2,175 research outputs found
The church for others: Protestant theology in communist East Germany
Reviewed Book: Baum, Gregory. The church for others: Protestant theology in communist East Germany. Grand Rapids: Eerdmans, 1996
Newman and conversion
Ker, Ian T. Newman and conversion. Edinburgh: T & T Clark; Notre Dame, Ind: Univ of Notre Dame Pr, 1997
Xps Characterization of Supported Iron/Ruthenium Carbon Monoxide Hydrogenation Catalyst Systems.
Literature in the field of catalysis is dominated by details of catalytic reactions, operating conditions, and product streams, with little regard for detailed physical characterization of the catalyst materials. It is now understood that knowledge of catalyst properties as a function of reaction properties may lead to the design of more active and/or selective catalysts. Thus, studies in the catalysis field are changing and the present investigation demonstrates the utility of an X-ray photelectron spectroscopic (XPS) characterization of supported iron, ruthenium, and iron-ruthenium bimetallic catalyst systems as a function of catalyst treatment(s). This physical and chemical information of the catalysts themselves, when coupled to kinetic investigations of the catalytic reaction provides an even greater understanding of the observed trends. This report focusses on the correlations between the catalysts\u27 properties and their ability to catalyze effectively carbon monoxide hydrogenation. XPS was found to effectively characterize the chemical properties of all but the initial materials. Ruthenium was reduced (in H(,2)) to Ru(0) and iron underwent a partial reduction. Except for iron in the mixed-metal catalyst, reaction conditions caused the further reduction of the metal binding energies. This effect can be attributed to a decrease in metal-support interaction, elimination/reduction of any matrix effects, and/or unequal charge compensation between the support and metal. Ruthenium always oxidized upon exposure to H(,2)S, whereas iron oxidized only in the monometallic case. H(,2)S also prevented the decrease in metal binding energies upon exposure to reaction conditions. In the bimetallic case, H(,2)S pretreatment caused an increase in the Fe:Si XPS intensity ratio upon exposure to reaction conditions, where in the non-sulfided case, the Ru:Si ratio increased. The kinetic results indicated that the bimetallic catalyst performed like the ruthenium-only catalyst; however, H(,2)S caused the catalyst to acquire more characteristics of the Fe-only catalyst (increased olefin and C(,2)-C(,4) hydrocarbon production). Argon ion implantation was used to eliminate the matrix effect in several supported ruthenium catalysts in order to determine the extent of metal-support interaction occurring. The degree of metal-support interaction varied as Al(,2)O(,3) \u3e NaY \u3e SiO(,2)
Fermi-Hubbard physics with atoms in an optical lattice
The Fermi-Hubbard model is a key concept in condensed matter physics and
provides crucial insights into electronic and magnetic properties of materials.
Yet, the intricate nature of Fermi systems poses a barrier to answer important
questions concerning d-wave superconductivity and quantum magnetism. Recently,
it has become possible to experimentally realize the Fermi-Hubbard model using
a fermionic quantum gas loaded into an optical lattice. In this atomic approach
to the Fermi-Hubbard model the Hamiltonian is a direct result of the optical
lattice potential created by interfering laser fields and short-ranged
ultracold collisions. It provides a route to simulate the physics of the
Hamiltonian and to address open questions and novel challenges of the
underlying many-body system. This review gives an overview of the current
efforts in understanding and realizing experiments with fermionic atoms in
optical lattices and discusses key experiments in the metallic,
band-insulating, superfluid and Mott-insulating regimes.Comment: Posted with permission from the Annual Review of of Condensed Matter
Physics Volume 1 \c{opyright} 2010 by Annual Reviews,
http://www.annualreviews.or
A Unifying Theory for SIDS
The Sudden Infant Death Syndrome (SIDS) has four distinctive characteristics that must be explained by any theory proposed for it.
(1) A characteristic male fraction of approximately 0.61 for all postneonatal SIDS in the US; (2) a distinctive lognormal-type age distribution arising from zero at birth, mode at about 2 months, median at about 3 months, and an exponential decrease with age going towards zero beyond one year; (3) a marked decrease in SIDS rate from the discovery that changing the recommended infant sleep position from prone to supine reduced the rate of SIDS, but it did not change the form of the age or gender distributions cited above; (4) a seasonal variation, maximal in winter and minimal in summer, that implies subsets of SIDS displaying evidence of seasonal low-grade respiratory infection and nonseasonal neurological prematurity. A quadruple-risk model is presented that fits these conditions but requires confirmatory testing by finding a dominant X-linked allele protective against cerebral anoxia that is missing in SIDS
Post-training load-related changes of auditory working memory: An EEG study
Working memory (WM) refers to the temporary retention and manipulation of information, and its capacity is highly susceptible to training. Yet, the neural mechanisms that allow for increased performance under demanding conditions are not fully understood. We expected that post-training efficiency in WM performance modulates neural processing during high load tasks. We tested this hypothesis, using electroencephalography (EEG) (N = 39), by comparing source space spectral power of healthy adults performing low and high load auditory WM tasks. Prior to the assessment, participants either underwent a modality-specific auditory WM training, or a modality-irrelevant tactile WM training, or were not trained (active control). After a modality-specific training participants showed higher behavioral performance, compared to the control. EEG data analysis revealed general effects of WM load, across all training groups, in the theta-, alpha-, and beta-frequency bands. With increased load theta-band power increased over frontal, and decreased over parietal areas. Centro-parietal alpha-band power and central beta-band power decreased with load. Interestingly, in the high load condition a tendency toward reduced beta-band power in the right medial temporal lobe was observed in the modality-specific WM training group compared to the modality-irrelevant and active control groups. Our finding that WM processing during the high load condition changed after modality-specific WM training, showing reduced beta-band activity in voice-selective regions, possibly indicates a more efficient maintenance of task-relevant stimuli. The general load effects suggest that WM performance at high load demands involves complementary mechanisms, combining a strengthening of task-relevant and a suppression of task-irrelevant processing
Time interval distributions of atoms in atomic beams
We report an experimental investigation of two-particle correlations between neutral atoms in a Hanbury Brown and Twiss experiment. Both an atom laser beam and a pseudo-thermal atomic beam are extracted from a Bose-Einstein condensate and the atom flux is measured with a single atom counter. We determine the conditional and the unconditional detection probabilities for the atoms in the beam and find good agreement with the theoretical prediction
Dynamical coupling between a Bose-Einstein condensate andacavity optical lattice
A Bose-Einstein condensate is dispersively coupled to a single mode of an ultra-high finesse optical cavity. The system is governed by strong interactions between the atomic motion and the light field even at the level of single quanta. While coherently pumping the cavity mode the condensate is subject to the cavity optical lattice potential whose depth depends nonlinearly on the atomic density distribution. We observe optical bistability already below the single photon level and strong back-action dynamics which tunes the coupled system periodically out of resonanc
- …