3,256 research outputs found
Surface treatments to modulate bioadhesion: A critical review
On account of the recent increase in importance of biological and microbiological adhesion in industries such as healthcare and food manufacturing many researchers are now turning to the study of materials, wettability and adhesion to develop the technology within these industries further. This is highly significant as the stem cell industry alone, for example, is currently worth £3.5 million in the United Kingdom (UK) alone. This paper reviews the current state-of-the-art techniques used for surface treatment with regards to modulating biological adhesion including laser surface treatment, plasma treatment, micro/nano printing and lithography, specifically highlighting areas of interest for further consideration by the scientific community. What is more, this review discusses the advantages and disadvantages of the current techniques enabling the assessment of the most attractive means for modulating biological adhesion, taking in to account cost effectiveness, complexity of equipment and capabilities for processing and analysis
A major histocompatibility complex class I–dependent subset of memory phenotype CD8+ cells
Most memory phenotype (MP) CD44hi CD8+ cells are resting interleukin (IL)-15–dependent cells characterized by high expression of the IL-2/IL-15 receptor β (CD122). However, some MP CD8+ cells have a CD122lo phenotype and are IL-15 independent. Here, evidence is presented that the CD122lo subset of MP CD8+ cells is controlled largely by major histocompatibility complex (MHC) class I molecules. Many of these cells display surface markers typical of recently activated T cells (CD62Llo, CD69hi, CD43hi, and CD127lo) and show a high rate of background proliferation. Cells with this phenotype are highly enriched in common γ chain–deficient mice and absent from MHC-I−/− mice. Unlike CD122hi CD8+ cells, CD122lo MP CD8+ cells survive poorly after transfer to MHC-I−/− hosts and cease to proliferate. Although distinctly different from typical antigen-specific memory cells, CD122lo MP CD8+ cells closely resemble the antigen-dependent memory CD8+ cells found in chronic viral infections
The Sloan Digital Sky Survey Reverberation Mapping Project: Velocity Shifts of Quasar Emission Lines
Quasar emission lines are often shifted from the systemic velocity due to
various dynamical and radiative processes in the line-emitting region. The
level of these velocity shifts depends both on the line species and on quasar
properties. We study velocity shifts for the line peaks of various narrow and
broad quasar emission lines relative to systemic using a sample of 849 quasars
from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. The
coadded (from 32 epochs) spectra of individual quasars have sufficient
signal-to-noise ratio (SNR) to measure stellar absorption lines to provide
reliable systemic velocity estimates, as well as weak narrow emission lines.
The sample also covers a large dynamic range in quasar luminosity (~2 dex),
allowing us to explore potential luminosity dependence of the velocity shifts.
We derive average line peak velocity shifts as a function of quasar luminosity
for different lines, and quantify their intrinsic scatter. We further quantify
how well the peak velocity can be measured for various lines as a function of
continuum SNR, and demonstrate there is no systematic bias in the line peak
measurements when the spectral quality is degraded to as low as SNR~3 per SDSS
pixel. Based on the observed line shifts, we provide empirical guidelines on
redshift estimation from [OII]3728, [OIII]5008, [NeV]3426, MgII, CIII],
HeII1640, broad Hbeta, CIV, and SiIV, which are calibrated to provide unbiased
systemic redshifts in the mean, but with increasing intrinsic uncertainties of
46, 56, 119, 205, 233, 242, 400, 415, and 477 km/s, in addition to the
measurement uncertainties. These more realistic redshift uncertainties are
generally much larger than the formal uncertainties reported by the redshift
pipelines for spectroscopic quasar surveys, and demonstrate the infeasibility
of measuring quasar redshifts to better than ~200 km/s with only broad lines.Comment: matched to the published version; minor changes and conclusions
unchange
Successful ventricular tachycardia ablation in a patient with a biventricular ventricular assist device and heparin-induced thrombocytopenia using bivalirudin.
Enhanced Optical Trapping
Optical tweezers have contributed substantially to the advancement of micro-manipulation. However, they do have restrictions, mainly the limited range of materials that yield to optical trapping. Here we propose a method of employing optically trapped objects to manipulate the surrounding fluid and thus particles freely diffusing within it. We create and investigate a reconfigurable active-feedback system of optically trapped actuators, capable of manipulating translational and rotational motion of one or more nearby free objects
Gene Transfer of Engineered Calmodulin Alleviates Ventricular Arrhythmias in a Calsequestrin-Associated Mouse Model of Catecholaminergic Polymorphic Ventricular Tachycardia
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a familial arrhythmogenic syndrome characterized by sudden death. There are several genetic forms of CPVT associated with mutations in genes encoding the cardiac ryanodine receptor (RyR2) and its auxiliary proteins including calsequestrin (CASQ2) and calmodulin (CaM). It has been suggested that impairment of the ability of RyR2 to stay closed (ie, refractory) during diastole may be a common mechanism for these diseases. Here, we explore the possibility of engineering CaM variants that normalize abbreviated RyR2 refractoriness for subsequent viral-mediated delivery to alleviate arrhythmias in non-CaM-related CPVT
Characterizing unknown systematics in large scale structure surveys
Photometric large scale structure (LSS) surveys probe the largest volumes in
the Universe, but are inevitably limited by systematic uncertainties. Imperfect
photometric calibration leads to biases in our measurements of the density
fields of LSS tracers such as galaxies and quasars, and as a result in
cosmological parameter estimation. Earlier studies have proposed using
cross-correlations between different redshift slices or cross-correlations
between different surveys to reduce the effects of such systematics. In this
paper we develop a method to characterize unknown systematics. We demonstrate
that while we do not have sufficient information to correct for unknown
systematics in the data, we can obtain an estimate of their magnitude. We
define a parameter to estimate contamination from unknown systematics using
cross-correlations between different redshift slices and propose discarding
bins in the angular power spectrum that lie outside a certain contamination
tolerance level. We show that this method improves estimates of the bias using
simulated data and further apply it to photometric luminous red galaxies in the
Sloan Digital Sky Survey as a case study.Comment: 24 pages, 6 figures; Expanded discussion of results, added figure 2;
Version to be published in JCA
The Sloan Digital Sky Survey Reverberation Mapping Project: Ensemble Spectroscopic Variability of Quasar Broad Emission Lines
We explore the variability of quasars in the MgII and Hbeta broad emission
lines and UV/optical continuum emission using the Sloan Digital Sky Survey
Reverberation Mapping project (SDSS-RM). This is the largest spectroscopic
study of quasar variability to date: our study includes 29 spectroscopic epochs
from SDSS-RM over months, containing 357 quasars with MgII and 41 quasars
with Hbeta . On longer timescales, the study is also supplemented with
two-epoch data from SDSS-I/II. The SDSS-I/II data include an additional
quasars with MgII and 572 quasars with Hbeta. The MgII emission line is
significantly variable ( 10% on 100-day timescales), a necessary
prerequisite for its use for reverberation mapping studies. The data also
confirm that continuum variability increases with timescale and decreases with
luminosity, and the continuum light curves are consistent with a damped
random-walk model on rest-frame timescales of days. We compare the
emission-line and continuum variability to investigate the structure of the
broad-line region. Broad-line variability shows a shallower increase with
timescale compared to the continuum emission, demonstrating that the broad-line
transfer function is not a -function. Hbeta is more variable than MgII
(roughly by a factor of ), suggesting different excitation mechanisms,
optical depths and/or geometrical configuration for each emission line. The
ensemble spectroscopic variability measurements enabled by the SDSS-RM project
have important consequences for future studies of reverberation mapping and
black hole mass estimation of quasars.Comment: 20 pages, 25 figures. ApJ accepted: minor revisions following referee
repor
The Sloan Digital Sky Survey Reverberation Mapping Project: No Evidence for Evolution in the M-sigma Relation to z~1
We present host stellar velocity dispersion measurements for a sample of 88
broad-line quasars at 0.10.6) from the Sloan Digital Sky Survey
Reverberation Mapping (SDSS-RM) project. High signal-to-noise ratio coadded
spectra (average S/N~30 per 69 km/s pixel) from SDSS-RM allowed decomposition
of the host and quasar spectra, and measurement of the host stellar velocity
dispersions and black hole (BH) masses using the single-epoch (SE) virial
method. The large sample size and dynamic range in luminosity
(L5100=10^(43.2-44.7) erg/s) lead to the first clear detection of a correlation
between SE virial BH mass and host stellar velocity dispersion far beyond the
local universe. However, the observed correlation is significantly flatter than
the local relation, suggesting that there are selection biases in high-z
luminosity-threshold quasar samples for such studies. Our uniform sample and
analysis enable an investigation of the redshift evolution of the M-sigma
relation free of caveats by comparing different samples/analyses at disjoint
redshifts. We do not observe evolution of the M-sigma relation in our sample,
up to z~1, but there is an indication that the relation flattens towards higher
redshifts. Coupled with the increasing threshold luminosity with redshift in
our sample, this again suggests certain selection biases are at work, and
simple simulations demonstrate that a constant M-sigma relation is favored to
z~1. Our results highlight the scientific potential of deep coadded
spectroscopy from quasar monitoring programs, and offer a new path to probe the
co-evolution of BHs and galaxies at earlier times.Comment: replaced with the accepted version (minor changes and updated
references); ApJ in press; changed title to highlight the main resul
- …