244 research outputs found
Donor states in modulation-doped Si/SiGe heterostructures
We present a unified approach for calculating the properties of shallow
donors inside or outside heterostructure quantum wells. The method allows us to
obtain not only the binding energies of all localized states of any symmetry,
but also the energy width of the resonant states which may appear when a
localized state becomes degenerate with the continuous quantum well subbands.
The approach is non-variational, and we are therefore also able to evaluate the
wave functions. This is used to calculate the optical absorption spectrum,
which is strongly non-isotropic due to the selection rules. The results
obtained from calculations for Si/SiGe quantum wells allow us to
present the general behavior of the impurity states, as the donor position is
varied from the center of the well to deep inside the barrier. The influence on
the donor ground state from both the central-cell effect and the strain arising
from the lattice mismatch is carefully considered.Comment: 17 pages, 10 figure
Evolutionary History of Chemosensory-Related Gene Families across the Arthropoda
Chemosensory-related gene (CRG) families have been studied extensively in insects, but their evolutionary history across the Arthropoda had remained relatively unexplored. Here, we address current hypotheses and prior conclusions on CRG family evolution using a more comprehensive data set. In particular, odorant receptors were hypothesized to have proliferated during terrestrial colonization by insects (hexapods), but their association with other pancrustacean clades and with independent terrestrial colonizations in other arthropod subphyla have been unclear. We also examine hypotheses on which arthropod CRG family is most ancient. Thus, we reconstructed phylogenies of CRGs, including those from new arthropod genomes and transcriptomes, and mapped CRG gains and losses across arthropod lineages. Our analysis was strengthened by including crustaceans, especially copepods, which reside outside the hexapod/branchiopod clade within the subphylum Pancrustacea. We generated the first high-resolution genome sequence of the copepod Eurytemora affinis and annotated its CRGs. We found odorant receptors and odorant binding proteins present only in hexapods (insects) and absent from all other arthropod lineages, indicating that they are not universal adaptations to land. Gustatory receptors likely represent the oldest chemosensory receptors among CRGs, dating back to the Placozoa. We also clarified and confirmed the evolutionary history of antennal ionotropic receptors across the Arthropoda. All antennal ionotropic receptors in E. affinis were expressed more highly in males than in females, suggestive of an association with male mate-recognition behavior. This study is the most comprehensive comparative analysis to date of CRG family evolution across the largest and most speciose metazoan phylum Arthropoda
Determining the Dirac CP Violation Phase in the Neutrino Mixing Matrix from Sum Rules
Using the fact that the neutrino mixing matrix
, where and
result from the diagonalisation of the charged lepton
and neutrino mass matrices, we analyse the sum rules which
the Dirac phase present in
satisfies when has a form dictated by,
or associated with, discrete symmetries and
has a ``minimal'' form (in
terms of angles and phases it contains)
that can provide the requisite
corrections to , so that
reactor, atmospheric and solar neutrino mixing angles
, and
have values compatible with the current data.
The following symmetry forms are considered:
i) tri-bimaximal (TBM), ii) bimaximal (BM)
(or corresponding to the conservation of the
lepton charge (LC)),
iii) golden ratio type A (GRA),
iv) golden ratio type B (GRB),
and v) hexagonal (HG).
We investigate the predictions
for in the cases of
TBM, BM (LC), GRA, GRB and HG forms
using the exact and the leading order sum rules
for proposed in the literature,
taking into account also the uncertainties
in the measured values of
, and .
This allows us, in particular, to assess
the accuracy of the predictions for
based on the leading order sum rules and
its dependence on the values
of the indicated neutrino mixing parameters
when the latter are varied in their respective
3 experimentally allowed ranges
Predicting the values of the leptonic CP violation phases in theories with discrete flavour symmetries
Using the fact that the neutrino mixing matrix
, where and
result from the diagonalisation of the charged lepton
and neutrino mass matrices, we consider a
number of
forms of associated with a variety
of discrete symmetries:
i) bimaximal (BM) and ii) tri-bimaximal (TBM) forms,
the forms corresponding iii) to the conservation of the
lepton charge (LC),
iv) to golden ratio type A (GRA) mixing,
v) golden ratio type B (GRB) mixing,
and vi) to hexagonal (HG) mixing.
Employing the minimal form of , in terms of angles and
phases it contains, that can provide the requisite
corrections to so that
reactor, atmospheric and solar neutrino mixing angles
, and
have values compatible with the current data,
including a possible sizable deviation of
from , we discuss the possibility to obtain
predictions for the CP violation phases
in the neutrino mixing matrix.
Considering the ``standard ordering''
of the the 12 and the 23 rotations
in and following the approach
developed in \cite{Marzocca:2013cr}
we derive predictions for the Dirac phase
and the rephasing invariant
in the cases of GRA, GRB and HG forms of
(results for the TBM and BM (LC) forms
were obtained in \cite{Marzocca:2013cr}).
We show also that under rather general conditions
within the scheme considered the values of
the Majorana phases in the PMNS matrix
can be predicted for each of the
forms of discussed. We give examples
of these predictions and of their implications
for neutrinoless double beta decay.
In the GRA, GRB and HG cases,
as in the TBM one, relatively large CP
violation effects in neutrino oscillations
are predicted ().
Distinguishing between the TBM,
BM (LC), GRA, GRB and HG forms of requires
a measurement of or a
relatively high precision measurement of
Prunella vulgaris: A comprehensive review of chemical constituents, pharmacological effects and clinical applications.
Prunella vulgaris (PV) is a perennial herb belonging to the Labiate family and is widely distributed in northeastern Asian countries such as Korea, Japan, and China. It is reported to display diverse biological activities including anti-microbial, anti-cancer, and anti-inflammation as determined by in vitro or in vivo studies. So far, about 200 compounds have been isolated from PV plant and majority of these have been characterized mainly as triterpenoids, sterols and flavonoids, followed by coumarins, phenylpropanoids, polysaccharides and volatile oils. This review summarizes and analyzes the current knowledge on the chemical constituents, pharmacological activities, mechanisms of action and clinical applications of the PV plant including its potential as a future medicinal plant. Although some of the chemical constituents of the PV plant and their mechanism of action have been investigated the biological activities of many of these remain unknown and further clinical trials are required to further enhance its reputation as a medicinal plant
Generalised geometrical CP violation in a T' lepton flavour model
We analyse the interplay of generalised CP transformations and the non-Abelian discrete group T \u2032 and use the semi-direct product G f = T \u2032 caH CP, as family symmetry acting in the lepton sector. The family symmetry is shown to be spontaneously broken in a geometrical manner. In the resulting flavour model, naturally small Majorana neutrino masses for the light active neutrinos are obtained through the type I see-saw mechanism. The known masses of the charged leptons, lepton mixing angles and the two neutrino mass squared differences are reproduced by the model with a good accuracy. The model allows for two neutrino mass spectra with normal ordering (NO) and one with inverted ordering (IO). For each of the three spectra the absolute scale of neutrino masses is predicted with relatively small uncertainty. The value of the Dirac CP violation (CPV) phase \u3b4 in the lepton mixing matrix is predicted to be \u3b4 = \u3c0/2 or 3\u3c0/2. Thus, the CP violating effects in neutrino oscillations are predicted to be maximal (given the values of the neutrino mixing angles) and experimentally observable. We present also predictions for the sum of the neutrino masses, for the Majorana CPV phases and for the effective Majorana mass in neutrinoless double beta decay. The predictions of the model can be tested in a variety of ongoing and future planned neutrino experiments
All-sky search for long-duration gravitational wave transients with initial LIGO
We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society
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