1,516 research outputs found
Size distribution of galaxies in SDSS DR7: weak dependence on halo environment
Using a sample of galaxies selected from the Sloan Digital Sky Survey Data
Release 7 (SDSS DR7) and a catalog of bulge-disk decompositions, we study how
the size distribution of galaxies depends on the intrinsic properties of
galaxies, such as concentration, morphology, specific star formation rate
(sSFR), and bulge fraction, and on the large-scale environments in the context
of central/satellite decomposition, halo environment, the cosmic web: \cluster,
\filament, \sheet ~and \void, as well as galaxy number density. We find that
there is a strong dependence of the luminosity- or mass-size relation on the
galaxy concentration, morphology, sSFR, and bulge fraction. Compared with
late-type (spiral) galaxies, there is a clear trend of smaller sizes and
steeper slope for early-type (elliptical) galaxies. Similarly, galaxies with
high bulge fraction have smaller sizes and steeper slope than those with low
bulge fraction. Fitting formula of the average luminosity- and mass-size
relations are provided for galaxies of these different intrinsic properties.
Examining galaxies in terms of their large scale environments, we find that the
mass-size relation has some weak dependence on the halo mass and
central/satellite segregation for galaxies within mass range , where satellites or galaxies in more massive halos have
slightly smaller sizes than their counterparts. While the cosmic web and local
number density dependence of the mass-size relation is almost negligible.Comment: 12 pages, 11 figure
Nonlinearities in modified gravity cosmology. II. Impacts of modified gravity on the halo properties
The statistics of dark matter halos is an essential component of
understanding the nonlinear evolution in modified gravity cosmology. Based on a
series of modified gravity N-body simulations, we investigate the halo mass
function, concentration and bias. We model the impact of modified gravity by a
single parameter \zeta, which determines the enhancement of particle
acceleration with respect to GR, given the identical mass distribution (\zeta=1
in GR). We select snapshot redshifts such that the linear matter power spectra
of different gravity models are identical, in order to isolate the impact of
gravity beyond modifying the linear growth rate. At the baseline redshift
corresponding to z_S=1.2 in the standard \Lambda CDM, for a 10% deviation from
GR(|\zeta-1|=0.1), the measured halo mass function can differ by about 5-10%,
the halo concentration by about 10-20%, while the halo bias differs
significantly less. These results demonstrate that the halo mass function
and/or the halo concentration are sensitive to the nature of gravity and may be
used to make interesting constraints along this line.Comment: 8 pages, 7 figures, accepted for publication in Physical Review
Auto-Generation of Pipelined Hardware Designs for Polar Encoder
This paper presents a general framework for auto-generation of pipelined
polar encoder architectures. The proposed framework could be well represented
by a general formula. Given arbitrary code length and the level of
parallelism , the formula could specify the corresponding hardware
architecture. We have written a compiler which could read the formula and then
automatically generate its register-transfer level (RTL) description suitable
for FPGA or ASIC implementation. With this hardware generation system, one
could explore the design space and make a trade-off between cost and
performance. Our experimental results have demonstrated the efficiency of this
auto-generator for polar encoder architectures
Security Constrained Multi-Stage Transmission Expansion Planning Considering a Continuously Variable Series Reactor
This paper introduces a Continuously Variable Series Reactor (CVSR) to the
transmission expansion planning (TEP) problem. The CVSR is a FACTS-like device
which has the capability of controlling the overall impedance of the
transmission line. However, the cost of the CVSR is about one tenth of a
similar rated FACTS device which potentially allows large numbers of devices to
be installed. The multi-stage TEP with the CVSR considering the security
constraints is formulated as a mixed integer linear programming model. The
nonlinear part of the power flow introduced by the variable reactance is
linearized by a reformulation technique. To reduce the computational burden for
a practical large scale system, a decomposition approach is proposed. The
detailed simulation results on the IEEE 24-bus and a more practical Polish
2383-bus system demonstrate the effectiveness of the approach. Moreover, the
appropriately allocated CVSRs add flexibility to the TEP problem and allow
reduced planning costs. Although the proposed decomposition approach cannot
guarantee global optimality, a high level picture of how the network can be
planned reliably and economically considering CVSR is achieved.Comment: Accepted by IEEE Transactions on Power System
Development of Glycan Based Diagnostics to Detect Pathogens
Numerous toxins and pathogens gain entry into mammalian cells using cell surface glycans. The Iyer group at Georgia State University is working on the development of glycoconjugates for the accurate detection of infectious agents. In this thesis, I have focused on the development of glycans to detect influenza virus and norovirus.
In the first section, I have focused on influenza viruses. A panel of synthetic glycans was synthesized as receptor mimics for the specific capture of influenza viruses. The synthetic glycans were printed onto commercial glass slides using a free amine at the end of a spacer to generate a small focused microarray. This glycan printed microarray was evaluated for its ability to capture three strains of influenza viruses. The analytical limit of detection is ~10 pfu/ml, (plaque forming units/milliliter) which is clinical relevant as 102 viral particles are typically required to cause infection. We also tested the drug susceptibility of current antivirals, Zanamivir and Ostelamivir using the microarray and determined the feasibility of this system to determine antiviral resistance for different strains.
In addition to optical detection, I developed an electrochemical assay to rapidly detect influenza viruses. Here, we utilized an unique property of influenza viral surface enzyme, Neuraminidase (NA), which cleaves terminal N-Acetyl Neuraminic acid (sialic acid) from cell surfaces and proteins. We designed an electrochemical assay that uses glucose bearing sialic acid substrates. Glucose is released when exposed to viral NA or intact viruses. The released glucose can be detected using repurposed glucose meters. Thus, personal glucose meters that were designed to assist diabetics and prediabetics monitor blood glucose can potentially be used to detect pathogens. Using this approach, we have detected 19 unique strains of influenza viruses. We also demonstrated drug susceptibility using this assay. The limit of detection of this assay is 102 pfu/sample, which is clinically relevant. The results were validated plaque assays and polymerase chain reaction (PCR).
In the second part of this thesis, I focused on norovirus detection. I developed a focused glycan microarray that comprised of a library of histo blood group antigens (HBGAs). The HBGAs were attached to a carrier protein and printed onto activated glass slides. A panel of norovirus virus like particles (VLPs) and strains that included different genogroups was exposed to the microarray. We found that different VLPs and strains give rise to unique binding patterns. When the binding pattern of VLPs for a particular strain were compared to the corresponding intact virus, the binding patterns didn\u27t match well, presumably because the virus does not recognize the same antibody as the VLPs. Unfortunately, antibodies for the virus cannot be generated because the virus cannot be grown in a laboratory setting. Indeed, all norovirus samples are obtained from human challenge studies. I also used surface plasmon resonance (SPR) studies in an effort to determine the binding affinities. Divalent biotinylated H type glycans were synthesized and their binding affinities with different VLPs and viral strains were determined. Initial studies suggest that the binding affinities are strain specific. These results demonstrate that glycans can be used to capture and isolate norovirus, although more research is required to develop glycan based norovirus detection kits
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