Effects of Hydrothermal Treatment on Mesopore Structure and Connectivity in Doped Ceria-Zirconia Mixed Oxides.

Pore size and pore connectivity control diffusion-based transport in mesopores, a crucial property governing the performance of heterogeneous catalysts. In many cases, transition-metal oxide catalyst materials are prepared from molecular precursors involving hydrothermal treatment followed by heat treatment. Here, we investigate the effects of such a hydrothermal aftertreatment step, using an aqueous ammonia solution, on the disordered mesopore network of CexZr1-x-y-zYyLazO2-δ mixed oxides. This procedure is a common synthesis step in the preparation of such ceria-based oxygen storage materials applied in three-way catalysis, employed to improve the materials' thermal stability. We perform state-of-the-art Ar-physisorption analysis, especially advanced hysteresis scanning, to paint a detailed picture of the alterations in mesopore space caused by the hydrothermal aftertreatment and subsequent aging at 1050 °C. Furthermore, we investigate the network characteristics by electron tomography in combination with suitable statistical analysis, enabling a consistent interpretation of the desorption scans (physisorption). The results indicate that the hydrothermal aftertreatment enhances the mesopore connectivity of the continuous 3D network by widening pores and especially necks, hence facilitating accessibility to the particles' internal surface area and the ability to better withstand high temperatures.

Tuning Mesopore Accessibility of Ce0.18Zr0.64Y0.15La0.03O2-δ by Hydrothermal Post-treatment─A Case Study for Ceria-Based Oxidation Storage Materials.

The connectivity and thermal stability of pores in heterogeneous, mesoporous metal oxide catalysts are key properties controlling their (long-term) efficacy. In this study, we investigate the influence of pH and temperature during a common hydrothermal aftertreatment step in the synthesis of mesoporous CexZr1-x-y-zYyLazO2-δ oxides obtained from molecular precursors via hydrothermal synthesis. This study has a strong focus on the methodological approach, elucidating whether and how even the smallest changes in morphology and connectivity may be unraveled and related to the underlying chemical processes to uncover key parameters for the ongoing improvement of material properties. Deep insights into the mesopore space were obtained by state-of-the-art physisorption (including hysteresis scanning), electron tomography, and small-angle X-ray scattering (SAXS) analysis. We also provide a simple tool to simulate SAXS curves from electron tomography data that allow direct comparison to experimentally obtained SAXS curves. Furthermore, the impact on surface-bound nitrate groups and the development during calcination were studied in detail by thermogravimetric analysis coupled with mass spectrometry. The key observations indicate a significant increase in thermal stability at temperatures as high as 1050 °C and improved mesopore accessibility with an increase in pH of the aftertreatment solution. The combined observations from the employed methods suggest a pH-dependent removal of surface-bound nitrate groups as well as a dissolution and reprecipitation-based fusing of the primary particles that constitute the mesopore skeleton. This transformation yields a mechanically and thermally stronger mesopore space with the capability to endure high temperatures.

Development of Pore Morphology During Nitrate Group Removal by Calcination of Mesoporous CexZr1-x-y-zYyLazO2-δ Powders.

Here, we present a study of the development of the micro- and mesoporosity of a CexZr1-x-y-zYyLazO2-δ oxygen storage material upon treatment at temperatures up to 1050 °C. The investigated powder, obtained from nitrate-based metal oxide precursors in a specially developed hydrothermal synthesis, is highly crystalline, features a high surface area and does not show phase segregation at high temperatures. By employing an advanced methodology, consisting of state-of-the-art argon physisorption, thermogravimetric analysis coupled with mass spectrometry (TG-MS) and X-ray powder diffraction (XRD) along with Raman spectroscopy, we correlate the stability of the mesopore system to the presence of surface-bound nitrate groups introduced during synthesis, which prevent sintering up to a temperature of 600 °C. In addition, the connectivity of mesopores was further studied by hysteresis scanning within the argon physisorption measurements. These advanced physisorption experiments suggest a three-dimensionally interconnected pore system and, in turn, a 3D network of the material itself on the nanometer scale which appears to be beneficial to endow the mesopore space with enhanced stability against sintering and mesopore collapse once the removal of nitrate groups is completed.

Atraumatic femoral head necrosis: a biomechanical, histological and radiological examination compared to primary hip osteoarthritis.

INTRODUCTION: Atraumatic necrosis of the femoral head (AFHN) is a common disease with an incidence of 5000-7000 middle-aged adults in Germany. There is no uniform consensus in the literature regarding the configuration of the bone in AFHN. The clinical picture of our patients varies from very hard bone, especially in idiopathic findings, and rather soft bone in cortisone-induced necrosis. A better understanding of the underlying process could be decisive for establishing a morphology-dependent approach. The aim of this study is the closer examination of the condition of the bone in the AFHN compared to the primary hip osteo arthritis (PHOA). MATERIALS AND METHODS: The preparations were obtained as part of elective endoprosthetic treatment of the hip joint. Immediately after sample collection, thin-slice CT of the preserved femoral heads was performed to determine the exact density of the bone in the necrosis zone. Reconstruction was done in 0.8-1 mm layers in two directions, coronary and axial, starting from the femoral neck axis. Density of the femoral heads was determined by grey value analysis. The value in Hounsfield units per sample head was averaged from three individual measurements to minimize fluctuations. For biomechanical and histomorphological evaluation, the samples were extracted in the load bearing zone perpendicular to the surface of the femoral head. Group-dependent statistical evaluation was performed using single factor variance analysis (ANOVA). RESULTS: A total of 41 patients with a mean age of 64.44 years were included. The mean bone density of the AFHN samples, at 1.432 g/cm3, was about 7% higher than in the PHOA group with a mean value of 1.350 g/cm3 (p = 0.040). The biomechanical testing in the AFHN group showed a 22% higher-but not significant-mean compressive strength (20.397 MPa) than in the PHOA group (16.733 MPa). On the basis of histological analysis, no differentiation between AFHN and PHOA samples was possible. CONCLUSIONS: The present study (NCT, evidence level II) shows that AFHN has a very well detectable higher bone density compared to PHOA. However, neither biomechanical stress tests nor histomorphological evaluation did show any significant difference between the groups. The results allow the conclusion that there is no "soft" necrosis at all in the AFHN group.

Comprehensive Characterization of a Mesoporous Cerium Oxide Nanomaterial with High Surface Area and High Thermal Stability.

In the present study, the pore space of a mesoporous cerium oxide material is investigated, which forms by the self-assembly of primary particles into a spherical secondary structure possessing a disordered mesopore space. The material under study exhibits quite stable mesoporosity upon aging at high temperatures (800 °C) and is, thus, of potential interest in high-temperature catalysis. Here, different characterization techniques were applied to elucidate the structural evolution taking place between heat treatment at 400 °C and aging at 800 °C, i.e., in a water-containing atmosphere, which is usually detrimental to nanoscaled porosity. The changes in the mesoporosity were monitored by advanced physisorption experiments, including hysteresis scanning, and electron tomography analysis coupled with a 3D reconstruction of the mesopore space. These methods indicate that the 3D spatial arrangement of the primary particles during the synthesis under hydrothermal conditions via thermal hydrolysis is related to the thermal stability of the hierarchical mesopore structure. The assembly of the primary CeO2 particles (∼4 nm in size) results in an interparticulate space constituting an open 3D mesopore network, as revealed by skeleton analysis of tomography data, being in conformity with hysteresis scanning. At elevated temperatures (800 °C), sinter processes occur resulting in the growth of the primary particles, but the 3D mesopore network and the spherical secondary structure are preserved.

The hydrophobic effect characterises the thermodynamic signature of amyloid fibril growth.

Many proteins have the potential to aggregate into amyloid fibrils, protein polymers associated with a wide range of human disorders such as Alzheimer's and Parkinson's disease. The thermodynamic stability of amyloid fibrils, in contrast to that of folded proteins, is not well understood: the balance between entropic and enthalpic terms, including the chain entropy and the hydrophobic effect, are poorly characterised. Using a combination of theory, in vitro experiments, simulations of a coarse-grained protein model and meta-data analysis, we delineate the enthalpic and entropic contributions that dominate amyloid fibril elongation. Our prediction of a characteristic temperature-dependent enthalpic signature is confirmed by the performed calorimetric experiments and a meta-analysis over published data. From these results we are able to define the necessary conditions to observe cold denaturation of amyloid fibrils. Overall, we show that amyloid fibril elongation is associated with a negative heat capacity, the magnitude of which correlates closely with the hydrophobic surface area that is buried upon fibril formation, highlighting the importance of hydrophobicity for fibril stability.

Cyclo-Dipnictadialanes.

Using the AlI precursor Cp3t Al in conjunction with triphosphiranes (PAr)3 (Ar=Mes, Dip, Tip) we have succeeded in preparing Lewis base-free cyclic diphosphadialanes with both the Al and P atoms bearing three substituents. Using the sterically more demanding Dip and Tip substituents the first 1,2-diphospha-3,4-dialuminacyclobutanes were obtained, whereas with Mes substituents [Cp3t Al(µ-PMes)]2 is formed. This divergent reactivity was corroborated by DFT studies, which indicated the thermodynamic preference for the 1,2-diphospha-3,4-dialuminacyclobutane form for sterically more demanding groups on phosphorus. Using Cp*Al we could extend this concept to the corresponding cyclic diarsadialanes [Cp*Al(µ-AsAr)]2 (Ar=Dip, Tip) and additionally add the phosphorus variants [Cp*Al(µ-PAr)]2 (P=Mes, Dip, Tip). The reactivity of one variant [Cp3t Al(µ-PPh)]2 towards NHCs was tested and resulted in double NHC-stabilised [Cp3t (IiPr2 )Al(µ-PPh)]2 .

Boranediyl- and Diborane(4)-1,2-diyl-Bridged Platinum A-Frame Complexes.

Diplatinum A-frame complexes with a bridging (di)boron unit in the apex position were synthesized in a single step by the double oxidative addition of dihalo(di)borane precursors at a bis(diphosphine)-bridged Pt0 2 complex. While structurally analogous to well-known µ-borylene complexes, in which delocalized dative three-center-two-electron M-B-M bonding prevails, theoretical investigations into the nature of Pt-B bonding in these A-frame complexes show them to be rare dimetalla(di)boranes displaying two electron-sharing Pt-B σ-bonds. This is experimentally reflected in the low kinetic stability of these compounds, which are prone to loss of the (di)boron bridgehead unit.

Peering into the Formation of Cerium Oxide Colloidal Particles in Solution by In Situ Small-Angle X-ray Scattering.

The formation of CeO2 colloidal particles upon heating an aqueous solution of (NH4)2Ce(NO3)6 to 100 °C was investigated by time-resolved in situ SAXS analysis using synchrotron radiation, providing absolute intensity data. In particular, the experiments were performed by applying different temperatures between room temperature and 100 °C as well as under variation of the ionic strength and concentration. Using validated SAXS evaluation tools (SASfit and McSAS software), the analyses revealed the presence of two types of particle populations possessing average dimensions of ca. 2 nm and 5-15 nm, with the latter being agglomerates of the 2 nm particles rather than single crystallites. The analysis revealed not only the changes in the size, but also the relative volume fractions of these two CeO2 particle populations as a function of the aforementioned parameters. Increasing the temperature increases the number of the 5-15 nm agglomerates on one hand by the enhanced nucleation rate of the primary particles. On the other hand, especially at high temperatures (90 and 100 °C) the larger agglomerate particles precipitate, resulting in interesting trends in the fractions of the two populations as a function of time, temperature, ionic strength, and precursor concentration. The experimental studies are complemented by calculating colloidal interaction energies based on classical DLVO theory. Thereby, this study provides detailed insight into the nucleation, growth, and agglomeration of CeO2 nanoparticles. The primary objective of this study is to provide a better understanding of the nucleation and growth of particles by the hydrolysis of the tetravalent cerium ion in aqueous solutions.

Open reduction and internal fixation of acetabular fractures in patients of old age.

MATERIAL AND METHODS: There is an ongoing debate on which treatment for acetabular fractures in elderly patients is the most appropriate. This study was set up to identify the role of open reduction and internal fixation of acetabular fractures in persons of old age. We retrospectively reviewed the medical charts and radiological data of all patients older than 65 years, who suffered an isolated acetabular fracture and were admitted in our Department between 2010 and 2014 (5-year period). Complications, outcome and mortality were recorded. Of all surviving patients, quality of life (QoL), mobility and independence were graded with European Quality of Life 5 Dimensions 3 Level (EQ-5D-3L), European Quality of Life 5 Dimensions Visual Analogue Scale (EQ-5D-VAS), Numeric Rating Scale (NRS), Elderly Mobility Scale (EMS) and Tinetti Mobility Test (TMT). RESULTS: Seventy patients could be identified. There were 52 men (74%) and 18 women (26%) with a median age of 79.0 years (range: 65-104 years). Forty-six patients (66%) had been treated with open reduction and internal fixation (ORIF), 24 (34%) conservatively. There were negative predictive factors-subchondral impaction, damage to the femoral head and multiple fragments-in 54% of the operative group. With ORIF, an anatomical reduction could be achieved in 27 patients (59%), an acceptable in 18 (39%) and a poor in one (2%). At follow-up, 18 patients (26%) had died and 23 (33%) were not able to participate. The follow-up rate of the surviving operatively treated patients was 77%. Eleven of 46 operated patients (24%) needed a conversion to a total hip arthroplasty (THA). All patients undergoing conversion had imperfect reduction after surgery. No patient in the non-operative group underwent conversion to THA during follow-up. The median follow-up time of operatively treated patients without conversion (n = 17) was 30 months (range, 16-73 months), of patients with THA (n = 9) 30 months after conversion (range, 17-55 months). Quality of reduction correlated to QoL, mobility and independence in all recorded parameters. Patients with secondary THA had similar good outcomes as patients after ORIF without later conversion. Men had better outcome than women. CONCLUSION: ORIF of acetabular fractures in patients of old age results in excellent outcomes at short-term follow-up when anatomical reduction can be achieved. In case of negative predictive factors, ORIF cannot be regarded as a definitive solution, rather as the construction of a stable socket for secondary THA. The decision of therapy should be made dependent on pre-operative radiographic parameters.

Traumatic brain injury enhances the formation of heterotopic ossification around the hip: an animal model study.

INTRODUCTION: The incidence of heterotopic ossification (HO) is at its highest when trauma of the hip or pelvis concurs with traumatic brain injury (TBI). The pathogenic mechanisms underlying the neurogenic enhancement of the formation of HO remain, however, poorly understood. Hence, the goal of the present study was to develop a novel small animal model that combines hip and brain trauma that can prove the enhancement of HO around the hip after TBI. MATERIALS AND METHODS: Forty male Wistar rats were divided into four groups, to undergo hip surgery alone (group 1), hip surgery + moderate TBI (group 2), hip surgery + severe TBI (group 3) and only severe TBI (group 4). The femoral canal was reamed up to 2 mm and a muscle lesion was made to simulate hip surgery. An established controlled cortical impact model was used to create a TBI. Twelve weeks after surgery, the hip with the proximal half of the femur and the pelvic bone was removed and subjected to micro-computed tomography (µCT) analysis. A quantitative analysis using a modified Brooker score as well as a quantitative analysis using a bone-to-tissue ratio was used. RESULTS: No HO could be found in all the ten animals that did not undergo hip surgery (group 4). In the animals that did undergo surgery to the hip, no HO was found in only one animal (group 1). All the other animals developed HO. In this study, significantly more HO was found in animals that underwent an additional severe TBI. CONCLUSION: The newly developed rat model, with a combined hip and brain trauma, showed an enhancement of the HO formation around the hip after severe TBI.

[Complex treatment of pyoderma gangrenosum after minor trauma and primary surgical intervention with suspected necrotizing fasciitis]. / Komplexe Therapie des Pyoderma gangraenosum nach Bagatelltrauma und primär chirurgischer Intervention bei Verdacht auf nekrotisierende Fasziitis.

This article presents the case of a rapidly progressing pyoderma gangrenosum (PG) following a minor trauma and surgical intervention. A 46-year-old patient was admitted to hospital after a minor trauma of the right lower leg with a suspected diagnosis of erysipelas bullosum. A magnetic resonance imaging (MRI) scan showed the suspicion of necrotizing fasciitis (NF) with indications for immediate incision and fascia resection. According to the results of the histopathological analysis and microbiological assessment without signs for a bacterial infection, high-dose steroid treatment and immunosuppressive treatment with cyclosporin A were initiated under the assumption of PG. Additionally, the patient was treated with hyperbaric oxygenation (HBO). The 2­year follow-up showed a gradual restitution of the soft tissues.

The pathogenesis of heterotopic ossification after traumatic brain injury. A review of current literature.

Neurogenic heterotopic ossification (NHO), mostly defined as a benign process of formation of bone outside the skeletal system, after traumatic brain injury (TBI) is a musculoskeletal disorder that causes pain and reduces the range of motion, often leading to marked impairment of quality of life. The pathogenic factors that link the brain and bone and cause the formation of heterotopic bone are largely unknown. This article will try to summarize the current literature on the pathogenesis of NHO and accelerated fracture healing after TBI. The heterotopic formation of bone after TBI seems to be inducted by a complex interplay between local and systemic factors. For all different forms of HO, the same three conditions are required for the formation of ectopic bone : The presence of osteoprogenitor cells, a permissive environment, and a stimulating factor. The osteoprogenitor cells are thought to be of mesenchymal origin, however recent research suggests a possible neural origin. The permissive environment is created mainly by reactions to hypoxia and both local and sensory nerve inflammation. Many possible inducing factors have been described ; the endogenic route is thought to be the most dominant in the stimulation of HO formation after TBI. The pathogenesis of NHO remains largely unknown, recent research, however, has discovered interesting topics for further research and new possible targets in the prevention of NHO.

Planar Cyclopenten-4-yl Cations: Highly Delocalized π Aromatics Stabilized by Hyperconjugation.

Theoretical studies predicted the planar cyclopenten-4-yl cation to be a classical carbocation, and the highest-energy isomer of C5 H7 + . Hence, its existence has not been verified experimentally so far. We were now able to isolate two stable derivatives of the cyclopenten-4-yl cation by reaction of bulky alanes CpR AlBr2 with AlBr3 . Elucidation of their (electronic) structures by X-ray diffraction and quantum chemistry studies revealed planar geometries and strong hyperconjugation interactions primarily from the C-Al σ bonds to the empty p orbital of the cationic sp2 carbon center. A close inspection of the molecular orbitals (MOs) and of the anisotropy of current (induced) density (ACID), as well as the evaluation of various aromaticity descriptors indicated distinct aromaticity for these cyclopenten-4-yl derivatives, which strongly contrasts the classical description of this system. Here, strong delocalization of π electrons spanning the whole carbocycle has been verified, thus providing rare examples of π aromaticity involving saturated sp3 carbon atoms.

trans-Selective Insertional Dihydroboration of a cis-Diborene: Synthesis of Linear sp3 -sp2 -sp3 -Triboranes and Subsequent Cationization.

The reaction of aryl- and amino(dihydro)boranes with dibora[2]ferrocenophane 1 leads to the formation 1,3-trans-dihydrotriboranes by formal hydrogenation and insertion of a borylene unit into the B=B bond. The aryltriborane derivatives undergo reversible photoisomerization to the cis-1,2-µ-H-3-hydrotriboranes, while hydride abstraction affords cationic triboranes, which represent the first doubly base-stabilized B3 H4 + analogues.

Heterodiatomic Multiple Bonding in Group†13: A Complex with a Boron-Aluminum π†Bond Reduces CO2.

Heterodiatomic multiple bonds have never been observed within Group 13. Herein, we disclose a method that generates [(CAAC)PhB=AlCp3t ] (1), a complex featuring π bonding between boron and aluminum through the association of singlet fragments. We present the properties of this multiple bond as well as the reactivity of the complex with carbon dioxide, which yields a boron CO complex via an unusual metathesis reaction.

Aluminum(I)/Boron(III) Redox Reactions.

Reactions between BIII species and the novel nucleophilic cyclopentadienyl-stabilized AlI reagent (1) result in a diversity of complexes bearing different Al/B oxidation states and coordination geometries. With the triarylborane B(C6 F5 )3 , a simple AlI →BIII adduct is formed. In contrast, a bulky aryldihaloborane undergoes oxidative addition with the formation of a covalent bora-alane species. With an N-heterocyclic carbene-stabilized amino(bromo)borenium ion, a redox reaction was observed, where the product is a borylene-alane BI →AlIII complex. Additionally, reaction of 1 with BI3 results in complete scrambling of all of the Al/B-bound substituents, and the formation of a cyclopentadienylboron(I)→AlI3 complex. These latter reactions are the first examples of the reduction of a boron(III) compound to a borylene by a p-block reagent, and illustrate how subtle changes in the nature of the borane can result in highly divergent reaction outcomes.

A Boradiselenirane and a Boraditellurirane: Isolable Heavy Analogs of Dioxiranes and Dithiiranes.

The isolation of BE2 heterocycles (E = Te, Se, S) from the reaction of a manganese borylene complex with elemental chalcogens is reported. The BTe2 and BSe2 cycles-a boraditellurirane and a boradiselenirane, respectively-are the first analogs of dioxiranes based on heavy chalcogens. While the BTe2 unit is still found datively bound to manganese, the Se and S analogs were isolated in their free forms. All heterocycles have been shown to transfer a chalcogen atom, allowing for the isolation of novel borachalcones and their dimerization products.

Lewis-Base-Induced Disproportionation of a Dialane.

The reaction of a pentamethylcyclopentadienyl-substituted dialane with a variety of Lewis bases results in unexpected disproportionation of the dialane into AlI and AlIII species. Use of a transition-metal Lewis base allows for the formation of metal-only Lewis pairs. Furthermore, the synthesis of a Lewis base bis-adduct was successful with the Lewis base 4-dimethylaminopyridine.

Paget's disease of the lumbar spine: decompressive surgery following 17 years of bisphosphonate treatment.

BACKGROUND: We present a rare case of Paget's disease (PD) with involvement of the lumbar spine over a period of 19 years. We discuss the diagnostic process to rule out alternative diagnoses and medical and surgical treatment strategies. CASE DESCRIPTION: A 58-year-old man first diagnosed with PD in 1998 with solid involvement of the 4th lumbar vertebra has been undergoing periodic examinations over a period of 18 years. Since then, the patient has been treated conservatively with bisphosphonates. When conservative treatment options have been exhausted, surgery was indicated due to a progressively reduced ability to walk. Surgery with undercutting decompression via laminotomy was performed. PD was confirmed by biopsy. Bisphosphonate treatment was continued pre- and postoperatively. Follow-up examinations showed an improvement in clinical outcome measures. CONCLUSIONS: Conservative treatment remains the gold standard for PD with spinal involvement. This patient had been asymptomatic on bisphosphonate therapy for almost 17 years, but presented with new onset back pain. In such cases, fracture and rare conversion into sarcoma must be ruled out, and biopsy should be performed even in the absence of signs of malignancy. Currently, there are no clear treatment recommendations available in the literature regarding cases of PD with expansive growth and involvement of the spinal canal causing neurologic deficits. Furthermore, laminectomy has been shown to cause complications in up to 27% of cases with the risk of early postoperative death. In contrast, extended laminotomy and undercutting decompression should be considered.