A model to simulate the haemodynamic effects of right heart pulsatile flow after modified Fontan procedure.

PubMed

Tamaki, S; Kawazoe, K; Yagihara, T; Abe, T

1992-02-01

The effect of pulsatile pulmonary flow after the modified Fontan procedure was examined in a model that simulated the right heart. An inlet overflow tank (preload), axial pulsatile pump, Wind-Kessel model (afterload), and an outlet overflow tank were connected in series. The standard conditions were flow 2.00 l/min with 12 mm Hg preload pressure, 3.0 Wood units resistance, and an outlet overflow tank pressure at 6 mm Hg. The pump rate was set at 80 beats/min. The simulated pulmonary arterial pressure and pulmonary flow waves produced by this model closely resembled those obtained from patients who had undergone the modified Fontan procedure. All variables except the preload were fixed and changes in pulmonary flow were examined at preload pressures of 8, 12, 15, and 17 mm Hg. As the peak pulmonary arterial pressure increased so did pulmonary flow, until it was greater than during the non-pulsatile state. Because the afterload of this model was fixed, this result suggests that there was a concomitant decrease in resistance. This model indicates that pulsatile pulmonary blood flow is likely to have a beneficial effect on the pulmonary circulation after the modified Fontan procedure.

Functionally univentricular heart and the fontan operation: lessons learned about patterns of practice and outcomes from the congenital heart surgery databases of the European association for cardio-thoracic surgery and the society of thoracic surgeons.

PubMed

Jacobs, Jeffrey Phillip; Maruszewski, Bohdan

2013-10-01

"The term "functionally univentricular heart" describes a spectrum of congenital cardiovascular malformations in which the ventricular mass may not readily lend itself to partitioning that commits one ventricular pump to the systemic circulation and another to the pulmonary circulation." The purpose of this article is to review patterns of practice and outcomes in the Congenital Heart Surgery Databases (CHSDBs) of the European Association for Cardio-Thoracic Surgery (EACTS) and the Society of Thoracic Surgeons (STS) in patients with functionally univentricular hearts undergoing the Fontan operation. We examined all index operations performed on patients with functionally univentricular hearts in the EACTS and STS-CHSDBs over 4 years from 2007 to 2010, inclusive. The most common diagnostic categories are hypoplastic left heart syndrome, tricuspid atresia, and double inlet left ventricle. The Fontan operation makes up 3.2% of all cardiac operations in the EACTS and STS-CHSDBs over 4 years from 2007 to 2010, inclusive. Of all the patients undergoing a Fontan procedure, 65.1% had an extracardiac Fontan, 21.5% had a lateral tunnel, and 5.8% had a Fontan revision or conversion (Re-do Fontan). In operations where fenestration status is known, 68.5% of the Fontan operations were fenestrated. During the four years of this analysis, only 5 patients had ventricular septation. Exclusive of Fontan revision or conversion (Re-do Fontan), all remaining Fontan operations had a discharge mortality of 2.3%. Fontan revision or conversion (Re-do Fontan) had a discharge mortality of 12.8%. The STS database is largest CHSDB in North America. The EACTS database is largest CHSDB in Europe. This review of data from EACTS and STS allows for unique documentation of practice patterns and outcomes. From this analysis, it is clear that patients with functionally univentricular hearts present a challenging problem; however, exclusive of Fontan revision or conversion (Re-do Fontan), the Fontan operation has a discharge mortality of 2.3%.

Improving outcomes of the Fontan operation in children with atrial isomerism and heterotaxy syndromes.

PubMed

Azakie, A; Merklinger, S L; Williams, W G; Van Arsdell, G S; Coles, J G; Adatia, I

2001-11-01

The historic outcome of the Fontan procedure in children with single ventricle and heterotaxy syndrome has been poor, and in the current era it has been incompletely described. From January 1993 through April 2000, 30 patients (age range, 5.3 +/- 3.6 years) had total cavopulmonary connection for single ventricle and isomerism and heterotaxy syndrome. Right atrial isomerism and heterotaxy (n = 19) or left atrial isomerism and heterotaxy (n = 11) were associated with a morphologic right ventricle (n = 26), a common atrioventricular valve (n = 25), pulmonary atresia (n = 9) or stenosis (n = 17), anomalous pulmonary venous drainage (partial, n = 7; total, n = 11; obstructed, n = 4), and interrupted inferior vena cava (n = 13). A previous systemic to pulmonary artery shunt had been performed in 21 patients, and 3 patients had previous pulmonary artery banding. The Fontan procedure was staged in all but 3 patients at a median age of 12 months (range, 3 to 114 months). Before the Fontan procedure, atrial arrhythmia was present in 7 patients (23%). An extracardiac conduit was constructed in 22 patients (median diameter, 20 mm; range, 16 to 27 mm), and a lateral tunnel was constructed in 4 patients. Associated procedures included pulmonary artery augmentation (n = 17), repair of anomalous pulmonary venous drainage (n = 7), and repair of a regurgitant atrioventricular valve (n = 2). The mean cardiopulmonary bypass time was 134 +/- 57 minutes. Cardioplegic cardiac arrest was used in 12 patients for a mean duration of 62 +/- 28 minutes. There were four hospital deaths (13%), three that occurred in children having concomitant repair of anomalous pulmonary venous drainage (previously undetected in one). Thirteen children (41%) developed early postoperative atrial arrhythmias, 11 of the 13 children required temporary pacing. There was one late death. Follow-up (3.4 +/- 2.7 years) was available on 24 of 25 survivors. All but 2 patients were in sinus rhythm. Early and midterm outcomes after the Fontan procedure in this patient group improved and may be further ameliorated by detecting and repairing associated obstruction to pulmonary venous flow and performing atrioventricular valvuloplasty before the Fontan procedure.

Mechanical circulatory support of a univentricular Fontan circulation with a continuous axial-flow pump in a piglet model.

PubMed

Wei, Xufeng; Sanchez, Pablo G; Liu, Yang; Li, Tieluo; Watkins, A Claire; Wu, Zhongjun J; Griffith, Bartley P

2015-01-01

Despite the significant contribution of the Fontan procedure to the therapy of complex congenital heart diseases, many patients progress to failure of their Fontan circulation. The use of ventricular assist devices to provide circulatory support to these patients remains challenging. In the current study, a continuous axial-flow pump was used to support a univentricular Fontan circulation. A modified Fontan circulation (atrio-pulmonary connection) was constructed in six Yorkshire piglets (8-14 kg). A Dacron conduit (12 mm) with two branches was constructed to serve as a complete atrio-pulmonary connection without the use of cardiopulmonary bypass. The Impella pump was inserted into the conduit through an additional Polytetrafluoroethylene (PTFE) graft in five animals. Hemodynamic data were collected for 6 hours under the supported Fontan circulation. The control animal died after initiating the Fontan circulation independent of resuscitation. Four pump supported animals remained hemodynamically stable for 6 hours with pump speeds between 18,000 rpm and 22,000 rpm (P1-P3). Oxygen saturation was maintained between 95% and 100%. Normal organ perfusion was illustrated by blood gas analysis and biochemical assays. A continuous axial-flow pump can be used for temporal circulatory support to the failing Fontan circulation as "bridge" to heart transplantation or recovery.

Where Is the “Optimal” Fontan Hemodynamics?

PubMed Central

2017-01-01

Fontan circulation is generally characterized by high central venous pressure, low cardiac output, and slightly low arterial oxygen saturation, and it is quite different from normal biventricular physiology. Therefore, when a patient with congenital heart disease is selected as a candidate for this type of circulation, the ultimate goals of therapy consist of 2 components. One is a smooth adjustment to the new circulation, and the other is long-term circulatory stabilization after adjustment. When either of these goals is not achieved, the patient is categorized as having “failed” Fontan circulation, and the prognosis is dismal. For the first goal of smooth adjustment, a lot of effort has been made to establish criteria for patient selection and intensive management immediately after the Fontan operation. For the second goal of long-term circulatory stabilization, there is limited evidence of successful strategies for long-term hemodynamic stabilization. Furthermore, there have been no data on optimal hemodynamics in Fontan circulation that could be used as a reference for patient management. Although small clinical trials and case reports are available, the results cannot be generalized to the majority of Fontan survivors. We recently reported the clinical and hemodynamic characteristics of early and late failing Fontan survivors and their association with all-cause mortality. This knowledge could provide insight into the complex Fontan pathophysiology and might help establish a management strategy for long-term hemodynamic stabilization. PMID:29035429

Respiratory exacerbation in a young adult with cystic fibrosis and tricuspid atresia.

PubMed

Wood, Jamie; Sawyer, Abbey; Mulrennan, Siobhain; Bullock, Andrew

2018-07-01

Tricuspid atresia (TAt) is a complex congenital heart defect (CHD) characterized by the absence of the tricuspid valve and right ventricular hypoplasia requiring surgery in childhood, the Fontan procedure. We present a case of a 21-year-old male with TAt and cystic fibrosis (CF), who underwent a Fontan procedure in childhood, presenting to an adult CF clinic with severe deterioration in his respiratory status and multi-organ dysfunction associated with CF. This report describes problems associated with the management of a CF respiratory exacerbation and extrapulmonary manifestations of CF in the unique situation of a Fontan circulation, a circulation with absence of a subpulmonary ventricle and pulsatile pulmonary arterial blood flow where maintenance of systemic cardiac output is totally dependent on good respiratory function and low pulmonary artery pressures.

[Comparative results of Fontan surgery in patients with and without hypoplastic left heart syndrome].

PubMed

Becker Rencoret, Pedro; Besa Bandeira, Santiago; Riveros González, Sergio; Frangini Sanhueza, Patricia; Springmüller Pinto, Daniel; González Foretic, Rodrigo; Urcelay Montecinos, Gonzalo

During the last few years, numerous patients with univentricular heart disease have been treated surgically with total cavopulmonary anastomosis according to a staged surgery protocol in our institution. To evaluate the perioperative outcomes and survival of patients with hypoplastic left heart syndrome (HLHS) after the Fontan procedure and compare them with other types of univentricular heart disease. A total of 102 patients underwent a Fontan procedure between April 1996 and March 2014, 25 with HLHS (group I), and 77 patients with other types of univentricular heart disease (group II). Groups survival, demographics, hemodinamic studies, morbimortality, mechanical ventilation, surgical drains, post-operative stay, isotopes score, pacemaker use, and requiriment of Fontan takedown were analyzed. Intraoperative mortality was 4% (n=1) for group I, and 7.8% (n=6) for group II (P=.451). A difference was only found in hospital length of stay (LOS), being 17 days (6-47) for group I and 12 days (5-103) for group II (P=.017). Mean follow-up was 4.24±2.08 years for group I, and 8.7±4.67 for group II. Survival rate at 8 years for both groups was 88%, and 81% at 10 years for group II. The Fontan procedure had similar mortality, but longer LOS, in patients with HLHS compared to those with another types of single ventricle anatomy. Long term survival was comparable between both groups. Copyright © 2016 Sociedad Chilena de Pediatría. Publicado por Elsevier España, S.L.U. All rights reserved.

Management of the failing Fontan.

PubMed

De Rita, Fabrizio; Crossland, David; Griselli, Massimo; Hasan, Asif

2015-01-01

With and increasing number of early survivors after the palliation of the single ventricle physiology there is a burgeoning Fontan population worldwide that will pose unique challenges because of the inevitable sequelae related to the absence of the alleged "needless" sub-pulmonic ventricle. The increasing number and older-age single-ventricle patients highlights the results of successful contemporary surgical palliation in children, leading to the development of an adult single-ventricle population with unpredictable socio-economic and health service impacts. The wide variability in clinical status of patients with Fontan circulation reflects not only the broadened spectrum of morphological substrates involved, but also the evolving surgical techniques during the last four decades. This has come in the wake of a gradual understanding of an incredibly tricky physiology. The magnitude of the disease, the physio-pathological mechanisms, and the therapeutic options to optimize the "failing Fontan" status and to delay the irreversible deterioration of "Fontan failure" condition are discussed in this review. Copyright © 2015 Elsevier Inc. All rights reserved.

Recurrent protein-losing enteropathy and tricuspid valve insufficiency in a transplanted heart: a causal relationship?

PubMed

Aggarwal, Sanjeev; Delius, Ralph E; Walters, Henry L; L'Ecuyer, Thomas J

2012-01-01

This case report describes a toddler who developed a protein-losing enteropathy (PLE) 4 years after orthotopic heart transplantation (OHT). He was born with a hypoplastic left heart syndrome for which he underwent a successful Norwood procedure, a Hemi-Fontan palliation, and a Fontan palliation at 18 months of age. Fifteen months following the Fontan operation, he developed a PLE and Fontan failure requiring OHT. Four years after OHT, he developed a severe tricuspid regurgitation and a PLE. His PLE improved after tricuspid valve replacement. It is now 2 years since his tricuspid valve replacement and he remains clinically free of ascites and peripheral edema with a normal serum albumin level. His prosthetic tricuspid valve is functioning normally. © 2011 Wiley Periodicals, Inc.

The Cost Differential Between Warfarin Versus Aspirin Treatment After a Fontan Procedure.

PubMed

Schilling, Chris; Dalziel, Kim; Iyengar, Ajay J; d'Udekem, Yves

2017-08-01

The use of aspirin versus warfarin for treatment of patients after a Fontan procedure remains contentious. Current preference-based models of treatment across Australia and New Zealand show variation in care that is unlikely to reflect patient differences and/or clinical risk. We combine data from the Australian and New Zealand Fontan Registry and a home INR (International Normalised Ratio) monitoring program (HINRMP) from the Royal Children's Hospital (RCH) Melbourne, to estimate the cost difference for Fontan recipients receiving aspirin versus warfarin for 2015. We adopt a societal perspective to costing which includes cost to the health system (e.g. medical consults, pathology tests) and costs to patients and carers (e.g. travel and time), but excludes costs of adverse events. Costs are presented in Australian 2015 dollars; any costs from previous years have been inflated using appropriate rates from the Australian Bureau of Statistics. We find that warfarin patients face additional costs of $825 per annum, with the majority ($584 or 71%) of those borne by the patient or family. If aspirin is as clinically as effective as warfarin, Fontan recipients could be enjoying far less costly, invasive and time-consuming treatment. While achieving such clinical consensus can be difficult, economics shows us that there are large costs associated with a failure to achieve it. Copyright © 2017. Published by Elsevier B.V.

Intrahepatic cholangiocarcinoma after Fontan procedure in an adult with visceral heterotaxy.

PubMed

Wang, Dehua; Marshall, Darren; Veldtman, Gruschen; Gupta, Anita; Trout, Andrew T; Villafane, Juan; Bove, Kevin

2018-06-01

Hepatic dysfunction, including development of hepatocellular carcinoma and other liver lesions has been increasingly reported following Fontan procedure for congenital heart disease. We report a unique case of intrahepatic cholangiocarcinoma 28 years after a Fontan procedure in a 31year old female with heterotaxy syndrome. The subcapsular mass-forming tumor was composed of poorly differentiated tumor cells arranged in small vague glandular or slit-lumen nests, and focally fused or anastomosing large trabecular patterns within the prominent fibrotic stroma. The tumor cells with immunoreactivity to CK7, CK19, Cam5.2, COX2, EMA, BCL-2, MOC-31 and AE1/AE3, supported a diagnosis of intrahepatic cholangiocarcinoma. Focal atypical ductular proliferation within the background liver may represent a precursor lesion to this tumor. Dysmorphic cilia observed by electron microscopy examination in the background liver may suggest cholangiociliopathy in heterotaxy. MYST3 mutation at Q1388H detected in intrahepatic cholangiocarcinoma is reported for the first time. Copyright © 2018 Elsevier GmbH. All rights reserved.

Improving results of the modified Fontan operation in patients with heterotaxy syndrome.

PubMed

Stamm, Christof; Friehs, Ingeborg; Duebener, Lennart F; Zurakowski, David; Mayer, John E; Jonas, Richard A; del Nido, Pedro J

2002-12-01

Historically the Fontan operation in patients with single ventricle heterotaxy syndrome and atrial isomerism has been associated with high mortality. We studied whether recent modifications of the surgical technique have improved outcome. A retrospective review of 135 patients with heterotaxy syndrome who underwent a Fontan operation between 1981 and 2000 was performed. There were 93 patients with right isomerism and 42 with left isomerism. Anomalies of venous return included 25 patients with extracardiac pulmonary venous connection (19%) and 37 patients with an interrupted inferior vena cava (27%). Thirty-six patients (27%) had at least moderate atrioventricular valve regurgitation. The type of Fontan procedure included 17 patients with an atriopulmonary Fontan connection, 67 with a lateral tunnel modification, 19 with an intraatrial tube graft, 25 with an extracardiac tubegraft, and 7 with an intra-extra atrial tube graft. A fenestration was placed in 93 patients (78%). Early mortality was 19% before 1991, 3% since 1991, and no patient has died early since 1993. Ten-year survivals were 70% for Fontan operations before 1990 and 93% for Fontan operations after 1990. Thirty-two patients (23%) had prolonged pleural effusions. Risk factors for death included anomalous pulmonary venous connection (p = 0.02) and higher preoperative pulmonary vascular resistance (p = 0.002). Sixty-two patients (47%) had some form of early postoperative arrhythmia. At 10 years, freedom from late bradyarrhythmia and late tachyarrhythmia were 78% and 70%, respectively. Preoperative arrhythmias, older age at operation, and anatomic features were each independent predictors of late arrhythmia. The Fontan operation can now be performed in patients with heterotaxy syndrome with excellent survival. However, morbidity in terms of postoperative arrhythmias and prolonged pleural effusions remains significant. Fontan staging, appropriate choice of Fontan modification, aggressive treatment of concomitant malformations, and use of a baffle fenestration contribute to improved outcome.

Arterial stiffness in adult patients after Fontan procedure

PubMed Central

2014-01-01

Objectives Increased arterial stiffness is a risk factor of atherosclerosis and cardio-vascular complications. The aim of the study was to determine whether peripheral vascular function might be an early marker of impaired health status in patients with a single ventricle after Fontan procedure. Methods and results Twenty five consecutive adults (11 women and 14 men) aged 24.7 ± 6.2 years after the Fontan procedure and 25 sex, age and BMI match healthy volunteers underwent physical examination, blood analysis, transthoracic echocardiography and noninvasive assessment of aortic stiffness. Augmented pressure and Augmentation Index (AIx) were both significantly elevated in Fontan when compared to the controls (6,08 ± 0,7 vs. 2,0 ± 3,7; p = 0.002 and 17,01 ± 3,3 vs. 6,05 ± 11; p < 0.001, respectively). There were no differences in pulse wave velocity (PWV), mean blood pressure (BP), brachial pulse pressure (PP), central: systolic BP, diastolic BP and PP. In Fontan group we find negative correlation between PWV and SatO2 (r = −0.68; p = 0.04) and positive correlation with WBC (0.72; p = 0.72; p = 0.013), INR (0.81; p = 0.008), TNFα (r = 0.45; p = 0.04), and postoperative time (r = 0.77; p = 0.02). AIx correlates positively only with age at surgery (r = 0.45; p = 0.04). Bilirubin level correlates positively with brachial PP (r = 0.71; p = 0.02) and central PP (r = 0.68; p = 0.03). The multivariate model showed that SatO2 (β = −0.44, p = 0.04) was the only independent predictor of PWV (R2 = 0.32, p = 0.03). Conclusion Adult Fontan patients have an increased arterial stiffness assessed by a noninvasive technique. Low arterial oxygen saturation postoperative time, age at surgery, white blood cells, TNFα and bilirubin level are associated with arterial stiffening in these patients. The combination of blood parameters of the hepatic function and noninvasive measurements of arterial stiffness could be helpful in comprehensive care of patients with Fontan circulation. PMID:24716671

Recovery of atrial transport function after a maze procedure for atrial fibrillation in conversion of a failing Fontan circulation

PubMed Central

Bogers, A.J.J.C.; Kik, Ch.; de Jong, P.L.; Meijboom, F.J.

2008-01-01

Surgical ablation for atrial arrhythmias at conversion of atriopulmonary or ventriculopulmonary Fontan to a total cavopulmonary connection is feasible with recovery of both sinus rhythm and atrial transport function. Recovery of the patient’s physical condition may take up to a year. (Neth Heart J 2008;16:170-2.18566699) PMID:18566699

Cavopulmonary assist: (Em)powering the univentricular Fontan circulation

PubMed Central

Rodefeld, Mark D; Frankel, Steven H; Giridharan, Guruprasad A

2011-01-01

Since the Fontan/Kreutzer procedure was introduced, evolutionary clinical advances via a staged surgical reconstructive approach have markedly improved outcomes for patients with functional single ventricle. However, significant challenges remain. Early stage mortality risk seems impenetrable. Serious morbidities - construed as immutable consequences of palliation - have hardly been addressed. Late functional status is increasingly linked to pathophysiologic consequences of prior staged procedures. As more single ventricle patients survive into adulthood, Fontan failure is emerging as an intractable problem for which there is no targeted therapy. Incremental solutions to address these ongoing problems have not had a measurable impact. Therefore, a fundamental reconsideration of the overall approach is reasonable and warranted. The ability to provide a modest pressure boost (2-6 mmHg) to existing blood flow at the total cavopulmonary connection can effectively restore more stable biventricular status. This would impact not only treatment of late Fontan failure, but also facilitate early surgical repair. A realistic means to provide such a pressure boost has never been apparent. Recent advances are beginning to unravel the unique challenges which must be addressed to realize this goal, with promise to open single ventricle palliation to new therapeutic vistas. PMID:21444049

Successful diuretics treatment of protein-losing enteropathy in Noonan syndrome.

PubMed

Mizuochi, Tatsuki; Suda, Kenji; Seki, Yoshitaka; Yanagi, Tadahiro; Yoshimoto, Hironaga; Kudo, Yoshiyuki; Iemura, Motofumi; Tanikawa, Ken; Matsuishi, Toyojiro

2015-04-01

There are few reports on successful high-dose spironolactone treatment of refractory protein-losing enteropathy (PLE) caused by Fontan procedure. We report successful diuretics treatment with spironolactone and furosemide at standard dose, of refractory PLE in a patient with Noonan syndrome and repaired congenital heart disease. This is the first successful application of diuretics treatment in a patient with refractory PLE without Fontan procedure. This case illustrates that diuretics treatment can be the first-line treatment of PLE regardless of the causative physiology, and can be effective in refractory PLE with Noonan syndrome. © 2015 Japan Pediatric Society.

Quantification of hepatic flow distribution using particle tracking for patient specific virtual Fontan surgery

NASA Astrophysics Data System (ADS)

Yang, Weiguang; Vignon-Clementel, Irene; Troianowski, Guillaume; Shadden, Shawn; Mohhan Reddy, V.; Feinstein, Jeffrey; Marsden, Alison

2010-11-01

The Fontan surgery is the third and final stage in a palliative series to treat children with single ventricle heart defects. In the extracardiac Fontan procedure, the inferior vena cava (IVC) is connected to the pulmonary arteries via a tube-shaped Gore-tex graft. Clinical observations have shown that the absence of a hepatic factor, carried in the IVC flow, can cause pulmonary arteriovenous malformations. Although it is clear that hepatic flow distribution is an important determinant of Fontan performance, few studies have quantified its relation to Fontan design. In this study, we virtually implanted three types of grafts (T-junction, offset and Y-graft) into 5 patient specific models of the Glenn (stage 2) anatomy. We then performed 3D time-dependent simulations and systematically compared the IVC flow distribution, energy loss, and pressure levels in different surgical designs. A robustness test is performed to evaluate the sensitivity of hepatic distribution to pulmonary flow split. Results show that the Y-graft design effectively improves the IVC flow distribution, compared to traditional designs and that surgical designs could be customized on a patient-by-patient basis.

Outcomes of hospitalization in adults with Fontan palliation: The Mayo Clinic experience.

PubMed

Egbe, Alexander; Khan, Arooj R; Al-Otaibi, Mohamad; Said, Sameh M; Connolly, Heidi M

2018-04-01

The outcomes of hospitalization in the Fontan population have not been specifically studied. The purpose of this study was to describe outcomes of hospitalization (frequency and indications for hospitalization, and in-hospital mortality) in this population and to determine how these outcomes differ from those of other adults with congenital heart disease (CHD). This was a retrospective study of adult Fontan patients hospitalized at Mayo Clinic Rochester in 1990-2015. We selected age- and gender-matched control group of patients with repaired CHD and biventricular circulation hospitalized within the study period. A total of 367 Fontan patients (age 31±7 years and 259 [71%] with atriopulmonary Fontan) had 853 hospital admissions in 4 years (58 hospitalizations per 100 patient-years). The most common indications were arrhythmia (n=188, 22%), heart failure (n=169, 20%), and cardiac surgery (n=133, 16%). Overall in-hospital mortality was 4% (n=38), and the highest in-hospital mortality occurred in patients hospitalized for cardiac surgery (n=15, 11%) and heart failure (n=13, 8%). In comparison to the repaired CHD and biventricular circulation group, the Fontan group had more frequent hospitalizations (22 vs 58 per 100 patient-years, P<.001) and higher overall in-hospital mortality (1% vs 5%, P<.001), mortality after cardiac surgery (2% vs 11%, P=.01), and mortality for heart failure-related hospitalizations (2% vs 8%, P=.04). Adults with Fontan palliation had more frequent hospitalization and in-hospital mortality compared to the rest of the CHD population. Arrhythmia and heart failure were the most common indications for hospitalization. Perhaps optimal management of heart failure and arrhythmia may improve outcomes in this population. Copyright © 2017 Elsevier Inc. All rights reserved.

Functional capacity following univentricular repair--midterm outcome.

PubMed

Sen, Supratim; Bandyopadhyay, Biswajit; Eriksson, Peter; Chattopadhyay, Amitabha

2012-01-01

Previous studies have seldom compared functional capacity in children following Fontan procedure alongside those with Glenn operation as destination therapy. We hypothesized that Fontan circulation enables better midterm submaximal exercise capacity as compared to Glenn physiology and evaluated this using the 6-minute walk test. Fifty-seven children aged 5-18 years with Glenn (44) or Fontan (13) operations were evaluated with standard 6-minute walk protocols. Baseline SpO(2) was significantly lower in Glenn patients younger than 10 years compared to Fontan counterparts and similar in the two groups in older children. Postexercise SpO(2) fell significantly in Glenn patients compared to the Fontan group. There was no statistically significant difference in baseline, postexercise, or postrecovery heart rates (HRs), or 6-minute walk distances in the two groups. Multiple regression analysis revealed lower resting HR, higher resting SpO(2) , and younger age at latest operation to be significant determinants of longer 6-minute walk distance. Multiple regression analysis also established that younger age at operation, higher resting SpO(2) , Fontan operation, lower resting HR, and lower postexercise HR were significant determinants of higher postexercise SpO(2) . Younger age at operation and exercise, lower resting HR and postexercise HR, higher resting SpO(2) and postexercise SpO(2) , and dominant ventricular morphology being left ventricular or indeterminate/mixed had significant association with better 6-minute work on multiple regression analysis. Lower resting HR had linear association with longer 6-minute walk distances in the Glenn patients. Compared to Glenn physiology, Fontan operation did not have better submaximal exercise capacity assessed by walk distance or work on multiple regression analysis. Lower resting HR, higher resting SpO(2) , and younger age at operation were factors uniformly associated with better submaximal exercise capacity. © 2012 Wiley Periodicals, Inc.

Hepatic changes in the failing Fontan circulation

PubMed Central

Kiesewetter, Christoph H; Sheron, Nick; Vettukattill, Joseph J; Hacking, Nigel; Stedman, Brian; Millward‐Sadler, Harry; Haw, Marcus; Cope, Richard; Salmon, Anthony P; Sivaprakasam, Muthukumaran C; Kendall, Tim; Keeton, Barry R; Iredale, John P; Veldtman, Gruschen R

2007-01-01

Background The failing Fontan circulation is associated with hepatic impairment. The nature of this liver injury is poorly defined. Objective To establish the gross and histological liver changes of patients with Fontan circulation relative to clinical, biochemical and haemodynamic findings. Methods Patients were retrospectively assessed for extracardiac Fontan conversion between September 2003 and June 2005, according to an established clinical protocol. Twelve patients, mean age 24.6 (range 15.8–43.4) years were identified. The mean duration since the initial Fontan procedure was 14.1 (range 6.9–26.4) years. Results Zonal enhancement of the liver (4/12) on CT was more common in patients with lower hepatic vein pressures (p = 0.007), and in those with absent cardiac cirrhosis on histological examination (p = 0.033). Gastro‐oesophageal varices (4/12) were more common in patients with higher hepatic vein pressure (21 (6.3) vs 12.2 (2.2) mm Hg, p = 0.013) and associated with more advanced cirrhosis (p = 0.037). The extent of cirrhosis (7/12) was positively correlated with the hepatic vein pressure (r = 0.83, p = 0.003). A significant positive correlation was found between the Fontan duration and the degree of hepatic fibrosis (r = 0.75, p = 0.013), as well as presence of broad scars (r = 0.71, p = 0.021). Protein‐losing enteropathy (5/12) occurred more frequently in patients with longer Fontan duration (11.7 (3.2) vs 17.9 (6.1) years, p = 0.038). Conclusions Liver injury, which can be extensive in this patient group, is related to Fontan duration and hepatic vein pressures. CT scan assists non‐invasive assessment. Cardiac cirrhosis with the risk of developing gastro‐oesophageal varices and regenerative liver nodules, a precursor to hepatocellular carcinoma, is common in this patient group. PMID:17005713

Assessment of Diastolic Function in Single Ventricle Patients Following the Fontan Procedure

PubMed Central

Margossian, Renee; Sleeper, Lynn A.; Pearson, Gail D.; Barker, Piers C.; Mertens, Luc; Quartermain, Michael D.; Su, Jason T.; Shirali, Girish; Chen, Shan; Colan, Steven D.

2016-01-01

Objectives Patients with functional single ventricles (FSV) following the Fontan procedure have abnormal cardiac mechanics. We sought to determine factors that influence diastolic function and to describe associations of diastolic function with current clinical status. Methods Echocardiograms were obtained as part of the Pediatric Heart Network Fontan Cross-Sectional Study. Diastolic function grade (DFG) was assessed as normal (grade 0), impaired relaxation (grade 1), pseudonormalization (grade 2), restrictive (grade 3). Studies were also classified dichotomously (restrictive pattern present or absent). Relationships between DFG and pre-Fontan variables (e.g., ventricular morphology, age at Fontan, history of volume-unloading surgery), and current status (e.g., systolic function, valvar regurgitation, exercise performance) were explored. Results DFG was calculable in 326/546 subjects (60%); mean age = 11.7±3.3 years. Overall, 32% of patients had grade 0, 9% grade 1, 37% grade 2, and 22% grade 3. Although there was no association between ventricular morphology and DFG, there was an association between ventricular morphology and E’, which was lowest in those with right ventricular morphology (p<.001); this association remained significant when using z-scores adjusted for age (p=<.001). DFG was associated with achieving maximal effort on exercise testing (p=.004); the majority (64%) of those not achieving maximal effort had DFG 2 or 3.No additional significant associations of DFG with laboratory or clinical measures were identified. Conclusion Assessment of diastolic function by current algorithms results in a high percentage of patients with abnormal DFG, but we found few clinically or statistically significant associations. This may imply a lack of impact of abnormal diastolic function upon clinical outcome in this cohort, or may indicate that the methodology may not be applicable to pediatric FSV patients. PMID:27624592

[The conversion of a modified Fontan procedure to a total extracardiac cavo-pulmonary conduit. The Medico-Surgical Cardiology Group].

PubMed

Abella, R F; Marianeschi, S M; De la Torre, T; Smedile, G; Masetti, P; Cipriani, A; Magherini, A; Meli, M; Iorio, F S; Marcelletti, C F

1998-06-01

After a modified Fontan procedure with atriopulmonary or atrioventricular conduit, some patients present stress intolerance, supraventricular arrhythmia, recurrent pleuropericardial or ascitic effusions, and protein-losing enteropathy, all of which are signs that the previous procedure has failed. The aim of this study was to evaluate the midterm outcome after surgical therapy for this condition. Between August 1994 and December 1997, nine patients (6 males and 3 females), age 10 to 39 (mean 21.5) years, underwent conversion of previous modified Fontan procedure to total extracardiac cavo-pulmonary connection. Time from the previous procedure was 6 to 18 years (mean 10). Diagnosis was tricuspid atresia with pulmonary stenosis (n = 2), double-inlet left ventricle and concordant ventriculoarterial connection (n = 3), double-inlet left ventricle and discordant ventriculoarterial connection (n = 3), Holmes heart (n = 1). Nine patients presented decreased stress tolerance, seven had arrhythmia, five had pleuropericardial effusions and two had protein-losing enteropathy. In all but one patient, right atrial pressure was higher than 15 mmHg, while in six patients the cardiac index was less than 2 l/min/m2. A polytetrafluoroethylene non-valved conduit was interposed between the inferior vena cava and the right pulmonary artery for conversion in all patients. A bidirectional cavo-pulmonary anastomosis (modified Glenn) was associated in all patients. Evaluation was done by NYHA Class and by an arbitrary score assigned to patients based on 7 parameters. There was no perioperative mortality. All patients were clinically improved at a mean follow-up of 24 months (range: 3 to 46). No patient had effusions, and the arrhythmias disappeared in 4 patients and were controlled by medical therapy in one. The two patients with protein-losing enteropathy improved markedly within 30 days and the score dropped below 10 points. The conversion of the modified Fontan procedure to total extracardiac cavo-pulmonary connection improves clinical condition by decreasing the right atrium-pulmonary gradient and right atrial preload, and by providing a laminar cavo-pulmonary flow without any need for intracardiac anastomoses. This procedure should be undertaken early in this subset of patients, before ventricular failure ensues.

Hemodynamic Effects of Ventricular Assist Device Implantation on Norwood, Glenn, and Fontan Circulation: A Simulation Study.

PubMed

Di Molfetta, Arianna; Amodeo, Antonio; Gagliardi, Maria G; Trivella, Maria G; Fresiello, Libera; Filippelli, Sergio; Toscano, Alessandra; Ferrari, Gianfranco

2016-01-01

The growing population of failing single-ventricle (SV) patients might benefit from ventricular assist device (VAD) support as a bridge to heart transplantation. However, the documented experience is limited to isolated case reports. Considering the complex and different physiopathology of Norwood, Glenn, and Fontan patients and the lack of established experience, the aim of this work is to realize and test a lumped parameter model of the cardiovascular system able to simulate SV hemodynamics and VAD implantation effects to support clinical decision. Hemodynamic and echocardiographic data of 30 SV patients (10 Norwood, 10 Glenn, and 10 Fontan) were retrospectively collected and used to simulate patients' baseline. Then, the effects of VAD implantation were simulated. Simulation results suggest that the implantation of VAD: (i) increases the cardiac output and the mean arterial systemic pressure in all the three palliation conditions (Norwood 77.2 and 19.7%, Glenn 38.6 and 32.2%, and Fontan 17.2 and 14.2%); (ii) decreases the SV external work (Norwood 55%, Glenn 35.6%, and Fontan 41%); (iii) decreases the pressure pulsatility index (Norwood 65.2%, Glenn 81.3%, and Fontan 64.8%); (iv) increases the pulmonary arterial pressure in particular in the Norwood circulation (Norwood 39.7%, Glenn 12.1% and Fontan 3%); and (v) decreases the atrial pressure (Norwood 2%, Glenn 10.6%, and Fontan 8.6%). Finally, the VAD work is lower in the Norwood circulation (30.4 mL·mm Hg) in comparison with Fontan (40.3 mL·mm Hg) and to Glenn (64.5 mL·mm Hg) circulations. The use of VAD in SV physiology could be helpful to bridge patients to heart transplantations by increasing the CO and unloading the SV with a decrement of the atrial pressure and the SV external work. The regulation of the pulmonary flow is challenging because the Pap is increased by the presence of VAD. The hemodynamic changes are different in the different SV palliation step. The use of numerical models could be helpful to support patient and VAD selection to optimize the clinical outcome. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

An international multicenter study comparing arrhythmia prevalence between the intracardiac lateral tunnel and the extracardiac conduit type of Fontan operations.

PubMed

Balaji, Seshadri; Daga, Ankana; Bradley, David J; Etheridge, Susan P; Law, Ian H; Batra, Anjan S; Sanatani, Shubayan; Singh, Anoop K; Gajewski, Kelly K; Tsao, Sabrina; Singh, Harinder R; Tisma-Dupanovic, Svjetlana; Tateno, Shigeru; Takamuro, Motoki; Nakajima, Hiromichi; Roos-Hesselink, Jolien W; Shah, Maully

2014-08-01

The study objective was to determine whether the extracardiac conduit Fontan confers an arrhythmia advantage over the intracardiac lateral tunnel Fontan. This multicenter study of 1271 patients compared bradyarrhythmia (defined as need for pacing) and tachyarrhythmia (defined as needing antiarrhythmic therapy) between 602 patients undergoing the intracardiac Fontan and 669 patients undergoing the extracardiac Fontan. The median age at the time of the Fontan procedure was 2.1 years (interquartile range, 1.6-3.2 years) for the intracardiac group and 3.0 years (interquartile range, 2.4-3.9) for the extracardiac group (P < .0001). The median follow-up was 9.2 years (interquartile range, 5-12.8) for the intracardiac group and 4.7 years (interquartile range, 2.8-7.7) for the extracardiac group (P < .0001). Early postoperative (<30 days) bradyarrhythmia occurred in 24 patients (4%) in the intracardiac group and 73 patients (11%) in the extracardiac group (P < .0001). Early postoperative (<30 days) tachyarrhythmia occurred in 32 patients (5%) in the intracardiac group and 53 patients (8%) in the extracardiac group (P = not significant). Late (>30 days) bradyarrhythmia occurred in 105 patients (18%) in the intracardiac group and 63 patients (9%) in the extracardiac group (P < .0001). Late (>30 days) tachyarrhythmia occurred in 58 patients (10%) in the intracardiac group and 23 patients (3%) in the extracardiac group (P < .0001). By multivariate analysis factoring time since surgery, more patients in the extracardiac group had early bradycardia (odds ratio, 2.9; 95% confidence interval, 1.8-4.6), with no difference in early tachycardia, late bradycardia, or late tachycardia. Overall arrhythmia burden is similar between the 2 groups, but the extracardiac Fontan group had a higher incidence of early bradyarrhythmias. There was no difference in the incidence of late tachyarrhythmias over time between the 2 operations. Therefore, the type of Fontan performed should be based on factors other than an anticipated reduction in arrhythmia burden from the extracardiac conduit. Copyright © 2014 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

Anthropometric Measures After Fontan Procedure: Implications for Suboptimal Functional Outcome

PubMed Central

Cohen, Meryl S.; Zak, Victor; Atz, Andrew M.; Printz, Beth F.; Pinto, Nelangi; Lambert, Linda; Pemberton, Victoria; Li, Jennifer S.; Margossian, Renee; Dunbar-Masterson, Carolyn; McCrindle, Brian W.

2010-01-01

Background Abnormal height and adiposity are observed after the Fontan operation. These abnormalities may be associated with worse functional outcome. Methods We analyzed data from the NHLBI Pediatric Heart Network cross-sectional study of Fontan patients. Groups were defined by height (z-score < −1.5 or ≥ −1.5) and body mass index (BMI z-score ≤ −1.5 or −1.5 to 1.5 or ≥ 1.5). Associations of anthropometric measures with measurements from clinical testing (exercise, echocardiography, MRI) were determined adjusting for demographics, anatomy, and pre-Fontan status. Relationships between anthropometric measures and functional health status (FHS) were assessed using the Child Health Questionnaire. Results Mean age of the cohort (n=544) was 11.9±3.4 years. Lower height-z patients (n=124, 23%) were more likely to have pre-Fontan atrioventricular valve regurgitation (p=0.029), as well as orthopedic and developmental problems (both p<0.001). Lower height-z patients also had lower physical and psychosocial FHS summary scores (both p <0.01). Higher BMI-z patients (n=45, 8%) and lower BMI-z patients (n=53, 10%) did not have worse FHS compared to midrange BMI-z patients (n=446, 82%). However, higher BMI-z patients had higher ventricular mass-to-volume ratio (p =0.03) and lower % predicted maximum work (p=0.004) compared to midrange and lower BMI-z patients. Conclusions Abnormal anthropometry is common in Fontan patients. Shorter stature is associated with poorer FHS and non-cardiac problems. Increased adiposity is associated with more ventricular hypertrophy and poorer exercise performance, which may have significant long-term implications in this at-risk population. PMID:21146663

Reduced pleural drainage, length of stay, and readmissions using a modified Fontan management protocol.

PubMed

Pike, Nancy A; Okuhara, Carol A; Toyama, Joy; Gross, Barbara P; Wells, Winfield J; Starnes, Vaughn A

2015-09-01

Persistent pleural effusions after the Fontan procedure contribute to prolonged hospitalization and increased costs. We report our experience using a modified Wisconsin Fontan protocol to reduce chest tube drainage and hospital length of stay (LOS). Single institutional retrospective chart review of 120 consecutive patients (60 before and 60 after initiation of our protocol) undergoing an extracardiac Fontan procedure from January 2004 to February 2007. Protocol influence was assessed by comparing group differences on duration of pleural drainage, requirement for nothing by mouth/total parenteral nutrition, hospital LOS, readmission for pleural effusion, and total hospital costs. Groups were similar in demographic characteristics, single ventricle morphology, preoperative hemodynamic parameters, and operative and immediate postoperative management. Median duration of pleural drainage and hospital LOS was reduced in the post- versus preprotocol groups: 4 days (interquartile range [IQR], 4-5 days) pre versus 6 days (IQR, 5-10 days) (P < .0001) and 6 days (IQR, 5-9 days) versus 8 days (IQR, 6-13 days) (P = .005), respectively. Pleural drainage lasting >1 week was also less common postprotocol: 23 (38%) before versus 7 (12%) after (P = .001). Fewer postprotocol patients required nothing by mouth/total parenteral nutrition to control effusions: 5 pre versus 0 post (P = .06), and fewer readmissions for effusions (14 before vs 7 after [P = .1]). An average total cost savings of 22% and readmissions savings of 29% resulted in nearly $500,000 in institutional savings over the study period. A modified Fontan protocol resulted in reduced time to chest tube removal, hospital LOS, and chest tube drainage lasting >1 week. There was a strong trend toward avoiding nothing by mouth/total parenteral nutrition to control pleural effusion and lower hospital costs. Copyright © 2015 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

Computational fluid-structure interaction: methods and application to a total cavopulmonary connection

NASA Astrophysics Data System (ADS)

Bazilevs, Yuri; Hsu, M.-C.; Benson, D. J.; Sankaran, S.; Marsden, A. L.

2009-12-01

The Fontan procedure is a surgery that is performed on single-ventricle heart patients, and, due to the wide range of anatomies and variations among patients, lends itself nicely to study by advanced numerical methods. We focus on a patient-specific Fontan configuration, and perform a fully coupled fluid-structure interaction (FSI) analysis of hemodynamics and vessel wall motion. To enable physiologically realistic simulations, a simple approach to constructing a variable-thickness blood vessel wall description is proposed. Rest and exercise conditions are simulated and rigid versus flexible vessel wall simulation results are compared. We conclude that flexible wall modeling plays an important role in predicting quantities of hemodynamic interest in the Fontan connection. To the best of our knowledge, this paper presents the first three-dimensional patient-specific fully coupled FSI analysis of a total cavopulmonary connection that also includes large portions of the pulmonary circulation.

Pulmonary Arteriovenous Malformations After the Superior Cavopulmonary Shunt: Mechanisms and Clinical Implications

PubMed Central

Kavarana, Minoo N.; Jones, Jeffrey A.; Stroud, Robert E.; Bradley, Scott M.; Ikonomidis, John S.; Mukherjee, Rupak

2015-01-01

Children with functional single ventricle heart disease are commonly palliated down a staged clinical pathway toward a Fontan completion procedure (total cavopulmonary connection). The Fontan physiology is fraught with long term complications associated with lower body systemic venous hypertension, eventually resulting in significant morbidity and mortality. The bidirectional Glenn shunt or superior cavopulmonary connection (SCPC) is commonly the transitional stage in single ventricle surgical management and provides excellent palliation. Some studies have demonstrated lower morbidity and mortality with the SCPC when compared with the Fontan. Unfortunately the durability of the SCPC is significantly limited by the development of pulmonary arteriovenous malformations (PAVMs) which have been commonly attributed to the absence of hepatic venous blood flow and the lack of pulsatile flow to the affected lungs. Abnormal angiogenesis has been suggested as a final common pathway to PAVM development. Understanding these fundamental mechanisms through the investigation of angiogenic pathways associated with the pathogenesis of PAVMs would help to develop medical therapies that could prevent or reverse this complication following SCPC. Such therapies could improve the longevity of the SCPC, potentially eliminate or significantly postpone the Fontan completion with its associated complications, and improve long-term survival in children with single ventricle disease. PMID:24758411

Computational Modeling of Pathophysiologic Responses to Exercise in Fontan Patients

PubMed Central

Kung, Ethan; Perry, James C.; Davis, Christopher; Migliavacca, Francesco; Pennati, Giancarlo; Giardini, Alessandro; Hsia, Tain-Yen; Marsden, Alison

2014-01-01

Reduced exercise capacity is nearly universal among Fontan patients. Although many factors have emerged as possible contributors, the degree to which each impacts the overall hemodynamics is largely unknown. Computational modeling provides a means to test hypotheses of causes of exercise intolerance via precisely controlled virtual experiments and measurements. We quantified the physiological impacts of commonly encountered, clinically relevant dysfunctions introduced to the exercising Fontan system via a previously developed lumped-parameter model of Fontan exercise. Elevated pulmonary arterial pressure was observed in all cases of dysfunction, correlated with lowered cardiac output, and often mediated by elevated atrial pressure. Pulmonary vascular resistance was not the most significant factor affecting exercise performance as measured by cardiac output. In the absence of other dysfunctions, atrioventricular valve insufficiency alone had significant physiological impact, especially under exercise demands. The impact of isolated dysfunctions can be linearly summed to approximate the combined impact of several dysfunctions occurring in the same system. A single dominant cause of exercise intolerance was not identified, though several hypothesized dysfunctions each led to variable decreases in performance. Computational predictions of performance improvement associated with various interventions should be weighed against procedural risks and potential complications, contributing to improvements in routine patient management protocol. PMID:25260878

Challenges of univentricular physiology in heterotaxy.

PubMed

Jacobs, Marshall L; Mavroudis, Constantine

2011-04-01

Patients with heterotaxy syndrome exhibit an extensive constellation of congenital cardiac malformations, making these patients a challenging group to manage surgically. Many of these patients' hearts do not lend themselves to separation of the pulmonary and systemic circulations except by some modification of the Fontan procedure. Palliative procedures early in life are directed at creating a satisfactory balance of pulmonary and systemic blood flow and at the same time ensuring unobstructed pulmonary venous return. Early conversion from parallel pulmonary and systemic circulations to superior cavopulmonary connections is important, to reduce volume work of the systemic ventricle. Heterotaxy patients are generally considered a high-risk population with respect to eventual Fontan procedure. It is important to appreciate the unique and variable anatomy of the sinus node and conduction system and the potential for occult pulmonary venous obstruction, atrioventricular valve regurgitation, and recurrent cyanosis, which may be related to the development of pulmonary arteriovenous malformations.

Neurodevelopmental Outcome and Health-related Quality of Life in Children With Single-ventricle Heart Disease Before Fontan Procedure.

PubMed

Reich, Bettina; Heye, Kristina; Tuura, Ruth; Beck, Ingrid; Wetterling, Kristina; Hahn, Andreas; Hofmann, Karoline; Schranz, Dietmar; Akintürk, Hakan; Latal, Beatrice; Knirsch, Walter

2017-12-05

Neurodevelopmental impairment and impaired quality of life constitute a major source of morbidity among children with complex congenital heart disease, in particular for single-ventricle (SV) morphologies. Risk factors and quality of life determining clinical and neurodevelopmental outcome at 2 years of age are examined. In a 2-center cohort study, 48 patients with SV morphology (26 hypoplastic left heart syndrome and 22 other types of univentricular heart defect) have been examined before Fontan procedure between 2010 and 2015. Patients were assessed with the Bayley Scales of Infant and Toddler Development, Third Version (Bayley-III), and the Preschool Children Quality of Life (TAPQOL) questionnaire. A total of 44 patients underwent hybrid procedure (n = 25), Norwood procedure (n = 7), or shunt or banding procedure (n = 12) as first surgery before subsequent bidirectional cavopulmonary anastomosis (n = 48). Median cognitive, language, and motor composite scores on the Bayley-III were 100 (range 65-120), 97 (68-124), and 97 (55-124), respectively. The language composite score was significantly below the norm (P = 0.025). Risk factors for poorer neurodevelopmental outcome were prolonged mechanical ventilation, longer days of hospital stay, and more reinterventions (all P < 0.05). Parents reported a good quality of life for their children. Children undergoing Fontan procedure show a favorable development and good quality of life. More complicated postoperative course and reinterventions constitute risk factors for impaired neurodevelopment. Improving postoperative management and implementing routine follow-up assessments aremeasures to further improve the neurodevelopmental outcome of this high-risk patient population. Copyright © 2017 Elsevier Inc. All rights reserved.

Current Surgical Outcomes of Congenital Heart Surgery for Patients With Down Syndrome in Japan.

PubMed

Hoashi, Takaya; Hirahara, Norimichi; Murakami, Arata; Hirata, Yasutaka; Ichikawa, Hajime; Kobayashi, Junjiro; Takamoto, Shinichi

2018-01-25

Current surgical outcomes of congenital heart surgery for patients with Down syndrome are unclear.Methods and Results:Of 29,087 operations between 2008 and 2012 registered in the Japan Congenital Cardiovascular Surgery Database (JCCVSD), 2,651 were carried out for patients with Down syndrome (9%). Of those, 5 major biventricular repair procedures [ventricular septal defect repair (n=752), atrioventricular septal defect repair (n=452), patent ductus arteriosus closure (n=184), atrial septal defect repair (n=167), tetralogy of Fallot (TOF) repair (n=108)], as well as 2 major single ventricular palliations [bidirectional Glenn (n=21) and Fontan operation (n=25)] were selected and their outcomes were compared. The 90-day and in-hospital mortality rates for all 5 major biventricular repair procedures and bidirectional Glenn were similarly low in patients with Down syndrome compared with patients without Down syndrome. On the other hand, mortality after Fontan operation in patients with Down syndrome was significantly higher than in patients without Down syndrome (42/1,558=2.7% vs. 3/25=12.0%, P=0.005). Although intensive management of pulmonary hypertension is essential, analysis of the JCCVSD revealed favorable early prognostic outcomes after 5 major biventricular procedures and bidirectional Glenn in patients with Down syndrome. Indication of the Fontan operation for patients with Down syndrome should be carefully decided.

LABORATORY MEASURES OF EXERCISE CAPACITY AND VENTRICULAR CHARACTERISTICS AND FUNCTION ARE WEAKLY ASSOCIATED WITH FUNCTIONAL HEALTH STATUS AFTER FONTAN

PubMed Central

McCrindle, Brian W.; Zak, Victor; Sleeper, Lynn A.; Paridon, Stephen M.; Colan, Steven D.; Geva, Tal; Mahony, Lynn; Li, Jennifer S.; Breitbart, Roger E.; Margossian, Renee; Williams, Richard V.; Gersony, Welton M.; Atz, Andrew M.

2009-01-01

Background Patients after Fontan are at risk for suboptimal functional health status, and associations with laboratory measures are important for planning interventions and outcome measures for clinical trials. Methods and Results Parents completed the generic Child Health Questionnaire (CHQ) for 511 Fontan Cross-Sectional Study patients aged 6–18 years (61% male). Associations of CHQ Physical and Psychosocial Functioning Summary Scores (FSS) with standardized measurements from prospective exercise testing, echocardiography, magnetic resonance imaging (MRI), and measurement of brain natriuretic peptide (BNP) were determined by regression analyses. For exercise variables for maximal effort patients only, the final model showed higher Physical FSS was associated only with higher maximum work rate, accounting for 9% of variation in Physical FSS. For echocardiography, lower Tei index (particularly for patients with extracardiac lateral tunnel connections), lower indexed end-systolic volume, and the absence of atrioventricular valve regurgitation for patients having Fontan at age <2 years were associated with higher Physical FSS, accounting for 14% of variation in Physical FSS. For MRI, lower mass to end-diastolic volume ratio, and mid-quartiles of indexed end-systolic volume (non-linear) were associated with higher Physical FSS, accounting for 11% of variation. Lower BNP was significantly but weakly associated with higher Physical FSS (1% of variation). Significant associations for Psychosocial FSS with laboratory measures were fewer and weaker than for Physical FSS. Conclusions In relatively healthy Fontan patients, laboratory measures account for a small proportion of the variation in functional health status and, therefore, may not be optimal surrogate endpoints for trials of therapeutic interventions. PMID:20026781

Use of Ventricular Assist Device in Univentricular Physiology: The Role of Lumped Parameter Models.

PubMed

Di Molfetta, Arianna; Ferrari, Gianfranco; Filippelli, Sergio; Fresiello, Libera; Iacobelli, Roberta; Gagliardi, Maria G; Amodeo, Antonio

2016-05-01

Failing single-ventricle (SV) patients might benefit from ventricular assist devices (VADs) as a bridge to heart transplantation. Considering the complex physiopathology of SV patients and the lack of established experience, the aim of this work was to realize and test a lumped parameter model of the cardiovascular system, able to simulate SV hemodynamics and VAD implantation effects. Data of 30 SV patients (10 Norwood, 10 Glenn, and 10 Fontan) were retrospectively collected and used to simulate patients' baseline. Then, the effects of VAD implantation were simulated. Additionally, both the effects of ventricular assistance and cavopulmonary assistance were simulated in different pathologic conditions on Fontan patients, including systolic dysfunction, diastolic dysfunction, and pulmonary vascular resistance increment. The model can reproduce patients' baseline well. Simulation results suggest that the implantation of VAD: (i) increases the cardiac output (CO) in all the three palliation conditions (Norwood 77.2%, Glenn 38.6%, and Fontan 17.2%); (ii) decreases the SV external work (SVEW) (Norwood 55%, Glenn 35.6%, and Fontan 41%); (iii) increases the mean pulmonary arterial pressure (Pap) (Norwood 39.7%, Glenn 12.1%, and Fontan 3%). In Fontan circulation, with systolic dysfunction, the left VAD (LVAD) increases CO (35%), while the right VAD (RVAD) determines a decrement of inferior vena cava pressure (Pvci) (39%) with 34% increment of CO. With diastolic dysfunction, the LVAD increases CO (42%) and the RVAD decreases the Pvci. With pulmonary vascular resistance increment, the RVAD allows the highest CO (50%) increment with the highest decrement of Pvci (53%). The single ventricular external work (SVEW) increases (decreases) increasing the VAD speed in cavopulmonary (ventricular) assistance. Numeric models could be helpful in this challenging and innovative field to support patients and VAD selection to optimize the clinical outcome and personalize the therapy. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Treatment of Children with Protein – Losing Enteropathy After Fontan and Other Complex Congenital Heart Disease Procedures in Condition with Limited Human and Technical Resources

PubMed Central

Bejiqi, Ramush; Retkoceri, Ragip; Zeka, Naim; Bejiqi, Hana; Vuqiterna, Armend; Maloku, Arlinda

2014-01-01

Background Protein-losing enteropathy (PLE) is a disorder characterized by abnormal and often profound enteric protein loss. It’s relatively uncommon complication of Fontan and other complex congenital heart disease (CCHD) procedures. Because of the complexity and rarity of this disease process, the pathogenesis and pathophysiology of protein-losing enteropathy remain poorly understood, and attempts at treatment seldom yield long-term success. Aim of presentation is to describe single centre experience in diagnosis, evaluation, management and treatment of children with protein-losing enteropathy after Fontan and other CCHD procedures in the current era and in centre with limited human and technical resources, follows with a comprehensive review of protein-losing enteropathy publications, and concludes with suggestions for prevention and treatment. Material and methodology Retrospectively we analyzed patients with CCHD and protein-losing enteropathy in our institution, starting from January 2000 to December 2012. The including criteria were age between two and 17 years, to have a complex congenital heart disease and available complete documentation of cardiac surgery under cardiopulmonary bypass. Results Of all patients we evaluated 18 cases with protein-losing enteropathy, aged 6 to 19 years (mean 14±9); there were three children who had undergone screening procedure for D-transposition, one Tetralogy of Fallot, and remaining 14 patients had undergone Fontan procedures; (anatomic diagnosis are: six with tricuspid atresia, seven with d-transposition, double outlet right ventricle and pulmonary atresia and two with hypoplastic left heart syndrome). The diagnosis of protein-losing enteropathy was made at median age of 5.6 years, ranging from 13 months to 15 years. Diagnosis was made using alpha 1-antitrypsin as a gold marker in stool. By physical examination in 14 patients edema was found, in three ascites, and six patients had pleural effusion. Laboratory findings at the time of diagnosis are: abnormal enteric protein loss was documented at the time of diagnosis in all 18 patients. At the time of diagnosis all patients receiving some form of anticoagulation, 17 patients receiving other medication: 17 – diuretics and ACE inhibitors, 12 digoxin, 9 antiarrhytmics. Cross-sectional echocardiography was performed for all patients and different abnormalities were registered. In 14 patients also magnetic resonance was performed. Therapeutic approach was based on the non-specific medication (diet, diuretics, digoxin, ACE inhibitors, and anticoagulants), heparin and corticosteroids therapy. Long-term response to this type of therapy was registered in three patients. Nine patients underwent treatment with heparin and corticosteroids and no one experienced long term benefit. Despite of needs for catheter therapy or surgical intervention in our study, in the absent of technical and human resources now any one had underwent those procedures. Six patients has been transferred abroad and in five of them surgical intervention was perform. Conclusion Protein-losing enteropathy remains a devastating complication of Fontan procedure and despite in advantages in surgical and medical therapy there is no evidence that protein-losing enteropathy is less common in the current area. PMID:24757400

Optimization and surgical design for applications in pediatric cardiology

NASA Astrophysics Data System (ADS)

Marsden, Alison; Bernstein, Adam; Taylor, Charles; Feinstein, Jeffrey

2007-11-01

The coupling of shape optimization to cardiovascular blood flow simulations has potential to improve the design of current surgeries and to eventually allow for optimization of surgical designs for individual patients. This is particularly true in pediatric cardiology, where geometries vary dramatically between patients, and unusual geometries can lead to unfavorable hemodynamic conditions. Interfacing shape optimization to three-dimensional, time-dependent fluid mechanics problems is particularly challenging because of the large computational cost and the difficulty in computing objective function gradients. In this work a derivative-free optimization algorithm is coupled to a three-dimensional Navier-Stokes solver that has been tailored for cardiovascular applications. The optimization code employs mesh adaptive direct search in conjunction with a Kriging surrogate. This framework is successfully demonstrated on several geometries representative of cardiovascular surgical applications. We will discuss issues of cost function choice for surgical applications, including energy loss and wall shear stress distribution. In particular, we will discuss the creation of new designs for the Fontan procedure, a surgery done in pediatric cardiology to treat single ventricle heart defects.

Comparison of risk factors and outcomes for pediatric patients listed for heart transplantation after bidirectional Glenn and after Fontan: an analysis from the Pediatric Heart Transplant Study.

PubMed

Kovach, Joshua R; Naftel, David C; Pearce, F Bennett; Tresler, Margaret A; Edens, R Erik; Shuhaiber, Jeffrey H; Blume, Elizabeth D; Fynn-Thompson, Francis; Kirklin, James K; Zangwill, Steven D

2012-02-01

Patients listed for transplant after the bidirectional Glenn (BDG) may have better outcomes than patients listed after Fontan. This study examined and compared outcomes after listing for BDG and Fontan patients. All patients listed for transplant after the BDG in the Pediatric Heart Transplant Study between January 1993 and December 2008 were evaluated. Comparisons were made with Fontan patients and with a matched cohort of congenital heart disease patients. Competing outcomes analysis and actuarial survival were evaluated for the study populations, including an examination of various risk factors. Competing outcomes analysis for BDG and Fontan patients after listing were similar. There was no difference in actuarial survival after listing or transplant among the 3 cohorts. Mechanical ventilation, United Network of Organ Sharing status, and age were risk factors for death after listing in BDG and Fontan patients, but ventilation at the time of transplant was significant only for the Fontan patients. Mortality was increased in Fontan patients listed < 6 months after surgery compared with patients listed > 6 months after surgery, but no difference was observed in BDG patients. There was a trend toward improved survival after listing for both populations across 3 eras of the study, but this did not reach statistical significance. Outcomes after listing for BDG and Fontan patients are similar. Mechanical ventilation at the time of transplant remains a significant risk factor for death in the Fontan population, as does listing for transplant soon after the Fontan, suggesting that some patients may benefit from transplant instead of Fontan completion. Copyright © 2012 International Society for Heart and Lung Transplantation. Published by Elsevier Inc. All rights reserved.

Liver cirrhosis in Fontan patients does not affect 1-year post-heart transplant mortality or markers of liver function.

PubMed

Simpson, Kathleen E; Esmaeeli, Amir; Khanna, Geetika; White, Francis; Turnmelle, Yumirle; Eghtesady, Pirooz; Boston, Umar; Canter, Charles E

2014-02-01

Liver cirrhosis is recognized with long-term follow-up of patients after the Fontan procedure. The effect of liver cirrhosis on the use of heart transplant (HT) and on post-HT outcomes is unknown. We reviewed Fontan patients evaluated for HT from 2004 to 2012 with hepatic computed tomography (CT) imaging, classified as normal, non-cirrhotic changes, or cirrhosis. The primary outcome was 1-year all-cause mortality, and the secondary outcome was differences in serial post-HT liver evaluation. CT imaging in 32 Fontan patients evaluated for HT revealed 20 (63%) with evidence of liver disease, including 13 (41%) with cirrhosis. Twenty underwent HT, including 5 non-cirrhotic and 7 cirrhosis patients. Characteristics at listing between normal or non-cirrhotic (n = 13) and cirrhosis (n = 7) groups were similar, except cirrhosis patients were older (median 17.6 vs 9.6 years, p = 0.002) and further from Fontan (median 180 vs 50 months, p < 0.05). Serial liver evaluation was similar, including aspartate aminotransferase, alanine aminotransferase, bilirubin, albumin, and tacrolimus dose at 1, 3, 6, 9, and 12 months. Overall patient survival was 80% at 1 year, with no difference between cirrhosis and non-cirrhosis patients (86% vs 77%, p = 0.681). Liver biopsies were performed in 7 patients before HT, and all specimens showed architectural changes with bridging fibrosis. Most patients evaluated for HT had abnormal liver findings by CT, with cirrhosis in 41%. One-year mortality and serial liver evaluation were similar between groups after HT. Liver cirrhosis identified by CT imaging may not be an absolute contraindication to HT alone in this population. © 2014 International Society for Heart and Lung Transplantation Published by International Society for the Heart and Lung Transplantation All rights reserved.

Catheter interventions in the staged management of hypoplastic left heart syndrome.

PubMed

Reinhardt, Zdenka; De Giovanni, Joseph; Stickley, John; Bhole, Vinay K; Anderson, Benjamin; Murtuza, Bari; Mehta, Chetan; Miller, Paul; Dhillon, Rami; Stumper, Oliver

2014-04-01

To analyse the current practice and contribution of catheter interventions in the staged management of patients with hypoplastic left heart syndrome. This study is a retrospective case note review of 527 patients undergoing staged Norwood/Fontan palliation at a single centre between 1993 and 2010. Indications and type of catheter interventions were reviewed over a median follow-up period of 7.5 years. A staged Norwood/Fontan palliation for hypoplastic left heart syndrome was performed in 527 patients. The 30-day survival rate after individual stages was 76.5% at Stage I, 96.3% at Stage II, and 99.4% at Stage III. A total of 348 interventions were performed in 189 out of 527 patients. Freedom from catheter intervention in survivors was 58.2% before Stage II and 46.7% before Stage III. Kaplan-Meier freedom from intervention post Fontan completion was 55% at 10.8 years of follow-up. Post-stage I interventions were mostly directed to relieve aortic arch obstruction--84 balloon angioplasties--and augment pulmonary blood flow--15 right ventricle-to-pulmonary conduit interventions; post-Stage II interventions centred on augmenting size of the left pulmonary artery--73 procedures and abolishing systemic venous collaterals--32 procedures. After Stage III, the focus was on manipulating the size of the fenestration--42 interventions--and the left pulmonary artery -31 procedures. Interventional cardiac catheterisation constitutes an integral part in the staged palliative management of patients with hypoplastic left heart syndrome. Over one-third (37%) of patients undergoing staged palliation required catheter intervention over the follow-up period.

Pulmonary vasodilator therapy in the failing Fontan circulation: rationale and efficacy.

PubMed

Snarr, Brian S; Paridon, Stephen M; Rychik, Jack; Goldberg, David J

2015-12-01

The Fontan operation is the final step of palliation for patients with a functionally single ventricle. Since its introduction in the 1970s, the Fontan surgery has become part of a successful surgical strategy that has improved single ventricle mortality. In recent years, we have become more aware of the limitations and long-term consequences of the Fontan physiology. Pulmonary vascular resistance plays an important role in total cavopulmonary circulation, and has been identified as a potential therapeutic target to mitigate Fontan sequelae. In this review, we will discuss the results of different pulmonary vasodilator trials and the use of pulmonary vasodilators as a treatment strategy for Fontan patients.

Cavopulmonary support with a microaxial pump for the failing Fontan physiology.

PubMed

Zhu, Jiaquan; Kato, Hideyuki; Fu, Yaqin Y; Zhao, Lisa; Foreman, Celeste; Davey, Lisa; Weisel, Richard D; Van Arsdell, Glen S; Honjo, Osami

2015-01-01

The number of patients with the failing Fontan physiology is increasing. We tested a novel in situ microaxial pump (Impella) to support the failing atrio-pulmonary Fontan circulation in an acute pig model. A Fontan model was established in eight juvenile pigs by connecting the right atrium to the main pulmonary artery after tricuspid valve destruction. The Impella pump was inserted retrograde from the distal main pulmonary artery into the right atrium. Hemodynamics, blood gas, and echocardiographic data were compared among baseline, pure Fontan physiology (10 minutes), and mechanically assisted Fontan physiology (up to 12 hours). The Impella system generated a blood flow of 75-85 ml/kg/minute in six animals, and 55-65 ml/kg/minute in two animals. The mechanically assisted Fontan attained a significantly higher mean blood pressure (39.6 ± 7 vs. 24.7 ± 3.3 mm Hg, p < 0.01), lower central venous pressure (5 ± 2.4 vs. 12.8 ± 1.7 mm Hg, p < 0.01), and higher mixed venous saturation (60.4 ± 10.8 vs. 23.4 ± 8.4 mm Hg, p < 0.01) compared with pure Fontan physiology. Cardiac output and stroke volume were similar during baseline and mechanically assisted Fontan (p = not significant). This acute pig study demonstrated the feasibility of mechanical circulatory support in the failing Fontan physiology. The in situ microaxial pump maintained cardiac output while increasing blood pressure and reducing venous pressure.

Experimental investigation of the effects of inserting a bovine venous valve in the inferior vena cava of Fontan circulation

NASA Astrophysics Data System (ADS)

Santhanakrishnan, Arvind; Johnson, Jacob; Kotz, Monica; Tang, Elaine; Khiabani, Reza; Yoganathan, Ajit; Maher, Kevin

2012-11-01

The Fontan procedure is a palliative surgery performed on patients with single ventricle (SV) congenital heart defects. The SV is used for systemic circulation and the venous return from the inferior vena cava (IVC) and superior vena cava (SVC) is routed to the pulmonary arteries (PA), resulting in a total cavopulmonary connection (TCPC). Hepatic venous hypertension is commonly manifested in the Fontan circulation, leading to long-term complications including liver congestion and cirrhosis. Respiratory intrathoracic pressure changes affect the venous return from the IVC to the PA. Using a physical model of an idealized TCPC, we examine placement of a unidirectional bovine venous valve within the IVC as a method of alleviating hepatic venous hypertension. A piston pump is used to provide pulsatility in the internal flow through the TCPC, while intrathoracic pressure fluctuations are imposed on the external walls of the model using a pair of linear actuators. When implanted in the extrathoracic position, the hepatic venous pressure is lowered from baseline condition. The effects of changing caval flow distribution and intrathoracic pressure on TCPC hemodynamics will be examined.

Modification of hemi-Fontan operation for patients with functional single ventricle and anomalous pulmonary venous connection to the superior vena cava: mid-term results†

PubMed Central

Ito, Hiroki; Murata, Masaya; Ide, Yujiro; Sugano, Mikio; Kanno, Kazuyoshi; Imai, Kenta; Ishido, Motonori; Fukuba, Ryohei; Sakamoto, Kisaburo

2016-01-01

OBJECTIVES Fontan candidates with mixed totally anomalous pulmonary venous connection often have postoperative pulmonary venous obstruction after cavopulmonary anastomosis. Because some pulmonary venous obstructions have no intimal hypertrophy at reoperation, we considered such pulmonary venous obstructions to be caused by 3D deformities arising from dissection or mobilization of the vessels, and hypothesized that keeping the pulmonary venous branches in a natural position could avoid such obstruction. Here, we evaluated a modified hemi-Fontan strategy consisting of minimal dissection with no division of vessels and patch separation between systemic and pulmonary venous flow. METHODS We retrospectively reviewed clinical records of infants with a functional single ventricle and supracardiac anomalous pulmonary venous connection who had undergone this procedure between 2002 and 2012. RESULTS Nine infants underwent this procedure (median age, 5.6 months; range 3.2–30), all with right atrial isomerism and several pulmonary venous branches directly and separately connecting to the superior vena cava. In 5 patients, all pulmonary veins drained into the superior vena cava; in 1, the right pulmonary veins drained into the superior vena cava and in 3, a pulmonary venous branch drained into the superior vena cava. The median follow-up was 6.9 years (0.8–13 years). Three patients underwent reoperation for postoperative pulmonary venous obstruction caused by intimal hypertrophy; however, we confirmed no pulmonary venous obstruction caused by 3D deformities on the pulmonary venous branches connecting separately to the superior vena cava. Although 2 patients were effectively relieved from pulmonary venous obstruction, 1 died due to recurrent pulmonary venous obstruction. There was no late death and no sinus-node dysfunction. Eight patients underwent successful Fontan operation and catheterization. The median interval from the Fontan operation to the latest catheterization was 3.7 years (0.9–3.7 years). The median arterial oxygen saturation was 94% (91–97%) and the central venous pressure was 12 mmHg (8–14 mmHg); no deficiency of pulmonary arteries and veins was noted. CONCLUSIONS For patients with functional single ventricle and anomalous pulmonary venous connections to the superior vena cava, our novel strategy of second-stage palliation could avoid postoperative pulmonary venous obstruction caused by 3D deformities, but may not eliminate pulmonary venous obstruction caused by intimal hypertrophy. PMID:26860898

Management of older single functioning ventricles with outlet obstruction due to a restricted "VSD" in double inlet left ventricle and in complex double outlet right ventricle.

PubMed

Lacour-Gayet, Francois

2009-01-01

The occurrence of a restriction of the bulbo-ventricular foramen (BVF) in older patient with double inlet left ventricle (DILV) or tricuspid atresia (TA) with ventriculo-arterial discordance is a well-known condition. Today, the surgical management is to perform a Damus-type operation at the time of the bi-directional Glenn or at the Fontan completion. The ventricular septal defect (VSD) enlargement, associated with muscular resection and a patch enlargement of the subaortic accessory ventricular chamber, is rarely performed but remains indicated in cases with pulmonary valve atresia or regurgitation. This condition is essentially prevented by doing an early Norwood-type operation in the presence of DILV/TA with transposition of the great arteries associated with an aortic arch obstruction. The palliative switch operation is an option that was abandoned because of poor control of the pulmonary blood flow. It is only in cases of large unobstructed BVF that pulmonary artery banding could be undertaken in neonates, followed by close echocardiographic follow-up. The occurrence of a restriction or a closure of the VSD in complex DORV following a Fontan operation is a dramatic event and is quite "new business." It has been recently recognized that the VSD becomes restricted in a number of patients with DORV-nc-VSD treated with a Fontan palliation. This new condition is not surprising knowing that 75% of the VSDs must be enlarged preventively in DORV-nc-VSD repair. In the setting of a Fontan circulation, the supra-systemic left ventricle has severe consequences the right ventricle performance. Attempts at surgical VSD enlargement or catheter-based procedures have resulted in almost constant recurrence. This recently reported complication is in favor of also performing a VSD enlargement at the time of the Fontan completion in complex DORV. It justifies the biventricular repair in complex DORV with two viable ventricles.

Does superior caval vein pressure impact head growth in Fontan circulation?

PubMed

Trachsel, Tina; Balmer, Christian; Wåhlander, Håkan; Weber, Roland; Dave, Hitendu; Poretti, Andrea; Kretschmar, Oliver; Cavigelli-Brunner, Anna

2016-10-01

Patients with bidirectional cavopulmonary anastomosis have unphysiologically high superior caval vein pressure as it equals pulmonary artery pressure. Elevated superior caval vein pressure may cause communicating hydrocephalus and macrocephaly. This study analysed whether there exists an association between head circumference and superior caval vein pressure in patients with single ventricle physiology. We carried out a retrospective analysis of infants undergoing Fontan completion at our institution from 2007 to 2013. Superior caval vein pressures were measured during routine catheterisation before bidirectional cavopulmonary anastomosis and Fontan completion as well as head circumference, adjusted to longitudinal age-dependent percentiles. We included 74 infants in our study. Median ages at bidirectional cavopulmonary anastomosis and Fontan were 4.8 (1.6-12) and 27.9 (7-40.6) months, respectively. Head circumference showed significant growth from bidirectional cavopulmonary anastomosis until Fontan completion (7th (0-100th) versus 20th (0-100th) percentile). There was no correlation between superior caval vein pressure and head circumference before Fontan (R2=0.001). Children with lower differences in superior caval vein pressures between pre-bidirectional cavopulmonary anastomosis and pre-Fontan catheterisations showed increased growth of head circumference (R2=0.19). Patients with moderately elevated superior caval vein pressure associated with single ventricle physiology did not have a tendency to develop macrocephaly. There is no correlation between superior caval vein pressure before Fontan and head circumference, but between bidirectional cavopulmonary anastomosis and Fontan head circumference increases significantly. This may be explained by catch-up growth of head circumference in patients with more favourable haemodynamics and concomitant venous pressures in the lower range. Further studies with focus on high superior caval vein pressures are needed to exclude or prove a correlation.

Noninvasive assessment of vascular function and hydraulic power and efficiency in pediatric Fontan patients.

PubMed

Myers, Kimberley A; Leung, Mande T; Terri Potts, M; Potts, James E; Sandor, George G S

2013-10-01

Invasive studies have shown that children with Fontan palliation have abnormal arterial stiffness, impedance, and hydraulic power and efficiency. The aim of this study was to assess these indexes noninvasively in a cohort of children with Fontan circulation using Doppler echocardiography and compare their results with those of healthy peers. This was a case-control study of 22 Fontan patients and 31 healthy control children. Using standard two-dimensional, M-mode, and Doppler echocardiographic imaging and carotid artery applanation tonometry, aortic flows, dimensions, and pulse-wave velocity were measured, and vascular impedance and arterial stiffness were calculated. Hydraulic power and efficiency were calculated from standard fluid dynamics formulae. The median age was similar between groups. Stroke volume index (39 vs 39 mL/min/m(2)) and cardiac index (2.6 vs 2.5 L/min/m(2)) were similar. Aortic cross-sectional area (3.3 vs 2.8 cm(2)), peak aortic flow (302 vs 261 cm(3)/sec), and myocardial performance index (0.47 vs 0.25) were higher and ejection fraction (50% vs 66%) was lower in Fontan patients. Input impedance (61 vs 83 dyne · sec/cm(5)/m(2)) was lower in Fontan patients. Pulse-wave velocity (488 vs 364 cm/sec), elastic pressure-strain modulus (305 vs 263 torr), and stiffness index (4.15 vs 3.04) were higher in Fontan patients. Total arterial compliance (1.29 vs 1.32 mL/torr/m(2)) and mean power (606 vs 527 mW/m(2)) were similar and total hydraulic power (716 vs 627 mW/m(2)) was higher in Fontan patients. Efficiency and the power cost per unit of forward flow were similar. Despite stiffer aortas, Fontan patients generate more hydraulic power associated with decreased ventricular function to achieve a similar hydraulic efficiency. In Fontan patients, therapy that is given to improve ventricular function may need to target vascular stiffness as well. This technique may be used to monitor the efficacy of therapeutic interventions. Copyright © 2013 American Society of Echocardiography. Published by Mosby, Inc. All rights reserved.

Fontan-associated liver disease: Spectrum of US findings.

PubMed

Bae, Jung Min; Jeon, Tae Yeon; Kim, Jung Sun; Kim, Seokhwi; Hwang, Sook Min; Yoo, So-Young; Kim, Ji Hye

2016-04-01

To describe ultrasonography (US) findings of Fontan-associated liver disease (FALD) and to determine whether screening US examinations can identify FALD before biochemical hepatic dysfunction. This retrospective study included 55 patients who underwent Fontan procedure over a 20-year period. Hepatobiliary US findings (n=55), CT or MRI findings (n=19), biochemical hepatic function tests (n=49), and histopathological results (n=4) were analyzed. Images were reviewed focusing on the hepatic parenchymal changes, presence of focal lesions, and signs of portal hypertension. Hepatic parenchymal changes (either heterogeneous echotexture or surface nodularity) evident on US were present in 67% (37/55) and showed positive correlation with the Fontan duration. Hyper-echoic lesions were noted in 35% (19/55) and showed a predilection for multiplicity, small size, right lobe location, and irregular margin on high-frequency transducer. These lesions were not demonstrated by CT or MRI or by low-frequency transducer. Histopathological results of targeted biopsy for hyper-echoic lesions revealed lesser degree of patchy sinusoidal and portal fibrosis than seen in cases with surface nodularity. Abnormal parenchymal enhancement was commonly seen with CT or MRI in 63% (12/19) and hypervascular nodules in 21% (4/19). Most patients (82%, 40/49) showed normal biochemical hepatic function tests, despite the presence of hepatic parenchymal changes on imaging. The common US findings of FALD included heterogeneous parenchymal echotexture, surface nodularity, and hyper-echoic lesions. We suggest that hyper-echoic lesions without surface nodularity detected by high-frequency transducer may represent the early stage of fibrosis. US examination may be useful for identifying the progression of FALD before biochemical hepatic dysfunction. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

AngioVac Aspiration for Paradoxical Emboli Protection through a Fenestrated Fontan During Central Venous Thrombus Manipulation

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

Al-Hakim, Ramsey, E-mail: ralhakim@mednet.ucla.edu; Patel, Komal, E-mail: kdpatel@mednet.ucla.edu; Moriarty, John M., E-mail: jmoriarty@mednet.ucla.edu

2015-06-15

This case reports describes a 39-year-old female with a history of surgically repaired hypoplastic left heart syndrome who presented with a left peripherally inserted central catheter (PICC) with associated large volume subclavian and brachiocephalic vein thrombus. Due to the presence of a right-to-left shunt via a fenestrated Fontan, there was clinical concern for a paradoxical embolism during removal of the PICC. The AngioVac aspiration system was successfully utilized to aspirate thromboemboli from the level of the proximal Glenn shunt during manipulation and removal of the PICC. This is the first reported case to demonstrate the safe and effective use ofmore » the AngioVac aspiration system for protection of paradoxical emboli through a cardiac right-to-left shunt during a procedure at high risk for thromboembolism.« less

AngioVac Aspiration for Paradoxical Emboli Protection through a Fenestrated Fontan During Central Venous Thrombus Manipulation.

PubMed

Al-Hakim, Ramsey; Patel, Komal; Moriarty, John M

2015-06-01

This case reports describes a 39-year-old female with a history of surgically repaired hypoplastic left heart syndrome who presented with a left peripherally inserted central catheter (PICC) with associated large volume subclavian and brachiocephalic vein thrombus. Due to the presence of a right-to-left shunt via a fenestrated Fontan, there was clinical concern for a paradoxical embolism during removal of the PICC. The AngioVac aspiration system was successfully utilized to aspirate thromboemboli from the level of the proximal Glenn shunt during manipulation and removal of the PICC. This is the first reported case to demonstrate the safe and effective use of the AngioVac aspiration system for protection of paradoxical emboli through a cardiac right-to-left shunt during a procedure at high risk for thromboembolism.

Structural cerebral abnormalities and neurodevelopmental status in single ventricle congenital heart disease before Fontan procedure.

PubMed

Knirsch, Walter; Mayer, Kristina Nadine; Scheer, Ianina; Tuura, Ruth; Schranz, Dietmar; Hahn, Andreas; Wetterling, Kristina; Beck, Ingrid; Latal, Beatrice; Reich, Bettina

2017-04-01

Neonates with single ventricle congenital heart disease are at risk for structural cerebral abnormalities. Little is known about the further evolution of cerebral abnormalities until Fontan procedure. Between August 2012 and July 2015, we conducted a prospective cross-sectional two centre study using cerebral magnetic resonance imaging (MRI) and neuro-developmental outcome assessed by the Bayley-III. Forty-seven children (31 male) were evaluated at a mean age of 25.9 ± 3.4 months with hypoplastic left heart syndrome (25) or other single ventricle (22). Cerebral MRI was abnormal in 17 patients (36.2%) including liquor space enlargements (10), small grey (9) and minimal white (5) matter injuries. Eight of 17 individuals had combined lesions. Median (range) cognitive composite score (CCS) (100, 65-120) and motor composite score (MCS) (97, 55-124) were comparable to the reference data, while language composite score (LCS) (97, 68-124) was significantly lower ( P  = 0.040). Liquor space enlargement was associated with poorer performance on all Bayley-III subscores (CCS: P  = 0.02; LCS: P  = 0.002; MCS: P  = 0.013). The number of re-operations [odds ratio (OR) 2.2, 95% confidence interval (CI) 1.1-4.3] ( P  = 0.03) and re-interventions (OR 2.1, 95% CI 1.1-3.8) ( P  = 0.03) was associated with a higher rate of overall MRI abnormalities. Cerebral MRI abnormalities occur in more than one third of children with single ventricle, while the neuro-developmental status is less severely affected before Fontan procedure. Liquor space enlargement is the predominant MRI finding associated with poorer neuro-developmental status, warranting further studies to determine aetiology and further evolution until school-age. © The Author 2016. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Serial cardiac MRIs in adult Fontan patients detect progressive hepatic enlargement and congestion.

PubMed

Lewis, Matthew J; Hecht, Elizabeth; Ginns, Jonathan; Benton, Joshua; Prince, Martin; Rosenbaum, Marlon S

2017-03-01

The progression of hepatic disease in adult Fontan patients is not well understood. They reviewed the experience with serial cardiac MRIs (CMR) in adult Fontan patients to determine if hepatic anatomic markers of prolonged Fontan exposure were present and if clinical predictors of progressive hepatic congestion could be identified. A retrospective cohort study of all adult Fontan patients who had undergone at least two CMRs was performed. Hepatic dimensions, inferior vena cava (IVC) size, right hepatic vein (RHV) size and spleen diameter were determined from images acquired at the time of clinically guided CMR. Two radiologists with expertise in hepatic imaging graded congestion and liver size independently using post-gadolinium contrast sequences. Twenty-seven patients met inclusion criteria. Over a mean time of 5.1 years between CMRs, there was a significant increase in mean lateral-medial hepatic dimension (P = .005), mean RHV diameter (P = .004), and mean splenic diameter (P = .001). Serial post-gadolinium imaging was available in 25/27 (93%) patients of which 15/27 (55%) showed evidence of progressive hepatic congestion across serial studies. Progressive hepatic congestion was associated with single ventricle ejection fraction (SVEF) less than 50% (P = .008), and larger indexed end-diastolic (EDVI) and end-systolic volume (ESVI). RHV diameter was the only anatomic variable significantly correlated with time from Fontan completion (P = .004). Serial CMRs detected progressive liver and hepatic vein enlargement in our cohort of adult Fontan patients over a mean time of 5.2 years. Progressive hepatic congestion occurs in a significant number of adult Fontan patients and may be associated with ventricular enlargement and decreased ventricular function by CMR. © 2016 Wiley Periodicals, Inc.

Relationship Between Habitual Exercise and Performance on Cardiopulmonary Exercise Testing Differs Between Children With Single and Biventricular Circulations.

PubMed

O'Byrne, Michael L; Desai, Sanyukta; Lane, Megan; McBride, Michael; Paridon, Stephen; Goldmuntz, Elizabeth

2017-03-01

Increasing habitual exercise has been associated with improved cardiopulmonary exercise testing (CPET) performance, specifically maximal oxygen consumption in children with operatively corrected congenital heart disease. This has not been studied in children following Fontan palliation, a population in whom CPET performance is dramatically diminished. A single-center cross-sectional study with prospective and retrospective data collection was performed that assessed habitual exercise preceding a clinically indicated CPET in children and adolescents with Fontan palliation, transposition of the great arteries following arterial switch operation (TGA), and normal cardiac anatomy without prior operation. Data from contemporaneous clinical reports and imaging studies were collected. The association between percent predicted VO 2max and habitual exercise duration adjusted for known covariates was tested. A total of 175 subjects (75 post-Fontan, 20 with TGA, and 80 with normal cardiac anatomy) were enrolled. VO 2max was lower in the Fontan group than patients with normal cardiac anatomy (p < 0.0001) or TGA (p < 0.0001). In Fontan subjects, both univariate and multivariate analysis failed to demonstrate a significant association between habitual exercise and VO 2max (p = 0.6), in sharp contrast to cardiac normal subjects. In multivariate analysis, increasing age was the only independent risk factor associated with decreasing VO 2max in the Fontan group (p = 0.003). Habitual exercise was not associated with VO 2max in subjects with a Fontan as compared to biventricular circulation. Further research is necessary to understand why their habitual exercise is ineffective and/or what aspects of the Fontan circulation disrupt this association.

Relationship between habitual exercise and performance on cardio-pulmonary exercise testing differs between children with single and bi-ventricular circulation

PubMed Central

O'Byrne, Michael L; Desai, Sanyukta; Lane, Megan; McBride, Michael; Paridon, Stephen; Goldmuntz, Elizabeth

2016-01-01

Background Increasing habitual exercise has been associated with improved cardiopulmonary exercise testing (CPET) performance, specifically maximal oxygen consumption in children with operatively corrected congenital heart disease. This has not been studied in children following Fontan palliation, a population in whom CPET performance is dramatically diminished. Methods A single-center cross-sectional study with prospective and retrospective data collection was performed that assessed habitual exercise preceding a clinically indicated CPET in children and adolescents with Fontan palliation, transposition of the great arteries following arterial switch operation (TGA), and normal cardiac anatomy without prior operation. Data from contemporaneous clinical reports and imaging studies were collected. The association between percent predicted VO2max and habitual exercise duration adjusted for known covariates was tested. Results A total of 175 subjects (75 post Fontan, 20 with TGA, and 80 with normal cardiac anatomy) were enrolled. VO2max was lower in the Fontan group than patients with normal cardiac anatomy (p<0.0001) or TGA (p<0.0001). In Fontan subjects, both univariate and multivariate analysis failed to demonstrate a significant association between habitual exercise and VO2max (p=0.6), in sharp contrast to cardiac normal subjects. In multivariate analysis, increasing age was the only independent risk factor associated with decreasing VO2max in the Fontan group (p=0.003). Discussion Habitual exercise was not associated with VO2max in subjects with a Fontan as compared to biventricular circulation. Further research is necessary to understand why their habitual exercise is ineffective and/or what aspects of the Fontan circulation disrupt this association. PMID:27878634

[Safety of repeat median sternotomy in the palliative treatment of patients with a univentricular heart].

PubMed

Díliz-Nava, Héctor; Meléndez-Sagaón, Isis; Tamaríz-Cruz, Orlando; García-Benítez, Luis; Araujo-Martínez, Aric; Palacios-Macedo, Alexis

To establish the morbidity and mortality of patients with univentricular hearts who underwent a repeat median sternotomy at the Instituto Nacional de Pediatría. A retrospective review was performed on the clinical charts of all patients who underwent a repeat median sternotomy from 2001 to 2016. Sixty-five patients underwent 76 surgeries by repeat median sternotomy. Fifty-nine patients had a first repeat median sternotomy, with a mean age of 36 months (range: 4-176 months) and a mean weight of 12.2 kg (range: 3.2-21.5 kg). Forty patients had a Glenn procedure, and 19 patients had a Fontan procedure. There were 17 patients with a second repeat median sternotomy, with a mean age of 89 months (range 48-156 months), and a mean weight of 22.7 kg (14.4-41 kg). A Fontan procedure was performed on all these 17 patients. A section of the right coronary artery with electrocardiographic changes and a right atrium tear that caused hypotension occurred during first repeat sternotomy. An aortic tear occurred during a second repeat sternotomy with massive bleeding and subsequent death. This represents 3.9% of re-entry injuries. It is concluded that repeat median sternotomy is a safe procedure. Copyright © 2016 Instituto Nacional de Cardiología Ignacio Chávez. Publicado por Masson Doyma México S.A. All rights reserved.

Atrial isomerism: a surgical experience.

PubMed

Sinzobahamvya, N; Arenz, C; Brecher, A M; Urban, A E

1999-06-01

Most publications on atrial isomerism are autopsy or case reports. The authors review 41 consecutive children operated on from 1980 through to 1996 with emphasis on associated cardiac anomalies, surgical procedures and outcome. Left atrial isomerism was present in 23 patients. Interruption of the inferior vena cava (56%), atrio-ventricular septal defect (47%), common atrium (38%) and cor triatriatum sinistrum (30%) were the most common diagnoses. Biventricular repair was achieved in 17 children and total cavo-pulmonary connection in two. Three underwent staged palliation: modified Blalock-Taussig shunt for two and bidirectional Glenn anastomosis for one. The remainder received a cardiac pacemaker. One patient died early after repair. Two underwent reoperation to correct a regurgitant left atrio-ventricular valve: one of these, in another hospital, had peroperative death. Three died later. Actuarial survival rate after repair and total cavo-pulmonary connection that was stabilized after 2 years was 84%. In the 18 children with right atrial isomerism, pulmonary atresia or stenosis predominated (89%) with discordant ventriculo-arterial connection (72%), atrio-ventricular septal defect (72%), 'single' ventricle (55%) and extracardiac total anomalous pulmonary venous drainage (50%). Biventricular repair was achieved in two patients and complete Fontan circulation in eight. The other eight underwent various staged palliative procedures and correction of extracardiac total anomalous pulmonary venous drainage. Five patients died postoperatively: two in our unit after modified Blalock-Taussig shunt and total cavo-pulmonary connection, three in other hospitals after repair (n = 1) and Fontan (n = 2). Five died later. One was lost for review. Survival after repair and Fontan stabilized after 6 months at 49%. In conclusion, the cardiovascular malformations associated with left atrial isomerism can often be successfully corrected. Those accompanying right atrial isomerism usually preclude a biventricular repair, require staged palliation and carry a poor prognosis.

Results of total cavopulmonary connection in the treatment of patients with a functional single ventricle.

PubMed

Stein, D G; Laks, H; Drinkwater, D C; Permut, L C; Louie, H W; Pearl, J M; George, B L; Williams, R G

1991-08-01

Total cavopulmonary connection was proposed as a modification of the Fontan procedure that might have greater benefits than previous methods. To assess this procedure we reviewed case histories of 38 patients (aged 17 months to 30 years) who underwent Fontan procedures with cavopulmonary anastomoses between January 1987 and December 1989. The group included 32 patients with univentricular heart, 2 with pulmonary atresia and intact ventricular septum, 3 with tricuspid atresia, and 1 with hypoplastic left heart syndrome. One or more previous palliative procedures were performed in 34 patients, including 19 systemic-pulmonary shunts, 16 pulmonary artery bandings, 7 atrial septectomies/septostomies, 7 Glenn shunts, and 1 patent ductus arteriosus ligation. Preoperative hemodynamics showed a pulmonary artery pressure of 12 mm Hg (range 6 to 22 mm Hg), pulmonary-systemic flow ratio of 1.6 (range 0.37 to 3.0), left ventricular end-diastolic pressure 9 mm Hg (range 3 to 15 mm Hg), and systemic arterial oxygen saturation of 82% (range 67% to 94%). Concomitant with cavopulmonary connection, 13 patients underwent additional procedures, including 9 atrioventricular valve annuloplasties, 4 Damus-Stansel-Kaye procedures, and 2 resections of subaortic membranes. Modifying the Fontan procedure in this fashion was particularly useful in the management of 2 patients with pulmonary atresia and intact ventricular septum who had right ventricular-dependent coronary blood flow. Cavopulmonary anastomosis and atrial septectomy were performed in both patients, with resultant inflow of oxygenated blood to the right ventricle and coronary arteries. Excellent postoperative results were noted in each. Postextubation hemodynamics for the entire group included a mean right atrial pressure of 13 mm Hg (range 11 to 17 mm Hg), a mean left atrial pressure of 6 mm Hg (range 3 to 12 mm Hg), and a room air oxygen saturation of 96% (range 92% to 98%). Seven patients had pleural effusions, 3 required postoperative pacemaker placement, and 2 required reoperation for tamponade. A venous assist device was required in one patient on the second postoperative day, but the patient was weaned successfully within 24 hours. One early death (2.6%) occurred in a patient who had intractable ventricular fibrillation 2 days after operation. There was one late cardiac death (2.7%) caused by ventricular failure and one late noncardiac death. These results demonstrate that total cavopulmonary connection provides excellent early definitive treatment, with low morbidity and mortality, for a variety of complex congenital heart lesions.

Experimental characterization of powered Fontan hemodynamics in an idealized total cavopulmonary connection model

NASA Astrophysics Data System (ADS)

Kerlo, Anna-Elodie M.; Delorme, Yann T.; Xu, Duo; Frankel, Steven H.; Giridharan, Guruprasad A.; Rodefeld, Mark D.; Chen, Jun

2013-08-01

A viscous impeller pump (VIP) based on the Von Karman viscous pump is specifically designed to provide cavopulmonary assist in a univentricular Fontan circulation. The technology will make it possible to biventricularize the univentricular Fontan circulation. Ideally, it will reduce the number of surgeries required for Fontan conversion from three to one early in life, while simultaneously improving physiological conditions. Later in life, it will provide a currently unavailable means of chronic support for adolescent and adult patients with failing Fontan circulations. Computational fluid dynamics simulations demonstrate that the VIP can satisfactorily augment cavopulmonary blood flow in an idealized total cavopulmonary connection (TCPC). When the VIP is deployed at the TCPC intersection as a static device, it stabilizes the four-way flow pattern and is not obstructive to the flow. Experimental studies are carried out to assess performance, hemodynamic characteristics, and flow structures of the VIP in an idealized TCPC model. Stereoscopic particle image velocimetry is applied using index-matched blood analog. Results show excellent performance of the VIP without cavitation and with reduction of the energy losses. The non-rotating VIP smoothes and accelerates flow, and decreases stresses and turbulence in the TCPC. The rotating VIP generates the desired low-pressure Fontan flow augmentation (0-10 mmHg) while maintaining acceptable stress thresholds.

Use of ACE inhibitors in Fontan: Rational or irrational?

PubMed

Wilson, Thomas G; Iyengar, Ajay J; Winlaw, David S; Weintraub, Robert G; Wheaton, Gavin R; Gentles, Thomas L; Ayer, Julian; Grigg, Leeanne E; Justo, Robert N; Radford, Dorothy J; Bullock, Andrew; Celermajer, David S; Dalziel, Kim; Schilling, Chris; d'Udekem, Yves

2016-05-01

Despite a lack of evidence supporting the use of angiotensin-converting enzyme (ACE) inhibitors in patients with a Fontan circulation, their use is frequent. We decided to identify the rationale for ACE inhibitor therapy in patients within the Australia and New Zealand Fontan Registry. All patients in the Registry taking an ACE inhibitor at last follow up were identified, and a review of medical records was undertaken to determine the rationale for treatment initiation and reasons for treatment continuation or dose increase. In 2015, 36% of the surviving patients in the Registry (462/1268) were taking an ACE inhibitor. Indications for initiation of therapy were ventricular systolic or diastolic dysfunction (29%), atrioventricular valve regurgitation (19%), preservation of normal ventricular function (7%), prolonged effusions at Fontan (6%), hypertension (6%), other (6%) and unknown (2%). No indication was stated in the remaining patients (25%). Those with hypoplastic left heart syndrome were more likely to be on an ACE inhibitor than those with an alternative primary morphology (70% vs 32%; p<0.001). Only 36% of the patients treated with an ACE inhibitor at last follow up (166/462) had an indication that would generally justify treatment in a two-ventricle circulation. It is likely that the use of ACE inhibitors in patients with a Fontan circulation is excessive within our region. The coordination of prospective, multicentre studies and initiatives such as the Australia and New Zealand Fontan Registry will facilitate further investigations to guide treatment decisions in the growing Fontan population. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

The Miracle Baby Grows Up: Hypoplastic Left Heart Syndrome in the Adult.

PubMed

Lewis, Matthew; Rosenbaum, Marlon

2017-08-01

Hypoplastic left heart syndrome (HLHS) is characterized by underdevelopment of the mitral valve, left ventricle, and aorta and is ultimately palliated with a single-ventricle repair. Universally fatal in infancy prior to the advent of modern surgical techniques, the majority of HLHS patients will now reach adulthood. However, despite improvements in early survival, the HLHS population continues to face significant morbidity and early mortality. This review delineates common sources of patient morbidity and highlights areas in need of additional research for this growing segment of the adult congenital heart disease population. It has become increasingly clear that palliated adult single ventricle patients, like those with HLHS, face significant life-long morbidity from elevated systemic venous pressures as a consequence of the Fontan procedure. Downstream organ dysfunction secondary to elevated Fontan pressures has the potential to significantly impact long-term management decisions, including strategies of organ allocation. Because of the presence of a morphologic systemic right ventricle, HLHS patients may be at even higher risk than other adult patients with a Fontan. Because the adult HLHS population continues to grow, recognition of common sources of patient morbidity and mortality is becoming increasingly important. A coordinated effort between patients and providers is necessary to address the many remaining areas of clinical uncertainty to help ensure continued improvement in patient prognosis and quality of life.

Gastrointestinal haemorrhage due to lymphangiectasia caused by protein-losing enteropathy in the Fontan circulation.

PubMed

Gras, Pauline; Gottrand, Frédéric; Godart, François

2017-10-01

We report the case of a 14-year-old boy with severe protein-losing enteropathy after Fontan surgery that led to lymphangiectasia, which caused gastrointestinal haemorrhage and required invasive treatment to stop the bleeding. Through this case and a review of the literature on protein-losing enteropathy after Fontan surgery, we highlight a rare and serious presentation of the disease and the difficulties of diagnosis and management.

Anesthetic management of pial synangiosis and intracranial hemorrhage with a Fontan circulation.

PubMed

Subramaniam, Balachundhar; Soriano, Sulpicio G; Michael Scott, R; Kussman, Barry D

2006-01-01

We report the case of a 11-year-old girl with Moyamoya syndrome, who had undergone staged-repair of tricuspid atresia to a Fontan circulation, scheduled to undergo bilateral pial synangiosis. Surgery for the first hemisphere was complicated by intracranial hemorrhage requiring an emergency craniotomy. The case highlights the importance of understanding Fontan physiology and its interrelationship with the cerebral circulation in the setting of cerebrovascular insufficiency and raised intracranial pressure.

Hypoplastic left heart syndrome: a review

PubMed Central

Gobergs, Roberts; Salputra, Elza; Lubaua, Ingūna

2016-01-01

Background. Hypoplastic left heart syndrome (HLHS) is an etiologically multifactorial congenital heart disease affecting one in 5,000 newborns. Thirty years ago there were no treatment options for this pathology and the natural course of the disease led to death, usually within the first weeks of life. Recently surgical palliative techniques have been developed allowing for a five-year survival in more than half the cases. Materials and methods. We reviewed literature available on HLHS, specifically its anatomy, embryology and pathophysiology, and treatment. The Pubmed and ClinicalKey databases were searched using the key words hypoplastic left heart syndrome, foetal aortic valvuloplasty, foetal septoplasty, Norwood procedure, bidirectional Glenn procedure, Fontan procedure, hybrid procedure. The relevant literature was reviewed and included in the article. We reported a case from Children’s Clinical University Hospital, Riga, to illustrate treatment tactics in Latvia. Results. There are three possible directions for therapy in newborns with HLHS: orthotopic heart transplantation, staged surgical palliation and palliative non-surgical treatment or comfort care. Another treatment mode – foetal therapy – has arisen. Staged palliation and full Fontan circulation is a temporary solution, however, the only means for survival until heart transplantation. Fifty to 70% of patients who have gone through all three stages of palliation live to the age of five years. Conclusions. The superior mode of treatment is not yet clear and the management must be based on each individual case, the experience of each clinic, as well as the financial aspects and will of the patient’s parents. PMID:28356795

Cardiac magnetic resonance and the need for routine cardiac catheterization in single ventricle patients prior to Fontan: a comparison of 3 groups: pre-Fontan CMR versus cath evaluation.

PubMed

Fogel, Mark A; Pawlowski, Thomas W; Whitehead, Kevin K; Harris, Matthew A; Keller, Marc S; Glatz, Andrew C; Zhu, Winnie; Shore, David; Diaz, Laura K; Rome, Jonathan J

2012-09-18

This study investigated whether cardiac magnetic resonance (CMR) and echocardiography (echo) can replace catheterization (cath) for routine evaluation prior to Fontan and under what circumstances CMR and cath are used together. Routine cath prior to Fontan has been utilized for years; noninvasive methods, however, may be sufficient. This study reviews clinical data in 119 consecutive patients investigating 3 groups: those who underwent CMR alone (MR; n = 41), cath alone (C; n = 41), or both cath and CMR (C+M; n = 37) prior to Fontan. No clinically significant differences were noted in patient characteristics, hemodynamics, or clinical status prior to or after surgery between the C and MR groups. CMR added information in 82%. There were no discrepant findings between CMR and cath data in the C+M group. Diagnostic success was ≥95% in all groups. Of those undergoing Fontan completion, the C+M group had similar outcomes to C and MR; C and CMR were utilized in combination to assess aortopulmonary collaterals or the need for an intervention or evaluate its success. Echo could not delineate pulmonary arterial anatomy in 46% to 53% of patients. The C+M and C groups were exposed to 6.8 ± 4.1 mSv of radiation. Single ventricle patients not requiring an intervention can undergo successful Fontan completion with CMR and echo alone with similar short-term outcomes to C, which was used as a control, preventing an invasive test and exposure to radiation. CMR can add information in a significant number of patients. Cath and CMR are utilized together for interventions and assessment of aortopulmonary collaterals. Copyright © 2012 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Fontan Circulation in Adult Patients: Acoustic Radiation Force Impulse Elastography as a Useful Tool for Liver Assessment.

PubMed

Melero-Ferrer, Josep Lluís; Osa-Sáez, Ana; Buendía-Fuentes, Francisco; Ballesta-Cuñat, Antonio; Flors, Lucía; Rodríguez-Serrano, María; Calvillo-Batllés, Pilar; Arnau-Vives, Miguel-Ángel; Palencia-Pérez, Miguel A; Rueda-Soriano, Joaquín

2014-07-01

The development of liver fibrosis and cirrhosis due to long-standing liver congestion is known to occur in adult patients with Fontan circulation. Hepatic elastography has shown to be a useful tool for the noninvasive assessment and staging of liver fibrosis in chronic liver diseases, although the utility of this technique in Fontan patients remains to be adequately studied. Twenty-one patients with Fontan circulation underwent an abdominal ultrasound and an acoustic radiation force impulse (ARFI) elastography. In order to compare the results from this group, a cohort of 14 healthy controls and another group containing 17 patients with cirrhosis were included. The association between the velocity values measured with elastography and clinical and analytical parameters were also studied. Mean shear waves propagation velocity in liver tissue in the Fontan group was 1.86 ± 0.5 m/s, with 76% of patients over the cirrhosis threshold (1.55 m/s). The control group had a mean velocity of 1.09 ± 0.06 m/s, while the cirrhotic group obtained 2.71 ± 0.51 m/s. Seven patients with Fontan circulation had increased liver enzymes. Liver ultrasound showed evidence of chronic liver disease in six patients. Velocity values obtained in the presence or absence of analytical or liver ultrasound abnormalities showed significant differences in the univariate analysis (P = .04 and P = .03 respectively). In conclusion, ARFI elastography showed increased wave propagation velocity values in the Fontan population suggesting increased liver stiffness which could be related to advanced fibrosis. A statistically significant association between ARFI values and the presence of analytical and ultrasound abnormalities has been demonstrated. © The Author(s) 2014.

Decreased Diastolic Ventricular Kinetic Energy in Young Patients with Fontan Circulation Demonstrated by Four-Dimensional Cardiac Magnetic Resonance Imaging.

PubMed

Sjöberg, Pia; Heiberg, Einar; Wingren, Pär; Ramgren Johansson, Jens; Malm, Torsten; Arheden, Håkan; Liuba, Petru; Carlsson, Marcus

2017-04-01

Four-dimensional (4D) flow magnetic resonance imaging (MRI) enables quantification of kinetic energy (KE) in intraventricular blood flow. This provides a novel way to understand the cardiovascular physiology of the Fontan circulation. In this study, we aimed to quantify the KE in functional single ventricles. 4D flow MRI was acquired in eleven patients with Fontan circulation (median age 12 years, range 3-29) and eight healthy volunteers (median age 26 years, range 23-36). Follow-up MRI after surgical or percutaneous intervention was performed in 3 patients. Intraventricular KE was calculated throughout the cardiac cycle and indexed to stroke volume (SV). The systolic/diastolic ratio of KE in Fontan patients was similar to the ratio of the controls' left ventricle (LV) or right ventricle (RV) depending on the patients' ventricular morphology (Cohen´s κ = 1.0). Peak systolic KE/SV did not differ in patients compared to the LV in controls (0.016 ± 0.006 mJ/ml vs 0.020 ± 0.004 mJ/ml, p = 0.09). Peak diastolic KE/SV in Fontan patients was lower than in the LV of the control group (0.028 ± 0.010 mJ/ml vs 0.057 ± 0.011 mJ/ml, p < 0.0001). The KE during diastole showed a plateau in patients with aortopulmonary collaterals. This is to our knowledge the first study that quantifies the intraventricular KE of Fontan patients. KE is dependent on the morphology of the ventricle, and diastolic KE indexed to SV in patients is decreased compared to controls. The lower KE in Fontan patients may be a result of impaired ventricular filling.

Quantitative echocardiographic measures in the assessment of single ventricle function post-Fontan: Incorporation into routine clinical practice.

PubMed

Rios, Rodrigo; Ginde, Salil; Saudek, David; Loomba, Rohit S; Stelter, Jessica; Frommelt, Peter

2017-01-01

Quantitative echocardiographic measurements of single ventricular (SV) function have not been incorporated into routine clinical practice. A clinical protocol, which included quantitative measurements of SV deformation (global circumferential and longitudinal strain and strain rate), standard deviation of time to peak systolic strain, myocardial performance index (MPI), dP/dT from an atrioventricular valve regurgitant jet, and superior mesenteric artery resistance index, was instituted for all patients with a history of Fontan procedure undergoing echocardiography. All measures were performed real time during clinically indicated studies and were included in clinical reports. A total of 100 consecutive patients (mean age = 11.95±6.8 years, range 17 months-31.3 years) completed the protocol between September 1, 2014 to April 29, 2015. Deformation measures were completed in 100% of the studies, MPI in 93%, dP/dT in 55%, and superior mesenteric artery Doppler in 82%. The studies were reviewed to assess for efficiency in completing the protocol. The average time for image acquisition was 27.4±8.8 (range 10-62 minutes). The average time to perform deformation measures was 10.8±5.5 minutes (range 5-35 minutes) and time from beginning of imaging to report completion was 53.4±13.7 minutes (range 27-107 minutes). There was excellent inter-observer reliability when deformation indices were blindly repeated. Patients with a single left ventricle had significantly higher circumferential strain and strain rate, longitudinal strain and strain rate, and dP/dT compared to a single right ventricle. There were no differences in quantitative indices of ventricular function between patients <10 vs. >10 years post-Fontan. Advanced quantitative assessment of SV function post-Fontan can be consistently and efficiently performed real time during clinically indicated echocardiograms with excellent reliability. © 2016, Wiley Periodicals, Inc.

Comparative Evaluation of Flow Quantification across the Atrioventricular Valve in Patients with Functional Univentricular Heart after Fontan's Surgery and Healthy Controls: Measurement by 4D Flow Magnetic Resonance Imaging and Streamline Visualization.

PubMed

She, Hoi Lam; Roest, Arno A W; Calkoen, Emmeline E; van den Boogaard, Pieter J; van der Geest, Rob J; Hazekamp, Mark G; de Roos, Albert; Westenberg, Jos J M

2017-01-01

To evaluate the inflow pattern and flow quantification in patients with functional univentricular heart after Fontan's operation using 4D flow magnetic resonance imaging (MRI) with streamline visualization when compared with the conventional 2D flow approach. Seven patients with functional univentricular heart after Fontan's operation and twenty-three healthy controls underwent 4D flow MRI. In two orthogonal two-chamber planes, streamline visualization was applied, and inflow angles with peak inflow velocity (PIV) were measured. Transatrioventricular flow quantification was assessed using conventional 2D multiplanar reformation (MPR) and 4D MPR tracking the annulus and perpendicular to the streamline inflow at PIV, and they were validated with net forward aortic flow. Inflow angles at PIV in the patient group demonstrated wide variation of angles and directions when compared with the control group (P < .01). The use of 4D flow MRI with streamlines visualization in quantification of the transatrioventricular flow had smaller limits of agreement (2.2 ± 4.1 mL; 95% limit of agreement -5.9-10.3 mL) when compared with the static plane assessment from 2DFlow MRI (-2.2 ± 18.5 mL; 95% limit of agreement agreement -38.5-34.1 mL). Stronger correlation was present in the 4D flow between the aortic and trans-atrioventricular flow (R 2 correlation in 4D flow: 0.893; in 2D flow: 0.786). Streamline visualization in 4D flow MRI confirmed variable atrioventricular inflow directions in patients with functional univentricular heart with previous Fontan's procedure. 4D flow aided generation of measurement planes according to the blood flood dynamics and has proven to be more accurate than the fixed plane 2D flow measurements when calculating flow quantifications. © 2016 Wiley Periodicals, Inc.

Staged surgical palliation in hypoplastic left heart syndrome and its variants.

PubMed

Delmo Walter, Eva Maria B; Hübler, Michael; Alexi-Meskishvili, Vladimir; Miera, Oliver; Weng, Yuguo; Loforte, Antonio; Berger, Felix; Hetzer, Roland

2009-01-01

Surgical options for infants with hypoplastic left heart syndrome (HLHS) and/or its variants are cardiac transplantation or the heart-preserving staged palliation with Norwood operation,followed by a two-staged Fontan procedure. We describe our 17-year experience with staged palliation of HLHS and/or its variants. Between December 1989 and December 2006, 64 patients with HLHS and/or its variants underwent a Norwood procedure (mean age/weight, 11.8+/-2.5 days/3.4 kg). Forty-four patients had classical HLHS. Twenty-eight percent had associated congenital cardiac, structural, and genetic anomalies. Subsequently, 25 patients underwent a bidirectional Glenn procedure (stage II) and 11 patients a modified Fontan procedure (stage III). Others await stage II and/or stage III. The follow-up was 143.2 patient-years. Including the learning curve, overall early mortality from 1989 to 1999 after the Norwood procedure was 39.06%. This decreased tremendously for the last seven years, and reduced to 12.8% in 2000 to 2003 until 0% in 2004 to 2006 (p < 0.005). The causes of mortality were sepsis, capillary leak,or heart failure. Three patients died between stages II and III. One patient underwent heart transplantation after the second stage because of heart failure. Among 34 Norwood survivors, four are slightly tachypneic from a mild pulmonary hyperperfusion; one presents symptoms of minimal brain disease. This report identified an outcome improvement after staged palliation of HLHS, attributed to an increase in experience and expertise gained over time. Lower operative weight, ascending aortic size, prolonged duration of cardiopulmonary bypass, and hypothermic circulatory arrest were identified to significantly influence early mortality after the Norwood procedure.

Dor procedure for pulmonary atresia with intact ventricular septum in an infant.

PubMed

Kang, Yoonjin; Kwak, Jae Gun; Kim, Eung Rae; Kim, Woong-Han

2018-02-01

Pulmonary atresia with intact ventricular septum and right ventricle-dependent coronary circulation confers a high risk for myocardial infarction and complications of ischaemia, including left ventricle aneurysms. We describe an infant with pulmonary atresia with intact ventricular septum and right ventricle-dependent coronary circulation and a left ventricle apical aneurysm who successfully underwent the Dor procedure and a subsequent Fontan operation. Surgery for postinfarction left ventricle aneurysm can be considered in infants. © The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Cardiovascular anatomy in children with bidirectional Glenn anastomosis, regarding the transcatheter Fontan completion.

PubMed

Sizarov, Aleksander; Raimondi, Francesca; Bonnet, Damien; Boudjemline, Younes

2018-04-01

Transcatheter stent-secured completion of total cavopulmonary connection (TCPC) after surgical preparations during the Glenn anastomosis procedure has been reported, but complications from this approach have precluded its clinical acceptance. To analyse cardiovascular morphology and dimensions in children with bidirectional Glenn anastomosis, regarding the optimal device design for transcatheter Fontan completion without special surgical "preconditionings". We retrospectively analysed 60 thoracic computed tomography and magnetic resonance angiograms performed in patients with a median age of 4.1 years (range: 1.8-17.1 years). Additionally, we simulated TCPC completion using different intra-atrial stent-grafts in a three-dimensional model of the representative anatomy, and performed calculations to determine the optimal stent-graft dimensions, using measured distances. Two types of cardiovascular arrangement were identified: left atrium interposing between the right pulmonary artery (RPA) and inferior vena cava, with the right upper pulmonary vein (RUPV) orifice close to the intercaval axis (65%); and intercaval axis traversing only the right(-sided) atrial cavity, with the RUPV located posterior to the atrial wall (35%). In the total population, the shortest median RPA-to-atrial wall distance was 1.9mm (range: 0.6-13.8mm), while the mean intra-atrial distance along the intercaval axis was 50.1±11.2mm. Regardless of the arrangement, 83% of all patients required a deviation of at least 5.9±2.4mm (range: 1.2-12.7mm) of the stent-graft centre at the RUPV level anteriorly to the intercaval axis to avoid covering or compressing this vein. Fixing the anterior deviation of the curved stent-graft centre at 10mm significantly decreased the range of bend angle per every given RUPV-RPA distance. For both types of cardiovascular arrangement, after conventional bidirectional Glenn anastomosis, the intra-atrial curved stent-graft seemed most suitable for achieving uncomplicated TCPC completion percutaneously without previous surgical "preconditionings" in the majority of children. Experimental study is necessary to validate this conclusion. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Can endurance training improve physical capacity and quality of life in young Fontan patients?

PubMed

Hedlund, Eva R; Lundell, Bo; Söderström, Liselott; Sjöberg, Gunnar

2018-03-01

Children after Fontan palliation have reduced exercise capacity and quality of life. Our aim was to study whether endurance training could improve physical capacity and quality of life in Fontan patients. Fontan patients (n=30) and healthy age- and gender-matched control subjects (n=25) performed a 6-minute walk test at submaximal capacity and a maximal cycle ergometer test. Quality of life was assessed with Pediatric Quality of Life Inventory Version 4.0 questionnaires for children and parents. All tests were repeated after a 12-week endurance training programme and after 1 year. Patients had decreased submaximal and maximal exercise capacity (maximal oxygen uptake 35.0±5.1 ml/minute per·kg versus 43.7±8.4 ml/minute·per·kg, p<0.001) and reported a lower quality of life score (70.9±9.9 versus 85.7±8.0, p<0.001) than controls. After training, patients improved their submaximal exercise capacity in a 6-minute walk test (from 590.7±65.5 m to 611.8±70.9 m, p<0.05) and reported a higher quality of life (p<0.01), but did not improve maximal exercise capacity. At follow-up, submaximal exercise capacity had increased further and improved quality of life was sustained. The controls improved their maximal exercise capacity (p<0.05), but not submaximal exercise capacity or quality of life after training. At follow-up, improvement of maximal exercise capacity was sustained. We believe that an individualised endurance training programme for Fontan patients improves submaximal exercise capacity and quality of life in Fontan patients and the effect on quality of life appears to be long-lasting.

Neurologic Injury and Cerebral Blood Flow In Single Ventricles Throughout Staged Surgical Reconstruction

PubMed Central

Fogel, Mark A.; Li, Christine; Elci, Okan U.; Pawlowski, Tom; Schwab, Peter J.; Wilson, Felice; Nicolson, Susan C.; Montenegro, Lisa M.; Diaz, Laura; Spray, Thomas L.; Gaynor, J William; Fuller, Stephanie; Mascio, Christopher; Keller, Marc S.; Harris, Matthew A.; Whitehead, Kevin K.; Bethel, Jim; Vossough, Arastoo; Licht, Daniel J.

2017-01-01

Background Single ventricle patients experience a high rate of brain injury and adverse neurodevelopmental outcome, however, the incidence of brain abnormalities throughout surgical reconstruction and its relationship with cerebral blood flow, oxygen delivery and carbon dioxide reactivity remains unknown. Methods Single ventricle patients were studied with MRI scans immediately prior to bidirectional Glenn (pre-BDG), prior to Fontan and then 3–9 months after Fontan reconstruction. Results One hundred and sixty eight consecutive subjects recruited into the project underwent 235 scans: 63 pre-BDG (mean age 4.8+1.7 months), 118 BDG (2.9+1.4 years) and 54 after Fontan (2.4+1.0 years). Non-acute ischemic white matter changes on T2 weighted imaging, focal tissue loss, and ventriculomegaly were all more commonly detected in BDG and Fontans compared to pre-BDG (P<0.05). BDG patients has significantly higher CBF than Fontan patients. The odds of discovering brain injury adjusting for surgical stage as well as 2 or more co-existing lesions within a patient all decreased (63–75% and 44% respectively) with increasing amount of cerebral blood flow (P<0.05). In general, there was no association of oxygen delivery (with the exception of ventriculomegaly in the BDG group) or carbon dioxide reactivity with neurological injury. Conclusion Significant brain abnormalities are commonly present in single ventricle patients and detection of these lesions increase as children progress through staged surgical reconstruction with multiple co-existing lesions more common earlier than later. In addition, this study demonstrated that BDG patients had greater CBF than Fontan patients and that there exists an inverse association of various indices of CBF with these brain lesions, however, CO2 reactivity, oxygen delivery (with one exception) were not associated with brain lesion development. PMID:28031423

Growth and Obesity Among Older Single Ventricle Patients Presenting for Fontan Conversion.

PubMed

Freud, Lindsay R; Webster, Gregory; Costello, John M; Tsao, Sabrina; Rychlik, Karen; Backer, Carl L; Deal, Barbara J

2015-10-01

Long-term growth outcomes and the prevalence of obesity among older single ventricle (SV) patients have not been well characterized. We investigated these parameters, as well as the impact of obesity on survival, in an older cohort of SV patients presenting for Fontan conversion. We analyzed preoperative height, weight, and body mass index (BMI) of patients who underwent Fontan conversion. Overweight and obese were defined as BMI ≥85 percentile and ≥95 percentile for patients <20 years and BMI 25 to 30 kg/m(2) and ≥30 kg/m(2) for patients ≥20 years, respectively. Postoperative transplant-free survival was assessed among obese, overweight, and normal weight patients. We evaluated 139 patients presenting for Fontan conversion at a median age of 23.2 years. Patients had shorter stature compared to the normal population (mean Z score -0.6, P < .001). Younger patients had lower BMI compared to the normal population (<20 years: mean Z score -0.5, P = .02), while older patients had elevated BMI (≥20 years: mean Z score +0.4, P < .001). The mean BMI among older patients approached overweight at 24.6 kg/m(2). The prevalence of obesity increased with advancing age, with 36% overweight and 14% obese at >30 years. At a median of 8.2 years following Fontan conversion, obesity and overweight status were not associated with transplant-free survival. Older SV patients presenting for Fontan conversion had shorter stature compared to the normal population as well as a high prevalence of overweight and obesity. Although there was no relationship between weight status and early postoperative survival, further investigation of long-term outcomes is warranted. © The Author(s) 2015.

Prediction of Fontan-Associated Liver Disease Using a Novel Cine Magnetic Resonance Imaging "Vortex Flow Map" in the Right Atrium.

PubMed

Ishizaki, Umiko; Nagao, Michinobu; Shiina, Yumi; Fukushima, Kenji; Takahashi, Tatsunori; Shimomiya, Yamato; Matsuo, Yuka; Inai, Kei; Sakai, Shuji

2018-05-18

Long-term hepatic dysfunction is an increasingly recognized complication of the Fontan operation for univentricular hearts. The purpose of this study was to determine whether Fontan-associated liver disease (FALD) could be predicted by flow dynamics in the right atrium (RA) of Fontan circulation.Methods and Results:Cardiac MRI and the serum levels of total bilirubin (TBil) and hyaluronic acid (HA) were analyzed in 36 patients who underwent an atriopulmonary connection type of Fontan operation. The mean follow-up period was 53 months. Three views (axial, coronal, and sagittal) of the cine images were scanned for the maximum cross-section of the RA obtained with1.5-Tesla scanner. We developed a "vortex flow map" to demonstrate the ratio of the circumferential voxel movement in each phase to the total movement throughout a cardiac cycle towards the center of the RA. The maximum ratio was used as the magnitude of vortex flow (MVF%) in the 3 views of the RA cine imaging. Patients with coronal MVF ≥13.6% had significantly lower free rates of TBil ≥1.8 mg/dL than those with coronal MVF <13.6% (log-rank value=4.50; P<0.05; hazard ratio=4.54). Patients with sagittal MVF ≥14.0% had significantly lower free rates of HA ≥50 ng/mL than those with coronal MVF <14.0% (log-rank value=4.40; P<0.05; hazard ratio=4.12). A reduced vortex flow in the RA during the late phase of the Fontan operation was associated with the development of FALD. MVF can be used as an imaging biomarker to predict FALD.

In vitro validation of a self-driving aortic-turbine venous-assist device for Fontan patients.

PubMed

Pekkan, Kerem; Aka, Ibrahim Basar; Tutsak, Ece; Ermek, Erhan; Balim, Haldun; Lazoglu, Ismail; Turkoz, Riza

2018-03-11

Palliative repair of single ventricle defects involve a series of open-heart surgeries where a single-ventricle (Fontan) circulation is established. As the patient ages, this paradoxical circulation gradually fails, because of its high venous pressure levels. Reversal of the Fontan paradox requires an extra subpulmonic energy that can be provided through mechanical assist devices. The objective of this study was to evaluate the hemodynamic performance of a totally implantable integrated aortic-turbine venous-assist (iATVA) system, which does not need an external drive power and maintains low venous pressure chronically, for the Fontan circulation. Blade designs of the co-rotating turbine and pump impellers were developed and 3 prototypes were manufactured. After verifying the single-ventricle physiology at a pulsatile in vitro circuit, the hemodynamic performance of the iATVA system was measured for pediatric and adult physiology, varying the aortic steal percentage and circuit configurations. The iATVA system was also tested at clinical off-design scenarios. The prototype iATVA devices operate at approximately 800 revolutions per minute and extract up to 10% systemic blood from the aorta to use this hydrodynamic energy to drive a blood turbine, which in turn drives a mixed-flow venous pump passively. By transferring part of the available energy from the single-ventricle outlet to the venous side, the iATVA system is able to generate up to approximately 5 mm Hg venous recovery while supplying the entire caval flow. Our experiments show that a totally implantable iATVA system is feasible, which will eliminate the need for external power for Fontan mechanical venous assist and combat gradual postoperative venous remodeling and Fontan failure. Copyright © 2018 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

Fontan completion in patients with atrial isomerism and separate hepatic venous drainage.

PubMed

Nakata, Tomohiro; Fujimoto, Yoshifumi; Hirose, Keiichi; Osaki, Masaki; Tosaka, Yuko; Ide, Yujiro; Tachi, Maiko; Sakamoto, Kisaburo

2010-06-01

Fontan completion in patients with atrial isomerism, in which the inferior vena cava (IVC) and the hepatic vein (HV) drain separately, is technically challenging. Herein, we review our surgical approach to these patients. The medical records of 50 consecutive patients with atrial isomerism who underwent Fontan completion between 1998 and 2008 were reviewed retrospectively. Separate HV drainage was present in 17 patients. Patients with interrupted IVC were excluded. Patient characteristics were as follows: median age, 26 months (range 15-149); median weight, 9.6 kg (range 8.1-47.2); right atrial isomerism, 16 patients; and left atrial isomerism, one. The IVC and the separate HV at the level of diaphragm were contralateral in 16 patients, and ipsilateral in one. The surgical procedures for directing blood flow from the IVC and the separate HV to the pulmonary arteries were as follows: en bloc resection of the IVC and the HV and anastomosing these veins to an extracardiac conduit in 10 patients; connecting the IVC to the HV in a side-to-side fashion before anastomosing them to an extracardiac conduit in one; and lateral tunnel in another. When the IVC and the HV were widely separated by the vertebrae, we chose an intra-extracardiac conduit (intra-atrial septation) in four patients and an extracardiac conduit for the IVC and the right HV and lateral tunnel for the separate left HV in one. There was no mortality. Five re-operations were performed (pacemaker in two patients; one each of fenestration, release of outflow obstruction and ligation of collateral arteries). Sixteen patients underwent follow-up catheterisation, which revealed central venous pressure of 12.0 + or - 2.0 mmHg and arterial oxygen saturation of 92% + or - 6%. The mid-term results of the Fontan completion in patients with atrial isomerism and separate HV drainage were excellent. The distance between the IVC and the separate HV and the position of the vertebrae should be considered when choosing a surgical technique. Copyright 2010. Published by Elsevier B.V.

Delayed puberty and abnormal anthropometry and its associations with quality of life in young Fontan survivors: A multicenter cross-sectional study.

PubMed

Menon, Shaji C; Al-Dulaimi, Ragheed; McCrindle, Brian W; Goldberg, David J; Sachdeva, Ritu; Goldstein, Bryan H; Seery, Thomas; Uzark, Karen C; Chelliah, Anjali; Butts, Ryan; Henderson, Heather; Johnson, Tiffanie; Williams, Richard V

2018-05-01

We sought to evaluate the prevalence of delayed puberty and abnormal anthropometry and its association with quality of life (QoL) in young Fontan survivors. This was a cross-sectional study at 11 Pediatric Heart Network centers. Demographic and clinical data, anthropomety, and Tanner stage were collected. Anthropometric measurements and pubertal stage were compared to US norms. QoL was assessed using Pediatric Quality of Life inventory (PedsQL). Mixed effects regression modeling adjusting for clustering by center was used to evaluate factors associated with abnormal anthropometry and delayed puberty and associations with QoL. Of the 299 subjects, 42% were female. The median enrollment age was 13.9 years, and the median age at Fontan was 3 years. Fontan survivors had a higher prevalence of short stature relative to normative data (20% vs 5%, P < .0001) and an increased prevalence of abnormal BMI (16% vs 10%, P < .0001) (low [43%] and high [57%]). Fontan subjects, both males (58%) and females (58%), had a delay of 1.5-2 years in ≥1 Tanner stage parameter compared to normal population. There was no association between delayed puberty and QoL. Abnormal anthropometry was associated with lower overall (62.3 ± 17.3 vs 72.5 ± 16.6; P < .001) and physical appearance scores (72.2 ± 27.4 vs 79.8 ± 21.5; P < .01). Lower exercise capacity was associated with abnormal anthropometry and >2 surgeries before Fontan was associated with delayed puberty. Lower family income (<$25 000) and hypoplastic left heart syndrome were associated with lower QoL. Compared to the normal population, Fontan survivors have high prevalence of short stature, abnormal BMI and delayed puberty. Abnormal anthropometry, but not delayed puberty, was associated with lower overall QoL and perceived physical appearance scores. Routine screening for abnormal anthropometry, especially in HLHS and in lower socioeconomic status families, should be considered to allow interventions, which might ameliorate the negative psychosocial impact. © 2018 Wiley Periodicals, Inc.

Transbaffle Mapping and Ablation for Atrial Tachycardias After Mustard, Senning, or Fontan Operations

PubMed Central

Correa, Rafael; Walsh, Edward P.; Alexander, Mark E.; Mah, Douglas Y.; Cecchin, Frank; Abrams, Dominic J.; Triedman, John K.

2013-01-01

Background In Fontan and atrial switch patients, transcatheter ablation is limited by difficult access to the pulmonary venous atrium. In recent years, transbaffle access (TBA) has been described, but limited data document its safety and utility. Methods and Results All ablative electrophysiological study cases of this population performed between January 2006 and December 2010 at Boston Children's Hospital were reviewed. Pre‐case and follow‐up clinical characteristics were documented. Adverse events were classified by severity and attributability to the intervention. We included 118 cases performed in 90 patients. TBA was attempted in 74 cases and was successful in 96%: in 20 via baffle leak or fenestration and in 51 (94%) of 54 using standard or radiofrequency transseptal techniques. There were 10 procedures with adverse events ranked as moderate or more severe. The event rate was similar in both groups (TBA 8% versus non‐TBA 9%, P=1), and no events were directly attributable to TBA. There was a trend to higher proportion of cases having a >5‐point drop in saturations from baseline in the TBA group versus the non‐TBA group in Fontan cases (15% vs 0%, P=0.14). When cases with follow‐up >90 and >365 days were analyzed, the median initial arrhythmia score of 5 significantly changed −3 points in both time periods (P≤0.001). Conclusions TBA is feasible in this population; its use was not associated with a higher incidence of adverse events; and changes in clinical scores support its efficacy. Desaturation observed in some patients is of uncertain significance but warrants postablation monitoring and prospective study. PMID:24052498

Outcomes of Patients Undergoing Primary Fontan Operation Beyond First Decade of Life.

PubMed

Talwar, Sachin; Singh, Sukhjeet; Sreenivas, Vishnubhatla; Kapoor, Kulwant Singh; Gupta, Saurabh Kumar; Ramakrishnan, Sivasubramanian; Kothari, Shyam Sunder; Saxena, Anita; Juneja, Rajnish; Choudhary, Shiv Kumar; Airan, Balram

2017-07-01

Studies on older patients undergoing primary Fontan operation (FO) are limited, with conflicting results. We review our experience with these patients beyond the first decade of life. Between January 2000 and December 2014, a total of 105 patients ≥10 years of age (mean 15.6 ± 4.9, range 10-31, median 15 years) underwent primary FO without a prior bidirectional superior cavopulmonary anastomosis (Bidirectional Glenn [BDG]). Mean preoperative New York Heart Association (NYHA) class was 2.2 ± 0.57. Operative procedure was extra-cardiac FO in 62 patients (8 were fenestrated). Forty-three had a lateral tunnel FO (26 were fenestrated). There were 11 (10.5%) early deaths. Fourteen of the 94 early survivors experienced prolonged pleural effusions, 7 had arrhythmias, and 2 had thromboembolic events. Two patients underwent Fontan takedown. On univariate analysis, NYHA functional class III, mean pulmonary artery (PA) pressure ≥15 mm Hg, hematocrit ≥60%, preoperative ventricular dysfunction, and atrioventricular valve regurgitation (AVVR) were associated with early mortality. Median follow-up was 78 (mean 88.9 ± 6.3) months. In 94 survivors, 6 (6.4%) late deaths were encountered. At last follow-up, 81 (86.2%) survivors were in NYHA class I. Actuarial survival was 84.7% ± 3.7% at 5, 10, and 15 years. Carefully selected adolescents and young adults can safely undergo the primary FO. However, persistent pleural effusions, arrhythmias, thromboembolic events, and the need for reoperation mandate regular follow-up in such patients. Preoperative NYHA functional class III, mean PA pressure ≧ 15 mm Hg, hematocrit ≥ 60%, ventricular dysfunction, and AVVR were associated with early mortality, suggesting that primary FO should be avoided in such patients.

Outcomes of cardiac pacing in adult patients after a Fontan operation.

PubMed

Egbe, Alexander C; Huntley, Geoffery D; Connolly, Heidi M; Ammash, Naser M; Deshmukh, Abhishek J; Khan, Arooj R; Said, Sameh M; Akintoye, Emmanuel; Warnes, Carole A; Kapa, Suraj

2017-12-01

Cardiac pacing can be challenging after a Fontan operation, and limited data exist regarding pacing in adult Fontan patients. The objectives of our study were to determine risk factors for pacing and occurrence of device-related complications (DRCs) and pacemaker reinterventions. We performed a retrospective review of Fontan patients from 1994 through 2014. We defined DRCs as lead failure, lead recall, cardiac perforation, lead thrombus/vegetation, or device-related infection, and cardiovascular adverse events (CAEs) as venous thrombosis, stroke, death, or heart transplant. Pacemaker reintervention was defined as lead failure or recall. Of 439 patients, 166 (38%) had pacemakers implanted (79 during childhood; 87, adulthood); 114 patients (69%) received epicardial leads initially, and 52 (31%), endocardial leads. Pacing was initially atrial in 52 patients (31%); ventricular, 30 (18%); or dual chamber, 84 (51%). There were 37 reinterventions (1.9% per year) and 48 DRCs (2.4% per year). Pacemaker implantation during childhood was a risk factor for DRCs (hazard ratio, 2.01 [CI, 1.22-5.63]; P = .03). There were 70 CAEs (venous thrombosis, 5; stroke, 11; transplant, 8; and death, 46), yielding a rate of 3.5% per year. DRCs, CAEs, and reintervention rates were comparable for patients with epicardial or endocardial leads. More than one-third of adult Fontan patients referred to Mayo Clinic had pacemaker implantation. Epicardial leads were associated with high rate of pacemaker reinterventions but similar DRC rates in comparison to endocardial leads. Copyright © 2017 Elsevier Inc. All rights reserved.

Neurological Injury and Cerebral Blood Flow in Single Ventricles Throughout Staged Surgical Reconstruction.

PubMed

Fogel, Mark A; Li, Christine; Elci, Okan U; Pawlowski, Tom; Schwab, Peter J; Wilson, Felice; Nicolson, Susan C; Montenegro, Lisa M; Diaz, Laura; Spray, Thomas L; Gaynor, J William; Fuller, Stephanie; Mascio, Christopher; Keller, Marc S; Harris, Matthew A; Whitehead, Kevin K; Bethel, Jim; Vossough, Arastoo; Licht, Daniel J

2017-02-14

Patients with a single ventricle experience a high rate of brain injury and adverse neurodevelopmental outcome; however, the incidence of brain abnormalities throughout surgical reconstruction and their relationship with cerebral blood flow, oxygen delivery, and carbon dioxide reactivity remain unknown. Patients with a single ventricle were studied with magnetic resonance imaging scans immediately prior to bidirectional Glenn (pre-BDG), before Fontan (BDG), and then 3 to 9 months after Fontan reconstruction. One hundred sixty-eight consecutive subjects recruited into the project underwent 235 scans: 63 pre-BDG (mean age, 4.8±1.7 months), 118 BDG (2.9±1.4 years), and 54 after Fontan (2.4±1.0 years). Nonacute ischemic white matter changes on T2-weighted imaging, focal tissue loss, and ventriculomegaly were all more commonly detected in BDG and Fontan compared with pre-BDG patients ( P <0.05). BDG patients had significantly higher cerebral blood flow than did Fontan patients. The odds of discovering brain injury with adjustment for surgical stage as well as ≥2 coexisting lesions within a patient decreased (63%-75% and 44%, respectively) with increasing amount of cerebral blood flow ( P <0.05). In general, there was no association of oxygen delivery (except for ventriculomegaly in the BDG group) or carbon dioxide reactivity with neurological injury. Significant brain abnormalities are commonly present in patients with a single ventricle, and detection of these lesions increases as children progress through staged surgical reconstruction, with multiple coexisting lesions more common earlier than later. In addition, this study demonstrated that BDG patients had greater cerebral blood flow than did Fontan patients and that an inverse association exists of various indexes of cerebral blood flow with these brain lesions. However, CO 2 reactivity and oxygen delivery (with 1 exception) were not associated with brain lesion development. URL: http://www.clinicaltrials.gov. Unique identifier: NCT02135081. © 2016 American Heart Association, Inc.

Long-term survival, modes of death, and predictors of mortality in patients with Fontan surgery.

PubMed

Khairy, Paul; Fernandes, Susan M; Mayer, John E; Triedman, John K; Walsh, Edward P; Lock, James E; Landzberg, Michael J

2008-01-01

To better define determinants of mortality in patients with univentricular physiology, a database registry was created of patients born in 1985 or earlier with Fontan surgery who were followed up at Children's Hospital Boston. A total of 261 patients, 121 of whom (46.4%) were women, had a first Fontan surgery at a median age of 7.9 years: right atrium-to-pulmonary artery connection in 135 (51.7%); right atrium to right ventricle in 25 (9.6%); and total cavopulmonary connection in 101 (38.7%). Over a median of 12.2 years, 76 (29.1%) died, 5 (1.9%) had cardiac transplantation, 5 (1.9%) had Fontan revision, and 21 (8.0%) had Fontan conversion. Perioperative mortality decreased steadily over time and accounted for 68.4% of all deaths. In early survivors, actuarial freedom from death or transplantation was 93.7%, 89.9%, 87.3%, and 82.6% at 5, 10, 15, and 20 years, respectively, with no significant difference between right atrium to pulmonary artery versus total cavopulmonary connection. Late deaths were classified as sudden in 7 patients (9.2%), thromboembolic in 6 (7.9%), heart failure-related in 5 (6.7%), sepsis in 2 (2.6%), and other in 4 (5.2%). Most sudden deaths were of presumed arrhythmic origin with no identifiable predictor. Independent risk factors for thromboembolic death were lack of antiplatelet or anticoagulant therapy (hazard ratio [HR], 91.6; P=0.0041) and clinically diagnosed intracardiac thrombus (HR, 22.7; P=0.0002). Independent predictors of heart failure death were protein-losing enteropathy (HR, 7.1; P=0.0043), single morphologically right ventricle (HR, 10.5; P=0.0429), and higher right atrial pressure (HR, 1.3 per 1 mm Hg; P=0.0016). In perioperative survivors of Fontan surgery, gradual attrition occurs predominantly from thromboembolic, heart failure-related, and sudden deaths.

Fontan Operation: Indications, Short and Long Term Outcomes.

PubMed

Rao, P Syamasundar

2015-12-01

Fontan operation, since its original description, has undergone a number of modifications so that it is now a staged, total cavo-pulmonary connection with fenestration. Stage I is palliation, depending upon the pathophysiology of the defect complex in early life, Stage II is bidirectional Glenn at about the age of 6 mo and Stage III is transfer of inferior vena caval blood to the pulmonary circuit along with fenestration between 2 to 4 y. Any patient that has only one functioning ventricle is a candidate for Fontan surgery. The morbidity and mortality have remarkably improved since the institution of staged, total cavo-pulmonary connection with fenestration. Complications during follow up continue to occur, though diminished with the newer modifications, and should be promptly addressed.

The Society of Thoracic Surgeons Congenital Heart Surgery Database: 2017 Update on Outcomes and Quality.

PubMed

Jacobs, Jeffrey P; Mayer, John E; Mavroudis, Constantine; O'Brien, Sean M; Austin, Erle H; Pasquali, Sara K; Hill, Kevin D; Overman, David M; St Louis, James D; Karamlou, Tara; Pizarro, Christian; Hirsch-Romano, Jennifer C; McDonald, Donna; Han, Jane M; Becker, Susan; Tchervenkov, Christo I; Lacour-Gayet, Francois; Backer, Carl L; Fraser, Charles D; Tweddell, James S; Elliott, Martin J; Walters, Hal; Jonas, Richard A; Prager, Richard L; Shahian, David M; Jacobs, Marshall L

2017-03-01

The Society of Thoracic Surgeons Congenital Heart Surgery Database is the largest congenital and pediatric cardiac surgical clinical data registry in the world. It is the platform for all activities of The Society of Thoracic Surgeons related to the analysis of outcomes and the improvement of quality in this subspecialty. This report summarizes current aggregate national outcomes in congenital and pediatric cardiac surgery and reviews related activities in the areas of quality measurement, performance improvement, and transparency. The reported data about aggregate national outcomes are exemplified by an analysis of 10 benchmark operations performed from January 2012 to December 2015. This analysis documents the overall aggregate operative mortality (interquartile range among all participating programs) for the following procedural groups: off-bypass coarctation repair, 1.3% (0.0% to 1.8%); ventricular septal defect repair, 0.6% (0.0% to 0.9%); tetralogy of Fallot repair, 1.1% (0.0% to 1.4%); complete atrioventricular canal repair, 3.0% (0.0% to 4.7%); arterial switch operation, 2.7% (0.0% to 4.1%); arterial switch operation and ventricular septal defect repair, 5.3% (0.0% to 6.7%); Glenn/hemi-Fontan, 2.5% (0.0% to 4.5%); Fontan operation, 1.2% (0.0% to 1.2%); truncus arteriosus repair, 9.4% (0.0% to 16.7%); and Norwood procedure, 15.7% (8.9% to 25.0%). Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Fontan Surgical Planning: Previous Accomplishments, Current Challenges, and Future Directions.

PubMed

Trusty, Phillip M; Slesnick, Timothy C; Wei, Zhenglun Alan; Rossignac, Jarek; Kanter, Kirk R; Fogel, Mark A; Yoganathan, Ajit P

2018-04-01

The ultimate goal of Fontan surgical planning is to provide additional insights into the clinical decision-making process. In its current state, surgical planning offers an accurate hemodynamic assessment of the pre-operative condition, provides anatomical constraints for potential surgical options, and produces decent post-operative predictions if boundary conditions are similar enough between the pre-operative and post-operative states. Moving forward, validation with post-operative data is a necessary step in order to assess the accuracy of surgical planning and determine which methodological improvements are needed. Future efforts to automate the surgical planning process will reduce the individual expertise needed and encourage use in the clinic by clinicians. As post-operative physiologic predictions improve, Fontan surgical planning will become an more effective tool to accurately model patient-specific hemodynamics.

A tribute to francis fontan, MD, and guillermo kreutzer, MD.

PubMed

Mavroudis, Constantine

2012-04-01

At the Third Scientific Meeting of the World Society for Pediatric and Congenital Heart Surgery in June 2011 in Istanbul, Turkey, Professor Francis Fontan and Dr Guillermo Kreutzer were honored for their contributions to the world of pediatric and congenital heart surgery. The presentation included a video of each physician being interviewed about their clinical and historical experiences. The presentation and videos are summarized herein.

Can a Home-based Cardiac Physical Activity Program Improve the Physical Function Quality of Life in Children with Fontan Circulation?

PubMed

Jacobsen, Roni M; Ginde, Salil; Mussatto, Kathleen; Neubauer, Jennifer; Earing, Michael; Danduran, Michael

2016-01-01

Patients after Fontan operation for complex congenital heart disease (CHD) have decreased exercise capacity and report reduced health-related quality of life (HRQOL). Studies suggest hospital-based cardiac physical activity programs can improve HRQOL and exercise capacity in patients with CHD; however, these programs have variable adherence rates. The impact of a home-based cardiac physical activity program in Fontan survivors is unclear. This pilot study evaluated the safety, feasibility, and benefits of an innovative home-based physical activity program on HRQOL in Fontan patients. A total of 14 children, 8-12 years, with Fontan circulation enrolled in a 12-week moderate/high intensity home-based cardiac physical activity program, which included a home exercise routine and 3 formalized in-person exercise sessions at 0, 6, and 12 weeks. Subjects and parents completed validated questionnaires to assess HRQOL. The Shuttle Test Run was used to measure exercise capacity. A Fitbit Flex Activity Monitor was used to assess adherence to the home activity program. Of the 14 patients, 57% were male and 36% had a dominant left ventricle. Overall, 93% completed the program. There were no adverse events. Parents reported significant improvement in their child's overall HRQOL (P < .01), physical function (P < .01), school function (P = .01), and psychosocial function (P < .01). Patients reported no improvement in HRQOL. Exercise capacity, measured by total shuttles and exercise time in the Shuttle Test Run and calculated VO2 max, improved progressively from baseline to the 6 and 12 week follow up sessions. Monthly Fitbit data suggested adherence to the program. This 12-week home-based cardiac physical activity program is safe and feasible in preteen Fontan patients. Parent proxy-reported HRQOL and objective measures of exercise capacity significantly improved. A 6-month follow up session is scheduled to assess sustainability. A larger study is needed to determine the applicability and reproducibility of these findings in other age groups and forms of complex CHD. © 2016 Wiley Periodicals, Inc.

Simulation of Ventricular, Cavo-Pulmonary, and Biventricular Ventricular Assist Devices in Failing Fontan.

PubMed

Di Molfetta, Arianna; Amodeo, Antonio; Fresiello, Libera; Trivella, Maria Giovanna; Iacobelli, Roberta; Pilati, Mara; Ferrari, Gianfranco

2015-07-01

Considering the lack of donors, ventricular assist devices (VADs) could be an alternative to heart transplantation for failing Fontan patients, in spite of the lack of experience and the complex anatomy and physiopathology of these patients. Considering the high number of variables that play an important role such as type of Fontan failure, type of VAD connection, and setting (right VAD [RVAD], left VAD [LVAD], or biventricular VAD [BIVAD]), a numerical model could be useful to support clinical decisions. The aim of this article is to develop and test a lumped parameter model of the cardiovascular system simulating and comparing the VAD effects on failing Fontan. Hemodynamic and echocardiographic data of 10 Fontan patients were used to simulate the baseline patients' condition using a dedicated lumped parameter model. Starting from the simulated baseline and for each patient, a systolic dysfunction, a diastolic dysfunction, and an increment of the pulmonary vascular resistance were simulated. Then, for each patient and for each pathology, the RVAD, LVAD, and BIVAD implantations were simulated. The model can reproduce patients' baseline well. In the case of systolic dysfunction, the LVAD unloads the single ventricle and increases the cardiac output (CO) (35%) and the arterial systemic pressure (Pas) (25%). With RVAD, a decrement of inferior vena cava pressure (Pvci) (39%) was observed with 34% increment of CO, but an increment of the single ventricle external work (SVEW). With the BIVAD, an increment of Pas (29%) and CO (37%) was observed. In the case of diastolic dysfunction, the LVAD increases CO (42%) and the RVAD decreases the Pvci, while both increase the SVEW. In the case of pulmonary vascular resistance increment, the highest CO (50%) and Pas (28%) increment is obtained with an RVAD with the highest decrement of Pvci (53%) and an increment of the SVEW but with the lowest VAD power consumption. The use of numerical models could be helpful in this innovative field to evaluate the effect of VAD implantation on Fontan patients to support patient and VAD type selection personalizing the assistance. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Arterialised hepatic nodules in the Fontan circulation: hepatico-cardiac interactions.

PubMed

Bryant, Timothy; Ahmad, Zaheer; Millward-Sadler, Harry; Burney, Kashif; Stedman, Brian; Kendall, Tim; Vettukattil, Joseph; Haw, Marcus; Salmon, Anthony P; Cope, Richard; Hacking, Nigel; Breen, David; Sheron, Nick; Veldtman, Gruschen R

2011-09-15

Hypervascular nodules occur commonly when there is hepatic venous outlet obstruction. Their nature and determinants in the Fontan circulation is poorly understood. We reviewed the records of 27 consecutive Fontan patients who had computerized tomography scan (CT) over a 4 year period for arterialised nodules and alterations in hepatic flow patterns during contrast enhanced CT scans and related these findings to cardiac characteristics. Mean patient age was 24 ± 5.8 years, (range 16.7-39.8) and mean Fontan duration was 16.8 ± 4.8 years (range 7.3-28.7). Twenty-two patients demonstrated a reticular pattern of enhancement, 4 a zonal pattern and only 1 demonstrated normal enhancement pattern. Seven (26%) patients had a median of 4 (range 1-22) arterialised nodules, mean size 1.8 cm (range 0.5 to 3.2 cm). All nodules were located in the liver periphery, their outer aspect lying within 2 cm of the liver margin. Patients with nodules had higher mean RA pressures (18 mmHg ± 5.6 vs. 13 mmHg ± 4, p=0.025), whereas their mixed venous saturation and aortic saturation was not significantly different (70% ± 11 vs. 67% ± 9 and 92% ± 10 vs. 94% ± 4, p>0.05). Post-mortem histology suggests focal nodular hyperplasia is the underlying pathology. ConclusionsAbnormalities of hepatic blood flow and the presence of arterialised nodules are common in the failing Fontan circulation. They occur especially when central venous pressures are high, and very likely indicate arterialisation of hepatic blood flow and reciprocal portal venous deprivation. The underlying pathology is most likely focal nodular hyperplasia. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Evaluation of blood flow distribution asymmetry and vascular geometry in patients with Fontan circulation using 4-D flow MRI

PubMed Central

Jarvis, Kelly; Schnell, Susanne; Barker, Alex J.; Garcia, Julio; Lorenz, Ramona; Rose, Michael; Chowdhary, Varun; Carr, James; Robinson, Joshua D.; Rigsby, Cynthia K.; Markl, Michael

2016-01-01

Background Asymmetrical caval to pulmonary blood flow is suspected to cause complications in patients with Fontan circulation. The aim of this study was to test the feasibility of 4-D flow MRI for characterizing the relationship between 3-D blood flow distribution and vascular geometry. Objective We hypothesized that both flow distribution and geometry can be calculated with low interobserver variability and will detect a direct relationship between flow distribution and Fontan geometry. Materials and methods Four-dimensional flow MRI was acquired in 10 Fontan patients (age: 16±4 years [mean ± standard deviation; range 9–21 years]). The Fontan connection was isolated by 3-D segmentation to evaluate flow distribution from the inferior vena cava (IVC) and superior vena cava (SVC) to the left and right pulmonary arteries (LPA, RPA) and to characterize geometry (cross-sectional area, caval offset, vessel angle). Results Flow distribution results indicated SVC flow tended toward the RPA while IVC flow was more evenly distributed (SVC to RPA: 78%±28 [9–100], IVC to LPA: 54%±28 [4–98]). There was a significant relationship between pulmonary artery cross-sectional area and flow distribution (IVC to RPA: R2=0.50, P=0.02; SVC to LPA: R2=0.81, P=0.0004). Good agreement was found between observers and for flow distribution when compared to net flow values. Conclusion Four-dimensional (4-D) flow MRI was able to detect relationships between flow distribution and vessel geometry. Future studies are warranted to investigate the potential of patient specific hemodynamic analysis to improve diagnostic capability. PMID:27350377

Experimental measurements of energy augmentation for mechanical circulatory assistance in a patient-specific Fontan model.

PubMed

Chopski, Steven G; Rangus, Owen M; Moskowitz, William B; Throckmorton, Amy L

2014-09-01

A mechanical blood pump specifically designed to increase pressure in the great veins would improve hemodynamic stability in adolescent and adult Fontan patients having dysfunctional cavopulmonary circulation. This study investigates the impact of axial-flow blood pumps on pressure, flow rate, and energy augmentation in the total cavopulmonary circulation (TCPC) using a patient-specific Fontan model. The experiments were conducted for three mechanical support configurations, which included an axial-flow impeller alone in the inferior vena cava (IVC) and an impeller with one of two different protective stent designs. All of the pump configurations led to an increase in pressure generation and flow in the Fontan circuit. The increase in IVC flow was found to augment pulmonary arterial flow, having only a small impact on the pressure and flow in the superior vena cava (SVC). Retrograde flow was neither observed nor measured from the TCPC junction into the SVC. All of the pump configurations enhanced the rate of power gain of the cavopulmonary circulation by adding energy and rotational force to the fluid flow. We measured an enhancement of forward flow into the TCPC junction, reduction in IVC pressure, and only minimally increased pulmonary arterial pressure under conditions of pump support. Copyright © 2014 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Hybrid procedures for an infant with hypoplastic left heart syndrome with intact atrial septum.

PubMed

Suzuki, Shoji; Kise, Hiroaki; Kaga, Shigeaki; Hoshiai, Minako; Koizumi, Keiichi; Hasebe, Yohei; Motohashi, Shinya; Matsumoto, Masahiko

2015-08-01

A boy, prenatally diagnosed as hypoplastic left heart syndrome (HLHS) with intact atrial septum (IAS) was successfully treated by hybrid procedures. He underwent emergent catheter atrial septostomy and stent insertion in the atrial septum on Day 1 and then underwent bilateral pulmonary artery banding, ductal stent insertion, modified Norwood operation, bidirectional Glenn's operation and finally Fontan type operation at 2 years of age. Considering the presence of decompression pathway from the left atrium in HLHS with IAS, we should organize a treatment team for collaborative work and plan an appropriate treatment strategy before delivery. Although his clinical course has been uneventful until now, closer medical observation is warranted because he may have coexisting pulmonary disease.

Fluid-structure interaction simulations of the Fontan procedure using variable wall properties.

PubMed

Long, C C; Hsu, M-C; Bazilevs, Y; Feinstein, J A; Marsden, A L

2012-05-01

Children born with single ventricle heart defects typically undergo a staged surgical procedure culminating in a total cavopulmonary connection (TCPC) or Fontan surgery. The goal of this work was to perform physiologic, patient-specific hemodynamic simulations of two post-operative TCPC patients by using fluid-structure interaction (FSI) simulations. Data from two patients are presented, and post-op anatomy is reconstructed from MRI data. Respiration rate, heart rate, and venous pressures are obtained from catheterization data, and inflow rates are obtained from phase contrast MRI data and are used together with a respiratory model. Lumped parameter (Windkessel) boundary conditions are used at the outlets. We perform FSI simulations by using an arbitrary Lagrangian-Eulerian finite element framework to account for motion of the blood vessel walls in the TCPC. This study is the first to introduce variable elastic properties for the different areas of the TCPC, including a Gore-Tex conduit. Quantities such as wall shear stresses and pressures at critical locations are extracted from the simulation and are compared with pressure tracings from clinical data as well as with rigid wall simulations. Hepatic flow distribution and energy efficiency are also calculated and compared for all cases. There is little effect of FSI on pressure tracings, hepatic flow distribution, and time-averaged energy efficiency. However, the effect of FSI on wall shear stress, instantaneous energy efficiency, and wall motion is significant and should be considered in future work, particularly for accurate prediction of thrombus formation. Copyright © 2012 John Wiley & Sons, Ltd.

Multiblock High Order Large Eddy Simulation of Powered Fontan Hemodynamics: Towards Computational Surgery

PubMed Central

Delorme, Yann T.; Rodefeld, Mark D.; Frankel, Steven H.

2016-01-01

Children born with only one functional ventricle must typically undergo a series of three surgeries to obtain the so-called Fontan circulation in which the blood coming from the body passively flows from the Vena Cavae (VCs) to the Pulmonary Arteries (PAs) through the Total Cavopulmonary Connection (TCPC). The circulation is inherently inefficient due to the lack of a subpulmonary ventricle. Survivors face the risk of circulatory sequelae and eventual failure for the duration of their lives. Current efforts are focused on improving the outcomes of Fontan palliation, either passively by optimizing the TCPC, or actively by using mechanical support. We are working on a chronic implant that would be placed at the junction of the TCPC, and would provide the necessary pressure augmentation to re-establish a circulation that recapitulates a normal two-ventricle circulation. This implant is based on the Von Karman viscous pump and consists of a vaned impeller that rotates inside the TCPC. To evaluate the performance of such a device, and to study the flow features induced by the presence of the pump, Computational Fluid Dynamics (CFD) is used. CFD has become an important tool to understand hemodynamics owing to the possibility of simulating quickly a large number of designs and flow conditions without any harm for patients. The transitional and unsteady nature of the flow can make accurate simulations challenging. We developed and in-house high order Large Eddy Simulation (LES) solver coupled to a recent Immersed Boundary Method (IBM) to handle complex geometries. Multiblock capability is added to the solver to allow for efficient simulations of complex patient specific geometries. Blood simulations are performed in a complex patient specific TCPC geometry. In this study, simulations without mechanical assist are performed, as well as after virtual implantation of the temporary and chronic implants being developed. Instantaneous flow structures, hepatic factor distribution, and statistical data are presented for all three cases. PMID:28649147

Staged Single Ventricle Palliation and Homozygous Sickle Cell Disease.

PubMed

Maddali, Madan Mohan; Junghare, Minakshi Sandip; Nishant, Arora Ram; Kandachar, Pranav Subbaraya; Valliattu, Johan

2016-04-01

Hypoxemia is a well-known trigger for precipitating a sickling crisis in patients with sickle cell disease. Patients undergoing staged single ventricle palliation have hypoxemia during the initial stages of the Fontan pathway. The successful completion of staged single ventricle palliation in a child with a combination of homozygous sickle cell disease and a single ventricle physiology that tolerate prolonged hypoxemia during earlier stages of Fontan pathway is described. © 2016 Wiley Periodicals, Inc.

Comparison of echocardiographic and cardiac magnetic resonance imaging measurements of functional single ventricular volumes, mass, and ejection fraction (from the Pediatric Heart Network Fontan Cross-Sectional Study).

PubMed

Margossian, Renee; Schwartz, Marcy L; Prakash, Ashwin; Wruck, Lisa; Colan, Steven D; Atz, Andrew M; Bradley, Timothy J; Fogel, Mark A; Hurwitz, Lynne M; Marcus, Edward; Powell, Andrew J; Printz, Beth F; Puchalski, Michael D; Rychik, Jack; Shirali, Girish; Williams, Richard; Yoo, Shi-Joon; Geva, Tal

2009-08-01

Assessment of the size and function of a functional single ventricle (FSV) is a key element in the management of patients after the Fontan procedure. Measurement variability of ventricular mass, volume, and ejection fraction (EF) among observers by echocardiography and cardiac magnetic resonance imaging (CMR) and their reproducibility among readers in these patients have not been described. From the 546 patients enrolled in the Pediatric Heart Network Fontan Cross-Sectional Study (mean age 11.9 +/- 3.4 years), 100 echocardiograms and 50 CMR studies were assessed for measurement reproducibility; 124 subjects with paired studies were selected for comparison between modalities. Interobserver agreement for qualitative grading of ventricular function by echocardiography was modest for left ventricular (LV) morphology (kappa = 0.42) and weak for right ventricular (RV) morphology (kappa = 0.12). For quantitative assessment, high intraclass correlation coefficients were found for echocardiographic interobserver agreement (LV 0.87 to 0.92, RV 0.82 to 0.85) of systolic and diastolic volumes, respectively. In contrast, intraclass correlation coefficients for LV and RV mass were moderate (LV 0.78, RV 0.72). The corresponding intraclass correlation coefficients by CMR were high (LV 0.96, RV 0.85). Volumes by echocardiography averaged 70% of CMR values. Interobserver reproducibility for the EF was similar for the 2 modalities. Although the absolute mean difference between modalities for the EF was small (<2%), 95% limits of agreement were wide. In conclusion, agreement between observers of qualitative FSV function by echocardiography is modest. Measurements of FSV volume by 2-dimensional echocardiography underestimate CMR measurements, but their reproducibility is high. Echocardiographic and CMR measurements of FSV EF demonstrate similar interobserver reproducibility, whereas measurements of FSV mass and LV diastolic volume are more reproducible by CMR.

An artificial right ventricle for failing fontan: in vitro and computational study.

PubMed

Lacour-Gayet, François G; Lanning, Craig J; Stoica, Serban; Wang, Rui; Rech, Bryan A; Goldberg, Steven; Shandas, Robin

2009-07-01

The aim of this study is to develop a destination low-pressure artificial right ventricle (ARV) to correct the impaired hemodynamics in the failing Fontan circulation. An in vitro model circuit of the Fontan circulation was created to reproduce the hemodynamics of the failing Fontan and test ARV performance under various central venous pressures (CVP) and flows. A novel geometry of the extracardiac conduit was designed to adapt to the need of the pump. The ARV was a low-pressure axial flow pump designed to produce a low suction inflow pressure and moderate outflow increase. With the power off, the passive forward gradient across the propeller is 2 mm Hg at 4.5 L/min. The ARV would require 4 watts at a rotation of 5000 rpm. To examine the shear loading on the red blood cells, virtual particles were injected upstream of the ARV inducer and tracked by computerized modeling. The effect of the ARV on the failing Fontan was studied at various CVP pressures and flows, and under constant values of lung resistances and left atrial pressure set respectively to 2.5 Woods Units and 7 mm Hg. The CVP pressures decreased respectively from 25, 22.5, 20, 17.5, 15, and 10 mm Hg to a minimal value of 2 to 5 mm Hg with a pump speed varying from 1700 to 4500 rpm. The pulmonary artery pressures increased moderately between 12.5 and 25 mm Hg at 4500 rpm. Cardiac output at 4500 rpm was increased by an average gain of 2 L/min. The average blood damage index was 0.92%, far below the 5% value considered to cause hemolysis. The flow structure produced by the pump was suitable. The performance of this novel low-pressure ARV was satisfactory, showing good decrease of CVP pressures, a moderate increase of pulmonary artery pressures, adequate increase of cardiac output, and minimal hemolysis. The use of a mock Fontan model circuit facilitates device prototyping and design to a far greater extent than can be achieved using animal studies, and is an essential first step for rapid design iteration of a novel ARV device. The next steps are the manufacturing of this device, including an electromagnetic engine, a regulatory system, and further testing the device in a survival animal experiment.

Heart transplantation for adults with congenital heart disease: current status and future prospects.

PubMed

Matsuda, Hikaru; Ichikawa, Hajime; Ueno, Takayoshi; Sawa, Yoshiki

2017-06-01

Increased survival rates after corrective or palliative surgery for complex congenital heart disease (CHD) in infancy and childhood are now being coupled with increased numbers of patients who survive to adulthood with various residual lesions or sequelae. These patients are likely to deteriorate in cardiac function or end-organ function, eventually requiring lifesaving treatment including heart transplantation. Although early and late outcomes of heart transplantation have been improving for adult survivors of CHD, outcomes and pretransplant management could still be improved. Survivors of Fontan procedures are a vulnerable cohort, particularly when single ventricle physiology fails, mostly with protein-losing enteropathy and hepatic dysfunction. Therefore, we reviewed single-institution and larger database analyses of adults who underwent heart transplantation for CHD, to enable risk stratification by identifying the indications and outcomes. As the results, despite relatively high early mortality, long-term results were encouraging after heart transplantation. However, further investigations are needed to improve the indication criteria for complex CHD, especially for failed Fontan. In addition, the current system of status criteria and donor heart allocation system in heart transplantation should be arranged as suitable for adults with complex CHD. Furthermore, there is a strong need to develop ventricular assist devices as a bridge to transplantation or destination therapy, especially where right-sided circulatory support is needed.

Cytochrome P450 2C9 gene polymorphism and warfarin maintenance dosage in pediatric patients: A systematic review and meta-analysis.

PubMed

Zhang, Jinhua; Tian, Lihong; Huang, Jinlong; Huang, Sihan; Chai, Tingting; Shen, Jianzhen

2017-02-01

To assess the effect of Cytochrome P450 2C9 (CYP2C9) gene polymorphism on pediatric warfarin maintenance dosage requirement. A previously developed search strategy was conducted in PubMed, EMBASE, and the Cochrane Library. Eligible studies published prior to January 27, 2016, were identified and compared against strict inclusion/exclusion criteria. Required data were extracted, and researchers were consulted for additional data if needed. Review Manager version 5.2.3 software was used to analyze the relationship between CYP2C9 polymorphisms and warfarin maintenance doses in pediatric patients. Eight articles with a combined total of 507 pediatric patients were included in the meta-analysis. Maintenance warfarin doses in patients with CYP2C9 *1/*2 genotype, CYP2C9 *1/*3 genotype, and CYP2C9 variant carriers which contain at least one variant allele (*2 or *3) were from 15% to 41% lower than doses in patients with the wild-type allele (CYP2C9 *1/*1): All differences were significant with P-values <.05. The Fontan procedure as a medical indication for anticoagulation was also associated with a lower warfarin maintenance dose; however, target INR range was not. We found that CYP2C9 gene polymorphism (referring to the presence of *1/*2, *1/*3, and variant genotypes in the population in addition to the wild type) was significantly associated with decreased warfarin maintenance dose requirements. Additionally, a specific indication for warfarin, the Fontan procedure, was associated with a lower daily warfarin dose. However, the results of our study require confirmation from more research with larger numbers of pediatric patients. © 2016 John Wiley & Sons Ltd.

Atrial cardiomyoplasty in a Fontan circulation.

PubMed

Voss, Bernhard; Sack, Falk-Udo; Saggau, Werner; Hagl, Siegfried; Lange, Rüdiger

2002-05-01

The Fontan circulation is a direct connection between the systemic veins and the pulmonary artery (PA). Consequently, the pulmonary flow is passive due to the gradient between the right and left atrial pressure. In patients with increased pulmonary vascular resistance, the surgical procedure of atrio-pulmonary connection is therefore prone to failure. The goal of this experiment was to increase the pulmonary flow in an experimental model of a Fontan circulation by performing a right atrial cardiomyoplasty (ACMP). In 19 Foxhounds the left m. latissimus dorsi (LD) was mobilised and transferred as a pedicle into the chest. After sternotomy a 'Fontan circulation' was created under cardiopulmonary bypass (CPB) by connecting the right atrium (RA) with the PA by a valveless conduit. The tricuspid valve was closed with a patch. In 11 dogs (group 1) a valve was implanted in the inferior vena cava (IVC) and pulmonary inflow impedance was increased by partial occlusion of the conduit to a gradient of 10 mmHg between RA and PA. In the other eight dogs (group 2) no valve was implanted, but flowmeters were placed in the IVC and the superior vena cava (SVC). In all dogs the RA was enlarged by a fascia lata patch before the LD was wrapped over the RA and stimulated synchronously to the R-wave with burst impulses. After coming off CPB, relatively high central venous pressures (22.5+/-5.8 mmHg) were necessary to maintain haemodynamic stability. With LD-stimulation in a 1:3 mode in group 1, RA pressure (P) increased from 23.1+/-7.7 to 45+/-10.5 mmHg (P<0.001), pulmonary atrial pressure (PAP) from 15.5+/-4.3 to 25.5+/-7.6 mmHg (P<0.001) and central venous pressure increased to 33.1+/-11.3 mmHg (P<0.05). Stroke volume increase from 11.4+/-4.7 to 17.2+/-4.3 ml and peak conduit-flow from 1286.3+/-880.3 to 2329+/-1173 ml/min (all P<0.001). In a 1:1 stimulation mode a pulsatile pressure/flow profile was obtained in the PA-conduit. Furthermore, at higher frequencies of about 120 beats/min muscle relaxation was still fast enough as not to interfere with the RA filling. In group 2 caval flow without stimulation occurred mainly during diastole. However, with LD-stimulation, a strong backflow into IVC and SVC was observed resulting in a less pronounced pressure/flow increase in the PA. Our experimental model demonstrates the possibility of a 'ventricularisation' of the RA by using the force of the LD. However, the haemodynamic benefit of ACMP was achieved only, when a valve was implanted in the ICV.

Proposal for Prevention or Alleviation of Protein/Lymph-Losing Enteropathy (PLE/LLE) After Fontan Circulation Treatment of Univentricular Hearts: Restoration of Lymph Balance With a "Lymphatic Right-to-Left Shunt."

PubMed

James, H; Witte, M H; Bernas, M; Barber, B

2016-09-01

In Fontan circulations created for univentricular hearts, systemic venous return is diverted to the lungs before returning to the heart. The Total Cavopulmonary Connection (TCPC) is often the preferred surgical procedure whereby a 4-way anastomosis is created with inflow from the superior vena cava (SVC) and inferior vena cava (IVC) and outflow to the right and left branches of the pulmonary artery. In this arrangement, the systemic venous pressure must be elevated sufficiently to perfuse the lungs passively without the normal boost of the right ventricle. Hence, unlike surgical corrections for other congenital heart conditions, the systemic venous pressures in a Fontan circuit must be elevated to make the circulation work. It is proposed here that the incidence of PLE/LLE is directly related to elevated venous and lymphatic pressures, which cause leakage of proteins/lymph into the gastrointestinal tract (GIT) and expulsion from the body. It is commonly held that elevated venous pressures are relatively better tolerated in the upper body, but much less so in the heptatosplanchnic circulation and the lower body. It is also well established that elevated venous pressure increases lymph formation, most of which is produced in the hepatosplanchnic region (liver and intestine). It is further argued here that the increase in lymph filling pressure arising from the higher lymph flow, in association with the backpressure exerted by elevated venous pressure at the main drainage point into the venous system, results in a substantial increase in pressure in the thoracic duct. This pressure is transmitted back to the intestinal lymphatics, causing dilatation with lacteal rupture and protein or bulk lymph leakage into the intestine. We propose in this paper a new approach, based on experimental evidence, to prevent and/or alleviate this condition by draining or redirecting the thoracic duct (or, alternatively, a more localized intestinal lymphatic vessel) into one of the pulmonary veins or the left atrium, which are typically at near-normal pressure in a Fontan circulation. This “lymphatic-venous right-to-left” shunt maneuver would significantly reduce the venous backpressure on the lymphatics as well as improve lymph circulation, resulting in a decrease in the intestinal lymphatic pressure and thereby prevent or alleviate protein/lymph loss, i.e. lymph balance would be restored. Moreover, the greatly facilitated lymphatic flow would encourage further capillary filtration to relieve excessive venous pressure in the hepatosplanchnic region and protect the liver and kidneys. This paper is intended as a discussion document for elicitation of comments on the soundness and viability of this proposal as well as on technical challenges and steps to explore and advance it.

Pacing and Defibrillators in Complex Congenital Heart Disease

PubMed Central

Chubb, Henry; O’Neill, Mark; Rosenthal, Eric

2016-01-01

Device therapy in the complex congenital heart disease (CHD) population is a challenging field. There is a myriad of devices available, but none designed specifically for the CHD patient group, and a scarcity of prospective studies to guide best practice. Baseline cardiac anatomy, prior surgical and interventional procedures, existing tachyarrhythmias and the requirement for future intervention all play a substantial role in decision making. For both pacing systems and implantable cardioverter defibrillators, numerous factors impact on the merits of system location (endovascular versus non-endovascular), lead positioning, device selection and device programming. For those with Fontan circulation and following the atrial switch procedure there are also very specific considerations regarding access and potential complications. This review discusses the published guidelines, device indications and the best available evidence for guidance of device implantation in the complex CHD population. PMID:27403295

Mechanical support of total cavopulmonary connection with an axial flow pump.

PubMed

Riemer, R Kirk; Amir, Gabriel; Reichenbach, Steven H; Reinhartz, Olaf

2005-08-01

Even under optimal circumstances, total cavopulmonary connection is associated with a continuous late risk of death. Hemodynamics are distinctly abnormal, with increased systemic venous pressures and frequent low cardiac output. Our study uses a sheep model of total cavopulmonary connection to test the response to axial flow pump (Thoratec HeartMate II; Thoratec Corporation (Pleasanton, Calif)) support of total cavopulmonary connection, which might be suitable to treat patients with failing Fontan circulation. Eight sheep (42-48 kg) were studied. After pilot studies in 3 animals, 5 underwent both pump-supported and nonsupported total cavopulmonary connection in alternating sequence for up to 2 hours. This was achieved with a 12-mm polytetrafluoroethylene graft from the (distally ligated) superior vena cava to the main pulmonary artery and a cannula placed in the inferior vena cava with an attached 16-mm Dacron graft to the main pulmonary artery. Pressures (arterial, inferior vena cava, left atrium, and pulmonary artery) and flows (ascending aorta and inferior vena cava) were recorded over 1 hour both with unsupported total cavopulmonary connection and after placing an axial flow pump (Thoratec HeartMate II) between the inferior vena caval inflow cannula and the main pulmonary artery. Under nonsupported total cavopulmonary connection circulation, inferior vena caval and aortic blood flow decreased by nearly 50%. Inferior vena caval pressure nearly doubled, whereas arterial pressure decreased by one third. Pulmonary artery pressure became nonpulsatile; however, mean pulmonary artery pressure and left atrial pressure did not change significantly. With pump-supported Fontan circulation, cardiac output, inferior vena caval flow, and arterial pressure returned to baseline. Inferior vena caval pressure decreased to below baseline levels. Mean pulmonary artery pressure and left atrial pressure again remained unchanged. Axial flow pump support from the inferior vena cava to the pulmonary artery can prevent the substantial decrease of aortic flow and pressure associated with total cavopulmonary connection and can reverse its poor hemodynamics. This is a simple model that can be used to further evaluate the potential of mechanical support as a treatment option in failing Fontan circulation.

Social media methods for studying rare diseases.

PubMed

Schumacher, Kurt R; Stringer, Kathleen A; Donohue, Janet E; Yu, Sunkyung; Shaver, Ashley; Caruthers, Regine L; Zikmund-Fisher, Brian J; Fifer, Carlen; Goldberg, Caren; Russell, Mark W

2014-05-01

For pediatric rare diseases, the number of patients available to support traditional research methods is often inadequate. However, patients who have similar diseases cluster "virtually" online via social media. This study aimed to (1) determine whether patients who have the rare diseases Fontan-associated protein losing enteropathy (PLE) and plastic bronchitis (PB) would participate in online research, and (2) explore response patterns to examine social media's role in participation compared with other referral modalities. A novel, internet-based survey querying details of potential pathogenesis, course, and treatment of PLE and PB was created. The study was available online via web and Facebook portals for 1 year. Apart from 2 study-initiated posts on patient-run Facebook pages at the study initiation, all recruitment was driven by study respondents only. Response patterns and referral sources were tracked. A total of 671 respondents with a Fontan palliation completed a valid survey, including 76 who had PLE and 46 who had PB. Responses over time demonstrated periodic, marked increases as new online populations of Fontan patients were reached. Of the responses, 574 (86%) were from the United States and 97 (14%) were international. The leading referral sources were Facebook, internet forums, and traditional websites. Overall, social media outlets referred 84% of all responses, making it the dominant modality for recruiting the largest reported contemporary cohort of Fontan patients and patients who have PLE and PB. The methodology and response patterns from this study can be used to design research applications for other rare diseases. Copyright © 2014 by the American Academy of Pediatrics.

Control of respiration-driven retrograde flow in the subdiaphragmatic venous return of the Fontan circulation

PubMed Central

Vukicevic, M; Conover, T; Jaeggli, M; Zhou, J; Pennati, G; Hsia, TY; Figliola, RS

2014-01-01

Respiration influences the subdiaphragmatic venous return in the total cavopulmonary connection (TCPC) of the Fontan circulation whereby both the inferior vena cava (IVC) and hepatic vein flows can experience retrograde motion. Controlling retrograde flows could improve patient outcomes. Using a patient-specific model within a Fontan mock circulatory system with respiration, we inserted a valve into the IVC to examine its effects on local hemodynamics while varying retrograde volumes by changing vascular impedances. A bovine valved conduit reduced IVC retrograde flow to within 3% of antegrade flow in all cases. The valve closed only under conditions supporting retrograde flow and its effects on local hemodynamics increased with larger retrograde volume. Liver and TCPC pressures improved only while the valve leaflets were closed while cycle-averaged pressures improved only slightly (italic>1 mm Hg). Increased pulmonary vascular resistance raised mean circulation pressures but the valve functioned and cardiac output improved and stabilized. Power loss across the TCPC improved by 12–15% (pbold>0.05) with a valve. The effectiveness of valve therapy is dependent on patient vascular impedance. PMID:24814833

New concepts: development of a survivorship programme for patients with a functionally univentricular heart.

PubMed

Goldberg, David J; Dodds, Kathryn; Rychik, Jack

2011-12-01

Children with functionally univentricular hearts are now surviving into their third and fourth decades of life. Although survival alone is a remarkable achievement, a lot must still be done to improve the quality and duration of life after the Fontan operation. Challenges that may be faced by these patients include the impact of the Fontan operation on the liver and the density of bone, protein-losing enteropathy, and plastic bronchitis. Paediatric cardiologists are familiar with the haemodynamic issues inherent in Fontan physiology; however, training in cardiology is often not sufficient to give us a complete understanding of the pathophysiology of the complications or of the options for treatment. Collaboration with other subspecialists including gastroenterologists, endocrinologists, and pulmonologists is essential in order to provide the rigorous and nuanced care that our patients need and deserve. A clinic in which a patient can see multiple subspecialists, and in which the subspecialists, as a group, can discuss each patient, can provide a unique and valuable service for patients with a functionally univentricular heart.

Impact of empiric nesiritide or milrinone infusion on early postoperative recovery after Fontan surgery: a randomized, double-blind, placebo-controlled trial.

PubMed

Costello, John M; Dunbar-Masterson, Carolyn; Allan, Catherine K; Gauvreau, Kimberlee; Newburger, Jane W; McGowan, Francis X; Wessel, David L; Mayer, John E; Salvin, Joshua W; Dionne, Roger E; Laussen, Peter C

2014-07-01

We sought to determine whether empirical nesiritide or milrinone would improve the early postoperative course after Fontan surgery. We hypothesized that compared with milrinone or placebo, patients assigned to receive nesiritide would have improved early postoperative outcomes. In a single-center, randomized, double-blinded, placebo-controlled, multi-arm parallel-group clinical trial, patients undergoing primary Fontan surgery were assigned to receive nesiritide, milrinone, or placebo. A loading dose of study drug was administered on cardiopulmonary bypass followed by a continuous infusion for ≥12 hours and ≤5 days after cardiac intensive care unit admission. The primary outcome was days alive and out of the hospital within 30 days of surgery. Secondary outcomes included measures of cardiovascular function, renal function, resource use, and adverse events. Among 106 enrolled subjects, 35, 36, and 35 were randomized to the nesiritide, milrinone, and placebo groups, respectively, and all were analyzed based on intention to treat. Demographics, patient characteristics, and operative factors were similar among treatment groups. No significant treatment group differences were found for median days alive and out of the hospital within 30 days of surgery (nesiritide, 20 [minimum to maximum, 0-24]; milrinone, 18 [0-23]; placebo, 20 [0-23]; P=0.38). Treatment groups did not significantly differ in cardiac index, arrhythmias, peak lactate, inotropic scores, urine output, duration of mechanical ventilation, intensive care or chest tube drainage, or adverse events. Compared with placebo, empirical perioperative nesiritide or milrinone infusions are not associated with improved early clinical outcomes after Fontan surgery. http://www.clinicaltrials.gov. Unique identifier: NCT00543309. © 2014 American Heart Association, Inc.

Towards a proposal for a universal diagnostic definition of protein-losing enteropathy in Fontan patients: a systematic review.

PubMed

Udink Ten Cate, Floris Ea; Hannes, Tobias; Germund, Ingo; Khalil, Markus; Huntgeburth, Michael; Apitz, Christian; Brockmeier, Konrad; Sreeram, Narayanswami

2016-07-15

A standardised diagnostic definition of protein-losing enteropathy (PLE) in Fontan patients serves both patient care and research. The present study determined whether a diagnostic definition of PLE was routinely used in published clinical Fontan studies, and to identify potentially relevant diagnostic criteria for composing a uniform PLE definition. A systematic review was conducted in adherence to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) recommendations. Published clinical Fontan studies that were written in English and included at least four patients with PLE were selected. PLE definitions were quantitatively analysed using a lateral thinking tool in which definitions were fractionated into constituent pieces of information (building blocks or diagnostic criteria). We identified 364 papers. In the final analysis, data from 62 published articles were extracted. A diagnostic definition of PLE was used in only 27/62 (43.5%) of selected studies, and definitions were very heterogeneous. We identified eight major diagnostic criteria. Hypoalbuminaemia (n=23 studies, 85.2%), clinical presentation (n=18, 66.7%), documentation of enteric protein loss (n=16, 59.3%) and exclusion of other causes of hypoproteinaemia (n=17, 63.0%), were the most frequently used diagnostic criteria. Most studies used three diagnostic variables (n=13/27, 48.1%). Cut-off values for laboratory parameters (serum albumin, protein or faecal α-1-antitrypsin) were frequently incorporated in the PLE definition (n=16, 59.3%). Establishment of a universally accepted PLE definition for routine use in clinical research and daily practice is required. The diagnostic criteria may help constitute a diagnostic PLE definition. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Reduction in postoperative high-density lipoprotein cholesterol levels in children undergoing the Fontan operation.

PubMed

Zyblewski, Sinai C; Argraves, W Scott; Graham, Eric M; Slate, Elizabeth H; Atz, Andrew M; Bradley, Scott M; McQuinn, Tim C; Wilkerson, Brent A; Wing, Shane B; Argraves, Kelley M

2012-10-01

Despite the emerging relevance of high-density lipoprotein (HDL) in the inflammatory cascade and vascular barrier integrity, HDL levels in children undergoing cardiac surgery are unexplored. As a measure of HDL levels, the HDL-cholesterol (HDL-C) in single-ventricle patients was quantified before and after the Fontan operation, and it was determined whether relationships existed between the duration and the type of postoperative pleural effusions. The study prospectively enrolled 12 children undergoing the Fontan operation. Plasma HDL-C levels were measured before and after cardiopulmonary bypass. The outcome variables of interest were the duration and type of chest tube drainage (chylous vs. nonchylous). The Kendall rank correlation coefficient and the Wilcoxon rank sum test were used. There were 11 complete observations. The median preoperative HDL-C level for all the subjects was 30 mg/dl (range, 24-53 mg/dl), and the median postcardiopulmonary bypass level was 21 mg/dl (range, 14-46 mg/dl) (p = 0.004). There was a tendency toward a moderate inverse correlation (-0.42) between the postcardiopulmonary bypass HDL-C level and the duration of chest tube drainage, but the result was not statistically significant (p = 0.07). In the chylous effusion group, the median postcardiopulmonary bypass HDL-C tended to be lower (16 vs. 23 mg/dl; p = 0.09). After the Fontan operation, the plasma HDL-C levels in children are significantly reduced. It is reasonable to conclude that the reduction in HDL-C reflects reduced plasma levels of HDL particles, which may have pertinent implications in postoperative pleural effusions given the antiinflammatory and endothelial barrier functions of HDL.

Can time-averaged flow boundary conditions be used to meet the clinical timeline for Fontan surgical planning?

PubMed

Wei, Zhenglun Alan; Trusty, Phillip M; Tree, Mike; Haggerty, Christopher M; Tang, Elaine; Fogel, Mark; Yoganathan, Ajit P

2017-01-04

Cardiovascular simulations have great potential as a clinical tool for planning and evaluating patient-specific treatment strategies for those suffering from congenital heart diseases, specifically Fontan patients. However, several bottlenecks have delayed wider deployment of the simulations for clinical use; the main obstacle is simulation cost. Currently, time-averaged clinical flow measurements are utilized as numerical boundary conditions (BCs) in order to reduce the computational power and time needed to offer surgical planning within a clinical time frame. Nevertheless, pulsatile blood flow is observed in vivo, and its significant impact on numerical simulations has been demonstrated. Therefore, it is imperative to carry out a comprehensive study analyzing the sensitivity of using time-averaged BCs. In this study, sensitivity is evaluated based on the discrepancies between hemodynamic metrics calculated using time-averaged and pulsatile BCs; smaller discrepancies indicate less sensitivity. The current study incorporates a comparison between 3D patient-specific CFD simulations using both the time-averaged and pulsatile BCs for 101 Fontan patients. The sensitivity analysis involves two clinically important hemodynamic metrics: hepatic flow distribution (HFD) and indexed power loss (iPL). Paired demographic group comparisons revealed that HFD sensitivity is significantly different between single and bilateral superior vena cava cohorts but no other demographic discrepancies were observed for HFD or iPL. Multivariate regression analyses show that the best predictors for sensitivity involve flow pulsatilities, time-averaged flow rates, and geometric characteristics of the Fontan connection. These predictors provide patient-specific guidelines to determine the effectiveness of analyzing patient-specific surgical options with time-averaged BCs within a clinical time frame. Copyright © 2016 Elsevier Ltd. All rights reserved.

[Comparison of atrio-ventricular and total cavo-pulmonary connections versus atrio-pulmonary anastomosis for repair of tricuspid atresia in dogs].

PubMed

Yu, C; Liu, Y; Zhu, X; Li, Y; Li, Y

2000-03-01

To compare the hemodynamic effect and energy loss of atrio-ventricular and total cavo-pulmonary connections versus atrio-pulmonary anastomosis for modified Fontan in dogs. Fifteen adult mongrel dogs were divided into three groups. Group I underwent right atrium to right ventricle (using 50% and 25% right ventricular chamber, respectively) connection with the flap of valved homo-pulmonary artery (modified Bjoerk procedure). Group II underwent total cavo-pulmonary connection. Group III received atrio-pulmonary anastomosis. Right atrium pressure, pulmonary artery pressure, and cardiac output were measured by Swan-Ganz catheter. The volumes of the right pulmonary artery, left pulmonary artery, superior vena cava and inferior vena cava were measured by electromagnetic flowmeter. The flow-rate of the right pulmonary artery, left pulmonary artery, superior vena cava and inferior vena cava were measured echocardiographically. The fluid energy loss was calculated. The postoperative right atrium pressure in group I was lower than in group III (P < 0.05). The postoperative stroke index in group I and group II was higher than in group III (P < 0.01). The fluid energy loss was decreased when 50% or 25% right ventricle chamber was used (P < 0.01) and the fluid energy less in group II was less than in group III. Our experience suggested that atrio-ventricular connection and total cavo-pulmonary connection would be better than atrio-pulmonary anastomosis for modified Fontan repair of tricuspid valve atresia.

Massive Air Embolism in a Fontan Patient

PubMed Central

Matte, Gregory S.; Kussman, Barry D.; Wagner, Joseph W.; Boyle, Sharon L.; Howe, Robert J.; Pigula, Frank A.; Emani, Sitaram M.

2011-01-01

Abstract: Most institutions performing cardiopulmonary bypass for congenital heart disease patients use an integrated hard shell cardiotomy and venous reservoir attached to an oxygenator. It is of paramount importance that the integrated reservoir be vented so as not to cause pressurization. A pressurized sealed cardiotomy has been reported to occur secondary to issues with vacuum assisted venous drainage systems as well as improper venting in general. We report a case of air embolus caused by retrograde propulsion of air through the venous line secondary to a pressurized cardiotomy reservoir in a patient with Fontan circulation. The mechanism of cardiotomy pressurization is described, and the scenario simulated in a mock circuit. PMID:21848177

Massive air embolism in a Fontan patient.

PubMed

Matte, Gregory S; Kussman, Barry D; Wagner, Joseph W; Boyle, Sharon L; Howe, Robert J; Pigula, Frank A; Emani, Sitaram M

2011-06-01

Most institutions performing cardiopulmonary bypass for congenital heart disease patients use an integrated hard shell cardiotomy and venous reservoir attached to an oxygenator. It is of paramount importance that the integrated reservoir be vented so as not to cause pressurization. A pressurized sealed cardiotomy has been reported to occur secondary to issues with vacuum assisted venous drainage systems as well as improper venting in general. We report a case of air embolus caused by retrograde propulsion of air through the venous line secondary to a pressurized cardiotomy reservoir in a patient with Fontan circulation. The mechanism of cardiotomy pressurization is described, and the scenario simulated in a mock circuit.

Patient-Specific Modeling of Hemodynamics: Supporting Surgical Planning in a Fontan Circulation Correction.

PubMed

van Bakel, Theodorus M J; Lau, Kevin D; Hirsch-Romano, Jennifer; Trimarchi, Santi; Dorfman, Adam L; Figueroa, C Alberto

2018-04-01

Computational fluid dynamics (CFD) is a modeling technique that enables calculation of the behavior of fluid flows in complex geometries. In cardiovascular medicine, CFD methods are being used to calculate patient-specific hemodynamics for a variety of applications, such as disease research, noninvasive diagnostics, medical device evaluation, and surgical planning. This paper provides a concise overview of the methods to perform patient-specific computational analyses using clinical data, followed by a case study where CFD-supported surgical planning is presented in a patient with Fontan circulation complicated by unilateral pulmonary arteriovenous malformations. In closing, the challenges for implementation and adoption of CFD modeling in clinical practice are discussed.

Planning of vessel grafts for reconstructive surgery in congenital heart diseases

NASA Astrophysics Data System (ADS)

Rietdorf, U.; Riesenkampff, E.; Schwarz, T.; Kuehne, T.; Meinzer, H.-P.; Wolf, I.

2010-02-01

The Fontan operation is a surgical treatment for patients with severe congenital heart diseases, where a biventricular correction of the heart can't be achieved. In these cases, a uni-ventricular system is established. During the last step of surgery a tunnel segment is placed to connect the inferior caval vein directly with the pulmonary artery, bypassing the right atrium and ventricle. Thus, the existing ventricle works for the body circulation, while the venous blood is passively directed to the pulmonary arteries. Fontan tunnels can be placed intra- and extracardially. The location, length and shape of the tunnel must be planned accurately. Furthermore, if the tunnel is placed extracardially, it must be positioned between other anatomical structures without constraining them. We developed a software system to support planning of the tunnel location, shape, and size, making pre-operative preparation of the tunnel material possible. The system allows for interactive placement and adjustment of the tunnel, affords a three-dimensional visualization of the virtual Fontan tunnel inside the thorax, and provides a quantification of the length, circumferences and diameters of the tunnel segments. The visualization and quantification can be used to plan and prepare the tunnel material for surgery in order to reduce the intra-operative time and to improve the fit of the tunnel patch.

The effect of resolution on viscous dissipation measured with 4D flow MRI in patients with Fontan circulation: Evaluation using computational fluid dynamics

PubMed Central

Cibis, Merih; Jarvis, Kelly; Markl, Michael; Rose, Michael; Rigsby, Cynthia; Barker, Alex J.; Wentzel, Jolanda J.

2016-01-01

Viscous dissipation inside Fontan circulation, a parameter associated with the exercise intolerance of Fontan patients, can be derived from computational fluid dynamics (CFD) or 4D flow MRI velocities. However, the impact of spatial resolution and measurement noise on the estimation of viscous dissipation is unclear. Our aim was to evaluate the influence of these parameters on viscous dissipation calculation. Six Fontan patients underwent whole heart 4D flow MRI. Subject-specific CFD simulations were performed. The CFD velocities were down-sampled to isotropic spatial resolutions of 0.5 mm, 1 mm, 2 mm and to MRI resolution. Viscous dissipation was compared between (1) high resolution CFD velocities, (2) CFD velocities down-sampled to MRI resolution, (3) down-sampled CFD velocities with MRI mimicked noise levels, and (4) in-vivo 4D flow MRI velocities. Relative viscous dissipation between subjects was also calculated. 4D flow MRI velocities (15.6±3.8 cm/s) were higher, although not significantly different than CFD velocities (13.8±4.7 cm/s, p=0.16), down-sampled CFD velocities (12.3±4.4 cm/s, p=0.06) and the down-sampled CFD velocities with noise (13.2±4.2 cm/s, p=0.06). CFD-based viscous dissipation (0.81±0.55 mW) was significantly higher than those based on down-sampled CFD (0.25±0.19 mW, p=0.03), down-sampled CFD with noise (0.49±0.26 mW, p=0.03) and 4D flow MRI (0.56±0.28 mW, p=0.06). Nevertheless, relative viscous dissipation between different subjects was maintained irrespective of resolution and noise, suggesting that comparison of viscous dissipation between patients is still possible. PMID:26298492

Heparin-Induced Thrombocytopenia with Associated Thrombosis in Children after the Fontan Operation

PubMed Central

Porcelli, Rosalia; Moskowitz, Bonnie C.; Cetta, Frank; Graham, Lynn C.; Godwin, John E.; Eidem, Benjamin W.; Prechel, M. Margaret; Walenga, Jeanine M.

2003-01-01

Heparin-induced thrombocytopenia is a widely recognized clinical disorder. The spectrum of disease ranges from clinically insignificant to severe thrombosis (heparin-induced thrombocytopenia with associated thrombosis). Overall, thrombosis occurs in approximately 33% of adults diagnosed with heparin-induced thrombocytopenia and has been associated with high morbidity and mortality rates. Diagnostic testing for this disorder is not standard in children with thrombocytopenia who are receiving heparin, despite the fact that children with congenital heart disease may be exposed to heparin frequently. There are few reported cases of heparin-induced thrombocytopenia with associated thrombosis in children; herein, we describe the cases of 2 children who developed this disorder after undergoing a Fontan operation. (Tex Heart Inst J 2003;30:58–61) PMID:12638673

Using of porous portion to simulate pulmonary resistance in the computational fluid dynamic models of Fontan connection.

PubMed

Sun, Qi; Liu, Jinlong; Qian, Yi; Hong, Haifa; Liu, Jinfen

2013-01-01

In this study, we performed computational fluid dynamic (CFD) simulations in a patient-specific three-dimensional extracardiac conduit Fontan connection. The pulmonary resistance was incorporated in the CFD model by connecting porous portions in the left and right pulmonary arteries. The pressure in the common atrium was set as boundary conditions at the outlets of the pulmonary arteries. The flow rate in the innominate veins and the inferior vena cava (IVC) was set as inflow boundary conditions. Furthermore, the inflow rate of IVC was increased to 2 and 3 times of that measured to perform another two simulations and the resistance provided by the porous portions was compared among these three conditions. We found out that the pulmonary resistance set as porous portion in the CFD models remains relatively steady despite the change of the inflow rate. We concluded that, in the CFD simulations for the Fontan connections, porous portion could be used to represent pulmonary resistance steadily. The pulmonary resistance and pressure in the common atrium could be acquired directly by clinical examination. The employment of porous portion together with pressure in the common atrium in the CFD model could facilitate and accurate the set of outlet boundary conditions especially for those actual pulmonary flow splits was unpredictable such as virtual operative designs related CFD simulations.

Staged single-ventricle palliation in 2011: outcomes and expectations.

PubMed

Petit, Christopher J

2011-01-01

Outcomes for staged palliation for single-ventricle heart disease have improved over the past two decades. As outcomes improve, parental expectations for survival and quality of life have risen accordingly. Nevertheless, the number of interventions and complications these patients must endure remain high. The final surgical destination of the single-ventricle patient, the total cavopulmonary connection (or Fontan operation) successfully separates systemic venous and pulmonary venous blood flow but does so at great cost. Fontan patients remain at significant risk of complications despite what are perceived to be "favorable" hemodynamics. The outcomes in this population are discussed in this review, with particular attention to the history behind our current strategies as well as to recent salient studies. © 2011 Copyright the Author. Congenital Heart Disease © 2011 Wiley Periodicals, Inc.

Overview of adult congenital heart transplants

PubMed Central

Morales, David

2018-01-01

Transplantation for adult patients with congenital heart disease (ACHD) is a growing clinical endeavor in the transplant community. Understanding the results and defining potential high-risk patient subsets will allow optimization of patient outcomes. This review summarizes the scope of ACHD transplantation, the mechanisms of late ventricular dysfunction, the ACHD population at risk of developing heart failure, the indications and potential contraindications for transplant, surgical considerations, and post-transplant outcomes. The findings reveal that 3.3% of adult heart transplants occur in ACHD patients. The potential mechanisms for the development of late ventricular dysfunction include a morphologic systemic right ventricle, altered coronary perfusion, and ventricular noncompaction. The indications for transplant in ACHD patients include systemic ventricular failure refractory medical therapy, Fontan patients failing from chronic passive pulmonary circulation, and progressive cyanosis leading to functional decline. Transplantation in ACHD patients can be quite complex and may require extensive reconstruction of the branch pulmonary arteries, systemic veins, or the aorta. Vasoplegia, bleeding, and graft right ventricular dysfunction can complicate the immediate post-transplant period. The post-transplant operative mortality ranges between 14% and 39%. The majority of early mortality occurs in ACHD patients with univentricular congenital heart disease. However, there has been improvement in operative survival in more contemporary studies. In conclusion, the experience with cardiac transplantation for ACHD patients with end-stage heart failure is growing, and high-risk patient subsets have been defined. Significant strides have been made in developing evidence-based guidelines of indications for transplant, and the intraoperative management of complex reconstruction has evolved. With proper patient selection, more aggressive use of mechanical circulatory support, and earlier referral of patients with failing Fontan physiology, outcomes should continue to improve. PMID:29492392

Accuracy and Reproducibility of Strain by Speckle Tracking in Pediatric Subjects with Normal Heart and Single Ventricular Physiology: A 2D Speckle Tracking Echocardiography and Magnetic Resonance Imaging Correlative Study

PubMed Central

Singh, Gautam K.; Cupps, Brian; Pasque, Michael; Woodard, Pamela K.; Holland, Mark R.; Ludomirsky, Achiau

2013-01-01

Background Myocardial strain is a sensitive measure of ventricular systolic function. Two-dimensional speckle-tracking echocardiography (2DSE) is an angle-independent method for strain measurement but has not been validated in pediatric subjects. We evaluated the accuracy and reproducibility of 2DSE-measured strain against reference tagged MRI-measured strain in pediatric subjects with normal hearts and those with single ventricle (SV) of left ventricle (LV) morphology s/p Fontan procedure. Methods Peak systolic circumferential (CS) and longitudinal (LS) strains in segments (n = 16) of LVs in age and BSA matched 20 healthy and 12 pediatric subjects with tricuspid atresia s/p Fontan procedure were measured by 2DSE and tagged MRI. Average (global) and regional segmental strains measured by two methods were compared using Spearman and Bland-Altman analyses. Results 2DSE and tagged MRI measured global strains demonstrated close agreements, which were better for LS than CS and in normal LVs than in SVs (95% limits of agreement: +0.0% to +3.12%, −2.48 % to +1.08%, −4.6% to +1.8% and −3.6% to +1.8% respectively). There was variability in agreement between regional strains with wider limits in apical than in basal regions in normal LVs and heterogeneous in SVs. The strain values were significantly (p < 0.05) higher in normal LVs than in SVs except for basal LSs, which were similar in both cohorts. The regional strains in normal LVs demonstrated an apico-basal magnitude gradient whereas SVs showed heterogeneity. The reproducibility was the most robust for images obtained with frame rates between 60 and 90 frame/sec; global LS in both cohorts; and basal strains in normal LVs. Conclusions 2DSE-measured strains agree with MRI-measured strain globally but vary regionally particularly in SVs. Global strain may be more robust tool for the cardiac function evaluation than regional strain in SV physiology. The reliability of 2DSE measured strain is affected by the frame rate, nature of strain, and ventricular geometry. PMID:20850945

Acute Kidney Injury in Patients Undergoing the Extracardiac Fontan Operation With and Without the Use of Cardiopulmonary Bypass.

PubMed

Algaze, Claudia A; Koth, Andrew M; Faberowski, Lisa W; Hanley, Frank L; Krawczeski, Catherine D; Axelrod, David M

2017-01-01

To describe the prevalence and risk factors for acute kidney injury in patients undergoing the extracardiac Fontan operation with and without cardiopulmonary bypass, and to determine whether acute kidney injury is associated with duration of mechanical ventilation, cardiovascular ICU and hospital postoperative length of stay, and early mortality. Single-center retrospective cohort study. Pediatric cardiovascular ICU, university-affiliated children's hospital. Patients with a preoperative creatinine before undergoing first-time extracardiac Fontan between January 1, 2004, and April 30, 2012. None. Acute kidney injury occurred in 55 of 138 patients (39.9%), including 41 (29.7%) with stage 1, six (4.4%) with stage 2, and eight (5.8%) with stage 3 acute kidney injury. Cardiopulmonary bypass was strongly associated with a higher risk of any acute kidney injury (adjusted odds ratio, 4.8 [95% CI, 1.4-16.0]; p = 0.01) but not stage 2/3 acute kidney injury. Lower renal perfusion pressure on the day of surgery (postoperative day, 0) was associated with a higher risk of stage 2/3 acute kidney injury (adjusted odds ratio, 1.2 [95% CI, 1.0-1.5]; p = 0.03). Higher vasoactive-inotropic score on postoperative day 0 was associated with a higher risk for stage 2/3 acute kidney injury (adjusted odds ratio, 1.9 [95% CI, 1.0-3.4]; p = 0.04). Stage 2/3 acute kidney injury was associated with longer cardiovascular ICU length of stay (mean, 7.3 greater d [95% CI, 3.4-11.3]; p < 0.001) and hospital postoperative length of stay (mean, 6.4 greater d [95% CI, 0.06-12.5]; p = 0.04). Postoperative acute kidney injury in patients undergoing the extracardiac Fontan operation is common and is associated with lower postoperative renal perfusion pressure and higher vasoactive-inotropic score. Cardiopulmonary bypass was strongly associated with any acute kidney injury, although not stage 2/3 acute kidney injury. Stage 2/3 acute kidney injury is a compelling risk factor for longer cardiovascular ICU and hospital postoperative length of stay. Increased attention to and management of renal perfusion pressure may reduce postoperative acute kidney injury and improve outcomes.

Pregnancy in complex CHD: focus on patients with Fontan circulation and patients with a systemic right ventricle.

PubMed

Khan, Abigail; Kim, Yuli Y

2015-12-01

The majority of children with congenital heart disease (CHD) now survive into adulthood, and many women with CHD want to pursue pregnancy. Pregnancy represents a complex issue for the CHD care provider. It requires balancing the interests of the woman against the risk to her health during pregnancy, while also factoring in the long-term risks to her health and the risk to her fetus. Our knowledge about this subject has been historically limited by lack of data regarding the outcome of pregnancy in CHD; however, in recent years, more data have begun to emerge. In this review, we will summarise what is known about risk assessment in pregnant CHD patients. We provide a framework for healthcare providers managing pregnancy in this population, with focus on the systemic right ventricle and the Fontan operation.

Adult Congenital Heart Disease with Pregnancy

PubMed Central

2018-01-01

The number of women with congenital heart disease (CHD) at risk of pregnancy is growing because over 90% of them are grown-up into adulthood. The outcome of pregnancy and delivery is favorable in most of them provided that functional class and systemic ventricular function are good. Women with CHD such as pulmonary hypertension (Eisenmenger syndrome), severe left ventricular outflow stenosis, cyanotic CHD, aortopathy, Fontan procedure and systemic right ventricle (complete transposition of the great arteries [TGA] after atrial switch, congenitally corrected TGA) carry a high-risk. Most frequent complications during pregnancy and delivery are heart failure, arrhythmias, bleeding or thrombosis, and rarely maternal death. Complications of fetus are prematurity, low birth weight, abortion, and stillbirth. Risk stratification of pregnancy and delivery relates to functional status of the patient and is lesion specific. Medication during pregnancy and post-delivery (breast feeding) is a big concern. Especially prescribing medication with teratogenicity should be avoidable. Adequate care during pregnancy, delivery, and the postpartum period requires a multidisciplinary team approach with cardiologists, obstetricians, anesthesiologists, neonatologists, nurses and other related disciplines. Caring for a baby is an important issue due to temporarily pregnancy-induced cardiac dysfunction, and therefore familial support is mandatory especially during peripartum and after delivery. Timely pre-pregnancy counseling should be offered to all women with CHD to prevent avoidable pregnancy-related risks. Successful pregnancy is feasible for most women with CHD at relatively low risk when appropriate counseling and optimal care are provided. PMID:29625509

The role of milrinone in children with cardiovascular compromise: review of the literature.

PubMed

Meyer, Sascha; Gortner, Ludwig; Brown, Kate; Abdul-Khaliq, Hashim

2011-04-01

Cardiovascular instability is a common complication in children after cardiac surgery and in various forms of shock. Systematic literature review. Four randomized controlled trials (RCTs) were included in this systematic literature review. In children after corrective surgery for congenital heart disease milrinone significantly reduced the risk of development of LCOS compared with placebo. In another study in children with high pulmonary vascular resistance and impaired oxygenation after Fontan operation, inhalation of NO with milrinone led to the most significant reduction of pulmonary vascular resistance and improvement of oxygenation. When only milrinone was given these changes were less pronounced. In non-hyperdynamic septic shock, CI, SVI, and DO₂ significantly increased while SVRI significantly decreased after milrinone when compared to placebo. There are a limited number of RCTs in children that suggest a beneficial effect of milrinone in the optimization of cardiovascular function after cardiac surgery and in septic shock.

Total Cavopulmonary Connection for Functionally Single Ventricle without Cardiopulmonary Bypass Support.

PubMed

Bangash, Sohail Khan; Pathan, Iqbal Hussain; Zaki, Saad Bader

2016-10-01

A heart with two atriums but one ventricle, an anatomy with a unique physiology, is responsible for many creative surgical and interventional approaches in history. Different surgical techniques have been used to address this strange physiology of parallel circulation. All these attempts met with failure till the concept of Fontan circulation was described. Currently, controversy exists between multistage vs. single stage total cavopulmonary connections. Total cavopulmonary connection is the only definitive procedure performed to provide palliation for patients with complex congenital heart defects which cannot support a biventricular circulation. We report a case with tricuspid atresia with transposition of great arteries and pulmonary stenosis with persistant left-sided superior vena cava and functionally single ventricle. Patient successfully underwent single stage extra-cardiac total cavopulmonary connection. In this case, bilateral Glenn with extra-cardiac inferior vena cava to main pulmonary artery shunt was performed off-pump.

The paediatric cardiac centre for Africa--proceedings of the March 2012 symposium.

PubMed

Kinsley, Robin H; Edwin, Frank; Entsua-Mensah, Kow

2013-04-01

The Pediatric Cardiac Centre for Africa (PCCA) was opened by national patron Mr Nelson Mandela on November 7, 2003. In 2008, the Centre's international pediatric cardiac symposium was introduced as a learning forum for pediatric cardiac surgeons and cardiologists in the continent. The symposium has consistently grown in attendance and attracted distinguished leaders in the field. The 2012 symposium featured Dr. Thomas Spray of Children's Hospital of Philadelphia, Dr. David Barron of Birmingham Children's Hospital, and Dr. John Brown of Indiana University School of Medicine as guest speakers. Experience of the Fontan procedure, the small aortic root, hypoplastic left heart syndrome, right ventricular outflow tract reconstruction, transposition of the great arteries, and interrupted aortic arch were the highlights of the symposium. In the "African Corner," centers in South Africa, Ghana, and Angola presented work done from across the African continent.

Infective endocarditis prophylaxis: current practice trend among paediatric cardiologists: are we following the 2007 guidelines?

PubMed

Naik, Ronak J; Patel, Neil R; Wang, Ming; Shah, Nishant C

2016-08-01

In 2007, the American Heart Association modified the infective endocarditis prophylaxis guidelines by limiting the use of antibiotics in patients with cardiac conditions associated with the highest risk of adverse outcomes after infective endocarditis. Our objective was to evaluate current practice for infective endocarditis prophylaxis among paediatric cardiologists. A web-based survey focussing on current practice, describing the use of antibiotics for infective endocarditis prophylaxis in various congenital and acquired heart diseases, was distributed via e-mail to paediatric cardiologists. The survey was kept anonymous and was distributed twice. Data from 253 participants were analysed. Most paediatric cardiologists discontinued infective endocarditis prophylaxis in patients with simple lesions such as small ventricular septal defect, patent ductus arteriosus, and bicuspid aortic valve without stenosis or regurgitation; however, significant disagreement persists in prescribing infective endocarditis prophylaxis in certain conditions such as rheumatic heart disease, Fontan palliation without fenestration, and the Ross procedure. Use of antibiotic prophylaxis in certain selected conditions for which infective endocarditis prophylaxis has been indicated as per the current guidelines varies from 44 to 83%. Only 44% follow the current guidelines exclusively, and 34% regularly discuss the importance of oral hygiene with their patients at risk for infective endocarditis. Significant heterogeneity still persists in recommending infective endocarditis prophylaxis for several cardiac lesions among paediatric cardiologists. More than half of the participants (56%) do not follow the current guidelines exclusively in their practice. Counselling for optimal oral health in patients at risk for infective endocarditis needs to be optimised in the current practice.

Experimental and numeric investigation of Impella pumps as cavopulmonary assistance for a failing Fontan.

PubMed

Haggerty, Christopher M; Fynn-Thompson, Francis; McElhinney, Doff B; Valente, Anne Marie; Saikrishnan, Neelakantan; Del Nido, Pedro J; Yoganathan, Ajit P

2012-09-01

This study sought to evaluate the performance of microaxial ventricular assist devices for the purposes of supporting failing Fontan physiology by decreasing central venous pressure. Three Abiomed Impella pumps (Abiomed, Inc, Danvers, Mass) were evaluated in a mock circulatory system of the Fontan circuit. The local response of pressures and flows to pump function was assessed as a function of pump speed and pulmonary vascular resistance at a high baseline central venous pressure. For one device, subsequent modeling studies were conducted using a lumped parameter model of the single ventricle circuit. The left ventricular devices (Impella 2.5, 5.0) were shown to be suboptimal as single device solutions for cavopulmonary support. The small area of these devices relative to vessel diameter led to significant flow recirculation without an obstructive separator in place. Furthermore, downstream pressure augmentation adversely affected the pressure in the superior vena cava. The use of 2 devices would be mandatory for successful support. The right-sided device (Impella RP), whose outflow was positioned in the left pulmonary artery, demonstrated decreased flow recirculation and did not impede superior caval venous flow. Although static pressure is still required to drive flow through the opposite lung, numeric modeling demonstrated the potential for modest but significant improvements in lowering the central venous pressure (2-8 mm Hg). Left-sided microaxial pumps are not well suited for cavopulmonary support because of severe flow recirculation and the need for multiple devices. The right-ventricular Impella device provides improved performance by directing flow into the pulmonary artery, resulting in modest decreases in central venous pressure. Copyright © 2012 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

Brain Magnetic Resonance Immediately Prior To Surgery In Single Ventricles and Surgical Postponement

PubMed Central

Fogel, Mark A.; Pawlowski, Tom; Schwab, Peter J.; Nicolson, Susan C.; Montenegro, Lisa M.; Berenstein, Laura Diaz; Spray, Thomas L.; Gaynor, J William; Fuller, Stephanie; Keller, Marc S.; Harris, Matthew A.; Whitehead, Kevin K.; Vossough, Arastoo; Licht, Daniel J.

2014-01-01

Background Single ventricle patients undergoing surgical reconstruction experience a high rate of brain injury; incidental findings on pre-operative brain scans may result in safety considerations involving hemorrhage extension during cardiopulmonary bypass that result in surgical postponement. Methods Single ventricle patients were studied with brain scans immediately preoperatively as part of a National Institute of Health study and were reviewed by neuroradiology immediately prior to cardiopulmonary bypass. Results One hundred and thirty four consecutive subjects recruited into the project were studied: 33 prior to stage I (3.7±1.8 days), 34 prior to bidirectional Glenn (5.8±3.5 months) and 67 prior to Fontan (3.3±1.1 years). Six (4.5%) surgeries were postponed because of concerning imaging findings on brain MRI; 2 prior to stage I, 3 prior to bidirectional Glenn and 1 prior to Fontan. Five were due to unexpected incidental findings of acute intracranial hemorrhage and one due to diffuse cerebellar cytotoxic edema; none who proceeded to surgery had these lesions. Prematurity as well as genetic syndromes were not present in any with postponed surgery. Four of 4 prior to bidirectional Glenn/Fontan with surgical delays had hypoplastic left heart syndrome compared with 44/97 who did not (P=0.048). After observation and follow up, all eventually had successful surgeries with bypass. Conclusion Preoperative brain MRI performed in children with single ventricles disclosed injuries in 4.5% leading to surgical delay; hemorrhagic lesions were most common and raised concerns for extension during surgery. The true risk of progression and need for delay of surgery due to heparinization associated with these lesions remains uncertain. PMID:25149046

Pulmonary hypertension in children with congenital heart disease (PAH-CHD, PPHVD-CHD). Expert consensus statement on the diagnosis and treatment of paediatric pulmonary hypertension. The European Paediatric Pulmonary Vascular Disease Network, endorsed by ISHLT and DGPK.

PubMed

Kozlik-Feldmann, Rainer; Hansmann, Georg; Bonnet, Damien; Schranz, Dietmar; Apitz, Christian; Michel-Behnke, Ina

2016-05-01

Pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD) is a complex disease that presents with a broad spectrum of morphological and haemodynamic findings of varying severity. Recently, the aspect of paediatric pulmonary hypertensive vascular disease (PPHVD) has been introduced to expand the understanding of the full spectrum of pulmonary hypertension and increased pulmonary vascular resistance. Evaluation and treatment of PAH-CHD/PPHVD-CHD can be divided into in different topics. First, defining criteria for operability and initiation of advanced therapies preoperatively and postoperatively is an unresolved issue. Second, management of Eisenmenger syndrome is still an important question, with recent evidence on the severity of the disease and a more rapidly progressive course than previously described. Third, the Fontan circulation with no subpulmonary ventricle requires a distinct discussion, definition and classification since even a mild rise in pulmonary vascular resistance may lead to the so-called failing Fontan situation. Patients with CHD and single-ventricle physiology (Fontan/total cavopulmonary anastomosis) require a particularly stepwise and individualised approach. This consensus statement is on the current evidence for the most accurate evaluation and treatment of increased pulmonary artery pressure and resistance, as well as ventricular dysfunction, in children with congenital heart defects, and provides according practical recommendations. To optimise preoperative and postoperative management in patients with PAH-CHD, diagnostic and treatment algorithms are provided. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

High Overweight and Obesity in Fontan Patients: A 20-Year History.

PubMed

Chung, Stephanie T; Hong, Borah; Patterson, Lance; Petit, Christopher J; Ham, J Nina

2016-01-01

The prevalence of obesity in long-term survivors with complex congenital heart disease may be increasing, and little is known about the timing and onset of weight gain and growth patterns in these high-risk patients. Prevalence rates of overweight/obesity and longitudinal changes in body mass index (BMI) with age were determined in 606 patients with Fontan circulation seen at a tertiary care cardiology center from 1992 to 2012. The number of clinic encounters (n) was stratified by age group (n = 401, 2-5 years; n = 333, 6-11 years; n = 217, 12-19 years; and n = 129, >20 years). Among adults, 39% were overweight/obese at last clinic visit; 22% overweight, and 17% obese. Childhood anthropometric data were available for 82 adults, of which 15% (n = 12/82) were overweight/obese in childhood. The likelihood of being overweight/obese as an adult was three times higher if there was a BMI ≥ 85th percentile in childhood (CI 2.1-4.5, P < 0.01). Overweight/obesity in adulthood was associated with lower heart failure rates (4 vs. 19%, P = 0.03). Pediatric rates of overweight/obesity were comparable to national data (NHANES 2011-2012) in every age group: at 2-5 years, (25 vs. 23%), 6-11 years (26 vs. 34%), and 12-19 years (15 vs. 35%). Systolic blood pressure was higher in overweight/obese children as young as 2-5 years of age. Childhood and adult survivors with Fontan circulation have high rates of overweight/obesity. Childhood obesity is a strong predictor of future adiposity and is linked to changes in systolic blood pressure at a very young age.

Dynamic mode decomposition of Fontan hemodynamics in an idealized total cavopulmonary connection

NASA Astrophysics Data System (ADS)

Delorme, Yann T.; Kerlo, Anna-Elodie M.; Anupindi, Kameswararao; Rodefeld, Mark D.; Frankel, Steven H.

2014-08-01

Univentricular heart disease is the leading cause of death from any birth defect in the first year of life. Typically, patients have to undergo three open heart surgical procedures within the first few years of their lives to eventually directly connect the superior and inferior vena cavae to the left and right pulmonary arteries forming the total cavopulmonary connection (TCPC). The end result is a weak circulation where the single working ventricle pumps oxygenated blood to the body and de-oxygenated blood flows passively through the TCPC into the lungs. The fluid dynamics of the TCPC junction involve confined impinging jets resulting in a highly unstable flow, significant mechanical energy dissipation and undesirable pressure loss. Understanding and predicting such flows is important for improving the surgical procedure and for the design of mechanical cavopulmonary assist devices. In this study, dynamic mode decomposition (DMD) is used to analyze previously obtained stereoscopic particle imaging velocimetry (SPIV) data and large eddy simulation (LES) results for an idealized TCPC. Analysis of the DMD modes from the SPIV and LES serves to both highlight the unsteady vortical dynamics and the qualitative agreement between measurements and simulations.

Staged surgical management of hypoplastic left heart syndrome: a single institution 12 year experience

PubMed Central

McGuirk, S P; Griselli, M; Stumper, O F; Rumball, E M; Miller, P; Dhillon, R; de Giovanni, J V; Wright, J G; Barron, D J; Brawn, W J

2006-01-01

Objective To describe a 12 year experience with staged surgical management of the hypoplastic left heart syndrome (HLHS) and to identify the factors that influenced outcome. Methods Between December 1992 and June 2004, 333 patients with HLHS underwent a Norwood procedure (median age 4 days, range 0–217 days). Subsequently 203 patients underwent a bidirectional Glenn procedure (stage II) and 81 patients underwent a modified Fontan procedure (stage III). Follow up was complete (median interval 3.7 years, range 32 days to 11.3 years). Results Early mortality after the Norwood procedure was 29% (n  =  95); this decreased from 46% (first year) to 16% (last year; p < 0.05). Between stages, 49 patients died, 27 before stage II and 22 between stages II and III. There were one early and three late deaths after stage III. Actuarial survival (SEM) was 58% (3%) at one year and 50% (3%) at five and 10 years. On multivariable analysis, five factors influenced early mortality after the Norwood procedure (p < 0.05). Pulmonary blood flow supplied by a right ventricle to pulmonary artery (RV‐PA) conduit, arch reconstruction with pulmonary homograft patch, and increased operative weight improved early mortality. Increased periods of cardiopulmonary bypass and deep hypothermic circulatory arrest increased early mortality. Similar factors also influenced actuarial survival after the Norwood procedure. Conclusion This study identified an improvement in outcome after staged surgical management of HLHS, which was primarily attributable to changes in surgical technique. The RV‐PA conduit, in particular, was associated with a notable and independent improvement in early and actuarial survival. PMID:15939721

Health-related quality of life in paediatric patients with congenital heart defects: association with the type of heart defect and the surgical technique.

PubMed

Heusch, A; Kahl, H J; Hensel, K O; Calaminus, G

2017-11-01

The aim of the study was to investigate the impact of a number of surgical interventions for a various congenital cardiac defects (CHDs) on self-reported HRQoL. Patients who had received corrective surgery of several congenital heart defects (surgical VSD closure, Fallot, TGA after atrial or arterial switch or Fontan-type circulation for univentricular AV-connection) were interviewed in the office of their home peadiatric cardiologist. HRQoL in children along 7 dimensions was assessed using a standardised questionnaire (PEDQoL); information on the medical case history of each respondent was also collected. HRQoL was assessed in the questionnaire by asking about the frequency (never, rarely, often, always) of specific negative experiences; more frequent experiences indicate a lower quality of life. Frequency expressions were transformed into numerical values (25, 50, 75, 100%), and mean values for HRQoL were calculated for each patient and for each domain. Differences in HRQoL among patients with different types of interventions were analysed using the Mann-Whitney Test or the Kruskal-Wallis Test as appropriate; p values <0.05 were considered to indicate significant differences, while p values <0.1 were considered to indicate notable trends. Patients: 169 patients (60% male, 40% female) were part of the study. The mean age was 11.6 years; 50 patients had surgical VSD closure, 52 surgeries for Tetralogy of Fallot (22 transannular patch, 18 no transannular patch, 12 inaccurate description), 40 had complete transposition of the great arteries (28 atrial switch, 12 arterial switch), 22 had a Fontan-type procedure for univentricular AV-connection. HRQoL differed little among patients with different CHDs for the items "relation to friends," "interactions in the affected families", and "own body image". For other items, notable differences emerged: patients with univentricular hearts rated their physical capacity worse and showed a tendency towards negative ratings in other domains. On the other hand, patients after Fallot or TGA correction tended to rate their HRQoL in several domains as relatively high. Focusing on the mode of surgery for Fallot repair, respectively, TGA correction the only significant difference was found for "physical capacity" in TGA (atrial vs. arterial repair). Mustard patients tended to rate most items worse. Physical capacity was rated worst by patients with a Fontan circulation. Repeated surgery led to lower ratings for all domains except "physical capacity" and "body image". Different surgical techniques for CHD do not affect children's and adolescents' self-reported HRQoL to the extent that one would expect. This observation is in line with observations in groups of children with different chronic diseases. Specialised psychosocial support is necessary in order to maintain this positive self-evaluation and to ensure patients are able to lead autonomous personal and professional lives.

Waldmann's Disease (Primary Intestinal Lymphangiectasia) with Atrial Septal Defect.

PubMed

Aroor, Shrikiran; Mundkur, Suneel; Kanaparthi, Shravan; Kumar, Sandeep

2017-04-01

Waldmann's disease or Primary Intestinal Lymphangiectasia (PIL) is a rare disorder of gastrointestinal tract characterized by dilated lymphatics and widened villi causing leakage of lymph into intestinal lumen. Loss of lymph leads to hypoalbuminemia, hyogammaglobulinemia and lymphopenia. Secondary lymphangiectasia occurs secondary to an elevated lymphatic pressure as in lymphoma, systemic lupus erythematosus, constrictive pericarditis, cardiac surgeries (Fontan's procedure), inflammatory bowel disease and malignancies. We, hereby present a five-year-old male child who presented with abdominal distension and poor weight gain. He had hypoalbuminemia, lymphocytopenia and hypogammaglobulinemia. Upper gastrointestinal endoscopy showed normal gastric mucosa and punctate white lesions in duodenal mucosa with biopsy confirming intestinal lymphangiectasia. Secondary causes of intestinal lymphangiectasia were ruled out. Echocardiography revealed atrial septal defect which is an uncommon association with Waldmann's disease. He was started on low fat, high protein diet and medium chain triglyceride supplementation following which he improved symptomatically. High index of suspicion, early diagnosis and appropriate dietary treatment are necessary to alleviate symptoms as well as to achieve a sustainable growth and development in these children.

Physiologic Simulation of the Fontan Surgery with Variable Wall Properties and Respiration

NASA Astrophysics Data System (ADS)

Long, Christopher; Bazilevs, Yuri; Feinstein, Jeffrey; Marsden, Alison

2010-11-01

Children born with single ventricle heart defects typically undergo a surgical procedure known as a total cavopulmonary connection (TCPC). The goal of this work is to perform hemodynamic simulations accounting for motion of the arterial walls in the TCPC. We perform fluid structure interactions (FSI) simulations using an Arbitrary Lagrangian Eulerian (ALE) finite element framework into a patient-specific model of the TCPC. The patient's post-op anatomy is reconstructed from MRI data. Respiration rate, heart rate, and venous pressures are obtained from catheterization data, and flowrates are obtained from phase contrast MRI data and are used together with a respiratory model. Lumped parameter (RCR) boundary conditions are used at the outlets. This study is the first to introduce variable elastic properties for the different areas of the TCPC, including a Gore-Tex conduit. Quantities such as wall shear stresses and pressures at critical junctions are extracted from the simulation and are compared with pressure tracings from clinical data as well as with rigid wall simulations.

Mock Circulatory System of the Fontan Circulation to Study Respiration Effects on Venous Flow Behavior

PubMed Central

Vukicevic, M.; Chiulli, J.A.; Conover, T.; Pennati, G.; Hsia, T.Y.; Figliola, R.S.

2013-01-01

We describe an in vitro model of the Fontan circulation with respiration to study subdiaphragmatic venous flow behavior. The venous and arterial connections of a total cavopulmonary connection (TCPC) test section were coupled with a physical lumped parameter (LP) model of the circulation. Intrathoracic and subdiaphragmatic pressure changes associated with normal breathing were applied. This system was tuned for two patients (5 years, 0.67 m2; 10 years, 1.2 m2) to physiological values. System function was verified by comparison to the analytical model on which it was based and by consistency with published clinical measurements. Overall, subdiaphragmatic venous flow was influenced by respiration. Flow within the arteries and veins increased during inspiration but decreased during expiration with retrograde flow in the inferior venous territories. System pressures and flows showed close agreement with the analytical LP model (p < 0.05). The ratio of the flow rates occurring during inspiration to expiration were within the clinical range of values reported elsewhere. The approach used to setup and control the model was effective and provided reasonable comparisons with clinical data. PMID:23644612

Statistical Shape Modeling for Cavopulmonary Assist Device Development: Variability of Vascular Graft Geometry and Implications for Hemodynamics.

PubMed

Bruse, Jan L; Giusti, Giuliano; Baker, Catriona; Cervi, Elena; Hsia, Tain-Yen; Taylor, Andrew M; Schievano, Silvia

2017-06-01

Patients born with a single functional ventricle typically undergo three-staged surgical palliation in the first years of life, with the last stage realizing a cross-like total cavopulmonary connection (TCPC) of superior and inferior vena cavas (SVC and IVC) with both left and right pulmonary arteries, allowing all deoxygenated blood to flow passively back to the lungs (Fontan circulation). Even though within the past decades more patients survive into adulthood, the connection comes at the prize of deficiencies such as chronic systemic venous hypertension and low cardiac output, which ultimately may lead to Fontan failure. Many studies have suggested that the TCPC's inherent insufficiencies might be addressed by adding a cavopulmonary assist device (CPAD) to provide the necessary pressure boost. While many device concepts are being explored, few take into account the complex cardiac anatomy typically associated with TCPCs. In this study, we focus on the extra cardiac conduit vascular graft connecting IVC and pulmonary arteries as one possible landing zone for a CPAD and describe its geometric variability in a cohort of 18 patients that had their TCPC realized with a 20mm vascular graft. We report traditional morphometric parameters and apply statistical shape modeling to determine the main contributors of graft shape variability. Such information may prove useful when designing CPADs that are adapted to the challenging anatomical boundaries in Fontan patients. We further compute the anatomical mean 3D graft shape (template graft) as a representative of key shape features of our cohort and prove this template graft to be a significantly better approximation of population and individual patient's hemodynamics than a commonly used simplified tube geometry. We therefore conclude that statistical shape modeling results can provide better models of geometric and hemodynamic boundary conditions associated with complex cardiac anatomy, which in turn may impact on improved cardiac device development.

Ablation of post-surgical intra-atrial reentrant tachycardia. Predilection target sites and mapping approach.

PubMed

Anné, W; van Rensburg, H; Adams, J; Ector, H; Van de Werf, F; Heidbüchel, H

2002-10-01

Atrial arrhythmias are a frequent complication of atrial surgery. The location of these tachycardias is very diverse due to the individual difference in the original anatomy, surgical corrections, and effects of atrial fibrosis. Nevertheless some recurrent patterns are emerging. Forty-five patients underwent 51 ablation procedures between September 1995 and March 2001 using conventional mapping and temperature-controlled ablation. A duadecapolar catheter was swept from anterior to posterior in the right (and/or left) atrium, allowing for rapid mapping followed by entrainment confirmation. Twenty-eight patients had corrected congenital heart disease, 17 surgery for acquired heart disease. One hundred and sixteen arrhythmias were found, 86 circuits were targeted, 81 with success (94%). Despite the heterogeneous anatomy, the same targets were often encountered: the posterior isthmus between the inferior vena cava and the tricuspid ring (62%), the gap between the inferior vena cava and the atriotomy scar (49%), and the region around the atriopulmonary connection in Fontans (two out of four patients). After a mean follow-up of 24 months, 13 patients had a recurrent arrhythmia (29%) after their last procedure. There was a significant association between the number of circuits found during the initial procedure and the likelihood of recurrent arrhythmias. Knowledge of anatomical predilection sites and mapping the right (and/or left) atrium with a 'sweeping Halo technique' allow for effective ablation of most post-surgical atrial tachycardias. Severely damaged atria with multiple arrhythmias may require 'preventive' ablation of all recognizable channels.

Early- and Middle-Term Surgical Outcomes in Patients with Heterotaxy Syndrome.

PubMed

Chen, Weidan; Ma, Li; Cui, Hujun; Yang, Shengchun; Xia, Yuansheng; Zou, Minghui; Chen, Xinxin

2016-01-01

Heterotaxy syndrome is a recognized risk factor for surgical cardiac interventions. We evaluated the early- and middle-term results of a surgical intervention for patients with heterotaxy syndrome. A total of 42 patients with heterotaxy syndrome were enrolled (September 2008 to March 2015). Left and right atrial isomerism were identified in 26% (11 out of 42) and 74% of patients (31 out of 42), respectively. The median age of the patients at the time of surgery was 6.8 months (range: 5 days to 22.3 years). Biventricular repair was completed in 3 patients with left atrial isomerism. Seventeen out of 39 patients who were scheduled for single ventricular repair completed a modified Fontan procedure. The hospital mortality rate was 4.7% (2 out of 42). Another 5 deaths occurred in the remaining survivors following hospital discharge with a follow-up duration of 45.8 ± 23.6 months (range: 13-111 months). The 1-year and 5-year survival rates were 88.1% (37/42) and 83.3% (35/42), respectively. Univariate analysis and multivariate analysis identified pulmonary venous obstruction and atrioventricular valve replacement as additional risk factors for mortality. Right ventricular bypass surgery remains the preferred palliative procedure for patients with heterotaxy syndrome. Based on the current results, the early- and middle-term outcomes are satisfactory. © 2015 S. Karger AG, Basel.

First report of atretic coronary sinus stenting in a 5-kg infant resulting in dramatic improvement of ventricular function in functional single ventricle.

PubMed

El-Said, Howaida; Hegde, Sanjeet; Moore, John

2014-01-01

The patient was a male infant with L-transposition of great arteries (L-TGA), Ebstein's anomaly of the tricuspid valve, subvalvar aortic stenosis, ventricular septal defect (VSD), hypoplastic right ventricle, arch hypoplasia, and congenital complete heart block. He underwent a Norwood procedure, aortic arch repair, permanent pacemaker implantation, and a 3.5-mm aortopulmonary shunt at 4 days of age. At the time of his surgery, left ventricular function was in the normal range (ejection fraction [EF] = 67%). However by 3 months of age, he was noted to have developed moderate-severe biventricular dysfunction (left ventricular ejection fraction [LVEF] = 34%). Atresia of the coronary sinus with a small left superior venacava (LSVC) and a bridging vein was discovered during cardiac catheterization at this time. The coronary sinus mean pressure was 17 mm Hg, and the common atrial mean pressure was 6 mmHg. We opened the atretic coronary sinus ostium using radiofrequency ablation and stent placement. There was dramatic improvement in ventricular function observed over a 2-month period. Follow-up cardiac catheterization 5 months later revealed the stent in the coronary sinus to be widely patent with no intimal buildup, and the ventricular function was normal (LVEF = 58%). The patient had a bidirectional Glenn procedure with an uncomplicated postoperative course and is currently awaiting Fontan completion. © 2013 Wiley Periodicals, Inc.

Modeling the Transformational Communications System Urban Land Mobile Satellite Channel

DTIC Science & Technology

2007-12-01

interference of time - delayed signals). The “slow” variations are usually associated with specific shadowing events by foliage, terrain or buildings. The...by F. P. Fontan et al. [24].......................11 Figure 4. Short, medium and long-term variation of signal strength with time . Long- term...long-term variation of signal strength with time . Long- term (“very slow”) variation is modeled by state transitions shown in Figure 3. C

Transcatheter recanalization of ligated main pulmonary artery.

PubMed

Bhole, Vinay; Wright, John G C; Stumper, Oliver

2007-04-01

A 12.5-year-old boy with tricuspid atresia and quadriplegic cerebral palsy presented with increasing cyanosis after previous palliation with a cavopulmonary shunt and ligation of the main pulmonary artery (MPA). Because of severe physical disabilities he was not considered suitable for Fontan completion. He underwent successful transcatheter stent recanalization of the ligated MPA. This re-established anterograde flow to the pulmonary arteries resulting in marked improvement in saturations.

Electrophysiology and structural interventions in adults with congenital heart disease: Comparison of combined versus separate procedures.

PubMed

Lindsay, Ian; Nik-Ahd, Farnoosh; Aboulhosn, Jamil A; Moore, Jeremy P

2018-05-18

Electrophysiologic (EP) and structural interventions in adult congenital heart disease (ACHD) are typically completed during separate hospital encounters. With planning/coordination, these cases can be combined. We hypothesized that this integrated approach would yield patient and health system benefits. Consecutive ACHD patients undergoing combined interventions were matched to controls with identical but separate procedures. Primary endpoints of total hospital length of stay and cost were compared. Sixty-six combined cases and 120 controls were identified (45% male, mean age 36.2 ± 14.2 years). The most common diagnoses were Fontan (27%), tetralogy of Fallot (23%), and transposition complexes (20%). The most common EP procedure was catheter ablation (n = 30) followed by electrophysiologic study (n = 13); the most common structural intervention was transcatheter valve replacement (n = 16) followed by angioplasty/stenting (n = 14). Compared to controls, cases showed shorter anesthesia duration (323 [IQR 238-405] vs. 355 minutes [270-498], P = 0.06), smaller contrast dose (130 [50-189] vs. 177 mL [94-228], P = 0.045), fewer venipunctures (4 [3-4] vs. 6 [5-7], P < 0.001), and fewer work days missed (2 [2-5] vs. 4 [4-6], P < 0.001). There was shorter hospital stay (30 [19-35] vs. 38 hours [26-50], P = 0.023) and a 37% reduction in hospital charges ($117,894 vs. $187,648; P = 0.039) and 27% reduction in payments ($65,757 vs. $88,859; P = 0.016), persisting after adjustment for group differences. There were no significant differences in number of complications or efficacy. There appear to be advantages to combining ACHD interventional procedures that include reductions in hospital length of stay and cost, without detectable difference in procedural outcome. Published 2018. This article is a U.S. Government work and is in the public domain in the U.S.A.

Clinical Research Priorities in Adult Congenital Heart Disease

PubMed Central

Cotts, Timothy; Khairy, Paul; Opotowsky, Alexander R.; John, Anitha S.; Valente, Anne Marie; Zaidi, Ali N.; Cook, Stephen C.; Aboulhosn, Jamil; Ting, Jennifer Grando; Gurvitz, Michelle; Landzberg, Michael J.; Verstappen, Amy; Kay, Joseph; Earing, Michael; Franklin, Wayne; Kogon, Brian; Broberg, Craig S.

2014-01-01

Background Adult congenital heart disease (ACHD) clinicians are hampered by the paucity of data to inform clinical decision-making. The objective of this study was to identify priorities for clinical research in ACHD. Methods A list of 45 research questions was developed by the Alliance for Adult Research in Congenital Cardiology (AARCC), compiled into a survey, and administered to ACHD providers. Patient input was sought via the Adult Congenital Heart Association at community meetings and online forums. The 25 top questions were sent to ACHD providers worldwide via an online survey. Each question was ranked based on perceived priority and weighted based on time spent in ACHD care. The top 10 topics identified are presented and discussed. Results The final online survey yielded 139 responses. Top priority questions related to tetralogy of Fallot (timing of pulmonary valve replacement and criteria for primary prevention ICDs), patients with systemic right ventricles (determining the optimal echocardiographic techniques for measuring right ventricular function, and indications for tricuspid valve replacement and primary prevention ICDs), and single ventricle/Fontan patients (role of pulmonary vasodilators, optimal anticoagulation, medical therapy for preservation of ventricular function, treatment for protein losing enteropathy). In addition, establishing criteria to refer ACHD patients for cardiac transplantation was deemed a priority. Conclusions The ACHD field is in need of prospective research to address fundamental clinical questions. It is hoped that this methodical consultation process will inform researchers and funding organizations about clinical research topics deemed to be of high priority. PMID:24411207

Clinical research priorities in adult congenital heart disease.

PubMed

Cotts, Timothy; Khairy, Paul; Opotowsky, Alexander R; John, Anitha S; Valente, Anne Marie; Zaidi, Ali N; Cook, Stephen C; Aboulhosn, Jamil; Ting, Jennifer Grando; Gurvitz, Michelle; Landzberg, Michael J; Verstappen, Amy; Kay, Joseph; Earing, Michael; Franklin, Wayne; Kogon, Brian; Broberg, Craig S

2014-02-15

Adult congenital heart disease (ACHD) clinicians are hampered by the paucity of data to inform clinical decision-making. The objective of this study was to identify priorities for clinical research in ACHD. A list of 45 research questions was developed by the Alliance for Adult Research in Congenital Cardiology (AARCC), compiled into a survey, and administered to ACHD providers. Patient input was sought via the Adult Congenital Heart Association at community meetings and online forums. The 25 top questions were sent to ACHD providers worldwide via an online survey. Each question was ranked based on perceived priority and weighted based on time spent in ACHD care. The top 10 topics identified are presented and discussed. The final online survey yielded 139 responses. Top priority questions related to tetralogy of Fallot (timing of pulmonary valve replacement and criteria for primary prevention ICDs), patients with systemic right ventricles (determining the optimal echocardiographic techniques for measuring right ventricular function, and indications for tricuspid valve replacement and primary prevention ICDs), and single ventricle/Fontan patients (role of pulmonary vasodilators, optimal anticoagulation, medical therapy for preservation of ventricular function, treatment for protein losing enteropathy). In addition, establishing criteria to refer ACHD patients for cardiac transplantation was deemed a priority. The ACHD field is in need of prospective research to address fundamental clinical questions. It is hoped that this methodical consultation process will inform researchers and funding organizations about clinical research topics deemed to be of high priority. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Vortex Flow in the Right Atrium Surrogates Supraventricular Arrhythmia and Thrombus After Atriopulmonary Connection-Type Fontan Operation: Vortex Flow Analysis Using Conventional Cine Magnetic Resonance Imaging.

PubMed

Shiina, Yumi; Inai, Kei; Takahashi, Tatsunori; Shimomiya, Yamato; Ishizaki, Umiko; Fukushima, Kenji; Nagao, Michinobu

2018-02-01

We developed a novel imaging technique, designated as vortex flow (VF) mapping, which presents a vortex flow visually on conventional two-dimensional (2D) cine MRI. Using it, we assessed circumferential VF patterns and influences on RA thrombus and supraventricular tachycardia (SVT) in AP connection-type Fontan circulation. Retrospectively, we enrolled 27 consecutive patients (25.1 ± 9.2 years) and 7 age-matched controls who underwent cardiac MRI. Conventional cine images acquired using a 1.5-Tesla scanner were scanned for axial and coronal cross section of the RA. We developed "vortex flow mapping" to demonstrate the ratio of the circumferential voxel movement at each phase to the total movement throughout a cardiac cycle towards the RA center. The maximum ratio was used as a magnitude of vortex flow (MVF%) in RA cine imaging. We also measured percentages of strong and weak VF areas (VFA%). Furthermore, in 10 out of 27, we compared VF between previous CMR (3.8 ± 1.5 years ago) and latest CMR. Of the patients, 15 had cardiovascular complications (Group A); 12 did not (Group B). A transaxial image showed that strong VFA% in Group A was significantly smaller than that in Group B or controls. A coronal view revealed that strong VFA% was also smaller, and weak VFA% was larger in Group A than in Group B or controls (P < 0.05, and P < 0.05). Maximum MVF% in Group A was significantly smaller than in other groups (P < 0.001). Univariate logistic analyses revealed weak VFA% on a coronal image, and serum total bilirubin level as factors affecting cardiovascular complications (Odds ratio 1.14 and 66.1, 95% CI 1.004-1.30 and 1.59-2755.6, P values < 0.05 and < 0.05, respectively). Compared to the previous CMR, smaller maximum VMF%, smaller strong VFA%, and larger weak VFA% were identified in the latest CMR. Circumferentially weak VFA% on a coronal image can be one surrogate marker of SVT and thrombus in AP connection-type Fontan circulation. This simple VF assessment is clinically useful to detect blood stagnation.

Advances in cardiovascular fluid mechanics: bench to bedside.

PubMed

Dasi, Lakshmi P; Sucosky, Philippe; de Zelicourt, Diane; Sundareswaran, Kartik; Jimenez, Jorge; Yoganathan, Ajit P

2009-04-01

This paper presents recent advances in cardiovascular fluid mechanics that define the current state of the art. These studies include complex multimodal investigations with advanced measurement and simulation techniques. We first discuss the complex flows within the total cavopulmonary connection in Fontan patients. We emphasize the quantification of energy losses by studying the importance of caval offsets as well as the differences among various Fontan surgical protocols. In our studies of the fluid mechanics of prosthetic heart valves, we reveal for the first time the full three-dimensional complexity of flow fields in the vicinity of bileaflet and trileaflet valves and the microscopic hinge flow dynamics. We also present results of these valves functioning in a patient-specific native aorta geometry. Our in vitro mitral valve studies show the complex mechanism of the native mitral valve apparatus. We demonstrate that the different components of the mitral valve have independent and synergistically complex functions that allow the valve to operate efficiently. We also show how valve mechanics change under pathological and repair conditions associated with enlarged ventricles. Finally, our ex vivo studies on the interactions between the aortic valve and its surrounding hemodynamic environment are aimed at providing insights into normal valve function and valve pathology. We describe the development of organ- and tissue-culture systems and the biological response of the tissue subjected to their respective simulated mechanical environment. The studies noted above have enhanced our understanding of the complex fluid mechanics associated with the cardiovascular system and have led to new translational technologies.

Differences in coagulation among Asians and Caucasians and the implication for reconstructive microsurgery.

PubMed

Singhal, Dhruv; Smorodinsky, Emmanuil; Guo, Lifei

2011-01-01

Microvascular reconstructive surgery has seen a revival with the introduction of muscle-sparing perforator flaps. Recognition of potential ethnic differences in coagulation profiles would be important to a microvascular surgeon. Based on clinical observations, we hypothesize that Asian patients have a less thrombogenic coagulation profile than Caucasians. An extensive retrospective review was performed. The annual incidence of venous thromboembolism in the United States is generally accepted to range from 70 to 120 events per 100,000 people versus 16 to 17 events per 100,000 persons in Asia. Autopsy analysis of pulmonary embolism incidence was noted to be 15% in North Americans and less than 1% in Asian populations. Thromboelastography analysis of Asian and Caucasian patients undergoing cholecystectomy revealed different hemostatic mechanisms. Comparison of Asians and Caucasians undergoing the Fontan procedure revealed significantly lower postoperative factor levels in Asians than Caucasians. Baseline comparison of factor and serum levels revealed Asians with the least thrombogenic profiles compared with other ethnic groups. Asians and Caucasians demonstrate different baseline rates of deep vein thrombosis and pulmonary embolism, different hemostatic responses to surgery, and different baseline levels of clotting factors. Further study may lead to better pre-, intra-, and postoperative care of the free flap patient based on their ethnic coagulation profile. © Thieme Medical Publishers.

Single Center Experience with the AngioVac Aspiration System

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

Salsamendi, Jason, E-mail: jsalsamendi@med.miami.edu; Doshi, Mehul, E-mail: mdoshi@med.miami.edu; Bhatia, Shivank, E-mail: sbhatia1@med.miami.edu

2015-08-15

PurposeThe AngioVac catheter system is a mechanical suction device designed for removal of intravascular material using extracorporeal veno-venous bypass circuit. The purpose of this study is to present the outcomes in patients treated with the AngioVac aspiration system and to discuss its efficacy in different vascular beds.Materials and MethodsA retrospectively review was performed of seven patients treated with AngioVac between October 2013 and December 2014. In 6/7 cases, the AngioVac cannula was inserted percutaneously and the patient was placed on veno-venous bypass. In one of the cases, the cannula was inserted directly into the Fontan circuit after sternotomy and themore » patient was maintained on cardiopulmonary bypass. Thrombus location included iliocaval (2), SVC (1), pulmonary arteries (1), Fontan circuit and Glenn shunt with pulmonary artery extension (1), right atrium (1), and IVC with renal vein extension (1).ResultsThe majority of thrombus (50–95 %) was removed in 5/7 cases, and partial thrombus removal (<50 %) was confirmed in 2/7 cases. Mean follow-up was 205 days (range 64–403 days). All patients were alive at latest follow-up. Minor complications included three neck hematomas in two total patients. No major complications occurred.ConclusionAngioVac is a useful tool for acute thrombus removal in the large vessels. The setup and substantial cost may limit its application in straightforward cases. More studies are needed to establish the utility of AngioVac in treatment of intravascular and intracardiac material.« less

Increasing mortality burden among adults with complex congenital heart disease.

PubMed

Greutmann, Matthias; Tobler, Daniel; Kovacs, Adrienne H; Greutmann-Yantiri, Mehtap; Haile, Sarah R; Held, Leonhard; Ivanov, Joan; Williams, William G; Oechslin, Erwin N; Silversides, Candice K; Colman, Jack M

2015-01-01

Progress in management of congenital heart disease has shifted mortality largely to adulthood. However, adult survivors with complex congenital heart disease are not cured and remain at risk of premature death as young adults. Thus, our aim was to describe the evolution and mortality risk of adult patient cohorts with complex congenital heart disease. Among 12,644 adults with congenital heart disease followed at a single center from 1980 to 2009, 176 had Eisenmenger syndrome, 76 had unrepaired cyanotic defects, 221 had atrial switch operations for transposition of the great arteries, 158 had congenitally corrected transposition of the great arteries, 227 had Fontan palliation, and 789 had repaired tetralogy of Fallot. We depict the 30-year evolution of these 6 patient cohorts, analyze survival probabilities in adulthood, and predict future number of deaths through 2029. Since 1980, there has been a steady increase in numbers of patients followed, except in cohorts with Eisenmenger syndrome and unrepaired cyanotic defects. Between 1980 and 2009, 308 patients in the study cohorts (19%) died. At the end of 2009, 85% of survivors were younger than 50 years. Survival estimates for all cohorts were markedly lower than for the general population, with important differences between cohorts. Over the upcoming two decades, we predict a substantial increase in numbers of deaths among young adults with subaortic right ventricles, Fontan palliation, and repaired tetralogy of Fallot. Anticipatory action is needed to prepare clinical services for increasing numbers of young adults at risk of dying from complex congenital heart disease. © 2014 The Authors. Congenital Heart Disease Published by Wiley Periodicals, Inc.

Parental mental health moderates the efficacy of exercise training on health-related quality of life in adolescents with congenital heart disease.

PubMed

Dulfer, Karolijn; Duppen, Nienke; Van Dijk, Arie P J; Kuipers, Irene M; Van Domburg, Ron T; Verhulst, Frank C; Van der Ende, Jan; Helbing, Willem A; Utens, Elisabeth M W J

2015-01-01

To evaluate the moderating influence of parental variables on changes in health-related quality of life (HRQoL) in adolescents with Tetralogy of Fallot (ToF) or a Fontan circulation after participation in standardized exercise training. A multicenter randomized controlled trail in which 56 patients, aged 10-15, were randomly allocated (stratified by age, gender, and congenital heart disease) to a 12-week period with either: (a) 3 times per week standardized exercise training or (b) care-as-usual (randomization ratio 2:1). Adolescents and their parents filled in online questionnaires at baseline and at 12-week follow-up. In this randomized controlled trail, primary analyses involved influence of parental mental health and parental social support for exercise on changes in the TNO/AZL Child Quality of Life Questionnaire Child Form at follow-up. Secondary analyses concerned comparing levels of parental characteristics with normative data. Compared with controls, adolescents in the exercise group reported a decrease in social functioning when their parents had more anxiety/insomnia or severe depression themselves. Adolescents also reported a decrease in social functioning when their parents showed poorer overall mental health themselves. Parents reported comparable or even better mental health compared with normative data. The effect of a standardized exercise program on HRQoL changes in adolescents with ToF or a Fontan circulation is moderated by parental mental health, more specifically by parental anxiety/insomnia and severe depression. The trial registration number of this article is NTR2731 ( www.trialregister.nl ).

Electroanatomic Mapping-Guided Catheter Ablation of Supraventricular Tachycardia in Children with Ebstein's Anomaly.

PubMed

Ergul, Yakup; Koca, Serhat; Akdeniz, Celal; Tuzcu, Volkan

2018-06-07

In Ebstein's anomaly (EA), tachycardia substrates are complex, and accessory pathway (AP) ablations are often challenging. This study demonstrates the utility of the EnSite Velocity system (St. Jude Medical, St Paul, MN) in the catheter ablation of supraventricular tachycardia in children with EA. Twenty patients [Female/Male = 8/12, median age 11.5 years (2.6-18)] with EA who underwent catheter ablation guided by the EnSite Velocity system between December 2011 and December 2016 were retrospectively evaluated. Five patients had severe EA, and two of them were at Fontan palliation pathway. The most common indications for ablations were palpitations/syncope and treatment-resistant arrhythmias. Thirty-one tachycardia substrate foci (21 manifest AP, 2 concealed AP, 4 Mahaim AP, 3 focal atrial tachycardias, and 1 typical atrioventricular nodal reentrant tachycardia) were detected in 20 patients. There were multiple tachycardia substrates in 11 patients (55%). The patient-based acute procedure success rate was 19/20 (95%), and the tachycardia-based success rate was 30/31 (97%). The mean procedure time was 170 ± 43 min (90-265). Fluoroscopy was not used in 15 (75%) patients. The mean fluoroscopy time in the remaining five patients was 3.6 ± 2.9 min (0.7-7.8). During a mean follow-up of 35.1 ± 20.3 months (6-60), tachycardia recurred in four patients (4/19, 21%). No complications were seen. Catheter ablation of arrhythmias can be performed effectively and safely in pediatric EA patients by using a limited fluoroscopic approach with the help of electroanatomical mapping systems. However, the rate of tachycardia recurrence at follow-up remains high.

Management of Coronary Sinus Ostial Atresia during a Staged Operation of a Functional Single Ventricle.

PubMed

Kang, Seung Ri; Park, Won Kyoun; Kwon, Bo Sang; Ko, Jae Kon; Goo, Hyun Woo; Park, Jeong-Jun

2018-04-01

Coronary sinus ostial atresia (CSOA) with persistent left superior vena cava (LSVC) in the absence of an unroofed coronary sinus is a benign and rare anomaly that may be taken lightly in most instances. However, if overlooked in patients undergoing univentricular heart repair such as bidirectional Glenn or Fontan-type surgery, fatal surgical outcomes may occur due to coronary venous drainage failure. We report a case of CSOA with a persistent LSVC that was managed through coronary sinus rerouting during a total cavopulmonary connection, and provide a review of the literature regarding this rare anomaly.

Optimal False Discovery Rate Control for Dependent Data

PubMed Central

Xie, Jichun; Cai, T. Tony; Maris, John; Li, Hongzhe

2013-01-01

This paper considers the problem of optimal false discovery rate control when the test statistics are dependent. An optimal joint oracle procedure, which minimizes the false non-discovery rate subject to a constraint on the false discovery rate is developed. A data-driven marginal plug-in procedure is then proposed to approximate the optimal joint procedure for multivariate normal data. It is shown that the marginal procedure is asymptotically optimal for multivariate normal data with a short-range dependent covariance structure. Numerical results show that the marginal procedure controls false discovery rate and leads to a smaller false non-discovery rate than several commonly used p-value based false discovery rate controlling methods. The procedure is illustrated by an application to a genome-wide association study of neuroblastoma and it identifies a few more genetic variants that are potentially associated with neuroblastoma than several p-value-based false discovery rate controlling procedures. PMID:23378870

Development of Multiobjective Optimization Techniques for Sonic Boom Minimization

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; Rajadas, John Narayan; Pagaldipti, Naryanan S.

1996-01-01

A discrete, semi-analytical sensitivity analysis procedure has been developed for calculating aerodynamic design sensitivities. The sensitivities of the flow variables and the grid coordinates are numerically calculated using direct differentiation of the respective discretized governing equations. The sensitivity analysis techniques are adapted within a parabolized Navier Stokes equations solver. Aerodynamic design sensitivities for high speed wing-body configurations are calculated using the semi-analytical sensitivity analysis procedures. Representative results obtained compare well with those obtained using the finite difference approach and establish the computational efficiency and accuracy of the semi-analytical procedures. Multidisciplinary design optimization procedures have been developed for aerospace applications namely, gas turbine blades and high speed wing-body configurations. In complex applications, the coupled optimization problems are decomposed into sublevels using multilevel decomposition techniques. In cases with multiple objective functions, formal multiobjective formulation such as the Kreisselmeier-Steinhauser function approach and the modified global criteria approach have been used. Nonlinear programming techniques for continuous design variables and a hybrid optimization technique, based on a simulated annealing algorithm, for discrete design variables have been used for solving the optimization problems. The optimization procedure for gas turbine blades improves the aerodynamic and heat transfer characteristics of the blades. The two-dimensional, blade-to-blade aerodynamic analysis is performed using a panel code. The blade heat transfer analysis is performed using an in-house developed finite element procedure. The optimization procedure yields blade shapes with significantly improved velocity and temperature distributions. The multidisciplinary design optimization procedures for high speed wing-body configurations simultaneously improve the aerodynamic, the sonic boom and the structural characteristics of the aircraft. The flow solution is obtained using a comprehensive parabolized Navier Stokes solver. Sonic boom analysis is performed using an extrapolation procedure. The aircraft wing load carrying member is modeled as either an isotropic or a composite box beam. The isotropic box beam is analyzed using thin wall theory. The composite box beam is analyzed using a finite element procedure. The developed optimization procedures yield significant improvements in all the performance criteria and provide interesting design trade-offs. The semi-analytical sensitivity analysis techniques offer significant computational savings and allow the use of comprehensive analysis procedures within design optimization studies.

Effect of Fontan geometry on exercise haemodynamics and its potential implications.

PubMed

Tang, Elaine; Wei, Zhenglun Alan; Whitehead, Kevin K; Khiabani, Reza H; Restrepo, Maria; Mirabella, Lucia; Bethel, James; Paridon, Stephen M; Marino, Bradley S; Fogel, Mark A; Yoganathan, Ajit P

2017-11-01

Exercise intolerance afflicts Fontan patients with total cavopulmonary connections (TCPCs) causing a reduction in quality of life. Optimising TCPC design is hypothesised to have a beneficial effect on exercise capacity. This study investigates relationships between TCPC geometries and exercise haemodynamics and performance. This study included 47 patients who completed metabolic exercise stress test with cardiac magnetic resonance (CMR). Phase-contrast CMR images were acquired immediately following supine lower limb exercise. Both anatomies and exercise vessel flow rates at ventilatory anaerobic threshold (VAT) were extracted. The vascular modelling toolkits were used to analyse TCPC geometries. Computational simulations were performed to quantify TCPC indexed power loss (iPL) at VAT. A highly significant inverse correlation was found between the TCPC diameter index, which factors in the narrowing of TCPC vessels, with iPL at VAT (r=-0.723, p<0.001) but positive correlations with exercise performance variables, including minute oxygen consumption (VO 2 ) at VAT (r=0.373, p=0.01), VO 2 at peak exercise (r=0.485, p=0.001) and work at VAT/weight (r=0.368, p=0.01). iPL at VAT was negatively correlated with VO 2 at VAT (r=-0.337, p=0.02), VO 2 at peak exercise (r=-0.394, p=0.007) and work at VAT/weight (r=-0.208, p=0.17). Eliminating vessel narrowing in TCPCs and reducing elevated iPL at VAT could enhance exercise tolerance for patients with TCPCs. These findings could help plan surgical or catheter-based strategies to improve patients' exercise capacity. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Oral anticoagulant therapy in adults with congenital heart disease and atrial arrhythmias: Implementation of guidelines.

PubMed

Yang, H; Heidendael, J F; de Groot, J R; Konings, T C; Veen, G; van Dijk, A P J; Meijboom, F J; Sieswerda, G Tj; Post, M C; Winter, M M; Mulder, B J M; Bouma, B J

2018-04-15

Current guidelines on oral anticoagulation (OAC) in adults with congenital heart disease (ACHD) and atrial arrhythmias (AA) consist of heterogeneous and divergent recommendations with limited level of evidence, possibly leading to diverse OAC management and different outcomes. Therefore, we aimed to evaluate real-world implementation and outcome of three guidelines on OAC management in ACHD patients with AA. The ESC GUCH 2010, PACES/HRS 2014 and ESC atrial fibrillation (AF) 2016 guidelines were assessed for implementation. ACHD patients with recurrent or sustained non-valvular AA from 5 tertiary centers were identified using a national ACHD registry. After two years of prospective follow-up, thromboembolism, major bleeding and death were assessed. In total, 225 adults (mean age 54±15years, 55% male) with various defects (simple 43%; moderate 37%; complex 20%) and AA were included. Following the most strict indication (OAC is recommended in all three guidelines), one should treat a mere 37% of ACHD patients with AA, whereas following the least strict indication (OAC is recommended in any one of the three guidelines), one should treat 98% of patients. The various guidelines were implemented in 54-80% of patients. From all recommendations, Fontan circulation, CHA2DS2-VASc≥1 and AF were independently associated with OAC prescription. Superiority of any guideline in identifying outcome (n=15) could not be demonstrated. The implementation of current guidelines on OAC management in ACHD patients with AA is low, probably due to substantial heterogeneity among guidelines. OAC prescription in daily practice was most consistent in patients with AF and CHA2DS2-VASc≥1 or Fontan circulation. Copyright © 2017 Elsevier B.V. All rights reserved.

Systemic Right Ventricle in Adults With Congenital Heart Disease: Anatomic and Phenotypic Spectrum and Current Approach to Management.

PubMed

Brida, Margarita; Diller, Gerhard-Paul; Gatzoulis, Michael A

2018-01-30

The systemic right ventricle (SRV) is commonly encountered in congenital heart disease representing a distinctly different model in terms of its anatomic spectrum, adaptation, clinical phenotype, and variable, but overall guarded prognosis. The most common clinical scenarios where an SRV is encountered are complete transposition of the great arteries with previous atrial switch repair, congenitally corrected transposition of the great arteries, double inlet right ventricle mostly with previous Fontan palliation, and hypoplastic left heart syndrome palliated with the Norwood-Fontan protocol. The reasons for the guarded prognosis of the SRV in comparison with the systemic left ventricle are multifactorial, including distinct fibromuscular architecture, shape and function, coronary artery supply mismatch, intrinsic abnormalities of the tricuspid valve, intrinsic or acquired conduction abnormalities, and varied SRV adaptation to pressure or volume overload. Management of the SRV remains an ongoing challenge because SRV dysfunction has implications on short- and long-term outcomes for all patients irrespective of underlying cardiac morphology. SRV dysfunction can be subclinical, underscoring the need for tertiary follow-up and timely management of target hemodynamic lesions. Catheter interventions and surgery have an established role in selected patients. Cardiac resynchronization therapy is increasingly used, whereas pharmacological therapy is largely empirical. Mechanical assist device and heart transplantation remain options in end-stage heart failure when other management strategies have been exhausted. The present report focuses on the SRV with its pathological subtypes, pathophysiology, clinical features, current management strategies, and long-term sequelae. Although our article touches on issues applicable to neonates and children, its main focus is on adults with SRV. © 2018 American Heart Association, Inc.

Computational study of engine external aerodynamics as a part of multidisciplinary optimization procedure

NASA Astrophysics Data System (ADS)

Savelyev, Andrey; Anisimov, Kirill; Kazhan, Egor; Kursakov, Innocentiy; Lysenkov, Alexandr

2016-10-01

The paper is devoted to the development of methodology to optimize external aerodynamics of the engine. Optimization procedure is based on numerical solution of the Reynolds-averaged Navier-Stokes equations. As a method of optimization the surrogate based method is used. As a test problem optimal shape design of turbofan nacelle is considered. The results of the first stage, which investigates classic airplane configuration with engine located under the wing, are presented. Described optimization procedure is considered in the context of multidisciplinary optimization of the 3rd generation, developed in the project AGILE.

The fenestrated Kawashima operation for single ventricle with interrupted inferior vena cava.

PubMed

Hannan, Robert L; Rossi, Anthony F; Nykanen, David G; Lopez, Leo; Alonso, Francisco; White, Jeffrey A; Burke, Redmond P

2003-01-01

An 8-month-old boy with double outlet right ventricle with hypoplastic left ventricle, heterotaxy, left atrial isomerism, bilateral superior vena cavae without bridging vein, and interruption of the inferior vena cava with azygous continuation to the left superior cava underwent a bilateral bidirectional cavopulmonary anastomosis. A calibrated 3-mm connection between the right pulmonary artery and the common atrium was constructed with the proximal right superior vena cava to allow right to left shunting, analogous to a fenestration in a Fontan operation. We hypothesize that in small young patients undergoing the Kawashima operation a fenestration may improve postoperative hemodynamics.

Procedures for shape optimization of gas turbine disks

NASA Technical Reports Server (NTRS)

Cheu, Tsu-Chien

1989-01-01

Two procedures, the feasible direction method and sequential linear programming, for shape optimization of gas turbine disks are presented. The objective of these procedures is to obtain optimal designs of turbine disks with geometric and stress constraints. The coordinates of the selected points on the disk contours are used as the design variables. Structural weight, stress and their derivatives with respect to the design variables are calculated by an efficient finite element method for design senitivity analysis. Numerical examples of the optimal designs of a disk subjected to thermo-mechanical loadings are presented to illustrate and compare the effectiveness of these two procedures.

Enhanced Multiobjective Optimization Technique for Comprehensive Aerospace Design. Part A

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; Rajadas, John N.

1997-01-01

A multidisciplinary design optimization procedure which couples formal multiobjectives based techniques and complex analysis procedures (such as computational fluid dynamics (CFD) codes) developed. The procedure has been demonstrated on a specific high speed flow application involving aerodynamics and acoustics (sonic boom minimization). In order to account for multiple design objectives arising from complex performance requirements, multiobjective formulation techniques are used to formulate the optimization problem. Techniques to enhance the existing Kreisselmeier-Steinhauser (K-S) function multiobjective formulation approach have been developed. The K-S function procedure used in the proposed work transforms a constrained multiple objective functions problem into an unconstrained problem which then is solved using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm. Weight factors are introduced during the transformation process to each objective function. This enhanced procedure will provide the designer the capability to emphasize specific design objectives during the optimization process. The demonstration of the procedure utilizes a computational Fluid dynamics (CFD) code which solves the three-dimensional parabolized Navier-Stokes (PNS) equations for the flow field along with an appropriate sonic boom evaluation procedure thus introducing both aerodynamic performance as well as sonic boom as the design objectives to be optimized simultaneously. Sensitivity analysis is performed using a discrete differentiation approach. An approximation technique has been used within the optimizer to improve the overall computational efficiency of the procedure in order to make it suitable for design applications in an industrial setting.

Performance optimization of helicopter rotor blades

NASA Technical Reports Server (NTRS)

Walsh, Joanne L.

1991-01-01

As part of a center-wide activity at NASA Langley Research Center to develop multidisciplinary design procedures by accounting for discipline interactions, a performance design optimization procedure is developed. The procedure optimizes the aerodynamic performance of rotor blades by selecting the point of taper initiation, root chord, taper ratio, and maximum twist which minimize hover horsepower while not degrading forward flight performance. The procedure uses HOVT (a strip theory momentum analysis) to compute the horse power required for hover and the comprehensive helicopter analysis program CAMRAD to compute the horsepower required for forward flight and maneuver. The optimization algorithm consists of the general purpose optimization program CONMIN and approximate analyses. Sensitivity analyses consisting of derivatives of the objective function and constraints are carried out by forward finite differences. The procedure is applied to a test problem which is an analytical model of a wind tunnel model of a utility rotor blade.

Least-squares/parabolized Navier-Stokes procedure for optimizing hypersonic wind tunnel nozzles

NASA Technical Reports Server (NTRS)

Korte, John J.; Kumar, Ajay; Singh, D. J.; Grossman, B.

1991-01-01

A new procedure is demonstrated for optimizing hypersonic wind-tunnel-nozzle contours. The procedure couples a CFD computer code to an optimization algorithm, and is applied to both conical and contoured hypersonic nozzles for the purpose of determining an optimal set of parameters to describe the surface geometry. A design-objective function is specified based on the deviation from the desired test-section flow-field conditions. The objective function is minimized by optimizing the parameters used to describe the nozzle contour based on the solution to a nonlinear least-squares problem. The effect of the changes in the nozzle wall parameters are evaluated by computing the nozzle flow using the parabolized Navier-Stokes equations. The advantage of the new procedure is that it directly takes into account the displacement effect of the boundary layer on the wall contour. The new procedure provides a method for optimizing hypersonic nozzles of high Mach numbers which have been designed by classical procedures, but are shown to produce poor flow quality due to the large boundary layers present in the test section. The procedure is demonstrated by finding the optimum design parameters for a Mach 10 conical nozzle and a Mach 6 and a Mach 15 contoured nozzle.

Optimization for minimum sensitivity to uncertain parameters

NASA Technical Reports Server (NTRS)

Pritchard, Jocelyn I.; Adelman, Howard M.; Sobieszczanski-Sobieski, Jaroslaw

1994-01-01

A procedure to design a structure for minimum sensitivity to uncertainties in problem parameters is described. The approach is to minimize directly the sensitivity derivatives of the optimum design with respect to fixed design parameters using a nested optimization procedure. The procedure is demonstrated for the design of a bimetallic beam for minimum weight with insensitivity to uncertainties in structural properties. The beam is modeled with finite elements based on two dimensional beam analysis. A sequential quadratic programming procedure used as the optimizer supplies the Lagrange multipliers that are used to calculate the optimum sensitivity derivatives. The method was perceived to be successful from comparisons of the optimization results with parametric studies.

Development of a turbomachinery design optimization procedure using a multiple-parameter nonlinear perturbation method

NASA Technical Reports Server (NTRS)

Stahara, S. S.

1984-01-01

An investigation was carried out to complete the preliminary development of a combined perturbation/optimization procedure and associated computational code for designing optimized blade-to-blade profiles of turbomachinery blades. The overall purpose of the procedures developed is to provide demonstration of a rapid nonlinear perturbation method for minimizing the computational requirements associated with parametric design studies of turbomachinery flows. The method combines the multiple parameter nonlinear perturbation method, successfully developed in previous phases of this study, with the NASA TSONIC blade-to-blade turbomachinery flow solver, and the COPES-CONMIN optimization procedure into a user's code for designing optimized blade-to-blade surface profiles of turbomachinery blades. Results of several design applications and a documented version of the code together with a user's manual are provided.

Multidisciplinary design optimization using multiobjective formulation techniques

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; Pagaldipti, Narayanan S.

1995-01-01

This report addresses the development of a multidisciplinary optimization procedure using an efficient semi-analytical sensitivity analysis technique and multilevel decomposition for the design of aerospace vehicles. A semi-analytical sensitivity analysis procedure is developed for calculating computational grid sensitivities and aerodynamic design sensitivities. Accuracy and efficiency of the sensitivity analysis procedure is established through comparison of the results with those obtained using a finite difference technique. The developed sensitivity analysis technique are then used within a multidisciplinary optimization procedure for designing aerospace vehicles. The optimization problem, with the integration of aerodynamics and structures, is decomposed into two levels. Optimization is performed for improved aerodynamic performance at the first level and improved structural performance at the second level. Aerodynamic analysis is performed by solving the three-dimensional parabolized Navier Stokes equations. A nonlinear programming technique and an approximate analysis procedure are used for optimization. The proceduredeveloped is applied to design the wing of a high speed aircraft. Results obtained show significant improvements in the aircraft aerodynamic and structural performance when compared to a reference or baseline configuration. The use of the semi-analytical sensitivity technique provides significant computational savings.

New Method of Calibrating IRT Models.

ERIC Educational Resources Information Center

Jiang, Hai; Tang, K. Linda

This discussion of new methods for calibrating item response theory (IRT) models looks into new optimization procedures, such as the Genetic Algorithm (GA) to improve on the use of the Newton-Raphson procedure. The advantages of using a global optimization procedure like GA is that this kind of procedure is not easily affected by local optima and…

47 CFR 1.2202 - Competitive bidding design options.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Section 1.2202 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL PRACTICE AND PROCEDURE Grants...) Procedures that utilize mathematical computer optimization software, such as integer programming, to evaluate... evaluating bids using a ranking based on specified factors. (B) Procedures that combine computer optimization...

Fully integrated aerodynamic/dynamic optimization of helicopter rotor blades

NASA Technical Reports Server (NTRS)

Walsh, Joanne L.; Lamarsh, William J., II; Adelman, Howard M.

1992-01-01

This paper describes a fully integrated aerodynamic/dynamic optimization procedure for helicopter rotor blades. The procedure combines performance and dynamics analyses with a general purpose optimizer. The procedure minimizes a linear combination of power required (in hover, forward flight, and maneuver) and vibratory hub shear. The design variables include pretwist, taper initiation, taper ratio, root chord, blade stiffnesses, tuning masses, and tuning mass locations. Aerodynamic constraints consist of limits on power required in hover, forward flight and maneuver; airfoil section stall; drag divergence Mach number; minimum tip chord; and trim. Dynamic constraints are on frequencies, minimum autorotational inertia, and maximum blade weight. The procedure is demonstrated for two cases. In the first case the objective function involves power required (in hover, forward flight, and maneuver) and dynamics. The second case involves only hover power and dynamics. The designs from the integrated procedure are compared with designs from a sequential optimization approach in which the blade is first optimized for performance and then for dynamics. In both cases, the integrated approach is superior.

Fully integrated aerodynamic/dynamic optimization of helicopter rotor blades

NASA Technical Reports Server (NTRS)

Walsh, Joanne L.; Lamarsh, William J., II; Adelman, Howard M.

1992-01-01

A fully integrated aerodynamic/dynamic optimization procedure is described for helicopter rotor blades. The procedure combines performance and dynamic analyses with a general purpose optimizer. The procedure minimizes a linear combination of power required (in hover, forward flight, and maneuver) and vibratory hub shear. The design variables include pretwist, taper initiation, taper ratio, root chord, blade stiffnesses, tuning masses, and tuning mass locations. Aerodynamic constraints consist of limits on power required in hover, forward flight and maneuvers; airfoil section stall; drag divergence Mach number; minimum tip chord; and trim. Dynamic constraints are on frequencies, minimum autorotational inertia, and maximum blade weight. The procedure is demonstrated for two cases. In the first case, the objective function involves power required (in hover, forward flight and maneuver) and dynamics. The second case involves only hover power and dynamics. The designs from the integrated procedure are compared with designs from a sequential optimization approach in which the blade is first optimized for performance and then for dynamics. In both cases, the integrated approach is superior.

Modeling Training Site Vegetation Coverage Probability with a Random Optimizing Procedure: An Artificial Neural Network Approach.

DTIC Science & Technology

1998-05-01

Coverage Probability with a Random Optimization Procedure: An Artificial Neural Network Approach by Biing T. Guan, George Z. Gertner, and Alan B...Modeling Training Site Vegetation Coverage Probability with a Random Optimizing Procedure: An Artificial Neural Network Approach 6. AUTHOR(S) Biing...coverage based on past coverage. Approach A literature survey was conducted to identify artificial neural network analysis techniques applicable for

40 CFR 91.316 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2011 CFR

2011-07-01

... periodic optimization of detector response. Prior to introduction into service and at least annually... nitrogen. (2) One of the following procedures is required for FID or HFID optimization: (i) The procedure outlined in Society of Automotive Engineers (SAE) paper No. 770141, “Optimization of Flame Ionization...

Study of flutter related computational procedures for minimum weight structural sizing of advanced aircraft

NASA Technical Reports Server (NTRS)

Oconnell, R. F.; Hassig, H. J.; Radovcich, N. A.

1976-01-01

Results of a study of the development of flutter modules applicable to automated structural design of advanced aircraft configurations, such as a supersonic transport, are presented. Automated structural design is restricted to automated sizing of the elements of a given structural model. It includes a flutter optimization procedure; i.e., a procedure for arriving at a structure with minimum mass for satisfying flutter constraints. Methods of solving the flutter equation and computing the generalized aerodynamic force coefficients in the repetitive analysis environment of a flutter optimization procedure are studied, and recommended approaches are presented. Five approaches to flutter optimization are explained in detail and compared. An approach to flutter optimization incorporating some of the methods discussed is presented. Problems related to flutter optimization in a realistic design environment are discussed and an integrated approach to the entire flutter task is presented. Recommendations for further investigations are made. Results of numerical evaluations, applying the five methods of flutter optimization to the same design task, are presented.

How Near is a Near-Optimal Solution: Confidence Limits for the Global Optimum.

DTIC Science & Technology

1980-05-01

or near-optimal solutions are the only practical solutions available. This paper identifies and compares some procedures which use independent near...approximate or near-optimal solutions are the only practical solutions available. This paper identifies and compares some procedures which use inde- pendent...The objective of this paper is to indicate some relatively new statistical procedures for obtaining an upper confidence limit on G Each of these

Numerical modeling and optimization of the Iguassu gas centrifuge

NASA Astrophysics Data System (ADS)

Bogovalov, S. V.; Borman, V. D.; Borisevich, V. D.; Tronin, V. N.; Tronin, I. V.

2017-07-01

The full procedure of the numerical calculation of the optimized parameters of the Iguassu gas centrifuge (GC) is under discussion. The procedure consists of a few steps. On the first step the problem of a hydrodynamical flow of the gas in the rotating rotor of the GC is solved numerically. On the second step the problem of diffusion of the binary mixture of isotopes is solved. The separation power of the gas centrifuge is calculated after that. On the last step the time consuming procedure of optimization of the GC is performed providing us the maximum of the separation power. The optimization is based on the BOBYQA method exploring the results of numerical simulations of the hydrodynamics and diffusion of the mixture of isotopes. Fast convergence of calculations is achieved due to exploring of a direct solver at the solution of the hydrodynamical and diffusion parts of the problem. Optimized separative power and optimal internal parameters of the Iguassu GC with 1 m rotor were calculated using the developed approach. Optimization procedure converges in 45 iterations taking 811 minutes.

Relationship of cerebral blood flow to aortic-to-pulmonary collateral/shunt flow in single ventricles

PubMed Central

Fogel, Mark A; Li, Christine; Wilson, Felice; Pawlowski, Tom; Nicolson, Susan C; Montenegro, Lisa M; Berenstein, Laura Diaz; Spray, Thomas L; Gaynor, J William; Fuller, Stephanie; Keller, Marc S; Harris, Matthew A; Whitehead, Kevin K; Clancy, Robert; Elci, Okan; Bethel, Jim; Vossough, Arastoo; Licht, Daniel J

2016-01-01

Objective Patients with single ventricle can develop aortic-to-pulmonary collaterals (APCs). Along with systemic-to-pulmonary artery shunts, these structures represent a direct pathway from systemic to pulmonary circulations, and may limit cerebral blood flow (CBF). This study investigated the relationship between CBF and APC flow on room air and in hypercarbia, which increases CBF in patients with single ventricle. Methods 106 consecutive patients with single ventricle underwent 118 cardiac magnetic resonance (CMR) scans in this cross-sectional study; 34 prior to bidirectional Glenn (BDG) (0.50±0.30 years old), 50 prior to Fontan (3.19±1.03 years old) and 34 3–9 months after Fontan (3.98±1.39 years old). Velocity mapping measured flows in the aorta, cavae and jugular veins. Analysis of variance (ANOVA) and multiple linear regression were used. Significance was p<0.05. Results A strong inverse correlation was noted between CBF and APC/shunt both on room air and with hypercarbia whether CBF was indexed to aortic flow or body surface area, independent of age, cardiopulmonary bypass time, Po2 and Pco2 (R=−0.67–−0.70 for all patients on room air, p<0.01 and R=−0.49–−0.90 in hypercarbia, p<0.01). Correlations were not different between surgical stages. CBF was lower, and APCs/shunt flow was higher prior to BDG than in other stages. Conclusions There is a strong inverse relationship between CBF and APC/shunt flow in patients with single ventricle throughout surgical reconstruction on room air and in hypercarbia independent of other factors. We speculate that APC/shunt flow may have a negative impact on cerebral development and neurodevelopmental outcome. Interventions on APC may modify CBF, holding out the prospect for improving neurodevelopmental trajectory. Trial Registration Number NCT02135081. PMID:26048877

Model of complete separation of the hepatic veins from the systemic venous system.

PubMed

Brizard, C P; Goussef, N; Chachques, J C; Carpentier, A F

2000-12-01

In patients undergoing a Fontan operation, partial diversion of the hepatic veins to the pulmonary venous atrium has been tried with various techniques. They failed because of the development of intrahepatic collaterals leading to an unacceptable right-to-left shunting. We postulate that to avoid the formation of intrahepatic collaterals, the totality of the liver has to be drained into the same pressure compartment. We have designed a model of cavopulmonary anastomosis in which a prosthetic conduit reproduces an azygos continuation, associated with the diversion of the totality of the hepatic venous return. This article reports on the early hemodynamics and the fate of the separation of the two venous compartments in long-term survivors. Eighteen goats were operated on; the pulmonary artery and hepatic vein pressures were recorded. During month 2, an opacification of the inferior vena cava and the cavopulmonary connection was performed. Between months 6 and 14, another opacification was performed, together with pressure recording at both ends of the conduit. Postoperatively the pulmonary artery pressure was pulsatile with a mean of 10 mm Hg and the hepatic vein pressure was 0 mm Hg. The first angiogram showed patent tubes with fast progression of the contrast. Throughout the inferior vena cava injection, there was no opacification of the portal or hepatic veins. The late study showed a narrowed conduit in all animals. During the injection, a collateral was injected, feeding into the inferior mesenteric vein. No collateral circulation could be seen draining directly into the liver. The median gradient between the two ends of the conduit was 11 mm Hg. The isolation of the entire hepatic venous drainage is feasible and efficient for the separation of two pressure compartments. No intrahepatic collaterals are observed with this model at short- or long-term follow-up. The separation of the hepatic venous drainage should persist without collateral circulation as long as the inferior vena cava pressure stays at the levels observed in Fontan circulation.

Relationship of cerebral blood flow to aortic-to-pulmonary collateral/shunt flow in single ventricles.

PubMed

Fogel, Mark A; Li, Christine; Wilson, Felice; Pawlowski, Tom; Nicolson, Susan C; Montenegro, Lisa M; Diaz Berenstein, Laura; Spray, Thomas L; Gaynor, J William; Fuller, Stephanie; Keller, Marc S; Harris, Matthew A; Whitehead, Kevin K; Clancy, Robert; Elci, Okan; Bethel, Jim; Vossough, Arastoo; Licht, Daniel J

2015-08-01

Patients with single ventricle can develop aortic-to-pulmonary collaterals (APCs). Along with systemic-to-pulmonary artery shunts, these structures represent a direct pathway from systemic to pulmonary circulations, and may limit cerebral blood flow (CBF). This study investigated the relationship between CBF and APC flow on room air and in hypercarbia, which increases CBF in patients with single ventricle. 106 consecutive patients with single ventricle underwent 118 cardiac magnetic resonance (CMR) scans in this cross-sectional study; 34 prior to bidirectional Glenn (BDG) (0.50±0.30 years old), 50 prior to Fontan (3.19±1.03 years old) and 34 3-9 months after Fontan (3.98±1.39 years old). Velocity mapping measured flows in the aorta, cavae and jugular veins. Analysis of variance (ANOVA) and multiple linear regression were used. Significance was p<0.05. A strong inverse correlation was noted between CBF and APC/shunt both on room air and with hypercarbia whether CBF was indexed to aortic flow or body surface area, independent of age, cardiopulmonary bypass time, Po2 and Pco2 (R=-0.67--0.70 for all patients on room air, p<0.01 and R=-0.49--0.90 in hypercarbia, p<0.01). Correlations were not different between surgical stages. CBF was lower, and APCs/shunt flow was higher prior to BDG than in other stages. There is a strong inverse relationship between CBF and APC/shunt flow in patients with single ventricle throughout surgical reconstruction on room air and in hypercarbia independent of other factors. We speculate that APC/shunt flow may have a negative impact on cerebral development and neurodevelopmental outcome. Interventions on APC may modify CBF, holding out the prospect for improving neurodevelopmental trajectory. NCT02135081. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Development and application of an optimization procedure for flutter suppression using the aerodynamic energy concept

NASA Technical Reports Server (NTRS)

Nissim, E.; Abel, I.

1978-01-01

An optimization procedure is developed based on the responses of a system to continuous gust inputs. The procedure uses control law transfer functions which have been partially determined by using the relaxed aerodynamic energy approach. The optimization procedure yields a flutter suppression system which minimizes control surface activity in a gust environment. The procedure is applied to wing flutter of a drone aircraft to demonstrate a 44 percent increase in the basic wing flutter dynamic pressure. It is shown that a trailing edge control system suppresses the flutter instability over a wide range of subsonic mach numbers and flight altitudes. Results of this study confirm the effectiveness of the relaxed energy approach.

Model Specification Searches Using Ant Colony Optimization Algorithms

ERIC Educational Resources Information Center

Marcoulides, George A.; Drezner, Zvi

2003-01-01

Ant colony optimization is a recently proposed heuristic procedure inspired by the behavior of real ants. This article applies the procedure to model specification searches in structural equation modeling and reports the results. The results demonstrate the capabilities of ant colony optimization algorithms for conducting automated searches.

Beyond the drugs: nonpharmacologic strategies to optimize procedural care in children.

PubMed

Leroy, Piet L; Costa, Luciane R; Emmanouil, Dimitris; van Beukering, Alice; Franck, Linda S

2016-03-01

Painful and/or stressful medical procedures mean a substantial burden for sick children. There is good evidence that procedural comfort can be optimized by a comprehensive comfort-directed policy containing the triad of nonpharmacological strategies (NPS) in all cases, timely or preventive procedural analgesia if pain is an issue, and procedural sedation. Based both on well-established theoretical frameworks as well as an increasing body of scientific evidence NPS need to be regarded an inextricable part of procedural comfort care. Procedural comfort care must always start with a child-friendly, nonthreatening environment in which well-being, confidence, and self-efficacy are optimized and maintained. This requires a reconsideration of the medical spaces where we provide care, reduction of sensory stimulation, normalized professional behavior, optimal logistics, and coordination and comfort-directed and age-appropriate verbal and nonverbal expression by professionals. Next, age-appropriate distraction techniques and/or hypnosis should be readily available. NPS are useful for all types of medical and dental procedures and should always precede and accompany procedural sedation. NPS should be embedded into a family-centered, care-directed policy as it has been shown that family-centered care can lead to safer, more personalized, and effective care, improved healthcare experiences and patient outcomes, and more responsive organizations.

40 CFR 90.316 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) Initial and periodic optimization of detector response. Prior to initial use and at least annually... nitrogen. (2) Use of one of the following procedures is required for FID or HFID optimization: (i) The procedure outlined in Society of Automotive Engineers (SAE) paper No. 770141, “Optimization of a Flame...

Optimization of flexible wing structures subject to strength and induced drag constraints

NASA Technical Reports Server (NTRS)

Haftka, R. T.

1977-01-01

An optimization procedure for designing wing structures subject to stress, strain, and drag constraints is presented. The optimization method utilizes an extended penalty function formulation for converting the constrained problem into a series of unconstrained ones. Newton's method is used to solve the unconstrained problems. An iterative analysis procedure is used to obtain the displacements of the wing structure including the effects of load redistribution due to the flexibility of the structure. The induced drag is calculated from the lift distribution. Approximate expressions for the constraints used during major portions of the optimization process enhance the efficiency of the procedure. A typical fighter wing is used to demonstrate the procedure. Aluminum and composite material designs are obtained. The tradeoff between weight savings and drag reduction is investigated.

Integrated aerodynamic/dynamic/structural optimization of helicopter rotor blades using multilevel decomposition

NASA Technical Reports Server (NTRS)

Walsh, Joanne L.; Young, Katherine C.; Pritchard, Jocelyn I.; Adelman, Howard M.; Mantay, Wayne R.

1995-01-01

This paper describes an integrated aerodynamic/dynamic/structural (IADS) optimization procedure for helicopter rotor blades. The procedure combines performance, dynamics, and structural analyses with a general-purpose optimizer using multilevel decomposition techniques. At the upper level, the structure is defined in terms of global quantities (stiffness, mass, and average strains). At the lower level, the structure is defined in terms of local quantities (detailed dimensions of the blade structure and stresses). The IADS procedure provides an optimization technique that is compatible with industrial design practices in which the aerodynamic and dynamic designs are performed at a global level and the structural design is carried out at a detailed level with considerable dialog and compromise among the aerodynamic, dynamic, and structural groups. The IADS procedure is demonstrated for several examples.

Multilevel decomposition approach to integrated aerodynamic/dynamic/structural optimization of helicopter rotor blades

NASA Technical Reports Server (NTRS)

Walsh, Joanne L.; Young, Katherine C.; Pritchard, Jocelyn I.; Adelman, Howard M.; Mantay, Wayne R.

1994-01-01

This paper describes an integrated aerodynamic, dynamic, and structural (IADS) optimization procedure for helicopter rotor blades. The procedure combines performance, dynamics, and structural analyses with a general purpose optimizer using multilevel decomposition techniques. At the upper level, the structure is defined in terms of local quantities (stiffnesses, mass, and average strains). At the lower level, the structure is defined in terms of local quantities (detailed dimensions of the blade structure and stresses). The IADS procedure provides an optimization technique that is compatible with industrial design practices in which the aerodynamic and dynamic design is performed at a global level and the structural design is carried out at a detailed level with considerable dialogue and compromise among the aerodynamic, dynamic, and structural groups. The IADS procedure is demonstrated for several cases.

An integrated optimum design approach for high speed prop rotors

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; Mccarthy, Thomas R.

1995-01-01

The objective is to develop an optimization procedure for high-speed and civil tilt-rotors by coupling all of the necessary disciplines within a closed-loop optimization procedure. Both simplified and comprehensive analysis codes are used for the aerodynamic analyses. The structural properties are calculated using in-house developed algorithms for both isotropic and composite box beam sections. There are four major objectives of this study. (1) Aerodynamic optimization: The effects of blade aerodynamic characteristics on cruise and hover performance of prop-rotor aircraft are investigated using the classical blade element momentum approach with corrections for the high lift capability of rotors/propellers. (2) Coupled aerodynamic/structures optimization: A multilevel hybrid optimization technique is developed for the design of prop-rotor aircraft. The design problem is decomposed into a level for improved aerodynamics with continuous design variables and a level with discrete variables to investigate composite tailoring. The aerodynamic analysis is based on that developed in objective 1 and the structural analysis is performed using an in-house code which models a composite box beam. The results are compared to both a reference rotor and the optimum rotor found in the purely aerodynamic formulation. (3) Multipoint optimization: The multilevel optimization procedure of objective 2 is extended to a multipoint design problem. Hover, cruise, and take-off are the three flight conditions simultaneously maximized. (4) Coupled rotor/wing optimization: Using the comprehensive rotary wing code CAMRAD, an optimization procedure is developed for the coupled rotor/wing performance in high speed tilt-rotor aircraft. The developed procedure contains design variables which define the rotor and wing planforms.

Design of Quiet Rotorcraft Approach Trajectories

NASA Technical Reports Server (NTRS)

Padula, Sharon L.; Burley, Casey L.; Boyd, D. Douglas, Jr.; Marcolini, Michael A.

2009-01-01

A optimization procedure for identifying quiet rotorcraft approach trajectories is proposed and demonstrated. The procedure employs a multi-objective genetic algorithm in order to reduce noise and create approach paths that will be acceptable to pilots and passengers. The concept is demonstrated by application to two different helicopters. The optimized paths are compared with one another and to a standard 6-deg approach path. The two demonstration cases validate the optimization procedure but highlight the need for improved noise prediction techniques and for additional rotorcraft acoustic data sets.

Optimization of contoured hypersonic scramjet inlets with a least-squares parabolized Navier-Stokes procedure

NASA Technical Reports Server (NTRS)

Korte, J. J.; Auslender, A. H.

1993-01-01

A new optimization procedure, in which a parabolized Navier-Stokes solver is coupled with a non-linear least-squares optimization algorithm, is applied to the design of a Mach 14, laminar two-dimensional hypersonic subscale flight inlet with an internal contraction ratio of 15:1 and a length-to-throat half-height ratio of 150:1. An automated numerical search of multiple geometric wall contours, which are defined by polynomical splines, results in an optimal geometry that yields the maximum total-pressure recovery for the compression process. Optimal inlet geometry is obtained for both inviscid and viscous flows, with the assumption that the gas is either calorically or thermally perfect. The analysis with a calorically perfect gas results in an optimized inviscid inlet design that is defined by two cubic splines and yields a mass-weighted total-pressure recovery of 0.787, which is a 23% improvement compared with the optimized shock-canceled two-ramp inlet design. Similarly, the design procedure obtains the optimized contour for a viscous calorically perfect gas to yield a mass-weighted total-pressure recovery value of 0.749. Additionally, an optimized contour for a viscous thermally perfect gas is obtained to yield a mass-weighted total-pressure recovery value of 0.768. The design methodology incorporates both complex fluid dynamic physics and optimal search techniques without an excessive compromise of computational speed; hence, this methodology is a practical technique that is applicable to optimal inlet design procedures.

Optimal Parameters for Intervertebral Disk Resection Using Aqua-Plasma Beams.

PubMed

Yoon, Sung-Young; Kim, Gon-Ho; Kim, Yushin; Kim, Nack Hwan; Lee, Sangheon; Kawai, Christina; Hong, Youngki

2018-06-14

 A minimally invasive procedure for intervertebral disk resection using plasma beams has been developed. Conventional parameters for the plasma procedure such as voltage and tip speed mainly rely on the surgeon's personal experience, without adequate evidence from experiments. Our objective was to determine the optimal parameters for plasma disk resection.  Rate of ablation was measured at different procedural tip speeds and voltages using porcine nucleus pulposi. The amount of heat formation during experimental conditions was also measured to evaluate the thermal safety of the plasma procedure.  The ablation rate increased at slower procedural speeds and higher voltages. However, for thermal safety, the optimal parameters for plasma procedures with minimal tissue damage were an electrical output of 280 volts root-mean-square (V rms ) and a procedural tip speed of 2.5 mm/s.  Our findings provide useful information for an effective and safe plasma procedure for disk resection in a clinical setting. Georg Thieme Verlag KG Stuttgart · New York.

Aerodynamic Design Using Neural Networks

NASA Technical Reports Server (NTRS)

Rai, Man Mohan; Madavan, Nateri K.

2003-01-01

The design of aerodynamic components of aircraft, such as wings or engines, involves a process of obtaining the most optimal component shape that can deliver the desired level of component performance, subject to various constraints, e.g., total weight or cost, that the component must satisfy. Aerodynamic design can thus be formulated as an optimization problem that involves the minimization of an objective function subject to constraints. A new aerodynamic design optimization procedure based on neural networks and response surface methodology (RSM) incorporates the advantages of both traditional RSM and neural networks. The procedure uses a strategy, denoted parameter-based partitioning of the design space, to construct a sequence of response surfaces based on both neural networks and polynomial fits to traverse the design space in search of the optimal solution. Some desirable characteristics of the new design optimization procedure include the ability to handle a variety of design objectives, easily impose constraints, and incorporate design guidelines and rules of thumb. It provides an infrastructure for variable fidelity analysis and reduces the cost of computation by using less-expensive, lower fidelity simulations in the early stages of the design evolution. The initial or starting design can be far from optimal. The procedure is easy and economical to use in large-dimensional design space and can be used to perform design tradeoff studies rapidly. Designs involving multiple disciplines can also be optimized. Some practical applications of the design procedure that have demonstrated some of its capabilities include the inverse design of an optimal turbine airfoil starting from a generic shape and the redesign of transonic turbines to improve their unsteady aerodynamic characteristics.

Aerodynamic shape optimization using preconditioned conjugate gradient methods

NASA Technical Reports Server (NTRS)

Burgreen, Greg W.; Baysal, Oktay

1993-01-01

In an effort to further improve upon the latest advancements made in aerodynamic shape optimization procedures, a systematic study is performed to examine several current solution methodologies as applied to various aspects of the optimization procedure. It is demonstrated that preconditioned conjugate gradient-like methodologies dramatically decrease the computational efforts required for such procedures. The design problem investigated is the shape optimization of the upper and lower surfaces of an initially symmetric (NACA-012) airfoil in inviscid transonic flow and at zero degree angle-of-attack. The complete surface shape is represented using a Bezier-Bernstein polynomial. The present optimization method then automatically obtains supercritical airfoil shapes over a variety of freestream Mach numbers. Furthermore, the best optimization strategy examined resulted in a factor of 8 decrease in computational time as well as a factor of 4 decrease in memory over the most efficient strategies in current use.

Validation of the procedures. [integrated multidisciplinary optimization of rotorcraft

NASA Technical Reports Server (NTRS)

Mantay, Wayne R.

1989-01-01

Validation strategies are described for procedures aimed at improving the rotor blade design process through a multidisciplinary optimization approach. Validation of the basic rotor environment prediction tools and the overall rotor design are discussed.

Design and Implementation of a Prospective Adult Congenital Heart Disease Biobank.

PubMed

Opotowsky, Alexander R; Loukas, Brittani; Ellervik, Christina; Moko, Lilamarie E; Singh, Michael N; Landzberg, Elizabeth I; Rimm, Eric B; Landzberg, Michael J

2016-11-01

Adults with congenital heart disease (ACHD) comprise a growing, increasingly complex population. The Boston Adult Congenital Heart Disease Biobank is a program for the collection and storage of biospecimens to provide a sustainable resource for scientific biomarker investigation in ACHD. We describe a protocol to collect, process, and store biospecimens for ACHD or associated diagnoses developed based on existing literature and consultation with cardiovascular biomarker epidemiologists. The protocol involves collecting urine and ∼48.5 mL of blood. A subset of the blood and urine undergoes immediate clinically relevant testing. The remaining biospecimens are processed soon after collection and stored at -80°C as aliquots of ethylenediaminetetraacetic acid (EDTA) and lithium heparin plasma, serum, red cell and buffy coat pellet, and urine supernatant. Including tubes with diverse anticoagulant and clot accelerator contents will enable flexible downstream use. Demographic and clinical data are entered into a database; data on biospecimen collection, processing, and storage are managed by an enterprise laboratory information management system. Since implementation in 2012, we have enrolled more than 650 unique participants (aged 18-80 years, 53.3% women); the Biobank contains over 11,000 biospecimen aliquots. The most common primary CHD diagnoses are single ventricle status-post Fontan procedure (18.8%), repaired tetralogy of Fallot with pulmonary stenosis or atresia (17.6%), and left-sided obstructive lesions (17.5%). We describe the design and implementation of biospecimen collection, handling, and storage protocols with multiple levels of quality assurance. These protocols are feasible and reflect the size and goals of the Boston ACHD Biobank. © The Author(s) 2016.

Design optimization of axial flow hydraulic turbine runner: Part II - multi-objective constrained optimization method

NASA Astrophysics Data System (ADS)

Peng, Guoyi; Cao, Shuliang; Ishizuka, Masaru; Hayama, Shinji

2002-06-01

This paper is concerned with the design optimization of axial flow hydraulic turbine runner blade geometry. In order to obtain a better design plan with good performance, a new comprehensive performance optimization procedure has been presented by combining a multi-variable multi-objective constrained optimization model with a Q3D inverse computation and a performance prediction procedure. With careful analysis of the inverse design of axial hydraulic turbine runner, the total hydraulic loss and the cavitation coefficient are taken as optimization objectives and a comprehensive objective function is defined using the weight factors. Parameters of a newly proposed blade bound circulation distribution function and parameters describing positions of blade leading and training edges in the meridional flow passage are taken as optimization variables.The optimization procedure has been applied to the design optimization of a Kaplan runner with specific speed of 440 kW. Numerical results show that the performance of designed runner is successfully improved through optimization computation. The optimization model is found to be validated and it has the feature of good convergence. With the multi-objective optimization model, it is possible to control the performance of designed runner by adjusting the value of weight factors defining the comprehensive objective function. Copyright

78 FR 53237 - Establishment of Area Navigation (RNAV) Routes; Washington, DC

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-29

... ``Optimization of Airspace and Procedures in a Metroplex (OAPM)'' effort in that this rule did not include T.... The new routes support the Washington, DC Optimization of Airspace and Procedures in a Metroplex (OAPM...

Multiparameter optimization of mammography: an update

NASA Astrophysics Data System (ADS)

Jafroudi, Hamid; Muntz, E. P.; Jennings, Robert J.

1994-05-01

Previously in this forum we have reported the application of multiparameter optimization techniques to the design of a minimum dose mammography system. The approach used a reference system to define the physical imaging performance required and the dose to which the dose for the optimized system should be compared. During the course of implementing the resulting design in hardware suitable for laboratory testing, the state of the art in mammographic imaging changed, so that the original reference system, which did not have a grid, was no longer appropriate. A reference system with a grid was selected in response to this change, and at the same time the optimization procedure was modified, to make it more general and to facilitate study of the optimized design under a variety of conditions. We report the changes in the procedure, and the results obtained using the revised procedure and the up- to-date reference system. Our results, which are supported by laboratory measurements, indicate that the optimized design can image small objects as well as the reference system using only about 30% of the dose required by the reference system. Hardware meeting the specification produced by the optimization procedure and suitable for clinical use is currently under evaluation in the Diagnostic Radiology Department at the Clinical Center, NH.

Distributed Method to Optimal Profile Descent

NASA Astrophysics Data System (ADS)

Kim, Geun I.

Current ground automation tools for Optimal Profile Descent (OPD) procedures utilize path stretching and speed profile change to maintain proper merging and spacing requirements at high traffic terminal area. However, low predictability of aircraft's vertical profile and path deviation during decent add uncertainty to computing estimated time of arrival, a key information that enables the ground control center to manage airspace traffic effectively. This paper uses an OPD procedure that is based on a constant flight path angle to increase the predictability of the vertical profile and defines an OPD optimization problem that uses both path stretching and speed profile change while largely maintaining the original OPD procedure. This problem minimizes the cumulative cost of performing OPD procedures for a group of aircraft by assigning a time cost function to each aircraft and a separation cost function to a pair of aircraft. The OPD optimization problem is then solved in a decentralized manner using dual decomposition techniques under inter-aircraft ADS-B mechanism. This method divides the optimization problem into more manageable sub-problems which are then distributed to the group of aircraft. Each aircraft solves its assigned sub-problem and communicate the solutions to other aircraft in an iterative process until an optimal solution is achieved thus decentralizing the computation of the optimization problem.

Optimization applications in aircraft engine design and test

NASA Technical Reports Server (NTRS)

Pratt, T. K.

1984-01-01

Starting with the NASA-sponsored STAEBL program, optimization methods based primarily upon the versatile program COPES/CONMIN were introduced over the past few years to a broad spectrum of engineering problems in structural optimization, engine design, engine test, and more recently, manufacturing processes. By automating design and testing processes, many repetitive and costly trade-off studies have been replaced by optimization procedures. Rather than taking engineers and designers out of the loop, optimization has, in fact, put them more in control by providing sophisticated search techniques. The ultimate decision whether to accept or reject an optimal feasible design still rests with the analyst. Feedback obtained from this decision process has been invaluable since it can be incorporated into the optimization procedure to make it more intelligent. On several occasions, optimization procedures have produced novel designs, such as the nonsymmetric placement of rotor case stiffener rings, not anticipated by engineering designers. In another case, a particularly difficult resonance contraint could not be satisfied using hand iterations for a compressor blade, when the STAEBL program was applied to the problem, a feasible solution was obtained in just two iterations.

Neural Net-Based Redesign of Transonic Turbines for Improved Unsteady Aerodynamic Performance

NASA Technical Reports Server (NTRS)

Madavan, Nateri K.; Rai, Man Mohan; Huber, Frank W.

1998-01-01

A recently developed neural net-based aerodynamic design procedure is used in the redesign of a transonic turbine stage to improve its unsteady aerodynamic performance. The redesign procedure used incorporates the advantages of both traditional response surface methodology (RSM) and neural networks by employing a strategy called parameter-based partitioning of the design space. Starting from the reference design, a sequence of response surfaces based on both neural networks and polynomial fits are constructed to traverse the design space in search of an optimal solution that exhibits improved unsteady performance. The procedure combines the power of neural networks and the economy of low-order polynomials (in terms of number of simulations required and network training requirements). A time-accurate, two-dimensional, Navier-Stokes solver is used to evaluate the various intermediate designs and provide inputs to the optimization procedure. The optimization procedure yields a modified design that improves the aerodynamic performance through small changes to the reference design geometry. The computed results demonstrate the capabilities of the neural net-based design procedure, and also show the tremendous advantages that can be gained by including high-fidelity unsteady simulations that capture the relevant flow physics in the design optimization process.

Helicopter Flight Procedures for Community Noise Reduction

NASA Technical Reports Server (NTRS)

Greenwood, Eric

2017-01-01

A computationally efficient, semiempirical noise model suitable for maneuvering flight noise prediction is used to evaluate the community noise impact of practical variations on several helicopter flight procedures typical of normal operations. Turns, "quick-stops," approaches, climbs, and combinations of these maneuvers are assessed. Relatively small variations in flight procedures are shown to cause significant changes to Sound Exposure Levels over a wide area. Guidelines are developed for helicopter pilots intended to provide effective strategies for reducing the negative effects of helicopter noise on the community. Finally, direct optimization of flight trajectories is conducted to identify low noise optimal flight procedures and quantify the magnitude of community noise reductions that can be obtained through tailored helicopter flight procedures. Physically realizable optimal turns and approaches are identified that achieve global noise reductions of as much as 10 dBA Sound Exposure Level.

Aerodynamic design of axisymmetric hypersonic wind-tunnel nozzles using least-squares/parabolized Navier-Stokes procedure

NASA Technical Reports Server (NTRS)

Korte, John J.

1992-01-01

A new procedure unifying the best of present classical design practices, CFD and optimization procedures, is demonstrated for designing the aerodynamic lines of hypersonic wind tunnel nozzles. This procedure can be employed to design hypersonic wind tunnel nozzles with thick boundary layers where the classical design procedure has been demonstrated to break down. Advantages of this procedure allow full utilization of powerful CFD codes in the design process, solves an optimization problem to determine the new contour, may be used to design new nozzles or improve sections of existing nozzles, and automatically compensates the nozzle contour for viscous effects as part of the unified design procedure.

Optimization of a Tube Hydroforming Process

NASA Astrophysics Data System (ADS)

Abedrabbo, Nader; Zafar, Naeem; Averill, Ron; Pourboghrat, Farhang; Sidhu, Ranny

2004-06-01

An approach is presented to optimize a tube hydroforming process using a Genetic Algorithm (GA) search method. The goal of the study is to maximize formability by identifying the optimal internal hydraulic pressure and feed rate while satisfying the forming limit diagram (FLD). The optimization software HEEDS is used in combination with the nonlinear structural finite element code LS-DYNA to carry out the investigation. In particular, a sub-region of a circular tube blank is formed into a square die. Compared to the best results of a manual optimization procedure, a 55% increase in expansion was achieved when using the pressure and feed profiles identified by the automated optimization procedure.

Iterative pass optimization of sequence data

NASA Technical Reports Server (NTRS)

Wheeler, Ward C.

2003-01-01

The problem of determining the minimum-cost hypothetical ancestral sequences for a given cladogram is known to be NP-complete. This "tree alignment" problem has motivated the considerable effort placed in multiple sequence alignment procedures. Wheeler in 1996 proposed a heuristic method, direct optimization, to calculate cladogram costs without the intervention of multiple sequence alignment. This method, though more efficient in time and more effective in cladogram length than many alignment-based procedures, greedily optimizes nodes based on descendent information only. In their proposal of an exact multiple alignment solution, Sankoff et al. in 1976 described a heuristic procedure--the iterative improvement method--to create alignments at internal nodes by solving a series of median problems. The combination of a three-sequence direct optimization with iterative improvement and a branch-length-based cladogram cost procedure, provides an algorithm that frequently results in superior (i.e., lower) cladogram costs. This iterative pass optimization is both computation and memory intensive, but economies can be made to reduce this burden. An example in arthropod systematics is discussed. c2003 The Willi Hennig Society. Published by Elsevier Science (USA). All rights reserved.

[Orthogonal experiment using SFE-CO2 in extraction of essential oil from fresh Houttuynia cordata and analysis of essential oil by GC-MS].

PubMed

Meng, Jiang; Dong, Xiao-ping; Zhou, Yi-sheng; Jiang, Zhi-hong; Leung, Kelvin Sze-Yin; Zhao, Zhong-zhen

2007-02-01

To optimize the extraction procedure of essential oil from H. cordata using the SFE-CO2 and analyze the chemical composition of the essential oil. The extraction procedure of essential oil from fresh H. cordata was optimized with the orthogonal experiment. Essential oil of fresh H. cordata was analysed by GC-MS. The optimize preparative procedure was as follow: essential oil of H. cordata was extracted at a temperature of 35 degrees C, pressure of 15,000 kPa for 20 min. 38 chemical components were identified and the relative contents were quantified. The optimum preparative procedure is reliable and can guarantee the quality of essential oil.

A CFD-based aerodynamic design procedure for hypersonic wind-tunnel nozzles

NASA Technical Reports Server (NTRS)

Korte, John J.

1993-01-01

A new procedure which unifies the best of current classical design practices, computational fluid dynamics (CFD), and optimization procedures is demonstrated for designing the aerodynamic lines of hypersonic wind-tunnel nozzles. The new procedure can be used to design hypersonic wind tunnel nozzles with thick boundary layers where the classical design procedure has been shown to break down. An efficient CFD code, which solves the parabolized Navier-Stokes (PNS) equations using an explicit upwind algorithm, is coupled to a least-squares (LS) optimization procedure. A LS problem is formulated to minimize the difference between the computed flow field and the objective function, consisting of the centerline Mach number distribution and the exit Mach number and flow angle profiles. The aerodynamic lines of the nozzle are defined using a cubic spline, the slopes of which are optimized with the design procedure. The advantages of the new procedure are that it allows full use of powerful CFD codes in the design process, solves an optimization problem to determine the new contour, can be used to design new nozzles or improve sections of existing nozzles, and automatically compensates the nozzle contour for viscous effects as part of the unified design procedure. The new procedure is demonstrated by designing two Mach 15, a Mach 12, and a Mach 18 helium nozzles. The flexibility of the procedure is demonstrated by designing the two Mach 15 nozzles using different constraints, the first nozzle for a fixed length and exit diameter and the second nozzle for a fixed length and throat diameter. The computed flow field for the Mach 15 least squares parabolized Navier-Stokes (LS/PNS) designed nozzle is compared with the classically designed nozzle and demonstrates a significant improvement in the flow expansion process and uniform core region.

Right parasternal imaging: an underutilized echocardiographic technique.

PubMed

Marcella, C P; Johnson, L E

1993-01-01

If the echocardiographer uses only standard imaging planes, he or she may fail to obtain vital information about the aorta, atrial septum, superior and inferior vena cavae, and the coronary arteries. The evaluation of caval-to-systemic venous atrial connections (Senning or Mustard) in transposition of the great arteries of systemic vena caval or right atrial-to-pulmonary anastomosis (Fontan) in tricuspid atresia and single ventricle may not be adequately seen when only the standard left parasternal, apical, subcostal, and suprasternal imaging planes are used. Therefore, the use of the right parasternal imaging plane may help to provide crucial information regarding these areas when the standard views are unable to delineate them adequately. The right parasternal window is an additional echocardiographic window that should become part of a complete echocardiographic examination.

Documentation for a Structural Optimization Procedure Developed Using the Engineering Analysis Language (EAL)

NASA Technical Reports Server (NTRS)

Martin, Carl J., Jr.

1996-01-01

This report describes a structural optimization procedure developed for use with the Engineering Analysis Language (EAL) finite element analysis system. The procedure is written primarily in the EAL command language. Three external processors which are written in FORTRAN generate equivalent stiffnesses and evaluate stress and local buckling constraints for the sections. Several built-up structural sections were coded into the design procedures. These structural sections were selected for use in aircraft design, but are suitable for other applications. Sensitivity calculations use the semi-analytic method, and an extensive effort has been made to increase the execution speed and reduce the storage requirements. There is also an approximate sensitivity update method included which can significantly reduce computational time. The optimization is performed by an implementation of the MINOS V5.4 linear programming routine in a sequential liner programming procedure.

Application of controller partitioning optimization procedure to integrated flight/propulsion control design for a STOVL aircraft

NASA Technical Reports Server (NTRS)

Garg, Sanjay; Schmidt, Phillip H.

1993-01-01

A parameter optimization framework has earlier been developed to solve the problem of partitioning a centralized controller into a decentralized, hierarchical structure suitable for integrated flight/propulsion control implementation. This paper presents results from the application of the controller partitioning optimization procedure to IFPC design for a Short Take-Off and Vertical Landing (STOVL) aircraft in transition flight. The controller partitioning problem and the parameter optimization algorithm are briefly described. Insight is provided into choosing various 'user' selected parameters in the optimization cost function such that the resulting optimized subcontrollers will meet the characteristics of the centralized controller that are crucial to achieving the desired closed-loop performance and robustness, while maintaining the desired subcontroller structure constraints that are crucial for IFPC implementation. The optimization procedure is shown to improve upon the initial partitioned subcontrollers and lead to performance comparable to that achieved with the centralized controller. This application also provides insight into the issues that should be addressed at the centralized control design level in order to obtain implementable partitioned subcontrollers.

Automation and Optimization of Multipulse Laser Zona Drilling of Mouse Embryos During Embryo Biopsy.

PubMed

Wong, Christopher Yee; Mills, James K

2017-03-01

Laser zona drilling (LZD) is a required step in many embryonic surgical procedures, for example, assisted hatching and preimplantation genetic diagnosis. LZD involves the ablation of the zona pellucida (ZP) using a laser while minimizing potentially harmful thermal effects on critical internal cell structures. Develop a method for the automation and optimization of multipulse LZD, applied to cleavage-stage embryos. A two-stage optimization is used. The first stage uses computer vision algorithms to identify embryonic structures and determines the optimal ablation zone farthest away from critical structures such as blastomeres. The second stage combines a genetic algorithm with a previously reported thermal analysis of LZD to optimize the combination of laser pulse locations and pulse durations. The goal is to minimize the peak temperature experienced by the blastomeres while creating the desired opening in the ZP. A proof of concept of the proposed LZD automation and optimization method is demonstrated through experiments on mouse embryos with positive results, as adequately sized openings are created. Automation of LZD is feasible and is a viable step toward the automation of embryo biopsy procedures. LZD is a common but delicate procedure performed by human operators using subjective methods to gauge proper LZD procedure. Automation of LZD removes human error to increase the success rate of LZD. Although the proposed methods are developed for cleavage-stage embryos, the same methods may be applied to most types LZD procedures, embryos at different developmental stages, or nonembryonic cells.

Shape optimization of road tunnel cross-section by simulated annealing

NASA Astrophysics Data System (ADS)

Sobótka, Maciej; Pachnicz, Michał

2016-06-01

The paper concerns shape optimization of a tunnel excavation cross-section. The study incorporates optimization procedure of the simulated annealing (SA). The form of a cost function derives from the energetic optimality condition, formulated in the authors' previous papers. The utilized algorithm takes advantage of the optimization procedure already published by the authors. Unlike other approaches presented in literature, the one introduced in this paper takes into consideration a practical requirement of preserving fixed clearance gauge. Itasca Flac software is utilized in numerical examples. The optimal excavation shapes are determined for five different in situ stress ratios. This factor significantly affects the optimal topology of excavation. The resulting shapes are elongated in the direction of a principal stress greater value. Moreover, the obtained optimal shapes have smooth contours circumscribing the gauge.

Design optimization studies using COSMIC NASTRAN

NASA Technical Reports Server (NTRS)

Pitrof, Stephen M.; Bharatram, G.; Venkayya, Vipperla B.

1993-01-01

The purpose of this study is to create, test and document a procedure to integrate mathematical optimization algorithms with COSMIC NASTRAN. This procedure is very important to structural design engineers who wish to capitalize on optimization methods to ensure that their design is optimized for its intended application. The OPTNAST computer program was created to link NASTRAN and design optimization codes into one package. This implementation was tested using two truss structure models and optimizing their designs for minimum weight, subject to multiple loading conditions and displacement and stress constraints. However, the process is generalized so that an engineer could design other types of elements by adding to or modifying some parts of the code.

Development of methodologies for the estimation of thermal properties associated with aerospace vehicles

NASA Technical Reports Server (NTRS)

Scott, Elaine P.

1993-01-01

Thermal stress analyses are an important aspect in the development of aerospace vehicles such as the National Aero-Space Plane (NASP) and the High-Speed Civil Transport (HSCT) at NASA-LaRC. These analyses require knowledge of the temperature within the structures which consequently necessitates the need for thermal property data. The initial goal of this research effort was to develop a methodology for the estimation of thermal properties of aerospace structural materials at room temperature and to develop a procedure to optimize the estimation process. The estimation procedure was implemented utilizing a general purpose finite element code. In addition, an optimization procedure was developed and implemented to determine critical experimental parameters to optimize the estimation procedure. Finally, preliminary experiments were conducted at the Aircraft Structures Branch (ASB) laboratory.

Development of methodologies for the estimation of thermal properties associated with aerospace vehicles

NASA Astrophysics Data System (ADS)

Scott, Elaine P.

1993-12-01

Thermal stress analyses are an important aspect in the development of aerospace vehicles such as the National Aero-Space Plane (NASP) and the High-Speed Civil Transport (HSCT) at NASA-LaRC. These analyses require knowledge of the temperature within the structures which consequently necessitates the need for thermal property data. The initial goal of this research effort was to develop a methodology for the estimation of thermal properties of aerospace structural materials at room temperature and to develop a procedure to optimize the estimation process. The estimation procedure was implemented utilizing a general purpose finite element code. In addition, an optimization procedure was developed and implemented to determine critical experimental parameters to optimize the estimation procedure. Finally, preliminary experiments were conducted at the Aircraft Structures Branch (ASB) laboratory.

Incorporating deliverable monitor unit constraints into spot intensity optimization in intensity modulated proton therapy treatment planning

PubMed Central

Cao, Wenhua; Lim, Gino; Li, Xiaoqiang; Li, Yupeng; Zhu, X. Ronald; Zhang, Xiaodong

2014-01-01

The purpose of this study is to investigate the feasibility and impact of incorporating deliverable monitor unit (MU) constraints into spot intensity optimization in intensity modulated proton therapy (IMPT) treatment planning. The current treatment planning system (TPS) for IMPT disregards deliverable MU constraints in the spot intensity optimization (SIO) routine. It performs a post-processing procedure on an optimized plan to enforce deliverable MU values that are required by the spot scanning proton delivery system. This procedure can create a significant dose distribution deviation between the optimized and post-processed deliverable plans, especially when small spot spacings are used. In this study, we introduce a two-stage linear programming (LP) approach to optimize spot intensities and constrain deliverable MU values simultaneously, i.e., a deliverable spot intensity optimization (DSIO) model. Thus, the post-processing procedure is eliminated and the associated optimized plan deterioration can be avoided. Four prostate cancer cases at our institution were selected for study and two parallel opposed beam angles were planned for all cases. A quadratic programming (QP) based model without MU constraints, i.e., a conventional spot intensity optimization (CSIO) model, was also implemented to emulate the commercial TPS. Plans optimized by both the DSIO and CSIO models were evaluated for five different settings of spot spacing from 3 mm to 7 mm. For all spot spacings, the DSIO-optimized plans yielded better uniformity for the target dose coverage and critical structure sparing than did the CSIO-optimized plans. With reduced spot spacings, more significant improvements in target dose uniformity and critical structure sparing were observed in the DSIO- than in the CSIO-optimized plans. Additionally, better sparing of the rectum and bladder was achieved when reduced spacings were used for the DSIO-optimized plans. The proposed DSIO approach ensures the deliverability of optimized IMPT plans that take into account MU constraints. This eliminates the post-processing procedure required by the TPS as well as the resultant deteriorating effect on ultimate dose distributions. This approach therefore allows IMPT plans to adopt all possible spot spacings optimally. Moreover, dosimetric benefits can be achieved using smaller spot spacings. PMID:23835656

Geometrical Optimization Approach to Isomerization: Models and Limitations.

PubMed

Chang, Bo Y; Shin, Seokmin; Engel, Volker; Sola, Ignacio R

2017-11-02

We study laser-driven isomerization reactions through an excited electronic state using the recently developed Geometrical Optimization procedure. Our goal is to analyze whether an initial wave packet in the ground state, with optimized amplitudes and phases, can be used to enhance the yield of the reaction at faster rates, driven by a single picosecond pulse or a pair of femtosecond pulses resonant with the electronic transition. We show that the symmetry of the system imposes limitations in the optimization procedure, such that the method rediscovers the pump-dump mechanism.

The use of optimization techniques to design controlled diffusion compressor blading

NASA Technical Reports Server (NTRS)

Sanger, N. L.

1982-01-01

A method for automating compressor blade design using numerical optimization, and applied to the design of a controlled diffusion stator blade row is presented. A general purpose optimization procedure is employed, based on conjugate directions for locally unconstrained problems and on feasible directions for locally constrained problems. Coupled to the optimizer is an analysis package consisting of three analysis programs which calculate blade geometry, inviscid flow, and blade surface boundary layers. The optimizing concepts and selection of design objective and constraints are described. The procedure for automating the design of a two dimensional blade section is discussed, and design results are presented.

Optimum Design of High-Speed Prop-Rotors

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; McCarthy, Thomas Robert

1993-01-01

An integrated multidisciplinary optimization procedure is developed for application to rotary wing aircraft design. The necessary disciplines such as dynamics, aerodynamics, aeroelasticity, and structures are coupled within a closed-loop optimization process. The procedure developed is applied to address two different problems. The first problem considers the optimization of a helicopter rotor blade and the second problem addresses the optimum design of a high-speed tilting proprotor. In the helicopter blade problem, the objective is to reduce the critical vibratory shear forces and moments at the blade root, without degrading rotor aerodynamic performance and aeroelastic stability. In the case of the high-speed proprotor, the goal is to maximize the propulsive efficiency in high-speed cruise without deteriorating the aeroelastic stability in cruise and the aerodynamic performance in hover. The problems studied involve multiple design objectives; therefore, the optimization problems are formulated using multiobjective design procedures. A comprehensive helicopter analysis code is used for the rotary wing aerodynamic, dynamic and aeroelastic stability analyses and an algorithm developed specifically for these purposes is used for the structural analysis. A nonlinear programming technique coupled with an approximate analysis procedure is used to perform the optimization. The optimum blade designs obtained in each case are compared to corresponding reference designs.

Congenital portosystemic venous connections and other abdominal venous abnormalities in patients with polysplenia and functionally univentricular heart disease: a case series and literature review.

PubMed

McElhinney, Doff B; Marx, Gerald R; Newburger, Jane W

2011-01-01

Published case reports suggest that congenital portosystemic venous connections (PSVC) and other abdominal venous anomalies may be relatively frequent and potentially important in patients with polysplenia syndrome. Our objective was to investigate the frequency and range of portal and other abdominal systemic venous anomalies in patients with polysplenia and inferior vena cava (IVC) interruption who underwent a cavopulmonary anastomosis procedure at our center, and to review the published literature on this topic and the potential clinical importance of such anomalies. Retrospective cohort study and literature review were used. Among 77 patients with heterotaxy, univentricular heart disease, and IVC interruption who underwent a bidirectional Glenn and/or modified Fontan procedure, pulmonary arteriovenous malformations were diagnosed in 33 (43%). Bilateral superior vena cavas were present in 42 patients (55%). Despite inadequate imaging in many patients, a partial PSVC, dual IVCs, and/or renal vein anomalies were detected in 15 patients (19%). A PSVC formed by a tortuous vessel running from the systemic venous system to the extrahepatic portal vein was found in six patients (8%). Abdominal venous anomalies other than PSVC were documented in 13 patients (16%), including nine (12%) with some form of duplicated IVC system, with a large azygous vein continuing to the superior vena cava and a parallel, contralateral IVC of similar or smaller size, and seven with renal vein anomalies. In patients with a partial PSVC or a duplicate IVC that connected to the atrium, the abnormal connection allowed right-to-left shunting. PSVC and other abdominal venous anomalies may be clinically important but under-recognized in patients with IVC interruption and univentricular heart disease. In such patients, preoperative evaluation of the abdominal systemic venous system may be valuable. More data are necessary to determine whether there is a pathophysiologic connection between the polysplenia variant of heterotaxy, PSVC, and cavopulmonary anastomosis-associated pulmonary arteriovenous malformations. © 2011 Copyright the Authors. Congenital Heart Disease © 2011 Wiley Periodicals, Inc.

Shape Optimization for Additive Manufacturing of Removable Partial Dentures - A New Paradigm for Prosthetic CAD/CAM

PubMed Central

2015-01-01

With ever-growing aging population and demand for denture treatments, pressure-induced mucosa lesion and residual ridge resorption remain main sources of clinical complications. Conventional denture design and fabrication are challenged for its labor and experience intensity, urgently necessitating an automatic procedure. This study aims to develop a fully automatic procedure enabling shape optimization and additive manufacturing of removable partial dentures (RPD), to maximize the uniformity of contact pressure distribution on the mucosa, thereby reducing associated clinical complications. A 3D heterogeneous finite element (FE) model was constructed from CT scan, and the critical tissue of mucosa was modeled as a hyperelastic material from in vivo clinical data. A contact shape optimization algorithm was developed based on the bi-directional evolutionary structural optimization (BESO) technique. Both initial and optimized dentures were prototyped by 3D printing technology and evaluated with in vitro tests. Through the optimization, the peak contact pressure was reduced by 70%, and the uniformity was improved by 63%. In vitro tests verified the effectiveness of this procedure, and the hydrostatic pressure induced in the mucosa is well below clinical pressure-pain thresholds (PPT), potentially lessening risk of residual ridge resorption. This proposed computational optimization and additive fabrication procedure provides a novel method for fast denture design and adjustment at low cost, with quantitative guidelines and computer aided design and manufacturing (CAD/CAM) for a specific patient. The integration of digitalized modeling, computational optimization, and free-form fabrication enables more efficient clinical adaptation. The customized optimal denture design is expected to minimize pain/discomfort and potentially reduce long-term residual ridge resorption. PMID:26161878

Optimization of proximity ligation assay (PLA) for detection of protein interactions and fusion proteins in non-adherent cells: application to pre-B lymphocytes.

PubMed

Debaize, Lydie; Jakobczyk, Hélène; Rio, Anne-Gaëlle; Gandemer, Virginie; Troadec, Marie-Bérengère

2017-01-01

Genetic abnormalities, including chromosomal translocations, are described for many hematological malignancies. From the clinical perspective, detection of chromosomal abnormalities is relevant not only for diagnostic and treatment purposes but also for prognostic risk assessment. From the translational research perspective, the identification of fusion proteins and protein interactions has allowed crucial breakthroughs in understanding the pathogenesis of malignancies and consequently major achievements in targeted therapy. We describe the optimization of the Proximity Ligation Assay (PLA) to ascertain the presence of fusion proteins, and protein interactions in non-adherent pre-B cells. PLA is an innovative method of protein-protein colocalization detection by molecular biology that combines the advantages of microscopy with the advantages of molecular biology precision, enabling detection of protein proximity theoretically ranging from 0 to 40 nm. We propose an optimized PLA procedure. We overcome the issue of maintaining non-adherent hematological cells by traditional cytocentrifugation and optimized buffers, by changing incubation times, and modifying washing steps. Further, we provide convincing negative and positive controls, and demonstrate that optimized PLA procedure is sensitive to total protein level. The optimized PLA procedure allows the detection of fusion proteins and protein interactions on non-adherent cells. The optimized PLA procedure described here can be readily applied to various non-adherent hematological cells, from cell lines to patients' cells. The optimized PLA protocol enables detection of fusion proteins and their subcellular expression, and protein interactions in non-adherent cells. Therefore, the optimized PLA protocol provides a new tool that can be adopted in a wide range of applications in the biological field.

Detonation energies of explosives by optimized JCZ3 procedures

NASA Astrophysics Data System (ADS)

Stiel, Leonard I.; Baker, Ernest L.

1998-07-01

Procedures for the detonation properties of explosives have been extended for the calculation of detonation energies at adiabatic expansion conditions. The use of the JCZ3 equation of state with optimized Exp-6 potential parameters leads to lower errors in comparison to JWL detonation energies than for other methods tested.

[Preparation procedures of anti-complementary polysaccharides from Houttuynia cordata].

PubMed

Zhang, Juanjuan; Lu, Yan; Chen, Daofeng

2012-07-01

To establish and optimize the preparation procedures of the anti-complementary polysaccharides from Houttuynia cordata. Based on the yield and anti-complementary activity in vitro, the conditions of extraction and alcohol precipitating process were optimized by orthogonal tests. The optimal condition of deproteinization was determined according to the results of protein removed and polysaccharide maintained. The best decoloring method was also optimized by orthogonal experimental design. The optimized preparation procedures were given as follows: extract the coarse powder 3 times with 50 times volume of water at 90 degrees C for 2 hours every time, combine the extracts and concentrate appropriately, equivalent to 0.12 g of H. cordata per milliliter. Add 4 times volume of 90% ethanol to the extract, allow to stand for 24 hours to precipitate totally, filter and the precipitate was successfully washed with anhydrous alcohol, acetone and anhydrous ether. Resolve the residue with water, add trichloroacetic acid (TCA) to a concentration of 20% to remove protein. Decoloration was at a concentration of 3% with activated carbon at pH 3.0, 50 degrees C for 50 min. The above procedures above were tested 3 times, resulting in the average yield of polysaccharides at 4.03% (RSD 0.96%), the average concentrations of polysaccharides and protein at 80.97% (RSD 1.5%) and 2.02% (RSD 2.3%), and average CH50 at 0.079 g x L-(-1) (RSD 3.6%). The established and optimized procedures are repeatable and reliable to prepare the anti-complementary polysaccharides with high quality and activity from H. cordata.

Implementation and application of moving average as continuous analytical quality control instrument demonstrated for 24 routine chemistry assays.

PubMed

Rossum, Huub H van; Kemperman, Hans

2017-07-26

General application of a moving average (MA) as continuous analytical quality control (QC) for routine chemistry assays has failed due to lack of a simple method that allows optimization of MAs. A new method was applied to optimize the MA for routine chemistry and was evaluated in daily practice as continuous analytical QC instrument. MA procedures were optimized using an MA bias detection simulation procedure. Optimization was graphically supported by bias detection curves. Next, all optimal MA procedures that contributed to the quality assurance were run for 100 consecutive days and MA alarms generated during working hours were investigated. Optimized MA procedures were applied for 24 chemistry assays. During this evaluation, 303,871 MA values and 76 MA alarms were generated. Of all alarms, 54 (71%) were generated during office hours. Of these, 41 were further investigated and were caused by ion selective electrode (ISE) failure (1), calibration failure not detected by QC due to improper QC settings (1), possible bias (significant difference with the other analyzer) (10), non-human materials analyzed (2), extreme result(s) of a single patient (2), pre-analytical error (1), no cause identified (20), and no conclusion possible (4). MA was implemented in daily practice as a continuous QC instrument for 24 routine chemistry assays. In our setup when an MA alarm required follow-up, a manageable number of MA alarms was generated that resulted in valuable MA alarms. For the management of MA alarms, several applications/requirements in the MA management software will simplify the use of MA procedures.

Mathematical calibration procedure of a capacitive sensor-based indexed metrology platform

NASA Astrophysics Data System (ADS)

Brau-Avila, A.; Santolaria, J.; Acero, R.; Valenzuela-Galvan, M.; Herrera-Jimenez, V. M.; Aguilar, J. J.

2017-03-01

The demand for faster and more reliable measuring tasks for the control and quality assurance of modern production systems has created new challenges for the field of coordinate metrology. Thus, the search for new solutions in coordinate metrology systems and the need for the development of existing ones still persists. One example of such a system is the portable coordinate measuring machine (PCMM), the use of which in industry has considerably increased in recent years, mostly due to its flexibility for accomplishing in-line measuring tasks as well as its reduced cost and operational advantages compared to traditional coordinate measuring machines. Nevertheless, PCMMs have a significant drawback derived from the techniques applied in the verification and optimization procedures of their kinematic parameters. These techniques are based on the capture of data with the measuring instrument from a calibrated gauge object, fixed successively in various positions so that most of the instrument measuring volume is covered, which results in time-consuming, tedious and expensive verification and optimization procedures. In this work the mathematical calibration procedure of a capacitive sensor-based indexed metrology platform (IMP) is presented. This calibration procedure is based on the readings and geometric features of six capacitive sensors and their targets with nanometer resolution. The final goal of the IMP calibration procedure is to optimize the geometric features of the capacitive sensors and their targets in order to use the optimized data in the verification procedures of PCMMs.

Recent advances in integrated multidisciplinary optimization of rotorcraft

NASA Technical Reports Server (NTRS)

Adelman, Howard M.; Walsh, Joanne L.; Pritchard, Jocelyn I.

1992-01-01

A joint activity involving NASA and Army researchers at NASA LaRC to develop optimization procedures to improve the rotor blade design process by integrating appropriate disciplines and accounting for all of the important interactions among the disciplines is described. The disciplines involved include rotor aerodynamics, rotor dynamics, rotor structures, airframe dynamics, and acoustics. The work is focused on combining these five key disciplines in an optimization procedure capable of designing a rotor system to satisfy multidisciplinary design requirements. Fundamental to the plan is a three-phased approach. In phase 1, the disciplines of blade dynamics, blade aerodynamics, and blade structure are closely coupled while acoustics and airframe dynamics are decoupled and are accounted for as effective constraints on the design for the first three disciplines. In phase 2, acoustics is integrated with the first three disciplines. Finally, in phase 3, airframe dynamics is integrated with the other four disciplines. Representative results from work performed to date are described. These include optimal placement of tuning masses for reduction of blade vibratory shear forces, integrated aerodynamic/dynamic optimization, and integrated aerodynamic/dynamic/structural optimization. Examples of validating procedures are described.

Recent advances in multidisciplinary optimization of rotorcraft

NASA Technical Reports Server (NTRS)

Adelman, Howard M.; Walsh, Joanne L.; Pritchard, Jocelyn I.

1992-01-01

A joint activity involving NASA and Army researchers at NASA LaRC to develop optimization procedures to improve the rotor blade design process by integrating appropriate disciplines and accounting for all of the important interactions among the disciplines is described. The disciplines involved include rotor aerodynamics, rotor dynamics, rotor structures, airframe dynamics, and acoustics. The work is focused on combining these five key disciplines in an optimization procedure capable of designing a rotor system to satisfy multidisciplinary design requirements. Fundamental to the plan is a three-phased approach. In phase 1, the disciplines of blade dynamics, blade aerodynamics, and blade structure are closely coupled while acoustics and airframe dynamics are decoupled and are accounted for as effective constraints on the design for the first three disciplines. In phase 2, acoustics is integrated with the first three disciplines. Finally, in phase 3, airframe dynamics is integrated with the other four disciplines. Representative results from work performed to date are described. These include optimal placement of tuning masses for reduction of blade vibratory shear forces, integrated aerodynamic/dynamic optimization, and integrated aerodynamic/dynamic/structural optimization. Examples of validating procedures are described.

An artificial system for selecting the optimal surgical team.

PubMed

Saberi, Nahid; Mahvash, Mohsen; Zenati, Marco

2015-01-01

We introduce an intelligent system to optimize a team composition based on the team's historical outcomes and apply this system to compose a surgical team. The system relies on a record of the procedures performed in the past. The optimal team composition is the one with the lowest probability of unfavorable outcome. We use the theory of probability and the inclusion exclusion principle to model the probability of team outcome for a given composition. A probability value is assigned to each person of database and the probability of a team composition is calculated from them. The model allows to determine the probability of all possible team compositions even if there is no recoded procedure for some team compositions. From an analytical perspective, assembling an optimal team is equivalent to minimizing the overlap of team members who have a recurring tendency to be involved with procedures of unfavorable results. A conceptual example shows the accuracy of the proposed system on obtaining the optimal team.

Status of systemic to pulmonary arterial collateral flow after the fontan procedure.

PubMed

Whitehead, Kevin K; Harris, Matthew A; Glatz, Andrew C; Gillespie, Matthew J; DiMaria, Michael V; Harrison, Neil E; Dori, Yoav; Keller, Marc S; Rome, Jonathan J; Fogel, Mark A

2015-06-15

The investigators recently validated a method of quantifying systemic-to-pulmonary arterial collateral flow using phase-contrast magnetic resonance imaging velocity mapping. Cross-sectional data suggest decreased collateral flow in patients with total cavopulmonary connections (TCPCs) compared with those with superior cavopulmonary connections (SCPCs). However, no studies have examined serial changes in collateral flow from SCPCs to TCPCs in the same patients. The aim of this study was to examine differences in collateral flow between patients with SCPCs and those with TCPCs. Collateral flow was quantified by 2 independent measures from 250 single-ventricle studies in 219 different patients (115 SCPC and 135 TCPC studies, 31 patients with both) and 18 controls, during routine studies using through-plane phase-contrast magnetic resonance imaging. Collateral flow was indexed to body surface area, aortic flow, and pulmonary venous flow. Regardless of indexing method, SCPC patients had significantly higher collateral flow than TCPC patients (1.64 ± 0.8 vs 1.03 ± 0.8 L/min/m(2), p <0.001). In 31 patients who underwent serial examinations, collateral flow as a fraction of aortic flow increased early after TCPC completion. In TCPC patients, indexed collateral flow demonstrated a significant negative correlation with time from TCPC. In conclusion, SCPC and TCPC patients demonstrate substantial collateral flow, with SCPC patients having higher collateral flow than TCPC patients overall. On the basis of the paired subset analysis, collateral flow does not decrease in the short term after TCPC completion and trends toward an increase. In the long term, however, collateral flow decreases over time after TCPC completion. Copyright © 2015 Elsevier Inc. All rights reserved.

An efficient constraint to account for mistuning effects in the optimal design of engine rotors

NASA Technical Reports Server (NTRS)

Murthy, Durbha V.; Pierre, Christophe; Ottarsson, Gisli

1992-01-01

Blade-to-blade differences in structural properties, unavoidable in practice due to manufacturing tolerances, can have significant influence on the vibratory response of engine rotor blade. Accounting for these differences, also known as mistuning, in design and in optimization procedures is generally not possible. This note presents an easily calculated constraint that can be used in design and optimization procedures to control the sensitivity of final designs to mistuning.

Optimized postweld heat treatment procedures for 17-4 PH stainless steels

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

Bhaduri, A.K.; Sujith, S.; Srinivasan, G.

1995-05-01

The postweld heat treatment (PWHT) procedures for 17-4 PH stainless steel weldments of matching chemistry was optimized vis-a-vis its microstructure prior to welding based on microstructural studies and room-temperature mechanical properties. The 17-4 PH stainless steel was welded in two different prior microstructural conditions (condition A and condition H 1150) and then postweld heat treated to condition H900 or condition H1150, using different heat treatment procedures. Microstructural investigations and room-temperature tensile properties were determined to study the combined effects of prior microstructural and PWHT procedures.

A seismic optimization procedure for reinforced concrete framed buildings based on eigenfrequency optimization

NASA Astrophysics Data System (ADS)

Arroyo, Orlando; Gutiérrez, Sergio

2017-07-01

Several seismic optimization methods have been proposed to improve the performance of reinforced concrete framed (RCF) buildings; however, they have not been widely adopted among practising engineers because they require complex nonlinear models and are computationally expensive. This article presents a procedure to improve the seismic performance of RCF buildings based on eigenfrequency optimization, which is effective, simple to implement and efficient. The method is used to optimize a 10-storey regular building, and its effectiveness is demonstrated by nonlinear time history analyses, which show important reductions in storey drifts and lateral displacements compared to a non-optimized building. A second example for an irregular six-storey building demonstrates that the method provides benefits to a wide range of RCF structures and supports the applicability of the proposed method.

Efficient Simulation Budget Allocation for Selecting an Optimal Subset

NASA Technical Reports Server (NTRS)

Chen, Chun-Hung; He, Donghai; Fu, Michael; Lee, Loo Hay

2008-01-01

We consider a class of the subset selection problem in ranking and selection. The objective is to identify the top m out of k designs based on simulated output. Traditional procedures are conservative and inefficient. Using the optimal computing budget allocation framework, we formulate the problem as that of maximizing the probability of correc tly selecting all of the top-m designs subject to a constraint on the total number of samples available. For an approximation of this corre ct selection probability, we derive an asymptotically optimal allocat ion and propose an easy-to-implement heuristic sequential allocation procedure. Numerical experiments indicate that the resulting allocatio ns are superior to other methods in the literature that we tested, and the relative efficiency increases for larger problems. In addition, preliminary numerical results indicate that the proposed new procedur e has the potential to enhance computational efficiency for simulation optimization.

A Robust Adaptive Autonomous Approach to Optimal Experimental Design

NASA Astrophysics Data System (ADS)

Gu, Hairong

Experimentation is the fundamental tool of scientific inquiries to understand the laws governing the nature and human behaviors. Many complex real-world experimental scenarios, particularly in quest of prediction accuracy, often encounter difficulties to conduct experiments using an existing experimental procedure for the following two reasons. First, the existing experimental procedures require a parametric model to serve as the proxy of the latent data structure or data-generating mechanism at the beginning of an experiment. However, for those experimental scenarios of concern, a sound model is often unavailable before an experiment. Second, those experimental scenarios usually contain a large number of design variables, which potentially leads to a lengthy and costly data collection cycle. Incompetently, the existing experimental procedures are unable to optimize large-scale experiments so as to minimize the experimental length and cost. Facing the two challenges in those experimental scenarios, the aim of the present study is to develop a new experimental procedure that allows an experiment to be conducted without the assumption of a parametric model while still achieving satisfactory prediction, and performs optimization of experimental designs to improve the efficiency of an experiment. The new experimental procedure developed in the present study is named robust adaptive autonomous system (RAAS). RAAS is a procedure for sequential experiments composed of multiple experimental trials, which performs function estimation, variable selection, reverse prediction and design optimization on each trial. Directly addressing the challenges in those experimental scenarios of concern, function estimation and variable selection are performed by data-driven modeling methods to generate a predictive model from data collected during the course of an experiment, thus exempting the requirement of a parametric model at the beginning of an experiment; design optimization is performed to select experimental designs on the fly of an experiment based on their usefulness so that fewest designs are needed to reach useful inferential conclusions. Technically, function estimation is realized by Bayesian P-splines, variable selection is realized by Bayesian spike-and-slab prior, reverse prediction is realized by grid-search and design optimization is realized by the concepts of active learning. The present study demonstrated that RAAS achieves statistical robustness by making accurate predictions without the assumption of a parametric model serving as the proxy of latent data structure while the existing procedures can draw poor statistical inferences if a misspecified model is assumed; RAAS also achieves inferential efficiency by taking fewer designs to acquire useful statistical inferences than non-optimal procedures. Thus, RAAS is expected to be a principled solution to real-world experimental scenarios pursuing robust prediction and efficient experimentation.

Jig-Shape Optimization of a Low-Boom Supersonic Aircraft

NASA Technical Reports Server (NTRS)

Pak, Chan-Gi

2018-01-01

A simple approach for optimizing the jig-shape is proposed in this study. This simple approach is based on an unconstrained optimization problem and applied to a low-boom supersonic aircraft. In this study, the jig-shape optimization is performed using the two-step approach. First, starting design variables are computed using the least-squares surface fitting technique. Next, the jig-shape is further tuned using a numerical optimization procedure based on an in-house object-oriented optimization tool. During the numerical optimization procedure, a design jig-shape is determined by the baseline jig-shape and basis functions. A total of 12 symmetric mode shapes of the cruise-weight configuration, rigid pitch shape, rigid left and right stabilator rotation shapes, and a residual shape are selected as sixteen basis functions. After three optimization runs, the trim shape error distribution is improved, and the maximum trim shape error of 0.9844 inches of the starting configuration becomes 0.00367 inch by the end of the third optimization run.

Design and Optimization of Composite Gyroscope Momentum Wheel Rings

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Arnold, Steven M.

2007-01-01

Stress analysis and preliminary design/optimization procedures are presented for gyroscope momentum wheel rings composed of metallic, metal matrix composite, and polymer matrix composite materials. The design of these components involves simultaneously minimizing both true part volume and mass, while maximizing angular momentum. The stress analysis results are combined with an anisotropic failure criterion to formulate a new sizing procedure that provides considerable insight into the design of gyroscope momentum wheel ring components. Results compare the performance of two optimized metallic designs, an optimized SiC/Ti composite design, and an optimized graphite/epoxy composite design. The graphite/epoxy design appears to be far superior to the competitors considered unless a much greater premium is placed on volume efficiency compared to mass efficiency.

Fuel Injector Design Optimization for an Annular Scramjet Geometry

NASA Technical Reports Server (NTRS)

Steffen, Christopher J., Jr.

2003-01-01

A four-parameter, three-level, central composite experiment design has been used to optimize the configuration of an annular scramjet injector geometry using computational fluid dynamics. The computational fluid dynamic solutions played the role of computer experiments, and response surface methodology was used to capture the simulation results for mixing efficiency and total pressure recovery within the scramjet flowpath. An optimization procedure, based upon the response surface results of mixing efficiency, was used to compare the optimal design configuration against the target efficiency value of 92.5%. The results of three different optimization procedures are presented and all point to the need to look outside the current design space for different injector geometries that can meet or exceed the stated mixing efficiency target.

A Fast Proceduere for Optimizing Thermal Protection Systems of Re-Entry Vehicles

NASA Astrophysics Data System (ADS)

Ferraiuolo, M.; Riccio, A.; Tescione, D.; Gigliotti, M.

The aim of the present work is to introduce a fast procedure to optimize thermal protection systems for re-entry vehicles subjected to high thermal loads. A simplified one-dimensional optimization process, performed in order to find the optimum design variables (lengths, sections etc.), is the first step of the proposed design procedure. Simultaneously, the most suitable materials able to sustain high temperatures and meeting the weight requirements are selected and positioned within the design layout. In this stage of the design procedure, simplified (generalized plane strain) FEM models are used when boundary and geometrical conditions allow the reduction of the degrees of freedom. Those simplified local FEM models can be useful because they are time-saving and very simple to build; they are essentially one dimensional and can be used for optimization processes in order to determine the optimum configuration with regard to weight, temperature and stresses. A triple-layer and a double-layer body, subjected to the same aero-thermal loads, have been optimized to minimize the overall weight. Full two and three-dimensional analyses are performed in order to validate those simplified models. Thermal-structural analyses and optimizations are executed by adopting the Ansys FEM code.

Performance evaluation of different types of particle representation procedures of Particle Swarm Optimization in Job-shop Scheduling Problems

NASA Astrophysics Data System (ADS)

Izah Anuar, Nurul; Saptari, Adi

2016-02-01

This paper addresses the types of particle representation (encoding) procedures in a population-based stochastic optimization technique in solving scheduling problems known in the job-shop manufacturing environment. It intends to evaluate and compare the performance of different particle representation procedures in Particle Swarm Optimization (PSO) in the case of solving Job-shop Scheduling Problems (JSP). Particle representation procedures refer to the mapping between the particle position in PSO and the scheduling solution in JSP. It is an important step to be carried out so that each particle in PSO can represent a schedule in JSP. Three procedures such as Operation and Particle Position Sequence (OPPS), random keys representation and random-key encoding scheme are used in this study. These procedures have been tested on FT06 and FT10 benchmark problems available in the OR-Library, where the objective function is to minimize the makespan by the use of MATLAB software. Based on the experimental results, it is discovered that OPPS gives the best performance in solving both benchmark problems. The contribution of this paper is the fact that it demonstrates to the practitioners involved in complex scheduling problems that different particle representation procedures can have significant effects on the performance of PSO in solving JSP.

Optimization and validation of moving average quality control procedures using bias detection curves and moving average validation charts.

PubMed

van Rossum, Huub H; Kemperman, Hans

2017-02-01

To date, no practical tools are available to obtain optimal settings for moving average (MA) as a continuous analytical quality control instrument. Also, there is no knowledge of the true bias detection properties of applied MA. We describe the use of bias detection curves for MA optimization and MA validation charts for validation of MA. MA optimization was performed on a data set of previously obtained consecutive assay results. Bias introduction and MA bias detection were simulated for multiple MA procedures (combination of truncation limits, calculation algorithms and control limits) and performed for various biases. Bias detection curves were generated by plotting the median number of test results needed for bias detection against the simulated introduced bias. In MA validation charts the minimum, median, and maximum numbers of assay results required for MA bias detection are shown for various bias. Their use was demonstrated for sodium, potassium, and albumin. Bias detection curves allowed optimization of MA settings by graphical comparison of bias detection properties of multiple MA. The optimal MA was selected based on the bias detection characteristics obtained. MA validation charts were generated for selected optimal MA and provided insight into the range of results required for MA bias detection. Bias detection curves and MA validation charts are useful tools for optimization and validation of MA procedures.

Improving the Unsteady Aerodynamic Performance of Transonic Turbines using Neural Networks

NASA Technical Reports Server (NTRS)

Rai, Man Mohan; Madavan, Nateri K.; Huber, Frank W.

1999-01-01

A recently developed neural net-based aerodynamic design procedure is used in the redesign of a transonic turbine stage to improve its unsteady aerodynamic performance. The redesign procedure used incorporates the advantages of both traditional response surface methodology and neural networks by employing a strategy called parameter-based partitioning of the design space. Starting from the reference design, a sequence of response surfaces based on both neural networks and polynomial fits are constructed to traverse the design space in search of an optimal solution that exhibits improved unsteady performance. The procedure combines the power of neural networks and the economy of low-order polynomials (in terms of number of simulations required and network training requirements). A time-accurate, two-dimensional, Navier-Stokes solver is used to evaluate the various intermediate designs and provide inputs to the optimization procedure. The procedure yielded a modified design that improves the aerodynamic performance through small changes to the reference design geometry. These results demonstrate the capabilities of the neural net-based design procedure, and also show the advantages of including high-fidelity unsteady simulations that capture the relevant flow physics in the design optimization process.

Design of controlled elastic and inelastic structures

NASA Astrophysics Data System (ADS)

Reinhorn, A. M.; Lavan, O.; Cimellaro, G. P.

2009-12-01

One of the founders of structural control theory and its application in civil engineering, Professor Emeritus Tsu T. Soong, envisioned the development of the integral design of structures protected by active control devices. Most of his disciples and colleagues continuously attempted to develop procedures to achieve such integral control. In his recent papers published jointly with some of the authors of this paper, Professor Soong developed design procedures for the entire structure using a design — redesign procedure applied to elastic systems. Such a procedure was developed as an extension of other work by his disciples. This paper summarizes some recent techniques that use traditional active control algorithms to derive the most suitable (optimal, stable) control force, which could then be implemented with a combination of active, passive and semi-active devices through a simple match or more sophisticated optimal procedures. Alternative design can address the behavior of structures using Liapunov stability criteria. This paper shows a unified procedure which can be applied to both elastic and inelastic structures. Although the implementation does not always preserve the optimal criteria, it is shown that the solutions are effective and practical for design of supplemental damping, stiffness enhancement or softening, and strengthening or weakening.

Optimization of wearable microwave antenna with simplified electromagnetic model of the human body

NASA Astrophysics Data System (ADS)

Januszkiewicz, Łukasz; Barba, Paolo Di; Hausman, Sławomir

2017-12-01

In this paper the problem of optimization design of a microwave wearable antenna is investigated. Reference is made to a specific antenna design that is a wideband Vee antenna the geometry of which is characterized by 6 parameters. These parameters were automatically adjusted with an evolution strategy based algorithm EStra to obtain the impedance matching of the antenna located in the proximity of the human body. The antenna was designed to operate in the ISM (industrial, scientific, medical) band which covers the frequency range of 2.4 GHz up to 2.5 GHz. The optimization procedure used the finite-difference time-domain method based full-wave simulator with a simplified human body model. In the optimization procedure small movements of antenna towards or away of the human body that are likely to happen during real use were considered. The stability of the antenna parameters irrespective of the movements of the user's body is an important factor in wearable antenna design. The optimization procedure allowed obtaining good impedance matching for a given range of antenna distances with respect to the human body.

Development of multidisciplinary design optimization procedures for smart composite wings and turbomachinery blades

NASA Astrophysics Data System (ADS)

Jha, Ratneshwar

Multidisciplinary design optimization (MDO) procedures have been developed for smart composite wings and turbomachinery blades. The analysis and optimization methods used are computationally efficient and sufficiently rigorous. Therefore, the developed MDO procedures are well suited for actual design applications. The optimization procedure for the conceptual design of composite aircraft wings with surface bonded piezoelectric actuators involves the coupling of structural mechanics, aeroelasticity, aerodynamics and controls. The load carrying member of the wing is represented as a single-celled composite box beam. Each wall of the box beam is analyzed as a composite laminate using a refined higher-order displacement field to account for the variations in transverse shear stresses through the thickness. Therefore, the model is applicable for the analysis of composite wings of arbitrary thickness. Detailed structural modeling issues associated with piezoelectric actuation of composite structures are considered. The governing equations of motion are solved using the finite element method to analyze practical wing geometries. Three-dimensional aerodynamic computations are performed using a panel code based on the constant-pressure lifting surface method to obtain steady and unsteady forces. The Laplace domain method of aeroelastic analysis produces root-loci of the system which gives an insight into the physical phenomena leading to flutter/divergence and can be efficiently integrated within an optimization procedure. The significance of the refined higher-order displacement field on the aeroelastic stability of composite wings has been established. The effect of composite ply orientations on flutter and divergence speeds has been studied. The Kreisselmeier-Steinhauser (K-S) function approach is used to efficiently integrate the objective functions and constraints into a single envelope function. The resulting unconstrained optimization problem is solved using the Broyden-Fletcher-Goldberg-Shanno algorithm. The optimization problem is formulated with the objective of simultaneously minimizing wing weight and maximizing its aerodynamic efficiency. Design variables include composite ply orientations, ply thicknesses, wing sweep, piezoelectric actuator thickness and actuator voltage. Constraints are placed on the flutter/divergence dynamic pressure, wing root stresses and the maximum electric field applied to the actuators. Numerical results are presented showing significant improvements, after optimization, compared to reference designs. The multidisciplinary optimization procedure for the design of turbomachinery blades integrates aerodynamic and heat transfer design objective criteria along with various mechanical and geometric constraints on the blade geometry. The airfoil shape is represented by Bezier-Bernstein polynomials, which results in a relatively small number of design variables for the optimization. Thin shear layer approximation of the Navier-Stokes equation is used for the viscous flow calculations. Grid generation is accomplished by solving Poisson equations. The maximum and average blade temperatures are obtained through a finite element analysis. Total pressure and exit kinetic energy losses are minimized, with constraints on blade temperatures and geometry. The constrained multiobjective optimization problem is solved using the K-S function approach. The results for the numerical example show significant improvements after optimization.

Development of an ELISA for evaluation of swab recovery efficiencies of bovine serum albumin.

PubMed

Sparding, Nadja; Slotved, Hans-Christian; Nicolaisen, Gert M; Giese, Steen B; Elmlund, Jón; Steenhard, Nina R

2014-01-01

After a potential biological incident the sampling strategy and sample analysis are crucial for the outcome of the investigation and identification. In this study, we have developed a simple sandwich ELISA based on commercial components to quantify BSA (used as a surrogate for ricin) with a detection range of 1.32-80 ng/mL. We used the ELISA to evaluate different protein swabbing procedures (swabbing techniques and after-swabbing treatments) for two swab types: a cotton gauze swab and a flocked nylon swab. The optimal swabbing procedure for each swab type was used to obtain recovery efficiencies from different surface materials. The surface recoveries using the optimal swabbing procedure ranged from 0-60% and were significantly higher from nonporous surfaces compared to porous surfaces. In conclusion, this study presents a swabbing procedure evaluation and a simple BSA ELISA based on commercial components, which are easy to perform in a laboratory with basic facilities. The data indicate that different swabbing procedures were optimal for each of the tested swab types, and the particular swab preference depends on the surface material to be swabbed.

Network placement optimization for large-scale distributed system

NASA Astrophysics Data System (ADS)

Ren, Yu; Liu, Fangfang; Fu, Yunxia; Zhou, Zheng

2018-01-01

The network geometry strongly influences the performance of the distributed system, i.e., the coverage capability, measurement accuracy and overall cost. Therefore the network placement optimization represents an urgent issue in the distributed measurement, even in large-scale metrology. This paper presents an effective computer-assisted network placement optimization procedure for the large-scale distributed system and illustrates it with the example of the multi-tracker system. To get an optimal placement, the coverage capability and the coordinate uncertainty of the network are quantified. Then a placement optimization objective function is developed in terms of coverage capabilities, measurement accuracy and overall cost. And a novel grid-based encoding approach for Genetic algorithm is proposed. So the network placement is optimized by a global rough search and a local detailed search. Its obvious advantage is that there is no need for a specific initial placement. At last, a specific application illustrates this placement optimization procedure can simulate the measurement results of a specific network and design the optimal placement efficiently.

Evolutionary algorithm based optimization of hydraulic machines utilizing a state-of-the-art block coupled CFD solver and parametric geometry and mesh generation tools

NASA Astrophysics Data System (ADS)

S, Kyriacou; E, Kontoleontos; S, Weissenberger; L, Mangani; E, Casartelli; I, Skouteropoulou; M, Gattringer; A, Gehrer; M, Buchmayr

2014-03-01

An efficient hydraulic optimization procedure, suitable for industrial use, requires an advanced optimization tool (EASY software), a fast solver (block coupled CFD) and a flexible geometry generation tool. EASY optimization software is a PCA-driven metamodel-assisted Evolutionary Algorithm (MAEA (PCA)) that can be used in both single- (SOO) and multiobjective optimization (MOO) problems. In MAEAs, low cost surrogate evaluation models are used to screen out non-promising individuals during the evolution and exclude them from the expensive, problem specific evaluation, here the solution of Navier-Stokes equations. For additional reduction of the optimization CPU cost, the PCA technique is used to identify dependences among the design variables and to exploit them in order to efficiently drive the application of the evolution operators. To further enhance the hydraulic optimization procedure, a very robust and fast Navier-Stokes solver has been developed. This incompressible CFD solver employs a pressure-based block-coupled approach, solving the governing equations simultaneously. This method, apart from being robust and fast, also provides a big gain in terms of computational cost. In order to optimize the geometry of hydraulic machines, an automatic geometry and mesh generation tool is necessary. The geometry generation tool used in this work is entirely based on b-spline curves and surfaces. In what follows, the components of the tool chain are outlined in some detail and the optimization results of hydraulic machine components are shown in order to demonstrate the performance of the presented optimization procedure.

A linearized theory method of constrained optimization for supersonic cruise wing design

NASA Technical Reports Server (NTRS)

Miller, D. S.; Carlson, H. W.; Middleton, W. D.

1976-01-01

A linearized theory wing design and optimization procedure which allows physical realism and practical considerations to be imposed as constraints on the optimum (least drag due to lift) solution is discussed and examples of application are presented. In addition to the usual constraints on lift and pitching moment, constraints are imposed on wing surface ordinates and wing upper surface pressure levels and gradients. The design procedure also provides the capability of including directly in the optimization process the effects of other aircraft components such as a fuselage, canards, and nacelles.

Optimum Design of High Speed Prop-Rotors

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi

1992-01-01

The objective of this research is to develop optimization procedures to provide design trends in high speed prop-rotors. The necessary disciplinary couplings are all considered within a closed loop optimization process. The procedures involve the consideration of blade aeroelastic, aerodynamic performance, structural and dynamic design requirements. Further, since the design involves consideration of several different objectives, multiobjective function formulation techniques are developed.

Clinical Outcomes of an Optimized Prolate Ablation Procedure for Correcting Residual Refractive Errors Following Laser Surgery.

PubMed

Chung, Byunghoon; Lee, Hun; Choi, Bong Joon; Seo, Kyung Ryul; Kim, Eung Kwon; Kim, Dae Yune; Kim, Tae-Im

2017-02-01

The purpose of this study was to investigate the clinical efficacy of an optimized prolate ablation procedure for correcting residual refractive errors following laser surgery. We analyzed 24 eyes of 15 patients who underwent an optimized prolate ablation procedure for the correction of residual refractive errors following laser in situ keratomileusis, laser-assisted subepithelial keratectomy, or photorefractive keratectomy surgeries. Preoperative ophthalmic examinations were performed, and uncorrected distance visual acuity, corrected distance visual acuity, manifest refraction values (sphere, cylinder, and spherical equivalent), point spread function, modulation transfer function, corneal asphericity (Q value), ocular aberrations, and corneal haze measurements were obtained postoperatively at 1, 3, and 6 months. Uncorrected distance visual acuity improved and refractive errors decreased significantly at 1, 3, and 6 months postoperatively. Total coma aberration increased at 3 and 6 months postoperatively, while changes in all other aberrations were not statistically significant. Similarly, no significant changes in point spread function were detected, but modulation transfer function increased significantly at the postoperative time points measured. The optimized prolate ablation procedure was effective in terms of improving visual acuity and objective visual performance for the correction of persistent refractive errors following laser surgery.

American Society for Pain Management Nursing (ASPMN) position statement: male infant circumcision pain management.

PubMed

O'Conner-Von, Susan; Turner, Helen N

2013-12-01

The ASPMN strongly recommends that infants who are being circumcised must receive optimal pain management. ‘‘If a decision for circumcision is made, procedural analgesia should be provided’’ (AAP, 1999, p. 691). Therefore, it is the position of the ASPMN that optimal pain management must be provided throughout the circumcision process. Furthermore, parents must be prepared for the procedure and educated about infant pain assessment. They must also be informed of pharmacologic and integrative pain management therapies that are appropriate before, during, and after the procedure.

Tricuspid valve dysplasia with severe tricuspid regurgitation: fetal pulmonary artery size predicts lung viability in the presence of small lung volumes.

PubMed

Nathan, A T; Marino, B S; Dominguez, T; Tabbutt, S; Nicolson, S; Donaghue, D D; Spray, T L; Rychik, J

2010-01-01

Congenital tricuspid valve disease (Ebstein's anomaly, tricuspid valve dysplasia) with severe tricuspid regurgitation and cardiomegaly is associated with poor prognosis. Fetal echocardiography can accurately measure right atrial enlargement, which is associated with a poor prognosis in the fetus with tricuspid valve disease. Fetal lung volumetric assessments have been used in an attempt to predict viability of fetuses using ultrasonogram and prenatal MRI. We describe a fetus with tricuspid dysplasia, severe tricuspid regurgitation, right atrial enlargement and markedly reduced lung volumes. The early gestational onset of cardiomegaly with bilateral lung compression raised the possibility of severe lung hypoplasia with decreased broncho-alveolar development. Use of fetal echocardiography with measurement of pulmonary artery size combined with prenatal MRI scanning of lung volumes resulted in an improved understanding of this anomaly and directed the management strategy towards a successful Fontan circulation. 2010 S. Karger AG, Basel.

Flexible Approximation Model Approach for Bi-Level Integrated System Synthesis

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, Jaroslaw; Kim, Hongman; Ragon, Scott; Soremekun, Grant; Malone, Brett

2004-01-01

Bi-Level Integrated System Synthesis (BLISS) is an approach that allows design problems to be naturally decomposed into a set of subsystem optimizations and a single system optimization. In the BLISS approach, approximate mathematical models are used to transfer information from the subsystem optimizations to the system optimization. Accurate approximation models are therefore critical to the success of the BLISS procedure. In this paper, new capabilities that are being developed to generate accurate approximation models for BLISS procedure will be described. The benefits of using flexible approximation models such as Kriging will be demonstrated in terms of convergence characteristics and computational cost. An approach of dealing with cases where subsystem optimization cannot find a feasible design will be investigated by using the new flexible approximation models for the violated local constraints.

Steepest descent method implementation on unconstrained optimization problem using C++ program

NASA Astrophysics Data System (ADS)

Napitupulu, H.; Sukono; Mohd, I. Bin; Hidayat, Y.; Supian, S.

2018-03-01

Steepest Descent is known as the simplest gradient method. Recently, many researches are done to obtain the appropriate step size in order to reduce the objective function value progressively. In this paper, the properties of steepest descent method from literatures are reviewed together with advantages and disadvantages of each step size procedure. The development of steepest descent method due to its step size procedure is discussed. In order to test the performance of each step size, we run a steepest descent procedure in C++ program. We implemented it to unconstrained optimization test problem with two variables, then we compare the numerical results of each step size procedure. Based on the numerical experiment, we conclude the general computational features and weaknesses of each procedure in each case of problem.

Large Scale Bacterial Colony Screening of Diversified FRET Biosensors

PubMed Central

Litzlbauer, Julia; Schifferer, Martina; Ng, David; Fabritius, Arne; Thestrup, Thomas; Griesbeck, Oliver

2015-01-01

Biosensors based on Förster Resonance Energy Transfer (FRET) between fluorescent protein mutants have started to revolutionize physiology and biochemistry. However, many types of FRET biosensors show relatively small FRET changes, making measurements with these probes challenging when used under sub-optimal experimental conditions. Thus, a major effort in the field currently lies in designing new optimization strategies for these types of sensors. Here we describe procedures for optimizing FRET changes by large scale screening of mutant biosensor libraries in bacterial colonies. We describe optimization of biosensor expression, permeabilization of bacteria, software tools for analysis, and screening conditions. The procedures reported here may help in improving FRET changes in multiple suitable classes of biosensors. PMID:26061878

Procedure for minimizing the cost per watt of photovoltaic systems

NASA Technical Reports Server (NTRS)

Redfield, D.

1977-01-01

A general analytic procedure is developed that provides a quantitative method for optimizing any element or process in the fabrication of a photovoltaic energy conversion system by minimizing its impact on the cost per watt of the complete system. By determining the effective value of any power loss associated with each element of the system, this procedure furnishes the design specifications that optimize the cost-performance tradeoffs for each element. A general equation is derived that optimizes the properties of any part of the system in terms of appropriate cost and performance functions, although the power-handling components are found to have a different character from the cell and array steps. Another principal result is that a fractional performance loss occurring at any cell- or array-fabrication step produces that same fractional increase in the cost per watt of the complete array. It also follows that no element or process step can be optimized correctly by considering only its own cost and performance

Sampling design optimization for spatial functions

USGS Publications Warehouse

Olea, R.A.

1984-01-01

A new procedure is presented for minimizing the sampling requirements necessary to estimate a mappable spatial function at a specified level of accuracy. The technique is based on universal kriging, an estimation method within the theory of regionalized variables. Neither actual implementation of the sampling nor universal kriging estimations are necessary to make an optimal design. The average standard error and maximum standard error of estimation over the sampling domain are used as global indices of sampling efficiency. The procedure optimally selects those parameters controlling the magnitude of the indices, including the density and spatial pattern of the sample elements and the number of nearest sample elements used in the estimation. As an illustration, the network of observation wells used to monitor the water table in the Equus Beds of Kansas is analyzed and an improved sampling pattern suggested. This example demonstrates the practical utility of the procedure, which can be applied equally well to other spatial sampling problems, as the procedure is not limited by the nature of the spatial function. ?? 1984 Plenum Publishing Corporation.

Efficient Robust Optimization of Metal Forming Processes using a Sequential Metamodel Based Strategy

NASA Astrophysics Data System (ADS)

Wiebenga, J. H.; Klaseboer, G.; van den Boogaard, A. H.

2011-08-01

The coupling of Finite Element (FE) simulations to mathematical optimization techniques has contributed significantly to product improvements and cost reductions in the metal forming industries. The next challenge is to bridge the gap between deterministic optimization techniques and the industrial need for robustness. This paper introduces a new and generally applicable structured methodology for modeling and solving robust optimization problems. Stochastic design variables or noise variables are taken into account explicitly in the optimization procedure. The metamodel-based strategy is combined with a sequential improvement algorithm to efficiently increase the accuracy of the objective function prediction. This is only done at regions of interest containing the optimal robust design. Application of the methodology to an industrial V-bending process resulted in valuable process insights and an improved robust process design. Moreover, a significant improvement of the robustness (>2σ) was obtained by minimizing the deteriorating effects of several noise variables. The robust optimization results demonstrate the general applicability of the robust optimization strategy and underline the importance of including uncertainty and robustness explicitly in the numerical optimization procedure.

Approximate approach for optimization space flights with a low thrust on the basis of sufficient optimality conditions

NASA Astrophysics Data System (ADS)

Salmin, Vadim V.

2017-01-01

Flight mechanics with a low-thrust is a new chapter of mechanics of space flight, considered plurality of all problems trajectory optimization and movement control laws and the design parameters of spacecraft. Thus tasks associated with taking into account the additional factors in mathematical models of the motion of spacecraft becomes increasingly important, as well as additional restrictions on the possibilities of the thrust vector control. The complication of the mathematical models of controlled motion leads to difficulties in solving optimization problems. Author proposed methods of finding approximate optimal control and evaluating their optimality based on analytical solutions. These methods are based on the principle of extending the class of admissible states and controls and sufficient conditions for the absolute minimum. Developed procedures of the estimation enabling to determine how close to the optimal founded solution, and indicate ways to improve them. Authors describes procedures of estimate for approximately optimal control laws for space flight mechanics problems, in particular for optimization flight low-thrust between the circular non-coplanar orbits, optimization the control angle and trajectory movement of the spacecraft during interorbital flights, optimization flights with low-thrust between arbitrary elliptical orbits Earth satellites.

Multi-objective design optimization of antenna structures using sequential domain patching with automated patch size determination

NASA Astrophysics Data System (ADS)

Koziel, Slawomir; Bekasiewicz, Adrian

2018-02-01

In this article, a simple yet efficient and reliable technique for fully automated multi-objective design optimization of antenna structures using sequential domain patching (SDP) is discussed. The optimization procedure according to SDP is a two-step process: (i) obtaining the initial set of Pareto-optimal designs representing the best possible trade-offs between considered conflicting objectives, and (ii) Pareto set refinement for yielding the optimal designs at the high-fidelity electromagnetic (EM) simulation model level. For the sake of computational efficiency, the first step is realized at the level of a low-fidelity (coarse-discretization) EM model by sequential construction and relocation of small design space segments (patches) in order to create a path connecting the extreme Pareto front designs obtained beforehand. The second stage involves response correction techniques and local response surface approximation models constructed by reusing EM simulation data acquired in the first step. A major contribution of this work is an automated procedure for determining the patch dimensions. It allows for appropriate selection of the number of patches for each geometry variable so as to ensure reliability of the optimization process while maintaining its low cost. The importance of this procedure is demonstrated by comparing it with uniform patch dimensions.

Subgrid-scale scalar flux modelling based on optimal estimation theory and machine-learning procedures

NASA Astrophysics Data System (ADS)

Vollant, A.; Balarac, G.; Corre, C.

2017-09-01

New procedures are explored for the development of models in the context of large eddy simulation (LES) of a passive scalar. They rely on the combination of the optimal estimator theory with machine-learning algorithms. The concept of optimal estimator allows to identify the most accurate set of parameters to be used when deriving a model. The model itself can then be defined by training an artificial neural network (ANN) on a database derived from the filtering of direct numerical simulation (DNS) results. This procedure leads to a subgrid scale model displaying good structural performance, which allows to perform LESs very close to the filtered DNS results. However, this first procedure does not control the functional performance so that the model can fail when the flow configuration differs from the training database. Another procedure is then proposed, where the model functional form is imposed and the ANN used only to define the model coefficients. The training step is a bi-objective optimisation in order to control both structural and functional performances. The model derived from this second procedure proves to be more robust. It also provides stable LESs for a turbulent plane jet flow configuration very far from the training database but over-estimates the mixing process in that case.

Synthesis of Aromatic Thiolate-Protected Gold Nanomolecules by Core Conversion: The Case of Au36(SPh-tBu)24.

PubMed

Theivendran, Shevanuja; Dass, Amala

2017-08-01

Ultrasmall nanomolecules (<2 nm) such as Au 25 (SCH 2 CH 2 Ph) 18 , Au 38 (SCH 2 CH 2 Ph) 24 , and Au 144 (SCH 2 CH 2 Ph) 60 are well studied and can be prepared using established synthetic procedures. No such synthetic protocols that result in high yield products from commercially available starting materials exist for Au 36 (SPh-X) 24 . Here, we report a synthetic procedure for the large-scale synthesis of highly stable Au 36 (SPh-X) 24 with a yield of ∼42%. Au 36 (SPh-X) 24 was conveniently synthesized by using tert-butylbenzenethiol (HSPh-tBu, TBBT) as the ligand, giving a more stable product with better shelf life and higher yield than previously reported for making Au 36 (SPh) 24 from thiophenol (PhSH). The choice of thiol, solvent, and reaction conditions were modified for the optimization of the synthetic procedure. The purposes of this work are to (1) optimize the existing procedure to obtain stable product with better yield, (2) develop a scalable synthetic procedure, (3) demonstrate the superior stability of Au 36 (SPh-tBu) 24 when compared to Au 36 (SPh) 24 , and (4) demonstrate the reproducibility and robustness of the optimized synthetic procedure.

Efficient sensitivity analysis and optimization of a helicopter rotor

NASA Technical Reports Server (NTRS)

Lim, Joon W.; Chopra, Inderjit

1989-01-01

Aeroelastic optimization of a system essentially consists of the determination of the optimum values of design variables which minimize the objective function and satisfy certain aeroelastic and geometric constraints. The process of aeroelastic optimization analysis is illustrated. To carry out aeroelastic optimization effectively, one needs a reliable analysis procedure to determine steady response and stability of a rotor system in forward flight. The rotor dynamic analysis used in the present study developed inhouse at the University of Maryland is based on finite elements in space and time. The analysis consists of two major phases: vehicle trim and rotor steady response (coupled trim analysis), and aeroelastic stability of the blade. For a reduction of helicopter vibration, the optimization process requires the sensitivity derivatives of the objective function and aeroelastic stability constraints. For this, the derivatives of steady response, hub loads and blade stability roots are calculated using a direct analytical approach. An automated optimization procedure is developed by coupling the rotor dynamic analysis, design sensitivity analysis and constrained optimization code CONMIN.

Use of different sample temperatures in a single extraction procedure for the screening of the aroma profile of plant matrices by headspace solid-phase microextraction.

PubMed

Martendal, Edmar; de Souza Silveira, Cristine Durante; Nardini, Giuliana Stael; Carasek, Eduardo

2011-06-17

This study proposes a new approach to the optimization of the extraction of the volatile fraction of plant matrices using the headspace solid-phase microextraction (HS-SPME) technique. The optimization focused on the extraction time and temperature using a CAR/DVB/PDMS 50/30 μm SPME fiber and 100mg of a mixture of plants as the sample in a 15-mL vial. The extraction time (10-60 min) and temperature (5-60 °C) were optimized by means of a central composite design. The chromatogram was divided into four groups of peaks based on the elution temperature to provide a better understanding of the influence of the extraction parameters on the extraction efficiency considering compounds with different volatilities/polarities. In view of the different optimum extraction time and temperature conditions obtained for each group, a new approach based on the use of two extraction temperatures in the same procedure is proposed. The optimum conditions were achieved by extracting for 30 min with a sample temperature of 60 °C followed by a further 15 min at 5 °C. The proposed method was compared with the optimized conventional method based on a single extraction temperature (45 min of extraction at 50 °C) by submitting five samples to both procedures. The proposed method led to better results in all cases, considering as the response both peak area and the number of identified peaks. The newly proposed optimization approach provided an excellent alternative procedure to extract analytes with quite different volatilities in the same procedure. Copyright © 2011 Elsevier B.V. All rights reserved.

A mixed optimization method for automated design of fuselage structures.

NASA Technical Reports Server (NTRS)

Sobieszczanski, J.; Loendorf, D.

1972-01-01

A procedure for automating the design of transport aircraft fuselage structures has been developed and implemented in the form of an operational program. The structure is designed in two stages. First, an overall distribution of structural material is obtained by means of optimality criteria to meet strength and displacement constraints. Subsequently, the detailed design of selected rings and panels consisting of skin and stringers is performed by mathematical optimization accounting for a set of realistic design constraints. The practicality and computer efficiency of the procedure is demonstrated on cylindrical and area-ruled large transport fuselages.

Optimal feed-forward compensation for PWM dc/dc converters with 'linear' and 'quadratic' conversion ratio

NASA Astrophysics Data System (ADS)

Calderone, Luigi; Pinola, Licia; Varoli, Vincenzo

1992-04-01

The paper describes an analytical procedure to optimize the feed-forward compensation for any PWM dc/dc converters. The aims of achieving zero dc audiosusceptibility was found to be possible for the buck, buck-boost, Cuk, and SEPIC cells; for the boost converter, however, only nonoptimal compensation is feasible. Rules for the design of PWM controllers and procedures for the evaluation of the hardware-introduced errors are discussed. A PWM controller implementing the optimal feed-forward compensation for buck-boost, Cuk, and SEPIC cells is described and fully experimentally characterized.

Thermal/Structural Tailoring of Engine Blades (T/STAEBL) User's manual

NASA Technical Reports Server (NTRS)

Brown, K. W.

1994-01-01

The Thermal/Structural Tailoring of Engine Blades (T/STAEBL) system is a computer code that is able to perform numerical optimizations of cooled jet engine turbine blades and vanes. These optimizations seek an airfoil design of minimum operating cost that satisfies realistic design constraints. This report documents the organization of the T/STAEBL computer program, its design and analysis procedure, its optimization procedure, and provides an overview of the input required to run the program, as well as the computer resources required for its effective use. Additionally, usage of the program is demonstrated through a validation test case.

Thermal/Structural Tailoring of Engine Blades (T/STAEBL): User's manual

NASA Astrophysics Data System (ADS)

Brown, K. W.

1994-03-01

The Thermal/Structural Tailoring of Engine Blades (T/STAEBL) system is a computer code that is able to perform numerical optimizations of cooled jet engine turbine blades and vanes. These optimizations seek an airfoil design of minimum operating cost that satisfies realistic design constraints. This report documents the organization of the T/STAEBL computer program, its design and analysis procedure, its optimization procedure, and provides an overview of the input required to run the program, as well as the computer resources required for its effective use. Additionally, usage of the program is demonstrated through a validation test case.

Neural networks for structural design - An integrated system implementation

NASA Technical Reports Server (NTRS)

Berke, Laszlo; Hafez, Wassim; Pao, Yoh-Han

1992-01-01

The development of powerful automated procedures to aid the creative designer is becoming increasingly critical for complex design tasks. In the work described here Artificial Neural Nets are applied to acquire structural analysis and optimization domain expertise. Based on initial instructions from the user an automated procedure generates random instances of structural analysis and/or optimization 'experiences' that cover a desired domain. It extracts training patterns from the created instances, constructs and trains an appropriate network architecture and checks the accuracy of net predictions. The final product is a trained neural net that can estimate analysis and/or optimization results instantaneously.

On the functional optimization of a certain class of nonstationary spatial functions

USGS Publications Warehouse

Christakos, G.; Paraskevopoulos, P.N.

1987-01-01

Procedures are developed in order to obtain optimal estimates of linear functionals for a wide class of nonstationary spatial functions. These procedures rely on well-established constrained minimum-norm criteria, and are applicable to multidimensional phenomena which are characterized by the so-called hypothesis of inherentity. The latter requires elimination of the polynomial, trend-related components of the spatial function leading to stationary quantities, and also it generates some interesting mathematics within the context of modelling and optimization in several dimensions. The arguments are illustrated using various examples, and a case study computed in detail. ?? 1987 Plenum Publishing Corporation.

Structural Tailoring of Advanced Turboprops (STAT)

NASA Technical Reports Server (NTRS)

Brown, Kenneth W.

1988-01-01

This interim report describes the progress achieved in the structural Tailoring of Advanced Turboprops (STAT) program which was developed to perform numerical optimizations on highly swept propfan blades. The optimization procedure seeks to minimize an objective function, defined as either direct operating cost or aeroelastic differences between a blade and its scaled model, by tuning internal and external geometry variables that must satisfy realistic blade design constraints. This report provides a detailed description of the input, optimization procedures, approximate analyses and refined analyses, as well as validation test cases for the STAT program. In addition, conclusions and recommendations are summarized.

Turbomachinery Airfoil Design Optimization Using Differential Evolution

NASA Technical Reports Server (NTRS)

Madavan, Nateri K.; Biegel, Bryan A. (Technical Monitor)

2002-01-01

An aerodynamic design optimization procedure that is based on a evolutionary algorithm known at Differential Evolution is described. Differential Evolution is a simple, fast, and robust evolutionary strategy that has been proven effective in determining the global optimum for several difficult optimization problems, including highly nonlinear systems with discontinuities and multiple local optima. The method is combined with a Navier-Stokes solver that evaluates the various intermediate designs and provides inputs to the optimization procedure. An efficient constraint handling mechanism is also incorporated. Results are presented for the inverse design of a turbine airfoil from a modern jet engine. The capability of the method to search large design spaces and obtain the optimal airfoils in an automatic fashion is demonstrated. Substantial reductions in the overall computing time requirements are achieved by using the algorithm in conjunction with neural networks.

A Rapid Aerodynamic Design Procedure Based on Artificial Neural Networks

NASA Technical Reports Server (NTRS)

Rai, Man Mohan

2001-01-01

An aerodynamic design procedure that uses neural networks to model the functional behavior of the objective function in design space has been developed. This method incorporates several improvements to an earlier method that employed a strategy called parameter-based partitioning of the design space in order to reduce the computational costs associated with design optimization. As with the earlier method, the current method uses a sequence of response surfaces to traverse the design space in search of the optimal solution. The new method yields significant reductions in computational costs by using composite response surfaces with better generalization capabilities and by exploiting synergies between the optimization method and the simulation codes used to generate the training data. These reductions in design optimization costs are demonstrated for a turbine airfoil design study where a generic shape is evolved into an optimal airfoil.

Reduced state feedback gain computation. [optimization and control theory for aircraft control

NASA Technical Reports Server (NTRS)

Kaufman, H.

1976-01-01

Because application of conventional optimal linear regulator theory to flight controller design requires the capability of measuring and/or estimating the entire state vector, it is of interest to consider procedures for computing controls which are restricted to be linear feedback functions of a lower dimensional output vector and which take into account the presence of measurement noise and process uncertainty. Therefore, a stochastic linear model that was developed is presented which accounts for aircraft parameter and initial uncertainty, measurement noise, turbulence, pilot command and a restricted number of measurable outputs. Optimization with respect to the corresponding output feedback gains was performed for both finite and infinite time performance indices without gradient computation by using Zangwill's modification of a procedure originally proposed by Powell. Results using a seventh order process show the proposed procedures to be very effective.

Investigation of Low-Reynolds-Number Rocket Nozzle Design Using PNS-Based Optimization Procedure

NASA Technical Reports Server (NTRS)

Hussaini, M. Moin; Korte, John J.

1996-01-01

An optimization approach to rocket nozzle design, based on computational fluid dynamics (CFD) methodology, is investigated for low-Reynolds-number cases. This study is undertaken to determine the benefits of this approach over those of classical design processes such as Rao's method. A CFD-based optimization procedure, using the parabolized Navier-Stokes (PNS) equations, is used to design conical and contoured axisymmetric nozzles. The advantage of this procedure is that it accounts for viscosity during the design process; other processes make an approximated boundary-layer correction after an inviscid design is created. Results showed significant improvement in the nozzle thrust coefficient over that of the baseline case; however, the unusual nozzle design necessitates further investigation of the accuracy of the PNS equations for modeling expanding flows with thick laminar boundary layers.

Three-dimensional aerodynamic shape optimization of supersonic delta wings

NASA Technical Reports Server (NTRS)

Burgreen, Greg W.; Baysal, Oktay

1994-01-01

A recently developed three-dimensional aerodynamic shape optimization procedure AeSOP(sub 3D) is described. This procedure incorporates some of the most promising concepts from the area of computational aerodynamic analysis and design, specifically, discrete sensitivity analysis, a fully implicit 3D Computational Fluid Dynamics (CFD) methodology, and 3D Bezier-Bernstein surface parameterizations. The new procedure is demonstrated in the preliminary design of supersonic delta wings. Starting from a symmetric clipped delta wing geometry, a Mach 1.62 asymmetric delta wing and two Mach 1. 5 cranked delta wings were designed subject to various aerodynamic and geometric constraints.

Traveling-Wave Tube Cold-Test Circuit Optimization Using CST MICROWAVE STUDIO

NASA Technical Reports Server (NTRS)

Chevalier, Christine T.; Kory, Carol L.; Wilson, Jeffrey D.; Wintucky, Edwin G.; Dayton, James A., Jr.

2003-01-01

The internal optimizer of CST MICROWAVE STUDIO (MWS) was used along with an application-specific Visual Basic for Applications (VBA) script to develop a method to optimize traveling-wave tube (TWT) cold-test circuit performance. The optimization procedure allows simultaneous optimization of circuit specifications including on-axis interaction impedance, bandwidth or geometric limitations. The application of Microwave Studio to TWT cold-test circuit optimization is described.

Performance, optimization, and latest development of the SRI family of rotary cryocoolers

NASA Astrophysics Data System (ADS)

Dovrtel, Klemen; Megušar, Franc

2017-05-01

In this paper the SRI family of Le-tehnika rotary cryocoolers is presented (SRI401, SRI423/SRI421 and SRI474). The Stirling coolers cooling power range starts from 0.25W to 0.75W at 77K with available temperature range from 60K to 150K and are fitted to typical dewar detector sizes and powers supply voltages. The DDCA performance optimizing procedure is presented. The procedure includes cooler steady state performance mapping and optimization and cooldown optimization. The current cryogenic performance status and reliability evaluation method and figures are presented on the existing and new units. The latest improved SRI401 demonstrated MTTF close to 25'000 hours and the test is still on going.

Wave drag as the objective function in transonic fighter wing optimization

NASA Technical Reports Server (NTRS)

Phillips, P. S.

1984-01-01

The original computational method for determining wave drag in a three dimensional transonic analysis method was replaced by a wave drag formula based on the loss in momentum across an isentropic shock. This formula was used as the objective function in a numerical optimization procedure to reduce the wave drag of a fighter wing at transonic maneuver conditions. The optimization procedure minimized wave drag through modifications to the wing section contours defined by a wing profile shape function. A significant reduction in wave drag was achieved while maintaining a high lift coefficient. Comparisons of the pressure distributions for the initial and optimized wing geometries showed significant reductions in the leading-edge peaks and shock strength across the span.

Optimized tomography of continuous variable systems using excitation counting

NASA Astrophysics Data System (ADS)

Shen, Chao; Heeres, Reinier W.; Reinhold, Philip; Jiang, Luyao; Liu, Yi-Kai; Schoelkopf, Robert J.; Jiang, Liang

2016-11-01

We propose a systematic procedure to optimize quantum state tomography protocols for continuous variable systems based on excitation counting preceded by a displacement operation. Compared with conventional tomography based on Husimi or Wigner function measurement, the excitation counting approach can significantly reduce the number of measurement settings. We investigate both informational completeness and robustness, and provide a bound of reconstruction error involving the condition number of the sensing map. We also identify the measurement settings that optimize this error bound, and demonstrate that the improved reconstruction robustness can lead to an order-of-magnitude reduction of estimation error with given resources. This optimization procedure is general and can incorporate prior information of the unknown state to further simplify the protocol.

Optimizing Travel Time to Outpatient Interventional Radiology Procedures in a Multi-Site Hospital System Using a Google Maps Application.

PubMed

Mandel, Jacob E; Morel-Ovalle, Louis; Boas, Franz E; Ziv, Etay; Yarmohammadi, Hooman; Deipolyi, Amy; Mohabir, Heeralall R; Erinjeri, Joseph P

2018-02-20

The purpose of this study is to determine whether a custom Google Maps application can optimize site selection when scheduling outpatient interventional radiology (IR) procedures within a multi-site hospital system. The Google Maps for Business Application Programming Interface (API) was used to develop an internal web application that uses real-time traffic data to determine estimated travel time (ETT; minutes) and estimated travel distance (ETD; miles) from a patient's home to each a nearby IR facility in our hospital system. Hypothetical patient home addresses based on the 33 cities comprising our institution's catchment area were used to determine the optimal IR site for hypothetical patients traveling from each city based on real-time traffic conditions. For 10/33 (30%) cities, there was discordance between the optimal IR site based on ETT and the optimal IR site based on ETD at non-rush hour time or rush hour time. By choosing to travel to an IR site based on ETT rather than ETD, patients from discordant cities were predicted to save an average of 7.29 min during non-rush hour (p = 0.03), and 28.80 min during rush hour (p < 0.001). Using a custom Google Maps application to schedule outpatients for IR procedures can effectively reduce patient travel time when more than one location providing IR procedures is available within the same hospital system.

Computer program to minimize prediction error in models from experiments with 16 hypercube points and 0 to 6 center points

NASA Technical Reports Server (NTRS)

Holms, A. G.

1982-01-01

A previous report described a backward deletion procedure of model selection that was optimized for minimum prediction error and which used a multiparameter combination of the F - distribution and an order statistics distribution of Cochran's. A computer program is described that applies the previously optimized procedure to real data. The use of the program is illustrated by examples.

Optimal Averages for Nonlinear Signal Decompositions - Another Alternative for Empirical Mode Decomposition

DTIC Science & Technology

2014-10-01

nonlinear and non-stationary signals. It aims at decomposing a signal, via an iterative sifting procedure, into several intrinsic mode functions ...stationary signals. It aims at decomposing a signal, via an iterative sifting procedure into several intrinsic mode functions (IMFs), and each of the... function , optimization. 1 Introduction It is well known that nonlinear and non-stationary signal analysis is important and difficult. His- torically

Calculating an optimal box size for ligand docking and virtual screening against experimental and predicted binding pockets.

PubMed

Feinstein, Wei P; Brylinski, Michal

2015-01-01

Computational approaches have emerged as an instrumental methodology in modern research. For example, virtual screening by molecular docking is routinely used in computer-aided drug discovery. One of the critical parameters for ligand docking is the size of a search space used to identify low-energy binding poses of drug candidates. Currently available docking packages often come with a default protocol for calculating the box size, however, many of these procedures have not been systematically evaluated. In this study, we investigate how the docking accuracy of AutoDock Vina is affected by the selection of a search space. We propose a new procedure for calculating the optimal docking box size that maximizes the accuracy of binding pose prediction against a non-redundant and representative dataset of 3,659 protein-ligand complexes selected from the Protein Data Bank. Subsequently, we use the Directory of Useful Decoys, Enhanced to demonstrate that the optimized docking box size also yields an improved ranking in virtual screening. Binding pockets in both datasets are derived from the experimental complex structures and, additionally, predicted by eFindSite. A systematic analysis of ligand binding poses generated by AutoDock Vina shows that the highest accuracy is achieved when the dimensions of the search space are 2.9 times larger than the radius of gyration of a docking compound. Subsequent virtual screening benchmarks demonstrate that this optimized docking box size also improves compound ranking. For instance, using predicted ligand binding sites, the average enrichment factor calculated for the top 1 % (10 %) of the screening library is 8.20 (3.28) for the optimized protocol, compared to 7.67 (3.19) for the default procedure. Depending on the evaluation metric, the optimal docking box size gives better ranking in virtual screening for about two-thirds of target proteins. This fully automated procedure can be used to optimize docking protocols in order to improve the ranking accuracy in production virtual screening simulations. Importantly, the optimized search space systematically yields better results than the default method not only for experimental pockets, but also for those predicted from protein structures. A script for calculating the optimal docking box size is freely available at www.brylinski.org/content/docking-box-size. Graphical AbstractWe developed a procedure to optimize the box size in molecular docking calculations. Left panel shows the predicted binding pose of NADP (green sticks) compared to the experimental complex structure of human aldose reductase (blue sticks) using a default protocol. Right panel shows the docking accuracy using an optimized box size.

Optimizing cost-efficiency in mean exposure assessment - cost functions reconsidered

PubMed Central

2011-01-01

Background Reliable exposure data is a vital concern in medical epidemiology and intervention studies. The present study addresses the needs of the medical researcher to spend monetary resources devoted to exposure assessment with an optimal cost-efficiency, i.e. obtain the best possible statistical performance at a specified budget. A few previous studies have suggested mathematical optimization procedures based on very simple cost models; this study extends the methodology to cover even non-linear cost scenarios. Methods Statistical performance, i.e. efficiency, was assessed in terms of the precision of an exposure mean value, as determined in a hierarchical, nested measurement model with three stages. Total costs were assessed using a corresponding three-stage cost model, allowing costs at each stage to vary non-linearly with the number of measurements according to a power function. Using these models, procedures for identifying the optimally cost-efficient allocation of measurements under a constrained budget were developed, and applied on 225 scenarios combining different sizes of unit costs, cost function exponents, and exposure variance components. Results Explicit mathematical rules for identifying optimal allocation could be developed when cost functions were linear, while non-linear cost functions implied that parts of or the entire optimization procedure had to be carried out using numerical methods. For many of the 225 scenarios, the optimal strategy consisted in measuring on only one occasion from each of as many subjects as allowed by the budget. Significant deviations from this principle occurred if costs for recruiting subjects were large compared to costs for setting up measurement occasions, and, at the same time, the between-subjects to within-subject variance ratio was small. In these cases, non-linearities had a profound influence on the optimal allocation and on the eventual size of the exposure data set. Conclusions The analysis procedures developed in the present study can be used for informed design of exposure assessment strategies, provided that data are available on exposure variability and the costs of collecting and processing data. The present shortage of empirical evidence on costs and appropriate cost functions however impedes general conclusions on optimal exposure measurement strategies in different epidemiologic scenarios. PMID:21600023

Optimizing cost-efficiency in mean exposure assessment--cost functions reconsidered.

PubMed

Mathiassen, Svend Erik; Bolin, Kristian

2011-05-21

Reliable exposure data is a vital concern in medical epidemiology and intervention studies. The present study addresses the needs of the medical researcher to spend monetary resources devoted to exposure assessment with an optimal cost-efficiency, i.e. obtain the best possible statistical performance at a specified budget. A few previous studies have suggested mathematical optimization procedures based on very simple cost models; this study extends the methodology to cover even non-linear cost scenarios. Statistical performance, i.e. efficiency, was assessed in terms of the precision of an exposure mean value, as determined in a hierarchical, nested measurement model with three stages. Total costs were assessed using a corresponding three-stage cost model, allowing costs at each stage to vary non-linearly with the number of measurements according to a power function. Using these models, procedures for identifying the optimally cost-efficient allocation of measurements under a constrained budget were developed, and applied on 225 scenarios combining different sizes of unit costs, cost function exponents, and exposure variance components. Explicit mathematical rules for identifying optimal allocation could be developed when cost functions were linear, while non-linear cost functions implied that parts of or the entire optimization procedure had to be carried out using numerical methods.For many of the 225 scenarios, the optimal strategy consisted in measuring on only one occasion from each of as many subjects as allowed by the budget. Significant deviations from this principle occurred if costs for recruiting subjects were large compared to costs for setting up measurement occasions, and, at the same time, the between-subjects to within-subject variance ratio was small. In these cases, non-linearities had a profound influence on the optimal allocation and on the eventual size of the exposure data set. The analysis procedures developed in the present study can be used for informed design of exposure assessment strategies, provided that data are available on exposure variability and the costs of collecting and processing data. The present shortage of empirical evidence on costs and appropriate cost functions however impedes general conclusions on optimal exposure measurement strategies in different epidemiologic scenarios.

Multidisciplinary design optimization - An emerging new engineering discipline

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, Jaroslaw

1993-01-01

A definition of the multidisciplinary design optimization (MDO) is introduced, and functionality and relationship of the MDO conceptual components are examined. The latter include design-oriented analysis, approximation concepts, mathematical system modeling, design space search, an optimization procedure, and a humane interface.

Optimal experimental designs for the estimation of thermal properties of composite materials

NASA Technical Reports Server (NTRS)

Scott, Elaine P.; Moncman, Deborah A.

1994-01-01

Reliable estimation of thermal properties is extremely important in the utilization of new advanced materials, such as composite materials. The accuracy of these estimates can be increased if the experiments are designed carefully. The objectives of this study are to design optimal experiments to be used in the prediction of these thermal properties and to then utilize these designs in the development of an estimation procedure to determine the effective thermal properties (thermal conductivity and volumetric heat capacity). The experiments were optimized by choosing experimental parameters that maximize the temperature derivatives with respect to all of the unknown thermal properties. This procedure has the effect of minimizing the confidence intervals of the resulting thermal property estimates. Both one-dimensional and two-dimensional experimental designs were optimized. A heat flux boundary condition is required in both analyses for the simultaneous estimation of the thermal properties. For the one-dimensional experiment, the parameters optimized were the heating time of the applied heat flux, the temperature sensor location, and the experimental time. In addition to these parameters, the optimal location of the heat flux was also determined for the two-dimensional experiments. Utilizing the optimal one-dimensional experiment, the effective thermal conductivity perpendicular to the fibers and the effective volumetric heat capacity were then estimated for an IM7-Bismaleimide composite material. The estimation procedure used is based on the minimization of a least squares function which incorporates both calculated and measured temperatures and allows for the parameters to be estimated simultaneously.

Optimal design of a hybrid MR brake for haptic wrist application

NASA Astrophysics Data System (ADS)

Nguyen, Quoc Hung; Nguyen, Phuong Bac; Choi, Seung-Bok

2011-03-01

In this work, a new configuration of a magnetorheological (MR) brake is proposed and an optimal design of the proposed MR brake for haptic wrist application is performed considering the required braking torque, the zero-field friction torque, the size and mass of the brake. The proposed MR brake configuration is a combination of disc-type and drum-type which is referred as a hybrid configuration in this study. After the MR brake with the hybrid configuration is proposed, braking torque of the brake is analyzed based on Bingham rheological model of the MR fluid. The zero-field friction torque of the MR brake is also obtained. An optimization procedure based on finite element analysis integrated with an optimization tool is developed for the MR brake. The purpose of the optimal design is to find the optimal geometric dimensions of the MR brake structure that can produce the required braking torque and minimize the uncontrollable torque (passive torque) of the haptic wrist. Based on developed optimization procedure, optimal solution of the proposed MR brake is achieved. The proposed optimized hybrid brake is then compared with conventional types of MR brake and discussions on working performance of the proposed MR brake are described.

Teaching Simulation and Computer-Aided Separation Optimization in Liquid Chromatography by Means of Illustrative Microsoft Excel Spreadsheets

ERIC Educational Resources Information Center

Fasoula, S.; Nikitas, P.; Pappa-Louisi, A.

2017-01-01

A series of Microsoft Excel spreadsheets were developed to simulate the process of separation optimization under isocratic and simple gradient conditions. The optimization procedure is performed in a stepwise fashion using simple macros for an automatic application of this approach. The proposed optimization approach involves modeling of the peak…

Systematic and efficient side chain optimization for molecular docking using a cheapest-path procedure.

PubMed

Schumann, Marcel; Armen, Roger S

2013-05-30

Molecular docking of small-molecules is an important procedure for computer-aided drug design. Modeling receptor side chain flexibility is often important or even crucial, as it allows the receptor to adopt new conformations as induced by ligand binding. However, the accurate and efficient incorporation of receptor side chain flexibility has proven to be a challenge due to the huge computational complexity required to adequately address this problem. Here we describe a new docking approach with a very fast, graph-based optimization algorithm for assignment of the near-optimal set of residue rotamers. We extensively validate our approach using the 40 DUD target benchmarks commonly used to assess virtual screening performance and demonstrate a large improvement using the developed side chain optimization over rigid receptor docking (average ROC AUC of 0.693 vs. 0.623). Compared to numerous benchmarks, the overall performance is better than nearly all other commonly used procedures. Furthermore, we provide a detailed analysis of the level of receptor flexibility observed in docking results for different classes of residues and elucidate potential avenues for further improvement. Copyright © 2013 Wiley Periodicals, Inc.

Optimization of reinforced concrete slabs

NASA Technical Reports Server (NTRS)

Ferritto, J. M.

1979-01-01

Reinforced concrete cells composed of concrete slabs and used to limit the effects of accidental explosions during hazardous explosives operations are analyzed. An automated design procedure which considers the dynamic nonlinear behavior of the reinforced concrete of arbitrary geometrical and structural configuration subjected to dynamic pressure loading is discussed. The optimum design of the slab is examined using an interior penalty function. The optimization procedure is presented and the results are discussed and compared with finite element analysis.

Optimizing a liquid propellant rocket engine with an automated combustor design code (AUTOCOM)

NASA Technical Reports Server (NTRS)

Hague, D. S.; Reichel, R. H.; Jones, R. T.; Glatt, C. R.

1972-01-01

A procedure for automatically designing a liquid propellant rocket engine combustion chamber in an optimal fashion is outlined. The procedure is contained in a digital computer code, AUTOCOM. The code is applied to an existing engine, and design modifications are generated which provide a substantial potential payload improvement over the existing design. Computer time requirements for this payload improvement were small, approximately four minutes in the CDC 6600 computer.

An integrated optimum design approach for high speed prop-rotors including acoustic constraints

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; Wells, Valana; Mccarthy, Thomas; Han, Arris

1993-01-01

The objective of this research is to develop optimization procedures to provide design trends in high speed prop-rotors. The necessary disciplinary couplings are all considered within a closed loop multilevel decomposition optimization process. The procedures involve the consideration of blade-aeroelastic aerodynamic performance, structural-dynamic design requirements, and acoustics. Further, since the design involves consideration of several different objective functions, multiobjective function formulation techniques are developed.

Detonation Energies of Explosives by Optimized JCZ3 Procedures

NASA Astrophysics Data System (ADS)

Stiel, Leonard; Baker, Ernest

1997-07-01

Procedures for the detonation properties of explosives have been extended for the calculation of detonation energies at adiabatic expansion conditions. Advanced variable metric optimization routines developed by ARDEC are utilized to establish chemical reaction equilibrium by the minimization of the Helmholtz free energy of the system. The use of the JCZ3 equation of state with optimized Exp-6 potential parameters leads to lower errors in JWL detonation energies than the TIGER JCZ3 procedure and other methods tested for relative volumes to 7.0. For the principal isentrope with C-J parameters and freeze conditions established at elevated pressures with the JCZ3 equation of state, best results are obtained if an alternate volumetric relationship is utilized at the highest expansions. Efficient subroutines (designated JAGUAR) have been developed which incorporate the ability to automatically generate JWL and JWLB equation of state parameters. abstract.

Evaluation of Genetic Algorithm Concepts Using Model Problems. Part 2; Multi-Objective Optimization

NASA Technical Reports Server (NTRS)

Holst, Terry L.; Pulliam, Thomas H.

2003-01-01

A genetic algorithm approach suitable for solving multi-objective optimization problems is described and evaluated using a series of simple model problems. Several new features including a binning selection algorithm and a gene-space transformation procedure are included. The genetic algorithm is suitable for finding pareto optimal solutions in search spaces that are defined by any number of genes and that contain any number of local extrema. Results indicate that the genetic algorithm optimization approach is flexible in application and extremely reliable, providing optimal results for all optimization problems attempted. The binning algorithm generally provides pareto front quality enhancements and moderate convergence efficiency improvements for most of the model problems. The gene-space transformation procedure provides a large convergence efficiency enhancement for problems with non-convoluted pareto fronts and a degradation in efficiency for problems with convoluted pareto fronts. The most difficult problems --multi-mode search spaces with a large number of genes and convoluted pareto fronts-- require a large number of function evaluations for GA convergence, but always converge.

Cryogenic Tank Structure Sizing With Structural Optimization Method

NASA Technical Reports Server (NTRS)

Wang, J. T.; Johnson, T. F.; Sleight, D. W.; Saether, E.

2001-01-01

Structural optimization methods in MSC /NASTRAN are used to size substructures and to reduce the weight of a composite sandwich cryogenic tank for future launch vehicles. Because the feasible design space of this problem is non-convex, many local minima are found. This non-convex problem is investigated in detail by conducting a series of analyses along a design line connecting two feasible designs. Strain constraint violations occur for some design points along the design line. Since MSC/NASTRAN uses gradient-based optimization procedures. it does not guarantee that the lowest weight design can be found. In this study, a simple procedure is introduced to create a new starting point based on design variable values from previous optimization analyses. Optimization analysis using this new starting point can produce a lower weight design. Detailed inputs for setting up the MSC/NASTRAN optimization analysis and final tank design results are presented in this paper. Approaches for obtaining further weight reductions are also discussed.

Inverse Modelling to Obtain Head Movement Controller Signal

NASA Technical Reports Server (NTRS)

Kim, W. S.; Lee, S. H.; Hannaford, B.; Stark, L.

1984-01-01

Experimentally obtained dynamics of time-optimal, horizontal head rotations have previously been simulated by a sixth order, nonlinear model driven by rectangular control signals. Electromyography (EMG) recordings have spects which differ in detail from the theoretical rectangular pulsed control signal. Control signals for time-optimal as well as sub-optimal horizontal head rotations were obtained by means of an inverse modelling procedures. With experimentally measured dynamical data serving as the input, this procedure inverts the model to produce the neurological control signals driving muscles and plant. The relationships between these controller signals, and EMG records should contribute to the understanding of the neurological control of movements.

Computer-oriented synthesis of wide-band non-uniform negative resistance amplifiers

NASA Technical Reports Server (NTRS)

Branner, G. R.; Chan, S.-P.

1975-01-01

This paper presents a synthesis procedure which provides design values for broad-band amplifiers using non-uniform negative resistance devices. Employing a weighted least squares optimization scheme, the technique, based on an extension of procedures for uniform negative resistance devices, is capable of providing designs for a variety of matching network topologies. It also provides, for the first time, quantitative results for predicting the effects of parameter element variations on overall amplifier performance. The technique is also unique in that it employs exact partial derivatives for optimization and sensitivity computation. In comparison with conventional procedures, significantly improved broad-band designs are shown to result.

Structural optimization of framed structures using generalized optimality criteria

NASA Technical Reports Server (NTRS)

Kolonay, R. M.; Venkayya, Vipperla B.; Tischler, V. A.; Canfield, R. A.

1989-01-01

The application of a generalized optimality criteria to framed structures is presented. The optimality conditions, Lagrangian multipliers, resizing algorithm, and scaling procedures are all represented as a function of the objective and constraint functions along with their respective gradients. The optimization of two plane frames under multiple loading conditions subject to stress, displacement, generalized stiffness, and side constraints is presented. These results are compared to those found by optimizing the frames using a nonlinear mathematical programming technique.

Jig-Shape Optimization of a Low-Boom Supersonic Aircraft

NASA Technical Reports Server (NTRS)

Pak, Chan-gi

2018-01-01

A simple approach for optimizing the jig-shape is proposed in this study. This simple approach is based on an unconstrained optimization problem and applied to a low-boom supersonic aircraft. In this study, the jig-shape optimization is performed using the two-step approach. First, starting design variables are computed using the least squares surface fitting technique. Next, the jig-shape is further tuned using a numerical optimization procedure based on in-house object-oriented optimization tool.

Methodological aspects of an adaptive multidirectional pattern search to optimize speech perception using three hearing-aid algorithms

NASA Astrophysics Data System (ADS)

Franck, Bas A. M.; Dreschler, Wouter A.; Lyzenga, Johannes

2004-12-01

In this study we investigated the reliability and convergence characteristics of an adaptive multidirectional pattern search procedure, relative to a nonadaptive multidirectional pattern search procedure. The procedure was designed to optimize three speech-processing strategies. These comprise noise reduction, spectral enhancement, and spectral lift. The search is based on a paired-comparison paradigm, in which subjects evaluated the listening comfort of speech-in-noise fragments. The procedural and nonprocedural factors that influence the reliability and convergence of the procedure are studied using various test conditions. The test conditions combine different tests, initial settings, background noise types, and step size configurations. Seven normal hearing subjects participated in this study. The results indicate that the reliability of the optimization strategy may benefit from the use of an adaptive step size. Decreasing the step size increases accuracy, while increasing the step size can be beneficial to create clear perceptual differences in the comparisons. The reliability also depends on starting point, stop criterion, step size constraints, background noise, algorithms used, as well as the presence of drifting cues and suboptimal settings. There appears to be a trade-off between reliability and convergence, i.e., when the step size is enlarged the reliability improves, but the convergence deteriorates. .

Experimental design for evaluating WWTP data by linear mass balances.

PubMed

Le, Quan H; Verheijen, Peter J T; van Loosdrecht, Mark C M; Volcke, Eveline I P

2018-05-15

A stepwise experimental design procedure to obtain reliable data from wastewater treatment plants (WWTPs) was developed. The proposed procedure aims at determining sets of additional measurements (besides available ones) that guarantee the identifiability of key process variables, which means that their value can be calculated from other, measured variables, based on available constraints in the form of linear mass balances. Among all solutions, i.e. all possible sets of additional measurements allowing the identifiability of all key process variables, the optimal solutions were found taking into account two objectives, namely the accuracy of the identified key variables and the cost of additional measurements. The results of this multi-objective optimization problem were represented in a Pareto-optimal front. The presented procedure was applied to a full-scale WWTP. Detailed analysis of the relation between measurements allowed the determination of groups of overlapping mass balances. Adding measured variables could only serve in identifying key variables that appear in the same group of mass balances. Besides, the application of the experimental design procedure to these individual groups significantly reduced the computational effort in evaluating available measurements and planning additional monitoring campaigns. The proposed procedure is straightforward and can be applied to other WWTPs with or without prior data collection. Copyright © 2018 Elsevier Ltd. All rights reserved.

An Optimal Bahadur-Efficient Method in Detection of Sparse Signals with Applications to Pathway Analysis in Sequencing Association Studies.

PubMed

Dai, Hongying; Wu, Guodong; Wu, Michael; Zhi, Degui

2016-01-01

Next-generation sequencing data pose a severe curse of dimensionality, complicating traditional "single marker-single trait" analysis. We propose a two-stage combined p-value method for pathway analysis. The first stage is at the gene level, where we integrate effects within a gene using the Sequence Kernel Association Test (SKAT). The second stage is at the pathway level, where we perform a correlated Lancaster procedure to detect joint effects from multiple genes within a pathway. We show that the Lancaster procedure is optimal in Bahadur efficiency among all combined p-value methods. The Bahadur efficiency,[Formula: see text], compares sample sizes among different statistical tests when signals become sparse in sequencing data, i.e. ε →0. The optimal Bahadur efficiency ensures that the Lancaster procedure asymptotically requires a minimal sample size to detect sparse signals ([Formula: see text]). The Lancaster procedure can also be applied to meta-analysis. Extensive empirical assessments of exome sequencing data show that the proposed method outperforms Gene Set Enrichment Analysis (GSEA). We applied the competitive Lancaster procedure to meta-analysis data generated by the Global Lipids Genetics Consortium to identify pathways significantly associated with high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, and total cholesterol.

Structural tailoring of engine blades (STAEBL)

NASA Technical Reports Server (NTRS)

Platt, C. E.; Pratt, T. K.; Brown, K. W.

1982-01-01

A mathematical optimization procedure was developed for the structural tailoring of engine blades and was used to structurally tailor two engine fan blades constructed of composite materials without midspan shrouds. The first was a solid blade made from superhybrid composites, and the second was a hollow blade with metal matrix composite inlays. Three major computerized functions were needed to complete the procedure: approximate analysis with the established input variables, optimization of an objective function, and refined analysis for design verification.

Optimal Artificial Boundary Condition Configurations for Sensitivity-Based Model Updating and Damage Detection

DTIC Science & Technology

2010-09-01

matrix is used in many methods, like Jacobi or Gauss Seidel , for solving linear systems. Also, no partial pivoting is necessary for a strictly column...problems that arise during the procedure, which in general, converges to the solving of a linear system. The most common issue with the solution is the... iterative procedure to find an appropriate subset of parameters that produce an optimal solution commonly known as forward selection. Then, the

Multi-level optimization of a beam-like space truss utilizing a continuum model

NASA Technical Reports Server (NTRS)

Yates, K.; Gurdal, Z.; Thangjitham, S.

1992-01-01

A continuous beam model is developed for approximate analysis of a large, slender, beam-like truss. The model is incorporated in a multi-level optimization scheme for the weight minimization of such trusses. This scheme is tested against traditional optimization procedures for savings in computational cost. Results from both optimization methods are presented for comparison.

Computational benefits using artificial intelligent methodologies for the solution of an environmental design problem: saltwater intrusion.

PubMed

Papadopoulou, Maria P; Nikolos, Ioannis K; Karatzas, George P

2010-01-01

Artificial Neural Networks (ANNs) comprise a powerful tool to approximate the complicated behavior and response of physical systems allowing considerable reduction in computation time during time-consuming optimization runs. In this work, a Radial Basis Function Artificial Neural Network (RBFN) is combined with a Differential Evolution (DE) algorithm to solve a water resources management problem, using an optimization procedure. The objective of the optimization scheme is to cover the daily water demand on the coastal aquifer east of the city of Heraklion, Crete, without reducing the subsurface water quality due to seawater intrusion. The RBFN is utilized as an on-line surrogate model to approximate the behavior of the aquifer and to replace some of the costly evaluations of an accurate numerical simulation model which solves the subsurface water flow differential equations. The RBFN is used as a local approximation model in such a way as to maintain the robustness of the DE algorithm. The results of this procedure are compared to the corresponding results obtained by using the Simplex method and by using the DE procedure without the surrogate model. As it is demonstrated, the use of the surrogate model accelerates the convergence of the DE optimization procedure and additionally provides a better solution at the same number of exact evaluations, compared to the original DE algorithm.

78 FR 54509 - Tenth Meeting: RTCA Next Gen Advisory Committee (NAC)

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-04

... Capabilities Work Group. Recommendation for Future Metroplex Optimization Activity. [cir] Recommendation for Future Use of Optimization of Airspace and Procedures in the Metroplex (OAPM) developed by the...

Reliability- and performance-based robust design optimization of MEMS structures considering technological uncertainties

NASA Astrophysics Data System (ADS)

Martowicz, Adam; Uhl, Tadeusz

2012-10-01

The paper discusses the applicability of a reliability- and performance-based multi-criteria robust design optimization technique for micro-electromechanical systems, considering their technological uncertainties. Nowadays, micro-devices are commonly applied systems, especially in the automotive industry, taking advantage of utilizing both the mechanical structure and electronic control circuit on one board. Their frequent use motivates the elaboration of virtual prototyping tools that can be applied in design optimization with the introduction of technological uncertainties and reliability. The authors present a procedure for the optimization of micro-devices, which is based on the theory of reliability-based robust design optimization. This takes into consideration the performance of a micro-device and its reliability assessed by means of uncertainty analysis. The procedure assumes that, for each checked design configuration, the assessment of uncertainty propagation is performed with the meta-modeling technique. The described procedure is illustrated with an example of the optimization carried out for a finite element model of a micro-mirror. The multi-physics approach allowed the introduction of several physical phenomena to correctly model the electrostatic actuation and the squeezing effect present between electrodes. The optimization was preceded by sensitivity analysis to establish the design and uncertain domains. The genetic algorithms fulfilled the defined optimization task effectively. The best discovered individuals are characterized by a minimized value of the multi-criteria objective function, simultaneously satisfying the constraint on material strength. The restriction of the maximum equivalent stresses was introduced with the conditionally formulated objective function with a penalty component. The yielded results were successfully verified with a global uniform search through the input design domain.

Optimizing Chromatographic Separation: An Experiment Using an HPLC Simulator

ERIC Educational Resources Information Center

Shalliker, R. A.; Kayillo, S.; Dennis, G. R.

2008-01-01

Optimization of a chromatographic separation within the time constraints of a laboratory session is practically impossible. However, by employing a HPLC simulator, experiments can be designed that allow students to develop an appreciation of the complexities involved in optimization procedures. In the present exercise, a HPLC simulator from "JCE…

Improved optimization of polycyclic aromatic hydrocarbons (PAHs) mixtures resolution in reversed-phase high-performance liquid chromatography by using factorial design and response surface methodology.

PubMed

Andrade-Eiroa, Auréa; Diévart, Pascal; Dagaut, Philippe

2010-04-15

A new procedure for optimizing PAHs separation in very complex mixtures by reverse phase high performance (RPLC) is proposed. It is based on changing gradually the experimental conditions all along the chromatographic procedure as a function of the physical properties of the compounds eluted. The temperature and speed flow gradients allowed obtaining the optimum resolution in large chromatographic determinations where PAHs with very different medium polarizability have to be separated. Whereas optimization procedures of RPLC methodologies had always been accomplished regardless of the physico-chemical properties of the target analytes, we found that resolution is highly dependent on the physico-chemical properties of the target analytes. Based on resolution criterion, optimization process for a 16 EPA PAHs mixture was performed on three sets of difficult-to-separate PAHs pairs: acenaphthene-fluorene (for the optimization procedure in the first part of the chromatogram where light PAHs elute), benzo[g,h,i]perylene-dibenzo[a,h]anthracene and benzo[g,h,i]perylene-indeno[1,2,3-cd]pyrene (for the optimization procedure of the second part of the chromatogram where the heavier PAHs elute). Two-level full factorial designs were applied to detect interactions among variables to be optimized: speed flow, temperature of column oven and mobile-phase gradient in the two parts of the studied chromatogram. Experimental data were fitted by multivariate nonlinear regression models and optimum values of speed flow and temperature were obtained through mathematical analysis of the constructed models. An HPLC system equipped with a reversed phase 5 microm C18, 250 mm x 4.6mm column (with acetonitrile/water mobile phase), a column oven, a binary pump, a photodiode array detector (PDA), and a fluorimetric detector were used in this work. Optimum resolution was achieved operating at 1.0 mL/min in the first part of the chromatogram (until 45 min) and 0.5 mL/min in the second one (from 45 min to the end) and by applying programmed temperature gradient (15 degrees C until 30 min and progressively increasing temperature until reaching 40 degrees C at 45 min). (c) 2009 Elsevier B.V. All rights reserved.

Heuristic query optimization for query multiple table and multiple clausa on mobile finance application

NASA Astrophysics Data System (ADS)

Indrayana, I. N. E.; P, N. M. Wirasyanti D.; Sudiartha, I. KG

2018-01-01

Mobile application allow many users to access data from the application without being limited to space, space and time. Over time the data population of this application will increase. Data access time will cause problems if the data record has reached tens of thousands to millions of records.The objective of this research is to maintain the performance of data execution for large data records. One effort to maintain data access time performance is to apply query optimization method. The optimization used in this research is query heuristic optimization method. The built application is a mobile-based financial application using MySQL database with stored procedure therein. This application is used by more than one business entity in one database, thus enabling rapid data growth. In this stored procedure there is an optimized query using heuristic method. Query optimization is performed on a “Select” query that involves more than one table with multiple clausa. Evaluation is done by calculating the average access time using optimized and unoptimized queries. Access time calculation is also performed on the increase of population data in the database. The evaluation results shown the time of data execution with query heuristic optimization relatively faster than data execution time without using query optimization.

MO-G-18A-01: Radiation Dose Reducing Strategies in CT, Fluoroscopy and Radiography

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

Mahesh, M; Gingold, E; Jones, A

2014-06-15

Advances in medical x-ray imaging have provided significant benefits to patient care. According to NCRP 160, there are more than 400 million x-ray procedures performed annually in the United States alone that contributes to nearly half of all the radiation exposure to the US population. Similar growth trends in medical x-ray imaging are observed worldwide. Apparent increase in number of medical x-ray imaging procedures, new protocols and the associated radiation dose and risk has drawn considerable attention. This has led to a number of technological innovations such as tube current modulation, iterative reconstruction algorithms, dose alerts, dose displays, flat panelmore » digital detectors, high efficient digital detectors, storage phosphor radiography, variable filters, etc. that are enabling users to acquire medical x-ray images at a much lower radiation dose. Along with these, there are number of radiation dose optimization strategies that users can adapt to effectively lower radiation dose in medical x-ray procedures. The main objectives of this SAM course are to provide information and how to implement the various radiation dose optimization strategies in CT, Fluoroscopy and Radiography. Learning Objectives: To update impact of technological advances on dose optimization in medical imaging. To identify radiation optimization strategies in computed tomography. To describe strategies for configuring fluoroscopic equipment that yields optimal images at reasonable radiation dose. To assess ways to configure digital radiography systems and recommend ways to improve image quality at optimal dose.« less

Determination of full piezoelectric complex parameters using gradient-based optimization algorithm

NASA Astrophysics Data System (ADS)

Kiyono, C. Y.; Pérez, N.; Silva, E. C. N.

2016-02-01

At present, numerical techniques allow the precise simulation of mechanical structures, but the results are limited by the knowledge of the material properties. In the case of piezoelectric ceramics, the full model determination in the linear range involves five elastic, three piezoelectric, and two dielectric complex parameters. A successful solution to obtaining piezoceramic properties consists of comparing the experimental measurement of the impedance curve and the results of a numerical model by using the finite element method (FEM). In the present work, a new systematic optimization method is proposed to adjust the full piezoelectric complex parameters in the FEM model. Once implemented, the method only requires the experimental data (impedance modulus and phase data acquired by an impedometer), material density, geometry, and initial values for the properties. This method combines a FEM routine implemented using an 8-noded axisymmetric element with a gradient-based optimization routine based on the method of moving asymptotes (MMA). The main objective of the optimization procedure is minimizing the quadratic difference between the experimental and numerical electrical conductance and resistance curves (to consider resonance and antiresonance frequencies). To assure the convergence of the optimization procedure, this work proposes restarting the optimization loop whenever the procedure ends in an undesired or an unfeasible solution. Two experimental examples using PZ27 and APC850 samples are presented to test the precision of the method and to check the dependency of the frequency range used, respectively.

Optimization experiments with a double Gauss lens

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

Brixner, B.; Klein, M.M.

1988-05-01

This paper describes how a lens can be generated by starting from plane surfaces. Three different experiments, using the Los Alamos National Laboratory optimization procedure, all converged on the same stable prescriptions in the optimum minimum region. The starts were made first from an already optimized lens appearing in the literature, then from a powerless plane-surfaces configuration, and finally from a crude Super Angulon configuration. In each case the result was a double Gauss lens, which suggests that this type of lens may be the best compact six-glass solution for one imaging problem: an f/2 aperture and a moderate fieldmore » of view. The procedures and results are discussed in detail.« less

Optimization Experiments With A Double Gauss Lens

NASA Astrophysics Data System (ADS)

Brixner, Berlyn; Klein, Morris M.

1988-05-01

This paper describes how a lens can be generated by starting from plane surfaces. Three different experiments, using the Los Alamos National Laboratory optimization procedure, all converged on the same stable prescriptions in the optimum minimum region. The starts were made first from an already optimized lens appearing in the literature, then from a powerless plane-surfaces configuration, and finally from a crude Super Angulon configuration. In each case the result was a double Gauss lens, which suggests that this type of lens may be the best compact six-glass solution for one imaging problem: an f/2 aperture and a moderate field of view. The procedures and results are discussed in detail.

Static deflection control of flexible beams by piezo-electric actuators

NASA Technical Reports Server (NTRS)

Baz, A. M.

1986-01-01

This study deals with the utilization of piezo-electric actuators in controlling the static deformation of flexible beams. An optimum design procedure is presented to enable the selection of the optimal location, thickness and excitation voltage of the piezo-electric actuators in a way that would minimize the deflection of the beam to which these actuators are bonded. Numerical examples are presented to illustrate the application of the developed optimization procedure in minimizing the structural deformation of beams of different materials when subjected to different loading and end conditions using ceramic or polymeric piezo-electric actuators. The results obtained emphasize the importance of the devised rational procedure in designing beam-actuator systems with minimal elastic distortions.

A hybrid framework for coupling arbitrary summation-by-parts schemes on general meshes

NASA Astrophysics Data System (ADS)

Lundquist, Tomas; Malan, Arnaud; Nordström, Jan

2018-06-01

We develop a general interface procedure to couple both structured and unstructured parts of a hybrid mesh in a non-collocated, multi-block fashion. The target is to gain optimal computational efficiency in fluid dynamics simulations involving complex geometries. While guaranteeing stability, the proposed procedure is optimized for accuracy and requires minimal algorithmic modifications to already existing schemes. Initial numerical investigations confirm considerable efficiency gains compared to non-hybrid calculations of up to an order of magnitude.

Kuhn-Tucker optimization based reliability analysis for probabilistic finite elements

NASA Technical Reports Server (NTRS)

Liu, W. K.; Besterfield, G.; Lawrence, M.; Belytschko, T.

1988-01-01

The fusion of probability finite element method (PFEM) and reliability analysis for fracture mechanics is considered. Reliability analysis with specific application to fracture mechanics is presented, and computational procedures are discussed. Explicit expressions for the optimization procedure with regard to fracture mechanics are given. The results show the PFEM is a very powerful tool in determining the second-moment statistics. The method can determine the probability of failure or fracture subject to randomness in load, material properties and crack length, orientation, and location.

A design procedure and handling quality criteria for lateral directional flight control systems

NASA Technical Reports Server (NTRS)

Stein, G.; Henke, A. H.

1972-01-01

A practical design procedure for aircraft augmentation systems is described based on quadratic optimal control technology and handling-quality-oriented cost functionals. The procedure is applied to the design of a lateral-directional control system for the F4C aircraft. The design criteria, design procedure, and final control system are validated with a program of formal pilot evaluation experiments.

Optimization of cathodic arc deposition and pulsed plasma melting techniques for growing smooth superconducting Pb photoemissive films for SRF injectors

NASA Astrophysics Data System (ADS)

Nietubyć, Robert; Lorkiewicz, Jerzy; Sekutowicz, Jacek; Smedley, John; Kosińska, Anna

2018-05-01

Superconducting photoinjectors have a potential to be the optimal solution for moderate and high current cw operating free electron lasers. For this application, a superconducting lead (Pb) cathode has been proposed to simplify the cathode integration into a 1.3 GHz, TESLA-type, 1.6-cell long purely superconducting gun cavity. In the proposed design, a lead film several micrometres thick is deposited onto a niobium plug attached to the cavity back wall. Traditional lead deposition techniques usually produce very non-uniform emission surfaces and often result in a poor adhesion of the layer. A pulsed plasma melting procedure reducing the non-uniformity of the lead photocathodes is presented. In order to determine the parameters optimal for this procedure, heat transfer from plasma to the film was first modelled to evaluate melting front penetration range and liquid state duration. The obtained results were verified by surface inspection of witness samples. The optimal procedure was used to prepare a photocathode plug, which was then tested in an electron gun. The quantum efficiency and the value of cavity quality factor have been found to satisfy the requirements for an injector of the European-XFEL facility.

General approach and scope. [rotor blade design optimization

NASA Technical Reports Server (NTRS)

Adelman, Howard M.; Mantay, Wayne R.

1989-01-01

This paper describes a joint activity involving NASA and Army researchers at the NASA Langley Research Center to develop optimization procedures aimed at improving the rotor blade design process by integrating appropriate disciplines and accounting for all of the important interactions among the disciplines. The disciplines involved include rotor aerodynamics, rotor dynamics, rotor structures, airframe dynamics, and acoustics. The work is focused on combining these five key disciplines in an optimization procedure capable of designing a rotor system to satisfy multidisciplinary design requirements. Fundamental to the plan is a three-phased approach. In phase 1, the disciplines of blade dynamics, blade aerodynamics, and blade structure will be closely coupled, while acoustics and airframe dynamics will be decoupled and be accounted for as effective constraints on the design for the first three disciplines. In phase 2, acoustics is to be integrated with the first three disciplines. Finally, in phase 3, airframe dynamics will be fully integrated with the other four disciplines. This paper deals with details of the phase 1 approach and includes details of the optimization formulation, design variables, constraints, and objective function, as well as details of discipline interactions, analysis methods, and methods for validating the procedure.

Optimal spatial sampling techniques for ground truth data in microwave remote sensing of soil moisture

NASA Technical Reports Server (NTRS)

Rao, R. G. S.; Ulaby, F. T.

1977-01-01

The paper examines optimal sampling techniques for obtaining accurate spatial averages of soil moisture, at various depths and for cell sizes in the range 2.5-40 acres, with a minimum number of samples. Both simple random sampling and stratified sampling procedures are used to reach a set of recommended sample sizes for each depth and for each cell size. Major conclusions from statistical sampling test results are that (1) the number of samples required decreases with increasing depth; (2) when the total number of samples cannot be prespecified or the moisture in only one single layer is of interest, then a simple random sample procedure should be used which is based on the observed mean and SD for data from a single field; (3) when the total number of samples can be prespecified and the objective is to measure the soil moisture profile with depth, then stratified random sampling based on optimal allocation should be used; and (4) decreasing the sensor resolution cell size leads to fairly large decreases in samples sizes with stratified sampling procedures, whereas only a moderate decrease is obtained in simple random sampling procedures.

Metafitting: Weight optimization for least-squares fitting of PTTI data

NASA Technical Reports Server (NTRS)

Douglas, Rob J.; Boulanger, J.-S.

1995-01-01

For precise time intercomparisons between a master frequency standard and a slave time scale, we have found it useful to quantitatively compare different fitting strategies by examining the standard uncertainty in time or average frequency. It is particularly useful when designing procedures which use intermittent intercomparisons, with some parameterized fit used to interpolate or extrapolate from the calibrating intercomparisons. We use the term 'metafitting' for the choices that are made before a fitting procedure is operationally adopted. We present methods for calculating the standard uncertainty for general, weighted least-squares fits and a method for optimizing these weights for a general noise model suitable for many PTTI applications. We present the results of the metafitting of procedures for the use of a regular schedule of (hypothetical) high-accuracy frequency calibration of a maser time scale. We have identified a cumulative series of improvements that give a significant reduction of the expected standard uncertainty, compared to the simplest procedure of resetting the maser synthesizer after each calibration. The metafitting improvements presented include the optimum choice of weights for the calibration runs, optimized over a period of a week or 10 days.

Aerodynamic design using numerical optimization

NASA Technical Reports Server (NTRS)

Murman, E. M.; Chapman, G. T.

1983-01-01

The procedure of using numerical optimization methods coupled with computational fluid dynamic (CFD) codes for the development of an aerodynamic design is examined. Several approaches that replace wind tunnel tests, develop pressure distributions and derive designs, or fulfill preset design criteria are presented. The method of Aerodynamic Design by Numerical Optimization (ADNO) is described and illustrated with examples.

Optimization of pencil beam f-theta lens for high-accuracy metrology

NASA Astrophysics Data System (ADS)

Peng, Chuanqian; He, Yumei; Wang, Jie

2018-01-01

Pencil beam deflectometric profilers are common instruments for high-accuracy surface slope metrology of x-ray mirrors in synchrotron facilities. An f-theta optical system is a key optical component of the deflectometric profilers and is used to perform the linear angle-to-position conversion. Traditional optimization procedures of the f-theta systems are not directly related to the angle-to-position conversion relation and are performed with stops of large size and a fixed working distance, which means they may not be suitable for the design of f-theta systems working with a small-sized pencil beam within a working distance range for ultra-high-accuracy metrology. If an f-theta system is not well-designed, aberrations of the f-theta system will introduce many systematic errors into the measurement. A least-squares' fitting procedure was used to optimize the configuration parameters of an f-theta system. Simulations using ZEMAX software showed that the optimized f-theta system significantly suppressed the angle-to-position conversion errors caused by aberrations. Any pencil-beam f-theta optical system can be optimized with the help of this optimization method.

Ventriculoarterial coupling in palliated hypoplastic left heart syndrome: Noninvasive assessment of the effects of surgical arch reconstruction and shunt type.

PubMed

Biglino, Giovanni; Giardini, Alessandro; Ntsinjana, Hopewell N; Schievano, Silvia; Hsia, Tain-Yen; Taylor, Andrew M

2014-10-01

To assess the coupling efficiency in hypoplastic left heart syndrome, considering the effect of surgical arch reconstruction and the shunt type received during the Norwood procedure. Ventriculoarterial coupling was assessed before Fontan completion in 32 patients with hypoplastic left heart syndrome (19 modified Blalock-Taussig and 13 Sano shunts at stage 1). Cardiovascular magnetic resonance data were analyzed, deriving functional parameters and 3-dimensional volumes. Dimensional indexes were computed from 3-dimensional data sets as the area ratio of the isthmus to the descending aorta (Risthmus) and the isthmus to surgically enlarged transverse arch (Rarch). Wave intensity was calculated from cardiac magnetic resonance, using the peaks of the forward compression and expansion waves in early and late systole as surrogate indicators of ventriculoarterial coupling. Aortic distensibility (3.6±2.7×10(-3) 1/mm Hg) was not associated with the time elapsed from stage 1 palliation (P=.94), suggesting an early loss of elasticity that did not progress thereafter. Risthmus was 1.0±0.4, and Rarch was 0.3±0.1, indicating the dilated reconstructed arch was the main anatomic feature. The forward compression wave correlated significantly with Rarch (R2=0.23, P=.006) but not with Risthmus (R2<0.01, P=.63). Patients with a reduced ejection fraction exhibited a larger ventricular mass (R2=0.28, P=.003). The Sano shunt patients had a lower ejection fraction (51%±6% vs 57%±6%, P=.02); however, neither the forward compression nor expansion wave varied significantly between shunt type or the other functional parameters. Ventriculoarterial coupling in operated hypoplastic left heart syndrome was affected by aortic arch size mismatch but not by the type of shunt placed at the Norwood operation. Copyright © 2014 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

Impact of noncardiac congenital and genetic abnormalities on outcomes in hypoplastic left heart syndrome.

PubMed

Patel, Angira; Hickey, Edward; Mavroudis, Constantine; Jacobs, Jeffrey P; Jacobs, Marshall L; Backer, Carl L; Gevitz, Melanie; Mavroudis, Constantine D

2010-06-01

Hypoplastic left heart syndrome may coexist with noncardiac congenital defects or genetic syndromes. We explored the impact of such lesions on outcomes after staged univentricular palliation. Society of Thoracic Surgeons database 2002 to 2006: Children diagnosed with hypoplastic left heart syndrome who underwent stage 1 Norwood (n = 1,236), stage 2 superior cavopulmonary anastamosis (n = 702) or stage 3 Fontan (n = 553) procedures were studied. In-hospital mortality, postoperative complications, and length of stay were compared at each stage between those with and without noncardiac-genetic defects. Congenital Heart Surgeons' Society database 1994 to 2001: All 703 infants enrolled in the Congenital Heart Surgeons' Society critical left ventricular outflow tract obstruction study who underwent primary stage 1 palliation were reviewed. The impact of noncardiac defects-syndromes on survival was explored using multivariable parametric models with bootstrap bagging. Society of Thoracic Surgeons database: Stage 1 in-hospital mortality (26% vs 20%, p = 0.04) and mean postoperative length of stay (42 versus 31 days, p < 0.0001) were greater, and postoperative complications significantly more prevalent in infants with noncardiac-genetic defects. Congenital Heart Surgeons' Society database: Noncardiac-genetic defects were present in 55 (8%). Early hazard for death after Norwood was significantly worse in infants with noncardiac defects-syndromes (p = 0.008). Chromosomal defects (n = 14) were highly unfavorable: the early risk of death was doubled (10-year survival 25 +/- 9% vs 54 +/- 2%, p = 0.005). Turner syndrome accounted for the majority of chromosomal defects in this population (11 of 14, 79%). Mode of death was rarely attributable to the noncardiac-genetic defect. Survival in hypoplastic left heart syndrome is strongly influenced by the presence of noncardiac abnormalities. Strategies to improve mortality in infants with noncardiac abnormalities should be explored. Presence of chromosomal defects, especially Turner syndrome, should enter decision-management options for parents and physicians. 2010 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Current Expectations for Cardiac Transplantation in Patients With Congenital Heart Disease.

PubMed

Kirklin, James K; Carlo, Waldemar F; Pearce, F Bennett

2016-11-01

Congenital heart disease accounts for 40% of pediatric heart transplants and presents unique challenges to the transplant team. Suitability for transplantation is defined in part by degree of sensitization, pulmonary vascular resistance, and hepatic reserves. The incremental transplant risk for patients with congenital heart disease occurs within the first 3 months, after which survival is equivalent to transplantation for cardiomyopathy. Single ventricle with prior palliation, and especially the failing Fontan, carry the highest risk for transplantation and are least amenable to bridging with mechanical circulatory support. More effective bridging to transplant with mechanical circulatory support will require improvements in the adverse event profile of available pumps and the introduction of miniaturized continuous flow technology. The major barriers to routine long-term survival are chronic allograft failure and allograft vasculopathy. Despite these many challenges, continuing improvements in the care of pediatric heart transplant patients have pushed the median posttransplant survival past 15 years for children and to 20 years for infants. © The Author(s) 2016.

Clinical-Physiological Considerations in Patients Undergoing Staged Palliation for a Functionally Single Ventricle.

PubMed

Penny, Daniel J; Krishnamurthy, Rajesh

2016-08-01

The objectives of this review are to discuss the pathophysiology of the circulation with a functionally univentricular heart, with a focus on the unique physiologic characteristics, which provide the underpinnings for the management of these complex patients. MEDLINE and PubMed. The circulation of the patient with a functionally univentricular heart displays unique physiologic characteristics, which are quite different from those of the normal biventricular circulation. There are profound differences within the heart itself in terms of ventricular function, interventricular interactions, and myocardial architecture, which are likely to have significant implications for the efficiency of ventricular ejection and metabolism. The coupling between the systemic ventricle and the aorta also displays unique features. The 3D orientation of the Fontan anastomosis itself can profoundly impact cardiac output, although the "portal" pulmonary arterial bed is a crucial determinant of overall cardiovascular function. As a result, disease-specific approaches to improve cardiovascular function are required at all stages during the care of these complex patients.

Aircraft wing structural design optimization based on automated finite element modelling and ground structure approach

NASA Astrophysics Data System (ADS)

Yang, Weizhu; Yue, Zhufeng; Li, Lei; Wang, Peiyan

2016-01-01

An optimization procedure combining an automated finite element modelling (AFEM) technique with a ground structure approach (GSA) is proposed for structural layout and sizing design of aircraft wings. The AFEM technique, based on CATIA VBA scripting and PCL programming, is used to generate models automatically considering the arrangement of inner systems. GSA is used for local structural topology optimization. The design procedure is applied to a high-aspect-ratio wing. The arrangement of the integral fuel tank, landing gear and control surfaces is considered. For the landing gear region, a non-conventional initial structural layout is adopted. The positions of components, the number of ribs and local topology in the wing box and landing gear region are optimized to obtain a minimum structural weight. Constraints include tank volume, strength, buckling and aeroelastic parameters. The results show that the combined approach leads to a greater weight saving, i.e. 26.5%, compared with three additional optimizations based on individual design approaches.

On Optimizing an Archibald Rubber-Band Heat Engine.

ERIC Educational Resources Information Center

Mullen, J. G.; And Others

1978-01-01

Discusses the criteria and procedure for optimizing the performance of Archibald rubber-band heat engines by using the appropriate choice of dimensions, minimizing frictional torque, maximizing torque and balancing the rubber band system. (GA)

A Comparison of Heuristic Procedures for Minimum within-Cluster Sums of Squares Partitioning

ERIC Educational Resources Information Center

Brusco, Michael J.; Steinley, Douglas

2007-01-01

Perhaps the most common criterion for partitioning a data set is the minimization of the within-cluster sums of squared deviation from cluster centroids. Although optimal solution procedures for within-cluster sums of squares (WCSS) partitioning are computationally feasible for small data sets, heuristic procedures are required for most practical…

Aerodynamic design optimization using sensitivity analysis and computational fluid dynamics

NASA Technical Reports Server (NTRS)

Baysal, Oktay; Eleshaky, Mohamed E.

1991-01-01

A new and efficient method is presented for aerodynamic design optimization, which is based on a computational fluid dynamics (CFD)-sensitivity analysis algorithm. The method is applied to design a scramjet-afterbody configuration for an optimized axial thrust. The Euler equations are solved for the inviscid analysis of the flow, which in turn provides the objective function and the constraints. The CFD analysis is then coupled with the optimization procedure that uses a constrained minimization method. The sensitivity coefficients, i.e. gradients of the objective function and the constraints, needed for the optimization are obtained using a quasi-analytical method rather than the traditional brute force method of finite difference approximations. During the one-dimensional search of the optimization procedure, an approximate flow analysis (predicted flow) based on a first-order Taylor series expansion is used to reduce the computational cost. Finally, the sensitivity of the optimum objective function to various design parameters, which are kept constant during the optimization, is computed to predict new optimum solutions. The flow analysis of the demonstrative example are compared with the experimental data. It is shown that the method is more efficient than the traditional methods.

The Multiple-Minima Problem in Protein Folding

NASA Astrophysics Data System (ADS)

Scheraga, Harold A.

1991-10-01

The conformational energy surface of a polypeptide or protein has many local minima, and conventional energy minimization procedures reach only a local minimum (near the starting point of the optimization algorithm) instead of the global minimum (the multiple-minima problem). Several procedures have been developed to surmount this problem, the most promising of which are: (a) build up procedure, (b) optimization of electrostatics, (c) Monte Carlo-plus-energy minimization, (d) electrostatically-driven Monte Carlo, (e) inclusion of distance restraints, (f) adaptive importance-sampling Monte Carlo, (g) relaxation of dimensionality, (h) pattern-recognition, and (i) diffusion equation method. These procedures have been applied to a variety of polypeptide structural problems, and the results of such computations are presented. These include the computation of the structures of open-chain and cyclic peptides, fibrous proteins and globular proteins. Present efforts are being devoted to scaling up these procedures from small polypeptides to proteins, to try to compute the three-dimensional structure of a protein from its amino sequence.

Optimization of a wet microalgal lipid extraction procedure for improved lipid recovery for biofuel and bioproduct production.

PubMed

Sathish, Ashik; Marlar, Tyler; Sims, Ronald C

2015-10-01

Methods to convert microalgal biomass to bio based fuels and chemicals are limited by several processing and economic hurdles. Research conducted in this study modified/optimized a previously published procedure capable of extracting transesterifiable lipids from wet algal biomass. This optimization resulted in the extraction of 77% of the total transesterifiable lipids, while reducing the amount of materials and temperature required in the procedure. In addition, characterization of side streams generated demonstrated that: (1) the C/N ratio of the residual biomass or lipid extracted (LE) biomass increased to 54.6 versus 10.1 for the original biomass, (2) the aqueous phase generated contains nitrogen, phosphorous, and carbon, and (3) the solid precipitate phase was composed of up to 11.2 wt% nitrogen (70% protein). The ability to isolate algal lipids and the possibility of utilizing generated side streams as products and/or feedstock material for downstream processes helps promote the algal biorefinery concept. Copyright © 2015 Elsevier Ltd. All rights reserved.

Development of a multiple-parameter nonlinear perturbation procedure for transonic turbomachinery flows: Preliminary application to design/optimization problems

NASA Technical Reports Server (NTRS)

Stahara, S. S.; Elliott, J. P.; Spreiter, J. R.

1983-01-01

An investigation was conducted to continue the development of perturbation procedures and associated computational codes for rapidly determining approximations to nonlinear flow solutions, with the purpose of establishing a method for minimizing computational requirements associated with parametric design studies of transonic flows in turbomachines. The results reported here concern the extension of the previously developed successful method for single parameter perturbations to simultaneous multiple-parameter perturbations, and the preliminary application of the multiple-parameter procedure in combination with an optimization method to blade design/optimization problem. In order to provide as severe a test as possible of the method, attention is focused in particular on transonic flows which are highly supercritical. Flows past both isolated blades and compressor cascades, involving simultaneous changes in both flow and geometric parameters, are considered. Comparisons with the corresponding exact nonlinear solutions display remarkable accuracy and range of validity, in direct correspondence with previous results for single-parameter perturbations.

Use of multilevel modeling for determining optimal parameters of heat supply systems

NASA Astrophysics Data System (ADS)

Stennikov, V. A.; Barakhtenko, E. A.; Sokolov, D. V.

2017-07-01

The problem of finding optimal parameters of a heat-supply system (HSS) is in ensuring the required throughput capacity of a heat network by determining pipeline diameters and characteristics and location of pumping stations. Effective methods for solving this problem, i.e., the method of stepwise optimization based on the concept of dynamic programming and the method of multicircuit optimization, were proposed in the context of the hydraulic circuit theory developed at Melentiev Energy Systems Institute (Siberian Branch, Russian Academy of Sciences). These methods enable us to determine optimal parameters of various types of piping systems due to flexible adaptability of the calculation procedure to intricate nonlinear mathematical models describing features of used equipment items and methods of their construction and operation. The new and most significant results achieved in developing methodological support and software for finding optimal parameters of complex heat supply systems are presented: a new procedure for solving the problem based on multilevel decomposition of a heat network model that makes it possible to proceed from the initial problem to a set of interrelated, less cumbersome subproblems with reduced dimensionality; a new algorithm implementing the method of multicircuit optimization and focused on the calculation of a hierarchical model of a heat supply system; the SOSNA software system for determining optimum parameters of intricate heat-supply systems and implementing the developed methodological foundation. The proposed procedure and algorithm enable us to solve engineering problems of finding the optimal parameters of multicircuit heat supply systems having large (real) dimensionality, and are applied in solving urgent problems related to the optimal development and reconstruction of these systems. The developed methodological foundation and software can be used for designing heat supply systems in the Central and the Admiralty regions in St. Petersburg, the city of Bratsk, and the Magistral'nyi settlement.

Optimization in the utility maximization framework for conservation planning: a comparison of solution procedures in a study of multifunctional agriculture

PubMed Central

Stoms, David M.; Davis, Frank W.

2014-01-01

Quantitative methods of spatial conservation prioritization have traditionally been applied to issues in conservation biology and reserve design, though their use in other types of natural resource management is growing. The utility maximization problem is one form of a covering problem where multiple criteria can represent the expected social benefits of conservation action. This approach allows flexibility with a problem formulation that is more general than typical reserve design problems, though the solution methods are very similar. However, few studies have addressed optimization in utility maximization problems for conservation planning, and the effect of solution procedure is largely unquantified. Therefore, this study mapped five criteria describing elements of multifunctional agriculture to determine a hypothetical conservation resource allocation plan for agricultural land conservation in the Central Valley of CA, USA. We compared solution procedures within the utility maximization framework to determine the difference between an open source integer programming approach and a greedy heuristic, and find gains from optimization of up to 12%. We also model land availability for conservation action as a stochastic process and determine the decline in total utility compared to the globally optimal set using both solution algorithms. Our results are comparable to other studies illustrating the benefits of optimization for different conservation planning problems, and highlight the importance of maximizing the effectiveness of limited funding for conservation and natural resource management. PMID:25538868

Design of piezoelectric transformer for DC/DC converter with stochastic optimization method

NASA Astrophysics Data System (ADS)

Vasic, Dejan; Vido, Lionel

2016-04-01

Piezoelectric transformers were adopted in recent year due to their many inherent advantages such as safety, no EMI problem, low housing profile, and high power density, etc. The characteristics of the piezoelectric transformers are well known when the load impedance is a pure resistor. However, when piezoelectric transformers are used in AC/DC or DC/DC converters, there are non-linear electronic circuits connected before and after the transformer. Consequently, the output load is variable and due to the output capacitance of the transformer the optimal working point change. This paper starts from modeling a piezoelectric transformer connected to a full wave rectifier in order to discuss the design constraints and configuration of the transformer. The optimization method adopted here use the MOPSO algorithm (Multiple Objective Particle Swarm Optimization). We start with the formulation of the objective function and constraints; then the results give different sizes of the transformer and the characteristics. In other word, this method is looking for a best size of the transformer for optimal efficiency condition that is suitable for variable load. Furthermore, the size and the efficiency are found to be a trade-off. This paper proposes the completed design procedure to find the minimum size of PT in need. The completed design procedure is discussed by a given specification. The PT derived from the proposed design procedure can guarantee both good efficiency and enough range for load variation.

Optimization in the utility maximization framework for conservation planning: a comparison of solution procedures in a study of multifunctional agriculture

USGS Publications Warehouse

Kreitler, Jason R.; Stoms, David M.; Davis, Frank W.

2014-01-01

Quantitative methods of spatial conservation prioritization have traditionally been applied to issues in conservation biology and reserve design, though their use in other types of natural resource management is growing. The utility maximization problem is one form of a covering problem where multiple criteria can represent the expected social benefits of conservation action. This approach allows flexibility with a problem formulation that is more general than typical reserve design problems, though the solution methods are very similar. However, few studies have addressed optimization in utility maximization problems for conservation planning, and the effect of solution procedure is largely unquantified. Therefore, this study mapped five criteria describing elements of multifunctional agriculture to determine a hypothetical conservation resource allocation plan for agricultural land conservation in the Central Valley of CA, USA. We compared solution procedures within the utility maximization framework to determine the difference between an open source integer programming approach and a greedy heuristic, and find gains from optimization of up to 12%. We also model land availability for conservation action as a stochastic process and determine the decline in total utility compared to the globally optimal set using both solution algorithms. Our results are comparable to other studies illustrating the benefits of optimization for different conservation planning problems, and highlight the importance of maximizing the effectiveness of limited funding for conservation and natural resource management.

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

Kwon, Deukwoo; Little, Mark P.; Miller, Donald L.

Purpose: To determine more accurate regression formulas for estimating peak skin dose (PSD) from reference air kerma (RAK) or kerma-area product (KAP). Methods: After grouping of the data from 21 procedures into 13 clinically similar groups, assessments were made of optimal clustering using the Bayesian information criterion to obtain the optimal linear regressions of (log-transformed) PSD vs RAK, PSD vs KAP, and PSD vs RAK and KAP. Results: Three clusters of clinical groups were optimal in regression of PSD vs RAK, seven clusters of clinical groups were optimal in regression of PSD vs KAP, and six clusters of clinical groupsmore » were optimal in regression of PSD vs RAK and KAP. Prediction of PSD using both RAK and KAP is significantly better than prediction of PSD with either RAK or KAP alone. The regression of PSD vs RAK provided better predictions of PSD than the regression of PSD vs KAP. The partial-pooling (clustered) method yields smaller mean squared errors compared with the complete-pooling method.Conclusion: PSD distributions for interventional radiology procedures are log-normal. Estimates of PSD derived from RAK and KAP jointly are most accurate, followed closely by estimates derived from RAK alone. Estimates of PSD derived from KAP alone are the least accurate. Using a stochastic search approach, it is possible to cluster together certain dissimilar types of procedures to minimize the total error sum of squares.« less

A TOTP-based enhanced route optimization procedure for mobile IPv6 to reduce handover delay and signalling overhead.

PubMed

Shah, Peer Azmat; Hasbullah, Halabi B; Lawal, Ibrahim A; Aminu Mu'azu, Abubakar; Tang Jung, Low

2014-01-01

Due to the proliferation of handheld mobile devices, multimedia applications like Voice over IP (VoIP), video conferencing, network music, and online gaming are gaining popularity in recent years. These applications are well known to be delay sensitive and resource demanding. The mobility of mobile devices, running these applications, across different networks causes delay and service disruption. Mobile IPv6 was proposed to provide mobility support to IPv6-based mobile nodes for continuous communication when they roam across different networks. However, the Route Optimization procedure in Mobile IPv6 involves the verification of mobile node's reachability at the home address and at the care-of address (home test and care-of test) that results in higher handover delays and signalling overhead. This paper presents an enhanced procedure, time-based one-time password Route Optimization (TOTP-RO), for Mobile IPv6 Route Optimization that uses the concepts of shared secret Token, time based one-time password (TOTP) along with verification of the mobile node via direct communication and maintaining the status of correspondent node's compatibility. The TOTP-RO was implemented in network simulator (NS-2) and an analytical analysis was also made. Analysis showed that TOTP-RO has lower handover delays, packet loss, and signalling overhead with an increased level of security as compared to the standard Mobile IPv6's Return-Routability-based Route Optimization (RR-RO).

Improvement of the insertion axis for cochlear implantation with a robot-based system.

PubMed

Torres, Renato; Kazmitcheff, Guillaume; De Seta, Daniele; Ferrary, Evelyne; Sterkers, Olivier; Nguyen, Yann

2017-02-01

It has previously reported that alignment of the insertion axis along the basal turn of the cochlea was depending on surgeon' experience. In this experimental study, we assessed technological assistances, such as navigation or a robot-based system, to improve the insertion axis during cochlear implantation. A preoperative cone beam CT and a mastoidectomy with a posterior tympanotomy were performed on four temporal bones. The optimal insertion axis was defined as the closest axis to the scala tympani centerline avoiding the facial nerve. A neuronavigation system, a robot assistance prototype, and software allowing a semi-automated alignment of the robot were used to align an insertion tool with an optimal insertion axis. Four procedures were performed and repeated three times in each temporal bone: manual, manual navigation-assisted, robot-based navigation-assisted, and robot-based semi-automated. The angle between the optimal and the insertion tool axis was measured in the four procedures. The error was 8.3° ± 2.82° for the manual procedure (n = 24), 8.6° ± 2.83° for the manual navigation-assisted procedure (n = 24), 5.4° ± 3.91° for the robot-based navigation-assisted procedure (n = 24), and 3.4° ± 1.56° for the robot-based semi-automated procedure (n = 12). A higher accuracy was observed with the semi-automated robot-based technique than manual and manual navigation-assisted (p < 0.01). Combination of a navigation system and a manual insertion does not improve the alignment accuracy due to the lack of friendly user interface. On the contrary, a semi-automated robot-based system reduces both the error and the variability of the alignment with a defined optimal axis.

Expected p-values in light of an ROC curve analysis applied to optimal multiple testing procedures.

PubMed

Vexler, Albert; Yu, Jihnhee; Zhao, Yang; Hutson, Alan D; Gurevich, Gregory

2017-01-01

Many statistical studies report p-values for inferential purposes. In several scenarios, the stochastic aspect of p-values is neglected, which may contribute to drawing wrong conclusions in real data experiments. The stochastic nature of p-values makes their use to examine the performance of given testing procedures or associations between investigated factors to be difficult. We turn our focus on the modern statistical literature to address the expected p-value (EPV) as a measure of the performance of decision-making rules. During the course of our study, we prove that the EPV can be considered in the context of receiver operating characteristic (ROC) curve analysis, a well-established biostatistical methodology. The ROC-based framework provides a new and efficient methodology for investigating and constructing statistical decision-making procedures, including: (1) evaluation and visualization of properties of the testing mechanisms, considering, e.g. partial EPVs; (2) developing optimal tests via the minimization of EPVs; (3) creation of novel methods for optimally combining multiple test statistics. We demonstrate that the proposed EPV-based approach allows us to maximize the integrated power of testing algorithms with respect to various significance levels. In an application, we use the proposed method to construct the optimal test and analyze a myocardial infarction disease dataset. We outline the usefulness of the "EPV/ROC" technique for evaluating different decision-making procedures, their constructions and properties with an eye towards practical applications.

In-hospital rehabilitation after multiple joint procedures of the lower extremities in haemophilia patients: clinical guidelines for physical therapists.

PubMed

De Kleijn, P; Fischer, K; Vogely, H Ch; Hendriks, C; Lindeman, E

2011-11-01

This project aimed to develop guidelines for use during in-hospital rehabilitation after combinations of multiple joint procedures (MJP) of the lower extremities in persons with haemophilia (PWH). MJP are defined as surgical procedures on the ankles, knees and hips, performed in any combination, staged, or during a single session. MJP that we studied included total knee arthroplasty, total hip arthroplasty and ankle arthrodesis. Literature on rheumatoid arthritis demonstrated promising functional results, fewer hospitalization days and days lost from work. However, the complication rate is higher and rehabilitation needs optimal conditions. Since 1995, at the Van Creveldkliniek, 54 PWH have undergone MJP. During the rehabilitation in our hospital performed by experienced physical therapists, regular guidelines seemed useless. Guidelines will guarantee an optimal physical recovery and maximum benefit from this enormous investment. This will lead to an optimal functional capability and optimal quality of life for this elderly group of PWH. There are no existing guidelines for MJP, in haemophilia, revealed through a review of the literature. Therefore, a working group was formed to develop and implement such guidelines and the procedure is explained. The total group of PWH who underwent MJP is described, subdivided into combinations of joints. For these subgroups, the number of days in hospital, complications and profile at discharge, as well as a guideline on the clinical rehabilitation, are given. It contains a general part and a part for each specific subgroup. © 2011 Blackwell Publishing Ltd.

Optimal locations and orientations of piezoelectric transducers on cylindrical shell based on gramians of contributed and undesired Rayleigh-Ritz modes using genetic algorithm

NASA Astrophysics Data System (ADS)

Biglar, Mojtaba; Mirdamadi, Hamid Reza; Danesh, Mohammad

2014-02-01

In this study, the active vibration control and configurational optimization of a cylindrical shell are analyzed by using piezoelectric transducers. The piezoelectric patches are attached to the surface of the cylindrical shell. The Rayleigh-Ritz method is used for deriving dynamic modeling of cylindrical shell and piezoelectric sensors and actuators based on the Donnel-Mushtari shell theory. The major goal of this study is to find the optimal locations and orientations of piezoelectric sensors and actuators on the cylindrical shell. The optimization procedure is designed based on desired controllability and observability of each contributed and undesired mode. Further, in order to limit spillover effects, the residual modes are taken into consideration. The optimization variables are the positions and orientations of piezoelectric patches. Genetic algorithm is utilized to evaluate the optimal configurations. In this article, for improving the maximum power and capacity of actuators for amplitude depreciation of negative velocity feedback strategy, we have proposed a new control strategy, called "Saturated Negative Velocity Feedback Rule (SNVF)". The numerical results show that the optimization procedure is effective for vibration reduction, and specifically, by locating actuators and sensors in their optimal locations and orientations, the vibrations of cylindrical shell are suppressed more quickly.

Parameter Optimization for Feature and Hit Generation in a General Unknown Screening Method-Proof of Concept Study Using a Design of Experiment Approach for a High Resolution Mass Spectrometry Procedure after Data Independent Acquisition.

PubMed

Elmiger, Marco P; Poetzsch, Michael; Steuer, Andrea E; Kraemer, Thomas

2018-03-06

High resolution mass spectrometry and modern data independent acquisition (DIA) methods enable the creation of general unknown screening (GUS) procedures. However, even when DIA is used, its potential is far from being exploited, because often, the untargeted acquisition is followed by a targeted search. Applying an actual GUS (including untargeted screening) produces an immense amount of data that must be dealt with. An optimization of the parameters regulating the feature detection and hit generation algorithms of the data processing software could significantly reduce the amount of unnecessary data and thereby the workload. Design of experiment (DoE) approaches allow a simultaneous optimization of multiple parameters. In a first step, parameters are evaluated (crucial or noncrucial). Second, crucial parameters are optimized. The aim in this study was to reduce the number of hits, without missing analytes. The obtained parameter settings from the optimization were compared to the standard settings by analyzing a test set of blood samples spiked with 22 relevant analytes as well as 62 authentic forensic cases. The optimization lead to a marked reduction of workload (12.3 to 1.1% and 3.8 to 1.1% hits for the test set and the authentic cases, respectively) while simultaneously increasing the identification rate (68.2 to 86.4% and 68.8 to 88.1%, respectively). This proof of concept study emphasizes the great potential of DoE approaches to master the data overload resulting from modern data independent acquisition methods used for general unknown screening procedures by optimizing software parameters.

Development of a Composite Tailoring Procedure for Airplane Wings

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi

2000-01-01

The quest for finding optimum solutions to engineering problems has existed for a long time. In modern times, the development of optimization as a branch of applied mathematics is regarded to have originated in the works of Newton, Bernoulli and Euler. Venkayya has presented a historical perspective on optimization in [1]. The term 'optimization' is defined by Ashley [2] as a procedure "...which attempts to choose the variables in a design process so as formally to achieve the best value of some performance index while not violating any of the associated conditions or constraints". Ashley presented an extensive review of practical applications of optimization in the aeronautical field till about 1980 [2]. It was noted that there existed an enormous amount of published literature in the field of optimization, but its practical applications in industry were very limited. Over the past 15 years, though, optimization has been widely applied to address practical problems in aerospace design [3-5]. The design of high performance aerospace systems is a complex task. It involves the integration of several disciplines such as aerodynamics, structural analysis, dynamics, and aeroelasticity. The problem involves multiple objectives and constraints pertaining to the design criteria associated with each of these disciplines. Many important trade-offs exist between the parameters involved which are used to define the different disciplines. Therefore, the development of multidisciplinary design optimization (MDO) techniques, in which different disciplines and design parameters are coupled into a closed loop numerical procedure, seems appropriate to address such a complex problem. The importance of MDO in successful design of aerospace systems has been long recognized. Recent developments in this field have been surveyed by Sobieszczanski-Sobieski and Haftka [6].

Improving Empirical Magnetic Field Models by Fitting to In Situ Data Using an Optimized Parameter Approach

DOE PAGES

Brito, Thiago V.; Morley, Steven K.

2017-10-25

A method for comparing and optimizing the accuracy of empirical magnetic field models using in situ magnetic field measurements is presented in this paper. The optimization method minimizes a cost function—τ—that explicitly includes both a magnitude and an angular term. A time span of 21 days, including periods of mild and intense geomagnetic activity, was used for this analysis. A comparison between five magnetic field models (T96, T01S, T02, TS04, and TS07) widely used by the community demonstrated that the T02 model was, on average, the most accurate when driven by the standard model input parameters. The optimization procedure, performedmore » in all models except TS07, generally improved the results when compared to unoptimized versions of the models. Additionally, using more satellites in the optimization procedure produces more accurate results. This procedure reduces the number of large errors in the model, that is, it reduces the number of outliers in the error distribution. The TS04 model shows the most accurate results after the optimization in terms of both the magnitude and direction, when using at least six satellites in the fitting. It gave a smaller error than its unoptimized counterpart 57.3% of the time and outperformed the best unoptimized model (T02) 56.2% of the time. Its median percentage error in |B| was reduced from 4.54% to 3.84%. Finally, the difference among the models analyzed, when compared in terms of the median of the error distributions, is not very large. However, the unoptimized models can have very large errors, which are much reduced after the optimization.« less

A stepwise approach for the reproducible optimization of PAMO expression in Escherichia coli for whole-cell biocatalysis

PubMed Central

2012-01-01

Background Baeyer-Villiger monooxygenases (BVMOs) represent a group of enzymes of considerable biotechnological relevance as illustrated by their growing use as biocatalyst in a variety of synthetic applications. However, due to their increased use the reproducible expression of BVMOs and other biotechnologically relevant enzymes has become a pressing matter while knowledge about the factors governing their reproducible expression is scattered. Results Here, we have used phenylacetone monooxygenase (PAMO) from Thermobifida fusca, a prototype Type I BVMO, as a model enzyme to develop a stepwise strategy to optimize the biotransformation performance of recombinant E. coli expressing PAMO in 96-well microtiter plates in a reproducible fashion. Using this system, the best expression conditions of PAMO were investigated first, including different host strains, temperature as well as time and induction period for PAMO expression. This optimized system was used next to improve biotransformation conditions, the PAMO-catalyzed conversion of phenylacetone, by evaluating the best electron donor, substrate concentration, and the temperature and length of biotransformation. Combining all optimized parameters resulted in a more than four-fold enhancement of the biocatalytic performance and, importantly, this was highly reproducible as indicated by the relative standard deviation of 1% for non-washed cells and 3% for washed cells. Furthermore, the optimized procedure was successfully adapted for activity-based mutant screening. Conclusions Our optimized procedure, which provides a comprehensive overview of the key factors influencing the reproducible expression and performance of a biocatalyst, is expected to form a rational basis for the optimization of miniaturized biotransformations and for the design of novel activity-based screening procedures suitable for BVMOs and other NAD(P)H-dependent enzymes as well. PMID:22720747

Improving Empirical Magnetic Field Models by Fitting to In Situ Data Using an Optimized Parameter Approach

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

Brito, Thiago V.; Morley, Steven K.

A method for comparing and optimizing the accuracy of empirical magnetic field models using in situ magnetic field measurements is presented in this paper. The optimization method minimizes a cost function—τ—that explicitly includes both a magnitude and an angular term. A time span of 21 days, including periods of mild and intense geomagnetic activity, was used for this analysis. A comparison between five magnetic field models (T96, T01S, T02, TS04, and TS07) widely used by the community demonstrated that the T02 model was, on average, the most accurate when driven by the standard model input parameters. The optimization procedure, performedmore » in all models except TS07, generally improved the results when compared to unoptimized versions of the models. Additionally, using more satellites in the optimization procedure produces more accurate results. This procedure reduces the number of large errors in the model, that is, it reduces the number of outliers in the error distribution. The TS04 model shows the most accurate results after the optimization in terms of both the magnitude and direction, when using at least six satellites in the fitting. It gave a smaller error than its unoptimized counterpart 57.3% of the time and outperformed the best unoptimized model (T02) 56.2% of the time. Its median percentage error in |B| was reduced from 4.54% to 3.84%. Finally, the difference among the models analyzed, when compared in terms of the median of the error distributions, is not very large. However, the unoptimized models can have very large errors, which are much reduced after the optimization.« less

Supercritical tests of a self-optimizing, variable-Camber wind tunnel model

NASA Technical Reports Server (NTRS)

Levinsky, E. S.; Palko, R. L.

1979-01-01

A testing procedure was used in a 16-foot Transonic Propulsion Wind Tunnel which leads to optimum wing airfoil sections without stopping the tunnel for model changes. Being experimental, the optimum shapes obtained incorporate various three-dimensional and nonlinear viscous and transonic effects not included in analytical optimization methods. The method is a closed-loop, computer-controlled, interactive procedure and employs a Self-Optimizing Flexible Technology wing semispan model that conformally adapts the airfoil section at two spanwise control stations to maximize or minimize various prescribed merit functions subject to both equality and inequality constraints. The model, which employed twelve independent hydraulic actuator systems and flexible skins, was also used for conventional testing. Although six of seven optimizations attempted were at least partially convergent, further improvements in model skin smoothness and hydraulic reliability are required to make the technique fully operational.

Approach for Input Uncertainty Propagation and Robust Design in CFD Using Sensitivity Derivatives

NASA Technical Reports Server (NTRS)

Putko, Michele M.; Taylor, Arthur C., III; Newman, Perry A.; Green, Lawrence L.

2002-01-01

An implementation of the approximate statistical moment method for uncertainty propagation and robust optimization for quasi 3-D Euler CFD code is presented. Given uncertainties in statistically independent, random, normally distributed input variables, first- and second-order statistical moment procedures are performed to approximate the uncertainty in the CFD output. Efficient calculation of both first- and second-order sensitivity derivatives is required. In order to assess the validity of the approximations, these moments are compared with statistical moments generated through Monte Carlo simulations. The uncertainties in the CFD input variables are also incorporated into a robust optimization procedure. For this optimization, statistical moments involving first-order sensitivity derivatives appear in the objective function and system constraints. Second-order sensitivity derivatives are used in a gradient-based search to successfully execute a robust optimization. The approximate methods used throughout the analyses are found to be valid when considering robustness about input parameter mean values.

Application of mixture experimental design in the formulation and optimization of matrix tablets containing carbomer and hydroxy-propylmethylcellulose.

PubMed

Petrovic, Aleksandra; Cvetkovic, Nebojsa; Ibric, Svetlana; Trajkovic, Svetlana; Djuric, Zorica; Popadic, Dragica; Popovic, Radmila

2009-12-01

Using mixture experimental design, the effect of carbomer (Carbopol((R)) 971P NF) and hydroxypropylmethylcellulose (Methocel((R)) K100M or Methocel((R)) K4M) combination on the release profile and on the mechanism of drug liberation from matrix tablet was investigated. The numerical optimization procedure was also applied to establish and obtain formulation with desired drug release. The amount of TP released, release rate and mechanism varied with carbomer ratio in total matrix and HPMC viscosity. Increasing carbomer fractions led to a decrease in drug release. Anomalous diffusion was found in all matrices containing carbomer, while Case - II transport was predominant for tablet based on HPMC only. The predicted and obtained profiles for optimized formulations showed similarity. Those results indicate that Simplex Lattice Mixture experimental design and numerical optimization procedure can be applied during development to obtain sustained release matrix formulation with desired release profile.

K-Minimax Stochastic Programming Problems

NASA Astrophysics Data System (ADS)

Nedeva, C.

2007-10-01

The purpose of this paper is a discussion of a numerical procedure based on the simplex method for stochastic optimization problems with partially known distribution functions. The convergence of this procedure is proved by the condition on dual problems.

Surgical Treatment for Chronic Pancreatitis: Past, Present, and Future

PubMed Central

Welte, Maria; Izbicki, Jakob R.; Bachmann, Kai

2017-01-01

The pancreas was one of the last explored organs in the human body. The first surgical experiences were made before fully understanding the function of the gland. Surgical procedures remained less successful until the discovery of insulin, blood groups, and finally the possibility of blood donation. Throughout the centuries, the surgical approach went from radical resections to minimal resections or only drainage of the gland in comparison to an adequate resection combined with drainage procedures. Today, the well-known and standardized procedures are considered as safe due to the high experience of operating surgeons, the centering of pancreatic surgery in specialized centers, and optimized perioperative treatment. Although surgical procedures have become safer and more efficient than ever, the overall perioperative morbidity after pancreatic surgery remains high and management of postoperative complications stagnates. Current research focuses on the prevention of complications, optimizing the patient's general condition preoperatively and finding the appropriate timing for surgical treatment. PMID:28819358

Hair Transplantation Controversies.

PubMed

Avram, Marc R; Finney, Robert; Rogers, Nicole

2017-11-01

Hair transplant surgery creates consistently natural appearing transplanted hair for men. It is increasingly popular procedure to restore natural growing hair for men with hair loss. To review some current controversies in hair transplant surgery. Review of the English PubMed literature and specialty literature in hair transplant surgery. Some of the controversies in hair transplant surgery include appropriate donor harvesting technique including elliptical donor harvesting versus follicular unit extraction whether manual versus robotic, the role of platelet-rich plasma and low-level light surgery in hair transplant surgery. Hair transplant surgery creates consistently natural appearing hair. As with all techniques, there are controversies regarding the optimal method for performing the procedure. Some of the current controversies in hair transplant surgery include optimal donor harvesting techniques, elliptical donor harvesting versus follicular unit extraction, the role of low-level light therapy and the platelet-rich plasma therapy in the procedure. Future studies will further clarify their role in the procedure.

Production and characterization of alginate microcapsules produced by a vibrational encapsulation device.

PubMed

Mazzitelli, S; Tosi, A; Balestra, C; Nastruzzi, C; Luca, G; Mancuso, F; Calafiore, R; Calvitti, M

2008-09-01

The optimization, through a Design of Experiments (DoE) approach, of a microencapsulation procedure for isolated neonatal porcine islets (NPI) is described. The applied method is based on the generation of monodisperse droplets by a vibrational nozzle. An alginate/polyornithine encapsulation procedure, developed and validated in our laboratory for almost a decade, was used to embody pancreatic islets. We analyzed different experimental parameters including frequency of vibration, amplitude of vibration, polymer pumping rate, and distance between the nozzle and the gelling bath. We produced calcium-alginate gel microbeads with excellent morphological characteristics as well as a very narrow size distribution. The automatically produced microcapsules did not alter morphology, viability and functional properties of the enveloped NPI. The optimization of this automatic procedure may provide a novel approach to obtain a large number of batches possibly suitable for large scale production of immunoisolated NPI for in vivo cell transplantation procedures in humans.

Optimal tree-stem bucking of northeastern species of China

Treesearch

Jingxin Wang; Chris B. LeDoux; Joseph McNeel

2004-01-01

An application of optimal tree-stem bucking to the northeastern tree species of China is reported. The bucking procedures used in this region are summarized, which are the basic guidelines for the optimal bucking design. The directed graph approach was adopted to generate the bucking patterns by using the network analysis labeling algorithm. A computer-based bucking...

Exact Identification of a Quantum Change Point

NASA Astrophysics Data System (ADS)

Sentís, Gael; Calsamiglia, John; Muñoz-Tapia, Ramon

2017-10-01

The detection of change points is a pivotal task in statistical analysis. In the quantum realm, it is a new primitive where one aims at identifying the point where a source that supposedly prepares a sequence of particles in identical quantum states starts preparing a mutated one. We obtain the optimal procedure to identify the change point with certainty—naturally at the price of having a certain probability of getting an inconclusive answer. We obtain the analytical form of the optimal probability of successful identification for any length of the particle sequence. We show that the conditional success probabilities of identifying each possible change point show an unexpected oscillatory behavior. We also discuss local (online) protocols and compare them with the optimal procedure.

Exact Identification of a Quantum Change Point.

PubMed

Sentís, Gael; Calsamiglia, John; Muñoz-Tapia, Ramon

2017-10-06

The detection of change points is a pivotal task in statistical analysis. In the quantum realm, it is a new primitive where one aims at identifying the point where a source that supposedly prepares a sequence of particles in identical quantum states starts preparing a mutated one. We obtain the optimal procedure to identify the change point with certainty-naturally at the price of having a certain probability of getting an inconclusive answer. We obtain the analytical form of the optimal probability of successful identification for any length of the particle sequence. We show that the conditional success probabilities of identifying each possible change point show an unexpected oscillatory behavior. We also discuss local (online) protocols and compare them with the optimal procedure.

Tetrahedron Formation Control

NASA Technical Reports Server (NTRS)

Petruzzo, Charles; Guzman, Jose

2004-01-01

This paper considers the preliminary development of a general optimization procedure for tetrahedron formation control. The maneuvers are assumed to be impulsive and a multi-stage optimization method is employed. The stages include (1) targeting to a fixed tetrahedron location and orientation, and (2) rotating and translating the tetrahedron. The number of impulsive maneuvers can also be varied. As the impulse locations and times change, new arcs are computed using a differential corrections scheme that varies the impulse magnitudes and directions. The result is a continuous trajectory with velocity discontinuities. The velocity discontinuities are then used to formulate the cost function. Direct optimization techniques are employed. The procedure is applied to the NASA Goddard Magnetospheric Multi-Scale (MMS) mission to compute preliminary formation control fuel requirements.

A Standard Platform for Testing and Comparison of MDAO Architectures

NASA Technical Reports Server (NTRS)

Gray, Justin S.; Moore, Kenneth T.; Hearn, Tristan A.; Naylor, Bret A.

2012-01-01

The Multidisciplinary Design Analysis and Optimization (MDAO) community has developed a multitude of algorithms and techniques, called architectures, for performing optimizations on complex engineering systems which involve coupling between multiple discipline analyses. These architectures seek to efficiently handle optimizations with computationally expensive analyses including multiple disciplines. We propose a new testing procedure that can provide a quantitative and qualitative means of comparison among architectures. The proposed test procedure is implemented within the open source framework, OpenMDAO, and comparative results are presented for five well-known architectures: MDF, IDF, CO, BLISS, and BLISS-2000. We also demonstrate how using open source soft- ware development methods can allow the MDAO community to submit new problems and architectures to keep the test suite relevant.

MARKOV: A methodology for the solution of infinite time horizon MARKOV decision processes

USGS Publications Warehouse

Williams, B.K.

1988-01-01

Algorithms are described for determining optimal policies for finite state, finite action, infinite discrete time horizon Markov decision processes. Both value-improvement and policy-improvement techniques are used in the algorithms. Computing procedures are also described. The algorithms are appropriate for processes that are either finite or infinite, deterministic or stochastic, discounted or undiscounted, in any meaningful combination of these features. Computing procedures are described in terms of initial data processing, bound improvements, process reduction, and testing and solution. Application of the methodology is illustrated with an example involving natural resource management. Management implications of certain hypothesized relationships between mallard survival and harvest rates are addressed by applying the optimality procedures to mallard population models.

Toxicity Minimized Cryoprotectant Addition and Removal Procedures for Adherent Endothelial Cells

PubMed Central

Davidson, Allyson Fry; Glasscock, Cameron; McClanahan, Danielle R.; Benson, James D.; Higgins, Adam Z.

2015-01-01

Ice-free cryopreservation, known as vitrification, is an appealing approach for banking of adherent cells and tissues because it prevents dissociation and morphological damage that may result from ice crystal formation. However, current vitrification methods are often limited by the cytotoxicity of the concentrated cryoprotective agent (CPA) solutions that are required to suppress ice formation. Recently, we described a mathematical strategy for identifying minimally toxic CPA equilibration procedures based on the minimization of a toxicity cost function. Here we provide direct experimental support for the feasibility of these methods when applied to adherent endothelial cells. We first developed a concentration- and temperature-dependent toxicity cost function by exposing the cells to a range of glycerol concentrations at 21°C and 37°C, and fitting the resulting viability data to a first order cell death model. This cost function was then numerically minimized in our state constrained optimization routine to determine addition and removal procedures for 17 molal (mol/kg water) glycerol solutions. Using these predicted optimal procedures, we obtained 81% recovery after exposure to vitrification solutions, as well as successful vitrification with the relatively slow cooling and warming rates of 50°C/min and 130°C/min. In comparison, conventional multistep CPA equilibration procedures resulted in much lower cell yields of about 10%. Our results demonstrate the potential for rational design of minimally toxic vitrification procedures and pave the way for extension of our optimization approach to other adherent cell types as well as more complex systems such as tissues and organs. PMID:26605546

A Polyhedral Outer-approximation, Dynamic-discretization optimization solver, 1.x

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

Bent, Rusell; Nagarajan, Harsha; Sundar, Kaarthik

2017-09-25

In this software, we implement an adaptive, multivariate partitioning algorithm for solving mixed-integer nonlinear programs (MINLP) to global optimality. The algorithm combines ideas that exploit the structure of convex relaxations to MINLPs and bound tightening procedures

Optimum design of high speed prop rotors including the coupling of performance, aeroelastic stability and structures

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; Mccarthy, Thomas R.; Madden, John F., III

1992-01-01

An optimization procedure is developed for the design of high speed prop-rotors to be used in civil tiltrotor applications. The goal is to couple aerodynamic performance, aeroelastic stability, and structural design requirements inside a closed-loop optimization procedure. The objective is to minimize the gross weight and maximize the propulsive efficiency in high speed cruise. Constraints are imposed on the rotor aeroelastic stability in both hover and cruise and rotor figure of merit in hover. Both structural and aerodynamic design variables are used.

Development of a composite tailoring procedure for airplane wing

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; Zhang, Sen

1995-01-01

The development of a composite wing box section using a higher order-theory is proposed for accurate and efficient estimation of both static and dynamic responses. The theory includes the effect of through-the-thickness transverse shear deformations which is important in laminated composites and is ignored in the classical approach. The box beam analysis is integrated with an aeroelastic analysis to investigate the effect of composite tailoring using a formal design optimization technique. A hybrid optimization procedure is proposed for addressing both continuous and discrete design variables.

Synthesis of aircraft structures using integrated design and analysis methods

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, J.; Goetz, R. C.

1978-01-01

A systematic research is reported to develop and validate methods for structural sizing of an airframe designed with the use of composite materials and active controls. This research program includes procedures for computing aeroelastic loads, static and dynamic aeroelasticity, analysis and synthesis of active controls, and optimization techniques. Development of the methods is concerned with the most effective ways of integrating and sequencing the procedures in order to generate structural sizing and the associated active control system, which is optimal with respect to a given merit function constrained by strength and aeroelasticity requirements.

Digital adaptive flight controller development

NASA Technical Reports Server (NTRS)

Kaufman, H.; Alag, G.; Berry, P.; Kotob, S.

1974-01-01

A design study of adaptive control logic suitable for implementation in modern airborne digital flight computers was conducted. Two designs are described for an example aircraft. Each of these designs uses a weighted least squares procedure to identify parameters defining the dynamics of the aircraft. The two designs differ in the way in which control law parameters are determined. One uses the solution of an optimal linear regulator problem to determine these parameters while the other uses a procedure called single stage optimization. Extensive simulation results and analysis leading to the designs are presented.

Standardized Methods for Electronic Shearography

NASA Technical Reports Server (NTRS)

Lansing, Matthew D.

1997-01-01

Research was conducted in development of operating procedures and standard methods to evaluate fiber reinforced composite materials, bonded or sprayed insulation, coatings, and laminated structures with MSFC electronic shearography systems. Optimal operating procedures were developed for the Pratt and Whitney Electronic Holography/Shearography Inspection System (EH/SIS) operating in shearography mode, as well as the Laser Technology, Inc. (LTI) SC-4000 and Ettemeyer SHS-94 ISTRA shearography systems. Operating practices for exciting the components being inspected were studied, including optimal methods for transient heating with heat lamps and other methods as appropriate to enhance inspection capability.

Robot-assisted procedures in pediatric neurosurgery.

PubMed

De Benedictis, Alessandro; Trezza, Andrea; Carai, Andrea; Genovese, Elisabetta; Procaccini, Emidio; Messina, Raffaella; Randi, Franco; Cossu, Silvia; Esposito, Giacomo; Palma, Paolo; Amante, Paolina; Rizzi, Michele; Marras, Carlo Efisio

2017-05-01

OBJECTIVE During the last 3 decades, robotic technology has rapidly spread across several surgical fields due to the continuous evolution of its versatility, stability, dexterity, and haptic properties. Neurosurgery pioneered the development of robotics, with the aim of improving the quality of several procedures requiring a high degree of accuracy and safety. Moreover, robot-guided approaches are of special interest in pediatric patients, who often have altered anatomy and challenging relationships between the diseased and eloquent structures. Nevertheless, the use of robots has been rarely reported in children. In this work, the authors describe their experience using the ROSA device (Robotized Stereotactic Assistant) in the neurosurgical management of a pediatric population. METHODS Between 2011 and 2016, 116 children underwent ROSA-assisted procedures for a variety of diseases (epilepsy, brain tumors, intra- or extraventricular and tumor cysts, obstructive hydrocephalus, and movement and behavioral disorders). Each patient received accurate preoperative planning of optimal trajectories, intraoperative frameless registration, surgical treatment using specific instruments held by the robotic arm, and postoperative CT or MR imaging. RESULTS The authors performed 128 consecutive surgeries, including implantation of 386 electrodes for stereo-electroencephalography (36 procedures), neuroendoscopy (42 procedures), stereotactic biopsy (26 procedures), pallidotomy (12 procedures), shunt placement (6 procedures), deep brain stimulation procedures (3 procedures), and stereotactic cyst aspiration (3 procedures). For each procedure, the authors analyzed and discussed accuracy, timing, and complications. CONCLUSIONS To the best their knowledge, the authors present the largest reported series of pediatric neurosurgical cases assisted by robotic support. The ROSA system provided improved safety and feasibility of minimally invasive approaches, thus optimizing the surgical result, while minimizing postoperative morbidity.

Teleportation of squeezing: Optimization using non-Gaussian resources

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

Dell'Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio

2010-12-15

We study the continuous-variable quantum teleportation of states, statistical moments of observables, and scale parameters such as squeezing. We investigate the problem both in ideal and imperfect Vaidman-Braunstein-Kimble protocol setups. We show how the teleportation fidelity is maximized and the difference between output and input variances is minimized by using suitably optimized entangled resources. Specifically, we consider the teleportation of coherent squeezed states, exploiting squeezed Bell states as entangled resources. This class of non-Gaussian states, introduced by Illuminati and co-workers [F. Dell'Anno, S. De Siena, L. Albano, and F. Illuminati, Phys. Rev. A 76, 022301 (2007); F. Dell'Anno, S. Demore » Siena, and F. Illuminati, ibid. 81, 012333 (2010)], includes photon-added and photon-subtracted squeezed states as special cases. At variance with the case of entangled Gaussian resources, the use of entangled non-Gaussian squeezed Bell resources allows one to choose different optimization procedures that lead to inequivalent results. Performing two independent optimization procedures, one can either maximize the state teleportation fidelity, or minimize the difference between input and output quadrature variances. The two different procedures are compared depending on the degrees of displacement and squeezing of the input states and on the working conditions in ideal and nonideal setups.« less

Optimization of cathodic arc deposition and pulsed plasma melting techniques for growing smooth superconducting Pb photoemissive films for SRF injectors

DOE PAGES

Nietubyc, Robert; Lorkiewicz, Jerzy; Sekutowicz, Jacek; ...

2018-02-14

Superconducting photoinjectors have a potential to be the optimal solution for moderate and high current cw operating free electron lasers. For this application, a superconducting lead (Pb) cathode has been proposed to simplify the cathode integration into a 1.3 GHz, TESLA-type, 1.6-cell long purely superconducting gun cavity. In the proposed design, a lead film several micrometres thick is deposited onto a niobium plug attached to the cavity back wall. Traditional lead deposition techniques usually produce very non-uniform emission surfaces and often result in a poor adhesion of the layer. A pulsed plasma melting procedure reducing the non-uniformity of the leadmore » photocathodes is presented. In order to determine the parameters optimal for this procedure, heat transfer from plasma to the film was first modelled to evaluate melting front penetration range and liquid state duration. The obtained results were verified by surface inspection of witness samples. The optimal procedure was used to prepare a photocathode plug, which was then tested in an electron gun. In conclusion, the quantum efficiency and the value of cavity quality factor have been found to satisfy the requirements for an injector of the European-XFEL facility.« less

Optimization of cathodic arc deposition and pulsed plasma melting techniques for growing smooth superconducting Pb photoemissive films for SRF injectors

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

Nietubyc, Robert; Lorkiewicz, Jerzy; Sekutowicz, Jacek

Superconducting photoinjectors have a potential to be the optimal solution for moderate and high current cw operating free electron lasers. For this application, a superconducting lead (Pb) cathode has been proposed to simplify the cathode integration into a 1.3 GHz, TESLA-type, 1.6-cell long purely superconducting gun cavity. In the proposed design, a lead film several micrometres thick is deposited onto a niobium plug attached to the cavity back wall. Traditional lead deposition techniques usually produce very non-uniform emission surfaces and often result in a poor adhesion of the layer. A pulsed plasma melting procedure reducing the non-uniformity of the leadmore » photocathodes is presented. In order to determine the parameters optimal for this procedure, heat transfer from plasma to the film was first modelled to evaluate melting front penetration range and liquid state duration. The obtained results were verified by surface inspection of witness samples. The optimal procedure was used to prepare a photocathode plug, which was then tested in an electron gun. In conclusion, the quantum efficiency and the value of cavity quality factor have been found to satisfy the requirements for an injector of the European-XFEL facility.« less

Preclinical Feasibility of a Technology Framework for MRI-guided Iliac Angioplasty

PubMed Central

Rube, Martin A.; Fernandez-Gutierrez, Fabiola; Cox, Benjamin F.; Holbrook, Andrew B.; Houston, J. Graeme; White, Richard D.; McLeod, Helen; Fatahi, Mahsa; Melzer, Andreas

2015-01-01

Purpose Interventional MRI has significant potential for image guidance of iliac angioplasty and related vascular procedures. A technology framework with in-room image display, control, communication and MRI-guided intervention techniques was designed and tested for its potential to provide safe, fast and efficient MRI-guided angioplasty of the iliac arteries. Methods A 1.5T MRI scanner was adapted for interactive imaging during endovascular procedures using new or modified interventional devices such as guidewires and catheters. A perfused vascular phantom was used for testing. Pre-, intra- and post-procedural visualization and measurement of vascular morphology and flow was implemented. A detailed analysis of X-Ray fluoroscopic angiography workflow was conducted and applied. Two interventional radiologists and one physician in training performed 39 procedures. All procedures were timed and analyzed. Results MRI-guided iliac angioplasty procedures were successfully performed with progressive adaptation of techniques and workflow. The workflow, setup and protocol enabled a reduction in table time for a dedicated MRI-guided procedure to 6 min 33 s with a mean procedure time of 9 min 2 s, comparable to the mean procedure time of 8 min 42 s for the standard X-Ray guided procedure. Conclusions MRI-guided iliac vascular interventions were found to be feasible and practical using this framework and optimized workflow. In particular the real-time flow analysis was found to be helpful for pre- and post-interventional assessments. Design optimization of the catheters and in vivo experiments are required before clinical evaluation. PMID:25102933

HEURISTIC OPTIMIZATION AND ALGORITHM TUNING APPLIED TO SORPTIVE BARRIER DESIGN

EPA Science Inventory

While heuristic optimization is applied in environmental applications, ad-hoc algorithm configuration is typical. We use a multi-layer sorptive barrier design problem as a benchmark for an algorithm-tuning procedure, as applied to three heuristics (genetic algorithms, simulated ...

Optimized in vitro procedure for assessing the cytocompatibility of magnesium-based biomaterials.

PubMed

Jung, Ole; Smeets, Ralf; Porchetta, Dario; Kopp, Alexander; Ptock, Christoph; Müller, Ute; Heiland, Max; Schwade, Max; Behr, Björn; Kröger, Nadja; Kluwe, Lan; Hanken, Henning; Hartjen, Philip

2015-09-01

Magnesium (Mg) is a promising biomaterial for degradable implant applications that has been extensively studied in vitro and in vivo in recent years. In this study, we developed a procedure that allows an optimized and uniform in vitro assessment of the cytocompatibility of Mg-based materials while respecting the standard protocol DIN EN ISO 10993-5:2009. The mouse fibroblast line L-929 was chosen as the preferred assay cell line and MEM supplemented with 10% FCS, penicillin/streptomycin and 4mM l-glutamine as the favored assay medium. The procedure consists of (1) an indirect assessment of effects of soluble Mg corrosion products in material extracts and (2) a direct assessment of the surface compatibility in terms of cell attachment and cytotoxicity originating from active corrosion processes. The indirect assessment allows the quantification of cell-proliferation (BrdU-assay), viability (XTT-assay) as well as cytotoxicity (LDH-assay) of the mouse fibroblasts incubated with material extracts. Direct assessment visualizes cells attached to the test materials by means of live-dead staining. The colorimetric assays and the visual evaluation complement each other and the combination of both provides an optimized and simple procedure for assessing the cytocompatibility of Mg-based biomaterials in vitro. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Recent developments in large-scale structural optimization

NASA Technical Reports Server (NTRS)

Venkayya, Vipperla B.

1989-01-01

A brief discussion is given of mathematical optimization and the motivation for the development of more recent numerical search procedures. A review of recent developments and issues in multidisciplinary optimization is also presented. These developments are discussed in the context of the preliminary design of aircraft structures. A capability description of programs FASTOP, TSO, STARS, LAGRANGE, ELFINI and ASTROS is included.

Optimization and evaluation of a method to detect adenoviruses in river water

EPA Pesticide Factsheets

This dataset includes the recoveries of spiked adenovirus through various stages of experimental optimization procedures. This dataset is associated with the following publication:McMinn , B., A. Korajkic, and A. Grimm. Optimization and evaluation of a method to detect adenoviruses in river water. JOURNAL OF VIROLOGICAL METHODS. Elsevier Science Ltd, New York, NY, USA, 231(1): 8-13, (2016).

Dynamic programming for optimization of timber production and grazing in ponderosa pine

Treesearch

Kurt H. Riitters; J. Douglas Brodie; David W. Hann

1982-01-01

Dynamic programming procedures are presented for optimizing thinning and rotation of even-aged ponderosa pine by using the four descriptors: age, basal area, number of trees, and time since thinning. Because both timber yield and grazing yield are functions of stand density, the two outputs-forage and timber-can both be optimized. The soil expectation values for single...

A LSQR-type method provides a computationally efficient automated optimal choice of regularization parameter in diffuse optical tomography.

PubMed

Prakash, Jaya; Yalavarthy, Phaneendra K

2013-03-01

Developing a computationally efficient automated method for the optimal choice of regularization parameter in diffuse optical tomography. The least-squares QR (LSQR)-type method that uses Lanczos bidiagonalization is known to be computationally efficient in performing the reconstruction procedure in diffuse optical tomography. The same is effectively deployed via an optimization procedure that uses the simplex method to find the optimal regularization parameter. The proposed LSQR-type method is compared with the traditional methods such as L-curve, generalized cross-validation (GCV), and recently proposed minimal residual method (MRM)-based choice of regularization parameter using numerical and experimental phantom data. The results indicate that the proposed LSQR-type and MRM-based methods performance in terms of reconstructed image quality is similar and superior compared to L-curve and GCV-based methods. The proposed method computational complexity is at least five times lower compared to MRM-based method, making it an optimal technique. The LSQR-type method was able to overcome the inherent limitation of computationally expensive nature of MRM-based automated way finding the optimal regularization parameter in diffuse optical tomographic imaging, making this method more suitable to be deployed in real-time.

Application of a derivative-free global optimization algorithm to the derivation of a new time integration scheme for the simulation of incompressible turbulence

NASA Astrophysics Data System (ADS)

Alimohammadi, Shahrouz; Cavaglieri, Daniele; Beyhaghi, Pooriya; Bewley, Thomas R.

2016-11-01

This work applies a recently developed Derivative-free optimization algorithm to derive a new mixed implicit-explicit (IMEX) time integration scheme for Computational Fluid Dynamics (CFD) simulations. This algorithm allows imposing a specified order of accuracy for the time integration and other important stability properties in the form of nonlinear constraints within the optimization problem. In this procedure, the coefficients of the IMEX scheme should satisfy a set of constraints simultaneously. Therefore, the optimization process, at each iteration, estimates the location of the optimal coefficients using a set of global surrogates, for both the objective and constraint functions, as well as a model of the uncertainty function of these surrogates based on the concept of Delaunay triangulation. This procedure has been proven to converge to the global minimum of the constrained optimization problem provided the constraints and objective functions are twice differentiable. As a result, a new third-order, low-storage IMEX Runge-Kutta time integration scheme is obtained with remarkably fast convergence. Numerical tests are then performed leveraging the turbulent channel flow simulations to validate the theoretical order of accuracy and stability properties of the new scheme.

Design enhancement tools in MSC/NASTRAN

NASA Technical Reports Server (NTRS)

Wallerstein, D. V.

1984-01-01

Design sensitivity is the calculation of derivatives of constraint functions with respect to design variables. While a knowledge of these derivatives is useful in its own right, the derivatives are required in many efficient optimization methods. Constraint derivatives are also required in some reanalysis methods. It is shown where the sensitivity coefficients fit into the scheme of a basic organization of an optimization procedure. The analyzer is to be taken as MSC/NASTRAN. The terminator program monitors the termination criteria and ends the optimization procedure when the criteria are satisfied. This program can reside in several plances: in the optimizer itself, in a user written code, or as part of the MSC/EOS (Engineering Operating System) MSC/EOS currently under development. Since several excellent optimization codes exist and since they require such very specialized technical knowledge, the optimizer under the new MSC/EOS is considered to be selected and supplied by the user to meet his specific needs and preferences. The one exception to this is a fully stressed design (FSD) based on simple scaling. The gradients are currently supplied by various design sensitivity options now existing in MSC/NASTRAN's design sensitivity analysis (DSA).

NASA progress in aircraft noise prediction

NASA Technical Reports Server (NTRS)

Raney, J. P.; Padula, S. L.; Zorumski, W. E.

1981-01-01

Some of the essential features of aircraft noise prediction are described and the basis for evaluating its capability and future potential is discussed. A takeoff noise optimizing procedure is described which calculates a minimum noise takeoff procedure subject to multiple site noise constraints.

Optimal Synthesis of Compliant Mechanisms using Subdivision and Commercial FEA (DETC2004-57497)

NASA Technical Reports Server (NTRS)

Hull, Patrick V.; Canfield, Stephen

2004-01-01

The field of distributed-compliance mechanisms has seen significant work in developing suitable topology optimization tools for their design. These optimal design tools have grown out of the techniques of structural optimization. This paper will build on the previous work in topology optimization and compliant mechanism design by proposing an alternative design space parameterization through control points and adding another step to the process, that of subdivision. The control points allow a specific design to be represented as a solid model during the optimization process. The process of subdivision creates an additional number of control points that help smooth the surface (for example a C(sup 2) continuous surface depending on the method of subdivision chosen) creating a manufacturable design free of some traditional numerical instabilities. Note that these additional control points do not add to the number of design parameters. This alternative parameterization and description as a solid model effectively and completely separates the design variables from the analysis variables during the optimization procedure. The motivation behind this work is to create an automated design tool from task definition to functional prototype created on a CNC or rapid-prototype machine. This paper will describe the proposed compliant mechanism design process and will demonstrate the procedure on several examples common in the literature.

A TOTP-Based Enhanced Route Optimization Procedure for Mobile IPv6 to Reduce Handover Delay and Signalling Overhead

PubMed Central

Shah, Peer Azmat; Hasbullah, Halabi B.; Lawal, Ibrahim A.; Aminu Mu'azu, Abubakar; Tang Jung, Low

2014-01-01

Due to the proliferation of handheld mobile devices, multimedia applications like Voice over IP (VoIP), video conferencing, network music, and online gaming are gaining popularity in recent years. These applications are well known to be delay sensitive and resource demanding. The mobility of mobile devices, running these applications, across different networks causes delay and service disruption. Mobile IPv6 was proposed to provide mobility support to IPv6-based mobile nodes for continuous communication when they roam across different networks. However, the Route Optimization procedure in Mobile IPv6 involves the verification of mobile node's reachability at the home address and at the care-of address (home test and care-of test) that results in higher handover delays and signalling overhead. This paper presents an enhanced procedure, time-based one-time password Route Optimization (TOTP-RO), for Mobile IPv6 Route Optimization that uses the concepts of shared secret Token, time based one-time password (TOTP) along with verification of the mobile node via direct communication and maintaining the status of correspondent node's compatibility. The TOTP-RO was implemented in network simulator (NS-2) and an analytical analysis was also made. Analysis showed that TOTP-RO has lower handover delays, packet loss, and signalling overhead with an increased level of security as compared to the standard Mobile IPv6's Return-Routability-based Route Optimization (RR-RO). PMID:24688398

Optimizing Positioning for In-Office Otology Procedures.

PubMed

Govil, Nandini; DeMayo, William M; Hirsch, Barry E; McCall, Andrew A

2017-01-01

Objective Surgeons often report musculoskeletal discomfort in relation to their practice, but few understand optimal ergonomic positioning. This study aims to determine which patient position-sitting versus supine-is ergonomically optimal for performing otologic procedures. Study Design Observational study. Setting Outpatient otolaryngology clinic setting in a tertiary care facility. Subjects and Methods We observed 3 neurotologists performing a standardized simulated cerumen debridement procedure on volunteers in 2 positions: sitting and supine. The Rapid Upper Limb Assessment (RULA)-a validated tool that calculates stress placed on the upper limb during a task-was used to evaluate ergonomic positioning. Scores on this instrument range from 1 to 7, with a score of 1 to 2 indicating negligible risk of developing posture-related injury. The risk of musculoskeletal disorders increases as the RULA score increases. Results In nearly every trial, RULA scores were lower when the simulated patient was placed in the supine position. When examined as a group, the median RULA scores were 5 with the patient sitting and 3 with the patient in the supine position ( P < .0001). When the RULA scores of the 3 neurotologists were examined individually, each had a statistically significant decrease in score with the patient in the supine position. Conclusion This study indicates that patient position may contribute to ergonomic stress placed on the otolaryngologist's upper limb during in-office otologic procedures. Otolaryngologists should consider performing otologic procedures with the patient in the supine position to decrease their own risk of developing upper-limb musculoskeletal disorders.

The PDB_REDO server for macromolecular structure model optimization.

PubMed

Joosten, Robbie P; Long, Fei; Murshudov, Garib N; Perrakis, Anastassis

2014-07-01

The refinement and validation of a crystallographic structure model is the last step before the coordinates and the associated data are submitted to the Protein Data Bank (PDB). The success of the refinement procedure is typically assessed by validating the models against geometrical criteria and the diffraction data, and is an important step in ensuring the quality of the PDB public archive [Read et al. (2011 ▶), Structure, 19, 1395-1412]. The PDB_REDO procedure aims for 'constructive validation', aspiring to consistent and optimal refinement parameterization and pro-active model rebuilding, not only correcting errors but striving for optimal interpretation of the electron density. A web server for PDB_REDO has been implemented, allowing thorough, consistent and fully automated optimization of the refinement procedure in REFMAC and partial model rebuilding. The goal of the web server is to help practicing crystallo-graphers to improve their model prior to submission to the PDB. For this, additional steps were implemented in the PDB_REDO pipeline, both in the refinement procedure, e.g. testing of resolution limits and k-fold cross-validation for small test sets, and as new validation criteria, e.g. the density-fit metrics implemented in EDSTATS and ligand validation as implemented in YASARA. Innovative ways to present the refinement and validation results to the user are also described, which together with auto-generated Coot scripts can guide users to subsequent model inspection and improvement. It is demonstrated that using the server can lead to substantial improvement of structure models before they are submitted to the PDB.

The PDB_REDO server for macromolecular structure model optimization

PubMed Central

Joosten, Robbie P.; Long, Fei; Murshudov, Garib N.; Perrakis, Anastassis

2014-01-01

The refinement and validation of a crystallographic structure model is the last step before the coordinates and the associated data are submitted to the Protein Data Bank (PDB). The success of the refinement procedure is typically assessed by validating the models against geometrical criteria and the diffraction data, and is an important step in ensuring the quality of the PDB public archive [Read et al. (2011 ▶), Structure, 19, 1395–1412]. The PDB_REDO procedure aims for ‘constructive validation’, aspiring to consistent and optimal refinement parameterization and pro-active model rebuilding, not only correcting errors but striving for optimal interpretation of the electron density. A web server for PDB_REDO has been implemented, allowing thorough, consistent and fully automated optimization of the refinement procedure in REFMAC and partial model rebuilding. The goal of the web server is to help practicing crystallo­graphers to improve their model prior to submission to the PDB. For this, additional steps were implemented in the PDB_REDO pipeline, both in the refinement procedure, e.g. testing of resolution limits and k-fold cross-validation for small test sets, and as new validation criteria, e.g. the density-fit metrics implemented in EDSTATS and ligand validation as implemented in YASARA. Innovative ways to present the refinement and validation results to the user are also described, which together with auto-generated Coot scripts can guide users to subsequent model inspection and improvement. It is demonstrated that using the server can lead to substantial improvement of structure models before they are submitted to the PDB. PMID:25075342

Architecture and settings optimization procedure of a TES frequency domain multiplexed readout firmware

NASA Astrophysics Data System (ADS)

Clenet, A.; Ravera, L.; Bertrand, B.; den Hartog, R.; Jackson, B.; van Leeuwen, B.-J.; van Loon, D.; Parot, Y.; Pointecouteau, E.; Sournac, A.

2014-11-01

IRAP is developing the readout electronics of the SPICA-SAFARI's TES bolometer arrays. Based on the frequency domain multiplexing technique the readout electronics provides the AC-signals to voltage-bias the detectors; it demodulates the data; and it computes a feedback to linearize the detection chain. The feedback is computed with a specific technique, so called baseband feedback (BBFB) which ensures that the loop is stable even with long propagation and processing delays (i.e. several μ s) and with fast signals (i.e. frequency carriers of the order of 5 MHz). To optimize the power consumption we took advantage of the reduced science signal bandwidth to decouple the signal sampling frequency and the data processing rate. This technique allowed a reduction of the power consumption of the circuit by a factor of 10. Beyond the firmware architecture the optimization of the instrument concerns the characterization routines and the definition of the optimal parameters. Indeed, to operate an array TES one has to properly define about 21000 parameters. We defined a set of procedures to automatically characterize these parameters and find out the optimal settings.

Sequential-Optimization-Based Framework for Robust Modeling and Design of Heterogeneous Catalytic Systems

DOE PAGES

Rangarajan, Srinivas; Maravelias, Christos T.; Mavrikakis, Manos

2017-11-09

Here, we present a general optimization-based framework for (i) ab initio and experimental data driven mechanistic modeling and (ii) optimal catalyst design of heterogeneous catalytic systems. Both cases are formulated as a nonlinear optimization problem that is subject to a mean-field microkinetic model and thermodynamic consistency requirements as constraints, for which we seek sparse solutions through a ridge (L 2 regularization) penalty. The solution procedure involves an iterative sequence of forward simulation of the differential algebraic equations pertaining to the microkinetic model using a numerical tool capable of handling stiff systems, sensitivity calculations using linear algebra, and gradient-based nonlinear optimization.more » A multistart approach is used to explore the solution space, and a hierarchical clustering procedure is implemented for statistically classifying potentially competing solutions. An example of methanol synthesis through hydrogenation of CO and CO 2 on a Cu-based catalyst is used to illustrate the framework. The framework is fast, is robust, and can be used to comprehensively explore the model solution and design space of any heterogeneous catalytic system.« less

Optimal error functional for parameter identification in anisotropic finite strain elasto-plasticity

NASA Astrophysics Data System (ADS)

Shutov, A. V.; Kaygorodtseva, A. A.; Dranishnikov, N. S.

2017-10-01

A problem of parameter identification for a model of finite strain elasto-plasticity is discussed. The utilized phenomenological material model accounts for nonlinear isotropic and kinematic hardening; the model kinematics is described by a nested multiplicative split of the deformation gradient. A hierarchy of optimization problems is considered. First, following the standard procedure, the material parameters are identified through minimization of a certain least square error functional. Next, the focus is placed on finding optimal weighting coefficients which enter the error functional. Toward that end, a stochastic noise with systematic and non-systematic components is introduced to the available measurement results; a superordinate optimization problem seeks to minimize the sensitivity of the resulting material parameters to the introduced noise. The advantage of this approach is that no additional experiments are required; it also provides an insight into the robustness of the identification procedure. As an example, experimental data for the steel 42CrMo4 are considered and a set of weighting coefficients is found, which is optimal in a certain class.

On the preventive management of sediment-related sewer blockages: a combined maintenance and routing optimization approach.

PubMed

Fontecha, John E; Akhavan-Tabatabaei, Raha; Duque, Daniel; Medaglia, Andrés L; Torres, María N; Rodríguez, Juan Pablo

In this work we tackle the problem of planning and scheduling preventive maintenance (PM) of sediment-related sewer blockages in a set of geographically distributed sites that are subject to non-deterministic failures. To solve the problem, we extend a combined maintenance and routing (CMR) optimization approach which is a procedure based on two components: (a) first a maintenance model is used to determine the optimal time to perform PM operations for each site and second (b) a mixed integer program-based split procedure is proposed to route a set of crews (e.g., sewer cleaners, vehicles equipped with winches or rods and dump trucks) in order to perform PM operations at a near-optimal minimum expected cost. We applied the proposed CMR optimization approach to two (out of five) operative zones in the city of Bogotá (Colombia), where more than 100 maintenance operations per zone must be scheduled on a weekly basis. Comparing the CMR against the current maintenance plan, we obtained more than 50% of cost savings in 90% of the sites.

Stochastic optimization of broadband reflecting photonic structures.

PubMed

Estrada-Wiese, D; Del Río-Chanona, E A; Del Río, J A

2018-01-19

Photonic crystals (PCs) are built to control the propagation of light within their structure. These can be used for an assortment of applications where custom designed devices are of interest. Among them, one-dimensional PCs can be produced to achieve the reflection of specific and broad wavelength ranges. However, their design and fabrication are challenging due to the diversity of periodic arrangement and layer configuration that each different PC needs. In this study, we present a framework to design high reflecting PCs for any desired wavelength range. Our method combines three stochastic optimization algorithms (Random Search, Particle Swarm Optimization and Simulated Annealing) along with a reduced space-search methodology to obtain a custom and optimized PC configuration. The optimization procedure is evaluated through theoretical reflectance spectra calculated by using the Equispaced Thickness Method, which improves the simulations due to the consideration of incoherent light transmission. We prove the viability of our procedure by fabricating different reflecting PCs made of porous silicon and obtain good agreement between experiment and theory using a merit function. With this methodology, diverse reflecting PCs can be designed for any applications and fabricated with different materials.

Sequential-Optimization-Based Framework for Robust Modeling and Design of Heterogeneous Catalytic Systems

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

Rangarajan, Srinivas; Maravelias, Christos T.; Mavrikakis, Manos

Here, we present a general optimization-based framework for (i) ab initio and experimental data driven mechanistic modeling and (ii) optimal catalyst design of heterogeneous catalytic systems. Both cases are formulated as a nonlinear optimization problem that is subject to a mean-field microkinetic model and thermodynamic consistency requirements as constraints, for which we seek sparse solutions through a ridge (L 2 regularization) penalty. The solution procedure involves an iterative sequence of forward simulation of the differential algebraic equations pertaining to the microkinetic model using a numerical tool capable of handling stiff systems, sensitivity calculations using linear algebra, and gradient-based nonlinear optimization.more » A multistart approach is used to explore the solution space, and a hierarchical clustering procedure is implemented for statistically classifying potentially competing solutions. An example of methanol synthesis through hydrogenation of CO and CO 2 on a Cu-based catalyst is used to illustrate the framework. The framework is fast, is robust, and can be used to comprehensively explore the model solution and design space of any heterogeneous catalytic system.« less

Inverse optimal design of the radiant heating in materials processing and manufacturing

NASA Astrophysics Data System (ADS)

Fedorov, A. G.; Lee, K. H.; Viskanta, R.

1998-12-01

Combined convective, conductive, and radiative heat transfer is analyzed during heating of a continuously moving load in the industrial radiant oven. A transient, quasi-three-dimensional model of heat transfer between a continuous load of parts moving inside an oven on a conveyor belt at a constant speed and an array of radiant heaters/burners placed inside the furnace enclosure is developed. The model accounts for radiative exchange between the heaters and the load, heat conduction in the load, and convective heat transfer between the moving load and oven environment. The thermal model developed has been used to construct a general framework for an inverse optimal design of an industrial oven as an example. In particular, the procedure based on the Levenberg-Marquardt nonlinear least squares optimization algorithm has been developed to obtain the optimal temperatures of the heaters/burners that need to be specified to achieve a prescribed temperature distribution of the surface of a load. The results of calculations for several sample cases are reported to illustrate the capabilities of the procedure developed for the optimal inverse design of an industrial radiant oven.

Conjugate gradient optimization programs for shuttle reentry

NASA Technical Reports Server (NTRS)

Powers, W. F.; Jacobson, R. A.; Leonard, D. A.

1972-01-01

Two computer programs for shuttle reentry trajectory optimization are listed and described. Both programs use the conjugate gradient method as the optimization procedure. The Phase 1 Program is developed in cartesian coordinates for a rotating spherical earth, and crossrange, downrange, maximum deceleration, total heating, and terminal speed, altitude, and flight path angle are included in the performance index. The programs make extensive use of subroutines so that they may be easily adapted to other atmospheric trajectory optimization problems.

Optimal domain decomposition strategies

NASA Technical Reports Server (NTRS)

Yoon, Yonghyun; Soni, Bharat K.

1995-01-01

The primary interest of the authors is in the area of grid generation, in particular, optimal domain decomposition about realistic configurations. A grid generation procedure with optimal blocking strategies has been developed to generate multi-block grids for a circular-to-rectangular transition duct. The focus of this study is the domain decomposition which optimizes solution algorithm/block compatibility based on geometrical complexities as well as the physical characteristics of flow field. The progress realized in this study is summarized in this paper.

Review of dynamic optimization methods in renewable natural resource management

USGS Publications Warehouse

Williams, B.K.

1989-01-01

In recent years, the applications of dynamic optimization procedures in natural resource management have proliferated. A systematic review of these applications is given in terms of a number of optimization methodologies and natural resource systems. The applicability of the methods to renewable natural resource systems are compared in terms of system complexity, system size, and precision of the optimal solutions. Recommendations are made concerning the appropriate methods for certain kinds of biological resource problems.

Development and validation of a numerical model for cross-section optimization of a multi-part probe for soft tissue intervention.

PubMed

Frasson, L; Neubert, J; Reina, S; Oldfield, M; Davies, B L; Rodriguez Y Baena, F

2010-01-01

The popularity of minimally invasive surgical procedures is driving the development of novel, safer and more accurate surgical tools. In this context a multi-part probe for soft tissue surgery is being developed in the Mechatronics in Medicine Laboratory at Imperial College, London. This study reports an optimization procedure using finite element methods, for the identification of an interlock geometry able to limit the separation of the segments composing the multi-part probe. An optimal geometry was obtained and the corresponding three-dimensional finite element model validated experimentally. Simulation results are shown to be consistent with the physical experiments. The outcome of this study is an important step in the provision of a novel miniature steerable probe for surgery.

Cost-Based Optimization of a Papermaking Wastewater Regeneration Recycling System

NASA Astrophysics Data System (ADS)

Huang, Long; Feng, Xiao; Chu, Khim H.

2010-11-01

Wastewater can be regenerated for recycling in an industrial process to reduce freshwater consumption and wastewater discharge. Such an environment friendly approach will also lead to cost savings that accrue due to reduced freshwater usage and wastewater discharge. However, the resulting cost savings are offset to varying degrees by the costs incurred for the regeneration of wastewater for recycling. Therefore, systematic procedures should be used to determine the true economic benefits for any water-using system involving wastewater regeneration recycling. In this paper, a total cost accounting procedure is employed to construct a comprehensive cost model for a paper mill. The resulting cost model is optimized by means of mathematical programming to determine the optimal regeneration flowrate and regeneration efficiency that will yield the minimum total cost.

Computer-aided diagnostic strategy selection.

PubMed

Greenes, R A

1986-03-01

Determination of the optimal diagnostic work-up strategy for the patient is becoming a major concern for the practicing physician. Overlap of the indications for various diagnostic procedures, differences in their invasiveness or risk, and high costs have made physicians aware of the need to consider the choice of procedure carefully, as well as its relation to management actions available. In this article, the author discusses research approaches that aim toward development of formal decision analytic methods to allow the physician to determine optimal strategy; clinical algorithms or rules as guides to physician decisions; improved measures for characterizing the performance of diagnostic tests; educational tools for increasing the familiarity of physicians with the concepts underlying these measures and analytic procedures; and computer-based aids for facilitating the employment of these resources in actual clinical practice.

The Krigifier: A Procedure for Generating Pseudorandom Nonlinear Objective Functions for Computational Experimentation

NASA Technical Reports Server (NTRS)

Trosset, Michael W.

1999-01-01

Comprehensive computational experiments to assess the performance of algorithms for numerical optimization require (among other things) a practical procedure for generating pseudorandom nonlinear objective functions. We propose a procedure that is based on the convenient fiction that objective functions are realizations of stochastic processes. This report details the calculations necessary to implement our procedure for the case of certain stationary Gaussian processes and presents a specific implementation in the statistical programming language S-PLUS.

A new design approach to innovative spectrometers. Case study: TROPOLITE

NASA Astrophysics Data System (ADS)

Volatier, Jean-Baptiste; Baümer, Stefan; Kruizinga, Bob; Vink, Rob

2014-05-01

Designing a novel optical system is a nested iterative process. The optimization loop, from a starting point to final system is already mostly automated. However this loop is part of a wider loop which is not. This wider loop starts with an optical specification and ends with a manufacturability assessment. When designing a new spectrometer with emphasis on weight and cost, numerous iterations between the optical- and mechanical designer are inevitable. The optical designer must then be able to reliably produce optical designs based on new input gained from multidisciplinary studies. This paper presents a procedure that can automatically generate new starting points based on any kind of input or new constraint that might arise. These starting points can then be handed over to a generic optimization routine to make the design tasks extremely efficient. The optical designer job is then not to design optical systems, but to meta-design a procedure that produces optical systems paving the way for system level optimization. We present here this procedure and its application to the design of TROPOLITE a lightweight push broom imaging spectrometer.

Critical evaluation and comparison of enrichment efficiency of multi-walled carbon nanotubes, C18 silica and activated carbon towards some pesticides from environmental waters.

PubMed

El-Sheikh, Amjad H; Sweileh, Jamal A; Al-Degs, Yahya S; Insisi, Ahmad A; Al-Rabady, Nancy

2008-02-15

In this work, optimization of multi-residue solid phase extraction (SPE) procedures coupled with high-performance liquid chromatography for the determination of Propoxur, Atrazine and Methidathion from environmental waters is reported. Three different sorbents were used in this work: multi-walled carbon nanotubes (MWCNTs), C18 silica and activated carbon (AC). The three optimized SPE procedures were compared in terms of analytical performance, application to environmental waters, cartridge re-use, adsorption capacity and cost of adsorbent. Although the adsorption capacity of MWCNT was larger than AC and C18, however, the analytical performance of AC could be made close to the other sorbents by appropriate optimization of the SPE procedures. A sample of AC was then oxidized with various oxidizing agents to show that ACs of various surface properties has different enrichment efficiencies. Thus researchers are advised to try AC of various surface properties in SPE of pollutants prior to using expensive sorbents (such as MWCNT and C18 silica).

Optimization of Ammonium Sulfate Concentration for Purification of Colorectal Cancer Vaccine Candidate Recombinant Protein GA733-FcK Isolated from Plants.

PubMed

Park, Se-Ra; Lim, Chae-Yeon; Kim, Deuk-Su; Ko, Kisung

2015-01-01

A protein purification procedure is required to obtain high-value recombinant injectable vaccine proteins produced in plants as a bioreactor. However, existing purification procedures for plant-derived recombinant proteins are often not optimized and are inefficient, with low recovery rates. In our previous study, we used 25-30% ammonium sulfate to precipitate total soluble proteins (TSPs) in purification process for recombinant proteins from plant leaf biomass which has not been optimized. Thus, the objective in this study is to optimize the conditions for plant-derived protein purification procedures. Various ammonium sulfate concentrations (15-80%) were compared to determine their effects on TSPs yield. With 50% ammonium sulfate, the yield of precipitated TSP was the highest, and that of the plant-derived colorectal cancer-specific surface glycoprotein GA733 fused to the Fc fragment of human IgG tagged with endoplasmic reticulum retention signal KDEL (GA733(P)-FcK) protein significantly increased 1.8-fold. SDS-PAGE analysis showed that the purity of GA733(P)-FcK protein band appeared to be similar to that of an equal dose of mammalian-derived GA733-Fc (GA733(M)-Fc). The binding activity of purified GA733(P)-FcK to anti-GA733 mAb was as efficient as the native GA733(M)-Fc. Thus, the purification process was effectively optimized for obtaining a high yield of plant-derived antigenic protein with good quality. In conclusion, the purification recovery rate of large quantities of recombinant protein from plant expression systems can be enhanced via optimization of ammonium sulfate concentration during downstream processes, thereby offering a promising solution for production of recombinant GA733-Fc protein in plants.

High-pressure balloon valvuloplasty for severe pulmonary valve stenosis: a prospective observational pilot study in 25 dogs.

PubMed

Belanger, Catherine; Gunther-Harrington, Catherine T; Nishimura, Satoko; Oldach, Maureen S; Fousse, Samantha L; Visser, Lance C; Stern, Joshua A

2018-04-01

We aimed to evaluate safety and efficacy of high-pressure balloon valvuloplasty (HPBVP) for treatment of canine severe pulmonary valve stenosis (PS). A secondary aim was to provide pre-procedure predictors of success. Twenty-five dogs. Prospective observational study. Dogs with severe PS (echocardiographically derived trans-pulmonary peak/maximum pressure gradient (EDPG) ≥80 mmHg) were recruited. All dogs underwent echocardiography before and 20-24hrs after HPBVP using a high-pressure balloon with rated burst pressures ranging from 12 to 18 ATM. Procedural success was defined as a post-HPBVP EDPG reduction of ≥50% or reduction into at least the moderate category of PS (50-79 mmHg). Optimal result was defined as a post-procedural EDPG ≤30 mmHg. Initial median (IQR) EDPG for all dogs was 96 (88, 127) mmHg with a post-operative median of 48 (36, 65) mmHg. The median EDPG reduction provided by HPBVP was 63% (39, 68); procedural success rate was 92% (23 dogs). Optimal results were achieved in 56% (14 dogs). There were no significant correlations between EDPG reduction and valve morphology (Type A and Type B) or severity of right ventricular hypertrophy. Pulmonary valve annulus diameter was the only echocardiographic variable that was significantly correlated to EDPG reduction (p = 0.02; r = -0.46). No dog experienced any anesthetic or surgical complications, and all patients survived the procedure. In this cohort of 25 dogs with severe PS, HPBVP was safe and effective. The procedural success rate and high number of optimal results achieved with HPBVP suggest future randomized controlled trials comparing HPBVP to conventional valvuloplasty are warranted. Copyright © 2018 Elsevier B.V. All rights reserved.

Optimized Non-Obstructive Particle Damping (NOPD) Treatment for Composite Honeycomb Structures

NASA Technical Reports Server (NTRS)

Panossian, H.

2008-01-01

Non-Obstructive Particle Damping (NOPD) technology is a passive vibration damping approach whereby metallic or non-metallic particles in spherical or irregular shapes, of heavy or light consistency, and even liquid particles are placed inside cavities or attached to structures by an appropriate means at strategic locations, to absorb vibration energy. The objective of the work described herein is the development of a design optimization procedure and discussion of test results for such a NOPD treatment on honeycomb (HC) composite structures, based on finite element modeling (FEM) analyses, optimization and tests. Modeling and predictions were performed and tests were carried out to correlate the test data with the FEM. The optimization procedure consisted of defining a global objective function, using finite difference methods, to determine the optimal values of the design variables through quadratic linear programming. The optimization process was carried out by targeting the highest dynamic displacements of several vibration modes of the structure and finding an optimal treatment configuration that will minimize them. An optimal design was thus derived and laboratory tests were conducted to evaluate its performance under different vibration environments. Three honeycomb composite beams, with Nomex core and aluminum face sheets, empty (untreated), uniformly treated with NOPD, and optimally treated with NOPD, according to the analytically predicted optimal design configuration, were tested in the laboratory. It is shown that the beam with optimal treatment has the lowest response amplitude. Described below are results of modal vibration tests and FEM analyses from predictions of the modal characteristics of honeycomb beams under zero, 50% uniform treatment and an optimal NOPD treatment design configuration and verification with test data.

A structural topological optimization method for multi-displacement constraints and any initial topology configuration

NASA Astrophysics Data System (ADS)

Rong, J. H.; Yi, J. H.

2010-10-01

In density-based topological design, one expects that the final result consists of elements either black (solid material) or white (void), without any grey areas. Moreover, one also expects that the optimal topology can be obtained by starting from any initial topology configuration. An improved structural topological optimization method for multi- displacement constraints is proposed in this paper. In the proposed method, the whole optimization process is divided into two optimization adjustment phases and a phase transferring step. Firstly, an optimization model is built to deal with the varied displacement limits, design space adjustments, and reasonable relations between the element stiffness matrix and mass and its element topology variable. Secondly, a procedure is proposed to solve the optimization problem formulated in the first optimization adjustment phase, by starting with a small design space and advancing to a larger deign space. The design space adjustments are automatic when the design domain needs expansions, in which the convergence of the proposed method will not be affected. The final topology obtained by the proposed procedure in the first optimization phase, can approach to the vicinity of the optimum topology. Then, a heuristic algorithm is given to improve the efficiency and make the designed structural topology black/white in both the phase transferring step and the second optimization adjustment phase. And the optimum topology can finally be obtained by the second phase optimization adjustments. Two examples are presented to show that the topologies obtained by the proposed method are of very good 0/1 design distribution property, and the computational efficiency is enhanced by reducing the element number of the design structural finite model during two optimization adjustment phases. And the examples also show that this method is robust and practicable.

How to formulate and solve "optimal stand density over time" problems for even-aged stands using dynamic programming.

Treesearch

Chung M. Chen; Dietmar W. Rose; Rolfe A. Leary

1980-01-01

Describes how dynamic programming can be used to solve optimal stand density problems when yields are given by prior simulation or by a new stand growth equation that is a function of the decision variable. Formulations of the latter type allow use of a calculus-based search procedure; they determine exact optimal residual density at each stage.

TARCMO: Theory and Algorithms for Robust, Combinatorial, Multicriteria Optimization

DTIC Science & Technology

2016-11-28

objective 9 4.6 On The Recoverable Robust Traveling Salesman Problem . . . . . 11 4.7 A Bicriteria Approach to Robust Optimization...be found. 4.6 On The Recoverable Robust Traveling Salesman Problem The traveling salesman problem (TSP) is a well-known combinatorial optimiza- tion...procedure for the robust traveling salesman problem . While this iterative algorithms results in an optimal solution to the robust TSP, computation

Geometrical optimization of the transmission and dispersion properties of arrayed waveguide gratings using two stigmatic point mountings.

PubMed

Muñoz, P; Pastor, D; Capmany, J; Martínez, A

2003-09-22

In this paper, the procedure to optimize flat-top Arrayed Waveguide Grating (AWG) devices in terms of transmission and dispersion properties is presented. The systematic procedure consists on the stigmatization and minimization of the Light Path Function (LPF) used in classic planar spectrograph theory. The resulting geometry arrangement for the Arrayed Waveguides (AW) and the Output Waveguides (OW) is not the classical Rowland mounting, but an arbitrary geometry arrangement. Simulation using previous published enhanced modeling show how this geometry reduces the passband ripple, asymmetry and dispersion, in a design example.

GENESUS: a two-step sequence design program for DNA nanostructure self-assembly.

PubMed

Tsutsumi, Takanobu; Asakawa, Takeshi; Kanegami, Akemi; Okada, Takao; Tahira, Tomoko; Hayashi, Kenshi

2014-01-01

DNA has been recognized as an ideal material for bottom-up construction of nanometer scale structures by self-assembly. The generation of sequences optimized for unique self-assembly (GENESUS) program reported here is a straightforward method for generating sets of strand sequences optimized for self-assembly of arbitrarily designed DNA nanostructures by a generate-candidates-and-choose-the-best strategy. A scalable procedure to prepare single-stranded DNA having arbitrary sequences is also presented. Strands for the assembly of various structures were designed and successfully constructed, validating both the program and the procedure.

Formulation procedure and spectral data for a coatings system optimally employing the high intrinsic reflectance of barium sulphate

NASA Technical Reports Server (NTRS)

Schutt, J. B.; Stromberg, E.; Shai, C. M.; Arens, J. F.

1972-01-01

The use of polyvinyl alcohol as a binder for barium sulphate does not allow the intrinsically high reflectance of this material in the near vacuum ultraviolet to be optimally employed. In an effort to better utilize this property, completely inorganic coatings systems are described, where from the intrinsically high reflectance of barium sulphate in this spectral region can be gotten. Potassium sulphate turns out to be the preferred binder. Compositions, formulating procedures, and application techniques are included. For completeness, absolute and relative reflectance data are included for intra- and intersystem comparisons.

Base norms and discrimination of generalized quantum channels

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

Jenčová, A.

2014-02-15

We introduce and study norms in the space of hermitian matrices, obtained from base norms in positively generated subspaces. These norms are closely related to discrimination of so-called generalized quantum channels, including quantum states, channels, and networks. We further introduce generalized quantum decision problems and show that the maximal average payoffs of decision procedures are again given by these norms. We also study optimality of decision procedures, in particular, we obtain a necessary and sufficient condition under which an optimal 1-tester for discrimination of quantum channels exists, such that the input state is maximally entangled.

Chemical optimization of protein extraction from sweet potato (Ipomoea batatas) peel

USDA-ARS?s Scientific Manuscript database

Proteins isolated from sweet potatoes (Ipomoea batatas) have been shown to possess antidiabetic, antioxidant, and antiproliferative properties. The objective of this study was to chemically optimize a process for extracting proteins from sweet potato peel. The extraction procedure involved mixing pe...

Cellular traction force recovery: An optimal filtering approach in two-dimensional Fourier space.

PubMed

Huang, Jianyong; Qin, Lei; Peng, Xiaoling; Zhu, Tao; Xiong, Chunyang; Zhang, Youyi; Fang, Jing

2009-08-21

Quantitative estimation of cellular traction has significant physiological and clinical implications. As an inverse problem, traction force recovery is essentially susceptible to noise in the measured displacement data. For traditional procedure of Fourier transform traction cytometry (FTTC), noise amplification is accompanied in the force reconstruction and small tractions cannot be recovered from the displacement field with low signal-noise ratio (SNR). To improve the FTTC process, we develop an optimal filtering scheme to suppress the noise in the force reconstruction procedure. In the framework of the Wiener filtering theory, four filtering parameters are introduced in two-dimensional Fourier space and their analytical expressions are derived in terms of the minimum-mean-squared-error (MMSE) optimization criterion. The optimal filtering approach is validated with simulations and experimental data associated with the adhesion of single cardiac myocyte to elastic substrate. The results indicate that the proposed method can highly enhance SNR of the recovered forces to reveal tiny tractions in cell-substrate interaction.

Parallel-vector computation for linear structural analysis and non-linear unconstrained optimization problems

NASA Technical Reports Server (NTRS)

Nguyen, D. T.; Al-Nasra, M.; Zhang, Y.; Baddourah, M. A.; Agarwal, T. K.; Storaasli, O. O.; Carmona, E. A.

1991-01-01

Several parallel-vector computational improvements to the unconstrained optimization procedure are described which speed up the structural analysis-synthesis process. A fast parallel-vector Choleski-based equation solver, pvsolve, is incorporated into the well-known SAP-4 general-purpose finite-element code. The new code, denoted PV-SAP, is tested for static structural analysis. Initial results on a four processor CRAY 2 show that using pvsolve reduces the equation solution time by a factor of 14-16 over the original SAP-4 code. In addition, parallel-vector procedures for the Golden Block Search technique and the BFGS method are developed and tested for nonlinear unconstrained optimization. A parallel version of an iterative solver and the pvsolve direct solver are incorporated into the BFGS method. Preliminary results on nonlinear unconstrained optimization test problems, using pvsolve in the analysis, show excellent parallel-vector performance indicating that these parallel-vector algorithms can be used in a new generation of finite-element based structural design/analysis-synthesis codes.

Approach for Uncertainty Propagation and Robust Design in CFD Using Sensitivity Derivatives

NASA Technical Reports Server (NTRS)

Putko, Michele M.; Newman, Perry A.; Taylor, Arthur C., III; Green, Lawrence L.

2001-01-01

This paper presents an implementation of the approximate statistical moment method for uncertainty propagation and robust optimization for a quasi 1-D Euler CFD (computational fluid dynamics) code. Given uncertainties in statistically independent, random, normally distributed input variables, a first- and second-order statistical moment matching procedure is performed to approximate the uncertainty in the CFD output. Efficient calculation of both first- and second-order sensitivity derivatives is required. In order to assess the validity of the approximations, the moments are compared with statistical moments generated through Monte Carlo simulations. The uncertainties in the CFD input variables are also incorporated into a robust optimization procedure. For this optimization, statistical moments involving first-order sensitivity derivatives appear in the objective function and system constraints. Second-order sensitivity derivatives are used in a gradient-based search to successfully execute a robust optimization. The approximate methods used throughout the analyses are found to be valid when considering robustness about input parameter mean values.

Torsional Ultrasound Sensor Optimization for Soft Tissue Characterization

PubMed Central

Melchor, Juan; Muñoz, Rafael; Rus, Guillermo

2017-01-01

Torsion mechanical waves have the capability to characterize shear stiffness moduli of soft tissue. Under this hypothesis, a computational methodology is proposed to design and optimize a piezoelectrics-based transmitter and receiver to generate and measure the response of torsional ultrasonic waves. The procedure employed is divided into two steps: (i) a finite element method (FEM) is developed to obtain a transmitted and received waveform as well as a resonance frequency of a previous geometry validated with a semi-analytical simplified model and (ii) a probabilistic optimality criteria of the design based on inverse problem from the estimation of robust probability of detection (RPOD) to maximize the detection of the pathology defined in terms of changes of shear stiffness. This study collects different options of design in two separated models, in transmission and contact, respectively. The main contribution of this work describes a framework to establish such as forward, inverse and optimization procedures to choose a set of appropriate parameters of a transducer. This methodological framework may be generalizable for other different applications. PMID:28617353

A study of optimization techniques in HDR brachytherapy for the prostate

NASA Astrophysics Data System (ADS)

Pokharel, Ghana Shyam

Several studies carried out thus far are in favor of dose escalation to the prostate gland to have better local control of the disease. But optimal way of delivery of higher doses of radiation therapy to the prostate without hurting neighboring critical structures is still debatable. In this study, we proposed that real time high dose rate (HDR) brachytherapy with highly efficient and effective optimization could be an alternative means of precise delivery of such higher doses. This approach of delivery eliminates the critical issues such as treatment setup uncertainties and target localization as in external beam radiation therapy. Likewise, dosimetry in HDR brachytherapy is not influenced by organ edema and potential source migration as in permanent interstitial implants. Moreover, the recent report of radiobiological parameters further strengthen the argument of using hypofractionated HDR brachytherapy for the management of prostate cancer. Firstly, we studied the essential features and requirements of real time HDR brachytherapy treatment planning system. Automating catheter reconstruction with fast editing tools, fast yet accurate dose engine, robust and fast optimization and evaluation engine are some of the essential requirements for such procedures. Moreover, in most of the cases we performed, treatment plan optimization took significant amount of time of overall procedure. So, making treatment plan optimization automatic or semi-automatic with sufficient speed and accuracy was the goal of the remaining part of the project. Secondly, we studied the role of optimization function and constraints in overall quality of optimized plan. We have studied the gradient based deterministic algorithm with dose volume histogram (DVH) and more conventional variance based objective functions for optimization. In this optimization strategy, the relative weight of particular objective in aggregate objective function signifies its importance with respect to other objectives. Based on our study, DVH based objective function performed better than traditional variance based objective function in creating a clinically acceptable plan when executed under identical conditions. Thirdly, we studied the multiobjective optimization strategy using both DVH and variance based objective functions. The optimization strategy was to create several Pareto optimal solutions by scanning the clinically relevant part of the Pareto front. This strategy was adopted to decouple optimization from decision such that user could select final solution from the pool of alternative solutions based on his/her clinical goals. The overall quality of treatment plan improved using this approach compared to traditional class solution approach. In fact, the final optimized plan selected using decision engine with DVH based objective was comparable to typical clinical plan created by an experienced physicist. Next, we studied the hybrid technique comprising both stochastic and deterministic algorithm to optimize both dwell positions and dwell times. The simulated annealing algorithm was used to find optimal catheter distribution and the DVH based algorithm was used to optimize 3D dose distribution for given catheter distribution. This unique treatment planning and optimization tool was capable of producing clinically acceptable highly reproducible treatment plans in clinically reasonable time. As this algorithm was able to create clinically acceptable plans within clinically reasonable time automatically, it is really appealing for real time procedures. Next, we studied the feasibility of multiobjective optimization using evolutionary algorithm for real time HDR brachytherapy for the prostate. The algorithm with properly tuned algorithm specific parameters was able to create clinically acceptable plans within clinically reasonable time. However, the algorithm was let to run just for limited number of generations not considered optimal, in general, for such algorithms. This was done to keep time window desirable for real time procedures. Therefore, it requires further study with improved conditions to realize the full potential of the algorithm.

Optimization of a point-focusing, distributed receiver solar thermal electric system

NASA Technical Reports Server (NTRS)

Pons, R. L.

1979-01-01

This paper presents an approach to optimization of a solar concept which employs solar-to-electric power conversion at the focus of parabolic dish concentrators. The optimization procedure is presented through a series of trade studies, which include the results of optical/thermal analyses and individual subsystem trades. Alternate closed-cycle and open-cycle Brayton engines and organic Rankine engines are considered to show the influence of the optimization process, and various storage techniques are evaluated, including batteries, flywheels, and hybrid-engine operation.

Development of Decision-Making Automated System for Optimal Placement of Physical Access Control System’s Elements

NASA Astrophysics Data System (ADS)

Danilova, Olga; Semenova, Zinaida

2018-04-01

The objective of this study is a detailed analysis of physical protection systems development for information resources. The optimization theory and decision-making mathematical apparatus is used to formulate correctly and create an algorithm of selection procedure for security systems optimal configuration considering the location of the secured object’s access point and zones. The result of this study is a software implementation scheme of decision-making system for optimal placement of the physical access control system’s elements.

A computerized traffic control algorithm to determine optimal traffic signal settings. Ph.D. Thesis - Toledo Univ.

NASA Technical Reports Server (NTRS)

Seldner, K.

1977-01-01

An algorithm was developed to optimally control the traffic signals at each intersection using a discrete time traffic model applicable to heavy or peak traffic. Off line optimization procedures were applied to compute the cycle splits required to minimize the lengths of the vehicle queues and delay at each intersection. The method was applied to an extensive traffic network in Toledo, Ohio. Results obtained with the derived optimal settings are compared with the control settings presently in use.

Representing and comparing protein structures as paths in three-dimensional space

PubMed Central

Zhi, Degui; Krishna, S Sri; Cao, Haibo; Pevzner, Pavel; Godzik, Adam

2006-01-01

Background Most existing formulations of protein structure comparison are based on detailed atomic level descriptions of protein structures and bypass potential insights that arise from a higher-level abstraction. Results We propose a structure comparison approach based on a simplified representation of proteins that describes its three-dimensional path by local curvature along the generalized backbone of the polypeptide. We have implemented a dynamic programming procedure that aligns curvatures of proteins by optimizing a defined sum turning angle deviation measure. Conclusion Although our procedure does not directly optimize global structural similarity as measured by RMSD, our benchmarking results indicate that it can surprisingly well recover the structural similarity defined by structure classification databases and traditional structure alignment programs. In addition, our program can recognize similarities between structures with extensive conformation changes that are beyond the ability of traditional structure alignment programs. We demonstrate the applications of procedure to several contexts of structure comparison. An implementation of our procedure, CURVE, is available as a public webserver. PMID:17052359

Optimization of Skill Retention in the U. S. Army through Initial Training Analysis and Design: Skill Sustainment Exercises. Volume 3.

DTIC Science & Technology

1983-05-01

Firing data cards. PROCEDURES I. Prior to live fire exercises all firers must be oriented on range procedures. 2. Preparatory marksmanship training...Ordnance detail. 2. Range safety officer. 7. Medical personnel. 3. Firing line safety NCOs. 8. Control tower operators. i 4. Scorer (I per firer ). 9. Pit...phones and wire (for PIT commo). PROCEDURES I. Prior to live fire exercises, all firers must be oriented on range procedures. 2. Scorers are responsible

Towards Robust Designs Via Multiple-Objective Optimization Methods

NASA Technical Reports Server (NTRS)

Man Mohan, Rai

2006-01-01

Fabricating and operating complex systems involves dealing with uncertainty in the relevant variables. In the case of aircraft, flow conditions are subject to change during operation. Efficiency and engine noise may be different from the expected values because of manufacturing tolerances and normal wear and tear. Engine components may have a shorter life than expected because of manufacturing tolerances. In spite of the important effect of operating- and manufacturing-uncertainty on the performance and expected life of the component or system, traditional aerodynamic shape optimization has focused on obtaining the best design given a set of deterministic flow conditions. Clearly it is important to both maintain near-optimal performance levels at off-design operating conditions, and, ensure that performance does not degrade appreciably when the component shape differs from the optimal shape due to manufacturing tolerances and normal wear and tear. These requirements naturally lead to the idea of robust optimal design wherein the concept of robustness to various perturbations is built into the design optimization procedure. The basic ideas involved in robust optimal design will be included in this lecture. The imposition of the additional requirement of robustness results in a multiple-objective optimization problem requiring appropriate solution procedures. Typically the costs associated with multiple-objective optimization are substantial. Therefore efficient multiple-objective optimization procedures are crucial to the rapid deployment of the principles of robust design in industry. Hence the companion set of lecture notes (Single- and Multiple-Objective Optimization with Differential Evolution and Neural Networks ) deals with methodology for solving multiple-objective Optimization problems efficiently, reliably and with little user intervention. Applications of the methodologies presented in the companion lecture to robust design will be included here. The evolutionary method (DE) is first used to solve a relatively difficult problem in extended surface heat transfer wherein optimal fin geometries are obtained for different safe operating base temperatures. The objective of maximizing the safe operating base temperature range is in direct conflict with the objective of maximizing fin heat transfer. This problem is a good example of achieving robustness in the context of changing operating conditions. The evolutionary method is then used to design a turbine airfoil; the two objectives being reduced sensitivity of the pressure distribution to small changes in the airfoil shape and the maximization of the trailing edge wedge angle with the consequent increase in airfoil thickness and strength. This is a relevant example of achieving robustness to manufacturing tolerances and wear and tear in the presence of other objectives.

Gaussian process regression for geometry optimization

NASA Astrophysics Data System (ADS)

Denzel, Alexander; Kästner, Johannes

2018-03-01

We implemented a geometry optimizer based on Gaussian process regression (GPR) to find minimum structures on potential energy surfaces. We tested both a two times differentiable form of the Matérn kernel and the squared exponential kernel. The Matérn kernel performs much better. We give a detailed description of the optimization procedures. These include overshooting the step resulting from GPR in order to obtain a higher degree of interpolation vs. extrapolation. In a benchmark against the Limited-memory Broyden-Fletcher-Goldfarb-Shanno optimizer of the DL-FIND library on 26 test systems, we found the new optimizer to generally reduce the number of required optimization steps.

Reserve design to maximize species persistence

Treesearch

Robert G. Haight; Laurel E. Travis

2008-01-01

We develop a reserve design strategy to maximize the probability of species persistence predicted by a stochastic, individual-based, metapopulation model. Because the population model does not fit exact optimization procedures, our strategy involves deriving promising solutions from theory, obtaining promising solutions from a simulation optimization heuristic, and...

Optimal decision making on the basis of evidence represented in spike trains.

PubMed

Zhang, Jiaxiang; Bogacz, Rafal

2010-05-01

Experimental data indicate that perceptual decision making involves integration of sensory evidence in certain cortical areas. Theoretical studies have proposed that the computation in neural decision circuits approximates statistically optimal decision procedures (e.g., sequential probability ratio test) that maximize the reward rate in sequential choice tasks. However, these previous studies assumed that the sensory evidence was represented by continuous values from gaussian distributions with the same variance across alternatives. In this article, we make a more realistic assumption that sensory evidence is represented in spike trains described by the Poisson processes, which naturally satisfy the mean-variance relationship observed in sensory neurons. We show that for such a representation, the neural circuits involving cortical integrators and basal ganglia can approximate the optimal decision procedures for two and multiple alternative choice tasks.

Interactive Reference Point Procedure Based on the Conic Scalarizing Function

PubMed Central

2014-01-01

In multiobjective optimization methods, multiple conflicting objectives are typically converted into a single objective optimization problem with the help of scalarizing functions. The conic scalarizing function is a general characterization of Benson proper efficient solutions of non-convex multiobjective problems in terms of saddle points of scalar Lagrangian functions. This approach preserves convexity. The conic scalarizing function, as a part of a posteriori or a priori methods, has successfully been applied to several real-life problems. In this paper, we propose a conic scalarizing function based interactive reference point procedure where the decision maker actively takes part in the solution process and directs the search according to her or his preferences. An algorithmic framework for the interactive solution of multiple objective optimization problems is presented and is utilized for solving some illustrative examples. PMID:24723795

Aerodynamic shape optimization of a HSCT type configuration with improved surface definition

NASA Technical Reports Server (NTRS)

Thomas, Almuttil M.; Tiwari, Surendra N.

1994-01-01

Two distinct parametrization procedures of generating free-form surfaces to represent aerospace vehicles are presented. The first procedure is the representation using spline functions such as nonuniform rational b-splines (NURBS) and the second is a novel (geometrical) parametrization using solutions to a suitably chosen partial differential equation. The main idea is to develop a surface which is more versatile and can be used in an optimization process. Unstructured volume grid is generated by an advancing front algorithm and solutions obtained using an Euler solver. Grid sensitivity with respect to surface design parameters and aerodynamic sensitivity coefficients based on potential flow is obtained using an automatic differentiator precompiler software tool. Aerodynamic shape optimization of a complete aircraft with twenty four design variables is performed. High speed civil transport aircraft (HSCT) configurations are targeted to demonstrate the process.

Capabilities and applications of the Program to Optimize Simulated Trajectories (POST). Program summary document

NASA Technical Reports Server (NTRS)

Brauer, G. L.; Cornick, D. E.; Stevenson, R.

1977-01-01

The capabilities and applications of the three-degree-of-freedom (3DOF) version and the six-degree-of-freedom (6DOF) version of the Program to Optimize Simulated Trajectories (POST) are summarized. The document supplements the detailed program manuals by providing additional information that motivates and clarifies basic capabilities, input procedures, applications and computer requirements of these programs. The information will enable prospective users to evaluate the programs, and to determine if they are applicable to their problems. Enough information is given to enable managerial personnel to evaluate the capabilities of the programs and describes the POST structure, formulation, input and output procedures, sample cases, and computer requirements. The report also provides answers to basic questions concerning planet and vehicle modeling, simulation accuracy, optimization capabilities, and general input rules. Several sample cases are presented.

Design optimization of an axial-field eddy-current magnetic coupling based on magneto-thermal analytical model

NASA Astrophysics Data System (ADS)

Fontchastagner, Julien; Lubin, Thierry; Mezani, Smaïl; Takorabet, Noureddine

2018-03-01

This paper presents a design optimization of an axial-flux eddy-current magnetic coupling. The design procedure is based on a torque formula derived from a 3D analytical model and a population algorithm method. The main objective of this paper is to determine the best design in terms of magnets volume in order to transmit a torque between two movers, while ensuring a low slip speed and a good efficiency. The torque formula is very accurate and computationally efficient, and is valid for any slip speed values. Nevertheless, in order to solve more realistic problems, and then, take into account the thermal effects on the torque value, a thermal model based on convection heat transfer coefficients is also established and used in the design optimization procedure. Results show the effectiveness of the proposed methodology.

Team-based Service Delivery for Students with Disabilities: Practice Options and Guidelines for Success.

ERIC Educational Resources Information Center

Ogletree, Billy T.; Bull, Jeannette; Drew, Ruby; Lunnen, Karen Y.

2001-01-01

This article reviews the assessment procedures, treatment procedures, and the advantages and disadvantages of three professional-family team models: multidisciplinary teams, interdisciplinary teams, and transdisciplinary teams. Guidelines for optimal team participation are provided. The importance of mission statements, communication, trust,…

Electro-thermal battery model identification for automotive applications

NASA Astrophysics Data System (ADS)

Hu, Y.; Yurkovich, S.; Guezennec, Y.; Yurkovich, B. J.

This paper describes a model identification procedure for identifying an electro-thermal model of lithium ion batteries used in automotive applications. The dynamic model structure adopted is based on an equivalent circuit model whose parameters are scheduled on the state-of-charge, temperature, and current direction. Linear spline functions are used as the functional form for the parametric dependence. The model identified in this way is valid inside a large range of temperatures and state-of-charge, so that the resulting model can be used for automotive applications such as on-board estimation of the state-of-charge and state-of-health. The model coefficients are identified using a multiple step genetic algorithm based optimization procedure designed for large scale optimization problems. The validity of the procedure is demonstrated experimentally for an A123 lithium ion iron-phosphate battery.

Computation of output feedback gains for linear stochastic systems using the Zangnill-Powell Method

NASA Technical Reports Server (NTRS)

Kaufman, H.

1975-01-01

Because conventional optimal linear regulator theory results in a controller which requires the capability of measuring and/or estimating the entire state vector, it is of interest to consider procedures for computing controls which are restricted to be linear feedback functions of a lower dimensional output vector and which take into account the presence of measurement noise and process uncertainty. To this effect a stochastic linear model has been developed that accounts for process parameter and initial uncertainty, measurement noise, and a restricted number of measurable outputs. Optimization with respect to the corresponding output feedback gains was then performed for both finite and infinite time performance indices without gradient computation by using Zangwill's modification of a procedure originally proposed by Powell. Results using a seventh order process show the proposed procedures to be very effective.

Teleportation of squeezing: Optimization using non-Gaussian resources

NASA Astrophysics Data System (ADS)

Dell'Anno, Fabio; de Siena, Silvio; Adesso, Gerardo; Illuminati, Fabrizio

2010-12-01

We study the continuous-variable quantum teleportation of states, statistical moments of observables, and scale parameters such as squeezing. We investigate the problem both in ideal and imperfect Vaidman-Braunstein-Kimble protocol setups. We show how the teleportation fidelity is maximized and the difference between output and input variances is minimized by using suitably optimized entangled resources. Specifically, we consider the teleportation of coherent squeezed states, exploiting squeezed Bell states as entangled resources. This class of non-Gaussian states, introduced by Illuminati and co-workers [F. Dell’Anno, S. De Siena, L. Albano, and F. Illuminati, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.76.022301 76, 022301 (2007); F. Dell’Anno, S. De Siena, and F. Illuminati, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.81.012333 81, 012333 (2010)], includes photon-added and photon-subtracted squeezed states as special cases. At variance with the case of entangled Gaussian resources, the use of entangled non-Gaussian squeezed Bell resources allows one to choose different optimization procedures that lead to inequivalent results. Performing two independent optimization procedures, one can either maximize the state teleportation fidelity, or minimize the difference between input and output quadrature variances. The two different procedures are compared depending on the degrees of displacement and squeezing of the input states and on the working conditions in ideal and nonideal setups.

Continuous Shape Estimation of Continuum Robots Using X-ray Images

PubMed Central

Lobaton, Edgar J.; Fu, Jinghua; Torres, Luis G.; Alterovitz, Ron

2015-01-01

We present a new method for continuously and accurately estimating the shape of a continuum robot during a medical procedure using a small number of X-ray projection images (e.g., radiographs or fluoroscopy images). Continuum robots have curvilinear structure, enabling them to maneuver through constrained spaces by bending around obstacles. Accurately estimating the robot’s shape continuously over time is crucial for the success of procedures that require avoidance of anatomical obstacles and sensitive tissues. Online shape estimation of a continuum robot is complicated by uncertainty in its kinematic model, movement of the robot during the procedure, noise in X-ray images, and the clinical need to minimize the number of X-ray images acquired. Our new method integrates kinematics models of the robot with data extracted from an optimally selected set of X-ray projection images. Our method represents the shape of the continuum robot over time as a deformable surface which can be described as a linear combination of time and space basis functions. We take advantage of probabilistic priors and numeric optimization to select optimal camera configurations, thus minimizing the expected shape estimation error. We evaluate our method using simulated concentric tube robot procedures and demonstrate that obtaining between 3 and 10 images from viewpoints selected by our method enables online shape estimation with errors significantly lower than using the kinematic model alone or using randomly spaced viewpoints. PMID:26279960

Continuous Shape Estimation of Continuum Robots Using X-ray Images.

PubMed

Lobaton, Edgar J; Fu, Jinghua; Torres, Luis G; Alterovitz, Ron

2013-05-06

We present a new method for continuously and accurately estimating the shape of a continuum robot during a medical procedure using a small number of X-ray projection images (e.g., radiographs or fluoroscopy images). Continuum robots have curvilinear structure, enabling them to maneuver through constrained spaces by bending around obstacles. Accurately estimating the robot's shape continuously over time is crucial for the success of procedures that require avoidance of anatomical obstacles and sensitive tissues. Online shape estimation of a continuum robot is complicated by uncertainty in its kinematic model, movement of the robot during the procedure, noise in X-ray images, and the clinical need to minimize the number of X-ray images acquired. Our new method integrates kinematics models of the robot with data extracted from an optimally selected set of X-ray projection images. Our method represents the shape of the continuum robot over time as a deformable surface which can be described as a linear combination of time and space basis functions. We take advantage of probabilistic priors and numeric optimization to select optimal camera configurations, thus minimizing the expected shape estimation error. We evaluate our method using simulated concentric tube robot procedures and demonstrate that obtaining between 3 and 10 images from viewpoints selected by our method enables online shape estimation with errors significantly lower than using the kinematic model alone or using randomly spaced viewpoints.

Windprofiler optimization using digital deconvolution procedures

NASA Astrophysics Data System (ADS)

Hocking, W. K.; Hocking, A.; Hocking, D. G.; Garbanzo-Salas, M.

2014-10-01

Digital improvements to data acquisition procedures used for windprofiler radars have the potential for improving the height coverage at optimum resolution, and permit improved height resolution. A few newer systems already use this capability. Real-time deconvolution procedures offer even further optimization, and this has not been effectively employed in recent years. In this paper we demonstrate the advantages of combining these features, with particular emphasis on the advantages of real-time deconvolution. Using several multi-core CPUs, we have been able to achieve speeds of up to 40 GHz from a standard commercial motherboard, allowing data to be digitized and processed without the need for any type of hardware except for a transmitter (and associated drivers), a receiver and a digitizer. No Digital Signal Processor chips are needed, allowing great flexibility with analysis algorithms. By using deconvolution procedures, we have then been able to not only optimize height resolution, but also have been able to make advances in dealing with spectral contaminants like ground echoes and other near-zero-Hz spectral contamination. Our results also demonstrate the ability to produce fine-resolution measurements, revealing small-scale structures within the backscattered echoes that were previously not possible to see. Resolutions of 30 m are possible for VHF radars. Furthermore, our deconvolution technique allows the removal of range-aliasing effects in real time, a major bonus in many instances. Results are shown using new radars in Canada and Costa Rica.

Aero/structural tailoring of engine blades (AERO/STAEBL)

NASA Technical Reports Server (NTRS)

Brown, K. W.

1988-01-01

This report describes the Aero/Structural Tailoring of Engine Blades (AERO/STAEBL) program, which is a computer code used to perform engine fan and compressor blade aero/structural numerical optimizations. These optimizations seek a blade design of minimum operating cost that satisfies realistic blade design constraints. This report documents the overall program (i.e., input, optimization procedures, approximate analyses) and also provides a detailed description of the validation test cases.

Impacts of Intelligent Automated Quality Control on a Small Animal APD-Based Digital PET Scanner

NASA Astrophysics Data System (ADS)

Charest, Jonathan; Beaudoin, Jean-François; Bergeron, Mélanie; Cadorette, Jules; Arpin, Louis; Lecomte, Roger; Brunet, Charles-Antoine; Fontaine, Réjean

2016-10-01

Stable system performance is mandatory to warrant the accuracy and reliability of biological results relying on small animal positron emission tomography (PET) imaging studies. This simple requirement sets the ground for imposing routine quality control (QC) procedures to keep PET scanners at a reliable optimal performance level. However, such procedures can become burdensome to implement for scanner operators, especially taking into account the increasing number of data acquisition channels in newer generation PET scanners. In systems using pixel detectors to achieve enhanced spatial resolution and contrast-to-noise ratio (CNR), the QC workload rapidly increases to unmanageable levels due to the number of independent channels involved. An artificial intelligence based QC system, referred to as Scanner Intelligent Diagnosis for Optimal Performance (SIDOP), was proposed to help reducing the QC workload by performing automatic channel fault detection and diagnosis. SIDOP consists of four high-level modules that employ machine learning methods to perform their tasks: Parameter Extraction, Channel Fault Detection, Fault Prioritization, and Fault Diagnosis. Ultimately, SIDOP submits a prioritized faulty channel list to the operator and proposes actions to correct them. To validate that SIDOP can perform QC procedures adequately, it was deployed on a LabPET™ scanner and multiple performance metrics were extracted. After multiple corrections on sub-optimal scanner settings, a 8.5% (with a 95% confidence interval (CI) of [7.6, 9.3]) improvement in the CNR, a 17.0% (CI: [15.3, 18.7]) decrease of the uniformity percentage standard deviation, and a 6.8% gain in global sensitivity were observed. These results confirm that SIDOP can indeed be of assistance in performing QC procedures and restore performance to optimal figures.

The Optimization Based Dynamic and Cyclic Working Strategies for Rechargeable Wireless Sensor Networks with Multiple Base Stations and Wireless Energy Transfer Devices

PubMed Central

Ding, Xu; Han, Jianghong; Shi, Lei

2015-01-01

In this paper, the optimal working schemes for wireless sensor networks with multiple base stations and wireless energy transfer devices are proposed. The wireless energy transfer devices also work as data gatherers while charging sensor nodes. The wireless sensor network is firstly divided into sub networks according to the concept of Voronoi diagram. Then, the entire energy replenishing procedure is split into the pre-normal and normal energy replenishing stages. With the objective of maximizing the sojourn time ratio of the wireless energy transfer device, a continuous time optimization problem for the normal energy replenishing cycle is formed according to constraints with which sensor nodes and wireless energy transfer devices should comply. Later on, the continuous time optimization problem is reshaped into a discrete multi-phased optimization problem, which yields the identical optimality. After linearizing it, we obtain a linear programming problem that can be solved efficiently. The working strategies of both sensor nodes and wireless energy transfer devices in the pre-normal replenishing stage are also discussed in this paper. The intensive simulations exhibit the dynamic and cyclic working schemes for the entire energy replenishing procedure. Additionally, a way of eliminating “bottleneck” sensor nodes is also developed in this paper. PMID:25785305

The optimization based dynamic and cyclic working strategies for rechargeable wireless sensor networks with multiple base stations and wireless energy transfer devices.

PubMed

Ding, Xu; Han, Jianghong; Shi, Lei

2015-03-16

In this paper, the optimal working schemes for wireless sensor networks with multiple base stations and wireless energy transfer devices are proposed. The wireless energy transfer devices also work as data gatherers while charging sensor nodes. The wireless sensor network is firstly divided into sub networks according to the concept of Voronoi diagram. Then, the entire energy replenishing procedure is split into the pre-normal and normal energy replenishing stages. With the objective of maximizing the sojourn time ratio of the wireless energy transfer device, a continuous time optimization problem for the normal energy replenishing cycle is formed according to constraints with which sensor nodes and wireless energy transfer devices should comply. Later on, the continuous time optimization problem is reshaped into a discrete multi-phased optimization problem, which yields the identical optimality. After linearizing it, we obtain a linear programming problem that can be solved efficiently. The working strategies of both sensor nodes and wireless energy transfer devices in the pre-normal replenishing stage are also discussed in this paper. The intensive simulations exhibit the dynamic and cyclic working schemes for the entire energy replenishing procedure. Additionally, a way of eliminating "bottleneck" sensor nodes is also developed in this paper.

Multidisciplinary optimization in aircraft design using analytic technology models

NASA Technical Reports Server (NTRS)

Malone, Brett; Mason, W. H.

1991-01-01

An approach to multidisciplinary optimization is presented which combines the Global Sensitivity Equation method, parametric optimization, and analytic technology models. The result is a powerful yet simple procedure for identifying key design issues. It can be used both to investigate technology integration issues very early in the design cycle, and to establish the information flow framework between disciplines for use in multidisciplinary optimization projects using much more computational intense representations of each technology. To illustrate the approach, an examination of the optimization of a short takeoff heavy transport aircraft is presented for numerous combinations of performance and technology constraints.

AIAA/USAF/NASA/OAI Symposium on Multidisciplinary Analysis and Optimization, 4th, Cleveland, OH, Sept. 21-23, 1992, Technical Papers. Pts. 1 & 2

NASA Technical Reports Server (NTRS)

1992-01-01

The papers presented at the symposium cover aerodynamics, design applications, propulsion systems, high-speed flight, structures, controls, sensitivity analysis, optimization algorithms, and space structures applications. Other topics include helicopter rotor design, artificial intelligence/neural nets, and computational aspects of optimization. Papers are included on flutter calculations for a system with interacting nonlinearities, optimization in solid rocket booster application, improving the efficiency of aerodynamic shape optimization procedures, nonlinear control theory, and probabilistic structural analysis of space truss structures for nonuniform thermal environmental effects.

An iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions, Addendum

NASA Technical Reports Server (NTRS)

Peters, B. C., Jr.; Walker, H. F.

1975-01-01

New results and insights concerning a previously published iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions were discussed. It was shown that the procedure converges locally to the consistent maximum likelihood estimate as long as a specified parameter is bounded between two limits. Bound values were given to yield optimal local convergence.

The appropriateness of use of percutaneous transluminal coronary angioplasty in Spain.

PubMed

Aguilar, M D; Fitch, K; Lázaro, P; Bernstein, S J

2001-05-01

The rapid increase in the number of percutaneous transluminal coronary angioplasty (PTCA) procedures performed in Spain in recent years raises questions about how appropriately this procedure is being used. To examine this issue, we studied the appropriateness of use of PTCA in Spanish patients and factors associated with inappropriate use. We applied criteria for the appropriate use of PTCA developed by an expert panel of Spanish cardiologists and cardiovascular surgeons to a random sample of 1913 patients undergoing PTCA in Spain in 1997. The patients were selected through a two-step sampling process, stratifying by hospital type (public/private) and volume of procedures (low/medium/high). We examined the association between inappropriate use of PTCA and different clinical and sociodemographic factors. Overall, 46% of the PTCA procedures were appropriate, 31% were uncertain and 22% were inappropriate. Two factors contributing to inappropriate use were patients' receipt of less than optimal medical therapy and their failure to undergo stress testing. Institutional type and volume of procedures were not significantly related with inappropriate use. One of every five PTCA procedures in Spain is done for inappropriate reasons. Assuring that patients receive optimal medical therapy and undergo stress testing when indicated could contribute to more appropriate use of PTCA.

Optimization of the Inverse Algorithm for Estimating the Optical Properties of Biological Materials Using Spatially-resolved Diffuse Reflectance Technique

USDA-ARS?s Scientific Manuscript database

Determination of the optical properties from intact biological materials based on diffusion approximation theory is a complicated inverse problem, and it requires proper implementation of inverse algorithm, instrumentation, and experiment. This work was aimed at optimizing the procedure of estimatin...

Optimizing How We Teach Research Methods

ERIC Educational Resources Information Center

Cvancara, Kristen E.

2017-01-01

Courses: Research Methods (undergraduate or graduate level). Objective: The aim of this exercise is to optimize the ability for students to integrate an understanding of various methodologies across research paradigms within a 15-week semester, including a review of procedural steps and experiential learning activities to practice each method, a…

Simultaneous Optimization of Decisions Using a Linear Utility Function.

ERIC Educational Resources Information Center

Vos, Hans J.

1990-01-01

An approach is presented to simultaneously optimize decision rules for combinations of elementary decisions through a framework derived from Bayesian decision theory. The developed linear utility model for selection-mastery decisions was applied to a sample of 43 first year medical students to illustrate the procedure. (SLD)

Optimizing Your K-5 Engineering Design Challenge

ERIC Educational Resources Information Center

Coppola, Matthew Perkins; Merz, Alice H.

2017-01-01

Today, elementary school teachers continue to revisit old lessons and seek out new ones, especially in engineering. Optimization is the process by which an existing product or procedure is revised and refined. Drawn from the authors' experiences working directly with students in grades K-5 and their teachers and preservice teachers, the…

Encapsulated Multifunction Corrosion Inhibitive Primer.

DTIC Science & Technology

1983-11-01

Optimization of Microcapsule Preparation ...................... 162 24 Optimized Procedure for Polyurea Microencapsulation ................... 166 25... microcapsules , which suggests that a nearly quantitative yield of microencapsulated inhibitor was achieved. The burst ratio is defined as the conductivity after...effectiveness of the microencapsulation approach in achieving sustained release. 4. Loading Determination of Polyurea Microcapsules In studies relating

The mean-square error optimal linear discriminant function and its application to incomplete data vectors

NASA Technical Reports Server (NTRS)

Walker, H. F.

1979-01-01

In many pattern recognition problems, data vectors are classified although one or more of the data vector elements are missing. This problem occurs in remote sensing when the ground is obscured by clouds. Optimal linear discrimination procedures for classifying imcomplete data vectors are discussed.

An efficient and accurate solution methodology for bilevel multi-objective programming problems using a hybrid evolutionary-local-search algorithm.

PubMed

Deb, Kalyanmoy; Sinha, Ankur

2010-01-01

Bilevel optimization problems involve two optimization tasks (upper and lower level), in which every feasible upper level solution must correspond to an optimal solution to a lower level optimization problem. These problems commonly appear in many practical problem solving tasks including optimal control, process optimization, game-playing strategy developments, transportation problems, and others. However, they are commonly converted into a single level optimization problem by using an approximate solution procedure to replace the lower level optimization task. Although there exist a number of theoretical, numerical, and evolutionary optimization studies involving single-objective bilevel programming problems, not many studies look at the context of multiple conflicting objectives in each level of a bilevel programming problem. In this paper, we address certain intricate issues related to solving multi-objective bilevel programming problems, present challenging test problems, and propose a viable and hybrid evolutionary-cum-local-search based algorithm as a solution methodology. The hybrid approach performs better than a number of existing methodologies and scales well up to 40-variable difficult test problems used in this study. The population sizing and termination criteria are made self-adaptive, so that no additional parameters need to be supplied by the user. The study indicates a clear niche of evolutionary algorithms in solving such difficult problems of practical importance compared to their usual solution by a computationally expensive nested procedure. The study opens up many issues related to multi-objective bilevel programming and hopefully this study will motivate EMO and other researchers to pay more attention to this important and difficult problem solving activity.

Evaluation of laser cutting process with auxiliary gas pressure by soft computing approach

NASA Astrophysics Data System (ADS)

Lazov, Lyubomir; Nikolić, Vlastimir; Jovic, Srdjan; Milovančević, Miloš; Deneva, Heristina; Teirumenieka, Erika; Arsic, Nebojsa

2018-06-01

Evaluation of the optimal laser cutting parameters is very important for the high cut quality. This is highly nonlinear process with different parameters which is the main challenge in the optimization process. Data mining methodology is one of most versatile method which can be used laser cutting process optimization. Support vector regression (SVR) procedure is implemented since it is a versatile and robust technique for very nonlinear data regression. The goal in this study was to determine the optimal laser cutting parameters to ensure robust condition for minimization of average surface roughness. Three cutting parameters, the cutting speed, the laser power, and the assist gas pressure, were used in the investigation. As a laser type TruLaser 1030 technological system was used. Nitrogen as an assisted gas was used in the laser cutting process. As the data mining method, support vector regression procedure was used. Data mining prediction accuracy was very high according the coefficient (R2) of determination and root mean square error (RMSE): R2 = 0.9975 and RMSE = 0.0337. Therefore the data mining approach could be used effectively for determination of the optimal conditions of the laser cutting process.

Estimating cellular parameters through optimization procedures: elementary principles and applications.

PubMed

Kimura, Akatsuki; Celani, Antonio; Nagao, Hiromichi; Stasevich, Timothy; Nakamura, Kazuyuki

2015-01-01

Construction of quantitative models is a primary goal of quantitative biology, which aims to understand cellular and organismal phenomena in a quantitative manner. In this article, we introduce optimization procedures to search for parameters in a quantitative model that can reproduce experimental data. The aim of optimization is to minimize the sum of squared errors (SSE) in a prediction or to maximize likelihood. A (local) maximum of likelihood or (local) minimum of the SSE can efficiently be identified using gradient approaches. Addition of a stochastic process enables us to identify the global maximum/minimum without becoming trapped in local maxima/minima. Sampling approaches take advantage of increasing computational power to test numerous sets of parameters in order to determine the optimum set. By combining Bayesian inference with gradient or sampling approaches, we can estimate both the optimum parameters and the form of the likelihood function related to the parameters. Finally, we introduce four examples of research that utilize parameter optimization to obtain biological insights from quantified data: transcriptional regulation, bacterial chemotaxis, morphogenesis, and cell cycle regulation. With practical knowledge of parameter optimization, cell and developmental biologists can develop realistic models that reproduce their observations and thus, obtain mechanistic insights into phenomena of interest.

Computerized optimization of multiple isocentres in stereotactic convergent beam irradiation

NASA Astrophysics Data System (ADS)

Treuer, U.; Treuer, H.; Hoevels, M.; Müller, R. P.; Sturm, V.

1998-01-01

A method for the fully computerized determination and optimization of positions of target points and collimator sizes in convergent beam irradiation is presented. In conventional interactive trial and error methods, which are very time consuming, the treatment parameters are chosen according to the operator's experience and improved successively. This time is reduced significantly by the use of a computerized procedure. After the definition of target volume and organs at risk in the CT or MR scans, an initial configuration is created automatically. In the next step the target point positions and collimator diameters are optimized by the program. The aim of the optimization is to find a configuration for which a prescribed dose at the target surface is approximated as close as possible. At the same time dose peaks inside the target volume are minimized and organs at risk and tissue surrounding the target are spared. To enhance the speed of the optimization a fast method for approximate dose calculation in convergent beam irradiation is used. A possible application of the method for calculating the leaf positions when irradiating with a micromultileaf collimator is briefly discussed. The success of the procedure has been demonstrated for several clinical cases with up to six target points.

Class Identification Efficacy in Piecewise GMM with Unknown Turning Points

ERIC Educational Resources Information Center

Ning, Ling; Luo, Wen

2018-01-01

Piecewise GMM with unknown turning points is a new procedure to investigate heterogeneous subpopulations' growth trajectories consisting of distinct developmental phases. Unlike the conventional PGMM, which relies on theory or experiment design to specify turning points a priori, the new procedure allows for an optimal location of turning points…

40 CFR 91.316 - Hydrocarbon analyzer calibration.

Code of Federal Regulations, 2010 CFR

2010-07-01

... operating adjustment using the appropriate fuel (see § 91.312) and purified synthetic air or zero-grade nitrogen. (2) One of the following procedures is required for FID or HFID optimization: (i) The procedure...) Initial and periodic calibration. Prior to introduction into service and monthly thereafter, or within one...

Optimizing the extraction, storage, and analysis of airborne endotoxins

USDA-ARS?s Scientific Manuscript database

While the Limulus amebocyte lysate (LAL) assay is part of most procedures to assess airborne endotoxin exposure, there is no universally agreed upon standard procedure. The purpose of this study was to fill in additional knowledge gaps with respect to the extraction, storage, and analysis of endotox...

Procedures for Empirical Determination of En-Route Criterion Levels.

ERIC Educational Resources Information Center

Moncrief, Michael H.

En-route Criterion Levels (ECLs) are defined as decision rules for predicting pupil readiness to advance through an instructional sequence. This study investigated the validity of present ELCs in an individualized mathematics program and tested procedures for empirically determining optimal ECLs. Retest scores and subsequent progress were…

Distributed Cooperative Optimal Control for Multiagent Systems on Directed Graphs: An Inverse Optimal Approach.

PubMed

Zhang, Huaguang; Feng, Tao; Yang, Guang-Hong; Liang, Hongjing

2015-07-01

In this paper, the inverse optimal approach is employed to design distributed consensus protocols that guarantee consensus and global optimality with respect to some quadratic performance indexes for identical linear systems on a directed graph. The inverse optimal theory is developed by introducing the notion of partial stability. As a result, the necessary and sufficient conditions for inverse optimality are proposed. By means of the developed inverse optimal theory, the necessary and sufficient conditions are established for globally optimal cooperative control problems on directed graphs. Basic optimal cooperative design procedures are given based on asymptotic properties of the resulting optimal distributed consensus protocols, and the multiagent systems can reach desired consensus performance (convergence rate and damping rate) asymptotically. Finally, two examples are given to illustrate the effectiveness of the proposed methods.

In Vitro Simulation and Validation of the Circulation with Congenital Heart Defects

PubMed Central

Figliola, Richard S.; Giardini, Alessandro; Conover, Tim; Camp, Tiffany A.; Biglino, Giovanni; Chiulli, John; Hsia, Tain-Yen

2010-01-01

Despite the recent advances in computational modeling, experimental simulation of the circulation with congenital heart defect using mock flow circuits remains an important tool for device testing, and for detailing the probable flow consequences resulting from surgical and interventional corrections. Validated mock circuits can be applied to qualify the results from novel computational models. New mathematical tools, coupled with advanced clinical imaging methods, allow for improved assessment of experimental circuit performance relative to human function, as well as the potential for patient-specific adaptation. In this review, we address the development of three in vitro mock circuits specific for studies of congenital heart defects. Performance of an in vitro right heart circulation circuit through a series of verification and validation exercises is described, including correlations with animal studies, and quantifying the effects of circuit inertiance on test results. We present our experience in the design of mock circuits suitable for investigations of the characteristics of the Fontan circulation. We use one such mock circuit to evaluate the accuracy of Doppler predictions in the presence of aortic coarctation. PMID:21218147

Soft computing modelling of moisture sorption isotherms of milk-foxtail millet powder and determination of thermodynamic properties.

PubMed

Simha, H V Vikram; Pushpadass, Heartwin A; Franklin, Magdaline Eljeeva Emerald; Kumar, P Arun; Manimala, K

2016-06-01

Moisture sorption isotherms of spray-dried milk-foxtail millet powder were determined at 10, 25 and 40 °C. Sorption data was fitted using classical and soft-computing approaches. The isotherms were of type II, and equilibrium moisture content (EMC) was temperature dependent. The BET monolayer moisture content decreased from 3.30 to 2.67 % as temperature increased from 10 to 40 °C. Amongst the classical models, Ferro-Fontan gave the best fit of EMC-aw data. However, the Sugeno-type adaptive neuro-fuzzy inference system (ANFIS) with generalized bell-shaped membership function performed better than artificial neural network and classical models with RMSE as low as 0.0099. The isosteric heat of sorption decreased from 150.32 kJ mol(-1) at 1 % moisture content to 44.11 kJ mol(-1) at 15 % moisture. The enthalpy-entropy compensation theory was validated, and the isokinetic and harmonic mean temperatures were determined as 333.1 and 297.5 K, respectively.

Acrylamide in potato crisps prepared from 20 UK-grown varieties: Effects of variety and tuber storage time

PubMed Central

Elmore, J. Stephen; Briddon, Adrian; Dodson, Andrew T.; Muttucumaru, Nira; Halford, Nigel G.; Mottram, Donald S.

2015-01-01

Twenty varieties of field-grown potato were stored for 2 months and 6 months at 8 °C. Mean acrylamide contents in crisps prepared from all varieties at both storage times ranged from 131 μg/kg in Verdi to 5360 μg/kg in Pentland Dell. In contrast to previous studies, the longer storage period did not affect acrylamide formation significantly for most varieties, the exceptions being Innovator, where acrylamide formation increased, and Saturna, where it decreased. Four of the five varieties designated as suitable for crisping produced crisps with acrylamide levels below the European Commission indicative value of 1000 μg/kg (Saturna, Lady Rosetta, Lady Claire, and Verdi); the exception was Hermes. Two varieties more often used for French fries, Markies and Fontane, also produced crisps with less than 1000 μg/kg acrylamide. Correlations between acrylamide, its precursors and crisp colour are described, and the implications of the results for production of potato crisps are discussed. PMID:25842300

MATLAB-implemented estimation procedure for model-based assessment of hepatic insulin degradation from standard intravenous glucose tolerance test data.

PubMed

Di Nardo, Francesco; Mengoni, Michele; Morettini, Micaela

2013-05-01

Present study provides a novel MATLAB-based parameter estimation procedure for individual assessment of hepatic insulin degradation (HID) process from standard frequently-sampled intravenous glucose tolerance test (FSIGTT) data. Direct access to the source code, offered by MATLAB, enabled us to design an optimization procedure based on the alternating use of Gauss-Newton's and Levenberg-Marquardt's algorithms, which assures the full convergence of the process and the containment of computational time. Reliability was tested by direct comparison with the application, in eighteen non-diabetic subjects, of well-known kinetic analysis software package SAAM II, and by application on different data. Agreement between MATLAB and SAAM II was warranted by intraclass correlation coefficients ≥0.73; no significant differences between corresponding mean parameter estimates and prediction of HID rate; and consistent residual analysis. Moreover, MATLAB optimization procedure resulted in a significant 51% reduction of CV% for the worst-estimated parameter by SAAM II and in maintaining all model-parameter CV% <20%. In conclusion, our MATLAB-based procedure was suggested as a suitable tool for the individual assessment of HID process. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Cognitive Fatigue Facilitates Procedural Sequence Learning.

PubMed

Borragán, Guillermo; Slama, Hichem; Destrebecqz, Arnaud; Peigneux, Philippe

2016-01-01

Enhanced procedural learning has been evidenced in conditions where cognitive control is diminished, including hypnosis, disruption of prefrontal activity and non-optimal time of the day. Another condition depleting the availability of controlled resources is cognitive fatigue (CF). We tested the hypothesis that CF, eventually leading to diminished cognitive control, facilitates procedural sequence learning. In a two-day experiment, 23 young healthy adults were administered a serial reaction time task (SRTT) following the induction of high or low levels of CF, in a counterbalanced order. CF was induced using the Time load Dual-back (TloadDback) paradigm, a dual working memory task that allows tailoring cognitive load levels to the individual's optimal performance capacity. In line with our hypothesis, reaction times (RT) in the SRTT were faster in the high- than in the low-level fatigue condition, and performance improvement was higher for the sequential than the motor components. Altogether, our results suggest a paradoxical, facilitating impact of CF on procedural motor sequence learning. We propose that facilitated learning in the high-level fatigue condition stems from a reduction in the cognitive resources devoted to cognitive control processes that normally oppose automatic procedural acquisition mechanisms.

Three-Dimensional Viscous Alternating Direction Implicit Algorithm and Strategies for Shape Optimization

NASA Technical Reports Server (NTRS)

Pandya, Mohagna J.; Baysal, Oktay

1997-01-01

A gradient-based shape optimization based on quasi-analytical sensitivities has been extended for practical three-dimensional aerodynamic applications. The flow analysis has been rendered by a fully implicit, finite-volume formulation of the Euler and Thin-Layer Navier-Stokes (TLNS) equations. Initially, the viscous laminar flow analysis for a wing has been compared with an independent computational fluid dynamics (CFD) code which has been extensively validated. The new procedure has been demonstrated in the design of a cranked arrow wing at Mach 2.4 with coarse- and fine-grid based computations performed with Euler and TLNS equations. The influence of the initial constraints on the geometry and aerodynamics of the optimized shape has been explored. Various final shapes generated for an identical initial problem formulation but with different optimization path options (coarse or fine grid, Euler or TLNS), have been aerodynamically evaluated via a common fine-grid TLNS-based analysis. The initial constraint conditions show significant bearing on the optimization results. Also, the results demonstrate that to produce an aerodynamically efficient design, it is imperative to include the viscous physics in the optimization procedure with the proper resolution. Based upon the present results, to better utilize the scarce computational resources, it is recommended that, a number of viscous coarse grid cases using either a preconditioned bi-conjugate gradient (PbCG) or an alternating-direction-implicit (ADI) method, should initially be employed to improve the optimization problem definition, the design space and initial shape. Optimized shapes should subsequently be analyzed using a high fidelity (viscous with fine-grid resolution) flow analysis to evaluate their true performance potential. Finally, a viscous fine-grid-based shape optimization should be conducted, using an ADI method, to accurately obtain the final optimized shape.

RARtool: A MATLAB Software Package for Designing Response-Adaptive Randomized Clinical Trials with Time-to-Event Outcomes.

PubMed

Ryeznik, Yevgen; Sverdlov, Oleksandr; Wong, Weng Kee

2015-08-01

Response-adaptive randomization designs are becoming increasingly popular in clinical trial practice. In this paper, we present RARtool , a user interface software developed in MATLAB for designing response-adaptive randomized comparative clinical trials with censored time-to-event outcomes. The RARtool software can compute different types of optimal treatment allocation designs, and it can simulate response-adaptive randomization procedures targeting selected optimal allocations. Through simulations, an investigator can assess design characteristics under a variety of experimental scenarios and select the best procedure for practical implementation. We illustrate the utility of our RARtool software by redesigning a survival trial from the literature.

Deviation pattern approach for optimizing perturbative terms of QCD renormalization group invariant observables

NASA Astrophysics Data System (ADS)

Khellat, M. R.; Mirjalili, A.

2017-03-01

We first consider the idea of renormalization group-induced estimates, in the context of optimization procedures, for the Brodsky-Lepage-Mackenzie approach to generate higher-order contributions to QCD perturbative series. Secondly, we develop the deviation pattern approach (DPA) in which through a series of comparisons between lowerorder RG-induced estimates and the corresponding analytical calculations, one could modify higher-order RG-induced estimates. Finally, using the normal estimation procedure and DPA, we get estimates of αs4 corrections for the Bjorken sum rule of polarized deep-inelastic scattering and for the non-singlet contribution to the Adler function.

Hubble Systems Optimize Hospital Schedules

NASA Technical Reports Server (NTRS)

2009-01-01

Don Rosenthal, a former Ames Research Center computer scientist who helped design the Hubble Space Telescope's scheduling software, co-founded Allocade Inc. of Menlo Park, California, in 2004. Allocade's OnCue software helps hospitals reclaim unused capacity and optimize constantly changing schedules for imaging procedures. After starting to use the software, one medical center soon reported noticeable improvements in efficiency, including a 12 percent increase in procedure volume, 35 percent reduction in staff overtime, and significant reductions in backlog and technician phone time. Allocade now offers versions for outpatient and inpatient magnetic resonance imaging (MRI), ultrasound, interventional radiology, nuclear medicine, Positron Emission Tomography (PET), radiography, radiography-fluoroscopy, and mammography.

Optimization of a gene electrotransfer procedure for efficient intradermal immunization with an hTERT-based DNA vaccine in mice

PubMed Central

Calvet, Christophe Y; Thalmensi, Jessie; Liard, Christelle; Pliquet, Elodie; Bestetti, Thomas; Huet, Thierry; Langlade-Demoyen, Pierre; Mir, Lluis M

2014-01-01

DNA vaccination consists in administering an antigen-encoding plasmid in order to trigger a specific immune response. This specific vaccine strategy is of particular interest to fight against various infectious diseases and cancer. Gene electrotransfer is the most efficient and safest non-viral gene transfer procedure and specific electrical parameters have been developed for several target tissues. Here, a gene electrotransfer protocol into the skin has been optimized in mice for efficient intradermal immunization against the well-known telomerase tumor antigen. First, the luciferase reporter gene was used to evaluate gene electrotransfer efficiency into the skin as a function of the electrical parameters and electrodes, either non-invasive or invasive. In a second time, these parameters were tested for their potency to generate specific cellular CD8 immune responses against telomerase epitopes. These CD8 T-cells were fully functional as they secreted IFNγ and were endowed with specific cytotoxic activity towards target cells. This simple and optimized procedure for efficient gene electrotransfer into the skin using the telomerase antigen is to be used in cancer patients for the phase 1 clinical evaluation of a therapeutic cancer DNA vaccine called INVAC-1. PMID:26015983

Optimization of robotic welding procedures for maintenance repair of hydraulic turbines

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

Lamarche, L.; Galopin, M.; Simoneau, R.

1996-12-31

A six axes super-compact robot is used for field repair of cavitation damages found on the discharge ring of hydraulic turbines. Optimization of overlay welding procedures to minimize surface distortion and reduce tearing forces on anchors in concrete, were studied through experimentation and FEM modelling. Planned experimentation has been used to develop optimum pulsed GMAW schedules of stainless steel overlays in 2G position. Best welding sequence was resolved through over lay welding of free plates. Each overlay consisted in one or two layers which were welded in the longitudinal and/or transverse direction of the rectangular plate. A bidirectional welding mode,more » a longitudinal layer followed by a transverse layer position and no cooling between the two layers, were found to be most effective in reducing distortion. The optimized 2G welding procedure was applied to a simulated field repair. Plate was anchored on a massive iron bracket with a set of instrumented bolts, to understand how normal tearing forces in anchors evolve. Preliminary results on FEM modelling of lateral force on anchors indicate good correlation with experiments, for an elementary design.« less