Coupling of pinned magnetic moments in an antiferromagnet to a ferromagnet and its role for exchange bias

The interaction between uncompensated pinned magnetic moments within an antiferromagnetic (AFM) layer and an adjacent ferromagnetic (FM) layer responsible for the existence of exchange bias is explored in epitaxially grown trilayers of the form FM2/AFM/FM1 on Cu3Au(0 0 1) where FM1 is ~12 atomic monolayers (ML) Ni, FM2 is 21–25 ML Ni, and AFM is 27 ML or 50 ML Ni~25Mn~75. Field cooling for parallel or antiparallel alignment of the out-of-plane magnetizations of the two FM layers does not make a difference for the temperature-dependent coercivity (H C), magnitude of exchange bias field (H eb), AFM ordering temperature (T AFM), and blocking temperature for exchange bias (T b). We explain this by a model in which the uncompensated pinned magnetic moments distributed within the volume of the AFM layer interact with both of the FM layers, albeit with different strength. Parallel and antiparallel coupling between the magnetization of the pinned moments and the FM layers equally exists. This leads to the experimentally observed independence of H C, H eb, as well as of T AFM and T b on the magnetization direction of the FM layers during field cooling. These results provide new and detailed insight into revealing the subtle and complex nature of the exchange bias effect

Temperature-induced sign change of the magnetic interlayer coupling in Ni/Ni25Mn75/Ni trilayers on Cu3Au(001)

We investigated the magnetic interlayer coupling between two ferromagnetic (FM) Ni layers through an antiferromagnetic (AFM) Ni 25Mn75 layer and the influence of this coupling on the exchange bias phenomenon. The interlayer coupling energy of an epitaxial trilayer of 14 atomic monolayers (ML) Ni/45 ML Ni 25Mn75/16 ML Ni on Cu3Au(001) was extracted from minor-loop magnetization measurements using in-situ magneto-optical Kerr effect. The interlayer coupling changes from ferromagnetic to antiferromagnetic when the temperature is increased above 300 K. This sign change is interpreted as the result of the competition between an antiparallel Ruderman-Kittel-Kasuya-Yosida (RKKY)-type interlayer coupling, which dominates at high temperature, and a stronger direct exchange coupling across the AFM layer, which is present only below the Néel temperature of the AFM layer

Growth, Structure, and Magnetic Properties of Artificially Layered NiMn in Contact to Ferromagnetic Co on Cu3Au(001)

Single-crystalline antiferromagnetic artificially layered [Ni/Mn] films of different thicknesses, covered by ferromagnetic Co layers, are deposited on Cu3Au(001).Their structural and magnetic properties are characterized by low-energy electron diffraction (LEED) and magneto-optical Kerr effect, respectively, and compared with disordered NixMn100-x alloy films with the same Ni/Mn ratio and the same film thickness. LEED intensity-versus-energy curves show that the perpendicular inter-atomic lattice distance is decreased in the artificially layered [Ni/Mn] samples incomparison to the disordered NixMn100-x alloy films.At the same time, the artificially layered [Ni/Mn] films exhibit higher coercivity and exchange bias of the adjacent Co layer compared to those of NixMn100-x/Co. This is discussed as a consequence of the different interatomic lattice distance, presumably caused by an ordered buckling in the artificially layered [Ni/Mn] samples, leading to a stronger interlayer exchange coupling

Automatically extracted Antarctic coastline using remotely-sensed data: an update

The temporal and spatial variability of the Antarctic coastline is a clear indicator of change in extent and mass balance of ice sheets and shelves. In this study, the Canny edge detector was utilized to automatically extract high-resolution information of the Antarctic coastline for 2005, 2010, and 2017, based on optical and microwave satellite data. In order to improve the accuracy of the extracted coastlines, we developed the Canny algorithm by automatically calculating the local low and high thresholds via the intensity histogram of each image to derive thresholds to distinguish ice sheet from water. A visual comparison between extracted coastlines and mosaics from remote sensing images shows good agreement. In addition, comparing manually extracted coastline, based on prior knowledge, the accuracy of planimetric position of automated extraction is better than two pixels of Landsat images (30 m resolution). Our study shows that the percentage of deviation (7 km2 (2005) to 1.3537 × 107 km2 (2010) and 1.3657 × 107 km2 (2017). We have found that the decline of the Antarctic area between 2005 and 2010 is related to the breakup of some individual ice shelves, mainly in the Antarctic Peninsula and off East Antarctica. We present a detailed analysis of the temporal and spatial change of coastline and area change for the six ice shelves that exhibited the largest change in the last decade. The largest area change (a loss of 4836 km2) occurred at the Wilkins Ice Shelf between 2005 and 2010

A Moment Method for the Second Order Two-point Boundary Value Problems

In this paper a Moment method based on the second, third and fourth kindChebyshev polynomials is proposed to approximate the solution of a linear twopointboundary value problem of the second order. The proposed method isflexible, easy to program and efficient. Two numerical examples are given forconciliating the results of this method, all the computation results are obtainedusing Matlab

‘In the dark’: Voices of parents in marginalised stepfamilies: perceptions and experiences of their parenting support needs

The fastest growing family type in the UK is the stepfamily with social parenting an increasingly normal practice. Parenting policy and practice, which has increased exponentially over the last two decades, has historically been modelled on the biological nuclear family model with marginalised families the main recipients. The possibility that parents in marginalised stepfamilies might have separate and discrete parenting support needs to biological parents seems to be overlooked in policy, practice and research. Rather, the historical legacy of deficit, dysfunction and a ‘whiff’ of poor parenting in marginalised stepfamilies lingers on. The focus of the research was to determine marginalised parents’ perceptions and experiences of parenting in their stepfamily and their parenting support needs. Thematic analysis of the data revealed accounts that were interwoven throughout with strong moral undertones which seemed to categorise their lives. The parenting issues were different and more complex than those they had encountered before. The parents adopted biological family identities, but these didn’t fit with their social roles and often rendered them powerless in their relationships with stepchildren. This appeared to have a cumulative effect which impacted on the already fragile couple relationship. Despite the parents easy articulation of the parenting issues there was a contrasting unease and ambivalence in discussing parenting support needs. Parenting support seemed to be an irrelevance that could be disregarded. Ultimately the moral significance of the parents marginalised class positions appeared to be central to their lives, which has important implications for policy and practice

SARS-2 COVID-19-induced immunity response, a new prognostic marker for the pregnant population correlates inversely with neonatal Apgar score

Background: The COVID-19 infection has impacted pregnancy outcomes; however, few studies have assessed the association between haematological parameters and virus-related pregnancy and neonatal outcomes. We hypothesised differences in routine haematology indices in pregnant and non-pregnant COVID-19 patients as well as COVID-19-negative pregnant subjects and observed neonatal outcomes in all pregnant populations. Further, we tested if pattern identification in the COVID-19 pregnant population would facilitate prediction of neonates with a poor Apgar score. Methods: We tested our hypothesis in 327 patients (111 COVID-19-positive pregnant females, 169 COVID-19-negative pregnant females and 47 COVID-19-positive non-pregnant females) in whom standard routine laboratory indices were collected on admission. Results: Pregnant COVID-19-positive patients exhibited higher WBC, neutrophil, monocyte counts as well as neutrophil/lymphocyte and neutrophil/eosinophil ratio compared to non-pregnant COVID-19-positive patients (p = 0.00001, p = 0.0023, p = 0.00002, p = 0.0402, p = 0.0161, p = 0.0352, respectively). Preterm delivery was more prevalent in COVID-19-positive pregnant patients accompanied with a significantly lower birth weight (2894.37 (± 67.50) g compared with 3194.16 (± 50.61) g, p = 0.02) in COVID-19-negative pregnant patients. The COVID-19-Induced Immunity Response (CIIR) was defined as (WBC × neutrophil) / eosinophil; Apgar scores were significantly and inversely correlated with the CIIR index (r =—0.162). Interpretation: Pregnancy appears to give rise to an increased immune response to COVID-19 which appears to protect the mother, however may give rise to complications during labour as well as neonatal concerns. CIIR is a simple metric that predicts neonatal distress to aid clinicians in determining the prognosis of COVID-19 and help provide early intensive intervention to reduce complications

Novel controlled-release polylactic-co-glycolic acid (PLGA) nanoparticles for sodium thiosulphate, a hydrogen sulphide donor, retains pro-angiogenic potential of hydrogen sulphide

Hydrogen sulphide (H2S) is an endogenous gaseous signalling molecule observing cardioprotective qualities in various experimental models. However, its therapeutic application is limited due to rapid release in vivo and potential toxicity. Controlled-release nanoparticles (NPs), such as polylactic-co-glycolic acid (PLGA) NPs entrapping H2S compounds may address these issues. PLGA NPs’ encapsulating sodium thiosulphate (STS), a H2S donor, were prepared by emulsification and sonication-solvent evaporation in polyvinyl alcohol (PVA). Sonication time was varied between 15 and 45 s and PVA concentration varied between 0.3 and 0.7% w/v. NPs were characterised, cellular uptake, H2S generation and encapsulated STS angiogenic potential was explored. An increase in sonication time as well as PVA concentration decreased NPs size resulting in an increase in STS release kinetics and cellular uptake over 24 h. Encapsulated STS gave a controlled release of H2S over 24 h whereas non-encapsulated STS peaked at 2 h. Finally, we observed entrapped STS maintained pro-angiogenic potential. PLGA NPs are a promising controlled-release delivery system with potential to offer sustained H2S levels. Results of this study demonstrate formulation of STS-loaded PLGA NPs provides a controlled-release of STS and therefore H2S. NPs are internalised into cells and critically, PLGA NPs are able to maintain the pro-angiogenic potential of H2S