Effect of Mouthguards on Head Responses and Mandible Forces in Football Helmet Impacts

The potential for mouthguards to change the risk of concussion was studied in football helmet impacts. The Hybrid III head was modified with an articulating mandible, dentition, and compliant temporomandibular joints (TMJ). It was instrumented for triaxial head acceleration and triaxial force at the TMJs and upper dentition. Mandible force and displacement were validated against cadaver impacts to the chin. In phase 1, one of five mouthguards significantly lowered HIC in 6.7 m/s impacts (p = 0.025) from the no mouthguard condition but not in 9.5 m/s tests. In phase 2, eight mouthguards increased HIC from +1 to +17% in facemask impacts that loaded the chinstraps and mandible; one was statistically higher (p = 0.018). Peak head acceleration was +1 to +15% higher with six mouthguards and 2–3% lower with two others. The differences were not statistically significant. Five of eight mouthguards significantly reduced forces on the upper dentition by 40.8–63.9%. Mouthguards tested in this study with the Hybrid III articulating mandible lowered forces on the dentition and TMJ, but generally did not influence HIC or concussion risks.     

Measuring Head Kinematics in Football: Correlation Between the Head Impact Telemetry System and Hybrid III Headform

Over the last decade, advances in technology have enabled researchers to evaluate concussion biomechanics through measurement of head impacts sustained during play using two primary methods: (1) laboratory reconstruction of open-field head contact, and (2) instrumented helmets. The purpose of this study was to correlate measures of head kinematics recorded by the Head Impact Telemetry (HIT) System (Simbex, NH) with those obtained from a Hybrid III (HIII) anthropometric headform under conditions that mimicked impacts occurring in the NFL. Linear regression analysis was performed to correlate peak linear acceleration, peak rotational acceleration, Gadd Severity Index (GSI), and Head Injury Criterion (HIC₁₅) obtained from the instrumented helmet and HIII. The average absolute location error between instrumented helmet impact location and the direction of HIII head linear acceleration were also calculated. The HIT System overestimated Hybrid III peak linear acceleration by 0.9% and underestimated peak rotational acceleration by 6.1% for impact sites and velocities previously identified by the NFL as occurring during play. Acceleration measures for all impacts were correlated; however, linear was higher (r ² = 0.903) than rotational (r ² = 0.528) primarily due to lower HIT System rotational acceleration estimates at the frontal facemask test site. Severity measures GSI and HIC were also found to be correlated, albeit less than peak linear acceleration, with the overall difference between the two systems being less than 6.1% for either measure. Mean absolute impact location difference between systems was 31.2 ± 46.3° (approximately 0.038 ± 0.050 m), which was less than the diameter of the impactor surface in the test. In instances of severe helmet deflection (2.54–7.62 cm off the head), the instrumented helmet accurately measured impact location but overpredicted all severity metrics recorded by the HIII. Results from this study indicate that measurements from the two methods of study are correlated and provide a link that can be used to better interpret findings from future study using either technology.     

An Instrumented Mouthguard for Measuring Linear and Angular Head Impact Kinematics in American Football

The purpose of this study was to evaluate a novel instrumented mouthguard as a research device for measuring head impact kinematics. To evaluate kinematic accuracy, laboratory impact testing was performed at sites on the helmet and facemask for determining how closely instrumented mouthguard data matched data from an anthropomorphic test device. Laboratory testing results showed that peak linear acceleration (r ² = 0.96), peak angular acceleration (r ² = 0.89), and peak angular velocity (r ² = 0.98) measurements were highly correlated between the instrumented mouthguard and anthropomorphic test device. Normalized root-mean-square errors for impact time traces were 9.9 ± 4.4% for linear acceleration, 9.7 ± 7.0% for angular acceleration, and 10.4 ± 9.9% for angular velocity. This study demonstrates the potential of an instrumented mouthguard as a research tool for measuring in vivo impacts, which could help uncover the link between head impact kinematics and brain injury in American football.     

A Headform for Testing Helmet and Mouthguard Sensors that Measure Head Impact Severity in Football Players

A headform is needed to validate and compare helmet- and mouthguard-based sensors that measure the severity and direction of football head impacts. Our goal was to quantify the dynamic response of a mandibular load-sensing headform (MLSH) and to compare its performance and repeatability to an unmodified Hybrid III headform. Linear impactors in two independent laboratories were used to strike each headform at six locations at 5.5 m/s and at two locations at 3.6 and 7.4 m/s. Impact severity was quantified using peak linear acceleration (PLA) and peak angular acceleration (PAA), and direction was quantified using the azimuth and elevation of the PLA. Repeatability was quantified using coefficients of variation (COV) and standard deviations (SD). Across all impacts, PLA was 1.6 ± 1.8 g higher in the MLSH than in the Hybrid III (p = 0.002), but there were no differences in PAA (p = 0.25), azimuth (p = 0.43) and elevation (p = 0.11). Both headforms exhibited excellent or acceptable repeatability for PLA (HIII:COV = 2.1 ± 0.8%, MLSH:COV = 2.0 ± 1.2%, p = 0.98), but site-specific repeatability ranging from excellent to poor for PAA (HIII:COV = 7.2 ± 4.0%, MLSH:COV = 8.3 ± 5.8%, p = 0.58). Direction SD were generally <1° and did not vary between headforms. Overall, both headforms are similarly suitable for validating PLA in sensors that measure head impact severity in football players, however their utility for validating sensor PAA values varies with impact location.     

A Method to Determine the Presence of Averaged Event-Related Fields Using Randomization Tests

We present a simple and effective method to test whether an event consistently activates a set of brain electric sources across repeated measurements of event-related scalp field data. These repeated measurements can be single trials, single subject ERPs, or ERPs from different studies. The method considers all sensors simultaneously, but can be applied separately to each time frame or frequency band of the data. This allows limiting the analysis to time periods and frequency bands where there is positive evidence of a consistent relation between the event and some brain electric sources. The test may therefore avoid false conclusions about the data resulting from an inadequate selection of the analysis window and bandpass filter, and permit the exploration of alternate hypotheses when group/condition differences are observed in evoked field data. The test will be called topographic consistency test (TCT). The statistical inference is based on simple randomization techniques. Apart form the methodological introduction, the paper contains a series of simulations testing the statistical power of the method as function of number of sensors and observations, a sample analysis of EEG potentials related to self-initiated finger movements, and Matlab source code to facilitate the implementation. Furthermore a series of measures to control for multiple testing are introduced and applied to the sample data.     

Family-Based Association Tests for Different Family Structures Using Pooled DNA

DNA pooling is a cost‐effective strategy for genomewise association studies to identify disease genes. In the context of family‐based association studies, Risch & Teng (1998) mainly considered families of identical structures to detect associations between genetic markers and disease, and suggested possible approaches to incorporating different family types without a thorough study of their properties. However, families collected in real genetic studies often have different structures and, more importantly, the informativeness of each family structure depends on the disease model which is generally unknown. So there is a need to develop and investigate statistical methods to combine information from diverse family types. In this article, we propose a general strategy to incorporate different family types by assigning each family an “optimal” weight in association tests. In addition, we consider measurement errors in our analysis. When we evaluate our approach under different disease models and measurement errors, we find that our weighting scheme may lead to a substantial reduction in sample size required over the approach suggested by Risch & Teng (1998) , and measurement errors may have significant impact on the required sample size when the error rates are not negligible.     

Assessment of Ankle-Subtalar-Joint-Complex Laxity Using an Instrumented Ankle Arthrometer: An Experimental Cadaveric Investigation

OBJECTIVE: To show the relationship between direct measurements of tibial-calcaneal bone motion and instrumented measurements of ankle-subtalar-joint-complex laxity using a portable ankle arthrometer; to assess within and between-tester measurement reliability; and to determine if the ankle arthrometer can detect increased mechanical laxity of the ankle-subtalar-joint-complex after simulated injury of the lateral ankle ligaments. DESIGN AND SETTING: We used linear regression analysis to examine the relationship between direct measurements of tibial-calcaneal bone motion and instrumented measurements of ankle-subtalar-joint-complex laxity. An intraclass correlation coefficient (2,1) was calculated to determine intratester and intertester reliability for instrumented measurements of ankle-subtalar-joint-complex laxity. In addition, 2 separate, one-way, repeated-measures analyses of variance were used to compare instrumented measures of anteroposterior displacement and inversion-eversion rotation among the intact ankles after sectioning the anterior talofibular ligament and both the anterior talofibular and calcaneofibular ligaments. Data were collected in a biomechanics laboratory setting. SUBJECTS: Six fresh-frozen human-cadaver ankle specimens were studied. MEASUREMENTS: Testing involved the concurrent measurement of tibial-calcaneal bone motion and ankle-subtalar-joint-complex motion during the application of external loads. An instrumented ankle arthrometer was used to load the ankle in a controlled manner. Two spatial kinematic linkages measured the 3-dimensional motion of the calcaneus relative to the tibia and the motion of the arthrometer's footplate relative to the tibia. RESULTS: The correlation between tibial-calcaneal bone motion and instrumented measurement for anterior-posterior displacement was.878 (P =.0001). Its linear relationship with bone motion accounted for approximately 77% of the variance of the instrumented measurement. The correlation between tibial-calcaneal bone motion and instrumented measurement for inversion-eversion rotation was.858 (P =.0001), with approximately 74% of the variance of the instrumented measurement accounted for by its linear relationship with bone motion. High intratester and intertester reliability coefficients (ICC [2,1] =.80 to.97) were observed for instrumented measurements of ankle-subtalar-joint-complex laxity. In addition, ligamentous sectioning resulted in significantly increased ankle-subtalar-joint-complex laxity. When compared with the intact condition, sectioning both the anterior talofibular and calcaneofibular ligaments produced significant increases in anterior-posterior displacement (P =.0001) and inversion-eversion rotation (P =.002). CONCLUSIONS: We found a strong relationship between tibial-calcaneal bone motion and arthrometric measurements of ankle-subtalar-joint-complex laxity. The instrumented ankle arthrometer may be suitable as a diagnostic tool for the evaluation of lateral ankle-ligament laxity.     

经颅磁刺激中大鼠真实头模型感应电场分布的研究

经颅磁刺激是一种利用时变磁场产生的感应电流刺激大脑的技术,现在已经广泛地应用于精神疾病的治疗及脑功能的研究.本文建立了经颅磁刺激中大鼠真实头模型,并利用有限元方法计算了模型中感应电场的空间分布情况.该模型可用于动物实验方案的设计和实验结果的解释.     

Diagnosis of Human Immunodeficiency Virus Type 1 Infection with Different Subtypes Using Rapid Tests

We evaluated six rapid tests for their sensitivity and specificity in diagnosing human immunodeficiency virus type 1 (HIV-1) infection using 241 specimens (172 HIV-1 positive, 69 HIV-1 negative) representing different HIV-1 subtypes (A [n = 40], B [n = 47], C [n = 28], E [n = 42], and F [n = 7]). HIVCHEK, Multispot, RTD and SeroStrip were 100% sensitive and specific. Capillus failed to identify two of eight subtype C specimens (overall sensitivity of 98.85%), while the SUDS test (the only test approved by the Food and Drug Administration) gave false-positive results for 5 of 69 seronegative specimens (specificity of 93.24%). Our results suggest that although rapid tests perform well in general, it may be prudent to evaluate a rapid test for sensitivity and specificity in a local population prior to its widespread use.     

The Effect of Visual and Sensory Performance on Head Impact Biomechanics in College Football Players

The development of prevention strategies is critical to address the rising prevalence of sport-related concussions. Visual and sensory performance may influence an individual’s ability to interpret environmental cues, anticipate opponents’ actions, and create appropriate motor responses limiting the severity of an impending head impact. The purpose of this study was to determine the relationship between traditional and visual sensory reaction time measures, and the association between visual and sensory performance and head impact severity in college football players. Thirty-eight collegiate football players participated in the study. We used real-time data collection instrumentation to record head impact biomechanics during games and practices. Our findings reveal no significant correlations between reaction time on traditional and visual sensory measures. We found a significant association between head impact severity and level of visual and sensory performance for multiple assessments, with low visual and sensory performers sustaining a higher number of severe head impacts. Our findings reveal a link between level of visual and sensory performance and head impact biomechanics. Future research will allow clinicians to have the most appropriate testing batteries to identify at-risk athletes and create interventions to decrease their risk of injurious head impacts.     

Modeling Pressure Drop Using Generalized Scaffold Characteristics in an Axial-Flow Bioreactor for Soft Tissue Regeneration

The goal of this study was to better understand how analytical permeability models based on scaffold architecture can facilitate a non-invasive technique to real time monitoring of pressure drop in bioreactors. In particular, we evaluated the permeability equations for electrospun and freeze dried scaffolds via pressure drop comparison in an axial-flow bioreactor using computational fluid dynamic (CFD) and experimentation. The polycaprolactone–cellulose acetate fibers obtained by co-axial electrospinning technique and Chitosan–Gelatin scaffolds prepared using freeze-drying techniques were utilized. Initially, the structural properties (fiber size, pore size and porosity) and mechanical properties (elastic modulus and Poisson’s ratio) of scaffolds in phosphate buffered saline at 37 °C were evaluated. The CFD simulations were performed by coupling fluid flow, described by Brinkman equation, with structural mechanics using a moving mesh. The experimentally obtained pressure drop values for both 1 mm thick and 2 mm thick scaffolds agreed with simulation results. To evaluate the effect of permeability and elastic modulus on pressure drop, CFD predictions were extended to a broad range of permeabilities spanning synthetic scaffolds and tissues, elastic moduli, and Poisson’s ratio. Results indicated an increase in pressure drop with increase in permeability. Scaffolds with higher elastic modulus performed better and the effect of Poisson’s ratio was insignificant. Flow induced deformation was negligible in axial-flow bioreactor. In summary, scaffold permeabilities can be calculated using scaffold microarchitecture and can be used in non-invasive monitoring of tissue regeneration.     

中医色诊图像采集系统的设计与实现及实验研究

研制中医色诊图像采集系统.整体制作为箱体式上下结构,系统选择色温5500K的氙灯模拟日光光源,反射率大于96％的聚四氟乙烯悬浮树脂涂层积分球漫射照明,分辨率为4 752像素×3 168像素的调谐数码相机采集图像.长时间光源稳定性和光线均匀性实验表明:图像采集系统光源稳定性大于99.1％、显色性大于95％,光线均匀性大于98.6％;不同照度下,图像色度偏差小于1.24％;40例中青年和60例老年人面部图像采集实验证明:面部图像采集系统可以用RGB和Lab颜色空间的数据准确定量人脸面部的特征色诊信息,采集的数据可为中医色诊信息的客观化研究提供参考.     

一种基于两种不同范式的混合型脑-机接口系统

混合模式脑机接口是脑-机接口研究的一个新方向,它为进一步提高脑-机接口系统性能提供了可能。现有的混合模式脑-机接口所采用的范式通常需要借助较强的视觉刺激,容易引起受试者疲劳等问题。本研究提出将运动想象和运动起始时刻视觉诱发电位两种无需强烈视觉刺激的范式以串行的方式相结合,通过运动起始时刻视觉诱发电位控制字符的输入,通过运动想象控制界面的开关和允许输入下一字符,实现了一种可用于字符输入的混合模式脑-机接口系统。为了验证系统的可行性,共完成了5例实验。实验中受试者首先进行两种范式的训练,然后进行开关系统界面和输入字符的测试。实验结果显示,经过一定训练的受试可以较好地完成系统的操作,运动想象单步操作平均时间最短为3.9 s,字符输入的正确率最高可达93.3%。除了不容易令受试者产生疲劳外,本系统相比单一感觉模式的脑-机接口也具有可完成任务种类多、控制方式灵活等优势。     

基于计算机的尿滴自动计数检测与分析系统设计

采用计算机和电子技术,自动检测和分析生理实验中动物的尿液变化。设计光电受滴器检测尿滴,信号放大后送计算机进行自动的检测处理。采用Visual Basic及Borland C 语言编程,设计软件界面和输入输出控制程序,根据实验要求提供参数设置、采样、保存和回放数据等多种功能。实验表明该系统能准确采集和记录数据。该系统操作简便、自动化程度高,能很好地满足生理实验的需要。     

不同程度溶血标本对临床化学检测结果的影响

目的 分析不同程度溶血标本对临床化学检测结果的影响.方法 收集血液标本65例,分别对溶血前及溶血后的标本进行临床化学项目的检测,并根据溶血后血红蛋白的含量进行分组,比较不同程度溶血对临床化学项目检测的影响.结果 总体来说,钾(K)、丙氨酸氨基转移酶(ALT)、天门冬氨酸氨基转移酶(AST)、乳酸脱氢酶(LDH)、α-羟丁酸脱氢酶(HBDH)、肌酸激酶(CK)、肌酸激酶同工酶(CK-MB)、无机磷(PHOS)、胆固醇(CHOL)、甘油三脂(TrG)、铁(Fe)、总蛋白(TP)、前白蛋白(PALB)、超氧化物歧化酶(SOD)、同型半胱氨酸(HCY)溶血后的检测结果明显高于未溶血对照组(P＜0.05);二氧化碳(CO2)、γ-谷氨酰转肽酶(GGT)、碱性磷酸酶(ALP)、直接胆红素(DBIL)溶血后的检测结果明显低于未溶血对照组(P＜0.05);其余项目两组间比较无明显差异.根据溶血程度分组比较发现,溶血越严重,在临床化学检测项目中受影响的项目数越多.结论 标本溶血会对部分临床化学检测结果产生影响,如果进行这些项目的检测应避免使用溶血标本.     

不同占空比低强度脉冲电磁场对大鼠成骨细胞的影响

目的：研究磁感应强度为1mT、频率为15Hz不同占空比的脉冲电磁场（pulsedelectromagneticfields,PEMFs）对体外培养大鼠成骨细胞增殖与细胞分化的影响。方法：取新生SD大鼠仔鼠头盖骨,用骨组织块培养法分离成骨细胞,培养至第3代后,分另q对其进行场强1mT、频率15Hz,占空比10％、20％、40％、60％的脉冲电磁场作用,8h／d,持续作用3d．应用MTT法、碱性磷酸酶测定检测成骨细胞增殖、分化情况。结果：不同占空比PEMFs对大鼠成骨细胞增殖与分化影响程度不同,20％、40％和60％占空比组显著提高成骨细胞增殖水平（P〈0．05）,其中40％和60％占空比组作用效果最显著（P〈0．01）。10％、20％、40％和60％占空比组均能促进成骨细胞分化（P〈0．05）,其中以60％占空比组的效果最为明显fP〈O．01）。结论：本研究进一步证实了低强度PEMFs能够促进成骨细胞的增殖与分化,并且PEMFs对成骨细胞的影响依赖于占空比参数的选择．而且有可能存在“占空比”窗口。