Hypothetical Source Research Articles

Comparison of the hypothetical (57)Co brachytherapy source with the (192)Ir source.

Aim of the studyThe 57Co radioisotope has recently been proposed as a hypothetical brachytherapy source due to its high specific activity, appropriate half-life (272 days) and medium energy photons (114.17 keV on average). In this study, Task Group No. 43 dosimetric parameters were calculated and reported for a hypothetical 57Co source.Material and methodsA hypothetical 57Co source was simulated in MCNPX, consisting of an active cylinder with 3.5 mm length and 0.6 mm radius encapsulated in a stainless steel capsule. Three photon energies were utilized (136 keV [10.68%], 122 keV [85.60%], 14 keV [9.16%]) for the 57Co source. Air kerma strength, dose rate constant, radial dose function, anisotropy function, and isodose curves for the source were calculated and compared to the corresponding data for a 192Ir source.ResultsThe results are presented as tables and figures. Air kerma strength per 1 mCi activity for the 57Co source was 0.46 cGyh–1 cm 2 mCi–1. The dose rate constant for the 57Co source was determined to be 1.215 cGyh–1U–1. The radial dose function for the 57Co source has an increasing trend due to multiple scattering of low energy photons. The anisotropy function for the 57Co source at various distances from the source is more isotropic than the 192Ir source.ConclusionsThe 57Co source has advantages over 192Ir due to its lower energy photons, longer half-life, higher dose rate constant and more isotropic anisotropic function. However, the 192Ir source has a higher initial air kerma strength and more uniform radial dose function. These properties make 57Co a suitable source for use in brachytherapy applications.

A comparison study on various low energy sources in interstitial prostate brachytherapy.

PurposeLow energy sources are routinely used in prostate brachytherapy. 125I is one of the most commonly used sources. Low energy 131Cs source was introduced recently as a brachytherapy source. The aim of this study is to compare dose distributions of 125I, 103Pd, and 131Cs sources in interstitial brachytherapy of prostate.Material and methodsProstaSeed 125I brachytherapy source was simulated using MCNPX Monte Carlo code. Additionally, two hypothetical sources of 103Pd and 131Cs were simulated with the same geometry as the ProstaSeed 125I source, while having their specific emitted gamma spectra. These brachytherapy sources were simulated with distribution of forty-eight seeds in a phantom including prostate. The prostate was considered as a sphere with radius of 1.5 cm. Absolute and relative dose rates were obtained in various distances from the source along the transverse and longitudinal axes inside and outside the tumor. Furthermore, isodose curves were plotted around the sources.ResultsAnalyzing the initial dose profiles for various sources indicated that with the same time duration and air kerma strength, 131Cs delivers higher dose to tumor. However, relative dose rate inside the tumor is higher and outside the tumor is lower for the 103Pd source.ConclusionsThe higher initial absolute dose in cGy/(h.U) of 131Cs brachytherapy source is an advantage of this source over the others. The higher relative dose inside the tumor and lower relative dose outside the tumor for the 103Pd source are advantages of this later brachytherapy source. Based on the total dose the 125I source has advantage over the others due to its longer half-life.

Estimating ozone and secondary PM2.5 impacts from hypothetical single source emissions in the central and eastern United States

Secondary pollutant impacts from emissions of single sources may need to be assessed to satisfy a variety of regulatory requirements including the Clean Air Act New Source Review and Prevention of Significant Deterioration programs and the National Environmental Policy Act. In this work, single source impacts on O3 and secondary PM2.5 are estimated with annual 2011 photochemical grid model simulations where new hypothetical sources are added to the central and eastern United States with varying precursor emission rates and emission release heights. Impacts from these hypothetical sources are tracked with photochemical grid model source apportionment. Single source impacts on downwind 8-hr maximum O3 tend to increase as emissions of NOX or VOC increase. Downwind impacts on PM2.5 sulfate and nitrate also tend to increase as emissions of SO2 and NOX increase. For all secondary pollutants, impacts from these hypothetical sources tend to decrease as distance from the source increases. However, peak impacts on O3 and secondary PM2.5 are not at the facility fence-line but typically within 50–100 km depending on the emissions rate, precursor pollutant, and emissions release point. Downwind impacts are not uniform directionally from these sources due to varying downwind availability of chemical reactants and prevailing meteorology. Peak impacts for O3 (∼15 ppb) and PM2.5 sulfate (∼8 μg/m3) were within 50 km of these hypothetical sources and peak impacts for PM2.5 nitrate (∼1 μg/m3) were within 125 km. The daily maximum 8-hr O3 and maximum daily average PM2.5 sulfate and nitrate ion impacts for the new hypothetical sources modeled here are generally consistent with those reported in literature. Additional assessments of single source impacts on secondary pollutants are still needed to provide a more comprehensive assessment of different source types and source environments.

First Century Galilee: A Fresh Examination of the Sources by Bradley W. Root (review)

FIRST CENTURY GALILEE: A FRESH EXAMINATION OF THE SOURCES By Bradley W. Root. Wissenschaftliche Untersuchungen zum Neuen Testament 2. Reihe 378. Tubingen: Mohr Siebeck, 2014. xvii + 228 pp.Bradley W. Root makes a significant contribution to ongoing conversations about the cultural, religious, and economic environment of first-century Galilee. His study, based on the 2009 University of California, San Diego history dissertation he wrote under David Goodblatt, focuses on seven issues: ethnicity, urbanization, economic conditions, political climate, religious ethos, Jewish-Gentile relations, and Galilean-Judean relations. In exploring these themes, Root argues that scholars often prematurely jump to historical reconstruction without sufficiently wrestling with the methodological problems posed by their sources. He thus devotes the bulk of his twelve-chapter book to critical analysis of individual sources, leaving historical synthesis for the end. He sifts through the writings of Josephus, the classic four sources of the Synoptic Gospels (Mark, the hypothetical sayings source Q, special Matthean material, and special Lukan material), the Gospel of Thomas, the Gospel of John, and published archaeological reports. He does not engage rabbinic texts in depth because of the methodological difficulty of identifying traditions that accurately preserve glimpses of the first century.In combing through Josephus's Jewish War, Jewish Antiquities, and Life, Root takes his methodological cues from scholars such as Steve Mason and Shaye J. D. Cohen. Noting the oft-discussed inconsistencies in Josephus's works, Root rightly concludes that some are so dramatic that they probably reflect a conscious decision by Josephus to alter his presentation of events. Furthermore, he observes, is about the events that took place in that region [Galilee] that Josephus had the greatest incentive to lie (11). Nonetheless, Root argues that the consistency of Josephus's comments about region suggests their general accuracy. Though Josephus drastically exaggerated the size of Galilee's population to boost his own prestige as its military commander, he probably not far off the mark when praising the region's agricultural productivity and general prosperity. Josephus was unable to come up with any major problems that Galilee experienced while Antipas Tetrarch (21) and he did not report the same level of mid-century banditry there that he does for Judea. Though Josephus depicted rural Galileans as hostile toward Sepphoris during the revolt, he did not attribute such antipathy to class, ethnic, or economic tensions. In short, Josephus's portrayal suggests a region that fared well in many respects for most of the first century, with relatively few communities suffering even in the revolt.Root's exploration of gospel materials pays careful attention to issues of provenance and Tendenz, finding varying amounts of information applicable to his chosen focal points. He finds little explicit support for views of the region as extensively hellenized or romanized, thoroughly urbanized, and in the midst of widespread upheaval because of economic crisis, and considerable evidence for a predominantly Jewish population with strong cultural ties to Judea. Though the Gospel of Thomas has figured prominently in much recent historical Jesus research, Root's evaluation of it finds few sayings that shed much light on Galilee's cultural ethos. …

Evaluation of hypothetical 153Gd source for use in brachytherapy

AimThe purpose of this work is to evaluate the dosimetric parameters of a hypothetical 153Gd source for use in brachytherapy and comparison of the dosimetric parameters with those of 192Ir and 125I sources. Materials and methodsDose rate constant, the radial dose function and the two dimensional (2D) anisotropy function data for the hypothetical 153Gd source were obtained by simulation of the source using MCNPX code and then were compared with the corresponding data reported by Enger et al. A comprehensive comparison between this hypothetical source and a 192Ir source with similar geometry and a 125I source was performed as well. ResultsExcellent agreement was shown between the results of the two studies. Dose rate constant values for the hypothetical 153Gd, 192Ir, 125I sources are 1.173cGyh−1U−1, 1.044cGyh−1U−1, 0.925cGyh−1U−1, respectively. Radial dose function for the hypothetical 153Gd source has an increasing trend, while 192Ir has more uniform and 125I has more rapidly falling off radial dose functions. 2D anisotropy functions for these three sources indicate that, except at 0.5cm distance, 192Ir and 125I have more isotropic trends as compared to the 153Gd source. ConclusionA more uniform radial dose function, and 2D anisotropy functions with more isotropy, a much higher specific activity are advantages of 192Ir source over 153Gd. However, a longer half-life of 153Gd source compared to the other two sources, and lower energy of the source with respect to 192Ir are advantages of using 153Gd in brachytherapy versus 192Ir source.

Examining single-source secondary impacts estimated from brute-force, decoupled direct method, and advanced plume treatment approaches

In regulatory assessments, there is a need for reliable estimates of the impacts of precursor emissions from individual sources on secondary PM2.5 (particulate matter with aerodynamic diameter less than 2.5 microns) and ozone. Three potential methods for estimating these impacts using Eulerian grid photochemical models are the brute-force (B–F) method, the decoupled direct method (DDM), and advanced plume treatment (APT). Here, we systematically inter-compare and assess the B–F, DDM, and APT approaches using hypothetical sources in a consistent modeling platform for a wide range of source conditions (i.e., emissions amount and composition, location within two California air basins, and stack parameters). The impacts of NOx and VOC sources on ozone and SO2 sources on PM2.5 sulfate calculated by these methods are in general agreement. The agreement is evident in the similar magnitudes, spatial patterns, and strong correlations among the impacts. This result, along with previous model evaluations based on similar Eulerian grid modeling, builds confidence in the reliability of the impact estimates. Disagreement among methods is evident in calculations of PM2.5 nitrate impacts associated with NH3 and NOx sources. Numerical instabilities in DDM sensitivity calculations compromise the nitrate impact estimates from that approach. The B–F and APT methods, which use brute-force differencing to identify impacts, are affected by numerical artifacts to a lesser degree than (H)DDM, with the artifacts being more prominent for APT than B–F. Overall, our results indicate that the (H)DDM, B–F, and APT approaches are viable for use in estimating single-source impacts for ozone and secondary PM2.5 sulfate, while the B–F method appears to be the most reliable for estimating nitrate impacts. There is a need for additional field study measurements to better constrain model estimates of single-source secondary impacts.

Linking Europa’s plume activity to tides, tectonics, and liquid water

Much of the geologic activity preserved on Europa’s icy surface has been attributed to tidal deformation, mainly due to Europa’s eccentric orbit. Although the surface is geologically young (30–80Myr), there is little information as to whether tidally-driven surface processes are ongoing. However, a recent detection of water vapor near Europa’s south pole suggests that it may be geologically active. Initial observations indicated that Europa’s plume eruptions are time-variable and may be linked to its tidal cycle. Saturn’s moon, Enceladus, which shares many similar traits with Europa, displays tidally-modulated plume eruptions, which bolstered this interpretation. However, additional observations of Europa at the same time in its orbit failed to yield a plume detection, casting doubt on the tidal control hypothesis. The purpose of this study is to analyze the timing of plume eruptions within the context of Europa’s tidal cycle to determine whether such a link exists and examine the inferred similarities and differences between plume activity on Europa and Enceladus. To do this, we determine the locations and orientations of hypothetical tidally-driven fractures that best match the temporal variability of the plumes observed at Europa. Specifically, we identify model faults that are in tension at the time in Europa’s orbit when a plume was detected and in compression at times when the plume was not detected. We find that tidal stress driven solely by eccentricity is incompatible with the observations unless additional mechanisms are controlling the eruption timing or restricting the longevity of the plumes. The addition of obliquity tides, and corresponding precession of the spin pole, can generate a number of model faults that are consistent with the pattern of plume detections. The locations and orientations of these hypothetical source fractures are robust across a broad range of precession rates and spin pole directions. Analysis of the stress variations across the fractures suggests that the plumes would be best observed earlier in the orbit (true anomaly ∼120°). Our results indicate that Europa’s plumes, if confirmed, differ in many respects from the Enceladean plumes and that either active fractures or volatile sources are rare.

Evaluation of (101)Rh as a brachytherapy source.

PurposeRecently a number of hypothetical sources have been proposed and evaluated for use in brachytherapy. In the present study, a hypothetical 101Rh source with mean photon energy of 121.5 keV and half-life of 3.3 years, has been evaluated as an alternative to the existing high-dose-rate (HDR) sources. Dosimetric characteristics of this source model have been determined following the recommendation of the Task Group 43 (TG-43) of the American Association of the Physicist in Medicine (AAPM), and the results are compared with the published data for 57Co source and Flexisource 192Ir sources with similar geometries.Material and methodsMCNPX Monte Carlo code was used for simulation of the 101Rh hypothetical HDR source design. Geometric design of this hypothetical source was considered to be similar to that of Flexisource 192Ir source. Task group No. 43 dosimetric parameters, including air kerma strength per mCi, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated for the 101Rh source through simulations.ResultsAir kerma strength per activity and dose rate constant for the hypothetical 101Rh source were 1.09 ± 0.01 U/mCi and 1.18 ± 0.08 cGy/(h.U), respectively. At distances beyond 1.0 cm in phantom, radial dose function for the hypothetical 101Rh source is higher than that of 192Ir. It has also similar 2D anisotropy functions to the Flexisource 192Ir source.Conclusions101Rh is proposed as an alternative to the existing HDR sources for use in brachytherapy. This source provides medium energy photons, relatively long half-life, higher dose rate constant and radial dose function, and similar 2D anisotropy function to the Flexisource 192Ir HDR source design. The longer half-life of the source reduces the frequency of the source exchange for the clinical environment.

Study and development of digital signal processor based real-time simulation platform for photovoltaic system with buck converter for maximum power tracking

This paper discusses the development of real-time simulation platform using digital signal processor (DSP) for photovoltaic (PV) system to study maximum power tracking algorithms in the laboratory. In this paper, PV module is simulated and deployed in TMS320F28335 to emulate the characteristics of PV at different temperature and irradiation with two DC voltage source. Further, maximum power point tracking (MPPT) of PV module with statistical method is developed. In order to evaluate the performance of the proposed MPPT control algorithm, the authors propose a real-time PV simulation system consisting of a PV module with a buck converter using a DSP and two DC voltage source to emulate the temperature and irradiation. Further, the proposed statistical MPPT is compared with the performance of the existing perturb and observe MPPT algorithm. Also, the performance of MPPT algorithms is tested with PV and a buck converter at different temperature and irradiation using hypothetical source. This scheme is validated with that of standard conditions given on the PV data sheet. This work may enable more researchers to study the integration of renewable energy sources and power electronics circuits at a low-cost without damaging the system.

Sediment Sources and Transport Pathway Identification Based on Grain-Size Distributions on the SW Coast of Portugal

Espichel-Sines is an embayed coast in SW Portugal, consisting of two capes at both extremities, a tidal inlet and associated ebb tidal delta, a barrier spit, sandy beaches, sea cliffs, and a submarine canyon. Beach berm, backshore, near shore and inner shelf sediment samples were taken. Samples were analyzed for their grain-size compositions. This study ranks the hypothetical sediment sources influences on the sediment distributions in the study area using the multivariate Empirical Orthogonal Function (EOF) techniques. Transport pathways in this study were independently identified using the grain size trend analysis (GSTA) technique to verify the EOF findings. The results show that the cliff-erosion sediment is composed of pebbles and sand and is the most important sediment source for the entire embayment. The sediment at the inlet mouth is a mixture of pebbles, sand, silt, and clay, which is a minor sediment source that only has local influence. The overall grain-size distributions on the shelf are dominated by the sand except for the high mud content around the tidal delta front in the northern embayment. Sediment transport patterns on the inner shelf at the landward and north sides of the canyon head are landward and northward along the barrier spit, respectively. On the south side of the canyon head, the prevailing sediment transport is seaward. Sediment transport occurs in both directions along the shore.

A projection-based approach to diffraction tomography on curved boundaries

An approach to diffraction tomography is investigated for two-dimensional image reconstruction of objects surrounded by an arbitrarily-shaped curve of sources and receivers. Based on the integral theorem of Helmholtz and Kirchhoff, the approach relies upon a valid choice of the Green’s functions for selected conditions along the (possibly-irregular) boundary. This allows field projections from the receivers to an arbitrary external location. When performed over all source locations, it will be shown that the field caused by a hypothetical source at this external location is also known along the boundary. This field can then be projected to new external points that may serve as a virtual receiver. Under such a reformation, data may be put in a form suitable for image construction by synthetic aperture methods. Foundations of the approach are shown, followed by a mapping technique optimized for the approach. Examples formed from synthetic data are provided.

Paleohydrology of Eberswalde crater, Mars

Eberswalde crater, Mars, contains a well-preserved fluvial distributary network in a likely deltaic setting. The meandering inverted paleochannels and closed drainage basin of this deposit support relatively well constrained estimates of channel-forming discharge (over an individual event flood timescale), runoff production (event and annual timescales), and longevity of deposition (geologic timescale) during the Late Hesperian to Early Amazonian Epochs. The width and meander dimensions of two inverted paleochannels reflect the channel-forming discharge from event floods (~200 to 400m3/s), the deposit surface indicates the level (−1400 to −1350m) and surface area (410 to 810km2) of the likely paleolake, and the topography and mapped extent of tributaries constrain the watershed area (5000 to 17,000km2). Based on these results and terrestrial empirical constraints on evaporation and sediment concentration, we evaluated three hypothetical water sources: meltwater liberated by the nearby Holden crater impact (continuous deposition over ~101–102years), intermittent rainfall or snowmelt during finite periods controlled by orbital evolution (deposition over ~104–106years), and highly infrequent runoff or melting of accumulated snowpacks following distant impacts or secular changes in orbital parameters. Local impact-generated runoff and highly infrequent rainfall or snowmelt require unreasonably high and low rates of evaporation, respectively, to maintain the paleolake level. The local impact hypothesis alternatively depends on one flooding episode with very high concentrations of fluvial sediment that are inconsistent with morphologic considerations. Multiple primary impact craters in the area postdate Holden ejecta but were later dissected, indicating fluvial erosion long after the Holden impact. Intermittent rainfall of ~1cm/day and seasonal snowmelt are both consistent with our results over a deposition timescale totaling ~104–106years.

A Genome-Wide Study of Modern-Day Tuscans: Revisiting Herodotus's Theory on the Origin of the Etruscans

BackgroundThe origin of the Etruscan civilization (Etruria, Central Italy) is a long-standing subject of debate among scholars from different disciplines. The bulk of the information has been reconstructed from ancient texts and archaeological findings and, in the last few years, through the analysis of uniparental genetic markers.MethodsBy meta-analyzing genome-wide data from The 1000 Genomes Project and the literature, we were able to compare the genomic patterns (>540,000 SNPs) of present day Tuscans (N = 98) with other population groups from the main hypothetical source populations, namely, Europe and the Middle East.ResultsAdmixture analysis indicates the presence of 25–34% of Middle Eastern component in modern Tuscans. Different analyses have been carried out using identity-by-state (IBS) values and genetic distances point to Eastern Anatolia/Southern Caucasus as the most likely geographic origin of the main Middle Eastern genetic component observed in the genome of modern Tuscans.ConclusionsThe data indicate that the admixture event between local Tuscans and Middle Easterners could have occurred in Central Italy about 2,600–3,100 years ago (y.a.). On the whole, the results validate the theory of the ancient historian Herodotus on the origin of Etruscans.

Phylogeographic Reconstructions of a Rift Valley Fever Virus Strain Reveals Transboundary Animal Movements from Eastern Continental Africa to the Union of the Comoros.

Major explosive outbreaks of Rift Valley fever (RVF), an arthropod borne zoonotic disease, occur in humans and animals with significant mortality and economic impact across continental Africa and the Indian Ocean region (Madagascar, the Comoros archipelago). Recently, sporadic human cases have been reported in Mayotte and Grande Comore, two islands belonging to the Comoros archipelago. To identify the hypothetical source of virus introduction in an inter-epidemic or a post-epidemic period, a longitudinal survey of livestock was set up in Comorian ruminant populations, known to be susceptible hosts. The phylogeographic genomic analysis has shown that RVF virus (RVFV) detected in a zebu collected in Anjouan in August 2011 seems to be related to the last known epidemic of RVF which occurred in East Africa and Madagascar (2007-2009). This result highlights the fact that RVFV is maintained within local livestock populations and transboundary animal movements from eastern continental Africa to Indian Ocean islands likely result in RVFV crossover.

Limitations of the TG‐43 formalism for skin high‐dose‐rate brachytherapy dose calculations

In skin high-dose-rate (HDR) brachytherapy, sources are located outside, in contact with, or implanted at some depth below the skin surface. Most treatment planning systems use the TG-43 formalism, which is based on single-source dose superposition within an infinite water medium without accounting for the true geometry in which conditions for scattered radiation are altered by the presence of air. The purpose of this study is to evaluate the dosimetric limitations of the TG-43 formalism in HDR skin brachytherapy and the potential clinical impact. Dose rate distributions of typical configurations used in skin brachytherapy were obtained: a 5 cm × 5 cm superficial mould; a source inside a catheter located at the skin surface with and without backscatter bolus; and a typical interstitial implant consisting of an HDR source in a catheter located at a depth of 0.5 cm. Commercially available HDR(60)Co and (192)Ir sources and a hypothetical (169)Yb source were considered. The Geant4 Monte Carlo radiation transport code was used to estimate dose rate distributions for the configurations considered. These results were then compared to those obtained with the TG-43 dose calculation formalism. In particular, the influence of adding bolus material over the implant was studied. For a 5 cm × 5 cm(192)Ir superficial mould and 0.5 cm prescription depth, dose differences in comparison to the TG-43 method were about -3%. When the source was positioned at the skin surface, dose differences were smaller than -1% for (60)Co and (192)Ir, yet -3% for (169)Yb. For the interstitial implant, dose differences at the skin surface were -7% for (60)Co, -0.6% for (192)Ir, and -2.5% for (169)Yb. This study indicates the following: (i) for the superficial mould, no bolus is needed; (ii) when the source is in contact with the skin surface, no bolus is needed for either (60)Co and (192)Ir. For lower energy radionuclides like (169)Yb, bolus may be needed; and (iii) for the interstitial case, at least a 0.1 cm bolus is advised for (60)Co to avoid underdosing superficial target layers. For (192)Ir and (169)Yb, no bolus is needed. For those cases where no bolus is needed, its use might be detrimental as the lack of radiation scatter may be beneficial to the patient, although the 2% tolerance for dose calculation accuracy recommended in the AAPM TG-56 report is not fulfilled.

The Semantics of Words Comprising Phraseological Structures – the Observations of Polish Corpus of Wrocław University of Technology Editor

The aim of the article is to present several problems encountered by the editor compiling the Corpus of Wroclaw University of Technology. The problems are connected with the application of the method of disambiguation of meanings of words in text (WSD – Word Sense Disambiguation) during the work on material of phraseological character. Any researcher using this method confronts the problem of the lack of semantic independence of words entering into the composition of fixed word combinations. The necessity to develop a unique procedure of conduct for this type of words, inclined the author of the article to experiment in the isolation of independent meanings of words co-forming phraseologisms and to make an attempt at their typologization. The isolation of such meanings has proved possible, although the accuracy of their description is very unstable: in some cases the motivation of semantic changes—which the meaning of a word undergoes under the influence of “being petrified” in a set phrase—is transparent, in other cases, however, we can speak of a hypothetical source of changes rather than a definite modification of meaning. It is worth mentioning here about the rigour imposed by the adopted WSD marking method: a set of all meanings which a given word form may assume in the analysed text must be entered into the database. That is why the problem of providing the definition of words forming phraseologisms is vital from the point of view of a linguist dealing with machine processing of language.

KURT 환경 자료를 이용한 가상의 다중 발생원에서의 누출 핵종의 이동 시간 평가

KURT(KAERI Underground Research Tunnel) 부지 부근에 가상의 처분장을 설정하고, 해당 부지의 세 지점에서 방사성폐기물로부터 누출된다고 가정한 방사성 핵종의 이동 시간을 계산하였다. 핵종의 이동 경로는 핵종 누출 지점에서 천부 지하수대까지로 설정하고 KURT 주변 지하수 유동계 모의를 통해 결정하였다. 세 지점은 지하수가 빠르게 유동하는 구조(highly water-conductive feature)를 지나가기 때문에 천부 지하수까지 도달하는데 상대적으로 적은 시간이 걸리는 지점으로 선정되었다. 핵종의 이동 시간은 TDRW(Time-Domain Random Walk) 기법을 통해 계산하였다. 지하수 내의 핵종의 이동 시간을 계산하기 위해, 이류(advection)와 분산(dispersion) 이외에 암반 기질(rock matrix)로의 확산(diffusion)과 기질 내부에서의 흡착(sorption)이 고려되었고, 핵종의 붕괴 및 변환에 의한 영향도 몇 개의 붕괴 사슬(decay chain)을 이용하여 계산에 반영하였다. 계산 결과를 보면, 지표 부근의 천부 지하수에 도달하는 핵종의 시간당 이동량(mass flux)은 복수의 이동 경로뿐만 아니라 핵종의 반감기와 암반 기질 내에서의 핵종의 흡착 분배 계수에 크게 영향을 받는 것으로 나타났다. 따라서 보다 안정적이고 불확실성이 감소된 심지층 처분장의 안전성 평가를 위해 우선적으로 필요한 사항으로는, 장반감기 핵종에 대한 평가가 이동 과정 이외에 저장 용기에 들어있는 상태에서부터 면밀하게 이루어져야 하고, 암반 기질에서 발생하는 핵종의 흡착 과정이 심부 현장 조건을 반영하여 평가되어야 할 것으로 생각된다. A hypothetical repository was assumed to be located at the KURT (KAERI Underground Research Tunnel) site, and the travel times of radionuclides released from three source positions were calculated. The groundwater flow around the KURT site was simulated and the groundwater pathways from the hypothetical source positions to the shallow groundwater were identified. Of the pathways, three pathways were selected because they had highly water-conductive features. The transport travel times of the radionuclides were calculated by a TDRW (Time-Domain Random Walk) method. Diffusion and sorption mechanisms in a host rock matrix as well as advection-dispersion mechanisms under the KURT field condition were considered. To reflect the radioactive decay, four decay chains with the radionuclides included in the high-level radioactive wastes were selected. From the simulation results, the half-life and distribution coefficient in the rock matrix, as well as multiple pathways, had an influence on the mass flux of the radionuclides. For enhancing the reliability of safety assessment, this reveals that identifying the history of the radionuclides contained in the high-level wastes and investigating the sorption processes between the radionuclides and the rock matrix in the field condition are preferentially necessary.

Tsunami hazard assessment of Canada

We present a preliminary probabilistic tsunami hazard assessment of Canadian coastlines from local and far-field, earthquake, and large submarine landslide sources. Analyses involve published historical, palaeotsunami and palaeoseismic data, modelling, and empirical relations between fault area, earthquake magnitude, and tsunami run-up. The cumulative estimated tsunami hazard for potentially damaging run-up (≥1.5 m) of the outer Pacific coastline is ~40–80 % in 50 years, respectively one and two orders of magnitude greater than the outer Atlantic (~1–15 %) and the Arctic (<1 %). For larger run-up with significant damage potential (≥3 m), Pacific hazard is ~10–30 % in 50 years, again much larger than both the Atlantic (~1–5 %) and Arctic (<1 %). For outer Pacific coastlines, the ≥1.5 m run-up hazard is dominated by far-field subduction zones, but the probability of run-up ≥3 m is highest for local megathrust sources, particularly the Cascadia subduction zone; thrust sources further north are also significant, as illustrated by the 2012 Haida Gwaii event. For Juan de Fuca and Georgia Straits, the Cascadia megathrust dominates the hazard at both levels. Tsunami hazard on the Atlantic coastline is dominated by poorly constrained far-field subduction sources; a lesser hazard is posed by near-field continental slope failures similar to the 1929 Grand Banks event. Tsunami hazard on the Arctic coastline is poorly constrained, but is likely dominated by continental slope failures; a hypothetical earthquake source beneath the Mackenzie delta requires further study. We highlight areas susceptible to locally damaging landslide-generated tsunamis, but do not quantify the hazard.

Photon activation therapy: a Monte Carlo study on dose enhancement by various sources and activation media

In the present study, a number of brachytherapy sources and activation media were simulated using MCNPX code and the results were analyzed based on the dose enhancement factor values. Furthermore, two new brachytherapy sources (¹³¹Cs and a hypothetical ¹⁷⁰Tm) were evaluated for their application in photon activation therapy (PAT). ¹²⁵I, ¹⁰³Pd, ¹³¹Cs and hypothetical ¹⁷⁰Tm brachytherapy sources were simulated in water and their dose rate constant and the radial dose functions were compared with previously published data. The sources were then simulated in a soft tissue phantom which was composed of Ag, I, Pt or Au as activation media uniformly distributed in the tumour volume. These simulations were performed using the MCNPX code, and dose enhancement factor (DEF) was obtained for 7, 18 and 30 mg/ml concentrations of the activation media. Each source, activation medium and concentration was evaluated separately in a separate simulation. The calculated dose rate constant and radial dose functions were in agreement with the published data for the aforementioned sources. The maximum DEF was found to be 5.58 for a combination of the ¹⁷⁰Tm source with 30 mg/ml concentration of I. The DEFs for ¹³¹Cs and ¹⁷⁰Tm sources for all the four activation media were higher than those for other sources and activation media. From this point of view, these two sources can be more useful in photon activation therapy with photon emitter sources. Furthermore, ¹³¹Cs and ¹⁷⁰Tm brachytherapy sources can be proposed as new options for use in the field of PAT.

Late Cenozoic magmatic transitions in the central Great Xing'an Range, Northeast China: Geochemical and isotopic constraints on petrogenesis

The Wuchagou and Halaha volcanic fields are located in the central Great Xing'an Range, Northeast China, cover an area of ~1400km2 in China, and continue westward into Mongolia. These regions provide an important opportunity to study temporal changes in magma source regions accompanying the evolution of geodynamic-processes. Late Miocene (10.5–8.0Ma) volcanic rocks from the Wuchagou volcanic field are composed of basaltic andesite and andesite. The characteristics of these rocks include a high concentration of Si (SiO2=55.7–59.2wt.%), a pronounced negative Nb―Ta anomaly, and a slightly LREE enriched pattern with (La/Yb)N ratios varying from 2.1 to 6.9. They have Sr and Nd isotopic compositions indicative of long-term incompatible element enrichment (87Sr/86Sr=0.7053–0.7067, 143Nd/144Nd=0.5118 to 0.5122), with a trend toward the EM1 component. Their isotopic compositions can also be described as Dupal-like, but with less-radiogenic Pb isotopic ratios (206Pb/204Pb=16.99–17.83, 207Pb/204Pb=15.46–15.52, 208Pb/204Pb=37.42–37.91). Quaternary (2.0Ma to Holocene) lavas from the Halaha volcanic field consist of alkali olivine basalt and olivine tholeiite, which show alkalic affinities and are characterised by ocean island basalt-like REE and trace element patterns, typical of an intraplate sodic basalt composition. The low 87Sr/86Sr (0.7034–0.7041), high 143Nd/144Nd (0.5128 to 0.5130), and moderately radiogenic 206Pb/204Pb (18.39–18.55), 207Pb/204Pb (15.54–5.55), and 208Pb/204Pb (38.32–38.47) ratios are similar to those of most late Cenozoic basalts of South China and the Abaga region, Inner Mongolia. The different melt compositions between the volcanic rocks of the two volcanic fields are most likely due to changes in geodynamic processes and magma sources. A possible scenario for the genesis of these volcanic rocks is that Wuchagou andesitic magma formed by high degrees of partial melting of the subcontinental lithospheric mantle with some lower-crust contamination as a result of the thermal reactivation of the continental lithosphere by shallow-level rifting following the cessation of the Japan Sea opening. During the Quaternary, extensive volcanism resumed, with eruptions along deep rifting systems in the Halaha volcanic field, which might have been related to the geodynamic forcing of the continuous piling up and upward thickening of the stagnant subducted Pacific slab beneath Northeast China. Basaltic magmas of this stage were primarily produced by melting of convecting asthenosphere. Using the batch melting of a hypothetical LREE-enriched mantle source in the garnet stability field proposed by Xu et al. (2005), we estimated that the Halaha basalts could be generated from 9 to 14% of partial melting of garnet peridotites.