Model-based methods to identify multiple cluster structures in a data set

There is an interest in the problem of identifying different partitions of a given set of units obtained according to different subsets of the observed variables (multiple cluster structures). A model-based procedure has been previously developed for detecting multiple cluster structures from independent subsets of variables. The method relies on model-based clustering methods and on a comparison among mixture models using the Bayesian Information Criterion. A generalization of this method which allows the use of any model-selection criterion is considered. A new approach combining the generalized model-based procedure with variable-clustering methods is proposed. The usefulness of the new method is shown using simulated and real examples. Monte Carlo methods are employed to evaluate the performance of various approaches. Data matrices with two cluster structures are analyzed taking into account the separation of clusters, the heterogeneity within clusters and the dependence of cluster structures.     

Clotrimazole nanoparticle gel for mucosal administration

In this study a formulation suitable to be applied on oral and/or vaginal mucosa has been developed for the treatment of fungal infections.The aim of the research is a comparison between clotrimazole (CLO) containing semisolid formulations based on monoolein aqueous dispersion (MAD) or nanostructured lipid carrier (NLC). MAD and NLC have been characterized in terms of morphology and dimensional distribution by cryogenic Transmission Electron Microscopy (cryo-TEM) and Photon Correlation Spectroscopy (PCS). CLO was encapsulated with high entrapment efficiency both in MAD and in NLC, according to Sedimentation Field Flow Fractionation (SdFFF) combined with HPLC. CLO recovery in MAD and NLC has been investigated by time.In order to obtain formulations with suitable viscosity for mucosal application, MAD was diluted with a carbomer gel, while NLC was directly viscosized by the addition of poloxamer 407 in the dispersion. The rheological properties of MAD and NLC after viscosizing have been investigated.Franz cell has been employed to study CLO diffusion from the different vehicles, evidencing diffusion rates from MAD and NLC superimposable to that obtained using Canesten^®.An anticandidal activity study demonstrated that both CLO-MAD and CLO-NLC were more active against Candida albicans with respect to the pure drug.     

Computations in the ring of quaternionic polynomials

In this paper we study basic division properties in the ring of regular quaternionic polynomials. We obtain a Bezout-like theorem and we calculate the module syzygy for any vector of polynomials.     

Integration of absolute ventricular fibrillation voltage correlateswith successful defibrillation

Previous work has suggested that at higher absolute ventricular fibrillation voltages (AVFV), the heart is more amenable to defibrillation. This study investigated in a canine model whether voltage integration of the AVFV is associated with the defibrillation success rate. The moving-average filter was used to process the ventricular fibrillation (VF) waveform recorded from Lead II of the electrocardiogram (ECG). In seven animals, defibrillation trials were analyzed using a DC shock (DCS) successful approximately 50% of the time when delivered randomly. For each of a total of 84 DCS (40% successes, 60% failures), the fibrillation waveform just prior to DCS was analyzed. The integration of the AVPV waveform was performed over various sample sizes including 1, 4, 8, 16, 64, and 128 ms, as well as the time equal to the mean VF cycle length. The results suggest that dc shocks delivered at instants of higher values of integrated AVFV over the various window sizes are associated with successful defibrillation. Window sizes less than 16 ms appeared to offer the best discrimination. The integration of AVFV over the entire VF cycle length was significantly higher for successful rather than unsuccessful DCS. This interesting observation is consistent with the clinical observation that “coarse” VF (high AVFV) is easier to defibrillate than “fine” VF (low AVFV). The use of voltage integration of AVFV may have potential implications in the improvement of defibrillation success in implantable devices     

The Role of CNTs in Promoting Hybrid Filler Networking and Synergism with Carbon Black in the Mechanical Behavior of Filled Polyisoprene

The filler networking process promoted by multiwalled CNTs is studied in neat and CB‐filled poly(1,4‐cis‐isoprene) matrices. TEM analysis, tensile, dynamic‐mechanical, and electrical measurements reveal that the CNTs form a filler network at low concentration in neat PI and a continuous hybrid filler network at a lower CNT concentration in the presence of CB, with a remarkable increase of the nonlinear dynamic‐mechanical behavior of the nanocomposites at low deformation. A synergistic effect between CB and CNTs is demonstrated. The addition of CNTs to the CB‐filled PI matrix leads to initial modulus values much larger than those calculated by simple addition of the two initial moduli of the composites containing only CB and only CNTs, respectively.

     

Distributed optical control plane for dynamic lightpath establishment in translucent optical networks based on reachability graph

In transparent optical networks, physical layer impairments (PLIs) incurred by non-ideal optical transmission media accumulate along an optical path, and the overall effect determines the optical feasibility of the lightpaths. In addition, transparent optical networks suffer from inefficient wavelength utilization, as a connection request may be rejected because of non-availability of a common wavelength on all the links along the chosen route. To increase optical reach, resource utilization, and average call acceptance ratio (and hence revenues), network operators are resort to translucent optical networks. In these networks a limited number of regenerators are placed at a selected set of nodes. In this scenario development of an optical control plane which is aware of PLIs, location and number of regenerators, is of paramount importance for on-demand lightpath provisioning. In this paper, we propose a novel approach of constructing a reachability graph of the physical network considering PLIs and regenerators. If there is no transparent path in the physical network, we route the connections with multiple transparent segments on the reachability graph. We propose efficient mechanisms and corresponding GMPLS protocol extensions for impairment and regenerator aware routing and wavelength assignment (IRA-RWA) in translucent optical networks. The simulation results suggest that our proposed approach together with LSP stitching signaling mechanism is feasible to implement and close to deployment.     

A practical strategy for sEMG-based knee joint moment estimation during gait and its validation in individuals with cerebral palsy

Individuals with cerebral palsy have neurological deficits that may interfere with motor function and lead to abnormal walking patterns. It is important to know the joint moment generated by the patient's muscles during walking in order to assist the suboptimal gait patterns. In this paper, we describe a practical strategy for estimating the internal moment of a knee joint from surface electromyography (sEMG) and knee joint angle measurements. This strategy requires only isokinetic knee flexion and extension tests to obtain a relationship between the sEMG and the knee internal moment, and it does not necessitate comprehensive laboratory calibration, which typically requires a 3-D motion capture system and ground reaction force plates. Four estimation models were considered based on different assumptions about the functions of the relevant muscles during the isokinetic tests and the stance phase of walking. The performance of the four models was evaluated by comparing the estimated moments with the gold standard internal moment calculated from inverse dynamics. The results indicate that an optimal estimation model can be chosen based on the degree of cocontraction. The estimation error of the chosen model is acceptable (normalized root-mean-squared error: 0.15-0.29, R: 0.71-0.93) compared to previous studies (Doorenbosch and Harlaar, 2003; Doorenbosch and Harlaar, 2004; Doorenbosch, Joosten, and Harlaar, 2005), and this strategy provides a simple and effective solution for estimating knee joint moment from sEMG.     

A leakage current model for sub-micron lightly-doped drain-offset polysilicon TFTs

Lightly-doped drain-offset polysilicon thin film transistors (LDO-TFTs) are very attractive as low leakage load elements in CMOS Static Random Access Memory (SRAM) cells. LDO-TFTs with different offset lengths and doses were fabricated and characterized. A model based on the Poole-Frenkel effect and thermionic field emission was developed to account for the leakage mechanism. The model was then applied to determine the sensitivity of the leakage current to process variations. It was found that the two most important factors influencing the leakage current are the net dose in the offset region and the distance between the channel/drain junction and the sidewall oxide.     

The Effects of Distant Cardiac Electrical Events on Local Activation in Unipolar Epicardial Electrograms

The effect of potentials generated during depolarization of the left ventricle on epicardial unipolar electrograms recorded from the right ventricle was studied using the right ventricular isolation procedure. This surgical technique disrupts electrical conduction and prevents activation wavefronts from propagating between the ventricles. Following the procedure, the ventricles were paced asynchronously with the left ventricle paced 100 ms before the right ventricle to geparate the electrogram into its local (due to depolarization of the right ventricle) and distant (due to depolarization of the left ventricle) components or with an interval of 20 ms or less between pacing the ventricles to mimic electrograms resulting from normal (synchronous) activration. Electrical activity in the left ventricle significantly affected the magnitude of the slope of the most rapid deflection and the timing of the maximum and minimum potentials of right ventricular unipolar electrograms. However, distant activity did not significantly alter the timing of the fastest 1 ms downstroke. No electrograms of distant components had negative slopes with magnitudes greater than 1.3 mV/ms, nor did any slopes of electrograms containing only local components have magnitudes less than 1.5 mV/ms. Simulated electrograms, calculated from the local and distant components, correlated well (r = 0.83 to 1.00, N = 48) with electrograms recorded during synchronous pacing.