Generic and facile mechanochemical access to versatile lattice-confined Pd(ii)-based heterometallic sites.

Metal-organic frameworks (MOFs) show remarkable potential in a broad array of applications given their physical and chemical versatility. Classical synthesis of MOFs is performed using solution chemistry at elevated temperatures to achieve reversible metal-ligand bond formation. These harsh conditions may not be suitable for chemical species sensitive to high temperature or prone to deleterious reactions with solvents. For instance, Pd(ii) is susceptible to reduction under solvothermal conditions and is not a common metal node of MOFs. We report a generic and facile mechanochemical strategy that directly incorporates a series of Pd(ii)-based heterobimetallic clusters into MOFs as metal nodes without Pd(ii) being reduced to Pd(0). Mechanochemistry features advantages of short reaction time, minimum solvent, high reaction yield, and high degree of synthetic control. Catalytic performances of lattice-confined heterobimetallic sites are examined for nitrene transfer reactions and we demonstrate that the chemoselectivity for allylic amination versus olefin aziridination is readily tuned by the identity of the first-row metal ion in Pd(ii)-based heterobimetallic clusters.

The fate of inhaled uranium-containing particles upon clearance to gastrointestinal tract.

Uranium-bearing respirable dust can cause various health problems, such as cardiovascular and neurological disorders, cancers, immunosuppression, and autoimmunity. Exposure to elevated levels of uranium is linked to many such health conditions in Navajo Nation residents in northwestern New Mexico. Most studies have focused on the fate of inhaled dust particles (<4 µm) in the lungs. However, larger-sized inhaled particles (10-20 µm) can be cleared to the human gastrointestinal tract (GIT), thereby enabling them to interact with stomach and intestinal fluids. Despite the vital importance of understanding the fate of uranium-bearing solids entering the human GIT and their impact on body tissues, cells, and gut microbiota, our understanding remains limited. This study investigated uranium solubility from dust and sediment samples collected near two uranium mines in the Grants Mining District in New Mexico in two simulated gastrointestinal fluids representing fasting conditions in the GIT: Simulated Gastric Fluid (SGF) and Simulated Intestinal Fluid (SIF). The dissolution of uranium from dust depends on its mineralogy, fluid pH, and composition. The dust samples from the Jackpile mine favored higher solubility in the SIF solution, whereas the sediment samples from the St. Anthony Mine favored higher solubility in the SGF solution. Further, geochemical calculations performed with the PHREEQC modeling program suggested that samples rich in the minerals andersonite, tyuyamunite, and/or autunite have higher uranium dissolution in the SIF solution than in the SGF solution. We also tested the effect of added kaolinite and microcline, which are both present in some samples. The ratio of dissolved uranium in SGF relative to SIF decreases with the addition of kaolinite for all mineral phases but andersonite. With the addition of microcline, the ratio of dissolved uranium in SGF relative to SIF decreases for all the tested uranium minerals. The most prevalent oxidation state of dissolved uranium was computationally determined as +6, U(VI). The geochemical calculations made with PHREEQC agree with the experimentally observed results. Therefore, this study gives insight into the mineralogy-controlled toxicological assessment of uranium-containing inhaled dust cleared to the gastrointestinal tract.

Mechanochemistry of Group 4 Element-Based Metal-Organic Frameworks.

Mechanochemical synthesis is emerging as an environmentally friendly yet efficient approach to preparing metal-organic frameworks (MOFs). Herein, we report our systematic investigation on the mechanochemical syntheses of Group 4 element-based MOFs. The developed mechanochemistry allows us to synthesize a family of Hf4O4(OH)4(OOC)12-based MOFs. Integrating [Zr6O4(OH)4(OAc)12]2 and [Hf6O4(OH)4(OAc)12]2 under the mechanochemical conditions leads to a unique family of cluster-precise multimetallic MOFs that cannot be accessed by the conventional solvothermal synthesis. Extensive efforts have not yielded an effective pathway for preparing TiIV-derived MOFs, tentatively because of the relatively low Ti-O bond dissociation energy.

Outbreak of nonfermentative Gram-negative bacteria (Ralstonia pickettii and Stenotrophomonas maltophilia) in a hemodialysis center.

We report a case series of seven patients with nonfermentative Gram-negative bacteria infections in a single dialysis center; four patients with Ralstonia pickettii and three patients with Stenotrophomonas maltophilia. Two of the seven patients were admitted to hospital for intravenous antibiotic treatment, while the rest were treated with oral antibiotics at home. Both the admitted patients had temporary vascular catheter infections from the aforementioned pathogens. We conclude that the outbreak is due to colonization of treated reverse osmosis water, presumably through contamination via polluted filters and compounded by the usage of reprocessed dialysers in the dialysis center. This is especially relevant because contaminated treated water is directly introduced into the blood compartment of the dialysers during reprocessing. In addition, there seems to be a propensity for both organisms to cause prolonged febrile reactions in patients with temporary vascular catheters, likely through the early development of biofilm. Intensification of general sterilization procedures, servicing and replacement of old decrepit components of the water treatment system and temporary cessation of dialyser reuse practice seem to have halted the outbreak. Due to the virulent nature and difficult resistant profile of nonfermentative Gram-negative bacteria, we strongly recommend meticulous vigilance in the surveillance of culture isolates in routine microbiological specimens from dialysis centers, especially if there is a senescent water treatment system and a practice of reprocessing dialysers.