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Search Results: 1 - 10 of 3944 matches for " Johan Holm "
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Angular Momentum of Electromagnetic Radiation. Fundamental physics applied to the radio domain for innovative studies of space and development of new concepts in wireless communications
Johan Sj?holm,Kristoffer Palmer
Physics , 2009,
Abstract: In this diploma thesis we study the characteristics of electromagnetic fields carrying orbital angular momentum (OAM) by analyzing and utilizing results achieved in optics and then apply them to the radio domain to enable innovative radio studies of space and the development of new concepts in wireless communications. With the recent advent of fast digital converters it has become possible, over a wide radio frequency range, to manipulate not only the modulation properties of any given signal carried by a radio beam, but also the physical field vectors which make up the radio beam itself. Drawing inferences from results obtained in optics and quantum communication research during the past 10-15 years, we extract the core information about fields carrying orbital angular momentum. We show that with this information it is possible to design an array of antennas which, together with digital receivers/transmitters, can readily produce, under full software control, a radio beam that carries electromagnetic orbital angular momentum, a classical electrodynamics quantity known for a century but so far preciously little utilized in radio, if at all. This electromagnetic field is then optimized with the help of various antenna array techniques to improve the radio vector field qualities. By explicit numerical solution of the Maxwell equations from first principles, using a de facto industrial standard antenna software package, we show that the field indeed carries orbital angular momentum, and give a hint on how to detect and measure orbital angular momentum in radio beams. Finally, we discuss and give an explanation of what this can be used for and what the future might bring in this area.
Noninvasive Assessment of Autonomic Cardiovascular Function in Patients after Arterial Switch Operation for Transposition of the Great Arteries  [PDF]
Joanna Hlebowicz, Maja Rooth, Sandra Lindstedt, Johan Holm, Ulf Thilén
Surgical Science (SS) , 2015, DOI: 10.4236/ss.2015.63020
Abstract:

Background: Children born with transposition of the great arteries (TGA) must undergo corrective surgery for survival, arterial switch being the standard surgical procedure. The sympathetic innervation of the heart may be damaged during the operation. This study was designed to determine whether adults who were born with TGA and who had arterial switch operation (ASO) in infancy exhibit denervation of the heart, measured as heart rate variability (HRV) with electrocardiography (ECG). Methods: Nine patients with transposition of the great arteries (four men and five women; mean age 26 ± 1 years) who underwent the ASO at a mean age of 85 ± 35 days, and nine healthy adults (five men and five women; mean age 26 ± 2) were included in the study. Cardiac autonomic nerve function was determined by the variation in RR intervals during maximal deep breathing, monitored by continuous ECG. The mean values were calculated for each group from six inspirations (I) and expirations (E), and the E:I ratios were calculated. Results: The E:I ratio did not differ between patients with an arterial switch and healthy controls (P= 0.161). Two patients had signs of denervation of the heart up to 30 years after the arterial switch operation. Conclusions: Reinnervation of the heartmay take place in patients who have undergone the ASO in infancy, and these patients would not necessarily suffer from autonomic dysfunction. The HRV, measured by ECG, has the potential to identify arterially switched patients at risk of developing silent myocardial ischemia.

Manual correction of semi-automatic three-dimensional echocardiography is needed for right ventricular assessment in adults; validation with cardiac magnetic resonance
Ellen Ostenfeld, Marcus Carlsson, Kambiz Shahgaldi, Anders Roijer, Johan Holm
Cardiovascular Ultrasound , 2012, DOI: 10.1186/1476-7120-10-1
Abstract: 62 non-selected patients were examined with 3DE (Sonos 7500 and iE33) and with CMR (1.5T). Endocardial RV contours of 3DE-images were semi-automatically assessed and manually corrected in all patients. End-diastolic (EDV), end-systolic (ESV) volumes, stroke volume (SV) and ejection fraction (EF) were computed.53 patients (85%) had 3DE-images feasible for examination. Correlation coefficients and Bland Altman biases between 3DE with manual correction and CMR were r = 0.78, -22 ± 27 mL for EDV, r = 0.83, -7 ± 16 mL for ESV, r = 0.60, -12 ± 18 mL for SV and r = 0.60, -2 ± 8% for EF (p < 0.001 for all r-values). Without manual correction r-values were 0.77, 0.77, 0.70 and 0.49 for EDV, ESV, SV and EF, respectively (p < 0.001 for all r-values) and biases were larger for EDV, SV and EF (-32 ± 26 mL, -21 ± 15 mL and - 6 ± 9%, p ≤ 0.01 for all) compared to manual correction.Manual correction of the 3DE semi-automatic RV delineation decreases the bias and is needed for acceptable clinical accuracy. 3DE is highly feasible for visualizing the RV in an adult clinical setting.Assessment of the right ventricular volumes and function is of great importance in the diagnosis of various heart diseases e.g. pulmonary hypertension and congenital heart disease [1-3], for the choice of therapeutical strategies [4] and not least of prognostic value [5-7].Two-dimensional echocardiography (2DE) is the most commonly used clinical imaging modality in the evaluation of the right ventricle (RV). The complex geometrical structure of the RV with both a crescent shape and an outspread inflow and outflow tract requires a combination of several different scan planes for estimation of size and function with 2DE. M-Mode and tissue Doppler imaging of the free lateral wall of the RV are measurements in one point and are used as surrogates for the RV function. Hence, current echocardiographic techniques are not suitable for calculating right ventricular volumes and function accurately with a simple algor
Lactobacillus reuteri Maintains a Functional Mucosal Barrier during DSS Treatment Despite Mucus Layer Dysfunction
Johan Dicksved, Olof Schreiber, Ben Willing, Joel Petersson, Sara Rang, Mia Phillipson, Lena Holm, Stefan Roos
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0046399
Abstract: Treatment with the probiotic bacterium Lactobacillus reuteri has been shown to prevent dextran sodium sulfate (DSS)-induced colitis in rats. This is partly due to reduced P-selectin-dependent leukocyte- and platelet-endothelial cell interactions, however, the mechanism behind this protective effect is still unknown. In the present study a combination of culture dependent and molecular based T-RFLP profiling was used to investigate the influence of L. reuteri on the colonic mucosal barrier of DSS treated rats. It was first demonstrated that the two colonic mucus layers of control animals had different bacterial community composition and that fewer bacteria resided in the firmly adherent layer. During DSS induced colitis, the number of bacteria in the inner firmly adherent mucus layer increased and bacterial composition of the two layers no longer differed. In addition, induction of colitis dramatically altered the microbial composition in both firmly and loosely adherent mucus layers. Despite protecting against colitis, treatment with L. reuteri did not improve the integrity of the mucus layer or prevent distortion of the mucus microbiota caused by DSS. However, L. reuteri decreased the bacterial translocation from the intestine to mesenteric lymph nodes during DSS treatment, which might be an important part of the mechanisms by which L. reuteri ameliorates DSS induced colitis.
The importance of rectal cancer MRI protocols on iInterpretation accuracy
Chikako Suzuki, Michael R Torkzad, Soichi Tanaka, Gabriella Palmer, Johan Lindholm, Torbj?rn Holm, Lennart Blomqvist
World Journal of Surgical Oncology , 2008, DOI: 10.1186/1477-7819-6-89
Abstract: MR-examinations of 37 patients with locally advanced disease were divided into two groups; compliant and noncompliant, based on the imaging protocol, without knowledge of the histopathological results. A compliant rectal cancer imaging protocol was defined as including T2-weighted imaging in the sagittal and axial planes with supplementary coronal in low rectal tumors, alongside a high-resolution plane perpendicular to the rectum at the level of the primary tumor. Protocols not complying with these criteria were defined as noncompliant. Histopathological results were used as gold standard.Compliant rectal imaging protocols showed significantly better correlation with histopathological results regarding assessment of anterior organ involvement (sensitivity and specificity rates in compliant group were 86% and 94%, respectively vs. 50% and 33% in the noncompliant group). Compliant imaging protocols also used statistically significantly smaller voxel sizes and fewer number of MR sequences than the noncompliant protocolsAppropriate MR imaging protocols enable more accurate local staging of locally advanced rectal tumors with less number of sequences and without intravenous gadolinium contrast agents.Total mesorectal excision (TME) is the standard surgical treatment used for patients with primary rectal cancer. TME involves removal of a distinct anatomic compartment, the mesorectum, containing the rectal tumor, all local draining nodes and the mesorectal fat, by means of sharp dissection along the mesorectal fascia [1-3]. There is substantial evidence for efficacy of neoadjuvant therapy in combination with TME as being important to reduce local tumor recurrence rates [4-7]. When performing TME, knowledge of the relationship of the tumor to the circumferential resection margin (CRM) is of importance. When CRM is involved by the tumor, the risk of local recurrence is high [8-16]. The local prognostic factors assessed at preoperative magnetic resonance imaging (MRI) of rect
Endogenous Acute Phase Serum Amyloid A Lacks Pro-Inflammatory Activity, Contrasting the Two Recombinant Variants That Activate Human Neutrophils through Different Receptors
Karin Christenson,Lena Bj?rkman,Sofie Ahlin,Maja Olsson,Kajsa Sj?holm,Anna Karlsson,Johan Bylund
Frontiers in Immunology , 2013, DOI: 10.3389/fimmu.2013.00092
Abstract: Most notable among the acute phase proteins is serum amyloid A (SAA), levels of which can increase 1000-fold during infections, aseptic inflammation, and/or trauma. Chronically elevated SAA levels are associated with a wide variety of pathological conditions, including obesity and rheumatic diseases. Using a recombinant hybrid of the two human SAA isoforms (SAA1 and 2) that does not exist in vivo, numerous in vitro studies have given rise to the notion that acute phase SAA is a pro-inflammatory molecule with cytokine-like properties. It is however unclear whether endogenous acute phase SAA per se mediates pro-inflammatory effects. We tested this in samples from patients with inflammatory arthritis and in a transgenic mouse model that expresses human SAA1. Endogenous human SAA did not drive production of pro-inflammatory IL-8/KC in either of these settings. Human neutrophils derived from arthritis patients displayed no signs of activation, despite being exposed to severely elevated SAA levels in circulation, and SAA-rich sera also failed to activate cells in vitro. In contrast, two recombinant SAA variants (the hybrid SAA and SAA1) both activated human neutrophils, inducing L-selectin shedding, production of reactive oxygen species, and production of IL-8. The hybrid SAA was approximately 100-fold more potent than recombinant SAA1. Recombinant hybrid SAA and SAA1 activated neutrophils through different receptors, with recombinant SAA1 being a ligand for formyl peptide receptor 2 (FPR2). We conclude that even though recombinant SAAs can be valuable tools for studying neutrophil activation, they do not reflect the nature of the endogenous protein.
Molecular subtypes of breast cancer are associated with characteristic DNA methylation patterns
Karolina Holm, Cecilia Hegardt, Johan Staaf, Johan Vallon-Christersson, G?ran J?nsson, H?kan Olsson, ?ke Borg, Markus Ringnér
Breast Cancer Research , 2010, DOI: 10.1186/bcr2590
Abstract: We analysed methylation status of 807 cancer-related genes in 189 fresh frozen primary breast tumours and four normal breast tissue samples using an array-based methylation assay.Unsupervised analysis revealed three groups of breast cancer with characteristic methylation patterns. The three groups were associated with the luminal A, luminal B and basal-like molecular subtypes of breast cancer, respectively, whereas cancers of the HER2-enriched and normal-like subtypes were distributed among the three groups. The methylation frequencies were significantly different between subtypes, with luminal B and basal-like tumours being most and least frequently methylated, respectively. Moreover, targets of the polycomb repressor complex in breast cancer and embryonic stem cells were more methylated in luminal B tumours than in other tumours. BRCA2-mutated tumours had a particularly high degree of methylation. Finally, by utilizing gene expression data, we observed that a large fraction of genes reported as having subtype-specific expression patterns might be regulated through methylation.We have found that breast cancers of the basal-like, luminal A and luminal B molecular subtypes harbour specific methylation profiles. Our results suggest that methylation may play an important role in the development of breast cancers.Breast cancer is a complex and heterogeneous disease and one of the leading causes of death among women. Tumourigenesis is a multistep process resulting from the accumulation of genetic alterations such as mutations, rearrangements and copy number variations, but also epigenetic alterations such as promoter methylation and histone modification [1,2]. DNA methylation plays an essential role in development, chromosomal stability, and for maintaining gene expression states [1]. DNA methylation occurs when methyl groups are added to cytosines in CpG dinucleotides, leading to a closed chromatin conformation and gene silencing. CpGs are often found at increased frequ
20-Year Climatology of and Wet Deposition at Ny-lcurlyb\AArcurlyblesund, Svalbard
Rafael Kühnel,Tjarda J. Roberts,Mats P. Bj rkman,Elisabeth Isaksson,Wenche Aas,Kim Holmén,Johan Str m
Advances in Meteorology , 2011, DOI: 10.1155/2011/406508
Abstract: A 20-year dataset of weekly precipitation observations in Ny-Ålesund, Svalbard, was analysed to assess atmospheric wet deposition of nitrogen. Mean annual total nitrogen deposition was 74 mg N/(m2 yr) but exhibited large interannual variability and was dominated by highly episodic “strong” events, probably caused by rapid transport from European sources. The majority (90%) of precipitation samples were defined as “weak” (<2 mg N/m2) and contributed an annual baseline of ~17 mg N/(m2 yr), whereas 10% of precipitation samples were defined as “strong” (>2 mg N/m2) and additionally contributed up to 225 mg N/(m2 yr). Nitrate deposition largely occurred in samples within the solid-precipitation season (16 September–2 June), and ammonium deposition occurred equally in both solid and liquid seasons. Trends of reactive nitrogen emissions from Europe are uncertain, and increasing cyclonic activity over the North Atlantic caused by a changing climate might lead to more strong deposition events in Svalbard.
20-Year Climatology of and Wet Deposition at Ny-lcurlyb\AArcurlyblesund, Svalbard
Rafael Kühnel,Tjarda J. Roberts,Mats P. Bj?rkman,Elisabeth Isaksson,Wenche Aas,Kim Holmén,Johan Str?m
Advances in Meteorology , 2011, DOI: 10.1155/2011/406508
Abstract: A 20-year dataset of weekly precipitation observations in Ny-?lesund, Svalbard, was analysed to assess atmospheric wet deposition of nitrogen. Mean annual total nitrogen deposition was 74?mg?N/(m2?yr) but exhibited large interannual variability and was dominated by highly episodic “strong” events, probably caused by rapid transport from European sources. The majority (90%) of precipitation samples were defined as “weak” (<2?mg?N/m2) and contributed an annual baseline of ~17?mg?N/(m2?yr), whereas 10% of precipitation samples were defined as “strong” (>2?mg?N/m2) and additionally contributed up to 225?mg?N/(m2?yr). Nitrate deposition largely occurred in samples within the solid-precipitation season (16 September–2 June), and ammonium deposition occurred equally in both solid and liquid seasons. Trends of reactive nitrogen emissions from Europe are uncertain, and increasing cyclonic activity over the North Atlantic caused by a changing climate might lead to more strong deposition events in Svalbard. 1. Introduction Human activities release reactive nitrogen such as NH3 and (NO + NO2) to the atmosphere through energy production, fertilizer production, and cultivation of crops [1–4]. The resulting nitrogen-enriched air masses can be transported into remote, nutrient-limited regions such as the Arctic [5], primarily in the form of PAN (peroxyacetyl nitrate), but also as nitrate and ammonium aerosol. Furthermore, deposition of reactive nitrogen through precipitation is considered to be the main pathway for transfer of atmospheric nitrogen to the high Arctic surface [6]. The deposition of reactive nitrogen in the Arctic therefore results from the complex interplay of emissions, atmospheric transport, chemistry, precipitation, and snowpack processes as described below. Ice core analyses from Svalbard [7] and Greenland [8] showed an increase in nitrate concentrations in the 1950’s, followed by a drop in the 1980’s in the Svalbard ice cores. A trend analysis of recent precipitation observations in Europe could not find any significant trends for nitrate in Ny-?lesund [9, 10]. In Europe and North America, the nitrogen emissions are expected to further decrease due to current and future legislations though there are regional differences which may affect the Arctic in particular. The expected intensification of shipping activity might lead to an increase of nitrogen emissions in the Arctic [4]. Reduction protocols and improvements in technology counteract the increase of nitrogen emissions, and some progress has been made in reducing emissions in the last decade [11,
Properties of Lorenz Curves for Transformed Income Distributions  [PDF]
Johan Fellman
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.25091
Abstract: Redistributions of income can be considered as variable transformations of the initial income variable. The transformation is usually assumed to be positive, monotone-increasing and continuous, but discontinuous transformations have also been discussed recently. If the transformation is a tax or a transfer policy, the transformed variable is either the post-tax or the post-transfer income. A central problem has been the Lorenz dominance between the initial and the transformed income. This study considers analyses of other properties of the transformed Lorenz curves, especially its limits. We take in account mainly two cases (a) the transformed variable Lorenz dominates the initial one and (b) the initial Lorenz dominates the transformed one. For applications, the first case is more important than the second. The limits obtained are not accurate for a specific transformation, but do hold generally for all distributions and a broad class of transformations so that, if one pursues general conditions the inequalities obtained cannot be improved.
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