Calibration update of the COMBO-17 CDFS catalogue

We present an update to the photometric calibration of the COMBO-17 catalogue on the Extended Chandra Deep Field South, which is now consistent with the GaBoDS and MUSYC catalogues. As a result, photometric redshifts become slightly more accurate, with <0.01 rms and little bias in the delta_z/(1+z) of galaxies with R<21 and of QSOs with R<24. With increasing photon noise the rms of galaxies reaches 0.02 for R<23 and 0.035 at R~23.5. Consequences for the rest-frame colours of galaxies at z<1 are discussed.Comment: A&A research note, resubmitted 02 Oct 2008, 4 pages in print forma

How has the Louisiana Scholarship Program Affected students? A Comprehensive Summary of Effects After Three Years

School choice reforms comprise a broad category of policies aimed at improving public education through the introduction of market forces that expand customer choice and competition between schools. Here we summarize our research to date on the effects of a large statewide school voucher initiative, the Louisiana Scholarship Program (LSP), and draw the following conclusions: • Overall, participating in the LSP had no statistically significant impact on student English Language Arts (ELA) or math scores after using an LSP scholarship for three years. • The subgroup of students who were lower achieving before applying to the program did show significant gains in ELA after three years of scholarship usage. Students applying to lower grades demonstrated significant losses in math. • Students without disabilities were less likely to be identified to receive special education services if they participated in the LSP than if they did not. Students with disabilities were more likely to be de-identified as requiring special education services if they participated in the private school choice program. • The private schools that chose to participate in the LSP were disproportionately Catholic, had low tuitions, had low enrollments, and served a high percentage of minority students. We discuss these findings in the remainder of this brief and in greater detail in the three accompanying technical reports. Combined with prior evidence, these results are informative about the specific design of voucher and other choice policies and about how the effects of choice evolve over time as programs mature

The Effects of the Louisiana Scholarship Program on Student Achievement After Two Years

The Louisiana Scholarship Program (LSP) is a statewide initiative offering publicly-funded vouchers to enroll in local private schools to students in low-performing schools with family income no greater than 250 percent of the poverty line. Initially established in 2008 as a pilot program in New Orleans, the LSP was expanded statewide in 2012. This paper examines the experimental effects of using an LSP scholarship to enroll in a private school on student achievement in the first two years following the program’s expansion. Our results indicate that the use of an LSP scholarship has negatively impacted both ELA and math achievement, although only the latter estimates are statistically significant. Moreover, we observe less negative effect estimates in the second year of the program

Neutron Stars

Several authors have suggested that the recently discovered extraterrestrial sources of x rays may be hot neutron stars. The plausibility of this suggestion, and in fact the likelihood that astronomers will ever be able to observe neutron stars by their x-ray emission, depend critically upon the cooling times of the hot stars

The location of the UK cotton textiles industry in 1838 : a quantitative analysis

We examine the geography of cotton textiles in Britain in 1838 to test claims about why the industry came to be so heavily concentrated in Lancashire. Our analysis considers both first and second nature aspects of geography including the availability of water power, humidity, coal prices, market access and sunk costs. We show that some of these characteristics have substantial explanatory power. Moreover, we exploit the change from water to steam power to show that the persistent effect of first nature characteristics on industry location can be explained by a combination of sunk costs and agglomeration effects

A deterministic sandpile automaton revisited

The Bak-Tang-Wiesenfeld (BTW) sandpile model is a cellular automaton which has been intensively studied during the last years as a paradigm for self-organized criticality. In this paper, we reconsider a deterministic version of the BTW model introduced by Wiesenfeld, Theiler and McNamara, where sand grains are added always to one fixed site on the square lattice. Using the Abelian sandpile formalism we discuss the static properties of the system. We present numerical evidence that the deterministic model is only in the BTW universality class if the initial conditions and the geometric form of the boundaries do not respect the full symmetry of the square lattice.Comment: 7 pages, 8 figures, EPJ style, accepted for publication in European Physical Journal

Spike Onset Dynamics and Response Speed in Neuronal Populations

Recent studies of cortical neurons driven by fluctuating currents revealed cutoff frequencies for action potential encoding of several hundred Hz. Theoretical studies of biophysical neuron models have predicted a much lower cutoff frequency of the order of average firing rate or the inverse membrane time constant. The biophysical origin of the observed high cutoff frequencies is thus not well understood. Here we introduce a neuron model with dynamical action potential generation, in which the linear response can be analytically calculated for uncorrelated synaptic noise. We find that the cutoff frequencies increase to very large values when the time scale of action potential initiation becomes short

Inhomogeneous superconductivity and the "pseudogap state of novel superconductors

Novel superconducting compounds such as the high Tc oxides are intrinsically inhomogeneous systems. An inhomogeneous structure is created by doping and the statistical nature of the distribution of dopants. Consequently, the critical temperature is spatially dependent: Tc = Tc (r).Comment: 63 pages text, 13 figures and 1 tabl