277 research outputs found
Testing Isotropy of Cosmic Microwave Background Radiation
We introduce new symmetry-based methods to test for isotropy in cosmic
microwave background radiation. Each angular multipole is factored into unique
products of power eigenvectors, related multipoles and singular values that
provide 2 new rotationally invariant measures mode by mode. The power entropy
and directional entropy are new tests of randomness that are independent of the
usual CMB power. Simulated galactic plane contamination is readily identified,
and the new procedures mesh perfectly with linear transformations employed for
windowed-sky analysis. The ILC -WMAP data maps show 7 axes well aligned with
one another and the direction Virgo. Parameter free statistics find 12
independent cases of extraordinary axial alignment, low power entropy, or both
having 5% probability or lower in an isotropic distribution. Isotropy of the
ILC maps is ruled out to confidence levels of better than 99.9%, whether or not
coincidences with other puzzles coming from the Virgo axis are included. Our
work shows that anisotropy is not confined to the low l region, but extends
over a much larger l range.Comment: 40 pages 15 figure
Coexpression of PPE 34.9 Antigen of Mycobacterium avium subsp. Paratuberculosis with Murine Interferon Gamma in HeLa Cell Line and Study of Their Immunogenicity in Murine Model
Mycobacterium avium subsp. paratuberculosis (Map) is the causative agent of johne's disease whose immunopathology mainly depends on cell mediated immuneresponse. Genome sequencing revealed various PPE (Proline-Proline-Glutamic acid) protein family of Map which are immunologically importance candidate genes In present study we have developed a bicistrionic construct pIR PPE/IFN containing a 34.9 kDa PPE protein (PPE 34.9) of Map along with a cytokine gene encoding murine gamma Interferon gene (IFNγ) and a monocistrionic construct pIR PPE using a mammalian vector system pIRES 6.1. The construct were transfected in HeLa cell line and expression were studied by Western blot as well as Immunefluroscent assay using recombinant sera. Further we have compared the immunereactivity of these two constructs in murine model by means of DTH study, LTT, NO assay and ELISA. DTH response was higher in pIR PPE/IFN than pIR PPE group of mice, similar finding also observed in case of LTT and NO production assay . ELISA titer of the pIR PPE/IFN was less than that with PPE only. These preliminary finding can revealed a CMI response of this PPE protein of Map and IFNγ having synergistic effect on this PPE protein to elicit a T cell based immunity in mice
Expression of a Gene Encoding 34.9 kDa PPE Antigen of Mycobacterium avium subsp. paratuberculosis in E. coli
Mycobacterium avium subsp. paratuberculosis (Map) contains PPE family antigens which are Proline and glutamic acid rich and may play important role as T cell antigens. Hence the identification and generation of antigens are necessary for immunological characterization. In the present study, the epitopic region of a unique PPE gene encoding 34.9 kDa protein from Map was amplified by polymerase chain reaction. The gene was cloned into Escherichia coli vector pQE30 UA. The recombinant plasmid designated as pQPPE was transformed into E. coli M15 and induced with IPTG revealed the high level expression of 37.1 kDa His-fusion protein (34.9 kDa PPE and 2.2 kDa His-tag), which was confirmed by immunoblotting. Recombinant PPE protein was then purified by Ni-NTA agarose chromatography. The polyclonal antiserum raised against purified recombinant PPE protein reacted with expressed 37.1 kDa His-fusion protein as well as with Map sonicate. The protein elicited significant delayed type hypersensitivity (DTH) skin reaction in mice sensitized with Map. The results indicated that the recombinant PPE protein of Map was associated with cellular immune response
Electric field driven destabilization of the insulating state in nominally pure LaMnO3
We report an electric field driven destabilization of the insulating state in
nominally pure LaMnO3 single crystal with a moderate field which leads to a
resistive state transition below 300 K. The transition is between the
insulating state in LaMnO3 and a high resistance bad metallic state that has a
temperature independent resistivity. The transition occurs at a threshold field
(Eth) which shows a steep enhancement on cooling. While at lower temperatures
the transition is sharp and involves large change in resistance but it softens
on heating and eventually absent above 280K. When the Mn4+ content is increased
by Sr substitution up to x=0.1, the observed transition though observable in
certain temperature range, softens considerably. The observation has been
explained as bias driven percolation type transition between two coexisting
phases, where the majority phase is a charge and orbitally ordered polaronic
insulating phase and the minority phase is a bad metallic phase. The mobile
fraction f of the bad metallic phase deduced from the experimental data follows
an activated kinetics with the activation energy nearly equal to 200 meV and
the prefactor fo is a strong function of the field that leads to a rapid
enhancement of f on application of field leading to the resistive state
transition. We suggest likely scenarios for such co-existing phases in
nominally pure LaMnO3 that can lead to the bias driven percolation type
transition.Comment: Accepted in JPC
Atomistic simulations of adiabatic coherent electron transport in triple donor systems
A solid-state analogue of Stimulated Raman Adiabatic Passage can be
implemented in a triple well solid-state system to coherently transport an
electron across the wells with exponentially suppressed occupation in the
central well at any point of time. Termed coherent tunneling adiabatic passage
(CTAP), this method provides a robust way to transfer quantum information
encoded in the electronic spin across a chain of quantum dots or donors. Using
large scale atomistic tight-binding simulations involving over 3.5 million
atoms, we verify the existence of a CTAP pathway in a realistic solid-state
system: gated triple donors in silicon. Realistic gate profiles from commercial
tools were combined with tight-binding methods to simulate gate control of the
donor to donor tunnel barriers in the presence of cross-talk. As CTAP is an
adiabatic protocol, it can be analyzed by solving the time independent problem
at various stages of the pulse - justifying the use of time-independent
tight-binding methods to this problem. Our results show that a three donor CTAP
transfer, with inter-donor spacing of 15 nm can occur on timescales greater
than 23 ps, well within experimentally accessible regimes. The method not only
provides a tool to guide future CTAP experiments, but also illuminates the
possibility of system engineering to enhance control and transfer times.Comment: 8 pages, 5 figure
The Advantage of Increased Resolution in the Study of Quasar Absorption Systems
We compare a new R = 120,000 spectrum of PG1634+706 (z_QSO = 1.337,m_V =
14.9) obtained with the HDS instrument on Subaru to a R = 45, 000 spectrum
obtained previously with HIRES/Keck. In the strong MgII system at z = 0.9902
and the multiple cloud, weak MgII system at z = 1.0414, we find that at the
higher resolution, additional components are resolved in a blended profile. We
find that two single-cloud weak MgII absorbers were already resolved at R =
45,000, to have b = 2 - 4 km/s. The narrowest line that we measure in the R =
120, 000 spectrum is a component of the Galactic NaI absorption, with b =
0.90+/-0.20 km/s. We discuss expectations of similarly narrow lines in various
applications, including studies of DLAs, the MgI phases of strong MgII
absorbers, and high velocity clouds. By applying Voigt profile fitting to
synthetic lines, we compare the consistency with which line profile parameters
can be accurately recovered at R = 45,000 and R = 120,000. We estimate the
improvement gained from superhigh resolution in resolving narrowly separated
velocity components in absorption profiles. We also explore the influence of
isotope line shifts and hyperfine splitting in measurements of line profile
parameters, and the spectral resolution needed to identify these effects. Super
high resolution spectra of quasars, which will be routinely possible with
20-meter class telescopes, will lead to greater sensitivity for absorption line
surveys, and to determination of more accurate physical conditions for cold
phases of gas in various environments.Comment: To appear in AJ. Paper with better resolution images available at
http://www.astro.psu.edu/users/anand/superhigh.AJ.pd
Signals of statistical anisotropy in WMAP foreground-cleaned maps
Recently, a symmetry-based method to test for statistical isotropy of the cosmic microwave background was developed. We apply the method to template-cleaned 3- and 5-years Wilkinson Microwave Anisotropy Probe-Differencing Assembly maps. We examine a wide range of angular multipoles from 2 < l < 300. The analysis detects statistically significant signals of anisotropy inconsistent with an isotropic cosmic microwave background in some of the foreground-cleaned maps. We are unable to resolve whether the anomalies have a cosmological, local astrophysical or instrumental origin. Assuming the anisotropy arises due to residual foreground contamination, we estimate the residual foreground power in the maps. For the W-band maps, we also find a highly improbable degree of isotropy we cannot explain. We speculate that excess isotropy may be caused by faulty modelling of detector noise
Orbital Stark effect and quantum confinement transition of donors in silicon
Adiabatic shuttling of single impurity bound electrons to gate induced
surface states in semiconductors has attracted much attention in recent times,
mostly in the context of solid-state quantum computer architecture. A recent
transport spectroscopy experiment for the first time was able to probe the
Stark shifted spectrum of a single donor in silicon buried close to a gate.
Here we present the full theoretical model involving large-scale quantum
mechanical simulations that was used to compute the Stark shifted donor states
in order to interpret the experimental data. Use of atomistic tight-binding
technique on a domain of over a million atoms helped not only to incorporate
the full band structure of the host, but also to treat realistic device
geometries and donor models, and to use a large enough basis set to capture any
number of donor states. The method yields a quantitative description of the
symmetry transition that the donor electron undergoes from a 3D Coulomb
confined state to a 2D surface state as the electric field is ramped up
adiabatically. In the intermediate field regime, the electron resides in a
superposition between the states of the atomic donor potential and that of the
quantum dot like states at the surface. In addition to determining the effect
of field and donor depth on the electronic structure, the model also provides a
basis to distinguish between a phosphorus and an arsenic donor based on their
Stark signature. The method also captures valley-orbit splitting in both the
donor well and the interface well, a quantity critical to silicon qubits. The
work concludes with a detailed analysis of the effects of screening on the
donor spectrum.Comment: 10 pages, 10 figures, journa
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