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Search Results: 1 - 10 of 401264 matches for " M. Hult "
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Message posting Or dialogue? On the dialectics of online practice in adult education
David Hamilton,Ethel Dahlgren,Agneta Hult,Tor S?derstr?m
Seminar.net , 2005,
Abstract: This paper examines on-line communication in liberal adult education. It highlights the problematic space between message posting and the promotion of dialogue. Conference software in Swedish adult education is widely based on message posting. But can message posting also foster the democratic practices associated with reasoned discussion or dialogue?
Teachers’ Invisible Presence in Net-based Distance Education
Agneta Hult,Ethel Dahlgren,David Hamilton,Tor S?derstr?m
International Review of Research in Open and Distance Learning , 2005,
Abstract: Conferencing – or dialogue – has always been a core activity in liberal adult education. More recently, attempts have been made to transfer such conversations online in the form of computer-mediated conferencing. This transfer has raised a range of pedagogical questions, most notably “Can established practices be continued? Or must new forms of participation and group management be established? This paper addresses these questions. It is based on two sources: (1) 3,700 online postings from a variety of Net-based adult education courses in Sweden; and (2) interviews with participants and course-leaders. It comprises a discussion of online conversational activity and, in particular, the absent presence and pedagogic orientation of teachers who steer learners towards explicit and implicit course goals. In other words, it is a reminder that adult education is not a free-floating form of self instruction but, rather, operates within boundaries created and managed by other human beings.
Quantification of uranium-238 in environmental samples using gamma-ray spectrometry
Hult M.,Andreotti E.,González de Ordu?a R.,Pommé S.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122407005
Abstract: A large number of environmental samples are routinely measured world-wide using gamma-ray spectrometry some of its assets being easy sample preparation and comprehensive data for many radionu-clides in one analysis. Although other techniques can be considered more suitable for analysing 238U in environmental samples, it is also routinely done by gamma-ray spectrometry. One mainly uses γ-ray emissions following the decay of the first daughter, 234Th, for determining the 238U activity. However, the low-energy gamma-rays at 63 keV and 92.5 keV are very difficult to quantify in a robust way due to high attenuation and interferences. This paper quantifies parameters affecting the possibility of making robust quantification of 238U via 234Th using gamma-ray spectrometry. It addresses the use of correct decay data, suitable detectors, optimised sample size, enhanced spectral amplification, correction for peak interferences and control of background.
Arachidonate 15-Lipoxygenase Enzyme Products Increase Platelet Aggregation and Thrombin Generation
Carolina Vijil, Cecilia Hermansson, Anders Jeppsson, G?ran Bergstr?m, Lillemor Mattsson Hultén
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0088546
Abstract: Atherosclerotic cardiovascular diseases are the leading causes of morbidity and mortality worldwide. We have previously shown that arachidonate 15-lipoxygenase B (ALOX15B) is highly expressed in atherosclerotic carotid plaques, and elucidation of mechanisms downstream of activated lipoxygenases may be relevant to our understanding of the genesis of atherosclerotic diseases. We examined 120 carotid plaques from patients with symptomatic carotid artery stenosis and showed that the extent of ALOX15B staining was significantly increased in carotid plaques with thrombosis. Impedance aggregometry analyses showed that the ALOX15B enzyme products 15-HETE and 15-HPETE increased platelet aggregation. By using a calibrated automatic thrombin assay, we showed that the ALOX15B products also increased both peak levels of thrombin and the total endogenous thrombin potential. Moreover, platelet aggregation was increased by addition of cell lysates from ischemic human macrophages, whereas platelet aggregation was reduced after knockdown of ALOX15B in human macrophages. Our data show that ALOX15B expression in human carotid plaques is associated with thrombus formation and that enzyme products of ALOX15B increase platelet aggregation and thrombin generation. We therefore propose that activated ALOX15B in macrophages may play a role in the induction of atherothrombotic events by increasing platelet aggregation and thrombin generation.
Search for $α$ decay of $^{151}$Eu to the first excited level of $^{147}$Pm using underground $γ$-ray spectrometry
F. A. Danevich,E. Andreotti,M. Hult,G. Marissens,V. I. Tretyak,A. Yuksel
Physics , 2013, DOI: 10.1140/epja/i2012-12157-7
Abstract: The alpha decay of $^{151}$Eu to the first excited level of $^{147}$Pm ($J^\pi = 5/2^+$, $E_{exc}=91.1$ keV) was searched for at the HADES underground laboratory ($\approx 500$ m w.e.). A sample of high purity europium oxide with mass of 303 g and a natural isotopic composition has been measured over 2232.8 h with a high energy resolution ultra-low background n-type semi-planar HPGe detector (40 cm$^3$) with sub-micron deadlayer. The new improved half-life limit has been set as $T_{1/2} \geq 3.7\times 10^{18}$ yr at 68% C.L. Possibilities to improve the sensitivity of the experiment, which is already near the theoretical predictions, are discussed. New half-life limit for $\alpha$ decay of $^{153}$Eu is also set as $T_{1/2} \geq 5.5\times 10^{17}$ yr.
The Effect of Mutual Coupling on a High Altitude Platform Diversity System Using Compact Antenna Arrays
Tommy Hult,Abbas Mohammed
International Journal of Antennas and Propagation , 2010, DOI: 10.1155/2010/492915
Abstract: We analyze the destructive effects of mutual coupling and spatial correlation between the separate antenna elements on a combined diversity system consisting of multiple HAPs (High-Altitude Platforms) employing various compact MIMO (Multiple-Input Multiple-Output) antenna array configurations, in order to enhance the mutual information in HAP communication links. In addition, we assess the influence of the separation angle between HAPs on system performance, and determine the optimal separation angles that maximize the total mutual information of the system for various compact MIMO antennas. Simulation results show that although the mutual information is degraded by mutual coupling and spatial correlation, the proposed HAP diversity system still provides better performance compared to a nondiversity system for all tested scenarios. 1. Introduction High-Altitude Platforms (HAPs) are quasistationary aerial platforms operating in the stratosphere. This emerging technology is preserving many of the advantages of both satellite and terrestrial systems [1–6] and presently started to attract considerable attention in Europe through the European Union COST 297 Action [1]. Using narrow bandwidth repeaters on HAPs for high speed data traffic has several advantages compared to using satellites [1], especially when operating in a local geographical area. In this paper, we propose a multiple HAP diversity system in order to enhance the mutual information in HAP communication links. To further enhance the system performance, independent spatial or polarization channels can be acquired by means of multiple antenna elements at both the transmitter and the receiver, and thus this technique is referred to as Multiple-Input Multiple-Output (MIMO) communications. The MIMO wireless communication is also combined with OFDM (Orthogonal Frequency Division Multiplexing) to form a combined HAP MIMO-OFDM diversity system. The proposed system consists of virtual MIMO spatial channels (created by multiple HAP diversity) in conjunction with the polarization and antenna pattern diversity (formed via special compact MIMO antenna arrays), as shown in Figure 1. Two compact MIMO antenna array configurations (the MIMO-Cube and MIMO-Tetrahedron) will be investigated, and their performance, in term has of mutual information, is analysed. The enhanced mutual information that is obtained through use of these compact MIMO antenna arrays, and of multiple HAPs, will degrade if the signals of the virtual MIMO spatial channels are correlated. Correlation of the signals can be caused by either low
On the origin of crossover interference: A chromosome oscillatory movement (COM) model
Maj A Hultén
Molecular Cytogenetics , 2011, DOI: 10.1186/1755-8166-4-10
Abstract: The Chromosome Oscillatory Movement (COM) model for crossover/chiasma interference implies that, during Prophase of Meiosis I, oscillatory movements of the telomeres (attached to the nuclear membrane) and the kinetochores (within the centromeres) create waves along the length of chromosome pairs (bivalents) so that crossing-over and chiasma formation is facilitated by the proximity of parental homologs induced at the nodal regions of the waves thus created. This model adequately explains the salient features of crossover/chiasma interference, where (1) there is normally at least one crossover/chiasma per bivalent, (2) the number is correlated to bivalent length, (3) the positions are dependent on the number per bivalent, (4) interference distances are on average longer over the centromere than along chromosome arms, and (5) there are significant changes in carriers of structural chromosome rearrangements.The crossover/chiasma frequency distribution in humans and mice with normal karyotypes as well as in carriers of structural chromosome rearrangements are those expected on the COM model. Further studies are underway to analyze mechanical/mathematical aspects of this model for the origin of crossover/chiasma interference, using string replicas of the homologous chromosomes at the Prophase stage of Meiosis I. The parameters to vary in this type of experiment will include: (1) the mitotic karyotype, i.e. ranked length and centromere index of the chromosomes involved, (2) the specific bivalent/multivalent length and flexibility, dependent on the way this structure is positioned within the nucleus and the size of the respective meiocyte nuclei, (3) the frequency characteristics of the oscillatory movements at respectively the telomeres and the kinetochores.Positive crossover interference, also termed genetic or chiasma interference, i.e. the non-random placement of crossovers along the length of individual chromosomes with a reduced probability of occurrence of one cross
Evaluation of the Economic Return of Preventive Health Care (FRISKKO) at Herd Level in Dairy Herds in Sweden
Hult Lena,Sandgren Charlotte
Acta Veterinaria Scandinavica , 2003, DOI: 10.1186/1751-0147-44-s1-p121
Abstract:
Suppression of EM Fields using Active Control Algorithms and MIMO Antenna System
T. Hult,A. Mohammed
Radioengineering , 2004,
Abstract: Active methods for attenuating acoustic pressure fields have beensuccessfully used in many applications. In this paper we investigatesome of these active control methods in combination with a MIMO antennasystem in order to assess their validity and performance when appliedto electromagnetic fields. The application that we evaluated in thispaper is a model of a mobile phone equipped with one ordinarytransmitting antenna and two actuator-antennas which purpose is toreduce the electromagnetic field at a specific area in space (e.g. atthe human head). Simulation results show the promise of using theadaptive active control algorithms and MIMO system to attenuate theelectromagnetic field power density.
The Effects of MIMO Antenna System Parameters and Carrier Frequency on Active Control Suppression of EM Fields
A. Mohammed,T. Hult
Radioengineering , 2007,
Abstract: In this paper we propose a new approach employing adaptive active control algorithms combined with a Multiple-Input Multiple-Output (MIMO) antenna system to suppress the electromagnetic field at a certain volume in space (e.g., at the human head). We will investigate the effects of the size and number of MIMO antenna elements on the system performance and test the algorithms at different carrier frequencies (e.g., GSM bands and UMTS).
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