Final Shell Research Articles

Ingestion, digestion, growth and survival of green mussel Perna viridis pediveliger larvae fed different microalgae

Nutrition plays a critical role in the growth and development of green mussel Perna viridis larvae. In this study, three species of tropical microalgae were investigated to determine their efficacy as feed source for the pediveliger stage. Larvae (2 larvae ml−1) were given Isochrysis galbana (Iso), Chaetoceros calcitrans (Cc), and Tetraselmis tetrahele (Tt) at 100,000 cells ml−1. No statistically significant difference in survival was found among treatments. The Cc diet promoted maximum growth in terms of final shell height and shell length, as well as instantaneous growth rate. Filtration rates were high, but were not significantly different. A significantly higher ingestion rate was observed in Cc-fed compared with Iso- and Tt-fed larvae. Moreover, all diets examined were readily ingested and digested by the larvae, with faster cell digestion in Cc-fed larvae based on epifluorescence microscopy. This study demonstrated that C. calcitrans, I. galbana, and T. tetrahele were all acceptable and digestible for the animals, but in terms of growth parameters and filtration and ingestion rates, C. calcitrans performed best. Information on food digestibility and feeding habits of green mussel will provide us with a better understanding of the appropriate food to be given that will suit their feeding biology and improve their production in captivity.

Optimization of Joule-Thomson cryocooler heat exchanger using one-dimensional numerical modeling

Abstract Steady state operation of the heat exchanger of a Joule-Thomson cryocooler is studied numerically through a one-dimensional model. Argon is used as the working fluid. The developed model is first verified using a cooler configuration that is studied extensively in the literature. Then the model is improved in several ways. A major mistake seen in many of the previous studies is related to the mismatch of the friction coefficient correlation and the conservation of momentum equation of the tube side flow. With the use of consistent correlations, the calculated tube side pressure drop turned out to be 81% smaller. Additionally, the effect of pressure dependency of enthalpy is considered in the energy conservation equation, resulting in 37% increase in the cooling power. Other improvements are; (i) use of Collins tubing friction correlation for the shell side, (ii) defining the exit pressure of the shell side as atmospheric pressure and calculating the inlet pressure from the pressure drop, (iii) determining the inlet temperature of shell side as saturation temperature at the calculated pressure, and (iv) defining the emissivity of the shield as a function of temperature. An optimization study is performed using the improved model with two objectives (maximization of the specific cooling power which allows decreasing flow rate and minimization of the shell side pressure drop which results in a decreased working temperature). Five design parameters (heat exchanger length, finned capillary inner diameter, fin pitch, fin length and fin thickness) are selected through a sensitivity analysis of all possible design parameters. The optimum geometry is obtained using grid search method to maximize the optimization function formed by a weighted sum of two contradicting objectives. The optimum geometry allows a decrease of the flow rate by 46% within the defined constraints. The final shell side pressure drop is decreased by 90%.

Comparison of ionic polymers in the targeted drug delivery applications as the coating materials on the Fe3O4 nanoparticles

The objective of the study was to obtain multifunctional core shell nanostructures of superparamagnetic iron oxide nanoparticles (Fe3O4) coated with various ionic biopolymers that can optimize toxicity to healthy cells, colloidal instabilities and drug loading capacities. These nanostructures can also allow drug delivery to tumor tissue because of their magnetic properties, accumulation and drug release at tumor site could be controlled by means of an external magnetic field. The impact of the biopolymers with different ionic properties to final core shell structures were investigated and compared in terms of their colloidal properties, cytotoxicities, drug adsorption and drug delivery capacities. Besides, the effect of the surface charges on the healthy cells and cancer cells is very important factor affecting toxicity and drug delivery. The results showed that the drug delivery agents coated with cationic biopolymers with cationic surface properties significantly reduced cancer cell viability compared to the anionic and nonionic polymer coatings even though their drug loading capacities were found to be the lowest.

Facile preparation of Hollow Si/SiC/C yolk-shell anode by one-step magnesiothermic reduction

Abstract Silicon is a promising anodic material used in lithium-ion battery (LIB) to improve the specific energy. While the huge volume change during lithiation/delithiation and low intrinsic conductivity has been a bottle neck of silicon anode. For this sake, carbon shell was used to enhance the conductivity, and hollow structure to buffer the volume swelling/shrinking during cycles. In this work, we synthesized a hollow yolk-shell structure Si/SiC/C (SSC) anode by one-step magnesiothermic reductive reaction. At first, polydopamine (PODA) was used as carbon source to optimize the dosage of magnesium powder and reaction temperature. Then resorcinol formaldehyde (RF) resin was used as another carbon source to prepare several samples with different carbon shell thicknesses. A vital parameter, critical thickness, about 10nm of final shell was proposed to keep the hollow yolk-shell morphology. During this one-step exothermic reaction, Si and C spontaneously reacted and formed inter SiC layer with high modulus. The half-cell with SSC anode delivered a capacity of 505.8 mA h g-1 after 220 cycles at a current density of 100 mA g-1. This novel method is facile to realize and might be used in other fields like composite plating and material modification etc.

Delayed Casting of UHPFRC Elements

Because of high durability and excellent material properties, innovative (thin-walled, shell) structures should be designed. Ultra - High Performance Fiber Reinforced concrete might be used for a specific application with very complex design and very complex shape. Usually, in design UHPFRC structure a reinforcement bars are replaced by a scattered reinforcement. Load bearing capacity in bending of the final shell or thin-walled structure might be influenced by many other factors, including fiber distribution, type and orientation, casting position (for example for up-side down casting) of the shell part of the structure and others. Very significant factor should be a cold joint in term of possible time delay between two batches (simulation of breakdown of the mixer, waiting time to air leakage). At the actual paper focus on an experimental program on cold joint between two batches of fresh UHPFRC poured into the thin wall and deck panels with longitudinal rib. These cold joints are caused by time delay between previous and next batch. Time between two batches differs in range of 10 – 90 minutes.

A transition from a large open pit into a novel “macroblock variant” block caving geometry at Chuquicamata mine, Codelco Chile

Abstract With a history of more than 100 years, Chuquicamata has become one of the largest open pits in the world. Its current depth of 1100 m, length of 4500 m and width of 3000 m, resulting in haulage distances of over 11,000 m from pit bottom to the processing plant or waste dumps, with waste/ore ratio greater than 4 and much lower grades, are effectively determining its profitable limit by the end of this decade. Currently, there are over 4300 Mt of geological resources containing 0.7% of copper and 340 ppm (1 ppm = 1 g/t) of molybdenum below the final pit shell. The corresponding orebody geometry is 3000 m northsouth, 300–800 m eastwest and the drilling campaign suggested the existence of more than 900 m of mineable ore from the final pit bottom. This is in spite of the fact that the Chuquicamata orebody is still open at depth. The business case to continue with the mining of the Chuquicamata orebody is to change from the current large open pit to a novel macroblock variant block caving geometry. This requires a production rate of 140,000 t/d (50 Mt per annum), with a continuous material handling system to achieve the 7-year ramp-up to full production. The resolution of a number of known technical, operational and logistical challenges outside current industry practises which Chuquicamata will face over its projected 40-year mine life is therefore essential. These challenges include simultaneous operations of open pit and underground macroblocks and from the initial lift to the second lift, rapid ramp-up and optimum sequencing of the planned macroblocks, early dilution from the west fault and late dilution from potential slope failures, and the potential for major operational hazards. An equally important issue to be addressed is cultural given that the mining history in the northern region of Chile, which includes Chuquicamata, is predominantly open pit. This paper presents a synopsis of the main challenges that the Chuquicamata underground project will face in order to meet the objectives of its corresponding business case. Those discussed and how they were resolved are: simultaneous operations, rapid ramp-up and optimum sequencing of the planned macroblocks, and early and late dilutions. The project is an example of the fact that there are no recipes or cook books in cave mining.

Growth of the Asian ClamCorbicula fluminea(Müller, 1774) Cultured in Çine Creek, Aydin, Turkey

Natural stocks of the Asian clam Corbicula fluminea (Muller, 1774) provide an important food source predominantly in Southern Asia. It is, therefore, important not only to assess the sustainability of natural stocks, but also to facilitate aquaculture efforts of this species. This study investigated the growth and survival rate of C. fluminea in bottom net culture over 13 mo in Cine Creek, Aydin, Turkey, in a temperate Mediterranean climate zone. Water temperature ranged between 10 and 24°C and food availability (measured by concentrations of chlorophyll-a (Chl-a) and suspended particulate organic matter) peaked during the autumn and spring. The final shell length (SL) and total body weight of C. fluminea (mean ± SE) were 29.02 ± 0.5 mm (initially 23.76 mm) and 12.17 ± 0.5 g (initially 6.65 g), respectively. Maximum growth rates were significantly higher during the autumn and spring months. A strong positive correlation was found between the availability of food (Chl-a) and total particulate matter concentrations and growth rates (in terms of SL and total weight). Survival was high (97%) by the end of the study and environmental conditions in Cine Creek supported good growth of clams. The species Corbicula fluminea, either as a native or introduced species, can be considered as a promising candidate species for the diversification of aquaculture in the region.

Hollow TiO2 flake prepared from TiO2 coated glass flake for solar heat protection and their thermal performance

Abstract Hollow TiO2 flake (HTFs) for use as a solar protection material were prepared using TiO2 coated glass flake (TGF), followed by the etching of their core. Rutile TiO2, with high refractive index applied for solar heat protection, was densely and completely coated onto the glass flake (GF) surface using a titration method and a final shell thickness of 200–400 nm was achieved. The solar reflectance of the TGF improved to 89% with increasing CIE lightness (L*). Furthermore, HTF with a hollowed out size of approximately 1–2 × 20 μm were also obtained by etching their core GF with HF solution, resulting in a reduced thermal conductivity. The UV–Vis-NIR spectra, optical properties, and thermal conductivity of the hollow TiO2 flake was investigated to determine their solar heat protection capabilities. The HTF exhibits a higher solar reflectance (90%) and lower thermal conductivity (80 mW/m·k) than solid GF and TGF. Hence, HTF is a suitable candidate for developing solar heat protection materials with a dual function.

Diketopyrrolopyrrole pigment core@multi-layer SiO2 shell with improved photochemical stability

A model organic pigment (diketopyrrolopyrrole) is encapsulated by a silica coating in order to improve its photochemical stability. Unlike in previous works where single-layer silica coatings were used for similar purposes, we here propose creation of a multi-layer silica shell synthesized via in-situ sol-gel method, which should significantly improve the homogeneity and thus the protection ability of the coating. This is done by repeating the basic two-step process (pigment surface modification and silica encapsulation) several times, creating the final protective shell in a layer-by-layer fashion. The compositional and structural properties of the prepared coatings is studied using Fourier-transform infrared spectroscopy, differential thermal and thermogravimetric analysis, nitrogen adsorption measurements and transmission electron microscopy. Photochemical stability of non-encapsulated and encapsulated pigment particles is evaluated via the so-called fast-irradiation method. Various correlations between the essential coating properties, such as thickness, porosity, SiO2 content, and the corresponding photochemical stability of the samples are established and discussed in detail. As a whole, our results confirm the basic hypothesis, that multiple-layered silica shells show improved pigment protection ability in comparison to the single-layer coatings.

Extension of the string-on-foundation method to study the shock wave response of an immersed cylinder

Abstract This paper presents a simplified method for assessing the damage of a non-stiffened immersed cylinder subjected to the primary shock wave produced by an underwater explosion. The interaction between water and cylinder is split into two different phases. In the first phase, the kinetic energy which is transmitted by the shock wave to the cylinder is derived from explosion parameters. In the second phase, the cylinder deforms and the additional pressure created by interaction between water and deforming shell is calculated. To simulate the response of a cylinder clamped at its extremities, an analytical method based on the so-called rigid-plastic string on rigid-plastic foundation model is proposed. Closed-form expression is derived for evaluating the final shell deflection and used to highlight the influence of water added mass on cylinder damage. The proposed method is then validated by comparing, for a given cylinder and different shock factors, the resulting damage with finite element results. It appears that for high shock factors (i.e. K ≥ 2), the method allows for a good estimation of the cylinder shell deflection. It however underestimates significantly the deformed area when the shock factor is around 1.5 or lower. Additional research work is on-going to take into account deep immersion effects as well as ring-stiffening of the cylindrical shell.

Zika Immunoassay Based on Surface-Enhanced Raman Scattering Nanoprobes.

Zika virus (ZIKV) was considered a public health emergency of international concern after the 2015 outbreak. Serological tests based on immunoassay platforms is one of the methods applied on the diagnosis of ZIKV and Dengue virus (DENV). However, the high limits of detection (LOD) and the cross-reactivity between ZIKV and DENV are still limitations in immunological tests. In order to tackle these issues, we have designed an immune-specific assay based on surface-enhanced Raman scattering (SERS) nanoprobes. Gold shell-isolated nanoparticles (Au-SHINs) were synthesized with 100 nm Au nanoparticles and 4 nm silica shell thickness coated with Nile Blue (Raman reporter). Then, the SERS nanoprobes were wrapped in a final silica shell and functionalized with monoclonal anti-ZIKV NS1 antibodies. Concentrations of ZIKV NS1 down to 10 ng/mL were probed free of cross-reactivity with DENV NS1 antigens.

Superplastic forming of shells from sheet blanks with thermally unstable coatings

The article is devoted to superplastic forming of non-uniformly heated sheet blanks from aluminum alloy AMg6M. To create an uneven temperature field over the surface of the blank, coatings made of sublimated substances were used from at temperatures 50…150°C below the superplastic forming temperature (450°C for AMg6M alloy). An aqueous solute of chloride and ammonium iodide having a sublimation temperature at normal pressure and a latent heat of conversion equal to 338 and 404°C, 330 and 355kJ/kg, respectively, was sprayed onto the central zones of the blanks. Superplastic forming of shells was carried out in two modes: 1) with simultaneous sublimation of the coating; 2) with the beginning of the sublimation of the coating upon reaching the height, which is formed by the workpiece, equal to 20-30% of the final shell height. The experiments showed a decrease in the thickness of the shells to be formed up to 4-10% on the working surface of the shells (without taking into account their flange zones) and the savings of sublimate during superplastic forming in the second mode. The optimal subliming coating for AMg6M alloy was ammonium chloride.

An experimental study on the coaxial electrospinning of silk fibroin/poly(vinyl alcohol)–salicylic acid core-shell nanofibers and process optimization using response surface methodology

Core-shell nanofiber of silk fibroin as shell and blend of salicylic acid/poly(vinyl alcohol) as core was fabricated successfully via coaxial electrospinning. Effects of concentration, viscosity, and electrical conductivity of the core and shell solutions on the final diameter of nanofibers and release behavior of salicylic acid were studied by viscometry, electrical conductometry, ultraviolet spectrophotometry, scanning electron microscope and transmission electron microscope methods. Response surface methodology was used to predict the relation between average fiber diameter as well as release rate of salicylic acid with core and shell concentrations. Direct relation between final nanofibers diameters and shell solution concentration was observed, while increase in core solution concentration was not significantly affected the final diameter of electrospun nanofibers. According to the results of release profiles, ratio of component in core and shell are effective parameters in rate and profile of salicylic acid release from these structures. Response surface methodology analysis indicates that the nanofibers diameters are more responsive to the changes in shell solution concentration and the release rate of salicylic acid is responsive to the changes in both shell and core solutions concentrations.

Geometrical optimization of quasi-spherical wire-array implosion

A geometrical optimization method based on the multi-element model is developed for electromagnetic implosion of quasi-spherical wire-array loads. The shapes of the initial quasi-spherical wire arrays are described with the parabolic formation, and the shapes of the final plasma shells are estimated with the multipole expansion method. By scanning the aspect ratios of the initial loads, we can obtain the most nearly-spherical final plasma shell with certain mean radius, i.e. the shell has the smallest quadrupole and hexadecapole deformation. As a typical case, starting with the preshaped cylindrical load (with height of 15.4 mm and with diameter of 8 mm), the imploding plasma shell with mean radius of 1.5 mm is almost spherical when the initial aspect ratio takes the value of 1.089, and the results is consistent with the synchronization analysis. The optimization calculations for different current waveforms and different initial load masses indicate that the shape of the optimized plasma shell is not sensitive to the drive current and load mass. The geometrical optimization method here can be served as a primary designing tool for the quasi-spherical wire-array load.

Crystal Structure of Faradaurate-279: Au279(SPh-tBu)84 Plasmonic Nanocrystal Molecules.

We report the discovery of an unprecedentedly large, 2.2 nm diameter, thiolate protected gold nanocrystal characterized by single crystal X-ray crystallography (sc-XRD), Au279(SPh-tBu)84 named Faradaurate-279 (F-279) in honor of Michael Faraday's (1857) pioneering work on nanoparticles. F-279 nanocrystal has a core-shell structure containing a truncated octahedral core with bulk face-centered cubic-like arrangement, yet a nanomolecule with a precise number of metal atoms and thiolate ligands. The Au279S84 geometry was established from a low-temperature 120 K sc-XRD study at 0.90 Å resolution. The atom counts in core-shell structure of Au279 follows the mathematical formula for magic number shells: Au@Au12@Au42@Au92@Au54, which is further protected by a final shell of Au48. Au249 core is protected by three types of staple motifs, namely: 30 bridging, 18 monomeric, and 6 dimeric staple motifs. Despite the presence of such diverse staple motifs, Au279S84 structure has a chiral pseudo-D3 symmetry. The core-shell structure can be viewed as nested, concentric polyhedra, containing a total of five forms of Archimedean solids. A comparison between the Au279 and Au309 cuboctahedral superatom model in shell-wise growth is illustrated. F-279 can be synthesized and isolated in high purity in milligram quantities using size exclusion chromatography, as evidenced by mass spectrometry. Electrospray ionization-mass spectrometry independently verifies the X-ray diffraction study based heavy atoms formula, Au279S84, and establishes the molecular formula with the complete ligands, namely, Au279(SPh-tBu)84. It is also the smallest gold nanocrystal to exhibit metallic behavior, with a surface plasmon resonance band around 510 nm.

Numerical investigation of in-mold electromagnetic stirring process for fluid flow and solidification

PurposeThe purpose of present investigation is to analyze the in-mold electromagnetic stirring (M-EMS) process and the effect of stirrer frequency on fluid flow and solidification in a continuous casting billet caster mold.Design/methodology/approachA hybrid approach involving finite element and finite volume method has been used for the study. Finite element model is used to calculate time variable magnetic field, which is further coupled with fluid flow and solidification equations for magneto-hydrodynamic analysis with finite volume model.FindingsResults show that though superheat given to steel before its entry into the mold is quickly removed, solid shell formation is delayed by the use of M-EMS. Final solid shell thickness, however, is slightly reduced. Increase in frequency is found to increase the magnetic flux density and tangential velocity of liquid steel and decrease in diameter of liquid core.Practical implicationsThe work is of great industrial relevance. The model may be used to design industrial setup of in-mold electromagnetic stirrer and process could be analyzed and optimized numerically.Originality/valueThe paper evaluates the influence of M-EMS and its frequency on solidification and flow behavior in the continuous casting mold. The iso-surface temperatures from pouring temperature to liquidus temperature inside the mold have been shown. The findings may be useful for the steelmakers to reduce the defect in continuous casting.

Interface formation during silica encapsulation of colloidal CdSe/CdS quantum dots observed by in situ Raman spectroscopy.

We investigate the encapsulation of CdSe/CdS quantum dots (QDs) in a silica shell by in situ Raman spectroscopy and find a distinct shift of the CdS Raman signal during the first hours of the synthesis. This shift does not depend on the final silica shell thickness but on the properties of the initial core-shell QD. We find a correlation between the Raman shift rate and the speed of the silica formation and attribute this to the changing configuration of the outermost layers of the QD shell, where an interface to the newly formed silica is created. This dependence of Raman shift rate on the speed of silica formation process will give rise to many possible studies concerning the growth mechanism in the water-in-oil microemulsion, rendering in situ Raman a valuable instrument in monitoring this type of reaction.

Comparison of growth and heterosis of body parameters of two varieties of snail [Archachatina marginata (Swainson1821)] and their crosses reared under tropical conditions

The main objective of this paper was to compare growth traits and heterosis of body parameters of two varieties of Archachatina marginata (var. ovum and var. saturalis) and their crosses under experimental conditions. Three hundred (300) juvenile snails (Archachatina marginata), one hundred (100) each of A. marginata var. ovum, A. marginata var. saturalis and their crosses with mean body weights of 12.40 ± 0.58 g were used for the study. The snails were randomly allotted using completely randomized design into three (3) treatment varieties. Results from the study showed significant variety effect (P 0.05) variety effect was observed on daily weight gain, total feed intake, daily feed intake and feed conversion ratio. The crossbred variety recorded the highest final body weight and final shell width, indicating heterotic effects on these two bodies and shell parameters. Significant variety effects (P<0.05) were observed on body weight, shell length and shell “mouth” length. The low heterotic values obtained for body weight and the shell parameters supported the assertion that growth traits have low heterotic values which may be due to their high heritability. Though, low and positive heterotic values were obtained for all parameters studied, the crossbred variety recorded the highest heterotic values, which indicated that it may have heterotic advantage over the purebred varieties.

Morphology-Controlled Coating of Colloidal Particles with Silica: Influence of Particle Surface Functionalization.

We present a general, convenient, and efficient synthetic concept for the coating of colloidal particles with a silica (SiO2) shell of well-defined and precisely controlled morphology and porosity. Monodisperse submicroscopic polystyrene (PS) particles were synthesized via two-stage emulsifier-free emulsion polymerization and subsequent swelling polymerization, enabling selective particle surface modification by the incorporation of ionic (methacrylic acid, MAA) or nonionic (hydroxyethyl methacrylate, HEMA or methacrylamide, MAAm) comonomers, which could be proven by zeta potential measurements as well as by determining the three-phase contact angle of the colloidal particles adsorbed at the air-water and n-decane-water interface. The functionalized particles could be directly coated with silica shells of variable thickness, porosity, and controlled surface roughness in a seeded sol-gel process from tetraethoxysilane (TEOS), leading to hybrid PS@silica particles with morphologies ranging from core-shell (CS) to raspberry-type architectures. The experimental results demonstrated that the silica coating could be precisely tailored by the type of surface functionalization, which strongly influences the surface properties of the colloidal particles and thus the morphology of the final silica shell. Furthermore, the PS cores could be easily removed by thermal treatment, yielding extremely uniform hollow silica particles, while maintaining their initial shell architecture. These particles are highly stable against irreversible aggregation and could be readily dried, purified, and redispersed in various solvents. Herein we show a first example of coating semiconducting CdSe/ZnS nanocrystals with smooth and spherical silica shells by applying the presented method that are expected to be suitable systems for applications as markers in biology and life science by using fluorescence microscopy methods, which are also briefly discussed.

Deposition of hermetic silver shells onto copper flakes

Continuous silver shells were deposited on copper flakes using a two-stage precipitation process. A tightly packed layer of silver nanoparticles was first formed on the surface of the base metal by galvanic displacement. The size of the noble metal particles and their distribution on the substrate were controlled using complexing agents and dispersants. A continuous Ag deposit was subsequently grown by reducing slowly [Ag(NH3)2]+ ions with glucose. The final shell thickness was controlled by varying the amount of metal deposited in the second step. The electrical properties of resulting silver coated copper flakes are comparable to those measured for silver flakes of similar size and aspect ratio. By preventing the oxidation of copper cores up to 400°C, the hermetic noble metal shell dramatically extends the temperature range in which Ag/Cu flakes can successfully replace pure silver.