Shell Components Research Articles

Core-shell structured nets for biofouling control in aquaculture

This study demonstrates a robust, flexible interpenetrated composite based on 3D spined fabrics as core material and polydimethylsiloxane (PDMS) as shell material. The penetration of the shell component into the core material enables the mechanical interlocking at the micro and macro scale, providing mechanical stability and at the same time, introducing hydrophobic surface properties. Pure PDMS is a well-known biofouling-release material, showing drawbacks with respect to mechanical strength and adhesion-to-substrate, which can be overcome by the presented approach. Nowadays, antifouling strategies for aquaculture nets are realized by using biocide-containing coatings to avoid the attachment of organisms or repel them. Up to now, there are no coatings available on the market that provide adequate biofouling protection for aquaculture nets during the whole production cycle of the cultured stock. Even biocidal coatings exhibit a limited efficiency and need to be regularly cleaned, causing a substantial loss of the coating and increased emissions of biocides into seawater. This proof-of-concept study covers the scope from the design and production of the composite up to the first field tests in the Baltic Sea. The presented approach enabled by material science facilitates a fundamentally different approach in biofouling management and contributes to sustainable aquaculture.

Optimized oxygen reduction activity by tuning shell component in Pd@Pt-based core-shell electrocatalysts

Combining the interests of core-shell and alloy structures, herein we report the versatile co-reduction synthesis of Pd@Pt-based core-shell nanoparticles. The current strategy can effectively tune the component of shell, from isolated Pt to binary PtNi alloy, then ternary PtNi-M (M = Fe or Cu) alloy. Further, significant improvement of oxygen reduction reaction (ORR) activity is optimized by the change in shell component. Compared to Pd@Pt/C, Pd@PtNi/C catalyst presents the ORR-helpful mass activity of 1.29 A mg-1Pt. By incorporating a third metal (M) into shell layer, the optimized mass activity of Pd@PtNiFe/C and Pd@PtNiCu/C catalysts is 1.1 times and 1.4 times higher than that of Pd@PtNi/C, respectively. Meanwhile, the lower activity decays of 11.0% for Pd@PtNiFe/C and 10.6% for Pd@PtNiCu/C are obtained compared with that of Pd@PtNi/C (12.4%) after 5,000 cycles, respectively.

Interface Reaction between Directional Solidified Superalloy DZ40M and Ceramic Mould

The interfaces between DZ40M directional solidified superalloy and ceramic mould (SiO2-base core and Al2O3-base shell) was studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that there was a serious interface reaction between DZ40M and ceramic cores，which resulted in many reaction pits (~100μm deep), Si rich residue alloys and Zr rich subglobose oxides on the inner surface. And the interface reaction between DZ40M and ceramic shell induced a ~50μm of pink sand burning layer. The thermal analysis showed that the reactions between DZ40M and core or shell were similar: the active alloy constituents (Zr, Al, Ti and Cr) were oxidized and became oxides or solid solution with the core or shell components (SiO2, Al2O3 or Fe2O3), but the interface characterization of DZ40M/core and DZ40M/shell was different because the shell had the main content of Al2O3 and impurity of Fe2O3, while those of the core were SiO2 and CaO, respectively.

A bioenergetic model to address carbon sequestration potential of shellfish farming: example from Ruditapes philippinarum in the Venice lagoon

Abstract Shellfish are increasingly been looked at as sustainable food sources that provide additional ecosystem services. However, their role as CO2 sinks or sources is still debated. To quantify it, shell accretion dynamics should be accounted for. However, the shell component is usually calculated with allometric scaling, in most bivalve models. With this study, shell accretion was added to a bioenergetic model of the Manilla clam (Ruditapes philippinarum), and a parameter linking assimilated energy towards shell growth (KSH) was calibrated for four sites, where clams from the same cohort were monitored during a transplant experiment. The model was then used to calculate CO2 fluxes resulting from respiration and shell calcification, taking into account CaCO3 stocked in the shell and CO2 emission. The findings show that KSH varied slightly among sites and that clams played a role as a moderate sink of CO2 over a whole year. CO2 fluxes were characterized by a seasonal variability: clams were net sources in wintertime and sinks in summer time, suggesting the need of accounting for seasonality and growth should shellfish farming be included in carbon markets.

ALMA View of the ρ Ophiuchi A PDR with a 360 au Beam: The [C i] Emission Originates from the Plane-parallel PDR and Extended Gas

Abstract We present the results of data analysis of the [C i] (3 P 1–3 P 0) emission from the ρ Ophiuchi A photon-dominated region (PDR) obtained in the ALMA ACA standalone mode with a spatial resolution of 2.″6 (360 au). The [C i] emission shows filamentary structures with a width of ∼1000 au, which are adjacent to the shell structure seen in the 4.5 μm map. We found that the 4.5 μm emission, C0, and CO are distributed in this order from the excitation star (S1) in a complementary pattern. These results indicate that [C i] is emitted from a thin layer in the PDR generated by the excitation star, as predicted in the plane-parallel PDR model. In addition, extended [C i] emission was also detected, which shows nearly uniform integrated intensity over the entire field of view (1.′6 × 1.′6). The line profile of the extended component is different from that of the above shell component. The column density ratio of C0 to CO in the extended component was ∼2, which is significantly higher than those of Galactic massive star-forming regions (0.1–0.2). These results suggest that [C i] is emitted also from the extended gas with a density of cm−3, which is not greatly affected by the excitation star.

DSPC or DPPC As Main Shell Component Influences Ligand Distribution and Binding Area of Lipid‐Coated Targeted Microbubbles

Eur. J. Lipid Sci. Technol. 2014, 116, 1217 https://doi.org/10.1002/ejlt.201300434 The authors regret that there was a mistake in calculating the mol% of the microbubble coating composition used. For all experiments the unit in mg mL−1 was utilized and the conversion mistake only came when converting to mol% in order to define the ratio between the coating formulation components. The correct molecular weight of PEG-40 stearate is 2046.54 g mol−1,[1, 2] not 328.53 g mol−1. On page 1219, Section 2.2.1, it should read: “Biotinylated lipid-coated microbubbles (composition in mol %: DSPC or DPPC 84.8; PEG-40 stearate 8.2; DSPE-PEG2000 5.9, DSPE-PEG2000-biotin 1.1) with a C4F10 gas core were made by sonication for 10 s using the method described by Klibanov et al.[30]” This correction does not change the conclusions published in this work. The authors apologize for any inconvenience caused.

Ultrasonic measurement model-based non-destructive detection method for curved components using an immersion spherically focused transducer

ABSTRACT The ultrasonic measurement model (UMM) has been theoretically studied over the past few decades, but there is little published work on its practical application for guiding defect detection. In this work, we present a model-based ultrasonic method to detect flaws in curved components using immersion of spherically focused transducers. The UMM of focused transducers is further investigated theoretically and verified experimentally, and some key issues in the model with focused transducers are addressed, including the necessity of correctly using effective geometrical parameters and the corresponding transfer function. The UMM is employed to guide the inspection of a magnesium alloy shell component which consists of several curved surfaces. The alignment between the transducer and the shell is conducted by comparing the measured and theoretically predicted interface-echo signals, the water path is selected by simulating the effective detection region, and the system gain is set by quantitatively analysing the amplitudes of flaw signals and noises. When the inspection conditions are determined, a variable threshold based on the predicted flaw signals is introduced to distinguish noise and flaw signals. The ultrasonic C-scan images of the shell are compared with the digital radiography (DR) images, and the comparison shows that the flaws of interest can be detected in the C-scan images, which verifies the effectiveness of the UMM-based detection method.

Eigenfrequencies of prestressed variable stiffness composite shells

The introduction of the variable stiffness concept has broadened the design space for high-performance lightweight composite structures. In particular, when considering prestressed dynamically excited aerospace components, a wider design space allows designers to find more effective solutions with higher overall stiffness and fundamental frequency. In this context, an efficient and versatile Ritz method for the eigenfrequency analysis of prestressed variable stiffness laminated doubly-curved shells is presented. First-order shear deformation theory is considered without further assumptions on the shallowness or on the thinness of the structure. A rational Bézier surface representation is adopted for the description of the shell, allowing general orthogonal surfaces to be represented. The proposed approach is validated by comparison with published benchmark results and finite element solutions, showing great accuracy with 65% to an order of magnitude fewer variables. Due to the reliability and efficiency of the Ritz method for eigenfrequency analysis, original parametric studies are carried out, showing the flexibility given by the variable stiffness concept for finding trade-off solutions for prestressed shell components.

Hybrid Toroidal Resonance Response in Planar Core-Shell THz Metasurfaces

Toroidal resonance of planar structure is feasible and interesting for many appealing applications. We numerically and experimentally investigated the toroidal resonances in a planar metamaterial comprising core-shell structures and its constituent core and shell components at THz frequencies. The investigated structure demonstrated sharp toroidal and hybrid toroidal resonance modes in 0.2–0.3 THz range. Our analysis showed that these modes could be explained by the interaction of resonance toroidal modes of the shell and core components. The response of the investigated planar core-shell toroidal metasurface is notably geometry dependent and can be easily tuned by tailoring the device geometry. Presented work can be used for advanced THz photonics applications, including precise bio-sensing, narrow-band filters, fast-switching, and modulation.

Toward Precisely Controllable Acoustic Response of Shell-Stabilized Nanobubbles: High Yield and Narrow Dispersity.

Understanding the pressure dependence of the nonlinear behavior of ultrasonically excited phospholipid-stabilized nanobubbles (NBs) is important for optimizing ultrasound exposure parameters for implementations of contrast enhanced ultrasound, critical to molecular imaging. The viscoelastic properties of the shell can be controlled by the introduction of membrane additives, such as propylene glycol as a membrane softener or glycerol as a membrane stiffener. We report on the production of high-yield NBs with narrow dispersity and different shell properties. Through precise control over size and shell structure, we show how these shell components interact with the phospholipid membrane, change their structure, affect their viscoelastic properties, and consequently change their acoustic response. A two-photon microscopy technique through a polarity-sensitive fluorescent dye, C-laurdan, was utilized to gain insights on the effect of membrane additives to the membrane structure. We report how the shell stiffness of NBs affects the pressure threshold (Pt) for the sudden amplification in the scattered acoustic signal from NBs. For narrow size NBs with 200 nm mean size, we find Pt to be between 123 and 245 kPa for the NBs with the most flexible membrane as assessed using C-Laurdan, 465–588 kPa for the NBs with intermediate stiffness, and 588–710 kPa for the NBs with stiff membranes. Numerical simulations of the NB dynamics are in good agreement with the experimental observations, confirming the dependence of acoustic response to shell properties, thereby substantiating further the development in engineering the shell of ultrasound contrast agents. The viscoelastic-dependent threshold behavior can be utilized for significantly and selectively enhancing the diagnostic and therapeutic ultrasound applications of potent narrow size NBs.

Novel Strategy for Engineering the Metal-Oxide@MOF Core@Shell Architecture and Its Applications in Cataluminescence Sensing.

Cataluminescence is an attractive oxydic luminescence on the gas-solid interface, and metal-oxide@MOF core@shell architectures show great potential for cataluminescence sensing due to their integrated synergistic effect from core and shell components. However, restricting the direct nucleation and growth of metal-organic frameworks (MOFs) on the topologically distinct surface of metal oxides is a great challenge, owing to the high interface energy from the topology mismatch. Herein, for the first time, a novel liquid-phase concentration-controlled nucleation strategy is exploited to induce the direct assembly of a ZIF-8 layer on the surface of CeO2 nanospheres without any sacrificial templates or further surface modifications. The results show that the construction of the CeO2@ZIF-8 core@shell architecture can be accomplished within 1 min under the mediation of boosted nucleation kinetics. Furthermore, the universality of this developed strategy is demonstrated by the encapsulation of other metal-oxide cores such as magnetic Fe3O4 and ZnCo2O4 core particles with a ZIF-8 shell. Notably, compared to the pure CeO2 and ZIF-8, the obtained CeO2@ZIF-8 nanocomposite exhibits enhanced analytical performance for the cataluminescence sensing of propanal, in which the shell acts as the major catalytic reaction center, while the core contributes to further improving the catalytic efficiency. The proposed facile synthesis strategy with excellent simplicity, rapidity, and universality brings new insights into the engineering of core@shell advanced functional materials with mismatched topologies for catering to the diverse application demands.

Free vibration of FGM conical–spherical shells

Natural frequencies of a conical–spherical functionally graded material (FGM) shell are obtained in this study. It is assumed that the conical and spherical shell components have identical thickness. The system of joined shell is made from FGMs, where properties of the shell are graded through the thickness direction. The first order shear deformation theory of shells is used to investigate the effects of shear strains and rotary inertia. The Donnel type of kinematic assumptions are adopted to establish the general equations of motion and the associated boundary and continuity conditions with the aid of Hamilton’s principle. The resulting system of equations are discretized using the semi-analytical generalized differential quadrature (GDQ) method. Considering various types of boundary conditions for the shell ends and intersection continuity conditions, an eigenvalue problem is established to examine the vibration frequencies. After proving the efficiency and validity of the present method for the case of thin isotropic homogeneous joined shells with the data of conventional finite element software, parametric studies are carried out for the system of combined moderately thick conical–spherical joined shells made of FGMs and various types of end supports.

Vibration analysis of combined conical-cylindrical shells based on the dynamic stiffness method

An analytic dynamic stiffness method (DSM) is extended to analyze the free and forced vibration of combined conical-cylindrical shells with general boundary conditions in this paper. Flügge shell theory is utilized to formulate the motion equations of each shell component. Based on the exact general solutions of the motion equations, the dynamic stiffness matrices for each shell segment are established separately and the global dynamic stiffness matrix for the whole structure is established by assembling the dynamic stiffness matrices for each shell segment similarly as finite element method (FEM) did. Natural frequencies and forced responses of the combined shells are obtained based on the global dynamic stiffness matrix. Through comparing vibration results of DSM with ones from open literature and FEM, rapid convergence, good accuracy, and high efficiency of the DSM are demonstrated. In the numerical examples, the influences of boundary conditions, axial and circumferential mode numbers, and semi-vertex angles on the free vibration are studied. The effects of direction and location of external force and structural damping on the forced vibration are also discussed.

Long-term photospheric instabilities and envelopes dynamics in the post-AGB binary system 89 Herculis

ABSTRACT We present a long-term optical spectroscopic study of the post-asymptotic giant branch (AGB) binary system 89 Herculis, with the aim to characterize the relationship between photospheric instabilities and dynamics in the close circumstellar environment of the system. This study is based on spectra acquired with the high-resolution Catania Astrophysical Observatory Spectropolarimeter and archive data, covering a time interval between 1978 and 2018. We find long-term changes in the radial velocity curve of the system, occurring mostly in amplitude, which correlate with the variability observed in the blueshifted absorption component of the P Cygni-like H α profile. Two possible scenarios are discussed. We also find strong splitting in the s-process elements of Ba ii 6141.713- and 6496.898-Å lines, with short-term morphological variations. A Gaussian decomposition of such profiles allows us to distinguish four shell components, two expanding and two infalling toward the central star, which are subject to the orbital motion of the system and are not affected by the long-term instabilities. Finally, we find that the numerous metal lines in emission could originate in regions of a structured circumbinary disc that have sizes proportional to the energy of the corresponding upper level transition Eup. This study demonstrates the potential of long-term high-resolution spectroscopy in linking together the instability processes occurring during the late evolutionary stages of post-AGBs and the subsequent phase of PNe.

Scattering with Critically-Singular and $$\delta $$-Shell Potentials

The authors consider a scattering problem for electric potentials that have a component which is critically singular in the sense of Lebesgue spaces, and a component given by a measure supported on a compact Lipschitz hypersurface. They study direct and inverse point-source scattering under the assumptions that the potentials are real-valued and compactly supported. To solve the direct scattering problem, the authors introduce two functional spaces ---sort of Bourgain type spaces--- that allow to refine the classical resolvent estimates of Agmon and H\"ormander, and Kenig, Ruiz and Sogge. These spaces seem to be very useful to deal with the critically-singular and $\delta$-shell components of the potentials at the same time. Furthermore, these spaces and their corresponding resolvent estimates turn out to have a strong connection with the estimates for the conjugated Laplacian used in the context of the inverse Calder\'on problem. In fact, the authors derive the classical estimates by Sylvester and Uhlmann, and the more recent ones by Haberman and Tataru after some embedding properties of these new spaces. Regarding the inverse scattering problem,the authors prove uniqueness for the potentials from point-source scattering data at fix energy. To address the question of uniqueness the authors combine some of the most advanced techniques in the construction of complex geometrical optics solutions.

Experimental Characterization of a High-Damping Viscoelastic Material Enclosed in Carbon Fiber Reinforced Polymer Components

This work aims to identify the damping properties of a commercial viscoelastic material that can be embedded and cured between the layers of composite laminates. The material may be adopted for reducing the vibration response of composite panels, typically used in automotive and aerospace applications, e.g., as vehicle body shell components. In order to objectively estimate the actual potential to enhance the noise vibration and harshness aspects, the effects of the viscoelastic material on the modal parameters of carbon/epoxy thin panels are quantitatively assessed through experimental modal analysis. Two different experiments are conducted, namely impact hammer tests and shaker excitation measurements. Based on the results of the experimental campaign, the investigated material is confirmed as a promising solution for possibly reducing the severity of vibrations in composite panels, thanks to its high damping properties. Indeed, the presence of just one layer proves to triple the damping properties of a thin panel. An approximate damping model is derived from the measured data in order to effectively simulate the dynamic response of new design solutions, including thin composite panels featuring the viscoelastic material.

Harmful and Beneficial Effects of the Land Snail Monacha Sp. التأثیرات الضارة و المفیدة للقوقع الأرضى من نوع الموناکا

The harmful and beneficial effects of the land snail Monacha sp . were studied in Sharkiah Governorate.Harmful effects were brightly observed in microbiological examination of gastropod and mucus in laboratory, and evaluating its damage on cabbage plant in laboratory and field. Microbial examination revealed that the gastropod was contaminated with (Klepcella) a harmful bacteria of man and animals and (Burkhelderia ceptacia) a non-useful bacteria in mucus. Few data were dealing with contamination of Monacha land snail in Egypt so, this study aims to highlight in this respect for taking into a sustainable infection when contact and thoroughly washing vegetables and fruits that are favorable food for Monacha land snails.Our results showed noticeable damage of cabbage leaves by Monacha snails in laboratory (26. 93%) and field (39. 23%) as a general mean value of cabbage consumption. Beneficial effects were revealed through biochemical analysis of both gastropod and shell components. Analysis revealed that Monacha sp.rich in protean (17.9%) and minerals such as calcium, phosphorus, magnesium and potassium. Calcium determined the highest (Ca, 13%), followed by phosphorus (Ph., 0.60%), magnesium (Mg, 0.12%) and potassium (K, 0.094%) so, the second aim of our study is the revealing of the economic feature of Monacha land snails as an addition to the fodder of farm animals and in traditional medicine.

Electrorheological display loading medium of core/shell polystyrene/polyvinyltetrazole microspheres for on-site visualization of lead(II)

Polystyrene microspheres (PSM) were obtained by emulsifier-free polymerization to coat polyacrylonitrile (PSM@PAN) as core/shell-structured microspheres of precursors. Core/shell polystyrene/polyvinyltetrazole (PSM@PVT) microspheres were obtained after a cyano-to-tetrazole conversion reaction loaded in an electrorheological display (ERD) that exhibits a low transmittance in the absence of an alternating electric field (AEF). The microspheres carrying negative and positive charges at two sides bound to each other as column-like structure along the direction of AEF enhancing the transmittance. Characteristic frequency (Fc), regarded as a mark to monitor the shell component, is defined to generate the highest degree of transmittance under an AEF. Fc of PSM@PVT shifted from 350 kHz to 100 kHz after the adsorption of lead(II) within the PVT coating. Transmittance of the ERD loading of PSM@PVT with lead(II) increased linearly with the concentration of lead(II). Approximately 30 ng mL−1 of the limit of detection was recognized within 10 s according to ERD transmittance under an AEF at 100 kHz. The Fc of the PSM@PVT absorbing the lead(II) was not influenced by the Na(I), K(I), Ca(II), Mg(II), Fe(III), and Zn(II) coexisting in the ERD. This platform provides a simple technology for heavy ion detection and may be a potential on-site ion-visualizing sensor.

Stable Components in the Parameter Plane of Transcendental Functions Of Finite Type

We study the parameter planes of certain one-dimensional, dynamically-defined slices of holomorphic families of entire and meromorphic transcendental maps of finite type. Our planes are defined by constraining the orbits of all but one of the singular values, and leaving free one asymptotic value. We study the structure of the regions of parameters, which we call shell components, for which the free asymptotic value tends to an attracting cycle of non-constant multiplier. The exponential and the tangent families are examples that have been studied in detail, and the hyperbolic components in those parameter planes are shell components. Our results apply to slices of both entire and meromorphic maps. We prove that shell components are simply connected, have a locally connected boundary and have no center, i.e., no parameter value for which the cycle is superattracting. Instead, there is a unique parameter in the boundary, the virtual center, which plays the same role. For entire slices, the virtual center is always at infinity, while for meromorphic ones it maybe finite or infinite. In the dynamical plane we prove, among other results, that the basins of attraction which contain only one asymptotic value and no critical points are simply connected. Our dynamical plane results apply without the restriction of finite type.

Influence of core and shell components on the Ni-rich layered oxides with core–shell and dual-shell structures

To understand the effect of core–shell structure on the electrochemical performance of Ni-rich layered oxides, LiNi0.6Co0.2Mn0.2O2 is redesigned to three core–shell structures on the foundation of LiNiO2-LiCoO2-LiMnO2 triangle phase diagram. After evaluated the electrochemical performances of the three core–shell structures, the optimized one, which used LiNi0.40Co0.2Mn0.4O2 as the shell component, were redesigned into dual-shell structure, which has the same outer shell with the core–shell structure to further investigate the influence of core component on the electrochemical performance of Ni-rich layered oxides. The core–shell structures are certified by the EDS results of a cross-section of particles. The electrochemical performances reveal that the dual-shell sample with LiNi0.8Co0.1Mn0.1O2 core exhibits the excellent electrochemical performances, which may be because LiNi0.8Co0.1Mn0.1O2 core can balance the capacity and structural stability in samples with dual-shell structure. This work reveal the relationship between the structure and electrochemical properties of Ni-rich layered oxides with core–shell structure, and provide a new clue to design high performance Ni-rich layered oxides for advanced Li-ion batteries.