Proton-inclusive cross sections from 600 MeV proton-nucleus reactions

Proton-inclusive cross sections were measured for 600 MeV proton bombardment of ²⁷Al and ¹⁸¹Ta targets using the SREL synchrocyclotron. Proton energies were measured with a plastic scintillator time-of-flight system, and a 10.2 cm thick NaI detector was used for particle identification. The results of classical many-body and knock-on calculations are compared with the data.     

PSM studies III. A model of post-stimulatory masking phenomena

The experimental results obtained from a study of post-stimulatory masking phenomena are summarized. Two mechanisms are postulated to explain these results. A model, based on these two mechanisms, is derived, and comprises the input from the auditory senses, on which preliminary decisions and actions are taken, followed by a selective filter and limited capacity channel leading to the higher brain centres which can effect overriding control on the system. This model is used to provide explanations of the experimental results obtained in this study.     

Spectroscopic Evidence for Symmetry-Restricted π-Interaction in Vanadyl β-Keto-enolates

Theoretical treatments of the distorted square pyramidal co-ordination observed in vanadyl β-keto-enolates predict restricted interligand conjugation and minimal π-interaction in the oxovanadium-ligand bonds. The effects of ligand substitution on the vibrational and electronic spectra of vanadyl β-keto-enolates yield evidence that strong σ-bonding and ionic contributions are chiefly responsible for the strong vanadium-ligand bonding.     

Polyhedral aza­borane chemistry, 6‐(C5H5N)‐arachno‐4‐NB8H11

The title compound, 6‐pyridyl‐4‐aza‐arachno‐nonaborane(11), C₅H₁₆B₈N₂, has an arachno nine‐vertex {4‐NB₈H₁₁} cluster structure with a pyridine ligand in the exo‐6‐position. The cluster has close geometric similarities to the thia­borane and carbaborane analogues.     

4′‐Vinyl‐2,2′:6′,2′′‐ter­pyridine

The title compound, C₁₇H₁₃N₃, is a versatile precursor for polymeric ter­pyridine derivatives and their metal complexes. The mol­ecule has transoid and near‐coplanar pyridine rings. However, the vinyl group is forced out of the plane of the terpyridyl moiety by a close H?H contact.     

Positive integer solutions of the diophantine equation x 2 − L n xy + (−1) n y 2 = ±5 r

In this paper, we consider the equation x ²?L _n x y+(?1) ⁿ y ² = ±5 ^r and determine the values of n for which the equation has positive integer solutions x and y. Moreover, we give all positive integer solutions of the equation x ²?L _n x y+(?1) ⁿ y ² = ±5 ^r when the equation has positive integer solutions.     

Protic ionic liquids as recyclable solvents for the acid catalysed synthesis of diphenylmethyl thioethers

The acid catalysed formation of diphenylmethyl (DPM) thioethers was successfully achieved using the protic ionic liquid (pIL) triethylamine:methanesulfonic acid (TeaMs) as the reaction solvent under microwave irradiation. A slight excess of methanesulfonic acid (10% v/v) was required to facilitate the reaction, which was applied to a variety of thiols. Aliphatic, aromatic and heterocyclic aromatic thiols were converted to their corresponding DPM thioethers in high yields (63–99%), in short reaction times (5–20 min) and using mild temperatures (80–100 °C). Finally, the pIL (TeaMS) was recycled five times without loss of yield.     

Echolocation signals of Heaviside's dolphins (Cephalorhynchus heavisidii)

Field recordings of echolocation signals produced by Heaviside's dolphins (Cephalorhynchus heavisidii) were made off the coast of South Africa using a hydrophone array system. The system consisted of three hydrophones and an A-tag (miniature stereo acoustic data-logger). The mean centroid frequency was 125 kHz, with a -3 dB bandwidth of 15 kHz and -10 dB duration of 74 μs. The mean back-calculated apparent source level was 173 dB re 1 μPa(p.-p.). These characteristics are very similar to those found in other Cephalorhynchus species, and such narrow-band high-frequency echolocation clicks appear to be a defining characteristic of the Cephalorhynchus genus. Click bursts with very short inter-click intervals (up to 2 ms) were also recorded, which produced the "cry" sound reported in other Cephalorhynchus species. Since inter-click intervals correlated positively to click duration and negatively to bandwidth, Heaviside's dolphins may adjust their click duration and bandwidth based on detection range. The bimodal distribution of the peak frequency and stable bimodal peaks in spectra of individual click suggest a slight asymmetry in the click production mechanism.