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31.
Byrne AJ Viemeister NF Stellmack MA 《The Journal of the Acoustical Society of America》2011,129(2):593-596
Highly detectable, time-reversed triangular amplitude modulation, with linear increases and decreases in amplitude, was used in an adaptive task to measure just-noticeable differences for changes in the direction of envelope temporal asymmetry for different modulation depths (m = 1.0 and 0.5) and rates (8, 16, and 32 Hz). Thresholds were analyzed using three different measures of the modulator's shape based on (1) the change in the position of the peak within a cycle, (2) the change in the slope of the modulator's increasing amplitude portion, and (3) the change in slope measured in units of amplitude per unit cycle rather than amplitude per unit time. The amplitude per unit cycle measure resulted in the best fit to all the data, and predicted additional data that were gathered with roved modulation frequency. The results suggest that a time normalization process may be involved in the perception and discrimination of envelope shape. 相似文献
32.
Craig F Ferris Tara Stolberg Praveen Kulkarni Murali Murugavel Robert Blanchard D Caroline Blanchard Marcelo Febo Mathew Brevard Neal G Simon 《BMC neuroscience》2008,9(1):111
Background
With the advent of functional magnetic resonance imaging (fMRI) in awake animals it is possible to resolve patterns of neuronal activity across the entire brain with high spatial and temporal resolution. Synchronized changes in neuronal activity across multiple brain areas can be viewed as functional neuroanatomical circuits coordinating the thoughts, memories and emotions for particular behaviors. To this end, fMRI in conscious rats combined with 3D computational analysis was used to identifying the putative distributed neural circuit involved in aggressive motivation and how this circuit is affected by drugs that block aggressive behavior. 相似文献33.
Neal G. Anderson 《Physics letters. A》2008,372(34):5552-5555
The physical cost of information erasure is considered within a new approach that regards erasure as loss of correlation between the state of an erasable quantum system and that of an enduring “referent” system holding classical information. A physical model of information erasure built on this referential picture is described in detail, and lower bounds on entropic and energetic costs are obtained from quantum dynamics and entropic inequalities alone. 相似文献
34.
Elisa Musella Dr. Isacco Gualandi Dr. Erika Scavetta Dr. Massimo Gazzano Arianna Rivalta Dr. Elisabetta Venuti Dr. Meganne Christian Dr. Vittorio Morandi Prof. Dr. Domenica Tonelli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(71):16301-16310
Layered double hydroxides (LDHs) have been widely studied for their plethora of fascinating features and applications. The potentiostatic electrodeposition of LDHs has been extensively applied in the literature as a fast and direct method to substitute classical chemical routes. However, the electrochemical approach does not usually allow for a fine control of the MII/MIII ratio in the synthesized material. By employing a recently proposed potentiodynamic method, LDH films of controlled composition are herein prepared with good reproducibility, using different ratios of the trivalent (Fe or Al) to bivalent (Co) cations in the electrolytic solution. All the obtained materials are shown to be effective oxygen evolution reaction (OER) catalysts, and are thoroughly characterized by a multi-technique approach, including FE-SEM, XRD, Raman, AES and a wide range of electrochemical procedures. 相似文献
35.
Parallel to the study of finite-dimensional Banach spaces, there is a growing interest in the corresponding local theory of operator spaces. We define a family of Hilbertian operator spaces , , generalizing the row and column Hilbert spaces and , and we show that an atomic subspace that is the range of a contractive projection on is isometrically completely contractive to an -sum of the and Cartan factors of types 1 to 4. In particular, for finite-dimensional , this answers a question posed by Oikhberg and Rosenthal. Explicit in the proof is a classification up to complete isometry of atomic w-closed -triples without an infinite-dimensional rank 1 w-closed ideal.
36.
Abachi S Derrick M Kooijman P Musgrave B Price LE Repond J Sugano K Blockus D Brabson B Brom J Jung C Ogren H Rust DR Akerlof C Chapman J Errede D Ken MT Meyer DI Neal H Nitz D Thun R Tschirhart R Baringer P Bylsma BG DeBonte R Koltick D Low EH McIlwain RL Miller DH Ng CR Shibata EI 《Physical review D: Particles and fields》1989,40(3):902-905
37.
38.
Dr. Antonio Del Vecchio Arianna Sinibaldi Valeria Nori Giuliana Giorgianni Dr. Graziano Di Carmine Dr. Fabio Pesciaioli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(49):e202200818
Synergistic catalysis offers the unique possibility of simultaneous activation of both the nucleophile and the electrophile in a reaction. A requirement for this strategy is the stability of the active species towards the reaction conditions and the two concerted catalytic cycles. Since the beginning of the century, aminocatalysis has been established as a platform for the stereoselective activation of carbonyl compounds through HOMO-raising or LUMO-lowering. The burgeoning era of aminocatalysis has been driven by a deep understanding of these activation and stereoinduction modes, thanks to the introduction of versatile and privileged chiral amines. The aim of this review is to cover recent developments in synergistic strategies involving aminocatalysis in combination with organo-, metal-, photo-, and electro-catalysis, focusing on the evolution of privileged aminocatalysts architectures. 相似文献
39.
Mechanism of carotenoid singlet excited state energy transfer in modified bacterial reaction centers
Lin S Katilius E Ilagan RP Gibson GN Frank HA Woodbury NW 《The journal of physical chemistry. B》2006,110(31):15556-15563
Ultrafast transient laser spectroscopy has been used to investigate carotenoid singlet excited state energy transfer in various Rhodobacter (Rb.) sphaeroides reaction centers (RCs) modified either genetically or chemically. The pathway and efficiency of energy transfer were examined as a function of the structures and energies of the donor and acceptor molecules. On the donor side, carotenoids with various extents of pi-electron conjugation were examined. RCs studied include those from the anaerobically grown wild-type strain containing the carotenoid spheroidene, which has 10 conjugated carbon-carbon double bonds; the GA strain containing neurosporene, which has nine conjugated double bonds; and aerobically grown wild-type cells, as well as aerobically grown H(M182)L mutant, both containing the carbonyl-containing carotenoid spheroidenone, which has 11 conjugated double bonds. By varying the structure of the carotenoid, we observed the effect of altering the energies of the carotenoid excited states on the rate of energy transfer. Both S(1)- and S(2)-mediated carotenoid-to-bacteriochlorophyll energy transfer processes were observed. The highest transfer efficiency, from both the S(1) and S(2) states, was observed using the carotenoid with the shortest chain. The S(1)-mediated carotenoid-to- bacteriochlorophyll energy transfer efficiencies were determined to be 96%, 84%, and 73% for neurosporene, spheroidene, and spheroidenone, respectively. The S(2)-mediated energy transfer efficiencies follow the same trend but could not be determined quantitatively because of limitations in the time resolution of the instrumentation. The dependence of the energy transfer rate on the energetics of the energy transfer acceptor was verified by performing measurements with RCs from the H(M182)L mutant. In this mutant, the bacteriochlorophyll (denoted B(B)) located between the carotenoid and the RC special pair (P) is replaced by a bacteriopheophytin (denoted phi(B)), where the Q(X) and Q(Y) bands of phi(B) are 1830 and 1290 cm(-1), respectively, higher in energy than those of B(B). These band shifts associated with phi(B) in the H(M182)L mutant significantly alter the spectral overlap between the carotenoid and phi(B), resulting in a significant decrease of the transfer efficiency from the carotenoid S(1) state to phi(B). This leaves energy transfer from the carotenoid S(2) state to phi(B) as the dominant channel. Largely because of this change in mechanism, the overall efficiency of energy transfer from the carotenoid to P decreases to less than 50% in this mutant. Because the spectral signature of phi(B) is different from that of B(A) in this mutant, we were able to demonstrate clearly that the carotenoid-to-P energy transfer is via phi(B). This finding supports the concept that, in wild-type RCs, the carotenoid-to-P energy transfer occurs through the cofactor located at the B(B) position. 相似文献
40.
Devaraj NK Dinolfo PH Chidsey CE Collman JP 《Journal of the American Chemical Society》2006,128(6):1794-1795
We demonstrate selective functionalization of independently addressed microelectrodes by electrochemical activation and deactivation of a coupling catalyst. 1,2,3-Triazole formation between terminal acetylenes and organic azides is efficiently catalyzed by copper(I) complexes (a Sharpless "click" reaction), while the oxidized copper(II) complexes are inactive. By electrochemically activating or deactivating the catalyst by switching its redox state, we demonstrate control over triazole formation between surface-immobilized azides and ethynylferrocene. The reaction proceeds on the time scale of minutes using submicromolar concentration of reactants and catalyst, requires mild potentials for catalyst activation and deactivation, and works in aqueous and mixed aqueous-organic solvents. By appropriate biasing of each electrode, we selectively modify one of two chemically identical 10-mum-wide electrodes separated by 10 mum in an interdigitated array. The ability to switch on or off the reaction by electrical addressing together with the chemoselectivity of this reaction makes Cu(I)-catalyzed triazole formation an ideal method for the chemical modification of multielectrode arrays. 相似文献