Forward masking of amplitude modulation: basic characteristics

In this study we demonstrate an effect for amplitude modulation (AM) that is analogous to forward making of audio frequencies, i.e., the modulation threshold for detection of AM (signal) is raised by preceding AM (masker). In the study we focused on the basic characteristics of the forward-masking effect. Functions representing recovery from AM forward masking measured with a 150- ms 40- Hz masker AM and a 50- ms signal AM of the same rate imposed on the same broadband-noise carrier, showed an exponential decay of forward masking with increasing delay from masker offset. Thresholds remained elevated by more than 2 dB over an interval of at least 150 ms following the masker. Masked-threshold patterns, measured with a fixed signal rate (20, 40, and 80 Hz) and a variable masker rate, showed tuning of the AM forward-masking effect. The tuning was approximately constant across signal modulation rates used and consistent with the idea of modulation-rate selective channels. Combining two equally effective forward maskers of different frequencies did not lead to an increase in forward masking relative to that produced by either component alone. Overall, the results are consistent with modulation-rate selective neural channels that adapt and recover from the adaptation relatively quickly.     

Einige Bemerkungen zur Struktur des Kohlensuboxidpolymeren

Zusammenfassung Das Quarz-Ultraviolettspektrum und das Infrarotspektrum des Polymeren (C₃O₂) _n das man bei Zimmertemperatur in geringer Konzentration durch Blockpolymerisation erhalten hat, wurde untersucht. Im Infrarotspektrum stellte man fest, daß eine Gruppe C=O im Polymeren vorhanden ist. Außerdem bemerkte man eine Absorption des in Chloroform gelösten Polymeren um 255 und 308 nm; sie wird als Übergang der CO-Gruppe durch deren Aufspaltung infolge einer Schwingungskopplung in der Struktur des Dimertyps des Kohlensuboxidpolymeren (C₃O₂) _n interpretiert. So können wir eine Dimerstruktur für das Polymer (C₃O₂) _n , das wir bei niedrigen Temperaturen gewonnen haben, vorschlagen. Weiters wird der Übergang dieser Struktur in die vonBlake diskutiert.

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The UV and IR spectra of (C₃O₂) _n polymer were investigated. The (C₃O₂) _n polymer was obtained from C₃O₂ by block-polymerization at room temperature in small concentrations. The UV spectrum of the polymer in CHCl₃ has maxima at 255 nm and 308 nm. These two bands are interpreted by the vibronic splitting of the n—*·transition of groups in the dimer. A dimeric structure of the (C₃O₂) _n polymer obtained at room temperature is postulated. The transition between dimeric andBlake's structure is discussed.

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Mit 2 Abbildungen     

Photochemical properties of ferrocene,cobaltocene and nickelocene and their complexes with 2,2,2-trichloroethanol in liquid phase

Summary Photochemical changes in the solutions of ferrocene, cobaltocene, nickelocene and their complexes with 2,2,2-trichloroethanol exposed to near u.v. and argon laser (=514.5 nm) radiation were investigated. The solutions of cobaltocene, nickelocene and their complexes were found to undergo photolysis, whereas ferrocene solutions are not sensitive to this kind of irradiation and the ferrocene bound in a complex undergoes photooxidation to give the ferricenium cation. The activating effect of laser irradiation of ferrocene was revealed as a tendency to complex formation. The quantum yield of the investigated photoreactions, equilibrium constant of complex formation,K, and their molar extinction coefficients, _c, were determined.     

Synthesis of titanium dioxide nanocrystalline layers using hexaprismatic shaped μ-oxo Ti(IV) alkoxo carboxylates as precursors

The reaction between Ti(OR)₄ (R = ⁿBu, ⁱBu, SiMe₃) and 2,2-dimethylpropionic acid lead to the formation of hexanuclear μ-oxo titanium(IV) alkoxo carboxylato complexes of the general formula [Ti₆O₆(OR)₆(OOC^tBu)₆]. Thermal decomposition pathways of these compounds and their potential application in the preparation of TiO₂ nanolayers using chemical vapor deposition (CVD) methods have been discussed. The type of the alkoxide ligands causes differences in the thermolysis pathway, and the type of the volatile decomposition products. Among the examined complexes only [Ti₆O₆(OR)₆(OOC^tBu)₆] (R = ⁱBu, SiMe₃) show promising properties for their application as precursors in CVD methods. The TiO₂ films were grown in a wide range of substrate temperatures (653–873 °K), under the total reactor pressure 2.0–3.0 mbar. The crystallinity and the composition of layers were analyzed by X-ray diffraction (XRD). It was found that the formation of TiO₂ amorphous, anatase or rutile films depends on the deposition temperature and gas phase composition.     

The explosive reaction of tetranitromethane with ferrocene

Summary The literature contains a number of publications and patent reports on the application of tetranitromethane, TNM, as an oxidizing agent in different conventional^{(1, 2)} and rocket^3–5) fuels as well as explosive materials^{(6, 7)}. Ferrocene, Cp₂Fe, has applications as an antiknock agent and combustion activator in liquid fuels^(8–10) and is deployed in combination with aromatic amines for powder production⁽¹¹⁾. There are no data available, however, on the interaction of Cp₂Fe and TNM.As a result of our initial experiments we find that addition of solid Cp₂Fe to pure liquid TNM causes a violent, exothermic explosion accompanied by an intense flash. The emission spectrum of the light measured with a medium dispersion Zeiss Q24 spectrograph covers the visible range, 370–500 nm, and is of a continuous character with faintly visible lines at short wavelength possibly indicative of iron.     

C2-symmetrical bis(camphorsulfonamides) as chiral ligands for enantioselective addition of diethylzinc to benzaldehyde

Purpose of the research was to determine the activity of chiral bis(sulfonamide) ligands derived from camphor in the addition of diethylzinc to benzaldehyde. Chiral bis(ketosulfonamides) and bis(hydroxysulfonamides), have been synthesized in a reaction of diamines with camphorsulfonic acid chloride. Their activity in a reaction of asymmetric addition of dialkylzinc to benzaldehyde in a presence of titanium(IV) tetraisopropoxide was determined. The bis(ketosulfonamide) ligands reveal low enantioselectivity, with the ee% not exceeding 12%. The bis(hydroxysulfonamides) reveal much higher asymmetric induction in the investigated ZnEt₂ addition. The best enantiomeric excess (62%) has been observed for bis(hydroxysulfonamide) obtained from 1,3-diaminepropane. The yields of the reaction obtained after 18 h are 92–96%. Crystal structures have been solved for bis(ketosulfonamide) ligands obtained from diamines based on C₂ to C₄ chain. The (2R) configuration in the rings systems of bis(hydroxysulfonamide) containing the C₃ bridge was also determined by the crystal structure analysis. The sulfonamides have been characterized by IR, ¹H and ¹³C NMR.