Lines Of Tension Research Articles

Atrioventricular valves of the mouse: III. Collagenous skeleton and myotendinous junction

The leaflet tissue of the mouse atrioventricular (AV) valves contains a system of wavy collagen bundles that organize like tendons, orientate along lines of tension, and constitute an essential component of the valve tissue. The organization of these bundles is different in the two AV valves, reflecting differences in the anatomy of the entire valvular complex. Further insights into this kind of organization are needed to gain a complete understanding of the functional anatomy of the mouse AV valves. The endocardial covering of the mouse AV valves (from 21 days to 1 year of age) was eliminated by the sonication or the maceration method. This allowed us to study in situ the organization of the collagenous valve skeleton, as well as the structure of the myotendinous junction. The leaflets of the two AV valves are formed by a fibrous layer (on the ventricular side) and a spongy layer (on the atrial side). The fibrosa is formed by undulating collagen bundles that organize and orientate differently on the right and left sides. The spongiosa is formed, on both sides, by a loose network of thin collagen fibers with no apparent orientation. Myocardial cells in the papillary muscles of the tricuspid valve are elongated and show cone-shaped tips. Collagen fibers attach to the myocyte surface. Collagen struts and thin septa can also be recognized. On the other hand, the collagenous components of the mitral leaflets attach tangentially to the mitral papillary muscles. On the two sides, the myocytes appear to be ensheathed in a layer of collagenous tissue. The sheaths are formed by circularly arranged fibers and appear to be tightly interconnected. The differences in the collagenous organization between the two AV valves reflect differences in the gross anatomy of the valves. The attachment of collagen to the papillary myocytes in the tricuspid valve resembles that of a typical myotendinous junction. However, the collagen-muscle junction in the mitral valve is more similar to the structure of a pennate muscle. The collagen matrix of the heart has been divided into endomysial, perimysial, and epimysial components. The presence of sheaths housing individual myocytes and capillaries, struts, and thin septa, corresponds to the endomysium. The absence of perimysial septa, which aggregate myocytes into groups, is striking, but this may just be a species difference. The appropriateness of the term epimysium, as applied to the heart, is discussed.

The keloid triad hypothesis (KTH): a basis for keloid etiopathogenesis and clues for prevention

The basis of keloid formation and its subsequent behavior, the very high incidence of recurrence after resection, and other forms of treatment are not fully understood. Keloids still remain a dilemma in plastic surgery. Analyzing the etiopathogenesis of keloids in a large number of patients in Ghana and in Poland led to a concept of keloid triad hypothesis (KTH). This is defined as a group of three etiologic factors which must simultaneously coexist and interact for keloids to form. The etiological factors are: genetic links; bacterial, viral or any type of infective agent; type of surgery - sutures, tension of suture lines, location of sutures in relationship to the body skin lines of tension; etc. At least three of these factors must be present, inter-correlate, in order to form a keloid. These factors have been sub-divided into two groups - major (or main) and minor (or auxiliary) and are analyzed in this paper. In each situation at least one major factor must be present in order for a keloid to form.

The Role of Distraction Osteogenesis in the Reconstruction of the Mandible in Unilateral Craniofacial Microsomia

Laboratory and clinical studies have shown that mandibular distraction is an effective and powerful reconstructive surgical technique. It is safely performed without the need for blood transfusion or bone graft. Because of concomitant expansion of the functional matrix (the associated skin, subcutaneous fat, and muscles of mastication), there is a multidimensional expansion of the lower jaw with minimal, if any, evidence of relapse. Moreover, the surgical reconstruction can be commenced by 2 years of age, and the vector of distraction can be controlled by preoperative design. Finally, the increase in resulting mandibular bone stock will provide more reconstructive options in the future for traditional orthognathic surgical techniques. The technique has been criticized, either for the cutaneous incision for the approach to the mandible or for the scar resulting from the path of the distracting screws. However, with careful placement of the device, the resulting scar can be placed in the lines of minimal tension with a resulting satisfactory scar. It has been assumed that the osteotomy results in interruption of the inferior alveolar nerve. However, questioning of the older patients has failed to detect any change in sensation of the lower lip. The status of the inferior alveolar nerve in the hypoplastic mandible has also never been studied. Insertion of the screws required an area of bone stock that is edentulous, and this finding can make application of the device difficult in some patients. The length of treatment has been criticized--approximately 3 months. However, this is offset by the ease of treatment, the degree of safety, and the reduction in hospital time without the need for blood transfusion or bone graft. The results to date indicate that the technique can be applied to the correction of the milder mandibular deficiencies.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxidative effects of ozone on the aging of structural silicone elastomers

AbstractThe changes in the physical properties of three different commercial silicone sealants used in structural glazing applications were monitored as a function of various aging factors. The variables included, simultaneous exposure to ozone and moisture in which the pH of the moisture was maintained at discrete levels of 3 and 11. The extremes of the pH range represent recorded values for acid rain (pH = 3) and basic cleaning solutions (pH = 11), respectively. A second portion of the study involved studying the effect of loading on the sealant performance. The experimental coupons were cut from cast sheets of DC‐790, DC‐995, and DC‐983. An Instron tester was used to measure the changes in the engineering properties such as Young's modulus, relaxation time, and ultimate tensile stress of the test samples as a function of time of exposure to the different variables. Unexposed samples, kept at ambient laboratory conditions, were used as the control. Results of these tests indicate that the Young's modulus of the samples decreases during an initial period as a result of their exposure. After this initial decrease the sample moduli showed a steady increase with time. Surface cracking was observed during the initial period, even though the moduli continued to increase. Moreover, the acid and ozone appear to act synergistically in the deterioration of the sealant. Samples exposed to the higher pH level did not show this kind of behavior. The effect of tensile loading on the sealant was significant only for DC‐983, the high modulus formulation. This was perhaps because of the creation of high stress centers. The medium modulus material exhibited good resistance to the synergistic effects causing deterioration. Ozone resulted in discoloration, softening, and change in structure in the low modulus formulation. Although the ozone did not react aggressively with silicone, its slow attack or degradation should still be of concern. In spite of the use of inhibitors, severe and acute cracks appeared on the surface of the rubber material at angles of ninety degrees across the line of tension. It is hoped that these accelerated test results can lead to more informed decisions concerning silicone sealant life following their exposure to ozone and acid precipitation. © 1994 John Wiley & Sons, Inc.

Prevention and treatment of postburn scars and contracture.

The management of postburn reconstruction is complicated by the frequent occurrence of multiple reconstructive needs in a single patient. This article presents a simple, comprehensive approach to burn scar reconstruction. The primary aim of the surgeon is to prevent burn scar deformity by rapid wound closure, correction of tissue deficiencies, and assiduous attention to postoperative splinting and compression therapy. The initial step in managing secondary deformities is to prioritize reconstructive needs. Reconstruction is then carried out in a stepwise fashion aiming to restore active function first, followed by passive function, and finally addressing aesthetic reconstruction. Reconstructive techniques are applied in a hierarchy from simplest to most complex. Primary excision and closure of scars by reorientating the scar to the lines of relaxed skin tension can significantly improve appearance. The use of z-plasty, flap repair, and tissue expansion are also reviewed. Skin expansion, in particular, has become the standard management of postburn alopecia and, although associated with a relatively high rate of complication, has significantly improved the aesthetic appearance of such patients. The management of common problems affecting the face is discussed with particular reference to management of the eyelids, oral commissure, and lips. These areas need to be reconstructed as aesthetic units and each requires individualized management of donor tissue. The reconstruction of the burn patient is often a long process requiring multiple procedures. The approach presented here advocates a stepwise, prioritized approach aiming at both maximum function as well as optimal appearance.

A new method for reducing hysteresis of torque sensors: Cross magnetic shaking

Cross magnetic shaking, a new method for reducing hysteresis, is proposed for shaft torque sensors based on the magnetostrictive effect of the steel shaft. In this method, an auxiliary magnetic field (shaking field) is superposed perpendicularly to the exciting field while differences in permeabilities along lines of tension and of compression are detected by the field at the shaft surface. Hysteresis measured for a quench-hardened steel shaft of 25 mm diameter under the applied torque from −490 to 490 Nm was reduced by about nine times and sensitivity increased by a factor of 2.

Herniation of the Bladder into the Rectum in a Dog

SummaryIn the dog, the pelvis is frequently injured following motor vehicle accidents (1). Injuries to the lower urinary and intestinal tracts may accompany pelvic fractures in man (2, 3, 4, 5) and the dog (1, 6, 7). This paper describes an unsual case of bladder retroflexion and herniation through a tear, into the rectum of a dog, following traumatic fracture of the pelvis. The successful management and repair is outlined and a biomechanical sequence leading to the abnormal bladder position is proposed.An unusual case of bladder retroflexion and herniation through a tear, into the rectum of a dog, following traumatic fracture of the pelvis is described. Repair was accomplished by manipulation of the bladder into its normal position through a coeliotomy incision and suturing of the rectal tear after prolapsing the rectum through the anus. The proposed biomechanical sequence leading to this injury is tearing by the inwardly rotated, fractured left hemipelvis as well as or alternatively, shearing forces along lines of excessive tension.

Sensory transduction and the mammalian epidermis

This paper constitutes, in its main intent, an introduction to the mammalian epidermis as a surface for biosensor applications. In particular, the structure and function of the epidermis of the newborn rat are examined as a model for studies of the human state. Data are presented illustrating an anisotropic organization of the dorsal surface of the neonatal rodent with regard to lines of tension and thermal gradients. The dependence of the mechanical properties of the epidermis upon calcium is examined by means of an in-vitro assay of epidermal retraction. The potential role of keratin tonofilaments as piezo-electric and pyroelectric elements in the epidermis is introduced and the spatial alignment of these macromolecular arrays is demonstrated to be a function of physiological tensions. These findings are discussed in the context of noninvasive epidermal sensors utilized to understand mechanisms of sensory development and physiological regulation. Optoelectronic (infrared) imaging of the dorsal temperature field and the alteration in this field by treatment with epidermal growth factor are presented as examples of this methodologic approach. It is concluded that a detailed examination of the material and physical properties of mammalian epidermis is a reasonable goal of biosensor development and research. Hypothetically, such studies may reveal important molecular and cellular mechanisms by which sensory data are transmitted or transduced at the organism—environmental interface.

Organizational Theories: Some Criteria for Evaluation

A set of ground rules and vocabulary to facilitate focused discussion about the structure of organization and management theories are proposed. The many previous efforts at defining and evaluating theory help establish criteria for theory construction and evaluation. In the establishment of these criteria, description is distinguished from theory, and a matrix of criteria for evaluating the variables, constructs, and relationships that together compose a theory is developed. The proposed matrix may be useful both for defining the necessary components of good theory and for evaluating and/or comparing the quality of alternative theories. Finally, a discussion of the way theories fit together to give a somewhat broader picture of empirical reality reveals the lines of tension between the two main criteria for evaluating theory.

Drie kortverhale van Maarten’t Hart - literêr-esteties en lewensbeskoulik bekyk II

The autobiographical manner of presentation of Maarten ’t Hart’s stories has the consequence that the narrative distance is particularly small - so that the effect on the reader is greater, and he is strongly addressed by the message of each story. This gives rise to the fact that the relevant stories can be evaluated not only on the basis of the literary aesthetic qualities, but also on the basis of lifeview. The three stories, “De zaterdagvliegers”, “Ouderlingenbezoek” and “De witte nacht” consistently reveal a sustained line of emotional tension, and style and structural means are well applied to support the thematic concerns. In “De witte nacht” especially an exceptional measure of textural density is obtained and the story reveals a close coherence. In the ethical sense the existential sense of life which is revealed by the stories as well as the one-sided characterisation of the representatives of the Christian faith is obtrusive. These two characteristics of his work reveal a particular awareness of the spirit of the time in which 't Hart is caught and explains to some extent why he is one of the most widely-read Dutch authors since 1945.

Drie kortverhale van Maarten ’t Hart - Literêr-esteties en lewensbeskoulik bekyk (I)

The autobiographical manner of presentation of Maarten 't Hart’s stories has the consequence that the narrative distance is particularly small - so that the effect on the reader is greater, and he is strongly addressed by the message of each story. This gives rise to the fact that the relevant stories can be evaluated not only on the bais of the literary aesthetic qualities, but also on the basis of lifeview. The three stories, De zaterdagvliegers, Ouderlingenbezoek and De wine nacht consistently reveal a sustained line of emotional tension, and style and structural means are well applied to support the thematic concerns. In De witte nacht especially an exceptional measure of textural density is obtained and the story reveals a close coherence. In the ethical sense the existential sense of life which is revealed by the stories as well as the one-sided characterisation of the representatives of the Christian faith is obtrusive. These two characteristics of his work reveal aparticular awareness of the spirit of the time in which ’t Hart is caught and explains to some extent why he is one of the most widely-read Dutch authors since 1945.

IN VITRO FORMATION OF SAGITTAL HELICES FROM NEWBORN RAT SKIN: CHIRALITY, ONTOGENY, AND LINEAR DIMENSIONS

Organ culture explants adapt to conditions in vitro by forming “figures of equilibrium” with their environment (conformations of minimal surface energy). We propose that explant “morphogenesis” during in vitro adaptation is a function of in vivo tissue organization and lines of tension. In this report, we used a Mcllwain tissue chopper to prepare 1mm x 20mm strips of newborn rat dorsal skin and compared the figures of equilibrium obtained from perpendicularly oriented sections. Transversely cut strips remained extended or formed gentle “u's” in culture. Sagittal strips, however, rapidly formed helices of opposite handedness in serum free Waymouth's media. Measurements of 18 sagittal strips from newborn (day 0) pups are shown:The number of coils was stable for 24h in culture. In 3-day-old rat pups, mean coil number was 2.5 + 0.2 (N=30).Conclusions: 1) In the newborn rat, sagittal skin strips form helices in vitro which retain their in vivo chirality; 2) sagittal helices are conical rather than cylindrical with the tightest coil located at the caudal end; 3) helix formation is stable for 24h in vitro; 4) the number of coils formed per sagittal centimeter of skin decreases rapidly after birth.

Effects of mechanical tension on protrusive activity and microfilament and intermediate filament organization in an epidermal epithelium moving in culture.

Mechanical tension influences tissue morphogenesis and the synthetic, mitotic, and motile behavior of cells. To determine the effects of tension on epithelial motility and cytoskeletal organization, small, motile clusters of epidermal cells were artificially extended with a micromanipulated needle. Protrusive activity perpendicular to the axis of tension was dramatically suppressed. To determine the ultrastructural basis for this phenomenon, cells whose exact locomotive behavior was recorded cinemicrographically were examined by transmission electron microscopy. In untensed, forward-moving lamellar protrusions, microfilaments appear disorganized and anisotropically oriented. But in cytoplasm held under tension by micromanipulation or by the locomotive activity of other cells within the epithelium, microfilaments are aligned parallel to the tension. In non-spreading regions of the epithelial margin, microfilaments lie in tight bundles parallel to apparent lines of tension. Thus, it appears that tension causes alignment of microfilaments. In contrast, intermediate filaments are excluded from motile protrusions, being confined to the thicker, more central part of the cell. They roughly follow the contours of the cell, but are not aligned relative to tension even when microfilaments in the same cell are. This suggests that the organization of intermediate filaments is relatively resistant to physical distortion and the intermediate filaments may act as passive structural support within the cell. The alignment of microfilaments under tension suggests a mechanism by which tension suppresses protrusive activity: microfilaments aligned by forces exerted through filament-surface or filament-filament interconnections cannot reorient against such force and so cannot easily extend protrusions in directions not parallel to tension.

The transverse posterior approach to the neck.

Traditional posterior approaches to the neck use a vertical craniocaudal incision which often leaves an unsightly scar. An incision along Langer's transverse lines of tension divides only the cross-fibres of the dermis and we have found the results of this approach encouraging: wound healing was uncomplicated and the cosmetic appearance excellent.

Hadron mass calculations with Susskind and Wilson fermions in the fundamental-adjoint plane

We report the results of hadron mass calculations in the valence (quenched) approximation, on an 8 3 × 16 lattice. For Wilson fermions with the standard Wilson action we find good agreement with results form the hopping parameter expansion on a 16 4 lattice at β = 5.7, with only a small finite size effect in the anticipated direction. The proton-to-rho mass ration is however too high by 60% and the delta-proton mass difference is too small. We have repeated these calculations at two points of the same string tension in the plane of the fundamental and adjoint couplings, in an attempt to avoid the unphysical critical point there; within statistical errors the meson masses remain the same, there is an improvement in the delta-proton splitting and the proton mass decreases slightly, but not enough to produce agreement with experiment. The estimates of lines of constant string tension obtained as a preliminary to the mass calculation are in good agreement with weak coupling expansions at the larger β values and cross over towards strong coupling predictions around β = 5.7. Also, crude estimates reveal the disappearance of the specific heat peak as one moves away from the unphysical singularity. For Susskind fermions we find some measure of agreement with other results form a 10 3 × 16 lattice, but large, apparently finite size, effects in the rho mass at low quark mass. Meson masses in lattice units disagree with the Wilson fermion results by as much as a factor of 2. This disagreement persists in the fundamental-adjoint plane, suggesting the importance of studying improved fermion actions. At β = 6.0, Wilson fermion results show clear finite size effects on the 8 3 × 16 lattice.

The thermodynamics of a liquid lens

The conditions of equilibrium of a small lens of one liquid at the surface of another are obtained in terms of the surface and line tensions. Gravity is neglected. The intersection of the three surfaces of tension, which is also the line of tension, is separated from the surfaces and lines on which surface and linear adsorptions vanish by distances of the order of the range of the intermolecular forces. These separations determine how the surface and line tensions depend on curvature. Experimental and theoretical values of the line tension, although uncertain, allow estimates to be made of the size of systems in which these effects are appreciable.

A sliding flap to cover dorsal skin defects over the proximal interphalangeal joint

Conventional transposition flaps may produce a conflict between the line of maximum tension across the flap and the line of desired maximum extensibility necessary for the achievement of a full range of proximal interphalangeal joint flexion. A sliding transposition flap is described which has the advantage that it has less tension in its transposed position than it has in its normal resting position and that there is no conflict between the pivot point line and the desired production of proximal interphalangeal joint movement. This is possible because of the presence of a large dog-ear which provides a longitudinal skin redundancy exactly where it is needed. The flap is obliquely placed and is usually an axial pattern flap and inherently safe.

Arnold van Gennep: The Hermit of Bourg‐la‐Reine

Arnold van Gennep was a leader in the field of French folklore and ethnology. His life was one of prolific publication, constant intellectual growth, and incisive criticism of the French social sciences. Yet he remained an outcast from the French academic life. From a survey of his writings and those of members of L'Année Sociologique, the lines of tension which resulted in van Gennep's exclusion from academe are traced. [Arnold van Gennep, Emile Durkheim, history of anthropology and folklore, French folklore, French sociology]

Zigzag Incisions for Improved Exposure and Scarring

Incisions for elective orthopedic procedures frequently result in scars that are unesthetic (wide and hypertrophied) and impeded function (are inelastic). The best cicatrix is obtained when the operation can be performed through an incision that follows the lines of skin tension (transverse exposure). If longitudinal exposure is required to gain access to the deeper structures, the best esthetic and functional result is obtained by the zigzag incision. Moreover, the zigzag incision affords a wider exposure than a long straight incision, thus greatly facilitating the operative procedure.

Development of Cleavage Line Patterns in the Human Fetus

The dermal fibroelastic connective tissue of the fetus is arranged in such a manner as to represent cleavage lines (lines of tension). Cleavage lines were observed as early as the 28 mm stage but in most cases they do not appear until the 50 mm stage. The various regions of the body present individual cleavage line patterns which undergo alterations as the fetus grows. The pattern alterations are influenced by (1) rate of proportional growth and (2) principal direction of growth of certain structures in the various regions. The cleavage line pattern of the newborn differs from that of the adult in certain regions.