| 1. |
- Kalmykova, Yuliya, 1981, et al.
(författare)
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Portable battery lifespans and new estimation method for battery collection rate based on a lifespan modeling approach
- 2017
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Ingår i: Resources, Conservation and Recycling. - : Elsevier BV. - 0921-3449 .- 1879-0658. ; 120, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 The Author(s)Separate collection and recycling of used batteries is required in the EU member states and other countries, as a measure for environmentally sound management of batteries. Monitoring of collection rate of the separate battery stream is important for decision making, in particular for implementing interventions to improve the separate collection and evaluating their results. Limitations of the currently applied method for the estimation of battery collection rate are discussed and a new method, which improves the estimation, is suggested. The method utilizes a more accurate way of estimating the total battery waste generation. This estimation is based on batteries historical consumption estimated with material flow analysis method and distributions of batteries lifespan obtained from empirical data. Empirical data from two decades of battery consumption and disposal in Sweden were analyzed and lifespan distributions have been found for eight different types of batteries by dating over 5000 disposed batteries. The lifespans stretched from 1 to 28 years, with a median lifespan of 3–8 years. It is shown how the use of lifespan distributions in the suggested method could considerably improve the estimation of the collection rate. Consequently, the intervention potentials can be identified more accurately and the decision making for investments in the collection system can be improved. The observed lifespans are also useful for understanding batteries fate in households as well as trends in battery consumption and disposal.
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| 2. |
- Patricio, Joao, 1984, et al.
(författare)
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Uncertainty in Material Flow Analysis Indicators at Different Spatial Levels
- 2015
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Ingår i: Journal of Industrial Ecology. - : Wiley. - 1088-1980 .- 1530-9290. ; 19:5, s. 837-852
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Tidskriftsartikel (refereegranskat)abstract
- Material flow analysis (MFA) is a tool for research and decision support in environmental policy and management. In order to promote the use of MFA at different spatial scales, a quantification of the uncertainty in nationwide, regional, and urban MFA methodologies is provided. In particular, the impact of the input data quality on the main MFA indicators is analyzed and the sources and extent of uncertainties for different spatial scales are listed. The types, origin, and extent of the errors are described in detail and several imputation methods are explained and evaluated. By introducing a novel approach to account measurement errors in data sets with very few details on the measurement errors, this article aims at contributing to the development of a standardized method to account for the uncertainty in MFA studies. This study uses the time series of MFA data for 1996-2011 at three spatial scalesnationwide (Sweden), regional (the Stockholm Region), and metropolitan (Stockholm, Gothenburg, and Malmo)to determine how propagation of measurement errors affects the MFA results. The following MFA indicators were studied: direct material input; domestic processed output; and domestic material consumption. Generally, availability decreased as the spatial scale was lowered, whereas data errors increased. In the specific case of Sweden, the data on freight transport by rail and on waste produced by economic activities at the regional and metropolitan level should be improved.
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| 3. |
- Burman, C. F., et al.
(författare)
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The dual test: Safeguarding p-value combination tests for adaptive designs
- 2010
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Ingår i: Statistics in Medicine. - : Wiley. - 0277-6715 .- 1097-0258. ; 29:7-8, s. 797-807
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Tidskriftsartikel (refereegranskat)abstract
- Many modern adaptive designs apply an analysis where p-values from different stages are weighted together to an overall hypothesis test. One merit of this combination approach is that the design can be made very flexible. However, combination tests violate the sufficiency and conditionality principles. As a consequence, combination tests may lead to absurd conclusions, such as 'proving' a positive effect while the average effect is negative. We explore the possibility of modifying the test so that such illogical conclusions are no longer possible. The dual test requires both the weighted combination test and a nave test, ignoring the adaptations, to be statistically significant. The result is that the flexibility and type I error level control of the combination test are preserved, while the nave test adds a safeguard against unconvincing results. The dual test is, by construction, at least as conservative as the combination test. However, many design changes will not lead to any power loss. A typical situation where the combination approach can be used is two-stage sample size reestimation (SSR). For this case, we give a complete specification of all sample size modifications for which the two tests are equally powerful. We also study the overall power loss for some suggested SSR rules. Rules based on conditional power generally lead to ignorable power loss while a decision analytic approach exhibits clear discrepancies between the two tests.
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| 4. |
- Bärgman, Jonas, 1972, et al.
(författare)
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How does glance behavior influence crash and injury risk? A ‘what-if’ counterfactual simulation using crashes and near-crashes from SHRP2
- 2015
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Ingår i: Transportation Research Part F: Traffic Psychology and Behaviour. - : Elsevier BV. - 1369-8478. ; 35, s. 152-169
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Tidskriftsartikel (refereegranskat)abstract
- As naturalistic driving data become increasingly available, new analyses are revealing the significance of drivers’ glance behavior in traffic crashes. Due to the rarity of crashes, even in the largest naturalistic datasets, near-crashes are often included in the analyses and used as surrogates for crashes. However, to date we lack a method to assess the extent to which driver glance behavior influences crash and injury risk across both crashes and near-crashes. This paper presents a novel method for estimating crash and injury risk from off-road glance behavior for crashes and near-crashes alike; this method can also be used to evaluate the safety impact of secondary tasks (such as tuning the radio). We apply a ‘what-if’ (counterfactual) simulation to 37 lead-vehicle crashes and 186 lead-vehicle near-crashes from lead-vehicle scenarios identified in the SHRP2 naturalistic driving data. The simulation combines the kinematics of the two conflicting vehicles with a model of driver glance behavior to estimate two probabilities: (1) that each event becomes a crash, and (2) that each event causes a specific level of injury. The usefulness of the method is demonstrated by comparing the crash and injury risk of normal driving with the risks of driving while performing one of three secondary tasks: the Rockwell radio-tuning task and two hypothetical tasks. Alternative applications of the method and its metrics are also discussed. The method presented in this paper can guide the design of safer driver–vehicle interfaces by showing the best tradeoff between the percent of glances that are on-road, the distribution of off-road glances, and the total task time for different tasks.
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| 5. |
- Hellstrand Tang, Ulla, 1956, et al.
(författare)
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Comparison of plantar pressure in three types of insole given to patients with diabetes at risk of developing foot ulcers – A two-year, randomized trial
- 2014
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Ingår i: Journal of Clinical and Translational Endocrinology. - : Elsevier BV. - 2214-6237. ; 1:4, s. 121-132
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Tidskriftsartikel (refereegranskat)abstract
- Background: Special insoles and shoes designed to prevent foot ulcers caused by repetitive high pressures are recommended for patients with diabetes who have any of the following risk factors: neuropathy; peripheral vascular disease; foot deformities; previous ulcers; amputation; and skin pathologies. However, there is a need for increased knowledge regarding: a) differences in the peak pressure (PP) and pressure time integral (PTI) for different types of insoles; and b) the properties of the pressure distribution for insoles used over a period of several months. We present the results of a randomized trial to compare the plantar pressures of three commonly used insoles. Objectives: The primary objective was to compare the PP and PTI between three types of insoles. The secondary objective was to explore the long-term pattern of peak plantar pressure distribution and variations in specific regions of interest (ROI). The tertiary objective was to investigate the impacts of insole adjustments, how much the insoles were used, and the levels of patient satisfaction. Methods In a 2-year trial, 114 patients with type 1 (N = 31) or type 2 (N = 83) diabetes (62 men and 52 women; mean age, 57.7 ± 15.4 years; duration of diabetes, 12.3 ± 11.2 years; neuropathy, 38%), were randomized to be supplied with one of three different insoles. The ethylene vinyl acetate (EVA) insoles were used in outdoor walking shoes. The 35 EVA group (N = 39) received soft custom-made insoles composed of EVA of 35 shore A hardness, the 55 EVA group (N = 37) received custom-made insoles composed of EVA of 55 shore hardness, and the control group (N = 38) received prefabricated insoles composed of a hard core with a top layer of soft 12 shore hardness microfiber. Using F-Scan®, the in-shoe plantar pressures were measured at seven ROI (hallux, metatarsal head 1, metatarsal head 2, metatarsal head 4, metatarsal head 5, lateral aspect of the mid-foot, heel) on five occasions during the study period. The plantar-pressure variables used were PP (main outcome) and PTI. The plantar patterns of load were explored, satisfaction and usage of the insoles were rated by the participants, and insole adjustments were recorded. Results:A mixed model analysis estimated lower PP values in the heel regions for the 35 EVA and 55 EVA insoles (171 ± 13 and 161 ± 13 kPa, respectively) than for the prefabricated insoles (234 ± 10 kPa) (p
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| 6. |
- Hellstrand Tang, Ulla, 1956, et al.
(författare)
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Foot deformities, function in the lower extremities, and plantar pressure in patients with diabetes at high risk to develop foot ulcers
- 2015
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Ingår i: Diabetic Foot & Ankle. - : Informa UK Limited. - 2000-625X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Objective : Foot deformities, neuropathy, and dysfunction in the lower extremities are known risk factors that increase plantar peak pressure (PP) and, as a result, the risk of developing foot ulcers in patients with diabetes. However, knowledge about the prevalence of these factors is still limited. The aim of the present study was to describe the prevalence of risk factors observed in patients with diabetes without foot ulcers and to explore possible connections between the risk factors and high plantar pressure. Patients and methods : Patients diagnosed with type 1 ( n= 27) or type 2 ( n= 47) diabetes (mean age 60.0±15.0 years) were included in this cross-sectional study. Assessments included the registration of foot deformities; test of gross function at the hip, knee, and ankle joints; a stratification of the risk of developing foot ulcers according to the Swedish National Diabetes Register; a walking test; and self-reported questionnaires including the SF-36 health survey. In-shoe PP was measured in seven regions of interests on the sole of the foot using F-Scan ® . An exploratory analysis of the association of risk factors with PP was performed. Results : Neuropathy was present in 28 (38%), and 39 (53%) had callosities in the heel region. Low forefoot arch was present in 57 (77%). Gait-related parameters, such as the ability to walk on the forefoot or heel, were normal in all patients. Eighty percent had normal function at the hip and ankle joints. Gait velocity was 1.2±0.2 m/s. All patients were stratified to risk group 3. Hallux valgus and hallux rigidus were associated with an increase in the PP in the medial forefoot. A higher body mass index (BMI) was found to increase the PP at metatarsal heads 4 and 5. Pes planus was associated with a decrease in PP at metatarsal head 1. Neuropathy did not have a high association with PP. Conclusions: This study identified several potential risk factors for the onset of diabetic foot ulcers (DFU). Hallux valgus and hallux rigidus appeared to increase the PP under the medial forefoot and a high BMI appeared to increase the PP under the lateral forefoot. There is a need to construct a simple, valid, and reliable assessment routine to detect potential risk factors for the onset of DFU.
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| 7. |
- Hellstrand Tang, Ulla, 1956, et al.
(författare)
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The D-Foot, for prosthetists and orthotists, a new eHealth tool useful in useful in risk classification and foot assessment in diabetes
- 2017
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Ingår i: Foot and Ankle Online Journal. - : International Foot & Ankle Foundation. - 1941-6806. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- Background: The prevention and care of foot problems in diabetes begins with a risk classification. Today, the prosthetists and orthotists (CPO) and other health care professionals assess the risk of developing foot ulcers more or less subjectively. The objective of the study was to describe the construction of an eHealth tool, the D-Foot, which generates a risk classification. The reliability of the D-Foot was tested. Methods: The D-Foot includes 22 clinical assessments and four self-reported questions. The content validity was assured by expert group consensus and the reliability was assessed through an empirical test-retest study. Inter- and intra-rater reliability was calculated using patients referred to four departments of prosthetics and orthotics (DPO). Results: The agreement for the risk classification generated using the D-Foot was 0.82 (pooled kappa 0.31, varying from 0.16 to 1.00 at single DPOs). The inter-rater agreement was > 0.80 regarding the assessments of amputation, Charcot deformity, foot ulcer, gait deviation, hallux valgus/hallux varus and risk grade. The inter- and intra-rater agreements for the discrete measurements were > 0.59 and > 0.72 respectively. For continuous measurements, the inter- and intra-rater correlation varied (0.33-0.98 and 0.25-0.99 respectively). Conclusion: The D-Foot gave a reliable risk foot classification. However, there was a variation in the inter- and intra-rater reliability of the assessments included and refinements are needed for variables with low agreement. Based on the results, the D-Foot will be revised before it is implemented in clinical practice.
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| 8. |
- Imberg, Henrik, 1991, et al.
(författare)
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Optimization of Two-Phase Sampling Designs With Application to Naturalistic Driving Studies
- 2022
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Ingår i: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; 23:4, s. 3575-88
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Tidskriftsartikel (refereegranskat)abstract
- Naturalistic driving studies (NDS) generate tremendous amounts of traffic data and constitute an important component of modern traffic safety research. However, analysis of the entire NDS database is rarely feasible, as it often requires expensive and time-consuming annotations of video sequences. We describe how automatic measurements, readily available in an NDS database, may be utilized for selection of time segments for annotation that are most informative with regards to detection of potential associations between driving behavior and a consecutive safety critical event. The methodology is illustrated and evaluated on data from a large naturalistic driving study, showing that the use of optimized instance selection may reduce the number of segments that need to be annotated by as much as 50%, compared to simple random sampling. IEEE
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| 9. |
- Kneider, Maria, et al.
(författare)
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Upper Respiratory Infections and MRI Activity in Relapsing-Remitting Multiple Sclerosis
- 2015
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Ingår i: Neuroepidemiology. - : S. Karger AG. - 0251-5350 .- 1423-0208. ; 45:2, s. 83-89
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Tidskriftsartikel (refereegranskat)abstract
- Background: Although clinical reports have suggested a relationship between systemic infections and multiple sclerosis (MS) relapses, MRI evidence supporting an association is conflicting. Here we evaluated the temporal relationship between upper respiratory infections (URIs) and MRI activity in relapsing-remitting (RR) MS. Methods: We combined individual data on URI with data on active lesions in pre-scheduled MRI examinations performed every 4 weeks for 28 weeks in 69 patients. A 4-week at-risk (AR) period started, by definition, 1 week before the onset of a URI. We recorded the relationship between the number of active lesions in each MRI with (1) the number of days of AR time in the immediately preceding 4-week period and (2) the number of days passed since the onset of a preceding URI. Results: Average MRI lesions/day showed no difference between AR (0.0764) and not-AR (0.0774) periods. The number of lesions in 483 pre-scheduled MRI examinations did not correlate with the AR proportion in the prior 4-week period (rho = -0.03), and time from URI onset did not correlate with lesion number on the next MRI examination (rho = 0.003). Conclusion: The occurrence of a URI did not increase the risk of MRI activity evaluated in an adjacent 4-week window in RRMS.
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| 10. |
- Lisovskaja, Vera, 1984
(författare)
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A contribution to the design and analysis of phase III clinical trials
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Clinical trials are an established methodology for evaluation of the effects of a new medical treatment. These trials are usually divided into several phases, namely phase I through IV. The earlier phases (I and II) are relatively small and have a more exploratory nature. The later phase III is confirmatory and aims to demonstrate the efficacy and safety of the new treatment. This phase is the final one before the treatment is marketed, with phase IV consisting of post-marketing studies. Phase III is initiated only if the conductors of the clinical study judge that the evidence from earlier stages indicates clearly that the new treatment is effective. However, several studies performed in recent years show that this assessment is not always correct. Two papers written on the subject point out average attrition rates of around 45\% and 30\%. In other words, it is estimated that only around two thirds of the compounds that enter phase III finish it successfully. This thesis examines some of the possible ways of improving efficiency in phase III clinical trials. The thesis consists of four papers on various topics that touch this subject, these topics being adaptive designs (paper I), number of doses (paper II) and multiplicity correction procedures (papers III and IV). The first paper examines the properties of the so called dual test, which can be applied in adaptive designs with sample size re-estimation. This test serves as a safeguard against unreasonable conclusions that may otherwise arise if an adaptive design is used. However, there is a price of possible power loss as compared to the standard test that is applied in such situations. The dual test is evaluated by considering several scenarios where its use would be natural. In many cases the power loss is minimal or non-existing. The second paper considers the optimal number and placement of doses used in phase III, with the probability of success of the trial used as optimality criterion. One common way of designing phase III trials is to divide the patients into two groups, one group receiving the new drug and another a control. However, as is demonstrated in paper II, this approach will be inferior to a design with two different doses and a control if there is enough uncertainty in the dose-response model prior to the initiation of the trial. The last two papers study possible gain that results from optimization of the multiplicity correction procedure that is applied if more than one hypothesis is tested in the same trial. Two families of such procedures are considered. The first one, examined in paper III, consists of a combination of a weighted Bonferroni test statistic with the principle of closed testing. The second one, examined in paper IV, is based on combining the same principle with a "pooled" test statistic. Paper III demonstrates that optimizing a multiplicity testing procedure can lead to a significant power increase as compared to simpler, non-optimized, procedures. The optimization is performed with respect to expected utility, an approach that originates from decision theory. Paper IV examines the difference between the Bonferroni-based and the pooled-based multiplicity corrections, finding the latter to be superior to the former if the test statistics follow a known multivariate Normal distribution.
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