1,721,609 research outputs found
1,2-metallate rearrangements of a-alkoxyvinylborates
No full textThe rearrangement of borates derived from the addition of a trialkylborane to a lithiated enol ether was investigated, with a view to further functional-isation of the rearrangement product to afford a synthesis of tri-substituted double bonds.It was demonstrated that such borates may undergo rearrangement by one of two mechanisms, depending on the reaction conditions. In either case oxidation of the reaction mixture leads to formation of a keto alcohol, whilst treatment with a carboxylic acid prior to oxidation leads in one case to a diol and in the other to an alkenol.The former case rearranges by ^-addition onto the double bond, with concomitant 1,2-alkyl migration from boron onto the a-carbon. Oxidation then affords the keto alcohol, whilst treatment with a carboxylic acid induces a second, Matteson-type rearrangement, to afford a diol after peroxide oxidation. This mechanism, therefore, does not proceed through the intermediacy of a vinyl borane.The latter case rearranges, with assistance from chlorotrimethylsilane, via 1,2-alkyl migration from boron onto carbon, with opening of the dihydro-furanyl ring and hence does proceed through the intermediacy of a vinylbo-rane. Vinylborane chemistry may then be applied to this intermediate, such as halogenolysis or transmetallation followed by an electrophilic quench, to afford a synthesis of tri-substituted double bonds.The latter mechanism is also applicable to the rearrangement of borates derived from the addition of a trialkylborane to an ot-lithiated enol car-bamate, although chlorotrimethylsilane is not necessary for rearrangement to occur. Again, vinylborane chemistry may be applied to the reaction intermediate to afford a synthesis of tri-substituted double bonds.</p
Improving Auditory CAPTCHA Security
Full text linkCAPTCHAs are tests used by resource-rich websites to ensure that humans, but not malicious automated programs, have access to their resources. Most CAPTCHAs are visual tests (e.g. identifying distorted text), but auditory versions are necessary to provide access to the visually impaired, and are currently deployed at commonly used websites such as Google and Facebook. To be effective at deterring automated programs, they must be at least as secure as their visual counterparts. Assuming that the attacks against auditory CAPTCHAs will depend on automatic speech recognition systems (ASRs), we undertook the project of designing auditory CAPTCHAs that would take advantage of the weaknesses in ASRs as compared to the human auditory system. Examples of such weaknesses of ASRs, relative to humans, include impeded recognition in the presence of broadband and time-varying noise such as multiple simultaneous speakers. Results show that a combination of such disruptive noise types can outperform currently employed techniques while still maintaining human intelligibility.NSF #064732
EEG-MEG
No full textData collected from normal hearing younger adults (18-30) and from normal hearing and hearing impaired older adults (>= 60) to study age-related deficits in the representation of speech in noise. EEG data were collected with Biosemi system by using the ABR module from one electrode placed in Cz and reference with respect to the left and right ear lobes. The data uploaded are the raw ones in bdf format. BDF files can be opened by using matlab scripts that can be found in toolboxes such as EEGLab or that can be found directly from Biosemi's website. Each mat file contains information about sampling frequency, channels, triggers, etc. Each participants was tested in 9 conditions: Quiet, +3 dB, 0 dB, -3 dB and -6 dB with English (H) and Dutch (L) speakers used as background noise. Files were named based on the SNR and background speaker used. For instance, S01_M3_H, means Subject 01, SNR = -3 dB and English speaker in the background, while S01_P3_L, means Subject 01, SNR = +3 dB and Dutch speaker in the background. The "Q" denomination is used for the condition in quiet. Subjects id# from 1 to 17 are younger adults, subjects with id# from 21 to 35 are normal hearing older adults and subjects named S01_HL.....S17_HL are older adults with hearing loss.
MEG data were collected from 157 sensors. Each mat file contains information about the data, such as sampling frequency. A 3D matrix is used to store the 3 repetitions recorded from each conditions. Each participants was tested in 10 conditions: Quiet, +3 dB, 0 dB, -3 dB and -6 dB with English (H) and Dutch (L) speakers used as background noise. Two conditions in quiet were played. Files were named based on the SNR and background speaker used, in the same way as for the EEG data.
Auditory stimuli were also uploaded. The stimuli have been pre-processed as described in our publications "Evidence of degraded representation of speech in noise, in the aging midbrain and cortex" and "Effect of informational content of noise on speech representation in the aging midbrain and cortex". The envelope needs to be extracted.University of Maryland College Park (UMCP) Department of Hearing and Speech Sciences, UMCP ADVANCE Program for Inclusive Excellence (NSF HRD1008117), and National Institute on Deafness and Other Communication Disorders (Grants R01DC008342;, R01DC014085;, and T32DC-00046).https://doi.org/10.1152/jn.00372.2016https://doi.org/10.1152/jn.00373.201
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
Data from: Neural speech restoration at the cocktail party
No full textThis dataset is incremental to http://hdl.handle.net/1903/21109 and contains independent component analysis (ICA) used for additional preprocessing, gammatone stimulus representations, and STRFs that were used to generate the figures. The ICA is stored in MNE *-ica.fif files which can be opened with MNE-Python (http://mne.tools). Gammatone spectrograms and STRFs are stored in Python pickle files which require the Eelbrain library to be opened (http://eelbrain.readthedocs.io).Data from the article titled: Neural speech restoration at the cocktail party: Auditory cortex recovers masked speech of both attended and ignored speakers.This work was supported by a National Institutes of Health grant R01-DC-014085 (to JZS) and by a University of Maryland Seed Grant (to LEH and JZS).https://doi.org/10.1371/journal.pbio.300088
Variations 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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