The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Howard M. Colquhoun - One of the best experts on this subject based on the ideXlab platform.
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Exchange Reactions of Poly(arylene ether ketone) DithioKetals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether Ketal)s
Macromolecules, 2017Co-Authors: Ioannis Manolakis, Paul Cross, Howard M. ColquhounAbstract:The dithioKetal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether Ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether Ketal)s reported here are not accessible from Ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential dithioKetalization, dithioKetal–Ketal exchange, Ketal hydrolysis, and redithioKetalization. Poly(arylene ether Ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials.
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Exchange Reactions of Poly(arylene ether ketone) DithioKetals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether Ketal)s
2017Co-Authors: Ioannis Manolakis, Paul Cross, Howard M. ColquhounAbstract:The dithioKetal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether Ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether Ketal)s reported here are not accessible from Ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential dithioKetalization, dithioKetal–Ketal exchange, Ketal hydrolysis, and redithioKetalization. Poly(arylene ether Ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials
T Kohl - One of the best experts on this subject based on the ideXlab platform.
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fetal echocardiography new grounds to explore during fetal cardiac intervention
Pediatric Cardiology, 2002Co-Authors: T KohlAbstract:Over the past decade, revolutionary advances in ultrasound imaging technology have allowed the study of the evolution of congenital heart disease during fetal life. The frustration arising from watching the prenatal progression of severe semilunar valve obstructions and therapy-refractory fetal arrhythmias has prompted the interest in developing procedures for fetal cardiac intervention. Ultrasound techniques as the primary diagnostic and monitoring modalities in fetal medicine will play a key role in defining patient groups, peri-interventional assessment of fetal hemodynamics, and monitoring during these procedures. The purpose of this article is to provide pediatric cardiologists and perinatal medicine specialists an overview over the various technical approaches at fetal cardiac intervention and the special tasks that fetal echocardiography will have to accomplish. It also aims at illustrating the potential of fetal echocardiography for fetal selection.
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fetoscopic direct fetal cardiac access in sheep an important experimental milestone along the route to human fetal cardiac intervention
Circulation, 2000Co-Authors: T Kohl, Danja Strumper, Ralf Witteler, Gregor Merschhoff, Rasa Alexiene, Claudia Callenbeck, Boulos Asfour, Julia Reckers, Sebastian Aryee, Christian VahlhausAbstract:Background—Fetal cardiac interventions by direct ultrasound-guided approaches or open fetal cardiac surgery have been fraught with technical difficulties, as well as with significant maternal and fetal morbidity in humans. Therefore, the purpose of our study in sheep was to assess the feasibility and potential of fetoscopic direct fetal cardiac access. Methods and Results—In 15 anesthetized pregnant ewes (88 to 109 days of gestation; term, 145 days), 3 to 4 trocars were percutaneously placed in the uterus. Using videofetoscopic equipment, we assessed the feasibility of achieving direct fetal cardiac access. Minimally invasive direct fetal cardiac access by operative fetoscopy was achieved in 10 of the 15 fetal sheep. In 7 fetuses, the approach was successfully tested for fetal cardiac pacing (n=5) or antegrade fetal cardiac catheterization (n=2). Access was not achieved in 5 fetuses because of bleeding complications (n=2) or because the fetoscopic setup could not be established (n=3). All but 2 fetal shee...
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fetoscopic and open transumbilical fetal cardiac catheterization in sheep potential approaches for human fetal cardiac intervention
Circulation, 1997Co-Authors: T Kohl, Michael R. Harrison, Norman H. Silverman, Zoltan Szabo, Kenji Suda, Edwin Petrossian, Deniz Kececioglu, Philip Moore, Tony M Chou, Frank L HanleyAbstract:Background Shortening the prenatal disease course of severe aortic and pulmonary stenoses by balloon valvuloplasty may diminish their postnatal expression. The purpose of this study in fetal sheep was to assess the feasibility of fetoscopic and open transumbilical fetal cardiac catheterization guided by fetal transesophageal echocardiography to provide alternative approaches for human fetal cardiac intervention. Methods and Results We studied a total of nine fetal sheep (95 to 103 days of gestation; term=145 to 150 days) and performed transumbilical fetal cardiac catheterization by a minimally invasive fetoscopic (n=6) or an open fetal surgical approach (n=3). Monitored by fetal transesophageal echocardiography, with an 8F or 10F, 10-MHz intravascular ultrasound catheter we placed guidewires and interventional catheters via the umbilical arterial route into the fetal heart. In three of the fetuses, we created supravalvar pulmonary artery stenosis by open fetal cardiac surgery. After fetal and maternal recovery, we exteriorized these fetuses and performed open transumbilical fetal cardiac catheterization with successful pulmonary arterial angioplasty in two. Three fetuses survived fetoscopic transumbilical catheterization for 1 or 2 days and died most likely of blood loss after sheath dislodgment (n=1) or removal (n=2). By securing the sheath insertion site with a suture, we prevented sheath dislodgment and minimized bleeding during sheath removal in three fetuses. These fetuses then survived fetoscopic transumbilical fetal cardiac catheterization for 1 to 2 weeks before being killed. Conclusions This study in fetal sheep demonstrates that fetoscopic and open transumbilical fetal cardiac catheterization are feasible and, guided by fetal transesophageal echocardiography, provide potential alternative approaches for human fetal cardiac intervention.
Ioannis Manolakis - One of the best experts on this subject based on the ideXlab platform.
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Exchange Reactions of Poly(arylene ether ketone) DithioKetals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether Ketal)s
Macromolecules, 2017Co-Authors: Ioannis Manolakis, Paul Cross, Howard M. ColquhounAbstract:The dithioKetal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether Ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether Ketal)s reported here are not accessible from Ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential dithioKetalization, dithioKetal–Ketal exchange, Ketal hydrolysis, and redithioKetalization. Poly(arylene ether Ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials.
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Exchange Reactions of Poly(arylene ether ketone) DithioKetals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether Ketal)s
2017Co-Authors: Ioannis Manolakis, Paul Cross, Howard M. ColquhounAbstract:The dithioKetal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether Ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether Ketal)s reported here are not accessible from Ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential dithioKetalization, dithioKetal–Ketal exchange, Ketal hydrolysis, and redithioKetalization. Poly(arylene ether Ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials
Tekoa King - One of the best experts on this subject based on the ideXlab platform.
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Fetal heart rate monitoring: is it salvageable?
American Journal of Obstetrics and Gynecology, 2000Co-Authors: Julian T. Parer, Tekoa KingAbstract:Fetal heart rate monitoring was introduced in the 1960s. After a number of randomized controlled trials in the mid 1980s, doubt arose regarding the efficacy of fetal heart rate monitoring in improving fetal outcome. The potential reasons why fetal heart rate monitoring has not been shown to be efficacious are (1) use of an outcome measure that is not related to variant fetal heart rate monitoring patterns, (2) lack of standardized interpretation of fetal heart rate patterns, (3) disagreement regarding algorithms for intervention of specific fetal heart rate patterns, and (4) the inability to demonstrate the reliability, validity, and ability of fetal heart rate monitoring to allow timely intervention. A recent National Institutes of Health committee proposed detailed, quantitative, standardized definitions of fetal heart rate patterns, which can serve as a basis for determining whether fetal heart rate monitoring is reliable and valid. In this article we examine reasons why fetal heart rate monitoring did not live up to its original expectations and why the randomized controlled trials did not demonstrate efficacy, and we make suggestions for determining whether electronic fetal heart rate monitoring should be abandoned.
Dale L Boger - One of the best experts on this subject based on the ideXlab platform.
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intramolecular 1 2 and 3 2 cycloaddition reactions of cyclopropenone Ketals
ChemInform, 2010Co-Authors: Paresma R Patel, Dale L BogerAbstract:The first intramolecular thermal reactions of cyclopropenone Ketals are reported and the work examined substrates tethered to an electron-deficient olefin bearing a single electron-withdrawing substituent. Whereas the intermolecular variants of the reactions provide only the products of an endo-selective [1 + 2] cycloaddition or a carbonyl addition reaction of a thermally generated π-delocalized singlet vinylcarbene, the intramolecular variants provide either [1 + 2] or [3 + 2] cycloadducts in reactions that depend on the reaction conditions, the alkene-activating substituent, and the nature of the tethering. In addition to providing key mechanistic insights into the thermal [3 + 2] cycloaddition reaction for such substrates, they were also found to proceed under conditions that reflect the ease and regioselectivity of the cyclopropenone Ketal cleavage for π-delocalized singlet vinylcarbene generation. The most effective combination of structural features that impact the reactivity was observed with subst...
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diels alder reactions of cyclopropenone Ketals a concise tropolone annulation applicable to rubrolone c ring introduction
Journal of Organic Chemistry, 1994Co-Authors: Dale L Boger, Yan ZhuAbstract:A concise tropolone annulation applicable to rubrolone C ring introduc- tion is detailed based on the room-temperature [4+2] cycloaddition rea- ction of the cyclopropenone Ketal (10) with the oxygenated diene (9). Conversion of the sensitive [4+2] cycloadduct (11) to the norcaradiene (18), low temperature electrocyclic rearrangement to a cycloheptatrie- none Ketal, and tautomerization to (12) provided a fully oxygenated tropolone analogous to that found in rubrolone
