Constraining the geometry of the neutron star RX J1856.5−3754

RX J1856.5−3754 is one of the brightest, nearby isolated neutron stars (NSs), and considerable observational resources have been devoted to its study. In previous work, we found that our latest models of a magnetic, hydrogen atmosphere match well the entire spectrum, from X-rays to optical (with best-fitting NS radius   R ≈ 14  km, gravitational redshift   z _g∼ 0.2  , and magnetic field   B ≈ 4 × 10¹²  G). A remaining puzzle is the non-detection of rotational modulation of the X-ray emission, despite extensive searches. The situation changed recently with XMM–Newton observations that uncovered 7-s pulsations at the     level. By comparing the predictions of our model (which includes simple dipolar-like surface distributions of magnetic field and temperature) with the observed brightness variations, we are able to constrain the geometry of RX J1856.5−3754, with one angle <6° and the other angle     , though the solutions are not definitive, given the observational and model uncertainties. These angles indicate a close alignment between the rotation and the magnetic axes or between the rotation axis and the observer. We discuss our results in the context of RX J1856.5−3754 being a normal radio pulsar and a candidate for observation by future X-ray polarization missions such as Constellation-X or XEUS .     

Simulation of the extreme waves generated by typhoon Bolaven (1215) in the East China Sea and Yellow Sea

Record-breaking high waves occurred during the passage of the typhoon Bolaven (1215) (TYB) in the East China Sea (ECS) and Yellow Sea (YS) although its intensity did not reach the level of a super typhoon. Winds and directional wave measurements were made using a range of in-situ instruments mounted on an ocean tower and buoys. In order to understand how such high waves with long duration occurred, analyses have been made through measurement and numerical simulations. TYB winds were generated using the TC96 typhoon wind model with the best track data calibrated with the measurements. And then the wind fields were blended with the reanalyzed synoptic-scale wind fields for a wave model. Wave fields were simulated using WAM4.5 with adjustment of C_d for gust of winds and bottom friction for the study area. Thus the accuracy of simulations is considerably enhanced, and the computed results are also in better agreement with measured data than before. It is found that the extremely high waves evolved as a result of the superposition of distant large swells and high wind seas generated by strong winds from the front/right quadrant of the typhoon track. As the typhoon moved at a speed a little slower than the dominant wave group velocity in a consistent direction for two days, the wave growth was significantly enhanced by strong wind input in an extended fetch and non-linear interaction.     

Distribution of dinoflagellate cysts in Yellow Sea sediments

To investigate the distribution,abundance,and species composition of dinoflagellate cysts in the Yellow Sea,surface sediment samples were collected at 37 sites,including the Korean dump site.Twenty-one dinoflagellate cyst taxa were identified,with the assemblages dominated mainly by Spiniferites bulloideus,Operculodinium centrocarpum,and cyst of Alexandrium catenella/tamarense type.A high frequency of O.centrocarpum in the Yellow Sea was observed for the first time,and it is likely that this can be attributed to the dynamics of the Yellow Sea Cold Water Mass and the Changjiang(Yangtze) River runoff.Total cyst concentrations ranged from 23 to 48 442 cysts/g dry weight,and high cyst concentrations were recorded adjacent to the dumping site.This result suggests that anthropogenic activities such as ocean dumping stimulate the growth of dinoflagellates in the Yellow Sea,which in turn leads to high levels of dinoflagellate cyst production.     

Grain size trend and hydrodynamic condition of tirumalairajan River estuary,east coast of India

The estuary can be considered as environments characterized by high productivity and uncommensurable ecological value. However, marine ecosystems are also subjected to high human pressures that increase their vulnerability. The aim of this work is to analyze grain size trend of sediment due to the action of the main hydrodynamic condition. The spatial distribution patterns of sediments were monitored according to season. The grain-size trend of surficial sediments revealed a dominant sediment transport trend towards the eastern and south eastern part of study area. This study shows that there is an agreement among sediments path ways, hydrodynamic condition and the sediment spatial distribution in the estuarine environment. The agitation by waves is an important sorting mechanism in the study area. The findings are based on the grain size trend and also corroborated by short term observations of the estuarine sediment dynamics and transport during the monsoon, postmonsoon, summer and premonson seasons in Tirumalairajan River estuary.     

Indian summer monsoon onset vortex formation during recent decades

This study investigates the decrease in the frequency of onset vortex of summer monsoon during recent decades using the National Center for Environmental Prediction–National Center for Atmospheric Research reanalysis (1982–2011) data. Onset vortices are known to occur over the Arabian Sea mini warm pool where the sea surface temperature peaks just before the onset of monsoon. Even though the Arabian Sea mini warm pool intensifies during the recent decades, they are not seen as a regular feature. It is found from the analysis of irrotational and non-divergent wind component at 850 and 200 hPa that during the recent decades, convergent winds dominate at upper levels and divergent winds at lower levels which inhibits convection. Moreover, the cyclonic shear vorticity shows a decrease in the recent decades which tend to reduce the boundary layer moisture convergence and lower tropospheric humidity which is an important component for the initiation of a cyclonic system. The recent decades are characterized by weak convection due to the presence of strong northerlies and descending motion at lower levels in the southeast Arabian Sea. The response of atmospheric circulation to the interdecadal variations in the warm pool and the corresponding decrease in the frequency of onset vortex formation is analyzed in detail.     

Evaluation of I-wall in New Orleans with back-calculated total stress soil parameters

This study back-calculated moduli and shear strength of soils in London Canal Ave., New Orleans, using full-scale load test data, and re-evaluated the behavior of the I-wall to explore how the existing levees and floodwalls may be reliably retrofitted and future levees and floodwalls may be designed. From the back-calculation, it turned out that the moduli of the field soils were mostly higher (1–12 times) than magnitudes appeared in Interagency Performance Evaluation Task Force (IPET). But the shear strength of a water-glazed Marsh layer in the gap turned out to be substantially lower (0.2–0.25 times) than the magnitude appeared in IPET. This much strength reduction was confirmed by field vane shear tests: tests with artificial water infiltration into the field vane hole presented immeasurably low disturbed strength and resulted in very high sensitivity that might contributed to the failure. This study also shows that the gap development and strength reduction in the water-glazed Marsh layer are two main causes of levee failure, which have been predicted in previous research. The stiffer-than-expected moduli of underlain layers did not affect the failure mechanism of the levee substantially because these underlain layers remained elastic. Therefore, retrofitting solutions should be the ones that may prevent the gap development and to reinforce the Marsh layer.     

A study on the sociospatial context of ethnic politics and entrepreneurial growth in Koreatown and Monterey Park

The study examines the various sociospatial features of immigrant populations in two transnationally-linked ethnic enclaves in terms of how they may facilitate and constrain the politics of growth and development. In recent decades, the growing ethnic enclave economies of Koreatown and Monterey Park have witnessed the emergence of progrowth ethnic interest groups comprised of immigrant capitalists, entrepreneurs, developers, and organizations, who are playing key roles in politically spearheading (re)development projects in the Los Angeles metropolitan area. Our aim is to understand how the sociospatial, entrepreneurial, and residential layout of these host municipalities set the context for the politics of growth in these ethnic enclave economies based on an analysis of GIS spatial mapping, 2000–2010 census data, and other secondary sources. The data suggests that Korean and Chinese elite face different political opportunities and challenges because of their different sociospatial characteristics—the former based on their greater entrepreneurial influence and weak electoral impact and the latter on their stronger political presence as residents.