Asymmetric sound scattering by gratings of monopolar and dipolar resonators in a viscoelastic materiala).

A self-consistent analytical model of a locally resonant coating exhibiting strong asymmetric wave scattering is presented. Gratings of resonant inclusions composed of cavities and hard particles embedded in a soft matrix are translated to the problem of sound scattering by monopolar and dipolar type resonators in a one-dimensional waveguide. Equations of motion for gratings of cavities and hard particles are developed that incorporate added mass, damping, and restoration forces to take into account multiple scattering effects. Expressions for the impedances of the resonators are derived from which the particle velocity fields are obtained. Monopole and dipole strengths are also calculated in terms of polarizability tensor components, which in turn are obtained from a retrieval method. Sound scattering by monopolar and dipolar resonators of different size and distribution within the waveguide are examined. Using detailed understanding of the interaction between groups of resonators, optimized solutions for a new class of acoustic materials can be designed by selecting layers of resonators to produce a given response.

Response to Comment on "Pushing the frontiers of density functionals by solving the fractional electron problem".

Gerasimov et al. claim that the ability of DM21 to respect fractional charge (FC) and fractional spin (FS) conditions outside of the training set has not been demonstrated in our paper. This is based on (i) asserting that the training set has a ~50% overlap with our bond-breaking benchmark (BBB) and (ii) questioning the validity and accuracy of our other generalization examples. We disagree with their analysis and believe that the points raised are either incorrect or not relevant to the main conclusions of the paper and to the assessment of general quality of DM21.

Pushing the frontiers of density functionals by solving the fractional electron problem.

Density functional theory describes matter at the quantum level, but all popular approximations suffer from systematic errors that arise from the violation of mathematical properties of the exact functional. We overcame this fundamental limitation by training a neural network on molecular data and on fictitious systems with fractional charge and spin. The resulting functional, DM21 (DeepMind 21), correctly describes typical examples of artificial charge delocalization and strong correlation and performs better than traditional functionals on thorough benchmarks for main-group atoms and molecules. DM21 accurately models complex systems such as hydrogen chains, charged DNA base pairs, and diradical transition states. More crucially for the field, because our methodology relies on data and constraints, which are continually improving, it represents a viable pathway toward the exact universal functional.

Procaine spinal anesthesia: a pilot study of the incidence of transient neurologic symptoms.

STUDY OBJECTIVES: To determine the approximate incidence of transient neurologic symptoms (TNS) [formerly known as transient radicular irritation (TRI)] associated with procaine spinal anesthesia, and whether fentanyl prolongs the duration of procaine spinal anesthesia. DESIGN: Unrandomized pilot study. SETTING: Community teaching hospital. PATIENTS: 106 consecutive patients scheduled for spinal anesthesia for procedures anticipated to last less than 90 minutes. INTERVENTIONS: All patients received 5% procaine for spinal anesthesia. Fentanyl 20 micrograms was added for procedures anticipated to last longer than 45 minutes (but less than 90 min). Intraoperatively the adequacy of duration, level, and intensity of anesthesia were observed. Time from injection of local anesthetic until knee-bending was recorded. Three days postoperatively, patients were questioned intensively in an effort to determine whether back pain and/or symptoms consistent with TNS had occurred. MEASUREMENTS AND MAIN RESULTS: Duration of anesthesia was adequate in all but one instance. The intensity and the sensory level of anesthesia were satisfactory with one exception, a woman who had an unexpectedly low sensory level (L1) after 60 mg of procaine for cerclage, and who was also was the only patients to develop TNS. The incidence of TNS (0.9%) was markedly less than that reported after lidocaine and similar to the incidence observed after bupivacaine. Mild back pain without radiation occurred in 11 patients (10%), an incidence that is similar to that seen after bupivacaine and lidocaine. Compared with procaine alone, the addition of fentanyl significantly (p = 0.0001) prolonged the time to bending knees from 72 minutes to 97 minutes. CONCLUSIONS: Procaine may be a useful alternative to lidocaine for short procedures, and it is less likely to produce TNS. Fentanyl prolongs motor block when added to procaine.

Negative-pressure pulmonary edema after endotracheal intubation.

A review of complications occurring in conjunction with general anesthesia identified eight patients with laryngospasm-induced negative-pressure pulmonary edema after endotracheal intubation. Six male and two female patients (mean age, 31.9 years) developed pulmonary edema immediately or up to 25 minutes after extubation. Radiographs obtained 15-165 minutes after symptoms developed revealed alveolar edema and predominating interstitial edema in four patients each. Seven of eight had bilateral centralized patterns, and one had unilateral pulmonary edema. The mean vascular pedicle width was 67 mm +/- 12, a value 40% higher than the normal mean of 48 mm. The mean cardiothoracic ratio was 0.54 +/- .07 (normal mean, 0.53). There were no radiologic abnormalities of the trachea. Negative-pressure pulmonary edema should be suspected in young patients with findings of bilateral centralized pulmonary edema, a wide vascular pedicle, and a normal cardiothoracic ratio in the immediate postoperative period.

Rapid sequence induction using vecuronium.

The purpose of this study was to determine the ideal priming and total dose of vecuronium when used as the relaxant during rapid sequence induction of anesthesia and tracheal intubation. Seventy patients were studied. Various priming and total dose schedules using vecuronium were compared with succinylcholine, 1.5 mg/kg. The mean onset times, intubating conditions, and mean duration times were compared. A priming dose of 10 micrograms/kg produced good intubation conditions with both 70 micrograms/kg and 150 micrograms/kg (total doses), but the mean onset times remained significantly longer than succinylcholine 1.5 mg/kg (P less than 0.05). A priming dose of 15 micrograms/kg of vecuronium with 100 micrograms/kg total dose, on the other hand, not only produced excellent intubating conditions but also resulted in a mean onset time not significantly different from succinylcholine, 1.5 mg/kg. This latter dose schedule of vecuronium is recommended for rapid sequence induction when succinylcholine is contraindicated. Vecuronium is preferable to pancuronium for rapid sequence induction because of its lack of cardiovascular side effects and short duration.

Fentanyl/alfentanil for pelvic laparoscopy.

Alfentanil, a new narcotic analgesic, was compared to fentanyl in a technique of balanced anaesthesia using thiopentone 5 mg X kg-1 for induction of anaesthesia, and pancuronium 60 micrograms X kg-1 to facilitate intubation. The study group consisted of 80 female patients scheduled for pelvic laparoscopy. The total dose of alfentanil averaged 2.06 mg (range 1.5-2.5 mg) whereas the dose of fentanyl averaged 0.21 mg (range 0.1-0.25 mg). There was no significant difference between the two groups in duration of anaesthesia, time to extubation, verbal response time or time to orientation to person, place and time. Following intubation, there was a significant rise in heart rate and blood pressure (p less than 0.01) in both groups, but, again, there was no difference between groups. Postoperatively, the respiratory rate was not below 12 per minute for any patient in the study and was comparable for the two groups. The only significant side effect was postoperative nausea which occurred in over 40 per cent of patients and was not significantly different between the two groups. We conclude that alfentanil is a suitable narcotic drug for short surgical procedures on ambulatory patients, but the drug has no marked advantage over fentanyl for these procedures.

Maximal inspiratory volume and postoperative pulmonary complications.

The results of this study indicate that, in order to use any method of respiratory therapy intelligently and effectively in the postoperative period, it is imperative to know the preoperative maximal inspiratory volume of the patient and to measure the inspired volume during treatment. Only then can a physician determine if specific treatment is necessary at all, and if it is, whether or not incentive spirometry would be of greater benefit to the patient than intermittent positive pressure breathing therapy.