Detailed High-resolution Study Research Articles

On the possibility of PhotoEmission Electron Microscopy for E. coli advanced studies

The novel approach was proposed for detailed high-resolution studies of morphology and physico-chemical properties concomitantly at one measurement spot of E. coli bacterial cells culture immobilized onto silicon wafer surface in UHV conditions applying PhotoEmission Electron Microscopy under Hg lamp irradiation. For the E. coli characterization scanning electron microscopy (electron beam) and X-ray photoelectron spectroscopy (X-ray tube radiation) were applied prior to PhotoEmission Electron Microscopy measurements. In spite of irradiation doses collected for the cell arrays we were successful in detection of high-resolution images even of single E. coli bacterium by PhotoEmission Electron Microscopy technique followed by detailed high-resolution morphology studies by scanning electron microscopy. These results revealed widespread stability of the E. coli membranes shape after the significant number of applied characterization techniques.

Fingerprinting fluid sources in Troodos ophiolite complex orbicular glasses using high spatial resolution isotope and trace element geochemistry

The Troodos igneous complex (Cyprus) is a ca. 90Ma old, well preserved supra-subduction zone ophiolite. Troodos is unique in that it shows evidence of fluid-saturation throughout the complex, from its base (i.e. podiform chromitites) to its uppermost units – the upper pillow lavas (UPL). However, it is unclear what the source of dissolved water in UPL tholeiites is, with possibilities including shallow seawater infiltration, assimilation of altered Troodos oceanic crust, recycled serpentinized oceanic crust, or subducted pelagic sediments. In order to identify and characterize these components we have carried out a detailed high-resolution study on tholeiitic lavas on orbicular structures and glasses from the UPL in Troodos. Basaltic orbicules were measured for their Sr–Nd–Hf–Pb isotope compositions, and in situ for their B isotopes using LA-MC-ICP-MS. UPL orbicules display a very narrow range in ∊Nd and ∊Hf (+7 to +8 and +13 to +15, respectively) indicating melting of a depleted mantle source. Lead isotopes, specifically 207Pb/204Pb vs. 206Pb/204Pb, form a mixing array with pelagic sediments. Furthermore, high-resolution characterization of individual orbicules revealed that UPL tholeiites display strong variability in 87Sr/86Sr (0.7039–0.7060) at the outcrop scale. Samples display δ11B between −8.2 (±0.5)‰ and +5.9 (±1.1)‰ with an average B content of ca. 5μg/g. Contrary to expectation, altered orbicules and their associated hyaloclastite matrixes display lower δ11B (down to −10‰) and higher B contents (max. 200μg/g) when compared to fresh glass. Furthermore, the orbicules studied here show little or no evidence of interaction with seawater, which is supported by their trace element contents and isotope compositions. When all isotope systems are taken into account, UPL lavas reflect melting of a depleted mantle source that was overprinted by hydrous sediment melts, and potentially, fluid-like subduction components that in part originate from serpentinized oceanic crust. Subsequent low-temperature alteration then drove δ11B to lower values coupled with increased B uptake due to its adsorption into palagonite.

Mid-infrared interferometry of 23 AGN tori: On the significance of polar-elongated emission

Context. Detailed high resolution studies of AGN with mid-infrared (MIR) interferometry have revealed parsec-sized dust emission elongated in the polar direction in four sources. Aims. Using a larger, coherently analyzed sample of AGN observed with MIR interferometry, we aim to identify elongated mid-infrared emission in a statistical sample of sources. More specifically we wish to determine if there is indeed a preferred direction of the elongation and whether this direction is consistent with a torus-like structure or with a polar emission. Methods. We investigate the significance of the detection of an elongated shape in the MIR emission by fitting elongated Gaussian models to the interferometric data at 12 um. We pay special attention to 1) the uncertainties caused by an inhomogeneous (u,v) coverage, 2) the typical errors in the measurements and 3) the spatial resolution achieved for each object. Results. From our sample of 23 sources we are able to find elongated parsec-scale MIR emission in five sources: three type 2s, one type 1i and one type 1. Elongated emission in four of these sources has been published before; NGC5506 is a new detection. The observed axis ratios are typically around 2 and the position angle of the 12 um emission for all the elongated sources seems to be always closer to the polar axis of the system than to the equatorial axis. Two other objects, NGC4507 and MCG-5-23-16 with a reasonably well mapped (u,v) coverage and good signal-to-noise ratios, appear to have a less elongated 12 um emission. Conclusions. Our finding that sources showing elongated mid-infrared emission are preferentially extended in polar direction sets strong constraints on torus models or implies that both the torus and the NLR/outflow region have to be modeled together. Especially also models used for SED fitting will have to be revised to include emission from polar dust.

IVINE - Ionization in the parallel tree/sph code VINE: first results on the observed age-spread around O-stars

We present a three-dimensional, fully parallelized, efficient implementation of ionizing ultraviolet (UV) radiation for smoothed particle hydrodynamics (SPH) including self-gravity. Our method is based on the SPH/TREE code VINE. We therefore call it iVINE (for Ionization + VINE). This approach allows detailed high-resolution studies of the effects of ionizing radiation from, for example, young massive stars on their turbulent parental molecular clouds. In this paper, we describe the concept and the numerical implementation of the radiative transfer for a plane-parallel geometry and we discuss several test cases demonstrating the efficiency and accuracy of the new method. As a first application, we study the radiatively driven implosion of marginally stable molecular clouds at various distances of a strong UV source and show that they are driven into gravitational collapse. The resulting cores are very compact and dense exactly as it is observed in clustered environments. Our simulations indicate that the time of triggered collapse depends on the distance of the core from the UV source. Clouds closer to the source collapse several 10 5 yr earlier than more distant clouds. This effect can explain the observed age spread in OB associations where stars closer to the source are found to be younger. We discuss possible uncertainties in the observational derivation of shock front velocities due to early stripping of protostellar envelopes by ionizing radiation.

Neutron-scattering studies of spin waves in rare-earth orthoferrites

Iron sublattice spin waves have been studied in TmFe${\mathrm{O}}_{3}$ and ErFe${\mathrm{O}}_{3}$ by inelastic neutron scattering. In TmFe${\mathrm{O}}_{3}$ magnon dispersion curves were measured along several symmetry directions and the results fitted to an isotropic Heisenberg Hamiltonian with near-neighbor exchange constant ${J}^{\ensuremath{'}}=(\ensuremath{-}1.9\ifmmode\pm\else\textpm\fi{}0.2)$ \ifmmode^\circ\else\textdegree\fi{}K and next-nearest-neighbor exchange $J=(\ensuremath{-}29.1\ifmmode\pm\else\textpm\fi{}0.6)$ \ifmmode^\circ\else\textdegree\fi{}K. A detailed high-resolution study of the long-wavelength spin waves was performed near the moment reorientation transformation. In TmFe${\mathrm{O}}_{3}$, the lowest magnon frequency renormalizes in qualitative agreement with the soft-mode theory of the transformation. In ErFe${\mathrm{O}}_{3}$ mode softening was observed only at the lower transformation temperature. Improved estimates are made of the twofold and fourfold anisotropy energies in TmFe${\mathrm{O}}_{3}$.

The ageing behavior of an isothermally transformed 0.5%Ti−0.1%C steel

Electron microscopy and field-ion microscopy have been combined in a detailed high resolution study of the microstructure of an isothermally transformed Fe−0.5%Ti−0.1%C alloy. The alloy exhibits optimum mechanical properties during the early stages of transformation when a very fine banded dispersion of titanium carbide particles is formed by nucleation at the γ α interfaces. Aspects of the microstructure studied include the overall nature of the dispersions, the morphology, size and orientation of the precipitates and the nature of the particle/matrix interface; this information is correlated with the mechanical properties of the alloy.

The Bakerian Lecture, The spectra and structures of free methyl and free methylene

The spectra of many diatomic free radicals like those of CH, OH, NH, C 2 , CN have been known and identified as such almost since the beginning of molecular spectroscopy. They occur readily in emission in a variety of flames (including the ordinary Bunsen burner) and in electric discharges. It was through the study of these spectra that our knowledge of the structure of diatomic molecules was developed and in particular that the different coupling conditions between the electron spin and the other angular momenta were recognized. Most of the resonance transitions of the diatomic free radicals lie in the visible or near ultra-violet region where a detailed high-resolution study is easily possible. It is for this reason also that these spectra play a most prominent part in the spectra of astrophysical sources: comets, low-temperature stars and the interstellar medium. The spectra of free polyatomic radicals have become recognized and analyzed only in the last ten or fifteen years. The reason for this delay is the much greater complexity of the spectra of polyatomic as compared to the spectra of diatomic molecules combined with the greater difficulty of exciting these spectra in emission. Ordinary polyatomic molecules can easily be studied in infra-red absorption or by means of the Raman effect. The infra-red and Raman spectra are simpler than the electronic spectra and their interpretation has been established for a long time; but up to now no infra-red (or Raman) spectrum of a free polyatomic radical has been obtained. One is entirely dependent on electronic spectra for the study of the structure of polyatomic free radicals, and these electronic spectra exhibit many complexities.