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C Dujardin

Publications and source records attributed to C Dujardin.

At least 19 recordsLinked to original sources
PubMed2006

Structural transition in rare earth oxide clusters.

Size effects, such as structure transition, have been reported in small clusters of alkali halide compounds. We extend the study to rare earth sesquioxide (Gd(2)O(3)) clusters which are as ionic as the alkali halide compounds, but have a more complicated structure. In a clean and controlled environment (ultra high vacuum), such particles are well crystallized, facetted and tend to adopt a rhombic dodecahedron shape. This indicates the major role of highly ionic bonds in preserving the crystal lattice even at small sizes (a few lattice parameter). Based on both cathodo-luminescence and transmission electron microscopy, we report the existence of a structural transition from bcc to monoclinic at small sizes.

Journal Article↗
PubMed2006

CO adsorption on CoMo and NiMo sulfide catalysts: a combined IR and DFT study.

Experimental IR spectra of carbon monoxide adsorbed on a series of Mo/Al2O3, CoMo/Al2O3, and NiMo/Al2O3 sulfided catalysts have been compared to ab initio DFT calculations of CO adsorption on CoMo and NiMo model surfaces. This approach allows the main IR features of CO adsorbed on the sulfide phase to be assigned with an uncertainty of 15 cm(-1). On the CoMo system, the band at 2070 cm(-1) is specific of the promotion by Co and is assigned to CO interacting either with a Co atom or with a Mo atom adjacent to a Co atom. On the NiMo system, CO adsorption on Ni centers of the promoted phase leads to a high-wavenumber band at approximately 2120 cm(-1) that strongly overlaps the band at 2110 cm(-1) characteristic of nonpromoted Mo sites. For NiMo and CoMo catalysts, broad shoulders at low wave numbers (below 2060 cm(-1)) are characteristic of Mo centers adjacent to promoter atoms, indicating a partial decoration of the MoS2 edges by the promoter.

Journal Article↗
PubMed2005

A new experimental cell for in situ and operandoX-ray absorption measurements in heterogeneous catalysis.

A new X-ray absorption cell dedicated to in situ and operando experiments in heterogeneous catalysis has been built and tested. The cell consists of several boron nitride and stainless steel plates linked together using graphite seals. It allows the measurement of XANES and EXAFS spectra of heterogeneous catalysts within a wide range of photon energies in transmission mode under the flow of various oxidative and reductive gas mixtures at elevated temperatures. The cell is compact and easy to build. Catalysts are loaded into the cell as powders. The use of boron nitride and a small beam pathlength in the cell result in a low absorption of the X-ray beam at lower energies. The cell was tested by in situ characterizing cobalt species during oxidative and reductive pre-treatments of a silica-supported Fischer-Tropsch catalyst. An operando study of methanol conversion over alumina-supported molybdenum catalysts was also carried out.

Journal Article↗
PubMed2005

[Rupture of the flexor tendons on an anterior plate for distal radial fracture: four cases and a review of the literature].

We report four cases of flexor tendon ruptures which occurred after distal radial fracture and reviewed the 25 other cases reported in the literature since 1932. Analysis of these 29 cases disclosed the causes of these ruptures. A deformed callus after distal radial fracture or presence of an anterior osteosynthesis plate can under certain conditions lead to secondary flexor tendon tears. It was also found that tears of the flexor pollicis longus rupture predominate, followed by injury to the flexor digitorum profundis and superficialis of the index finger. Other tendons have only been involved in only a few cases. In order to avoid this complication, we propose systematic removal of anterior plates or secondary replacement if the reduction is not totally anatomic. Surgeons should recall the importance of anatomic reduction of distal radial fractures.

Aged↗
PubMed2004

Synthesis and properties of europium-based phosphors on the nanometer scale: Eu2O3, Gd2O3:Eu, and Y2O3:Eu.

Nanocrystals of oxides containing europium as the main constituent or as a doping element in RE2O3 ( RE=Y, Gd) have been prepared by direct oxide precipitation in high-boiling polyalcohol solutions and characterized by high-resolution TEM, absorption spectroscopy, and luminescence spectroscopy. The samples obtained consisted of concentrated and colloidally stable suspensions of luminescent oxide nanoparticles with an average grain diameter in the range 2-5 nm. The nanoparticles were found to be highly crystalline despite their ultrasmall size and the low temperature of 180 degrees C applied during the synthesis. Upon UV excitation, the red luminescence relative to the 5D0-->7Fn transition within the cubic form of RE2O3 exhibits some important differences from that usually found in bulk materials.

Journal Article↗
PubMed2003

A study of reproducibility of an original method of CT measurement of the lateralization of the intertubercular groove and humeral retroversion.

An original method of CT measurement of the lateralization of the humeral intertubercular groove is described based on geometric construction following Thales theorem. A study of intra- and interobserver reproducibility was done of this measurement and humeral retroversion on 32 healthy volunteers. The results show good reproducibility of these measurements. The average value of humeral retroversion was lower than the average values found in the literature: 11.71 degrees on average on the dominant side and 7.03 degrees on average on the non-dominant side with a large spread of values. The reasons for these differences are discussed. The average values of lateralization of the intertubercular groove were 114.97 degrees on the dominant side and 121.9 degrees on the non-dominant side. These CT measurements are important to consider in the pathophysiology of chronic anterior instability of the shoulder.

Adult↗
PubMed2003

[Coverage of heel tissue loss by two pediculated flaps in a single procedure].

We report the case of a traffic accident victim who suffered major tissue loss of the heal. We used two pediculated flaps to close the gap in a single procedure. The remaining tissue presented zones of necrosis from the plantar aspect to the posterior half of the calcaneum, up to the insertion of the calcaneus tendon, extending 5 cm on the posterior aspect of the heal. We decided to combine a medial plantar flap with a lateral supramalleolar flap. The thick medial plantar flap allowed cover of the calcaneum and sensitivity. The calcaneus tendon was covered with the lateral supramalleolar flap. The thickness of the flap was adapted to match the tissue defect. At six months, the patient had recovered walking function with satisfactory weight bearing on the heal. Flap sensitivity was satisfactory with no slipping phenomenon.

Accidents, Traffic↗
PubMed2003

[Arthroscopy-guided treatment of fractures of the distal radius: 16 wrists].

PURPOSE OF THE STUDY: We report our experience with arthroscopy-guided treatment of fractures of the distal radius. MATERIAL AND METHODS: Between November 2001 and June 2002, 16 patients (10 men, 6 women, mean age 51 years, age range 24-75 years) underwent arthroscopy-guided treatment of articular fractures of the distal radius. Patients were installed with the arm held in a horizontal position with a brace, the wrist under traction. The same procedure was used in all cases: introduction of the arthroscope, joint cleaning and shaving, search for lesions, arthroscopy-guided treatment. Kirschner 2-mm pins were used for fixation in all cases, combined with 1.2-mm pins in the event of ligament injury. RESULTS: Arthroscopic exploration revealed cartilage impaction in 25% of the wrists and ligament injuries in 30%. One fixation disassembled and was not remounted. There were two cases of reflex dystrophy. There were no arthroscopy-related complications. Bone healing was achieved in eight weeks in all cases. The mean DASH score was 22.5 at six months follow-up (range 3-10). DISCUSSION CONCLUSION: Arthroscopy-guided treatment of fractures of the distal radius was attempted for the first time in the early 90s. Per-operative arthroscopy enables a good view of the fracture and associated lesions (cartilage impaction, scapholunate, lunotriquetral ligament injury) and facilitates control of the reduction. Arthroscopy is technically simple and is the technique of choice due to the lack of morbidity. Several authors have reported their experience in more or less extensive series. Two notions should be emphasized. First, defective intra-articular reduction greater than 1 mm may lead to osteoarthritis of the wrist in 90% of the cases. Secondly, intra-operative imaging (fluoroscopy) does not provide sufficient precision to visualize a 1-mm stairstep in the articular surface, raising the risk of radiocarpal degeneration at mid term despite often satisfactory postoperative x-rays. We thus propose intra-operative arthroscopy to control the treatment of all articular wrist fractures, with or without displacement, in order to ensure satisfactory reduction with less than 1-mm defect in the articular surface and to search for and treat any associated bone or ligament injuries not diagnosed before surgery.

Adult↗
PubMed1999

[Homolateral transposition of the internal jugular vein for axillo-subclavian venous thrombosis (of effort)].

UNLABELLED: Indications for treating subclavian vein obstruction are still being developed, especially for endovascular procedures with or without first rib resection. This article explores our experience with chronic and acute subclavian vein thrombosis persisting after medical treatment. In our department of vascular surgery, we have observed 2 cases of subclavian vein obstruction in 2 patients with Paget-Schroetler syndrome who developed major pain and edema in the dominant upper limb. Initially, we managed these patients medically with thrombolysis and anticoagulation. Then, as the significant symptoms persisted and venous thrombolysis developed, we decided on surgical treatment. Because of hypertrophic venous impairment, we used an aggressive procedure with venous bypass using jugular vein transposition and temporary arteriovenous fistula. We observed significant symptom relief and also perfect permeability of the venous bypass at 30 months. CONCLUSION: On the basis of our anecdotal experience and reports by other groups, aggressive treatment with decompression (first rib resection and scalenectomy) and jugular vein transposition could be recommended for persistent subclavian vein thrombosis. Because of the presence of a thoraco-brachial outlet syndrome the endovascular procedures should be completed by first rib resection.

Adult↗
PubMed1979

[Low postero-medial approach to the leg (author's transl)].

It is possible to prolong a postero-medial surgical approach to the leg as far as the tarsal canal in order to gain access to the posterioir aspect of the diaphysis and of the shaft of the tibia up to the tibio-tarsal line. The tendons and vessels must be displaced backwards, held by a tape and moved as necessary according to the desired approach. In addition, the morphology of the posterior aspect of the tibia is such that osteosynthesis is much simpler than via any other approach. Four years' experience of more than 30 cases enable the authors to advise the use of this approach in surgery of the lower end of the tibia.

Fracture Fixation↗