Specific Target Points Research Articles

Effect of optimized transcranial direct current stimulation on motor cortex activation in patients with sub-acute or chronic stroke: a study protocol for a single-blinded cross-over randomized control trial.

Transcranial direct current stimulation (tDCS) has shown positive but inconsistent results in stroke rehabilitation. This could be attributed to inter-individual variations in brain characteristics and stroke lesions, which limit the use of a single tDCS protocol for all post-stroke patients. Optimizing the electrode location in tDCS for each individual using magnetic resonance imaging (MRI) to generate three-dimensional computer models and calculate the electric field (E-field) induced by tDCS at a specific target point in the primary motor cortex may help reduce these inconsistencies. In stroke rehabilitation, locating the optimal position that generates a high E-field in a target area can influence motor recovery. Therefore, this study was designed to determine the effect of personalized tDCS electrode positions on hand-knob activation in post-stroke patients. This is a crossover study with a sample size of 50 participants, who will be randomly assigned to one of six groups and will receive one session of either optimized-active, conventional-active, or sham tDCS, with 24 h between sessions. The tDCS parameters will be 1 mA (5 × 5 cm electrodes) for 20 min. The motor-evoked potential (MEP) will be recorded before and after each session over the target area (motor cortex hand-knob) and the MEP hotspot. The MEP amplitude at the target location will be the primary outcome. We hypothesize that the optimized-active tDCS session would show a greater increase in MEP amplitude over the target area in patients with subacute and chronic stroke than conventional and sham tDCS sessions.Clinical trial registration: https://cris.nih.go.kr, identifier KCT0007536.

Topology optimization of large ultrasonic tools for uniform vibration using density model

The uniform vibration of vibrating tools for ultrasonic welding is important for industrial applications but the design requires considerable know-how due to the nature of the wave phenomena. Topology optimization is a structural optimization technique that achieves the desired objective by controlling the material distribution in the design region including voids. In this study, we propose an objective function that maximizes the amplitude of a specific target point in phase with the input. A uniform vibration is obtained by maximizing the point with the smallest amplitude among multiple target points. Optimization is performed using a commonly used density model, resulting in a vibration distribution with an aligned phase on the output surface. In addition, we perform an eigenvalue analysis of the structure by isosurface extraction to study the frequency error and the deterioration in the uniformity of the assumed vibration mode.

Pathfinding for Mobile Robot Navigation by Exerting the Quarter-Sweep Modified Accelerated Overrelaxation (QSMAOR) Iterative Approach via the Laplacian Operator

Mobile robots are often in a situation where they need to find a bump-free path or navigation in their environment from any starting to a specific target point. Within this study, improving the navigation problem of a mobile robot iteratively by using a numerical method based on the potential field method is one of the main aims. This potential field will lean on the use of Laplace’s equation to restrain the formation of a potential function across regions within the mobile robot configuration area. The present paper proposed a Quarter-Sweep Modified Accelerated Overrelaxation (QSMAOR) approach to improve the pathfinding of mobile robots in a given environment. The experiment shows that, by using a finite difference method, it is capable of producing an optimal path and creating a smooth path between the starting and target point. The results of the simulation also show that this numerical approach works more rapidly and provides a smoother/clearer direction than the previous study.

DNLS: A Detection Method Based on Normalized Short-Time Fourier Transform-Radon Transform for Low Frequency Sonar Pulse Signal

Under low-frequency background noise environments, due to the characteristics of poor stability and many interference targets of noise, the detection of unknown low-frequency sonar signals faces huge challenge. And sonar pulse signal detection methods based on time domain or frequency domain have the limitation of insufficient detection Signal-to-Noise Ratio (SNR). In order to improve the detection capability of weak sonar pulse signal in low frequency background noise environments, a Detection method based on normalized short-time Fourier transform-Radon transform for Low frequency Sonar pulse signal (DNLS) is proposed, which is a constant false alarm detection method in normalized short-time Fourier transform-Radon transform domain. In DNLS method, after the normalized short-time Fourier transform-Radon transformation, low-frequency noise energy to be dispersed into the entire transformation domain, and the sonar pulse signal energy containing the Linear Frequency Modulation (LFM) component is concentrated at a specific target point in the normalized short-time Fourier transform-Radon transform transformation domain, which can obtain a higher local SNR than the time-domain SNR. Moreover, the specific target point is distinguishable from the background noise, and the impulse signal detection decision is completed by constructing hypothesis test statistics on the target point data. The DNLS method solves the detection problems of low-frequency background such as poor stability, large fluctuations, and more interference. And the method of obtaining the test statistics of the constant false alarm detection, estimating the background noise and calculating the detection threshold is given. Extensive simulation results and actual data processing show that, under the simulation condition, in the minimum detection SNR of LFM, Continuous Wave(CW)-LFM and pulse trains of frequency modulated pulse signals with the same pulse width, compared with the dual-threshold constant false alarm rate energy detection method, the DNLS method is improved by 15dB, 13dB and 4dB, respectively. Under actual data conditions, in the detection of CW-LFM pulse signals with the same pulse width, compared with the double-threshold constant false alarm rate energy detection method, the detection performance of the DNLS method in the case of no ship radiated noise interference and strong radiated noise interference improves by 5dB and 5.5dB, respectively. The data analysis results show that the DNLS method has very good detection performance for LFM, pulse trains of frequency modulated, CW-LFM and other sonar pulse signals at low SNR, and can effectively detect the sonar pulse signals under the background of strong ship radiated noise.

Exacerbating Algorithmic Bias through Fairness Attacks

Algorithmic fairness has attracted significant attention in recent years, with many quantitative measures suggested for characterizing the fairness of different machine learning algorithms. Despite this interest, the robustness of those fairness measures with respect to an intentional adversarial attack has not been properly addressed. Indeed, most adversarial machine learning has focused on the impact of malicious attacks on the accuracy of the system, without any regard to the system's fairness. We propose new types of data poisoning attacks where an adversary intentionally targets the fairness of a system. Specifically, we propose two families of attacks that target fairness measures. In the anchoring attack, we skew the decision boundary by placing poisoned points near specific target points to bias the outcome. In the influence attack on fairness, we aim to maximize the covariance between the sensitive attributes and the decision outcome and affect the fairness of the model. We conduct extensive experiments that indicate the effectiveness of our proposed attacks.

Optimization of concentric tube continuum robot based on accuracy and overall length of the robot via genetic algorithm

Concentric Tube Continuum Robot (CTR) is a group of continuum robots which is composed of concentric tubes that can be axially translated and rotated at the base relative to one another. Their inverse kinematic is challenging due to their redundancy. On the other hand, knowledge about the inverse kinematics of the concentric-tube continuum robot is essential for control purposes. There are many solutions for reaching to a specific target point because of the redundancy of these kinds of robots. In this paper, a new method for solving the inverse kinematics of these kinds of robots is presented. The most common type of these robots consisting of three tubes is considered for this study, and the genetic algorithm technique is employed to optimize the solution of this problem. Minimum energy principle equations are used in this method. It is assumed that the robot moves in a free space, so the environment force on this robot is neglected. Also, it is supposed that the curvature of each tube remains constant along the tube. According to the results, a small error of the order 0.01mm was observed using the presented method, which is acceptable for most applications. Finally, the parameters of robot is optimized with concentration on accuracy and the overall length of the robot, which is an important parameter for stability.

Automatic calibration and selection of optimal performance criterion of a water quality model for a river controlled by total maximum daily load (TMDL).

When manually calibrating water quality models, considerable time and attention are required. Hence, developing an automated model that allows for efficient and objective automatic calibration is highly desirable. The QUAL2Kw model calibrates the QUAL2K automatically using a genetic algorithm (GA). This study analyzes auto-calibration results and selects the optimal criterion for each objective function from six performance criteria. Additionally, a multi-objective auto-calibration was conducted using two kinds of performance statistics as the objective function of the GA. The auto-calibration model was applied to the Yeongsan River and the total maximum daily load (TMDL) was established to achieve water quality goals at specific target points of this river. Among the six auto-calibration results based on a single performance criterion, Nash-Sutcliffe model efficiency (NSE) was the best criterion for calculating fitness through auto-calibration. To consider the calibration accuracies of the TMDL target points and the entire river simultaneously, an objective function using multiple performance criteria, specifically the weighted average of the normalized root mean squares error (CV(RMSE)) and the ratio of the RMSE to the standard deviation of the observed data (the RSR), was selected as the final auto-calibration of the model. The model calibration performance was good across the whole region as well as at the target points.

A morphometric and analytical cadaver dissection study of a tumor-simulation balloon model

We quantified the effects on anatomical cadaver dissection of a balloon-inflation tumor model positioned in the parasellar region and approached through an orbitozygomatic (OZ) craniotomy. A modified supraorbital OZ was performed bilaterally on 5 silicon-injected cadaver heads. Ten predetermined anatomical points assigned using a frameless stereotactic device were used to measure the working area of exposure, degree of surgical freedom, and horizontal and vertical angles of attack to specific target points before and after inflation of a balloon catheter mimicking a parasellar tumor. Balloon inflation displaced the central anatomical structures (pituitary stalk, lamina terminalis, anterior chiasm, and internal carotid artery [ICA]–posterior communicating artery and ICA-A1 junctions) by 14–51% (p ≤ .05). With tumor simulation, the vertical angle of attack increased by 67% (p < .01), while the area of exposure increased by 83% (p < .01) and surgical freedom increased by 58% (p < .01). This tumor model also significantly displaced central anatomical sella-associated structures. Compared to a normal anatomical configuration, the tumor simulation (balloon) opened surgical corridors (especially vertical) and acted as a natural retractor, widening the angle of access to the infundibular apex–hypothalamic junction. Although this model cannot exactly mimic a tumor mass in a patient, the effects of tumor compression and sequential displacement of important structures can be combined into and then assessed in a cadaveric neurosurgical anatomical scenario for training and research.

Goalkeeper’s position for defending short range shots

The purpose of the study was to analyze and quantify the ability of the goalkeeper while defending shots from left and right sides of penalty area or the goal area, which frequently occurs in an actual game situation. In other words, the study aimed at verifying the reaction ability of the goalkeeper to defend goals in two different defense positions across a 3 m width area without performing dives. Eleven male goalkeepers from a university soccer league participated in the study. The goalkeepers were assigned to react to a specific target point, i.e. high, middle, low, left and right in response to the LED signal positioned at the front. Three-dimensional motion analysis system was used to perform kinematical analysis through which variables such as the approach time of reaching specific target points and the movement used to cover the defensive area were observed. In results, no significant differences were observed in approach time of the hand to the target point in both defense positions, i.e. Type-A (defense posture of positioning the hand at knee height) and Type-B (defense posture of positioning the hand at waist height). But Type-B defense position average velocity was observed faster than Type-A for blocking shots of low-middle heights. Hence, the results obtained from the study showed a possibility that being prepared in Type-A defense position will be more accurate and stable. Moreover, goalkeepers were able to occupy wider defense range in Type-A defense position than Type-B within the time period of 0.7 ∼ 0.8 s after triggering of the LED signal. In conclusion, the results obtained from the study pointed out that Type-A defense position can be much more effective in soccer for blocking shots from the left and right sides of the penalty area. The defense posture of positioning the hand at low height is considered more effective when defending a ball shot from areas near the penalty area than the high hand position. It was also confirmed that the available defense area can be defended widely and effectively by moving the center of the body. Further studies need to be performed to consider the cognitive perspective by applying various methods.

Apoptotic pathways of macrophages within osteolytic interface membrane in periprosthestic osteolysis after total hip replacement.

Macrophage apoptosis in interface membrane, which occurs through either death receptor, mitochondrion, or endoplasmic reticulum (ER) stress pathways, has been suggested to play an important role in promoting osteolysis. However, how and why macrophage apoptosis originates and the correlation among these apoptotic pathways is not yet clear. The objective of this study was to identify the apoptotic mechanism of macrophages, and to explore the relationship between the apoptotic pathways and progression of osteolysis. Transmission electron microscopy (TEM) was utilized to analyze the tissue ultrastructure of wear particles, and in situ apoptotic macrophage identification was performed by TUNEL staining. We analyzed the expression of the key biomarkers of apoptotic pathways via immunohistochemistry and Western blotting. Our results demonstrated that the majority of wear particles within osteolytic interface membrane was in the 30-60 nm range, and that macrophage apoptotic ratio increased along with osteolysis progression. Normal hip dysplasia and mechanical loosening of tissues showed low expression levels of biomarkers for ER stress (Ca2+ , JNK, cleaved Caspase-4, IRE1-α, Grp78/Bip, and CHOP), mitochondrion (Bcl-2, Bax, and Cytochrome c), and death receptor (Fas and cleaved Caspase-8) pathways, while osteolytic interface membrane tissues expressed high levels of these biomarkers. In addition, we found that the ER stress intensity was in complete conformity with mitochondrial dysfunction and was consistent with the results of death receptor activation. Thus, our findings suggested that wear particles generated at implant interface can accelerate macrophage apoptosis through changes in apoptotic pathways and ultimately aggravate the symptom of osteolysis. These data represent a preferential apoptotic signaling pathway of macrophages as specific target points for the prevention and therapeutic modulation of periprosthetic osteolysis.

레이저 펄스 부호화를 이용한 원거리 고해상도 3D 스캐닝 라이다

본 논문에서는 DS-OCDMA(direct sequence optical code division multiple access)와 스캐닝 방식의 MEMS (microelectromechanical system) 거울을 이용하여 픽셀별로 스캐닝하는 라이다 시스템(light detection and ranging, LIDAR)의 설계와 시뮬레이션 결과를 기술한다. 제안하는 라이다는 <TEX>$848{\times}480$</TEX> 해상도의 거리 영상을 1초에 60번 측정한다. 영상을 구성하는 각각의 픽셀마다 픽셀 정보와 체크섬을 DS-OCDMA로 부호화한 레이저 펄스로 방출하므로, 반사파를 검출하기 위하여 대기할 필요없이 연속으로 거리 측정이 가능하다. MEMS 거울은 부호화된 레이저 펄스를 반사하여 측정을 원하는 방향으로 보내기 위한 용도로 사용한다. 하나의 거리 영상을 구성하는 픽셀 정보의 처리가 모두 완료되면, 픽셀 개개의 반사파 비행시간을 이용하여 포인트 클라우드를 생성한다. This paper presents the design and simulation of a three-dimensional pixel-by-pixel scanning light detection and ranging (LIDAR) system with a microelectromechanical system (MEMS) scanning mirror and direct sequence optical code division multiple access (DS-OCDMA) techniques. It measures a frame with <TEX>$848{\times}480$</TEX> pixels at a refresh rate of 60 fps. The emitted laser pulse waves of each pixel are coded with DS-OCDMA techniques. The coded laser pulse waves include the pixel's position in the frame, and a checksum. The LIDAR emits the coded laser pulse waves periodically, without idle listening time to receive returning light at the receiver. The MEMS scanning mirror is used to deflect and steer the coded laser pulse waves to a specific target point. When all the pixels in a frame have been processed, the travel time is used by the pixel-by-pixel scanning LIDAR to generate point cloud data as the measured result.

Feasibility Study of Needle Placement in Percutaneous Vertebroplasty: Cone-Beam Computed Tomography Guidance Versus Conventional Fluoroscopy

To investigate the accuracy, procedure time, fluoroscopy time, and dose area product (DAP) of needle placement during percutaneous vertebroplasty (PVP) using cone-beam computed tomography (CBCT) guidance versus fluoroscopy. On 4 spine phantoms with 11 vertebrae (Th7-L5), 4 interventional radiologists (2 experienced with CBCT guidance and two inexperienced) punctured all vertebrae in a bipedicular fashion. Each side was randomization to either CBCT guidance or fluoroscopy. CBCT guidance is a sophisticated needle guidance technique using CBCT, navigation software, and real-time fluoroscopy. The placement of the needle had to be to a specific target point. After the procedure, CBCT was performed to determine the accuracy, procedure time, fluoroscopy time, and DAP. Analysis of the difference between methods and experience level was performed. Mean accuracy using CBCT guidance (2.61mm) was significantly better compared with fluoroscopy (5.86mm) (p<0.0001). Procedure time was in favor of fluoroscopy (7.39 vs. 10.13min; p=0.001). Fluoroscopy time during CBCT guidance was lower, but this difference is not significant (71.3 vs. 95.8s; p=0.056). DAP values for CBCT guidance and fluoroscopy were 514 and 174mGy cm(2), respectively (p<0.0001). There was a significant difference in favor of experienced CBCT guidance users regarding accuracy for both methods, procedure time of CBCT guidance, and added DAP values for fluoroscopy. CBCT guidance allows users to perform PVP more accurately at the cost of higher patient dose and longer procedure time. Because procedural complications (e.g., cement leakage) are related to the accuracy of the needle placement, improvements in accuracy are clinically relevant. Training in CBCT guidance is essential to achieve greater accuracy and decrease procedure time/dose values.

자기변형 트랜스듀서의 위상차를 이용한 평판에서의 Lamb파 집속 기초 실험

The ultrasonic guided wave phased array using magnetostrictive patch transducers is proposed. The magnetostrictive transducer has received much attention because it is cost-effective and capable to generate ultrasonic waves with a simple configuration. However, it has not been used for ultrasonic guided wave phased array applications until now. In this paper, we propose a magnetostrictive transducer based phased array system consisting of a multi-channel function generator, power amplifiers and Lamb wave magnetostrictive transducers. To check the performance of the ultrasonic guided wave phased array, several Lamb wave focusing experiments were carried out in an aluminum plate. The results demonstrated the capability of the developed array to focus the Lamb waves at specific target points.

Distribution of first-passage times to specific targets on compactly explored fractal structures

The distribution of the first passage times (FPT) of a one-dimensional random walker to a target site follows a power law F(t)~t(-3/2). We generalize this result to another situation pertinent to compact exploration and consider the FPT of a random walker with specific source and target points on an infinite fractal structure with spectral dimension d(s)<2. We show that the probability density of the first return to the origin has the form F(t)~t(d(s)/2-2), and the FPT to a specific target at distance r follows the law F(r,t)~r(d(w)-d(f)) t(d(s)/2-2), where d(w) and d(f) are the walk dimension and the fractal dimension of the structure, respectively. The distance dependence of F(r,t) reproduces the one of the mean FPT of a random walk in a confined domain.

A deterministic electron, photon, proton and heavy ion transport suite for the study of the Jovian moon Europa

A Langley research center (LaRC) developed deterministic suite of radiation transport codes describing the propagation of electron, photon, proton and heavy ion in condensed media is used to simulate the exposure from the spectral distribution of the aforementioned particles in the Jovian radiation environment. Based on the measurements by the Galileo probe (1995–2003) heavy ion counter (HIC), the choice of trapped heavy ions is limited to carbon, oxygen and sulfur (COS). The deterministic particle transport suite consists of a coupled electron photon algorithm (CEPTRN) and a coupled light heavy ion algorithm (HZETRN). The primary purpose for the development of the transport suite is to provide a means to the spacecraft design community to rapidly perform numerous repetitive calculations essential for electron, photon, proton and heavy ion exposure assessment in a complex space structure. In this paper, the reference radiation environment of the Galilean satellite Europa is used as a representative boundary condition to show the capabilities of the transport suite. While the transport suite can directly access the output electron and proton spectra of the Jovian environment as generated by the jet propulsion laboratory (JPL) Galileo interim radiation electron (GIRE) model of 2003; for the sake of relevance to the upcoming Europa Jupiter system mission (EJSM), the JPL provided Europa mission fluence spectrum, is used to produce the corresponding depth dose curve in silicon behind a default aluminum shield of 100 mils (∼0.7 g/cm 2). The transport suite can also accept a geometry describing ray traced thickness file from a computer aided design (CAD) package and calculate the total ionizing dose (TID) at a specific target point within the interior of the vehicle. In that regard, using a low fidelity CAD model of the Galileo probe generated by the authors, the transport suite was verified versus Monte Carlo (MC) simulation for orbits JOI–J35 of the Galileo probe extended mission. For the upcoming EJSM mission with an expected launch date of 2020, the transport suite is used to compute the depth dose profile for the traditional aluminum silicon as a standard shield target combination, as well as simulating the shielding response of a high charge number (Z) material such as tantalum (Ta). Finally, a shield optimization algorithm is discussed which can guide the instrument designers and fabrication personnel with the choice of graded-Z shield selection and analysis.

A gravitational task model with arbitrary anchor points for target sensitive real-time applications

Classic task models for real-time systems focus on execution windows expressing earliest start times and deadlines of tasks for feasibility. Only within these windows the execution of tasks is feasible, and it is considered of uniform utility. Some tasks, however, have target demands in addition: a task should preferably execute at a specific target point within its execution window, but can execute around this point, albeit at lower utility. Examples of such applications include control and media processing. In this paper, we present a task model based on a gravitational analogy to address these issues. Tasks are considered as massive bobs hanging on a pendulum: a single task, left to itself, will execute at the bottom, the target point. If a force, such as the weight of other tasks, is applied, it can be shifted around this point. Thus, tasks' importance and their utility around target points can be expressed. Since the execution of a task cannot be mapped to a point in time, the model allows tasks to express an arbitrary point with its execution to represent the whole execution. This point is called the anchor point. Moreover, we show an example of a scheduling algorithm for this model which finds an approximation to the best compromise of tasks' interests based on the equilibrium state of a pendulum. Nonetheless, this task model is not restricted to a particular scheduling algorithm. Results from a simulation study show the effectiveness of the approach.

Biologie des systèmes appliqués aux cancers

Cancer Systems Biology is now accepted and recognized as a promising field both in biological and clinical research. It relies on a rigorous formalization of regulation networks into precise and unambiguous languages. It provides both detailed and modular views of the complex biological system of interest (which in cancer research is typically an interaction network governing essential cellular events such as proliferation, differentiation, cell death...) in order to facilitate the interpretation of molecular profiles of tumors. The translation of these networks into mathematical models allows prediction of the evolution of the system in time and under certain perturbations. As a result, it can not only propose specific target points for pharmaceutical purposes, but also anticipate the evolution of tumors as well as their classifications. These characteristics emphasize the important role of Systems Biology of Cancer in the future of biomedical research.

Clinical review of Iressa for the treatment of NSCLC

Following development of basic science and the advancement of tumor molecular biology, molecular-target therapy has evolved as a new field for cancer treatment. The agents used act at specific target points such as receptors, kinases and signal transduction systems which are related to tumor growth. These actions result in inhibting proliferation, metastasis, vascularization, and promoting tumor apoptosis. Iressa (gefitinib) which is used for the treatment of NSCLC is a small molecular weight agent acting by inhibition of epidermal growth factor receptor-tyrosine kinase. Iressa was the first approved agent for target therapy for the treatment of NSCLC. This article focuses on the results from clinical trials and the potential of Iressa for the treatment of NSCLC.

조향 자기변형 트랜스듀서를 이용한 평판 결함진단

In this work, we propose a new ultrasonic damage inspection method in plate structures. The proposed method employs an OPMT(orientation-adjustable patch-type magnetostrictive transducer) in order to make the ultrasonic waves directed to a specific target point. For experiments, virtual grid points were set up at every 50 mm in an aluminum plate and two OPMTs were used for inspection. If there exists a crack in a plate, the reflected Lamb wave from the crack is measured in addition to the direct waves from the transmitting transducer to the receiving transducer.

Apoptosis in interface membranes of aseptically loose total hip arthroplasty.

The terminal events leading to periprosthetic osteolysis are multifactorial in nature and modulation of this process after the stage of osteolytic mediator release has been futile. Recently, the demonstration of the ability of bisphosphonates to inhibit bone resorption that is mediated by particle-stimulated macrophages and their induction of osteoclast apoptosis suggests a potent area for modulation of osteolysis at the prosthesis-bone interface. The purpose of this study was to determine the mode of cell death that occurs at the osteolytic interface of failed total hip arthroplasty (THA). TUNEL staining, DNA laddering, and immunodetection of poly(ADP-ribose)polymerase (PARP) protein were used to identify the presence of apoptosis in interface membranes from 25 patients aged 28-88 years old (mean, 58 years) harvested at the time of hip revision surgery. Our results demonstrated positive TUNEL stain in 100% of specimens with an average 37% of cells (range 12-60%) positively stained for TUNEL whereas less than 8% of control tissue cells showed positive staining. DNA laddering, a characteristic feature of apoptotic cells, was observed in 82% (28/34) of specimens studied at both the acetabular and femoral side of aseptically loose THAs. No laddering was observed in control tissues. Finally, using Western blot analysis, we observed the appearance of the 89 kDa PARP fragment associated with apoptosis in 92% of specimens (30/33). Our results demonstrate the presence of apoptotic cell death in interface membranes of THAs suggesting that apoptosis-related events are indeed associated with periprosthetic osteolysis and could serve as a specific target point for therapeutic modulation.