Cranial Ontogeny of the Early Triassic Basal Cynodont Galesaurus planiceps

Ontogenetic changes in the skull and mandible of thirty‐one specimens of Galesaurus planiceps, a basal non‐mammaliaform cynodont from the Early Triassic of South Africa, are documented. The qualitative survey indicated eight changes in the craniomandibular apparatus occurred during growth, dividing the sample into three ontogenetic stages: juvenile, subadult, and adult. Changes in the temporal region, zygomatic arch, occiput, and mandible occurred during the transition from the subadult to adult stage at a basal skull length of 90 mm. At least four morphological and allometric differences divided the adult specimens into two morphs, indicating the presence of sexual dimorphism in Galesaurus. Differences include extensive lateral flaring of the zygomatic arches in the “male” morph resulting in a more anterior orientation of the orbits, and a narrower snout in the “female”. This is the first record of sexual dimorphism in a basal cynodont, and the first time it is quantitatively documented in a non‐mammaliaform cynodont. An ontogenetic comparison between Galesaurus and the more derived basal cynodont Thrinaxodon revealed differences in the timing and extent of sagittal crest development. In Galesaurus, the posterior sagittal crest, located behind the parietal foramen, developed relatively later in ontogeny, and the anterior sagittal crest rarely formed suggesting the anterior fibres of the temporalis were less developed than in Thrinaxodon. In contrast, craniomandibular features related to the masseters became more developed during the ontogeny of Galesaurus. The development of the adductor musculature appears to be one of the main factors influencing skull growth in these basal non‐mammaliaform cynodonts. Anat Rec, 300:353–381, 2017. © 2016 Wiley Periodicals, Inc.     

大学生就业压力、人格特质与择业取向的关系

目的:探讨本科毕业生人格特质在就业压力与择业取向间的中介作用。方法:采用大学生择业取向量表,大学生就业压力量表和大五人格量表对314名本科毕业生进行集体施测。结果:男生在择业目的、职业定位和薪酬期望上得分高于女生,而在择业标准上低于女生(P0.05);在择业标准、职业定位和薪酬期望得分上理文艺术,而在地域选择上,理科生得分要低于文科生和艺术生(P0.05)。就业压力与择业目的呈显著正相关(r=0.248,P0.01),与择业标准和薪酬期望呈显著负相关(r=-0.175,-0.143;P0.01)。中介效应分析表明,外向性在就业压力与薪酬期望之间起部分中介作用,中介效应占总效应的16.5%;情绪稳定性和尽责性在就业压力与择业目的之间起部分中介作用,中介效应分别占总效应的26.9%和15.8%。结论:大学生的就业压力直接或间接地通过人格特质影响其择业取向。     

珠三角地区青少年未来取向与学习倦怠的关系:应对方式的中介作用

目的:探讨应对方式在中职生未来取向与学习倦怠之间的关系中是否存在中介作用,为减少中职生学习倦怠感提供实证依据和支持。方法:采用青少年未来取向问卷、简易应对方式问卷和青少年学习倦怠量表对700名广东省珠三角地区中职生进行调查。结果:学习倦怠与未来取向的3个因子未来认知、未来情感和未来意志行为均呈负相关(r=-0.10,-0.08,-0.43;P0.05),与积极应对呈显著负相关(r=-0.21,P0.01),与消极应对呈显著正相关(r=0.17,P0.01);消极应对与未来认知、未来情感和未来意志行为呈显著负相关(r=-0.28,-0.25,-0.12;P0.05),积极应对与未来认知、未来情感和未来意志行为呈显著正相关(r=0.40,0.28,0.48;P0.01),积极应对在未来认知与学习倦怠的关系之间起着完全中介作用(Z=-2.75,P0.01)。结论:中职生的未来认知通过积极应对方式从而降低其学习倦怠水平。     

基于局部Radon变换和卡尔曼滤波的超声图像肌束方向自动跟踪方法

超声成像是一种无创、实时和便捷的成像方法,已被广泛用于人体肌肉运动分析。临床上目前主要采用手工处理的方法来提取超声图像中的形态结构, 不仅依赖于操作者的主观经验,且耗时严重、重复性低。提出一种自动计算与跟踪超声图像序列中肌束方向的新方法,利用基于约束互信息的自由变换算法自动提取感兴趣区域,然后基于局部Radon变换对超声图像进行投影,并利用相邻帧间肌束的连贯性,采用卡尔曼滤波的图像处理方法。对6名试验对象进行步行实验,共采集小腿内侧腓肠肌的动态超声影像1 080帧,并用所提出的方法计算肌束方向。实验结果表明,所提出的自动检测方法有较好的鲁棒性。与人工检测结果相比,两者的平均相关系数为0.92±0.02,平均误差为0.30°±0.62°。该方法可以一定程度地替代人工测量,在处理大量超声数据时具有较大的优势。     

Simultaneous estimation of muscle fibre conduction velocity and muscle fibre orientation using 2D multichannel surface electromyogram

The paper presents a new approach for simultaneous estimation of muscle fibre conduction velocity (MFCV) and muscle fibre orientation (MFO) for motor units (MUs) in two-dimensional (2D) multichannel surface electromyography recordings. This is an important tool for detecting changes and abnormalities in muscle function and structure. In addition, simultaneous estimation of MFO and MFCV avoids the necessity of manual electrode alignment. The proposed method detected propagating MU action potentials (MUAPs) in a running time window as moving components in amplitude maps. Thereafter, estimations were obtained by fitting a three-dimensional function to these maps. The performance was evaluated using synthetic MU signals at 10 dB SNR and authentic biceps brachii measurements. Results demonstrated MFCV and MFO estimates with standard deviations of less than 0.05 m s⁻¹ and 1° for simulated signals, and less than 0.2 m s⁻¹ and 4° for experimental data. However, standard deviations as low as 0.12 m s⁻¹ and 1.6° from real signals were demonstrated. It was concluded that the method performs as well as, or better than, linear array multichannel methods when individual propagating MUAPs can be identified, even if electrodes are not aligned with fibre direction.     

Vestibular–Podokinetic interaction without vestibular perception

After prolonged stepping in place relative to space over the center of a rotating turntable, blindfolded subjects cannot step on the stationary platform without unknowingly turning themselves relative to space, a phenomenon termed podokinetic after rotation (PKAR). We asked what role the resulting vestibular stimulation might play in the expression of this form of PKAR. A method of servo-stabilizing the body relative to space during PKAR was devised to compare PKAR expression with and without significant vestibular stimulation. Simulated estimates of average central vestibular response profiles were obtained by passing the averaged unidirectional body angular velocity profiles relative to space through a first-order model of the canal system (τ=15 s). Such simulation results suggested that during normal PKAR performed on a stationary platform, the average central vestibular response would likely rise to peak levels equivalent to that induced by about 9°/s within the frequency range of natural head movement. In the servo-stabilized condition, the simulated response was reduced to insignificant levels. Experimental results demonstrated that in the unstabilized condition the rate of rise of PKAR angular velocity was roughly four times slower than in the stabilized condition. We conclude that the normal expression of PKAR conducted on a stationary platform tends to be substantially slowed by interaction with an unperceived vestibular response.     

Additive Effects of Older Brothers and Homosexual Brothers in the Prediction of Marriage and Cohabitation

Research has shown that male homosexuality tends to cluster in families and that homosexual males have, on average, a greater number of older brothers than do heterosexual males. This study investigated whether the former, between-families effect and the latter, within-families effect are additive. The subjects were 717 full siblings over age 40 reported by 343 heterosexual and homosexual male probands examined in Southern Ontario in 1994–1995. The sibling's history of legal marriage or cohabitation in a heterosexual relationship was taken as a proxy variable for sexual orientation. There were no significant findings for the female siblings. As expected, the never-married male siblings were more likely to come from the sibships of the homosexual probands, and they had a greater average number of older brothers. A bootstrapped logistic regression analysis showed that an additive model best explained the male siblings' data. The results suggest that the familial aggregation of male homosexuality cannot be explained by the birth order effect and that older brothers and family membership reflect separate influences on sexual orientation or sexual orientation-correlated behavior.     

A longitudinal birth cohort study of early life conditions,psychosocial factors,and emerging adolescent sexual orientation

This study tested whether previously reported associations between early life factors and later adolescent sexual orientation could be replicated in another prospective birth cohort, the UK Millennium Cohort Study (MCS). We used data on 9,795 youth from the MCS. Emerging sexual orientation was assessed using measures of sexual attraction to males and females in separate items at 14 years. Factors including birthweight, breastfeeding, sibling composition, parental ages, maternal psychopathology, parent-child relationship, and contextual risks were separated into three developmental periods: prenatal (n = 5 factors), before 7 years (n = 6 factors), and after 7 years (n = 5 factors). We controlled for handedness as a putative marker of prenatal androgen exposure and the possibility of mischievous responding statistically. Girls with greater maternal psychological distress since age 7 and greater pubertal body mass index were more likely to be nonheterosexual but the effect sizes were very small. Among boys there were no significant associations between any early life conditions and later sexual orientation. However, focusing on effect sizes rather than significance levels, there were small associations between preterm birth and nonheterosexuality. The results offer further evidence that psychosocial influences in the development of adolescent sexual orientation are weak or non-existent.     

The relationship between facet tropism and cervical disc herniation

Many studies have demonstrated the association between facet tropism and disc herniation in the lumbar spine. Some of them found that lumbar disc herniation was on the side of the more sagittal facet joint interface. However, little is understood about the association of facet tropism with disc herniation in the cervical spine. As the relationship between the facet orientation and the side of cervical disc herniation (CDH) is unclear, the purpose of this study is to investigate that relationship. Ninety-six patients with single-level CDH (C4-C5, C5-C6 or C6-C7) were included in the CDH group of this study. Another 50 age-matched and gender-matched healthy participants who accepted physical examinations were enrolled as the control group. The cervical facet angles of two sides were measured using axial computed tomography (CT). The intersection angle of the midsagittal line of the vertebra to the facet line represents the facet angle. Facet tropism was defined as the angular difference of 7º between the left and the right sides. Facet tropism angle was recorded as the absolute value of the difference of facet angles between two sides. There were 20 herniations at C4–C5 level, 50 herniations at C5–C6 level and 26 herniations at C6-C7 level. The present study showed that more cases in the CDH group had facet tropism than did those in the control group at C4-C5, C5-C6 and C6-C7 level (p = .021, p = .001, p = .015, respectively). The facet tropism angles in the CDH group were significantly bigger than those in the control group at C4-C5, C5-C6 and C6-C7 level (p = .001, p = .002, p = .028, respectively). In the CDH group, the facet angles on the herniated side were found to be significantly bigger than those on the healthy side at C4-C5, C5-C6 and C6-C7 level (p = .000, p = .000, p = .037, respectively). The findings of this present study suggest that facet tropism is associated with the disc herniation in the cervical spine. We also found that cervical disc herniates towards the side of the bigger facet angle with respect to the sagittal plane. There is a need for future studies to verify the biomechanical impact of facet tropism on CDH.     

Differences in muscle mechanics underlie divergent optimality criteria between feeding and locomotor systems

Tetrapod musculoskeletal diversity is usually studied separately in feeding and locomotor systems. However, direct comparisons between these systems promise important insight into how natural selection deploys the same basic musculoskeletal toolkit—connective tissues, bones, nerves, and skeletal muscle—to meet the differing performance criteria of feeding and locomotion. Recent studies using this approach have proposed that the feeding system is optimized for precise application of high forces and the locomotor system is optimized for wide and rapid joint excursions for minimal energetic expenditure. If this hypothesis is correct, then it stands to reason that other anatomical and biomechanical variables within the feeding and locomotor systems should reflect these diverging functions. To test this hypothesis, we compared muscle moment arm lengths, mechanical advantages, and force vector orientations of two jaw elevator muscles (m. temporalis and m. superficial masseter), an elbow flexor (m. brachialis) and extensor (m. triceps- lateral head), and a knee flexor (m. biceps femoris-short head) and extensor (m. vastus lateralis) across 18 species of primates. Our results show that muscles of the feeding system are more orthogonally oriented relative to the resistance arm (mandible) and operate at relatively large moment arms and mechanical advantages. Moreover, these variables show relatively little change across the range of jaw excursion. In contrast, the representative muscles of the locomotor system have much smaller mechanical advantages and, depending on joint position, smaller muscle moment arm lengths and almost parallel orientations relative to the resistance arm. These patterns are consistent regardless of phylogeny, body mass, locomotor mode, and feeding specialization. We argue that these findings reflect fundamental functional dichotomies between tetrapod locomotor and feeding systems. By organizing muscles in a manner such that moment arms and mechanical advantage are relatively small, the locomotor system can produce broad joint excursions and high angular velocities with only small muscular contraction. As such, the anatomical organization of muscles within the limbs allows striding animals to move relatively rapidly and with minimal energetic expenditure. In contrast, the anatomical configuration of muscles in the feeding system, at least m. superficial masseter and m. temporalis, favors their force-producing capacity at the expense of excursion and velocity.