Allylation and Thermosetting of Acetosolv Wheat Straw Lignin.

The acetosolv extraction, allylation and subsequent cross-linking of wheat straw lignin to thermoset biomaterials is herein described. The extraction temperature proved to be of great importance for the quality of the resulting lignin, with moderate temperature being key for preservation of β-O-4' linkages. The allylation of the acetosolv lignin was carried out using three different synthetic strategies, resulting in selective installation of either benzylic or phenolic allyl ethers, or unselective allylation of various hydroxyl groups via etherification and carboxyallylation.

Is Wear Still a Concern in Total Knee Arthroplasty With Contemporary Conventional and Highly Crosslinked Polyethylene Tibial Inserts in the mid- to Long-Term?

Background: Modern literature has brought into question if wear of tibial inserts made from conventional or highly crosslinked polyethylene (HXL PE) is still a factor limiting longevity of total knee arthroplasty (TKA) in the mid- to long-term. It is the objective of this study to determine: 1) most common causes of mid- to long-term TKA failure, 2) the prevalence of delamination, and 3) the medial/lateral linear wear rates of conventional and HXL PE tibial inserts retrieved in the mid- to long-term.

Methods: A tibial insert retrieval cohort of 107 inserts (79 conventional, 28 HXL PE) with a minimum time in situ of 6.

Impact of Prophylactic Cerclage Location on Femoral Fracture Propagation: A Biomechanical Study.

Objectives: Prophylactic cerclage cables are often placed intraoperatively about a fracture to prevent propagation. However, biomechanical data supporting optimal cable placement location are lacking. The objective of this study was to evaluate the impact of prophylactic cerclage placement location on the propagation of femoral shaft fractures.

Fretting-corrosion Apparatus with Low Magnitude Micro-motion (≤5 μm): Development and Preliminary Outcome.

Fretting-corrosion is one of the failure processes in many applications, including biomedical implants. For example, the modern design of hip implants with multiple components offers better flexibility and inventory storage. However, it will trigger the fretting at the implant interfaces with a small displacement amplitude (< 5 µm) and usually in a partial slip region.

Development of a computational-experimental framework for enhanced mechanical characterization and cross-species comparison of the articular cartilage superficial zone.

To provide a better understanding of the contribution of specific constituents (i.e. proteoglycan, collagen, fluid) to the mechanical behavior of the superficial zone of articular cartilage, a complex biological tissue with several time-dependent properties, a finite element model was developed.

Effect of Femoral Head Material, Surgeon Experience, and Assembly Technique on Simulated Head-Neck Total Hip Arthroplasty Impaction Forces.

Background: There is no standard method for assembling the femoral head onto the femoral stem during total hip arthroplasty (THA). This study aimed to measure and record dynamic 3-dimensional (3D) THA head-neck assembly loads from residents, fellows, and attending surgeons, for metal and ceramic femoral heads.

Methods: An instrumented apparatus measured dynamic 3D forces applied through the femoral stem taper in vitro for 31 surgeons (11 attendings, 14 residents, 6 fellows) using their preferred technique (ie, number of hits or mallet strikes).

Effect of Lumbar Fusion and Pelvic Fixation Rigidity on Hip Joint Stress: A Finite Element Analysis.

Study Design: This study compared hip stress among different types of lumbopelvic fusion based on finite element (FE) analysis.

Objective: We believe that the number and placement of S2 alar iliac (AI) screws and whether the screws loosen likely influence hip joint stress in the FE model.

Summary Of Background Data: Spinopelvic fixation has been shown to increase the risk of progression for hip joint osteoarthritis.

Electroreductive Desulfurative Transformations with Thioethers as Alkyl Radical Precursors.

Thioethers are highly prevalent functional groups in organic compounds of natural and synthetic origin but remain remarkably underexplored as starting materials in desulfurative transformations. As such, new synthetic methods are highly desirable to unlock the potential of the compound class. In this vein, electrochemistry is an ideal tool to enable new reactivity and selectivity under mild conditions.

Effect on bone anabolic markers of daily cheese intake with and without vitamin K: a randomised clinical trial.

Background: Daily intake of 57 g Jarlsberg cheese has been shown to increase the total serum osteocalcin (tOC). Is this a general cheese effect or specific for Jarlsberg containing vitamin K and 1,4-dihydroxy-2naphtoic acid (DHNA)?

Methods: 66 healthy female volunteers (HV) were recruited. By skewed randomisation (3:2), 41 HV were allocated to daily intake of 57 g Jarlsberg (J-group) and 25-50 g Camembert (C-group) in 6 weeks.

Electrosynthetic C-O Bond Activation in Alcohols and Alcohol Derivatives.

Alcohols and their derivatives are ubiquitous and versatile motifs in organic synthesis. Deoxygenative transformations of these compounds are often challenging due to the thermodynamic penalty associated with the cleavage of the C-O bond. However, electrochemically driven redox events have been shown to facilitate the C-O bond cleavage in alcohols and their derivatives either through direct electron transfer or through the use of electron transfer mediators and electroactive catalysts.

Electrosynthetic C-F bond cleavage.

Fluorinated organic compounds are common among pharmaceuticals, agrochemicals and materials. The significant strength of the C-F bond results in chemical inertness that, depending on the context, is beneficial, problematic or simply a formidable synthetic challenge. Electrosynthesis is a rapidly expanding methodology that can enable new reactivity and selectivity for cleavage and formation of chemical bonds.

Model validation for estimating taper microgroove deformation during total hip arthroplasty head-neck assembly.

Total hip arthroplasty (THA) failure and the need for revision surgery can result from fretting-corrosion damage of the head-neck modular taper junctions. Prior work has shown that implant geometry, such as microgrooves, influences damage on retrieved implants. Microgroove deformation within the modular taper junction occurs when the female head taper meets the male stem taper during THA surgical procedure.

Interaction of surface topography and taper mismatch on head-stem modular junction contact mechanics during assembly in modern total hip replacement.

Implant failure due to fretting corrosion at the head-stem modular junction is an increasing problem in modular total hip arthroplasty. The effect of varying microgroove topography on modular junction contact mechanics has not been well characterized. The aim of this study was to employ a novel, microgrooved finite element (FEA) model of the hip taper interface and assess the role of microgroove geometry and taper mismatch angle on the modular junction mechanics during assembly.

Are Damage Modes Related to Microstructure and Material Loss in Severely Damaged CoCrMo Femoral Heads?

Background: Fretting and corrosion in metal-on-polyethylene total hip arthoplasty (THA) modular junctions can cause adverse tissue reactions that are responsible for 2% to 5% of revision surgeries. Damage within cobalt-chromium-molybdenum (CoCrMo) alloy femoral heads can progress chemically and mechanically, leading to damage modes such as column damage, imprinting, and uniform fretting damage. At present, it is unclear which of these damage modes are most detrimental and how they may be linked to implant alloy metallurgy.

Modelling changes in modular taper micromechanics due to surgeon assembly technique in total hip arthroplasty.

Aims: The aim of this study was to develop a novel computational model for estimating head/stem taper mechanics during different simulated assembly conditions.

Methods: Finite element models of generic cobalt-chromium (CoCr) heads on a titanium stem taper were developed and driven using dynamic assembly loads collected from clinicians. To verify contact mechanics at the taper interface, comparisons of deformed microgroove characteristics (height and width of microgrooves) were made between model estimates with those measured from five retrieved implants.

Can a gait-dependent model predict wear on retrieved total knee arthroplasty components?

Aims: A retrospective longitudinal study was conducted to compare directly volumetric wear of retrieved polyethylene inserts to predicted volumetric wear modelled from individual gait mechanics of total knee arthroplasty (TKA) patients.

Methods: In total, 11 retrieved polyethylene tibial inserts were matched with gait analysis testing performed on those patients. Volumetric wear on the articular surfaces was measured using a laser coordinate measure machine and autonomous reconstruction.

Sensitivity of total knee replacement wear to variability in motion and load input: A parametric finite element analysis study.

Polyethylene wear remains a contributor to long term failure in total knee replacements (TKRs). Advances in materials have improved polyethylene wear rates, therefore further wear reductions require a better understanding of patient-specific factors that lead to wear. Variability of gait within patients is considerable and could lead to significant variability in wear rates that cannot be predicted by standard testing methods.

Kinetic Analysis as an Optimization Tool for Catalytic Esterification with a Moisture-Tolerant Zirconium Complex.

This work describes the use of kinetics as a tool for rational optimization of an esterification process with down to equimolar ratios of reagents using a recyclable commercially available zirconocene complex in catalytic amounts. In contrast to previously reported group IV metal-catalyzed esterification protocols, the work presented herein circumvents the use of water scavengers and perfluorooctane sulfonate (PFOS) ligands. Insights into the operating mechanism are presented.

Contact conditions for total hip head-neck modular taper junctions with microgrooved stem tapers.

Implant failure due to fretting-corrosion of head-neck modular junctions is a rising problem in total hip arthroplasty. Fretting-corrosion initiates when micromotion leads to metal release; however, factors leading to micromotion, such as microgrooves on the stem taper, are not fully understood. The purpose of this study is to describe a finite element analysis technique to determine head-neck contact mechanics and investigate the effect of stem taper microgroove height during head-neck assembly.

Hindered dialkyl ether synthesis with electrogenerated carbocations.

Hindered ethers are of high value for various applications; however, they remain an underexplored area of chemical space because they are difficult to synthesize via conventional reactions. Such motifs are highly coveted in medicinal chemistry, because extensive substitution about the ether bond prevents unwanted metabolic processes that can lead to rapid degradation in vivo. Here we report a simple route towards the synthesis of hindered ethers, in which electrochemical oxidation is used to liberate high-energy carbocations from simple carboxylic acids.

iQCAR: A Demonstration of an Inter-Query Contention Analyzer for Cluster Computing Frameworks.

Unpredictability in query runtimes can arise in a shared cluster as a result of resource contentions caused by inter-query interactions. iQCAR - nter uery ontention nalyze is a system that formally models these interferences between concurrent queries and provides a framework to attribute blame for contentions. iQCAR leverages a multi-level directed acyclic graph called iQC-Graph to diagnose the aberrations in query schedules that lead to these resource contentions.