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排序方式: 共有717条查询结果,搜索用时 15 毫秒
1.
M J Gatti M E Fraga C Magnoli A M Dalcero C A da Rocha Rosa 《Food Additives & Contaminants》2003,20(12):1120-1126
A mycological survey was carried out on 115 samples of whole dried black pepper seeds, from two main production regions of Brazil (Pará and Espírito Santo). A high incidence of contamination was verified in both regions when 99.1% of the samples showed filamentous fungi contamination. A total of 497 species of nine different genera were isolated (Aspergillus, Eurotium, Rhizopus, Penicillium, Curvularia, Cladosporium, Absidia, Emericella and Paecilomyces). The genus Aspergillus was the predominant (53.5%) followed by species from the Eurotium genus (24.5%). Eurotium chevalieri (16.4%) was the most predominant species followed by A. flavus (14.6%) present on 55 samples of black pepper (47.8%) analysed. Twenty-five samples (21.7%) were contaminated with aflatoxigenic strains of A. flavus and A. parasiticus. In relation to the types of aflatoxins produced by mycotoxigenic strains, it was observed that 25 strains (44.6%) of 56 isolated of A. flavus produced aflatoxins. From 12 samples, A. ochraceus species were isolated in low frequency (3.5%). Two strains of A. ochraceus from 16 isolated were producers of ochratoxin A. With respect to the aflatoxins and ochratoxin A natural contamination, none of the samples presented detectable levels of these mycotoxins using thin-layer chromatographic analysis. 相似文献
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Lorenzo Gatti Marco Guerini Oliviero Stock Carlo Strapparava 《Computational Intelligence》2015,31(4):669-683
The need for creativity is ubiquitous, and mobile devices connected to Web services can help us. Linguistic creativity is widely used in advertisements to surprise us, to get our attention, and to stick concepts in our memory. However, creativity can also be used as a defense. When we walk in the street, we are overwhelmed by messages that try to get our attention with any persuasive device at hand. As messages get ever more aggressive, often our basic cognitive defenses—trying not to perceive those messages—are not sufficient. One advanced defensive technique is based on transforming the perceived message into something different (for instance, making use of irony or hyperbole) from what was originally meant in the message. In this article, we describe an implemented application for smartphones, which creatively modifies the linguistic expression in a virtual copy of a poster encountered on the street. The mobile system is inspired by the subvertising practice of countercultural art. 相似文献
4.
Emanuele Viola 《Computational Complexity》2009,18(3):337-375
We prove new results on the circuit complexity of approximate majority, which is the problem of computing the majority of a given bit string whose fraction of 1’s is bounded away from 1/2 (by
a constant). We then apply these results to obtain new relationships between probabilistic time, BPTime (t), and alternating time, ∑O(1)Time (t). Our main results are the following:
相似文献
1. | We prove that depth-3 circuits with bottom fan-in (log n)/2 that compute approximate majority on n bits must have size at least 2n0.12^{n^{0.1}}. As a corollary we obtain that there is no black-box proof that BPTime (t) í ?2\subseteq \sum_2Time (o(t2)). This complements the (black-box) result that BPTime (t) í ?2\subseteq \sum_2Time (t2 · poly log t) (Sipser and Gács, STOC ’83; Lautemann, IPL ’83). |
2. | We prove that approximate majority is computable by uniform polynomial-size circuits of depth 3. Prior to our work, the only known polynomial-size depth-3 circuits for approximate majority were non-uniform (Ajtai, Ann. Pure Appl. Logic ’83). We also prove that BPTime (t) í ?3\subseteq \sum_3Time (t · poly log t). This complements our results in (1). |
3. | We prove new lower bounds for solving QSAT3 ? ?3\in \sum_3Time (n · poly log n) on probabilistic computational models. In particular, we prove that solving QSAT3 requires time n1+Ω(1) on Turing machines with a random-access input tape and a sequential-access work tape that is initialized with random bits. No nontrivial lower bound was previously known on this model (for a function computable in linear space). |
5.
Daniele Di Gioacchino Nicola Poccia Martijn Lankhorst Claudio Gatti Bruno Buonomo Luca Foggetta Augusto Marcelli Hans Hilgenkamp 《Journal of Superconductivity and Novel Magnetism》2017,30(2):359-363
The current frontiers in the investigation of high-energy particles demand for new detection methods. Higher sensitivity to low-energy deposition, high-energy resolution to identify events and improve the background rejection, and large detector masses have to be developed to detect even an individual particle that weakly interacts with ordinary matter. Here, we will describe the concept and the layout of a novel superconducting proximity array which show dynamic vortex Mott insulator to metal transitions, as an ultra-sensitive compact radiation-particle detector. 相似文献
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A synchronizing word for a given synchronizing DFA is called minimal if none of its proper factors is synchronizing. We characterize the class of synchronizing automata having only finitely many minimal synchronizing words (the class of such automata is denoted by FG). Using this characterization we prove that any such automaton possesses a synchronizing word of length at most 3n-5. We also prove that checking whether a given DFA A is in FG is co-NP-hard and provide an algorithm for this problem which is exponential in the number of states A. 相似文献
8.
Emanuele Maiorana Jordi Solé-Casals Patrizio Campisi 《Machine Vision and Applications》2016,27(8):1351-1360
Electroencephalography (EEG) has been recently investigated as a biometric modality for automatic people recognition purposes. Several studies have shown that brain signals possess subject-specific traits that allow distinguishing people. Nonetheless, extracting discriminative characteristics from EEG recordings may be a challenging task, due to the significant presence of artifacts in the acquired data. In order to cope with such issue, in this paper we evaluate the effectiveness of some preprocessing techniques in automatically removing undesired EEG contributions, with the aim of improving the achievable recognition rates. Specifically, methods based on blind source separation and sample entropy estimation are here investigated. An extensive set of experimental tests, performed over a large database comprising recordings taken from 50 healthy subjects during three distinct sessions spanning a period of about one month, in both eyes-closed and eyes-open conditions, is carried out to analyze the performance of the proposed approaches. 相似文献
9.
This paper proposes a novel class of Command Governor (CG) strategies for input and state-related constrained discrete-time LTI systems subject to bounded disturbances in the absence of explicit state or output measurements. While in traditional CG schemes the set-point manipulation is undertaken on the basis of either the actual measure of the state or its suitable estimation, it is shown here that the CG design problem can be solved, with limited performance degradation and with similar properties, also in the case that such an explicit measure is not available. This approach, which will be referred to as the Feed-Forward CG (FF-CG) approach, may be a convenient alternative CG solution in all situations whereby the cost of measuring the state may be a severe limitation, e.g. in distributed or decentralized applications. In order to evaluate the method proposed here, numerical simulations on a physical example have been undertaken and comparisons with the standard state-based CG solution reported. 相似文献
10.
We study the problem of the amount of information required to perform fast broadcasting in tree networks. The source located
at the root of a tree has to disseminate a message to all nodes. In each round each informed node can transmit to one child.
Nodes do not know the topology of the tree but an oracle knowing it can give a string of bits of advice to the source which can then pass it down the tree with the source message. The quality of a broadcasting algorithm with
advice is measured by its competitive ratio: the worst case ratio, taken over n-node trees, between the time of this algorithm and the optimal broadcasting time in the given tree. Our goal is to find a
trade-off between the size of advice and the best competitive ratio of a broadcasting algorithm for n-node trees. We establish such a trade-off with an approximation factor of O(n
ε
), for an arbitrarily small positive constant ε. This is the first communication problem for which a trade-off between the size of advice and the efficiency of the solution
is shown for arbitrary size of advice. 相似文献