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Search Results: 1 - 10 of 227750 matches for " Lars R Knudsen "
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Small Size Hashes with Enhanced Security
Lars R Knudsen
International Journal of Network Security , 2006,
Abstract: This paper contains techniques for enhancing the strength of any cryptographic hash function. For an ``ideal'', traditional hash function with an m-bit result, the complexity of a collision attack is approximately 2^{m/2}. Here constructions are presented where collisions are harder to find.
In-hospital resuscitation evaluated by in situ simulation: a prospective simulation study
Frederik Mondrup, Mikkel Brabrand, Lars Folkestad, Jakob Oxlund, Karsten R Wiborg, Niels P Sand, Torben Knudsen
Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine , 2011, DOI: 10.1186/1757-7241-19-55
Abstract: A prospective observational study of 16 unannounced simulated cardiopulmonary arrest scenarios was conducted. The participants of the study involved all health care personel on duty who responded to a cardiac arrest. We measured NFR and time to detection of initial rhythm on defibrillator and performed a comparison between the first responders and the cardiac arrest team.Data from 13 out of 16 simulations was used to evaluate the ability of generating resuscitation performance data in simulated cardiac arrest. The defibrillator arrived after median 214 seconds (180-254) and detected initial rhythm after median 311 seconds (283-349). A significant difference in no flow ratio (NFR) was observed between the first responders, median NFR 38% (32-46), and the resuscitation teams, median NFR 25% (19-29), p < 0.001. The difference was significant even after adjusting for pulse and rhythm check and shock delivery.The main finding of this study was a significant difference between the first responders and the cardiac arrest team with the latter performing more adequate cardiopulmonary resuscitation with regards to NFR. Future research should focus on the educational potential for in-situ simulation in terms of improving skills of hospital staff and patient outcome.Recent investigations highlight the importance of reducing interruptions in chest compressions and early defibrillation as vital factors of cardiopulmonary resuscitation (CPR), and the European Resuscitation Council 2010 Guidelines (ERC 2010) further emphasize these elements [1-9].Despite clear recommendations on CPR performance, several studies reports insufficient CPR quality during training (simulation) and during out-of-hospital and in-hospital cardiac arrests [10-14]. Documentation of resuscitation management may be difficult in the acute situation and it has been reported to be insufficient [15,16]. Furthermore, the retrospective nature of documentation in records represents a pitfall due to incompletion or in
Effects of erythropoietin on depressive symptoms and neurocognitive deficits in depression and bipolar disorder
Kamilla W Miskowiak, Maj Vinberg, Catherine J Harmer, Hannelore Ehrenreich, Gitte M Knudsen, Julian Macoveanu, Allan R Hansen, Olaf B Paulson, Hartwig R Siebner, Lars V Kessing
Trials , 2010, DOI: 10.1186/1745-6215-11-97
Abstract: The trial has a double-blind, placebo-controlled, parallel-group design. 40 patients with treatment-resistant major depression and 40 patients with bipolar disorder in remission are recruited and randomised to receive weekly infusions of Epo (Eprex; 40,000 IU) or saline (NaCl 0.9%) for 8 weeks. Randomisation is stratified for age and gender. The primary outcome parameters for the two studies are: depression severity measured with the Hamilton Depression Rating Scale 17 items (HDRS-17) [1] in study 1 and, in study 2, verbal memory measured with the Rey Auditory Verbal Learning Test (RAVLT) [2,3]. With inclusion of 40 patients in each study we obtain 86% power to detect clinically relevant differences between intervention and placebo groups on these primary outcomes.The trial is approved by the Local Ethics Committee: H-C-2008-092, Danish Medicines Agency: 2612-4020, EudraCT: 2008-04857-14, Danish Data Agency: 2008-41-2711 and ClinicalTrials.gov: NCT 00916552.Depression and bipolar disorder are associated with neurodegenerative processes, reduced neuroplasticity and neuropsychological dysfunction, which often persist even after clinical remission. Current pharmacological treatment strategies have several limitations including a significant treatment-onset-response delay, only partial or no response in a large group of patients and limited effects on their cognitive deficits, which often persist into periods of remission [4-9]. These enduring cognitive impairments affect patients' psychosocial and occupational function, quality of life and prognosis [7,8,10,11]. Better treatment options are thus required to improve the onset of efficacy, address patients who are treatment resistant and remediate neurocognitive deficits. Converging evidence suggests that neural atrophy and reduced neuroplasticity are involved in depression and bipolar disorder, while restoration of synaptic plasticity may be an important mechanism of chronic antidepressant and mood stabilising drug trea
Breakdown of disordered media by surface loads
Jakob Knudsen,A. R. Massih
Physics , 2004, DOI: 10.1103/PhysRevE.72.036129
Abstract: We model an interface layer connecting two parts of a solid body by N parallel elastic springs connecting two rigid blocks. We load the system by a shear force acting on the top side. The springs have equal stiffness but are ruptured randomly when the load reaches a critical value. For the considered system, we calculate the shear modulus, G, as a function of the order parameter, \phi, describing the state of damage, and also the ``spalled'' material (burst) size distribution. In particular, we evaluate the relation between the damage parameter and the applied force and explore the behaviour in the vicinity of material breakdown. Using this simple model for material breakdown, we show that damage, caused by applied shear forces, is analogous to a first-order phase transition. The scaling behaviour of G with \phi is explored analytically and numerically, close to \phi=0 and \phi=1 and in the vicinity of \phi_c, when the shear load is close but below the threshold force that causes material breakdown. Our model calculation represents a first approximation of a system subject to wear induced loads.
Risk scoring systems for adults admitted to the emergency department: a systematic review
Mikkel Brabrand, Lars Folkestad, Nicola Clausen, Torben Knudsen, Jesper Hallas
Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine , 2010, DOI: 10.1186/1757-7241-18-8
Abstract: Even though most scoring systems are not meant to be used on an individual level, they can support the more inexperienced doctors and nurses in assessing the risk of deterioration of their patients.We therefore performed a systematic review on the level of evidence of literature on scoring systems developed or validated in the MAU. We hypothesized that existing scoring systems would have a low level of evidence and only few systems would have been externally validated.We conducted a systematic search using Medline, EMBASE and the Cochrane Library, according to the PRISMA guidelines, on scoring systems developed to assess medical patients at admission.The primary endpoints were in-hospital mortality or transfer to the intensive care unit. Studies derived for only a single or few diagnoses were excluded.The ability to identify patients at risk (discriminatory power) and agreement between observed and predicted outcome (calibration) along with the method of derivation and validation (application on a new cohort) were extracted.We identified 1,655 articles. Thirty were selected for further review and 10 were included in this review.Eight systems used vital signs as variables and two relied mostly on blood tests.Nine systems were derived using regression analysis and eight included patients admitted to a MAU. Six systems used in-hospital mortality as their primary endpoint.Discriminatory power was specified for eight of the scoring systems and was acceptable or better in five of these. The calibration was only specified for four scoring systems. In none of the studies impact analysis or inter-observer reliability were analyzed.None of the systems reached the highest level of evidence.None of the 10 scoring systems presented in this article are perfect and all have their weaknesses. More research is needed before the use of scoring systems can be fully implemented to the risk assessment of acutely admitted medical patients.Patients referred to a medical admission unit (MA
Earlier reperfusion in patients with ST-elevation Myocardial infarction by use of helicopter
Knudsen Lars,Stengaard Carsten,Hansen Troels,Lassen Jens
Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine , 2012, DOI: 10.1186/1757-7241-20-70
Abstract: Background In patients with ST-elevation myocardial infarction (STEMI) reperfusion therapy should be initiated as soon as possible. This study evaluated whether use of a helicopter for transportation of patients is associated with earlier initiation of reperfusion therapy. Material and methods A prospective study was conducted, including patients with STEMI and symptom duration less than 12 hours, who had primary percutaneous coronary intervention (PPCI) performed at Aarhus University Hospital in Skejby. Patients with a health care system delay (time from emergency call to first coronary intervention) of more than 360 minutes were excluded. The study period ran from 1.1.2011 until 31.12.2011. A Western Denmark Helicopter Emergency Medical Service (HEMS) project was initiated 1.6.2011 for transportation of patients with time-critical illnesses, including STEMI. Results The study population comprised 398 patients, of whom 376 were transported by ambulance Emergency Medical Service (EMS) and 22 by HEMS. Field-triage directly to the PCI-center was used in 338 of patients. The median system delay was 94 minutes among those field-triaged, and 168 minutes among those initially admitted to a local hospital. Patients transported by EMS and field-triaged were stratified into four groups according to transport distance from the scene of event to the PCI-center: ≤25 km., 26–50 km., 51–75 km. and > 75 km. For these groups, the median system delay was 78, 89, 99, and 141 minutes. Among patients transported by HEMS and field-triaged the estimated median transport distance by ground transportation was 115 km, and the observed system delay was 107 minutes. Based on second order polynomial regression, it was estimated that patients with a transport distance of >60 km to the PCI-center may benefit from helicopter transportation, and that transportation by helicopter is associated with a system delay of less than 120 minutes even at a transport distance up to 150 km. Conclusion The present study indicates that use of a helicopter should be considered for field-triage of patients with STEMI to the PCI-center in case of long transportation. Such a strategy may ensure that patients living up to 150 km. from the PCI-center can be treated within 120 minutes of emergency call.
A General Mathematical Framework Suitable for Studying Signaling Cascades
Elisenda Feliu,Lars N. Andersen,Michael Knudsen,Carsten Wiuf
Quantitative Biology , 2010,
Abstract: We define a general mathematical framework for studying post-translational modification processes under the assumption of mass action kinetics.
An Algebraic Approach to Signaling Cascades with n Layers
Elisenda Feliu,Michael Knudsen,Lars N. Andersen,Carsten Wiuf
Quantitative Biology , 2010,
Abstract: Posttranslational modification of proteins is key in transmission of signals in cells. Many signaling pathways contain several layers of modification cycles that mediate and change the signal through the pathway. Here, we study a simple signaling cascade consisting of n layers of modification cycles, such that the modified protein of one layer acts as modifier in the next layer. Assuming mass-action kinetics and taking the formation of intermediate complexes into account, we show that the steady states are solutions to a polynomial in one variable, and in fact that there is exactly one steady state for any given total amounts of substrates and enzymes. We demonstrate that many steady state concentrations are related through rational functions, which can be found recursively. For example, stimulus-response curves arise as inverse functions to explicit rational functions. We show that the stimulus-response curves of the modified substrates are shifted to the left as we move down the cascade. Further, our approach allows us to study enzyme competition, sequestration and how the steady state changes in response to changes in the total amount of substrates. Our approach is essentially algebraic and follows recent trends in the study of posttranslational modification systems.
Use of Quantitative Real-Time PCR to Unravel Ecological Complexity in a Biological Control System  [PDF]
Guy R. Knudsen, Tae Gwan Kim, Yeoung-Seuk Bae, L.-M. C. Dandurand
Advances in Bioscience and Biotechnology (ABB) , 2015, DOI: 10.4236/abb.2015.64023
Abstract: Biological control of soilborne plant pathogens using beneficial fungi, such as the mycoparasite Trichoderma harzianum, offers the prospect of environmentally benign pest control. However, biocontrol organisms have their own natural enemies; for example the fungivorous nematode Aphelenchoides saprophilus preys on T. harzianum. A trophic cascade occurs when three or more trophic levels are present in a food chain, and consumption of the intermediate species affects biomass or productivity of a lower trophic level; such an interaction in this system might reduce the biocontrol efficacy of T. harzianum. However, the presence of refuges, where intermediate-level species are protected from predation, may reduce the ecological impact of a trophic cascade. Interactions among microscopic organisms in a complex medium such as soil are difficult to observe and quantify. We evaluated the potential of quantitative real-time PCR (qRT-PCR) as a tool to investigate the trophic cascade interaction among T. harzianum, A. saprophilus, and the plant pathogen Sclerotinia sclerotiorum. Results indicate that the mycoparasite colonized and persisted inside structures (sclerotia) of the target plant pathogen, where it was relatively protected from predation compared to the surrounding soil environment. In this way, colonization of sclerotia may provide a refuge that reduces trophic cascade effects in this system. qRT-PCR provided a sensitive method to investigate fungal dynamics over time in this multitrophic system.
Microscopy Method to Compare Cyst Nematode Infection of Different Plant Species  [PDF]
Rinu Kooliyottil, Louise-Marie Dandurand, Byju N. Govindan, Guy R. Knudsen
Advances in Bioscience and Biotechnology (ABB) , 2016, DOI: 10.4236/abb.2016.76029
Abstract: The cyst nematode, Globodera pallida, is an obligate, biotrophic pathogen of potato, causing up to 80% yield loss. In the present study, a non-destructive imaging technique was used to compare the development and behavior of G. pallida in its host Solanum tuberosum and in the non-host S. sisymbriifolium. We used microscopy-rhizosphere chambers coupled with the fluorescent stain PKH26, and compared this with destructively sampled acid fuchsin staining. No significant difference (P ≥ 0.90) in G. pallida numbers was found whether stained with PKH26 or acid fuchsin for either plant species indicating no toxic effect from the vital stain. PKH26 labelled J2s successfully located and penetrated roots of both S. tuberosum and S. sisymbriifolium. Two days after inoculation, PKH26 stained G. pallida was clearly observed migrating intercellularly through root tissues of both S. tuberosum and the non-host S. sisymbriifolium. Overall, more nematodes were observed in S. tuberosum than in S. sisymbriifolium roots. No live J2s were observed in S. sisymbriifolium roots stained with either acid fuchsin or PKH26 after 8 days. Understanding the time line of development of G. pallida in S. sisymbriifolium is important towards comprehensive understanding of plant defense responses.
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