650 research outputs found
A new dromaeosaurid (Dinosauria: Theropoda) from the Upper Cretaceous Wulansuhai Formation of Inner Mongolia, China
We describe a new dromaeosaurid theropod from the Upper Cretaceous Wulansuhai Formation of Bayan Mandahu, Inner
Mongolia. The new taxon, Linheraptor exquisitus gen. et sp. nov., is based on an exceptionally well-preserved, nearly
complete skeleton. This specimen represents the fifth dromaeosaurid taxon recovered from the Upper Cretaceous
Djadokhta Formation and its laterally equivalent strata, which include the Wulansuhai Formation, and adds to the known
diversity of Late Cretaceous dromaeosaurids. Linheraptor exquisitus closely resembles the recently reported Tsaagan
mangas. Uniquely among dromaeosaurids, the two taxa share a large, anteriorly located maxillary fenestra and a contact
between the jugal and the squamosal that excludes the postorbital from the infratemporal fenestra. These features suggest
a sister-taxon relationship between L. exquisitus and T. mangas, which indicates the presence of a unique dromaeosaurid
lineage in the Late Cretaceous of Asia. A number of cranial and dental features seen in L. exquisitus and T. mangas, and
particularly some postcranial features of L. exquisitus, suggest that these two taxa are probably intermediate in
systematic position between known basal and derived dromaeosaurids. The discovery of Linheraptor exquisitus is thus
important for understanding the evolution of some salient features seen in the derived dromaeosaurids
Magnetic relaxation in Fe-(SiO\u3csub\u3e2\u3c/sub\u3e) granular films
Magnetic relaxation of granular Fe-(SiO2) solids with low metal-volume fraction has been studied by employing dc SQUID (superconducting quantum interference device) magnetometry and Mössbauer spectroscopy with the characteristic measuring time differing by nine orders of magnitude. The blocking temperatures (TB), extrapolated to zero external field as measured by the two techniques maintain a constant ratio of 0.35 independent of samples. Arrhenius law was found adequate in describing the relaxation process, with a well-defined relaxation-time constant of τ0≃10-13 sec. A cusp in the susceptibility is observed at TB, below which irreversible difference between the field-cooled and zero-field-cooled magnetizations occurs. Despite this spin-glass-like behavior, granular magnetic systems are found to be fundamentally different from spin glasses
Berry Curvature in Graphene: A New Approach
In the present paper we have directly computed the Berry curvature terms
relevant for Graphene in the presence of an \textit{inhomogeneous} lattice
distortion. We have employed the generalized Foldy Wouthuysen framework,
developed by some of us \cite{ber0,ber1,ber2}. We show that a non-constant
lattice distortion leads to a valley-orbit coupling which is responsible to a
valley-Hall effect. This is similar to the valley-Hall effect induced by an
electric field proposed in \cite{niu2} and is the analogue of the spin-Hall
effect in semiconductors \cite{MURAKAMI, SINOVA}. Our general expressions for
Berry curvature, for the special case of homogeneous distortion, reduce to the
previously obtained results \cite{niu2}. We also discuss the Berry phase in the
quantization of cyclotron motion.Comment: Slightly modified version, to appear in EPJ
Lepton Flavor Violation in the SUSY-GUT Models with Lopsided Mass Matrix
The tiny neutrino masses measured in the neutrino oscillation experiments can
be naturally explained by the supersymmetric see-saw mechanism. If the
supersymmetry breaking is mediated by gravity, the see-saw models may predict
observable lepton flavor violating effects. In this work, we investigate the
lepton flavor violating process in the kind of neutrino mass
models based on the idea of the ``lopsided'' form of the charged lepton mass
matrix. The constraints set by the muon anomalous magnetic moment are taken
into account. We find the present models generally predict a much larger
branching ratio of than the experimental limit. Conversely,
this process may give strong constraint on the lepton flavor structure.
Following this constraint we then find a new kind of the charged lepton mass
matrix. The feature of the structure is that both the elements between the 2-3
and 1-3 generations are ``lopsided''. This structure produces a very small 1-3
mixing and a large 1-2 mixing in the charged lepton sector, which naturally
leads to small and the LMA solution for the solar neutrino
problem.Comment: 24 pages, 8 figure
Modeling realistic Earth matter density for CP violation in neutrino oscillation
We examine the effect of a more realistic Earth matter density model which
takes into account of the local density variations along the baseline of a
possi ble 2100 km very long baseline neutrino oscillation experiment. Its
influence to the measurement of CP violation is investigated and a comparison
with the commonly used global density models made. Significant differences are
found in the comparison of the results of the different density models.Comment: 16 pages, 8 figure
Effects of different probiotics on the gut microbiome and metabolites in the serum and caecum of weaning piglets
The objective of the study was to determine the effects of antibiotics, yeast culture (YC), and Lactobacillus culture (LC) on the gut microbiome and metabolites in the serum and caecum of weaning piglets. Twenty-four weaning piglets were divided into four treatment groups: control, antibiotic (1% chlortetracycline), 1.8% yeast culture (YC), and 1.6% Lactobacillus culture groups (LC). Each group had six replicated pens with one pig per pen. Feed and water were available ad libitum. Dietary supplementation with antibiotics, YC and LC increased the abundance of phylum, Firmicutes, and decreased the abundance of phylum, Proteobacteria. Beneficial bacteria such as Lactobacillus and Megasphaera in YC and LC groups increased, whereas the proportion of Shigella was decreased. Genera Alloprevotella and Lachnospira were biomarkers in the control and antibiotic groups, respectively. Phylum, Bacteroidetes, and genus, Collinsella, were biomarkers in the YC group, and Mitsuokella, Anaerotruncus, Syntrophococcus and Sharpea were biomarkers in the LC group. Dietary supplementation with different probiotics changed the serum and caecum metabolite profiles too. Antibiotic supplementation increased the levels of D-mannose, D-glucose, and hexadecanoic acid in the serum, and the levels of myo-inositol, D-mannose and benzenepropanoic acid in the caecum. LC increased the concentrations of D-mannose, cis-9-hexadecenoic acid and heptadecanoic acid in caecum compared with the control group. YC and LC supplementation in the weaning diet could improve the abundance of beneficial bacteria by changing the concentrations of some metabolites in the serum and caecum. Therefore, dietary supplementation with YC or LC could be used as additives instead of antibiotics in weaning piglets.Keywords: antibiotic; lactobacillus culture; yeast culture; high-throughput sequencing; gas chromatography mass spectrometr
Highly Charged Ions in Rare Earth Permanent Magnet Penning Traps
A newly constructed apparatus at the National Institute of Standards and
Technology (NIST) is designed for the isolation, manipulation, and study of
highly charged ions. Highly charged ions are produced in the NIST electron-beam
ion trap (EBIT), extracted through a beamline that selects a single mass/charge
species, then captured in a compact Penning trap. The magnetic field of the
trap is generated by cylindrical NdFeB permanent magnets integrated into its
electrodes. In a room-temperature prototype trap with a single NdFeB magnet,
species including Ne10+ and N7+ were confined with storage times of order 1
second, showing the potential of this setup for manipulation and spectroscopy
of highly charged ions in a controlled environment. Ion capture has since been
demonstrated with similar storage times in a more-elaborate Penning trap that
integrates two coaxial NdFeB magnets for improved B-field homogeneity. Ongoing
experiments utilize a second-generation apparatus that incorporates this
two-magnet Penning trap along with a fast time-of-flight MCP detector capable
of resolving the charge-state evolution of trapped ions. Holes in the
two-magnet Penning trap ring electrode allow for optical and atomic beam
access. Possible applications include spectroscopic studies of one-electron
ions in Rydberg states, as well as highly charged ions of interest in atomic
physics, metrology, astrophysics, and plasma diagnostics.Comment: Proceedings of CDAMOP-2011, 13-16 Dec 2011, Delhi, India. To be
published by Springer Verla
Neutrino Masses with "Zero Sum" Condition:
It is well known that the neutrino mass matrix contains more parameters than
experimentalists can hope to measure in the foreseeable future even if we
impose CP invariance. Thus, various authors have proposed ansatzes to restrict
the form of the neutrino mass matrix further. Here we propose that ; this ``zero sum'' condition can occur in certain
class of models, such as models whose neutrino mass matrix can be expressed as
commutator of two matrices. With this condition, the absolute neutrino mass can
be obtained in terms of the mass-squared differences. When combined with the
accumulated experimental data this condition predicts two types of mass
hierarchies, with one of them characterized by eV, and the other by eV and eV. The mass ranges
predicted is just below the cosmological upper bound of 0.23 eV from recent
WMAP data and can be probed in the near future. We also point out some
implications for direct laboratory measurement of neutrino masses, and the
neutrino mass matrix.Comment: Latex 12 pages. No figures. New references adde
Nonlinear wave transmission and pressure on the fixed truncated breakwater using NURBS numerical wave tank
Fully nonlinear wave interaction with a fixed breakwater is investigated in a numerical wave tank (NWT). The potential theory and high-order boundary element method are used to solve the boundary value problem. Time domain simulation by a mixed Eulerian-Lagrangian (MEL) formulation and high-order boundary integral method based on non uniform rational B-spline (NURBS) formulation is employed to solve the equations. At each time step, Laplace equation is solved in Eulerian frame and fully non-linear free-surface conditions are updated in Lagrangian manner through material node approach and fourth order Runge-Kutta time integration scheme. Incident wave is fed by specifying the normal flux of appropriate wave potential on the fixed inflow boundary. To ensure the open water condition and to reduce the reflected wave energy into the computational domain, two damping zones are provided on both ends of the numerical wave tank. The convergence and stability of the presented numerical procedure are examined and compared with the analytical solutions. Wave reflection and transmission of nonlinear waves with different steepness are investigated. Also, the calculation of wave load on the breakwater is evaluated by first and second order time derivatives of the potential
Dark Energy and Neutrino CPT Violation
In this paper we study the dynamical CPT violation in the neutrino sector
induced by the dark energy of the Universe. Specifically we consider a dark
energy model where the dark energy scalar derivatively interacts with the
right-handed neutrinos. This type of derivative coupling leads to a
cosmological CPT violation during the evolution of the background field of the
dark energy. We calculate the induced CPT violation of left-handed neutrinos
and find the CPT violation produced in this way is consistent with the present
experimental limit and sensitive to the future neutrino oscillation
experiments, such as the neutrino factory.Comment: 10 pages, 2 figures. Typos corrected and references added. To be
published in EPJ
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