Pole Arrangements that Introduce Prismatic Joints into the Design Space of Four- and Five-Position Rigid-Body Synthesis

Although a general five-position, rigid-body guidance problem admits a discrete number of revolute–revolute (RR) dyads, this paper identifies arrangements of five task positions that result in a center-point curve. For these special arrangements, a one-dimensional set of revolute-prismatic (RP) dyads exist to achieve the task positions. Other five-position arrangements are identified where a one-dimensional set of prismatic-revolute (PR) dyads exist to achieve the task positions. For a general case of five task positions, neither PR nor RP dyads are possible. In a general case of four-position rigid-body guidance problems, a unique PR dyad and RP dyad exist. Four-position arrangements are identified where the associated center-point curve includes the line at infinity and admits a PR dyad with a line of slide in any direction. Likewise, arrangements of the four positions are identified where the circle-point curve includes the line at infinity, permitting a one-dimensional set of RP dyads. These special four and five positions lead to dyads that can be coupled to solve a rigid-body guidance synthesis problem with a PRRP or RPPR device which is generally not possible. These solutions are particularly useful in design situations where actuation through a prismatic joint is desired

Kinematic Synthesis of Planar, Shape-Changing, Rigid Body Mechanisms for Design Profiles with Significant Differences in Arc Length

This paper presents a kinematic procedure to synthesize planar mechanisms capable of approximating a shape change defined by a general set of curves. These “morphing curves,” referred to as design profiles, differ from each other by a combination of displacement in the plane, shape variation, and notable differences in arc length. Where previous rigid-body shape-change work focused on mechanisms composed of rigid links and revolute joints to approximate curves of roughly equal arc length, this work introduces prismatic joints into the mechanisms in order to produce the different desired arc lengths. A method is presented to iteratively search along the profiles for locations that are best suited for prismatic joints. The result of this methodology is the creation of a chain of rigid bodies connected by revolute and prismatic joints that can approximate a set of design profiles

Kinematic synthesis of planar, shape-changing, rigid body mechanisms for design profiles with significant differences in arc length

This paper presents a kinematic procedure to synthesize planar mechanisms capable of approximating a shape change defined by a general set of curves. These “morphing curves,” referred to as design profiles, differ from each other by a combination of displacement in the plane, shape variation, and notable differences in arc length. Where previous rigid-body shape-change work focused on mechanisms composed of rigid links and revolute joints to approximate curves of roughly equal arc length, this work introduces prismatic joints into the mechanisms in order to produce the different desired arc lengths. A method is presented to iteratively search along the profiles for locations that are best suited for prismatic joints. The result of this methodology is the creation of a chain of rigid bodies connected by revolute and prismatic joints that can approximate a set of design profiles

Development of a Spring-Based Automotive Starter

Automotive starting systems require substantial amounts of mechanical energy in a short period of time. Lead-acid batteries have historically provided that energy through a starter motor. Springs have been identified as an alternative energy storage medium and are well suited to engine-starting applications due to their ability to rapidly deliver substantial mechanical power and their long service life. This paper presents the development of a conceptual, spring-based starter. The focus of the study was to determine whether a spring of acceptable size could provide the required torque and rotational speed to start an automotive engine. Engine testing was performed on a representative 600 cc, inline 4-cylinder internal combustion engine to determine the required torque and engine speed during the starting cycle. An optimization was performed to identify an appropriate spring design, minimizing its size. Results predict that the test engine could be started by a torsional steel spring with a diameter and length of approximately 150 mm, similar in size, but lower weight than an electrical starting system of the engine. A proof-of-concept prototype has been constructed and evaluated

A Mechanical Regenerative Brake and Launch Assist Using an Open Differential and Elastic Energy Storage

Regenerative brake and launch assist (RBLA) systems are used to capture kinetic energy while a vehicle decelerates and subsequently use that stored energy to assist propulsion. Commercially available hybrid vehicles use generators, batteries and motors to electrically implement RBLA systems. Substantial increases in vehicle efficiency have been widely cited. This paper presents the development of a mechanical RBLA that stores energy in an elastic medium. An open differential is coupled with a variable transmission to store and release energy to an axle that principally rotates in a single direction. The concept applies regenerative braking technology to conventional automobiles equipped with only an internal combustion engine where the electrical systems of hybrid vehicles are not available. Governing performance equations are formulated and design parameters are selected based on an optimization of the vehicle operation over a simulated urban driving cycle. The functionality of this elastically-based regenerative brake device has been demonstrated on a physical prototype

The Synthesis of Function Generating Mechanisms for Periodic Curves Using Large Numbers of Double-Crank Linkages

This paper presents a methodology for synthesizing planar linkages to approximate any prescribed periodic function. The mechanisms selected for this task are the slider-crank and the geared five-bar with connecting rod and sliding output (GFBS), where any number of double-crank (or drag-link) four-bars are used as drivers. A slider-crank mechanism, when comparing the input crank rotation to the output slider displacement, produces a sinusoid-like function. Instead of directly driving the input crank, a drag-link four-bar may be added to drive the crank from its output via a rigid connection between the two. Driving the input of the added four-bar results in a function that modifies the sinusoid-like curve. This process can be continued through the addition of more drag-link mechanisms to the device, progressively altering the curve toward any periodic function with a single maximum. For periodic functions with multiple maxima, a GFBS is used as the terminal linkage added to the chain of drag-link mechanisms. The synthesis process starts by analyzing one period of the function to design either the terminal slidercrank or terminal GFBS. MATLAB's fmincon command is then utilized as the four-bars are added to reduce the structural error between the desired function and the input-output function of the mechanism. Mechanisms have been synthesized in this fashion to include a large number of links that are capable of closely producing functions with a variety of intriguing features

Two types of bone necrosis in the middle triassic pistosaurus longaevus bones: The results of integrated studies

Avascular necrosis, diagnosed on the basis of either a specific pathological modification of the articular surfaces of bone or its radiologic appearance in vertebral centra, has been recognized in many Mesozoic marine reptiles as well as in present-day marine mammals. Its presence in the zoological and paleontologic record is usually associated with decompression syndrome, a disease that affects secondarily aquatic vertebrates that could dive. Bone necrosis can also be caused by infectious processes, but it differs in appearance from decompression syndrome-associated aseptic necrosis. Herein, we report evidence of septic necrosis in the proximal articular surface of the femur of a marine reptile, Pistosaurus longaevus, from the Middle Triassic of Poland and Germany. This is the oldest recognition of septic necrosis associated with septic arthritis in the fossil record so far, and the mineralogical composition of pathologically altered bone is described herein in detail. The occurrence of septic necrosis is contrasted with decompression syndrome-associated avascular necrosis, also described in Pistosaurus longaevus bone from Middle Triassic of Germany

Molecular basis for passive immunotherapy of Alzheimer's disease

Amyloid aggregates of the amyloid-{beta} (A{beta}) peptide are implicated in the pathology of Alzheimer's disease. Anti-A{beta} monoclonal antibodies (mAbs) have been shown to reduce amyloid plaques in vitro and in animal studies. Consequently, passive immunization is being considered for treating Alzheimer's, and anti-A{beta} mAbs are now in phase II trials. We report the isolation of two mAbs (PFA1 and PFA2) that recognize A{beta} monomers, protofibrils, and fibrils and the structures of their antigen binding fragments (Fabs) in complex with the A{beta}(1–8) peptide DAEFRHDS. The immunodominant EFRHD sequence forms salt bridges, hydrogen bonds, and hydrophobic contacts, including interactions with a striking WWDDD motif of the antigen binding fragments. We also show that a similar sequence (AKFRHD) derived from the human protein GRIP1 is able to cross-react with both PFA1 and PFA2 and, when cocrystallized with PFA1, binds in an identical conformation to A{beta}(1–8). Because such cross-reactivity has implications for potential side effects of immunotherapy, our structures provide a template for designing derivative mAbs that target A{beta} with improved specificity and higher affinity

Expanded binding specificity of the human histone chaperone NASP

NASP (nuclear autoantigenic sperm protein) has been reported to be an H1-specific histone chaperone. However, NASP shares a high degree of sequence similarity with the N1/N2 family of proteins, whose members are H3/H4-specific histone chaperones. To resolve this paradox, we have performed a detailed and quantitative analysis of the binding specificity of human NASP. Our results confirm that NASP can interact with histone H1 and that this interaction occurs with high affinity. In addition, multiple in vitro and in vivo experiments, including native gel electrophoresis, traditional and affinity chromatography assays and surface plasmon resonance, all indicate that NASP also forms distinct, high specificity complexes with histones H3 and H4. The interaction between NASP and histones H3 and H4 is functional as NASP is active in in vitro chromatin assembly assays using histone substrates depleted of H1