Large-Angle, Multifunctional Metagratings Based on Freeform Multimode Geometries.

We show that silicon-based metagratings capable of large-angle, multifunctional performance can be realized using inverse freeform design. These devices consist of nonintuitive nanoscale patterns and support a large number of spatially overlapping optical modes per unit area. The quantity of modes, in combination with their optimized responses, provides the degrees of freedom required to produce high-efficiency devices. To demonstrate the power and versatility of our approach, we fabricate metagratings that can efficiently deflect light to 75° angles and multifunctional devices that can steer beams to different diffraction orders based on wavelength. A theoretical analysis of the Bloch modes supported by these devices elucidates the spatial mode profiles and coupling dynamics that make high-performance beam deflection possible. This approach represents a new paradigm in nano-optical mode engineering and utilizes different physics from the current state-of-the-art, which is based on the stitching of noninteracting waveguide structures. We envision that inverse design will enable new classes of high-performance photonic systems and new strategies toward the nanoscale control of light fields.

Analysis of material selection on dielectric metasurface performance.

Dielectric metasurfaces are ultra-thin devices that can shape optical wavefronts with extreme control. While an assortment of materials possessing a wide range of dielectric constants have been proposed and implemented, the minimum dielectric contrast required for metasurfaces to achieve high-efficiency performance, for a given device function and feature size constraint, is unclear. In this Article, we examine the impact of dielectric material selection on metasurface efficiency at optical frequencies. As a model system, we design transmissive, single-layer periodic metasurfaces (i.e., metagratings) using topology optimization, and we sweep device thickness and light deflection angle for differing material types. We find that for modest deflection angles below 40 degrees, materials with relatively low dielectric constants near 4 can be used to produce metagratings with efficiencies over 80%. However, ultra-high-efficiency devices designed for large deflection angles and multiple functions require materials with high dielectric constants comparable to silicon. We also identify, for all materials, a minimum device thickness required for optimal metagrating performance that scales inversely with dielectric constant. Our work presents materials selection guidelines for high-performance metasurfaces operating at visible and infrared wavelengths.

Topology-optimized metasurfaces: impact of initial geometric layout.

Topology optimization is a powerful iterative inverse design technique in metasurface engineering and can transform an initial layout into a high-performance device. With this method, devices are optimized within a local design phase space, making the identification of suitable initial geometries essential. In this Letter, we examine the impact of initial geometric layout on the performance of large-angle (75 deg) topology-optimized metagrating deflectors. We find that when conventional metasurface designs based on dielectric nanoposts are used as initial layouts for topology optimization, the final devices have efficiencies around 65%. In contrast, when random initial layouts are used, the final devices have ultra-high efficiencies that can reach 94%. Our numerical experiments suggest that device topologies based on conventional metasurface designs may not be suitable to produce ultra-high-efficiency, large-angle metasurfaces. Rather, initial geometric layouts with non-trivial topologies and shapes are required.

Simple analytical expression for the peak-frequency shifts of plasmonic resonances for sensing.

We derive a closed-form expression that accurately predicts the peak frequency shift and broadening induced by tiny perturbations of plasmonic nanoresonators without critically relying on repeated electrodynamic simulations of the spectral response of nanoresonator for various locations, sizes, or shapes of the perturbing objects. In comparison with other approaches of the same kind, the force of the present approach is that the derivation is supported by a mathematical formalism based on a rigorous normalization of the resonance modes of nanoresonators consisting of lossy and dispersive materials. Accordingly, accurate predictions are obtained for a large range of nanoparticle shapes and sizes used in various plasmonic nanosensors even beyond the quasistatic limit. The expression gives quantitative insight and, combined with an open-source code, provides accurate and fast predictions that are ideally suited for preliminary designs or for interpretation of experimental data. It is also valid for photonic resonators with large mode volumes.

Evaluation of a gene information summarization system by users during the analysis process of microarray datasets.

BACKGROUND: Summarization of gene information in the literature has the potential to help genomics researchers translate basic research into clinical benefits. Gene expression microarrays have been used to study biomarkers for disease and discover novel types of therapeutics and the task of finding information in journal articles on sets of genes is common for translational researchers working with microarray data. However, manually searching and scanning the literature references returned from PubMed is a time-consuming task for scientists. We built and evaluated an automatic summarizer of information on genes studied in microarray experiments. The Gene Information Clustering and Summarization System (GICSS) is a system that integrates two related steps of the microarray data analysis process: functional gene clustering and gene information gathering. The system evaluation was conducted during the process of genomic researchers analyzing their own experimental microarray datasets. RESULTS: The clusters generated by GICSS were validated by scientists during their microarray analysis process. In addition, presenting sentences in the abstract provided significantly more important information to the users than just showing the title in the default PubMed format. CONCLUSION: The evaluation results suggest that GICSS can be useful for researchers in genomic area. In addition, the hybrid evaluation method, partway between intrinsic and extrinsic system evaluation, may enable researchers to gauge the true usefulness of the tool for the scientists in their natural analysis workflow and also elicit suggestions for future enhancements. AVAILABILITY: GICSS can be accessed online at: http://ir.ohsu.edu/jianji/index.html.

Applying the Effective Technology Use Model to Implementation of Electronic Consult Management Software.

Theoretical models of technology acceptance are critical to scope projects, select interventions, and measure adoption. We describe use of the Effective Technology Use (ETU) model in the design and deployment of software supporting electronic consult management. We applied the model to four project phases: (1) needs assessment; (2) software design; (3) deployment; and (4) uptake assessment. In this paper, we describe how we used the ETU to plan stakeholder meetings, conduct usability simulations, and organize findings from a qualitative analysis to identify implementation facilitators and barriers.

Free-Form Diffractive Metagrating Design Based on Generative Adversarial Networks.

A key challenge in metasurface design is the development of algorithms that can effectively and efficiently produce high-performance devices. Design methods based on iterative optimization can push the performance limits of metasurfaces, but they require extensive computational resources that limit their implementation to small numbers of microscale devices. We show that generative neural networks can train from images of periodic, topology-optimized metagratings to produce high-efficiency, topologically complex devices operating over a broad range of deflection angles and wavelengths. Further iterative optimization of these designs yields devices with enhanced robustness and efficiencies, and these devices can be utilized as additional training data for network refinement. In this manner, generative networks can be trained, with a one-time computation cost, and used as a design tool to facilitate the production of near-optimal, topologically complex device designs. We envision that such data-driven design methodologies can apply to other physical sciences domains that require the design of functional elements operating across a wide parameter space.

High-efficiency, large-area, topology-optimized metasurfaces.

Metasurfaces are ultrathin optical elements that are highly promising for constructing lightweight and compact optical systems. For their practical implementation, it is imperative to maximize the metasurface efficiency. Topology optimization provides a pathway for pushing the limits of metasurface efficiency; however, topology optimization methods have been limited to the design of microscale devices due to the extensive computational resources that are required. We introduce a new strategy for optimizing large-area metasurfaces in a computationally efficient manner. By stitching together individually optimized sections of the metasurface, we can reduce the computational complexity of the optimization from high-polynomial to linear. As a proof of concept, we design and experimentally demonstrate large-area, high-numerical-aperture silicon metasurface lenses with focusing efficiencies exceeding 90%. These concepts can be generalized to the design of multifunctional, broadband diffractive optical devices and will enable the implementation of large-area, high-performance metasurfaces in practical optical systems.

Realization of near-perfect absorption in the whole reststrahlen band of SiC.

Materials used for outdoor radiative cooling technologies need not only be transparent in the solar spectral region, but also need to have a broadband perfect absorption in the infrared atmospheric transparency window (infrared-ATW). Silicon carbide (SiC) has been thought to be a potential candidate for such materials. However, due to the near-perfect reflection of electromagnetic waves in the whole reststrahlen band (RB) of SiC, which is within the infrared-ATW, perfect absorption in the whole RB remains a challenge. Here by constructing a cone-pillar double-structure surface on SiC, a near-perfect absorption (>97%) of normally incident electromagnetic waves in the whole RB has been realized experimentally. Simulation results reveal that the dominant reason for the near-perfect absorption is the efficient coupling of incident electromagnetic waves into the bulk evanescent waves in the free-space wavelength range (10.33 µm, 10.55 µm) and the efficient coupling of incident electromagnetic waves into the surface phonon polaritons in the free-space wavelength range (10.55 µm, 12.6 µm). Our findings open up an avenue to enhance the absorption performance of SiC in infrared-ATW, and may lead to many new applications.

Advancing biomedical image retrieval: development and analysis of a test collection.

OBJECTIVE: Develop and analyze results from an image retrieval test collection. METHODS: After participating research groups obtained and assessed results from their systems in the image retrieval task of Cross-Language Evaluation Forum, we assessed the results for common themes and trends. In addition to overall performance, results were analyzed on the basis of topic categories (those most amenable to visual, textual, or mixed approaches) and run categories (those employing queries entered by automated or manual means as well as those using visual, textual, or mixed indexing and retrieval methods). We also assessed results on the different topics and compared the impact of duplicate relevance judgments. RESULTS: A total of 13 research groups participated. Analysis was limited to the best run submitted by each group in each run category. The best results were obtained by systems that combined visual and textual methods. There was substantial variation in performance across topics. Systems employing textual methods were more resilient to visually oriented topics than those using visual methods were to textually oriented topics. The primary performance measure of mean average precision (MAP) was not necessarily associated with other measures, including those possibly more pertinent to real users, such as precision at 10 or 30 images. CONCLUSIONS: We developed a test collection amenable to assessing visual and textual methods for image retrieval. Future work must focus on how varying topic and run types affect retrieval performance. Users' studies also are necessary to determine the best measures for evaluating the efficacy of image retrieval systems.

Light emission in nanogaps: overcoming quenching.

Very large spontaneous-emission-rate enhancements (∼1000) are obtained for quantum emitters coupled with tiny plasmonic resonance, especially when emitters are placed in the mouth of nanogaps formed by metal nanoparticles that are nearly in contact. This fundamental effect of light emission at subwavelength scales is well documented and understood as resulting from the smallness of nanogap modes. In contrasts, it is much less obvious to figure out whether the radiation efficiency is high in these gaps, or if the emission is quenched by metal absorption especially for tiny gaps a few nanometers wide; the whole literature only contains scattered electromagnetic calculations on the subject, which suggest that absorption and quenching can be kept at a small level despite the emitter proximity to metal. Thus through analytical derivations in the limit of small gap thickness, it is our objective to clarify why quantum emitters in nanogap antennas offer good efficiencies, what are the circumstances in which high efficiency is obtained, and whether there exists an upper bound for the maximum efficiency achievable.

Immunocytochemical identification of cell types in the mormyrid electrosensory lobe.

The electrosensory lobes (ELLs) of mormyrid and gymnotid fish are useful sites for studying plasticity and descending control of sensory processing. This study used immunocytochemistry to examine the functional circuitry of the mormyrid ELL. We used antibodies against the following proteins and amino acids: the neurotransmitters glutamate and gamma-aminobutyric acid (GABA); the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD); GABA transporter 1; the anchoring protein for GABA and glycine receptors, gephyrin; the calcium binding proteins calbindin and calretinin; the NR1 subunit of the N-methyl-D-aspartate glutamate receptor; the metabotropic glutamate receptors mGluR1alpha, mGluR2/3, and mGluR5; and the intracellular signaling molecules calcineurin, calcium calmodulin kinase IIalpha (CAMKIIalpha) and the receptor for inositol triphosphate (IP3R1alpha). Selective staining allowed for identification of new cell types including a deep granular layer cell that relays sensory information from primary afferent fibers to higher order cells of ELLS. Selective staining also allowed for estimates of relative numbers of different cell types. Dendritic staining of Purkinje-like medium ganglion cells with antibodies against metabotropic glutamate receptors and calcineurin suggests hypotheses concerning mechanisms of the previously demonstrated synaptic plasticity in these cells. Finally, several cell types including the above-mentioned granular cells, thick-smooth dendrite cells, and large multipolar cells of the intermediate layer were present in the two zones of ELL that receive input from mormyromast electroreceptors but were absent in the zone of ELL that receives input from ampullary electroreceptors, indicating markedly different processing for these two types of input. J. Comp. Neurol. 483:124-142, 2005. (c) 2005 Wiley-Liss, Inc.

Outpatient antibiotic prescribing in a low-risk veteran population with acute respiratory symptoms.

BACKGROUND: Acute respiratory tract infections are usually caused by viruses and are self-limited in healthy adults. Providers frequently provide antibiotic prescriptions for sinusitis, bronchitis, pharyngitis, and nonspecific upper respiratory tract infections, despite no evidence of improved clinical outcomes. We sought to determine: 1) primary care providers' antibiotic prescribing practices for acute respiratory tract infections in low-risk outpatient veterans and 2) short-term health outcome differences between those receiving and not receiving an antibiotic prescription. METHODS: We performed a retrospective electronic medical record review for veterans presenting to 1 of 3 primary care outpatient Veterans Affairs clinics in Portland, OR between July 1, 2008 and June 30, 2009 for acute respiratory symptoms. Demographics, signs and symptoms, antibiotic prescriptions, nonantibiotic prescriptions, and laboratory and imaging study variables were abstracted from medical charts. Descriptive frequencies, bivariate analyses (t tests, rank sums, Chi square tests, and Fisher's exact tests), and multivariate analyses (logistic regression) were performed. RESULTS: 35.4% of patients received antibiotic prescriptions. Of those antibiotics, 87.8% were not indicated. Antibiotic regimen prescriptions varied widely for each diagnosis. Short-term outcomes of hospitalization, follow-up visits, later antibiotic prescriptions, and death at 30 days were not associated with receipt of antibiotics. CONCLUSION: Many low-risk veterans received antibiotics for acute respiratory tract infections despite guidelines indicating that symptomatic treatment is sufficient for most patients. Novel interventions are required to reduce unnecessary and potentially harmful antibiotic use for low-risk outpatients with acute respiratory complaints.

Addressing the sociotechnical drivers of quality improvement: a case study of post-operative DVT prophylaxis computerised decision support.

BACKGROUND: Quality improvement (QI) initiatives characterised by iterative cycles of quantitative data analysis do not readily explain the organisational determinants of change. However, the integration of sociotechnical theory can inform more effective strategies. Our specific aims were to (1) describe a computerised decision support intervention intended to improve adherence with deep venous thrombosis (DVT) prophylaxis recommendations; and (2) show how sociotechnical theory expressed in 'Fit between Individuals, Task and Technology' framework (FITT) can identify and clarify the facilitators and barriers to QI work. METHODS: A multidisciplinary team developed and implemented electronic menus with DVT prophylaxis recommendations. Stakeholders were interviewed and human factors were analysed to optimise integration. Menu exposure, order placement and clinical performance were measured. Vista tool extraction and chart review were used. Performance compliance pre-implementation was 77%. RESULTS: There were 80-110 eligible cases per month. Initial menu use rate was 20%. After barriers were classified and addressed using the FITT framework, use improved 50% to 90%. Tasks, users and technology issues in the FITT model and their interfaces were identified and addressed. Workflow styles, concerns about validity of guidelines, cycle times and perceived ambiguity of risk were issues identified. CONCLUSIONS: DVT prophylaxis in a surgical setting is fraught with socio-political agendas, cognitive dissonance and misaligned expectations. These must be sought and articulated if organisations are to respond to internal resistance to change. This case study demonstrates that QI teams using information technology must understand the clinical context, even in mature electronic health record environments, in order to implement sustainable systems.

SYRIAC: The systematic review information automated collection system a data warehouse for facilitating automated biomedical text classification.

Automatic document classification can be valuable in increasing the efficiency in updating systematic reviews (SR). In order for the machine learning process to work well, it is critical to create and maintain high-quality training datasets consisting of expert SR inclusion/exclusion decisions. This task can be laborious, especially when the number of topics is large and source data format is inconsistent.To approach this problem, we build an automated system to streamline the required steps, from initial notification of update in source annotation files to loading the data warehouse, along with a web interface to monitor the status of each topic. In our current collection of 26 SR topics, we were able to standardize almost all of the relevance judgments and recovered PMIDs for over 80% of all articles. Of those PMIDs, over 99% were correct in a manual random sample study. Our system performs an essential function in creating training and evaluation data sets for SR text mining research.

Morphological analysis of the mormyrid cerebellum using immunohistochemistry, with emphasis on the unusual neuronal organization of the valvula.

This study used immunohistochemistry, Golgi impregnation, and electron microscopy to examine the circuitry of the cerebellum of mormyrid fish. We used antibodies against the following antigens: the neurotransmitters glutamate and gamma-aminobutyric acid (GABA); the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD); GABA transporter 1; the anchoring protein for GABA and glycine receptors, gephyrin; the calcium binding proteins calbindin and calretinin; the NR1 subunit of the N-methyl-D-aspartate glutamate receptor; the metabotropic glutamate receptors mGluR1alpha and mGluR2/3; the intracellular signaling molecules calcineurin and calcium calmodulin kinase IIalpha (CAMKIIalpha); and the receptor for inositol triphosphate (IP3RIalpha). Purkinje cells are immunoreactive to anti-IP3R1alpha, anticalcineurin, and anti-mGluR1alpha. Cerebellar efferent cells (eurydendroid cells) are anticalretinin and anti-NR1 positive in the valvula but not in the corpus and caudal lobe. In contrast, climbing fibers are anticalretinin and anti-NR1 immunopositive in the corpus and caudal lobe but not in the valvula. Purkinje cells, Golgi cells, and stellate cells are GABA positive, whereas efferent cells are glutamate positive. Unipolar brush cells are immunoreactive to anti-mGluR2/3, anticalretinin, and anticalbindin. We describe a "new" cell type in the mormyrid valvula, the deep stellate cell. These cells are GABA, calretinin, and calbindin positive. They are different from superficial stellate cells in having myelinated axons that terminate massively with GAD- and gephyrin-positive terminals on the cell bodies and proximal dendrites of efferent cells. We discuss how the valvula specializations described here may act in concert with the palisade pattern of Purkinje cell dendrites for analyzing spatiotemporal patterns of parallel fiber activity.

Automatic summarization of mouse gene information by clustering and sentence extraction from MEDLINE abstracts.

Tools to automatically summarize gene information from the literature have the potential to help genomics researchers better interpret gene expression data and investigate biological pathways. The task of finding information on sets of genes is common for genomic researchers, and PubMed is still the first choice because the most recent and original information can only be found in the unstructured, free text biomedical literature. However, finding information on a set of genes by manually searching and scanning the literature is a time-consuming and daunting task for scientists. We built and evaluated a query-based automatic summarizer of information on mouse genes studied in microarray experiments. The system clusters a set of genes by MeSH, GO and free text features and presents summaries for each gene by ranked sentences extracted from MEDLINE abstracts. Evaluation showed that the system seems to provide meaningful clusters and informative sentences are ranked higher by the algorithm.

A data mining and survey study on diseases associated with paraesophageal hernia.

Paraesophageal hernia is a severe form of hiatal hernia, characterized by the upward dislocation of the gastric fundus into the thoracic cavity. In this study, the 1999 National Inpatient Sample dataset of the Healthcare Cost and Utilization Project was analyzed using data mining techniques to explore disorders associated with paraesophageal hernia. The result of this data mining process was compared with a subsequent expert knowledge survey of 97 gastrointestinal tract surgeons. This two-step analysis showed that the results of data mining and expert knowledge are consistent in some factors that are highly associated with paraesophageal hernia: older age, other gastrointestinal tract disorders and obesity, for example. But the data mining approach revealed some other related disorders that were not known to the experts or reported in the literature, for example, hypertension, peritoneal adhesions and gall bladder/bile duct diseases. These findings lay a framework for subsequent hypothesis-driven research.

Functional gene group summarization by clustering MEDLINE abstract sentences.

Tools to automatically summarize functional gene group information from the biomedical literature will help genomics researchers both better interpret gene expression data and understand biological pathways. In this study, we built a system that takes in a set of genes and MEDLINE records and outputs clusters of genes along with summaries of each cluster by sentence extraction from MEDLINE abstracts. Our preliminary use-case evaluation shows that this approach can identify gene clusters similar to manually generated groupings.