Particles Of Different Sizes Research Articles

Selective On-Site Detection and Quantification of Polystyrene Microplastics in Water Using Fluorescence-Tagged Peptides and Electrochemical Impedance Spectroscopy

In this study, we developed a method for the on-site selective detection and quantification of microplastics in various water matrices using fluorescence-tagged peptides combined with electrochemical impedance spectroscopy (EIS). Among the types of plastics found in seawater, polystyrene (PS) microplastics were selected. Fluorometry, scanning electron microscopy (SEM), and Raman spectroscopy were used to verify the specific interaction of these peptides with PS spherical particles of different sizes (ranging from 0.1 to 250µm). Principal component analysis (PCA) was employed to determine the effects of temperature (25-65 °C), incubation time (5 and 10minutes), and particle size on plastic-peptide bonding efficiency, based on fluorescence intensity. For each water type (pure, tap, NaCl (0.5M), and seawater), EIS plots (Nyquist and Bode) were generated. Significant factors affecting the EIS response, including particle size, shape, and material, were analyzed by measuring electrical parameters for different microplastic concentrations (50 ppb to 20 ppm). The EIS parameters changed with increasing plastic concentration, determining a limit of detection (LOD) of 50 ppb (ng/mL) for pure and tap water and 400 ppb for saline water, as the lowest concentration producing a significant change in EIS parameters compared to the baseline. The sensor proved highly effective for detecting microplastics in low ionic strength environments such as pure and tap water. However, in high ionic strength environments like saline and seawater, the detection capability diminished, likely due to the masking effect of ions on the EIS response.

The Influence of Fibers from Domestic Laundry Wastewater on the Clogging Process of a Filter

This study presents the impact of the size and shape of particles in laundry wastewater on the clogging process of a porous material. Clogging can be defined as a mechanical limitation of flow through porous media. The process of mechanical clogging was investigated in this study. The research was conducted in laboratory conditions in a filter column filled with glass beads whose diameter corresponded to coarse sand. The results reveal the influence of graywater quality on filter hydraulic conductivity and bed clogging, showing the impact of fiber particles in wastewater (sewage from home laundry) on the clogging process in soil. The results confirm that fiber particles significantly reduce filter permeability, particularly due to the formation of a filter cake. As analyzed in this paper, the distribution of quantitative data on particles of different sizes found in laundry wastewater indicates that they mainly accumulate in the upper layer, where particles with fiber lengths ranging from 0 to 1600 µm can be found. The average length of the fibers decreased with increasing depth. At a depth of approximately 10 cm, fibers with dimensions in the range of 0 to 100 μm were predominantly observed.

Evaluating microplastic particles as vectors of exposure for plastic additive chemicals using a food web model

Microplastic particles (MPs) represent potential hazards for humans and wildlife, including as vectors for chemical exposure (e.g. plastic additives and pollutants sorbed from the surrounding environment). The leaching of chemicals from MPs has been identified as a potential exposure pathway but the relative magnitude of this pathway under environmentally relevant conditions remains unclear. Here, we describe a modification of the ACC-HUMANSTEADY bioaccumulation model to include dietary exposure to MPs containing either accumulated chemicals from the surrounding environment or embedded plastic additive chemicals (PACs). Chemical transfer to humans and wildlife is described using two-film resistance concepts assuming spheroidal particles of different sizes. The relative contribution of MPs and environmental media to the estimated daily chemical intake in humans was assessed in various exposure scenarios, for a range of hypothetical chemicals with varying octanol-water and air-water partition coefficients (KOW and KAW, respectively; i.e. 0 < log KOW <8 and − 5 < log KAW < 3). Results imply that MPs could act as sources of exposure to chemical additives when the ingestion rate of 1 μm MPs is ≥ 10 mg d− 1, and the concentration of hydrophobic plastic additive is ≥ 5% wt wt− 1. The contribution made by MPs as vectors of exposure decreased with increasing particle size and decreasing ingestion rates of MPs. Human health risks were evaluated for four specific PACs to illustrate the application of the model for risk assessment. Risks were negligible when the ingestion rate of MPs was < 100 μg d− 1. Uncertainties are high regarding the characterization and quantification of ingestion of MPs by humans and wildlife, including particle sizes and polymer composition, as well as on the presence of PACs in MPs. These data gaps need to be addressed if the issue of MPs as vectors of chemical exposure is to be fully understood. The work illustrates that mechanistic models, which account for all major exposure pathways, can be used to identify the importance of different exposure pathways, help prioritize research needs and support decision making.

Deep insight into the effect of smithsonite particle size on surface heterogeneity and adsorption behavior: A case of fatty acid system

The studies for microfine mineral flotation have focused on the two main directions of increasing the apparent mineral particle size and reducing the bubble size, while little research has been reported on the special surface properties and adsorption mechanisms of mineral particles of different sizes. In this study, sodium oleate was chosen as a typical surfactant. The mechanism of the effect of smithsonite particle size on the heterogeneity and adsorption behavior of the mineral surface was explored in depth. Through microflotation experiments, BET area tests, Washburn contact angle tests, particle agglomeration tests, adsorption tests and inorganic carbon analysis, it was pointed out that the smaller the size of the particles, the greater the surface wettability, and the smaller the density and thickness of adsorbed oleate on the surface. The difficulty of encapsulating the mineral surface with a hydrophobic layer of oleate hydrocarbon chains, as well as suboptimal particle aggregation sizes, are key reasons for the poor flotation behavior of fine smithsonite. Furthermore, the inhomogeneity of active sites and charge distribution of surface components of smithsonite with different sizes was revealed from a microscopic point of view by DRIFT spectroscopic analysis, XPS analysis and zeta potential measurements. As the particle size of smithsonite decreases, the positive charge density on the surface is higher and the hydration tendency is more intense, hindering the adsorption of oleate. This work is expected to guide the full particle size recovery of minerals in the flotation from a novel microscopic point of view.

Synthesis of ZnTe powders from green solvents by a solvothermal method. Study of the sensing properties in a CO atmosphere

AbstractIn this work, the characterization and testing of sensing properties of ZnTe powders for detecting carbon monoxide were investigated. The ZnTe synthesis was reached by a solvothermal process, using three different green solvents, methanol, ethanol, and isopropanol. The structural, morphological, and compositional properties of ZnTe powders were analyzed by X-ray diffraction, XRD, scanning electron microscopy, SEM, and atomic force microscopy, AFM, and X-ray energy dispersion (EDS), respectively. XRD confirmed the zincblende-type cubic phase of ZnTe, with crystallite sizes of the order of 69 nm. SEM images of all synthesized samples showed a surface covered with particles of different sizes and irregular morphologies. Finally, the sensing response of ZnTe samples to CO was measured for concentrations varying from 1 to 500 ppm at different operating temperatures, 100, 200, and 300 °C. The highest sensitivity, 18.4, was obtained for ZnTe samples synthesized from isopropanol as solvent, so ZnTe powders showed a good response for CO detection, resulting these materials promising to be applied as gas sensors.

Continuous Inertial Alignment and Isolation of Spherical Microparticles and Nonspherical Flagellate Microalgae

Flagellate microalgae play an increasingly significant role in environmental management and biotechnology for valuable bioproducts, excellent photosynthetic capability, and autonomic movement. However, multiple flagellate microalgae practically live together in the ocean and lake areas, and they are susceptible to contamination as a result of improper operations. Enthused by these aspects, we develop a reliable inertial microfluidic method to overcome the influence of flagella movement and non-spherical shape on the alignment and isolation of target flagellate microalgae. Firstly, a computational model incorporating fluid-structure interaction was established to investigate influence of releasing position and shape parameters on the displacement and rotation of non-spherical microalgal cells and numerically studied the processes of shape- and size-based particle separation. Secondly, the movement of different-size particles under diverse flow rates in the channel was explored, and the capability of this method was validated by aligning and separating 10 μm and 20 μm polystyrene particles. Thirdly, this method was applied to align H. pluvialis and isolate Dunaliella salina from the mixed microalgal samples to explore the influence of flow rate on the alignment and isolation of flagellate microalgae. Fourthly, this method was engineered to select 20 μm polystyrene particles from three types of particles and isolate H. pluvialis from the mixture of multiple microalgae species. Finally, we leveraged this approach to realize separation of H. pluvialis and Synedra ulna to explore the performance of this method in shape-based cell separation, and we isolated Euglena from microalgal cell wastes, including dead cells, bacteria, and particles. This method has promising prospects to be a reliable tool to isolate target flagellate microalgae to address problematic issues in environmental monitoring, pharmaceutical synthesis, and chronic wound treatment for the advantage of good adaptability and reliability.

Evaluation of static and rolling friction coefficients of granulated sugar using the discrete element method in a rolling mode rotating drum

PurposeThis research investigates the behavior of granulated sugar particles of different sizes in a rotating drum at varying speeds, using the discrete element method (DEM) as a mathematical modeling approach.Design/methodology/approachThe study conducted a data scan to determine both static and rolling friction coefficients. Based on benchmark studies, the Hertz–Mindlin contact model with rolling history elastic-plastic spring-dashpot (EPSD) and CDT (directional constant torque) models were employed to simulate the behavior of granulated sugar particles in a rotating drum under varying speeds.FindingsIn this research, the static and rolling friction coefficients presented the best values for granulated sugar near 0.60 and 1.5, respectively, applying the CDT model. The method demonstrated great accuracy in replicating experimental data.Originality/valueThis study enables comprehension of the behavior of the particles and particle system in a rotating drum at different speeds. The method may develop models that characterize and predict the main effects of particle systems to reduce project time and expense, especially in the food industry.

Exploiting the Tunneling Coffee Ring Effect of Universal Colorimetric Nanomaterials for Ultrafast On-Site Microbial Monitoring.

The coffee-ring effect is an eye-catching circle originating from a material-suspended liquid droplet at a solid substrate after liquid evaporation, but the low speediness has restricted practical applications. When nanomaterial aqueous solutions are dropped onto porous nitrocellulose (NC), the liquid is immediately absorbed through the porous tunnels of paper fibers, and nanomaterials are rapidly enriched on the contact lines between droplets and membranes. We called this ultrafast variant of the coffee ring effect the "tunneling coffee ring" (TCR). When nanomaterial sizes are smaller than that of pores, a larger-diameter ring of nanomaterials quickly materializes. The real-time particle size-dependent TCRs and liquid diffusion rings exhibit a dual-ring pattern on the NC membrane. The tunneling speed of the capillary effect is so fast that the pattern appears within seconds. We apply the TCR effect as a size-surface affinity-particle/fluid separation sensor for bacteria. Dextran-modified Au and MoS2 nanostructures are proposed to be antibody-free microbe kits. Our TCR effect is used to distinguish between particles of different sizes and affinities, which are highly relevant in complicated systems without electricity and equipment in resource-poor settings.

Electric properties for thin films of microwave treated hydrophilic graphite fabricated by liquid-liquid interface

Abstract This paper reports the results of an attempt to combine microwave treated hydrophilic graphite (MwHG), a new carbon material that is both hydrophilic and electrically conductive, with a new deposition method using the interface between the aqueous and organic phases, the liquid-liquid interface deposition method (L-L method). The synthesized MwHG was characterized by X-ray diffraction (XRD) and Raman spectroscopy, and the deposited MwHG films were characterized by scanning electron microscopy (SEM) and electrical properties. It was found that the crystallinity of MwHG was changed by changing the microwave irradiation time during the synthesis of MwHG. It was also found that the high electrical conductivity was related to the microwave irradiation time or the order in which the films were deposited. Furthermore, the surface morphology of the films consisted of agglomerations of particles of different sizes with pores, and the size of the particles decreased with the number of depositions.

Hydroxyapatite in oral care products: in vitro effects on erosion/abrasion and analysis of formulation components.

Hydroxyapatite (HAP) is promoted as biomimetic material in dentistry. The aim of the study was to investigate whether HAP-containing formulations can reduce erosive/abrasive tissue loss and to analyse components in these formulations. Two HAP toothpastes with and two without fluoride and a HAP mouthrinse were investigated, controls were active-agent-free toothpaste, SnF2 toothpaste and F/Sn mouthrinse. For 10 d, human enamel samples were eroded for 2 min, 6x/d in 0.5% citric acid and immersed for 2 min, 2x/d in toothpaste slurries or mouthrinse. Half were additionally brushed for 15s, 2x/d. The particulate fraction was extracted and examined morphologically and with element analyses. Other parameters were REA, RDA, fluoride and calcium content. The F/Sn mouthrinse almost completely prevented tissue loss; none of the HAP formulations reduced tissue loss compared to the negative control, two increased it instead. Brushing increased tissue loss in all groups except the F/Sn mouthrinse. All toothpastes contained amorphous particles of different sizes. Elemental analysis identified Si and O, additionally Ca and P were present in small amounts on the particles of the HAP toothpastes and one HAP+F toothpaste. In the liquid phase, elevated calcium levels were found in one HAP toothpaste and in both HAP+F toothpastes; in the formulation with the highest value, the fluoride concentration was low. REA and RDA values were not associated with tissue loss. Whether alone or in combination with fluoride, HAP formulations had either no or a detrimental effect on erosive tissue loss and could not reduce abrasion. In the context of erosive tooth wear, HAP seems to be neither an alternative to fluoride nor a suitable supplement to it.

ExoSloNano: Multi-Modal Nanogold Tags for identification of Macromolecules in Live Cells & Cryo-Electron Tomograms.

In situ cryo-Electron Microscopy (cryo-EM) enables the direct interrogation of structure-function relationships by resolving macromolecular structures in their native cellular environment. Tremendous progress in sample preparation, imaging and data processing over the past decade has contributed to the identification and determination of large biomolecular complexes. However, the majority of proteins are of a size that still eludes identification in cellular cryo-EM data, and most proteins exist in low copy numbers. Therefore, novel tools are needed for cryo-EM to identify the vast majority of macromolecules across multiple size scales (from microns to nanometers). Here, we introduce and validate novel nanogold probes that enable the detection of specific proteins using cryo-ET (cryo-Electron Tomography) and resin-embedded correlated light and electron microscopy (CLEM). We demonstrate that these nanogold probes can be introduced into live cells, in a manner that preserves intact molecular networks and cell viability. We use this system to identify both cytoplasmic and nuclear proteins by room temperature EM, and resolve associated structures by cryo-ET. We further employ gold particles of different sizes to enable future multiplexed labeling and structural analysis. By providing high efficiency protein labeling in live cells and molecular specificity within cryo-ET tomograms, we establish a broadly enabling tool that significantly expands the proteome available to electron microscopy.

Effects of Particle Size and Shape on the Texture Property of a Solid-Liquid Dispersion System With Gel Particles.

Food texture is one of the most important factors for assessing the quality and acceptability of food. However, the study of food texture has been delayed compared with other factors, such as flavor and taste, due to the difficulty of quantitative analysis related to real physiological senses. Furthermore, the numerical and systematic evaluation of the texture property of dispersion systems, in which solid particles are dispersed in a liquid medium, is very difficult, despite most foods being in a solid-liquid dispersion state during mastication in the human mouth. In this study, the texture property of a solid-liquid dispersion system with spherical and cubic gel particles of agar and konjac was examined to evaluate the physical behavior of food during mastication using the back extrusion method. The yield stress of the system strongly depended on the size and shape of the particles, the mixing ratio of particles of different sizes and shapes, and the concentration of components in the particles. The proposed index, reflecting the size, shape, and number of particles and the yield stress of a single particle, expressed well the measured yield stress of the entire dispersion system. However, the adhesiveness and recoverability showed relatively little dependence on particle size. The findings obtained in this study will contribute to elucidating the texture property of various foods and to the development of new and novel food products and cuisines, thereby benefiting food science and industry.

Silicon dioxide particles induce DNA oxidative damage activating the AIM2-mediated PANoptosis in mice cerebellum

Silicon dioxide (SiO2) particles are novel materials with wide-ranging applications across various fields, posing potential neurotoxic effects. This study investigates the toxicological mechanisms of SiO2 particles of different sizes on murine cerebellar tissue and cells. Six-week-old C57BL/6 mice were orally administered SiO2 particles of three sizes (1 μm, 300 nm, 50 nm) for 21 days to establish an in vivo model, and mice cerebellar astrocytes (C8-D1A cells) were cultured in vitro. Indicators of oxidative stress, DNA damage, and the PANoptosis pathway were detected using methods such as immunofluorescence staining, comet assay, western blotting, and qRT-PCR. The results show that SiO2 particles induce oxidative stress leading to DNA oxidative damage. The aberrant DNA is recognized by AIM2 (absent in melanoma 2), which activates the assembly of the PANoptosome complex, subsequently triggering PANoptosis. Furthermore, the extent of damage is inversely correlated with the size of SiO2 particles. This study elucidates the toxicological mechanism of SiO2 particles causing cerebellar damage via PANoptosis, extending research on PANoptosis in neurotoxicology, and aiding in the formulation of stricter safety standards and protective measures to reduce the potential toxic risk of SiO2 particles to humans.

Enhancing Capillary Pressure of Porous Aluminum Wicks by Controlling Bi-Porous Structure Using Different-Sized NaCl Space Holders.

Capillary pressure and permeability of porous media are important for heat transfer devices, including loop heat pipes. In general, smaller pore sizes enhance capillary pressure but decrease permeability. Introducing a bi-porous structure is promising for solving this trade-off relation. In this study, the bi-porous aluminum was fabricated by the space holder method using two different-sized NaCl particles (approximately 400 and 40 μm). The capillary pressure and permeability of the bi-porous Al were evaluated and compared with those of mono-porous Al fabricated by the space holder method. Increasing the porosity of the mono-porous Al improved the permeability but reduced the capillary pressure because of better-connected pores and increased effective pore size. The fraction of large and small pores in the bi-porous Al was successfully controlled under a constant porosity of 70%. The capillary pressure of the bi-porous Al with 40% large and 30% small pores was higher than the mono-porous Al with 70% porosity without sacrificing the permeability. However, the bi-porous Al with other fractions of large and small pores did not exhibit properties superior to the mono-porous Al. Thus, accurately controlling the fractions of large and small pores is required to enhance the capillary performance by introducing the bi-porous structure.

Advancing particle forces and motion dynamics in centrifugal concentrator based on flow field simulation

ABSTRACT The forces and motion state of particles within the fluid domain of the Knelson concentrator have long been a focal point for researchers. Presently, Stokes’ flow laws are commonly employed as the basis for theoretical calculations. However, this approach somewhat deviates from reality due to challenges in determining the Reynolds number of particles in the centrifugal force field during practical work. Additionally, the relationship between the Reynolds number and the drag coefficient remains undetermined in certain ranges. This study presents a high predictive relationship curve, obtained using fitting software, to supplement and rectify the limitations in the existing relationship. Leveraging fluid simulation software, this research determines the Reynolds number of particles of different sizes and densities within the fluid, offering a methodological reference for similar flow field problems. A new drag coefficient function is proposed and validated for the Reynolds number range of 1 to 20, addressing a gap in existing theoretical models. The simulation results indicate that under the suitable separation conditions of −0.074 + 0.02 mm particles, the concentrate particles overcome the flushing effect of the reverse washing water and move in the opposite direction to the fluid. This advancement not only improves the theoretical framework but also offers significant academic and practical value by enhancing the efficiency of particle separation in the Knelson concentrator.

Synthesis and Characterization of Monolayer Colloidal Sheets.

Sheet-like colloidal assemblies represent model systems to investigate the structure and properties of two-dimensional materials. Here, we report a simple yet versatile method for the preparation of colloidal monolayer sheet-like assemblies that affords control over the size, crystalline order, flexibility, and defect density. The protocol that we report relies on self-assembly of colloids as a sessile drop of dispersion is evaporated on an oil-covered substrate. In this case, the contact line continually moves as the drop shrinks. Polyethyleneimine polymer-covered micrometer-sized colloidal particles are transported to the air-water interface and assemble to form a monolayer sheet as the drop dries. Cross-linking the polymer renders the colloidal assembly permanent. Interestingly, monodisperse colloidal particles form disordered assemblies when dried from low concentration dispersions, while polycrystalline ordered assemblies form at higher concentrations. We demonstrate that increasing the cross-linker to polymer ratio decreases the flexibility of the assembly. Introduction of different-sized colloidal particles in a sheet leads to increased disorder. Removal of sacrificial particles from the sheet allowed the introduction of "holes" in the sheets. Thus, these colloidal sheets are models for probing the effects of disorder, doping, and vacancies in two-dimensional systems.

A comprehensive study on the validation and application of multi-lognormal distribution models for atmospheric particles

The particle number size distribution (PNSD) is crucial for evaluating air quality and mitigating environmental pollution, as particles of different sizes have diverse effects on human health and climate. However, obtaining a comprehensive understanding of PNSD is challenging due to its inherent complexities and variability. Multi-lognormal distribution models are employed to fit PNSD, as seen in climate models, but discrepancies between model fits and observed PNSD persist. This study adopts hourly data from 2017 to 2020 across eight monitoring sites in diverse environments—rural, urban, mountainous, and polar, and compares the observed PNDS with those simulated by multi-lognormal distribution models. The results demonstrated that the model generally achieved a high correlation with observed PNSD data (r2 > 0.75), effectively capturing key characteristics of nucleation and Aitken mode particles. However, the model had a tendency to overestimate the total number concentration by approximately 1.09 times, particularly noticeable under conditions of high concentrations of smaller particles. The model successfully represented prevalent bimodal size distribution patterns in urban areas with high ultrafine particle concentrations, though its performance was slightly less accurate in scenarios involving trimodal distributions. Despite these strong correlations and the model's ability to reflect diurnal and seasonal variations, which suggests its broad applicability and utility, there were notable limitations on smaller time scales and in specific particle size ranges. These limitations were particularly evident in capturing detailed phenomena relevant to new particle formation events, indicating areas where model refinement is necessary. The results highlighted the importance of investigating discrepancies between model predictions and actual observations, which is crucial for refining climate models that utilize PNDS. The uniform comparison facilitated a detailed exploration of particle properties from model results, offering deeper insights into aerosol behavior and its environmental impacts.

Pharmacokinetics of nano- and microcrystal formulations of low solubility compounds after intramuscular injection to mice.

The aim of this study was to investigate the pharmacokinetics (PK) of poorly soluble compounds when administered intramuscularly (i.m.) as crystalline particles of different sizes. Three uncharged compounds (griseofulvin, AZ'72, and AZ'07) with varying aqueous solubility were dosed to mice at 10 and 50mg/kg as nano- and microparticle formulations. The PK of the compounds was evaluated. The smaller particles of the drugs resulted in higher maximum plasma concentration (Cmax) and area under the plasma concentration-time profile (AUC) at 50mg/kg. There was a dose-proportional increase in AUC but less than dose dose-proportional increase in Cmax. The evaluation at 10mg/kg was more complex as increased exposure for nanoparticles was only observed for griseofulvin which has the highest solubility. In addition, there was an increase in half-life with an increase in dose. This study highlights that general expectations based on in vitro dissolution (i.e. that smaller particles dissolve faster than larger particles when surrounded by liquid) do not always translate to in vivo and demonstrates the importance of understanding the physicochemical properties of the drug, the characteristics of the formulations and the microphysiology at the delivery site.

Study on the hydraulic conveyance characteristics of suspended coarse particles within pipelines

The Flow Regime Transition Device transforms the gelled crude oil mass into gelled crude oil particles for hydraulic conveying. The gelled crude oil particles may reaggregate into gelled crude oil mass at the later stage of hydraulic conveying. Therefore, understanding the patterns of hydraulic suspension conveying gelled crude oil particles is vital for safely gathering and efficiently conveying crude oil. This paper employs the CFD-DEM coupling technique to conduct a numerical study on the hydraulic conveying characteristics of gelled crude oil particles. The accuracy of the model and the solution method is verified by comparing them with the experimental data of particle concentration distribution, and single particle rise behavior, and particle transport flow of gelled crude oil. The size range of gelled crude oil particles spans from 0.0001 m to 0.003 m. We operate the transportation within a velocity range of 0.5 to 4 m/s and a concentration range of 0.022 to 0.0537. Simulation results indicate two flow regimes in the hydraulic conveying of gelled crude oil particles: an upper-moving bed flow and a heterogeneous suspension flow. With increased conveying velocity, the upper moving bed flow gradually transitions to a heterogeneous suspension flow. Beneath the upper moving bed flow, some scattered particles exist, likely resulting from the action of turbulent diffusion. Changes in conveying concentration and particle size have a minor impact on the velocity distribution of particles and fluid but a more significant effect on the particle distribution across the pipe cross-section. Also, when conveying particles of different sizes, most smaller particles travel along the pipe wall.

Effects of Zinc Oxide Particles of Different Sizes, Concentrations, and Exposure Durations on Behavioral Changes of Caenorhabditis elegans and Expressions of cep-1 and pmk-1

Effects of Zinc Oxide Particles of Different Sizes, Concentrations, and Exposure Durations on Behavioral Changes of <i>Caenorhabditis elegans</i> and Expressions of <i>cep-1</i> and <i>pmk-1</i>