A biomechanical comparison of intramedullary nail and crossed lag screw fixation for tibiotalocalcaneal arthrodesis

A series of Pyrazolo[1,5-a]pyrido[3,4-e]pyrimidin-6-ones (4a-p) was prepared by a simple synthetic procedure based on the reaction of hydroxylamine or methoxyamine with 2,3-substituted ethyl 7-dimethylaminovinyl pyrazolo[1,5-a]pyrimidin-6-carboxylates (3a-p). The antimicrobial activity of the obtained compounds was evaluated on a series of standard strains of Gram positive, Gram negative bacteria and fungi. None of the tested compounds showed significant activity.     

Simulation of dry powder inhalers: Combining micro‐scale,meso‐scale and macro‐scale modeling

The flow of carrier particles, coated with active drug particles, is studied in a prototype dry powder inhaler. A novel, multiscale approach consisting of a discrete element model (DEM) to describe the particles coupled with a dynamic large eddy simulation (LES) model to describe the dynamic nature of the flow is applied. The model consists of three different scales: the micro‐scale, the meso‐scale, and the macro‐scale. At the micro‐scale, the interactions of the small active drug particles with larger carrier particles, with the wall, with the air flow, and with each other is thoroughly studied using discrete element modeling and detailed computational fluid dynamics (CFD), i.e., resolving the flow structures around the particles. This has led to the development of coarse‐grained models, describing the interaction of the small active drug particles at the larger scales. At the meso‐scale the larger carrier particles, and all of their interactions are modeled individually using DEM and CFD‐LES. Collisions are modeled using a visco‐elastic model to describe the local deformation at each point of particle‐particle contact in conjunction with a model to account for cohesion. At the macro‐scale, simulations of a complete prototype inhaler are carried out. By combining the relevant information of each of the scales, simulations of the inhalation of one dose from a prototype inhaler using a patient relevant air flow profile show that fines leave the inhaler faster than the carrier particles. The results also show that collisions are not important for particle‐particle momentum exchange initially but become more important as the particles accelerate. It is shown that for the studied prototype inhaler the total release efficiency of the fine particles is between 10 and 30%, depending on the Hamaker constant, using typical settings for the properties of both particles. The results are also used to study regions of recirculation, where carrier particles can become trapped, and regions where fines adhere to the wall of the device. © 2016 American Institute of Chemical Engineers AIChE J, 63: 501–516, 2017     

Dewetting of thin liquid films on chemically patterned substrates: front propagation along narrow lyophobic stripes and stripe arrays

Using experiments and numerical simulations, we investigate the dewetting of thin liquid films on chemically patterned substrates. The patterns consist of long and narrow hydrophobic stripes, separated by larger hydrophilic domains. We characterize the morphology and dynamics of the dewetting front starting from an initially present dry-spot. Moreover, we study the distortion of the liquid film on the adjacent hydrophilic domains as a function of film thickness, hydrophobic contact angle and pattern dimensions. Implications of our results on the solution processing of organic electronic devices on chemically patterned surfaces are discussed.     

A numerical study exploring the effect of particle properties on the fluidization of adhesive particles

The effects of varying the elastic modulus, coefficient of restitution, and coefficient of friction of adhesive particles on fluidized bed dynamics have been investigated via numerical simulations. It is found that lower values of the elastic modulus and coefficient of restitution lead to a greater degree of particle clustering, and the formation of smaller bubbles. Coordination numbers are found to initially increase, and then fall, with increasing coefficient of friction, while bubble velocities follow the opposite trend. It is concluded that artificially reducing the elastic modulus of adhesive particles has a significant impact on the fluidization behavior. The change in dynamics of the fluidized bed due to varying the coefficient of friction is more complex: particle clustering increases up to a point, beyond which clusters become increasingly rigid. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1467–1477, 2016     

Kinetics studies and characterization of poly(furfuryl alcohol) for use as bio‐based furan novolacs

Poly(furfuryl alcohol) (PFA) is an attractive target for the development of bio‐based novolac resins. However, control of the polycondensation reaction is not well understood and side reactions are an important factor for PFA and the development of new resins. The polymerization reactions and kinetics of furfuryl alcohol and 2‐furyl ethanol into polymeric resins are detailed in this work. Nuclear magnetic resonance spectroscopy analysis of reaction kinetics, molecular weight analysis, and rheology analysis confirm that the polymerization reaction rate of 2‐furyl ethanol is much faster than that of furfuryl alcohol because the addition of this methyl group serves to stabilize the carbocation transition state. Side reactions, such as Diels–Alder crosslinking and in particular branching, are quantified and were found to be much more prevalent in the polymerization of PFA. The glass transition temperature was measured to be 376 K for PFA and only 294 K for poly(2‐furyl ethanol). Molecular dynamics simulations showed that the alternative structure that forms in PFA that causes branching results in greater backbone rigidity causing its higher glass transition temperature. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46608.     

Ductile and brittle material removal mechanisms in natural nacre—A model for novel implant materials

Nacre is a composite material found in the inner layer of sea shells. It consists of soft organic and hard inorganic components arranged in a complex hierarchical structure. Due to this arrangement, nacre exhibits outstanding mechanical properties (elastic modulus: 64.70 ± 3.50 GPa, hardness: 4.41 ± 0.45 GPa, density: 2.6 g/cm³). Therefore, nacreous implant materials have a high potential in many fields. In medical science, these materials might be used for bone replacement. This article provides an insight into the material removal mechanisms occurring in the scratching of natural nacre. Scratch tests are a simplification of the grinding process and are used to investigate the influence of single input parameters on the material removal. Different scratch tool geometries and varying processing parameters are applied, so that the material removal efficiency can be evaluated by analyzing the process forces. Additionally, the scratch geometry is examined by using a scanning electron microscope (SEM) and optical profilometer images as well as photomicrographs. The results of these examinations provide knowledge on the machinability of nacre and also on the machinability of new nacreous materials.     

Biodegradable magnesium implants for orthopedic applications

The clinical application of degradable orthopedic magnesium implants is a tangible vision in medical science. This interdisciplinary review discusses many different aspects of magnesium alloys comprising the manufacturing process and the latest research. We present the challenges of the manufacturing process of magnesium implants with the risk of contamination with impurities and its effect on corrosion. Furthermore, this paper provides a summary of the current examination methods used in in vitro and in vivo research of magnesium alloys. The influence of various parameters (most importantly the effect of the corrosive media) in in vitro studies and an overview about the current in vivo research is given.     

Significance of residual stress in PVD-coated carbide cutting tools

The performance of PVD-coated carbide cutting tools is influenced by their residual stress state, where coating and substrate subsurface have to be considered. The substrate stress is the result of different impacts caused by pre-coating processes and the PVD-coating itself. This presentation demonstrates the significance of residual stress in coating and substrate as well as the influence of each step of a conventional commercial process chain on the respective residual stress state for the manufacture of PVD-coated carbide cutting tools. Alterations of the process chain for tool micro geometry preparation by laser beam removal are considered.     

Adaptive process planning

The success of companies with job shop production strongly depends on their production flexibility. This is often significantly influenced by the process planning and production control. Aiming at maximizing production flexibility, this paper presents an approach to further integration of process planning and production control by combining and optimizing already existing planning methods. Essentially, in a rough planning stage, all process chains which are technological relevant to the manufacturing of a given product are taken into consideration. Applying a dynamic multi-criteria evaluation to all process chains ensures that the most appropriate, situation-specific process chain is chosen for production. This is done based on pre-established production targets, which facilitates a flexible response to incidents and other unplanned production events. The structure and functionalities of the presented approach are thoroughly explained in this paper and its feasibility is demonstrated with an example.     

In silico screening of carbon-capture materials

One of the main bottlenecks to deploying large-scale carbon dioxide capture and storage (CCS) in power plants is the energy required to separate the CO(2) from flue gas. For example, near-term CCS technology applied to coal-fired power plants is projected to reduce the net output of the plant by some 30% and to increase the cost of electricity by 60-80%. Developing capture materials and processes that reduce the parasitic energy imposed by CCS is therefore an important area of research. We have developed a computational approach to rank adsorbents for their performance in CCS. Using this analysis, we have screened hundreds of thousands of zeolite and zeolitic imidazolate framework structures and identified many different structures that have the potential to reduce the parasitic energy of CCS by 30-40% compared with near-term technologies.