Nano-composite single grain YBa2Cu3O 7-δ/Y2Ba4CuBiOy bulk superconductors

We have succeeded recently in synthesizing a chemically stable, inert family of materials of composition Y2Ba4CuMOy (Y-2411 where M Nb, Ta, Mo, W, Zr, Hf) within the superconducting YBa 2Cu3O7-δ (Y-123) phase matrix that forms effective flux pinning centers of nano-scale dimensions. In this paper we report the synthesis of the Y2Ba4CuBiOy phase with nano-scale dimensions that is similarly compatible with the Y-123 matrix and which does not impair the properties of the bulk superconductor. YBa 2Cu3O7-δ/Y2BaCuO5 (Y-123/Y-211) precursor powders enriched with various amounts of Bi 2O3 and Y2Ba4CuBiOy have been fabricated successfully in the form of large, single grains by the top seeded melt growth (TSMG) process. Microstructural studies of these composites reveal the presence of nanometer-sized Y2Ba4CuBiO y and much larger Y-211 phase particles (∼1 νm) embedded in the Y-123 phase matrix. The critical current density of the nano-composites is observed to increase significantly compared to undoped YBCO. © 2006 IOP Publishing Ltd

The Primary Structure of Selected Peptides from Chymotryptic Digests of Nifungin

Nifungin, an antifungal peptide produced by Aspergillus giganteus, was studied and partially characterized. The amino acid composition of the antifungal peptide was investigated , and eighty-seven percent of the peptide constituents were identified. The presence of free –SH groups in the peptide was studies by spectrophototmetric titration of the peptide with p-hydroroxymercuribenzoate. Performic acid oxidation was used to disrupt the disulfide bridges present in the molecule, and subsequent enzymatic digestion of the oxidized peptide was accomplished with alpha chymotrypsin. Chromatographic separation of the digestion mixture produced eleven chymotryptic peptides. Six of these peptides were selected for amino acid sequence analysis by the Edman degradation method. The results of this study indicated that nifungin is a basic peptide containing a minimum of forty-nine amino acid residues. It contains no tryptophan, histidine or methionine. The peptide has no free –SH groups, but incorporates four disulfine bridges within its structure. The sequence studies on the six chymotryptic peptides showed that these peptides had unusual end-group residues in some instances, based on the specificity of the digesting enzyme, suggesting that the overall nifungin structure was complex

How the COVID-19 Pandemic Highlights the Effects of Genetic Conflict During Pregnancy

Pregnancy is often viewed as a cooperative endeavor between mother and fetus. However, biologists have documented that under the surface, pregnancy is better characterized as a time where genetic conflict between maternal and paternal genes over fetal development can run rampant. While genetic conflict is a typical aspect of pregnancy, uncontrolled genetic conflict has the potential to result in pregnancy complications for both the mother (e.g., miscarriage, stillbirth, preterm birth) and the fetus (e.g., intrauterine growth restrictions, low birth weight). But, unexpectedly, the COVID-19 pandemic has presented researcher with a case study to investigate genetic conflict during pregnancy. Specifically, medical doctors noted changes in the frequency of pregnancy complications (e.g., premature births, miscarriages, stillbirths) theorized to be influence by genetic conflict. As the biology of these complications did not change during the pandemic, we wanted to investigate potential behavioral changes that influenced the expression of genetic conflict in pregnancy complications using archival data. Understanding these relationships can elucidate how cultural and behavioral changes influence biological processes such as the occurrence of pregnancy complications

Signalment risk factors for cutaneous and renal glomerular vasculopathy (Alabama rot) in dogs in the UK

Seasonal outbreaks of cutaneous and renal glomerular vasculopathy (CRGV) have been reported annually in UK dogs since 2012, yet the aetiology of the disease remains unknown. The objectives of this study were to explore whether any breeds had an increased or decreased risk of being diagnosed with CRGV, and to report on age and sex distributions of CRGV cases occurring in the UK. Multivariable logistic regression was used to compare 101 dogs diagnosed with CRGV between November 2012 and May 2017 with a denominator population of 446,453 dogs from the VetCompass database. Two Kennel Club breed groups—hounds (odds ratio (OR) 10.68) and gun dogs (OR 9.69)—had the highest risk of being diagnosed with CRGV compared with terriers, while toy dogs were absent from among CRGV cases. Females were more likely to be diagnosed with CRGV (OR 1.51) as were neutered dogs (OR 3.36). As well as helping veterinarians develop an index of suspicion for the disease, better understanding of the signalment risk factors may assist in the development of causal models for CRGV and help identify the aetiology of the disease

Spatiotemporal patterns and agro-ecological risk factors for cutaneous and renal glomerular vasculopathy (Alabama Rot) in dogs in the UK

Seasonal outbreaks of cutaneous and renal glomerular vasculopathy (CRGV) have been reported annually in UK dogs since 2012, yet the aetiology of the disease remains unknown. The objectives of this study were to explore whether any breeds had an increased or decreased risk of being diagnosed with CRGV, and to report on age and sex distributions of CRGV cases occurring in the UK. Multivariable logistic regression was used to compare 101 dogs diagnosed with CRGV between November 2012 and May 2017 with a denominator population of 446,453 dogs from the VetCompass database. Two Kennel Club breed groups—hounds (odds ratio (OR) 10.68) and gun dogs (OR 9.69)—had the highest risk of being diagnosed with CRGV compared with terriers, while toy dogs were absent from among CRGV cases. Females were more likely to be diagnosed with CRGV (OR 1.51) as were neutered dogs (OR 3.36). As well as helping veterinarians develop an index of suspicion for the disease, better understanding of the signalment risk factors may assist in the development of causal models for CRGV and help identify the aetiology of the disease

Superconducting properties of Gd-Ba-Cu-O single grains processed from a new, Ba-rich precursor compound

Gd-Ba-Cu-O (GdBCO) single grains have been previously melt-processed successfully in air using a generic Mg-Nd-Ba-Cu-O (Mg-NdBCO) seed crystal. Previous research has revealed that the addition of a small amount of BaO2 to the precursor powders prior to melt processing can suppress the formation of Gd/Ba solid solution, and lead to a significant improvement in superconducting properties of the single grains. Research into the effects of a higher Ba content on single grain growth, however, has been limited by the relatively small grain size in the earlier studies. This has been addressed by developing Ba-rich precursor compounds Gd-163 and Gd-143, fabricated specifically to enable the presence of greater concentrations of Ba during the melt process. In this study, we propose a new processing route for the fabrication of high performance GdBCO single grain bulk superconductors in air by enriching the precursor powder with these new Ba rich compounds. The influence of the addition of the new compounds on the microstructures and superconducting properties of GdBCO single grains is reported

Simulating the in-field AC and DC performance of high-temperature superconducting coils

In this paper, the authors investigate numerically the in-field behaviour of high-temperature superconducting (HTS) coils and a method to potentially improve their performance using ferromagnetic material as a flux diverter. The ability to accurately predict the electromagnetic behaviour of superconductors in complex geometries and electromagnetic environments is crucial to the design of commercially-viable superconductor-based electrical devices, such as power transmission cables, superconducting fault current limiters, transformers, and motors and generators. The analysis is carried out using a two-dimensional (2D) axisymmetric model of a circular pancake coil based on the H-formulation and implemented in Comsol Multiphysics 4.3a. We explore the use of flux diverters to improve an HTS coil’s performance with respect to its DC (maximum allowable/critical current) and AC (AC loss) characteristics, for various background magnetic fields. It is found that while flux diverters can improve the AC properties of coils, they can be detrimental to the DC properties in this particular configuration.Dr Mark Ainslie would like to acknowledge the support of a Royal Academy of Engineering Research Fellowship. Di Hu and Jin Zou would like to acknowledge support of Churchill College, Cambridge, the China Scholarship Council and the Cambridge Commonwealth, European and International Trust.This is the accepted manuscript. The final published version is available from IEEE at http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6965596&sortType%3Dasc_p_Sequence%26filter%3DAND%28p_IS_Number%3A6353170%29%26rowsPerPage%3D100

Numerical analysis of non-uniformities and anisotropy in high-temperature superconducting coils

—High-temperature superconducting (HTS) coils play an important role in a number of large-scale engineering applications, such as electric machines employing HTS coated conductors. Non-uniformities and anisotropy in the properties of the coated conductor along its length and width can have a large impact on the performance of the tape, which directly influences the performance of an HTS electric machine. In this paper, the specific influences of non-uniformity and anisotropy on the dc properties of coils, such as the maximum allowable dc current, and the ac properties, such as ac loss, are analyzed using a numerical model based on the H formulation. It is found that non-uniformity along the conductor width has a large effect on the ac properties (i.e., ac loss) of a coil, but a relatively small effect on the dc properties (i.e., critical current). Conversely, non-uniformity along the length has a small effect on the ac coil properties, but has a large effect on the dc properties. Index Terms—AC loss, critical current density (superconductivity), high-temperature superconductors, numerical analysis, superconducting coils, transport ac loss.This work was supported in part by a Henan International Cooperation Grant, China: 144300510014. The work of D. Hu and J. Zou was supported in part by Churchill College, by the China Scholarship Council, and by the Cambridge Commonwealth, European, and International Trust. The work of M. D. Ainslie was supported by a Royal Academy of Engineering Research Fellowship.This is the accepted manuscript. The final version is available from IEEE at http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6983573

Influence of time-varying external magnetic fields on trapped fields in bulk superconductors

Large, single-grain bulk high-temperature superconductors (HTS) can trap magnetic fields over 17 T below 30 K and up to 3 T at 77 K, and have significant potential to replace permanent magnets, the fields from which are limited to significantly less than 2 T. Therefore, bulk HTS samples are ideal candidates to develop more compact and efficient devices, such as actuators, magnetic levitation systems, flywheel energy storage systems and electric machines. In electric machines, in particular, the higher flux density improves the power density of the machine, resulting in smaller, lighter devices. However, in a real electric machine environment, bulk HTS samples can be exposed to AC magnetic field fluctuations that can affect the distribution of the supercurrent in the material and attenuate the trapped field, leading to a reduction in the magnetic loading of the machine, and in some cases, full demagnetisation. In this paper, the variation of trapped field with the frequency and magnitude of an external time-varying magnetic field is analysed numerically, and the mechanisms of the attenuation of the trapped field in HTS bulks are investigated using a two-dimensional (2D) axisymmetric finite-element model based on the H-formulation, considering both the electromagnetic and thermal behaviour of the bulk sample.This work was supported in part by a Henan International Cooperation Grant, China: 144300510014. . M. D. Ainslie would like to acknowledge financial support from a Royal Academy of Engineering Research Fellowship. D. Hu and J. Zou would like to acknowledge financial support from Churchill College, the China Scholarship Council and the Cambridge Commonwealth, European and International Trust.This is the accepted manuscript. The final version is available from IEEE at http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=6983588&sortType%3Dasc_p_Sequence%26filter%3DAND%28p_Publication_Number%3A77%29%26pageNumber%3D5%26rowsPerPage%3D100

Mitigation of Demagnetization of Bulk Superconductors by Time-Varying External Magnetic Fields

Large, single-grain high-temperature superconducting (HTS) bulks have significant potential to replace permanent magnets in various engineering applications. However, based on our previous research, the trapped field in a bulk superconductor can be attenuated or even erased when a bulk is subjected to a time-varying, external magnetic field. Therefore, it is important to develop a method to protect bulks from demagnetization by (a) improving the thermal conduction of the bulk and/or (b) reducing AC losses. Improvement in the thermal conduction of bulks involves modification of the material fabrication process, which may have a detrimental effect on its superconducting properties. Employing shielding materials around a bulk helps to decrease the AC losses, but also provides a durable way to maintain the original material properties. In this paper, two shielding cases are proposed and evaluated numerically: ring-shaped shielding with a copper coil, and surface shielding with a ferromagnetic material. Based on the numerical modelling results, the ring-shaped coil works well for externally applied AC fields of larger magnitude and higher frequency. However, the ferromagnetic material was preferable for surface shielding for relatively lower fields. Finally, an optimal shield design is presented.M. D. Ainslie would like to acknowledge financial support from a Royal Academy of Engineering Research Fellowship. D. Hu and J. Zou would like to acknowledge financial support from Churchill College, the China Scholarship Council and the Cambridge Commonwealth, European and International Trust. This work was supported in part by a Henan International Cooperation Grant, China: 144300510014.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/TASC.2016.252582