6,799 research outputs found
Recommended from our members
Multi-Nozzle Biopolymer Deposition for Freeform Fabrication of Tissue Constructs
Advanced freeform fabrication techniques have been recently used for the construction of tissue
scaffolds because of the process repeatability and capability of high accuracy in fabrication
resolution at the macro and micro scales. Among many applicable tissue scaffolding materials,
polymeric materials have unique properties in terms of the biocompatibility and degradation, and
have thus been widely utilized in tissue engineering applications. Hydrogels, such as alginate,
has been one of the most important polymer scaffolding materials because of its biocompatibility
and internal structure similarity to that of the extracellular matrix of many tissues, and its
relatively moderate processing. Three-dimensional deposition has been an entreating freeform
fabrication method of biopolymer and particularly hydrogel scaffolds because of its readiness to
deposit fluids at ambient temperatures. This paper presents a recent development of biopolymer
deposition based freeform fabrication for 3-diemnsinal tissue scaffolds. The system
configuration of multi-nozzles used in the deposition of sodium alginate solutions and Poly-?-
Caprolactone (PCL) are described. Studies on polymer deposition feasibility and structural
formability are conducted, and the preliminary results are presented.Mechanical Engineerin
On the X-ray Properties of OH Megamaser Sources: Chandra Snapshot Observations
We present Chandra snapshot observations for a sample of 7 sources selected
from the Arecibo OH megamaser (OHM) survey at z~0.13-0.22 and with far-infrared
luminosities in excess of 10^{11} L_sun. In contrast with the known H2O
megamasers, which are mostly associated with powerful Active Galactic Nuclei
(AGN), the situation is far less clear for OHMs, which have been poorly studied
in the X-ray band thus far. All of the observed sources are X-ray weak, with
only one OHM, IRAS FSC 03521+0028 (z=0.15), being detected by Chandra (with 5
counts). The results from this pilot program indicate that the X-ray emission,
with luminosities of less than ~10^{42} erg/s, is consistent with that from
star formation (as also suggested in some cases by the optical spectra) and
low-luminosity AGN emission. If an AGN is present, its contribution to the
broad-band emission of OHM galaxies is likely modest. Under reasonable
assumptions about the intrinsic X-ray spectral shape, the observed count
distribution from stacking analysis suggests absorption of ~10^{22} cm^{-2}.Comment: 8 pages, 3 figures, accepted for publication in MNRA
HI and OH absorption in the lensing galaxy of MG J0414+0534
We report the detection of \HI 21-cm absorption in the early-type
lensing galaxy towards MG J0414+0534 with the Green Bank Telescope. The
absorption, with total , is resolved into two strong components, probably due to the two
strongest lens components, which are separated by 0.4\arcsec. Unlike the other
three lenses which have been detected in \HI, J0414+0534 does not exhibit
strong OH absorption, giving a OH/\HI column density ratio of N_{\rm
OH}/N_{\rm HI}\lapp10^{-6} (for K, K and
). This underabundance of molecular gas may indicate
that the extreme optical--near-IR colour () along the line-of-sight
is not due to the lens. We therefore suggest that despite the strong upper
limits on molecular absorption at the quasar redshift, as traced by millimetre
lines, the extinction occurs primarily in the quasar host galaxy.Comment: Accepted by MNRAS Letters, 5 (and a bit) pages, 5 figure
'Notes on a Scandal': Why do Females Engage in Abuse of Trust Behaviours?
Although an evident reality in organisations where females work with young people, there has been no specific research to date exploring why females in positions of trust engage in sexually abusive relationships with adolescents. This study investigated the subject through a qualitative analysis of ten case studies from England drawn from the employment and safeguarding environment, comparing findings with existing studies into female sexual offenders in general, research into male 'professional perpetrators' and Gannon et al.'s (2008) Descriptive Model of Female Sexual Offending. The research highlighted a number of key similarities and differences between those who abuse in positions of trust and those female sexual offenders who abuse children in wider contexts. With respect to etiological factors the similarities included unstable lifestyle, relationship difficulties, low self-esteem, cognitive distortions and emotional self-management problems. Motivations for this sample appeared to be primarily driven by intimacy needs. Differences were identified relating to lower levels of substance abuse, a higher age range and socio-economic status, less prevalence of severe social skills deficits and chaotic and abusive backgrounds in this subject group. All of the women in the study followed an Implicit Disorganised pathway of abuse and maternal approach to the abusive behaviour
ALMA Observations of Circumnuclear Disks in Early Type Galaxies: 12CO(2-1) and Continuum Properties
We present results from an Atacama Large Millimeter/submillimeter Array
(ALMA) Cycle 2 program to map CO(2-1) emission in nearby early-type galaxies
(ETGs) that host circumnuclear gas disks. We obtained resolution
Band 6 observations of seven ETGs selected on the basis of dust disks in Hubble
Space Telescope images. We detect CO emission in five at high signal-to-noise
ratio with the remaining two only faintly detected. All CO emission is
coincident with the dust and is in dynamically cold rotation. Four ETGs show
evidence of rapid central rotation; these are prime candidates for
higher-resolution ALMA observations to measure the black hole masses. In this
paper we focus on the molecular gas and continuum properties. Total gas masses
and H column densities for our five CO-bright galaxies are on average
and cm over the kpc-scale
disks, and analysis suggests that these disks are stabilized against
gravitational fragmentation. The continuum emission of all seven galaxies is
dominated by a central, unresolved source, and in five we also detect a
spatially extended component. The 230 GHz nuclear continua are modeled as
power laws ranging from to within the
observed frequency band. The extended continuum profiles of the two
radio-bright (and CO-faint) galaxies are roughly aligned with their radio jet
and suggests resolved synchrotron jets. The extended continua of the CO-bright
disks are coincident with optically thick dust absorption and have spectral
slopes that are consistent with thermal dust emission.Comment: 20 pages, 10 figures; accepted for publication in Ap
High-dimensional quantum dynamics of adsorption and desorption of H at Cu(111)
We performed high-dimensional quantum dynamical calculations of the
dissociative adsorption and associative desorption of hydrogen on Cu(111). The
potential energy surface (PES) is obtained from density functional theory
calculations. Two regimes of dynamics are found, at low energies sticking is
determined by the minimum energy barrier, at high energies by the distribution
of barrier heights. Experimental results are well-reproduced qualitatively, but
some quantitative discrepancies are identified as well.Comment: 4 two column pages, revtex, 4 figures, to appear in Phys. Rev. Let
A measurement of the turbulence-driven density distribution in a non-star-forming molecular cloud
Molecular clouds are supersonically turbulent. This turbulence governs the initial mass function and the star formation rate. In order to understand the details of star formation, it is therefore essential to understand the properties of turbulence, in particular the probability distribution of density in turbulent clouds. We present H2CO volume density measurements of a non-star-forming cloud along the line of sight toward W49A. We use these measurements in conjunction with total mass estimates from 13CO to infer the shape of the density probability distribution function. This method is complementary to measurements of turbulence via the column density distribution and should be applicable to any molecular cloud with detected CO. We show that turbulence in this cloud is probably compressively driven, with a compressive-to-total Mach number ratio . We measure the standard deviation of the density distribution, constraining it to the range 1.5 < σ s < 1.9, assuming that the density is lognormally distributed. This measurement represents an essential input into star formation laws. The method of averaging over different excitation conditions to produce a model of emission from a turbulent cloud is generally applicable to optically thin line observations
- …