Positioned Flush Research Articles

Mechanisms of mobile bearing dislocation in lateral unicompartmental knee replacement.

Mobile bearing dislocation occurs in 1- 6% of Oxford Domed Lateral replacements. Dislocations are predominantly medial, but can occur anteriorly or posteriorly. They tend to occur when the knee is flexed. It is not clear how dislocations can be prevented. A previously described mechanical rig for assessing mobile bearing dislocation was updated so as to study dislocation with the knee in flexion. Sub-categories for the description of each type of dislocation were introduced. Dislocation was only possible when the knee was distracted. As the amount of distraction possible in the knee is variable, the risk of dislocation is related to the amount of distraction in the rig necessary for a dislocation. The type of dislocation requiring the least distraction was medial `edge' dislocation in which the edge of the bearing dislocates onto the tibial wall, which is the most common type of dislocation. The amount of distraction necessary decreased the further the bearing was from the wall and with 50% posterior overhang. Rotation of the knee did not influence the amount of distraction. In conclusion dislocation can only occur if the lateral compartment is distracted. To reduce the dislocation risk, surgeons should aim to position the femoral and tibial components so that the bearing is as close as possible to the wall without jamming against it and the tibial component should be positioned flush with the posterior tibial cortex. If, during the surgery, the mobile bearing can easily be dislocated onto the wall the surgeon should consider changing to a fixed bearing. The tibial component should also be positioned flush with the posterior tibial cortex, as if it is too far forward this may contribute to dislocation.

PIV mapping of pressure and velocity fields in the plane magnetohydrodynamic Couette flow

We present the first simultaneous mapping of two-dimensional, time-dependent velocity and pressure fields in a plane Couette flow pervaded by a transverse magnetic field. While electromagnetic forces are strongest in fluids of high electric conductivity such as liquid metals, their opacity excludes optical optical measurement methods. We circumvent this difficulty using a transparent electrolyte (Sulfuric acid), whose weaker conductivity is offset by higher magnetic fields. We describe an experimental rig based on this idea, where the Couette flow is entrained by a tape immersed in sulfuric acid and positioned flush onto the bore of large superconducting magnet, so that most of the flow is pervaded by a sufficiently homogeneous transverse magnetic field. Velocity and pressure fields are obtained by means of a bespoke PIV system, capable of recording the fluid's acceleration as well as its velocity. Both fields are then fed into a finite difference solver that extracts the pressure field from the magnetohydrodynamic governing equations. This method constitutes the first implementation of the pressure PIV technique to an MHD flow. Thanks to it, we obtain the first experimental velocity and pressure profiles in an MHD Couette flows and show that the transitional regime between laminar and turbulent states is dominated by near-wall, isolated, anisotropic perturbations.

Latarjet Procedure for the Treatment of Anterior Glenohumeral Instability.

Anterior glenohumeral instability is common, with 21.9 first-time dislocations per 100,000 individuals per year. Recurrent instability is more likely to occur in patients who are younger, of male sex, and have bone defects or ligament laxity. The open Latarjet procedure is effective for the treatment of recurrent anterior glenohumeral instability and is preferred over arthroscopic Bankart repair in the presence of glenoid bone loss. The Latarjet procedure involves transferring the coracoid to the anterior aspect of the glenoid in the following steps. Step 1: Preoperative planning includes an assessment of glenoid deformation and the integrity of the rotator cuff. The degree of bone loss is measured with use of the circle-line method. Step 2: The patient is in the beach-chair position with the arm in a pneumatic arm holder. A parallel drill guide system with 3.75-mm cannulated screws is utilized. Step 3: A 5-to-6-cm incision is made along the anterior axillary line. The deltopectoral interval is established, and the cephalic vein is mobilized laterally. The coracoacromial ligament is transected 15 mm lateral to the coracoid to allow later repair to the anterior capsule. The pectoralis minor is released subperiosteally off the medial coracoid. A 90° oscillating saw is used to transect the coracoid medially to laterally. The coracohumeral ligament is released. Step 4: Two 4.0-mm drill-holes are made 1 cm apart through the coracoid. The undersurface is decorticated. Step 5: The subscapularis is split at the junction of the upper two-thirds and lower one-third. A longitudinal capsulotomy is performed parallel to the glenoid. Step 6: Soft tissue, including the capsule and labrum, is removed from the anterior aspect of the glenoid. The bone is decorticated with an osteotome and a rasp. Step 7: The coracoid is positioned flush or 1 mm recessed relative to the glenoid. Two 1.6-mm guidewires are placed with use of a parallel drill guide followed by a cannulated reamer and two 3.75-mm cannulated screws. Step 8: The coracoacromial ligament is repaired to the capsule. Step 9: The subscapularis split is repaired laterally. The deltopectoral interval and skin are closed in a standard fashion. A standardized rehabilitation protocol is employed postoperatively. The Latarjet procedure results in significantly lower rates of recurrent glenohumeral instability and revision compared with the arthroscopic Bankart procedure (3% and 1% compared with 28.4% and 21%, respectively); however, complication rates as high as 30% have been reported, as well as a risk for nerve injury. The videos included in this article highlight the critical steps required to optimize outcomes and minimize complications when performing the Latarjet procedure.

Arthroscopic Latarjet: Suture-Button Fixation Is a Safe and Reliable Alternative to Screw Fixation

To evaluate mid-term clinical outcomes, complications, bone-block healing, and positioning using suture-button fixation for an arthroscopic Latarjet procedure. Patients with traumatic recurrent anterior instability and glenoid bone loss underwent guided arthroscopic Latarjet with suture-button fixation. We included patients with anterior shoulder instability, glenoid bone loss >20%, and radiographic and clinical follow-up minimum of 24months. Patients with glenoid bone loss <20% or those that refused computed tomography imaging were excluded. Bone-block fixation was accomplished with 2 cortical buttons connected with a looped suture (4 strands). The looped suture was tied posteriorly with a sliding-locking knot. After transfer of the bone block on the anterior neck of the scapula, compression (100N) was obtained with the help of a tensioning device. Clinical assessment was performed at 2 weeks, 3 months, 6 months, and then yearly with computed tomography completed at 2 weeks and 6 months to confirm bony union. A consecutive series of 136 patients underwent arthroscopic Latarjet with 121 patients (89%; mean age 27 years) available at final follow-up (mean follow-up, 26months; range, 24-47months). No neurologic complications or hardware failures were observed; no patients had secondary surgery for implant removal. The transferred coracoid process healed to the scapular neck in 95% of the cases (115/121). The bone block did not heal in 4 patients; it was fractured in 1 and lysed in another. Smoking was a risk factor associated with nonunion (P < .001). The coracoid graft was positioned flush to the glenoid face in 95% (115/121) and below the equator in 92.5% (112/121). At final follow-up, 93% had returned to sports, whereas 4 patients (3%) had a recurrence of shoulder instability. The subjective shoulder value for sports was 94 ± 3.7%. Mean Rowe and Walch-Duplay scores were 90 (range, 40-100) and 91 (range, 55-100), respectively. Suture-button fixation is an alternative to screw fixation for the Latarjet procedure, obtaining predictable healing with excellent graft positioning, and avoiding hardware-related complications. There was no need for hardware removal after suture-button fixation. The systematic identification of the axillary and musculocutaneous nerves reduced risk of neurologic injury. A low instability recurrence rate and excellent return to pre-injury activity level was found. Suture-button fixation is simple, safe, and may be used for both open and arthroscopic Latarjet procedure. Level IV, therapeutic case series.

Analysis of lower limb movement to determine the effect of manipulating the appearance of stairs to improve safety: a linked series of laboratory-based, repeated measures studies

BackgroundFalls on stairs are a common and dangerous problem for older people. This series of studies evaluated whether or not selected changes to the appearance of stairs could make them safer for older people to negotiate.ObjectivesTo determine the effect of (1) a step edge highlighter and its position and (2) an optimised horizontal–vertical (H–V) visual illusion placed on a step riser on gait safety during stair descent and ascent.DesignA series of studies using a repeated measures, laboratory-based design, investigating gait control and safety in independently mobile older people.SettingThe University of Bradford Vision and Mobility Laboratory.ParticipantsFit and healthy older people aged 60 years of age or more, independently mobile, reasonably active and with normal healthy eyes and corrected vision.InterventionsA step edge highlighter in a variety of offsets from the stair edge and an optimised H–V visual illusion placed on the stair riser. The H–V illusion was provided on a staircase by horizontal step edge highlighters on the tread edges and vertical stripes on the step risers.Main outcome measuresGait parameters that are important for safe stepping in ascent and descent, particularly toe clearance during stair ascent and heel clearance during stair descent.ResultsThe step edge highlighter increased the precision of heel clearance during stepping and its positioning relative to the tread edge determined the extent of heel clearance over the tread edge. Positioning the highlighter away from the tread edge, as is not uncommonly provided by friction strips, decreased heel clearance significantly and led to greater heel scuffs. Although psychophysics experiments suggested that higher spatial frequencies of the H–V illusion might provide greater toe clearance on stair ascent, gait trials showed similar increased toe clearances for all spatial frequencies. When a 12 cycle per step spatial frequency H–V illusion was used, toe clearance increases of approximately 1 cm (17.5%) occurred without any accompanying changes in other important gait parameters or stability measures.ConclusionsHigh-contrast tread edge highlighters present on steps and stairs and positioned flush with the edge of the tread or as near to this as possible should improve stair descent safety in older people. A H–V illusion positioned on the riser of a raised surface/walkway (e.g. kerbs) and/or the top and/or bottom of a stairway is likely to increase foot clearance over the associated step/stair edge, and appears not to lead to any decrement in postural stability. Thus, their use is likely to reduce trip risk and hence improve stair ascent safety. The effect of the step and stair modifications should be assessed in older people with visual impairment. The only other remaining assessment that could be made would be to assess fall prevalence on steps and stairs, perhaps in public buildings, with and without these modifications.FundingThe National Institute for Health Research Public Health Research programme.

What you see is what you step: the horizontal-vertical illusion increases toe clearance in older adults during stair ascent.

Falls on stairs are a significant cause of morbidity and mortality in elderly people. A simple safety strategy to avoid tripping on stairs is increasing foot clearance. We determined whether a horizontal-vertical illusion superimposed onto stairs to create an illusory perceived increase in stair-riser height would increase stair ascent foot clearance in older participants. Preliminary experiments determined the optimum parameters for the horizontal-vertical illusion. Fourteen older adults (mean age ± 1 SD, 68.5 ± 7.4 years) ascended a three-step staircase with the optimized version of the horizontal-vertical illusion (spatial frequency: 12 cycles per stair riser) positioned either on the bottom or top stair only, or on the bottom and top stair simultaneously. These were compared to a control condition, which had a plain stair riser with edge highlighters positioned flush with each stair-tread edge. Foot clearance and measures of postural stability were compared across conditions. The optimized illusion on the bottom and top stair led to a significant increase in foot clearance over the respective stair edge, compared to the control condition. There were no significant decreases in postural stability. An optimized horizontal-vertical visual illusion led to significant increases in foot clearance in older adults when ascending a staircase, but the effects did not destabilize their postural stability. Inclusion of the horizontal-vertical illusion on raised surfaces (e.g., curbs) or the bottom and top stairs of staircases could improve stair ascent safety in older adults.

Safety on stairs: Influence of a tread edge highlighter and its position

BackgroundFalls sustained when descending stairs are the leading cause of accidental death in older adults. Highly visible edge highlighters/friction strips (often set back from the tread edge) are sometimes used to improve stair safety, but there is no evidence for the usefulness of either. ObjectiveTo determine whether an edge highlighter and its location relative to the tread edge affect foot placement/clearance and accidental foot contacts when descending stairs. MethodSixteen older adults (mean±1SD age; 71±7years) with normal vision (experiment 1) and eight young adults (mean±1SD age; 24±4years) with visual impairment due to simulated age-related cataract (experiment 2) completed step descent trials during which a high contrast edge highlighter was either not present, placed flush with the tread edge, or set back from the edge by 10mm or 30mm. Foot placement/clearance and the number of accidental foot contacts were compared across conditions. ResultsIn experiment 1, a highlighter set back by 30mm led to a reduction in final foot placement (p<0.001) and foot clearance (p<0.001) compared to a highlighter placed flush with the tread edge, and the percentage of foot clearances that were less than 5mm increased from 2% (abutting) to 17% (away30). In experiment 2, a highlighter placed flush with the tread edge led to a decrease in within-subject variability in final foot placement (p=0.004) and horizontal foot clearance (p=0.022), a decrease in descent duration (p=0.009), and a decrease in the number of low clearances (<5mm, from 8% to 0%) and the number of accidental foot contacts (15% to 3%) when compared to a tread edge with no highlighter present. ConclusionsChanges to foot clearance parameters as a result of highlighter presence and position suggest that stairs with high-contrast edge highlighters positioned flush with the tread edge will improve safety on stairs, particularly for those with age-related visual impairment.

Impact of Body and Clothing on a Wearable Textile Dual Band Antenna at Digital Television and Wireless Communications Bands

A dual band textile antenna designed for Digital Television (DTV) and many wireless standards including GSM 900, WLAN 2.45/5.8 GHz, Wimax 3.5 GHz, Hyperlan 5.2 GHz and UMTS-LTE-advanced is described. The impact of the body on antenna performance is assessed for return loss, radiation patterns and antenna efficiency in a wide frequency range. Full three dimensional radiation patterns were measured with the antenna backed by a phantom in order to simulate a human body. While the return loss was found to be only marginally affected when the antenna was mounted at various positions on the human body, the measured efficiency was observed to decrease by up to 90% when the antenna was positioned flush to the phantom. The return loss response was little affected when the antenna was worn on the back and further covered with a number of garments including a thick woolen jumper and a ski jacket. Although antenna efficiency was substantially affected by the presence of the body, interposing a layer of felt fabric between the antenna and the phantom typically improved efficiency by over 50%. This unique soft antenna is a good candidate for receiving digital television and wireless communications in a smart clothing environment.

An instrument for measuring heat flux from an isothermal surface

This paper describes an instrument for measuring heat flux distribution on an isothermal surface. The isothermal surface consisted of walls made from thick-walled copper block with high thermal conductivity and heated by cartridge heaters. The heaters were inserted inside the copper block and were separately controlled by a proportional–integral–derivative (PID) control system to create a uniform wall temperature boundary condition on the surface to within ±0.2 °C. A specially designed balance type heat flux sensor was positioned flush with the surface of the heated copper block to enable measurement of the local time-average heat flux at various positions along an isothermal surface. This isothermal heat flux sensor consisted of a thin and narrow nickel/chromium ribbon embedded in, but thermally and electrically insulated from, the heated copper block walls on all sides. Differential thermocouples were mounted on the ribbon to measure differences in temperature between the ribbon and the wall at various positions along the ribbon. An uncertainty analysis revealed that the sensor had a heat flux uncertainty of 6.62% for a convective heat flux of 120 W/m 2. The instrument was tested for a laminar slot-jet impinging on the isothermal wall and the experimental results were in a good agreement with the numerical data.

Arthroscopic Grafting of Chondral Defects and Subchondral Cysts of the Acetabulum

We present a novel arthroscopic-assisted technique to graft chondral defects and subchondral cysts of the acetabular socket using a synthetic osteochondral plug. Four patients with groin pain, solitary cysts in the roof of the acetabulum and radiographic evidence of early osteoarthritis were treated. A bone tunnel was prepared from the region of the iliac crest to the acetabular articular surface. A synthetic osteochondral plug was inserted in an ante-grade fashion and positioned flush with the lunate articular cartilage. The minimum follow-up from surgery was 8 months (mean 10 months, range 8 to 11 months). There were no peri-operative complications related to the procedure. All patients reported an improvement in symptoms and function at the latest follow-up. One of the patients underwent a re-look arthroscopy at 5 months for persistent dull groin and buttock pain. Capsular adhesions of the labrum were identified and released. The mean non-arthritic hip score improved from 53.8 (range 43.8 to 70) pre-operatively to 84.6 (range 78.8 to 87.5) at 6 months. Computed tomography and magnetic resonance imaging at 6 months confirmed the stability of the osteochondral plugs and on-going healing. This procedure offers an arthroscopic means to treat patients with solitary acetabular cysts and may prove effective for chondral grafting of denuded acetabular areas in early to moderate degenerative hip disease.

An Extreme Surface Proximity Push for Embedded SiGe in pMOSFETs Featuring Self-Aligned Silicon Reflow

This letter proposes a novel process to modulate the distance, or proximity, between the tip of embedded silicon–germanium (e-SiGe) and the channel region in pMOSFETs. Traditionally, sophisticated etching treatment is adopted in a spacer structure; however, process-induced variation in the e-SiGe proximity may lead to serious variation in pMOSFET performance. In this letter, an extremely close proximity is achieved using self-aligned silicon reflow (SASR) in hydrogen ambient. As opposed to conventional approaches which have e-SiGe proximity determined by spacer width, the tip of e-SiGe with SASR can be positioned flush with the gate edge, as corroborated by both the TEM analyses and TCAD simulation. A significant improvement in pMOSFET performance is also measured.

Design and characterization of a laminar flow-through dissolution apparatus: Comparison of hydrodynamic conditions to those of common dissolution techniques

A flow-through dissolution apparatus was designed and evaluated to screen small quantities of pharmaceutical drug compounds early in development. The apparatus was designed to mount on a microscope slide such that a compacted solid drug was positioned flush along one wall and the fluid flow in the apparatus was laminar flow in a rectangular duct. Stereomicroscopic digital images and Raman spectra of the solid were taken during dissolution and the effluent dissolution medium was collected in fractions to determine the dissolution rate by fluorescence or HPLC/UV. Three compounds, triamterene, ketoprofen, and β-naphthoic acid were investigated in the dissolution flow cell at various hydrodynamic conditions. In conditions where no solvent-mediated conversion was expected, there was a decrease in dissolution rate with time in the flow through cell that was associated with surface smoothing. This phenomenon also occurred in rotating disk experiments. In either case, the magnitude and time course of the decrease in dissolution rate with time is generally different enough to distinguish from the decrease in dissolution rate due to solvent-mediated conversion.

Micro-hot-embossing of 316L stainless steel micro-structures

In this paper, the fabrication of an array of 316L stainless steel cylindrical micro-structures by hot-embossing is studied. The effects of various embossing parameters on the filling of the micro-cavities of silicon mold insert and the demolding of micro-structures are investigated. They include different silicon mold insert configurations, embossing pressure, embossing temperature, embossing time and the thickness of embossing substrate on which the micro-structures stand. Two types of silicon mold insert configurations are investigated. Hot-embossing study with the silicon mold insert attached on the upper mold plate shows that it is not feasible to achieve complete filling. Incomplete filling occurs and increasing the embossing pressure causes excessive thinning of the embossing substrate, so that micro-structures are torn off during demolding. Experiments show that the configuration that the silicon mold insert is positioned flush with lower mold surface improves complete filling. Using suitable embossing pressure and temperature, the larger substrate thickness and longer embossing time ensure the fabrication of defect-free fully filled micro-structures.

Porous plug gas injection systems for studies of hydrocarbon dissociation and transport in the DIII-D tokamak

A probe has been designed, constructed, and successfully used to inject methane into the DIII-D lower divertor in a manner imitating natural release by chemical erosion. This porous plug injector (PPI) probe consists of a self-contained gas reservoir with an integrated pressure gauge and a 3 cm diameter porous surface through which gas is injected into the lower divertor of the tokamak. The probe is positioned flush with the divertor target surface by means of the divertor materials evaluation system. Two gas delivery systems were developed: in the first, gas flow is regulated by a remotely controlled microvalve and in the second by a fixed micro-orifice flow restrictor. Because of the large area of the porous surface through which gas is admitted, the injected hydrocarbon molecules see a local carbon surface (>90% carbon) similar to that seen by hydrocarbons being emitted by chemical sputtering from surrounding carbon tiles. The distributed gas source also reduces the disturbance to the local plasma while providing sufficient signal for spectroscopic detection. In situ spectroscopic measurements with the PPI in DIII-D allow the direct calibration of response for measured plasma conditions from a known influx of gas.

Measurement of charge distribution around a rising bubble in a 2-D fluidized bed

A technique has been developed to determine the charge distribution around single rising bubbles in a two-dimensional fluidized bed. Four induction probes positioned flush with the outside wall of the column and connected to charge amplifiers record induced charge signals as bubbles pass. The charge distribution surrounding a single bubble is then reconstructed with the assumption that the bubble is symmetrical and that the charge around the bubble remains constant as it rises. The emulsion phase far from the bubble in a two-dimensional fluidized bed of glass beads was found to be charged negatively and, contrary to our previous assumptions, the charge density decreased gradually toward the bubble-dense phase interface, with a nearly zero charge density inside the bubble. The wake of the bubble is more negatively charged than the emulsion phase, supporting our previous speculations. © 2005 American Institute of Chemical Engineers AIChE J, 2006

Effects of bone block position and orientation within the tibial tunnel for posterior cruciate ligament graft reconstructions: a cyclic loading study of bone-patellar tendon-bone allografts.

Posterior laxity occurring after posterior cruciate ligament reconstruction with a tibial tunnel could be related to thinning and permanent elongation of the graft as it is cyclically loaded in vivo. The orientation and position of the bone block within the tibial tunnel will have a significant effect on thinning and elongation of the graft after cyclic loading. Controlled laboratory study. In test series 1 (27 fresh-frozen graft pairs), all bone blocks were positioned flush with the posterior opening of the tibial tunnel; 1 graft was oriented with the bone block facing posteriorly, whereas its pair was tested with the bone block facing anteriorly. In test series 2 (20 graft pairs), all grafts were oriented with the bone block facing posteriorly; 1 graft had the bone block positioned flush with the posterior tunnel opening, whereas its pair was tested with the bone block recessed 1 cm from the posterior opening. In series 1, 3 of 27 grafts with posterior bone block orientations failed at the tunnel edge before 2000 cycles of testing could be completed; all specimens with anterior bone block placements survived the testing intact. In series 2, 3 of 20 grafts with recessed bone blocks failed at the tunnel edge, whereas all those with flush bone blocks survived. The best position for the bone block of a bone-patellar tendon-bone graft was flush with the posterior tunnel opening with the bone block facing anteriorly in the tibial tunnel.

Comparative morphology of the peritremes of Varroa and Euvarroa (Varroidae), parasites of honey bees (Apidae)

The morphology of the peritremes of the genera Varroa and Euvarroa in the family Varroidae are described. In the genus Varroa, the moveable emergent peritreme lies flat along the venter laterad of legs III and IV but can be lowered 90° as necessary. The sclerotized peritremal groove consists of an ascending and a shorter descending arm thus forming a hook around the tip of the peritreme. The interior of the groove and stigmatal atrium are lined with micropapillae (=microtricheae). The remainder of the peritreme is a sac-like structure that is continuous with the body hemocoel. The peritreme of Euvarroa does not appear to be moveable or only slightly so and is positioned flush with the soft cuticle of the body laterad and somewhat posterior to legs IV. The sclerotized peritrematic groove is U-shaped and lined with micropapillae. The stigmata are open but are not continuous with the peritrematic groove as in Varroa.

Human auditory system response to pulsed radiofrequency energy in RF coils for magnetic resonance at 2.4 to 170 MHz

The threshold conditions for an auditory perception of pulsed radiofrequency (RF) energy absorption in the human head have been studied on six volunteers with RF coils for magnetic resonance (MR) imaging. For homogeneous RF exposure with MR head coils in the 2.4- to 170-MHz range and pulse widths 3 microseconds less than or equal to Tp less than 100 microseconds, the auditory thresholds were observed at 16 +/- 4 mJ pulse energy. Localized RF exposure with optimized surface coils positioned flush with the ear lowers the auditory threshold to only 3 +/- 0.6 mJ. The hearing threshold of RF pulses with Tp greater than 200 microseconds occurs at more or less constant peak power levels of typically 150 +/- 50 W for head coils and as low as 20 W for surface coils. The results from this study confirm theoretical predictions from a thermoelastic expansion model and compare well with reported thresholds from near field antenna measurements at 425 to 3000 MHz. Details of the threshold dependence on RF pulse length reveal primary sites of RF to acoustic energy conversion at the mastoid and temporal bone region and the outer layer of the brain from where thermoelastically generated pressure transients excite audible pressure waves at the resonance modes of the skull around 1.7 kHz and of the brain around 11 kHz. If not masked by usually dominating noise from switched gradients, the conditions for hearing RF pulses, as applied to head coils in MR studies with flip angle alpha at main field B0, is given by Tp/ms less than or equal to 0.4 (alpha/pi)B0/[T]. At peak power levels up to 15 kW presently available in clinical MR systems, there is no evidence known for detrimental health effects arising from the RF auditory phenomenon which is a secondary cause associated with primary RF to thermal energy conversion in body tissues. To avoid the RF-evoked sound pressure levels in the head rising above the discomfort threshold at 110 dB SPL, an upper limit of 30 kW applied peak pulse power is suggested for head coils and 6 kW for surface coils.

Neuromast topography in anuran amphibians.

Generalized anuran tadpoles across families exhibit a similar neuromast morphology on their heads, as follows: (1) all neuromast lines known for anurans are present; (2) within these lines total neuromast number ranges from about 250 to 320; (3) neuromasts form linear stitches composed of two to three, but sometimes up to five, neuromasts; (4) neuromast linear dimensions are ⩽ 10 μm; and (5) neuromasts contain ⩽ 15 hair cells. Compared with generalized forms, stream, arboreal, carnivorous, and desert-pond forms have fewer neuromasts but they contain more hair cells. They do not, however, form stitches. Obligate midwater suspension-feeding forms, including Xenopus (Pipidae), Rhinophrynus (Rhinophyrnidae), and Phrynomerus (Microhylidae), form stitches that contain > six, but potentially up to 18 or more, loosely aggregated neuromasts. Xenopus and Rhinophrynus have large neuromasts (up to 40 μm across). Chiasmocleis (Microhylidae) tadpoles form stiches that are linearly arranged with up to ten neuromasts. Whereas urodeles can have more than one neuromast row per line and may form both linear and transverse stitches, anurans have only one row of neuromasts per line and form only transverse stitches. Neuromasts in anurans tend to be smaller and more circular than in urodeles and positioned flush with the epidermal surface. A greater percentage of anurans form stitches, and anurans have greater intrafamilial variation in stitch formation than do urodeles.

Convective Heat Transfer From a Desert Surface

The convective heat transfer relations for atmospheric flow over sparsely vegetated areas are reviewed and compared to existing relations for flow in rough ducts. Experimental convection coefficients obtained at four desert sites are compared to the analytical relations. The experimental equipment for measuring the heat transfer convection coefficient between air and ground in a desert environment consists of two electrically heated plates positioned flush with the ground. Measurements of power dissipation and surface temperatures allow direct calculation of the convection coefficient. The experimental heat transfer results are correlated with micrometeorological models from which a soil roughness height is calculated. This roughness parameter is shown to characterize air flow near the soil surface, and may be significantly different from the roughness parameter ordinarily determined from velocity profiles. A simplified heat transfer correlation is presented for desert surfaces.