Catalysis research of relevance to carbon management: progress, challenges, and opportunities.

The goal of the "Opportunities for Catalysis Research in Carbon Management" workshop was to review within the context of greenhouse gas/carbon issues the current state of knowledge, barriers to further scientific and technological progress, and basic scientific research needs in the areas of H2 generation and utilization, light hydrocarbon activation and utilization, carbon dioxide activation, utilization, and sequestration, emerging techniques and research directions in relevant catalysis research, and in catalysis for more efficient transportation engines. Several overarching themes emerge from this review. First and foremost, there is a pressing need to better understand in detail the catalytic mechanisms involved in almost every process area mentioned above. This includes the structures, energetics, lifetimes, and reactivities of the species thought to be important in the key catalytic cycles. As much of this type of information as is possible to acquire would also greatly aid in better understanding perplexing, incomplete/inefficient catalytic cycles and in inventing new, efficient ones. The most productive way to attack such problems must include long-term, in-depth fundamental studies of both commercial and model processes, by conventional research techniques and, importantly, by applying various promising new physicochemical and computational approaches which would allow incisive, in situ elucidation of reaction pathways. There is also a consensus that more exploratory experiments, especially high-risk, unconventional catalytic and model studies, should be undertaken. Such an effort will likely require specialized equipment, instrumentation, and computational facilities. The most expeditious and cost-effective means to carry out this research would be by close coupling of academic, industrial, and national laboratory catalysis efforts worldwide. Completely new research approaches should be vigorously explored, ranging from novel compositions, fabrication techniques, reactors, and reaction conditions for heterogeneous catalysts, to novel ligands and ligation geometries (e.g., biomimetic), reaction media, and activation methods for homogeneous ones. The interplay between these two areas involving various hybrid and single-site supported catalyst systems should also be productive. Finally, new combinatorial and semicombinatorial means to rapidly create and screen catalyst systems are now available. As a complement to the approaches noted above, these techniques promise to greatly accelerate catalyst discovery, evaluation, and understanding. They should be incorporated in the vigorous international research effort needed in this field.

Tricarbonyl[1,1',1"-ethylidynetris(pyrazole-kappaN2)]rhenium(I) bromide and tricarbonyl[methylidynetris(pyrazole-kappaN2)]rhenium(I) iodide ethanol hemisolvate.

The two title compounds, [Re(C(10)H(10)N(6))(CO)(3)]Br and [Re(C(11)H(12)N(6))(CO)(3)]I.0.5C(2)H(6)O, have slightly distorted octahedral geometries about the rhenium centers. The distortions result from the constraints of the eta(3)-coordinated tris(pyrazol-1-yl)methane ligands in each case which reduce the N-Re-N bond angles well below the preferred value of 90 degrees for facially disposed ligands at a six-coordinate metal center.

Synthesis and properties of fac-Re(dmbpy)(CO)3CHO (dmbpy = 4,4'-dimethyl-2,2'-bipyridine), a possible intermediate in reductions of CO2 catalyzed by fac-Re(dmbpy)(CO)3Cl.

Synthesis of fac-Re(dmbpy)(CO)3CHO 2 and its reactions with CO2 in DMF and DMSO have been conducted; 2 transfers hydride to CO2 to give Re(dmbpy)(CO)4+ OCHO- 5 which is rapidly transformed to fac-Re(dmbpy)(CO)3(OCHO) 3 in DMF, thus supporting the viability of 2 in photocatalytic reactions of fac-Re(dmbpy)(CO)3Cl with CO2.

Rollback in posterior cruciate ligament-retaining total knee arthroplasty. A radiographic analysis.

A clinical and radiographic study of 49 posterior cruciate ligament-retaining total knee arthroplasties in 38 patients (11 bilateral, 27 unilateral), using prostheses of the same design, was undertaken to quantify the amount of in vivo rollback (ie, the anteroposterior translation of the tibia with respect to the femur during flexion). The mean difference in the distances between the contact points of the knees in full extension and in 90 degrees flexion (ie, the rollback distance) was a posterior translation of the contact point of -0.2 mm (-12.7 to +7l6 mm; SD, 4.7 mm) relative to the prosthetic tibial tray, corresponding to an average translation of 0% of the prosthetic tibial tray depth, and -0.2 mm (-12.5 to +9.1 mm; SD, 4.8 mm) relative to the tibia itself, corresponding to an average translation of 0% of the true tibial surface depth. The differences between the rollback values obtained from the 90 degrees and full-extension radiographs relative to the prosthetic tibial tray (P = .63) and the true tibia (P = .89) were not statistically significant. Intraobserver (P = .27-.50) and interobserver (P = .13-.72) reliability tests showed that the differences between radiographic measurements taken by the same observer at two different points in time and by two different observers were not statistically significant. No correlations were found between the degree of translation of the tibiofemoral contact point relative to the prosthetic tibial tray and the posterior tilt of the tibial tray (R2 = .12), the preoperative tibiofemoral angle (R2 = .34), and the postoperative tibiofemoral angle (R2 = .027). No correlations were found between the degree of translation of the tibiofemoral contact point relative to the true tibia and the posterior tilt of the tibial tray (R2 = .16), the preoperative tibiofemoral angle (R2 = .14), and the postoperative tibiofemoral angle (R2 = .034). In conclusion, this study indicated no demonstrable rollback occurring in the posterior cruciate ligament-retaining total knee arthroplasty used in this study.

Non-specific protection against pulmonary Legionella pneumophila infection in guinea-pigs immunized and challenged with mycobacteria.

Experiments were designed to test the ability of the non-specific efferent limb of cell mediated immunity (CMI) to protect guinea-pigs against a lethal L. pneumophila challenge. A secondary CMI response was generated in the lungs of guinea-pigs using an established protocol which consisted of intraperitoneal infection with Mycobacterium bovis BCG followed by intravenous infection with Mycobacterium tuberculosis H37Ra. The animals were challenged with L. pneumophila (100 LD50) by the aerosol route 3, 6 or 10 days after the H37Ra infection, and pyrexia and survival were monitored. Lungs were taken from animals killed at intervals for histology and enumeration of viable L. pneumophila. Normal guinea-pigs and others infected with either BCG or H37Ra alone were challenged with L. pneumophila as controls. Of the animals which received both BCG and H37Ra, all those challenged 3 days after H37Ra survived but this level of protection fell progressively in groups challenged 6 or 10 days after H37Ra. None of the control animals survived. Mycobacterial lung lesions were granulomatous and were readily distinguished from the acute exudative Legionella lesions. The protected animals showed evidence of a more substantial anti-mycobacterial CMI response and a delay in the development of Legionella lesions. The numbers of L. pneumophila present in the lungs indicated that protection did not result from early elimination of the Legionella challenge. The bacterial counts together with the histopathology suggest that the L. pneumophila was more effectively contained in the protected animals so that exudative damage was reduced.

Studies on ciprofloxacin therapy of experimental Legionnaires' disease.

The concentration of ciprofloxacin in the serum and tissues of normal guinea-pigs was monitored after intramuscular and oral administration. Significant concentrations were attained in the kidneys, but higher doses were required before serum and lung concentrations became measurable. Ciprofloxacin, given parenterally, prevented pyrexia and death of guinea-pigs infected by aerosols of Legionella pneumophila. Although it markedly reduced the number of bacteria in the lungs, it did not prevent the development of pulmonary lesions. Ciprofloxacin administered orally was not so effective in preventing death, although pyrexia was prevented and numbers of bacteria in the lungs of guinea-pigs were reduced. The low minimum inhibitory and bactericidal concentrations of ciprofloxacin against L. pneumophila together with the in vivo results observed suggest that this antibiotic could be of value in the treatment of human beings suffering from Legionnaires' disease.

Antibiotic therapy of experimental airborne Legionnaires' disease.

The efficacy of erythromycin, gentamicin and rifampicin has been compared in the treatment of experimental airborne Legionnaires' disease in guinea-pigs. Evaluation was based on survival of animals after 1LD50 or 10LD50 infection, on numbers of Legionella pneumophila in the lungs and on the extent of histopathological lesions. All three drugs were effective in increasing survival in 1LD50 infections, but only rifampicin gave any protection against 10LD50 infection. Rifampicin was the most effective agent in eliminating viable L. pneumophila from the lungs and also in preventing pulmonary lesions.

Persistence in serum and lungs of guinea pigs of erythromycin, gentamicin, chloramphenicol and rifampicin and their in-vitro activities against Legionella pneumophila.

The penetration and persistence in the serum and lungs of guinea pigs after parenteral administration of erythromycin, gentamicin, chloramphenicol and rifampicin, and their in-vitro activities against Legionella pneumophila were investigated. The most active agent was rifampicin (MIC 0.0625 mg/l, MBC 0.125 mg/l) and effective levels of this drug were present in serum and lungs up to 10 h after injection. Erythromycin accumulated to very high levels in the lungs and had good bacteriostatic activity in vitro. Gentamicin was highly bactericidal in liquid culture but showed poor lung penetration on injection. Chloramphenicol, the least inhibitory of the four antibiotics, had an MIC of 1.0 mg/l. Active chloramphenicol was not detected in guinea pig serum and lungs following ip or im administration. The differences in the penetration and persistence of these drugs in the lungs of guinea pigs may explain the reported poor correlation between in-vitro and in-vivo activity against L. pneumophila. The results are useful for evaluating regimens for therapy of Legionnaires' disease in the aerosol infected guinea pig model.

Studies on protective immunity to aerosol challenge with Legionella pneumophila.

Guinea pigs exposed to 1, 2 or 3 sub-lethal aerosol infections with L. pneumophila developed ELISA serum antibodies after each infection, but were not protected against a lethal aerosol challenge. They died earlier than untreated control animals, though with the same acute exudative bronchopneumonia. Lung bacterial counts were lower in the immunized animals. The extent of pulmonary lesions increased with each successive sublethal infection and lymphoid cell infiltration was prominent after the second. Animals immunized with serotype-specific antigen developed serum antibodies, but were also not protected against lethal aerosol challenge and died earlier than controls.