| 1. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 2. |
- Andersson, Lars M, et al.
(författare)
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En man med många talanger
- 2002
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Ingår i: På historiens slagfält. En festskrift tillägnad Sverker Oredsson. - Uppsala : Sisyfos. - 9163131048 ; , s. 19-23
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Andersson, Mathias H, et al.
(författare)
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A framework for regulating underwater noise during pile driving
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Pile driving is a common technique used during the construction of bridges, offshore wind power, and underwater infrastructure or shoreline structures. It is the process by which a foundation, beam or pole is hammered or vibrated down into the bottom, which can generate extremely loud noise that propagates throughout the surrounding water and sediment. The noise can reach such high levels that marine animals are at risk of disturbance, injury or even death.Sweden currently lacks established thresholds stating the level at which underwater noise potentially disturbs or injures marine animals. Hence, there are no guidance values for allowable underwater noise levels from noiseproducing activities to avoid serious environmental impacts. Several countries in Europe have defined thresholds for when underwater noise can result in severe negative environmental impacts as well as standards for measuring, analysing and reporting underwater noise levels.The purpose of this study is to review the scientific literature on underwater noise from pile driving and its effects on marine life. The study aims to define the noise levels that can cause injury and other negative effects and, on this basis, recommend noise levels that can be used to establish guidance values for regulating underwater noise for Swedish waters and species. The study presents examples of the factors that contribute to sound propagation in Swedish waters and how this influences the noise level from a pile strike as a function of distance at four study areas along the Swedish coast. Additionally, the study contains a thorough technical description of pile driving activities, basic underwater acoustics and noise effects on marine animals. These effects (injury and behavioral, e.g., flight, but not subtle effects) are demonstrated on representative species such as the harbour porpoise (Phocoena phocoena), Atlantic cod (Gadus morhua), Atlantic herring (Clupea harengus) and on fish larvae and eggs. The study’s authors look atthe original sources of information that other countries base their guidelines and thresholds on, so the recommendations follow scientifically determined levels rather than values that have been rounded off or otherwise altered.The study presents sound levels in three different units, each with different biological relevance to the effects caused by a pile driving activity. None of the sound levels have been frequency weighted for a specific species, as this method is not yet fully established. The first unit used is the sound pressure level SPL(peak), which is the maximum overpressure or underpressure of the noise pulse generated by the pile strike. This unit has a high relevance for behavioural effects. The sound exposure level, SEL, is the calculated energy level over a period of time and expresses the energy of the entire sound pulse. SEL is the unit most related to hearing impairing effects. SEL(ss) is the value for a single strike while SEL(cum) is the cumulative value of a determined number of pulses over a period of time. The review revealed that for Atlantic cod and Atlantic herring there are currently no studies that can be used to determine a species’ specific threshold value for injury, but studies show that loud noise can affect both species negatively. Because of this, the recommended noise levels for injury are based mainly on studies on other species exposed to pile driving noise in laboratory environments, supported by studies conducting large-scale experiments in tanks and oceans. The levels at which fish are at risk of death or sustaining serious injury to internal organs is SPL 207 dB re 1 μPa, SEL(ss) 174 dB re 1 μPa2s and SEL(cum) 204 dB re 1 μPa2s. Note that for injury in fish, the cumulative sound exposure level has higher relevance than the single-strike level as the cited studies found injuries after a certain time period of exposure. The thresholds for fish larvae and eggs are based on the fact that no negative effects were observed at exposures of up to SPL(peak) 217 dB re 1 μPa, SEL(ss) 187 dB re 1 μPa2s and SEL(cum) 207 dB re 1 μPa2s. However, there are relatively few studies on early life stages of fish. There are more species-specific studies on harbour porpoises regarding noise than there are for Atlantic cod and Atlantic herring. Nonetheless, only a few can be used to determine thresholds that will lead to injury or negative behavioural effects. The levels at which there is a risk of a temporary impact on hearing, i.e. temporary threshold shift (TTS), for the harbour porpoises is SPL(peak) 194 dB re 1 μPa, SEL(ss) 164 dB re 1 μPa2s and SEL(cum) 175 dB re 1 μPa2s. When it comes to TTS, the cumulative sound exposure level, SEL(cum), is of primary importance. However, this unit is dependent on a specific time and number of pulses. For permanent threshold shift (PTS), the level is set to SPL(peak) 200 dB re 1 μPa, SEL(ss) 179 dB re 1 μPa2s and SEL(cum) 190 dB re 1 μPa2s. The recommended level should be revised as new relevant studies are conducted.
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| 4. |
- Andersson, Mathias H., et al.
(författare)
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Underlag för reglering av undervattensljud vid pålning
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Vid byggnation av broar, havsbaserad vindkraft och andra havsbaserade eller strandnära konstruktioner används det oftast någon form av pålningsteknik för att få ner konstruktionen i botten. Detta innebär att ett fundament, balk eller spont hamras eller vibreras ner i botten, vilket kan generera mycket höga ljudnivåer som sprids ut i vattnet och ner i botten. Ljudnivåerna är så höga att marina organismer kan störas, skadas eller till och med dödas. Idag saknar Sverige fastställda ljudnivåer för när undervattensbuller blir så högt att de kan skada djur i havet. Det saknas därför också vedertagna begränsningsvärden som anger vilka nivåer av undervattensbuller som kan tillåtas för bullrande aktiviteter utan att riskera allvarliga miljöeffekter. Flera länder i Europa har någon form av gränsvärden för när bullernivån under vattnet kan ge upphov till allvarlig miljöpåverkan liksom standarder för hur undervattensbuller skall mätas och rapporteras. Syftet med denna studie var att ta fram ett vetenskapligt underlag rörande ljudet från pålning i havet och dess påverkan på det marina livet. Slutmålet var att utifrån den vetenskapliga information som finns idag ge förslag på ljudnivåer för skador och negativ påverkan som sedan kan användas för att ta fram begränsningsvärden för reglering av undervattensbuller anpassade för svenska vatten och arter. Studien ger ett antal exempel på vilka faktorer som påverkar ljudutbredningen i svenska vatten och hur detta påverkar ett pålningsslags ljudnivå som funktion av avstånd i fyra typområden kring den svenska kusten. Vidare presenteras ingående både tekniska beskrivningar av pålningsaktiviteter, undervattensakustik samt påverkan på marina djur. Denna påverkan (skada och flyktbeteende men ej subtila effekter) demonstreras med hjälp av ett antal typarter som tandvalen tumlare (Phocoena phocoena) och fiskarterna torsk (Gadus morhua) och sill (Clupea clupea) samt fiskägg och fisklarver. I denna studie har författarna gått tillbaka till de originalkällor av information som andra länders gränsvärden grundas på, så att rekommendationerna bygger på vetenskapliga nivåer och inte värden som har avrundats eller på annat sätt ändrats.Studien presenterar ljudnivåer i tre olika enheter då dessa har olika biologisk relevans för påverkan från en pålningsaktivitet. Inga av dessa värden har frekvensviktats för att anpassas för en specifik art då denna metod ännu inte är helt vedertagen. Den första enheten är ljudtrycksnivå SPL(topp), d.v.s. det maximala över- eller undertryck som den av pålningsslaget genererade ljudpulsen har. Denna enhet har hög relevans för beteendepåverkan. För ljudexponeringsnivå SEL, beräknas ljudnivån över en viss tid och tar då med energin i hela ljudpulsen. SEL är den enhet som visats vara bäst relaterad till hörselskador. SEL(enkel) är värdet för en enkel puls och för det kumulativa SEL(kum) har antalet pulser under en viss tid summerats.Litteraturstudien på torsk och sill visar att det i dagsläget inte finns några studier som kan användas för att fastställa en artspecifik ljudnivå för skada men litteraturen visar tydligt på att höga bullernivåer kan påverka torsk och sill negativt. Istället baseras de föreslagna nivåerna i huvudsak på studier på andra arter som har exponerats för pålningsljud i laboratoriemiljö med stöd av studier från mer storskaliga experiment i tankar och hav. De nivåer då fisk riskerar att dödas eller få allvarliga skador på inre organ är 207 dB re 1 μPa SPL(topp), 174 dB re 1 μPa2s SEL(enkel) och 204 dB re 1 μPa2s SEL(kum). Notera att för skada på fisk har det kumulativa värdet högre relevans än enkelvärdet för SEL eftersom studier visar att skador uppkommer efter en viss tids exponering. Nivåerna för påverkan på fiskägg och larver grundas i att inga negativa effekter har observerats vid exponering för ljudtryck från pålning upp till 217 dB re 1 μPa SPL(topp), 187 dB re 1 μPa2s SEL(enkel) och 207 dB re 1 μPa2s SEL(kum). Det finns emellertid mycket få studier relaterat till pålningsljud för dessa livsstadier. För tumlare finns det fler artspecifika studier gjorda relaterat till buller än för torsk och sill. Det är dock endast ett fåtal som kan användas för att bestämma ljudnivåer som leder till skada eller negativ beteendepåverkan. De ljudnivåer som riskerar ge tillfällig hörselnedsättning (TTS) hos tumlare är 194 dB re 1 μPa SPL(topp), 164 dB re 1 μPa2s SEL(enkel) och 175 dB re 1 μPa2s SEL(kum). Det är framförallt den kumulativa ljudexponeringsnivån SEL(kum) som har stor betydelse för just TTS, dock hänger detta värde ihop med en specifik tid och antalet pulser vilket kan vara svårt att uppskatta i förväg. Vidare avseende permanent hörselskada (PTS) är ljudnivån 200 dB re 1 μPa SPL(topp), 179 dB re 1 μPa2s SEL(enkel) och 190 dB re 1 μPa2s SEL(kum). Föreslagna nivåer bör uppdateras när nya relevanta forskningsstudier tillkommer.
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| 5. |
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| 6. |
- Andersson, Peter, 1981-, et al.
(författare)
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Simulation of the response of a segmented High-Purity Germanium detector for gamma emission tomography of nuclear fuel
- 2020
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Ingår i: SN Applied Sciences. - : Springer. - 2523-3963 .- 2523-3971. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- Irradiation testing of nuclear fuel is routinely performed in nuclear test reactors. For qualification and licensing of Accident Tolerant Fuels or Generation IV reactor fuels, an extensive increase in irradiation testing is foreseen in order to fill the gaps of existing validation data, both in normal operational conditions and in order to identify operational limits.Gamma Emission Tomography (GET) has been demonstrated as a viable technique for studies of the behavior of irradiated nuclear fuel, e.g. measurement of fission gas release and inspection of fuel behavior under Loss-Of-Coolant Accident conditions. In this work, the aim is to improve the technique of GET for irradiated nuclear fuel by developing a detector concept for an improved tomography system that allows for a higher spatial resolution and/or faster interrogation.We present the working principles of a novel concept for gamma emission tomography using a segmented High Purity Germanium (HPGe) detector. The performance of this concept was investigated using the Monte Carlo particle transport code MCNP. In particular, the data analysis of the proposed detector was evaluated, and the performance, in terms of full energy efficiency and localization failure rate, has been evaluated.We concluded that the segmented HPGe detector has an advantageous performance as compared to the traditional single-channel detector systems. Due to the scattering nature of gamma rays, a trade-off is presented between efficiency and cross-talk; however, the performance is nevertheless a substantial improvement over the currently used single-channel HPGe detector systems.
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| 7. |
- Atak, Haluk, et al.
(författare)
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The degradation of gamma-ray mass attenuation of UOX and MOX fuel with nuclear burnup
- 2020
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Ingår i: Progress in nuclear energy (New series). - : Elsevier BV. - 0149-1970 .- 1878-4224. ; 125
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Tidskriftsartikel (refereegranskat)abstract
- Nondestructive gamma-ray spectrometry of nuclear fuel is routinely performed in axial gamma scanning devices and more recently with gamma emission tomography. Following the irradiation of a fresh nuclear fuel with high intensity neutron flux in a nuclear reactor core, a great number of gamma-emitting radionuclides are created. These can be utilized for gamma spectrometric techniques. However, due to the high density and atomic number of the nuclear fuel, self-attenuation of gamma-rays is a challenge, which requires attenuation correction in order to perform accurate analysis of the source activity in the fuel.In this study, the degradation of the gamma-ray mass attenuation with burnup was investigated and, in addition, a predictive model was created by investigating the attenuation change at various gamma energies caused by the burnup of the nuclear fuel. This model is intended for use by spectrometry practitioners inspecting nuclear fuel. To this aim, the energy-dependent gamma-ray mass-attenuation coefficients were investigated as a function of burnup for UOX, and three MOX fuels having different initial Pu contents. The Serpent 2 reactor physics code was used to simulate the burnup history of the fuel pins. The nuclide inventory of the Serpent 2 output is combined with the NIST XCOM database to calculate the mass attenuation coefficients.The mass attenuation coefficient of the fuel was found to decrease with the fuel burnup, in the range of a few percent, depending on the burnup and gamma energy. Also, a theoretical burnup dependent swelling model was imposed on fuel density to see how linear attenuation coefficient of fuel material is changed. Furthermore, greater effect may be expected on the transmitted intensity, where a simulation study of a PWR assembly revealed that the contribution from the inner rods in a scanned fuel assembly increased by tens of percent compared to the one with non-irradiated fresh fuels, when shielded by the outer rods of the assembly. A sensitivity analysis was performed in order to test the effect of a number of geometrical and operational reactor parameters that were considered to potentially effect the mass attenuation coefficient. Finally, a simple-to-use predictive model was constructed providing the mass-attenuation coefficient [cm2/g] of fuel as a function of burnup [MWd/kgHM] and initial Pu content [wt%]. The resulting predictive model was optimized by using the nonlinear regression method.
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| 8. |
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| 9. |
- Hibar, Derrek P., et al.
(författare)
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Novel genetic loci associated with hippocampal volume
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (r(g) = -0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness.
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| 10. |
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| 11. |
- Nordanstig, Joakim, et al.
(författare)
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Mortality with Paclitaxel-Coated Devices in Peripheral Artery Disease.
- 2020
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Ingår i: The New England journal of medicine. - : Massachusetts Medical Society. - 1533-4406 .- 0028-4793. ; 383, s. 2538-46
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Tidskriftsartikel (refereegranskat)abstract
- The results of a recent meta-analysis aroused concern about an increased risk of death associated with the use of paclitaxel-coated angioplasty balloons and stents in lower-limb endovascular interventions for symptomatic peripheral artery disease.We conducted an unplanned interim analysis of data from a multicenter, randomized, open-label, registry-based clinical trial. At the time of the analysis, 2289 patients had been randomly assigned to treatment with drug-coated devices (the drug-coated-device group, 1149 patients) or treatment with uncoated devices (the uncoated-device group, 1140 patients). Randomization was stratified according to disease severity on the basis of whether patients had chronic limb-threatening ischemia (1480 patients) or intermittent claudication (809 patients). The single end point for this interim analysis was all-cause mortality.No patients were lost to follow-up. Paclitaxel was used as the coating agent for all the drug-coated devices. During a mean follow-up of 2.49 years, 574 patients died, including 293 patients (25.5%) in the drug-coated-device group and 281 patients (24.6%) in the uncoated-device group (hazard ratio, 1.06; 95% confidence interval, 0.92 to 1.22). At 1 year, all-cause mortality was 10.2% (117 patients) in the drug-coated-device group and 9.9% (113 patients) in the uncoated-device group. During the entire follow-up period, there was no significant difference in the incidence of death between the treatment groups among patients with chronic limb-threatening ischemia (33.4% [249 patients] in the drug-coated-device group and 33.1% [243 patients] in the uncoated-device group) or among those with intermittent claudication (10.9% [44 patients] and 9.4% [38 patients], respectively).In this randomized trial in which patients with peripheral artery disease received treatment with paclitaxel-coated or uncoated endovascular devices, the results of an unplanned interim analysis of all-cause mortality did not show a difference between the groups in the incidence of death during 1 to 4 years of follow-up. (Funded by the Swedish Research Council and others; ClinicalTrials.gov number, NCT02051088.).
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| 12. |
- Rathore, Vikram, et al.
(författare)
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Calculation of Spatial Response of a Collimated Segmented HPGe detector for Gamma Emission Tomography by MCNP Simulations
- 2022
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 69:4, s. 714-721
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Tidskriftsartikel (refereegranskat)abstract
- We have proposed a planar electronically segmented HPGe detector concept in combination with a multi-slit collimator for gamma emission tomography. In this work, the spatial resolution achievable by using the collimated segmented HPGe detector was evaluated, prior to the manufacture and operation of the detector. The spatial response of a collimated segmented HPGe detector concept was evaluated using simulations performed with Monte Carlo N-Particle transport code MCNP6. The full detector and multi-slit collimator system were modeled and for the quantification of the spatial response, the Modulation Transfer Function (MTF) was chosen as a performance metric. The MTF curve was obtained through the calculation of the Line Spread Function (LSF) by analyzing simulated projection data. In addition, tomographic reconstructions of the simulated simplified test objects were made to demonstrate the performance of the segmented HPGe detector in the planned application. For 662 keV photons, the spatial resolution obtained was approximately the same as the collimator slit width for both 100 and 150 mm long collimators. The corresponding spatial resolution at 1596 keV photon energy was almost twice the slit width for 100 mm collimator, due to the partial penetration of the high-energy gamma rays through the collimator bulk. For a 150 mm long collimator, an improved resolution was obtained.
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| 13. |
- Rathore, Vikram, et al.
(författare)
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First experimental demonstration of the use of a novel planar segmented HPGe detector for gamma emission tomography of mockup fuel rods
- 2023
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Ingår i: Nuclear Technology. - 0029-5450 .- 1943-7471.
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Tidskriftsartikel (refereegranskat)abstract
- Post-irradiation examination of nuclear fuel is routinely performed to characterize the important properties of the current and the future fuel. Gamma emission tomography is a proven non-invasive technique for this purpose. Among various measurement elements of the technique, a gamma-ray detector is an important element whose spectroscopic abilities and detection efficiency affect the overall results. Finding a combination of high detection efficiency and excellent energy resolution in a single detector is often a challenge. We have designed a novel planar segmented HPGe detector which offers simultaneous measurement in six lines of sight with excellent energy resolution. The simultaneous detection ability enables faster data acquisition in a tomographic measurement which may facilitate achieving higher spatial resolution. In this work, we have demonstrated the first use of the detector by performing a full tomographic measurement of mockup fuel rods. Two methods of detector data analysis were used to make spectra and the images (tomograms) were reconstructed using the filtered back projection algorithm. The reconstructed images validate the successful use of the detector for tomographic measurement. The use of the detector for real fuel measurement is being planned and will be performed in the near future.
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| 14. |
- Rathore, Vikram, et al.
(författare)
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Geometrical optimisation of a segmented HPGe detector for spectroscopic gamma emission tomography : A simulation study
- 2021
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 998
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Tidskriftsartikel (refereegranskat)abstract
- Segmented coaxial HPGe (High Purity Germanium) detectors have recently been shown to be feasible for Gamma Emission Tomography (GET). This type of detector allows for a combination of high efficiency and high energy resolution in gamma spectrometry of irradiated nuclear fuel. The ultimate aim of developing segmented HPGe for GET measurements is to achieve a high spatial resolution to facilitate imaging of rod-internal features and interrogation of smaller irradiated fuel samples.In this work, we present the optimisation of a segmented HPGe detector through a simulation study using the Monte Carlo particle transport code MCNP. Constraints to each dimension of the detector were identified, from manufacturing limitations and requirements arising from the use of a finite-sized collimator slit. In particular, a relationship between the minimum inner radius of the coaxial detector and the segments azimuthal dimension was derived based on the identified constraints. Segment azimuthal and radial dimensions have been varied (based on the derived relationship between the azimuthal and radial dimension) and the full energy efficiency and misidentification rate were evaluated to obtain the optimal dimensions. The optimal ranges of the segment dimensions were determined.
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| 15. |
- Saveer, Ahmed, et al.
(författare)
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A herbivore-induced plant volatile interferes with host plant and mate location in moths through suppression of olfactory signalling pathways
- 2015
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Ingår i: BMC Biology. - : Springer Science and Business Media LLC. - 1741-7007. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Background: Plants under herbivore attack release volatiles that attract natural enemies, and herbivores in turn avoid such plants. Whilst herbivore-induced plant volatile blends appeared to reduce the attractiveness of host plants to herbivores, the volatiles that are key in this process and particularly the way in which deterrence is coded in the olfactory system are largely unknown. Here we demonstrate that herbivore-induced cotton volatiles suppress orientation of the moth Spodoptera littoralis to host plants and mates.Results: We found that (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), an induced volatile, is key in herbivore deterrence: DMNT suppressed plant odour-and pheromone-induced behaviours. We then dissected the neurophysiological basis of this interaction. DMNT-responding glomeruli were also activated by other plant compounds, suggesting that S. littoralis possesses no segregated olfactory circuit dedicated exclusively to DMNT. Instead, DMNT suppressed responses to the main pheromone component, (Z)-9-(E)-11-tetradecenyl acetate, and primarily to (Z)-3-hexenyl acetate, a host plant attractant.Conclusion: Our study shows that olfactory sensory inhibition, which has previously been reported without reference to an animal's ecology, can be at the core of coding of ecologically relevant odours. As DMNT attracts natural enemies and deters herbivores, it may be useful in the development or enhancement of push-pull strategies for sustainable agriculture.
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| 16. |
- Senis, Lorenzo, et al.
(författare)
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A computational methodology for estimating the detected energy spectra of the gamma-ray flux from irradiated nuclear fuel
- 2022
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Ingår i: IEEE Transactions on Nuclear Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9499 .- 1558-1578. ; 69:4, s. 703-713
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Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray spectrometry using collimated detectors is a well-established examination method for irradiated nuclear fuel. However, the feasibility of examining a particular nuclide of interest is subject to constraints; the peak must be statistically determinable with the desired precision and the total spectrum count rate in the detector should not cause throughput issues. Methods were assembled for gamma spectrum prediction to optimize instruments for gamma emission tomography and to enable a priori feasibility evaluation of determination of single peaks of irradiated nuclear fuel. The aim was to find reliable results (~10% accuracy) regarding total spectrum and peak count rates with faster computation time than a full-Monte Carlo approach. For this purpose, the method is based on depletion calculations with SERPENT2, a point-source kernel method for the collimator response, a rig response matrix and a detector response matrix, both computed with MCNP6. The computational methodology uses as input the fuel properties (dimensions, materials, power history, and cooling time), and the instrumental setup (collimator and detector dimensions and materials). The prediction method was validated using measured data from a high-burnup, short-cooled test fuel rodlet from the Halden reactor. Absolute count rates and ratios of characteristic peaks were compared between predicted and measured spectra, showing a total count rate overestimation of 7% and discrepancies between 2-20% for the single peaks (same order of magnitude of the uncertainty). This level of agreement is deemed sufficient for measurement campaigns planning, and the optimization of spectroscopic instruments for use in gamma scanning and tomography of nuclear fuel.
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| 17. |
- Senis, Lorenzo, et al.
(författare)
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Evaluation of gamma-ray transmission through rectangular collimator slits for application in nuclear fuel spectrometry
- 2021
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 1014
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Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray spectrometry is widely applied in several science fields, and in particular in non-destructive gamma scanning and gamma emission tomography of irradiated nuclear fuel. Often, a collimator is used in the experimental setup, to selectively interrogate a region of interest in the fuel. For the optimization of instrument design, as well as for planning measurement campaigns, predictive models for the transmitted gamma-ray intensity through the collimator are needed. Commonly, Monte Carlo Radiation Transport tools are used for accurate prediction of gamma-ray transport, however, the long computation time requirements when used in low-efficiency experimental setups present challenges.In this work, the full-energy peak intensity transmitted through a rectangular collimator slit was examined. A uniform planar surface source emitting isotropically was considered, and the rate of photons reaching an ideal counter plane on the opposite side of the collimator was evaluated by analytical integration. To find a closed-form primitive function, some idealizations were required, and thereby parametric models were obtained for the optical field of view, dependent on slit dimensions (length, height and width) and source-to-collimator distance. It was shown that the count rate in the detector is independent of the collimator-to-source distance. For contributions from outside the optical field of view, where a closed-form expression cannot be found, instead fast numerical integration methods were proposed.The results were validated using the Monte Carlo code MCNP6. For the analytical method, deviations were larger, the shorter the collimator, with up to 25% of underestimation obtained for the shortest examined collimator of 10 cm length. However, the longer the collimator, the better the observed agreement. This accuracy is deemed to be sufficient for instrument design and measurement planning, where often the order of magnitude of the count rate is not a priori known. For the numerical method, the results showed an agreement within 3 % for all evaluated collimator settings. The methods are planned for use in iterative optimization routines in the design of Gamma Emission Tomography devices, as well as for the prediction of gamma spectra obtained in the planning of fuel inspections. An application of the proposed method was demonstrated in spectrum prediction for a short cooling-time fuel rod test from the Halden reactor.
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| 18. |
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| 19. |
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| 20. |
- Abdalla, Maie, et al.
(författare)
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Anorectal Function After Ileo-Rectal Anastomosis Is Better than Pelvic Pouch in Selected Ulcerative Colitis Patients
- 2020
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Ingår i: Digestive Diseases and Sciences. - : Springer-Verlag New York. - 0163-2116 .- 1573-2568. ; , s. 250-259
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: With a lifelong perspective, 12% of ulcerative colitis patients will need a colectomy. Further reconstruction via ileo-rectal anastomosis or pouch can be affected by patients' perspective of their quality of life after surgery.AIM: To assess the function and quality of life after restorative procedures with either ileo-rectal anastomosis or ileal pouch-anal anastomosis in relation to the inflammatory activity on endoscopy and in biopsies.METHOD: A total of 143 UC patients operated with subtotal colectomy and ileo-rectal anastomosis or pouches between 1992 and 2006 at Linköping University Hospital were invited to participate. Those who completed the validated questionnaires (Öresland score, SF-36, Short Health Scale) were offered an endoscopic evaluation including multiple biopsies. Associations between anorectal function and quality of life with type of restorative procedure and severity of endoscopic and histopathologic grading of inflammation were evaluated.RESULTS: Some 77 (53.9%) eligible patients completed questionnaires, of these 68 (88.3%) underwent endoscopic evaluation after a median follow-up of 12.5 (range 3.5-19.4) years after restorative procedure. Patients with ileo-rectal anastomosis reported better overall Öresland score: median = 3 (IQR 2-5) for ileo-rectal anastomosis (n = 38) and 10 (IQR 5-15) for pouch patients (n = 39) (p < 0.001). Anorectal function (Öresland score) and endoscopic findings (Baron-Ginsberg score) were positively correlated in pouch patients (tau: 0.28, p = 0.006).CONCLUSION: Patients operated with ileo-rectal anastomosis reported better continence compared to pouches. Minor differences were noted regarding the quality of life. Ileo-rectal anastomosis is a valid option for properly selected ulcerative colitis patients if strict postoperative endoscopic surveillance is carried out.
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| 21. |
- Abdalla, Maie, et al.
(författare)
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Risk of Rectal Cancer After Colectomy for Patients With Ulcerative Colitis: A National Cohort Study
- 2017
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Ingår i: Clinical Gastroenterology and Hepatology. - : Elsevier. - 1542-3565 .- 1542-7714. ; 15:7, s. 1055-1060
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND amp; AIMS: Patients with ulcerative colitis (UC) have an increased risk of rectal cancer, therefore reconstruction with an ileal pouch-anal anastomosis (IPAA) generally is preferred to an ileorectal anastomosis (IRA) after subtotal colectomy. Similarly, completion proctectomy is recommended for patients with ileostomy and a diverted rectum, although this approach has been questioned because anti-inflammatory agents might reduce cancer risk. We performed a national cohort study in Sweden to assess the risk of rectal cancer in patients with UC who have an IRA, IPAA, or diverted rectum after subtotal colectomy.METHODS: We collected data from the Swedish National Patient Register for a cohort of 5886 patients with UC who underwent subtotal colectomy with an IRA, IPAA, or diverted rectum from 1964 through 2010. Patients who developed rectal cancer were identified from the Swedish National Cancer Register. The risk of rectal cancer was compared between this cohort and the general population by standardized incidence ratio analysis.RESULTS: Rectal cancer occurred in 20 of 1112 patients (1.8%) who received IRA, 1 of 1796 patients (0.06%) who received an IPAA, and 25 of 4358 patients (0.6%) with a diverted rectum. Standardized incidence ratios for rectal cancer were 8.7 in patients with an IRA, 0.4 in patients with an IPAA, and 3.8 in patients with a diverted rectum. Risk factors for rectal cancer were primary sclerosing cholangitis in patients with an IRA (hazard ratio, 6.12), and colonic severe dysplasia or cancer before subtotal colectomy in patients with a diverted rectum (hazard ratio, 3.67).CONCLUSIONS: In an analysis of the Swedish National Patient Register, we found that the risk for rectal cancer after colectomy in patients with UC is low, in relative and absolute terms, after reconstruction with an IPAA. An IRA and diverted rectum are associated with an increased risk of rectal cancer, compared with the general population, but the absolute risk is low. Patients and their health care providers should consider these findings in making decisions to leave the rectum intact, perform completion proctectomy, or reconstruct the colon with an IRA or IPAA.
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| 22. |
- Abdollahi Sani, Negar, et al.
(författare)
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Flexible lamination-fabricated ultra-high frequency diodes based on self-supporting semiconducting composite film of silicon micro-particles and nano-fibrillated cellulose
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Low cost and flexible devices such as wearable electronics, e-labels and distributed sensors will make the future "internet of things" viable. To power and communicate with such systems, high frequency rectifiers are crucial components. We present a simple method to manufacture flexible diodes, operating at GHz frequencies, based on self-adhesive composite films of silicon micro-particles (Si-ΌPs) and glycerol dispersed in nanofibrillated cellulose (NFC). NFC, Si-ΌPs and glycerol are mixed in a water suspension, forming a self-supporting nanocellulose-silicon composite film after drying. This film is cut and laminated between a flexible pre-patterned Al bottom electrode and a conductive Ni-coated carbon tape top contact. A Schottky junction is established between the Al electrode and the Si-ΌPs. The resulting flexible diodes show current levels on the order of mA for an area of 2 mm2, a current rectification ratio up to 4 × 103 between 1 and 2 V bias and a cut-off frequency of 1.8 GHz. Energy harvesting experiments have been demonstrated using resistors as the load at 900 MHz and 1.8 GHz. The diode stack can be delaminated away from the Al electrode and then later on be transferred and reconfigured to another substrate. This provides us with reconfigurable GHz-operating diode circuits.
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| 23. |
- Ahmed, Mobyen Uddin, Dr, 1976-, et al.
(författare)
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A machine learning approach for biomass characterization
- 2019
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; , s. 1279-1287
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Konferensbidrag (refereegranskat)abstract
- The aim of this work is to apply and evaluate different chemometric approaches employing several machine learning techniques in order to characterize the moisture content in biomass from data obtained by Near Infrared (NIR) spectroscopy. The approaches include three main parts: a) data pre-processing, b) wavelength selection and c) development of a regression model enabling moisture content measurement. Standard Normal Variate (SNV), Multiplicative Scatter Correction and Savitzky-Golay first (SG1) and second (SG2) derivatives and its combinations were applied for data pre-processing. Genetic algorithm (GA) and iterative PLS (iPLS) were used for wavelength selection. Artificial Neural Network (ANN), Gaussian Process Regression (GPR), Support Vector Regression (SVR) and traditional Partial Least Squares (PLS) regression, were employed as machine learning regression methods. Results shows that SNV combined with SG1 first derivative performs the best in data pre-processing. The GA is the most effective methods for variable selection and GPR achieved a high accuracy in regression modeling while having low demands on computation time. Overall, the machine learning techniques demonstrate a great potential to be used in future NIR spectroscopy applications. © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 - The 10th International Conference on Applied Energy.
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| 24. |
- Ahnesjö, Magnus, et al.
(författare)
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Tomographic reconstructions and predictions of radial void distribution in BWR fuel bundle with part-length rods
- 2015
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Konferensbidrag (refereegranskat)abstract
- The Westinghouse FRIGG facility, in Västerås/Sweden, is dedicated to the measurement of critical power,stability and pressure drop in fuel rod bundles under BWR operating conditions (steady-state andtransient). Capability to measure cross-sectional void and radial void distributions during steady-stateoperation was already considered when the facility was built in the late 1960s, using gamma transmissionmeasurements. In the 1990s, redesigned equipment was installed to allow for full 2D tomography andsome test campaigns were successfully run where the void was measured in the Westinghouse SVEA-96fuel bundle geometry with and without part-length rods.In this paper, the tomographic raw data from the SVEA-96 void measurement campaigns are revisitedusing various tomographic reconstruction techniques. This includes an algebraic method and a filteredback-projection method. Challenges, for example due to artifacts created by high difference in gammaabsorption, or to accurately identify the location of the bundle structure, are resolved. The resultingdetailed void distributions are then averaged over entire sub-channels or within the steam core only, forcomparison against sub-channel simulations.The resulting void distributions are compared against sub-channel void predictions using the VIPREW/MEFISTO code. The region downstream the part-length rods are of particular interest to investigatehow the void in the steam core is redistributed within the open region of the bundle. The comparisonshows a reasonable agreement between the measurements and the predictions.
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| 25. |
- Aliverti, A., et al.
(författare)
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Effects of propofol anaesthesia on thoraco-abdominal volume variations during spontaneous breathing and mechanical ventilation
- 2011
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 55:5, s. 588-596
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Tidskriftsartikel (refereegranskat)abstract
- Background Anaesthesia based on inhalational agents has profound effects on chest wall configuration and breathing pattern. The effects of propofol are less well characterised. The aim of the current study was to evaluate the effects of propofol anaesthesia on chest wall motion during spontaneous breathing and positive pressure ventilation. Methods We studied 16 subjects undergoing elective surgery requiring general anaesthesia. Chest wall volumes were continuously monitored by opto-electronic plethysmography during quiet breathing (QB) in the conscious state, induction of anaesthesia, spontaneous breathing during anaesthesia (SB), pressure support ventilation (PSV) and pressure control ventilation (PCV) after muscle paralysis. Results The total chest wall volume decreased by 0.41 +/- 0.08 l immediately after induction by equal reductions in the rib cage and abdominal volumes. An increase in the rib cage volume was then seen, resulting in total chest wall volumes 0.26 +/- 0.09, 0.24 +/- 0.10, 0.22 +/- 0.10 l lower than baseline, during SB, PSV and PCV, respectively. During QB, rib cage volume displacement corresponded to 34.2 +/- 5.3% of the tidal volume. During SB, PSV and PCV, this increased to 42.2 +/- 4.9%, 48.2 +/- 3.6% and 46.3 +/- 3.2%, respectively, with a corresponding decrease in the abdominal contribution. Breathing was initiated by the rib cage muscles during SB. Conclusion Propofol anaesthesia decreases end-expiratory chest wall volume, with a more pronounced effect on the diaphragm than on the rib cage muscles, which initiate breathing after apnoea.
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