Pollution in the open oceans: 2009-2013

This review of pollution in the open oceans updates a report on this topic prepared by GESAMP five years previously (Reports and Studies No. 79, GESAMP, 2009). The latter report, the first from GESAMP focusing specifically on the oceans beyond the 200 m depth contour, was prepared for purposes of the Assessment of Assessments, the preparatory phase of a regular process for assessing the state of the marine environment, led jointly by the United Nations Environment Programme (UNEP) and the Intergovernmental Oceanographic Commission (UNESCO-IOC)

Locating Boosted Kerr and Schwarzschild Apparent Horizons

We describe a finite-difference method for locating apparent horizons and illustrate its capabilities on boosted Kerr and Schwarzschild black holes. Our model spacetime is given by the Kerr-Schild metric. We apply a Lorentz boost to this spacetime metric and then carry out a 3+1 decomposition. The result is a slicing of Kerr/Schwarzschild in which the black hole is propagated and Lorentz contracted. We show that our method can locate distorted apparent horizons efficiently and accurately.Comment: Submitted to Physical Review D. 12 pages and 22 figure

Quantum Hall induced currents and the magnetoresistance of a quantum point contact

We report an investigation of quantum Hall induced currents by simultaneous measurements of their magnetic moment and their effect on the conductance of a quantum point contact (QPC). Features in the magnetic moment and QPC resistance are correlated at Landau-level filling factors nu=1, 2 and 4, which demonstrates the common origin of the effects. Temperature and non-linear sweep rate dependences are observed to be similar for the two effects. Furthermore, features in the noise of the induced currents, caused by breakdown of the quantum Hall effect, are observed to have clear correlations between the two measurements. In contrast, there is a distinct difference in the way that the induced currents decay with time when the sweeping field halts at integer filling factor. We attribute this difference to the fact that, while both effects are sensitive to the magnitude of the induced current, the QPC resistance is also sensitive to the proximity of the current to the QPC split-gate. Although it is clearly demonstrated that induced currents affect the electrostatics of a QPC, the reverse effect, the QPC influencing the induced current, was not observed

Remote Inspection, Measurement and Handling for LHC

Personnel access to the LHC tunnel will be restricted to varying extents during the life of the machine due to radiation, cryogenic and pressure hazards. The ability to carry out visual inspection, measurement and handling activities remotely during periods when the LHC tunnel is potentially hazardous offers advantages in terms of safety, accelerator down time, and costs. The first applications identified were remote measurement of radiation levels at the start of shut-down, remote geometrical survey measurements in the collimation regions, and remote visual inspection during pressure testing and initial machine cool-down. In addition, for remote handling operations, it will be necessary to be able to transmit several real-time video images from the tunnel to the control room. The paper describes the design, development and use of a remotely controlled vehicle to demonstrate the feasibility of meeting the above requirements in the LHC tunnel. Design choices are explained along with operating experience to-date and future development plans

Magnetic ordering of the antiferromagnet Cu2MnSnS4 from magnetization and neutron-scattering measurements

Magnetization and neutron-diffraction measurements were performed on a single crystal of Cu2MnSnS4. This quartenary magnetic semiconductor has the stannite structure (derived from the zinc-blende structure which is common to many II-VI dilute magnetic semiconductors), and it orders antiferromagnetically at low temperature. The neutron data for the nuclear structure confirm that the space group is I42̄m. Both the neutron and magnetization data give TN=8.8 K for the Néel temperature. The neutron data show a collinear antiferromagnetic (AF) structure with a propagation vector k=[1/2,0,1/2], in agreement with earlier neutron data on a powder. However, the deduced angle θ between the spin axis and the crystallographic c direction is between 6° and 16°, in contrast to the earlier value of 40°. The magnetization curve at T≪TN shows the presence of a spin rotation (analogous to a spin flop), which indicates that the spin axis is indeed close to the c direction. The deduced magnetic anisotropy gives an anisotropy field HA≅2 kOe. At high magnetic fields the magnetization curve at T≪TN shows the transition between the canted (spin-flop) phase and the paramagnetic phase. The transition field, H=245.5 kOe, yields an intersublattice exchange field HE= 124 kOe. The exchange constants deduced from HE and the Curie-Weiss temperature Θ=-25 K show that the antiferromagnetic interactions are an order of magnitude smaller than in II-VI dilute magnetic semiconductors (DMS's). The much weaker antiferromagnetic interactions are expected from the difference in the crystal structures (stannite versus zincblende). A more surprising result is that the exchange constant which controls the AF order below TN is not between Mn ions with the smallest separation. This result contrasts with a prediction made for the related II-VI DMS, according to which the exchange constants decrease rapidly with distance.The work at Tufts University was partially supported by NSF Grant No. DMR-9219727. The research in Zaragoza was supported by CICYT Grant No. MAT94-0043. The work at Brown University was supported by NSF Grant No. DMR-9221141. The Francis Bitter National Magnet Laboratory was supported by NSF.Peer Reviewe

Association of Changes in Neighborhood-Level Racial Residential Segregation With Changes in Blood Pressure Among Black Adults: The CARDIA Study

Importance: Despite cross-sectional evidence linking racial residential segregation to hypertension prevalence among non-Hispanic blacks, it remains unclear how changes in exposure to neighborhood segregation may be associated with changes in blood pressure. Objective: To examine the association of changes in neighborhood-level racial residential segregation with changes in systolic and diastolic blood pressure over a 25-year period. Design, Setting, and Participants: This observational study examined longitudinal data of 2280 black participants of the Coronary Artery Risk Development in Young Adults (CARDIA) study, a prospective investigation of adults aged 18 to 30 years who underwent baseline examinations in field centers in 4 US locations from March 25, 1985, to June 7, 1986, and then were re-examined for the next 25 years. Racial residential segregation was assessed using the Getis-Ord Gi* statistic, a measure of SD between the neighborhood\u27s racial composition (ie, percentage of black residents) and the surrounding area\u27s racial composition. Segregation was categorized as high (Gi* \u3e 1.96), medium (Gi* 0-1.96), and low (Gi* \u3c 0). Fixed-effects linear regression modeling was used to estimate the associations of within-person change in exposure to segregation and within-person change in blood pressure while tightly controlling for time-invariant confounders. Data analyses were performed between August 4, 2016, and February 9, 2017. Main Outcomes and Measures: Within-person changes in systolic and diastolic blood pressure across 6 examinations over 25 years. Results: Of the 2280 participants at baseline, 974 (42.7%) were men and 1306 (57.3%) were women. Of these, 1861 (81.6%) were living in a high-segregation neighborhood; 278 (12.2%), a medium-segregation neighborhood; and 141 (6.2%), a low-segregation neighborhood. Systolic blood pressure increased by a mean of 0.16 (95% CI, 0.06-0.26) mm Hg with each 1-SD increase in segregation score after adjusting for interactions of time with age, sex, and field center. Of the 1861 participants (81.6%) who lived in high-segregation neighborhoods at baseline, reductions in exposure to segregation were associated with reductions in systolic blood pressure. Mean differences in systolic blood pressure were -1.33 (95% CI, -2.26 to -0.40) mm Hg when comparing high-segregation with medium-segregation neighborhoods and -1.19 (95% CI, -2.08 to -0.31) mm Hg when comparing high-segregation with low-segregation neighborhoods after adjustment for time and interactions of time with baseline age, sex, and field center. Changes in segregation were not associated with changes in diastolic blood pressure. Conclusions and Relevance: Decreases in exposure to racial residential segregation are associated with reductions in systolic blood pressure. This study adds to the small but growing body of evidence that policies that reduce segregation may have meaningful health benefits