Slow Magnetic Relaxation of a 12-Metallacrown-4 Complex with a Manganese(III)-Copper(II) Heterometallic Ring Motif.

The heterobimetallic metallacrown (MC), (TMA)2{Mn(OAc)2[12-MCMn(III)Cu(II)N(shi)-4](CH3OH)}·2.90CH3OH, 1, where TMA+ is tetramethylammonium, -OAc is acetate, and shi3- is salicylhydroximate, consists of a MnII ion captured in the central cavity and alternating unambiguous and ordered manganese(III) and copper(II) sites about the MC ring, a first for the archetypal MC structure design. DC-magnetometry characterization and subsequent simulation with the Spin Hamiltonian H = -J1(s1 + s3)·s5 - J2(s2 + s4)·s5 - J3Σi=14si·si+1 + d(sz,12 + sz,32) + µBΣj=15gjsj·B indicates an S = 5/2 ground state and a sizable axial zero-field splitting on MnIII. AC-susceptibility measurements reveal that 1 displays slow magnetization relaxation akin to single-molecule magnet (SMM) behavior.

Unravelling biocomplexity of electroactive biofilms for producing hydrogen from biomass.

Leveraging nature's biocomplexity for solving human problems requires better understanding of the syntrophic relationships in engineered microbiomes developed in bioreactor systems. Understanding the interactions between microbial players within the community will be key to enhancing conversion and production rates from biomass streams. Here we investigate a bioelectrochemical system employing an enriched microbial consortium for conversion of a switchgrass-derived bio-oil aqueous phase (BOAP) into hydrogen via microbial electrolysis (MEC). MECs offer the potential to produce hydrogen in an integrated fashion in biorefinery platforms and as a means of energy storage through decentralized production to supply hydrogen to fuelling stations, as the world strives to move towards cleaner fuels and electricity-mediated transportation. A unique approach combining differential substrate and redox conditions revealed efficient but rate-limiting fermentation of the compounds within BOAP by the anode microbial community through a division of labour strategy combined with multiple levels of syntrophy. Despite the fermentation limitation, the adapted abilities of the microbial community resulted in a high hydrogen productivity of 9.35 L per L-day. Using pure acetic acid as the substrate instead of the biomass-derived stream resulted in a three-fold improvement in productivity. This high rate of exoelectrogenesis signifies the potential commercial feasibility of MEC technology for integration in biorefineries.

Transthoracic dobutamine stress echocardiography in patients undergoing bariatric surgery.

BACKGROUND: The feasibility and value of transthoracic dobutamine stress echocardiography (DSE) in patients scheduled for bariatric surgery has not been investigated. METHODS: We evaluated 611 patients (86.6% female, 42 +/- 10 years, 136 +/- 18 kg, BMI 48.0 +/- 6.1 kg/m2) referred for DSE prior to surgery between February 2000 and July 2005. Mortality and major cardiovascular events (cardiac death, acute coronary syndrome, and urgent revascularization) were recorded 30-days postoperatively and at 6 months. RESULTS: Adequate baseline imaging quality was achieved in 590 patients (96.6%), with use of echocardiographic contrast agents in 426 patients (72.2%); the remaining 21 patients (3.4%) were referred for alternative preoperative testing. There were no serious adverse events during DSE, which was negative in 545 patients (92.4%). The test was inconclusive in 38 patients (6.4%), requiring alternative investigations, and positive in 7 patients (1.2%). Eventually, 595 patients proceeded to surgery: 539 with DSE-based risk stratification and 56 with risk stratification based on alternative testing. Laparoscopic procedures were employed in 77.0% of patients. There were 3 perioperative deaths, all attributed to sepsis (perioperative mortality 0.50%), but no major cardiovascular events at 30-days. One patient (evaluated prior to surgery with alternative testing) experienced an acute coronary syndrome during the following 6 months (event rate 0.17%). CONCLUSION: Transthoracic DSE is feasible and safe in morbidly obese patients undergoing bariatric surgery; implementation of echocardiographic contrast agents allows for adequate imaging quality in the majority of these patients. However, the very low risk of contemporary bariatric procedures questions the need for routine preoperative stress testing in asymptomatic patients.

Residents' performance in the interpretation of on-call "triple-rule-out" CT studies in patients with acute chest pain.

RATIONALE AND OBJECTIVES: To evaluate the performance of radiology residents in the interpretation of on-call, emergency "triple-rule-out" (TRO) computed tomographic (CT) studies in patients with acute chest pain. MATERIALS AND METHODS: The study was institutional review board-approved and Health Insurance Portability and Accountability Act compliant. Data from 617 on-call TRO studies were analyzed. Dedicated software enables subspecialty attendings to grade discrepancies in interpretation between preliminary trainee reports and their final interpretation as "unlikely to be significant" (minor discrepancies) or "likely to be significant" for patient management (major discrepancies). The frequency of minor, major and all discrepancies in resident's TRO interpretations was compared to 609 emergent non-electrocardiography (ECG)-synchronized chest CT studies using Pearson χ(2) test. RESULTS: Minor discrepancies occurred more often in the TRO group (9.1% vs. 3.9%, P < .001), but there was no difference in the frequency of major discrepancies (2.1% vs. 2.8%, P = .55). Minor discrepancies in the TRO group most commonly resulted from missed extrathoracic findings with missed liver lesions being the most frequent. Major discrepancies mostly encompassed cardiac and extracardiac vascular findings but did not result in unnecessary interventions, significant immediate changes in management, or adverse patient outcomes. CONCLUSIONS: On-call resident interpretation of TRO CT studies in patients with acute chest pain is congruent with final subspecialty attending interpretation in the overwhelming majority of cases. The rate of discrepancies likely to affect patient management in this domain is not different from emergent non-ECG-synchronized chest CT.