Bleeding risk evaluation in cerebral cavernous malformation, the role of medications, and hemorrhagic factors: a case-control study

Objective: Cerebral cavernous malformations (CCMs) are vascular lesions with an overall risk of rupture from 2% to 6% per year, which is associated with significant morbidity and mortality. The diagnostic incidence is increasing, so it is of paramount importance to stratify patients based on their risk of rupture. Data in the literature seem to suggest that specific medications, particularly antithrombotic and cardiovascular agents, are associated with a reduced risk of bleeding. However, the effect of the patient coagulative status on the cumulative bleeding risk remains unclear. The aim of this study was to assess the impact of different radiological, clinical, and pharmacological factors on the bleeding risk of CCMs and to assess the predictive power of an already validated scale for general bleeding risk, the HAS-BLED (hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly, drugs/alcohol concomitantly). Method: This was a multicenter retrospective observational study. The authors collected imaging, clinical status, and therapy data on patients with bleeding and nonbleeding CCMs. Univariate analysis and subsequent multivariate logistic regression were performed between the considered variables and bleeding or nonbleeding status to identify potential independent predictors of bleeding. Results: The authors collected data on 257 patients (46.7% male, 25.3% with bleeding CCMs). Compared with patients with nonbleeding lesions, those with bleeding CCMs were younger, less frequently had hypertension, and less frequently required antiplatelet drugs and beta-blockers (all p < 0.05). Bleeding lesions, however, had significantly higher median volumes (1050 mm3 vs 523 mm3 , p < 0.001). On multivariate analyses, after adjusting for age, history of hypertension and diabetes, and use of antiplatelet drugs or beta-blockers, lesion volume ≥ 300 mm3 was the only significant predictor of bleeding (adjusted OR 3.11, 95% CI 1.09-8.86). When the diagnostic accuracy of different volume thresholds was explored, volume ≥ 300 mm3 showed a limited sensitivity (36.7%, 95% CI 24.6%-50.0%), but a high specificity 78.2% (95% CI 71.3%-84.2%), with an area under the curve of 0.57 (95% CI 0.51-0.64). Conclusions: This study supports previous findings that the CCM volume is the only factor influencing the bleeding risk. Antithrombotic agents and propranolol seem to have a protective role against the bleeding events. A high HAS-BLED score was not associated with an increased bleeding risk. Further studies are needed to confirm these results

Noise parametric identification and whitening for LIGO 40-meter interferometer data

We report the analysis we made on data taken by Caltech 40-meter prototype interferometer to identify the noise power spectral density and to whiten the sequence of noise. We concentrate our study on data taken in November 1994, in particular we analyzed two frames of data: the 18nov94.2.frame and the 19nov94.2.frame. We show that it is possible to whiten these data, to a good degree of whiteness, using a high order whitening filter. Moreover we can choose to whiten only restricted band of frequencies around the region we are interested in, obtaining a higher level of whiteness.Comment: 11 pages, 15 figures, accepted for publication by Physical Review

Reactive Power and Current Harmonic Control Using a Dual Hybrid Power Filter for Unbalanced Non-Linear Loads

An important power quality issue is related to current harmonic components demanded by non-linear loads. A solution to mitigate this issue is to use hybrid power filters (HPFs), that apply low power active filters with passive filters. Some dual-converter topologies have been shown to be attractive due to a better compensation performance compared with single filters, where the HPFs give a reactive power support (an extra feature) together with harmonic compensation. On the other hand, the drawback of dual converters is the high number of active switches. Besides that, due to the high number of unbalanced non-linear loads connected to the electrical grid, triplen harmonics can appear. However, traditional HPFs do not compensate triplen harmonics, which usually have considerable values. Therefore, in this paper, a dual HPF based on the nine-switch inverter (DHPF-NSI) is proposed to compensate current harmonics and to provide reactive power support. The NSI presents a reduced number of switches when compared with classical dual topologies. The compensation of the third harmonic caused by unbalanced nonlinear loads was also inserted in the control system. Experimental results are presented for the DHPF-NSI in order to demonstrate the reactive power and harmonic compensation performances

Modeling and Control Design of the Symmetrical Interleaved Coupled-Inductor-Based Boost DC-DC Converter with Clamp Circuits

The symmetrical input-interleaved high-gain DC-DC converters are suitable candidates to be used as the first stage in PV microinverters and as parallel-connected power optimizers. In both applications, they are responsible for boosting the PV module DC voltage to a higher value and executing the maximum power point tracking control. However, such converters have many state variables, some of them discontinuous, and many operation stages, which make the development of the small-signal model a challenging task. Therefore, the aim of this paper is to propose a reduced-order improved average method (ROIAM) to model the family member of converters that present characteristics such as symmetry, interleaved operation, and discontinuous state-space variables. ROIAM is applied to model for the first time in the literature the symmetrically-interleaved coupled inductor-based boost (SICIBB), leading to a fourth-order mathematical model (reduced-order model). The complete eighth-order mathematical model is developed as well to prove that the reduced-order model represents correctly the dynamic behavior of the SICIBB converter by employing only four state variables, reducing considerably the effort of the modeling. Based on the reduced-order proposed model, a closed-loop control is designed and tested in a 300-W prototype of the SICIBB converter

An Overview of Voltage Boosting Techniques and Step-Up DC-DC Converters Topologies for PV Applications

The development of technologies to improve the performance of photovoltaic (PV) module integrated converters (MICs) is fundamental to increase the use of distributed generation systems with photovoltaic power source in large urban centers, mainly for complex residential roofs. For two-stage PV MICs, high step-up DC-DC converters are required to boost the low PV module voltage to a higher voltage, in order to suit the DC bus voltage requirements of grid-tied inverters. Thus, to support researchers interested in developing DC-DC power conversion for PV microinverters, this paper classifies the DC-DC converters according to their operational and constructive characteristics and presents some elementary voltage-boosting techniques to aid in analyzing and understanding more complex topologies. Finally, high step-up DC-DC converters based on magnetic coupling and switched capacitor widely cited by important works related to PV applications are presented, with their principles of operation analysed in a simple and objective way, but sufficient to understand their capability to provide high voltage gain. The approach presented by this paper leads to insight into how to place the energy storage elements to create new topologies of DC-DC converters, so that high voltage gain is achieved, and how to analise the high voltage gain capability of complex topologie