Straight-line Length Research Articles

The Use of Transition Curves in Airport Runway Rapid Exit Taxiways (RETs)

This paper describes a study result focused on the transition curves used in airport rapid exit taxiways (RETs). Such geometric elements are not currently made explicit by standards, and major international government agencies, such as the International Civil Aviation Organization and the Federal Aviation Administration, are limited to providing some layouts consisting of only constant curvature elements, although the aircrafts speed in RETs is variable. In addition to the clothoid that has unitary shape parameter “n” and the multiparameter clothoids (generalized Cornu spirals), the study analyzes the Bloss curve employment. Regarding the multiparameter clothoids, four schemes with shape parameter equal to 1.25, 1.50, 1.75, and 2.00 were considered, respectively. The proposed curves’ effectiveness was evaluated by analyzing the main geometric and kinematic variables trend, that is, curvature, transversal acceleration, lateral jerk, speed, travel time, longitudinal deceleration, and centrifugal force. To ensure the analysis effectiveness, the study layouts were designed from those used for runways codes 1‐2 and 3‐4 maintaining the main geometric elements dimensions unchanged (length of straight lines, radii of circular curves, exit angles, etc.). The kinematic variables values along the design RETs were calculated “point by point” by MATLAB software to take into account nonuniform motion regimen. The obtained results show that both the Bloss curve and the multiparameter clothoid having a shape factor equal to 2 are capable of better contribution in terms of safety and comfort. Implications in the airport construction field are related to the possibility of using lower deceleration values compared to current standards, that is, allowing higher exit speed for the same deceleration. This allows aircrafts to vacate the runway more quickly and, therefore, to increase runway capacity without taking expensive RETs repositioning.

Assessment of glenoid bone loss and other osseous shoulder pathologies comparing MR-based CT-like images with conventional CT

ObjectivesTo evaluate and compare the diagnostic performance of CT-like images based on a 3D T1-weighted spoiled gradient-echo sequence (T1 GRE), an ultra-short echo time sequence (UTE), and a 3D T1-weighted spoiled multi-echo gradient-echo sequence (FRACTURE) with conventional CT in patients with suspected osseous shoulder pathologies.Materials and methodsPatients with suspected traumatic dislocation of the shoulder (n = 46, mean age 40 ± 14.5 years, 19 women) were prospectively recruited and received 3-T MR imaging including 3D T1 GRE, UTE, and 3D FRACTURE sequences. CT was performed in patients with acute fractures and served as standard of reference (n = 25). Agreement of morphological features between the modalities was analyzed including the glenoid bone loss, Hill-Sachs interval, glenoid track, and the anterior straight-line length. Agreement between the modalities was assessed using Bland-Altman plots, Student’s t-test, and Pearson’s correlation coefficient. Inter- and intrareader assessment was evaluated with weighted Cohen’s κ and intraclass correlation coefficient.ResultsAll osseous pathologies were detected accurately on all three CT-like sequences (n = 25, κ = 1.00). No significant difference in the percentage of glenoid bone loss was found between CT (mean ± standard deviation, 20.3% ± 8.0) and CT-like MR images (FRACTURE 20.6% ± 7.9, T1 GRE 20.4% ± 7.6, UTE 20.3% ± 7.7, p > 0.05). When comparing the different measurements on CT-like images, measurements performed using the UTE images correlated best with CT.ConclusionAssessment of bony Bankart lesions and other osseous pathologies was feasible and accurate using CT-like images based on 3-T MRI compared with conventional CT. Compared to the T1 GRE and FRACTURE sequence, the UTE measurements correlated best with CT.Clinical relevance statementIn an acute trauma setting, CT-like images based on a T1 GRE, UTE, or FRACTURE sequence might be a useful alternative to conventional CT scan sparing associated costs as well as radiation exposure.Key Points• No significant differences were found for the assessment of the glenoid bone loss when comparing measurements of CT-like MR images with measurements of conventional CT images.• Compared to the T1 GRE and FRACTURE sequence, the UTE measurements correlated best with CT whereas the FRACTURE sequence appeared to be the most robust regarding motion artifacts.• The T1 GRE sequence had the highest resolution with high bone contrast and detailed delineation of even small fractures but was more susceptible to motion artifacts.

Quality influencing factors of dispersion curves from short period dense arrays based on a convolutional neural network across the north section of the Xiaojiang fault area

The number of dispersion curves increases significantly when the scale of a short-period dense array increases. Owing to a substantial increase in data volume, it is important to quickly evaluate dispersion curve quality as well as select the available dispersion curve. Accordingly, this study quantitatively evaluated dispersion curve quality by training a convolutional neural network model for ambient noise tomography using a short-period dense array. The model can select high-quality dispersion curves that exhibit a ≤ 10% difference between the results of manual screening and the proposed model. In addition, this study established a dispersion curve loss function by analyzing the quality of the dispersion curve and the corresponding influencing factors, thereby estimating the number of available dispersion curves for the existing observation systems. Furthermore, a Monte Carlo simulation experiment is used to illustrates the station-pair interval distance probability density function, which is independent of station number in the observational system with randomly deployed stations. The results suggested that the straight-line length should exceed 15 km to ensure that loss rate of dispersion curves remains < 0.5, while maintaining the threshold ambient noise tomography accuracy within the study area.

General principle and optimization of magneto-acousto-electrical tomography based on image distortion evaluation.

As a novel non-invasive multi-physics imaging methodology, the magneto-acousto-electrical (MAE) technology is capable of detecting electric conductivity changes for biological tissues, exhibiting prosperous perspectives in medical applications. However, the acoustic beam was often simplified to a straight line or a focused one, being perpendicular to layered boundaries of tissues in previous studies. Linear-scanning measurements were carried out to reconstruct B-mode MAE images for layered models without considering the radiation pattern of transducers. Obvious image distortions in both shape and brightness were observed in experiments without any reasonable explanation. This study aims to establish a general physical model for MAE measurements and solve the problem of B-mode image distortion, and hence provide theoretical and technical supports for the improvement of MAE imaging in practical applications. By considering the radiation pattern of actual transducers and the inclined angle of electric conductivity boundaries, a general principal of MAE measurements applicable for objects of arbitrary shapes is proposed based on the theories of acoustic radiation, Hall Effect and electrical detection. The influences of inclined conductivity boundaries and transducer directivities are numerically analyzed with Matlab programming and also demonstrated by experimental measurements. To evaluate the degree of B-mode image distortion, the deformation length (3dB amplitude decrease) of approximate straight lines for a circular model is defined as L=dtan(βm /2), with d and βm being the measurement distance and the half radiation angle of the main-lobe, respectively. The rotary-scanning-based MAE tomography (MAET) is employed to reduce the image distortion, and the rotation angle step is further optimized based on the criterion of the boundary radius fluctuation coefficient <0.01mm. The experimental results of MAE signals and B-mode images as well as MAETs show good agreements with simulations. It is demonstrated that, as the increase of the inclined angle, the MAE decreases rapidly with an extended time interval and reaches the 20dB amplitude decrease when the angle exceeds 12°. Meanwhile, the deformation length of B-mode MAE imaging increases with the increase of the radiation angle for the transducer with a weaker radiation pattern, and hence results in a more serious image distortion. A smaller rotation angle step should be adopted to the MAET system with a longer deformation length, and the optimized maximum angle step of 12° is also achieved for the omnidirectional radiation of point sources with a long deformation length. The image distortion is originated from the amplitude decrease, the time shift and the time interval expansion of MAE signals introduced by the deformation length and the incident angle. The favorable results demonstrate that the fast high-resolution imaging can be accomplished by the minimum rotations of the rotary-scanning-based MAET using an actual transducer, and also provide an optimized scheme for the rotary-based MAET without scanning using a linear array of point sources.

Iliofemoral venous configurations from three-dimensional computed tomography venogram and their relevance to stent design

ObjectiveIliofemoral venous stenting has become the standard of care for patients presenting with quality-of-life impairing symptoms of chronic iliofemoral venous obstruction not responding to conservative measures. This has led to an increased use of venous stenting over the last several years. However, iliofemoral venous anatomy in patients requiring such intervention remains poorly elucidated. This study attempts to fill that gap. MethodsTwenty-two consecutive patients with intravascular ultrasound examination-confirmed chronic iliofemoral venous obstruction underwent three-dimensional reconstruction of their computed tomography venogram images. Relevant angles, tortuosity (tort index-ratio between centerline length, and straight line length), lengths, and diameters were computed and analyzed. We used t tests for comparisons between the right and left sides. A P value of .05 or less was considered significant. ResultsOf the angles calculated, the median of the angles between the horizontal and common iliac vein (CIV) was 66° on the right and 60° on the left (P < .01). The median inferior vena cava-CIV angle was 172° on the right and 165° on the left (P < .0001). The CIV-EIV angle was 159° on the right and 151° on the L (P = .01). Overall, the median tortuosity was 1.07 on the right and 1.12 on the left (P = .007). The median centerline length of the CIV was 42mm on the right and 60mm on the left (P < .0001). The median external iliac vein length was 73 mm on the right and 88 mm on the left (P < .0001). The overall median iliac vein length was 220 mm on the right and 237 mm on the left (P < .01). The median diameters of the inferior vena cava at the iliocaval confluence, 20, 40, and 60 mm cranial to the confluence, were 23, 20, 22, and 23 mm, respectively. ConclusionsOverall, the left side has steeper angles, greater tortuosity, and longer lengths than the right side. These disparities should be considered during femoroiliocaval stent construction.

An automatic numerical approach to optimize flexible serpentine structure design

The serpentine shape has been increasingly popular for the conductor design in flexible electronics due to its superior compliance and stretchability performance. The stretchability of the serpentine structure is highly dependent on the material strain threshold, serpentine geometry design, and the attachment substrate property. Therefore, identifying the parameters and their corresponding importance factors to the stretchability of the structure will help optimize the serpentine geometry. In the current work, a fully automated finite-element model has been developed to calculate the normalized maximum strain in the free-standing serpentine structure under uniaxial stretch loading conditions. A parametric study has been conducted to understand the serpentine geometry impacts on the maximum strain in the serpentine structure under the equivalent 10% uniaxial strain loading condition. The study shows that longer straight-line length, larger arc segment angle, and smaller serpentine with a fixed arc segment radius can help to reduce the maximum strain in the serpentine structure under uniaxial stretching. A random forest machine learning model suggests that the serpentine width and arc segment angle have the highest impact on the maximum strain in the serpentine structure. In the end, the proposed optimization strategy has also been used to optimize the strain distribution when the serpentine structure is attached to a polymer substrate.

The Application of Clothing Intelligent 3D Display with Uncertainty Models Technology in Clothing Marketing

As a result of the development of new technologies such as satellite communication, digitalization, and multimedia computer networks, new media such as blogs, online magazines, and wireless network media have sparked a lot of interest. This study uses 3D clothing display technologies to improve the customer experience of online clothing marketing, aid in the improvement of online clothing marketing efficacy, and extensively discuss the digital clothing anthropometric model. Furthermore, this study employs the convex hull approach and NURBS fitting technology to address concerns with digital clothing anthropometric measurement and provides a practical solution for measuring straight line length, circumference length, and curve length. Furthermore, this research incorporates 3D intelligent technology to develop an online fitting system as well as an intelligent display system for garments. The simulation experiment investigation revealed that the smart clothing 3D display system proposed in this work has a substantial impact on growing online e‐commerce clothing marketing as well as improving clothing marketing effectiveness.

Increased intracranial arterial tortuosity is associated with worse cardiovascular outcome in patients with Loeys-Dietz syndrome

The aim of our study was to evaluate the association between intracranial arterial tortuosity and cardiovascular outcome in patients with Loeys-Dietz syndrome (LDS). We performed a retrospective analysis of all patients with genetically confirmed LDS who underwent at least one brain MRA at our institution (n = 32); demographic and clinical features were evaluated in relation to the tortuosity of intracranial arteries as measured by tortuosity index (TI), which was calculated using the formula: [(centerline length) / (straight-line length)-1] × 100. Receiver operating characteristic curve analysis for intracranial TI and the binary end point of aortic surgery showed vertebrobasilar TI (VBTI) to be the best classifier among the examined arterial segments (AUC = 0.822). Patients with higher VBTI showed a greater incidence of aortic surgery (p < 0.001) and underwent more surgical and endovascular procedures (p = 0.006), with a higher rate of operations (p = 0.002). Kaplan-Meier analysis showed a significantly longer surgery-free survival in patients with lower arterial tortuosity (p < 0.001). At multivariate analysis, higher VBTI was associated with an increased risk of surgery (p < 0.001), which was independent of gene mutation and patient age. Increased VBTI is a marker of adverse cardiovascular outcome in patients with LDS, which can be easily measured on brain MRA, and may be useful in the management of this heterogeneous patient population.

River sinuosity describes a continuum between randomness and ordered growth

AbstractRiver channels are among the most common landscape features on Earth. An essential characteristic of channels is sinuosity: their tendency to take a circuitous path, which is quantified as along-stream length divided by straight-line length. River sinuosity is interpreted as a characteristic that either forms randomly at channel inception or develops over time as meander bends migrate. Studies tend to assume the latter and thus have used river sinuosity as a proxy for both modern and ancient environmental factors including climate, tectonics, vegetation, and geologic structure. But no quantitative criterion for planform expression has distinguished between random, initial sinuosity and that developed by ordered growth through channel migration. This ambiguity calls into question the utility of river sinuosity for understanding Earth's history. We propose a quantitative framework to reconcile these competing explanations for river sinuosity. Using a coupled analysis of modeled and natural channels, we show that while a majority of observed sinuosity is consistent with randomness and limited channel migration, rivers with sinuosity ≥1.5 likely formed their geometry through sustained, ordered growth due to channel migration. This criterion frames a null hypothesis for river sinuosity that can be applied to evaluate the significance of environmental interpretations in landscapes shaped by rivers. The quantitative link between sinuosity and channel migration further informs strategies for preservation and restoration of riparian habitat and guides predictions of fluvial deposits in the rock record and in remotely sensed environments from the seafloor to planetary surfaces.

Greater Curvature, Centerline or Straightened Centerline Length - Which length is Most Accurate for Preprocedural Planning in Thoracic Endovascular Aortic Repair?

BackgroundAutomated centerline (CL) measurements have been conventionally used for stent-graft length estimation during thoracic endovascular aortic repair (TEVAR). The purpose of this study was to assess the accuracy of greater curvature length (GL), semiautomated CL and straightened centerline length (SCL) for preprocedural planning in TEVAR. MethodsImmediate postprocedural CT Angiographies of 30 patients (22 males, age-49.2 ± 10.1years) who underwent TEVAR between 2015 and 2017 were retrospectively analyzed. CL, GL, SCL and the straightline length(SL) were measured between proximal and distal ends of the stent-graft and results were compared with the true length of the stent-graft (TL). Tortuosity index (TI = CL/SL) was calculated. ResultsGL (17.92 ± 4.78 cm) was the closest in predicting the TL (17.75 ± 4.29 cm) (P = 0.414) overall, as well as in both dissection and aneurysm subgroups (P= 0.9). There was a significant difference between CL (16.67 ± 4.07 cm) and TL (P< 0.0001) as well as between SCL (16.86 ± 4.16 cm) and TL (P= 0.001). These differences were greater in dissection subgroup than in the aneurysm group (P< 0.0001 and P= 0.03 for TL-CL and TL-SCL, respectively). The extent of mismatch between GL or CL and TL did not correlate with tortuosity, but the difference between TL and SCL had a significant positive correlation with tortuosity (r = 0.375, P= 0.04). TL-GL had a negative linear correlation with the stent-graft length (TL) in the dissection group (r = 0.50, P= 0.03). ConclusionsThe greater curvature length predicts the actual total length of the deployed stent-graft more accurately than centerline or straightened centerline lengths. Hence, it should be used in planning for the length of stent-graft required for TEVAR.

Straightness metric for measurement of turbulence-induced distortion in long-range imaging.

Algorithms used for mitigation of the effects of atmospheric turbulence on video sequences often rely on a process for creating a reference image to register all of the frames. Because such a pristine image is generally not available, no-reference image quality metrics can be used to identify frames in a sequence that have minimum distortion. Here, we propose a metric that quantifies image warping by measuring image straightness based on line detection. The average length of straight lines in a frame is used to select best frames in a sequence and to generate a reference frame for a subsequent dewarping algorithm. We perform tests with this metric on simulated data that exhibits varying degrees of distortion and blur and spans normalized turbulence strengths between 0.75 and 4.5. We show, through these simulations, that the metric can differentiate between weak and moderate turbulence effects. We also show in simulations that the optical flow that uses a reference frame generated by this metric produces consistently improved image quality. This improvement is even higher when we employ the metric to guide optical flow that is applied to three real video sequences taken over a 7 km path.

Application of modern geodetic tools in the operation of railway reconstructions

This research considers the survey of the circular curve of the operating railway using an electronic total station, which determines the coordinates of points on the curve and calculates the coordinates of the main points of the circular curve. The goal is obtaining information with sufficient accuracy about the spatial position of the parameters of the railway plan, i.e. the device of the railway plan: turning angles, radiuses, lengths of straight lines and curves. Recommendations for determining the elements necessary to locate the main points of curves and their coordinates are considered. The advantage of this method is the simplicity of calculation, which allows the compiled program and high efficiency of determining the main points of curves using a modern geodetic device-the electronic total station Trimble VX (USA).

An algorithm for extracting groove rail area based on improved Hough transform

In order to improve the accuracy and real-time performance of the automatic cleaning of groove rails in modern trams, this paper proposes a groove rail region extraction algorithm based on improved Hough transform. First, in order to speed up the detection and remove noise, the algorithm performs a series of pre-processing on the images collected by the camera, and then use the Canny edge detection method to extract the edge feature information of the groove rail. Finally, the algorithm is improved on the basis of the traditional Hough transform method according to the actual environment. The algorithm proposes three constraints from the straight line length, the slope of the straight line and the distance between the left and right edges, making the algorithm more feasible and accurate in extracting groove rail area. The extraction accuracy reached 97.9%, and the average extraction speed was 0.1903s, laying the foundation for the automatic cleaning of trough rails of modern trams.

Computational study of kinematics of the anterior cruciate ligament double-bundle structure during passive knee flexion–extension

The anterior cruciate ligament (ACL) comprises an anteromedial bundle (AMB) and posterolateral bundle (PLB). Cadaver studies showed that this double-bundle structure exhibits reciprocal function during passive knee flexion–extension, with the PLB taut in knee extension and the AMB taut in knee flexion. In vivo measurements indicated that straight-line lengths of both bundles decrease with increasing knee-flexion angle (KFA). To interpret these seemingly conflicting facts, we developed a computational ACL model simulating the kinematics of the double-bundle structure during passive knee flexion–extension. Tibial and femoral shapes were reconstructed from computed-tomography images of a cadaver knee and used to construct an idealized model of an ACL including its bundles at the tibiofemoral joint. The ACL deformations at various KFAs were computed by finite element analysis. Results showed that the PLB was stretched in knee extension (KFA = 0∘) and slackened with increasing KFA. The AMB was stretched in knee extension (KFA = 0∘) and remained stretched on the medial side when the knee flexed (KFA = 90∘), but its straight-line length decreased with increasing KFA. These findings are consistent with cadaver and in vivo experimental results and highlight the usefulness of a computational approach for understanding ACL functional anatomy.

Horizontal Alignment Security Design Theory and Application of Superhighways

In China, the maximum design speed of highways is 120 km/h, which first appeared in the Highway Engineering Technical Standard (Trial) in 1951. However, vehicle performance, road design, and construction technology have been greatly improved over the past 68 years. To adapt to the development demands of highway design speeds above 120 km/h in the future, it is urgent to study superhighway alignment design theory. Therefore, the horizontal alignment security design theory of superhighways was developed in this paper. First, the definition, classification, and construction mode of a superhighway and suitable vehicles of different grades are presented. Then, the lengths of straight lines were limited to reduce driving fatigue. Next, the minimum radii of circular curves were calculated based on driver characteristics and stress analysis of operating vehicles. Finally, the minimum lengths of transition curves were calculated based on the centrifugal acceleration of the operating vehicles, the travel time, and the passenger visual characteristics. The calculation and analysis results show that the superhighway linear features conform to the vehicle operating characteristics, and can ensure the safety of driving.

The Neurological Foundation of Geometry

Geometry is based on vision. Hence, the visual information processing of the nervous system regulates the structure of geometry. In this paper, we shall construct geometry following the process of visual information processing in the nervous system. Firstly, photons are captured by photoreceptor cells in the retina. At this stage, the retinal bitmap image is constructed using photo- receptor cells as pixels. The retinal bitmap is the foundation of quantitative properties of images throughout the visual processing. Secondly, the edge of the object is extracted in the primary visual cortex. When a three-dimensional object is projected in two dimensions, the edge of the object is ideally a line without width. While Euclid defined the line as the length without width. Surprisingly, a type of cells in the primary visual cortex react the Euclidean line. At this stage, Euclidean geometry without curves is constructed. Thirdly, curves are recognized in the visual area V4. At this stage, Euclidean geometry with curves is constructed. The next problem is the compatibility of these stages. The problem of the compatibility between the first and second stages is that there are irrational lengths in Euclidean geometry. Ancient Greeks used the double contradiction to solve the compatibility problem. An irra- tional number is defined as a number that divides rational numbers into larger and smaller rational numbers. The double contradiction is a method of defining non-rational numbers using rational numbers. Also, double contra- diction is used to solve the compatibility problem between the second and third stages. Even though the length of the curve is not defined in Elements, the length of a curve can be defined by the length of straight lines. Similarly, properties of curves are defined by straight lines. In differentiation, the slope of the curve is defined by the slope of the line. In integration, the area under the curve is defined by the total area of thin rectangles. Finally, as a logical basis for calculus, the double contradiction should be rethought.

Investigation on wear-induced edge passivation of fine-blanking punch

Edge passivation of the punch is a common phenomenon that is induced by wear and which would affect tool life and part quality. To investigate the edge passivation of fine-blanking punch, a wear tester based on sheet metal extrusion was designed. The relevance of the designed tester in terms of the stress state to the fine-blanking process was analyzed via finite element methods. Meanwhile, material flow at the punch edge was studied with pad printing technology, and the effects of the punch geometry and extrusion stroke on the worn profile have been discussed. The results shows that reducing the length of straight lines and radius of arcs results in a large relative sliding distance of material at the punch edge, and for a punch with circular and linear edges, wear on the circular segment is more severe than that on the linear segment. In addition, from the viewpoint of simulation, adaption of the wear coefficient in different periods could lead to a more precise worn profile of the punch.

Quantification of optic nerve length and tortuosity in thyroid eye disease

To objectively quantify the length and tortuosity of optic nerves (ONs) in patients with thyroid eye disease (TED), in relation to the occurrence of dysthyroid optic neuropathy (DON). All patients seen by 2 of the senior authors over a period of 12 years were screened for study entry. The primary outcome was the quantitative measurement of ON tortuosity and length in relation to the occurrence of DON. Image analysis involved the creation of a 3-dimensional reconstruction of the ON from the anterior clinoid process to the posterior globe using image analysis software. A centreline was created through the middle of the reconstruction, and the length of the ON was calculated as the length of this centreline. Tortuosity was calculated by creating a ratio between the straight-line length of the ON and the actual length (centreline length). The final sample included 50 patients who contributed 100 orbits, of which 26 orbits had DON. There were no differences in the Hertel exophthalmometry readings between patients with and without DON (p = 0.56). There was no significant relationship between the length (p = 0.39) and tortuosity (p = 0.82) of the ON and occurrence of DON. There is no significant relationship between the length and tortuosity of the ON and development of DON in patients with TED.

Length optimization of straight line connecting turnout on main line in high-speed railway station yard

Taking the development of high-speed railway in China as background, and referring to the dynamic theory and wheel-rail contact mode, dynamic analysis model was established, considering the setting position of straight lines and running conditions of train in high-speed railway station yard. Using the established model, and choosing vehicle lateral acceleration and wheel suspension as the evaluation indexes, dynamic characteristic of vehicle traveling in turnout and adjacent area on main line was analyzed, and effects on travelling safety and stability of train aroused by length variation of straight lines were calculated based on analyzing the damping rules of vibration. The results show that, a certain length of straight lines can alleviate the vibration aroused in turnout and curve (turnout), length of straight lines connecting turnouts in different sections on main line was proposed to meet the demand of traveling stability, and shortening or cancelation of straight line for the scale limitation of station yard has less influence on operation safety of train.

MK-801 reduces sensitivity to Müller-Lyer's illusion in capuchin monkeys

The Müller-Lyer’s illusion (MLI) is a visual illusion in which the presence of contextual cues (i.e., the orientation of arrowheads) changes the perception of the length of straight lines. An altered sensitivity to the MLI has been proposed as a marker for the progression of perceptual deficits in schizophrenia. Since dizocilpine (MK-801), a noncompetitive antagonist of the NMDA glutamate receptor, induces schizophrenic-like sensory impairments, it may have potential value for investigating the neurochemical basis of the perceptual changes in schizophrenia. Here we tested the effects of MK-801 on the perception of the MLI in a nonhuman primate. Five capuchin monkeys Sapajus spp. were trained on a MLI task using a touch screen monitor. After training, the Point of Subjective Equality (PSE; i.e., the minimum difference in length between two lines which the subject can distinguish) was determined for each subject. Then, during 12 consecutive days, we evaluated changes in PSE in response to vehicle, MK-801 (5.6μg/kg, i.m.) and a no-treatment protocol (post- test). Each of these was given as a single daily treatment, on four consecutive days. Results showed that MK-801 increased the monkeys’ performance in the MLI task, suggesting that NMDA receptor modulation reduces sensitivity to this illusion, similar to prodromal stage in schizophrenia patients. The MLI protocol may thus be used in nonhuman primates to screen potential antipsychotic drugs for early stages of this disease.