Particulate Fraction Research Articles

Preparation, characterisation and pharmacokinetics evaluation of dry power inhalation formulations of Polymyxin B.

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) has strong invasiveness, not only causing local lung inflammation, but also capable of penetrating alveolar epithelial cells and entering the bloodstream, thereby triggering systemic infection. This study aims at develop an alternative and effective drug delivery system through the inhalation therapy to address the limitations of polymyxin B (PMB) intravenous treatment for multidrug-resistant CRPA pneumonia, such as low lung concentration and nephrotoxicity, while also achieving systemic therapeutic effects. We prepared PMB dry powder inhalers (DPIs) using air jet milling and spray drying techniques. The prepared DPIs were characterized in terms of micromorphology, geometric particle size distribution, density, flowability, and surface roughness. Furthermore, we assessed the in vitro lung deposition and antibacterial efficacy of these inhalers.To compare the systemic exposure following changes in administration routes, blood concentration measurements were conducted for different routes of administration Spherical PMB particles, measuring 3 microns in diameter, achieved the highest fine particle fraction (FPF) of 53%. When particles transition from regular shapes to irregular blocks, a decrease of 1 micron in particle size results in an approximate 20% increase in FPF. Moreover, the FPF of PMB particles combined with smooth-surfaced lactose is approximately 10% less than that of PMB particles combined with rough-surfaced mannitol. The bioavailability of PMB DPI reached a peak of 77.46% within 10 minutes. In a murine model of acute lung infection, treatment with PMB DPI significantly reduced the bacterial load in lung tissues compared to the control group, with no observed fatalities, in contrast to the outcomes of intravenous PMB administration. In summary, particles with reduced size and increased sphericity displayed a greater FPF led to enhanced therapeutic efficacy and safety.

Evaluation of a cardboard-based spacer for enhancing aerosol delivery from pressurized metered dose inhalers.

The current study aimed to evaluate a novel paper card-based spacer (MDI Plus) in vitro and in vivo as a cost-effective alternative to traditional spacers (AeroChamber Plus). The in-vitro part evaluated salbutamol's aerodynamic particle size distribution (APSD) after 0, 20, 50, 120, and 200 uses of Ventolin pressurized metered dose inhaler (pMDI) when connected to MDI Plus using an Andersen cascade impactor at an inhalation flow of 28.3 L/min. The in-vivo part recruited a cohort of adult asthmatic patients. It assessed their pMDI usage and the number of training sessions to enhance their ability to use their pMDI alone and in combination with MDI Plus and AeroChamber Plus. Moreover, the amount of salbutamol deposited within the spacer devices, on the pMDI, and on the hand of the patients after 0, 20, 50, 120, and 200 uses were evaluated. The durability tests revealed that while there were reductions in aerodynamic performance over the lifespan of the pMDI, the decreases were insufficient to render the spacer ineffective. The fine particle fraction decreased slightly, and the mass median aerodynamic diameter increased somewhat, but the spacer maintained functional performance. The study indicated that spacers significantly improved patients' ability to use their MDIs correctly with minimal training. The MDI Plus showed a slightly significant positive impact (p < 0.05), requiring fewer training sessions for effective use. The amount left in the MDI Plus was significantly lower than within the AeroChamber Plus (p < 0.05). The amount deposited on the MDI and the hands of the patients after multiple storage in the MDI Plus box and uses was insignificant and within the allowed limits. The MDI Plus simultaneously can act as an pMDI packaging box and spacer, serving as a practical, affordable, and accessible alternative to traditionally commercially available plastic spacers, particularly in resource-limited settings.

Collective dynamic length increases monotonically in pinned and unpinned glass forming systems.

The Random First-Order Transition (RFOT) theory predicts that transport proceeds by the cooperative movement of particles in domains, whose sizes increase as a liquid is compressed above a characteristic volume fraction, ϕd. The rounded dynamical transition around ϕd, which signals a crossover to activated transport, is accompanied by a growing correlation length that is predicted to diverge at the thermodynamic glass transition density (>ϕd). Simulations and imaging experiments probed the single particle dynamics of mobile particles in response to pinning all the particles in a semi-infinite space or randomly pinning (RP) a fraction of particles in a liquid at equilibrium. The extracted dynamic length increases non-monotonically with a peak around ϕd, which not only depends on the pinning method but is also different from ϕd of the actual liquid. This finding is at variance with the results obtained using the small wavelength limit of a four-point structure factor for unpinned systems. To obtain a consistent picture of the growth of the dynamic length, one that is impervious to the use of RP, we introduce a multiparticle structure factor, Smpc(q,t), that probes collective dynamics. The collective dynamical length, calculated from the small wave vector limit of Smpc(q,t), increases monotonically as a function of the volume fraction in a glass-forming binary mixture of charged colloidal particles in both unpinned and pinned systems. This prediction, which also holds in the presence of added monovalent salt, may be validated using imaging experiments.

Evaluation of Permeability, Safety, and Stability of Nanosized Ketoprofen Co-Spray-Dried with Mannitol for Carrier-Free Pulmonary Systems

Pulmonary drug delivery presents a promising approach for managing respiratory diseases, enabling localized drug deposition and minimizing systemic side effects. Building upon previous research, this study investigates the cytotoxicity, permeability, and stability of a novel carrier-free dry powder inhaler (DPI) formulation comprising nanosized ketoprofen (KTP) and mannitol (MNT). The formulation was prepared using wet media milling to produce KTP-nanosuspensions, followed by spray drying to achieve combined powders suitable for inhalation. Cell viability and permeability were conducted in both alveolar (A549) and bronchial (CFBE) models. Stability was assessed after storage in hydroxypropyl methylcellulose (HPMC) capsules under stress conditions (40 °C, 75% RH), as per ICH guidelines. KTP showed good penetration through both models, with lower permeability through the CFBE barrier. The MNT-containing sample (F1) increased permeability by 1.4-fold in A549. All formulations had no effect on cell barrier integrity or viability after the impedance test, confirming their safety. During stability assessment, the particle size remained consistent, and the partially amorphous state of KTP was retained over time. However, moisture absorption induced surface roughening and partial agglomeration, leading to reduced fine particle fraction (FPF) and emitted fraction (EF). Despite these changes, the mass median aerodynamic diameter (MMAD) remained stable, confirming the formulation’s continued applicability for pulmonary delivery. Future research should focus on optimizing excipient content, alternative capsule materials, and storage conditions to mitigate moisture-related issues. Hence, the findings demonstrate that the developed ketoprofen–mannitol DPI retains its quality and performance characteristics over an extended period, making it a viable option for pulmonary drug delivery.

Liquid metal ion source based on magnetic suspensions for field emission electric propulsion (FEEP)

This work presents a process for the creation of emitter structures for liquid metal ion sources based on suspensions of iron and nickel in gallium-based room temperature liquid metal alloys. The process does not require needle etching or vacuum wetting of the emitter. Tip radii of less than 3 μm have been achieved. In addition, first measurements and observations from single emitter emission experiments are presented, including current-voltage characteristics, vacuum stability, degradation mechanisms and first thruster characteristics for the use in field emission electric propulsion. The impedance of the magnetic liquid metal emitters was found to correlate with the mass fraction of particles suspended in the liquid metal. Total impedances up to 30 MΩ have been achieved, indicating the feasibility of emitter clustering. Thrust measurements were performed with a commercial of the shelf load cell and verified in a dedicated setup for field emission electric propulsion testing, featuring a sub micro newton counterbalanced double pendulum thrust balance.

Migration of magnetic microparticles through a liquid–liquid interface under an external magnetic field

Liquid–liquid interfaces play a pivotal role in various microfluidic processes involving microparticles, including coating, dissolution, controlled release of polyelectrolytes or drugs, and self-assembly processes. In all of these cases, noninvasive techniques to manipulate the microparticle transport are essential. Magnetic manipulation offers an accessible and straightforward means of controlling the motion of magnetic particles within microfluidic devices. Magnetic microparticles are commonly used for conformal polyelectrolyte coating and drug encapsulation by passing them through a liquid–liquid interface due to their high saturation magnetization, stability, and low toxicity. In this work, we draw inspiration from the lack of studies on the behavior of magnetic particles near a liquid–liquid interface under conditions of low Reynolds numbers and high capillary action, despite its engineering relevance in microfluidic systems. We consider a canonical flow configuration in which particle motion is driven by the stagnation-point flow that is generated when two different liquids flow toward one another. We show how the operating conditions dictate whether the particle will pierce the interface and become coated or not and illustrate this via parameter-space plots. We use the results of this analysis to understand how the operating conditions influence the fraction of particles that pass through the liquid–liquid interface and are conformally coated, which may be used to guide a variety of industrial processes.

Optimization of formulation and device design for carrier-based nasal powder of influenza vaccine to maximize the delivery capability to the target site in the nasal cavity

Previously, a nasal powder formulation of the influenza vaccine was proposed to ensure its stability over fifteen months at room temperature and to have sufficient moisture-resistant characteristics to enable handling without special humidity control. In this study, a carrier-based concept: a physical mixture of the antigen powder and the carrier powder, was adopted for this nasal powder formulation. The physical properties of both components were optimized to maximize the delivery capability to the target site located behind the nasal cavity using a human nasal cast model. Preliminary evaluation with a prototype device (Device A) revealed that the physical properties of the antigen powder influenced the delivery efficiency mainly through their effect on the discharge rate from the device. Since it is obvious that the discharge rate from the device must be secured as a prerequisite for increasing the target site delivery, Device B with an improved discharge rate was developed, and the optimal powder properties were re-evaluated. The delivery rate of antigen powder to the target site was broken down into two elements: the discharge rate from the device and the delivery efficiency of emitted powder to the target site, and then the effect of the particle size of antigen powder and the carrier powder on each element was analyzed separately. As a result, an optimal particle size region was identified for each element as a design space on a two-dimensional map described by the antigen particle size and the carrier particle size. Besides this analysis, the fine particle fraction (aerodynamic particle size less than 5 μm) was evaluated in a separate experiment considering the risk of invasion into the lung and a condition of particle size to minimize the fine particle fraction was identified. By integrating the results of the above analysis, an optimal space was determined on the two-dimensional map to maximize the delivery efficiency to the target site while minimizing unintended exposure to the lungs.

Fate of a toxic Microcystis aeruginosa bloom introduced into a subtropical estuary from a flow-managed canal and management implications.

The Caloosahatchee Estuary in southwest Florida, USA, is regularly subject to the introduction of toxic Microcystis aeruginosa blooms, often originating from the eutrophic Lake Okeechobee via the C-43 Canal. The focus of this study was to determine the responses of one of these introduced blooms to progressively elevated salinity levels as the bloom water mass moved through the estuary. In the upper estuary, salinities were freshwater, and surface blooms of large colonies of M. aeruginosa were observed, along with peak microcystin toxin concentrations up to 107μgL-1, all in the particulate fraction. In the mid-estuary, salinity levels increased to 2-6, and surface blooms were again observed, with peak microcystin concentrations up to 259μgL-1, however, significant levels of extracellular toxin were also observed (i.e., 17.8μgL-1), suggesting a level of osmotic stress on M. aeruginosa. In the lower estuary, salinities ranged from 6 to 25 and very few viable M. aeruginosa colonies were observed, but significant levels of extracellular microcystin (i.e., 0.5μgL-1) were present throughout the water column. It is noteworthy that average total microcystin concentrations in the water column (i.e., particulate+extracellular) remained constant throughout the movement of the bloom water mass during its transit through the estuary, revealing the negligible rate of microcystin degradation during the ten-day transit. The results also provide insights into the changes in the distribution of particulate and extracellular microcystin along the salinity gradient, which has implications for management of risks for ecosystem and human health, and how these risks may be affected by management of releases from three water control structures in the C-43 Canal. Discharge rates from the water control structures play major roles in the rate of movement of blooms through the C-43 Canal-Caloosahatchee Estuary ecosystem. The potential implications of discharge regulation for the management of M. aeruginosa in the ecosystem are discussed from the perspectives of blooms of allochthonous and autochthonous origin.

Inhalable spray-dried dry powders combining ivermectin and niclosamide to inhibit SARS-CoV-2 infection in vitro.

SARS-CoV-2, the virus responsible for the COVID-19 pandemic, predominantly affects the respiratory tract, underscoring the need to develop antiviral agents in an inhalable formulation that can be delivered as prophylactic and/or therapeutic drugs directly to the infection site. Since the beginning of the pandemic, our group has been exploring the possibility of developing combinations of antiviral drugs that can be delivered as inhalable therapy, including combinations of remdesivir and ebselen or remdesivir and disulfiram prepared using a spray-drying technique. In this study, we used a similar spray-drying technique to develop inhalable dry powders combining the controversial drugs ivermectin and niclosamide, which have been reported to exhibit synergistic activity against SARS-CoV-2 in vitro. The combined dry powders were within the size range of 1-5 μm, amorphous in nature and displayed characteristic morphology after spray drying. The emitted dose (ED) of the spray-dried powders ranged from 68 to 83 %, whereas the fine particle fraction (FPF) ranged between 50 and 74 %. All the prepared dry powders remained stable under different humidity conditions (<15 % RH and 53 % RH). Interestingly, the optimized combinational dry powder of ivermectin and niclosamide showed an improved cytotoxic profile (CC50 value of 45.99 µM) and enhanced anti-SARS-CoV-2 activity in vitro (EC50 of 2.67 µM) compared to the single dry powders of ivermectin (CC50 = 20.25 µM and EC50 = 8.61 µM) and niclosamide (CC50 = 21.36 µM and EC50 = 5.28 µM). In summary, we developed a stable and inhalable combinational dry powder containing ivermectin and niclosamide, capable of inhibiting SARS-CoV-2 replication in vitro, demonstrating the potential to prepare dry powders that could be developed and delivered as inhalable antiviral drugs to prevent and/or treat SARS-CoV-2 or similar respiratory viruses.

Bioaerosol Characterization with Vibrational Spectroscopy: Overcoming Fluorescence with Photothermal Infrared (PTIR) Spectroscopy.

Aerosols containing biological material (i.e., bioaerosols) impact public health by transporting toxins, allergens, and diseases and impact the climate by nucleating ice crystals and cloud droplets. Single particle characterization of primary biological aerosol particles (PBAPs) is essential, as individual particle physicochemical properties determine their impacts. Vibrational spectroscopies, such as infrared (IR) or Raman spectroscopy, provide detailed information about the biological components within atmospheric aerosols but these techniques have traditionally been limited due to the diffraction limit of IR radiation (particles >10 μm) and fluorescence of bioaerosol components overwhelming the Raman signal. Herein, we use photothermal infrared spectroscopy (PTIR) to overcome these limitations and characterize individual PBAPs down to 0.18 μm. Both optical-PTIR (O-PTIR) and atomic force microscopy-PTIR (AFM-PTIR) were used to characterize bioaerosol particles generated from a cyanobacterial harmful algal bloom (cHAB) dominated by Planktothrix agardhii. PTIR spectra contained modes consistent with traditional Fourier transform infrared (FTIR) spectra for biological species, including amide I (1630-1700 cm-1) and amide II (1530-1560 cm-1). The fractions of particles containing biological materials were greater in supermicron particles (1.8-3.2 μm) than in submicron particles (0.18-0.32 and 0.56-1.0 μm) for aerosolized cHAB water. These results demonstrate the potential of both O-PTIR and AFM-PTIR for studying a range of bioaerosols with vibrational spectroscopy.

Influence of matrix stiffness on microstructure evolution and magnetization of magneto-active elastomers.

Field-induced microstructure evolution can play an important role in defining the coupled magneto-mechanical response of Magneto-Active Elastomers (MAEs). The behavior of these materials is classically modeled using mechanical, magnetic and coupled magneto-mechanical contributions to their free energy function. If the MAE sample is fully clamped so it cannot deform, the mechanical coupling is reduced to the internal microscopic deformations caused by the particles moving and deforming the elastic medium that surrounds them. In the present study, we build on a unified mean-field theoretical approach which takes the microscopic elastic energy into account. Combined with experiment, this approach reveals how microstructure evolution affects the magnetization behavior of isotropic MAEs. MAE disks with various matrix stiffness and volume fraction of particles were fabricated and the magnetization curves were measured by vibrating sample magnetometry. We demonstrate that the idea of columnar structures forming from randomly distributed particles upon the application of an external magnetic field provides an effective approach in modeling microstructure evolution in these materials. Our unified mean-field model, using few and physically meaningful parameters, shows good quantitative agreement with the experimental data on magnetization and magnetic differential susceptibility of MAE samples. More importantly, our model can estimate microstructure evolution in highly filled samples, for which measurements are very challenging. Since changes in magnetization and stiffness are both driven by microstructural evolution, a quantitative relationship can be established between the two effects, as they represent different macroscopic manifestations of the same microscopic process. Therefore, our model can be used in conjunction with magnetization measurements to predict the mechanical modulus of MAEs without the need for elastic testing.

Microstructure response of concentrated suspensions to flow reversal.

We study experimentally at the macroscopic and microstructure scale a dense suspension of non-Brownian neutrally buoyant spherical particles experiencing periodic reversals of flow at constant rate between parallel plates and tracked individually. We first characterize the quasi-steady state reached at the end of half periods. The volume fraction of particles increases from the walls to the center as a result of migration induced by the nonuniform strain rate. Except very close to the walls and the center, the particle pair distribution is fore-aft asymmetric with depletions of pairs in the extensional quadrants, similar to that reported for shear flows of same volume fraction as the local one. The dynamics of the periodic rearrangements occurring after each flow reversal are characterized by a microstructure tensor component. The relaxation time characterizing the reorganization increases from the walls to the center due to the inhomogeneous strain rate. On the other hand, the local accumulated strain required for this reorganization decreases with the volume fraction, like for viscosity measurements in uniform strain rate conditions. However, the variation of the microstructure with the accumulated strain is faster than that of the viscosity, showing the complementarity of the two measurements.

Auto-Deposited Microparticle Composite Coating for Low-Cost and Efficient Daytime Radiative Cooling.

Radiative cooling is an excellent strategy for mitigating global warming, by enhancing heat fluxes away from the Earth, thus balancing the Earth's heat flow. However, for randomly particle-dispersed radiative cooling materials, the particle content as high as 94-96 wt % or 60 vol %, far exceeds the critical pigment percentage (40-50%) of traditional coatings, preventing its large-scale application. Here, inspired by particle deposition under gravity in solution, we demonstrate an auto-deposited SiO2 composite radiative cooling coating (ADRC) which reduces the amounts of particles required and lowers costs. This particle density gradient structure enhances the local volume fraction of particles, thereby the coating exhibits high solar reflectance (93%) and infrared emissivity (89%), contributing to a daytime subambient temperature drop of 12 °C. The cooling energy-saving potential of buildings in China utilizing the ADRC as roofs ranges from 6.42 to 13.52%. This low-cost and scalable radiative cooler is expected to reduce energy consumption and carbon emissions, addressing global warming issues.

NIR-Reflective Black Photonic Films Designed for Effective LiDAR Recognition.

Conventional dark-tone paints absorb both visible light and near-infrared (NIR) wavelengths, posing a challenge for light detection and ranging (LiDAR) recognition in autonomous driving. To overcome this issue, various chemical and structural coating materials have been explored to selectively reflect NIR. In this study, we newly propose colloidal photonic crystals with a stopband in the NIR range, fabricated through the spontaneous formation of crystalline arrays of silica particles dispersed in a photocurable resin, as a potential solution. The stopband position is finely adjusted by controlling the volume fraction of particles, and the translucent films are rendered black by incorporating carbon black nanoparticles into the interstitial regions. By optimizing the concentration of carbon black, we achieve a balance of low visible light and high LiDAR intensity. These black photonic films demonstrate superior LiDAR intensity compared to commercial dark-tone paints and perform on par with the perylene black-deposited white coating, one of the most promising LiDAR-assistive materials currently available, under normal reflection conditions. Additionally, the photonic films are highly durable, thermally stable, nontoxic, and environmentally friendly, making them promising candidates for LiDAR-assistive coatings.

Mixed Signals: interpreting mixing patterns of different soil bioturbation processes through luminescence and numerical modelling

Abstract. Soil bioturbation plays a key role in soil functions such as carbon and nutrient cycling. Despite its importance, fundamental knowledge on how different organisms and processes impact the rates and patterns of soil mixing during bioturbation is lacking. However, this information is essential for understanding the effects of bioturbation in present-day soil functions and on long-term soil evolution. Luminescence, a light-sensitive mineral property, serves as a valuable tracer for long-term soil bioturbation over decadal to millennial timescales. The luminescence signal resets (bleaches) when a soil particle is exposed to daylight at the soil surface and accumulates when the particle is buried in the soil, acting as a proxy for subsurface residence times. In this study, we compiled three luminescence datasets of soil mixing by different biota and compared them to numerical simulations of bioturbation using the ChronoLorica soil-landscape evolution model. The goal was to understand how different mixing processes affect depth profiles of luminescence-based metrics, such as the modal age, width of the age distributions and fraction of the bleached particles. We focus on two main bioturbation processes: mounding (advective transport of soil material to the surface) and subsurface mixing (diffusive subsurface transport). Each process has a distinct effect on the luminescence metrics, which we summarized in a conceptual diagram to help with qualitative interpretation of luminescence-based depth profiles. A first attempt to derive quantitative information from luminescence datasets through model calibration showed promising results but also highlighted gaps in the data that must be addressed before accurate, quantitative estimates of bioturbation rates and processes are possible. The new numerical formulations of bioturbation, which are provided in an accompanying modelling tool, provide new possibilities for calibration and more accurate simulation of the processes in soil function and soil evolution models.

In Situ Tracking of Nanoparticles During Electrophoresis in Hydrogels Using a Fiber-Based UV-Vis System

Gel electrophoresis is a powerful method for the separation of nanoparticulate suspensions into several fractions with distinct particle properties. To monitor particle migration through the three-dimensional net structure of the gel and gain insights about the separation process, this study introduces a self-designed fiber-based UV-Vis measurement system equipped with five probes for the sequential in situ recording of absorption spectra. The system was employed to investigate the migration and separation of Au and Fe3O4 particles within hydrogels of varying agarose concentrations (0.15–0.50 wt.-%), revealing an increase in scattering with higher agarose content. The identification of specific particle fractions with a spherical or rod-shaped morphology was successfully achieved within the gels due to characteristic absorption peaks, allowing the real-time observation of particle separation. For the separation of a binary mixture, an adequate migration distance is needed according to the difference in the electrophoretic mobility of the two samples. The particle tracking and an additional mathematical deconvolution allowed the analysis of mixed particle samples within the gel so that their weight ratio could be determined. Finally, the system was calibrated for the determination of the particle concentration within the gel matrix, quantitatively revealing the particle concentration at a specific position in the gel.

Full-Spectrum Mechanochromic Photonic Films with Large Interparticle Distance.

Non-close-packed crystalline arrays of colloidal particles in an elastic matrix exhibit mechanochromism. However, small interparticle distances often limit the range of reversible color shifts and reduce reflectivity during a blueshift. A straightforward, reproducible strategy using matrix swelling to increase interparticle distance and improve mechanochromic performance is presented. Photonic composites are initially prepared with silica particle arrays embedded in an elastomer matrix at volume fractions of 0.35-0.5. To increase interparticle distance, the composites are immersed in an elastomer-forming monomer, causing the matrix to swell, followed by photopolymerization, thereby producing liquid-free composites. The degree of swelling is controllable up to 3.16, depending on monomer choice, matrix volume fraction, and crosslinking density. The process can be repeated to further increase swelling up to 10.36. This method can reduce the volume fraction of silica particles from 40% to 3.8%, while interparticle distance increases from 53 to 257nm. The swollen photonic composites exhibit a full visible spectrum under compression, while minimizing reflectivity loss. This allows red-colored photonic composites to be transformed into vivid multicolor patterns when compressed with stamps featuring spatial height variations.

Real-World Particle Emissions from a Modern Heavy-Duty Diesel Vehicle during Normal Operation and DPF Regeneration Events: Impacts on Disadvantaged Communities.

We assessed the real-world particulate emissions of a goods movement diesel vehicle, with an emphasis on total particle number and solid particle number emissions at different cutoff sizes. The vehicle was tested on routes in the South Coast Air Basin (SCAB) of California, representative of typical goods movement operation between the ports to warehouses and logistic centers with a mixture of urban and highway driving, as well as elevation change. We evaluated emissions during normal vehicle operation and diesel particulate filter (DPF) active regeneration events. Results revealed small variations in particle emissions between the routes, with particles below 23 nm and even 10 nm being abundant in the exhaust. Both total and solid particle number emissions were about 3 to 246 times higher during DPF regeneration compared to normal vehicle operation, with higher fractions of sub-10 nm solid particles. We showed that typical daily routes for goods movement operation in SCAB, especially the more urban routes, mostly occurred within disadvantaged communities, with minority populations and high indices for poverty, unemployment, and poor education. Our results indicated the vehicles spent a higher fraction of their total time within these areas at low speed and idling conditions, resulting in disproportionately higher exposures to ultrafine particles.

Flow of SWCNT and MWCNT based hybrid nanofluids in a semi-circular enclosure with corrugated wall

Heat transfer mechanisms participate to fulfill the necessities of modern technologies. The phenomenon of heat transport has implementations in multiple fields including metal working, heating systems, thermal management in spacecraft, solar energy, and automobile engines. In the current novel work, heat transfer mechanism in a semi-circular enclosure with corrugated circular wall is studied numerically. A hybrid nanofluid consisting of water as the base fluid and solid particles of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) is considered. Prevailing mathematical equations are explained by finite element method with the help of COMSOL Multiphysics. The study examines various volume fractions of solid particles over a broad range. The SWCNT volume fraction is adjusted from 0.02% to 0.1%, while the MWCNT volume fraction ranged from 0.01% to 0.04%. Velocity, temperature, and pressure contours are imagined. Local and average Nusselt numbers are studied for each of the cases. The results indicate that heat transfer in the semi-circular enclosure improves with higher volume fractions of solid particles. As the volume fraction of solid particles increases, the average Nusselt number over the heated surface decreases.

Discovery of collective nonjumping motions leading to Johari–Goldstein process of stress relaxation in model ionic glass

The slow β, or Johari–Goldstein (JG) relaxation process, has been widely observed in glasses and is known to induce the stress relaxation associated with mechanical properties. So far, jumping motions of only a fraction of the particles were believed to contribute to the JG process in glass. However, there is no direct experimental evidence of the atomic-scale images due to the difficulties in microscopic observation. In this study, atomic motions in the quasi-spherical model ionic-glass-former Ca0.4K0.6(NO3)1.4 were microscopically observed with one-angstrom resolution, the highest resolution to date, using X-ray time-domain interferometry. The microscopic experiment directly indicated that most particles underwent angstrom-scale motions in the time scale of the JG relaxation. This result was further supported by molecular dynamics (MD) simulations. A combined study of experiments and MD simulations revealed that most particles contributed to the JG process through unexpected collective nonjumping motions with angstrom-scale displacement, activated by jumping motions of a fraction of particles. The discovery of nonjumping motions by our atomic-scale dynamic observations has considerably advanced our understanding of the puzzling mechanism of the JG process.