Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the time-averaged void distribution in these loops. Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed. In this article, three axially symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm, and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper. Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020, and 0.022 cm(-1), solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful indication on the flow mode, and a visualization of the radial material distribution can be obtained. A benefit of this system is its potential to be mounted at any axial height of a two-phase test section without requirements for pre-fabricated entrances or windows. This could mean a significant increase in flexibility of the void distribution assessment capability at many existing two-phase test loops.

Status and operation of the Linac4 ion source prototypes

CERN's Linac4 45 kV H(-) ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma, and pulsed high voltages are described. The first experimental results of two prototypes relying on 2 MHz RF-plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H(-) beam of 16-22 mA which has successfully been used for the commissioning of the Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ) accelerator, and chopper of Linac4.

Establishing a database of radionuclide transfer parameters for freshwater wildlife

Environmental assessments to evaluate potentials risks to humans and wildlife often involve modelling to predict contaminant exposure through key pathways. Such models require input of parameter values, including concentration ratios, to estimate contaminant concentrations in biota based on measurements or estimates of concentrations in environmental media, such as water. Due to the diversity of species and the range in physicochemical conditions in natural ecosystems, concentration ratios can vary by orders of magnitude, even within similar species. Therefore, to improve model input parameter values for application in aquatic systems, freshwater concentration ratios were collated or calculated from national grey literature, Russian language publications, and refereed papers. Collated data were then input into an international database that is being established by the International Atomic Energy Agency. The freshwater database enables entry of information for all radionuclides listed in ICRP (1983), in addition to the corresponding stable elements, and comprises a total of more than 16,500 concentration ratio (CRwo-water) values. Although data were available for all broad wildlife groups (with the exception of birds), data were sparse for many organism types. For example, zooplankton, crustaceans, insects and insect larvae, amphibians, and mammals, for which there were CRwo-water values for less than eight elements. Coverage was most comprehensive for fish, vascular plants, and molluscs. To our knowledge, the freshwater database that has now been established represents the most comprehensive set of CRwo-water values for freshwater species currently available for use in radiological environmental assessments.

A new approach to predicting environmental transfer of radionuclides to wildlife: a demonstration for freshwater fish and caesium

The application of the concentration ratio (CR) to predict radionuclide activity concentrations in wildlife from those in soil or water has become the widely accepted approach for environmental assessments. Recently both the ICRP and IAEA have produced compilations of CR values for application in environmental assessment. However, the CR approach has many limitations, most notably, that the transfer of most radionuclides is largely determined by site-specific factors (e.g. water or soil chemistry). Furthermore, there are few, if any, CR values for many radionuclide-organism combinations. In this paper, we propose an alternative approach and, as an example, demonstrate and test this for caesium and freshwater fish. Using a Residual Maximum Likelihood (REML) mixed-model regression we analysed a dataset comprising 597 entries for 53 freshwater fish species from 67 sites. The REML analysis generated a mean value for each species on a common scale after REML adjustment taking account of the effect of the inter-site variation. Using an independent dataset, we subsequently test the hypothesis that the REML model outputs can be used to predict radionuclide, in this case radiocaesium, activity concentrations in unknown species from the results of a species which has been sampled at a specific site. The outputs of the REML analysis accurately predicted (137)Cs activity concentrations in different species of fish from 27 Finnish lakes; these data had not been used in our initial analyses. We recommend that this alternative approach be further investigated for other radionuclides and ecosystems.

The IAEA handbook on radionuclide transfer to wildlife

An IAEA handbook presenting transfer parameter values for wildlife has recently been produced. Concentration ratios (CRwo-media) between the whole organism (fresh weight) and either soil (dry weight) or water were collated for a range of wildlife groups (classified taxonomically and by feeding strategy) in terrestrial, freshwater, marine and brackish generic ecosystems. The data have been compiled in an on line database, which will continue to be updated in the future providing the basis for subsequent revision of the Wildlife TRS values. An overview of the compilation and analysis, and discussion of the extent and limitations of the data is presented. Example comparisons of the CRwo-media values are given for polonium across all wildlife groups and ecosystems and for molluscs for all radionuclides. The CRwo-media values have also been compared with those currently used in the ERICA Tool which represented the most complete published database for wildlife transfer values prior to this work. The use of CRwo-media values is a pragmatic approach to predicting radionuclide activity concentrations in wildlife and is similar to that used for screening assessments for the human food chain. The CRwo-media values are most suitable for a screening application where there are several conservative assumptions built into the models which will, to varying extents, compensate for the variable data quality and quantity, and associated uncertainty.

Sequences of multiple bacterial genomes and a Chlamydia trachomatis genotype from direct sequencing of DNA derived from a vaginal swab diagnostic specimen

Ultra-deep Illumina sequencing was performed on whole genome amplified DNA derived from a Chlamydia trachomatis-positive vaginal swab. Alignment of reads with reference genomes allowed robust SNP identification from the C. trachomatis chromosome and plasmid. This revealed that the C. trachomatis in the specimen was very closely related to the sequenced urogenital, serovar F, clade T1 isolate F-SW4. In addition, high genome-wide coverage was obtained for Prevotella melaninogenica, Gardnerella vaginalis, Clostridiales genomosp. BVAB3 and Mycoplasma hominis. This illustrates the potential of metagenome data to provide high resolution bacterial typing data from multiple taxa in a diagnostic specimen.

Correction for dynamic bias error in transmission measurements of void fraction

Dynamic bias errors occur in transmission measurements, such as X-ray, gamma, or neutron radiography or tomography. This is observed when the properties of the object are not stationary in time and its average properties are assessed. The nonlinear measurement response to changes in transmission within the time scale of the measurement implies a bias, which can be difficult to correct for. A typical example is the tomographic or radiographic mapping of void content in dynamic two-phase flow systems. In this work, the dynamic bias error is described and a method to make a first-order correction is derived. A prerequisite for this method is variance estimates of the system dynamics, which can be obtained using high-speed, time-resolved data acquisition. However, in the absence of such acquisition, a priori knowledge might be used to substitute the time resolved data. Using synthetic data, a void fraction measurement case study has been simulated to demonstrate the performance of the suggested method. The transmission length of the radiation in the object under study and the type of fluctuation of the void fraction have been varied. Significant decreases in the dynamic bias error were achieved to the expense of marginal decreases in precision.

The prevalence of atrial fibrillation in a geographically well-defined population in northern Sweden: implications for anticoagulation prophylaxis

OBJECTIVES

The aims of this study were to evaluate the community-based prevalence of atrial fibrillation (AF) in a western society using a geographically well-defined population in the northern part of Sweden as a reference and to estimate the proportion of patients eligible for oral anticoagulation (OAC) prophylactic therapy according to the stroke risk indices CHADS2 and CHA2 DS2 -VASc. Bleeding risk was assessed using the HAS-BLED score.

DESIGN

The study population was recruited from AURICULA, a Swedish national quality register for patients receiving anticoagulation treatment. All patients with the diagnosis AF in the catchment area are registered in AURICULA.

RESULTS

Of the 65 532 inhabitants in the catchment area, 1616 were diagnosed with AF (1200 cases were characterized as chronic AF). Thus, the overall prevalence of AF was 2.5%. The prevalence increased with age from 6.3% in patients over 55 years of age to 13.8% in those over 80 years. The prevalence was higher in men than in women in all age groups. Overall, 56.3% and 85.1% of the population were at high risk of stroke (≥2 points) according to CHADS2 and CHA2 DS2 -VASc, respectively. In addition, 26.9% had an increased bleeding risk according to HAS-BLED.

CONCLUSION

Within this large Caucasian population, we identified the highest community-based prevalence of AF to date. The prevalence was strongly associated with increasing age and male gender. Using CHA2 DS2 -VASc instead of CHADS(2) widened the indication for OAC prophylactic therapy of AF in this population.

Long-term quality of life in patients with permanent sigmoid colostomy

AIM

The study aimed to assess quality of life (QoL) in patients with a sigmoid colostomy using a simple general and disease-specific instrument. A subgroup not doing well was identified and examined further.

METHOD

The Short Health Scale (SHS) is a four-item instrument exploring severity of symptoms, function in daily life, worry, and general well-being, using visual analogue scales ranging from 0 to 100 where 100 is the worst possible situation. The SHS was delivered to 206 patients with a sigmoid colostomy. It was returned by 181 (87.9%) patients [88 men; median age 73 (33-91) years]. Follow-up was 61 (10-484) months for 178 (86.4%) patients returning usable questionnaires. A subgroup of 16 patients scoring more than 50 in all four items of the SHS was further examined with StomaQOL where 100 is best possible.

RESULTS

The median score for severity of symptoms was 18 (2-95), function in daily life 21 (0-95), worry 17 (3-98) and general well-being 22 (0-99). A score of < 50 in the SHS was recorded in 84.9%, 82.1%, 79.9% and 70.5% respectively. In the group scoring more than 50 in all four items patients diagnosed with irritable bowel syndrome constituted 43.8% to compare with 5.6% in the entire study group (P < 0.001). Median score for StomaQOL was 37 (22-62) in this group.

CONCLUSION

Most patients with a permanent sigmoid colostomy have a good QoL consistent with previous findings. However, this is reduced in a subgroup of patients diagnosed with irritable bowel syndrome.

Split stoma in resectional surgery of high-risk patients with ileocolonic Crohn's disease

AIM

The aim of this retrospective study of ileocolonic resection in patients with Crohn's disease was to compare the outcome of primary anastomosis with that of split stoma and delayed anastomosis in a high-risk setting.

METHOD

From 1995 to 2006, 132 patients had 146 operations for ileocolonic Crohn's disease. Preoperative data, including risk factors for complications, were obtained from a prospectively registered database. Operations on patients who had two or more preoperative risk factors (n = 76) were considered to be high-risk operations and formed the main study. Primary outcome variables were postoperative anastomotic complications and the alteration in the number of preoperative risk factors achieved by a delayed anastomosis. Secondary outcome was time in hospital and the number of operations performed.

RESULTS

Early anastomotic complications were diagnosed in 19% (11/57) of patients receiving a primary anastomosis compared with 0% (0/19) of patients after a delayed anastomosis (P = 0.038). The mean number of risk factors in the split stoma group was 3.5 at the time of resection and 0.2 when the split stoma was reversed (P < 0.0001). The total number of operations was 1.9 ± 1.5 (mean ± SD) after a primary anastomosis and 2.0 ± 0.2 after a split stoma (P = 0.70). Total in-hospital time for all operations was 20.9 ± 35.6 days after a primary anastomosis and 17.8 ± 10.4 days after a delayed anastomosis (P = 0.74).

CONCLUSION

Delayed anastomosis after ileocolonic resection in high-risk Crohn's disease patients was associated with a reduction in the number of preoperative risk factors and fewer anastomotic complications. Hospital stay and number of operations were similar after delayed and primary anastomosis in high-risk patients.

Beam purification by photodetachment (invited)

Ion beam purity is of crucial importance to many basic and applied studies in nuclear science. Selective photodetachment has been proposed to suppress unwanted species in negative ion beams while preserving the intensity of the species of interest. A highly efficient technique based on photodetachment in a gas-filled radio frequency quadrupole ion cooler has been demonstrated. In off-line experiments with stable ions, up to 10(4) times suppression of the isobar contaminants in a number of interesting radioactive negative ion beams has been demonstrated. For selected species, this technique promises new experimental possibilities in studies on exotic nuclei, accelerator mass spectrometry, and fundamental properties of negative atomic and molecular ions.

WIN55,212-2 induces cytoplasmic vacuolation in apoptosis-resistant MCL cells

Cannabinoid receptors 1 (CB1) and/or 2 (CB2) are overexpressed in many types of human malignancies including mantle cell lymphoma (MCL). Agonists to CB1 and CB2 promote ceramide de novo synthesis, p38–mitogen-activated protein kinase-dependent activation of caspase-3 and apoptotic cell death in most MCLs. However, in this report we describe that in some MCLs the response to treatment with cannabinoids decreased cell viability as assessed by metabolic activity but did not involve the caspase-3 cascade or loss of plasma membrane integrity. Both primary cells from one MCL patient and the MCL cell line Granta519 responded to treatment with cannabinoids by formation of cycloheximide-sensitive cytoplasmic vacuoles, but did not enter apoptosis. The persistent expression of mammalian homolog of Atg8 with microtubule-associated protein-1 light chain-3 II (LC3 II) and p62, as well as the lack of protection from chloroquine, indicates that lysosomal degradation is not involved in this cytoplasmic vacuolation process, distinguishing from classical autophagy. Transmission electron microscopy images and immunofluorescence staining of endoplasmic reticulum (ER) chaperone calreticulin showed that the vacuoles were of ER origin and that chromatin remained normal. These features resemble paraptosis-like cell death—a third type of a programmed cell death not previously described in response to cannabinoids.

The invisible work with tobacco cessation - strategies among dental hygienists

OBJECTIVE

This study elucidates dental hygienists' experiences of work with tobacco cessation among patients who smoke or use snuff.

METHODS

Data were obtained and categorized by interviewing 12 dental hygienists, who worked actively with tobacco cessation interventions. Qualitative content analysis was used for analysis.

RESULTS

The latent content was formulated into the core category 'the invisible oral health promotion work'. The informants thought that they had a responsibility to work with tobacco cessation. They perceived the financial system in which they perform the activity as frustrating, because tobacco cessation has no treatment code in the dental care insurance. This was one of several reasons why they had to integrate it in other treatment procedures. The results identified three categories: 'balance in the meeting', 'possibilities and hindrance' and 'procedures'. In the narratives, both positive and negative aspects were displayed.

CONCLUSIONS

The financial conditions for tobacco cessation interventions need to be reformed and the activity has to be given a higher priority in the organization of dental care. Practical training in performing tobacco cessation interventions is important during the dental hygiene education; otherwise, tobacco cessation interventions will remain invisible in oral health promotion in the future.

Evaluation of the Dental Hygienist Beliefs Survey; test-retest assessment in a group of general dental patients

OBJECTIVE

To evaluate the Dental Hygienist Beliefs Survey (DHBS) and the test-retest reliability of DHBS in a group of general dental patients.

MATERIAL AND METHODS

The DHBS, which is a questionnaire constructed to assess patients' specific attitudes towards dental hygienists (DHs), was distributed together with the Dental Anxiety Scale adapted to specifically assess fear of DH treatment (DHAS). It was hypothesized that DHBS would correlate with DHAS and gender. The questionnaires were consecutively distributed to 80 patients at their first visit and after a clinical examination performed by a DH student. Retest assessments of DHBS were conducted approximately two weeks later in conjunction with the next visit at the DH student and before treatment (scaling session). The final study sample included 77 adult general dental patients in treatment at an education clinic for DH students.

RESULTS

The results verified a statistically significant correlation between DHBS and DHAS. The DHBS sum of scores showed high internal consistency with Cronbach's a coefficient of 0.88 and 0.91 at the first and second assessments, respectively, and the test-retest reliability of the DHBS was acceptable with intraclass correlation coefficient of 0.76. No statistically significant association was found between DHBS and gender.

CONCLUSION

The results suggest that the DHBS is a reliable and stable scale to use to assess patients' specific attitudes towards DHs. Moreover, DH beliefs are associated with fear of DH treatment.

Ion optical design of a collinear laser-negative ion beam apparatus

An apparatus for photodetachment studies on atomic and molecular negative ions of medium up to heavy mass (M ≃ 500) has been designed and constructed. Laser and ion beams are merged in the apparatus in a collinear geometry and atoms, neutral molecules and negative ions are detected in the forward direction. The ion optical design and the components used to optimize the mass resolution and the transmission through the extended field-free interaction region are described. A 90° sector field magnet with 50 cm bending radius in combination with two slits is used for mass dispersion providing a resolution of M∕ΔM≅800 for molecular ions and M∕ΔM≅400 for atomic ions. The difference in mass resolution for atomic and molecular ions is attributed to different energy distributions of the sputtered ions. With 1 mm slits, transmission from the source through the interaction region to the final ion detector was determined to be about 0.14%.