595 research outputs found
Stroma and epithelial interactions in three dimensional cell biology models of ovarian cancer
Over the past years it has become increasingly apparent that the tumour microenvironment plays a crucial role in tumour initiation/development/metastasis. The interactions of the tumour microenvironment and the malignant epithelial cells in epithelial ovarian cancer (EOC) biology remain poorly understood. This is in part due to the lack of representative in vitro models of disease that closely resemble the in vivo situation. A tumour exhibits a three-dimensional (3D) architecture comprising the malignant epithelial cells surrounded by the tumour stroma, which predominately contains the so-called cancer associated fibroblasts (CAFs). In vitro 3D models using primary epithelial cancer cell lines showed striking morphological similarities with the primary tumours. Immunohistochemistry and proteomic profiling further revealed that 3D models more closely resemble the primary tumour compared to traditional 2D culture methods. To further develop these 3D models and to recreate the interactions of epithelial cells with the microenvironment in vitro, heterotypic 3D models were established. Mesenchymal stem cells (MSCs) and immortalized normal ovarian fibroblasts (INOFs) were used to represent the tumour stroma and co-cultured with malignant and non-malignant epithelial ovarian cells. These 3D models proved an improvement to the previously established homotypic 3D models and offered a very good representation of the in vivo tumour. Finally, the recruitment of CAFs into the tumour stroma by EOC cell lines was investigated. Both MSCs and INOFs showed the ability to transdifferentiate into CAFs upon treatment with conditioned medium from an EOC cell line. Transdifferentiation was assessed by the expression of a-smooth muscle actin (aSMA), Vimentin and fibroblast specific protein (FSP). Both differentiated cell lines were also able to induce increased proliferation and invasion rates in a transformed ovarian surface epithelial cell line. These results provide in vitro evidence that both MSCs and INOFs can serve as precursor cell types of CAFs in EOC
Debris and micrometeorite impact measurements in the laboratory
A method was developed to simulate space debris in the laboratory. This method, which is an outgrowth of research in inertial confinement fusion (ICF), uses laser ablation to accelerate material. Using this method, single 60 micron aluminum spheres were accelerated to 15 km/sec and larger 500 micron aluminum spheres were accelerated to 2 km/sec. Also, many small (less than 10 micron diameter) irregularly shaped particles were accelerated to speeds of 100 km/sec
Modelling time course gene expression data with finite mixtures of linear additive models
Summary: A model class of finite mixtures of linear additive models is presented. The component-specific parameters in the regression models are estimated using regularized likelihood methods. The advantages of the regularization are that (i) the pre-specified maximum degrees of freedom for the splines is less crucial than for unregularized estimation and that (ii) for each component individually a suitable degree of freedom is selected in an automatic way. The performance is evaluated in a simulation study with artificial data as well as on a yeast cell cycle dataset of gene expression levels over time
Constructional design of echinoid endoskeleton: main structural components and their potential for biomimetic applications
The endoskeleton of echinoderms (Deuterostomia: Echinodermata) is of mesodermal origin and
consists of cells, organic components, as well as an inorganic mineral matrix. The echinoderm
skeleton forms a complex lattice-system, which represents a model structure for naturally inspired
engineering in terms of construction, mechanical behaviour and functional design. The sea urchin
(Echinodermata: Echinoidea) endoskeleton consists of three main structural components: test,
dental apparatus and accessory appendages. Although, all parts of the echinoid skeleton consist of
the same basic material, their microstructure displays a great potential in meeting several
mechanical needs according to a direct and clear structure–function relationship. This versatility
has allowed the echinoid skeleton to adapt to different activities such as structural support, defence,
feeding, burrowing and cleaning. Although, constrained by energy and resource efficiency, many of
the structures found in the echinoid skeleton are optimized in terms of functional performances.
Therefore, these structures can be used as role models for bio-inspired solutions in various
industrial sectors such as building constructions, robotics, biomedical and material engineering.
The present review provides an overview of previous mechanical and biomimetic research on the
echinoid endoskeleton, describing the current state of knowledge and providing a reference for
future studies
Probing Interstellar Dust With Space-Based Coronagraphs
We show that space-based telescopes such as the proposed Terrestrial Planet
Finder Coronagraph will be able to detect the light scattered by the
interstellar grains along lines of sight passing near stars in our Galaxy. The
relative flux of the scattered light within one arcsecond of a star at 100 pc
in a uniform interstellar medium of 0.1 H atoms cm^-3 is about 10^-7. The halo
increases in strength with the distance to the star and is unlikely to limit
the coronagraphic detection of planets around the nearest stars. Grains passing
within 100 AU of Sun-like stars are deflected by radiation, gravity and
magnetic forces, leading to features in the scattered light that can
potentially reveal the strength of the stellar wind, the orientation of the
stellar magnetic field and the relative motion between the star and the
surrounding interstellar medium.Comment: Accepted for publication in ApJ Supplement
Measurement of air and nitrogen fluorescence light yields induced by electron beam for UHECR experiments
Most of the Ultra High Energy Cosmic Ray (UHECR) experiments and projects
(HiRes, AUGER, TA, EUSO, TUS,...) use air fluorescence to detect and measure
extensive air showers (EAS). The precise knowledge of the Fluorescence Light
Yield (FLY) is of paramount importance for the reconstruction of UHECR. The
MACFLY - Measurement of Air Cherenkov and Fluorescence Light Yield - experiment
has been designed to perform such FLY measurements. In this paper we will
present the results of FLY in the 290-440 nm wavelength range for dry air and
pure nitrogen, both excited by electrons with energy of 1.5 MeV, 20 GeV and 50
GeV. The experiment uses a 90Sr radioactive source for low energy measurement
and a CERN SPS electron beam for high energy. We find that the FLY is
proportional to the deposited energy (E_d) in the gas and we show that the air
fluorescence properties remain constant independently of the electron energy.
At the reference point: atmospheric dry air at 1013 hPa and 23C, the ratio
FLY/E_d=17.6 photon/MeV with a systematic error of 13.2%.Comment: 19 pages, 8 figures. Accepted for publication in Astroparticle
Physic
Perspectives on Interstellar Dust Inside and Outside of the Heliosphere
Measurements by dust detectors on interplanetary spacecraft appear to
indicate a substantial flux of interstellar particles with masses exceeding
10^{-12}gram. The reported abundance of these massive grains cannot be typical
of interstellar gas: it is incompatible with both interstellar elemental
abundances and the observed extinction properties of the interstellar dust
population. We discuss the likelihood that the Solar System is by chance
located near an unusual concentration of massive grains and conclude that this
is unlikely, unless dynamical processes in the ISM are responsible for such
concentrations. Radiation pressure might conceivably drive large grains into
"magnetic valleys". If the influx direction of interstellar gas and dust is
varying on a ~10 yr timescale, as suggested by some observations, this would
have dramatic implications for the small-scale structure of the interstellar
medium.Comment: 13 pages. To appear in Space Science Review
Athermal annealing of Si-implanted GaAs and InP
GaAs and InP crystals ion implanted with Si were athermally annealed by exposing each crystal at
a spot of ~2 mm diameter to a high-intensity 1.06 μm wavelength pulsed laser radiation with ~4
J pulse energy for 35 ns in a vacuum chamber. As a result a crater is formed at the irradiated spot.
The crater is surrounded by a dark-colored ring-shaped region which is annealed by mechanical
energy generated by rapidly expanding hot plasma that formed on the exposed spot. The electrical
characteristics of this annealed region are comparable to those of a halogen-lamp annealed sample.
No redistribution of impurities due to transient diffusion is observed in the implant tail region. In
x-ray diffraction measurements, a high angle side satellite peak due to lattice strain was observed in
the crater and near crater regions of the athermally annealed sample in addition to the main Bragg
peak that corresponds to the pristine sample. This high angle side satellite peak is not observed in
regions away from the crater (≥5 mm from the center of the crater in GaAs)
All-optical trion generation in single walled carbon nanotubes
We present evidence of all optical trion generation and emission in undoped
single walled carbon nanotubes (SWCNTs). Luminescence spectra, recorded on
individual SWCNTs over a large CW excitation intensity range, show trion
emission peaks red-shifted with respect to the bright exciton peak. Clear
chirality dependence is observed for 22 separate SWCNT species, allowing for
determination of electron-hole exchange interaction and trion binding energy
contributions. Luminescence data together with ultrafast pump probe experiments
on chirality sorted bulk samples suggest that exciton-exciton annihilation
processes generate dissociated carriers that allow for trion creation upon a
subsequent photon absorption event.Comment: 13 pages, 4 figure
A diverse Pleistocene marsupial trackway assemblage from the Victorian Volcanic Plains, Australia
A diverse assemblage of late Pleistocene marsupial trackways on a lake bed in south-western Victoria provides the first information relating to the gaits and morphology of several megafaunal species, and represents the most speciose and best preserved megafaunal footprint site in Australia. The 60-110 ka volcaniclastic lacustrine sedimentary rocks preserve trackways of the diprotodontid Diprotodon optatum, a macropodid (probably Protemnodon sp.) and a large vombatid (perhaps Ramsayia magna or '. Phascolomys' medius) and possible prints of the marsupial lion, Thylacoleo carnifex. The footprints were imprinted within a short time period, demonstrating the association of the taxa present, rather than the time-averaged accumulations usually observed in skeletal fossil deposits. Individual manus and pes prints are distinguishable in some trackways, and in many cases some digital pad morphology is also present. Several parameters traditionally used to differentiate ichnotaxa, including trackway gauge and the degree of print in-turning relative to the midline, are shown to be subject to significant intraspecific variation in marsupials. Sexual dimorphism in the trackway proportions of Diprotodon, and its potential for occurrence in all large bodied, quadrupedal marsupials, is identified here for the first time
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