A universal six-joint robot controller

A general purpose six-axis robotic manipulator controller was designed and implemented to serve as a research tool for the investigation of the practical and theoretical aspects of various control strategies in robotics. A 80286-based Intel System 310 running the Xenix operating servo software as well as the higher level software (e.g., kinematics and path planning) were employed. A Multibus compatible interface board was designed and constructed to handle I/O signals from the robot manipulator's joint motors. From the design point of view, the universal controller is capable of driving robot manipulators equipped with D.C. joint motors and position optical encoders. To test its functionality, the controller is connected to the joint motor D.C. power amplifier of a PUMA 560 arm bypassing completely the manufacturer-supplied Unimation controller. A controller algorithm consisting of local PD control laws was written and installed into the Xenix operating system. Additional software drivers were implemented to allow application programs access to the interface board. All software was written in the C language

Nanoscale topography and wear of ceramic interfaces and their effect on macroscale friction

500 years ago, Leonardo da Vinci systematically investigated the relation between the frictional force and normal force. Da Vinci concluded that the frictional force is proportional to the normal force. The proportionality constant that links the frictional force and normal force is defined as the coefficient of friction (CoF). Although the CoF is an empirical number that resulted from da Vinci’s experiments and does not explain the fundamental origin of friction, this simple relation between frictional force and normal force successfully captures most dry sliding friction behavior between macroscopic objects. However, when the sliding surfaces strongly adhere to each other or are atomically smooth, the proportionality between frictional force and normal force may breakdown and, in this case, the frictional force is proportional to the area of real contact. John Frederick Archard proposed a simple multiple-contacts model in which the cross-sectional area of the contact points is increased linearly with applied load when the contact points are plastically deformed. More analytical models have been proposed, such as the Greenwood and Williamson (GW) model and Persson’s contact theory, to quantify the area of real contact at multi-asperity interfaces. Experimentally it remains challenging to access and measure the area of real contact hidden from view by the contacting objects. To quantify the area of real contact, numerical methods, such as the boundary element method, have been developed. The calculation of contact mechanics either by analytical or numerical methods provides further insight into the formation of contacts which leads to friction. In this thesis, we investigate the interplay between friction, surface topography, capillary adhesion and third body formation at macroscopic sliding interfaces between ceramic materials

Parallel processing architecture for computing inverse differential kinematic equations of the PUMA arm

In advanced robot control problems, on-line computation of inverse Jacobian solution is frequently required. Parallel processing architecture is an effective way to reduce computation time. A parallel processing architecture is developed for the inverse Jacobian (inverse differential kinematic equation) of the PUMA arm. The proposed pipeline/parallel algorithm can be inplemented on an IC chip using systolic linear arrays. This implementation requires 27 processing cells and 25 time units. Computation time is thus significantly reduced

Neurotrophic keratitis after micropulse transscleral diode laser cyclophotocoagulation.

PurposeTo report two cases of neurotrophic keratitis (NK) after micropulse transscleral cyclophotocoagulation (MP-TCP).ObservationsTwo patients with predisposing factors for decreased corneal sensation developed NK 1 month after MP-TCP. Both patients did not heal with initial treatment with topical antibiotic and preservative free artificial tears. One patient required use of a bandage contact lens and the other patient required tarsorrhaphy. Both eyes experienced recurrence of NK.Conclusions and importanceNK can be triggered after MP-TCP in patients with underlying predisposing factors for decreased corneal sensation. This uncommon but vision-threatening complication should be discussed preoperatively with high-risk patients as a possible adverse event after MP-TCP and followed closely postoperatively

A Hemoglobin-Based Multifunctional Therapeutic: Polynitroxylated Pegylated Hemoglobin

Polynitroxylated pegylated hemoglobin (PNPH) as a multifunctional therapeutic takes advantage of the ability of hemoglobin (Hb) to transport oxygen, the antioxidative stress activities from the redox coupling of nitroxide and heme iron, and the hypercolloid properties of pegylation. The published preclinical data demonstrating that PNPH acts as a neurovascular protective multifunctional therapeutic in an animal model simulating prehospital resuscitation of traumatic brain injury (TBI) with hemorrhagic shock (HS) are reviewed. Preliminary results on the potential utility of PNPH for neurovascular protection in thrombolytic stroke therapy and for correction of vascular dysfunction through transfusion in sickle-cell disease (SCD) are also discussed. We hypothesize that with PNPH, Hb has more than been tamed--it has become a therapeutic and not just a nontoxic extracellular oxygen carrier--and that successful PNPH development as a multifunctional therapeutic that protects the neurovasculature and reduces oxidative stress may represent a paradigm shift in transfusion and critical care medicine, which may meet a number of unmet medical needs resulting from oxidative stress and inadequate blood flow, such as HS, TBI, SCD, and stroke

Mediastinal Choriocarcinoma Masquerading as Relapsed Hodgkin Lymphoma

Primary mediastinal choriocarcinoma is a rare extragonadal germ cell malignancy. We describe the first case of a patient who developed mediastinal choriocarcinoma after treatment for Hodgkin lymphoma (HL). A 25-year-old man with classic HL, nodular sclerosis subtype, underwent treatment with splenectomy followed by radiation therapy. Unfortunately, his disease relapsed with a paraspinal mass, and he was subsequently treated with MOPP (mechlorethamine, Oncovin, procarbazine, and prednisone) alternating with ABVD (Adriamycin, bleomycin, vinblastine, and dacarbazine). He achieved a complete remission after 6 cycles. Ten years after treatment, the patient presented with a persistent cough, haemoptysis, right supraclavicular lymphadenopathy, and weight loss. His chest X-ray showed opacification of the lower right hemithorax with a widened mediastinum. Given unresponsiveness to several antibiotics and lack of evidence for lung volume loss, there were concerns over lung infiltration with relapsed lymphoma. Transbronchial fine needle aspiration biopsy suggested recurrence of his HL. MOPP alternating with ABVD was again given. Due to disease progression, brachytherapy as well as a cocktail of dexamethasone, cytarabine, and cisplatin were also tried. However, on a subsequent excisional lymph node biopsy, it turned out that the tumour was in fact choriocarcinoma and not relapsed HL. Unfortunately, despite aggressive therapy, the patient's disease rapidly progressed, and he died within 2 weeks

HUBBLE SPACE TELESCOPE OBSERVATIONS AND GEOMETRIC MODELS OF COMPACT MULTIPOLAR PLANETARY NEBULAE

published_or_final_versio

Capillary adhesion governs the friction behavior of electrochemically corroded polycrystalline diamond

The friction behavior of rough polycrystalline diamond (PCD) surfaces is important in many applications and devices that are required to operate in various harsh environments and it can be argued that a thorough understanding of the friction behavior is essential to the application performance. However, the interplay between electrochemical corrosion, capillary adhesion and friction behavior of PCD in multi-asperity contacts is still poorly understood. In this work, we quantify the interfacial capillary adhesion at contact interfaces and its effect on the friction response, between a colloidal microsphere and rough PCD films before and after electrochemical corrosion, for water-immersed, low RH, and humid air conditions. For these multi-asperity contacts, we demonstrate how electrochemical corrosion influences the surface hydrophilicity of the PCD surfaces, and how capillary adhesion due to water condensation contributes to the friction force. We estimate the capillary forces from both the microscopic lateral force experiments and elastoplastic boundary element method (BEM) contact calculations. The combined results indicate strongly that the observed increase in friction force on electrochemically-corroded PCD surfaces is governed by enhanced capillary adhesion at the contact interface, as affected by surface hydrophilicity and environmental humidity

Transformations of Progesterone by Subcellular Fractions of Human Skin

Homogenates of human skin metabolize progesterone-4-14C to the same products as whole skin. Studies with subcellular fractions obtained by differential centrifugation indicate the presence in skin of a membrane-bound 5α-reductase and a soluble 20α-hydroxysteroid dehydrogenase (20α-HSD), both of which utilize TPNH as cofactor. The 20α-HSD has a pH optimum of 6.2 and a Km of approximately 7 μM. Unlike placental preparations, the 105,000 × g supernatant fraction prepared from human skin has more 20α-HSD than 17β-hydroxy-steroid dehydrogenase activity. This soluble skin enzyme acting on steroid hormones is distinct from previously reported particulate enzymes