Control by model error estimation

Modern control theory relies upon the fidelity of the mathematical model of the system. Truncated modes, external disturbances, and parameter errors in linear system models are corrected by augmenting to the original system of equations an 'error system' which is designed to approximate the effects of such model errors. A Chebyshev error system is developed for application to the Large Space Telescope (LST)

Short time-scale optical variability of the dwarf Seyfert nucleus in NGC 4395

We present optical spectroscopic observations of the least-luminous known Seyfert 1 galaxy, NGC 4395, which was monitored every half-hour over the course of 3 nights. The continuum emission varied by ~35 per cent over the course of 3 nights, and we find marginal evidence for greater variability in the blue continuum than the red. A number of diagnostic checks were performed on the data in order to constrain any systematic or aperture effects. No correlations were found that adequately explained the observed variability, hence we conclude that we have observed real intrinsic variability of the nuclear source. No simultaneous variability was measured in the broad H-beta line, although given the difficulty in deblending the broad and narrow components it is difficult to comment on the significance of this result. The observed short time-scale continuum variability is consistent with NGC 4395 having an intermediate-mass (~10^5 solar masses) central supermassive black hole, rather than a very low accretion rate. Comparison with the Seyfert 1 galaxy NGC 5548 shows that the observed variability seems to scale with black hole mass in roughly the manner expected in accretion models. However the absolute time-scale of variability differs by several orders of magnitude from that expected in simple accretion disc models in both cases.Comment: 16 pages, 14 figures, 5 tables, accepted for publication in MNRA

Gene sequences encoding ribosome-inactivating proteins from soapwort (Saponaria officinalis L.)

Ribosome-inactivating proteins (RIPs) are found in a wide variety of plant species. They possess an RNA N-glycosidase activity whereby the removal of a specific adenine residue from 28 S RNA renders a eukaryotic ribosome inactive. Type II RIPS contain both an active polypeptide and a sugar-binding polypeptide. Type I RIPs are composed of a single polypeptide functionally homologous to the active type II polypeptide. This thesis describes studies of the gene sequences of RIPs representative of each class: Ricin, a type II RIP from the castor oil plant (Ricinus communis h.), and saporin, a type I RIP from soapwort (Saponaria officinalis L.). Two ricin gene sequences were isolated from a Ricinus genomic library and partially characterised. One gene was a badly damaged ricin-like pseudogene whilst the other was shown to encode an active polypeptide. A second ricin sequence encoding an active polypeptide was isolated using Polymerase Chain Reaction (PGR) DNA amplification. The specificity of PGR amplification was investigated using the ricin and related agglutinin gene sequences. Partial amino acid sequence data derived from protein sequencing of saporin-6 was used to synthesise degenerate inosine-containing oligonucleotides. These directed the PGR amplification of part of the saporin coding sequence from genomic DNA. The product was used as a saporin-specific hybridisation probe. Southern analysis of Saponaria genomic DNA indicated that saporin sequences comprised a small multigene family. Three independent saporin containing genomic clones were isolated from a Saponaria genomic library. Two clones were truncated whilst the third contained a complete saporin coding sequence. The saporin and ricin coding sequences were expressed in vitro and shown to inhibit protein synthesis. Aniline cleavage assays of ribosomal RNA extracted from ribosomes exposed to the products of the RIP coding sequences were carried out. These indicated that the polypeptides encoded by the RIP gene sequences had specific RNA N-glycosidase activity

Comparative analysis of 1st, 2nd, and 4th year MD students' attitudes toward Complementary Alternative Medicine (CAM)

<p>Abstract</p> <p>Background</p> <p>To identify and report the attitudes and beliefs of 1^st, 2^nd, and 4^thyear medical students toward complementary alternative medicine (CAM).</p> <p>Methods</p> <p>The previously validated and reliability tested CHBQ was administered to medical students attending the University of South Florida School of Medicine.</p> <p>Results</p> <p>Significant changes were found between both 1^st(46.0 ± 7.7) and 4^th(37.8 ± 15.7) year students and 2^nd(48.3 ± 7.8) and 4^th(37.8 ± 15.7) year students. No significant difference was found between 1^st(46.0 ± 7.7) and 2^nd(48.3 ± 7.8) year students. When comparing scores based on gender, a significant difference was present between males (41.2 ± 12.2) and females (46.1 ± 11.0).</p> <p>Conclusion</p> <p>CHBQ scores were significantly more positive in both 1^stand 2^ndyear medical students in comparison with 4^thyear student's scores. These findings suggest that as student exposure to allopathic techniques and procedures increases during the last year of medical school, their attitudes toward CAM decrease. Females were also significantly more likely to have stronger positive attitudes toward CAM than males, though both genders represented an overall positive attitude toward CAM.</p

Classificació paleoecològica de les formes dels rudistes -una eina per a l'anàlisi paleoambiental

Els rudistes com a suspensívors epibentònics sèssils sols podien adaptar-se a les pressions ambientals per mitjà del creixement de la closca. Per això, les closques dels rudistes mostren una sèrie de formes, les característiques bàsiques de les quals estan en estreta relació amb el caràcter de l'hàbitat que ocupaven. Skelton & Gili (en premsa) classifiquen les closques dels rudistes en tres morfotipus ecològics generals, basats en els paradigmes definits per Skelton (1979a). En aquest treball exposem els trets principals d'aquesta classificació, fent ressaltar les seves implicacions paleoecològiques. Elevadors (elevators): tot el marge de creixement de la valva fixa estava involucrat en el creixement cap amunt. L'índex d'elevació, E, que comprèn la mitjana entre la màxima (α) i la mínima (β) inclinació de la paret externa del marge de creixement de la valva fixa, s'aproximava a 90°. E podia variar, pero el límit inferior per al creixement normal és per definició E=45°. Aconseguien l'estabilització per la implantació passiva de la valva fixa en el sediment, eventualment reforçada per la fixació lateral en els veïns. Ocupaven substrats tous, generalment fangosos, amb acumulació neta positiva. Els rudistes elevadors estaven, doncs, restringits a ambients d'energia baixa a moderada, rarament subjectes a torrents tractius. Adherents (clingers): una part del marge de creixement de la valva fixa creixia directament sobre el substrat, cimentant-se, si era dur, (adherents fixos) o adaptant-se a la seva superfície (adherents friccionals). Com que (β tendia aixi a 0°, E havia de ser per definició 0.75. Ocupaven substrats des de relativament estables a durs amb sedimentació neta de negligible a positiva, però amb fluxos de sediment solament ocasionals. La majoria dels rudistes adherents podien afrontar entrades de sediment intermitents fent crèixer cap amunt, escalonadament, la superfície de creixement basal. Les condicions de corrent associades podien implicar la inhibició freqüent o regular de deposició, però els torrents tractius eren rars. Ajaçats (recumbents): la clau d'aquest morfotipus era també l'estabilització, generant amb els marges Mures de les valves sobre el substrat una base ampla per a la closca. E era així, una altra vegada < 45°. Però a diferència de l'adherent, l'àrea de contacte amb el substrat (inestable), A, tenia poca importància per a 1'estabilització. Els rudistes ajaçats extremaven els diàmetres efectius del contorn de la base de la closca (és a dir A') de manera que aquesta adquiria una forma arquejada o estrellada que resistia la boleiada i soscavació dels corrents. En consequència, A/A' era menor que 1, i per definició havia de ser < 0.75. Ocupaven sorres calcàries mòbils, amb removiments de sediment freqüents i sedimentació positiva neta negigible

Hypelasma salevensis (FAVRE, 1913) from the Upper Kimmeridgian of the French Jura, and the Origin of the Rudist Family Requieniidae

The requieniid rudist species ‘Matheronia’ salevensis FAVRE, first described from the Tithonian of Mont Saleve, eastern France, is transferred to the genus Hypelasma PAQUIER, which is distinguished from Matheronia by possession of a posterior myophoral ledge in the left (attached) valve. Diminutive specimens from the Upper Kimmeridgian of the southern Jura are described and placed in this species. Hence, Hypelasma salevensis (FAVRE) is the stratigraphically oldest known member of the Family Requieniidae. It may also provide another example of phyletic size increase among rudists. Revised diagnoses are given for the family, genus and species. The main distinction between the requieniids and the diceratids, from among which they arose, concerns the angle between the coiling axis of the left valve and the commissural plane. In diceratids, this angle is large, such that the often sub-equal umbones tend to twist outwards from the commissural plane, so avoiding mutual interference. In requieniids, by contrast, this angle is small, such that the prominent umbo of the left valve tends to coil across the commissural plane in trochospiral to helicospiral fashion, while that of the right valve is suppressed in compensation, producing an exogyriform morphology. The requieniid modification of growth geometry, already present in H. salevensis, generated an extended basal surface on the flattened anterior wall of the left valve, implying specialized adaptation of these rudists as frictional or attached clingers. Requieniid ancestry should be sought among species of the pre-existing diceratid genera Epidiceras or Plesiodiceras, which also attached by the left valve. Although Plesiodiceras is favoured by its already more or less operculiform right valve and relatively small size, the derived condition of its posterior myophoral organisation is problematical. However, its juvenile shell shows some similarity of external form to H. salevensis, suggesting the possibility of paedomorphic evolution

Childhood and the politics of scale: Descaling children's geographies?

This is the post-print version of the final published paper that is available from the link below. Copyright @ 2008 SAGE Publications.The past decade has witnessed a resurgence of interest in the geographies of children's lives, and particularly in engaging the voices and activities of young people in geographical research. Much of this growing body of scholarship is characterized by a very parochial locus of interest — the neighbourhood, playground, shopping mall or journey to school. In this paper I explore some of the roots of children's geographies' preoccupation with the micro-scale and argue that it limits the relevance of research, both politically and to other areas of geography. In order to widen the scope of children's geographies, some scholars have engaged with developments in the theorization of scale. I present these arguments but also point to their limitations. As an alternative, I propose that the notion of a flat ontology might help overcome some difficulties around scalar thinking, and provide a useful means of conceptualizing sociospatiality in material and non-hierarchical terms. Bringing together flat ontology and work in children's geographies on embodied subjectivity, I argue that it is important to examine the nature and limits of children's spaces of perception and action. While these spaces are not simply `local', they seldom afford children opportunities to comment on, or intervene in, the events, processes and decisions that shape their own lives. The implications for the substance and method of children's geographies and for geographical work on scale are considered