Low-energy pions in nuclear matter and ππ photoproduction within a BUU transport model

In the present paper we investigate a method to describe low-energy scattering events of pions and nuclei within a Boltzmann-Uehling-Uhlenbeck (BUU) transport model. Implementing different scenarios of medium modifications, we studied the mean-free path of pions in nuclear matter at low momenta and compared pion absorption simulations to data. Pursuing these studies we have shown, that also in a regime of a long pionic wave length the semi-classical BUU model still generates reasonable results. We present results on π-induced events in the regime of 10 MeV≤T _kin ^π ≤130 MeV and photo-induced ππ production at incident beam energies of 400–460 MeV.     

The binaural temporal window in adults and children

This study investigated the binaural temporal window in adults and children 5-10.5 years of age. Detection thresholds were estimated for a brief, interaurally out-of-phase (Spi) 500 Hz pure tone signal masked by bandpass, 100-2000 Hz Gaussian noise. In one set of conditions, the masker was consistently either in phase (No) or out of phase (Npi). In another set of conditions, the masker changed abruptly in interaural phase (NoNpi or NpiNo), and threshold was estimated at a range of delays with respect to the phase transition. Masked thresholds were also obtained in further conditions where the masker interaural phase was steady and the signal was of long duration. Age effects obtained with dynamic maskers could be accounted for by positing that children have a binaural temporal window with a relatively prolonged leading edge or that the children position the binaural temporal window relatively late with respect to the signal. Modeling of the reduced masking-level difference shown by children for a brief Spi signal presented in a steady No or Npi masker was more consistent with late placement of a symmetrical binaural temporal window than a binaural temporal window having a relatively prolonged leading edge.     

The masking level difference for signals placed in masker envelope minima and maxima

Previous data on the masking level difference (MLD) have suggested that NoSpi detection for a long-duration signal is dominated by signal energy occurring in masker envelope minima. This finding was expanded upon using a brief 500-Hz tonal signal that coincided with either the envelope maximum or minimum of a narrow-band Gaussian noise masker centered at 500 Hz, and data were collected at a range of masker levels. Experiment 1 employed a typical MLD stimulus, consisting of a 30-ms signal and a 50-Hz-wide masker with abrupt spectral edges, and experiment 2 used stimuli generated to eliminate possible spectral cues. Results were quite similar for the two types of stimuli. At the highest masker level the MLD for signals coinciding with masker envelope minima was substantially larger than that for signals coinciding with envelope maxima, a result that was primarily due to decreased NoSpi thresholds in masker minima. For most observers this effect was greatly reduced or eliminated at the lowest masker level. These level effects are broadly consistent with the presence of physiological background noise and with a level-dependent binaural temporal window. Comparison of these results with predictions of a published model suggest that basilar-membrane compression alone does not account for this level effect.     

Temporal processing deficits in the pre-senescent auditory system

This study tested the hypothesis that temporal processing deficits are evident in the pre-senescent (middle-aged) auditory system for listening tasks that involve brief stimuli, across-frequency-channel processing, and/or significant processing loads. A gap duration discrimination (GDD) task was employed that used either fixed-duration gap markers (experiment 1) or random-duration markers (experiment 2). Independent variables included standard gap duration (0, 35, and 250 ms), marker frequency (within- and across-frequency), and task complexity. A total of 18 young and 23 middle-aged listeners with normal hearing participated in the GDD experiments. Middle age was defined operationally as 40-55 years of age. The results indicated that middle-aged listeners performed more poorly than the young listeners in general, and that this deficit was sometimes, but not always, exacerbated by increases in task complexity. A third experiment employed a categorical perception task that measured the gap duration associated with a perceptual boundary. The results from 12 young and 12 middle-aged listeners with normal hearing indicated that the categorical boundary was associated with shorter gaps in the young listeners. The results of these experiments indicate that temporal processing deficits can be observed relatively early in the aging process, and are evident in middle age.     

Effects of non-simultaneous masking on the binaural masking level difference

The present study sought to clarify the role of non-simultaneous masking in the binaural masking level difference for maskers that fluctuate in level. In the first experiment the signal was a brief 500-Hz tone, and the masker was a bandpass noise (100-2000 Hz), with the initial and final 200-ms bursts presented at 40-dB spectrum level and the inter-burst gap presented at 20-dB spectrum level. Temporal windows were fitted to thresholds measured for a range of gap durations and signal positions within the gap. In the second experiment, individual differences in out of phase (NoSπ) thresholds were compared for a brief signal in a gapped bandpass masker, a brief signal in a steady bandpass masker, and a long signal in a narrowband (50-Hz-wide) noise masker. The third experiment measured brief tone detection thresholds in forward, simultaneous, and backward masking conditions for a 50- and for a 1900-Hz-wide noise masker centered on the 500-Hz signal frequency. Results are consistent with comparable temporal resolution in the in phase (NoSo) and NoSπ conditions and no effect of temporal resolution on individual observers' ability to utilize binaural cues in narrowband noise. The large masking release observed for a narrowband noise masker may be due to binaural masking release from non-simultaneous, informational masking.     

Schwingungsspektren fester,flüssiger und gelöster Metallpolysulfide. II. Polysulfide Rb2Sn und Cs2Sn (n ⩾ 4) sowie Na2S4

Vibrational Spectra of Solid, Liquid, and Soluted Metal Polysulphides. II Polysulphides Rb₂S_n (n ? 4) and Na₂S₄ All compounds have been prepared from the elements in liquid ammonia. Whereas Rb₂S₄ has no defined composition, the vibrational spectra of Cs₂S₄ and their structure similar to Na₂S₄ indicate that Cs₂S₄ is a well-defined compound in contrast to former suggestions. Rb₂S₅ and Cs₂S₆ are the members with the greatest chainlength of their homologe series. While Na₂S₄ still exists of S₄^2? chains in the melt the other polysulhpides disproportionate to S₃^? radicals and probably monosulphide. In the melt of Cs₂S₆, quenched to room temperature, a double branched chain structure, the thio-analogue of dithionite, S₂S₄^2?, is suggested. All polysulphides have a mean valence frequency, which is independent of the cation and decreases with increasing chainlength.     

Die Kristallstruktur von Kalium-trithiowolframat-chlorid K3(WOS3)Cl

A recently prepared new thiotungstate has been characterized by three-dimensional X-ray structure analysis, to be a double salt, containing K₂WOS₃ and KCl in equimolar proportions: potassium trithiotungstate chloride, K₃(WOS₃)Cl. Space group: Pca2₁ with a = 12.507, b = 6.317, c = 12,371 Å, Z = 4. The compound represents a new structure type with stoichiometry M^I₂XY₄ · M^IZ. Besides isolated tetrahedral WOS₃^2- ions (bond lengths W–O 1.760 Å, W–S 2.208, 2.197, 2.196 Å) the structure contains Cl^? ions octahedrally co-ordinated by K⁺, the K⁺ ions having 5S + 10 + 2Cl as neighbours. The dimensions of the WOS₃^2? ions in this compound show that, as in other transition metal oxo-, thio- and selenoanions, strong π bonding is present, the W–S bonds taking part in the π bond system.