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Direct flow valve

Chris E Freye, Robert E Synovec
A high temperature diaphragm valve-based two-dimensional (2D) gas chromatography (GC×GC) with time-of-flight mass spectrometry (TOFMS) instrument, with the valve mounted directly in the GC oven, is demonstrated with separations up to 325°C. Use of the diaphragm valve allowed for the use of uncoupled carrier gas flows for (1)D (first column dimension) and (2)D (second column dimension), with a (1)D flow rate of 1ml/min, and a (2)D flow rate 3ml/min. The 3ml/min flow rate on (2)D was selected to ensure compatibility with most TOFMS detectors...
December 1, 2016: Talanta
Shehrin Sayed, Seokmin Hong, Supriyo Datta
It is experimentally established that charge current flowing in a channel with spin-momentum locking such as topological insulator surface states or Rashba interfaces induces a spin voltage, which can be electrically measured with a ferromagnetic contact along the current path. Using this fact in conjunction with Onsager reciprocity arguments, we make the surprising prediction that the anti-parallel resistance of a spin valve can be either larger or smaller than the parallel resistance depending on the direction of spin flow relative to the direction of spin-momentum locking...
October 21, 2016: Scientific Reports
Stephan Kische, Giuseppe D'Ancona, Hüseyin U Agma, Gihan El-Achkar, Martin Dißmann, Jasmin Ortak, Hüseyin Ince
OBJECTIVES: To analyze our single center experience with the Direct Flow Medical (DFM). BACKGROUND: The DFM has been recently introduced to the market and large real world experiences are lacking. METHODS: A total of 126 patients with severe aortic valve stenosis (AVS) were treated by the same team from March 2013 to May 2015. Device success and procedural safety were classified, according to valve academic research consortium (VARC) criteria, for the entire cohort, including patients treated in the early phases of our learning curve...
October 14, 2016: Catheterization and Cardiovascular Interventions
Giuseppe D'Ancona, Hüseyin U Agma, Hüseyin Ince, Gihan El-Achkar, Martin Dißmann, Jasmin Ortak, Stephan Kische
OBJECTIVES: We present our single center experience with the direct flow medical (DFM) prosthesis addressing the impact of native aortic valve (AV) calcification degree on outcomes. BACKGROUND: The DFM® has been introduced for transcatheter aortic valve implantation (TAVI). The valve has a nonmetallic and inflatable support structure. METHODS: Patients were divided in two groups according to preoperative cardiac computed tomography (CT): group I moderate calcification and group II heavy calcification of the total AV area...
October 14, 2016: Catheterization and Cardiovascular Interventions
K Cao, P Sucosky
Computational characterizations of aortic valve hemodynamics have typically discarded the effects of coronary flow. The objective of this study was to complement our previous fluid-structure interaction aortic valve model with a physiologic coronary circulation model to quantify the impact of coronary flow on aortic sinus hemodynamics and leaflet wall shear stress (WSS). Coronary flow suppressed vortex development in the two coronary sinuses and altered WSS magnitude and directionality on the three leaflets, with the most substantial differences occurring in the belly and tip regions...
October 7, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Ulrich Nöchel, Marc Behl, Maria Balk, Andreas Lendlein
Shape-memory hydrogels enable directed movements of a specimen in response to temperature, whereby crystallizable switching segments incorporated as side chains resulted in constant degrees of swelling during the shape-memory cycle. Here we report about hydrogels exhibiting a thermally induced triple-shape effect that allows complex movements of soft materials with two almost independent shape changes. Potential applications for those soft triple-shape materials are two-step self-unfolding devices or temperature-sensitive hydrogel actuators, for example, smart valves for flow rate control in aqueous media...
October 10, 2016: ACS Applied Materials & Interfaces
Kai Xiao, Yahong Zhou, Xiang-Yu Kong, Ganhua Xie, Pei Li, Zhen Zhang, Liping Wen, Lei Jiang
Regulating and controlling the transport of water across nanochannels is of great importance in both fundamental research and practical applications, because it is difficult to externally control water flow through nanochannels as in biological channels. To date, only a few hydrophobic nanochannels controlling the transport of water have been reported, all of which use exotic hydrophobic molecules. However, the effect of electrostatic charges, which plays an indispensable role in membrane proteins and dominates the energetics of water permeation across aquaporins, has not gained enough attention to control water transport through solid-state nanochannel/nanopore...
September 20, 2016: ACS Nano
Georgina Palau-Caballero, John Walmsley, John Gorcsan, Joost Lumens, Tammo Delhaas
BACKGROUND: Assessment of aortic regurgitation (AR) severity is often based on Doppler echocardiographic imaging. Hemodynamic responses to AR are influenced by the interplay among cardiovascular properties, including left ventricular (LV) and aortic tissue properties, that cannot be measured directly. The aim of this study was to investigate how both echocardiographic measures of AR severity and the hemodynamic consequences of AR are influenced by LV and aortic stiffness. METHODS: AR was simulated using the CircAdapt computational model of the human cardiovascular system...
September 13, 2016: Journal of the American Society of Echocardiography
Daniel Rüschen, Miriam Rimke, Jonas Gesenhues, Steffen Leonhardt, Marian Walter
BACKGROUND AND OBJECTIVES: Sufficient cardiac output is one of the main goals of ventricular assist device therapy. To date, there is no adequate method to estimate the combined amount of blood the native heart and a continuous-flow assist device pump through the circulatory system. This paper presents an approach to estimate total cardiac output based on the signals provided by optical pressure sensors mounted on the inlet and outlet of an Abiomed Impella CP pump. METHODS: Two Kalman filters were used in parallel for joint estimation of the aortic flow rate and the hydraulic resistance of the aortic valve...
August 30, 2016: Computer Methods and Programs in Biomedicine
Keyvan Amini Khoiy, Dipankar Biswas, Thomas N Decker, Kourosh T Asgarian, Francis Loth, Rouzbeh Amini
Quantification of the tricuspid valve leaflets mechanical strain is important in order to understand valve pathophysiology and to develop effective treatment strategies. Many of the traditional methods used to dynamically open and close the cardiac valves in vitro via flow simulators require valve dissection. Recent studies, however, have shown that restriction of the atrioventricular valve annuli could significantly change their in-vivo deformation. For the first time, the porcine valve leaflets deformation was measured in a passive ex-vivo beating heart without isolating and remounting the valve annuli...
September 6, 2016: Journal of Biomechanical Engineering
Hasan Bushnaq, Dietrich Metz, Asen Petrov, Stefan Frantz, Ulrich Hofmann, Christoph Raspé, Hendrik Treede
OBJECTIVE: The standard procedure of transcatheter aortic valve implantation involves transfemoral access. Nevertheless, the use of this access route is limited by the vessel diameter, calcification, and tortuosity, making a subgroup of patients ineligible for peripheral access. We report the first use of direct aortic transcatheter aortic valve implantation with the Direct Flow Medical valve (Direct Flow Medical, Inc, Santa Rosa, Calif) in 15 patients at the Halle-Wittenberg University...
August 12, 2016: Journal of Thoracic and Cardiovascular Surgery
Hojin Ha, Guk Bae Kim, Jihoon Kweon, Sang Joon Lee, Young-Hak Kim, Namkug Kim, Dong Hyun Yang
Since the first observation of a helical flow pattern in aortic blood flow, the existence of helical blood flow has been found to be associated with various pathological conditions such as bicuspid aortic valve, aortic stenosis, and aortic dilatation. However, an understanding of the development of helical blood flow and its clinical implications are still lacking. In our present study, we hypothesized that the direction and angle of aortic inflow can influence helical flow patterns and related hemodynamic features in the thoracic aorta...
2016: Scientific Reports
Uwe Pfeil, Subhashini Bharathala, Ghulam Murtaza, Petra Mermer, Tamara Papadakis, Andreas Boening, Wolfgang Kummer
Heart valves are highly organized structures determining the direction of blood flow through the heart. Smooth muscle cells within the valve are thought to play an active role during the heart cycle, rather than being just passive flaps. The mature heart valve is composed of extracellular matrix (ECM), various differentiations of valvular interstitial cells (VIC), smooth muscle cells and overlying endothelium. VIC are important for maintaining the structural integrity of the valve, thereby affecting valve function and ECM remodelling...
August 23, 2016: Cell and Tissue Research
Vinícius G Ferreira, Gabriel M Leme, Alberto J Cavalheiro, Cristiano S Funari
Current methods employed for the analysis of the chemical composition of solid matrices (such as plant, animal, or human tissues; soil; etc.) often require many sample treatment steps, including an extraction step with exclusively dedicated solvents. This work describes an optimized analytical setup in which the extraction of a solid sample is directly coupled to its analysis by high-performance liquid chromatography. This approach avoids (i) the use of pumps and valves other than those comprising the HPLC instrument, (ii) the use of solvents other than those of the mobile phase, and (iii) the need to stop the mobile phase flow at any time during the full analytical procedure...
September 6, 2016: Analytical Chemistry
Christopher J Broyd, Michael Mullen, Man Fai Shiu
No abstract text is available yet for this article.
August 8, 2016: JACC. Cardiovascular Interventions
Paul S Pagel, Brent T Boettcher, Derek J De Vry, Julie K Freed, Zafar Iqbal
OBJECTIVE: Transmitral blood flow produces a vortex ring (quantified using vortex formation time [VFT]) that enhances the efficiency of left ventricular (LV) filling. VFT is attenuated in LV hypertrophy resulting from aortic valve stenosis (AS) versus normal LV geometry. Many patients with AS also have aortic insufficiency (AI). The authors tested the hypothesis that moderate AI falsely elevates VFT by partially inhibiting mitral leaflet opening in patients with AS. DESIGN: Observational study...
October 2016: Journal of Cardiothoracic and Vascular Anesthesia
John N Maina
Among the extant air-breathing vertebrates, the avian respiratory system is structurally the most complex and functionally the most efficient gas exchanger. Having been investigated for over four centuries, some aspects of its biology have been extremely challenging and highly contentious and others still remain unresolved. Here, while assessing the most recent findings, four notable aspects of the structure and function of the avian respiratory system are examined critically to highlight the questions, speculations, controversies and debates that have arisen from past research...
July 28, 2016: Biological Reviews of the Cambridge Philosophical Society
R Guidoin, R Zegdi, J Lin, J Mao, O Rochette-Drouin, D How, X Guan, P Bruneval, L Wang, L Germain, Z Zhang
INTRODUCTION: Prior to deployment, the percutaneous heart valves must be crimped and loaded into sheaths of diameters that can be as low as 6mm for a 23mm diameter valve. However, as the valve leaflets are fragile, any damage caused during this crimping process may contribute to reducing its long-term durability in vivo. MATERIAL AND METHOD: Bovine pericardium percutaneous valves were manufactured as follows. The leaflets were sutured on a nitinol frame. A polyester cuff fabric served as a buffer between the pericardium and the stent...
July 22, 2016: Morphologie: Bulletin de L'Association des Anatomistes
Agnieszka A Książek, Katharyn J Mitchell, Laurent Morax, Colin C Schwarzwald, Simon P Hoerstrup, Benedikt Weber
BACKGROUND: Heterotopic heart transplantation (HHT) in rodent animal models represents an important technique enabling studies on organ transplantation immunology and pharmaceutical development. Recent investigations used nonworking HHT designs, with the left ventricle (LV) bypassed in the anastomosis system. In spite of their principal success, the lack of orthogonal ventricular filling leads to myocardial atrophy. However, when focusing on the cellular and molecular mechanisms involved in the in vivo remodeling of the myocardium or cell-based cardiovascular implants, a nonworking model is suboptimal as it lacks the native-analogous hemodynamic and metabolic situation...
July 20, 2016: European Surgical Research. Europäische Chirurgische Forschung. Recherches Chirurgicales Européennes
Hilary P Grocott, Emma Ambrose, Mike Moon
PURPOSE: Selective antegrade cerebral perfusion (SACP) involving cannulation of either the axillary or innominate artery is a commonly used technique for maintaining cerebral blood flow (CBF) during the use of hypothermic cardiac arrest (HCA) for operations on the aortic arch. Nevertheless, asymmetrical CBF with hypoperfusion of the left cerebral hemisphere is a common occurrence during SACP. The purpose of this report is to describe an adjunctive maneuver to improve left hemispheric CBF during SACP by applying extrinsic compression to the left carotid artery...
October 2016: Canadian Journal of Anaesthesia, Journal Canadien D'anesthésie
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