Shell Features Research Articles

Free vibration and nonlinear transient analysis of functionally graded graphene origami-enabled auxetic metamaterial cylindrical shells: Analytical and artificial neural network approaches

This study examines the free vibration and nonlinear transient response of functionally graded graphene origami-enabled auxetic metamaterial (GOEAM) cylindrical shells under thermal conditions. The multilayered shells feature GOri distributions across their thickness, introducing distinct auxetic and thermal properties. Material properties are modeled using micromechanical models optimized via genetic programming. Employing Reddy’s third-order shear deformation theory and von Kármán’s nonlinear geometric assumptions, nonlinear kinematic relationships are formulated and solved using Galerkin method. A novel contribution is the analysis of Winkler-Pasternak elastic foundations in two configurations: centrally distributed along the shell length and concentrated at both ends. Foundation effects are quantified by integrating stiffness coefficients across contact areas, offering insights into foundation-shell interactions. Artificial Neural Networks (ANNs) are developed to predict natural frequencies with high accuracy. Trained using the Levenberg-Marquardt algorithm and tan-sigmoid transfer function, these models demonstrate robust performance through metrics like validation performance plots, regression analysis, and error histograms. Validation against literature confirms the reliability of both ANN and analytical approaches. Key findings reveal that increased GOri folding enhances the negative Poisson’s ratio but reduces Young’s modulus, decreasing shell stiffness, natural frequencies, and increasing vibration amplitudes. Additionally, centrally concentrated elastic foundations yield higher natural frequencies and smaller vibration amplitudes compared to foundations distributed at the shell ends. By integrating advanced analytical techniques with state-of-the-art ANN modeling, this study not only provides a comprehensive understanding of the dynamic behavior of FG-GOEAM cylindrical shells but also offers valuable insights for the design, optimization, and application of auxetic metamaterial structures in thermal environments.

A positionally stable anatomic smooth breast implant

The voluntary recall of textured breast implants due to their association with breast implant-associated anaplastic large cell lymphoma has resulted in the loss of the primary advantage of the textured surface: positional stability. We have engineered a novel soft gel-filled smooth implant with a surface that promotes positional stability without texture, known as the positionally stable smooth implant (PSSI). Miniature anatomically shaped breast implant shells were fabricated from polydimethylsiloxane using 3D-printed molds. The implant shell design incorporates cylindrical wells 1-4 mm in diameter. Implants were filled with commercial breast implant-derived silicone gel. Smooth and textured implants were also fabricated, serving as controls. Six implants per group were implanted subcutaneously into the bilateral rat dorsum. Rotation was measured every 2 weeks for a total of 12 weeks to assess stability. Animals were sacrificed at 4 and 12 weeks, and implant-capsule units were explanted for histological and Micro-computed tomography (MicroCT) analyzes. Four weeks after implantation, PSSI conditions showed tissue ingrowth and conformation to well dimensions, as assessed by histological staining and MicroCT imaging. Twelve weeks post implantation, textured implants and PSSI conditions with larger widths, depths, and well number demonstrated statistically significant increased stability compared to smooth implants (p< 0.05). Tissue ingrowth into shell features occurred by 4 weeks and remained throughout longer time points. No significant differences were found in capsule thickness or collagen content between groups. These results suggest a promising alternative to textured surfaces for inducing implant positional stability.

Uncovering tidal treasures: automated classification of faint tidal features in DECaLS data

ABSTRACT Tidal features are a key observable prediction of the hierarchical model of galaxy formation and contain a wealth of information about the properties and history of a galaxy. Modern wide-field surveys such as LSST and Euclid will revolutionize the study of tidal features. However, the volume of data will prohibit visual inspection to identify features, thereby motivating a need to develop automated detection methods. This paper presents a visual classification of ∼2000 galaxies from the DECaLS survey into different tidal feature categories: arms, streams, shells, and diffuse. We trained a convolutional neural network (CNN) to reproduce the assigned visual classifications using these labels. Evaluated on a testing set where galaxies with tidal features were outnumbered $\sim 1:10$, our network performed very well and retrieved a median $98.7\pm 0.3$, $99.1\pm 0.5$, $97.0\pm 0.8$, and $99.4^{+0.2}_{-0.6}$ per cent of the actual instances of arm, stream, shell, and diffuse features respectively for just 20 per cent contamination. A modified version that identified galaxies with any feature against those without achieved scores of $0.981^{+0.001}_{-0.003}$, $0.834^{+0.014}_{-0.026}$, $0.974^{+0.008}_{-0.004}$, and $0.900^{+0.073}_{-0.015}$ for the accuracy, precision, recall, and F1 metrics, respectively. We used a gradient-weighted class activation mapping analysis to highlight important regions on images for a given classification to verify the network was classifying the galaxies correctly. This is the first demonstration of using CNNs to classify tidal features into sub-categories, and it will pave the way for the identification of different categories of tidal features in the vast samples of galaxies that forthcoming wide-field surveys will deliver.

Antioxidant Performance in the Shell Is Substantially Modified by Season and Locality in Hazelnut Cultivars

Hazelnut (Corylus avellana L.) is of great agroeconomic importance, prized for its nutritional value and antioxidant properties. Its yield and quality may differ due to factors such as season (S), locality (L) and cultivar (C). Our objective was to determine the adaptive behavior of morphological features and antioxidant properties in nuts of the Barcelona and Tonda di Giffoni (TDG) cultivars planted at two localities (Cunco and Perquenco) during three productive seasons (S1, S2 and S3). Barcelona grown in Perquenco in S1 and S3 (less precipitation, more solar radiation) performed better than in Cunco with respect to most morphological nut, kernel and shell features, and the same parameters generally had the same trends for TDG in S2 and S3. Among the seasons at the same localities, the differences between the predominant condition defects for both cultivars were in the decreasing order wrinkled/deformed kernels, double kernels, blank and mold kernels, with about 75% of hazelnuts without defects. In both cultivars, the shell had higher antioxidant properties that increased in S1 and S3 at both localities and were consistently higher than in the kernels. Lipid peroxidation was higher in the kernel than shell in both cultivars and localities for S1 and S3. The results of this study suggest that the different hazelnut cultivar features including physical and chemical components depend on season and locality, which offers important clues for all those interested in the hazelnut industry.

Next step in Monachacantiana (Montagu, 1803) phylogeography: northern French and Dutch populations (Eupulmonata, Stylommatophora, Hygromiidae).

Features of shell and genitalia as well as nucleotide sequences of selected mitochondrial and nuclear genes of specimens of Monachacantiana from ten northern French and two Dutch populations were compared with the same features of British and Italian populations. They were found to be very similar to populations previously identified as belonging to the CAN-1 lineage of M.cantiana. This confirms previous suggestions that M.cantiana was introduced to western Europe (England, France and the Netherlands) in historical times.

PRODUCTION AND RESEARCH OF SORBENTS FROM FOOD PLANT WASTES FOR WATER PURIFICATION

The article describes the results of research on production of modified types of sorbents based on waste food plants and the possibility of drinking water purification from Ca2+ and Mg2+ ions. Sunflower and buckwheat wastes widely spread in the East Kazakhstan region were selected for production of modified sorbent. Structural features of sunflower and buckwheat shells were studied. It was found that samples of the initial form of buckwheat and sunflower, washed with distilled water, consist of very dense and small micropores. It was found that the surface of the sorbents particles is changed by washing with alcohol solution, with pores and hillocks appearing on the surface of sunflower husk particles. In acid-base-treated sorbents, an increase in the number of macropores and a change in the general morphological structure are observed. As a result of defining the sorption capacity of sorbents produced by acid-alkaline activation, it is on average 0.06 mg/g in iodine and 1.3 mg/g in methylene blue higher than that of medical activated carbon. The results of materials sorption capacity study produced from sunflower husk, sequentially treated with 8.2% hydrochloric acid solution and 16,5% sodium hydroxide solution, indicated effect respect to Ca2+ and Mg2+ ions showed a high purification effect of 98.7% and 95.8%, respectively. The above-mentioned modified sorbent is proposed as a sorption material in the production of filters for drinking water purification.

Overlooked shell features: asymmetrical columellar folds in volutid gastropods

ABSTRACT Many gastropods have columellar folds, defined as continuous spiral ridges extending from the aperture to the shell interior on the adaxial side of the aperture. Despite their ubiquity, columellar folds have received little phylogenetic or functional study. In the vast majority of cases, columellar folds have a symmetrical profile, with the anterior (abapical) slope similar to the posterior (adapical) slope. Here I draw attention to the highly unusual phenomenon of asymmetry of columellar folds, where the anterior slope is markedly less inclined than the posterior slope of each fold. I have detected this condition in the volutid genera Scaphella Swainson, 1832; Cymbiola Swainson, 1831 and Lyrischapa Aldrich, 1911; as well as in the Palaeocene and Eocene genus Eovasum Douvillé, 1920. Following a review of Lyrischapa and Eovasum, I suggest that these two genera are closely related members of the volutid subfamily Indovolutinae, and that asymmetrical columellar folds have evolved three times in Volutidae. Although their function remains elusive, asymmetrical folds might prevent abapical displacement of the soft parts during rapid extension of the foot or feeding organs.

Development of Skin and Dermal Bone of the Shell in &lt;i&gt;Pelodiscus maackii&lt;/i&gt; (Testudines: Trionychidae)

The article is devoted to the study of the ontogenetic development of the skin and the structure of the skin-bone shell of the trionychid turtle Pelodiscus maackii (Brandt, 1858). The process of formation of the epidermis and dermis, as well as their derivatives (epidermal scales and dermal ossifications), is described. The development of epidermal scales in Pelodiscus maackii has been shown to be similar to the development of asymmetric scales in other reptiles. Five stages of formation of the definitive structure of the dermal bones have been identified. Structural differences between the internal and external parts of the bony plates (rod-shaped elements and bony callosities) are due to the previous stratification of the dermis into histologically distinct strata: hypodermal, fibrous and papillary. In particular, the fibrous stratum, consisting of several layers of orthogonally oriented collagen bundles, is a precursor to the plywood-like structure of the trionychid bony plates. The growth of bone tissue around the vascular network in the papillary layer is the reason for the formation of surface ornamentation of the trionychid callosities. Some questions of the evolutionary significance of the unique features of the trionychid shell are discussed.

Formation of misoriented blocks during single-crystal CVD diamond growth

This paper presents the results of a CVD diamond crystal growth experiment on an HPHT type IIa substrate (9 × 9 mm). Data acquired through cathodoluminescence and EBSD methods shed light on the aspects of the formation of a polycrystalline shell around a single crystal of CVD diamond. CVD diamond exhibits orientation features of the polycrystalline shell, microblocks, low-angle boundaries, and linear hexagonal macrostructures of dislocation origin. Crystal splitting occurs when the dislocation density increases from the geometric center to the periphery. Such CVD diamonds exhibit a continuous transition from single crystal to polycrystal through a block-type crystal.

Evaluation of the Antiviral Activity of Drugs from the Group of Polymer Electrolyte Derivatives against a Wide Range of Viruses

Background. The modern healthcare system is constantly improving and introducing new measures to protect the population from viral diseases, but the experience of the COVID-19 pandemic has shown that infections cannot always be controlled on global scale. In this regard, the development of new broad-spectrum antiviral drugs is more relevant than ever.The aim of the study was to investigate the antiviral activity and cytotoxicity of copolymers of sodium styrene sulfonate and vinyl monomers of various chemical structures, as well as to identify promising polymers for the development of new antiviral agents.Materials and methods. 14 copolymers of sodium styrene sulfonate (NaSS) with various functional comonomers were synthesized. Three viruses with different reproduction strategies and transmission methods — respiratory syncytial virus, influenza virus, and herpes virus — were selected for the assessment of antiviral activity.Results. The screening identified copolymers that showed high activity against all three viruses. It was found that the introduction of various functional groups into the structure of NaSS did not decrease antiviral activity, but significantly reduced cytotoxicity. The molecular weight has also shown a noticeable effect on the activity. Different sensitivity of viruses and cells to the studied polymers was revealed, likely due to the structural features of the virus shell and cell wall.Conclusions. The results demonstrate the potential of sodium styrene sulfonate copolymers as a model for developing a broad-spectrum antiviral drug.

Free vibration analysis of barrel-shaped sandwich shells with auxetic honeycomb core using modified thick shell theory

Modern engineering extensively employs complexly curved shell structures, presenting mathematical challenges in analyzing their mechanical behavior due to geometric intricacies. The recent trend of incorporating advanced lightweight materials into these structures drives the need to develop improved theories and methods. This study presents an investigation into the free vibration analysis of barrel-shaped sandwich (BSS) shells using a modified thick shell theory (MTST). These sandwich shells feature functionally graded (FG) ceramic-metal layers on both inner and outer surfaces, with a lightweight honeycomb core. Notably, the honeycomb layer's thickness surpasses that of the inner and outer layers, necessitating the application of thick shell theory for accurate analysis. However, previous studies have often used classical theories for thin shells, and those applying thick shell theory sometimes neglected the curvature effects in the fundamental equations and rotary inertia components. Thus, this research employs the MTST to overcome these limitations. The study includes comparative validations and explores the impact of material parameters and curvature radii on the natural frequencies of these barrel-shaped sandwich shells through numerical examples.

La2O3-carbon composite with core–shell structure and features of its gas-phase oxidation

The synthesis of new carbon nanoflake (CNF)-supported composites with a La2O3/CNFs@C core–shell structure is described. The carbon surface is functionalized by oxidation with nitric acid vapor for 1, 3, or 6 h. The evolutions of the structure and composition are investigated by transmission electron microscopy and X-ray photoelectron spectroscopy.

Tailoring the pore structure of iron oxide core@stellate mesoporous silica shell nanocomposites: effects on MRI and magnetic hyperthermia properties and applicability to anti-cancer therapies.

Core-shell nanocomposites made of iron oxide core (IO NPs) coated with mesoporous silica (MS) shells are promising theranostic agents. While the core is being used as an efficient heating nanoagent under alternating magnetic field (AMF) and near infra-red (NIR) light and as a suitable contrast agent for magnetic resonance imaging (MRI), the MS shell is particularly relevant to ensure colloidal stability in a biological buffer and to transport a variety of therapeutics. However, a major challenge with such inorganic nanostructures is the design of adjustable silica structures, especially with tunable large pores which would be useful, for instance, for the delivery of large therapeutic biomolecule loading and further sustained release. Furthermore, the effect of tailoring a porous silica structure on the magneto- or photothermal dissipation still remains poorly investigated. In this work, we undertake an in-depth investigation of the growth of stellate mesoporous silica (STMS) shells around IO NPs cores and of their micro/mesoporous features respectively through time-lapse and in situ liquid phase transmission electron microscopy (LPTEM) and detailed nitrogen isotherm adsorption studies. We found here that the STMS shell features (thickness, pore size, surface area) can be finely tuned by simply controlling the sol-gel reaction time, affording a novel range of IO@STMS core@shell NPs. Finally, regarding the responses under alternating magnetic fields and NIR light which are evaluated as a function of the silica structure, IO@STMS NPs having a tunable silica shell structure are shown to be efficient as T2-weighted MRI agents and as heating agents for magneto- and photoinduced hyperthermia. Furthermore, such IO@STMS are found to display anti-cancer effects in pancreatic cancer cells under magnetic fields (both alternating and rotating).

Cobalt nanoparticles confined in silica networks with 3D hierarchical porous features for Fischer-Tropsch synthesis.

Silica network-encapsulated cobalt nanoparticles with an adjustable pore structure as model Fischer-Tropsch synthesis catalysts were successfully prepared. The well-developed shell pore structure of the core-shell catalyst is of great importance for reducing the selectivity of methane, increasing the selectivity of heavy hydrocarbons, and the probability of carbon chain growth. Benefiting from its uniform distribution of cobalt particles and 3D open hierarchical porous shell features, Co@H-mSiO2 catalysts exhibited excellent stability and activity, achieving up to 61.4% selectivity of C5-C20 hydrocarbon products at 6 SL h-1 g-1, 220 °C and 1.0 MPa.

Possibility of stable thin-shell around wormholes within string cloud and quintessential field via the van der Waals and polytropic EOS

In this work, we present the Einstein field equations (EFE) in the framework of a modified matter source and thus find out the solutions for the Wormhole. To obtain characteristic solutions set, we employ two kinds of equations of states (EOS), i.e., the van der Waals and polytropic EOS to the EFE. We adopt embedding class as a general technique for the system and discuss several physical attributes of the stellar system under embedded wormhole solutions. Detailed discussion about the matter contents of the thin-shell developed around the obtained wormhole solutions in the background of Schwarzschild BH surrounded by cloud and quintessence-type fluid distribution by using a well-known cut and paste approach. We have also performed stability analysis using the linearized radial perturbation method for the van der Waals EOS and polytropic EOS. Several interesting points have evolved from the entire investigation along with the features of the thin shell around the wormhole. It is interesting to mention that the van der Walls equation of state plays a remarkable role to maintain the stability of the thin-shell around the wormhole structure as compared to polytropic model for both choices of shape functions.

Two new phreatic snails (Mollusca, Caenogastropoda, Cochliopidae) from the Edwards and Edwards-Trinity aquifers, Texas

The Edwards and Edwards-Trinity Aquifers of Texas have diverse stygofauna, including fifteen species of snails found in phreatic and hyporheic habitats. These species have the hallmarks of adaptation to subterranean environments including extremely small body size and the loss of pigmentation and eyes. Here we use an integrative taxonomic approach, using shell, radula, and anatomical features as well as mitochondrial and nuclear DNA data, to circumscribe a new genus and two new cavesnail species from Central Texas. Vitropyrgus lillianaegen. et sp. nov. is described from Comal Springs (Comal County) and Fessenden Springs (Kerr County) and distinguished by a glassy, highly sculptured shell and distinctively simple, unornamented penial morphology. We also describe Phreatodrobia bullasp. nov. from Hidden Springs (Bell County), and several other springs in Bell &amp; Williamson Counties, Texas. This species has a smooth, unsculptured teleoconch, a reflected and flared lip, and deeply concave operculum.

A new genus and species of the Assimineidae (Caenogastropoda: Truncatelloidea) from temperate mainland Japan

ABSTRACT Xenassiminea nana n. gen. and n. sp. is described from estuaries of temperate mainland Japan (central to western Honshū, Shikoku and Kyūshū). This species has a minute, colourless, translucent, depressed and helicoid shell and resembles some so-called skeneimorphs. However, the anatomical characters of the head–foot, radula and reproductive system indicate that this species belongs to the Assimineidae, in spite of the dissimilarity in shell features. The presence of basal cusps of the central radular teeth and the extremely rudimentary cephalic tentacles indicate that it should be assigned to the subfamily Assimineinae. The shell size (0.8 mm in length, 1.1 mm in diameter) is the smallest among known assimineids. It lives beneath stones deeply buried in sandy mud flats at the innermost parts of large bays and can be regarded as threatened by the rapid loss of these habitats in recent years.

Dechlorination of wastewater from shell-based glucosamine processing by mangrove wetland-derived fungi.

Wastewater from processing crustacean shell features ultrahigh chloride content. Bioremediation of the wastewater is challenging due to the high chloride ion content, making it inhospitable for most microorganisms to survive and growth. In this study, mangrove wetland-derived fungi were first tested for their salt tolerance, and the highly tolerant isolates were cultured in shrimp processing wastewater and the chloride concentration was monitored. Notably, the filamentous fungal species Aspergillus piperis could remove over 70% of the chloride in the wastewater within 3 days, with the fastest biomass increase (2.01 times heavier) and chloride removal occurring between day one and two. The chloride ions were sequestered into the fungal cells. The genome of this fungal species contained Cl- conversion enzymes, which may have contributed to the ion removal. The fungal strain was found to be of low virulence in larval models and could serve as a starting point for further considerations in bioremediation of shell processing wastewater, promoting the development of green technology in the shell processing industry.

Picking up the pieces: Assessing alternative methods for reconstructing whole red abalone (Haliotis rufescens) shell size from fragments

Dense layers of red abalone shells (“red abalone middens”) have been heavily studied along the California coast for their implications for pre-contact subsistence, paleo-sea surface temperatures, and nearshore ecology. However, shells in these deposits are typically broken which lessens their scientific value. To compensate for this problem, we evaluate four alternative methods for predicting the size of whole abalone shells from fragments. The first was a template made up of the outlines of complete modern and archaeological shells. The others were based on regression formulas that rely on measurements of shell features that potentially track with shell growth: (1) maximum diameter of the last developed aperture, (2) distance between the last two developed apertures, (3) maximum diameter of the muscle scar. We conducted a blind study with archaeological laboratory volunteers to evaluate the accuracy of these methods, and found that the template outperformed the allometric methods, and, of the latter, the muscle scar measurement was the most accurate. Our results provide a framework for future studies to assess variation in abalone size from fragmented shells as a proxy for past climate change and harvesting pressure. They also provide a methodological approach for reconstructing sizes of other shell species found in midden deposits elsewhere.

Molecular phylogeny of the land snail family Euconulidae in Thailand and its position in the superfamily Trochomorphoidea (Stylommatophora: Limacoidei), with description of a new genus

The Euconulidae is a globally distributed land snail family but there is no record of this family from Thailand. In this study, we describe a new genus, Siamoconus gen. nov., based on comparative studies of the shell characteristics, external morphology of animals, radula, genital and spermatophore structures, and molecular phylogeny. We performed phylogenetic analyses of two mitochondrial gene fragment (cytochrome c oxidase I, COI; and 16S rRNA) and one nuclear (28S rRNA) gene fragment to clarify the relationships with other euconulid genera and its position in the superfamily Trochomorphoidea. We also analysed shell morphometrics, male genitalia and mantle pigmentation of Siamoconus gen. nov., confirming the status of three new species with keeled shells (S. boreas sp. nov., S. coleus sp. nov. and S. geotrochoides sp. nov.) and one new species with a rounded shell (S. destitutus sp. nov.). These new species are restricted to limestone areas in northern and north-eastern Thailand. We also re-examined the status of other genera in the superfamily Trochomorphoidea based on shell features, body pigmentation, radula, genital anatomy, spermatophore morphology, and a phylogenetic analysis of all available trochomorphoidean DNA sequences. Our analysis suggests that the family Geotrochidae, previously synonymised with the Trochomorphidae, should be resurrected to represent the genus Geotrochus from Borneo, and this family is retrieved as the sister clade of the Dyakiidae. ZooBank: urn:lsid:zoobank.org:pub:C5205F4E-5DDE-42E6-A532-761CAFE099C3