9,144 research outputs found
A Novel Scheme to Search for Fractional Charge Particles in Low Energy Accelerator Experiments
In the Standard Model of particle physics, the quarks and anti-quarks have
fractional charge equal to or of the electron's charge. There
has been a large number of experiments searching for fractional charge,
isolatable, elementary particles using a variety of methods, including
collisions using dE/dx ionization energy loss measurements, but no evidence has
been found to confirm existence of free fractional charge particles, which
leads to the quark confinement theory. In this paper, a proposal to search for
this kind particles is presented, which is based on the conservation law of
four-momentum. Thanks to the CLEOc and BESIII detectors' large coverage, good
particle identification, precision measurements of tracks' momenta and their
large recorded data samples, these features make the scheme feasible in
practice. The advantage of the scheme is independent of any theoretical models
and sensitive for a small fraction of the quarks transitioning to the
unconfinement phase from the confinement phase.Comment: 9 page
Unique Structural Features of Mule Deer Prion Protein Provide Insights into Chronic Wasting Disease
Chronic wasting disease (CWD) is a highly infectious prion disease of cervids. Accumulation of prions, the disease-specific structural conformers of the cellular prion protein (PrPC), in the central nervous system, is the key pathological event of the disorder. The analysis of cervid PrPC sequences revealed the existence of polymorphism at position 226, in which deer PrP contains glutamine (Q), whereas elk PrP contains glutamate (E). The effects of this polymorphism on CWD are still unknown. We determined the high-resolution nuclear magnetic resonance structure of the mule deer prion protein that was compared to previously published PrP structures of elk and white-tailed deer. We found that the polymorphism Q226E could influence the long-range intramolecular interactions and packing of the \u3b22-\u3b12 loop and the C-terminus of the \u3b13 helix of cervid PrP structures. This solvent-accessible epitope is believed to be involved in prion conversion. Additional differences were observed at the beginning of the well-defined C-terminus domain, in the \u3b12-\u3b13 region, and in its interactions with the \u3b11 helix. Here, we highlight the importance of the PrP structure in prion susceptibility and how single amino acid differences might influence the overall protein folding
Enantiomerically pure β-phenylalanine analogues from α–β-phenylalanine mixtures in a single reactive extraction step
An efficient and selective method for the extraction of α-amino acids in preference over their β-isomers using PdCl2(PPh3)2 was discovered, which enables the separation of product mixtures obtained in the enantioselective enzymatic formation of β-amino acids.
On the dilaton and the axion potentials
We extend the Vecchia-Veneziano-Witten (VVW) model of QCD in the chiral limit
and for large colour number , by introducing an effective dilaton-gluon
coupling from which we derive both the axion and dilaton potentials.
Furthermore, using a string inspired model, we determine a new interquark
potential as a perturbative series in terms of the interquark distance . Our
potential goes beyond Dick one obtained in [8] and shares the same features as
the Bian-Huang-Shen potential which depends only on odd powers of
[22].Comment: 15 pages, Late
A novel method for deriving the aerosol hygroscopicity parameter based only on measurements from a humidified nephelometer system
Aerosol hygroscopicity is crucial for understanding roles
of aerosol particles in atmospheric chemistry and aerosol climate effects.
Light-scattering enhancement factor f(RH, λ) is one of the
parameters describing aerosol hygroscopicity, which is defined as
f(RH, λ) = σsp(RH, λ)∕σsp(dry, λ), where
σsp(RH, λ) or σsp(dry, λ) represents σsp at
wavelength λ under certain relative humidity (RH) or dry conditions.
Traditionally, an overall hygroscopicity parameter κ can be
retrieved from measured f(RH, λ), hereinafter referred to as
κf(RH), by combining concurrently measured particle number
size distribution (PNSD) and mass concentration of black carbon. In this
paper, a new method is proposed to directly derive κf(RH)
based only on measurements from a three-wavelength humidified nephelometer
system. The advantage of this newly proposed approach is that
κf(RH) can be estimated without any additional information
about PNSD and black carbon. This method is verified with measurements from
two different field campaigns. Values of κf(RH) estimated
from this new method agree very well with those retrieved by using the
traditional method: all points lie near the 1 : 1 line and the square of
correlation coefficient between them is 0.99. The verification results
demonstrate that this newly proposed method of deriving
κf(RH) is applicable at different sites and in seasons of
the North China Plain and might also be applicable in other regions around
the world
Understanding AGN-Host Connection in Partially Obscured Active Galactic Nuclei. Part I: The Nature of AGN+HII Composites
The goal of our serial papers is to examine the evolutionary connection
between AGN and star formation in its host galaxy in the partially obscured
AGNs (i.e., Seyfert 1.8 and 1.9 galaxies). Taking advantage of these galaxies,
the properties of both components can be studied together by direct
measurements. In this paper, we focus on the broad-line composite galaxies
(composite AGNs) which are located between the theoretical and empirical
separation lines in the [NII]/Ha vs. [OIII]/Hb diagram. These galaxies are
searched for from the composite galaxies provided by the SDSS DR4 MPA/JHU
catalogs. After re-analyze the spectra, we perform a fine classification for
the 85 composite AGNs in terms of the BPT diagrams. All the objects located
below the three theoretical separation lines are associated with a young
stellar population (<1Gyrs), while either a young or old stellar population is
identified in the individual multiply-classified object. The
multiply-classified objects with a very old stellar population are located in
the LINER region in the [OI]/Ha vs. [OIII]/Hb diagram. We then consider the
connection between AGN and star formation to derive the key results. The
Eddington ratio inferred from the broad Ha emission, the age of the stellar
population of AGN's host as assessed by D_n(4000), and the line ratio [OI]/Ha
are found to be related with each other. These relations strongly support the
evolutionary scenario in which AGNs evolve from high L/L_Edd state with soft
spectrum to low L/L_Edd state with hard spectrum as young stellar population
ages and fades. The significant correlation between the line ratio [OI]/Ha and
D_n(4000) leads us to suggest that the line ratio could be used to trace the
age of stellar population in type I AGNs.Comment: 39 pages, 11 figures, 1 table, accepted by Ap
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