7,341 research outputs found

    The Response of Zigadenus fremontii to Variation in Fire Regime

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    California\u27s chaparral shrub communities are naturally exposed to dry-season fire. It could be reasoned that prescription burns set during the wet season by land managers would have more detrimental effects on plant regeneration than dry season fires because wet season burns are more likely to kill newly emergent seedlings and damage newly emerged leaves of mature plants. Six field sites with flowering Zigadenus fremontii, an herbaceous perennial geophyte common to chapparal and part of the post-fire bloom, were established at Henry W. Coe State Park in Nothern California. Three sites were part of the September 2007 Lick Wildfire and three were part of a February 2007 prescription burn. The sites were monitored for Z. fremontii regeneration over two years. Z. fremontii exposed to the prescription burn fared better than the wildfire plants, with inflorescence height being significantly higher in prescribed burn sites. Bulbs were transplanted into soil from the prescription burn, wildfire, and unburned area to determine differences in regeneration due to soil characteristics. There were no significant differences due to soil types, but only bulbs from the prescription burn sites had the ability to produce flowers in multiple years subsequent to fire. Differences in germination rates between seeds grown in soil from the wildfire, prescription burn, and unburned soil were investigated via a controlled germination experiment. There was a trend for increased germination in burned soils compared to unburned soils. The evidence from this study suggests that geophytes can benefit from fires set outside of the natural fire season of chaparral

    Analogy, Mind, and Life

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    I'll show that the kind of analogy between life and information [argue for by authors such as Davies (2000), Walker and Davies (2013), Dyson (1979), Gleick (2011), Kurzweil (2012), Ward (2009)] – that seems to be central to the effect that artificial mind may represents an expected advance in the life evolution in Universe – is like the design argument and that if the design argument is unfounded and invalid, the argument to the effect that artificial mind may represents an expected advance in the life evolution in Universe is also unfounded and invalid. However, if we are prepared to admit (though we should not do) this method of reasoning as valid, I'll show that the analogy between life and information to the effect that artificial mind may represents an expected advance in the life evolution in Universe seems suggest some type of reductionism of life to information, but biology respectively chemistry or physics are not reductionist, contrary to what seems to be suggested by the analogy between life and information

    Non-sinusoidal current and current reversals in a gating ratchet

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    In this work, the ratchet dynamics of Brownian particles driven by an external sinusoidal (harmonic) force is investigated. The gating ratchet effect is observed when another harmonic is used to modulate the spatially symmetric potential in which the particles move. For small amplitudes of the harmonics, it is shown that the current (average velocity) of particles exhibits a sinusoidal shape as a function of a precise combination of the phases of both harmonics. By increasing the amplitudes of the harmonics beyond the small-limit regime, departures from the sinusoidal behavior are observed and current reversals can also be induced. These current reversals persist even for the overdamped dynamics of the particles.Comment: 11 pages, 9 figure

    Study of Instruments and Tools to Anticipate the Effects of Industrial Change - Portuguese report

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    This study was produced for the “Study of Instruments and Tools to anticipate the effects of industrial change on employment, trades and vocational qualifications” and for DG V (Employment) of the European Commission in the late 1994. It started when the previous Portuguese government was still ruling, the main policies were defined, and the available instruments were not used in a minimum extend. The new Government, issued from the 1995 elections, proposed “employment” as a major objective with horizontal responsibility. That’s also why there is now a Ministry for Qualifications and Employment, and another one for Solidarity and Social Affairs, not one for Employment and Social Affairs as the previous Government had. But more than that, this objective is considered to need a coordinated and consistent action that involves external affairs, industrial and regional policies, and the policies on education, training and employment, among others. The promotion of the “quality of employment” is being recently done at the working conditions, remuneration, social protection, occupational promotion levels, and the equality of opportunities towards employment and vocational training levels, and finally, the levels of qualification of human resources for a better labour market, education policy and training policy developments. In Portugal, the influence of the industrial change is produced in a top-down way; with (in some cases) an ex post analysis process to formulated training needs. This means that the industrial change impact is produced (normally, unexpectedly), and afterwards the responsible at the company level tries to know which training needs should be formulated in order those effects could be the smoother possible. The training needs at the company level is not based on anticipatory studies, neither is done any long term forecast on qualification, or even employment level.employment; qualifications; Portugal; labour market; working conditions; human resources; foresight; forecasting

    Occipital and left temporal instantaneous amplitude and frequency oscillations correlated with access and phenomenal consciousness

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    Given the hard problem of consciousness (Chalmers, 1995) there are no brain electrophysiological correlates of the subjective experience (the felt quality of redness or the redness of red, the experience of dark and light, the quality of depth in a visual field, the sound of a clarinet, the smell of mothball, bodily sensations from pains to orgasms, mental images that are conjured up internally, the felt quality of emotion, the experience of a stream of conscious thought or the phenomenology of thought). However, there are brain occipital and left temporal electrophysiological correlates of the subjective experience (Pereira, 2015). Notwithstanding, as evoked signal, the change in event-related brain potentials phase (frequency is the change in phase over time) is instantaneous, that is, the frequency will transiently be infinite: a transient peak in frequency (positive or negative), if any, is instantaneous in electroencephalogram averaging or filtering that the event-related brain potentials required and the underlying structure of the event-related brain potentials in the frequency domain cannot be accounted, for example, by the Wavelet Transform (WT) or the Fast Fourier Transform (FFT) analysis, because they require that frequency is derived by convolution rather than by differentiation. However, as I show in the current original research report, one suitable method for analyse the instantaneous change in event-related brain potentials phase and accounted for a transient peak in frequency (positive or negative), if any, in the underlying structure of the event-related brain potentials is the Empirical Mode Decomposition with post processing (Xie et al., 2014) Ensemble Empirical Mode Decomposition (postEEMD) and Hilbert-Huang Transform (HHT)

    Phase transitions in optimal strategies for betting

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    Kelly's criterion is a betting strategy that maximizes the long term growth rate, but which is known to be risky. Here, we find optimal betting strategies that gives the highest capital growth rate while keeping a certain low value of risky fluctuations. We then analyze the trade-off between the average and the fluctuations of the growth rate, in models of horse races, first for two horses then for an arbitrary number of horses, and for uncorrelated or correlated races. We find an analog of a phase transition with a coexistence between two optimal strategies, where one has risk and the other one does not. The above trade-off is also embodied in a general bound on the average growth rate, similar to thermodynamic uncertainty relations. We also prove mathematically the absence of other phase transitions between Kelly's point and the risk free strategy.Comment: 23 pages, 5 figure

    Axiomatics for the external numbers of nonstandard analysis

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    Neutrices are additive subgroups of a nonstandard model of the real numbers. An external number is the algebraic sum of a nonstandard real number and a neutrix. Due to the stability by some shifts, external numbers may be seen as mathematical models for orders of magnitude. The algebraic properties of external numbers gave rise to the so-called solids, which are extensions of ordered fields, having a restricted distributivity law. However, necessary and sufficient conditions can be given for distributivity to hold. In this article we develop an axiomatics for the external numbers. The axioms are similar to, but mostly somewhat weaker than the axioms for the real numbers and deal with algebraic rules, Dedekind completeness and the Archimedean property. A structure satisfying these axioms is called a complete arithmetical solid. We show that the external numbers form a complete arithmetical solid, implying the consistency of the axioms presented. We also show that the set of precise elements (elements with minimal magnitude) has a built-in nonstandard model of the rationals. Indeed the set of precise elements is situated between the nonstandard rationals and the nonstandard reals whereas the set of non-precise numbers is completely determined
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