Contact area, pressure distribution and mechanical stability in external arthrodesis of the ankle joint

The ankle joint is often affected by arthritis, giving a joint that is painful, stiff, and restricts movement. This can result in a huge loss of mobility for the sufferer. Unlike replacement of the hip, the replacement of a diseased ankle joint is not as straightforward and the outcomes do not reach the same success levels. The preferred surgical choice is arthrodesis, a procedure whereby the two bones forming the joint are fused together to eliminate the joint and hence pain. The success of the procedure is dependent upon several factors, two of the most significant being the levels of contact area and pressure achieved during the compression period, during which bone growth occurs across the two bones being compressed together. These factors influence joint stability and micromotion at the bone to bone interface during this growth phase. This study investigates the levels of contact areas and pressures that can be achieved for different arthodesis variables. These variables include the joint shape, which can be curved or flat, and the position of the compression pin within the talus, namely anteriorly or centrally positioned with reference to the talar dome. Influence of the Achilles tendon in joint stability is also investigated. A test rig was developed allowing load/deflection curves to be determined for various configurations of these variables. Models representing the bones under consideration, together with pressure sensitive film, allowed measurement of contact areas and pressures within the joint under compression, achieved using pins and instrumented compression rods. Results indicate there is little significant variation in contact area and pressure for the different shaped joint cuts, however, if the talar pin is placed in a more anterior position then the contact area can be improved over a centrally positioned pin. Anterior pin placement also gives increased resistance to motion and mechanical stability. It has been established that the athrodesis construct is especially weak in terms of rotation about the tibial axis, and the results from this study indicate that through the use of a curved joint shape the resistance to this motion can be improved greatly

Inhibition of hepatitis C virus RNA replication by ISG15 does not require its conjugation to protein substrates by the HERC5 E3 ligase

Chronic infection of the liver by hepatitis C virus (HCV) induces a range of host factors including IFN-stimulated genes such as ISG15. ISG15 functions as an antiviral factor that limits virus replication. Previous studies have suggested that ISG15 could influence HCV replication in both a positive and a negative manner. In this report, we determined the effect of ISG15 on HCV RNA replication in two independent cell lines that support viral genome synthesis by inhibiting ISG15 expression through small interfering RNA, short-hairpin RNA and CRISPR/Cas9 gene knockout approaches. Our results demonstrated that ISG15 impairs HCV RNA replication in both the presence and absence of IFN stimulation, consistent with an antiviral role for ISG15 during HCV infection. ISG15 conjugation to protein substrates typically requires the E3 ligase, HERC5. Our results showed that the inhibitory effect of ISG15 on HCV RNA replication does not require its conjugation to substrates by HERC5

Plans for the first balloon flight of the gamma-ray polarimeter experiment (GRAPE)

We have developed a design for a hard X-ray polarimeter operating in the energy range from 50 to 500 keV. This modular design, known as GRAPE (Gamma-Ray Polarimeter Experiment), has been successfully demonstrated in the lab using partially polarized gamma-ray sources and using fully polarized photon beams at Argonne National Laboratory. In June of 2007, a GRAPE engineering model, consisting of a single detector module, was flown on a high altitude balloon flight to further demonstrate the design and to collect background data. We are currently preparing a much larger balloon payload for a flight in the fall of 2011. Using a large (16-element) array of detector modules, this payload is being designed to search for polarization from known point sources of radiation, namely the Crab and Cygnus X-1. This first flight will not only provide a scientific demonstration of the GRAPE design (by measuring polarization from the Crab nebula), it will also lay the foundation for subsequent long duration balloon flights that will be designed for studying polarization from gamma-ray bursts and solar flares. Here we shall present data from calibration of the first flight module detectors, review the latest payload design and update the predicted polarization sensitivity for both the initial continental US balloon flight and the subsequent long-duration balloon flights

GRAPE: a balloon-borne gamma-ray polarimeter

The Gamma-RAy Polarimeter Experiment (GRAPE) is a concept for an astronomical hard X-ray Compton polarimeter operating in the 50 - 500 keV energy band. The instrument has been optimized for wide-field polarization measurements of transient outbursts from energetic astrophysical objects such as gamma-ray bursts and solar flares. The GRAPE instrument is composed of identical modules, each of which consists of an array of scintillator elements read out by a multi-anode photomultiplier tube (MAPMT). Incident photons Compton scatter in plastic scintillator elements and are subsequently absorbed in inorganic scintillator elements; a net polarization signal is revealed by a characteristic asymmetry in the azimuthal scattering angles. We have constructed a prototype GRAPE module that has been calibrated at a polarized hard X-ray beam and flown on an engineering balloon test flight. A full-scale scientific balloon payload, consisting of up to 36 modules, is currently under development. The first flight, a one-day flight scheduled for 2011, will verify the expected scientific performance with a pointed observation of the Crab Nebula. We will then propose long-duration balloon flights to observe gamma-ray bursts and solar flares

Forum Guest Editors’ Introduction: Disability Studies in Education “At Work”

This introductory article serves as the springboard for a greater discussion of the question: How applicable are the ideas of Disability Studies in Education to educational policy and the practice of teaching? As guest editors of the special forum of RDS, we illustrate how DSE continues to inform educational theory, research, policy, and practice. First, we chronicle the rapid growth of DSE over the past decade. Second, as educators of teachers, we raise three topics to contemplate further for our field: (1) improving the relationship between science and ethics, (2) better connecting knowledge, beliefs, and values to practice, and (3) determining the position of DSE scholars within the field of special education. Third, we briefly highlight the four featured articles from Belgium, New Zealand, Scotland, and the USA that constitute this special forum. Finally, we urge the field of education to be more critical of special education practices and continue to be receptive toward DSE

The effect of bubble size on the performance of ebullated bed hydroprocessors

A recent cold-flow study has revealed that modifying gas distributor design in three-phased fluidized beds can have a significant effect on overall phase hold-ups and regime transition velocities, even at equivalent phase velocities. It is conjectured that this can be attributed to changes in the bubble-size distribution within the reactor. This study aims to develop a complete kinetic-hydrodynamic model of a resid hydroprocessing ebullated bed reactor with internal recycle in order to study the effects of bubble size distribution on performance metrics of industrial significance. The model consists of combined catalytic and ther-mal reaction models, phase separation efficiency correlations obtained through CFD modelling, catalyst fouling and deactivation models, boiling-point based Vapour-Liquid Equilibria (VLE) relations, and specialized phase hold-up corre-lations developed for resid hydroprocessing applications. A preliminary hydrodynamic model comparing monodisperse bubble sizes between 0.5 mm and 4 mm has been performed. At the lowest bubble size, gas entrainment (and hence gas hold-up) were maximal, while ideal phase separation was achieved at the largest bubble size. Bed gas hold-ups ranged from 10 % to 40 %. Increased gas entrainment was also associated with a decrease in internal liquid recycle ratio required for design ebullation height. The effect of bubble size was most pronounced near a diameter of 1 mm. Ongoing analysis into the effect of bubble recycle on bed gas phase com-position in a reactive system is being performed. The effect of bubble size on liquid residence time and hence conversion will be studied with the objective of determining the optimal bubble size for maximizing key conversion parameters

Survey of European Green Crabs and Asian Shore Crabs in Salem Sound

The European green crab (Carcinus maenas) has been the dominant crab species in New England rocky intertidal zones since the late 1800’s, but since around 2000 they have begun to be outcompeted by a new invasive species, the Asian shore crab (Hemigrapsus sanguineus). Rocky intertidal zones at Chandler Hovey Park in Marblehead, MA and Pavilion Beach in Ipswich, MA were surveyed for both species monthly at low tide from June 2019 through March 2020. Asian shore crabs made up 94% of all crabs surveyed compared to European green crabs (6%). Also, at both sites, the average carapace width of European green crabs was found to be larger than that of the Asian shore crabs collected. From this survey, it appears that Asian shore crabs are outcompeting European green crabs at these locations

Fusion of Diverse Performance Inertial Sensors for Improved Attitude Estimation Within a Stabilisation Platform for Electro-optic Systems

Within line of sight pointing and stabilisation of EO (Electro-optic) systems operating under motion disturbances it is desirable to measure the inertial orientation of different parts of the system, not just the line of sight - this would allow additional information to be added to the control loop. To implement this a framework to fuse the multiple inertial sensors of the EO system is considered, with an example implemented. The fusion of higher performance sensors located at the line of sight is implemented within the proposed framework, to improve the performance of the estimate at the location of the lower performance sensor. The fusion framework makes use of cascaded Multiplicative Extended Kalman Filter that estimate the multiplicative error of the quaternion orientation estimate

Simulations of a monolithic lanthanum bromide gamma-ray detector

We have been working on the development of a detector design for a large area coded aperture imaging system operating in the 10-600 keV energy range. The detector design is based on an array of Lanthanum Bromide (LaBr3) scintillators, each directly coupled to a Hamamatsu 64-channel multi-anode photomultiplier tube (MAPMT). This paper focuses on the development of the GEANT4-based simulations as an aid in the optimization of the detector design. The simulations have been validated by comparisons with various laboratory data sets. We will summarize the current status and latest findings from this study