Rim Length Research Articles

Rim Effects in the Adsorption of CO2 on Silica-Supported Copper Oxide Clusters: Identifying Active Sites Utilizing Electron Beam Lithography

Electron beam lithography (EBL) was used to nanofabricate so-called model-nanoarray catalysts, which consist of a predetermined lattice of clusters. In doing so, 12, 35, and 63 nm Cu clusters, supported on silica, were studied by experimental surface science techniques. The Cu EBL clusters were subsequently oxidized to CuOx, as characterized by X-ray photoelectron and Auger electron spectroscopy, respectively. The catalytic activity of these clusters was probed by thermal desorption spectroscopy and supersonic molecular beam scattering. CO2 was used as the probe molecule because it is part of the syngas for the industrial methanol synthesis that utilizes copper-based catalysts. CO2 adsorption is molecular and nonactivated. Adsorption transients were recorded as a function of surface temperature and CO2 impact energy. The transients are consistent with precursor models, as expected from the so-called capture zone (CZ) model. Cluster size effects are evident, in agreement with the CZ model. Unexpectedly, the CO2 saturation coverage does not simply scale with the clusters’ area but rather with the rim length of the clusters. Therefore, the active sites for CO2 adsorption (rim sites) were identified using a simple kinetics technique and EBL-fabricated model catalysts.

Adsorption Dynamics of CO on Silica Supported CuOx Clusters: Utilizing Electron Beam Lithography To Study Methanol Synthesis Model Systems

Electron beam lithography was used to nanofabricate 12 and 63 nm Cu clusters supported on silica (model nanoarray catalysts). The Cu clusters could reversibly be oxidized and reduced at ultrahigh vacuum conditions. The chemical activity of these clusters was probed by Auger and X-ray photoelectron spectroscopy, thermal desorption spectroscopy, and molecular beam scattering. CO was used as the probe molecule. Scanning electron microscopy was used to obtain cluster size distributions. CO adsorption is molecular and nonactivated. CO binding energies on the oxidic clusters are larger than for the metallic clusters. Adsorption transients, recorded as a function of surface temperature and CO impact energy, are consistent with precursor models, as expected from the so-called capture zone model (CZM). Cluster size effects are evident, as predicted by the CZM. However, unexpectedly, the CO saturation coverage does not simply scale with the cluster area but depends also on the rim length of the deposits. Metallic Cu clusters are more reactive than oxidic clusters, in part not only due to the cluster size effect but apparently also because of the electronic effect.

298 Percutaneous closure of atrial septal defects in children: what are the predictive factors of success?

Percutaneous atrial septal defect (ASD) closure is now a safe and efficient alternative to surgery in adults. In paediatric population, its feasibility is still uncertain and limited in young children with large defect. Our aim was to determine predictive factors of success of percutaneous ASD closure in this population. All patients less than 12 years-old who underwent an attempt of a percutaneous ASD closure using Amplatzer septal occluder device were retrospectively reviewed. We analysed by echocardiography ASD diameter, length of rims surrounding, length of atrial septum, and during catheterization balloon-stretched diameter. ASD area was calculated and normalized to the body surface area of patients. The procedure was abandoned when the device placement failed after three attempts. 140 patients (age 7.7 ± 2.5 years, weight 25.3 ± 9 kg) were included. Echocardiographic ASD diameter was 15 ± 4.1 mm, balloon-stretched diameter 19.8 ± 4.7 mm, length of atrial septum 34.8 ± 5.9 mm, diameter of implanted device 18.6 ± 4.3 mm. All rims surrounded ASD measuring at least 3 mm. Percutaneous closure was successfully performed in 131 patients and failed in 8 patients. One device embolization into right atria occurred without any complication leads to surgery. Predictive factors of success included smaller ASD echocardiographic and balloon-stretched diameters (14.6 ± 3.8 vs 19.9 ± 4.4 mm, p<0.001 and 19.0 ± 0.6 vs 25.6 ± 6.3 mm, p<0.001), smaller ratio ASD area/body surface area (338 ± 139 vs 569 ± 210, p<0.05), smaller device size (18.3 ± 3.9 vs 22.4 ± 5.7 mm, p<0.05), and smaller gap between balloon-stretched and implanted device diameters (−1.0 ± 0.6 vs 3.1 ± 2.8 mm). Percutaneous ASD closure using Amplatzer device is feasible and safe in most of children. Small ASD and an appropriate size device are predictive of success. In the larger ASD and in the younger patients, normalization of ASD area to body surface area may help to choice the best treatment.

Assessment of atrial septal defect size and residual rim using real-time 3D transesophageal echocardiography

Accurate preoperative determination of defect location and size is important for successful transcatheter closure of atrial septal defects (ASD). Real-time 3D transesophageal echocardiography (3DTEE) has the potential to delineate the shape of ASD in 3D space. Full volume and 3D zoom datasets by 3DTEE were acquired in 17 ASD patients. Using quantitative software, maximal/minimal diameter, defect area and residual rim length were measured and compared to the standard 2D measurements. Real-time 3DTEE allowed delineation of the en-face view of the ASDs. The defect typically had an oval shape, and its size changed dynamically, having its minimal size at end-diastole and maximal at end-systole. A good correlation was noted between the maximal defect area by 3DTEE and 2DTEE (r=0.93, p<0.001). Successful delineation of rim length to the specific cardiac structure was 100% by 3DTEE and 88% by 2DTEE. There was a fair correlation of residual rim length between 3DTEE and 2DTEE (r=0.69, p<0.001). Eight patients underwent transcatheter closure of the ASD. Excellent correlation was noted between 3D-derived maximal defect diameter and device diameter (r=0.97, p<0.001). Real-time 3DTEE allows measurements of the temporal and spatial changes of ASD size and shape. This methodology provides detailed information on defect dynamics.

Relationship of Retinal Vascular Caliber with Optic Disc and Macular Structure

To examine the relationships of retinal vascular caliber with optic disc, macular, and retinal nerve fiber layer (RNFL) characteristics as measured with optical coherence tomography (OCT). Observational cross-sectional study. This study included a subset of healthy children enrolled in the Singapore Cohort Study of the Risk Factors of Myopia (SCORM). Optic disc, macular, and RNFL morphology were measured with Stratus OCT 3. Digital retinal photography was performed and retinal arteriolar and venular caliber measured using validated imaging software. One hundred and four children (mean age 11.51 +/- 0.52 years; 50% male) were included. In multivariate analyses, smaller horizontal integrated rim width and rim area were associated with narrower retinal arterioles and venules (all P < .05), and shorter horizontal rim length was associated with narrower venules (P = .04). Optic disc diameter was not associated with arteriolar or venular caliber. Larger vertical cup-to-disc ratios and cup-to-disc-area ratios were associated with narrower venules but not arterioles (P = .01 and P = .003, respectively). A thinner average RNFL measurement was associated with narrower arterioles and venules, and smaller total macular volume was associated with narrower venules. Thinner optic disc rims and RNFL measurements were associated with narrower retinal arterioles and venules, and larger cup-to-disc ratios with narrower venules. These findings suggest that retinal vessel caliber varies systematically with morphologic differences in the optic nerve head, retina, and macula.

Orbicularis Oculi Myocutaneous Advancement Flap for Upper Eyelid Reconstruction

Reconstruction of large full-thickness defects of the upper eyelids is challenging because of their complex anatomy and specialized functions. The authors present and discuss a new, simple surgical technique for upper eyelid reconstruction. This is a single-stage procedure and has produced satisfactory to excellent results in the authors' patients. It presents the reconstructive surgeon with several advantages over other techniques. The eyelid tumor is excised surgically until clear margins are obtained. The V-shaped orbicularis oculi myocutaneous advancement flap is marked on the remaining superior eyelid tissue and mobilized, leaving the base of the pedicle intact with submuscular tissue attachment. Posterior lamella reconstruction is performed with mucoperiosteal graft harvested from the hard palate in patients with full-thickness defects. Then, the flap is advanced to the defect and the donor site is closed primarily. Eight patients, aged 17 to 72 years, have been operated on with this technique for upper eyelid reconstruction. Follow-up included assessment of position, closure, length of palpebral rim, eyelid opening, aesthetic balance, presence of corneal erosion, ulcer or entropion, levator function, and donor-site morbidity. The flap was viable in every patient, without total or partial necrosis. No patient required surgical revision. The oncologic result was good, and no recurrence was noted. This method is a simpler, single-stage operation; does not damage the lower lid; provides a thin, mobile eyelid; and, above all, is less invasive than other techniques, and at the same time allows a good functional and aesthetic reconstruction.

Changes in Anthropometric Values of Paired Craniofacial Measurements of Patients With Right Coronal Synostosis

Quantitative changes of the 5 paired (right and left) projective linear measurements of the craniofacial complex were analyzed by anthropometric methods in 26 patients (9 males and 17 females) with right coronal synostosis, 16 in infancy (0-5 and 6-12 months) and 10 in early childhood (1-10 years). Measurements were taken from 3 regions: the supraorbital rim length of the head (t-g), the length (en-ex) and height (ps-pi) of the eye fissures in orbits, and the width (pra-pa) and length (sa-sba) of the ears. None of the patients had undergone corrective surgery.Anthropometric analysis of patients in infancy showed a large percentage of subnormal supraorbital rim lengths (t-g) on the right side of the head, with a higher frequency in females (90.9%) than in males (80.0%). Eye fissure lengths (en-ex) were subnormal more often in males than in females on both sides, while heights were generally normal bilaterally in both sexes (72.7-100% of cases). Ears of normal width (pra-pa) and length (sa-sba) were more frequent in females. In males, the frequency of subnormal ear widths and lengths surpassed those in females. The most remarkable changes between infancy and early childhood were noted in the orbital region, in which subnormal eye fissure lengths became bilaterally normal in both sexes.

Optimization of the artificial urinary sphincter: modelling and experimental validation

The artificial urinary sphincter should be long enough to prevent strangulation effects of the urethral tissue and short enough to avoid the improper dissection of the surrounding tissue. To optimize the sphincter length, the empirical three-parameter urethra compression model is proposed based on the mechanical properties of the urethra: wall pressure, tissue response rim force and sphincter periphery length. In vitro studies using explanted animal or human urethras and different artificial sphincters demonstrate its applicability. The pressure of the sphincter to close the urethra is shown to be a linear function of the bladder pressure. The force to close the urethra depends on the sphincter length linearly. Human urethras display the same dependences as the urethras of pig, dog, sheep and calf. Quantitatively, however, sow urethras resemble best the human ones. For the human urethras, the mean wall pressure corresponds to (−12.6 ± 0.9) cmH2O and (−8.7 ± 1.1) cmH2O, the rim length to (3.0 ± 0.3) mm and (5.1 ± 0.3) mm and the rim force to (60 ± 20) mN and (100 ± 20) mN for urethra opening and closing, respectively. Assuming an intravesical pressure of 40 cmH2O, and an external pressure on the urethra of 60 cmH2O, the model leads to the optimized sphincter length of (17.3 ± 3.8) mm.

Total and Subtotal Upper Eyelid Reconstruction with the Nasal Chondromucosal Flap: A 10-Year Experience

The authors review their 10-year experience with the nasal chondromucosal flap for total and subtotal upper eyelid reconstruction. After several modifications, the flap is now designed along the lateral nasal wall and is based on the terminal branch of the dorsal nasal artery, to include the subcutaneous tissues down to the periosteum and the cranial portion of the upper lateral cartilage. A skin graft is applied for cutaneous coverage. The flap can be harvested unilaterally or contralaterally. Fifteen patients, aged 50 to 75 years, have been operated on with this technique for total or subtotal defects of the upper eyelid since 1993. Follow-up included assessment of position, closure, presence of epiphora, length of palpebral rim, eyelid opening, levator function, aesthetic balance, and donor-site morbidity. The flap result was viable in every patient, without total or partial necrosis. Static parameters were within normal ranges, and 8 to 18 mm of levator function (mean, 13 mm) was achieved. Compared with other frequently used techniques, namely, the Cutler-Beard advancement flap and the Mustarde lid switch flap, this procedure is a one-stage operation, does not damage the lower lid, and provides a thin, mobile eyelid with an anatomically complete reconstruction. The nasal chondromucosal flap has thus become the authors' standard for large full-thickness defects of the upper lid.

Absent posteroinferior and anterosuperior atrial septal defect rims: factors affecting nonsurgical closure of large secundum defects using the amplatzer occluder

Using transesophageal echocardiography, we sought to determine the anatomic characteristics of the secundum atrial septal defects (ASDs) that extend into the inferior sinus venosus and have no posteroinferior (PI) rim, to determine the factors related to potential closure with an Amplatzer occluder. We also sought to understand why large secundum ASDs with a PI but without an anterosuperior (AS) rim may require special techniques to reorient the left atrial disk before deployment of the waist and right atrial disk. We measured the lengths of 5 separate rims of the circumferences of 76 secundum ASDs, including anteroinferior, AS, superior, posterosuperior, and PI rims. We also measured anteroposterior and superoinferior defect diameters, total septal lengths, and the ratios of defect diameter to total septal length. The atrial depth was measured at the axial angle of the delivery sheath in 5 defects with no AS rim for which special techniques were required to achieve successful closure. Of 76 secundum ASDs, 13 (17%) had no PI rim. Each defect extended from the fossa ovalis into the inferior sinus venosus. Compared with defects with a PI rim, the factors related to potential closure included 100% larger defect diameters, shorter posterosuperior rim lengths, larger defect to total septal length ratios, and completely flat posterior atrial walls. When the AS rim was absent the factors related to the need for special techniques included diameters ≥ 22 mm, atrial depth < the calculated Amplatzer occluder left atrial disk diameter, rigid wire/disk interface, and obligatory left atrial disk orientation more or less perpendicular to the atrial septal plane.

Transesophageal Echocardiography to Evaluate Success of Transcatheter Closure of Large Secundum Atrial Septal Defects in Adults Using the Buttoned Device

To determine the success rate of transcatheter closure of secundum atrial septal defects (ASDs) in adults and to characterize anatomical structures predisposing to unsatisfactory results. Preinterventional and follow-up transesophageal echocardiography of 17 consecutive patients treated with a Sideris buttoned device was reviewed. Residual jet size of 5 mm or smaller was considered an adequate result; jet size larger than 5 mm was inadequate. Maximal ASD diameter, ASD area, and anterior, posterior, superior, and inferior septal rims were measured. The 7 patients with adequate results (41%) had smaller defects before implantation of a buttoned device (mean +/- SD maximal ASD diameter, 12 +/- 4 vs 19 +/- 5 mm; P<.005). Total rim length (mean +/- SD) was longer in patients with an adequate result (71 +/- 8 vs 46 +/- 11 mm; P<.001). The ASD size and length of the superior septal rim were independent predictors for an adequate result. Only 3 patients, all with ASD diameter less than 13 mm, had completely closed defects. All patients with ASD diameter greater than 20 mm had inadequate results and an unsatisfactory device position. The defect size (mean +/- SD) was similarly reduced in patients with adequate and inadequate results (9 +/- 3 vs 8 +/- 4 mm). Adults with a small ASD are more likely to have an adequate result after treatment with the buttoned device. A sufficiently large superior septal rim is particularly important for an adequate result. Most patients with a large ASD have inadequate results, although their ASD size is reduced by a similar absolute area as in patients with an adequate result.

Crystallization and gravitationally controlled ponding during the formation of mound springs, terraces, and “black smoker” flanges

We present a series of laboratory experiments in which hot, dense aqueous solutions were cooled and crystallized by contact with cold ambient solutions as they flowed on horizontal, sloping, or nearly vertical boundaries. In each case, the crystals grew to form “dams” on the boundary, behind which the input fluid ponded before overflowing the rim. On a sloping boundary, simultaneous crystallization of a number of dams led to the growth of terraces that are reminiscent of natural travertine and sinter terraces. This phenomenon is not critically dependent on the composition, concentration, or flow rate of the fluid. If the fluid overflowing the rim becomes undersaturated, uniform crystallization is replaced by dissolution that soon focuses at one point of the rim, leading to a “breakout” of the ponded fluid. In an appendix, we also examine quantitatively the flow of water over the rim of mound springs and terraces and show that surface tension can determine both the two‐dimensional volume flow rate and the length of rim overflowed.

Root stresses of thin-rimmed spur gears with spokes.

This paper presents a study on root stresses of thin-rimmed. spur gears with spokes. The stress analysis by the 2.dimensional finite element method (FEM) and static loading test for thin-rimmed spur gears with a fan-shaped hole were carried out, and the effects of the rim thickness and the rim length on the root stress and the position of the maximum root stress were examined. Root stresses of thin-rimmed spur gears with spokes were computed by FEM, and the relation between the root stress and the position of the loaded tooth, the effect of number of spokes on the root stress, the position of the maximum root stress and the stress change during one revolution were investigated. Furthermore the tooth deflection of a spoked gear was also examined.

The Effective Emitter Area of Power Transistors

The theoretical derivation in this paper is concerned first with the determination of an effective emitter area for a transistor with cylindrical geometry. From this it follows that out of the total emitter area only the border region in a width of one diffusion length is effective. This result is applied to a geometry of concentric emitter and base rings, each being considerably broader than two diffusion lengths. For comparing theory and experiment in such a geometry, different emitter rim lengths are realized easily when the different base rings are connected successively with one another and the emitter rings are also treated in the same manner. Theory and experiments agree. As a second theoretical contribution, the Appendix contains a rigorous solution for a special three-dimensional transistor model.