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- Gamage, Eranga H., et al.
(author)
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As-Se Pentagonal Linkers to Induce Chirality and Polarity in Mixed-Valent Fe-Se Tetrahedral Chains Resulting in Hidden Magnetic Ordering
- 2022
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:25, s. 11283-11295
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Journal article (peer-reviewed)abstract
- A novel mixed-valent hybrid chiral and polar compound, Fe7As3Se12(en)(6)(H2O), has been synthesized by a single-step solvothermal method. The crystal structure consists of 1D [Fe5Se9] chains connected via [As3Se2]-Se pentagonal linkers and charge-balancing interstitial [Fe(en)(3)](2+) complexes (en = ethylenediamine). Neutron powder diffraction verified that interstitial water molecules participate in the crystal packing. Magnetic polarizability of the produced compound was confirmed by X-ray magnetic circular dichroism (XMCD) spectroscopy. X-ray absorption spectroscopy (XAS) and Fe-57 Mossbauer spectroscopy showed the presence of mixed-valent Fe2+/Fe3+ in the Fe-Se chains. Magnetic susceptibility measurements reveal strong antiferromagnetic nearest neighbor interactions within the chains with no apparent magnetic ordering down to 2 K. Hidden short-range magnetic ordering below 70 K was found by Fe-57 Mossbauer spectroscopy, showing that a fraction of the Fe3+/Fe2+ in the chains are magnetically ordered. Nevertheless, complete magnetic ordering is not achieved even at 6 K. Analysis of XAS spectra demonstrates that the fraction of Fe3+ in the chain increases with decreasing temperature. Computational analysis points out several competing ferrimagnetic ordered models within a single chain. This competition, together with variation in the Fe oxidation state and additional weak intrachain interactions, is hypothesized to prevent long-range magnetic ordering.
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- Kamali, Alexander, et al.
(author)
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What decides the suspicion of acute coronary syndrome in acute chest pain patients?
- 2014
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In: BMC Emergency Medicine. - 1471-227X. ; 14:9
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Journal article (peer-reviewed)abstract
- BACKGROUND: Physicians assessing chest pain patients in the emergency department (ED) base the likelihood of acute coronary syndrome (ACS) mainly on ECG, symptom history and blood markers of myocardial injury. Among these, the ECG has been stated to be the most important diagnostic tool. We aimed to analyze the relative contributions of these three diagnostic modalities to the ED physicians' evaluation of ACS likelihood in clinical practice.METHODS: 1151 consecutive ED chest pain patients were prospectively included. The ED physician's subjective assessment of the patient's likelihood of ACS (obvious ACS, strong, vague or no suspicion of ACS), the symptoms and the ECG were recorded on a special form. The ED TnT value was retrieved from the medical records. Frequency tables and logistic regression models were used to evaluate the contributions of the diagnostic tests to the level of ACS suspicion.RESULTS: Symptoms determined whether the physician had any suspicion of ACS (odds ratio, OR 526 for symptoms typical compared to not suspicious of ACS) since neither ECG nor TnT contributed significantly (ORs not significantly different from 1) to this assessment. ACS was suspected in only one in ten patients with symptoms not suspicious of ACS. Symptoms were also more important (OR 620 for typical symptoms) than ECG (OR 31 for ischemic ECG) and TnT (OR 3.4 for a positive TnT) for the assessment of obvious ACS/strong suspicion versus vague/no suspicion. Of the patients with ST-elevation on ECG, 71% were considered to have an obvious ACS, as opposed to only 6% of those with symptoms typical of ACS and 10% of those with a positive TnT.CONCLUSION: The ED physicians used symptoms as the most important assessment tool and applied primarily the symptoms to determine the level of ACS suspicion and to rule out ACS. The ECG was primarily used to rule in ACS. The TnT level played a minor role for the assessment of ACS likelihood. Further studies regarding ACS prediction based on symptoms may help improve decision-making in ED patients with possible ACS.
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- Kamali Sarvestani, Iman, et al.
(author)
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A computational model of visually guided locomotion in lamprey
- 2013
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In: Biological Cybernetics. - : Springer Science and Business Media LLC. - 0340-1200 .- 1432-0770. ; 107:5, s. 497-512
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Journal article (peer-reviewed)abstract
- This study addresses mechanisms for the generation and selection of visual behaviors in anamniotes. To demonstrate the function of these mechanisms, we have constructed an experimental platform where a simulated animal swims around in a virtual environment containing visually detectable objects. The simulated animal moves as a result of simulated mechanical forces between the water and its body. The undulations of the body are generated by contraction of simulated muscles attached to realistic body components. Muscles are driven by simulated motoneurons within networks of central pattern generators. Reticulospinal neurons, which drive the spinal pattern generators, are in turn driven directly and indirectly by visuomotor centers in the brainstem. The neural networks representing visuomotor centers receive sensory input from a simplified retina. The model also includes major components of the basal ganglia, as these are hypothesized to be key components in behavior selection. We have hypothesized that sensorimotor transformation in tectum and pretectum transforms the place-coded retinal information into rate-coded turning commands in the reticulospinal neurons via a recruitment network mimicking the layered structure of tectal areas. Via engagement of the basal ganglia, the system proves to be capable of selecting among several possible responses, even if exposed to conflicting stimuli. The anatomically based structure of the control system makes it possible to disconnect different neural components, yielding concrete predictions of how animals with corresponding lesions would behave. The model confirms that the neural networks identified in the lamprey are capable of responding appropriately to simple, multiple, and conflicting stimuli.
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- Schulz, Sebastian A., et al.
(author)
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Roadmap on photonic metasurfaces
- 2024
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In: APPLIED PHYSICS LETTERS. - 0003-6951 .- 1077-3118. ; 124:26
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Journal article (peer-reviewed)abstract
- Here we present a roadmap on Photonic metasurfaces. This document consists of a number of perspective articles on different applications, challenge areas or technologies underlying photonic metasurfaces. Each perspective will introduce the topic, present a state of the art as well as give an insight into the future direction of the subfield.
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- Zelenin, Sergey, et al.
(author)
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AQP4 role in renal K+ transport
- 2009
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In: The FASEB Journal. - : American Societies for Experimental Biology. - 0892-6638 .- 1530-6860. ; 23, s. 867.2-
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Journal article (other academic/artistic)abstract
- The collecting duct principle cells (PC) play a major role for concentration of urine and regulation of K+ homeostasis. Two water channels, AQP3 and AQP4, are expressed in the PC basolateral membrane (BLM). Here we present evidence that AQP4 participates in regulation of renal K+ transport. K+ enters the cell via Na+,K+-ATPase mediated transport in BLM. The presence of K+ channels in BLM, which is deeply infolded, thus providing a diffusion limited space, permits K+ recirculation, considered important for maintenance of membrane potential. Here we show with co-immunoprecipitation and GST pulldown assays, that in rat renal papilla, AQP4, but not AQP3, assembles with Na+,K+-ATPase and the K+ channel Kir7.1. This led us to hypothesize that AQP4, Na+,K+-ATPase and Kir7.1 form a K+ transporting microdomain, where AQP4 water transport maintains a favorable gradient for K+ efflux and stabilizes membrane potential. A mathematical model of K+ transport across an epithelial cells with a deeply infolded BLM supported the hypothesis and predicted an even higher impact of AQP water transport on K+ transport if AQP water permeability is sensitive to fluctuations in extracellular K+ concentration ([K+]o). To test this, AQP3 and AQP4 were expressed in MDCK cells, a cell line with much in common with PC. Water permeability was increased when [K+]o was 12mM in cells expressing AQP4 but not in cells expressing AQP3.
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- Zelenina, Marina, et al.
(author)
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A role for AQP4 in renal K+ transport
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Other publication (other academic/artistic)abstract
- The principal cells of the collecting duct carry out two major tasks: concentration of urine and regulation of K+ homeostasis. Two water channels, AQP3 and AQP4, are expressed in the principal cell basolateral membrane. We propose that AQP4 participates in the regulation of K+ transport in the principal cells. K+ enters the cell via Na+, K+-ATPase-mediated transport in the basolateral membrane. The presence of K+ channels in this membrane permits some K+ recirculation, considered important for maintenance of membrane potential. Here we show that AQP4, but not AQP3, assembles with both Na+, K+-ATPase and an inwardly rectifying K+ channel Kir7.1. We hypothesize that AQP4, Na+, K+-ATPase and Kir7.1 form a K+-transporting microdomain and that AQP4 serves to maintain a favorable concentration gradient for K+ efflux into the diffusion-limited space within the deep infoldings in principal cell basal membrane. The hypothesis is tested in a mathematical model. The model predicts that the impact of AQP-mediated water transport on K+ transport is more significant if AQP water permeability is sensitive to fluctuations in extracellular K+ concentration ([K+]e). We measured water permeability of AQP4 expressed in a renal epithelial cell line and found that it is upregulated when [K+]e is increased to 8 mM, and downregulated when [K+]e is decreased to 1 mM. Studies in an oocyte system indicate that AQP4 does not possess a voltage or K+ sensor. Finally, we show that the expression of AQP4 in rat renal medulla is, in contrast to the expression of AQP2 and AQP3, resistant to changes in K+ intake. Our experimental data, together with the mathematical model, support the concept that AQP4 is involved in principal cell K+ transport processes.
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