Photodissociative Regulation of Star Formation in Metal-Free Pregalactic Clouds

We study the H2 photodissociation regions around OB stars in primordial gas clouds whose virial temperatures are between a few hundred and a few thousand Kelvin. In such small objects, a single O star can photodissociate a mass equal to that of the cloud itself. As a result, the clouds deplete their molecular coolant and cannot cool in a free-fall time, and subsequent star formation is totally quenched. This indicates that stars do not form efficiently in small objects and that these objects contribute little to the reionization of the universe.Comment: 9 pages. ApJ, 518, in pres

From eco-civilization to city branding: A neo-marxist perspective of sustainable urbanization in China

While the national discourse on 'eco-civilization' drives conceptual thinking on sustainable urban development in China, in practice a systematic implementation gap appears to exist when it comes to local implementation. This paper examines how the leakage occurring in the trajectory from central government ideas to municipal and district level construction projects can be explained. More specifically, it aims to spot whether it is merely the result of mismatches resulting from ineffective interactions among players in the policy process, institutional misalignment between policy goals and policy instruments, or even if the mobilization of bias in the policy process is systematic enough to justify a neo-Marxist explanation of the abovementioned implementation gap. I found two main sources of structural bias: capital accumulation in the mechanisms for urban development and power accumulation in the mechanisms underlying the administrative process

Destruction of Molecular Hydrogen During Cosmological Reionization

We investigate the ability of primordial gas clouds to retain molecular hydrogen (H_2) during the initial phase of the reionization epoch. We find that before the Stromgren spheres of the individual ionizing sources overlap, the UV background below the ionization threshold is able to penetrate large clouds and suppress their H_2 abundance. The consequent lack of H_2 cooling could prevent the collapse and fragmentation of clouds with virial temperatures T_vir < 10^4 K (or masses 10^8 Msun [(1+z_vir)/10]^{-3/2}). This negative feedback on structure-formation arises from the very first ionizing sources, and precedes the feedback due to the photoionization heating.Comment: 14 pages, uuencoded compressed Postscript, 4 figures included. To appear in Ap

A Deep Photometric Look at Two of Andromeda's Dwarf Spheroidals: X and XVII

We use deep wide-field photometry from the Large Binocular Camera to study the stellar and structural properties of the recently discovered Andromeda X and Andromeda XVII (And X and And XVII) dwarf galaxies. Using the mean apparent magnitude of the horizontal branch (HB), we derive distances of 621 +- 20 kpc to And X and 734+- 23 kpc to And XVII, closer by >60 kpc than the previous estimates which were based on red giant branch (RGB) observations. Thus our results warrant against the use of the RGB tip method for determining distances to systems with sparsely populated RGBs, and show how crucial HB observations are in obtaining accurate distances in systems such as these. We find that And X is a relatively faint (MV = -7.36), highly elongated (e = 0.48) system at a distance of 174 +- 62 kpc from Andromeda. And XVII is brighter (MV = -8.61) with an M31-centric distance of 73 kpc which makes it one of the closest satellites to Andromeda. Both galaxies are metal-poor: we derive =-2.2 for And X, while And XVII shows = -2.0, consistent with the relation of higher luminosity dwarfs being more metal- rich. Additionally, both galaxies show considerable intrinsic spreads in metallicity (0.2 and 0.3 dex for And X and And XVII respectively), consistent with multiple stellar populations.Comment: 8 pages, 6 figure

The multi-level governance of formulating regional brand identities: Evidence from three Mega City Regions in China

The emergence and expansion of clusters of large metropolitan areas also known as Mega City Regions (MCRs) is a worldwide phenomenon. In China, governmental attempts are made to develop so-called regional brand identities for them. Regional brand identities, as a subspecies of place brand identities, differ from regional identities in the sense that they are the result of conscious branding efforts on the part of public authorities rather than more historically evolved regional identities as experienced by citizens. In this study, the establishment of regional brand identities for three MCRs in China is examined, as these are constituted through and institutionally embedded in intergovernmental relations. We map the perceptions of national, provincial and municipal governments of regional brand identities based on planning documents and relevant interviews. The emergence and stabilization of the regional profiles for China's largest MCRs Pearl River Delta (PRD), Yangtze River Delta (YRD) and Jing-Jin-Ji (JJJ) are featured in their dynamic territorial boundaries, centralized institutionalization and various symbolic meanings. The national government promotes the regional brands to reinforce the strategic awareness and future direction of the region, and these profiles are diffused at the provincial and municipal level

Universality of Shot-Noise in Multiterminal Diffusive Conductors

We prove the universality of shot-noise in multiterminal diffusive conductors of arbitrary shape and dimension for purely elastic scattering as well as for hot electrons. Using a Boltzmann-Langevin approach we reduce the calculation of shot-noise correlators to the solution of a diffusion equation. We show that shot-noise in multiterminal conductors is a non-local quantity and that exchange effects can occur without quantum phase coherence even at zero electron temperature. Concrete numbers for shot-noise are given that can be tested experimentally.Comment: 4 double-column pages, REVTeX, 1 eps figure embedded with eps

Nouveauté or Cliché? Assessment on island ecological vulnerability to Tourism: Application to Zhoushan, China

In comparison with coastal zones, islands are even more vulnerable to anthropogenic disturbance, especially to tourism and tourism-induced activities. Despite a great number of studies on either island tourism or island vulnerability reviewed in this paper, knowledge and practice of the impact from tourism upon island ecological vulnerability (IEV) still needs to be expanded. In this contribution, the IEV of four administrative regions in Zhoushan, China is assessed between 2012 and 2017 based on an “exposure (E)-sensitivity (S)-adaptive capacity (A)” framework and by means of coupling coordination degree modeling (CCDM) for determination of the overall development level of E-S-A subsystems in each region. The assessment results show that: (1) An index system consisting of 1 objective, 3 sub-objectives, 7 elements, and 20 indicators can be established and tested to reflect the IEV to tourism; (2) As the most attractive tourist destinations, Shengsi and Putuo inevitably have the highest IEV values; (3) Dinghai's moderate low level of IEV comes as a surprise, due to its direct connectivity to its neighboring coastal city of Ningbo; (4) The more balanced the coupling coordination degree (CCD) values among E-S-A subsystems are, the higher the IEV values in the four tourist destinations of Zhoushan. In conclusion, tourism can be a double-edged sword for islands, the overall benefits of which outweigh the negative impacts upon island ecological conditions

Toward a Commonly Shared Public Policy Perspective for Analyzing Risk Coping Strategies

The concept of risk has received scholarly attention from a variety of angles in the social, technical, and natural sciences. However, public policy scholars have not yet generated a comprehensive overview, shared understanding and conceptual framework of the main problem-solving approaches applied by governments in coping with risks. In this regard, our main aim is to examine existing perspectives on prevailing risk coping strategies, find a common denominator among them and contribute to current policy and risk science literature through providing a conceptual framework that systematically spans the spectrum of risk coping strategies and incorporates the essence of the most relevant insights. To this end, we first examine the concept of risk in-depth by exploring various definitions and types of risk. We then review different approaches proposed by different strands of research for addressing risk. Finally, we assess current knowledge and develop an amalgamated perspective for examining how risks can be addressed by classifying them into six general types of response (no response; prevention; control; precaution; toleration; and adaptation) as well as indicators to identify these responses. We argue that these strategies can function as a heuristic tool fo

Hanbury Brown Twiss effects in channel mixing normal-superconducting systems

An investigation of the role of the proximity effect in current cross correlations in multiterminal, channel-mixing, normal-superconducting systems is presented. The proposed experiment is an electrical analog of the optical Hanbury Brown Twiss intensity cross correlation experiment. A chaotic quantum dot is connected via quantum point contacts to two normal and one superconducting reservoir. For dominating coupling of the dot to the superconducting reservoir, a magnetic flux of the order of a flux quantum in the dot suppresses the proximity effect and reverses the sign of the cross correlations, from positive to negative. In the opposite limit, for a dominating coupling to the normal reservoirs, the proximity effect is weak and the cross correlation are positive for a nonideal contact between the dot and the superconducting reservoir. We show that in this limit the correlations can be explained with particle counting arguments.Comment: Invited talk at LT2

Examining the density and diversity of human activity in the built environment: The case of the pearl river delta, China

Rapid urbanization in China has been accompanied by spatial inefficiency in patterns of human activity, of which 'ghost towns' are the most visible result. In this study, we measure the density and diversity of human activity in the built environment and relate this to various explanatory factors. Using the Pearl River Delta (PRD) as an empirical case, our research demonstrates the distribution of human activity by multi-source data and then explores its dynamics within these areas. This empirical study is comprised of two parts. The first part explores location information regarding human activity in urbanized areas and shows density and diversity. Regression models are applied to explore how density and diversity are affected by urban scale, morphology and by a city's administrative level. Results indicate that: 1) cities with smaller populations are more likely to be faced with lower density and diversity, but they derive greater marginal benefits from improving land use efficiency; 2) the compactness of the layout of urban land, an index reflecting the plane shapes of the built environment, is highly correlated with density and diversity in built-up areas; and 3) the administrative importance of a city has a significant and positive impact on the density of human activity, but no obvious influence on its diversity