1,721,139 research outputs found
Maize yield and N dynamics after cover crops introduction
Full text linkThe use of cover crops (CCs) is widely suggested as a sustainable agricultural practice. Nevertheless, conflicting results have been reported about the short-term effect of CCs on cash crop yields and the soil nitrogen (N) dynamics. Within this framework, the present study aims to examine the short-term impact of CC introduction into a conventional agricultural system on silage maize yield and the N dynamics (maize N uptake, N use efficiency (NUE), soil nitrate content (Nmin), and apparent soil N mineralization and immobilization processes) in northern Italy. The CC systems (∼5.5 ha) included a fixed treatment (FI) with a gramineous species (triticale), a 2-year gramineous-legume species succession (SU) (rye, clover), and a weed-covered control treatment (NoCC). In the first year, triticale and rye had the same total (aboveground + root) final biomass (2.5 Mg ha−1 on average), C:N ratio (29), and N uptake (36.4 kg ha−1). However, triticale developed faster in the first winter months. Both grass species equally reduced the soil Nmin content over the winter season (as valid catch crops), but they caused apparent N immobilization during the following maize growing season. In the second year, clover produced the same total biomass as triticale did (1.8 Mg ha−1), but with a higher total N content (72.5 kg ha−1) and lower C:N ratio (27) which determined a lower apparent N immobilization. The introduction of CCs did not affect the yield of maize. During the maize growing season, lower N uptake and NUE were recorded after CCs grasses species cultivation compared to clover and NoCC. These observations suggest that a key aspect to be considered when dealing with CCs is understanding the N mineralization-immobilization processes related to CC residue decomposition, which might determine N availability for the subsequent crop and in turn its production quality (N uptake), even when the yield is not affected
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Time Irreversibility and complexity of heart rate variability
No full textIntrodution. The heart rate variability is based on measuring (time) intervals between R-peaks (of RRintervals) of an electrocardiogram and plotting a rhythmogram on their basis with its subsequent analysis by
various mathematical methods. Using nonlinear methods in HRV and ECG analysis has proven to be very
advantageous. Time irreversibility is a fundamental parameter of a system, it defines justification and
necessity of applying nonlinear methods for analysis of a system s dynamics.
Objective. We propose an algorithm for testing the probability of a time series' irreversibility, showing its
effectiveness in the process of HRV analysis. In this article, complexity of HRV will be described by two
parameters: entropy EnRE [18] and correlation dimension D2 [19]. Naturally, the chosen parameters EnRE
and D2 in no way can be used for comprehensive description of complexity of HRV, but we will be able to
tress the necessary sufficiency of such an approach.
Materials and methods. We used long-term HRV records by Massachusetts Institute of Technology
Beth Israel Hospital (MIT-BIH) from [15], a free-access, on-line archive of physiological signals for
Normal Sinus Rhythm (NSR) RR Interval, Congestive Heart Failure (CHF) RR Interval and Atrial Fibrillation
(AF) Databases [16]. In [17], we have developed a special modification to the classic Mann-Whitney (MW)
U-test in order to use the test for comparison of Time Series with an equal number of elements N Time
Series MW M-test. Here the new statistical -test was proposed for finding the probability of time series'
irreversibility.
Conclusion. In this article, we propose a statistical -test for assessment of probability of irreversibility
of time series. It has been shown that the new statistical -test accurately identifies times series reversibility
and irreversibility in known cases of synthetic data. For long-term HRV records of MIT-BIH database for
NSR, CHF and AF groups, we have compared values of z-score, which statistically defines the limit of
irreversibility of time series, and values of HRV complexity indicators: entropy EnRE and correlation
dimension D2. We have noted the following:
HRV is time irreversible nonlinear dynamic process, with the exception of AF episodes;
nonlinear indicators of HRV complexity entropy EnRE and correlation dimension D2 have been
analyzed, and there is a conclusive difference between NSR and analyzed pathological states;
analyzed time series have been presented in D2-z-EnRE phase space, and their reliable separability has
been shown. It can be stated that the analyzed D2-z-EnRE phase space is sufficient for research of nonlinear
HRV events in this cas
Commentario alla Convenzione europea per la tutela dei diritti dell'uomo e delle libertà fondamentali
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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