Density Of Shells Research Articles

Modified Polyethylene Foams for Insulation Systems.

Effective insulation of buildings and other industrial objects requires the use of materials and system solutions that ensure maximum uniformity and density of insulation shells. The study focuses on the development of insulation systems based on expanded polyethylene and, in particular, on the development of modified polyethylene with reduced flammability containing a flame-retardant modified montmorillonite clay, which does not hinder gas formation, and silicate nanofillers in layered construction. Active experiments based on mathematical design methods allowed us to establish an analytical relationship between flame-retardant and modifier consumption and extruder pressure and response functions: average density of polyethylene foam and flammability criterion. The flammability criterion was taken as the oxygen index of the modified polyethylene foam. A foaming agent masterbatch was used as the flame retardant. Analytical optimization of mathematical models obtained as a result of active experiments allowed us to determine the optimal flame-retardant consumption, which was 3.7-3.8% of the polymer mass. Optimised systems for average density and oxygen index of flammability of modified polyethylene were obtained. A nomogram for predicting the material properties and selecting the composition, and an algorithm for a computer program for evaluating the properties of modified polyethylene foam as a function of the values of various factors, were developed. Taking into account the possible expansion of the scope of application of rolled polyethylene foam and seamless insulation shells based on it, possible solutions for insulation systems were studied using the program THERM, and a combined insulation system was adopted.

Interhemispheric ionosphere-plasmasphere system shows a high sensitivity to the exospheric neutral hydrogen density: a caution of the global reference atmospheric model hydrogen density

This study explores the impact of the exosphere hydrogen (H) density on the ionosphere-plasmasphere system using a model whose key inputs are constrained by ionosphere observations at both ends of the magnetic field line with an L-value of 1.75 in the American longitudinal sector during a period with low solar and magnetic activities. This study is the first to be validated by ground-based and satellite data in the plasmasphere and both hemispheres. The main finding is that the entire ionosphere-plasmasphere system is very sensitive to the neutral hydrogen density in the lower exosphere. It was found that an increase in the H density by a factor of 2.75 from the commonly accepted values was necessary to bring the simulated plasma density into satisfactory agreement with Arase satellite measurements in the plasmasphere and also with DMSP satellite measurements in the topside ionospheres of the northern and southern hemispheres. A factor of 2.75 increase in the H density increases the simulated plasma density in the afternoon plasmasphere up to ∼80% and in the nighttime topside ionosphere up to ∼100%. These results indicate prominently that using the commonly accepted empirical model of the H density causes unacceptable errors in the simulated plasma density of the near-Earth plasma shells. We alert the space science community of this problem.

Morphometric composition analysis of Sinanodonta woodiana based on depth stratification in Tributaries Meureubo West Aceh

Clams are aquatic biota that do not have a spine, belonging to the phylum Molluscs class Bivalvia. This study aims to determine the density, morphomteric differences of S. woodiana clams based on depth. The sampling technique used Purposive sampling method, with 1x1 meter plot and repetition 3 times. Data collection was carried out in July 2022 until completion. The results showed that the highest density of S. woodiana clams was found at a depth of 0-50 cm with an average density of 29.3 individuals/meter. Small size clams were dominantly found at a depth of 0-50 cm with a percentage reaching 97.92%, 54.46% of medium size clams were found at a depth of 50-100 cm, while 83.33% of large size clams were found at a depth of 100-150 cm. Anova test results showed significant differences with a 95% confidence interval. At a depth of 100-150 cm, the weight value of S. woodiana clams was 24.87 ± 3.36 grams, shell length 43.73 ± 1.21 cm, shell width 38.73 ± 1.76 cm, and umbo height 22.83 ± 0.76 cm. The results of this study can be concluded that the shallower the waters, the higher the density of shells, but the large size of the shells, the smaller the density.

Density of Meretrix meretrix Clamps Under Ecological Pressure on Different Substrate Texture at the Kambu River of Kendari Bay, Southeast Sulawesi

White clams at the mouth of the Kambu River in Kendari Bay have a preference for different substrate textures and are under ecological pressure. This study aims to determine the density of tofu shells at the mouth of the Kambu River, Kendari Bay, Southeast Sulawesi. This research was conducted at the estuary of the Wanggu River, Kendari Bay, Southeast Sulawesi from August 2021 to January 2022. White clams were taken manually using a 1x1 m squared transect. These shellfish samples were taken 6 times in repetition/station in each month of observation. Samples found in the field were counted. Taking the texture of the aquatic substrate together with the sampling of shellfish. The results showed that the maximum density of white clams at the mouth of the Kambu River, Kendari Bay, was 7.3 ind/m2. The highest density of white clams was found at stations I and II, while the lowest density was found at station III. The highest density of shellfish was found in the type of substrate which was dominated by the fine sand fraction, while the lowest density was found in the type of substrate which was dominated by the silt fraction.

Acoustic radiation force dependence on properties of elastic spherical shells in standing waves

In this study, we theoretically investigate the acoustic radiation force acting on elastic spherical shells in standing waves in the dimensionless frequency range of 0<ka<0.7 (k is the wave number in the host fluid and a is the outer radius of the spherical shells), we show that in the low-frequency range (0<ka<0.2), the acoustic radiation force on core–shell spheres can vary from positive to negative by decreasing the effective density and effective bulk modulus of the spherical shells, while the effective density and bulk modulus are dependent on the hollow ratio of the core–shell spheres, the density and bulk modulus ratios of the shell to the core. Thus, the core–shell spheres cannot only be trapped from the pressure node to the pressure antinode by increasing the hollow ratio or decreasing the shell’s density or longitudinal or shear velocity, but are also unresponsive to ultrasound waves with an optimal hollow ratio, density, or acoustic velocity of the shell. We further show that in the relatively low-frequency range of0<ka<0.7, the acoustic radiation force on core–shell spheres can be significantly enhanced around resonant frequencies. The acoustic radiation force could be enhanced at lower frequencies by increasing the hollow ratio or decreasing the shell’s density or shear wave velocity. Our results pave the way for optimising the design of core–shell particles for efficient ultrasound-mediated drug delivery.

Experimental study and modeling the tensile strength of 3D‐printed aluminium polylactic acid (PLA) parts using artificial neural networks

Background: High quality 3D printed products are in high demand, resulting in an increase in the production of 3D printed parts with precise tolerances, improved surface roughness, and overall durability. The processing parameters of 3D printers have a significant impact on the quality of 3D printed parts. Three-dimensionally printed parts must be durable, especially in terms of tensile strength, and its impact on the printer's process parameters must be investigated. Methods: Tensile test specimens were printed in the Makerbot 3D printer with aluminium polylactic acid (PLA) material. The three controllable input parameters taken into consideration were layer thickness, infill density and number of shells. The three levels for each of the respective parameters were 0.1mm, 0.2mm and 0.3mm for layer thickness; 2,3 and 4 for number of shells; 20% 40% and 60% for Infill density. Tensile testing was carried out on the specimens and data was tabulated. Using these data, an artificial neural network model was created using Matlab R2021b software’s neural network toolbox (alternatively Scilab can be used). Results: A high layer thickness (0.3mm) and a 40% infill density were found to be the most effective among all other parameters. The specimen with the lowest layer thickness of 0.1mm, four shells, and a 20% infill density had the highest tensile strength. With the tensile test data, a Matlab ANN model was developed. Validation was done by comparing the values obtained from the model with the experimental data by using random layer thickness, infill density, and number of shells. Conclusions: In conclusion, higher layer thickness has lower tensile strengths. However, as the number of shells and infill density increases, the tensile strength increases. In summary an ANN model was successfully developed and validated to predict 3D printed aluminium parts.

Decrease in volume and density of foraminiferal shells with progressing ocean acidification

Rapid increases in anthropogenic atmospheric CO2 partial pressure have led to a decrease in the pH of seawater. Calcifying organisms generally respond negatively to ocean acidification. Foraminifera are one of the major carbonate producers in the ocean; however, whether calcification reduction by ocean acidification affects either foraminiferal shell volume or density, or both, has yet to be investigated. In this study, we cultured asexually reproducing specimens of Amphisorus kudakajimensis, a dinoflagellate endosymbiont-bearing large benthic foraminifera (LBF), under different pH conditions (pH 7.7–8.3, NBS scale). The results suggest that changes in seawater pH would affect not only the quantity (i.e., shell volume) but also the quality (i.e., shell density) of foraminiferal calcification. We proposed that pH and temperature affect these growth parameters differently because (1) they have differences in the contribution to the calcification process (e.g., Ca2+-ATPase and Ω) and (2) pH mainly affects calcification and temperature mainly affects photosynthesis. Our findings also suggest that, under the IPCC RCP8.5 scenario, both ocean acidification and warming will have a significant impact on reef foraminiferal carbonate production by the end of this century, even in the tropics.

Tuning the morphology of bimetallic gold-platinum nanorods in a microflow synthesis

An automated microfluidic system with computer-controlled syringe pumps was applied for screening a three-dimensional concentration space for the formation of binary gold-platinum metal nanorods. Leveraging the micro segmented flow technique, precise residence and reactant addition timings as well as concentration spaces were addressed. The density and thickness of quasi-isotropic platinum shells on gold nanorod cores were tuned from isolated spots to a dense arrangement of high-aspect-ratio columns. The changing optical properties of the particles in the platinum deposition were used for monitoring the reaction progress and the products by the means of a fiber based micro flow-through spectrophotometer allowing to optimize process times. From our data, we propose an electrochemical model, postulating a diode-like effect and limitations for the formation of Pt nuclei on the gold surface and the formation of nano local elements. This point of view is supported by the observed decoration effects of gold facets and to the formation of columnar structures of the platinum shell.

Changes in algal coverage and sea urchins fauna, density of turban shells and abalone in &lt;i&gt;Diadema&lt;/i&gt; removal area of Haidaura Bay, Mie Prefecture

Changes in algal coverage and sea urchins fauna, density of turban shells and abalone in &lt;i&gt;Diadema&lt;/i&gt; removal area of Haidaura Bay, Mie Prefecture

Physicochemical properties of Walnuts (Juglans regia L.) shells and kernels growing in different locations in Kurdistan region-Iraq

Some physicochemical properties of walnut shell, kernel and oil of fifteen samples of walnut grown in different locations in Kurdistan region-Iraq were determined. Three principal dimensions such as length, width and thickness, volume and projected area of walnut and its kernels were measured using image processing technique. Based on three principal dimensions, some dimensional properties including geometric mean diameter, arithmetic mean diameter, sphericity, volume and surface area of the nuts and kernels were calculated. Also gravimetric properties of nuts and kernels such as true density of nuts and kernels were studied. Furthermore other physical properties such as weight of nut, weight of kernel, percentage yield of walnut, total oil content, ash contents, moisture contents, pH value, relative density and refractive index of the oils were also determined. The variations in physical properties such as size dimensions, arithmetic mean diameter, geometric mean diameter, unit mass, sphericity, surface area, true density and volume of shells and kernel of walnuts as a function of the moisture content were determined. With an increase in the moisture content, the surface area, sphericity, true density and volume of shells and kernel of walnuts increased. In addition, the oil yields from the kernels had ranged between 36.07% to 70.24%. The moisture contents of shells and kernels ranged between 6.34% to 10.11% and 3.68% to 5.62%, respectively; and the ash content of kernels were ranged between 0.94% to 2.2%. On the other hand, the refractive index of oils were determined between 1.4734 and 1.4767, pH-values of kernel oils were ranged between 6.23 and 7.02 and the relative density were determined between 0.9746 and 0.9801. Finally the present study was showed that the walnut kernels in Kurdistan region did not show any considerable significant variations with reference to their physical and chemical properties.

Mud Clam’s (Anodentia edentula) Density and Distribution Pattern in Kalangan Mangrove Forest Ecosystem

The excessive use of Mud Shells (Anodentia edentula) as a staple food by the people of Kalangan Village, Central Tapanuli Regency caused the decline of the shellfish population. This is marked by the scattering of mud shells at research sites and often people conduct shell-searching activities at low tide. Therefore, a scientific study is needed to know the density and distribution patterns as the basis for the possibility of cultivation activities, management of mud shell germplasm (Anodentia edentula), and mangrove ecosystems in kalangan area in the future optimally, sustainably, and sustainably. The study was conducted in September 2020, using the 1x1m2 transect method purposive sampling at low tide. The results showed that the density of Mud Shells (Anodentia edentula) amounted to 150 ind/m2 in Station I, 0 ind/m2 in Station II with distribution pattern clustering, and 43 ind/m2 in Station III with distribution pattern random. With the evidence that there is a research station that contain zero mud clam and with unsimilarity in distribution pattern that should be clustering in every research station, therefore it can be concluded that the abudance of mud clam in the ecosystem already decline both quantifically and qualitativelyand requires conservation and cultivation action to ensure its existence in the future.

Distinguishing core and flank facies based on shell fabrics in Lower Jurassic lithiotid shell beds

Lower Jurassic larger bivalves, mostly represented by the monospecific lithiotid genera Lithiotis, Cochlearites and Lithioperna, formed large shell accumulations in the shallow-water carbonate Tethyan and Panthalassa margins. A quantitative analysis of lithiotid accumulations from the Trento Platform (northern Italy) was carried out in order to distinguish the distribution of autochthonous, parautochthonous and allochthonous lithiotids in the accumulation core and flanks. Various representative accumulations are characterized with respect to systematic content, shell cover, shell density, disarticulation, shell fragmentation and orientation of individual shells. Lithioperna shows a high shell cover within the accumulation core while that of Cochlearites is variable and Lithiotis is rare. All three lithiotids occur in high densities in the accumulation flanks. As expected, autochthonous individuals of all three genera are frequent in the accumulation cores where they are preserved in life position. In the flanks, most bivalves are parautochthonous except for Lithioperna which can grow in life position. All bivalves in allochthonous shell beds are highly fragmented and disarticulated. The studied traits are potentially useful as proxies for distinguishing core or flank facies when the accumulation does not crop out as a whole.

Live and dead deep-sea benthic foraminiferal macrofauna of the Levantine basin (SE Mediterranean) and their ecological characteristics

The present study sought to quantitatively characterize the live and dead benthic foraminifera communities of the deep southeastern Levantine basin of the Mediterranean Sea (33.4º–31.7 ºN, 31.3º–34.9 ºE; 100–1900 m water depth) and their relationships to environmental conditions. Box corer samples were collected at 50 sites between June and July 2013. The foraminiferal macrofauna (> 250 µm) were enumerated and identified (76% to the species level). Six live foraminiferal assemblages were identified, inhabiting six biotopes, the shelf margin (SM), two upper continental slopes (UCS1 and UCS2), the lower continental slope (LCS), the eastern bathyal plain (EBP) and the western bathyal plain (WBP). The dead communities were divided into four biotopes, generally compatible with the live ones, excluding the UCS2 and the EBP. The foraminiferal density in the various live biotopes was relatively stable across the studied area, excluding the UCS2 and EBP, unlike the density of the dead shells, which increased with depth. The number of taxa per biotope was estimated by rarefaction curves and compared to the observed numbers, with a decreasing number of live taxa with water depth. The alpha-diversity, which was evaluated in relation to the number of sampled individuals, reached an asymptote in all biotopes, with very low values in the WBP. The within-biotope heterogeneity was evaluated by the average Chao-Sørensen similarity index and by a beta-diversity index (exp(gamma diversity) - exp(alpha diversity)), revealing variable heterogeneities in both assemblages. Water depth, sediment grain size mode, CaCO3 (wt%), and clay fraction (wt%) were jointly but feebly correlated with live faunal composition.

Characterizing subcritical assemblies with time of flight fixed by energy estimation distributions

We present the Time of Flight Fixed by Energy Estimation (TOFFEE) as a measure of the fission chain dynamics in subcritical assemblies. TOFFEE is the time between correlated gamma rays and neutrons, subtracted by the estimated travel time of the incident neutron from its proton recoil. The measured subcritical assembly was the BeRP ball, a 4.482 kg sphere of α-phase weapons grade plutonium metal, which came in five configurations: bare, 0.5, 1, and 1.5 in iron, and 1 in nickel closed fitting shell reflectors. We extend the measurement with MCNPX-PoliMi simulations of shells ranging up to 6 inches in thickness, and two new reflector materials: aluminum and tungsten. We also simulated the BeRP ball with different masses ranging from 1 to 8 kg. A two-region and single-region point kinetics models were used to model the behavior of the positive side of the TOFFEE distribution from 0 to 100 ns. The single region model of the bare cases gave positive linear correlations between estimated and expected neutron decay constants and leakage multiplications. The two-region model provided a way to estimate neutron multiplication for the reflected cases, which correlated positively with expected multiplication, but the nature of the correlation (sub or superlinear) changed between material types. Finally, we found that the areal density of the reflector shells had a linear correlation with the integral of the two-region model fit. Therefore, we expect that with knowledge of reflector composition, one could determine the shell thickness, or vice versa. Furthermore, up to a certain amount and thickness of the reflector, the two-region model provides a way of distinguishing bare and reflected plutonium assemblies.

Enantioselective Dihydroxylation of Alkenes Catalyzed by 1,4‐Bis(9‐O‐dihydroquinidinyl)phthalazine‐Modified Binaphthyl–Osmium Nanoparticles

AbstractA series of unprecedented binaphthyl–osmium nanoparticles (OsNPs) with chiral modifiers were applied in the heterogeneous asymmetric dihydroxylation of alkenes. A remarkable size effect of the OsNPs, depending on the density of the covalent organic shells, on the reactivity and enantioselectivity of the dihydroxylation reaction was revealed. Successful recycling of the OsNPs was also demonstrated and high reaction efficiency and enantioselectivity were maintained.

Spatial distribution of star formation related to ionized regions throughout the inner Galactic plane

We present a comprehensive statistical analysis of star-forming objects located in the vicinities of 1360 bubble structures throughout the Galactic plane and their local environments. The compilation of ~70 000 star-forming sources, found in the proximity of the ionized (Hii) regions and detected in both Hi-GAL and GLIMPSE surveys, provided a broad overview of the different evolutionary stages of star-formation in bubbles, from prestellar objects to more evolved young stellar objects (YSOs). Surface density maps of star-forming objects clearly reveal an evolutionary trend where more evolved star-forming objects (Class II YSO candidates) are found spatially located near the center, while younger star-forming objects are found at the edge of the bubbles. We derived dynamic ages for a subsample of 182 H ii regions for which kinematic distances and radio continuum flux measurements were available. We detect approximately 80% more star-forming sources per unit area in the direction of bubbles than in the surrounding fields. We estimate the clump formation efficiency (CFE) of Hi-GAL clumps in the direction of the shell of the bubbles to be ~15%, around twice the value of the CFE in fields that are not affected by feedback effects. We find that the higher values of CFE are mostly due to the higher CFE of protostellar clumps, in particular in younger bubbles, whose density of the bubble shells is higher. We argue that the formation rate from prestellar to protostellar phase is probably higher during the early stages of the (H ii ) bubble expansion. Furthermore, we also find a higher fraction of massive YSOs (MYSOs) in bubbles at the early stages of expansion (&lt;2 Myr) than older bubbles. Evaluation of the fragmentation time inside the shell of bubbles advocates the preexistence of clumps in the medium before the bubble expansion in order to explain the formation of MYSOs in the youngest H ii regions (&lt;1 Myr), as supported by numerical simulations. Approximately 23% of the Hi-GAL clumps are found located in the direction of a bubble, with 15% for prestellar clumps and 41% for protostellar clumps. We argue that the high fraction of protostellar clumps may be due to the acceleration of the star-formation process cause by the feedback of the (Hii) bubbles.

Modern level for properties prediction of iodine-containing organic compounds: the halogen bonds formed by iodine

The modern concepts on specific features of anisotropy of the electron density of valence shells of bound atoms and chemical bonds providing the successful description of the properties of halogen bonds formed by the iodine molecule in compounds with useful physicochemical properties are generalized in the review. The prognoses of basicity by the diiodine basicity scale for the nitrogen-containing compounds are illustrated. The regularities and peculiarities of shifting bands in Raman spectra of iodine-containing organic crystals are considered. The methodical and specific problems of modeling appeared when the electronic characteristics of the iodine compounds are estimated and briefly discussed.

Atomic structure of Fe90Sc10 glassy nanoparticles and nanoglasses

Glassy nanoparticles of a Fe90Sc10 alloy have been studied using small- and wide-angle X-ray scattering. The results indicate that the surface shells have an electron density that is lower than the electron density in the cores of the glassy nanoparticles. The lower electron density seems to result primarily from a lower atomic packing density of the surface shells rather than from compositional variations due to surface segregation. During the consolidation of the glassy nanoparticles, the short-range order and the extra free volume content present in the shells may be transferred into the interfaces of the resulting bulk Fe90Sc10 nanoglasses.

What makes a good home for hermits? Assessing gastropod shell density and relative strength

ABSTRACTThe survival and reproductive success of hermit crabs is intrinsically linked to the quality of their domicile shells. Because damaged or eroded shells can result in greater predation, evaluating shell structure may aid our understanding of population dynamics. We assessed the structural attributes of Cerithium atratum shells through assessments of (a) density using a novel approach involving computed tomography and (b) tolerance to compressive force. Our goal was to investigate factors that may influence decision making in hermit crabs, specifically those that balance the degree of protection afforded by a shell (i.e. density and strength) with the energetic costs of carrying such resources. We compared the density and relative strength (i.e. using compression tests) of shells inhabited by live gastropods, hermit crabs (Pagurus criniticornis) and those found empty in the environment. Results failed to show any relationship between density and shell size, but there was a notable effect of shell density among treatment groups (gastropod/empty/hermit crab). There was also a predictable effect of shell size on maximum compressive force, which was consistent among occupants. Our results suggest that hermit crabs integrate multiple sources of information, selecting homes that while less dense (i.e. reducing the energy costs of carrying these resources), still offer sufficient resistance to compressive forces (e.g. such as those inflicted by shell-breaking predators). Lastly, we show that shell size generally reflects shell strength, thus explaining the motivation of hermit crabs to search for and indeed fight over the larger homes.

Electrophoretic mobility of charged porous shells or microcapsules and electric conductivity of their dilute suspensions

Abstract An analysis is presented for the electrophoresis and electric conduction in a dilute suspension of charged spherical porous shells or permeable microcapsules with electric double layers of arbitrary thickness in an electrolyte solution. With the assumption that the system is slightly perturbed from equilibrium, the linearized electrokinetic equations governing the ionic electrochemical potential energy and fluid velocity distributions are solved as series expansions in the small fixed charge density of the porous shells. Explicit formulas for the electrophoretic mobility of the porous shells and effective electric conductivity of the suspension are derived. Both the electrophoretic mobility and the effective conductivity decrease monotonically with a decrease in the relative thickness of the porous shells, but these decreases are not conspicuous until the porous shells are quite thin. When the fluid permeability of the porous shells is smaller or the electric double layers are thicker, the effect of this relative thickness on the electrophoretic mobility and effective conductivity becomes more significant. In the limiting case of zero inner radius of the porous shells, our formulas reduce to the corresponding results obtained for the electrophoresis and electric conduction in a suspension of charged porous spheres.