High-density Particles Research Articles

How can the D-Wave machine exhibit long-time quantum behaviour

Extensive experiments have demonstrated quantum behaviour in the long-time operation of the D-Wave quantum computer. The decoherence time of a single flux qubit is reported to be on the order of nanoseconds [1], which is much shorter than the time required to carry out a computation on the timescale of seconds [2, 3]. Previous judgements of whether the D-Wave device should be thought of as a quantum computer have been based on correlations of the input-output behaviour of the D-Wave machine with a quantum model, called simulated quantum annealing, or classical models, called simulated annealing and classical spin dynamics [4]. Explanations for a factor of 108 discrepancy between the single flux qubit decoherence time and the long-time coherent quantum behaviour of many integrated flux qubits of the D-Wave device have not been offered so far. In our contribution we investigate a model of four qubits with one qubit coupled to a phonon and (optionally) to environmental particles of high density of states, called gravonons. The calculations indicate that when no gravonons are present, the current in the qubit is flipped at some time and adiabatic evolution is discontinued. The time dependent wave functional becomes a non-correctable superposition of many excited states. The results demonstrate the possibility of effectively suppressing the current flip and allowing for continued adiabatic evolution when the entanglement to gravonons is included. This adiabatic evolution is, however, a coherent evolution in high dimensional spacetime and cannot be understood as a solution of Schrödinger's time dependent equation in 4 dimensional spacetime. Compared to Schrödinger's time development in 4D, the evolution is considerably slowed down, though still adiabatic. The properties of our model reflect correctly the experimentally found behaviour of the D-Wave machine and explain the factor of 108 discrepancy between decoherence time and quantum computation time. The observation and our explanation are in anology to the 108 discrepancy factor found, when comparing experimental results on adsorbate quantum diffusion rate with predictions of Schrödinger's time dependent equation, which can also be resolved in a model with the coupling to gravonons included.

Intermittent fluctuations in the TCV scrape-off layer

Probe measurements in the scrape-off layer of tokamak plasmas show that the ion saturation current signal is dominated by large amplitude bursts. Analysis of data time series from tokamak á configuration variable of unprecedented duration reveals that both burst amplitudes and waiting times are exponentially distributed. The average burst wave form has an exponential shape with a characteristic time that is independent of the burst amplitude. These results support a novel stochastic model, which suggests that the high particle density in the far scrape-off layer is due to the radial motion of uncorrelated blob-like structures. Predictions of the model describe the broad range of universality of plasma fluctuations in the boundary region of tokamak plasmas.

Method for evaluating packing condition of particles in coal water slurry

In the coal water slurry (CWS) industry, it is essential to achieve high packing density of product particles in order to obtain a high concentration without affecting the flowability. In this study, a method based on an index E is proposed for evaluating the packing density of particles in CWS with given particle size distribution (PSD) and tested on bituminous and lignite coal. These two types of coal were ground and mixed in different proportions to obtain different packing densities. The experimental results show that the CWS concentration increased with E, implying the good applicability of the proposed method. By calculating E for different PSDs, it was found that the packing got closest when the parameters in Rosin–Rammler equation and Alfred equation were 0.75–0.85 and ~0.5, respectively. In addition, the packing density for unimodal PSD is generally lower than that for multimodal PSD. In contrast, the average sizes of the mixed samples did not affect the packing status in CWS and the product concentration consistently. With some adjustments, the proposed method can also be used to evaluate the tapped packing density of dry coal powders, with some applicability.

Contact temperature under three-body dry friction conditions

Particles (wear debris, particle contaminants, or abrasive particles) are often present at contact interfaces. These particles affect the contact temperature and the real contact area between two rough surfaces. In this paper, we used a three-body micro-contact model and contact temperature theory to evaluate particle-to-surface and surface-to-surface contact temperatures between two surfaces with different particle sizes, particle densities, surface roughnesses, relative speeds, and applied loads.The results show that the values of the particle-to-surface and surface-to-surface temperature rise parameters are highly dependent on the contact load ratio, i.e., the proportion of the total load borne by the contact between the two surfaces. For a given relative speed and applied load, the particle temperature rise parameter value increases with increasing particle size and particle density and with decreasing surface roughness. On the other hand, for a given relative speed, the surface temperature rise parameter value decreases with decreasing applied load and surface roughness and with increasing particle density and particle diameter. For hybrid friction contact conditions, the particle temperature rise parameter value increases almost linearly with an increasing ratio of particle size to surface roughness, xa/σ, for a given surface roughness and contact load. For a given surface roughness and contact load, the surface temperature rise parameter value remains almost unchanged under hybrid friction contact conditions when xa/σ is less than 1.0, whereas at xa/σ values greater than 1.0, the surface temperature rise parameter value decreases as the ratio of particle size to surface roughness increases. The results also show that even for a relatively low load, the particle temperature may be higher than the surface temperature for large debris sizes or high particle densities, suggesting an abnormal wear process. High particle temperatures are believed to play an important role in fatigue, wear, and failure mechanisms. The results indicate that to reduce the interfacial temperature, the larger the contact load is, the smaller the surface roughness value must be. Under hybrid friction contact conditions, the difference between the surface and particle contact temperatures is relatively small.

Electrochemical Deposition of Pt Nanoclusters on WC for Hydrogen Evolution Reaction in Acid

Water splitting by electrolysis is an effective and renewable way to produce hydrogen fuel from acid or alkaline electrolytes. Presently, alkaline water electrolyzers are being the most widely employed, largely due to the use of low-cost catalysts. Yet, there is strong interest for expanded use of acid water electrolyzers in future because of better device performance than the alkaline. In this work, we explore and develop new fabrication techniques that could minimize the use of the Pt catalyst that is highly active, but too expensive to be used for hydrogen evolution reaction (HER) in acid water electrolyzers. Of our particular interest is to grow Pt monolayer films and nanostructures on tungsten carbide (WC) supports by electrodeposition. Fig. 1 shows Pt deposition as a function of applied potential from a NaCl-supporting electrolyte. An interesting finding is that the deposition of Pt is prevented at potentials below -0.5 V, in spite of high driving forces for Pt clusters to form and grow. This talk will present ways in which this anomalous deposition behavior can be exploited for preparing novel Pt catalysts. A brief summary will be given for Pt deposition on Au [[1]] and Ni [[2]] electrodes where a monolayer-thick Pt film is deposited at -0.8 V but additional growth is quenched. For WC substrates, we will discuss challenges associated with the lack of Pt depositing at -0.80 V, before introducing to a new approach that is developed to facilitate the formation of Pt nuclei. The proposed method involves cycling the potential between -0.8 V and -0.45 V at a fast rate of 50 mV/s. As shown in Fig. 2, Pt nanoclusters with high particle density could be grown on WC, and their average size is about 5 nm. To gain mechanistic insights on Pt nanostructure nucleation and growth, the deposits were analyzed using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and underpotentially deposited (UPD) hydrogen and copper. Correlations between deposition potential cycle and particle growth and particle density will be discussed. Finally, Pt deposits were examined as catalysts for HER in 0.5 M sulfuric acid. The dependence of HER activity on the number of deposition cycles is shown in Fig. 3 where the HER activity approaches that of bulk platinum as the deposition cycles increase even though the expected total amount of platinum is far less than a complete coverage. This work illustrates that electrodeposition provides a simple and scalable way for preparing Pt nanocluster/WC catalysts, which exhibit high activity and durability toward HER in acid media. [1] Y. Liu, D. Gokcen, U. Bertocci, T. P. Moffat, Science, 338, 1327 (2012). [2] Y. Liu, C. M. Hangarter, D. Garcia, T. P. Moffat, Surf. Sci. (2014) dx.doi.org/10.1016/j.susc.2014.06.002 Figure 1

A dual-tracer approach to estimate upwelling velocity in coastal Southern California

The distribution of the cosmogenic radionuclide 7Be (t1/2=53d) in the surface ocean has previously been used to estimate upwelling velocity in the open ocean. However, the loss of 7Be to particle export has limited this approach in high particle density environments like the continental margins. In this study, we combine a mass balance of 7Be with a 234Th budget in the surface ocean to constrain the loss of 7Be to particle sinking at the San Pedro Ocean Time-series (SPOT) in the inner Southern California Bight during spring 2013. Upwelling velocities (all in m d−1) determined from the 7Be mass balance were observed to increase from 0.5±0.6 in January to 2.5±1.3 in May, then decrease to 1.2±0.5 in June. These results agree within uncertainty with upwelling velocities derived from the monthly Bakun Upwelling Index, which ranged from 0.1 to 2.8 m d−1, supporting the pressure-field-based approach. Evidence from a heat budget and the nutrient distribution over the course of the study supports that the upwelling signal at SPOT (20 km offshore) is not transported from coastal upwelling near shore, but instead is dominantly a local signal, likely driven by wind-stress curl.

Investigation of fluidization behavior of high density particle in spouted bed using CFD–DEM coupling method

CFD–DEM coupling simulation method is used to study the fluidization behavior of particle with different densities in the spouted bed. The simulation results show that the particle spouting behavior is incoherent and periodic in the stable spouting state. The cycle periods of the whole bed and single particle are obtained from particle trajectory and compared with experimental results. The relationships between the minimum spouting gas velocity, the steady pressure drop and the particle density are obtained. It can be found that the gas velocity range of stable spouting state expands when the particle density increases. The dual, single and multiple dominant frequencies are found in the stable spouting process of high density particle. Through detailed analysis on the mechanism of spouting dominant frequency, the flow pattern map with different superficial gas velocities and particle densities is given and can be divided into five regions: fixed bed with internal spouting, transitional stable spouting state with dual dominant frequency, main stable spouting state with single dominant frequency, transitional stable spouting state with multiple dominant frequency, and unstable spouting state. The stable spouting gas velocity is influenced by the particle density, while the dominant frequency of the particle spouting process will keep invariant even if the particle density increases, as long as Ug/Ums is not changed. The influence of particle density on the particle residence time distribution in the spout region, which can be used to characterize the gas solid contact efficiency, is also discussed based on simulation results.

Implantation-synthesized Cu/Cu–Zn core/shell nanoparticles in SiO_2 and their optical properties

Silica glasses were pre-implanted with 60 keV Zn ions at different fluences of 1 × 1016 and 1 × 1017 cm−2, respectively, and were then subjected to implantation of 45 keV Cu ions at a fluence of 5 × 1016 cm−2. The formation of metallic nanoparticles (NPs) as well as their optical properties has been studied in details. Our results clearly show that Zn ion preimplantation at a low fluence of 1.0 × 1016 cm–2 can give rise to the formation of large Cu NPs with a double-layer arrangement, which contribute a greatly enhanced surface plasmon resonance (SPR) absorption at about 572 nm. As the Zn ion fluence increases to 1.0 × 1017 cm–2, Cu/Cu–Zn core/shell NPs with a high particle density and a narrow size distribution can be obtained, resulting in a strong and broad SPR absorption band around 528 nm. Besides, the dually implanted samples also exhibit excellent third-order nonlinear optical properties comparing with the Cu solely implanted sample. The possible mechanisms for the nucleation and growth of NPs as well as for the enhancements of linear and nonlinear optical properties have been discussed.

Biochemical properties in membrane of rat astrocytes under oxidative stress

Oxidative stress induced by the treatment with 100µM hydrogen peroxide (H2O2) for 10min enhances release of cytosolic proteins along with fibroblast growth factor 1 (FGF-1) from rat astrocytes without inducing apoptosis. FGF-1 promotes the generation of apolipoprotein E-containing high-density lipoprotein-like particles (apoE/HDL) in astrocytes, which contributes to cholesterol homeostasis in the brain. In this work, we studied various effects of oxidative stress on rat astrocyte׳s membrane to understand the mechanism underlying release of cytosolic proteins and FGF-1. The oxidative stress using 100µM H2O2 enhanced lipid release from rat astrocytes in addition to suppression of lipid synthesis. The lipid synthesis, however, was hardly suppressed by H2O2 in the cell lines such as bovine endothelial cells and HepG2 cells from which the release of cytosolic proteins is not increased by H2O2 unlike rat astrocytes. The treatment of rat astrocytes with H2O2 changed the distribution of lipids and proteins in the caveolin-1-rich domain of membrane to the non-raft domain, which was canceled by the pretreatment of cells with low-density lipoproteins (LDL). These findings suggest that oxidative stress induced by H2O2 changes lipid level of the plasma membrane to make the membrane structure fragile in rat astrocytes. The direct treatment with H2O2 of membrane fraction prepared from rat astrocytes did not enhance lipid release from the membrane. The lipid release, however, was enhanced from the isolated membrane fraction, after the cells were treated with H2O2 and incubated in H2O2-free DPBS. Hydrogen peroxide enhanced phosphorylation of protein kinases such as Akt, MEK, and ERK in intact astrocytes without injury and stress. A MEK inhibitor, U0126, suppressed not only the H2O2-induced ERK phosphorylation but also cytosolic protein release from rat astrocytes. These findings suggest that the H2O2-induced release of cytosolic proteins depends on imbalance of lipid level in the membrane through suppressing lipid synthesis and increasing lipid release induced by the intracellular biochemical reaction such as signal transduction generated in intact rat astrocytes treated with H2O2.

Physical Transformation Processes Of Forest Biomass: Chipping, Bundling, Drying And Control Of Particle Size Distribution

Forest biomass is characterized by physical properties such as high moisture content, low density and heterogeneous particle size, which condition its direct use for combustion. Hence, processes of physical transformation are previously required to obtain products of higher energetic value, reducing transport costs and allowing for homogeneous boiler feeding. The biomass harvesting processes, as well as the logistic options for chipping and bundling, are described in this chapter, which offers a summary of the costs of such operations measured in forest biomass logistic studies in Spain. Studies on natural versus controlled drying of chips and bundles are also discussed, and general recommendations for the management of moisture content and the prevention of self-ignition risk during storage are given. Finally, experiments to date involving the screening and size reduction of forest biomass are summarized.

Dispersion behavior and aqueous foams in mixtures of a vesicle-forming surfactant and edible nanoparticles.

In an attempt to prepare ultrastable aqueous foams composed entirely of food-grade ingredients, we describe the foamability and foam stability of aqueous phases containing either calcium carbonate particles (CaCO3), sodium stearoyl lactylate surfactant (SSL), or their mixtures. Techniques including zeta potential measurements, adsorption isotherm determination, contact angles and optical and cryo-scanning electron microscopy are used to probe the interaction between particles and surfactant molecules. Aqueous dispersions of inherently hydrophilic cationic CaCO3 nanoparticles do not foam to any great extent. By contrast, aqueous dispersions of anionic SSL, which forms a lamellar phase/vesicles, foam progressively on increasing the concentration. Despite their foamability being low compared to that of micelle-forming surfactant sodium dodecyl sulfate, they are much more stable to collapse with half-lives (of up to 40 days) of around 2 orders of magnitude higher above the respective aggregation concentrations. We believe that, in addition to surfactant lamellae around bubbles, the bilayers within vesicles contain surfactant chains in a solidlike state yielding indestructible aggregates that jam the aqueous films between bubbles, reducing the drainage rate and both bubble coalescence and gas-transfer between bubbles. In mixtures of particles and surfactant, the adsorption of SSL monomers occurs on particle surfaces, leading to an increase in their hydrophobicity, promoting particle adsorption to bubble surfaces. Ultrastable foams result with half-lives of around an order of magnitude higher again at low concentrations and foams which lose only around 30% of their volume within a year at high concentrations. In the latter case, we evidence a high surface density of discrete surfactant-coated particles at bubble surfaces, rendering them stable to coalescence and disproportionation.

CFD Simulations of Hydrodynamics of Conical Spouted Bed Nuclear Fuel Coaters

AbstractThe ability of the two fluid method (TFM) to predict the gas‐solid flow phenomenon in conical spouted beds operated with high density (6050 kg m−3) particles simulating the nuclear fuel coating conditions is investigated. The effects of geometric and operational factors, such as conical angle and static bed height, are also assessed. The results show that TFM predicts the time‐averaged bed pressure drop quite well. The qualitative variation of the particle velocity, solids volume fraction, and axial particle flux with axial height are captured by the simulations. The simulated trends observed in the investigation of the effects of static bed height and conical angle on the particle velocity, solids volume fraction, and axial particle flux agree well with those of the experimental measurements.

Tracking molecular dynamics without tracking: image correlation of photo-activation microscopy

Measuring protein dynamics in the plasma membrane can provide insights into the mechanisms of receptor signaling and other cellular functions. To quantify protein dynamics on the single molecule level over the entire cell surface, sophisticated approaches such as single particle tracking (SPT), photo-activation localization microscopy (PALM) and fluctuation-based analysis have been developed. However, analyzing molecular dynamics of fluorescent particles with intermittent excitation and low signal-to-noise ratio present at high densities has remained a challenge. We overcame this problem by applying spatio-temporal image correlation spectroscopy (STICS) analysis to photo-activated (PA) microscopy time series. In order to determine under which imaging conditions this approach is valid, we simulated PA images of diffusing particles in a homogeneous environment and varied photo-activation, reversible blinking and irreversible photo-bleaching rates. Further, we simulated data with high particle densities that populated mobile objects (such as adhesions and vesicles) that often interfere with STICS and fluctuation-based analysis. We demonstrated in experimental measurements that the diffusion coefficient of the epidermal growth factor receptor (EGFR) fused to PAGFP in live COS-7 cells can be determined in the plasma membrane and revealed differences in the time-dependent diffusion maps between wild-type and mutant Lck in activated T cells. In summary, we have developed a new analysis approach for live cell photo-activation microscopy data based on image correlation spectroscopy to quantify the spatio-temporal dynamics of single proteins.

The effect of an apolipoprotein A-I–containing high-density lipoprotein–mimetic particle (CER-001) on carotid artery wall thickness in patients with homozygous familial hypercholesterolemia: The Modifying Orphan Disease Evaluation (MODE) study

Patients with homozygous familial hypercholesterolemia (HoFH) are at extremely elevated risk for early cardiovascular disease because of exposure to elevated low-density lipoprotein cholesterol (LDL-C) plasma levels from birth. Lowering LDL-C by statin therapy is the cornerstone for cardiovascular disease prevention, but the residual risk in HoFH remains high, emphasizing the need for additional therapies. In the present study, we evaluated the effect of serial infusions with CER-001, a recombinant human apolipoprotein A-I (apoA-I)-containing high-density lipoprotein-mimetic particle, on carotid artery wall dimensions in patients with HoFH. Twenty-three patients (mean age 39.4 ± 13.5 years, mean LDL-C 214.2 ± 81.5 mg/dL) with genetically confirmed homozygosity or compound heterozygosity for LDLR, APOB, PCSK9, or LDLRAP1 mutations received 12 biweekly infusions with CER-001 (8 mg/kg). Before and 1 hour after the first infusion, lipid values were measured. Magnetic resonance imaging (3-T magnetic resonance imaging) scans of the carotid arteries were acquired at baseline and after 24 weeks to assess changes in artery wall dimensions. After CER-001 infusion, apoA-I increased from 114.8 ± 20.7 mg/dL to 129.3 ± 23.0 mg/dL. After 24 weeks, mean vessel wall area (primary end point) decreased from 17.23 to 16.75 mm(2) (P = .008). A trend toward reduction of mean vessel wall thickness was observed (0.75 mm at baseline and 0.74 mm at follow-up, P = .0835). In HoFH, 12 biweekly infusions with an apoA-I-containing high-density lipoprotein-mimetic particle resulted in a significant reduction in carotid mean vessel wall area, implying that CER-001 may reverse atherogenic changes in the arterial wall on top of maximal low-density lipoprotein-lowering therapy. This finding supports further clinical evaluation of apoA-I-containing particles in patients with HoFH.

Sound waves and modulational instabilities on continuous-wave solutions in spinor Bose-Einstein condensates

We analyze sound waves (phonons, i.e. Bogoliubov excitations) propagating on continuous-wave (cw) solutions of repulsive $F=1$ spinor Bose-Einstein condensates (BECs) such as $^{23}\mathrm{Na}$ (which is antiferromagnetic or polar) and $^{87}\mathrm{Rb}$ (which is ferromagnetic). Zeeman splitting by a uniform magnetic field is included. All cw solutions to ferromagnetic BECs with vanishing ${M}_{F}=0$ particle density and nonzero components in both ${M}_{F}=\ifmmode\pm\else\textpm\fi{}1$ fields are subject to modulational instability (MI). Modulational instability increases with increasing particle density. Modulational instability also increases with differences in the components' wave numbers; this effect is larger at lower densities but becomes insignificant at higher particle densities. Continuous-wave solutions to antiferromagnetic (polar) BECs with vanishing ${M}_{F}=0$ particle density and nonzero components in both ${M}_{F}=\ifmmode\pm\else\textpm\fi{}1$ fields do not suffer MI if the wave numbers of the components are the same. If there is a wave-number difference, MI initially increases with increasing particle density and then peaks before dropping to zero beyond a given particle density. The cw solutions with particles in both ${M}_{F}=\ifmmode\pm\else\textpm\fi{}1$ components and nonvanishing ${M}_{F}=0$ components do not have MI if the wave numbers of the components are the same, but do exhibit MI when the wave numbers are different. Direct numerical simulations of a continuous wave with weak white noise confirm that weak noise grows fastest at wave numbers with the largest MI and show some of the results beyond small-amplitude perturbations. Phonon dispersion curves are computed numerically; we find analytic solutions for the phonon dispersion in a variety of limiting cases.

Dynamics of Glycine Receptors and their Interactions with Gephyrin Scaffolds Revealed with High-Density Single Particle Tracking and Bayesian Inference

The scaffold protein gephyrin plays a critical regulatory role in the transmission of nerve signals in inhibitory synapses.. Its interactions with receptors of inhibitory neurotransmitters, such as glycine or GABA, are postulated to be a key molecular mechanism of synaptic formation and plasticity. Previous studies have shown that glycine receptors transiently bind to gephyrin scaffolds inside the synapse, however there is limited knowledge of the strength of this interaction. This is due, in part, to the consensus view that the synapse is a complex and dynamic assembly that is sensitive to a host of stimuli including neuronal activity, hormones, and pathological states. Therefore, a beneficial approach to improve our understanding is to reconstitute gephyrin scaffolds and their interactions with receptors in non-neuronal cells. To this end, in a greatly simplified system we use a transmembrane construction that consists of the large intracellular s-Loop that directly interacts with the gephyrin scaffold, mimicking the actions of the endogenous glycine receptor.Based on high-density single-particle tracking, we use a robust Bayesian inference approach to spatially map the dynamics inside receptor-scaffold sites in non-neuronal cells. Through adaptive spatial meshing techniques, we are able to conform our maps to highly heterogeneous trajectory and diffusion distributions and, notably, generate whole-cell landscapes of interaction energies. Importantly, we treat the inherently multi-scale nature of receptor motion in a faithful and reproducible manner.We show that our method allows us to distinguish interactions between different s-Loop mutants, effectively correlating protein-level modifications to quantifiable metrics of receptor dynamics. This is an important advance that reinforces the treatment of complex biological systems with statistical methods.

Characterization of Gas Atomized Ni-Mn-Ga Powders

Gas atomization is a well-known process for obtaining high quality metallic powders. It produces spherical high-density particles with a controllable particle size distribution. We used gas atomization to obtain two different Ni-Mn-Ga powders and investigated their microstructure, transformation temperatures and magnetic properties as well as the effects of heat treatment on those. The phase and magnetic transformation temperatures of the powders were considerably lower as compared to similar conventionally prepared alloys. Nevertheless, heat treatment of the atomized powder was found to recover the magnetic properties of the materials, probably by releasing the residual strains generated by the rapid solidification during the gas atomization process. Sintering of powders seemed to start at a significantly lower temperature when compared to the powder prepared by ball milling of bulk Ni-Mn-Ga-alloys.

Concurrent Integration of Science-Based Mechanistic Relationships with Computational Thermodynamics and Kinetic Simulations for Strengthening Magnesium Alloys at Elevated Temperatures

Integrated computational materials engineering approaches to alloy development leverage the hierarchical, interconnected nature of materials systems to rapidly optimize material performance. Particular emphasis is placed on the use of predictive models and simulation tools to elucidate fundamental relationships within the processing-structure-processing materials paradigm. For the current work, computational simulation results were used in combination with mechanistic, science-based models to assist alloy design. Two case studies are presented as illustrative examples that focus on high-temperature magnesium (Mg) alloy development. Solid solution strengthening potency and solute-based effects on creep rate were discussed in the first case study to guide strategies for solute selection in alloy development. This analysis was completed through the identification of composition-sensitive microstructural parameters that were subsequently evaluated in a predictive fashion. The second case study used computational thermo-kinetic simulations to evaluate Mg alloy precipitate systems for their ability to nucleate a high number density of coarsening-resistant particles. This nucleation and growth analysis was then applied to a Mg-Sn-Al alloy to highlight the utility of the current methodology in predicting multicomponent alloy precipitation behavior. This paper ultimately seeks to provide insight into an integrative approach that captures the important underlying material physics through relationships parameterized by descriptive thermodynamic and kinetic factors, where these factors can be readily calculated with a commercially available suite of computational tools in concert with accessible data in the literature.

Nature of soil organo-mineral assemblage examined by sequential density fractionation with and without sonication: Is allophanic soil different?

Organic matter (OM) bound to soil mineral particles (higher-density particles) tends to be more stabilized, enriched in 13C and 15N, and has a lower C:N ratio. Yet how these variations in OM chemistry are linked to the nature of organo-mineral assemblage remains poorly understood, especially in allophanic soils where high amounts of OM are stabilized by interactions with reactive inorganic phases such as short-range-order (SRO) minerals. We thus assessed the extent to which the degree of aggregation and its disruption during fractionation control the distribution and chemistry of the soil organo-mineral particles across six density fractions using a volcanic soil (allophanic Andisol) based on selective dissolution, microscopy (SEM), solid-state 13C NMR spectroscopy and δ13C and δ15N analyses. Intermediate-density fractions (2.0–2.5gcm−3) accounted for 63–86% of organic C and N, 73–93% of pyrophosphate-extractable iron and aluminum (Fep, Alp), and 78–95% of oxalate-extractable metals (Feo, Alo) in the bulk soil sample. While air-drying pretreatment had little effect, sonication during fractionation led to (i) fragmentation of both plant detritus and some of the aggregates of 30–100mm sizes, (ii) release of occluded low-density fraction (<1.6gcm−3) which largely originated from the aggregates of 1.6–2.0gcm−3 density range, and (iii) redistribution of organo-mineral particles (15–16% of total OM and 7–19% of the extractable metals) within the intermediate density fractions. Positive correlation of Alp with C:N ratio and negative correlation of Alp with δ15N among the fractions suggest preferential binding of Alp phase (e.g., organo-Al complexes) to decaying plant detritus. Positive correlation of Alo and Feo with δ15N, together with theoretical density calculations of idealistic organo-mineral association modes, suggests that 15N enrichment may be coupled with OM binding to SRO minerals and with the formation of physically-stable aggregates of micron/submicron sizes in accord with our conceptual model (Asano and Wagai, 2014). The general pattern of 13C and 15N enrichment and C:N decline with increasing particle density remained largely unchanged despite the sonication effects detected, indicating that sonication-resistant organo-mineral assemblages largely control the observed patterns. The similarity in the density-dependent changes of OM chemistry between the studied Andisol and the soils with crystalline clay and metal oxide mineralogies in previous studies strongly suggests a common biogeochemical control which deserves further investigation.

Terahertz emission from multiple-microcavity exciton-polariton lasers

Terahertz emission between exciton-polariton branches in semiconductor microcavities is expected to be strongly stimulated in the polariton laser regime due to the high density of particles in the lower state (final-state stimulation effect). However, nonradiative scattering processes depopulate the upper state and greatly hinder the efficiency of such terahertz sources. In this work, we suggest a scheme using multiple microcavities and exploiting the transition between two interband polariton branches located below the exciton level. We compare the nonradiative processes loss rates in single and double cavity devices and we show that a dramatic reduction can be achieved in the latter, enhancing the efficiency of the terahertz emission.