Recent Developments in the Design, Capabilities and Autonomous Operations of a Lightweight Surface Manipulation System and Test-bed

The first generation of a versatile high performance device for performing payload handling and assembly operations on planetary surfaces, the Lightweight Surface Manipulation System (LSMS), has been designed and built. Over the course of its development, conventional crane type payload handling configurations and operations have been successfully demonstrated and the range of motion, types of operations and the versatility greatly expanded. This enhanced set of 1st generation LSMS hardware is now serving as a laboratory test-bed allowing the continuing development of end effectors, operational techniques and remotely controlled and automated operations. This paper describes the most recent LSMS and test-bed development activities, that have focused on two major efforts. The first effort was to complete a preliminary design of the 2nd generation LSMS that has the capability for limited mobility and can reposition itself between lander decks, mobility chassis, and fixed base locations. A major portion of this effort involved conducting a study to establish the feasibility of, and define, the specifications for a lightweight cable-drive waist joint. The second effort was to continue expanding the versatility and autonomy of large planetary surface manipulators using the 1st generation LSMS as a test-bed. This has been accomplished by increasing manipulator capabilities and efficiencies through both design changes and tool and end effector development. A software development effort has expanded the operational capabilities of the LSMS test-bed to include; autonomous operations based on stored paths, use of a vision system for target acquisition and tracking, and remote command and control over a communications bridge

Modeling the impact of floating oyster (Crassostrea virginica) aquaculture on sediment−water nutrient and oxygen fluxes

Bivalve aquaculture relies on naturally occurring phytoplankton, zooplankton, and detritus as food sources, thereby avoiding external nutrient inputs that are commonly associated with finfish aquaculture. High filtration rates and concentrated bivalve biomass within aquacul- ture operations, however, result in intense biodeposition of particulate organic matter (POM) on surrounding sediments, with potential adverse environmental impacts. Estimating the net deposi- tional flux is difficult in shallow waters due to methodological constraints and dynamic processes such as resuspension and advection. In this study, we combined sediment trap deployments with simulations from a mechanistic sediment flux model to estimate seasonal POM deposition, resus- pension, and processing within sediments in the vicinity of an eastern oyster Crassostrea virginica farm in the Choptank River, Maryland, USA. The model is the stand-alone version of a 2-layer sediment flux model currently implemented within larger models for understanding ecosystem responses to nutrient management. Modeled sediment−water fluxes were compared to observed denitrification rates and nitrite + nitrate (NO2 −+NO3 −), phosphate (PO4 3−) and dissolved O2 fluxes. Model-derived estimates of POM deposition, which represent POM incorporated and processed within the sediment, comprised a small fraction of the material collected in sediment traps. These results highlight the roles of biodeposit resuspension and transport in effectively removing oyster biodeposits away from this particular farm, resulting in a highly diminished local environmental impact. This study highlights the value of sediment models as a practical tool for computing inte- grated measures of nitrogen cycling as a function of seasonal dynamics in the vicinity of aquaculture operations

Viral Endomyocardial Infection Is an Independent Predictor and Potentially Treatable Risk Factor for Graft Loss and Coronary Vasculopathy in Pediatric Cardiac Transplant Recipients

ObjectivesThis study sought to evaluate the outcome and prevalence of viral endomyocardial infection after cardiac transplantation.BackgroundViral myocardial infection causes heart failure, but its role after cardiac transplantation is unclear. We hypothesized that viral infection of the cardiac allograft reduces graft survival.MethodsBetween June 1999 and November 2004, 94 pediatric cardiac transplant patients were screened for the presence of viral genome in serial endomyocardial biopsies (EMBs) using polymerase chain reaction (PCR) assays. Graft loss, advanced transplant coronary artery disease (TCAD), and acute rejection (AR) were compared in the PCR-positive (n = 37) and PCR-negative (n = 57) groups, using time-dependent Kaplan-Meier and Cox regression analyses. From November 2002 to November 2004, intravenous immunoglobulin therapy (IVIG) was administered to patients with PCR-positive EMBs. The outcomes of the IVIG-treated, PCR-positive patients (n = 20) were compared with IVIG-untreated, PCR-positive patients (n = 17).ResultsViral genomes were detected in EMBs from 37 (39%) patients; parvovirus B19, adenovirus, and Epstein-Barr virus (EBV) were the most common. The PCR-positive group (n = 37, 25% graft loss at 2.4 years) had decreased graft survival (p < 0.001) compared with the PCR-negative group (n = 57, 25% graft loss at 8.7 years) and developed advanced TCAD prematurely (p = 0.001). The number of AR episodes was similar in both groups. On multivariate analysis, presence of viral genome was an independent risk factor for graft loss (relative risk: 4.2, p = 0.015). The time to advanced TCAD after becoming PCR-positive was longer in the IVIG-treated patients (p = 0.03) with a trend toward improved graft survival (p = 0.06).ConclusionsViral endomyocardial infection is an independent predictor of graft loss in pediatric cardiac transplant recipients. This effect appears to be mediated through premature development of advanced TCAD. IVIG therapy in this subgroup may improve survival and merits further investigation

Mode coupling in the nonlinear response of black holes

We study the properties of the outgoing gravitational wave produced when a non-spinning black hole is excited by an ingoing gravitational wave. Simulations using a numerical code for solving Einstein's equations allow the study to be extended from the linearized approximation, where the system is treated as a perturbed Schwarzschild black hole, to the fully nonlinear regime. Several nonlinear features are found which bear importance to the data analysis of gravitational waves. When compared to the results obtained in the linearized approximation, we observe large phase shifts, a stronger than linear generation of gravitational wave output and considerable generation of radiation in polarization states which are not found in the linearized approximation. In terms of a spherical harmonic decomposition, the nonlinear properties of the harmonic amplitudes have simple scaling properties which offer an economical way to catalog the details of the waves produced in such black hole processes.Comment: 17 pages, 20 figures, abstract and introduction re-writte

Simulating (electro)hydrodynamic effects in colloidal dispersions: smoothed profile method

Previously, we have proposed a direct simulation scheme for colloidal dispersions in a Newtonian solvent [Phys.Rev.E 71,036707 (2005)]. An improved formulation called the ``Smoothed Profile (SP) method'' is presented here in which simultaneous time-marching is used for the host fluid and colloids. The SP method is a direct numerical simulation of particulate flows and provides a coupling scheme between the continuum fluid dynamics and rigid-body dynamics through utilization of a smoothed profile for the colloidal particles. Moreover, the improved formulation includes an extension to incorporate multi-component fluids, allowing systems such as charged colloids in electrolyte solutions to be studied. The dynamics of the colloidal dispersions are solved with the same computational cost as required for solving non-particulate flows. Numerical results which assess the hydrodynamic interactions of colloidal dispersions are presented to validate the SP method. The SP method is not restricted to particular constitutive models of the host fluids and can hence be applied to colloidal dispersions in complex fluids

Non-homologous end-joining pathway associated with occurrence of myocardial infarction: gene set analysis of genome-wide association study data

&lt;p&gt;Purpose: DNA repair deficiencies have been postulated to play a role in the development and progression of cardiovascular disease (CVD). The hypothesis is that DNA damage accumulating with age may induce cell death, which promotes formation of unstable plaques. Defects in DNA repair mechanisms may therefore increase the risk of CVD events. We examined whether the joints effect of common genetic variants in 5 DNA repair pathways may influence the risk of CVD events.&lt;/p&gt; &lt;p&gt;Methods: The PLINK set-based test was used to examine the association to myocardial infarction (MI) of the DNA repair pathway in GWAS data of 866 subjects of the GENetic DEterminants of Restenosis (GENDER) study and 5,244 subjects of the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER) study. We included the main DNA repair pathways (base excision repair, nucleotide excision repair, mismatch repair, homologous recombination and non-homologous end-joining (NHEJ)) in the analysis.&lt;/p&gt; &lt;p&gt;Results: The NHEJ pathway was associated with the occurrence of MI in both GENDER (P = 0.0083) and PROSPER (P = 0.014). This association was mainly driven by genetic variation in the MRE11A gene (PGENDER = 0.0001 and PPROSPER = 0.002). The homologous recombination pathway was associated with MI in GENDER only (P = 0.011), for the other pathways no associations were observed.&lt;/p&gt; &lt;p&gt;Conclusion: This is the first study analyzing the joint effect of common genetic variation in DNA repair pathways and the risk of CVD events, demonstrating an association between the NHEJ pathway and MI in 2 different cohorts.&lt;/p&gt

Pallium Canada's curriculum development model: A framework to support large-scale courseware development and deployment

The need to improve access to palliative care across multiple settings and disease groups has been identified. This requires equipping health care professionals from many different professions, including physicians and nurses, among others, with basic palliative care competencies to provide a palliative care approach. Pallium Canada’s Curriculum Development Framework supports the development, deployment, and dissemination, on a large scale, of multiple courses targeting health care professionals across multiple settings of care and disease groups. The Framework is made up of eight phases: (1) Concept, (2) Decision, (3) Curriculum Planning, (4) Prototype Development, (5) Piloting, (6) Dissemination, (7) Language and Cultural Adaptation, and (8) Ongoing Maintenance and Updates. Several of these phases include iterative cyclical activities. The framework allows multiple courses to be developed simultaneously, staggered in a production line with each phase and their corresponding activities requiring different levels of resources and stakeholder engagement. The framework has allowed Pallium Canada to develop, launch, and maintain numerous versions of its Learning Essential Approaches to Palliative Care (LEAP) courses concurrently. It leverages existing LEAP courses and curriculum materials to produce new LEAP courses, allowing significant efficiencies and maximizing output. This article describes the framework and its various activities, which we believe could be very useful for other jurisdictions undertaking the work of developing education programs to spread the palliative care approach across multiple settings, specialties, and disease groups

Grazing Collisions of Black Holes via the Excision of Singularities

We present the first simulations of non-headon (grazing) collisions of binary black holes in which the black hole singularities have been excised from the computational domain. Initially two equal mass black holes $m$ are separated a distance $\approx10m$ and with impact parameter $\approx2m$. Initial data are based on superposed, boosted (velocity $\approx0.5c$) solutions of single black holes in Kerr-Schild coordinates. Both rotating and non-rotating black holes are considered. The excised regions containing the singularities are specified by following the dynamics of apparent horizons. Evolutions of up to $t \approx 35m$ are obtained in which two initially separate apparent horizons are present for $t\approx3.8m$. At that time a single enveloping apparent horizon forms, indicating that the holes have merged. Apparent horizon area estimates suggest gravitational radiation of about 2.6% of the total mass. The evolutions end after a moderate amount of time because of instabilities.Comment: 2 References corrected, reference to figure update