cDNA and derived amino acid sequence of the hypusine containing protein from Dictyostelium discoideum

AbstractThe eukaryotic translation initiation factor eIF-4D is the only protein known to contain the unusual amino acid hypusine, a posttranslationally modified lysine. For the production of monoclonal antibodies the hypusine-containing protein (HP) was isolated from Dictyostelium discoideum. Using these monoclonal antibodies, a full-length cDNA clone was isolated from a λgt11 library. The D. discoideum HP consists of 169 amino acids and has a molecular mass of 18.3 kDa. It is encoded by a single gene. Tryptic and cyanogen bromide peptides were prepared from the purified protein and sequenced. The hypusine residue is located at amino acid position 65 of the HP. The corresponding mRNA of approx. 0.6 kb is present throughout the life cycle of D. discoideum

The influence of the interface coefficient of friction upon the propensity to judder in automotive clutches

This paper presents an investigation of the driveline torsional vibration behaviour, referred to as judder, which takes place during the clutch engagement process, particularly on small trucks with diesel engines. A non-linear multibody dynamic model of the clutch mechanism is employed to study the effect of various clutch system and driveline components on the clutch actuation performance. The paper demonstrates that judder is affected by driveline inertial changes, variation in the coefficient of friction, μ, of the friction disc linings with slip speed, v, and the loss of clamp load. The results of the simulations show that various friction materials with different μ–v characteristics produce torsional self-excited vibrations of the driveline. The results also show that loss of clamp load relating to the speed of clutch actuation also contributes to judder. Furthermore, it is shown that the simulation results conform closely to the experimental findings

An appraisal on the sustainability payback of additively manufactured molds with conformal cooling

The use of Additive Manufacturing (AM) in the production of tooling for injection molding has led to the introduction of conformal cooling as an effective way to lower the cycle time of the process. As the cooling cycle is responsible for a large portion of the energy consumed during the injection molding process, conformal cooling allows increasing the energy efficiency. However, AM could create a large upfront cost of energy for the manufacturing phase. This paper investigates a case study where a cradle-to-grave life-cycle assessment is used to evaluate the cumulative energy demand of conventional or conformal cooling molds

On the effect of multiple parallel nonlinear absorbers in palliation of torsional response of automotive drivetrain

Torsional vibrations transmitted from the engine to the drivetrain system induce a plethora of noise, vibration and harshness (NVH) concerns, such a transmission gear rattle and clutch in-cycle vibration, to name but a few. The main elements of these oscillations are variations in the inertial imbalance and the constituents of combustion power torque, collectively referred to as engine order vibration. To attenuate the effect of these transmitted vibrations and their oscillatory effects in the drive train system, a host of palliative measures are employed in practice, such as clutch pre-dampers, slipping discs, dual mass flywheel and others, all of which operate effectively over a narrow band of frequencies and have various unintended repercussions. These include increased powertrain inertia, installation package space and cost. This paper presents a numerical study of the use of multiple Nonlinear Energy Sinks (NES) as a means of attenuating the torsional oscillations for an extended frequency range and under transient vehicle manoeuvres. Frequency–Energy Plots (FEP) are used to obtain the nonlinear absorber parameters for multiple NES coupled in parallel to the clutch disc of a typical drivetrain configuration. The results obtained show significant reduction in the oscillations of the transmission input shaft, effective over a broad range of response frequencies. It is also noted that the targeted reduction of the acceleration amplitude of the input shaft requires significantly lower NES inertia, compared with the existing palliative measures

Heat generation and transfer in automotive dry clutch engagement

Dynamic behaviour of automotive dry clutches depends on the frictional characteristics of the contact between the friction lining material, the flywheel, and the pressure plate during the clutch engagement process. During engagement due to high interfacial slip and relatively high contact pressures, generated friction gives rise to contact heat, which affects the material behaviour and the associated frictional characteristics. In practice excess interfacial slipping and generated heat during torque transmission can result in wear of the lining, thermal distortion of the friction disc, and reduced useful life of the clutch. This paper provides measurement of friction lining characteristics for dry clutches for new and worn state under representative operating conditions pertaining to interfacial slipping during clutch engagement, applied contact pressures, and generated temperatures. An analytical thermal partitioning network model of the clutch assembly, incorporating the flywheel, friction lining, and the pressure plate is presented, based upon the principle of conservation of energy. The results of the analysis show a higher coefficient of friction for the new lining material which reduces the extent of interfacial slipping during clutch engagement, thus reducing the frictional power loss and generated interfacial heating. The generated heat is removed less efficiently from worn lining. This might be affected by different factors observed such as the reduced lining thickness and the reduction of density of the material but mainly because of poorer thermal conductivity due to the depletion of copper particles in its microstructure as the result of wear. The study integrates frictional characteristics, microstructural composition, mechanisms of heat generation, effect of lining wear, and heat transfer in a fundamental manner, an approach not hitherto reported in literature

Processing of thick section epoxy powder composite structures

The use of epoxy powder as the primary matrix in thick fibre-reinforced composite parts is investigated. The characteristics of three epoxy powders are assessed using several experimental techniques, focusing on their curing behaviour. At least one epoxy powder is shown to have advantageous characteristics for manufacturing thick-section composites. Material models are developed which can describe the processing behaviour (cure kinetics, viscosity change, etc.) of an epoxy powder. The cure kinetics model makes use of an additional rate constant to better describe the rate of cure at both high and low temperatures. The chemorheological model is based on an existing model for toughened epoxies. A one-dimensional simulation tool for manufacturing thick-section composite laminates is developed in MATLAB. The simulation tool employs a resin flow model for vacuum-bag-only prepregs to describe the infusion process and subsequent thickness change. This thickness change is coupled to a model for through-thickness heat transfer which can be solved numerically for various thermal boundary conditions. The model is used to explore the suitability of epoxy powders for the manufacturing thick-section composite structures. The aforementioned simulation tool is validated against experimental results for thick-section composite laminates. The experiments are carried out using a modified heated tool and test apparatus which apply known thermal boundary conditions. A linear variable differential transformer is used to measure the thickness change of each laminate during testing, while thermocouples are used to measure the temperatures at various positions within each laminate. The results of the tests show good agreement with the one-dimensional simulation tool. Additional simulations are performed to investigate the influence of material format, thickness change, and heating methods. Methods for reducing thermal and cure gradients are explored also. A method is outlined for implementing the process models within commercial finite element software, Abaqus FEA. User subroutines for heat transfer and thermal expansion are used to define the various process models. One-dimensional simulations are validated, and a convergence study is performed on time step size and element size. Simulations show the effect of in-plane heating for glass-fibre and carbon-fibre laminates, and the processing of a wind turbine blade root section is investigated. Overall, it is shown that thick-section composite structures can be manufactured using a low-cost commodity epoxy powder from the coating industry, and that these structures do not suffer from the risk of uncontrolable thermal events

Application of compact laser-driven accelerator X-ray sources for industrial imaging

X-rays generated by betatron oscillations of electrons in a laser-driven plasma accelerator were characterised and applied to imaging industrial samples. With a 125TW laser, a low divergence beam with 5.2±1.7 × 107photonsmrad−2 per pulse was produced with a synchrotron spectrum with a critical energy of 14.6±1.3keV. Radiographs were obtained of a metrology test sample, battery electrodes, and a damage site in a composite material. These results demonstrate the suitability of the source for non-destructive evaluation applications. The potential for industrial implementation of plasma accelerators is discussed

Study of the effect of contact force model on the dynamic response of mechanical systems with dry clearance joints : computational and experimental approaches

The main objective of this work is to present a computational and experimental study on the contact forces developed in revolute clearance joints. For this purpose, a well-known slider-crank mechanism with a revolute clearance joint between the connecting rod and slider is utilized. The intra-joint contact forces that generated at this clearance joints are computed by considered several different elastic and dissipative approaches, namely those based on the Hertz contact theory and the ESDU tribology-based for cylindrical contacts, along with a hysteresis-type dissipative damping. The normal contact force is augmented with the dry Coulomb’s friction force. In addition, an experimental apparatus is use to obtained some experimental data in order to verify and validate the computational models. From the outcomes reported in this paper, it is concluded that the selection of the appropriate contact force model with proper dissipative damping plays a significant role in the dynamic response of mechanical systems involving contact events at low or moderate impact velocities.Fundação para a Ciência e a Tecnologia (FCT