New data and the hard pomeron

New structure-function data are in excellent agreement with the existence of a hard pomeron, with intercept about 1.4. It gives a very economical description of the data. Having fixed 2 parameters from the data for the real-photon cross section $\sigma^{\gamma p}$, we need just 5 further parameters to fit the data for $F_2(x,Q^2)$ with $x\leq 0.001$. The available data range from $Q^2=0.045$ to 35 GeV$^2$. With guesses consistent with dimensional counting for the $x$ dependences of our three separate terms, the fit extends well to larger $x$ and to $Q^2=5000$ GeV$^2$. With no additional parameters, it gives a good description of data for the charm structure function $F_2^c(x,Q^2)$ from $Q^2=0$ to 130 GeV$^2$. The two pomerons also give a good description of both the $W$ and the $t$ dependence of $\gamma p\to J/\psi p$.Comment: 11 pages, plain tex, with 10 figures embedded using epsf. (Spurious figure removed.

Scaling metagenome sequence assembly with probabilistic de Bruijn graphs

Deep sequencing has enabled the investigation of a wide range of environmental microbial ecosystems, but the high memory requirements for {\em de novo} assembly of short-read shotgun sequencing data from these complex populations are an increasingly large practical barrier. Here we introduce a memory-efficient graph representation with which we can analyze the k-mer connectivity of metagenomic samples. The graph representation is based on a probabilistic data structure, a Bloom filter, that allows us to efficiently store assembly graphs in as little as 4 bits per k-mer, albeit inexactly. We show that this data structure accurately represents DNA assembly graphs in low memory. We apply this data structure to the problem of partitioning assembly graphs into components as a prelude to assembly, and show that this reduces the overall memory requirements for {\em de novo} assembly of metagenomes. On one soil metagenome assembly, this approach achieves a nearly 40-fold decrease in the maximum memory requirements for assembly. This probabilistic graph representation is a significant theoretical advance in storing assembly graphs and also yields immediate leverage on metagenomic assembly

Mapping the e-Learning Assessment Domain: Concept Maps for Orientation and Navigation

Concept or Topic Maps have long been used as a method of categorizing and organizing information about a domain. Building them can help people conceptualize an area and spot trends or gaps, and as a presentation method they quickly provide an overview and general impression of a space. We are currently constructing a Reference Model of the Assessment Domain that takes the form of a highly interlinked dynamic website. This represents the assessment domain via the software, projects, standards and use cases of which it is composed. In this paper we present our efforts to create complimentary concept maps of the assessment domain, not as an overview, but for navigation and orientation within the domain. These concept maps, which model resources and activities independently, have been corroborated with practitioners in the e-learning community

Lens mounting techniques for precise radial location of fragile lenses in the NGS2 and Veloce instruments

We present novel methods for mounting lenses in a pair of instruments that presented challenging optical and mechanical requirements. The first instrument is the replacement Natural Guide Star Sensor (NGS2) for CANOPUS at Gemini South, which incorporates an objective consisting of a stack of six lenses mounted in a common bore. A compliant radial spacer was used to eliminate lens decentre resulting from the additional radial clearance required to accommodate differential thermal strains between the low thermal expansion lenses and a common bore. In the same instrument, tangent contact toroidal spacers were deployed in place of traditional conical spacers to further reduce contact stresses in fragile calcium fluoride lens elements. The toroidal faces were specified with a 10µm profile tolerance to avoid possible edge contact between the spacers and lenses. We investigated milling and turning machining processes for the production of the spacers by comparing their results via Coordinate Measuring Machine (CMM) measurements. In the second instrument, Veloce, built for the Anglo-Australian Telescope, a lens decentre requirement of 40µm led us to develop a simple means of in-situ centring adjustment of the cell mounted lens. Physical testing of the finished instruments verified the performance of each of these methods. NGS2 produced images at the factory acceptance test in which 94% of encircled energy was captured by a single 16um detector pixel, surpassing the specification of 80%. Bench testing of Veloce during assembly showed that the adjustment mechanism allowed centring of the lens over a range of +/- 0.1mm with a precision of 5µm

Growth of Literature on Bradford's Law

ABSTRACTThis paper analyzes the literature produced on Bradford's Law from 1934 to June 2012. The study compiled 936 documents produced by 1,123 authors, working in sixteen languages to communicate the results of their research, with English the leading language, followed by Chinese, Spanish and Portuguese. The study reveals the fifteen most productive authors, all of which work in English in both academic journals and conference settings. This literature is growing exponentially (R2=0.974), at a rate of 5.4% per year and doubling in size every 13.2 years

The Missing Link of Jewish European Ancestry: Contrasting the Rhineland and the Khazarian Hypotheses

The question of Jewish ancestry has been the subject of controversy for over two centuries and has yet to be resolved. The "Rhineland Hypothesis" proposes that Eastern European Jews emerged from a small group of German Jews who migrated eastward and expanded rapidly. Alternatively, the "Khazarian Hypothesis" suggests that Eastern European descended from Judean tribes who joined the Khazars, an amalgam of Turkic clans that settled the Caucasus in the early centuries CE and converted to Judaism in the 8th century. The Judaized Empire was continuously reinforced with Mesopotamian and Greco-Roman Jews until the 13th century. Following the collapse of their empire, the Judeo-Khazars fled to Eastern Europe. The rise of European Jewry is therefore explained by the contribution of the Judeo-Khazars. Thus far, however, their contribution has been estimated only empirically; the absence of genome-wide data from Caucasus populations precluded testing the Khazarian Hypothesis. Recent sequencing of modern Caucasus populations prompted us to revisit the Khazarian Hypothesis and compare it with the Rhineland Hypothesis. We applied a wide range of population genetic analyses - including principal component, biogeographical origin, admixture, identity by descent, allele sharing distance, and uniparental analyses - to compare these two hypotheses. Our findings support the Khazarian Hypothesis and portray the European Jewish genome as a mosaic of Caucasus, European, and Semitic ancestries, thereby consolidating previous contradictory reports of Jewish ancestry.Comment: 21 pages, 7 figures, 1 table, 7 supplementary figures, 7 supplementary table