Radial Shield Research Articles

Optimized design of small sized low noise magnetic shielding cylinder

Magnetic shielded cylinder (MSC) is crucial in various applications, especially in the realm of medical weak magnetic signal measurement. However, designing a small volume, low noise MSC is a multi-objective optimization problem, with the objectives conflict with each other. To address the complexity arising from numerous variables in the optimal design of MSC with a small volume and low-noise, this paper proposes an optimal design method based on non-dominated sorting genetic algorithm II (NSGA-II) to realize the optimal design of MSC with a high shielding factor, small volume and low-noise. Firstly, an analytical model for the shielding factor of the MSC is established, and a multi-objective optimization model is given. Then, the NSGA-II algorithm is employed to obtain a series of Pareto frontier optimal solutions. Finally, the efficacy of this method is evaluated through simulation and experimentation. The results reveal that the radial and axial shielding factors of the optimized MSC achieve maximum values of 8.6 × 107 and 9.5 × 106 respectively. Meanwhile, the average axial noise and radial noise of the MSC between 1 and 100 Hz are 22 fT/Hz1/2 and 20 fT/Hz1/2 respectively. Practice has proven that this method can be used to optimize the design of small-volume, low-noise magnetic shields to improve the performance of magnetic shields.

Deepest known novel species of the genus Ophiuroglypha Hertz, 1927 (Echinodermata: Ophiuroidea) from the central rift zone, Philippine Sea

A new species of brittle star was collected in 2021 by the manned submersible “Fendouzhe” from the central rift zone deep waters, Philippine Sea, at a depth of 7729 m. It is described as Ophiuroglypha fendouzhe sp. nov., and is distinguished from its congeners based on the following features: slender arms, separated dorsal and ventral arm plates, overlapping large disc scales, and distally contiguous radial shields. We provide comprehensive descriptions of the external morphological features, including characteristics of the arm skeleton, and a phylogenetic analysis based on COI sequences. The interspecific genetic distance variation in the genus Ophiuroglypha found in this study was 3.89% to 24.25%. The new species constitutes the deepest known record for the genus Ophiuroglypha.

Astrocharis margarita sp. nov., a new snake star (Echinodermata, Ophiuroidea, Euryalidae) from a seamount in the Western Pacific.

During the scientific expedition of the R/V Kexue in 2014, a new species belonging to the genus Astrocharis Koehler, 1904 was collected from a seamount near the Yap Trench. Astrocharis margarita sp. nov. is distinguished from the other species of Astrocharis by the following characters: radial shields are partly naked or completely covered by polygonal ossicles, and the body color is uniformly light pink. Maximum Likelihood Tree and Bayesian Tree, based on a concatenated dataset of COI, 16S, and 18S genes analyses, indicated that the monophyly of Astrocharis was not supported, which suggested the genus needs to be revised.

Optimization of a High Screening Performance and Low Noise Magnetically Shielded Cylinder for SERF Atomic Magnetometer

To resolve the contradiction between the shielding performance and the magnetic noise in the design of magnetically shielded cylinder (MSC), an MSC optimization design method based on particle swarm optimization with multistage inertia weights algorithm (MW-PSO) is proposed. Using the segmented magnetic noise and material volume as constraints and taking the axial shielding factor as the target, the structure of a four-layer MSC is optimized to achieve the expected results. According to the previous optimization results, the relationship curve between the change rate of the axial shielding factor and that of the magnetic noise is obtained, and the structure parameters of the optimal four-layer MSC are determined by the extreme points of the curve. The simulation analyses are conducted to verify the effectiveness of the method. The results show that compared with the initial MSC designed by the conventional method, the axial and radial shielding factors of the optimized MSC are increased by 17.95 times and 15.3 times, respectively; meanwhile, the magnetic noise is decreased by 15%.

A High-Performance Magnetic Shield with MnZn Ferrite and Mu-Metal Film Combination for Atomic Sensors.

This study proposes a high-performance magnetic shielding structure composed of MnZn ferrite and mu-metal film. The use of the mu-metal film with a high magnetic permeability restrains the decrease in the magnetic shielding coefficient caused by the magnetic leakage between the gap of magnetic annuli. The 0.1–0.5 mm thickness of mu-metal film prevents the increase of magnetic noise of composite structure. The finite element simulation results show that the magnetic shielding coefficient and magnetic noise are almost unchanged with the increase in the gap width. Compared with conventional ferrite magnetic shields with multiple annuli structures under the gap width of 0.5 mm, the radial shielding coefficient increases by 13.2%, and the magnetic noise decreases by 21%. The axial shielding coefficient increases by 22.3 times. Experiments verify the simulation results of the shielding coefficient of the combined magnetic shield. The shielding coefficient of the combined magnetic shield is 16.5%. It is 91.3% higher than the conventional ferrite magnetic shield. The main difference is observed between the actual and simulated relative permeability of mu-metal films. The combined magnetic shielding proposed in this study is of great significance to further promote the performance of atomic sensors sensitive to magnetic field.

Development of reactive-transport models simulating the formation of a silica gel barrier under CO2 storage conditions

Geological storage of carbon dioxide (CO2) is a means of reducing greenhouse gas emissions. Key to the successful implementation of this technology is the ability to prevent CO2 leakage from the storage reservoir. One promising leakage abatement technology involves forming a geochemical barrier through reaction of an alkaline sodium silicate solution with CO2-enriched water or supercritical CO2. To investigate the feasibility of this technology at the field scale, three reactive-transport models were developed. The first simulations replicated previous laboratory studies (Castañeda-Herrera et al., 2018a), the second and third predicted the formation of a radial shield around the well and an impermeable silica gel layer serving as a flow diverter above the CO2 injection point. Good agreement with the experimental results was observed. Results also show the pH-dependent silica gel formation and its location deep in the reservoir strongly depend on the rate and the sequence of reagent injection as well as their efficient mixing in the reservoir. An alternative field application of the silica gel barrier is proposed to enhance capillary trapping beneath a lateral flow diverter. The application of silica gel barriers could make CO2 sequestration both safer and more efficient, enhancing further uptake of carbon capture and storage.

Overlooked for over a century: Ophioderma occultum sp. nov. (Echinodermata), a new species of brittle star from the Eastern Pacific

ABSTRACT We describe a new species of ophiodermatid brittle star from the Eastern Pacific: Ophioderma occultum sp. nov. This species has been mistakenly recorded since 1899 as a colour phase of one of its congeners, Ophioderma panamense. However, the integrative use of morphological and molecular data, and comparison with type material of other Eastern Pacific Ophioderma, led to its differentiation as a novel species. Ophioderma occultum sp. nov. is characterised by having radial shields and adoral shields covered with granules, dorsal arm plates divided typically into two pieces, and a particular colour pattern: a dark grey to brown body, and arms with subtle lighter transverse bands and parallel longitudinal white bands over some median and distal segments. Molecular information based on the mitochondrial genes cytochrome oxidase subunit I (COI) and 16S also supported the species’ validity, coinciding with the morphological observations. In particular, the molecular marker 16S had not been used before for species delimitation in this genus and was proven here to be resolutive. In contrast to most species of Ophioderma from the area, Ophioderma occultum sp. nov. shows a restricted distribution to the northern Mexican Pacific (Gulf of California and islas Revillagigedo). This new species is the 10th Ophioderma described from the Eastern Pacific and the 34th worldwide. http://www.zoobank.org/urn:lsid:zoobank.org:pub:A5FFAC55-E5BE-42F6-8371-7B745911F157

Description of a new species of Histampica (Ophiuroidea: Ophiothamnidae) from cold seeps in the South China Sea and analysis of its mitochondrial genome

Ophiuroids are widely distributed marine benthic organisms, but very few species of ophiuroids have been reported from deep-sea chemosynthetic habitats including hydrothermal vents and cold seeps. In this study, a new species of Ophiothamnidae, Histampica haimaensis sp. nov., collected from cold seeps in the South China Sea, was described based on morphological and genetic analyses. The new species, representing the first known occurrence of Histampica from chemosynthetic habitats, is distinct from its congeners in having long triangular or half elliptical radial shields that are not in contact with each other, four stout, tapering and blunt arm spines, and three or four lateral oral papillae on each side of the jaw, including distally two large and broad papillae and proximally one or two small and narrow papillae. Phylogenetic analysis based on mitochondrial COX1 gene supports the morphological identification. A complete mitochondrial genome (mtgenome) of the new species was characterized by genome skimming. It is 15,759 base pairs in length and contains 37 genes including 13 protein coding genes, two ribosomal RNA genes and 22 transfer RNA (tRNA) genes. Among the tRNA genes, trnL and trnS are duplicated. When compared with the mtgenomes from the same family of ophiuroids, the mtgenome of H. haimaensis sp. nov. has undergone four potential historical gene order reversals, and one tandem duplication random loss event. ND1, ND2 and ND5 each contains a positively selected site, while COX2 contains three positively selected sites This study provides morphological description to H. haimaensis sp. nov. and reports the first cold-seep ophiuroid mitochondrial genome with a novel gene order arrangement and signals of positive selection, which may have contributed to adaption of Ophiuroidea to the deep-sea chemosynthetic environments.

Description of three species of ophioplinthacids, including a new species, from a deep seamount in the Northwest Pacific Ocean.

Five specimens of brittle star were collected from a deep-sea seamount in the Northwest Pacific, and identified into three species. One which is new to science, Ophioplinthaca grandisquama n. sp., can be easily distinguished from its congeners by the distinctly elongated and stout tentacle scales, stout and long disc spines, capitate with typically elongate to flaring head bearing numerous distinct thorns, radial shields roughly triangular and contiguous distally. One specimen was identified as Ophioplinthaca semele (Clark, 1949), which had been reported in Hawaii seamounts, is a new record of this species in the Northwest Pacific. The remaining specimen was an unknown species of Ophioplinthaca, with some different characteristics from other species of Ophioplinthaca. However, we, herein, prefer not to attach a name to this specimen until more morphological characteristics are available. The finding of this new species and two new records further enriches the distribution of Ophioplinthaca in the seamount of Northwest Pacific, providing useful information for marine protection in the cobalt-rich area.

Multilayer magnetic shielding for testing a superconducting single-flux-quantum circuit chip in liquid helium dewar

In order to reduce the influence of environmental magnetic field on the test of superconducting single-flux-quantum (SFQ) circuit chip in a liquid helium dewar, a multilayer magnetic shielding structure is designed to provide a clean magnetic field lower than 50 nT and achieve a shielding effectiveness higher than 60 dB. The magnetic shielding structure consists of three cylindrical layers with uniform 1 mm thickness. The first inner layer is made of NbTi which works as a strong diamagnet shell, while the outer two layers are made of permalloy which has high permeability at helium temperature. The superconducting quantum interference device (SQUID) was used to test the shielding performance of the structure under low frequency (0.1–100 Hz) magnetic interference at helium temperature. The results show that the radial and axial shielding effectiveness (SE) are about 80 dB and 68 dB, respectively, indicating that the multilayer structure has good shielding performance and can be used in the testing system of superconducting single-flux-quantum circuit chip.

Morphometry and Relative Growth of Ophiolepis crassa (Echinodermata: Ophiuroidea), a Brittle Star from the Eastern Pacific.

Tropical ophiuroid fauna belonging to the family Ophiolepididae are almost unknown. This study deals with the relative growth and morphometric traits of the ophiuroid Ophiolepis crassa from the Gulf of California, Mexico. Specimens examined in this study came from the Colección Nacional de Equinodermos, Universidad Nacional Autónoma de México, and were collected over soft bottoms off Punta Gorda. Thirteen anatomical features were measured in a total of 152 specimens, including disk diameter, arm length, as well as length and width of dorsal and ventral arm plates, and radial, oral, and adoral shields. Based on the range of values of the disk diameter, varying from 4 to 19 mm, we provided quantitative data on each anatomical measurement considering three size classes. Morphometric data were adjusted to a power equation to detect the degree of allometry in the growth of anatomical traits. Results indicated that all the ventral and dorsal plates, as well as the radial, oral, and adoral shields, suffer changes in shape during growth, but these changes are stronger in the plates. In addition, an analysis of symmetry applied to both right and left radial shields revealed that these structures remain nearly symmetrical during growth. The disk diameter vs arm/disk relationship indicated that the species is a surface dweller inhabitant of the seafloor. This study, based on a single sample collected in a restricted area of the eastern Pacific, provides useful quantitative information for further taxonomic, systematic, or biogeographic studies.

A New Species of the Genus Ophiomonas Djakonov (Echinodermata: Ophiuroidea: Amphilepididae) from the Deep-Sea of Japan.

A new species, Ophiomonas shinseimaruae, is described based on five specimens collected from deep water settings, southeast of Cape Erimo, Hokkaido, Japan. Ophiomonas shinseimaruae sp. n. is distinguished from other congeners based on the following characters: elongate semi-circular and separated radial shields; triangular oral shields; flat and broad tentacle scales on the second tentacle pore; octagonal dorsal arm plates, approximately three times wider than long on proximal portion of the arm; and three arm spines present proximally on the arm. This is the first record of the genus Ophiomonas from Japanese waters. The COI nucleotide sequence for Ophiomonas shinseimaruae sp. n. is provided.

Ophioderma hendleri sp. nov. (Echinodermata: Ophiuroidea: Ophiodermatidae) and its congeners from the Eastern Pacific

The widespread Ophioderma hendleri sp. nov., from the Eastern Tropical Pacific (Mexico to Colombia) is distinguished from its congeners by having radial shields covered by granules, naked adoral shields, up to 11 arm spines, and by its brown and beige coloration. Ophioderma hendleri sp. nov. belongs to the group of species with naked adoral shields (i.e., O. pentacanthum H.L. Clark, 1917, O. variegatum Lütken, 1856), and it has frequently been misidentified as O. panamense Lütken, 1859 or O. variegatum. Therefore, the main aim of the present work was to describe Ophioderma hendleri sp. nov. and differentiate it from its congeners. The original description of O. panamense was incomplete; thus, we provide a redescription. Due to the confusion in previous designations of its type material, we designate a lectotype and paralectotype of O. variegatum. Finally, we expand the distribution range of O. pentacanthum to Cocos Island, Costa Rica. With this work, the total number of valid species of Ophioderma Müller & Troschel, 1840 in the world increases to 33 and in the Eastern Pacific to nine species.

Analyses and verifications of magnetic shielding of long pipelines aiming for pipeline orientation measurements

So far, none of conventional magnetic shielding models can model a field long pipeline consisting of many welded short sections with different permeabilities. This paper demonstrates the magnetic shielding model of long pipelines via simulation analyses based on the finite element method (FEM) and experimental verifications of the magnetic shielding of short pipes, torus pipes, and field long pipelines. The radial and axial shielding factors of a finite pipe can be accurately calculated by the FEM. As the pipe length increases, the axial factor rapidly converges to a value less than 1, and the convergence value is independent of the pipe length because of the magnetic charges at the two ends. For a long pipeline consisting of many short sections, the averaged shielding factors over a couple of adjacent sections are equal to that of an ideal infinite pipeline, and the axial factor is always equal to 1. An “average” strategy for field pipeline orientations that employs the averaged magnetic fields and shielding factors over several sections is then proposed and demonstrated. As the geomagnetic field is taken as the absolute reference, this orientation measurement method has no risk of divergence over a long time and distance. Index Terms—cylindrical magnetic shield, magnetic fields, pipeline orientation.

Taxonomic review of Ophiothrix Müller & Troschel, 1840 (Echinodermata: Ophiuroidea) from Brazil, with the description of four new species

Brittle stars are considered one of the main benthic groups at the Brazilian coast, where they occur in high abundance and diversity. Ophiothrix Müller Troschel, 1840 is among the most common genera of ophiuroids, with hundreds of specimens deposited in Brazilian Zoological Collections. Here we reviewed the species of Ophiothrix of Brazil and elucidated the taxonomic status of the six species previously reported in Brazilian waters-Ophiothrix ailsae Tommasi, 1970, Ophiothrix angulata (Say, 1825), Ophiothrix brachyactis H. L. Clark, 1915, Ophiothrix rathbuni Ludwig, 1882, Ophiothrix suensoni Lütken, 1856 and Ophiothrix trindadensis Tommasi, 1970. Three of these were not found among the 1.134 specimens analyzed in this study-O. ailsae, O. angulata and O. brachyactis. Most specimens previously attributed to these three taxa are here assigned to Ophiothrix brasiliensis n. sp. due having disc covered by short spines with 2-6 thorns at the apex and triangular radial shields covered only by short bifid and trifid spines. Three other new species are also described. Ophiothrix spiniformis n. sp. has a disc covered by long spines with denticules along their complete length and an apex with spinelets and radial shields covered by short bifid and trifid spines. Ophiothrix tommasii n. sp. is characterized by the interradial regions of the disc and radial shields being covered by spines with 2-7 thorns at the tip, and by the presence of small spines on the first dorsal arm plate. Ophiothrix troscheli n. sp. has a disc covered by long conical spines and naked, triangular radial shields. An identification key for the Ophiothrix species of Brazil is provided.

A Modelling of Paraffin Shielding for BNCT Facility at Kartini Reactor Research using MCNPX

The development of cancer in the world is very high. According to the World Health Organization (WHO) 1.69 million people die from cancer per year in the world, while the cases of cancer in Indonesia are also not much different. Some areas have a high prevalence of cancer, namely D.I Yogyakarta. Cancer has become a scourge for many people. There are many treatments available, such as chemotherapy, surgery, and radiation. Additionally, there is radiotherapy using neutron capture of boron-10 with energy 0.025 Ev. This treatment does not damage other tissue because the resulting particles such as He-4 and Lithium-7 have ranges that are a distance of 4.5-10 μm, so that the deposited energy is limited to the diameter of a single cell. The treatment is called Boron Neutron Capture Therapy (BNCT). There are several BNCT facilities such as a reactor, radial piercing beam port, thermal column, and shielding. The function of shielding is to absorb the neutron and alpha radiation. The shielding is made using paraffin material that is excellent in absorbing neutron radiation. In addition to paraffin there are also other materials, such as lead, used as paraffin casing. In a shielding simulation using MCNPX software, the resulting dose rate of radiation exposure outside of the BNCT facility in vitro and vivo tests is equal to 6.5 μSv / h. The thickness of the shielding paraffin used is 40 cm, Pb casing 25 cm, and 5 cm soft tissue.

Gorgonocephalus eucnemis (Echinodermata: Ophiuroidea) and Bursal Ventilation.

The basket star Gorgonocephalus eucnemis is an aerobic organism highly dependent on dissolved oxygen in surrounding waters. Previous observations on the anatomy of Gorgonocephalus state that five pairs of ossicles (the radial shields and genital plates) regulate the position of the roof of the body disc and are responsible for flushing seawater into and out of the bursae, though this seems never to have been empirically tested. In the current study, rates of bursal ventilation were investigated in response to an increase in the availability of food and, separately, exposure to hypoxic levels of dissolved oxygen. When fed with suspended krill particles, basket stars increased rates of bursal ventilation, ranging from 13% to 155%, resulting in a similar increase in volume of water moved in and out of bursae. This rate remained elevated for an average of 25 minutes after active feeding ended. Bursal ventilation rates also increased significantly (~60% average increase) when basket stars were exposed to hypoxic conditions (dissolved oxygen ≤ 3.5 mg O2 L-1 = 2.45 mL O2 L-1). Some specimens exhibited a loss of coordination in hypoxic conditions. All specimens recovered and resumed a normal rate of bursal ventilation when returned to normoxic conditions. Measurements show that dissolved oxygen levels decreased from outside to inside bursae and suggest that dissolved oxygen is absorbed in bursae during bursal ventilations. Increasing rates of bursal ventilation may help meet the increased oxygen demands when feeding and may help animals endure some exposures to hypoxia.

A fast reactor transmutation system for 6 LLFP nuclides

A fast reactor transmutation system with enhanced transmutation efficiency for six long-lived fission products (LLFP: 79Se, 93Zr, 99Tc, 107Pd, 129I, and 135Cs) was evaluated. A new fast reactor transmutation system concept consisting of three fast reactor cores was constructed by loading six LLFP nuclides on a radial blanket, axial blanket and shield using YD2 and YH2 moderators. By combining three MONJU-class fast reactors, the ratio of the amount of transmuted nuclides in the three reactors to the amount of nuclides produced in the three reactors were achieved 1 or more for all six LLFP nuclides, and the effective half-lives were significantly reduced.

IMPACT OF PELVIC AND RAD-BOARD LEAD SHIELDS ON OPERATOR AND PATIENT RADIATION DOSE IN TRANS-RADIAL CORONARY PROCEDURES.

Trans-radial approach for cardiac catheterisation procedures has long been associated with high operator and patient radiation dose. The aim of the present study was to determine the effect of pelvic and radial shields on decreasing coronary procedure radiation doses. A total of 418 patients randomly underwent diagnostic and therapeutic cardiac procedures with and without the pelvic and rad-board lead shields during the procedures. The operator and patient doses were then determined by means of a personal dosimeter and dose area product (DAP), respectively. The shields decreased the operator radiation dose by 40% in coronary angiography (CA) and by 45% during angioplasty (PCI). These results were achieved at the cost of increased patient radiation dose. Pelvic lead shields combined with rad-board shields are highly effective in reducing operator radiation dose in trans-radial approach, but it is only achieved at the cost of increased patient DAP.

A New Fissiparous Brittle Star, Ophiacantha scissionis sp. nov. (Echinodermata, Ophiuroidea, Ophiacanthida), from Jeju Island, Korea.

A new species of Ophiuroidea, Ophiacantha scissionis sp. nov., is described. It was collected from Munseom Island, Jeju-do, South Korea at a depth of 28-36 m, by SCUBA diving. Ophiacantha scissionis has unique and distinct morphological characteristics: small disk, densely covered by small trifid spines, radial shields completely concealed by disk spines, six arms with four arm spines proximally, fissiparous. In addition, this species is clearly distinguished from other species of Ophiacantha by mitochondrial COI. This species is usually hexamerous and reproduces asexually by fissiparity. It is the first report of fissiparous reproduction in the genus Ophiacantha.