3,668 research outputs found

    How long is co-operation in genomics sustainable?

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    Publications on the 16 yeast chromosome sequences group together over 400 different authors from Europe, Japan, Australia and the USA. When research is not organised in networks, it is carried out in large sequencing centres such as the Sanger Centre in Britain, the Helix Institute in Japan or Saint Louis University in the USA. Both cases illustrate the collective nature of knowledge creation. Other examples of co-operation between numerous researchers in various countries, more closely related to innovation, might also be mentioned, such as the development of software for comparing proteins or DNA sequences. Collective publications reveal the collective nature of research, whether it is carried out by major consortia (the case of yeast) or around large research facilities (such as the synchrotron or major genome sequencing centres). This collective nature stems from two factors: (1) the advantages of co-ordinating efforts on major projects (e.g. economies of scale and of collection) and (2) very strong interdependency in the creation and utilisation of knowledge (related to cumulativeness).

    Profile of public laboratories, industrial partnerships and organisation of R & D: the dynamics of industrial relationships in a large research organisation

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    There is a paucity of papers dealing with the system characteristics of laboratories or, put in another way, the institutional character of research organisations. Neither R & D economics nor the sociology of science, as traditionally conceived, has made much headway in providing insight into sets of R & D laboratories and their evolution. Drawing upon an empirical study in the plant breeding and biochemical industry, this paper presents a typology of public research laboratories which is based on three dimensions: scientific production and visibility, type of funding (public or private) and homogeneity of research themes. Three types of public laboratory emerge: the first, called “research centres for the profession”, is composed essentially of laboratories with close ties with small and medium firms (SMEs) and industry associations. The second, called “designers of generic tools and methods”, is oriented towards basic research and themes of general interest to the industry as a whole. The third type, called “basic and specialised laboratories”, strives to develop its scientific visibility. Contracts between this type of laboratory and industry are mainly bilateral and demonstrate the complementarity between public and private research. Each type of laboratory develops specific types of relationship with private partners. The authors have identified three logics underlying these relationships: proximity, market and club. The main objective of contracts based on a proximity logic is to test a hypothesis, while the knowledge produced is mostly tacit and specific. By contrast, knowledge is entirely coded and specific in the market logic, where the aim of the contract is to implement expertise in order to relieve a scientific bottleneck. In a club logic, the aim of contracts is to produce a technical referent. In each kind of contract, the learning trajectories, modes of co-ordination, role of trust and degree to which contracts are complete or not, are different.

    A Systematic Analysis of Fe II Emission in Quasars: Evidence for Inflow to the Central Black Hole

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    Broad Fe II emission is a prominent feature of the optical and ultraviolet spectra of quasars. We report on a systematical investigation of optical Fe II emission in a large sample of 4037 z < 0.8 quasars selected from the Sloan Digital Sky Survey. We have developed and tested a detailed line-fitting technique, taking into account the complex continuum and narrow and broad emission-line spectrum. Our primary goal is to quantify the velocity broadening and velocity shift of the Fe II spectrum in order to constrain the location of the Fe II-emitting region and its relation to the broad-line region. We find that the majority of quasars show Fe II emission that is redshifted, typically by ~ 400 km/s but up to 2000 km/s, with respect to the systemic velocity of the narrow-line region or of the conventional broad-line region as traced by the Hbeta line. Moreover, the line width of Fe II is significantly narrower than that of the broad component of Hbeta. We show that the magnitude of the Fe II redshift correlates inversely with the Eddington ratio, and that there is a tendency for sources with redshifted Fe II emission to show red asymmetry in the Hbeta line. These characteristics strongly suggest that Fe II originates from a location different from, and most likely exterior to, the region that produces most of Hbeta. The Fe II-emitting zone traces a portion of the broad-line region of intermediate velocities whose dynamics may be dominated by infall.Comment: 20 pages, 14 figures, accepted for publication in Ap

    A striking correspondence between the dynamics generated by the vector fields and by the scalar parabolic equations

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    The purpose of this paper is to enhance a correspondence between the dynamics of the differential equations y˙(t)=g(y(t))\dot y(t)=g(y(t)) on Rd\mathbb{R}^d and those of the parabolic equations u˙=Δu+f(x,u,u)\dot u=\Delta u +f(x,u,\nabla u) on a bounded domain Ω\Omega. We give details on the similarities of these dynamics in the cases d=1d=1, d=2d=2 and d3d\geq 3 and in the corresponding cases Ω=(0,1)\Omega=(0,1), Ω=T1\Omega=\mathbb{T}^1 and dim(Ω\Omega)2\geq 2 respectively. In addition to the beauty of such a correspondence, this could serve as a guideline for future research on the dynamics of parabolic equations

    Curvature tensors on distorted Killing horizons and their algebraic classification

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    We consider generic static spacetimes with Killing horizons and study properties of curvature tensors in the horizon limit. It is determined that the Weyl, Ricci, Riemann and Einstein tensors are algebraically special and mutually aligned on the horizon. It is also pointed out that results obtained in the tetrad adjusted to a static observer in general differ from those obtained in a free-falling frame. This is connected to the fact that a static observer becomes null on the horizon. It is also shown that finiteness of the Kretschmann scalar on the horizon is compatible with the divergence of the Weyl component Ψ3\Psi_{3} or Ψ4\Psi_{4} in the freely falling frame. Furthermore finiteness of Ψ4\Psi_{4} is compatible with divergence of curvature invariants constructed from second derivatives of the Riemann tensor. We call the objects with finite Krestschmann scalar but infinite Ψ4\Psi_{4} ``truly naked black holes''. In the (ultra)extremal versions of these objects the structure of the Einstein tensor on the horizon changes due to extra terms as compared to the usual horizons, the null energy condition being violated at some portions of the horizon surface. The demand to rule out such divergencies leads to the constancy of the factor that governs the leading term in the asymptotics of the lapse function and in this sense represents a formal analog of the zeroth law of mechanics of non-extremal black holes. In doing so, all extra terms in the Einstein tensor automatically vanish.Comment: 21 pages, To appear in Class. Quant. Gra

    The UV Properties of the Narrow Line Quasar I Zwicky 1

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    I Zw 1 is the prototype narrow line quasar. We report here the results of our study of the UV emission of I Zw 1 using a high S/N (50-120) spectrum obtained with the HST FOS. The following main new results are obtained: 1. The Mg II and Al III doublets are partially/fully resolved. The measured doublet ratios verify theoretical predictions that the lines are thermalized in the BLR. 2. A weak associated UV absorption system is detected in N~V, and possibly also in C IV and Lya, suggesting an outflow with a velocity of 1870 km/s and velocity dispersion <300 km/s. 3. Lines from ions of increasing ionization level show increasing excess blue wing flux, and an increasing line peak velocity shift, reaching a maximum blueshift of about 2000 km/s for He II 1640. This may indicate an out-flowing component in the BLR, where the ionization level increases with velocity, and which is visible only in the approaching direction. The highest velocity part of this outflow may produce the associated UV absorption system. 4. The small C III] 1909 EW, and the small C III] 1909/Lya and C III] 1909/Si III] 1892 flux ratios indicate a typical BLR density of 10^11, i.e. about an order of magnitude larger than implied by C III] 1909 in most quasars. A BLR component of a higher density is implied by the EW and doublet ratio of the Al III 1857 doublet. 5. Prominent Fe II UV 191 emission is seen, together with weaker line emission at 1294 and 1871 A. These three features have been proposed as evidence for significant Lya pumping of the 8-10 eV levels of Fe II. 6. Significant Fe III emission is present. The Fe III UV 34 and UV 48 multiplets are clearly resolved, and Fe III UV 1, UV 47, UV 50, and UV 68 may also be present. (Shortened version)Comment: 28 pages, 1 table and 7 figures included. Uses aas2pp4.sty. Scheduled for the Astrophysical Journal November 10, 1997 issue, Vol. 48

    Exposure in utero to maternal diabetes leads to glucose intolerance and high blood pressure with no major effects on lipid metabolism

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    AIM: Recent evidence shows that adult metabolic disease may originate from an adverse fetal environment that can alter organ development and function in postnatal life. This study aimed to analyze the effect of exposure in utero to maternal diabetes on the development of the metabolic syndrome in the offspring. METHODS: Pregnant rats were made diabetic (blood glucose was 20mM) with a single streptozotocin injection on day 0 of gestation. Offspring from diabetic mothers (DMO) and control mothers (CMO) were followed from birth to 12 months of age. In these animals, metabolic parameters, such as glucose tolerance, insulin sensitivity and plasma lipid levels, as well as pancreatic insulin and morphology were studied. RESULTS: Compared with controls, DMO offspring had normal birth weights, but impaired postnatal growth that persisted throughout life. Metabolic tests revealed that DMO offspring also showed impaired glucose tolerance at six months associated with decreased insulin sensitivity and low insulin secretion. In older animals (12 months old), this phenotype persisted, but to a lesser extent. The DMO offspring also presented with high blood pressure and decreased levels of fasting plasma triglycerides, but normal plasma NEFA, and HDL and total cholesterol. CONCLUSION: Altogether, these results show that our model of exposure in utero to maternal diabetes led to normal birth weights, and induced transient glucose intolerance and increased blood pressure with no major effects on lipid metabolism. It also suggests that a hyperglycaemic fetal environment may be able to \u27programme\u27 hypertension and glucose intolerance, but not alter lipid metabolism

    The Intrinsically X-ray Weak Quasar PHL 1811. II. Optical and UV Spectra and Analysis

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    This is the second of two papers reporting observations and analysis of the unusually bright (m_b=14.4), luminous (M_B=-25.5), nearby (z=0.192) narrow-line quasar PHL 1811. The first paper reported that PHL 1811 is intrinsically X-ray weak, and presented a spectral energy distribution (SED). Here we present HST STIS optical and UV spectra, and ground-based optical spectra. The optical and UV line emission is very unusual. There is no evidence for forbidden or semiforbidden lines. The near-UV spectrum is dominated by very strong FeII and FeIII, and unusual low-ionization lines such as NaID and CaII H&K are observed. High-ionization lines are very weak; CIV has an equivalent width of 6.6A, a factor of ~5 smaller than measured from quasar composite spectra. An unusual feature near 1200A can be deblended in terms of Ly\alpha, NV, SiII, and CIII* using the blueshifted CIV profile as a template. Photoionization modeling shows that the unusual line emission can be explained qualitatively by the unusually soft SED. Principally, a low gas temperature results in inefficient emission of collisionally excited lines, including the semiforbidden lines generally used as density diagnostics. The emission resembles that of high-density gas; in both cases this is a consequence of inefficient cooling. PHL 1811 is very unusual, but we note that quasar surveys are generally biased against finding similar objects.Comment: Accepted for publication in ApJS. Full resolution figures available here: http://www.nhn.ou.edu/~leighly/phl1811_paper1.pd
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