Study of EVA operations associated with satellite services

Extravehicular mobility unit (EMU) factors associated with satellite servicing activities are identified and the EMU improvements necessary to enhance satellite servicing operations are outlined. Areas of EMU capabilities, equipment and structural interfaces, time lines, EMU modifications for satellite servicing, environmental hazards, and crew training are vital to manned Eva/satellite services and as such are detailed. Evaluation of EMU capabilities indicates that the EMU can be used in performing near term, basic satellite servicing tasks; however, satellite servicing is greatly enhanced by incorporating key modifications into the EMU. The servicing missions involved in contamination sensitive payload repair are illustrated. EVA procedures and equipment can be standardized, reducing both crew training time and in orbit operations time. By standardizing and coordinating procedures, mission cumulative time lines fall well within the EMU capability

The utility of unmanned probes in lunar exploration

Utility of unmanned probes of Ranger or Surveyor class in Apollo exploration program - Lunar scientific exploratio

Custodians of contemporary pluralism? Acas' evolving role in addressing conflict during a time of economic and regulatory flux

AbstractThis paper charts the development of Acas over the last two decades as it responds to the changing context of British employment relations. While dispute resolution services have evolved to focus on individual disputes, Acas has remained true to its pluralist roots through its training and advisory services that continue to promote ‘good employment relations’

Topological Phase Transitions and Holonomies in the Dimer Model

We demonstrate that the classical dimer model defined on a toroidal hexagonal lattice acquires holonomy phases in the thermodynamic limit. When all activities are equal the lattice sizes must be considered mod 6 in which case the finite size corrections to the bulk partition function correspond to a massless Dirac Fermion in the presence of a flat connection with nontrivial holonomy. For general bond activities we find that the phase transition in this model is a topological one, where the torus degenerates and its modular parameter becomes real at the critical temperature. We argue that these features are generic to bipartite dimer models and we present a more general lattice whose continuum partition function is that of a massive Dirac Fermion.Comment: 7 pages, 4 figures. Minor corrections with additional figure

Reverse graded relaxed buffers for high Ge content SiGe virtual substrates

An innovative approach is proposed for epitaxial growth of high Ge content, relaxed Si1−xGex buffer layers on a Si(001) substrate. The advantages of the technique are demonstrated by growing such structures via chemical vapor deposition and their characterization. Relaxed Ge is first grown on the substrate followed by the reverse grading approach to reach a final buffer composition of 0.78. The optimized buffer structure is only 2.8 µm thick and demonstrates a low surface threading dislocation density of 4×106 cm−2, with a surface roughness of 2.6 nm. The buffers demonstrate a relaxation of up to 107%

Relaxation of strained silicon on Si0.5Ge0.5 virtual substrates

Strain relaxation has been studied in tensile strained silicon layers grown on Si0.5Ge0.5 virtual substrates, for layers many times the critical thickness, using high resolution x-ray diffraction. Layers up to 30 nm thick were found to relax less than 2% by the glide of preexisting 60° dislocations. Relaxation is limited because many of these dislocations dissociate into extended stacking faults that impede the dislocation glide. For thicker layers, nucleated microtwins were observed, which significantly increased relaxation to 14%. All these tensile strained layers are found to be much more stable than layers with comparable compressive strain

Meltwater Intrusions Reveal Mechanisms for Rapid Submarine Melt at a Tidewater Glacier

Submarine melting has been implicated as a driver of glacier retreat and sea level rise, but to date melting has been difficult to observe and quantify. As a result, melt rates have been estimated from parameterizations that are largely unconstrained by observations, particularly at the near-vertical termini of tidewater glaciers. With standard coefficients, these melt parameterizations predict that ambient melting (the melt away from subglacial discharge outlets) is negligible compared to discharge-driven melting for typical tidewater glaciers. Here, we present new data from LeConte Glacier, Alaska, that challenges this paradigm. Using autonomous kayaks, we observe ambient meltwater intrusions that are ubiquitous within 400 m of the terminus, and we provide the first characterization of their properties, structure, and distribution. Our results suggest that ambient melt rates are substantially higher (×100) than standard theory predicts and that ambient melting is a significant part of the total submarine melt flux. We explore modifications to the prevalent melt parameterization to provide a path forward for improved modeling of ocean-glacier interactions.This work was funded by NSF OPP Grants 1503910, 1504191, 1504288, and 1504521 and National Geographic Grant CP4-171R-17. Additionally, this research was supported by the NOAA Climate and Global Change Postdoctoral Fellowship Program, administered by UCAR’s Cooperative Programs for the Advancement of Earth System Science (CPAESS) under award #NA18NWS4620043B. These observations would not be possible without the skilled engineering team who developed the autonomous kayaks—including Jasmine Nahorniak, June Marion, Nick McComb, Anthony Grana, and Corwin Perren—and also the Captain and crew of the M/V Amber Anne. We thank Donald Slater and an anonymous reviewer for valuable feedback that improved this manuscript. Data availability: All of the oceanographic data collected by ship and kayak have been archived with the National Centers for Environmental Information (Accession 0189574, https://accession.nodc.noaa.gov/ 0189574). The glacier data have been archived at the Arctic Data Center (https://doi.org/10.18739/A22G44).Ye

Efeito do período pós-parto na fertilidade de vacas de corte submetidas à re-sincronização do estro.

Um grupo de 118 vacas dividido segundo o período pós-parto em G1 (<42 dias pós-parto) e G2 (3 42 dias) foi submetido a sincronização do estro e inseminação artificial em momento pre-estabelecido (IAME). Doze dias depois procedeu-se a re-sincronização com um implante de 6 mg de norgestomet, que foi retirado nove dias depois. Uma segunda IAME foi feita 48 horas depois, apenas nas vacas nao-prenhes a 1 IAME. As vacas do G2 tiveram taxa de prenhez maior na IAME inicial. As taxas de prenhez a 2 IA e cumulativa não deferiram entre grupos

An ecomimicry design approach for extensive green roofs

Extensive green roofs (EGRs) have been promoted as a multifunctional urban green infrastructure (UGI) solution that can ameliorate some of the negative environmental effects associated with urbanisation and provide habitat for wildlife. To date ecological EGR research remains limited, yet studying and understanding the ecology and ecological processes of these novel urban ecosystems could maximise their potential to conserve biodiversity and deliver multiple ecosystem services to urban areas. Here we present an overview of how a novel ‘ecomimicry’ approach can be used to ensure that locally important habitats are created and restored as part of urban green infrastructure strategies, and that biodiversity is embedded at the heart of EGR design. This can help urban developments meet sustainability targets and contribute to the goal of no-net-loss of biodiversity. Conserving urban biodiversity through ecomimicry will increase opportunities for urban communities to reconnect with nature and improve the quality of life for people in cities

Competition of airline and high-speed rail in terms of price and frequency: Empirical study from China

High-speed rail (HSR) is developing at an unprecedented speed in China, however its impact on the air market is under-investigated. In order to fully assess strategic response behaviour, two aspects of competition should be considered: fares and frequency. We present the first ex-post analysis of HSR's influence on both air pricing and frequencies in China using a panel dataset of 30 different routes. In modelling frequency we use a novel application of Instrumental Variables to address the potential bias arising from the co-dependency between modal frequencies. Our results indicate that the presence of inter-modal competition can induce air to reduce fares and frequencies greatly: air fares are 0.397 CNY/km (34%) lower and air frequencies are 60.2% less on the routes with HSR. Where competition from HSR exists, air fares and frequencies are found to be higher on the routes with lower HSR frequencies and lower air travel times relative to those of HSR. We find that the inter-temporal price discrimination (IPD) of air fares can also be influenced by HSR competition: the J-curve of air prices reaches a minimum value earlier, ie more days ahead of departure, on the routes with HSR services. Air fares' variation by distance is also influenced by HSR competition: fares per kilometre reach their minimum at longer distances (around 1500 km) on the routes with HSR services