Radiation hardness testing of an organic liquid scintillator detector for use in high dose rate accident response scenarios

Organic liquid scintillation detectors offer the advantage relative to many alternatives that they are sensitive to both fast neutrons and gamma rays, whilst radiation type can be discerned on the basis of pulse-shape discrimination. Mixed radiation fields of this type can arise in the context of reactor accidents via, for example, 137Cs (gamma) and 244Cm (neutrons). However, performance degradation of such scintillators, such as EJ-301, is a significant possibility that might limit the use of this technology in accident response applications. The premise behind the high dose rate testing of such a liquid scintillator described in this paper is for fuel debris characterisation at Fukushima Daiichi, which has expected dose rates of up to 1000 Gy/hr in close proximity to fuel debris. The tests carried out for this investigation involved using the 60Co gamma irradiation facility at the Dalton Cumbria Facility, Cumbria, United Kingdom to expose the detector to a similar dose rate to that which is estimated within the primary containment vessel for survivability tests. Radiation hardness tests have rarely been reported for such devices and it is expected that the performance will be dependent on the survival of the window of the photomultiplier tube rather than the liquid scintillant itself. A major advantage of the use of this detector is its physical size, due to the limitations on access into Fukushima reactors physical space is a premium. The research described in this paper presents the results of the dose rate exposure of the detector before signal was lost with the total dose observed providing information on any degradation affecting the performance of the device post-irradiatio

Predictive importance of left ventricular myocardial stiffness for the prognosis of patients with congestive heart failure

SummaryObjectivesThis study was designed to determine the prognostic importance of left ventricular (LV) myocardial stiffness, a hemodynamic index which is closely related to B-type natriuretic peptide (BNP) concentration in patients with congestive heart failure (CHF).BackgroundWhile elevated BNP, an abnormality of cardiac neurohormones, is known to be an independent marker of death or re-admission, it remains to be clarified whether there is also a strong predictor directly related to cardiac dysfunction.MethodsLV performance variables and stress–strain analyses including diastolic myocardial stiffness constant (Km) were obtained from 37 patients with initial CHF by the combined simultaneous measurement of echocardiographic and hemodynamic data. Survivors were monitored for a mean of 23 months, with the main endpoint being combined death or first re-admission for CHF.ResultsTen patients (27%) were primary endpoint cases. Both Km and plasma BNP levels were higher in the event than in the event-free group. By Cox proportional hazards analysis, Km≥4.0 was identified as the only variable with significant and independently incremental predictive power to affect the primary endpoint (adjusted hazard ratio=7.354, 95% confidence interval 1.379–39.232, p=0.02).ConclusionsIn patients with CHF, increased myocardial stiffness may have greater prognostic significance compared to other conventional predictors. Increased myocardial stiffness may be considered to be an important prognostic factor independent of the loading conditions

A Wide Symbiotic Channel to Type Ia Supernovae

As a promising channel to Type Ia supernovae (SNe Ia), we have proposed a symbiotic binary system consisting of a white dwarf (WD) and a low mass red-giant (RG), where strong winds from the accreting WD play a key role to increase the WD mass to the Chandrasekhar mass limit. Here we propose two new evolutionary processes which make the symbiotic channel to SNe Ia much wider. (1) We first show that the WD + RG close binary can form from a wide binary even with such a large initial separation as $a_i \lesssim 40000 R_\odot$. Such a binary consists of an AGB star and a low mass main-sequence (MS) star, where the AGB star is undergoing superwind before becoming a WD. If the superwind at the end of AGB evolution is as fast as or slower than the orbital velocity, the wind outflowing from the system takes away the orbital angular momentum effectively. As a result the wide binary shrinks greatly to become a close binary. Therefore, the WD + RG binary can form from much wider binaries than our earlier estimate. (2) When the RG fills its inner critical Roche lobe, the WD undergoes rapid mass accretion and blows a strong optically thick wind. Our earlier analysis has shown that the mass transfer is stabilized by this wind only when the mass ratio of RG/WD is smaller than 1.15. Our new finding is that the WD wind can strip mass from the RG envelope, which could be efficient enough to stabilize the mass transfer even if the RG/WD mass ratio exceeds 1.15. With the above two new effects (1) and (2), the symbiotic channel can account for the inferred rate of SNe Ia in our Galaxy.Comment: 29 pages including 14 firgures, to be published in ApJ, 521, No.

On the design of a remotely-deployed detection system for reactor assessment at Fukushima Daiichi

The premise behind this research is the design of a system that will allow fuel debris characterisation at Fukushima Daiichi. The precise location of the debris is not known for example as to whether it remains within the reactor pressure vessel or it has leaked through into the base of the pedestal below, additionally the state of the fuel is also in question as to whether this has corroded from within its encasing or if it is intact. The most likely scenario is a combination of all four of these situations. The flooding of the reactor floors immediately following the Fukushima accident adds an extra element of complexity for the detection system requiring it to be submersible and to hold any detector system in water tight confinement. The research carried out has involved extensive modifications to a previously-designed low-cost small-scale AVEXIS submersible inspection vehicle and the incorporation of a variety of radiation detectors. The latter has been designed to allow for mapping and determination of the situation that is present within the primary containment vessels. The challenges addressed with the detection system arise from the high dose rates that have been recorded around the reactor pressure vessels which can be as high as 1000 Gy/hr. In such a harsh environment not only will the radiation detectors struggle to operate but the components that make up the remote-operated vehicle are also likely to suffer radiation damage after only a relatively short period of time. The research presented here evaluates the components currently incorporated into the AVEXIS system in terms of their radiation tolerability as well as presenting the combination of detectors to be used in the remote probe for the investigation of the fuel debris

Lineage analysis of early and advanced tubular adenocarcinomas of the stomach: continuous or discontinuous?

<p>Abstract</p> <p>Background</p> <p>Eradication of early gastric carcinoma (GC) is thought to contribute to reduction in the mortality of GC, given that most of the early GCs progress to the advanced GCs. However, early GC is alternatively considered a dormant variant of GC, and it infrequently progresses to advanced GC. The aim of this study was to clarify the extent of overlap of genetic lineages between early and advanced tubular adenocarcinomas (TUBs) of the stomach.</p> <p>Methods</p> <p>Immunohistochemical staining for p53 was performed using 28 surgically resected stomachs with 13 intramucosal and 15 invasive TUBs. By chromosome- and array-based comparative genomic hybridization (CGH), genomic copy number constitution was compared between the mucosal and invasive parts of the invasive TUBs and between the mucosal parts of the invasive and intramucosal TUBs, using 25 and 22 TUBs, respectively. <it>TP53 </it>mutation in exons 5-8 was examined in 20 TUBs.</p> <p>Results</p> <p>Chromosomal CGH revealed that 4q+ and 11q+ were more common in advanced and early TUBs, respectively, whereas copy number changes in 8q and 17p showed no significant differences between early and advanced TUBs. However, array CGH revealed that, of the 13 intramucosal TUBs examined, loss of <it>MYC </it>(<it>MYC</it>-) and gain of <it>TP53 </it>(<it>TP53</it>+) was detected in 9 TUBs and <it>MYC</it>+ and/or <it>TP53</it>- was detected in 3 TUBs. Of the mucosal samples of 9 invasive TUBs, 7 showed <it>MYC</it>-/<it>TP53</it>+ and none showed <it>MYC</it>+ and/or <it>TP53</it>-. Of the 9 samples from the invasive parts, 1 (from submucosal cancers) showed <it>MYC</it>-/<it>TP53</it>+ and 6 (1 from submucosal and 5 from advanced cancers) showed <it>MYC</it>+ and/or <it>TP53</it>-. The latter 6 tumours commonly showed a mutant pattern (diffuse or null) in p53 immunohistochemistry, and 4 of the 6 tumours assessable for <it>TP53 </it>sequence analysis revealed mutations. The overall array CGH pattern indicated that, between the mucosal and invasive parts, genetic lineage was found discontinuous in 5 advanced cancers and continuous in 3 submucosal cancers.</p> <p>Conclusions</p> <p>Genetic lineages often differed between early and advanced TUBs. <it>MYC</it>-/<it>TP53</it>+ and <it>MYC </it>+ and/or <it>TP53</it>- may be the signatures of dormant and aggressive TUBs, respectively, in the stomach.</p