Transverse resonance island buckets for synchrotron-radiation based electron time-of-flight spectroscopy.

At the Metrology Light Source (MLS), the compact electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB) with a circumference of 48 m, a specific operation mode with two stable closed orbits for stored electrons was realized by transverse resonance island buckets. One of these orbits is closing only after three turns. In combination with single-bunch operation, the new mode was applied for electron time-of-flight spectroscopy with an interval of the synchrotron radiation pulses which is three times the revolution period at the MLS of 160 ns. The achievement is of significant importance for PTB's future programs of angular-resolved electron spectroscopy with synchrotron radiation and similar projects at other compact electron storage rings. The scheme applied here for selecting the photons originating from a particular orbit by optical imaging has been used before in fs slicing applications and may be relevant for the BESSY VSR project of the Helmholtz-Zentrum Berlin.

Performance of a short "magnetic bottle" electron spectrometer.

In this article, a newly constructed electron spectrometer of the magnetic bottle type is described. The instrument is part of an apparatus for measuring the electron spectra of free clusters using synchrotron radiation. Argon and helium outer valence photoelectron spectra have been recorded in order to investigate the characteristic features of the spectrometer. The energy resolution (E/ΔE) has been found to be ∼30. Using electrostatic retardation of the electrons, it can be increased to at least 110. The transmission as a function of kinetic energy is flat, and is not impaired much by retardation with up to 80% of the initial kinetic energy. We have measured a detection efficiency of most probably 0.6(-0.1) (+0.05), but at least of 0.4. Results from testing the alignment of the magnet, and from trajectory simulations, are also discussed.

Fragmentation pathways of H+(H2O)2 after extreme ultraviolet photoionization.

Photofragmentation of the protonated water dimer H+(H2O)_{2}, a fundamental system both in aqueous solutions and gas-phase water clusters, has been studied at 13.8 nm using the Free Electron Laser FLASH in Hamburg. In a crossed-beam experiment using time-resolved, single-molecule fragment imaging, the two-body breakup into H2O++H3O+ was found as a prominent fragmentation channel with a kinetic energy release of up to 10 eV. This channel was observed with at least a similar yield as events with stronger fragmentation, producing protons together with neutral fragments and showing an absolute cross section of (0.5 ± 0.2) × 10(-18) cm2.

Labial talon cusp: a case study of pre-European-contact American Indians.

BACKGROUND: First documented by Mitchell in 1892, the talon cusp is a rare and much-debated morphological variant. The author presents a case study from a pre-European-contact American Indian population. In addition, the author addresses debates in the literature regarding the definition, etiology and description of the talon cusp and provides new evidence within an archaeological context. METHODS: The author examined the dentition of 301 skeletons for the presence or absence of talon cusp; five skeletons (2 percent) in the population had the trait. RESULTS: This skeletal sample exhibited variations of the labial talon cusp that can be graded. CONCLUSIONS: The results of this study provide further evidence of the antiquity of labial talon cusp in the assemblage of modern humans and, in particular, in American Indians.

Ituglanis cahyensis, a new catfish from Bahia, Brazil (Siluriformes: Trichomycteridae)

A new trichomycterid catfish of the genus Ituglanis is described from the rio Palmares, a tributary of the rio Cahy in southeast Bahia State, Brazil. Ituglanis cahyensis is distinguished from all other congeners through a combination of characters, as the supraorbital laterosensory canal branch with pores s3 and s6 present, the low count of branched pectoral fin rays, and low number of paired ribs. It is further distinguished in proportional measurements, such as elongate nasal, maxillary, and rictal barbels, and small eye diameter.

É descrito um novo trichomycterídeo do gênero Ituglanis, capturado no rio Palmares, um tributário do rio Cahy, na costa sudeste do estado da Bahia, Brasil. Ituglanis cahyensis distingue-se das demais espécies congêneres por uma combinação de caracteres, como o canal laterosensorial supraorbital com os poros s3 e s6 presentes, um pequeno número de raios ramificados nas nadadeiras peitorais, e um pequeno número de costelas. Distingue-se ainda quanto a proporções morfométricas, como os barbilhões nasal, maxilar e rictal alongados, e o pequeno diâmetro ocular.