Particles In Field Research Articles

Effect of drum structure on particle mixing behavior based on DEM method

The optimization of the drum structure is beneficial to improve the particle motion and mixing in rotary drums. In this work, two kinds of drum structures, Lacy cylinder drum (LC) and Lacy-lifters cylinder drum (LLC), are developed on the basic of cylinder drum to enhance the heat transfer area. The particle motion and mixing process are simulated by DEM method. Based on the grid independence and model validation, the contact number between particles and wall, particle velocity profile, thickness of active layer, particle exchange coefficient, particle concentration profile and mixing index are demonstrated. The influences of the drum structure and the operation parameters are further evaluated. The results show that the contact number between particles and wall is improved in LC and LLC compared to cylinder drum. The particle velocity in LC is higher than that in cylinder drum at high rotating speed, and the particle velocity of the particle falling region is significantly improved in LLC. Compared to cylinder drum and LC, the thickness of active layer in LLC is smaller, while the local particle mixing quality is proved to be the best in the active region. In addition, the particle exchange coefficients between static region and active region in the three drums are compared and LLC is found tending to weaken the particle flow. Besides, the fluctuations of particle concentration in the active region, static region, and boundary region are weakened in LLC, and the equilibrium state is reached earlier. In addition, the overall particle mixing performance in cylinder drum, LC and LLC is analyzed. The particle mixing performance in cylinder drum is the worst, while the difference in mixing quality of LC and LLC depends on the operation conditions.

Next-to-leading order scalar contributions to μ→e conversion

Within a class of models in which lepton flavor violation is induced dominantly by scalar particle exchanges, we estimate the $\ensuremath{\mu}\ensuremath{\rightarrow}e$ conversion rate in several nuclei. We include next-to-leading order (NLO) terms in the one- and two-nucleon interactions in chiral effective theory, rectifying some incorrect results in the previous literature. We provide an uncertainty budget for the conversion rates and we find that NLO contributions affect the amplitudes at the level of $10%$, which could be larger than the uncertainty on the leading order couplings, dominated by the strange and nonstrange nucleon sigma terms. We study the implications of our results for testing Higgs-mediated charged lepton flavor violation (CLFV) in the future by combining results from various experimental searches, such as $\ensuremath{\mu}\ensuremath{\rightarrow}e$ conversion in multiple target nuclei and $\ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma}$.

Simulation of the crystallization processes by population balance model using a linear separation method

Abstract Crystallization problem is one of the popular problems in wide area of science. The first principles are not used to design a crystallizer in which complicated processes include nucleation, crystal growth, attrition and agglomeration of crystals. It is modeled by the population balance model, which is one of the important models of mathematical biology and engineering, is a nonlinear partial integro-differential equation and examines the exchange of particles and the production of new particles in a system of particles. For the crystallization problem, one-dimensional and multi-dimensional models are considered and semi-analytical solutions are obtained via the linear separation method.

Evidences of accumulation points: Effect of high voltage DC conditioning on concave electrodes insulated by large vacuum gaps

Counterintuitive experimental evidences have been observed during High Voltage Direct Current (HVDC) tests of two concave, axial-symmetric, electrodes insulated by large vacuum gaps of 3 and 7 cm with voltages from 150 to 370 kVdc. The dissipation of microdischarge power during the conditioning procedure occurs mostly on the anodic side in a region close to the axis of the system where the electric field is at a minimum, far from the positions where the breakdowns have been observed. The analyses of the phenomena are carried out by comparing the temporal evolution of voltages, currents, pressure, measurements of x-ray energy spectra, and images from infrared and visible light cameras. Numerical simulations, based on ray-tracing algorithm, correctly identify the positions where the power dissipation of microdischarges occurs. A mutual exchange of charged particles in the electrostatic field between electrodes seems a reasonable physical mechanism to interpret the observations. These findings suggest a new perspective to review the current literature and interpret new results considering geometric details which were so far omitted: the areas with the most intense electric field, typically located on the surfaces of the electrodes under test, are not necessarily the sole surfaces involved in the HVDC conditioning in high vacuum.

Dermal Lymphatic Capillaries Do Not Obey Murray's Law.

Lymphatic vessels serve as a major conduit for the transport of interstitial fluid, immune cells, lipids and drugs. Therefore, increased knowledge about their development and function is relevant to clinical issues ranging from chronic inflammation and edema, to cancer metastasis to targeted drug delivery. Murray's Law is a widely-applied branching rule upheld in diverse circulatory systems including leaf venation, sponge canals, and various human organs for optimal fluid transport. Considering the unique and diverse functions of lymphatic fluid transport, we specifically address the branching of developing lymphatic capillaries, and the flow of lymph through these vessels. Using an empirically-generated dataset from wild type and genetic lymphatic insufficiency mouse models we confirmed that branching blood capillaries consistently follow Murray's Law. However surprisingly, we found that the optimization law for lymphatic vessels follows a different pattern, namely a Murray's Law exponent of ~1.45. In this case, the daughter vessels are smaller relative to the parent than would be predicted by the hypothesized radius-cubed law for impermeable vessels. By implementing a computational fluid dynamics model, we further examined the extent to which the assumptions of Murray's Law were violated. We found that the flow profiles were predominantly parabolic and reasonably followed the assumptions of Murray's Law. These data suggest an alternate hypothesis for optimization of the branching structure of the lymphatic system, which may have bearing on the unique physiological functions of lymphatics compared to the blood vascular system. Thus, it may be the case that the lymphatic branching structure is optimized to enhance lymph mixing, particle exchange, or immune cell transport, which are particularly germane to the use of lymphatics as drug delivery routes.

Clinical Utility of Small, Dense LDL as an Atherogenic Risk Marker

Low-density lipoprotein (LDL) has a major role in the origination and development of atherosclerosis and Cardio Vascular Diseases (CVD). Over the past few years, many studies have been concerned with different subclasses of LDLs and their atherogenicity. Low-density lipoproteins (LDLs) include many subclasses. The most common are large buoyant (LB), intermediate and small dense (sd) low-density lipoprotein particles. Small dense low-density lipoproteins attracted a lot of attention. Small dense LDL (sdLDL) has recently been proven to be more atherogenic than other lipoproteins containing apolipoprotein B, which have the potential to trigger atherosclerotic reactions. Many researchers have reported that small dense low-density lipoproteins are the superior biomarker for the prediction of atherosclerosis and CVDs regarding all other markers, including total low-density lipoprotein cholesterol(LDL-C), and total serum cholesterol, non-high-density lipoprotein (non-HDL-C), high-density lipoprotein cholesterol (HDL-C), and triglyceride content. Circulating small dense, low-density lipoproteins go through several modifications in the blood, rendering them more atherogenic. These modifications may include glycation, oxidation, and desialylation. Modified particles are strong inducers of inflammation resulting in many cardiovascular diseases, making them the primary target during the treatment of coronary artery disease. This article will elaborate on the clinical utility of sdLDL as an early marker to predict atherosclerosis and CVDs, and why it is considered superior to other atherosclerotic markers.

A Metastable Amorphous Intermediate Is Responsible for Laser-Induced Nucleation of Glycine.

Laser-induced crystal nucleation through optical tweezing, and in particular polymorph selection through laser polarization, promises unprecedented control over crystallization. However, in the absence of a nearby liquid-liquid critical point or miscibility gap, the origin of the required mesoscale clusters remains unclear. A number of recent studies of so-called nonclassical nucleation have suggested the presence of large amorphous clusters. Here, we show that supersaturated aqueous glycine solutions form metastable intermediate particles that are off the direct path to crystal nucleation. Laser-induced crystal nucleation only occurs when the laser "activates" one of these particles. In situ low-frequency Raman spectroscopy is used to demonstrate their amorphous or partially ordered character and transformation to various crystal polymorphs. The requirement for solution aging in many previously reported laser-induced crystal nucleation experiments strongly suggests that the presence of amorphous intermediates is a general requirement.

Axion isocurvature collider

Cosmological colliders can preserve information from interactions at very high energy scale, and imprint them on cosmological observables. Taking the squeezed limit of cosmological perturbation bispectrum, information of the intermediate particle can be directly extracted from observations such as cosmological microwave background (CMB). Thus cosmological colliders can be powerful and promising tools to test theoretical models. In this paper, we study extremely light axions (including QCD axions and axion-like-particles), and consider them constituting cold dark matter (CDM) at late times. We are interested in inflationary isocurvature modes by such axions, and try to figure out how axion perturbations can behave as isocurvature colliders. We work out an example where the intermediate particle is a boson, and show that, in the squeezed limit, it is possible to provide a clock signal of significant amplitudes, with a characteristic angular dependence. This provides a channel to contribute and analyze clock signals of isocurvature bispectrum, which we may hopefully see in future experiments.

Dispersion of particles in two-dimensional monopolar and dipolar vortices using a Lagrangian stochastic model

The dispersion of particles in two-dimensional vortices, two circular monopoles, and the Chaplygin–Lamb dipole is studied numerically with a Lagrangian stochastic model. The monopoles are the Rankine and the steady Oseen vortex, whose azimuthal velocity profile is irrotational at a long radial distance. The total velocity of each particle is divided into two parts: the deterministic field due to the vortex plus a stochastic velocity representing homogeneous turbulence. The experiments are carried out with thousands of particles to calculate the dispersion as a function of time. The dispersion in the monopoles grows rapidly and then increases at a lower rate as the particles transit toward the potential region. This transition occurs more quickly in the Rankine vortex, so the Oseen vortex has a wider time-lapse to generate a more significant dispersion. In the case of the Chaplygin–Lamb dipole, having an internal and external flow, the dispersion has different behavior depending on which region the particles depart. The dispersion curves describe the exchange of particles between the poles and the outer flow as the dipole drifts. We discuss the capacity of the dipole to transport particles through long distances.

Quantum states from mixtures of equilibrium distributions

We construct and explore a family of states for quantum systems in contact with two or more heath reservoirs. The reservoirs are described by equilibrium distributions. The interaction of each reservoir with the bulk of the system is encoded in a probability, which characterises the particle exchange among them and depends in general on the particle momentum. The convex combination of the reservoir distributions, weighted with the aforementioned probabilities, defines a new distribution. We establish the existence of an emission–absorption regime in which the new distribution generates a non-equilibrium quantum state. We develop a systematic field theory framework for constructing this state and illustrate its physical properties on a simple model. In this context we derive the particle current full counting statistics, the heat current and the Lorenz number. The entropy production and the relative quantum fluctuations are also determined.

Ultraviolet dimensional reduction of spacetime with zero-point length

Among the many disparate approaches towards quantum gravity, the reduction of spacetime dimension in the ultraviolet regime is expected to be a common thread. The spectral dimension of spacetime is defined in the context of diffusion processes on a manifold. We show that a spacetime with zero-point length has spectral dimension 3.5 when the characteristic diffusion time has the size of the zero-point length. The spectral dimension (negatively) diverges for an even shorter diffusion time, thus preventing reliable physical interpretation in the deep ultraviolet regime. The thermodynamic dimension is defined by realizing that the free energy F(beta ) of a free field or ideal gas at finite temperature (beta ^{-1}) in D dimensions scales as Fsim beta ^{-D}. Using Schwinger’s proper time formalism, we show that for spacetime incorporating a zero-point length, the thermodynamic dimension reduces to 1.5 near the Planck scale and then to 1 in the deep ultraviolet regime. This signifies a “phase-transition” in which a (massless) bosonic ideal gas in four dimensions essentially behaves like radiation (w=1/3) at low energies, whereas near the Planck scale, it behaves equivalently to having an equation of state parameter w=2. Furthermore, dimension can be deduced from the potential V_D(r) of interaction between two point-like sources separated at a distance r as its scaling depends on D. Comparing with the scaling behavior of conventional Yukawa-like potentials at short distances, we show that the ultraviolet dimension appears to be either 2 or 3 depending on the use of massive or massless force carriers as probes.

Mass independent isotopic fractionation: A key to plasma chemistry

We propose a numerical model allowing to calculate the relative variations of isotopic ratios involved in a mass-independent isotopic fractionation (MIF) effect. This model is derived from classical trajectory simulation performed to reproduce the reactions yielding the isotopomers of ozone. In the ozone simulation, we did not introduce quantum mechanical selection rules for trajectories or the potential surface, but we separated instead exchange and non-exchange collisions, in order to introduce the fundamental quantum mechanical requirement according to which, for indistinguishable isotopes, the two possible reaction channels (elastic scattering or particle exchange) have to be superposed. The MIF effect is related to the molecular symmetry of the complex by the result that a different fraction of isotopically asymmetric complexes (formed by distinguishable isotopes) is stabilized than for symmetric ones (formed by indistinguishable isotopes).The model is applied on the results obtained experimentally for Mg and Ti isotopes in plasma. In plasma, Mg and Ti radicals resulting from the molecular dissociation of chlorides react with their parent molecules. In presence of hydrocarbons, isotope exchange rates are greatly enhanced when the intermediate activated complexes are adsorbed at the surface of the carbonaceous grains growing in the plasma. If a chemical reaction with the grain stabilizes the complex faster than its dissociation, MIF effects are observed. In such a chemical situation, the isotopic fractionation greatly exceed the usual theoretical predictions. Several characteristics of the MIF isotopic patterns are reproduced by the model.

Exploring the Properties of Micronized Natural Zeolitic Volcanic Tuff as Cosmetic Ingredient.

This study explores the characteristics of a micronized natural zeolitic volcanic tuff (MZ) as ingredient in cosmetic formulations. In particular, the purpose was to prepare and investigate the organoleptic and physicochemical properties of two representative cosmetic formulations containing MZ. The MZ samples were characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. pH, cation exchange capacity (CEC), apparent density, chemical composition and particle size distribution of MZ samples were also determined. The micronization treatment applied did not produce significant structural and physicochemical changes with respect to the raw zeolitic volcanic tuff. The prepared formulations containing 5% MZ with different particle sizes (100–125 µm and 125–250 µm) were subjected to preliminary and accelerated stability tests, and the pH and organoleptic properties were also evaluated. The cosmetic formulations presented a pH of 4.3, a pleasant touch, good spreadability, easy application on skin, no color alteration and a good stability after 15, 30 and 60 days of storage at room temperature, low temperature and freezer during the accelerated stability tests. The obtained results endorse the MZ as suitable for the development of formulations exploiting the clinoptilolite properties as a cosmetic ingredient.

Dynamics of Excitons in Conjugated Molecules and Organic Semiconductor Systems.

The exciton, an excited electron-hole pair bound by Coulomb attraction, plays a key role in photophysics of organic molecules and drives practically important phenomena such as photoinduced mechanical motions of a molecule, photochemical conversions, energy transfer, generation of free charge carriers, etc. Its behavior in extended π-conjugated molecules and disordered organic films is very different and very rich compared with exciton behavior in inorganic semiconductor crystals. Due to the high degree of variability of organic systems themselves, the exciton not only exerts changes on molecules that carry it but undergoes its own changes during all phases of its lifetime, that is, birth, conversion and transport, and decay. The goal of this review is to give a systematic and comprehensive view on exciton behavior in π-conjugated molecules and molecular assemblies at all phases of exciton evolution with emphasis on rates typical for this dynamic picture and various consequences of the above dynamics. To uncover the rich variety of exciton behavior, details of exciton formation, exciton transport, exciton energy conversion, direct and reverse intersystem crossing, and radiative and nonradiative decay are considered in different systems, where these processes lead to or are influenced by static and dynamic disorder, charge distribution symmetry breaking, photoinduced reactions, electron and proton transfer, structural rearrangements, exciton coupling with vibrations and intermediate particles, and exciton dissociation and annihilation as well.

Static electric dipole moment of the francium atom induced by axionlike particle exchange

The francium atom is considered as a prospective candidate system to search for the T,P-violating electron electric dipole moment [T. Aoki et al Quantum Sci. Technol. 6, 044008 (2021)]. We demonstrate that the same experiment can be used for axionlike particles (ALP) search. For this, we calculate electronic structure constants of ALP-mediated interaction for a wide range of ALP masses. Using the recently updated constraints on the ALP-electron and ALP-nucleon coupling constants, we show that the contribution of considered interactions corresponding to these constraints can give significant contribution to atomic electric dipole moment. Therefore, obtainment of stronger restrictions for ALP characteristics in the francium atom electric dipole moment experiment is possible.

A novel route to the synthesis of α-Fe2O3@C@SiO2/TiO2 nanocomposite from the metal-organic framework as a photocatalyst for water treatment

In this study, an attempt was made to synthesize metal-organic frameworks (MOFs) based magnetic iron particles as photocatalysts for textile dye wastewater. Improvement strategy was a novel two-step dry method without using conventional methods to eliminate the consumption of chemical reagents. First, the heterogeneous photocatalyst of Fe-MOFs derived magnetic carbon nanocomposite with carboxylic acid surface functional groups (Fe@C–COOH) was achieved. Next, the α-Fe2O3@C@SiO2/TiO2 was successfully synthesized followed by a sol-gel method to coat the SiO2 shell and a solvothermal method to coat the surface of the intermediate TiO2 particles. The as-synthesized nanocomposite materials were characterized and physicochemical analytical equipment. Further, the investigation on magnetic photocatalytic nanocomposite α-Fe2O3@C@SiO2/TiO2 performance of dye degradation and photocatalytic activity on Reactive yellow 145 (RY145), using as an indicator was conducted. The as-synthesized nanocomposite particles were characterized using X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), X-ray energy dispersive spectroscopy (EDX), and scanning electron microscopy (SEM) techniques. The structural characterization of the as-synthesized materials proved that these methods generate oxygen-containing functional groups, such as, –OH, –CO, and –COOH, which increases the polarity and hydrophilicity of the photocatalyst. The photocatalytic oxidation of RY145 dye under UVc light was discussed by the apparent first-order reaction rate and the kinetic model of the Langmuir-Hinshelwood followed a better fitting. The optimal performance of the composite is at pH = 2, 15 mg/100 mL of photocatalyst dose, 150 mg/L concentration of the dye RY145 at 25 °C temperature under UVc lamp irradiation for 90 min, and with the apparent reaction rate constant was 0.0165 min−1. The thermodynamic analysis of activation parameters computed by the Eyring model and based on transition state theory (TST), an endothermic reaction with a positive value for Δ‡Ho (50.16 kJ mol−1) and a negative value for Δ‡So (−153 J/mol K) both contribute toward achieving positive values for Δ‡Go and a nonspontaneous process. The proposed α-Fe2O3@C@SiO2/TiO2 demonstrated a high capability of photocatalytic degradation up to 97% after five successive cycles at the optimal condition compared to that of Fe3O4@C (18.74%) and Fe@C–COOH (77.9%) without reusability.

A Comparative Study of Thermal, Luminous, and Infrared Radiation Characteristics of Natural gas Flame in the Presence of Alkali, Alkali-Earth, and Transition Metallic Solution Additives

Abstract Experiments were performed to find out the effect of alkali, alkali-earth, and transition metallic additives on thermal, luminous, IR, and total radiative properties of natural gas flame. A total of 25 mL of 0.5 M alkali salts of NaNO3 and KNO3, alkali-earth salts of Ca(NO3)2, Ba(NO3)2, and Sr(NO3)2 and transition nitrate salts of Cu(NO3)2 and Mn(NO3)2 (Merck company) were prepared, and flame tests were done on each solution by using a Bunsen burner with the equivalence ratio of 1.05, which is close to the condition of stoichiometric air–fuel mixing. The optical characteristics of flame were measured in visible and infrared radiation (IR) spectrums by a TES-1332A luminance meter, BOMEM FTIR, and IR flame photography technique. Also, the total radiation was gauged by a HFP01 sensor. The results indicated that, in general, due to the increased rate of nucleation of intermediate soot particles, the flame in the presence of alkali metal additives has higher total, luminous, and IR radiation than in the presence of other metal additives. Also, the metallic additives do not significantly change the flame temperature. The results also revealed that although all metallic additives enhance the luminous radiation of flame, which is due to chemiluminescence phenomenon or atomic emission, luminous radiation of metal additives is negligible in comparison with their radiation in IR wavelengths. Furthermore, the results show that the boiling temperature of metallic salt solutions has a greater impact on flame luminosity than their ionization energy does.

Abstract P041: Increases In Low-density Lipoprotein Subclasses During The Menopause Transition Are Associated With Greater Risk Of Coronary Calcification And Carotid Atherosclerosis: The SWAN HDL Study

Objectives: Increase in LDL-C occurs within 1 year of the final menstrual period (FMP), and this increase has been linked to a greater plaque risk. LDL subclasses have been linked to CAD beyond LDL-C, promising a better risk stratification. We aim to characterize changes in LDL subclasses over the menopause transition (MT) and assess associations of these changes with presence of coronary artery calcification (CAC Agatston score ≥10) and carotid intima-media thickness (cIMT), and test the effect modification of time relative to FMP on these associations. Design: Midlife women with nuclear magnetic resonance spectroscopy LDL subclasses measured over the MT for a maximum of 5 timepoints were included (n=471; baseline age 50.19 ± 2.7 years; 81.0% Pre-/Early perimenopausal). A subset of women had CAC and cIMT measured for a maximum of 2 timepoints (n=221). LOESS plots were used to characterize changes in LDL subclasses over the MT in the full sample. Inflection points identified from the LOESS plots suggested timing of changes in slope (Figure). Linear mixed effect models or generalized estimating equation was used for analysis. Effect modification by time relative to FMP was tested. Results: All LDL metrics increased around the FMP except for Intermediate LDL Particles (IDL-P), which declined (Figure). Higher total LDL particles (LDL-P) and greater ApoB independently associated with higher CAC prevalence and greater cIMT. Although none of the associations of LDL metrics with cIMT or CAC were modified by time relative to FMP, higher LDL-C, ApoB and total LDL-P were associated with higher cIMT during peri- or postmenopausal stages (Table), while higher LDL-C, small LDL-P and large LDL-P were associated with greater CAC prevalence, mainly during perimenopause stage in adjusted models (Table). Conclusions: During the MT women experience significant increases in LDL subclasses found to be related to greater cIMT levels and CAC prevalence. Monitoring LDL subclasses over the MT may help in identifying women at greater risk for future CAD.

A new view on Redox processes in aquatic systems

In the present paper, the redox processes in the aquatic environment were studied, by conducting fundamental research and the mechanisms of chemical reactions with the participation of natural oxidizing agents in the presence of transition metals. It is a synthesis of scientific results including a new vision regarding the chemical reactions with one or two electrons transfer, which explains how the free radicals and complex compounds with partial charge transfer are formed. This view includes an explanation for the phenomenon of aggressive free radical generation that “kills” biota, rather than destroying pollutants, and why the intermediate particles resulting from chemical and biochemical processes act much softer.

A Novel Framework for Simulating Particle Deposition With Moving Bedforms

AbstractPrevious modeling studies of hyporheic exchange induced by moving bedforms have used a moving reference frame, typically corresponding to an individual moving bedform. However, this approach is not suitable for simulating the exchange and accumulation of immobile fine particles beneath moving bedforms, which commonly occurs in sand‐bed streams, as both moving and stationary features must be considered. Here we present a novel simulation framework that may represent arbitrarily shaped, generally aperiodic mobile bedforms within a stationary reference frame. We combine this approach with particle tracking to successfully reproduce observations of clay deposition in sand beds, and the resulting development of a low‐conductivity layer near the scour zone. We find that increased bedform celerity and filtration both lead to a shallower depth of clay deposition and a more compact deposition layer. While increased filtration causes more clay to deposit, increased celerity reduces deposition by flattening hyporheic exchange flowpaths.