Light Shell Research Articles

북한강 엷은재첩, Corbicula papyracea (Heude) 의 번식생태

북한강에 서식하고 있는 엷은재첩의 산란생태를 파악하기 위하여, 생식소 발달단계에 따른 생식주기, 군성숙도, 난경의 월별변화를 조사하였다. 각장에 대한 각고, 각폭, 전중, 육중간 의 상대성장식에서 상관계수 (<TEX>$R^2$</TEX>) 는 0.921-0.984로 높은 상관관계를 나타내었다. 엷은재첩은 기수재첩 보다는 소형종이었으며, 동시자웅동체로서 체내에서 수정되어 아가미 보육낭에서 부화되어 체외로 방출하는 난태생종이었다. 월별 비만도는 0.14-0.21 범위로 동계인 12월-2월에 낮은 값을 보이다가 2월부터 서서히 높아지기 시작하여 5월에 0.21로 정점을 보였다. 월별 육중량비는 25.9-38.7%로 비만도의 월별 변화와 같은 경향을 나타내었다. 비만도와 육중량비의 정점이 생식세포의 최성숙기와 1-2개월 차이가 있었다. 생식소의 조직상, 비만도 및 생식세포의 월별 변화를 종합하면 북한강산 엷은재첩 생식년주기는 분열증식기(12-2월), 성장기(2-5월), 성숙기(6-8월), 완숙 및 발생기(8-11월), 회복기(11-12월) 로 구분되어 하계산란종이었다. 군성숙 각장은 12.6 mm 였으며, 16 mm 이상의 개체는 모두 성숙하여 아가미에 보육낭을 형성하였다. Gonadal development and maturation mechanism were studied on the freshwater marsh clam Corbicula papyracea (Heude), which is the endangered species in Korea. The specimens were collected in the rearing ponds and waterway of NFRDI in Gapyeong-gun, Gyeonggi-do from January to December 2004, and then investigated by condition factor, relative growth, gonadal development phases and gonad histological characters based on 30-50 individuals every month. Comparing with the freshwater marsh clam, C. papyracea is small, light olive brown shell and violet interior. The hermaphrodite individuals of C. papyracea take an internal fertilization and fertilized eggs are stored in the foster-sack in the gills, then the hatched juveniles are released outside after an ovoviviparous process. The average water temperature of inhabit area was in range of <TEX>$1.8-27.0^{\circ}C$</TEX> and usually took great effects on the gonad maturation of C. papyracea. The condition factor ranged from 0.14 to 0.21 throughout the year, which was the lowest during winter season (December-February), and gradually increased to the highest value of 0.21 in May. The ratio of meat weight to total weight was 25.9-38.7%, indicating the similar trend with condition factor. The highest values of condition factor and the ratio of meat weight appeared 1-2 months later than gonadosomatic index reached the peak value, it was probably because that the ovoviviparous eggs would spend a long period before hatching from the foster-sack in the gills. To synthesize the characters of meat weight, condition factor and gonad development by histological study, reproductive cycle of C. papyracea could be divided into five successive stages: multiplicative stage (December to February), growing stage (February to May), mature stage (June to August), spawning stage (August to November), recovery stage (November to December). The smallest shell length of matured C. papyracea was 12.6 mm, and individuals, larger than 16 mm, was formed the nursery in the gills.

Qualitative Characteristics and Suture Measurements of Two Breeds of Snail Reared in Nigeria

Heliculture is gradually gaining more attention in Nigeria. There are still constraint to snail production en mass which include breed and strain identification ,feeding, management and health. In this study, the Qualitative characteristics and suture measurement of two breed of snails were observed. A total of 90 snails comprising of 50 Archachatina marginataand 40 Achatina achatinawere purchased at different markets in towns around Ayetoro. Most (64%) of theA.marginatahad brown shell colour, a few (36%) had brown with light yellow shell colour. 100% of A. achatinahad brown with light brown-yellow shell colour. 22% ofA. marginatahad black foot, 64% had brown and 14% hadbrown-black foot colour. 100% ofA. achatinahad brown-black foot colour. There is a significant difference (P<0.01) in the brown-black foot colour ofA. achatinaand A. marginata. 94% ofA. marginatahad broad and wide apex, 6% had pointed apex, (0%) narr ow and wider apex while 100% A. achatinahad narrow and wider apex.A. achatinahad zig zag thick brown lines on the shell which was significantly different (P<0.01) from the A. marginata.The distance between the 1

Principles of geometrical shaping effective shell structures forms

The paper concerns geometrical shaping of shell structures composed of individual shells arranged effectively in space that is in a way similar to properties of a regular, geometrical surface with taking into account straight lines and planes normal to the base surface. The individual segments are made up of unidirectional folded flat sheets transformed into shell shapes. A freedom of transversal width increments of these sheets is assured while transforming, which ensures their possible small effort – such a deformation of a material intended for transferring functional loads but which makes restrictions concerning the shell sheets shapes. These shape restrictions are provoked by the strictly determined stiffness characteristics of the shell sheets and cause of the edge or discontinuous areas between adjacent shells segments in the shell structure. The method of delimiting great diversity of effective, compound shell forms whose general shapes are close to regular, geometrical surfaces characterized by any sign of the Gaussian curvature is presented. Innovation of the way also consists in integration of the form of a whole building object (walls and shell roof). It is achieved by division of the elevation walls into flat areas contained in planes close to planes normal to the base surface as accurate as possible. The segment’s directrices are also contained in these planes. The presented issues are the ground for elaborating a method of shaping of the light gauge steel shell structures and their further integration with whole building objects.

Polyacrylamide Wastewater Treatment in a Nested Biofilm Airlift Suspension Reactor

Polyacrylamide has been widely used in tertiary oil recovery. Oilfield produced water in a large scale contain polyacrylamide, leading to oilfield environment pollution. In this paper, the nested loops biofilm airlift suspension reactor was used in polyacrylamide wastewater treatment. In the reactor, wastewater can alternately flow through the hypoxic environment fixed light carriers and aerobic environment suspended walnut shell biological carriers, achieving simultaneous removal of organic matter and nitrogen. The influencing factors on the organic compound degradation and denitrification performance were studied. Biological and hydrodynamic model of nitrogen and carbon removal was established. Also, the biological phase structure of the carrier biofilm was observed. The results show that polyacrylamide degradation and ammonia nitrogen removal rate are around 30% and 95%, respectively when the experimental hydraulic retention time is 24h. Due to poor denitrification efficiency; nitrate removal rate is only 20%. The carrier biofilm thickness is appropriate, and filamentous bacteria occupy the dominant position.

Nondaily Deposition of Striae in the Bay ScallopArgopecten irradians(Concentricus) in the Laboratory

Small (∼15 mm) and large (∼30 mm) calcein-marked bay scallops, Argopecten irradians, held for 2, 4, and 6 wk in the laboratory under natural illumination and conditions of high and low flow rates deposited significantly more striae on the surface of the left (dark) shell valve compared with the right (light) shell valve. Small scallops deposited an average of 0.55 stria per day, 0.42 stria per day, and 0.34 stria per day, respectively, during the 2-, 4-, and 6-wk experiments, whereas large scallops had a lower frequency of stria formation (0.20 stria per day, 0.18 stria per day, and 0.17 stria per day, respectively). Striae deposition and interstria distance were highly variable among small A. irradians. No relationship in interstria distance was obvious in A. irradians that deposited the same number of striae during 6 wk (0.45 striae per day) and held under conditions of high flow rate, indicating that stria formation is not synchronous with changes in the environment. Our results demonstrate unequivocally that in, A. irradians, stria formation is nondaily and is related to shell growth rate. The largest and oldest scallops (∼30 mm and 1.4 y old) formed striae at a rate of 0.17–0.2 stria per day whereas smaller and younger fast-growing A. irradians formed between 0.34 striae per day and 0.55 stria per day—clear evidence of nondaily and nonrhythmic deposition of striae in this pectinid species. Thus, striae cannot be used as a chronological marker with which environmental conditions can be compared.

Generation of nanosize 3D dark spots with a light shell by plasmonic conical probe with metallic nano-rod

Nanosize three-dimensional (3D) dark spots with a light shell in enhanced local optical fields generated by a plasmonic metal-coated conical dielectric probe with a nano-rod are investigated numerically. The 3D dark spots are due to interference among plasmon-enhanced local fields. It is found that two kinds of 3D dark spots are generated in the free space in the vicinity of the nano-rod. One is generated near the rod end and has a disk shape. The other is generated around the nano-rod and has a toroidal shape. Both kinds of 3D dark spots have nanoscale dimensions, because they are generated by interference between near fields.

Vibrations of spherical core-shell nanoparticles

The acoustic vibration modes of spherical composite nanoparticles formed by a core and an arbitrary number of shells are computed using a semianalytic approach based on elastic theory. The modes observed in time-resolved pump-probe experiments are identified in the case of metal-dielectric-based spherical composite nanoparticles, and results are illustrated in the case of Ag@SiO${}_{2}$ core-shell nanoparticles. The presence of a light dielectric shell is shown to only weakly shift the frequency of the dominant mode observed in time-resolved experiments. Moreover, a large impact of the mechanical contact between the different materials forming the particle on the vibrational mode frequency and damping is predicted, offering the possibility of experimentally addressing this parameter.

Configuration and Pyrological Performance of Self Thermal Insulating Blocks

Energy conservation is a hot topic in the field of construction. To increase the thermal resistance of the enclosing structure of buildings, a T-shaped self thermal insulating block is designed. The particular shape, light weight concrete shell and heat insulating materials filled in the cavities result in a good heat insulating effect. Thermal bridges on the wall can significantly be reduced, which leads to a great improvement in thermal resistance, and performance of energy conservation. The thermal conductivity of wall made of this kind of blocks could be as low as 0.088W/ m·K, by which energy consumption could be saved by 65% comparing with wall made of bricks in 1980s.

Phytosynthesis of Au, Ag and Au–Ag bimetallic nanoparticles using aqueous extract and dried leaf of Anacardium occidentale

Present study reports a green chemistry approach for the biosynthesis of Au, Ag, Au–Ag alloy and Au core–Ag shell nanoparticles using the aqueous extract and dried powder of Anacardium occidentale leaf. The effects of quantity of extract/powder, temperature and pH on the formation of nanoparticles are studied. The nanoparticles are characterized using UV–vis and FTIR spectroscopies, XRD, HRTEM and SAED analyses. XRD studies show that the particles are crystalline in the cubic phase. The formation of Au core–Ag shell nanoparticles is evidenced by the dark core and light shell images in TEM and is supported by the appearance of two SPR bands in the UV–vis spectrum. FTIR spectra of the leaf powder before and after the bioreduction of nanoparticles are used to identify possible functional groups responsible for the reduction and capping of nanoparticles. Water soluble biomolecules like polyols and proteins are expected to bring about the bio-reduction.

Generation of three-dimensional dark spots with a perfect light shell with a radially polarized Laguerre–Gaussian beam

The theoretical analyses in this paper show that a highly focused double-ring radially polarized Laguerre-Gaussian beam with a topological charge of 1 (R-LG(11)) can generate a small three-dimensional (3D) dark spot surrounded by an almost 100% uniform light shell in all directions. The cleanness and size of the 3D dark spot, the uniformity and strength of the light shell surrounding the dark spot, and the light efficiency all depend on the truncation parameter β of the R-LG(11) beam and the numerical aperture (NA) of the system. When β=1.6 and the NA is close to its utmost, an almost 100% uniform light shell surrounding the 3D dark spot can be achieved and the dark spot is very clean. If the NA is lowered but β is increased to 1.95, we can also achieve an almost 100% uniform light shell and light efficiency can reach 90%, but the disadvantage is that the center of the dark spot is not too clean. A not-too-clean 3D dark spot, if the light shell surrounding it is very uniform, is acceptable for many applications. Therefore, 3D dark spots surrounded by a high uniform light shell, generated by simply adjusting the truncation parameter of the R-LG(11) beam and the NA of the system, are useful for superresolution fluorescence microscopy, dark spot microscopy, and the dark spot trap.

Copper isotopic zonation in the Northparkes porphyry Cu–Au deposit, SE Australia

Significant, systematic Cu isotopic variations have been found in the Northparkes porphyry Cu–Au deposit, NSW, Australia, which is an orthomagmatic porphyry Cu deposit. Copper isotope ratios have been measured in sulfide minerals (chalcopyrite and bornite) by both solution and laser ablation multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). The results from both methods show a variation in δ 65Cu of hypogene sulfide minerals of greater than 1‰ (relative to NIST976). Significantly, the results from four drill holes through two separate ore bodies show strikingly similar patterns of Cu isotope variation. The patterns are characterized by a sharp down-hole decrease from up to 0.8‰ (0.29 ± 0.56‰, 1 σ, n = 20) in the low-grade peripheral alteration zones (phyllic–propylitic alteration zone) to a low of ∼−0.4‰ (−0.25 ± 0.36‰, 1 σ, n = 30) at the margins of the most mineralized zones (Cu grade >1 wt%). In the high-grade cores of the systems, the compositions are more consistent at around 0.2‰ (0.19 ± 0.14‰, 1 σ, n = 40). The Cu isotopic zonation may be explained by isotope fractionation of Cu between vapor, solution and sulfides at high temperature, during boiling and sulfide precipitation processes. Sulfur isotopes also show an isotopically light shell at the margins of the high-grade ore zones, but these are displaced from the low δ 65Cu shells, such that there is no correlation between the Cu and S isotope signatures. Fe isotope data do not show any discernable variation along the drill core. This work demonstrates that Cu isotopes show a large response to high-temperature porphyry mineralizing processes, and that they may act as a vector to buried mineralization.

Soft X-ray emissions from neon gas-puff Z-pinch powered by Qiang Guang-I accelerator

AbstractThe X-ray emission, especially the K-shell emission, from a neon gas-puff Z-pinch powered by the Qiang Guang-I accelerator, about 1.5 MA in amplitude and 100 ns in rise time, were calculated based on the two-level model and measured with X-ray diodes and an eight-frame X-ray pinhole camera. The simulation results showed that the K-shell yield is highly sensitive to the peak current. The experimental results confirmed that the matching of the Z-pinch load (mass and initial radius) to the current is crucial for getting a higher X-ray yield. Being determined by the imploding time, the pinch current plays a more important role than the current amplitude in K-shell emission. It seems that the preferable imploding time is about 110 ns. The K-shell radiation power with double shells, as a whole, is higher than that using single neon shell. While an implosion of a light (32 µg/cm) and small (20 mm in diameter) neon shell evolves with rather twist and asymmetries, a heavier (41 µg/cm) and bigger (25 mm in diameter) neon shell implodes more symmetrically. The double neon shells, 30 mm and 30 µg/cm for the outer shell, and 15-mm and 10 µg/cm for the inner shell, create almost “perfect” implosions evidenced by the early-time plasma shells with little perturbation and late stagnated pinch liners with a good axial uniformity. It was found that the “Zippering” effect leads to an earlier K-shell emission in the cathode region than that in the anode region, which extends the pulse width of K-shell emission.

Weight difference threshold during shell selection relates to growth rate in the semi-terrestrial hermit crab Coenobita compressus

[To minimize the energetic expenditure imposed by carrying a protective gastropod shell, terrestrial hermit crabs should discriminate the weight difference between available shells; if the difference exceeds a certain amount — the threshold — the lighter shell should be accepted because of the cost of growing in a shell that is too heavy, while swapping between similar shells (less different than the threshold) may be inconsequential. We assigned shells of different weight adjusted to the crab's size to individually-housed crabs to (1) establish the weight difference at which crabs systematically reject a heavy shell and (2) compare growth rates of crabs confined to shells that were lighter- or heavier than the weight differential threshold. Crabs were significantly more likely to reject a heavy shell over a lighter one if the difference between the two was >50%, and when the shell weight exceeded 60% of the crab's weight. Crabs living in shells 50% heavier. This suggests that hermit crabs reject a heavier shell if a meaningful threshold is exceeded: this finding should prompt research into the neurophysiologic mechanism involved in shell assessment., To minimize the energetic expenditure imposed by carrying a protective gastropod shell, terrestrial hermit crabs should discriminate the weight difference between available shells; if the difference exceeds a certain amount — the threshold — the lighter shell should be accepted because of the cost of growing in a shell that is too heavy, while swapping between similar shells (less different than the threshold) may be inconsequential. We assigned shells of different weight adjusted to the crab's size to individually-housed crabs to (1) establish the weight difference at which crabs systematically reject a heavy shell and (2) compare growth rates of crabs confined to shells that were lighter- or heavier than the weight differential threshold. Crabs were significantly more likely to reject a heavy shell over a lighter one if the difference between the two was >50%, and when the shell weight exceeded 60% of the crab's weight. Crabs living in shells 50% heavier. This suggests that hermit crabs reject a heavier shell if a meaningful threshold is exceeded: this finding should prompt research into the neurophysiologic mechanism involved in shell assessment.]

Triplodon chodo, a new species of pearly fresh water mussel from the Amazon Basin (Mollusca: Bivalvia: Unionoida: Hyriidae)

A new species of the genus Triplodon Spix, 1827 is described based on shell samples collected on Rivers Jamari (Rondônia State) and Aripuanã (Amazonas State) from the Madeira River Basin; on the Amazon at Oriximiná and on the mouth of Tapajós River at Alter do Chão (Pará State). Triplodon chodo is a new species considered closely related to T. stevensi Lea, 1871, (described from the part of the River Essequibo which borders the Guianas). Triplodon chodo is distinguished from the latter by its smaller, lighter shell, the absence of a wing in the anterior region and by the delicate shape of the external sculpture, which is composed of minuscule nodules organized in rows that converge and crosses on the centre of the valves. The straight and vertical posterior margin forms a right or slightly obtuse angle with the shell's dorsal and ventral margins. The anterior region is short, low and slightly tapering, with the distal extremity situated on the half of the shell height. The dorsal and ventral margins are equally curved.

Change in flow and transport patterns in horizontal subsurface flow constructed wetlands as a result of biological growth

In order to investigate the influence of biological growth on flow and transport patterns in horizontal subsurface flow constructed wetlands, bromide tracer experiments were conducted in two 3 m long tanks. The tanks were filled with light weight aggregates and shell sand, respectively. The hydraulic conductivity, drainable porosity and dispersivity of the two filter media were determined before and after biological growth. The obtained breakthrough curves of bromide tracer showed that biological growth caused a pronounced reduction in drainable porosity, mainly for shell sand, whereas its effect on saturated hydraulic conductivity was negligible. The spatial distribution of the bromide after biological growth in the two filter media showed that the flow occurred preferentially along certain paths. However, in the light–weight aggregates filter medium, biological growth with possible clogging effects seems to reduce the efficiency of some preferential flow paths, increase the retention time, and hence, improves the system treatment efficiency. This study showed that selecting a filter medium including coarse fractions to some extent can mitigate the potential negative effects of bioclogging.

Shell characteristics and sexual dimorphism in the Namaqualand speckled padloper, Homopus signatus signatus

There is little quantitative information regarding the two subspecies of the world's smallest tortoise, Homopus signatus. To help characterise the northern subspecies H. s. signatus and evaluate the development of shell size and colour patterns, we measured shell characteristics of wild juvenile, male and female H. s. signatus. When scaling shell dimensions on carapace length, male shell size represented an extension of juvenile shell size for shell height, width and volume, but not plastron length. The slope of plastron length scaled on carapace length was smaller for males than for juveniles or females, suggesting differential growth of the plastron. The smaller male plastron translates to large shell openings, perhaps to improve locomotion and to facilitate tail movement during copulation. Conversely, the slope of female shell height, width and volume (scaled) was larger than for juveniles or males, presumably providing more space to accommodate follicles and the large egg. Serration of the marginal scutes and shell colour changed with body size, and shell colour pattern differed between sexes. The carapace was darker at intermediate body sizes (large juveniles and small adults); the increase in dark appearance resulted primarily from widening of the dark pigment band around scute margins as growth laminae were added. Both the lighter shell colour and reduced serration of large adults may be due to shell wear; large adults may produce less dark pigment, and older laminae disappear due to flaking or peeling. Females had a darker overall colour, more rays and fewer speckles than did males. This dimorphism may relate to thermoregulation, gamete protection or intraspecific communication. Both male and female patterns may confer crypsis if the sexes use microhabitats differently.

Cranked Nilsson-Strutinsky vs the spherical shell model: A comparative study ofpf-shell nuclei

A comparative study is performed of a deformed mean field theory, represented by the cranked Nilsson-Strutinsky (CNS) model, and the spherical shell model. Energy spectra, occupation numbers, B(E2)-values, and spectroscopic quadrupole moments in the light pf shell nuclei are calculated in the two models and compared. The result is also compared to available experimental data which are generally well described by the shell model. Although the Nilsson-Strutinsky calculation does not include pairing, both the subshell occupation numbers and quadrupole properties are found to be rather similar in the two models. It is also shown that ``unpaired'' shell model calculations produce very similar energies as the CNS at all spins. The role of the pairing energy in the description of backbending and signature splitting in odd-mass nuclei is also discussed.

Simple analytical models of gravitational collapse

Most general relativity textbooks devote considerable attention to the simplest example of a black hole containing a singularity, the Schwarzschild geometry. Only a few discuss the dynamical process of gravitational collapse by which black holes and singularities form. We present two simple analytical models that describe this process. The first involves collapsing spherical shells of light and is analyzed mainly in Eddington-Finkelstein coordinates; the second involves collapsing spheres filled with a perfect fluid and is analyzed mainly in Painleve-Gullstrand coordinates. Our main goal is simplicity and algebraic completeness, but we also present a few more sophisticated results such as the collapse of a light shell in Kruskal-Szekeres coordinates.

Long‐term costs of using heavy shells in terrestrial hermit crabs (Coenobita compressus) and the limits of shell preference: an experimental study

AbstractTerrestrial hermit crabs use mollusc shells to protect their soft bodies from predation and desiccation, but their use is costly. The energetic short‐term cost of using shells has been demonstrated, yet this could theoretically be overcome by increasing feeding rate or food quality. In the long term, shells have the potential to constrain growth, which may in turn have a negative effect on fitness. Thus crabs should choose the lightest (least expensive to carry) shell amongst those of a size that permit growth. Since in nature lighter shells are also thinner‐walled, these may provide insufficient protection from predation or desiccation, facing the crabs with a trade‐off between protection and growth. This potential trade‐off was investigated in the terrestrial hermit crab Coenobita compressus. Crabs were individually maintained in captivity for a variable period of between 1 and 7 months, during which light or heavy replicates of the preferred shell were available. In a second experiment, crabs were given a choice between a thick (and heavy) or a thin (and light) shell. In addition, the resistance and water retention capacity of thin and thick shells was compared. As predicted, crab growth was negatively correlated with the weight of the shell used, but crabs rejected the thin (light) shells. Thin shells were more likely to break when crabs used the normal ‘rolling’ behaviour in response to perceived threats. In addition, thin shells lost water at a faster rate than thick ones. Since two putative functions of shell use in terrestrial hermit crabs are protection against predation and against desiccation, it is inferred that the preference for shells of intermediate weight in C. compressus results from a balance between the need to grow and the cost of carrying a brittle shell that is not sufficiently water tight.

On chaotic behavior of gravitating stellar shells

Motion of two gravitating spherical stellar shells around a massive central body is considered. Each shell consists of point particles with the same specific angular momenta and energies. In the case when one can neglect the influence of gravitation of one ("light") shell onto another ("heavy") shell ("restricted problem") the structure of the phase space is described. The scaling laws for the measure of the domain of chaotic motion and for the minimal energy of the light shell sufficient for its escape to infinity are obtained.