Tensiography and Liquid Drop Metrology

This research focused on drop metrology and the use of camera technology and vibration analysis influence on theoretical and practical tensiography. Drop shape and Tensiography are explained and how they relate to each other. Studies shows a relationship between vibration frequency and surface tension of liquids. However they also reveal the need for a theoretical understanding of the vibration tensiotrace of drops. Camera studies on large diameter dropheads used in tensiography are explored. Various image analysis methods were investigated for determining drop shape from camera images. Examination of the digital image reveals measurement issues. High speed camera images reveal new details of the drop separation process. An examination of drop modelling methods from camera images and the principles of such modelling were undertaken. Camera studies were developed which enabled the practical investigation of edge-detection. The theory developed links the drop shape with the tensiotrace of drops examined. The ray tracing method of the modelling of drop shape would have to be consolidated by establishing a definitive relationship between drop shape and the tensiotrace. This lead to acquiring photo images of real drops to get the profile of its edge or the drop shape. Various methods are used and assumptions are made in finding the edge of a drop from a photo image, in particular to the measurement of length, radii and angles

État des lieux au printemps 2003 de la reconnaissance des acquis (RA) dans les établissements d'enseignement postsecondaire publics du Canada première partie /

Titre de l'écran-titre (visionné le 15 août 2005

Exact sampling of self-avoiding paths via discrete Schramm-Loewner evolution

We present an algorithm, based on the iteration of conformal maps, that produces independent samples of self-avoiding paths in the plane. It is a discrete process approximating radial Schramm-Loewner evolution growing to infinity. We focus on the problem of reproducing the parametrization corresponding to that of lattice models, namely self-avoiding walks on the lattice, and we propose a strategy that gives rise to discrete paths where consecutive points lie an approximately constant distance apart from each other. This new method allows us to tackle two non-trivial features of self-avoiding walks that critically depend on the parametrization: the asphericity of a portion of chain and the correction-to-scaling exponent.Comment: 18 pages, 4 figures. Some sections rewritten (including title and abstract), numerical results added, references added. Accepted for publication in J. Stat. Phy

Are debris disks self-stirred?

This paper considers the evidence that debris disks are self-stirred by the formation of Plutos. A model for the dust produced during self-stirring is applied to statistics for A stars. As there is no significant difference between excesses of A-stars <50Myr old, we focus on reproducing the broad trends, the "rise and fall" of the fraction of stars with excesses. Using a population model, we find that the statistics and trends can be reproduced with a self-stirring model of planetesimal belts with radii distributed between 15-120AU. Disks must have this 15AU minimum radius to show a peak in disk fraction, rather than a monotonic decline. Populations of extended disks with fixed inner and/or outer radii fail to fit the statistics, due mainly to the slow 70um evolution as stirring moves further out in the disk. This conclusion, that debris disks are narrow belts, is independent of the significance of 24um trends for young A-stars. We show that the statistics can also be reproduced with a model in which disks are stirred by secular perturbations from a nearby eccentric planet. Detailed imaging is therefore the best way to characterise the stirring mechanism. From a more detailed look at beta Pictoris Moving Group and TW Hydrae Association A-stars we find that the disk around beta Pictoris is likely the result of secular stirring by the proposed planet at ~10AU; the structure of the HR 4796A disk also points to sculpting by a planet. The two other stars with disks, HR 7012 and eta Tel, possess transient hot dust, though the outer eta Tel disk is consistent with a self-stirred origin. Planet formation provides a natural explanation for the belt-like nature of debris disks, with inner regions cleared by planets that may also stir the disk, and the outer edges set by where planetesimals can form. [abridged]Comment: Accepted to MNRA

Variations on Debris Disks II. Icy Planet Formation as a Function of the Bulk Properties and Initial Sizes of Planetesimals

We describe comprehensive calculations of the formation of icy planets and debris disks at 30-150 AU around 1-3 solar mass stars. Disks composed of large, strong planetesimals produce more massive planets than disks composed of small, weak planetesimals. The maximum radius of icy planets ranges from roughly 1500 km to 11,500 km. The formation rate of 1000 km objects - `Plutos' - is a useful proxy for the efficiency of icy planet formation. Plutos form more efficiently in massive disks, in disks with small planetesimals, and in disks with a range of planetesimal sizes. Although Plutos form throughout massive disks, Pluto production is usually concentrated in the inner disk. Despite the large number of Plutos produced in many calculations, icy planet formation is inefficient. At the end of the main sequence lifetime of the central star, Plutos contain less than 10% of the initial mass in solid material. This conclusion is independent of the initial mass in the disk or the properties of planetesimals. Debris disk formation coincides with the formation of planetary systems containing Plutos. As Plutos form, they stir leftover planetesimals to large velocities. A cascade of collisions then grinds the leftovers to dust, forming an observable debris disk. In disks with small (< 1-10 km) planetesimals, collisional cascades produce luminous debris disks with maximum luminosity roughly 0.01 times the stellar luminosity. Disks with larger planetesimals produce much less luminous debris disks. Observations of debris disks around A-type and G-type stars strongly favor models with small planetesimals. In these models, our predictions for the time evolution and detection frequency of debris disks agree with published observations. We suggest several critical observations that can test key features of our calculations.Comment: 61 pages of text, 24 tables, and 34 figures; submitted to ApJS; comments welcome; revised version accepted to ApJS, changed text, modified tables, added references, no major changes to conclusion

Berezinskii-Kosterlitz-Thouless Transition of Spin-1 XXZ Chains in a Staggered Magnetic Field

Phase diagram of S=1 XXZ chain in a staggered magnetic field is obtained numerically. The Berezinskii-Kosterlitz-Thouless transition between the XY and the antiferromagnetic phases is studied by the level-spectroscopy. Moreover we find that there is no distinction between the Haldane and the antiferromagnetic phases, since the Gaussian critical line does not appear, in contrast to the $S=1/2$ case. It is expected that some hidden $Z_2\times Z_2$ symmetry breaking happens not only in the Haldane phase but also in the antiferromagnetic one.Comment: 4 pages, LaTex(JPSJstyle), 8 figures, to appear in J.Phys.Soc.Jp

Visual stimulation increases regional cerebral blood flow and metabolism in the goldfish

Studies with radioactive antipyrene and deoxyglucose indicate that both blood flow and metabolism are enhanced in the goldfish optic tectum following a brief visual stimulation. It is concluded that the brain of cold-blooded animals demonstrates regionally regulated physiological alterations, previously reported only in warm-blooded species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23651/1/0000616.pd

Phase diagram of the S=1/2 quantum spin chain with bond alternation

We study the ground state properties of the bond alternating $S=1/2$ quantum spin chain whose Hamiltonian is H=\sum_j (S_{2j}^x S_{2j+1}^x +S_{2j}^y S_{2j+1}^y +\lambda S_{2j}^z S_{2j+1}^z ) +\beta \sum_j {\bf S}_{2j-1} \cdot {\bf S}_{2j} . When $\beta=0$, the ground state is a collection of local singlets with a finite excitation gap. In the limit of strong ferromagnetic coupling $\beta \to - \infty$, this is equivalent to the $S=1 \ XXZ$ Hamiltonian. It has several ground state phases in the $\lambda$-$\beta$ plane including the gapful Haldane phase. They are characterized by a full breakdown, partial breakdowns and a non-breakdown of the hidden discrete $Z_2 \times Z_2$ symmetry. The ground state phase diagram is obtained by series expansions.Comment: 25 pages, RevTex 2.0, 9 Figures available on request, Tec.rep. of ISSP No.A265