130 research outputs found
On the Classical Theory of the Electron
A classical theory of the electron, proposed by one of us several years ago and based on finite-difference equations, is discussed by considering the three possible following cases: radiating electron, absorbing electron and nonradiating, nonabsorbing electron. In particular the so-called transmission laws necessary to determine, in conjunction with the dynamical equations, the motion of a charged particle corresponding to given initial values of position and velocity are critically reconsidered. The general characteristics of the one-dimensional motion in the non-relativistic approximation are discussed in detail. It is found that in the case of the radiating electron the particle position tends asimptotically to the point of stable equilibrium. The present theory is, therefore, free from the unphysical phenomenon of runaway solutions. These general results are illustrated by studying the motion of a particle under the action of a restoring elastic force and under the action of purely time-dependent forces
Heat Flow in Classical and Quantum Systems and Thermal Rectification
The understanding of the underlying dynamical mechanisms which determine the
macroscopic laws of heat conduction is a long standing task of non-equilibrium
statistical mechanics. A better understanding of the mechanism of heat
conduction may lead to potentially interesting applications based on the
possibility to control the heat flow. Indeed, different models of thermal
rectifiers has been recently proposed in which heat can flow preferentially in
one direction. Although these models are far away from a prototype realization,
the underlying mechanisms are of very general nature and, as such, are suitable
of improvement and may eventually lead to real applications. We briefly discuss
the problem of heat transport in classical and quantum systems and its relation
to the chaoticity of the dynamics. We then study the phenomenon of thermal
rectification and briefly discuss the different types of microscopic mechanisms
that lead to the rectification of heat flow.Comment: 11 pages, 5 figures. Contribution to the proceedings of CTNEXT0
Effects of Two Target-controlled Concentrations (1 and 3 ng/ml) of Remifentanil on MACBARof Sevoflurane
Background
The aim of this prospective, randomized, double-blind study was to determine the effects of two different target-controlled concentrations of remifentanil (1 and 3 ng/ml) on the sevoflurane requirement for blunting sympathetic responses after surgical incision (MACBAR).
Methods
Seventy-four patients aged 20-50 yr, with American Society of Anesthesiologists physical status I, were anesthetized with propofol, cisatracurium, and sevoflurane with a mixture of 60% nitrous oxide in oxygen. Then, patients were randomly allocated to receive no remifentanil infusion (n = 27) or a target-controlled plasma concentration of 1 ng/ml (n = 27) or 3 ng/ml remifentanil (n = 20). Sympathetic responses to surgical incision (presence or absence of an increase in either heart rate or mean arterial blood pressure of 15% or more above the mean of the values measured during the 2 min before skin incision) were determined after a 20-min period of stable end-tidal sevoflurane and target-controlled remifentanil concentrations. Predetermined end-tidal sevoflurane concentrations and the MACBAR for each group were determined using an up-and-down sequential-allocation technique.
Results
The MACBAR of sevoflurane was higher in the group receiving no remifentanil (2.8% [95% confidence interval: 2.5-3.0%]) as compared with patients of the groups receiving 1 ng/ml (1.1% [0.9-1.3%]; P = 0.012) and 3 ng/ml remifentanil (0.2% [0.1-0.3%]; P = 0.006). When considering a minimum anesthetic concentration (MAC) value in this age population and the contribution of 60% nitrous oxide (0.55 MAC), the combined MACBAR values, expressed as multiples of the MAC, were 1.95 MAC, 1.1 MAC, and 0.68 MAC, in the three groups, respectively.
Conclusion
A target-controlled concentration of 1 ng/ml remifentanil results in a 60% decrease in the MACBAR of sevoflurane combined with 60% nitrous oxide. Increasing the target concentration of remifentanil to 3 ng/ml produces a further 30% decrease in the MACBAR values of sevoflurane
Rethinking and Recomputing the Value of ML Models
In this paper, we argue that the way we have been training and evaluating ML
models has largely forgotten the fact that they are applied in an organization
or societal context as they provide value to people. We show that with this
perspective we fundamentally change how we evaluate, select and deploy ML
models - and to some extent even what it means to learn. Specifically, we
stress that the notion of value plays a central role in learning and
evaluating, and different models may require different learning practices and
provide different values based on the application context they are applied. We
also show that this concretely impacts how we select and embed models into
human workflows based on experimental datasets. Nothing of what is presented
here is hard: to a large extent is a series of fairly trivial observations with
massive practical implications
Remarkable multicuspid teeth in a new elusive skate (Chondrichthyes, Rajiformes) from the Mediterranean Pliocene
AbstractHere we report on four highly peculiar skate teeth from Arcille and Certaldo, two Pliocene localities of Tuscany (central Italy). While being attributable to Rajiformes and somewhat reminiscent ofDipturusandRostroraja, these specimens display an unusual multicuspid tooth design that does not match any extinct or extant skate taxon known to date. The studied teeth are thus referred to a new genus and species of Rajiformes,Nebriimimus wardigen. et sp. nov., which is here tentatively assigned to the family Rajidae. Based on pronounced morphological similarities between the rather large-sized teeth of the latter and those of extant nurse sharks, we hypothesise thatN. wardimight have been capable of actively foraging upon relatively large food items compared to other rays. This extinct skate species was likely not a common component of the Pliocene Tuscan marine vertebrate assemblages. The palaeoenvironmental scenarios thatN. wardiinhabited were marginal-marine and open shelf settings characterised by tropical climate conditions. AsN. wardiis currently known only from lower to mid-Pliocene deposits of the Mediterranean Basin, it is tempting to speculate that its speciation dates back to an earliest Pliocene phase of diversification that also contributed to the emergence of the Mediterranean endemic stock of extant skate species
Conceptualising the geographic world: the dimensions of negotiation in crowdsourced cartography
In crowdsourced cartographic projects, mappers coordinate their efforts
through online tools to produce digital geospatial artefacts, such as maps and
gazetteers, which were once the exclusive territory of professional surveyors and
cartographers. In order to produce meaningful and coherent data, contributors
need to negotiate a shared conceptualisation that defines the domain concepts,
such as road, building, train station, forest, and lake, enabling the communi-
cation of geographic knowledge. Considering the OpenStreetMap Wiki website
as a case study, this article investigates the nature of this negotiation, driven
by a small group of mappers in a context of high contribution inequality. De-
spite the apparent consensus on the conceptualisation, the negotiation keeps
unfolding in a tension between alternative representations, which are often in-
commensurable, i.e., hard to integrate and reconcile. In this study, we identify
six complementary dimensions of incommensurability that recur in the nego-
tiation: (i) ontology, (ii) cartography, (iii) culture and language, (iv) lexical
definitions, (v) granularity, and (vi) semantic overload and duplication
The classification of hospitalized patients with hyperglycemia and its implication on outcome: results from a prospective observational study in Internal Medicine
Evolution and Expression of Tandem Duplicated Maize Flavonol Synthase Genes
Flavonoids are specialized compounds widely distributed and with diverse functions throughout the plant kingdom and with several benefits for human health. In particular, flavonols, synthesized by flavonol synthase (FLS), protect plants against UV-B radiation and are essential for male fertility in maize and other plants. We have recently characterized a UV-B inducible ZmFLS1, corresponding to the first to be described in monocot plants. Interestingly, the new assembly of the B73 maize genome revealed the presence of a second putative FLS gene (ZmFLS2), with very high identity with ZmFLS1. ZmFLSs expression was analyzed in different maize tissues, and by combining electrophoretic mobility shift assays and transient expression experiments, we show that both genes are direct targets of anthocyanin (C1/PL1 + R/B) and 3-deoxy flavonoid (P1) transcriptional regulators. ZmFLS expression analyses show higher levels of both transcripts in high altitude landraces than inbred lines, and both genes are regulated by UV-B radiation in all lines analyzed. Moreover, the high sequence conservation of the ZmFLS promoters between maize lines suggests that the differences observed in ZmFLS expression are due to allelic variations in the transcription factors that regulate their activities. Finally, we generated pFLS1::FLS1-RFP transgenic plants and analyzed ZmFLS1 expression in different maize tissues; we found that this enzyme is localized in the ER and the perinuclear region
Enhancing reuse of data and biological material in medical research : from FAIR to FAIR-Health
The known challenge of underutilization of data and biological material from biorepositories as potential resources
formedical research has been the focus of discussion for over a decade. Recently developed guidelines for improved
data availability and reusability—entitled FAIR Principles (Findability, Accessibility, Interoperability, and
Reusability)—are likely to address only parts of the problem. In this article,we argue that biologicalmaterial and data
should be viewed as a unified resource. This approach would facilitate access to complete provenance information,
which is a prerequisite for reproducibility and meaningful integration of the data. A unified view also allows for
optimization of long-term storage strategies, as demonstrated in the case of biobanks.Wepropose an extension of the
FAIR Principles to include the following additional components: (1) quality aspects related to research reproducibility
and meaningful reuse of the data, (2) incentives to stimulate effective enrichment of data sets and biological
material collections and its reuse on all levels, and (3) privacy-respecting approaches for working with the human
material and data. These FAIR-Health principles should then be applied to both the biological material and data. We
also propose the development of common guidelines for cloud architectures, due to the unprecedented growth of
volume and breadth of medical data generation, as well as the associated need to process the data efficiently.peer-reviewe
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