439 research outputs found
Ossetian: Revisiting Inflectional Morphology
Ossetian, a language of the Northeastern group of the Indo-Iranian branch of the Indo-European stock of languages, has not received as much linguistic attention as it deserves. A few major studies on Ossetian were written in the 19th and 20th centuries, most of them in Russian. While these works are a solid foundation in the study of Ossetian, its description is not complete.
The present work, written in English, offers Ossetian to a wider international audience. Relying on new developments in linguistic theory, it reexamines phenomena in the inflectional morphology of Ossetian.
The preliminary chapter on phonology provides an overview of the phonemic inventory of Ossetian. In the chapter on nominal morphology, the variety and nature of case and number suffixes is re-analyzed and they are described as phrasal affixes. In the chapter on verbal morphology, the forms previously described as infinitives are discussed and one of them is reanalyzed as a derived noun or adjective; the majority of verbs are regarded as having one stem form; tense is analyzed as a suffix that attaches to the stem; mood, person, number and transitivity marking is analyzed as one fused suffix
Evaluation of crack-terminating angles in heat-treated silica DCDC-specimens
Cracks terminating at free surfaces are affected by local stresses in the surface region. Under residual compression, the crack front must retard and under residual tensile stresses advance, both compared with the crack contour in the absence of stresses. This effect can be used for an estimation of residual surface stresses in silica generated during the silica/water reaction and caused by volume swelling. A strong shielding stress intensity factor of about -2.5 MPa was found for DCDC specimen heat-treated for 192h at 250°C in water. This result is a clear indication for compressive stresses developing in the water diffusion zone at the surface
Inert strength measurement on silica soaked at 250°C in liquid water and water vapour
The effect of water soaking and heat-treatment in saturated water vapour at
250°C for 192 h on the strength of silica glass is studied. Bending strength
meaurements in liquid nitrogen showed a clear increase of the inert strength
for heat-treated specimens over that of the untreated material. The increase
in strength is interpreted as the consequence of water diffusion into exposed
surfaces of the test specimen, which results in swelling of the glass and
shielding of cracks, present in the surface of the glass. Experimental results
are compared with theoretical predictions
Breakdown of the few-level approximation in collective systems
The validity of the few-level approximation in dipole-dipole interacting
collective systems is discussed. As example system, we study the archetype case
of two dipole-dipole interacting atoms, each modelled by two complete sets of
angular momentum multiplets. We establish the breakdown of the few-level
approximation by first proving the intuitive result that the dipole-dipole
induced energy shifts between collective two-atom states depend on the length
of the vector connecting the atoms, but not on its orientation, if complete and
degenerate multiplets are considered. A careful analysis of our findings
reveals that the simplification of the atomic level scheme by artificially
omitting Zeeman sublevels in a few-level approximation generally leads to
incorrect predictions. We find that this breakdown can be traced back to the
dipole-dipole coupling of transitions with orthogonal dipole moments. Our
interpretation enables us to identify special geometries in which partial
few-level approximations to two- or three-level systems are valid
Role of the CipA Scaffoldin Protein in Cellulose Solubilization, as Determined by Targeted Gene Deletion and Complementation in Clostridium thermocellum
The CipA scaffoldin protein plays a key role in the Clostridium thermocellum cellulosome. Previous studies have revealed that mutants deficient in binding or solubilizing cellulose also exhibit reduced expression of CipA. To confirm that CipA is, in fact, necessary for rapid solubilization of crystalline cellulose, the gene was deleted from the chromosome using targeted gene deletion technologies. The CipA deletion mutant exhibited a 100-fold reduction in cellulose solubilization rate, although it was eventually able to solubilize 80% of the 5 g/liter cellulose initially present. The deletion mutant was complemented by a copy of cipA expressed from a replicating plasmid. In this strain, Avicelase activity was restored, although the rate was 2-fold lower than that in the wild type and the duration of the lag phase was increased. The cipA coding sequence is located at the beginning of a gene cluster containing several other genes thought to be responsible for the structural organization of the cellulosome, including olpB, orf2p, and olpA. Tandem mass spectrometry revealed a 10-fold reduction in the expression of olpB, which may explain the lower growth rate. This deletion experiment adds further evidence that CipA plays a key role in cellulose solubilization by C. thermocellum, and it raises interesting questions about the differential roles of the anchor scaffoldin proteins OlpB, Orf2p, and SdbA
Coherent control in a decoherence-free subspace of a collective multi-level system
Decoherence-free subspaces (DFS) in systems of dipole-dipole interacting
multi-level atoms are investigated theoretically. It is shown that the
collective state space of two dipole-dipole interacting four-level atoms
contains a four-dimensional DFS. We describe a method that allows to populate
the antisymmetric states of the DFS by means of a laser field, without the need
of a field gradient between the two atoms. We identify these antisymmetric
states as long-lived entangled states. Further, we show that any single-qubit
operation between two states of the DFS can be induced by means of a microwave
field. Typical operation times of these qubit rotations can be significantly
shorter than for a nuclear spin system.Comment: 15 pages, 11 figure
Primary stability of a press-fit cup in combination with impaction grafting in an acetabular defect model
The objectives of this study were to (a) assess primary stability of a press-fit cup in a simplified acetabular defect model, filled with compacted cancellous bone chips, and (b) to compare the results with primary stability of a press-fit cup combined with two different types of bone graft substitute in the same defect model. A previously developed acetabular test model made of polyurethane foam was used, in which a mainly medial contained defect was implemented. Three test groups (N = 6 each) were prepared: Cancellous bone chips (bone chips), tricalciumphosphate tetrapods + collagen matrix (tetrapods + coll), bioactive glass S53P4 + polyethylene glycol-glycerol matrix (b.a.glass + PEG). Each material was compacted into the acetabulum and a press-fit cup was implanted. The specimens were loaded dynamically in the direction of the maximum resultant force during level walking. Relative motion between cup and test model was assessed with an optical measurement system. At the last load step (3000 N), inducible displacement was highest for bone chips with median [25th percentile; 75th percentile] value of 113 [110; 114] µm and lowest for b.a.glass + PEG with 91 [89; 93] µm. Migration at this load step was highest for b.a.glass + PEG with 868 [845; 936] µm and lowest for tetrapods + coll with 491 [487; 497] µm. The results show a comparable behavior under load of tetrapods + coll and bone chips and suggest that tetrapods + coll could be an attractive alternative to bone chips. However, so far, this was found for one specific defect type and primary stability should be further investigated in additional/more severe defects
Measuring the quantum efficiency of single radiating dipoles using a scanning mirror
Using scanning probe techniques, we show the controlled manipulation of the
radiation from single dipoles. In one experiment we study the modification of
the fluorescence lifetime of a single molecular dipole in front of a movable
silver mirror. A second experiment demonstrates the changing plasmon spectrum
of a gold nanoparticle in front of a dielectric mirror. Comparison of our data
with theoretical models allows determination of the quantum efficiency of each
radiating dipole.Comment: 4 pages, 4 figure
Comparative shotgun proteomic analysis of Clostridium acetobutylicum from butanol fermentation using glucose and xylose
<p>Abstract</p> <p>Background</p> <p>Butanol is a second generation biofuel produced by <it>Clostridium acetobutylicum </it>through acetone-butanol-ethanol (ABE) fermentation process. Shotgun proteomics provides a direct approach to study the whole proteome of an organism in depth. This paper focuses on shotgun proteomic profiling of <it>C. acetobutylicum </it>from ABE fermentation using glucose and xylose to understand the functional mechanisms of <it>C. acetobutylicum </it>proteins involved in butanol production.</p> <p>Results</p> <p>We identified 894 different proteins in <it>C. acetobutylicum </it>from ABE fermentation process by two dimensional - liquid chromatography - tandem mass spectrometry (2D-LC-MS/MS) method. This includes 717 proteins from glucose and 826 proteins from the xylose substrate. A total of 649 proteins were found to be common and 22 significantly differentially expressed proteins were identified between glucose and xylose substrates.</p> <p>Conclusion</p> <p>Our results demonstrate that flagellar proteins are highly up-regulated with glucose compared to xylose substrate during ABE fermentation. Chemotactic activity was also found to be lost with the xylose substrate due to the absence of CheW and CheV proteins. This is the first report on the shotgun proteomic analysis of <it>C. acetobutylicum </it>ATCC 824 in ABE fermentation between glucose and xylose substrate from a single time data point and the number of proteins identified here is more than any other study performed on this organism up to this report.</p
Electronic interactions in fullerene spheres
The electron-phonon and Coulomb interactions inC, and larger fullerene
spheres are analyzed. The coupling between electrons and intramolecular
vibrations give corrections meV to the electronic energies for
C, and scales as in larger molecules. The energies associated
with electrostatic interactions are of order eV, in C and
scale as . Charged fullerenes show enhanced electron-phonon coupling,
meV, which scales as . Finally, it is argued that non only
C, but also C are highly polarizable molecules. The
polarizabilities scale as and , respectively. The role of this large
polarizability in mediating intermolecular interactions is also discussed.Comment: 12 pages. No figure
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