Silica‐Coating of Hematite Nanoparticles Using Reactive Water‐Soluble Polyalkoxysiloxanes

In this article, we report on a new one‐step synthetic route to obtain multi‐functional silica‐coated hematite particles using a water‐based surfactant‐free technology. The synthesis and properties of uniform silica‐coated hematite particles with adjustable size, morphology, and silica shell thickness are discussed in detail. The developed method allows simultaneous formation of the silica shell around hematite core and incorporation of reactive groups on the surface of core–shell nanoparticles. Vinyl groups are introduced to the silica surface at once by pre‐functionalization of a water‐soluble hyperbranched polyalkoxysiloxanes with active double bonds. The reactivity of these surface‐immobilized vinyl groups is demonstrated by covalent attachment of rhodamine B using a thiol‐en click reaction.     

Effects of mobile phone exposure on time frequency fine structure of transiently evoked otoacoustic emissions

Mobile phones have become very commonly used worldwide within a short period of time. To date there is only limited knowledge about interaction between electromagnetic fields (EMFs) emitted by mobile phones and the auditory function. Moreover, there is widespread concern that there may be potential for harm. The aim of this study was to assess potential subtle changes in cochlear function by measuring the temporal and spectral fine structure of transiently evoked otoacoustic emissions (TEOAE) in normal hearing subjects after exposure to EMFs emitted by Global System for Mobile Communication (GSM) mobile phones. TEOAEs were recorded in 27 healthy young adults before and after 10 min of real or sham exposure in a double-blind design. TEOAE data were analyzed both globally (broadband analysis) and using the Wavelet Transform (analysis of the time-frequency fine structure). The broadband analysis revealed no significant effect on TEOAEs related to exposure, confirming results of previous studies; in addition, no significant change was detected in the analysis of the elementary wavelet components, suggesting that the temporal and spectral fine structure of TEOAEs is not affected by 10 min exposure to low-intensity EMFs emitted by GSM mobile phones.     

A Functional Analytic Approach to Perturbations of the Lorentz Gas

We present a functional analytic framework based on the spectrum of the transfer operator to study billiard maps associated with perturbations of the periodic Lorentz gas. We show that recently constructed Banach spaces for the billiard map of the classical Lorentz gas are flexible enough to admit a wide variety of perturbations, including: movements and deformations of scatterers; billiards subject to external forces; nonelastic reflections with kicks and slips at the boundaries of the scatterers; and random perturbations comprised of these and possibly other classes of maps. The spectra and spectral projections of the transfer operators are shown to vary continuously with such perturbations so that the spectral gap enjoyed by the classical billiard persists and important limit theorems follow.     

Quantitative Detection of Superoxide Ions in Whole Blood of the American Alligator (Alligator mississippiensis)

WST-1 and nitroblue tetrazolium (NBT) were used to quantify production of superoxide ions by leukocytes of the American alligator in whole blood. Because of the difficulty of isolating healthy leukocytes in alligators, these compounds were employed in whole blood instead of leukocyte preparations commonly used in other studies. The detection of superoxide was concentration- and time-dependent and linear with serial dilutions of whole blood. WST-1 reduction was inhibited by superoxide dismutase, indicating that the reduction was due to the presence of superoxide. Light microscopy revealed that superoxide production occurred in leukocytes, with no detectable contributions from other blood components.     

Quantitative assessment of motion correction for high angular resolution diffusion imaging

Several methods have been proposed for motion correction of high angular resolution diffusion imaging (HARDI) data. There have been few comparisons of these methods, partly due to a lack of quantitative metrics of performance. We compare two motion correction strategies using two figures of merit: displacement introduced by the motion correction and the 95% confidence interval of the cone of uncertainty of voxels with prolate tensors. What follows is a general approach for assessing motion correction of HARDI data that may have broad application for quality assurance and optimization of postprocessing protocols. Our analysis demonstrates two important issues related to motion correction of HARDI data: (1) although neither method we tested was dramatically superior in performance, both were dramatically better than performing no motion correction, and (2) iteration of motion correction can improve the final results. Based on the results demonstrated here, iterative motion correction is strongly recommended for HARDI acquisitions.     

Quantum Dots Microstructural Metrology: From Time-Resolved Spectroscopy to Spatially Resolved Electron Microscopy

Colloidal quantum dots (QDs) have unique optical and electrical properties with promising applications in next-generation semiconductor technologies, including displays, lighting, solar cells, photodetectors, and image sensors. Advanced analytical tools to probe the optical, morphological, structural, compositional, and electrical properties of QDs and their ensemble solid films are of paramount importance for the understanding of their device performance. In this review, comprehensive studies on the state-of-the-art metrology approaches used in QD research are introduced, with particular focus on time-resolved (TR) and spatially resolved (SR) spectroscopy and microscopy. Through discussing these analysis techniques in different QD system, such as various compositions, sizes, and shell structures, the critical roles of these TR-spectroscopic and SR-microscopic techniques are highlighted, which provide the structural, morphological, compositional, optical, and electrical information to precisely design QDs and QD solid films. The employment of TR and SR analysis in integrated QD device systems is also discussed, which can offer detailed microstructural information for achieving high performance in specific applications. In the end, the current limitations of these analytical tools are discussed, and the future development of the possibility of interdisciplinary research in both QD fundamental and applied fields is prospected.     

BOLD sensitivity to cortical activation induced by microstimulation: comparison to visual stimulation

Electrical microstimulation via intracortical electrodes is a widely used method for deducing functions of the brain. In this study, we compared the spatial extent and amplitude of BOLD responses evoked by intracortical electrical stimulation in primary visual cortex with BOLD activations evoked by visual stimulation. The experiments were performed in anesthetized rhesus monkeys. Visual stimulation yielded activities larger than predicted from the well-established visual magnification factor. However, electrical microstimulation yielded an even greater spread of the BOLD response. Our results confirm that the effects of electrical microstimulation extend beyond the brain region expected to be excited by direct current spread.     

Laser Doppler imaging through tissues phantoms by using self-mixing interferometry with a laser diode

Laser Doppler imaging has been widely used for the evaluation of cutaneous blood flow. We report on how the self-mixing interferometry configuration with a laser diode is explored for what is believed to be the first time to generate flow maps. The experiment was carried out by sensing the laser intensity power spectrum at each pixel as the laser was scanned over a model that mimics the properties of skin and circulating blood.     

Quantum-confined electronic states in atomically well-defined graphene nanostructures

Despite the enormous interest in the properties of graphene and the potential of graphene nanostructures in electronic applications, the study of quantum-confined states in atomically well-defined graphene nanostructures remains an experimental challenge. Here, we study graphene quantum dots (GQDs) with well-defined edges in the zigzag direction, grown by chemical vapor deposition on an Ir(111) substrate by low-temperature scanning tunneling microscopy and spectroscopy. We measure the atomic structure and local density of states of individual GQDs as a function of their size and shape in the range from a couple of nanometers up to ca. 20 nm. The results can be quantitatively modeled by a relativistic wave equation and atomistic tight-binding calculations. The observed states are analogous to the solutions of the textbook "particle-in-a-box" problem applied to relativistic massless fermions.     

Galilean-invariant scalar fields can strengthen gravitational lensing

The mystery of dark energy suggests that there is new gravitational physics on long length scales. Yet light degrees of freedom in gravity are strictly limited by Solar System observations. We can resolve this apparent contradiction by adding a Galilean-invariant scalar field to gravity. Called Galileons, these scalars have strong self-interactions near overdensities, like the Solar System, that suppress their dynamical effect. These nonlinearities are weak on cosmological scales, permitting new physics to operate. In this Letter, we point out that a massive-gravity-inspired coupling of Galileons to stress energy can enhance gravitational lensing. Because the enhancement appears at a fixed scaled location for dark matter halos of a wide range of masses, stacked cluster analysis of weak lensing data should be able to detect or constrain this effect.