44 research outputs found
Propargyl carbamate-functionalized Cu(II)-metal organic framework after reaction with chloroauric acid: An x-ray photoelectron spectroscopy data record
A copper-containing metal organic framework was prepared using the new organic linker 5-(2-{[(prop-2-yn-1-yloxy)carbonyl]-amino} ethoxy)isophthalic acid [1,3-H2YBDC (where Y = alkYne and BDC = Benzene DiCarboxylate)] and functionalized with gold particles by reaction with HAuCl4 under thermal treatment in methanol. The resulting system was investigated by complementary techniques to obtain information on its structure and morphology. In the present work, x-ray photoelectron spectroscopy (XPS) was employed to analyze the chemical composition of a representative specimen. Besides wide scan spectra, data obtained by the analysis of the C 1s, O 1s, N 1s, Cu 2p, and Au 4f signals are presented and critically discussed. The results highlight the reduction of Au(III) to mostly Au(I) species. Overall, the data presented herein may act as useful guidelines for the eventual tailoring of material properties and their possible implementation toward functional applications in heterogeneous catalysis
Four-electron deoxygenative reductive coupling of carbon monoxide at a single metal site
Carbon dioxide is the ultimate source of the fossil fuels that are both central to modern life and problematic: their use increases atmospheric levels of greenhouse gases, and their availability is geopolitically constrained. Using carbon dioxide as a feedstock to produce synthetic fuels might, in principle, alleviate these concerns. Although many homogeneous and heterogeneous catalysts convert carbon dioxide to carbon monoxide, further deoxygenative coupling of carbon monoxide to generate useful multicarbon products is challenging. Molybdenum and vanadium nitrogenases are capable of converting carbon monoxide into hydrocarbons under mild conditions, using discrete electron and proton sources. Electrocatalytic reduction of carbon monoxide on copper catalysts also uses a combination of electrons and protons, while the industrial Fischer–Tropsch process uses dihydrogen as a combined source of electrons and electrophiles for carbon monoxide coupling at high temperatures and pressures6. However, these enzymatic and heterogeneous systems are difficult to probe mechanistically. Molecular catalysts have been studied extensively to investigate the elementary steps by which carbon monoxide is deoxygenated and coupled, but a single metal site that can efficiently induce the required scission of carbon–oxygen bonds and generate carbon–carbon bonds has not yet been documented. Here we describe a molybdenum compound, supported by a terphenyl–diphosphine ligand, that activates and cleaves the strong carbon–oxygen bond of carbon monoxide, enacts carbon–carbon coupling, and spontaneously dissociates the resulting fragment. This complex four-electron transformation is enabled by the terphenyl–diphosphine ligand, which acts as an electron reservoir and exhibits the coordinative flexibility needed to stabilize the different intermediates involved in the overall reaction sequence. We anticipate that these design elements might help in the development of efficient catalysts for converting carbon monoxide to chemical fuels, and should prove useful in the broader context of performing complex multi-electron transformations at a single metal site
Hamilton-Jacobi Renormalization for Lifshitz Spacetime
Just like AdS spacetimes, Lifshitz spacetimes require counterterms in order
to make the on-shell value of the bulk action finite. We study these
counterterms using the Hamilton-Jacobi method. Rather than imposing boundary
conditions from the start, we will derive suitable boundary conditions by
requiring that divergences can be canceled using only local counterterms. We
will demonstrate in examples that this procedure indeed leads to a finite bulk
action while at the same time it determines the asymptotic behavior of the
fields. This puts more substance to the belief that Lifshitz spacetimes are
dual to well-behaved field theories. As a byproduct, we will find the analogue
of the conformal anomaly for Lifshitz spacetimes.Comment: 27 pages; minor improvements, references added, published versio
Relevance of laboratory testing for the diagnosis of primary immunodeficiencies: a review of case-based examples of selected immunodeficiencies
The field of primary immunodeficiencies (PIDs) is one of several in the area of clinical immunology that has not been static, but rather has shown exponential growth due to enhanced physician, scientist and patient education and awareness, leading to identification of new diseases, new molecular diagnoses of existing clinical phenotypes, broadening of the spectrum of clinical and phenotypic presentations associated with a single or related gene defects, increased bioinformatics resources, and utilization of advanced diagnostic technology and methodology for disease diagnosis and management resulting in improved outcomes and survival. There are currently over 200 PIDs with at least 170 associated genetic defects identified, with several of these being reported in recent years. The enormous clinical and immunological heterogeneity in the PIDs makes diagnosis challenging, but there is no doubt that early and accurate diagnosis facilitates prompt intervention leading to decreased morbidity and mortality. Diagnosis of PIDs often requires correlation of data obtained from clinical and radiological findings with laboratory immunological analyses and genetic testing. The field of laboratory diagnostic immunology is also rapidly burgeoning, both in terms of novel technologies and applications, and knowledge of human immunology. Over the years, the classification of PIDs has been primarily based on the immunological defect(s) ("immunophenotype") with the relatively recent addition of genotype, though there are clinical classifications as well. There can be substantial overlap in terms of the broad immunophenotype and clinical features between PIDs, and therefore, it is relevant to refine, at a cellular and molecular level, unique immunological defects that allow for a specific and accurate diagnosis. The diagnostic testing armamentarium for PID includes flow cytometry - phenotyping and functional, cellular and molecular assays, protein analysis, and mutation identification by gene sequencing. The complexity and diversity of the laboratory diagnosis of PIDs necessitates many of the above-mentioned tests being performed in highly specialized reference laboratories. Despite these restrictions, there remains an urgent need for improved standardization and optimization of phenotypic and functional flow cytometry and protein-specific assays. A key component in the interpretation of immunological assays is the comparison of patient data to that obtained in a statistically-robust manner from age and gender-matched healthy donors. This review highlights a few of the laboratory assays available for the diagnostic work-up of broad categories of PIDs, based on immunophenotyping, followed by examples of disease-specific testing
RF-sputtering preparation of gold-nanoparticle-modified ITO electrodes for electrocatalytic applications
The preparation of gold-nanoparticle (AuNPs)-modified indium tin oxide (ITO) electrodes (AuNPs/ITO) was performed by radio-frequency (RF) sputtering from Ar plasmas at
temperatures as low as 60\ub0C, tailoring the AuNP morphology and content as a function of the sole sputtering time. The latter parameter was varied from 5 to 20 min in order to investigate the influence of gold amount and distribution on the electrochemical performances of the resulting
AuNPs/ITO systems. The electrodes were characterized using field emission-scanning electron
microscopy (FE-SEM), UV\u2013vis absorption and x-ray photoelectron spectroscopies (XPS);
moreover variable scan rate cyclic voltammetry (CV) studies were performed to examine their
electrochemical behavior. The electrocatalytic activity of the nanostructured AuNPs/ITO
electrodes toward methanol oxidation was investigated and compared with a continuous gold
film (Aufilm/ITO). The catalytic efficiency of the AuNPs/ITO systems was found to increase with
the gold content and the AuNPs\u2013support boundary region in the corresponding samples. For the
longest sputtering time (i.e. 20 min) the performances of the nanostructured electrode were
better than the Aufilm/ITO reference, despite the much lower catalyst amount. Furthermore,
conversely from the AuNPs/ITO samples, in the Aufilm/ITO case the gold film displayed a poor
adhesion to the substrate and the electrode could be used only for a limited number of electrochemical cycles