Low Particle Concentrations Research Articles

Triglyceride-Rich Lipoprotein Cholesterol, Small Dense LDL Cholesterol, and Incident Cardiovascular Disease

BackgroundElevated triglyceride-rich lipoprotein (TRL) and small-dense low-density lipoprotein (sdLDL) particles are hallmarks of atherogenic dyslipidemia, and their cholesterol content is hypothesized to drive atherosclerotic risk. Prospective epidemiological data pertaining to cholesterol content of TRLs and sdLDL in primary prevention populations are mostly limited to coronary heart disease. ObjectivesThe purpose of this study was to prospectively evaluate whether triglyceride-rich lipoprotein cholesterol (TRL-C) and small-dense low-density lipoprotein cholesterol (sdLDL-C) concentrations associate with composite and individual incident cardiovascular disease (CVD) outcomes including myocardial infarction (MI), ischemic stroke (IS), and peripheral artery disease (PAD). MethodsIn a prospective case-cohort study within the Women’s Health Study, TRL-C and sdLDL-C (mg/dl) were directly measured in baseline blood specimens of case subjects (n = 480) and the reference subcohort (n = 496). Risk associations were evaluated for total CVD (MI, IS, PAD, and CVD death), coronary and cerebrovascular disease (MI, IS, CVD death), and individual outcomes (MI, IS, and PAD). Models were adjusted for traditional risk factors, low-density lipoprotein cholesterol, and high-sensitivity C-reactive protein. ResultsThe risk of both composite outcomes significantly increased across quartiles of TRL-C and sdLDL-C. TRL-C was significantly associated with MI and PAD (MI hazard ratio [HR]Q4: 3.05 [95% confidence interval (CI): 1.46 to 6.39]; ptrend = 0.002; PAD HRQ4: 2.58 [95% CI: 1.18 to 5.63]; ptrend = 0.019), whereas sdLDL-C was significantly associated with MI alone (HRQ4: 3.71 [95% CI: 1.59 to 8.63]; ptrend < 0.001). Both markers weakly associated with IS. Association patterns were similar for continuous exposures and, for TRL-C, among subjects with low atherogenic particle concentrations (apolipoprotein B <100 mg/dl). ConclusionsTRL-C strongly associates with future MI and PAD events, whereas sdLDL-C strongly associates with MI alone. These findings signal that the cholesterol content of TRLs and sdLDL influence atherogenesis independently of low-density lipoprotein cholesterol, and high sensitivity C-reactive protein, with potentially different potency across vascular beds. (Women’s Health Study; NCT00000479)

Design of electrical conductive poly(lactic acid)/carbon black composites by induced particle aggregation

AbstractThe electrical conductivity of ternary composites composed of a biopolymer blend with conductive particles (carbon black [CB]) is induced by the control of particle dispersion in the dispersed phase. If the CB particles have higher chemical affinity for the secondary phase (poly(caprolactone) [PCL]]) than the matrix (poly(lactic acid) [PLA]), especially as the concentration of the PCL phase decreases significantly to 4 wt%, the PCL phase induces the aggregation of CB particles beyond the selective localization, resulting in a shift of the particle percolation threshold to a lower concentration of particles (2.44 wt% CB). Moreover, the mixing ratio between the CB and the PCL phase significantly affects the formation of percolation of particles. When the mixing ratio of CB to PCL is equivalent (1:1), the ternary composite shows high electrical DC conductivity above 1 S/m with 10 wt% CB. The addition of a small amount of PCL induces the formation of particle aggregates with a high aspect ratio, providing more electron transfer pathways due to the multiple points of contact between the particle aggregates (power law scaling exponent of the composites ~2.14). Meanwhile, a binary composite (PLA/CB) never reaches high electrical conductivity of 1 S/m and even requires a greater concentration of CB (13 wt% CB for 10−3 S/m) to accomplish electron transfer because of the small aspect ratio of randomly dispersed particle aggregates (power law scaling exponent ~3.20).

Measurement and modeling of the thermal conductivity of nanorefrigerants with low volume concentrations

Nanorefrigerants with low particle concentration (≤0.1 vol. %) would bring more benefits in industrial application. In this article, R141b based nanorefrigerants containing Al2O3, TiO2 and SiO2 nanoparticles with concentrations of 0.02 − 0.1 vol. % were prepared and characterized. Thermal conductivities of these nanorefrigerants were measured in the temperature range of 278 − 298 K. The effect of concentration, temperature, and particle size on the thermal conductivity of nanorefrigerants was investigated. Meanwhile, a model for thermal conductivity of nanorefrigerants was proposed considering the mechanisms of interfacial layer, aggregation and Brownian motion. Results show that the thermal conductivity increased with increasing temperature, concentration, while decreased with increasing particle size. Thermal conductivity was increased by reducing particle size in all cases. Also, the deviation of the data obtained by present model from the experimental values was mostly < 3%. For nanorefrigerants with low concentration, the contribution of dynamic mechanism to thermal conductivity enhancement is dominant.

Structure and rheology during catastrophic phase inversion of Pickering emulsions stabilized with fumed silica particles

Oil in water Pickering emulsions undergoing catastrophic phase inversion were investigated. Two polydimethylsiloxane (PDMS) oils of various viscosity have been emulsified in water and stabilized with fumed silica particles. The concentration of particles and the oil volume fraction were varied from 0.1 to 1 wt% and from 10 to 90 vol%, respectively. Upon increasing the oil content, a phase inversion occurred from oil-in-water to water-in-oil as evidenced from macroscopic and microscopic observations. At low concentration of particles, phase inversion occurred at lower oil volume fraction for the more viscous PDMS. Rheological measurements showed a strong increase of the elastic modulus of the emulsions with increasing the amount of oil up to a maximum value where the catastrophic phase inversion took place. The viscoelastic behaviour of the emulsions was discussed considering their structure but also the rheology of the particle suspensions that have been dispersed in both oil and water phases.

Friction and Lubrication Behavior of a Selective Laser Melted Hydraulic Spool Valve Under Contaminated Conditions

Abstract Selective laser melting (SLM) technology has a great potential to reduce size and weight of hydraulic valves. However, the tribological performance of an SLMed valve has not been studied which is crucial for the performance and reliability of the valve, especially under contaminated conditions. In this study, the friction and lubrication behavior between an SLMed valve body and a traditional spool were studied using a scaled reciprocating test rig under various contaminated conditions (frequency at 5 Hz and 25 Hz; particle concentration at 0.4 mg/ml and 4 mg/ml; particle size at 1.6 µm and 15 µm). Three types of SLMed samples were fabricated using different exposure times: one has many large surface pores (pores area &amp;gt; 1000 µm2 accounts for 7.167% of the sample surface); one has a few small surface pores (pores area between 100 µm2 and 1000 µm2 accounts for 0.574% of the sample surface); and one only has micropores (pores area &amp;lt; 300 µm2 accounts for 0.168% of the sample surface). The density, hardness, microstructures, and pore characterization of the SLMed samples were investigated. The results indicated that the frequency greatly influenced friction and lubrication behaviors by determining lubrication regimes. The influence of surface pores on the lubrication and friction depends on contact conditions: pores which served as particle containers to reduce friction are prominent under 5 Hz frequency and high particle concentration; extra lubrication by the surface pores is observed under 25 Hz frequency and low particle concentration.

Conjugated Polymer Nanoparticles as Unique Coinitiator-Free, Water-Soluble, Visible-Light Photoinitiators of Vinyl Polymerization.

The use of conjugated polymer nanoparticles (CP NPs) of poly(9,9-dioctylfluorene-alt-benzothiadiazole) and poly(9,9-di-n-octylfluorenyl-2,7-diyl) as efficient photoinitiator systems (PIS) of vinyl polymerization in water is reported herein. CP NPs are biocompatible, excitable with blue commercial LEDs and, unlike visible light Type II PIS, do not need co-initiators to trigger a monomer chain reaction. CP NPs photoinitiate polymerization of a variety of acrylic monomers with initiation rates comparable to those observed for well-known Type II PIS. Given the extraordinarily large molar absorption coefficients of CP NPs (≈108 m-1 cm-1 ) very low particle concentration is required for effective polymerization. Additionally, CP NPs behave as conventional macrophotoinitiators significantly reducing contamination risks due to leaching of low molecular weight byproducts. These combined features make CP NPs PIS suitable to synthesize polymeric materials for many healthcare and biomedical applications including drug delivery, tissue engineering, prosthetic implants, and food/medicine packaging. These CP NPs PIS are also used to synthesize nano-hydrogels with a relatively narrow and controlled size distribution in the absence of surfactants. It is proposed that polymerization is initiated at the CP NPs surface by photogenerated free polarons, in close analogy to the mechanism previously described for PIS based on inorganic semiconductor NPs.

Initiation of dilute and concentrated pyroclastic currents from collapsing mixtures and origin of their proximal deposits

Numerical solution of the time-dependent conservation equations for mass, momentum, specific internal energy, and granular temperature in flows involving gas-particle mixtures is used to explore the initiation of pyroclastic currents from collapsing mixtures such as during fountaining eruptions. One objective is to determine when a depth-averaged granular flow model or a box model for dilute currents is most applicable for hazards modeling of pyroclastic currents produced by column collapse; a second objective is to gain insight into the formation of proximal breccia facies of ignimbrites. Collapsing gas-particle mixtures impacting a flat surface are modeled with mixtures of coarse particles that are poorly coupled with the gas phase and well-coupled fine particles. Resulting lateral flows are sensitive to the impact speed, overall particle concentration, and proportions of fine and coarse particles. For total particle concentrations of around 1 vol.%, an impacting mixture consisting of at least ~ 50% coarse particles, relative to fines, will tend to form a concentrated lateral underflow, which can be approximated by a depth-averaged granular flow model for hazard assessment purposes starting from the impact zone. Low total particle concentrations (e.g., total concentrations of ~ 0.1 vol.%) tend to produce dilute lateral flows that could be simplified to box model approaches for dilute pyroclastic currents. Larger total particle concentrations in impacting mixtures (~ 10 vol.%) produce granular underflows if they have any coarse particles, but these can be complicated by Mach number effects. For intermediate concentrations of the impacting mixture, a rough threshold for development of a concentrated underflow versus a dilute-only current is based upon the flux per unit area of coarse particles to the impact and their Stokes numbers. In general, some knowledge of the eruption column (fountain) conditions is required in order to make an informed decision as to which hazards modeling approach is most applicable for a given scenario. Modeling indicates that proximal breccias are related to influxes of coarse wall-rock material into an eruptive mixture, which increase both the total particle concentration and the proportion of coarse, dense clasts in the mixture that subsequently collapses and impacts the ground. The breccias record concentration of dominantly coarse clasts immediately upon impact and formation of concentrated flows that propagate laterally while expelled fines and gas flow rapidly overhead as dilute currents. Lateral and vertical heterogeneity in proximal deposits likely record rapid time and space variations in avalanches of material into eruptive vents, and the occurrence of breccia hummocks might record the temporary positions of impact zones.

VOF-DEM simulation of single bubble behavior in gas–liquid–solid mini-fluidized bed

The single bubble behavior in a 3 mm rectangular gas–liquid–solid mini-fluidized bed with 90 μm particles was simulated using the combination of VOF and DEM, and the results were validated by experiments. The simulation on the expansion of liquid–solid mini-fluidized shows that the profiles of liquid and particle velocities are consistent, and both become more concentrated as the expansion ratio decreases. The bubble formation size does not change with the increase of the solid holdup from 0.25 to 0.45, while the bubble rise velocity becomes lower. The upward liquid velocity in the bubble wake exceeds 50% of the instantaneous bubble velocity. The size of the low particle concentration bubble wake reducing with the increase of solid holdup can be attributed to the decrease in the bubble rise velocity and the enhancement in the inertia effect of the liquid–solid flow.

An improved particle shifting algorithm for multiphase flows in SPH method

Multiphase flows, such as underwater explosions, rising bubbles, flooding of damaged cabins, etc., are widespread in nature and engineering. When conventional Eulerian mesh-based methods are adopted in the simulation of multiphase flows, some challenges are always encountered, including the large deformation and fragmentation of fluid, the capture of the multiphase interface, and so on. Therefore, many scholars turned their attention to meshless particle methods. As an important member of meshfree methods, smoothed particle hydrodynamics (SPH) was invented to solve astrophysical problems, and then it was applied to the simulation of hydrodynamics. In the SPH method, the computational domain is represented by a collection of particles whose properties, including density, velocity, internal energy, etc, are updated by the interaction between particles. Since the SPH method is free from the restriction of the mesh, it is good at handling large deformations of fluid. More importantly, the free-surface or multiphase interface does not need to be detected because the interface of the particles of different phases is also the interface of fluid. For these reasons, the SPH method has been widely used in the simulation of multiphase flows. Due to the natural Lagrangian characteristic of the SPH method, particles move strictly along streamlines, which may lead to uneven particle distributions and thus reducing the numerical accuracy in some cases. To solve this problem, some particle regularization schemes have been developed in the SPH method, in which the particle shifting algorithm is the most widely used one. The core idea of the shifting algorithm is to artificially move particles from a region with a high concentration of particles to a region with a low concentration of particles in each time step, thereby obtaining uniform particle distributions throughout simulations. In the published literature, there have been several multiphase models in the SPH method, and some of them adopt the particle shifting algorithm to make the discontinuous multiphase interface more stable and accurate. At present, the most commonly used shifting algorithm for multiphase flows is proposed by Mokos et al. When it is adopted, the moving material interface should be firstly detected. Then particles belonging to different phases are shifted by applying different treatments, aiming to avoid mutual mixing of different phase materials. These treatments are generally complicated and time-consuming, and sometimes they may result in unphysical gaps near the multiphase interface, reducing the numerical accuracy and stability. To tackle the problems mentioned above, a simpler and more accurate shifting algorithm is proposed in this paper. In this algorithm, the treatments applied to different fluids are consistent. Meanwhile, to ensure the clarity of the multiphase interface, the shifting magnitude of the particles near the interface is slightly increased. Compared with the shifting algorithm proposed by Mokos et al., the improved shifting algorithm is simpler and more efficient. More importantly, through the simulations of several classical multiphase problems in the SPH method, the proposed improved shifting algorithm is proved to be able to maintain perfectly uniform particle distributions near the interface even for long-term simulations, and thus the numerical accuracy and energy conservation are enhanced.

Effects of Ag NPs on denitrification in suspended sediments via inhibiting microbial electron behaviors

The wide use of silver nanoparticles (Ag NPs) inevitably leads to their increasing emission into aquatic environments. However, before their final deposition into sediments, the ecological effects of Ag NPs in suspended sediment (SPS) systems have not received much attention. Herein, we investigated the influences of Ag NPs on denitrification in SPS systems, and explored the potential toxicity mechanism through microbial metabolism (electron behaviors) and isotope tracing (added 15NO3−). After exposure to 10 mg/L Ag NPs, electron generation, transport and consumption during denitrification were clearly inhibited, which led to a decrease in the SPS denitrification rate. Specifically, the generation of NADH (electron donor) was significantly decreased to 59.92–86.47% with the Ag NPs treatments by affecting the degradation of glucose, one of the major reasons for the decreased denitrification. It also indicated that Ag NPs could affect nitrogen metabolism by influencing carbon metabolism. In addition, ETSA was clearly inhibited by the affected electron transfer and reception during denitrification; that was the most direct way in the microbial electron transport chain to affect the SPS denitrification rate. Furthermore, the particle size and concentration of SPS affected the toxicity of Ag NPs. The denitrification process in SPS systems with a smaller particle size and lower particle concentration was easily affected by Ag NPs, suggesting that SPS systems dominated by clay (particle size < 3.9 μm) or that less turbulence (having low SPS concentration) might be at greater risk factor when exposed to NPs. Thus, it is important to understand the risks of pollutants, such as Ag NPs, to biogeochemical cycles and ecosystem function in SPS systems.

Effects of staphylococcal infection and aseptic inflammation on bone mass and biomechanical properties in a rabbit model

Background/objectiveOrthopaedic implants are important devices aimed at relieving pain and improving mobility. Staphylococcal infection and aseptic loosening are two common events associated with inflammatory osteolysis that lead to implant failures. Bone mass and biomechanical properties are important indicators that could influence patient outcomes after revision surgery. However, the dynamics of bacterial infections and their influence on bone mass and biomechanical properties remain unclear. Hence, in this study, we developed rabbit aseptic inflammation and staphylococcal infection models to determine the effects of coagulase-positive and coagulase-negative bacterial infection, as well as aseptic inflammation, on the mass and biomechanical properties of the bone. MethodsSixty New Zealand white rabbits were randomly assigned to 6 groups, and each group had 10 rabbits. The medullary cavities in rabbits of each group were injected with phosphate-buffered saline (100 ​μL), titanium (Ti)-wear particles (300 μg/100 ​μL), a low concentration of Staphylococcus epidermidis (105/100 ​μL), a high concentration of S. epidermidis (108/100 ​μL), a low concentration of Staphylococcus aureus (105/100 ​μL), and a high concentration of S. aureus (108/100 ​μL), respectively. At four and eight weeks after surgery, the rabbits were sacrificed, and the tibias on the surgical side were analysed via histopathology, microcomputed tomography, and nanoindentation testing. ResultsHistopathological analysis demonstrated that inflammatory responses and bacterial loads caused by high concentrations of staphylococcal infections, particularly coagulase-positive staphylococci, are more detrimental than low concentrations of bacterial infection and Ti-wear particles. Meanwhile, microcomputed tomography and nanoindentation testing showed that high concentrations of S. aureus caused the highest loss in bone mass and most biomechanical function impairment in rabbits experiencing aseptic inflammation and staphylococcal infections. ConclusionsInflammatory osteolysis caused by a high concentration of coagulase-positive staphylococci is significantly associated with low bone mass and impaired biomechanical properties. The translational potential of this articleIt is necessary to obtain an overall assessment of the bone mass and biomechanical properties before revision surgery, especially when S. aureus infection is involved. In addition, a better understanding of these two parameters might help develop a reasonable treatment regimen and reduce the risk of adverse events after revision surgery.

Classification performance of model coal mill classifiers with swirling and non-swirling inlets

Abstract The classification performance of model coal mill classifiers with different bottom incoming flow inlets was experimentally and numerically studied. The flow field adjacent to two neighboring impeller blades was measured using the particle image velocimetry technique. The results showed that the flow field adjacent to two neighboring blades with the swirling inlet was significantly different from that with the non-swirling inlet. With the swirling inlet, there was a vortex located between two neighboring blades, while with the non-swirling inlet, the vortex was attached to the blade tip. The vorticity of the vortex with the non-swirling inlet was much lower than that with the swirling inlet. The classifier with the non-swirling inlet demonstrated a larger cut size than that with the swirling inlet when the impeller was stationary (~ 0 r⋅min-1). As the impeller rotational speed increased, the cut size of the cases with non-swirling and swirling inlets both decreased, and the one with the non-swirling inlet decreased more dramatically. The values of the cut size of the two classifiers were close to each other at a high impeller rotational speed (≥ 120 r⋅min-1). The overall separation efficiency of the classifier with the non-swirling inlet was lower than that with the swirling inlet, and monotonically increased as the impeller rotational speed increased. With the swirling inlet, the overall separation efficiency first increased with the impeller rotational speed and then decreased when the rotational speed was above 120 r⋅min-1, and the variation trend of the separation efficiency was more moderate. As the initial particle concentration increased, the cut sizes of both swirling and non-swirling inlet cases decreased first and then barely changed. At a low initial particle concentration (

Effects of step height and particle diameter on the heat transfer and fluid flow of water-nanoencapsulated phase change material over the backward step

In this work, effects of step height and particle diameter on the average heat transfer coefficient, pressure drop and thermal performance index of mixture of water and nanoencapsulated phase change material (NEPCM) over the backward step is examined numerically at different values of Reynolds number, wall heat flux and particle concentration. To validate numerical model, comparisons were made with experimental and other available works in the literature and good agreements were observed. Results show that an increase in the step height causes the heat transfer to decrease and increase thereafter. It is shown that addition of NEPCM to the pure water could enhance the heat transfer rate at high step height. Numerical findings declare that an increase in the particle diameter causes the heat transfer rate to increase and this increase is of little significance at low particle concentration. It is found that the increase in the step height dramatically results in the increase in the pressure drop while an increase in the particle diameter has nearly no effect on the pressure loss. Results indicate that the thermal performance index is a strong function of particle concentration and the best thermal performance index is obtained at low particle concentration.

Development of a comprehensive understanding of aggregation-settling movement of CeO2 nanoparticles in natural waters

Parameters such as the settling rate, aggregation rate, and collision frequency in predictive models used to describe the fate of nanoparticles (NPs) are very important for the risk assessment of NPs in the environment. In this study, CeO2 NPs were chosen as the model particles to investigate such parameters through aggregation-settling experiments under environmentally relevant conditions. The results indicate that natural colloids (Ncs) have no effect on the settling of NPs in seawaters, whereas they stabilize the NPs at a low initial particle concentration and promote the heteroaggregation of NPs at a high initial particle concentration in lake waters. In all cases, a suspended sediment absorbs the NPs and Ncs as mixed aggregates, resulting in a rapid settling. Furthermore, the calculation results of the model indicate that the shear force increases the collision frequency of the NPs by 4–5 orders of magnitude higher than that in quiescent waters. However, the break-up effect by the shear force is more obvious, namely, the shear force hinders the aggregation of NPs in natural waters, instead of promoting aggregation. Remarkably, a negative value of the dis-heteroaggregation rate based on the combined von Smoluchowski–Stokes equation can reflect the hindering effect on the aggregation process. The results of this study will provide scientific and accurate guidance for the parameter selection in the existing prediction model and contribute to a prediction of the fate and transport of NPs in the environment.

Material-selective separation of mixed microparticles via insulator-based dielectrophoresis.

Insulator-based dielectrophoresis (iDEP) has become a powerful tool for biomicrofluidic separation and analysis because it is capable to selectively separate biological particle systems according to properties like size, material, and shape. However, it has rarely been used to solve challenging separation problems involving nonbiological particles, namely, for systems that are prone to particle agglomeration. Here, we demonstrate material-selective separation of nonbiological systems, i.e., polystyrene and gold-coated polystyrene particles of two different sizes, using iDEP at high accuracy. For this purpose, we present a method to generate fluorescent gold-coated particles. We further introduce a method to reduce the static backpressure that builds up between in- and outlet reservoir due to electroosmotic flow. Moreover, we found that particle agglomeration makes their separation impossible when conventional iDEP routines are applied. Therefore, two solutions to reduce particle agglomeration are presented: A combination of AC and DC potentials and adjustment of pH and conductivity of the suspending medium. Both approaches allow separating particles under challenging conditions such as initially low absolute particle zeta potentials and high particle concentrations. Since those conditions can also be present in biological iDEP separation processes, the results are of general value for biological and nonbiological iDEP operations.

Light Extinction Method for Measuring a Low Particle Concentration with White Cell Optics: Relationship between Light Transmittance and Particle Properties

Because particulate matter (PM) emission standards of coal-fired power plants in China are becoming increasingly stricter, a higher sensitivity of traditional PM emission monitoring systems is required to adapt to the proposed ultralow emission (ULE) levels. In this study, a commercial optical structure, white cell optics, was introduced into the traditional extinction system to enhance particulate extinction and lower the detection limit by increasing the light path length. By connecting an aerosol generator and an electrical low-pressure impactor system, the white cell light extinction (WC-LE) system was tested to predict the low particle concentration of spherical silica aerosol and fly ash aerosol. According to the results of real-time testing with spherical silica aerosol, a good response between extinction signal and particle concentration was generally observed over the concentration range of 0–10 mg/m³. An excellent linear correlation between the extinction and particle concentration was obtained from data from short periods without violent feeding fluctuation. Based on the linear correlation, the particle concentration was calculated from the real-time extinction signal. For silica aerosols with different size distributions, the calculated concentration generally showed good correlation with the experimental value; the variation in extinction coefficients derived from the linear correlations was smaller than the theoretical values calculated with the measured size distribution, which seemed to be related to the in-cell mass loss. By testing the system with fly ash aerosols, the real-time response, linear correlation between signals, and concentration measurement also showed satisfactory results. The results of this study show that the WC-LE system is sensitive to small fluctuations in the particle concentration and provides a reliable correlation between the extinction signal and particle concentration, which allows the system to be considered a promising solution for particle emission monitoring at ULE levels.

Functional responses of filter feeders increase with elevated metal contamination: Are these good or bad signs of environmental health?

Fast urbanization in coastal areas has increased the load of contaminants entering estuaries worldwide, threatening the diversity and provision of services by these important systems. Contamination causes structural changes in ecosystems, but the consequences for their functioning are still overlooked. Here we investigated filtration and biodeposition rates of the mussel Mytilaster solisianus across different concentrations of metals, nutrients and suspended material, and levels of urbanization. As expected, filtration rates increased with the number of particles in the water column. However, in areas with low particle concentration, filtering increased in mussels with higher metal concentrations (Cu/Zn/Ni), which were, in turn, related to high urbanization. Similarly, biodeposition rates were positively related to metal concentration in mussels. The increased functional responses observed here is likely a symptom of stress, caused by potential compensatory mechanisms to the energetic costs of cell maintenance and body detoxification of mussels, rather than an indication of healthy systems/organisms. CAPSULE: Increased functional responses of mussels can be a sign of environmental stress.

Experimental study of the effects of nanofluids on wicking ability and thermal performance of a vertical open microgrooves heat sink

Open microgrooves heat sinks (OMHSs) are one kind of capillary-driven heat transfer systems and achieve highly efficient heat transfer by evaporation and boiling. Thermal performance of an OMHS depends on its wicking ability, which is evaluated by the axial wetting length (AWL). This work investigated the effects of Fe3O4-water nanofluids on wicking ability and thermal performance of a vertical OMHS at relatively low particle concentrations. The AWL was characterized by infrared thermal imaging. At each concentration, the wall superheat is reduced significantly due to the enhanced wicking. There exists an optimum concentration, 0.00375 vol% which leads to a 41% decrease in the wall superheat and a 22% increase in the AWL compared with those for the base liquid. Either increasing or decreasing the concentration reduces the enhancements. It is demonstrated that the suspended particles in the liquid and the particle deposition are all important for enhancing the wicking ability and thermal performance and their contributions to the enhancements are simultaneously maximized at 0.00375 vol%. The suspended particles are supposed to promote liquid wetting and the pinning of three-phase contact line by inducing an additional structural disjoining pressure. At 0.00375 vol%, the pinning in the corner-flow region was confirmed and found to be responsible for the rise of AWL when boiling occurred.

Ice Microphysical Properties near the Tops of Deep Convective Cores Implied by the GPM Dual-Frequency Radar Observations

Abstract Using three years of observations from the Dual-Frequency Precipitation Radar (DPR) aboard the Global Precipitation Measurement (GPM) Core Observatory, properties of the cores of deep convection are examined. First, deep convective systems are selected, defined as GPM precipitation features with maximum 20-dBZ echo-top heights above 10 km. The cores of deep convection are described by the profiles of Ku- and Ka-band radar reflectivity at the location of the highest echo top in each deep convective system. Then the dual-frequency ratio (DFR) profile is derived by subtracting Ka-band from Ku-band radar reflectivity. It is found that values of DFR are larger over land than over ocean in general near the top of the convection, which is consistent with larger ice particles in stronger updrafts in continental convection. The magnitude of DFR at 12 km is positively correlated with the convection intensity indicated by 20- and 30-dBZ echo tops. The microphysical properties including volume-weighted mean diameter, ice water content, and total ice particle number concentration are derived using a simple lookup table approach. Under the same particle size distribution assumption, the cores of deep convection over land have larger ice particle size, higher ice water content, and lower particle concentration than those over ocean at levels above 10 km, but with some distinct regional variations.

Infrared spectral analysis of low concentration magnetoactive polymers

ABSTRACTThis work concerns an area of magnetoactive polymer (MAP) research seldom considered. Traditionally only MAP with high concentrations of magnetic filler (typically between 10 and 90 wt%) have been investigated. This article deals with a hitherto neglected aspect of research, namely MAP containing lower magnetic filler concentrations (1 to 3 wt%). This article utilizes a range of spectroscopic analysis methods (Raman and FTIR) and their applicability to MAP characterization at wavelengths ranging from 2.5 to 25 μm. Particular attention is paid to low carbonyl iron particle (CIP) concentrations in MAP for which the emergence of capillary doublets at a critical 2 wt% concentration is revealed. This results in measurable magnetic field‐dependent changes in IR absorption at a wavelength of 4.255 μm together with a detectable CO2 susceptibility. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals Inc. J. Appl. Polym. Sci. 2020, 137, 48366.