•Four point fatigue testing is effectively determines machining subsurface deformation.•Bespoke machining and fatigue testing technique is applicable to a range of aerospace materials.•Increased ...metal removal rates of 50% reduced of cycles to failure in low cycle failure mode by 50%.•Dominant crack initiation in Ti-5553 is alpha basal planes at the machined subsurface.•Modifications to the upstream forging prior to machining could increase Ti-5553 service life.
Metastable beta titanium alloys such as Ti-5Al-5Mo-5V-3Cr (Ti-5553) are used for large aero-structural components. During processing these alloys are subject to costly machining operations. There is an industry demand to machine at improved metal removal rates (MRR) to meet increasing aircraft orders. To understand the effects of MRR on subsurface deformation and fatigue performance, fatigue coupons were end milled under two different industrial conditions. The surface roughness, residual stress and subsurface deformation was characterised and a custom four point bend fatigue testing was designed to determine the effect of MMR on cycles to failure. The study has demonstrated that an increase in MMR of 50% resulted in a LCF reduction of 57.37%. This was a direct result of increased subsurface damage and residual stresses.
The Super Dual Auroral Radar Network (SuperDARN) has been operating as an international co-operative organization for over 10 years. The network has now grown so that the fields of view of its 18 ...radars cover the majority of the northern and southern hemisphere polar ionospheres. SuperDARN has been successful in addressing a wide range of scientific questions concerning processes in the magnetosphere, ionosphere, thermosphere, and mesosphere, as well as general plasma physics questions. We commence this paper with a historical introduction to SuperDARN. Following this, we review the science performed by SuperDARN over the last 10 years covering the areas of ionospheric convection, field-aligned currents, magnetic reconnection, substorms, MHD waves, the neutral atmosphere, and E-region ionospheric irregularities. In addition, we provide an up-to-date description of the current network, as well as the analysis techniques available for use with the data from the radars. We conclude the paper with a discussion of the future of SuperDARN, its expansion, and new science opportunities.
This study employs observations from several sources to determine the location of the polar cap boundary, or open/closed field line boundary, at all local times, allowing the amount of open flux in ...the magnetosphere to be quantified. These data sources include global auroral images from the Ultraviolet Imager (UVI) instrument on board the Polar spacecraft, SuperDARN HF radar measurements of the convection flow, and low altitude particle measurements from Defense Meteorological Satellite Program (DMSP) and National Oceanographic and Atmospheric Administration (NOAA) satellites, and the Fast Auroral SnapshoT (FAST) spacecraft. Changes in the open flux content of the magnetosphere are related to the rate of magnetic reconnection occurring at the magnetopause and in the magnetotail, allowing us to estimate the day- and nightside reconnection voltages during two substorm cycles. Specifically, increases in the polar cap area are found to be consistent with open flux being created when the IMF is oriented southwards and low-latitude magnetopause reconnection is ongoing, and decreases in area correspond to open flux being destroyed at substorm breakup. The polar cap area can continue to decrease for 100 min following the onset of substorm breakup, continuing even after substorm-associated auroral features have died away. An estimate of the dayside reconnection voltage, determined from plasma drift measurements in the ionosphere, indicates that reconnection can take place at all local times along the dayside portion of the polar cap boundary, and hence presumably across the majority of the dayside magnetopause. The observation of ionospheric signatures of bursty reconnection over a wide extent of local times supports this finding.Key words. Ionosphere (plasma convection; polar ionosphere) – Magnetospheric physics (magnetospheric configuration and dynamics)
Using atomistic calculations with a Finnis-Sinclair type potential and molecular statics and dynamics methods, we performed a series of deformation tests on nanocrystallised tungsten samples ...presenting various microstructures; we calculated the elastic constants of polycrystalline tungsten for average grain diameters ranging from 2.7 to 6.7 nm. The results show that both Young’s and the shear moduli decrease by over 60% as the average grain diameter decreases below 3 nm. This diminution appears to be highly correlated to the grain boundary volume fraction. The results are compared to conclusions from other authors.
Magnetic reconnection is the most significant process that results in the transport of magnetized plasma into and out of the Earth's magnetosphere‐ionosphere system. There is also compelling ...observational evidence that it plays a major role in the dynamics of the solar corona, and it may also be important for understanding cosmic rays, accretion disks, magnetic dynamos, and star formation. The Earth's magnetosphere and ionosphere are presently the most accessible natural plasma environments where magnetic reconnection and its consequences can be measured, either in situ or by remote sensing. This paper presents a complete methodology for the remote sensing of magnetic reconnection in the magnetosphere from the ionosphere. This method combines measurements of ionospheric plasma convection and the ionospheric footprint of the reconnection separatrix. Techniques for measuring both the ionospheric plasma flow and the location and motion of the reconnection separatrix are reviewed, and the associated assumptions and uncertainties are assessed, using new analyses where required. Application of the overall methodology is demonstrated by the study of a 2‐h interval from 26 December 2000 using a wide range of spacecraft and ground‐based measurements of the Northern Hemisphere ionosphere. This example illustrates how spatial and temporal variations in the reconnection rate, as well as changes in the balance of magnetopause (dayside) and magnetotail (nightside) reconnection, can be routinely monitored, affording new opportunities for understanding the universal reconnection process and its influence on all aspects of space weather.
Multidisciplinary, evidence-based guidelines for quality assurance in colorectal cancer screening and diagnosis have been developed by experts in a project coordinated by the International Agency for ...Research on Cancer. The full guideline document covers the entire process of population-based screening. It consists of 10 chapters and over 250 recommendations, graded according to the strength of the recommendation and the supporting evidence. The 450-page guidelines and the extensive evidence base have been published by the European Commission. The chapter on communication includes 35 graded recommendations. The content of the chapter is presented here to promote international discussion and collaboration by making the principles and standards recommended in the new EU Guidelines known to a wider professional and scientific community. Following these recommendations has the potential to enhance the control of colorectal cancer through improvement in the quality and effectiveness of screening programmes and services.
The retinoblastoma tumour-suppressor protein Rb inhibits cell proliferation by repressing a subset of genes that are controlled by the E2F family of transcription factors and which are involved in ...progression from the G1 to the S phase of the cell cycle. Rb, which is recruited to target promoters by E2F1 (ref. 3), represses transcription by masking the E2F1 transactivation domain and by inhibiting surrounding enhancer elements, an active repression that could be crucial for the proper control of progression through the cell cycle. Some transcriptional regulators act by acetylating or deacetylating the tails protruding from the core histones, thereby modulating the local structure of chromatin: for example, some transcriptional repressors function through the recruitment of histone deacetylases. We show here that the histone deacetylase HDAC1 physically interacts and cooperates with Rb. In HDAC1, the sequence involved is an LXCXE motif, similar to that used by viral transforming proteins to contact Rb. Our results strongly suggest that the Rb/HDAC1 complex is a key element in the control of cell proliferation and differentiation and that it is a likely target for transforming viruses.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Cross-track ion drifts measured by the DMSP satellites are compared with line-of-sight SuperDARN HF velocities in approximately the same directions. Good overall agreement is found for a data set ...comprising of 209 satellite passes over the field of view of nine SuperDARN radars in both the Northern and Southern Hemispheres. The slope of the best linear fit line relating the SuperDARN and DMSP velocities is of the order of 0.7 with a tendency for SuperDARN velocities to be smaller. The agreement implies that the satellite and radar data can be merged into a common set provided that spatial and temporal variations of the velocity as measured by both instruments are smooth. Keywords. Ionosphere (Ionospheric irregularities; Plasma convection; Auroral ionosphere)
Determining reliable proxies for the ionospheric signature of the open-closed field line boundary (OCB) is crucial for making accurate ionospheric measurements of many magnetospheric processes (e.g. ...magnetic reconnection). This study compares the latitudes of Spectral Width Boundaries (SWBs), identified in the morning sector ionosphere using the Super Dual Auroral Radar Network (SuperDARN), with Particle Precipitation Boundaries (PPBs) determined using the low-altitude Defense Meteorological Satellite Program (DMSP) spacecraft, in order to determine whether the SWB represents a good proxy for the ionospheric projection of the OCB. The latitudes of SWBs and PPBs were identified using automated algorithms applied to 5 years (1997-2001) of data measured in the 00:00-12:00 Magnetic Local Time (MLT) range. A latitudinal difference was measured between each PPB and the nearest SWB within a ±10min Universal Time (UT) window and within a ±1h MLT window. The results show that the SWB represents a good proxy for the OCB close to midnight (~00:00-02:00 MLT) and noon (~08:00-12:00 MLT), but is located some distance (~2°-4°) equatorward of the OCB across much of the morning sector ionosphere (~02:00-08:00 MLT). On the basis of this and other studies we deduce that the SWB is correlated with the poleward boundary of auroral emissions in the Lyman-Birge-Hopfield ``Long" (LBHL) UV emission range and hence, that spectral width is inversely correlated with the energy flux of precipitating electrons. We further conclude that the combination of two factors may explain the spatial distribution of spectral width values in the polar ionospheres. The small-scale structure of the convection electric field leads to an enhancement in spectral width in regions close to the OCB, whereas increases in ionospheric conductivity (relating to the level of incident electron energy flux) lead to a reduction in spectral width in regions just equatorward of the OCB.
PDF
