Safety of Stress Cardiac Magnetic Resonance in Patients With Moderate to Severe Aortic Valve Stenosis

Janek Salatzki,Andreas Ochs,Nadja Kirchgäßner,Jannick Heins,Sebastian Seitz,Hauke Hund,Derliz Mereles,Matthias G. Friedrich,Hugo A. Katus,Norbert Frey,Florian André,Marco M. Ochs 한국심초음파학회 2023 Journal of Cardiovascular Imaging (J Cardiovasc Im Vol.31 No.1

BACKGROUND: Dobutamine and adenosine stress cardiac magnetic resonance (CMR) imaging is relatively contraindicated in patients with moderate to severe aortic valve stenosis (AS). We aimed to determine the safety of dobutamine and adenosine stress CMR in patients with moderate to severe AS. METHODS: In this retrospective study patients with AS who underwent either dobutamine or adenosine stress CMR for exclusion of obstructive coronary artery disease were enrolled. We recorded clinical data, CMR and echocardiography findings, and complications as well as minor symptoms. Patients with AS were compared to matched individuals without AS. RESULTS: A total of 187 patients with AS were identified and compared to age-, gender- and body mass index-matched 187 patients without AS. No severe complications were reported in the study nor the control group. The reported frequency of non-severe complications and minor symptoms were similar between the study and the control groups. Nineteen patients with AS experienced non-severe complications or minor symptoms during dobutamine stress CMR compared to eighteen patients without AS (p = 0.855). One patient with AS and two patients without AS undergoing adenosine stress CMR experienced minor symptoms (p = 0.562). Four examinations were aborted because of chest pain, paroxysmal atrial fibrillation and third-degree atrioventricular block. Inducible ischaemia, prior coronary artery bypass grafting, prior stroke and age were associated with a higher incidence of complications and minor symptoms. CONCLUSIONS: Moderate to severe AS was not associated with complications during CMR stress test. The incidence of non-severe complications and minor symptoms was greater with dobutamine.

Hoarseness : Guide to Diagnosis

Janeke, Johan n. Medical Publications Korea 1993 Medical Progress Vol.15 No.10

Defect Chemistry of the Mixed Conducting Cage Compound Ca₁₂Al₁₄O₃₃

Janek, J.,Lee, D.K. The Korean Ceramic Society 2010 한국세라믹학회지 Vol.47 No.2

The electrical transport properties of mayenite ($Ca_{12}Al_{14}O_{33}$ or $12CaO{\cdot}7Al_2O_3$; mostly abbreviated as $C_{12}A_7$) can be controlled in a wide range by varying the oxygen deficiency: At high temperatures mayenite becomes either an oxygen solid electrolyte, a mixed ionic/electronic conductor or an inorganic electride with metal-like properties upon chemical reduction (removing oxygen). The underlying defect chemistry can be understood on the basis of a relatively simple model-despite the complex cage structure: A point defect model based on the assumption that the framework $[Ca_{12}Al_{14}O_{32}]^{2+}$ acts as a pseudo-donor describes well the high temperature transport properties. It accounts for the observed conductivity plateau at higher oxygen activities and also describes the experimentally observed oxygen activity dependence of the electronic conductivity with -1/4 slope at temperatures between 800 and $1000^{\circ}C$. Doping effects in mayenite are still not well explored, and we review briefly the existing data on doping by different elements. Hydration of mayenite plays a crucial role, as Mayenite is hygroscopic, which may be a major obstacle for technical applications.

Degradation of Functional Materials in Temperature Gradients - Thermodiffusion and the Soret Effect

Janek, Jurgen,Sann, Joachim,Mogwitz, Boris,Rohnke, Marcus,Kleine-Boymann, Matthias The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.1

Functional materials are often exposed to high temperatures and inherent temperature gradients. These temperature gradients act as thermodynamic driving forces for the diffusion of mobile components. The detailed consequences of thermodiffusion depend on the boundary conditions of the non-isothermal sample: Once the boundaries of the sample are inert and closed for exchange of the mobile components, thermodiffusion leads to their pile-up in the stationary state (the so called Soret effect). Once the system is open for an exchange of the mobile component, chemical diffusion adds to the Soret effect, and stationary non-zero component fluxes are additionally observed in the stationary state. In this review, the essential aspects of thermodiffusion and Soret effect in inorganic functional materials are briefly summarized and our current practical knowledge is reviewed. Major examples include nonstoichiometric binary compounds (oxides and other chalcogenides) and ternary solid solutions. The potential influence of the Soret effect on the long term stability of high temperature thermoelectrics is briefly discussed. Typical Soret coefficients for nonstoichiometric compounds are found to be of the order of (d${\delta}$/dT) ${\approx}$ 1%/K.

Defect Chemistry of the Mixed Conducting Cage Compound Ca12Al14O33

J. Janek,D.-K. Lee 한국세라믹학회 2010 한국세라믹학회지 Vol.47 No.2

The electrical transport properties of mayenite (Ca12Al14O33 or 12CaO·7Al2O3; mostly abbreviated as C12A7) can be controlled in a wide range by varying the oxygen deficiency: At high temperatures mayenite becomes either an oxygen solid electrolyte, a mixed ionic/electronic conductor or an inorganic electride with metal-like properties upon chemical reduction (removing oxygen). The underlying defect chemistry can be understood on the basis of a relatively simple model – despite the complex cage structure: A point defect model based on the assumption that the framework [Ca12Al14O32]2+ acts as a pseudo-donor describes well the high temperature transport properties. It accounts for the observed conductivity plateau at higher oxygen activities and also describes the experimentally observed oxygen activity dependence of the electronic conductivity with −1/4 slope at temperatures between 800 and 1000oC. Doping effects in mayenite are still not well explored, and we review briefly the existing data on doping by different elements. Hydration of mayenite plays a crucial role, as Mayenite is hygroscopic, which may be a major obstacle for technical applications.

Degradation of Functional Materials in Temperature Gradients -Thermodiffusion and the Soret Effect

Jürgen Janek,Joachim Sann,Boris Mogwitz,Marcus Rohnke,Matthias Kleine-Boymann 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.1

Functional materials are often exposed to high temperatures and inherent temperature gradients. These temperature gradients act as thermodynamic driving forces for the diffusion of mobile components. The detailed consequences of thermodiffusion depend on the boundary conditions of the non-isothermal sample: Once the boundaries of the sample are inert and closed for exchange of the mobile components, thermodiffusion leads to their pile-up in the stationary state (the so called Soret effect). Once the system is open for an exchange of the mobile component, chemical diffusion adds to the Soret effect, and stationary non-zero component fluxes are additionally observed in the stationary state. In this review, the essential aspects of thermodiffusion and Soret effect in inorganic functional materials are briefly summarized and our current practical knowledge is reviewed. Major examples include nonstoichiometric binary compounds (oxides and other chalcogenides) and ternary solid solutions. The potential influence of the Soret effect on the long term stability of high temperature thermoelectrics is briefly discussed. Typical Soret coefficients for nonstoichiometric compounds are found to be of the order of (dδ/dT) ≈ 1%/K.

Interphase formation in solid-state batteries studied in situ by photoelectron spectroscopy

Thomas LEICHTWEISS,Sebastian WENZEL,Joachim SANN,Juergen JANEK 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

Oxidation kinetics of nitrogen doped TiO_{2−<i>δ</i>} thin films

Shi, Jianmin,Lee, Doh-Kwon,Yoo, Han-Ill,Janek, Jü,rgen,Becker, Klaus-Dieter The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.37

<P>The oxidation kinetics of nitrogen doped, oxygen deficient titanium dioxide thin films has been studied in atmospheres of pure oxygen or nitrogen at 500 °C, 550 °C, and 600 °C, respectively, by means of <I>in situ</I> optical spectroscopy. The thin films show high electronic absorbance in the visible and NIR region, accompanied by a red shift of the absorption edge of about 0.4 eV, <I>e.g.</I>, from about 2.9 to 2.5 eV at 600 °C. The time dependent decrease of absorbance due to oxidation is found to follow a parabolic rate law. An activation energy of about 1.96 eV can be obtained from the temperature dependence of the parabolic oxidation rate constant. In the framework of a microscopic oxidation model, this energy barrier is attributed to the diffusion of titanium interstitials in the re-oxidized part of the thin films as a rate-determining process. In addition, an attempt is made to evaluate the kinetics of nitrogen release from the time dependent blue shift of the absorption edge during re-oxidation.</P> <P>Graphic Abstract</P><P>Oxidation kinetics of N-doped TiO<SUB>2−<I>δ</I></SUB> thin film has been studied using optical spectroscopy under <I>in situ</I> conditions, revealing the dominance of Ti<SUP>4+</SUP>-interstitial diffusion. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp42559a'> </P>

Mesoporous TiO₂: Comparison of Classical Sol−Gel and Nanoparticle Based Photoelectrodes for the Water Splitting Reaction

Hartmann, Pascal,Lee, Doh-Kwon,Smarsly, Bernd M.,Janek, Juergen American Chemical Society 2010 ACS NANO Vol.4 No.6

<P>This paper describes a systematic comparison of the photoelectrochemical properties of mesoporous TiO<SUB>2</SUB> films prepared by the two most prevalent templating methods: The use of preformed, crystalline nanoparticles is generally considered advantageous compared to the usage of molecular precursors such as TiCl<SUB>4</SUB>, since the latter requires a separate heat treatment at elevated temperature to induce crystallization. However, our photoelectrochemical experiments clearly show that sol−gel derived mesoporous TiO<SUB>2</SUB> films cause an about 10 times higher efficiency for the water splitting reaction than their counterparts obtained from crystalline TiO<SUB>2</SUB> nanoparticles. This result indicates that for electrochemical applications the performance of nanoparticle-based metal oxide films might suffer from insufficient electronic connectivity.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-6/nn1004765/production/images/medium/nn-2010-004765_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn1004765'>ACS Electronic Supporting Info</A></P>

Single Crystals of C12A7 (Ca₁₂Al₁₄O₃₃) Substituted with 1 mol % Iron

Ebbinghaus, Stefan G.,Krause, Holger,Lee, Doh-Kwon,Janek, Jü,rgen American Chemical Society 2014 Crystal Growth & Design Vol.14 No.5

<P>Single crystals of Ca<SUB>12</SUB>Al<SUB>14</SUB>O<SUB>33</SUB> (C12A7, mayenite) substituted with 1 mol % Fe were grown by the floating zone technique in an atmosphere of 2% O<SUB>2</SUB>/98% N<SUB>2</SUB>. The iron substitution leads to an increase of the unit cell parameter by roughly 0.002 Å. Optical spectroscopy reveals an additional broad absorption band at 310 nm for the iron-substituted sample reflecting the yellow color of the crystals. XANES measurements at the Fe–K absorption edge prove the incorporation of Fe<SUP>3+</SUP> on the aluminum sites. Measurements of the magnetic susceptibility resulted in a value of 5.8 μ<SUB>B</SUB> per iron ion as expected for high-spin Fe<SUP>3+</SUP>. C12A7 is known to be a very good oxygen ion conductor at high temperatures. In pure oxygen, the iron substitution leads to a slightly reduced conductivity between approximately 500 and 800 °C, while at higher temperatures, the conductivity is very similar to the pristine material. Under reducing conditions, the slope of log(σ) vs log(<I>p</I>(O<SUB>2</SUB>)) of the iron-substituted sample was found to be steeper than that for pure C12A7.</P><P>Yellow-colored single crystals of iron-substituted Ca<SUB>12</SUB>Al<SUB>14</SUB>O<SUB>33</SUB> were grown by the floating zone technique. Fe−K XANES, optical spectroscopy, and magnetic measurements prove the incorporation of 1 mol % Fe<SUP>3+</SUP> on the aluminum sites. Compared with pristine C12A7, a slightly enhanced activation energy for the oxide ion conductivity was found. At high temperatures and under reducing atmosphere, the conductivity of C12A7:Fe strongly increases.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cgdefu/2014/cgdefu.2014.14.issue-5/cg401823k/production/images/medium/cg-2013-01823k_0007.gif'></P>