Spontaneous exchange bias formation driven by a structural phase transition in the antiferromagnetic material

Most of the magnetic devices in advanced electronics rely on the exchange bias effect, a magnetic interaction that couples a ferromagnetic and an antiferromagnetic material, resulting in a unidirectional displacement of the ferromagnetic hysteresis loop by an amount called the 'exchange bias field'. Setting and optimizing exchange bias involves cooling through the Néel temperature of the antiferromagnetic material in the presence of a magnetic field. Here we demonstrate an alternative process for the generation of exchange bias. In IrMn/FeCo bilayers, a structural phase transition in the IrMn layer develops at room temperature, exchange biasing the FeCo layer as it propagates. Once the process is completed, the IrMn layer contains very large single-crystal grains, with a large density of structural defects within each grain, which are promoted by the FeCo layer. The magnetic characterization indicates that these structural defects in the antiferromagnetic layer are behind the resulting large value of the exchange bias field and its good thermal stability. This mechanism for establishing the exchange bias in such a system can contribute towards the clarification of fundamental aspects of this exchange interaction.

Early spectra of the gravitational wave source GW170817: Evolution of a neutron star merger

On 17 August 2017, Swope Supernova Survey 2017a (SSS17a) was discovered as the optical counterpart of the binary neutron star gravitational wave event GW170817. We report time-series spectroscopy of SSS17a from 11.75 hours until 8.5 days after the merger. Over the first hour of observations, the ejecta rapidly expanded and cooled. Applying blackbody fits to the spectra, we measured the photosphere cooling from [Formula: see text] to [Formula: see text] kelvin, and determined a photospheric velocity of roughly 30% of the speed of light. The spectra of SSS17a began displaying broad features after 1.46 days and evolved qualitatively over each subsequent day, with distinct blue (early-time) and red (late-time) components. The late-time component is consistent with theoretical models of r-process-enriched neutron star ejecta, whereas the blue component requires high-velocity, lanthanide-free material.

Light curves of the neutron star merger GW170817/SSS17a: Implications for r-process nucleosynthesis

On 17 August 2017, gravitational waves (GWs) were detected from a binary neutron star merger, GW170817, along with a coincident short gamma-ray burst, GRB 170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a), was subsequently identified as the counterpart of this event. We present ultraviolet, optical, and infrared light curves of SSS17a extending from 10.9 hours to 18 days postmerger. We constrain the radioactively powered transient resulting from the ejection of neutron-rich material. The fast rise of the light curves, subsequent decay, and rapid color evolution are consistent with multiple ejecta components of differing lanthanide abundance. The late-time light curve indicates that SSS17a produced at least ~0.05 solar masses of heavy elements, demonstrating that neutron star mergers play a role in rapid neutron capture (r-process) nucleosynthesis in the universe.

Generation of coherent spin-wave modes in yttrium iron garnet microdiscs by spin-orbit torque

In recent years, spin–orbit effects have been widely used to produce and detect spin currents in spintronic devices. The peculiar symmetry of the spin Hall effect allows creation of a spin accumulation at the interface between a metal with strong spin–orbit interaction and a magnetic insulator, which can lead to a net pure spin current flowing from the metal into the insulator. This spin current applies a torque on the magnetization, which can eventually be driven into steady motion. Tailoring this experiment on extended films has proven to be elusive, probably due to mode competition. This requires the reduction of both the thickness and lateral size to reach full damping compensation. Here we show clear evidence of coherent spin–orbit torque-induced auto-oscillation in micron-sized yttrium iron garnet discs of thickness 20 nm. Our results emphasize the key role of quasi-degenerate spin-wave modes, which increase the threshold current.

Spin-orbit interactions allow for pure spin current to be injected into a ferromagnetic insulator from a current-carrying heavy metal, generating torque on the magnetization. Here, the authors evidence magnetic auto-oscillations driven by spin-orbit torque in thin film microdiscs of yttrium iron garnet.

Full control of the spin-wave damping in a magnetic insulator using spin-orbit torque

It is demonstrated that the threshold current for damping compensation can be reached in a 5  μm diameter YIG(20  nm)|Pt(7  nm) disk. The demonstration rests upon the measurement of the ferromagnetic resonance linewidth as a function of I(dc) using a magnetic resonance force microscope (MRFM). It is shown that the magnetic losses of spin-wave modes existing in the magnetic insulator can be reduced or enhanced by at least a factor of 5 depending on the polarity and intensity of an in-plane dc current I(dc) flowing through the adjacent normal metal with strong spin-orbit interaction. Complete compensation of the damping of the fundamental mode by spin-orbit torque is reached for a current density of ∼3×10(11)  A·m(-2), in agreement with theoretical predictions. At this critical threshold the MRFM detects a small change of static magnetization, a behavior consistent with the onset of an auto-oscillation regime.

Membrane biophysics define neuron and astrocyte progenitors in the neural lineage

Neural stem and progenitor cells (NSPCs) are heterogeneous populations of self-renewing stem cells and more committed progenitors that differentiate into neurons, astrocytes, and oligodendrocytes. Accurately identifying and characterizing the different progenitor cells in this lineage has continued to be a challenge for the field. We found previously that populations of NSPCs with more neurogenic progenitors (NPs) can be distinguished from those with more astrogenic progenitors (APs) by their inherent biophysical properties, specifically the electrophysiological property of whole cell membrane capacitance, which we characterized with dielectrophoresis (DEP). Here, we hypothesize that inherent electrophysiological properties are sufficient to define NPs and APs and test this by determining whether isolation of cells solely by these properties specifically separates NPs and APs. We found NPs and APs are enriched in distinct fractions after separation by electrophysiological properties using DEP. A single round of DEP isolation provided greater NP enrichment than sorting with PSA-NCAM, which is considered an NP marker. Additionally, cell surface N-linked glycosylation was found to significantly affect cell fate-specific electrophysiological properties, providing a molecular basis for the cell membrane characteristics. Inherent plasma membrane biophysical properties are thus sufficient to define progenitor cells of differing fate potential in the neural lineage, can be used to specifically isolate these cells, and are linked to patterns of glycosylation on the cell surface.

Quantitative in situ magnetization reversal studies in Lorentz microscopy and electron holography

A generalized procedure for the in situ application of magnetic fields by means of the excitation of the objective lens for magnetic imaging experiments in Lorentz microscopy and electron holography is quantitatively described. A protocol for applying magnetic fields with arbitrary in-plane magnitude and orientation is presented, and a freeware script for Digital Micrograph(™) is provided to assist the operation of the microscope. Moreover, a method to accurately reconstruct hysteresis loops is detailed. We show that the out-of-plane component of the magnetic field cannot be always neglected when performing quantitative measurements of the local magnetization. Several examples are shown to demonstrate the accuracy and functionality of the methods.

Light echoes reveal an unexpectedly cool η Carinae during its nineteenth-century Great Eruption

η Carinae is one of the most massive binary stars in the Milky Way. It became the second-brightest star in our sky during its mid-nineteenth-century 'Great Eruption', but then faded from view (with only naked-eye estimates of brightness). Its eruption is unique in that it exceeded the Eddington luminosity limit for ten years. Because it is only 2.3 kiloparsecs away, spatially resolved studies of the nebula have constrained the ejected mass and velocity, indicating that during its nineteenth-century eruption, η Car ejected more than ten solar masses in an event that released ten per cent of the energy of a typical core-collapse supernova, without destroying the star. Here we report observations of light echoes of η Carinae from the 1838-1858 Great Eruption. Spectra of these light echoes show only absorption lines, which are blueshifted by -210 km s(-1), in good agreement with predicted expansion speeds. The light-echo spectra correlate best with those of G2-to-G5 supergiants, which have effective temperatures of around 5,000 kelvin. In contrast to the class of extragalactic outbursts assumed to be analogues of the Great Eruption of η Carinae, the effective temperature of its outburst is significantly lower than that allowed by standard opaque wind models. This indicates that other physical mechanisms such as an energetic blast wave may have triggered and influenced the eruption.

Accuracy of age estimation in children using radiograph of developing teeth

The aims of this study were: first, to determine the accuracy of the Cameriere method for assessing chronological age in children based on the relationship between age and measurement of open apices in teeth and, second, to compare the accuracy of this method with the widely used Demirjian et al. method and with the method proposed by Willems et al. Orthopantomographs taken from white Italian, Spain and Croatian children (401 girls, 355 boys) aged between 5 and 15 years were analysed following the Cameriere, Demirjian and Willems methods. The difference between chronological and dental age was calculated for each individual and each method (residual). The accuracy of each method was assessed using the mean of the absolute values of the residuals (mean prediction error). Results showed that the Cameriere method slightly underestimated the real age of children. The median of the residuals was 0.081 years (interquartile range, IQR=0.668 years) for girls and 0.036 years for boys (interquartile range, IQR=0.732 years). The Willems method showed an overestimation of the real age of boys, with a median residual error of -0.247 years and an underestimation of the real age of girls (median residual error=0.073 years). Lastly, the Demirjian method overestimated the real age of both boys and girls, with a median residual error of -0.750 years for girls and -0.611 years for boys. The Cameriere method yielded a mean prediction error of 0.407 years for girls and 0.380 years for boys. Although the accuracy of this method was better for boys than for girls, the difference between the two mean prediction errors was not statistically significant (p=0.19). The Demirjian method was found to overestimate age for both boys and girls but the mean prediction error for girls was significantly greater than that for boys (p=0.024), and was significantly less accurate than the Cameriere method (p<0.001). The Willems method was better than that of Demirjian (p=0.0032), but was significantly less accurate than that of Cameriere (p<0.001).

The 11 March 2004 Madrid terrorist attacks: the importance of the mortuary organisation for identification of victims. A critical review

On the morning of 11 March 2004, Madrid lived the worst terrorist attack in its modern history, resulting to 191 people killed and more than 1,800 injured. The attacks evidenced a series of significant deficiencies in forensic task planning, especially in using standardised post-mortem data forms and gathering ante-mortem medical and dental data, responsible for the delay in identifying corpses in the worst state, which had to wait for DNA analysis. Fortunately, the ultimate result can be considered satisfactory, given the rapid response of the forensic team in examination and identification of the large number of victims (80% of the victims were identified within 40 h), consequence of a good mortuary organization in the Pavilion 6 of the Madrid Trade Fair (IFEMA), the professional fervor whereupon the different involved professionals acted, some personal initiatives and the good general state of most of the corpses.

Giant sharp and persistent converse magnetoelectric effects in multiferroic epitaxial heterostructures

Magnetoelectric coupling between magnetic and electrical properties presents valuable degrees of freedom for applications. The two most promising scenarios are magnetic-field sensors that could replace low-temperature superconducting quantum interference devices, and electric-write magnetic-read memory devices that combine the best of ferroelectric and magnetic random-access memory. The former scenario requires magnetically induced continuous and reversible changes in electrical polarization. These are commonly observed, but the coupling constants thus obtained are invalid for data-storage applications, where the more difficult to achieve and rarely studied magnetic response to an electric field is required. Here, we demonstrate electrically induced giant, sharp and persistent magnetic changes (up to 2.3 x 10(-7) s m(-1)) at a single epitaxial interface in ferromagnetic 40 nm La(0.67)Sr(0.33)MnO(3) films on 0.5 mm ferroelectric BaTiO(3) substrates. X-ray diffraction confirms strain coupling via ferroelastic non-180( composite function) BaTiO(3) domains. Our findings are valid over a wide range of temperatures including room temperature, and should inspire further study with single epitaxial interfaces.

Development of crop-specific transposable element (SINE) markers for studying gene flow from oilseed rape to wild radish

The screening of wild populations for evidence of gene flow from a crop to a wild related species requires the unambiguous detection of crop genes within the genome of the wild species, taking into account the intraspecific variability of each species. If the crop and wild relatives share a common ancestor, as is the case for the Brassica crops and their wild relatives (subtribe Brassiceae), the species-specific markers needed to make this unambiguous detection are difficult to identify. In the model oilseed rape (Brassica napus, AACC, 2n = 38)-wild radish (Raphanus raphanistrum, RrRr, 2n = 18) system, we utilized the presence or absence of a short-interspersed element (SINE) at a given locus to develop oilseed rape-specific markers, as SINE insertions are irreversible. By means of sequence-specific amplified polymorphism (SINE-SSAP) reactions, we identified and cloned 67 bands specific to the oilseed rape genome and absent from that of wild radish. Forty-seven PCR-specific markers were developed from three combinations of primers anchored either in (1) the 5'- and 3'-genomic sequences flanking the SINE, (2) the 5'-flanking and SINE internal sequences or (3) the SINE internal and flanking 3'-sequences. Seventeen markers were monomorphic whatever the oilseed rape varieties tested, whereas 30 revealed polymorphism and behaved either as dominant (17) or co-dominant (13) markers. Polymorphic markers were mapped on 19 genomic regions assigned to ten linkage groups. The markers developed will be efficient tools to trace the occurrence and frequency of introgressions of oilseed rape genomic region within wild radish populations.

The evolutionary origin and genomic organization of SINEs in Arabidopsis thaliana

We have characterized the two families of SINE retroposons present in Arabidopsis thaliana. The origin, distribution, organization, and evolutionary history of RAthE1 and RAthE2 elements were studied and compared to the well-characterized SINE S1 element from Brassica. Our studies show that RAthE1, RAthE2, and S1 retroposons were generated independently from three different tRNAs. The RAthE1 and RAthE2 families are older than the S1 family and are present in all tested Cruciferae species. The evolutionary history of the RAthE1 family is unusual for SINEs. The 144 RAthE1 elements of the Arabidopsis genome cannot be classified in distinct subfamilies of different evolutionary ages as is the case for S1, RAthE2, and mammalian SINEs. Instead, most RAthE1 elements were probably derived steadily from a single source gene that was maintained intact and active for at least 12-20 Myr, a result suggesting that the RAthE1 source gene was under selection. The distribution of RAthE1 and RAthE2 elements on the Arabidopsis physical map was studied. We observed that, in contrast to other Arabidopsis transposable elements, SINEs are not concentrated in the heterochromatic regions. Instead, SINEs are grouped in the euchromatic chromosome territories several hundred kilobase pairs long. In these territories, SINE elements are closely associated with genes. A retroposition partnership between Arabidopsis SINEs and LINEs is proposed.

A DNA-binding activity for the promoter of the gene encoding C(4) phosphoenolpyruvate carboxylase is modulated by phosphorylation during greening of the Sorghum leaf

Electrophoresis mobility shift assay (EMSA) identified nuclear proteins with binding activity to a 430 bp promoter fragment of the Sorghum C(4) phosphoenolpyruvate carboxylase gene (SvC4). The DNA binding activities (two main retarded bands; PC1 and PC2) were high in nuclear extracts from etiolated leaves, decreased during greening and became very low or null in nuclear extracts from green leaves. This process was found to be mediated by phytochrome and was apparently irreversible since the DNA-binding activities were not restored in green plants kept in continuous darkness. The AT-rich region of the promoter fragment was identified to be the interaction domain of PC2. The detection of PC2 with EMSA was markedly reduced by preincubation of nuclear protein extracts with Mg-ATP or Mg-GTP and restored in the presence of a general protein serine/threonine-kinase inhibitor, K252a. The results suggested that the PC2 binding activity was modulated by phosphorylation during the greening process of the Sorghum leaf.

Determinations of Par j 1 by a competitive enzyme immunoassay using human specific IgE and IgG. Validation by skin prick testing

Par j 1 is the major allergen of Parietaria judaica. The objectives of this study were the following: 1) to purify Par j 1; 2) to develop an enzyme immunoassay based on the bivalent properties of specific IgE and IgG to determine the Par j 1 content in several batches of P. judaica extracts; and, 3) to study the contribution of Par j 1 to the total allergenicity and antigenicity of P. judaica extracts. P. judaica pollen was extracted and subjected to hydrophobic interaction and gel filtration chromatography for the purification of Par j 1. Inhibition enzyme immunoassays, SDS-PAGE and immunoblotting were used to characterize the allergen content. The in vivo biological potency of the extracts was estimated by skin prick testing 26 P. judaica clinically sensitive patients. The new enzyme immunoassay showed a high degree of specificity and sensitivity, detecting from 2 to 100 ng Par j 1/ml. The range of Par j 1 content in nine batches ranged from 23% to 78% of the total protein in the extracts. The Par j 1 content showed a significant correlation with the allergenic potency of these extracts evaluated by specific IgE inhibition and skin prick testing; the correlation with the specific IgG inhibition capacity was not significant. Purified Par j 1 shows great specific IgE and IgG binding capacity; its content can be determined using this newly developed enzyme immunoassay. Par j 1 levels exhibit a significant correlation with the biological potency of the extracts. This method allows the detection of Par j 1 isoforms.

Sensitivity and maximal response to methacholine in perennial and seasonal allergic rhinitis

BACKGROUND

Airway hyperresponsiveness to pharmacological agonists is a common feature in subjects with allergic rhinitis.

OBJECTIVE

The aim of this study was to investigate differences in threshold value and shape of the concentration-response curves to methacholine between subjects with perennial allergic rhinitis and subjects with seasonal rhinitis.

METHODS

We studied a sample of 72 non-asthmatic patients with allergic rhinitis. They were subdivided into two groups: subjects with only seasonal symptoms and skin sensitization to grass and/or Parietaria pollen allergens (seasonal group, n = 38), and subjects with perennial symptoms and skin sensitization to house dust mite, alone or with other allergens (perennial group, n = 34). They were challenged with methacholine (up to 200 mg/mliter), and concentration-response curves were characterized by the threshold value (PC20 = provocative concentration of methacholine required to produce a 20% fall in FEV1) and maximal response plateau, if possible. The measurements in the seasonal group were done within the pollen season.

RESULTS

The geometric mean methacholine PC20 for subjects of the perennial group was 6.9 mg/mliter, compared with 23.4 mg/mliter in subjects of the seasonal group (P < 0.01). A plateau response was detected in 16 subjects of the perennial group and in 28 subjects of the seasonal group (P < 0.05). Moreover, the level of plateau was higher in subjects of the perennial group when compared with subjects of the seasonal group (23.8 +/- 2.0% vs 19.2 +/- 1.6%, P < 0.05).

CONCLUSION

In subjects with allergic rhinitis, sensitization to perennial allergens is associated not only with lower methacholine threshold values, but also with lower prevalence and higher level of plateau than sensitization to pollen allergens.

[Primary hyperparathyroidism (author's transl)]

Experience gained from 100 patients with surgically and histologically proven primary hyperparathyroidism over a period of 14 years led to simplification of diagnostic procedures and development of a surgical scheme. Over the years patients with discrete disease symptoms or with asymptomatic disease were observed more frequently. This can be seen as the result of earlier diagnosis due to increasing spread of laboratory autoanalysers and the resulting routine calcium determination. Development of surgical intervention is characterised by omitting preoperative diagnostic procedures to determine localisation, a schematised operation, and more reliance on macroscopic criteria rather than on quick sections during surgery.