Automatic Spatial Calibration of Ultra-Low-Field MRI for High-Accuracy Hybrid MEG--MRI

With a hybrid MEG--MRI device that uses the same sensors for both modalities, the co-registration of MRI and MEG data can be replaced by an automatic calibration step. Based on the highly accurate signal model of ultra-low-field (ULF) MRI, we introduce a calibration method that eliminates the error sources of traditional co-registration. The signal model includes complex sensitivity profiles of the superconducting pickup coils. In ULF MRI, the profiles are independent of the sample and therefore well-defined. In the most basic form, the spatial information of the profiles, captured in parallel ULF-MR acquisitions, is used to find the exact coordinate transformation required. We assessed our calibration method by simulations assuming a helmet-shaped pickup-coil-array geometry. Using a carefully constructed objective function and sufficient approximations, even with low-SNR images, sub-voxel and sub-millimeter calibration accuracy was achieved. After the calibration, distortion-free MRI and high spatial accuracy for MEG source localization can be achieved. For an accurate sensor-array geometry, the co-registration and associated errors are eliminated, and the positional error can be reduced to a negligible level.Comment: 11 pages, 8 figures. This work is part of the BREAKBEN project and has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 68686

No Effect of Steady Rotation on Solid 4^4He in a Torsional Oscillator

We have measured the response of a torsional oscillator containing polycrystalline hcp solid $^{4}$He to applied steady rotation in an attempt to verify the observations of several other groups that were initially interpreted as evidence for macroscopic quantum effects. The geometry of the cell was that of a simple annulus, with a fill line of relatively narrow diameter in the centre of the torsion rod. Varying the angular velocity of rotation up to 2\,rad\,s$^{-1}$ showed that there were no step-like features in the resonant frequency or dissipation of the oscillator and no history dependence, even though we achieved the sensitivity required to detect the various effects seen in earlier experiments on other rotating cryostats. All small changes during rotation were consistent with those occurring with an empty cell. We thus observed no effects on the samples of solid $^4$He attributable to steady rotation.Comment: 8 pages, 3 figures, accepted in J. Low Temp. Phy

Positron states at vacancy-impurity pairs in semiconductors

Positron states at pure monovacancies and divacancies and vacancy-phosphorus pairs in Si as well as at As vacancies and As-vacancy–As-antisite pairs in GaAs are calculated. The dependence of the positron lifetime on the lattice relaxation around the defects is studied, and the effects related to the screening of positrons are discussed. The calculations are based on superimposing free atoms. The ability of the method to describe positron states at charged defects is demonstrated.Peer reviewe

Composite repetition-aware data structures

In highly repetitive strings, like collections of genomes from the same species, distinct measures of repetition all grow sublinearly in the length of the text, and indexes targeted to such strings typically depend only on one of these measures. We describe two data structures whose size depends on multiple measures of repetition at once, and that provide competitive tradeoffs between the time for counting and reporting all the exact occurrences of a pattern, and the space taken by the structure. The key component of our constructions is the run-length encoded BWT (RLBWT), which takes space proportional to the number of BWT runs: rather than augmenting RLBWT with suffix array samples, we combine it with data structures from LZ77 indexes, which take space proportional to the number of LZ77 factors, and with the compact directed acyclic word graph (CDAWG), which takes space proportional to the number of extensions of maximal repeats. The combination of CDAWG and RLBWT enables also a new representation of the suffix tree, whose size depends again on the number of extensions of maximal repeats, and that is powerful enough to support matching statistics and constant-space traversal.Comment: (the name of the third co-author was inadvertently omitted from previous version

Design of an electrical floor heating panel manufactured by transfer foil technology

Abstract. In this thesis, a heater-integrated floor material and its possibilities in the field of floor heating were examined. The heater was designed to be manufactured by transfer foil technology. LTSpice and COMSOL simulation tools were utilized to model power losses and heating power, and three different heater versions were designed with Altium designer, and their simulation results and other properties of the heaters were compared. The main goal of the work was to find out the possibility of making floor heating for large surface areas from these heating panels and it was found that it would be possible to make over 100m² surfaces with under 1 ºC tolerance for the desired heating temperature.Siirtokalvotekniikalla valmistettavan sähköisen lattialämmityspaneelin suunnittelu. Tiivistelmä. Tässä työssä tarkasteltiin siirtokalvotekniikalla valmistettavan lämmitysvastuksen integroimista lattiamateriaaliin ja sen mahdollisuuksia lattialämmityksen saralla. Työssä hyödynnettiin LTSpice- ja COMSOL-simulointityökaluja lämmitystehon ja tehohäviöiden mallinnukseen ja piirrettiin Altiumilla kolme eri lämmitinversiota ja vertailtiin niiden simulointituloksia sekä lämmittimien muita ominaisuuksia. Työn tärkeimpänä tavoitteena oli selvittää mahdollisuutta tehdä lämmityspaneeleista lattialämmitys suurille lattiapinta-aloille. Saatiin selville, että näillä lämmityspaneeleilla olisi mahdollista tehdä yli 100m² lattiapintoja alle yhden asteen toleranssilla halutulle lämpötilalle

Blurred Responsibilities of Disaster Governance: The American Red Cross in the US and Haiti

The influence of private actors, such as non-profit organizations (NPOs) and firms, has been increasing in disaster governance. Previous literature has interrogated the responsibilities of states towards citizens in disasters, but the roles of private actors have been insufficiently challenged. The article politicizes the entangled relations between NPOs, states, and disaster-affected people. It proposes the Rawlsian division of moral labor as a useful, normative framework for interrogating the justice of disaster governance arrangements in which ‘liberal’ states are involved. Liberal states have two types of responsibilities in disasters: humanitarian and political. The humanitarian responsibilities imply provision of basic resources needed for the capacity to make autonomous choices (domestically and abroad), while the political responsibilities imply provision of the institutions needed for the liberal democratic citizenship (domestically). Through this analytical lens and building on the wealth of existing scholarship, we illustrate the disaster governance role of the American Red Cross in the United States (a 2005 hurricane) and in Haiti (the 2010 earthquake). Where, in Rawlsian terms, United States is interpreted as a ‘liberal’ society, Haiti is framed as a ‘burdened’ society. The article proposes five points to consider in analyzing disaster governance arrangements under neoliberal regimes, structured around the division of humanitarian and political responsibilities. The article illustrates how NPOS are instrumental in blurring the boundaries between humanitarian and political responsibilities. This might result ultimately in actual vulnerabilities remaining unaddressed. While the Rawlsian approach challenges the privatization and lack of coordination in disaster governance, it is limited in analyzing the political construction of ‘burdened’ societies