Distribution Of MC Research Articles

Effect of stacking position on drying rate during radio-frequency vacuum combined with mechanical press drying of Douglas-fir and Radiata pine

In this study, the effect of stacking position in the dryer on the drying rate during radio-frequency vacuum combined with mechanical press (RF/VP) drying was investigated for Douglas-fir and Radiata pine. Drying test was performed at a temperature of 40 °C using RF/VP dryer with approximately 3 m3. The results showed that the stacking position has a significant effect on the drying rate, with a more pronounced decrease in drying rate as the stacking position of specimens approaches the ground plate. Previous moisture content was an important factor in determining the drying rate in both species. The MC distribution of specimens in the dryer before drying was very irregular, but over time, specimens stacked on the RF charge plate side in the dryer tended to have lower MC distributions than those stacked on the ground plate side, which was serious at the specimens in contact with the upper ground plate. In addition, as the MC decreases below the fiber saturation point during RF/VP drying, the difference in MC distribution within the dryer according to the stacking position became clearer. These findings provide new insights into the effect of stacking position on drying rate during the RF/VP drying and are expected to improve RF/VP drying technology.

Effect of hafnium content on the microstructural evolution and stress rupture properties of K4750 nickel-based superalloy

The microstructural evolution of K4750 nickel-based superalloy with different hafnium (Hf) contents was investigated by thermodynamic calculations (TC) and experiments. According to TC, with the increases of Hf content from 0 wt% to 1.5 wt%, the redissolving temperature of MC carbide first decreased rapidly and then tended to be relatively stable, the precipitated temperature of M23C6 carbide decreased gradually, while the γ′ weight fraction increased first and then stabilized. Three alloys containing 0 wt%, 0.11 wt%, and 0.28 wt% Hf were then prepared to further study the evolution of the microstructure. The experimental results showed that the increase of Hf content changed the morphology of MC carbide from long strip to rodlike and blocky, which is caused by the decrease of Ti and Nb contents and the increase of Hf content in MC carbides. The addition of Hf also changed the morphology of M23C6 carbide from continuous to granular due to the different MC distribution at grain boundaries (GBs). In addition, a small amount of Hf segregated into the γ′ phase, reducing the Al and Nb contents of the γ′ phase, resulting in an increased γ/γ′ lattice mismatch. As the Hf content increased from 0 wt% to 0.11 wt% and 0.28 wt%, the mean stress rupture life at 750 °C and 430 MPa increased from 99.54 h to 105.73 h and 170.96 h, which was closely related to the evolution of MC, M23C6 and γ′ precipitates. Therefore, the relationship between microstructure and stress rupture properties was discussed in detail.

Effects of Recrystallization on Tensile Anisotropic Properties for IN738LC Fabricated by Laser Powder Bed Fusion

This study demonstrates the effects of recrystallization on tensile properties and the anisotropy of IN738LC, a typical γ’ precipitation-strengthened alloy, at both room and high temperatures via the laser powder bed fusion process. The nonrecrystallized columnar microstructure, subjected to standard IN738LC heat treatment up to 1120 °C, and the almost fully recrystallized microstructure, heat-treated at 1204 °C, were compared. The tensile properties strongly depend on whether recrystallization was completed as well as the tensile direction. This can be explained by microstructure characterization, featuring the Taylor factor in the tensile direction, average grain size estimated by ellipse approximation, and the relationship between the grain shape and tensile direction. The shape of the recrystallized grains and the distribution of coarse MC carbides inside the recrystallized grains were determined by the microstructure in an as-built state. In high-temperature tensile tests conducted in the horizontal direction, the separation of the columnar grains caused a brittle fracture. In contrast, dimples were observed at the fracture surface after recrystallization, indicating scope for further improvement in ductility.

Diagnosis and treatment of vulnerable migrants: a retrospective study at a Doctors of the World clinic in Stockholm

BackgroundAt Doctors of the World Medical Clinic in Stockholm (DWMCS), medical care is offered to migrants who live under particularly vulnerable conditions and who lack access to subsidized care. The demographic, diagnostic and therapeutic panorama of vulnerable migrants is unknown.MethodsA quantitative, retrospective study mapping gender, age, diagnostic group, primary diagnosis, therapeutics, referrals, and session timing (whether the care session took place in summer -April to September, or winter - October to March) by reading all patients’ electronic journals at DWMCS between 2014-04-01 and 2017-12-31. Diagnostic groups were classified according to the classification system ICPC-2 which contains six diagnostic groups: symptoms/complaints, infections, neoplasms, injuries, congenital anomalies and other diagnoses. Primary diagnosis was defined as the diagnosis that was first in the diagnosis list for the visit. Difference in median age was calculated with the Mann-Whitney test (MW), and two-group analysis of nominal data was performed with Monte Carlo simulations (MC) and chi square test´s (X2).ResultsThe study included 1323 patients: 838 women and 485 men. The median age for women 37 years (29-47) was slightly lower than for men, 40 years (31-47) MW (p = 0.002). The largest diagnostic group was symptoms / complaints. The five most common primary diagnoses were cough (4%), back symptom / complaint (4%), cystitis (3%), upper respiratory infection acute (3%) and abdominal pain epigastric (2%). The most common therapeutic (55%) was pharmaceutical. Referrals accounted for 12% of the therapeutics and 25% of the referrals were to an emergency room. Tests of significance indicated an uneven distribution of diagnostic groups MC (p = 0.003), infectious primary diagnoses MC (p = 0.0001) and referrals MC (p = 0.006) between men and women and an uneven seasonal distribution among the Other diagnoses MC (0.04) and ten most common drug treatments MC (p=0.002).ConclusionsThe demographic, diagnostic and therapeutic panorama of vulnerable migrants at DWMCS was elucidated. Vulnerable migrants have differences in morbidity depending on gender and season, differences in therapeutics depending on gender and differences among their most common drug treatments depending on season. This knowledge is important when addressing the health problems of vulnerable migrants.

Effect of Cryogenic Treatment on the Microstructure Modification of SKH51 Steel

This research aimed to investigate the microstructure modification mechanism used to improve the hardness and wear resistance of SKH51 steel. The cryogenic treatment (CT), including both shallow cryogenic treatment (SCT) and deep cryogenic treatment (DCT), was used to modify the microstructure of SKH51 steel in this research. The effect of short and long holding time (12 and 36 h) in CT was studied. The microstructures were evaluated by using a light optical microscopy (LOM) and a scanning electron microscopy (SEM). The phase identifications of the matrix, carbides, and a-parameter of the matrix were analyzed by using X-ray diffraction (XRD). The M6C and MC carbides size, aspect ratio, and distribution were analyzed using digimizer image analysis software on the SEM micrographs. Micro-Vickers were employed to evaluate the hardness of the targeted samples. Wear tests were performed by using a 6 mm diameter WC ball as the indenter and 5-N-constant load with a ball-on-disk wear tester. The results suggested that the increase of the secondary carbide was caused by the contraction and expansion phenomena of the matrix’s lattice, forcing the carbon atom out and acting as the carbide nucleation. The influence of holding time in the SCT and DCT regions was different. For the SCT, increasing the holding time increased the volume’s fraction of MC carbide. Conversely, the M6C carbide size grew with increasing holding time in the DCT region, while no significant increase in the number of MC carbide was observed. The cryogenic treatment was found to increase the volume fraction of the MC carbide by up to 10% compared to the conventional heat treatment (CHT) condition in the SCT region (both 12 and 36 h) and DCT with 12 h holding time. Due to the microstructure modification, it was found that the cryogenic treatment can improve material hardness and lead to an increase in the wear resistance of SKH51 by up to 70% compared to the CHT treated material. This was due to the increase in the compressive residual stress, precipitation of the MC, and growth of the M6C primary carbide.

Linear stability analysis of three-dimensional natural convection at low Prandtl number in an annular enclosure in the presence of a toroidal magnetic field

The natural convection of a liquid metal in an annular enclosure with a square cross section in the presence of a toroidal static magnetic field was investigated by linear stability analysis. Three-dimensional steady disturbances were obtained in an annular enclosure where the walls parallel to the gravitational field were heated and cooled. The Prandtl number Pr was set to 0.025 and the radius ratio of the enclosure κ was set to 0.5, while the Rayleigh number Ra, the Hartmann number Ha, and the angular wavenumber m were considered as parameters. The dimensionless governing equations were discretized by the finite difference method. Since the newly developed dual staggered grid was employed, the interpolation in the outer product terms was not required. The linear growth rate for a standing wave mode was amplified by increasing Ra and attenuated by increasing Ha. For any integer m, the neutral Rayleigh number Ran at Ha = 0 and the neutral Hartmann number Han for Ran ≤ Ra ≤ 200 000 were identified. Based on these, the neutral lines for a given m were obtained as Han ∼ (Ra − Ran)1/3. Furthermore, the critical values Rac, Hac, and mc were obtained, where mc was not necessarily limited to an integer. The distribution of mc was approximated by the power of Ra. The disturbances had symmetry in the azimuthal direction and constituted a pair of vortices rotating in opposite directions. These vortices were elongated along the main stream.

Determining volume fractions of γ, γ′, γ″, δ, and MC-carbide phases in Inconel 718 as a function of its processing history using an advanced neutron diffraction procedure

In this work, quantitative crystallographic and microstructural analyses of γ, γ′, γ″, δ, and MC carbide phases are performed on wrought samples, samples fabricated via additive manufacturing (AM), and samples that underwent hot isostatic pressing (HIP) after AM of alloy Inconel 718 (IN718). In doing so, an advanced neutron diffraction-based procedure is developed facilitating the determination of volume fractions of every detectable phase in the alloy. To supplement the diffraction procedure, precipitate sizes are measured by scanning electron microscopy. Moreover, semi-quantitative elemental analyses are performed by energy dispersive spectroscopy. Finally, image thresholding is carried out on micrographs of samples that underwent cathodic dissolution to create secondary electron contrast between phases to verify the phase fractions determined from the neutron diffraction datasets. The study reveals a significantly higher volume fraction of δ phase and a significantly lower volume fraction of γ″ phase governing a higher strength of the AM material relative to the lower strength AM + HIP and wrought materials. Furthermore, γ′ and MC volume fractions are found similar in the materials despite the differences in MC morphology, elemental composition and distribution controlling the dispersion strengthening. These results are presented and discussed in this paper along with the procedure developed for determining volume fractions of all detectable phases present in the alloy.

Aggregation shapes of amphiphilic ring polymers: from spherical to toroidal micelles

The self-assembly of Janus ring polymers is studied via a coarse-grained molecular dynamics employing a bead spring model including bending rigidity contributions to the Hamiltonian. We examine the formation and the morphology of amphiphilicity-driven clusters in the system using the number density ρN, the temperature T, the fraction of solvophobic monomers α, and the stiffness of the polymer rings κ as control parameters. We present a quantitative analysis of several characteristics for the formed clusters of Janus rings. Measured quantities include the distribution of the cluster size MC and the shape of the clusters in the form of the prolate/oblate factor Q and shape factors sf. We demonstrate Janus rings form polymorphic micelles that vary from a spherical shape, akin to that known for linear block copolymers, to a novel type of toroidal shape, and we highlight the role played by the key physical parameters leading to the stabilization of such structures.Grapical abstract

Determination of Effective Coefficient of Chinese Fir (Cunninghamia Lanceolata) During Adsorption and Desorption Process

Establishing an accurate moisture transport model in wood is essential to analyze the hygroscopic behavior and estimate the stability of wood structures in the ambient environment. In this article, the effective diffusion coefficients (EDCs) of Chinese fir in radial and tangential directions during absorption and desorption processes were measured based on the differential model, and numerical simulations were performed to verify the rationality of measured results. The results show that 1) for adsorption process, the surface emission coefficient (SEC) and EDC of Chinese fir are all greater in the radial direction; 2) for desorption process, the SEC is higher in the radial directions, whereas the EDC in the tangential direction is higher than that in the radial direction when the MC is greater than 10%; 3) the SEC and EDC in the adsorption process are larger than those in the desorption process. Because there is a reasonable agreement between experimental and mumerical simulation results, the measured results could be used to predict the MC distribution of Chinese fir in the ambient environment.

Effects of Reactivity Ratios on Network Topology and Thermomechanical Properties in Vinyl Ester/Styrene Thermosets: Molecular Dynamics Simulations

AbstractStyrene‐based thermoset polymers using vinyl ester crosslinkers offer the potential ability to tune material properties via control of network topology, measured primarily by the distribution of poly(styrene) molecular weight between vinyl esters. Clearly, demonstrating a relationship between topology and properties in the glassy state has so far proven difficult using experimental approaches. Here, an approach to control network topology in molecular simulations of randomly crosslinking systems via relative reactivity is presented. Several models of nearly fully cured (vinyl ester)/styrene (VE/ST) thermosets at fixed monomer composition but with a large range of distributions of molecular weight between crosslinks, Mc, are generated. It is found that fully cured VE/ST thermosets have glass transition temperatures and glassy Young's moduli that are insensitive to Mc distributions at fixed monomer composition. Using extreme cases of relative reactivity, it is also established that glassy‐state thermomechanical properties are sensitive to the overall density of crosslinks.

The relationship of gross upper and lower limb motor competence to measures of health and fitness in adolescents aged 13–14 years

IntroductionMotor competence (MC) is an important factor in the development of health and fitness in adolescence.AimsThis cross-sectional study aims to explore the distribution of MC across school students aged 13–14...

Mast Cell Degranulation Is Accompanied by the Release of a Selective Subset of Extracellular Vesicles That Contain Mast Cell-Specific Proteases.

Mast cells (MC) are well known for their effector role in allergic disorders; moreover, they are associated with diverse modulatory effects in innate and adaptive immunity. It is largely unclear how MC exert these modulating functions. In this article, we show that IgE-mediated MC degranulation leads to a rapid release of high quantities of extracellular vesicles (EV), comparable to the release of preformed mediators. EV are submicron structures composed of lipid bilayers, proteins, and nucleic acids that are released by cells in a regulated fashion and are involved in intercellular communication. Primary murine mucosal-type MC and connective tissue-type MC released phenotypically different EV populations depending on the stimulus they received. Although unstimulated MC constitutively released CD9+ EV, degranulation was accompanied by the release of CD63+ EV, which correlated with release of the soluble mediator β-hexosaminidase. This CD63+ EV subset was smaller and exhibited a higher buoyant density and distinct phospholipid composition compared with CD9+ EV. Marked differences were observed for phosphatidylinositol, phosphatidic acid, and bis(monoacylglycero)phosphate species. Strikingly, proteomic analysis of CD63+ EV from connective tissue-type MC unveiled an abundance of MC-specific proteases. With regard to carboxypeptidase A3, it was confirmed that the enzyme was EV associated and biologically active. Our data demonstrate that, depending on their activation status, MC release distinct EV subsets that differ in composition and protease activity and are indicative of differential immunological functions. Concerning the strategic tissue distribution of MC and the presence of degranulated MC in various (allergic) disorders, MC-derived EV should be considered potentially important immune regulators.

Quantitative study on the homogeneity of networks synthesized by nitroxide-mediated radical copolymerization of styrene and divinylbenzene

The nitroxide-mediated radical copolymerization (NMRP) of styrene and divinylbenzene was studied using a Monte Carlo simulation. The model predictions were validated by comparing to experimental results gathered from literature. Polymer network microstructure was studied through complete molar mass distribution (including the gel part) of the polymer and by quantitative representation of the homogeneity of the network, i.e. the broadness of the distribution of the molar mass between crosslinking points (Mc). The nitroxide mediated radical polymerization led to a narrower Mc distribution compared to free radical polymerization, and the average Mc did not change significantly through the reaction. The narrower Mc distribution is an indicator of more homogenous network and clarifies many conflicting statements in the literature on homogeneity of the network obtained by controlled radical polymerization.

The location of Modic changes in the lumbar spine: a meta-analysis.

This meta-analysis was to study the location of Modic changes in the lumbar spine. The electronic databases including MEDLINE, Web of science, Cochrane Central Register of Controlled Trials, OVID, CBM were searched. Relevant studies that described the patients with Modic Changes were included. Data were extracted and analysed using the version 12.0STATAsoftware. Thirty-one studies were selected and analyzed (2346 total patients). No significant differences of the incidence of MC were identified between superior and the inferior end plates adjacent to discs [RR=1.04, 95% CI (0.74, 1.53)], the same result was detected for the distribution of MC type I between L4/5 and L5/S1 [RR=0.80, 95% CI (0.64, 1.02)]. While lower lumbar spine (L4/5, L5/S1) had significant greater incidence of MC [RR=0.20, 95% CI (0.15, 0.25)], especially in L5/S1 [RR=0.82, 95% CI (0.72, 0.92)]. For MC type II, it also significantly appeared in L5/S1 [RR=0.80, 95% CI (0.67, 0.95), P=0.010]. In this study, Modic Changes was more common in the lowest two levels, especially in L5/S1. Additionally, the sub-types (type I and type II) were also more likely to appear in L5/S1. It appeared that there existed a correlation between MC and biomechanics. And it seemed that local biomechanical stress might contributed to the distribution of MC and the conversion of type I to type II for the patients treated conservatively.

Effect of Gas Tungsten Arc Welding Parameters on Hydrogen-Assisted Cracking of Type 321 Stainless Steel

The susceptibility of AISI type 321 stainless steel welded by the gas tungsten arc welding (GTAW) process to hydrogen-assisted cracking (HAC) was studied in a tensile test combined with in situ cathodic charging. Specimen charging causes a decrease in ductility of both the as-received and welded specimens. The mechanical properties of welds depend on welding parameters. For example, the ultimate tensile strength and ductility increase with growing shielding gas (argon) rate. More severe decrease in the ductility was obtained after post-weld heat treatment (PWHT). In welded steels, in addition to discontinuous grain boundary carbides (M23C6) and dense distribution of metal carbides MC ((Ti, Nb)C) precipitated in the matrix, the appearance of delta-ferrite phase was observed. The fracture of sensitized specimens was predominantly intergranular, whereas the as-welded specimens exhibited mainly transgranular regions. High-dislocation density regions and stacking faults were found in delta-ferrite formed after welding. Besides, thin stacking fault plates and epsilon-martensite were found in the austenitic matrix after the cathodic charging.

Powder metallurgy of high speed-steel produced by solid state sintering and heat treatment

Abstract High-speed steel is successfully fabricated by solid state sintering of Fe, Co, WC, Mo2C, Cr3C2 and VC powders under vacuum. The sintering density, microstructure, phase structure, hardness, and transverse rupture strength of the specimens are examined. Results show that the density increases with increasing sintering temperature. Nearly full density is obtained without microstructural coarsening in the sintering temperature range of 1190–1210°C. The optimum sintering temperature for the steel is 1200°C. The suitable quenching temperatures range from 1200 to 1240°C. After heat treatments, the microstructure consists of a martensitic matrix (grain size ≈5 μm) with a homogeneous distribution of MC and M 6C carbides (average size lower than 1 μm). The highest hardness of 68.5 ± 0.3 HRC and the maximum transverse rupture strength of 3.58 ± 0.12 GPa is obtained for the specimen tempered at 560°C.

Integrating phylogeny, geographic niche partitioning and secondary metabolite synthesis in bloom-forming Planktothrix.

Toxic freshwater cyanobacteria form harmful algal blooms that can cause acute toxicity to humans and livestock. Globally distributed, bloom-forming cyanobacteria Planktothrix either retain or lose the mcy gene cluster (encoding the synthesis of the secondary metabolite hepatotoxin microcystin or MC), resulting in a variable spatial/temporal distribution of (non)toxic genotypes. Despite their importance to human well-being, such genotype diversity is not being mapped at scales relevant to nature. We aimed to reveal the factors influencing the dispersal of those genotypes by analyzing 138 strains (from Europe, Russia, North America and East Africa) for their (i) mcy gene cluster composition, (ii) phylogeny and adaptation to their habitat and (iii) ribosomally and nonribosomally synthesized oligopeptide products. Although all the strains from different species contained at least remnants of the mcy gene cluster, various phylogenetic lineages evolved and adapted to rather specific ecological niches (for example, through pigmentation and gas vesicle protein size). No evidence for an increased abundance of specific peptides in the absence of MC was found. MC and peptide distribution rather depended on phylogeny, ecophysiological adaptation and geographic distance. Together, these findings provide evidence that MC and peptide production are primarily related to speciation processes, while within a phylogenetic lineage the probability that strains differ in peptide composition increases with geographic distance.

Dose rates modeling of pressurized water reactor primary loop components with SCALE6.0

The SCALE6.0 simulation model of a typical PWR primary loop components for effective dose rates calculation based on hybrid deterministic–stochastic methodology was created. The criticality sequence CSAS6/KENO-VI of the SCALE6.0 code package, which includes KENO-VI Monte Carlo code, was used for criticality calculations, while neutron and gamma dose rates distributions were determined by MAVRIC/Monaco shielding sequence. A detailed model of a combinatorial geometry, materials and characteristics of a generic two loop PWR facility is based on best available input data. The sources of ionizing radiation in PWR primary loop components included neutrons and photons originating from critical core and photons from activated coolant in two primary loops. Detailed calculations of the reactor pressure vessel and the upper reactor head have been performed. The efficiency of particle transport for obtaining global Monte Carlo dose rates was further examined and quantified with a flexible adjoint source positioning in phase-space. It was demonstrated that generation of an accurate importance map (VR parameters) is a paramount step which enabled obtaining Monaco dose rates with fairly uniform uncertainties. Computer memory consumption by the SN part of hybrid methodology represents main obstacle when using meshes with large number of cells together with high SN/PN parameters. Detailed voxelization (homogenization) process in Denovo together with high SN/PN parameters is essential for precise VR parameters generation which will result in optimized MC distributions. Shielding calculations were also performed for the reduced PWR facility model which included only reactor core and adjacent concrete structures with the steam generator and the pump. Hybrid FW-CADIS methodology appears to be very effective for shielding calculations of complicated MC geometries. It was demonstrated that definition of air as a global adjoint source gave lower uncertainty of photon dose rates. Activation of the primary loop coolant, which becomes additional gamma source in operating reactor, was considered. Compared with analog MC simulations, the hybrid methodology drastically improved Monaco distributions in quality as well in space coverage.The SCALE6.0 hybrid stochastic methodology was thoroughly investigated and its versatile ability for deep penetration models was proved. A careful selection of parameters can relax high CPU time and hardware requirements.

Tuning and Validation of the Lundcharm Model with J/ψ Decays

Using J/ψ decays collected with the BES III detector, Lundcharm model parameters are optimized with J/ψ light hadron decays. The dependence of the response function on model parameters is approximated up to the quadratic term, and the model parameters are optimized by simultaneously fitting J/ψ inclusive charged track distributions and event shapes. The Monte Carlo simulations show that optimal parameters yield satisfactory MC distributions as compared to both the J/ψ and ψ(2S) data distributions. These optimal values are suggested for the Lundcharm model to produce J/ψ and ψ(2S) decays to light hadrons.

5-Azacytidine Improves the Osteogenic Differentiation Potential of Aged Human Adipose-Derived Mesenchymal Stem Cells by DNA Demethylation

The therapeutic value of adipose-derived mesenchymal stem cells (Ad-MSCs) for bone regeneration is critically discussed. A possible reason for reduced osteogenic potential may be an age-related deterioration of the Ad-MSCs. In long term in vitro culture, epigenomic changes in DNA methylation are known to cause gene silencing, affecting stem cell growth as well as the differentiation potential. In this study, we observed an age-related decline in proliferation of primary human Ad-MSCs. Decreased Nanog, Oct4 and Lin28A and increased Sox2 gene-expression was accompanied by an impaired osteogenic differentiation potential of Ad-MSCs isolated from old donors (>60 a) as compared to Ad-MSCs isolated from younger donors (<45 a). 5-hydroxymethylcytosine (5 hmC) and 5-methylcytonsine (5 mC) distribution as well as TET gene expression were evaluated to assess the evidence of active DNA demethylation. We observed a decrease of 5 hmC in Ad-MSCs from older donors. Incubation of these cells with 5-Azacytidine induced proliferation and improved the osteogenic differentiation potential in these cells. The increase in AP activity and matrix mineralization was associated with an increased presence of 5 hmC as well as with an increased TET2 and TET3 gene expression. Our data show, for the first time, a decrease of DNA hydroxymethylation in Ad-MSCs which correlates with donor-age and that treatment with 5-Azacytidine provides an approach which could be used to rejuvenate Ad-MSCs from aged donors.