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Accuracy of Stereolithography Parts: Mechanism and Modes of Distortion for a "Letter-H" Diagnostic Part
Rapid Prototyping and Manufacturing (RP&M) users need to compare the accuracy of various
commercially available RP&M materials and processes. A good diagnostic test for both material and the
fabrication process involves a 4-inch long "letter-H" diagnostic part. This diagnostic part, known as "H-4", was
developed to measure the inherent dimensional characteristics ofvarious RP&M build materials. It is also less
dependent on the calibration status of particular RP&M machines, and is excellent for the purpose of generating
simple but meaningful accuracy information, which can be used to further understand the mechanism and the
modes of distortion in RP&M materials. H-4 parts were prepared and built in Stereolithography Apparatus (SLA)
using Ciba-Geigy epoxy based resins SL 5170 and SL 5180, and results were compared to acrylate based SL 5149.
Experimental data involving the magnitude, mechanism, and the modes of distortion for these three resins are
analyzed in this paper.Mechanical Engineerin
Endoscopic versus open subfascial division of incompetent perforating veins in the treatment of venous leg ulceration: A randomized trial
AbstractPurpose: Subfascial division of incompetent perforating veins plays an important role in the surgical treatment of patients with venous ulceration of the lower leg. To minimize the high incidence of postoperative wound complications after open exploration, endoscopic approaches have recently been developed. We carried out a prospective, randomized comparison of open and endoscopic treatment of these patients that was aimed at ulcer healing and postoperative wound complications. Methods: Patients with current venous ulceration on the medial side of the lower leg were randomly allocated to open exploration by the modified Linton approach or endoscopic exploration by use of a mediastinoscope. Results: Thirty-nine patients were randomized, 19 to open exploration and 20 to endoscopic exploration. The incidence of wound infections after open exploration was 53%, compared with 0% in the endoscopic group (p < 0.001). Patients in the open group needed longer hospital stays (mean, 7 days; range, 3 to 39 days) than patients in the endoscopic group (mean, 4 days; range, 2 to 6 days; p = 0.001). Four months after operation, the ulcers of 17 patients (90%) in the open group and 17 patients (85%) in the endoscopic group had healed. During a mean follow-up of 21 months (range, 16 to 29 months), no recurrences were noticed in either group. Conclusions: Endoscopic division of incompetent perforating veins is equally as effective as open surgical exploration for the treatment of venous ulceration of the lower leg but leads to significantly fewer wound healing complications. Endoscopic division is therefore the preferred method. (J Vasc Surg 1997;26:1049-54.
Incisional hernia recurrence following 'vest-over-pants' or vertical mayo repair of primary hernias of the midline
A series of 68 primary midline incisional hernias with a vertical Mayo repair was evaluated retrospectively. Patients without documented hernia recurrence following this repair were invited for physical examination. Life- table methods were used for statistical analysis. The 1-, 3-, 5-, and 10- year cumulative recurrence rates were 35%, 46%, 48%, and 54%, respectively. Also, generally accepted risk factors were studied. Multivariate analysis identified the size of the hernia (p = 0.02) and the use of steroids (p = 0.04) as the most important independent risk factors of first time recurrent incisional hernia. Considering the high recurrence rates found, the results of this study strongly suggest that the vest-over-pants repair should no longer be used for closure of midline incisional hernias
ULTRA-TRACE DETERMINATION OF IRIDIUM BY ETV/ICP-MS USING CHEMICAL MODIFIERS
Joint Research on Environmental Science and Technology for the Eart
Long-term pulmonary sequelae in children with congenital diaphragmatic hernia.
Neonates with congenital diaphragmatic hernia (CDH) often suffer from respiratory
insufficiency due to lung hypoplasia and pulmonary hypertension. Artificial
ventilation is frequently required, and this leads to a high incidence of
bronchopulmonary dysplasia. Long-term follow-up studies have shown persisting
airway obstruction. To evaluate the long-term pulmonary sequelae in CDH, we
studied 40 CDH patients of age 7 to 18 yr (median 11.7 yr) and 65 age-matched
controls without CDH and lung hypoplasia who underwent similar neonatal
treatment. Mild airway obstruction was found in both groups with more peripheral
airway obstruction in CDH patients than in control subjects. Both groups had
normal TLC and single-breath carbon monoxide diffusion capacity (DLCO). CDH
patients had increased residual volume (RV) and RV/TLC compared with controls.
Increased airway responsiveness to methacholine (MCH) was common but
bronchoconstriction to inhaled metabisulfite (MBS) was rare both in CDH and
control subjects. We conclude that this group of CDH patients has minor residual
lung function impairment. Mild airway obstruction and increased airway
responsiveness to inhaled MCH but not to MBS suggest that structural changes in
distal airways are involved and not autonomic nerve dysfunction. Both artificial
ventilation in the neonatal period and residual lung hypoplasia seem important
determinants of persistent lung function abnormalities in CDH patients
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