Average Particle Density Research Articles

Development and characterization of a new adsorbent for biomolecule separation: intercalation and adsorption of clavulanic acid in layered double hydroxides

AbstractBACKGROUNDA new layered double hydroxide (LDH) material has been developed through a pioneering approach, with the goal of being an alternative adsorbent for the separation of biomolecules, such as clavulanic acid (CA).RESULTSZn2Cr‐CA hybrid LDH assemblies were prepared through a coprecipitation method to evaluate the affinity between the CA molecule and the interlayer sites. The resulting inorganic–organic ‘sandwich’ structure was characterized by a combination of techniques showing an expansion of the layered structure from 0.78 nm up to values of 2.30 nm upon CA intercalation. Isotherm studies were carried out to evaluate the adsorption capacity of LDH towards CA. The Freundlich adsorption model was found to fit the experimental data well, indicating a relatively large adsorption capacity for the adsorbent Zn2Cr‐NO3, as high as 73.63, 128.76, and 229.62 mg1‐nFLnFg−1 at 20, 30, and 35 °C, respectively.CONCLUSIONZn2Cr‐NO3 adsorption capacity was not influenced by the presence of amino acids, thus underlining that it is a LDH composition which may be a suitable alternative for the separation of CA. LDH micro‐particles were additionally encapsulated with calcium alginate gel (LDHME) and characterized for particle average diameter (dp = 171 µm), bulk density (ρbulk = 0.63 g cm−3), particle density (ρp = 2.2 g cm−3), particle porosity (ϵp = 0.71) and bed porosity (ϵB = 0.40). The application of LDHME in the separation of CA from complex mixtures, containing tyrosine and proline, was considered satisfactory based on purification factors of about 2.32 and degrees of purity higher than 99%. © 2015 Society of Chemical Industry

Induced gravitational collapse in the BATSE era: The case of GRB 970828

Following the recently established "Binary-driven HyperNova" (BdHN) paradigm, we here interpret GRB 970828 in terms of the four episodes typical of such a model. The "Episode 1", up to 40 s after the trigger time t_0, with a time varying thermal emission and a total energy of E_{iso,1st} = 2.60 x 10^{53} erg, is interpreted as due to the onset of an hyper-critical accretion process onto a companion neutron star, triggered by the companion star, an FeCO core approaching a SN explosion. The "Episode 2", observed up t_0+90 s, is interpreted as a canonical gamma ray burst, with an energy of E^{e^+e^-}_{tot} = 1.60 x 10^{53} erg, a baryon load of B = 7 x 10^{-3} and a bulk Lorentz factor at transparency of \Gamma = 142.5. From this Episode 2, we infer that the GRB exploded in an environment with a large average particle density <n> \approx 10^3 particles/cm^3 and dense clouds characterized by typical dimensions of (4 \div 8) x 10^{14} cm and \delta n / n ~ 10. The "Episode 3" is identified from t_0+90 s all the way up to 10^{5-6} s: despite the paucity of the early X-ray data, typical in the BATSE, pre-Swift era, we find extremely significant data points in the late X-ray afterglow emission of GRB 970828, which corresponds to the ones observed in all BdHNe sources. The "Episode 4", related to the Supernova emission, does not appear to be observable in this source, due to the presence of darkening from the large density of the GRB environment, also inferred from the analysis of the Episode 2.

Modeling Fine-Particle (Dusty) Plasmas and Charge-Stabilized Colloidal Suspensions as Inhomogeneous Yukawa Systems

In order to give a basis for the structure and correlation analysis of fine particle (dusty) plasma and colloidal suspensions, thermodynamic treatment of mixtures of macroscopic and microscopic charged particles within the adiabatic response of the latter is extended to include the case where the system is finite and weakly inhomogeneous. It is shown that the effective potential for macroscopic particles is composed of two elements: mutual Yukawa repulsion and a confining (attractive) Yukawa potential from their `shadow' (the average charge density of macroscopic particles multiplied by the minus sign). The result clarifies the relation between two approaches hitherto taken where either a parabolic one-body potential is assumed or the average distribution is assumed to be flat with finite extension. Since the satisfaction of the charge neutrality is largely enhanced by the existence of macroscopic particles, the assumption of the flat electrostatic potential and therefore flat average distribution of macroscopic particles in the domain of their existence is expected to be closer to reality than the assumption of the parabolic potential in that domain.

Transient measurement of the effective particle density of cigarette smoke

The real-time effective particle density of cigarette smoke was determined using a Centrifugal Particle Mass Analyzer (CPMA) and Differential Mobility Spectrometer (DMS). A Puff Inhale Exhale (PIE) simulator was used to produce the smoke from various research and commercial cigarettes following the International Standard Organization (ISO) puffing parameters (35ml puff of 2s duration, every 60s) or the Health Canada Intense (HCI) puffing parameters (55ml puff of 2s duration, every 30s). The impact of modifying parameters, such as smoke mass, cigarette format, filter type, inhalation volume and mouth hold period, on the effective particle density was also investigated. All of the effective density functions were found to be independent of particle size within the bias uncertainty of the measurement system, indicating that the cigarette smoke particles likely had a spherical morphology. Trends in the average effective particle densities were observed for the different cigarettes and puffing parameters. While all of these shifts were within the bias uncertainty of the CPMA–DMS system, two-sample t-tests and the Tukey method were used to identify where the shifts were statistically probable. However due to the complexity of cigarette smoke, the aerosol mechanisms behind most of these shifts were unknown and require further investigation. For all of the tested cases the average effective particle density, considering puffs 3–6, varied from 1090 to 1518kg/m3, with a majority (9 out of 16 cases) falling within 1300 to 1394kg/m3. The Tukey method identified no statistical change in the effective particle density over the duration of an ISO puff, but it did identify significant differences between effective densities produced by different cigarettes.

Particle densities of the pulsed dielectric barrier discharges in nitrogen at atmospheric pressure

Pulsed dielectric barrier discharges (DBDs) have become a promising solution to generate atmospheric-pressure non-equilibrium plasmas. In this work, a one-dimensional fluid model is carried out to research particle densities of the pulsed nitrogen DBDs at atmospheric pressure. Averaged particle densities, time evolutions of axial distributions of particle densities and influences of discharge gap distance dg on the particle densities are systematically illustrated and discussed. The calculation results show that averaged electron densities are lower than averaged N2+ densities, but higher than other averaged ion densities. Time evolutions of axial distributions of electron, N+ and N2+ densities show two peaks during rising and falling phases of applied voltage when dg is 0.2 cm but present gradual increases during pulse width when dg is 0.6 cm, which are similar to those of N2(a′) and N2(B). Maximums of N3+ densities are close to the momentary cathode under dg of 0.2 cm but locate near the grounded electrode under dg of 0.6 cm, which are alike to those of N2(A) and N2(C). Besides, N4+ densities nearby the momentary anode are higher than those nearby the momentary cathode when dg is 0.2 cm. N(2D) has low averaged particle densities and complex time evolutions compared to N.

Cumulative hadron production in pA collisions in the framework of z-scaling

Data on cumulative particle production in pA collisions with momentum [Formula: see text] are analyzed in the [Formula: see text]-scaling approach. Scaling function [Formula: see text] is constructed for different types of target nuclei and inclusive particle angle. The function is expressed via respective inclusive cross section and average multiplicity density of charged particles. This regime corresponds to low [Formula: see text] (low transverse momentum [Formula: see text]). Validity of the concept was verified for this data. A-dependence of the scaling function is studied for low-[Formula: see text] region. Self-similarity of hadron production in pA collisions is confirmed over a wide kinematic range.

Muli bamboo (Melocanna baccifera) as a new source of microcrystalline cellulose

Microcrystalline cellulose (MCC) was prepared by hydrochloric acid hydrolysis from Muli bamboo (Melocanna baccifera) fibers to tap its potential as a green source of MCC. The cellulose and α-cellulose yield from the original material were 62.5 and 54.8 % respectively. The physicochemical properties of the prepared MCC were investigated using Avicel PH101 as a comparator. Micromeritic properties of the powder MCC samples were analyzed by determining its average particle size, flow properties, particle porosity and density. The total ash and moisture content along with the swelling index were also determined. The prepared MCC was also characterized by fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and x-ray diffraction spectroscopy (XRD). Results from these analyses indicate that the Muli bamboo can be used as a green source of MCC.

Direct observation of metal nanoparticles as heterogeneous nuclei for the condensation of supersaturated organic vapors: nucleation of size-selected aluminum nanoparticles in acetonitrile and n-hexane vapors.

This work reports the direct observation and separation of size-selected aluminum nanoparticles acting as heterogeneous nuclei for the condensation of supersaturated vapors of both polar and nonpolar molecules. In the experiment, we study the condensation of supersaturated acetonitrile and n-hexane vapors on charged and neutral Al nanoparticles by activation of the metal nanoparticles to act as heterogeneous nuclei for the condensation of the organic vapor. Aluminum seed nanoparticles with diameters of 1 and 2 nm are capable of acting as heterogeneous nuclei for the condensation of supersaturated acetonitrile and hexane vapors. The comparison between the Kelvin and Fletcher diameters indicates that for the heterogeneous nucleation of both acetonitrile and hexane vapors, particles are activated at significantly smaller sizes than predicted by the Kelvin equation. The activation of the Al nanoparticles occurs at nearly 40% and 65% of the onset of homogeneous nucleation of acetonitrile and hexane supersaturated vapors, respectively. The lower activation of the charged Al nanoparticles in acetonitrile vapor is due to the charge-dipole interaction which results in rapid condensation of the highly polar acetonitrile molecules on the charged Al nanoparticles. The charge-dipole interaction decreases with increasing the size of the Al nanoparticles and therefore at low supersaturations, most of the heterogeneous nucleation events are occurring on neutral nanoparticles. No sign effect has been observed for the condensation of the organic vapors on the positively and negatively charged Al nanoparticles. The present approach of generating metal nanoparticles by pulsed laser vaporization within a supersaturated organic vapor allows for efficient separation between nucleation and growth of the metal nanoparticles and, consequently controls the average particle size, particle density, and particle size distribution within the liquid droplets of the condensing vapor. Strong correlation is found between the seed nanoparticle's size and the degree of the supersaturation of the condensing vapor. This result and the agreement among the calculated Kelvin diameters and the size of the nucleating Al nanoparticles determined by transmission electron microscopy provide strong proof for the development of a new approach for the separation and characterization of heterogeneous nuclei formed in organic vapors. These processes can take place in the atmosphere by a combination of several organic species including polar compounds which could be very efficient in activating charged nanoparticles and cluster ions of atmospheric relevance.

Self-similarity of Low-p T cumulative pion production in proton-nucleus collisions at U70

The data on inclusive momentum spectra of π± mesons produced in p + A collisions over the range pL =15–65 GeV/c and θlab = 159° at U70 are analyzed in the framework of z-scaling approach. Self-similarity of the pion production in the low-pT cumualtive region is verified. Scaling function ψ(z) for Be, C, Al, Ti, Mo, W nuclei is constructed. It is expressed via the invariant cross section and the average multiplicity density of charged particles. Results of the analysis are compared with data obtained by J. Cronin, R. Sulyaev, and D. Jaffe groups at pL = 70, 400 GeV/c, pT > 1 GeV/c and θcms − 90°. A microscopic scenario of p + A interactions in terms of momentum fractions x1, x2 is discussed. Indication on self-similarity of the low-pT cumulative pion production in p + A collisions was found. Universality of the shape of the scaling function is used to predict inclusive cross sections of π+ and π− pions produced in p + A collisions on Be, C, Al, Ti, Mo, W targets in the deep-cumulative region (x2 ≫ 1/A).

Self-similarity of high-p T cumulative hadron production in p + A collisions at high energies at U70

New data on inclusive transverse momentum spectra of charged hadrons produced in p + A collisions at U70 are analyzed in the framework of the z-scaling approach. Self-similarity of the hadron production in the high-pT cumualtive region is verified. Scaling function ψ(z) for C, Al, Cu, W nuclei is constructed. It is expressed via the invariant cross section and the average multiplicity density of charged particles. Results of analysis are compared with the data obtained by J. Cronin, R. Sulyaev and D.Jaffe groups. Self-similarity of the hadron production in p + A collisions over a wide kinematical range is verified. A microscopic scenario of p + A interactions in terms of momentum fractions x1, x2 is discussed. Indication on self-similarity of the high-pT cumulative hadron production in p + A collisions over a wide kinematical range has been found. Based on the universality of the shape of the scaling function the inclusive cross sections of h− and h+ hadrons produced in p + A collisions on C, Al, Cu, W targets in the high-pT deep-cumulatice region are predicted.

Self-similarity of low-p T cumulative pion production in proton-nucleus collisions at high energies

The experimental data on inclusive spectra of the π+ mesons produced in p + A collisions at the incident proton momentum of 400 GeV/c obtained by G. Leksin group at FNAL are analyzed in the framework of z-scaling. Self-similarity of the hadron production in the low-pT cumulative region is verified. Scaling function ψ(z) for the Li, Be, C, Al, Cu, Ta nuclei is constructed. It is expressed via the invariant cross section and average multiplicity density of charged particles. Results of the analysis of the low-pT data are compared with the high-pT data sets obtained by J. Cronin, R. Sulyaev and D. Jaffe groups. A microscopic scenario of p + A interactions in terms of momentum fractions x1, x2 is discussed. Indication on self-similarity of the cumulative pion production in p + A collisions over a wide kinematical range has been found. Based on the universality of the shape of the scaling function the inclusive cross sections of the π+ mesons produced in p + A collisions on the Li, Be, C, Al, Cu, Ta targets in deep-cumulative region (x2 ≫ 1/A) are predicted.

Atributos físico-hídricos de um Argissolo amarelo sob floresta e savana naturais convertidas para pastagem em Roraima

O Estado de Roraima apresenta ampla diversidade pedológica e de ecossistemas, sendo gradativamente ocupados com pastagem, que dependendo do manejo podem estar associadas à degradação física do solo. Dentro desse contexto, este trabalho foi realizado com os objetivos de avaliar e comparar os atributos físico-hídricos de um Argissolo Amarelo sob os ecossistemas de savana e floresta natural, convertidos em pastagem para pecuária. Os tratamentos principais foram savana natural (SN), savana convertida em pastagem (SC), floresta natural (FN) e floresta convertida em pastagem (FC) e os tratamentos secundários foram as profundidades de amostragem do solo, 0-10, 10-20 e 20-40 cm. Os atributos avaliados foram: granulometria, densidade do solo (DS) e de partículas (DP), resistência à penetração (RP), porosidade total (PT), umidade gravimétrica (UG), capacidade de armazenamento de água (CAD) e matéria orgânica do solo (MOS). A DS foi superior nas duas áreas de Savana, não havendo diferença entre SC e SN em nenhuma das profundidades. A RP variou em função das áreas e da profundidade, verificando-se influência da conversão nesse atributo. A PT foi maior na FN e menor na SC; houve diminuição da porosidade com a profundidade. A CAD foi maior na FN apenas na profundidade de 0-10 cm. A MOS foi superior nas áreas de FN e FC. Portanto, a conversão dos ambientes naturais em pastagem provocou alterações significativas na RP, DS, CAD, PT e MOS, com maior expressividade nas áreas da FC em razão da supressão da cobertura vegetal natural, que tem na matéria orgânica o condicionador da qualidade físico-hídrica do solo. Na SC, por sua vez, a supressão da cobertura vegetal natural não provocou a mesma expressividade por causa dos teores significativamente inferiores de MOS.

A case study considering the comparability of mass and volumetric suspended sediment data

Contemporary real-time instruments that advance suspended sediment monitoring capabilities often provide results in units (e.g. volumetric) that are not easily comparable to traditional mass (e.g. gravimetric) methods. A Midwest case study was initiated to assess the accuracy of three methods commonly used to convert volumetric data to mass. Water samples from rural, suburban, and urban stream reaches were analyzed for suspended sediment concentration using laser diffraction and wet sieving methods, resulting in paired volumetric (μl/l) and mass (mg/l) suspended sediment concentrations. Observed volumetric data were converted to mass using an assumed particle density (Pd) of 2.65 g/cm3, a calculated Pd, and linear regression. Using the assumed Pd, estimated mass data differed from observed mass data by as much as 60 %. Dividing mass concentration (mg/l) by the volumetric concentration (μl/l) resulted in site-specific average suspended sediment particle densities ranging from 2.17, 1.99, 1.76 g/cm3 for different land use types. Using a calculated Pd, estimated mass data differed from observed mass data by as much as 45 %. Paired sample t tests showed observed and estimated mass values to be significantly different (p < 0.01). R2 values for regression equations ranged from 0.82 to 0.88. Conversion difficulties likely result from temporal and spatial variations of Pd. The results illustrate the imprecision of conversion methods and highlight possible estimation errors assuming idealized conditions. Continued work is necessary to improve quantitative relationship(s) between mass and volumetric suspended sediment data and the utility of both types of information for science and land management practices.

Evolution of Microstructure, Precipitate and Magnetic Properties with the Different Annealing Temperature in High Grade Nonoriented Electrical Steels

The evolution of microstructure, precipitate and magnetic properties in nonoriented electrical steels with different annealing temperature was studied. The iron loss of steel decreases with an increase in the final annealing temperature ranging from 800~900°C. This phenomenon is associated with grains recovery; recrystallization and grains grow up with the temperature increasing. Grain size continues to increase, but the average particle size decreases and particle density increases at 880~900°C which show precipitates have dissolved. It approved that the dissolution process of a lot of precipitates occurred after grains growing up. Precipitates are mainly of the second phase particles MnS and AlN. The magnetic induction increased firstly at 800~880°C and then increasing at 880~900°C.It can be found that the proportion of the texture for [{100} +Gos/ {111} at 900°C is higher than that at 880°C and the proportion of Gauss texture is higher at 900°C than that at 880°C. Gauss texture in high grade silicon steel plays an important role which promotes magnetic induction to increase.

SPECTRAL VARIABILITY OF IRAS 18325-5926 AND CONSTRAINTS ON THE GEOMETRY OF THE SCATTERING MEDIUM

We analyze Suzaku and XMM-Newton data of the highly variable Seyfert 2, IRAS 18325-5926. The spectra of the source are well modeled as a primary component described as an absorbed power law and a secondary power law component which is consistent with being scattered emission from an on-axis extended highly ionized medium. We show that while the primary component varies on a wide range of timescales from $10^{4} - 10^{8}$ s, the scattered emission is variable only on timescales longer than $10^{5}$ s. This implies that the extent of the scattering medium is greater than $10^{16}$ cm. The ratio of the scattered to primary flux ($\sim 0.03$) implies a column density for the scattering medium to be $\sim 10^{23}$ cm$^{-2}$. We argue that for such a medium to be highly ionized it must be located less than $10^{17}$ cm from the X-ray source. Thus we localize the position and extent of scattering region to be $\sim$ a few $\times 10^{16}$ cm, with an average particle density of $\sim 10^{6}$ cm$^{-3}$. We consider the physical interpretation of these results and as an aside, we confirm the presence of a broad Iron line emission in both the {\it XMM-Newton} and {\it Suzaku} observations.

Unveiling the corona of the Milky Way via ram-pressure stripping of dwarf satellites

The spatial segregation between dSphs and dIrrs in the Local Group has long been regarded as evidence of an interaction with their host galaxies. In this paper, we assume that ram-pressure stripping is the dominant mechanism that removed gas from the dSphs and we use this to derive a lower bound on the density of the corona of the Milky Way at large distances (50-90 kpc) from the Galactic centre. At the same time, we derive an upper bound by demanding that the interstellar medium of the dSphs is in pressure equilibrium with the hot corona. We consider two dwarfs (Sextans and Carina) with well-determined orbits and star formation histories. Our approach introduces several novel features: we use the measured star formation histories of the dwarfs to derive the time at which they last lost their gas, and (via a modified version of the Kennicutt-Schmidt relation) their internal gas density at that time; we use a large suite of 2D hydrodynamical simulations to model the gas stripping; and we include supernova feedback tied to the gas content. Despite having very different orbits and star formation histories, we find results for the two dSphs that are in excellent agreement with one another. We derive an average particle density of the corona of the Milky Way at 50-90 kpc in the range 1.3-3.6 10^{-4} cm^{-3}. Including additional constraints from X-ray emission limits and pulsar dispersion measurements, we extrapolate Galactic coronal density profiles and we estimate the fraction of baryons that can exist within the virial radius of the Milky Way. For an isothermal corona (T=1.8 10^6 K) this is small, 10-20 % of the universal baryon fraction. Only a hot (T=3 10^6 K) and adiabatic corona can contain all of the Galaxy's missing baryons. Models for the Milky Way must explain why its corona is in a hot adiabatic thermal state or why a large fraction of its baryons lie beyond the virial radius.

Prediction of bed pressure drop and top packed bed formation in gas-liquid-solid semi-fluidized bed with irregular homogeneous binary mixtures

We studied the hydrodynamics of a gas-liquid-solid semi-fluidized bed relating to packed bed formation and bed pressure drop with irregular homogeneous binary mixtures in a 0.05 m internal diameter Perspex column, with water and air (secondary) as fluidizing medium at constant static bed height of 0.08 m. A homogeneous binary mixture has been taken for easy formation of a semi-fluidized bed. Air is supplied centrally below the bottom grid in radial direction with a special design air sparger after the bed is first fluidized by the liquid. Experimental parameters studied included superficial gas and liquid velocities, average particle size and density and the bed expansion ratio. Empirical and semi-empirical models were developed. The calculated values from predicted models were compared with the experimental values and fairly good agreement was obtained.

Synthesis of functionally graded nano Al2O3–Ni composite coating by pulse electrodeposition

The main goal of this research is the synthesis of functionally graded nickel–nano Al2O3 composite coatings by using pulse deposition in which the amount of the embedded nano alumina particles changes in the cross section of the composite. For producing functionally graded nanocomposite coatings by pulse electrodeposition under ultrasonic agitation, frequency and duty cycle changes can be applied and in this research, the influence of both parameters has been studied. Microstructure of these coatings investigated by SEM, EBSD and XRD methods. By changing the duty cycle from 90% to 10% at different frequency, the microstructure of the coatings did not change significantly. These coatings showed ductile structure with {001} texture at primary layers and small randomly oriented grains at final layers. The most important factor affecting the microstructure of the nickel matrix was the average current density and incorporation of nano alumina particles does not have significant effect on the microstructure. The optimum condition for production of functionally graded nano Al2O3–Ni coating was changing of the duty cycle from 90% to 10% at fixed frequency of 10Hz.

SPH simulation of selective withdrawal from microcavity

The selective withdrawal of weakly compressible fluids is investigated by smoothed particle hydrodynamics (SPH) with a revised model of surface tension. In our model problem, fluid is withdrawn from a two-dimensional microcavity through a narrow outlet above the interface of two immiscible fluids. The outflow boundary is implemented by a particular zone of fluid particles with prescribed velocity, together with the introduction of artificial boundary particles. Based on the average number density of fluid particles, the effective contribution of boundary particles is corrected for the compressible context. It is found that there exists a critical withdrawal rate for each initial interface height, beyond which the lower phase becomes entrained in a thin spout along with the upper phase. Besides, the Froude number with redefinition for this kind of multiphase flow could serve as a criterion of flow behavior. Furthermore, larger surface tension, smaller dynamical viscosity and density of the upper phase all lead to longer threshold time of formation of the spout state, and thus are favorable to the withdrawal of upper phase both in terms of higher efficiency and larger quantity.

Falling plumes of point particles in viscous fluid

The growth of radial bulges on the conduit of a falling viscous plume of particles, reported by Pignatel et al. for a finite starting plume [F. Pignatel, M. Nicolas, E. Guazzelli, and D. Saintillan, “Falling jets of particles in viscous fluids,” Phys. Fluids 21, 123303 (2009)10.1063/1.3276235], is investigated both numerically and analytically. As a model for the plume conduit, an infinite vertical cylinder of identical non-Brownian point particles falling under gravity in Stokes flow is considered. Numerically, this is implemented with periodic boundary conditions of a large, but finite, period. The quasi-periodic numerical simulations exhibit qualitatively similar behaviour to that previously observed for the finite plume, demonstrating that neither the plume head nor the plume source play a role in the growth of the radial bulges. This growth is instead shown to be due to fluctuations in the average number density of particles along the plume about its mean value n, which leads to an initial growth rat...