Large Shell Research Articles

Three-dimensional water mapping of succulent Agave victoriae-reginae leaves by terahertz imaging

While terahertz imaging has been used before for the determination of water content in vegetative tissue, most studies have either presented measurements of the temporal evolution of water content at a single-point of the plant or have presented two-dimensional images of leaves, demonstrating the potential of the technique, but relatively little of such information has been used to support biologically relevant conclusions. In this article we introduce terahertz time-domain spectroscopic imaging as a technique for the determination of the three-dimensional distribution of water in succulent plant tissues. We present the first three-dimensional water mapping of an agave leaf, which demonstrates an unprecedented capability to study the water retention mechanisms within succulent plants. We found that agave leaves are composed of a low-hydration outer tissue layer, defined by the outermost layer of vascular tissue that surrounds a high-hydration tissue, the carbohydrate rich hydrenchyma. The findings are supported by histological images and the correlation between the water content and carbohydrate presence is consistent with recently published findings of a remarkably large hydration shell associated with agave fructans.

Impact of electron capture rates for nuclei far from stability on core-collapse supernovae

The impact of electron-capture (EC) cross sections on neutron-rich nuclei on the dynamics of core-collapse during infall and early post-bounce is studied performing spherically symmetric simulations in general relativity using a multigroup scheme for neutrino transport and full nuclear distributions in extended nuclear statistical equilibrium models. We thereby vary the prescription for EC rates on individual nuclei, the nuclear interaction for the EoS, the mass model for the nuclear statistical equilibrium distribution and the progenitor model. In agreement with previous works, we show that the individual EC rates are the most important source of uncertainty in the simulations, while the other inputs only marginally influence the results. A recently proposed analytic formula to extrapolate microscopic results on stable nuclei for EC rates to the neutron rich region, with a functional form motivated by nuclear-structure data and parameters fitted from large scale shell model calculations, is shown to lead to a sizable (16%) reduction of the electron fraction at bounce compared to more primitive prescriptions for the rates, leading to smaller inner core masses and slower shock propagation. We show that the EC process involves $\approx$ 130 different nuclear species around 86 Kr mainly in the N = 50 shell closure region, and establish a list of the most important nuclei to be studied in order to constrain the global rates.

Pointing at fossils: pXRF identification of a fossilized shell projectile point

A shell artifact recovered during wet-screening of cultural sediments from CA-SDI-39 (San Diego, CA) had several unusual properties. Fashioned into a triangular projectile point using lithic flaking techniques, the artifact was unlike any other shell tools in the associated assemblage or reported elsewhere in California. Unlike other shell tools in the assemblage, the artifact was not flakey, and appeared to have been formed from a very large shell. This combination of characteristics suggested possible origins from fossilized shells in Pliocene-Pleistocene aged marine terraces. Destructive sampling was not possible, so pXRF was used to investigate chemical evidence for fossilization, or other possible treatments. Results suggest that this artifact was formed from shell that formed under substantially different water conditions than present, evidencing recrystallization consistent with fossil or subfossil shell, but an incomplete mineral conversion.

Improvement in mechanical, thermal conductivity and corrosion performances of a new high-thermally conductive Al-Si-Fe alloy through a novel R-HPDC process

Abstract A low-cost, new casting Sr-modified Al-7.5Si-0.8Fe alloy with high-thermal conductivity was prepared into large thin-wall heat-dissipating shells for 5G communication base stations using a traditional high pressure die-casting (HPDC) process and a rheological HPDC (R-HPDC) technique. Their microstructure, tensile property, hardness, thermal conductivity, and corrosion behavior were analyzed. The R-HPDC Al-7.5Si-0.8Fe alloy shows a refined microstructure in terms of α1-Al particles, α2-Al grains, fibrous β-Al5FeSi, and granular eutectic silicons when compared to traditional HPDC alloys. The R-HPDC alloy has a thermal conductivity, elongation-to-failure value, ultimate tensile strength, yield strength, and Vickers hardness of 186 W/(m.K), 12.4 %, 235 MPa, 114 MPa, and 70 HV, respectively. These values are respectively 6 %, 91 %, 22 %, 14 %, and 11 % higher than those reported for conventional HPDC alloys. Moreover, the R-HPDC Al-Si-Fe alloy shows a superior corrosion resistance in comparison to HPDC alloys. This observation is supported by scanning Kelvin probe (SKP) measurements and electrochemical tests. The improved performances arise mostly from the refinement of the iron-rich intermetallics (β-Al5FeSi) and eutectic silicons, the increase in the area proportion of α2-Al grains relative to eutectic silicon, and the reduction in the potential difference between the aluminum matrices and the iron-rich intermetallics.

The energetic costs of living in the surf and impacts on zonation of shells occupied by hermit crabs.

Crashing waves create a hydrodynamic gradient in which the most challenging effects occur at the wave breaking zone and decrease towards the upper protected tide pools. Hydrodynamic forces depend on the shape of the submerged body; streamlined shapes decrease drag forces compared with bluff or globose bodies. Unlike other animals, hermit crabs can choose their shell shape to cope with the effects of water flow. Hermit crabs occupy larger and heavier shells (conical shape) in wave-exposed sites than those used in protected areas (globose shape). First, we investigated whether a behavioral choice could explain the shells used in sites with different wave action. Then, we experimentally tested whether the shells most frequently used in sites with different wave action reduce the energetic cost of coping with water flow. Metabolic rate was measured using a respirometric system fitted with propellers in opposite walls to generate bidirectional water flow. The choice of shell size when a large array of sizes are available was consistent with the shell size used in different intertidal sites; hermit crabs chose heavier conical shells in water flow conditions than in still water, and the use of heavy conical shells reduced the energetic cost of coping with water motion. In contrast to conical shells, small globose shells imposed lower energy costs of withstanding water flow than large globose shells. The size and type of shells used in different zones of the rocky shore were consistent with an adaptive response to reduce the energetic costs of withstanding wave action.

Programming stiff inflatable shells from planar patterned fabrics.

Lack of stiffness often limits thin shape-shifting structures to small scales. The large in-plane transformations required to distort the metrics are indeed commonly achieved by using soft hydrogels or elastomers. We introduce here a versatile single-step method to shape-program stiff inflated structures, opening the door for numerous large scale applications, ranging from space deployable structures to emergency shelters. This technique relies on channel patterns obtained by heat-sealing superimposed flat quasi-inextensible fabric sheets. Inflating channels induces an anisotropic in-plane contraction and thus a possible change of Gaussian curvature. Seam lines, which act as a director field for the in-plane deformation, encode the shape of the deployed structure. We present three patterning methods to quantitatively and analytically program shells with non-Euclidean metrics. In addition to shapes, we describe with scaling laws the mechanical properties of the inflated structures. Large deployed structures can resist their weight, substantially broadening the palette of applications.

Разработка конструкторско-технологических решений для оптимизации аппаратурного оформления процесса изготовления крупногабаритных латексных оболочек

Разработка конструкторско-технологических решений для оптимизации аппаратурного оформления процесса изготовления крупногабаритных латексных оболочек

Intertidal sedimentary dynamics in Mont-Saint-Michel bay, a study of its natural evolution and man-made modifications

Due to its exceptional tidal range and the immensity of its intertidal zones, Mont-Saint-Michel is a favored model for research on coastal hydro-sedimentary processes, present-day sedimentary dynamics and the reconstruction of coastal paleo-environments. The purpose of this article is to analyze the erosion/sedimentation processes which govern the sedimentary dynamics and the recent evolution of the characteristic sedimentary environments of the bay. The western bay head is made up of tidal sand and silt deposits, where the extent of the surface sediment reworking is less than 10 cm and linked to the nature of the substrate and the wind direction. Added to these tidal dynamics are the dynamics of the swell, which set coarse bioclastic sands in motion as the waves wash away the shore. These sands migrate on the tidal flat at rates of several dozen m/year and accumulate on the upper tidal flat, forming a relatively stable non-continuous coastal barrier of large shell banks. The eastern part of the bay is an estuarine zone, where the morpho-dynamics of the sandy tidal flat are constrained by shifting channels. Studies of the interaction between vegetation and sedimentation around Mont-Saint-Michel show sedimentary accretion rates varying from 0.2 to 10 cm/year, depending on the morpho-dynamic context of the salt marsh front. The volume of sediment deposited by the tide leads to cyclical deposition of calcareous muds followed by the steady advance of salt marshes at a rate of about 17 ha/year between La Chapelle Sainte-Anne and the Roche Torin point. The bay has filled for thousands of years to the rhythm of sea level oscillations, leading to the gradual infilling of the Dol marsh and the advance of the shoreline. In addition to this natural evolution, human activities have developed in the bay, both on the western tidal flat (fixed fisheries and shellfish farming) and on the eastern estuarine side (polder formation, construction of dikes and a dam) and have altered the landscapes, the historical evolution of which was reconstructed from old documents.

Effect of shell diameter and shell thickness on coconut-shell-halving force

Design of any product is primarily based on the characteristics of various parameters that will be having direct influence on their functionality. The aim of this study is to understand the influence of physical parameters of coconuts, viz. shell diameter and shell thickness on the shell halving force, so that proper designing and development of an efficient energy efficient shell-splitting tool can be done. In line with this objective, experimental investigations have been carried out on 50 green and 50 dry fully matured coconuts to measure force needed in compression for rupturing the shell equatorially. The experimentations have been carried out using a Universal Testing Machine. Results suggest a negative correlation between shell diameter and shell halving force. However, influence of shell thickness on shell halving force has been found to be less significant. Combined analysis of the results suggests that coconuts having large shell diameter and small thickness require lower shell halving force.

Synthesis and mechanical properties of large size silica shell microcapsules for self-healing cementitious materials

Synthesis of inorganic shell microcapsules is very challenging in the field of self-healing cementitious materials. Here, we report successful fabrication of epoxy resins encapsulated into silica shell microcapsules with average particle size greater than 100 μm via interfacial polymerization. The silica shell microcapsules show good thermal stability. The nanoindentation test was used to determine the micromechanical properties of the microcapsules. The results show that silica shell microcapsules exhibit brittle rupture, high Young’s modulus and hardness of the shell, with a better deformation resistance. The observed micromechanical properties are attributed to the regular tetrahedral crystal structure of the silica shell materials.

Patterns of growth, brooding and offspring size in the invasive mussel Sinanodonta woodiana (Lea, 1834) (Bivalvia: Unionidae) from an anthropogenic heat island

In freshwater temperate environments, waterbodies warmed by power plants can serve as a stepping stone in the spread of tropical and subtropical species. This offers a unique opportunity to acquire an insight into the life history of organisms undergoing range expansions beyond their native habitat. Here, we studied the patterns of offspring production and growth in the Asian mussel Sinanodonta woodiana inhabiting the thermal plume of the Odra River in Central Europe. Compared to the S. woodiana males, females had more convex shells and had a greater tendency to continue post-maturation growth and thus follow an indeterminate growth pattern. Gravid females were observed all-year round, and individuals with either large or more convex shells brooded more offspring. The proportion of incubating females, brood size and glochidia size were linked to gonadal activity and changed seasonally. Females with a higher amount of nutritive substances in the ovaries produced more and larger offspring. The smallest and the largest offspring occurred in the summer and in the winter, respectively. Sinanodonta woodiana incubated different offspring generations simultaneously, constantly releasing them into the environment. Using a life history evolution perspective, we discuss our results in view of allocation trade-offs between growth and offspring production.

3D Simulation of Large Hull Shell Surface based on 3D Digital Video

ABSTRACT Zhong, J., 2019. 3D simulation of large hull shell surface based on 3D digital video. In: Hoang, A.T. and Aqeel Ashraf, M. (eds.), Research, Monitoring, and Engineering of Coastal, Port, a...

Minimum Value Approach for Modelling of the Buckling Resistance of Welded I-Section High Strength Steel Columns

AbstractThe paper deals with determination of flexural resistance buckling curves for welded I-section steel members made of high strength steel (S 690). In the paper the previously proposed BF analytical model is used for approximation of FEM results obtained using moderately large deformation shell theory and ABAQUS/Standard software. Final formulation of flexural resistance buckling curves is possible through the use of the Merchant-Rankine-Murzewski approach adopted extensively in the authors’ previous papers. For nonlinear optimization, which is needed for analytical model parameters determination, the Wolfram Mathematica package is used. Obtained results for S 690 steel are presented against the results for S 355 steel.

Optimization Strategies for Grid Shells: The Role of Joints

AbstractStructural optimization techniques are being usefully employed for the design of large grid shell structures. Indeed, thanks to the use of innovative strategies and mathematical algorithms,...

Bryozoans and brachiopods from the Lower Miocene deposits of the Qom Formation in North-East Isfahan (Central Iran)

A study of bryozoans and brachiopods from the Varton, Zefreh and Kuh-e-Charkheh sections from the Esfahan-Sirjan fore-arc basin of the Qom Formation of Central Iran has yielded 30 bryozoan taxa, including one new species Gigantopora vartonensis, and six brachiopod species. Both assemblages co-occur with large oyster shells with some of the ventral valves of brachiopods directly attached to their shells. The paleoenvironment is interpreted as an oyster bank ('oyster reef') in shallow, tropical-subtropical marine waters, producing cryptic habitats for other groups of organisms.

Fabrication of functional hollow magnetic polymeric nanoparticles with controllable magnetic location

Hollow magnetic polymeric particles (HoMPs) with controllable location of magnetic nanoparticles and functionality of polymeric double shell were fabricated by means of the facile soft templating method in one-pot. During the in situ miniemulsion polymerization, hexadecane, the Ostwald suppressing agent, acted as a soft template, which later formed a controllable void size. Adjusting ratio and polarity of monomers caused the difference in polymerization kinetics and phase separation, which resulted in HoMPs with two internal architectures, i.e., HoMPs-I with magnetic at the inner shell/void interface and HoMPs-II with magnetic-embedded shell. Both HoMPs-I and II contained high magnetic content (30–50%wt) with sufficient saturation magnetization (16–30 emu/g). With large void volume (>50%) and distinct shell polarity, either hydrophilic Rhodamine B or hydrophobic fluorescein isothiocyanate dye was selectively loaded. After functionalization with a cancer cell targeting ligand, folic acid (FA), the cellular uptake of HoMPs-FA in HeLa cell was improved with 100% cell viability and without cell destruction. This fabrication method provides a facile mean to tailor surface chemistry and architectures of hollow hybrid particles, which would be potentially used for efficient treatment of cancer tumors.

피뿔고둥(Rapana venosa)에 감염된 흡충류(trematodes)에 관한 보고

The large gastropod purple shell, Rapana venosa, inhabit in the western and southern coasts of Korea at a depth of approximately 10m. Identification of trematodes found in R. venosa from Sihwa lake, Gyeonggi-do, Korea, was conducted in this study. Trematode infection sites were examined using light microscope and genomic DNAs were extracted from the infected tissues of boiled R. venosa. Mitochondrial cytochrome c oxidase subunit 1 region (mt COI), internal transcribed spacers rDNA regions (ITS1-5.8S-ITS2) and 28S rRNA region of the trematode DNA were amplified by polymerase chain reaction (PCR), and compared with those already registered in GeneBank. Cercaria and redia of trematodes were found by light microscopy. Although the DNA sequence of mt COI gene did not match with the Parorchis sp. mt COI sequence, there was a high genetic similarities of ITS1-5.8S-ITS2 and 28S rRNA genes with those of Parorchis sp. (ITS: 97%, 28S: 99%). The phylogenetic analysis also showed our samples were closely clustered with Parorchis sp. All of these data suggest that our samples found in R. venosa are Parorchis sp., but further studies such as electron microscopic observation with fresh samples will be necessary for clear identification at the species level.

Investigation of accurate forming of a semi-ellipsoidal shell part by an electromagnetic forming method

Forming a sheet into a predesigned die cavity is an effective way to improve the dimensional accuracy of deformed parts. However, it is difficult to obtain good die-fitting quality for workpiece deformed at high speed during the one-time discharge electromagnetic forming (EMF) process. To address this challenge, a numerical simulation model was established to help optimize the forming process that affects the die-fitting quality in the formation of a semi-ellipsoid shell part. Then, experiments were conducted according to the optimized forming process. Finally, the dynamic deformation behavior of the workpiece was revealed. The results showed that the drawing deformation mode can effectively improve the die-fitting quality as well as the effective plastic strain distribution of the shell part compared with the bulging deformation mode. Moreover, reducing the initial blank diameter is a more effective way to improve draw-in compared with adjusting the blank holder force. Furthermore, a semi-ellipsoid shell part was manufactured with a maximum die-fitting gap of no more than 1.4 mm at a one-time discharge voltage of 11.5 kV. The deviation was only 1.45% of the maximum forming height. The results provide a foundation for forming a large semi-ellipsoidal shell part by the one-time discharge EMF method.

Molecular dynamics study of the intercalation and conformational transition of poly (N-vinyl caprolactam), a thermosensitive polymer in hydrated Na-montmorillonite

In this study, we performed molecular dynamics (MD) simulations of the intercalation of poly (N-vinyl caprolactam) (PNVCL) into Na-montmorillonite (Na–Mt) to evaluate the solvation dynamics, the ordering of H2O molecules and the effect of interlayer attractive forces in inducing conformational transitions in PNVCL from 275 to 335 K. Conformational transformation of PNVCL into Na–Mt and in bulk water were compared and contrasted to understand the effects of interlayer attractive forces on PNVCL. The results showed that the coil-to-globule transition of PNVCL appeared at 305 K when in bulk water and not into Na–Mt due to the reduction of the hydrophobic interaction between PNVCL residues by the electrostatic forces in the interlayer. H2O molecules formed H-bonded cage-like structure around PNVCL, and the amount of these H-bonds and H2O molecules decreased with the thermal perturbation. Our investigations suggest that the solubility, solvation dynamics and the conformation transformation of PNVCL into Na–Mt are determined by the electrostatics forces existing in the interlayer and the structure of proximal H2O molecules when the temperature increased. PNVCL exhibited good inhibition effect on Na–Mt by reducing its interlayer particles mobility. The radial distribution function curves and the solvent accessibility surface area indicated that PNVCL was more exposed to H2O molecules into Na–Mt than in bulk water due to their proximity with the large hydration shells formed around Na cations and the strong H-bonds formed between clay mineral surface and H2O molecules. H-bonds analysis into Na–Mt showed that clay mineral surface was more likely to form H-bond with H2O molecules than PNVCL because of their hydrophilic properties. These results highlight the conformational transition of PNVCL into hydrated Na–Mt and predict its stability against environmental condition changes.

New species of the long-necked chelid Yaminuechelys from the Upper Cretaceous (Campanian–Maastrichtian) of Chubut, Argentina

A new species of a long-necked chelid from the uppermost Cretaceous (Campanian–Maastrichtian) is presented in this contribution. Yaminuechelys sulcipeculiaris sp. nov. is found in outcrops of the La Colonia Formation in the northeast part of Chubut province, Argentina. This new species is mainly represented by carapacial, plastral, and postcranial remains (vertebrae and long bones). It was assigned to Yaminuechelys because it presents characters shared with the species Yaminuechelys gasparinii de la Fuente, Lapparent de Broin, and Manera de Bianco, 2001 and Yaminuechelys maior (Staesche, 1929). Those characters are a large shell with irregular polygons distributed on the external surface, the difference in length between the anterior and posterior peripheral bones, and the neural series separated from the suprapygal bones. Other characters, like the position of the sulcus between vertebral 5 and marginal 12 crossing the suprapygal and the location of the sulcus between the vertebral 5 and the marginal 11 crossing the costal 8 and suprapygal, suggest it is a new species. According to the phylogenetic analysis performed, the new species forms a monophyletic group together with Y. maior, and Y. gasparinii. The survival of Yaminuechelys to the K/Pg extinction event is also discussed.