43,437 research outputs found
An empirical model of long-term thermospheric density change
No full textPredicting the positions of satellites in Low Earth Orbit (LEO) requires a comprehensive understanding of the dynamic nature of the atmosphere. For objects in LEO the most significant orbit perturbation is atmospheric drag, which is a function of the local atmospheric density from a layer in the atmosphere called the thermosphere. For long-term predictions of satellite orbits and ephemerides, any density trend in the thermosphere is a necessary consideration, not only for satellite operators, but also for studies of the future LEO environment in terms of space debris. Numerous studies of long-term thermospheric density change have been performed.Predictions by Roble & Ramesh (2002), along with evidence by Keating (2000), Emmert et al.(2004), Marcos et al. (2005), Qian et al. (2006) and Emmert et al. (2008), strongly suggest the existence of such a phenomenon. Therefore, the objective of the research presented in this thesis is to provide a novel method to evaluate quantitatively thermospheric density change. Satellite drag data is an effective medium through which one can investigate local thermospheric density and changes thereof. There are many ways of determining atmospheric density, but inferring thermospheric density from satellite drag data is a relatively cost-effective way of gathering in-situ measurements. To do this, knowledge about a satellite’s physical properties that are intrinsic to atmospheric drag is required. A study by Saunders et al. (2009) highlighted problems with estimating a satellite’s physical properties directly from data given explicitly by Two-Line Element (TLE) sets. This prompted an investigation into ways to estimate ballistic coefficients: a required satellite parameter associated with drag coefficient and area-to-mass ratio. A novel way of estimating satellite ballistic coefficients was derived and is presented in this thesis. Additionally, novel consideration of atmospheric chemical composition was applied on long-term drag coefficient variability. Using a quantitative estimate of a ballistic coefficient one can propagate numerically a satellite’s orbit and predict the effects of atmospheric drag. Given an initial satellite orbit from TLE data, one approach is to use an orbital propagator to predict the satellite’s state at some time ahead and then to compare that state with TLE data at the same epoch. The difference between the semi-major axes of the initial orbit and that after the orbit propagation is then integrated and can be used to estimate the global average density. The method employed in this study utilises this process. To achieve this, a specially developed, computer-based, numerical orbital propagator was written in the programming language C/C++. The underlying theories and implementation tests for this propagator are presented in this thesis
yarkin(g n also yorkin(g
No full textyarkincp _OED_ yerk, yark v 'to draw stitches tight..as a shoemaker in sewing' (1430-1822), _EDD_ yark v� 14 'to bind tightly' Sc; yarkin(g sb 'side seam of a shoe Sc Nb 1 A line passed through the meshes of a net and fastened to the rope attached to floats which suspend the net in the water 1955 ENGLISH 37 Yarkin--lines to fasten a net to the head rope. P56 [-]G[-] C Story Yorking--a fastening of mesh of a net to a headrope. T C48-64 P Saunders You take your mesh [of cod-trap] here and one yorkin..now yorkins they call those,Spare GMSUsed I and SupUsed I and SupUsed IReverse of card contains an entry for "extra", image file E_13539. Card is filed under "E"
A re-classification of the Acrochaetiales based on molecular and morphological data, and establishment of the Colaconematales ord. nov. (Florideophyceae, Rhodophyta)
No full textSystematics of the red algal order Acrochaetiales and related taxa was investigated using combined small- and large-subunit nuclear ribosomal DNA (SSU and LSU rDNA, respectively) sequence data. These data were subjected to distance, parsimony and maximum likelihood analyses. The resulting phylogenies were congruent with previously published SSU results in that all included orders (Balbianiales, Batrachospermales, Nemaliales, Palmariales and Thoreales) were resolved as monophyletic except the Acrochaetiales, which consisted of two lineages (Acrochaetiales I and II). The Batrachospermales and Thoreales occupied equivocal positions as early diverging lineages, while the Balbianiales generally resolved as sister to an Acrochaetiales–Nemaliales–Palmariales (ANP) complex. Relationships among the four lineages of the ANP complex were not completely resolved, but detailed analyses weakly positioned Acrochaetiales II as sister to the Nemaliales, whereas Acrochaetiales I displayed a moderate to strong affiliation with the Palmariales. Acrochaetiales I included representatives of the genera Acrochaetium, Audouinellaand Rhodochorton, whereas Acrochaetiales II had a number of acrochaetioid species including a representative of the genus Colaconema. Compared with published SSU phylogenies, bootstrap values within the two Acrochaetiales lineages increased substantially in combined SSU/LSU analyses. Based on these results, emended generic descriptions are provided for Acrochaetium, Audouinella, Colaconemaand Rhodochorton, and a new family of acrochaetioid algae is described, the Colaconemataceae J. T. Harper etG. W. Saunders. The Acrochaetiaceae now includes the genera Acrochaetium, Audouinellaand Rhodochorton, while the Colaconemataceae is considered monogeneric at this time. It is quite likely that additional genera will be recognized within the Colaconemataceae pending further investigation. Acrochaetiaceae is retained as the sole family of the Acrochaetiales, although the tenuous recognition of the Palmariales as distinct from this order is discussed, whereas Colaconemataceae is transferred to the new order Colaconematales J. T. Harper et G. W. Saunders.Peer reviewedfinal article publishedAcrochaetiaceaesmall-subunit rDNARhodophytaPhylogenymolecular systematicslarge-subunit rDNAFlorideophyceaeColaconematales ord. nov.Colaconemataceae fam. nov.Acrochaetiale
Diffraction modelling of mobile radio wave propagation in built-up areas
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis examines theoretical methods of modelling radio wave propagation in built-up areas, with particular application to mobile radio systems Theoretical approaches allow precise quantitative description of the environment in terms of parameters such as mean building heights and densities, in contrast to the ambiguous nature of more conventional empirical models. The models are constructed using both scalar and vector field analysis techniques. The vector analysis is accomplished using the Geometrical Theory of Diffraction to describe the detailed effects of building shape and positioning, particularly for short-range situations. Over longer ranges propagation can often be described in terms of multiple edge diffraction over building rooftops using a scalar field representation. This mechanism accounts well for measured field strength variations, but is time consuming to calculate accurately using standard methods. A rapid algorithm for calculating scalar diffraction over multiple building edges with arbitrary positioning is constructed. This model can be used for deterministic prediction of sector median field strengths including slow fading variations when appropriate building data exists. It is also applicable to terrain diffraction problems. For the case when only average building parameters are available a closed form solution to the problem of multiple diffraction over buildings of equal heights and spacings is derived. The solution is applicable to any antenna heights and so provides a rapid and efficient way to predict gross propagation characteristics. Both models are tested against measurements made in the UHF band and are found to yield good prediction accuracy.This work is funded by the Science and Engineering Research Council under award number 889088999 and by Philips Radio Communication Systems Ltd. of Cambridge under an industrial studentship
Psiliglossa odyneroides subsp. odyneroides odyneroides (S. S. SAUNDERS 1850
No full textPsiliglossa odyneroides odyneroides (S. S. SAUNDERS 1850) Raphiglossa odyneroides S. S. SAUNDERS 1850 - Trans. R. ent. Soc. London (2) 1: 17. V e r b r e i t u n g: Türkei, Griechenland, Bulgarien,Sizilien.Published as part of Gusenleitner, J., 2013, Die Gattungen der Eumeninae im Nahen Osten, in Nordafrika und in Arabien (Hymenoptera: Vespidae: Eumeninae), pp. 5-107 in Linzer biologische Beiträge 45 (1) on page 73, DOI: 10.5281/zenodo.452608
William Tarn, Hellenistic Civilisation. Third Edition revised by the Author and G. T. Griffith
No full textNachtergael Georges. William Tarn, Hellenistic Civilisation. Third Edition revised by the Author and G. T. Griffith. In: L'antiquité classique, Tome 44, fasc. 2, 1975. p. 782
William Tarn, Hellenistic Civilisation. Third Edition revised by the Author and G. T. Griffith
No full textNachtergael Georges. William Tarn, Hellenistic Civilisation. Third Edition revised by the Author and G. T. Griffith. In: L'antiquité classique, Tome 44, fasc. 2, 1975. p. 782
Lugand (Lt-Colonel), Reussner (Α.), Villate (Colonel R.), Fox (Colonel), D'Ornano (Chef d'Escadron), Saunders (Commander M. G.), Le Goas- ter (Lt-Colonel J.), Wauquier (Commandant Α.), Dhers (P.), Les- tien (Général), Willequet ( J.), De Jong (G. T.), Castellan ( G.). La Campagne· de France (mai-juin 1940).
No full textVanwelkenhuyzen Jean. Lugand (Lt-Colonel), Reussner (Α.), Villate (Colonel R.), Fox (Colonel), D'Ornano (Chef d'Escadron), Saunders (Commander M. G.), Le Goas- ter (Lt-Colonel J.), Wauquier (Commandant Α.), Dhers (P.), Les- tien (Général), Willequet ( J.), De Jong (G. T.), Castellan ( G.). La Campagne· de France (mai-juin 1940). . In: Revue belge de philologie et d'histoire, tome 32, fasc. 4, 1954. pp. 1204-1206
Selective tumor cell death induced by irradiated riboflavin through recognizing DNA G-T mismatch
No full textRiboflavin (vitamin B2) has been thought to be a promising antitumoral agent in photodynamic therapy, though the further application of the method was limited by the unclear molecular mechanism. Our work reveals that riboflavin was able to recognize G-T mismatch specifically and induce singlestrand breaks in duplex DNA targets efficiently under irradiation. In the presence of riboflavin, the photo-irradiation could induce the death of tumor cells that are defective in mismatch repair system selectively, highlighting the G-T mismatch as potential drug target for tumor cells. Moreover, riboflavin is a promising leading compound for further drug design due to its inherent specific recognition of the G-T mismatch
Psiliglossa algeriensis E. SAUNDERS 1905
No full text<i>Psiliglossa algeriensis</i> E. SAUNDERS 1905 <p> <i>Psiliglossa algeriensis</i> E. SAUNDERS 1905 - Trans. R. ent. Soc. London <b>1905</b>: 400.</p> <p>V e r b r e i t u n g: Algerien, Marokko.</p>Published as part of <i>Gusenleitner, J., 2013, Die Gattungen der Eumeninae im Nahen Osten, in Nordafrika und in Arabien (Hymenoptera: Vespidae: Eumeninae), pp. 5-107 in Linzer biologische Beiträge 45 (1)</i> on page 72, DOI: <a href="http://zenodo.org/record/4526087">10.5281/zenodo.4526087</a>
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