4,096 research outputs found
RH-RT: A Data Analytics Framework for Reducing Wait Time at Emergency Departments and Centres for Urgent Care
No full textRight Hospital – Right Time (RH-RT) is the conceptualization of the use of descriptive, predictive and prescriptive analytics with real-time data from Accident & Emergency (A&E)/Emergency Departments (ED) and centers for urgent care; its objective is to derive maximum value from wait time data by using data analytics techniques, and making them available to both patients and healthcare organizations. The paper presents an architecture for the implementation of RH-RT that is specific to the authors’ current work on a digital platform (NHSquicker) that makes available live waiting time from multiple centers of urgent care (e.g., A&E/ED, Minor Injury Units) in Devon and Cornwall. The focus of the paper is on the development of a Hybrid Systems Model (HSM) comprising of healthcare business intelligence, forecasting techniques and computer simulation. The contribution of the work is the conceptual RH-RT framework and its implementation architecture that relies on near real-time data from NHSquicker
Challenging the Major/Minor Concept in Rh-Catalyzed Asymmetric Hydrogenation
No full textHerein, we provide evidence showing
that the long-held major–minor
concept for catalytic asymmetric reactions needs to be readdressed.
The asymmetric hydrogenation of enamide <b>1</b> catalyzed by
the chiral Rh(I) complex of (<i>R</i>,<i>R</i>)-BenzP* quantitatively yields the corresponding hydrogenated <i>R</i>-product <b>2</b> with 89.6% ee. The most abundant
catalyst–substrate species in the reaction pool was found to
be [Rh((<i>R</i>,<i>R</i>)-BenzP*)(Ph(MeCONH)CCH<sub>2</sub>)]<sup>+</sup>SbF<sub>6</sub><sup>–</sup> (<b>5</b>). This species is also the most reactive to hydrogen among the various
Rh complexes. Low-temperature hydrogenation experiments showed direct
transformation of <b>5</b> to <b>2</b> with over 98% ee
(<i>R</i>). However, the oxidative addition of H<sub>2</sub> to <b>5</b> would yield the <i>S</i>-product. Computation
has now revealed a low-energy <i>R</i>-enantioselective
route, whereby H<sub>2</sub> addition to <b>5</b> is followed
by π-bond dissociation, isomerization of nonchelating Rh species,
and recoordination of the double bond before C–H bond formation
occurs
Unveiling the Structure Sensitivity for Direct Conversion of Syngas to C2-Oxygenates with a Multicomponent-Promoted Rh Catalyst
No full textAbstract: Mn and Li promoted Rh catalysts supported on SiO2 with a thin TiO2 layer were synthesized by stepwise incipient wetness impregnation approach. The thin TiO2 layer on the surface of SiO2 was proved to stabilize those small Rh nanoparticles and hinder their agglomeration. The reducibility of Rh on these catalysts depends on Rh particle size as well as the position of manganese oxide, and large Rh nanoparticles with MnO on Rh nanoparticles can be only reduced at an elevated temperature. Catalyst with large Rh particles exhibits a higher CO conversion and higher products selectivity towards long chain hydrocarbons and C2-oxygenates at the expense of decreasing methane formation than a similar catalyst with smaller Rh particles. This was attributed to the synergistic effect of Mn and Li promotion and molar ratio between Rh0 and Rhδ+ sites on the surface of Rh nanoparticles. Moreover, Rh nanoparticles on MnO are proved to be more efficient in promoting hydrogenation of acetaldehyde to ethanol than its counterpart with MnO on Rh nanoparticles. Finally, in order to target high C2-oxygenates selectivity, low reaction temperature together with a low H2/CO ratio in the feed is recommended. Graphic Abstract: [Figure not available: see fulltext.].ChemE/Catalysis EngineeringChemE/O&O groe
Computational Exploration of Rh-III/Rh-V and Rh-III/Rh-I Catalysis in Rhodium(III)-Catalyzed C-H Activation Reactions of N-Phenoxyacetamides with Alkynes
No full textThe selective rhodium-catalyzed functionalization of arenes is greatly facilitated by oxidizing directing groups that, act both as directing groups and internal oxidants. We report density functional theory (B3LYP and M06) investigations on the mechanism of rhodium(III)-catalyzed redox coupling reaction of N-phenoxyacetamides with alkynes. The results elucidated the role of the internal oxidizing directing group, and the role of Rh-III/Rh-I and Rh-III/Rh-V catalysis of C-H functionalizations. A novel Rh-III/Rh-V-Rh-III cycle successfully rationalizes recent experimental observations by Liu and Lu et al. (Liu, G. Angew. Chem. Int. Ed. 2013, 52, 6033) on the reactions of N-phenoxyacetamides with alkynes in different solvents. Natural Bond Orbital (NBO) analysis confirms the identity of Rhy intermediate in the catalytic cycle.National Natural Science Foundation of China [21133002, 21203004]; Shenzhen Peacock Program [KQTD201103]; National Science Foundation of the USA [CHE-1361104]; National Science Foundation under the CCI Center for Selective C-H Functionalization [CHE-1205646]; National Science Foundation [OCI-1053575]SCI(E)[email protected]; [email protected]
Solvent effects in heterogeneous selective hydrogenation of acetophenone: differences between Rh/C and Rh/Al2O3 catalysts and the superiority of water as a functional solvent
No full textSelective hydrogenation of acetophenone (AP) to 1-phenylethanol (PhE) was investigated over Rh/Al2O3 and Rh/C catalysts in 13 solvents including water and conventional organic solvents. Strong solvent effects on the overall rate of AP conversion were observed in different manners depending on the catalysts used. The conversion obtained is correlated with hydrogen-bond-donation (HBD) capability for Rh/C but with hydrogen-bond-acceptance (HBA) capacity for Rh/Al2O3. The solvent effects should result from interactions between the carbonyl group of AP and the solvent molecules through hydrogen bonding for Rh/C and from those between the solvent molecules and the catalyst surface for Rh/Al2O3 having HBD hydroxyl groups on its surface. Water is the most effective functional solvent in the selective hydrogenation of AP for C and Al2O3-supported Rh catalysts due to its high HBD capability (a) and low HBA capability (beta), respectively. For the hydrogenation with Rh/Al2O3 in water, its large polarity/polarizability index (pi*) may contribute to the high selectivity to PhE
Adverse effects of potassium on NO<sub>x</sub> reduction over Di-Air catalyst (Rh/La-Ce-Zr)
No full textThe influence of potassium in Rh on a lanthium promoted zirconia stablised ceria (CZ) catalysts was studied toward NOxreduction reactivity and selectivity. The results are compared with a Rh/CZ catalyst. The samples were characterised by N2 adsorption, XRD, SEM, ICP, and H2-TPR. The study highlighted the importance of stored NOx regeneration over potassium in determining the overall performance of the Rh/K/CZ catalyst. The NOx stored over Rh/K/CZ in the previous NO gas stream cannot be regenerated sufficiently during the C3H6 gas stream, and stored NOxgradually decreased from one cycle to the next, resulting in deteriorating performance of Rh/K/CZ. Besides, problem of NOx slip, the formation of both NH3 and N2O (selectivities up to 30% for each side product) were observed by the addition of potassium into the Rh/CZ catalyst system, depending on the reaction conditions applied and the severity of the catalyst deactivation.</p
Structure-function relationship during CO2 methanation over Rh/Al2O3 and Rh/SiO2 catalysts under atmospheric pressure conditions
No full textThe effect of the support material and chemical state of Rh in Rh/A2O3 and Rh/SiO2 model catalysts during CO2 hydrogenation were studied by a combined array of in situ characterisation techniques including diffuse reflectance infrared Fourier transform spectroscopy, energy-dispersive X-ray absorption spectroscopy and high-energy X-ray diffraction at 250-350 °C and atmospheric pressure. CO2 methanation proceeds via intermediate formation of adsorbed CO species on metallic Rh, likely followed by their hydrogenation to methane. The linearly-bonded CO species is suggested to be a more active precursor in the hydrogenation compared to the bridge-bonded species, which seems to be related to particle size effects: for larger particles mainly the formation of inactive bridge-bonded CO species takes place. Further, analysis of the chemical state of Rh under the reaction conditions reveal a minor formation of RhOx from dissociation of CO2, which is a consequence of the increased activity observed over the Rh/Al2O3 catalyst
Rh promoted In2O3 as a highly active catalyst for CO2 hydrogenation to methanol
No full textSynthesis of methanol with high selectivity and productivity through hydrogenation of CO2 is highly attractive. This work uses a Rh doped In2O3 catalyst to achieve a high methanol productivity of 1.0 g(MeOH) h(-1) g(cat)(-1) while maintaining the intrinsic high selectivity of pure In2O3. Rh facilitated the dissociation of H-2 leading to creation of oxygen vacancies over the In2O3 surface. In addition, Rh atoms also participated in the activation of CO2 to produce formate species with a low activation barrier as evidenced by DFT calculation. Rh species were atomically dispersed in the In2O3 matrix and were stable during a long term reaction. Under reaction conditions, the surface Rh atoms were reduced and were stabilized by charge transfer from neighbouring In atoms. Our results show that incorporation of atomic Rh species in In2O3 can lead to high methanol productivity by creation of oxygen vacancies as well as Rh centred active sites for CO2 activation
Development of interior relative humidity due to self-desiccation in blended cementitious system
No full textIn engineering practise, interior relative humidity (RH) of concrete significantly affects the transport properties and thus the service life of concrete structures. In this paper, the development of RH due to self-desiccation in blended cement pastes was studied from 1 day to 1.5 years. The pore structure and non-evaporable water content at same ages were determined by mercury intrusion porosimetry and thermogravimetric analysis, respectively. The results revealed that interior RH was significantly reduced at the first 105 days’ curing and falls off slightly afterwards, regardless of water to binder ratios and type of blends. Compared to ordinary Portland cement (OPC) paste, the OPC paste blended with slag shows much lower interior RH, whereas the addition of fly ash slightly increases the interior RH. Minor amount of limestone addition i.e., 5% wt. greatly increases the RH in ternary system consisting of OPC, slag and limestone, whilst slightly decreases the RH in OPC paste blended with fly ash. In the presence of blends, high total porosity corresponds to low interior RH. In case of self-desiccation, it is concluded that interior RH is mainly controlled by average pore size in the cement-based materials.Materials and Environmen
Rh(III)-Photosensitized Interconversion of Norbornadiene and Quadricyclane
No full textThe utility of two Rh(III) diimine complexes,
Rh(phen)33+ and
Rh(phi)2(phen)3+ (phen =
1,10-phenanthroline,
phi = 9,10-phenanthrenequinone diimine), as sensitizers for the
interconversion of norbornadiene (N) and
quadricyclane (Q) has been investigated using steady-state
photochemical and laser flash photolysis (LFP)
techniques. Irradiation of acetonitrile solutions of
Rh(phen)33+ and N causes slow
conversion to Q. The
reaction is reversible; irradiation of
Rh(phen)33+ in the presence of
Q leads to N. Irradiation of
acetonitrile
solutions of Rh(phi)2(phen)3+ and
Q yields N. However, this reaction is
irreversible; irradiation of the Rh(III) complex in the presence of N fails to afford
Q. Irradiation of methanol solutions of either
Rh(III)
complex in the presence of N or Q affords minor
amounts of two methanol-C7 adducts but fails to quench
the N−Q interconversion reaction. The
results are consistent with N−Q interconversion
via an exciplex
intermediate. The Rh(III)-sensitized deazatization of two
cyclic azoalkane derivatives (Azo-N, Azo-Q) of
N
and Q was also investigated. Deazatization was achieved
by Rh(phen)33+ but not
Rh(phi)2(phen)3+
sensitization.
The results are consistent with a mechanism involving triplet
energy transfer, but the involvement of exciplex
intermediates cannot be ruled out. Bimolecular rate constants for
quenching of the Rh(III) excited states by
N, Q, Azo-N, and Azo-Q were
determined by LFP
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