Additional Slips Research Articles

A Study of Anatomical Variability of the Omohyoid Muscle and its Clinical Relevance

OBJECTIVEThe omohyoid muscle is a long, thin muscle consisting of superior and inferior bellies and an intermediate tendon, which runs obliquely in the lateral cervical region. The omohyoid is important in neck dissections because it is the surgical landmark for level III and IV lymph node metastases.METHODSIn the present study, the anterior and posterior triangle of the neck was dissected in 35 male cadavers and observed for variations in the omohyoid bilaterally. Observations were focused on variations in number, attachments, and position of omohyoid.RESULTSAmong the 35 cadavers studied, double omohyoid was present in one cadaver, inferior belly originated from the clavicle in three cadavers, superior belly merged with the sternohyoid in two cadavers, and the omohyoid received additional slips from the sternum in one cadaver. Standard attachment and position of the omohyoid was observed in the remaining cadavers.CONCLUSIONVariations of this muscle are important because of its close relation to the large vessels and brachial plexus. Because of the direct adhesion of the intermediate tendon to the anterior wall of the internal jugular vein and its connection with it through a thin lamina of the pretracheal layer of the cervical fascia, the contraction of the omohyoid muscle has a direct effect on the lumen of this vessel.

Anatomical Variations in the Insertion of the Peroneus (Fibularis) Longus Tendon

Multiple pathologies are associated with the peroneus longus tendon including traumatic injury, tendinitis, tenosynovitis, dislocation, acute rupture, chronic tear, and avulsion fractures. While the description of insertion points for the peroneus longus tendon exists in numerous texts and articles, none are consistent in describing the incidence of variation of the insertional slips. Dissection was performed on the feet of 30 adult, embalmed cadaver limbs disarticulated at the knee and ankle joint. All 30 specimens had a consistent attachment to the base of the first metatarsal by a strong band. A slip to the medial cuneiform was observed in 26 specimens (86.6%). The anterior and posterior frenular ligaments were present in 25 (83.3%) and four (13.3%) specimens, respectively. Another thick and strong fibrous band, termed additional band (AB), was observed close to the metatarsocuneiform joint in nine specimens (30%). Additional slips to the neck of first metatarsal, bases of second, fourth, and fifth metatarsals also were noted. We have described the incidences of variations of the insertion of the peroneus longus tendon and an additional band, which gives rise to various muscles. The results of this study may be important to better understand the symptoms associated with peroneus longus tendon pathologies and the role played by the peroneus longus tendon in maintaining the arch of the foot.

Fatigue Crack Nucleation at Σ3(1 1 2) Boundary in a Ferritic Stainless Steel

The effect of a geometrical relationship between a grain boundary (GB) plane and a tensile axis on intergranular fatigue cracking along Σ3(1 1 2) twin boundaries has been investigated in Fe-30%Cr alloy crystals. Fatigue experiments were carried out on the three kinds of the specimens containing the Σ3(1 1 2) twin boundary. It was found that the fatigue cracking behavior was sensitive to the geometry of the GB plane. In a specimen where both the GB plane and a slip vector lying in the GB plane in adjacent grains are inclined to the tensile axis at 45°, the fatigue cracks were nucleated preferentially along the twin boundary at a stress amplitude of 170 MPa. The specimen with the GB plane normal to the tensile axis showed that the fatigue crack was initiated from a slip band formed within a constituent grain at a stress amplitude of 300 MPa. When the GB plane was inclined to the tensile axis but the slip vector lying in the GB plane was normal to the tensile axis, development of additional slips formed perpendicular to the GB plane were observed at a specific site of the GB. Initiation of intergranular fatigue cracks at the site was recognized at a stress amplitude of 250 MPa. It can be suggested that the GB plane normal to the tensile axis provides the highest fatigue performance among them. The difference in the cracking property among these specimens could be understood in terms of the effective Schmid factor derived from elastically incompatible stress.

Analysis of Multiple Slip in Aluminum Bicrystals. Latent Hardening Model for Multiple Slip State.

A model of latent hardening due to dislocation interaction is proposed, which can express strain hardening properties of fcc single crystal in various tensile directions. Tensile properties of an aluminum bicrystal composed of crystals initially oriented for single slip and <100> tensile direction are analyzed on the basis of crystal plasticity theory incorporated with the proposed hardening model. In numerical results, several slip systems are activated near the grain boundary of <100> grain due to the local stress which arises from plastic incompatibility. Flow stress of the bicrystal is larger than the average of component single crystals due to such additional slips, but this difference is smaller than the experimental observation. As deformation proceeds, slip state of <100> grain changes from 8 symmetric slips to a smaller number of slips. This tendency is stronger for the latent hardening model than for the isotropic model.

Accessory fasciculi of the human pronator teres muscle: Incidence, morphological characteristics and relation to the median nerve

The purpose of this study is to determine the incidence of the accessory fasciculi of the pronator teres muscle and to evaluate the predispositional role of its morphological characteristics to median nerve entrapment. The accessory fasciculi of the pronator teres muscle have been found in 8.3% of 60 upper extremities which were studied. These fasciculi arose from the tendon of the brachialis muscle (5.0%), from the radial tendon of the biceps brachii muscle (3.3%), from the Gantzer's muscle (1.6%) or from the flexor digitorum superficialis muscle (1.6%). They were slips of origin of the deep head of the pronator teres muscle. They represented the deep head, when there was no other origin slip, or they were additional origin slips when the deep head also had a coronoid origin. Only the accessory fasciculi that represented the deep head and the accessory fasciculi located inside to the coronoid fasciculus were related directly to the median nerve. Three characteristics of these accessory fasciculi adjacent to the median nerve could be considered to be factors that predispose to the nerve entrapment: 1) the location dorsal to the superficial head of the pronator teres muscle, because it increases the area of contact with the median nerve; 2) the location between the superficial head and the coronoid fasciculus, because it reduces the space occupied by the median nerve; and 3) the tendinous nature of considerable segments of short accessory fasciculi because they are less extensible.

Anatomical studies on the extensor carpi radialis longus and brevis muscles in Japanese.

In order to determine whether the muscle bellies of the extensor carpi radialis longus and brevis (including additional slips) show laminar disposition, they were observed in 490 upper limbs of 245 Japanese cadavers. The author examined them from the point of view of lamination of the muscle slips (bellies) and classified them into 22 types in this study. The extensor carpi radialis longus muscle consists of five layers (A, B, C, D and E). Their proximal portions are disposed from radial deep to ulnar superficial as A, B, C, D and E, and the distal portions from ulnar deep to radial superficial as A, B, C, D and E. C is the main part of the extensor carpi radialis longus muscle, and A, B, D and E are additional (accessory) slips. The main part (C) is inserted into the second metacarpal bone A and B cross beneath the main part (C) to the ulnar side of the hand and are inserted into the third to second metacarpal bones. D and E pass across on the main part (C) to the radial side of the hand and are inserted into the second to first metacarpal bones. The extensor carpi radialis brevis consists of three layers (X, Y and Z). Their proximal portions are disposed from radial deep to ulnar superficial as X, Y and Z, and the distal portions from ulnar deep to radial superficial as X, Y and Z. Y is the main part of the extensor carpi radialis brevis muscle, and X and Z are additional (accessory) slips. The main part (Y) is inserted into the third metacarpal bone. X passes deep to Y to the ulnar side of the hand and is inserted into the fourth or third metacarpal bone. Z passes superficial to Y to the radial side of the hand and is inserted into the third or second metacarpal bone. The extensor carpi radialis longus muscle showed the normal form (C only present) in 326 of 490 cases, and had the main part (C) and one to three additional slips (A, B, D, E) in 164. The extensor carpi radialis brevis showed the normal form (Y only present) in 389, and had the main part (Y) and one or two accessory slips (X, Z) in 101 of 490 cases.

Frictional heating and pore pressure rise due to a fault slip

Summary. Accurate estimation of frictional stress is crucial to determining the bounds of pre- and post-earthquake states of stress. A long-term average value of 10 MPa, deduced from heat flow data in the San Andreas fault zone, is frequently cited, but it may or may not represent the resistive stress of an individual slip event. Based on 1-D modelling, this paper deals with frictional heating, pore pressure rise, and migration of fluid, and speculates upon their consequences for triggering of earthquakes and emission of earthquake light. Analytic solutions are obtained for temperature and pore pressure rises due to frictional heating. Results are obtained for three heating models: 1, instantaneous heating; 11, constant heating rate; and 111, heating rate proportional to inverse square root of time. For the same total heat generation and physical parameters, solutions indicate that, for times less than twice the slip duration or distances with two thermal diffusion distances, temperature and pressure distributions are sensitive to heating models; at greater times and distances, they are insensitive to models. Though temperature rise due to I-m slip under 10MPa frictional stress may reach 200K or more on the slip surface, the rise is not measurable in practice at a distance beyond about 10 m from the slip surface. Estimates of pore pressure rise (0.2-2MPa) depends crucially upon permeability and slip duration. Darcy flow may exceed lO-'m s-' at one thermal diffusion distance; and immediately after the slip ends, reverse flow towards slip surface develops. Because the pore pressure front can advance beyond the temperature front by 100-1000 times, measurement of pore pressure variation is an alternative to temperature measurement for estimating frictional stress. A rise of 500Pa is measurable at 330m within 30 days for a fault slip with frictional heat production of 10MJm-2. It is speculated that the propagating pressure front created by an initial slip, rather than the fluid flow itself, may weaken the frictional strength elsewhere and lead to additional minor slips and perhaps a larger earthquake. With large frictional stress and displacement, heating may also

Using a social carrying capacity model to estimate the effects of marina development at the Apostle Islands National Lakeshore

Abstract This research focuses on a policy question: What will be the effects of adding additional marina slips on the boating experience at the Apostle Islands National Lakeshore? It also explores a more basic research issue. Can a social carrying capacity model developed on relatively linear wilderness systems be useful in more complex systems involving nonwilderness type recreation? Descriptive data determined the number of boats leaving the existing marina and the mooring locations of these boats among the islands. Using these data it was possible to predict the effects of additional slips on the number of boats moored at each of the two most popular locations among the islands. Survey data showed that boaters had clear preferences for mooring with fifteen or fewer boats at each site. The projections showed that up to 200 new slips could be added at mainland sites before this preference standard was greatly exceeded. An increase of 400 new slips would produce situations where the social carrying capacity at the island mooring sites was often exceeded. The social carrying capacity model was found to be useful both for developing projections and measuring visitor preferences, suggesting that it is applicable to complex nonwilderness settings.