Trapped Field Research Articles

3D Acoustic Manipulation of Living Cells and Organisms Based On 2D Array.

Flexible manipulation techniques for living cells and organisms are extremely useful tools for fundamental biomedical and life science research. Acoustic tweezers, which permit non-contact, label-free manipulation, are particularly suited to micromanipulation tasks as they provide a large acoustic radiation force and can be applied in various media. Here, we describe the design and fabrication of a 3 MHz, 64-element (8 × 8), 2D planar ultrasound array that realizes the multidimensional translation, rotation, orientation, and levitation of living cells and organisms. The focusing vortex and twin fields are generated using the holographic acoustic elements framework method. We demonstrate that the eggs and larvae of brine shrimp can be translated along a preset trajectory by controlling the central position of the vortex. By multiplexing counterclockwise vortices, clockwise vortices, and twin trap fields in a time sequence, the rotation direction of the shrimp eggs can be switched in real time, while non-spherical larvae can be reoriented. Moreover, the reflection of the acoustic beam can lift eggs and larvae from the bottom of the culture dish and further manipulate them in the vertical and horizontal directions. Additionally, we present quantitative analyses of the shrimp-egg rotation frequency with respect to the focal depths, topological charges of the vortex, and excitation voltages. These results indicate that acoustic tweezers based on 2D matrix arrays can realize complex and selective manipulation of living cells and organisms, thereby demonstrating their value for advancing research in the fields of cell assembly, tissue engineering, and micro-robot driving.

A new MgB2 bulk ring fabrication technique for use in magnetic shielding or bench-top NMR systems

We report a new methodology in bulk MgB2 ring production for use in small-scale magnetic shielding or bench-top nuclear magnetic resonance systems. This process is a modified field-assisted sintering technique (mFAST) which enables direct formation of the rings without the need for machining or additives into the precursor powder. The shielding and trapped field capabilities of three mFAST MgB2 rings were determined using zero-field- and field-cooled magnetic experiments. Individual bulks trap magnetic fields up to 1.24 T at 20 K comparable to the highest published data for a ring sample. It is anticipated that for many applications, multiple rings will be stacked to form the required experimental structure. We find, for the three ring stack, a trapped field of 2.04 T and a maximum shielded field of 1.74 T at 20 K. The major factor limiting performance at low temperatures are flux jumps which cause rapid loss of the trapped field or shielding capability. Preliminary studies of magnetic field ramp rate dependence on flux jumps were conducted illustrating that even at very slow ramp rates (0.007 T min−1) they remain a significant issue. Despite this concern, we conclude that mFAST represents an exciting new fabrication methodology for bulk MgB2 rings.

Effect of thickness on magnetic properties of single domain GdBCO bulk superconductors

To study the influence of thickness on the magnetic properties of ReBCO (Re = Y, Gd, Sm, Nd, etc.) bulk superconductors, a single domain gadolinium barium copper oxide (GdBCO) bulk superconductor fabricated by the Re + 011 top seeded infiltration growth (Re + 011 TSIG) method was continuously sliced along the bottom to obtain samples of different thickness. The levitation force and attractive force of these samples were tested at 77 K in the zero-field-cooled (ZFC) state. It is found that as the sample thickness decreases, the levitation force decreases gradually whereas the attractive force increases. This is related to the varied ability to resist the penetration of magnetic field occasioned by varying sample thickness, which are deeply revealed by combining with the characteristics of the non-ideal type-II superconductor. Further, the levitation force exhibits a trend of slow initial change followed by rapid change, which may be attributed to the growth of the sample. Measurement of the trapped field shows that a similar distribution of trapped field at the top and bottom surfaces can be achieved by removing some materials from the bottom of the bulk. These results provide a reference for meeting the actual requirements of ReBCO bulks of different thicknesses and greatly contribute to practical designs and applications.

Portable, desktop high-field magnet systems using bulk, single-grain RE–Ba–Cu–O high-temperature superconductors

Bulk high-temperature superconducting materials can trap magnetic fields up to an order of magnitude larger than conventional permanent magnets. Recent advances in pulsed field magnetization (PFM) techniques now provide a fast and cost-effective method to magnetize bulk superconductors to fields of up to 5 T. We have developed a portable, desktop bulk high-temperature superconducting magnet system by combining advanced PFM techniques with state-of-the-art cryocooler technology and single-grain, RE–Ba–Cu–O [(RE)BCO, where RE is a rare-earth element or yttrium] bulk superconducting materials. The base temperature of the system is 41 K and it takes about 1 h for the system to cool down to 50 K from room temperature. A capacitor bank, combined with easily-interchangeable, solenoid- or split-type copper magnetizing coils and an insulated bipolar gate transistor acting as a high-speed switch, allows magnetic pulses to be generated with different pulse profiles. The system is capable of trapping magnetic fields of up to ∼3 T. In this work, we report the results of the magnetization of a range of single-grain Y–Ba–Cu–O, Eu–Ba–Cu–O and Gd–Ba–Cu–O (GdBCO), bulk superconducting discs using this system. A higher trapped field was recorded using a split coil incorporating iron yokes at temperatures of 65 K and above, whereas at lower temperatures, a higher trapped field was obtained using the solenoid coil. The GdBCO sample achieved the highest trapped field for both single-pulse (SP) and two-stage-multi-pulse (TSMP) methods using the solenoid coil. Maximum trapped fields of 2.26 T at 55 K and 2.85 T at 49 K were recorded at the centre of the top surface of the GdBCO sample for the SP and TSMP methods, respectively. The PFM process is substantially an adiabatic process so, therefore, the thermal contact between the sample and sample holder is of critical importance for cooling the bulk sample during application of the pulse. The design of the sample holder can be modified easily to enhance the thermal stability of the sample in order to achieve a higher trapped field.

Effects of Zn doping on superconducting properties of melt textured Y–Ba–Cu–O bulk superconductors

Zn doping which may induce a second peak effect in YBa2Cu3O7−δ (YBCO) has been opted as a regular technique to improve the trapped field and flux pinning stability of YBCO bulk superconductors for practical applications, such as quasi-permanent or maglev magnets. Here, the effects of Zn doping on the flux trapping performance of single domain YBCO bulk superconductors have been systematically investigated. The doping amount x varies from 0 to 1.0 mol%. We analyzed the critical transition temperature (T c), critical current density (J c), trapped field (B t) and the flux relaxation at various temperatures, and measured in addition the levitation force (F L) for comparison. The doping amount of 0.6 mol% has been proven to be the optimal value, which enhances self-field J c by 243.3% at 30 K with an obvious secondary peak effect, resulting in great improvements in trapped field and flux stability. The holistic and local superconducting performances exhibit good agreement, demonstrating Zn-doping an effective method to improve flux pinning properties for practical applications.

Efficacy of nanocapsules loaded with Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae) sex pheromone as evaluated in wind tunnel and field trapping experiments

Efficacy of nanocapsules loaded with Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae) sex pheromone as evaluated in wind tunnel and field trapping experiments

Static and Dynamic Magnetization of HTSs With Various Pinning Landscapes

Monte Carlo simulations have been used to study the magnetic responses of HTSs to pulsed and static magnetization. Various types of pinning distribution have been considered. The influence of temperature on the resulting trapped field has been studied. The distribution profiles of trapped field have been obtained for each sample. The differences in the magnetization performance have been demonstrated for the considered pinning landscapes: the interstitial flux was efficiently trapped inside areas enclosed by defects in kagome lattices and distributions with non-unit bases. The graded array also showed high trapped fields but required special magnetization techniques.

Waveform Control Pulsed Field Magnetization of RE-Ba-Cu-O Bulk Superconducting Rings

One of the potential applications of ring-shaped, single grain RE-Ba-Cu-O bulk superconductors is in desktop magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) systems as an alternative to conventional permanent magnets. The higher magnetic field available from magnetized bulk superconductors could significantly improve the performance of such systems, as well as reduce their size and increase portability. The pulsed field magnetization (PFM) method provides a fast, compact and cost-effective method for magnetizing these materials as trapped field magnets. However, bulk superconducting rings are very susceptible to thermomagnetic instabilities during the PFM process, and thus, to date, the reported trapped fields in ring bulks magnetized by PFM are less than 0.35 T at the centre of single rings. In this work, we demonstrate that the trapped field in a superconducting ring bulk can be enhanced significantly by optimizing the waveform of the magnetizing pulse used in the PFM method. This optimization can be achieved easily by using an Insulated Gate Bipolar Transistor as a fast-switching device with a controllable switching frequency in the pulse-generating electric circuit. Our findings represent a key step forward in utilizing bulk, single-grain superconducting rings magnetized by PFM in portable magnet systems.

Flux Pinning Docking Interfaces in Satellites Using Superconducting Foams as Trapped Field Magnets

Flux-Pinning Docking Interfaces (FPDI) in satellite systems were developed using bulk superconductors and permanent magnets in previous works. However, such FPDIs have limited magnetic field strength, consist of heavy-weight material, and can only be used with a single purpose, i.e., as chasing or docking satellite. Replacing the magnetic material in the FPDI by a trapped field (TF)-magnet would enable the interface to operate for both purposes, i.e., generating a (stronger) magnetic field and trapping it. We show the requirements for such a system and discuss the possible gains when using a TF-FPDI in satellites. To reduce the system weight, the use of superconducting foams as superconducting material is discussed in detail. Furthermore, the use of superconducting foams, the size of which can be easily upscaled, may also comprise the function of the damping material, so even more weight could be saved for the payload.

Suitability for salt-lick tourism: A preliminary assessment on the natural salt-licks at Segaliud-Lokan Forest Reserve, Sandakan, Sabah

The natural salt-licks are visited by various species of terrestrial mammals, hence ideal for mammal watching, although the suitability for salt-lick tourism is influenced by other factors. Preliminary research was conducted on the suitability of four natural salt-licks for mammal watching in Segaliud-Lokan Forest Reserve (SLFR), Sabah. The camera trapping survey and field assessment were conducted for eight months, and then the assessment criteria applied in this study included the lick accessibility, detection frequency, species richness, viewable activity sighting probability, reliability and visibility on the terrestrial mammals, at a given lick. A total of 12 different mammal species were recorded, where Sambar Deer, Bearded Pig, Banteng, and Bornean Orang-utan were determined as the main visitor species of this study. Among the four selected salt-licks, the rating score of SL50A (Score=1.71) was significantly lower than those of SL50B, SL56 and SL59 (Score=2.57 respectively, χ2 2 =6.794, p=0.042), hence highlighting that SL50A was not suitable for conducting mammal watching activity, unlike the other three natural licks at SLFR. The assessment on the compatibility between the supply (mammalian physical availability) and demand (highly anticipated species) was excluded from this research, therefore emphasizing the need to fill up this particular research gap in the future.

Comparison of the Microstructure and Superconducting Properties of Eu–Ba–Cu–O and Gd–Ba–Cu–O Single Grain Samples

Bulk Rare Earth–Ba–Cuprate [(RE)BCO] superconductors fabricated in the form of large single grains consisting of a REBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-</sub> δ (RE-123) matrix and RE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> BaCuO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> (RE-211) inclusions can generate trapped magnetic fields that are up to ten times higher than the maximum fields obtainable in conventional Fe-based permanent magnets. The choice of the Rare Earth (RE) element plays a key role in determining the growth rate of single grains, the precise microstructure, mechanical properties and hence the final superconducting properties of the bulk samples, and also the likelihood of RE substitution onto the Ba site which can degrade the performance. In this work, we have studied the growth and microstructure of (RE)BCO single grains with RE = Gd and Eu, where the degree of Ba substitution is known to be very different. We have carried out detailed microstructural characterization of the phase distribution and composition using high resolution electron microscopy to understand the effects of Gd and Eu on the uniformity of the samples, the distribution of the secondary 211 phase, porosity and chemical variations in different regions of the melt-grown single grains.

Pulsed Field Magnetization of YBa2Cu3O7-δ Bulk Assembly for Motor Application

A high-temperature superconducting (HTS) motor has been developed using bulk superconductors as quasi-cryo-permanent magnets to allow a stronger remanent field. In this work, we focus on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-situ</i> magnetization of the bulk superconductors which is considered one of the main challenges. YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-δ</sub> bulks that had been used in the motor were magnetized via pulsed field magnetization (PFM) as single samples and assembly. The peak trapped field achieved via PFM is similar to that achieved via field cooling magnetization at 77 K. For the bulk assembly, the existence of a neighboring bulk superconductor was found to affect the penetration of the magnetic flux during the PFM process especially under low applied fields. This leads to a 3% to 4% reduction in peak trapped field, and 10% to 13% reduction in integrated magnetic flux.

Compensation Effect of Superconducting Hybrid Trapped Field Magnet

The so-called ring-shape superconducting trapped field magnet has great potential for commercial application due to its flexible size and joint-less structure. However, due to the spatial asymmetry of the structure, the trapped magnetic field has a non-negligible magnetic declination, which becomes the major obstacle to its application. To compensate the magnetic declination, a new concept of superconducting hybrid magnet consisting of the ring-shape magnet and the HTS bulk is proposed. By adjusting the placement of the HTS bulk in the central air gap, magnetic declination can be effectively compensated. Both experiments and 3D numerical model are used to evaluate the magnetic uniformity after compensation. The results show that the proposed hybrid magnet will have an obvious compensation effect on the magnetic declination. And the hybrid magnets have promising applications with requirements on the uniformity of magnetic field such as potable MRI.

Reconfigurable multi-band water-graphene cascade metamaterial perfect absorbers loaded with vanadium dioxide.

We demonstrate the perfect trapping of electromagnetic fields over multi-band frequencies through all-dielectric terahertz absorbers using water graphene cascade metamaterials. More specifically, the coating water layer greatly enhances the higher-order Fabry-Pérot resonant absorbing modes and can achieve more than 8 absorbing peaks with the absorptions exceeding 99% in the spectrum below 3 THz. Especially such multiple perfect absorbing bands can readily be reset when the proposed water-graphene metamaterial absorbers integrate with thermal controlled vanadium dioxide. Such a perfect absorbing capacity would also be valid for the wide angular illuminations with different polarizations, and the reconfigurable characteristics of graphene can also enable the dynamically tuning of the absorbing frequencies, offering great freedom of extensive applications in energy harvesting and wave manipulation.

An in situ self-assembly strategy for exact-(110)-plane-controlled crystallization of high-performance YBa2Cu3O7−δ single grains

YBa2Cu3O7−δ (YBCO) single grain, as a pivotal and popular oxide ceramic, is of great importance in practical applications for its considerable potential in magnetic properties. Normally, sizable YBCO bulk superconductors are fabricated by multi-seeded melt-growth for time saving. However, the performance of such bulks has long suffered from certain methodological barriers related to artificially induced imperfect-seeding, involving unreliable precision in seeding alignment and detrimental impact on grain boundaries. Here, a facile but effective in situ self-assembly (ISSA) strategy is reported for seeding structural design, in which exactly (110)/(110)-aligned twin-seeds naturally arise through the self-replication of crystallographic orientation from one small seed during thermal procedure. Distinctively, after two induced grains impinging, a [110]-oriented growth zone emerges and expands to the edge of the sample, leading to a contamination-free homo-combination. As a result, 25 mm diameter fully-grown bulks with single-grain quality were reliably attained, which exhibited superior levitation forces up to 65.1 N and field trapping capability up to 0.8943 T with a prominent feature of mono-peak. The ISSA seeding strategy in this work, with its nature in achieving exact seeding alignment, is widely applicable for the preparation of other high-performance bulks in the YBCO family.

Identification of a unique three-component sex pheromone produced by the tea black tussock moth, Dasychira baibarana (Lepidoptera: Erebidae: Lymantriinae).

The tea black tussock moth Dasychira baibarana Matsumura is a devastating pest in tea plantations that causes substantial economic losses. Presently, there is no effective method to control this pest other than pesticide application. The identified sex pheromone of D. baibarana could be used for detecting and monitoring this pest. Gas chromatography-electroantennogram detection showed that D. baibarana male moth antennae responded strongly to three components in the female sex pheromone gland, which were identified as: (3Z,6Z)-cis-9,10-epoxyhenicosa-3,6-diene (Z3,Z6,epo9-21:H) (I), (3Z,6Z,11E)-cis-9,10-epoxyhenicosa-3,6,11-triene (Z3,Z6,epo9,E11-21:H) (II) and (3Z,6Z)-henicosa-3,6-dien-11-one (Z3,Z6-21:11-one) (III). Dasychira baibarana uses a unique composition of an epoxydiene, epoxytriene, and dienone with the same 3,6-dienyl motif as its sex pheromone. The epoxytriene and dienone were not previously characterized as insect pheromone components. Electroantennogram analysis showed that each synthetic compound strongly stimulated male antennae, and compounds II and III elicited stronger responses than compound I. A wind tunnel bioassay and field trapping experiments proved that, ternary blends of compounds I-III attracted D. baibarana. Efficient attraction was achieved with a rubber septum baited with 500 μg of a mixture of compounds I-III at the ratio 25:20:55. The three identified compounds elicited an electroantennogram response in D. baibarana male moth antennae, and a mixture of the three components at the ratio 25:20:55 attracted D. baibarana male moths in a wind tunnel assay and field trapping experiments. This blend could be used for integrated management of D. baibarana in tea plantations. © 2022 Society of Chemical Industry.

Mechanism of the levitation force of a magnetized GdBCO bulk superconductor

A single domain gadolinium barium-copper-oxide (GdBCO) bulk superconductor was fabricated by the top-seeded infiltration and growth (Gd + 011 TSIG) method and was used to investigate the mechanism of levitation force (FL). First, the FL of the magnetized sample was measured continuously in multiple cycles. The results prove that the magnetized sample's remainder trapped field (Brtr) is the key factor in determining FL, rather than the trapped field. Then, the sample was magnetized by cylindrical Permanent Magnets (PMs) to explore the influence of the Brtr on the FL. An ideal physical model is proposed herein based on the electromagnetic theory to analyze and formulate the FL. The FL of the magnetized GdBCO bulk comprises the induced currents magnetic force (FLin) and the flux pinning magnetic force (FLp). This ideal model can analyze the mechanism of the FL of a magnetized superconductor bulk. The results are helpful to design and control the FL of magnetized REBCO bulk superconductors in practical applications.

Attraction of Choristoneura rosaceana to pheromone blends in ratios produced in glands or emitted by females

AbstractTrap captures of obliquebanded leafroller, Choristoneura rosaceana (Harris), to pheromone blends in ratios approximating those reported in pheromone glands and a novel blend based on a volatile headspace collection from live virgin females were evaluated in field experiments in Michigan apple orchards. In an initial field trapping study, pheromone lures composed of either a three‐ or four‐component blend approximation of the blend present in female pheromone glands at doses ranging from 0.1 to 20 mg/lure were compared. The four‐component blend was a combination of (Z)‐11‐tetradecenyl acetate (Z11‐14:Ac), (E)‐11‐tetradecenyl acetate (E11‐14:Ac), (Z)‐11‐tetradecenol (Z11‐14:OH) and (Z)‐11‐tetradecenal (Z11‐14:Al) in a ratio of 96.5:1.8:1.4:0.2, respectively, while the three‐component blend lacked Z11‐14:Al. Pheromone emissions by groups of virgin females and commercial lures were collected in the laboratory and analysed by gas chromatography. These data were used to formulate a new pheromone lure that was compared to a commercial lure in a second trapping study. In the first field study, traps baited with 10 mg pheromones or above captured significantly more moths than traps baited with 1 mg or less, regardless of the blend. Surprisingly, groups of virgin females only emitted two detectable pheromone components, Z11‐14:Ac and Z11‐14:OH in a ratio of 37:63, which was substantially different from the blends detected in pheromone glands in the literature. The newly formulated pheromone lure based on females’ emission was more than twice as attractive as the commercial lure which emitted a 74:5:21 three‐component blend of Z11‐14:Ac, E11‐14:Ac and Z11‐14:OH. Our results suggested that the actual pheromones released by females may not translate directly to the content of pheromone glands.

Plant volatile organic compounds attractive to Lygus pratensis.

Lygus pratensis, an important agricultural pest, is seriously detrimental to cotton in China. For the research and development of attractants, the present study screened and identified plant volatiles with activity against the pest. Out of the total 20 volatiles identified from seven hosts, 16 volatiles were selected and evaluated. Electrophysiological test results revealed the highest electroantennogram values of heptacosane, heptadecane, decanal, (E)-4-hexen-1-ol, dodecane, β-pinene, and cis-3-hexenyl isovalerate on adult insects. A significant difference in the behavior of female adults (P < 0.01) was noted in the trend behavioral tests when the concentration of heptacosane, nonadecane, heptadecane, decanal, 3-hexen-1-ol, and dodecane was 10−3 (V/V), and that of β-pinene was 10−4 (V/V). The field trapping test confirmed a significant difference in the trapping effect of heptadecane at 10−2 (V/V) and 10−3 (V/V), decanal at 10−1 (V/V) and 10−3 (V/V), β-pinene at 10−2 (V/V), and dodecane at 10−4 (V/V) compared to that of other volatiles (P < 0.05). These findings suggested the strong attractant effect of heptadecane, dodecane, decanal, and β-pinene on adults, indicating their potential application as effective attractants for the ecological control of L. pratensis.

Lure design for Drosophila suzukii based on liquid culture of fruit epiphytic yeasts: Comparing the attractivity of fermentation volatiles for seasonal morphs

AbstractThe spotted‐wing vinegar fly (Drosophila suzukii) is currently one of the most serious, invasive pest of berry crops worldwide. Most drosophilids are known to be attracted to fermentation volatiles produced by fruit epiphytic yeasts. Therefore, vinegar and wine baits are widely used in field trapping. However, these traps are not selective for spotted‐wing drosophila. We wished to exploit the previously discovered tight‐knit relationship between this vinegar fly and a fruit‐colonizing yeast, Hanseniaspora uvarum, and utilize this in the design of a selective lure. Field trapping experiments were carried out in a commercial cherry orchard to evaluate the attractiveness of bottle traps baited with liquid culture of four epiphytic yeast species on stone fruits and soft‐skinned fruits: H. uvarum, Metschnikowia pulcherrima, Pichia terricola and Saccharomyces cerevisiae as well as the mixed culture of the first two species. We also completed experiments using apple juice inoculated with H. uvarum. We compared the attractivity of yeast culture baits for D. suzukii and other drosophilids with that of apple cider vinegar. To explore the relationship between lure volatile emission and trap efficiency, solid‐phase microextraction (SPME) was used to measure the headspace of the freshly prepared and 3‐day‐old lures collected from the field. Headspace samples were analysed for their volatilome with gas chromatography coupled mass spectroscopy. The H. uvarum‐containing lures were more specific for D. suzukii than other yeast tested, and the attractivity was significantly higher if it was inoculated in apple juice. H. uvarum‐fermented apple juice lures were more specific for female D. suzukii than the traditional apple cider vinegar lures. Winter‐morph females showed an altered preference for yeast volatiles in the absence of fruit substrate.