Approaches for chatter reduction in deep cavity and intricate surface milling

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998.Includes bibliographical references (leaf 119).The goal of the project was to increase the metal removal rate or improve the surface quality of an intricate surface cut by a long overhang tool. The results of the metal cutting tests show that the surface quality of a finish cut at conventional milling speeds can be improved by approximately 50% by using a stepped or tapered tool. In applications with straight walls or intricate surfaces where the larger diameter base of the tool interferes with the workpiece, a high stiffness 5 axis machine can achieve the desired geometry. Damping treatments such as the squeeze film damped tool and the viscoelastic ring were developed that could significantly increase the dynamic stiffness of a long overhang tool. These damping treatments did not improve the workpiece surface finish at conventional milling speeds. However, metal cutting theory indicates that more damping could be beneficial in high speed milling applications in which the vibration amplitude of the tool's resonant cantilever mode limits the stable depth of cut. This study has also produced an analytic model and damping methods that will enable designers to tailor the dynamic response of a tool to attenuate the vibrations that cause chatter at higher spindle speeds.by Gaurav Rohatgi.S.M

Interconnected Microphysiological Systems for Quantitative Biology and Pharmacology Studies

Microphysiological systems (MPSs) are in vitro models that capture facets of in vivo organ function through use of specialized culture microenvironments, including 3D matrices and microperfusion. Here, we report an approach to co-culture multiple different MPSs linked together physiologically on re-useable, open-system microfluidic platforms that are compatible with the quantitative study of a range of compounds, including lipophilic drugs. We describe three different platform designs - "4-way", "7-way", and "10-way" - each accommodating a mixing chamber and up to 4, 7, or 10 MPSs. Platforms accommodate multiple different MPS flow configurations, each with internal re-circulation to enhance molecular exchange, and feature on-board pneumatically-driven pumps with independently programmable flow rates to provide precise control over both intra- and inter-MPS flow partitioning and drug distribution. We first developed a 4-MPS system, showing accurate prediction of secreted liver protein distribution and 2-week maintenance of phenotypic markers. We then developed 7-MPS and 10-MPS platforms, demonstrating reliable, robust operation and maintenance of MPS phenotypic function for 3 weeks (7-way) and 4 weeks (10-way) of continuous interaction, as well as PK analysis of diclofenac metabolism. This study illustrates several generalizable design and operational principles for implementing multi-MPS "physiome-on-a-chip" approaches in drug discovery.United States. Army Research Office (Grant W911NF-12-2-0039

Primary osteogenic osteosarcoma of the left zygomatic arch - A case report

Osteosarcoma accounts for 40–60% of primary malignant bone tumors. About 10% occur in the head and neck region, frequently in the mandible and maxilla. Zygomatic arch is a very rare site of involvement. We report a rare case of primary osteosarcoma of the left zygomatic arch in a 30-year-old male with a review of literature. Only six cases of primary osteogenic sarcoma of zygomatic arch have been reported in the literature. The present case is the 7th in the series of reported cases of osteosarcoma of zygomatic arch till date

Intraosseous angiolipoma of head of humerus - An extremely rare entity, with review of literature

Lipoma is a common soft tissue tumor. There are only very few reported cases of intraosseous lipoma in the literature. Intraosseousangiolipomas are even rarer. Angiolipomas are benign tumors consisting of mature adipose tissue and abnormal vessels that occur inpatients during their teens or early twenties. Most are found as multiple lesions, often located on the arm or trunk. Predominantly,they are subcutaneous lesions; intraosseous angiolipomas are primarily found in the mandible, ribs, and calvarium. Exact nature ofthese lesions is debatable. To the best of our knowledge, this is the first reported case of intraosseous angiolipoma of the head ofhumerus and 9th in the series of reported cases of intraosseous angiolipoma including four of mandible, two of ribs, and two of skull

BAP1 promotes osteoclast function by metabolic reprogramming

Abstract Treatment of osteoporosis commonly diminishes osteoclast number which suppresses bone formation thus compromising fracture prevention. Bone formation is not suppressed, however, when bone degradation is reduced by retarding osteoclast functional resorptive capacity, rather than differentiation. We find deletion of deubiquitinase, BRCA1-associated protein 1 (Bap1), in myeloid cells (Bap1 ∆LysM ), arrests osteoclast function but not formation. Bap1 ∆LysM osteoclasts fail to organize their cytoskeleton which is essential for bone degradation consequently increasing bone mass in both male and female mice. The deubiquitinase activity of BAP1 modifies osteoclast function by metabolic reprogramming. Bap1 deficient osteoclast upregulate the cystine transporter, Slc7a11, by enhanced H2Aub occupancy of its promoter. SLC7A11 controls cellular reactive oxygen species levels and redirects the mitochondrial metabolites away from the tricarboxylic acid cycle, both being necessary for osteoclast function. Thus, in osteoclasts BAP1 appears to regulate the epigenetic-metabolic axis and is a potential target to reduce bone degradation while maintaining osteogenesis in osteoporotic patients