Cellular mechanism underlying the efficacy of the sotalol-quinidine combination

The combination of quinidine and sotalol is very effective in prevention of recurrent sustained ventricular tachycardia (SVT). The cellular mechanisms underlying this efficacy were examined in guinea pig papillary muscle, using standard microelectrode techniques and stimulation frequencies of 1, 2, and 3 Hz. Action potential duration (APD) and effective refractory period (ERP) were measured under control conditions, after 30-min perfusion with quinidine (5 microM) or sotalol (6 microM), and after an additional 30 min of quinidine + sotalol (5 and 6 microM, respectively). Quinidine, sotalol, and quinidine + sotalol all prolonged APD at 90% repolarization (APD90) by 9 +/- 1, 13 +/- 1, and 15 +/- 2%, respectively (at 3 Hz; p = NS, comparison of the three drugs; p < 0.05 for each drug as compared with control). Quinidine + sotalol prolonged ERP (at 3 Hz) by 27 +/- 2% as compared with 11 +/- 2% after sotalol and 18 +/- 2% after quinidine alone (p < 0.05). As a result, the ERP/APD ratio was increased by the combination to 0.87 +/- 0.2 (p < 0.05) as compared with 0.78 +/- 0.2 for control 0.79 +/- 0.1 for sotalol, and 82 +/- 0.1 for quinidine (at 3 Hz). Although sotalol alone decreased the maximum rate of depolarization of phase 0 of the AP (Vmax) by only 3 +/- 2% (p = NS), sotalol attenuated Vmax decrease of quinidine (at 3 Hz) from 40 +/- 4 to 16 +/- 3% (p < 0.05). Effects at 1 and 2 Hz were similar.(ABSTRACT TRUNCATED AT 250 WORDS)     

Elasto-plastic impact of a rotating link with a massive surface

This study presents the impact with friction of a rigid or a flexible body against a half-space, each with a small region of contact compliance where the compliance is obtained from the Jackson and Green theory. The model consists of a system of nonlinear differential equations which considers a nonlinear contact force as well as frictional effects at the contacting end, and allows one to predict the motion after the impact. The initial incidence angle, the initial impact velocity, and the contact radius of the link are found to influence the coefficient of restitution with friction. Analytical and experimental results were compared to establish the accuracy of the model.     

Identification of CYP106A2 as a regioselective allylic bacterial diterpene hydroxylase

The cytochrome P450 monooxygenase CYP106A2 from Bacillus megaterium ATCC 13368 catalyzes hydroxylations of a variety of 3-oxo-Δ(4) -steroids such as progesterone and deoxycorticosterone (DOC), mainly in the 15β-position. We combined a high-throughput screening and a rational approach for identifying new substrates of CYP106A2. The diterpene resin acid abietic acid was found to be a substrate and was docked into the active site of a CYP106A2 homology model to provide further inside into the structural basis of the regioselectivity of hydroxylation. The products of the hydroxylation reaction were analyzed by HPLC and the V(max) and K(m) values were calculated. The corresponding reaction products were analyzed by NMR spectroscopy and identified as 12α- and 12β-hydroxyabietic acid. CYP106A2 was therefore identified as the first reported bacterial cytochrome P450 diterpene hydroxylase. Furthermore, an effective whole-cell catalyst for the selective allylic 12α- and 12β-hydroxylation was applied to produce the hydroxylated products.     

Influence of substrate absorption on the optical and geometrical characterization of thin dielectric films

The role played by a glass substrate on the accurate determination of the optical constants and the thickness of a thin dielectric film deposited on it, when well-known envelope methods are used, is discussed. Analytical expressions for the two envelopes of the optical transmission spectra corresponding to film. with both uniform and nonuniform thicknesses are derived, assuming the substrate to be a weakly absorbing layer. It is shown that accurate determination of the refractive index and the film thickness is notably improved when the absorption of the substrate is considered. The analytical expressions for the upper and lower envelope, are used to characterize optically and geometrically both uniform and nonuniform amorphous chalcogenide films. The results obtained are compared with those derived by use of expressions for the envelopes that neglect the substrate absorption. The comparison shows that overestimated refractive indexes and underestimated thicknesses are obtained when the conventional approach, in which the substrate absorption is neglected, is used.     

Better than Taguchi orthogonal tables

There has been a great amount of publicity about Taguchi orthogonal tables. This paper will evaluate the pros and cons of that approach. In addition an American approach, having the same initial goals of the Taguchi approach, will be presented in detail, representing a significant improvement in meeting those goals without confounding interactions with any main effect or with other interactions. In addition, this constructive alternative generally requires a much smaller number of tests.     

Earth Observation application development based on the Grid oriented ESIP satellite image processing platform

Satellite images supply important information on earth surface, weather, clime, geographic areas, vegetation, and natural phenomena. Processing of satellite data requires high computation resources and flexible tools in order to search, discover, and reveal the main information, to experiment new algorithms, and to include them into new Earth Observation applications. This paper describes the features and the architectures of the ESIP and gProcess platforms, supporting the Grid based satellite imagery processing. The development methodology of Earth Observation applications is highlighted as well in order to hide the Grid complexity to the user.     

An LIF characterization of supersonic BO (X2Σ+) and CN (X2Σ+) radical sources for crossed beam studies

Various ablation sources generating supersonic boron monoxide (BO; X(2)Σ(+)) radical beams utilizing oxygen (O(2)), carbon dioxide (CO(2)), methanol (CH(3)OH), and water (H(2)O) as seeding gases were characterized in a crossed molecular beams setup by mass resolved time-of-flight spectroscopy and spectroscopically via laser induced fluorescence. Intensities of the sources as well as rovibrational energy distributions were analyzed. The molecular oxygen source was found to produce excessive amount of an unwanted BO(2) byproduct. Internal vibrational energy of boron monoxide generated in the water and methanol sources was too high to be considered for the study of dynamics of ground state radicals. The best combination of intensity, purity, and low internal energy was found in the carbon dioxide source to generate boron monoxide. We successfully tested the boron monoxide (BO; X(2)Σ(+)) radical beam source in crossed beams reactions with acetylene (C(2)H(2)) and ethylene (C(2)H(4)). The source was also compared with supersonic beams of the isoelectronic cyano (CN; X(2)Σ(+)) radical.     

“Solving” ambiguity in the virtual space: communication strategies in a collaborative virtual environment

Collaborative virtual environments (CVE) face the challenge of succeeding in incorporating critical dimensions of cooperation and communication in everyday working situations. One of these dimensions, situation ambiguity, is scarcely considered in studies on CVE although it can prove a key factor in future use of CVE in real work situations. Many computer-supported cooperative environments and telecommunication systems, like those currently used in telemedicine, would benefit from the incorporation of some degree of situation ambiguity allowing users to deploy their diagnostic and interpretive abilities. In the perspective adopted in this study, ambiguity is the contingent outcome of the ongoing interaction taking place between the environment and the interests of social actors. The research focuses on the cooperation within couples of participants facing situation ambiguity in a virtual environment: a simulated city named Babylon. Participants moved in the city through an avatar and could communicate in one of the following conditions: face-to-face, phone or chat. Their goal was that of meeting somewhere in the city, in a place that they did not know previously. Babylon contained elements designed to allow both production and detection of ambiguity. Ambiguity emerged when participants realized the presence of inconsistencies in the way they perceived the situations they had to face. The moments in which ambiguity was perceived—called “critical events” (CE)—were measured and described through qualitative (ethnographically oriented) methods. The different strategies that participants used to “solve” ambiguity were characterized as: looking for environmental cues, narrowing the focus of attention and investing on cooperation. Both CEs and strategies were analyzed with respect to the three communication conditions: face-to-face, phone and chat. All the communication conditions allowed the emergence of ambiguity and the negotiation of strategies to solve ambiguity between partners: according to literature, chat is very costly in terms of time spent on writing but this disadvantage did not block completely the emergence of ambiguity and the development of adequate strategies of solution. All navigations but three (on a total of 18 couples) succeeded: the partners did meet in a short time (less than 15 min) relying on their pragmatic resources in a new virtual place. Further research is required to clarify the possible factors influencing the choice of one strategy over the others, the order in which strategies follow each other and the role of leadership in ambiguity detection and solution.