Assessing the environmental benefit of palladium-based single-atom heterogeneous catalysts for Sonogashira coupling.

The Pd-Cu catalysed Sonogashira coupling of terminal alkynes and aryl halides is a cornerstone synthetic strategy for C-C bond formation. Homogeneous organometallic systems conventionally applied are typically not reusable and require efficient downstream Pd removal steps for product purification, making it challenging to fully recover the precious metal. A holistic cradle-to-gate life cycle assessment (LCA) unveils that process footprint can be improved up to two orders of magnitude from repeated catalyst reuse. New classes of heterogeneous catalysts based on isolated metal atoms (single-atom catalysts, SACs) demonstrate promising potential to synergise the benefits of solid and molecular catalysts for efficient Pd utilisation. Here we show that using Pd atoms anchored on nitrogen-doped carbon permits full recovery of the metal and reuse of the catalyst over multiple cycles. A hybrid process using the Pd-SAC with a homogeneous CuI cocatalyst is more effective than a fully heterogeneous analogue based on a bimetallic Pd-Cu SAC, which deactivates severely due to copper leaching. In some scenarios, the LCA-based metrics demonstrate the footprint of the hybrid homogeneous-heterogeneous catalytic process is leaner than the purely homogeneous counterpart already upon single reuse. Combining LCA with experimental evaluation will be a useful guide to the implementation of solid, reusable catalysts for sustainable organic transformations.

Structural analysis of IPC zeolites and related materials using positron annihilation spectroscopy and high-resolution argon adsorption.

The advanced investigation of pore networks in isoreticular zeolites and mesoporous materials related to the IPC family was performed using high-resolution argon adsorption experiments coupled with the development of a state-of-the-art non-local density functional theory approach. The optimization of a kernel for model sorption isotherms for materials possessing the same layer structure, differing only in the interlayer connectivity (e.g. oxygen bridges, single- or double-four-ring building units, mesoscale pillars etc.) revealed remarkable differences in their porous systems. Using high-resolution adsorption data, the bimodal pore size distribution consistent with crystallographic data for IPC-6, IPC-7 and UTL samples is shown for the first time. A dynamic assessment by positron annihilation lifetime spectroscopy (PALS) provided complementary insights, simply distinguishing the enhanced accessibility of the pore network in samples incorporating mesoscale pillars and revealing the presence of a certain fraction of micropores undetected by gas sorption. Nonetheless, subtle differences in the pore size could not be discriminated based on the widely-applied Tao-Eldrup model. The combination of both methods can be useful for the advanced characterization of microporous, mesoporous and hierarchical materials.

Correction: Synthesis, characterisation, and catalytic evaluation of hierarchical faujasite zeolites: milestones, challenges, and future directions.

Correction for 'Synthesis, characterisation, and catalytic evaluation of hierarchical faujasite zeolites: milestones, challenges, and future directions' by D. Verboekend et al., Chem. Soc. Rev., 2015, DOI: .

Synthesis, characterisation, and catalytic evaluation of hierarchical faujasite zeolites: milestones, challenges, and future directions.

Faujasite (X, Y, and USY) zeolites represent one of the most widely-applied and abundant catalysts and sorbents in the chemical industry. In the last 5 years substantial progress was made in the synthesis, characterisation, and catalytic exploitation of hierarchically-structured variants of these zeolites. Hererin, we provide an overview of these contributions, highlighting the main advancements regarding the evaluation of the nature and functionality of introduced secondary porosity. The novelty, efficiency, versatility, and sustainability of the reported bottom-up and (predominately) top-down strategies are discussed. The crucial role of the relative stability of faujasites in aqueous media is highlighted. The interplay between the physico-chemical properties of the hierarchical zeolites and their use in petrochemical and biomass-related catalytic processes is assessed.

Seroprevalence of Toxoplasma gondii in domestic sheep in Oaxaca State, Mexico.

The seroprevalence of Toxoplasma gondii infection in sheep in southern Mexico is largely unknown. Antibodies to T. gondii were determined in serum samples of 429 sheep from 4 farms in 2 geographical regions in Oaxaca State, Mexico, using the modified agglutination test (MAT); 99 (23.1%) of the 429 sheep had positive MAT titers: 1:25 in 35, 1:50 in 18, 1:100 in 7, 1:200 in 1, 1:400 in 3, 1:800 in 10, 1:1,600 in 5, and 1:3,200, or higher, in 20. Seroprevalence of T. gondii infection varied with management, breed of sheep, and location. It was significantly higher in sheep raised under semi-intensive (grazed on cultivated pasture and hay) conditions than in those raised under semi-extensive conditions (grazed on communal natural grass land). The seroprevalence of T. gondii infection was significantly higher in mixed-breed sheep than in pure breeds. Sheep raised in temperate climate in municipalities at 1,560-1,600 m above sea level (Central Valley region) had a significantly higher seroprevalence of T. gondii infection than those raised in semiarid and warm-humid climates in municipalities at 1,020-1,080 m of altitude (Cañada region) (29.8% vs. 7.1%, respectively). This is the first report of T. gondii infection in sheep in Oaxaca State, Mexico.

High prevalence of Toxoplasma gondii antibodies in domestic pigs in Oaxaca State, Mexico.

Pigs are important in the epidemiology of toxoplasmosis in North America. Seroprevalence of Toxoplasma gondii infection in 525 domestic pigs (337 backyard raised, 188 farm raised) in Oaxaca State, Mexico was determined using the modified agglutination test (MAT, cutoff 1:25). Antibodies to T. gondii were found in 58 (17.2%) of the 337 backyard pigs with MAT titers of 1:25 in 10, 1:50 in 12, 1:100 in 18, 1:200 in 6, 1:400 in 6, 1:800 in 3, and 1:1,600 in 3. Seropositive pigs were found in 39 (37.9%) of 103 homes in all 7 municipalities surveyed. Seroprevalence of T. gondii infection in backyard pigs varied with age, gender, geographic region, climate, and altitude. High seroprevalence was found in pigs ≥ 9-mo-old (40%), in females (40%), in pigs from the Istmo region (33.3%), and in those raised in a tropical climate (65%). Seroprevalence was higher (24.5%) in pigs raised at 100-660 m above sea level than in those at 20-60 m of altitude (14.2%). With respect to farm pigs, only 1 (0.5%, MAT titer 1:100) of 188 pigs from 5 farms was positive for anti- T. gondii antibodies. The results affirm that the management system (outdoor vs. indoor system with biosecurity) is a key factor in the epidemiology of porcine toxoplasmosis. Because there is no national system of determining the T. gondii infection status at the time of slaughter, precautions should be taken while handling pig carcasses, and all pork should be cooked thoroughly before human consumption.

Periodic DFT study of the structural and electronic properties of bulk CoAl2O4 spinel.

In this study, structural and electronic properties of CoAl2O4 spinel are investigated for the first time by means of quantum chemical computational tools. Coupling supercell periodic calculations under the density functional theory formalism with a nonempirical quasi-harmonic Debye model, we examine the influence of temperature on the relative stability of several cation distributions of Co2+ and Al3+ over tetrahedral and octahedral interstices of the oxygen sublattice. Our simulations are able to reproduce the experimentally observed trend: (i) the normal spinel is calculated to be the stable structure at static and low-temperature conditions, and (ii) as the temperature increases, the preference of structures with Al3+ at tetrahedral sites (and Co2+ at octahedral sites) is found to progress following an asymptotic conduct. The effects of the cation distributions on geometrical variations of electronic and magnetic properties of CoAl2O4 can be interpreted as dominated by the local behavior of Co2+ at octahedral sites.

Nanoplatelet-based reconstructed hydrotalcites: towards more efficient solid base catalysts in aldol condensations.

Rehydration of Mg-Al hydrotalcite in the liquid phase using ultrasounds or a high stirring speed leads to nanoplatelets with surface areas of 400 m(2) g(-1), displaying catalytic activities in aldol condensations up to 8 times higher than the best catalytic system reported in the literature.

DFT characterization of adsorbed NH(x) species on Pt(100) and Pt(111) surfaces.

Periodic density functional theory (DFT) calculations using plane waves have been performed to systematically investigate the adsorption and relative stability of ammonia and its dehydrogenated species on Pt(111) and Pt(100) surfaces. Different adsorption geometries and positions have been studied, and in each case, the equilibrium configuration has been determined by relaxation of the system. The vibrational spectra of the various ammonia fragments have been computed, and band assignments have been compared in detail with available experimental data. The adsorption of NH3 (on top) and NH2 (bridge) is more favorable on Pt(100) than on Pt(111), while similar adsorption energies were computed for NH (hollow) and N (hollow) on both surfaces. The remarkably lower adsorption energy of NH2 over Pt(111) as compared with Pt(100) (the difference being approximately 0.7 eV) can be related to different geometric and electronic factors associated with this particular intermediate. Accordingly, the type of platinum surface determines the most stable NH(x) fragment: Pt(100) has more affinity for NH2 species, whereas NH species are preferred over Pt(111).

Techniques and complications of ileostomy takedown.

OBJECTIVE: We use a loop ileostomy for temporary fecal diversion because of ease of technical construction and assumed low complication rate. Here, we review our complications of loop ileostomy and takedown using three techniques of closure. METHODS: We reviewed charts of all patients who had temporary ileostomies constructed during 1987 to 1995 (n = 366). Ileostomy takedown was performed in 339 patients using one of three closure techniques: enterotomy suture (65%), resection with handsewn anastomosis (20%), and stapled anastomosis (15%). Complications were recorded for pre-takedown and 30-day post-takedown intervals. RESULTS: Overall complication rate was 28%. Pre-takedown complications occurred in 21 patients (5.7%), including small bowel obstruction (2.5%) and dehydration/electrolyte derangement (2.2%). Post-takedown complications occurred in 83 patients (24.5%), including wound infection (14.2%), small bowel obstruction (5%), anastomotic leak (2.9%), and 1 death from a cardiac event. Post-takedown obstruction was higher for closure using resection with sutured anastomosis (12%) compared with enterotomy suture (2.3%), P < or = 0.003. Stapled anastomosis had an intermediate rate of obstruction (7.7%). Anastomotic leak was similar between closure techniques. CONCLUSIONS: Loop ileostomy and takedown are associated with low rates of serious complications (5% or less). As such, we continue to advocate use of loop ileostomy as a diversion procedure. Closure by enterotomy suture is preferred over resection. However, if resection is required, closure by stapled anastomosis is preferred over suture anastomosis.

[Treatment of severe arterial hypertension with captopril (SQ 14.225) (author's transl)]. / Traitement de l'hypertension artérielle grave par le captopril (SQ 14225).

Captopril, an inhibitor of the angiotensin-converting enzyme, was administered for 9 to 13 months to 11 patients with severe arterial hypertension and/or hypertension resistant to conventional treatments. The drug had to be discontinued in 2 patients on account of skin rash or peripheral neuropathy. In the remaining 9 patients, return of blood pressure to normal levels was obtained with combined captopril and diuretic treatment, except in one case where captopril alone proved sufficient. The anti-hypertensive effect developed over several weeks. No rebound phenomenon was observed after temporary arrest of captopril. Positive correlation was noted between the fall in blood pressure induced by the first dose of captopril and the patients' initial plasma renin activity. Captopril appears to be of considerable interest for the treatment of severe hypertension, even when it is associated with renal insufficiency.