Background: The current study examines the relationship between speed and accuracy of performance in a reaction time setting and explores the informative value of the inverse efficiency score (IES) regarding the possibility to reflect age-related cognitive changes.Objectives: To study the characteristics of speed and accuracy while performing psychophysiological tests throughout the lifespan; to examine the speed-accuracy ratio in age groups and to apply IES to discriminative visual-motor reaction task; and to figure out the predictive potential of psychophysiological tests to identify IES values.Methods: We utilize nonparametric statistical tests, regression analysis, and supervised machine learning methods.Results and Conclusion: The examinees under 20 and over 60 years of age share one tendency regarding the speed-accuracy ratio without speed-accuracy trade-off. Both at the time of active developmental changes in adolescence and during ongoing atrophic changes in elderly there is a tendency toward a rise of the number of mistakes while slowing the reaction. In the age range from 20 to 60 the relationship between the speed and accuracy is opposite and speed-accuracy trade-off is present. In our battery, complex visual-motor reaction is the only test with the significant negative association between reaction time and error rate in the subcohort of young and midlife adults taken together. On average, women perform more slowly and accurately than men in the speed-accuracy task, however most of the gender-related differences are insignificant. Using results of other psychophysiological tests, we predicted IES values for the visual-motor reaction with high accuracy . The regression model shows the best performance in the cognitively preserved population groups of young and middle-aged adults (20–60 years). Because of the individual rate of neurodevelopment in youth and cognitive decline in the elderly, the regression model for these subcohorts has a low predictive performance. IES accounts for different cognitive subdomains and may reflect their disproportional changes throughout the lifespan. This encourages us to proceed to explore the combination of executive functioning and psychophysiological test results utilizing machine learning models. The latter can be designed as a reliable computer-aided detector of cognitive changes at early stages. A speed-accuracy trade-off (SAT) in behavioral decisions is a physiological phenomenon that accounts for the adjustment of species to living conditions. SAT is a feature of the individual's psychophysiological status that can dynamically change in a certain range of values under certain conditions, otherwise, it remains stable  with age in both genders in a variety of tasks. Fozard et al.  conducteimpairment of response inhibition in old age. As an outcome of this, the elderly may experience difficulty with sustaining attention to the stimuli exclusively. Presumably, this is caused by a decreased ability to inhibit irrelevant thoughts  length is determined by cognitive processes and by an individual's use of the feedback information. However, the performance metrics  may deteriorate if the examinee is set for speed vs. accuracy, or vice versa Fitts, . The reaFormerly, authors tried to compare velocity and accuracy characteristics of test performance when subjects are set for speed or correctness. They figured out that error rate may become very small in circumstances where the penalty for errors is sufficiently high, but it never becomes zero as long as the speed of response is given any importance at all Hick, . Howell decision making at high levels of accuracy  describe cognitive functioning in terms of domains of functioning. As the cognitive functions are closely linked, it is a challenging task to interpret the changes that may account for mutual compensation . The compensation accounts for the different rate of decline within different cognitive domains. Worsening of diverse performance metrics may start at any age and progress independently. For example, playing tennis preserves high accuracy in coincidence timing performance  represents the interference effect (interference score). In parallel to this, the error scores are recorded. The dualism of executive functions provoked researchers to elaborate a new neuropsychological test that would assess concurrently both inhibition and switching. Such was Stroop switching test. Additionally to the classic interference condition (the situation when the word meaning and the ink color doesn't fit), it included switching in-between tasks. The possible clinical application of the idea is to reveal early executive dysfunction that remains undetected with standard neuropsychological tests. So, as opposed to other tests, the compensation strategies do not hinder the early stages of executive dysfunctioning in Stroop switching test. By following the same pipeline, Belghali and Decker  is often assessed with the d Decker  created To study SAT with the tests, researchers combine speed and accuracy into a single dependent variable called the inverse efficiency score (IES). The variable derives from the mean RT and ER. From Equation (1), IES is expressed in milliseconds as well as RT, however, it indicates roughly the time spent for correct responses. When there is a trade-off between speed and accuracy, the IES effect will compensate for the differences in the percentage of incorrect responses.To get insight as to whether speed-accuracy ratio can serve as a potential biomarker of individual cognitive status while aging we address the following sub-objectives:To study the characteristics of speed and accuracy while performing psychophysiological tests throughout the lifespan.To study the association of the speed-accuracy ratios with the age and cognitive subdomains.To examine the speed-accuracy ratio in age groups and with regard to the gender.To figure out the predictive potential of PTs to identify the values of inverse efficiency scores.The battery of neurophysiological tasks we used fits the idea of our study: it contains PTs with both accuracy and time performance metrics. It has a well-considered structure and reflects a set of cognitive subdomains that underlie goal-targeted behavior. The examinees were paid neither for taking part in the study nor for the achieved results  otherwise this would be a limiting non-physiological factor that could spoil outcomes of the research. Structurally, the dataset consists of a list of deidentified subject records, a patient per row, and stored in the comma-separated value format files.The dataset is named after the title of the project Psychophysiological Outcomes of Brain Atrophy (POBA). POBA consists of about 100 features reflecting the overall psychophysiological status of examinees. The battery of tests covers diverse aspects of cognitive functioning, both high-level and basic-level ones. It includes 231 cases of MRI examination and PT of people of different ages (4–83 yo). Written patient's consent or parental consent with assent from minors for being tested and scanned was obtained in each case. All the examinees are either patients who suffer from periodic headaches and are anxious about having organic brain pathology or healthy participants examined at the beginning of their professional sports career. The exclusion criteria were as follows: organic brain pathology, mental disorders, injury to the head. The dataset is provided on demand (See section 7). The following tests' form POBA dataset:1. Simple visual-motor reaction (SVMR). SVMR is the test with the only type of stimulus requiring one and the same response. RT, deemed as the time elapsing between the onset of the stimulus and the initiation of the response, is the major dependent variable. SVMR_mean (ms) is the mean value calculated out of over 30  subsequent episodes of testing with unequal intervals of time between them. SVMR_mean (ms) is the value calculated out of over 30 subsequent episodes of testing  with unequal intervals of time between them.The median (SVMR_median) and the mode (SVMR_mode) values also describe the sample. The measures of how the length of the reaction are scattered in time are the standard deviation (SVMR_variance), the kurtosis (SVMR_kurtosis), the asymmetry (SVMR_ass), the quartile values , and the half-size interquartile range (SVMR_(q75-q25)/2).From the physiologic point of view, they may serve as markers of how stable the reaction is in time. Another dependent variable is the number of mistakes made by the examinee (SVMR_mistakes). The mistakes fall into two categories. These are 1. missing the targeted events (SVMR_passes) and 2. preliminary responding . Another dependent variable derived from the test is the Whipple's accuracy coefficient (SVMR_acc_coef). It shows the ratio of errors to correct responses. The lower the indicator is the higher is the performance accuracy. It reflects how stable the attention is and how balanced nervous processes are. In other words, it is a marker of the balance of the excitatory and inhibitory processes.To assess the sensorimotor response the system also calculates the following indices by Loskutova: system functional level (SVMR_sfl), the reaction stability (SVMR_rs), and the functional ability level  TD, . SVMR_sfWith SVMR time, one can assess the mobility of nervous processes: the shorter RT is, the higher the more mobile the nervous processes are. The variance of the variable (SVMR_variance) depicts the balance of the processes, i.e., the smaller the standard deviation is, the more balanced the nervous system is. SVMR_mean value under 177 ms accounts for the pronounced mobility of nervous processes. Its value of 177–200 ms is a characteristic of a mobile type of nervous processes. With 200–210 ms SVMR_mean length the average type of nervous processes is diagnosed. SVMR_mean value of 210–233 ms is typical for the inertia of nervous processes. Finally, if the reaction lasts more than 233 ms, the pronounced inertia of nervous processes is reported.Studying the dynamics of RT indicators throughout a day is a way to estimate the strength of the nervous system. With a strong  nervous system, RT does not change significantly during the day and within the framework of one examination.2. Complex visual-motor reaction (CVMR) is a variant of choice reaction test. A visual stimulus is presented to a subject whose task is to make a motor response quickly and accurately. We used the go/no-go test in which the examinee is asked to push the response button at green indicator light. In contrast, when the indicator lights up with red color no motor response is required. The system records the time elapsed between the onset of a stimulus and a response to. CVMR_mean is the mean length of response time calculated after 30 subsequent presentations of the triggering stimulus. CVMR_mistakes is the number of the fault responses. In the data analysis we use a derivative variable called error rate (ER) (see Equation 3). As in CVMR, we implemented the error rate derivative variables in other tests as well . There is one more type of the mistakes in the complex reaction compared to the simple one. It is a false reaction to the triggering stimulus of the wrong color, i.e., the responding to the red splash rather than to the green one . Similarly to the simple reaction, the complex one also has such dependent variables as CVMR_median, CVMR_mode, CVMR_variance, CVMR_kurtosis, CVMR_ass, CVMR_q25, CVMR_q75, CVMR_passes, CVMR_falstart, CVMR_acc_coef.Decision-making time (DMT) is the difference between the length of the simple visual-motor reaction and the complex one (see Equation 2). DMT reflects the time cost of the response selection. At the time of making the choice the individual affiliates the cognitive subdomains of switching and inhibition, i.e., the person inhibits prepotent responses and shifts between tasks.3. Attention study technique (AST) is the test in which the examinee is asked to respond to visual stimuli that flick one after another 30 times in diverse parts of the computer screen. Instead of targeting a single point like in the simple visual-motor reaction, the participant is to concentrate attention on the entire PC screen and respond as soon as possible by allocating the same motor reaction as recently.Reasonably, the dependent variables of AST are similar to that ones in the simple motor-visual reaction time. These are RT , the standard deviation (AST_variance), the kurtosis (AST_kurtosis), the asymmetry (AST_ass), the total number of errors with the number of missed stimuli and preliminary responding inside of them , the Whipple's accuracy coefficient (AST_acc_coef), and the indices by Loskutova the system functional level (AST_sfl), the reaction stability (AST_rs), the functional ability level .Additionally, the system provides two estimators that are specific to AST test. These are the attention stability (AST_stability) and the concentration of attention (AST_concentration).4. Interference resilience technique (IRT) is a bit more complex since the triggering stimuli are obscured with additional interfering objects that appear on the PC screen overlapping the targeted ones , the standard deviation (IRT_variance), the kurtosis (IRT_kurtosis), the asymmetry (IRT_ass), the total number of errors with the number of missed stimuli and preliminary responding inside of them , the Whipple's accuracy coefficient (IRT_acc_coef), and the indices by Loskutova the system functional level (IRT_sfl), the reaction stability (IRT_rs), the functional ability level .In analogy to DMT, we calculate the time delay in responding to the targeted stimulus because of visual interfering objects (TRVI) as in Formula 4 by substituting of the mean RT without interfering objects (AST_mean) from the study technique with them (IRT_mean).5. Reaction to a moving object technique (RMO) reflects either the balance of two opposite processes in the central nervous system  or the predominance of any of them. At the time of the task a circle appears on the screen with two marks of red and green color arranged radially. It is gradually filled quickly with yellow color, from some starting point to the finishing line in a clockwise direction, like, in The examinee should respond when the yellow sector passes through the red finishing line. There is a total number of over 30 trials . The result is processed as a mean value (RMO_mean) of positive (the time delays) and negative values (the premature responses). When the RMO_mean value is negative, it indicates the predominance of excitation of the central nervous system. If being positive, RMO_mean reveals the predominance of inhibition of the central nervous system. The tester counts the number of responses that were accurate in time (RMO_acc), the delayed ones (RMO_delays), and the fault starts . Also, the application sums up the time of them . All the trials disregarding their accuracy pertain to any of two classes, i.e., the “positive” trials when the response comes at any time after the targeted event and the “negative” ones when the response comes before the event. There are summary counters for the number of positive trials (RMO_positiveCount) and the number of negative ones (RMO_negativeCount).Like the tests mentioned above, RMO also has such dependent variables as RMO_variance, RMO_median, RMO_mode, RMO_ass, RMO_kurtosis, RMO_q25, RMO_q75. Additionally, there are such metrics as entropy (RMO_entropy), the number of responses6. Wrist dynamometry is a way of evaluating the maximum muscular strength of the right (WDR_MMS) and the left hands (WDL_MMS). Asymmetry coefficient (AC) is calculated from Equation (5).We calculate the inverse efficiency scores  as Formulas 6-9 state.For the comparison of age cohorts, we added attribute “Groups” to the POBA dataset. The range of years corresponding to age groups is as follow: Adolescent age ∈ [0, 20), Young adults age ∈ [20, 40), Midlife adults age ∈ [40, 60) and Older adults age is ≥ 60.To address the first objective, we used both the descriptive statistics and the machine learning approach.As the variables of our dataset had non-normal distribution, we utilized non-parametric tests for the analysis. In age groups, the relationships between continuous features were assessed with Kruskal-Wallis test.Also we analyzed the charts that describe age-related changes of the mean RT and accuracy. To build the trendlines we used non-linear Locally Weighted Scatterplot Smoothing (LOEWSS), which is a non-parametric regression method that combines multiple regression models in a k-nearest-neighbor-based meta-model.To address the second objective we proposed new psychophysiological indices equivalent to inverse efficiency score in EF tests. As the paradigm of the psychophysiological tests we worked with fitted the idea of SAT, we came up with the indices equivalent to the inverse efficiency score in EF tests. These are SVMR_IES, CVMR_IES, AST_IES, and IRT_IES (see Formulas 6–9). RMO test results include variables that estimate time and mistakes done. However, in this test, the time variables are the additional estimators of the reaction accuracy  rather than RT. So, the test doesn't fit the concept of SAT, and it cannot provide researchers with an efficiency score.In the first part of objective number two, we inspected possible associations between the age and the newly proposed scores. For this, we built the ordinary least squares (OLS) regression trendlines with a 95% confidence interval. By using Ridge regression we approximated the parameters of the model  with the polynomial function of degree one and assessed the performance of the models.t-test.To compare the lifelong dynamics of the IES scores for different tests  we tested the linear models for statistically significant differences between the slopes. For this we used statistical hypothesis tests, specifically To improve the reproducibility and interpretability of the age-related trends we also did sensitivity analyses, in which the RT and error outliers were removed.Working on the second part of objective two, we assessed the relationship between age, tests results that reflect diverse cognitive subdomains and the proposed scores. To do so, we calculated Spearman rank correlation coefficients and checked the associations of variables for the significancy.To address the third objective we inspected possible associations between the mean RT and the overall number of mistakes in age and gender groups. We analyzed the OLS regression trendlines with a 95% confidence interval.We studied whether the age and gender affected the impact of the RT change on the error rate, i.e., if there is an interaction effect. For this we tested our data for statistically significant differences between the slopes.The second part of the third objective was to find, whether the gender influences the dynamics of age-related changes in RT, efficiency score, mistakes. The statistical approach to this objective was the same as mentioned above. For the gender comparison, we removed outliers from the cohorts of females and males separately and then plotted the trendlines. We assessed the relationships between continuous features with Mann-Whitney U-test.In the fourth objective we figured out if IES provides a summary of the findings obtained while testing individuals. This could give the insight to what extent the novel inverse efficiency score reflects the overall psychophysiological status (PS).CVMR_IES value, we used the following predictors: “DMT,” “SVMR_mean,” “SVMR_mistakes,” “AST_mean,” “AST_mistakes,” “IRT_mean,” “IRT_mistakes,” “TRVI,” “RMO_mean,” “RMO_mistakes,” “WDL_MMS,” “WDR_MMS,” “AC,” “age.”To evaluate the prediction potential of the PS estimates to reflect the R2) performance metrics were used.For addressing the objectives of the study we utilized supervised machine learning methods, namely regression models. We did this because the predicted values were continuous. Doing this, we used a common approach to data analysis. First, we chose the set of predictors and did a data standardization  as usually required by many machine learning estimators. Then the data were shuffled and fed to the ML regression models in a 10-fold cross-validation manner. In this study, we used such regression algorithms as Lasso, Support Vector Regression with radial basis function kernel, K-nearest neighbors, Gradient Boosting, AdaBoost, and Random Forest. To evaluate the performance of regressors, mean absolute error (MAE), root mean squared error (RMSE), and coefficient of determination . The supposed reason for this is that TRVI values were highly scattered in the time scale in the group of adolescents (59.85 ± 60.46 ms). The values of the DMT are heteroscedastic throughout the lifespan, showing the high variance in adolescent group (63.08 ± 52.97 ms).The results of Kruskal-Wallis test state that median values of the variables mentioned above differ significantly in the age groups. We also noticed that all groups are drawn from people with different median values of t-test.To compare the lifelong dynamics of the IES scores from different tests  we analyzed the linear models. Specifically, we wanted to figure out if there is statistically significant differences between the variables' growth rate(slopes). For this we used statistical hypothesis tests, specifically To study the relationship between the mean reaction time and the overall number of mistakes in age-groups, we analyzed the OLS regression trendlines with a 95% confidence interval. p < 0.05) whilst the number of elderly women studied was significantly higher compared to men (29.85 vs. 15.46%).To perform the comparison we approximated the parameters of the model with the polynomial function of the degree one. We built the model for the overall study sample  and for p = 0.00000866). Interestingly, males keep a stable accuracy level during the lifespan while the task performance accuracy drops with aging in the opposite gender.Information on statistically significant differences between the intercepts and the slopes of the gender-specific models is in R2) are presented in We built up a prediction model for the check-up if IES provides a summary of the findings obtained while testing individuals. The performance metrics of the regression model such as mean absolute error (MAE), root mean squared error (RMSE), and coefficient of determination  vary insignificantly across age groups.Conducting the cross-sectional study we tried to find out if the slowing of the RT goes uniformly along with the decline in accuracy while aging. First, we studied the age-related changes in the time estimates of the tests . From Kruskal-Wallis test see , it is eAfter studying the time estimates we shifted our study to the lifelong dynamics of the accuracy . One may expect the same lifelong dynamics of the accuracy of CVMR performance as in the reaction time. However, it is different . The numR2 = 0.10976 vs. 0.088361 for AST; 0.108747 vs. 0.06731 for IRT). To sum up, IES for PT undergo age-related changes that can be described as the neurocognitive slowing, i.e., the latencies increase steadily. We may consider IES as markers of the brain aging because they incorporate information both on RT and accuracy. We also showed the ambiguity of the removal of the dataset outliers for the reproducibility of the data.In total, the statements about the data encompassing the POBA dataset and the assumptions that come from their analysis is consistent with the concept of speed-accuracy trade-off and its age-related changes. Studying the lifelong tendencies of the tests see , we see p = 0.02224). This is in consistency with the other researchers who found a difference in the time for processing the simple reaction task (0.5 ms/yr) vs. the complex one (1.6 ms/yr) . The interfering objects in IRT test add the switching condition which is absent in AST similarly like CVMR has a switching condition while SVMR does not. Because of the switching condition we expected that the lifelong dynamics of IRT should differ significantly from AST. As it was not so, we decided to proceed with the exploration of the CVMR_IES, its age-related trends, and gender-specific features.As the battery of PT provides a set of time and accuracy estimates, several IES scores derive from diverse task paradigms. This rises up a question of the comparison of the scores and their association with the age. On p ≤ 0.001) than with IRT_IES . This was another reason for us to decide to preserve CVMR_IES as the major marker of the speed-accuracy performance for the battery of tests.Another way of comparing the proposed IES for PT is by using the cognitive approach. We looked for the score that has the strongest informative power to reflect changes in cognitive subdomains. From Thus, it looks promising to propose IES for PT to cognitive studies in aging neuroscience for a set of reasons. First, there is an evident dynamics of the indices throughout the lifespan. Second, neurocognitive slowing estimated with IES-like indices correlates with task difficulty. Finally, the indices are reflective of cognitive subdomains (e.g. switching and inhibition).in adolescence and during ongoing atrophic changes in elderly there is the tendency toward the rise of the number of mistakes while slowing the reaction. The quicker the task is done the better the accuracy is or vice versa. We hypothesize that there are two options when we talk about an 'older adult: the person is either cognitively preserved and has a good task performance or the individual is somehow cognitively impaired, which reduces all metrics of performance . The examinees in the age range from 20 to 60 show the opposite relationship between the speed and accuracy. Slow reaction (long reaction time) is associated with the low number of mistakes which makes sense for the regular condition of an adult. So, in this age group we see the presence of SAT. In our battery of tests CVMR was the only one with the significant negative association between RT and ER in the subcohorts of young and midlife adults taken together  than in CVMR_mean . Many researchers do not follow the recommendations of Townsend and Ashby to check if RT and PE are positively correlated before using IES .The known limitation of the study lies in the speed-accuracy ratio and payoff conception itself. It turns out that the assumption on the relative time cost of correct decision works for the summary statistics of the overall results obtained throughout the entire test. But if analyzed separately, the average reaction time for the error responses is faster than that for the correct ones.Moreover, the time cost of making an error depends on the level of accuracy at which one is operating at the moment. An error saves more time at high levels of accuracy than at low levels. This means that the initial intent to figure out the time cost of making an error does not make sense. It is rather meant to estimate how long it requires to improve the confidence of the confidence of the examinee's judgment by a factor of two or ten compared to the present level of performance.IES score is potentially a clinically useful metric for summarizing the overall efficiency of decision making. It can be a particularly reliable tool when applied to psychophysiological test results as it reflects speed-accuracy performance and age-related changes. As a dependent variable for the complex visual-motor reaction test, IES is the best out of four newly proposed indices. IES accounts for different cognitive subdomains and may reflect their disproportional changes throughout the lifespan. This encourages us to explore psychophysiological test results utilizing machine learning models that can be designed as a reliable computer-aided detector of cognitive changes at an early stage.The examinees under 20 and over 60 years of age share one tendency regarding the speed-accuracy ratio without speed-accuracy trade-off. Both at the time of active developmental changes in adolescence and during ongoing atrophic changes in elderly there is a tendency toward a rise of the number of mistakes while slowing the reaction. In the age range from 20 to 60 the relationship between the speed and accuracy is opposite. In our battery, complex visual-motor reaction is the only test with the significant negative association between reaction time and error rate in the subcohort of young and midlife adults taken together.On average, women perform more slowly and accurately than men in the speed-accuracy task, however most of the gender-related differences are insignificant. Interestingly, males keep a stable accuracy level during the lifespan while the task performance accuracy drops with aging in the opposite gender.R2= 0.77 ± 0.08; mean absolute error/IES range = 3.37%). The regression model shows the best performance in the cognitively preserved population groups of young and middle-aged adults (20–60 yrs). The individual rate of neurodevelopment in youth and atrophy in elderly results in worse prediction performance of the regression model.The IES index for PT is a reliable index that describes the individual psychophysiological status. Using results of other psychophysiological tests, we predicted IES values for the visual-motor reaction with high accuracy (https://bi-dac.com.The datasets presented in this study can be found in online repositories. The POBA dataset generated for this study can be found at the site of Data Analytics Group at: The studies involving human participants were reviewed and approved by United Arab Emirates University Human Research Ethics Committee. Written informed consent to participate in this study was provided by the participants' legal guardian/next of kin.YS and TH contributed to the conceptual idea of the paper. YS formulated the objectives and wrote the manuscript. TH performed the statistical analysis, prepared the figures and tables for data presentation and illustration. KG with NZ and TA contributed to the literature review and data analysis. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


The incidence of secondary bile duct injury occurs between 0.2-0.3% in the open technique, while for the laparoscopic is 0.5-0.8%Among the vascular injuries associated with the cholecystectomy, almost 90% are in right hepatic artery. There are rare vascular injuries associated with bile duct injury that include the hepatic artery proper, the common hepatic artery, the main trunk of the portal vein, the right branch of the portal vein or a major venous injury associated with injury of the right hepatic artery. The literature contains few reports of these cases of major biliovascular injury.,Hepatic ischemia with hepatic parenchymal infarction occurs frequently and may require liver resection or transplant. Death associated with this type of injury is close to 50%Fifty-six old male with history of high blood pressure, gastroesophageal reflux, depression and hypothyroidism consulted for abdominal pain in the upper right quadrant of 20 days’ duration that had intensified in the previous two days, adding nausea and vomiting. He was admitted hemodynamically stable, afebrile, with diagnosis of mild lithiasic acute cholecystitis. He was operated laparoscopically, where a complex cholecystectomy was described with laceration of the right portal vein; therefore, the operation was converted to open laparotomy, with bleeding of up to three liters. A red blood cell transfusion was indicated. The bleeding was brought under control, and bile filtration was observed, which is why the bile duct was explored and a Strasberg E4 bile duct injury was describedth postoperative day.Computed tomography of abdomen and pelvis A suggestDespite the cholecystectomy being common in our environment, the bile duct injury with associated vascular injury continues to be present, and this was an extreme case that required multidisciplinary management.The literature contains few reports of major biliovascular injuries; in most cases they are associated with hepatic ischemia or hepatic dysfunction, which may require a liver resection or transplant. The mortality rate associated with such injuries is close to 50%,In some cases of this type of injury, hepatic resection with reconstruction of the bile duct has been preferred over the liver transplant In this case, we faced the challenge of a right portal vein injury with hemi-liver ischemia and injury of the hepatic artery proper with involvement of the left hepatic artery. Endovascular revascularization of the hepatic artery proper was very important to ensure the flow to the left hepatic artery.Other challenge was to define the point to perform the hepatic resection on a patient with liver ischemia and necrosis with risk of developing infection and sepsis.With the few cases that exist in the literature, it is impossible to determine the superiority of the early hepatectomy over the deferred hepatectomy. In this case, achieving reperfusion of the left hepatic artery was very important to obtain adequate perfusion of the post-hepatectomy remnant.During evolution and programming the liver resection, the patient developed infection in the right hemi-liver with necrosis. The initial treatment was drainage of the collection and antibiotic therapy, with no improvement; therefore, it was decided to perform an emergency hepatic resection. The hepaticostomy malfunctioned, producing cholestasis despite the improvement in the patient’s organic dysfunction; then, decision was to perform a Roux-en-Y hepaticojejunostomy anastomosis. In this case, as in all cases of bile duct reconstruction, we considered the use of magnification and microsurgical technique fundamentalAfter the biliary reconstruction and persistence of cholestasis, imaging is very important to ensure an adequate perfusion for remnant liver and to rule out biliary complications.


In physical human–robot interaction environment, ankle joint muscle reflex control remains significant and promising in human bipedal stance. The reflex control mechanism contains rich information of human joint dynamic behavior, which is valuable in the application of real-time decoding motion intention. Thus, investigating the human muscle reflex mechanism is not only meaningful in human physiology study but also useful for the robotic system design in the field of human–robot physical interaction. In this paper, a specialized ankle joint muscle reflex control algorithm for human upright standing push-recovery is proposed. The proposed control algorithm is composed of a proportional-derivative (PD)-like controller and a positive force controller, which are employed to mimic the human muscle stretch reflex and muscle tendon force reflex, respectively. Reflex gains are regulated by muscle activation levels of contralateral ankle muscles. The proposed method was implemented on a self-designed series elastic robot ankle joint (SERAJ), where the series elastic actuator (SEA) has the potential to mimic human muscle–tendon unit (MTU). During the push-recovery experimental study, the surface electromyography (sEMG), ankle torque, body sway angle, and velocity of each subject were recorded in the case where the SERAJ was unilaterally kneed on each subject. The experimental results indicate that the proposed muscle reflex control method can easily realize upright standing push-recovery behavior, which is analogous to the original human behavior. The mechanical ability of the ankle joint to stand upright steadily is of great significance in human daily lives. However, due to the high center of mass (about 64% of body height aboveground) and the disproportionately small supporting feet, it is not easy for human beings to stably maintain upright stance Roberts, . So far,Human upright standing push-recovery results from additive interactions of the senses, including vestibular, tactile, and proprioception, under the neuromuscular control mechanism. The muscle reflex, such as stretch reflex, is independent from cortical involvement and works as the most basic control mechanism of the central nervous system (CNS). Hence, the muscle reflex has relatively short afferent and efferent transmission delays, which consequently enhances the fast response ability of human muscle to external disturbances. The muscle reflex alone is powerful to maintain human upright balance during quiet standing in the case where only small environmental interference is considered McMahon, . In the Since the muscle reflex mechanism can not only provide insights to the study on human ankle joint properties but also suggest clues to the intelligent control of bionic robots physically interacted with humans to maintain upright stance, it has aroused extensive research interests of different researchers from the fields of human physiology and robotics. Winter et al.  have provia experiments from four aspects: relationship between ankle torque and sway angle, stability faced with external disturbances, influence on the other ankle muscles, as well as ankle joint dynamic properties during upright standing push-recovery. The experimental results reveal that the proposed reflex control algorithm can easily achieve human upright standing push-recovery, analogous to the original human behavior.Developing a bio-inspiration-based controller to maintain upright stance in the present of external disturbance for a unilateral prosthetics is meaningful as the robotic device should not only provide enough recovery torque but also follow the regulation mechanism of human to achieve a successful cooperation movement . Aiming at effectively achieving human upright standing push-recovery, this paper first proposes a specialized ankle joint muscle reflex control algorithm. Afterward, the proposed control algorithm is employed on a self-designed compliant actuation device which is named series elastic robot ankle joint (SERAJ) to mimic the muscle–tendon unit (MTU). Lastly, the feasibility of the proposed control algorithm is verified Muscle-Tendon Unit and Muscle Reflex Control section introduces MTU and human muscle reflex for push-recovery. The mechanical design of the SERAJ is stated in the Mechanical Design of Robot Ankle Joint section. The Reflex Control Strategy section describes the proposed reflex control strategy. The experimental tests and results are shown and analyzed in the Experimental Setup and Experimental Results sections, respectively. The last section concludes this study and shows some future works pertaining to this paper.The remainder of this paper is organized as follows. The The function of MTU during locomotion and the schematic of muscle control for upright standing push-recovery are stated in the hereafter contents of this section due to the fact that they contain important inspirational functions for the mechanic design of the compliant robot ankle joint and reflex control strategy.In addition to the muscle function, the tightly integrated and complementary function of tendon remains necessary and essential for generating joint torque and power during human push-recovery movement. The mechanical role of MTU provides a key energy-conserving mechanism that the elastic energy storage and recovery process is achieved in tendon from the body movement  is quite different. There is much less movement involved in ankle strategy standing balance. Although inconspicuously, muscle reflex compensation is necessary as intrinsic stiffness is not enough to keep upright stance balance  activates muscles around the ankle joint, so that torques pulling the body back to an upright posture can be yielded. Note that the block “switch” in Based on the research work done by Fitzpatrick et al. , the schIt is worth mentioning that the push-recovery schematic displayed in During human upright standing push-recovery movement, muscle reflex responds to joint or body kinematics/kinetics state variations. Muscle spindle is sensitive to the fiber length change and its change rate. When muscle is stretched, the spindle generates corresponding bio-electrical signal transmitting to spinal cord. Spinal cord generates feedback signals to activate muscle fibers. Muscle fibers contract to against the stretch. The following PD-like mathematic form is often used to describe this function .This paper selects and applies the sEMG signals of SOL and GAS to quantify the muscle activation level because these two muscles have been found to play important roles in human push-recovery movement. When converting sEMG signals into the muscle activation level, this paper adopts a commonly used method proposed by Jacobs and Horak  to procea(t) is calculated as follows:After processing the raw sEMG signals following the method stated above, the muscle activation level 1, and β2 are set as 2.25, 0.5, and 0.5 following our previous study  is more meaningful than the amplitude in this work.where Equation (2) represents the muscle activation dynamics, and Equation (3) is used to non-linearize the results. Equation (2) represents a discretized second-order relationship between e(t) and u(t), which is the dynamic between muscle activation and muscle force generation. According to Buchanan et al. , it needs et al. . EquatioFMTU force can be mathematically given by:Hill-type muscular model is implemented to calculate tension of MTUs. Tensions of MTUs are summed to predict ankle torque. This paper borrows the conventional form described in Fitzpatrick et al.  to calcuFT is the tendon tension. FPE and FCE are the passive and the active forces generated by muscle fiber, respectively. θp indicates the current pennation angle. Note that θp can be regarded as constant in this study since the variation of ankle joint angle is small enough.where r) of different muscles are obtained from OpenSim modelMoment arms  optimization method Hansen,  was usedankle is ankle torque. τe denotes disturbance torque. I and m are the inertia and mass of the body, respectively. Ankle joint angle θ can be read from the angular transducer or the motion capture system.where τvia cables, to compress spring , a speed control loop, and a current control loop. A feed-forward mechanism is used to change reflex gain in reflex control for adaptable compliance of SERAJ. The control scheme of the proposed ankle joint muscle reflex control strategy is shown in In this paper, similar to the study conducted by Winter et al. , 2001, hTo mimic stretch reflex control, a PD-like form is adopted, in which the proportional part stands for the response of muscle spindle to muscle fiber length change and the derivative part represents the response to fiber length changing rate. According to the structure design of SERAJ, the deformation of spring, which can be calculated by the joint angle, is regarded as the muscle fiber length change. As a consequence, joint angular velocity represents the fiber length changing rate. A variation in ankle angular velocity indicates the direction and intensity of restoration torque at the ankle joint in the next time instant. The desired restoration muscle activation level used in the developed reflex control loop is given as follows:Ar is the restoration muscle activation level. Ks and D stand for the proportion and derivative reflex gains, respectively.where In order to provide a stable force compensation in the developed muscle reflex control framework, similar to Prochazka et al. , a positTaindicates ankle torque. Tr stands for the restoration torque produced by Equations  using Ar as the input. Tc denotes compensation torque and can be obtained as:where C represents the compensation coefficient, and Tsis the mechanical torque generated by compression spring.where As stated above, a compression spring is added between the reducer output end and the load to increase the compliance of the self-designed SERAJ. Apart from this advance, such a structure design also increases the shock tolerance of the device and turns the torque control problem into a position control issue, so that the torque accuracy can be improved. Since the ankle torque in SERAJ is proportional to the spring compression multiplied by its spring constant and moment arm, the ankle torque can be obtained by:Ke is spring constant and set to be 76.59 N/mm. ls is the spring compression and can be gained via Equation (7).where During the application of the self-designed SERAJ, a maxon RE 40 motor driver is applied as the driving source. Since the maxon EPOS2 controller offers a fast and reliable way to automatically tune the regulation gains of the current and velocity and can easily adaptively adjust its parameters online, which is in full compliance with the control requirements of the maxon RE 40 motor, this controller is selected to control the speed and current of the motor applied in SERAJ.Muscle-Tendon Unit and Muscle Reflex Control section, the reflex proportional gain is numerically related to the muscle activation, and muscle activation can be obtained by the processed sEMG signals. The left ankle reflex proportional gain used in the stiffness regulation loop can be obtained as follows  and only muscle reflex control is included  have been recruited in the experiment study. Each subject has signed a written informed consent proved by Wuhan University of Technology on the usage of humans as experimental participants for the experimental study prior to participating. Prior to conducting the human push-recovery experimental tests, the feasibility of proposed control algorithm on the designed SERAJ needs to be experimentally tested.via a serial port to examine whether or not the ankle angle data and torque are linearly related to each other.During the device experimental test, the SERAJ is horizontally fixed at one test-bed to ensure that the foot of this device is the only movable part. The foot is manually rotated within a certain range, creating ankle torque under the reflex control. The ankle angle and torque data of the device are collected by an optimal incremental encoder. After collecting these data of the device, they are sent to a laptop Aiming to test the response ability of the device to external disturbance, another experimental test needs to be conducted on the device with the control algorithm prior to the human-including push-recovery experimental test. In this experimental test, the SERAJ is also fixed the same way as described in the first device experimental test. Then, a small transient force is applied on the toe of the device. Again, the ankle angle and torque data of the device are collected through three optimal incremental encoders. Then, both of these two collected data are sent to a laptop to examine (1) whether or not the ankle angle and torque can be fast responsible to external disturbance; (2) whether or not the static errors of these two data can be acceptable.During conducting the human push-recovery experimental tests, the SERAJ device is kneed on the right ankle of each subject and the “Ball-disturbance” platform described in T-tests were used to verify differences in mean ankle angle, ankle torque, and muscle activation level between different conditions. Differences among subjects are not considered in this paper as joint-level dynamic variation commonly existed during movement. p < 0.05 is considered statistically significant for all tests.In this section, experimental results are discussed from four perspectives to test the feasibility of the proposed reflex control algorithm. The four perspectives are (1) the relationship between the ankle torque and sway angle; (2) response faced with external disturbances; (3) ankle joint dynamic properties during upright standing push-recovery; and (4) influence on the contralateral ankle muscles. Note that the first two perspectives are carried out in the case where only the proposed control algorithm is inserted into the SERAJ without the subject being included. The last two perspectives are executed under the circumstance where the proposed control algorithm is inserted into the SERAJ with the subject being included.Experimental Setup section, the relationship between ankle torque and sway angle under different stiffness settings is visualized in R2 > 0.9) and the error is limited within 5%, which is a completely acceptable error. In other words, operation characteristics of the SERAJ can meet the anticipated effectiveness requirement in the “ball disturbance” push-recovery application.Following the first device experimental test depicted in the The dynamic responses of SERAJ to external disturbance controlled with different reflex proportion parameters are depicted in With the increasing of quasi-stiffness, the response oscillation and peak–peak joint deviation amplitude are attenuated. When the quasi-stiffness is set as 300 Nm/rad, the foot of the SERAJ device first vibrates twice about original position and the magnitude of ankle joint angle is about 0.025 rad when the external force is acted on the device. Then, the disturbed device can return to the original balance state around in 200 ms without deviation. This implies that the SERAJ can fast reply to the external disturbance with a zero static error when the device is controlled by our proposed control algorithm. This, to a certain degree, can further confirm the feasibility of the proposed method on the device in the case where no subject is involved.The “ball-disturbance” exerts an impulse-like perturbation (as shown in p < 0.05) in all the five subjects except subject A. There are significant differences in leaning forward duration (p = 0.026) and return back duration (p = 0.037) between SERAJ unmounted and mounted cases for subject C. However, the correlation values of leaning forward curve and return back curve between SERAJ unmounted and mounted case are 0.91 and 0.87, respectively. These high correlation values indicate that the trends of leaning forward when SERAJ is mounted are similar to the trend when SERAJ is not mounted. The correlation values of leaning forward and return back are relatively high among all the six subjects  can be found. The increasing trend is significant  alone, without the SERAJ kneed on his right ankle, is impacted by a rubber ball from 2.5 m height on the back. The sEMG signals of the subject's left ankle muscle are measured to analyze muscle activation. In the second group, the same subject repeats the experiment mentioned above in equal conditions except that the SERAJ is kneed on the right ankle this time. The activation of the subject's left ankle muscle also is analyzed to compare it with the last experimental result, as shown in The purpose of the exoskeleton device is to enhance the human joint, whereas the prosthesis intends to replace the joint and replicate the original biomechanical function. So, the question remains: Is there an additional effect on the subject's contralateral ankle motion with the use of SERAJ? Interestingly, sEMG as the electrical manifestation of muscle contraction contains rich information for decoding motion intention, including the simultaneous recognition of both motion types and developed force  by 0.13 and 0.06, respectively. As the same in sway angle and ankle torque situation, correlation values of Gas and Sol between SERAJ mounted and unmounted are close to 1 . The increased trend can be found in all the six subjects, except that Gas activation value decreased in SERAJ mounted case for subject B. It can be indicated that subjects intend to activate contralateral joint muscles (the left ankle) more when the right ankle is replaced by SERAJ, whereas the activation dynamic profiles trend keep the same. All the six subjects muscle activation values are listed in Compared with no SERAJ case, muscle activations of Gas and Sol averagely increase significantly  because the base of support of human is limited in foot-in-place upright stance  in two conditions. The same profiles of left ankle joint indicate that the dynamic behavior of the SERAJ performed during push-recovery task is similar with the right ankle. As a consequence, the proposed muscle reflex control realized on SERAJ could be analogous to the human behavior intention. The increasing muscle activation and joint torque imply that contralateral ankle output more work when wearing SERAJ. Subjects seem to intend to rely on their own ankle which can be controlled by themselves. Due to several objective factors, such as SERAJ's weight, which is not quite identical to the own leg of subject, and how the SERAJ is worn, there is no doubt that subject's left ankle could have to face extra burden that can be seen from the difference of activation level in the same muscle for upright push-recovery when wearing SERAJ. Most likely due to the higher activation level of the left ankle, the torque of the left ankle joint built up more rapidly and greater when wearing SERAJ. Moreover, subjects tend to utilize muscle synergy to coordinate muscles to keep balance, in which sensory information from whole body are input for the CNS. In our experimental protocol, each subject is required to knee on SERAJ. This may influence the sensation system as the right foot of each subject is suspended. As a consequence, each subject may adopt an alternation synergy in which the left ankle muscles are activated more.The drawback of SERAJ structure is that electric motor is hanging on the leg part which removes the inertia of SERAJ from the vertical line of the subject's thigh. However, the effect is limited to our experiments as the push is in a sagittal plane and the entire weight of SERAJ is smaller than that of each subject's leg. Moreover, the target of this study is to test the proposed muscle reflex controller, rather than a novel prosthesis design used in daily life. The improvement of the device can be considered as an extension of this study in the near future.In this study, a specialized muscle reflex control for robot ankle joint is presented to complete upright standing push-recovery during “ball-disturbance.” The dynamic properties of the unmounted SERAJ ankle joint are analyzed to assess the feasibility of the control. Experiments have shown that the dynamic performance, especially the trend of the dynamic profile of the contralateral ankle joint is almost consistent before and after using SERAJ. As many studies focus on large disturbance push-recovery using exoskeleton device or under locomotion circumstances, our results show that the proposed reflex control algorithm can guarantee upright standing balance using unilateral powered ankle joint prosthetics in ankle strategy situation, which is a common situation during daily living.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation, to any qualified researcher.YC made a contribution to building up a framework of muscle reflex control. KX made a contribution to designing a series elastic actuator. BT made a contribution to guiding experiments. ZJ made a contribution to analysis of experimental data. MP made a contribution to building upright standing push-recovery model with reflex control.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Regular physical activity is proven to help prevent and treat noncommunicable diseases such as heart disease, stroke, diabetes, and breast and colon cancer. The exercise data generated by health and fitness devices  are very important for health management service providers to develop personalized training programs. However, at present, there is little research on a unified interoperability framework in the health and fitness domain, and there are not many solutions; besides, the privatized treadmill data transmission scheme is not conducive to data integration and analysis.This article will expand the IEEE 11073-PHD standard protocol family, develop standards for health and fitness device (using treadmill as an example) based on the latest version of the 11073-20601 optimized exchange protocol, and design protocol standards compliance testing process and inspection software, which can automatically detect whether the instantiated object of the treadmill meets the standard.The study includes the following steps: (1) Map the data transmitted by the treadmill to the 11073-PHD objects; (2) Construct a programming language structure corresponding to the 11073-PHD application protocol data unit (APDU) to complete the coding and decoding part of the test software; and (3) Transmit the instantiated simulated treadmill data to the gateway test software through transmission control protocol for standard compliance testing.According to the characteristics of the treadmill, a data exchange framework conforming to 11073-PHD is constructed, and a corresponding testing framework is developed; a treadmill agent simulation is implemented, and the interoperability test is performed. Through the designed testing process, the corresponding testing software was developed to complete the standard compliance testing of the treadmill.The extended research of IEEE 11073-PHD in the field of health and fitness provides a potential new idea for the data transmission framework of sports equipment such as treadmills, which may also provide some help for the development of sports health equipment interoperability standards. In order to prevent noncommunicable diseases, the World Health Organization recommends that the world establish special actions to encourage and guide people to participate in more sports, and therefore released the global action plan on physical activity 2018-2030 }Because the above data transmission framework is derived from the 11073-20601 optimization exchange protocol, it is necessary to determine whether the data stream sent by the instantiated object that implements this standard meets the 20601 standard . If the The test of DIM is mainly based on the events of MDS.MDS-Configuration-Event: If the manager cannot learn the current agent configuration information from the associated historical records, the agent sends the event to the manager during the startup of the “configuration” state. This event provides static information about the measurement functions supported by the agent.MDS-Dynamic-Data-Update-Var: This event provides dynamic data  from the agent for the objects supported by the agent, and reports the object’s data in the format of a common attribute list variable.MDS-Dynamic-Data-Update-Fixed: Use the fixed format defined by the Attribute-Value-Map attribute of the measured object or MDS object to report data. The specific test items are shown in The service model provides the basic function of data access sent between the agent and the manager, and is used to exchange data derived from the DIM. The inspection items mainly include the command to obtain MDS device information (GET) and data report (Event Report). The specific test items are shown in The connection state machine defines a series of states and substates experienced between the agent and manager, including states related to connection, association, and operation. The communication model also defines the entry, exit, and error conditions of various states during the various running processes of measurement data transmission, which should be detected. The specific test items are illustrated in The test software is mainly divided into 5 modules: Abstract Syntax Notation One (ASN.1)  module, The ASN.1 module, which defines all data types and data structures of C struct, reuses the ASN.1 code block in the Continua Enabling Software Library (CESL)  open souThe encoding module generates an APDU binary data stream according to the instantiated APDU object and the Medical Device Encoding Rules used in 11073-20601.The decoding module, which refers to the ASN.1 module, converts the binary data stream of the data buffer into an instantiated APDU structure.The communication module adopts the abstract factory pattern, calls different subclass factories to produce and initialize instantiated objects of different underlying connection methods, and establishes data connections under the application layer.The test module will carry out the testing procedures according to the instantiated object returned by the decoding module, and generate a test result report.The data stream sent by the treadmill is transmitted to the application layer listening port of the test software via transmission control protocol (TCP)/USB/Bluetooth/Zigbee or other methods, and then the instantiated object produced by the communication module abstract factory  calls thAccording to the APDU to be sent, refer to the ASN.1 module to establish the initialization APDU object, and then call the application programming interface function to assign the initialization object. The encoding module uses the Medical Device Encoding Rules to encode the assigned APDU object and generate a binary data stream. The communication module calls the message sending function to send the data to the simulated treadmill. The entire workflow of the test software is shown in To verify the feasibility of the above standards, we built a simulated treadmill device based on the CESL open source software package. The treadmill device transmits the age, height, weight, maximum recommended heart rate, and other information once using the MDS-Dynamic-Data-Update-Var method (variable format data report); the MDS-Dynamic-Data-Update-Fixed (fixed format data report) method is used to transfer the Session and Subsession, dynamic heart rate, speed, energy consumption, and other information multiple times. The fixed format data report eliminates the description information such as data length and attribute ID. This is because the treadmill includes its own data format context in the configuration report and sends it to the test software before reaching the operating state. For fixed data sent periodically, fixed format data reports can save some byte streams. Here, the test software also plays the role of a manager, receiving the data stream sent by the treadmill to the binding port through the socket communication method of TCP, completing the test work according to the process, and then generating the final test result set report. The test software provides TCP, user datagram protocol, Zigbee, and other low-level interface connection methods, and provides optional MDS test attributes in the initial interface. In this article, we propose a treadmill data interoperability protocol based on 11073-PHD, and design a set of standard compliance testing methods that match it. Using the testing software, we tested the data stream sent by the simulated treadmill equipment and generated a corresponding test result report.In previous work, most manufacturers of sports and health equipment such as treadmills have their own set of data transmission standards, which is very unfavorable for data integration analysis and processing between different manufacturers and different sports and health equipment. In our work, through tailoring and customizing the existing 11073-PHD, we designed a set of protocol standards suitable for the transmission of treadmill data. This not only provides a possibility to unify the data transmission standards of treadmill equipment among various manufacturers, but more importantly, it also provides an idea for unifying the application layer data format of other sports and health equipment. Sports health equipment is designed based on the 11073-PHD-based customized design, so that they have the same semantic syntax, making it possible for a gateway device to integrate multiple sports health data.We have investigated 4 popular treadmill private protocols used in the market to transmit key data , and comHowever, this work plan only supports some common data information functions of treadmills in the usual sense. Some plans, such as Hlink’s running posture detection, are not completely covered. This requires a more comprehensive arrangement and improvement in the next step. In addition, the treadmill we define is just acting as an agent. However, if you add some additional equipment that can be connected to a treadmill, such as a sports watch, the treadmill plays a dual role. When the treadmill is responsible for receiving data from the sports watch, it acts as a master device; at the same time, the treadmill transmits all its data to the gateway device. At this time, it acts as an agent device. The above situation covers only a small number of applications in the treadmill market, and our standard is only applicable for treadmills with common features at this stage. Finally, there is a lack of information expression regarding the working state of the treadmill itself (the working state of the electronic control board and the working state of the sensing components). Further information describing whether the speed and slope adjustment unit is working properly can be added.


In experiments reported here, batches of hand-sewn electrodes from six novice embroiderers are tested for (i) manufacturing consistency, and (ii) myographic data acquisition against conventional gelled and machine-sewn electrodes. First, the electrical properties of the created electrodes are assessed through simple resistance measurements. Then, linear regression is performed using electromyography data to test if force-variation detection is feasible. The results demonstrate that hand-sewn electrodes provide similar sensitivity to force variation as their machine-sewn counterparts according to the linear regression gradients calculated (Surface electromyography is used for non-invasive evaluations of the neuromuscular system and conventionally involves electrodes placed on the skin to collect electrical signals associated with muscle activity. Recently, embroidered electrodes have been presented as a low-cost alternative to the current commercial solutions. However, the high cost of equipment used in their fabrication forms a barrier to deployment. To address this, this paper presents the first study into the  Surface electromyography (SEMG) is a technology used in the diagnosis, treatment and management of physical disabilities. SEMG is a non-invasive technique used for sensing the electrical activity of targeted muscles through electrodes placed on the skin. It allows the measurement of motor unit recruitment during activity and has a number of clinical applications such as the characterisation of pathologies of the neuromuscular system , the assWith the global population currently aging at an increasing rate, demographic studies in developing world posit that the expected number of stroke victims is going to raise in the future ,5. It isountries . These aountries  in thesedry electrodes that consist of rigid metal electrodes combined with sophisticated signal processing techniques to gain a signal; and (ii) gel electrodes that consist of disposable, adhesive patches. High-end, commercial dry-electrode systems or Biometrics Datalite EMG systems ) provide highly reliable measurements. They are also reusable and often come in convenient packages . However, the cost per sensor for such systems is typically around At present, in the developed world, two types of systems are commonly used for SEMG, namely, that use: (i) Recent studies have shown the possibility to create low-cost and efficient SEMG data acquisition systems (consisting of an amplifier and wireless transmitter) for only £60 , which i of work ). On the contact . Both kih is the thickness and Recent research into smart textiles has resulted in a more affordable alternative to these traditional SEMG systems . SpecifiThe machine-embroidered electrodes suffer prohibitive fabrication costs in terms of equipment and infrastructure: the digital sewing machines used to produce existing electrode designs cost around hand-stitching techniques. It assesses the potential for fabrication of textile SEMG electrodes within a resource-constrained setting, by local people with little or no technical knowledge in the operation or electronics of SEMG systems. fabrication consistency and quality of a total of functionality and reliability of electrodes fabricated by the objectively more skilled subjects was then evaluated through an isometric grip force test performed with easily learnt by those with no prior experience, and that electrodes fabricated in this manner show comparable performance to machine-made electrodes, suggesting their suitability for developing world use.With these challenges in mind, this study proposes a new approach to fabrication of electrodes through simple, This study presents dual experimental investigations into: (i) the training of non-technical volunteers in fabrication of SEMG electrodes through hand-embroidery; and (ii) the functionality of the resultant electrodes for data capture. The following describes the experimental procedure, materials and methods for the two experiments in turn. All subjects gave their informed consent for inclusion before they participated in the study. The study was conducted under the approval of the King’s College London Research Ethics Committee, LRS-16/17-4213.The first step of the experiment assessed the abilities of non-technical workers to hand-craft textile electrodes to a functional standard. For this, volunteers were invited to participate in a pair of one-day workshops to learn the necessary skills. In the results presented here, the experimental participants  to make the connection to a data acquisition device.In both workshops, participants used multimeters for resistance measurements, embroidery hoops and support fabric  making sure that the electrode is always flat on the table. This measure was chosen since the level and inter-electrode consistency of the resistance is an indicator of the expected quality of the SEMG signal: having lower resistance and matched impedance between pairs of electrodes leads to better sensitivity and filtering of noise . ConsistThe first workshop was designed to give all participants a basic training in sewing and electrical testing, to ensure they all start from the same level of knowledge. For this, several different sewing techniques and electrical tests were introduced to the participants with the help of two workshop facilitators and a set of printed teaching materials see . A demonThe participants were taught to hand-sew electrodes according to the same specifications of the best performing machine-embroidered electrodes presented in ; the desAfter the participants produced five electrodes (one per sewing technique), the facilitators showed them how to operate the multimeter and perform the desired resistance measurement as an electrical quality check. At the end of the workshop, feedback was sought from participants on their preferred sewing technique for independent fabrication of a batch of electrodes in the second workshop for later use in functional tests. In the experiments reported here, the group chose the float stitch technique, being perceived as the easiest technique to perform accurately.During the second workshop, the same participants were asked to hand-craft electrodes using their chosen sewing technique (float stitch) with the teaching materials only. As a reminder to participants, the float stitch technique and electrical tests were presented by the facilitators once at the beginning of the session. The participants were then asked to work independently to create a batch of electrodes for functional testing. Each participant was asked to produce 10 electrodes.To assess participants’ ability to independently test the electrical properties of their electrodes, each participant was asked to report 10 resistance measurements per electrode using the testing technique learned in the first workshop. After the workshop, these measurements were repeated by an expert electrical tester (workshop facilitator) for comparison against the participants’ reported measurements. Finally, the electrodes produced in this workshop were collected to evaluate their use in SEMG measurement using .reported measurements) was computed. For comparison, the same measures were computed on the measurements found by the expert tester  on the same set of electrodes. These values were compared for each participant. An ANOVA test was used to determine whether the mean resistance value reported (by a specific participant) varies significantly or not from the mean resistance values found by the expert tester on the same electrodes.To assess the participants’ skill in fabrication and electrical testing, the mean and standard deviation of the resistance measurements reported by each participant for the electrodes they created  a conventional gel-based approach; and (ii) a state-of-the-art machine-embroidered electrode approach.Following similar studies in the literature, two channels of SEMG data acquisition were used in the grip-force experiment see . One paiBiTalino (r)evolution Plugged Kit BT  was used to sample data from the two SEMG channels synchronously at a rate of 1 kHz via Bluetooth. During data acquisition, signals were monitored by the experimenter to verify good contact with the skin (poor contact is indicated by high-amplitude noise) using the OpenSignal software package  to plot the time-dependent signal in real-time. A synthetic kinesiology tape and elastic straps  were used to affix the electrodes to the subject’s right arm at the desired skin contact locations. For data acquisition, the For comparison, the measurements were repeated using MSE and conventional disposable Ag/AgCl GE . The MSE were those developed at the Centre for Robotics Research, King’s College London. The latter were created using a Pfaff Creative 3.0  programmable sewing machine, employing the design detailed in , i.e., tThe experiment was designed following the theory in , where fDuring the experiment, the participant was seated with their forearm on a table and was asked to grasp a dynamometer  with their dominant hand without moving the arm for 10 s at five different force levels, with 10 s rest in between. The force values were 5, During each experiment, raw data from two SEMG channels were recorded. Pre-processing was applied to the data to perform statistical analysis of the signal. The data of each trial were first segmented into equally-sized sections that correspond to a specific force application. To compensate for the short delay between the onset of gripping and the point at which the desired force level was reached, the first 3 s of each sample was discarded  . After tith force level, at time step t. The data were first centred around zero by subtracting the mean value of each segmentDenote red data . Each elr and the coefficient of determination First, the reliability of the SEMG data within-session was assessed by computing the coefficient of variation of each segment expected . The sumAll participants in the experiment showed the ability to create HSE using the techniques taught in Workshop 1 with varying degrees of skill. Typical examples of the participants’ handiwork are shown in The participant-reported and expert-verified resistance of the hand-sewn electrodes created during Workshop 2 are shown in p-value equal to: As can be seen, the self-reported measurements for three of the participants  can be overcome. To this end: (i) the feasibility of hand-crafting as a means to production  was tested; and (ii) the functional performance of hand-sewn electrodes for muscle activity measurement was assessed.The results show that, in regard to (i), embroidered electrodes can be created by hand to a similar quality  as the machine made electrodes. This statement must, however, be qualified in light of the results reported here. First, it appears that hand-crafting of electrodes requires an aptitude to sewing only seen in a subset of the population: in the results reported here, only a half of the participants of the workshops were able to sew electrodes with satisfactory electrical characteristics. This, however, only reflects the fact that people have diverse skills, and it is to be expected that, in commercial production, those exhibiting the greater skill would likely become the more prolific producers. In addition, it is important to notice that the duration of the activity could have impacted the quality of the final products as participant’s engagement could have changed during the workshop. The reported electrical testing suggest that the participants were not able to measure accurately the resistance of the electrodes; one way to improve this would be by providing a range of acceptable resistance values to measure. These results motivate to further the study in the electrical characterisation of the HSE in order to have a precise description of the resistance at the surface of the electrodes. Future resistance measurements for the electrical characterisation of the HSE should be performed in a laboratory following the standards in   even more remarkable. This may be partially attributable to the fact that textile working is near-universal across countries at all stages of development, hence even if participants have no direct prior experience of sewing, they have some basic level of knowledge about it. This also suggests that, were such approaches deployed more widely for fabricating healthcare devices, there would be a ready population of textile workers to draw upon.The functional tests in SEMG capture shows that it is feasible to record muscle activity and detect force variation with HSE. In addition, the reliability test shows that the data recorded with HSE are in good agreement with the signal quality of traditional GE. Observations during the experiment can explain that the higher coefficient of variation with MSE is due to the fact that some participants twitched during the exercise of force contraction (to reach the target grip force) after performing trials with the HSE and GE. These cases have not been disregarded in order to keep the same sample size for comparison across participants and gender diversity in the group of participants. In force-variation assessment, the performance of the HSE is lower than that of GE overall, and marginally lower than MSE. This can be explained by several factors in the design and production of the different electrodes. The fact the MSE have two iterations of embroidery , whereas


N = 19) freely viewing 15 paintings in the 20th-century Australian collection room at the Art Gallery of New South Wales. In particular, we focus on how aspects of viewing behavior including viewing distance in the gallery condition and eye gaze measures such as fixation count, total fixation duration and average fixation duration are affected by the artworks’ physical characteristics including size and image statistics properties such as Fourier amplitude spectrum, fractal dimension and entropy. In addition, the same artworks were viewed in the laboratory, either scaled to fit most of the screen (N = 22) or to preserve their relative size as in the museum condition (N = 17) to assess the robustness of these relationships across different presentation contexts. We find that the effects of presentation context are modulated by the artworks’ physical characteristics.While aesthetic experiences are not limited to any particular context, their sensorial, cognitive and behavioral properties can be profoundly affected by the circumstances in which they occur. Given the ubiquitous nature of contextual effects in nearly all aspects of behavior, investigations aimed at delineating the context-dependent and context-independent aspects of aesthetic experience and engagement with aesthetic objects in a diverse range of settings are important in empirical aesthetics. Here, we analyze the viewing behavior of visitors ( Alt-Segeberg Bürgerhaus museum that enables people to visit the museum by using a virtual reality headset remotely, which aims to provide a more “real” experience that includes body movements in the tour  in Sydney, Australia. The two important issues that we aim to explore in this study are the effect of the context on viewing behavior  and the influence of characteristics of the artwork on viewing behavior in both contexts.While studies considering the experience of artworks in different contexts often utilize the explicit ratings of artworks to directly measure various aspects of aesthetic experience, we opted to focus on the viewing behavior as an index of spontaneous engagement with such objects. Preferential looking at artworks in an exhibition space is not only a defining feature of an art museum visit but, arguably, can be taken as an immediate and objective index of our engagement with such objects. This idea is not only central to the preferential looking paradigm in general, but has also received support in the aesthetics domain .The fine-grained analysis of precisely what and how participants look at art exhibits still remains a topic of enormous theoretical and practical interest, especially for visitor-centered art institutions such as art museums and galleries. While it has been well-established that allocation of attention in any physical context is a complex interplay between “top down” (viewer-centered) and “bottom up” (stimulus-driven) factors, our approach is aligned with the attempts to explore the role of physical, statistical properties in the perception of and interaction with images, including artworks. The physical characteristics of the artworks considered were physical size, and image statistical properties such as Fourier amplitude spectrum, fractal dimension and entropy. All these are general physical characteristics of objects and images known to be effective in capturing attention , or inflThe present study explores the viewing behavior of gallery visitors freely viewing paintings with a particular focus on how the aspects of viewing behavior, including viewing distance and eye gaze measures such as fixation count, total fixation duration and average fixation duration are affected by the artworks’ physical characteristics including physical size and image statistics properties.Three Musicians) or low (Joan Miro’s Blue II).While the studies of visitor behavior in museums have acknowledged that larger artworks are generally more effective in attracting and holding attention , relativThe physical size of artworks has also been found to affect viewing distance. a), fractal dimension (FD), and Shannon Entropy (SE).Despite the apparent heterogeneity and even randomness, artworks, like natural scenes, have characteristic, and regular structure related to the degree of spatial redundancy they exhibit. The spatial redundancy is related to the extent to which the surface properties at any locations can be predicted by the known values at nearby locations, and is intimately coupled with the notions of both spatial information and the scale-invariant, fractal-like properties of both artworks and natural scenes . Here wea amplitude spectrum quantifies contribution of coarse spatial structure  vs. fine spatial detail  in an image and has a value of approximately 1 for both natural scenes and artworks  which can be used to describe and quantify patterns which exhibit self-similarity in geometrical-spatial structure at different levels of magnification . FractalShannon entropy (SE) measures the degree to which an image or a spatial form vary unpredictably, or randomly and is inversely related to the notion of spatial redundancy . Those iOur selection of these measures of statistical structure was motivated as follows. Firstly, these measures have been used to investigate and characterize the spatial structure of a wide range of different artworks with findings indicating a remarkable similarity in Fourier-based image statistics of artworks from different regions or time periods . Most reMore importantly, all three measures exemplify the objective measures of complexity, a notion that belongs amongst the most influential in empirical aesthetics: from Artworks are often analyzed or classified as belonging to a particular style, typically based on a period, country, cultural group, or art movement. In addition to these predominantly art historical considerations, different art movements are often associated with distinctive visual qualities, which in turn can be associated with their physical features and statistical properties . Our stuIn addition to the AGNSW museum condition, the same artworks were viewed on computer monitors in our laboratory, either scaled to preserve their relative size or presented to fit most of the screen in order to assess the robustness of the effect of artworks’ physical characteristics across different presentation contexts. The details of physical dimensions of both artworks and their digital reproductions are shown in the Method section.Across the three presentation conditions  we compare the average number of fixations (NF), average total fixation duration (TFD), and average fixation duration (AFD) with mixed effects ANOVA with the presentation condition as the between-subject and Paintings as the within-subject factor. In each presentation condition we also perform regression analyses with the average NF, TFD and AFD as dependent variables and the artwork physical size, Fourier amplitude spectrum and fractal dimension as predictors.A total of nineteen AGNSW visitors  volunteered to participate in this study. All participants reported normal or corrected-to-normal vision. All participants were over 18. Eleven participants were Sydney residents, two were interstate visitors and six participants were international visitors. Sixteen out of 19 participants reported a university degree or postgraduate studies as their highest level of education. Participant recruitment and all other procedures for the in-museum study were approved by the University of New South Wales, Human Research Ethics Advisory Panel B- Arts, Humanities and Law .Thirty-nine UNSW students  volunteered to participate through the UNSW online SONA system in exchange for course credit or a small monetary reward of AU$5). All subjects reported normal or corrected-to-normal vision and were over the age of 18. Participants were randomly assigned to either on-screen full size (22) or on-screen relative size (17) condition. Participant recruitment and all other procedures were approved by the University of New South Wales, Human Research Ethics Advisory Panel C- Psychology .The sample size in the two viewing conditions is quite small due to both convenience sampling and time limited chance to collect data. Nevertheless, in the museum condition the number of participants in our study is either comparable to or higher than in other eye tracking studies . As suchThe Australian Art gallery at the Art Gallery of New South Wales measures 9.5 × 27.3 m room and contains 15 paintings, as shown in The physical dimensions and image statistics of artworks are shown in t13 = 1.849, p = 0.087), nor was the difference in Shannon Entropy . The two groups differed with respect to their average Fourier slope  and fractal dimension  values. In particular, the Indigenous paintings have a lower average Fourier amplitude spectrum slope and higher average fractal dimension value, consistent with the high level of fine spatial detail (dots) in these artworks.We note a high degree of variability in physical size and image statistic measures between individual paintings, both within and between the two painting style groups. The average image statistic values for the two groups are detailed and compared in r = −0.841, p < 0.001). Importantly, there were no significant correlations between the painting area and image statistic measures.In 2) was approximately 65.5 times larger than the area of the smallest painting (IA1 = 0.13 m2)], keeping the relative sizes in the on-screen condition true to the physical sizes would have been impossible as the smallest paintings would be virtually impossible to resolve.Given the very large differences in the area of individual paintings  and look at the paintings as you would normally do. Take as long as you wish. When you finish, please come back to us.” In order to preserve the museum condition as natural as possible, the experimenter was not present in the exhibition room. For the same reason, there were no attempts to control the crowd density in the exhibition room.AGNSW visitors were recruited in the foyer of the museum. After providing informed consent, participants were fitted with the Tobii Pro Glasses 2 at a research table in the same location. A calibration procedure was performed in order to ensure accuracy of eye movements recording. Participants were then invited to “visit that room , the total fixation duration . The same was the case for the total fixation duration  with the area , fractal dimension  and amplitude spectrum slope  as significant predictors. None of the image statistics measures were significant predictors of the average fixation duration .To examine the extent to which image statistics measures can be used to predict variance in eye gaze measures we performed three separate multiple regression analyses (enter method) with the number of fixations, total fixation duration and average fixation duration as dependant variables with the area, amplitude spectrum slope, fractal dimension and Shannon entropy as predictors in each case. These analyses show that the area , total duration of fixations  and average fixation duration  for each painting are shown in F = 5.856, p < 0.001] and the significant paintings x on-screen presentation condition interaction . However, the main effect of on-screen presentation condition was not significant .The mean number of fixations per painting was 49.9 in the full-screen condition, compared to the mean of 27.03 for the relative size condition. The two-way mixed-effect model (REML) revealed the significant main effect of paintings . The main effect of on-screen presentation condition was not significant , nor was the paintings’ x on-screen presentation condition interaction .The mean fixation duration per painting was 13.39 s in the Full-screen condition, compared to the mean of 7.44 s for the relative size condition. The two-way mixed-effect model (REML) revealed the significant main effect of paintings , as well as the significant paintings x on-screen presentation condition interaction . The main effect of on-screen presentation condition was not significant .The mean fixation duration per painting was 0.273 s in the full-screen condition, compared to the mean of 0.296 s for the relative size condition. The two-way mixed-effect model (REML) revealed the significant main effect of paintings . However, the Shannon Entropy  was the significant predictor of the average fixation duration . The same was the case for the total fixation duration . Negative standardized b coefficient suggests that the average fixation length was shorter for the paintings with higher entropy values.Even though there were no major changes in the area, or the visual angle subtended by different paintings in this condition, the area was kept as one of the predictors to keep the parameters of regression analyses comparable across different presentation conditions. The results show that none of the image statistics measures were significant predictors of the average number of fixations , fixation duration , or average fixation length .The results show that none of the image statistics measures were significant predictors for the number of fixations , but the interaction between the presentation condition and painting style was significant . The main effect of painting style was also significant . The significant interaction indicates that the difference in number of fixations for the two painting styles was pronounced only in the museum condition.The main effect of presentation condition did not reach significance  and painting style  did not reach significance, but the interaction between the presentation condition and painting style was significant . Analogous to the pattern with number of fixations, the difference in the total fixation duration for the two painting styles was visible only in the museum condition.The main effects of presentation condition  such that overall the average fixation duration for the Indigenous paintings was longer than for the non-Indigenous paintings. This trend seems to be more pronounced in the museum and in the on-screen relative size conditions, but the interaction between painting style and presentation condition was not significant . The main effect of presentation condition was not significant .The main effect of painting style was significant [In order to provide further qualitative and quantitative insights in viewing behavior across the three different contexts used in our study, we have generated heatmaps of total fixations for each artwork in each condition. They are summarized for the non-Indigenous and some of the Indigenous paintings in To provide a low-level visual baseline we computed an objective, visual saliency map of each image using the Graph-Based Visual Saliency method  which arThough differing in the overall number of fixations, the spatial layout of fixated locations is remarkably similar across the three different contexts in which the artworks were viewed from different distances, for different durations, at different visual angles and in different mediums. This similarity is consistent with the two-stage model proposed by used a ScanMatch MatLab toolbox  to quantN = 19) freely viewing 15 paintings in a room containing 20th-century Australian artworks at the Art Gallery of New South Wales. We examined how aspects of viewing behavior including viewing distance in the gallery condition and eye gaze measures such as fixation count, total fixation duration and average fixation duration are affected by the artworks’ physical characteristics of size and image statistics properties such as Fourier amplitude spectrum, fractal dimension and entropy. Given the diversity of artworks in the collection, we have also considered the painting style, Indigenous Australian vs. non-Indigenous Australian as an additional characteristic of interest in our study.In this study we investigated the viewing behavior of visitors  compared to Indigenous paintings (1.4 m). There was also a positive relationship, although only for the non-Indigenous paintings, between the painting area and viewing distance, as observed by Our eye gaze measures in the gallery condition revealed that on average participants made 44.24 fixations per painting with an average total fixation duration of 12.44 s and fixation length of 0.270 ms. Although the total fixation duration observed in our study is shorter than the average viewing times reported in earlier studies , our valHowever, when the same artworks were viewed in the laboratory, either scaled to fit most of the screen or to preserve their relative size as in the museum condition, none of the image statistics measures could be used to predict the average number of fixations and fixation duration. The only exception was Shannon entropy, which correlated negatively with the fixation duration and length, suggesting the shorter fixation duration and average length for paintings with higher entropy values.Overall, when museum and on-screen presentation conditions were directly compared, our results reveal a strong interaction between presentation conditions and the effect of painting style and associated physical characteristics of artworks. We suggest that in order to be able to fully characterize the effect of presentation context in engaging with aesthetic objects, a finer grained analysis of their physical characteristics seem promising.In conclusion, our study indicate that individual paintings exert a strong influence of viewing behavior. Some of that influence can be attributed to the paintings’ physical and statistical image properties, especially when these properties coincide with differences in painting style. However, the experience of artworks in different contexts remains a complex question that requires a more robust and parametric manipulation of these factors. Concurrent measures of aesthetic experience should also be incorporated in future studies in this area.The datasets generated for this study are available on request to the corresponding author.The studies involving human participants were reviewed and approved by the University of New South Wales Human Research Ethics Advisory Panel B  and Panel C (Psychology). The participants provided written informed consent to participate in this study.VE-G, MG, SE, and BS contributed to the conception and design of the study. VG-E, MG, and SE contributed to the data collection at the AGNSW. VG-E and BS contributed to the data collection in laboratory and analyzed data. All authors contributed to the writing of the manuscript and approved its submission.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.