951 research outputs found
Lessons Learned from the Flight Unit Testing of the Near Earth Asteroid Scout Flight System
The Near Earth Asteroid Scout flight mission is set to launch on the maiden voyage of the Space Launch System as a secondary payload. The spacecraft will be jettisoned in cis-lunar space and embark on an ambitious 2.5 year mission to image an asteroid. The spacecraft is uniquely equipped with an 85m2 solar sail as the main propulsion system. The monolithic sail system is designed to package within a 6U volume for launch and then deploy during flight. The NEA Scout team has presented in the past to the International Symposium on Solar Sailing topics related to the engineering development unit and design efforts to achieve flight hardware build. This paper will focus on the lessons learned from building and testing the NEA Scout flight system. Focus will be on the mechanical, software, and electrical interfaces as well as preparation for subsystem environmental tests, including thermal vacuum. Due to the unique design of the spacecraft, the solar sail subsystem was required to be located in the center of the spacecraft. This requirement lead to design challenges such as designing and accommodating critical cable harnesses to run through the center of the sail subsystem, packaging and deployment design of the sail subsystem, and integrated testing efforts through an avionics test bed to verify and validate a complete system architecture
The electric double layer has a life of its own
Using molecular dynamics simulations with recently developed importance
sampling methods, we show that the differential capacitance of a model ionic
liquid based double-layer capacitor exhibits an anomalous dependence on the
applied electrical potential. Such behavior is qualitatively incompatible with
standard mean-field theories of the electrical double layer, but is consistent
with observations made in experiment. The anomalous response results from
structural changes induced in the interfacial region of the ionic liquid as it
develops a charge density to screen the charge induced on the electrode
surface. These structural changes are strongly influenced by the out-of-plane
layering of the electrolyte and are multifaceted, including an abrupt local
ordering of the ions adsorbed in the plane of the electrode surface,
reorientation of molecular ions, and the spontaneous exchange of ions between
different layers of the electrolyte close to the electrode surface. The local
ordering exhibits signatures of a first-order phase transition, which would
indicate a singular charge-density transition in a macroscopic limit
Thermoelastic Damping in Micro- and Nano-Mechanical Systems
The importance of thermoelastic damping as a fundamental dissipation
mechanism for small-scale mechanical resonators is evaluated in light of recent
efforts to design high-Q micrometer- and nanometer-scale electro-mechanical
systems (MEMS and NEMS). The equations of linear thermoelasticity are used to
give a simple derivation for thermoelastic damping of small flexural vibrations
in thin beams. It is shown that Zener's well-known approximation by a
Lorentzian with a single thermal relaxation time slightly deviates from the
exact expression.Comment: 10 pages. Submitted to Phys. Rev.
A field study of team working in a new human supervisory control system
This paper presents a case study of an investigation into team behaviour in an energy distribution company. The main aim was to investigate the impact of major changes in the company on system performance, comprising human and technical elements. A socio-technical systems approach was adopted. There were main differences between the teams investigated in the study: the time of year each control room was studied (i.e. summer or winter),the stage of development each team was in (i.e. 10 months), and the team structure (i.e. hierarchical or heterarchical). In all other respects the control rooms were the same: employing the same technology and within the same organization. The main findings were: the teams studied in the winter months were engaged in more `planning’ and `awareness’ type of activities than those studies in the summer months. Newer teams seem to be engaged in more sharing of information than older teams, which maybe indicative of the development process. One of the hierarchical teams was engaged in more `system-driven’ activities than the heterarchical team studied at the same time of year. Finally, in general, the heterarchical team perceived a greater degree of team working culture than its hierarchical counterparts. This applied research project confirms findings from laboratory research and emphasizes the importance of involving ergonomics in the design of team working in human supervisory control
Robust Myco-Composites as a Platform for Versatile Hybrid-Living Structural Materials
Fungal mycelium, a living network of filamentous threads, thrives on
lignocellulosic waste and exhibits rapid growth, hydrophobicity, and intrinsic
regeneration, offering a potential means to create next-generation sustainable
and functional composites. However, existing hybrid-living mycelium composites
(myco-composites) are tremendously constrained by conventional mold-based
manufacturing processes, which are only compatible with simple geometries and
coarse biomass substrates that enable gas exchange. Here we introduce a class
of structural myco-composites manufactured with a novel platform that harnesses
high-resolution biocomposite additive manufacturing and robust mycelium
colonization with indirect inoculation. We leverage principles of hierarchical
composite design and selective nutritional provision to create a robust
myco-composite that is scalable, tunable, and compatible with complex
geometries. To illustrate the versatility of this platform, we characterize the
impact of mycelium colonization on mechanical and surface properties of the
composite, finding that it yields the strongest mycelium composite reported to
date, and demonstrate fabrication of unique foldable bio-welded containers and
flexible mycelium textiles. This study bridges the gap between biocomposite and
hybrid-living materials research, opening the door to advanced structural
mycelium applications and demonstrating a novel platform for development of
diverse hybrid-living materials
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Filter-Based Assay for Escherichia coli in Aqueous Samples Using Bacteriophage-Based Amplification
This paper describes a method to detect the presence of bacteria in aqueous samples, based on the capture of bacteria on a syringe filter, and the infection of targeted bacterial species with a bacteriophage (phage). The use of phage as a reagent provides two opportunities for signal amplification: i) the replication of phage inside a live bacterial host (1000-fold amplification for M13 phage in E. coli K12), and ii) the rapid conversion of a colorless substrate to a colored or fluorescent product by an enzyme that is co-expressed with the phage (in this demonstration β- galactosidase, which has a turnover rate of ~ 600 molecules/second). This method can detect a single colony-forming unit (CFU) of E. coli in one liter of water with an overnight culture-based assay, or 50 CFUs of E. coli in 1 liter of water (or 10 mL of orange juice, or 10 mL of skim milk) in less than four hours with a solution-based assay with visual readout. The solution-based assay does not require specialized equipment or access to a laboratory, and is more rapid than existing tests that are suitable for use at the point of access. This method could be applied to the detection of many different bacteria, in parallel, with bacteriophages that express enzymes not natively expressed in the target bacteria.Chemistry and Chemical Biolog
Diagnóstico ecográfico de afecciones hepáticas en caninos
Actualmente, la ecografía es la modalidad de diagnóstico por imagen de primera elección en las patologías hepáticas, ya que permite observar el parénquima, la vesícula biliar y la vasculatura, así como evaluar la relación del hígado con otros órganos. Además, facilita la realización de toma de muestras tanto para citología como histopatología. Este trabajo describe la casuística de alteraciones ecográficas de hígado en caninos que asistieron al Servicio de Diagnóstico por Imágenes del Hospital de Clínica de la Facultad de Ciencias Veterinarias de la Universidad Nacional del Nordeste (Corrientes, Argentina) durante el período 2007–2009. Del total de pacientes que asistieron a la consulta externa del hospital (n=14.627), 52 casos fueron remitidos por sospechas de patologías hepáticas con síntomas clínicos asociados a alteraciones bioquímicas. De esos 52 pacientes, el 27% (n=14) presentó hallazgos ecográficos sólo en hígado, el resto de los casos observados (73%, n=38) presentaron alteraciones tanto en hígado como en otros órganos. El 63% (n=33) evidenció aumento del tamaño del hígado, el 8% (n= 4) disminución y el 29% (n=15) se mantuvo dentro de los límites normales. Referente a las variaciones de la arquitectura del órgano, en un 79% de los casos la distribución fue heterogénea y en un 21% homogénea. Respecto a la ecogenicidad hepática, el 81% evidenció alteraciones difusas y el 19% alteraciones focales. Las asociaciones de patologías del hígado con vesícula biliar se observaron en el 13% de los casos (n=7) y, si bien se trabajó con ecografía convencional, pudieron detectarse pacientes con trastornos vasculares (27%, n=14). Aunque la ecografía hepática presenta ciertas limitaciones en cuanto a especificidad y sensibilidad, brinda información sustancial que permite considerar enfermedades que de otra manera hubieran pasado desapercibidas
Visible light accelerated hydrosilylation of alkynes using platinum-[acyclic diaminocarbene] photocatalysts
Shocked molecular gas towards the SNR G359.1-0.5 and the Snake
We have found a bar of shocked molecular hydrogen (H2) towards the OH(1720
MHz) maser located at the projected intersection of supernova remnant (SNR)
G359.1-0.5 and the nonthermal radio filament, known as the Snake. The H2 bar is
well aligned with the SNR shell and almost perpendicular to the Snake. The
OH(1720 MHz) maser is located inside the sharp western edge of the H2 emission,
which is consistent with the scenario in which the SNR drives a shock into a
molecular cloud at that location. The spectral-line profiles of 12CO, HCO+ and
CS towards the maser show broad-line absorption, which is absent in the 13CO
spectra and most probably originates from the pre-shock gas. A density gradient
is present across the region and is consistent with the passage of the SNR
shock while the H2 filament is located at the boundary between the pre--shocked
and post-shock regions.Comment: 8 pages, 12 figures, accepted by the MNRAS, typos fixe
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