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81.
Caroline K. Williams Gavin A. McCarver Ashwin Chaturvedi Dr. Soumalya Sinha Marcus Ang Prof. Konstantinos D. Vogiatzis Prof. Jianbing “Jimmy” Jiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(52):e202201323
Electrocatalytic hydrogen gas production is considered a potential pathway towards carbon-neutral energy sources. However, the development of this technology is hindered by the lack of efficient, cost-effective, and environmentally benign catalysts. In this study, a main-group-element-based electrocatalyst, SbSalen , is reported to catalyze the hydrogen evolution reaction (HER) in an aqueous medium. The heterogenized molecular system achieved a Faradaic efficiency of 100 % at −1.4 V vs. NHE with a maximum current density of −30.7 mA/cm2. X-ray photoelectron spectroscopy of the catalyst-bound working electrode before and after electrolysis confirmed the molecular stability during catalysis. The turnover frequency was calculated as 43.4 s−1 using redox-peak integration. The kinetic and mechanistic aspects of the electrocatalytic reaction were further examined by computational methods. This study provides mechanistic insights into main-group-element electrocatalysts for heterogeneous small-molecule conversion. 相似文献
82.
Konstantinos Tsouvalas 《代数通讯》2018,46(8):3397-3412
We define Euler characteristics on classes of residually finite and virtually torsion free groups and we show that they satisfy certain formulas in the case of amalgamated free products and HNN extensions over finite subgroups. These formulas are obtained from a general result which applies to the rank gradient and the first L2?Betti number of a finitely generated group. 相似文献
83.
Morgan A. Higgins Christopher R. Maroon Jacob Townsend Xinyi Wang Konstantinos D. Vogiatzis Brian K. Long 《Journal of polymer science. Part A, Polymer chemistry》2020,58(18):2644-2653
Polymeric membranes have shown tremendous promise for the separation of CO2 from flue gas streams. However, few systematic studies have been conducted to better understand the impact that chemical functionalities have on membrane-based gas separation performance. To address this gap, we herein describe the synthesis and gas separation performance of a series of vinyl-addition polynorbornenes bearing various CO2-philic functional groups. To facilitate direct comparison between functional groups, each material was designed to maintain a common polymer backbone. Though the incorporation of CO2-philic moieties within a dense polymeric membrane is frequently hypothesized to enhance CO2 solubility, and thereby increase CO2/N2 selectivity, our results demonstrate that the incorporation of CO2-philic groups onto a common polymer backbone do not necessarily result in increased gas separation performance. Experimental and computational results demonstrate that the incorporation of amidoxime groups onto a polynorbornene backbone increase CO2/N2 selectivity, whereas commonly employed ethereal side chains only increased permeability. 相似文献
84.
Probing hemoglobin structure by means of traveling-wave ion mobility mass spectrometry 总被引:1,自引:0,他引:1
Charlotte A. Scarff Vibhuti J. Patel Konstantinos Thalassinos James H. Scrivens 《Journal of the American Society for Mass Spectrometry》2009,20(4):625-631
Hemoglobin (Hb) is a tetrameric noncovalent complex consisting of two α- and two β-globin chains each associated with a heme group. Its exact assembly pathway is a matter of debate. Disorders of hemoglobin
are the most common inherited disorders and subsequently the molecule has been extensively studied. This work attempts to
further elucidate the structural properties of the hemoglobin tetramer and its components. Gas-phase conformations of hemoglobin
tetramers and their constituents were investigated by means of traveling-wave ion mobility mass spectrometry. Sickle (HbS)
and normal (HbA) hemoglobin molecules were analyzed to determine whether conformational differences in their quaternary structure
could be observed. Rotationally averaged collision cross sections were estimated for tetramer, dimer, apo-, and holo-monomers
with reference to a protein standard with known cross sections. Estimates of cross section obtained for the tetramers were
compared to values calculated from X-ray crystallographic structures. HbS was consistently estimated to have a larger cross
section than that of HbA, comparable with values obtained from X-ray crystallographic structures. Nontetrameric species observed
included apo- and holo- forms of α- and β-monomers and heterodimers; α- and β-monomers in both apo- and holo- forms were found to have similar cross sections, suggesting they maintain a similar fold
in the gas phase in both the presence and the absence of heme. Heme-deficient dimer, observed in the spectrum when analyzing
commercially prepared Hb, was not observed when analyzing fresh blood. This implies that holo-α-apo-β is not an essential intermediate within the Hb assembly pathway, as previously proposed. 相似文献
85.
Aristidis E. Niotis Christos Mastichiadis Panagiota S. Petrou Ion Christofidis Athanasia Siafaka-Kapadai Konstantinos Misiakos Sotirios E. Kakabakos 《Analytical and bioanalytical chemistry》2009,393(3):1081-1086
An optical capillary waveguide fluoroimmunosensor based on glass capillaries internally coated with an ultrathin poly(dimethylsiloxane)
(PDMS) film is presented. The evaluation of the capillaries developed was done in comparison with aminosilanized [3-(aminopropyl)triethoxysilane,
APTES] glass and poly(methylpentene) (PMP) capillaries by immobilizing rabbit γ-globulins on the internal capillary wall.
Following reaction with (R)-phycoerythrin-labelled antibody, the capillary was scanned with a laser beam and the fluorescence waveguided through the
capillary wall was detected by a photomultiplier placed at one of its ends. The capillaries developed provided considerably
improved protein coating homogeneity (intracapillary coefficients of variation 2.9–6.6%) and repeatability (intercapillary
coefficients of variation 2.1–5.0%) compared with APTES-treated ones (7.9–13.4 and 8.5–15.2%, respectively). With use of these
capillaries in a sandwich-type immunosensor for the determination of rabbit γ-globulins, the assay detection limit was improved
eightfold (4.4 ng/mL) compared with that obtained using PMP capillaries (35.3 ng/mL), whereas the assay repeatability was
improved threefold (intra-assay coefficients of variation 5.9–13.1%) compared with APTES-treated capillaries (15.6–36%).
Optoelectronic set-up used to scan the capillaries (left) and representative fluorescence scannings of dual-band poly(methylpentene)
(PMP), PDMS-modified glass and APTES treated glass capillaries 相似文献
86.
Kararizou E Likomanos D Gkiatas K Markou I Triantafyllou N Kararizos G 《Magnetic resonance imaging》2006,24(2):205-207
Gliomatosis cerebri (GC) is characterized by a diffuse infiltration of neoplastic glial cells with preservation of neuronal architecture. It can be very difficult to diagnose during life because the clinical manifestations are protean and tests are often nondiagnostic. The diagnosis of GC needs to be based on radiological, clinical and pathological criteria. We present a patient with GC, which initially presented as acute stroke attack. We discuss the usefulness of noninvasive methods, such a MR spectroscopy, in the diagnosis, grading and management of GC. 相似文献
87.
Daniele Farrace Kyoungseoun Chung Michele Bolla Yuri M. Wright Konstantinos Boulouchos Epaminondas Mastorakos 《Combustion Theory and Modelling》2018,22(3):411-431
A finite volume large eddy simulation–conditional moment closure (LES-CMC) numerical framework for premixed combustion developed in a previous studyhas been extended to account for differential diffusion. The non-unity Lewis number CMC transport equation has an additional convective term in sample space proportional to the conditional diffusion of the progress variable, that in turn accounts for diffusion normal to the flame front and curvature-induced effects. Planar laminar simulations are first performed using a spatially homogeneous non-unity Lewis number CMC formulation and validated against physical-space fully resolved reference solutions. The same CMC formulation is subsequently used to numerically investigate the effects of curvature for laminar flames having different effective Lewis numbers: a lean methane–air flame with Leeff = 0.99 and a lean hydrogen–air flame with Leeff = 0.33. Results suggest that curvature does not affect the conditional heat release if the effective Lewis number tends to unity, so that curvature-induced transport may be neglected. Finally, the effect of turbulence on the flame structure is qualitatively analysed using LES-CMC simulations with and without differential diffusion for a turbulent premixed bluff body methane–air flame exhibiting local extinction behaviour. Overall, both the unity and the non-unity computations predict the characteristic M-shaped flame observed experimentally, although some minor differences are identified. The findings suggest that for the high Karlovitz number (from 1 to 10) flame considered, turbulent mixing within the flame weakens the differential transport contribution by reducing the conditional scalar dissipation rate and accordingly the conditional diffusion of the progress variable. 相似文献
88.
Orestis L. Katsamenis Vagelis Karoutsos Konstantinos Kontostanos Elias C. Panagiotopoulos Helen Papadaki Nikolaos Bouropoulos 《Crystal Research and Technology》2012,47(11):1201-1209
Meniscus is a fibrocartilaginous tissue composed mainly of water and a dense elaborate collagen network with a predominantly circumferential alignment. Crystal formation and accumulation on meniscal tissue is frequently observed especially in elderly. In this study, we used X‐ray diffraction (XRD), FTIR and FT‐Raman for the structural identification of the depositions and Optical microscopy, Scanning Electron microscopy (SEM/EDX) and Atomic Force microscopy (AFM), in order to investigate the structural relationship between the crystal deposits and the collagen fibers of human meniscal tissues. We are reporting on the formation of intercalary “colonies” of Calcium Pyrophosphate Dihydrate (CPPD) crystals with two distinct morphologies corresponding to the monoclinic and the triclinic phase, as well as the formation of micro‐aggregations composed of nano‐crystalline HAP aggregations which are developed along the longitudinal axis of collagen fibers without extensively disturbing the collagens arrangement. 相似文献
89.
Colodrero RM Olivera-Pastor P Losilla ER Hernández-Alonso D Aranda MA Leon-Reina L Rius J Demadis KD Moreau B Villemin D Palomino M Rey F Cabeza A 《Inorganic chemistry》2012,51(14):7689-7698
Multifunctional materials, especially those combining two or more properties of interest, are attracting immense attention due to their potential applications. MOFs, metal organic frameworks, can be regarded as multifunctional materials if they show another useful property in addition to the adsorption behavior. Here, we report a new multifunctional light hybrid, MgH(6)ODTMP·2H(2)O(DMF)(0.5) (1), which has been synthesized using the tetraphosphonic acid H(8)ODTMP, octamethylenediamine-N,N,N',N'-tetrakis(methylenephosphonic acid), by high-throughput methodology. Its crystal structure, solved by Patterson-function direct methods from synchrotron powder X-ray diffraction, was characterized by a 3D pillared open framework containing cross-linked 1D channels filled with water and DMF. Upon H(2)O and DMF removal and subsequent rehydration, MgH(6)ODTMP·2H(2)O (2) and MgH(6)ODTMP·6H(2)O (3) can be formed. These processes take place through crystalline-quasi-amorphous-crystalline transformations, during which the integrity of the framework is maintained. A water adsorption study, at constant temperature, showed that this magnesium tetraphosphonate hybrid reversibly equilibrates its lattice water content as a function of the water partial pressure. Combination of the structural study and gas adsorption characterization (N(2), CO(2), and CH(4)) indicates an ultramicroporous framework. High-pressure CO(2) adsorption data are also reported. Finally, impedance data indicates that 3 has high proton conductivity σ = 1.6 × 10(-3) S cm(-1) at T = 292 K at ~100% relative humidity with an activation energy of 0.31 eV. 相似文献
90.
The present work concerns with the investigation of the interior transmission problem, which is naturally associated to the
inverse elastic scattering problem of determining the support of an isotropic homogeneous penetrable body from a knowledge
of the time harmonic incident plane waves and the far-field patterns of the corresponding scattered wave-fields. Our approach
combines a boundary integral formulation of the problem and a compact perturbation argument to establish the discreteness
of the set of transmission eigenvalues and the well-posedness of the interior transmission problem under the most general
assumptions on the elastic parameters of the underlying media.
相似文献