Transverse Extensions Research Articles

Transverse Oscillations and Kelvin–Helmholtz Instability in Curved Arcade Loops with Siphon Flows

The effect of plasma flow in curved arcade loops on transverse waves and oscillations is examined analytically. The model under study is a semicircular magnetic slab with finite transverse extensions and a mass flow inside, in the zero-β plasma approximation. It is found that in the quasi-perpendicular propagation limit, the model supports two fast surface modes: one with higher (FSW+) and another with lower (FSW−) frequency. For a weak flow, the frequency of the FSW+ (FSW−) increases (decreases) as the flow speed grows in both propagating and quasi-standing wave regimes. We show that the FSW+ and FSW− are subjected to the Kelvin–Helmholtz (KH) instability, and the threshold flow is greater (less than) the internal Alfvén speed for the FSW+ (FSW−). The presence of plasma flow results in modifying the period ratio P 1/2P 2 of the fundamental harmonic to the first overtone with P 1/2P 2 less (more) than 1 for the FSW+ (FSW−), and this effect degenerates in the straight waveguide limit. The sub-Alfvénic flow can prohibit resonant absorption of kink modes when the frequencies of the FSW+ and FSW− become out of the Alfvén continuum. It is also shown that in the static case and for a weak flow case, the FSW+ (FSW−) is interpreted as a vertically (horizontally) polarized kink mode, while for moderate flow, both modes have oblique polarization. We apply the developed theory to interpret the observational cases of kink oscillations in coronal loops with signatures of a siphon flow and the onset of KH instability induced by the blowout jet along a loop-shaped magnetic structure.

Thighplasty at the Time of Stage-1 Bone-Anchored Osseointegration Surgery.

For patients with transfemoral amputations and difficulty tolerating conventional socket-based prostheses, osseointegrated (OI) implants have enabled increased prosthetic use, improved patient satisfaction, and shown promising functional outcomes1,2. Although the use of OI implants effectively eliminates the soft-tissue-related challenges that have plagued socket-based prostheses, the presence of a permanent, percutaneous implant imparts a host of new soft-tissue challenges that have yet to be fully defined. In patients undergoing OI surgery who have redundant soft tissue, we perform a thighplasty to globally reduce excess skin and fat, tighten the soft-tissue envelope, and improve the contour of the residual limb. First, the orthopaedic surgical team prepares the residual femur for implantation of the OI device. After the implant is inserted, the residual hamstrings and quadriceps musculature are closed over the end of the femur, and the subcutaneous tissue and skin are closed in a layered fashion. Although the anatomic location and amount of excess soft tissue are patient-dependent, we perform a standard pinch test to determine the amount of soft tissue that can be safely removed for the thighplasty. Once the proposed area of resection is marked, we proceed with longitudinal, sharp dissection down to the level of the muscular fascia. At this point, we use another pinch test to confirm the amount of soft-tissue resection that will allow for adequate resection without undue tension3. Excess subcutaneous fat and skin are carefully removed along the previously marked incisions, typically overlying the medial compartment of the thigh in the setting of patients with transfemoral amputations. The thighplasty incision is closed in a layered fashion over 1 or 2 Jackson-Pratt drains, depending on the amount of resection. Depending on the amount of redundant soft tissue, thighplasty may not be necessary at the time of OI surgery; however, in our experience, excess soft tissue surrounding the transcutaneous aperture can predispose the patient to increased shear forces at the aperture, increased drainage, and increased risk of infection4. Although superficial infectious complications are most common following OI surgery, the need for soft-tissue refashioning and excision is one of the most common reasons for reoperation1,5. Our group has been more aggressive than most in our use of a vertical thighplasty procedure to globally reduce soft-tissue motion in the residual limb to avoid reoperation. Although much of the OI literature has focused on infectious complications, recent studies have demonstrated reoperation rates of 18% to 36% for redundant soft tissue following OI surgery1,5. We believe that thighplasty at the time of OI not only reduces the likelihood of reoperation but may also decrease infectious complications by reducing relative motion and inflammation at the skin-implant interface4,6. The thighplasty procedure is ideally performed as part of the first stage of the OPRA (Osseointegrated Prosthesis for the Rehabilitation of Amputees) procedure to limit the likelihood of problematic ischemia-related complications.We utilize a confirmatory pinch test both before and throughout the thighplasty procedure to ensure adequate resection without undue tension.The thighplasty excision pattern utilizes a long vertical limb designed to decrease the circumferential laxity of the residual limb. Maximal tension is borne on the vertical limb and not on the transverse extensions, as these are prone to scar widening and distortion of surrounding tissues.Closed-suction drainage is utilized liberally to decrease the likelihood of a symptomatic seroma. OI = osseointegratedOPRA = Osseointegrated Prosthesis for the Rehabilitation of AmputeesPVNS = pigmented villonodular synovitisT-GCT = tenosynovial giant-cell tumor.BMI = body mass indexPMH = past medical history.

One Source, Two Source(s): Ribs and Tethers

We present the unique and challenging case of a radio galaxy in Abell 3266 observed as part of the MeerKAT Galaxy Cluster Legacy Survey. It has quasi-periodic bright patches along the tail which connect to never-before-seen thin transverse extensions, which we call “ribs”, reaching up to ∼50 kpc from the central axis of the tail. At a distance of ∼400 kpc from the host (assuming the z=0.0594 redshift of Abell 3266) we found what appears to be a triple source with its own apparent host at a photometric redshift of 0.78. Mysteriously, the part of the tail far from the host and the triple are connected by a series of thin filaments, which we call “tethers”. The far tail, tethers and triple also have similar spectra and Faraday rotation measures, suggesting that there is only one—quite complicated—source, with a serendipitous background AGN in the triple. We look at possible causes for the “rib” and “tether” structures, and the emerging phenomena of intracluster medium filaments associated with radio galaxies.

The Role of the Tail or Lack Thereof in the Evolution of Tetrapod Aquatic Propulsion.

Secondary aquatic vertebrates exhibit a diversity of swimming modes that use paired limbs and/or the tail. Various secondarily aquatic tetrapod clades, including amphibians, reptiles, and mammals use transverse undulations or oscillations of the tail for swimming. These movements have often been classified according to a kinematic gradient that was established for fishes but may not be appropriate to describe the swimming motions of tetrapods. To understand the evolution of movements and design of the tail in aquatic tetrapods, we categorize the types of tails used for swimming and examine swimming kinematics and hydrodynamics. From a foundation of a narrow, elongate ancestral tail, the tails used for swimming by aquatic tetrapods are classified as tapered, keeled, paddle, and lunate. Tail undulations are associated with tapered, keeled, and paddle tails for a diversity of taxa. Propulsive undulatory waves move down the tail with increasing amplitude toward the tail tip, while moving posteriorly at a velocity faster than the anterior motion of the body indicating that the tail is used for thrust generation. Aquatic propulsion is associated with the transfer of momentum to the water from the swimming movements of the tail, particularly at the trailing edge. The addition of transverse extensions and flattening of the tail increases the mass of water accelerated posteriorly and affects vorticity shed into the wake for more aquatically adapted animals. Digital Particle Image Velocimetry reveals that the differences were exhibited in the vortex wake between the morphological and kinematic extremes of the alligator with a tapering undulating tail and the dolphin with oscillating wing-like flukes that generate thrust. In addition to exploring the relationship between the shape of undulating tails and the swimming performance across aquatic tetrapods, the role of tail reduction or loss of a tail in aquatic-tetrapod swimming was also explored. For aquatic tetrapods, the reduction would have been due to factors including locomotor and defensive specializations and phylogenetic and physiological constraints. Possession of a thrust-generating tail for swimming, or lack thereof, guided various lineages of secondarily aquatic vertebrates into different evolutionary trajectories for effective aquatic propulsion (i.e., speed, efficiency, and acceleration).

Composite Strips with U-Shaped CFRP Wrap Anchor Systems for Strengthening Reinforced Concrete Beams

The contribution of carbon fiber reinforced polymer (CFRP) wrap as an anchorage system of CFRP plates, used for flexural strengthening, is investigated. Eighteen concrete beams (100 × 150 × 1400 mm3) were cast and cured for 28 days before strengthening with both CFRP plates (1.2 × 50 mm2) and anchorage-used, U-shaped CFRP wraps. These were adhered on the top of the CFRP plates at different longitudinal and transverse extensions. The mechanical response of the concrete beams was examined under four-point loading including measurements of load versus deflection, bond stress versus slippage and strain in CFRP plates. Crack formation and failure modes were also monitored and characterized. End anchorage regimes, using 300-mm-long U-shaped segmented CFRP wraps, impart the best improvement to load capacity, rigidity, and toughness (up to 80, 57, and 40%, respectively) without harming tangibly ductility in terms of deflection at failure. Anchorage cases involving attaching continuous single or double layers of U-shaped CFRP wrap on the top of CFRP plates impart lower but tangible overall improvements in mechanical performance of CFRP-strengthened beams. A simple empirical model is developed to predict ultimate strain in CFRP plate based on present results before examining using available literature data. Moreover, the efficiency of the present technique is compared to that present in literature.

Transverse debridement and acute shortening followed by distraction histogenesis in the treatment of open tibial fractures with bone and soft tissue loss

This retrospective case series evaluates the technique of transverse debridement, acute shortening and subsequent distraction histogenesis in the management of open tibial fractures with bone and soft tissue loss, thereby avoiding the need for a soft tissue flap to cover the wound. Thirty-one patients with Gustilo grade III open tibial fractures between 2001 and 2011 were initially managed with transverse wound extensions, debridement and shortening to provide bony apposition and allowing primary wound closure without tension, or coverage with mobilization of soft tissue and split skin graft. Temporary monolateral external fixation was used to allow soft tissues resuscitation, followed by Ilizarov frame for definitive fracture stabilization. Leg length discrepancy was corrected by corticotomy and distraction histogenesis. Union was evaluated radiologically and clinically. Patients’ mean age was 37.3 years (18.3–59.3). Mean bone defect was 3.2 cm (1–8 cm). Mean time to union was 40.1 weeks (12.6–80.7 weeks), and median frame index was 75 days/cm. Median lengthening index (time in frame after corticotomy for lengthening) was 63 days/cm. Mean clinic follow-up was 79 weeks (23–174). Six patients had a total of seven complications. Four patients re-fractured after frame removal, one of whom required a second frame. Two patients required a second frame for correction of residual deformity, and one patient developed a stiff non-union which united following a second frame. There were no cases of deep infection. Acute shortening followed by distraction histogenesis is a safe method for the acute treatment of open tibial fractures with bone and soft tissue loss. This method also avoids the cost, logistical issues and morbidity associated with the use of local or free-tissue transfer flaps and has a low rate of serious complications despite the injury severity.

Experimental study on merging behaviors of two identical buoyant diffusion flames under an unconfined ceiling with varying heights

This paper presents an experimental study on the flame merging behaviors of two identical square propane burners with the side length of 15 cm burning under an unconfined ceiling. The total heat release rate of the two burners, burner edge spacing and ceiling height above the burner were varied. The flame merging probability, both the longitudinal and transverse ceiling flame extensions respectively along and perpendicular to the line connecting the centers of the two burners were measured. Based on the dimensional analysis, a piecewise linear function for the flame merging probability was developed and the criteria of the beginning and fully merging of the ceiling flames were thus determined, which provides a guidance of the safety distance between combustibles in buildings. The flame length is defined as the half of the total ceiling flame length in this work. Due to the interaction of two burners, the longitudinal and transverse flame lengths are different. Experimental results showed that as the spacing increases, the longitudinal flame length increases while the transverse flame length decreases. Based on the energy distribution model developed for the vertical and ceiling flames, correlations for predicting the merging ceiling flame lengths in the two directions were respectively established as the functions of the total heat release rate, burner size and spacing, ceiling height and the free flame height of two burners with zero spacing. The proposed models for the ceiling flame lengths can help to better understand the fire ignition and spread probability and flame radiation properties.

Dynamics of premixed swirl flames under the influence of transverse acoustic fluctuations

Flame dynamics in the presence of transverse acoustic fluctuations is an aspect of relevance to modern annular combustors. In particular, it is a key element underlying the occurrence and characteristics of thermoacoustic instability in annular combustors, which primarily involves azimuthal acoustic modes. In this paper, we present our experimental investigation of the response of a generic swirl-stabilized premixed flame to various transverse acoustic forcing configurations. Experiments were performed on a single burner rig featuring a combustor with transverse extensions. The flame was subjected to transverse acoustic fluctuations by generating controlled standing acoustic modes in this combustor. Two main results constitute this study: First, the obtained results reveal that flame response to transverse acoustic pressure fluctuations is quantitatively different when compared to axial forcing for low frequencies. Second, transverse acoustic velocity affects flame response to axial forcing such that the effects are dependent on the amplitude of transverse velocity fluctuations, the phase difference between axial and transverse forcing, and the inherent asymmetry of the flame.

A B-splines based nonlinear GBT formulation for elastoplastic analysis of prismatic thin-walled members

A beam finite element method based on Generalized Beam Theory (GBT) is developed for the modeling of nonlinear elastoplastic behavior of prismatic thin-walled members. The kinematic relationships, strains and nonlinear equilibrium equations are derived, and the corresponding numerical discretization and implementation schemes are presented. The buckling, warping and transverse extensions of cross-sections are defined by the linear combination of GBT cross-section deformation modes, and the longitudinal variation of amplitude of each GBT mode is approximated by the cubic B-splines. The cross-section rigid-body motion concerning global longitudinal extension, major/minor-axis bending and torsion is described by three translational displacements and three consecutive Euler angles (only four of them are independent variables). The J2-plasticity conjugated return mapping algorithm is introduced to integrate the rate equations of the constitutive model. In order to track the post-collapse equilibrium path, the arc-length control technique is utilized in solving the nonlinear equilibrium equations. Five illustrative examples are employed, and the validation of the proposed GBT formulation is verified by comparing GBT results with ANSYS FEM outputs. The modal decomposition analyses of five thin-wall members also provide a deep insight into their mechanical behavior, e.g., collapse mechanisms.

1121 SWIRL FLAME INTERACTION WITH TRANSVERSE AND AXIAL ACOUSTIC FORCING

The present study is an experimental investigation on the effect of axial and transverse acoustic excitation on a swirl-stabilized flame. A single burner test-rig with transverse extensions to facilitate transverse acoustic excitation is employed in this experimental study. The swirl flow is established using a generic radial swirl generator. Results presented here include phase-averaged crosswise flow field oscillations at isothermal flow conditions and partial orthogonal decomposition (POD) analysis of flow field acquired in the streamwise plane at isothermal and reacting conditions. Through analysis of radial velocity profile oscillations obtained from crosswise measurements and modal decomposition of the velocity field in the streamwise direction, conclusions have been derived for flow and flame response to transverse forcing. It is found that while out-of-phase transverse forcing can interact with natural helical oscillations in the swirl flow, the effect of in-phase forcing is dominantly observed in the form of flow response to induced axial oscillations. The study complements previous investigations on swirl flow and flame interaction with transverse acoustics, and provides information for future efforts on the issue of thermoacoustic instability in annular combustors.

GBT-based buckling mode decomposition from finite element analysis of thin-walled members

This paper presents an original method based on the Generalised Beam Theory (GBT) capable to decompose the elastic buckling modes from a shell finite element analysis (FEA) of an isotropic thin-walled member, into pure buckling modes of global, distorsional or local nature. The main novelty lies in using only the GBT cross-sectional deformation modes instead of member base mode shapes. The contribution of each pure buckling mode can be calculated, allowing a better understanding of the member post-buckling behaviour and strength reserve. Following the GBT classical assumptions, the membrane shear strains and transverse extensions are neglected. The modal participations obtained from FEA are in good agreement with the values calculated via classical GBT approach.

‘Normal’ Fanaroff-Riley type II radio galaxies as a probe of the nature of X-shaped radio sources

We present a multiwavelength radio study of a sample of nearby Fanaroff-Riley class II (FRII) radio galaxies, matched with the sample of known X-shaped radio sources in size, morphological properties and redshift, using new Giant Metrewave Radio Telescope (GMRT) data and archival data from the Very Large Array (VLA). Our principal aim in this paper is to provide a control sample for earlier studies of samples of `X-shaped' radio sources, which have similar luminosities and small-scale radio structures to our targets but exhibit large-scale extensions to their lobes that more typical FRII sources lack; earlier spectral work with the GMRT has suggested that these `wings' sometimes have flat spectral indices at low frequencies, in contrast to expectations from models in which the wings are formed hydrodynamically or by jet reorientation. In our new observations we find that almost all of our target FRII radio galaxies show standard spectral steepening as a function of distance from the hotspot at the low frequencies (610 MHz and 240 MHz) provided by the GMRT data, even when transverse extensions to the lobes are present. However, one source, 3C321, has a low-surface-brightness extension to one lobe that shows a flatter spectral index than the high-surface-brightness hotspots/lobes, as found in X-shaped sources.

Modification of smooth muscle Ca2+-sparks by tetracaine: Evidence for sequential RyR activation

Spontaneous Ca2+-sparks were imaged using confocal line scans of fluo-4 loaded myocytes in retinal arterioles. Tetracaine produced concentration-dependent decreases in spark frequency, and modified the spatiotemporal characteristics of residual sparks. Tetracaine (10μM) reduced the rate of rise but prolonged the average rise time so that average spark amplitude was unaltered. The mean half-time of spark decay was also unaffected, suggesting that spark termination, although delayed, remained well synchronized. Sparks spread transversely across the myocytes in these vessels, and the speed of spread within individual sparks was slowed by approximately 60% in 10μM tetracaine, as expected if the spark was propagated across the cell but the average Po for RyRs was reduced. Staining of isolated vessels with BODIPY-ryanodine and di-4-ANEPPS showed that RyRs were located both peripherally, adjacent to the plasma membrane, and in transverse extensions of the SR from one side of the cell to the other. Immuno-labelling of retinal flat mounts demonstrated the presence RyR2 in arteriole smooth muscle but not RyR1. We conclude that Ca2+-sparks in smooth muscle can result from sequential activation of RyRs distributed over an area of several μm2, rather than from tightly clustered channels as in striated muscle.

Asymptotic behavior of eigenvalues of the Laplace operator in infinite cylinders perturbed by transverse extensions

We present sufficient conditions for the existence of an eigenvalue of the Laplace operator with zero Dirichlet conditions in a weakly perturbed infinite cylinder in the case of localized perturbations which are extensions along the transverse coordinates with coefficients depending on the longitudinal coordinate. If such an eigenvalue exists, then, for this eigenvalue, we obtain an asymptotic formula with respect to a small parameter characterizing the values of extensions.

THE CLASSIC: Anterior Spinal Fusion

Professor Arthur Hodgson ("Hoddy") turned 75 years old in June 1990 (Figure not shown). This was the year of the 35th anniversary of the first anterior surgical approach for spinal tuberculosis. In 1955, three patients were surgically treated with this procedure and received follow-up treatment for several months. At this stage, the patients had solid healing of the bone grafts and no sign of paraparesis. It was then decided, on the basis of these initial surgical observations, to proceed. Since then, Hodgson's contribution has been legendary. A paper that reported the surgical treatment of the first 50 patients was published in the British Journal of Surgery in 1956. During the next few years, large series of patients were reported with dramatic recovery of Pott's paraplegia and a very high rate of anterior bone graft fusion. Doctor Hodgson, his wife Monica, and their five children arrived in Hong Kong in 1951. He had left Rochester, England, where he was a senior registrar, and sailed to Hong Kong to take up the post as lecturer in orthopaedic surgery within the Department of General Surgery at Hong Kong University. During these early years in Hong Kong, Hodgson also had to deal with endemic poliomyelitis, osteomyelitis, and all the Third World orthopaedic problems. His first assistant in these early years was Dr. Harry Fang. By 1960, his work was well recognized, and he was made the first professor of the new Department of Orthopaedic Surgery, separate from the Department of General Surgery in which he began this monumental work. I was fortunate to spend eight years as lecturer in the department, leaving at the end of 1975. During this period, there was a renaissance in spinal surgery that was solely attributable to the hard work and clear thinking of Hodgson. Not only did he think and write clearly (his papers are few in number, but classical in quality), but he provided a great stimulus and influence on many leaders in spinal surgery during the past quarter of a century, including Doctors John Hall, Kenton Leatherman, and the late Alan Dwyer. It is no secret that without Hodgson's continuing support for Dwyer's screw and cable technique, it probably would have failed. All told, he spent 24 years in orthopaedic surgery at Hong Kong University, 15 of these as professor and head of the department. This volume of Clinical Orthopaedics and Related Research is a tribute to Professor Hodgson. I personally thank those who made the effort to put together their thoughts. The spinal papers in this Symposium represent much of the latest contemporary thought in spinal surgery, and would have been strongly approved of and encouraged by Professor Hodgson himself. As he looks back during his years of contribution to spinal surgery, Hodgson can be more than gratified by the knowledge that this concepts and ideas have been disseminated throughout the world. His contribution and the development of the anterior approach to spinal tuberculosis remain a milestone; from this flowed the anterior approach for so many other diseases of the vertebral column as we know it today. Professor Hodgson died on November 16, 1993 at the age of 78. His leadership in spinal surgery will be sorely missed throughout the world.

The elastic anisotropy of nematic elastomers

We examine the robustness of order in nematic elastomers under mechanical strains imposed along and perpendicularly to the director when director rotation is prohibited. In contrast to electric and magnetic fields applied to conventional nematics, mechanical fields are shown theoretically and experimentally to greatly affect the degree of nematic order and related quantities. Unlike in liquid nematics, one can impose fields perpendicular to the director, thereby inducing biaxial order which should be susceptible to experimental detection. Nematic elastomers with unchanging director and degree of order should theoretically have the same elastic moduli for longitudinal and transverse extensions. This is violated when nematic order is permitted to relax in response to strains. Near the transition we predict the longitudinal modulus to be smaller than the transverse modulus; at lower temperatures the converse is true, with a crossover a few degrees below the transition. The differences are ascribed to the different temperature dependence of the stiffness of uniaxial and biaxial order. We synthesised side chain single-crystal nematic polymer networks, performed DSC, X-ray, birefringence, and thermo-mechanical characterisations, and then obtained linear moduli from stress-strain measurements.

Defocusing regimes of nonlinear waves in media with negative dispersion.

Defocusing regimes of quasimonochromatic waves governed by a nonlinear Schr{umlt o}dinger equation with mixed-sign dispersion are investigated. For a power-law nonlinearity, we show that localized solutions to this equation defined at the so-called {ital critical} dimension cannot collapse in finite time in the sense that their transverse (anomalously dispersing) and longitudinal (normally dispersing) extensions never vanish. Solutions defined at the {ital supercritical} dimension are proved to exhibit a nonvanishing mean longitudinal size, and cannot transversally collapse if they are assumed to shrink along each spatial direction. {copyright} {ital 1996 The American Physical Society.}

Mitochondrial size and shape in equine skeletal muscle: a three-dimensional reconstruction study.

Individual mitochondria were reconstructed from ultrathin serial sections of selected muscle fibers in the M. semitendinosus of a horse, over a length of nearly two sarcomeres. Mitochondria were found to be highly variable, with size and complexity of single mitochondria increasing with the fractional part of a fiber occupied by mitochondria. In fibers with a mitochondrial volume density of less than 4%, corresponding to the mitochondrial content of fast-twitch glycolytic fibers, mitochondria were generally rather simple cylindrical shapes, oriented parallel to the myofibrils. In fibers with a mitochondrial volume density of more than 7%, corresponding to the mitochondrial content of slow-oxidative or fast-oxidative glycolytic fibers, mitochondria were generally cylindrical at the A-band and Z-plate level of the muscle sarcomeres. However, these mitochondria often had transverse extensions or interconnections that occurred at the I-band level. Volumes of individual mitochondria ranged from as small as a few thousandths of a micron3 up to several micron3 for the incompletely reconstructed portions of the largest mitochondria. Mitochondrial profiles that one would classify from single sections as subsarcolemmal were found to interconnect with other profiles deeper within the fiber. This suggests that it is unlikely that subsarcolemmal and interfibrillar mitochondria are two structurally distinct populations. However, we found no evidence of a reticulum completely interlinking all mitochondrial material in a muscle fiber.

Effects of Transverse Panel Strand Extensions on the Behavior of Precast Prestressed Panel Bridges

O ne of the newer types of composite bridge construction, in common use today, involves the use of precast prestressed concrete panels which span between longitudinal girders and act as formwork and support for the cast-inplace deck (Fig. 1). This type of bridge has been studied previously,'6 and has generally performed well. Typically, 3 in. (76 mm) prestressing strand extensions project from the sides of the panels (Fig. 1). Elimination of the extensions would facilitate continuous bed manufacture of the panels. This study was undertaken to investigate the structural performance of panels without strand extensions. The study is described in detail in Ref. 7, and is summarized here. Scope and Objectives: A full scale bridge specimen was constructed and tested in the lahoratory_ The northern half of the specimen was made using panels with 3 in. (76 mm) transverse strand extensions, and the southern half, using panels without such extensions. In all other respects, the bridge was similar to actual bridges built for the Texas State Department of Highways and Public Transportation (Texas SDHPT). The specimen was tested under static, fatigue, and concentrated loadings. The primary objective was to determine if the absence of transverse panel strand extensions would affect the bridge's performance under fatigue and static loading conditions. Other objectives were to evaluate the response of the deck to concentrated loads, and to

Scanning electron microscopy of the walls of tubules in human coronal dentine

Twenty-one fully-formed healthy human premolars were fixed, resin-impregnated and freeze-fractured. Specimens were critical-point dried. The wall of the dentinal tubules was lined with a two-layered structure which extended from the pulp-predentine border to the dentine-enamel junction; there was a fibrous outer layer and an amorphous, membrane-like inner layer. The lining sheath was separated from the odontoblast process by a space which widened toward the outer surface of the dentine, although occasionally in the mid and outer dentine the lumen was constricted by transverse septa of the sheath which were in close proximity with the odontoblast process. Some tubules were divided into a system of chambers by transverse extensions of the membrane-like inner layer of the sheath.