Modifying the surface electronic properties of YBa2Cu3O7-delta with cryogenic scanning probe microscopy

We report the results of a cryogenic study of the modification of YBa2Cu3O7-delta surface electronic properties with the probe of a scanning tunneling microscope (STM). A negative voltage applied to the sample during STM tunneling is found to modify locally the conductance of the native degraded surface layer. When the degraded layer is removed by etching, the effect disappears. An additional surface effect is identified using Scanning Kelvin Probe Microscopy in combination with STM. We observe reversible surface charging for both etched and unetched samples, indicating the presence of a defect layer even on a surface never exposed to air.Comment: 6 pages, 4 figures. To appear in Superconductor Science and Technolog

Formation of Sub-galactic Clouds under UV Background Radiation

The effects of the UV background radiation on the formation of sub-galactic clouds are studied by means of one-dimensional hydrodynamical simulations. The radiative transfer of the ionizing photons due to the absorption by HI, HeI and HeII, neglecting the emission, is explicitly taken into account. We find that the complete suppression of collapse occurs for the clouds with circular velocities typically in the range V_c \sim 15-40 km/s and the 50% reduction in the cooled gas mass with V_c \sim 20-55 km/s. These values depend most sensitively on the collapse epoch of the cloud, the shape of the UV spectrum, and the evolution of the UV intensity. Compared to the optically thin case, previously investigated by Thoul & Weinberg (1996), the absorption of the external UV photon by the intervening medium systematically lowers the above threshold values by \Delta V_c \sim 5 km/s. Whether the gas can contract or keeps expanding is roughly determined by the balance between the gravitational force and the thermal pressure gradient when it is maximally exposed to the external UV flux. Based on our simulation results, we discuss a number of implications on galaxy formation, cosmic star formation history, and the observations of quasar absorption lines. In Appendix, we derive analytical formulae for the photoionization coefficients and heating rates, which incorporate the frequency/direction-dependent transfer of external photons.Comment: 38 pages, 16 figures, accepted for publication in Ap

Metagenomics reveals our incomplete knowledge of global diversity

Financial support was provided by projects BFU2006-06003 from the Spanish Ministry of Education and Science (MEC) and GV/2007/050 from the Generalitat Valenciana, Spain. J.T. is a recipient of a contract in the FIS Program from ISCIII, Spanish Ministry of Health.Pignatelli, M.; Aparicio Pla, G.; Blanquer Espert, I.; Hernández García, V.; Moya, A.; Tamames, J. (2008). Metagenomics reveals our incomplete knowledge of global diversity. Bioinformatics. 24(18):2124-2125. https://doi.org/10.1093/bioinformatics/btn355S212421252418Koski, L. B., & Golding, G. B. (2001). The Closest BLAST Hit Is Often Not the Nearest Neighbor. Journal of Molecular Evolution, 52(6), 540-542. doi:10.1007/s002390010184Krause, L., Diaz, N. N., Goesmann, A., Kelley, S., Nattkemper, T. W., Rohwer, F., … Stoye, J. (2008). Phylogenetic classification of short environmental DNA fragments. Nucleic Acids Research, 36(7), 2230-2239. doi:10.1093/nar/gkn038Mavromatis, K., Ivanova, N., Barry, K., Shapiro, H., Goltsman, E., McHardy, A. C., … Kyrpides, N. C. (2007). Use of simulated data sets to evaluate the fidelity of metagenomic processing methods. Nature Methods, 4(6), 495-500. doi:10.1038/nmeth1043Tamames, J., & Moya, A. (2008). Estimating the extent of horizontal gene transfer in metagenomic sequences. BMC Genomics, 9(1), 136. doi:10.1186/1471-2164-9-136Tringe, S. G. (2005). Comparative Metagenomics of Microbial Communities. Science, 308(5721), 554-557. doi:10.1126/science.1107851Tringe, S. G., Zhang, T., Liu, X., Yu, Y., Lee, W. H., Yap, J., … Ruan, Y. (2008). The Airborne Metagenome in an Indoor Urban Environment. PLoS ONE, 3(4), e1862. doi:10.1371/journal.pone.0001862COLE, F. N. (1900). AMERICAN MATHEMATICAL SOCIETY. Science, 11(263), 66-67. doi:10.1126/science.11.263.6

Tony Blair and John Howard: comparative predominance and 'Institution Stretch' in the UK and Australia

It has recently been argued that the UK premier enjoys a level of executive power unavailable to US presidents, but how does he or she compare to another prime minister operating within a broadly similar system? Commonalities of intra-executive influence and capacity exist under the premierships in the UK and Australia. Discrete institutional constraints and deviations are evident, but trends and similarities in resource capacity can be clearly identified. These include: the growth of the leaders' office; broadening and centralising of policy advice and media operations; and strengthening of the role and function of ministerial advisers. I contend that this amounts to 'institution stretch', with new structures, processes and practices becoming embedded in the political system by the incumbents. © 2007 The Author. Journal compilation © 2007 Political Studies Association

The roles of the formal and informal sectors in the provision of effective science education

For many years, formal school science education has been criticised by students, teachers, parents and employers throughout the world. This article presents an argument that a greater collaboration between the formal and the informal sector could address some of these criticisms. The causes for concern about formal science education are summarised and the major approaches being taken to address them are outlined. The contributions that the informal sector currently makes to science education are identified. It is suggested that the provision of an effective science education entails an enhanced complementarity between the two sectors. Finally, there is a brief discussion of the collaboration and communication still needed if this is to be effective

Korarchaeota Diversity, Biogeography, and Abundance in Yellowstone and Great Basin Hot Springs and Ecological Niche Modeling Based on Machine Learning

Over 100 hot spring sediment samples were collected from 28 sites in 12 areas/regions, while recording as many coincident geochemical properties as feasible (>60 analytes). PCR was used to screen samples for Korarchaeota 16S rRNA genes. Over 500 Korarchaeota 16S rRNA genes were screened by RFLP analysis and 90 were sequenced, resulting in identification of novel Korarchaeota phylotypes and exclusive geographical variants. Korarchaeota diversity was low, as in other terrestrial geothermal systems, suggesting a marine origin for Korarchaeota with subsequent niche-invasion into terrestrial systems. Korarchaeota endemism is consistent with endemism of other terrestrial thermophiles and supports the existence of dispersal barriers. Korarchaeota were found predominantly in >55°C springs at pH 4.7–8.5 at concentrations up to 6.6×106 16S rRNA gene copies g−1 wet sediment. In Yellowstone National Park (YNP), Korarchaeota were most abundant in springs with a pH range of 5.7 to 7.0. High sulfate concentrations suggest these fluids are influenced by contributions from hydrothermal vapors that may be neutralized to some extent by mixing with water from deep geothermal sources or meteoric water. In the Great Basin (GB), Korarchaeota were most abundant at spring sources of pH<7.2 with high particulate C content and high alkalinity, which are likely to be buffered by the carbonic acid system. It is therefore likely that at least two different geological mechanisms in YNP and GB springs create the neutral to mildly acidic pH that is optimal for Korarchaeota. A classification support vector machine (C-SVM) trained on single analytes, two analyte combinations, or vectors from non-metric multidimensional scaling models was able to predict springs as Korarchaeota-optimal or sub-optimal habitats with accuracies up to 95%. To our knowledge, this is the most extensive analysis of the geochemical habitat of any high-level microbial taxon and the first application of a C-SVM to microbial ecology

Human redemption in (and of) the matrix of technological modernity

Despite the indifferent responses to the second and third instalments of 'The Matrix' series, the trilogy is nevertheless a valuable contribution to popular debate about the human implications of a rapidly emerging technoculture. In this essay, I will develop a reading of the Matrix scenario, not so much as a cautionary warning about the folly of developing intelligent machines, but as a reflection on the moral meanings of becoming increasingly immersed in a technological milieu. I argue that whilst 'The Matrix', the first of the trilogy, depicts a simplisitic opposition between humans and machines, 'Reloaded' and 'Revolutions' open up a more dialectical understanding of human meaning in a technological world and instead explore the tension between two competing moral trajectories of technological existence: The first, the unfolding of a bleak, nihilistic instrumentalism, the second, a reflexive recovery of human relationship made possible by the renewal of a moral ontology of sacrificial self-giving

Technology and citizenship

The renewal of a discourse of active citizenship1 in western liberal democratic polities in recent years has been in large part a reaction to the ascendancy of neo-liberalism in social policy and its consequent corrosive impact on public life and social institutions (Meredyth 1997; Mouffe 1988). Recent poststructuralist analyses of this renewed civic discourse has been critical of the abstractness of notions of ‘civil society’, ‘citizenship’ and the like and has focused on developing more detailed genealogical accounts of the ways in which these and other such notions have functioned within the government of populations (Burchell 1995). In this chapter I’m interested in two rather different features of such discourse. The first is the sometimes explicit, though mostly implicit (and in the case of poststructuralists rather more muted), moral concern which animates much of the critical response to neo-liberalism and the advocacy of active citizenship. Notwithstanding our critical reservations in an academic context about moral discourse, when it comes to public policy issues, those of us who come from a more or less leftist, feminist or social democratic background feel a sense of moral dismay when we observe the effects of neo-liberal social policies on people: the growing inequality of wealth, income and life chances, the increasing surveillance, the dismantling or reconstruction of public institutions as profit making companies, the growing callousness and meanness of public life. We have a perhaps poorly articulated but deeply felt sense of the unfairness of it all, a sense of dismay at the erosion of human dignity and the withdrawal of social rights, especially for the poorest and the most vulnerable. We still believe that government should act for the ‘common good’ (however difficult that may be to define), providing resources for health, education, welfare and employment generation to enable ordinary people to flourish as individuals and as communities. We still have an intuitive sense of citizenship as a moral practice, of the virtues of being involved in civic issues, of the rightness of fighting developers, cost cutting governments and so on. Yet in the context of postmodern and poststructuralist critiques of modernist grand narratives we find it hard to develop any rational foundation for such moral feelings. Indeed, we are uncomfortable, even suspicious, of normative discourse altogether. We deconstruct the language of morality as a technique of governmentality, ethics as a moral technology (Rose 1990). Thus, despite our moral feelings, in the end we are uncertain as to whether it is possible to talk about citizenship as a moral practice at all. As a consequence, in so far as our responses are typical of academics on the left more generally, by default the language of morality in public life ends up being coopted by conservatives and reactionaries for the cause of moral prohibition, racism and sometimes xenophobic nationalism