Vitamin K and childhood cancer: a population based case-control study in Lower Saxony, Germany.

OBJECTIVE--To confirm or refute a possible association of parenteral vitamin K prophylaxis and childhood cancer. DESIGN--Population based case-control study. Comparison of vitamin K exposure in children with leukaemia or other common tumours with two control groups. SETTING--State of Lower Saxony (north western part of Germany); case recruitment from the German childhood cancer registry. SUBJECTS--272 children with leukaemia, nephroblastoma, neuroblastoma, rhabdomyosarcoma, and tumours of the central nervous system diagnosed between 1 July 1988 and 30 June 1993; children were aged between 30 days and 15 years at diagnosis. 334 population based controls without diagnoses of cancer matched to the leukaemia cases for age and sex. MAIN EXPOSURE MEASURES--Parenteral vitamin K prophylaxis (intramuscular and subcutaneous) versus oral and no vitamin K prophylaxis. RESULTS--An association between parenteral vitamin K exposure and childhood cancer (leukaemias and other tumours combined) could not be confirmed (odds ratio 1.04, 95% confidence interval 0.74 to 1.48). For leukaemias the observed odds ratio was only 0.98 (0.64 to 1.50) (comparison of leukaemia cases with local controls 1.24 (0.68 to 2.25); state controls 0.82 (0.50 to 1.36)). These odds ratios remained almost unchanged when several potential confounders were considered in the logistic regression model. CONCLUSIONS--This population based study adds substantial evidence that there is no association between parenteral vitamin K and childhood cancer

Tailor-made functional composite components using AM and HIP

The combination of Additive Manufacturing (AM) and Hot Isostatic Pressing (HIP) offers great potential for industrial applications. Skillfully connecting AM and HIP creates a manufacturing process that unites the advantages of both processes. We demonstrate a production route for composite components by AM + HIP. A capsule made of wear-resistant or corrosion-resistant steel is additively manufactured by Laser-Powder Bed Fusion (LPBF). Before building, the geometry of the capsule is optimized by FEM simulation to obtain a desired shape. In a second step, the capsule is filled with structural steel powder and sealed in a conventional powder HIP process. The capsule remains on the component as an outer layer. In this way a complex-shaped, functional net shape composite component is produced. The composite components created by this route are characterized by metallographic investigations

Tailor-Made Net-Shape Composite Components by Combining Additive Manufacturing and Hot Isostatic Pressing

A promising production route for high quality tailor-made parts can be established by combining Additive Manufacturing (AM) and Hot Isostatic Pressing (HIP): By using a numerical simulation routine, the shape change during HIP can be controlled. These shape-controlled parts are built by Laser Powder Bed Fusion (L-PBF) and consolidated by HIP. After HIP, they exhibit a net-shape geometry that requires only little or even no post-processing at all. In this study, open thin-walled capsules are manufactured by L-PBF, filled conventionally with metal powder, evacuated and sealed and hot-isostatically pressed. Using this processing route, it is possible to combine different materials for the capsule and the powder filling. If capsule and bulk material are identical, the expensive removal of the capsule after HIP can be omitted. By using two different powders, it is possible to produce composite components with a core of high strength and toughness and a wear- or corrosion-resistant surface layer, offering an alternative and competitive production route to conventional HIP cladding. Here three materials are investigated in different combinations: austenitic stainless steel AISI 316L (DIN X2CrNiMo1 7-13-3), martensitic tool steel AISI L6 (DIN 55NiCrMoV7) and the wear resistant high carbon steel AISI A 1 1 (DIN X245VCrMo8-5-1). A number of technical challenges need to be addressed: the production of dense, thin-walled capsules by L-PBF; L-PBF of carbide rich steels; and controlling the diffusion between corrosion resistant steel and carbon steel. The success of the new process route is demonstrated by metallographic and geometrical investigations

Influence of powder bed temperature on microstructure and post heat treatment of high speed steel AISI M50 processed by laser-powder bed fusion

Laser powder bed fusion is an additive manufacturing process that enables the production of complex structures without material removal. For industrial use, the mechanical properties of LPBF parts have to be at least equal to the conventionally produced parts. High carbon steels expose a tendency to create stress-induced cracks during the LPBF process. An increase in powder bed temperature often decreases the danger of crack formation during the process. In this study, the steel M50 processed by LPBF at two different powder bed temperatures is analyzed. The structures are compared by hardness, light microscopy and X-ray diffraction. Scanning electron microscopy and electron backscatter diffraction are used for a closer investigation of the microstructure and texture. The influence of the resulting LPBF structure on a possible post heat treatment is analyzed by a dilatometric determination of a time-temperature-transformation diagram and a comparison to the behavior of the conventionally produced material