Enhanced reactivity of nanoscale iron particles through a vacuum annealing process

A reactivity study was undertaken to compare and assess the rate of dechlorination of chlorinated aliphatic hydrocarbons (CAHs) by annealed and non-annealed nanoscale iron particles. The current study aims to resolve the uncertainties in recently published work studying the effect of the annealing process on the reduction capability of nanoscale Fe particles. Comparison of the normalized rate constants (m²/h/L) obtained for dechlorination reactions of trichloroethene (TCE) and cis-1,2-dichloroethene (cis-1,2-DCE) indicated that annealing nanoscale Fe particles increases their reactivity ~30-fold. An electron transfer reaction mechanism for both types of nanoscale particles was found to be responsible for CAH dechlorination, rather than a reduction reaction by activated H₂ on the particle surface (i.e., hydrogenation, hydrogenolysis). Surface analysis of the particulate material using X-ray diffraction (XRD) and transmission electron microscopy (TEM) together with surface area measurement by Brunauer, Emmett, Teller (BET) indicate that the vacuum annealing process decreases the surface area and increases crystallinity. BET surface area analysis recorded a decrease in nanoscale Fe particle surface area from 19.0 to 4.8 m²/g and crystallite dimensions inside the particle increased from 8.7 to 18.2 nm as a result of annealing.     

Contrast-enhanced MR angiography with frequency-dependent mask subtraction

One of the main challenges for high-resolution contrast-enhanced magnetic resonance angiography (CE-MRA) is the limited signal-to-noise ratio (SNR). In conventional CE-MRA, spoiled gradient-recalled echo sequence is typically used to acquire raw data before and after contrast material injection, followed by mask subtraction to improve vessel contrast at the cost of increased image noise. We reported here on a frequency-dependent mask subtraction technique where only low spatial frequency data were subject to mask subtraction to improve image contrast and reduce motion artifact while high spatial frequency data were not subtracted to preserve image noise level. The feasibility of this technique was demonstrated through phantom, animal, and human volunteer studies. The lowest half, quarter, 1/8 and 1/16 of all spatial frequencies were subject to mask subtraction, respectively. These partial subtraction techniques were compared with conventional mask subtraction in terms of SNR and artifact power. An SNR gain up to 37% was achieved without significant artifact power increase for quarter-subtraction where only the central one quarter k-space data were subject to mask subtraction.     

Transient Response of Particle Distribution in a Chamber to Transient Particle Injection

We inject a large number of newly created nano‐particle aggregates into a chamber for the purpose of removing harmful contents in an indoor environment. This study is to experimentally and numerically investigate transient response of particle distributions to particle injections. A room‐sized chamber of 4 m × 2.1 m × 2.4 m is connected to a specially designed particle‐injection system, with two Optical Particle Counters used to simultaneously measure particle‐number densities with the size range from 0.3 μm to 10 μm at the inlet and in the chamber. A velocity probe measures the flow that is up to 1 m/s. An Euler‐type particulate‐phase‐transport model is developed and validated by comparing with experimental data. The study shows that the transient behavior of particle distributions is determined by many factors, including particle size, particle settling speed, sampling location, and velocity distribution. Particle number densities decrease in time more quickly for large particles than for small particles, and locations farther downstream in the chamber correlate more weakly with the inlet injection.     

Ferroelectricity and ferromagnetism in fine-grained multiferroic BaTiO3/(Ni0.5Zn0.5)Fe2O4 composites prepared by a novel hybrid process

Dense, homogeneous, and fine-grained multiferroic BaTiO₃/(Ni_0.5Zn_0.5)Fe₂O₄ composite ceramics are synthesized by a novel powder-in-sol precursor hybrid processing route. This route includes the dispersion of nanosized BaTiO₃ ferroelectric powders prepared via conventional sold-state ceramic process into (Ni_0.5Zn_0.5)Fe₂O₄ ferromagnetic sol-gel precursor prepared via a sol-gel wet chemistry process. The composite ceramics show coexistence of obvious ferroelectric and ferromagnetic hysteresis loops at room temperature. Very low dielectric loss of about 0.02–0.0067 in the range of 10 kHz–10 MHz can be achieved, which is about an order of magnitude lower than the results of many reports using conventional processes at room temperature. The combination of high permeability and permittivity with low losses in the ceramics enables significant miniaturization of electronic devices based on the ceramics.     

An asymptotic solving method for the periodic solution of a class of disturbed nonlinear evolution equation

<正>A class of disturbed evolution equation is considered using a simple and valid technique.We first introduce the periodic traveling-wave solution of a corresponding typical evolution equation.Then the approximate solution for an original disturbed evolution equation is obtained using the asymptotic method.We point out that the series of approximate solution is convergent and the accuracy of the asymptotic solution is studied using the fixed point theorem for the functional analysis.     

Probing the zero-field splitting in the ordered N@C60 in buckycatcher C60H28 studied by EPR spectroscopy

The electronic structure of the endohedral fullerene ¹⁴N@C₆₀ spatially ordered in the crystal state by its supramolecular assembly with a buckycatcher C₆₀H₂₈ was investigated by X-band electron paramagnetic resonance (EPR) spectroscopy. The zero-field splitting (ZFS) found in the complex is significantly enhanced in comparison to the earlier reported data for the analogous systems. The large ZFS, presumably induced by the molecular order in the supramolecular complex makes it an attractive material for the future quantum control and coherence studies.     

Differential effects of synchronous and asynchronous multifinger coactivation on human tactile performance

Background  

Repeated execution of a tactile task enhances task performance. In the present study we sought to improve tactile performance with unattended activation-based learning processes (i.e., focused stimulation of dermal receptors evoking neural coactivation (CA)). Previous studies show that the application of CA to a single finger reduced the stationary two-point discrimination threshold and significantly increased tactile acuity. These changes were accompanied by an expansion of the cortical finger representation in primary somatosensory cortex (SI). Here we investigated the effect of different types of multifinger CA on the tactile performance of each finger of the right hand.     

Role of NMDA receptor subtypes in different forms of NMDA-dependent synaptic plasticity

Background  

The involvement of different NMDA receptor (NMDAR) subunits has been implicated in several forms of synaptic plasticity. However, it is still controversial to what extent the involvement is specific, and little is known about the role of NMDAR subunits in certain "non-conventional" forms of plasticity. In this study we used subunit-specific blockers to test the roles of NR2A- and NR2B-containing NMDARs in a type of chemical long-term depression (LTD) induced by brief bath application of the NMDAR agonist NMDA to hippocampal slices from 12–18 days old rats. For comparison, we also examined other forms of plasticity, including a "slow LTD" induced by 0.1 Hz stimulation under low Mg²⁺ conditions as well as long-term potentiation (LTP).     

Mixing characteristics of motionless mixers

Motionless mixers have found a large range of applications, including blending, reaction, dispersion, heat transfer and mass transfer. Understanding the mixing processes that occur in these diverse systems is essential for predicting many aspects of practical importance. The objective of this study is to perform the experimental investigations of mixing characteristics for three different motionless mixers. The red color dye tracer was mixed in the main stream of green hair styling gel, and then the mixing efficiency was quantified by calculating the percentage area concentration of red color at the outlet cross section using a digital image processing technique. In the Sulzer SMX and YHC mixer, a single element mixes the fluid nearly in two dimensions, and three-dimensional mixing is accomplished by the next elements aligned at 90o to their former one. In the Sulzer SMX mixer, the flow appears to be globally well mixed after 5 elements, while in the YHC and YNU mixers, it is necessary to globally well mix more than 1 and 2 elements.