Distribution Of Shells Research Articles

Optimization of precursor structure by dispersants to promote nitrogen reduction process to prepare high-quality VN

In this study, three dispersants of polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG) and citric acid (CA) are used to optimize the structure of the precursor in order to prepare high quality VN. Under optimum condition, the VN with nitrogen content of 17.94 % is prepared by adding 5 % PVP. The sequence of phase evolution from the precursor to VN is: APV → V2O5 → V6O13 → V7O13 → VO2 → V3O5 → V2O3 → (VC) → VN. The precursors of adding 5 % PVP have lower Ea of 0.17 kJ mol−1, 20.51 kJ mol−1 and 62.70 kJ mol−1 during reduction and nitration process, which is easier to be reduced and nitridated. PVP not only promotes the uniform dispersion of the carbon powders in the vanadium rich solution but also enhance the hydrogen bonding of APV ions to promote their nucleation and growth. The precursor with uniform and concentrated particle size distribution, complete and stable encapsulation of shell of APV and core of carbon powder, and uniform and moderate thickness of APV shell is successfully prepared by adding PVP. The precursor has a larger phase reaction interface and more reactive sites during the nitriding reduction process, which results in a faster reduction and nitriding rate. In comparison with the current process, the nitriding reaction temperature has been reduced from 1400 ∼ 1500 °C to 1150 ∼ 1200 °C, the reaction time has been shortened by 75 %, and the N2 consumption has been reduced by 40 %.

Digital twin method for the stress field of a deep-diving spherical shell based on a simulation database

In this paper, a Digital Twin (DT) method is proposed for quickly predicting the stress fields of deep-diving spherical shells based on a simulation database. The DT method can completely cover the stress field distribution of the entire pressure-resistant shell and provide stress predictions for different sizes of deep-diving protection shells. The DT model has a three-level structure. The Level-1 DT maps the Finite Element Model to the digital model, which is verified by experiments. The difference between the experimental and numerical results is less than 9.4%. Then, the Level-2 DT deduces the digital model and expands the simulation database samples. The uncalculated stress field results in the simulation database could be obtained by the local Lagrangian interpolation method. Furthermore, the Level-3 DT can rapidly predict the stress field distribution in deep-diving spherical shell digital models. By comparison with different optimization algorithms, the Particle Swarm Optimization algorithm demonstrates strong optimization capabilities and fast convergence, and the error compared with the simulation results is less than 1%. Finally, combined with actual sensor measurements and historical experience data, this method can be used to carry out real-time mapping and synchronous deduction of the service state of the dynamic stress digital twin.

Impact of pretreatment with photocatalysis sequential coupling Fenton oxidation on physicochemical properties, pyrolysis behaviors, and product distribution of walnut shell

Naturally occurring alkali and alkaline earth metals (AAEMs) in biomass can adversely affect its pyrolysis behavior and product distribution and contribute to ash deposition in boilers. To address these challenges, we proposed a new idea of photocatalysis sequential coupling Fenton oxidation for biomass pretreatment. Our findings revealed that sequential pretreatment has the optimal moderating effects on biomass relative to individual photocatalysis and Fenton oxidation. The lignin and AAEMs in biomass were effectively reduced via sequential pretreatment, which was accompanied by cellulose content increased by 80.78% relative to untreated. Also, the slagging/fouling inclinations of biomass were successfully alleviated, and the pyrolysis performance was effectively improved. The kinetic parameters obtained based on the Coats-Redfern method can characterize the pyrolysis behavior well. During fast pyrolysis, sequential pretreatment caused the productivity of bio-oil was increased by 30.14% relative to untreated. In particular, the productivity of levoglucosan in bio-oil was increased by 364.71%. This study presented a novel and effective pretreatment strategy to improve the pyrolysis behavior and product distribution of biomass and alleviate ash deposition problems in boilers.

Experimental validation study on snap through and coiling up of deployable composite shells

AbstractBistable reeled composite shells (BRCS) have been widely used in deployable space structures due to advanced properties of light weight and large volume reduction. A finite element simulation and experimental validation to study the transition of BRCS between their two stable states are performed. In this article, multiscale representative volume element (RVE) modeling is used to compute the equivalent mechanical properties of carbon/epoxy plain woven fabrics that were utilized to construct the deployable composite laminates, followed by experimental verification. The deformation characteristics and strain energy distribution of the deployable composite shell (DCS) during snap through and coiling up are investigated using finite element analysis (FEA) and verified by strain‐gauge and digital image correlation (DIC) tests. The results show that the strain energy distribution in the snap through and coiling up of the carbon/epoxy plain woven BRCS with laminate stacking sequence of [+45/−45] is approximately symmetric. Additionally, an offset phenomena is observed during the coiling up of the BRCS in the finite element modeling. A parametric analysis is complemented to investigate effects of fiber angles on the deformation characteristics and strain energy distribution of the shell structures during snap through and coiling up.Highlights Shell deformation during snap through and coiling up was investigated. DIC test was performed to capture the shell deformation. Strain energy distribution of the deployable composite shell was discussed. Offset phenomena are observed during the coiling up.

The distributions and variations of Quaternary Thames River Terrace deposits of Greater London

A database containing c. 27 000 records of Quaternary lithostratigraphy extracted from c. 5800 boreholes drilled to a variety of depths has been compiled from information contained in logs recorded and held by the British Geological Survey (BGS) and from the Crossrail project. After ‘cleaning’ and quality assessment the raw borehole log data have been investigated for patterns in distribution, and variations in the Quaternary facies across Greater London. In particular, the analysis of Quaternary River Terrace Deposits has been focused on here and a summary of relevant published terminology and nomenclature is also included in this Technical Note, as an aid to understanding. The spatial distributions of each major Quaternary lithostratigraphic interval, as identified in the log descriptions, are also presented as point locations in map form, and in comparison with the corresponding BGS mapped outcrop patterns of the respective lithostratigraphic units. The presence of various specific clasts in the log descriptions (e.g. cobbles and chalk clasts) is also presented at stratigraphic member levels against their apparent source outcrops. For instance, cobbles recorded from the Boyne Hill Terrace intervals are concentrated in the eastern outcrops and reflect the Wealden source and former river system of the Darrent–Wid towards the Essex coast at Maldon. Similarly, the presence and distribution of shell and chalk clasts within river terrace sands and gravels reflect the geology of the underlying subcrop strata of Lower Shelly Clay and Chalk respectively. The Crossrail data also include some grain-size information from sieve analysis and some engineering in situ test values, which require careful analysis beyond the scope of this work but are potentially useful. The grain-size distributions for some of the samples from the river terrace sands and gravels show fining-up and coarsening-up sequences, and geographical grain-size trends in various stratigraphic intervals. The recorded presence of faults, fractures and fissures, as identified by the drilling contractors or logging geologists, is also extracted and mapped. Supplementary evidence, from repeated stratigraphy or improbable spatial proximity changes in subcrop depths, suggests a cause other than deposition for such changes and, on the presumption that their cause is natural, is interpreted as likely to be representative of faulting of some kind, including low-angle thrust faults. Faulting is also considered to have controlled the distribution of several interglacial silt members and is the subject of considerable research in the deeper intervals of London stratigraphy, so is only briefly dealt with here. To define the period over which tectonic structures, now known to exist within the strata of the London Basin, were active requires an analysis of Quaternary deposits that overlie them. This Technical Note provides an initial review of the data available from boreholes for such work and for any other studies requiring knowledge of these deposits. Supplementary material : Spreadsheets (and other files), and notes on the name and significance of each, are available at https://doi.org/10.6084/m9.figshare.c.6700313 Thematic collection: This article is part of the Geology of London and its implications for ground engineering collection available at: https://www.lyellcollection.org/topic/collections/geology-of-london-and-its-implications-for-ground-engineering

Numerical and Theoretical Study on Failure Characteristics and Damage Assessment Model of Curved Steel-Concrete-Steel Sandwich Shells Subjected to Impact Load

In this study, damage assessment model of curved steel–concrete–steel (CSCS) sandwich shells subjected to impact loads was investigated. A numerical simulation method was applied to obtain failure modes of CSCS sandwich shells under impact load by changing the impact velocity as well as the mass and diameter of the hammer. From the 108 finite element (FE) models, three failure modes were found: local deformation, top steel plate fracture, and penetration. The failure mechanism for each failure mode was analyzed based on numerical simulation results, such as impact force and displacement-time histories, varying internal energy, and deformation modes of the structures. The law of failure mode distribution of the CSCS sandwich shell was also summarized. Moreover, the impact force–displacement relationship was obtained using an analytical method, and the FE results were in acceptable agreement with experiments. Finally, damage assessment model of the CSCS sandwich shells was obtained by comparing the hammer initial kinetic energy with the maximum absorbed energy of the CSCS sandwich shell. This model can be used as a quick tool to judge the failure status of the CSCS sandwich shell. The work presented in this paper is of significance and can fill the gap of the damage assessment model of CSCS sandwich shells subjected to impact loads.

Dynamic response characteristics of grooved cylindrical shells in Taylor impact experiments

Buffer energy absorbing structures have very high use value in daily life, industrial production, aerospace and other fields. Cylindrical shells are used as a highly efficient buffer and energy absorbing structure due to their own structure and good mechanical properties. Taylor impact experiments were conducted on three types of structural cylindrical shells (non grooved, inner grooved, and outer grooved) and numerical model was also established to study and analyze the dynamic response characteristics of the three types of structural cylindrical shells. Finally, the deformation mechanism of the cylindrical shell was analyzed theoretically to explore the impact of grooving treatment on the deformation of the cylindrical shell. The results show that with the increase of impact velocity, the length of the cylindrical shells of the three structures decreased, and the diameter of the impact end and the maximum diameter increased. Each of the three specimens had a convergence velocity(convergence velocity: The impact end diameter of cylindrical shell is the initial impact velocity at the maximum diameter), that is, when the impact velocity was greater than or equal to the convergence velocity, its maximum diameter was equal to the diameter of the impact end. When the impact velocity exceeded a certain value, the deformation modes of the three types of cylindrical shells changed. The comparison of experimental and simulation results proved the effectiveness of the numerical model. The maximum stress was always above the impact end face. It was concluded from the theoretical analysis Due to the stress concentration at the groove, the stress distribution and internal stress distribution of the cylindrical shell were affected, which in turn affected the deformation and energy absorption capacity of the cylindrical shell. At the same impact velocity, the outer grooved cylindrical shell has the shortest buffer time and the BW specimen had the most gentle buffer curve before 35μs .

Exploring detailed microcosmic mechanisms of sodium chloride deposition in supercritical water reactors from the aspect of solvation structure: A combination of MD and QM simulations

The dissolution characteristics and microscopic dissolution process of salt in supercritical water (SCW) are the fundamental influence of scale formation. In this paper, molecular dynamics (MD) and quantum mechanics (QM) were used to study the solubility and solvation structure of sodium chloride in supercritical water. The potential mean force (PMF), radial distribution function (RDF) and coordination number (CN) indicate that the solubility of sodium chloride in SCW decreases with the increase of temperature and the decrease of density. As the system density decreases from 0.3 g/cm3 to 0.1 g/cm3 and the temperature increases from 600 K to 900 K, the CN of water molecules in the solvation shell decreases from 2.89 to 1.01, which is consistent with the trend of the experimental results. The electrostatic potential distribution and intermolecular interaction of the solvation shell around Na+ were obtained by QM method. The solution free energy of Na+–3H2O in implicit solvent was obtained. In the condition range of this study, when the temperature is the lowest and the dielectric constant is the largest, the free energy of dissolution is the smallest, which is −0.0991 a.u. This study will lay a foundation for the study of salt deposition in SCW.

Membrane-Fusion-Mediated Multiplex Engineering of Tumor Cell Surface Glycans for Enhanced NK Cell Therapy.

Natural killer (NK) cell therapies show potential for tumor treatment but are immunologically resisted by the overexpressed immunosuppressing tumor cell surface glycans. To reverse this glycan-mediated immunosuppression, the surface NK-inhibitory glycan expressions need to be downregulated and NK-activating glycan levels should be elevated synchronously with optimal efficiency. Here, a core-shell membrane-fusogenic liposome (MFL) is designed to simultaneously achieve the physical modification of NK-activating glycans and biological inhibition of immunosuppressing glycans on the tumor cell surface via a membrane-fusion manner. Loaded into a tumor-microenvironment-triggered-degradable thermosensitive hydrogel, MFLs could be conveniently injected and controllably released into local tumor. Through fusion with tumor cell membrane, the released MFLs could simultaneously deliver sialyltransferase-inhibitor-loaded core into cytoplasm, and anchor NK-activating-glycan-modified shell onto tumor surface. This spatially-differential distribution of core and shell in one cell ensures the effective inhibition of intracellular sialyltransferase to downregulate immunosuppressing sialic acid, and direct presentation of NK-activating Lewis X trisaccharide (LeX) on tumor surface simultaneously. Consequentially, the sialic acid-caused immunosuppression of tumor surface is reprogrammed to be LeX-induced NK activation, resulting in sensitive susceptibility to NK-cell-mediated recognition and lysis for improved tumor elimination. This MFL provides a novel platform for multiplexcell engineering and personalized regulation of intercellular interactions for enhanced cancer immunotherapy.

Measurements of parameters of structures of C-C composites to ensure the computation of change in FV shape and aerodynamic characteristics

The paper provides a designed under the supervision and with the participation of authors of the paper complex of methods of accounting for structural inhomogeneities of elements of a Thermal Protection System (TPS) made of C-C composites used to estimate ablated shapes of high-speed Flight Vehicles (FVs) and corresponding methods of measuring and processing of the needed structural parameters of C-C composites. During the mass ablation along a flight trajectory reinforcing elements and a graphitized matrix ablate differently, and there appears primary large-scale roughness on the surface. Moreover, pores, shells, and other fine-grained inhomogeneities outcrop forming the secondary finely divided roughness. Roughness impacts heat exchange, and summary equivalent roughness parameters are used to estimate FVs ablated shapes. A C-C composite graphitation degree that is defined with the X-ray diffraction study also influences an ablation rate. The density of materials is linearly related to their porosity, and for a number of currently in use and promising materials the density distributions were studied using computer tomography as well as the distribution of pores, shells, and other fine-grained inhomogeneities over volume of TPS elements was examined with electron microscopes. X-ray diffraction studies of the C-C composites were also carried out. Comparative computations of ablated shapes and aerodynamic characteristics of a model cylindrical FV with applied TPS elements of the examined C-C composites were performed with the use of obtained results of tomography, electron microscopic and X-ray diffraction studies.

Complex Building Forms Roofed with Transformed Shell Units and Defined by Saddle Surfaces.

A novel method and description of creating diversified complex original building forms roofed with a number of transformed folded shell units developed on the basis of a novel reference polyhedral network and arranged according to a reference surface with the negative Gaussian curvature is presented. For that purpose, specific reference polyhedral networks is are defined as a complex material deliberately composed of many regular tetrahedrons that are arranged regularly to obtain original attractive complex general building forms. The proposed method is a significant extension of the previous method for shaping roof structures with the positive Gaussian curvature and fills existing gaps in current scientific knowledge. The extended method enables the designer to significantly increase the variety of the created complex shell roof forms and plane-walled folded elevation forms of buildings and to define the shapes of their rod structural systems. It allows one to overcome the existing significant geometric and material limitations related to shape transformations of nominally flat rectangular folded steel sheets into different shell forms. The developed extension is based on formation of a set of properly connected tetrahedra as a material determining different (a) inclination of elevation walls to the vertical, and (b) distribution of many individual warped roof shells in accordance with the properties of a regular surface with negative Gaussian curvature. A number of the adopted specific sets of division coefficients (parameters) is used for determining the entire network and its complete tetrahedra. The presented description makes it possible to adopt appropriate assumptions and data and then employ the innovative method to obtain the expected characteristics of the unconventional building form shaped. The presented three different special forms created with the help of the novel method and the appropriately selected diversified values of the division coefficients of pairs of the vertices of a polyhedral reference network, a polygonal eaves network and points of a reference surface confirm the innovative scientific nature of the obtained results. The method has to be computationally aided due to the complexity of mathematical operations and the need to visualize the designed forms.

Preparation and characterization of Perilla essential oil composite microcapsule based on the complex coacervation and interface polymerization.

In this paper, we prepared a novel double-layer Perilla essential oil composite membrane microcapsule (PEOCM) by the composite methods of complex coacervation and interface polymerization. The particle size distribution, morphology, pressure resistance, thermal stability, and elemental proportions of the microcapsule shell of the obtained microcapsules were characterized by laser particle size analyzer, scanning electron microscopy (SEM), dynamic rheometer, thermogravimetric analysis (TGA), and energy spectrometer. In order to further examine the application effect of the PEOCM, we carried out a fresh-keeping experiment on nectarines. The results showed that the average volume diameter of the microcapsules was 226.9µm, with a completely spherical shape and a slight depression on the surface and had good pressure resistance and thermal stability. The results also demonstrated that microencapsulation does not change the composition of Perilla essential oil, and the polyurea membrane with amide structure (-NH-CO-NH-) was formed successfully. Furthermore, the total soluble solids content and peroxidase activity of nectarines indicated that the PEOCM can be a preservative of food. PRACTICAL APPLICATION: We prepared a double-layer Perilla essential oil composite membrane microcapsule by the composite methods of complex coacervation and interface polymerization. The encapsulation conditions of the microcapsules were optimized, the structure of the microcapsule was characterized, and the fresh-keeping effects of the microcapsule on nectarine were studied. The results showed that microcapsules had a completely spherical shape and a slight depression on the surface and had good pressure resistance, good thermal stability, and good fresh-keeping ability. The above characteristics indicated that the double-layer microcapsules have good application prospect and plays an important role in food fresh-keeping and the preservation of essential oils.

Occurrence and Preservation of Gastropod Shells in Recent Riverine and Estuarine Sediments of Chennai, SE-India

Objectives: The distribution of aquatic gastropod shells was investigated in riverine and coastal sediments of Chennai, India. Next to taxonomic identification, the shell preservation was characterized and quantified with a taphonomic grade. Methods: Sediments of the Adyar and Cooum rivers as well as of coastal backwaters of the metropolitan area were taken down to a maximum depth of 81 cm using a handheld geoslicer and inspected by optical and electron microscopy. Taphonomic features (i.e. exfoliation, external luster, cracking, fragmentation, edge preservation, bioerosion, encrustation) reflecting different destructive post-mortem processes were observed, individually ranked and averaged in a composite taphonomic grade for each specimen. Results: Shells and shell fragments of various families occur with markedly different abundances between 63.7 and < 1% (in decreasing order Potamididae, Bithyniidae, Stenothyridae, Planorbidae, Thiaridae, Bullinidae, Nassariidae, Neritidae, Paludomidae). Their distribution invokes salinity as a major factor controlling occurrence in a habitat. The lack of larger and globose shells in freshwater river sediments may reflect the preference of stagnant water habitats and limited preservation in sedimentary transport. The predominance of Pirenella cingulata among the shells found in sediments of brackish environments probably reflects mechanical robustness and its extreme abundance in tidal flats. Due to post-mortem destruction most shells are incomplete. Roughly 25% of all specimens are almost complete shells not only showing spire and body whorl but at least in part also apex and/or aperture and outer lip. More than 50% represent spires or combinations of apex and spire. Composite taphonomic grades for gastropod families show a large range and reach high values. The lowest grades, indicative of best preservation, are observed for Stenothyra blanfordiana and Bithynia sp. Novelty: The distribution of gastropods in riverine and coastal environments represents a valuable ecosystem characteristic. Shell preservation shown here for sediments of Chennai is the basis for retrospective environmental characterization. Keywords: Gastropods; shells; river sediments; taphonomy; Chennai

(1-x)[0.90NN-0.10Bi(Mg2/3Nb1/3)O3]-x(Bi0.5Na0.5)0.7Sr0.3TiO3 ceramics with core–shell structures: A pathway for simultaneously achieving high polarization and breakdown strength

Modern electronics and electrical power systems demand a large energy storage density (Wrec), high efficiency (η), and board operating temperature to deliver high performance. Nevertheless, the inverse correlation between polarization and dielectric breakdown strength hinders Pb-free dielectric ceramics from providing sufficient energy density and consequently limits their practical applications. This study demonstrates the effectiveness of (1-x)[0.90NN-0.10Bi(Mg2/3Nb1/3)O3]-x(Bi0.5Na0.5)0.7Sr0.3TiO3 (abbreviated as xBNST) ceramics with a core−shell structure in overcoming these challenges. Phase-field simulations reveal that the existence of a polar core in the grain effectively reduces the local electric field distribution of the weak polar shell, thereby significantly improving the breakdown strength. Further analyses of intrinsic electronic structure reveal the intrinsic mechanism for enhancing the breakdown strength via first-principles calculations based on density functional theory. Accompanied by the unique structure, grain inhomogeneity featuring the coexistence of strong polar and weak polar clusters contributes to the enhancement of the polarization difference. Consequently, the ceramics exhibit comprehensive energy storage performances [high Wrec = 7.72 J/cm3, large η = 83.78%, and broad usage temperature range (between −40 and 200 °C)]. These findings are expected to provide a feasible way to develop high-performance capacitors for advanced energy storage materials and applications.

Local freshwater shell bead production at Cluny Fortified Village (EePf-1), south-central Alberta

Beads in many forms were used as decorative items on the Great Plains during the historic and prehistoric periods. Cluny Fortified Village (EePf-1) on the Northwestern Plains is a unique Late Prehistoric period site where excavations have revealed over 1,600 shell artifacts including beads, bead preforms or “blanks,” and substantial waste from shell bead production. These shell artifacts provide insight into local prehistoric bead production using two local bivalve species Lampsilis siliquoidea (fatmucket) and Lasmigona complanata (white heelsplitter). Experimental drilling on shell produced distinctive stepping and striation patterns that identify the method of drilling: either holding the drill in the hand or mounting the drill on a shaft. Most beads from the site exhibit patterns indicative of hafted drill use. In addition, the distribution of shell at the site indicates bead production areas as well as a cache of finished and unfinished beads.

Shell colors and microstructures of four pearl oyster species in the South China Sea

Wild marine pearl oyster shells have rich colors, and the color and gloss of pearls cultivated by pearl oysters are closely related to the pearl layer color of the mantle. Therefore, in this study, four important wild marine pearl oyster species (Pinctada maxima, Pteria penguin, Pinctada margaritifera, and Pinctada fucata) were collected from the South China Sea, and a colorimeter was used to measure the color of their inner and outer shells. We analyzed the color range of their shells and the correlation between the color parameters; additionally, we observed the microstructure of their shells using a scanning electron microscope. The results showed that the color distribution and brightness of the inner shells of the four species were wider than that of the outer shells. In addition, the color distribution range of the outer and inner shells of the four pearl oyster species were P. fucata > P. margaritifera > P. maxima > Pt. penguin and Pt. penguin > P. fucata > P. margaritifera > P. maxima, respectively. Concerning the microstructures of the four pearl oysters, the shell structures of P. maxima, P. margaritifera and P. fucata had a honeycomb arrangement, whereas Pt. penguin had an irregular polygon structure. The P. maxima and P. margaritifera with a strong nacre secretion ability that area and thickness of the single crystal particles were larger than those of Pt. penguin and P. fucata.

Point pattern analysis as a tool for assessing disease spread and population features in remaining sanctuaries of the critically endangered bivalve Pinna nobilis

An emergent disease has relegated populations of the Mediterranean pen shell, Pinna nobilis L. critically endangered to sanctuaries featuring salinities outside the 36.5 to 39 range. Point pattern analysis was used in three areas of the Alfacs Bay (Ebro Delta) still hosting pen shells to assess the possible undergoing of disease spread by comparing the spatial distribution of live individuals vs. empty shells across spatial scales. We also evaluated the importance of other ecological aspects of conservation relevance such as the size distribution of individuals, and the possible association to seagrass habitats. The population assessment showed no recent mortality and a clear dominance of large adults among empty shells (97.3%) pointing to no disease spread during the study period. At the low spatial scale Nearest Neighbor (NN) analyses evidenced significant clustering (NN Ratios of 0.4–0.8), but in one of the zones NN distances were closer in empty shells than in live individuals, suggesting a former localized outbreak. At the larger spatial scale, MDSCA confirmed clustering patterns up to distances of 115 to 190 m, with higher aggregation of empty shells at the same study zone. The bay also featured low juvenile availability (3.2%), which risks the continuity of the population. No evidence for habitat or conspecific selection could be observed from abundance patterns and variation in NN across study regions. Our research provides a tool for assessing population condition in paralic environments, where salinity conditions tend to slow down disease spread, thus allowing a time gap for undertaking conservation decisions.

Exploring coexistence mechanisms in a three-species assemblage

Interactions among species are essential in shaping ecological communities, although it is not always clear under what conditions they can persist when the number of species involved is higher than two. Here we describe a three-species assemblage involving the seagrass Cymodocea nodosa, the pen shell Pinna nobilis and the herbivore sea urchin Paracentrotus lividus, and we explore the mechanisms allowing its persistence through field observations and manipulative experiments. The abundance of pen shells was higher in seagrass beds than in bare sand, suggesting a recruitment facilitation. The presence of sea urchins, almost exclusively attached or around pen shells, indicated habitat facilitation for sea urchins, which overgrazed the meadow around the pen shells forming seagrass-free halos. Our results suggest that this system persists thanks to: (i) the behavioral reluctance of sea urchins to move far from pen shells, making their impact on seagrass strictly local, (ii) the sparse distribution of pen shells and (iii) the plant's resistance mechanisms to herbivory. Unpacking these mechanisms allows a better understanding of how ecological communities are assembled.

Distribution and Abundance of Blood Shells (Anadara granosa) on the Coast of Concong Luar Village Indragiri Hilir Regency

This study was conducted in September 2021, around the coastal of Concong luar village Indragiri Hilir Regency with the aim to find out the abundance, distribution, and morphometrics of blood shell (Anadara granosa). The method used survey methods, in which blood shell sampling and aquatic substrates, as well as measurements of environmental parameters, were conducted in the field and in the laboratory. Determination of sampling location by purposive sampling is based on the character of the environment in the location of the research. Based on the results of research that has been obtained an abundance value at the station 1 = 4,8 Ind/m2, station 2 = 8,7 Ind/m2, and station 3 = 3 Ind/m2. The pattern of blood shell levy in the waters of Concong Luar Village stations 1 and 2 is clustered, while station 3 is evenly distributed. Furthermore, the results of measurement of the width of the highest blood shells are 16 - 30 mm in 70 individuals, followed by size &gt;31 mm of 43 individuals, the lowest measurement result is &lt;15 mm in 27 individuals, and the highest measurement of the length of the blood shells 16 – 30 mm of 77 ind, followed by a size &gt;31 mm of 42 ind, and the lowest measurement result is &lt;15 mm of 29 ind.

Properties, kinetics and pyrolysis products distribution of oxidative torrefied camellia shell in different oxygen concentration

Bio-energy would become an important energy supply in the future, but the inherent defects of biomass limit its energy utilization. Torrefaction could improve the energy performance for biomass, and oxidative torrefaction is more practical to reduce the energy consumption and improve the efficiency. In present work, the properties, kinetics and pyrolytic products distribution of oxidative torrefied camellia shell (CS) have been investigated with the oxygen concentration of 0–8% in torrefaction atmosphere. The results show that oxidative torrefaction would alter the cellulose crystals from Iα to Iβ of CS and improve their hydrophobicity, and their surface functional groups have also undergone major changes. Based on the Flynn-Wall-Ozawa method and Distributed Activation Energy Model, torrefaction causes the pyrolysis activation energy to increase first and then decrease. According to the evaluated by Criado method, order of reaction and random nucleation have been identified as the most likely mechanism for thermal degradation of torrefied CS. In addition, Oxidative torrefaction would improve the phenols compounds in pyrolytic products. The present work may provide a reference for the energy utilization of CS.