A Surface-based Volume Haptics Approach and Applications in Surgical Simulation

Volume haptics algorithms are widely studied to provide multi-sensory feedback during data exploration. Efficient haptics rendering of consistent surface topology from a structured volumetric data set is desired by applications but has not been thoroughly explored. We presented a proxy-based volume haptics approach inspired by a fast voxel traversal algorithm that delivers efficient and robust surface representation. The technique has the flexibility to work either as an independent volume haptics rendering module or as an extension to incorporate volume haptics into polygonal-based haptics modules. The volume haptics approach is efficient at handling large volume data set and it scales decently with voxel density. This technique enables us to develop virtual reality based surgical simulations with comprehensive procedures. With the reliable surface-based volume haptics module, we developed cranial and spinal surgical simulations involving bone removal and extensive contact interactions. Our applications leverages the advantages of virtual reality based simulators over traditional training methods

Reducing Capacities and Distribution of Redox-Active Functional Groups in Low Molecular Weight Fractions of Humic Acids

Humic substances (HS) are redox-active organic compounds with a broad spectrum of molecular sizes and reducing capacities, that is, number of electrons donated or accepted. However, it is unknown which role the distribution of redox-active functional groups in different molecule sizes plays for HS redox reactions in varying pore sizes microenvironments. We used dialysis experiments to separate bulk humic acids (HA) into low molecular weight fractions (LMWF) and retentate, for example, the remaining HA in the dialysis bag. LMWF accounted for only 2% of the total organic carbon content of the HA. However, their reducing capacities per gram of carbon were up to 33 times greater than either those of the bulk HA or the retentate. For a structural/mechanistic understanding of the high reducing capacity of the LMWF, we used fluorescence spectroscopy. We found that the LWMF showed significant fluorescence intensities for quinone-like functional groups, as indicated by the quinoid π–π* transition, that are probably responsible for the high reducing capacities. Therefore, the small-sized HS fraction can play a major role for redox transformation of metals or pollutants trapped in soil micropores (<2.5 nm diameter)

Dependence of the Electronic and Optical Properties of Methylammonium Lead Triiodide on Ferroelectric Polarization Directions and Domains: A First Principles Computational Study

Organic–inorganic perovskites, and in particular methylammonium (MA) lead triiodide, recently emerged as promising for thin-film solar cell applications and, as a result, have attracted much attention. However, some important phenomena have been less examined in these systems, e.g., effects of ferroelectric domains on the optoelectronic properties. In this work, we investigate the effects of the polarization direction in single domains, and of uncharged and charged ferroelectric domains, on the electronic and optical properties of MA lead triiodide by first principles calculations. Highly accurate quasiparticle band gap calculations enabled characterization of the electronic structure of charged and uncharged domains in comparison to single domains. Additionally, analysis of the effects of a potential on the Born effective charges and respective density of states provided an understanding of changes in the band gap, as dependent on the type of domain, and on the MA moiety direction. Agreement between experimental and calculated optical spectra was achieved by inclusion of electron–hole interactions, also discerning specific transitions. However, due to the flexibility in the MA moiety’s orientation that causes spectral broadening, consideration of a statistical ensemble of configurations is required, which is not taken into account in a single computation. Indeed, our analysis in considering a number of MA directions leads to better agreement with experiment. The calculations predict that the optical response is rather sensitive to the type and size of ferroelectric domains, which implies that such a response could be used for their characterization, thus calling for further experimental exploration

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Genotype frequencies of rs1337185, rs5275, rs5277, rs7575934, rs3213718 and rs162509 in controls and case

Systematic Study of Structure, Stability, and Electronic Absorption of Tetrahedral CdSe Clusters with Carboxylate and Amine Ligands

In this work, we carried out a systematic investigation to assess the effects of ligands on the structure, stability, and absorption spectra of ultrasmall CdSe tetrahedral quantum dots, where the cores of small tetrahedral quantum dots have been postulated to be stabilized by amine and carboxylate ligands. We found that amine and carboxylate ligands form extensive hydrogen bonding networks, which provide thermodynamic stability to the clusters. On the basis of the optimized structures, good agreement between observed and computed spectra was obtained. The ligands were also found to have a large influence on the color and intensity of the electronic absorption spectra, particularly for the small clusters, which were previously monitored with in situ UV–visible absorbance spectroscopy. Our work provides an understanding of the effect of ligands that influence thermodynamic stability and electronic absorption of ultrasmall quantum dots, thus potentially motivating further experimental exploration

Systematic Study of Structure, Stability, and Electronic Absorption of Tetrahedral CdSe Clusters with Carboxylate and Amine Ligands

In this work, we carried out a systematic investigation to assess the effects of ligands on the structure, stability, and absorption spectra of ultrasmall CdSe tetrahedral quantum dots, where the cores of small tetrahedral quantum dots have been postulated to be stabilized by amine and carboxylate ligands. We found that amine and carboxylate ligands form extensive hydrogen bonding networks, which provide thermodynamic stability to the clusters. On the basis of the optimized structures, good agreement between observed and computed spectra was obtained. The ligands were also found to have a large influence on the color and intensity of the electronic absorption spectra, particularly for the small clusters, which were previously monitored with in situ UV–visible absorbance spectroscopy. Our work provides an understanding of the effect of ligands that influence thermodynamic stability and electronic absorption of ultrasmall quantum dots, thus potentially motivating further experimental exploration

A Hydrophilic Mixed Lanthanide Metal–Organic Framework Monitoring H₂O in D₂O

Lanthanide metal–organic framework (Ln-MOF) luminescent sensors monitoring the H2O content in D2O are still rare. We designed and built a hydrophilic mixed Ln-MOF (Eu0.4Tb0.6-MOF) monitoring the H2O content in D2O. By designing a ligand and controlling the synthesis method, we achieved a balance between the structural stability and sensing capacity. When the H2O content ranges from 0 to 100%, the photoluminescence color of Eu0.4Tb0.6-MOF can change from yellow to green, which can be observed by the naked eye. The mechanism is that the photoluminescence intensity of Eu3+ decreases faster than that of Tb3+ when the H2O content increases. The sensing mechanism was studied further by transient fluorescence spectrometry

Near-Infrared Electrogenerated Chemiluminescence from Aqueous Soluble Lipoic Acid Au Nanoclusters

Strong electrogenerated chemiluminescence (ECL) is detected from dithiolate Au nanoclusters (AuNCs) in aqueous solution under ambient conditions. A novel mechanism to drastically enhance the ECL is established by covalent attachment of coreactants <i>N</i>,<i>N</i>-diethylethylenediamine (DEDA) onto lipoic acid stabilized Au (Au-LA) clusters with matching redox activities. The materials design reduces the complication of mass transport between the reactants during the lifetime of radical intermediates involved in conventional ECL generation pathway. The intracluster reactions are highly advantageous for applications by eliminating additional and high excess coreactants otherwise needed. The enhanced ECL efficiency also benefits uniquely from the multiple energy states per Au cluster and multiple DEDA ligands in the monolayer. Potential step and sweeping experiments reveal an onset potential of 0.78 V for oxidative-reduction ECL generation. Multifolds higher efficiency is found for the Au clusters alone in reference to the standard Rubpy with high excess TPrA. The ECL in near-IR region (beyond 700 nm) is highly advantageous with drastically reduced interference signals over visible ones. The features of ECL intensity responsive to electrode potential and solution pH under ambient conditions make Au-LA-DEDA clusters promising ECL reagents for broad applications. The strategy to attach coreactants on Au clusters is generalizable for other nanomaterials

Highly Ordered and Field-Free 3D DNA Nanostructure: The Next Generation of DNA Nanomachine for Rapid Single-Step Sensing

Herein, by directly using Watson–Crick base pairing, a highly ordered and field-free three-dimensional (3D) DNA nanostructure is self-assembled by azobenzene (azo)-functionalized DNA nippers in a few minutes, which was applied as a 3D DNA nanomachine with an improved movement efficiency compared to traditional Au-based 3D nanomachines due to the organized and high local concentration of nippers on homogeneous DNA nanostructure. Once microRNA (miRNA) interacts with the 3D nanomachine, the nippers “open” to hybridize with the miRNA. Impressively, photoisomerization of the azo group induces dehybridization/hybridization of the nippers and miRNA under irradiation at different wavelengths, which easily solves one main technical challenge of DNA nanotechnology and biosensing: reversible locomotion in one step within 10 min. As a proof of concept, the described 3D machine is successfully applied in the rapid single-step detection of a biomarker, which gives impetus to the design of new generations of mechanical devices beyond the traditional ones with ultimate applications in sensing analysis and diagnostic technologies

Genotype/allele frequency of SREBF-1(rs2297508) in EC patients and normal controls.

<p>OR odds ratio Cl confidence limit.</p