symmetry

对称性
  • 文章类型: Journal Article
    我们调查了视觉意识在模态完成中的参与,特别是,视觉意识是否在局部完成和全局完成中起着不同的作用,使用基本形状辨别范例和颜色对手闪烁技术来使基本不可见。在四个实验中,参与者区分了目标的形状,然后是部分遮挡或中性的素数。所有素数都是发散的遮挡模式,其中局部完成基于遮挡点处轮廓的良好延续,而全局完成基于最大对称性。目标对应于由于局部或整体完成闭塞的灌注而可能出现的形状。对于每个具有不可见质数的实验,我们都进行了一个具有可见质数的版本。我们的结果表明,当地竣工,但不是全球完成,部分遮挡的形状可以在没有视觉意识的情况下发生,但显然只有当可见的遮挡形状产生一个,本地完成。没有完成,无论是本地还是全球,当可见的遮挡形状产生多个完井时,似乎发生在没有视觉意识的情况下。讨论了这些结果对视觉意识在局部和全球完井中的不同作用以及多次完井与无意识的完井之间的关系的影响。
    We investigated the involvement of visual awareness in amodal completion, and specifically, whether visual awareness plays a differential role in local versus global completion, using a primed shape discrimination paradigm and the color-opponent flicker technique to render the prime invisible. In four experiments, participants discriminated the shape of a target preceded by a partly occluded or a neutral prime. All primes were divergent occlusion patterns in which the local completion is based on good continuation of the contours at the point of occlusion and the global completion is based on maximum symmetry. The target corresponded to the shape that could arise as a result of local or global completion of the occluded prime. For each experiment with an invisible prime we conducted a version with a visible prime. Our results suggest that local completion, but not global completion, of a partly occluded shape can take place in the absence of visual awareness, but apparently only when the visible occluded shape generates a single, local completion. No completion, either local or global, appears to take place in the absence of visual awareness when the visible occluded shape generates multiple completions. The implications of these results to the differential role of visual awareness in local and global completions and to the relationship between multiple completions and unconscious amodal completions are discussed.
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  • 文章类型: Journal Article
    使用[n]环-4,10-pyrene(n=6-21)作为说明性示例,研究了大环芳基的阻转异构现象,并给出了两个简单的假设:(1)交替构型(R,S,R,S,,,)是热力学上最稳定的,和(2)三个连续的相同配置(R,R,R或S,S,S)被阻止。Ni介导的5,9-二碘芘偶联在一锅反应中产生了一系列直接连接的环状芘低聚物。合成后的环状六聚体被指定为(R,S,S,R,R,S)结构,转换成(R,S,R,S,R,S)-在加热时形成。环状七聚体由两种类型的C2对称结构组成,由假设(2)预测,其中一个通过加热相互会聚。通过1H核磁共振(NMR)光谱从可能的五种候选物中分析了环状八聚体的三种阻转异构体,和转换过程为(R,S,R,S,R,S,R,研究了加热时的S)构型。总的来说,根据两个简单的规则,反异构现象的分析可以顺利进行。
    An atropisomerism of large cycloarylenes was studied using [n]cyclo-4,10-pyrenylenes (n=6-21) as an illustrative example with two simple assumptions: (1) alternating configurations (R,S,R,S,…) are thermodynamically most stable, and (2) three consecutive identical configurations (R,R,R or S,S,S) are prevented. Ni-mediated coupling of a 5,9-diiodopyrene gave a series of directly-linked cyclic pyrene oligomers in one-pot reaction. As-synthesized cyclic hexamer was assigned as an (R,S,S,R,R,S) structure, converted into an (R,S,R,S,R,S)-form upon heating. Cyclic heptamer consists of two types of C2 symmetric structures predicted from assumption (2), one of which was convergent to one another by heating. Three atropisomers of cyclic octamer were analyzed from the possible five candidates by means of 1 H nuclear magnetic resonance (NMR) spectroscopy, and the conversion process to (R,S,R,S,R,S,R,S) configurations upon heating was investigated. In total, according to two simple rules, the analysis of atropisomerism could be performed smoothly.
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  • 文章类型: Journal Article
    可以通过使用一组合适的对称适应模式来描述晶体中发生的结构和物理现象。Fabrykiewicz等人介绍了晶体中磁模的分类。[ActaCryst。(2021),A77,327-338]扩展到晶体中的电和环形(anapole)模式的分类。这三种分类是基于磁点组,在两种情况下使用:(i)磁性晶体类的磁性点组和(ii)感兴趣的Wyckoff位置的磁性位点对称点组。磁性的分类,电模式和环形模式基于三个广义反演的性质:空间反演1,时间反演1\'和时空反演1\'。要强调的是,这三个倒置中没有一个比其他两个更重要。提出了对称运算符号和磁点组符号的新表示法;每个操作都表示为一个适当旋转和一个广义反转的乘积。对于磁性,电和环形排序有64种模式:三种纯铁(磁/电/环形)模式,13混合铁(磁/电/环形)和反铁(磁/电/环形)模式,和48纯反铁(磁/电/环形)模式。所提出的模式分类导致了有用的观察结果:电模式和环形模式具有许多对称限制,类似于已知的磁模式。例如,磁矩或电矩或环形矩的连续重新定向只能在三斜对称或单斜对称的情况下进行。具有弱垂直铁(磁/电/环形)分量的反铁(磁/电/环形)排序仅在单斜或正交对称下是可能的。磁性的一般分类,对于NdFeO3,提出了电模式和环形模式。
    The structure and the physical phenomena that occur in a crystal can be described by using a suitable set of symmetry-adapted modes. The classification of magnetic modes in crystals presented in Fabrykiewicz et al. [Acta Cryst. (2021), A77, 327-338] is extended to a classification of electric and toroidal (anapole) modes in crystals. These three classifications are based on magnetic point groups, which are used in two contexts: (i) the magnetic point group of the magnetic crystal class and (ii) the magnetic site-symmetry point group of the Wyckoff position of interest. The classifications for magnetic, electric and toroidal modes are based on the properties of the three generalized inversions: space inversion 1, time inversion 1\' and the space-and-time inversion 1\'. It is emphasized that none of these three inversions is more important than the other two. A new notation for symmetry operation symbols and magnetic point group symbols is proposed; each operation is presented as a product of one proper rotation and one generalized inversion. For magnetic, electric and toroidal orderings there are 64 modes: three pure ferro(magnetic/electric/toroidal) modes, 13 mixed ferro(magnetic/electric/toroidal) and antiferro(magnetic/electric/toroidal) modes, and 48 pure antiferro(magnetic/electric/toroidal) modes. The proposed classification of modes leads to useful observations: the electric and toroidal modes have many symmetry limitations similar to those already known for the magnetic modes, e.g. a continuous reorientation of the magnetic or electric or toroidal moments is possible only in triclinic or monoclinic symmetry. An antiferro(magnetic/electric/toroidal) ordering with a weak perpendicular ferro(magnetic/electric/toroidal) component is possible only in monoclinic or orthorhombic symmetry. The general classifications of magnetic, electric and toroidal modes are presented for the case of NdFeO3.
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  • 文章类型: Journal Article
    背景:多发性硬化症(MS)的特征是大脑和脊髓中神经组织的进行性脱髓鞘恶化,导致神经系统部分传输信号的能力中断。尽管在神经病理学研究中背柱通路受损,步态控制评估,尤其是速度效应,在女士中研究不足。
    目的:本研究旨在比较MS患者自我选择和快速步态的双侧协调性,并将这些发现与疾病严重程度(扩展残疾状态量表(EDSS))和年龄相关。
    方法:进行了年龄匹配和性别匹配的病例对照研究,以通过评估由惯性测量单元传感器捕获的步态时空参数来评估26名MS受试者的步态的双侧协调性。双侧变异性,准确度,和整体协调(可变性和准确性的总和)以自我选择和快速的速度进行评估,并与疾病严重程度和年龄相关。
    结果:与自选择的步行速度相比,所有步态控制参数在较快的速度下都得到了改善(对于所有比较,p<0.05)。步态的双侧协调性与疾病严重程度和年龄中度相关(p<0.05),步态时空参数与疾病严重程度相关(从R=0.66到R=0.70,p<0.001)。
    结论:与快速相比,MS患者在自我选择时步态的双侧协调性明显受损。在不同的速度进行分析时,应谨慎进行功能移动性测试和运动干预。在运动研究中,旨在提高速度的干预措施可能是一种适当且安全的策略。
    BACKGROUND: Multiple sclerosis (MS) is characterized by progressive demyelinating deterioration of nervous tissues in the brain and cord, leading to a disruption in the ability of parts of the nervous system to transmit signals. Although dorsal column pathways are compromised in neuropathological studies, gait control assessments, especially on speed effects, have been understudied in MS.
    OBJECTIVE: This study aimed to compare bilateral coordination of gait in subjects with MS at self-selected and fast speed and to relate these findings to disease severity (Expanded Disability Status Scale (EDSS)) and age.
    METHODS: An age-matched and sex-matched case-control study was performed to assess the bilateral coordination of gait of 26 MS subjects by evaluating the gait spatiotemporal parameters captured by an inertial measurement unit sensor. The bilateral variability, accuracy, and overall coordination (the sum of variability and accuracy) were assessed at a self-selected and fast speed, and correlated with disease severity and age.
    RESULTS: All gait control parameters improved at the fast speed compared to the self-selected walking speed (p<0.05 for all comparisons). The bilateral coordination of gait was moderately related to disease severity and age (p<0.05), and the gait spatiotemporal parameters were related to disease severity (p<0.001, from R=0.66 to R=0.70).
    CONCLUSIONS: Patients with MS showed significant impairment in the bilateral coordination of gait at self-selected compared to fast speed. Functional mobility tests and locomotor interventions should be cautious when analyzed at different paces. Interventions aiming to increase speed can be a proper and safe strategy in locomotor studies.
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  • 文章类型: Journal Article
    报道GUCY2D相关常染色体显性遗传(AD)锥杆营养不良(COD/CORD)的欧洲患者队列的临床表型和相关基因型,我们回顾性分析了25例患者(17例女性,范围12-68)与来自欧洲三个主要学术中心的GUCY2D相关AD-COD/CORD,并回顾了先前发表的148名患者的数据(视力(VA),中央凹厚度,首发症状的年龄,和遗传变异)。考虑到所有的病人,据报道,首发症状的中位年龄为7岁(四分位距5-19岁,n=78),主要包括VA减少,畏光和色觉异常。该疾病在VA(n=165,Spearman'sρ=0.85,p<0.0001)和中央凹厚度(Spearman'sρ=0.96,n=38,p<0.0001)方面表现出高度的眼间对称性。通过绘制VA作为年龄的函数来评估疾病进展(n=170)。线性最佳拟合分析表明每十年损失0.17logMAR(p<0.0001)。我们分析了迄今为止描述的最大队列(n=173),发现最常见的突变是p.(Arg838Cys)和p.(Arg838His)。此外,大多数患者在成年期有严重的视力丧失,突出潜在干预的机会之窗。这项研究揭示的新兴模式可能有助于设计前瞻性自然史研究,以进一步定义未来介入试验的终点。
    To report the clinical phenotype and associated genotype of a European patient cohort with GUCY2D-related autosomal-dominant (AD) cone-/cone-rod dystrophy (COD/CORD), we retrospectively analyzed 25 patients (17 female, range 12-68) with GUCY2D-related AD-COD/CORD from three major academic centers in Europe and reviewed the previously published data of 148 patients (visual acuity (VA), foveal thickness, age of first symptoms, and genetic variant). Considering all the patients, the onset of first symptoms was reported at a median age of 7 years (interquartile range 5-19 years, n = 78), and mainly consisted of reduced VA, photophobia and color vision abnormality. The disease showed a high degree of inter-eye symmetry in terms of VA (n = 165, Spearman\'s ρ = 0.85, p < 0.0001) and foveal thickness (Spearman\'s ρ = 0.96, n = 38, p < 0.0001). Disease progression was assessed by plotting VA as a function of age (n = 170). A linear best-fit analysis suggested a loss of 0.17 logMAR per decade (p < 0.0001). We analyzed the largest cohort described so far (n = 173), and found that the most common mutations were p.(Arg838Cys) and p.(Arg838His). Furthermore, the majority of patients suffered severe vision loss in adulthood, highlighting a window of opportunity for potential intervention. The emerging patterns revealed by this study may aid in designing prospective natural history studies to further define endpoints for future interventional trials.
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  • 文章类型: Case Reports
    少数病例伴有其他几种病变的腹壁脂肪瘤,包括特定形式的钙化和脑畸形,已被报道。我们介绍了一名无症状的83岁男性,其颅骨中线具有特殊的对称形态。我们认为,病变始于胚胎早期,并与颅神经c细胞密切相关。我们报告了这种特征性病变的神经放射学发现,并讨论了有关其形成过程的一些文献综述。
    Few cases of pericallosal lipoma with several other lesions, including specific forms of calcification and brain malformations, have been reported. We present the case of an asymptomatic 83-year-old man with a pericallosallipoma with peculiar symmetrical morphology in the midline of the skull. We posit that the lesions began forming in the very early embryonic period and were closely associated with the cranial neural crest cells. We report the neuroradiological findings of this characteristic lesion and discuss several literature reviews on the process of its formation.
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  • 文章类型: Journal Article
    众所周知,对称性在化学反应性中起关键作用。在这里,我们探讨了其在电荷转移(CT)络合反应的振动强耦合(VSC)中的作用。通过研究三甲基化苯-I2CT络合物,我们发现VSC引起CT复合体平衡常数KDA的大变化,反映反应ΔG°值的变化。此外,通过将微流体腔模式调整为三甲基化苯的不同IR振动,ΔG°仅根据耦合的正常模式的对称性而增大或减小。这一结果揭示了对称性在VSC中的关键作用,反过来,解释了为什么VSC引起的化学变化的幅度远大于拉比分裂,也就是说,由VSC引起的能量扰动。这些发现进一步证实了VSC是分子科学的强大而通用的工具。
    It is well known that symmetry plays a key role in chemical reactivity. Here we explore its role in vibrational strong coupling (VSC) for a charge-transfer (CT) complexation reaction. By studying the trimethylated-benzene-I2 CT complex, we find that VSC induces large changes in the equilibrium constant KDA of the CT complex, reflecting modifications in the ΔG° value of the reaction. Furthermore, by tuning the microfluidic cavity modes to the different IR vibrations of the trimethylated benzene, ΔG° either increases or decreases depending only on the symmetry of the normal mode that is coupled. This result reveals the critical role of symmetry in VSC and, in turn, provides an explanation for why the magnitude of chemical changes induced by VSC are much greater than the Rabi splitting, that is, the energy perturbation caused by VSC. These findings further confirm that VSC is powerful and versatile tool for the molecular sciences.
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  • 文章类型: Journal Article
    The timing of operation for trigonocephaly is recommended before the age of 1 year. To evaluate the outcome of a consecutive series operated in a single centre, the current study was performed. The study cohort comprised a retrospective single-centre series of 20 patients with trigonocephaly operated before the age of 12 months. Intra- and postoperative clinical data, as well as aesthetic outcome measured by two-dimensional asymmetry index (2D AI) and correction of the curvature on lateral and pictures from above were evaluated. Furthermore, to evaluate postoperative aesthetic outcome, a new classification (Grades I-IV) was proposed. The mean age of the cohort was 7.9 months. 2D AI changed from 0.049 pre- to 0.03 postoperatively (P=0.165). The correction of the curvature in lateral pictures yielded a significant change on postoperative pictures (P=0.002) as well as on pictures from above. Using the proposed classification, 16/20 (80%) patients had a postoperative outcome of Grade I, 4/20 (20%) Grade II. In patients operated before the age of 12 months an excellent (Grade I, AI <0.03) or good aesthetic (Grade II, adequate parents\' or surgeon\'s opinion) result could be reached in all patients.
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  • 文章类型: Journal Article
    Landing is a crucial factor in gymnastics competitions, but the underlying biomechanical and neuromuscular strategies remains unclear. This study aimed to investigate the biomechanical characteristics and neuromuscular strategies of landing for backward somersault. A 19-segment human model was developed and bilateral lower-limb joint loadings were estimated using computer stimulation. Bilateral lower-limb joint angles, vertical ground reaction force (vGRF), impulse, joint reaction force, joint torque, power, work, stiffness and electromyogram (EMG) of the rectus femoris, biceps femoris, tibialis anterior, and lateral gastrocnemius were presented during initial (touchdown to peak vGRF) and terminal impact-phases of landing (peak vGRF to vGRF equaling to body weight). The hip, knee, and ankle joints were rapidly flexed (8º, 20º, and 18º, respectively) during initial impact-phase and maintained at around 90º, 120º, and 60º, respectively terminal impact-phase. Flexor and extensor torques were demonstrated for lower-limb joints during initial and terminal impact-phases, respectively. The stiffness of lower limb joints and the EMGs amplitude of all examined muscles during terminal impact-phase were several times larger than that during initial impact-phase. The absolute symmetry indexes were less than 10% for lower limb joint angles and larger than 10% for the kinetics and muscle activation. The findings demonstrated symmetrical motion for lower limb joints with flexing rapidly at initial impact-phase and maintaining unchanged at terminal impact-phase and asymmetry in joint loading and muscle activation during landing.
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  • 文章类型: Journal Article
    不对称的肢体负荷被认为会导致下肢截肢者的健康问题,并且在斜坡上行走时会加剧。与传统的假足相比,液压阻尼的踝足改善了斜坡上的地面顺应性。微处理器控制的液压踝足通过动态调节粘弹性阻尼特性提供进一步的适应。
    使用案例系列设计,对4名经胫骨截肢者进行步态分析.有两种行走条件(斜坡上升和下降)和两种假脚条件(微处理器控制开和关-MPF开和关)。在足部条件下比较了总支撑力矩积分(MIsup)和不对称程度。
    在斜坡下降期间,假肢踝关节力矩从背屈过渡到plant屈发生在站立阶段较早,减慢柄的角速度。在斜坡上升期间,MPF-背屈/前屈力矩转变发生较晚,这意味着在早期站立时对小腿旋转的阻力较小,行走速度提高了6%。对于两种斜坡条件,肢体MIsup随着MPF的开启而普遍下降(下降4-13%,3-11%上升)。
    液压踝足的微处理器控制减少了健全肢体关节的总负荷,对于两种行走条件,对于所有参与者。这可能对长期的关节健康和步行效率具有有益的后果。
    UNASSIGNED: Asymmetrical limb loading is believed to cause health problems for lower limb amputees and is exacerbated when walking on slopes. Hydraulically damped ankle-feet improve ground compliance on slopes compared to conventional prosthetic feet. Microprocessor-controlled hydraulic ankle-feet provide further adaptation by dynamically adjusting viscoelastic damping properties.
    UNASSIGNED: Using a case series design, gait analysis was performed with four trans-tibial amputees. There were two walking conditions (ramp ascent and descent) and two prosthetic foot conditions (microprocessor-control on and off - MPF-on and MPF-off). Total support moment integral ( M I sup ) and degree-of-asymmetry were compared across foot conditions.
    UNASSIGNED: During ramp descent, the transition of prosthetic ankle moment from dorsiflexion to plantarflexion occurred earlier in stance phase with MPF-on, slowing the angular velocity of the shank. During ramp ascent, the MPF-on dorsiflexion/plantarflexion moment transition occurred later, meaning less resistance to shank rotation in early stance and increasing walking speed by up to 6%. For both slope conditions, sound limb M I sup was universally decreased with MPF-on (4-13% descent, 3-11% ascent).
    UNASSIGNED: Microprocessor-control of hydraulic ankle-feet reduced the total loading of the sound limb joints, for both walking conditions, for all participants. This may have beneficial consequences for long-term joint health and walking efficiency.
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