Thunder Bay Regional Research Institute
Thunder Bay Regional Research Institute
Thunder Bay Regional Research Institute | Date: 2017-02-08
PbO-based photoconductive X-ray imaging devices are disclosed in which the PbO photoconductive layer exhibits an amorphous crystal structure. According to selected embodiments, the amorphous PbO photoconductive layer may be formed by providing a substrate inside an evacuated evaporation chamber and evaporating lead oxide to deposit a photoconductive lead oxide layer onto the substrate, while subjecting the photoconductive layer to ion bombardment with oxygen ions having an ion energy between 25 and 100 eV. X-ray direct detection imaging devices formed from such amorphous PbO photoconductive layers are shown to exhibit image lag that is suitable for fluoroscopic imaging.
Mani S.,Lakehead University |
Untereiner A.,Lakehead University |
Untereiner A.,Thunder Bay Regional Research Institute |
Wu L.,Lakehead University |
And 2 more authors.
Antioxidants and Redox Signaling | Year: 2014
Significance: Stigmatized as a toxic environmental pollutant for centuries, hydrogen sulfide (H2S) has gained recognition over the last decade as an important gasotransmitter that functions in physiological and pathophysiological conditions, such as atherosclerosis. Recent Advances: Atherosclerosis is a common disease that stems from the buildup of fatty/cholesterol plaques on the endothelial cells of arteries. The deposits mitigate thickening and stiffening of arterial tissue, which contributes to concomitant systemic or localized vascular disorders. Recently, it has been recognized that H2S plays an anti-atherosclerotic role, and its deficiency leads to early development and progression of atherosclerosis. This review article presents multiple lines of evidence for the protective effects of H2S against the development of atherosclerosis. Also highlighted are the characterization of altered metabolism of H2S in the development of atherosclerosis, underlying molecular and cellular mechanisms, and potential therapeutic intervention based on H2S supplementation for atherosclerosis management. Critical Issues: Although a protective role of H2S against atherosclerosis has emerged, controversy remains regarding the mechanisms underlying H2S-induced endothelial cell proliferation and angiogenesis as well as its anti-inflammatory properties. The therapeutic value of H2S to this pathophysiological condition has not been tested clinically but, nonetheless, it shows tremendous promise. Future Directions: The efficiency and safety profile of H2S-based therapeutic approaches should be refined, and the mechanisms by which H 2S exerts its beneficial effects should be elucidated to develop more specific and potent therapeutic strategies to treat atherosclerosis. Whether the therapeutic effects of H2S in animal studies are transferable to clinical studies merits future investigation. Antioxid. Redox Signal. 20, 805-817. © 2014, Mary Ann Liebert, Inc.
Curiel L.,Thunder Bay Regional Research Institute |
Hynynen K.,University of Toronto
Ultrasound in Medicine and Biology | Year: 2011
Recently, an in vivo real-time ultrasound-based monitoring technique that uses localized harmonic motion (LHM) to detect changes in tissues during focused ultrasound surgery (FUS) has been proposed to control the exposure. This technique can potentially be used as well for targeting imaging. In the present study, we evaluated the potential of using LHM to detect changes in stiffness and the feasibility of using it for imaging purposes in phantoms and in vivo tumor detection. A single-element FUS transducer (80 mm focal length, 100 mm diameter, 1.485 MHz) was used for inducing a localized harmonic motion and a separate ultrasound diagnostic transducer excited by a pulser/receiver (5 kHz PRF, 5 MHz) was used to track motion. The motion was estimated using cross-correlation techniques on the acquired radio-frequency (RF) signal. Silicon phantom studies were performed to determine the size of inclusion that was possible to detect using this technique. Inclusions were discerned from the surroundings as a reduction on LHM amplitude and it was possible to depict inclusions as small as 4 mm. The amplitude of the induced LHM was always lower at the inclusions compared with the one obtained at the surroundings. Ten New Zealand rabbits had VX2 tumors implanted on their thighs and LHM was induced and measured at the tumor region. Tumors (as small as 10 mm in length and 4 mm in width) were discerned from the surroundings as a reduction on LHM amplitude. © 2011 World Federation for Ultrasound in Medicine & Biology.
Mani S.,Lakehead University |
Li H.,Lakehead University |
Untereiner A.,Thunder Bay Regional Research Institute |
Wu L.,Thunder Bay Regional Research Institute |
And 6 more authors.
Circulation | Year: 2013
Background-Cystathionine γ-lyase (CSE) produces hydrogen sulfide (H2S) in the cardiovascular system. The deficiency of CSE in mice leads to a decreased endogenous H2S level, an age-dependent increase in blood pressure, and impaired endothelium-dependent vasorelaxation. To date, there is no direct evidence for a causative role of altered metabolism of endogenous H2S in atherosclerosis development. Methods and Results-Six-week-old CSE gene knockout and wild-type mice were fed with either a control chow or atherogenic paigen-type diet for 12 weeks. Plasma lipid profile and homocysteine levels, blood pressure, oxidative stress, atherosclerotic lesion size in the aortic roots, cell proliferation, and adhesion molecule expression were then analyzed. CSE-knockout mice fed with atherogenic diet developed early fatty streak lesions in the aortic root, elevated plasma levels of cholesterol and low-density lipoprotein cholesterol, hyperhomocysteinemia, increased lesional oxidative stress and adhesion molecule expression, and enhanced aortic intimal proliferation. Treatment of CSE-knockout mice with NaHS, but not N-acetylcysteine or ezetimibe, inhibited the accelerated atherosclerosis development. Double knockout of CSE and apolipoprotein E gene expression in mice exacerbated atherosclerosis development more than that in the mice with only apolipoprotein E or CSE knockout. Conclusions-Endogenously synthesized H2S protects vascular tissues from atherogenic damage by reducing vessel intimal proliferation and inhibiting adhesion molecule expression. Decreased endogenous H2S production predisposes the animals to vascular remodeling and early development of atherosclerosis. The CSE/H2S pathway is an important therapeutic target for protection against atherosclerosis. © 2013 American Heart Association, Inc.
Tang G.,Lakehead University |
Yang G.,Lakehead University |
Jiang B.,Lakehead University |
Ju Y.,Lakehead University |
And 3 more authors.
Antioxidants and Redox Signaling | Year: 2013
Aims: Endothelium-dependent vasorelaxation is mediated by endothelium-derived relaxing factor and endothelium-derived hyperpolarizing factor (EDHF). However, the molecular entity of EDHF remains unclear. The present study examined whether hydrogen sulfide (H2S) acts as EDHF and how H2S mediates EDHF pathways from endothelial origination to downstream target of smooth muscle cells (SMCs). Results: We found that knocking-out the expression of cystathionine γ-lyase (CSE) in mice (CSE-knockout [KO]) elevated resting-membrane-potential of SMCs and eliminated methacholine-induced endothelium-dependent relaxation of mesenteric arteries, but not that of aorta. Methacholine, a cholinergic-muscarinic agonist, hyperpolarized SMC in endothelium-intact mesenteric arteries from wide-type mice. This effect was inhibited by muscarinic antagonist (atropine) or the co-application of charybdotoxin and apamin, which blocked intermediate- and small-conductance KCa (IKCa and SKCa) channels, or abolished in CSE-KO mice. Supplementation of exogenous H2S hyperpolarized vascular SMCs and endothelial cells from wide-type and CSE-KO mice. Both methacholine and H2S induced greater SMC hyperpolarization of female wide-type mesenteric arteries than that of male ones. H 2S-induced hyperpolarization is blocked by -SH oxidants and -SSH inhibitor. The expression of SK2.3 but not IK3.1 channel in vascular tissues was increased by H2S and decreased by CSE inhibitor or CSE gene KO. Innovation and Conclusions: Taken together, H 2S is an EDHF. The identification of H2S as an EDHF will not only solve one of the long-lasting perplexing puzzles for the mechanisms underlying endothelium-dependent vasorelaxation, but also shed light on potential therapeutic effects of H2S on pathological abnormalities in peripheral resistance arteries. © Mary Ann Liebert, Inc.
Thunder Bay Regional Research Institute | Date: 2011-11-16
Methods and apparatus are provided for the alignment of an interferometric system. A spatial filter comprising a reflective pinhole is provided at the output of the interferometer, and tilt is measured by a tilt detection subsystem positioned to reimage the pinhole. A shear detection subsystem is positioned to image an offset of the interferometer beams. Tilt and shear offsets are determined by comparing measurements obtained from the tilt and shear subsystems with pre-recorded measurements obtained for an aligned state. The tilt and shear offsets are employed to realign the system using positioning controls corresponding a reduced number of dominant degrees of freedom of the system.
Uddin M.,Lakehead University |
Hafeez M.,Thunder Bay Regional Research Institute
IEEE Transactions on Industry Applications | Year: 2012
This paper presents a fuzzy logic hysteresis comparator-based direct torque control (DTC) scheme of an induction motor (IM) under varying dynamic conditions. The fuzzy logic controller (FLC) is used to adjust the bandwidth of the torque hysteresis controller in order to reduce the torque and flux ripples and, hence, to improve motor dynamic response. The effects of torque hysteresis bandwidth on the amplitude of torque ripples of an IM are also discussed in this paper. Based on the slopes of motor-estimated torque and stator current, an FLC is designed to select the optimum bandwidth of the torque hysteresis controller. This paper also proposes a simpler algorithm than the conventional trigonometric function-based algorithm to evaluate the sector number (required for DTC scheme) of the stator flux-linkage space vector. The proposed algorithm reduces the computational burden on the microprocessor. In order to test the performance of the proposed FLC-based DTC scheme for IM drive, a complete simulation model is developed using MATLAB/Simulink. The proposed FLC-based DTC scheme is also implemented in real time using DSP board DS1104 for a prototype 1/3 hp motor. The performance of the proposed drive is tested in both simulation and experiment. © 2011 IEEE.
Pichardo S.,Thunder Bay Regional Research Institute |
Sin V.W.,Guided Therapeutics |
Hynynen K.,Guided Therapeutics
Physics in Medicine and Biology | Year: 2011
For medical applications of ultrasound inside the brain, it is necessary to understand the relationship between the apparent density of skull bone and its corresponding speed of sound and attenuation coefficient. Although there have been previous studies exploring this phenomenon, there is still a need to extend the measurements to cover more of the clinically relevant frequency range. The results of measurements of the longitudinal speed of sound and attenuation coefficient are presented for specimens of human calvaria. The study was performed for the frequencies of 0.27, 0.836, 1.402, 1.965 and 2.525 MHz. Specimens were obtained from fresh cadavers through a protocol with the Division of Anatomy of the University of Toronto. The protocol was approved by the Research Ethics Board of Sunnybrook Health Sciences Centre. The specimens were mounted in polycarbonate supports that were marked for stereoscopic positioning. Computer tomography (CT) scans of the skulls mounted on their supports were performed, and a three-dimensional skull surface was reconstructed. This surface was used to guide a positioning system to ensure the normal sound incidence of an acoustic signal. This signal was produced by a focused device with a diameter of 5 cm and a focal length of 10 cm. Measurements of delay in time of flight were carried out using a needle hydrophone. Measurements of effective transmitted energy were carried out using a radiation force method with a 10 μg resolution scale. Preliminary functions of speed of sound and attenuation coefficient, both of which are related to apparent density, were established using a multi-layer propagation model that takes into account speed of sound, density and thickness of the layer. An optimization process was executed from a large set of random functions and the best functions were chosen for those ones that closest reproduced the experimental observations. The final functions were obtained after a second pass of the optimization process was executed, but this time using a finite-difference time-difference solution of the Westervelt equation, which is more precise than the multi-layer model but much more time consuming for computation. For six of seven specimens, measurements were carried out on five locations on the calvaria, and for the other specimen three measurements were made. In total, measurements were carried out on 33 locations. Results indicated the presence of dispersion effects and that these effects are different according to the type of bone in the skull (cortical and trabecular). Additionally, both the speed of sound and attenuation showed dependence on the skull density that varied with the frequency. Using the optimal functions and the information of density from the CT scans, the average values (±s.d.) of the speed of sound for cortical bone were estimated to be 2384(±130), 2471(±90), 2504(±120), 2327(±90) and 2053(±40) m s-1 for the frequencies of 270, 836, 1402, 1965 and 2526 kHz, respectively. For trabecular bone, and in the same order of frequency values, the speeds of sound were 2140(±130), 2300(±100), 2219(±200), 2133(±130) and 1937(±40) m s-1, respectively. The average values of the attenuation coefficient for cortical bone were 33(±9), 240(±9) and 307(±30) Np m-1 for the frequencies of 270, 836, and 1402, respectively. For trabecular bone, and in the same order of frequency values, the average values of the attenuation coefficient were 34(±13), 216(±16) and 375(±30) Np m -1, respectively. For frequencies of 1.965 and 2.525 MHz, no measurable radiation force was detected with the setup used. © 2011 Institute of Physics and Engineering in Medicine.
Thunder Bay Regional Research Institute | Date: 2010-10-01
An optical imaging device which receives an optical collimated input beam, the device having a pair of axicon lenses through which a beam is directed to generate a collimated ring beam, wherein the ring beam is scattered from a substance to generate a return beam, and to bypass a reflector that redirects the return beam to prevent the return beam from interfering with the input beam; and a detector which detects an image projected by the return beam.
Thunder Bay Regional Research Institute | Date: 2011-09-13
Systems and methods of resetting a blocking-type photoconductive imaging detector are provided. In one embodiment, after having obtained an image, the imaging detector may be reset by applying a reversed bias potential difference and illuminating the imaging radiation detector with photoexcitation radiation. The photoexcitation radiation has a wavelength selected to excite mobile charges within the photoconductive layer and a spatial intensity profile related to the measured image for neutralizing the trapped charges in a spatially compensated manner. In another embodiment, a photoionizing beam is directed onto an x-ray light valve having a liquid crystal layer in contact with a photoconductive layer. The beam passes through an optically transmissive surface of the x-ray light valve and photoionizes a species within the liquid crystal layer, generating mobile charged entities that at least partially neutralize charges trapped at the interface, improving the performance of the x-ray light valve when performing subsequent x-ray imaging.