Assessment of prosthetic aortic valve performance by magnetic resonance velocity imaging

Objectives Magnetic resonance (MRI) velocity mapping was used to evaluate non-invasively the flow profiles of the ascending aorta in normal volunteers and in patients with an aortic (mechanical) valve prosthesis. Background In patients with artificial aortic valves the flow profile in the ascending aorta is severely altered. These changes have been associated with an increased risk of thrombus formation and mechanical hemolysis. Methods Velocity profiles were determined 30 mm distal to the aortic valve in six healthy volunteers and seven patients with aortic valve replacement (replacement within the last 2 years) using ECG triggered phase contrast MRI. Peak flow, mean flow and mean reverse flow were measured in intervals of 25 ms during the entire heart cycle. Systolic reverse flow, end-systolic closing and diastolic leakage volume were calculated for all subjects. Results Peak flow velocity during mid-systole was significantly higher in patients with valvular prosthesis than in normals (mean±SD, 1.9±0.4 m/s vs. 1.2±0.03 m/s,P<0.001) with a double peak and a zone of reversed flow close to the inner (left lateral) wall of the ascending aorta of the patients. Closing volume was significantly larger in patients than in controls (−3.3±1.2 ml/beat vs. −0.9±0.5 ml/beat;P<0.001). There was reverse flow during systole in valvular patients amounting to 15.7±6.7% of total cardiac output compared to 2.3±1.2% in controls (P<0.001). Diastolic mean flow was negative in patients after valve replacement but not in controls (−11.0±15.2 ml/beat vs. 6.8±3.2 ml/beat;P<0.01). Conclusions The following three major quantitative observations have been made in the present study: (1) Mechanical valve prostheses have an increased peak flow velocity with a systolic reverse flow at the inner (left lateral) wall of the ascending aorta. (2) A double peak flow velocity pattern can be observed in patients with bileaflet (mechanical) prosthesis. (3) The blood volume required for leaflet closure and the diastolic leakage blood volume are significantly higher for the examined bileaflet valve than for native heart valves.     

Zur Heck-Reaktion von 1-Chloralk-1-inen – Synthese und Charakterisierung von 1,3-disubstituierten 7-(Prop-2-inyliden)bicyclo[2.2.1]heptanen und anderen Bicyclen

The Heck reaction of cyclohexene with 1-chloroalk-1-ynes ClC≡CR 1 (R = Ph a , c-Hex b , n-Bu c , n-Oct d ) using [Pd(OAc)₂]/NaO₂CH/[NEt₃Bz]Cl as catalyst system (DMF, 25 °C) affords 1,3-disubstituted 7-(prop-2-ynylidene)bicyclo[2.2.1]heptanes 2 as tandem products by reaction of cyclohexene and ClC≡CR in a ratio of 1:2. To a smaller extent, substituted 7-[(cyclohexenyl)methylidene]bicyclo-[2.2.1]heptanes 3 (tandem products by reaction of cyclohexene and ClC≡CR in a ratio of 2:1) and the regular Heck products (alkynylcyclohexenes 4 ) are formed. The homocoupling of 1 to give RC≡C–C≡CR does not take place, except for R = n-Oct where it proceeds as side reaction. The analogous reaction of ClC≡CR with cycloheptene affords the 2:1 products (substitued 8-[(cycloheptenyl)methylidene]biyclo[3.2.1]octanes 6 ) as main products and the 1:2 products (1,3-disubstituted 7-(prop-2-ynylidene)bicyclo[3.2.1]-octanes 5 ) as well as the regular Heck products (alkynylcycloheptenes 7 ) as side products. The ratio 5 : 6 is strongly influenced by the ratio cycloheptene : 1 . The products 2 , 5a and 6 were isolated and characterized by means of ¹H and ¹³C NMR spectroscopy. The molecular structures of 7-(1,3-diphenylprop-2-ynylidene)bicyclo[2.2.1]heptane ( 2a ) and 8-[(cyclo-heptenyl)phenylmethylidene)]bicyclo[3.2.1]octane ( 6a ) (as mixture of the cyclohept-3- and -4-enyl double bond isomers) were determined by single-crystal X-ray structure analysis.     

Hydrophobic treatment enabling analysis of wettable surfaces using a liquid microjunction surface sampling probe/electrospray ionization-mass spectrometry system

An aerosol application procedure involving one or more commercially available silicone-based products was developed to create hydrophobic surfaces that enable analysis of otherwise wettable, absorbent surfaces using a liquid microjunction surface sampling probe/electrospray ionization mass spectrometry system. The treatment process resulted in a hydrophobic surface that enabled formation of the requisite probe-to-surface liquid microjunction for sampling and allowed efficient extraction of the analytes from the surface, but did not contribute significant chemical background in the mass spectra. The utility of this treatment process was demonstrated with the treatment of wettable high-performance thin layer chromatography plates, post-plate development, and their subsequent analysis with the sampling probe. The surface treatment process for different surface types was described and explained and the effectiveness of the treatment and subsequent analysis was illustrated using alkaloids from goldenseal (Hydrastis canadensis) root separated on a normal phase silica gel 60 F(254S) plate and peptides from protein tryptic digests separated on a ProteoChrom HPTLC Silica gel 60 F(254S) plate and a ProteoChrom HPTLC Cellulose sheet. This simple surface treatment process significantly expands the analytical surfaces that can be analyzed with the liquid microjunction surface sampling probe, and therefore, also expands the analytical utility of this liquid extraction based surface sampling approach.     

More Constructions of Lossy and Correlation-Secure Trapdoor Functions

We propose new and improved instantiations of lossy trapdoor functions (Peikert and Waters in STOC’08, pp. 187–196, 2008), and correlation-secure trapdoor functions (Rosen and Segev in TCC’09, LNCS, vol. 5444, pp. 419–436, 2009). Our constructions widen the set of number-theoretic assumptions upon which these primitives can be based, and are summarized as follows:

• Lossy trapdoor functions based on the quadratic residuosity assumption. Our construction relies on modular squaring, and whereas previous such constructions were based on seemingly stronger assumptions, we present the first construction that is based solely on the quadratic residuosity assumption. We also present a generalization to higher-order power residues.
• Lossy trapdoor functions based on the composite residuosity assumption. Our construction guarantees essentially any required amount of lossiness, where at the same time the functions are more efficient than the matrix-based approach of Peikert and Waters.
• Lossy trapdoor functions based on the d-Linear assumption. Our construction both simplifies the DDH-based construction of Peikert and Waters and admits a generalization to the whole family of d-Linear assumptions without any loss of efficiency.
• Correlation-secure trapdoor functions related to the hardness of syndrome decoding.

     

Kostengünstige Kreislaufwirtschaft mit PFPE-Ölen

Due to their extraordinary properties liquids based on perfluoro-polyethers (PFPE) have claimed to have a settled place in the vacum technologie. The disposal after using the liquids will be a problem because the used liquids are toxic waste. Regeneration of used PFPE express an alternative way which protecting the environment and cost cutting. The following article describes a process for the carefull regeneration of used PFPE. The regenerated product has the same technical datas like the original product. No restrictions for use are known. The several repeat of the process with the regenerated product is possible. The output of the regeneration process is more than 90 percent. The quality of the regenerated product will be controlling permanently by physical and chemical analysis.     

The intravascular contrast agent Clariscan™ (NC 100150 injection) for 3D MR coronary angiography in patients with coronary artery disease

4. Conclusion In our experience Clariscan^TM improves image quality, thus, increasing the visual length and improving the actual visible dimensions of the coronary arteries. Distal segments improved to a higher extent than the proximal parts. In that way sensitivity and specificity for the detection of significant coronary artery disease could be improved. Better SNR and CNR can be used to improve spatial resolution or to reduce scan time by techniques like SENSE or SMASH [14,15].     

Partial order behaviour and structure of Petri nets

This paper argues that partial order semantics can be used profitably in the proofs of some nontrivial results in Petri net theory. We show that most of Commoner's and Hack's structure theory of free choice nets can be phrased and proved in terms of partial order behaviour. The new proofs are considerably shorter (and, arguably, more lucid) than the old ones; they also generalise the results from (safe) free choice nets to (bounded) extended free choice nets.Work partly done while both authors were with the Institut für Methodische Grundlagen, Gesellschaft für Mathematik und Datenverarbeitung, D-520S Sankt Augustin, and supported in part by Esprit Basic Research Action No. 3148: DEMON.     

Compositional generation of home states in free choice nets

Free choice nets are a class of Petri nets which allow the modelling of concurrency and nondeterministic choice, but with the restriction that choices cannot be influenced externally. Home states are initial states which lead to a strongly connected state graph, that is, a home state can be reached from any of its successor states. The main result of this paper characterises the home states of a well-formed free choice net compositionally by recourse to its decomposition into T-components.     

S-enriched porous polymer derived N-doped porous carbons for electrochemical energy storage and conversion

Porous polymers have been recently recognized as one of the most important precursors for fabrication of heteroatom-doped porous carbons due to the intrinsic porous structure, easy available heteroatom-containing monomers and versatile polymerization methods. However, the heteroatom elements in as-produced porous carbons are quite relied on monomers. So far, the manipulating of heteroatom in porous polymer derived porous carbons are still very rare and challenge. In this work, a sulfur-enriched porous polymer, which was prepared from a diacetylene-linked porous polymer, was used as precursor to prepare S-doped and/or N-doped porous carbons under nitrogen and/or ammonia atmospheres. Remarkably, S content can sharply decrease from 36.3% to 0.05% after ammonia treatment. The N content and specific surface area of as-fabricated porous carbons can reach up to 1.32% and 1508 m²·g⁻¹, respectively. As the electrode materials for electrical double-layer capacitors, as-fabricated porous carbons exhibit high specific capacitance of up to 431.6 F·g⁻¹ at 5 mV·s⁻¹ and excellent cycling stability of 99.74% capacitance retention after 3000 cycles at 100 mV·s⁻¹. Furthermore, as the electrochemical catalysts for oxygen reduction reaction, as-fabricated porous carbons presented ultralow half-wave-potential of 0.78 V versus RHE. This work not only offers a new strategy for manipulating S and N doping features for the porous carbons derived from S-containing porous polymers, but also paves the way for the structure-performance interrelationship study of heteroatoms co-doped porous carbon for energy applications.