A New Algorithm to Diagnose Atrial Ectopic Origin from Multi Lead ECG Systems - Insights from 3D Virtual Human Atria and Torso

PubMed Central

Alday, Erick A. Perez; Colman, Michael A.; Langley, Philip; Butters, Timothy D.; Higham, Jonathan; Workman, Antony J.; Hancox, Jules C.; Zhang, Henggui

2015-01-01

Rapid atrial arrhythmias such as atrial fibrillation (AF) predispose to ventricular arrhythmias, sudden cardiac death and stroke. Identifying the origin of atrial ectopic activity from the electrocardiogram (ECG) can help to diagnose the early onset of AF in a cost-effective manner. The complex and rapid atrial electrical activity during AF makes it difficult to obtain detailed information on atrial activation using the standard 12-lead ECG alone. Compared to conventional 12-lead ECG, more detailed ECG lead configurations may provide further information about spatio-temporal dynamics of the body surface potential (BSP) during atrial excitation. We apply a recently developed 3D human atrial model to simulate electrical activity during normal sinus rhythm and ectopic pacing. The atrial model is placed into a newly developed torso model which considers the presence of the lungs, liver and spinal cord. A boundary element method is used to compute the BSP resulting from atrial excitation. Elements of the torso mesh corresponding to the locations of the placement of the electrodes in the standard 12-lead and a more detailed 64-lead ECG configuration were selected. The ectopic focal activity was simulated at various origins across all the different regions of the atria. Simulated BSP maps during normal atrial excitation (i.e. sinoatrial node excitation) were compared to those observed experimentally (obtained from the 64-lead ECG system), showing a strong agreement between the evolution in time of the simulated and experimental data in the P-wave morphology of the ECG and dipole evolution. An algorithm to obtain the location of the stimulus from a 64-lead ECG system was developed. The algorithm presented had a success rate of 93%, meaning that it correctly identified the origin of atrial focus in 75/80 simulations, and involved a general approach relevant to any multi-lead ECG system. This represents a significant improvement over previously developed algorithms. PMID:25611350

Computation and projection of spiral wave trajectories during atrial fibrillation: a computational study.

PubMed

Pashaei, Ali; Bayer, Jason; Meillet, Valentin; Dubois, Rémi; Vigmond, Edward

2015-03-01

To show how atrial fibrillation rotor activity on the heart surface manifests as phase on the torso, fibrillation was induced on a geometrically accurate computer model of the human atria. The Hilbert transform, time embedding, and filament detection were compared. Electrical activity on the epicardium was used to compute potentials on different surfaces from the atria to the torso. The Hilbert transform produces erroneous phase when pacing for longer than the action potential duration. The number of phase singularities, frequency content, and the dominant frequency decreased with distance from the heart, except for the convex hull. Copyright © 2015 Elsevier Inc. All rights reserved.

Adenosine-Induced Atrial Fibrillation: Localized Reentrant Drivers in Lateral Right Atria due to Heterogeneous Expression of Adenosine A1 Receptors and GIRK4 Subunits in the Human Heart

PubMed Central

Li, Ning; Csepe, Thomas A.; Hansen, Brian J.; Sul, Lidiya V.; Kalyanasundaram, Anuradha; Zakharkin, Stanislav O.; Zhao, Jichao; Guha, Avirup; Van Wagoner, David R.; Kilic, Ahmet; Mohler, Peter J; Janssen, Paul ML; Biesiadecki, Brandon; Hummel, John D; Weiss, Raul; Fedorov, Vadim V.

2016-01-01

Background Adenosine provokes atrial fibrillation (AF) with a higher activation frequency in right atria (RA) versus left atria (LA) in patients, but the underlying molecular and functional substrates are unclear. We tested the hypothesis that adenosine-induced AF is driven by localized reentry in RA areas with highest expression of adenosine A1 receptor (A1R) and its downstream GIRK channels (IK,Ado). Methods We applied bi-atrial optical mapping and immunoblot mapping of various atrial regions to reveal the mechanism of adenosine-induced AF in explanted failing and non-failing human hearts (n=37). Results Optical mapping of coronary-perfused atria (n=24) revealed that adenosine perfusion (10–100μM) produced more significant shortening of action potential durations (APD80) in RA (from 290±45ms to 239±41ms, 17.3±10.4%; p<0.01) than LA (from 307±24ms to 286±23ms, 6.7±6.6%; p<0.01). In ten hearts, adenosine induced AF (317±116 sec) that, when sustained (≥2 min), was primarily maintained by one/two localized reentrant drivers in lateral RA. Tertiapin (10–100nM), a selective GIRK channel blocker, counteracted adenosine-induced APD shortening and prevented AF induction. Immunoblotting showed that the superior/middle lateral RA had significantly higher A1R (2.7±1.7 fold; p<0.01) and GIRK4 (1.7±0.8 fold; p<0.05) protein expression than lateral/posterior LA. Conclusions This study revealed a three-fold RA-to-LA A1R protein expression gradient in the human heart, leading to significantly greater RA vs. LA repolarization sensitivity in response to adenosine. Sustained adenosine-induced AF is maintained by reentrant drivers localized in lateral RA regions with the highest A1R/GIRK4 expression. Selective atrial GIRK channel blockade may effectively treat AF during conditions with increased endogenous adenosine. PMID:27462069

Adenosine-Induced Atrial Fibrillation: Localized Reentrant Drivers in Lateral Right Atria due to Heterogeneous Expression of Adenosine A1 Receptors and GIRK4 Subunits in the Human Heart.

PubMed

Li, Ning; Csepe, Thomas A; Hansen, Brian J; Sul, Lidiya V; Kalyanasundaram, Anuradha; Zakharkin, Stanislav O; Zhao, Jichao; Guha, Avirup; Van Wagoner, David R; Kilic, Ahmet; Mohler, Peter J; Janssen, Paul M L; Biesiadecki, Brandon J; Hummel, John D; Weiss, Raul; Fedorov, Vadim V

2016-08-09

Adenosine provokes atrial fibrillation (AF) with a higher activation frequency in right atria (RA) versus left atria (LA) in patients, but the underlying molecular and functional substrates are unclear. We tested the hypothesis that adenosine-induced AF is driven by localized reentry in RA areas with highest expression of adenosine A1 receptor and its downstream GIRK (G protein-coupled inwardly rectifying potassium channels) channels (IK,Ado). We applied biatrial optical mapping and immunoblot mapping of various atrial regions to reveal the mechanism of adenosine-induced AF in explanted failing and nonfailing human hearts (n=37). Optical mapping of coronary-perfused atria (n=24) revealed that adenosine perfusion (10-100 µmol/L) produced more significant shortening of action potential durations in RA (from 290±45 to 239±41 ms, 17.3±10.4%; P<0.01) than LA (from 307±24 to 286±23 ms, 6.7±6.6%; P<0.01). In 10 hearts, adenosine induced AF (317±116 s) that, when sustained (≥2 minutes), was primarily maintained by 1 to 2 localized reentrant drivers in lateral RA. Tertiapin (10-100 nmol/L), a selective GIRK channel blocker, counteracted adenosine-induced action potential duration shortening and prevented AF induction. Immunoblotting showed that the superior/middle lateral RA had significantly higher adenosine A1 receptor (2.7±1.7-fold; P<0.01) and GIRK4 (1.7±0.8-fold; P<0.05) protein expression than lateral/posterior LA. This study revealed a 3-fold RA-to-LA adenosine A1 receptor protein expression gradient in the human heart, leading to significantly greater RA versus LA repolarization sensitivity in response to adenosine. Sustained adenosine-induced AF is maintained by reentrant drivers localized in lateral RA regions with the highest adenosine A1 receptor/GIRK4 expression. Selective atrial GIRK channel blockade may effectively treat AF during conditions with increased endogenous adenosine. © 2016 American Heart Association, Inc.

Increased expression of mineralocorticoid receptor and 11beta-hydroxysteroid dehydrogenase type 2 in human atria during atrial fibrillation.

PubMed

De-An, Pei; Li, Li; Zhi-Yun, Xu; Jin-Yu, Huang; Zheng-Ming, Xu; Min, Wang; Qiang, Yao; Shi-Eng, Huang

2010-01-01

Atrialfibrillation (AF) is associated with the activation of the renin-angiotensin-aldosterone system in the atria. It is not clear whether the expression of a mineralocorticoid receptor (MR), or 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2), conferring aldosterone specificity to the MR, in patients with AF is altered. Patients with AF may be associated with increased expression of MR and 11betaHSD2 in the atria. Atrial tissue samples of 25 patients with rheumatic heart valve disease undergoing a valve replacement operation were examined. A total of 13 patients had chronic persistent AF (>6 mo) and 12 patients had no history of AF. The MR and 11betaHSD2 expression were analyzed at the mRNA and protein level. The localization of MR and 11betaHSD2 in atrial tissue was performed using specific immunohistochemistry staining. The results of real-time quantitative polymerase chain reaction (PCR) showed that AF groups, in comparison with sinus rhythm, had a higher mRNA expression level of MR or 11betaHSD2 (all P < 0.01). Both the MR and 11betaHSD2 protein expression level in atrial tissue were also significantly increased in patients with AF compared with patients with sinus rhythm (P < 0.05 or P < 0.01). The immunohistochemical staining of MR or 11betaHSD2 demonstrated that MR and 11betaHSD2 predominately located in the cytoplasm of myocardial cells in the atrium and the intensity and density of immunostaining appeared to be increased in the atria of patients with AF compared to those without AF. Increasing expression of MR and 11betaHSD2 in the atria during AF is one of the molecular mechanisms for development of atrial interstitial fibrosis in patients with AF. These findings may have an important impact on the treatment of AF with aldosterone antagonists. Copyright 2010 Wiley Periodicals, Inc.

Diabetes Alters the Expression and Translocation of the Insulin-Sensitive Glucose Transporters 4 and 8 in the Atria

PubMed Central

Maria, Zahra; Campolo, Allison R.; Lacombe, Veronique A.

2015-01-01

Although diabetes has been identified as a major risk factor for atrial fibrillation, little is known about glucose metabolism in the healthy and diabetic atria. Glucose transport into the cell, the rate-limiting step of glucose utilization, is regulated by the Glucose Transporters (GLUTs). Although GLUT4 is the major isoform in the heart, GLUT8 has recently emerged as a novel cardiac isoform. We hypothesized that GLUT-4 and -8 translocation to the atrial cell surface will be regulated by insulin and impaired during insulin-dependent diabetes. GLUT protein content was measured by Western blotting in healthy cardiac myocytes and type 1 (streptozotocin-induced, T1Dx) diabetic rodents. Active cell surface GLUT content was measured using a biotinylated photolabeled assay in the perfused heart. In the healthy atria, insulin stimulation increased both GLUT-4 and -8 translocation to the cell surface (by 100% and 240%, respectively, P<0.05). Upon insulin stimulation, we reported an increase in Akt (Th308 and s473 sites) and AS160 phosphorylation, which was positively (P<0.05) correlated with GLUT4 protein content in the healthy atria. During diabetes, active cell surface GLUT-4 and -8 content was downregulated in the atria (by 70% and 90%, respectively, P<0.05). Akt and AS160 phosphorylation was not impaired in the diabetic atria, suggesting the presence of an intact insulin signaling pathway. This was confirmed by the rescued translocation of GLUT-4 and -8 to the atrial cell surface upon insulin stimulation in the atria of type 1 diabetic subjects. In conclusion, our data suggest that: 1) both GLUT-4 and -8 are insulin-sensitive in the healthy atria through an Akt/AS160 dependent pathway; 2) GLUT-4 and -8 trafficking is impaired in the diabetic atria and rescued by insulin treatment. Alterations in atrial glucose transport may induce perturbations in energy production, which may provide a metabolic substrate for atrial fibrillation during diabetes. PMID:26720696

Diabetes Alters the Expression and Translocation of the Insulin-Sensitive Glucose Transporters 4 and 8 in the Atria.

PubMed

Maria, Zahra; Campolo, Allison R; Lacombe, Veronique A

2015-01-01

Although diabetes has been identified as a major risk factor for atrial fibrillation, little is known about glucose metabolism in the healthy and diabetic atria. Glucose transport into the cell, the rate-limiting step of glucose utilization, is regulated by the Glucose Transporters (GLUTs). Although GLUT4 is the major isoform in the heart, GLUT8 has recently emerged as a novel cardiac isoform. We hypothesized that GLUT-4 and -8 translocation to the atrial cell surface will be regulated by insulin and impaired during insulin-dependent diabetes. GLUT protein content was measured by Western blotting in healthy cardiac myocytes and type 1 (streptozotocin-induced, T1Dx) diabetic rodents. Active cell surface GLUT content was measured using a biotinylated photolabeled assay in the perfused heart. In the healthy atria, insulin stimulation increased both GLUT-4 and -8 translocation to the cell surface (by 100% and 240%, respectively, P<0.05). Upon insulin stimulation, we reported an increase in Akt (Th308 and s473 sites) and AS160 phosphorylation, which was positively (P<0.05) correlated with GLUT4 protein content in the healthy atria. During diabetes, active cell surface GLUT-4 and -8 content was downregulated in the atria (by 70% and 90%, respectively, P<0.05). Akt and AS160 phosphorylation was not impaired in the diabetic atria, suggesting the presence of an intact insulin signaling pathway. This was confirmed by the rescued translocation of GLUT-4 and -8 to the atrial cell surface upon insulin stimulation in the atria of type 1 diabetic subjects. In conclusion, our data suggest that: 1) both GLUT-4 and -8 are insulin-sensitive in the healthy atria through an Akt/AS160 dependent pathway; 2) GLUT-4 and -8 trafficking is impaired in the diabetic atria and rescued by insulin treatment. Alterations in atrial glucose transport may induce perturbations in energy production, which may provide a metabolic substrate for atrial fibrillation during diabetes.

Atrial fibrillation is associated with the fibrotic remodelling of adipose tissue in the subepicardium of human and sheep atria.

PubMed

Haemers, Peter; Hamdi, Hadhami; Guedj, Kevin; Suffee, Nadine; Farahmand, Patrick; Popovic, Natasa; Claus, Piet; LePrince, Pascal; Nicoletti, Antonino; Jalife, Jose; Wolke, Carmen; Lendeckel, Uwe; Jaïs, Pierre; Willems, Rik; Hatem, Stéphane N

2017-01-01

Accumulation of atrial adipose tissue is associated with atrial fibrillation (AF). However, the underlying mechanisms remain poorly understood. We examined the relationship between the characteristics of fatty infiltrates of the atrial myocardium and the history of AF. Atrial samples, collected in 92 patients during cardiac surgery and in a sheep model of persistent AF, were subjected to a detailed histological analysis. In sections of human right atrial samples, subepicardial fatty infiltrations were commonly observed in the majority of patients. A clear difference in the appearance and fibrotic content of these fatty infiltrations was observed. Fibro-fatty infiltrates predominated in patients with permanent AF (no AF: 37 ± 24% vs. paroxysmal AF: 50 ± 21% vs. permanent AF: 64 ± 23%, P < 0.001). An inverse correlation between fibrotic remodelling and the amount of subepicardial adipose tissue suggested the progressive fibrosis of fatty infiltrates with permanent AF. This hypothesis was tested in a sheep model of AF. In AF sheep, an increased accumulation of peri-atrial fat depot was observed on cardiac magnetic resonance imaging and dense fibro-fatty infiltrations predominated in the left atria of AF sheep. Cellular inflammation, mainly consisting of functional cytotoxic T lymphocytes, was observed together with adipocyte cell death in human atria. Atrial fibrillation is associated with the fibrosis of subepicardial fatty infiltrates, a process in which cytotoxic lymphocytes might be involved. This remodelling of the atrial subepicardium could contribute to structural remodelling forming a substrate for AF. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.

Translation of First North American 50 and 70 cc Total Artificial Heart Virtual and Clinical Implantations: Utility of 3D Computed Tomography to Test Fit Devices.

PubMed

Ferng, Alice S; Oliva, Isabel; Jokerst, Clinton; Avery, Ryan; Connell, Alana M; Tran, Phat L; Smith, Richard G; Khalpey, Zain

2017-08-01

Since the creation of SynCardia's 50 cc Total Artificial Hearts (TAHs), patients with irreversible biventricular failure now have two sizing options. Herein, a case series of three patients who have undergone successful 50 and 70 cc TAH implantation with complete closure of the chest cavity utilizing preoperative "virtual implantation" of different sized devices for surgical planning are presented. Computed tomography (CT) images were used for preoperative planning prior to TAH implantation. Three-dimensional (3D) reconstructions of preoperative chest CT images were generated and both 50 and 70 cc TAHs were virtually implanted into patients' thoracic cavities. During the simulation, the TAHs were projected over the native hearts in a similar position to the actual implantation, and the relationship between the devices and the atria, ventricles, chest wall, and diaphragm were assessed. The 3D reconstructed images and virtual modeling were used to simulate and determine for each patient if the 50 or 70 cc TAH would have a higher likelihood of successful implantation without complications. Subsequently, all three patients received clinical implants of the properly sized TAH based on virtual modeling, and their chest cavities were fully closed. This virtual implantation increases our confidence that the selected TAH will better fit within the thoracic cavity allowing for improved surgical outcome. Clinical implantation of the TAHs showed that our virtual modeling was an effective method for determining the correct fit and sizing of 50 and 70 cc TAHs. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Heart-specific overexpression of (pro)renin receptor induces atrial fibrillation in mice.

PubMed

Lian, Hong; Wang, Xiaojian; Wang, Juan; Liu, Ning; Zhang, Li; Lu, Yingdong; Yang, Yanmin; Zhang, Lianfeng

2015-04-01

Atrial fibrillation (AF) is the most common cardiac arrhythmia, causing substantial cardiovascular morbidity and mortality. The renin-angiotensin system (RAS) has been shown to be involved in the pathophysiology of AF. The (pro)renin receptor [(p)RR] is the last identified member of RAS. However, the role of (p)RR in AF is still unknown. Circulating levels of (p)RR were determined using an immunosorbent assay in 22 patients with AF (paroxysmal or persistent) and 22 healthy individuals. The plasma levels of (p)RR increased 3.6-fold in AF patients (P<0.001), indicating a relationship between (p)RR and AF. To investigate the role of (p)RR in the regulation of cardiac arrhythmia, we generated a transgenic mouse with overexpression of human (p)RR gene specifically in the heart. Electrocardiograms from (p)RR transgenic mice showed typical atrial flutter since 2 months, then spontaneously converted to atrial fibrillation by 10 months. The atria of the transgenic mice demonstrated significant dilation and fibrosis, and exhibited a high incidence of sudden death. Additionally, the genes of SERCA and HCN4, which are involved in the electrophysiology of AF, were significantly down-regulated and up-regulated respectively in transgenic mice atria. The phosphorylation of Erk1/2 significantly increased in the atria of the transgenic mice, and the activated Erk1/2 was found predominantly in cardiac fibroblasts, suggesting that the transgenic (p)RR gene may induce atrial fibrillation by activation of Erk1/2 in the cardiac fibroblasts of the atria. (p)RR promotes atrial structural and electrical remodeling in vivo, which indicates that (p)RR plays an important role in the pathological development of AF. Copyright © 2015. Published by Elsevier Ireland Ltd.

Electrophysiological effects of acute atrial stretch on persistent atrial fibrillation in patients undergoing open heart surgery.

PubMed

Elvan, Arif; Adiyaman, Ahmet; Beukema, Rypko J; Sie, Hauw T; Allessie, Maurits A

2013-03-01

The electrophysiologic effects of acute atrial dilatation and dedilatation in humans with chronic atrial fibrillation remains to be elucidated. To study the electrophysiological effects of acute atrial dedilatation and subsequent dilatation in patients with long-standing persistent atrial fibrillation (AF) with structural heart disease undergoing elective cardiac surgery. Nine patients were studied. Mean age was 71 ± 10 years, and left ventricular ejection was 46% ± 6%. Patients had at least moderate mitral valve regurgitation and dilated atria. After sternotomy and during extracorporal circulation, mapping was performed on the beating heart with 2 multielectrode arrays (60 electrodes each, interelectrode distance 1.5 mm) positioned on the lateral wall of the right atrium (RA) and left atrium (LA). Atrial pressure and size were altered by modifying extracorporal circulation. AF electrograms were recorded at baseline after dedilation and after dilatation of the atria afterward. At baseline, the median AF cycle length (mAFCL) was 184 ± 27 ms in the RA and 180 ± 17 ms in the LA. After dedilatation, the mAFCL shortened significantly to 168 ± 13 ms in the RA and to 168 ± 20 ms in the LA. Dilatation lengthened mAFCL significantly to 189 ± 17 ms in the RA and to 185 ± 23 ms in the LA. Conduction block (CB) at baseline was 14.3% ± 3.6% in the RA and 17.3% ± 5.5% in the LA. CB decreased significantly with dedilatation to 7.4% ± 2.9% in the RA and to 7.9% ± 6.3% in the LA. CB increased significantly with dilatation afterward to 15.0% ± 8.3% in the RA and to 18.5% ± 16.0% in the LA. Acute dedilatation of the atria in patients with long-standing persistent AF causes a decrease in the mAFCL in both atria. Subsequent dilatation increased the mAFCL. The amount of CB decreased with dedilatation and increased with dilatation afterward in both atria. Copyright © 2013 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Antagonist effects of seglitide (MK 678) at somatostatin receptors in guinea-pig isolated right atria.

PubMed Central

Dimech, J.; Feniuk, W.; Humphrey, P. P.

1993-01-01

Somatostatin (SS) exerts a negative inotropic effect in isolated atria. Here we report that in guinea-pig isolated right atria, seglitide, a potent cyclic hexapeptide somatostatin agonist, behaves as a competitive somatostatin receptor antagonist with pA2 values against SS14, SS25 and SS28, of 6.50 +/- 0.40, 6.24 +/- 0.08 and 6.09 +/- 0.06, respectively. Seglitide had little or no effect on the negative inotropic action of carbachol or N6-cyclohexyladenosine. Our findings indicate that the receptor-response coupling characteristics of guinea-pig atria are such that in this preparation seglitide has low intrinsic activity and behaves specifically as a somatostatin receptor antagonist. PMID:8104651

Synergistic Anti-arrhythmic Effects in Human Atria with Combined Use of Sodium Blockers and Acacetin

PubMed Central

Ni, Haibo; Whittaker, Dominic G.; Wang, Wei; Giles, Wayne R.; Narayan, Sanjiv M.; Zhang, Henggui

2017-01-01

Atrial fibrillation (AF) is the most common cardiac arrhythmia. Developing effective and safe anti-AF drugs remains an unmet challenge. Simultaneous block of both atrial-specific ultra-rapid delayed rectifier potassium (K+) current (IKur) and the Na+ current (INa) has been hypothesized to be anti-AF, without inducing significant QT prolongation and ventricular side effects. However, the antiarrhythmic advantage of simultaneously blocking these two channels vs. individual block in the setting of AF-induced electrical remodeling remains to be documented. Furthermore, many IKur blockers such as acacetin and AVE0118, partially inhibit other K+ currents in the atria. Whether this multi-K+-block produces greater anti-AF effects compared with selective IKur-block has not been fully understood. The aim of this study was to use computer models to (i) assess the impact of multi-K+-block as exhibited by many IKur blokers, and (ii) evaluate the antiarrhythmic effect of blocking IKur and INa, either alone or in combination, on atrial and ventricular electrical excitation and recovery in the setting of AF-induced electrical-remodeling. Contemporary mathematical models of human atrial and ventricular cells were modified to incorporate dose-dependent actions of acacetin (a multichannel blocker primarily inhibiting IKur while less potently blocking Ito, IKr, and IKs). Rate- and atrial-selective inhibition of INa was also incorporated into the models. These single myocyte models were then incorporated into multicellular two-dimensional (2D) and three-dimensional (3D) anatomical models of the human atria. As expected, application of IKur blocker produced pronounced action potential duration (APD) prolongation in atrial myocytes. Furthermore, combined multiple K+-channel block that mimicked the effects of acacetin exhibited synergistic APD prolongations. Synergistically anti-AF effects following inhibition of INa and combined IKur/K+-channels were also observed. The attainable maximal AF-selectivity of INa inhibition was greatly augmented by blocking IKur or multiple K+-currents in the atrial myocytes. This enhanced anti-arrhythmic effects of combined block of Na+- and K+-channels were also seen in 2D and 3D simulations; specially, there was an enhanced efficacy in terminating re-entrant excitation waves, exerting improved antiarrhythmic effects in the human atria as compared to a single-channel block. However, in the human ventricular myocytes and tissue, cellular repolarization and computed QT intervals were modestly affected in the presence of actions of acacetin and INa blockers (either alone or in combination). In conclusion, this study demonstrates synergistic antiarrhythmic benefits of combined block of IKur and INa, as well as those of INa and combined multi K+-current block of acacetin, without significant alterations of ventricular repolarization and QT intervals. This approach may be a valuable strategy for the treatment of AF. PMID:29218016

Regional distribution of T-tubule density in left and right atria in dogs.

PubMed

Arora, Rishi; Aistrup, Gary L; Supple, Stephen; Frank, Caleb; Singh, Jasleen; Tai, Shannon; Zhao, Anne; Chicos, Laura; Marszalec, William; Guo, Ang; Song, Long-Sheng; Wasserstrom, J Andrew

2017-02-01

The peculiarities of transverse tubule (T-tubule) morphology and distribution in the atrium-and how they contribute to excitation-contraction coupling-are just beginning to be understood. The objectives of this study were to determine T-tubule density in the intact, live right and left atria in a large animal and to determine intraregional differences in T-tubule organization within each atrium. Using confocal microscopy, T-tubules were imaged in both atria in intact, Langendorf-perfused normal dog hearts loaded with di-4-ANEPPS. T-tubules were imaged in large populations of myocytes from the endocardial surface of each atrium. Computerized data analysis was performed using a new MatLab (Mathworks, Natick, MA) routine, AutoTT. There was a large percentage of myocytes that had no T-tubules in both atria with a higher percentage in the right atrium (25.1%) than in the left atrium (12.5%) (P < .02). The density of transverse and longitudinal T-tubule elements was low in cells that did contain T-tubules, but there were no significant differences in density between the left atrial appendage, the pulmonary vein-posterior left atrium, the right atrial appendage, and the right atrial free wall. In contrast, there were significant differences in sarcomere spacing and cell width between different regions of the atria. There is a sparse T-tubule network in atrial myocytes throughout both dog atria, with significant numbers of myocytes in both atria-the right atrium more so than the left atrium-having no T-tubules at all. These regional differences in T-tubule distribution, along with differences in cell width and sarcomere spacing, may have implications for the emergence of substrate for atrial fibrillation. Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

A new lumbriculid genus and species from North America (Clitellata, Lumbriculidae)

USGS Publications Warehouse

Fend, S.V.; Gustafson, D.L.

2001-01-01

Secubelmis limpida n. sp., n. gen., is described from Montana, U.S.A. The monotypic genus resembles the lumbriculid genera Rhynchelmis and Tatriella in having atria in X, spermathecae in VIII, and semi-prosoporous male ducts. It differs from Tatriella in having paired atria and spermathecae, and from Rhynchelmis in having petiolate atria. The single prostate gland is unique within the Lumbriculidae. The new species appears to have a restricted range in the northern Rocky Mountains.

Interactions between acetylcholine, 5-hydroxytryptamine, nicotine and morphine on isolated rabbit atria

PubMed Central

Chittal, S. M.; Dadkar, N. K.; Gaitondé, B. B.

1968-01-01

1. The effects of 5-hydroxytryptamine (5-HT) and morphine on the responses to acetylcholine and nicotine of isolated rabbit atria were studied. 2. 5-Hydroxytryptamine (10 μg/ml.) and morphine (20 μg/ml.) blocked the negative chronotropic and inotropic actions of acetylcholine. 3. Nicotine (20 μg/ml.) produced stimulation of the atria, which was blocked by dichlorisoprenaline, morphine, 5-HT, bretylium and hemicholinium. Hemicholinium block was reversed by choline. 4. In reserpinized preparations, nicotine produced inhibition of atria and this action was also blocked by atropine, 5-HT and morphine. Inhibition induced by nicotine was potentiated by physostigmine. 5. 5-Hydroxytryptamine (20 μg/ml.) produced stimulation of atria. This was blocked by bretylium and reduced by hemicholinium. Hemicholinium block was reversed by choline. 6. It is concluded that 5-HT in low concentrations acts as a weak agonist at the cholinoceptive receptors and therefore blocks the action of acetylcholine. Furthermore, nicotine and larger doses of 5-HT have actions on ganglionic structures and liberate acetylcholine, which in turn releases catecholamines. PMID:4386371

Atrial fibrillation driven by micro-anatomic intramural re-entry revealed by simultaneous sub-epicardial and sub-endocardial optical mapping in explanted human hearts.

PubMed

Hansen, Brian J; Zhao, Jichao; Csepe, Thomas A; Moore, Brandon T; Li, Ning; Jayne, Laura A; Kalyanasundaram, Anuradha; Lim, Praise; Bratasz, Anna; Powell, Kimerly A; Simonetti, Orlando P; Higgins, Robert S D; Kilic, Ahmet; Mohler, Peter J; Janssen, Paul M L; Weiss, Raul; Hummel, John D; Fedorov, Vadim V

2015-09-14

The complex architecture of the human atria may create physical substrates for sustained re-entry to drive atrial fibrillation (AF). The existence of sustained, anatomically defined AF drivers in humans has been challenged partly due to the lack of simultaneous endocardial-epicardial (Endo-Epi) mapping coupled with high-resolution 3D structural imaging. Coronary-perfused human right atria from explanted diseased hearts (n = 8, 43-72 years old) were optically mapped simultaneously by three high-resolution CMOS cameras (two aligned Endo-Epi views (330 µm2 resolution) and one panoramic view). 3D gadolinium-enhanced magnetic resonance imaging (GE-MRI, 80 µm3 resolution) revealed the atrial wall structure varied in thickness (1.0 ± 0.7-6.8 ± 2.4 mm), transmural fiber angle differences, and interstitial fibrosis causing transmural activation delay from 23 ± 11 to 43 ± 22 ms at increased pacing rates. Sustained AF (>90 min) was induced by burst pacing during pinacidil (30-100 µM) perfusion. Dual-sided sub-Endo-sub-Epi optical mapping revealed that AF was driven by spatially and temporally stable intramural re-entry with 107 ± 50 ms cycle length and transmural activation delay of 67 ± 31 ms. Intramural re-entrant drivers were captured primarily by sub-Endo mapping, while sub-Epi mapping visualized re-entry or 'breakthrough' patterns. Re-entrant drivers were anchored on 3D micro-anatomic tracks (15.4 ± 2.2 × 6.0 ± 2.3 mm2, 2.9 ± 0.9 mm depth) formed by atrial musculature characterized by increased transmural fiber angle differences and interstitial fibrosis. Targeted radiofrequency ablation of the tracks verified these re-entries as drivers of AF. Integrated 3D structural-functional mapping of diseased human right atria ex vivo revealed that the complex atrial microstructure caused significant differences between Endo vs. Epi activation during pacing and sustained AF driven by intramural re-entry anchored to fibrosis-insulated atrial bundles. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.

Atrial fibrillation driven by micro-anatomic intramural re-entry revealed by simultaneous sub-epicardial and sub-endocardial optical mapping in explanted human hearts

PubMed Central

Hansen, Brian J.; Zhao, Jichao; Csepe, Thomas A.; Moore, Brandon T.; Li, Ning; Jayne, Laura A.; Kalyanasundaram, Anuradha; Lim, Praise; Bratasz, Anna; Powell, Kimerly A.; Simonetti, Orlando P.; Higgins, Robert S.D.; Kilic, Ahmet; Mohler, Peter J.; Janssen, Paul M.L.; Weiss, Raul; Hummel, John D.; Fedorov, Vadim V.

2015-01-01

Aims The complex architecture of the human atria may create physical substrates for sustained re-entry to drive atrial fibrillation (AF). The existence of sustained, anatomically defined AF drivers in humans has been challenged partly due to the lack of simultaneous endocardial–epicardial (Endo–Epi) mapping coupled with high-resolution 3D structural imaging. Methods and results Coronary-perfused human right atria from explanted diseased hearts (n = 8, 43–72 years old) were optically mapped simultaneously by three high-resolution CMOS cameras (two aligned Endo–Epi views (330 µm2 resolution) and one panoramic view). 3D gadolinium-enhanced magnetic resonance imaging (GE-MRI, 80 µm3 resolution) revealed the atrial wall structure varied in thickness (1.0 ± 0.7–6.8 ± 2.4 mm), transmural fiber angle differences, and interstitial fibrosis causing transmural activation delay from 23 ± 11 to 43 ± 22 ms at increased pacing rates. Sustained AF (>90 min) was induced by burst pacing during pinacidil (30–100 µM) perfusion. Dual-sided sub-Endo–sub-Epi optical mapping revealed that AF was driven by spatially and temporally stable intramural re-entry with 107 ± 50 ms cycle length and transmural activation delay of 67 ± 31 ms. Intramural re-entrant drivers were captured primarily by sub-Endo mapping, while sub-Epi mapping visualized re-entry or ‘breakthrough’ patterns. Re-entrant drivers were anchored on 3D micro-anatomic tracks (15.4 ± 2.2 × 6.0 ± 2.3 mm2, 2.9 ± 0.9 mm depth) formed by atrial musculature characterized by increased transmural fiber angle differences and interstitial fibrosis. Targeted radiofrequency ablation of the tracks verified these re-entries as drivers of AF. Conclusions Integrated 3D structural–functional mapping of diseased human right atria ex vivo revealed that the complex atrial microstructure caused significant differences between Endo vs. Epi activation during pacing and sustained AF driven by intramural re-entry anchored to fibrosis-insulated atrial bundles. PMID:26059724

Human urotensin-II is a potent spasmogen of primate airway smooth muscle

PubMed Central

Hay, Douglas W P; Luttmann, Mark A; Douglas, Stephen A

2000-01-01

The contractile profile of human urotensin-II (hU-II) was examined in primate airway and pulmonary vascular tissues. hU-II contracted tissues from different airway regions with similar potencies (pD2s from 8.6 to 9.2). However, there were regional differences in the efficacy of hU-II, with a progressive increase in the maximum contraction from trachea to smaller airway regions (from 9 to 41% of the contraction to 10 μM carbachol). hU-II potently contracted pulmonary artery tissues from different regions with similar potencies and efficacies: pD2s=8.7 to 9.3 and maximal contractions=79 to 86% of 60 mM KCl. hU-II potently contracted pulmonary vein preparations taken proximal to the atria, but had no effect in tissues from distal to the atria. This is the first report describing the contractile activity of hU-II in airways and suggests that the potential pathophysiological role of this peptide in lung diseases warrants investigation. PMID:10960062

Wolff-Parkinson-White Syndrome and Accessory Pathways

MedlinePlus

... is generated by the SA node, and that electricity spreads through the right and left atria, directing ... in that it is the only pathway for electricity that communicates from the upper chambers (atria) to ...

Mechanical behaviour of the human atria.

PubMed

Bellini, Chiara; Di Martino, Elena S; Federico, Salvatore

2013-07-01

This work was aimed at providing a local mechanical characterisation of tissues from the healthy human atria. Thirty-two tissue specimens were harvested from nine adult subjects whose death was not directly related to cardiovascular diseases. Tissues were kept in Tyrode's solution and tested using a planar biaxial device. Results showed that tissues from healthy human atria undergo large deformations under in-plane distributed tensions roughly corresponding to an in vivo pressure of 15 mmHg. The material was modelled as hyperelastic and a Fung-type elastic strain energy potential was chosen. This class of potentials is based on a function of a quadratic form in the components of the Green-Lagrange strain tensor, and it has been previously proved that the fourth-order tensor of this quadratic form is proportional to the linear elasticity tensor of the linearised theory. This has three important consequences: (i) the coefficients in Fung-type potentials have a precise physical meaning; (ii) whenever a microstructural description for the linear elasticity tensor is available, this is automatically inherited by the Fung-type potential; (iii) because of the presence of the linear elasticity tensor in the definition of a Fung-type potential, each of the three normal stresses is coupled with all three normal strains.We propose to include information on the microstructure of the atrium by writing the linear elasticity tensor as the volumetric-fraction-weighed sum of the linear elasticity tensors of the three constituents of the tissue: the ground matrix, the main fibre family and the secondary fibre family. To the best of our knowledge, this is the first time that a Fung-type potential is given a precise structural meaning, based on the directions and the material properties of the fibres. Because of the coupling between normal strains and normal stresses, this structurally-based Fung-type potential allows for discriminating among all testing protocols in planar biaxial stretch.

Possible mechanism of the negative inotropic effect of α1-adrenoceptor agonists in rat isolated left atria after exposure to free radicals

PubMed Central

Peters, Stephan L M; Batink, Harry D; Michel, Martin C; Pfaffendorf, Martin; van Zwieten, Pieter A

1998-01-01

This study was designed to investigate the mechanism(s) of the negative inotropic effects of α1-adrenoceptor agonists observed in rat isolated left atria after exposure to free radicals.Ouabain and calphostin C were used in contraction experiments to block the sodium pump and protein kinase C. Methoxamine-induced phospholipase C and Na+/K+ ATPase activities were measured.Methoxamine (300 μM) increased contractile force by 1.6±0.2 mN in control atria but decreased contractile force in electrolysis-treated atria by 2.0±0.1 mN (P<0.05), as determined 10 min after methoxamine addition. In contrast, the positive inotropic effects of endothelin-1 (30 nM) and isoprenaline (10 μM) were reduced from 2.6±0.3 to 1.3±0.1 mN and from 2.6±0.3 to 1.7±0.2 mN, respectively, by electrolysis treatment (P<0.05), but not converted into a negative inotropic action.In an inositol phosphate assay we observed that the stimulation of phospholipase C by methoxamine was attenuated by electrolysis when the (electrolyzed) medium from the organ bath was used, but the phospholipase C responses were restored by the use of fresh medium. However, fresh medium did not counteract the negative inotropic effect of methoxamine. Accordingly, the negative inotropic effect of methoxamine is not directly related to the impaired phospholipase C responses seen in atria subjected to electrolysis.Ouabain (10 μM) and the protein kinase C inhibitor calphostin C (50 nM), completely prevented the negative inotropic effect of 300 μM methoxamine in electrolysis-treated atria.Measurement of the Na+/K+ ATPase activity, revealed that in control atria, α1-adrenoceptor stimulation with 300 μM methoxamine, decreased the Na+/K+ ATPase activity by 14.4±7.7%. In contrast, methoxamine increased the Na+/K+ ATPase activity by 48.8±8.9% (P<0.05) in electrolysis-treated atria. Interestingly, this increase in Na+/K+ ATPase activity was completely counteracted by calphostin C (1.4±0.1% over basal).These results indicate that the negative inotropic effects of α1-adrenoceptor agonists, observed in rat isolated left atria exposed to free radicals, are likely to be caused by protein kinase C-mediated phosphorylation and subsequent activation of the Na+/K+ ATPase. PMID:9535025

Mechanisms of Atrial Fibrillation: Rotors, Ionic Determinants and Excitation Frequency

PubMed Central

Berenfeld, Omer; Jalife, José

2017-01-01

Summary Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in humans. However its mechanisms are poorly understood and AF therapy is often sub-optimal. This article reviews recent experimental, numerical and clinical data on dynamics of wave propagation during AF and its mechanistic link to ionic and structural properties of the atria. At the outset, we review numerical and optical mapping data suggesting that the sustained activity of periodic drivers (rotors) with exceedingly high dominant frequencies (DF) of excitation underlies the spatial dispersion and irregularity of activation rates that characterize AF. We show how optical mapping of the fibrillating atria in isolated normal sheep hearts has revealed that the rotors tend to localize in the left atrium (LA). We then discuss exciting new data in the sheep model of tachypacing induced AF demonstrating that the DF of paroxysmal AF episodes increases progressively over days or weeks during the transition to persistent AF (PeAF) and that the rate of the DF increase predicts the onset of PeAF. The data show that the DF increase during the transition may be explained by rotor acceleration secondary to upregulation of IK1 and downregulation of ICaL. The article concludes with a discussion on how translation of experimentally derived knowledge on the behavior and frequency of rotors may find its way into the clinic. We focus on studies in which the analysis of the spatial patterns of DF distribution in the atria of patients with paroxysmal vs persistent has increased our understanding of human AF and how that knowledge might contribute to improve the outcome of AF ablation procedures. PMID:26968663

At the Atrioventricular Crossroads: Dual Pathway Electrophysiology in the Atrioventricular Node and its Underlying Heterogeneities

PubMed Central

George, Sharon A; Faye, N Rokhaya; Murillo-Berlioz, Alejandro; Lee, K Benjamin; Trachiotis, Gregory D; Efimov, Igor R

2017-01-01

The atrioventricular node (AVN) is a complex structure that performs a variety of functions in the heart. The AVN is primarily an electrical gatekeeper between the atria and ventricles and introduces a delay between atrial and ventricular excitation, allowing for efficient ventricular filling. The AVN is composed of several compartments that safely transmit electrical excitation from the atria to the ventricles via the fast or slow pathways. There are many electrophysiological differences between these pathways, including conduction time and electrical refractoriness, that increase the predisposition of the atrioventricular junction to arrhythmias such as atrioventricular nodal re-entrant tachycardia. These varied electrophysiological characteristics of the fast and slow pathways stem from their unique structural and molecular composition (tissue and cellular geometry, ion channels and gap junctions). This review summarises the structural and molecular heterogeneities of the human AVN and how they result in electrophysiological variations and arrhythmias. PMID:29326832

Reactive oxygen species potentiate the negative inotropic effect of cardiac M2-muscarinic receptor stimulation.

PubMed

Peters, S L; Sand, C; Batinik, H D; Pfaffendorf, M; van Zwieten, P A

2001-08-01

The aim of the present study was to investigate the influence of reactive oxygen species (ROS) on the contractile responses of rat isolated left atria to muscarinic receptor stimulation. ROS were generated by means of electrolysis (30 mA, 75 s) of the organ bath fluid. Twenty minutes after the electrolysis period, the electrically paced atria (3 Hz) were stimulated with the adenylyl cyclase activator forskolin (1 microM). Subsequently, cumulative acetylcholine concentration-response curves were constructed (0.01 nM-10 microM). In addition, phosphoinositide turnover and adenylyl cyclase activity under basal and stimulated conditions were measured. For these biochemical experiments we used the stable acetylcholine analogue carbachol. The atria exposed to reactive oxygen species were influenced more potently (pD2 control: 6.2 vs. 7.1 for electrolysis-treated atria, P<0.05) and more effectively (Emax control: 40% vs. 90% reduction of the initial amplitude, P<0.05) by acetylcholine. In contrast, ROS exposure did not alter the responses to adenosine, whose receptor is also coupled via a Gi-protein to adenylyl cyclase. The basal (40% vs. control, P<0.05) as well as the carbachol-stimulated (-85% vs. control, P<0.05) inositol-phosphate formation was reduced in atria exposed to ROS. The forskolin-stimulated adenylyl cyclase activity was identical in both groups but carbachol stimulation induced a more pronounced reduction in adenylyl cyclase activity in the electrolysis-treated atria. Accordingly we may conclude that ROS enhance the negative inotropic response of isolated rat atria to acetylcholine by both a reduction of the positive (inositide turnover) and increase of the negative (adenylyl cyclase inhibition) inotropic components of cardiac muscarinic receptor stimulation. This phenomenon is most likely M2-receptor specific, since the negative inotropic response to adenosine is unaltered by ROS exposure.

The Na+/K+ pump is an important modulator of refractoriness and rotor dynamics in human atrial tissue.

PubMed

Sánchez, Carlos; Corrias, Alberto; Bueno-Orovio, Alfonso; Davies, Mark; Swinton, Jonathan; Jacobson, Ingemar; Laguna, Pablo; Pueyo, Esther; Rodríguez, Blanca

2012-03-01

Pharmacological treatment of atrial fibrillation (AF) exhibits limited efficacy. Further developments require a comprehensive characterization of ionic modulators of electrophysiology in human atria. Our aim is to systematically investigate the relative importance of ionic properties in modulating excitability, refractoriness, and rotor dynamics in human atria before and after AF-related electrical remodeling (AFER). Computer simulations of single cell and tissue atrial electrophysiology were conducted using two human atrial action potential (AP) models. Changes in AP, refractory period (RP), conduction velocity (CV), and rotor dynamics caused by alterations in key properties of all atrial ionic currents were characterized before and after AFER. Results show that the investigated human atrial electrophysiological properties are primarily modulated by maximal value of Na(+)/K(+) pump current (G(NaK)) as well as conductances of inward rectifier potassium current (G(K1)) and fast inward sodium current (G(Na)). G(NaK) plays a fundamental role through both electrogenic and homeostatic modulation of AP duration (APD), APD restitution, RP, and reentrant dominant frequency (DF). G(K1) controls DF through modulation of AP, APD restitution, RP, and CV. G(Na) is key in determining DF through alteration of CV and RP, particularly in AFER. Changes in ionic currents have qualitatively similar effects in control and AFER, but effects are smaller in AFER. The systematic analysis conducted in this study unravels the important role of the Na(+)/K(+) pump current in determining human atrial electrophysiology.

An automated system using spatial oversampling for optical mapping in murine atria. Development and validation with monophasic and transmembrane action potentials.

PubMed

Yu, Ting Yue; Syeda, Fahima; Holmes, Andrew P; Osborne, Benjamin; Dehghani, Hamid; Brain, Keith L; Kirchhof, Paulus; Fabritz, Larissa

2014-08-01

We developed and validated a new optical mapping system for quantification of electrical activation and repolarisation in murine atria. The system makes use of a novel 2nd generation complementary metal-oxide-semiconductor (CMOS) camera with deliberate oversampling to allow both assessment of electrical activation with high spatial and temporal resolution (128 × 2048 pixels) and reliable assessment of atrial murine repolarisation using post-processing of signals. Optical recordings were taken from isolated, superfused and electrically stimulated murine left atria. The system reliably describes activation sequences, identifies areas of functional block, and allows quantification of conduction velocities and vectors. Furthermore, the system records murine atrial action potentials with comparable duration to both monophasic and transmembrane action potentials in murine atria. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

A preliminary study on atrial epicardial mapping signals based on Graph Theory.

PubMed

Sun, Liqian; Yang, Cuiwei; Zhang, Lin; Chen, Ying; Wu, Zhong; Shao, Jun

2014-07-01

In order to get a better understanding of atrial fibrillation, we introduced a method based on Graph Theory to interpret the relations of different parts of the atria. Atrial electrograms under sinus rhythm and atrial fibrillation were collected from eight living mongrel dogs with cholinergic AF model. These epicardial signals were acquired from 95 unipolar electrodes attached to the surface of the atria and four pulmonary veins. Then, we analyzed the electrode correlations using Graph Theory. The topology, the connectivity and the parameters of graphs during different rhythms were studied. Our results showed that the connectivity of graphs varied from sinus rhythm to atrial fibrillation and there were parameter gradients in various parts of the atria. The results provide spatial insight into the interaction between different parts of the atria and the method may have its potential for studying atrial fibrillation. Copyright © 2014 IPEM. Published by Elsevier Ltd. All rights reserved.

List of RAE Translations Issued during the Period 1 January 1980 to 31 March 1981,

DTIC Science & Technology

1981-04-01

the heart sucks blood into the atria during systole. X-ray cinematography and kymography were used in studies on ;animals and humans with and without...THE MECHANICAL PROPERTIES OF FIBRE J.J. Gerharz COTMPOSITE .mATERIALS - ANALYSIS OF THE STATE OF THE ART - D. Schitz Vo I ume I (Fraunhofer-Institut fur

In vivo evaluation of virtual electrode mapping and ablation utilizing a direct endocardial visualization ablation catheter.

PubMed

Chik, William W B; Barry, M A; Malchano, Zach; Wylie, Bryan; Pouliopoulos, Jim; Huang, Kaimin; Lu, Juntang; Thavapalachandran, Sujitha; Robinson, David; Saadat, Vahid; Thomas, Stuart P; Ross, David L; Kovoor, Pramesh; Thiagalingam, Aravinda

2012-01-01

Radiofrequency (RF) ablation utilizing direct endocardial visualization (DEV) requires a "virtual electrode" to deliver RF energy while preserving visualization. This study aimed to: (1) examine the virtual electrode RF ablation efficacy; (2) determine the optimal power and duration settings; and (3) evaluate the utility of virtual electrode unipolar electrograms. The DEV catheter lesions were compared to lesions formed using a 3.5 mm open irrigated tip catheter within the right atria of 12 sheep. Generator power settings for DEV were titrated from 12W, 14W and 16W for 20, 30 and 40 seconds duration with 25 mL/min saline irrigation. Standard irrigated tip catheter settings of 30W, 50°C for 30 seconds and 30 mL/min were used. The DEV lesions were significantly greater in surface area and both major and minor axes compared to irrigated tip lesions (surface area 19.43 ± 9.09 vs 10.88 ± 4.72 mm, P<0.01) with no difference in transmurality (93/94 vs 46/47) or depth (1.86 ± 0.75 vs 1.85 ± 0.57 mm). Absolute electrogram amplitude reduction was greater for DEV lesions (1.89 ± 1.31 vs 1.49 ± 0.78 mV, P = 0.04), but no difference in percentage reduction. Pre-ablation pacing thresholds were not different between DEV (0.79 ± 0.36 mA) and irrigated tip (0.73 ± 0.25 mA) lesions. There were no complications noted during ablation with either catheter. Virtual electrode ablation consistently created wider lesions at lower power compared to irrigated tip ablation. Virtual electrode electrograms showed a comparable pacing and sensing efficacy in detecting local myocardial electrophysiological changes. © 2011 Wiley Periodicals, Inc.

Histopathological Study of Left and Right Atria in Isolated Rheumatic Mitral Stenosis With and Without Atrial Fibrillation.

PubMed

Shenthar, Jayaprakash; Kalpana, Saligrama Ramegowda; Prabhu, Mukund A; Rai, Maneesh K; Nagashetty, Ravikumar Kalyani; Kamlapurkar, Giridhar

2016-09-01

Mitral stenosis (MS) has the highest incidence of atrial fibrillation (AF) in chronic rheumatic valvular disease. There are very few studies in isolated MS comparing histopathological changes in patients with sinus rhythm (SR) and AF. To analyze the histological changes associated with isolated MS and compare between changes in AF and SR. This was a prospective study in patients undergoing valve replacement surgery for symptomatic isolated MS who were divided into 2 groups, Group I AF (n = 13) and Group II SR (n = 10). Intra-operative biopsies performed from 5 different sites from both atria were analyzed for 10 histopathologic changes commonly associated with AF. On multivariate analysis, myocytolysis (odds ratio [OR]: 1.48, P = 0.05) was found to be associated with AF, whereas myocyte hypertrophy (OR: 0.21, P = 0.003), and glycogen deposition (OR: 0.43, P = 0.002) was associated with SR. Interstitial fibrosis the commonest change was uniformly distributed across both atria irrespective of the rhythm. In rheumatic MS, SR is associated with myocyte hypertrophy whereas AF is associated with myocytolysis. Endocardial inflammation is more common in left atrial appendage irrespective of rhythm. Interstitial fibrosis is seen in >90% of patients distributed in both the atria and is independent of the rhythm. Amyloid and Aschoff bodies are uncommon and the rest of the changes are uniformly distributed across both the atria. © 2016 Wiley Periodicals, Inc.

Phase synchrony reveals organization in human atrial fibrillation

PubMed Central

Vidmar, David; Narayan, Sanjiv M.

2015-01-01

It remains unclear if human atrial fibrillation (AF) is spatially nonhierarchical or exhibits a hierarchy of organization sustained by sources. We utilize activation times obtained at discrete locations during AF to compute the phase synchrony between tissue regions, to examine underlying spatial dynamics throughout both atria. We construct a binary synchronization network and show that this network can accurately define regions of coherence in coarse-grained in silico data. Specifically, domains controlled by spiral waves exhibit regions of high phase synchrony. We then apply this analysis to clinical data from patients experiencing cardiac arrhythmias using multielectrode catheters to simultaneously record from a majority of both atria. We show that pharmaceutical intervention with ibutilide organizes activation by increasing the size of the synchronized domain in AF and quantify the increase in temporal organization when arrhythmia changes from fibrillation to tachycardia. Finally, in recordings from 24 patients in AF we show that the level of synchrony is spatially broad with some patients showing large spatially contiguous regions of synchronization, while in others synchrony is localized to small pockets. Using computer simulations, we show that this distribution is inconsistent with distributions obtained from simulations that mimic multiwavelet reentry but is consistent with mechanisms in which one or more spatially conserved spiral waves is surrounded by tissue in which activation is disorganized. PMID:26475585

Parallel Optimization of 3D Cardiac Electrophysiological Model Using GPU

PubMed Central

Xia, Yong; Zhang, Henggui

2015-01-01

Large-scale 3D virtual heart model simulations are highly demanding in computational resources. This imposes a big challenge to the traditional computation resources based on CPU environment, which already cannot meet the requirement of the whole computation demands or are not easily available due to expensive costs. GPU as a parallel computing environment therefore provides an alternative to solve the large-scale computational problems of whole heart modeling. In this study, using a 3D sheep atrial model as a test bed, we developed a GPU-based simulation algorithm to simulate the conduction of electrical excitation waves in the 3D atria. In the GPU algorithm, a multicellular tissue model was split into two components: one is the single cell model (ordinary differential equation) and the other is the diffusion term of the monodomain model (partial differential equation). Such a decoupling enabled realization of the GPU parallel algorithm. Furthermore, several optimization strategies were proposed based on the features of the virtual heart model, which enabled a 200-fold speedup as compared to a CPU implementation. In conclusion, an optimized GPU algorithm has been developed that provides an economic and powerful platform for 3D whole heart simulations. PMID:26581957

Parallel Optimization of 3D Cardiac Electrophysiological Model Using GPU.

PubMed

Xia, Yong; Wang, Kuanquan; Zhang, Henggui

2015-01-01

Large-scale 3D virtual heart model simulations are highly demanding in computational resources. This imposes a big challenge to the traditional computation resources based on CPU environment, which already cannot meet the requirement of the whole computation demands or are not easily available due to expensive costs. GPU as a parallel computing environment therefore provides an alternative to solve the large-scale computational problems of whole heart modeling. In this study, using a 3D sheep atrial model as a test bed, we developed a GPU-based simulation algorithm to simulate the conduction of electrical excitation waves in the 3D atria. In the GPU algorithm, a multicellular tissue model was split into two components: one is the single cell model (ordinary differential equation) and the other is the diffusion term of the monodomain model (partial differential equation). Such a decoupling enabled realization of the GPU parallel algorithm. Furthermore, several optimization strategies were proposed based on the features of the virtual heart model, which enabled a 200-fold speedup as compared to a CPU implementation. In conclusion, an optimized GPU algorithm has been developed that provides an economic and powerful platform for 3D whole heart simulations.

Ginseng-Aconite Decoction elicits a positive inotropic effect via the reverse mode Na+/Ca2+ exchanger in beating rabbit atria.

PubMed

Cui, Hao Zhen; Kim, Hye Yoom; Kang, Dae Gill; Lee, Ho Sub

2013-07-09

Ginseng-Aconite Decoction (GAD), a traditional oriental medicine composed of Panax ginseng C.A. Mey. (Araliaceae) and Aconitum carmichaeli Debx. (Ranunculaceae) has been used as treatment for cardiovascular diseases from Song Dynasty of China. The purpose of the present study was to elucidate the possible mechanisms of GAD-induced positive inotropic effect. GAD-induced changes in atrial dynamics and cAMP efflux were determined in isolated perfused beating rabbit atria. GAD significantly increased atrial dynamics such as stroke volume, pulse pressure and augmented cAMP efflux in beating rabbit atria. The inotropic effect was significantly attenuated by pre-treatment with KB-R7943, a reverse mode Na(+)/Ca(2+) exchanger blocker. The GAD-induced increase in atrial dynamics was also markedly inhibited by staurosporine, a non-selective protein kinase inhibitor, and partly blocked by KT5720, a selective PKA inhibitor. The effect of GAD on atrial dynamics was not altered by pre-treatment with propranolol, a β-adrenergic receptor inhibitor, or diltiazem, an L-type Ca(2+)channel blocker. The phosphodiesterase (PDE) inhibitor 3-isobutyl-1-methylxanthine (IBMX) failed to modulate the GAD-induced increase in atrial dynamics, but markedly attenuated cAMP efflux in the beating atria. These results suggest that the GAD-induced positive inotropic effect in beating rabbit atria may be attributable to stimulation of the reverse mode Na(+)/Ca(2+) exchanger, while PKA activity would, at least in part, be participated in the course. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Electrical remodelling of the left and right atria due to rheumatic mitral stenosis.

PubMed

John, Bobby; Stiles, Martin K; Kuklik, Pawel; Chandy, Sunil T; Young, Glenn D; Mackenzie, Lorraine; Szumowski, Lukasz; Joseph, George; Jose, Jacob; Worthley, Stephen G; Kalman, Jonathan M; Sanders, Prashanthan

2008-09-01

To characterize the atrial remodelling in mitral stenosis (MS). Twenty-four patients with severe MS undergoing commissurotomy and 24 controls were studied. Electrophysiological evaluation was performed in 12 patients in each group by positioning multi-electrode catheters in both atria to determine the following: effective refractory period (ERP) at 10 sites at 600 and 450 ms; conduction time; conduction delay at the crista terminalis (CT); and vulnerability for atrial fibrillation (AF). P-wave duration (PWD) was determined on the surface ECG. In the remaining 12 patients in each group, electroanatomic maps of both atria were created to determine conduction velocity and identify regions of low voltage and electrical silence. Patients with MS had larger left atria (LA) (P < 0.0001); prolonged PWD (P = 0.0007); prolonged ERP in both LA (P < 0.0001) and right atria (RA) (P < 0.0001); reduced conduction velocity in the LA (P = 0.009) and RA (P < 0.0001); greater number (P < 0.0001) and duration (P< 0.0001) of bipoles along the CT with delayed conduction; lower atrial voltage in the LA (P < 0.0001) and RA (P < 0.0001); and more frequent electrical scar (P = 0.001) compared with controls. Five of twelve with MS and none of the controls developed AF with extra-stimulus (P = 0.02). Atrial remodelling in MS is characterized by LA enlargement, loss of myocardium, and scarring associated with widespread and site-specific conduction abnormalities and no change or an increase in ERP. These abnormalities were associated with a heightened inducibility of AF.

Glycoproteomics Reveals Decorin Peptides With Anti-Myostatin Activity in Human Atrial Fibrillation.

PubMed

Barallobre-Barreiro, Javier; Gupta, Shashi K; Zoccarato, Anna; Kitazume-Taneike, Rika; Fava, Marika; Yin, Xiaoke; Werner, Tessa; Hirt, Marc N; Zampetaki, Anna; Viviano, Alessandro; Chong, Mei; Bern, Marshall; Kourliouros, Antonios; Domenech, Nieves; Willeit, Peter; Shah, Ajay M; Jahangiri, Marjan; Schaefer, Liliana; Fischer, Jens W; Iozzo, Renato V; Viner, Rosa; Thum, Thomas; Heineke, Joerg; Kichler, Antoine; Otsu, Kinya; Mayr, Manuel

2016-09-13

Myocardial fibrosis is a feature of many cardiac diseases. We used proteomics to profile glycoproteins in the human cardiac extracellular matrix (ECM). Atrial specimens were analyzed by mass spectrometry after extraction of ECM proteins and enrichment for glycoproteins or glycopeptides. ECM-related glycoproteins were identified in left and right atrial appendages from the same patients. Several known glycosylation sites were confirmed. In addition, putative and novel glycosylation sites were detected. On enrichment for glycoproteins, peptides of the small leucine-rich proteoglycan decorin were identified consistently in the flowthrough. Of all ECM proteins identified, decorin was found to be the most fragmented. Within its protein core, 18 different cleavage sites were identified. In contrast, less cleavage was observed for biglycan, the most closely related proteoglycan. Decorin processing differed between human ventricles and atria and was altered in disease. The C-terminus of decorin, important for the interaction with connective tissue growth factor, was detected predominantly in ventricles in comparison with atria. In contrast, atrial appendages from patients in persistent atrial fibrillation had greater levels of full-length decorin but also harbored a cleavage site that was not found in atrial appendages from patients in sinus rhythm. This cleavage site preceded the N-terminal domain of decorin that controls muscle growth by altering the binding capacity for myostatin. Myostatin expression was decreased in atrial appendages of patients with persistent atrial fibrillation and hearts of decorin null mice. A synthetic peptide corresponding to this decorin region dose-dependently inhibited the response to myostatin in cardiomyocytes and in perfused mouse hearts. This proteomics study is the first to analyze the human cardiac ECM. Novel processed forms of decorin protein core, uncovered in human atrial appendages, can regulate the local bioavailability of antihypertrophic and profibrotic growth factors. © 2016 American Heart Association, Inc.

[Comparison of the HAS-BLED and ATRIA scores for the risk of bleeding in patients aged 75 and over receiving vitamin K antagonist (VKA) therapy and educated VKA-management].

PubMed

Soave, Claire; Chidlovskii, Elena; Lebelhomme, Audrey; Gaboreau, Yoann; Pernod, Gilles; Bosson, Jean Luc; Couturier, Pascal

2015-09-01

Bleeding is the main complication on vitamin K antagonist treatment (VKA), particularly in elderly patients. However, the bleeding risk prediction in geriatric patients remains difficult. We evaluated the predictive value of the HAS-BLED and ATRIA bleeding scores in VKA-treated patients aged 75 and over. Various clinical bleeding risk factors in elderly were also studied. 208 patients were included in a case-control study: 52 hemorrhages cases were compared to 156 hemorrhage-free cases (controls), mean age 83.1 years in cases and 82.6 in controls. This elderly subgroup was provided from the prospective SCORE cohort study (study designed to validate the use of bleeding scores in an ambulatory population). The patients were included during a VKA-therapeutic education between May 2009 and May 2010 in 4 French hospitals, and followed for 1 year. The primary endpoint, collected prospectively, was the occurrence of severe and clinically relevant bleeding events. According to the Receiver operating characteristics (ROC), the ATRIA score was as effective as HAS- BLED to predict all bleeding (c-statistic: 0.59 [95% CI 0.50-0.68] vs 0.56 [0.48-0.65]) including severe bleeding (c-statistic: 0.64 [95% CI 0.49-0.79] vs 0.62 [0.49-0.75]). Multivariate Cox regression analysis showed increasing bleeding risk with anemia (OR = 2.6 [95% CI 1.34-5.23], p = 0.005), serotonin reuptake inhibitors (2.8 [1.08-7.47], 0.034), and family-management of VKA-treatment (2.8 [1.28-6.15], 0.01). ATRIA hemorrhage predictive value can be improved by adding such parameters as family-management of VKA-treatment and serotonin reuptake inhibitors treatment. ATRIA appears as relevant as HAS-BLED in predicting all bleeding including major hemorrhages in elderly patients educated VKA-management. The ATRIA bleeding score is improved by including items of serotonin reuptake inhibitors treatment and family-management of VKA-treatment.

Effects of platelet activating factor on contractile force and 45Ca fluxes in guinea-pig isolated atria.

PubMed Central

Diez, J.; Delpón, E.; Tamargo, J.

1990-01-01

1. The effects of platelet activating factor (PAF) were studied on the electromechanical properties and 45Ca2+ fluxes of guinea-pig isolated atria. 2 Both in spontaneously beating and electrically driven atria, PAF (10(-12)-10(-7) M) increased atrial rate but produced a biphasic effect on contractile force. At low concentrations (up to 10(-10) M) it produced a positive inotropic effect, while at higher concentrations PAF exerted a negative inotropic effect. A similar biphasic effect was observed in the slow contractions elicited by isoprenaline in K(+)-depolarized atrial fibres. 3. The positive inotropic effect of PAF was prevented by verapamil, whereas pretreatment of atria with propranolol, phentolamine, indomethacin or atropine did not modify its positive and negative inotropic actions. BN 52021, a specific PAF antagonist, abolished both the positive and negative inotropic effects. 4. PAF had no effect on the characteristics of the action potentials recorded in either normally polarized or K(+)-depolarized (slow action potential) atrial fibres. 5. At concentrations at which it increased contractile force, PAF potentiated the contractile responses to Ca2+ (0.9-9 mM), whereas at negative inotropic concentrations it inhibited them. The negative inotropic effect of PAF was partially reversed in 70% Na+ medium. 6. At 10(-11) M, PAF increased 45Ca2+ uptake and reduced the rate coefficient (kcm) for the 45Ca2+ efflux. This increase in 45Ca2+ uptake was abolished in atria pretreated with verapamil or BN 52021. However, 10(-7) M PAF modified neither 45Ca2+ uptake nor efflux in atrial muscle.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2379035

Biatrial reduction plasty with reef imbricate technique as an adjunct to maze procedure for permanent atrial fibrillation associated with giant left atria.

PubMed

Wang, William; Guo, L Ray; Martland, Anne Marie; Feng, Xiao-Dong; Ma, Jie; Feng, Xi Qing

2010-04-01

Success of the modified maze procedure after valvular operation with giant atria and permanent atrial fibrillation (AF) remains suboptimal. We report an aggressive approach for these patients utilizing biatrial reduction plasty with a reef imbricate suture technique concomitantly with valvular and maze procedure for AF. From January 1999 to December 2006, 122 consecutive Chinese patients with permanent AF and biatrial enlargement who required mitral valve+/-tricuspid valve (TV) surgery underwent aggressive left atrial reduction combined with radiofrequency bipolar full maze procedure. Left atrial dimensions were measured by TTE or TEE. There were 71 women (58.1%) and 51 men (41.9%) and their mean age was 45+/-9.5 years. Mean duration of AF was 48.4+/-21.4 months. All patients underwent left atrial reduction plasty with reef imbricate suture technique and full maze procedure. Their preoperative left atria measured 64+/-12 mm in the enlarged left atria (ELA) group and 86+/-17 mm in the giant left atria (GLA). Mitral valve replacement (MVR) combined with TV repair was performed in 102 patients (83%) while 21 patients underwent MVRs combined with aortic valve replacements (17%). Sixty-six (54%) patients required additional procedures and 61 (50%) of the patients also underwent left atrial appendage clot evacuation. Postoperative left atrial size was reduced to 49+/-8 mm (ELA) and 51+/-11 mm (GLA), respectively (P<0.05). Ninety-three of 122 (76%) patients were restored in normal sinus rhythm after one year clinical follow-up. Aggressive biatrial reduction plasty combined with full maze procedure is an effective treatment for patients with permanent AF undergoing concomitant valvular surgery. Further studies utilizing the reef imbricate suture technique for atrial reduction need to subsequently be evaluated.

Effects of nesfatin-1 on atrial contractility and thoracic aorta reactivity in male rats.

PubMed

Barutcigil, Ayşe; Tasatargil, Arda

2017-10-13

This study aimed to examine the effects of nesfatin-1 on thoracic aorta vasoreactivity and to investigate the inotropic and chronotropic effects of nesfatin-1 on the spontaneous contractions of the isolated rat atria. Isolated right atria and thoracic aorta were used in organ baths. The reactivity of the thoracic aorta was evaluated by potassium chloride (KCl), phenylephrine (Phe), acetylcholine (ACh), and sodium nitroprusside (SNP). The effects of nesfatin-1 on the spontaneous contractions of the rat atria were also examined. Nesfatin-1 (0.1-100 ng/ml) produced a concentration-dependent relaxation response in rat thoracic aorta. The relaxant responses to nesfatin-1 were inhibited by the removal of endothelium, NO synthase blocker N-nitro-L-arginine methyl ester (L-NAME, 10 -4  M), and soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 -5  M). Nesfatin-1 (10 ng/ml, 30 min) increased the relaxation responses to either ACh or SNP, and the contractile response to both Phe and KCl did not significantly change in the arteries that were incubated with nesfatin-1 compared with the controls. The thoracic aorta contractions induced by the stepwise addition of Ca 2+ to a high KCl solution with no Ca 2+ were not significantly changed by nesfatin-1. Under calcium-free conditions, the contractions of the thoracic aorta rings incubated with nesfatin-1 in response to Phe were not significantly lower than those of the rings from the control rats. Nesfatin-1 showed positive inotropic and chronotropic effects on rat atria. Nesfatin-1 significantly changed the vascular responsiveness in rat thoracic aorta and produced positive inotropic and chronotropic effects on rat atria.

The cardiac proteome in patients with congenital ventricular septal defect: A comparative study between right atria and right ventricles.

PubMed

Bond, A R; Iacobazzi, D; Abdul-Ghani, S; Ghorbel, M T; Heesom, K J; George, S J; Caputo, M; Suleiman, M-S; Tulloh, R M

2018-03-20

Right ventricle (RV) remodelling occurs in neonatal patients born with ventricular septal defect (VSD). The presence of a defect between the two ventricles allows for shunting of blood from the left to right side. The resulting RV hypertrophy leads to molecular remodelling which has thus far been largely investigated using right atrial (RA) tissue. In this study we used proteomic and phosphoproteomic analysis in order to determine any difference between the proteomes for RA and RV. Samples were therefore taken from the RA and RV of five infants (0.34 ± 0.05 years, mean ± SEM) with VSD who were undergoing cardiac surgery to repair the defect. Significant differences in protein expression between RV and RA were seen. 150 protein accession numbers were identified which were significantly lower in the atria, whereas none were significantly higher in the atria compared to the ventricle. 19 phosphorylation sites (representing 19 phosphoproteins) were also lower in RA. This work has identified differences in the proteome between RA and RV which reflect differences in contractile activity and metabolism. As such, caution should be used when drawing conclusions based on analysis of the RA and extrapolating to the hypertrophied RV. RV hypertrophy occurs in neonatal patients born with VSD. Very little is known about how the atria responds to RV hypertrophy, especially at the protein level. Access to tissue from age-matched groups of patients is very rare, and we are in the unique position of being able to get tissue from both the atria and ventricle during reparative surgery of these infants. Our findings will be beneficial to future research into heart chamber malformations in congenital heart defects. Copyright © 2018. Published by Elsevier B.V.

White Phosphorus-Felt Smoke: Effects on Reproduction in the Rat

DTIC Science & Technology

1982-07-01

group exhibited unilateral anophthalmia . Four had prominent renal pelvises, three had underdeveloped testicles, one had narrow atria, and one had an...alive +Significant at p = 0.05. 4. DISCUSSION The major teratogenic effects observed in this study included one case each of unilateral anophthalmia ... anophthalmia and one had narrow atria. With only single incidences of the malformations occurring in each group ., and none in the Fj offspring from the

Factors affecting basket catheter detection of real and phantom rotors in the atria: A computational study.

PubMed

Martinez-Mateu, Laura; Romero, Lucia; Ferrer-Albero, Ana; Sebastian, Rafael; Rodríguez Matas, José F; Jalife, José; Berenfeld, Omer; Saiz, Javier

2018-03-01

Anatomically based procedures to ablate atrial fibrillation (AF) are often successful in terminating paroxysmal AF. However, the ability to terminate persistent AF remains disappointing. New mechanistic approaches use multiple-electrode basket catheter mapping to localize and target AF drivers in the form of rotors but significant concerns remain about their accuracy. We aimed to evaluate how electrode-endocardium distance, far-field sources and inter-electrode distance affect the accuracy of localizing rotors. Sustained rotor activation of the atria was simulated numerically and mapped using a virtual basket catheter with varying electrode densities placed at different positions within the atrial cavity. Unipolar electrograms were calculated on the entire endocardial surface and at each of the electrodes. Rotors were tracked on the interpolated basket phase maps and compared with the respective atrial voltage and endocardial phase maps, which served as references. Rotor detection by the basket maps varied between 35-94% of the simulation time, depending on the basket's position and the electrode-to-endocardial wall distance. However, two different types of phantom rotors appeared also on the basket maps. The first type was due to the far-field sources and the second type was due to interpolation between the electrodes; increasing electrode density decreased the incidence of the second but not the first type of phantom rotors. In the simulations study, basket catheter-based phase mapping detected rotors even when the basket was not in full contact with the endocardial wall, but always generated a number of phantom rotors in the presence of only a single real rotor, which would be the desired ablation target. Phantom rotors may mislead and contribute to failure in AF ablation procedures.

Factors affecting basket catheter detection of real and phantom rotors in the atria: A computational study

PubMed Central

Romero, Lucia; Rodríguez Matas, José F.; Berenfeld, Omer; Saiz, Javier

2018-01-01

Anatomically based procedures to ablate atrial fibrillation (AF) are often successful in terminating paroxysmal AF. However, the ability to terminate persistent AF remains disappointing. New mechanistic approaches use multiple-electrode basket catheter mapping to localize and target AF drivers in the form of rotors but significant concerns remain about their accuracy. We aimed to evaluate how electrode-endocardium distance, far-field sources and inter-electrode distance affect the accuracy of localizing rotors. Sustained rotor activation of the atria was simulated numerically and mapped using a virtual basket catheter with varying electrode densities placed at different positions within the atrial cavity. Unipolar electrograms were calculated on the entire endocardial surface and at each of the electrodes. Rotors were tracked on the interpolated basket phase maps and compared with the respective atrial voltage and endocardial phase maps, which served as references. Rotor detection by the basket maps varied between 35–94% of the simulation time, depending on the basket’s position and the electrode-to-endocardial wall distance. However, two different types of phantom rotors appeared also on the basket maps. The first type was due to the far-field sources and the second type was due to interpolation between the electrodes; increasing electrode density decreased the incidence of the second but not the first type of phantom rotors. In the simulations study, basket catheter-based phase mapping detected rotors even when the basket was not in full contact with the endocardial wall, but always generated a number of phantom rotors in the presence of only a single real rotor, which would be the desired ablation target. Phantom rotors may mislead and contribute to failure in AF ablation procedures. PMID:29505583

Inotropic effects of diadenosine tetraphosphate (AP4A) in human and animal cardiac preparations.

PubMed

Vahlensieck, U; Bokník, P; Gombosová, I; Huke, S; Knapp, J; Linck, B; Lüss, H; Müller, F U; Neumann, J; Deng, M C; Scheld, H H; Jankowski, H; Schlüter, H; Zidek, W; Zimmermann, N; Schmitz, W

1999-02-01

Diadenosine tetraphosphate (AP4A) is an endogenous compound and exerts diverse physiological effects in animal systems. However, the effects of AP4A on inotropy in ventricular cardiac preparations have not yet been studied. The effects of AP4A on force of contraction (FOC) were studied in isolated electrically driven guinea pig and human cardiac preparations. Furthermore, the effects of AP4A on L-type calcium current and [Ca]i were studied in isolated guinea pig ventricular myocytes. In guinea pig left atria, AP4A (0.1-100 microM) reduced FOC maximally by 36.5 +/- 4.3%. In guinea pig papillary muscles, AP4A (100 microM) alone was ineffective, but reduced isoproterenol-stimulated FOC maximally by 29.3 +/- 3.4%. The negative inotropic effects of AP4A in atria and papillary muscles were abolished by the A1-adenosine receptor antagonist 1, 3-dipropyl-cyclopentylxanthine. In guinea pig ventricular myocytes, AP4A (100 microM) attenuated isoproterenol-stimulated L-type calcium current and [Ca]i. In human atrial and ventricular preparations, AP4A (100 microM) alone increased FOC to 158.3 +/- 12.4% and 167.5 +/- 25.1%, respectively. These positive inotropic effects were abolished by the P2-purinoceptor antagonist suramin. On the other hand, AP4A (100 microM) reduced FOC by 27.2 +/- 7.4% in isoproterenol-stimulated human ventricular trabeculae. The latter effect was abolished by 1,3-dipropyl-cyclopentylxanthine. In summary, after beta adrenergic stimulation AP4A exerts negative inotropic effects in animal and human ventricular preparations via stimulation of A1-adenosine receptors. In contrast, AP4A alone can exert positive inotropic effects via P2-purinoceptors in human ventricular myocardium. Thus, P2-purinoceptor stimulation might be a new positive inotropic principle in the human myocardium.

The actions of some esters of 4-hydroxyquinuclidine on guinea-pig ileum, atria and rat fundus strip.

PubMed

Barlow, R B; Kitchen, R

1982-11-01

1 The acetyl, phenylacetyl, and diphenylacetyl esters of 4-hydroxyquinuclidine and their methiodides have been prepared.2 4-Diphenylacetoxyquinuclidine methiodide has higher affinity for muscarinic receptors than 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP methiodide) but it is less selective. At 30 degrees C its affinity for receptors in ileum is about 5 times that for receptors in atria, a difference similar to that found with diphenylacetoxytrophine methiodide. With 4-DAMP methiodide affinity for receptors in the ileum is over 10 times that for receptors in atria.3 4-Diphenylacetoxyquinuclidine methiodide has higher affinity for muscarinic receptors than 3-diphenylacetoxyquinuclidine hydrochloride or its methiodide.4 4-Acetoxyquinuclidine hydrochloride has less than one-hundredth of the activity of 3-acetoxyquinuclidine hydrochloride (acecyclidine) on guinea-pig ileum, atria, and rat fundus: however, 4-acetoxyquinuclidine methiodide is consistently more active than its 3-isomer, though it is only about 1/25 times as active as acecyclidine.5 4-Acetoxyquinuclidine hydrochloride is only a poor substrate for electric eel acetylcholinesterase: its affinity is similar to that of acecyclidine but it is greatly reduced by methylation.6 The relations between the structure and activity of the agonists are very different from the relations between the structure and affinity of the antagonists, which supports the view that agonists and antagonists bind to different conformations of the muscarinic receptor.

Antiarrhythmic properties of atrial pacing.

PubMed

Kliś, Magdalena; Sławuta, Agnieszka; Gajek, Jacek

2017-01-01

Bradycardia, atrial stretch and dilatation, autonomic nervous system disorders, and the presence of triggers such as atrial premature contractions, are factors which predispose a person to paroxysmal AF. Atrial pacing not only eliminates bradycardia but also prevents atrial premature contractions and dispersion of refractoriness, which are a substrate for atrial fibrillation. As the prolonged duration of atrial activation during pacing, especially from locations changing the physiological pattern of this activation (right atrium lateral wall, right atrium appendage), negatively influences both a mechanical and an electrical function of the atria, the atrial pacing site affects an atrial arrhythmogenesis. A conventional atrial lead location in the right atrium appendage causes non-physiological activation propagation, resulting in a prolongation of the activation time of both atria. This location is optimal according to a passive fixation of the atrial lead but the available contemporary active fixation leads could potentially be located in any area of the atrium. There is growing evidence of the benefit of pacing, imitating the physiological propagation of impulses within the atria. It seems that the Bachmann's bundle pacing is the best pacing site within the atria, not only positively influencing the atrial mechanical function but also best fulfilling the so-called atrial resynchronization function, in particular in patients with interatrial conduction delay. It can be effectively achieved using only one atrial electrode, and the slight shortening of atrioventricular conduction provides an additional benefit of this atrial pacing site.

Detailed Anatomical and Electrophysiological Models of Human Atria and Torso for the Simulation of Atrial Activation

PubMed Central

Ferrer, Ana; Sebastián, Rafael; Sánchez-Quintana, Damián; Rodríguez, José F.; Godoy, Eduardo J.; Martínez, Laura; Saiz, Javier

2015-01-01

Atrial arrhythmias, and specifically atrial fibrillation (AF), induce rapid and irregular activation patterns that appear on the torso surface as abnormal P-waves in electrocardiograms and body surface potential maps (BSPM). In recent years both P-waves and the BSPM have been used to identify the mechanisms underlying AF, such as localizing ectopic foci or high-frequency rotors. However, the relationship between the activation of the different areas of the atria and the characteristics of the BSPM and P-wave signals are still far from being completely understood. In this work we developed a multi-scale framework, which combines a highly-detailed 3D atrial model and a torso model to study the relationship between atrial activation and surface signals in sinus rhythm. Using this multi scale model, it was revealed that the best places for recording P-waves are the frontal upper right and the frontal and rear left quadrants of the torso. Our results also suggest that only nine regions (of the twenty-one structures in which the atrial surface was divided) make a significant contribution to the BSPM and determine the main P-wave characteristics. PMID:26523732

Mathematical Approaches to Understanding and Imaging Atrial Fibrillation: Significance for Mechanisms and Management

PubMed Central

Trayanova, Natalia A

2014-01-01

Atrial fibrillation (AF) is the most common sustained arrhythmia in humans. The mechanisms that govern AF initiation and persistence are highly complex, of dynamic nature, and involve interactions across multiple temporal and spatial scales in the atria. This articles aims to review the mathematical modeling and computer simulation approaches to understanding AF mechanisms and aiding in its management. Various atrial modeling approaches are presented, with descriptions of the methodological basis and advancements in both lower-dimensional and realistic geometry models. A review of the most significant mechanistic insights made by atrial simulations is provided. The article showcases the contributions that atrial modeling and simulation have made not only to our understanding of the pathophysiology of atrial arrhythmias, but also to the development of AF management approaches. A summary of the future developments envisioned for the field of atrial simulation and modeling is also presented. The review contends that computational models of the atria assembled with data from clinical imaging modalities that incorporate electrophysiological and structural remodeling could become a first line of screening for new AF therapies and approaches, new diagnostic developments, and new methods for arrhythmia prevention. PMID:24763468

Modulation of 3H-noradrenaline release by presynaptic opioid, cannabinoid and bradykinin receptors and β-adrenoceptors in mouse tissues

PubMed Central

Trendelenburg, A U; Cox, S L; Schelb, V; Klebroff, W; Khairallah, L; Starke, K

2000-01-01

Release-modulating opioid and cannabinoid (CB) receptors, β-adrenoceptors and bradykinin receptors at noradrenergic axons were studied in mouse tissues (occipito-parietal cortex, heart atria, vas deferens and spleen) preincubated with 3H-noradrenaline. Experiments using the OP1 receptor-selective agonists DPDPE and DSLET, the OP2-selective agonists U50488H and U69593, the OP3-selective agonist DAMGO, the ORL1 receptor-selective agonist nociceptin, and a number of selective antagonists showed that the noradrenergic axons innervating the occipito-parietal cortex possess release-inhibiting OP3 and ORL1 receptors, those innervating atria OP1, ORL1 and possibly OP3 receptors, and those innervating the vas deferens all four opioid receptor types. Experiments using the non-selective CB agonists WIN 55,212-2 and CP 55,940 and the CB1-selective antagonist SR 141716A indicated that the noradrenergic axons of the vas deferens possess release-inhibiting CB1 receptors. Presynaptic CB receptors were not found in the occipito-parietal cortex, in atria or in the spleen. Experiments using the non-selective β-adrenoceptor agonist isoprenaline and the β2-selective agonist salbutamol, as well as subtype-selective antagonists, demonstrated the occurrence of release-enhancing β2-adrenoceptors at the sympathetic axons of atria and the spleen, but demonstrated their absence in the occipito-parietal cortex and the vas deferens. Experiments with bradykinin and the B2-selective antagonist Hoe 140 showed the operation of release-enhancing B2 receptors at the sympathetic axons of atria, the vas deferens and the spleen, but showed their absence in the occipito-parietal cortex. The experiments document a number of new presynaptic receptor locations. They confirm and extend the existence of marked tissue and species differences in presynaptic receptors at noradrenergic neurons. PMID:10807669

Species differences in the negative inotropic effect of acetylcholine and soman in rat, guinea pig, and rabbit hearts. (Reannouncement with new availability information)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maxwell, D.M.; Thomsen, R.H.; Baskin, S.I.

1991-12-31

Acetylcholine reduced atrial contractions by 82.5% in guinea pig, 50.8% in rat, and 41.5% in rabbit. 2. The EC50, values for the negative inotropic effect of acetylcholine were 3.3 x 10(-7) M in rat and guinea pig atria and 4.1 x 10(-6) M in rabbit atria. 3. There was no correlation between the species differences in the negative inotropic effect of acetylcholine in atria and the density or affinity of acetylcholinesterase or muscarinic receptors. 4. Inhibition of atrial acetylcholinesterase with soman reduced the EC50 of acetylcholine three-fold in all species, but did not change the maximal inotropic effect of acetylcholine.more » 5. Species differences in the negative inotropic effect of acetylcholine may be caused by differences in the coupling between myocardial muscarinic receptors and the ion channels that mediate negative inotropy. Acetylcholine, cardiovascular response, species variation negative inotropic response.« less

Corticosteroid involvement in the changes in noradrenergic responsiveness of tissues from rats made hypertensive by short-term isolation

PubMed Central

Bennett, T.; Gardiner, Sheila M.

1978-01-01

1 The responses to noradrenaline and to noradrenergic nerve stimulation of spontaneously beating right atria, electrically driven left atria and vasa deferentia taken from rats made hypertensive by short-term isolation have been compared with the responses of tissues from normotensive, group-housed animals. 2 Adrenocortical activity of isolated animals was assessed by plasma corticosterone determinations and measurement of adrenal weights. 3 The hearts of the isolated animals were weighed and the myocardial contents of water, sodium, potassium and calcium were measured. 4 Spontaneously beating right atria from isolated animals showed a lower resting rate, no difference in the response to nerve stimulation but a greater sensitivity to noradrenaline compared to atria from group-housed animals. 5 Vasa deferentia from isolated animals showed a decreased maximal response to noradrenaline, but no change in noradrenaline sensitivity or in the response to transmural stimulation. 6 There were indications of hyperactivity of the adrenals throughout a 5 week period of isolation, manifest as elevated plasma corticosteroid levels and increased adrenal weights. 7 Myocardial levels of sodium and calcium were elevated at the same time as the tissue level of potassium was reduced, but heart weights did not significantly change. 8 It is possible that adrenal steroid action caused the changes in tissue ionic balance. These ionic disturbances may have been responsible for some of the changes in tissue sensitivity found in the isolated hypertensive animals. PMID:698476

Novel non-invasive algorithm to identify the origins of re-entry and ectopic foci in the atria from 64-lead ECGs: A computational study.

PubMed

Alday, Erick A Perez; Colman, Michael A; Langley, Philip; Zhang, Henggui

2017-03-01

Atrial tachy-arrhytmias, such as atrial fibrillation (AF), are characterised by irregular electrical activity in the atria, generally associated with erratic excitation underlain by re-entrant scroll waves, fibrillatory conduction of multiple wavelets or rapid focal activity. Epidemiological studies have shown an increase in AF prevalence in the developed world associated with an ageing society, highlighting the need for effective treatment options. Catheter ablation therapy, commonly used in the treatment of AF, requires spatial information on atrial electrical excitation. The standard 12-lead electrocardiogram (ECG) provides a method for non-invasive identification of the presence of arrhythmia, due to irregularity in the ECG signal associated with atrial activation compared to sinus rhythm, but has limitations in providing specific spatial information. There is therefore a pressing need to develop novel methods to identify and locate the origin of arrhythmic excitation. Invasive methods provide direct information on atrial activity, but may induce clinical complications. Non-invasive methods avoid such complications, but their development presents a greater challenge due to the non-direct nature of monitoring. Algorithms based on the ECG signals in multiple leads (e.g. a 64-lead vest) may provide a viable approach. In this study, we used a biophysically detailed model of the human atria and torso to investigate the correlation between the morphology of the ECG signals from a 64-lead vest and the location of the origin of rapid atrial excitation arising from rapid focal activity and/or re-entrant scroll waves. A focus-location algorithm was then constructed from this correlation. The algorithm had success rates of 93% and 76% for correctly identifying the origin of focal and re-entrant excitation with a spatial resolution of 40 mm, respectively. The general approach allows its application to any multi-lead ECG system. This represents a significant extension to our previously developed algorithms to predict the AF origins in association with focal activities.

Features of cholinergic cardia regulation under conditions of hypokinesia

NASA Technical Reports Server (NTRS)

Markova, Y. A.; Bondarenko, Y. I.; Bolyarskaya, V. A.; Fayfura, V. V.; Rosolovskiy, A. P.; Babinskaya, L. N.

1980-01-01

The features of cholinergic processes in the heart on the 4th, 8th, 16th and 30th days of hypokinesia were studied in experiments on 382 albino rats. It was shown that hypokinesia is attended by increased acetylcholine content in the atria, reduced choline acetyltransferase activity in the atria and ventricles and by increased activity of acetylcholinesterase in the ventricles and of pseudocholinesterase in both parts of the heart. The sensitivity of the heart to exogenic acetylcholine and to stimulation of the vagus nerve increases.

Morphological considerations pertaining to recognition of atrial isomerism. Consequences for sequential chamber localisation.

PubMed Central

Macartney, F J; Zuberbuhler, J R; Anderson, R H

1980-01-01

The atrial morphology and venous connections were assessed "blind" in 51 necropsy specimens from patients with visceral heterotaxy. This was compared with bronchial morphology as established by dissection. Six specimens were found to have both atria and bronchi in situs solitus or inversus, and were rejected. In the remainder, atrial isomerism was diagnosed, though this required minor revision of the atrial assessment in two patients. Thirty-four patients had isomeric right atria and bronchi, while 11 had isomeric left atria and bronchi. In seven cases, splenic status was unknown, but in seven of the remaining 38 (18.4%) atrial isomerism was not associated with either asplenia or polysplenia. Nevertheless, right isomerism was strongly associated with total anomalous pulmonary venous drainage (as is asplenia) and left isomerism was likewise associated with interruption of the inferior vena cava (as is polysplenia). Bilateral superior venae cavae and hepatic veins, and absence of the coronary sinus, were frequent in both forms of isomerism (as they are in asplenia and polysplenia). These findings suggest that atrial situs can be defined as solitus inversus, right isomerism, and left isomerism. This determination of atrial situs is quite independent of any other abnormalities of visceral situs. The high incidence of anomalies of both venous return and common atrium resulted in presumed complete mixing of blood at atrial level in all but one patient (97.8%), making the haemodynamic connection between atria and ventricles almost always ambiguous. To describe this anatomical connection as ambiguous when there are two ventricles present is therefore no more than recognition of anatomical and haemodynamic reality. Images PMID:7459148

Triggered Firing and Atrial Fibrillation in Transgenic Mice With Selective Atrial Fibrosis Induced by Overexpression of TGF-β1

PubMed Central

Choi, Eue-Keun; Chang, Po-Cheng; Lee, Young-Soo; Lin, Shien-Fong; Zhu, Wuqiang; Maruyama, Mitsunori; Fishbein, Michael C.; Chen, Zhenhui; der Lohe, Michael Rubart-von; Field, Loren J.; Chen, Peng-Sheng

2013-01-01

Background Calcium transient triggered firing (CTTF) is induced by large intracellular calcium (Cai) transient and short action potential duration (APD). We hypothesized that CTTF underlies the mechanisms of early afterdepolarization (EAD) and spontaneous recurrent atrial fibrillation (AF) in transgenic (Tx) mice with overexpression of transforming growth factor β1 (TGF-β1). Methods and Results MHC-TGFcys33ser Tx mice develop atrial fibrosis because of elevated levels of TGF-β1. We studied membrane potential and Cai transients of isolated superfused atria from Tx and wild-type (Wt) littermates. Short APD and persistently elevated Cai transients promoted spontaneous repetitive EADs, triggered activity and spontaneous AF after cessation of burst pacing in Tx but not Wt atria (39% vs. 0%, P=0.008). We were able to map optically 4 episodes of spontaneous AF re-initiation. All first and second beats of spontaneous AF originated from the right atrium (4/4, 100%), which is more severely fibrotic than the left atrium. Ryanodine and thapsigargin inhibited spontaneous re-initiation of AF in all 7 Tx atria tested. Western blotting showed no significant changes of calsequestrin or sarco/endoplasmic reticulum Ca2+-ATPase 2a. Conclusions Spontaneous AF may occur in the Tx atrium because of CTTF, characterized by APD shortening, prolonged Cai transient, EAD and triggered activity. Inhibition of Ca2+ release from the sarcoplasmic reticulum suppressed spontaneous AF. Our results indicate that CTTF is an important arrhythmogenic mechanism in TGF-β1 Tx atria. PMID:22447020

Isolation of canine coronary sinus musculature from the atria by radiofrequency catheter ablation prevents induction of atrial fibrillation.

PubMed

Morita, Hiroshi; Zipes, Douglas P; Morita, Shiho T; Wu, Jiashin

2014-12-01

The junction between the coronary sinus (CS) musculature and both atria contributes to initiation of atrial tachyarrhythmias. The current study investigated the effects of CS isolation from the atria by radiofrequency catheter ablation on the induction and maintenance of atrial fibrillation (AF). Using an optical mapping system, we mapped action potentials at 256 surface sites in 17 isolated and arterially perfused canine atrial tissues containing the entire musculature of the CS, right atrial septum, posterior left atrium, left inferior pulmonary vein, and vein of Marshal. Rapid pacing from each site before and after addition of acetylcholine (0.5 μmol/L) was applied to induce AF. Epicardial radiofrequency catheter ablation at CS-atrial junctions isolated the CS from the atria. Rapid pacing induced sustained AF in all tissues after acetylcholine. Microreentry within the CS drove AF in 88% of preparations. Reentries associated with the vein of Marshall (29%), CS-atrial junctions (53%), right atrium (65%), and pulmonary vein (76%) (frequently with 2-4 simultaneous circuits) were additional drivers of AF. Radiofrequency catheter ablation eliminated AF in 13 tissues before acetylcholine (P<0.01) and in 5 tissues after acetylcholine. Radiofrequency catheter ablation also abbreviated the duration of AF in 12 tissues (P<0.01). CS and its musculature developed unstable reentry and AF, which were prevented by isolation of CS musculature from atrial tissue. The results suggest that CS can be a substrate of recurrent AF in patients after pulmonary vein isolation and that CS isolation might help prevent recurrent AF. © 2014 American Heart Association, Inc.

Effects of Persistent Atrial Fibrillation-Induced Electrical Remodeling on Atrial Electro-Mechanics - Insights from a 3D Model of the Human Atria.

PubMed

Adeniran, Ismail; MacIver, David H; Garratt, Clifford J; Ye, Jianqiao; Hancox, Jules C; Zhang, Henggui

2015-01-01

Atrial stunning, a loss of atrial mechanical contraction, can occur following a successful cardioversion. It is hypothesized that persistent atrial fibrillation-induced electrical remodeling (AFER) on atrial electrophysiology may be responsible for such impaired atrial mechanics. This simulation study aimed to investigate the effects of AFER on atrial electro-mechanics. A 3D electromechanical model of the human atria was developed to investigate the effects of AFER on atrial electro-mechanics. Simulations were carried out in 3 conditions for 4 states: (i) the control condition, representing the normal tissue (state 1) and the tissue 2-3 months after cardioversion (state 2) when the atrial tissue recovers its electrophysiological properties after completion of reverse electrophysiological remodelling; (ii) AFER-SR condition for AF-remodeled tissue with normal sinus rhythm (SR) (state 3); and (iii) AFER-AF condition for AF-remodeled tissue with re-entrant excitation waves (state 4). Our results indicate that at the cellular level, AFER (states 3 & 4) abbreviated action potentials and reduced the Ca2+ content in the sarcoplasmic reticulum, resulting in a reduced amplitude of the intracellular Ca2+ transient leading to decreased cell active force and cell shortening as compared to the control condition (states 1 & 2). Consequently at the whole organ level, atrial contraction in AFER-SR condition (state 3) was dramatically reduced. In the AFER-AF condition (state 4) atrial contraction was almost abolished. This study provides novel insights into understanding atrial electro-mechanics illustrating that AFER impairs atrial contraction due to reduced intracellular Ca2+ transients.

Local cardiac effects of substance P: roles of acetylcholine and noradrenaline.

PubMed Central

Chiao, H; Caldwell, R W

1995-01-01

1. The local cardiac actions of substance P were examined in isolated perfused hearts and atria of the guinea-pig. 2. In both hearts and right atria, substance P caused negative inotropic and chronotropic effects. 3. Atropine (10(-6) M) or depletion of acetylcholine, by electrical stimulation and hemicholinium-3 perfusion, significantly attenuated the negative inotropic and chronotropic effects of substance P. alpha- and beta-adrenoceptor blockade by nadolol and phentolamine (10(-6) M each) did not prevent the negative inotropic and chronotropic effects of substance P. This indicates that cholinergic neurones, but not adrenergic neurones, partially mediate the effects of substance P. 4. There was no significant difference in the effects of substance P observed between groups with acetylcholine depletion and with cholinoceptor blockade. This suggests that substance P elicits its effects mainly through release of acetylcholine. 5. These results indicate that substance P has negative inotropic and chronotropic effects in guinea-pig hearts and right atria mediated partly by release of acetylcholine. Substance P also appears to have direct effects on cardiac tissue. PMID:7533612

Pharmacological and physiological assessment of serotonin formation and degradation in isolated preparations from mouse and human hearts.

PubMed

Gergs, Ulrich; Jung, Franziska; Buchwalow, Igor B; Hofmann, Britt; Simm, Andreas; Treede, Hendrik; Neumann, Joachim

2017-12-01

Using transgenic (TG) mice that overexpress the human serotonin (5-HT) 4a receptor specifically in cardiomyocytes, we wanted to know whether 5-HT can be formed and degraded in the mammalian heart and whether this can likewise lead to inotropic and chronotropic effects in this TG model. We noted that the 5-HT precursor 5-hydroxy-tryptophan (5-HTP) can exert inotropic and chronotropic effects in cardiac preparations from TG mice but not from wild-type (WT) mice; similar results were found in human atrial preparations as well as in intact TG animals using echocardiography. Moreover, by immunohistochemistry we could detect 5-HT metabolizing enzymes and 5-HT transporters in mouse hearts as well as in human atria. Hence, in the presence of an inhibitor of aromatic l-amino acid decarboxylase, the positive inotropic effects of 5-HTP were absent in TG and isolated human atrial preparations, and, moreover, inhibitors of enzymes involved in 5-HT degradation enhanced the efficacy of 5-HT in TG atria. A releaser of neurotransmitters increased inotropy in the isolated TG atrium, and this effect could be blocked by a 5-HT 4a receptor antagonist. Fluoxetine, an inhibitor of 5-HT uptake, elevated the potency of 5-HT to increase contractility in the TG atrium. In addition, inhibitors of organic cation and monoamine transporters apparently reduced the positive inotropic potency of 5-HT in the TG atrium. Hence, we tentatively conclude that a local production and degradation of 5-HT in the mammalian heart and more specifically in mammalian myocytes probably occurs. Conceivably, this formation of 5-HT and possibly impaired degradation may be clinically relevant in cases of unexplained tachycardia and other arrhythmias. NEW & NOTEWORTHY The present work suggests that inotropically active serotonin (5-HT) can be formed in the mouse and human heart and probably by cardiomyocytes themselves. Moreover, active degradation of 5-HT seems to occur in the mammalian heart. These findings may again increase the interest of researchers for cardiac effects of 5-HT. Copyright © 2017 the American Physiological Society.

Prejunctional angiotensin receptors involved in the facilitation of noradrenaline release in mouse tissues

PubMed Central

Cox, S L; Trendelenburg, A U; Starke, K

1999-01-01

The effect of angiotensin II, angiotensin III, angiotensin IV and angiotensin-(1–7) on the electrically induced release of noradrenaline was studied in preparations of mouse atria, spleen, hippocampus, occipito-parietal cortex and hypothalamus preincubated with [3H]-noradrenaline. The prejunctional angiotensin receptor type was investigated using the non-selective receptor antagonist saralasin (AT1/AT2) and the AT1 and AT2 selective receptor antagonists losartan and PD 123319, respectively. In atrial and splenic preparations, angiotensin II (0.01 nM–0.1 μM) and angiotensin III (0.01 and 0.1 nM–1 μM) increased the stimulation-induced overflow of tritium in a concentration-dependent manner. Angiotensin IV, only at high concentrations (1 and 10 μM), enhanced tritium overflow in the atria, while angiotensin-(1–7) (0.1 nM–10 μM) was without effect in both preparations. In preparations of hippocampus, occipito-parietal cortex and hypothalamus, none of the angiotensin peptides altered the evoked overflow of tritium. In atrial and splenic preparations, saralasin (0.1 μM) and losartan (0.1 and 1 μM), but not PD 123319 (0.1 μM), shifted the concentration-response curves of angiotensin II and angiotensin III to the right. In conclusion, in mouse atria and spleen, angiotensin II and angiotensin III facilitate the action potential induced release of noradrenaline via a prejunctional AT1 receptor. Only high concentrations of angiotensin IV are effective in the atria and angiotensin-(1–7) is without effect in both preparations. In mouse brain areas, angiotensin II, angiotensin III, angiotensin IV and angiotensin-(1–7) do not modulate the release of noradrenaline. PMID:10455273

[Morphological and electrophysiological changes of the heart atria in necropsy patients with atrial fibrillation - a pilot study].

PubMed

Matějková, Adéla; Steiner, Ivo

2014-01-01

Atrial fibrillation (AF), the most common supraventricular tachycardia, has a morphological base, so called remodelation of atrial myocardium, with its abnormal conduction pattern as a consequence. The remodelation regards electrical, contractile, and structural properties. In this pilot study we attempted to find relations between the myocardial morphological (scarring, amyloidosis, left atrial enlargement) and electrophysiological (ECG characteristics of the P-wave) changes in patients with AF. We examined 40 hearts of necropsy patients - 20 with a history of AF and 20 with no history of AF. Grossly, the heart weight and the size of the left atrium (LA) were evaluated. Histologically, 7 standard sites from the atria were examined. In each specimen, the degree of myocardial scarring and of deposition of isolated atrial amyloid (IAA) were assessed. We failed to show any significant difference in the P-wave pattern between patients with and without AF. Morphologically, however, there were several differences - the patients with AF had significantly heavier hearts, larger left atria, more severely scarred myocardium of the LA and the atrial septum, and more severe deposition of IAA in both atria in comparison to the control group of patients with sinus rhythm. The left atrial distribution of both fibrosis and amyloidosis was irregular. In patients with AF the former was most pronounced in the LA ceiling while the latter in the LA anterior wall. The entire series showed more marked amyloidosis in the left than in the right atrium. An interesting finding was the universal absence of IAA in the sinoatrial node. The knowledge of distribution of atrial myocardial structural changes could be utilized by pathologists in taking specimens for histology and also by cardiologists in targeting the radiofrequency ablation therapy.

Ranolazine effectively suppresses atrial fibrillation in the setting of heart failure.

PubMed

Burashnikov, Alexander; Di Diego, José M; Barajas-Martínez, Hector; Hu, Dan; Zygmunt, Andrew C; Cordeiro, Jonathan M; Moise, N Sydney; Kornreich, Bruce G; Belardinelli, Luiz; Antzelevitch, Charles

2014-07-01

There is a critical need for safer and more effective pharmacological management of atrial fibrillation (AF) in the setting of heart failure (HF). This study investigates the electrophysiological, antiarrhythmic, and proarrhythmic effects of a clinically relevant concentration of ranolazine (5 μmol/L) in coronary-perfused right atrial and left ventricular preparations isolated from the hearts of HF dogs. HF was induced by ventricular tachypacing (2-6 weeks at 200-240 beats per minute; n=17). Transmembrane action potentials were recorded using standard microelectrode techniques. In atria, ranolazine slightly prolonged action potential duration but significantly depressed sodium channel current-dependent parameters causing a reduction of maximum rate of rise of the action potential upstroke, a prolongation of the effective refractory period secondary to the development of postrepolarization refractoriness, and an increase in diastolic threshold of excitation and atrial conduction time. Ranolazine did not significantly alter these parameters or promote arrhythmias in the ventricles. Ranolazine produced greater inhibition of peak sodium channel current in atrial cells isolated from HF versus normal dogs. A single premature beat reproducibly induced self-terminating AF in 10 of 17 atria. Ranolazine (5 μmol/L) suppressed induction of AF in 7 of 10 (70%) atria. In the remaining 3 atria, ranolazine reduced frequency and duration of AF. Our results demonstrate more potent suppression of AF by ranolazine in the setting of HF than previously demonstrated in nonfailing hearts and absence of ventricular proarrhythmia. The data suggest that ranolazine may be of benefit as an alternative to amiodarone and dofetilide in the management of AF in patients with HF. © 2014 American Heart Association, Inc.

[Effects of liensinine on haemodynamics in rats and the physiologic properties of isolated rabbit atria].

PubMed

Wang, J L; Nong, Y; Jing, M X

1992-01-01

Liensinine(Lien), an alkaloid extracted from the green seed embryo of Nelumbo nucifera Gaertn, has been shown to have anti-arrhythmic action, its mechanism may be related to blockade of Ca2+, Na+ influx. Lien 3 mg/kg i.v. may temporarily inhibit all parameters of haemodynamics in anesthetized or pithed rats. The inhibitory effects on LVP, +dp/dtmax and SAP in anesthetized rats are slightly stronger than those of quinidine (Qui) 3 mg/kg. Lien 1-30 mg/kg dose-dependently produced these actions. Lien and Qui 12 mg/kg lowered LVP, +dp/dtmax and SAP by 33%, 37%, 29% and 9%, 12%, 9% respectively. While both of them inhibited the other parameters of haemodynamics with nearly equal degrees. The degrees of inhibitory effect of Lien 12 mg/kg on all haemodynamic parameters nearly corresponded to these of verapamil 1 mg/kg. Lien 1-100 mumol/L reduced the contractile force of isolated left atria and the spontaneously beating rate of isolated right atria of rabbits in concentration-dependent manner. These results indicate that the properties of the effect of Lien on haemodynamics may be similar to those of verapamil and different from those of Qui.

Effects of Persistent Atrial Fibrillation-Induced Electrical Remodeling on Atrial Electro-Mechanics – Insights from a 3D Model of the Human Atria

PubMed Central

Adeniran, Ismail; MacIver, David H.; Garratt, Clifford J.; Ye, Jianqiao; Hancox, Jules C.; Zhang, Henggui

2015-01-01

Aims Atrial stunning, a loss of atrial mechanical contraction, can occur following a successful cardioversion. It is hypothesized that persistent atrial fibrillation-induced electrical remodeling (AFER) on atrial electrophysiology may be responsible for such impaired atrial mechanics. This simulation study aimed to investigate the effects of AFER on atrial electro-mechanics. Methods and Results A 3D electromechanical model of the human atria was developed to investigate the effects of AFER on atrial electro-mechanics. Simulations were carried out in 3 conditions for 4 states: (i) the control condition, representing the normal tissue (state 1) and the tissue 2–3 months after cardioversion (state 2) when the atrial tissue recovers its electrophysiological properties after completion of reverse electrophysiological remodelling; (ii) AFER-SR condition for AF-remodeled tissue with normal sinus rhythm (SR) (state 3); and (iii) AFER-AF condition for AF-remodeled tissue with re-entrant excitation waves (state 4). Our results indicate that at the cellular level, AFER (states 3 & 4) abbreviated action potentials and reduced the Ca2+ content in the sarcoplasmic reticulum, resulting in a reduced amplitude of the intracellular Ca2+ transient leading to decreased cell active force and cell shortening as compared to the control condition (states 1 & 2). Consequently at the whole organ level, atrial contraction in AFER-SR condition (state 3) was dramatically reduced. In the AFER-AF condition (state 4) atrial contraction was almost abolished. Conclusions This study provides novel insights into understanding atrial electro-mechanics illustrating that AFER impairs atrial contraction due to reduced intracellular Ca2+ transients. PMID:26606047

The effect of endotoxin on heart rate dynamics in diabetic rats.

PubMed

Meamar, Morvarid; Dehpour, Tara; Mazloom, Roham; Sharifi, Fatemeh; Raoufy, Mohammad R; Dehpour, Ahmad R; Mani, Ali R

2015-05-01

The effect of endotoxin on heart rate variability (HRV) was assessed in diabetic and controls rats using a telemetric system. Endotoxin induced a reduction in sample entropy of cardiac rhythm in control animals. However, this effect was significantly blunted in streptozotocin-induced diabetic rats. Since uncoupling of cardiac pacemaker from cholinergic control is linked to reduced HRV in endotoxemia, chronotropic responsiveness to cholinergic stimulation was assessed in isolated atria. Endotoxemia was associated with impaired responsiveness to carbacholine in control rats. However, endotoxemia did not impair cholinergic responsiveness in diabetic atria. These findings corroborates with development of endotoxin tolerance in diabetic rats. Copyright © 2014 Elsevier B.V. All rights reserved.

Atrial fibrillation: Therapeutic potential of atrial K+ channel blockers.

PubMed

Ravens, Ursula; Odening, Katja E

2017-08-01

Despite the epidemiological scale of atrial fibrillation, current treatment strategies are of limited efficacy and safety. Ideally, novel drugs should specifically correct the pathophysiological mechanisms responsible for atrial fibrillation with no other cardiac or extracardiac actions. Atrial-selective drugs are directed toward cellular targets with sufficiently different characteristics in atria and ventricles to modify only atrial function. Several potassium (K + ) channels with either predominant expression in atria or distinct electrophysiological properties in atria and ventricles can serve as atrial-selective drug targets. These channels include the ultra-rapidly activating, delayed outward-rectifying Kv1.5 channel conducting I Kur , the acetylcholine-activated inward-rectifying Kir3.1/Kir3.4 channel conducting I K,ACh , the Ca 2+ -activated K + channels of small conductance (SK) conducting I SK , and the two pore domain K + (K2P) channels TWIK-1, TASK-1 and TASK-3 that are responsible for voltage-independent background currents I TWIK-1 , I TASK-1 , and I TASK-3 . Here, we briefly review the characteristics of these K + channels and their roles in atrial fibrillation. The antiarrhythmic potential of drugs targeting the described channels is discussed as well as their putative value in treatment of atrial fibrillation. Copyright © 2016 Elsevier Inc. All rights reserved.

Cardiac compartment-specific overexpression of a modified retinoic acid receptor produces dilated cardiomyopathy and congestive heart failure in transgenic mice.

PubMed

Colbert, M C; Hall, D G; Kimball, T R; Witt, S A; Lorenz, J N; Kirby, M L; Hewett, T E; Klevitsky, R; Robbins, J

1997-10-15

Retinoids play a critical role in cardiac morphogenesis. To examine the effects of excessive retinoid signaling on myocardial development, transgenic mice that overexpress a constitutively active retinoic acid receptor (RAR) controlled by either the alpha- or beta-myosin heavy chain (MyHC) promoter were generated. Animals carrying the alpha-MyHC-RAR transgene expressed RARs in embryonic atria and in adult atria and ventricles, but developed no signs of either malformations or disease. In contrast, beta-MyHC-RAR animals, where expression was activated in fetal ventricles, developed a dilated cardiomyopathy that varied in severity with transgene copy number. Characteristic postmortem lesions included biventricular chamber dilation and left atrial thrombosis; the incidence and severity of these lesions increased with increasing copy number. Transcript analyses showed that molecular markers of hypertrophy, alpha-skeletal actin, atrial natriuretic factor and beta-MyHC, were upregulated. Cardiac performance of transgenic hearts was evaluated using the isolated perfused working heart model as well as in vivo, by transthoracic M-mode echocardiography. Both analyses showed moderate to severe impairment of left ventricular function and reduced cardiac contractility. Thus, expression of a constitutively active RAR in developing atria and/ or in postnatal ventricles is relatively benign, while ventricular expression during gestation can lead to significant cardiac dysfunction.

Quantitative analysis of the expression and distribution of calcium channel alpha 1 subunit mRNA in the atria and ventricles of the rat heart.

PubMed

Larsen, Janice K; Mitchell, Jennifer W; Best, Philip M

2002-05-01

Two distinct calcium currents are present in mammalian cardiac myocytes. Utilizing quantitative RT-PCR methods, we have analysed the expression patterns and abundance of four calcium channel alpha 1 subunit mRNAs in different regions of the rat heart and compared them to the known density of calcium currents recorded from rat atria. Our results show that Ca(V)1.2 is the most abundant of the four alpha 1 subunit transcripts in the rat heart. The Ca(V)1.2 message is more abundant in ventricle than in atria and does not vary in expression as a function of developmental age. Ca(V)2.3, Ca(V)3.1 and Ca(V)3.2 mRNAs are 10-100 times less abundant than Ca(V)1.2. Interestingly, Ca(V)2.3, Ca(V)3.1 and Ca(V)3.2 are expressed in both atria and ventricle. The abundance of atrial Ca(V)3.1 mRNA does not change significantly during development and remains high in older animals. In contrast, levels of atrial Ca(V)3.2 mRNA are high in embryonic tissue and at 3- and 4-weeks postnatal but become undetectable at 5 weeks. Expression of atrial Ca(V)2.3 mRNA is highest at 4-weeks postnatal and then declines gradually. We have previously documented that the LVA calcium current density is highest within 4-5 weeks after birth and then declines gradually reaching less than 30% of its maximal value at 12-14 weeks. The complex relationship between atrial LVA current density and the abundance of Ca(V)2.3, Ca(V)3.1 and Ca(V)3.2 mRNA suggests that their contribution to the cardiac LVA current may vary as a function of postnatal age. Copyright 2002 Academic Press.

Aging-associated changes in L-type calcium channels in the left atria of dogs.

PubMed

Gan, Tian-Yi; Qiao, Weiwei; Xu, Guo-Jun; Zhou, Xian-Hui; Tang, Bao-Peng; Song, Jian-Guo; Li, Yao-Dong; Zhang, Jian; Li, Fa-Peng; Mao, Ting; Jiang, Tao

2013-10-01

Action potential (AP) contours vary considerably between the fibers of normal adult and aged left atria. The underlying ionic and molecular mechanisms that mediate these differences remain unknown. The aim of the present study was to investigate whether the L-type calcium current (I Ca.L ) and the L-type Ca 2+ channel of the left atria may be altered with age to contribute to atrial fibrillation (AF). Two groups of mongrel dogs (normal adults, 2-2.5 years old and older dogs, >8 years old) were used in this study. The inducibility of AF was quantitated using the cumulative window of vulnerability (WOV). A whole-cell patch-clamp was used to record APs and I Ca.L in left atrial (LA) cells obtained from the two groups of dogs. Protein and mRNA expression levels of the a1C (Cav1.2) subunit of the L-type calcium channel were assessed using western blotting and quantitative PCR (qPCR), respectively. Although the resting potential, AP amplitude and did not differ with age, the plateau potential was more negative and the APD 90 was longer in the aged cells compared with that in normal adult cells. Aged LA cells exhibited lower peak I Ca.L current densities than normal adult LA cells (P<0.05). In addition, the Cav1.2 mRNA and protein expression levels in LA cells were decreased in the aged group compared with those in the normal adult group. The lower AP plateau potential and the decreased I Ca.L of LA cells in aged dogs may contribute to the slow and discontinuous conduction of the left atria. Furthermore, the reduction of the expression levels of Cav1.2 with age may be the molecular mechanism that mediates the decline in I Ca.L with increasing age.

Virtual human versus human administration of photographic lineups.

PubMed

Daugherty, Brent; Babu, Sabarish; Wallendael, Lori Van; Cutler, Brian; Hodges, Larry F

2008-01-01

One solution to mistaken identification by a crime's victims and eyewitnesses is to use a virtual officer to conduct identification procedures. Results from a study comparing a virtual officer with a live human investigator indicate that the virtual officer performs comparably to the human in terms of identification accuracy, emotional affect, and ease of use.

Distinct contractile and molecular differences between two goat models of atrial dysfunction: AV block-induced atrial dilatation and atrial fibrillation.

PubMed

Greiser, Maura; Neuberger, Hans-Ruprecht; Harks, Erik; El-Armouche, Ali; Boknik, Peter; de Haan, Sunniva; Verheyen, Fons; Verheule, Sander; Schmitz, Wilhelm; Ravens, Ursula; Nattel, Stanley; Allessie, Maurits A; Dobrev, Dobromir; Schotten, Ulrich

2009-03-01

Atrial dilatation is an independent risk factor for thromboembolism in patients with and without atrial fibrillation (AF). In many patients, atrial dilatation goes along with depressed contractile function of the dilated atria. While some mechanisms causing atrial contractile dysfunction in fibrillating atria have been addressed previously, the cellular and molecular mechanisms of atrial contractile remodeling in dilated atria are unknown. This study characterized in vivo atrial contractile function in a goat model of atrial dilatation and compared it to a goat model of AF. Differences in the underlying mechanisms were elucidated by studying contractile function, electrophysiology and sarcoplasmic reticulum (SR) Ca2+ load in atrial muscle bundles and by analyzing expression and phosphorylation levels of key Ca2+-handling proteins, myofilaments and the expression and activity of their upstream regulators. In 7 chronically instrumented, awake goats atrial contractile dysfunction was monitored during 3 weeks of progressive atrial dilatation after AV-node ablation (AV block goats (AVB)). In open chest experiments atrial work index (AWI) and refractoriness were measured (10 goats with AVB, 5 goats with ten days of AF induced by repetitive atrial burst pacing (AF), 10 controls). Isometric force of contraction (FC), transmembrane action potentials (APs) and rapid cooling contractures (RCC, a measure of SR Ca2+ load) were studied in right atrial muscle bundles. Total and phosphorylated Ca2+-handling and myofilament protein levels were quantified by Western blot. In AVB goats, atrial size increased by 18% (from 26.6+/-4.4 to 31.6+/-5.5 mm, n=7 p<0.01) while atrial fractional shortening (AFS) decreased (from 18.4+/-1.7 to 12.8+/-4.0% at 400 ms, n=7, p<0.01). In open chest experiments, AWI was reduced in AVB and in AF goats compared to controls (at 400 ms: 8.4+/-0.9, n=7, and 3.2+/-1.8, n=5, vs 18.9+/-5.3 mmxmmHg, n=7, respectively, p<0.05 vs control). FC of isolated right atrial muscle bundles was reduced in AVB (n=8) and in AF (n=5) goats compared to controls (n=9) (at 2 Hz: 2.3+/-0.5 and 0.7+/-0.2 vs 5.5+/-1.0 mN/mm2, respectively, p<0.05). APs were shorter in AF, but unchanged in AVB goats. RCCs were reduced in AVB and AF versus control (AVB, 3.4+/-0.5 and AF, 4.1+/-1.4 vs 12.2+/-3.2 mN/mm2, p<0.05). Protein levels of protein kinase A (PKA) phosphorylated phospholamban (PLB) were reduced in AVB (n=8) and AF (n=8) vs control (n=7) by 37.9+/-12.4% and 29.7+/-10.1%, respectively (p<0.01), whereas calmodulin-dependent protein kinase II (CaMKII) phosphorylated ryanodine channels (RyR2) were increased by 166+/-55% in AVB (n=8) and by 146+/-56% in AF (n=8) goats (p<0.01). PKA-phosphorylated myosin-binding protein-C and troponin-I were reduced exclusively in AVB goat atria (by 75+/-10% and 55+/-15%, respectively, n=8, p<0.05). Atrial dilatation developing during slow ventricular rhythm after complete AV block as well as AF-induced remodeling are associated with atrial contractile dysfunction. Both AVB and AF goat atria show decreased SR Ca2+ load, likely caused by PLB dephosphorylation and RYR2 hyperphosphorylation. While shorter APs further compromise contractility in AF goat atria, reduced myofilament phosphorylation may impair contractility in AVB goat atria. Thus, atrial hypocontractility appears to have distinct molecular contributors in different types of atrial remodeling.

[Current problems in the data acquisition of digitized virtual human and the countermeasures].

PubMed

Zhong, Shi-zhen; Yuan, Lin

2003-06-01

As a relatively new field of medical science research that has attracted the attention from worldwide researchers, study of digitized virtual human still awaits long-term dedicated effort for its full development. In the full array of research projects of the integrated Virtual Chinese Human project, virtual visible human, virtual physical human, virtual physiome, and intellectualized virtual human must be included as the four essential constitutional opponents. The primary importance should be given to solving the problems concerning the data acquisition for the dataset of this immense project. Currently 9 virtual human datasets have been established worldwide, which are subjected to critical analyses in the paper with special attention given to the problems in the data storage and the techniques employed, for instance, in these datasets. On the basis of current research status of Virtual Chinese Human project, the authors propose some countermeasures for solving the problems in the data acquisition for the dataset, which include (1) giving the priority to the quality control instead of merely racing for quantity and speed, and (2) improving the setting up of the markers specific for the tissues and organs to meet the requirement from information technology, (3) with also attention to the development potential of the dataset which should have explicit pertinence to specific actual applications.

[Scientific significance and prospective application of digitized virtual human].

PubMed

Zhong, Shi-zhen

2003-03-01

As a cutting-edge research project, digitization of human anatomical information combines conventional medicine with information technology, computer technology, and virtual reality technology. Recent years have seen the establishment of, or the ongoing effort to establish various virtual human models in many countries, on the basis of continuous sections of human body that are digitized by means of computational medicine incorporating information technology to quantitatively simulate human physiological and pathological conditions, and to provide wide prospective applications in the fields of medicine and other disciplines. This article addresses 4 issues concerning the progress in virtual human model researches as the following: (1) Worldwide survey of sectioning and modeling of visible human. American visible human database was completed in 1994, which contains both a male and a female datasets, and has found wide application internationally. South Korea also finished the data collection for a male visible Korean human dataset in 2000. (2) Application of the dataset of Visible Human Project (VHP). This dataset has yielded plentiful fruits in medical education and clinical research, and further plans are proposed and practiced to construct a Physical Human and Physiological Human . (3) Scientific significance and prospect of virtual human studies. Digitized human dataset may eventually contribute to the development of many new high-tech industries. (4) Progress of virtual Chinese human project. The 174th session of Xiangshang Science Conferences held in 2001 marked the initiation of digitized virtual human project in China, and some key techniques have been explored. By now the data-collection process for 4 Chinese virtual human datasets have been successfully completed.

Hirarchical emotion calculation model for virtual human modellin - biomed 2010.

PubMed

Zhao, Yue; Wright, David

2010-01-01

This paper introduces a new emotion generation method for virtual human modelling. The method includes a novel hierarchical emotion structure, a group of emotion calculation equations and a simple heuristics decision making mechanism, which enables virtual humans to perform emotionally in real-time according to their internal and external factors. Emotion calculation equations used in this research were derived from psychologic emotion measurements. Virtual humans can utilise the information in virtual memory and emotion calculation equations to generate their own numerical emotion states within the hierarchical emotion structure. Those emotion states are important internal references for virtual humans to adopt appropriate behaviours and also key cues for their decision making. A simple heuristics theory is introduced and integrated into decision making process in order to make the virtual humans decision making more like a real human. A data interface which connects the emotion calculation and the decision making structure together has also been designed and simulated to test the method in Virtools environment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brodde, O.E.; Leifert, F.J.; Krehl, H.J.

We determined the amount of beta 1- and beta 2-adrenoceptors in right and left atria and ventricles of rabbits. For this purpose inhibition of specific (-)-/sup 3/H-dihydroalprenolol ((-)-/sup 3/H-DHA) binding (5 nM) by beta 1-selective (practolol, metoprolol) and beta 2-selective (zinterol, IPS 339) adrenergic drugs was determined and analyzed by pseudo-Scatchard (Hofstee) plots. For both atria, inhibition of binding by the four selective beta-adrenergic drugs resulted in non-linear Hofstee plots, suggesting the coexistence of both beta-adrenoceptor subtypes. From these plots we calculated a beta 1:beta 2-adrenoceptor ratio of 72:28 for the right atrium and of 82:18 for the left. Inmore » contrast, only a very small amount of beta 2-adrenoceptors (approximately 5-7% of the total beta-adrenoceptor population) could be detected in the ventricles. For comparison we analyzed the inhibition of specific (-)-/sup 3/H-DHA binding in tissues with homogeneous population of beta-adrenoceptors (beta 1:guinea pig left ventricle; beta 2: cerebellum of mature rats). For both tissues the four selective beta-adrenergic drugs showed linear Hofstee plots, demonstrating that in tissues with homogeneous beta-receptor population interaction of each drug with the receptor followed simple mass-action kinetics. We conclude that beta 1- and beta 2-adrenoceptors coexist in rabbit atria while the ventricles are predominantly endowed the beta 1-adrenoceptors.« less

Cardiovascular Pressures with Venous Gas Embolism and Decompression

NASA Technical Reports Server (NTRS)

Butler, B. D.; Robinson, R.; Sutton, T.; Kemper, G. B.

1995-01-01

Venous gas embolism (VGE) is reported with decompression to a decreased ambient pressure. With severe decompression, or in cases where an intracardiac septal defect (patent foramen ovale) exists, the venous bubbles can become arterialized and cause neurological decompression illness. Incidence rates of patent foramen ovale in the general population range from 25-34% and yet aviators, astronauts, and deepsea divers who have decompression-induced venous bubbles do not demonstrate neurological symptoms at these high rates. This apparent disparity may be attributable to the normal pressure gradient across the atria of the heart that must be reversed for there to be flow potency. We evaluated the effects of: venous gas embolism (0.025, 0.05 and 0.15 ml/ kg min for 180 min.) hyperbaric decompression; and hypobaric decompression on the pressure gradient across the left and right atria in anesthetized dogs with intact atrial septa. Left ventricular end-diastolic pressure was used as a measure of left atrial pressure. In a total of 92 experimental evaluations in 22 dogs, there were no reported reversals in the mean pressure gradient across the atria; a total of 3 transient reversals occurred during the peak pressure gradient changes. The reasons that decompression-induced venous bubbles do not consistently cause serious symptoms of decompression illness may be that the amount of venous gas does not always cause sufficient pressure reversal across a patent foramen ovale to cause arterialization of the venous bubbles.

Cardiac compartment-specific overexpression of a modified retinoic acid receptor produces dilated cardiomyopathy and congestive heart failure in transgenic mice.

PubMed Central

Colbert, M C; Hall, D G; Kimball, T R; Witt, S A; Lorenz, J N; Kirby, M L; Hewett, T E; Klevitsky, R; Robbins, J

1997-01-01

Retinoids play a critical role in cardiac morphogenesis. To examine the effects of excessive retinoid signaling on myocardial development, transgenic mice that overexpress a constitutively active retinoic acid receptor (RAR) controlled by either the alpha- or beta-myosin heavy chain (MyHC) promoter were generated. Animals carrying the alpha-MyHC-RAR transgene expressed RARs in embryonic atria and in adult atria and ventricles, but developed no signs of either malformations or disease. In contrast, beta-MyHC-RAR animals, where expression was activated in fetal ventricles, developed a dilated cardiomyopathy that varied in severity with transgene copy number. Characteristic postmortem lesions included biventricular chamber dilation and left atrial thrombosis; the incidence and severity of these lesions increased with increasing copy number. Transcript analyses showed that molecular markers of hypertrophy, alpha-skeletal actin, atrial natriuretic factor and beta-MyHC, were upregulated. Cardiac performance of transgenic hearts was evaluated using the isolated perfused working heart model as well as in vivo, by transthoracic M-mode echocardiography. Both analyses showed moderate to severe impairment of left ventricular function and reduced cardiac contractility. Thus, expression of a constitutively active RAR in developing atria and/ or in postnatal ventricles is relatively benign, while ventricular expression during gestation can lead to significant cardiac dysfunction. PMID:9329959

Getting the point across: exploring the effects of dynamic virtual humans in an interactive museum exhibit on user perceptions.

PubMed

Rivera-Gutierrez, Diego; Ferdig, Rick; Li, Jian; Lok, Benjamin

2014-04-01

We have created “You, M.D.”, an interactive museum exhibit in which users learn about topics in public health literacy while interacting with virtual humans. You, M.D. is equipped with a weight sensor, a height sensor and a Microsoft Kinect that gather basic user information. Conceptually, You, M.D. could use this user information to dynamically select the appearance of the virtual humans in the interaction attempting to improve learning outcomes and user perception for each particular user. For this concept to be possible, a better understanding of how different elements of the visual appearance of a virtual human affects user perceptions is required. In this paper, we present the results of an initial user study with a large sample size (n =333) ran using You, M.D. The study measured users’ reactions based on the user’s gender and body-mass index (BMI) when facing virtual humans with BMI either concordant or discordant from the user’s BMI. The results of the study indicate that concordance between the users’ BMI and the virtual human’s BMI affects male and female users differently. The results also show that female users rate virtual humans as more knowledgeable than male users rate the same virtual humans.

Diastolic Dysfunction

MedlinePlus

... the sinoatrial or SA node) sends out an electrical signal that causes the atria to contract. This ... when the ventricles are full of blood. The electrical signals cause the ventricles to contract and push ...

Human Resource Management in Virtual Organizations. Research in Human Resource Management Series.

ERIC Educational Resources Information Center

Heneman, Robert L., Ed.; Greenberger, David B., Ed.

This document contains 14 papers on human resources (HR) and human resource management (HRM) in virtual organizations. The following papers are included: "Series Preface" (Rodger Griffeth); "Volume Preface" (Robert L. Heneman, David B. Greenberger); "The Virtual Organization: Definition, Description, and…

Determining conduction patterns on a sparse electrode grid: Implications for the analysis of clinical arrhythmias

NASA Astrophysics Data System (ADS)

Vidmar, David; Narayan, Sanjiv M.; Krummen, David E.; Rappel, Wouter-Jan

2016-11-01

We present a general method of utilizing bioelectric recordings from a spatially sparse electrode grid to compute a dynamic vector field describing the underlying propagation of electrical activity. This vector field, termed the wave-front flow field, permits quantitative analysis of the magnitude of rotational activity (vorticity) and focal activity (divergence) at each spatial point. We apply this method to signals recorded during arrhythmias in human atria and ventricles using a multipolar contact catheter and show that the flow fields correlate with corresponding activation maps. Further, regions of elevated vorticity and divergence correspond to sites identified as clinically significant rotors and focal sources where therapeutic intervention can be effective. These flow fields can provide quantitative insights into the dynamics of normal and abnormal conduction in humans and could potentially be used to enhance therapies for cardiac arrhythmias.

An intelligent virtual human system for providing healthcare information and support.

PubMed

Rizzo, Albert A; Lange, Belinda; Buckwalter, John G; Forbell, Eric; Kim, Julia; Sagae, Kenji; Williams, Josh; Rothbaum, Barbara O; Difede, JoAnn; Reger, Greg; Parsons, Thomas; Kenny, Patrick

2011-01-01

Over the last 15 years, a virtual revolution has taken place in the use of Virtual Reality simulation technology for clinical purposes. Shifts in the social and scientific landscape have now set the stage for the next major movement in Clinical Virtual Reality with the "birth" of intelligent virtual humans. Seminal research and development has appeared in the creation of highly interactive, artificially intelligent and natural language capable virtual human agents that can engage real human users in a credible fashion. No longer at the level of a prop to add context or minimal faux interaction in a virtual world, virtual humans can be designed to perceive and act in a 3D virtual world, engage in spoken dialogues with real users and can be capable of exhibiting human-like emotional reactions. This paper will present an overview of the SimCoach project that aims to develop virtual human support agents to serve as online guides for promoting access to psychological healthcare information and for assisting military personnel and family members in breaking down barriers to initiating care. The SimCoach experience is being designed to attract and engage military Service Members, Veterans and their significant others who might not otherwise seek help with a live healthcare provider. It is expected that this experience will motivate users to take the first step--to empower themselves to seek advice and information regarding their healthcare and general personal welfare and encourage them to take the next step towards seeking more formal resources if needed.

Sick sinus syndrome

MedlinePlus

... the heart (atria). This area is the heart's pacemaker. It may be called the sinoatrial node, sinus ... do so. You may need a permanent implanted pacemaker if your symptoms are related to bradycardia (slow ...

Heart murmurs

MedlinePlus

Chest sounds - murmurs; Heart sounds - abnormal; Murmur - innocent; Innocent murmur; Systolic heart murmur; Diastolic heart murmur ... The heart has 4 chambers: Two upper chambers (atria) Two lower chambers (ventricles) The heart has valves that close ...

Modulation of visually evoked movement responses in moving virtual environments.

PubMed

Reed-Jones, Rebecca J; Vallis, Lori Ann

2009-01-01

Virtual-reality technology is being increasingly used to understand how humans perceive and act in the moving world around them. What is currently not clear is how virtual reality technology is perceived by human participants and what virtual scenes are effective in evoking movement responses to visual stimuli. We investigated the effect of virtual-scene context on human responses to a virtual visual perturbation. We hypothesised that exposure to a natural scene that matched the visual expectancies of the natural world would create a perceptual set towards presence, and thus visual guidance of body movement in a subsequently presented virtual scene. Results supported this hypothesis; responses to a virtual visual perturbation presented in an ambiguous virtual scene were increased when participants first viewed a scene that consisted of natural landmarks which provided 'real-world' visual motion cues. Further research in this area will provide a basis of knowledge for the effective use of this technology in the study of human movement responses.

Chronic nicotine in hearts with healed ventricular myocardial infarction promotes atrial flutter that resembles typical human atrial flutter.

PubMed

Miyauchi, Mizuho; Qu, Zhilin; Miyauchi, Yasushi; Zhou, Sheng-Mei; Pak, Hui; Mandel, William J; Fishbein, Michael C; Chen, Peng-Sheng; Karagueuzian, Hrayr S

2005-06-01

The potential of chronic nicotine exposure for atrial fibrillation (AF) and atrial flutter (AFL) in hearts with and without chronic myocardial infarction (MI) remains poorly explored. MI was created in dogs by permanent occlusion of the left anterior descending coronary artery, and dogs were administered nicotine (5 mg.kg(-1).day(-1) sc) for 1 mo using osmotic minipumps. High-resolution epicardial (1,792 bipolar electrodes) and endocardial Halo catheters were used to map activation during induced atrial rhythms. Nicotine promoted inducible sustained AFL at a mean cycle length of 134 +/- 10 ms in all MI dogs (n = 6) requiring pacing and electrical shocks for termination. No AFL could be induced in MI dogs (n = 6), control (non-MI) dogs (n = 3) not exposed to nicotine, and dogs with no MI and exposed to nicotine (n = 3). Activation maps during AFL showed a single reentrant wavefront in the right atrium that rotated either clockwise (60%) or counterclockwise (40%) around the crista terminalis and through the isthmus. Ablation of the isthmus prevented the induction of AFL. Nicotine caused a significant (P < 0.01) but highly heterogeneous increase in atrial interstitial fibrosis (2- to 10-fold increase in left and right atria, respectively) in the MI group but only a 2-fold increase in the right atrium in the non-MI group. Nicotine also flattened (P < 0.05) the slope of the epicardial monophasic action potential duration (electrical restitution) curve of both atria in the MI but not in non-MI dogs. Two-dimensional simulation in an excitable matrix containing an isthmus and nicotine's restitutional and reduced gap junctional coupling (fibrosis) parameters replicated the experiments. Chronic nicotine in hearts with MI promotes AFL that closely resembles typical human AFL. Increased atrial interstitial fibrosis and flattened electrical restitution are important substrates for the AFL.

21 CFR 870.5310 - Automated external defibrillator.

Code of Federal Regulations, 2010 CFR

2010-04-01

... shock of a maximum of 360 joules of energy used for defibrillating (restoring normal heart rhythm) the atria or ventricles of the heart. An AED analyzes the patient's electrocardiogram, interprets the...

21 CFR 870.5310 - Automated external defibrillator.

Code of Federal Regulations, 2014 CFR

2014-04-01

... shock of a maximum of 360 joules of energy used for defibrillating (restoring normal heart rhythm) the atria or ventricles of the heart. An AED analyzes the patient's electrocardiogram, interprets the...

21 CFR 870.5310 - Automated external defibrillator.

Code of Federal Regulations, 2012 CFR

2012-04-01

... shock of a maximum of 360 joules of energy used for defibrillating (restoring normal heart rhythm) the atria or ventricles of the heart. An AED analyzes the patient's electrocardiogram, interprets the...

21 CFR 870.5310 - Automated external defibrillator.

Code of Federal Regulations, 2011 CFR

2011-04-01

... shock of a maximum of 360 joules of energy used for defibrillating (restoring normal heart rhythm) the atria or ventricles of the heart. An AED analyzes the patient's electrocardiogram, interprets the...

21 CFR 870.5310 - Automated external defibrillator.

Code of Federal Regulations, 2013 CFR

2013-04-01

... shock of a maximum of 360 joules of energy used for defibrillating (restoring normal heart rhythm) the atria or ventricles of the heart. An AED analyzes the patient's electrocardiogram, interprets the...

Cardiac natriuretic peptide response to water restriction in the hormonal adaptation of two semidesert rodents from West Africa (Steatomys caurinus, Taterillus gracilis).

PubMed

Lacas, S; Allevard, A M; Ag'Atteinine, S; Gallo-Bona, N; Gauquelin-Koch, G; Hardin-Pouzet, H; Gharib, C; Sicard, B; Maurel, D

2000-11-01

Two African rodents, Taterillus gracilis and Steatomys caurinus, native to regions of alternate dry and wet seasons, were studied under laboratory conditions. These species differ in estivation behavior, one undergoing pseudoestivation and the other strong estivation. One group of animals of each species was provided with unlimited access to seed and vegetables rich in water, mimicking the food availability of the wet season (control group). A second group of animals of each species was subjected to water restriction for 8 days, mimicking the natural drought that occurs during the dry-hot season. The effects of water restriction on osmoregulation and body water content were assessed from hematocrit, and plasma and urinary osmolalities (PO, UO). Whether the natriuretic peptide system was modified by the osmoregulator adaptation to aridity of these semidesert rodents was examined from measurements of atrial natriuretic peptide (ANP) levels in plasma, atria, and ventricles, in parallel with morphological studies. In both species, UO was increased by water restriction. In water-deprived T. gracilis, ANP levels were about twice (right atria: 1.08 +/- 0.16 microg/mg protein vs control: 0.40 +/- 0.06 microg/mg protein) and plasma concentrations half (0.28 +/- 0.06 ng/ml vs control: 0.64 +/- 0.07 ng/ml) those in control animals. In S. caurinus these variables were not affected by water availability (right atria water restricted: 2. 20 +/- 0.15 microg/mg protein vs control: 2.86 +/- 0.37 microg/mg protein; plasma ANP water restricted: 0.80 +/- 0.12 ng/ml vs control: 0.90 +/- 0.16 ng/ml). Consistent with these quantitative results, immunohistochemical and ultrastructural observations showed an increase in immunostaining for both the N- and the C-terminal ANP and a larger number of granules in the atria of T. gracilis following water restriction, whereas there was no visible change in S. caurinus. Thus, water restriction induced a decrease in ANP secretion in T. gracilis, increasing cardiac storage alongside a reduced urine production. In contrast, in S. caurinus, the natriuretic system was not affected by an 8-day period of water restriction. Copyright 2000 Academic Press.

Healthy young adults implement distinctive avoidance strategies while walking and circumventing virtual human vs. non-human obstacles in a virtual environment.

PubMed

Souza Silva, Wagner; Aravind, Gayatri; Sangani, Samir; Lamontagne, Anouk

2018-03-01

This study examines how three types of obstacles (cylinder, virtual human and virtual human with footstep sounds) affect circumvention strategies of healthy young adults. Sixteen participants aged 25.2 ± 2.5 years (mean ± 1SD) were tested while walking overground and viewing a virtual room through a helmet mounted display. As participants walked towards a stationary target in the far space, they avoided an obstacle (cylinder or virtual human) approaching either from the right (+40°), left (-40°) or head-on (0°). Obstacle avoidance strategies were characterized using the position and orientation of the head. Repeated mixed model analysis showed smaller minimal distances (p = 0.007) while avoiding virtual humans as compared to cylinders. Footstep sounds added to virtual humans did not modify (p = 0.2) minimal distances compared to when no sound was provided. Onset times of avoidance strategies were similar across conditions (p = 0.06). Results indicate that the nature of the obstacle (human-like vs. non-human object) matters and can modify avoidance strategies. Smaller obstacle clearances in response to virtual humans may reflect the use of a less conservative avoidance strategy, due to a resemblance of obstacles to pedestrians and a recall of strategies used in daily locomotion. The lack of influence of footstep sounds supports the fact that obstacle avoidance primarily relies on visual cues and the principle of 'inverse effectiveness' whereby multisensory neurons' response to multimodal stimuli becomes weaker when the unimodal sensory stimulus (vision) is strong. Present findings should be taken into consideration to optimize the ecological validity of VR-based obstacle avoidance paradigms used in research and rehabilitation. Copyright © 2018 Elsevier B.V. All rights reserved.

Photorealistic virtual anatomy based on Chinese Visible Human data.

PubMed

Heng, P A; Zhang, S X; Xie, Y M; Wong, T T; Chui, Y P; Cheng, C Y

2006-04-01

Virtual reality based learning of human anatomy is feasible when a database of 3D organ models is available for the learner to explore, visualize, and dissect in virtual space interactively. In this article, we present our latest work on photorealistic virtual anatomy applications based on the Chinese Visible Human (CVH) data. We have focused on the development of state-of-the-art virtual environments that feature interactive photo-realistic visualization and dissection of virtual anatomical models constructed from ultra-high resolution CVH datasets. We also outline our latest progress in applying these highly accurate virtual and functional organ models to generate realistic look and feel to advanced surgical simulators. (c) 2006 Wiley-Liss, Inc.

Atrial Fibrillation: Treatment

MedlinePlus

... options include medicines, medical procedures, and lifestyle changes. Blood Clot Prevention People who have AFib are at increased ... the heart's upper chambers (the atria), causing a blood clot to form. If the clot breaks off and ...

Building Virtuality into University-Based Human Resources Policy in China's Universities

ERIC Educational Resources Information Center

Guoliang, Zhang

2005-01-01

On the basis of discussing the notion of virtual human resources and its structure, this paper analyzes the necessity of building up virtual university teaching staff and proposes a model for the structural makeup of virtual university teaching staff.

Development of the Hearts of Lizards and Snakes and Perspectives to Cardiac Evolution

PubMed Central

Jensen, Bjarke; van den Berg, Gert; van den Doel, Rick; Oostra, Roelof-Jan; Wang, Tobias; Moorman, Antoon F. M.

2013-01-01

Birds and mammals both developed high performance hearts from a heart that must have been reptile-like and the hearts of extant reptiles have an unmatched variability in design. Yet, studies on cardiac development in reptiles are largely old and further studies are much needed as reptiles are starting to become used in molecular studies. We studied the growth of cardiac compartments and changes in morphology principally in the model organism corn snake (Pantherophis guttatus), but also in the genotyped anole (Anolis carolinenis and A. sagrei) and the Philippine sailfin lizard (Hydrosaurus pustulatus). Structures and chambers of the formed heart were traced back in development and annotated in interactive 3D pdfs. In the corn snake, we found that the ventricle and atria grow exponentially, whereas the myocardial volumes of the atrioventricular canal and the muscular outflow tract are stable. Ventricular development occurs, as in other amniotes, by an early growth at the outer curvature and later, and in parallel, by incorporation of the muscular outflow tract. With the exception of the late completion of the atrial septum, the adult design of the squamate heart is essentially reached halfway through development. This design strongly resembles the developing hearts of human, mouse and chicken around the time of initial ventricular septation. Subsequent to this stage, and in contrast to the squamates, hearts of endothermic vertebrates completely septate their ventricles, develop an insulating atrioventricular plane, shift and expand their atrioventricular canal toward the right and incorporate the systemic and pulmonary venous myocardium into the atria. PMID:23755108

Influence of atrial substrate on local capture induced by rapid pacing of atrial fibrillation.

PubMed

Rusu, Alexandru; Jacquemet, Vincent; Vesin, Jean-Marc; Virag, Nathalie

2014-05-01

Preliminary studies showed that the septum area was the only location allowing local capture of both the atria during rapid pacing of atrial fibrillation (AF) from a single site. The present model-based study investigated the influence of atrial substrate on the ability to capture AF when pacing the septum. Three biophysical models of AF with an identical anatomy from human atria but with different AF substrates were used: (i) AF based on multiple wavelets, (ii) AF based on heterogeneities in vagal activation, (iii) AF based on heterogeneities in repolarization. A fourth anatomical model without Bachmann's bundle (BB) was also implemented. Rapid pacing was applied from the septum at pacing cycle lengths in the range of 50-100% of AF cycle length. Local capture was automatically assessed with 24 pairs of electrodes evenly distributed on the atrial surface. The results were averaged over 16 AF simulations. In the homogeneous substrate, AF capture could reach 80% of the atrial surface. Heterogeneities degraded the ability to capture during AF. In the vagal substrate, the capture tended to be more regular and the degradation of the capture was not directly related to the spatial extent of the heterogeneities. In the third substrate, heterogeneities induced wave anchorings and wavebreaks even in areas close to the pacing site, with a more dramatic effect on AF capture. Finally, BB did not significantly affect the ability to capture. Atrial fibrillation substrate had a significant effect on rapid pacing outcomes. The response to therapeutic pacing may therefore be specific to each patient.

Vision-based navigation in a dynamic environment for virtual human

NASA Astrophysics Data System (ADS)

Liu, Yan; Sun, Ji-Zhou; Zhang, Jia-Wan; Li, Ming-Chu

2004-06-01

Intelligent virtual human is widely required in computer games, ergonomics software, virtual environment and so on. We present a vision-based behavior modeling method to realize smart navigation in a dynamic environment. This behavior model can be divided into three modules: vision, global planning and local planning. Vision is the only channel for smart virtual actor to get information from the outside world. Then, the global and local planning module use A* and D* algorithm to find a way for virtual human in a dynamic environment. Finally, the experiments on our test platform (Smart Human System) verify the feasibility of this behavior model.

Tachycardia | Fast Heart Rate

MedlinePlus

... sinoatrial (SA) node --- the heart's natural pacemaker. A series of early beats in the atria speeds up the heart rate. The rapid heartbeat does not allow enough time for the heart to fill before it contracts ...

Free creatine available to the creatine phosphate energy shuttle in isolated rat atria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savabi, F.

1988-10-01

To measure the actual percentage of intracellular free creatine participating in the process of energy transport, the incorporation of (1-{sup 14}C)creatine into the free creatine and phosphocreatine (PCr) pools in spontaneously beating isolated rat atria, under various conditions, was examined. The atria were subjected to three consecutive periods, control, anoxia, and postanoxic recover, in medium containing tracers of (1-{sup 14}C)creatine. The tissue content and specific activity of creatine and PCr were determined at the end of each period. The higher specific activity found for tissue PCr (1.87 times) than creatine, independent of the percentage of total intracellular creatine that wasmore » present as free creatine, provides evidence for the existence of two separate pools of free creatine. Analysis of the data shows that in the normal oxygenated state {approx} 9% of the total intracellular creatine is actually free to participate in the process of energy transport (shuttle pool). About 36% of the total creatine is bound to unknown intracellular components and the rest exists as PCr. The creatine that was taken up and the creatine that was released from the breakdown of PCr have much greater access to the site of phosphorylation than the rest of the intracellular creatine. A sharp increase in the specific activity of residual PCr on prolongation of anoxic time was also observed. This provides evidence for a nonhomogeneous pool of PCr, for the most recently formed (radioactive) PCr appeared to be hydrolyzed last.« less

An Intelligent Virtual Human System For Providing Healthcare Information And Support

DTIC Science & Technology

2011-01-01

for clinical purposes. Shifts in the social and scientific landscape have now set the stage for the next major movement in Clinical Virtual Reality ...College; dMadigan Army Medical Center Army Abstract. Over the last 15 years, a virtual revolution has taken place in the use of Virtual Reality ... Virtual Reality with the “birth” of intelligent virtual humans. Seminal research and development has appeared in the creation of highly interactive

Human Rights and Private Ordering in Virtual Worlds

NASA Astrophysics Data System (ADS)

Oosterbaan, Olivier

This paper explores the application of human rights in (persistent) virtual world environments. The paper begins with describing a number of elements that most virtual environments share and that are relevant for the application of human rights in such a setting; and by describing in a general nature the application of human rights between private individuals. The paper then continues by discussing the application in virtual environments of two universally recognized human rights, namely freedom of expression, and freedom from discrimination. As these specific rights are discussed, a number of more general conclusions on the application of human rights in virtual environments are drawn. The first general conclusion being that, because virtual worlds are private environments, participants are subject to private ordering. The second general conclusion being that participants and non-participants alike have to accept at times that in-world expressions are to an extent private speech. The third general conclusion is that, where participants represent themselves in-world, other participants cannot assume that such in-world representation share the characteristics of the human player; and that where virtual environments contain game elements, participants and non-participants alike should not take everything that happens in the virtual environment at face value or literally, which does however not amount to having to accept a higher level of infringement on their rights for things that happen in such an environment.

Recognizing an Irregular Heart Rhythm

MedlinePlus

... a workout, consider checking your rhythm as well. Atrial fibrillation, also referred to as AF, is a common ... upper chambers, or atria, of the heart. “While atrial fibrillation is not common among young people, it can ...

Paroxysmal supraventricular tachycardia (PSVT)

MedlinePlus

PSVT; Supraventricular tachycardia; Abnormal heart rhythm - PSVT; Arrhythmia - PSVT; Rapid heart rate - PSVT; Fast heart rate - PSVT ... Normally, the chambers of the heart (atria and ventricles) contract in ... are caused by an electrical signal that begins in an area ...

Sense of presence and anxiety during virtual social interactions between a human and virtual humans.

PubMed

Morina, Nexhmedin; Brinkman, Willem-Paul; Hartanto, Dwi; Emmelkamp, Paul M G

2014-01-01

Virtual reality exposure therapy (VRET) has been shown to be effective in treatment of anxiety disorders. Yet, there is lack of research on the extent to which interaction between the individual and virtual humans can be successfully implanted to increase levels of anxiety for therapeutic purposes. This proof-of-concept pilot study aimed at examining levels of the sense of presence and anxiety during exposure to virtual environments involving social interaction with virtual humans and using different virtual reality displays. A non-clinical sample of 38 participants was randomly assigned to either a head-mounted display (HMD) with motion tracker and sterescopic view condition or a one-screen projection-based virtual reality display condition. Participants in both conditions engaged in free speech dialogues with virtual humans controlled by research assistants. It was hypothesized that exposure to virtual social interactions will elicit moderate levels of sense of presence and anxiety in both groups. Further it was expected that participants in the HMD condition will report higher scores of sense of presence and anxiety than participants in the one-screen projection-based display condition. Results revealed that in both conditions virtual social interactions were associated with moderate levels of sense of presence and anxiety. Additionally, participants in the HMD condition reported significantly higher levels of presence than those in the one-screen projection-based display condition (p = .001). However, contrary to the expectations neither the average level of anxiety nor the highest level of anxiety during exposure to social virtual environments differed between the groups (p = .97 and p = .75, respectively). The findings suggest that virtual social interactions can be successfully applied in VRET to enhance sense of presence and anxiety. Furthermore, our results indicate that one-screen projection-based displays can successfully activate levels of anxiety in social virtual environments. The outcome can prove helpful in using low-cost projection-based virtual reality environments for treating individuals with social phobia.

Virtual reality in surgical training.

PubMed

Lange, T; Indelicato, D J; Rosen, J M

2000-01-01

Virtual reality in surgery and, more specifically, in surgical training, faces a number of challenges in the future. These challenges are building realistic models of the human body, creating interface tools to view, hear, touch, feel, and manipulate these human body models, and integrating virtual reality systems into medical education and treatment. A final system would encompass simulators specifically for surgery, performance machines, telemedicine, and telesurgery. Each of these areas will need significant improvement for virtual reality to impact medicine successfully in the next century. This article gives an overview of, and the challenges faced by, current systems in the fast-changing field of virtual reality technology, and provides a set of specific milestones for a truly realistic virtual human body.

Human Factors Virtual Analysis Techniques for NASA's Space Launch System Ground Support using MSFC's Virtual Environments Lab (VEL)

NASA Technical Reports Server (NTRS)

Searcy, Brittani

2017-01-01

Using virtual environments to assess complex large scale human tasks provides timely and cost effective results to evaluate designs and to reduce operational risks during assembly and integration of the Space Launch System (SLS). NASA's Marshall Space Flight Center (MSFC) uses a suite of tools to conduct integrated virtual analysis during the design phase of the SLS Program. Siemens Jack is a simulation tool that allows engineers to analyze human interaction with CAD designs by placing a digital human model into the environment to test different scenarios and assess the design's compliance to human factors requirements. Engineers at MSFC are using Jack in conjunction with motion capture and virtual reality systems in MSFC's Virtual Environments Lab (VEL). The VEL provides additional capability beyond standalone Jack to record and analyze a person performing a planned task to assemble the SLS at Kennedy Space Center (KSC). The VEL integrates Vicon Blade motion capture system, Siemens Jack, Oculus Rift, and other virtual tools to perform human factors assessments. By using motion capture and virtual reality, a more accurate breakdown and understanding of how an operator will perform a task can be gained. By virtual analysis, engineers are able to determine if a specific task is capable of being safely performed by both a 5% (approx. 5ft) female and a 95% (approx. 6'1) male. In addition, the analysis will help identify any tools or other accommodations that may to help complete the task. These assessments are critical for the safety of ground support engineers and keeping launch operations on schedule. Motion capture allows engineers to save and examine human movements on a frame by frame basis, while virtual reality gives the actor (person performing a task in the VEL) an immersive view of the task environment. This presentation will discuss the need of human factors for SLS and the benefits of analyzing tasks in NASA MSFC's VEL.

A posthuman liturgy? Virtual worlds, robotics, and human flourishing.

PubMed

Shatzer, Jacob

2013-01-01

In order to inspire a vision of biotechnology that affirms human dignity and human flourishing, the author poses questions about virtual reality and the use of robotics in health care. Using the concept of 'liturgy' and an anthropology of humans as lovers, the author explores how virtual reality and robotics in health care shape human moral agents, and how such shaping could influence the way we do or do not pursue a 'posthuman' future.

A Test of Spatial Contiguity for Virtual Human's Gestures in Multimedia Learning Environments

ERIC Educational Resources Information Center

Craig, Scotty D.; Twyford, Jessica; Irigoyen, Norma; Zipp, Sarah A.

2015-01-01

Virtual humans are becoming an easily available and popular component of multimedia learning that are often used in online learning environments. There is still a need for systematic research into their effectiveness. The current study investigates the positioning of a virtual human's gestures when guiding the learner through a multimedia…

Commonly Asked Questions about Children and Heart Disease

MedlinePlus

... heart is a pump with a built-in electrical system. Normally, electricity starts in the upper chamber and spreads to ... function. Heart block occurs when the spread of electricity from the upper chambers (atria) to the lower ...

[The cholinergic non-excitability phenomenon in the atrial myocardium of lower vertebrates].

PubMed

Abramochkin, D V; Kuz'min, V S; Sukhova, G S; Rozenshtraukh, L V

2009-06-01

Changes of electric activity induced by acetylcholine were studied in atrial myocardium of fishes (cod and carp) and reptilians (lizard and grass-snake). Standart microelectrode technique and novel method of optical mapping were used in the study. Acetylcholine (1-50 microM) provoked decrease of the action potential amplitude down to full inhibition of electrical activity in wide regions of atrium of cod and carp. We define this phenomenon as cholinergic inexcitability. In other regions excitation persisted even during action of 500 microM acetylcholine. In atria of lizard and grass-snake acetylcholine caused shortening of action potential without changes in it's amplitude. Local cholinergic inexcitability, shown in the atrial myocardium of fishes, is quite similar to the phenomenon, that was described earlier in the atria of frogs. It presents the heart of fish as an interesting model for study of mechanisms of cholinergic atrial arrhythmias initiation.

Correlative anatomy for the electrophysiologist: ablation for atrial fibrillation. Part II: regional anatomy of the atria and relevance to damage of adjacent structures during AF ablation.

PubMed

Macedo, Paula G; Kapa, Suraj; Mears, Jennifer A; Fratianni, Amy; Asirvatham, Samuel J

2010-07-01

Ablation procedures for atrial fibrillation have become an established and increasingly used option for managing patients with symptomatic arrhythmia. The anatomic structures relevant to the pathogenesis of atrial fibrillation and ablation procedures are varied and include the pulmonary veins, other thoracic veins, the left atrial myocardium, and autonomic ganglia. Exact regional anatomic knowledge of these structures is essential to allow correlation with fluoroscopy and electrograms and, importantly, to avoid complications from damage of adjacent structures within the chest. We present this information as a series of 2 articles. In a prior issue, we have discussed the thoracic vein anatomy relevant to paroxysmal atrial fibrillation. In the present article, we focus on the atria themselves, the autonomic ganglia, and anatomic issues relevant for minimizing complications during atrial fibrillation ablation.

Sweet Chestnut (Castanea sativa Mill.) Bark Extract: Cardiovascular Activity and Myocyte Protection against Oxidative Damage

PubMed Central

Chiarini, Alberto; Micucci, Matteo; Ioan, Pierfranco; Fimognari, Carmela; Gallina Toschi, Tullia; Comandini, Patrizia; Hrelia, Silvana

2013-01-01

This work was aimed at evaluating the cardioprotective effects of Castanea sativa Mill. (CSM) bark extract characterized in its phenolic composition by HPLC-DAD-MS analysis. The study was performed using primary cultures of neonatal rat cardiomyocytes to investigate the antioxidant and cytoprotective effects of CSM bark extract and isolated guinea pig left and right atria, left papillary muscle, and aorta to evaluate its direct effect on cholinergic and adrenergic response. In cultured cardiomyocytes the CSM bark extract reduced intracellular reactive oxygen species formation and improved cell viability following oxidative stress in dose-dependent manner. Moreover, the extract decreased the contraction induced by noradrenaline (1 μM) in guinea pig aortic strips and induced transient negative chronotropic and positive inotropic effects without involvement of cholinergic or adrenergic receptors in the guinea pig atria. Our results indicate that CSM bark extract exhibits antioxidant activity and might induce cardioprotective effect. PMID:23533692

Muscarinic cholinergic and alpha/sub 1/ adrenergic receptors in murine atria: phosphatidylinositol breakdown and receptor interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scherer, R.W.

Upon stimulation of muscarinic cholinergic receptors, there is a decrease in the force of contraction rate of firing in heart, while stimulation of ..cap alpha.. adrenergic receptors causes an increase in the force of contraction with no change in the heart rate. Yet both receptors stimulate the breakdown of phosphatidylinositol (PI). Therefore, the breakdown of PI was examined to determine how the process differed between the two receptor systems. Murine atria, prelabelled with (/sup 3/H)inositol, were stimulated with the muscarinic cholinergic agonists, carbamylcholine (CARB), and oxotremorine (OXO); and with the ..cap alpha.. adrenergic agonists, norepinephrine (NE) and phenylephrine (PE); eithermore » singly or in combination. Breakdown of PI was assessed by measurement of individual inositol phosphates by anion exchange chromatography. Binding of CARB to atrial muscarinic receptors was measured by competition with (/sup 3/H)quinuclidinyl benzilate.« less

Human agency beliefs influence behaviour during virtual social interactions.

PubMed

Caruana, Nathan; Spirou, Dean; Brock, Jon

2017-01-01

In recent years, with the emergence of relatively inexpensive and accessible virtual reality technologies, it is now possible to deliver compelling and realistic simulations of human-to-human interaction. Neuroimaging studies have shown that, when participants believe they are interacting via a virtual interface with another human agent, they show different patterns of brain activity compared to when they know that their virtual partner is computer-controlled. The suggestion is that users adopt an "intentional stance" by attributing mental states to their virtual partner. However, it remains unclear how beliefs in the agency of a virtual partner influence participants' behaviour and subjective experience of the interaction. We investigated this issue in the context of a cooperative "joint attention" game in which participants interacted via an eye tracker with a virtual onscreen partner, directing each other's eye gaze to different screen locations. Half of the participants were correctly informed that their partner was controlled by a computer algorithm ("Computer" condition). The other half were misled into believing that the virtual character was controlled by a second participant in another room ("Human" condition). Those in the "Human" condition were slower to make eye contact with their partner and more likely to try and guide their partner before they had established mutual eye contact than participants in the "Computer" condition. They also responded more rapidly when their partner was guiding them, although the same effect was also found for a control condition in which they responded to an arrow cue. Results confirm the influence of human agency beliefs on behaviour in this virtual social interaction context. They further suggest that researchers and developers attempting to simulate social interactions should consider the impact of agency beliefs on user experience in other social contexts, and their effect on the achievement of the application's goals.

Web-based Three-dimensional Virtual Body Structures: W3D-VBS

PubMed Central

Temkin, Bharti; Acosta, Eric; Hatfield, Paul; Onal, Erhan; Tong, Alex

2002-01-01

Major efforts are being made to improve the teaching of human anatomy to foster cognition of visuospatial relationships. The Visible Human Project of the National Library of Medicine makes it possible to create virtual reality-based applications for teaching anatomy. Integration of traditional cadaver and illustration-based methods with Internet-based simulations brings us closer to this goal. Web-based three-dimensional Virtual Body Structures (W3D-VBS) is a next-generation immersive anatomical training system for teaching human anatomy over the Internet. It uses Visible Human data to dynamically explore, select, extract, visualize, manipulate, and stereoscopically palpate realistic virtual body structures with a haptic device. Tracking user’s progress through evaluation tools helps customize lesson plans. A self-guided “virtual tour” of the whole body allows investigation of labeled virtual dissections repetitively, at any time and place a user requires it. PMID:12223495

Web-based three-dimensional Virtual Body Structures: W3D-VBS.

PubMed

Temkin, Bharti; Acosta, Eric; Hatfield, Paul; Onal, Erhan; Tong, Alex

2002-01-01

Major efforts are being made to improve the teaching of human anatomy to foster cognition of visuospatial relationships. The Visible Human Project of the National Library of Medicine makes it possible to create virtual reality-based applications for teaching anatomy. Integration of traditional cadaver and illustration-based methods with Internet-based simulations brings us closer to this goal. Web-based three-dimensional Virtual Body Structures (W3D-VBS) is a next-generation immersive anatomical training system for teaching human anatomy over the Internet. It uses Visible Human data to dynamically explore, select, extract, visualize, manipulate, and stereoscopically palpate realistic virtual body structures with a haptic device. Tracking user's progress through evaluation tools helps customize lesson plans. A self-guided "virtual tour" of the whole body allows investigation of labeled virtual dissections repetitively, at any time and place a user requires it.

[The virtual reality simulation research of China Mechanical Virtual Human based on the Creator/Vega].

PubMed

Wei, Gaofeng; Tang, Gang; Fu, Zengliang; Sun, Qiuming; Tian, Feng

2010-10-01

The China Mechanical Virtual Human (CMVH) is a human musculoskeletal biomechanical simulation platform based on China Visible Human slice images; it has great realistic application significance. In this paper is introduced the construction method of CMVH 3D models. Then a simulation system solution based on Creator/Vega is put forward for the complex and gigantic data characteristics of the 3D models. At last, combined with MFC technology, the CMVH simulation system is developed and a running simulation scene is given. This paper provides a new way for the virtual reality application of CMVH.

A Virtual Campus Based on Human Factor Engineering

ERIC Educational Resources Information Center

Yang, Yuting; Kang, Houliang

2014-01-01

Three Dimensional or 3D virtual reality has become increasingly popular in many areas, especially in building a digital campus. This paper introduces a virtual campus, which is based on a 3D model of The Tourism and Culture College of Yunnan University (TCYU). Production of the virtual campus was aided by Human Factor and Ergonomics (HF&E), an…

Virtual agents in a simulated virtual training environment

NASA Technical Reports Server (NTRS)

Achorn, Brett; Badler, Norman L.

1993-01-01

A drawback to live-action training simulations is the need to gather a large group of participants in order to train a few individuals. One solution to this difficulty is the use of computer-controlled agents in a virtual training environment. This allows a human participant to be replaced by a virtual, or simulated, agent when only limited responses are needed. Each agent possesses a specified set of behaviors and is capable of limited autonomous action in response to its environment or the direction of a human trainee. The paper describes these agents in the context of a simulated hostage rescue training session, involving two human rescuers assisted by three virtual (computer-controlled) agents and opposed by three other virtual agents.

Atrial Fibrosis Hampers Non-invasive Localization of Atrial Ectopic Foci From Multi-Electrode Signals: A 3D Simulation Study

PubMed Central

Godoy, Eduardo Jorge; Lozano, Miguel; García-Fernández, Ignacio; Ferrer-Albero, Ana; MacLeod, Rob; Saiz, Javier; Sebastian, Rafael

2018-01-01

Introduction: Focal atrial tachycardia is commonly treated by radio frequency ablation with an acceptable long-term success. Although the location of ectopic foci tends to appear in specific hot-spots, they can be located virtually in any atrial region. Multi-electrode surface ECG systems allow acquiring dense body surface potential maps (BSPM) for non-invasive therapy planning of cardiac arrhythmia. However, the activation of the atria could be affected by fibrosis and therefore biomarkers based on BSPM need to take these effects into account. We aim to analyze the effect of fibrosis on a BSPM derived index, and its potential application to predict the location of ectopic foci in the atria. Methodology: We have developed a 3D atrial model that includes 5 distributions of patchy fibrosis in the left atrium at 5 different stages. Each stage corresponds to a different amount of fibrosis that ranges from 2 to 40%. The 25 resulting 3D models were used for simulation of Focal Atrial Tachycardia (FAT), triggered from 19 different locations described in clinical studies. BSPM were obtained for all simulations, and the body surface potential integral maps (BSPiM) were calculated to describe atrial activations. A machine learning (ML) pipeline using a supervised learning model and support vector machine was developed to learn the BSPM patterns of each of the 475 activation sequences and relate them to the origin of the FAT source. Results: Activation maps for stages with more than 15% of fibrosis were greatly affected, producing conduction blocks and delays in propagation. BSPiMs did not always cluster into non-overlapped groups since BSPiMs were highly altered by the conduction blocks. From stage 3 (15% fibrosis) the BSPiMs showed differences for ectopic beats placed around the area of the pulmonary veins. Classification results were mostly above 84% for all the configurations studied when a large enough number of electrodes were used to map the torso. However, the presence of fibrosis increases the area of the ectopic focus location and therefore decreases the utility for the electrophysiologist. Conclusions: The results indicate that the proposed ML pipeline is a promising methodology for non-invasive ectopic foci localization from BSPM signal even when fibrosis is present. PMID:29867517

Central endogenous histamine modulates sympathetic outflow through H3 receptors in the conscious rabbit

PubMed Central

Charles, Julian; Angus, James A; Wright, Christine E

2003-01-01

This study examined the role of histamine H3 receptors in vagal and sympathetic autonomic reflexes in the conscious rabbit, and in rabbit and guinea-pig isolated right atria. The baroreceptor-heart rate reflex (baroreflex), Bezold-Jarisch-like and nasopharyngeal reflexes were assessed after these treatments (i.v.; with H1 and H2 receptor block): (i) vehicle (saline; n=11); (ii) H3 receptor agonist, (R)-α-methylhistamine (R-α-MH) 100 μg kg−1+100 μg kg−1 h−1 (n=9); (iii) H3 receptor antagonist, thioperamide 1 mg kg−1+1 mg kg−1 h−1 (n=11); (iv) R-α-MH and thioperamide (n=6); and (v) H2 and H3 antagonist, burimamide 6.3 mg kg−1+6.3 mg kg−1 h−1 (n=4). R-α-MH caused a thioperamide-sensitive fall in mean arterial pressure (MAP) of 8±1 mmHg and tachycardia of 18±2 bpm (P<0.0005). Burimamide was without effect, however thioperamide elicited an increase in MAP of 4±1 mmHg (P<0.01), but no change in heart rate (HR). R-α-MH caused a 44% decrease in the average gain of the baroreflex (P=0.0001); this effect was antagonised by thioperamide. Thioperamide caused a parallel rightward shift in the barocurve with an increase in MAP of 5 mmHg (P<0.05). Burimamide had no effect on the baroreflex. The vagally mediated bradycardia elicited by the Bezold-Jarisch and nasopharyngeal reflexes was unaffected by H3 receptor ligand administration. R-α-MH (⩽10 μM) caused a thioperamide-sensitive depression of both sympathetic and vagal responses in guinea-pig atria, but had no effect in rabbit atria. As H3 receptor activation caused a significant decrease in baroreflex gain without affecting HR range, the former is unlikely to be simply due to peripheral sympatholysis (supported by the lack of effect in isolated atria). Central H3 receptors may have a tonic role in the baroreflex as thioperamide caused a rightward resetting of the barocurve. In contrast, the peripherally acting H3 antagonist burimamide was without effect. These findings suggest a role for central histamine H3 receptors in cardiovascular homeostasis in the rabbit. PMID:12839877

DHM simulation in virtual environments: a case-study on control room design.

PubMed

Zamberlan, M; Santos, V; Streit, P; Oliveira, J; Cury, R; Negri, T; Pastura, F; Guimarães, C; Cid, G

2012-01-01

This paper will present the workflow developed for the application of serious games in the design of complex cooperative work settings. The project was based on ergonomic studies and development of a control room among participative design process. Our main concerns were the 3D human virtual representation acquired from 3D scanning, human interaction, workspace layout and equipment designed considering ergonomics standards. Using Unity3D platform to design the virtual environment, the virtual human model can be controlled by users on dynamic scenario in order to evaluate the new work settings and simulate work activities. The results obtained showed that this virtual technology can drastically change the design process by improving the level of interaction between final users and, managers and human factors team.

NHE isoform switching and KChIP2 upregulation in aging porcine atria.

PubMed

Kant, Ritu; Hu, Zhaoyang; Malhotra, Jaideep K; Krogh-Madsen, Trine; Christini, David J; Heerdt, Paul M; Abbott, Geoffrey W

2013-01-01

Aging increases the risk of cardiac pathologies including atrial fibrillation and can alter myocardial responsiveness to therapeutic agents. Here, seeking molecular correlates of myocardial aging processes, we performed global "whole transcript" analysis of 25,388 genes using 572,667 probes to compare the left atrial (LA) transcriptomes of young adult (9 months old) versus elderly (10 years old) female swine. NHE2 (>9-fold) and KChIP2 (3.8-fold) exhibited the highest aging-related expression increases. Real-time qPCR recapitulated these findings and indicated a 50% decrease in LA NHE1, a twofold increase in right atrial KChIP2, but no significant changes for these transcripts in either ventricle. Notably, even in young adult pigs, NHE2 transcript was detectable and enriched in the atria over the ventricles. NHE1, the recognized cardiac isoform of the sodium hydrogen exchanger, has proven a compelling but clinically disappointing therapeutic target with respect to reperfusion arrhythmias. Our data challenge the dogma that NHE1 is alone in the myocardium and suggest that NHE2 could negatively impact the pharmacological responsiveness of atrial tissue to NHE1-specific inhibitors. KChIP2 is a cytosolic β subunit essential for generation of I to. The increased KChIP2 expression we observed with aging substantially shortened in silico atrial myocyte action potential duration, a predisposing factor in atrial fibrillation. Consistent with this, 4/5 elderly swine sustained pacing-induced AF≥15 s after cessation of stimulation, compared to 0/3 young swine. Our findings uncover potential molecular bases for increased arrhythmogenicity and reduced pharmacologic efficacy in the aging atrium, in a large animal model of human cardiac physiology.

Selective regulation of beta 1- and beta 2-adrenoceptors in the human heart by chronic beta-adrenoceptor antagonist treatment.

PubMed Central

Michel, M. C.; Pingsmann, A.; Beckeringh, J. J.; Zerkowski, H. R.; Doetsch, N.; Brodde, O. E.

1988-01-01

1. In 44 patients undergoing coronary artery bypass grafting, the effect of chronic administration of the beta-adrenoceptor antagonists sotalol, propranolol, pindolol, metoprolol and atenolol on beta-adrenoceptor density in right atria (containing 70% beta 1- and 30% beta 2-adrenoceptors) and in lymphocytes (having only beta 2-adrenoceptors) was studied. 2. beta-Adrenoceptor density in right atrial membranes and in intact lymphocytes was assessed by (-)-[125I]-iodocyanopindolol (ICYP) binding; the relative amount of right atrial beta 1- and beta 2-adrenoceptors was determined by inhibition of ICYP binding by the selective beta 2-adrenoceptor antagonist ICI 118,551 and analysis of the resulting competition curves by the iterative curve fitting programme LIGAND. 3. With the exception of pindolol, all beta-adrenoceptor antagonists increased right atrial beta-adrenoceptor density compared to that observed in atria from patients not treated with beta-adrenoceptor antagonists. 4. All beta-adrenoceptor antagonists increased right atrial beta 1-adrenoceptor density; on the other hand, only sotalol and propranolol also increased right atrial beta 2-adrenoceptor density, whereas metoprolol and atenolol did not affect it and pindolol decreased it. 5. Similarly, in corresponding lymphocytes, only sotalol or propranolol increased beta 2-adrenoceptor density, while metoprolol and atenolol did not affect it and pindolol decreased it. 6. It is concluded that beta-adrenoceptor antagonists subtype-selectively regulate cardiac and lymphocyte beta-adrenoceptor subtypes. The selective increase in cardiac beta 1-adrenoceptor density evoked by metoprolol and atenolol may be one of the reasons for the beneficial effects observed in patients with end-stage congestive cardiomyopathy following intermittent treatment with low doses of selective beta 1-adrenoceptor antagonists. PMID:2902891

Human responses to augmented virtual scaffolding models.

PubMed

Hsiao, Hongwei; Simeonov, Peter; Dotson, Brian; Ammons, Douglas; Kau, Tsui-Ying; Chiou, Sharon

2005-08-15

This study investigated the effect of adding real planks, in virtual scaffolding models of elevation, on human performance in a surround-screen virtual reality (SSVR) system. Twenty-four construction workers and 24 inexperienced controls performed walking tasks on real and virtual planks at three virtual heights (0, 6 m, 12 m) and two scaffolding-platform-width conditions (30, 60 cm). Gait patterns, walking instability measurements and cardiovascular reactivity were assessed. The results showed differences in human responses to real vs. virtual planks in walking patterns, instability score and heart-rate inter-beat intervals; it appeared that adding real planks in the SSVR virtual scaffolding model enhanced the quality of SSVR as a human - environment interface research tool. In addition, there were significant differences in performance between construction workers and the control group. The inexperienced participants were more unstable as compared to construction workers. Both groups increased their stride length with repetitions of the task, indicating a possibly confidence- or habit-related learning effect. The practical implications of this study are in the adoption of augmented virtual models of elevated construction environments for injury prevention research, and the development of programme for balance-control training to reduce the risk of falls at elevation before workers enter a construction job.

Atrial Model Development and Prototype Simulations: CRADA Final Report on Tasks 3 and 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Hara, T.; Zhang, X.; Villongco, C.

2016-10-28

The goal of this CRADA was to develop essential tools needed to simulate human atrial electrophysiology in 3-dimensions using an anatomical image-based anatomy and physiologically detailed human cellular model. The atria were modeled as anisotropic, representing the preferentially longitudinal electrical coupling between myocytes. Across the entire anatomy, cellular electrophysiology was heterogeneous, with left and right atrial myocytes defined differently. Left and right cell types for the “control” case of sinus rhythm (SR) was compared with remodeled electrophysiology and calcium cycling characteristics of chronic atrial fibrillation (cAF). The effects of Isoproterenol (ISO), a beta-adrenergic agonist that represents the functional consequences ofmore » PKA phosphorylation of various ion channels and transporters, was also simulated in SR and cAF to represent atrial activity under physical or emotional stress. Results and findings from Tasks 3 & 4 are described. Tasks 3 and 4 are, respectively: Input parameters prepared for a Cardioid simulation; Report including recommendations for additional scenario development and post-processing analytic strategy.« less

Prosthetic Leg Control in the Nullspace of Human Interaction.

PubMed

Gregg, Robert D; Martin, Anne E

2016-07-01

Recent work has extended the control method of virtual constraints, originally developed for autonomous walking robots, to powered prosthetic legs for lower-limb amputees. Virtual constraints define desired joint patterns as functions of a mechanical phasing variable, which are typically enforced by torque control laws that linearize the output dynamics associated with the virtual constraints. However, the output dynamics of a powered prosthetic leg generally depend on the human interaction forces, which must be measured and canceled by the feedback linearizing control law. This feedback requires expensive multi-axis load cells, and actively canceling the interaction forces may minimize the human's influence over the prosthesis. To address these limitations, this paper proposes a method for projecting virtual constraints into the nullspace of the human interaction terms in the output dynamics. The projected virtual constraints naturally render the output dynamics invariant with respect to the human interaction forces, which instead enter into the internal dynamics of the partially linearized prosthetic system. This method is illustrated with simulations of a transfemoral amputee model walking with a powered knee-ankle prosthesis that is controlled via virtual constraints with and without the proposed projection.

Future Cyborgs: Human-Machine Interface for Virtual Reality Applications

DTIC Science & Technology

2007-04-01

FUTURE CYBORGS : HUMAN-MACHINE INTERFACE FOR VIRTUAL REALITY APPLICATIONS Robert R. Powell, Major, USAF April 2007 Blue Horizons...SUBTITLE Future Cyborgs : Human-Machine Interface for Virtual Reality Applications 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER...Nicholas Negroponte, Being Digital (New York: Alfred A Knopf, Inc, 1995), 123. 23 Ibid. 24 Andy Clark, Natural-Born Cyborgs (New York: Oxford

Water Quality Criteria for White Phosphorus

DTIC Science & Technology

1987-08-01

by Caesarean section. The results are shown in Table 17. Major variations were unilateral anophthalmia , narrow atria, short tongue, bzachygnathia, and...eyes 1 Anophthalmia , unilateralb 1 Short tongueb 1 Brachygnathia b1 Skeletal Fourteenth rib extra 16 39 25 (rudimertary) Cleft sternebrae 2 0 2

Increased Susceptibility to Atrial Fibrillation Secondary to Atrial Fibrosis in Transgenic Goats Expressing Transforming Growth Factor-β1

PubMed Central

Davies, Christopher J.; Regouski, Misha; Hall, Justin; Olsen, Aaron L.; Meng, Qinggang; Rutigliano, Heloisa M.; Dosdall, Derek J.; Angel, Nathan A.; Sachse, Frank B.; Seidel, Thomas; Thomas, Aaron J.; Stott, Rusty; Panter, Kip E.; Lee, Pamela M.; Van Wettere, Arnaud J.; Stevens, John R.; Wang, Zhongde; MacLeod, Rob S.; Marrouche, Nassir F.; White, Kenneth L.

2016-01-01

Introduction Large animal models of progressive atrial fibrosis would provide an attractive platform to study relationship between structural and electrical remodeling in atrial fibrillation (AF). Here we established a new transgenic goat model of AF with cardiac specific overexpression of TGF-β1 and investigated the changes in the cardiac structure and function leading to AF. Methods and Results Transgenic goats with cardiac specific overexpression of constitutively active TGF-β1 were generated by somatic cell nuclear transfer. We examined myocardial tissue, ECGs, echocardiographic data, and AF susceptibility in transgenic and wild-type control goats. Transgenic goats exhibited significant increase in fibrosis and myocyte diameters in the atria compared to controls, but not in the ventricles. P-wave duration was significantly greater in transgenic animals starting at 12-month of age, but no significant chamber enlargement was detected, suggesting conduction slowing in the atria. Furthermore, this transgenic goat model exhibited a significant increase in AF vulnerability. Six of 8 transgenic goats (75%) were susceptible to AF induction and exhibited sustained AF (>2 minutes), whereas, none of 6 controls displayed sustained AF (P<0.01). Length of induced AF episodes was also significantly greater in the transgenic group compared to controls (687±212.02 vs. 2.50±0.88 seconds, P<0.0001), but no persistent or permanent AF was observed. Conclusion A novel transgenic goat model with a substrate for AF was generated. In this model, cardiac overexpression of TGF-β1 led to an increase in fibrosis and myocyte size in the atria, and to progressive P-wave prolongation. We suggest that these factors underlie increased AF susceptibility. PMID:27447370

Negative inotropic and chronotropic effects on the guinea pig atrium of extracts obtained from Averrhoa carambola L. leaves.

PubMed

Vasconcelos, C M L; Araújo, M S; Silva, B A; Conde-Garcia, E A

2005-07-01

It has been reported that star fruit can lead to a fatal outcome in uremic patients. The intoxication syndrome consists of hiccups, mental confusion, dizziness, and vomiting. On the other hand, folk medicine uses teas and infusions of carambola leaves to treat headache, vomiting, cough, insomnia, and diabetes. This motivated us to determine if Averrhoa carambola can act on the contractility and automaticity of the guinea pig heart. We measured the atrial isometric force in stimulated left atria and determined the chronotropic changes in spontaneously beating right atria. The carambola leaf extracts (1.5 mg/ml) abolished the contractile force in a concentration-dependent manner. Among the crude, methanolic, ethanolic, aqueous, and acetic extracts, the aqueous one was the most potent (EC50 = 520 +/- 94 microg/ml; flavonoids and tannins are the main constituents; Na+ and K+ contents in 1.0 mg/ml of aqueous extract were 0.12 +/- 0.016 and 1.19 +/- 0.15 mM, respectively). The aqueous extract abolished the positive Bowditch staircase phenomenon and reduced the inotropic response to CaCl2 (0.17-8.22 mM), events that are dependent on the cellular Ca2+ inward current. The adrenergic, muscarinic or opioid membrane receptors do not seem to participate in the mechanism of action of the cardioactive substance(s). In spontaneously beating atria, the aqueous extract promoted a negative chronotropic effect that was antagonized by 0.1 microM isoproterenol bitartrate. With this agonist, the EC50 of the aqueous extract increased from 133 +/- 58 to 650 +/- 100 microg/ml. These data regarding the effect of A. carambola on guinea pig atrial contractility and automaticity indicate an L-type Ca2+ channel blockade.

Spatial distribution of conduction disorders during sinus rhythm.

PubMed

Lanters, Eva A H; Yaksh, Ameeta; Teuwen, Christophe P; van der Does, Lisette J M E; Kik, Charles; Knops, Paul; van Marion, Denise M S; Brundel, Bianca J J M; Bogers, Ad J J C; Allessie, Maurits A; de Groot, Natasja M S

2017-12-15

Length of lines of conduction block (CB) during sinus rhythm (SR) at Bachmann's bundle (BB) is associated with atrial fibrillation (AF). However, it is unknown whether extensiveness of CB at BB represents CB elsewhere in the atria. We aim to investigate during SR 1) the spatial distribution and extensiveness of CB 2) whether there is a predilection site for CB and 3) the association between CB and incidence of post-operative AF. During SR, epicardial mapping of the right atrium (RA), BB and left atrium was performed in 209 patients with coronary artery disease. The amount of conduction delay (CD, Δlocal activation time ≥7ms) and CB (Δ≥12ms) was quantified as % of the mapping area. Atrial regions were compared to identify potential predilection sites for CD/CB. Correlations between CD/CB and clinical characteristics were tested. Areas with CD or CB were present in all patients, overall prevalence was respectively 1.4(0.2-4.0) % and 1.3(0.1-4.3) %. Extensiveness and spatial distribution of CD/CB varied considerably, however occurred mainly at the superior intercaval RA. Of all clinicalcharacteristics, CD/CB only correlated weakly with age and diabetes (P<0.05). A 1% increase in CD or CB caused a 1.1-1.5ms prolongation of the activation time (P<0.001). There was no correlation between CD/CB and post-operative AF. CD/CB during SR in CABG patients with electrically non-remodeled atria show considerable intra-atrial, but also inter-individual variation. Despite these differences, a predilection site is present at the superior intercaval RA. Extensiveness of CB at the superior intercaval RA or BB does not reflect CB elsewhere in the atria and is not associated with post-operative AF. Copyright © 2017 Elsevier B.V. All rights reserved.

Atrial Function after the Atrial Switch Operation for Transposition of the Great Arteries: Comparison with Arterial Switch and Normals by Cardiovascular Magnetic Resonance.

PubMed

Franzoso, Francesca D; Wohlmuth, Christoph; Greutmann, Matthias; Kellenberger, Christian J; Oxenius, Angela; Voser, Eva M; Valsangiacomo Buechel, Emanuela R

2016-09-01

The atria serve as reservoir, conduit, and active pump for ventricular filling. The performance of the atrial baffles after atrial switch repair for transposition of the great arteries may be abnormal and impact the function of the systemic right ventricle. We sought to assess atrial function in patients after atrial repair in comparison to patients after arterial switch repair (ASO) and to controls. Using magnetic resonance imaging, atrial volumes and functional parameters were measured in 17 patients after atrial switch repair, 9 patients after ASO and 10 healthy subjects. After the atrial switch operation, the maximum volume of the pulmonary venous atrium was significantly enlarged, but not of the systemic venous atrium. In both patients groups, independently from the surgical technique used, the minimum atrial volumes were elevated, which resulted in a decreased total empting fraction compared with controls (P < .01). The passive empting volume was diminished for right atrium, but elevated for left atrium after atrial switch and normal for left atrium after ASO; however, the passive empting fraction was diminished for both right atrium and left atrium after both operations (P < .01). The active empting volume was the most affected parameter in both atria and both groups and active empting fractions were highly significantly reduced compared with controls. Atrial function is abnormal in all patients, after atrial switch and ASO repair. The cyclic volume changes, that is, atrial filling and empting, are reduced when compared with normal subjects. Thus, the atria have lost part of their capacity to convert continuous venous flow into a pulsatile ventricular filling. The function of the pulmonary venous atrium, acting as preload for the systemic right ventricle, after atrial switch is altered the most. © 2015 Wiley Periodicals, Inc.

Antithrombotic therapy for atrial fibrillation and coronary artery disease in older patients

PubMed Central

Hess, Connie N.; Broderick, Samuel; Piccini, Jonathan P.; Alexander, Karen P.; Newby, L. Kristin; Shaw, Linda K.; Mahaffey, Kenneth W.; Alexander, John H.; Peterson, Eric D.; Granger, Christopher B.; Lopes, Renato D.

2013-01-01

Background Older patients with atrial fibrillation (AF) and coronary artery disease (CAD) face high risk of stroke and bleeding with antithrombotic therapy. Balancing safe and effective use of aspirin, clopidogrel, and warfarin in this population is important. Methods From the Duke Databank for Cardiovascular Disease, we identified patients with AF ≥65 years old with angiographically confirmed CAD from 2000 to 2010. Antithrombotic use was described across age and Congestive heart failure, Hypertension, Age >75 years, Diabetes, prior Stroke/transient ischemic attack (CHADS2) stroke risk and Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) bleeding scores. Death and the composite of death, myocardial infarction, and stroke by antithrombotic strategy were reported. Results Of 2,122 patients ≥65 years old with AF and CAD, 477 (22.5%) were ≥80 years old; 1,133 (53.4%) had acute coronary syndromes. Overall rates of aspirin, clopidogrel, and warfarin use were 83.4%, 34.6%, and 38.9%, respectively. Compared with patients 65 to 79 years old, more patients ≥80 years old were at high stroke risk (CHADS2 ≥2, 84.7% vs 57.8%) and high bleeding risk (ATRIA 5-10, 55.8% vs 23.3%). Warfarin use in both age groups increased with higher CHADS2 scores and decreased with higher ATRIA scores. Of patients ≥80 years old with CHADS2 ≥2, 150 (38.2%) received warfarin. Antithrombotic strategy was not associated with improved 1-year adjusted outcomes. Conclusions Among older patients with AF and CAD, overall warfarin use was low. Patients ≥80 years old at highest stroke risk received warfarin in similar proportions to the overall cohort. Further investigation into optimizing antithrombotic strategies in this population is warranted. PMID:23067921

Antithrombotic therapy for atrial fibrillation and coronary artery disease in older patients.

PubMed

Hess, Connie N; Broderick, Samuel; Piccini, Jonathan P; Alexander, Karen P; Newby, L Kristin; Shaw, Linda K; Mahaffey, Kenneth W; Alexander, John H; Peterson, Eric D; Granger, Christopher B; Lopes, Renato D

2012-10-01

Older patients with atrial fibrillation (AF) and coronary artery disease (CAD) face high risk of stroke and bleeding with antithrombotic therapy. Balancing safe and effective use of aspirin, clopidogrel, and warfarin in this population is important. From the Duke Databank for Cardiovascular Disease, we identified patients with AF ≥65 years old with angiographically confirmed CAD from 2000 to 2010. Antithrombotic use was described across age and Congestive heart failure, Hypertension, Age >75 years, Diabetes, prior Stroke/transient ischemic attack (CHADS(2)) stroke risk and Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) bleeding scores. Death and the composite of death, myocardial infarction, and stroke by antithrombotic strategy were reported. Of 2,122 patients ≥65 years old with AF and CAD, 477 (22.5%) were ≥80 years old; 1,133 (53.4%) had acute coronary syndromes. Overall rates of aspirin, clopidogrel, and warfarin use were 83.4%, 34.6%, and 38.9%, respectively. Compared with patients 65 to 79 years old, more patients ≥80 years old were at high stroke risk (CHADS(2) ≥2, 84.7% vs 57.8%) and high bleeding risk (ATRIA 5-10, 55.8% vs 23.3%). Warfarin use in both age groups increased with higher CHADS(2) scores and decreased with higher ATRIA scores. Of patients ≥80 years old with CHADS(2) ≥2, 150 (38.2%) received warfarin. Antithrombotic strategy was not associated with improved 1-year adjusted outcomes. Among older patients with AF and CAD, overall warfarin use was low. Patients ≥80 years old at highest stroke risk received warfarin in similar proportions to the overall cohort. Further investigation into optimizing antithrombotic strategies in this population is warranted. Copyright © 2012 Mosby, Inc. All rights reserved.

Features of intrinsic ganglionated plexi in both atria after extensive pulmonary isolation and their clinical significance after catheter ablation in patients with atrial fibrillation.

PubMed

Kurotobi, Toshiya; Shimada, Yoshihisa; Kino, Naoto; Ito, Kazato; Tonomura, Daisuke; Yano, Kentaro; Tanaka, Chiharu; Yoshida, Masataka; Tsuchida, Takao; Fukumoto, Hitoshi

2015-03-01

The features of intrinsic ganglionated plexi (GP) in both atria after extensive pulmonary vein isolation (PVI) and their clinical implications have not been clarified in patients with atrial fibrillation (AF). The purpose of this study was to assess the features of GP response after extensive PVI and to evaluate the relationship between GP responses and subsequent AF episodes. The study population consisted of 216 consecutive AF patients (104 persistent AF) who underwent an initial ablation. We searched for the GP sites in both atria after an extensive PVI. GP responses were determined in 186 of 216 patients (85.6%). In the left atrium, GP responses were observed around the right inferior GP in 116 of 216 patients (53.7%) and around the left inferior GP in 57 of 216 (26.4%). In the right atrium, GP responses were observed around the posteroseptal area: inside the CS in 64 of 216 patients (29.6%), at the CS ostium in 150 of 216 (69.4%), and in the lower right atrium in 45 of 216 (20.8%). The presence of a positive GP response was an independent risk factor for AF recurrence (hazard ratio 4.04, confidence interval 1.48-11.0) in patients with paroxysmal, but not persistent, AF. The incidence of recurrent atrial tachyarrhythmias in patients with paroxysmal AF with a positive GP response was 51% vs 8% in those without a GP response (P = .002). The presence of GP responses after extensive PVI was significantly associated with increased AF recurrence after ablation in patients with paroxysmal AF. Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Increased Susceptibility to Atrial Fibrillation Secondary to Atrial Fibrosis in Transgenic Goats Expressing Transforming Growth Factor-β1.

PubMed

Polejaeva, Irina A; Ranjan, Ravi; Davies, Christopher J; Regouski, Misha; Hall, Justin; Olsen, Aaron L; Meng, Qinggang; Rutigliano, Heloisa M; Dosdall, Derek J; Angel, Nathan A; Sachse, Frank B; Seidel, Thomas; Thomas, Aaron J; Stott, Rusty; Panter, Kip E; Lee, Pamela M; Van Wettere, Arnaud J; Stevens, John R; Wang, Zhongde; MacLeod, Rob S; Marrouche, Nassir F; White, Kenneth L

2016-10-01

Large animal models of progressive atrial fibrosis would provide an attractive platform to study relationship between structural and electrical remodeling in atrial fibrillation (AF). Here we established a new transgenic goat model of AF with cardiac specific overexpression of TGF-β1 and investigated the changes in the cardiac structure and function leading to AF. Transgenic goats with cardiac specific overexpression of constitutively active TGF-β1 were generated by somatic cell nuclear transfer. We examined myocardial tissue, ECGs, echocardiographic data, and AF susceptibility in transgenic and wild-type control goats. Transgenic goats exhibited significant increase in fibrosis and myocyte diameters in the atria compared to controls, but not in the ventricles. P-wave duration was significantly greater in transgenic animals starting at 12 months of age, but no significant chamber enlargement was detected, suggesting conduction slowing in the atria. Furthermore, this transgenic goat model exhibited a significant increase in AF vulnerability. Six of 8 transgenic goats (75%) were susceptible to AF induction and exhibited sustained AF (>2 minutes), whereas none of 6 controls displayed sustained AF (P < 0.01). Length of induced AF episodes was also significantly greater in the transgenic group compared to controls (687 ± 212.02 seconds vs. 2.50 ± 0.88 seconds, P < 0.0001), but no persistent or permanent AF was observed. A novel transgenic goat model with a substrate for AF was generated. In this model, cardiac overexpression of TGF-β1 led to an increase in fibrosis and myocyte size in the atria, and to progressive P-wave prolongation. We suggest that these factors underlie increased AF susceptibility. © 2016 Wiley Periodicals, Inc.

Verapamil eliminates the hierarchical nature of activation frequencies from the pulmonary veins to the atria during paroxysmal atrial fibrillation.

PubMed

Kushiyama, Yasunori; Osaka, Toshiyuki; Yokoyama, Eriko; Hasebe, Hideyuki; Kuroda, Yusuke; Kamiya, Kaichiro; Kodama, Itsuo

2010-05-01

There is evidence that verapamil promotes the persistence of paroxysmal atrial fibrillation (AF). Little is known about the underlying mechanisms. The purpose of this study was to determine the effect of verapamil on dominant frequencies (DFs) in the pulmonary veins (PVs) and atria during paroxysmal AF with reference to its potential arrhythmogenicity. Forty-three patients with paroxysmal AF were studied. Bipolar electrograms were recorded simultaneously during AF from the right atrial free wall (RAFW), coronary sinus (CS) and three PVs, or two PVs and the left atrial appendage (LAA). The DFs were obtained by fast Fourier transform analysis before and after infusion of verapamil (0.1 mg/kg, intravenously). At baseline, the maximum DF among the PVs (6.9 +/- 0.9 Hz) was significantly higher than the DF in the RAFW (6.2 +/- 0.7 Hz), CS (5.7 +/- 0.5 Hz), or LAA (5.9 +/- 0.7 Hz) (P<.01); there was a substantial PV-to-atrial DF gradient (RAFW 0.7 +/- 0.9, CS 1.1 +/- 0.7, LAA 0.7 +/- 0.9 Hz). Verapamil increased the atrial DF to 6.9 +/- 0.8, 6.6 +/- 0.7, and 7.2 +/- 1.0 Hz in the RAFW, CS, and LAA, respectively (P<.0001) but did not affect the maximum PV DF (7.1 +/- 0.7 Hz). The PV-to-atrial DF gradient was eliminated after verapamil (RAFW 0.2 +/- 0.8, CS 0.5 +/- 0.6, LAA -0.4 +/- 0.8 Hz; P<.01 vs. baseline). Verapamil increases the activation frequency in the atria but not in the PVs, eliminating the PV-to-atrial DF gradient during paroxysmal AF. Copyright 2010 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Morphologies of the atria and pulmonary veins in relation to lone atrial fibrillation progression: a dual-source computed tomography scan study.

PubMed

Liu, Xing-Peng; Xu, Xia; Tian, Ying; Tang, Ri-Bo; Yu, Rong-Hui; Long, De-Yong; Sang, Cai-Hua; Jiang, Chen-Xi; Ning, Man; Dong, Jian-Zeng; Ma, Chang-Sheng

2012-11-01

Atrial Remodeling and Lone Atrial Fibrillation. We sought to investigate the role of anatomic remodeling of the atria and pulmonary veins (PVs) in the progression of lone atrial fibrillation (AF) using dual-source computed tomography (DSCT). From 1,308 consecutive patients referred for an index ablation procedure for AF, we prospectively enrolled 29 consecutive patients with recently developed (<3 months) lone persistent AF (PsAF) and 23 consecutive patients with short-lasting (6-12 months) lone PsAF, all of whom had a history of paroxysmal AF (PAF). The control group consisted of 33 patients with lone PAF. On DSCT, the recently developed PsAF group showed more extensive atrial anatomic remodeling than the PAF group as shown by ∼40% higher spot biatrial volume, even though the mean duration of continuous AF was only 6 weeks. In contrast, the DSCT variables in the recently developed PsAF group and the short-lasting PsAF group were comparable, despite the fact that the mean duration of continuous AF in the latter group was 8 months. Series of cross-sectional areas of the ostial 1.5 cm of PV trunks were comparable in the PAF and PsAF groups in all but 3 ostial planes. A higher spot left atrial volume was the only independent factor associated with the progression of lone PAF to PsAF (OR: 1.06, 95% CI: 1.03-1.09, P<0.0001) on logistic regression. Prominent anatomic remodeling of the atria, rather than the PVs, underlies the mechanism of recent progression of lone paroxysmal AF to the persistent variety. © 2012 Wiley Periodicals, Inc.

Loss of atrial contractility is primary cause of atrial dilatation during first days of atrial fibrillation.

PubMed

Schotten, Ulrich; de Haan, Sunniva; Neuberger, Hans-Ruprecht; Eijsbouts, Sabine; Blaauw, Yuri; Tieleman, Robert; Allessie, Maurits

2004-11-01

Atrial fibrillation (AF) induces a progressive dilatation of the atria which in turn might promote the arrhythmia. The mechanism of atrial dilatation during AF is not known. To test the hypothesis that loss of atrial contractile function is a primary cause of atrial dilatation during the first days of AF, eight goats were chronically instrumented with epicardial electrodes, a pressure transducer in the right atrium, and piezoelectric crystals to measure right atrial diameter. AF was induced with the use of repetitive burst pacing. Atrial contractility was assessed during sinus rhythm, atrial pacing (160-, 300-, and 400-ms cycle length), and electrically induced AF. The compliance of the fibrillating right atrium was measured during unloading the atria with diuretics and loading with 1 liter of saline. All measurements were repeated after 6, 12, and 24 h of AF and then once a day during the first 5 days of AF. Recovery of the observed changes after spontaneous cardioversion was also studied. After 5 days of AF, atrial contractility during sinus rhythm or slow atrial pacing was greatly reduced. During rapid pacing (160 ms) or AF, the amplitude of the atrial pressure waves had declined to 20% of control. The compliance of the fibrillating atria increased twofold, whereas the right atrial pressure was unchanged. As a result, the mean right atrial diameter increased by approximately 12%. All changes were reversible within 3 days of sinus rhythm. We conclude that atrial dilatation during the first days of AF is due to an increase in atrial compliance caused by loss of atrial contractility during AF. Atrial compliance and size are restored when atrial contractility recovers after cardioversion of AF.

Manually locating physical and virtual reality objects.

PubMed

Chen, Karen B; Kimmel, Ryan A; Bartholomew, Aaron; Ponto, Kevin; Gleicher, Michael L; Radwin, Robert G

2014-09-01

In this study, we compared how users locate physical and equivalent three-dimensional images of virtual objects in a cave automatic virtual environment (CAVE) using the hand to examine how human performance (accuracy, time, and approach) is affected by object size, location, and distance. Virtual reality (VR) offers the promise to flexibly simulate arbitrary environments for studying human performance. Previously, VR researchers primarily considered differences between virtual and physical distance estimation rather than reaching for close-up objects. Fourteen participants completed manual targeting tasks that involved reaching for corners on equivalent physical and virtual boxes of three different sizes. Predicted errors were calculated from a geometric model based on user interpupillary distance, eye location, distance from the eyes to the projector screen, and object. Users were 1.64 times less accurate (p < .001) and spent 1.49 times more time (p = .01) targeting virtual versus physical box corners using the hands. Predicted virtual targeting errors were on average 1.53 times (p < .05) greater than the observed errors for farther virtual targets but not significantly different for close-up virtual targets. Target size, location, and distance, in addition to binocular disparity, affected virtual object targeting inaccuracy. Observed virtual box inaccuracy was less than predicted for farther locations, suggesting possible influence of cues other than binocular vision. Human physical interaction with objects in VR for simulation, training, and prototyping involving reaching and manually handling virtual objects in a CAVE are more accurate than predicted when locating farther objects.

A haptic interface for virtual simulation of endoscopic surgery.

PubMed

Rosenberg, L B; Stredney, D

1996-01-01

Virtual reality can be described as a convincingly realistic and naturally interactive simulation in which the user is given a first person illusion of being immersed within a computer generated environment While virtual reality systems offer great potential to reduce the cost and increase the quality of medical training, many technical challenges must be overcome before such simulation platforms offer effective alternatives to more traditional training means. A primary challenge in developing effective virtual reality systems is designing the human interface hardware which allows rich sensory information to be presented to users in natural ways. When simulating a given manual procedure, task specific human interface requirements dictate task specific human interface hardware. The following paper explores the design of human interface hardware that satisfies the task specific requirements of virtual reality simulation of Endoscopic surgical procedures. Design parameters were derived through direct cadaver studies and interviews with surgeons. Final hardware design is presented.

SimCoach: An Intelligent Virtual Human System for Proving Healthcare Information and Support

DTIC Science & Technology

2010-08-01

classrooms , offices, markets, etc.), the next important challenge will involve populating these environments with Virtual Human (VH) representations...in a virtual classroom (Parsons et al., 2007; Rizzo et al., 2006). Additionally, VHs have been used effectively for the conduct of social psychology...T Bowerly, J G Buckwalter and A A Rizzo (2007), A controlled clinical comparison of attention performance in children with ADHD in a virtual reality

Transmission failure in sympathetic nerves produced by hemicholinium

PubMed Central

Chang, V.; Rand, M. J.

1960-01-01

It has been shown by others that hemicholinium (α,α'-dimethylethanolamino-4,4'-biacetophenone) inhibits the synthesis of acetylcholine, an effect which is reversed by choline. Hemicholinium produces a failure of response to nerve stimulation in the following sympathetically innervated preparations: guinea-pig isolated vas deferens, rabbit isolated uterus, rabbit isolated colon, perfused rabbit ear, cat isolated atria and the piloerector muscles in the cat's tail. The blocking action of hemicholinium on the responses to postganglionic sympathetic stimulation resembles its blocking action against cholinergic nerve stimulation observed on rabbit isolated atria with vagus nerves, rabbit isolated vagina with pelvic nerves, and guinea-pig isolated diaphragm with phrenic nerve. The failure of transmission produced by hemicholinium in sympathetic nerves and in cholinergic nerves can be reversed by choline. It is suggested that if there were a cholinergic junction at sympathetic nerve endings the mechanism of the blocking action of hemicholinium at these endings could be explained by inhibition of acetylcholine synthesis. ImagesFIG. 13FIG. 14 PMID:13692344

Atrial remodeling and metabolic dysfunction in idiopathic isolated fibrotic atrial cardiomyopathy.

PubMed

Cui, Chang; Jiang, Xiaohong; Ju, Weizhu; Wang, Jiaxian; Wang, Daowu; Sun, Zheng; Chen, Minglong

2018-08-15

Idiopathic isolated fibrotic atrial cardiomyopathy (IIF-ACM) is a novel subtype of cardiomyopathy characterized by atrial fibrosis that does not involve the ventricular myocardium and is associated with significant atrial tachyarrhythmia. The mechanisms underlying its pathogenesis are unknown. Atrium samples were obtained from 3 patients with IIF-ACM via surgical intervention. Control samples were consisted of 3 atrium biopsies from patients with congenital heart disease and normal sinus rhythm, matched for gender, age and basic clinical characteristics. Comparative histology, immunofluorescence staining, electron microscopy and proteomics analyses were carried out to explore the unique pathogenesis of IIF-ACM. IIF-ACM atria displayed disordered myofibrils, profound fibrosis and mitochondrial damages compared to the control atria. Proteomics profiling identified metabolic pathways as the most profound changes in IIF-ACM. Our study suggested that metabolic changes in the atrial myocardium caused mitochondrial oxidative stress and potential cell damage, which further led to atrial fibrosis and myofibril disorganization, the characteristic phenotype of IIF-ACM. Copyright © 2018 Elsevier B.V. All rights reserved.

[Effects of 2-(p-dimethylaminostyryl) pyridine methycholide (DSPM-Ci) on ECG, left atrium contractivity and on papillary muscle action potentials].

PubMed

Jiang, X Y; Zhou, C M; Li, D M; Zhang, K J

1996-01-01

The effects of DSPM-Cl on ECG in rats, on the dose-effect curve in guinea pig left atria and on the fast action potential (AP), high-K+ depolarized slow action potential (SAP) in guinea pigs papillary muscle were examined electrophysiologically. DSPM-Cl (2 mg.kg-1) showed significant nagative frequency, negative conductivity effect, and prolonged the PP and PR interval. DSPM-CI (30-50 mumol.L-1) was shown to inhibit left atria contractility and shift the concentration-response curve of Iso and CaCl2 to the right with PD2' values of 4.60 and 4.13, respectively. In addition, DSPM-Cl was found to prolong the duration of action potential 90 (APD90) and effective refractory period (ERP), and decrease the maximal upstroke velocity (Vmax) in K(+)-depolarized guinea pigs papillary muscles. The results suggest that, like verpamil, DSPM-Cl might be a calcium antagonist.

Virtually Naked: Virtual Environment Reveals Sex-Dependent Nature of Skin Disclosure

PubMed Central

Lomanowska, Anna M.; Guitton, Matthieu J.

2012-01-01

The human tendency to reveal or cover naked skin reflects a competition between the individual propensity for social interactions related to sexual appeal and interpersonal touch versus climatic, environmental, physical, and cultural constraints. However, due to the ubiquitous nature of these constraints, isolating on a large scale the spontaneous human tendency to reveal naked skin has remained impossible. Using the online 3-dimensional virtual world of Second Life, we examined spontaneous human skin-covering behavior unhindered by real-world climatic, environmental, and physical variables. Analysis of hundreds of avatars revealed that virtual females disclose substantially more naked skin than virtual males. This phenomenon was not related to avatar hypersexualization as evaluated by measurement of sexually dimorphic body proportions. Furthermore, analysis of skin-covering behavior of a population of culturally homogeneous avatars indicated that the propensity of female avatars to reveal naked skin persisted despite explicit cultural norms promoting less revealing attire. These findings have implications for further understanding how sex-specific aspects of skin disclosure influence human social interactions in both virtual and real settings. PMID:23300580

Virtually naked: virtual environment reveals sex-dependent nature of skin disclosure.

PubMed

Lomanowska, Anna M; Guitton, Matthieu J

2012-01-01

The human tendency to reveal or cover naked skin reflects a competition between the individual propensity for social interactions related to sexual appeal and interpersonal touch versus climatic, environmental, physical, and cultural constraints. However, due to the ubiquitous nature of these constraints, isolating on a large scale the spontaneous human tendency to reveal naked skin has remained impossible. Using the online 3-dimensional virtual world of Second Life, we examined spontaneous human skin-covering behavior unhindered by real-world climatic, environmental, and physical variables. Analysis of hundreds of avatars revealed that virtual females disclose substantially more naked skin than virtual males. This phenomenon was not related to avatar hypersexualization as evaluated by measurement of sexually dimorphic body proportions. Furthermore, analysis of skin-covering behavior of a population of culturally homogeneous avatars indicated that the propensity of female avatars to reveal naked skin persisted despite explicit cultural norms promoting less revealing attire. These findings have implications for further understanding how sex-specific aspects of skin disclosure influence human social interactions in both virtual and real settings.

A Low-cost System for Generating Near-realistic Virtual Actors

NASA Astrophysics Data System (ADS)

Afifi, Mahmoud; Hussain, Khaled F.; Ibrahim, Hosny M.; Omar, Nagwa M.

2015-06-01

Generating virtual actors is one of the most challenging fields in computer graphics. The reconstruction of a realistic virtual actor has been paid attention by the academic research and the film industry to generate human-like virtual actors. Many movies were acted by human-like virtual actors, where the audience cannot distinguish between real and virtual actors. The synthesis of realistic virtual actors is considered a complex process. Many techniques are used to generate a realistic virtual actor; however they usually require expensive hardware equipment. In this paper, a low-cost system that generates near-realistic virtual actors is presented. The facial features of the real actor are blended with a virtual head that is attached to the actor's body. Comparing with other techniques that generate virtual actors, the proposed system is considered a low-cost system that requires only one camera that records the scene without using any expensive hardware equipment. The results of our system show that the system generates good near-realistic virtual actors that can be used on many applications.

21 CFR 870.5300 - DC-defribrillator (including paddles).

Code of Federal Regulations, 2010 CFR

2010-04-01

... of energy used for defibrillating (restoring normal heart rhythm) the atria or ventricles of the heart or to terminate other cardiac arrhythmias. This generic type of device includes low energy... either directly across the heart or on the surface of the body. (2) Classification. Class II (performance...

Heart Block

MedlinePlus

... to begin a new heartbeat 60 to 100 times a minute. From the SA node, the signal travels through the right and left atria. This causes ... AV node. This slowing allows the ventricles enough time to finish filling with ... leaves the AV node and travels along a pathway called the bundle of His. ...

21 CFR 870.5300 - DC-defribrillator (including paddles).

Code of Federal Regulations, 2012 CFR

2012-04-01

... of energy used for defibrillating (restoring normal heart rhythm) the atria or ventricles of the heart or to terminate other cardiac arrhythmias. This generic type of device includes low energy... either directly across the heart or on the surface of the body. (2) Classification. Class II (performance...

21 CFR 870.5300 - DC-defribrillator (including paddles).

Code of Federal Regulations, 2011 CFR

2011-04-01

... of energy used for defibrillating (restoring normal heart rhythm) the atria or ventricles of the heart or to terminate other cardiac arrhythmias. This generic type of device includes low energy... either directly across the heart or on the surface of the body. (2) Classification. Class II (performance...

21 CFR 870.5300 - DC-defibrillator (including paddles).

Code of Federal Regulations, 2013 CFR

2013-04-01

... of energy used for defibrillating (restoring normal heart rhythm) the atria or ventricles of the heart or to terminate other cardiac arrhythmias. This generic type of device includes low energy... either directly across the heart or on the surface of the body. (2) Classification. Class II (performance...

21 CFR 870.5300 - DC-defibrillator (including paddles).

Code of Federal Regulations, 2014 CFR

2014-04-01

... of energy used for defibrillating (restoring normal heart rhythm) the atria or ventricles of the heart or to terminate other cardiac arrhythmias. This generic type of device includes low energy... either directly across the heart or on the surface of the body. (2) Classification. Class II (performance...

Desensitization by noradrenaline of responses to stimulation of pre- and postsynaptic adrenoceptors

PubMed Central

Ball, N.; Danks, J.L.; Dorudi, S.; Nasmyth, P.A.

1982-01-01

1 The effect of exposing isolated preparations of rat aortic strip, rat atria and mouse vas deferens to perfusions of Krebs solution containing various concentrations of noradrenaline on their sensitivity to the drug has been determined. 2 The responses evoked by stimulation of postsynaptic adrenoceptors in all the tissues and presynaptic α-adrenoceptors in the mouse vas deferens were diminished by the perfusion of noradrenaline through the organ bath for 30 min. 3 The concentration of noradrenaline required to produce desensitization was higher in the mouse vas deferens than in the other tissues and more was required to desensitize the chronotropic responses than the inotropic responses in rat isolated atria. 4 The inclusion of cocaine (10-5 M) in the bathing solution to block uptake1 increased the sensitivity of most tissues to noradrenaline. With the possible exception of the response to stimulation of presynaptic receptors in the mouse vas deferens, desensitization was somewhat increased in its presence. 5 When uptake2 was blocked by oestradiol (10-5 M), it was not possible to desensitize the contractor responses of the aortic strip and vas deferens to exogenous noradrenaline, nor the inotropic response of the atria to the drug. However, oestradiol failed to block the desensitization of chronotropic responses and responses to stimulation of presynaptic receptors in the vas deferens. 6 Blockade of monoamine oxidase (MAO) with iproniazid (7.2 × 10-4 M) or with pargyline (5 × 10-4 M) did not affect the desensitization process in the aortic strip. 7 Blockade of catechol-O-methyltransferase (COMT) with U-0521 (5.3 × 10-5 M) greatly increased desensitization in the aortic strip and desensitization of inotropic responses in the atria. It had no effect on desensitization of chronotropic responses. Its effect on responses in the mouse vas deferens was not determined. 8 The perfusion of methoxamine at concentrations about 1000 times higher than those of noradrenaline also produced desensitization in the aortic strip. 9 The desensitization of presynaptic receptors in the mouse vas deferens was shown to be specific and that of the responses to postsynaptic receptor stimulation to be non-specific. 10 It is concluded that responses to adrenoceptor stimulation may be desensitized by accumulation of noradrenaline inside the cells bearing the receptors and that the desensitization is caused by noradrenaline itself not by a metabolite. Desensitization may also be caused without accumulation of noradrenaline in uptake2 and for some receptors these may not be alternative mechanisms. PMID:7082904

Physical environment virtualization for human activities recognition

NASA Astrophysics Data System (ADS)

Poshtkar, Azin; Elangovan, Vinayak; Shirkhodaie, Amir; Chan, Alex; Hu, Shuowen

2015-05-01

Human activity recognition research relies heavily on extensive datasets to verify and validate performance of activity recognition algorithms. However, obtaining real datasets are expensive and highly time consuming. A physics-based virtual simulation can accelerate the development of context based human activity recognition algorithms and techniques by generating relevant training and testing videos simulating diverse operational scenarios. In this paper, we discuss in detail the requisite capabilities of a virtual environment to aid as a test bed for evaluating and enhancing activity recognition algorithms. To demonstrate the numerous advantages of virtual environment development, a newly developed virtual environment simulation modeling (VESM) environment is presented here to generate calibrated multisource imagery datasets suitable for development and testing of recognition algorithms for context-based human activities. The VESM environment serves as a versatile test bed to generate a vast amount of realistic data for training and testing of sensor processing algorithms. To demonstrate the effectiveness of VESM environment, we present various simulated scenarios and processed results to infer proper semantic annotations from the high fidelity imagery data for human-vehicle activity recognition under different operational contexts.

Spontaneous Recovery of Human Spatial Memory in a Virtual Water Maze

ERIC Educational Resources Information Center

Luna, David; Martínez, Héctor

2015-01-01

The occurrence of spontaneous recovery in human spatial memory was assessed using a virtual environment. In Experiment 1, spatial memory was established by training participants to locate a hidden platform in a virtual water maze using a set of four distal landmarks. In Experiment 2, after learning about the location of a hidden platform, the…

Development of real-time motion capture system for 3D on-line games linked with virtual character

NASA Astrophysics Data System (ADS)

Kim, Jong Hyeong; Ryu, Young Kee; Cho, Hyung Suck

2004-10-01

Motion tracking method is being issued as essential part of the entertainment, medical, sports, education and industry with the development of 3-D virtual reality. Virtual human character in the digital animation and game application has been controlled by interfacing devices; mouse, joysticks, midi-slider, and so on. Those devices could not enable virtual human character to move smoothly and naturally. Furthermore, high-end human motion capture systems in commercial market are expensive and complicated. In this paper, we proposed a practical and fast motion capturing system consisting of optic sensors, and linked the data with 3-D game character with real time. The prototype experiment setup is successfully applied to a boxing game which requires very fast movement of human character.

The Virtual Physiological Human

PubMed Central

Coveney, Peter V.; Diaz, Vanessa; Hunter, Peter; Kohl, Peter; Viceconti, Marco

2011-01-01

The Virtual Physiological Human is synonymous with a programme in computational biomedicine that aims to develop a framework of methods and technologies to investigate the human body as a whole. It is predicated on the transformational character of information technology, brought to bear on that most crucial of human concerns, our own health and well-being.

Digital evaluation of sitting posture comfort in human-vehicle system under Industry 4.0 framework

NASA Astrophysics Data System (ADS)

Tao, Qing; Kang, Jinsheng; Sun, Wenlei; Li, Zhaobo; Huo, Xiao

2016-09-01

Most of the previous studies on the vibration ride comfort of the human-vehicle system were focused only on one or two aspects of the investigation. A hybrid approach which integrates all kinds of investigation methods in real environment and virtual environment is described. The real experimental environment includes the WBV(whole body vibration) test, questionnaires for human subjective sensation and motion capture. The virtual experimental environment includes the theoretical calculation on simplified 5-DOF human body vibration model, the vibration simulation and analysis within ADAMS/VibrationTM module, and the digital human biomechanics and occupational health analysis in Jack software. While the real experimental environment provides realistic and accurate test results, it also serves as core and validation for the virtual experimental environment. The virtual experimental environment takes full advantages of current available vibration simulation and digital human modelling software, and makes it possible to evaluate the sitting posture comfort in a human-vehicle system with various human anthropometric parameters. How this digital evaluation system for car seat comfort design is fitted in the Industry 4.0 framework is also proposed.

The Martian: Examining Human Physical Judgments across Virtual Gravity Fields.

PubMed

Ye, Tian; Qi, Siyuan; Kubricht, James; Zhu, Yixin; Lu, Hongjing; Zhu, Song-Chun

2017-04-01

This paper examines how humans adapt to novel physical situations with unknown gravitational acceleration in immersive virtual environments. We designed four virtual reality experiments with different tasks for participants to complete: strike a ball to hit a target, trigger a ball to hit a target, predict the landing location of a projectile, and estimate the flight duration of a projectile. The first two experiments compared human behavior in the virtual environment with real-world performance reported in the literature. The last two experiments aimed to test the human ability to adapt to novel gravity fields by measuring their performance in trajectory prediction and time estimation tasks. The experiment results show that: 1) based on brief observation of a projectile's initial trajectory, humans are accurate at predicting the landing location even under novel gravity fields, and 2) humans' time estimation in a familiar earth environment fluctuates around the ground truth flight duration, although the time estimation in unknown gravity fields indicates a bias toward earth's gravity.

Human Machine Interfaces for Teleoperators and Virtual Environments

NASA Technical Reports Server (NTRS)

Durlach, Nathaniel I. (Compiler); Sheridan, Thomas B. (Compiler); Ellis, Stephen R. (Compiler)

1991-01-01

In Mar. 1990, a meeting organized around the general theme of teleoperation research into virtual environment display technology was conducted. This is a collection of conference-related fragments that will give a glimpse of the potential of the following fields and how they interplay: sensorimotor performance; human-machine interfaces; teleoperation; virtual environments; performance measurement and evaluation methods; and design principles and predictive models.

Advanced Collaborative Environments Supporting Systems Integration and Design

DTIC Science & Technology

2003-03-01

concurrently view a virtual system or product model while maintaining natural, human communication . These virtual systems operate within a computer-generated...These environments allow multiple individuals to concurrently view a virtual system or product model while simultaneously maintaining natural, human ... communication . As a result, TARDEC researchers and system developers are using this advanced high-end visualization technology to develop future

Comparing Human-Human to Human-Computer Tutorial Dialogue

DTIC Science & Technology

2010-01-01

acknowledged what their tutor said and participated in rapport building with chit-chat. This seems to be driven by a need to be polite and courteous to the...An experiment on public speaking anxiety in response to three different types of virtual audiences. Presence: Teleoperators and Virtual

Estimating the gaze of a virtuality human.

PubMed

Roberts, David J; Rae, John; Duckworth, Tobias W; Moore, Carl M; Aspin, Rob

2013-04-01

The aim of our experiment is to determine if eye-gaze can be estimated from a virtuality human: to within the accuracies that underpin social interaction; and reliably across gaze poses and camera arrangements likely in every day settings. The scene is set by explaining why Immersive Virtuality Telepresence has the potential to meet the grand challenge of faithfully communicating both the appearance and the focus of attention of a remote human participant within a shared 3D computer-supported context. Within the experiment n=22 participants rotated static 3D virtuality humans, reconstructed from surround images, until they felt most looked at. The dependent variable was absolute angular error, which was compared to that underpinning social gaze behaviour in the natural world. Independent variables were 1) relative orientations of eye, head and body of captured subject; and 2) subset of cameras used to texture the form. Analysis looked for statistical and practical significance and qualitative corroborating evidence. The analysed results tell us much about the importance and detail of the relationship between gaze pose, method of video based reconstruction, and camera arrangement. They tell us that virtuality can reproduce gaze to an accuracy useful in social interaction, but with the adopted method of Video Based Reconstruction, this is highly dependent on combination of gaze pose and camera arrangement. This suggests changes in the VBR approach in order to allow more flexible camera arrangements. The work is of interest to those wanting to support expressive meetings that are both socially and spatially situated, and particular those using or building Immersive Virtuality Telepresence to accomplish this. It is also of relevance to the use of virtuality humans in applications ranging from the study of human interactions to gaming and the crossing of the stage line in films and TV.

Interactions with Virtual People: Do Avatars Dream of Digital Sheep?. Chapter 6

NASA Technical Reports Server (NTRS)

Slater, Mel; Sanchez-Vives, Maria V.

2007-01-01

This paper explores another form of artificial entity, ones without physical embodiment. We refer to virtual characters as the name for a type of interactive object that have become familiar in computer games and within virtual reality applications. We refer to these as avatars: three-dimensional graphical objects that are in more-or-less human form which can interact with humans. Sometimes such avatars will be representations of real-humans who are interacting together within a shared networked virtual environment, other times the representations will be of entirely computer generated characters. Unlike other authors, who reserve the term agent for entirely computer generated characters and avatars for virtual embodiments of real people; the same term here is used for both. This is because avatars and agents are on a continuum. The question is where does their behaviour originate? At the extremes the behaviour is either completely computer generated or comes only from tracking of a real person. However, not every aspect of a real person can be tracked every eyebrow move, every blink, every breath rather real tracking data would be supplemented by inferred behaviours which are programmed based on the available information as to what the real human is doing and her/his underlying emotional and psychological state. Hence there is always some programmed behaviour it is only a matter of how much. In any case the same underlying problem remains how can the human character be portrayed in such a manner that its actions are believable and have an impact on the real people with whom it interacts? This paper has three main parts. In the first part we will review some evidence that suggests that humans react with appropriate affect in their interactions with virtual human characters, or with other humans who are represented as avatars. This is so in spite of the fact that the representational fidelity is relatively low. Our evidence will be from the realm of psychotherapy, where virtual social situations are created that do test whether people react appropriately within these situations. We will also consider some experiments on face-to-face virtual communications between people in the same shared virtual environments. The second part will try to give some clues about why this might happen, taking into account modern theories of perception from neuroscience. The third part will include some speculations about the future developments of the relationship between people and virtual people. We will suggest that a more likely scenario than the world becoming populated by physically embodied virtual people (robots, androids) is that in the relatively near future we will interact more and more in our everyday lives with virtual people- bank managers, shop assistants, instructors, and so on. What is happening in the movies with computer graphic generated individuals and entire crowds may move into the space of everyday life.

Discovery of novel human acrosin inhibitors by virtual screening

NASA Astrophysics Data System (ADS)

Liu, Xuefei; Dong, Guoqiang; Zhang, Jue; Qi, Jingjing; Zheng, Canhui; Zhou, Youjun; Zhu, Ju; Sheng, Chunquan; Lü, Jiaguo

2011-10-01

Human acrosin is an attractive target for the discovery of male contraceptive drugs. For the first time, structure-based drug design was applied to discover structurally diverse human acrosin inhibitors. A parallel virtual screening strategy in combination with pharmacophore-based and docking-based techniques was used to screen the SPECS database. From 16 compounds selected by virtual screening, a total of 10 compounds were found to be human acrosin inhibitors. Compound 2 was found to be the most potent hit (IC50 = 14 μM) and its binding mode was investigated by molecular dynamics simulations. The hit interacted with human acrosin mainly through hydrophobic and hydrogen-bonding interactions, which provided a good starting structure for further optimization studies.

Human agency beliefs influence behaviour during virtual social interactions

PubMed Central

Brock, Jon

2017-01-01

In recent years, with the emergence of relatively inexpensive and accessible virtual reality technologies, it is now possible to deliver compelling and realistic simulations of human-to-human interaction. Neuroimaging studies have shown that, when participants believe they are interacting via a virtual interface with another human agent, they show different patterns of brain activity compared to when they know that their virtual partner is computer-controlled. The suggestion is that users adopt an “intentional stance” by attributing mental states to their virtual partner. However, it remains unclear how beliefs in the agency of a virtual partner influence participants’ behaviour and subjective experience of the interaction. We investigated this issue in the context of a cooperative “joint attention” game in which participants interacted via an eye tracker with a virtual onscreen partner, directing each other’s eye gaze to different screen locations. Half of the participants were correctly informed that their partner was controlled by a computer algorithm (“Computer” condition). The other half were misled into believing that the virtual character was controlled by a second participant in another room (“Human” condition). Those in the “Human” condition were slower to make eye contact with their partner and more likely to try and guide their partner before they had established mutual eye contact than participants in the “Computer” condition. They also responded more rapidly when their partner was guiding them, although the same effect was also found for a control condition in which they responded to an arrow cue. Results confirm the influence of human agency beliefs on behaviour in this virtual social interaction context. They further suggest that researchers and developers attempting to simulate social interactions should consider the impact of agency beliefs on user experience in other social contexts, and their effect on the achievement of the application’s goals. PMID:28948104

Visualization and simulated surgery of the left ventricle in the virtual pathological heart of the Virtual Physiological Human

PubMed Central

McFarlane, N. J. B.; Lin, X.; Zhao, Y.; Clapworthy, G. J.; Dong, F.; Redaelli, A.; Parodi, O.; Testi, D.

2011-01-01

Ischaemic heart failure remains a significant health and economic problem worldwide. This paper presents a user-friendly software system that will form a part of the virtual pathological heart of the Virtual Physiological Human (VPH2) project, currently being developed under the European Commission Virtual Physiological Human (VPH) programme. VPH2 is an integrated medicine project, which will create a suite of modelling, simulation and visualization tools for patient-specific prediction and planning in cases of post-ischaemic left ventricular dysfunction. The work presented here describes a three-dimensional interactive visualization for simulating left ventricle restoration surgery, comprising the operations of cutting, stitching and patching, and for simulating the elastic deformation of the ventricle to its post-operative shape. This will supply the quantitative measurements required for the post-operative prediction tools being developed in parallel in the same project. PMID:22670207

One New Method to Generate 3-Dimensional Virtual Mannequin

NASA Astrophysics Data System (ADS)

Xiu-jin, Shi; Zhi-jun, Wang; Jia-jin, Le

The personal virtual mannequin is very important in electronic made to measure (eMTM) system. There is one new easy method to generate personal virtual mannequin. First, the characteristic information of customer's body is got from two photos. Secondly, some human body part templates corresponding with the customer are selected from the templates library. Thirdly, these templates are modified and assembled according to certain rules to generate a personalized 3-dimensional human, and then the virtual mannequin is realized. Experimental result shows that the method is easy and feasible.

Using a Virtual Population to Authentically Teach Epidemiology and Biostatistics

ERIC Educational Resources Information Center

Dunn, Peter K.; Donnison, Sharn; Cole, Rachel; Bulmer, Michael

2017-01-01

Epidemiology is the study of the distribution of disease in human populations. This means that authentically teaching primary data collection in epidemiology is difficult as students cannot easily access suitable human populations. Using an action research methodology, this paper studied the use of a virtual human population (called "The…

Simultaneous epicardial and noncontact endocardial mapping of the canine right atrium: simulation and experiment.

PubMed

Sabouri, Sepideh; Matene, Elhacene; Vinet, Alain; Richer, Louis-Philippe; Cardinal, René; Armour, J Andrew; Pagé, Pierre; Kus, Teresa; Jacquemet, Vincent

2014-01-01

Epicardial high-density electrical mapping is a well-established experimental instrument to monitor in vivo the activity of the atria in response to modulations of the autonomic nervous system in sinus rhythm. In regions that are not accessible by epicardial mapping, noncontact endocardial mapping performed through a balloon catheter may provide a more comprehensive description of atrial activity. We developed a computer model of the canine right atrium to compare epicardial and noncontact endocardial mapping. The model was derived from an experiment in which electroanatomical reconstruction, epicardial mapping (103 electrodes), noncontact endocardial mapping (2048 virtual electrodes computed from a 64-channel balloon catheter), and direct-contact endocardial catheter recordings were simultaneously performed in a dog. The recording system was simulated in the computer model. For simulations and experiments (after atrio-ventricular node suppression), activation maps were computed during sinus rhythm. Repolarization was assessed by measuring the area under the atrial T wave (ATa), a marker of repolarization gradients. Results showed an epicardial-endocardial correlation coefficients of 0.80 and 0.63 (two dog experiments) and 0.96 (simulation) between activation times, and a correlation coefficients of 0.57 and 0.46 (two dog experiments) and 0.92 (simulation) between ATa values. Despite distance (balloon-atrial wall) and dimension reduction (64 electrodes), some information about atrial repolarization remained present in noncontact signals.

Simultaneous Epicardial and Noncontact Endocardial Mapping of the Canine Right Atrium: Simulation and Experiment

PubMed Central

Sabouri, Sepideh; Matene, Elhacene; Vinet, Alain; Richer, Louis-Philippe; Cardinal, René; Armour, J. Andrew; Pagé, Pierre; Kus, Teresa; Jacquemet, Vincent

2014-01-01

Epicardial high-density electrical mapping is a well-established experimental instrument to monitor in vivo the activity of the atria in response to modulations of the autonomic nervous system in sinus rhythm. In regions that are not accessible by epicardial mapping, noncontact endocardial mapping performed through a balloon catheter may provide a more comprehensive description of atrial activity. We developed a computer model of the canine right atrium to compare epicardial and noncontact endocardial mapping. The model was derived from an experiment in which electroanatomical reconstruction, epicardial mapping (103 electrodes), noncontact endocardial mapping (2048 virtual electrodes computed from a 64-channel balloon catheter), and direct-contact endocardial catheter recordings were simultaneously performed in a dog. The recording system was simulated in the computer model. For simulations and experiments (after atrio-ventricular node suppression), activation maps were computed during sinus rhythm. Repolarization was assessed by measuring the area under the atrial T wave (ATa), a marker of repolarization gradients. Results showed an epicardial-endocardial correlation coefficients of 0.80 and 0.63 (two dog experiments) and 0.96 (simulation) between activation times, and a correlation coefficients of 0.57 and 0.46 (two dog experiments) and 0.92 (simulation) between ATa values. Despite distance (balloon-atrial wall) and dimension reduction (64 electrodes), some information about atrial repolarization remained present in noncontact signals. PMID:24598778

Future Evolution of Virtual Worlds as Communication Environments

NASA Astrophysics Data System (ADS)

Prisco, Giulio

Extensive experience creating locations and activities inside virtual worlds provides the basis for contemplating their future. Users of virtual worlds are diverse in their goals for these online environments; for example, immersionists want them to be alternative realities disconnected from real life, whereas augmentationists want them to be communication media supporting real-life activities. As the technology improves, the diversity of virtual worlds will increase along with their significance. Many will incorporate more advanced virtual reality, or serve as major media for long-distance collaboration, or become the venues for futurist social movements. Key issues are how people can create their own virtual worlds, travel across worlds, and experience a variety of multimedia immersive environments. This chapter concludes by noting the view among some computer scientists that future technologies will permit uploading human personalities to artificial intelligence avatars, thereby enhancing human beings and rendering the virtual worlds entirely real.

KATP Channels in the Cardiovascular System

PubMed Central

Foster, Monique N.; Coetzee, William A.

2015-01-01

KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease. PMID:26660852

The impact of patients' gender, race, and age on health care professionals' pain management decisions: an online survey using virtual human technology.

PubMed

Wandner, Laura D; Heft, Marc W; Lok, Benjamin C; Hirsh, Adam T; George, Steven Z; Horgas, Anne L; Atchison, James W; Torres, Calia A; Robinson, Michael E

2014-05-01

Previous literature indicates that biases exist in pain ratings. Healthcare professionals have been found to use patient demographic cues such as sex, race, and age when making decisions about pain treatment. However, there has been little research comparing healthcare professionals' (i.e., physicians and nurses) pain decision policies based on patient demographic cues. The current study used virtual human technology to examine the impact of patients' sex, race, and age on healthcare professionals' pain ratings. One hundred and ninety-three healthcare professionals (nurses and physicians) participated in this online study. Healthcare professionals assessed virtual human patients who were male and African American to be experiencing greater pain intensity and were more willing to administer opioid analgesics to them than to their demographic counterparts. Similarly, nurses were more willing to administer opioids make treatment decisions than physicians. There was also a significant virtual human-sex by healthcare professional interaction for pain assessment and treatment decisions. The sex difference (male>female) was greater for nurses than physicians. Results replicated findings of previous studies using virtual human patients to assess the effect of sex, race, and age in pain decision-making. In addition, healthcare professionals' pain ratings differed depending on healthcare profession. Nurses were more likely to rate pain higher and be more willing to administer opioid analgesics than were physicians. Healthcare professionals rated male and African American virtual human patients as having higher pain in most pain assessment and treatment domains compared to their demographic counterparts. Similarly the virtual human-sex difference ratings were more pronounced for nurses than physicians. Given the large number of patients seen throughout the healthcare professionals' careers, these pain practice biases have important public health implications. This study suggests attention to the influence of patient demographic cues in pain management education is needed. Copyright © 2013 Elsevier Ltd. All rights reserved.

THE IMPACT OF PATIENTS’ GENDER, RACE, AND AGE ON HEALTH CARE PROFESSIONALS’ PAIN MANAGEMENT DECISIONS: AN ONLINE SURVEY USING VIRTUAL HUMAN TECHNOLOGY

PubMed Central

Wandner, Laura D.; Heft, Marc W.; Lok, Benjamin C.; Hirsh, Adam T.; George, Steven Z.; Horgas, Anne L.; Atchison, James W.; Torres, Calia A.; Robinson, Michael E.

2013-01-01

Background Previous literature indicates that biases exist in pain ratings. Healthcare professionals have been found to use patient demographic cues such as sex, race, and age when making decisions about pain treatment. However, there has been little research comparing healthcare professionals’ (i.e., physicians and nurses) pain decision policies based on patient demographic cues. Methods The current study used virtual human technology to examine the impact of patients’ sex, race, and age on healthcare professionals’ pain ratings. One hundred and ninety-three healthcare professionals (nurses and physicians) participated in this online study. Results Healthcare professionals assessed virtual human patients who were male and African American to be experiencing greater pain intensity and were more willing to administer opioid analgesics to them than to their demographic counterparts. Similarly, nurses were more willing to administer opioids make treatment decisions than physicians. There was also a significant virtual human-sex by healthcare professional interaction for pain assessment and treatment decisions. The sex difference (male > female) was greater for nurses than physicians. Conclusions Results replicated findings of previous studies using virtual human patients to assess the effect of sex, race, and age in pain decision-making. In addition, healthcare professionals” pain ratings differed depending on healthcare profession. Nurses were more likely to rate pain higher and be more willing to administer opioid analgesics than were physicians. Healthcare professionals rated male and African American virtual human patients as having higher pain in most pain assessment and treatment domains compared to their demographic counterparts. Similarly the virtual human-sex difference ratings were more pronounced for nurses than physicians. Given the large number of patients seen throughout the healthcare professionals’ careers, these pain practice biases have important public health implications. This study suggests attention to the influence of patient demographic cues in pain management education is needed. PMID:24128374

The assessment of virtual reality for human anatomy instruction

NASA Technical Reports Server (NTRS)

Benn, Karen P.

1994-01-01

This research project seeks to meet the objective of science training by developing, assessing, and validating virtual reality as a human anatomy training medium. In ideal situations, anatomic models, computer-based instruction, and cadaver dissection are utilized to augment the traditional methods of instruction. At many institutions, lack of financial resources limits anatomy instruction to textbooks and lectures. However, human anatomy is three dimensional, unlike the one dimensional depiction found in textbooks and the two dimensional depiction found on the computer. Virtual reality is a breakthrough technology that allows one to step through the computer screen into a three dimensional world. This technology offers many opportunities to enhance science education. Therefore, a virtual testing environment of the abdominopelvic region of a human cadaver was created to study the placement of body parts within the nine anatomical divisions of the abdominopelvic region and the four abdominal quadrants.

20p12.3 microdeletion predisposes to Wolff–Parkinson–White syndrome with variable neurocognitive deficits

USDA-ARS?s Scientific Manuscript database

Wolff–Parkinson–White syndrome (WPW) is a bypass re-entrant tachycardia that results from an abnormal connection between the atria and ventricles. Mutations in PRKAG2 have been described in patients with familial WPW syndrome and hypertrophic cardiomyopathy. Based on the role of bone morphogenetic p...

Synthesis and Biological Evaluation of New Combined α/β-Adrenergic Blockers.

PubMed

Némethy, Andrej; Vavrinec, Peter; Vavrincová-Yaghi, Diana; Čepcová, Diana; Mišúth, Svetozár; Král'ová, Eva; Čižmáriková, Ružena; Račanská, Eva

2017-06-01

The synthesis, characterization, and pharmacological evaluation of new aryloxyaminopropanol compounds based on substituted (4-hydroxyphenyl)ethanone with alterations in the alkoxymethyl side chain in position 2 and with 2-methoxyphenylpiperazine in the basic part of the molecule are reported. For the in vitro pharmacological evaluation, isolated aorta and atria from normotensive Wistar rats were used. Compared to naftopidil, compounds with ethoxymethyl, propoxymethyl, butoxymethyl, and methoxyethoxymethyl substituent displayed similar α 1 -adrenolytic potency. Compounds with methoxymethyl, ethoxymethyl, and propoxymethyl substituent caused a significant decrease in both spontaneous and isoproterenol-induced beating of isolated rat atria. Naftopidil and the tested substances containing a butoxymethyl and methoxyethoxymethyl substituent had no effect on the spontaneous or isoproterenol-induced beating. The tested substance that had the most pronounced effect was the compound with a propoxymethyl substituent. Its antihypertensive efficacy was investigated in vivo on spontaneously hypertensive rats (SHRs). The systolic blood pressure was found to be significantly lower in SHRs subjected to the treatment for 2 weeks than in untreated SHRs. Naftopidil had no significant effect. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Long-term biatrial recordings in post-operative atrial fibrillation.

PubMed

Masè, M; Graffigna, A; Sinelli, S; Pallaoro, G; Nollo, G; Ravelli, F

2010-01-01

Although atrial fibrillation (AF) is a common complication of cardiac surgery, its pathophysiology remains unclear. The study of post-operative AF demands for the recording of cardiac electrical activity in correspondence of AF onset and progression. Long-term recordings in post-surgery patients could provide this information, but, to date, have been limited to surface signals, which precludes a characterization of the arrhythmic triggers and substrate. In this study we demonstrate the feasibility of a continuous long-term recording of atrial electrical activities from the right and left atria in post-surgery patients. Local atrial epicardial electrograms are acquired by positioning temporary pacing wires in the right and left atria at the end of the intervention, while three day recordings are obtained by a digital holter recorder, adapted to epicardial signal features. The capability of the system to map local atrial activity and the possibility to obtain quantitative information on atrial rate and synchronization from the processed epicardial signals are proven in representative examples. The quantitative description of local atrial properties opens new perspective in the investigation of post-surgery AF.

Two new genera of Lumbriculidae (Annelida, Clitellata) from North Carolina, USA

USGS Publications Warehouse

Fend, S.V.; Lenat, D.R.

2007-01-01

Recent benthic macroinvertebrate collections from North Carolina contained many undescribed oligochaete taxa, mostly belonging to the family Lumbriculidae. Three of the new species had arrangements of spermathecae and atria previously unreported for the family, and were assigned to new two genera. Pilaridrilus is distinguished by the location of spermathecal pores five segments behind the male pores. The single species, Pilaridrilus uliginosus, also has unusually complex penes and spermathecae. Martinidrilus is distinguished by spermathecae beginning more than two segments anterior to the atrial segment, and also by the the vasa deferentia, which join a common duct before joining the atria. The two Martinidrilus species also have unusual digitiform blood vessels in posterior segments. Martinidrilus carolinensis has lateral spermathecae in VI, and Martinidrilus arenosus has dorsolateral spermathecae in VII and VIII. Because arrangement and morphology of reproductive organs do not resemble those of described lumbriculids, the phylogenetic affinities of the new species are not clear. These new genera and species were generally collected from areas of high water quality, suggesting that lumbriculids can be useful in water quality monitoring and conservation evaluation. Copyright ?? 2007 Magnolia Press.

The German VR Simulation Realism Scale--psychometric construction for virtual reality applications with virtual humans.

PubMed

Poeschl, Sandra; Doering, Nicola

2013-01-01

Virtual training applications with high levels of immersion or fidelity (for example for social phobia treatment) produce high levels of presence and therefore belong to the most successful Virtual Reality developments. Whereas display and interaction fidelity (as sub-dimensions of immersion) and their influence on presence are well researched, realism of the displayed simulation depends on the specific application and is therefore difficult to measure. We propose to measure simulation realism by using a self-report questionnaire. The German VR Simulation Realism Scale for VR training applications was developed based on a translation of scene realism items from the Witmer-Singer-Presence Questionnaire. Items for realism of virtual humans (for example for social phobia training applications) were supplemented. A sample of N = 151 students rated simulation realism of a Fear of Public Speaking application. Four factors were derived by item- and principle component analysis (Varimax rotation), representing Scene Realism, Audience Behavior, Audience Appearance and Sound Realism. The scale developed can be used as a starting point for future research and measurement of simulation realism for applications including virtual humans.

Complementary Machine Intelligence and Human Intelligence in Virtual Teaching Assistant for Tutoring Program Tracing

ERIC Educational Resources Information Center

Chou, Chih-Yueh; Huang, Bau-Hung; Lin, Chi-Jen

2011-01-01

This study proposes a virtual teaching assistant (VTA) to share teacher tutoring tasks in helping students practice program tracing and proposes two mechanisms of complementing machine intelligence and human intelligence to develop the VTA. The first mechanism applies machine intelligence to extend human intelligence (teacher answers) to evaluate…

Virtual Reality: A Dream Come True or a Nightmare.

ERIC Educational Resources Information Center

Cornell, Richard; Bailey, Dan

Virtual Reality (VR) is a new medium which allows total stimulation of one's senses through human/computer interfaces. VR has applications in training simulators, nano-science, medicine, entertainment, electronic technology, and manufacturing. This paper focuses on some current and potential problems of virtual reality and virtual environments…

Autophagy as a mechanism for myolysis of cardiomyocytes in mitral regurgitation.

PubMed

Chen, Mien-Cheng; Chang, Jen-Ping; Wang, Ya-Hui; Liu, Wen-Hao; Ho, Wan-Chun; Chang, Hsueh-Wen

2011-03-01

Myolysis of atrial cardiomyocytes occurs in patients with severe mitral and tricuspid regurgitation. This morphological remodelling may involve autophagy. This study comprised 20 patients (10 with long-standing persistent atrial fibrillation and 10 with sinus rhythm) with severe mitral and tricuspid regurgitation. Atrial appendageal tissues were obtained during surgery. The appearance of autophagosomes (LC3B) in myocytes can reflect autophagy induction. Complement 9 is used as a reliable marker of oncosis. In the fibrillating right atria, 68·4 ± 18·9% of total myocytes showed moderate-to-severe myolysis, while 64·2 ± 15·8% of total myocytes comprised these cells in right atrial myocardium with sinus rhythm. Immunohistochemical study revealed LC3B-positive myocytes in 8·0% of myocytes without myolysis, 11·9% of myocytes with mild myolysis and 49·4% of myocytes with moderate-to-severe myolysis in right atrial myocardium with sinus rhythm (P < 0·0001). Similarly, in the fibrillating right atria, LC3B-positive myocytes were observed in 5·9% of myocytes without myolysis, 12·2% of myocytes with mild myolysis and 50·7% of myocytes with moderate-to-severe myolysis (P < 0·0001). Moreover, in the fibrillating left atria, LC3B-positive myocytes were observed in 4·9% of myocytes without myolysis, 12·6% of myocytes with mild myolysis and 52·0% of myocytes with moderate-to-severe myolysis (P < 0·0001). None of the atrial myocytes displayed intracellular deposition of complement 9. Induction of autophagy, but not oncosis, occurs in most cases of atrial cardiomyocytes with severe mitral and tricuspid regurgitation, even those without atrial fibrillation, and is closely associated with the development of myolysis in this disease. © 2010 The Authors. European Journal of Clinical Investigation © 2010 Stichting European Society for Clinical Investigation Journal Foundation.

Neuropeptide Y is a prejunctional inhibitor of vagal but not sympathetic inotropic responses in guinea-pig isolated left atria

PubMed Central

Serone, Adrian P; Angus, James A

1999-01-01

The effects of NPY and related peptides were examined on basal contractile force and nerve-mediated inotropic responses to electrical field stimulation of the guinea-pig isolated left atrium.Electrical field stimulus (EFS)-inotropic response curves were constructed by applying 1-64 trains of four field pulses (200 Hz, 0.1 ms duration, 100 V) across isolated left atria (paced at 4 Hz, 2 ms, 1–4 V) within the atrial refractory period. Curves were constructed in presence of vehicle, propranolol (1 μM) or atropine (1 μM) to determine appropriate stimulus conditions.The effects of PYY (1–10,000 nM), NPY (0.01–10 μM), N-Ac-[Leu28,31]NPY(24–36) (N-A[L]NPY(24–36); 0.01–10 μM) and clonidine (0.1–1000 nM) were examined on the positive and negative inotropic responses to EFS (eight trains, four pulses per refractory period).NPY-related peptides had no effect on basal force of contraction nor on the inotropic concentration-response curves to bethanechol or isoprenaline. All three peptides inhibited vagally-mediated negative inotropic responses; rank order of potency PYY>NPY⩾N-A[L]NPY(24–36) was consistent with an action at prejunctional Y2-receptors. Clonidine concentration-dependently inhibited sympathetic inotropic responses. However, PYY, NPY and N-A[L]NPY(24–36) failed to mediate any significant inhibition of the positive inotropic response to EFS.These data demonstrate that NPY is an effective inhibitor of vagal but not sympathetically-mediated inotropic responses in the guinea-pig isolated left atria. This may suggest that endogenously co-released NPY is important in mediating cross talk between efferent components of the autonomic nervous system modulating cardiac contractility, acting overall to sustain positive inotropic responses. PMID:10385237

Predicting Major Bleeding in Ischemic Stroke Patients With Atrial Fibrillation.

PubMed

Hilkens, Nina A; Algra, Ale; Greving, Jacoba P

2017-11-01

Performance of risk scores for major bleeding in patients with atrial fibrillation and a previous transient ischemic attack or ischemic stroke is not well established. We aimed to validate risk scores for major bleeding in patients with atrial fibrillation treated with oral anticoagulants after cerebral ischemia and explore the net benefit of oral anticoagulants among bleeding risk categories. We analyzed 3623 patients with a history of transient ischemic attack or stroke included in the RE-LY trial (Randomized Evaluation of Long-Term Anticoagulation Therapy). We assessed performance of HEMORR 2 HAGES (hepatic or renal disease, ethanol abuse, malignancy, older age, reduced platelet count or function, hypertension [uncontrolled], anemia, genetic factors, excessive fall risk, and stroke), Shireman, HAS-BLED (hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly, drugs/alcohol concomitantly), ATRIA (Anticoagulation and Risk Factors in Atrial Fibrillation), and ORBIT scores (older age, reduced haemoglobin/haematocrit/history of anaemia, bleeding history, insufficient kidney function, and treatment with antiplatelet) with C statistics and calibration plots. Net benefit of oral anticoagulants was explored by comparing risk reduction in ischemic stroke with risk increase in major bleedings on warfarin. During 6922 person-years of follow-up, 266 patients experienced a major bleed (3.8 per 100 person-years). C statistics ranged from 0.62 (Shireman) to 0.67 (ATRIA). Calibration was poor for ATRIA and moderate for other models. The reduction in recurrent ischemic strokes on warfarin was larger than the increase in major bleeding risk, irrespective of bleeding risk category. Performance of prediction models for major bleeding in patients with cerebral ischemia and atrial fibrillation is modest but comparable with performance in patients with only atrial fibrillation. Bleeding risk scores cannot guide treatment decisions for oral anticoagulants but may still be useful to identify modifiable risk factors for bleeding. Clinical usefulness may be best for ORBIT, which is based on a limited number of easily obtainable variables and showed reasonable performance. © 2017 American Heart Association, Inc.

Effect of pilsicainide on dominant frequency in the right and left atria and pulmonary veins during atrial fibrillation: association with its atrial fibrillation terminating effect.

PubMed

Horiuchi, Daisuke; Iwasa, Atsushi; Sasaki, Kenichi; Owada, Shingen; Kimura, Masaomi; Sasaki, Shingo; Okumura, Ken

2009-04-17

Dominant frequency reflects the peak cycle length of atrial fibrillation. In 34 patients with atrial fibrillation, bipolar electrograms were recorded from multiple atrial sites and pulmonary veins and the effect of pilsicainide, class Ic antiarrhythmic drug, on dominant frequency was examined. At baseline, mean dominant frequencies (Hz) in the right and left atria, coronary sinus and right and left superior pulmonary veins were 5.87 +/- 0.76, 6.08 +/- 0.60, 5.65 +/- 0.95, 6.12 +/- 0.88 and 6.59 +/- 0.89, respectively (P < 0.05, left superior pulmonary vein vs right atrium and coronary sinus). After pilsicainide (1.0 mg/kg/5 min), dominant frequency decreased at all sites in all patients. Atrial fibrillation was terminated at 5.9 +/- 2.2 min in 16 patients (Group A) with a decrease in the average of mean dominant frequencies at all sites from 5.80 +/- 0.72 to 3.57 +/- 0.63 Hz, was converted to atrial flutter at 7.3 +/- 1.4 min in 5 (Group B) with a decrease in the average dominant frequency from 5.83 +/- 0.48 to 3.08 +/- 0.19 Hz, and was not terminated in the other 13 (Group C) despite the average dominant frequency decrease from 6.59 +/- 0.76 to 4.42 +/- 0.52 Hz. In 14 of the 21 Groups A and B patients (67%), mean dominant frequencies at all recording sites were < 4.0 after pilsicainide, while they were < 4.0 in 1 of the 13 Group C patients (8%, P < 0.01). In conclusion, the degree of dominant frequency decrease by pilsicainide is closely related to its atrial fibrillation terminating effect: When dominant frequency in the atria decreases to < 4.0 Hz, atrial fibrillation is terminated with 93% positive and 63% negative predictive values.

Increased expression of NF-AT3 and NF-AT4 in the atria correlates with procollagen I carboxyl terminal peptide and TGF-β1 levels in serum of patients with atrial fibrillation.

PubMed

Zhao, Fei; Zhang, ShiJiang; Chen, YiJiang; Gu, WeiDong; Ni, BuQing; Shao, YongFeng; Wu, YanHu; Qin, JianWei

2014-11-25

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice. Unfortunately, the precise mechanisms and sensitive serum biomarkers of atrial remodeling in AF remain unclear. The aim of this study was to determine whether the expression of the transcription factors NF-AT3 and NF-AT4 correlate with atrial structural remodeling of atrial fibrillation and serum markers for collagen I and III synthesis. Right and left atrial specimens were obtained from 90 patients undergoing valve replacement surgery. The patients were divided into sinus rhythm (n = 30), paroxysmal atrial fibrillation (n = 30), and persistent atrial fibrillation (n = 30) groups. NF-AT3, NF-AT4, and collagen I and III mRNA and protein expression in atria were measured. We also tested the levels of the carboxyl-terminal peptide from pro-collagen I, the N-terminal type I procollagen propeptides, the N-terminal type III procollagen propeptides, and TGF-β1 in serum using an enzyme immunosorbent assay. NF-AT3 and NF-AT4 mRNA and protein expression were increased in the AF groups, especially in the left atrium. NF-AT3 and NF-AT4 expression in the right atrium was increased in the persistent atrial fibrillation group compared the sinus rhythm group with similar valvular disease. In patients with AF, the expression levels of nuclear NF-AT3 and NF-AT4 correlated with those of collagens I and III in the atria and with PICP and TGF-β1 in blood. These data support the hypothesis that nuclear NF-AT3 and NF-AT4 participates in atrial structural remodeling, and that PICP and TGF-β1 levels may be sensitive serum biomarkers to estimate atrial structural remodeling with atrial fibrillation.

Human Robotic Study at Houghton Crater - virtual reality study from NASA Ames (FFC) Future Fight

NASA Technical Reports Server (NTRS)

2002-01-01

Human Robotic Study at Houghton Crater - virtual reality study from NASA Ames (FFC) Future Fight Central simulator tower L-R: Dr Geoffrey Briggs; Jen Jasper (seated); Dr Jan Akins and Mr. Tony Gross, Ames

Design of an efficient framework for fast prototyping of customized human-computer interfaces and virtual environments for rehabilitation.

PubMed

Avola, Danilo; Spezialetti, Matteo; Placidi, Giuseppe

2013-06-01

Rehabilitation is often required after stroke, surgery, or degenerative diseases. It has to be specific for each patient and can be easily calibrated if assisted by human-computer interfaces and virtual reality. Recognition and tracking of different human body landmarks represent the basic features for the design of the next generation of human-computer interfaces. The most advanced systems for capturing human gestures are focused on vision-based techniques which, on the one hand, may require compromises from real-time and spatial precision and, on the other hand, ensure natural interaction experience. The integration of vision-based interfaces with thematic virtual environments encourages the development of novel applications and services regarding rehabilitation activities. The algorithmic processes involved during gesture recognition activity, as well as the characteristics of the virtual environments, can be developed with different levels of accuracy. This paper describes the architectural aspects of a framework supporting real-time vision-based gesture recognition and virtual environments for fast prototyping of customized exercises for rehabilitation purposes. The goal is to provide the therapist with a tool for fast implementation and modification of specific rehabilitation exercises for specific patients, during functional recovery. Pilot examples of designed applications and preliminary system evaluation are reported and discussed. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

A rapid algorithm for realistic human reaching and its use in a virtual reality system

NASA Technical Reports Server (NTRS)

Aldridge, Ann; Pandya, Abhilash; Goldsby, Michael; Maida, James

1994-01-01

The Graphics Analysis Facility (GRAF) at JSC has developed a rapid algorithm for computing realistic human reaching. The algorithm was applied to GRAF's anthropometrically correct human model and used in a 3D computer graphics system and a virtual reality system. The nature of the algorithm and its uses are discussed.

The Socioemotional Effects of a Computer-Simulated Animal on Children's Empathy and Humane Attitudes

ERIC Educational Resources Information Center

Tsai, Yueh-Feng Lily; Kaufman, David M.

2009-01-01

This study investigated the potential of using a computer-simulated animal in a handheld virtual pet videogame to improve children's empathy and humane attitudes. Also investigated was whether sex differences existed in children's development of empathy and humane attitudes resulting from play, as well as their feelings for a virtual pet. The…

VERDEX: A virtual environment demonstrator for remote driving applications

NASA Technical Reports Server (NTRS)

Stone, Robert J.

1991-01-01

One of the key areas of the National Advanced Robotics Centre's enabling technologies research program is that of the human system interface, phase 1 of which started in July 1989 and is currently addressing the potential of virtual environments to permit intuitive and natural interactions between a human operator and a remote robotic vehicle. The aim of the first 12 months of this program (to September, 1990) is to develop a virtual human-interface demonstrator for use later as a test bed for human factors experimentation. This presentation will describe the current state of development of the test bed, and will outline some human factors issues and problems for more general discussion. In brief, the virtual telepresence system for remote driving has been designed to take the following form. The human operator will be provided with a helmet-mounted stereo display assembly, facilities for speech recognition and synthesis (using the Marconi Macrospeak system), and a VPL DataGlove Model 2 unit. The vehicle to be used for the purposes of remote driving is a Cybermotion Navmaster K2A system, which will be equipped with a stereo camera and microphone pair, mounted on a motorized high-speed pan-and-tilt head incorporating a closed-loop laser ranging sensor for camera convergence control (currently under contractual development). It will be possible to relay information to and from the vehicle and sensory system via an umbilical or RF link. The aim is to develop an interactive audio-visual display system capable of presenting combined stereo TV pictures and virtual graphics windows, the latter featuring control representations appropriate for vehicle driving and interaction using a graphical 'hand,' slaved to the flex and tracking sensors of the DataGlove and an additional helmet-mounted Polhemus IsoTrack sensor. Developments planned for the virtual environment test bed include transfer of operator control between remote driving and remote manipulation, dexterous end effector integration, virtual force and tactile sensing (also the focus of a current ARRL contract, initially employing a 14-pneumatic bladder glove attachment), and sensor-driven world modeling for total virtual environment generation and operator-assistance in remote scene interrogation.

Height effects in real and virtual environments.

PubMed

Simeonov, Peter I; Hsiao, Hongwei; Dotson, Brian W; Ammons, Douglas E

2005-01-01

The study compared human perceptions of height, danger, and anxiety, as well as skin conductance and heart rate responses and postural instability effects, in real and virtual height environments. The 24 participants (12 men, 12 women), whose average age was 23.6 years, performed "lean-over-the-railing" and standing tasks on real and comparable virtual balconies, using a surround-screen virtual reality (SSVR) system. The results indicate that the virtual display of elevation provided realistic perceptual experience and induced some physiological responses and postural instability effects comparable to those found in a real environment. It appears that a simulation of elevated work environment in a SSVR system, although with reduced visual fidelity, is a valid tool for safety research. Potential applications of this study include the design of virtual environments that will help in safe evaluation of human performance at elevation, identification of risk factors leading to fall incidents, and assessment of new fall prevention strategies.

Shader Lamps Virtual Patients: the physical manifestation of virtual patients.

PubMed

Rivera-Gutierrez, Diego; Welch, Greg; Lincoln, Peter; Whitton, Mary; Cendan, Juan; Chesnutt, David A; Fuchs, Henry; Lok, Benjamin

2012-01-01

We introduce the notion of Shader Lamps Virtual Patients (SLVP) - the combination of projector-based Shader Lamps Avatars and interactive virtual humans. This paradigm uses Shader Lamps Avatars technology to give a 3D physical presence to conversational virtual humans, improving their social interactivity and enabling them to share the physical space with the user. The paradigm scales naturally to multiple viewers, allowing for scenarios where an instructor and multiple students are involved in the training. We have developed a physical-virtual patient for medical students to conduct ophthalmic exams, in an interactive training experience. In this experience, the trainee practices multiple skills simultaneously, including using a surrogate optical instrument in front of a physical head, conversing with the patient about his fears, observing realistic head motion, and practicing patient safety. Here we present a prototype system and results from a preliminary formative evaluation of the system.

[The virtual library in equity, health, and human development].

PubMed

Valdés, América

2002-01-01

This article attempts to describe the rationale that has led to the development of information sources dealing with equity, health, and human development in countries of Latin America and the Caribbean within the context of the Virtual Health Library (Biblioteca Virtual en Salud, BVS). Such information sources include the scientific literature, databases in printed and electronic format, institutional directories and lists of specialists, lists of events and courses, distance education programs, specialty journals and bulletins, as well as other means of disseminating health information. The pages that follow deal with the development of a Virtual Library in Equity, Health, and Human Development, an effort rooted in the conviction that decision-making and policy geared toward achieving greater equity in health must, of necessity, be based on coherent, well-organized, and readily accessible first-rate scientific information. Information is useless unless it is converted into knowledge that benefits society. The Virtual Library in Equity, Health, and Human Development is a coordinated effort to develop a decentralized regional network of scientific information sources, with strict quality control, from which public officials can draw data and practical examples that can help them set health and development policies geared toward achieving greater equity for all.

The NASA Augmented/Virtual Reality Lab: The State of the Art at KSC

NASA Technical Reports Server (NTRS)

Little, William

2017-01-01

The NASA Augmented Virtual Reality (AVR) Lab at Kennedy Space Center is dedicated to the investigation of Augmented Reality (AR) and Virtual Reality (VR) technologies, with the goal of determining potential uses of these technologies as human-computer interaction (HCI) devices in an aerospace engineering context. Begun in 2012, the AVR Lab has concentrated on commercially available AR and VR devices that are gaining in popularity and use in a number of fields such as gaming, training, and telepresence. We are working with such devices as the Microsoft Kinect, the Oculus Rift, the Leap Motion, the HTC Vive, motion capture systems, and the Microsoft Hololens. The focus of our work has been on human interaction with the virtual environment, which in turn acts as a communications bridge to remote physical devices and environments which the operator cannot or should not control or experience directly. Particularly in reference to dealing with spacecraft and the oftentimes hazardous environments they inhabit, it is our hope that AR and VR technologies can be utilized to increase human safety and mission success by physically removing humans from those hazardous environments while virtually putting them right in the middle of those environments.

Varieties of virtualization

NASA Technical Reports Server (NTRS)

Ellis, Stephen R.

1991-01-01

Natural environments have a content, i.e., the objects in them; a geometry, i.e., a pattern of rules for positioning and displacing the objects; and a dynamics, i.e., a system of rules describing the effects of forces acting on the objects. Human interaction with most common natural environments has been optimized by centuries of evolution. Virtual environments created through the human-computer interface similarly have a content, geometry, and dynamics, but the arbitrary character of the computer simulation creating them does not insure that human interaction with these virtual environments will be natural. The interaction, indeed, could be supernatural but it also could be impossible. An important determinant of the comprehensibility of a virtual environment is the correspondence between the environmental frames of reference and those associated with the control of environmental objects. The effects of rotation and displacement of control frames of reference with respect to corresponding environmental references differ depending upon whether perceptual judgement or manual tracking performance is measured. The perceptual effects of frame of reference displacement may be analyzed in terms of distortions in the process of virtualizing the synthetic environment space. The effects of frame of reference displacement and rotation have been studied by asking subjects to estimate exocentric direction in a virtual space.

2D and 3D Traveling Salesman Problem

ERIC Educational Resources Information Center

Haxhimusa, Yll; Carpenter, Edward; Catrambone, Joseph; Foldes, David; Stefanov, Emil; Arns, Laura; Pizlo, Zygmunt

2011-01-01

When a two-dimensional (2D) traveling salesman problem (TSP) is presented on a computer screen, human subjects can produce near-optimal tours in linear time. In this study we tested human performance on a real and virtual floor, as well as in a three-dimensional (3D) virtual space. Human performance on the real floor is as good as that on a…

The Human Element in the Virtual Library.

ERIC Educational Resources Information Center

Saunders, Laverna M.

1999-01-01

Introduces the concept of the virtual library and explores how the increasing reliance on computers and digital information has affected library users and staff. Discusses users' expectations, democratization of access, human issues, organizational change, technostress, ergonomics, assessment, and strategies for success and survival. Contains 35…

Is there a superior simulator for human anatomy education? How virtual dissection can overcome the anatomic and pedagogic limitations of cadaveric dissection.

PubMed

Darras, Kathryn E; de Bruin, Anique B H; Nicolaou, Savvas; Dahlström, Nils; Persson, Anders; van Merriënboer, Jeroen; Forster, Bruce B

2018-03-23

Educators must select the best tools to teach anatomy to future physicians and traditionally, cadavers have always been considered the "gold standard" simulator for living anatomy. However, new advances in technology and radiology have created new teaching tools, such as virtual dissection, which provide students with new learning opportunities. Virtual dissection is a novel way of studying human anatomy through patient computed tomography (CT) scans. Through touchscreen technology, students can work together in groups to "virtually dissect" the CT scans to better understand complex anatomic relationships. This article presents the anatomic and pedagogic limitations of cadaveric dissection and explains what virtual dissection is and how this new technology may be used to overcome these limitations.

Human Pacman: A Mobile Augmented Reality Entertainment System Based on Physical, Social, and Ubiquitous Computing

NASA Astrophysics Data System (ADS)

Cheok, Adrian David

This chapter details the Human Pacman system to illuminate entertainment computing which ventures to embed the natural physical world seamlessly with a fantasy virtual playground by capitalizing on infrastructure provided by mobile computing, wireless LAN, and ubiquitous computing. With Human Pacman, we have a physical role-playing computer fantasy together with real human-social and mobile-gaming that emphasizes on collaboration and competition between players in a wide outdoor physical area that allows natural wide-area human-physical movements. Pacmen and Ghosts are now real human players in the real world experiencing mixed computer graphics fantasy-reality provided by using the wearable computers on them. Virtual cookies and actual tangible physical objects are incorporated into the game play to provide novel experiences of seamless transitions between the real and virtual worlds. This is an example of a new form of gaming that anchors on physicality, mobility, social interaction, and ubiquitous computing.

NASA Virtual Institutes: International Bridges for Space Exploration

NASA Technical Reports Server (NTRS)

Schmidt, Gregory K.

2016-01-01

NASA created the first virtual institute, the NASA Astrobiology Institute (NAI), in 2009 with an aim toward bringing together geographically disparate and multidisciplinary teams toward the goal of answering broad questions in the then-new discipline of astrobiology. With the success of the virtual institute model, NASA then created the NASA Lunar Science Institute (NLSI) in 2008 to address questions of science and human exploration of the Moon, and then the NASA Aeronautics Research Institute (NARI) in 2012 which addresses key questions in the development of aeronautics technologies. With the broadening of NASA's human exploration targets to include Near Earth Asteroids and the moons of Mars as well as the Moon, the NLSI morphed into the Solar System Exploration Research Virtual Institute (SSERVI) in 2012. SSERVI funds domestic research teams to address broad questions at the intersection of science and human exploration, with the underlying principle that science enables human exploration, and human exploration enables science. Nine domestic teams were funded in 2014 for a five-year period to address a variety of different topics, and nine international partners (with more to come) also work with the U.S. teams on a variety of topics of mutual interest. The result is a robust and productive research infrastructure that is not only scientifically productive but can respond to strategic topics of domestic and international interest, and which develops a new generation of researchers. This is all accomplished with the aid of virtual collaboration technologies which enable scientific research at a distance. The virtual institute model is widely applicable to a range of space science and exploration problems.

Using new non-invasive quick method to detect Borrelia Burgdorferi (B.B.) infection from specific parts of the heart in "seemingly normal" ECGs, and from the ECGs of Atrial Fibrillation (AF), a majority of AF ECGs are found to have: 1) Significant B.B. infection, 2) Markedly increased ANP, 3) Increased Cardiac Troponin I & 4) Markedly reduced Taurine. These 4 factors were mainly localized at infected areas of the SA node area, R-&L-Atria & pulmonary veins at the L-atrium.

PubMed

Omura, Yoshiaki; Lu, Dominic; Jones, Marilyn K; Nihrane, Abdallah; Duvvi, Harsha; Yapor, Dario; Shimotsuura, Yasuhiro; Ohki, Motomu

2015-01-01

Lyme disease is found in a majority of people we tested. Once Borrelia Burgdorferi (B.B.) spirochete enters human body, it not only causes pain by infecting joints, but it also often enters the brain and the heart. Infection of brain can be quickly detected from the pupil and infection of the heart by ECGs non-invasively. By evaluating recorded ECGs of atrial fibrillation (AF), using U.S. patented non-invasive highly sensitive electromagnetic field (EMF) resonance phenomenon between 2 identical molecules or between a molecule and its antibody, we examined 25 different AF patients' ECGs and found the majority of them suffer from various degrees of B.B. spirochete infection in SA node areas, also in the right & left atria, and pulmonary vein near and around its junction at left atrium & lesser degrees of infection at the AV node & His Bundle. When B.B. infection reaches over 224-600ng or higher at these areas, AF often appears in the majority of all AF analyzed. In order to develop AF, the 4 abnormal factors must be present simultaneously: 1) B.B. infection must be increased to 224-600ng or higher, 2) Atrial Natriuretic Peptide (ANP) must be markedly reduced from normal value of less than 4ng to over 100-400ng, 3) A significant increase of Cardiac Troponin I from normal value of less than 3ng to over 12ng and 4) Taurine must also be markedly reduced from normal value of 4-6ng to 0.25ng. These 4 changes were mainly found only at infected sites of the SA node area, both atria and between the end of the T wave & the beginning of the SA node area, which corresponds to U waves at recorded ECG. Origin of the U wave is mainly due to abnormal electrical potential of pulmonary vein at L-atrium. If all 4 factors do not occur at the infection site, no AF will develop. In seemingly normal ECGs, if using this method, one can detect invisible B.B. infection in early stages. Long before AF appears, AF can be prevented by improved treatment with Amoxicillin 500ng 3 times/day + Taurine 175mg x 3 times/day, with or without EPA 180 mg & DHA 120 mg, to avoid serious current limitations in the use of Doxycycline 100 mg 2 times/day, for 4 weeks.

Virtual Economies: Threats and Risks

NASA Astrophysics Data System (ADS)

Thorpe, Christopher; Hammer, Jessica; Camp, Jean; Callas, Jon; Bond, Mike

In virtual economies, human and computer players produce goods and services, hold assets, and trade them with other in-game entities, in the same way that people and corporations participate in "real-world" economies. As the border between virtual worlds and the real world grows more and more permeable, privacy and security in virtual worlds matter more and more.

The Virtual Liver Project: Simulating Tissue Injury Through Molecular and Cellular Processes

EPA Science Inventory

Efficiently and humanely testing the safety of thousands of environmental chemicals is a challenge. The US EPA Virtual Liver Project (v-Liver™) is aimed at simulating the effects of environmental chemicals computationally in order to estimate the risk of toxic outcomes in humans...

Modulation of thermal pain-related brain activity with virtual reality: evidence from fMRI.

PubMed

Hoffman, Hunter G; Richards, Todd L; Coda, Barbara; Bills, Aric R; Blough, David; Richards, Anne L; Sharar, Sam R

2004-06-07

This study investigated the neural correlates of virtual reality analgesia. Virtual reality significantly reduced subjective pain ratings (i.e. analgesia). Using fMRI, pain-related brain activity was measured for each participant during conditions of no virtual reality and during virtual reality (order randomized). As predicted, virtual reality significantly reduced pain-related brain activity in all five regions of interest; the anterior cingulate cortex, primary and secondary somatosensory cortex, insula, and thalamus (p<0.002, corrected). Results showed direct modulation of human brain pain responses by virtual reality distraction. Copyright 2004 Lippincott Williams and Wilkins

Clinically Normal Stereopsis Does Not Ensure Performance Benefit from Stereoscopic 3D Depth Cues

DTIC Science & Technology

2014-10-28

Stereopsis, Binocular Vision, Optometry , Depth Perception, 3D vision, 3D human factors, Stereoscopic displays, S3D, Virtual environment 16...Binocular Vision, Optometry , Depth Perception, 3D vision, 3D human factors, Stereoscopic displays, S3D, Virtual environment 1 Distribution A: Approved

An intelligent control and virtual display system for evolutionary space station workstation design

NASA Technical Reports Server (NTRS)

Feng, Xin; Niederjohn, Russell J.; Mcgreevy, Michael W.

1992-01-01

Research and development of the Advanced Display and Computer Augmented Control System (ADCACS) for the space station Body-Ported Cupola Virtual Workstation (BP/VCWS) were pursued. The potential applications were explored of body ported virtual display and intelligent control technology for the human-system interfacing applications is space station environment. The new system is designed to enable crew members to control and monitor a variety of space operations with greater flexibility and efficiency than existing fixed consoles. The technologies being studied include helmet mounted virtual displays, voice and special command input devices, and microprocessor based intelligent controllers. Several research topics, such as human factors, decision support expert systems, and wide field of view, color displays are being addressed. The study showed the significant advantages of this uniquely integrated display and control system, and its feasibility for human-system interfacing applications in the space station command and control environment.

Developing Trust in Virtual Teams

ERIC Educational Resources Information Center

Germain, Marie-Line

2011-01-01

Rapid globalization, advances in technology, flatter organizational structures, synergistic cooperation among firms, and a shift to knowledge work environments have led to the increasing use of virtual teams in organizations. Selecting, training, and socializing employees in virtual teamwork has therefore become an important human resource…

ENVIRONMENTAL REMOTE SENSING ANALYSIS USING OPEN SOURCE VIRTUAL EARTHS AND PUBLIC DOMAIN IMAGERY

EPA Science Inventory

Human activities increasingly impact natural environments. Globally, many ecosystems are stressed to unhealthy limits, leading to loss of valuable ecosystem services- economic, ecologic and intrinsic. Virtual earths (virtual globes) (-e.g., NASA World Wind, ossimPlanet, ArcGIS...

Exploring Learner Acceptance of the Use of Virtual Reality in Medical Education: A Case Study of Desktop and Projection-Based Display Systems

ERIC Educational Resources Information Center

Huang, Hsiu-Mei; Liaw, Shu-Sheng; Lai, Chung-Min

2016-01-01

Advanced technologies have been widely applied in medical education, including human-patient simulators, immersive virtual reality Cave Automatic Virtual Environment systems, and video conferencing. Evaluating learner acceptance of such virtual reality (VR) learning environments is a critical issue for ensuring that such technologies are used to…

Anatomical education and surgical simulation based on the Chinese Visible Human: a three-dimensional virtual model of the larynx region.

PubMed

Liu, Kaijun; Fang, Binji; Wu, Yi; Li, Ying; Jin, Jun; Tan, Liwen; Zhang, Shaoxiang

2013-09-01

Anatomical knowledge of the larynx region is critical for understanding laryngeal disease and performing required interventions. Virtual reality is a useful method for surgical education and simulation. Here, we assembled segmented cross-section slices of the larynx region from the Chinese Visible Human dataset. The laryngeal structures were precisely segmented manually as 2D images, then reconstructed and displayed as 3D images in the virtual reality Dextrobeam system. Using visualization and interaction with the virtual reality modeling language model, a digital laryngeal anatomy instruction was constructed using HTML and JavaScript languages. The volume larynx models can thus display an arbitrary section of the model and provide a virtual dissection function. This networked teaching system of the digital laryngeal anatomy can be read remotely, displayed locally, and manipulated interactively.

An interactive three-dimensional virtual body structures system for anatomical training over the internet.

PubMed

Temkin, Bharti; Acosta, Eric; Malvankar, Ameya; Vaidyanath, Sreeram

2006-04-01

The Visible Human digital datasets make it possible to develop computer-based anatomical training systems that use virtual anatomical models (virtual body structures-VBS). Medical schools are combining these virtual training systems and classical anatomy teaching methods that use labeled images and cadaver dissection. In this paper we present a customizable web-based three-dimensional anatomy training system, W3D-VBS. W3D-VBS uses National Library of Medicine's (NLM) Visible Human Male datasets to interactively locate, explore, select, extract, highlight, label, and visualize, realistic 2D (using axial, coronal, and sagittal views) and 3D virtual structures. A real-time self-guided virtual tour of the entire body is designed to provide detailed anatomical information about structures, substructures, and proximal structures. The system thus facilitates learning of visuospatial relationships at a level of detail that may not be possible by any other means. The use of volumetric structures allows for repeated real-time virtual dissections, from any angle, at the convenience of the user. Volumetric (3D) virtual dissections are performed by adding, removing, highlighting, and labeling individual structures (and/or entire anatomical systems). The resultant virtual explorations (consisting of anatomical 2D/3D illustrations and animations), with user selected highlighting colors and label positions, can be saved and used for generating lesson plans and evaluation systems. Tracking users' progress using the evaluation system helps customize the curriculum, making W3D-VBS a powerful learning tool. Our plan is to incorporate other Visible Human segmented datasets, especially datasets with higher resolutions, that make it possible to include finer anatomical structures such as nerves and small vessels. (c) 2006 Wiley-Liss, Inc.

Virtual fixtures as tools to enhance operator performance in telepresence environments

NASA Astrophysics Data System (ADS)

Rosenberg, Louis B.

1993-12-01

This paper introduces the notion of virtual fixtures for use in telepresence systems and presents an empirical study which demonstrates that such virtual fixtures can greatly enhance operator performance within remote environments. Just as tools and fixtures in the real world can enhance human performance by guiding manual operations, providing localizing references, and reducing the mental processing required to perform a task, virtual fixtures are computer generated percepts overlaid on top of the reflection of a remote workspace which can provide similar benefits. Like a ruler guiding a pencil in a real manipulation task, a virtual fixture overlaid on top of a remote workspace can act to reduce the mental processing required to perform a task, limit the workload of certain sensory modalities, and most of all allow precision and performance to exceed natural human abilities. Because such perceptual overlays are virtual constructions they can be diverse in modality, abstract in form, and custom tailored to individual task or user needs. This study investigates the potential of virtual fixtures by implementing simple combinations of haptic and auditory sensations as perceptual overlays during a standardized telemanipulation task.

75 FR 17756 - Blackstone River Valley National Heritage Corridor Commission: Notice of Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-07

... Corridor Commission: Notice of Meeting Notice is hereby given in accordance with Section 552b of Title 5... Corridor Commission will be held on Thursday, May 20, 2010. The Commission was established pursuant to... Corridor. The meeting will convene on May 20, 2010 at 9 a.m. at Atria Draper Place located at 25 Hopedale...

Cardiomyocyte marker expression in dogs with left atrial enlargement due to dilated cardiomyopathy or myxomatous mitral valve disease.

PubMed

Janus, Izabela; Kandefer-Gola, Malgorzata; Ciaputa, Rafal; Noszczyk-Nowak, Agnieszka; Paslawska, Urszula; Tursi, Massimiliano; Nowak, Marcin

2017-01-01

Dilated cardiomyopathy (DCM) and myxomatous mitral valve disease (MMVD) are common heart conditions in dogs. They have different etiology and pathogenesis and although other studies focused on changes in the left ventricles of the affected hearts, the aim of our study was to assess the expressions of some intrinsic proteins in the enlarged left atria. We performed an immunohistochemical analysis of left atrial specimens obtained from 15 dogs with DCM, 35 dogs with MMVD and six control dogs. We assessed the expression of following proteins: SERCA1, SERCA2, sarcomeric actinin, smooth muscle actin, and dystrophin. We noted a higher percentage of SERCA1-positive cells in the MMVD group and lower percentage of dystrophin-positive cells in the DCM group as compared to control group. The expression of other proteins was similar in the hearts of control dogs and dogs with heart diseases. The observed changes in the expression patterns of some proteins in the atria of dogs with DCM and MMVD suggest that atrial enlargement relies not only on volume overload, but also alterations of the intrinsic proteins can contribute to the pathogenesis of dilated cardiomyopathy.

Optimal pacing modes after cardiac transplantation: is synchronisation of recipient and donor atria beneficial?

PubMed Central

Parry, Gareth; Malbut, Katie; Dark, John H; Bexton, Rodney S

1992-01-01

Objective—To investigate the response of the transplanted heart to different pacing modes and to synchronisation of the recipient and donor atria in terms of cardiac output at rest. Design—Doppler derived cardiac output measurements at three pacing rates (90/min, 110/min and 130/min) in five pacing modes: right ventricular pacing, donor atrial pacing, recipient-donor synchronous pacing, donor atrial-ventricular sequential pacing, and synchronous recipient-donor atrial-ventricular sequential pacing. Patients—11 healthy cardiac transplant recipients with three pairs of epicardial leads inserted at transplantation. Results—Donor atrial pacing (+11% overall) and donor atrial-ventricular sequential pacing (+8% overall) were significantly better than right ventricular pacing (p < 0·001) at all pacing rates. Synchronised pacing of recipient and donor atrial segments did not confer additional benefit in either atrial or atrial-ventricular sequential modes of pacing in terms of cardiac output at rest at these fixed rates. Conclusions—Atrial pacing or atrial-ventricular sequential pacing appear to be appropriate modes in cardiac transplant recipients. Synchronisation of recipient and donor atrial segments in this study produced no additional benefit. Chronotropic competence in these patients may, however, result in improved exercise capacity and deserves further investigation. PMID:1389737

Atrial natriuretic peptide synthesis in atrial tumors of transgenic mice.

PubMed

Gardner, D G; Camargo, M J; Behringer, R R; Brinster, R L; Baxter, J D; Atlas, S A; Laragh, J H; Deschepper, C F

1992-04-01

Transgenic mice harboring a chimeric gene linking mouse protamine 1 5'-flanking sequence to the coding sequence of the simian virus 40 T-antigen develop spontaneous rhabdomyosarcomas of the right atria. The presence of the tumors is accompanied by dramatic elevations in plasma atrial natriuretic peptide (ANP) immunoreactivity (1,698 +/- 993 vs. 60 +/- 18 fmol/ml for controls) and hematocrit (56 +/- 8 vs. 51 +/- 2 for controls). The immunoreactive ANP (irANP) present in the tumors is similar in size to irANP found in normal mouse atria. ANP mRNA transcripts present in the tumors also appear to be very similar in overall size and 5'-termini to those produced in normal cardiac tissue. Microscopically, the tumors are composed of a disorganized array of densely packed abnormal-appearing cells. Immunocytochemistry and in situ hybridization analysis reveal considerable heterogeneity in ANP gene expression. ANP peptide and mRNA are detectable throughout the parenchyma of the tumors, but absolute levels of expression vary widely among different cells in the population. These tumors represent a potentially valuable model for the study of inappropriate ANP secretion and may provide a tissue source for the development of an ANP-producing atrial cell line.

Association of Atrial Fibrillation with Morphological and Electrophysiological Changes of the Atrial Myocardium.

PubMed

Matějková, Adéla; Šteiner, Ivo

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. For long time it was considered as pure functional disorder, but in recent years, there were identified atrial locations, which are involved in the initiation and maintenance of this arrhythmia. These structural changes, so called remodelation, start at electric level and later they affect contractility and morphology. In this study we attempted to find a possible relation between morphological (scarring, amyloidosis, left atrial (LA) enlargement) and electrophysiological (ECG features) changes in patients with AF. We examined grossly and histologically 100 hearts of necropsy patients - 54 with a history of AF and 46 without AF. Premortem ECGs were evaluated. The patients with AF had significantly heavier heart, larger LA, more severely scarred myocardium of the LA and atrial septum, and more severe amyloidosis in both atria. Severity of amyloidosis was higher in LAs vs. right atria (RAs). Distribution of both fibrosis and amyloidosis was irregular. The most affected area was in the LA anterior wall. Patients with a history of AF and with most severe amyloidosis have more often abnormally long P waves. Finding of long P wave may contribute to diagnosis of a hitherto undisclosed atrial fibrillation.

Recognition profile of emotions in natural and virtual faces.

PubMed

Dyck, Miriam; Winbeck, Maren; Leiberg, Susanne; Chen, Yuhan; Gur, Ruben C; Gur, Rurben C; Mathiak, Klaus

2008-01-01

Computer-generated virtual faces become increasingly realistic including the simulation of emotional expressions. These faces can be used as well-controlled, realistic and dynamic stimuli in emotion research. However, the validity of virtual facial expressions in comparison to natural emotion displays still needs to be shown for the different emotions and different age groups. Thirty-two healthy volunteers between the age of 20 and 60 rated pictures of natural human faces and faces of virtual characters (avatars) with respect to the expressed emotions: happiness, sadness, anger, fear, disgust, and neutral. Results indicate that virtual emotions were recognized comparable to natural ones. Recognition differences in virtual and natural faces depended on specific emotions: whereas disgust was difficult to convey with the current avatar technology, virtual sadness and fear achieved better recognition results than natural faces. Furthermore, emotion recognition rates decreased for virtual but not natural faces in participants over the age of 40. This specific age effect suggests that media exposure has an influence on emotion recognition. Virtual and natural facial displays of emotion may be equally effective. Improved technology (e.g. better modelling of the naso-labial area) may lead to even better results as compared to trained actors. Due to the ease with which virtual human faces can be animated and manipulated, validated artificial emotional expressions will be of major relevance in future research and therapeutic applications.

Recognition Profile of Emotions in Natural and Virtual Faces

PubMed Central

Dyck, Miriam; Winbeck, Maren; Leiberg, Susanne; Chen, Yuhan; Gur, Rurben C.; Mathiak, Klaus

2008-01-01

Background Computer-generated virtual faces become increasingly realistic including the simulation of emotional expressions. These faces can be used as well-controlled, realistic and dynamic stimuli in emotion research. However, the validity of virtual facial expressions in comparison to natural emotion displays still needs to be shown for the different emotions and different age groups. Methodology/Principal Findings Thirty-two healthy volunteers between the age of 20 and 60 rated pictures of natural human faces and faces of virtual characters (avatars) with respect to the expressed emotions: happiness, sadness, anger, fear, disgust, and neutral. Results indicate that virtual emotions were recognized comparable to natural ones. Recognition differences in virtual and natural faces depended on specific emotions: whereas disgust was difficult to convey with the current avatar technology, virtual sadness and fear achieved better recognition results than natural faces. Furthermore, emotion recognition rates decreased for virtual but not natural faces in participants over the age of 40. This specific age effect suggests that media exposure has an influence on emotion recognition. Conclusions/Significance Virtual and natural facial displays of emotion may be equally effective. Improved technology (e.g. better modelling of the naso-labial area) may lead to even better results as compared to trained actors. Due to the ease with which virtual human faces can be animated and manipulated, validated artificial emotional expressions will be of major relevance in future research and therapeutic applications. PMID:18985152

Assessment of the atrial electromechanical properties of patients with human immunodeficiency virus.

PubMed

Ertem, Ahmet G; Yayla, Çağrı; Açar, Burak; Ünal, Sefa; Erdol, Mehmet A; Sonmezer, Meliha Ç; Kaya Kiliç, Esra; Ataman Hatipoglu, Çiğdem; Gokaslan, Serkan; Kafes, Habibe; Akboga, Mehmet K; Aladag, Pelin; Demirtas, Koray; Tulek, Necla; Erdinç, Fatma S; Aydogdu, Sinan

The relationship between atrial fibrillation and human immunodeficiency virus (HIV) infection was evaluated. Electro-echocardiographic methods can be used to predict the development of atrial fibrillation (AF). In this study, we aimed to investigate the atrial electromechanical delay (AEMD) parameters of HIV (+) patients. Forty-two HIV (+) patients and 40 HIV (-) healthy volunteers were prospectively enrolled in this study. The electromechanical properties of the subjects' atria were evaluated with tissue Doppler imaging. The left-AEMD, right-AEMD and inter-AEMD were increased in the HIV (+) patients relative to the controls (p=0.003, p<0.001, and p<0.001, respectively). The CD4 count was inversely correlated with the inter-AEMD (r=-0.428, p<0.001). The CD4 count was an independent predictor of the inter-AEMD (β=0.523, p=0.007). Our study demonstrated that both the inter- and intra-atrial electromechanical delays were prolonged in the patients with HIV. This non-invasive and simple technique may provide significant contributions to the assessment of the risk of atrial arrhythmia in patients with HIV. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Effects of telework and the virtual enterprise on the organization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, R.A.

1996-12-31

This paper provides information on the growing trend towards telework and using {open_quotes}virtual employees{close_quotes} as a fundamental component of the human resource requirements for the conduct of business. As the organization moves from a traditional approach of fixed plant and permanent employees toward a more dynamic model of motile office arrangements and virtual workers, new challenges arise for workers, supervisors, and managers. These challenges pertain to both the individual and the organization and are rooted in both technology and human behavior. Notwithstanding the challenges, the opportunities created for increased productivity and cost-effective operations are propelling organizations globally to adopt themore » virtual enterprise model, to a greater or lesser extent. Management hierarchy is giving way to autonomous teams. Middle management is being replaced by better organizational communication systems, better information storage and retrieval systems, and a newly developing classification of software called groupware. In the midst of these changes, the business process of identifying and acquiring the services of the virtual team member seems to lie at an intersection where Human Resources, Information Systems, Contracts/Subcontracts, and the functional department requiring the services intersect. Human Resources departments are slowly coming to grips with the virtual worker model but are largely uncomfortable in the role. Information Systems departments can implement networks; but, dynamic links outside the traditional organization bring up a myriad of questions about compatibility and system security. The champion of the virtual worker is the Functional Department. This might be engineering, software development, the design department, the financial analysis group, or whichever department in the organization is faced with the responsibility of creating knowledge work product and has resource constraints and upper management support.« less

Suitability of virtual prototypes to support human factors/ergonomics evaluation during the design.

PubMed

Aromaa, Susanna; Väänänen, Kaisa

2016-09-01

In recent years, the use of virtual prototyping has increased in product development processes, especially in the assessment of complex systems targeted at end-users. The purpose of this study was to evaluate the suitability of virtual prototyping to support human factors/ergonomics evaluation (HFE) during the design phase. Two different virtual prototypes were used: augmented reality (AR) and virtual environment (VE) prototypes of a maintenance platform of a rock crushing machine. Nineteen designers and other stakeholders were asked to assess the suitability of the prototype for HFE evaluation. Results indicate that the system model characteristics and user interface affect the experienced suitability. The VE system was valued as being more suitable to support the assessment of visibility, reach, and the use of tools than the AR system. The findings of this study can be used as a guidance for the implementing virtual prototypes in the product development process. Copyright © 2016 Elsevier Ltd. All rights reserved.

Agency and Gender Influence Older Adults' Presence-Related Experiences in an Interactive Virtual Environment.

PubMed

Kothgassner, Oswald D; Goreis, Andreas; Kafka, Johanna X; Hlavacs, Helmut; Beutl, Leon; Kryspin-Exner, Ilse; Felnhofer, Anna

2018-05-01

While virtual humans are increasingly used to benefit the elderly, considerably little is still known about older adults' virtual experiences. However, due to age-related changes, older adults' perceptions of virtual environments (VEs) may be unique. Hence, our objective was to examine possible gender differences in immersion, flow, and emotional states as well as physical and social presence in elderly males and females interacting either with a computer-controlled agent or a human-controlled avatar. Seventy-eight German-speaking older adults were randomly assigned to an avatar or an agent condition and were exposed to a brief social encounter in a virtual café. Results indicate no overall gender differences, but a significant effect of agency on social presence, physical presence, immersion, and flow. Participants in the avatar condition reported higher levels in all measures, except for involvement. Furthermore, significant gender × agency interactions were found, with females showing more social presence, spatial presence, and flow when interacting with a human-controlled avatar and more realism when conversing with an agent. Also, all participants showed significant changes in their affect post exposure. In sum, older adults' virtual experiences seem to follow unique patterns, yet, they do not preclude the elderly from successfully participating in VEs.

An immersive virtual peer for studying social influences on child cyclists' road-crossing behavior.

PubMed

Babu, Sabarish V; Grechkin, Timofey Y; Chihak, Benjamin; Ziemer, Christine; Kearney, Joseph K; Cremer, James F; Plumert, Jodie M

2011-01-01

The goal of our work is to develop a programmatically controlled peer to bicycle with a human subject for the purpose of studying how social interactions influence road-crossing behavior. The peer is controlled through a combination of reactive controllers that determine the gross motion of the virtual bicycle, action-based controllers that animate the virtual bicyclist and generate verbal behaviors, and a keyboard interface that allows an experimenter to initiate the virtual bicyclist's actions during the course of an experiment. The virtual bicyclist's repertoire of behaviors includes road following, riding alongside the human rider, stopping at intersections, and crossing intersections through specified gaps in traffic. The virtual cyclist engages the human subject through gaze, gesture, and verbal interactions. We describe the structure of the behavior code and report the results of a study examining how 10- and 12-year-old children interact with a peer cyclist that makes either risky or safe choices in selecting gaps in traffic. Results of our study revealed that children who rode with a risky peer were more likely to cross intermediate-sized gaps than children who rode with a safe peer. In addition, children were significantly less likely to stop at the last six intersections after the experience of riding with the risky than the safe peer during the first six intersections. The results of the study and children's reactions to the virtual peer indicate that our virtual peer framework is a promising platform for future behavioral studies of peer influences on children's bicycle riding behavior. © 2011 IEEE Published by the IEEE Computer Society

Human-machine interface for a VR-based medical imaging environment

NASA Astrophysics Data System (ADS)

Krapichler, Christian; Haubner, Michael; Loesch, Andreas; Lang, Manfred K.; Englmeier, Karl-Hans

1997-05-01

Modern 3D scanning techniques like magnetic resonance imaging (MRI) or computed tomography (CT) produce high- quality images of the human anatomy. Virtual environments open new ways to display and to analyze those tomograms. Compared with today's inspection of 2D image sequences, physicians are empowered to recognize spatial coherencies and examine pathological regions more facile, diagnosis and therapy planning can be accelerated. For that purpose a powerful human-machine interface is required, which offers a variety of tools and features to enable both exploration and manipulation of the 3D data. Man-machine communication has to be intuitive and efficacious to avoid long accustoming times and to enhance familiarity with and acceptance of the interface. Hence, interaction capabilities in virtual worlds should be comparable to those in the real work to allow utilization of our natural experiences. In this paper the integration of hand gestures and visual focus, two important aspects in modern human-computer interaction, into a medical imaging environment is shown. With the presented human- machine interface, including virtual reality displaying and interaction techniques, radiologists can be supported in their work. Further, virtual environments can even alleviate communication between specialists from different fields or in educational and training applications.

Creating virtual humans for simulation-based training and planning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stansfield, S.; Sobel, A.

1998-05-12

Sandia National Laboratories has developed a distributed, high fidelity simulation system for training and planning small team Operations. The system provides an immersive environment populated by virtual objects and humans capable of displaying complex behaviors. The work has focused on developing the behaviors required to carry out complex tasks and decision making under stress. Central to this work are techniques for creating behaviors for virtual humans and for dynamically assigning behaviors to CGF to allow scenarios without fixed outcomes. Two prototype systems have been developed that illustrate these capabilities: MediSim, a trainer for battlefield medics and VRaptor, a system formore » planning, rehearsing and training assault operations.« less

Human-Computer Interaction and Virtual Environments

NASA Technical Reports Server (NTRS)

Noor, Ahmed K. (Compiler)

1995-01-01

The proceedings of the Workshop on Human-Computer Interaction and Virtual Environments are presented along with a list of attendees. The objectives of the workshop were to assess the state-of-technology and level of maturity of several areas in human-computer interaction and to provide guidelines for focused future research leading to effective use of these facilities in the design/fabrication and operation of future high-performance engineering systems.

Study of Human Barriers upon Development of Virtual Disciplines at University of Isfahan

ERIC Educational Resources Information Center

Nikoonezhad, Sepideh; Nili, Mohammadreza; Esfahani, Ahmadreza Nasr

2015-01-01

The present study has been carried out to investigate the human barriers of developing virtual majors at Isfahan University; therefore, considering its objective, it is a functional research. It was conducted in combined (quantitative-qualitative) manner via descriptive survey method. In order to do the research, investigating the texts, interview…

Closed-loop dialog model of face-to-face communication with a photo-real virtual human

NASA Astrophysics Data System (ADS)

Kiss, Bernadette; Benedek, Balázs; Szijárto, Gábor; Takács, Barnabás

2004-01-01

We describe an advanced Human Computer Interaction (HCI) model that employs photo-realistic virtual humans to provide digital media users with information, learning services and entertainment in a highly personalized and adaptive manner. The system can be used as a computer interface or as a tool to deliver content to end-users. We model the interaction process between the user and the system as part of a closed loop dialog taking place between the participants. This dialog, exploits the most important characteristics of a face-to-face communication process, including the use of non-verbal gestures and meta communication signals to control the flow of information. Our solution is based on a Virtual Human Interface (VHI) technology that was specifically designed to be able to create emotional engagement between the virtual agent and the user, thus increasing the efficiency of learning and/or absorbing any information broadcasted through this device. The paper reviews the basic building blocks and technologies needed to create such a system and discusses its advantages over other existing methods.

Virtual Scavenger Hunt: An AI-Powered Virtual Environment Designed for Training Individuals in Effective Teamwork, and Analyzing Cross-Cultural Behavior

DTIC Science & Technology

2009-03-20

involved the development of an environment within the Multiverse virtual world, oriented toward allowing individuals to acquire and reinforce skills via...PetBrain software G2: Creation of a scavenger hunt scenario in the Multiverse virtual world, in which humans and AIs can collaboratively play scavenger...carried out by Novamente LLC for AOARD during June 2008 ? February 2009. It involved the development of an environment within the Multiverse virtual world

The human phospholamban gene: structure and expression.

PubMed

McTiernan, C F; Frye, C S; Lemster, B H; Kinder, E A; Ogletree-Hughes, M L; Moravec, C S; Feldman, A M

1999-03-01

Phospholamban, through modulation of sarcoplasmic reticulum calcium-ATPase activity, is a key regulator of cardiac diastolic function. Alterations in phospholamban expression may define parameters of muscle relaxation. In experimental animals, phospholamban is differentially expressed in various striated and smooth muscles, and within the four chambers of the heart. Decreased phospholamban expression within the heart during heart failure has also been observed. Furthermore, regulatory elements of mammalian phospholamban genes remain poorly defined. To extend these studies to humans, we (1) characterized phospholamban expression in various human organs, (2) isolated genomic clones encoding the human phospholamban gene, and (3) prepared human phospholamban promoter/luciferase reporter constructs and performed transient transfection assays to begin identification of regulatory elements. We observed that human ventricle and quadriceps displayed high levels of phospholamban transcripts and proteins, with markedly lower expression observed in smooth muscles, while the right atria also expressed low levels of phospholamban. The human phospholamban gene structure closely resembles that reported for chicken, rabbit, rat, and mouse. Comparison of the human to other mammalian phospholamban genes indicates a marked conservation of sequence for at least 217 bp upstream of the transcription start site, which contains conserved motifs for GATA, CP1/NFY, M-CAT-like, and E-box elements. Transient transfection assays with a series of plasmids containing deleted 5' flanking regions (between -2530 and -66 through +85) showed that sequences between -169 and the CP1-box at -93 were required for maximal promoter activity in neonatal rat cardiomyocytes. Activity of these reporters in HeLa cells was markedly lower than that observed in rat cardiomyocytes, suggesting at least a partial tissue selectivity of these reporter constructs.

Telemanipulation, telepresence, and virtual reality for surgery in the year 2000

NASA Astrophysics Data System (ADS)

Satava, Richard M.

1995-12-01

The new technologic revolution in medicine is based upon information technologies, and telemanipulation, telepresence and virtual reality are essential components. Telepresence surgery returns the look and feel of `open surgery' to the surgeon and promises enhancement of physical capabilities above normal human performance. Virtual reality provides basic medical education, simulation of surgical procedures, medical forces and disaster medicine practice, and virtual prototyping of medical equipment.

Anatomical and spiral wave reentry in a simplified model for atrial electrophysiology.

PubMed

Richter, Yvonne; Lind, Pedro G; Seemann, Gunnar; Maass, Philipp

2017-04-21

For modeling the propagation of action potentials in the human atria, various models have been developed in the past, which take into account in detail the influence of the numerous ionic currents flowing through the cell membrane. Aiming at a simplified description, the Bueno-Orovio-Cherry-Fenton (BOCF) model for electric wave propagation in the ventricle has been adapted recently to atrial physiology. Here, we study this adapted BOCF (aBOCF) model with respect to its capability to accurately generate spatio-temporal excitation patterns found in anatomical and spiral wave reentry. To this end, we compare results of the aBOCF model with the more detailed one proposed by Courtemanche, Ramirez and Nattel (CRN model). We find that characteristic features of the reentrant excitation patterns seen in the CRN model are well captured by the aBOCF model. This opens the possibility to study origins of atrial fibrillation based on a simplified but still reliable description. Copyright © 2017 Elsevier Ltd. All rights reserved.

KATP Channels in the Cardiovascular System.

PubMed

Foster, Monique N; Coetzee, William A

2016-01-01

KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease. Copyright © 2016 the American Physiological Society.

Unusual Giant Right Atrium in Rheumatic Mitral Stenosis and Tricuspid Insufficiency

PubMed Central

Anzouan-Kacou, Jean Baptiste; Konin, Christophe; Coulibaly, Iklo; N'guetta, Roland; Adoubi, Anicet; Soya, Esaïe; Boka, Bénédicte

2011-01-01

Dilation and hypertrophy of the atria occur in patients with valvular heart disease especially in mitral regurgitation, mitral stenosis or tricuspid abnormalities. In sub-saharan Africa, rheumatic fever is still the leading cause of valvular heart disease. We report a case of an unusual giant right atrium in context of rheumatic stenosis and severe tricuspid regurgitation in a 58-year-old woman. PMID:24826228

A long-time, high spatiotemporal resolution optical recording system for membrane potential activity via real-time writing to the hard disk.

PubMed

Hirota, Akihiko; Ito, Shin-ichi

2006-06-01

Using real-time hard disk recording, we have developed an optical system for the long-duration detection of changes in membrane potential from 1,020 sites with a high temporal resolution. The signal-to-noise ratio was sufficient for analyzing the spreading pattern of excitatory waves in frog atria in a single sweep.

[Atrial fibrillation as consequence and cause of structural changes of atria].

PubMed

Aparina, O P; Chikhireva, L N; Stukalova, O V; Mironova, N A; Kashtanova, S Iu; Ternovoĭ, S K; Golitsyn, S P

2014-01-01

Changes of atrial structure and function are the contributors of atrial fibrillation clinical course, complications and treatment effectiveness. Effects of inflammation and mechanical stretch on atrial structural remodeling leading to atrial fibrillation are reviewed in the article. Contemporary invasive and non-invasive methods of evaluation (including late gadolinium enhancement magnetic resonance imaging) of patients with atrial structural remodeling in atrial fibrillation are also described.

Enhancement of noradrenaline release by angiotensin II and bradykinin in mouse atria: evidence for cross-talk between Gq/11 protein- and Gi/o protein-coupled receptors

PubMed Central

Cox, S L; Schelb, V; Trendelenburg, A U; Starke, K

2000-01-01

The interaction between α2-autoreceptors and receptors for angiotensin (AT1) and bradykinin (B2) was studied in mouse isolated atria. The preparations were labelled with [3H]-noradrenaline and then superfused with desipramine-containing medium and stimulated electrically. Angiotensin II (10−11–10−7 M), angiotensin III (10−10–10−6 M) and bradykinin (10−11–10−7 M) enhanced the evoked overflow of tritium when preparations were stimulated with conditions that led to marked α2-autoinhibition (120 pulses at 3 Hz), but not when stimulated with conditions that led to little α2-autoinhibition (20 pulses at 50 Hz). Blockade of α-adrenoceptors by phentolamine (1 or 10 μM) reduced or abolished the effect of angiotensin II and bradykinin on the overflow response to 120 pulses at 3 Hz. Addition of the δ-opioid agonist [D-Ser2]-leucine enkephalin-Thr (DSLET, 0.1 μM), or of neuropeptide Y (0.1 μM), together with phentolamine, restored the effect of angiotensin II and bradykinin. The β-adrenoceptor agonist terbutaline (10−9–10−4 M) enhanced the evoked overflow of tritium irrespective of the degree of autoinhibition. The experiments show that (i) a marked prejunctional facilitatory effect of angiotensin and bradykinin in mouse isolated atria requires prejunctional α2-autoinhibition; (ii) in the absence of α2-autoinhibition, activation of other prejunctional Gi/o protein-coupled reeptors, namely opioid and neuropeptide Y receptors, restores a marked effect of angiotensin II and bradykinin; and (iii) the facilitatory effect of terbutaline is not dependent upon the degree of α2-autoinhibition. The findings indicate that the major part of the release-enhancing effect elicited through prejunctional Gq/11 protein-coupled receptors is due to disruption of an ongoing, α2-autoreceptor-triggered Gi/o protein mediated inhibition. PMID:10725257

A comparison of the electrophysiologic and electroanatomic characteristics between the right and left atrium in persistent atrial fibrillation: Is the right atrium a window into the left?

PubMed

Prabhu, Sandeep; Voskoboinik, Aleksandr; McLellan, Alex J A; Peck, Kah Y; Pathik, Bhupesh; Nalliah, Chrishan J; Wong, Geoff R; Azzopardi, Sonia M; Lee, Geoffrey; Mariani, Justin; Ling, Liang-Han; Taylor, Andrew J; Kalman, Jonathan M; Kistler, Peter M

2017-10-01

The right atrium (RA) is readily accessible; however, it is unclear whether changes in the RA are representative of the LA. We performed detailed biatrial electroanatomic mapping to determine the electrophysiological relationship between the atria. Consecutive patients with persistent AF underwent biatrial electroanatomical mapping with a contact force catheter acquiring points with a CF >10 g prior to ablation. Points were analyzed for tissue voltage, complex electrograms, low voltage (<0.5 mV), scar (<0.05 mV), and conduction velocity (CV). Forty patients (mean age 59 ± 9.2 years, AF duration 12.9 ± 9.2 months, LA area: 28 ± 5.2, RA area: 25 ± 6.4 mm 2 , LVEF: 44 ± 15%) underwent mapping during CS pacing. Bipolar voltage (R = 0.57, P <0.001), unipolar voltage (R = 0.68, P <0.001), low voltage (<0.5 nV) (R = 0.48, P = 0.002), fractionation (R = 0.73, P <0.001), and CV (R = 0.49, P = 0.001) correlated well between atria. There was no difference in global bipolar voltage (LA 1.89 ± 0.77 vs. RA 1.77 ± 0.57 mV, P = 0.57); complex electrograms (LA 20% vs. RA 20%, P = 0.99) or low voltage (LA 15% vs. RA 16%, P = 0.84). Global unipolar voltage was significantly higher in the LA compared to the RA (2.95 ± 1.14 vs. 2.28 ± 0.65 mV, P = 0.002) and CV was significantly slower in the RA compared to the LA (0.93 ± 0.15 m/s vs. 1.01 ± 0.19 m/s, P = 0.001). AF is associated with remodeling processes affecting both atria. The more accessible RA provides an insight into the biatrial process associated with AF in various disease states without trans-septal access. © 2017 Wiley Periodicals, Inc.

Virtual Reality Anatomy: Is It Comparable with Traditional Methods in the Teaching of Human Forearm Musculoskeletal Anatomy?

ERIC Educational Resources Information Center

Codd, Anthony M.; Choudhury, Bipasha

2011-01-01

The use of cadavers to teach anatomy is well established, but limitations with this approach have led to the introduction of alternative teaching methods. One such method is the use of three-dimensional virtual reality computer models. An interactive, three-dimensional computer model of human forearm anterior compartment musculoskeletal anatomy…

Understanding Human Perception of Building Categories in Virtual 3d Cities - a User Study

NASA Astrophysics Data System (ADS)

Tutzauer, P.; Becker, S.; Niese, T.; Deussen, O.; Fritsch, D.

2016-06-01

Virtual 3D cities are becoming increasingly important as a means of visually communicating diverse urban-related information. To get a deeper understanding of a human's cognitive experience of virtual 3D cities, this paper presents a user study on the human ability to perceive building categories (e.g. residential home, office building, building with shops etc.) from geometric 3D building representations. The study reveals various dependencies between geometric properties of the 3D representations and the perceptibility of the building categories. Knowledge about which geometries are relevant, helpful or obstructive for perceiving a specific building category is derived. The importance and usability of such knowledge is demonstrated based on a perception-guided 3D building abstraction process.

An experiment on fear of public speaking in virtual reality.

PubMed

Pertaub, D P; Slater, M; Barker, C

2001-01-01

Can virtual reality exposure therapy be used to treat people with social phobia? To answer this question it is vital to known if people will respond to virtual humans (avatars) in a virtual social setting in the same way they would to real humans. If someone is extremely anxious with real people, will they also be anxious when faced with simulated people, despite knowing that the avatars are computer generated? In [17] we described a small pilot study that placed 10 people before a virtual audience. The purpose was to assess the extent to which social anxiety, specifically fear of public speaking, was induced by the virtual audience and the extent of influence of degree of immersion (head mounted display or desktop monitor. The current paper describes a follow up study conducted with 40 subjects and the results clearly show that not only is social anxiety induced by the audience, but the degree of anxiety experienced is directly related to the type of virtual audience feedback the speaker receives. In particular, a hostile negative audience scenario was found to generate strong affect in speakers, regardless of whether or not they normally suffered from fear of public speaking.

Objective structured clinical interview training using a virtual human patient.

PubMed

Parsons, Thomas D; Kenny, Patrick; Ntuen, Celestine A; Pataki, Caroly S; Pato, Michele T; Rizzo, Albert A; St-George, Cheryl; Sugar, Jeffery

2008-01-01

Effective interview skills are a core competency for psychiatry residents and developing psychotherapists. Although schools commonly make use of standardized patients to teach interview skills, the diversity of the scenarios standardized patients can characterize is limited by availability of human actors. Further, there is the economic concern related to the time and money needed to train standardized patients. Perhaps most damaging is the "standardization" of standardized patients -- will they in fact consistently proffer psychometrically reliable and valid interactions with the training clinicians. Virtual Human Agent (VHA) technology has evolved to a point where researchers may begin developing mental health applications that make use of virtual reality patients. The work presented here is a preliminary attempt at what we believe to be a large application area. Herein we describe an ongoing study of our virtual patients (VP). We present an approach that allows novice mental health clinicians to conduct an interview with a virtual character that emulates an adolescent male with conduct disorder. This study illustrates the ways in which a variety of core research components developed at the University of Southern California facilitates the rapid development of mental health applications.

Master-slave system with force feedback based on dynamics of virtual model

NASA Technical Reports Server (NTRS)

Nojima, Shuji; Hashimoto, Hideki

1994-01-01

A master-slave system can extend manipulating and sensing capabilities of a human operator to a remote environment. But the master-slave system has two serious problems: one is the mechanically large impedance of the system; the other is the mechanical complexity of the slave for complex remote tasks. These two problems reduce the efficiency of the system. If the slave has local intelligence, it can help the human operator by using its good points like fast calculation and large memory. The authors suggest that the slave is a dextrous hand with many degrees of freedom able to manipulate an object of known shape. It is further suggested that the dimensions of the remote work space be shared by the human operator and the slave. The effect of the large impedance of the system can be reduced in a virtual model, a physical model constructed in a computer with physical parameters as if it were in the real world. A method to determine the damping parameter dynamically for the virtual model is proposed. Experimental results show that this virtual model is better than the virtual model with fixed damping.

How virtual reality works: illusions of vision in "real" and virtual environments

NASA Astrophysics Data System (ADS)

Stark, Lawrence W.

1995-04-01

Visual illusions abound in normal vision--illusions of clarity and completeness, of continuity in time and space, of presence and vivacity--and are part and parcel of the visual world inwhich we live. These illusions are discussed in terms of the human visual system, with its high- resolution fovea, moved from point to point in the visual scene by rapid saccadic eye movements (EMs). This sampling of visual information is supplemented by a low-resolution, wide peripheral field of view, especially sensitive to motion. Cognitive-spatial models controlling perception, imagery, and 'seeing,' also control the EMs that shift the fovea in the Scanpath mode. These illusions provide for presence, the sense off being within an environment. They equally well lead to 'Telepresence,' the sense of being within a virtual display, especially if the operator is intensely interacting within an eye-hand and head-eye human-machine interface that provides for congruent visual and motor frames of reference. Interaction, immersion, and interest compel telepresence; intuitive functioning and engineered information flows can optimize human adaptation to the artificial new world of virtual reality, as virtual reality expands into entertainment, simulation, telerobotics, and scientific visualization and other professional work.

Sounds of silence: How to animate virtual worlds with sound

NASA Technical Reports Server (NTRS)

Astheimer, Peter

1993-01-01

Sounds are an integral and sometimes annoying part of our daily life. Virtual worlds which imitate natural environments gain a lot of authenticity from fast, high quality visualization combined with sound effects. Sounds help to increase the degree of immersion for human dwellers in imaginary worlds significantly. The virtual reality toolkit of IGD (Institute for Computer Graphics) features a broad range of standard visual and advanced real-time audio components which interpret an object-oriented definition of the scene. The virtual reality system 'Virtual Design' realized with the toolkit enables the designer of virtual worlds to create a true audiovisual environment. Several examples on video demonstrate the usage of the audio features in Virtual Design.

Virtual Reality Educational Tool for Human Anatomy.

PubMed

Izard, Santiago González; Juanes Méndez, Juan A; Palomera, Pablo Ruisoto

2017-05-01

Virtual Reality is becoming widespread in our society within very different areas, from industry to entertainment. It has many advantages in education as well, since it allows visualizing almost any object or going anywhere in a unique way. We will be focusing on medical education, and more specifically anatomy, where its use is especially interesting because it allows studying any structure of the human body by placing the user inside each one. By allowing virtual immersion in a body structure such as the interior of the cranium, stereoscopic vision goggles make these innovative teaching technologies a powerful tool for training in all areas of health sciences. The aim of this study is to illustrate the teaching potential of applying Virtual Reality in the field of human anatomy, where it can be used as a tool for education in medicine. A Virtual Reality Software was developed as an educational tool. This technological procedure is based entirely on software which will run in stereoscopic goggles to give users the sensation of being in a virtual environment, clearly showing the different bones and foramina which make up the cranium, and accompanied by audio explanations. Throughout the results the structure of the cranium is described in detailed from both inside and out. Importance of an exhaustive morphological knowledge of cranial fossae is further discussed. Application for the design of microsurgery is also commented.

Simulating Humans as Integral Parts of Spacecraft Missions

NASA Technical Reports Server (NTRS)

Bruins, Anthony C.; Rice, Robert; Nguyen, Lac; Nguyen, Heidi; Saito, Tim; Russell, Elaine

2006-01-01

The Collaborative-Virtual Environment Simulation Tool (C-VEST) software was developed for use in a NASA project entitled "3-D Interactive Digital Virtual Human." The project is oriented toward the use of a comprehensive suite of advanced software tools in computational simulations for the purposes of human-centered design of spacecraft missions and of the spacecraft, space suits, and other equipment to be used on the missions. The C-VEST software affords an unprecedented suite of capabilities for three-dimensional virtual-environment simulations with plug-in interfaces for physiological data, haptic interfaces, plug-and-play software, realtime control, and/or playback control. Mathematical models of the mechanics of the human body and of the aforementioned equipment are implemented in software and integrated to simulate forces exerted on and by astronauts as they work. The computational results can then support the iterative processes of design, building, and testing in applied systems engineering and integration. The results of the simulations provide guidance for devising measures to counteract effects of microgravity on the human body and for the rapid development of virtual (that is, simulated) prototypes of advanced space suits, cockpits, and robots to enhance the productivity, comfort, and safety of astronauts. The unique ability to implement human-in-the-loop immersion also makes the C-VEST software potentially valuable for use in commercial and academic settings beyond the original space-mission setting.

A Novel Computer-Based Set-Up to Study Movement Coordination in Human Ensembles

PubMed Central

Alderisio, Francesco; Lombardi, Maria; Fiore, Gianfranco; di Bernardo, Mario

2017-01-01

Existing experimental works on movement coordination in human ensembles mostly investigate situations where each subject is connected to all the others through direct visual and auditory coupling, so that unavoidable social interaction affects their coordination level. Here, we present a novel computer-based set-up to study movement coordination in human groups so as to minimize the influence of social interaction among participants and implement different visual pairings between them. In so doing, players can only take into consideration the motion of a designated subset of the others. This allows the evaluation of the exclusive effects on coordination of the structure of interconnections among the players in the group and their own dynamics. In addition, our set-up enables the deployment of virtual computer players to investigate dyadic interaction between a human and a virtual agent, as well as group synchronization in mixed teams of human and virtual agents. We show how this novel set-up can be employed to study coordination both in dyads and in groups over different structures of interconnections, in the presence as well as in the absence of virtual agents acting as followers or leaders. Finally, in order to illustrate the capabilities of the architecture, we describe some preliminary results. The platform is available to any researcher who wishes to unfold the mechanisms underlying group synchronization in human ensembles and shed light on its socio-psychological aspects. PMID:28649217

Virtual HRD and National Culture: An Information Processing Perspective

ERIC Educational Resources Information Center

Chung, Chih-Hung; Angnakoon, Putthachat; Li, Jessica; Allen, Jeff

2016-01-01

Purpose: The purpose of this study is to provide researchers with a better understanding of the cultural impact on information processing in virtual learning environment. Design/methodology/approach: This study uses a causal loop diagram to depict the cultural impact on information processing in the virtual human resource development (VHRD)…

Application of two segmentation protocols during the processing of virtual images in rapid prototyping: ex vivo study with human dry mandibles.

PubMed

Ferraz, Eduardo Gomes; Andrade, Lucio Costa Safira; dos Santos, Aline Rode; Torregrossa, Vinicius Rabelo; Rubira-Bullen, Izabel Regina Fischer; Sarmento, Viviane Almeida

2013-12-01

The aim of this study was to evaluate the accuracy of virtual three-dimensional (3D) reconstructions of human dry mandibles, produced from two segmentation protocols ("outline only" and "all-boundary lines"). Twenty virtual three-dimensional (3D) images were built from computed tomography exam (CT) of 10 dry mandibles, in which linear measurements between anatomical landmarks were obtained and compared to an error probability of 5 %. The results showed no statistically significant difference among the dry mandibles and the virtual 3D reconstructions produced from segmentation protocols tested (p = 0,24). During the designing of a virtual 3D reconstruction, both "outline only" and "all-boundary lines" segmentation protocols can be used. Virtual processing of CT images is the most complex stage during the manufacture of the biomodel. Establishing a better protocol during this phase allows the construction of a biomodel with characteristics that are closer to the original anatomical structures. This is essential to ensure a correct preoperative planning and a suitable treatment.

Virtual reality haptic human dissection.

PubMed

Needham, Caroline; Wilkinson, Caroline; Soames, Roger

2011-01-01

This project aims to create a three-dimensional digital model of the human hand and wrist which can be virtually 'dissected' through a haptic interface. Tissue properties will be added to the various anatomical structures to replicate a realistic look and feel. The project will explore the role of the medical artist and investigate the cross-discipline collaborations required in the field of virtual anatomy. The software will be used to train anatomy students in dissection skills before experience on a real cadaver. The effectiveness of the software will be evaluated and assessed both quantitatively as well as qualitatively.

The Ames Virtual Environment Workstation: Implementation issues and requirements

NASA Technical Reports Server (NTRS)

Fisher, Scott S.; Jacoby, R.; Bryson, S.; Stone, P.; Mcdowall, I.; Bolas, M.; Dasaro, D.; Wenzel, Elizabeth M.; Coler, C.; Kerr, D.

1991-01-01

This presentation describes recent developments in the implementation of a virtual environment workstation in the Aerospace Human Factors Research Division of NASA's Ames Research Center. Introductory discussions are presented on the primary research objectives and applications of the system and on the system's current hardware and software configuration. Principle attention is then focused on unique issues and problems encountered in the workstation's development with emphasis on its ability to meet original design specifications for computational graphics performance and for associated human factors requirements necessary to provide compelling sense of presence and efficient interaction in the virtual environment.

A three-dimensional finite element model of human atrial anatomy: New methods for cubic Hermite meshes with extraordinary vertices

PubMed Central

Gonzales, Matthew J.; Sturgeon, Gregory; Krishnamurthy, Adarsh; Hake, Johan; Jonas, René; Stark, Paul; Rappel, Wouter-Jan; Narayan, Sanjiv M.; Zhang, Yongjie; Segars, W. Paul; McCulloch, Andrew D.

2013-01-01

High-order cubic Hermite finite elements have been valuable in modeling cardiac geometry, fiber orientations, biomechanics, and electrophysiology, but their use in solving three-dimensional problems has been limited to ventricular models with simple topologies. Here, we utilized a subdivision surface scheme and derived a generalization of the “local-to-global” derivative mapping scheme of cubic Hermite finite elements to construct bicubic and tricubic Hermite models of the human atria with extraordinary vertices from computed tomography images of a patient with atrial fibrillation. To an accuracy of 0.6 millimeters, we were able to capture the left atrial geometry with only 142 bicubic Hermite finite elements, and the right atrial geometry with only 90. The left and right atrial bicubic Hermite meshes were G1 continuous everywhere except in the one-neighborhood of extraordinary vertices, where the mean dot products of normals at adjacent elements were 0.928 and 0.925. We also constructed two biatrial tricubic Hermite models and defined fiber orientation fields in agreement with diagrammatic data from the literature using only 42 angle parameters. The meshes all have good quality metrics, uniform element sizes, and elements with aspect ratios near unity, and are shared with the public. These new methods will allow for more compact and efficient patient-specific models of human atrial and whole heart physiology. PMID:23602918

New World View

NASA Astrophysics Data System (ADS)

Bainbridge, William Sims

This chapter reports the wide range of ideas in a pair of major scientific conference meetings held inside the most popular virtual world, World of Warcraft (WoW), May 9 and May 10, 2008, plus the challenges of organizing these online events. More than a hundred scholars and scientists contributed to each session, the first covering research on World of Warcraft, and the second examining how virtual worlds fit into the larger world of human experience. A third session, held on May 11, was the starting point for the concluding chapter of this volume. This chapter describes how WoW and other virtual worlds can be used as laboratories for studying human behavior, using both qualitative and quantitative methodologies, and the affordances of virtual worlds can be used to support scientific communication (Bainbridge 2007, in press).

Virtual Environment Computer Simulations to Support Human Factors Engineering and Operations Analysis for the RLV Program

NASA Technical Reports Server (NTRS)

Lunsford, Myrtis Leigh

1998-01-01

The Army-NASA Virtual Innovations Laboratory (ANVIL) was recently created to provide virtual reality tools for performing Human Engineering and operations analysis for both NASA and the Army. The author's summer research project consisted of developing and refining these tools for NASA's Reusable Launch Vehicle (RLV) program. Several general simulations were developed for use by the ANVIL for the evaluation of the X34 Engine Changeout procedure. These simulations were developed with the software tool dVISE 4.0.0 produced by Division Inc. All software was run on an SGI Indigo2 High Impact. This paper describes the simulations, various problems encountered with the simulations, other summer activities, and possible work for the future. We first begin with a brief description of virtual reality systems.

Effectiveness of educational technology to improve patient care in pharmacy curricula.

PubMed

Smith, Michael A; Benedict, Neal

2015-02-17

A review of the literature on the effectiveness of educational technologies to teach patient care skills to pharmacy students was conducted. Nineteen articles met inclusion criteria for the review. Seven of the articles included computer-aided instruction, 4 utilized human-patient simulation, 1 used both computer-aided instruction and human-patient simulation, and 7 utilized virtual patients. Educational technology was employed with more than 2700 students at 12 colleges and schools of pharmacy in courses including pharmacotherapeutics, skills and patient care laboratories, drug diversion, and advanced pharmacy practice experience (APPE) orientation. Students who learned by means of human-patient simulation and virtual patients reported enjoying the learning activity, whereas the results with computer-aided instruction were mixed. Moreover, the effect on learning was significant in the human-patient simulation and virtual patient studies, while conflicting data emerged on the effectiveness of computer-aided instruction.

Interviewing Suspects with Avatars: Avatars Are More Effective When Perceived as Human

PubMed Central

Ströfer, Sabine; Ufkes, Elze G.; Bruijnes, Merijn; Giebels, Ellen; Noordzij, Matthijs L.

2016-01-01

It has been consistently demonstrated that deceivers generally can be discriminated from truth tellers by monitoring an increase in their physiological response. But is this still the case when deceivers interact with a virtual avatar? The present research investigated whether the mere “belief” that the virtual avatar is computer or human operated forms a crucial factor for eliciting physiological cues to deception. Participants were interviewed about a transgression they had been seduced to commit, by a human-like virtual avatar. In a between-subject design, participants either deceived or told the truth about this transgression. During the interviews, we measured the physiological responses assessing participants' electrodermal activity (EDA). In line with our hypothesis, EDA differences between deceivers and truth tellers only were significant for participants who believed they interacted with a human operated (compared to a computer operated) avatar. These results have theoretical as well as practical implications which we will discuss. PMID:27148150

Virtual Habitat -a dynamic simulation of closed life support systems -human model status

NASA Astrophysics Data System (ADS)

Markus Czupalla, M. Sc.; Zhukov, Anton; Hwang, Su-Au; Schnaitmann, Jonas

In order to optimize Life Support Systems on a system level, stability questions must be in-vestigated. To do so the exploration group of the Technical University of Munich (TUM) is developing the "Virtual Habitat" (V-HAB) dynamic LSS simulation software. V-HAB shall provide the possibility to conduct dynamic simulations of entire mission scenarios for any given LSS configuration. The Virtual Habitat simulation tool consists of four main modules: • Closed Environment Module (CEM) -monitoring of compounds in a closed environment • Crew Module (CM) -dynamic human simulation • P/C Systems Module (PCSM) -dynamic P/C subsystems • Plant Module (PM) -dynamic plant simulation The core module of the simulation is the dynamic and environment sensitive human module. Introduced in its basic version in 2008, the human module has been significantly updated since, increasing its capabilities and maturity significantly. In this paper three newly added human model subsystems (thermal regulation, digestion and schedule controller) are introduced touching also on the human stress subsystem which is cur-rently under development. Upon the introduction of these new subsystems, the integration of these into the overall V-HAB human model is discussed, highlighting the impact on the most important I/F. The overall human model capabilities shall further be summarized and presented based on meaningful test cases. In addition to the presentation of the results, the correlation strategy for the Virtual Habitat human model shall be introduced assessing the models current confidence level and giving an outlook on the future correlation strategy. Last but not least, the remaining V-HAB mod-ules shall be introduced shortly showing how the human model is integrated into the overall simulation.

Model for Predicting the Performance of Planetary Suit Hip Bearing Designs

NASA Technical Reports Server (NTRS)

Cowley, Matthew S.; Margerum, Sarah; Hharvill, Lauren; Rajulu, Sudhakar

2012-01-01

Designing a space suit is very complex and often requires difficult trade-offs between performance, cost, mass, and system complexity. During the development period of the suit numerous design iterations need to occur before the hardware meets human performance requirements. Using computer models early in the design phase of hardware development is advantageous, by allowing virtual prototyping to take place. A virtual design environment allows designers to think creatively, exhaust design possibilities, and study design impacts on suit and human performance. A model of the rigid components of the Mark III Technology Demonstrator Suit (planetary-type space suit) and a human manikin were created and tested in a virtual environment. The performance of the Mark III hip bearing model was first developed and evaluated virtually by comparing the differences in mobility performance between the nominal bearing configurations and modified bearing configurations. Suited human performance was then simulated with the model and compared to actual suited human performance data using the same bearing configurations. The Mark III hip bearing model was able to visually represent complex bearing rotations and the theoretical volumetric ranges of motion in three dimensions. The model was also able to predict suited human hip flexion and abduction maximums to within 10% of the actual suited human subject data, except for one modified bearing condition in hip flexion which was off by 24%. Differences between the model predictions and the human subject performance data were attributed to the lack of joint moment limits in the model, human subject fitting issues, and the limited suit experience of some of the subjects. The results demonstrate that modeling space suit rigid segments is a feasible design tool for evaluating and optimizing suited human performance. Keywords: space suit, design, modeling, performance

Quantitative and Qualitative Changes in Teaching Histology by Means of Virtual Microscopy in an Introductory Course in Human Anatomy

ERIC Educational Resources Information Center

Husmann, Polly R.; O'Loughlin, Valerie Dean; Braun, Mark W.

2009-01-01

This study compares overall laboratory averages and individual test scores along with a student survey to determine the effects of using virtual microscopy in place of optical microscopes in a large undergraduate human anatomy course. T-tests revealed that the first two laboratory examinations (of four) and the overall laboratory averages were…

Interacting with a Computer-Simulated Pet: Factors Influencing Children's Humane Attitudes and Empathy

ERIC Educational Resources Information Center

Tsai, Yueh-Feng; Kaufman, David

2014-01-01

Previous research by Tsai and Kaufman (2010a, 2010b) has suggested that computer-simulated virtual pet dogs can be used as a potential medium to enhance children's development of empathy and humane attitudes toward animals. To gain a deeper understanding of how and why interacting with a virtual pet dog might influence children's social and…

Younger and Older Users’ Recognition of Virtual Agent Facial Expressions

PubMed Central

Beer, Jenay M.; Smarr, Cory-Ann; Fisk, Arthur D.; Rogers, Wendy A.

2015-01-01

As technology advances, robots and virtual agents will be introduced into the home and healthcare settings to assist individuals, both young and old, with everyday living tasks. Understanding how users recognize an agent’s social cues is therefore imperative, especially in social interactions. Facial expression, in particular, is one of the most common non-verbal cues used to display and communicate emotion in on-screen agents (Cassell, Sullivan, Prevost, & Churchill, 2000). Age is important to consider because age-related differences in emotion recognition of human facial expression have been supported (Ruffman et al., 2008), with older adults showing a deficit for recognition of negative facial expressions. Previous work has shown that younger adults can effectively recognize facial emotions displayed by agents (Bartneck & Reichenbach, 2005; Courgeon et al. 2009; 2011; Breazeal, 2003); however, little research has compared in-depth younger and older adults’ ability to label a virtual agent’s facial emotions, an import consideration because social agents will be required to interact with users of varying ages. If such age-related differences exist for recognition of virtual agent facial expressions, we aim to understand if those age-related differences are influenced by the intensity of the emotion, dynamic formation of emotion (i.e., a neutral expression developing into an expression of emotion through motion), or the type of virtual character differing by human-likeness. Study 1 investigated the relationship between age-related differences, the implication of dynamic formation of emotion, and the role of emotion intensity in emotion recognition of the facial expressions of a virtual agent (iCat). Study 2 examined age-related differences in recognition expressed by three types of virtual characters differing by human-likeness (non-humanoid iCat, synthetic human, and human). Study 2 also investigated the role of configural and featural processing as a possible explanation for age-related differences in emotion recognition. First, our findings show age-related differences in the recognition of emotions expressed by a virtual agent, with older adults showing lower recognition for the emotions of anger, disgust, fear, happiness, sadness, and neutral. These age-related difference might be explained by older adults having difficulty discriminating similarity in configural arrangement of facial features for certain emotions; for example, older adults often mislabeled the similar emotions of fear as surprise. Second, our results did not provide evidence for the dynamic formation improving emotion recognition; but, in general, the intensity of the emotion improved recognition. Lastly, we learned that emotion recognition, for older and younger adults, differed by character type, from best to worst: human, synthetic human, and then iCat. Our findings provide guidance for design, as well as the development of a framework of age-related differences in emotion recognition. PMID:25705105

Virtual embryology: a 3D library reconstructed from human embryo sections and animation of development process.

PubMed

Komori, M; Miura, T; Shiota, K; Minato, K; Takahashi, T

1995-01-01

The volumetric shape of a human embryo and its development is hard to comprehend as they have been viewed as a 2D schemes in a textbook or microscopic sectional image. In this paper, a CAI and research support system for human embryology using multimedia presentation techniques is described. In this system, 3D data is acquired from a series of sliced specimens. Its 3D structure can be viewed interactively by rotating, extracting, and truncating its whole body or organ. Moreover, the development process of embryos can be animated using a morphing technique applied to the specimen in several stages. The system is intended to be used interactively, like a virtual reality system. Hence, the system is called Virtual Embryology.

Aorta-atria-septum combined incision for aortic valve re-replacement

PubMed Central

Xu, Yiwei; Ye, Xiaofeng; Li, Zhaolong

2018-01-01

This case report illustrates a patient who underwent supra-annular mechanical aortic valve replacement then suffered from prosthesis dysfunction, increasing pressure gradient with aortic valve. She was successfully underwent aortic valve re-replacement, sub-annular pannus removing and aortic annulus enlargement procedures through combined cardiac incision passing through aortic root, right atrium (RA), and upper atrial septum. This incision provides optimal visual operative field and simplifies dissection. PMID:29850170

Conjoined twins: morphogenesis of the heart and a review.

PubMed

Gilbert-Barness, Enid; Debich-Spicer, Diane; Opitz, John M

2003-08-01

Five cases of conjoined twins have been studied. These included three thoracopagus twins, one monocephalus diprosopus (prosop = face), and one dicephalus dipus dibrachus. The thoracopagus twins were conjoined only from the upper thorax to the umbilicus with a normal foregut. These three cases shared a single complex multiventricular heart, one with a four chambered heart with one atrium and one ventricle belonging to each twin with complex venous and arterial connection; two had a seven chambered heart with four atria and three ventricles. The mono-cephalus diprosopus twins had a single heart with tetralogy of Fallot. The dicephalus twins had two separate axial skeletons to the sacrum, two separate hearts were connected between the right atria with a shared inferior vena cava. Thoracopagus twinning is associated with complex cardiac malformations. The cardiac anlagen in cephalopagus or diprosopus are diverted and divided along with the entire rostral end of the embryonic disc and result in two relatively normal shared hearts. However, in thoracopagus twins the single heart is multiventricular and suggests very early union with fusion of the cardiac anlagen before significant differentiation. Cardiac morphogenesis in conjoined twins therefore appears to depend on the site of the conjoined fusion and the temporal and spatial influence that determines morphogenesis as well as abnormally oriented embryonic axes. Copyright 2003 Wiley-Liss, Inc.

Effect of Mucuna pruriens Seed Extract Pretreatment on the Responses of Spontaneously Beating Rat Atria and Aortic Ring to Naja sputatrix (Javan Spitting Cobra) Venom

PubMed Central

Fung, Shin Yee; Tan, Nget Hong; Sim, Si Mui; Aguiyi, John C.

2012-01-01

Mucuna pruriens Linn. (velvet bean) has been used by native Nigerians as a prophylactic for snakebite. Rats pretreated with M. pruriens seed extract (MPE) have been shown to protect against the lethal and cardiovascular depressant effects of Naja sputatrix (Javan spitting cobra) venoms, and the protective effect involved immunological neutralization of the venom toxins. To investigate further the mechanism of the protective effect of MPE pretreatment against cobra venom toxicity, the actions of Naja sputatrix venom on spontaneously beating rat atria and aortic rings isolated from both MPE pretreated and untreated rats were studied. Our results showed that the MPE pretreatment conferred protection against cobra venom-induced depression of atrial contractility and atrial rate in the isolated atrial preparations, but it had no effect on the venom-induced contractile response of aortic ring preparation. These observations suggested that the protective effect of MPE pretreatment against cobra venom toxicity involves a direct protective action of MPE on the heart function, in addition to the known immunological neutralization mechanism, and that the protective effect does not involve action on blood vessel contraction. The results also suggest that M. pruriens seed may contain novel cardioprotective agent with potential therapeutic value. PMID:21785646

Potential Adverse Cardiovascular Effects From Excessive Endurance Exercise

PubMed Central

O'Keefe, James H.; Patil, Harshal R.; Lavie, Carl J.; Magalski, Anthony; Vogel, Robert A.; McCullough, Peter A.

2012-01-01

A routine of regular exercise is highly effective for prevention and treatment of many common chronic diseases and improves cardiovascular (CV) health and longevity. However, long-term excessive endurance exercise may induce pathologic structural remodeling of the heart and large arteries. Emerging data suggest that chronic training for and competing in extreme endurance events such as marathons, ultramarathons, ironman distance triathlons, and very long distance bicycle races, can cause transient acute volume overload of the atria and right ventricle, with transient reductions in right ventricular ejection fraction and elevations of cardiac biomarkers, all of which return to normal within 1 week. Over months to years of repetitive injury, this process, in some individuals, may lead to patchy myocardial fibrosis, particularly in the atria, interventricular septum, and right ventricle, creating a substrate for atrial and ventricular arrhythmias. Additionally, long-term excessive sustained exercise may be associated with coronary artery calcification, diastolic dysfunction, and large-artery wall stiffening. However, this concept is still hypothetical and there is some inconsistency in the reported findings. Furthermore, lifelong vigorous exercisers generally have low mortality rates and excellent functional capacity. Notwithstanding, the hypothesis that long-term excessive endurance exercise may induce adverse CV remodeling warrants further investigation to identify at-risk individuals and formulate physical fitness regimens for conferring optimal CV health and longevity. PMID:22677079

Atrial Fibrillation: The Science behind Its Defiance

PubMed Central

Czick, Maureen E.; Shapter, Christine L.; Silverman, David I.

2016-01-01

Atrial fibrillation (AF) is the most prevalent arrhythmia in the world, due both to its tenacious treatment resistance, and to the tremendous number of risk factors that set the stage for the atria to fibrillate. Cardiopulmonary, behavioral, and psychological risk factors generate electrical and structural alterations of the atria that promote reentry and wavebreak. These culminate in fibrillation once atrial ectopic beats set the arrhythmia process in motion. There is growing evidence that chronic stress can physically alter the emotion centers of the limbic system, changing their input to the hypothalamic-limbic-autonomic network that regulates autonomic outflow. This leads to imbalance of the parasympathetic and sympathetic nervous systems, most often in favor of sympathetic overactivation. Autonomic imbalance acts as a driving force behind the atrial ectopy and reentry that promote AF. Careful study of AF pathophysiology can illuminate the means that enable AF to elude both pharmacological control and surgical cure, by revealing ways in which antiarrhythmic drugs and surgical and ablation procedures may paradoxically promote fibrillation. Understanding AF pathophysiology can also help clarify the mechanisms by which emerging modalities aiming to correct autonomic imbalance, such as renal sympathetic denervation, may offer potential to better control this arrhythmia. Finally, growing evidence supports lifestyle modification approaches as adjuncts to improve AF control. PMID:27699086

Rhynchelmis subgenus Sutroa Eisen new rank, with two new species from western North America (Annelida, Clitellata, Lumbriculidae)

USGS Publications Warehouse

Fend, Steven V.; Carter, James L.

2014-01-01

The lumbriculid Rhynchelmis subgenus Sutroa Eisen, 1888 new rank is defined for a group of Nearctic species having multiple diverticula originating at the spermathecal ducts and eversible penial bulbs. Characters are confirmed in specimens of the type species, Rhynchelmis (Sutroa) rostrata (Eisen, 1888), collected from the type locality. Rhynchelmis (Sutroa) klamathensis Fend n. sp. is described from open water benthic habitats in Upper Klamath Lake, Oregon, USA. It resembles other R. (Sutroa) species in the paired spermathecal diverticula, the spermathecal and penial bulbs, the histological structure of the atria, the nonfunctional anterior male funnels, and the arrangement of blood vessels. Rhynchelmis klamathensis differs from all Nearctic Rhynchelmis in lacking a filiform proboscis. The combination of large body size, the elongate spermathecal ducts with paired and usually unbranched diverticula, the highly contorted atria, and the complex male pores with conical penes also distinguish typical R. klamathensis from other Rhynchelmis species. Smaller specimens with otherwise similar morphology, from the Sacramento River Delta, California, are also assigned to this species. Rhynchelmis (Sutroa) diespluviae Fend n. sp. is described from several stream sites, mostly in northern Idaho, USA. Rhynchelmis diespluviae differs from closely related species in morphology of the conical penes, and in the structure and anterolateral position of the paired spermathecae.

Human Machine Interfaces for Teleoperators and Virtual Environments Conference

NASA Technical Reports Server (NTRS)

1990-01-01

In a teleoperator system the human operator senses, moves within, and operates upon a remote or hazardous environment by means of a slave mechanism (a mechanism often referred to as a teleoperator). In a virtual environment system the interactive human machine interface is retained but the slave mechanism and its environment are replaced by a computer simulation. Video is replaced by computer graphics. The auditory and force sensations imparted to the human operator are similarly computer generated. In contrast to a teleoperator system, where the purpose is to extend the operator's sensorimotor system in a manner that facilitates exploration and manipulation of the physical environment, in a virtual environment system, the purpose is to train, inform, alter, or study the human operator to modify the state of the computer and the information environment. A major application in which the human operator is the target is that of flight simulation. Although flight simulators have been around for more than a decade, they had little impact outside aviation presumably because the application was so specialized and so expensive.

Virtually-augmented interfaces for tactical aircraft.

PubMed

Haas, M W

1995-05-01

The term Fusion Interface is defined as a class of interface which integrally incorporates both virtual and non-virtual concepts and devices across the visual, auditory and haptic sensory modalities. A fusion interface is a multi-sensory virtually-augmented synthetic environment. A new facility has been developed within the Human Engineering Division of the Armstrong Laboratory dedicated to exploratory development of fusion-interface concepts. One of the virtual concepts to be investigated in the Fusion Interfaces for Tactical Environments facility (FITE) is the application of EEG and other physiological measures for virtual control of functions within the flight environment. FITE is a specialized flight simulator which allows efficient concept development through the use of rapid prototyping followed by direct experience of new fusion concepts. The FITE facility also supports evaluation of fusion concepts by operational fighter pilots in a high fidelity simulated air combat environment. The facility was utilized by a multi-disciplinary team composed of operational pilots, human-factors engineers, electronics engineers, computer scientists, and experimental psychologists to prototype and evaluate the first multi-sensory, virtually-augmented cockpit. The cockpit employed LCD-based head-down displays, a helmet-mounted display, three-dimensionally localized audio displays, and a haptic display. This paper will endeavor to describe the FITE facility architecture, some of the characteristics of the FITE virtual display and control devices, and the potential application of EEG and other physiological measures within the FITE facility.

Reaction time for processing visual stimulus in a computer-assisted rehabilitation environment.

PubMed

Sanchez, Yerly; Pinzon, David; Zheng, Bin

2017-10-01

To examine the reaction time when human subjects process information presented in the visual channel under both a direct vision and a virtual rehabilitation environment when walking was performed. Visual stimulus included eight math problems displayed on the peripheral vision to seven healthy human subjects in a virtual rehabilitation training (computer-assisted rehabilitation environment (CAREN)) and a direct vision environment. Subjects were required to verbally report the results of these math calculations in a short period of time. Reaction time measured by Tobii Eye tracker and calculation accuracy were recorded and compared between the direct vision and virtual rehabilitation environment. Performance outcomes measured for both groups included reaction time, reading time, answering time and the verbal answer score. A significant difference between the groups was only found for the reaction time (p = .004). Participants had more difficulty recognizing the first equation of the virtual environment. Participants reaction time was faster in the direct vision environment. This reaction time delay should be kept in mind when designing skill training scenarios in virtual environments. This was a pilot project to a series of studies assessing cognition ability of stroke patients who are undertaking a rehabilitation program with a virtual training environment. Implications for rehabilitation Eye tracking is a reliable tool that can be employed in rehabilitation virtual environments. Reaction time changes between direct vision and virtual environment.

Discovery of Novel Human Epidermal Growth Factor Receptor-2 Inhibitors by Structure-based Virtual Screening.

PubMed

Shi, Zheng; Yu, Tian; Sun, Rong; Wang, Shan; Chen, Xiao-Qian; Cheng, Li-Jia; Liu, Rong

2016-01-01

Human epidermal growth factor receptor-2 (HER2) is a trans-membrane receptor like protein, and aberrant signaling of HER2 is implicated in many human cancers, such as ovarian cancer, gastric cancer, and prostate cancer, most notably breast cancer. Moreover, it has been in the spotlight in the recent years as a promising new target for therapy of breast cancer. Since virtual screening has become an integral part of the drug discovery process, it is of great significant to identify novel HER2 inhibitors by structure-based virtual screening. In this study, we carried out a series of elegant bioinformatics approaches, such as virtual screening and molecular dynamics (MD) simulations to identify HER2 inhibitors from Food and Drug Administration-approved small molecule drug as potential "new use" drugs. Molecular docking identified top 10 potential drugs which showed spectrum affinity to HER2. Moreover, MD simulations suggested that ZINC08214629 (Nonoxynol-9) and ZINC03830276 (Benzonatate) might exert potential inhibitory effects against HER2-targeted anti-breast cancer therapeutics. Together, our findings may provide successful application of virtual screening studies in the lead discovery process, and suggest that our discovered small molecules could be effective HER2 inhibitor candidates for further study. A series of elegant bioinformatics approaches, including virtual screening and molecular dynamics (MD) simulations were took advantage to identify human epidermal growth factor receptor-2 (HER2) inhibitors. Molecular docking recognized top 10 candidate compounds, which showed spectrum affinity to HER2. Further, MD simulations suggested that ZINC08214629 (Nonoxynol-9) and ZINC03830276 (Benzonatate) in candidate compounds were identified as potential "new use" drugs against HER2-targeted anti-breast cancer therapeutics. Abbreviations used: HER2: Human epidermal growth factor receptor-2, FDA: Food and Drug Administration, PDB: Protein Database Bank, RMSDs: Root mean square deviations, SPC: Single point charge, PME: Particle mesh Ewald, NVT: Constant volume, NPT: Constant pressure, RMSF: Root-mean-square fluctuation.

Virtual reality and planetary exploration

NASA Technical Reports Server (NTRS)

Mcgreevy, Michael W.

1992-01-01

Exploring planetary environments is central to NASA's missions and goals. A new computing technology called Virtual Reality has much to offer in support of planetary exploration. This technology augments and extends human presence within computer-generated and remote spatial environments. Historically, NASA has been a leader in many of the fundamental concepts and technologies that comprise Virtual Reality. Indeed, Ames Research Center has a central role in the development of this rapidly emerging approach to using computers. This ground breaking work has inspired researchers in academia, industry, and the military. Further, NASA's leadership in this technology has spun off new businesses, has caught the attention of the international business community, and has generated several years of positive international media coverage. In the future, Virtual Reality technology will enable greatly improved human-machine interactions for more productive planetary surface exploration. Perhaps more importantly, Virtual Reality technology will democratize the experience of planetary exploration and thereby broaden understanding of, and support for, this historic enterprise.

Virtual reality and planetary exploration

NASA Astrophysics Data System (ADS)

McGreevy, Michael W.

Exploring planetary environments is central to NASA's missions and goals. A new computing technology called Virtual Reality has much to offer in support of planetary exploration. This technology augments and extends human presence within computer-generated and remote spatial environments. Historically, NASA has been a leader in many of the fundamental concepts and technologies that comprise Virtual Reality. Indeed, Ames Research Center has a central role in the development of this rapidly emerging approach to using computers. This ground breaking work has inspired researchers in academia, industry, and the military. Further, NASA's leadership in this technology has spun off new businesses, has caught the attention of the international business community, and has generated several years of positive international media coverage. In the future, Virtual Reality technology will enable greatly improved human-machine interactions for more productive planetary surface exploration. Perhaps more importantly, Virtual Reality technology will democratize the experience of planetary exploration and thereby broaden understanding of, and support for, this historic enterprise.

Simulation Of Assembly Processes With Technical Of Virtual Reality

NASA Astrophysics Data System (ADS)

García García, Manuel; Arenas Reina, José Manuel; Lite, Alberto Sánchez; Sebastián Pérez, Miguel Ángel

2009-11-01

Virtual reality techniques use at industrial processes provides a real approach to product life cycle. For components manual assembly, the use of virtual surroundings facilitates a simultaneous engineering in which variables such as human factors and productivity take a real act. On the other hand, in the actual phase of industrial competition it is required a rapid adjustment to client needs and to market situation. In this work it is analyzed the assembly of the front components of a vehicle using virtual reality tools and following up a product-process design methodology which includes every life service stage. This study is based on workstations design, taking into account productive and human factors from the ergonomic point of view implementing a postural study of every assembly operation, leaving the rest of stages for a later study. Design is optimized applying this methodology together with the use of virtual reality tools. It is also achieved a 15% reduction on time assembly and of 90% reduction in muscle—skeletal diseases at every assembly operation.

Virtual arthroscopy of the visible human female temporomandibular joint.

PubMed

Ishimaru, T; Lew, D; Haller, J; Vannier, M W

1999-07-01

This study was designed to obtain views of the temporomandibular joint (TMJ) by means of computed arthroscopic simulation (virtual arthroscopy) using three-dimensional (3D) processing. Volume renderings of the TMJ from very thin cryosection slices of the Visible Human Female were taken off the Internet. Analyze(AVW) software (Biomedical Imaging Resource, Mayo Foundation, Rochester, MN) on a Silicon Graphics 02 workstation (Mountain View, CA) was then used to obtain 3D images and allow the navigation "fly-through" of the simulated joint. Good virtual arthroscopic views of the upper and lower joint spaces of both TMJs were obtained by fly-through simulation from the lateral and endaural sides. It was possible to observe the presence of a partial defect in the articular disc and an osteophyte on the condyle. Virtual arthroscopy provided visualization of regions not accessible to real arthroscopy. These results indicate that virtual arthroscopy will be a new technique to investigate the TMJ of the patient with TMJ disorders in the near future.

What Happens in a Virtual World Has a Real-World Impact, a Scholar Finds

ERIC Educational Resources Information Center

Foster, Andrea L.

2008-01-01

Forget the pills, hypnosis, and meditation. Losing weight or boosting self-confidence can be achieved by adopting an avatar and living in virtual reality, says Jeremy N. Bailenson, an assistant professor of communications at Stanford University. As the director of Stanford's Virtual Human Interaction Lab, Mr. Bailenson has explored ways that…

Using Virtual Interactive Training Agents (ViTA) with Adults with Autism and Other Developmental Disabilities

ERIC Educational Resources Information Center

Burke, Shanna L.; Bresnahan, Tammy; Li, Tan; Epnere, Katrina; Rizzo, Albert; Partin, Mary; Ahlness, Robert M.; Trimmer, Matthew

2018-01-01

Conversational virtual human (VH) agents are increasingly used to support role-play experiential learning. This project examined whether a Virtual Interactive Training Agent (ViTA) system would improve job interviewing skills in individuals with autism and developmental disabilities (N = 32). A linear mixed model was employed to evaluate adjusted…

Optical versus Virtual: Teaching Assistant Perceptions of the Use of Virtual Microscopy in an Undergraduate Human Anatomy Course

ERIC Educational Resources Information Center

Collier, Larissa; Dunham, Stacey; Braun, Mark W.; O'Loughlin, Valerie Dean

2012-01-01

Many studies that evaluate the introduction of technology in the classroom focus on student performance and student evaluations. This study focuses on instructor evaluation of the introduction of virtual microscopy into an undergraduate anatomy class. Semi-structured interviews were conducted with graduate teaching assistants (TA) and analyzed…

Virtual Worlds vs Books and Videos in History Education

ERIC Educational Resources Information Center

Ijaz, Kiran; Bogdanovych, Anton; Trescak, Tomas

2017-01-01

In this paper, we investigate an application of virtual reality and artificial intelligence (AI) as a technological combination that has a potential to improve the learning experience and engage with the modern generation of students. To address this need, we have created a virtual reality replica of one of humanity's first cities, the city of…

[Virtual Campus of Public Health: six years of human resources education in Mexico].

PubMed

Ramos Herrera, Igor; Alfaro Alfaro, Noé; Fonseca León, Joel; García Sandoval, Cristóbal; González Castañeda, Miguel; López Zermeño, María Del Carmen; Benítez Morales, Ricardo

2014-11-01

This paper discusses the gestation process, implementation methodology, and results obtained from the initiative to use e-learning to train human resources for health, six years after the launch of the Virtual Campus of Public Health of the University of Guadalajara (Mexico); the discussion is framed by Pan American Health Organization (PAHO) standards and practices. This is a special report on the work done by the institutional committee of the Virtual Campus in western Mexico to create an Internet portal that follows the guidelines of the strategic model established by Nodo México and PAHO for the Region of the Americas. This Virtual Campus began its activities in 2007, on the basis of the use of free software and institutional collaboration. Since the initial year of implementation of the node, over 500 health professionals have been trained using virtual courses, the node's educational platform, and a repository of virtual learning resources that are interoperable with other repositories in Mexico and the Region of the Americas. The University of Guadalajara Virtual Campus committee has followed the proposed model as much as possible, thereby achieving most of the goals set in the initial work plan, despite a number of administrative challenges and the difficulty of motivating committee members.

Geometric morphometrics and virtual anthropology: advances in human evolutionary studies.

PubMed

Rein, Thomas R; Harvati, Katerina

2014-01-01

Geometric morphometric methods have been increasingly used in paleoanthropology in the last two decades, lending greater power to the analysis and interpretation of the human fossil record. More recently the advent of the wide use of computed tomography and surface scanning, implemented in combination with geometric morphometrics (GM), characterizes a new approach, termed Virtual Anthropology (VA). These methodological advances have led to a number of developments in human evolutionary studies. We present some recent examples of GM and VA related research in human evolution with an emphasis on work conducted at the University of Tübingen and other German research institutions.

Efforts in Preparation for Jack Validation.

DTIC Science & Technology

1997-12-01

clothing, equipment attached to the body, age, or physical health. The skeleton’s size, structure, and proportions are affected by age, exercise ...things such as genetics, exercise , and dietary habit (Bailey, Malina, & Rasmussen, 1978). VIRTUAL HUMAN MODELS A virtual human models only a subset of...artistically modeled) surfaces. - Somatotype modeling is not considered. To understand what this implies, consider scaling the body using an average

Digital Adultery, "Meta-Anon Widows," Real-World Divorce, and the Need for a Virtual Sexual Ethic

NASA Astrophysics Data System (ADS)

Spencer, William David

Ethical issues that have emerged around relationships in virtual worlds can inform the way we approach the ethics of human/robot relationships. A workable ethic would be one that treats marriage as an enduring human institution and, while we value robots as worthy works of our hands, they are inappropriate partners for marital or sexual relationships.

Institutional, Public and Individual Learning Dynamics of the Andy Holt Virtual Library.

ERIC Educational Resources Information Center

Peckham, Robert

The Andy Holt Virtual Library, with a focus on the Humanities and Fine Arts, is free and open to the public, though designed to serve the learning communities within the College of Humanities and Fine Arts at the University of Tennessee-Martin (UT). It also plays a resource role in UT's New College and the Tennessee Governors School for the…

The virtual morphology and the main movements of the human neck simulations used for car crash studies

NASA Astrophysics Data System (ADS)

Ciunel, St.; Tica, B.

2016-08-01

The paper presents the studies made on a similar biomechanical system composed by neck, head and thorax bones. The models were defined in a CAD environment which includes Adams algorithm for dynamic simulations. The virtual models and the entire morphology were obtained starting with CT images made on a living human subject. The main movements analyzed were: axial rotation (left-right), lateral bending (left-right) and flexion- extension movement. After simulation was obtained the entire biomechanical behavior based on data tables or diagrams. That virtual model composed by neck and head can be included in complex system (as a car system) and supposed to several impact simulations (virtual crash tests). Also, our research team built main components of a testing device for dummy car crash neck-head system using anatomical data.

Trust Building in Virtual Communities

NASA Astrophysics Data System (ADS)

Mezgár, István

By using different types of communication networks various groups of people can come together according to their private or business interest forming a Virtual Community. In these communities cooperation and collaboration plays an important role. As trust is the base of all human interactions this fact is even more valid in case of virtual communities. According to different experiments the level of trust in virtual communities is highly influenced by the way/mode of communication and by the duration of contact. The paper discusses the ways of trust building focusing on communication technologies and security aspects in virtual communities.

Computational Virtual Reality (VR) as a human-computer interface in the operation of telerobotic systems

NASA Technical Reports Server (NTRS)

Bejczy, Antal K.

1995-01-01

This presentation focuses on the application of computer graphics or 'virtual reality' (VR) techniques as a human-computer interface tool in the operation of telerobotic systems. VR techniques offer very valuable task realization aids for planning, previewing and predicting robotic actions, operator training, and for visual perception of non-visible events like contact forces in robotic tasks. The utility of computer graphics in telerobotic operation can be significantly enhanced by high-fidelity calibration of virtual reality images to actual TV camera images. This calibration will even permit the creation of artificial (synthetic) views of task scenes for which no TV camera views are available.

The Virtual Teacher (VT) Paradigm: Learning New Patterns of Interpersonal Coordination Using the Human Dynamic Clamp

PubMed Central

2015-01-01

The Virtual Teacher paradigm, a version of the Human Dynamic Clamp (HDC), is introduced into studies of learning patterns of inter-personal coordination. Combining mathematical modeling and experimentation, we investigate how the HDC may be used as a Virtual Teacher (VT) to help humans co-produce and internalize new inter-personal coordination pattern(s). Human learners produced rhythmic finger movements whilst observing a computer-driven avatar, animated by dynamic equations stemming from the well-established Haken-Kelso-Bunz (1985) and Schöner-Kelso (1988) models of coordination. We demonstrate that the VT is successful in shifting the pattern co-produced by the VT-human system toward any value (Experiment 1) and that the VT can help humans learn unstable relative phasing patterns (Experiment 2). Using transfer entropy, we find that information flow from one partner to the other increases when VT-human coordination loses stability. This suggests that variable joint performance may actually facilitate interaction, and in the long run learning. VT appears to be a promising tool for exploring basic learning processes involved in social interaction, unraveling the dynamics of information flow between interacting partners, and providing possible rehabilitation opportunities. PMID:26569608

The Virtual Teacher (VT) Paradigm: Learning New Patterns of Interpersonal Coordination Using the Human Dynamic Clamp.

PubMed

Kostrubiec, Viviane; Dumas, Guillaume; Zanone, Pier-Giorgio; Kelso, J A Scott

2015-01-01

The Virtual Teacher paradigm, a version of the Human Dynamic Clamp (HDC), is introduced into studies of learning patterns of inter-personal coordination. Combining mathematical modeling and experimentation, we investigate how the HDC may be used as a Virtual Teacher (VT) to help humans co-produce and internalize new inter-personal coordination pattern(s). Human learners produced rhythmic finger movements whilst observing a computer-driven avatar, animated by dynamic equations stemming from the well-established Haken-Kelso-Bunz (1985) and Schöner-Kelso (1988) models of coordination. We demonstrate that the VT is successful in shifting the pattern co-produced by the VT-human system toward any value (Experiment 1) and that the VT can help humans learn unstable relative phasing patterns (Experiment 2). Using transfer entropy, we find that information flow from one partner to the other increases when VT-human coordination loses stability. This suggests that variable joint performance may actually facilitate interaction, and in the long run learning. VT appears to be a promising tool for exploring basic learning processes involved in social interaction, unraveling the dynamics of information flow between interacting partners, and providing possible rehabilitation opportunities.

Virtual Glovebox (VGX) Aids Astronauts in Pre-Flight Training

NASA Technical Reports Server (NTRS)

2003-01-01

NASA's Virtual Glovebox (VGX) was developed to allow astronauts on Earth to train for complex biology research tasks in space. The astronauts may reach into the virtual environment, naturally manipulating specimens, tools, equipment, and accessories in a simulated microgravity environment as they would do in space. Such virtual reality technology also provides engineers and space operations staff with rapid prototyping, planning, and human performance modeling capabilities. Other Earth based applications being explored for this technology include biomedical procedural training and training for disarming bio-terrorism weapons.

Web-based e-learning and virtual lab of human-artificial immune system.

PubMed

Gong, Tao; Ding, Yongsheng; Xiong, Qin

2014-05-01

Human immune system is as important in keeping the body healthy as the brain in supporting the intelligence. However, the traditional models of the human immune system are built on the mathematics equations, which are not easy for students to understand. To help the students to understand the immune systems, a web-based e-learning approach with virtual lab is designed for the intelligent system control course by using new intelligent educational technology. Comparing the traditional graduate educational model within the classroom, the web-based e-learning with the virtual lab shows the higher inspiration in guiding the graduate students to think independently and innovatively, as the students said. It has been found that this web-based immune e-learning system with the online virtual lab is useful for teaching the graduate students to understand the immune systems in an easier way and design their simulations more creatively and cooperatively. The teaching practice shows that the optimum web-based e-learning system can be used to increase the learning effectiveness of the students.

Usability Studies in Virtual and Traditional Computer Aided Design Environments for Fault Identification

DTIC Science & Technology

2017-08-08

Usability Studies In Virtual And Traditional Computer Aided Design Environments For Fault Identification Dr. Syed Adeel Ahmed, Xavier University...virtual environment with wand interfaces compared directly with a workstation non-stereoscopic traditional CAD interface with keyboard and mouse. In...the differences in interaction when compared with traditional human computer interfaces. This paper provides analysis via usability study methods

Trust, Isolation, and Presence: The Virtual Work Environment and Acceptance of Deep Organizational Change

ERIC Educational Resources Information Center

Rose, Laurence Michael

2013-01-01

The primary focus of this research was to explore through the use of a grounded theory methodology if the human perceptions of trust, isolation, and presence affected the virtual workers ability to accept deep organizational change. The study found that the virtual workers in the sample defined their acceptance of deep organizational change by…

Defining Virtual Interactions: A Taxonomy for Researchers and Practitioners

DTIC Science & Technology

1999-11-01

Engineering and Management of the Air Force Institute of Technology Air University Air Education and Training Command In Partial Fulfillment of the...information technology and produce the maximum benefits for all virtual components involved. Vlll DEFINING VIRTUAL INTERACTIONS: A TAXONOMY FOR...allow the human factor to maximize information exchange and provide high quality products to intelligence consumers. Applicability of this research In

Managing and Developing People in the Virtual Organization. Professional Practices in Adult Education and Human Resource Development Series.

ERIC Educational Resources Information Center

Colky, Deborah Lavin; Colky, Michael T.; Young, William H., III

Designed for managers and workers in virtual organizations as well as adult and continuing educators in higher education, associations, and private sector, this book outlines a customer-driven performance management system and explains its use as a development tool. The characteristics of virtual organizations are described, and the rationale for…

Australian DefenceScience. Volume 16, Number 2, Winter

DTIC Science & Technology

2008-01-01

Making Virtual Advisers speedily interactive To provide an authentically interactive experience for humans working with Virtual Advisers, the Virtual...peer trusted and strong authentication for checking of security credentials without recourse to third parties or infrastructure, thus eliminating...multiple passwords, or carry around multiple security tokens.” Each CodeStick device is readied for use with a biometric authentication process. Since

Social interactions in virtual reality exposure therapy: A proof-of-concept pilot study.

PubMed

Morina, Nexhmedin; Brinkman, Willem-Paul; Hartanto, Dwi; Kampmann, Isabel L; Emmelkamp, Paul M G

2015-01-01

Research on virtual reality exposure therapy (VRET) has demonstrated good treatment efficacy with regards to several anxiety disorders. Yet, there is lack of knowledge about the value of integrating interaction between clients and virtual humans in VRET. Such interaction might prove effective in treating psychological complaints that involve social interactions, such as social anxiety. A VRET system specifically designed to expose clients with social anxiety disorder to anxiety provoking social situations was applied to 16 and 18 individuals with high and low levels of social anxiety, respectively. Participants engaged in two exposure sessions in several free speech dialogues with virtual humans while being monitored by a therapist. Participants with high levels of social anxiety reported significantly lower levels of social anxiety three months after exposure to two virtual reality interaction sessions than before treatment (p < 0.01). In the group with low levels of social anxiety, no significant change of social anxiety was reported between pre-treatment and follow-up. Additionally, participants in both groups reported higher self-efficacy three months after treatment than before treatment (ps ≤ 0.001). These findings indicate that virtual reality technology that incorporates social interactions may be successfully applied for therapeutic purposes.

Body Image and Anti-Fat Attitudes: An Experimental Study Using a Haptic Virtual Reality Environment to Replicate Human Touch.

PubMed

Tremblay, Line; Roy-Vaillancourt, Mélina; Chebbi, Brahim; Bouchard, Stéphane; Daoust, Michael; Dénommée, Jessica; Thorpe, Moriah

2016-02-01

It is well documented that anti-fat attitudes influence the interactions individuals have with overweight people. However, testing attitudes through self-report measures is challenging. In the present study, we explore the use of a haptic virtual reality environment to physically interact with overweight virtual human (VH). We verify the hypothesis that duration and strength of virtual touch vary according to the characteristics of VH in ways similar to those encountered from interaction with real people in anti-fat attitude studies. A group of 61 participants were randomly assigned to one of the experimental conditions involving giving a virtual hug to a female or a male VH of either normal or overweight. We found significant associations between body image satisfaction and anti-fat attitudes and sex differences on these measures. We also found a significant interaction effect of the sex of the participants, sex of the VH, and the body size of the VH. Female participants hugged longer the overweight female VH than overweight male VH. Male participants hugged longer the normal-weight VH than the overweight VH. We conclude that virtual touch is a promising method of measuring attitudes, emotion and social interactions.

Emerging CAE technologies and their role in Future Ambient Intelligence Environments

NASA Astrophysics Data System (ADS)

Noor, Ahmed K.

2011-03-01

Dramatic improvements are on the horizon in Computer Aided Engineering (CAE) and various simulation technologies. The improvements are due, in part, to the developments in a number of leading-edge technologies and their synergistic combinations/convergence. The technologies include ubiquitous, cloud, and petascale computing; ultra high-bandwidth networks, pervasive wireless communication; knowledge based engineering; networked immersive virtual environments and virtual worlds; novel human-computer interfaces; and powerful game engines and facilities. This paper describes the frontiers and emerging simulation technologies, and their role in the future virtual product creation and learning/training environments. The environments will be ambient intelligence environments, incorporating a synergistic combination of novel agent-supported visual simulations (with cognitive learning and understanding abilities); immersive 3D virtual world facilities; development chain management systems and facilities (incorporating a synergistic combination of intelligent engineering and management tools); nontraditional methods; intelligent, multimodal and human-like interfaces; and mobile wireless devices. The Virtual product creation environment will significantly enhance the productivity and will stimulate creativity and innovation in future global virtual collaborative enterprises. The facilities in the learning/training environment will provide timely, engaging, personalized/collaborative and tailored visual learning.

A New Continent of Ideas

NASA Technical Reports Server (NTRS)

1990-01-01

While a new technology called 'virtual reality' is still at the 'ground floor' level, one of its basic components, 3D computer graphics is already in wide commercial use and expanding. Other components that permit a human operator to 'virtually' explore an artificial environment and to interact with it are being demonstrated routinely at Ames and elsewhere. Virtual reality might be defined as an environment capable of being virtually entered - telepresence, it is called - or interacted with by a human. The Virtual Interface Environment Workstation (VIEW) is a head-mounted stereoscopic display system in which the display may be an artificial computer-generated environment or a real environment relayed from remote video cameras. Operator can 'step into' this environment and interact with it. The DataGlove has a series of fiber optic cables and sensors that detect any movement of the wearer's fingers and transmit the information to a host computer; a computer generated image of the hand will move exactly as the operator is moving his gloved hand. With appropriate software, the operator can use the glove to interact with the computer scene by grasping an object. The DataSuit is a sensor equipped full body garment that greatly increases the sphere of performance for virtual reality simulations.

Virtual reality systems

NASA Technical Reports Server (NTRS)

Johnson, David W.

1992-01-01

Virtual realities are a type of human-computer interface (HCI) and as such may be understood from a historical perspective. In the earliest era, the computer was a very simple, straightforward machine. Interaction was human manipulation of an inanimate object, little more than the provision of an explicit instruction set to be carried out without deviation. In short, control resided with the user. In the second era of HCI, some level of intelligence and control was imparted to the system to enable a dialogue with the user. Simple context sensitive help systems are early examples, while more sophisticated expert system designs typify this era. Control was shared more equally. In this, the third era of the HCI, the constructed system emulates a particular environment, constructed with rules and knowledge about 'reality'. Control is, in part, outside the realm of the human-computer dialogue. Virtual reality systems are discussed.

Using the 12-lead ECG to localize the origin of ventricular and atrial tachycardias: part 1. Focal atrial tachycardia.

PubMed

Teh, Andrew W; Kistler, Peter M; Kalman, Jonathan M

2009-06-01

Focal atrial tachycardia is an unusual form of supraventricular tachycardia arising from defined anatomic locations and sites within the atria. Although recent advances in mapping technology have facilitated successful ablation, the surface ECG remains an important aid in localizing the focus. This review discusses the use of P-wave morphology on surface ECG to localize the site of focal atrial tachycardia.

Sex differences in virtual navigation influenced by scale and navigation experience.

PubMed

Padilla, Lace M; Creem-Regehr, Sarah H; Stefanucci, Jeanine K; Cashdan, Elizabeth A

2017-04-01

The Morris water maze is a spatial abilities test adapted from the animal spatial cognition literature and has been studied in the context of sex differences in humans. This is because its standard design, which manipulates proximal (close) and distal (far) cues, applies to human navigation. However, virtual Morris water mazes test navigation skills on a scale that is vastly smaller than natural human navigation. Many researchers have argued that navigating in large and small scales is fundamentally different, and small-scale navigation might not simulate natural human navigation. Other work has suggested that navigation experience could influence spatial skills. To address the question of how individual differences influence navigational abilities in differently scaled environments, we employed both a large- (146.4 m in diameter) and a traditional- (36.6 m in diameter) scaled virtual Morris water maze along with a novel measure of navigation experience (lifetime mobility). We found sex differences on the small maze in the distal cue condition only, but in both cue-conditions on the large maze. Also, individual differences in navigation experience modulated navigation performance on the virtual water maze, showing that higher mobility was related to better performance with proximal cues for only females on the small maze, but for both males and females on the large maze.

The Next Wave: Humans, Computers, and Redefining Reality

NASA Technical Reports Server (NTRS)

Little, William

2018-01-01

The Augmented/Virtual Reality (AVR) Lab at KSC is dedicated to " exploration into the growing computer fields of Extended Reality and the Natural User Interface (it is) a proving ground for new technologies that can be integrated into future NASA projects and programs." The topics of Human Computer Interface, Human Computer Interaction, Augmented Reality, Virtual Reality, and Mixed Reality are defined; examples of work being done in these fields in the AVR Lab are given. Current new and future work in Computer Vision, Speech Recognition, and Artificial Intelligence are also outlined.

Virtual temporal bone: an interactive 3-dimensional learning aid for cranial base surgery.

PubMed

Kockro, Ralf A; Hwang, Peter Y K

2009-05-01

We have developed an interactive virtual model of the temporal bone for the training and teaching of cranial base surgery. The virtual model was based on the tomographic data of the Visible Human Project. The male Visible Human's computed tomographic data were volumetrically reconstructed as virtual bone tissue, and the individual photographic slices provided the basis for segmentation of the middle and inner ear structures, cranial nerves, vessels, and brainstem. These structures were created by using outlining and tube editing tools, allowing structural modeling either directly on the basis of the photographic data or according to information from textbooks and cadaver dissections. For training and teaching, the virtual model was accessed in the previously described 3-dimensional workspaces of the Dextroscope or Dextrobeam (Volume Interactions Pte, Ltd., Singapore), whose interfaces enable volumetric exploration from any perspective and provide virtual tools for drilling and measuring. We have simulated several cranial base procedures including approaches via the floor of the middle fossa and the lateral petrous bone. The virtual model suitably illustrated the core facts of anatomic spatial relationships while simulating different stages of bone drilling along a variety of surgical corridors. The system was used for teaching during training courses to plan and discuss operative anatomy and strategies. The Virtual Temporal Bone and its surrounding 3-dimensional workspace provide an effective way to study the essential surgical anatomy of this complex region and to teach and train operative strategies, especially when used as an adjunct to cadaver dissections.

Beaming into the rat world: enabling real-time interaction between rat and human each at their own scale.

PubMed

Normand, Jean-Marie; Sanchez-Vives, Maria V; Waechter, Christian; Giannopoulos, Elias; Grosswindhager, Bernhard; Spanlang, Bernhard; Guger, Christoph; Klinker, Gudrun; Srinivasan, Mandayam A; Slater, Mel

2012-01-01

Immersive virtual reality (IVR) typically generates the illusion in participants that they are in the displayed virtual scene where they can experience and interact in events as if they were really happening. Teleoperator (TO) systems place people at a remote physical destination embodied as a robotic device, and where typically participants have the sensation of being at the destination, with the ability to interact with entities there. In this paper, we show how to combine IVR and TO to allow a new class of application. The participant in the IVR is represented in the destination by a physical robot (TO) and simultaneously the remote place and entities within it are represented to the participant in the IVR. Hence, the IVR participant has a normal virtual reality experience, but where his or her actions and behaviour control the remote robot and can therefore have physical consequences. Here, we show how such a system can be deployed to allow a human and a rat to operate together, but the human interacting with the rat on a human scale, and the rat interacting with the human on the rat scale. The human is represented in a rat arena by a small robot that is slaved to the human's movements, whereas the tracked rat is represented to the human in the virtual reality by a humanoid avatar. We describe the system and also a study that was designed to test whether humans can successfully play a game with the rat. The results show that the system functioned well and that the humans were able to interact with the rat to fulfil the tasks of the game. This system opens up the possibility of new applications in the life sciences involving participant observation of and interaction with animals but at human scale.

The development, assessment and validation of virtual reality for human anatomy instruction

NASA Technical Reports Server (NTRS)

Marshall, Karen Benn

1996-01-01

This research project seeks to meet the objective of science training by developing, assessing, validating and utilizing VR as a human anatomy training medium. Current anatomy instruction is primarily in the form of lectures and usage of textbooks. In ideal situations, anatomic models, computer-based instruction, and cadaver dissection are utilized to augment traditional methods of instruction. At many institutions, lack of financial resources limits anatomy instruction to textbooks and lectures. However, human anatomy is three-dimensional, unlike the one-dimensional depiction found in textbooks and the two-dimensional depiction found on the computer. Virtual reality allows one to step through the computer screen into a 3-D artificial world. The primary objective of this project is to produce a virtual reality application of the abdominopelvic region of a human cadaver that can be taken back to the classroom. The hypothesis is that an immersive learning environment affords quicker anatomic recognition and orientation and a greater level of retention in human anatomy instruction. The goal is to augment not replace traditional modes of instruction.

Enhanced emotional responses during social coordination with a virtual partner

PubMed Central

Dumas, Guillaume; Kelso, J.A. Scott; Tognoli, Emmanuelle

2016-01-01

Emotion and motion, though seldom studied in tandem, are complementary aspects of social experience. This study investigates variations in emotional responses during movement coordination between a human and a Virtual Partner (VP), an agent whose virtual finger movements are driven by the Haken-Kelso-Bunz (HKB) equations of Coordination Dynamics. Twenty-one subjects were instructed to coordinate finger movements with the VP in either inphase or antiphase patterns. By adjusting model parameters, we manipulated the ‘intention’ of VP as cooperative or competitive with the human's instructed goal. Skin potential responses (SPR) were recorded to quantify the intensity of emotional response. At the end of each trial, subjects rated the VP's intention and whether they thought their partner was another human being or a machine. We found greater emotional responses when subjects reported that their partner was human and when coordination was stable. That emotional responses are strongly influenced by dynamic features of the VP's behavior, has implications for mental health, brain disorders and the design of socially cooperative machines. PMID:27094374

Using Virtual Technology to Promote Functional Communication in Aphasia: Preliminary Evidence From Interactive Dialogues With Human and Virtual Clinicians.

PubMed

Kalinyak-Fliszar, Michelene; Martin, Nadine; Keshner, Emily; Rudnicky, Alex; Shi, Justin; Teodoro, Gregory

2015-11-01

We investigated the feasibility of using a virtual clinician (VC) to promote functional communication abilities of persons with aphasia (PWAs). We aimed to determine whether the quantity and quality of verbal output in dialogues with a VC would be the same or greater than those with a human clinician (HC). Four PWAs practiced dialogues for 2 sessions each with a HC and VC. Dialogues from before and after practice were transcribed and analyzed for content. We compared measures taken before and after practice in the VC and HC conditions. Results were mixed. Participants either produced more verbal output with the VC or showed no difference on this measure between the VC and HC conditions. Participants also showed some improvement in postpractice narratives. Results provide support for the feasibility and applicability of virtual technology to real-life communication contexts to improve functional communication in PWAs.

Headphone and Head-Mounted Visual Displays for Virtual Environments

NASA Technical Reports Server (NTRS)

Begault, Duran R.; Ellis, Stephen R.; Wenzel, Elizabeth M.; Trejo, Leonard J. (Technical Monitor)

1998-01-01

A realistic auditory environment can contribute to both the overall subjective sense of presence in a virtual display, and to a quantitative metric predicting human performance. Here, the role of audio in a virtual display and the importance of auditory-visual interaction are examined. Conjectures are proposed regarding the effectiveness of audio compared to visual information for creating a sensation of immersion, the frame of reference within a virtual display, and the compensation of visual fidelity by supplying auditory information. Future areas of research are outlined for improving simulations of virtual visual and acoustic spaces. This paper will describe some of the intersensory phenomena that arise during operator interaction within combined visual and auditory virtual environments. Conjectures regarding audio-visual interaction will be proposed.

Virtual reality as a tool for cross-cultural communication: an example from military team training

NASA Astrophysics Data System (ADS)

Downes-Martin, Stephen; Long, Mark; Alexander, Joanna R.

1992-06-01

A major problem with communication across cultures, whether professional or national, is that simple language translation if often insufficient to communicate the concepts. This is especially true when the communicators come from highly specialized fields of knowledge or from national cultures with long histories of divergence. This problem becomes critical when the goal of the communication is national negotiation dealing with such high risk items as arms negotiation or trade wars. Virtual Reality technology has considerable potential for facilitating communication across cultures, by immersing the communicators within multiple visual representations of the concepts, and providing control over those representations. Military distributed team training provides a model for virtual reality suitable for cross cultural communication such as negotiation. In both team training and negotiation, the participants must cooperate, agree on a set of goals, and achieve mastery over the concepts being negotiated. Team training technologies suitable for supporting cross cultural negotiation exist (branch wargaming, computer image generation and visualization, distributed simulation), and have developed along different lines than traditional virtual reality technology. Team training de-emphasizes the realism of physiological interfaces between the human and the virtual reality, and emphasizes the interaction of humans with each other and with intelligent simulated agents within the virtual reality. This approach to virtual reality is suggested as being more fruitful for future work.

Human-scale interaction for virtual model displays: a clear case for real tools

NASA Astrophysics Data System (ADS)

Williams, George C.; McDowall, Ian E.; Bolas, Mark T.

1998-04-01

We describe a hand-held user interface for interacting with virtual environments displayed on a Virtual Model Display. The tool, constructed entirely of transparent materials, is see-through. We render a graphical counterpart of the tool on the display and map it one-to-one with the real tool. This feature, combined with a capability for touch- sensitive, discrete input, results in a useful spatial input device that is visually versatile. We discuss the tool's design and interaction techniques it supports. Briefly, we look at the human factors issues and engineering challenges presented by this tool and, in general, by the class of hand-held user interfaces that are see-through.

The digital library: an oxymoron?

PubMed Central

Guédon, J C

1999-01-01

"Virtual libraries" and "digital libraries" have become stock phrases of our times. But what do they really mean? While digital refers to a new form of document encoding and must be approached from that perspective, virtual resonates with aspects that modern philosophy treats with benign neglect at best. The word virtual harbors the notion of potential, and therein lies its hidden strength. Although strong commercial interests try to use the shift to a digital environment to redefine the political economy of knowledge, and thus virtualize libraries into a state of almost complete impotence, all hope is not lost. Librarians of virtualized libraries may well discover that they have re-empowered institutions if they place human interaction at the heart of their operations. In other words, rather than envisioning themselves as knowledge bankers sitting on treasure vaults of knowledge, they should see themselves as "hearts" dynamizing human communities. They should also see themselves as an essential part of these communities, and not as external repositories of knowledge. In this fashion, they will avoid the fate of becoming an oxymoron. PMID:9934524

Virtual surface characteristics of a tactile display using magneto-rheological fluids.

PubMed

Lee, Chul-Hee; Jang, Min-Gyu

2011-01-01

Virtual surface characteristics of tactile displays are investigated to characterize the feeling of human touch for a haptic interface application. In order to represent the tactile feeling, a prototype tactile display incorporating Magneto-Rheological (MR) fluid has been developed. Tactile display devices simulate the finger's skin to feel the sensations of contact such as compliance, friction, and topography of the surface. Thus, the tactile display can provide information on the surface of an organic tissue to the surgeon in virtual reality. In order to investigate the compliance feeling of a human finger's touch, normal force responses of a tactile display under various magnetic fields have been assessed. Also, shearing friction force responses of the tactile display are investigated to simulate the action of finger dragging on the surface. Moreover, different matrix arrays of magnetic poles are applied to form the virtual surface topography. From the results, different tactile feelings are observed according to the applied magnetic field strength as well as the arrays of magnetic poles combinations. This research presents a smart tactile display technology for virtual surfaces.

Deploying Embodied AI into Virtual Worlds

NASA Astrophysics Data System (ADS)

Burden, David J. H.

The last two years have seen the start of commercial activity within virtual worlds. Unlike computer games where Non-Player-Character avatars are common, in most virtual worlds they are the exception — and until recently in Second Life they were non-existent. However there is real commercial scope for Als in these worlds — in roles from virtual sales staff and tutors to personal assistants. Deploying an embodied AI into a virtual world offers a unique opportunity to evaluate embodied Als, and to develop them within an environment where human and computer are on almost equal terms. This paper presents an architecture being used for the deployment of chatbot driven avatars within the Second Life virtual world, looks at the challenges of deploying an AI within such a virtual world, the possible implications for the Turing Test, and identifies research directions for the future.

A Typology of Ethnographic Scales for Virtual Worlds

NASA Astrophysics Data System (ADS)

Boellstorff, Tom

This chapter outlines a typology of genres of ethnographic research with regard to virtual worlds, informed by extensive research the author has completed both in Second Life and in Indonesia. It begins by identifying four confusions about virtual worlds: they are not games, they need not be graphical or even visual, they are not mass media, and they need not be defined in terms of escapist role-playing. A three-part typology of methods for ethnographic research in virtual worlds focuses on the relationship between research design and ethnographic scale. One class of methods for researching virtual worlds with regard to ethnographic scale explores interfaces between virtual worlds and the actual world, whereas a second examines interfaces between two or more virtual worlds. The third class involves studying a single virtual world in its own terms. Recognizing that all three approaches have merit for particular research purposes, ethnography of virtual worlds can be a vibrant field of research, contributing to central debates about human selfhood and sociality.

Control of repulsive force in a virtual environment using an electrorheological haptic master for a surgical robot application

NASA Astrophysics Data System (ADS)

Oh, Jong-Seok; Choi, Seung-Hyun; Choi, Seung-Bok

2014-01-01

This paper presents control performances of a new type of four-degrees-of-freedom (4-DOF) haptic master that can be used for robot-assisted minimally invasive surgery (RMIS). By adopting a controllable electrorheological (ER) fluid, the function of the proposed master is realized as a haptic feedback as well as remote manipulation. In order to verify the efficacy of the proposed master and method, an experiment is conducted with deformable objects featuring human organs. Since the use of real human organs is difficult for control due to high cost and moral hazard, an excellent alternative method, the virtual reality environment, is used for control in this work. In order to embody a human organ in the virtual space, the experiment adopts a volumetric deformable object represented by a shape-retaining chain linked (S-chain) model which has salient properties such as fast and realistic deformation of elastic objects. In haptic architecture for RMIS, the desired torque/force and desired position originating from the object of the virtual slave and operator of the haptic master are transferred to each other. In order to achieve the desired torque/force trajectories, a sliding mode controller (SMC) which is known to be robust to uncertainties is designed and empirically implemented. Tracking control performances for various torque/force trajectories from the virtual slave are evaluated and presented in the time domain.

Beaming into the Rat World: Enabling Real-Time Interaction between Rat and Human Each at Their Own Scale

PubMed Central

Normand, Jean-Marie; Sanchez-Vives, Maria V.; Waechter, Christian; Giannopoulos, Elias; Grosswindhager, Bernhard; Spanlang, Bernhard; Guger, Christoph; Klinker, Gudrun; Srinivasan, Mandayam A.; Slater, Mel

2012-01-01

Immersive virtual reality (IVR) typically generates the illusion in participants that they are in the displayed virtual scene where they can experience and interact in events as if they were really happening. Teleoperator (TO) systems place people at a remote physical destination embodied as a robotic device, and where typically participants have the sensation of being at the destination, with the ability to interact with entities there. In this paper, we show how to combine IVR and TO to allow a new class of application. The participant in the IVR is represented in the destination by a physical robot (TO) and simultaneously the remote place and entities within it are represented to the participant in the IVR. Hence, the IVR participant has a normal virtual reality experience, but where his or her actions and behaviour control the remote robot and can therefore have physical consequences. Here, we show how such a system can be deployed to allow a human and a rat to operate together, but the human interacting with the rat on a human scale, and the rat interacting with the human on the rat scale. The human is represented in a rat arena by a small robot that is slaved to the human’s movements, whereas the tracked rat is represented to the human in the virtual reality by a humanoid avatar. We describe the system and also a study that was designed to test whether humans can successfully play a game with the rat. The results show that the system functioned well and that the humans were able to interact with the rat to fulfil the tasks of the game. This system opens up the possibility of new applications in the life sciences involving participant observation of and interaction with animals but at human scale. PMID:23118987

Nature and origins of virtual environments - A bibliographical essay

NASA Technical Reports Server (NTRS)

Ellis, S. R.

1991-01-01

Virtual environments presented via head-mounted, computer-driven displays provide a new media for communication. They may be analyzed by considering: (1) what may be meant by an environment; (2) what is meant by the process of virtualization; and (3) some aspects of human performance that constrain environmental design. Their origins are traced from previous work in vehicle simulation and multimedia research. Pointers are provided to key technical references, in the dispersed, archival literature, that are relevant to the development and evaluation of virtual-environment interface systems.

Bile acids induce arrhythmias in human atrial myocardium--implications for altered serum bile acid composition in patients with atrial fibrillation.

PubMed

Rainer, Peter P; Primessnig, Uwe; Harenkamp, Sandra; Doleschal, Bernhard; Wallner, Markus; Fauler, Guenter; Stojakovic, Tatjana; Wachter, Rolf; Yates, Ameli; Groschner, Klaus; Trauner, Michael; Pieske, Burkert M; von Lewinski, Dirk

2013-11-01

High bile acid serum concentrations have been implicated in cardiac disease, particularly in arrhythmias. Most data originate from in vitro studies and animal models. We tested the hypotheses that (1) high bile acid concentrations are arrhythmogenic in adult human myocardium, (2) serum bile acid concentrations and composition are altered in patients with atrial fibrillation (AF) and (3) the therapeutically used ursodeoxycholic acid has different effects than other potentially toxic bile acids. Multicellular human atrial preparations ('trabeculae') were exposed to primary bile acids and the incidence of arrhythmic events was assessed. Bile acid concentrations were measured in serum samples from 250 patients and their association with AF and ECG parameters analysed. Additionally, we conducted electrophysiological studies in murine myocytes. Taurocholic acid (TCA) concentration-dependently induced arrhythmias in atrial trabeculae (14/28 at 300 µM TCA, p<0.01) while ursodeoxycholic acid did not. Patients with AF had significantly decreased serum levels of ursodeoxycholic acid conjugates and increased levels of non-ursodeoxycholic bile acids. In isolated myocytes, TCA depolarised the resting membrane potential, enhanced Na(+)/Ca(2+) exchanger (NCX) tail current density and induced afterdepolarisations. Inhibition of NCX prevented arrhythmias in atrial trabeculae. High TCA concentrations induce arrhythmias in adult human atria while ursodeoxycholic acid does not. AF is associated with higher serum levels of non-ursodeoxycholic bile acid conjugates and low levels of ursodeoxycholic acid conjugates. These data suggest that higher levels of toxic (arrhythmogenic) and low levels of protective bile acids create a milieu with a decreased arrhythmic threshold and thus may facilitate arrhythmic events.

Human Robotic Swarm Interaction Using an Artificial Physics Approach

DTIC Science & Technology

2014-12-01

calculates virtual forces that are summed and translated into velocity commands. The virtual forces are modeled after real physical forces such as...results from the physical experiments show that an artificial physics-based framework is an effective way to allow multiple agents to follow a human... modeled after real physical forces such as gravitational and Coulomb, forces but are not restricted to them, for example, the force magnitude may not be

Katja — the 24th week of virtual pregnancy for dosimetric calculations

NASA Astrophysics Data System (ADS)

Becker, Janine; Zankl, Maria; Fill, Ute; Hoeschen, Christoph

2008-01-01

Virtual human models, a.k.a. voxel models, are currently the state of the art in radiation protection for computing organ irradiation doses without difficult or morally unfeasible experiments. They are based on medical image data of human patients and offer a realistic, three dimensional representation of human anatomy. We present our newest voxel model Katja, a virtual woman in the 24th week of pregnancy. Katja integrates two previous voxel models, one obtained from the abdominal MRI scan of a pregnant patient and an already segmented model of a non-pregnant woman. The latter is the ICRP-AF, fitting the reference values for standard height, weight and organ masses given by the Internationals Committee of Radiological Protection (ICRP). The dataset was altered in order to fit the segmented foetus taken from the abdominal MRI scan. The resulting pregnant woman model, Katja, complies with the ICRP reference values for the adult female.

Using a virtual population to authentically teach epidemiology and biostatistics

NASA Astrophysics Data System (ADS)

Dunn, Peter K.; Donnison, Sharn; Cole, Rachel; Bulmer, Michael

2017-02-01

Epidemiology is the study of the distribution of disease in human populations. This means that authentically teaching primary data collection in epidemiology is difficult as students cannot easily access suitable human populations. Using an action research methodology, this paper studied the use of a virtual human population (called The Island) to enable students to experience many features of authentic primary data collection in epidemiological research. The Island was used in a course introducing epidemiology and biostatistics for students in non-quantitative disciplines. This paper discusses how The Island was introduced into the course, and then evaluates the change. Students were highly engaged, and students and teaching staff responded favourably to the use of The Island, with 70% of students agreeing or strongly agreeing that The Island was easy to use, and 64% agreeing or strongly agreeing that the use of a virtual population was beneficial to their understanding of epidemiology.

Heterogeneity of prejunctional NPY receptor-mediated inhibition of cardiac neurotransmission

PubMed Central

Serone, Adrian P; Wright, Christine E; Angus, James A

1999-01-01

Neuropeptide Y (NPY) has been proposed as the candidate inhibitory peptide mediating interactions between sympathetic and vagal neurotransmission in several species, including man. Here, we have defined the NPY receptors involved in modulation of cardiac autonomic neurotransmission using receptor-selective agonists and antagonists in the rabbit and guinea-pig isolated right atria.In isolated atrial preparations, sympathetically-mediated tachycardia (ST; with atropine 1 μM) or vagally-mediated bradycardia (VB; with propranolol 0.1–1 μM) in response to electrical field stimulation (EFS, 1–4 pulses) were tested 0–30 min after incubation with single concentrations of vehicle, NPY (0.01–10 μM), the Y2 receptor agonist N-Acetyl-[Leu28,31]NPY(24–36) (termed N-A[L]NPY(24–36)) or the Y1 receptor agonist [Leu31,Pro34]NPY (LP). The effect of NPY on the concentration-chronotropic response curves to isoprenaline and bethanechol were also assessed.Guinea-pig atria: NPY and N-A[L]NPY(24–36) caused concentration-dependent inhibition of VB and ST to EFS. Both peptides caused maximal inhibition of VB and ST within 10 min incubation and this remained constant. LP caused a concentration-dependent, transient inhibition of ST which was antagonized by the Y1-receptor antagonist GR231118 (0.3 μM), with apparent competitive kinetics. Rabbit atria: NPY (1 or 10 μM) had no effect on VB at any time point, but both NPY and LP caused a transient (∼10 min) inhibition of sympathetic tachycardia. This inhibition could be prevented by 0.3 μM GR231118. N-A[L]NPY(24–36) had no effect on ST. NPY had no effect on the response to β-adrenoceptor stimulation by isoprenaline nor muscarinic-receptor stimulation by bethanechol in either species.Thus, in the guinea-pig, NPY causes a stable inhibition of both VB and ST to EFS via Y2 receptors and transient inhibition of ST via Y1 receptors. In contrast in the rabbit, NPY has no effect on the cardiac vagus and prejunctional inhibition of ST is transient and mediated by a Y1-like receptor (rather than Y2). Therefore it would be surprising if NPY plays a functional role in modulation of cardiac neurotransmission in the rabbit. PMID:10369461

The extraneuronal accumulation of isoprenaline in trachea and atria of guinea-pig and cat

PubMed Central

Anning, Elizabeth N.; Bryan, Lesley J.; O'Donnell, Stella R.

1979-01-01

1 The Falck-Hillarp histochemical technique was used to locate extraneuronal sites of accumulation of isoprenaline in trachea and atria from guinea-pig and cat. With a tissue exposure time to formaldehyde gas of 3 h, isoprenaline was located as green fluorescence. 2 Quantitative microphotometry was used to measure fluorescence intensity within cells in the trachealis smooth muscle and the atrial myocardium of both species. 3 After incubation of tissues in 50 μM isoprenaline, specific fluorescence was seen in trachealis smooth muscle of both species and in the atrial myocardium of cat but not guinea-pig. In both species, fluorescence was also seen in the chondroblasts of the tracheal cartilage and in blood vessels in all tissues. 4 In trachealis smooth muscle of both species and in cat atrial myocardium, fluorescence brightness, resulting from incubation of tissues in 50 μM isoprenaline was significantly increased by 200 μM β-thujaplicin, an inhibitor of catechol-O-methyl transferase (COMT). In the presence of β-thujaplicin, fluorescence was not visible in guinea-pig atrial myocardium with 50 μM isoprenaline, although fluorescence brightness measured in myocardial cells was now greater than that in corresponding controls. 5 The fluorescence intensity seen in cat and guinea-pig trachealis smooth muscle cells and in cat atrial myocardial cells after incubation in 50 μM isoprenaline was decreased significantly in the presence of phenoxybenzamine (100 μM). In guinea-pig atria, phenoxybenzamine had no effect on myocardial fluorescence. Fluorescence intensity was also decreased if the incubation with isoprenaline was carried out at 0°C or if the post-incubation washing temperature was 37°C instead of 0 to 2°C. 6 The results demonstrate that the fluorescence histochemical technique can be used to locate isoprenaline in tissues. They also indicate that guinea-pig and cat trachealis smooth muscle cells and cat atrial myocardial cells can accumulate isoprenaline (a) by a mechanism sensitive to phenoxybenzamine and (b) into sites in which COMT plays a functional role in inactivating isoprenaline at the concentration used in these histochemical experiments (50 μM). In contrast, the guinea-pig atrial myocardial cells may have a minimal capacity to accumulate isoprenaline by a phenoxybenzamine-sensitive uptake mechanism. ImagesFigure 1Figure 2 PMID:367478

Major bleeding and intracranial hemorrhage risk prediction in patients with atrial fibrillation: Attention to modifiable bleeding risk factors or use of a bleeding risk stratification score? A nationwide cohort study.

PubMed

Chao, Tze-Fan; Lip, Gregory Y H; Lin, Yenn-Jiang; Chang, Shih-Lin; Lo, Li-Wei; Hu, Yu-Feng; Tuan, Ta-Chuan; Liao, Jo-Nan; Chung, Fa-Po; Chen, Tzeng-Ji; Chen, Shih-Ann

2018-03-01

While modifiable bleeding risks should be addressed in all patients with atrial fibrillation (AF), use of a bleeding risk score enables clinicians to 'flag up' those at risk of bleeding for more regular patient contact reviews. We compared a risk assessment strategy for major bleeding and intracranial hemorrhage (ICH) based on modifiable bleeding risk factors (referred to as a 'MBR factors' score) against established bleeding risk stratification scores (HEMORR 2 HAGES, HAS-BLED, ATRIA, ORBIT). A nationwide cohort study of 40,450 AF patients who received warfarin for stroke prevention was performed. The clinical endpoints included ICH and major bleeding. Bleeding scores were compared using receiver operating characteristic (ROC) curves (areas under the ROC curves [AUCs], or c-index) and the net reclassification index (NRI). During a follow up of 4.60±3.62years, 1581 (3.91%) patients sustained ICH and 6889 (17.03%) patients sustained major bleeding events. All tested bleeding risk scores at baseline were higher in those sustaining major bleeds. When compared to no ICH, patients sustaining ICH had higher baseline HEMORR 2 HAGES (p=0.003), HAS-BLED (p<0.001) and MBR factors score (p=0.013) but not ATRIA and ORBIT scores. When HAS-BLED was compared to other bleeding scores, c-indexes were significantly higher compared to MBR factors (p<0.001) and ORBIT (p=0.05) scores for major bleeding. C-indexes for the MBR factors score was significantly lower compared to all other scores (De long test, all p<0.001). When NRI was performed, HAS-BLED outperformed all other bleeding risk scores for major bleeding (all p<0.001). C-indexes for ATRIA and ORBIT scores suggested no significant prediction for ICH. All contemporary bleeding risk scores had modest predictive value for predicting major bleeding but the best predictive value and NRI was found for the HAS-BLED score. Simply depending on modifiable bleeding risk factors had suboptimal predictive value for the prediction of major bleeding in AF patients, when compared to the HAS-BLED score. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Innovative application of virtual display technique in virtual museum

NASA Astrophysics Data System (ADS)

Zhang, Jiankang

2017-09-01

Virtual museum refers to display and simulate the functions of real museum on the Internet in the form of 3 Dimensions virtual reality by applying interactive programs. Based on Virtual Reality Modeling Language, virtual museum building and its effective interaction with the offline museum lie in making full use of 3 Dimensions panorama technique, virtual reality technique and augmented reality technique, and innovatively taking advantages of dynamic environment modeling technique, real-time 3 Dimensions graphics generating technique, system integration technique and other key virtual reality techniques to make sure the overall design of virtual museum.3 Dimensions panorama technique, also known as panoramic photography or virtual reality, is a technique based on static images of the reality. Virtual reality technique is a kind of computer simulation system which can create and experience the interactive 3 Dimensions dynamic visual world. Augmented reality, also known as mixed reality, is a technique which simulates and mixes the information (visual, sound, taste, touch, etc.) that is difficult for human to experience in reality. These technologies make virtual museum come true. It will not only bring better experience and convenience to the public, but also be conducive to improve the influence and cultural functions of the real museum.

Addressing security issues related to virtual institute distributed activities

NASA Astrophysics Data System (ADS)

Stytz, Martin R.; Banks, Sheila B.

2008-03-01

One issue confounding the development and experimentation of distributed modeling and simulation environments is the inability of the project team to identify and collaborate with resources, both human and technical, from outside the United States. This limitation is especially significant within the human behavior representation area where areas such as cultural effects research and joint command team behavior modeling require the participation of various cultural and national representatives. To address this limitation, as well as other human behavior representation research issues, NATO Research and Technology Organization initiated a project to develop a NATO virtual institute that enables more effective and more collaborative research into human behavior representation. However, in building and operating a virtual institute one of the chief concerns must be the cyber security of the institute. Because the institute "exists" in cyberspace, all of its activities are susceptible to cyberattacks, subterfuge, denial of service and all of the vulnerabilities that networked computers must face. In our opinion, for the concept of virtual institutes to be successful and useful, their operations and services must be protected from the threats in the cyber environment. A key to developing the required protection is the development and promulgation of standards for cyber security. In this paper, we discuss the types of cyber standards that are required, how new internet technologies can be exploited and can benefit the promulgation, development, maintenance, and robustness of the standards. This paper is organized as follows. Section One introduces the concept of the virtual institutes, the expected benefits, and the motivation for our research and for research in this area. Section Two presents background material and a discussion of topics related to VIs, uman behavior and cultural modeling, and network-centric warfare. Section Three contains a discussion of the security challenges that face the virtual institute and the characteristics of the standards that must be employed. Section Four contains our proposal for documentation of the cybersecurity standards. Section Five contains the conclusion and suggestions for further work.

Advanced Technology for Portable Personal Visualization

DTIC Science & Technology

1993-01-01

have no cable to drag. " We submitted a short article describing the ceiling tracker and the requirements demanded of trackers in see-through systems...Newspaper/Magazine Articles : "Virtual Reality: It’s All in the Mind," Atlanta Consnrution, 29 September 1992 "Virtual Reality: Exploring the Future...basic scientific investigation of the human haptic system or to serve as haptic interfaces for virtual environments and teleloperation. 2. Research

Studying social interactions through immersive virtual environment technology: virtues, pitfalls, and future challenges

PubMed Central

Bombari, Dario; Schmid Mast, Marianne; Canadas, Elena; Bachmann, Manuel

2015-01-01

The goal of the present review is to explain how immersive virtual environment technology (IVET) can be used for the study of social interactions and how the use of virtual humans in immersive virtual environments can advance research and application in many different fields. Researchers studying individual differences in social interactions are typically interested in keeping the behavior and the appearance of the interaction partner constant across participants. With IVET researchers have full control over the interaction partners, can standardize them while still keeping the simulation realistic. Virtual simulations are valid: growing evidence shows that indeed studies conducted with IVET can replicate some well-known findings of social psychology. Moreover, IVET allows researchers to subtly manipulate characteristics of the environment (e.g., visual cues to prime participants) or of the social partner (e.g., his/her race) to investigate their influences on participants’ behavior and cognition. Furthermore, manipulations that would be difficult or impossible in real life (e.g., changing participants’ height) can be easily obtained with IVET. Beside the advantages for theoretical research, we explore the most recent training and clinical applications of IVET, its integration with other technologies (e.g., social sensing) and future challenges for researchers (e.g., making the communication between virtual humans and participants smoother). PMID:26157414

Studying social interactions through immersive virtual environment technology: virtues, pitfalls, and future challenges.

PubMed

Bombari, Dario; Schmid Mast, Marianne; Canadas, Elena; Bachmann, Manuel

2015-01-01

The goal of the present review is to explain how immersive virtual environment technology (IVET) can be used for the study of social interactions and how the use of virtual humans in immersive virtual environments can advance research and application in many different fields. Researchers studying individual differences in social interactions are typically interested in keeping the behavior and the appearance of the interaction partner constant across participants. With IVET researchers have full control over the interaction partners, can standardize them while still keeping the simulation realistic. Virtual simulations are valid: growing evidence shows that indeed studies conducted with IVET can replicate some well-known findings of social psychology. Moreover, IVET allows researchers to subtly manipulate characteristics of the environment (e.g., visual cues to prime participants) or of the social partner (e.g., his/her race) to investigate their influences on participants' behavior and cognition. Furthermore, manipulations that would be difficult or impossible in real life (e.g., changing participants' height) can be easily obtained with IVET. Beside the advantages for theoretical research, we explore the most recent training and clinical applications of IVET, its integration with other technologies (e.g., social sensing) and future challenges for researchers (e.g., making the communication between virtual humans and participants smoother).

Virtual Raters for Reproducible and Objective Assessments in Radiology

NASA Astrophysics Data System (ADS)

Kleesiek, Jens; Petersen, Jens; Döring, Markus; Maier-Hein, Klaus; Köthe, Ullrich; Wick, Wolfgang; Hamprecht, Fred A.; Bendszus, Martin; Biller, Armin

2016-04-01

Volumetric measurements in radiologic images are important for monitoring tumor growth and treatment response. To make these more reproducible and objective we introduce the concept of virtual raters (VRs). A virtual rater is obtained by combining knowledge of machine-learning algorithms trained with past annotations of multiple human raters with the instantaneous rating of one human expert. Thus, he is virtually guided by several experts. To evaluate the approach we perform experiments with multi-channel magnetic resonance imaging (MRI) data sets. Next to gross tumor volume (GTV) we also investigate subcategories like edema, contrast-enhancing and non-enhancing tumor. The first data set consists of N = 71 longitudinal follow-up scans of 15 patients suffering from glioblastoma (GB). The second data set comprises N = 30 scans of low- and high-grade gliomas. For comparison we computed Pearson Correlation, Intra-class Correlation Coefficient (ICC) and Dice score. Virtual raters always lead to an improvement w.r.t. inter- and intra-rater agreement. Comparing the 2D Response Assessment in Neuro-Oncology (RANO) measurements to the volumetric measurements of the virtual raters results in one-third of the cases in a deviating rating. Hence, we believe that our approach will have an impact on the evaluation of clinical studies as well as on routine imaging diagnostics.

Simulating the decentralized processes of the human immune system in a virtual anatomy model.

PubMed

Sarpe, Vladimir; Jacob, Christian

2013-01-01

Many physiological processes within the human body can be perceived and modeled as large systems of interacting particles or swarming agents. The complex processes of the human immune system prove to be challenging to capture and illustrate without proper reference to the spatial distribution of immune-related organs and systems. Our work focuses on physical aspects of immune system processes, which we implement through swarms of agents. This is our first prototype for integrating different immune processes into one comprehensive virtual physiology simulation. Using agent-based methodology and a 3-dimensional modeling and visualization environment (LINDSAY Composer), we present an agent-based simulation of the decentralized processes in the human immune system. The agents in our model - such as immune cells, viruses and cytokines - interact through simulated physics in two different, compartmentalized and decentralized 3-dimensional environments namely, (1) within the tissue and (2) inside a lymph node. While the two environments are separated and perform their computations asynchronously, an abstract form of communication is allowed in order to replicate the exchange, transportation and interaction of immune system agents between these sites. The distribution of simulated processes, that can communicate across multiple, local CPUs or through a network of machines, provides a starting point to build decentralized systems that replicate larger-scale processes within the human body, thus creating integrated simulations with other physiological systems, such as the circulatory, endocrine, or nervous system. Ultimately, this system integration across scales is our goal for the LINDSAY Virtual Human project. Our current immune system simulations extend our previous work on agent-based simulations by introducing advanced visualizations within the context of a virtual human anatomy model. We also demonstrate how to distribute a collection of connected simulations over a network of computers. As a future endeavour, we plan to use parameter tuning techniques on our model to further enhance its biological credibility. We consider these in silico experiments and their associated modeling and optimization techniques as essential components in further enhancing our capabilities of simulating a whole-body, decentralized immune system, to be used both for medical education and research as well as for virtual studies in immunoinformatics.

Virtual Reality: Real Promises and False Expectations.

ERIC Educational Resources Information Center

Homan, Willem J.

1994-01-01

Examines virtual reality (VR), and discusses the dilemma of defining VR, the limitations of the current technology, and the implications of VR for education. Highlights include a VR experience; human factors and the interface; and altered reality versus VR. (Author/AEF)

Yamaguchia toyensis n. sp., n. gen. (Annelida, Clitellata, Lumbriculidae) from profundal lake habitat in Japan

USGS Publications Warehouse

Fend, S.V.; Ohtaka, A.

2004-01-01

Yamaguchia toyensis n. sp., n. gen. is described from an oligotrophic caldera lake, Lake Toya, Hokkaido, Japan. Although the taxonomic affinities are unknown, the genus differs from all other Lumbriculidae in having the combination of testes and atria in X, a single, prosoporous male funnel per atrium, and spermathecae in XI. Unlike other Japanese lakes that have thus far been surveyed, Lake Toya supports abundant populations of lumbriculids in the profundal benthos.

Wolff-Parkinson-White syndrome and noncompaction in Leber's hereditary optic neuropathy due to the variant m.3460G>A.

PubMed

Finsterer, Josef; Stollberger, Claudia; Gatterer, Edmund

2018-05-01

This report describes a 66-year-old Caucasian male who acutely developed severe, bilateral impairment of visual acuity at 24 years of age. Leber's hereditary optic neuropathy (LHON) was suspected but the diagnosis was not genetically confirmed until the age of 49 years when the primary LHON mutation m.3460G>A was detected. Since onset, visual acuity had slightly improved. The family history was positive for LHON (brother, two sisters of mother, female cousin) and genetically confirmed in his brother and one aunt. Since the age of 65 years, he had experienced recurrent vertigo. His cardiological history was positive for arterial hypertension, noncompaction, myocardial thickening, intermittent right bundle-branch-block (RBBB) and Wolff-Parkinson-White (WPW) syndrome. In addition to LHON, he presented with polyneuropathy, hyperCKaemia, carotid artery occlusion, and a history of stroke. Cardiological investigations at 66 years of age revealed mildly reduced systolic function, enlarged atria, and nonsustained ventricular tachycardias. He underwent an electrophysiological investigation, but radiofrequency ablation was ruled out due to a 'bizarre' cardiac conduction system. Instead, an implantable cardioverter defibrillator was proposed but refused by the patient. Since the vertigo did not resolve it was attributed to polyneuropathy. This case demonstrates that LHON may be associated with noncompaction, myocardial thickening, reduced systolic function, enlarged atria, RBBB, WPW syndrome and nonsustained ventricular tachycardias. WPW syndrome in LHON may require invasive antiarrhythmic treatment.

Optimizing local capture of atrial fibrillation by rapid pacing: study of the influence of tissue dynamics.

PubMed

Uldry, Laurent; Virag, Nathalie; Jacquemet, Vincent; Vesin, Jean-Marc; Kappenberger, Lukas

2010-12-01

While successful termination by pacing of organized atrial tachycardias has been observed in patients, rapid pacing of AF can induce a local capture of the atrial tissue but in general no termination. The purpose of this study was to perform a systematic evaluation of the ability to capture AF by rapid pacing in a biophysical model of the atria with different dynamics in terms of conduction velocity (CV) and action potential duration (APD). Rapid pacing was applied during 30 s at five locations on the atria, for pacing cycle lengths in the range 60-110% of the mean AF cycle length (AFCL(mean)). Local AF capture could be achieved using rapid pacing at pacing sites located distal to major anatomical obstacles. Optimal pacing cycle lengths were found in the range 74-80% AFCL(mean) (capture window width: 14.6 ± 3% AFCL(mean)). An increase/decrease in CV or APD led to a significant shrinking/stretching of the capture window. Capture did not depend on AFCL, but did depend on the atrial substrate as characterized by an estimate of its wavelength, a better capture being achieved at shorter wavelengths. This model-based study suggests that a proper selection of the pacing site and cycle length can influence local capture results and that atrial tissue properties (CV and APD) are determinants of the response to rapid pacing.

VLDL from Metabolic Syndrome Individuals Enhanced Lipid Accumulation in Atria with Association of Susceptibility to Atrial Fibrillation.

PubMed

Lee, Hsiang-Chun; Lin, Hsin-Ting; Ke, Liang-Yin; Wei, Chi; Hsiao, Yi-Lin; Chu, Chih-Sheng; Lai, Wen-Ter; Shin, Shyi-Jang; Chen, Chu-Huang; Sheu, Sheng-Hsiung; Wu, Bin-Nan

2016-01-20

Metabolic syndrome (MetS) represents a cluster of metabolic derangements. Dyslipidemia is an important factor in MetS and is related to atrial fibrillation (AF). We hypothesized that very low density lipoproteins (VLDL) in MetS (MetS-VLDL) may induce atrial dilatation and vulnerability to AF. VLDL was therefore separated from normal (normal-VLDL) and MetS individuals. Wild type C57BL/6 male mice were divided into control, normal-VLDL (nVLDL), and MetS-VLDL (msVLDL) groups. VLDL (15 µg/g) and equivalent volumes of saline were injected via tail vein three times a week for six consecutive weeks. Cardiac chamber size and function were measured by echocardiography. MetS-VLDL significantly caused left atrial dilation (control, n = 10, 1.64 ± 0.23 mm; nVLDL, n = 7, 1.84 ± 0.13 mm; msVLDL, n = 10, 2.18 ± 0.24 mm; p < 0.0001) at week 6, associated with decreased ejection fraction (control, n = 10, 62.5% ± 7.7%, vs. msVLDL, n = 10, 52.9% ± 9.6%; p < 0.05). Isoproterenol-challenge experiment resulted in AF in young msVLDL mice. Unprovoked AF occurred only in elderly msVLDL mice. Immunohistochemistry showed excess lipid accumulation and apoptosis in msVLDL mice atria. These findings suggest a pivotal role of VLDL in AF pathogenesis for MetS individuals.

The mixed reality of things: emerging challenges for human-information interaction

NASA Astrophysics Data System (ADS)

Spicer, Ryan P.; Russell, Stephen M.; Rosenberg, Evan Suma

2017-05-01

Virtual and mixed reality technology has advanced tremendously over the past several years. This nascent medium has the potential to transform how people communicate over distance, train for unfamiliar tasks, operate in challenging environments, and how they visualize, interact, and make decisions based on complex data. At the same time, the marketplace has experienced a proliferation of network-connected devices and generalized sensors that are becoming increasingly accessible and ubiquitous. As the "Internet of Things" expands to encompass a predicted 50 billion connected devices by 2020, the volume and complexity of information generated in pervasive and virtualized environments will continue to grow exponentially. The convergence of these trends demands a theoretically grounded research agenda that can address emerging challenges for human-information interaction (HII). Virtual and mixed reality environments can provide controlled settings where HII phenomena can be observed and measured, new theories developed, and novel algorithms and interaction techniques evaluated. In this paper, we describe the intersection of pervasive computing with virtual and mixed reality, identify current research gaps and opportunities to advance the fundamental understanding of HII, and discuss implications for the design and development of cyber-human systems for both military and civilian use.

Virtual Environments in Scientific Visualization

NASA Technical Reports Server (NTRS)

Bryson, Steve; Lisinski, T. A. (Technical Monitor)

1994-01-01

Virtual environment technology is a new way of approaching the interface between computers and humans. Emphasizing display and user control that conforms to the user's natural ways of perceiving and thinking about space, virtual environment technologies enhance the ability to perceive and interact with computer generated graphic information. This enhancement potentially has a major effect on the field of scientific visualization. Current examples of this technology include the Virtual Windtunnel being developed at NASA Ames Research Center. Other major institutions such as the National Center for Supercomputing Applications and SRI International are also exploring this technology. This talk will be describe several implementations of virtual environments for use in scientific visualization. Examples include the visualization of unsteady fluid flows (the virtual windtunnel), the visualization of geodesics in curved spacetime, surface manipulation, and examples developed at various laboratories.

An Introduction to 3-D Sound

NASA Technical Reports Server (NTRS)

Begault, Durand R.; Null, Cynthia H. (Technical Monitor)

1997-01-01

This talk will overview the basic technologies related to the creation of virtual acoustic images, and the potential of including spatial auditory displays in human-machine interfaces. Research into the perceptual error inherent in both natural and virtual spatial hearing is reviewed, since the formation of improved technologies is tied to psychoacoustic research. This includes a discussion of Head Related Transfer Function (HRTF) measurement techniques (the HRTF provides important perceptual cues within a virtual acoustic display). Many commercial applications of virtual acoustics have so far focused on games and entertainment ; in this review, other types of applications are examined, including aeronautic safety, voice communications, virtual reality, and room acoustic simulation. In particular, the notion that realistic simulation is optimized within a virtual acoustic display when head motion and reverberation cues are included within a perceptual model.

The Major Role of IK1 in Mechanisms of Rotor Drift in the Atria: A Computational Study

PubMed Central

Berenfeld, Omer

2016-01-01

Maintenance of paroxysmal atrial fibrillation (AF) by fast rotors in the left atrium (LA) or at the pulmonary veins (PVs) is not fully understood. This review describes the role of the heterogeneous distribution of transmembrane currents in the PVs and LA junction (PV-LAJ) in the localization of rotors in the PVs. Experimentally observed heterogeneities in IK1, IKs, IKr, Ito, and ICaL in the PV-LAJ were incorporated into models of human atrial kinetics to simulate various conditions and investigate rotor drifting mechanisms. Spatial gradients in the currents resulted in shorter action potential duration, less negative minimum diastolic potential, slower upstroke and conduction velocity for rotors in the PV region than in the LA. Rotors under such conditions drifted toward the PV and stabilized at the less excitable region. Our simulations suggest that IK1 heterogeneity is dominant in determining the drift direction through its impact on the excitability gradient. These results provide a novel framework for understanding the complex dynamics of rotors in AF. PMID:28096699

Assessing biocomputational modelling in transforming clinical guidelines for osteoporosis management.

PubMed

Thiel, Rainer; Viceconti, Marco; Stroetmann, Karl

2011-01-01

Biocomputational modelling as developed by the European Virtual Physiological Human (VPH) Initiative is the area of ICT most likely to revolutionise in the longer term the practice of medicine. Using the example of osteoporosis management, a socio-economic assessment framework is presented that captures how the transformation of clinical guidelines through VPH models can be evaluated. Applied to the Osteoporotic Virtual Physiological Human Project, a consequent benefit-cost analysis delivers promising results, both methodologically and substantially.

Ultrafast Synthetic Transmit Aperture Imaging Using Hadamard-Encoded Virtual Sources With Overlapping Sub-Apertures.

PubMed

Ping Gong; Pengfei Song; Shigao Chen

2017-06-01

The development of ultrafast ultrasound imaging offers great opportunities to improve imaging technologies, such as shear wave elastography and ultrafast Doppler imaging. In ultrafast imaging, there are tradeoffs among image signal-to-noise ratio (SNR), resolution, and post-compounded frame rate. Various approaches have been proposed to solve this tradeoff, such as multiplane wave imaging or the attempts of implementing synthetic transmit aperture imaging. In this paper, we propose an ultrafast synthetic transmit aperture (USTA) imaging technique using Hadamard-encoded virtual sources with overlapping sub-apertures to enhance both image SNR and resolution without sacrificing frame rate. This method includes three steps: 1) create virtual sources using sub-apertures; 2) encode virtual sources using Hadamard matrix; and 3) add short time intervals (a few microseconds) between transmissions of different virtual sources to allow overlapping sub-apertures. The USTA was tested experimentally with a point target, a B-mode phantom, and in vivo human kidney micro-vessel imaging. Compared with standard coherent diverging wave compounding with the same frame rate, improvements on image SNR, lateral resolution (+33%, with B-mode phantom imaging), and contrast ratio (+3.8 dB, with in vivo human kidney micro-vessel imaging) have been achieved. The f-number of virtual sources, the number of virtual sources used, and the number of elements used in each sub-aperture can be flexibly adjusted to enhance resolution and SNR. This allows very flexible optimization of USTA for different applications.

Spatial memory: a Rosetta stone for rat and human hippocampal discourse: Theoretical comment on Goodrich-Hunsaker and Hopkins (2010).

PubMed

Sutherland, Robert J

2010-06-01

The article by Goodrich-Hunsaker and Hopkins (2010, this issue) takes up an important place among in the recent contributions on the role of the hippocampus in memory. They evaluate the effect of bilateral damage to the hippocampus on performance by human participants in a virtual 8-arm radial maze. The hippocampal damage appears to be highly selective and nearly complete. Exactly as with selective hippocampal damage in rats, the human participants showed a deficit in accurately choosing rewarded versus never-rewarded arms and a deficit in avoiding reentering recently visited arms. The results are triply significant: (1) They provide good support for the idea that the wealth of neurobiological information, from network to synapse to gene, on spatial memory in the rat may apply as a whole to the human hippocampal memory system; (2) They affirm the utility of human virtual task models of rat spatial memory tasks; (3) They support one interpretation of the dampening of the hippocampal functional MRI (fMRI) blood oxygen level-dependent (BOLD) signal during performance of the virtual radial arm maze observed by Astur et al. (2005).

Virtual reality in the operating room of the future.

PubMed

Müller, W; Grosskopf, S; Hildebrand, A; Malkewitz, R; Ziegler, R

1997-01-01

In cooperation with the Max-Delbrück-Centrum/Robert-Rössle-Klinik (MDC/RRK) in Berlin, the Fraunhofer Institute for Computer Graphics is currently designing and developing a scenario for the operating room of the future. The goal of this project is to integrate new analysis, visualization and interaction tools in order to optimize and refine tumor diagnostics and therapy in combination with laser technology and remote stereoscopic video transfer. Hence, a human 3-D reference model is reconstructed using CT, MR, and anatomical cryosection images from the National Library of Medicine's Visible Human Project. Applying segmentation algorithms and surface-polygonization methods a 3-D representation is obtained. In addition, a "fly-through" the virtual patient is realized using 3-D input devices (data glove, tracking system, 6-DOF mouse). In this way, the surgeon can experience really new perspectives of the human anatomy. Moreover, using a virtual cutting plane any cut of the CT volume can be interactively placed and visualized in realtime. In conclusion, this project delivers visions for the application of effective visualization and VR systems. Commonly known as Virtual Prototyping and applied by the automotive industry long ago, this project shows, that the use of VR techniques can also prototype an operating room. After evaluating design and functionality of the virtual operating room, MDC plans to build real ORs in the near future. The use of VR techniques provides a more natural interface for the surgeon in the OR (e.g., controlling interactions by voice input). Besides preoperative planning future work will focus on supporting the surgeon in performing surgical interventions. An optimal synthesis of real and synthetic data, and the inclusion of visual, aural, and tactile senses in virtual environments can meet these requirements. This Augmented Reality could represent the environment for the surgeons of tomorrow.

Human Behavior Representation in Constructive Simulation (La representation du comportement humain dans la simulation constructive)

DTIC Science & Technology

2009-09-01

Environmental Medicine USN United States Navy VAE Virtual Air Environment VACP Visual, Auditory, Cognitive, Psychomotor (demand) VR Virtual Reality ...0 .5 m/s. Another useful approach to capturing leg, trunk, whole body, or movement tasks comes from virtual reality - based training research and...referred to as semi-automated forces (SAF). From: http://www.sedris.org/glossary.htm#C_grp. Constructive Models Abstractions from the reality to

Proceedings of the 1993 Conference on Intelligent Computer-Aided Training and Virtual Environment Technology

NASA Technical Reports Server (NTRS)

Hyde, Patricia R.; Loftin, R. Bowen

1993-01-01

The volume 2 proceedings from the 1993 Conference on Intelligent Computer-Aided Training and Virtual Environment Technology are presented. Topics discussed include intelligent computer assisted training (ICAT) systems architectures, ICAT educational and medical applications, virtual environment (VE) training and assessment, human factors engineering and VE, ICAT theory and natural language processing, ICAT military applications, VE engineering applications, ICAT knowledge acquisition processes and applications, and ICAT aerospace applications.

Virtual Reality and Online Databases: Will "Look and Feel" Literally Mean "Look" and "Feel"? [and]"Online" Interviews Dr. Thomas A. Furness III, Virtual Reality Pioneer.

ERIC Educational Resources Information Center

Miller, Carmen

1992-01-01

The first of two articles discusses virtual reality (VR) and online databases; the second one reports on an interview with Thomas A. Furness III, who defines VR and explains work at the Human Interface Technology Laboratory (HIT). Sidebars contain a glossary of VR terms and a conversation with Toni Emerson, the HIT lab's librarian. (LRW)

Is it the real deal? Perception of virtual characters versus humans: an affective cognitive neuroscience perspective

PubMed Central

de Borst, Aline W.; de Gelder, Beatrice

2015-01-01

Recent developments in neuroimaging research support the increased use of naturalistic stimulus material such as film, avatars, or androids. These stimuli allow for a better understanding of how the brain processes information in complex situations while maintaining experimental control. While avatars and androids are well suited to study human cognition, they should not be equated to human stimuli. For example, the uncanny valley hypothesis theorizes that artificial agents with high human-likeness may evoke feelings of eeriness in the human observer. Here we review if, when, and how the perception of human-like avatars and androids differs from the perception of humans and consider how this influences their utilization as stimulus material in social and affective neuroimaging studies. First, we discuss how the appearance of virtual characters affects perception. When stimuli are morphed across categories from non-human to human, the most ambiguous stimuli, rather than the most human-like stimuli, show prolonged classification times and increased eeriness. Human-like to human stimuli show a positive linear relationship with familiarity. Secondly, we show that expressions of emotions in human-like avatars can be perceived similarly to human emotions, with corresponding behavioral, physiological and neuronal activations, with exception of physical dissimilarities. Subsequently, we consider if and when one perceives differences in action representation by artificial agents versus humans. Motor resonance and predictive coding models may account for empirical findings, such as an interference effect on action for observed human-like, natural moving characters. However, the expansion of these models to explain more complex behavior, such as empathy, still needs to be investigated in more detail. Finally, we broaden our outlook to social interaction, where virtual reality stimuli can be utilized to imitate complex social situations. PMID:26029133

Scripting human animations in a virtual environment

NASA Technical Reports Server (NTRS)

Goldsby, Michael E.; Pandya, Abhilash K.; Maida, James C.

1994-01-01

The current deficiencies of virtual environment (VE) are well known: annoying lag time in drawing the current view, drastically simplified environments to reduce that time lag, low resolution and narrow field of view. Animation scripting is an application of VE technology which can be carried out successfully despite these deficiencies. The final product is a smoothly moving high resolution animation displaying detailed models. In this system, the user is represented by a human computer model with the same body proportions. Using magnetic tracking, the motions of the model's upper torso, head and arms are controlled by the user's movements (18 degrees of freedom). The model's lower torso and global position and orientation are controlled by a spaceball and keypad (12 degrees of freedom). Using this system human motion scripts can be extracted from the user's movements while immersed in a simplified virtual environment. Recorded data is used to define key frames; motion is interpolated between them and post processing adds a more detailed environment. The result is a considerable savings in time and a much more natural-looking movement of a human figure in a smooth and seamless animation.

Virtually There.

ERIC Educational Resources Information Center

Lanier, Jaron

2001-01-01

Describes tele-immersion, a new medium for human interaction enabled by digital technologies. It combines the display and interaction techniques of virtual reality with new vision technologies that transcend the traditional limitations of a camera. Tele-immersion stations observe people as moving sculptures without favoring a single point of view.…

Closed Environment Module - Modularization and extension of the Virtual Habitat

NASA Astrophysics Data System (ADS)

Plötner, Peter; Czupalla, Markus; Zhukov, Anton

2013-12-01

The Virtual Habitat (V-HAB), is a Life Support System (LSS) simulation, created to perform dynamic simulation of LSS's for future human spaceflight missions. It allows the testing of LSS robustness by means of computer simulations, e.g. of worst case scenarios.

Photographer: Digital Telepresence: Dr Murial Ross's Virtual Reality Application for Neuroscience

NASA Technical Reports Server (NTRS)

1995-01-01

Photographer: Digital Telepresence: Dr Murial Ross's Virtual Reality Application for Neuroscience Research Biocomputation. To study human disorders of balance and space motion sickness. Shown here is a 3D reconstruction of a nerve ending in inner ear, nature's wiring of balance organs.

On Mediation in Virtual Learning Environments.

ERIC Educational Resources Information Center

Davies, Larry; Hassan, W. Shukry

2001-01-01

Discusses concepts of mediation and focuses on the importance of implementing comprehensive virtual learning environments. Topics include education and technology as they relate to cultural change, social institutions, the Internet and computer-mediated communication, software design and human-computer interaction, the use of MOOs, and language.…

Simulating Hepatic Lesions as Virtual Cellular Systems

EPA Science Inventory

The US EPA Virtual Liver (v-Liver) project is aimed at reducing the uncertainty in estimating the risk of toxic outcomes in humans by simulating the dose-dependent effects of environmental chemicals in silico. The v-Liver embodies an emerging field of research in computational ti...

A 3D visualization and simulation of the individual human jaw.

PubMed

Muftić, Osman; Keros, Jadranka; Baksa, Sarajko; Carek, Vlado; Matković, Ivo

2003-01-01

A new biomechanical three-dimensional (3D) model for the human mandible based on computer-generated virtual model is proposed. Using maps obtained from the special kinds of photos of the face of the real subject, it is possible to attribute personality to the virtual character, while computer animation offers movements and characteristics within the confines of space and time of the virtual world. A simple two-dimensional model of the jaw cannot explain the biomechanics, where the muscular forces through occlusion and condylar surfaces are in the state of 3D equilibrium. In the model all forces are resolved into components according to a selected coordinate system. The muscular forces act on the jaw, along with the necessary force level for chewing as some kind of mandible balance, preventing dislocation and loading of nonarticular tissues. In the work is used new approach to computer-generated animation of virtual 3D characters (called "Body SABA"), using in one object package of minimal costs and easy for operation.

Extending MAM5 Meta-Model and JaCalIV E Framework to Integrate Smart Devices from Real Environments.

PubMed

Rincon, J A; Poza-Lujan, Jose-Luis; Julian, V; Posadas-Yagüe, Juan-Luis; Carrascosa, C

2016-01-01

This paper presents the extension of a meta-model (MAM5) and a framework based on the model (JaCalIVE) for developing intelligent virtual environments. The goal of this extension is to develop augmented mirror worlds that represent a real and virtual world coupled, so that the virtual world not only reflects the real one, but also complements it. A new component called a smart resource artifact, that enables modelling and developing devices to access the real physical world, and a human in the loop agent to place a human in the system have been included in the meta-model and framework. The proposed extension of MAM5 has been tested by simulating a light control system where agents can access both virtual and real sensor/actuators through the smart resources developed. The results show that the use of real environment interactive elements (smart resource artifacts) in agent-based simulations allows to minimize the error between simulated and real system.

Extending MAM5 Meta-Model and JaCalIV E Framework to Integrate Smart Devices from Real Environments

PubMed Central

2016-01-01

This paper presents the extension of a meta-model (MAM5) and a framework based on the model (JaCalIVE) for developing intelligent virtual environments. The goal of this extension is to develop augmented mirror worlds that represent a real and virtual world coupled, so that the virtual world not only reflects the real one, but also complements it. A new component called a smart resource artifact, that enables modelling and developing devices to access the real physical world, and a human in the loop agent to place a human in the system have been included in the meta-model and framework. The proposed extension of MAM5 has been tested by simulating a light control system where agents can access both virtual and real sensor/actuators through the smart resources developed. The results show that the use of real environment interactive elements (smart resource artifacts) in agent-based simulations allows to minimize the error between simulated and real system. PMID:26926691

Virtual Doppelgangers: Psychological Effects of Avatars Who Ignore Their Owners

NASA Astrophysics Data System (ADS)

Bailenson, Jeremy N.; Segovia, Kathryn Y.

For a decade, the Virtual Human Interaction Lab has been creating doppelgangers, virtual versions of the self, for research purposes. This chapter considers how humans may be affected by confrontation with virtual versions of themselves, on the basis of well-established psychological theories, including social cognitive theory (social learning theory), media richness theory (information richness theory), and self-perception theory. Experiments carried out in the Lab, and informed by these theories, have explored such notable topics as health communication, marketing, and false memories. The findings of one series of studies suggest that doppelgangerscan show the rewards of exercise and proper eating habits, changing people's health-related behavior as a result. Other studies showed that doppelgangers are powerful marketing agents and can be used in advertisements to create favorable brand impressions among consumers. Other research documented that children have difficulty in distinguishing between an actual memory elicited by a physical world event and a false memory elicited by mental image or doppelganger.

Quantitative and qualitative changes in teaching histology by means of virtual microscopy in an introductory course in human anatomy.

PubMed

Husmann, Polly R; O'Loughlin, Valerie Dean; Braun, Mark W

2009-10-01

This study compares overall laboratory averages and individual test scores along with a student survey to determine the effects of using virtual microscopy in place of optical microscopes in a large undergraduate human anatomy course. T-tests revealed that the first two laboratory examinations (of four) and the overall laboratory averages were significantly increased compared with the previous year. We hypothesize that this is due to students' ability to use and understand the technology quickly as opposed to learning how to maneuver an optical microscope. Students also responded positively in a survey about the virtual microscope, indicating that increased accessibility, ease of use, and the ability to understand the material were important components of the virtual microscope. In addition, an increase in student collaboration was noted because multiple students were able to view the image at a time. This level of acceptance of virtual microscopy has been reported in previous studies, though this level of increased examination scores is rare. We attribute this to differences between the medical students, with whom this technology has been researched in the past, and undergraduate introductory students.

Inhibitors of Helicobacter pylori Protease HtrA Found by ‘Virtual Ligand’ Screening Combat Bacterial Invasion of Epithelia

PubMed Central

Schneider, Petra; Hoy, Benjamin; Wessler, Silja; Schneider, Gisbert

2011-01-01

Background The human pathogen Helicobacter pylori (H. pylori) is a main cause for gastric inflammation and cancer. Increasing bacterial resistance against antibiotics demands for innovative strategies for therapeutic intervention. Methodology/Principal Findings We present a method for structure-based virtual screening that is based on the comprehensive prediction of ligand binding sites on a protein model and automated construction of a ligand-receptor interaction map. Pharmacophoric features of the map are clustered and transformed in a correlation vector (‘virtual ligand’) for rapid virtual screening of compound databases. This computer-based technique was validated for 18 different targets of pharmaceutical interest in a retrospective screening experiment. Prospective screening for inhibitory agents was performed for the protease HtrA from the human pathogen H. pylori using a homology model of the target protein. Among 22 tested compounds six block E-cadherin cleavage by HtrA in vitro and result in reduced scattering and wound healing of gastric epithelial cells, thereby preventing bacterial infiltration of the epithelium. Conclusions/Significance This study demonstrates that receptor-based virtual screening with a permissive (‘fuzzy’) pharmacophore model can help identify small bioactive agents for combating bacterial infection. PMID:21483848

Maintaining Engagement in Long-term Interventions with Relational Agents

PubMed Central

Bickmore, Timothy; Schulman, Daniel; Yin, Langxuan

2011-01-01

We discuss issues in designing virtual humans for applications which require long-term voluntary use, and the problem of maintaining engagement with users over time. Concepts and theories related to engagement from a variety of disciplines are reviewed. We describe a platform for conducting studies into long-term interactions between humans and virtual agents, and present the results of two longitudinal randomized controlled experiments in which the effect of manipulations of agent behavior on user engagement was assessed. PMID:21318052

Virtual Teams and Human Work Interaction Design - Learning to Work in and Designing for Virtual Teams

NASA Astrophysics Data System (ADS)

Orngreen, Rikke; Clemmensen, Torkil; Pejtersen, Annelise Mark

The boundaries and work processes for how virtual teams interact are undergoing changes, from a tool and stand-alone application orientation, to the use of multiple generic platforms chosen and redesigned to the specific context. These are often at the same time designed both by professional software developers and the individual members of the virtual teams, rather than determined on a single organizational level. There may be no impact of the technology per se on individuals, groups or organizations, as the technology for virtual teams rather enhance situation ambiguity and disrupt existing task-artifact cycles. This ambiguous situation calls for new methods for empirical work analysis and interaction design that can help us understand how organizations, teams and individuals learn to organize, design and work in virtual teams in various networked contexts.

How to maintain the oral health of a child with Wolff-Parkinson-White syndrome: a case report.

PubMed

Petroniatis, Tsampikos; Ortu, Eleonora; Marchili, Nicola; Giannoni, Mario; Marzo, Giuseppe; Monaco, Annalisa

2014-09-30

Wolff-Parkinson-White syndrome is one of the most important disorders of the heart conduction system. It is caused by the presence of an abnormal accessory electrical conduction pathway between the atria and the ventricles. In the present report, we describe the correct oral health management of a 12-year-old Caucasian girl with Wolff-Parkinson-White syndrome. We successfully undertook the dental care of a girl with Wolff-Parkinson-White syndrome, which we describe here.

Virtual reality: Avatars in human spaceflight training

NASA Astrophysics Data System (ADS)

Osterlund, Jeffrey; Lawrence, Brad

2012-02-01

With the advancements in high spatial and temporal resolution graphics, along with advancements in 3D display capabilities to model, simulate, and analyze human-to-machine interfaces and interactions, the world of virtual environments is being used to develop everything from gaming, movie special affects and animations to the design of automobiles. The use of multiple object motion capture technology and digital human tools in aerospace has demonstrated to be a more cost effective alternative to the cost of physical prototypes, provides a more efficient, flexible and responsive environment to changes in the design and training, and provides early human factors considerations concerning the operation of a complex launch vehicle or spacecraft. United Space Alliance (USA) has deployed this technique and tool under Research and Development (R&D) activities on both spacecraft assembly and ground processing operations design and training on the Orion Crew Module. USA utilizes specialized products that were chosen based on functionality, including software and fixed based hardware (e.g., infrared and visible red cameras), along with cyber gloves to ensure fine motor dexterity of the hands. The key findings of the R&D were: mock-ups should be built to not obstruct cameras from markers being tracked; a mock-up toolkit be assembled to facilitate dynamic design changes; markers should be placed in accurate positions on humans and flight hardware to help with tracking; 3D models used in the virtual environment be striped of non-essential data; high computational capable workstations are required to handle the large model data sets; and Technology Interchange Meetings with vendors and other industries also utilizing virtual reality applications need to occur on a continual basis enabling USA to maintain its leading edge within this technology. Parameters of interest and benefit in human spaceflight simulation training that utilizes virtual reality technologies are to familiarize and assess operational processes, allow the ability to train virtually, experiment with "what if" scenarios, and expedite immediate changes to validate the design implementation are all parameters of interest in human spaceflight. Training benefits encompass providing 3D animation for post-training assessment, placement of avatars within 3D replicated work environments in assembling or processing hardware, offering various viewpoints of processes viewed and assessed giving the evaluators the ability to assess task feasibility and identify potential support equipment needs; and provide human factors determinations, such as reach, visibility, and accessibility. Multiple object motion capture technology provides an effective tool to train and assess ergonomic risks, simulations for determination of negative interactions between technicians and their proposed workspaces, and evaluation of spaceflight systems prior to, and as part of, the design process to contain costs and reduce schedule delays.

Distributed virtual environment for emergency medical training

NASA Astrophysics Data System (ADS)

Stytz, Martin R.; Banks, Sheila B.; Garcia, Brian W.; Godsell-Stytz, Gayl M.

1997-07-01

In many professions where individuals must work in a team in a high stress environment to accomplish a time-critical task, individual and team performance can benefit from joint training using distributed virtual environments (DVEs). One professional field that lacks but needs a high-fidelity team training environment is the field of emergency medicine. Currently, emergency department (ED) medical personnel train by using words to create a metal picture of a situation for the physician and staff, who then cooperate to solve the problems portrayed by the word picture. The need in emergency medicine for realistic virtual team training is critical because ED staff typically encounter rarely occurring but life threatening situations only once in their careers and because ED teams currently have no realistic environment in which to practice their team skills. The resulting lack of experience and teamwork makes diagnosis and treatment more difficult. Virtual environment based training has the potential to redress these shortfalls. The objective of our research is to develop a state-of-the-art virtual environment for emergency medicine team training. The virtual emergency room (VER) allows ED physicians and medical staff to realistically prepare for emergency medical situations by performing triage, diagnosis, and treatment on virtual patients within an environment that provides them with the tools they require and the team environment they need to realistically perform these three tasks. There are several issues that must be addressed before this vision is realized. The key issues deal with distribution of computations; the doctor and staff interface to the virtual patient and ED equipment; the accurate simulation of individual patient organs' response to injury, medication, and treatment; and an accurate modeling of the symptoms and appearance of the patient while maintaining a real-time interaction capability. Our ongoing work addresses all of these issues. In this paper we report on our prototype VER system and its distributed system architecture for an emergency department distributed virtual environment for emergency medical staff training. The virtual environment enables emergency department physicians and staff to develop their diagnostic and treatment skills using the virtual tools they need to perform diagnostic and treatment tasks. Virtual human imagery, and real-time virtual human response are used to create the virtual patient and present a scenario. Patient vital signs are available to the emergency department team as they manage the virtual case. The work reported here consists of the system architectures we developed for the distributed components of the virtual emergency room. The architectures we describe consist of the network level architecture as well as the software architecture for each actor within the virtual emergency room. We describe the role of distributed interactive simulation and other enabling technologies within the virtual emergency room project.

The Development of a Virtual Company to Support the Reengineering of the NASA/Goddard Hubble Space Telescope Control Center System

NASA Technical Reports Server (NTRS)

Lehtonen, Ken

1999-01-01

This is a report to the Third Annual International Virtual Company Conference, on The Development of a Virtual Company to Support the Reengineering of the NASA/Goddard Hubble Space Telescope (HST) Control Center System. It begins with a HST Science "Commercial": Brief Tour of Our Universe showing various pictures taken from the Hubble Space Telescope. The presentation then reviews the project background and goals. Evolution of the Control Center System ("CCS Inc.") is then reviewed. Topics of Interest to "virtual companies" are reviewed: (1) "How To Choose A Team" (2) "Organizational Model" (3) "The Human Component" (4) "'Virtual Trust' Among Teaming Companies" (5) "Unique Challenges to Working Horizontally" (6) "The Cultural Impact" (7) "Lessons Learned".

Guidelines for developing distributed virtual environment applications

NASA Astrophysics Data System (ADS)

Stytz, Martin R.; Banks, Sheila B.

1998-08-01

We have conducted a variety of projects that served to investigate the limits of virtual environments and distributed virtual environment (DVE) technology for the military and medical professions. The projects include an application that allows the user to interactively explore a high-fidelity, dynamic scale model of the Solar System and a high-fidelity, photorealistic, rapidly reconfigurable aircraft simulator. Additional projects are a project for observing, analyzing, and understanding the activity in a military distributed virtual environment, a project to develop a distributed threat simulator for training Air Force pilots, a virtual spaceplane to determine user interface requirements for a planned military spaceplane system, and an automated wingman for use in supplementing or replacing human-controlled systems in a DVE. The last two projects are a virtual environment user interface framework; and a project for training hospital emergency department personnel. In the process of designing and assembling the DVE applications in support of these projects, we have developed rules of thumb and insights into assembling DVE applications and the environment itself. In this paper, we open with a brief review of the applications that were the source for our insights and then present the lessons learned as a result of these projects. The lessons we have learned fall primarily into five areas. These areas are requirements development, software architecture, human-computer interaction, graphical database modeling, and construction of computer-generated forces.

Seamless 3D interaction for virtual tables, projection planes, and CAVEs

NASA Astrophysics Data System (ADS)

Encarnacao, L. M.; Bimber, Oliver; Schmalstieg, Dieter; Barton, Robert J., III

2000-08-01

The Virtual Table presents stereoscopic graphics to a user in a workbench-like setting. This device shares with other large- screen display technologies (such as data walls and surround- screen projection systems) the lack of human-centered unencumbered user interfaces and 3D interaction technologies. Such shortcomings present severe limitations to the application of virtual reality (VR) technology to time- critical applications as well as employment scenarios that involve heterogeneous groups of end-users without high levels of computer familiarity and expertise. Traditionally such employment scenarios are common in planning-related application areas such as mission rehearsal and command and control. For these applications, a high grade of flexibility with respect to the system requirements (display and I/O devices) as well as to the ability to seamlessly and intuitively switch between different interaction modalities and interaction are sought. Conventional VR techniques may be insufficient to meet this challenge. This paper presents novel approaches for human-centered interfaces to Virtual Environments focusing on the Virtual Table visual input device. It introduces new paradigms for 3D interaction in virtual environments (VE) for a variety of application areas based on pen-and-clipboard, mirror-in-hand, and magic-lens metaphors, and introduces new concepts for combining VR and augmented reality (AR) techniques. It finally describes approaches toward hybrid and distributed multi-user interaction environments and concludes by hypothesizing on possible use cases for defense applications.

Three-dimensional virtual acoustic displays

NASA Technical Reports Server (NTRS)

Wenzel, Elizabeth M.

1991-01-01

The development of an alternative medium for displaying information in complex human-machine interfaces is described. The 3-D virtual acoustic display is a means for accurately transferring information to a human operator using the auditory modality; it combines directional and semantic characteristics to form naturalistic representations of dynamic objects and events in remotely sensed or simulated environments. Although the technology can stand alone, it is envisioned as a component of a larger multisensory environment and will no doubt find its greatest utility in that context. The general philosophy in the design of the display has been that the development of advanced computer interfaces should be driven first by an understanding of human perceptual requirements, and later by technological capabilities or constraints. In expanding on this view, current and potential uses are addressed of virtual acoustic displays, such displays are characterized, and recent approaches to their implementation and application are reviewed, the research project at NASA-Ames is described in detail, and finally some critical research issues for the future are outlined.

Orthotic Body-Weight Support Through Underactuated Potential Energy Shaping with Contact Constraints

PubMed Central

Lv, Ge; Gregg, Robert D.

2015-01-01

Body-weight support is an effective clinical tool for gait rehabilitation after neurological impairment. Body-weight supported training systems have been developed to help patients regain mobility and confidence during walking, but conventional systems constrain the patient's treatment in clinical environments. We propose that this challenge could be addressed by virtually providing patients with body-weight support through the actuators of a powered orthosis (or exoskeleton) utilizing potential energy shaping control. However, the changing contact conditions and degrees of underactuation encountered during human walking present significant challenges to consistently matching a desired potential energy for the human in closed loop. We therefore introduce a generalized matching condition for shaping Lagrangian systems with holonomic contact constraints. By satisfying this matching condition for four phases of gait, we derive control laws to achieve virtual body-weight support through a powered knee-ankle orthosis. We demonstrate beneficial effects of virtual body-weight support in simulations of a human-like biped model, indicating the potential clinical value of this proposed control approach. PMID:26900254

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, Paul A.; Cooper, Candice Frances; Burnett, Damon J.

Light body armor development for the warfighter is based on trial-and-error testing of prototype designs against ballistic projectiles. Torso armor testing against blast is virtually nonexistent but necessary to ensure adequate protection against injury to the heart and lungs. In this report, we discuss the development of a high-fidelity human torso model, it's merging with the existing Sandia Human Head-Neck Model, and development of the modeling & simulation (M&S) capabilities necessary to simulate wound injury scenarios. Using the new Sandia Human Torso Model, we demonstrate the advantage of virtual simulation in the investigation of wound injury as it relates tomore » the warfighter experience. We present the results of virtual simulations of blast loading and ballistic projectile impact to the tors o with and without notional protective armor. In this manner, we demonstrate the ad vantages of applying a modeling and simulation approach to the investigation of wound injury and relative merit assessments of protective body armor without the need for trial-and-error testing.« less

Psychological and physiological human responses to simulated and real environments: A comparison between Photographs, 360° Panoramas, and Virtual Reality.

PubMed

Higuera-Trujillo, Juan Luis; López-Tarruella Maldonado, Juan; Llinares Millán, Carmen

2017-11-01

Psychological research into human factors frequently uses simulations to study the relationship between human behaviour and the environment. Their validity depends on their similarity with the physical environments. This paper aims to validate three environmental-simulation display formats: photographs, 360° panoramas, and virtual reality. To do this we compared the psychological and physiological responses evoked by simulated environments set-ups to those from a physical environment setup; we also assessed the users' sense of presence. Analysis show that 360° panoramas offer the closest to reality results according to the participants' psychological responses, and virtual reality according to the physiological responses. Correlations between the feeling of presence and physiological and other psychological responses were also observed. These results may be of interest to researchers using environmental-simulation technologies currently available in order to replicate the experience of physical environments. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Effects of Actual Human Size Display and Stereoscopic Presentation on Users' Sense of Being Together with and of Psychological Immersion in a Virtual Character

PubMed Central

Ahn, Dohyun; Seo, Youngnam; Kim, Minkyung; Kwon, Joung Huem; Jung, Younbo; Ahn, Jungsun

2014-01-01

Abstract This study examined the role of display size and mode in increasing users' sense of being together with and of their psychological immersion in a virtual character. Using a high-resolution three-dimensional virtual character, this study employed a 2×2 (stereoscopic mode vs. monoscopic mode×actual human size vs. small size display) factorial design in an experiment with 144 participants randomly assigned to each condition. Findings showed that stereoscopic mode had a significant effect on both users' sense of being together and psychological immersion. However, display size affected only the sense of being together. Furthermore, display size was not found to moderate the effect of stereoscopic mode. PMID:24606057

A distinct type of cell in myocardium: interstitial Cajal-like cells (ICLCs)

PubMed Central

Kostin, S; Popescu, L M

2009-01-01

Abstract The existence of a novel type of interstitial cells in the heart, interstitial Cajal-like cells (ICLCs), had been described for the first time in 2005. Their identification was mainly based on ultrastructural criteria: very long (tens up to hundreds of micrometres) and moniliform prolongations, which are extremely thin (less than 0.2 μm), below the resolving power of light microscopy. Myocardial ICLCs were also identified by methylene-blue vital staining, silver impregnation, and immunoreactivity for CD 34, vimentin, CD117/c-kit, etc. Although a series of studies provided evidence for the existence of ICLCs in human atria and rat ventricles, further investigations in other laboratories, using additional techniques, are required to substantiate the consistency of these findings. Here we provide further evidence for the existence of ICLCs in human and mammalian hearts (by transmission and scanning electron microscopy, as well as confocal laser scanning microscopy). Noteworthy, we confirm that ICLCs communicate with neighbouring cells via shedding (micro)vesicles. Although these so-called ICLCs represent a distinct type of cells, different from classical interstitial cells of Cajal, or fibroblasts, their role(s) in myocardium remain(s) to be established. Several hypotheses are proposed: (i) adult stromal (mesenchymal) stem cells, which might participate in cardiac repair/remodelling; (ii) intercellular signalling (e.g. via shedding microvesicles); (iii) chemo-mechanical transducers and (iv) players in pacemaking and/or arrhytmogenesis, and so on. PMID:19183408

Virtual reality anatomy: is it comparable with traditional methods in the teaching of human forearm musculoskeletal anatomy?

PubMed

Codd, Anthony M; Choudhury, Bipasha

2011-01-01

The use of cadavers to teach anatomy is well established, but limitations with this approach have led to the introduction of alternative teaching methods. One such method is the use of three-dimensional virtual reality computer models. An interactive, three-dimensional computer model of human forearm anterior compartment musculoskeletal anatomy was produced using the open source 3D imaging program "Blender." The aim was to evaluate the use of 3D virtual reality when compared with traditional anatomy teaching methods. Three groups were identified from the University of Manchester second year Human Anatomy Research Skills Module class: a "control" group (no prior knowledge of forearm anatomy), a "traditional methods" group (taught using dissection and textbooks), and a "model" group (taught solely using e-resource). The groups were assessed on anatomy of the forearm by a ten question practical examination. ANOVA analysis showed the model group mean test score to be significantly higher than the control group (mean 7.25 vs. 1.46, P < 0.001) and not significantly different to the traditional methods group (mean 6.87, P > 0.5). Feedback from all users of the e-resource was positive. Virtual reality anatomy learning can be used to compliment traditional teaching methods effectively. Copyright © 2011 American Association of Anatomists.

Estimating the Hepatic Effects of Xenobiotic Perturbations in a Virtual Liver

EPA Science Inventory

There are thousands of environmental chemicals and hundreds of new ones are introduced each year. Human health risk assessments for this number of chemicals is a challenge, and have been completed for only a fraction of these chemicals. The US EPA Virtual Liver (v-LiverTM) projec...

Revealing Preconditions for Trustful Collaboration in CSCL

ERIC Educational Resources Information Center

Gerdes, Anne

2010-01-01

This paper analyses preconditions for trust in virtual learning environments. The concept of trust is discussed with reference to cases reporting trust in cyberspace and through a philosophical clarification holding that trust in the form of self-surrender is a common characteristic of all human co-existence. In virtual learning environments,…

v-Liver: Simulating Hepatic Tissue Lesions as Virtual Cellular Systems

EPA Science Inventory

The US EPA Virtual Liver (v-Liver) project is aimed at reducing the uncertainty in estimating the risk of toxic outcomes in humans by simulating the dose-dependent effects of environmental chemicals in silico. The v-Liver embodies an emerging field of research in computational ti...

Virtual Reality as a Distraction Technique in Chronic Pain Patients

PubMed Central

Gao, Kenneth; Sulea, Camelia; Wiederhold, Mark D.

2014-01-01

Abstract We explored the use of virtual reality distraction techniques for use as adjunctive therapy to treat chronic pain. Virtual environments were specifically created to provide pleasant and engaging experiences where patients navigated on their own through rich and varied simulated worlds. Real-time physiological monitoring was used as a guide to determine the effectiveness and sustainability of this intervention. Human factors studies showed that virtual navigation is a safe and effective method for use with chronic pain patients. Chronic pain patients demonstrated significant relief in subjective ratings of pain that corresponded to objective measurements in peripheral, noninvasive physiological measures. PMID:24892196

Interpretations of virtual reality.

PubMed

Voiskounsky, Alexander

2011-01-01

University students were surveyed to learn what they know about virtual realities. The two studies were administered with a half-year interval in which the students (N=90, specializing either in mathematics and science, or in social science and humanities) were asked to name particular examples of virtual realities. The second, but not the first study, was administered after the participants had the chance to see the movie "Avatar" (no investigation was held into whether they really saw it). While the students in both studies widely believed that activities such as social networking and online gaming represent virtual realities, some other examples provided by the students in the two studies differ: in the second study the participants expressed a better understanding of the items related to virtual realities. At the same time, not a single participant reported particular psychological states (either regular or altered) as examples of virtual realities. Profound popularization efforts need to be done to acquaint the public, including college students, with virtual realities and let the public adequately understand how such systems work.

Direct stimulation of the retina by the method of virtual-quanta for heavy cosmic-ray nuclei

NASA Technical Reports Server (NTRS)

Mcnulty, P. J.; Madey, R.

1972-01-01

The contribution to the frequency of visual sensations induced in the dark-adapted eye by the virtual photon field was calculated, this field is associated with the heavy nuclei that exist in space beyond the geomagnetic field. In order to determine the probability that the virtual photon field induces a light flash, only the portion of the virtual photon spectrum that corresponds to the known frequency dependence of the sensitivity of human rods to visible light was utilized. The results can be expressed as a curve of the mean frequency of light flashes induced by the absorption of at least R virtual photons versus the threshold number R. The contribution to the light flash frequency from the virtual photon field of heavy cosmic ray nuclei is smaller than that from Cerenkov photons. The flux and energy spectra of galactic cosmic ray nuclei helium to iron were used.

Optical versus virtual: teaching assistant perceptions of the use of virtual microscopy in an undergraduate human anatomy course.

PubMed

Collier, Larissa; Dunham, Stacey; Braun, Mark W; O'Loughlin, Valerie Dean

2012-01-01

Many studies that evaluate the introduction of technology in the classroom focus on student performance and student evaluations. This study focuses on instructor evaluation of the introduction of virtual microscopy into an undergraduate anatomy class. Semi-structured interviews were conducted with graduate teaching assistants (TA) and analyzed through qualitative methods. This analysis showed that the teaching assistants found the virtual microscope to be an advantageous change in the classroom. They cite the ease of use of the virtual microscope, access to histology outside of designated laboratory time, and increasing student collaboration in class as the primary advantages. The teaching assistants also discuss principal areas where the use of the virtual microscope can be improved from a pedagogical standpoint, including requiring students to spend more time working on histology in class. Copyright © 2011 American Association of Anatomists.

Marshall Engineers Use Virtual Reality

NASA Technical Reports Server (NTRS)

1993-01-01

Virtual Reality (VR) can provide cost effective methods to design and evaluate components and systems for maintenance and refurbishment operations. Marshall Spce Flight Center (MSFC) is begirning to utilize VR for design analysis in the X-34 experimental reusable space vehicle. Analysts at MSFC's Computer Applications and Virtual Environments (CAVE) used Head Mounted Displays (HMD) (pictured), spatial trackers and gesture inputs as a means to animate or inhabit a properly sized virtual human model. These models are used in a VR scenario as a way to determine functionality of space and maintenance requirements for the virtual X-34. The primary functions of the virtual X-34 mockup is to support operations development and design analysis for engine removal, the engine compartment and the aft fuselage. This capability provides general visualization support to engineers and designers at MSFC and to the System Design Freeze Review at Orbital Sciences Corporation (OSC).

Virtual reality for dermatologic surgery: virtually a reality in the 21st century.

PubMed

Gladstone, H B; Raugi, G J; Berg, D; Berkley, J; Weghorst, S; Ganter, M

2000-01-01

In the 20th century, virtual reality has predominantly played a role in training pilots and in the entertainment industry. Despite much publicity, virtual reality did not live up to its perceived potential. During the past decade, it has also been applied for medical uses, particularly as training simulators, for minimally invasive surgery. Because of advances in computer technology, virtual reality is on the cusp of becoming an effective medical educational tool. At the University of Washington, we are developing a virtual reality soft tissue surgery simulator. Based on fast finite element modeling and using a personal computer, this device can simulate three-dimensional human skin deformations with real-time tactile feedback. Although there are many cutaneous biomechanical challenges to solve, it will eventually provide more realistic dermatologic surgery training for medical students and residents than the currently used models.

Computer Applications and Virtual Environments (CAVE)

NASA Technical Reports Server (NTRS)

1993-01-01

Virtual Reality (VR) can provide cost effective methods to design and evaluate components and systems for maintenance and refurbishment operations. Marshall SPace Flight Center (MSFC) is begirning to utilize VR for design analysis in the X-34 experimental reusable space vehicle. Analysts at MSFC's Computer Applications and Virtual Environments (CAVE) used Head Mounted Displays (HMD) (pictured), spatial trackers and gesture inputs as a means to animate or inhabit a properly sized virtual human model. These models are used in a VR scenario as a way to determine functionality of space and maintenance requirements for the virtual X-34. The primary functions of the virtual X-34 mockup is to support operations development and design analysis for engine removal, the engine compartment and the aft fuselage. This capability provides general visualization support to engineers and designers at MSFC and to the System Design Freeze Review at Orbital Sciences Corporation (OSC).

ComputerApplications and Virtual Environments (CAVE)

NASA Technical Reports Server (NTRS)

1993-01-01

Virtual Reality (VR) can provide cost effective methods to design and evaluate components and systems for maintenance and refurbishment operations. The Marshall Space Flight Center (MSFC) in Huntsville, Alabama began to utilize VR for design analysis in the X-34 experimental reusable space vehicle. Analysts at MSFC's Computer Applications and Virtual Environments (CAVE) used Head Mounted Displays (HMD) (pictured), spatial trackers and gesture inputs as a means to animate or inhabit a properly sized virtual human model. These models were used in a VR scenario as a way to determine functionality of space and maintenance requirements for the virtual X-34. The primary functions of the virtual X-34 mockup was to support operations development and design analysis for engine removal, the engine compartment and the aft fuselage. This capability providedgeneral visualization support to engineers and designers at MSFC and to the System Design Freeze Review at Orbital Sciences Corporation (OSC). The X-34 program was cancelled in 2001.

ComputerApplications and Virtual Environments (CAVE)

NASA Technical Reports Server (NTRS)

1993-01-01

Virtual Reality (VR) can provide cost effective methods to design and evaluate components and systems for maintenance and refurbishment operations. The Marshall Space Flight Centerr (MSFC) in Huntsville, Alabama began to utilize VR for design analysis in the X-34 experimental reusable space vehicle. Analysts at MSFC's Computer Applications and Virtual Environments (CAVE) used Head Mounted Displays (HMD) (pictured), spatial trackers and gesture inputs as a means to animate or inhabit a properly sized virtual human model. These models were used in a VR scenario as a way to determine functionality of space and maintenance requirements for the virtual X-34. The primary functions of the virtual X-34 mockup was to support operations development and design analysis for engine removal, the engine compartment and the aft fuselage. This capability provided general visualization support to engineers and designers at MSFC and to the System Design Freeze Review at Orbital Sciences Corporation (OSC). The X-34 program was cancelled in 2001.

A fast simulation method for radiation maps using interpolation in a virtual environment.

PubMed

Li, Meng-Kun; Liu, Yong-Kuo; Peng, Min-Jun; Xie, Chun-Li; Yang, Li-Qun

2018-05-10

In nuclear decommissioning, virtual simulation technology is a useful tool to achieve an effective work process by using virtual environments to represent the physical and logical scheme of a real decommissioning project. This technology is cost-saving and time-saving, with the capacity to develop various decommissioning scenarios and reduce the risk of retrofitting. The method utilises a radiation map in a virtual simulation as the basis for the assessment of exposure to a virtual human. In this paper, we propose a fast simulation method using a known radiation source. The method has a unique advantage over point kernel and Monte Carlo methods because it generates the radiation map using interpolation in a virtual environment. The simulation of the radiation map including the calculation and the visualisation were realised using UNITY and MATLAB. The feasibility of the proposed method was tested on a hypothetical case and the results obtained are discussed in this paper.

Modeling and Design of an Electro-Rheological Fluid Based Haptic System for Tele-Operation of Space Robots

NASA Technical Reports Server (NTRS)

Mavroidis, Constantinos; Pfeiffer, Charles; Paljic, Alex; Celestino, James; Lennon, Jamie; Bar-Cohen, Yoseph

2000-01-01

For many years, the robotic community sought to develop robots that can eventually operate autonomously and eliminate the need for human operators. However, there is an increasing realization that there are some tasks that human can perform significantly better but, due to associated hazards, distance, physical limitations and other causes, only robot can be employed to perform these tasks. Remotely performing these types of tasks requires operating robots as human surrogates. While current "hand master" haptic systems are able to reproduce the feeling of rigid objects, they present great difficulties in emulating the feeling of remote/virtual stiffness. In addition, they tend to be heavy, cumbersome and usually they only allow limited operator workspace. In this paper a novel haptic interface is presented to enable human-operators to "feel" and intuitively mirror the stiffness/forces at remote/virtual sites enabling control of robots as human-surrogates. This haptic interface is intended to provide human operators intuitive feeling of the stiffness and forces at remote or virtual sites in support of space robots performing dexterous manipulation tasks (such as operating a wrench or a drill). Remote applications are referred to the control of actual robots whereas virtual applications are referred to simulated operations. The developed haptic interface will be applicable to IVA operated robotic EVA tasks to enhance human performance, extend crew capability and assure crew safety. The electrically controlled stiffness is obtained using constrained ElectroRheological Fluids (ERF), which changes its viscosity under electrical stimulation. Forces applied at the robot end-effector due to a compliant environment will be reflected to the user using this ERF device where a change in the system viscosity will occur proportionally to the force to be transmitted. In this paper, we will present the results of our modeling, simulation, and initial testing of such an electrorheological fluid (ERF) based haptic device.

Three dimensional tracking with misalignment between display and control axes

NASA Technical Reports Server (NTRS)

Ellis, Stephen R.; Tyler, Mitchell; Kim, Won S.; Stark, Lawrence

1992-01-01

Human operators confronted with misaligned display and control frames of reference performed three dimensional, pursuit tracking in virtual environment and virtual space simulations. Analysis of the components of the tracking errors in the perspective displays presenting virtual space showed that components of the error due to visual motor misalignment may be linearly separated from those associated with the mismatch between display and control coordinate systems. Tracking performance improved with several hours practice despite previous reports that such improvement did not take place.

The scientific research potential of virtual worlds.

PubMed

Bainbridge, William Sims

2007-07-27

Online virtual worlds, electronic environments where people can work and interact in a somewhat realistic manner, have great potential as sites for research in the social, behavioral, and economic sciences, as well as in human-centered computer science. This article uses Second Life and World of Warcraft as two very different examples of current virtual worlds that foreshadow future developments, introducing a number of research methodologies that scientists are now exploring, including formal experimentation, observational ethnography, and quantitative analysis of economic markets or social networks.

Space Science

NASA Image and Video Library

2003-06-01

NASA’s Virtual Glovebox (VGX) was developed to allow astronauts on Earth to train for complex biology research tasks in space. The astronauts may reach into the virtual environment, naturally manipulating specimens, tools, equipment, and accessories in a simulated microgravity environment as they would do in space. Such virtual reality technology also provides engineers and space operations staff with rapid prototyping, planning, and human performance modeling capabilities. Other Earth based applications being explored for this technology include biomedical procedural training and training for disarming bio-terrorism weapons.

A Three-Dimensional Human Atrial Model with Fiber Orientation. Electrograms and Arrhythmic Activation Patterns Relationship

PubMed Central

Tobón, Catalina; Ruiz-Villa, Carlos A.; Heidenreich, Elvio; Romero, Lucia; Hornero, Fernando; Saiz, Javier

2013-01-01

The most common sustained cardiac arrhythmias in humans are atrial tachyarrhythmias, mainly atrial fibrillation. Areas of complex fractionated atrial electrograms and high dominant frequency have been proposed as critical regions for maintaining atrial fibrillation; however, there is a paucity of data on the relationship between the characteristics of electrograms and the propagation pattern underlying them. In this study, a realistic 3D computer model of the human atria has been developed to investigate this relationship. The model includes a realistic geometry with fiber orientation, anisotropic conductivity and electrophysiological heterogeneity. We simulated different tachyarrhythmic episodes applying both transient and continuous ectopic activity. Electrograms and their dominant frequency and organization index values were calculated over the entire atrial surface. Our simulations show electrograms with simple potentials, with little or no cycle length variations, narrow frequency peaks and high organization index values during stable and regular activity as the observed in atrial flutter, atrial tachycardia (except in areas of conduction block) and in areas closer to ectopic activity during focal atrial fibrillation. By contrast, cycle length variations and polymorphic electrograms with single, double and fragmented potentials were observed in areas of irregular and unstable activity during atrial fibrillation episodes. Our results also show: 1) electrograms with potentials without negative deflection related to spiral or curved wavefronts that pass over the recording point and move away, 2) potentials with a much greater proportion of positive deflection than negative in areas of wave collisions, 3) double potentials related with wave fragmentations or blocking lines and 4) fragmented electrograms associated with pivot points. Our model is the first human atrial model with realistic fiber orientation used to investigate the relationship between different atrial arrhythmic propagation patterns and the electrograms observed at more than 43000 points on the atrial surface. PMID:23408928

Assessment method of digital Chinese dance movements based on virtual reality technology

NASA Astrophysics Data System (ADS)

Feng, Wei; Shao, Shuyuan; Wang, Shumin

2008-03-01

Virtual reality has played an increasing role in such areas as medicine, architecture, aviation, engineering science and advertising. However, in the art fields, virtual reality is still in its infancy in the representation of human movements. Based on the techniques of motion capture and reuse of motion capture data in virtual reality environment, this paper presents an assessment method in order to evaluate the quantification of dancers' basic Arm Position movements in Chinese traditional dance. In this paper, the data for quantifying traits of dance motions are defined and measured on dancing which performed by an expert and two beginners, with results indicating that they are beneficial for evaluating dance skills and distinctiveness, and the assessment method of digital Chinese dance movements based on virtual reality technology is validity and feasibility.

Virtual reality in ophthalmology training.

PubMed

Khalifa, Yousuf M; Bogorad, David; Gibson, Vincent; Peifer, John; Nussbaum, Julian

2006-01-01

Current training models are limited by an unstructured curriculum, financial costs, human costs, and time constraints. With the newly mandated resident surgical competency, training programs are struggling to find viable methods of assessing and documenting the surgical skills of trainees. Virtual-reality technologies have been used for decades in flight simulation to train and assess competency, and there has been a recent push in surgical specialties to incorporate virtual-reality simulation into residency programs. These efforts have culminated in an FDA-approved carotid stenting simulator. What role virtual reality will play in the evolution of ophthalmology surgical curriculum is uncertain. The current apprentice system has served the art of surgery for over 100 years, and we foresee virtual reality working synergistically with our current curriculum modalities to streamline and enhance the resident's learning experience.

STRUCTURAL AND FUNCTIONAL BASES OF CARDIAC FIBRILLATION. DIFFERENCES AND SIMILARITIES BETWEEN ATRIA AND VENTRICLES

PubMed Central

Filgueiras-Rama, David; Jalife, José

2016-01-01

Evidence accumulated over the last 25 years suggests that, whether in the atria or ventricles, fibrillation may be explained by the self-organization of the cardiac electrical activity into rapidly spinning rotors giving way to spiral waves that break intermittently and result in fibrillatory conduction. The dynamics and frequency of such rotors depend on the ion channel composition, excitability and refractory properties of the tissues involved, as well as on the thickness and respective three-dimensional fiber structure of the atrial and ventricular chambers. Therefore, improving the understanding of fibrillation has required the use of multidisciplinary research approaches, including optical mapping, patch clamping and molecular biology, and the application of concepts derived from the theory of wave propagation in excitable media. Moreover, translation of such concepts to the clinic has recently opened new opportunities to apply novel mechanistic approaches to therapy, particularly during atrial fibrillation ablation. Here we review the current understanding of the manner in which the underlying myocardial structure and function influence rotor initiation and maintenance during cardiac fibrillation. We also examine relevant underlying differences and similarities between atrial fibrillation and ventricular fibrillation and evaluate the latest clinical mapping technologies used to identify rotors in either arrhythmia. Altogether, the data being discussed have significantly improved our understanding of the cellular and structural bases of cardiac fibrillation and pointed toward potentially exciting new avenues for more efficient and effective identification and therapy of the most complex cardiac arrhythmias. PMID:27042693

Hypotensive, vasorelaxant and cardiodepressant activities of the ethanol extract of Sideritis raeseri spp. raeseri Boiss & Heldr.

PubMed

Kitic, D; Brankovic, S; Radenkovic, M; Savikin, K; Zdunic, G; Kocic, B; Velickovic-Radovanovic, R

2012-10-01

Sideritis raeseri spp. raeseri Boiss & Heldr is a native plant from the Mediterranean region that is used due to its medicinal and culinary properties. The aim of this study was to evaluate the effects of ethanol extract of S. raeseri on the blood pressure, vascular and cardiac contractions. Arterial blood pressure was registered directly from the carotid artery in the anaesthetized rabbits. Aortic rings and the spontaneously beating atria were mounted in tissue bath. An intravenous injection of extract of S. raeseri (0.025-7.5 mg/kg) caused a dose dependent decrease of the arterial pressure and heart rate, with EC(50) value of 24.31±3.87 mg/kg and 88.14±7.51 mg/kg, respectively. In aortic preparations precontracted with KCl (80 mM), the extract of S. raeseri (0.005-1.5 mg/ml) elicited a vasodilatator action (EC(50) 0.11±0.008 mg/ml). In spontaneously beating rat atria, the extract of S. raeseri (0.005-1.5 mg/ml) produced decrease of chronotropic and inotropic activity (with EC(50) value of 0.63±0.03 mg/ml and 0.40±0.08 mg/ml). Administration of verapamil induced inhibition of force and rate of the atrial contraction. These results demonstrate that the ethanol extract of Sideritis raeseri spp. raeseri Boiss & Heldr can produce hypotension, vasodilatation, negative chronotropic and inotropic effects.

Atrial-selective K+ channel blockers: potential antiarrhythmic drugs in atrial fibrillation?

PubMed

Ravens, Ursula

2017-11-01

In the wake of demographic change in Western countries, atrial fibrillation has reached an epidemiological scale, yet current strategies for drug treatment of the arrhythmia lack sufficient efficacy and safety. In search of novel medications, atrial-selective drugs that specifically target atrial over other cardiac functions have been developed. Here, I will address drugs acting on potassium (K + ) channels that are either predominantly expressed in atria or possess electrophysiological properties distinct in atria from ventricles. These channels include the ultra-rapidly activating, delayed outward-rectifying Kv1.5 channel conducting I Kur , the acetylcholine-activated inward-rectifying Kir3.1/Kir3.4 channel conducting I K,ACh , the Ca 2+ -activated K + channels of small conductance (SK) conducting I SK , and the two-pore domain K + (K2P) channels (tandem of P domains, weak inward-rectifying K + channels (TWIK-1), TWIK-related acid-sensitive K + channels (TASK-1 and TASK-3)) that are responsible for voltage-independent background currents I TWIK-1 , I TASK-1 , and I TASK-3 . Direct drug effects on these channels are described and their putative value in treatment of atrial fibrillation is discussed. Although many potential drug targets have emerged in the process of unravelling details of the pathophysiological mechanisms responsible for atrial fibrillation, we do not know whether novel antiarrhythmic drugs will be more successful when modulating many targets or a single specific one. The answer to this riddle can only be solved in a clinical context.

Involvement of IL-1β and IL-6 in antiarrhythmic properties of atorvastatin in ouabain-induced arrhythmia in rats.

PubMed

Najjari, Mahya; Vaezi, Gholamhassan; Hojati, Vida; Mousavi, Zahra; Bakhtiarian, Azam; Nikoui, Vahid

2018-06-01

Evidence show that statins possess wide beneficial cardioprotective and anti-inflammatory effects; therefore, in the present experiment, we investigated the antiarrhythmic properties of atorvastatin in ouabain-induced arrhythmia in isolated rat atria and the role of several inflammatory cytokines in this effect. Male rats were pretreated with either of atorvastatin (10 mg/kg) or vehicle, orally once daily for 6 weeks. After induction of anesthesia, we isolated the atria and after incubation with ouabain, time of onset of arrhythmia and asystole as well as atrial beating rate and contractile force were recorded. We also measured the atrial levels of IL-1β, IL-6, and TNF-α after the injection of ouabain to animals. Pretreatment with atorvastatin significantly delayed the onset of arrhythmia and asystole compared with vehicle-treated group (p < .01, p < .001, respectively). Incubation of ouabain boosted both atrial beating rate and contractile force in vehicle-treated group (p < .05), while these responses in atorvastatin-treated group were not significant (p > .05). Injection of ouabain elevated the atrial levels of IL-1β, IL-6, and TNF-α, while pretreatment of animals with atorvastatin could reverse the ouabain-induced increase in atrial IL-1β and IL-6 (p < .01 and p < .05, respectively). It is concluded that observed antiarrhythmic effects of atorvastatin might be attributed to modulation of some inflammatory cytokines, at least IL-1β and IL-6.

Renal sympathetic denervation suppresses atrial fibrillation induced by acute atrial ischemia/infarction through inhibition of cardiac sympathetic activity.

PubMed

Zhou, Qina; Zhou, Xianhui; TuEr-Hong, ZuKe-la; Wang, Hongli; Yin, Tingting; Li, Yaodong; Zhang, Ling; Lu, Yanmei; Xing, Qiang; Zhang, Jianghua; Yang, Yining; Tang, Baopeng

2016-01-15

This study aims to explore the effects of renal sympathetic denervation (RSD) on atrial fibrillation (AF) inducibility and sympathetic activity induced by acute atrial ischemia/infarction. Acute ischemia/infarction was induced in 12 beagle dogs by ligating coronary arteries that supply the atria. Six dogs in the sham-RSD group did not undergo RSD, and six dogs without coronary artery ligation served as controls. AF induction rate, sympathetic discharge, catecholamine concentration and densities of tyrosine hydroxylase-positive nerves were measured. Acute atrial ischemia/infarction resulted in a significant increase of AF induction rate, which was decreased by RSD compared to controls (P<0.05). The root-mean-square peak value, peak area and number of sympathetic discharges were significantly augmented by atrial ischemia relative to the baseline and control (P<0.05). The number of sympathetic discharges was significantly reduced in the RSD group, compared to the control and sham-RSD groups (P<0.05). Norepinephrine and epinephrine concentrations in the atria, ventricle and kidney were elevated by atrial ischemia/infarction, but were reduced by RSD (P<0.05). Sympathetic hyperactivity was associated with pacing-induced AF after acute atrial ischemia/infarction. RSD has the potential to reduce the incidence of new-onset AF after acute atrial ischemia/infarction. The inhibition of cardiac sympathetic activity by RSD may be one of the major underlying mechanisms for the marked reduction of AF inducibility. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Brain shape in human microcephalics and Homo floresiensis.

PubMed

Falk, Dean; Hildebolt, Charles; Smith, Kirk; Morwood, M J; Sutikna, Thomas; Jatmiko; Saptomo, E Wayhu; Imhof, Herwig; Seidler, Horst; Prior, Fred

2007-02-13

Because the cranial capacity of LB1 (Homo floresiensis) is only 417 cm(3), some workers propose that it represents a microcephalic Homo sapiens rather than a new species. This hypothesis is difficult to assess, however, without a clear understanding of how brain shape of microcephalics compares with that of normal humans. We compare three-dimensional computed tomographic reconstructions of the internal braincases (virtual endocasts that reproduce details of external brain morphology, including cranial capacities and shape) from a sample of 9 microcephalic humans and 10 normal humans. Discriminant and canonical analyses are used to identify two variables that classify normal and microcephalic humans with 100% success. The classification functions classify the virtual endocast from LB1 with normal humans rather than microcephalics. On the other hand, our classification functions classify a pathological H. sapiens specimen that, like LB1, represents an approximately 3-foot-tall adult female and an adult Basuto microcephalic woman that is alleged to have an endocast similar to LB1's with the microcephalic humans. Although microcephaly is genetically and clinically variable, virtual endocasts from our highly heterogeneous sample share similarities in protruding and proportionately large cerebella and relatively narrow, flattened orbital surfaces compared with normal humans. These findings have relevance for hypotheses regarding the genetic substrates of hominin brain evolution and may have medical diagnostic value. Despite LB1's having brain shape features that sort it with normal humans rather than microcephalics, other shape features and its small brain size are consistent with its assignment to a separate species.

Design of virtual three-dimensional instruments for sound control

NASA Astrophysics Data System (ADS)

Mulder, Axel Gezienus Elith

An environment for designing virtual instruments with 3D geometry has been prototyped and applied to real-time sound control and design. It enables a sound artist, musical performer or composer to design an instrument according to preferred or required gestural and musical constraints instead of constraints based only on physical laws as they apply to an instrument with a particular geometry. Sounds can be created, edited or performed in real-time by changing parameters like position, orientation and shape of a virtual 3D input device. The virtual instrument can only be perceived through a visualization and acoustic representation, or sonification, of the control surface. No haptic representation is available. This environment was implemented using CyberGloves, Polhemus sensors, an SGI Onyx and by extending a real- time, visual programming language called Max/FTS, which was originally designed for sound synthesis. The extension involves software objects that interface the sensors and software objects that compute human movement and virtual object features. Two pilot studies have been performed, involving virtual input devices with the behaviours of a rubber balloon and a rubber sheet for the control of sound spatialization and timbre parameters. Both manipulation and sonification methods affect the naturalness of the interaction. Informal evaluation showed that a sonification inspired by the physical world appears natural and effective. More research is required for a natural sonification of virtual input device features such as shape, taking into account possible co- articulation of these features. While both hands can be used for manipulation, left-hand-only interaction with a virtual instrument may be a useful replacement for and extension of the standard keyboard modulation wheel. More research is needed to identify and apply manipulation pragmatics and movement features, and to investigate how they are co-articulated, in the mapping of virtual object parameters. While the virtual instruments can be adapted to exploit many manipulation gestures, further work is required to reduce the need for technical expertise to realize adaptations. Better virtual object simulation techniques and faster sensor data acquisition will improve the performance of virtual instruments. The design environment which has been developed should prove useful as a (musical) instrument prototyping tool and as a tool for researching the optimal adaptation of machines to humans.

Stability effects of singularities in force-controlled robotic assist devices

NASA Astrophysics Data System (ADS)

Luecke, Greg R.

2002-02-01

Force feedback is being used as an interface between humans and material handling equipment to provide an intuitive method to control large and bulky payloads. Powered actuation in the lift assist device compensates for the inertial characteristics of the manipulator and the payload to provide effortless control and handling of manufacturing parts, components, and assemblies. The use of these Intelligent Assist Devices (IAD) is being explored to prevent worker injury, enhance material handling performance, and increase productivity in the workplace. The IAD also provides the capability to shape and control motion in the workspace during routine operations. Virtual barriers can be developed to protect fixed objects in the workspace, and regions can be programmed that attract the work piece to a certain position and orientation. However, the robot is still under complete control of the human operator, with the trajectory being determined and commanded using the judgment of the operator to complete a given task. In many cases, the IAD is built in a configuration that may have singular points inside the workspace. These singularities can cause problems when the unstructured trajectory commands from the human cause interaction between the IAD and the virtual walls and fixtures at positions close to these singularities. The research presented here explores the stability effects of the interactions between the powered manipulator and the virtual surfaces when controlled by the operator. Because of the flexible nature of the human decisions determining the real time work piece paths, manipulator singularities that occur in conjunction with the virtual surfaces raise stability issues in the performance around these singularities. We examine these stability issues in the context of a particular IAD configuration, and present analytic results for the performance and stability of these systems in response to the real-time trajectory modification of the human operator.

A one degree of freedom haptic system to investigate issues in human perception with particular application to probing tissue.

PubMed

Dibble, Edward; Zivanovic, Aleksandar; Davies, Brian

2004-01-01

This paper presents the results of several early studies relating to human haptic perception sensitivity when probing a virtual object. A 1 degree of freedom (DoF) rotary haptic system, that was designed and built for this purpose, is also presented. The experiments were to assess the maximum forces applied in a minimally invasive surgery (MIS) procedure, quantify the compliance sensitivity threshold when probing virtual tissue and identify the haptic system loop rate necessary for haptic feedback to feel realistic.

Integrating multi-scale data to create a virtual physiological mouse heart.

PubMed

Land, Sander; Niederer, Steven A; Louch, William E; Sejersted, Ole M; Smith, Nicolas P

2013-04-06

While the virtual physiological human (VPH) project has made great advances in human modelling, many of the tools and insights developed as part of this initiative are also applicable for facilitating mechanistic understanding of the physiology of a range of other species. This process, in turn, has the potential to provide human relevant insights via a different scientific path. Specifically, the increasing use of mice in experimental research, not yet fully complemented by a similar increase in computational modelling, is currently missing an important opportunity for using and interpreting this growing body of experimental data to improve our understanding of cardiac function. This overview describes our work to address this issue by creating a virtual physiological mouse model of the heart. We describe the similarities between human- and mouse-focused modelling, including the reuse of VPH tools, and the development of methods for investigating parameter sensitivity that are applicable across species. We show how previous results using this approach have already provided important biological insights, and how these can also be used to advance VPH heart models. Finally, we show an example application of this approach to test competing multi-scale hypotheses by investigating variations in length-dependent properties of cardiac muscle.

Integrating multi-scale data to create a virtual physiological mouse heart

PubMed Central

Land, Sander; Niederer, Steven A.; Louch, William E.; Sejersted, Ole M.; Smith, Nicolas P.

2013-01-01

While the virtual physiological human (VPH) project has made great advances in human modelling, many of the tools and insights developed as part of this initiative are also applicable for facilitating mechanistic understanding of the physiology of a range of other species. This process, in turn, has the potential to provide human relevant insights via a different scientific path. Specifically, the increasing use of mice in experimental research, not yet fully complemented by a similar increase in computational modelling, is currently missing an important opportunity for using and interpreting this growing body of experimental data to improve our understanding of cardiac function. This overview describes our work to address this issue by creating a virtual physiological mouse model of the heart. We describe the similarities between human- and mouse-focused modelling, including the reuse of VPH tools, and the development of methods for investigating parameter sensitivity that are applicable across species. We show how previous results using this approach have already provided important biological insights, and how these can also be used to advance VPH heart models. Finally, we show an example application of this approach to test competing multi-scale hypotheses by investigating variations in length-dependent properties of cardiac muscle. PMID:24427525

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, Birchard P; Michel, Kelly D; Few, Douglas A

From stereophonic, positional sound to high-definition imagery that is crisp and clean, high fidelity computer graphics enhance our view, insight, and intuition regarding our environments and conditions. Contemporary 3-D modeling tools offer an open architecture framework that enables integration with other technologically innovative arenas. One innovation of great interest is Augmented Reality, the merging of virtual, digital environments with physical, real-world environments creating a mixed reality where relevant data and information augments the real or actual experience in real-time by spatial or semantic context. Pairing 3-D virtual immersive models with a dynamic platform such as semi-autonomous robotics or personnel odometrymore » systems to create a mixed reality offers a new and innovative design information verification inspection capability, evaluation accuracy, and information gathering capability for nuclear facilities. Our paper discusses the integration of two innovative technologies, 3-D visualizations with inertial positioning systems, and the resulting augmented reality offered to the human inspector. The discussion in the paper includes an exploration of human and non-human (surrogate) inspections of a nuclear facility, integrated safeguards knowledge within a synchronized virtual model operated, or worn, by a human inspector, and the anticipated benefits to safeguards evaluations of facility operations.« less

Soul on Silicon.

ERIC Educational Resources Information Center

Kurzweil, Raymond C.

1994-01-01

Summarizes recent advances in computer simulation and "reverse engineering" technologies, highlighting the Human Genome Project to scan the human genetic code; artificial retina chips to copy the human retina's neural organization; high-speed, high-resolution Magnetic Resonance Imaging scanners; and the virtual book. Discusses…

The Importance of Postural Cues for Determining Eye Height in Immersive Virtual Reality

PubMed Central

Leyrer, Markus; Linkenauger, Sally A.; Bülthoff, Heinrich H.; Mohler, Betty J.

2015-01-01

In human perception, the ability to determine eye height is essential, because eye height is used to scale heights of objects, velocities, affordances and distances, all of which allow for successful environmental interaction. It is well understood that eye height is fundamental to determine many of these percepts. Yet, how eye height itself is provided is still largely unknown. While the information potentially specifying eye height in the real world is naturally coincident in an environment with a regular ground surface, these sources of information can be easily divergent in similar and common virtual reality scenarios. Thus, we conducted virtual reality experiments where we manipulated the virtual eye height in a distance perception task to investigate how eye height might be determined in such a scenario. We found that humans rely more on their postural cues for determining their eye height if there is a conflict between visual and postural information and little opportunity for perceptual-motor calibration is provided. This is demonstrated by the predictable variations in their distance estimates. Our results suggest that the eye height in such circumstances is informed by postural cues when estimating egocentric distances in virtual reality and consequently, does not depend on an internalized value for eye height. PMID:25993274

Crowd behaviour during high-stress evacuations in an immersive virtual environment

PubMed Central

Kapadia, Mubbasir; Thrash, Tyler; Sumner, Robert W.; Gross, Markus; Helbing, Dirk; Hölscher, Christoph

2016-01-01

Understanding the collective dynamics of crowd movements during stressful emergency situations is central to reducing the risk of deadly crowd disasters. Yet, their systematic experimental study remains a challenging open problem due to ethical and methodological constraints. In this paper, we demonstrate the viability of shared three-dimensional virtual environments as an experimental platform for conducting crowd experiments with real people. In particular, we show that crowds of real human subjects moving and interacting in an immersive three-dimensional virtual environment exhibit typical patterns of real crowds as observed in real-life crowded situations. These include the manifestation of social conventions and the emergence of self-organized patterns during egress scenarios. High-stress evacuation experiments conducted in this virtual environment reveal movements characterized by mass herding and dangerous overcrowding as they occur in crowd disasters. We describe the behavioural mechanisms at play under such extreme conditions and identify critical zones where overcrowding may occur. Furthermore, we show that herding spontaneously emerges from a density effect without the need to assume an increase of the individual tendency to imitate peers. Our experiments reveal the promise of immersive virtual environments as an ethical, cost-efficient, yet accurate platform for exploring crowd behaviour in high-risk situations with real human subjects. PMID:27605166

Crowd behaviour during high-stress evacuations in an immersive virtual environment.

PubMed

Moussaïd, Mehdi; Kapadia, Mubbasir; Thrash, Tyler; Sumner, Robert W; Gross, Markus; Helbing, Dirk; Hölscher, Christoph

2016-09-01

Understanding the collective dynamics of crowd movements during stressful emergency situations is central to reducing the risk of deadly crowd disasters. Yet, their systematic experimental study remains a challenging open problem due to ethical and methodological constraints. In this paper, we demonstrate the viability of shared three-dimensional virtual environments as an experimental platform for conducting crowd experiments with real people. In particular, we show that crowds of real human subjects moving and interacting in an immersive three-dimensional virtual environment exhibit typical patterns of real crowds as observed in real-life crowded situations. These include the manifestation of social conventions and the emergence of self-organized patterns during egress scenarios. High-stress evacuation experiments conducted in this virtual environment reveal movements characterized by mass herding and dangerous overcrowding as they occur in crowd disasters. We describe the behavioural mechanisms at play under such extreme conditions and identify critical zones where overcrowding may occur. Furthermore, we show that herding spontaneously emerges from a density effect without the need to assume an increase of the individual tendency to imitate peers. Our experiments reveal the promise of immersive virtual environments as an ethical, cost-efficient, yet accurate platform for exploring crowd behaviour in high-risk situations with real human subjects. © 2016 The Authors.

The importance of postural cues for determining eye height in immersive virtual reality.

PubMed

Leyrer, Markus; Linkenauger, Sally A; Bülthoff, Heinrich H; Mohler, Betty J

2015-01-01

In human perception, the ability to determine eye height is essential, because eye height is used to scale heights of objects, velocities, affordances and distances, all of which allow for successful environmental interaction. It is well understood that eye height is fundamental to determine many of these percepts. Yet, how eye height itself is provided is still largely unknown. While the information potentially specifying eye height in the real world is naturally coincident in an environment with a regular ground surface, these sources of information can be easily divergent in similar and common virtual reality scenarios. Thus, we conducted virtual reality experiments where we manipulated the virtual eye height in a distance perception task to investigate how eye height might be determined in such a scenario. We found that humans rely more on their postural cues for determining their eye height if there is a conflict between visual and postural information and little opportunity for perceptual-motor calibration is provided. This is demonstrated by the predictable variations in their distance estimates. Our results suggest that the eye height in such circumstances is informed by postural cues when estimating egocentric distances in virtual reality and consequently, does not depend on an internalized value for eye height.

The human dynamic clamp as a paradigm for social interaction.

PubMed

Dumas, Guillaume; de Guzman, Gonzalo C; Tognoli, Emmanuelle; Kelso, J A Scott

2014-09-02

Social neuroscience has called for new experimental paradigms aimed toward real-time interactions. A distinctive feature of interactions is mutual information exchange: One member of a pair changes in response to the other while simultaneously producing actions that alter the other. Combining mathematical and neurophysiological methods, we introduce a paradigm called the human dynamic clamp (HDC), to directly manipulate the interaction or coupling between a human and a surrogate constructed to behave like a human. Inspired by the dynamic clamp used so productively in cellular neuroscience, the HDC allows a person to interact in real time with a virtual partner itself driven by well-established models of coordination dynamics. People coordinate hand movements with the visually observed movements of a virtual hand, the parameters of which depend on input from the subject's own movements. We demonstrate that HDC can be extended to cover a broad repertoire of human behavior, including rhythmic and discrete movements, adaptation to changes of pacing, and behavioral skill learning as specified by a virtual "teacher." We propose HDC as a general paradigm, best implemented when empirically verified theoretical or mathematical models have been developed in a particular scientific field. The HDC paradigm is powerful because it provides an opportunity to explore parameter ranges and perturbations that are not easily accessible in ordinary human interactions. The HDC not only enables to test the veracity of theoretical models, it also illuminates features that are not always apparent in real-time human social interactions and the brain correlates thereof.

Association of Burden of Atrial Fibrillation With Risk of Ischemic Stroke in Adults With Paroxysmal Atrial Fibrillation: The KP-RHYTHM Study.

PubMed

Go, Alan S; Reynolds, Kristi; Yang, Jingrong; Gupta, Nigel; Lenane, Judith; Sung, Sue Hee; Harrison, Teresa N; Liu, Taylor I; Solomon, Matthew D

2018-05-16

Atrial fibrillation is a potent risk factor for stroke, but whether the burden of atrial fibrillation in patients with paroxysmal atrial fibrillation independently influences the risk of thromboembolism remains controversial. To determine if the burden of atrial fibrillation characterized using noninvasive, continuous ambulatory monitoring is associated with the risk of ischemic stroke or arterial thromboembolism in adults with paroxysmal atrial fibrillation. This retrospective cohort study conducted from October 2011 and October 2016 at 2 large integrated health care delivery systems used an extended continuous cardiac monitoring system to identify adults who were found to have paroxysmal atrial fibrillation on 14-day continuous ambulatory electrocardiographic monitoring. The burden of atrial fibrillation was defined as the percentage of analyzable wear time in atrial fibrillation or flutter during the up to 14-day monitoring period. Ischemic stroke and other arterial thromboembolic events occurring while patients were not taking anticoagulation were identified through November 2016 using electronic medical records and were validated by manual review. We evaluated the association of the burden of atrial fibrillation with thromboembolism while not taking anticoagulation after adjusting for the Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) or CHA2DS2-VASc stroke risk scores. Among 1965 adults with paroxysmal atrial fibrillation, the mean (SD) age was 69 (11.8) years, 880 (45%) were women, 496 (25%) were persons of color, the median ATRIA stroke risk score was 4 (interquartile range [IQR], 2-7), and the median CHA2DS2-VASc score was 3 (IQR, 1-4). The median burden of atrial fibrillation was 4.4% (IQR ,1.1%-17.23%). Patients with a higher burden of atrial fibrillation were less likely to be women or of Hispanic ethnicity, but had more prior cardioversion attempts compared with those who had a lower burden. After adjusting for either ATRIA or CHA2DS2-VASc stroke risk scores, the highest tertile of atrial fibrillation burden (≥11.4%) was associated with a more than 3-fold higher adjusted rate of thromboembolism while not taking anticoagulants (adjusted hazard ratios, 3.13 [95% CI, 1.50-6.56] and 3.16 [95% CI, 1.51-6.62], respectively) compared with the combined lower 2 tertiles of atrial fibrillation burden. Results were consistent across demographic and clinical subgroups. A greater burden of atrial fibrillation is associated with a higher risk of ischemic stroke independent of known stroke risk factors in adults with paroxysmal atrial fibrillation.

Virtual Reality: An Experiential Tool for Clinical Psychology

ERIC Educational Resources Information Center

Riva, Giuseppe

2009-01-01

Several Virtual Reality (VR) applications for the understanding, assessment and treatment of mental health problems have been developed in the last 15 years. Typically, in VR the patient learns to manipulate problematic situations related to his/her problem. In fact, VR can be described as an advanced form of human-computer interface that is able…

Virtual Reality as a Leisure Activity for Young Adults with Physical and Intellectual Disabilities

ERIC Educational Resources Information Center

Yalon-Chamovitz, Shira; Weiss, Patrice L.

2008-01-01

Participation in leisure activities is a fundamental human right and an important factor of quality of life. Adults with intellectual disabilities (ID) and physical disabilities often experience limited opportunities to participate in leisure activities, virtual reality (VR) technologies may serve to broaden their repertoire of accessible leisure…

Immersive Virtual Worlds in University-Level Human Geography Courses

ERIC Educational Resources Information Center

Dittmer, Jason

2010-01-01

This paper addresses the potential for increased deployment of immersive virtual worlds in higher geographic education. An account of current practice regarding popular culture in the geography classroom is offered, focusing on the objectification of popular culture rather than its constitutive role vis-a-vis place. Current e-learning practice is…

Virtual Reality in Psychological, Medical and Pedagogical Applications

ERIC Educational Resources Information Center

Eichenberg, Christiane, Ed.

2012-01-01

This book has an aim to present latest applications, trends and developments of virtual reality technologies in three humanities disciplines: in medicine, psychology and pedagogy. Studies show that people in both educational as well as in the medical therapeutic range expect more and more that modern media are included in the corresponding demand…

Learning to Teach in Second Life: A Novice Adventure in Virtual Reality

ERIC Educational Resources Information Center

Ellis, Maureen; Anderson, Patricia

2011-01-01

Second Life (SL) is a social virtual world, which emphasizes the general use of immersive worlds for supporting a variety of human activities and interactions, presenting a plethora of new opportunities and challenges for enriching how we learn, work and play (Boulos, Hetherington & Wheeler, 2007; Prasolova-Førland, Sourin & Sourina,…

Evidence of Blocking with Geometric Cues in a Virtual Watermaze

ERIC Educational Resources Information Center

Redhead, Edward S.; Hamilton, Derek A.

2009-01-01

Three computer based experiments, testing human participants in a non-immersive virtual watermaze task, used a blocking design to assess whether two sets of geometric cues would compete in a manner described by associative models of learning. In stage 1, participants were required to discriminate between visually distinct platforms. In stage 2,…

Measuring Flow Experience in an Immersive Virtual Environment for Collaborative Learning

ERIC Educational Resources Information Center

van Schaik, P.; Martin, S.; Vallance, M.

2012-01-01

In contexts other than immersive virtual environments, theoretical and empirical work has identified flow experience as a major factor in learning and human-computer interaction. Flow is defined as a "holistic sensation that people feel when they act with total involvement". We applied the concept of flow to modeling the experience of…

Using Immersive Virtual Environments for Certification

NASA Technical Reports Server (NTRS)

Lutz, R.; Cruz-Neira, C.

1998-01-01

Immersive virtual environments (VEs) technology has matured to the point where it can be utilized as a scientific and engineering problem solving tool. In particular, VEs are starting to be used to design and evaluate safety-critical systems that involve human operators, such as flight and driving simulators, complex machinery training, and emergency rescue strategies.

Objective and subjective quality assessment of geometry compression of reconstructed 3D humans in a 3D virtual room

NASA Astrophysics Data System (ADS)

Mekuria, Rufael; Cesar, Pablo; Doumanis, Ioannis; Frisiello, Antonella

2015-09-01

Compression of 3D object based video is relevant for 3D Immersive applications. Nevertheless, the perceptual aspects of the degradation introduced by codecs for meshes and point clouds are not well understood. In this paper we evaluate the subjective and objective degradations introduced by such codecs in a state of art 3D immersive virtual room. In the 3D immersive virtual room, users are captured with multiple cameras, and their surfaces are reconstructed as photorealistic colored/textured 3D meshes or point clouds. To test the perceptual effect of compression and transmission, we render degraded versions with different frame rates in different contexts (near/far) in the scene. A quantitative subjective study with 16 users shows that negligible distortion of decoded surfaces compared to the original reconstructions can be achieved in the 3D virtual room. In addition, a qualitative task based analysis in a full prototype field trial shows increased presence, emotion, user and state recognition of the reconstructed 3D Human representation compared to animated computer avatars.

Real-time tracking of visually attended objects in virtual environments and its application to LOD.

PubMed

Lee, Sungkil; Kim, Gerard Jounghyun; Choi, Seungmoon

2009-01-01

This paper presents a real-time framework for computationally tracking objects visually attended by the user while navigating in interactive virtual environments. In addition to the conventional bottom-up (stimulus-driven) saliency map, the proposed framework uses top-down (goal-directed) contexts inferred from the user's spatial and temporal behaviors, and identifies the most plausibly attended objects among candidates in the object saliency map. The computational framework was implemented using GPU, exhibiting high computational performance adequate for interactive virtual environments. A user experiment was also conducted to evaluate the prediction accuracy of the tracking framework by comparing objects regarded as visually attended by the framework to actual human gaze collected with an eye tracker. The results indicated that the accuracy was in the level well supported by the theory of human cognition for visually identifying single and multiple attentive targets, especially owing to the addition of top-down contextual information. Finally, we demonstrate how the visual attention tracking framework can be applied to managing the level of details in virtual environments, without any hardware for head or eye tracking.

Genistein and tyrphostin AG556 decrease ultra-rapidly activating delayed rectifier K+ current of human atria by inhibiting EGF receptor tyrosine kinase.

PubMed

Xiao, Guo-Sheng; Zhang, Yan-Hui; Wu, Wei; Sun, Hai-Ying; Wang, Yan; Li, Gui-Rong

2017-03-01

The ultra-rapidly activating delayed rectifier K + current I Kur (encoded by K v 1.5 or KCNA5) plays an important role in human atrial repolarization. The present study investigates the regulation of this current by protein tyrosine kinases (PTKs). Whole-cell patch voltage clamp technique and immunoprecipitation and Western blotting analysis were used to investigate whether the PTK inhibitors genistein, tyrphostin AG556 (AG556) and PP2 regulate human atrial I Kur and hKv1.5 channels stably expressed in HEK 293 cells. Human atrial I Kur was decreased by genistein (a broad-spectrum PTK inhibitor) and AG556 (a highly selective EGFR TK inhibitor) in a concentration-dependent manner. Inhibition of I Kur induced by 30 μM genistein or 10 μM AG556 was significantly reversed by 1 mM orthovanadate (a protein tyrosine phosphatase inhibitor). Similar results were observed in HEK 293 cells stably expressing hK v 1.5 channels. On the other hand, the Src family kinase inhibitor PP2 (1 μM) slightly enhanced I Kur and hK v 1.5 current, and the current increase was also reversed by orthovanadate. Immunoprecipitation and Western blotting analysis showed that genistein, AG556, and PP2 decreased tyrosine phosphorylation of hK v 1.5 channels and that the decrease was countered by orthovanadate. The PTK inhibitors genistein and AG556 decrease human atrial I Kur and cloned hK v 1.5 channels by inhibiting EGFR TK, whereas the Src kinase inhibitor PP2 increases I Kur and hK v 1.5 current. These results imply that EGFR TK and the soluble Src kinases may have opposite effects on human atrial I Kur . © 2017 The British Pharmacological Society.

Proceedings of the 1993 Conference on Intelligent Computer-Aided Training and Virtual Environment Technology, Volume 1

NASA Technical Reports Server (NTRS)

Hyde, Patricia R.; Loftin, R. Bowen

1993-01-01

These proceedings are organized in the same manner as the conference's contributed sessions, with the papers grouped by topic area. These areas are as follows: VE (virtual environment) training for Space Flight, Virtual Environment Hardware, Knowledge Aquisition for ICAT (Intelligent Computer-Aided Training) & VE, Multimedia in ICAT Systems, VE in Training & Education (1 & 2), Virtual Environment Software (1 & 2), Models in ICAT systems, ICAT Commercial Applications, ICAT Architectures & Authoring Systems, ICAT Education & Medical Applications, Assessing VE for Training, VE & Human Systems (1 & 2), ICAT Theory & Natural Language, ICAT Applications in the Military, VE Applications in Engineering, Knowledge Acquisition for ICAT, and ICAT Applications in Aerospace.

Classification of EMG signals using artificial neural networks for virtual hand prosthesis control.

PubMed

Mattioli, Fernando E R; Lamounier, Edgard A; Cardoso, Alexandre; Soares, Alcimar B; Andrade, Adriano O

2011-01-01

Computer-based training systems have been widely studied in the field of human rehabilitation. In health applications, Virtual Reality presents itself as an appropriate tool to simulate training environments without exposing the patients to risks. In particular, virtual prosthetic devices have been used to reduce the great mental effort needed by patients fitted with myoelectric prosthesis, during the training stage. In this paper, the application of Virtual Reality in a hand prosthesis training system is presented. To achieve this, the possibility of exploring Neural Networks in a real-time classification system is discussed. The classification technique used in this work resulted in a 95% success rate when discriminating 4 different hand movements.

Comparison of 3D dynamic virtual model to link segment model for estimation of net L4/L5 reaction moments during lifting.

PubMed

Abdoli-Eramaki, Mohammad; Stevenson, Joan M; Agnew, Michael J; Kamalzadeh, Amin

2009-04-01

The purpose of this study was to validate a 3D dynamic virtual model for lifting tasks against a validated link segment model (LSM). A face validation study was conducted by collecting x, y, z coordinate data and using them in both virtual and LSM models. An upper body virtual model was needed to calculate the 3D torques about human joints for use in simulated lifting styles and to estimate the effect of external mechanical devices on human body. Firstly, the model had to be validated to be sure it provided accurate estimates of 3D moments in comparison to a previously validated LSM. Three synchronised Fastrak units with nine sensors were used to record data from one male subject who completed dynamic box lifting under 27 different load conditions (box weights (3), lifting techniques (3) and rotations (3)). The external moments about three axes of L4/L5 were compared for both models. A pressure switch on the box was used to denote the start and end of the lift. An excellent agreement [image omitted] was found between the two models for dynamic lifting tasks, especially for larger moments in flexion and extension. This virtual model was considered valid for use in a complete simulation of the upper body skeletal system. This biomechanical virtual model of the musculoskeletal system can be used by researchers and practitioners to give a better tool to study the causes of LBP and the effect of intervention strategies, by permitting the researcher to see and control a virtual subject's motions.

The perception of spatial layout in real and virtual worlds.

PubMed

Arthur, E J; Hancock, P A; Chrysler, S T

1997-01-01

As human-machine interfaces grow more immersive and graphically-oriented, virtual environment systems become more prominent as the medium for human-machine communication. Often, virtual environments (VE) are built to provide exact metrical representations of existing or proposed physical spaces. However, it is not known how individuals develop representational models of these spaces in which they are immersed and how those models may be distorted with respect to both the virtual and real-world equivalents. To evaluate the process of model development, the present experiment examined participant's ability to reproduce a complex spatial layout of objects having experienced them previously under different viewing conditions. The layout consisted of nine common objects arranged on a flat plane. These objects could be viewed in a free binocular virtual condition, a free binocular real-world condition, and in a static monocular view of the real world. The first two allowed active exploration of the environment while the latter condition allowed the participant only a passive opportunity to observe from a single viewpoint. Viewing conditions were a between-subject variable with 10 participants randomly assigned to each condition. Performance was assessed using mapping accuracy and triadic comparisons of relative inter-object distances. Mapping results showed a significant effect of viewing condition where, interestingly, the static monocular condition was superior to both the active virtual and real binocular conditions. Results for the triadic comparisons showed a significant interaction for gender by viewing condition in which males were more accurate than females. These results suggest that the situation model resulting from interaction with a virtual environment was indistinguishable from interaction with real objects at least within the constraints of the present procedure.

Human Activity Modeling and Simulation with High Biofidelity

DTIC Science & Technology

2013-01-01

Human activity Modeling and Simulation (M&S) plays an important role in simulation-based training and Virtual Reality (VR). However, human activity M...kinematics and motion mapping/creation; and (e) creation and replication of human activity in 3-D space with true shape and motion. A brief review is

Modelling Human Emotions for Tactical Decision-Making Games

ERIC Educational Resources Information Center

Visschedijk, Gillian C.; Lazonder, Ard W.; van der Hulst, Anja; Vink, Nathalie; Leemkuil, Henny

2013-01-01

The training of tactical decision making increasingly occurs through serious computer games. A challenging aspect of designing such games is the modelling of human emotions. Two studies were performed to investigate the relation between fidelity and human emotion recognition in virtual human characters. Study 1 compared five versions of a virtual…

Around Marshall

NASA Image and Video Library

1993-09-15

Virtual Reality (VR) can provide cost effective methods to design and evaluate components and systems for maintenance and refurbishment operations. Marshall SPace Flight Center (MSFC) is begirning to utilize VR for design analysis in the X-34 experimental reusable space vehicle. Analysts at MSFC's Computer Applications and Virtual Environments (CAVE) used Head Mounted Displays (HMD) (pictured), spatial trackers and gesture inputs as a means to animate or inhabit a properly sized virtual human model. These models are used in a VR scenario as a way to determine functionality of space and maintenance requirements for the virtual X-34. The primary functions of the virtual X-34 mockup is to support operations development and design analysis for engine removal, the engine compartment and the aft fuselage. This capability provides general visualization support to engineers and designers at MSFC and to the System Design Freeze Review at Orbital Sciences Corporation (OSC).

Around Marshall

NASA Image and Video Library

1993-12-15

Virtual Reality (VR) can provide cost effective methods to design and evaluate components and systems for maintenance and refurbishment operations. Marshall Spce Flight Center (MSFC) is begirning to utilize VR for design analysis in the X-34 experimental reusable space vehicle. Analysts at MSFC's Computer Applications and Virtual Environments (CAVE) used Head Mounted Displays (HMD) (pictured), spatial trackers and gesture inputs as a means to animate or inhabit a properly sized virtual human model. These models are used in a VR scenario as a way to determine functionality of space and maintenance requirements for the virtual X-34. The primary functions of the virtual X-34 mockup is to support operations development and design analysis for engine removal, the engine compartment and the aft fuselage. This capability provides general visualization support to engineers and designers at MSFC and to the System Design Freeze Review at Orbital Sciences Corporation (OSC).

Virtual environments for scene of crime reconstruction and analysis

NASA Astrophysics Data System (ADS)

Howard, Toby L. J.; Murta, Alan D.; Gibson, Simon

2000-02-01

This paper describes research conducted in collaboration with Greater Manchester Police (UK), to evalute the utility of Virtual Environments for scene of crime analysis, forensic investigation, and law enforcement briefing and training. We present an illustrated case study of the construction of a high-fidelity virtual environment, intended to match a particular real-life crime scene as closely as possible. We describe and evaluate the combination of several approaches including: the use of the Manchester Scene Description Language for constructing complex geometrical models; the application of a radiosity rendering algorithm with several novel features based on human perceptual consideration; texture extraction from forensic photography; and experiments with interactive walkthroughs and large-screen stereoscopic display of the virtual environment implemented using the MAVERIK system. We also discuss the potential applications of Virtual Environment techniques in the Law Enforcement and Forensic communities.

Virtualization of open-source secure web services to support data exchange in a pediatric critical care research network

PubMed Central

Sward, Katherine A; Newth, Christopher JL; Khemani, Robinder G; Cryer, Martin E; Thelen, Julie L; Enriquez, Rene; Shaoyu, Su; Pollack, Murray M; Harrison, Rick E; Meert, Kathleen L; Berg, Robert A; Wessel, David L; Shanley, Thomas P; Dalton, Heidi; Carcillo, Joseph; Jenkins, Tammara L; Dean, J Michael

2015-01-01

Objectives To examine the feasibility of deploying a virtual web service for sharing data within a research network, and to evaluate the impact on data consistency and quality. Material and Methods Virtual machines (VMs) encapsulated an open-source, semantically and syntactically interoperable secure web service infrastructure along with a shadow database. The VMs were deployed to 8 Collaborative Pediatric Critical Care Research Network Clinical Centers. Results Virtual web services could be deployed in hours. The interoperability of the web services reduced format misalignment from 56% to 1% and demonstrated that 99% of the data consistently transferred using the data dictionary and 1% needed human curation. Conclusions Use of virtualized open-source secure web service technology could enable direct electronic abstraction of data from hospital databases for research purposes. PMID:25796596

Ion Channels in the Heart

PubMed Central

Bartos, Daniel C.; Grandi, Eleonora; Ripplinger, Crystal M.

2015-01-01

Optimal cardiac function depends on proper timing of excitation and contraction in various regions of the heart, as well as on appropriate heart rate. This is accomplished via specialized electrical properties of various components of the system, including the sinoatrial node, atria, atrioventricular node, His-Purkinje system, and ventricles. Here we review the major regionally-determined electrical properties of these cardiac regions and present the available data regarding the molecular and ionic bases of regional cardiac function and dysfunction. Understanding these differences is of fundamental importance for the investigation of arrhythmia mechanisms and pharmacotherapy. PMID:26140724

Effect of varying ventricular function by extrasystolic potentiation on closure of the mitral valve.

NASA Technical Reports Server (NTRS)

Vandenberg, R. A.; Williams, J. C. P.; Sturm, R. E.; Wood , E. H.

1971-01-01

Mitral regurgitant indexes were measured by roentgen videodensitometry in anesthetized dogs without thoracotomy before, during and after extrasystolic potentiation of ventricular contraction while the atria and ventricles were driven in normal temporal sequence simultaneously or in such a way as to induce atrial fibrillation. Small amounts of mitral reflux were observed with simultaneous atrial and ventricular driving and with atrial fibrillation in the control measurements before initiation of extrasystolic potentiation. Reflux became negligible during extrasystolic potentiation and increased beyond control levels after termination of extrasystolic potentiation.

How to maintain the oral health of a child with Wolff-Parkinson-White syndrome: a case report

PubMed Central

2014-01-01

Introduction Wolff-Parkinson-White syndrome is one of the most important disorders of the heart conduction system. It is caused by the presence of an abnormal accessory electrical conduction pathway between the atria and the ventricles. Case presentation In the present report, we describe the correct oral health management of a 12-year-old Caucasian girl with Wolff-Parkinson-White syndrome. Conclusions We successfully undertook the dental care of a girl with Wolff-Parkinson-White syndrome, which we describe here. PMID:25269932

An enantiomer-based virtual screening approach: Discovery of chiral organophosphates as acetyl cholinesterase inhibitors.

PubMed

Zhang, Aiqian; Mu, Yunsong; Wu, Fengchang

2017-04-01

Chiral organophosphates (OPs) have been used widely around the world, very little is known about binding mechanisms with biological macromolecules. An in-depth understanding of the stereo selectivity of human AChE and discovering bioactive enantiomers of OPs can decrease health risks of these chiral chemicals. In the present study, a flexible molecular docking approach was conducted to investigate different binding modes of twelve phosphorus enantiomers. A pharmacophore model was then developed on basis of the bioactive conformations of these compounds. After virtual screening, twenty-four potential bioactive compounds were found, of which three compounds (Ethyl p-nitrophenyl phenylphosphonate (EPN), 1-naphthaleneacetic anhydride and N,4-dimethyl-N-phenyl-benzenesulfonamide) were tested by use of different in vitro assays. S-isomer of EPN was also found to exhibit greater inhibitory activity towards human AChE than the corresponding R-isomer. These findings affirm that stereochemistry plays a crucial role in virtual screening, and provide a new insight into designing safer organ phosphorus pesticides on human health. Copyright © 2017 Elsevier Inc. All rights reserved.

Virtual interface environment workstations

NASA Technical Reports Server (NTRS)

Fisher, S. S.; Wenzel, E. M.; Coler, C.; Mcgreevy, M. W.

1988-01-01

A head-mounted, wide-angle, stereoscopic display system controlled by operator position, voice and gesture has been developed at NASA's Ames Research Center for use as a multipurpose interface environment. This Virtual Interface Environment Workstation (VIEW) system provides a multisensory, interactive display environment in which a user can virtually explore a 360-degree synthesized or remotely sensed environment and can viscerally interact with its components. Primary applications of the system are in telerobotics, management of large-scale integrated information systems, and human factors research. System configuration, research scenarios, and research directions are described.

The Evolution of Sonic Ecosystems

NASA Astrophysics Data System (ADS)

McCormack, Jon

This chapter describes a novel type of artistic artificial life software environment. Agents that have the ability to make and listen to sound populate a synthetic world. An evolvable, rule-based classifier system drives agent behavior. Agents compete for limited resources in a virtual environment that is influenced by the presence and movement of people observing the system. Electronic sensors create a link between the real and virtual spaces, virtual agents evolve implicitly to try to maintain the interest of the human audience, whose presence provides them with life-sustaining food.

Human Activity Behavior and Gesture Generation in Virtual Worlds for Long- Duration Space Missions. Chapter 8

NASA Technical Reports Server (NTRS)

Sierhuis, Maarten; Clancey, William J.; Damer, Bruce; Brodsky, Boris; vanHoff, Ron

2007-01-01

A virtual worlds presentation technique with embodied, intelligent agents is being developed as an instructional medium suitable to present in situ training on long term space flight. The system combines a behavioral element based on finite state automata, a behavior based reactive architecture also described as subsumption architecture, and a belief-desire-intention agent structure. These three features are being integrated to describe a Brahms virtual environment model of extravehicular crew activity which could become a basis for procedure training during extended space flight.

Virtual reality haptic dissection.

PubMed

Erolin, Caroline; Wilkinson, Caroline; Soames, Roger

2011-12-01

This project aims to create a three-dimensional digital model of the human hand and wrist which can be virtually 'dissected' through a haptic interface. Tissue properties will be added to the various anatomical structures to replicate a realistic look and feel. The project will explore the role of the medical artist, and investigate cross-discipline collaborations in the field of virtual anatomy. The software will be used to train anatomy students in dissection skills, before experience on a real cadaver. The effectiveness of the software will be evaluated and assessed both quantitatively as well as qualitatively.

Ontological implications of being in immersive virtual environments

NASA Astrophysics Data System (ADS)

Morie, Jacquelyn F.

2008-02-01

The idea of Virtual Reality once conjured up visions of new territories to explore, and expectations of awaiting worlds of wonder. VR has matured to become a practical tool for therapy, medicine and commercial interests, yet artists, in particular, continue to expand the possibilities for the medium. Artistic virtual environments created over the past two decades probe the phenomenological nature of these virtual environments. When we inhabit a fully immersive virtual environment, we have entered into a new form of Being. Not only does our body continue to exist in the real, physical world, we are also embodied within the virtual by means of technology that translates our bodied actions into interactions with the virtual environment. Very few states in human existence allow this bifurcation of our Being, where we can exist simultaneously in two spaces at once, with the possible exception of meta-physical states such as shamanistic trance and out-of-body experiences. This paper discusses the nature of this simultaneous Being, how we enter the virtual space, what forms of persona we can don there, what forms of spaces we can inhabit, and what type of wondrous experiences we can both hope for and expect.

EMOTION RECOGNITION OF VIRTUAL AGENTS FACIAL EXPRESSIONS: THE EFFECTS OF AGE AND EMOTION INTENSITY

PubMed Central

Beer, Jenay M.; Fisk, Arthur D.; Rogers, Wendy A.

2014-01-01

People make determinations about the social characteristics of an agent (e.g., robot or virtual agent) by interpreting social cues displayed by the agent, such as facial expressions. Although a considerable amount of research has been conducted investigating age-related differences in emotion recognition of human faces (e.g., Sullivan, & Ruffman, 2004), the effect of age on emotion identification of virtual agent facial expressions has been largely unexplored. Age-related differences in emotion recognition of facial expressions are an important factor to consider in the design of agents that may assist older adults in a recreational or healthcare setting. The purpose of the current research was to investigate whether age-related differences in facial emotion recognition can extend to emotion-expressive virtual agents. Younger and older adults performed a recognition task with a virtual agent expressing six basic emotions. Larger age-related differences were expected for virtual agents displaying negative emotions, such as anger, sadness, and fear. In fact, the results indicated that older adults showed a decrease in emotion recognition accuracy for a virtual agent's emotions of anger, fear, and happiness. PMID:25552896

Assessing Upper Extremity Motor Function in Practice of Virtual Activities of Daily Living

PubMed Central

Adams, Richard J.; Lichter, Matthew D.; Krepkovich, Eileen T.; Ellington, Allison; White, Marga; Diamond, Paul T.

2015-01-01

A study was conducted to investigate the criterion validity of measures of upper extremity (UE) motor function derived during practice of virtual activities of daily living (ADLs). Fourteen hemiparetic stroke patients employed a Virtual Occupational Therapy Assistant (VOTA), consisting of a high-fidelity virtual world and a Kinect™ sensor, in four sessions of approximately one hour in duration. An Unscented Kalman Filter-based human motion tracking algorithm estimated UE joint kinematics in real-time during performance of virtual ADL activities, enabling both animation of the user’s avatar and automated generation of metrics related to speed and smoothness of motion. These metrics, aggregated over discrete sub-task elements during performance of virtual ADLs, were compared to scores from an established assessment of UE motor performance, the Wolf Motor Function Test (WMFT). Spearman’s rank correlation analysis indicates a moderate correlation between VOTA-derived metrics and the time-based WMFT assessments, supporting the criterion validity of VOTA measures as a means of tracking patient progress during an UE rehabilitation program that includes practice of virtual ADLs. PMID:25265612

Assessing upper extremity motor function in practice of virtual activities of daily living.

PubMed

Adams, Richard J; Lichter, Matthew D; Krepkovich, Eileen T; Ellington, Allison; White, Marga; Diamond, Paul T

2015-03-01

A study was conducted to investigate the criterion validity of measures of upper extremity (UE) motor function derived during practice of virtual activities of daily living (ADLs). Fourteen hemiparetic stroke patients employed a Virtual Occupational Therapy Assistant (VOTA), consisting of a high-fidelity virtual world and a Kinect™ sensor, in four sessions of approximately one hour in duration. An unscented Kalman Filter-based human motion tracking algorithm estimated UE joint kinematics in real-time during performance of virtual ADL activities, enabling both animation of the user's avatar and automated generation of metrics related to speed and smoothness of motion. These metrics, aggregated over discrete sub-task elements during performance of virtual ADLs, were compared to scores from an established assessment of UE motor performance, the Wolf Motor Function Test (WMFT). Spearman's rank correlation analysis indicates a moderate correlation between VOTA-derived metrics and the time-based WMFT assessments, supporting the criterion validity of VOTA measures as a means of tracking patient progress during an UE rehabilitation program that includes practice of virtual ADLs.

Framing the magic

NASA Astrophysics Data System (ADS)

Tsoupikova, Daria

2006-02-01

This paper will explore how the aesthetics of the virtual world affects, transforms, and enhances the immersive emotional experience of the user. What we see and what we do upon entering the virtual environment influences our feelings, mental state, physiological changes and sensibility. To create a unique virtual experience the important component to design is the beauty of the virtual world based on the aesthetics of the graphical objects such as textures, models, animation, and special effects. The aesthetic potency of the images that comprise the virtual environment can make the immersive experience much stronger and more compelling. The aesthetic qualities of the virtual world as born out through images and graphics can influence the user's state of mind. Particular changes and effects on the user can be induced through the application of techniques derived from the research fields of psychology, anthropology, biology, color theory, education, art therapy, music, and art history. Many contemporary artists and developers derive much inspiration for their work from their experience with traditional arts such as painting, sculpture, design, architecture and music. This knowledge helps them create a higher quality of images and stereo graphics in the virtual world. The understanding of the close relation between the aesthetic quality of the virtual environment and the resulting human perception is the key to developing an impressive virtual experience.

Telerobotic surgery: applications on human patients and training with virtual reality.

PubMed

Rovetta, A; Bejczy, A K; Sala, R

1997-01-01

This paper deals with the developed researches and applications on telerobotic surgery, devoted to human patients and with training by virtual reality. The researches have been developed in cooperation between Telerobotics Laboratory, Department of Mechanics, Politecnico di Milano, Italy, and Automation and Control Section, Jet Propulsion Laboratory, Pasadena, USA. The researches carried to a telesurgery robotic operation on a dummy on 7th July 1993, by means of satellites communications, to a prostatic biopsy on a human patient on 1st September 1995 with optical fibers, to results on time delay effects, to results on virtual reality applications for training on laparoscopy and surgery. The search implied time delay when the control input originated in Politecnico di Milano, Italy. The results were satisfactory, but also pointed out the need for specific new control transformations to ease the operator's or surgeon's visual/mental workload for hand-eye coordination. In the same research, dummy force commands from JPL to Milan were sent, and were echoed immediately back to JPL, measuring the round-trip time of the command signal. This, to some degree, simulates a contact force feedback situation. The results were very surprising; despite the fact that the ISDN calls are closed and "private" calls, the round-trip time exhibited great variations not only between calls but also within the same call. The results proved that telerobotics and telecontrol may be applied to surgery. Time latency variations are caused by features of communication network, of sending and receiving end computer software. The problem and its solution is also an architectural issue, and considerable improvements are possible. Virtual reality in the application of the research is a strong support to training on virtual objects and not on living beings.

User-Centered Iterative Design of a Collaborative Virtual Environment

DTIC Science & Technology

2001-03-01

cognitive task analysis methods to study land navigators. This study was intended to validate the use of user-centered design methodologies for the design of...have explored the cognitive aspects of collaborative human way finding and design for collaborative virtual environments. Further investigation of design paradigms should include cognitive task analysis and behavioral task analysis.

Learning Intercultural Communication Skills with Virtual Humans: Feedback and Fidelity

ERIC Educational Resources Information Center

Lane, H. Chad; Hays, Matthew Jensen; Core, Mark G.; Auerbach, Daniel

2013-01-01

In the context of practicing intercultural communication skills, we investigated the role of fidelity in a game-based, virtual learning environment as well as the role of feedback delivered by an intelligent tutoring system. In 2 experiments, we compared variations on the game interface, use of the tutoring system, and the form of the feedback.…

Orienting in Virtual Environments: How Are Surface Features and Environmental Geometry Weighted in an Orientation Task?

ERIC Educational Resources Information Center

Kelly, Debbie M.; Bischof, Walter F.

2008-01-01

We investigated how human adults orient in enclosed virtual environments, when discrete landmark information is not available and participants have to rely on geometric and featural information on the environmental surfaces. In contrast to earlier studies, where, for women, the featural information from discrete landmarks overshadowed the encoding…

Virtual Reality on a Desktop Hailed as New Tool in Distance Education.

ERIC Educational Resources Information Center

Young, Jeffrey R.

2000-01-01

Describes college and university educational applications of desktop virtual reality to provide a more human touch to interactive distance education programs and impress the brain with more vivid images. Critics suggest the technology is too costly and time consuming and may even distract students from the content of an online course. (DB)

Chemical Selection Via In Vitro-In Vivo Correlation of ToxCast and ToxRefDB Data to Evaluate the Virtual Liver

EPA Science Inventory

The Virtual Liver Project (v-LiverTM) is a US EPA effort to simulate the function of the human liver with sufficient accuracy to predict how environmental exposure to xenobiotic compounds will perturb homeostasis. The better we understand the liver, the better we will understand...

Working Memory in Wayfinding--A Dual Task Experiment in a Virtual City

ERIC Educational Resources Information Center

Meilinger, Tobias; Knauff, Markus; Bulthoff, Heinrich H.

2008-01-01

This study examines the working memory systems involved in human wayfinding. In the learning phase, 24 participants learned two routes in a novel photorealistic virtual environment displayed on a 220 degrees screen while they were disrupted by a visual, a spatial, a verbal, or--in a control group--no secondary task. In the following wayfinding…

The World Bank's Africa Virtual University Project: A Revisit

ERIC Educational Resources Information Center

Nafukho, Fredrick M.; Muyia, Machuma Helen

2013-01-01

Purpose: The main purpose of using technology in the delivery of virtual learning programs in higher education in Africa is to ensure access and equity as a strategy to develop human resources. Examining how specific educational innovations in higher education are working is necessary. The purpose of this study is to examine the World Bank's…

Hiding and Searching Strategies of Adult Humans in a Virtual and a Real-Space Room

ERIC Educational Resources Information Center

Talbot, Katherine J.; Legge, Eric L. G.; Bulitko, Vadim; Spetch, Marcia L.

2009-01-01

Adults searched for or cached three objects in nine hiding locations in a virtual room or a real-space room. In both rooms, the locations selected by participants differed systematically between searching and hiding. Specifically, participants moved farther from origin and dispersed their choices more when hiding objects than when searching for…

Exploring Arizona K-12 Virtual Educator Experiences and Perspectives Developing Collaborative Learning Communities

ERIC Educational Resources Information Center

Cross, Deborah Iyron

2015-01-01

Arizona Online Instruction (AOI) provided an instructional alternative to nearly fifty thousand K-12 students in Arizona during the 2012-2013 school year. Growth in online education underscores the importance of evolving the role of the K-12 virtual teacher as the human agent (Turvey, 2008) demonstrating social learning theory (Bandura, 1977) by…

Virtual Learning. A Revolutionary Approach to Building a Highly Skilled Workforce.

ERIC Educational Resources Information Center

Schank, Roger

This book offers trainers and human resource managers an alternative approach to train people more effectively and capitalize on multimedia-based tools. The approach is based on computer-based training and virtual learning theory. Chapter 1 discusses how to remedy problems caused by bad training. Chapter 2 focuses on simulating work and creating…

Learning at the Interstices; Locating Practical Philosophies for Understanding Physical/Virtual Inter-Spaces

ERIC Educational Resources Information Center

Savin-Baden, M.; Falconer, L.

2016-01-01

Virtual worlds are relatively recent developments, and so it is tempting to believe that they need to be understood through newly developed theories and philosophies. However, humans have long thought about the nature of reality and what it means to be "real." This paper examines the three persistent philosophical concepts of Metaxis,…

Televirtuality: "Being There" in the 21st Century.

ERIC Educational Resources Information Center

Jacobson, Robert

Virtual worlds technology (VWT) uses special computer hardware and software to link humans with computers in natural ways. A data model, or virtual world, is created and presented as a three-dimensional world of sights and sounds. The participant manipulates apparent objects in the world, and in so doing, alters the data model. VWT will become…

Ambient clumsiness in virtual environments

NASA Astrophysics Data System (ADS)

Ruzanka, Silvia; Behar, Katherine

2010-01-01

A fundamental pursuit of Virtual Reality is the experience of a seamless connection between the user's body and actions within the simulation. Virtual worlds often mediate the relationship between the physical and virtual body through creating an idealized representation of the self in an idealized space. This paper argues that the very ubiquity of the medium of virtual environments, such as the massively popular Second Life, has now made them mundane, and that idealized representations are no longer appropriate. In our artwork we introduce the attribute of clumsiness to Second Life by creating and distributing scripts that cause users' avatars to exhibit unpredictable stumbling, tripping, and momentary poor coordination, thus subtly and unexpectedly intervening with, rather than amplifying, a user's intent. These behaviors are publicly distributed, and manifest only occasionally - rather than intentional, conscious actions, they are involuntary and ambient. We suggest that the physical human body is itself an imperfect interface, and that the continued blurring of distinctions between the physical body and virtual representations calls for the introduction of these mundane, clumsy elements.

Interaction Design and Usability of Learning Spaces in 3D Multi-user Virtual Worlds

NASA Astrophysics Data System (ADS)

Minocha, Shailey; Reeves, Ahmad John

Three-dimensional virtual worlds are multimedia, simulated environments, often managed over the Web, which users can 'inhabit' and interact via their own graphical, self-representations known as 'avatars'. 3D virtual worlds are being used in many applications: education/training, gaming, social networking, marketing and commerce. Second Life is the most widely used 3D virtual world in education. However, problems associated with usability, navigation and way finding in 3D virtual worlds may impact on student learning and engagement. Based on empirical investigations of learning spaces in Second Life, this paper presents design guidelines to improve the usability and ease of navigation in 3D spaces. Methods of data collection include semi-structured interviews with Second Life students, educators and designers. The findings have revealed that design principles from the fields of urban planning, Human- Computer Interaction, Web usability, geography and psychology can influence the design of spaces in 3D multi-user virtual environments.

Current biochemistry, molecular biology, and clinical relevance of natriuretic peptides.

PubMed

Nishikimi, Toshio; Kuwahara, Koichiro; Nakao, Kazuwa

2011-03-01

The mammalian natriuretic peptide family consists of atrial (ANP), brain [B-type; BNP] and C-type natriuretic peptide (CNP) and three receptors, natriuretic receptors-A (NPR-A), -B (NPR-B) and -C (NPR-C). Both ANP and BNP are abundantly expressed in the heart and are secreted mainly from the atria and ventricles, respectively. By contrast, CNP is mainly expressed in the central nervous system, bone and vasculature. Plasma concentrations of both ANP and BNP are elevated in patients with cardiovascular disease, though the magnitude of the increase in BNP is usually greater than the increase in ANP. This makes BNP is a clinically useful diagnostic marker for several pathophysiological conditions, including heart failure, ventricular remodeling and pulmonary hypertension, among others. Recent studies have shown that in addition to BNP-32, proBNP-108 also circulates in human plasma and that levels of both forms are increased in heart failure. Furthermore, proBNP-108 is O-glycosylated and circulates at higher levels in patients with severe heart failure. In this review we discuss recent progress in our understanding of the biochemistry, molecular biology and clinical relevance of the natriuretic peptide system. Copyright © 2011 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

Head-mounted active noise control system with virtual sensing technique

NASA Astrophysics Data System (ADS)

Miyazaki, Nobuhiro; Kajikawa, Yoshinobu

2015-03-01

In this paper, we apply a virtual sensing technique to a head-mounted active noise control (ANC) system we have already proposed. The proposed ANC system can reduce narrowband noise while improving the noise reduction ability at the desired locations. A head-mounted ANC system based on an adaptive feedback structure can reduce noise with periodicity or narrowband components. However, since quiet zones are formed only at the locations of error microphones, an adequate noise reduction cannot be achieved at the locations where error microphones cannot be placed such as near the eardrums. A solution to this problem is to apply a virtual sensing technique. A virtual sensing ANC system can achieve higher noise reduction at the desired locations by measuring the system models from physical sensors to virtual sensors, which will be used in the online operation of the virtual sensing ANC algorithm. Hence, we attempt to achieve the maximum noise reduction near the eardrums by applying the virtual sensing technique to the head-mounted ANC system. However, it is impossible to place the microphone near the eardrums. Therefore, the system models from physical sensors to virtual sensors are estimated using the Head And Torso Simulator (HATS) instead of human ears. Some simulation, experimental, and subjective assessment results demonstrate that the head-mounted ANC system with virtual sensing is superior to that without virtual sensing in terms of the noise reduction ability at the desired locations.