532 research outputs found
DNA target sequence and FNR-dependent gene expression.
FNR proteins are global transcription regulators that respond to fluctuations in environmental oxygen. They recognise a DNA target consisting of an inverted repeat, TTGATN(1)N(2)N(3)N(4)ATCAA (where N(1-4) represents a non-conserved tetrad, NCT). Analysis of 68 known and predicted FNR sites from the Escherichia coli K12 genome revealed a bias toward A or T at positions N(2) and N(3) of the NCT. The effect of the NCT sequence on FNR-dependent transcription in vivo was assessed using a series of class II and class I model promoters with different NCT sequences. Changing the NCT sequence did not affect basal activity but altered anaerobic induction by as much as an order of magnitude. Thus, the NCT sequence is a fundamental component in setting the dynamic range of the FNR switch
Population-Specific Vital Rate Contributions Influence Management of an Endangered Ungulate
To develop effective management strategies for the recovery of threatened and endangered species, it is critical to identify those vital rates (survival and reproductive parameters) responsible for poor population performance and those whose increase will most efficiently change a population\u27s trajectory. In actual application, however, approaches identifying key vital rates are often limited by inadequate demographic data, by unrealistic assumptions of asymptotic population dynamics, and of equal, infinitesimal changes in mean vital rates. We evaluated the consequences of these limitations in an analysis of vital rates most important in the dynamics of federally endangered Sierra Nevada bighorn sheep (Ovis canadensis sierrae). Based on data collected from 1980 to 2007, we estimated vital rates in three isolated populations, accounting for sampling error, variance, and covariance. We used analytical sensitivity analysis, life-stage simulation analysis, and a novel non-asymptotic simulation approach to (1) identify vital rates that should be targeted for subspecies recovery; (2) assess vital rate patterns of endangered bighorn sheep relative to other ungulate populations; (3) evaluate the performance of asymptotic vs. non-asymptotic models for meeting short-term management objectives; and (4) simulate management scenarios for boosting bighorn sheep population growth rates. We found wide spatial and temporal variation in bighorn sheep vital rates, causing rates to vary in their importance to different populations. As a result, Sierra Nevada bighorn sheep exhibited population-specific dynamics that did not follow theoretical expectations or those observed in other ungulates. Our study suggests that vital rate inferences from large, increasing, or healthy populations may not be applicable to those that are small, declining, or endangered. We also found that, while asymptotic approaches were generally applicable to bighorn sheep conservation planning, our non-asymptotic population models yielded unexpected results of importance to managers. Finally, extreme differences in the dynamics of individual bighorn sheep populations imply that effective management strategies for endangered species recovery may often need to be population-specific
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Sunspot observations on 10 and 11 February 1917: a case study in collating known and previously undocumented records
An extensive investigation of shipsâ logs, as part of the âOld Weatherâ citizen-science project,
identified a sunspot observation made from HMS Hilary on 10 February 1917. This sunspot record was accompanied by detailed meteorological records that have enabled a reconstruction of the conditions under which the observation was made (overcast with detached clouds). Although there is no incontrovertible evidence that this was an unaided-eye observation, comparison with an unaided-eye observation recorded on the 11 February 1917 in a local
treatise from HĂ©nĂĄn province in China confirms that this sunspot group was visible to the unaided eye. White-light photographs from the Dehra Dun Observatory confirm the detailed description of the sunspot group provided by the naval observer. Moreover, comparisons with tabular data published by the Royal Observatory, Greenwich, confirm the statement that this was an unusually large sunspot group. Indeed, on 11 February 1917 the area of the sunspot group was greater than the area of any sunspot group recorded previously at the Royal Observatory, Greenwich. A comparison with a modern unaided-eye observation confirms that it is possible to observe sunspots under meteorological conditions similar to those experienced on-board HMS Hilary
Active Vibration Control Device
An active vibration control device for controlling vibration in a cantilevered member and a method for the same are disclosed. The device is comprised of a cantilevered member having a longitudinal axis comprising a sensor mounted near the free end of the member to measure motion of the member in a transverse direction and to produce a corresponding signal. A force generating assembly is mounted to the member near the free end to oppose the measured motion with a force thereby minimizing subsequent motion along the transverse axis caused by vibration
A further cost for the sicker sex? Evidence for male-biased parasite-induced vulnerability to predation
Males are typically the sicker sex. Data from multiple taxa indicate that they are more likely to be infected with parasites, and are less âtolerantâ, or less able to mitigate the fitness costs of a given infection, than females. One cost of infection for many animals is an increased probability of being captured by a predator. A clear, hitherto untested, prediction is therefore that this parasite-induced vulnerability to predation is more pronounced among males than females. We tested this prediction in the sexually size dimorphic guppy, Poecilia reticulata, in which females are typically larger than males. We either sham or experimentally infected guppies with Gyrodactylus turnbulli, elicited their escape response using an established protocol and measured the distance they covered during 60 ms. To discriminate between the effects of body size and those of other inherent sex differences, we size-matched fish across treatment groups. Infection with G. turnbulli reduced the distance covered during the escape response of small adults by 20.1%, whereas that of large fish was unaffected. This result implies that parasite-induced vulnerability to predation is male-biased in the wild: although there was no difference in escape response between our experimentally size-matched groups of males and females, males are significantly smaller across natural guppy populations. These results are consistent with Batemanâs principle for immunity: natural selection for larger body sizes and longevity in females seems to have resulted in the evolution of increased infection tolerance. We discuss the potential implications of male-biased parasite-induced vulnerability for the evolutionary ecology of this host-parasite interaction in natural communities
A closed-loop EKF and multi-failure diagnosis approach for cooperative GNSS positioning
Current cooperative positioning with Global Navigation Satellite System (GNSS) for connected vehicle application mainly uses pseudorange measurements. However the positioning accuracy offered cannot meet the requirements for lane-level positioning, collision avoidance and future automatic driving, which needs real-time positioning accuracy of better than 0.5m. Furthermore, there is an apparent lack of research into the integrity issue for these new applications under emerging driverless vehicle applications. In order to overcome those problems, a new Extended Kalman Filter (EKF) and a multi-failure diagnosis algorithm are developed to process both GNSS pseudorange and carrier phase measurements. We first introduce a new closed-loop EKF with partial ambiguity resolution (PAR) as feedback to address the low accuracy issue. Then a multi-failure diagnosis algorithm is proposed to improve integrity and reliability. The core of this new algorithm includes using Carrier phase based Receiver Autonomous Integrity Monitoring (CRAIM) method for failure detection, and the double extended w-test detectors to identify failure. A cooperative positioning experiment was carried out to validate the proposed method. The results show that the proposed closed-loop EKF can provide highly accurate positioning, and the multi-failure diagnosis method is effective in detecting and identifying failures for both code and carrier phase measurements
Nonlinear anomalous diffusion equation and fractal dimension: Exact generalized gaussian solution
In this work we incorporate, in a unified way, two anomalous behaviors, the
power law and stretched exponential ones, by considering the radial dependence
of the -dimensional nonlinear diffusion equation where , ,
, and are real parameters and is a time-dependent
source. This equation unifies the O'Shaugnessy-Procaccia anomalous diffusion
equation on fractals () and the spherical anomalous diffusion for
porous media (). An exact spherical symmetric solution of this
nonlinear Fokker-Planck equation is obtained, leading to a large class of
anomalous behaviors. Stationary solutions for this Fokker-Planck-like equation
are also discussed by introducing an effective potential.Comment: Latex, 6 pages. To appear in Phys. Rev.
The politicisation of evaluation: constructing and contesting EU policy performance
Although systematic policy evaluation has been conducted for decades and has been growing strongly within the European Union (EU) institutions and in the member states, it remains largely underexplored in political science literatures. Extant work in political science and public policy typically focuses on elements such as agenda setting, policy shaping, decision making, or implementation rather than evaluation. Although individual pieces of research on evaluation in the EU have started to emerge, most often regarding policy âeffectivenessâ (one criterion among many in evaluation), a more structured approach is currently missing. This special issue aims to address this gap in political science by focusing on four key focal points: evaluation institutions (including rules and cultures), evaluation actors and interests (including competencies, power, roles and tasks), evaluation design (including research methods and theories, and their impact on policy design and legislation), and finally, evaluation purpose and use (including the relationships between discourse and scientific evidence, political attitudes and strategic use). The special issue considers how each of these elements contributes to an evolving governance system in the EU, where evaluation is playing an increasingly important role in decision making
The Citation Field of Evolutionary Economics
Evolutionary economics has developed into an academic field of its own,
institutionalized around, amongst others, the Journal of Evolutionary Economics
(JEE). This paper analyzes the way and extent to which evolutionary economics
has become an interdisciplinary journal, as its aim was: a journal that is
indispensable in the exchange of expert knowledge on topics and using
approaches that relate naturally with it. Analyzing citation data for the
relevant academic field for the Journal of Evolutionary Economics, we use
insights from scientometrics and social network analysis to find that, indeed,
the JEE is a central player in this interdisciplinary field aiming mostly at
understanding technological and regional dynamics. It does not, however, link
firmly with the natural sciences (including biology) nor to management
sciences, entrepreneurship, and organization studies. Another journal that
could be perceived to have evolutionary acumen, the Journal of Economic Issues,
does relate to heterodox economics journals and is relatively more involved in
discussing issues of firm and industry organization. The JEE seems most keen to
develop theoretical insights
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