4,097 research outputs found
orbiculata
No full textViola orbiculata (A. Gray) Geyer ex B.D.Jacks.violette orbiculairewestern round-leaved violetNorth Kootenay PassK. McFadyenHeading N. back to parking on RH side of trail; below Pinus contorta and Pinuc glauca cover1473Vaccinium scoparium, Fragaria virginiana, Populus tremuloides>3
Fluoride, bifluoride and trifluoromethyl complexes of iridium(I) and rhodium(I)
No full textThe ERC (Advanced Researcher Award FUNCAT to SPN), the EPSRC and Sasol (Stipend to BJT) are gratefully acknowledged for support.Herein we report robust methods for the preparation and full characterisation of a range of Ir(I) and Rh(I) fluoride and bifluoride complexes using N-heterocyclic carbenes (NHCs) as ancillary ligands. The processes that link the fluoride and the bifluoride species are investigated and reports of the first Ir–bifluoride and Ir(I)–NHC and Rh(I)–NHC trifluoromethyl complexes are revealed.Peer reviewe
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
Dose-Dependent Effect of GABAA System on Antinociception Actions of Cuneiformis Nucleus in Brain Stem
No full textBackground and Objective: It's been established that midbrain region namely rostral ventromedial medulla (RVM) is the coring point of modulation of pain. It's well been documented that periaqueductal gray (PAG) matter is having an antinociception effect along with RVM. However, there are evidences demonstrating that RVM get a few connections from the cuneiformsnucleus (CnF) which might indicate CnF does have the same mechanism as PAG. Thus in this study, we are to explore the antinociception effects of CnF and GABAA circuits.
Methods: Rats were anesthetized with Thiopental drug. Using the stereotaxic apparatus and Paxinos atlas, the point representing for CnF location over the scalp has been designated. Following a week after the surgery, rats were now fully prepared for tests. Animals were chosen to be in three groups. First for control group, 0.5 µl of normal saline was injected into the CnF. Later, a few nanograms of bicucculline (as a GABAA antagonist) were administered into the CnF, dose dependently.
Results: From the results, it has been shown that CnF has a role in antinociception effect and it is because the injection of bicucculline has increased tail flick latency (TFL) and even further increased TFL when administered dose dependently (with high doses).
Conclusion: According to results of current study, CnF has a significant role in pain modulation and circuits of GABAergic system have also played a key role on its antinociception effect
Maternal Use of Antibiotics and the Risk of Childhood Febrile Seizures: A Danish Population-Based Cohort
No full textOBJECTIVE: In a large population-based cohort in Denmark to examine if maternal use of antibiotics during pregnancy, as a marker of infection, increases the risk of febrile seizures in childhood in a large population-based cohort in Denmark. METHODS: All live-born singletons born in Denmark between January 1, 1996 and September 25, 2004 and who were alive on the 90(th) day of life were identified from the Danish National Birth Registry. Diagnoses of febrile seizures were obtained from the Danish National Hospital Register and maternal use of antibiotics was obtained from the National Register of Medicinal Product Statistics. Hazard ratios (HR) and 95% confidence intervals (95% CI) were estimated by Cox proportional hazard regression models. RESULTS: We followed 551,518 singletons for up to 5 years and identified a total of 21,779 children with a diagnosis of febrile seizures. Slightly increased hazard ratios were observed among most exposure groups when compared to the unexposed group, ex. HR 1.08 95% CI: 1.05-1.11 for use of any systemic antibiotic during pregnancy. CONCLUSION: We found weak associations between the use of pharmacologically different antibiotics during pregnancy and febrile seizures in early childhood which may indicate that some infections, or causes or effects of infections, during pregnancy could affect the fetal brain and induce susceptibility to febrile seizures
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
Conformational Changes of the Predicted TASSER Models from the Crystal Structure of Bovine RH
No full text<div><p>Data are the average from those targets where bovine RH is a template with C-score greater than 1.3 (red diamonds). The green triangles denote the TASSER model for bovine RH when bovine RH itself is used as the template (ten missed residues in 1f88 are inserted in the TASSER modeling). This shows the inherent resolution of the TASSER model.</p><p>(A) Average distance of each residue of the TASSER models from the bovine RH template along the sequence. TM helices are marked in gray.</p><p>(B) Percentage of all helices with helix angle changes below the indicated thresholds.</p></div
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