Monitoring of the operating parameters of the KATRIN Windowless Gaseous Tritium Source

The Karlsruhe Tritium Neutrino (KATRIN) experiment will measure the absolute mass scale of neutrinos with a sensitivity of \m_{\nu} = 200 meV/c$^2$ by high-precision spectroscopy close to the tritium beta-decay endpoint at 18.6 keV. Its Windowless Gaseous Tritium Source (WGTS) is a beta-decay source of high intensity ($10^{11}$/s) and stability, where high-purity molecular tritium at 30 K is circulated in a closed loop with a yearly throughput of 10 kg. To limit systematic effects the column density of the source has to be stabilised at the 0.1% level. This requires extensive sensor instrumentation and dedicated control and monitoring systems for parameters such as the beam tube temperature, injection pressure, gas composition and others. Here we give an overview of these systems including a dedicated Laser-Raman system as well as several beta-decay activity monitors. We also report on results of the WGTS demonstrator and other large-scale test experiments giving proof-of-principle that all parameters relevant to the systematics can be controlled and monitored on the 0.1% level or better. As a result of these works, the WGTS systematics can be controlled within stringent margins, enabling the KATRIN experiment to explore the neutrino mass scale with the design sensitivity.Comment: 32 pages, 13 figures. modification to title, typos correcte

Blooming Artifact Reduction in Coronary Artery Calcification by A New De-blooming Algorithm: Initial Study

The aim of this study was to investigate the use of de-blooming algorithm in coronary CT angiography (CCTA) for optimal evaluation of calcified plaques. Calcified plaques were simulated on a coronary vessel phantom and a cardiac motion phantom. Two convolution kernels, standard (STND) and high-definition standard (HD STND), were used for imaging reconstruction. A dedicated de-blooming algorithm was used for imaging processing. We found a smaller bias towards measurement of stenosis using the deblooming algorithm (STND: bias 24.6% vs 15.0%, range 10.2% to 39.0% vs 4.0% to 25.9%; HD STND: bias 17.9% vs 11.0%, range 8.9% to 30.6% vs 0.5% to 21.5%). With use of de-blooming algorithm, specificity for diagnosing significant stenosis increased from 45.8% to 75.0% (STND), from 62.5% to 83.3% (HD STND); while positive predictive value (PPV) increased from 69.8% to 83.3% (STND), from 76.9% to 88.2% (HD STND). In the patient group, reduction in calcification volume was 48.1 ± 10.3%, reduction in coronary diameter stenosis over calcified plaque was 52.4 ± 24.2%. Our results suggest that the novel de-blooming algorithm could effectively decrease the blooming artifacts caused by coronary calcified plaques, and consequently improve diagnostic accuracy of CCTA in assessing coronary stenosis

Diagnostic value of non-invasive imaging techniques in the detection of carotid artery stenosis: a systematic review

The purpose of the study was to evaluate the diagnostic performance of non- invasive imaging methods of detecting carotid artery stenosis in comparison to digital subtraction angiography (DSA) by undertaking a systematic review of the literature. The non-invasive methods reviewed include multislice computed tomography (MSCT) angiography, duplex ultrasound (US) and magnetic resonance (MR) angiography.A search of medical databases (PubMed, Medline, ScienceDirect, Proquest) of the English literature was performed and 22 studies with 68 comparisons were found to meet the selection criteria and included in our study. 5 studies were performed with MSCT angiography, 11 with duplex US and 13 with MR angiography. Both duplex US and MR angiography were studied in 7 out of 24 US and MR studies. The diagnostic value of each imaging modality was reviewed in terms of the sensitivity and specificity compared to DSA, which is regarded as the standard method.The mean sensitivity and specificity for MSCT angiography, duplex US and MR angiography were 88% (95% CI: 83%, 92%) and 90% (95% CI: 85%, 94%), 88% (95% CI: 81%, 94%) and 89% (95% CI: 85%, 94%), 94% (95% CI: 90%, 97%) and 89% (95% CI: 85%, 92%), respectively based on overall assessment. The evaluation showed that contrast-enhanced MR angiography has high diagnostic value for detection of more than 50% stenosis of carotid artery stenosis with mean sensitivity and specificity being 95% (95% CI: 92%, 98%) and 91% (95% CI: 86% 95%). When assessment was based on a combination of MR angiography and duplex US, the sensitivity reached the highest value of 98% (95% CI: 96%, 100%). This analysis indicates that MR angiography, especially contrast-enhanced MR angiography could be used as a reliable alternative modality to DSA in the detection of carotid artery stenosis

Low Adiponectin Levels Are an Independent Predictor of Mixed and Non-Calcified Coronary Atherosclerotic Plaques

Atherosclerosis is the primary cause of coronary artery disease (CAD). There is increasing recognition that lesion composition rather than size determines the acute complications of atherosclerotic disease. Low serum adiponectin levels were reported to be associated with coronary artery disease and future incidence of acute coronary syndrome (ACS). The impact of adiponectin on lesion composition still remains to be determined. We measured serum adiponectin levels in 303 patients with stable typical or atypical chest pain, who underwent dual-source multi-slice CT-angiography to exclude coronary artery stenosis. Atherosclerotic plaques were classified as calcified, mixed or non-calcified. In bivariate analysis adiponectin levels were inversely correlated with total coronary plaque burden (r = -0.21, p = 0.0004), mixed (r = -0.20, p = 0.0007) and non-calcified plaques (r = -0.18, p = 0.003). No correlation was seen with calcified plaques (r = -0.05, p = 0.39). In a fully adjusted multivariate model adiponectin levels remained predictive of total plaque burden (estimate: -0.036, 95%CI: -0.052 to -0.020, p<0.0001), mixed (estimate: -0.087, 95%CI: -0.132 to -0.042, p = 0.0001) and non-calcified plaques (estimate: -0.076, 95%CI: -0.115 to -0.038, p = 0.0001). Adiponectin levels were not associated with calcified plaques (estimate: -0.021, 95% CI: -0.043 to -0.001, p = 0.06). Since the majority of coronary plaques was calcified, adiponectin levels account for only 3% of the variability in total plaque number. In contrast, adiponectin accounts for approximately 20% of the variability in mixed and non-calcified plaque burden. Adiponectin levels predict mixed and non-calcified coronary atherosclerotic plaque burden. Low adiponectin levels may contribute to coronary plaque vulnerability and may thus play a role in the pathophysiology of ACS

Is there a role for CT coronary angiography in patients with symptomatic angina? Effect of coronary calcium score on identification of stenosis

Present guidelines discourage the use of CT coronary angiography (CTCA) in symptomatic angina patients. We examined the relation between coronary calcium score (CS) and the performance of CTCA in patients with stable and unstable angina in order to understand under which conditions CTCA might be a gate-keeper to conventional coronary angiography (CCA) in such patients. We included 360 patients between 50 and 70 years old with stable and unstable angina who were clinically referred for CCA irrespective of CS. Patients received CS and CCTA on 64-slice scanners in a multicenter cross-sectional trial. The institutional review board approved the study. Diagnostic performance of CTCA to detect or rule out significant coronary artery disease was calculated on a per patient level in pre-defined CS categories. The prevalence of significant coronary artery disease strongly increased with CS. Negative CTCA were associated with a negative likelihood ratio of <0.1 independent of CS. Positive CTCA was associated with a high positive likelihood ratio of 9.4 if CS was <10. However, for higher CS the positive likelihood ratio never exceeded 3.0 and for CS >400 it decreased to 1.3. In the 62 (17%) patients with CS <10, CTCA reliably identified the 42 (68%) of these patients without significant CAD, at no false negative CTCA scans. In symptomatic angina patients, a negative CTCA reliably excludes significant CAD but the additional value of CTCA decreases sharply with CS >10 and especially with CS >400. In patients with CS <10, CTCA provides excellent diagnostic performance

Top-down contingent feature-specific orienting with and without awareness of the visual input

In the present article, the role of endogenous feature-specific orienting for conscious and unconscious vision is reviewed. We start with an overview of orienting. We proceed with a review of masking research, and the definition of the criteria of experimental protocols that demonstrate endogenous and exogenous orienting, respectively. Against this background of criteria, we assess studies of unconscious orienting and come to the conclusion that so far studies of unconscious orienting demonstrated endogenous feature-specific orienting. The review closes with a discussion of the role of unconscious orienting in action control

Dual-source CT for chest pain assessment

Comprehensive CT angiography protocols offering a simultaneous evaluation of pulmonary embolism, coronary stenoses and aortic disease are gaining attractiveness with recent CT technology. The aim of this study was to assess the diagnostic accuracy of a specific dual-source CT protocol for chest pain assessment. One hundred nine patients suffering from acute chest pain were examined on a dual-source CT scanner with ECG gating at a temporal resolution of 83 ms using a body-weight-adapted contrast material injection regimen. The images were evaluated for the cause of chest pain, and the coronary findings were correlated to invasive coronary angiography in 29 patients (27%). The files of patients with negative CT examinations were reviewed for further diagnoses. Technical limitations were insufficient contrast opacification in six and artifacts from respiration in three patients. The most frequent diagnoses were coronary stenoses, valvular and myocardial disease, pulmonary embolism, aortic aneurysm and dissection. Overall sensitivity for the identification of the cause of chest pain was 98%. Correlation to invasive coronary angiography showed 100% sensitivity and negative predictive value for coronary stenoses. Dual-source CT offers a comprehensive, robust and fast chest pain assessment

Life cycle greenhouse gas emissions of blended cement concrete including carbonation and durability

The final publication is available at Springer via http://dx.doi.org/10.1007/s11367-013-0614-0Purpose Blended cements use waste products to replace Portland cement, the main contributor to CO2 emissions in concrete manufacture. Using blended cements reduces the embodied greenhouse gas emissions; however, little attention has been paid to the reduction in CO2 capture (carbonation) and durability. The aim of this study is to determine if the reduction in production emissions of blended cements compensates for the reduced durability and CO2 capture. Methods This study evaluates CO2 emissions and CO2 capture for a reinforced concrete column during its service life and after demolition and reuse as gravel filling material. Concrete depletion, due to carbonation and the unavoidable steel embedded corrosion, is studied, as this process consequently ends the concrete service life. Carbonation deepens progressively during service life and captures CO2 even after demolition due to the greater exposed surface area. In this study, results are presented as a function of cement replaced by fly ash (FA) and blast furnace slag (BFS). Results and discussion Concrete made with Portland cement, FA (35%FA), and BFS blended cements (80%BFS) captures 47, 41, and 20 % of CO2 emissions, respectively. The service life of blended cements with high amounts of cement replacement, like CEM III/A (50 % BFS), CEM III/B (80 % BFS), and CEMII/B-V (35%FA), was about 10%shorter, given the higher carbonation rate coefficient. Compared to Portland cement and despite the reduced CO2 capture and service life, CEM III/B emitted 20 % less CO2 per year. Conclusions To obtain reliable results in a life cycle assessment, it is crucial to consider carbonation during use and after demolition. Replacing Portland cement with FA, instead of BFS, leads to a lower material emission factor, since FA needs less processing after being collected, and transport distances are usually shorter. However, greater reductions were achieved using BFS, since a larger amount of cement can be replaced. Blended cements emit less CO2 per year during the life cycle of a structure, although a high cement replacement reduces the service life notably. If the demolished concrete is crushed and recycled as gravel filling material, carbonation can cut CO2 emissions by half. A case study is presented in this paper demonstrating how the results may be utilized.This research was financially supported by the Spanish Ministry of Science and Innovation (research project BIA2011-23602). The authors thank the anonymous reviewers for their constructive comments and useful suggestions. 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Q^2 Dependence of the S_{11}(1535) Photocoupling and Evidence for a P-wave resonance in eta electroproduction

New cross sections for the reaction $ep \to e'\eta p$ are reported for total center of mass energy $W$=1.5--2.3 GeV and invariant squared momentum transfer $Q^2$=0.13--3.3 GeV$^2$. This large kinematic range allows extraction of new information about response functions, photocouplings, and $\eta N$ coupling strengths of baryon resonances. A sharp structure is seen at $W\sim$ 1.7 GeV. The shape of the differential cross section is indicative of the presence of a $P$-wave resonance that persists to high $Q^2$. Improved values are derived for the photon coupling amplitude for the $S_{11}$(1535) resonance. The new data greatly expands the $Q^2$ range covered and an interpretation of all data with a consistent parameterization is provided.Comment: 31 pages, 9 figure