Live Imaging of Endogenous PSD-95 Using ENABLED: A Conditional Strategy to Fluorescently Label Endogenous Proteins

Fortin, Dale A.,Tillo, Shane E.,Yang, Guang,Rah, Jong-Cheol,Melander, Joshua B.,Bai, Suxia,Soler-Cedeñ,o, Omar,Qin, Maozhen,Zemelman, Boris V.,Guo, Caiying,Mao, Tianyi,Zhong, Haining Society for Neuroscience 2014 The Journal of neuroscience Vol.34 No.50

<P>Stoichiometric labeling of endogenous synaptic proteins for high-contrast live-cell imaging in brain tissue remains challenging. Here, we describe a conditional mouse genetic strategy termed endogenous labeling via exon duplication (ENABLED), which can be used to fluorescently label endogenous proteins with near ideal properties in all neurons, a sparse subset of neurons, or specific neuronal subtypes. We used this method to label the postsynaptic density protein PSD-95 with mVenus without overexpression side effects. We demonstrated that mVenus-tagged PSD-95 is functionally equivalent to wild-type PSD-95 and that PSD-95 is present in nearly all dendritic spines in CA1 neurons. Within spines, while PSD-95 exhibited low mobility under basal conditions, its levels could be regulated by chronic changes in neuronal activity. Notably, labeled PSD-95 also allowed us to visualize and unambiguously examine otherwise-unidentifiable excitatory shaft synapses in aspiny neurons, such as parvalbumin-positive interneurons and dopaminergic neurons. Our results demonstrate that the ENABLED strategy provides a valuable new approach to study the dynamics of endogenous synaptic proteins <I>in vivo</I>.</P>

A Tension Distribution Algorithm for Cable-Driven Parallel Robots Operating Beyond their Wrench-Feasible Workspace

Alexis Fortin Cote,Philippe Cardou,Clement Gosselin 제어로봇시스템학회 2016 제어로봇시스템학회 국제학술대회 논문집 Vol.2016 No.10

One of the main concerns in the control of over-constrained cable driven parallel mechanisms is the handling of the tension distribution, which is crucial to the proper mechanism behaviour. For example, it dictates the power consumption and stiffness of the mechanism. One problem that remains to be addressed is the handling of cable tensions when the end-effector moves beyond its wrench-feasible workspace, a situation that can arise when the robot is used as a haptic interface. Most existing algorithms are capable of determining whether a specified wrench is unfeasible, but cannot return a suitable second-best tension distribution in such situations. This paper presents an algorithm based on quadratic programming that is capable of handling these situations in real time. The algorithm provides the exact tension distribution for exerting the prescribed wrench when the end-effector is inside the robot workspace. Moreover, when the end-effector is outside of the robot workspace, the algorithm returns a tension distribution that approximately generates the prescribed wrench. The effectiveness of the algorithm is first illustrated using the simulation of a simple cable-driven parallel robot (CDPR). Experimental results are then provided for an eight-cable six-degree-of-freedom CDPR using a real-time implementation.

Brett Freedman

Maryse Fortin,Octavian Dobrescu,Peter Jarzem,Jean Ouellet,Michael H. Weber 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.1

Study Design: Reliability study. Purpose: To examine the reliability of novice and experienced raters for measurements of the size and composition of the cervical extensor muscles using a thresholding technique. Overview of Literature: Although some authors have reported on the dependability of magnetic resonance imaging (MRI) measurements of the cervical muscles, there remains some variability regarding intrarater and interrater reliabilities, and few studies have examined the associated measurement error. Whether the rater’s experience noticeably influences the reliability and precision of such measurements has also not been examined. Methods: A sample of 10 patients with cervical pathologies was selected. Muscle cross-sectional area (CSA), functional crosssectional area (FCSA), and signal intensity of the cervical extensor muscles were acquired from axial T2-weighted MRIs by a novice and an experienced rater. All measurements were obtained twice, at least 5 days apart, while the raters were blinded to all earlier measurements. Results: Interrater reliability estimates (intraclass correlation coefficients) varied between 0.84 and 0.99 for the novice rater and between 0.94 and 0.99 for the experienced rater, indicating excellent reliability. The standard error of measurement for the novice rater was, however, noticeably higher for all cervical muscle measurements. Most of the interrater estimates showed excellent agreement with the exception of CSA measurement of the semispinalis cervicis at C4–C7 and FCSA measurement of the multifidus and semispinalis cervicis at C4–C7, which showed poor interrater reliability. Conclusions: The proposed method of investigating cervical muscle measurements was highly reliable; however, novice raters should receive adequate training before using this method for diagnostic, research, and clinical purposes.

Phase transitions and relaxation dynamics of Ising models exchanging particles

Goh, S.,Fortin, J.Y.,Choi, M.Y. Elsevier Science B.V., Amsterdam. 2017 PHYSICA A Vol.466 No.-

A variety of systems in nature and in society are open and subject to exchanging their constituents with other systems (e.g., environments). For instance, in biological systems, cells collect necessary energy and material by exchange of molecules or ions. Similarly, countries, cities or research institutes evolve as their constituents move in or out. To probe the corresponding particle exchange dynamics in such systems, we consider two Ising models exchanging particles and establish a master equation describing the equilibrium phases as well as the non-equilibrium dynamics of the system. It is found that an additional stable phase emerges as a consequence of the particle exchange process. Furthermore, we formulate the Ginzburg-Landau theory which allows to probe correlation effects. Accordingly, critical slowing down is manifested and the associated dynamic exponent is computed in the linear relaxation regime. In particular, this approach is relevant for investigating the grand canonical description of the system plus environment, with particle exchange and state transitions taken into account explicitly.

An Accurate Modeling Approach to Compute Noise Transfer Gain in Complex Low Power Plane Geometries of Power Converters

Tung Ngoc Nguyen,Handy Fortin Blanchette,Ruxi Wang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2

An approach based on a 2D lumped model is presented to quantify the voltage transfer gain (VTG) in power converter low power planes. The advantage of the modeling approach is the ease with which typical noise reduction devices such as decoupling capacitors or ferrite beads can be integrated into the model. This feature is enforced by a new modular approach based on effective matrix partitioning, which is presented in the paper. This partitioning is used to decouple power plane equations from external device impedance, which avoids the need for rewriting of a whole set of equation at every change. The model is quickly solved in the frequency domain, which is well suited for an automated layout optimization algorithm. Using frequency domain modeling also allows the integration of frequency-dependent devices such inductors and capacitors, which are required for realistic computation results. In order to check the precision of the modeling approach, VTGs for several layout configurations are computed and compared with experimental measurements based on scattering parameters.

PWM-based Integral Sliding-mode Controller for Unity Input Power Factor Operation of Indirect Matrix Converter

Lazhar Rmili,Mahmoud Hamouda,Salem Rahmani,Handy Fortin Blanchette,Kamal Al-Haddad 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4

An indirect matrix converter (IMC) is a modern power generation system that enables a direct ac/ac conversion without the need for any bulky and limited lifetime electrolytic capacitor. This system also allows four-quadrant operation, generation of sinusoidal output voltage waveforms with variable frequency and amplitude, and control of input power factor. This study proposes a pulse-width modulation-based sliding-mode controller to achieve unity input-power factor operation of the IMC independently of the active power exchanged with the grid, as well as a fast dynamic response. The designed equivalent control law determines, at each sampling period, the appropriate q-axis component of the modulated input current to be injected into the grid through the LC input filter. An integral term of the error is included in the expression of the sliding surface to increase the accuracy of the control method. A double space vector modulation method is used to synthesize the direction of the space vector of the input currents as required by the sliding-mode controller and the space vectors of the target output voltages. Simulation and experimental results are provided to show the effectiveness and evaluate the performance of the proposed control method.

Postoperative Assessment of Pedicle Screws and Management of Breaches: A Survey among Canadian Spine Surgeons and a New Scoring System

Ahmed Aoude,Saber Ghadakzadeh,Hamzah Alhamzah,Maryse Fortin,Peter Jarzem,Jean A. Ouellet,Michael H. Weber 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.1

Study Design: This study was designed as a survey amongst Canadian spine surgeon to determine a scoring system to standardize pedicle screw placement assessment. Purpose: This study aimed to obtain and analyze the opinions of spine surgeons regarding the assessment of pedicle screw accuracy, with the goal of establishing clinical guidelines for interventions for malpositioned pedicle screws. Overview of Literature: Accurate placement of pedicle screws is challenging, and misalignment can lead to various complications. To date, there is no recognized gold standard for assessing pedicle screw placement accuracy. The literature is lacking studies attempting to standardize pedicle screw placement accuracy assessment. Methods: A survey of the clinical methods and imaging criteria that are used for assessing pedicle screw placement accuracy was designed and sent to orthopedic and neurosurgery spine surgeons from the Canadian Spine Society for their anonymous participation. Results: Thirty-five surgeons completed the questionnaire. The most commonly used modalities for assessing pedicle screw position postoperatively were plain X-rays (97%) and computed tomography (CT, 97%). In both symptomatic and asymptomatic patients, the most and least worrisome breaches were medial and anterior breaches, respectively. The majority of surgeons tended not to re-operate on asymptomatic breaches. More than 60% of surgeons would re-operate on patients with new-onset pain and a ≤4-mm medial or inferior breach in both thoracic and lumbar regions. If a patient experienced sensory loss and a breach on CT, in either the thoracic or lumbar levels, 90% and 70% of the surgeons would re-operate for a medial breach and an inferior breach, respectively. Conclusions: Postoperative clinical presentation and imaging findings are crucial for interpreting aberrant pedicle screw placement. This study presents a preliminary scoring system for standardizing the classification of pedicle screws.

Decoupling the artificial special pair to slow down the rate of singlet energy transfer

Harvey, P.D.,Langlois, A.,Filatov, M.,Fortin, D.,Ohkubo, K.,Fukuzumi, S.,Guilard, R. John Wiley Sons 2012 Journal of porphyrins and phthalocyanines Vol.16 No.5

Reply to the Comment by A. Gadomski

Choi, M. Y.,Choi, H.,Fortin, J.-Y.,Choi, J. Editions de Physique 2010 Europhysics letters Vol.89 No.4

Prevalence and Complications of Postoperative Transfusion for Cervical Fusion Procedures in Spine Surgery: An Analysis of 11,588 Patients from the American College of Surgeons National Surgical Quality Improvement Program Database

Ahmed Aoude,Sultan Aldebeyan,Maryse Fortin,Anas Nooh,Peter Jarzem,Jean A. Ouellet,Michael H. Weber 대한척추외과학회 2017 Asian Spine Journal Vol.11 No.6

Study Design: Retrospective cohort study. Purpose: The purpose of this study was to assess the rate of blood transfusion after cervical fusion surgery, and its effect on complication rates. Overview of Literature: Cervical spine fusions have gained interest in the literature since these procedures are now ever more frequently being performed in an outpatient setting with few complications. Methods: The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database was used to identify patients that underwent cervical fusion from 2010 to 2013. Multivariate regression analysis was used to determine postoperative complications associated with transfusion and cervical fusion. Results: We identified 11,588 patients who had cervical fusion between 2010 and 2013. The rate of blood transfusion following cervical fusion found to be 1.47%. All transfused patients were found to have increased risk of venous thromboembolism (TBE) (odds ratio [OR], 3.19; 95% confidence interval [95% CI], 1.16–8.77), myocardial infarction (MI) (OR, 9.12; 95% CI, 2.53–32.8), increased length of stay (LOS) (OR, 28.03; 95% CI, 14.28–55.01) and mortality (OR, 4.14; 95% CI, 1.44–11.93). Single level fusion had increased risk of TBE (OR, 3.37; 95% CI, 1.01–11.33), MI (OR, 10.5; 95% CI, 1.88–59.89), and LOS (OR, 14.79; 95% CI, 8.2–26.67). Multilevel fusion had increased risk of TBE (OR, 5.64; 95% CI, 1.15–27.6), surgical site infection (OR, 16.29; 95% CI, 3.34–79.49), MI (OR, 10.84; 95% CI, 2.01–58.55), LOS (OR, 26.56; 95% CI, 11.8–59.78), and mortality (OR, 10.24; 95% CI, 2.45–42.71). Patients who had anterior cervical discectomy and fusion surgery and received a transfusion had an increased risk of TBE (OR, 4.87; 95% CI, 1.04–22.82), surgical site infection (OR, 9.73; 95% CI, 2.14–44.1), MI (OR, 9.88; 95% CI, 1.87–52.2), increased LOS of more than 2 days (OR, 28.34; 95% CI, 13.79–58.21) and increase in mortality (OR, 6.3; 95% CI, 1.76–22.48). While, transfused patients who had posterior fusion surgery had increased risk of MI (OR, 10.45; 95% CI, 1.42–77.12) and increased LOS of more than 6 days (OR, 4.42; 95% CI, 2.68–7.29). Conclusions: Our results demonstrate that although cervical fusions can be done as outpatient procedures special precautions and investigations should be done for patients who receive transfusion after cervical fusion. These patients are demonstrated to have higher rate of MI, TBE, wound infection and mortality when compared to those who do not receive transfusion.