292 research outputs found
ASSESSING THE EFFECTIVENESS OF MPP AND TEA ADVERTISING AND PROMOTION EFFORTS IN THE JAPANESE MARKET FOR MEATS
An Inverse Almost Ideal Demand System is utilized to determine the effectiveness of Market Promotion Program (MPP) and Target Export Assistance (TEA) advertising and promotion expenditures in the Japanese market for meat. Using annual data, it is found that beef advertising and promotion has had a positive and significant effect on the demand for beef. There is insufficient evidence to conclude that pork and poultry advertising and promotion increased the demand for either commodity.Marketing,
eNOS transfection of adipose-derived stem cells yields bioactive nitric oxide production and improved results in vascular tissue engineering.
This study evaluates the durability of a novel tissue engineered blood vessel (TEBV) created by seeding a natural vascular tissue scaffold (decellularized human saphenous vein allograft) with autologous adipose-derived stem cells (ASC) differentiated into endothelial-like cells. Previous work with this model revealed the graft to be thrombogenic, likely due to inadequate endothelial differentiation as evidenced by minimal production of nitric oxide (NO). To evaluate the importance of NO expression by the seeded cells, we created TEBV using autologous ASC transfected with the endothelial nitric oxide synthase (eNOS) gene to produce NO. We found that transfected ASC produced NO at levels similar to endothelial cell (EC) controls in vitro which was capable of causing vasorelaxation of aortic specimens ex vivo. TEBV (nâ=â5) created with NO-producing ASC and implanted as interposition grafts within the aorta of rabbits remained patent for two months and demonstrated a non-thrombogenic surface compared to unseeded controls (nâ=â5). Despite the xenograft nature of the scaffold, the TEBV structure remained well preserved in seeded grafts. In sum, this study demonstrates that upregulation of NO expression within adult stem cells differentiated towards an endothelial-like lineage imparts a non-thrombogenic phenotype and highlights the importance of NO production by cells to be used as endothelial cell substitutes in vascular tissue engineering applications
Revisiting ecological carrying capacity indices for bivalve culture
Ecological carrying capacity (ECC) indices for bivalve culture rely on key ecosystem turnover rates: 1. clearance time (CT), the time needed for the cultured bivalves to filter the entire bay volume; 2. renewal time (RT), the time required to replace the entire bay volume with external water; and 3. production time (PT), the time needed for phytoplankton biomass renewal via local primary production. These turnover rates are conceptually straightforward but lack measurement standardizations in the context of ECC assessments. This study compares simple turnover rate methods with more complex approaches designed to address key assumptions and improve accuracy. Method comparisons were performed across multiple embayments (systems) in Prince Edward Island, Canada. When crop aggregation and system-scale refiltration effects were considered, CT increased by a factor of 14 to 22 depending on the system and species under cultivation. Seasonal temperature considerations further impacted CT by a factor of 38 to 142. Regarding RT, validated hydrodynamic models and tidal prism models produced remarkably different outcomes; the tidal prism approach underestimated RT by 77â94% across the studied systems. Conversely, PT was unaffected by contrasting phytoplankton parameterization; pre-aquaculture (1969â1970) and contemporary (2011â2012) datasets led to similar PT outcomes. However, other metrics revealed a contemporary shift towards low phytoplankton biomass and smaller phytoplankton cells (picophytoplankton); these observations suggest that PT provides insufficient granularity regarding microalgae biomass replacement. Overall, the study rejects a common assumption that the bay-scale turnover rates serving the conventional CT/RT and CT/PT indices can be easily and accurately parameterized; these indices should be used cautiously in assessing the sustainability of farming activities.publishedVersio
Physiological differences between wild and cultured bivalves in Prince Edward Island, Canada
Bivalve culture in Canada increased by 25% from 2000 to 2016. In Prince Edward Island (PEI), bivalves are cultivated in bays and estuaries and there is limited space for further aquaculture expansion. Thus, there is merit in developing a numerical model determining the abundance of bivalve populations in relation to their food availability in order to assess the carrying capacity of shellfish growing areas. This modelling will take into account the different bivalve species present in the bay, as the cultivated Mytilus edulis and Crassostrea virginica and wild, M. edulis, C. virginica, Mya arenaria and Mercenaria mercenaria. As a first step toward a modelling goal, this study compared the physiological differences of the 6 bivalve groups. Three physiological parameters were measured: clearance rate, oxygen consumption and assimilation to determine the energy budget or scope for growth (SFG). These measurements were carried out on individuals contained in metabolic chamber at summer and autumn temperatures (20 and 8â°C, respectively). Our results show that M. edulis is best adapted to these temperature in PEI as it maintains high SFG at both temperatures. For C. virginica and M. arenaria, high physiological parameters under summer conditions were observed, followed by a decrease in autumn. For M. mercenaria rates were low at both temperatures indicating a persistently low growth potential. These results demonstrate the adaptive physiological capacity of each species and provide insight into the underlying reasons some species such as C. virginica and M. mercenaria are at their northern distribution limit in the Gulf of St. Lawrence. Finally, no differences in the SFG between cultivated and wild bivalves have been observed. These results are discussed within the context of estimating the impact of each bivalve group in bays environment from PEI and particularly on food availability
Social and structural determinants of injection drug use-associated bacterial and fungal infections: a qualitative systematic review and thematic synthesis
BACKGROUND AND AIMS: Injection drug use-associated bacterial and fungal infections are increasingly common, and social contexts shape individuals' injecting practices and treatment experiences. We sought to synthesize qualitative studies of social-structural factors influencing incidence and treatment of injecting-related infections. METHODS: We searched PubMed, EMBASE, Scopus, CINAHL, and PsycINFO from January 1, 2000, to February 18, 2021. Informed by Rhodes' "risk environment" framework, we performed thematic synthesis in three stages: (1) line-by-line coding; (2) organizing codes into descriptive themes, reflecting interpretations of study authors; (3) consolidating descriptive themes into conceptual categories to identify higher-order analytic themes. RESULTS: We screened 4,841 abstracts and included 26 qualitative studies on experiences of injecting-related bacterial and fungal infections. We identified six descriptive themes organized into two analytic themes. The first analytic theme, social production of risk, considered macro-environmental influences. Four descriptive themes highlighted pathways through which this occurs: (1) unregulated drug supply, leading to poor drug quality and solubility; (2) unsafe spaces, influenced by policing practices and insecure housing; (3) health care policies and practices, leading to negative experiences that discourage access to care; and (4) restrictions on harm reduction programs, including structural barriers to effective service provision. The second analytic theme, practices of care among people who use drugs, addressed protective strategies people employ within infection risk environments. Associated descriptive themes were: (5) mutual care, including assisted-injecting and sharing sterile equipment; and (6) self-care, including vein health and self-treatment. Within constraining risk environments, some protective strategies for bacterial infections precipitated other health risks (e.g., HIV transmission). CONCLUSIONS: Injecting-related bacterial and fungal infections are shaped by modifiable social-structural factors, including poor quality unregulated drugs, criminalization and policing enforcement, insufficient housing, limited harm reduction services, and harmful health care practices. People who inject drugs navigate these barriers while attempting to protect themselves and their community
Extrudable hydroxyapatite/plant oil-based biopolymer nanocomposites for biomedical applications: Mechanical testing and modeling
Towards developing bone-inspired, high performance composite biomaterials, two nanocomposite inks, consisting of a plant oil-based biopolymer resin (soybean oil epoxidized acrylate (SOEA)) and silanized nano-hydroxyapatite (Si-nHA) particles with and without diluent hydroxyethyl acrylate (HEA), were extruded using direct ink writing to fabricate filaments of differing volume fractions. HEA was hypothesized to lower ink viscosity, improve Si-nHA dispersion and extrudability, and therefore result in better relative improvements in mechanical properties over those of the base resin. Thermogravimetric analysis, scanning electron microscopy and uniaxial tensile tests were conducted. Strength, toughness, and stiffness of both resins were improved by the addition of Si-nHA. The HEA improved dispersion and extrudability. This resulted in better particle alignment and relatively greater augmentation of mechanical properties. The experimental data for both biopolymer resins were used to calibrate 3D representative volume element (RVE) finite element micromechanical models, while the experimental data for the nanocomposite filaments were employed to validate these models. The Young's moduli from the computational models were also compared with experimental data and with analytical predictions calculated using the Mori-Tanaka method. The predictions of 3D RVE models correlated well with the experimental data while, for higher volume fractions, the Mori-Tanaka results diverged, similar to previous reports.The authors thank the University of Waterloo and the Natural Sciences and Engineering Research Council of Canada (NSERC) for funding awarded to TLW and JM in support of this research
Characterization and calibration of the James Webb space telescope mirror actuators fine stage motion
The James Webb Space Telescopeâs (Webbâs) deployable primary and secondary mirrors are actively controlled to achieve and maintain precise optical alignment on-orbit. Each of the 18 primary mirror segment assemblies (PMSAs) and the secondary mirror assembly (SMA) are controlled in six degrees of freedom by using six linear actuators in a hexapod arrangement. In addition, each PMSA contains a seventh actuator that adjusts radius of curvature (RoC). The actuators are of a novel stepper motor-based cryogenic two-stage design that is capable of sub-10 nm motion accuracy over a 20 mm range. The nm-level motion of the 132 actuators were carefully tested and characterized before integration into the mirror assemblies. Using these test results as an initial condition, knowledge of each actuatorâs length (and therefore mirror position) has relied on software bookkeeping and configuration control to keep an accurate motor step count from which actuator position can be calculated. These operations have been carefully performed through years of Webb test operations using both ground support actuator control software as well as the flight Mirror Control Software (MCS). While the actuatorâs coarse stage length is cross-checked using a linear variable differential transformer (LVDT), no on-board cross-check exists for the nm-level length changes of the actuatorsâ fine stage. To ensure that the software bookkeeping of motor step count is still accurate after years of testing and to test that the actuator position knowledge was properly handed off from the ground software to the flight MCS, a series of optical tests were devised and performed through the Center of Curvature (CoC) ambient optical test campaigns at the Goddard Space Flight Center (GSFC) and during the thermal-vacuum tests of the entire optical payload that were conducted in Chamber A at Johnson Space Center (JSC). In each test, the actuator Fine Step Count (FSC) value is compared to an external measurement provided by an optical metrology tool with the goal of either confirming the MCS database value, or providing a recommendation for an updated calibration if the measured FSC differs significantly from the MCS-based expectation. During ambient testing of the PMSA hexapods, the nm-level actuator length changes were measured with a custom laser deflectometer by measuring tilts of the PMSA. The PMSA RoC fine stage characterization was performed at JSC using multi-wave interferometric measurements with the CoC Optical Assembly (COCOA). Finally, the SMA hexapod fine stage characterization test was performed at JSC using the NIRCam instrument in the âpass-and-a-halfâ test configuration using a test source from the Aft-Optics System Source Plate Assembly (ASPA). In this paper, each of these three tests, subsequent data analyses, and uncertainty estimations will be presented. Additionally, a summary of the ensemble state of Webbâs actuator fine stages is provided, along with a comparison to a Wavefront Sensing and Control (WFSC)-based requirement for FSC errors as they relate to the optical alignment convergence of the telescope on-orbit
A Year of Wavefront Sensing with JWST in Flight: Cycle 1 Telescope Monitoring and Maintenance Summary
We summarize JWST's measured telescope performance across science Cycle 1.
The stability of segments alignments is typically better than 10 nanometers RMS
between measurements every two days, leading to highly stable point spread
functions. The frequency of segment "tilt events" decreased significantly, and
larger tilt events ceased entirely, as structures gradually equilibrated after
cooldown. Mirror corrections every 1-2 months now maintain the telescope below
70 nm RMS wavefront error. Observed micrometeoroid impacts during cycle 1 had
negligible effect on science performance, consistent with preflight
predictions. As JWST begins Cycle 2, its optical performance and stability are
equal to, and in some ways better than, the performance reported at the end of
commissioning.Comment: STScI Technical Memo. 2.5 pages text, 1 figur
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