Efficient Alkyne Semihydrogenation Catalysis Enabled by Synergistic Chemical and Thermal Modifications of a PdIn MOF

Recently, there has been a growing interest in using MOF templating to synthesize heterogeneous catalysts based on metal nanoparticles on carbonaceous supports. Unlike the common approach of direct pyrolysis of PdIn-MOFs at high temperatures, this work proposes a reductive chemical treatment under mild conditions before pyrolysis (resulting in PdIn-QT). The resulting material (PdIn-QT) underwent comprehensive characterization via state-of-the-art aberration-corrected electron microscopy, N2 physisorption, X-ray absorption spectroscopy, Raman, X-ray photoelectron spectroscopy, and X-ray diffraction. These analyses have proven the existence of PdIn bimetallic nanoparticles supported on N-doped carbon. In situ DRIFT spectroscopy reveals the advantageous role of indium (In) in regulating Pd activity in alkyne semihydrogenation. Notably, incorporating a soft nucleation step before pyrolysis enhances surface area, porosity, and nitrogen content compared to direct MOF pyrolysis. The optimized material exhibits outstanding catalytic performance with 96% phenylacetylene conversion and 96% selectivity to phenylethylene in the fifth cycle under mild conditions (5 mmol phenylacetylene, 7 mg cat, 5 mL EtOH, R.T., 1 H2 bar).

Structure sensitivity reaction of chloroform hydrodechlorination to light olefins using Pd catalysts supported on carbon nanotubes and carbon nanofibers

The upgrading of wasted chloroform in hydrodechlorination for the production of olefins such as ethylene and propylene is studied by employing four catalysts (PdCl/CNT, PdCl/CNF, PdN/CNT, and PdN/CNF) prepared by different precursors (PdCl₂ and Pd(NO₃)₂) supported on carbon nanotubes (CNT) or carbon nanofibers (CNF). TEM and EXAFS-XANES results confirm that Pd nanoparticle size increases in the order: PdCl/CNT < PdCl/CNF ∼ PdN/CNT < PdN/CNF, descending the electron density of Pd nanoparticles in the same order. It illustrates that PdCl-based catalysts show donation of electrons from support to Pd nanoparticles, which is not observed in PdN-based catalysts. Moreover, this effect is more evident in CNT. The smallest and well-dispersed Pd nanoparticles (NPs) on PdCl/CNT with high electron density favor an excellent and stable activity and a remarkable selectivity to olefins. In contrast, the other three catalysts show lower selectivity to olefins and lower activities which suffer strong deactivation due to the formation of Pd carbides on their larger Pd nanoparticles with lower electron density, compared to PdCl/CNT.

Structural evolution after oxidative pretreatment and CO oxidation of Au nanoclusters with different ligand shell composition: a view on the Au core

The reactivity of supported monolayer protected Au nanoclusters is directly affected by their structural dynamics under pretreatment and reaction conditions. The effect of different types of ligands of Au clusters supported on CeO₂ on their core structure evolution, under oxidative pretreatment and CO oxidation reaction, was investigated. X-ray absorption and X-ray photoelectron spectroscopy studies revealed that the clusters evolve to a similar core structure above 250 °C in all the cases, indicating the active role of the ligand-support interaction in the reaction.

Rhodium Single-Atom Catalyst Design through Oxide Support Modulation for Selective Gas-Phase Ethylene Hydroformylation

A frontier challenge in single-atom (SA) catalysis is the design of fully inorganic sites capable of emulating the high reaction selectivity traditionally exclusive of organometallic counterparts in homogeneous catalysis. Modulating the direct coordination environment in SA sites, via the exploitation of the oxide support's surface chemistry, stands as a powerful albeit underexplored strategy. We report that isolated Rh atoms stabilized on oxygen-defective SnO₂ uniquely unite excellent TOF with essentially full selectivity in the gas-phase hydroformylation of ethylene, inhibiting the thermodynamically favored olefin hydrogenation. Density Functional Theory calculations and surface characterization suggest that substantial depletion of the catalyst surface in lattice oxygen, energetically facile on SnO₂ , is key to unlock a high coordination pliability at the mononuclear Rh centers, leading to an exceptional performance which is on par with that of molecular catalysts in liquid media.

Upfront transoral robotic surgery (TORS) versus intensity-modulated radiation therapy (IMRT) in HPV-positive oropharyngeal cancer: real-world data from a tertiary comprehensive cancer center

Objective

Methods

Results

Conclusions

Clinical and radiographical outcome after surgical treatment of periprosthetic type B proximal femur fractures: a retrospective study

PURPOSE

Periprosthetic fractures after hip prosthesis represent a constantly increasing clinical problem and a challenging complication to treat surgically. Among these, type B proximal femur fractures should be diagnosed correctly to be treated surgically. The aim of this study was to re-evaluate the type of surgical treatment of periprosthetic fractures.

METHODS

We examined the cases treated between January 2012 and February 2018, classifying them according to the U.C.S. AO/OTA. We evaluated the radiographic outcome according to the Beals and Tower criteria. Patients still alive were also re-evaluated according to the H.H.S. and the WOMAC score.

RESULTS

We treated 48 patients (12 men, 35 women, average age 81 years), divided into 24 type B1, 14 type B2 and 10 type B3 fractures. The overall consolidation rate was 95.4%, while the major complication (implant dislocation, pseudoarthrosis and deep infection) rate was 12.5%. Clinically, it was possible to reassess 34 patients with a mean follow-up of 38.4 months, an average HHS of 75.89 and a mean WOMAC score of 79.93.

CONCLUSIONS

Periprosthetic type B fractures are difficult to manage and require careful preoperative planning and appropriate intraoperative management. However, the overall clinical and radiographic result was satisfactory, although patients should still be aware of the risk of complications associated with this type of fracture.

Persistent postural perceptual dizziness following paroxysmal positional vertigo in migraine

Objective

This prospective study aimed to investigate the role of migraine in favouring the onset of persistent postural perceptual dizziness (PPPD) following paroxysmal positional vertigo (PPV).

Methods

A group of patients who came to our attention suffering of PPV with or without migraine and/or vestibular migraine (VM) was examined. Three months after the resolution, an anamnestic research was conducted aimed at establishing whether any patient-related dizziness could meet the diagnostic criteria for PPPD.

Results

12 of the 240 patients recruited met the diagnostic criteria for PPPD for an overall incidence of 5%, with 3 (1.85%) belonging to the non-migraine group and 9 (11.5%) to the migraine group. In the latter, 6 (28.6%) patients with VM and 3 (5.26%) without VM were affected.

Conclusions

The study shows a significant increase of PPPD diagnosis in migraine compared to patients without migraine (p = 0.003). Within migraine there was a significant increase in those with VM compared to patients without VM (p = 0.0016). No difference emerged between patients without migraine and migraine patients without VM (p > 0.05). The presence of VM in patient’s history, but not migraine without VM, appears to significantly increase the incidence of PPPD in patients with PPV.

Local structural distortions in SnTe investigated by EXAFS

Extended x-ray absorption fine structure (EXAFS) has been measured at theKedge of Sn in SnTe in the temperature range from 5 to 480 K. EXAFS results are consistent with the presence of a local rhombohedral distortion in the full temperature range from 5 to 300 K, even well above the ferroelectric transition temperature, suggesting a partial order-disorder character of the transition. At and above 300 K, the anomalous behaviour of the third and fourth EXAFS cumulants reveals a modification of the anharmonicity of the effective pair potential, possibly connected with the softening of high frequency modes or to the presence of multiple phases.

Local Structures of Oxygen-Deficient Perovskite Sr2ScGaO5 Polymorphs Explored by Total Neutron Scattering and EXAFS Spectroscopy

Depending on the synthesis route, the oxygen ion electrolyte Sr₂ScGaO₅ shows two polymorphs, a brownmillerite and a cubic perovskite framework. In order to better explore oxygen diffusion pathways and mechanisms, we report here on a multitechnical approach to characterize local structural changes for Sr₂ScGaO₅ polymorphs as a function of temperature, using a neutron pair distribution function (PDF) analysis together with an extended X-ray absorption fine structure (EXAFS) analysis. While for the brownmillerite type structure PDF and Rietveld refinements yield identical structural descriptions, considerable differences are found for the cubic oxygen-deficient polymorph. On a local scale a brownmillerite type vacancy structure could be evidenced for the cubic phase, suggesting a complex short-range ordering and respective microstructure. Both PDF and EXAFS data confirm an octahedral and tetrahedral coordination for Sc and Ga, respectively, at a local scale for both polymorphs. Related changes in the bond distances and oxygen vacancy ordering are discussed.

Head-Shaking Nystagmus in the Early Stage of Unilateral Meniere's Disease

OBJECTIVES

The aim of the present study was to evaluate the ability of head-shaking nystagmus (HSNy), evoked after the resolution of a vertigo spell, to predict an imminent crisis in the early stage of Meniere's disease (MD).

MATERIALS AND METHODS

A total of 20 patients in the early stage of MD were included in the study. The head-shaking test (HST) was performed twice, during the first visit within 24 h of vertigo spell (T0) and 48 h later (T1). The onset of a new vertigo episode during the 2 weeks following the first visit was recorded in each patient's medical record. The sensitivity and specificity of HSNy toward predicting a new vertigo episode were calculated.

RESULTS

At T0, an evoked ipsilesional HSNy in 15 (75%) patients was observed; in four of them, the HSNy had a biphasic component. The HSNy was present and persistent at T1 in 8 (42.1%) patients; among these cases, 6 patients had ipsilesional HSNy, and 2 patients a contralesional HSNy. None of the patients presented with a biphasic HSNy at T1. Seven (36.8%) patients experienced the recurrence of a vertigo crisis. Among these, 6 patients had ipsilesional HSNy at T1. Only 8 patients with ipsilesional HSNy at T0 did not have recurrence. The sensitivity of the ipsilesional HSNy in predicting the recurrence of vertigo in patients with MD was 100% at T0 and 85.7% at T1. The specificity was 46.6% and 100% at T0 and T1, respectively.

CONCLUSION

The HST can be a useful test in the early stages of MD to predict a new vertigo attack.

Intravenous vitamin K1 normalises prothrombin time in 1 hour in dogs with anticoagulant rodenticide toxicosis

Four dogs with anticoagulant rodenticide toxicosis were treated with intravenous vitamin K₁ in lieu of plasma transfusion due to client cost constraints. Two dogs experienced a suspected anaphylactoid reaction, necessitating cessation of the treatment in one dog. Prothrombin time was rechecked 1 h after treatment in the remaining three dogs and all results were within the normal reference range. All four dogs were discharged from hospital within 48 h of presentation. Intravenous vitamin K₁ rapidly reverses the coagulopathic state in dogs with anticoagulant rodenticide toxicosis. It is a viable alternative therapy to plasma transfusion if circumstances preclude its use; however, patients must be monitored for anaphylactoid reactions.

One-Pot Cooperation of Single-Atom Rh and Ru Solid Catalysts for a Selective Tandem Olefin Isomerization-Hydrosilylation Process

Realizing the full potential of oxide‐supported single‐atom metal catalysts (SACs) is key to successfully bridge the gap between the fields of homogeneous and heterogeneous catalysis. Here we show that the one‐pot combination of Ru₁/CeO₂ and Rh₁/CeO₂ SACs enables a highly selective olefin isomerization‐hydrosilylation tandem process, hitherto restricted to molecular catalysts in solution. Individually, monoatomic Ru and Rh sites show a remarkable reaction specificity for olefin double‐bond migration and anti‐Markovnikov α‐olefin hydrosilylation, respectively. First‐principles DFT calculations ascribe such selectivity to differences in the binding strength of the olefin substrate to the monoatomic metal centers. The single‐pot cooperation of the two SACs allows the production of terminal organosilane compounds with high regio‐selectivity (>95 %) even from industrially‐relevant complex mixtures of terminal and internal olefins, alongside a straightforward catalyst recycling and reuse. These results demonstrate the significance of oxide‐supported single‐atom metal catalysts in tandem catalytic reactions, which are central for the intensification of chemical processes.

Pd–Au bimetallic catalysts supported on ZnO for selective 1,3-butadiene hydrogenation

The effect of the ZnO morphology on the properties of Pd–Au bimetallic catalysts has been discussed.

Nature and evolution of Pd catalysts supported on activated carbon fibers during the catalytic reduction of bromate in water

Pd/ACF are active catalysts for the bromate reduction and their activity depends on the Pd crystal size with a pseudo-first order kinetic respect to BrO₃⁻ and H₂ partial pressure.

Use of Alkylarsonium Directing Agents for the Synthesis and Study of Zeolites

Expanding the previously known family of -onium (ammonium, phosphonium, and sulfonium) organic structure-directing agents (OSDAs) for the synthesis of zeolite MFI, a new member, the arsonium cation, is used for the first time. The new group of tetraalkylarsonium cations has allowed the synthesis of the zeolite ZSM-5 with several different chemical compositions, opening a route for the synthesis of zeolites with a new series of OSDA. Moreover, the use of As replacing N in the OSDA allows the introduction of probe atoms that facilitate the study of these molecules by powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (MAS NMR), and X-ray absorption spectroscopy (XAS). Finally, the influence of trivalent elements such as B, Al, or Ga isomorphically replacing Si atoms in the framework structure and its interaction with the As species has been studied. The suitability of the tetraalkylarsonium cation for carrying out the crystallization of zeolites is demonstrated along with the benefit of the presence of As atoms in the occluded OSDA, which allows its advanced characterization as well as the study of its evolution during OSDA removal by thermal treatments.

Single-use, patient-specific instrumentation technology in knee arthroplasty: a comparative study between standard instrumentation and PSI efficiency system

Patient-specific instrumentation is a surgical technique that was created to improve the accuracy of implantation, surgical time and workflow in total knee arthroplasty. This study is a single-center, single-surgeon randomized clinical trial. The aim of this work was to evaluate clinical efficacy of PSI versus standard surgical instrumentation in malalignment risk and blood loss reduction. From April 2015 to September 2016, 40 patients for a total of 40 knees were included in the randomization process. Each patient underwent CT scan of the lower limb including hip, knee and ankle joint with the realization of the PSI system and the TKA with Medacta GMK Primary^®. Patients were evaluated 1 month after surgery with X-ray and after 2 months with clinical examination and assessment by Knee Society Score (KSS). Blood loss was detected by adding the values calculated in the operative room and the blood loss in the vacuum systems. In the study group, mean value of KSS was 85.2 (IC 95% 81.2-88.5), mean blood loss was 657 ml (IC 95% 580.6-735.4), and mean value of femorotibial angle was 178.8° (IC 95% 178.5-179.3). In the control group, mean value of KSS was 87.2 (IC 95% 85.3-89.4), mean blood loss was 866.5 ml (IC 95% 763.3-972.5), and mean value of femorotibial angle was 178.9°(IC 95% 177.6-180.3). The Student t test detected a significant difference in blood loss between groups (p < 0.05), and no differences were found between KSS. The single-use instrumentation should improve precision, operative time, turnover time, sterilization and maintenance costs and could help to reduce infection risks. Our results confirm only the improvement on reducing blood loss. In our opinion, this technique should be used in selected patients when the surgeon could have some difficulties to perform femoral cuts on coronal plane or when patients need to have a very little blood loss due to other conditions.

A flexible cell for in situ combined XAS-DRIFTS-MS experiments

A new cell for in situ combined X-ray absorption, diffuse reflectance IR Fourier transform and mass spectroscopies (XAS-DRIFTS-MS) is presented. The cell stands out among others for its achievements and flexibility. It is possible to perform XAS measurements in transmission or fluorescence modes, and the cell is compatible with external devices like UV-light and Raman probes. It includes different sample holders compatible with the different XAS detection modes, different sample forms (free powder or self-supporting pellet) and different sample loading/total absorption. Additionally, it has a small dead volume and can operate over a wide range of temperature (up to 600°C) and pressure (up to 5 bar). Three research examples will be shown to illustrate the versatility of the cell. This cell covers a wider range of applications than any other cell currently known for this type of study.

Tuning Pt and Cu sites population inside functionalized UiO-67 MOF by controlling activation conditions

The exceptional thermal and chemical stability of the UiO-66, -67 and -68 classes of isostructural MOFs [J. Am. Chem. Soc., 2008, 130, 13850] makes them ideal materials for functionalization purposes aimed at introducing active centres for potential application in heterogeneous catalysis. We previously demonstrated that a small fraction (up to 10%) of the linkers in the UiO-67 MOF can be replaced by bipyridine-dicarboxylate (bpydc) moieties exhibiting metal-chelating ability and enabling the grafting of Pt(ii) and Pt(iv) ions in the MOF framework [Chem. Mater., 2015, 27, 1042] upon interaction with PtCl₂ or PtCl₄ precursors. Herein we extend this functionalization approach in two directions. First, we show that by controlling the activation of the UiO-67-Pt we can move from a material hosting isolated Pt(ii) sites anchored to the MOF framework with Pt(ii) exhibiting two coordination vacancies (potentially interesting for C-H bond activation) to the formation of very small Pt nanoparticles hosted inside the MOF cavities (potentially interesting for hydrogenation reactions). The second direction consists of the extension of the approach to the insertion of Cu(ii), obtained via interaction with CuCl₂, and exhibiting interesting redox properties. All materials have been characterized by in situ X-ray absorption spectroscopy at the Pt L₃- and Cu K-edges.

A robust iron catalyst for the selective hydrogenation of substituted (iso)quinolones

By applying N-doped carbon modified iron-based catalysts, the controlled hydrogenation of N-heteroarenes, especially (iso)quinolones, is achieved. Crucial for activity is the catalyst preparation by pyrolysis of a carbon-impregnated composite, obtained from iron(ii) acetate and N-aryliminopyridines. As demonstrated by TEM, XRD, XPS and Raman spectroscopy, the synthesized material is composed of Fe(0), Fe3C and FeN x in a N-doped carbon matrix. The decent catalytic activity of this robust and easily recyclable Fe-material allowed for the selective hydrogenation of various (iso)quinoline derivatives, even in the presence of reducible functional groups, such as nitriles, halogens, esters and amides. For a proof-of-concept, this nanostructured catalyst was implemented in the multistep synthesis of natural products and pharmaceutical lead compounds as well as modification of photoluminescent materials. As such this methodology constitutes the first heterogeneous iron-catalyzed hydrogenation of substituted (iso)quinolones with synthetic importance.

XAS/DRIFTS/MS spectroscopy for time-resolved operando investigations at high temperature

The combination of complementary techniques in the characterization of catalysts under working conditions is a very powerful tool for an accurate and in-depth comprehension of the system investigated. In particular, X-ray absorption spectroscopy (XAS) coupled with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectroscopy (MS) is a powerful combination since XAS characterizes the main elements of the catalytic system (selecting the absorption edge) and DRIFTS monitors surface adsorbates while MS enables product identification and quantification. In the present manuscript, a new reactor cell and an experimental setup optimized to perform time-resolved experiments on heterogeneous catalysts under working conditions are reported. A key feature of this setup is the possibility to work at high temperature and pressure, with a small cell dead volume. To demonstrate these capabilities, performance tests with and without X-rays are performed. The effective temperature at the sample surface, the speed to purge the gas volume inside the cell and catalytic activity have been evaluated to demonstrate the reliability and usefulness of the cell. The setup capability of combining XAS, DRIFTS and MS spectroscopies is demonstrated in a time-resolved experiment, following the reduction of NO by Rh nanoparticles supported on alumina.

Intermetallic nickel silicide nanocatalyst-A non-noble metal-based general hydrogenation catalyst

Hydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds including fine chemicals, agrochemicals, and pharmachemicals. On an industrial scale, hydrogenations are typically performed with precious metal catalysts or with base metal catalysts, such as Raney nickel, which requires special handling due to its pyrophoric nature. We report a stable and highly active intermetallic nickel silicide catalyst that can be used for hydrogenations of a wide range of unsaturated compounds. The catalyst is prepared via a straightforward procedure using SiO₂ as the silicon atom source. The process involves thermal reduction of Si-O bonds in the presence of Ni nanoparticles at temperatures below 1000°C. The presence of silicon as a secondary component in the nickel metal lattice plays the key role in its properties and is of crucial importance for improved catalytic activity. This novel catalyst allows for efficient reduction of nitroarenes, carbonyls, nitriles, N-containing heterocycles, and unsaturated carbon-carbon bonds. Moreover, the reported catalyst can be used for oxidation reactions in the presence of molecular oxygen and is capable of promoting acceptorless dehydrogenation of unsaturated N-containing heterocycles, opening avenues for H₂ storage in organic compounds. The generality of the nickel silicide catalyst is demonstrated in the hydrogenation of over a hundred of structurally diverse unsaturated compounds. The wide application scope and high catalytic activity of this novel catalyst make it a nice alternative to known general hydrogenation catalysts, such as Raney nickel and noble metal-based catalysts.

CO Hydrogenation on Cobalt-Based Catalysts: Tin Poisoning Unravels CO in Hollow Sites as a Main Surface Intermediate

Site poisoning is a powerful method to unravel the nature of active sites or reaction intermediates. The nature of the intermediates involved in the hydrogenation of CO was unraveled by poisoning alumina-supported cobalt catalysts with various concentrations of tin. The rate of formation of the main reaction products (methane and propylene) was found to be proportional to the concentration of multi-bonded CO, likely located in hollow sites. The specific rate of decomposition of these species was sufficient to account for the formation of the main products. These hollow-CO are proposed to be main reaction intermediates in the hydrogenation of CO under the reaction conditions used here, while linear CO are mostly spectators.

An in situ XAS study of the activation of precursor-dependent Pd nanoparticles

The activation of precursor-dependent Pd nanoparticles was comprehensively followed by in situ X-ray absorption spectroscopy on two inorganic supports for rationalizing the final catalytic activity.

Correction: A robust iron catalyst for the selective hydrogenation of substituted (iso)quinolones

Correction for ‘A robust iron catalyst for the selective hydrogenation of substituted (iso)quinolones’ by Basudev Sahoo et al., Chem. Sci., 2018, DOI: ; 10.1039/c8sc02744g.

Corrigendum: Generation of subnanometric platinum with high stability during transformation of a 2D zeolite into 3D

This corrects the article DOI: 10.1038/nmat4757.

Use of autologous bone marrow cells concentrate enriched with platelet-fibrin on extensor mechanism allograft reconstruction for extensor mechanism failure following total knee arthroplasty

Allografts techniques remain the best reconstructive strategy for chronic extensor mechanism lesions after total knee arthroplasty (3) but outcomes depend strictly on the host tissue-allograft junctions healing. The purpose of this study is to evaluate if modern techniques of adding autologous bone marrow cells concentrate enriched with platelet-rich fibrin, provide better healing of the allograft. We present the case of an 86 years old patient affected by patellar tendon rupture after TKA. A whole extensor mechanism allograft was performed adding a bone marrow cells concentrate enriched with platelet-rich fibrin on the host tissue-allograft junctions. Preoperatively and at each follow-up the value of Knee Society Score and radiographic consolidation signs were recorded. Radiographic controls showed clear signs of consolidation already at 1 months follow-up and a solid fusion at 3 months. This case report describes a valid method to improve healing using a tissue-construct engineered with stem cells and growth factors.