Control of trunk muscles activity while manual material handling symmetrically and asymmetrically, Based on Motor control strategy

[Purpose] Although lifting tasks has been recognized as a primary risk factor in low back pain, the concept of lifting asymmetry is relatively new subject. To address trunk function, biomechanical studies generally measure trunk muscle activity using surface electromyography (EMG). But so far, magnitude and similarity index (SI) obtained from EMG have not been studied as indicators of the motor control during lifting task. So, the purpose of this study is to compare the trunk muscles magnitude and SI during symmetric and asymmetric lifting. [Subjects and Methods] A total of 20 healthy male with no history of lumbar spine disorders participated. Surface electromyography data were recorded from the 7 trunk muscles while the participants performed symmetric and asymmetric lifting and lowering different loads. [Results] According to Multivariate ANOVAs the phase of motion (lifting, lowering) and condition (symmetry, asymmetry) have a significant effect on SI and magnitude (p≤0.05). Load changes have no effect on SI (p=0.969) but have a significant effect on magnitude (p≤0.05). The magnitude and SI value is higher in asymmetrical lifting and lowering compare to symmetrical condition. [Conclusion] The findings reveal the SI value is higher in asymmetric conditions. This means that the amount of muscles co-contracture increased during asymmetrical conditions. Increased muscles co-contracture reinforces the hypothesis of exerting more compression on the spine in asymmetrical movement. Keywords: Asymmetrical lifting, Motor control, Electromyography

A Proposed Cascaded Multilevel Inverter with R-Load at Different Carrier Frequencies

Cascaded multilevel inverter has the major problem as voltage imbalance across the capacitors connected in circuits which are acting like dc sources. The number of level generation depends on the number of DC sources and switches placed in cascaded multilevel inverter topology. In this proposed topology the positive levels and zero levels of the inverter have been explained. This topology also work in symmetrical condition. The topology is simulated in MATLAB and its THDs are calculated at different modulation index. The voltage stress and loss calculations are carried out at different carrier frequencies.

Simulation and Analysis of Novel Extendable Multilevel Inverter Topology

Multilevel inverter (MLI) has become more popular in high power, high voltage industries owing to its high quality output voltage waveform. This paper proposes a novel single phase extendable type MLI topology. The term ‘extendable’ is included since the presented topology can be extended with maximum number of dc voltage sources to synthesize larger output levels. This topology can be operated in both symmetrical and asymmetrical conditions. The major advantages of the proposed inverter topology include minimum switching components, reduced gate driver circuits, less harmonic distortion and reduced switching losses. The comparative analysis based on the number of switches, dc voltage sources and conduction switches between the proposed topology and other existing topologies is presented in this paper. The comparison results show that the proposed inverter topology requires fewer components. The performance of the proposed MLI topology has been analyzed in both symmetrical and asymmetrical conditions. The simulation model is developed using MATLAB/SIMULINK software to verify the performance of the proposed inverter topology and also the feasibility of the presented topology during the symmetrical condition has been validated experimentally.

Prenatal Diagnosis of Low-set Ears with Asymmetrical Microtia in the First Trimester

ABSTRACT Initially, the external ears are in the lower neck region, but with the development of the mandible, they ascend to the side of the head at the level of the eyes. Low-set ear is one of the features often associated with genetic disorders, and external ear defects are significant because they are often associated with other malformations. The problem may occur as a symmetrical condition but an asymmetrical condition is not rare, in which one side of the face is maldeveloped. This defect varies in severity; however, it always includes maldevelopment of the ear and the mandible. Recent advanced 3D HDlive ultrasound enables us to demonstrate fetal external ear position and development even as early as in the first trimester. The picture of the month clearly demonstrated low-set ears with asymmetrical development of the ear and face at 12 weeks of gestation. Early detection of ear abnormality leads to further genetic and morphologic investigation as well as to proper management and counseling. How to cite this article Pooh RK. Prenatal Diagnosis of Low-set Ears with Asymmetrical Microtia in the First Trimester. Donald School J Ultrasound Obstet Gynecol 2016;10(2):111-112.

Asymmetry Of The Node Of Ranvier

The nodal constrictions of Ranvier in normal limb nerves of mammals are bounded by asymmetric paranodal bulbs, the proximal bulb (nearer the cell body) being larger in all dimensions. This investigation was undertaken to determine whether the asymmetry results from partial damming of proximo-distally flowing axoplasm at the nodal constriction, or whether other features of local growth patterns are more relevant. The degree of asymmetry was estimated on teased, osmicated fibres from normal immature and mature limb nerves to skin and muscle and on ventral nerve roots. Estimates were also made on the central processes of dorsal root ganglionic cells with their contrasting direction of flow, after alteration of growth patterns in regenerates of crushed immature and mature nerves, and in the recurrent laryngeal nerve which pursues an exceptional course in relation to surrounding tissues. A polarization of asymmetry with larger proximal bulbs was found in uncomplicated limb nerves and after simultaneous regeneration and limb growth following crushing of immature nerves. Mixed populations (that is, with no preferred direction of asymmetry and often symmetrical bulbs) were found in dorsal and ventral nerve roots and the apical recurved segment of the recurrent laryngeal, whilst the mature regenerates closely approached the symmetrical condition. The descending and ascending limbs of the recurrent laryngeal nerve showed a reversal of polarization with respect to the cell body, but similar with respect to the cephalo-caudal body axis. It was concluded that damming of directionally flowing axoplasm was not causally related to the formation of asymmetric bulbs. The overall interstitial growth pattern of limb nerve elongation as revealed by internodal distance studies contrasts with the differential growth and maturation gradients shown by the various limb segments through which the nerve passes. These differences result in a relative movement between the myelinating and elongating Schwann cell and the surrounding limb tissues. The movements are considerable and unidirectional throughout most of the limb, the Schwann cells becoming relatively further removed from the limb apex, whilst the movements minimize at the limb root and apex. It is suggested that the altered mechanical conditions operating at the ‘advancing’ and ‘trailing’ ends of the cell are related to the dimensional differences of the paranodal apparatus comprising the bulb at each end of the cell, and secondarily result in asymmetric nodes of Ranvier.

PHOTOREACTIONS OF PARTIALLY BLINDED WHIP-TAIL SCORPIONS

The experiments dealt with in this paper were devised to ascertain (1) the relative effectiveness as photoreceptors of the whip-tail scorpion's median eyes, lateral eye groups, and cutaneous sensitive areas, and (2) the effect on orientation produced by symmetrical and by asymmetrical interference with the photoreceptive mechanism. Each of the receptors was eliminated unilaterally and bilaterally, singly and in combinations with other receptors. In all, sixteen different abnormal conditions of the photoreceptive apparatus were produced. The reactions of animals thus partially blinded were measured in terms of angular deflection from an initial path of locomotion. Measurements obtained under anterior, lateral, and bilaterally balanced illumination were compared with measurements made on normal animals under the same conditions of illumination. The change from the normal reaction induced by covering a photoreceptor was taken as an index of the effectiveness of the receptor prevented from functioning. By comparing the values of the changes from normal reactions produced by the elimination of the several receptors, their relative effectiveness is approximated as median eyes : lateral eyes : cutaneous sensitive areas :: 1:1.6:2.2. All animals in which the receptive mechanism was rendered functionally asymmetrical exhibited, when subJected to bilaterally balanced illumination, deflections toward the side which had been made less sensitive. In a series of measurements made on animals in ten different conditions of asymmetry the amplitudes of the deflections were proportional to the degree of unbalance which had been produced in the photosensitive mechanism. Animals in which the receptive mechanism was reduced but left in a symmetrical condition maintained an undisturbed balance of reaction when subjected to equal, opposed lights. Under lateral or anterior illumination the rate of attaining a new direction of orientation was reduced in proportion to the extent of the interference with the receptive mechanism. The reactions of symmetrically and asymmetrically blinded scorpions indicate that orientation is attained and maintained by a transmission of impulses to the muscles of locomotion which is proportional bilaterally to the excitation of the symmetrically located photoreceptors. In their effect on orientation the three pairs of receptors are completely coordinated. Orientation depends upon bringing the excitation of the receptive mechanism as a whole into bilateral equilibrium.