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Статті в журналах з теми "Hemodynamic response function delays":
1
Wang, Xin, Caio Seguin, Andrew Zalesky, Wan-wa Wong, Winnie Chiu-wing Chu, and Raymond Kai-yu Tong. "Synchronization lag in post stroke: relation to motor function and structural connectivity." Network Neuroscience 3, no. 4 (January 2019): 1121–40. http://dx.doi.org/10.1162/netn_a_00105.
Анотація:
Stroke is characterized by delays in the resting-state hemodynamic response, resulting in synchronization lag in neural activity between brain regions. However, the structural basis of this lag remains unclear. In this study, we used resting-state functional MRI (rs-fMRI) to characterize synchronization lag profiles between homotopic regions in 15 individuals (14 males, 1 female) with brain lesions consequent to stroke as well as a group of healthy comparison individuals. We tested whether the network communication efficiency of each individual’s structural brain network (connectome) could explain interindividual and interregional variation in synchronization lag profiles. To this end, connectomes were mapped using diffusion MRI data, and communication measures were evaluated under two schemes: shortest paths and navigation. We found that interindividual variation in synchronization lags was inversely associated with communication efficiency under both schemes. Interregional variation in lag was related to navigation efficiency and navigation distance, reflecting its dependence on both distance and structural constraints. Moreover, severity of motor deficits significantly correlated with average synchronization lag in stroke. Our results provide a structural basis for the delay of information transfer between homotopic regions inferred from rs-fMRI and provide insight into the clinical significance of structural-functional relationships in stroke individuals.
2
Braban, Andra, Robert Leech, Kevin Murphy, and Fatemeh Geranmayeh. "Cerebrovascular Reactivity Has Negligible Contribution to Hemodynamic Lag After Stroke: Implications for Functional Magnetic Resonance Imaging Studies." Stroke 54, no. 4 (April 2023): 1066–77. http://dx.doi.org/10.1161/strokeaha.122.041880.
Анотація:
Background: Functional magnetic resonance imaging (fMRI) is ubiquitously used to study poststroke recovery. However, the fMRI–derived hemodynamic responses are vulnerable to vascular insult which can result in reduced magnitude and temporal delays (lag) in the hemodynamic response function (HRF). The cause of HRF lag remains controversial, and a better understanding of it is required to ensure accurate interpretation of poststroke fMRI studies. In this longitudinal study, we investigate the relationship between hemodynamic lag and cerebrovascular reactivity (CVR) following stroke. Methods: Voxel-wise lag maps were calculated relative to a mean gray matter reference signal for 27 healthy controls and 59 patients with stroke across 2 time points (≈2 weeks and ≈4 months poststroke) and 2 conditions: resting-state and breath-holding. The breath-holding condition was additionally used to calculate CVR in response to hypercapnia. HRF lag was computed for both conditions across tissue compartments: lesion, perilesional tissue, unaffected tissue of the lesioned hemisphere, and their homolog regions in the unaffected hemisphere. CVR and lag maps were correlated. Group, condition, and time effects were assessed using ANOVA analyses. Results: Compared with the average gray matter signal, a relative hemodynamic lead was observed in the primary sensorimotor cortices in resting-state and bilateral inferior parietal cortices in the breath-holding condition. Whole-brain hemodynamic lag was significantly correlated across conditions irrespective of group, with regional differences across conditions suggestive of a neural network pattern. Patients showed relative lag in the lesioned hemisphere which significantly reduced over time. Breath-hold derived lag and CVR had no significant voxel-wise correlation in controls, or patients within the lesioned hemisphere or the homologous regions of the lesion and perilesional tissue in the right hemisphere (mean r <0.1). Conclusions: The contribution of altered CVR to HRF lag was negligible. We suggest that HRF lag is largely independent of CVR, and could partly reflect intrinsic neural network dynamics among other factors.
3
Rindler, Tara N., Valerie M. Lasko, Michelle L. Nieman, Motoi Okada, John N. Lorenz та Jerry B. Lingrel. "Knockout of the Na,K-ATPase α2-isoform in cardiac myocytes delays pressure overload-induced cardiac dysfunction". American Journal of Physiology-Heart and Circulatory Physiology 304, № 8 (15 квітня 2013): H1147—H1158. http://dx.doi.org/10.1152/ajpheart.00594.2012.
Анотація:
The α2-isoform of the Na,K-ATPase (α2) is the minor isoform of the Na,K-ATPase expressed in the cardiovascular system and is thought to play a critical role in the regulation of cardiovascular hemodynamics. However, the organ system/cell type expressing α2 that is required for this regulation has not been fully defined. The present study uses a heart-specific knockout of α2 to further define the tissue-specific role of α2 in the regulation of cardiovascular hemodynamics. To accomplish this, we developed a mouse model using the Cre/loxP system to generate a tissue-specific knockout of α2 in the heart using β-myosin heavy chain Cre. We have achieved a 90% knockout of α2 expression in the heart of the knockout mice. Interestingly, the heart-specific knockout mice exhibit normal basal cardiac function and systolic blood pressure, and in addition, these mice develop ACTH-induced hypertension in response to ACTH treatment similar to control mice. Surprisingly, the heart-specific knockout mice display delayed onset of cardiac dysfunction compared with control mice in response to pressure overload induced by transverse aortic constriction; however, the heart-specific knockout mice deteriorated to control levels by 9 wk post-transverse aortic constriction. These results suggest that heart expression of α2 does not play a role in the regulation of basal cardiovascular function or blood pressure; however, heart expression of α2 plays a role in the hypertrophic response to pressure overload. This study further emphasizes that the tissue localization of α2 determines its unique roles in the regulation of cardiovascular function.
4
van Meer, Maurits PA, Kajo van der Marel, Jan Willem Berkelbach van der Sprenkel, and Rick M. Dijkhuizen. "MRI of bilateral sensorimotor network activation in response to direct intracortical stimulation in rats after unilateral stroke." Journal of Cerebral Blood Flow & Metabolism 31, no. 7 (April 27, 2011): 1583–87. http://dx.doi.org/10.1038/jcbfm.2011.61.
Анотація:
Reinstatement of perilesional activation and connectivity may underlie functional recovery after stroke. To measure activation responsiveness in perilesional cortex in relation to white matter integrity, we performed functional functional magnetic resonance imaging during stimulation of the contralesional cortex, together with diffusion tensor imaging, 3 and 28 days after stroke in rats. Despite disturbed sensorimotor function and abnormal callosal appearance at day 3, activation amplitudes were preserved in the perilesional sensorimotor cortex, although time-to-peak was significantly delayed. This indicates that in spite of dysfunction, perilesional cortical tissue can be activated subacutely after stroke, while delay of the hemodynamic activation response suggests impaired neurovascular coupling.
5
Medeiros, Júlio, Marco Simões, João Castelhano, Rodolfo Abreu, Ricardo Couceiro, Jorge Henriques, Miguel Castelo-Branco, Henrique Madeira, César Teixeira, and Paulo de Carvalho. "EEG as a potential ground truth for the assessment of cognitive state in software development activities: A multimodal imaging study." PLOS ONE 19, no. 3 (March 7, 2024): e0299108. http://dx.doi.org/10.1371/journal.pone.0299108.
Анотація:
Cognitive human error and recent cognitive taxonomy on human error causes of software defects support the intuitive idea that, for instance, mental overload, attention slips, and working memory overload are important human causes for software bugs. In this paper, we approach the EEG as a reliable surrogate to MRI-based reference of the programmer’s cognitive state to be used in situations where heavy imaging techniques are infeasible. The idea is to use EEG biomarkers to validate other less intrusive physiological measures, that can be easily recorded by wearable devices and useful in the assessment of the developer’s cognitive state during software development tasks. Herein, our EEG study, with the support of fMRI, presents an extensive and systematic analysis by inspecting metrics and extracting relevant information about the most robust features, best EEG channels and the best hemodynamic time delay in the context of software development tasks. From the EEG-fMRI similarity analysis performed, we found significant correlations between a subset of EEG features and the Insula region of the brain, which has been reported as a region highly related to high cognitive tasks, such as software development tasks. We concluded that despite a clear inter-subject variability of the best EEG features and hemodynamic time delay used, the most robust and predominant EEG features, across all the subjects, are related to the Hjorth parameter Activity and Total Power features, from the EEG channels F4, FC4 and C4, and considering in most of the cases a hemodynamic time delay of 4 seconds used on the hemodynamic response function. These findings should be taken into account in future EEG-fMRI studies in the context of software debugging.
6
Yoshie, Koji, Pradeep S. Rajendran, Louis Massoud, OhJin Kwon, Vasudev Tadimeti, Siamak Salavatian, Jeffrey L. Ardell, Kalyanam Shivkumar, and Olujimi A. Ajijola. "Cardiac vanilloid receptor-1 afferent depletion enhances stellate ganglion neuronal activity and efferent sympathetic response to cardiac stress." American Journal of Physiology-Heart and Circulatory Physiology 314, no. 5 (May 1, 2018): H954—H966. http://dx.doi.org/10.1152/ajpheart.00593.2017.
Анотація:
Afferent fibers expressing the vanilloid receptor 1 (VR1) channel have been implicated in cardiac nociception; however, their role in modulating reflex responses to cardiac stress is not well understood. We evaluated this role in Yorkshire pigs by percutaneous epicardial application of resiniferatoxin (RTX), a toxic activator of the VR1 channel, resulting in the depletion of cardiac VR1-expressing afferents. Hemodynamics, epicardial activation recovery intervals, and in vivo activity of stellate ganglion neurons (SGNs) were recorded in control and RTX-treated animals. Stressors included inferior vena cava or aortic occlusion and rapid right ventricular pacing (RVP) to induce dyssynchrony and ischemia. In the epicardium, stellate ganglia, and dorsal root ganglia, immunostaining for the VR1 channel, calcitonin gene-related peptide, and substance P was significantly diminished by RTX. RTX-treated animals exhibited higher basal systolic blood pressures and contractility than control animals. Reflex responses to epicardial bradykinin and capsaicin were mitigated by RTX. Cardiovascular reflex function, as assessed by inferior vena cava or aortic occlusion, was similar in RTX-treated versus control animals. RTX-treated animals exhibited resistance to hemodynamic collapse induced by RVP. Activation recovery interval shortening during RVP, a marker of cardiac sympathetic outflow, was greater in RTX-treated animals and exhibited significant delay in returning to baseline values after cessation of RVP. The basal firing rate of SGNs and firing rates in response to RVP were also greater in RTX-treated animals, as was the SGN network activity in response to cardiac stressors. These data suggest that elimination of cardiac nociceptive afferents reorganizes the central-peripheral nervous system interaction to enhance cardiac sympathetic outflow. NEW & NOTEWORTHY Our work demonstrates a role for cardiac vanilloid receptor-1-expressing afferents in reflex processing of cardiovascular stress. Current understanding suggests that elimination of vanilloid receptor-1 afferents would decrease reflex cardiac sympathetic outflow. We found, paradoxically, that sympathetic outflow to the heart is instead enhanced at baseline and during cardiac stress.
7
Chen, Xiaoxiao, Javier A. Sala-Mercado, Robert L. Hammond, Masashi Ichinose, Soroor Soltani, Ramakrishna Mukkamala, and Donal S. O'Leary. "Dynamic control of maximal ventricular elastance via the baroreflex and force-frequency relation in awake dogs before and after pacing-induced heart failure." American Journal of Physiology-Heart and Circulatory Physiology 299, no. 1 (July 2010): H62—H69. http://dx.doi.org/10.1152/ajpheart.00922.2009.
Анотація:
We investigated to what extent maximal ventricular elastance ( Emax) is dynamically controlled by the arterial baroreflex and force-frequency relation in conscious dogs and to what extent these mechanisms are attenuated after the induction of heart failure (HF). We mathematically analyzed spontaneous beat-to-beat hemodynamic variability. First, we estimated Emax for each beat during a baseline period using the ventricular unstressed volume determined with the traditional multiple beat method during vena cava occlusion. We then jointly identified the transfer functions (system gain value and time delay per frequency) relating beat-to-beat fluctuations in arterial blood pressure (ABP) to Emax (ABP→ Emax) and beat-to-beat fluctuations in heart rate (HR) to Emax (HR→ Emax) to characterize the dynamic properties of the arterial baroreflex and force-frequency relation, respectively. During the control condition, the ABP→ Emax transfer function revealed that ABP perturbations caused opposite direction Emax changes with a gain value of −0.023 ± 0.012 ml−1, whereas the HR→ Emax transfer function indicated that HR alterations caused same direction Emax changes with a gain value of 0.013 ± 0.005 mmHg·ml−1·(beats/min)−1. Both transfer functions behaved as low-pass filters. However, the ABP→ Emax transfer function was more sluggish than the HR→ Emax transfer function with overall time constants (indicator of full system response time to a sudden input change) of 11.2 ± 2.8 and 1.7 ± 0.5 s ( P < 0.05), respectively. During the HF condition, the ABP→ Emax and HR→ Emax transfer functions were markedly depressed with gain values reduced to −0.0002 ± 0.007 ml−1 and −0.001 ± 0.004 mmHg·ml−1·(beats/min)−1 ( P < 0.1). Emax is rapidly and significantly controlled at rest, but this modulation is virtually abolished in HF.
8
Feige, Bernd, Klaus Scheffler, Fabrizio Esposito, Francesco Di Salle, Jürgen Hennig, and Erich Seifritz. "Cortical and Subcortical Correlates of Electroencephalographic Alpha Rhythm Modulation." Journal of Neurophysiology 93, no. 5 (May 2005): 2864–72. http://dx.doi.org/10.1152/jn.00721.2004.
Анотація:
Neural correlates of electroencephalographic (EEG) alpha rhythm are poorly understood. Here, we related EEG alpha rhythm in awake humans to blood-oxygen-level-dependent (BOLD) signal change determined by functional magnetic resonance imaging (fMRI). Topographical EEG was recorded simultaneously with fMRI during an open versus closed eyes and an auditory stimulation versus silence condition. EEG was separated into spatial components of maximal temporal independence using independent component analysis. Alpha component amplitudes and stimulus conditions served as general linear model regressors of the fMRI signal time course. In both paradigms, EEG alpha component amplitudes were associated with BOLD signal decreases in occipital areas, but not in thalamus, when a standard BOLD response curve (maximum effect at ∼6 s) was assumed. The part of the alpha regressor independent of the protocol condition, however, revealed significant positive thalamic and mesencephalic correlations with a mean time delay of ∼2.5 s between EEG and BOLD signals. The inverse relationship between EEG alpha amplitude and BOLD signals in primary and secondary visual areas suggests that widespread thalamocortical synchronization is associated with decreased brain metabolism. While the temporal relationship of this association is consistent with metabolic changes occurring simultaneously with changes in the alpha rhythm, sites in the medial thalamus and in the anterior midbrain were found to correlate with short time lag. Assuming a canonical hemodynamic response function, this finding is indicative of activity preceding the actual EEG change by some seconds.
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Storti, S. F., E. Formaggio, A. Bertoldo, P. Manganotti, A. Fiaschi, and G. M. Toffolo. "Modelling hemodynamic response function in epilepsy." Clinical Neurophysiology 124, no. 11 (November 2013): 2108–18. http://dx.doi.org/10.1016/j.clinph.2013.05.024.
10
Lesser, Ronald P. "Functional MRI of Interictal EEG Activity." Epilepsy Currents 2, no. 1 (January 2002): 17. http://dx.doi.org/10.1111/j.1535-7597.2002.00006.x.
Анотація:
Simultaneous EEG and Functional MRI of Epileptic Activity: A Case Report Baudewig J, Bittermann HJ, Paulus W, Frahm J Clin Neurophysiol 2001;112:1196–1200 Objectives Attempts to localize the source of epileptic activity by linking electroencephalographic (EEG) abnormalities to blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) signal alterations are hampered mainly by EEG distortions during MRI, subject motion, and unknown hemodynamic response characteristics. Methods Using T2*-weighted echo-planar imaging at 2.0 T (2 s temporal resolution, 2 × 2 × 4 mm(3) spatial resolution), this work demonstrates strategies to alleviate some of these problems while studying a patient who had idiopathic generalized epilepsy with poly-spike and slow-wave complexes. Results Continuous EEG recordings during dynamic MRI (500 ms scanning, 1500 ms delay) and post-examination derivation of an EEG reference function for MRI analysis revealed positive BOLD MRI responses with temporal characteristics similar to those obtained for functional challenges. Conclusions The ability to map focal epileptic activity and/or associated cognitive processing provides new potential for both epilepsy research and clinical patient management. Spatio-Temporal Imaging of Focal Interictal Epileptiform Activity Using EEG-Triggered Functional MRI Krakow K, Lemieux L, Messina D, Scott CA, Symms MR, Duncan JS, Fish DR Epileptic Disord 2001;3:67–74 EEG-triggered, blood oxygen level-dependent functional MRI (BOLD-fMRI) was used in 24 patients with localization-related epilepsy and frequent interictal epileptiform discharges (spikes) to identify those brain areas involved in generating the spikes, and to study the evolution of the BOLD signal change over time. The location of the fMRI activation was compared with the scalp EEG spike focus and the structural MR abnormality. Twelve patients (50%) had an fMRI activation concordant with the EEG focus and structural brain abnormalities where present (n = 7). In 2 other patients, the fMRI activation was non-concordant with electroclinical findings. The remaining 10 patients (41.7%) showed no significant fMRI activation. These patients had significantly lower mean spike amplitudes compared to those with positive fMRI results (p = 0.03). The time course of the BOLD response was studied in 3 patients and this revealed a maximum signal change 1.5 to 7.5 sec after the spike. In conclusion, EEG-triggered fMRI can directly identify the generators of interictal epileptiform activity, with high spatial resolution, in selected patients with frequent spikes. The superior spatial resolution obtainable through EEG-triggered fMRI may provide an additional non-invasive tool in the presurgical evaluation of patients with intractable focal seizures.
Дисертації з теми "Hemodynamic response function delays":
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Oota, Subba Reddy. "Modèles neurocomputationnels de la compréhension du langage : caractérisation des similarités et des différences entre le traitement cérébral du langage et les modèles de langage." Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0080.
Анотація:
Cette thèse explore la synergie entre l'intelligence artificielle (IA) et la neuroscience cognitive pour faire progresser les capacités de traitement du langage. Elle s'appuie sur l'idée que les avancées en IA, telles que les réseaux neuronaux convolutionnels et des mécanismes comme le « replay d'expérience », s'inspirent souvent des découvertes neuroscientifiques. Cette interconnexion est bénéfique dans le domaine du langage, où une compréhension plus profonde des capacités cognitives humaines uniques, telles que le traitement de structures linguistiques complexes, peut ouvrir la voie à des systèmes de traitement du langage plus sophistiqués. L'émergence de riches ensembles de données neuroimagerie naturalistes (par exemple, fMRI, MEG) aux côtés de modèles de langage avancés ouvre de nouvelles voies pour aligner les modèles de langage computationnels sur l'activité cérébrale humaine. Cependant, le défi réside dans le discernement des caractéristiques du modèle qui reflètent le mieux les processus de compréhension du langage dans le cerveau, soulignant ainsi l'importance d'intégrer des mécanismes inspirés de la biologie dans les modèles computationnels.En réponse à ce défi, la thèse introduit un cadre basé sur les données qui comble le fossé entre le traitement neurolinguistique observé dans le cerveau humain et les mécanismes computationnels des systèmes de traitement automatique du langage naturel (TALN). En établissant un lien direct entre les techniques d'imagerie avancées et les processus de TALN, elle conceptualise le traitement de l'information cérébrale comme une interaction dynamique de trois composantes critiques : le « quoi », le « où » et le « quand », offrant ainsi des perspectives sur la manière dont le cerveau interprète le langage lors de l'engagement avec des récits naturalistes. L'étude fournit des preuves convaincantes que l'amélioration de l'alignement entre l'activité cérébrale et les systèmes de TALN offre des avantages mutuels aux domaines de la neurolinguistique et du TALN. La recherche montre comment ces modèles computationnels peuvent émuler les capacités de traitement du langage naturel du cerveau en exploitant les technologies de réseau neuronal de pointe dans diverses modalités - langage, vision et parole. Plus précisément, la thèse met en lumière comment les modèles de langage pré-entraînés modernes parviennent à un alignement plus étroit avec le cerveau lors de la compréhension de récits. Elle examine le traitement différentiel du langage à travers les régions cérébrales, le timing des réponses (délais HRF) et l'équilibre entre le traitement de l'information syntaxique et sémantique. En outre, elle explore comment différentes caractéristiques linguistiques s'alignent avec les réponses cérébrales MEG au fil du temps et constate que cet alignement dépend de la quantité de contexte passé, indiquant que le cerveau code les mots légèrement en retard par rapport à celui actuel, en attendant plus de contexte futur. De plus, elle met en évidence la plausibilité biologique de l'apprentissage des états de réservoir dans les réseaux à état d'écho, offrant ainsi une interprétabilité, une généralisabilité et une efficacité computationnelle dans les modèles basés sur des séquences. En fin de compte, cette recherche apporte des contributions précieuses à la neurolinguistique, à la neuroscience cognitive et au TALNThis thesis explores the synergy between artificial intelligence (AI) and cognitive neuroscience to advance language processing capabilities. It builds on the insight that breakthroughs in AI, such as convolutional neural networks and mechanisms like experience replay 1, often draw inspiration from neuroscientific findings. This interconnection is beneficial in language, where a deeper comprehension of uniquely human cognitive abilities, such as processing complex linguistic structures, can pave the way for more sophisticated language processing systems. The emergence of rich naturalistic neuroimaging datasets (e.g., fMRI, MEG) alongside advanced language models opens new pathways for aligning computational language models with human brain activity. However, the challenge lies in discerning which model features best mirror the language comprehension processes in the brain, underscoring the importance of integrating biologically inspired mechanisms into computational models. In response to this challenge, the thesis introduces a data-driven framework bridging the gap between neurolinguistic processing observed in the human brain and the computational mechanisms of natural language processing (NLP) systems. By establishing a direct link between advanced imaging techniques and NLP processes, it conceptualizes brain information processing as a dynamic interplay of three critical components: "what," "where," and "when", offering insights into how the brain interprets language during engagement with naturalistic narratives. This study provides compelling evidence that enhancing the alignment between brain activity and NLP systems offers mutual benefits to the fields of neurolinguistics and NLP. The research showcases how these computational models can emulate the brain’s natural language processing capabilities by harnessing cutting-edge neural network technologies across various modalities—language, vision, and speech. Specifically, the thesis highlights how modern pretrained language models achieve closer brain alignment during narrative comprehension. It investigates the differential processing of language across brain regions, the timing of responses (Hemodynamic Response Function (HRF) delays), and the balance between syntactic and semantic information processing. Further, the exploration of how different linguistic features align with MEG brain responses over time and find that the alignment depends on the amount of past context, indicating that the brain encodes words slightly behind the current one, awaiting more future context. Furthermore, it highlights grounded language acquisition through noisy supervision and offers a biologically plausible architecture for investigating cross-situational learning, providing interpretability, generalizability, and computational efficiency in sequence-based models. Ultimately, this research contributes valuable insights into neurolinguistics, cognitive neuroscience, and NLP
2
Akyol, Halime Iclal. "Blind Deconvolution Techniques In Identifying Fmri Based Brain Activation." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613869/index.pdf.
Анотація:
In this thesis, we conduct functional Magnetic Resonance Imaging (fMRI) data analysis with the aim of grouping the brain voxels depending on their responsiveness to a neural task. We mathematically treat the fMRI signals as the convolution of the neural stimulus with the hemodynamic response function (HRF). We first estimate a time series including HRFs for each of the observed fMRI signals from a given set and we cluster them in order to identify the groups of brain voxels. The HRF estimation problem is studied within the Bayesian framework through a blind deconvolution algorithm using MAP approach under completely unsupervised and model-free settings, i.e, stimulus is assumed to be unknown and also no particular shape is assumed for the HRF. Only using a given fMRI signal together with a weak Gaussian prior distribution imposed on HRF favoring &lsquosmoothness&rsquo
, our method successfully estimates all the components of our framework: the HRF, the stimulus and the noise process. Then, we propose to use a modified version of Hausdorff distance to detect similarities within the space of HRFs, spectrally transform the data using Laplacian Eigenmaps and finally cluster them through EM clustering. According to our simulations, our method proves to be robust to lag, sampling jitter, quadratic drift and AWGN (Additive White Gaussian Noise). In particular, we obtained 100% sensitivity and specificity in terms of detecting active and passive voxels in our real data experiments. To conclude with, we propose a new framework for a mathematical treatment for voxel-based fMRI data analysis and our findings show that even when the HRF is unpredictable due to variability in cognitive processes, one can still obtain very high quality activation detection through the method proposed in this thesis.
3
Adli, Yilmaz Emine. "Wavelet Based Deconvolution Techniques In Identifying Fmri Based Brain Activation." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613870/index.pdf.
Анотація:
Functional Magnetic Resonance Imaging (fMRI) is one of the most popular neuroimaging methods for investigating the activity of the human brain during cognitive tasks. The main objective of the thesis is to identify this underlying brain
activation over time, using fMRI signal by detecting active and passive voxels. We performed two sub goals sequentially in order to realize the main objective. First, by using simple, data-driven Fourier Wavelet Regularized Deconvolution (ForWaRD) method, we extracted hemodynamic response function (HRF) which is the information that shows either a voxel is active or passive from fMRI signal. Second,
the extracted HRFs of voxels are classified as active and passive using Laplacian Eigenmaps. By this, the active and passive voxels in the brain are identified, and so are the activation areas. The ForWaRD method is directly applied to fMRI signals for the first time. The extraction method is tested on simulated and real block design fMRI signals, contaminated with noise from a time series of real MR images. The output of ForWaRD contains the HRF for each voxel. After HRF extraction, using Laplacian Eigenmaps algorithm, active and passive voxels are classified according to their HRFs. Also with this study, Laplacian Eigenmaps are used for HRF clustering for the first time. With the parameters used in this thesis, the extraction and clustering methods presented here are found to be robust to changes in signal properties. Performance analyses of the underlying methods are explained in terms of sensitivity and specificity metrics. These measurements prove the strength of our presented methods against different kinds of noises and changing signal properties.
4
Costantini, Isa. "Reconstruction régularisée et sans a-priori de l'activation cérébrale par IRMf." Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4022.
Анотація:
L'avènement de nouvelles techniques d'imagerie du cerveau comme l'IRM fonctionnelle (IRMf) au repos a conduit à la nécessité de nouvelles méthodes pour récupérer les activations fonctionnelles du cerveau sans connaissance du paradigme expérimental, comme dans l’IRMf basée sur tâche. Les méthodes conventionnelles, par example le modèle linéaire général, nécessitent la connaissance de la tâche pour pouvoir estimer la contribution du signal de chaque voxel à la tâche donnée. Pour surmonter ces limitations, des méthodes de déconvolution de la réponse dépendant du niveau d'oxygène dans le sang et de récupération des activations neurales sans avoir besoin d'informations préalables ont été proposées. Dans cette thèse, nous proposons d'abord une technique de déconvolution avec une regularisation temporelle qui utilise un opérateur exponentiel, dont la forme et la performance peuvent être ajustées.Avec cette méthode, nous avons réduit le nombre de paramètres à régler par l'utilisateur, par rapport à l'état de l'art. Ensuite, nous avons introduit un algorithme de régularisation qui s'applique à l'image IRMf 4-D, agissant simultanément dans les dimensions spatiale et temporelle. La méthode est basée sur l'idée que les grandes variations de l'image doivent être préservées car elles se produisent lors d'une activation et les petites variations doivent être lissées pour éliminer le bruit. Elle permet de lisser l'image IRMf avec une régularisation anisotrope, récupérant ainsi aveuglément la localisation des activations cérébrales et leur durée. Les deux méthodes ont été testées sur des données synthétiques et réelles et ont démontré une amélioration des résultats de l'état de l'artThe advent of new brain imaging techniques such as resting-state functional MRI (fMRI), has led to the need for new approaches to recover brain functional activations without a prior knowledge on the experimental paradigm, as it was the case for task-fMRI. Conventional methods, i.e. the general linear model, requires the knowledge of the task paradigm to estimate the contribution of each voxel's time course to the given task. To overcome this limitation, approaches to deconvolve the blood-oxygen-leveldependent (BOLD) response and recover the underlying neural activations without necessity of prior information has been proposed. Supposing the brain activates in constant blocks, frst we propose a temporal regularized deconvolution technique which uses an exponential operator, whose shape and performance can be adjusted, into a least absolute shrinkage and selection operator (LASSO) model solved via the Least-Angle Regression (LARS) algorithm. We reduced the number of parameters to be set by the user, when compared with the state of the art. Second, we introduce a paradigm-free regularization algorithm that applies on the 4-D fMRI image, acting simultaneously in the 3-D space and the 1-D time dimensions. The approach is based on the idea that large image variations should be preserved as they occur during an activation, whereas small variations should be smoothed to remove noise. It allows to smooth the whole fMRI image with an anisotropic regularization, thus blindly recovering the location of the brain activations in space and their timing and duration.Both approaches were tested on phantom and real data and were demonstrated to improve the results obtained in the state of the art
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Shao, Kuo-fang, and 邵國芳. "Investigating the Hemodynamic Response Function of Primary Visual Cortex in Hypercapnia." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/25369059707318641661.
Анотація:
碩士逢甲大學
生醫資訊暨生醫工程碩士學位學程
100
Functional magnetic resonance imaging (fMRI) using blood oxygenation level-dependent (BOLD) contrast has appeared to measure vascular oxygenation change due to neuron activity. BOLD signals have been used to investigate the cerebral neuronal activities and widely applied to clinical examinations. Recently, it is found that BOLD signals could be altered solely by hypercapnia. Such phenomenon might cause misinterpretation of fMRI studies with concurrent hypercapnia. Carbon dioxide (CO2) is a potent vasodilator that could increase the cerebral blood flow prominently. Most fMRI studies used long-time box-car stimulus design for evaluating BOLD effect in hypercapnia. In this study, instead of long-time box-car stimulus; event-related fMRI (ER-fMRI) with short-time visual stimulus is applied to investigate the transient hemodynamic response function (HRF). We aim the HRF change by different CO2 concentration inhalation. The study consisted of ten healthy volunteers with sixteen experiments for each subject under different fractions of inhaled CO2 and stimulus duration. The time curve of HRF is investigated in different visual stimulus duration (1, 2, 4 and 8 sec) and various CO2 concentration (room air, 3%, 5% and 7%). Peak-BOLD, full-width-at-half-maximum (FWHM) and time-to-peak (TTP) were used to evaluate HRF shape. Our study showed that the Peak-BOLD percent changes decrease corresponding to the increase of the inhaled CO2 fractions. The duration for FWHM and TTP prolongs proportional to the increase of inhaled CO2 fractions. This finding is consistent with the concept of cerebrovascular reserve, which might remain unchanged in lower CO2 fractions but be damped in higher CO2 fractions. In conclusion, we provide important concepts in HRF by the influence of inhaled CO2.
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Srikanth, R. "3D Coding Of MR Images And Estimation Of Hemodynamic Response Function From fMRI Data." Thesis, 2004. https://etd.iisc.ac.in/handle/2005/1175.
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Srikanth, R. "3D Coding Of MR Images And Estimation Of Hemodynamic Response Function From fMRI Data." Thesis, 2004. http://etd.iisc.ernet.in/handle/2005/1175.
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Batista, Catarina Guerra. "Brain response functions and neurovascular coupling in Type 2 Diabetes: insights from fMRI." Master's thesis, 2020. http://hdl.handle.net/10316/94050.
Анотація:
Trabalho de Projeto do Mestrado Integrado em Engenharia Biomédica apresentado à Faculdade de Ciências e TecnologiaA Diabetes Mellitus Tipo 2 (T2DM) é uma doença metabólica de caráter epidémico que promove várias complicações vasculares e potencialmente altera a neurofisiologia humana, tendo evidências crescentes de uma associação com o risco acrescido de desenvolvimento de perda de função cerebral, danos cognitivos a longo prazo e demência. Alterações vasculares patofisiológicas podem influenciar a regulação do fluxo sanguíneo na microvasculatura cerebral, possivelmente danificando o acoplamento neurovascular. Como estudado de forma não invasiva com pela imagem por ressonância magnética funcional, decréscimos do sinal Dependente do Nível de Oxigenação Sanguínea (BOLD) podem refletir baixa atividade neuronal ou acoplamento neurovascular pouco eficiente, pelo que as deficiências subjacentes da função cerebral podem ser indistinguíveis. Deste modo, torna-se fulcral a compreensão das correlações neurobiológicas da disfunção cerebral precoce nesta patologia. Neste projeto questionou-se se a Função de Resposta Hemodinâmica (HRF) estaria comprometida em indivíduos com T2DM, se dependeria da região cerebral ou se representaria um fenómeno cortical geral e/ou se seria influenciada pelo tipo de estímulo exibido ao medir a resposta BOLD a estímulos performance-matched de movimento visual. Foram processados os dados anatómicos e funcionais de ressonância magnética pertencentes a 141 sujeitos (64 pacientes com Diabetes Tipo 2 e 77 controlos), relativos à tarefa de estimulação psicofísica mencionada, que foi implementada distintamente em duas classes de paradigmas - paradigmas de blocos e event-related. A análise dos dados processados referentes à tarefa de estimulação de blocos permitiu localizar as regiões do cérebro por esta ativadas, nas quais, por meio de uma desconvolução, se extraiu a HRF durante a tarefa de estimulação de eventos. Por fim, foram avaliadas as diferenças entre as HRFs das duas populações.De forma geral, e como esperado, os pacientes diabéticos apresentavam HRFs significativamente diferentes. Notavelmente, este resultado estendeu-se a todas as regiões do cérebro, independentemente do tipo de estímulo, sugerindo tratar-se de um fenómeno geral. Os pacientes diabéticos exibiam HRFs com maior variabilidade, mais lentas e com menor amplitude de pico. As HRFs também incluíam um initial dip, maior que nos controlos, e, quando observado, um undershoot menos evidente, porém mais tardio e longo. A maioria dos parâmetros da HRF eram significativamente diferentes entre as duas populações, sendo a dispersão e a variabilidade maiores nos pacientes diabéticos. Para além disso, também evidenciavam uma maior latência de pico e menores declive relativo até ao pico, área abaixo da curva, área da secção positiva da curva e área da secção negativa da curva.Em suma, os resultados revelam uma função de resposta hemodinâmica comprometida nos estádios iniciais da T2DM, que se poderá dever a um desacoplamento neurovascular sem défices neurossensoriais, como demonstrado pelos limiares percetuais preservados. Deste modo, a HRF mostra ser uma ferramenta importante em estudos funcionais acerca da patologia mencionada, e deve ser considerada como um biomarcador no desenvolvimento e teste de estratégias de terapêutica nestes pacientes. No entanto, deve ser feita mais investigação relativamente ao acoplamento neurovascular e aos seus mecanismos para melhor entender e potencialmente prevenir a deterioração da função cerebral na T2DM.
Type 2 Diabetes Mellitus (T2DM) is an epidemic metabolic disease that promotes multiple vascular complications and potentially alters human neurophysiology, with growing evidence of an association with the increased risk for brain function loss, long-term cognitive impairment and dementia. Pathophysiological vascular changes can influence the blood flow regulation in cerebral microvasculature, possibly impairing the neurovascular coupling. As non-invasively studied with functional magnetic resonance imaging, decreases in the Blood Oxygenation Level-Dependent (BOLD) signal may reflect low neuronal activity or inefficient neurovascular coupling, thus underlying brain function impairments might be undistinguishable. Therefore, it becomes crucial to understand the neurobiological correlates of early brain dysfunction in this pathology. In this project, it was questioned whether the Hemodynamic Response Function (HRF) would be compromised in individuals with T2DM, whether it would depend on the brain region or would instead represent a general cortical phenomenon and/or whether it would rely on the displayed type of stimulus by measuring the BOLD response to performance-matched visual motion stimuli. Anatomical and functional magnetic resonance data from 141 subjects (64 patients with T2DM and 77 controls) in response to the aforementioned psychophysical stimulation task, which was separately implemented in two classes of paradigms - block and event-related paradigms, were processed. The analysis of the processed data concerning the block stimulation task allowed to localize activated brain regions, in which, by a deconvolution, we extracted the HRF during the event-related stimulation task. Ultimately, the differences between the HRFs of the two populations were assessed.Overall, and as expected, diabetic patients revealed significantly different HRFs. Notably, this outcome extended to all brain regions, regardless of the type of stimulus, suggesting that this is a general phenomenon. Diabetic patients displayed HRFs with higher variability, more sluggish, and with lower peak amplitude. The HRFs in T2DM also included an initial dip, which was larger than in controls, and when it was witnessed, a less prominent, but a later and longer undershoot. Most HRF parameters were significantly different between the two populations, with diabetic patients presenting a higher dispersion and variability. Furthermore, they also displayed a higher peak latency and lower relative slope to peak, area under the curve, positive curve section area, and negative curve section area.In short, the results unveiled an impaired hemodynamic response function in the early stages of T2DM, which may be due to a neurovascular uncoupling without neurosensory deficits, as demonstrated by preserved perceptual thresholds. Therefore, the HRF is proven to be a relevant tool in functional studies about the mentioned pathology, and it should be considered as a biomarker in the development and testing of therapeutic strategies in these patients. However, further research regarding neurovascular coupling and its mechanisms is required to better understand and potentially halt the deterioration of the brain function in T2DM.
Outro - DoIT – Diamarker: a consortium for the discovery of novel biomarkers in diabetes – QREN- COMPETE INFARMED Research Fund for Health (FIS-FIS-2015-01_DIA) - DiaMarkData European Foundation for the Study of Diabetes (EFSD) 2019 - Innovative Measurement of Diabetes Outcomes 2019
Частини книг з теми "Hemodynamic response function delays":
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Srikanth, R., R. Muralishankar, and A. G. Ramakrishnan. "Wavelet-Based Estimation of Hemodynamic Response Function." In Neural Information Processing, 1285–91. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-540-30499-9_200.
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Choukroun, Yoni, Lior Golgher, Pablo Blinder, and Lior Wolf. "Reconstructing the Hemodynamic Response Function via a Bimodal Transformer." In Lecture Notes in Computer Science, 371–81. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-43895-0_35.
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Zhang, Xiaoxu, and Jian Xu. "Time-Delay Identification for Linear Systems: A Practical Method Using the Frequency Response Function." In Advances in Delays and Dynamics, 333–48. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-53426-8_22.
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Bai, Ping, Young Truong, and Xuemei Huang. "Nonparametric Estimation of Hemodynamic Response Function: A Frequency Domain Approach." In Institute of Mathematical Statistics Lecture Notes - Monograph Series, 190–215. Beachwood, Ohio, USA: Institute of Mathematical Statistics, 2009. http://dx.doi.org/10.1214/09-lnms5712.
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Aggarwal, Priya, Anubha Gupta, and Ajay Garg. "Joint Estimation of Hemodynamic Response Function and Voxel Activation in Functional MRI Data." In Lecture Notes in Computer Science, 142–49. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-24553-9_18.
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Storti, S. F., E. Formaggio, A. Bertoldo, P. Manganotti, A. Fiaschi, and G. M. Toffolo. "Selection of Optimal Hemodynamic Response Function for FMRI Analysis on Acute Stroke Patients." In IFMBE Proceedings, 253–56. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03882-2_67.
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Hryniewicz, Nikodem, Rafał Rola, Kamil Lipiński, Ewa Piątkowska-Janko, and Piotr Bogorodzki. "Optimization of the BOLD Hemodynamic Response Function for EEG-FMRI Studies in Epilepsy." In The Latest Developments and Challenges in Biomedical Engineering, 131–46. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-38430-1_11.
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Kim, Jung Hwan, Amanda Taylor, and David Ress. "Simple Signed-Distance Function Depth Calculation Applied to Measurement of the fMRI BOLD Hemodynamic Response Function in Human Visual Cortex." In Computational Modeling of Objects Presented in Images. Fundamentals, Methods, and Applications, 216–28. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-54609-4_16.
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Marrelec, Guillaume, Philippe Ciuciu, Mélanie Pélégrini-Issac, and Habib Benali. "Estimation of the Hemodynamic Response Function in Event-Related Functional MRI: Directed Acyclic Graphs for a General Bayesian Inference Framework." In Lecture Notes in Computer Science, 635–46. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-540-45087-0_53.
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Srinivasan, Shrikanth, and Riddhi Kundu. "Fluid Management in Cardiogenic Shock." In Rational Use of Intravenous Fluids in Critically Ill Patients, 315–28. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-42205-8_15.
Анотація:
AbstractThis chapter discusses cardiogenic shock, a common condition encountered in the ICU. Cardiogenic shock results from decreased cardiac output and manifests as end-organ ischemia. The key diagnostic criteria for cardiogenic shock are identified, and the different clinical presentations of left and right heart failure are described. Fluid management in patients with an impaired cardiac function is complex, and clinicians traditionally titrate fluid therapy based on central venous pressure and clinical examination. However, there may be an overemphasis on fluid restriction in patients with heart failure, and physicians need to identify the subgroup of patients with cardiogenic shock who might actually benefit from fluid replacement. Fluid boluses need to be titrated to specific end points of end-organ perfusion guided by dynamic measures of fluid responsiveness and repeated echocardiographic assessments. While the pulmonary artery (PA) catheter continues to be the gold standard in assessing hemodynamics and fluid requirements in these patients, less invasive or noninvasive modes have shown potential in providing equivalent information without the risks associated with the PA catheter. Understanding the etiology and type of heart failure is crucial in providing additional information and the likelihood of a favorable response to fluid resuscitation. Take-home messages include the importance of identifying different subtypes of cardiogenic shock and etiology, the definitive role of ultrasound and other invasive or noninvasive hemodynamic monitors to guide fluid management, and the need for carefully titrated fluid boluses to specific end points in patients with impaired cardiac function.
Тези доповідей конференцій з теми "Hemodynamic response function delays":
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Shuvra, Lubna Tabassum, Sheikh Md Rabiul Islam, Nowrin Zaman, and Md Asif Hasan. "Analysis of Hemodynamic Response Function using fNIRS." In 2018 International Conference on Innovation in Engineering and Technology (ICIET). IEEE, 2018. http://dx.doi.org/10.1109/ciet.2018.8660933.
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Shah, Adnan, and Abd-Krim Seghouane. "Consistent estimation of the hemodynamic response function in fNIRS." In ICASSP 2013 - 2013 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). IEEE, 2013. http://dx.doi.org/10.1109/icassp.2013.6637857.
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Xue, Kaiqing, and Xue Tang. "Hemodynamic Response Function in Absence Epilepsy: An EEG-fMRI Study." In 2016 5th International Conference on Measurement, Instrumentation and Automation (ICMIA 2016). Paris, France: Atlantis Press, 2016. http://dx.doi.org/10.2991/icmia-16.2016.65.
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Afonso, David M., Joao M. Sanches, and Martin H. Lauterbach. "Neural physiological modeling towards a hemodynamic response function for fMRI." In 2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 2007. http://dx.doi.org/10.1109/iembs.2007.4352615.
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Marrelec, G. "Bayesian estimation of the hemodynamic response function in functional MRI." In BAYESIAN INFERENCE AND MAXIMUM ENTROPY METHODS IN SCIENCE AND ENGINEERING. AIP, 2002. http://dx.doi.org/10.1063/1.1477050.
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Forti, Rodrigo M., Andréa Alessio, and Rickson C. Mesquita. "Characterization of the NIRS Hemodynamic Response Function with Independent Component Analysis." In Biomedical Optics. Washington, D.C.: OSA, 2014. http://dx.doi.org/10.1364/biomed.2014.bs3a.21.
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Seghouane, Abd-Krim, and Leigh A. Johnston. "Consistent hemodynamic response estimation function in fMRI using sparse prior information." In 2014 IEEE 11th International Symposium on Biomedical Imaging (ISBI 2014). IEEE, 2014. http://dx.doi.org/10.1109/isbi.2014.6867941.
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Vallenilla, Natalia A., Samuel Montero-Hernandez, Hyochol Ahn, Hongyu Miao, and Luca Pollonini. "Hemodynamic Response Function from Osteoarthritic Pain using functional Near-Infrared Spectroscopy." In Bio-Optics: Design and Application. Washington, D.C.: OSA, 2021. http://dx.doi.org/10.1364/boda.2021.jtu4a.32.
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Seghouane, Abd-Krim, and Adnan Shah. "Consistent hemodynamic response function estimation in functional MRI by first order differencing." In 2013 IEEE 10th International Symposium on Biomedical Imaging (ISBI 2013). IEEE, 2013. http://dx.doi.org/10.1109/isbi.2013.6556467.
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Seghouane, Abd-Krim, and Adnan Shah. "Consistent estimation of the FMRI hemodynamic response function in AR(1) noise." In 2015 IEEE 12th International Symposium on Biomedical Imaging (ISBI 2015). IEEE, 2015. http://dx.doi.org/10.1109/isbi.2015.7163829.
Звіти організацій з теми "Hemodynamic response function delays":
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Hedrick, Jacob, and Timothy Jacobs. PR-457-14201-R02 Variable NG Composition Effects in LB 2S Compressor Engines Phase I Engine Response. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 2015. http://dx.doi.org/10.55274/r0010997.
Анотація:
This is the final report summarizing work completed during the first phase of the PRCI study on large bore two stroke lean burn integral compressor engine response to variable natural gas compositions for the purposes of engine control development. Accomplished tasks include the completion of a detailed literature review covering the research topic, a parametric study of laminar flame speeds and ignition delays for binary methane and ethane mixtures up to 30%, and a GT-Power engine model of the Colorado State GMV-4 research engine with associated validation data from CSU�s variable ethane effects study. The chemistry of the combustion reaction is crucial to accurate modeling; laminar flame speeds and ignition delays as function of composition were determined from the solutions to published chemical kinetics mechanisms GRI-Mech3.0 and Saudi Aramco Mech1.3, respectively. The Wiebe coefficients correlated to variations in ethane composition and spark timing were regressed from the crank angle resolved heat release rates. The Wiebe coefficients are the most significant achievement of this phase of the project, since they quantify the heat release as a function of composition. At this time, the Wiebe parameters only reflect the relative changes in the model since certain aspect of the models geometry are pending resolution. Future phases of the project could use the developed GT-Power model and Wiebe coefficients for development of control schemes that maintain emissions, speed and torque limits, and maximize thermal efficiency during a variable fuel composition event.
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Wideman, Jr., Robert F., Nicholas B. Anthony, Avigdor Cahaner, Alan Shlosberg, Michel Bellaiche, and William B. Roush. Integrated Approach to Evaluating Inherited Predictors of Resistance to Pulmonary Hypertension Syndrome (Ascites) in Fast Growing Broiler Chickens. United States Department of Agriculture, December 2000. http://dx.doi.org/10.32747/2000.7575287.bard.
Анотація:
Background PHS (pulmonary hypertension syndrome, ascites syndrome) is a serious cause of loss in the broiler industry, and is a prime example of an undesirable side effect of successful genetic development that may be deleteriously manifested by factors in the environment of growing broilers. Basically, continuous and pinpointed selection for rapid growth in broilers has led to higher oxygen demand and consequently to more frequent manifestation of an inherent potential cardiopulmonary incapability to sufficiently oxygenate the arterial blood. The multifaceted causes and modifiers of PHS make research into finding solutions to the syndrome a complex and multi threaded challenge. This research used several directions to better understand the development of PHS and to probe possible means of achieving a goal of monitoring and increasing resistance to the syndrome. Research Objectives (1) To evaluate the growth dynamics of individuals within breeding stocks and their correlation with individual susceptibility or resistance to PHS; (2) To compile data on diagnostic indices found in this work to be predictive for PHS, during exposure to experimental protocols known to trigger PHS; (3) To conduct detailed physiological evaluations of cardiopulmonary function in broilers; (4) To compile data on growth dynamics and other diagnostic indices in existing lines selected for susceptibility or resistance to PHS; (5) To integrate growth dynamics and other diagnostic data within appropriate statistical procedures to provide geneticists with predictive indices that characterize resistance or susceptibility to PHS. Revisions In the first year, the US team acquired the costly Peckode weigh platform / individual bird I.D. system that was to provide the continuous (several times each day), automated weighing of birds, for a comprehensive monitoring of growth dynamics. However, data generated were found to be inaccurate and irreproducible, so making its use implausible. Henceforth, weighing was manual, this highly labor intensive work precluding some of the original objectives of using such a strategy of growth dynamics in selection procedures involving thousands of birds. Major conclusions, solutions, achievements 1. Healthy broilers were found to have greater oscillations in growth velocity and acceleration than PHS susceptible birds. This proved the scientific validity of our original hypothesis that such differences occur. 2. Growth rate in the first week is higher in PHS-susceptible than in PHS-resistant chicks. Artificial neural network accurately distinguished differences between the two groups based on growth patterns in this period. 3. In the US, the unilateral pulmonary occlusion technique was used in collaboration with a major broiler breeding company to create a commercial broiler line that is highly resistant to PHS induced by fast growth and low ambient temperatures. 4. In Israel, lines were obtained by genetic selection on PHS mortality after cold exposure in a dam-line population comprising of 85 sire families. The wide range of PHS incidence per family (0-50%), high heritability (about 0.6), and the results in cold challenged progeny, suggested a highly effective and relatively easy means for selection for PHS resistance 5. The best minimally-invasive diagnostic indices for prediction of PHS resistance were found to be oximetry, hematocrit values, heart rate and electrocardiographic (ECG) lead II waves. Some differences in results were found between the US and Israeli teams, probably reflecting genetic differences in the broiler strains used in the two countries. For instance the US team found the S wave amplitude to predict PHS susceptibility well, whereas the Israeli team found the P wave amplitude to be a better valid predictor. 6. Comprehensive physiological studies further increased knowledge on the development of PHS cardiopulmonary characteristics of pre-ascitic birds, pulmonary arterial wedge pressures, hypotension/kidney response, pulmonary hemodynamic responses to vasoactive mediators were all examined in depth. Implications, scientific and agricultural Substantial progress has been made in understanding the genetic and environmental factors involved in PHS, and their interaction. The two teams each successfully developed different selection programs, by surgical means and by divergent selection under cold challenge. Monitoring of the progress and success of the programs was done be using the in-depth estimations that this research engendered on the reliability and value of non-invasive predictive parameters. These findings helped corroborate the validity of practical means to improve PHT resistance by research-based programs of selection.