Computationally Efficient Forward Operator for Photoacoustic Tomography Based on Coordinate Transformations

IEEE Photoacoustic tomography (PAT) is an imaging modality that utilizes the photoacoustic effect. In PAT, a photoacoustic image is computed from measured data by modeling ultrasound propagation in the imaged domain and solving an inverse problem utilizing a discrete forward operator. However, in realistic measurement geometries with several ultrasound transducers and relatively large imaging volume, an explicit formation and use of the forward operator can be computationally prohibitively expensive. In this work, we propose a transformation based approach for efficient modeling of photoacoustic signals and reconstruction of photoacoustic images. In the approach, the forward operator is constructed for a reference ultrasound transducer and expanded into a general measurement geometry using transformations that map the formulated forward operator in local coordinates to the global coordinates of the measurement geometry. The inverse problem is solved using a Bayesian framework. The approach is evaluated with numerical simulations and experimental data. The results show that the proposed approach produces accurate three-dimensional photoacoustic images with a significantly reduced computational cost both in memory requirements and in time. In the studied cases, depending on the computational factors such as discretization, over 30-fold reduction in memory consumption and was achieved without a reduction in image quality compared to a conventional approach

Characterization of ultrasound fields using a potential optical flow based synthetic schlieren tomography

Synthetic schlieren tomography is an optical imaging method for characterization of ultrasound fields based on observing bending of light due to acousto-optic effect. In this work, potential optical flow based pressure estimation method is introduced

Cooper-pair resonances and subgap Coulomb blockade in a superconducting single-electron transistor

We have fabricated and measured superconducting single-electron transistors with Al leads and Nb islands. At bias voltages below the gap of Nb we observe clear signatures of resonant tunneling of Cooper pairs, and of Coulomb blockade of the subgap currents due to linewidth broadening of the energy levels in the superconducting density of states of Nb. The experimental results are in good agreement with numerical simulations.Comment: 4 pages, 3 figure

Epigenetic and transcriptional analysis supports human regulatory T cell commitment at the CD4+CD8+thymocyte stage

The natural CD25 + FOXP3 + regulatory T cell (Treg) population is generated as a distinct lineage in the thymus, but the details of Treg development in humans remain unclear, and the timing of Treg commitment is also contested. Here we have analyzed the emergence of CD25 + cells at the CD4 + CD8 + double positive (DP) stage in the human thymus. We show that these cells share T cell receptor repertoire with CD25 + CD4 single-positive thymocytes, believed to be committed Tregs. They already have a fully demethylated FOXP3 enhancer region and thus display stable expression of FOXP3 and the associated Treg phenotype. Transcriptome analysis also grouped the DP CD25 + and CD4 CD25 + thymocytes apart from the CD25 - subsets. Together with earlier studies, our data are consistent with human Treg commitment already at the DP thymocyte stage. We suggest that the most important antigens and signals necessary for human Treg differentiation may be found in the thymic cortex.Peer reviewe

Profiling water vapor mixing ratios in Finland by means of a Raman lidar, a satellite and a model

We present tropospheric water vapor profiles measured with a Raman lidar during three field campaigns held in Finland. Co-located radio soundings are available throughout the period for the calibration of the lidar signals. We investigate the possibility of calibrating the lidar water vapor profiles in the absence of co-existing on-site soundings using water vapor profiles from the combined Advanced InfraRed Sounder (AIRS) and the Advanced Microwave Sounding Unit (AMSU) satellite product; the Aire Limitee Adaptation dynamique Developpement INternational and High Resolution Limited Area Model (ALADIN/HIRLAM) numerical weather prediction (NWP) system, and the nearest radio sounding station located 100 km away from the lidar site (only for the permanent location of the lidar). The uncertainties of the calibration factor derived from the soundings, the satellite and the model data are <2.8, 7.4 and 3.9 %, respectively. We also include water vapor mixing ratio intercomparisons between the radio soundings and the various instruments/model for the period of the campaigns. A good agreement is observed for all comparisons with relative errors that do not exceed 50% up to 8 km altitude in most cases. A 4-year seasonal analysis of vertical water vapor is also presented for the Kuopio site in Finland. During winter months, the air in Kuopio is dry (1.15 +/- 0.40 g kg(-1)); during summer it is wet (5.54 +/- 1.02 g kg(-1)); and at other times, the air is in an intermediate state. These are averaged values over the lowest 2 km in the atmosphere. Above that height a quick decrease in water vapor mixing ratios is observed, except during summer months where favorable atmospheric conditions enable higher mixing ratio values at higher altitudes. Lastly, the seasonal change in disagreement between the lidar and the model has been studied. The analysis showed that, on average, the model underestimates water vapor mixing ratios at high altitudes during spring and summer.Peer reviewe

Lapsen osallisuuden tukeminen päiväkodin arjessa

Tiivistelmä. Tutkielmassamme avaamme osallisuuden käsitettä teorioiden, niiden tulkintojen sekä osallisuutta haastavien tekijöiden kautta. Olemme myös koonneet yhteen osallisuutta tukevia keinoja. Tutkimme näitä seuraavien tutkimuskysymysten kautta: miten osallisuutta on määritelty varhaiskasvatuksessa ja mitkä tekijät haastavat osallisuutta sekä miten lapsen osallisuutta voidaan tukea päiväkodin arjessa. Osallisuus tarkoittaa lapsen mahdollisuuksia vaikuttaa häntä koskeviin päätöksiin. Lapsen tulee myös olla tietoinen siitä, että hänen mielipiteensä vaikuttavat päätöksiin. Lasten osallisuutta voidaan tukea monella tavalla. Varhaiskasvatuksen opettaja on avainasemassa mahdollistamassa lapsen osallisuutta. Osallisuutta tuetaan kuuntelemalla lasta ja keskustelemalla hänen kanssaan, kodin ja päiväkodin välisellä yhteistyöllä, joustavilla rutiineilla ja pienryhmätoiminnalla päiväkodissa, lasten mielenkiinnonkohteiden huomioimisella sekä toiminnan havainnoinnilla ja sen mahdollistamisella. Tutkielmamme aihe on ajankohtainen ja aiheen valintaan ovat vaikuttaneet myös omat kokemuksemme. Lasten osallisuus varhaiskasvatuksessa on noussut ajankohtaiseksi aiheeksi varhaiskasvatuslain (540/2018) päivityksen myötä. Olemme myös havainneet itse päiväkodissa työskennellessämme, että varhaiskasvatuksen opettajien ajatukset lasten osallisuudesta ovat hyvin erilaisia. Tämän vuoksi, päädyimme tutkimaan lasten osallisuutta päiväkodin arjessa. Kandidaatin tutkielmamme on toteutettu integroivana kirjallisuuskatsauksena. Integroiva kirjallisuuskatsaus mahdollistaa laajan aineiston käytön sekä aineistojen yhdistelemisen ja uuden tiedon luomisen. Laaja aineisto mahdollistaa tutkielmamme luotettavuutta ja yleistettävyyttä. Olemme valinneet tutkielmaamme kattavasti erilaisia tutkimuksia, joiden pohjalta olemme muodostaneet monipuolisen käsityksen lapsen osallisuuden haasteista sekä sen tukemisesta. Tutkielmamme tavoitteena on tuoda konkreettisia esimerkkejä varhaiskasvatuksen opettajille siitä, miten lasten osallisuutta voidaan päiväkodin arjessa tukea

Different Predictors of Right and Left Ventricular Metabolism in Healthy Middle-Aged Men

Dysfunction of the right ventricle (RV) plays a crucial role in the outcome of various cardiovascular diseases. Previous studies on RV metabolism are sparse although evidence implies it may differ from left ventricular (LV) metabolism. Therefore, the aims of this study were (1) to determine predictors of RV glucose uptake (GU) and free fatty acid uptake (FFAU) and (2) to compare them to predictors of LV metabolism in healthy middle-aged men. Altogether 28 healthy, sedentary, middle-aged (40-55 years) men were studied. Insulin-stimulated GU and fasting FFAU were measured by positron emission tomography and RV and LV structural and functional parameters by cardiac magnetic resonance. Several parameters related to whole-body health were also measured. Predictors of RV and LV metabolism were determined by pairwise correlation analysis, lasso regression models, and variable clustering using heatmap. RVGU was most strongly predicted by age and moderately by RV ejection fraction (EF). The strongest determinants of RVFFAU were exercise capacity (peak oxygen uptake), resting heart rate, LVEF, and whole body insulin stimulated glucose uptake rate. When considering LV metabolism, age and RVEF were associated also with LVGU. In addition, LVGU was strongly, and negatively, influenced by whole-body insulin-stimulated glucose uptake rate. LVFFAU was predicted only by LVEF. This study shows that while RV and LV metabolism have shared characteristics, they also have unique properties. Age of the subject should be taken into account when measuring myocardial glucose utilization. Ejection fraction is related to myocardial metabolism, and even so that RVEF may be more closely related to GU of both ventricles and LVEF to FFAU of both ventricles, a finding supporting the ventricular interdependence. However, only RV fatty acid utilization associates with exercise capacity so that better physical fitness in a relatively sedentary population is related with decreased RV fat metabolism. To conclude, this study highlights the need for further study designed specifically on less known RV as the results on LV metabolism and physiology may not be directly applicable to the RV.</p