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

Life cycle indicator comparison of copper, silver, zinc and aluminum nanoparticle production through electric arc evaporation or chemical reduction

Ways to produce metallic nanoparticles and the scale-up of these processes have seen increased interest as the industrial application of nanoparticles continues to grow. Their feasibility from an environmental point of view can be assessed by means of life cycle analysis (LCA). In this work two methods of metallic nanoparticle production, by evaporation/condensation of metal using electrical arc discharge reactors or by chemical reduction of metal salts in aqueous solutions or dry solid/solid mixtures, are evaluated based on the life cycle indicators. The evaporation of metal using electrical discharge reactors is a method studied in the European Commission 7th Framework Program “BUONAPART-E.” The environmental impact of the two different nanoparticle production approaches is here compared for four metals: copper, silver, zinc and aluminum. The chemical routes of producing nanoparticles require several different chemicals and reactions, while the electrical discharge routes use electricity to evaporate metal in a reactor under inert atmosphere. The nanoparticle production processes were modeled using “SimaPro” LCA software. Data for both the chemical production routes and the arc routes were taken from the literature. The choice of the best route for the production of each metal is strongly dependent on the final yield of the metallic nanoparticles. The yields for the chemical processes are not reported in the open literature, and therefore the comparisons have to be made with varying yields. At similar yields the electrical process has in general a lower environmental footprint than the studied chemical routes. The step or chemical with the greatest environmental impact varies significantly depending on process and metal being studied.Martin Slotte, Gregory Metha, Ron Zevenhove

AN EXERGY ANALYSIS FOR MINERAL CARBONATION

Magnesium oxide-based minerals such as serpentine and olivine may be used for long-term storage of CO2, from combustion of fossil fuels or industrial processes such as steel works, in the form of magnesium carbonate. Large resources of suitable minerals appear to exist in Finland and at many other locations worldwide. The efficiency of the mineral carbonation process can be evaluated using exergy analysis, which will allow for comparing different mineral deposits that are characterised by different composition and quality. Other factors that play a role are the temperature and pressure, the presence of other gases besides CO2 and the degree of magnesium carbonation that is reached. Important for the analysis is the calculation of the standard chemical exergy of the chemical species involved

Fluidised bed combustion of two species of energy crops

The use of biomass fuels for energy production through combustion has a growing application worldwide mainly for two reasons: first, the utilization of biomass for energy contributes to mitigate emission of green house gases; second, its use decreases the dependence of imported fossil fuels in Europe. The objective of this work was to study the combustion behaviour of two endogenous biomass species: cardoon (cynara cardunculus) and arundo (arundo donax), which were specially produced in energy crops plantations. Mixtures of cardoon and a forestry biomass specie (eucalyptus) were also studied to evaluate potential benefits from synergies between both biomass fuel types. The results showed that the utilization of cardoon, in pelletized form, and loose arundo as feedstock, did not give rise to any operational problems related with the feeding system. It was verified that the mono combustion of cardoon could pose problems at industrial scale in fluidised bed systems, considering the high levels of HCl and NOX emissions obtained and tendency to sinter the bed sand material. The addition of the forestry biomass to cardoon appeared to prevent the bed agglomeration problem. Furthermore, both the NOX and SO2 emissions were found to decrease at the same time suggesting potential synergy of blending different types of biomass regarding pollutant emissions and in bed agglomeration problems

Understanding the Interaction of Potassium Salts with an Ilmenite Oxygen Carrier under Dry and Wet Conditions

This study describes how potassium salts representative of those in bio ash affect the reactivity of the oxygen carrier ilmenite under moist and dry conditions. Ilmenite is a bench-mark oxygen carrier for chemical-looping combustion, a technique that can separate CO2 from flue gases with minimal energy penalty. Different potassium salts were mixed with ilmenite to a concentration of 4 wt % potassium. The salts used were K2CO3, K2SO4, KCl, and KH2PO4. Experiments were performed at 850 \ub0C under alternately oxidizing and reducing conditions in a dry atmosphere or in the presence of steam. Analyses of the oxygen carrier regarding changes in reactivity, structure, and composition followed the exposures. This study showed that salts such as K2CO3, K2SO4, and KCl increase the reactivity of the ilmenite. For the samples mixed with KCl, most of the salt was evaporated. KH2PO4 decomposed into KPO3, forming layers around the ilmenite particles that lead to agglomeration. Additionally, the KPO3 layer was more or less nonpermeable for CO and decreased the reactivity toward H2 significantly in both dry and wet conditions. This decreased reactivity indicates that the concentration of phosphorus in biofuel may have a significant effect on oxygen carrier degradation. It was also observed that the presence of steam changed the chemistry drastically for the nonphosphorus-containing salts. Alkali salts may react with steam, forming volatile KOH that evaporates partly. KOH may also form K-titanates by reaction with the oxygen carrier, leading to segregation of iron and titanium phases in the ilmenite. \ua

Mineral sequestration for CCS in Finland and abroad

Abstract: The long-term storage of CO 2 using mineral sequestration is becoming increasingly interesting in many regions, especially where CO 2 underground sequestration is considered impossible or unfeasible. Despite the recognised and documented advantages of CO 2 mineral sequestration, twenty years of R&D work did not yet result in mature, economically viable technology that can be applied on a large scale. Lacking other CCS options while having access to large resources of suitable rock material, a route for carbonation of magnesium silicate mineral is currently being optimised in Finland. It involves the production of magnesium hydroxide, Mg(OH) 2 from the mineral followed by carbonation of this in a pressurised fluidised bed reactor. Although the Mg(OH) 2 production requires energy the consequent carbonation step is exothermic and the overall process could still be rendered energy neutral. Significant amounts of iron oxides are obtained as by-products. Carbonation levels of ~50% of several 100 µm diameter Mg(OH) 2 particles were obtained within 10 minutes at pressures > 20 bar and temperatures up to 500ºC. This paper reports on the latest developments of the work, addressing also process energy efficiency. Also, the large-scale application of this in Finland and at the locations of project partners abroad is briefly addressed

Solving transient problems in ultra-low-field MRI

Magnetic resonance imaging (MRI) is widely used in clinical applications as well as in research. While the state of the art of MRI has developed towards using multiple-tesla magnetic fields, another approach has emerged, where the signal is measured in a magnetic field on the order of Earth's magnetic field (~ 100 µT). Such ultra-low-field (ULF) MRI is made possible by highly-sensitive magnetic-field sensor technology based on superconducting quantum interference devices (SQUIDs). For increasing the signal-to-noise ratio (SNR), the sample is pre-polarized in a larger field (~ 100 mT) before each acquisition cycle. ULF MRI has interesting characteristics including unique contrast mechanisms, safety, silent operation, and potential in low cost and in compatibility with other electromagnetically sensitive technology. MRI acquisition is based on measuring the nuclear magnetic resonance (NMR) resulting in the sample from applying various magnetic field pulses. Pulsing magnetic fields, especially the pre-polarizing field, however, causes a number of problems, mainly related to unwanted electromagnetic induction to other parts of the measurement apparatus and its surroundings. Eddy currents induced in the walls of the magnetically shielded room (MSR), which is required for low-noise measurements, are a particularly serious issue. The eddy currents generate a transient magnetic field, disturbing data acquisition and affecting the NMR. In this Thesis, I discuss the problems of pulse-induced transient effects and what they have in common. I adapt theory of linear systems to the effects and present methods and approaches for solving them. In particular, I derive a quantitative theory of eddy currents and magnetic shielding by them in the walls of an MSR. Some of these methods and approaches were applied to the ULF-MRI system at University of California, Berkeley. A number of upgrades were made to the system to solve several serious transient issues that made imaging impossible with a new coil setup meant to significantly improve the image quality. Among these upgrades, a new MSR was designed and constructed to reduce transient eddy currents. Time-dependent measurements of the eddy-current patterns in the MSR walls show excellent agreement with calculations based on the presented theory. Imaging tests show that the upgrades were successful. For transient suppression, I also present a method in which additional time-varying pulses are applied in the system to spatiotemporally couple to the transient effects, providing highly flexible means of simultaneously canceling transients at different time scales. A simulation study is presented, suggesting that this method can provide much better results than any pre-existing method

Jätteiden kierrätyksen ja polton ympäristövaikutukset ja kustannukset – jätehuollon vaihtoehtojen tarkastelu alueellisesta näkökulmasta

Jätehuollossa biohajoavan jätteen kaatopaikkasijoitusta ja kasvihuonekaasupäästöjä on vähennettävä mm. lisäämällä jätteiden hyödyntämistä materiaalina ja energiana. Tutkimushankkeessa ”Polttokelpoisten jätteiden hyödyntäminen ympäristö- ja kustannusvaikutusten kannalta (POLKU)” luotiin tietopohjaa hyödyntämisvaihtoehdoista alueellisen jätesuunnittelun ja päätöksenteon tueksi. POLKU-hankkeen rahoittajina olivat ympäristöministeriö ja Jätelaitosyhdistys ry. Hankkeen toteuttivat yhteistyössä SYKE, Helsingin yliopisto, Tampereen teknillinen yliopisto,  Åbo Akademi, Teknillinen korkeakoulu sekä Jätelaitosyhdistys ry. POLKU-hankkeessa tutkittiin kuuden jätelajin – sekajätteen, biojätteen, jätevesilietteen, sekä hyvälaatuisten muovi-, kuitu- ja puujätteen – hyödyntämismahdollisuuksien ympäristövaikutuksia ja kustannuksia kokonaisvaltaisesti elinkaariarvioinnin avulla. Tässä raportissa esitetään tarkastelun tulokset. Tutkimuksen pohjaksi koottu inventaariotieto mm. jätehuollon prosesseista raportoidaan erillisessä, Suomen ympäristökeskuksen raportteja -sarjan julkaisussa. POLKU-hankkeen tulokset osoittivat, että polttokelpoisten jätelajien hyötykäyttö tuottaa lähes aina ympäristöhyötyjä, joista merkittävimmät liittyvät ilmastonmuutoksen hillitsemiseen. Se, onko hyötykäyttö parempi toteuttaa polttaen vai kierrättäen, riippuu tuotettavista energia- ja materiaalituotteista ja ennen kaikkea siitä, minkälaisia tuotteita ne korvaavat. Elinkaaristen ympäristövaikutusten näkökulmasta katsottuna parhaat vaihtoehdot eivät välttämättä osoittautuneet yhteiskunnalle aiheutuvien nettokustannusten kannalta edullisimmiksi toimintamalleiksi. Tuloksiin vaikuttaneista tekijöistä merkittävimmiksi osoittautuivat jätteellä korvattava polttoaine ja jätteellä tuotetun energian tarve. Hankkeen jätelajikohtaisia tuloksia voidaan yleistää vain huomioimalla, että jätehuollon prosessien tiedot perustuvat esimerkkeihin, jätelajien laatu voi vaihdella alueittain ja että muutokset muissa tuote- ja energiajärjestelmissä riippuvat tarkasteltavan alueen teollisuudesta ja energiantuotantorakenteesta. Lopulliset johtopäätökset vaihtoehtojen paremmuudesta riippuvat siitä, painotetaanko ympäristövaikutuksia vai kustannuksia

Induction of small cell lung cancer by somatic inactivation of both Trp53 and Rb1 in a conditional mouse model

AbstractSmall cell lung cancer (SCLC) is a highly aggressive human tumor with a more than 95% mortality rate. Its ontogeny and molecular pathogenesis remains poorly understood. We established a mouse model for neuroendocrine (NE) lung tumors by conditional inactivation of Rb1 and Trp53 in mouse lung epithelial cells. Mice carrying conditional alleles for both Rb1 and Trp53 developed with high incidence aggressive lung tumors with striking morphologic and immunophenotypic similarities to SCLC. Most of these tumors, which we designate MSCLC (murine small cell lung carcinoma), diffusely spread through the lung and gave rise to extrapulmonary metastases. In our model, inactivation of both Rb1 and p53 was a prerequisite for the pathogenesis of SCLC

Bmi1 Controls Tumor Development in an Ink4a/Arf-Independent Manner in a Mouse Model for Glioma

SummaryThe Polycomb group and oncogene Bmi1 is required for the proliferation of various differentiated cells and for the self-renewal of stem cells and leukemic cancer stem cells. Repression of the Ink4a/Arf locus is a well described mechanism through which Bmi1 can exert its proliferative effects. However, we now demonstrate in an orthotopic transplantation model for glioma, a type of cancer harboring cancer stem cells, that Bmi1 is also required for tumor development in an Ink4a/Arf-independent manner. Tumors derived from Bmi1;Ink4a/Arf doubly deficient astrocytes or neural stem cells have a later time of onset and different histological grading. Moreover, in the absence of Ink4a/Arf, Bmi1-deficient cells and tumors display changes in differentiation capacity