112 research outputs found
Mitigating the Position Bias of Transformer Models in Passage Re-Ranking
Supervised machine learning models and their evaluation strongly depends on the quality of the underlying dataset. When we search for a relevant piece of information it may appear anywhere in a given passage. However, we observe a bias in the position of the correct answer in the text in two popular Question Answering datasets used for passage re-ranking. The excessive favoring of earlier positions inside passages is an unwanted artefact. This leads to three common Transformer-based re-ranking models to ignore relevant parts in unseen passages. More concerningly, as the evaluation set is taken from the same biased distribution, the models overfitting to that bias overestimate their true effectiveness. In this work we analyze position bias on datasets, the contextualized representations, and their effect on retrieval results. We propose a debiasing method for retrieval datasets. Our results show that a model trained on a position-biased dataset exhibits a significant decrease in re-ranking effectiveness when evaluated on a debiased dataset. We demonstrate that by mitigating the position bias, Transformer-based re-ranking models are equally effective on a biased and debiased dataset, as well as more effective in a transfer-learning setting between two differently biased datasets
Somato-dendritic vasopressin and oxytocin secretion in endocrine and autonomic regulation
Somato‐dendritic secretion was first demonstrated over 30 years ago. However, although its existence has become widely accepted, the function of somato‐dendritic secretion is still not completely understood. Hypothalamic magnocellular neurosecretory cells were among the first neuronal phenotypes in which somato‐dendritic secretion was demonstrated and are among the neurones for which the functions of somato‐dendritic secretion are best characterised. These neurones secrete the neuropeptides, vasopressin and oxytocin, in an orthograde manner from their axons in the posterior pituitary gland into the blood circulation to regulate body fluid balance and reproductive physiology. Retrograde somato‐dendritic secretion of vasopressin and oxytocin modulates the activity of the neurones from which they are secreted, as well as the activity of neighbouring populations of neurones, to provide intra‐ and inter‐population signals that coordinate the endocrine and autonomic responses for the control of peripheral physiology. Somato‐dendritic vasopressin and oxytocin have also been proposed to act as hormone‐like signals in the brain. There is some evidence that somato‐dendritic secretion from magnocellular neurosecretory cells modulates the activity of neurones beyond their local environment where there are no vasopressin‐ or oxytocin‐containing axons but, to date, there is no conclusive evidence for, or against, hormone‐like signalling throughout the brain, although it is difficult to imagine that the levels of vasopressin found throughout the brain could be underpinned by release from relatively sparse axon terminal fields. The generation of data to resolve this issue remains a priority for the field.http://wileyonlinelibrary.com/journal/jne2021-04-17hj2020Immunolog
All Oxide Ferromagnet/Semiconductor Epitaxial Heterostructures
Oxide based ferromagnet/semiconductor heterostructures offer substantial
advantages for spin electronics. We have grown (111) oriented Fe3O4 thin films
and Fe3O4/ZnO heterostructures on ZnO(0001) and Al2O3(0001) substrates by
pulsed laser deposition. High quality crystalline films with mosaic spread as
small as 0.03 degree, sharp interfaces, and rms surface roughness of 0.3 nm
were achieved. Magnetization measurements show clear ferromagnetic behavior of
the magnetite layers with a saturation magnetization of 3.2 muB/f.u. at 300 K.
Our results demonstrate that the Fe3O4/ZnO system is an intriguing and
promising candidate for the realization of multi-functional heterostructures.Comment: 4 pages, 3 figure
Optimizing the growth conditions of Al mirrors for superconducting nanowire single-photon detectors
We investigate the growth conditions for thin (less than 200 nm) sputtered
aluminum (Al) films. These coatings are needed for various applications, e.g.
for advanced manufacturing processes in the aerospace industry or for
nanostructures for quantum devices. Obtaining high-quality films, with low
roughness, requires precise optimization of the deposition process. To this
end, we tune various sputtering parameters such as the deposition rate,
temperature, and power, which enables 50 nm thin films with a root mean square
(RMS) roughness of less than 1 nm and high reflectivity. Finally, we confirm
the high quality of the deposited films by realizing superconducting
single-photon detectors integrated into multi-layer heterostructures consisting
of an aluminum mirror and a silicon dioxide dielectric spacer. We achieve an
improvement in detection efficiency at 780 nm from 40 % to 70 % by this
integration approach.Comment: 11 pages, 6 figure
Scaling behavior of the spin pumping effect in ferromagnet/platinum bilayers
We systematically measured the DC voltage V_ISH induced by spin pumping
together with the inverse spin Hall effect in ferromagnet/platinum bilayer
films. In all our samples, comprising ferromagnetic 3d transition metals,
Heusler compounds, ferrite spinel oxides, and magnetic semiconductors, V_ISH
invariably has the same polarity. V_ISH furthermore scales with the
magnetization precession cone angle with a universal prefactor, irrespective of
the magnetic properties, the charge carrier transport mechanism or type. These
findings quantitatively corroborate the present theoretical understanding of
spin pumping in combination with the inverse spin Hall effect
Scaling behavior of the spin pumping effect in ferromagnet/platinum bilayers
We systematically measured the DC voltage V_ISH induced by spin pumping
together with the inverse spin Hall effect in ferromagnet/platinum bilayer
films. In all our samples, comprising ferromagnetic 3d transition metals,
Heusler compounds, ferrite spinel oxides, and magnetic semiconductors, V_ISH
invariably has the same polarity. V_ISH furthermore scales with the
magnetization precession cone angle with a universal prefactor, irrespective of
the magnetic properties, the charge carrier transport mechanism or type. These
findings quantitatively corroborate the present theoretical understanding of
spin pumping in combination with the inverse spin Hall effect
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