pacific Basin participated in the same large-amplitude (∼30◦) rotation as continental lithosphere in the 160–145 Ma interval. Such coherent motion of a large majority of the Earth’s surface strongly supports the occurrence of TPW, suggesting that a combination of subducting slabs and rising mantle plumes was sufficient to significantly perturb the Earth’s inertia tensor in the Late Jurassic

Characterizing the Geomagnetic Field at High Southern Latitudes: Evidence From the Antarctic Peninsula

Due to a dearth of data from high-latitude paleomagnetic sites, it is not currently clear if the geocentric axial dipole (GAD) hypothesis accurately describes the long-term behavior of the geomagnetic field at high latitudes. Here we present new paleomagnetic and paleointensity data from the James Ross Island (JRI) volcanic group, located on the Antarctic Peninsula. This data set addresses a notable lack of data from the 60°–70°S latitude bin and includes 251 samples from 31 sites, spanning 0.99–6.8 Ma in age. We also include positive fold, conglomerate, and baked contact tests. Paleointensity data from three methods (Thellier- Thellier, pseudo-Thellier, and Tsunakawa-Shaw) were collected from all sites. The Thellier-Thellier method had low yields and produced unreliable data, likely due to sample alteration during heating. Results from the Tsunakawa-Shaw and pseudo-Thellier methods were more consistent, and we found a bimodal distribution of paleointensity estimates. Most sites yielded either \u3c15 μT or \u3e40 μT, which together span a range of estimates from long-term geomagnetic field models, but do not favor any model in particular. Alternating-field demagnetization of these samples, when combined with preexisting data, yields a revised paleomagnetic pole of −87.5°, 025°, α95 = 3.6° for the Antarctic Peninsula over the last ∼5 Ma, which suggests that the current data set is sufficiently large to “average out” secular variation. Finally, the C2r/C2n transition was probably found at a site on JRI, and further geochronological and paleomagnetic study of these units could refine the age of this reversal

Male Clients of Male Sex Workers in China: An Ignored High-Risk Population.

BackgroundThere is a high prevalence of HIV/syphilis among male sex workers, but no formal study has ever been conducted focusing on male clients of male sex workers (MCM). A detailed investigation was thus called for, to determine the burden and sociobehavioral determinants of HIV and syphilis among these MCM in China.MethodsAs part of a multicenter cross-sectional study, using respondent-driven and snowball sampling, 2958 consenting adult men who have sex with men (MSM) were recruited, interviewed, and tested for HIV and syphilis between 2008 and 2009. The distributions of sociodemographic characteristics, risk behaviors, and HIV/syphilis prevalence were determined and compared between MCM and other MSM.ResultsAmong recruited MSM, 5.0% (n = 148) were MCM. HIV prevalences for MCM and other MSM were 7.4% and 7.7%, whereas 18.9% and 14.0% were positive for syphilis, respectively. Condomless anal intercourse (CAI) was reported by 59.5% of MCM and 48.2% of MSM. Multiple logistic regression revealed that compared with other MSM, MCM were more likely to have less education [for ≤ elementary level, adjusted odds ratio (aOR) = 3.13, 95% confidence interval (95% CI): 1.42 to 6.90], higher income (for >500 US Dollars per month, aOR = 2.97, 95% CI: 1.53 to 5.77), more often found partners at parks/restrooms (aOR = 4.01, 95% CI: 2.34 to 6.85), reported CAI (aOR = 1.49, 95% CI: 1.05 to 2.10), reported a larger sexual network (for ≥ 10, aOR = 2.70, 95% CI: 1.44 to 5.07), and higher odds of syphilis (aOR = 1.54, 95% CI: 1.00 to 2.38).ConclusionsThe greater frequency of risk behaviors and high prevalence of HIV and syphilis indicated that HIV/syphilis prevention programs in China need to pay special attention to MCM as a distinct subgroup, which was completely ignored until date

History of the Solar Nebula from Meteorite Paleomagnetism

We review recent advances in our understanding of magnetism in the solar nebular and protoplanetary disks (PPDs). We discuss the implications of theory, meteorite measurements, and astronomical observations for planetary formation and nebular evolution. Paleomagnetic measurements indicate the presence of fields of 0.54$\pm$0.21 G at $\sim$1 to 3 astronomical units (AU) from the Sun and $\gtrsim$0.06 G at 3 to 7 AU until >1.22 and >2.51 million years (Ma) after solar system formation, respectively. These intensities are consistent with those predicted to enable typical astronomically-observed protostellar accretion rates of $\sim$10$^{-8}$ M$_\odot$ yr$^{-1}$, suggesting that magnetism played a central role in mass and angular momentum transport in PPDs. Paleomagnetic studies also indicate fields <0.006 G and <0.003 G in the inner and outer solar system by 3.94 and 4.89 Ma, respectively, consistent with the nebular gas having dispersed by this time. This is similar to the observed lifetimes of extrasolar protoplanetary disks.Comment: Revised version published in Science Advance

Efficient early global relaxation of asteroid Vesta

The asteroid Vesta is a differentiated planetesimal from the accretion phase of Solar System formation. Although its present-day shape is dominated by a non-hydrostatic fossil equatorial bulge and two large, mostly unrelaxed impact basins, Vesta may have been able to approach hydrostatic equilibrium during a brief early period of intense interior heating. We use a finite element viscoplastic flow model coupled to a 1D conductive cooling model to calculate the expected rate of relaxation throughout Vesta’s early history. We find that, given sufficient non-hydrostaticity, the early elastic lithosphere of Vesta experienced extensive brittle failure due to self-gravity, thereby allowing relaxation to a more hydrostatic figure. Soon after its accretion, Vesta reached a closely hydrostatic figure with 40–200 My after formation, depending on the assumed depth of megaregolith. The Veneneia and Rheasilvia giant impacts, which generated most non-hydrostatic topography, must have therefore occurred >40–200 My after formation. Based on crater retention ages, topography, and relation to known impact generated features, we identify a large region in the northern hemisphere that likely represents relic hydrostatic terrain from early Vesta. The long-wavelength figure of this terrain suggests that, before the two late giant impacts, Vesta had a rotation period of 5.02 h (6.3% faster than present) while its spin axis was offset by 3.0 ° from that of the present. The evolution of Vesta’s figure shows that the hydrostaticity of small bodies depends strongly on its age and specific impact history and that a single body may embody both hydrostatic and non-hydrostatic terrains and epochs.National Science Foundation (U.S.). Graduate Research Fellowship Progra

Accumulation of long-chain bases in yeast promotes their conversion to a long-chain base vinyl ether

Long-chain bases (LCBs) are the precursors to ceramide and sphingolipids in eukaryotic cells. They are formed by the action of serine palmitoyl-CoA transferase (SPT), a complex of integral membrane proteins located in the endoplasmic reticulum. SPT activity is negatively regulated by Orm proteins to prevent the toxic overaccumulation of LCBs. Here we show that overaccumulation of LCBs in yeast results in their conversion to a hitherto undescribed LCB derivative, an LCB vinyl ether. The LCB vinyl ether is predominantly formed from phytosphingosine (PHS) as revealed by conversion of odd chain length tracers C17-dihydrosphingosine and C17- PHS into the corresponding LCB vinyl ether derivative. PHS vinyl ether formation depends on ongoing acetyl-CoA synthesis, and its levels are elevated when the LCB degradative pathway is blocked by deletion of the major LCB kinase, LCB4, or the LCB phosphate lyase, DPL1. PHS vinyl ether formation thus appears to constitute a shunt for the LCB phosphate- and lyase-dependent degradation of LCBs. Consistent with a role of PHS vinyl ether formation in LCB detoxification, the lipid is efficiently exported from the cells

The Interior Dynamics of Water Planets

The ever-expanding catalog of detected super-Earths calls for theoretical studies of their properties in the case of a substantial water layer. This work considers such water planets with a range of masses and water mass fractions (2 to 5 M_Earth, 0.02% to 50% H2 O). First, we model the thermal and dynamical structure of the near-surface for icy and oceanic surfaces, finding separate regimes where the planet is expected to maintain a subsurface liquid ocean and where it is expected to exhibit ice tectonics. Newly discovered exoplanets may be placed into one of these regimes given estimates of surface temperature, heat flux, and gravity. Second, we construct a parameterized convection model for the underlying ice mantle of higher ice phases, finding that materials released from the silicate iron core should traverse the ice mantle on the timescale of 0.1 to 100 megayears. We present the dependence of the overturn times of the ice mantle and the planetary radius on total mass and water mass fraction. Finally, we discuss the implications of these internal processes on atmospheric observables.Comment: 9 page 4 figure

Testing the occurrence of Late Jurassic true polar wander using the La Negra volcanics of northern Chile

True polar wander (TPW) is the reorientation of the crust-mantle system driven by the redistribution of masses in the mantle and on the Earth’s surface. In the ideal case, characterization of TPW requires paleomagnetic constraints on the motion of all major plates and independent reconstructions of relative plate positions. While such complete datasets are absent for pre-Mesozoic TPW inferences due to the absence of oceanic plates, they are available for the Late Jurassic (165-145 Ma) “monster shift”, a ∼30◦ amplitude proposed TPW event. Here we perform paleomagnetic sampling and Ar-Ar geochronology on the La Negra volcanics of Northern Chile, producing two new paleomagnetic poles with ages 165.8 ± 1.8 Ma (1σ; 84.3◦N 0.9◦E; α95 = 7.6◦; N = 28) and 152.8 ± 0.8 Ma (84.5◦N 256.4◦E; α95 = 10.8◦; N = 18). By combining these data with other recently published results, we compute a net lithospheric rotation of 25.3◦ ± 7.3◦ (1σ ) at a mean rate of 1.21◦ ± 0.35◦ My−1 between 170 and 145 Ma with a peak rate of 1.46◦ ± 0.65◦ My−1 between 160 and 145 Ma. These rates are consistent with inferences from the Pacific Plate, implying true whole lithosphere rotation. Given coherent motion involving the entire lithosphere, we conclude that the Earth underwent rapid TPW between approximately 165 and 145 Ma, potentially driven by the cessation of subduction along the western North American margi

Musical instrument, personality and interpretation: Music cognition at a college-conservatory

Orchestral musicians have a tendency to stereotype one another based on their instruments. While research shows that musicians frequently hold these views of other players (Lipton, 1987), there is less research that links personality traits to instrument played. In large ensembles instruments often play ‘roles:' "basses determine rhythmic pulse," or "oboes' solos necessitate high artistic interpretation." Much of this is determined by training, reception history and instrumental sound. Our research sought to explore the feasibility of examining both personality traits and interpretation among a small sample of musicians focusing on a comparison of instrumental groups (strings, brass, woodwinds) as the independent variable. Our pilot study explored two primary questions: first, do musicians who play strings, woodwinds or brass exhibit different personality traits? Second, do musicians who play these instruments interpret music differently? Our study looked at differences in the ways instrumentalists interpreted three musical examples without markings other than time and key signatures. The 40+ students also took the "Big-Five" personality test. Preliminary data revealed that the Big-Five scores aligned with stereotypes (e.g., brass scoring lowest on neuroticism and woodwinds low on extraversion but high on neuroticism). Groups also displayed consistent differences in their interpretive approach to the musical examples