Transmission and fluorescence X-ray absorption spectroscopy cell/flow reactor for powder samples under vacuum or in reactive atmospheres.

X-ray absorption spectroscopy is an element-specific technique for probing the local atomic-scale environment around an absorber atom. It is widely used to investigate the structures of liquids and solids, being especially valuable for characterization of solid-supported catalysts. Reported cell designs are limited in capabilities-to fluorescence or transmission and to static or flowing atmospheres, or to vacuum. Our goal was to design a robust and widely applicable cell for catalyst characterizations under all these conditions-to allow tracking of changes during genesis and during operation, both under vacuum and in reactive atmospheres. Herein, we report the design of such a cell and a demonstration of its operation both with a sample under dynamic vacuum and in the presence of gases flowing at temperatures up to 300 °C, showing data obtained with both fluorescence and transmission detection. The cell allows more flexibility in catalyst characterization than any reported.

Structured Ni catalysts on porous anodic alumina membranes for methane dry reforming: NiAl2O4 formation and characterization.

This communication presents the successful design of a structured catalyst based on porous anodic alumina membranes for methane dry reforming. The catalyst with a strong Ni-NiAl2O4 interaction shows both excellent activity and stability.

Direct observation of supported W bis-methylidene from supported W-methyl/methylidyne species.

Extensive solid-state NMR analyses unambiguously determine the formation of silica supported W bis-methylidene methyl species by reaction of the corresponding methyl carbyne with trimethylphosphine or a cyclic olefin.

Non-oxidative coupling of methane catalysed by supported tungsten hydride onto alumina and silica-alumina in classical and H2 permeable membrane fixed-bed reactors.

Non-oxidative coupling of methane with high selectivity into ethane (>99% among hydrocarbon) in a classical fixed-bed reactor catalysed by SiO(2)-Al(2)O(3) or gamma-Al(2)O(3) supported tungsten hydride is presented. Continuous hydrogen separation, using a Pd-Ag membrane in a fixed-bed reactor, led to methane coupling far beyond the thermodynamic equilibrium conversion.

Dinitrogen dissociation on an isolated surface tantalum atom.

Both industrial and biochemical ammonia syntheses are thought to rely on the cooperation of multiple metals in breaking the strong triple bond of dinitrogen. Such multimetallic cooperation for dinitrogen cleavage is also the general rule for dinitrogen reductive cleavage with molecular systems and surfaces. We have observed cleavage of dinitrogen at 250 degrees C and atmospheric pressure by dihydrogen on isolated silica surface-supported tantalum(III) and tantalum(V) hydride centers [(identical with Si-O)2Ta(III)-H] and [(identical with Si-O)2Ta(V)H3], leading to the Ta(V) amido imido product [(identical with SiO)2Ta(=NH)(NH2)]: We assigned the product structure based on extensive characterization by infrared and solid-state nuclear magnetic resonance spectroscopy, isotopic labeling studies, and supporting data from x-ray absorption and theoretical simulations. Reaction intermediates revealed by in situ monitoring of the reaction with infrared spectroscopy support a mechanism highly distinct from those previously observed in enzymatic, organometallic, and heterogeneous N2 activating systems.

Hydrogenolysis of cyclohexane over Ir/SiO(2) catalyst: a mechanistic study of carbon--carbon bond cleavage on metallic surfaces.

The hydrogenolysis of cyclohexane catalyzed by supported Ir/SiO(2) has been studied to get mechanistic information on the elementary steps of C--C bond cleavage for cyclic saturated hydrocarbons. The reaction was studied under conditions in which no dehydrogenation to benzene occurs. When a mixture of cyclohexane and H(2) flows over a Ir/SiO(2) catalyst at 200 degrees C and for a H(2)/cyclohexane ratio superior to 40, methane, ethane, propane, n-butane, n-pentane, and n-hexane are identified to be primary products. The hydrogenolysis of ethane and n-hexane has also been studied to clarify several mechanistic questions. To account for the primary products in the above reactions, a mechanism is proposed in which the key step of the carbon--carbon bond cleavage occurs via concerted electronic transfer in dimetallacyclopentane intermediate. The comparison of product distributions in the hydrogenolysis of cyclohexane and that observed for n-hexane led to conclusions about the relative ease of carbon--carbon bond cleavage with respect to surface alkyl isomerization.

Supported metallocene catalysts by surface organometallic chemistry. Synthesis, characterization, and reactivity in ethylene polymerization of oxide-supported mono- and biscyclopentadienyl zirconium alkyl complexes: establishment of structure/reactivity relationships.

The reactions of CpZr(CH(3))(3), 1, and Cp(2)Zr(CH(3))(2), 2, with partially dehydroxylated silica, silica-alumina, and alumina surfaces have been carried out with careful identification of the resulting surface organometallic complexes in order to probe the relationship between catalyst structure and polymerization activity. The characterization of the supported complexes has been achieved in most cases by in situ infrared spectroscopy, surface microanalysis, qualitative and quantitative analysis of evolved gases during surface reactions with labeled surface, solid state (1)H and (13)C NMR using (13)C-enriched compounds, and EXAFS. 1 and 2 react with silica(500) and silica-alumina(500) by simple protonolysis of one Zr-Me bond by surface silanols with formation of a single well-defined neutral compound. In the case of silica-alumina, a fraction of the supported complexes exhibits some interactions with electronically unsaturated surface aluminum sites. 1 and 2 also react with the hydroxyl groups of gamma-alumina(500), leading to several surface structures. Correlation between EXAFS and (13)C NMR data suggests, in short, two main surface structures having different environments for the methyl group: [Al](3)-OZrCp(CH(3))(2) and [Al](2)-OZrCp(CH(3))(mu-CH(3))-[Al] for the monoCp series and [Al](2)-OZrCp(2)(CH(3)) and [Al]-OZrCp(2)(mu-CH(3))-[Al] for the bisCp series. Ethylene polymerization has been carried out with all the supported complexes under various reaction conditions. Silica-supported catalysts in the absence of any cocatalyst exhibited no activity whatsoever for ethylene polymerization. When the oxide contained Lewis acidic sites, the resulting surface species were active. The activity, although improved by the presence of additional cocatalysts, remained very low by comparison with that of the homogeneous metallocene systems. This trend has been interpreted on the basis of various possible parameters, including the (p-pi)-(d-pi) back-donation of surface oxygen atoms to the zirconium center.

[Our postoperative care and surveillance in surgery of stable sequelae of chronic otitis]. / Nos soins et surveillance postopératoires dans la chirurgie des séquelles stabilisées d'otite chronique.

After a brief summary of the technique used for myringoplasty (enlarged endaural approach, large flattened aponeurotic graft applied to deep surface of tympano-meatal flap after a "request" for boring) emphasis is given to the need for strict surveillance and postoperative care by the surgeon. Immediate postoperative care starts in the operating room and involves a deep intra-meatal dressing (1 or 2 Popes oto-wicks placed on a thin film of silastic or simply surrounded by Gelfoam) and a superficial dressing. The dressing is renewed on the 3rd day with the patient in bed and involves only the superficial one. Secondary postoperative care extends to the 10th or 15th day and includes exeresis of the deep pope-Gelfoam assemblage under careful binocular microscope control followed by audiometric examination. Hospital stay is a mean of 5 days and medical treatment (antibiotics, vasodilators, corticoids) is given as required. Late postoperative care can be summarized as involving regular surveillance and the application of certain rules that cause little disturbance in the patients life. Various rare and even exceptional incidents, benign in the majority of cases, are reviewed.

[Early diffuse hypertrophic osteitis recurrence. Unexpected and consternating development after a large évidement cavity. Apropos of 15 cases]. / La rechute ostéitique diffuse hypertrophique précoce (R.O.D.H.P.). Evolution inattendue et consternante après vaste cavité d'évidement. A propos de 15 cas.

The authors report 15 cases collected over a period of 13 years (1972 - 1984) of a particularly serious eventuality affecting certain evacuation cavities: Early recurrence of diffuse hypertrophic osteitis (E.R.D.H.O.). This is a rare complication, occurring in 1.5% of cases of chronic otitis. However, the fact of having operated upon 7 cases in 1984 alone, whilst during the previous 12 years, only 8 had been seen, raised the alarm. The classical pattern of this complication occurs in 3 stages, each involving surgical operation: at the outset, chronic otitis with cholesteatoma or osteitis, most often mixed, for which an "inadequate" surgical procedure is performed. then, after a variable period which may exceed 10 years, a very large evacuation cavity was created by the authors. finally, 3rd and final stage: within 6 months, this cavity filled progressively and, at operation, the authors discovered a cavity virtually completely filled with a "fantastic" "moist sugar" osteitis, requiring a new evacuation cavity, even larger than that created before. In all cases, a successful result was obtained within a varying period, sometimes accompanied by spectacular improvement in general condition. The most plausible etiopathogenic hypothesis advanced to attempt to explain this phenomenon is that of secondary infection by a varied microbial flora, including, on the one hand, aerobic organisms usually discovered in such cases (pseudomonas pyocyaneus, proteus mirabilis) and, secondly, this being of essential importance, "anaerobic" bacteria, the bacteriological diagnosis of which requires application of a strict protocol. The authors have taken three decisions following their bibliographic investigations.(ABSTRACT TRUNCATED AT 250 WORDS)

[Osteomatous chronic otitis. 27 new cases. 2 new forms]. / Otites chroniques ostéomateuses (O.C.O.). 27 nouveaux cas. 2 nouvelles formes.

The authors report 27 new cases of osteomatous chronic otitis, with (15) or without (12) cholesteatomas, with perforated (13) or intact (14) drum, the latter sometimes having a very atypical appearance (2), frankly purulent or simply inflammatory. This results in a wide range of clinical appearances. There are two macroscopic forms: the diffuse attico-antral form and localized forms (drum - C.S.C.L.). The authors emphasize: the primordial interest of tomography (or CT scan), the keystone of their discovery, as well as the dangers of their surgical treatment. In addition to review of these known concepts, two forms have been identified: 1) Osteomatous attico-chain monoblock, where the ossicles of the ear are adherent in their entirety, either to the external attical wall or, much more rarely, to the medial attical wall. They describe 13 cases, the pattern of which is very different, according to whether the diagnosis is one of cholesteatomatous chronic otitis or not. In the absence of cholesteatoma (8 cases), the clinical picture is suggestive of otospongiosis or of chronic otitis with intact drum. The surgical procedure is related to these findings: 1 completion of myringoplasty, 7 piston-malleus. In cases of cholesteatomatous chronic otitis (5 cases), the picture is completely different, the cholesteatoma developing at leisure, behind the impenetrable osteomatous shield. Once again, the surgical procedure is modified: 4 vast evacuation cavities and one mastoatticotomy for giant cholesteatoma with intact drum. 2) Diffuse and "progressive" osteomatous stenosis of the walls of the E.A.M. The authors describe 6 cases occurring either during cholesteatomatous chronic otitis, or within a few weeks, simulating chronic otitis with intact drum.

[Involvement of the tympanic bone in chronic otitis (44 cases)]. / Les atteintes du tympanal dans le cadre de l'otite chronique (44 observations).

44 cases of tympanic involvement in the context of chronic otitis are described. 34 occurred during active chronic otitis. This is a rare possibility (approximately 4% of our own cases of chronic otitis). The following may be mentioned amongst them: 21 cases of osteitis, for which the following concepts should be borne in mind: the extreme severity of the chronic otitis responsible, in most instances, ears which had undergone multiple surgery (17/21), lesions exclusively of osteitis, but very extensive in 2/3 of cases (14/21). 7 cases of osteolytic disease, occurring severe or atypical cholesteatomatous chronic otitis and quite often involving associated osteolysis affecting the main VII, the promontory, the bulb of the internal jugular vein, or even the carotid canal. 4 cases of diffuse sub-obstructive osteomatous disease of the walls of the E.A.M., "progressive" development of which over several months was noted in 3 cases. Finally, 2 cases of mixed disease: (osteitis--osteomatoma and osteitis--osteolysis). 8 cases occurred following myringoplasty: this is a rare eventuality (approximately 1%), 1 case only of osteolysis due to iatrogenic cholesteatoma, 7 cases of osteitis, either highly localized and not preventing further myringoplasty (4 cases), or very extensive, finally resulting in a vast evacuation cavity. In 2 cases, a malformation is the origin of involvement of the tympanic at the origin of chronic otitis was felt probable, without it being possible to reach any definite conclusion concerning auriculobranchial fistula or Huschke foramen.

[Changes in bone conduction in the surgery of chronic otitis and its sequelae (evaluation of 800 operations)]. / Etude des modifications de la conduction osseuse (CO) dans la chirurgie de l'otite chronique et de ses séquelles (bilan de 800 interventions).

The authors undertook a study of changes in bone conduction (BC) during 800 operations carried out over a 5 years period (1979-1984) for chronic otitis or sequelae of chronic otitis. After elimination of ears with deafness (47) and cases unsuitable for evaluation (39), they finally included 714 records in the study. Only comparison of free and post-operative BC was made and using 4 conversational frequencies, not taking into account a deviation of 5 DB for each of these 4 frequencies. The study involved 317 myringoplasties: In 271 (i.e. 85,5%) there was no change in BC. Amongst them, 37 patients nevertheless showed a transient fall in BC. Of particular importance is the fact that almost 1/3 (11 to be exact) recovered only during the 2nd semester following surgery, a period which was even exceeded in the other 5 cases. 46 (i.e. 14.5%) were classified as "permanent" falls in BC. Amongst these in only 17 (i.e. 5%) were there "only" the three standard aggression factors for the I.O.: aspiration--scraping--manipulation of the tympano-ossicular system, without it being possible to attribute a predominant role to one more than the other. With regard to reaming of the E.A.M., those cases in which this could be considered responsible appeared to be infinitesimal. Furthermore, there was no statistically significant difference (reduced deviation test--"chi"2 test) between the number of falls in BC seen following myringoplasty with or without reaming. 83 tympanoplasties by Piston-Malleus, study of which led to the same conclusions as for myringoplasties. 118 masto-atticotomies, including 23 with posterior tympanotomy. Despite peri-labyrinthine and peri-ossicular scraping, results were essentially identical. 196 evacuation cavities (227-31 deafness) of which somewhat less than half only (46%) were ears undergoing surgery for the first time. Percentage of unchanged BC was here much more unfavourable, with 49 "permanent" falls in BC, i.e. 25%, of which, it must be said, 5 were minimal falls, and with, in 25 cases, a follow-up of less than 3 months.

[Rare benign tumors of the nasal fossae and sinuses of the face (benign schwannoma, fibromyxoma]. / Tumeurs bénignes rares des fosses nasales et des sinus de la face (schwannomes bénins, fibromyxome).

The authors report the observation of two cases of benign schwannomas, one in the nasal cavities, the other in the maxillary sinus and a case of odontogenous fibromyxoma of the ethmoïdo-maxillary sinus. After a study of the observations, a literature review determines the benign character of these tumours, the possibilities of recurring in case of incomplete operation, the importance of computerized tomography to precise their extension, the histological difficulty of the diagnosis and the importance of ultrastructural study to identify them. Taking the cases of schwannomas, we settle two forms A and B (ie) Antoni, because of the myxoïde degeneration which predominate in the second type. Concerning the fibromyxomas histochemicals and ultrastructural studies allow us to definite the character of "myxoblast" or "fibroblast", Cells. Treatment of these lesions is essentially surgical and a long term prognosis is favourable.

[Ewing's inverted nasosinal papilloma. Critical study of therapeutic indications. Apropos of 14 cases]. / Papillomes inverses naso-sinusiens d'Ewing. Etude critique des indications thérapeutiques. A propos de 14 cas.

Fourteen cases of Ewing's inversed papilloma of the nose and sinuses were treated as primary lesions or after recurrence. Clinical and paraclinical, mainly radiologic, endoscopic, and biologic investigations are of fundamental importance and should be as extensive for primary as for recurrent lesions. Treatment is largely dependent on the results of these examinations, is essentially surgical, and should respond to two imperatives. First, it should lead to total excision under the best possible conditions, and second, it should involve a minimum of sequelae, particular esthetic complications. Techniques for excision through the natural pathways are described, followed by those using an external approach (canine fossa or para-lateronasal approaches), as well as their advantages and inconveniences. The preferred procedure is through an open, wide, para-lateronasal approach, enabling the most effective excision to be performed, this technique appearing to be essential for recurrent lesions.