Papers presented at the 22nd EPS conference on controlled fusion & plasma physics by the Alcator C-Mod Group

https://digitalcommons.ric.edu/alumni_news/1067/thumbnail.jp

IC 225: a dwarf elliptical galaxy with a peculiar blue core

We present the discovery of a peculiar blue core in the elliptical galaxy IC 225 by using images and spectrum from the Sloan Digital Sky Survey (SDSS). The outer parts of the surface brightness profiles of u-, g-, r-, i- and z-band SDSS images for IC 225 are well fitted with an exponential function. The fitting results show that IC 225 follows the same relations between the magnitude, scale length and central surface brightness for dwarf elliptical galaxies. Its absolute blue magnitude (M_B) is -17.14 mag, all of which suggest that IC 225 is a typical dwarf elliptical galaxy. The g-r color profile indicates a very blue core with a radius of 2 arcseconds, which is also clearly seen in the RGB image made of g-, r- and i-band SDSS images. The SDSS optical spectrum exhibits strong and very narrow nebular emission lines. The metal abundances derived by the standard methods, which are 12+log(O/H) = 8.98, log(N/O) = -0.77 and 12+log(S+/H+) = 6.76, turn out to be significantly higher than that predicted by the well-known luminosity-metallicity relation. After carefully inspecting the central region of IC 225, we find that there are two distinct nuclei, separated by 1.4 arcseconds, the off-nucleated one is even bluer than the nucleus of IC 225. The asymmetric line profiles of higher-order Balmer lines indicate that the emission lines are bluer shifted relative to the absorption lines, suggesting that the line emission arises from the off-center core, whose nature is a metal-rich Hii region. To the best of our knowledge, it is the first high-metallicity Hii region detected in a dwarf elliptical galaxy.Comment: 7 figures, accepted for publication in A

The HI and Ionized Gas Disk of the Seyfert Galaxy NGC 1144 = Arp 118: A Violently Interacting Galaxy with Peculiar Kinematics

We present observations of the distribution and kinematics of neutral and ionized gas in NGC 1144, a galaxy that forms part of the Arp 118 system. Ionized gas is present over a huge spread in velocity (1100 km/s) in the disk of NGC 1144, but HI emission is detected over only 1/3 of this velocity range, in an area that corresponds to the NW half of the disk. In the nuclear region of NGC 1144, a jump in velocity in the ionized gas component of 600 km/s is observed. Faint, narrow HI absorption lines are also detected against radio sources in the SE part of the disk of NGC 1144, which includes regions of massive star formation and a Seyfert nucleus. The peculiar HI distribution, which is concentrated in the NW disk, seems to be the inverse of the molecular distribution which is concentrated in the SE disk. Although this may partly be the result of the destruction of HI clouds in the SE disk, there is circumstantial evidence that the entire HI emission spectrum of NGC 1144 is affected by a deep nuclear absorption line covering a range of 600 km/s, and is likely blueshifted with respect to the nucleus. In this picture, a high column-density HI stream is associated with the nuclear ionized gas velocity discontinuity, and the absorption effectively masks any HI emission that would be present in the SE disk of NGC 1144.Comment: manuscript, arp118.ps: 28 pages; 1 Table: arp118.tab1.ps; 16 Figures: arp118.fig1-16.ps; Accepted to Ap

Processing graded feedback: Electrophysiological correlates of learning from small and large errors

Feedback processing is important for learning and therefore may affect the consolidation of skills. Considerable research demonstrates electrophysiological differences between correct and incorrect feedback, but how we learn from small versus large errors is usually overlooked. This study investigated electrophysiological differences when processing small or large error feedback during a time estimation task. Data from high-learners and low-learners were analyzed separately. In both high- and low-learners, large error feedback was associated with higher feedback-related negativity (FRN) and small error feedback was associated with a larger P300 and increased amplitude over the motor related areas of the left hemisphere. In addition, small error feedback induced larger desynchronization in the alpha and beta bands with distinctly different topographies between the two learning groups: The high-learners showed a more localized decrease in beta power over the left frontocentral areas, and the low-learners showed a widespread reduction in the alpha power following small error feedback. Furthermore, only the high-learners showed an increase in phase synchronization between the midfrontal and left central areas. Importantly, this synchronization was correlated to how well the participants consolidated the estimation of the time interval. Thus, although large errors were associated with higher FRN, small errors were associated with larger oscillatory responses, which was more evident in the high-learners. Altogether, our results suggest an important role of the motor areas in the processing of error feedback for skill consolidation

Validated Radiometric Mapping in 2012 of Areas in Japan Affected by the Fukushima-Daiichi Nuclear Accident.

On March 11 2011 the north-eastern region of Japan was hit by a magnitude 9 earthquake, which occurred underneath the sea-bed 70 km east of the Oshika peninsula in Tohoku. The north-eastern shore of Honshu was hit by a tsunami resulting from this earthquake. As a consequence, reactors 1-4 at the nuclear power station Fukushima-Daiichi suffered a completed loss of power and cooling causing a partial core meltdown in units 1, 2 and 3 followed by a series of explosions and the release of large quantities of radioactivity into the environment. The accident was rated level 7 (the highest level) on the International Nuclear Event Scale. While most of the emissions were driven towards the Pacific Ocean, a significant amount of radioactive material was deposited onto the Japanese land-mass, resulting in enhanced localised radiation exposure. This report covers measurements and detailed radiation maps conducted by a UK University team working with Japanese colleagues during a series of visits in 2012. They have been presented and shared locally in Japan at time of acquisition. Since then the data have been cross-validated relative to soil samples from a reference site established at the University of Fukushima, and analysed independently in the UK and in Japan. This report provides detailed descriptions of the data sets, validated radiometric maps for 134Cs, 137Cs and the overall gamma dose rates, together with a full account of the establishment of the calibration site. The work reported here demonstrates the utility of detailed radiometric maps in helping to understand the distribution of radionuclides in complex environmental systems. This information is potentially of use to help avoid unnecessary external radiation exposure in the outdoor environment, to help to visualise and target areas for remediation, to evaluate the effectiveness of clean-up and soil removal activities, to examine uptake of radioactivity from the environment through agricultural systems, and to monitor redistribution over time of the activity in the environment. The report includes full copies of digital data sets for the demonstration surveys. Radiometric methods provide means of measuring radioactivity with recognised roles in nuclear emergency response, and environmental applications. In the aftermath of nuclear accidents they are crucial to evaluate the environmental impact of the accident and guide remediation measures. The Scottish Universities Environmental Research Centre (SUERC) is a research centre attached to the University of Glasgow with extensive experience of radiometric mapping using airborne and ground based systems, conducting most of the UK post-Chernobyl radiation mapping using airborne systems and coordinating European projects to harmonise and cross-calibrate systems for nuclear emergency response purposes. In the early stages of major accidents the most pressing needs are for rapid, large scale, information. Airborne surveys of the affected area were conducted initially by a joint US/Japanese team and later on by The Ministry of Education Science and Technology (MEXT) and the Japanese Atomic Energy Agency (JAEA), eventually providing national scale radiation maps with a spatial resolution of several hundred meters. In later stages of accident recovery there are increasing needs for more detailed spatial information and increasing requirements for objective, traceable and cross validated analysis. Systems for this work need to be mobile, preferably portable, efficient, robust and well calibrated, providing detailed real time information directly on location. The SUERC Portable Gamma Spectrometry system fulfils these criteria. It provides a spatial resolution of better than 10 m for mapped data and allows a real time identification of spatial features down to 10-20 cm. In the work reported here, calibration sites have been established in Fukushima at the campus of Fukushima University and the Fukushima Prefecture Fruit Tree Research Institute to provide objective and internationally traceable validation of ground based instruments. High resolution HPGe spectrometry of soil samples conducted at laboratories at Fukushima University and SUERC was used for validation of the field instrument. Values of 137Cs activity concentration measured by the two laboratories were in full agreement to high precision. Agreement for the 134Cs activity concentration values was within 5-10%. The soil samples used in this process were analysed as a function of depth, revealing that while the majority of activity was retained in near surface layers, a small component of approximately 1% of the total activity appears to have migrated more rapidly to greater depths. This suggests complex transport behaviour in the soil columns which should be investigated further. The calibration sites are open for future use. These data establish a traceable record between local facilities and internationally acknowledged standards for future use. Deployment of the SUERC system in vehicles has demonstrated the ability of relatively small detectors to measure regional scale deposition patterns over a wide range of radioactivity levels, varying from 10,000 Bq per square meter up to more than 10 million Bq per square meter. These activity levels are broadly consistent with the national scale airborne maps for the study areas, but the ground based maps provide very high level of local detail, which allow small scale changes to be readily observed and related to the local soils, land cover and built environment. Areas covered in two surveys in March and July 2012, respectively, cover parts of the Fukushima Prefecture including parts of the evacuation and exclusion zones as well as areas directly affected by the 2011 tsunami. Short backpack surveys in urban areas associated with the car trips were also conducted e.g. in Fukushima City (in the heart of the prefecture), Ōkuma (within 3 km of the Fukushima Daichi reactors), Minami-Daira and Kawauchi-mura (within the initial evacuation zones), demonstrate the versatility of a system which can be rapidly moved from a vehicle to backpack where further detailed information is needed. With a fully spectrometric system as used in this study, it is possible to identify specific radioactive isotopes and to quantify the activity concentrations of natural and artificial sources spanning many orders of magnitude, from less than 10 kBq m-2 to above 10 MBq m-2 for radiocaesium. This information has been used to estimate the contribution to the dose rate from different sources, so that a comparison between the contributions from naturally occurring radioactive materials (not affected by the accident) and the different radiocaesium isotopes present following the accident can be readily made. These data provide vital information to the local population and emergency services in guiding remediation efforts, and also over the course of time, in observing the extent to which weathering and radioactivity decay processed are gradually reducing the relative contributions from the accident. In the long term it is hoped that this type of representation will help put the accident contributions into perspective, and to register improvements with time which may help to establish increased confidence in affected areas. In urbanised areas backpack systems provide the means of producing detailed surveys in locations where people spend their time. Surveys conducted of Fukushima University and Fukushima Iizaka have demonstrated the ability of detailed radiometric mapping to identify locations with highly varying levels of contamination, from more highly contaminated areas around drain pipes to the relatively low levels of contamination on roads and other hard surfaces where rain and snow melt have removed deposited activity. The effectiveness of the remediation work conducted on the University campus was evident, showing the ability of radiometric surveys to demonstrate the effectiveness of remediation and to identify where remaining activity is located. The remediation methods employed resulted in a three- to fourfold reduction in dose rate compared to untreated areas. Remediation efforts in orchards or woodland are particularly challenging. Given the economic importance of agriculture in the Fukushima area and the possible pathways from contaminated produce into the human body, a precise evaluation of the local radiation risk is of prime importance. The SUERC system has been demonstrated in orchards at the Fukushima Prefecture Fruit Tree Research Institute, and at other orchards in the Prefecture. Work has also been undertaken with agricultural research institutions at Tsukuba, Ibaraki Prefecture. The comparison of measurements taken at these same sites over the time of a year show a decrease in activity following the half-life of the radioisotopes deposited, superimposed by environmental factors like precipitation, illustrating self-remediation. Ongoing work on these sites will allow an assessment of transfer of activity from to the fruit, and the impact of measures to remediate the orchards or reduce uptake of activity in the fruit, and the evaluation of external doses to workers in the orchards. The data collected during this work contain the specific activity per isotope at a given surveyed location and at a given moment in time. The data accompanying this report are transparent, open and independently validated. They are made available for reference purposes and further utilisation. The work presented here highlights many of the difficult challenges ahead in the monitoring and remediation effort in the area affected by the accident in the Fukushima Dai-ichi nuclear power plant. It demonstrates the capabilities and methods at the disposal of the international community in aiding the Japanese efforts, demonstrating the value of international collaboration in helping to address some of the difficult problems associated with recovery from a serious nuclear accident. It is hoped that these data, and the methods which they demonstrate, will contribute, together with future work, to increased understanding of the environmental impacts of the accident, and that future cooperative work involving Japanese and international teams will contribute to recovery and restoration of confidence in affected areas and communities

Third-Generation W(CNAr)₆ Photoreductants (CNAr = Fused-Ring and Alkynyl-Bridged Arylisocyanides)

Homoleptic tungsten(0) arylisocyanides possess photophysical and photochemical properties that rival those of archetypal ruthenium(II) and iridium(III) polypyridine complexes. Previous studies established that extending the π-system of 2,6-diisopropylphenylisocyanide (CNDipp) by coupling aryl substituents para to the isocyanide functionality results in W(CNDippAr)₆ oligoarylisocyanide complexes with greatly enhanced metal-to-ligand charge transfer (MLCT) excited-state properties relative to those of W(CNDipp)₆. Extending electronic modifications to delineate additional design principles for this class of photosensitizers, herein we report a series of W(CNAr)₆ compounds with naphthalene-based fused-ring (CN-1-(2-ⁱPr)-Naph) and CNDipp-based alkynyl-bridged (CNDipp^(CC)Ar) arylisocyanide ligands. Systematic variation of the secondary aromatic system in the CNDippCCAr platform provides a straightforward method to modulate the photophysical properties of W(CNDipp^(CC)Ar)₆ complexes, allowing access to an extended range of absorption/luminescence profiles and highly reducing excited states, while maintaining the high molar absorptivity MLCT absorption bands, high photoluminescence quantum yields, and long excited-state lifetimes of previous W(CNAr)₆ complexes. Notably, W(CN-1-(2-iPr)-Naph)₆ exhibits the longest excited-state lifetime of all W(CNAr)₆ complexes explored thus far, highlighting the potential benefits of utilizing fused-ring arylisocyanide ligands in the construction of tungsten(0) photoreductants

Third-Generation W(CNAr)₆ Photoreductants (CNAr = Fused-Ring and Alkynyl-Bridged Arylisocyanides)

Homoleptic tungsten(0) arylisocyanides possess photophysical and photochemical properties that rival those of archetypal ruthenium(II) and iridium(III) polypyridine complexes. Previous studies established that extending the π-system of 2,6-diisopropylphenylisocyanide (CNDipp) by coupling aryl substituents para to the isocyanide functionality results in W(CNDippAr)₆ oligoarylisocyanide complexes with greatly enhanced metal-to-ligand charge transfer (MLCT) excited-state properties relative to those of W(CNDipp)₆. Extending electronic modifications to delineate additional design principles for this class of photosensitizers, herein we report a series of W(CNAr)₆ compounds with naphthalene-based fused-ring (CN-1-(2-ⁱPr)-Naph) and CNDipp-based alkynyl-bridged (CNDipp^(CC)Ar) arylisocyanide ligands. Systematic variation of the secondary aromatic system in the CNDippCCAr platform provides a straightforward method to modulate the photophysical properties of W(CNDipp^(CC)Ar)₆ complexes, allowing access to an extended range of absorption/luminescence profiles and highly reducing excited states, while maintaining the high molar absorptivity MLCT absorption bands, high photoluminescence quantum yields, and long excited-state lifetimes of previous W(CNAr)₆ complexes. Notably, W(CN-1-(2-iPr)-Naph)₆ exhibits the longest excited-state lifetime of all W(CNAr)₆ complexes explored thus far, highlighting the potential benefits of utilizing fused-ring arylisocyanide ligands in the construction of tungsten(0) photoreductants