Search

Gearbox development is significantly delayed due to the long lead times associated with the manufacturing of functional prototype gears by means of classical methods such as hobbing and grinding. This paper presents a novel method to machine a prototype gear using high precision 5-axis milling with the same geometrical and surface properties associated with aforementioned technologies, only reducing lead times from 10 weeks to less than 24hours. Different milling strategies and tools are shown to have an influence on the achieved geometrical properties such as roundness, pitch error and flank quality. A ground quality gear has been manufactured using an alternating milling strategy combined with tool wear compensation.

The time-to-market for automotive and other gear-involved products is still reducing. This demands new production technologies for the manufacturing of functional gear prototypes. At the moment gear prototypes are made using classical series production technologies, such as gear hobbing and grinding. However, these technologies require design specific dedicated tools, making the production of a functional gear prototype expensive and time-consuming. This paper presents an experimental investigation and comparison of different alternative production technologies for the manufacturing of functional gear prototypes. Wire-EDM, Selective Laser Melting and milling using standard milling tools, have been compared for the production of a spur gear out of 16MnCr5 steel. A strategy for the wire-cutting of a spur gear was developed, resulting in a total machining time of 22h – with very good gear quality in terms of geometrical accuracy and surface roughness. This same gear has been produced by SLM, with a total machining time of 17h. Two different milling strategies have been developed on a milling machine, resulting in a total machining time of 14h15min. The shape accuracy and surface roughness were compared using a CMM and a surface profiler. Taking these results into account and considering the fact that it is impossible to make helical gears or machine micro flank corrections using wire-EDM, it was concluded that the milling is the most promising production technology for functional gear prototypes. The fact that functional prototypes could be made without the current lead time (± 10 weeks) is a great improvement for the production of gear prototypes, meeting the shorter time-to-market requirements of today's industry.

This paper presents an experimental investigation on micromilling of fully sintered Zirconia ceramics by means of advanced cutting tools, including cBN and diamond coated mills. Zirconium oxide is selected because of its high hardness, resistance to wear, heat and chemicals.

AbstractBackground/Aims:Cystic fibrosis (CF) in infancy and childhood is often associated with failure to thrive (FTT). This would suggest that in countries without a newborn screening program for CF, FTT could be used as a clinical screening tool. The aim of this study is to assess the diagnostic performance of FTT for identifying children with CF. Methods:Longitudinal length and weight measurements up to 2.5 years of age were used from CF patients (n = 123) and a reference group (n = 2,151) in The Netherlands. Growth measurements after diagnosis were excluded. We developed five potential screening rules based upon length, weight and body mass index (BMI) standardized by age and gender (SDS). Outcome measures were sensitivity, specificity and positive predictive value (PPV). Results:BMI SDS had the highest sensitivity at low false-positive rates. An efficient scenario is a BMI SDS below –2.5 SD in combination with a decrease in BMI SDS of at least 0.5 SD. This scenario had a sensitivity of 32, a specificity of 98.3 and a PPV of 0.75. Conclusion:In the absence of a newborn screening program, young children with FTT for BMI are candidates to consider testing for CF.Copyright © 2009 S. Karger AG, Basel

Inflammatory bowel diseases (IBD) represent an aberrant immune response by the mucosal immune system to luminal bacteria. Because the oral mucosa harbors the first epithelial cells that interact with microorganisms, we assessed the immunologic activity of buccal epithelium in children with IBD and adults with Crohn disease.

Inflammatory bowel diseases (IBD) represent an aberrant immune response by the mucosal immune system to luminal bacteria. Because the oral mucosa harbors the first epithelial cells that interact with microorganisms, we assessed the immunologic activity of buccal epithelium in children with IBD and adults with Crohn disease. Buccal epithelial cells were obtained from 17 children and 14 adults with Crohn disease, 18 children with ulcerative colitis, and 40 controls. Cells were cultured with and without microbial stimulation. Chemokine levels were determined in culture supernatants by cytometric bead array and enzyme‐linked immunoabsorbent assay. CXCL‐8 production was studied by immunohistochemical analysis of these cells. CXCL‐8 production by lipopolysaccharide stimulated monocyte‐derived dendritic cells from these patients was determined. Compared with controls, pediatric ulcerative colitis patients, and adult Crohn disease patients, only in children with Crohn disease did buccal epithelial cells exhibit enhanced production of CXCL‐8, CXCL‐9, and CXCL‐10. In vitro stimulation with lipopolysaccharide or zymosan resulted in a further increase of chemokine levels only in cells from pediatric Crohn disease patients. CXCL‐8 production by stimulated monocyte‐derived dendritic cells from children with Crohn disease was equal to that of children with ulcerative colitis. Buccal epithelium of children with Crohn disease is immunologically active, even in the absence of oral lesions. The enhanced chemokine production is associated with pediatric Crohn disease and appears restricted to cells derived from the epithelial barrier. Assessment of chemokine production by buccal epithelial cells may become a new, rapid, noninvasive test for screening and classification of IBD in children.

The purpose of this study was to describe the clinical experience with the anti–tumor necrosis factor chimeric monoclonal antibody, infliximab, in pediatric patients with Crohn disease in The Netherlands. Descriptive. Clinical response and adverse effects of infliximab were recorded for pediatric patients with Crohn disease treated from October 1992 to January 2003. Thirty patients (aged 7–18 years) with refractory Crohn disease (with or without severe fistulas) were treated with infliximab. Patients were treated with up to 30 infusions. Mean follow-up was 25.3 months. A total of 212 infusions were administered. Thirteen patients had refractory Crohn disease without fistulas. Six patients showed good long-term response to infliximab treatment (defined as clinical index =10 points). Sixteen patients had refractory Crohn disease with draining fistulas. Nine showed good long-term response (closure or nonproductiveness of fistulas). One patient with metastatic Crohn disease in the skin had a good long-term response. Six patients developed an allergic reaction during infusion. In one patient, the allergic reaction occurred after an infliximab-free interval of 9 years. One patient died of sepsis. Infliximab was an effective therapy in 53% of patients with refractory pediatric Crohn disease, with or without fistulas. Approximately half of the patients become unresponsive to infliximab therapy. Randomized controlled studies are mandatory to assess long-term efficacy and safety to define the optimal therapeutic strategy of infliximab therapy in children with Crohn disease.

The purpose of this study was to describe the clinical experience with the anti–tumor necrosis factor chimeric monoclonal antibody, infliximab, in pediatric patients with Crohn disease in The Netherlands.

Abnormalities in transepithelial electrolyte transport in cystic fibrosis rectum were analyzed by short-circuit current measurements on 11 control subjects and 11 subjects with cystic fibrosis in a modified Ussing chamber. As judged by the amiloride-sensitive component of the short-circuit current, electrogenic sodium absorption appeared unmodified in cystic fibrosis. In contrast, the shortcircuit current response to specific stimuli of both cyclic adenosine monophosphate (cAMP)- and calcium-mediated chloride secretion was drastically altered in all of the cystic fibrosis biopsy specimens examined. Stimulation of the cAMP pathway by 8-bromo cAMP or forskolin resulted in a sustained increase in short-circuit current in control tissues (+2.51 ± 0.63 μA/cm2) but in a slight change in the opposite direction in cystic fibrosis (−0.56 ± 0.49 μA/cm2; P< 0.05). Carbachol, a calcium-linked secretagogue, provoked a transient increase in short-circuit current in all of the control tissues (peak response, +26.69 ± 3.63 μA/cm2) but a transient change in the opposite direction in 6 of 11 cystic fibrosis tissues (−12.46 ± 4.64 μA/cm2; P< 0.05). In 2 of 11 patients with cystic fibrosis, however, a significant but subnormal and transient increase in short-circuit current was observed (+2.62 ± 0.04 μA/cm2; P< 0.05), whereas in 3 of 11 patients with cystic fibrosis a transient change in the opposite direction (−9.83 ± 2.20 μA/cm2; P< 0.05) was followed by a small and transient increase (+2.89 ± 0.83 μA/cm2; P< 0.05). Using the calcium-mediated secretory response therefore, patients with cystic fibrosis could be divided into two categories: a major population showing defective anion secretion but active cation secretion and a subclass (including three siblings) showing residual but subnormal anion secretion. The easy accessibility of rectal samples and the inversed direction of the cAMP- or calcium-provoked short-circuit current is of considerable advantage in the diagnosis of cystic fibrosis.

This study was undertaken to determine baseline values of 24-hour pH-metry in children who had undergone correction for esophageal atresia.

This study was undertaken to determine baseline values of 24‐hour pH‐metry in children who had undergone correction for esophageal atresia. A 24‐hour pH‐metry without medication was conducted in 13 patients with an uncomplicated postoperative course after correction of esophageal atresia. The pH‐metry was performed in the hospital with a flexible glass electrode. The mean reflux index was 4.08%, the mean total number of reflux periods with a pH less than 4 was 21, and the mean number of periods of pH less than 4 lasting longer than 5 minutes was 2.5. Twenty‐four‐hour pH‐metry values in asymptomatic esophageal atresia patients are the same as in children from the same age group with normal anatomy.

Malnutrition and growth failure are complications of inflammatory bowel disease (IBD) in children. Contributing factors to these effects are malabsorption, inadequate food intake, enhanced loss of nutrients, and corticosteroid treatment. Increased resting energy expenditure (REE) may also contribute to the growth retardation. Twenty children with endoscopicaly and histologically proven ulcerative colitis (n=13) or Crohns disease (n = 7) and twenty age and sex matched controls were studied. REE was measured using a metabolic cart with principle of indirect calorimetry (Deltatrac, Datex, Finland), lean body mass (LBM) with bioelectrical impedance analysis (BIA). With Dual energy X-ray absorptiometry (DEXA) (Lunar Rad. Corp., USA) an analysis of bone mineral density (BMD) and of LBM was done. The median age of IBD children was 13,5 years (range 6-18), of controls 14 years (range 6-18). The mean REE in children was increased: 33 ± 1,7 versus 28,9 ± 1,5 Kcal/kg bodyweight (p<0.01). The LBM was significantly increased in children with IBD versus controls: 81,5 ± 1,7 versus 74,7 ± 1,6% of bodyweight. REE in Kcal/kg LBM was not different in children with IBD versus controls: 41,7 ± 2,1 versus 38,8 ± 2,1 Kcal/kg. No difference in REE was found between patients with low (n=14) and high disease activity (n = 6). In five patients (25%) a decreased BMD (>2 SD below mean value) of lumbar spine was found. An inverse relation between 8MD and cumulative prednison dose was found. The LBM values measured with BIA and with DEXA technique correlated very well (R =0.95).