| 1. |
- Baboukani, Payam Shahsavari, et al.
(författare)
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EEG Phase Synchrony Reflects SNR Levels During Continuous Speech-in-Noise Tasks
- 2021
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Ingår i: 2021 43RD ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY (EMBC). - : IEEE. - 9781728111797 ; , s. 531-534
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Konferensbidrag (refereegranskat)abstract
- Comprehension of speech in noise is a challenge for hearing-impaired (HI) individuals. Electroencephalography (EEG) provides a tool to investigate the effect of different levels of signal-to-noise ratio (SNR) of the speech. Most studies with EEG have focused on spectral power in well-defined frequency bands such as alpha band. In this study, we investigate how local functional connectivity, i.e. functional connectivity within a localized region of the brain, is affected by two levels of SNR. Twenty-two HI participants performed a continuous speech in noise task at two different SNRs (+3 dB and +8 dB). The local connectivity within eight regions of interest was computed by using a multivariate phase synchrony measure on EEG data. The results showed that phase synchrony increased in the parietal and frontal area as a response to increasing SNR. We contend that local connectivity measures can be used to discriminate between speech-evoked EEG responses at different SNRs.
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| 2. |
- Barforooshan, Mohsen, et al.
(författare)
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The Effect of Time Delay on the Average Data Rate and Performance in Networked Control Systems
- 2022
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Ingår i: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 67:1, s. 16-31
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Tidskriftsartikel (refereegranskat)abstract
- This paper studies the performance of a feedback control loop closed via an error-free digital communication channel with transmission delay. The system comprises a discrete-time noisy linear time-invariant (LTI) plant whose single measurement output is mapped into its single control input by a causal, but otherwise arbitrary, coding and control scheme. We consider a single-input multiple-output (SIMO) channel between the encoder-controller and the decoder-controller which is lossless and imposes random time delay. We derive a lower bound on the minimum average feedback data rate that guarantees achieving a certain level of average quadratic performance over all possible realizations of the random delay. For the special case of a constant channel delay, we obtain an upper bound by proposing linear source-coding schemes that attain desired performance levels with rates that are at most 1.254 bits per sample greater than the lower bound. We supplement our results with a numerical experiment demonstrating that the obtained bounds and operational rates are increasing functions of the constant delay.
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| 3. |
- Laustsen, Christoffer, et al.
(författare)
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High altitude may alter oxygen availability and renal metabolism in diabetics as measured by hyperpolarized [1-C-13]pyruvate magnetic resonance imaging
- 2014
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Ingår i: Kidney International. - : Elsevier BV. - 0085-2538 .- 1523-1755. ; 86:1, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- The kidneys account for about 10% of the whole body oxygen consumption, whereas only 0.5% of the total body mass. It is known that intrarenal hypoxia is present in several diseases associated with development of kidney disease, including diabetes, and when renal blood flow is unaffected. The importance of deranged oxygen metabolism is further supported by deterioration of kidney function in patients with diabetes living at high altitude. Thus, we argue that reduced oxygen availability alters renal energy metabolism. Here, we introduce a novel magnetic resonance imaging (MRI) approach to monitor metabolic changes associated with diabetes and oxygen availability. Streptozotocin diabetic and control rats were given reduced, normal, or increased inspired oxygen in order to alter tissue oxygenation. The effects on kidney oxygen metabolism were studied using hyperpolarized [1-C-13]pyruvate MRI. Reduced inspired oxygen did not alter renal metabolism in the control group. Reduced oxygen availability in the diabetic kidney altered energy metabolism by increasing lactate and alanine formation by 23% and 34%, respectively, whereas the bicarbonate flux was unchanged. Thus, the increased prevalence and severity of nephropathy in patients with diabetes at high altitudes may originate from the increased sensitivity toward inspired oxygen. This increased lactate production shifts the metabolic routs toward hypoxic pathways.
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| 4. |
- Laustsen, Christoffer, et al.
(författare)
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High Intrarenal Lactate Production Inhibits the Renal Pseudohypoxic Response to Acutely Induced Hypoxia in Diabetes
- 2019
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Ingår i: Tomography. - : GRAPHO PUBLICATIONS. - 2379-1381 .- 2379-139X. ; 5:2, s. 239-247
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Tidskriftsartikel (refereegranskat)abstract
- Intrarenal hypoxia develops within a few days after the onset of insulinopenic diabetes in an experimental animal model (ie, a model of type-1 diabetes). Although diabetes-induced hypoxia results in increased renal lactate formation, mitochondrial function is well maintained, a condition commonly referred to as pseudohypoxia. However, the metabolic effects of significantly elevated lactate levels remain unclear. We therefore investigated in diabetic animals the response to acute intrarenal hypoxia in the presence of high renal lactate formation to delineate mechanistic pathways and compare these findings to healthy control animals. Hyperpolarized C-13-MRI and blood oxygenation level-dependent 1H-MRI was used to investigate the renal metabolism of [1-C-13] pyruvate and oxygenation following acutely altered oxygen content in the breathing gas in a streptozotocin rat model of type-1 diabetes with and without insulin treatment and compared with healthy control rats. The lactate signal in the diabetic kidney was reduced by 12%-16% during hypoxia in diabetic rats irrespective of insulin supplementation. In contrast, healthy controls displayed the well-known Pasteur effect manifested as a 10% increased lactate signal following reduction of oxygen in the inspired air. Reduced expression of the monocarboxyl transporter-4 may account for altered response to hypoxia in diabetes with a high intrarenal pyruvate-to-lactate conversion. Reduced intrarenal lactate formation in response to hypoxia in diabetes shows the existence of a different metabolic phenotype, which is independent of insulin, as insulin supplementation was unable to affect the pyruvate-to-lactate conversion in the diabetic kidney.
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| 5. |
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| 6. |
- Laustsen, Christoffer, et al.
(författare)
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Insufficient insulin administration to diabetic rats increases substrate utilization and maintains lactate production in the kidney
- 2014
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Ingår i: Physiological Reports. - : Wiley. - 2051-817X. ; 2:12
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Tidskriftsartikel (refereegranskat)abstract
- Good glycemic control is crucial to prevent the onset and progression of late diabetic complications, but insulin treatment often fails to achieve normalization of glycemic control to the level seen in healthy controls. In fact, recent experimental studies indicate that insufficient treatment with insulin, resulting in poor glycemic control, has an additional effect on progression of late diabetic complications, than poor glycemic control on its own. We therefore compared renal metabolic alterations during conditions of poor glycemic control with and without suboptimal insulin administration, which did not restore glycemic control, to streptozotocin (STZ)-diabetic rats using noninvasive hyperpolarized (13)C-pyruvate magnetic resonance imaging (MRI) and blood oxygenation level-dependent (BOLD) (1)H-MRI to determine renal metabolic flux and oxygen availability, respectively. Suboptimal insulin administration increased pyruvate utilization and metabolic flux via both anaerobic and aerobic pathways in diabetic rats even though insulin did not affect kidney oxygen availability, HbA1c, or oxidative stress. These results imply direct effects of insulin in the regulation of cellular substrate utilization and metabolic fluxes during conditions of poor glycemic control. The study demonstrates that poor glycemic control in combination with suboptimal insulin administration accelerates metabolic alterations by increasing both anaerobic and aerobic metabolism resulting in increased utilization of energy substrates. The results demonstrate the importance of tight glycemic control in insulinopenic diabetes, and that insulin, when administered insufficiently, adds an additional burden on top of poor glycemic control.
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| 9. |
- Quevedo, Daniel E., et al.
(författare)
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Energy Efficient State Estimation With Wireless Sensors Through the Use of Predictive Power Control and Coding
- 2010
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X .- 1941-0476. ; 58:9, s. 4811-4823
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Tidskriftsartikel (refereegranskat)abstract
- We study state estimation via wireless sensors over fading channels. Packet loss probabilities depend upon time-varying channel gains, packet lengths and transmission power levels of the sensors. Measurements are coded into packets by using either independent coding or distributed zero-error coding. At the gateway, a time-varying Kalman filter uses the received packets to provide the state estimates. To trade sensor energy expenditure for state estimation accuracy, we develop a predictive control algorithm which, in an online fashion, determines the transmission power levels and codebooks to be used by the sensors. To further conserve sensor energy, the controller is located at the gateway and sends coarsely quantized power increment commands, only whenever deemed necessary. Simulations based on real channel measurements illustrate that the proposed method gives excellent results.
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| 10. |
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