Plausibility of Image Reconstruction Using a Proposed Flexible and Portable CT Scanner

The very hot and power-hungry x-ray filaments in today's computed tomography (CT) scanners constrain their design to be big and stationary. What if we built a CT scanner that could be deployed at the scene of a car accident to acquire tomographic images before moving the victim? Recent developments in nanotechnology have shown that carbon nanotubes can produce x-rays at room temperature, and with relatively low power needs. We propose a design for a portable and flexible CT scanner made up of an addressable array of tiny x-ray emitters and detectors. In this paper, we outline a basic design, propose a strategy for reconstruction, and demonstrate the feasibility of reconstruction using experiments on a software simulation of the flexible scanner. These simulations show that reconstruction quality is stable over a wide range of scanner geometries, while progressively larger errors in the scanner geometry induce progressively larger errors. We also raise a number of issues that still need to be overcome to build such a scanner.This work was supported by funding from the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canada Foundation for Innovation, and the Ontario Innovation Trust

Bismuth Sulfide Nanoflowers for Detection of X-rays in the Mammographic Energy Range

Nambiar, S., Osei, E. K., & Yeow, J. T. W. (2015). Bismuth Sulfide Nanoflowers for Detection of X-rays in the Mammographic Energy Range. Scientific Reports, 5, 9440. DOI: 10.1038/srep09440The increased use of diagnostic x-rays, especially in the field of medical radiology, has necessitated a significant demand for high resolution, real-time radiation detectors. In this regard, the photoresponse of bismuth sulfide (Bi2S3), an n-type semiconducting metal chalcogenide, to low energy x-rays has been investigated in this study. In recent years, several types of nanomaterials of Bi2S3 have been widely studied for optoelectronic and thermoelectric applications. However, photoresponse of Bi2S3 nanomaterials for dosimetric applications has not yet been reported. The photosensitivity of Bi2S3 with nanoscale “flower-like” structures was characterized under x-ray tube-potentials typically used in mammographic procedures. Both dark current and photocurrent were measured under varying x-ray doses, field sizes, and bias voltages for each of the tube potentials – 20, 23, 26 and 30 kV. Results show that the Bi2S3 nanoflowers instantaneously responded to even minor changes in the dose delivered. The photoresponse was found to be relatively high (few nA) at bias voltage as low as +1 V, and fairly repeatable for both short and long exposures to mammographic x-rays with minimal or no loss in sensitivity. The overall dose-sensitivity of the Bi2S3 nanoflowers was found to be similar to that of a micro-ionization chamber.This project was funded by the Waterloo Institute for Nanotechnology (University of Waterloo, Canada) as part of a collaboration program with Prof. C.N.R. Rao's laboratory at the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR, Bangalore, India)

On-chip cell lysis by antibacterial non-leaching reusable quaternary ammonium monolithic column

Reusable antibacterial non-leaching monolithic columns polymerized in microfluidic channels designed for on-chip cell lysis applications were obtained by the photoinitiated free radical copolymerization of diallyldimethylammonium chloride (DADMAC) and ethylene glycol diacrylate (EGDA) in the presence of a porogenic solvent. The microfluidic channels were fabricated in cross-linked poly(methyl methacrylate) (X-PMMA) substrates by laser micromachining. The monolithic columns have the ability to inhibit the growth of, kill and efficiently lyse gram-positive Micrococcus luteus (Schroeter) (ATCC 4698) and Kocuria rosea (ATCC 186), and gram-negative bacteria Pseudomonas putida (ATCC 12633) and Escherichia coli (ATCC 35218) by mechanically shearing the bacterial membrane when forcing the cells to pass through the narrow pores of the monolithic column, and simultaneously disintegrating the cell membrane by physical contact with the antibacterial surface of the column. Cell lysis was confirmed by off-chip PCR without the need for further purification. The influence of the cross-linking monomer on bacterial growth inhibition, leaching, lysis efficiency of the monolithic column and its mechanical stability within the microfluidic channel were investigated and analyzed for three different cross-linking monomers: ethylene glycol dimethacrylate (EGDA), ethylene glycol dimethacrylate (EGDMA) and 1,6-hexanediol dimethacrylate (1,6-HDDMA). Furthermore, the bonding efficiency of two X-PMMA substrates with different cross-linking levels was studied. The monolithic columns were shown to be stable, non-leaching, and reusable for over 30 lysis cycles without significant performance degradation or DNA carryover when they were back-flushed between lysis cycles

Antibacterial Porous Polymeric Monolith Columns with Amphiphilic and Polycationic Character on Cross-linked PMMA Substrates for Cell Lysis Applications

The application of porous polymeric monolith (PPM) columns as an effective tool for bacterial cell lysi within microfluidic chips is demonstrated. By taking advantage of the large surface area and controllable pore size inherent to PPMs, we developed a double mechanism cell lysis technique. The bacterial cell wall is mechanically sheared by flowing through the porous medium of the PPM column, but it is also damaged and disintegrated by physical contact with the antibacterial polymeric biocide covering the porous surface. This leads to leakage of the intracellular contents. The stable and nonleaching antibacterial column introduced in this work alleviates the need for chemical or enzymatic lysins and their potential release of polymerase chain reaction (PCR) inhibitors. The PPM columns were obtained by the photoinitiated free radical co polymerization of n-butyl methacrylate (BuMA) and N-(tert butyloxycarbonyl)aminoethyl methacrylate (Boc-AEMA) in the presence of a cross-linker and porogenic solvents. The porous network was synthesized directly inside a microfluidic channel fabricated in a cross-linked poly(methyl methacrylate) (X-PMMA) substrate by laser micromachining. After removing the Boc protecting group with phosphoric acid, an amphiphilic and cationic network structure reminiscent of synthetic mimics of antimicrobial peptides (SMAMPs) was obtained. The antibacterial activity of the PPM columns was tested against Bacillus subtilis (B. subtilis) and Escherichia coli (E. coli) cells. Cell lysis was evidenced by DNA release, which was then amplified by PCR and confirmed by gel electrophoresis, to verify that the antibacterial monolithic columns did not strongly interfere with the PCR process

A novel deflection shape function for rectangular capacitive micromachined ultrasonic transducer diaphragms

The final publication is available at Elsevier via http://dx.doi.org/10.2174/1874347101206010001. © 2015. This version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/A highly accurate analytical deflection shape function that describes the deflection profiles of capacitive micromachined ultrasonic transducers (CMUTs) with rectangular membranes under electrostatic pressure has been formulated. The rectangular diaphragms have a thickness range of 0.6–1.5 μm and a side length range of 100–1000 μm. The new deflection shape function generates deflection profiles that are in excellent agreement with finite element analysis (FEA) results for a wide range of geometry dimensions and loading conditions. The deflection shape function is used to analyze membrane deformations and to calculate the capacitances between the deformed membranes and the fixed back plates. In 50 groups of random tests, compared with FEA results, the calculated capacitance values have a maximum deviation of 1.486% for rectangular membranes. The new analytical deflection function can provide designers with a simple way of gaining insight into the effects of designed parameters for CMUTs and other MEMS-based capacitive type sensors.National Basic Research Program of China under Grant 2014CB845302 and by National Natural Science Foundation (NNSF) of China under Grants 61374036, 61273121, and Natural Science Foundation of Guangdong Province under Grant 2014A030313237, and by Natural Science and Engineering Research Council of Canada

A Review of Carbon Nanotubes-Based Gas Sensors

Gas sensors have attracted intensive research interest due to the demand of sensitive, fast response, and stable sensors for industry, environmental monitoring, biomedicine, and so forth. The development of nanotechnology has created huge potential to build highly sensitive, low cost, portable sensors with low power consumption. The extremely high surface-to-volume ratio and hollow structure of nanomaterials is ideal for the adsorption of gas molecules. Particularly, the advent of carbon nanotubes (CNTs) has fuelled the inventions of gas sensors that exploit CNTs' unique geometry, morphology, and material properties. Upon exposure to certain gases, the changes in CNTs' properties can be detected by various methods. Therefore, CNTs-based gas sensors and their mechanisms have been widely studied recently. In this paper, a broad but yet in-depth survey of current CNTs-based gas sensing technology is presented. Both experimental works and theoretical simulations are reviewed. The design, fabrication, and the sensing mechanisms of the CNTs-based gas sensors are discussed. The challenges and perspectives of the research are also addressed in this review

Compensated Row-Column Ultrasound Imaging System Using Fisher Tippett Multilayered Conditional Random Field Model

Ben Daya I, Chen AIH, Shafiee MJ, Wong A, Yeow JTW (2015) Compensated Row-Column Ultrasound Imaging System Using Fisher Tippett Multilayered Conditional Random Field Model. PLoS ONE 10(12): e0142817. doi:10.1371/journal.pone.01428173-D ultrasound imaging offers unique opportunities in the field of non destructive testing that cannot be easily found in A-mode and B-mode images. To acquire a 3-D ultrasound image without a mechanically moving transducer, a 2-D array can be used. The row column technique is preferred over a fully addressed 2-D array as it requires a significantly lower number of interconnections. Recent advances in 3-D row-column ultrasound imaging systems were largely focused on sensor design. However, these imaging systems face three intrinsic challenges that cannot be addressed by improving sensor design alone: speckle noise, sparsity of data in the imaged volume, and the spatially dependent point spread function of the imaging system. In this paper, we propose a compensated row-column ultrasound image reconstruction system using Fisher-Tippett multilayered conditional random field model. Tests carried out on both simulated and real row-column ultrasound images show the effectiveness of our proposed system as opposed to other published systems. Visual assessment of the results show our proposed system’s potential at preserving detail and reducing speckle. Quantitative analysis shows that our proposed system outperforms previously published systems when evaluated with metrics such as Peak Signal to Noise Ratio, Coefficient of Correlation, and Effective Number of Looks. These results show the potential of our proposed system as an effective tool for enhancing 3-D row-column imaging.This research was funded by the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs Program, and the Ontario Ministry of Research and Innovation