Charge trapping by iodine ions in photorefractive Sn2P2S6 crystals.

Electron paramagnetic resonance (EPR) is used to establish the role of iodine as an electron trap in tin hypothiodiphosphate (Sn2P2S6) crystals. Iodine ions are unintentionally incorporated when the crystals are grown by the chemical-vapor-transport method with SnI4 as the transport agent. The Sn2P2S6 crystals consist of Sn2+ ions and (P2S6)4- anionic groups. During growth, an iodine ion replaces a phosphorus in a few of the anionic groups, thus forming (IPS6)4- molecular ions. Following an exposure at low temperature to 633 nm laser light, these (IPS6)4- ions trap an electron and convert to EPR-active (IPS6)5- groups with S = 1/2. A concentration near 1.1 × 1017 cm-3 is produced. The EPR spectrum from the (IPS6)5- ions has well-resolved structure resulting from large hyperfine interactions with the 127I and 31P nuclei. Analysis of the angular dependence of the spectrum gives principal values of 1.9795, 2.0123, and 2.0581 for the g matrix, 232 MHz, 263 MHz, and 663 MHz for the 127I hyperfine matrix, and 1507 MHz, 1803 MHz, and 1997 MHz for the 31P hyperfine matrix. Results from quantum-chemistry modeling (unrestricted Hartree-Fock/second-order Møller-Plesset perturbation theory) support the (IPS6)5- assignment for the EPR spectrum. The transient two-beam coupling gain can be improved in these photorefractive Sn2P2S6 crystals by better controlling the point defects that trap charge.

Artificial neural network discovery of a switchable metasurface reflector.

Optical materials engineered to dynamically and selectively manipulate electromagnetic waves are essential to the future of modern optical systems. In this paper, we simulate various metasurface configurations consisting of periodic 1D bars or 2D pillars made of the ternary phase change material Ge2Sb2Te5 (GST). Dynamic switching behavior in reflectance is exploited due to a drastic refractive index change between the crystalline and amorphous states of GST. Selectivity in the reflection and transmission spectra is manipulated by tailoring the geometrical parameters of the metasurface. Due to the immense number of possible metasurface configurations, we train deep neural networks capable of exploring all possible designs within the working parameter space. The data requirements, predictive accuracy, and robustness of these neural networks are benchmarked against a ground truth by varying quality and quantity of training data. After ensuring trustworthy neural network advisory, we identify and validate optimal GST metasurface configurations best suited as dynamic switchable mirrors depending on selected light and manufacturing constraints.

Impact of patient handover structure on neonatal perioperative safety.

OBJECTIVE: To compare the incidence, severity, preventability, and contributing factors of non-routine events-deviations from optimal care based on the clinical situation-associated with team-based, nurse-to-nurse, and mixed handovers in a large cohort of surgical neonates. STUDY DESIGN: A prospective observational study and one-time cross-sectional provider survey were conducted at one urban academic children's hospital. 130 non-cardiac surgical cases in 109 neonates who received pre- and post-operative NICU care. RESULTS: The incidence of clinician-reported NREs was high (101/130 cases, 78%) but did not differ significantly across acuity-tailored neonatal handover practices. National Surgical Quality Improvement-Pediatric occurrences of major morbidity were significantly higher (p < 0.001) in direct team handovers than indirect nursing or mixed handovers. CONCLUSIONS: NREs occur at a high rate and are of variable severity in neonatal perioperative care. NRE rates and contributory factors were homogenous across handover types. Surveyed clinicians recommend structured handovers for all patients at every transfer point regardless of acuity.

Video capture of clinical care to enhance patient safety.

Experience from other domains suggests that videotaping and analyzing actual clinical care can provide valuable insights for enhancing patient safety through improvements in the process of care. Methods are described for the videotaping and analysis of clinical care using a high quality portable multi-angle digital video system that enables simultaneous capture of vital signs and time code synchronization of all data streams. An observer can conduct clinician performance assessment (such as workload measurements or behavioral task analysis) either in real time (during videotaping) or while viewing previously recorded videotapes. Supplemental data are synchronized with the video record and stored electronically in a hierarchical database. The video records are transferred to DVD, resulting in a small, cheap, and accessible archive. A number of technical and logistical issues are discussed, including consent of patients and clinicians, maintaining subject privacy and confidentiality, and data security. Using anesthesiology as a test environment, over 270 clinical cases (872 hours) have been successfully videotaped and processed using the system.

Human factors research in anesthesia patient safety.

Patient safety has become a major public concern. Human factors research in other high-risk fields has demonstrated how rigorous study of factors that affect job performance can lead to improved outcome and reduced errors after evidence-based redesign of tasks or systems. These techniques have increasingly been applied to the anesthesia work environment. This paper describes data obtained recently using task analysis and workload assessment during actual patient care and the use of cognitive task analysis to study clinical decision making. A novel concept of "non-routine events" is introduced and pilot data are presented. The results support the assertion that human factors research can make important contributions to patient safety. Information technologies play a key role in these efforts.

Computerised visual field deficits in tears of the retinal pigment epithelium.

Retinal Pigment epithelial tears have been well documented as a complication of pigment epithelial detachment in patients with age related macular degeneration. Spontaneous and iatrogenic separation of detached retinal pigment epithelium, with subsequent retraction and exposure of the underlying choriocapillaris and Bruch's membrane, usually results in poor visual function in the affected areas. However, exact characterisation of the resultant scotomas has not been previously described. We present two patients with spontaneous pigment epithelial tears who underwent Octopus computerised visual field analysis. The density and characteristics of their associated field loss is compared with their clinical and fluorescein angiographic appearance.

Monitor: an expert system that validates and interprets time-dependent partial data based on a cystic fibrosis home monitoring program.

The use of health diaries to monitor patients with chronic diseases has often been complicated by difficulties encountered in data quality assurance and interpretation. An expert system, Monitor, has been developed to predict the health status of cystic fibrosis patients based on daily home measurements of pulse, respiratory rate, weight, inspired vital capacity, and a check list of symptoms of acute illness. This system ensures data reliability beyond what can be achieved in most current automatic error detection procedures by validating inputs against patient-specific expectations. Its explicit representation of the time dimension and the hierarchical structure of its knowledge base facilitate the abstraction of trends and relationships among the time-dependent data. Dynamically imposed expectations also lend flexibility to the interpretation process by allowing the processing of partial (incomplete) data. Monitor correctly classified 86 percent (three-category classification) and 94 percent (two-category classification) of 111 cases. This demonstrates that expert systems can be a feasible approach in building more robust diary monitoring systems.

Using a symbiotic man/machine approach to evaluating visual clinical research data.

Some candidate medical expert system applications have a significant visual component. Knowledge engineers usually dismiss such task domains as potential expert systems applications. Our success in developing ESCA, a system for evaluating serial coronary angiograms, shows that such task domains should not be dismissed so quickly. We used a symbiotic approach between man and machine, where technologists provide the visual skills with an expert system imitating the conceptual skills of the expert, to produce a partially automated system that is more consistent and cost effective than one that is fully manual. The agreement between the system's conclusions and that of a panel of experts is good. The expert system actually has a slightly higher agreement rate with the expert panel than the agreement rate between two expert panel teams evaluating the same film pair.

An example of expert systems applied to clinical trials: analysis of serial graded exercise ECG test data.

Clinical trials collect large amounts of data over time. The use of statistical methods to compare and interpret these serial data often fall short of complete evaluation because the analysis requires clinical judgment. As an alternative, some trials use individual experts or panels of experts to evaluate data, but this method usually requires the participation of clinicians who must spend large amounts of time performing tedious, repetitive tasks. The authors examined the use of expert systems to analyze serial clinical trial data where the analyses required use of clinical judgment. A prototype expert system was built to assess the data obtained from a pair of serial graded exercise ECG tests and reach a decision that would duplicate the decision reached by a cardiologist. The experiment was successful. Expert systems should be further developed and tested in other areas, such as serial coronary arteriography data.

Characterization and evaluation of monoclonal antibodies developed for typing influenza A and influenza B viruses.

Monoclonal antibodies that are broadly reactive with influenza A or influenza B viruses were produced as stable reagents for typing influenza viruses. Monoclonal antibodies to influenza A were specific for either matrix protein or nucleoprotein. The antibodies to influenza B were specific for nucleoprotein or hemagglutinin protein. In an enzyme immunoassay procedure, influenza A antibodies detected H1N1, H2N2, and H3N2 influenza A virus strains collected between 1934 and 1984. Each of the influenza B antibodies detected influenza B reference viruses collected between 1940 and 1984. Pools of either influenza A or influenza B monoclonal antibodies were used to detect influenza viruses reisolated from clinical specimens in tissue culture. At 48 h after inoculation, the influenza A monoclonal antibodies detected 64% of H1N1 and 94% of H3N2 influenza A specimens, and the influenza B monoclonal antibodies detected 79% of the influenza B specimens. The results of this study suggest that the monoclonal antibodies described should provide useful diagnostic reagents for workers in virology laboratories who wish to isolate and identify influenza virus but have been unable to obtain consistent supplies of animal sera specific for influenza A or B viruses.

An intelligent control strategy for computer consultation.

Expert consultant systems often perform computations on a directed graph of associated propositions. Each proposition is represented by a node. Edges connecting these nodes are associated with rules which organize the propositions into antecedent/consequent relationships. A node may be assigned a value through the edges that bind it to its antecedents. Various strategies are employed to determine assignment sequences that result in efficient computer consultation. One such strategy, the merit system, has been successfully implemented in Battle, an expert consultant system for the Marine Corps. The merit strategy enables Battle to focus the consultation process on the most appropriate questions. The merit system, originally defined for logical functions in the Multiple program, has been extended to the Mycin style of propagation and to the method of subjective Bayesian assignments used by Prospector. A procedure for merit calculations with any differentiable, real-valued assignment function is presented. Our experience has shown that merit values provide an efficient flow of control for expert consultation.