Accurate localization of optic radiation during neurosurgery in an interventional MRI suite

Accurate localization of the optic radiation is key to improving the surgical outcome for patients undergoing anterior temporal lobe resection for the treatment of refractory focal epilepsy. Current commercial interventional magnetic resonance imaging (MRI) scanners are capable of performing anatomical and diffusion weighted imaging and are used for guidance during various neurosurgical procedures. We present an interventional imaging workflow that can accurately localize the optic radiation during surgery. The workflow is driven by a near real-time multichannel nonrigid image registration algorithm that uses both anatomical and fractional anisotropy pre- and intra-operative images. The proposed workflow is implemented on graphical processing units and we perform a warping of the pre-operatively parcellated optic radiation to the intra-operative space in under 3 min making the proposed algorithm suitable for use under the stringent time constraints of neurosurgical procedures. The method was validated using both a numerical phantom and clinical data using pre- and post-operative images from patients who had undergone surgery for treatment of refractory focal epilepsy and shows strong correlation between the observed post-operative visual field deficit and the predicted damage to the optic radiation. We also validate the algorithm using interventional MRI datasets from a small cohort of patients. This work could be of significant utility in image guided interventions and facilitate effective surgical treatments.     

BER Performance of OFDM Signals in Presence of Nonlinear Distortion due to SSPA

Orthogonal frequency division multiplexed signals typically exhibit large dynamic ranges due to superposition of a large number of subcarrier signals. As a result, such signals are highly vulnerable to distortion caused by high power amplifier (HPA) nonlinearity, leading to degradation in bit error rate (BER). In turn, the HPA operating point should be backed off to compensate for such degradation at the expense of the HPA efficiency. In this paper, the considered amplifier chain is a solid state power amplifier of Rapp’s model. We develop the factors contributing to BER degradation in terms of the input back-off (IBO) level assuming quadrature phase shift keying modulation. Consequently, the BER performance for such an amplifier model is developed as a function in IBO. Then, we show how this developed performance can be used to determine the required HPA operating point to achieve a certain required BER. Accordingly, an improvement in the amplifier efficiency is achieved. All developed analytic expressions are compared against simulation measurements, which show that good agreement exists.     

Toward the synthesis of (+)-peloruside A via an intramolecular vinylogous aldol reaction

The use of the intramolecular vinylogous aldol reaction for the preparation of an advanced intermediate for the synthesis of peloruside A is described. The reaction was applied to compound 19 and proceeds in high yield and good levels of diastereoselectivity. Application of the Achmatowicz reaction to this intermediate provided the corresponding pyranone, a late stage intermediate well positioned for conversion to the natural product.     

Impact of the meteorological parameters on the behaviour of 7Be at ground level in Tetouan city,Morocco from June 2015 to February 2017

For the first time, atmospheric aerosols were collected in Tetouan city (Morocco), from June 2015 to February 2017, through which ⁷Be activity was measured. We studied data variation by time series analyses and the impact of local meteorological factors on it. ⁷Be concentrations, in mBq/m³, ranged from 1.65 to 7.79 with mean value of 4.69. ⁷Be behaviour is mainly influenced by air temperature, precipitations, relative humidity and atmospheric pressure. A prediction model was suggested and validated. This study helps understanding climatic variables impact on the environmental processes as aerosols transport and deposit, and to predict ⁷Be behaviour in Mediterranean regions like Tetouan.

     

Assessment of an Evaporation Model in CFD Simulations of a Free Liquid Pool Fire Using the Mass Transfer Number Approach

In the present paper an evaporation model is implemented and assessed in a Computational Fluid Dynamics (CFD) code named ISIS. First, the influence of the cell size and time step on the temperature field is studied via simulations with a prescribed fuel Mass Loss Rate (MLR). Then, the evaporation model is assessed using predictive simulations. The experimental scenario is a 30 cm-diameter heptane pool fire. The average fuel Mass Loss Rate Per Unit Area (MLRPUA) is predicted within 5.5% deviation from the experimental value. In addition, an analysis of the temperature and heat fluxes at the surface of the liquid, the mass transfer coefficient and the temperature inside the liquid is performed.     

N-Halosuccinimide/SiCl4 as general, mild and efficient systems for the α-monohalogenation of carbonyl compounds and for benzylic halogenation

Combinations of N-halosuccinimide and tetrachlorosilane in acetonitrile were found to be efficient systems for the selective α-monohalogenation of carbonyl compounds as well as for benzylic halogenation under mild conditions.     

Radiation annealing of rapidly solidified Sn–6.7Sb–5.3Zn alloy by low-dose gamma ray

The radiation annealing of a rapidly solidified Sn–6.7Sb–5.3Zn (in atomic percent) melt-spun alloy was caused by low-dose gamma ray irradiation. This is observed from the increase in both the volume of unit cell and particle size of the Sn matrix, as revealed from X-ray diffraction analysis, and the decrease in the resistivity. The alloy was irradiated by gamma ray at doses 5, 10, 20, 40, 50, 60, 70, 80, and 100 Gy. The electrical resistivity was measured for the alloys subjected to these doses and it was found that the resistivity decreased by increasing the dose to a minimum value of 50 Gy and then increased by increasing the dose.     

An improved automated ultrasonic NDE system by wavelet and neuron networks

Despite of the widespread and increasing use of digitized signals, the ultrasonic testing community has not realized yet the full potential of the electronic processing. The performance of an ultrasonic flaw detection method is evaluated by the success of distinguishing the flaw echoes from those scattered by microstructures. So, de-noising of ultrasonic signals is extremely important as to correctly identify smaller defects, because the probability of detection usually decreases as the defect size decreases, while the probability of false call does increase. In this paper, the wavelet transform has been successfully experimented to suppress noise and to enhance flaw location from ultrasonic signal, with a good defect localization. The obtained result is then directed to an automatic Artificial Neuronal Networks classification and learning algorithm of defects from A-scan data. Since there is some uncertainty connected with the testing technique, the system needs a numerical modelling. So, knowing the technical characteristics of the transducer, we can preview which are the defects that experimental inspection should find. Indeed, the system performs simulation of the ultrasonic wave propagation in the material, and gives a very helpful tool to get information and physical phenomena understanding, which can help to a suitable prediction of the service life of the component.     

Dual-Frequency Behavior of Stacked High <Emphasis Type="Italic">T</Emphasis><Subscript><Emphasis Type="Italic">c</Emphasis></Subscript> Superconducting Microstrip Patches

The dual-frequency behavior of stacked high T _c superconducting rectangular microstrip patches fabricated on a two-layered substrate is investigated using a full-wave spectral analysis in conjunction with the complex resistive boundary condition. Using a matrix representation of each layer, the dyadic Green’s functions of the problem are efficiently determined in the vector Fourier transform domain. The stationary phase method is used for computing the radiation electric field of the antenna. The proposed approach is validated by comparison of the computed results with previously published data. Variations of the lower and upper resonant frequencies, bandwidth and quality factor with the operating temperature are given. Results showing the effects of the bottom patch thickness as well as the top patch thickness on the dual-frequency behavior of the stacked configuration are also presented and discussed. Finally, for a better comprehension of the dual-frequency operation, a comparison between the characteristics of the lower and upper resonances is given.     

Construction of a stable vehicular ad hoc network based on hybrid genetic algorithm

Telecommunication Systems - In vehicular ad hoc networks, the vehicle speed can exceed 120 kmph. Therefore, any node can enter or leave the network within a very short time. This mobility adversely...