Shell Dimensions Research Articles

Size-dependent optical properties and thermal response of Fe/Co/Ni@Au and Fe/Co/Ni@Ag core-shell nanospheres

In this work, Mie theory is employed to study the opto-thermal response of magneto plasmonic Fe/Co/Ni@Au and Fe/Co/Ni@Ag core-shell nanostructures of different sizes in the presence of dielectric media (i.e., water) is investigated numerically. The optical and thermal characteristics from the Fe, Co, and Ni as core material with noble metal Au and Ag as coating (shell) material are susceptible to being well-tuned by controlling the dimensions of both core and shell, based on the research being conducted at the moment. The SPR wavelength spectra of magnetic core Fe /Co /Ni (radii ranging from 10–40 nm) with Au and Ag coating (fixed shell thickness of 5, 10, and 15 nm), nanostructures are tuned from 231–528 nm and 364–420 nm, respectively. The maximum temperature obtained near the surface of Fe/Co/Ni@Au and Fe/Co/Ni@Ag nanospheres with the optimized size is 2.09℃ / 2.09 ℃ / 2.23 ℃ and 2.30 ℃ / 2.33 ℃ / 2.33 ℃, respectively. It can be observed that the surface plasmon resonance (SPR) is located in the vicinity of the ultraviolet (UV) and infrared (IR) domains of the electromagnetic (EM) spectra. The temperature rise noticed in the nanoparticle (NP) has been attributed to enhanced absorbance efficiency.

An Ecological Study of the Brown Garden snail Cornu aspersum (Müller, 1774) from selected habitats in Jadiriya in Baghdad vicinity.

The present study is considered a pioneer investigation that deal with the terrestrial brown garden snail Cornu aspersum (Müller), in Iraq. Cornu aspersum however is considered an exotic species in many parts of the world ,The species is most probably infiltrates with plants transferred from one place to another. The species has gained importance in many ways. Nutritionally, the species is consumed as food item in many countries, but in other cases it is considered as pest for the damage it causes when feeding on valuable plant shoots. It also has medical importance for its role and ability in healing wounds, burns and remedy of other skin problems. This snail species however may act as a vector for some parasitic nematodes that cause serious diseases. The species is also important in scientific research, usually referred to as ‘ecological indicator’ employed in environmental pollution problems such as the one caused by heavy metals. A great deal of research on this species has been carried out in different parts of the world, however, in Iraq, the scientific attention given to land snails in general and to Cornu aspersum in particular is rare and may be negligible in comparison with the research carried out on aquatic Mollusca species. A total of 1880 individuals of Cornu aspersum were collected from all sampling sites. The study was carried out for the period November 2007 to November 2008 on three sites within the Jadiriya district in Baghdad.. Growth, size classes and shell dimensions of Cornu aspersum populations, and their relationship with major environmental factors; ambient temperature; soil pH, moisture, texture; and the soil content of organic matter have been also investigated. Identification of the species was confirmed by the British Natural History Museum.The data were analyzed by means of standard statistical procedures.

Stability and evolution of skyrmionium and skyrmions in a spherical shell

The study of magnetic structures, particularly those with curved geometries such as spherical shells, has obtained significant interest due to their potential applications in data storage, spintronics, and other advanced technologies. However, the effects of material parameters, geometric dimensions, and magnetic fields on the equilibrium and induced behaviors of skyrmions remain largely unresolved. Here, based on micromagnetic simulations, we firstly investigate the influence of spherical shell dimensions, magnetic anisotropy, exchange interaction, and Dzyaloshinskii–Moriya interaction on the magnetic states of spherical shells. We find that curvature effects become more pronounced with increasing thickness and decreasing radius, providing evidence for the role of curvature-induced DMI-like interactions in skyrmion formation. Additionally, we observe that applying a magnetic field to the spherical shell induces behaviors similar to those in disks, including the topological transition between skyrmionium and skyrmion states, the annihilation of skyrmions, and polarity reversal. Our study aims to advance the understanding of magnetic phenomena in curved geometries and contribute to the development of novel magnetic devices.

Suspended culture of the Manabí oyster Crassostrea cf. corteziensis in a tropical estuary

Grow-out of the Manabí oyster (Crassostrea cf. corteziensis) under suspended culture conditions from the Chone River Estuary (Manabí, Ecuador) was evaluated. The culture was established in lanterns with 50 oysters/floor for seven months (July 2022 to February 2023) using juveniles (34.9±6.2 mm) collected from natural oyster beds in the same estuary. The growth and survival, as well as environmental variables in the culture site, were monitored. The growth in the shell dimension was continuous, reaching high rates during October and November. At the end of the study, 86.7±6.68 mm anteroposterior length, 110.7±19.04 g dry mass of the whole organism (with 3.7±0.67 g soft tissue), and survival of 92.6±2.62 % were obtained. No association was observed between the patterns of the growth curves and those of the environmental parameters; however, the decrease of body mass (during February 2023) was associated with increased temperature, decreased salinity, and lower phytoplankton content. Oysters of marketable size (80 mm) were obtained after seven months of culture. The results suggest the biological feasibility of cultivating the Manabí oyster C. cf. corteziensis in the Chone River Estuary, which could be an emerging species for aquaculture in Ecuador and the tropical American Pacific.

Synthesis and Characterisation of Core-Shell Microparticles Formed by Ni-Mn-Co Oxides.

In this work, core and core-shell microparticles formed by Ni-Mn-Co oxides with controlled composition were fabricated by an oxalate-assisted co-precipitation route, and their properties were analysed by diverse microscopy and spectroscopy techniques. The microparticles exhibit dimensions within the 2-6 μm range and mainly consist of NiO and NiMn2O4, the latter being promoted as the temperature of the treatment increases, especially in the shell region of the microparticles. Aspects such as the shell dimensions, the vibrational modes of the spinel compounds primarily observed in the shell region, the oxidation states of the cations at the surface of the microparticles, and the achievement of a Ni-rich 811 core and a Mn-rich 631 shell were thoroughly evaluated and discussed in this work.

Analytical Study on the Buckling of Cylindrical Shells With Circumferential Thickness Variation Under Varying External Pressure

Abstract In this article, the analytical buckling load coefficient formula for a cylinder with circumferential thickness variation subjected to varying external pressure is established for the first time by developing a quadratic perturbation method. Based on the presented formula, some specific examples that consider either circumferential shell thickness variation or varying lateral pressure are studied and compared with those in the published literature. First, classical cosine thickness variation is analyzed. The computed results of buckling load coefficients indicate that most of differences between the proposed formula and finite element (FE) analyses in previous literature are less than 5%. Second, wind-type pressure load is discussed, and the maximum difference of predicted buckling load coefficients between our formula and results in published article is 2.3%. Third, both circumferential thickness variation and linear liquid pressure are analyzed by the proposed analytical formula and validated by the Galerkin method when both thickness and load variations are small. Therefore, accuracy and reliability of the established formula are validated. For the purpose of engineering application, buckling of a circular shell with local circumferential thickness variation due to weld shrinkage under wind-type pressure is analytically investigated. The effects of thickness variation amplitude, load parameter, half angle of thickness variation, and shell dimensions on buckling load coefficients are studied in detail.

Discovery of an [O iii] Emission Shell around the X-Ray Binary CI Cam

We report the serendipitous discovery of a 8′×12′ emission shell brightest in [O iii] centered on the X-ray binary B[e] star, CI Cameleopardalis (CI Cam). This shell, detected during a survey of optical emission associated with the Galactic supernova remnant G150.3+4.5, is seen outside but immediately adjacent to the remnant’s optical filaments along its northwestern edge. Assuming this shell is related to CI Cam’s strong winds and transient outbursts, the adoption of CI Cam’s Gaia DR3 statistically corrected distance of 4.1 −0.2+0.3 kpc yields shell dimensions ≃9.5 pc × 14.3 pc. While the distance to the G150.3+4.5 remnant is uncertain, the appearance of CI Cam’s emission shell so close to the SNR’s optical filaments appears likely to be a chance coincidence.

Electron-donor-impurity polarizability in a semiconductor nanostructure under electric field: Geometrical effects in ellipsoidal quantum dots

The features of electron-impurity polarizability in a quantum nanostructure are investigated from the knowledge of allowed electron states coupled to a shallow-donor impurity. The influence of geometry on the carrier confinement and the presence of external probes such as electric fields are explicitly considered. For the sake of illustration, the example of CdS/ZnSe-based prolate ellipsoidal core/shell quantum dot (PECSQD) configuration is chosen. This problem allows to consider a finite confinement potential model, employing both the finite element method and the effective mass approximation. Within this framework, impurity-related energies and associated polarizability for the lowest states were determined as functions of the shell thickness, core dimensions, impurity position, and applied electric field strength - while keeping the shell dimensions fixed. Electron-impurity energies are largely affected by electric field values. Under thinner shell conditions, polarizability shows variations with field strength that include “anomalous” negative values for certain states. Then, the increase in shell thickness causes a significant increment in the polarizabilities, regardless impurity position.

Suppressed Magnitude of Spectral Diffusion in Cube-Shaped CdSe/CdS Core/Shell Nanocrystals with Exceedingly Stable Photoluminescence.

Colloidal semiconductor nanocrystals are promising candidates for quantum light sources, yet their application has been impeded by photoluminescence instability due to blinking and spectral diffusion. This study introduces a new category of cube-shaped CdSe/CdS core/shell nanocrystals with exceptionally stable photoluminescence characteristics. Under continuous excitation, the emissive quantum state remained consistent without alterations of the charge state for 4000 s, and the average photon energy variation stayed within the bounds of spectral resolution throughout this extended duration. Systematic examination of single-nanocrystal photoluminescence, upon variation of the core and shell dimensions, revealed that a thicker CdS shell and increased core edge length significantly curtail spectral diffusion, considering that the nanocrystals possess well-controlled CdSe-CdS and facet-ligand interfaces. This study advances the optimization of colloidal semiconductor nanocrystals as high-performance quantum light sources.

A New Species of Fossil Bistolida (Gastropoda: Cypraeidae) from the Miocene of West Java, Indonesia

A new species of Bistolida Cossmann, 1920 is described from the Miocene of the Cibalong area, Tasikmalaya Regency of western Java, Indonesia. Morphological analyses of the shell dimensions, outline, extremities, aperture shape, and apertural teeth shows a combination of characters that are typical of the genus Bistolida. Although the genus has not previously been reported from Java, its presence in the Miocene fossil record is supported by the six specimens that are shown here.

Free vibration of ferromagnetic functionally graded cylindrical shells subjected to magnetic and temperature fields

The free vibration characteristics of functionally graded cylindrical shells under magnetic and temperature fields are investigated. According to Donnell’s theory, the kinetic energy, deformation energy, and their variational expressions are obtained. Based on the electromagnetic elasticity theory, the eddy current electromagnetic and magnetization force models are established. Using Hamilton’s principle, the magneto-thermo-elastic free vibration partial differential equations are derived. The modal frequency differential matrix equation with diverse boundary conditions is derived from the Galerkin integral technique. Through numerical examples, the curves and three-dimensional surface diagrams depicting the variations for the natural frequency with diverse parameters are obtained. The feasibility of the proposed solution method in this paper is supported by literature examples. The influence of magnetic induction intensity, temperature, power-law index, wave number, and shell dimension on the natural frequencies are determined.

Design and Machining of a Spherical Shell Rotor for a Magnetically Levitated Momentum Ball

Ball-shell rotors with non-standard shapes, non-uniform conductive coatings, and eccentric masses machined by conventional processes constrain the improvement of levitation and torque accuracy of magnetically levitated momentum balls. This paper focuses on the machining method of multilayer ball-shell rotors to develop a ball-shell rotor with a standard shape and uniform conductive coating, which can improve the levitation and torque accuracy of magnetically levitated momentum balls. In this paper, a machining method for multi-coated ball-shell rotors is proposed. The machining process combining hemispherical surface and workpiece is adopted, and the whole sphere is assembled by threading, which effectively reduces the machining error. The influence of the cutting depth and feed rate of the tool on the cutting force of the ball shell was analyzed through the cutting force model. The effect of cutting force on the deformation of the ball shell was analyzed by the finite element method. The superiority of the machining method was verified by measuring the dimensions of the ball shell with a coordinate measuring machine. Compared with the traditional machining process and assembly method, the proposed ball-shell rotor machining method effectively improves the dimensional accuracy, reduces the center of mass to center of mass deviation, and ensures the levitation accuracy and output torque accuracy of the magnetically levitated momentum ball. Measurement results show that the diameter values of the pure iron ball shell are between 98.694 and 98.707 mm with a machining error of ±0.007 mm, and the diameter values of the spray-painted ball shell are between 99.490 and 99.510 mm with a machining error of ±0.01 mm. The machining static equilibrium of the pure iron ball shell and the spray-painted ball shell is good by the static equilibrium test method.

Combining computer vision and standardised protocols for improved measurement of live sea urchins for research and industry

AbstractTo allow sea urchin aquaculture to achieve its intended scale, efficient and precise methods for measuring large numbers of urchins in commercial‐scale operations are needed. Current protocols for measuring urchin test (shell) dimensions and mass are time‐consuming and prone to high measurement error, thus inconvenient in research and impractical in a commercial context. This study investigates and compares various measurement methods with a newly developed computer vision approach developed in this study, to establish a single protocol using precise, efficient and accessible methodology for measuring live urchins. We show that urchin wet mass can vary up to 8.73% depending on time out of water; this is significantly reduced to an average of 0.1% change by allowing urchins to drip‐dry for at least 90 s prior to weighing. We found the conventional vernier calliper method used to measure urchin dimensions to be both time‐consuming and imprecise (mean coefficient of variation (CV) of 2.41% for Tripneustes gratilla). Conversely, the computer vision programme we developed measures with higher precision (mean CV of 1.55% for T. gratilla) and is considerably faster. The software uses a series of hue saturation value filters, edge detection algorithms and distortions to measure the diameter of the test (excluding spines) of multiple urchins at once. The software is open‐source, and the protocol does not require specialised equipment (can be performed with a mobile phone camera). When the computer vision application is combined with the simple procedures described in this paper, to reduce measurement inaccuracies, urchin wet mass and diameter can be more efficiently and precisely determined. For a larger scale context, this software could easily be incorporated into various tools, such as a grading machine, to completely automate various farm processes. As such, this study has potential to assist urchin data collection in both research and commercial contexts.

Shell Dimension-Weight Relationship and Condition Index of the Invasive Mussel Mytella strigata in Sasmuan, Pampanga, Philippines

A total of 300 Mytella strigata were collected at three sampling points in the mussel coastal demonstration farm in Sasmuan, Pampanga, and subjected to morphometric and gravimetric measurements for the evaluation of its growth pattern and condition index. Designated sampling sites were based on the distances to the river mouth (200 m, 400 m, and 600 m) with varying water quality parameters (temperature, salinity, pH, water velocity, and chlorophyll-a). Mussels in Site 2 had significantly larger shell dimensions (SL = 2.862 cm, SW = 1.458 cm, SH = 0.926 cm), shell weight (0.640 g), and total live weight (1.150 g). Significantly higher (p < 0.05) soft-tissue dry weight (0.083 g), however, was obtained in Site 3, while comparable (p >0.05) soft tissue weight was observed in Site 2 (0.364 g) and Site 3 (0.413 g). Nevertheless, mussels in all sites demonstrated negative allometric growth (b < 3). The length-weight relationship revealed a weak to moderate, positive correlation. A significantly higher (p < 0.05) condition index was obtained in Site 3, which could have been influenced by higher chlorophyll-a and substantially lower water velocity. As such, this signifies its potential to have a well-established population in this spatial distance (600 m) from the river mouth. Hence, regular harvest and product development is recommended as strategic options to control its proliferation.

Modeling selective narrowband light absorption in coaxial InAs-GaAs0.1Sb0.9 nanowires with partial shell segment coverage

Vertical III-V nanowire (NW) arrays are promising candidates for infrared (IR) photodetection applications. Generally, NWs with large diameters are required for efficient absorption in the IR range. However, increasing the NW diameter results in a loss of spectral selectivity and an enhancement in the photodetector dark current. Here, we propose a nanophotonic engineering approach to achieving spectrally-selective light absorption while minimizing the volume of the absorbing medium. Based on simulations performed using rigorous coupled-wave analysis (RCWA) techniques, we demonstrate dramatic tunability of the short-wavelength infrared (SWIR) light absorption properties of InAs NWs with base segments embedded in a reflective backside Au layer and with partial GaAs0.1Sb0.9 shell segment coverage. Use of a backside reflector results in the generation of a delocalized evanescent field around the NW core segment that can be selectively captured by the partially encapsulating GaAs0.1Sb0.9 shell layer. By adjusting the core and shell dimensions, unity absorption can be selectively achieved in the 2 to 3 μm wavelength range. Due to the transparency of the GaAs0.1Sb0.9 shell segments, wavelength-selective absorption occurs only along the InAs core segments where they are partially encapsulated. The design presented in this work paves the path toward spectrally-selective and polarization-dependent NW array-based photodetectors, in which carrier collection efficiencies can be enhanced by positioning active junctions at the predefined locations of the partial shell segments.

A multivariate approach to morphological study of shell form in cowries (Gastropoda, Cypraeidae): a case study with Umbiliaarmeniaca (Verco, 1912).

Multivariate approaches to morphological study of shell form have rarely been applied to cowries (Gastropoda: Cypraeidae) with preference, instead, for comparing formulaic notations of shell form that report averages (i.e., means) for key morphometrics such as shell dimensions, their ratios, and counts of apertural teeth. Although widely applied, the "shell formula" does not account for variation among individuals or support statistical comparison between taxa. This study applied a multivariate approach to analyse shell form within the four accepted subspecies of the cowrie, Umbiliaarmeniaca (Verco, 1912) and included a previously unstudied, and most northerly, population of U.armeniaca from Lancelin, Western Australia. Multivariate analyses readily separated the recognised subspecies of U.armeniaca (U.a.armeniaca, U.a.diprotodon, U.a.clarksoni and U.a.andreyi), but did not separate the Lancelin population from U.a.andreyi, indicating that the former represents a northward extension of U.a.andreyi that is not morphometrically distinguishable. These results provide improved understanding of infraspecific differences in shell form of U.armeniaca across its broad distribution, and demonstrate the utility of multivariate morphometric methods for statistical comparison of shell form between taxa. This approach is complimentary to existing research practices and has broad potential application in future morphometric studies of both extant and fossil taxa within the family Cypraeidae.

Analytical investigation on the buckling of cylindrical shells under combined non-uniform axial compression and external pressure

This paper focuses on the buckling problem of cylindrical shells under combined non-uniform axial compression and external pressure. To obtain buckling loads, a completely new method called two-parameter perturbation method is established. Using this method, governing differential equations are solved and buckling loads expressed by load functions, load parameters, and shell dimensions are derived for the first time. Comparative studies show that buckling loads by the analytical formulas coincide with those for combined uniform loads or single wind load in literatures. Buckling of a cylinder subjected to combined bending and wind loads is analyzed, and confirmed by the Galerkin method for the case of small load variations. Therefore, the presented formulas are adequately validated. The numerical calculations are carried out to analyze the effects of non-uniform load parameters on buckling load coefficient. The obtained results in this paper can be applied to evaluate buckling loads for cylinders subjected to combined non-uniform loads in actual engineering.

An analytical method for free vibration analysis of multi-layered transversely isotropic cylindrical shells

This work presents an effective analytical method based on displacement potential functions (DPF) for solving 3-D free vibration problem of thick and multi-layered transversely isotropic cylindrical shells with simply supported end boundary conditions. By using the DPF method, the three-dimensional elasticity equations are simplified and decoupled into two linear partial differential equations of fourth and second order as governing differential equations. These equations are analytically solved using the separation of variables method in terms of fields that exactly satisfy end boundary conditions and the continuity of a closed cylinder in the hoop direction. One of the advantages of the present work is the analysis of thick cylindrical shells using an exact method without any approximations and simplifying assumptions in the distribution of stress or strain along the thickness of the shells. The analysis is extended to multi-layered cylindrical shells by applying appropriate boundary conditions at the interfacial surfaces of the layers. Numerical comparisons to other analytical works shows the accuracy of the present work and also due to the lack of study for multi-layered transversely isotropic cylindrical shells, 3-D finite element analysis has been performed for comparison. In addition, various more involved problems are studied and solved analytically for single and multi-layered shells of transversely isotropic material and the effect of various parameters such as shell dimensions, mechanical properties, number of layers and other parameters on shell behavior are evaluated. The results of the present study can be used as benchmark solutions for other studies.

Morphological variations among populations of Bulinus forskalii (Ehrenberg, 1831) from Cameroon

ABSTRACT Climatic stratification from equatorial rainforest to Sahelian savannah in Cameroon implies successive bioclimatic ecosystems, various natural and artificial situations that may generate morphological and genetic adaptation of populations of Bulinus forskalii (Ehrenberg, 1831) which is widely distributed throughout the country. The present research was undertaken on 955 snails sampled from 12 populations along a south–north transect to investigate morphological variations of shells. Shell colour varied from dark brown to whitish with Sudano–Sahelian shells being brownish through to whitish, shouldered and strongly carinate. Morphometric characters varied greatly from one population to another, with all shell parameters being highly correlated to shell height. Sudano–Sahelian shells were smaller than equatorial shells. From Sangmélima in the equatorial forest region to Marao in the Sudano–Sahelian region a gradual decrease of shell dimensions was apparent, indicating a morphocline. This could reflect the role played by ecological factors on snail population dynamics.

Shell morphology and size distribution of Turbo spp in Sepanjang Beach by shell collecting: An Initial Survey

Turbo spp. in Sepanjang Beach, Gunung Kidul, Indonesia, are at risk of depletion due to their popularity for consumption and decoration. Protecting this species demands sustainable management practices. This initial survey aimed to examine the shell morphology, size distribution, and shell growth patterns of Turbo spp. at Sepanjang Beach, Indonesia, to establish baseline data for future research. A total of 233 shells were collected randomly and analyzed for morphological parameters. Shell dimensions exhibited variations in size, shape, color, and whorl features. Shells ranged from 7.59 to 60.96 mm in length and 7.47 to 52.43 mm in width. Operculum dimensions varied from 3.14 to 29.75 mm in length and 3 to 22 mm in width. Size frequency distributions highlighted a peak at 30-35 mm shell length. The right-skewed size distribution indicated a prevalence of smaller individuals, possibly influenced by the environmental and genetic factors. Positive correlations between shell and operculum dimensions suggested an isometric growth pattern, implying symmetrical shell development. These insights are crucial for developing effective conservation strategies for Sepanjang Beach. Further research, including species genetics, size at first gonadal maturity, and environmental influences, is recommended for a comprehensive understanding of Turbo spp. sustainability in the region.