The many-body electronic interactions of Fe(II)-porphyrin.

Fe(II)-porphyrin complexes exhibit a diverse range of electronic interactions between the metal and macrocycle. Herein, the incremental full configuration interaction method is applied to the entire space of valence orbitals of a Fe(II)-porphyrin model using a modest basis set. A novel visualization framework is proposed to analyze individual many-body contributions to the correlation energy, providing detailed maps of this complex's highly correlated electronic structure. This technique is used to parse the numerous interactions of two low-lying triplet states (3A2g and 3Eg) and to show that strong metal d-d and macrocycle π-π orbital interactions preferentially stabilize the 3A2g state. d-π interactions, on the other hand, preferentially stabilize the 3Eg state and primarily appear when correlating six electrons at a time. Ultimately, the Fe(II)-porphyrin model's full set of 88 valence electrons are correlated in 275 orbitals, showing the interactions up to the 4-body level, which covers the great majority of correlations in this system.

Stepwise basis set selection.

The computational cost of quantum chemical methods grows rapidly with increasing level of theory and basis set size. At increasing costs, higher accuracies can be reached, forcing a compromise between cost and accuracy for most molecular systems. Heats of reaction, however, are mostly determined by a subset of atoms that experience significant bonding and/or electronic changes. To exploit this fact, the Stepwise Basis Builder (SBB) algorithm selectively adds basis functions to reactive atoms and maintains small basis sets on spectator atoms. This article introduces the SBB algorithm and how it chooses a basis for each atom, predicts calculation errors, and uses these predicted errors to reach target levels of accuracy. Benchmarks show SBB heats of reaction and activation barriers converge to values consistent with higher-quality calculations using a greatly reduced number of basis functions. © 2018 Wiley Periodicals, Inc.

The effect of delayed visual feedback on telerobotic surgery.

BACKGROUND: Telerobotic surgery is ideally suited for remote applications in which the instrument control console is stationed separately from the end-effectors at the patient's bedside. However, if the distance between the console and the patient is great enough, a lag effect or latency between end-effector manipulation and the depicted image leads to alterations in movement patterns. The purpose of this study was to determine the effect of visual delay on surgical task performance. METHODS: At an endoscopic skill station, an analogue delay device was interposed between the surgical field and monitor to delay the transmission of visual information, thus mimicking the distance effect of data transmission. Three surgeons with similar laparoscopic experience participated in the laparoscopic knot tying portion of the study, and seven residents participated in the accuracy and dexterity tasks. The time to complete a single throw was recorded in seconds after adding consecutively increasingly time delay in 50 ms increments. Similar time delay increments were added for the accuracy and dexterity tasks, which involved passing a needle through two adjacent circles and passing a small cylinder through a larger one to reproduce two-handed coordination and spatial resolution. Data were presented as the median time to complete each task. RESULTS: For all three tasks, an incremental increase in time delay was associated with a significant (p < 0.001) increase in the time to complete the task. For dexterity, a statistically significant (p

Caffeine intoxication: a near fatality.

A 37-year-old woman ingested approximately 27 g caffeine in a suicide attempt. After initial presentation with supraventricular tachycardia, hypotension, and coma, she suffered repeated episodes of ventricular fibrillation. Resin hemoperfusion was performed, with prompt stabilization of the patient's cardiovascular status. Methylxanthine toxicity is briefly reviewed.