Shell Thinning Research Articles

Optimization Design of Submerged-Entry-Nozzle Structure Using NSGA-II Genetic Algorithm in Ultra-Large Beam-Blank Continuous-Casting Molds.

To achieve uniform cooling and effective homogenization control in ultra-large beam-blank molds necessitates the optimization of submerged-entry-nozzle (SEN) structures. This study employed computational fluid dynamic (CFD) modeling to investigate the impact of two-port and three-port SEN configurations on fluid flow characteristics, free-surface velocities, temperature fields, and solidification behaviors. Subsequently, integrating numerical simulations with the non-dominated sorting genetic algorithm II (NSGA-II) and metallurgical quality-control expertise facilitated the multi-objective optimization of a three-port SEN structure suitable for beam-blank molds. The optimized parameters enabled the three-port SEN to deliver molten steel to the meniscus at an appropriate velocity while mitigating harmful effects such as SEN port backflow, excessive surface temperature differences, and shell thickness reduction due to fluid flow. The results indicated that the three-port SEN enhanced the molten-steel flow pattern and mitigated localized shell thinning compared with the two-port SEN. Additionally, the optimized design (op2) of the three-port SEN exhibited reduced boundary layer separation and superior fluid dynamics performance over the initial three-port SEN configuration.

Yolk-shell electron-rich Ru@hollow pyridinic-N-doped carbon nanospheres with tunable shell thickness and ultrahigh surface area for biomass-derived levulinic acid hydrogenation under mild conditions

Aiming to efficiently upgrade renewable biomass-derived levulinic acid (LA) into γ-valerolactone (GVL), we have devised yolk-shell electron-rich Ru@hollow pyridinic-N-doped carbon nanospheres, featuring a tunable shell thickness (20−70 nm) and an ultrahigh surface area (4016 m2 g−1). Experimental and theoretical investigations reveal that the strategic formation of the yolk-shell structure and appropriate thinning of the carbon shell facilitate the generation of electron-rich Ru0 and a positive shift of the d-band center towards the Fermi level by increasing surface pyridinic-N species. These modifications suitably intensify Ru0−H interaction, promote reactant adsorption, stimulate electron transfer between active H and the CO group of LA, and ultimately reduce apparent activation energy. Consequently, a high LA turnover frequency (18733.4 h−1 at 30 °C) and GVL selectivity (99.9%), alongside excellent stability up to eight cycles, are achieved, markedly outperforming externally-supported analogues. These findings afford valuable insights into designing yolk-shell nanostructures for biomass upgrading through microenvironment engineering.

Improved theory of the elastic-plastic response of spherical containment vessels subjected to internal blast loading and its application

Baker built the displacement equations of motion for a thin spherical shell to spherically symmetric internal blast loading, and further provided the analytical solution of the elastic-plastic response under a triangular decaying pressure, neglecting shell thinning and radius variation [1], which was widely used in the fields of analysis and design of explosion containment vessels. However, it appears that some improvements and corrections are needed when we revisit this classic problem. In this paper, the elastic-plastic response of thin spherical shells is investigated mathematically. The complete equations of motion for three models are developed. Then the main ideas of the analytical and numerical methods are presented, as well as some important procedures and results by using Laplace transform techniques, which are convenient to use and generalize. Three typical examples are solved to exhibit differences between our improved theory and Baker’s [1]. Furthermore, our models are employed to gain some insights into response regularities, including the effect of various degrees of strain-hardening on maximum displacements under impulsive loading, and the effect of loading duration on the shell displacement for a perfectly plastic material.

Features of the exogenic development of Passalurus ambiguus (Nematoda, Oxyuroidae) at different temperature regimes

Passalurosis is a prevalent disease among helminthiases of domestic rabbits. This invasion is caused by the nematode Passalurus ambiguus (Nematoda, Oxyuroidae), which is cosmopolitan and localized in the cecum and colon of rabbits. Passalurosis is highly contagious and capable of unlimited spread, due to the biological characteristics of its pathogen, such as the conditions that ensure maximum preservation of parasites at exogenous stages of their development. Experimental research in the laboratory established the timing of development of P. ambiguus eggs isolated from the gonads of female helminths, depending on temperature regimes and features of their growth and development. According to the morphological features of Passalurus eggs, four stages were distinguished in their exogenous development: zygote, cleavage and formation of blastomeres, formation of larvae and motile larvae. Depending on the cultivation temperature, the duration of embryogenesis ranged from 4 to 9 days, and egg viability ranged from 59.3% to 72.7%. The most favourable temperature regime for the development of P. ambiguus eggs was the temperature of 35 °C, at which 72.7% of eggs with motile larvae were formed within 4 days. At this temperature, the zygote stage lasted for 1 day of cultivation, the stage of cleaving and formation of blastomeres occurred on days 1–2, the stage of larval formation on days 1–3, and the stage of formation of motile larva on days 3–4. At lower temperatures, the term of development of Passalurus eggs increased, and the number of viable eggs decreased. At temperatures of 30 °С and 25 °С, the development of Passalurus eggs took place during 5 and 7 days, respectively, and the viability was 66.7% and 62.7%. At these temperatures, the zygote stage lasted 1–2 and 1–3 days, the stage of cleaving and formation of blastomeres occurred on days 1–3 and 1–4, the stage of larval formation lasted from days 2–4 and 2–6, and the stage of formation of motile larvae took place on days 3–5 and 4–7, respectively. The least favourable temperature for the development of P. ambiguus eggs was the temperature of 20 °С, at which the formation of motile larvae occurred in 9 days, and their viability was only 59.3%. At this temperature, the zygote stage lasted 1–4 days, the stage of cleaving and blastomere formation occurred on days 2–6, and the larval formation stage on days 3–8, and the motile larval stage happened on days 5–9. The growth and development of P. ambiguus eggs was accompanied by significant changes in morphometric parameters, such as the increase in egg width and thinning of egg shell at the egg shell plug. The obtained data will allow preventive measures to be effectively implemented on rabbit farms that are susceptible to pinworms, taking into account the terms of exogenous development of pathogens in different seasons.

Additive Effect on the Structure of PEDOT:PSS Dispersions and Its Correlation with the Structure and Morphology of Thin Films.

We reported on the interaction between poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and high-boiling-point additives in PEDOT:PSS aqueous dispersions and in the final polymer films with the aim of stablishing correlations between the structure of both inks and solid thin films. By Small-Angle X-ray Scattering (SAXS) using synchrotron radiation, it was found that the structural changes of dispersions of PEDOT:PSS with high-boiling-point additives can be explained as a two-step mechanism depending on the additive concentration. A compaction of PEDOT:PSS grains was observed at low concentrations while a swelling of the grains together with a phase segregation between PEDOT and PSS segments was evidenced at larger concentrations. Thin films’ morphology and structure were investigated by atomic force microscopy (AFM) and synchrotron Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) respectively. Our two-step model provides an explanation for the small and sharp domains of PEDOT:PSS thin films observed for low-additive concentrations (first step) and larger domains and roughness found for higher-additive concentrations (second step). A reduction of the ratio of PSS in PEDOT:PSS thin films upon the presence of additives was also observed. This can be related to a thinning of the PSS shells of PEDOT:PSS grains in the dispersion. The results discussed in this work provide the basis for a controlled tuning of PEDOT:PSS thin films structure and the subsequent electrical properties.

EXPERIMENTAL STUDY OF THE INTERACTION OF CORROSION DAMAGE AND OUT-OF-CIRCULARITY IN THE COLLAPSE OF SUBMARINE PRESSURE HULLS


 
 
 The effect of corrosion damage on overall collapse strength of submarine pressure hulls was studied experimentally. Ring-stiffened cylinders were machined from aluminium tubing and loaded to collapse under external pressure. In selected specimens, some of the outer shell material was machined away in large single patches, representing general corrosion. Other specimens had many smaller patches, representing corrosion pitting from the outside of the hull, followed by grinding. Large-amplitude out-of-circularity (OOC) was introduced by mechanically deforming selected cylinders. Clusters of artificial corrosion pits were found to have approximately the same effect on collapse pressure as equal-depth general corrosion covering the same region of plating. General corrosion was found to be most severe when it was “in-phase” with OOC, since, during pressure loading, high compressive stresses resulting from corrosion were compounded by compressive bending stresses associated with OOC, and furthermore, the corrosion tended to increase the geometric imperfection itself. On the other hand, out-of-phase corrosion reduced the effect of OOC, while at the same time the thinning-associated compressive stresses were counteracted by local tensile bending stresses associated with OOC, so that strength reductions were correspondingly smaller. Overall collapse pressures for corroded specimens were reduced by, on average, 0.85% for each 1% of shell thinning. That result is based on a linear approximation of the nonlinear relationship between thinning and collapse pressure. The linear trend-line, which was used to account for the experimental scatter, is based on specimens with 13 to 27% shell thinning, and with a variety of corrosion areas and OOC amplitudes.
 
 

Shell Measurements and Mold Thermal Mapping Approach to Characterize Steel Shell Formation in Peritectic Grade Steels

Herein, the prospects of detecting peritectic behavior in carbon steels (Fe–C) using solidified shell thickness measurements and real‐time mold thermal maps are investigated. Irregular steel shell thickness and localized shell thinning are negative conditions associated with the peritectic transformation in many steel grades. Detailed three dimensional (3D) thickness maps are generated to directly contrast peritectic from nonperitectic solidification features using a laboratory dip test. Characterization of the steel shell also includes measurement of 3D shell surface deviations from a nominally flat surface. The unevenness parameter, which is calculated using the coefficient of variation in shell thickness as a function of the carbon content in the steel, clearly peaks around 0.14%C. A distributed fiber‐optic sensor, embedded 1 mm from the working face of a 100 × 55 × 12 mm3 thick copper chill block, has been used to obtain real‐time mold thermal maps of the solidification event during immersion of the block into molten steel. A programmable drive is used to control the motion of the chill block during immersion into a steel bath to minimize variability in immersion speed, position, and time. The thermal mapping measurements are well correlated with the shell profile measurements.

Tannic Acid-Stabilized Self-Degrading Temperature-Sensitive Poly(2-n-propyl-2-oxazoline)/Gellan Gum Capsules for Lipase Delivery.

In recent years, stable hydrogen-bonded stimuli-responsive polymer capsules have been receiving great interest for the encapsulation and release of sensitive molecules such as lipase enzymes. Compartmental capsules having a liquid gel core stabilized with temperature-responsive hydrogen-bonded multilayers are advantageous over other conventional systems because of their ability to maintain hydrophilic lipase and other hydrophobic compounds in compatible protected molecular vehicle environments and prolong their native properties, e.g., in the body. In this work, we report a methodology to stabilize an aqueous liquid gellan gum (GG) core in a capsule using neutral and nontoxic building blocks, namely, poly(2-n-propyl-2-oxazoline) (PnPrOx) and tannic acid (TA), to fabricate temperature-responsive capsules, comprising both lipase and hydrophobic oil droplets. The capsules were fabricated by adding GG droplets to a PnPrOx suspension at a temperature (T) higher than its cloud point temperature (TCP). Notably, the formed capsules were not stable in water without TA stabilization via hydrogen bonding. Scanning electron microscopy (SEM) investigations of the GG/building block interphase revealed that the collapsed PnPrOx globules that are present above the TCP stabilized the GG interphase as a Pickering emulsion, while undergoing a configurational transformation into its linear form by interacting with TA in the next step of capsule formation resulting in a smooth PnPrOx/TA capsule wall. The encapsulation efficiencies of the capsules for model fluorescent molecules were found to be 52, 54, and 24% for FITC-dextran, rhodamine, and Nile red, respectively. The stability experiments exhibited swelling and shell thinning at certain locations followed by complete rupture of the capsules at 37 °C, while the capsules were stable for several weeks at temperatures below the TCP of PnPrOx. The capsules were found to be stable in stimulated gastric fluid (SGF) for several hours at 37 °C while successfully releasing the encapsulated lipase and Nile red (model hydrophobic compound) in stimulated intestinal fluid (SIF). The released lipase was found to retain almost 100% of its activity. The reported capsules have high potential for use as carriers for encapsulation and release of a variety of payloads ranging from proteins and vitamin supplements to enzymes and probiotics through the oral route of administration.

Otoconia Structure After Short- and Long-Duration Exposure to Altered Gravity.

Vertebrates use weight-lending otoconia in the inner ear otolith organs to enable detection of their translation during self or imposed movements and a change in their orientation with respect to gravity. In spaceflight, otoconia are near weightless. It has been hypothesized that otoconia undergo structural remodeling after exposure to weightlessness to restore normal sensation. A structural remodeling is reasoned to occur for hypergravity but in the opposite sense. We explored these hypotheses in several strains of mice within a Biospecimen Sharing Program in separate space- and ground-based projects. Mice were housed 90days on the International Space Station, 13days on two Shuttle Orbiter missions, or exposed to 90days of hindlimb unloading or net 2.38g via centrifugation. Corresponding flight habitat and standard cage vivarium controls were used. Utricular otoliths were visually analyzed using scanning electron microscopy and in selected samples before and after focused ion beam (FIB) milling. Results suggest a possible mass addition to the otoconia outer shell might occur after exposure to longer-duration spaceflight, but not short ones or hindlimb unloading. A destructive process is clearly seen after centrifugation: an ablation or thinning of the outer shell and cavitation of the inner core. This study provides a purely descriptive account of otoconia remodeling after exposures to altered gravity. The mechanism(s) underlying these processes must be identified and quantitatively validated to develop countermeasures to altered gravity levels during exploration missions.

A Protein Assembly Hypothesis for Population-Specific Decrease in Dementia with Time

A recent report in the journal, Neurology, documents age-normalized, nation-specific (e.g., United States and Western Europe), progressive decrease of dementia, beginning about 25 years ago. This observation has, thus far, not had explanation. We begin our proposed explanation with the following previous disease construct. (1) Some dementia is caused by innate immune over-response to infections. (2) The innate immune over-response occurs via excessive conversion of amyloid protein to α-sheet conformation. (3) This conversion evolved to inhibit invading microbes by binding microbe-associated α-sheet, e.g., in hyper-expanded capsid intermediates of some viruses. The rarity of human α-sheet makes this inhibition specific for microbial invaders. As foundation, here we observe directly, for the first time, extreme, sheet-like outer shell thinness in a hyper-expanded capsid of phage T3. Based on phage/herpesvirus homology, we propose the following. The above decrease in dementia is caused by varicella-zoster virus (VZV) vaccination, USFDA-approved about 25 years ago; VZV is a herpesvirus and causes chickenpox and shingles. In China and Japan, a cotemporaneous non-decrease is explained by lower anti-VZV vaccination. Co-assembly extension of α-sheet is relatively independent of amino acid sequence. Thus, we project that additional dementia is suppressible by vaccination against other viruses, including other herpesviruses.

2D PIV study of flow accelerated corrosion downstream a typical industrial gate valve

A critical degradation mechanism of piping systems in either nuclear power plant is Flow Accelerated Corrosion (FAC), which causes wall thinning of pipes and component shells from inside. The valves which are frequently used in power plant piping systems are mostly subjected to FAC. A Gate vale in the feed water piping system of a typical nuclear power plant that it’s downstream had been damaged due to the FAC was considered as a reference. In this study the effect of the mean flow velocity and the opening percentage of gate valve on the flow field downstream the valve was investigated by using 2D PIV. The locus where flow turbulences happen downstream the gate valve was determined by 2D PIV. It is found that there is a very good coincidence between the locus in which the maximum wall thinning measured by Ultrasonic Technique (UT) and that the flow turbulences happen downstream the gate valve determined by 2D PIV.It is observed that the locus of flow turbulences and intense velocity gradients is in the upper part of the pipe and over the domain of 0.2 <L/D < 2.4 along the pipe downstream the gate valves where the minimum wall thickness was measured by using UT. Flow turbulences and velocity gradients near the upper pipe wall result in higher wall shear stress and maximize the mass transfer from the pipe inner wall in turn result in wall thinning. The results of this paper can be useful for optimizing inspection plans in identifying and predicting the vulnerable FAC locations downstream the gate valves.

Numerical analysis of local heat flux and thin-slab solidification in a CSP funnel-type mold with electromagnetic braking

In this article, based on the actual monitored temperature data from mold copper plate with a dense thermocouple layout and the measured magnetic flux density values in a CSP thin-slab mold, the local heat flux and thin-slab solidification features in the funnel-type mold with electromagnetic braking are analyzed. The differences of local heat flux, fluid flow and solidified shell growth features between two steel grades of Q235B with carbon content of 0.19%C and DC01 of 0.03%C under varying operation conditions are discussed. The results show the maximum transverse local heat flux is near the meniscus region of over 0.3 m away from the center of the wide face, which corresponds to the upper flow circulation and the large turbulent kinetic energy in a CSP funnel-type mold. The increased slab width and low casting speed can reduce the fluctuation of the transverse local heat flux near the meniscus. There is a decreased transverse local heat flux in the center of the wide face after the solidified shell is pulled through the transition zone from the funnel-curve to the parallel-cure zone. In order to achieve similar metallurgical effects, the braking strength should increase with the increase of casting speed and slab width. Using the strong EMBr field in a lower casting speed might reverse the desired effects. There exist some differences of solidified shell thinning features for different steel grades in the range of the funnel opening region under the measured operating conditions, which may affect the optimization of the casting process in a CSP caster.

Solidifying shell waviness during continuous casting of AHSS slabs

Transverse cracking of continuously cast products has been encountered at almost every caster operation. Enormous efforts have been carried out in the past aiming at identifying the cause and reducing the problem, especially on steel grades with peritectic chemistries. So far, however, there is still no cost-effective solution with good trade-off for internal quality and productivity. In this study, a new cracking formation mechanism is proposed based on observations of equally spaced crack pattern and the undulation (shell thinning pattern) observed on the inside and/or outside (surface depression) of the breakout shell with similar spacing. This wavy solidification shell forms at initial solidification stage and induces the local shell thinning and reheating which in turn causes the local “Blown grains” inside the solidification shell. As observed on slab surfaces, these blown grains are closely related to transverse cracking problem.

Tidal dissipation in Enceladus' uneven, fractured ice shell

Analysis of Enceladus' gravity, topography and libration data suggests that the thickness of the ice crust significantly varies, which may have important consequences for the heat transfer across and the tidal dissipation within the ice shell. Understanding these processes is a critical prerequisite for analyzing Enceladus' thermal evolution and assessing the long-term stability of its subsurface ocean. Here, we investigate the impact of ice shell thickness variations on the tidal deformation of the moon and the associated heat production using a finite-element model that includes faults (“tiger stripes”) in the south polar region (SPR). Since the tidal deformation and the thermal structure of the ice shell are coupled through temperature and deviatoric stress, we simultaneously solve the equations governing the anelastic deformation of ice and also equations which model conductive heat transfer in the ice shell. We find that tidal heating is concentrated in a narrow low viscosity zone near the base of the ice shell and along faults. Outside the SPR, the thickness of this zone is about 1/10 of the local ice thickness and the associated volumetric heating is ≲10−6 W/m3, corresponding to less than 1 GW of dissipated power. In the SPR, the tidal effects are enhanced by the combined action of faults and ice shell thinning. Although the volumetric heating in this relatively small region may be larger than 10−4 W/m3, the total heat production in this region does not exceed 1.1 GW. Our computations show that tidal heating in the ice shell can explain only a small fraction of Enceladus' heat production derived from astrometric observations, implying that Enceladus' heat engine is powered by dissipation in the core or in the ocean.

Implications of nonsynchronous rotation on the deformational history and ice shell properties in the south polar terrain of Enceladus

Numerous studies of the south polar region of Saturn's moon Enceladus have focused on the four main fractures (the tiger stripes), their associated water plume, and the effects of diurnal tidal stresses on these fractures. However, due to their small magnitude (10–100 kPa), diurnal stresses alone are unable to completely explain the initial formation of the tiger stripes and the many additional fractures in the region. We suggest nonsynchronous rotation (NSR) stresses, induced by a freely rotating ice shell over a global ocean, are large enough to overcome the tensile strength of the ice shell and initiate fracturing on Enceladus. Using the tidal stress calculation program SatStressGUI, we demonstrate the dependence of the magnitude of the NSR stress on the thickness of the ice shell, particularly the brittle outer layer of the ice shell. We suggest the brittle layer in the south polar region is 2–4 km thick whereas in the more northern regions, it is 6–8 km. The difference is most likely due to the elevated energy flux at the south pole, compared to the regions to the north, resulting in a warmer and thinner ice shell in the south polar region. The thinner ice around the south pole permits NSR tensile stresses of ∼5 MPa, enough to fracture the ice. However, the thicker ice to the north reduces the NSR stress to less than 2 MPa making fracturing less likely. The difference in ice shell thickness, and resultant NSR stress, can help explain the activity in the south, but relative quiescence in the north. Our modeled NSR stress magnitudes and orientations suggests a NSR period on the order of 1 Myr and advocate that the tiger stripes have rotated ∼45° clockwise about the south pole since their initial formation in response to NSR of the ice shell. If the ice shell is rotating at a constant rate, the tiger stripes would thus be up to ∼100,000 years old. An apparent decreasing angular separation between consecutive fracture sets that formed in the south polar region suggests an ice shell that has weakened in strength over the course of its recent geologic history; this could be a result of increased heating, thinning of the ice shell, or a combination of the two. As the ice shell thinned, the NSR stresses were enhanced, making fracturing more likely after a smaller amount of NSR compared to the previous fracturing episode.

Raptors are still affected by environmental pollutants: Greenlandic Peregrines will not have normal eggshell thickness until 2034

Abstract The DDT-induced effects, eggshell thinning and breeding failure in Peregrine Falcon (Falco peregrinus) populations were reverted with restrictions on the use of the compound from the 1970s, and in most studied populations, the eggshell thickness is back to normal. In Greenland, a previous study of eggshell thinning in Peregrines found that shells had not yet reached pre-DDT levels. In this study, we extend the time series and reinterpret shell thinning data for 196 clutches covering a 45-year time span (1972–2017). There was a significant (P&lt;0.001) increase in the eggshell thickness of 0.23% per year. This corresponds to a change in eggshell thinning from 14.5% to 5.4% in 2017 compared to the pre-DDT mean. With the current rate of change, pre-DDT shell thickness is predicted to be reached around the year 2034. However, a few clutches are still below the critical limit. The relatively slower recovery of the shell thickness in the Greenland population is likely indicative of the slower phasing out of DDT in the Greenlandic Peregrines’ wintering grounds in Latin America. The shell thinning in the Greenlandic population probably never crossed the 17% threshold associated with population declines, contrary to the populations in many other parts of the world.

Dynamics of deformation and pinch-off of a migrating compound droplet in a tube

A computational fluid dynamic investigation has been carried out to study the dynamics of a moving compound droplet inside a tube. The motions associated with such a droplet is uncovered by solving the axisymmetric Navier-Stokes equations in which the spatiotemporal evolution of a pair of twin-deformable interfaces has been tracked employing the volume-of-fluid approach. The deformations at the interfaces and their subsequent dynamics are found to be stimulated by the subtle interplay between the capillary and viscous forces. The simulations uncover that when a compound drop composed of concentric inner and outer interfaces migrates inside a tube, initially in the unsteady domain of evolution, the inner drop shifts away from the concentric position to reach a morphology of constant eccentricity at the steady state. The coupled motions of the droplets in the unsteady regime causes a continuous deformation of the inner and outer interfaces to obtain a configuration with a (an) prolate (oblate) shaped outer (inner) interface. The magnitudes of capillary number and viscosity ratio are found to have significant influence on the temporal evolution of the interfacial deformations as well as the eccentricity of the droplets. Further, the simulations uncover that, following the asymmetric deformation of the interfaces, the migrating compound droplet can undergo an uncommon breakup stimulated by a rather irregular pinch-off of the outer shell. The breakup is found to initiate with the thinning of the outer shell followed by the pinch-off. Interestingly, the kinetics of the thinning of outer shell is found to follow two distinct power-law regimes-a swiftly thinning stage at the onset followed by a rate limiting stage before pinch-off, which eventually leads to the uncommon breakup of the migrating compound droplets.

Assessing multigenerational effects of prednisolone to the freshwater snail, Physa acuta (Gastropoda: Physidae)

Prednisolone (PDS), a potent synthetic glucocorticoid is widely prescribed for its exceptional anti-inflammatory properties. Several studies have detected the environmental presence of PDS in water bodies which has led to an ecological concern for its toxicity to non-target aquatic biota. The present study investigated the effects of exposure to PDS on different life-cycle stages and generations of the freshwater snail, Physa acuta. This continuous exposure over a period of multiple generations resulted in generational impairments at measured endpoints. LOEC values (p<0.001) for PDS exposure ranged from 32 to 4μg/L in exposed F0-F2 generations. Global DNA methylation (% 5-methyl cytosine) of adult progeny was found to be affected at higher test concentrations in comparison to the parent snails. Partially formed to completely missed growth components of shell structure and shell thinning in abnormally underdeveloped PDS exposed snails of F1 and F2 generation, was also observed in this multigenerational exposure experiment. The multigenerational study confirmed P. acuta as a promising bioindicator since critical effects of the long term glucocorticoid exposure opens up the way for further investigations on transgenerational toxicity in environmental toxicology and risk assessment and to monitor glucocorticoid pollution in aqueous ecosystem.

The Effects of a Submerged Entry Nozzle on Flow and Initial Solidification in a Continuous Casting Bloom Mold with Electromagnetic Stirring

The melt flow, level fluctuation, temperature field, and solidification behavior coupled with electromagnetic stirring (EMS) effects in the continuous casting mold region of U71Mn steel bloom were numerically analyzed by commercial computational fluid dynamics (CFD) software named ANSYS FLUENT. The effects of submerged entry nozzle (SEN) structures and the installation methods for optimized four-port SEN on the flow pattern, level fluctuation, heat transfer and initial solidification behavior in a bloom mold loaded with EMS were investigated. The aim is to propose a better SEN condition for the big bloom casting of high railway steel. The water simulation experiments were conducted to show the flow characteristics under different SEN conditions and verify the numerical model of flow pattern. The experimental and numerical simulation results showed that the optimized four-port SEN with diagonal installation cannot only improve the flow pattern of the molten steel by alleviating the level fluctuation and reducing the impact pressure to the wall. It is also beneficial for temperature variation at both bloom surface and corner, as well as the local solidified shell thinning phenomena due to the elimination of impingement effect.

Presence of persistent organic pollutants in a breeding common tern (Sterna hirundo) population in Ireland.

Persistent organic pollutants (POPs) are chemical compounds of environmental concern due to their toxic, persistent nature and their ability to bio-accumulate in biological tissue. Seabirds, for often being at the top of the food web, have been used as monitors of environmental pollutants. Adverse effects caused by POPs have been reported in common terns (Sterna hirundo) since the 1970s. Egg shell thinning, embryo and hatchling deformities have been reported for this species. Environmental legislation, such as the Oslo-Paris Convention (OSPAR), has agreed on the monitoring of concentration of POPs in common terns. This study set out to investigate contemporary concentrations of polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and brominated flame retardants (BFRs) in common terns breeding in Ireland, along with congener profiles. Investigation was conducted in live (n=15) and dead birds (n=20) to test for the efficiency of different methodologies using preen oil and feathers versus liver and preen gland. Mean concentrations of POPs followed the order: PCB (36.48ng/g ww feather) > PAH (30.01ng/g ww feather) > OCP (13.36ng/g ww feather) > BFR (1.98ng/g ww feather) in live birds; and PAH (46.65ng/g ww preen gland) > PCB (44.11ng/g ww preen gland) > OCP (15.15ng/g ww liver) > BFR (5.07ng/g ww liver) in dead birds. Comparison of contaminant results with toxicity pre-established levels concluded that this population of common terns in Ireland is not at risk of anomalies caused by POPs. However, some levels are higher in comparison to the ones established by OSPAR's EcoQO and must be monitored periodically.