102,405 research outputs found
Teverya (Israel), rooftop view of city showing Al-Amari Mosque
No full textTiberias [Teverya] & Sea of Galilee, from Tiberias Hotel. F.G.C. Apr. 3, 1934, Palestine [Israel]Al-Amari Mosque at left with minaret and dome.GrayscaleClapp Nitrate Negatives, Box
Applications of differential geometry to statistics
No full textChapters 1 and 2 are both surveys of the current work in applying
geometry to statistics. Chapter 1 is a broad outline of all the work done so far,
while Chapter 2 studies, in particular, the work of Amari and that of Lauritzen.
In Chapters 3 and 4 we study some open problems which have been raised
by Lauritzen's work. In particular we look in detail at some of the differential
geometric theory behind Lauritzen's defmition of a Statistical manifold.
The following chapters follow a different line of research. We look at a new
non symmetric differential geometric structure which we call a preferred point
manifold. We show how this structure encompasses the work of Amari and
Lauritzen, and how it points the way to many generalizations of their results. In
Chapter 5 we define this new structure, and compare it to the Statistical manifold
theory. Chapter 6 develops some examples of the new geometry in a statistical
context. Chapter 7 starts the development of the pure theory of these preferred
point manifolds.
In Chapter 8 we outline possible paths of research in which the new
geometry may be applied to statistical theory.
We include, in an appendix, a copy of a joint paper which looks at some
direct applications of differential geometry to a statistical problem, in this case it is
the problem of the behaviour of the Wald test with nonlinear restriction functions
3D magnetic configuration of the Halpha filament and X-ray sigmoid in NOAA AR 8151
No full textWe investigate the structure and relationship of an H filament and an X-ray sigmoid observed in active region NOAA 8151. We first examine the presence of such structures in the reconstructed 3D coronal magnetic field obtained from the non-constant- force-free field hypothesis using a photospheric vector magnetogram (IVM, Mees Solar Observatory). This method allows us to identify several flux systems: a filament (height 30 Mm, aligned with the polarity inversion line (PIL), magnetic field strength at the apex 49 G, number of turns 0.5-0.6), a sigmoid (height 45 Mm, aligned with the PIL, magnetic field strength at the apex 56 G, number of turns 0.5-0.6) and a highly twisted flux tube (height 60 Mm, magnetic field strength at the apex 36 G, number of turns 1.1-1.2). By searching for magnetic dips in the configuration, we identify a filament structure which is in good agreement with the H observations. We find that both filament and sigmoidal structures can be described by a long twisted flux tube with a number of turns less than 1 which means that these structures are stable against kinking. The filament and the sigmoid have similar absolute values of and Jz in the photosphere. However, the electric current density is positive in the filament and negative in the sigmoid: the filament is right-handed whereas the sigmoid is left-handed. This fact can explain the discrepancies between the handedness of magnetic clouds (twisted flux tubes ejected from the Sun) and the handedness of their solar progenitors (twisted flux bundles in the low corona). The mechanism of eruption in AR 8151 is more likely not related to the development of instability in the filament and/or the sigmoid but is associated with the existence of the highly twisted flux tube (~1.1-1.2 turns)
The molecular structure and crystal organization of rac-terfenadine/beta-cyclodextrin/tartaric acid multicomponent inclusion complex
No full textThe crystalline ternary inclusion complex terfenadine/beta-cyclodextrin/tartaric acid (TFN/betaCD/TA, 2:4:1) has been prepared from a aqueous solution (terfenadine, TFN, rac-alpha-[4-(1,1-dimethylethyl)phenyl]-4-(hydroxydiphenylmethyl)-1-piperidine-butanol). The solubility of the multicomponent system in water is remarkably different from that of the single components. The crystal structure shows that the TFN guest adopts an extended conformation and that the diphenyl end of the molecule is docked in the cavity formed by the association of two independent betaCD molecules through hydrogen bonds connecting their wide rims. The structure of the dimer is deformed with respect to uncomplexed betaCDs, due to the shape of the guest. The two aromatic rings interact differently with the macrocycles forming the dimer, one being included perpendicular in the central cavity of one betaCD, the other laying parallel to the interface between the two rims. The t-Bu- end of the guest is included in the cavity of a betaCD belonging to a different dimer, entering from the side of the narrow rim. The central part of the guest is surrounded by water molecules and tartaric acid, which creates a hydrophilic microenvironment in the interstices among dimers. The enhanced solubility of the multicomponent system could be related to the hydrogen bonds between the tartaric acid and the oxygens belonging to the wide rims. The overall structural arrangement of the betaCD units is driven by the shape of the TFN guest which needs a hydrophobic environment at both ends. The lipophilic interactions between TFN and betaCD cavities are responsible for the relevant perturbation in the regularity of the packing of the hosts
3D Coronal magnetic field from vector magnetograms: non-constant-alpha force-free configuration of the active region NOAA 8151
No full textThe Active Region 8151 (AR 8151) observed in February 1998 is the site of an eruptive event associated with a filament and a S-shaped structure, and producing a slow Coronal Mass Ejection (CME). In order to determine how the CME occurs, we compute the 3D coronal magnetic field and we derive some relevant parameters such as the free magnetic energy and the relative magnetic helicity. The 3D magnetic configuration is reconstructed from photospheric magnetic magnetograms (IVM, Mees Solar Observatory) in the case of a non-constant- force-free (nlff) field model. The reconstruction method is divided into three main steps: the analysis of vector magnetograms (transverse fields, vertical density of electric current, ambiguity of 180 degrees), the numerical scheme for the nlff magnetic field, the interpretation of the computed magnetic field with respect to the observations. For AR 8151, the nlff field matches the coronal observations from EIT/SOHO and from SXT/Yohkoh. In particular, three characteristic flux tubes are shown: a highly twisted flux tube, a long twisted flux tube and a quasi-potential flux tube. The maximum energy budget is estimated to 2.6 10^31 erg and the relative magnetic helicity to 4.7 10^34 G^2 cm^4. From the simple photospheric magnetic distribution and the evidence of highly twisted flux tubes, we argue that the flux rope model is the most likely to describe the initiation mechanism of the eruptive event associated with AR 8151
Amari : Chentsov connections and their geodesics on homogeneous spaces of diffeomorphism groups
No full textWe study the family of Amari-Chentsov α-connections on the homogeneous space D(M)/Dμ(M) of diffeomorphisms modulo volume-preserving diffeomorphims of a compact manifold M. We show that in some cases their geodesic equations yield completely integrable Hamiltonian systems.</p
The Crystal Structure of the Inclusion Complex of the Sodium Salt of Piroxicam with beta-Cyclodextrin
No full textThe structural characterization by X-ray diffraction analysis of the title compound is reported. Crystallographic details are: C42H70O35°C15H12N3O4 SNa·8D2O, triclinic, space group P1, a = 14.767(3), b = 12.237(2), c = 11.537(2)Å, α = 79.49(1), β = 110.91-(1), c = 104.61(1)°, d calc = 1.460 g/cm3, Z = 1, R = 0.045 for 6635 observed reflections. The crystal structure consists of head-to-tail β-cyclodextrin molecules (β-CD) linked together by piroxicam anions in infinite polymeric chains running along the c axis. In a chain each β-CD molecule takes up simultaneously two guest molecules including on the secondary hydroxyl end the benzene ring and on the primary hydroxyl end the pyridine ring of two adjacent piroxicam anions. The piroxicam anion is located with its central hydrophilic moiety at the interface between two adjacent β-CD molecules, forming with them hydrogen bonds through the enolate and amide oxygen atoms. Conformation of piroxicam is different from those observed for its neutral and zwitterionic forms. It assumes the ZZE conformation expected for the enolate. The six-coordinated sodium cation acts as a bridge between adjacent polymeric chains linking them along the b axis. This results in the formation of hydrophilic channels filled by deuterium oxide molecules
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