337,943 research outputs found
Cooling rates of neutron stars and the young neutron star in the Cassiopeia A supernova remnant
No full textWe explore the thermal state of the neutron star in the Cassiopeia A supernova remnant using the recent result of Ho & Heinke that the thermal radiation of this star is well described by a carbon atmosphere model and the emission comes from the entire stellar surface. Starting from neutron star cooling theory, we formulate a robust method to extract neutrino cooling rates of thermally relaxed stars at the neutrino cooling stage from observations of thermal surface radiation. We show how to compare these rates with the rates of standard candles – stars with non-superfluid nucleon cores cooling slowly via the modified Urca process. We find that the internal temperature of standard candles is a well-defined function of the stellar compactness parameter x=rg/R, irrespective of the equation of state of neutron star matter (R and rg are circumferential and gravitational radii, respectively). We demonstrate that the data on the Cassiopeia A neutron star can be explained in terms of three parameters: f?, the neutrino cooling efficiency with respect to the standard candle; the compactness x; and the amount of light elements in the heat-blanketing envelope. For an ordinary (iron) heat-blanketing envelope or a low-mass (? 10?13 M?) carbon envelope, we find the efficiency f?? 1 (standard cooling) for x? 0.5 and f?? 0.02 (slower cooling) for a maximum compactness x? 0.7. A heat blanket containing the maximum mass (?10?8 M?) of light elements increases f? by a factor of 50. We also examine the (unlikely) possibility that the star is still thermally non-relaxe
Study of Ho-doped Bi2Te3 topological insulator thin films
Full text linkThis publication arises from research funded by the John Fell Oxford University Press (OUP) Research Fund and the Research Complex at Harwell is acknowledged for their hospitality. This work was supported by a DARPA MESO project (No. N66001-11-1-4105). S.E.H. was supported by the VPGE (Stanford University). L.C.M. and A.A.B. acknowledge partial financial support from EPSRC (UK) through a Doctoral Training Award. Diamond Light Source is acknowledged for beamtime on I10 (proposal SI10207).Breaking time-reversal symmetry through magnetic doping of topological insulators has been identified as a key strategy for unlocking exotic physical states. Here, we report the growth of Bi2Te3 thin films doped with the highest magnetic moment element Ho. Diffraction studies demonstrate high quality films for up to 21% Ho incorporation. Superconducting quantum interference device magnetometry reveals paramagnetism down to 2 K with an effective magnetic moment of ∼5 μB/Ho. Angle-resolved photoemission spectroscopy shows that the topological surface state remains intact with Ho doping, consistent with the material's paramagnetic state. The large saturation moment achieved makes these films useful for incorporation into heterostructures, whereby magnetic order can be introduced via interfacial coupling.Peer reviewe
The 1961 Kampong Bukit Ho Swee fire and the making of modern Singapore
Full text linkBy 1970, Singapore’s urban landscape was dominated by high-rise blocks of planned public housing built by the People’s Action Party government, signifying the establishment of a high modernist nation-state. A decade earlier, the margins of the City had been dominated by kampongs, home to semi-autonomous communities of low-income Chinese families which freely built, and rebuilt, unauthorised wooden houses. This change was not merely one of housing but belied a more fundamental realignment of state-society relations in the 1960s. Relocated in Housing and Development Board flats, urban kampong families were progressively integrated into the social fabric of the emergent nation-state. This study examines the pivotal role of an event, the great Kampong Bukit Ho Swee fire of 1961, in bringing about this transformation. The redevelopment of the fire site in the aftermath of the calamity brought to completion the British colonial regime’s ‘emergency’ programmes of resettling urban kampong dwellers in planned accommodation, in particular, of building emergency public housing on the sites of major fires in the 1950s. The PAP’s far greater political resolve, and the timing of and state of emergency occasioned by the scale of the 1961 disaster, enabled the government to rehouse the Bukit Ho Swee fire victims in emergency housing in record time. This in turn provided the HDB with a strategic platform for clearing other kampongs and for transforming their residents into model citizens of the nation-state. The 1961 fire’s symbolic usefulness extended into the 1980s and beyond, in sanctioning the PAP’s new housing redevelopment schemes. The official account of the inferno has also become politically useful for the government of today for disciplining a new generation of Singaporeans against taking the nation’s progress for granted. Against these exalted claims of the fire’s role in the Singapore Story, this study also examines the degree of actual change and continuity in the social and economic lives of the people of Bukit Ho Swee after the inferno. In some crucial ways, the residents continued to occupy a marginal place in society while pondering, too, over the unresolved question of the cause of the fire. These continuities of everyday life reflect the ambivalence with which the citizenry regarded the high modernist state in contemporary Singapore
Structural analysis of the RE3Ba5Cu8O18 (RE = Dy, Gd, Ho, Sm, Y, Yb) superconductor system
No full textEn este artículo reportamos la síntesis y caracterización estructural del sistema RE3Ba5Cu8O18 (RE = Dy, Gd, Ho, Sm, Y, Yb), lo que viene a complementar lo ya reportado por Aliabadi, et al., quienes lograron una temperatura crítica (TC) de ∼ 100 K para el sistema superconductor Y3Ba5Cu8O18, y evaluó la respuesta estructural en una muestra. El nuevo sistema RE3Ba5Cu8O18 se obtuvo utilizando el método de reacción de estado sólido seguido de un proceso térmico similar al empleado para el superconductor RE: 123. Asimismo, los resultados experimentales obtenidos mediante la técnica de difracción de rayos X y el análisis de Rietveld evidenciaron que estas muestras tenían la estructura cristalina esperada; sin embargo, fue obvio que la presencia de fases no superconductoras no afectó la temperatura de transición superconductora. Además, los estudios magnéticos revelaron que las muestras de RE3Ba5Cu8O18 registraban una transición superconductora en el rango de 80 a 93 K dependiendo de la tierra rara.In this paper, we report the synthesis and structural characterization of the RE3Ba5Cu8O18 (RE = Dy, Gd, Ho, Sm, Y, Yb) system, which adds to the findings reported by Aliabadi, et al., who determined a critical temperature (TC) of ∼ 100 K for the superconducting Y3Ba5Cu8O18 system and evaluated its structural response in a sample. The new RE3Ba5Cu8O18 system was produced using the solidstate reaction method and a similar thermal process as the one used for the superconductor RE: 123. The experimental results obtained with X-ray diffraction and the Rietveld analysis showed that these samples had the expected crystal structure. However, it was obvious that the presence of non-superconducting phases did not affect the superconducting transition temperature. Moreover, magnetic studies revealed that RE3Ba5Cu8O18 samples showed a superconductivity transition within a temperature range of 80 - 93 K depending on the rare earth
HMOX1 gene promoter alleles and high HO-1 levels are associated with severe malaria in Gambian children.
Full text linkHeme oxygenase 1 (HO-1) is an essential enzyme induced by heme and multiple stimuli associated with critical illness. In humans, polymorphisms in the HMOX1 gene promoter may influence the magnitude of HO-1 expression. In many diseases including murine malaria, HO-1 induction produces protective anti-inflammatory effects, but observations from patients suggest these may be limited to a narrow range of HO-1 induction, prompting us to investigate the role of HO-1 in malaria infection. In 307 Gambian children with either severe or uncomplicated P. falciparum malaria, we characterized the associations of HMOX1 promoter polymorphisms, HMOX1 mRNA inducibility, HO-1 protein levels in leucocytes (flow cytometry), and plasma (ELISA) with disease severity. The (GT)(n) repeat polymorphism in the HMOX1 promoter was associated with HMOX1 mRNA expression in white blood cells in vitro, and with severe disease and death, while high HO-1 levels were associated with severe disease. Neutrophils were the main HO-1-expressing cells in peripheral blood, and HMOX1 mRNA expression was upregulated by heme-moieties of lysed erythrocytes. We provide mechanistic evidence that induction of HMOX1 expression in neutrophils potentiates the respiratory burst, and propose this may be part of the causal pathway explaining the association between short (GT)(n) repeats and increased disease severity in malaria and other critical illnesses. Our findings suggest a genetic predisposition to higher levels of HO-1 is associated with severe illness, and enhances the neutrophil burst leading to oxidative damage of endothelial cells. These add important information to the discussion about possible therapeutic manipulation of HO-1 in critically ill patients
Neoqiongphasma diaoluoshanense Ho 2013
No full textNeoqiongphasma diaoluoshanense Ho, 2013 E/T Neoqiongphasma diaoluoshanensis, Ho, 2013d: 408, figs. 1–3, 44. Type. Holotype: ♀, Diaoluoshan National Nature Reserve, Lingshui, Hainan, China, 7.VII.2011, George Ho Wai- Chun (SYSBM). Distribution. Hainan (Diaoluoshan), China.Published as part of Ho, George Wai-Chun, 2016, Contribution to the knowledge of Chinese Phasmatodea III: Catalogue of the phasmids of Hainan Island, China, with descriptions of one new genus, one new species and two new subspecies and proposals of three new combinations, pp. 314-340 in Zootaxa 4150 (3) on page 321, DOI: 10.11646/zootaxa.4150.3.4, http://zenodo.org/record/25841
Qiongphasma wuzhishanense Ho 2013
No full textQiongphasma wuzhishanense Ho, 2013 E/T Qiongphasma wuzhishanense, Ho, 2013d: 425, figs. 22–23, 43. Type. Holotype: ♂, 1800m, Wuzhishan National Nature Reserve, Hainan, China, 9.VII.2011, George Ho Wai- Chun (SYSBM). Distribution. Hainan (Wuzhishan), China.Published as part of Ho, George Wai-Chun, 2016, Contribution to the knowledge of Chinese Phasmatodea III: Catalogue of the phasmids of Hainan Island, China, with descriptions of one new genus, one new species and two new subspecies and proposals of three new combinations, pp. 314-340 in Zootaxa 4150 (3) on page 325, DOI: 10.11646/zootaxa.4150.3.4, http://zenodo.org/record/25841
Macellina qizhouense Ho 2015
No full textMacellina qizhouense Ho, 2015 E/T Macellina qizhouense, Ho, 2015: 97 (in Ho & Zhang, 2015), fig. 2. Type. Holotype: ♀, Qizhou Islands, Hainan, China, 27.VII.1934, unknown collector (SYSBM). Distribution. Hainan (Qizhou Islands), China.Published as part of Ho, George Wai-Chun, 2016, Contribution to the knowledge of Chinese Phasmatodea III: Catalogue of the phasmids of Hainan Island, China, with descriptions of one new genus, one new species and two new subspecies and proposals of three new combinations, pp. 314-340 in Zootaxa 4150 (3) on pages 328-329, DOI: 10.11646/zootaxa.4150.3.4, http://zenodo.org/record/25841
Hainanphasma diaoluoshanense Ho 2013
No full textHainanphasma diaoluoshanense Ho, 2013 E/T Hainanphasma diaoluoshanensis, Ho, 2013f: 207, figs. 7–9, 11, 14, 16. Type. Holotype: ♀, Diaoluoshan National Nature Reserve, Lingshui, Hainan, China, 6.VII.2011, George Ho Wai- Chun (SYSBM). Distribution. Hainan (Diaoluoshan), China.Published as part of Ho, George Wai-Chun, 2016, Contribution to the knowledge of Chinese Phasmatodea III: Catalogue of the phasmids of Hainan Island, China, with descriptions of one new genus, one new species and two new subspecies and proposals of three new combinations, pp. 314-340 in Zootaxa 4150 (3) on page 333, DOI: 10.11646/zootaxa.4150.3.4, http://zenodo.org/record/25841
Qiongphasma huishanense Ho 2013
No full textQiongphasma huishanense Ho, 2013 E/T Qiongphasma huishanensis, Ho, 2013d: 418, figs. 32–33. Type. Holotype: ♀, Huishan Nature Reserve, Qionghai, Hainan, China, 3.VII.2011, George Ho Wai-Chun (SYSBM). Distribution. Hainan (Huishan), China.Published as part of Ho, George Wai-Chun, 2016, Contribution to the knowledge of Chinese Phasmatodea III: Catalogue of the phasmids of Hainan Island, China, with descriptions of one new genus, one new species and two new subspecies and proposals of three new combinations, pp. 314-340 in Zootaxa 4150 (3) on page 325, DOI: 10.11646/zootaxa.4150.3.4, http://zenodo.org/record/25841
- …
