An Investigation into BMP9-induced postnatal maturation of articular cartilage

Postnatal maturation is a process of articular cartilage development in which the tissue acquires biomechanical properties allowing lifelong cyclical loading in adults. During postnatal maturation cartilage undergoes structural and morphological changes, including the reorganisation of the collagen network from isotropic to one that is anisotropic, forming distinct zonal regions of collagen architecture and chondrocyte organisation. However, the mechanisms underlying the process of maturation are poorly understood. Currently there are no in vitro biological models of maturation, limiting study of this phenomenon to snapshots of histological, biochemical and biophysical changes. In this study we have shown that in situ culture of immature bovine cartilage explants with BMP9 induces changes in collagen structure and chondrocyte organisation recapitulating the zonal features of mature articular cartilage. We found BMP9 stimulates reorganisation of the collagen network causing the reorientation of mid and deep zone fibres perpendicular to the cartilage surface. Inhibition of matrix metalloproteinases (MMPs) via doxycycline prevented the changes observed in collagen alignment. Our results demonstrate that there is increased MMP3 expression and a reduction in tissue inhibitors of metalloproteinases-1 and -2 resulting in an increase in proteoglycan turnover and uptake of water. Of significant note were observations that show that cellular proliferation is involved in maturation, contrary to findings in mouse cartilage postnatal development, and immunological data showing that remodelling of collagen does not require enzymatic cleavage of pre-existing fibres. Whilst observations of BMP9 induced postnatal maturation in explants were variable, in vitro analysis using isolated chondrocytes grown as pellet cultures provided unequivocal evidence of the role of BMP9 in postnatal organisation of collagen fibrils in immature chondrocytes. In addition, pellet cultures show that mature chondrocytes have an intrinsic ability to recapitulate the mature cartilage collagen architecture, but even this is enhanced in the presence of BMP9. Therefore, we have developed useful models of postnatal maturation that have shone light on several important mechanisms that regulate the transition to maturity. We anticipate that our models of BMP9 induced postnatal maturation will provide the basis for further research into understanding the detailed mechanisms involved, guiding the development of more successful tissue engineering strategies

Observations of spatiotemporal instabilities in the strong-driving regime of an AC-driven nonlinear Schr\"odinger system

Localized dissipative structures (LDS) have been predicted to display a rich array of instabilities, yet systematic experimental studies have remained scarce. We have used a synchronously-driven optical fiber ring resonator to experimentally study LDS instabilities in the strong-driving regime of the AC-driven nonlinear Schr\"odinger equation (also known as the Lugiato-Lefever model). Through continuous variation of a single control parameter, we have observed a string of theoretically predicted instability modes, including irregular oscillations and chaotic collapses. Beyond a critical point, we observe behaviour reminiscent of a phase transition: LDSs trigger localized domains of spatiotemporal chaos that invade the surrounding homogeneous state. Our findings directly confirm a number of theoretical predictions, and they highlight that complex LDS instabilities can play a role in experimental systems.Comment: 6 pages, 4 figure

TriMet & TOD – Opportunities for Growth

Staff of the Tri-County Metropolitan Transportation District of Oregon (TriMet) will present TriMet\u27s recently published Regional Transit-Oriented Development (TOD) plan, explaining its inception, creation, and delivery. The team will explain how the plan fits within a hierarchy of regional and sub-regional plans and how it delivers transparency to TriMet\u27s TOD program, enabling all stakeholders to participate. Current TOD project examples will be showcased to demonstrate how partnerships can enhance project outcomes and indicate how stakeholders from various backgrounds can influence projects.https://pdxscholar.library.pdx.edu/trec_seminar/1244/thumbnail.jp

Super cavity solitons and the coexistence of multiple nonlinear states in a tristable passive Kerr resonator

Passive Kerr cavities driven by coherent laser fields display a rich landscape of nonlinear physics, including bistability, pattern formation, and localised dissipative structures (solitons). Their conceptual simplicity has for several decades offered an unprecedented window into nonlinear cavity dynamics, providing insights into numerous systems and applications ranging from all-optical memory devices to microresonator frequency combs. Yet despite the decades of study, a recent theoretical study has surprisingly alluded to an entirely new and unexplored paradigm in the regime where nonlinearly tilted cavity resonances overlap with one another [T. Hansson and S. Wabnitz, J. Opt. Soc. Am. B 32, 1259 (2015)]. We have used synchronously driven fiber ring resonators to experimentally access this regime, and observed the rise of new nonlinear dissipative states. Specifically, we have observed, for the first time to the best of our knowledge, the stable coexistence of dissipative (cavity) solitons and extended modulation instability (Turing) patterns, and performed real time measurements that unveil the dynamics of the ensuing nonlinear structures. When operating in the regime of continuous wave tristability, we have further observed the coexistence of two distinct cavity soliton states, one of which can be identified as a "super" cavity soliton as predicted by Hansson and Wabnitz. Our experimental findings are in excellent agreement with theoretical analyses and numerical simulations of the infinite-dimensional Ikeda map that governs the cavity dynamics. The results from our work reveal that experimental systems can support complex combinations of distinct nonlinear states, and they could have practical implications to future microresonator-based frequency comb sources.Comment: 13 pages, 6 figure

AnimDiff: Comparing 3D Animations for Revision Control

The process of animating a complex 3D character can be a time consuming activity which may take several iterations and several artists working in collaboration, each iteration improving some elements of the animation but potentially introducing artifacts in others. At present there exists no formal process to collate these various revisions in a manner that allows for close examination of their differences, which would help speed up the creation of 3D animations. To address this we present a method for equivalence checking and displaying differences between differing versions of an animated 3D model. Implemented in a tool that allows selective blending of animations, this provides a first step towards a 3D animation revision control system

Differencing and Merging for 3D Animation Revision Control.

Version Control System (VCS) techniques for managing the creation of 3D computer generated models exist for static 3D models, however, there are no solutions for revision control of the animation data from animated 3D models. A precondition for any type of VCS is the ability to compare two versions of an item, to identify the differences between them and to combine these. To this end, we propose a novel 3-way difference, merging and conflict resolution technique for 3D animation data

Physical and Geochemical Characterization of Two Wetlands in the Experimental Lakes Area, North-western Ontario, Canada

Anthropogenic disruptions in the form of hydrological alterations, such as dam construction and the associated water diversions are a cause of much upheaval to local and regional ecosystems. Lake 626 within the Experimental Lakes Area of north-west Ontario, along with its downstream wetlands, 626A and 626B are one such system. Construction of a dam at the L626 inflow has completely restricted water flow, reducing and reshaping the watershed, increasing water retention time, and decreasing outflow into the wetlands. This study investigates the state of each wetland through physical and geochemical characterization during the first year following the diversion. Previous studies have found that hydrological diversions in wetlands can lower water table levels, altering soil chemistry and producing a shift in floral and faunal communities. Ultimate consequences involve significant loss of wetland area through conversion to upland habitat. This provides a model for climatic warming scenarios, wherein sustained drought conditions can produce the same result. Boreal wetlands are surprising fragile ecosystems that store massive quantities of carbon and are at risk of releasing it in such situations. One study showed that an extended summer drought in an otherwise average year with above average precipitation produced losses of 90 g C/m2 over the course of the year. Maintenance of reduced-flow in wetlands 626A and 626B is expected to convert the system into a carbon source and reduce overall wetland area. Radiocarbon dating has revealed that following deglaciation, both 626A and 626B basins were open water wetlands, depositing limnic peat for about 3200 and 1300 years respectively. Each site then transitioned into open sedge dominated fen – 626B to the present and 626A until about 2.5 ka BP when Sphagnum began to develop. Wetland 626B is decidedly an open shrub/sedge fen, supporting Myrica gale, Chamaedaphne calyculata and Carex rostrata / lasiocarpa communities. Wetland 626A is a bog/fen complex, sharing similar communities in the fen areas, but housing a large, centrally located bog of shrub species overlying Sphagnum hummocks. Tritium values in 626A were similar to cosmic background levels, indicating that recharge of basal pore water has not occurred in at least 60 years. Tritium in 626B was much higher, suggesting a substantial difference in hydrology or peat hydraulic conductivity between the basins. Measurement of DOC profiles showed high concentrations in near-surface water, reaching over 80 mg/L, and dropping to about 20 mg/L at maximum depths. An opposite trend was seen for DIC and CH4 profiles which increased concentration with depth (25 – 70 mg/L DIC; 75 – 700 μmol/L CH4). Isotopically however, 13C signatures from basal DIC were more positive while signatures from CH4 were typically more negative (-6 ‰ to +4 ‰ DIC; -57 ‰ to -73 ‰ CH4). Breakdown of DOC by LC-OCD showed high concentrations of humic substances and low molecular weight neutrals. The origin of humic substances in surface water became more pedogenic with increasing distance from the L626 outflow, indicating the influence of decaying wetland vegetation on the DOC of adjacent water. A comparison between contemporary and future characterization of boreal peatlands under drought-like conditions will provide a better understanding of the impacts suffered by wetlands during hydrological alterations. The high sensitivity of wetlands to changing hydrology should also provide a measure for gauging the effects of long term climate warming. This will assist in the development of environmental policies to better govern both the establishment of water diversions and the multitude of other practices leading to climate change