Learning and comparing functional connectomes across subjects

Functional connectomes capture brain interactions via synchronized fluctuations in the functional magnetic resonance imaging signal. If measured during rest, they map the intrinsic functional architecture of the brain. With task-driven experiments they represent integration mechanisms between specialized brain areas. Analyzing their variability across subjects and conditions can reveal markers of brain pathologies and mechanisms underlying cognition. Methods of estimating functional connectomes from the imaging signal have undergone rapid developments and the literature is full of diverse strategies for comparing them. This review aims to clarify links across functional-connectivity methods as well as to expose different steps to perform a group study of functional connectomes

Practical method for the determination of time step in non-orthogonal FDTD

The Non-Orthogonal FDTD algorithm is well-suited to the modelling of curved structures, however users of the technique frequently have difficulty determining an appropriate time step for the algorithm. This contribution presents a new method which is shown to be both a practical and reliable technique for determining the time step

Metal boundary modelling for non-orthogonal FDTD

This contribution looks into a technique to reduce numerical errors when employing non-orthogonal mesh in modelling curved structures. A novel technique is analysed using microstrip line and a patch antenna and the results are presented

High resolution thermal infrared mapping of Martian channels

Viking Infrared Thermal Mapper (IRTM) high resolution (2 to 5 km) data were compiled and compared to Viking Visual Imaging Subsystem (VIS) data and available 1:5M geologic maps for several Martian channels including Dao, Harmakhis, Mangala, Shalbatana, and Simud Valles in an effort to determine the surface characteristics and the processes active during and after the formation of these channels. Results show a dominance of aeolian processes active in and around the channels. These processes have left materials thick enough to mask any genuine channel deposits. Results also indicate that very comparable Martian channels and their surrounding terrain are blanketed by deposits which are homogeneous in their thermal inertia values. However, optimum IRTM data does not cover the entire Martian surface and because local deposits of high thermal inertia material may not be large enough in areal extent or may be in an unfavorable location on the planet, a high resolution data track may not always occur over these deposits. Therefore, aeolian processes may be even more active than the IRTM data tracts can always show

Wideband microstrip patch antenna design for breast cancer tumour detection

A patch antenna is presented which has been designed to radiate into human breast tissue. The antenna is shown by means of simulation and practical measurement to possess a wide input bandwidth, stable radiation patterns and a good front-to-back ratio. Consideration is also given to its ability to radiate a pulse, and in this respect it is also found to be suitable for the proposed application

Breast cancer tumour detection using microwave radar techniques

A breast cancer detection technique using multi-static radar is proposed herein. Images of a breast tumour are produced using this technique, with backscatter data. A wideband antenna design suitable for a breast cancer detection system is also described. Practical measurements are performed using a network analyser and a pair of antennas that are used to simulate an array. These initial images demonstrate the successful detection of a tumour phantom immersed in a liquid phantom with similar dielectric properties as the breast tissues

Breast tumour detection using a flat 16 element array

A new experimental prototype of a breast cancer detection technique using real aperture multi-static radar is presented. The system comprises a fully-populated 16 element flat array and an associated system to switch between different transmit and receive elements. 3D images are produced using backscatter signals from a synthetic breast phantom. After suppression of skin reflections, initial images demonstrate the successful detection of 4-mmdiameter tumours

Numerical analysis of microwave detection of breast tumours using synthetic focussing techniques

Microwave detection of breast tumours is a non-ionising and potentially low-cost and more certain alternative to X-ray mammography. Analogous to ground penetrating radar (GPR), microwaves are transmitted using an antenna array and the reflected signals, which contain reflections from tumours, are recorded. The work presented here employs a post reception synthetically focussed detection method developed for land mine detection (R. Benjamin et al., IEE Proc. Radar, Sonar and Nav., vol. 148, no.4, pp. 233-40, 2001); all elements of an antenna array transmit a broadband signal in turn, the elements sharing a field of view with the current transmit element then record the received signal. By predicting the path delay between transmit and receive antennas via any desired point in the breast, it is then possible to extract and time-align all signals from that point. Repeated for all points in the breast, this yields an image in which the distinct dielectric properties of malignant tissue are potentially visible. This contribution presents a theoretical evaluation of the breast imaging system using FDTD methods. The FDTD model realistically models a practical system incorporating wide band antenna elements. One major challenge in breast cancer detection using microwaves is the clutter arising from skin interface. Deeply located tumours can be detected using windowing techniques (R. Nilavalan et al., Electronics Letters, vol. 39, pp. 1787-1789, 2003); however tumours closer to the skin interface require additional consideration, as described herein