Calibration Using Matrix Completion with Application to Ultrasound Tomography

We study the calibration process in circular ultrasound tomography devices where the sensor positions deviate from the circumference of a perfect circle. This problem arises in a variety of applications in signal processing ranging from breast imaging to sensor network localization. We introduce a novel method of calibration/localization based on the time-of-flight (ToF) measurements between sensors when the enclosed medium is homogeneous. In the presence of all the pairwise ToFs, one can easily estimate the sensor positions using multi-dimensional scaling (MDS) method. In practice however, due to the transitional behaviour of the sensors and the beam form of the transducers, the ToF measurements for close-by sensors are unavailable. Further, random malfunctioning of the sensors leads to random missing ToF measurements. On top of the missing entries, in practice an unknown time delay is also added to the measurements. In this work, we incorporate the fact that a matrix defined from all the ToF measurements is of rank at most four. In order to estimate the missing ToFs, we apply a state-of-the-art low-rank matrix completion algorithm, OPTSPACE . To find the correct positions of the sensors (our ultimate goal) we then apply MDS. We show analytic bounds on the overall error of the whole process in the presence of noise and hence deduce its robustness. Finally, we confirm the functionality of our method in practice by simulations mimicking the measurements of a circular ultrasound tomography device.Comment: submitted to IEEE Transaction on Signal Processin

Ad Hoc Microphone Array Calibration: Euclidean Distance Matrix Completion Algorithm and Theoretical Guarantees

This paper addresses the problem of ad hoc microphone array calibration where only partial information about the distances between microphones is available. We construct a matrix consisting of the pairwise distances and propose to estimate the missing entries based on a novel Euclidean distance matrix completion algorithm by alternative low-rank matrix completion and projection onto the Euclidean distance space. This approach confines the recovered matrix to the EDM cone at each iteration of the matrix completion algorithm. The theoretical guarantees of the calibration performance are obtained considering the random and locally structured missing entries as well as the measurement noise on the known distances. This study elucidates the links between the calibration error and the number of microphones along with the noise level and the ratio of missing distances. Thorough experiments on real data recordings and simulated setups are conducted to demonstrate these theoretical insights. A significant improvement is achieved by the proposed Euclidean distance matrix completion algorithm over the state-of-the-art techniques for ad hoc microphone array calibration.Comment: In Press, available online, August 1, 2014. http://www.sciencedirect.com/science/article/pii/S0165168414003508, Signal Processing, 201

Supplementary health benefits of linoleic acid by improvement of vaginal cornification of ovariectomized rats

Purpose: This study aimed to evaluate the possible estrogenic activity of some ingredients of Nigella sativa including Linoleic acid and Gama-Linolenic acid by vaginal cornification assay. Methods: Forty ovariectomized (OVX) rats, aged 16 weeks were allotted randomly to five groups: negative control (taking 1 ml olive oil/ day); positive control (taking 0.2 mg/kg/day Conjucated Equine Estrogen-CEE); experimental groups (taking 50 mg/kg/day Linoleic acid or 10 mg/kg/day Gamma Linolenic acid or 15mg/kg/day Thymoquinone ). All of supplements administered via intragastric gavage for 21 consecutive days. To assess estrogen like activity, vaginal smear was examined daily and serum estradiol was measured at baseline, after 10 days and at the end of experiment. Results: The significant occurrence of vaginal cornification cell (p<0.05) after Linoleic acid supplementation indicated estrogenic activity of Linoleic acid which was in consistency with serum estradiol level, but this effect was not as much as CEE. Gama-Linolenic acid also exist a few cornified cell in smear which was not significantly differ from those control group. Conclusion: Linoleic acid showed the beneficial effects on OVX rats’ reproductive performance, thereby indicating its beneficial role in the treatment of the postmenopausal symptoms

Euclidean Distance Matrices: Essential Theory, Algorithms and Applications

Euclidean distance matrices (EDM) are matrices of squared distances between points. The definition is deceivingly simple: thanks to their many useful properties they have found applications in psychometrics, crystallography, machine learning, wireless sensor networks, acoustics, and more. Despite the usefulness of EDMs, they seem to be insufficiently known in the signal processing community. Our goal is to rectify this mishap in a concise tutorial. We review the fundamental properties of EDMs, such as rank or (non)definiteness. We show how various EDM properties can be used to design algorithms for completing and denoising distance data. Along the way, we demonstrate applications to microphone position calibration, ultrasound tomography, room reconstruction from echoes and phase retrieval. By spelling out the essential algorithms, we hope to fast-track the readers in applying EDMs to their own problems. Matlab code for all the described algorithms, and to generate the figures in the paper, is available online. Finally, we suggest directions for further research.Comment: - 17 pages, 12 figures, to appear in IEEE Signal Processing Magazine - change of title in the last revisio

Combining microfluidic devices with coarse capillaries to reduce the size of monodisperse microbubbles

In this work we report a significant advance for the preparation of monodispersed microbubbles, which are increasingly used and have become a key constituent in many advanced technologies. A new device comprising of two T-junctions containing coarse capillaries and operating in series was assembled. Microbubble generation was facilitated by using bovine serum albumin solution and nitrogen as the liquid and the gas phase, respectively. The effect of operating parameters such as gas pressure and liquid flow rate on the size of the microbubbles generated were investigated for the two T-junction systems and the results were compared with a single T-junction process. The experimental results showed that microbubbles produced via the double T-junction setup were smaller at any given gas pressure for both liquid flow rates of 100 and 200 μm studied in this work. A predictive model is developed from the experimental data, and the number of T-junctions was incorporated into this scaling model. It was demonstrated that the diameter of the monodisperse microbubbles generated can be tailored using multiple T-junctions while the operating parameters such as gas pressure and liquid flow rates were kept constant. The stability of the microbubbles produced was also examined and indicated that microbubbles produced through the double T-junction were more stable

Novel preparation of controlled porosity particle/fibre loaded scaffolds using a hybrid micro-fluidic and electrohydrodynamic technique.

The purpose of this research was to produce multi-dimensional scaffolds containing biocompatible particles and fibres. To achieve this, two techniques were combined and used: T-Junction microfluidics and electrohydrodynamic (EHD) processing. The former was used to form layers of monodispersed bovine serum albumin (BSA) bubbles, which upon drying formed porous scaffolds. By altering the T-Junction processing parameters, bubbles with different diameters were produced and hence the scaffold porosity could be controlled. EHD processing was used to spray or spin poly(lactic-co-glycolic) (PLGA), polymethysilsesquioxane (PMSQ) and collagen particles/fibres onto the scaffolds during their production and after drying. As a result, multifunctional BSA scaffolds with controlled porosity containing PLGA, PMSQ and collagen particles/fibres were obtained. Product morphology was studied by optical and scanning electron microscopy. These products have potential applications in many advanced biomedical, pharmaceutical and cosmetic fields e.g. bone regeneration, drug delivery, cosmetic cream lathers, facial scrubbing creams etc

Incision choice in laparatomy: a comparison of two incision techniques in ovariectomy of rats

The choice of surgical incision in the abdomen is determined by access for surgery. It has been suggested that utilizing a transverse or oblique rather than a midline incision may influence other parameters such as duration of surgery, recovery and complication rates. However, there is a little study as to whether a particular incision confers any advantage. The aim of the study was to determine whether a dorso-lateral incision or a transverse incision confers any advantage to the rats. Ninety five 16 weeks age female Sprague-Dawley rats were divided into two groups. Ovariectomy was preceded either by a single dorso-lateral incision (in the first group, n=45) or a single transverse lateral incision (in the second group, n=50). Animals in group A (vertical incision, n= 45) had a mean weight of 259.11±20.31 and those in group B (transverse incision, n=50) weighted 254.20±20.31 g, There was significant differences in the duration of surgery in the two groups (p<0.001). Although wound healing time for group B was slightly shorter than group A (9.46±0.973 day vs 9.78±1.380 day); none of the distributions of wound length and healing percentage per day showed significant variation between these two groups. The success of a surgery procedure performed through an abdominal incision depends on careful selection of the incision site and proper closure of the wound. In comparison of these two types incision for ovariectomy of rat, the operation as conducted in group B (Transverse Incision) was technically easier, less time consuming and less wound healing duration