163 research outputs found
XPS and in-situ IR investigation of Ru/Si02 catalyst
Cataloged from PDF version of article.Ru(NO)(N0&/Si02 catalyst precursors were characterized via XPS and in-situ reflectance IR spectroscopy before, during
and after reduction by hydrogen over the temperature range 300-800 K. IR results indicated that the catalyst precursor lost NO3
groups first, with subsequent loss of NO both in a reducing atmosphere and during thermal annealing. XPS was used to derive
information on the oxidation state of Ru in the various steps of the annealing and/or reduction processes. 0 1997 Elsevier
Science B.V
FTIR characterization of Ru/SiO2 catalyst for ammonia synthesis
Cataloged from PDF version of article.Carbon monoxide adsorption on a Ru/SiO2 catalyst was followed by IR spectroscopy to investigate the active sites. Using this
catalyst, ammonia synthesis was achieved at 3508C in an N2/H2 gas mixture (N2/H2 < 3 : 1) for different reaction times. In
addition to NH3 other NHx (x 1,2) species were also observed. CO adsorption after NH3 production was also performed to
investigate the change in nature of the active sites. Based on the experimental evidence participation of Ru0 sites in ammonia
synthesis was confirmed and a partial oxidation of the reduced Ru sites during the synthesis was observed. q 1999 Elsevier
Science B.V. All rights reserved
Pt-incorporated anatase TiO2(001) surface for solar cell applications : First-principles density functional theory calculations
First-principles density functional theory calculations were carried out to
determine the low energy geometries of anatase TiO(001) with Pt implants in
the sublayers as substitutional and interstitial impurities as well as on the
surface in the form of adsorbates. We investigated the effect of such a
systematic Pt incorporation in the electronic structure of this surface for
isolated and interacting impurities with an emphasis on the reduction in the
band gap to visible region. Comprehensive calculations, for 1x1 surface, showed
that Pt ions at interstitial cavities result in local segregation, forming
metallic wires inside, while substitution for bulk Ti and adsorption drives
four strongly dispersed impurity states from valence-bands up in the gap with a
narrowing of ~1.5 eV. Hence, such a contiguous Pt incorporation drives anatase
into infrared regime. Pt substitution for the surface Ti, on the other hand,
metallizes the surface. Systematic trends for 2x2 surface revealed that Pt can
be encapsulated inside to form stable structures as a result of strong Pt-O
interactions as well as the adsorptional and substitutional cases. Dilute
impurities considered for 2x2 surface models exhibit flat-like defect states
driven from the valence bands narrowing the energy gap suitable to obtain
visible light responsive titania.Comment: 15 pages, 8 figures, 4 tables. to appear on Phys. Rev
Effect of molecular and electronic structure on the light harvesting properties of dye sensitizers
The systematic trends in structural and electronic properties of perylene
diimide (PDI) derived dye molecules have been investigated by DFT calculations
based on projector augmented wave (PAW) method including gradient corrected
exchange-correlation effects. TDDFT calculations have been performed to study
the visible absorbance activity of these complexes. The effect of different
ligands and halogen atoms attached to PDI were studied to characterize the
light harvesting properties. The atomic size and electronegativity of the
halogen were observed to alter the relaxed molecular geometries which in turn
influenced the electronic behavior of the dye molecules. Ground state molecular
structure of isolated dye molecules studied in this work depends on both the
halogen atom and the carboxylic acid groups. DFT calculations revealed that the
carboxylic acid ligands did not play an important role in changing the
HOMO-LUMO gap of the sensitizer. However, they serve as anchor between the PDI
and substrate titania surface of the solar cell or photocatalyst. A
commercially available dye-sensitizer, ruthenium bipyridine (RuBpy), was also
studied for electronic and structural properties in order to make a comparison
with PDI derivatives for light harvesting properties. Results of this work
suggest that fluorinated, chlorinated, brominated, and iyodinated PDI compounds
can be useful as sensitizers in solar cells and in artificial photosynthesis.Comment: Single pdf file, 14 pages with 7 figures and 4 table
Small cell lung cancer stem cells display mesenchymal properties and exploit immune checkpoint pathways in activated cytotoxic T lymphocytes
Small cell lung cancer (SCLC) is an aggressive tumor type with early dissemination and distant metastasis capacity. Even though optimal chemotherapy responses are observed initially in many patients, therapy resistance is almost inevitable. Accordingly, SCLC has been regarded as an archetype for cancer stem cell (CSC) dynamics. To determine the immune-modulatory influence of CSC in SCLC, this study focused on the characterization of CD44(+)CD90(+) CSC-like subpopulations in SCLC. These cells displayed mesenchymal properties, differentiated into different lineages and further contributed to CD8(+) cytotoxic T lymphocytes (CTL) responses. The interaction between CD44(+)CD90(+) CSC-like cells and T cells led to the upregulation of checkpoint molecules PD-1, CTLA-4, TIM-3, and LAG3. In the patient-derived lymph nodes, CD44(+) SCLC metastases were also observed with T cells expressing PD-1, TIM-3, or LAG3. Proliferation and IFN-γ expression capacity of TIM-3 and LAG3 co-expressing CTLs are adversely affected over long-time co-culture with CD44(+)CD90(+) CSC-like cells. Moreover, especially through IFN-γ secreted by the T cells, the CSC-like SCLC cells highly expressed PD-L1 and PD-L2. Upon a second encounter with immune-experienced, IFN-γ-stimulated CSC-like SCLC cells, both cytotoxic and proliferation capacities of T cells were hampered. In conclusion, our data provide evidence for the superior potential of the SCLC cells with stem-like and mesenchymal properties to gain immune regulatory capacities and cope with cytotoxic T cell responses. With their high metastatic and immune-modulatory assets, the CSC subpopulation in SCLC may serve as a preferential target for checkpoint blockade immunotherapy
The construct validity and reliability of the Turkish version of Spreitzer's psychological empowerment scale
<p>Abstract</p> <p>Background</p> <p>Today, many organizations have adopted some kind of empowerment initiative for at least part of their workforce. Over the last two decades, two complementary perspectives on empowerment at work have emerged: structural and psychological empowerment. Psychological empowerment is a motivational construct manifested in four cognitions: meaning, competence, self-determination and impact. The aim of this article is to examine the construct validity and reliability of the Turkish translation of Spreitzer's psychological empowerment scale in a culturally diverse environment.</p> <p>Methods</p> <p>The scale contains four dimensions over 12 statements. Data were gathered from 260 nurses and 161 physicians. The dimensionality of the scale was evaluated by exploratory factor analyses. To investigate the multidimensional nature of the empowerment construct and the validity of the scale, first- and second-order confirmatory factor analysis was conducted. Furthermore, Cronbach alpha coefficients were assessed to investigate reliability.</p> <p>Results</p> <p>Exploratory factor analyses revealed that four factors in both solutions. The first- and second-order factor analysis indicated an acceptable fit between the data and the theoretical model for nurses and physicians. Cronbach alpha coefficients varied between 0.81-0.94 for both groups, which may be considered satisfactory.</p> <p>Conclusions</p> <p>The analyses indicated that the psychometric properties of the Turkish version of the scale can be considered satisfactory.</p
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