Wireless power transfer to deep-tissue microimplants Ho, John S.; Yeh, Alexander J.; Neofytou, Evgenios ...
Proceedings of the National Academy of Sciences - PNAS,
06/2014, Volume:
111, Issue:
22
Journal Article
Peer reviewed
Open access
The ability to implant electronic systems in the human body has led to many medical advances. Progress in semiconductor technology paved the way for devices at the scale of a millimeter or less ...(“microimplants”), but the miniaturization of the power source remains challenging. Although wireless powering has been demonstrated, energy transfer beyond superficial depths in tissue has so far been limited by large coils (at least a centimeter in diameter) unsuitable for a microimplant. Here, we show that this limitation can be overcome by a method, termed midfield powering, to create a high-energy density region deep in tissue inside of which the power-harvesting structure can be made extremely small. Unlike conventional near-field (inductively coupled) coils, for which coupling is limited by exponential field decay, a patterned metal plate is used to induce spatially confined and adaptive energy transport through propagating modes in tissue. We use this method to power a microimplant (2 mm, 70 mg) capable of closed-chest wireless control of the heart that is orders of magnitude smaller than conventional pacemakers. With exposure levels below human safety thresholds, milliwatt levels of power can be transferred to a deep-tissue (>5 cm) microimplant for both complex electronic function and physiological stimulation. The approach developed here should enable new generations of implantable systems that can be integrated into the body at minimal cost and risk.
To enable sophisticated optogenetic manipulation of neural circuits throughout the nervous system with limited disruption of animal behavior, light-delivery systems beyond fiber optic tethering and ...large, head-mounted wireless receivers are desirable. We report the development of an easy-to-construct, implantable wireless optogenetic device. Our smallest version (20 mg, 10 mm(3)) is two orders of magnitude smaller than previously reported wireless optogenetic systems, allowing the entire device to be implanted subcutaneously. With a radio-frequency (RF) power source and controller, this implant produces sufficient light power for optogenetic stimulation with minimal tissue heating (<1 °C). We show how three adaptations of the implant allow for untethered optogenetic control throughout the nervous system (brain, spinal cord and peripheral nerve endings) of behaving mice. This technology opens the door for optogenetic experiments in which animals are able to behave naturally with optogenetic manipulation of both central and peripheral targets.
The goal of the first BioCreAtIvE challenge (Critical Assessment of Information Extraction in Biology) was to provide a set of common evaluation tasks to assess the state of the art for text mining ...applied to biological problems. The results were presented in a workshop held in Granada, Spain March 28-31, 2004. The articles collected in this BMC Bioinformatics supplement entitled "A critical assessment of text mining methods in molecular biology" describe the BioCreAtIvE tasks, systems, results and their independent evaluation.
BioCreAtIvE focused on two tasks. The first dealt with extraction of gene or protein names from text, and their mapping into standardized gene identifiers for three model organism databases (fly, mouse, yeast). The second task addressed issues of functional annotation, requiring systems to identify specific text passages that supported Gene Ontology annotations for specific proteins, given full text articles.
The first BioCreAtIvE assessment achieved a high level of international participation (27 groups from 10 countries). The assessment provided state-of-the-art performance results for a basic task (gene name finding and normalization), where the best systems achieved a balanced 80% precision / recall or better, which potentially makes them suitable for real applications in biology. The results for the advanced task (functional annotation from free text) were significantly lower, demonstrating the current limitations of text-mining approaches where knowledge extrapolation and interpretation are required. In addition, an important contribution of BioCreAtIvE has been the creation and release of training and test data sets for both tasks. There are 22 articles in this special issue, including six that provide analyses of results or data quality for the data sets, including a novel inter-annotator consistency assessment for the test set used in task 2.
The stabilization of isolated grafted Fe3+ sites on siliceous supports is investigated by a comparative study of crystalline versus amorphous materials. Our synthetic approach treats crystalline ...delaminated zeolite DZ-1 and amorphous silica (SiO2) with an aqueous NaFeEDTA cation precursor complex, to result in grafting of isolated Fe3+ sites via covalent attachment to support hydroxyl groups. Thermogravimetric analysis and UV–visible spectroscopy demonstrate the complete detachment of chelating EDTA ligand upon Fe3+ grafting on both supports. Before calcination treatment, both Fe/DZ-1 and Fe/SiO2 have similar UV–visible spectral features, with absorption bands at 208–225 and 257 nm, characteristic of framework Fe3+ sites in zeolites. Calcination does not affect the UV–visible spectroscopic characteristics of Fe/DZ-1 but changes the spectrum of Fe/SiO2 to a single absorption band at 260 nm, indicating better thermal stability of Fe3+ sites in Fe/DZ-1 as compared to Fe/SiO2. This stability persists for Fe/DZ-1 even during alkane oxidation catalysis in the presence of hydrogen peroxide, which causes aggregation of Fe3+ into oxide oligomers for Fe/SiO2. 57Fe Mössbauer spectroscopy of calcined materials indicates a more uniform distribution of sites in Fe/DZ-1 relative to Fe/SiO2. We thus attribute the greater robustness and site uniformity of Fe/DZ-1 to the chelation of Fe3+ by the rigid crystalline silicate DZ-1 framework, engendered by the spatial preorganization of grafting hydroxyls groups within its uniform defect sites, which are templated by framework B3+ removal during delamination. Such preorganization enables cooperativity between neighboring hydroxyl groups. This contrasts with more randomly distributed hydroxyl groups on SiO2, which lack such preorganization, leading to decreased hydrothermal stability and an Fe3+ grafting density that is ∼7-fold lower for Fe/SiO2 relative to Fe/DZ-1. These observations reveal how the silicate surface onto which a cation is grafted can act as a relevant ligand, capable of controlling material synthesis and functionality akin to ligands in homogeneous metal complexes, and demonstrate the advantages of support crystallinity in having this ligand be hydrothermally stable and tunable via templating.
Samples with low loadings of metals on well-defined supports provide some of the best opportunities to determine the metal–support structure and bonding. We illustrate methods for characterizing ...atomically dispersed heavy metals on metal oxide supports by aberration-corrected scanning transmission electron microscopy (STEM) complemented by fluorescence detection extended X-ray absorption fine structure and infrared spectroscopies. STEM images of Ir atoms derived from Ir(C2H4)2(acac) (acac = acetylacetonato) on high-surface-area MgO powder were obtained with minimized electron beam damage by quickly recording images near where the focus had been established. The images show that iridium at a loading of 1.0 wt % on MgO calcined at 1073 K was atomically dispersed, populating much of the surface of the MgO particles, which had irregular shapesconsequently the Ir atoms were bonded at various sites to two or three surface O atoms. In contrast, MgO calcined at 1273 K consisted of almost perfectly cubic crystals, and Ir atoms at a loading of only 0.01 wt % on this nearly ideal support were anchored preferentially at edges and corners of the (100) faces and bonded to three surface O atoms. The latter results indicate a path forward for the determination of precise structures of atomically dispersed metals on crystalline metal oxide supports.
The biological research literature is a major repository of knowledge. As the amount of literature increases, it will get harder to find the information of interest on a particular topic. There has ...been an increasing amount of work on text mining this literature, but comparing this work is hard because of a lack of standards for making comparisons. To address this, we worked with colleagues at the Protein Design Group, CNB-CSIC, Madrid to develop BioCreAtIvE (Critical Assessment for Information Extraction in Biology), an open common evaluation of systems on a number of biological text mining tasks. We report here on task 1A, which deals with finding mentions of genes and related entities in text. "Finding mentions" is a basic task, which can be used as a building block for other text mining tasks. The task makes use of data and evaluation software provided by the (US) National Center for Biotechnology Information (NCBI).
15 teams took part in task 1A. A number of teams achieved scores over 80% F-measure (balanced precision and recall). The teams that tried to use their task 1A systems to help on other BioCreAtIvE tasks reported mixed results.
The 80% plus F-measure results are good, but still somewhat lag the best scores achieved in some other domains such as newswire, due in part to the complexity and length of gene names, compared to person or organization names in newswire.
We investigate the synthesis of accessible calix4arene-bound gold clusters consisting of open "coordinatively unsaturated" active sites, using a comparative approach that relies on calix4arene ...ligands with various upper- and lower-rim substituents. In contrast with a reported Au(I)-tert-butyl-calixarene phosphine complex, which exhibits a single cone conformer in solution, the H upper-rim analog exhibits multiple conformers in solution. This contrasts with observations of the tert-butyl upper-rim analog, which exhibits a single cone conformer in solution under similar conditions. In the solid state, as determined by single-crystal X-ray diffraction, both H and tert-butyl upper-rim analogs exhibit exclusively cone conformer. A detailed structural analysis of these two solid-state structures highlights a CH-π interaction involving a methoxy lower-rim substituent and phenyl substituent on P as the key feature that enforces a tight configuration of Au(I) atoms on the same side of the calix4arene lower-rim plane. We hypothesize that such a configuration promotes chelation of the ligand to a gold surface and facilitates the synthesis of small Au11-sized clusters after reduction of both complexes. The new cluster, like the one reported with the tert-butyl analog, has an extraordinary 25% of surface atoms that are open and accessible to a 2-NT (2-naphthalenethiol) probe in solution. We also investigated the effect of calix4arene lower-rim substituents that coordinate to the metal, by using N-heterocyclic carbene (NHC) functional groups rather than phosphines. Four small (<1.6 nm diameter) calix4arene NHC-bound gold clusters were synthesized, including three using novel calix4arene NHC ligands. The smallest calix4arene NHC-bound Au cluster consisted of a 1.2 nm gold core, and its number density of accessible and open surface sites was measured. This required development of a new titration method for open sites on gold clusters, using a SAMSA fluorescein dye molecule, which excites and emits at lower energy relative to the previously used 2-NT probe. The number density of open sites on the new calix4arene NHC-bound gold cluster measured by the SAMSA fluorescein probe strongly supports the generality of a mechanical model of accessibility, which does not depend on the functional group involved in binding to the gold surface and rather depends on the relative radii of curvature of bound ligands and the gold cluster core.
The sources of asymmetric induction in aldol reactions catalyzed by cinchona alkaloid-derived amines, and chiral vicinal diamines in general, have been determined by density functional theory ...calculations. Four vicinal diamine-catalyzed aldol reactions were examined. The cyclic transition states of these reactions involve nine-membered hydrogen-bonded rings in distinct conformations. Using nomenclature from eight-membered cycloalkanes, the heavy atoms of the low-energy transition states are in crown (chair-chair) and chair-boat conformations. The factors that control which of these are favored have been identified.
Planar immersion lens with metasurfaces Ho, John S.; Qiu, Brynan; Tanabe, Yuji ...
Physical review. B, Condensed matter and materials physics,
03/2015, Volume:
91, Issue:
12
Journal Article
Peer reviewed
Open access
The solid immersion lens is a powerful optical tool that allows light entering material from air or a vacuum to focus to a spot much smaller than the free-space wavelength. Conventionally, however, ...the lenses rely on semispherical topographies and are nonplanar and bulky, which limits their integration in many applications. Recently, there has been considerable interest in using planar structures, referred to as metasurfaces, to construct flat optical components for manipulating light in unusual ways. Here, we propose and demonstrate the concept of a planar immersion lens based on metasurfaces. The resulting planar device, when placed near an interface between air and dielectric material, can focus electromagnetic radiation incident from air to a spot in the material smaller than the free-space wavelength. As an experimental demonstration, we fabricate an ultrathin and flexible microwave lens and further show that it achieves wireless energy transfer in material mimicking biological tissue.
Our goal in BioCreAtIve has been to assess the state of the art in text mining, with emphasis on applications that reflect real biological applications, e.g., the curation process for model organism ...databases. This paper summarizes the BioCreAtIvE task 1B, the "Normalized Gene List" task, which was inspired by the gene list supplied for each curated paper in a model organism database. The task was to produce the correct list of unique gene identifiers for the genes and gene products mentioned in sets of abstracts from three model organisms (Yeast, Fly, and Mouse).
Eight groups fielded systems for three data sets (Yeast, Fly, and Mouse). For Yeast, the top scoring system (out of 15) achieved 0.92 F-measure (harmonic mean of precision and recall); for Mouse and Fly, the task was more difficult, due to larger numbers of genes, more ambiguity in the gene naming conventions (particularly for Fly), and complex gene names (for Mouse). For Fly, the top F-measure was 0.82 out of 11 systems and for Mouse, it was 0.79 out of 16 systems.
This assessment demonstrates that multiple groups were able to perform a real biological task across a range of organisms. The performance was dependent on the organism, and specifically on the naming conventions associated with each organism. These results hold out promise that the technology can provide partial automation of the curation process in the near future.
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