The effects of repeated high acceleration on implant osseointegration in SD rats / 实用口腔医学杂志

Objective:To investigate the effects of repeated high acceleration(+Gz)on implant osseointegration in SD rats.Methods:18 SD rats were divided into+Gz and control groups randomly(n=9),and 1 implant was placed in each femur of the rat's lower limb.24 hours postoperatively,the experimental rats were exposed to+Gz of 4 to 9 G with 1 G/s environment 3 times a week,while the con-trol rats were fed normally.3 rats from each of the 2 groups were sacrificed at 2,4 and 8 weeks after implantation.Micro-CT,sequential fluorescence double labeling,and histological examination were perfomed for the analysis of implant osseointegration.Results:The bone volume fraction(BV/TV),trabecular number(Tb.N),mineral apposition rate(MAR),implant-bone contact rate(BIC)and bone area in implant thread(BA)of the+Gz group were significantly lower than those of the control group at 2 weeks(P＜0.05),and so as to MAR,BA at 4 weeks(P＜0.05),while there was no significant difference of the parameters at 8 weeks after implantation.Conclusion:In SD rats early exposure to+Gz environment postoperatively may have a negative effect on initial osseointegration by slowing bone forma-tion.However,it will not lead to poorer bone mass when sustained over a long period.

Assessment of dynamic cerebral autoregulation in pilots after acute positive acceleration exposure / 中华超声影像学杂志

Objective:To explore the changes of dynamic cerebral autoregulation ability in pilots exposed to acute positive acceleration(+ Gz) by transcranial Doppler combined with beat-to-beat blood pressure.Methods:A total of 26 pilots enrolled in the + 8Gz manned centrifuge trial at the Air Force Medical Center, Air Force Medical University from June to October 2022 were prospectively included. Blood pressure and heart rate were monitored in the resting state before the trial and within 5 min after centrifugation. Transcranial Doppler combined with noninvasive continuous beat-to-beat blood pressure monitor were used to detect bilateral middle cerebral artery blood flow velocity and beat-to-beat pulse pressure respectively. The transfer function analysis was applied to derive the parameters of cerebral blood flow autoregulation in each frequency band from 0.02 to 0.50 Hz, and the phase, gain and coherence were calculated. The above parameters were compared between resting state and after acute + 8Gz positive acceleration exposure.Results:Compared with the resting state, in all of the 26 pilots after acute + 8Gz positive acceleration exposure, the systolic and diastolic blood pressure and heart rate increased significantly ( P<0.001), the phase significantly increased and the gain significantly decreased in the ultra-low frequency band (0.02-0.07 Hz) ( P<0.05); whereas there were no statistical differences of gain and phase in the low frequency band (0.07-0.20 Hz) and the high frequency band (0.20-0.50 Hz) (all P>0.05). Conclusions:Transcranial Doppler combined with beat-to-beat pulse pressure can be used for the assessment of changes in immediate dynamic cerebral autoregulation after acute + Gz exposure, and transfer function analysis of ultra-low frequency band parameters is suitable for this type of evaluation.

Clinical research progress on corticotomy and modified techniques for accelerating orthodontic tooth movement / 口腔疾病防治

@#Adjunctive interventions for accelerating orthodontic tooth movement have been a hot topic of interest in orthodontics. Prolonged orthodontic treatment is often associated with multiple potential complications, such as decalcification, caries, root resorption, and gingival inflammation. Therefore, applying adjunctive interventions that accelerate orthodontic tooth movement and reduce the duration of orthodontic treatment can provide patients with numerous benefits that are of profound clinical significance. Currently, adjunctive interventions for accelerating orthodontic tooth movement can be divided into two main categories: surgical and nonsurgical. Surgical interventions, represented by corticotomy and modified corticotomy procedures, are the most common in clinical practice and can minimize the treatment duration, augment alveolar bone, and expand the range of orthodontic tooth movement. However, these procedures are inevitably traumatic and have many risks and limitations that prevent them from being widely used in clinical practice. In recent years, multiple modified corticotomy techniques, such as corticision, piezocision, micro-osteoperforation, and discision, have been proposed; these techniques can reduce soft and hard tissue damage and the incidence of postoperative complications and are relatively easy to perform in the clinic. Corticotomy and other improved surgical techniques can shorten the duration of orthodontic treatment to a certain extent and promote the recovery of periodontal health with no adverse effects on periodontal, dental, or pulp tissues. However, in clinical application, several potential side effects (such as periodontal tissue damage, root resorption, loss of pulp vitality, etc) and shortcomings need further research with long-term follow-up.

The Mechanism of Brain Injury Induced by Rotational Motion / 医用生物力学

Traumatic brain injury ( TBI ) has caused serious economic and social burdens, but due to its heterogeneity, there is no effective treatment. In TBI with different severity, diffuse axonal injury (DAI) incidenceis high. The investigation on DAI will contribute to the diagnosis and treatment of TBI. In this study, the classification of TBI and the research status of DAI were summarized. The method to judge the severity of TBI and DAI, and animal experimental models and related injury criteria and thresholds were reviewed. The result show that DAI is mainly generated by rotational acceleration and it is related to angular acceleration, angular velocity and duration. Several TBI animal models can induce the pathology of DAI, and inertial rotation models which can produce only rotational acceleration have been developed. However, these models are instantaneous rotation models, and the rotation duration is uncontrollable, thus a longer duration is impossible, and DAI severity under long rotational motion cannot be studied. The study proposes that a new rotation animal model which can control rotation duration should be developed. The development of the animal model and investigation on pathomechanism of the model will contribute to the prevention and treatment of DAI.

Differences in Neck Injuries of Dummy Models at Different Backrest Angles under Horizontal Negative Acceleration / 医用生物力学

Objective Based on the dummy model, to study the relationship between different backrest angles and neck injuries under the effect of horizontal negative acceleration (-Gx ). Methods The dummy model was fixed on the base of the acceleration platform facing the orbital direction, and the backrest angle was set at 17°, 22°, 30°, respectively. Each experimental group performed 10 repeated tests according to the same acceleration curve, differences between the upper and lower acceleration of the cervical spine under the same -Gx conditions were compared, and the neck injury criteria (NIC) was calculated and compared through curve fitting. Results The time-acceleration curves of the upper and lower cervical spine in the anteroposterior and vertical directions had the same shape with peak differences. In the anteroposterior direction (X-axis), the acceleration peak of the 22° backrest angle experimental group was slightly higher than that of 17° and 30° backrest angle experimental groups, but in the vertical direction (Z-axis), the acceleration peak of the 22° backrest experimental group was lower than that of 17° and 30° backrest angle experimental groups. In the anteroposterior and vertical directions, the NICmax measured by 22° backrest angle experimental group was relatively smaller, NICmax measured by 30°backrest angle experimental group was in the middle, and NICmax measured by 30° backrest angle experimental group was relatively larger. Conclusions There was a nonlinear relationship between the backrest angle and theneck injury. The neck injury of the dummy model with the backrest angle of 22° was smallest under the effect of-Gx in this experiment.

Evaluation method of dynamic postural stability for functional ankle instability based on acceleration signals / 中国康复理论与实践

ObjectiveTo compare the retest reliability and discriminant validity of dynamic postural stability indices for functional ankle instability (FAI) obtained by different algorithms based on acceleration signals at different positions of human body. MethodsFrom April to June, 2021, 21 subjects with unilateral FAI and 21 subjects with normal ankle were recruited. Three inertial sensors were attached to the waist points, knee and ankle positions. The ground reaction force (GRF) and kinematics data of the subjects in multi-direction single leg landing test were collected synchronously by 3D force plate and inertial sensors. The unbounded third order polynomial (UTOP) fitting method was used to calculate the stability time, and the root mean square was used to caculate the stability index. ResultsMost of the indicators calculated based on acceleration signal correlated with that based on GRF with low coefficient (|r| = 0.116 to 0.368, P < 0.05). The stability time and stability index based on the acceleration signals of different positions of human body showed low to high retest reliability (CMC 0.30 to 0.91). For the females, among the stability time based on acceleration signal, eleven indexes achieved average to very high discriminant validity (AUC = 0.702 to 0.942, P < 0.05); eight of the stability indexes reached general level of discriminant validity (AUC = 0.717 to 0.782, P < 0.05). No algorithms achieved good discriminant effect in male subjects. ConclusionBased on the acceleration signal of waist point in single-leg landing stability test, the stability time calculated by UTOP algorithm can evaluate the dynamic postural stability of female FAI patients with high discriminant validity and medium to high retest reliability.

The relationship between jumping and sprinting performance in teenage sprinters / Relación entre el desempeño del salto y el sprint en velocistas adolescentes / Relação entre o desempenho de salto e sprint em velocistas adolescentes

ABSTRACT Objectives: This study aimed to examine the relationship between vertical jumping at forces of specific time phase and sprint performance in teenage sprinters. Methods: Fifteen male teenage sprinters (age: 14±2 years, height: 168±2 cm, weight: 61±1 kg) participated in the study. The subjects performed the following bilateral/unilateral jumps on a force platform: a) squat jump (SJ), b) unilateral SJ (USJ), c) 40cm drop jump (DJ), and d) 20cm unilateral DJ (UDJ). The 60m sprint test was administered on the second day. Brower split timers were positioned to record subjects' 5m, 10m, 50m and 60m split times. The variables for inclusion were vertical jump height, maximum force, and force output at 120ms in all jumps and sprint time measures. Results: The results of the Pearson Product Moment Correlation analysis showed that SJ120ms was correlated to 5m and USJ120ms was correlated to 10m. UDJ120ms showed a stronger correlation with 50m than DJ120ms. Although significant correlations using maximum force and height were observed, there were inconsistent results between bilateral and unilateral jumps. Conclusion: Our results highlighted that jumps that have similar form with certain force outputs at specific event timing could more precisely predict sprint performance in teenage sprinters. USJ120ms and UDJ120ms could better predict the acceleration (10m) and high-speed phase (50m) in sprint performance, respectively. Moreover, coaches and practitioners should be cautious when using only jump height or maximum force to predict sprint performance, since the results could be inaccurate when specific movement variables are not thoughtfully considered. Level of evidence III.

RESUMEN Objetivos: Este estudio tuvo como objetivo examinar la relación entre el salto vertical y la fuerza en tiempo específico y el desempeño del sprint en velocistas adolescentes. Métodos: Participaron en el estudio quince adolescentes varones velocistas (edades: 14 ± 2 años, estatura: 168 ± 2 cm, peso: 61 ± 1 kg). Los individuos realizaron los siguientes saltos bilaterales y unilaterales en una plataforma de fuerza: a) squat jump (SJ), b) SJ unilateral (USJ), c) drop jump (DJ) de 40 cm e d) DJ unilateral (UDJ) de 20 cm. La prueba de sprint de 60 m se realizó el segundo día. Los cronómetros en el entrenamiento fraccionado se ajustaron para registrar tiempos de 5 m, 10 m, 50 m y 60 m. Las variables que se incluyeron fueron la altura del salto vertical, la fuerza máxima y la salida de fuerza a 120 m en todos los saltos y mediciones del tiempo del sprint. Resultados: Los resultados del análisis de correlación producto-tiempo de Pearson revelaron que el SJ de 120 m estaba correlacionado con 5 m y el USJ de 120 m estaba correlacionado con 10 m. El UDJ de 120 m tuvo una mayor correlación con el DJ de 50 m que con el de 120 m. Aunque se observaron correlaciones significativas con la fuerza y la altura máximas, algunos resultados fueron inconsistentes entre los saltos bilaterales y unilaterales. Conclusiones: Nuestros resultados pusieron de manifiesto que los saltos con una forma similar a determinadas salidas de fuerza en un tiempo específico del evento pueden predecir con mayor precisión el desempeño en el sprint en adolescentes velocistas. El USJ de 120 m y el UDJ de 120 m pueden predecir mejor, respectivamente, la aceleración (10 m) y la fase de alta velocidad (50 m) en el desempeño del sprint. Además, los entrenadores y practicantes deben ser cautelosos a la hora de utilizar únicamente la altura del salto o la fuerza máxima para predecir el desempeño en el sprint, ya que los resultados pueden ser inexactos cuando no se tienen en cuenta con precisión las variables específicas del movimiento. Nivel de evidencia III.

RESUMO Objetivos: Este estudo teve como objetivo examinar a relação entre o salto vertical e a força em tempo específico e o desempenho de sprint em velocistas adolescentes. Métodos: Quinze adolescentes velocistas do sexo masculino (idade: 14 ± 2 anos, estatura: 168 ± 2 cm, peso: 61 ± 1 kg) participaram do estudo. Os indivíduos realizaram os seguintes saltos bilaterais e unilaterais em uma plataforma de força: a) squat jump (SJ), b) SJ unilateral (USJ), c) drop jump (DJ) de 40 cm e d) DJ unilateral (UDJ) de 20cm. O teste de sprint de 60 m foi realizado no segundo dia. Os cronômetros rastreadores para treinos fracionados foram posicionados para registrar os tempos fracionados de 5 m, 10 m, 50 m e 60 m. As variáveis para inclusão foram altura do salto vertical, força máxima e saída de força a 120 m em todos os saltos e medidas de tempo do sprint. Resultados: Os resultados da análise da correlação produto-tempo de Pearson mostraram que o SJ de 120 m foi correlacionado com 5 m e USJ de 120 m foi correlacionado com 10 m. O UDJ de 120 m teve correlação mais forte com DJ de 50 m do que de 120 m. Embora tenham sido observadas correlações significativas com força e altura máximas, alguns resultados foram inconsistentes entre os saltos bilaterais e unilaterais. Conclusões: Nossos resultados destacaram que os saltos com forma semelhante a certas saídas de força no tempo específico do evento podem prever com mais precisão o desempenho no sprint em adolescentes velocistas. O USJ de 120 m e o UDJ de 120 m podem prever melhor, respectivamente, a aceleração (10 m) e a fase de alta velocidade (50 m) no desempenho no sprint. Além disso, treinadores e praticantes devem ser cautelosos ao usar apenas a altura do salto ou a força máxima para prever o desempenho no sprint, uma vez que os resultados podem ser imprecisos quando variáveis específicas do movimento não forem consideradas com precisão. Nível de evidência III.

Logistic Regression Analysis of the Mechanism of Blunt Brain Injury Inference Based on CT Images / 法医学杂志

OBJECTIVES@#To study the correlation between CT imaging features of acceleration and deceleration brain injury and injury degree.@*METHODS@#A total of 299 cases with acceleration and deceleration brain injury were collected and divided into acceleration brain injury group and deceleration brain injury group according to the injury mechanism. Subarachnoid hemorrhage (SAH) and Glasgow coma scale (GCS), combined with skull fracture, epidural hematoma (EDH), subdural hematoma (SDH) and brain contusion on the same and opposite sides of the stress point were selected as the screening indexes. χ2 test was used for primary screening, and binary logistic regression analysis was used for secondary screening. The indexes with the strongest correlation in acceleration and deceleration injury mechanism were selected.@*RESULTS@#χ2 test showed that skull fracture and EDH on the same side of the stress point; EDH, SDH and brain contusion on the opposite of the stress point; SAH, GCS were correlated with acceleration and deceleration injury (P<0.05). According to binary logistic regression analysis, the odds ratio (OR) of EDH on the same side of the stress point was 2.697, the OR of brain contusion on the opposite of the stress point was 0.043 and the OR of GCS was 0.238, suggesting there was statistically significant (P<0.05).@*CONCLUSIONS@#EDH on the same side of the stress point, brain contusion on the opposite of the stress point and GCS can be used as key indicators to distinguish acceleration and deceleration injury mechanism. In addition, skull fracture on the same side of the stress point, EDH and SDH on the opposite of the stress point and SAH were relatively weak indicators in distinguishing acceleration and deceleration injury mechanism.

Automatic Identification of Brain Injury Mechanism Based on Deep Learning / 法医学杂志

OBJECTIVES@#To apply the convolutional neural network (CNN) Inception_v3 model in automatic identification of acceleration and deceleration injury based on CT images of brain, and to explore the application prospect of deep learning technology in forensic brain injury mechanism inference.@*METHODS@#CT images from 190 cases with acceleration and deceleration brain injury were selected as the experimental group, and CT images from 130 normal brain cases were used as the control group. The above-mentioned 320 imaging data were divided into training validation dataset and testing dataset according to random sampling method. The model classification performance was evaluated by the accuracy rate, precision rate, recall rate, F1-value and AUC value.@*RESULTS@#In the training process and validation process, the accuracy rate of the model to classify acceleration injury, deceleration injury and normal brain was 99.00% and 87.21%, which met the requirements. The optimized model was used to test the data of the testing dataset, the result showed that the accuracy rate of the model in the test set was 87.18%, and the precision rate, recall rate, F1-score and AUC of the model to recognize acceleration injury were 84.38%, 90.00%, 87.10% and 0.98, respectively, to recognize deceleration injury were 86.67%, 72.22%, 78.79% and 0.92, respectively, to recognize normal brain were 88.57%, 89.86%, 89.21% and 0.93, respectively.@*CONCLUSIONS@#Inception_v3 model has potential application value in distinguishing acceleration and deceleration injury based on brain CT images, and is expected to become an auxiliary tool to infer the mechanism of head injury.

Reconstruction and Quantitative Evaluation of Blunt Injury Cases by Finite Element Method / 法医学杂志

OBJECTIVES@#To reconstruct the cases of acceleration craniocerebral injury caused by blunt in forensic cases by finite element method (FEM), and to study the biomechanical mechanism and quantitative evaluation method of blunt craniocerebral injury.@*METHODS@#Based on the established and validated finite element head model of Chinese people, the finite element model of common injury tool was established with reference to practical cases in the forensic identification, and the blunt craniocerebral injury cases were reconstructed by simulation software. The cases were evaluated quantitatively by analyzing the biomechanical parameters such as intracranial pressure, von Mises stress and the maximum principal strain of brain tissue.@*RESULTS@#In case 1, when the left temporal parietal was hit with a round wooden stick for the first time, the maximum intracranial pressure was 359 kPa; the maximum von Mises stress of brain tissue was 3.03 kPa at the left temporal parietal; the maximum principal strain of brain tissue was 0.016 at the left temporal parietal. When the right temporal was hit with a square wooden stick for the second time, the maximum intracranial pressure was 890 kPa; the maximum von Mises stress of brain tissue was 14.79 kPa at the bottom of right temporal lobe; the maximum principal strain of brain tissue was 0.103 at the bottom of the right temporal lobe. The linear fractures occurred at the right temporal parietal skull and the right middle cranial fossa. In case 2, when the forehead and left temporal parietal were hit with a round wooden stick, the maximum intracranial pressure was 370 kPa and 1 241 kPa respectively, the maximum von Mises stress of brain tissue was 3.66 kPa and 26.73 kPa respectively at the frontal lobe and left temporal parietal lobe, and the maximum principal strain of brain tissue was 0.021 and 0.116 respectively at the frontal lobe and left temporal parietal lobe. The linear fracture occurred at the left posterior skull of the coronary suture. The damage evaluation indicators of the simulation results of the two cases exceeded their damage threshold, and the predicted craniocerebral injury sites and fractures were basically consistent with the results of the autopsy.@*CONCLUSIONS@#The FEM can quantitatively evaluate the degree of blunt craniocerebral injury. The FEM combined with traditional method will become a powerful tool in forensic craniocerebral injury identification and will also become an effective means to realize the visualization of forensic evidence in court.

Heart rate extraction algorithm based on adaptive heart rate search model / 生物医学工程学杂志

Photoplethysmography (PPG) is a non-invasive technique to measure heart rate at a lower cost, and it has been recently widely used in smart wearable devices. However, as PPG is easily affected by noises under high-intensity movement, the measured heart rate in sports has low precision. To tackle the problem, this paper proposed a heart rate extraction algorithm based on self-adaptive heart rate separation model. The algorithm firstly preprocessed acceleration and PPG signals, from which cadence and heart rate history were extracted respectively. A self-adaptive model was made based on the connection between the extracted information and current heart rate, and to output possible domain of the heart rate accordingly. The algorithm proposed in this article removed the interference from strong noises by narrowing the domain of real heart rate. From experimental results on the PPG dataset used in 2015 IEEE Signal Processing Cup, the average absolute error on 12 training sets was 1.12 beat per minute (bpm) (Pearson correlation coefficient: 0.996; consistency error: -0.184 bpm). The average absolute error on 10 testing sets was 3.19 bpm (Pearson correlation coefficient: 0.990; consistency error: 1.327 bpm). From experimental results, the algorithm proposed in this paper can effectively extract heart rate information under noises and has the potential to be put in usage in smart wearable devices.

Clinical Investigation of Key Parameter Range of AMG Muscle Relaxant Monitor / 中国医疗器械杂志

The accelerometry(AMG) muscle relaxant monitor is the most widely used quantitative muscle relaxant monitor to assess the degree of neuromuscular at present. In this study, the ulnar nerve was stimulated by using train of four stimulation(TOF) mode of the AMG muscle relaxant monitor, and the movement of the adductor pollicis muscle was monitored. In this way, the distribution range of key parameters (acceleration peak value, response time, and TOF ratio) of the adductor pollicis muscle during the use of muscle relaxant in clinical practice is analyzed and will provide a practical basis for the development and improvement of the muscle relaxant monitor.

Characterizing the magnitude of vibration imposed by stochastic whole-body vibration platforms used in rehabilitation and training: a preliminary study / Caracterização da magnitude da vibração imposta por plataformas vibratórias estocásticas de corpo inteiro utilizadas em reabilitação e treinamento: estudo preliminar

Abstract The use of devices that produce stochastic whole-body vibration as a resource for rehabilitation and training programs has been founded on the theory of stochastic resonance. However, the prescription of rehabilitation and training programs must be preceded by the verification of imposed-vibration magnitude and of how it can be affected by the presence of an individual on the devices. The aim of this research was to characterize and analyze the effect of an individual's mass on the vibratory stimulus provided by stochastic whole-body vibration (SWBV) devices. The sample consisted of 30 repetitions for each one of the 6 vibration levels of the SWBV device (level 02, 04, 06, 08, 10 and 12), performed in two experimental situations (Without Load; Load [70Kg]; ≈ 35 kg on the right and left surfaces of the platform). For the antero-posterior, latero-lateral, and vertical directions, all variables showed significant differences between treatments, levels and interaction between experimental factors (p<.05), except for the Disp variable between treatments (p=.075). To measure vibration magnitude, a triaxial accelerometer was attached at the center of the board of one of the platform surfaces. Load interferes with parameters of vibration imposed by SWBV platforms, increasing ARMS and APEAK in the latero-lateral and antero-posterior directions, reducing these same parameters in the vertical direction.

Resumo O uso de dispositivos que produzem vibração estocástica de corpo inteiro como recurso para programas de reabilitação e treinamento foi fundamentado na teoria da ressonância estocástica. Entretanto, a prescrição de programas de reabilitação e treinamento deve ser precedida da verificação da magnitude da vibração imposta e de como ela pode ser afetada pela presença de um indivíduo nos dispositivos. O objetivo deste estudo foi caracterizar e analisar o efeito da massa do indivíduo sobre o estímulo vibratório proporcionado por dispositivos de vibração estocástica de corpo inteiro. A amostra consistiu em 30 repetições para cada um dos 6 níveis de vibração de um dispositivo de vibração estocástica de corpo inteiro (nível 02, 04, 06, 08, 10 e 12), realizados em duas situações experimentais (Sem carga e Carga [70Kg], 35 kg nas superfícies direita e esquerda da plataforma). Para medir a magnitude da vibração, um acelerômetro triaxial foi fixado ao centro do assoalho de uma das superfícies da plataforma. Para os eixos ântero-posterior, látero-lateral e vertical, todas as variáveis mostraram diferenças entre tratamentos, níveis e interação entre fatores experimentais (p<.05), exceto para a variável de deslocamento pico - a - pico (Disp) entre tratamentos (p=.075). A carga interfere com parâmetros de vibração impostos sobre as plataformas de vibração estocástica de corpo inteiro, aumentando a aceleração média (ARMS) e de pico (APEAK) nas direções látero-lateral e ântero-posterior, reduzindo estes mesmos parâmetros na direção vertical.

Does the change of direction deficit measure the time of change of direction?

Abstract Aim: To determine whether the change of direction (COD) deficit can represent the time of the change of direction in professional under 17 years old (U-17) soccer players. Methods: Sixteen young soccer athletes performed the adapted 505 agility test with the stationary stance (2 straight lines of 5 m) and the 10 m linear running test (LR). In both tests, the partial and total times were recorded every 2.5 m by time gates (0-2.5 m; 2.5-7.5 m; 7.5-10 m). The best performances were recorded and used to determine the COD deficit (difference between the time for the LR and 505 tests). The paired t-test compared the initial acceleration (0-2.5 m) time, the COD time (2.5-7.5 m), and the COD deficit among the tests. Results: Times in the LR test were significantly shorter in the initial acceleration phase (0-2.5 m), and the change of direction deficit was also lower than the change of direction time (2.5-7.5 m) for both sides (p = 0.005). Conclusion: When an athlete is aware of an upcoming change of direction, a lower initial acceleration results in biases for determining the change of direction deficit. Therefore, acceleration capacity might not be suitable to assess using the 505 agility test.

COVID-19 epidemic curve in Brazil: a sum of multiple epidemics, whose inequality and population density in the states are correlated with growth rate and daily acceleration. An ecological study

ABSTRACT Background: The epidemic curve has been obtained based on the 7-day moving average of the events. Although it facilitates the visualization of discrete variables, it does not allow the calculation of the absolute variation rate. Recently, we demonstrated that the polynomial interpolation method can be used to accurately calculate the daily acceleration of cases and deaths due to COVID-19. This study aimed to measure the diversity of epidemic curves and understand the importance of socioeconomic variables in the acceleration, peak cases, and deaths due to COVID-19 in Brazilian states. Methods: Epidemiological data for COVID-19 from federative units in Brazil were obtained from the Ministry of Health's website from February 25 to July 11, 2020. Socioeconomic data were obtained from the Instituto Brasileiro de Geografia e Estatística (https://www.ibge.gov.br/). Using the polynomial interpolation methods, daily cases, deaths and acceleration were calculated. Moreover, the correlation coefficient between the epidemic curve data and socioeconomic data was determined. Results: The combination of daily data and case acceleration determined that Brazilian states were in different stages of the epidemic. Maximum case acceleration, peak of cases, maximum death acceleration, and peak of deaths were associated with the Gini index of the gross domestic product of Brazilian states and population density but did not correlate with the per capita gross domestic product of Brazilian states. Conclusions: Brazilian states showed heterogeneous data curves. Population density and socioeconomic inequality were correlated with a more rapid exponential growth in new cases and deaths.

Viés da Escalada, Daemons de Otimização, e a Influência da Narrativa Social Aceleracionista / Hill-Climbing Bias, Optimization Daemons, and the Influence of Accelerated Social Narratives

O fenômeno de aceleração social, intimamente ligado a nossa modernização tecnológica e os sistemas políticos e sociais que adotamos, vem sendo alvo de questionamentos por parte da teoria crítica por diversos filósofos e sociólogos, principalmente em relação a se tal "aceleração" seja algo que, possa ser justificável pelo bem comum da sociedade. De fato, as rápidas mudanças que ocorreram no último século causaram uma tremenda mudança em nossos estilos-de-vida, e na maneira como experienciamos o mundo. Que a nossa sociedade mudou e continua a mudar é um fato evidente quando olhamos criticamente para o passado e presente, e comparamos diferentes épocas da história humana. Neste ensaio tentaremos explorar algumas possíveis hipóteses que fundamentem o comportamento aceleracionista em certos fatores e mecanismo biológicos que caracterizam os sistemas de motivação e saciação humanos. Também tentaremos mostrar como certos fenômenos sociais podem auxiliar em fortalecer este tipo de comportamento, e suas possíveis origens evolutivas. Este estudo tem como objetivo principal fundamentar a Tese Aceleracionista em evidências neurofisiológicas, cognitivo-comportamentais, evolutivas e sociais.

The phenomenon of social acceleration is closely linked to our technological modernization and the political and social systems we have adopted, and it has been questioned by several philosophers and sociologists, especially in relation to whether such acceleration is something that can be justified for the common good of society. In fact, the rapid changes that have occurred in the last century have caused a tremendous change in our lifestyles, and in the way we experience the world. That society have changed and continues to change is an evident fact when we look critically to the past and our present and compare different times in human history. In this essay we will try to explore some possible hypotheses that underpin accelerated behavior, in certain biological factors and mechanisms that characterize human motivation and satiation systems. We will also try to show how certain social phenomena can help to strengthen this type of behavior, and its possible evolutionary origins. The main objective of this study is to base the Accelerationist Thesis on neurophysiological, cognitive-behavioral, evolutionary and also social evidence.

Effects of gantry acceleration limitations on VMAT plans / 中华放射医学与防护杂志

Objective:To study the effects of gantry acceleration limitations of a linear accelerator (linac) on the dosimetry of volumetric modulated arc therapy (VMAT) plans, machine efficiency, and dose verification result of VMAT plans and to explore the optimal selection of gantry motion models in the Pinnacle treatment planning system.Methods:Ten cases of nasopharyngeal carcinoma, non-small cell lung cancer, sigmoid adenocarcinoma with retroperitoneal lymph node metastasis, and invasive ductal carcinoma of the breast were each selected for this study. Then two models were set up in the Pinnacle v9.10 treatment planning system, namely the one allowing gantry acceleration and the one limiting gantry acceleration. The same field arrangement, optimized target parameters, and optimized weights of VMAT plans were adopted in the two models, in order to analyze the dosimetric variations in targets and organs at risk (OARs) and compare the differences in treatment time and gamma passing rates.Results:The treatment time of the enrolled patients under the model allowing gantry acceleration was significantly lower than that of the patients under the model limiting gantry acceleration was adopted ( t=-6.751, -0.209, -19.523, -28.999; P< 0.05) and decreased by 15.27%, 18.07%, 19.71%, and 28.75%, respectively. Meanwhile, the conformity and uniformity of target areas were affected, while there was no statistical significance in the gamma passing rates in the validation of VMAT plans ( P>0.05). For the cases of nasopharyngeal carcinoma (NPC), the maximum dose to brainstem PRV increased by 1.25%. For the cases of lung cancer, the maximum dose to the spinal cord and lung V20 increased by 1.19% and 1.21%, respectively, while lung V5 decreased by 1.21%. For the cases of sigmoid adenocarcinoma with retroperitoneal lymph node metastasis, the mean doses to bilateral kidneys, livers, small intestine, and colon all increased. For the cases of breast cancer, lung V10 on the opposite side of cancer increased by 1.66% and the mean dose to the lungs on the same side of cancer decreased by 7.45%. Conclusions:The model allowing gantry acceleration allows the treatment time to be significantly shortened and the treatment efficiency improved. Although this model had the shortcomings such as affecting the conformity and uniformity of target areas to a certain extent and increasing the doses to some OARs, clinical requirements for dosimetry were still met. Therefore, it is recommended to use the model allowing gantry acceleration in the Pinnacle planning system.

Optimization of Key Techniques for Maintaining Bus Voltage Stability in Variable Speed Turbine of Ventilator / 中国医疗器械杂志

OBJECTIVE@#To explore the optimization scheme of maintaining bus voltage stability during turbo-turbine acceleration and deceleration of ventilator.@*METHODS@#The ideal diode is used to replace the diode in the busbar power supply circuit, and a comparative discharge circuit is added to the busbar. When the busbar voltage is higher than the preset threshold, the comparator can be opened and the energy could be discharged through the power resistor.@*RESULTS@#When the turbine starts and stops rapidly, the optimized scheme can effectively reduce the bus impedance, and the discharge circuit can maintain the bus voltage fluctuation less than 2 V.@*CONCLUSIONS@#The optimization scheme proposed in this study can effectively improve the efficiency and stability of the turbine in the process of acceleration and braking, and provide reference for the design of the stability maintenance circuit of the ventilator turbine bus.

Research on Reliability Index and Realization of Magnetic Resonance (MR) Based on Clinical Use Condition / 中国医疗器械杂志

Combined with the clinical use condition of MR in use in Shanghai Sixth People's Hospital, MR components are divided into scanning type I and scanning type II. At the same time, combined with the main loss force of MR components, the research divides MR components into dynamic components and electric thermal components. In this study, a complete set of MR system reliability indexes and implementation methods are given, including system reliability index determination, system reliability allocation, component reliability index realization, system reliability prediction and system reliability verification. At the same time, this study also gives the methods of reliability prediction and reliability verification, and gives the MTBF calculation method of MR system based on clinical use data statistics.