Observer weighting of interaural cues in positive and negative envelope slopes of amplitude-modulated waveforms

The auditory system can encode interaural delays in highpass-filtered complex sounds by phase locking to their slowly modulating envelopes. Spectrotemporal analysis of interaurally time-delayed highpass waveforms reveals the presence of a concomitant interaural level cue. The current study systematically investigated the contribution of time and concomitant level cues carried by positive and negative envelope slopes of a modified sinusoidally amplitude-modulated (SAM) high-frequency carrier. The waveforms were generated from concatenation of individual modulation cycles whose envelope peaks were extended by the desired interaural delay, allowing independent control of delays in the positive and negative modulation slopes. In experiment 1, thresholds were measured using a 2-interval forced-choice adaptive task for interaural delays in either the positive or negative modulation slopes. In a control condition, thresholds were measured for a standard SAM tone. In experiment 2, decision weights were estimated using a multiple-observation correlational method in a single-interval forced-choice task for interaural delays carried simultaneously by the positive, and independently, negative slopes of the modulation envelope. In experiment 3, decision weights were measured for groups of 3 modulation cycles at the start, middle, and end of the waveform to determine the influence of onset dominance or recency effects. Results were consistent across experiments: thresholds were equal for the positive and negative modulation slopes. Decision weights were positive and equal for the time cue in the positive and negative envelope slopes. Weights were also larger for modulations cycles near the waveform onset. Weights estimated for the concomitant interaural level cue were positive for the positive envelope slope and negative for the negative slope, consistent with exclusive use of time cues.We thank Virginia M. Richards and Bruce G. Berg for helpful discussions. We also thank Brian C. J. Moore and an anonymous reviewer for their insightful comments on an earlier draft of the manuscript. Work supported by grants from the National Science Council, Taiwan NSC 98-2410-H-008-081-MY3 and NIH R01DC009659

Le musée français: guerras napoleônicas, coleções artísticas e o longínquo destino de um livro

This paper is about Le Musée Français [The French Museum], a book found in the collection of the library of the Imperial Academy of Fine Arts in Rio de Janeiro. As a catalog of the Napoleon Museum, it bears witness to the reorganization of the arts in Europe as a result of the Napoleonic wars and the project of making Paris a true successor to Athens and Rome, as the center of a new republic of the arts. This process was the object of a dispute where Quatremère de Quincy and Joachim Lebreton played an important role. It was also one of the causes leading to the exile of a group of artists who then helped to lay the foundations for an academic environment in Rio de Janeiro.O artigo trata de Le musée français, livro que fez parte da coleção da biblioteca da Academia Imperial das Belas Artes, no RiodeJaneiro. Como catálogo do Museu Napoleão, é testemunho do processo de reordenamento, resultante das guerras napoleônicas, do universo das artes na Europa e do projeto de fazer de Paris a legítima herdeira de Atenas e Roma, como centro de uma nova idéia de república das artes. Processo esse que foi objeto de disputa, em que se destacaram Quatremère de Quincy eJoachim Lebreton, e foi uma das causas do exílio do grupo de artistas que esteve na origem da formação do ambiente acadêmico no Rio de Janeiro

1927, third annual catalog : gladiolus, outdoor roses, hardy lilies, irises /

192

New and select gladiolus : 1926 fall price list /

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Discordant RbSr and PbPb whole rock isochron ages for the Archaean basement of Sierra Leone

Field mapping and structural studies in northern Sierra Leone by an I.G.S. team have established a stratigraphic sequence in this part of the Archaean of the West African Craton. An older “Leonian” granite-greenstone terrain is identified which experienced a tectonic-metamorphic event before the formation of the granite-greenstone terrain which ended with the Liberian tectonic-metamorphic event. Granite gneisses in the Fadugu district with Leonian structures yield statistically acceptable but discordant Pb-Pb and Rb-Sr whole-rock isochron ages of 2959±50 Ma and 2753±61 Ma, respectively (2 σ errors). These ages may be correlated with radiometric ages for the Leonian and Liberian structures elsewhere in Sierra Leone, and it is concluded that the Fadugu Rb-Sr whole-rock isochron has been reset by the Liberian event. The Pb-Pb whole-rock isochron for the Fadugu gneisses and a previously determined (but recomputed and partially checked) Rb-Sr whole-rock isochron age of 2980+80 Ma for granite gneisses from southeastern Sierra Leone provide a definitive age for the Leonian tectonic-metamorphic event at about 2970 Ma. Both the initial 87Sr/86Sr ratios and present-day first-stage model 238U/204Pb value for the Leonian granitoids are indistinguishable from mantle values, but do not preclude the possibility that these granitoids were derived from parental material with a short history in the crust or lower crust. The Rb-Sr whole-rock isochron age of 2753+61 Ma for the Fadugu granite gneiss provides a definitive age for the Liberian event in northern Sierra Leone. A succession of rocks older than the Leonian (i.e., older than 2970 Ma) has been identified in the field but not yet dated