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Search Results: 1 - 10 of 3180 matches for " Anders Jonsson "
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The Role of Macros in Tractable Planning
Anders Jonsson
Computer Science , 2014, DOI: 10.1613/jair.2891
Abstract: This paper presents several new tractability results for planning based on macros. We describe an algorithm that optimally solves planning problems in a class that we call inverted tree reducible, and is provably tractable for several subclasses of this class. By using macros to store partial plans that recur frequently in the solution, the algorithm is polynomial in time and space even for exponentially long plans. We generalize the inverted tree reducible class in several ways and describe modifications of the algorithm to deal with these new classes. Theoretical results are validated in experiments.
The Complexity of Planning Problems With Simple Causal Graphs
Omer Giménez,Anders Jonsson
Computer Science , 2011, DOI: 10.1613/jair.2432
Abstract: We present three new complexity results for classes of planning problems with simple causal graphs. First, we describe a polynomial-time algorithm that uses macros to generate plans for the class 3S of planning problems with binary state variables and acyclic causal graphs. This implies that plan generation may be tractable even when a planning problem has an exponentially long minimal solution. We also prove that the problem of plan existence for planning problems with multi-valued variables and chain causal graphs is NP-hard. Finally, we show that plan existence for planning problems with binary state variables and polytree causal graphs is NP-complete.
Planning over Chain Causal Graphs for Variables with Domains of Size 5 Is NP-Hard
Omer Giménez,Anders Jonsson
Computer Science , 2014, DOI: 10.1613/jair.2742
Abstract: Recently, considerable focus has been given to the problem of determining the boundary between tractable and intractable planning problems. In this paper, we study the complexity of planning in the class C_n of planning problems, characterized by unary operators and directed path causal graphs. Although this is one of the simplest forms of causal graphs a planning problem can have, we show that planning is intractable for C_n (unless P = NP), even if the domains of state variables have bounded size. In particular, we show that plan existence for C_n^k is NP-hard for k>=5 by reduction from CNFSAT. Here, k denotes the upper bound on the size of the state variable domains. Our result reduces the complexity gap for the class C_n^k to cases k=3 and k=4 only, since C_n^2 is known to be tractable.
Development of a Model System to Identify Differences in Spring and Winter Oat
Aakash Chawade, Pernilla Lindén, Marcus Br?utigam, Rickard Jonsson, Anders Jonsson, Thomas Moritz, Olof Olsson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029792
Abstract: Our long-term goal is to develop a Swedish winter oat (Avena sativa). To identify molecular differences that correlate with winter hardiness, a winter oat model comprising of both non-hardy spring lines and winter hardy lines is needed. To achieve this, we selected 294 oat breeding lines, originating from various Russian, German, and American winter oat breeding programs and tested them in the field in south- and western Sweden. By assaying for winter survival and agricultural properties during four consecutive seasons, we identified 14 breeding lines of different origins that not only survived the winter but also were agronomically better than the rest. Laboratory tests including electrolytic leakage, controlled crown freezing assay, expression analysis of the AsVrn1 gene and monitoring of flowering time suggested that the American lines had the highest freezing tolerance, although the German lines performed better in the field. Finally, six lines constituting the two most freezing tolerant lines, two intermediate lines and two spring cultivars were chosen to build a winter oat model system. Metabolic profiling of non-acclimated and cold acclimated leaf tissue samples isolated from the six selected lines revealed differential expression patterns of 245 metabolites including several sugars, amino acids, organic acids and 181 hitherto unknown metabolites. The expression patterns of 107 metabolites showed significant interactions with either a cultivar or a time-point. Further identification, characterisation and validation of these metabolites will lead to an increased understanding of the cold acclimation process in oats. Furthermore, by using the winter oat model system, differential sequencing of crown mRNA populations would lead to identification of various biomarkers to facilitate winter oat breeding.
Glycerol Enhances the Antifungal Activity of Dairy Propionibacteria
Helena Lind,Anders Broberg,Karin Jacobsson,Hans Jonsson,Johan Schnürer
International Journal of Microbiology , 2010, DOI: 10.1155/2010/430873
Abstract: Dairy propionibacteria are widely used in starter cultures for Swiss type cheese. These bacteria can ferment glucose, lactic acid, and glycerol into propionic acid, acetic acid, and carbon dioxide. This research examined the antifungal effect of dairy propionibacteria when glycerol was used as carbon source for bacterial growth. Five type strains of propionibacteria were tested against the yeast Rhodotorula mucilaginosa and the molds Penicillium commune and Penicillium roqueforti. The conversion of 13C glycerol by Propionibacterium jensenii was followed with nuclear magnetic resonance. In a dual culture assay, the degree of inhibition of the molds was strongly enhanced by an increase in glycerol concentrations, while the yeast was less affected. In broth cultures, decreased pH in glycerol medium was probably responsible for the complete inhibition of the indicator fungi. NMR spectra of the glycerol conversion confirmed that propionic acid was the dominant metabolite. Based on the results obtained, the increased antifungal effect seen by glycerol addition to cultures of propionibacteria is due to the production of propionic acid and pH reduction of the medium.
High RBM3 expression in prostate cancer independently predicts a reduced risk of biochemical recurrence and disease progression
Liv Jonsson, Alexander Gaber, David Ulmert, Mathias Uhlén, Anders Bjartell, Karin Jirstr?m
Diagnostic Pathology , 2011, DOI: 10.1186/1746-1596-6-91
Abstract: Immunohistochemical RBM3 expression was examined in a tissue microarray with malignant and benign prostatic specimens from 88 patients treated with radical prostatectomy for localized disease. While rarely expressed in benign prostate gland epithelium, RBM3 was found to be up-regulated in prostate intraepithelial neoplasia and present in various fractions and intensities in invasive prostate cancer. High nuclear RBM3 expression was significantly associated with a prolonged time to biochemical recurrence (BCR) (HR 0.56, 95% CI: 0.34-0.93, p = 0.024) and clinical progression (HR 0.09, 95% CI: 0.01-0.71, p = 0.021). These associations remained significant in multivariate analysis, adjusted for preoperative PSA level in blood, pathological Gleason score and presence or absence of extracapsular extension, seminal vesicle invasion and positive surgical margin (HR 0.41, 95% CI: 0.19-0.89, p = 0.024 for BCR and HR 0.06, 95% CI: 0.01-0.50, p = 0.009 for clinical progression).Our results demonstrate that high nuclear expression of RBM3 in prostate cancer is associated with a prolonged time to disease progression and, thus, a potential biomarker of favourable prognosis. The value of RBM3 for prognostication, treatment stratification and follow-up of prostate cancer patients should be further validated in larger studies.Prostate cancer is the leading cause of cancer death in men in economically developed countries [1] and there was an estimated 328 000 cases in Europe in 2008 which makes it the most common form of cancer in men [2]. For localized cancer, radical prostatectomy is the most common treatment and it has shown a benefit in cancer specific survival in comparison to watchful waiting [3]. Nevertheless, in some cases the cancer will recur with detectable prostate specific antigen (PSA) concentrations in blood, known as biochemical recurrence (BCR) [4]. Apart from PSA, no diagnostic or prognostic biomarkers have yet been incorporated into clinical protocols for management
Registration accuracy for MR images of the prostate using a subvolume based registration protocol
Joakim H Jonsson, Patrik Brynolfsson, Anders Garpebring, Mikael Karlsson, Karin S?derstr?m, Tufve Nyholm
Radiation Oncology , 2011, DOI: 10.1186/1748-717x-6-73
Abstract: Ten patients were imaged four times each over the course of radiotherapy treatment using a T2 weighted sequence. The images were registered to each other using a mean square distance metric and a step gradient optimizer for registration volumes of different sizes. The precision of the registrations was evaluated using the center of mass distance between the manually defined prostates in the registered images. The optimal size of the registration volume was determined by minimizing the standard deviation of these distances.We found that prostate position was most uncertain in the anterior-posterior (AP) direction using traditional full volume registration. The improvement in standard deviation of the mean center of mass distance between the prostate volumes using a registration volume optimized to the prostate was 3.9 mm (p < 0.001) in the AP direction. The optimum registration volume size was 0 mm margin added to the prostate gland as outlined in the first image series.Repeated MR imaging of the prostate for therapy set-up or therapy assessment will both require high precision tissue registration. With a subvolume based registration the prostate registration uncertainty can be reduced down to the order of 1 mm (1 SD) compared to several millimeters for registration based on the whole pelvis.The role of magnetic resonance imaging (MRI) in modern prostate external radiotherapy treatments has in recent years attracted a lot of scientific attention. The applications span from MRI based treatment planning [1-4] to assessment of treatment response using different MRI techniques such as dynamic contrast enhanced MRI (DCE-MRI) [5,6], diffusion weighted imaging (DWI) [7,8] and magnetic resonance spectroscopy (MRS) [9]. It is widely accepted in the radiotherapy community that MRI is the preferred choice for target delineation of e.g. prostate, due to its superior soft tissue contrast [10]. It has also been shown that multi-modal registration between MRI and computed tomograph
Glycerol Enhances the Antifungal Activity of Dairy Propionibacteria
Helena Lind,Anders Broberg,Karin Jacobsson,Hans Jonsson,Johan Schnürer
International Journal of Microbiology , 2010, DOI: 10.1155/2010/430873
Abstract: Dairy propionibacteria are widely used in starter cultures for Swiss type cheese. These bacteria can ferment glucose, lactic acid, and glycerol into propionic acid, acetic acid, and carbon dioxide. This research examined the antifungal effect of dairy propionibacteria when glycerol was used as carbon source for bacterial growth. Five type strains of propionibacteria were tested against the yeast Rhodotorula mucilaginosa and the molds Penicillium commune and Penicillium roqueforti. The conversion of 13C glycerol by Propionibacterium jensenii was followed with nuclear magnetic resonance. In a dual culture assay, the degree of inhibition of the molds was strongly enhanced by an increase in glycerol concentrations, while the yeast was less affected. In broth cultures, decreased pH in glycerol medium was probably responsible for the complete inhibition of the indicator fungi. NMR spectra of the glycerol conversion confirmed that propionic acid was the dominant metabolite. Based on the results obtained, the increased antifungal effect seen by glycerol addition to cultures of propionibacteria is due to the production of propionic acid and pH reduction of the medium. 1. Introduction During storage of grains, fruits, vegetables, silage, and processed foods, the contamination with molds and yeasts may cause spoilage, which can be associated with substantial economic losses and potential health hazards. To extend the shelf life of susceptible food and feed, considerable amounts of chemical preservatives are used. The development of natural preservatives, consisting of microorganisms generally recognized as safe (GRAS), might form an alternative to the chemicals. Both lactic acid bacteria (LAB) and propionibacteria are safe, well-characterized bacteria, commonly used in many industrial processes [1, 2]. The antifungal activity of LAB (reviewed in [3]) is explored in both applied systems [4–6] and at substance level [7–9]. The use of propionibacteria as a biopreservative culture has been tested alone [10, 11] and also in combination with LAB [12–15]. Propionibacteria are also found to produce antimicrobial compounds [16–18]. Glycerol is a colorless, odorless liquid, widely used in a great number of applications (e.g., skin care products and drug solvents). The rapid increase in biodiesel production seen in recent years [19] provides an abundant and inexpensive source of glycerol as a residue. Previously, studies on the antifungal activity of LAB found that addition of glycerol enhanced the antifungal effect of certain species [20]. In LAB, the coenzyme B12-dependent
Focus on the Tumour Periphery in MRI Evaluation of Soft Tissue Sarcoma: Infiltrative Growth Signifies Poor Prognosis
Josefin Fernebro,Marie Wiklund,Kjell Jonsson,P r-Ola Bendahl,Anders Rydholm,Mef Nilbert,Jacob Engellau
Sarcoma , 2006, DOI: 10.1155/srcm/2006/21251
Abstract: Purpose. Infiltrative microscopical peripheral growth of soft tissue sarcomas (STS) has been shown to be of prognostic importance and preoperative risk stratification could individualize neoadjuvant treatment. Patients and methods. We assessed peripheral tumour growth pattern on preoperative MRI from 78 STS. The findings were correlated to histopathology and to outcome. Results. The MRI-based peripheral tumour growth pattern was classified as pushing in 34 tumours, focally infiltrative in 25, and diffusely infiltrative in 19. All tumours with diffuse infiltration on MRI also showed microscopical infiltration, whereas MRI failed to identify infiltration in two-thirds of the microscopically infiltrative tumours. Diffusely infiltrative growth on MRI gave a 2.5 times increased risk of metastases (P=.01) and a 3.7 times higher risk of local recurrence (P=.02). Discussion. Based on this observation we suggest that MRI evaluation of STS should focus on the peripheral tumour growth pattern since it adds prognostic information of value for decisions on neoadjuvant therapies.
Parallel imaging: is GRAPPA a useful acquisition tool for MR imaging intended for volumetric brain analysis?
Terri L Lindholm, Lisa Botes, Eva-Lena Engman, Anders Frank, Tomas Jonsson, Leif Svensson, Per Julin
BMC Medical Imaging , 2009, DOI: 10.1186/1471-2342-9-15
Abstract: Optimisation studies were performed on a young healthy volunteer and the selected protocol (including the use of two different parallel imaging acceleration factors) was then tested on a cohort of 15 elderly volunteers including MCI and AD patients. In addition to automatic brain segmentation, hippocampus volumes were manually outlined and measured in all patients. The 15 patients were scanned on a second occasion approximately one week later using the same protocol and evaluated in the same manner to test repeatability of measurement using images acquired with the GRAPPA parallel imaging technique applied to the MPRAGE sequence.Intraclass correlation tests show that almost perfect agreement between repeated measurements of both segmented brain parenchyma fraction and regional measurement of hippocampi. The protocol is suitable for both global and regional volumetric measurement dementia patients.In summary, these results indicate that parallel imaging can be used without detrimental effect to brain tissue segmentation and volumetric measurement and should be considered for both clinical and research studies where longitudinal measurements of brain tissue volumes are of interest.Age is the strongest predicting factor for dementia. In total, dementia affects more than 25% of those aged over 85 years and between 30 and 50% of those aged over 90 years. Due to the population boom of the 1940's the elderly population is rapidly growing. Thus, the prevalence of dementia is expected to increase significantly over the coming decades. Rapid diagnosis and treatment is therefore of evermore-importance.One of the most widely accepted imaging biomarkers in the aging process is that of brain tissue atrophy and an increase in cerebral spinal fluid (CSF) volume. Much effort is put into correlating rates of brain atrophy with disease progression [1,2]in order that the imaging may be used as a diagnostic tool [3] rather than depending on mental ability tests only. As yet, there is no
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