Fretting corrosion in modular orthopedic implants is a well-documented process that may be associated with adverse local tissue reactions, pain, and revisions. Engineering modular junction interfaces ...to withstand applied fretting motion without surface abrasion could prevent implant degradation and surface damage. Previous work on geometrically modified Ti-6Al-4V/CoCrMo interfaces with increased compliance showed reduced fretting currents and surface damage during short term, variable-load in vitro testing. This study assesses the same interfaces under long-term conditions using an in vitro pin-on-disk fretting corrosion test apparatus. Preliminary variable-load frequency testing of typical control pin geometries showed a frequency-dependent current response, with underlying contact conditions of metal-metal interfaces that remained unchanged. One-million-cycle testing showed diminished fretting currents in all groups by 5 × 10
cycles, but consistently lower currents in the high-compliance group. Corresponding fretting currents and work of fretting measurements of high-compliance pins confirmed that minimal fretting was experienced at the interface, with elastic bending of the pin accounting for almost all applied displacement. Debris generated during testing were composed of titanium and chromium oxides, small amounts of cobalt and molybdenum oxides, and sodium and phosphate originating from the surrounding test solution. Post-test analyses of sample surfaces revealed substantially more surface damage on CoCrMo disks than Ti-6Al-4V pins, thought to be a result of adhesive wear of mixed oxide debris on the pin and abrasion of the disk by the oxide debris layer. Surface damage to high-compliance pins suggests some abrasion is unavoidable with geometric modifications.
Fretting-corrosion tests using varying cantilever-shaped contact geometries (representing varying compliances) were performed using Ti-6Al-4V and CoCrMo alloys in combination. Fretting mechanics and ...fretting corrosion currents were used to determine fretting corrosion regime boundaries between stick, stick-slip, and slip for each interfacial compliance. Results showed a highly-correlated and material-dependent relationship between work of fretting (dissipated energy) and fretting current. A high interfacial compliance reduced relative fretting micromotion, induced stick and stick-slip conditions at lower loads, and were more robust against smaller displacements. Additional alloy-dependent effects were observed. Fretting corrosion maps were developed to characterize each interface's contact conditions over a range of forces and displacements. These results could be used in design-based solutions that encourage head-neck taper locking, minimizing mechanically-assisted corrosion in vivo.
•Geometric changes to metal-metal junctions can reduce fretting corrosion damage.•Modified surface contact geometries can create a more compliant interface.•Compliant interfaces prevent oxide abrasion of metal surfaces, reducing damage.•Compliant geometries elastically bend during fretting, creating a ‘stick’ regime.•Fretting corrosion maps characterize contact mechanics over a range of conditions.
Rapid climate warming is altering Arctic and alpine tundra ecosystem structure and function, including shifts in plant phenology. While the advancement of green up and flowering are well-documented, ...it remains unclear whether all phenophases, particularly those later in the season, will shift in unison or respond divergently to warming. Here, we present the largest synthesis to our knowledge of experimental warming effects on tundra plant phenology from the International Tundra Experiment. We examine the effect of warming on a suite of season-wide plant phenophases. Results challenge the expectation that all phenophases will advance in unison to warming. Instead, we find that experimental warming caused: (1) larger phenological shifts in reproductive versus vegetative phenophases and (2) advanced reproductive phenophases and green up but delayed leaf senescence which translated to a lengthening of the growing season by approximately 3%. Patterns were consistent across sites, plant species and over time. The advancement of reproductive seasons and lengthening of growing seasons may have significant consequences for trophic interactions and ecosystem function across the tundra.
Personalized medicine strategies using genomic profiling are particularly pertinent for pancreas cancer. The Individualized Molecular Pancreatic Cancer Therapy (IMPaCT) trial was initially designed ...to exploit results from genome sequencing of pancreatic cancer under the auspices of the International Cancer Genome Consortium (ICGC) in Australia. Sequencing revealed small subsets of patients with aberrations in their tumor genome that could be targeted with currently available therapies.
The pilot stage of the IMPaCT trial assessed the feasibility of acquiring suitable tumor specimens for molecular analysis and returning high-quality actionable genomic data within a clinically acceptable timeframe. We screened for three molecular targets: HER2 amplification; KRAS wild-type; and mutations in DNA damage repair pathways (BRCA1, BRCA2, PALB2, ATM).
Tumor biopsy and archived tumor samples were collected from 93 patients and 76 were screened. To date 22 candidate cases have been identified: 14 KRAS wild-type, 5 cases of HER2 amplification, 2 mutations in BRCA2, and 1 ATM mutation. Median time from consent to the return of validated results was 21.5 days. An inability to obtain a biopsy or insufficient tumor content in the available specimen were common reasons for patient exclusion from molecular analysis while deteriorating performance status prohibited a number of patients from proceeding in the study.
Documenting the feasibility of acquiring and screening biospecimens for actionable molecular targets in real time will aid other groups embarking on similar trials. Key elements include the need to better prescreen patients, screen more patients, and offer more attractive clinical trial options.
Electronic health records (EHRs) have become ubiquitous tools and represent the standard of care for 96% of hospitals and 86% of ambulatory physicians in the United States. With adoption of EHRs came ...the promise of improved efficiency, higher-quality care, and lower costs. Unfortunately, some clinicians are now spending twice as much time on documentation as they spend seeing patients, and the documentation paradigm of problem-oriented medical records is contributing to this imbalance. It is time to consider new innovations. The collaborative wiki format offers many opportunities to ease the burden of documentation as well as to increase the usefulness of the recorded clinical data. Wikis support multiple authorship, have built-in features to track edits and changes, allow for contextual linkages (e.g., linking medical problems to their treatment), and support new technologies such as application programming interfaces, which allow for safe and secure exchange of information. In this Perspective, the authors describe the rationale for considering this approach to clinical documentation and propose a pilot to learn about its effectiveness. They believe wiki-based documentation will become increasingly attractive, especially as new legislation and directives from policymakers seek to reduce the crushing documentation burden and as the U.S. health care system transitions from an episode-based payment structure to a value-based, outcomes-focused system.
ABSTRACT
We present large-scale structure catalogues from the completed extended Baryon Oscillation Spectroscopic Survey (eBOSS). Derived from Sloan Digital Sky Survey (SDSS) IV Data Release 16 ...(DR16), these catalogues provide the data samples, corrected for observational systematics, and random positions sampling the survey selection function. Combined, they allow large-scale clustering measurements suitable for testing cosmological models. We describe the methods used to create these catalogues for the eBOSS DR16 Luminous Red Galaxy (LRG) and Quasar samples. The quasar catalogue contains 343 708 redshifts with 0.8 < z < 2.2 over 4808 deg2. We combine 174 816 eBOSS LRG redshifts over 4242 deg2 in the redshift interval 0.6 < z < 1.0 with SDSS-III BOSS LRGs in the same redshift range to produce a combined sample of 377 458 galaxy redshifts distributed over 9493 deg2. Improved algorithms for estimating redshifts allow that 98 per cent of LRG observations result in a successful redshift, with less than one per cent catastrophic failures (Δz > 1000 km s−1). For quasars, these rates are 95 and 2 per cent (with Δz > 3000 km s−1). We apply corrections for trends between the number densities of our samples and the properties of the imaging and spectroscopic data. For example, the quasar catalogue obtains a χ2/DoF = 776/10 for a null test against imaging depth before corrections and a χ2/DoF= 6/8 after. The catalogues, combined with careful consideration of the details of their construction found here-in, allow companion papers to present cosmological results with negligible impact from observational systematic uncertainties.
Porphyromonas gingivalis is a Gram-negative anaerobic periodontal microorganism strongly associated with tissue-destructive processes in human periodontitis. Following oral infection with P. ...gingivalis, the periodontal bone loss in mice is reported to require the engagement of Toll-like receptor 2 (TLR2). Serine-glycine lipodipeptide or glycine aminolipid classes of P. gingivalis engage human and mouse TLR2, but a novel lipid class reported here is considerably more potent in engaging TLR2 and the heterodimer receptor TLR2/TLR6. The novel lipid class, termed Lipid 1256, consists of a diacylated phosphoglycerol moiety linked to a serine-glycine lipodipeptide previously termed Lipid 654. Lipid 1256 is approximately 50-fold more potent in engaging TLR2 than the previously reported serine-glycine lipid classes. Lipid 1256 also stimulates cytokine secretory responses from peripheral blood monocytes and is recovered in selected oral and intestinal Bacteroidetes organisms. Therefore, these findings suggest that Lipid 1256 may be a microbial TLR2 ligand relevant to chronic periodontitis in humans.
Human vestibular processing involves distributed networks of cortical and subcortical regions which perform sensory and multimodal integrative functions. These functional hubs are also interconnected ...with areas subserving cognitive, affective, and body-representative domains. Analysis of these diverse components of the vestibular and vestibular-associated networks, and synthesis of their holistic functioning, is therefore vital to our understanding of the genesis of vestibular dysfunctions and aid treatment development. Novel neuroimaging methodologies, including functional and structural connectivity analyses, have provided important contributions in this area, but often require the use of atlases which are comprised of well-defined a priori regions of interest. Investigating vestibular dysfunction requires a more detailed atlas that encompasses cortical, subcortical, cerebellar, and brainstem regions. The present paper represents an effort to establish a compilation of existing, peer-reviewed brain atlases which collectively afford comprehensive coverage of these regions while explicitly focusing on vestibular substrates. It is expected that this compilation will be iteratively improved with additional contributions from researchers in the field.
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