Crystal and molecular structure of the centrosymmetric meso-valinomycin analogue--cyclo (D-Val-D-Hyi-D-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi-L-Val-D-Hyi-D-Val-L-Hy i) (C60H102N6O18)

The crystal structure of cyclo (D-Val-D-Hyi-D-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi -L-Val-D-Hyi-D-Val-L-Hyi).2H2O has been solved by x-ray direct methods. The crystals (grown from a mixture of octane/CH2Cl2) are an orthorhombic, centrosymmetric space group Pbca, cell parameters a = 11.458 (2), b = 25.613 (3), c = 23.691 (3) A, Z = 4; therefore the molecule lies on a center of inversion in the cell. The atomic coordinates for the C, N, and O atoms were refined in the anisotropic thermal motion approximation (allowing for H-atom contribution to Fcal) to a standard R-factor value of 0.081. In contrast to meso-valinomycin, the analogue under study does not adopt an octahedral cage bracelet conformation. It has an unusual centrosymmetric elongated form with two type II terminal beta-bends formed by N-H ... C=O 4-->1 type intramolecular H bonds. Two symmetry-related water molecules reside in the elongated molecular cavity of the centrosymmetric depsipeptide ring.     

2.5 GHz and 5 GHz harmonic mode-locking of a diode-pumped bulkerbium-ytterbium glass laser at 1.5 microns

Third-order harmonic mode locking of a diode-laser pumped bulk Er:Yb:glass laser by frequency modulation with a lithium niobate modulator is reported. Stable pulses at a repetition rate of 2.5 and 5 GHz with a pulse duration down to 9.6 ps are obtained. The average output power is 3 mW, the pulse peak power is 120 mW at 2.5 GHz repetition rate, and the pulses are approximately 1.4 times transform limited. The pulse duration can be increased up to 30 ps by decreasing the mode-locker drive power     

Vascular cell attachment and procoagulant activity on metal alloys

The attachment and growth of vascular smooth muscle cells on biomaterials used as components of devices implanted in the vascular space may influence the biocompatibility of such materials. The nature of the materials may affect the attachment and/or the activation of these cells' procoagulant responses. Therefore, the main objective of this study was to measure the strength of adhesion of these vascular cells to potential biomaterials (titanium, zirconium alloys, and stainless steel) by exposing them to a range of shear stresses (50-300 dyn cm(-2)) in a parallel plate flow chamber. The procoagulant responses of the cells were evaluated by measuring the tissue factor (TF) activity promoted by the different materials under flow conditions. The materials supported distinctly different levels of initial cell adhesion in static culture. However, the fraction of adherent cells did not decline significantly with incrementally increasing shear stress within the range tested. TF expression, as measured by factor Xa (FXa) production. was material-dependent. For example, cells cultured on Ti1313 exhibited more FXa production (13.2 nM 10(-5) cells) than Ti1313(DH) (8.5 nM 10(-5) cells) or stainless steel (2 nM 10(-5) cells). Thus, our studies indicate that the level of adhesion, strength of attachment and the expression of procoagulant activity of adherent vascular cells depend strongly on the nature of the underlying biomaterial.     

Discovering dangerous patterns in long-term ambulatory ECG recordings using a fast QRS detection algorithm and explorative data analysis

The next two decades will see dramatic changes in the health needs of the world's populations with chronic diseases as the leading causes of disability, according to recent World Health Organization reports. Increases in the senior population living "confined" in domestic area are also expected producing a steep increase in the need for long-term monitoring and home care services. Independently of the particular features and specific architectures, long-term monitoring systems usually produce a large amount of data to be analyzed and inspected by the practitioners and in particular by the cardiologists dealing with ECG recordings analysis. This problem is well known and regards also the traditional holter-based practice. In this paper we present a program for discovering patterns in ECG recordings, to be considered as a medical decision-making support. Computational methods are based on a QRS detector especially designed for noisy applications followed by a parameters space reduction operated by the KL transform modified on a "user-fit" basis. Events characterization is based on a recently introduced clustering method, called KHM (K-harmonic means). The most representative beat families and the corresponding prototypes (physiological and pathological) are then presented to the user through appropriate graphics to facilitate an easy and fast interpretation. We tested the QRS detection algorithm using the MIT-BIH arrhythmia database. Our method produced 565 false positive beats and 379 false negative beats and a total detection failure of 0.85% considering all the 109.809 annotated beats in the database. While a clinical experimentation of our program is on the way, we used the VALE Database to perform a preliminary evaluation of the methods used for data exploration (PCA, KHM). Considering the entire database, we succeeded in identifying pathological clusters in 97% of the cases.     

DMFC performance and methanol cross-over: Experimental analysis and model validation

A combined experimental and modelling approach is proposed to analyze methanol cross-over and its effect on DMFC performance. The experimental analysis is performed in order to allow an accurate investigation of methanol cross-over influence on DMFC performance, hence measurements were characterized in terms of uncertainty and reproducibility. The findings suggest that methanol cross-over is mainly determined by diffusion transport and affects cell performance partly via methanol electro-oxidation at the cathode. The modelling analysis is carried out to further investigate methanol cross-over phenomenon. A simple model evaluates the effectiveness of two proposed interpretations regarding methanol cross-over and its effects. The model is validated using the experimental data gathered. Both the experimental analysis and the proposed and validated model allow a substantial step forward in the understanding of the main phenomena associated with methanol cross-over. The findings confirm the possibility to reduce methanol cross-over by optimizing anode feeding.     

Anaerobic ammonium oxidation of ammonium-rich waste streams in fixed-bed reactors.

The feasibility of anaerobic ammonium oxidation (Anammox) in fixed-bed reactors was evaluated on laboratory and pilot scales. Using synthetic wastewater, the specific nitrogen removal rate was increased from 0.05-0.1 kgNm(-3)(reactor)d(-1) to 0.35-0.38 kgNm(-3)(reactor)d(-1) within a year (T= 22-27 degrees C) in all applications. However, the anammox activity was seriously and repeatedly inhibited at prolonged high nitrite concentrations (e.g. six days at 30-50 gNO2-Nm(-3)) and recovery was always a lengthy process. But even at a moderate nitrite concentration (11+/-10 gNO2-Nm(-3)), the observed specific growth rate was only 0.018 d(-1) at 26.4+/-0.8 degrees C, which corresponds to approximately 0.025 d(-1) at 30 degrees C (doubling time: 28 days). In a second experimental period for another 250 days, one of the laboratory reactors was fed with partially nitrified sludge liquors from a domestic wastewater treatment plant (WWTP). In this case, the specific elimination rate was as high as 3.5 kgNm(-3)(reactor)d(-1) at 26-27 degrees C. Independently of the feed, the average nitrogen elimination rate lay between 80-85% in all applications. An appropriate hydraulic design is essential to prevent clogging and local nitrite inhibition in fixed-bed reactors.