1,086 research outputs found
Finite-element modelling of mechanobiological factors influencing sesamoid tissue morphology in the patellar tendon of an ostrich
The appearance and shape of sesamoid bones within a tendon or ligament wrapping around a joint are understood to be influenced by both genetic and epigenetic factors. Ostriches (Struthio camelus) possess two sesamoid patellae (kneecaps), one of which (the distal patella) is unique to their lineage, making them a good model for investigating sesamoid tissue development and evolution. Here we used finite-element modelling to test the hypothesis that specific mechanical cues in the ostrich patellar tendon favour the formation of multiple patellae. Using three-dimensional models that allow application of loading conditions in which all muscles, or only distal or only proximal muscles to be activated, we found that there were multiple regions within the tendon where transformation from soft tissue to fibrocartilage was favourable and therefore a potential for multiple patellae based solely upon mechanical stimuli. While more studies are needed to better understand universal mechanobiological principles as well as full developmental processes, our findings suggest that a tissue differentiation algorithm using shear strain and compressive strain as inputs may be a roughly effective predictor of the tissue differentiation required for sesamoid development
Zonal circulation across 52°W in the North Atlantic
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C11008, doi:10.1029/2003JC002103.In July–August 1997, a hydrographic/Acoustic Doppler Current Profiler (ADCP)/tracer section was occupied along 52°W in the North Atlantic as part of the World Ocean Circulation Experiment Hydrographic Program. Underway and lowered ADCP (LADCP) data have been used to reference geostrophic velocities calculated from the hydrographic data; additional (small) velocity adjustments provided by an inverse model, constraining mass and silicate transports in 17 neutral density layers, yield the absolute zonal velocity field for 52°W. We find a vigorous circulation throughout the entire section, with an unusually strong Gulf Stream (169 Sv) and southern Deep Western Boundary Current (DWBC; 64 Sv) at the time of the cruise. At the northern boundary, on the west side of the Grand Banks of Newfoundland, we find the westward flowing Labrador Current (8.6 Sv), whose continuity from the Labrador Sea, east of our section, has been disputed. Directly to the south we identify the slopewater current (12.5 Sv eastward) and northern DWBC (12.5 Sv westward). Strong departures from strictly zonal flow in the interior, which are found in the LADCP data, make it difficult to diagnose the circulation there. Isolated deep property extrema in the southern portion, associated with alternating bands of eastward and westward flow, are consistent with the idea that the rough topography of the Mid-Atlantic Ridge, directly east of our section, causes enhanced mixing of Antarctic Bottom Water properties into overlying waters with distinctly different properties. We calculate heat and freshwater fluxes crossing 52°W that exceed estimates based on air-sea exchanges by a factor of 1.7.This work was supported by NSF grants
OCE95-29607, OCE 95-31864, OCE98-18266, and OCE-0219644
Microbiological and rheological studies on Portuguese kefir grains
Part of the data presented in this paper was included in a poster entitled Studies on kefir grains: microbiological characterization, biomass increase rate, and rheology of the polysaccharide produced, which was presented at the Prof.
Nicolau van Uden Portuguese Symposium of Applied Microbiology and Biotechnology – First Symposium on Yeasts, February 1993, Luso, Portugal.The native bacteria and yeasts present in Portuguese kefir grains stored under four
distinct sets of environmental conditions have been isolated and identified on the basis of morphology and biochemical tests. The microbial population of the kefir grains as a whole has been characterized in terms of rates of biomass production and formation of lactic acid and ethanol. The rheological properties of the purified polysaccharide (kefiran) produced by the microflora of the grains and accumulated therein were studied in a low water activity solvent and as a component of a binary gel containing either k-carrageenan or xanthan gum
Photometric Properties of Void Galaxies in the Sloan Digital Sky Survey DR7 Data Release
Using the sample presented in Pan:2011, we analyse the photometric properties
of 88,794 void galaxies and compare them to galaxies in higher density
environments with the same absolute magnitude distribution. In Pan et al.
(2011), we found a total of 1054 dynamically distinct voids in the SDSS with
radius larger than 10h^-1 Mpc. The voids are underdense, with delta rho/rho <
-0.9 in their centers. Here we study the photometric properties of these void
galaxies. We look at the u - r colours as an indication of star formation
activity and the inverse concentration index as an indication of galaxy type.
We find that void galaxies are statistically bluer than galaxies found in
higher density environments with the same magnitude distribution. We examine
the colours of the galaxies as a function of magnitude, and we fit each colour
distribution with a double-Gaussian model for the red and blue subpopulations.
As we move from bright to dwarf galaxies, the population of red galaxies
steadily decreases and the fraction of blue galaxies increases in both voids
and walls, however the fraction of blue galaxies in the voids is always higher
and bluer than in the walls. We also split the void and wall galaxies into
samples depending on galaxy type. We find that late type void galaxies are
bluer than late type wall galaxies and the same holds for early galaxies. We
also find that early type, dwarf void galaxies are blue in colour. We also
study the properties of void galaxies as a function of their distance from the
center of the void. We find very little variation in the properties, such as
magnitude, colour and type, of void galaxies as a function of their location in
the void. The only exception is that the dwarf void galaxies may live closer to
the center. The centers of voids have very similar density contrast and hence
all void galaxies live in very similar density environments (ABRIDGED)Comment: 10 pages, 25 figure
Understanding Work Practices of Autonomous Agile Teams: A Social-psychological Review
The purpose of this paper is to suggest additional aspects of social
psychology that could help when making sense of autonomous agile teams. To make
use of well-tested theories in social psychology and instead see how they
replicated and differ in the autonomous agile team context would avoid
reinventing the wheel. This was done, as an initial step, through looking at
some very common agile practices and relate them to existing findings in
social-psychological research. The two theories found that I argue could be
more applied to the software engineering context are social identity theory and
group socialization theory. The results show that literature provides
social-psychological reasons for the popularity of some agile practices, but
that scientific studies are needed to gather empirical evidence on these
under-researched topics. Understanding deeper psychological theories could
provide a better understanding of the psychological processes when building
autonomous agile team, which could then lead to better predictability and
intervention in relation to human factors
Stellar Population Diagnostics of Elliptical Galaxy Formation
Major progress has been achieved in recent years in mapping the properties of
passively-evolving, early-type galaxies (ETG) from the local universe all the
way to redshift ~2. Here, age and metallicity estimates for local cluster and
field ETGs are reviewed as based on color-magnitude, color-sigma, and
fundamental plane relations, as well as on spectral-line indices diagnostics.
The results of applying the same tools at high redshifts are then discussed,
and their consistency with the low-redshift results is assessed. Most low- as
well as high-redshift (z~1) observations consistently indicate 1) a formation
redshift z>~3 for the bulk of stars in cluster ETGs, with their counterparts in
low-density environments being on average ~1-2 Gyr younger, i.e., formed at
z>~1.5-2, 2) the duration of the major star formation phase anticorrelates with
galaxy mass, and the oldest stellar populations are found in the most massive
galaxies. With increasing redshift there is evidence for a decrease in the
number density of ETGs, especially of the less massive ones, whereas existing
data appear to suggest that most of the most-massive ETGs were already fully
assembled at z~1. Beyond this redshift, the space density of ETGs starts
dropping significantly, and as ETGs disappear, a population of massive,
strongly clustered, starburst galaxies progressively becomes more and more
prominent, which makes them the likely progenitors to ETGs.Comment: To appear on Annual Review of Astronomy & Astrophysics, Vol. 44
(2006). 46 pages with 16 figures. Replaced version includes updated
references, few typos less, and replaces Fig. 11 and Fig. 16 which had been
skrewed u
The Extragalactic Distance Scale without Cepheids IV
The Cepheid period-luminosity relation is the primary distance indicator used
in most determinations of the Hubble constant. The tip of the red giant branch
(TRGB) is an alternative basis. Using the new ANU SkyMapper Telescope, we
calibrate the Tully Fisher relation in the I band. We find that the TRGB and
Cepheid distance scales are consistent.Comment: ApJ in press 201
The human renal lymphatics under normal and pathological conditions
Ishikawa Y, Akasaka Y, Kiguchi H, Akishima-Fukasawa Y, Hasegawa T, Ito K, Kimura-Matsumoto M, Ishiguro S, Morita H, Sato S, Soh S & Ishii T (2006) Histopathology 49, 265–273 The human renal lymphatics under normal and pathological conditions AIMS: The renal lymphatics have not been fully documented in humans. The aim of this study was to clarify the morphology of the human renal lymphatic system under normal and pathological conditions by immunohistochemistry using anti-D2-40 antibody. METHODS AND RESULTS: Normal and pathological renal tissues obtained at autopsy as well as nephrectomy specimens with renal cell carcinoma (RCC) were used. Thin sections were immunostained with antibodies against D2-40 and CD31. In normal kidney, D2-40+ lymphatics were abundant in the interstitium around the interlobar and arcuate arteries/veins but sporadic in those around the glomeruli or between the tubules in the cortex. A few lymphatics contained erythrocytes in their lumina. Lymphatics were seldom present in the medulla. In RCC cases, lymphatics were evident at the tumour margin, whereas CD31+ capillaries were abundant throughout the tumour and lymphatics were increased in the fibrous interstitium around the tumour. Lymphatic invasion by RCC cells was also detectable. D2-40+ lymphatics were evident in other pathological conditions and end-stage kidney had a denser lymphatic distribution than normal kidney. CONCLUSIONS: Lymphatics are abundant around the arteries/veins and are also present in the renal cortex and medulla. D2-40 immunostaining is helpful for investigating the pathophysiological role of renal lymphatics
Clustering of Luminous Red Galaxies IV: Baryon Acoustic Peak in the Line-of-Sight Direction and a Direct Measurement of H(z)
We study the clustering of LRG galaxies in the latest spectroscopic SDSS data
releases, DR6 and DR7, which sample over 1 Gpc^3/h^3 to z=0.47. The 2-point
correlation function \xisp is estimated as a function of perpendicular
and line-of-sight (radial) directions. We find a significant
detection of a peak at Mpc/h, which shows as a circular ring in
the plane. There is also significant evidence for a peak along the
radial direction whose shape is consistent with its originating from the
recombination-epoch baryon acoustic oscillations (BAO). A \xisp model with no
radial BAO peak is disfavored at , whereas a model with no
magnification bias is disfavored at . The radial data enable, for the
first time, a direct measurement of the Hubble parameter as a function
of redshift. This is independent from earlier BAO measurements which used the
spherically averaged (monopole) correlation to constrain an integral of .
Using the BAO peak position as a standard ruler in the radial direction, we
find: km/s/Mpc for z=0.15-0.30 and
km/s/Mpc for . The first
error is a model independent statistical estimation and the second accounts for
systematics both in the measurements and in the model. For the full sample,
, we find km/s/Mpc.Comment: Minor revision to match version accepted for publication in MNRAS.
Includes comparison to DR7, a Table with the measurements and errors.
Includes extended analysis on systematic errors. Some figures have been
omitted. Main results and conclusions remain unchange
- …