6,277 research outputs found
Atomic Entanglement vs Photonic Visibility for Quantum Criticality of Hybrid System
To characterize the novel quantum phase transition for a hybrid system
consisting of an array of coupled cavities and two-level atoms doped in each
cavity, we study the atomic entanglement and photonic visibility in comparison
with the quantum fluctuation of total excitations. Analytical and numerical
simulation results show the happen of quantum critical phenomenon similar to
the Mott insulator to superfluid transition. Here, the contour lines
respectively representing the atomic entanglement, photonic visibility and
excitation variance in the phase diagram are consistent in the vicinity of the
non-analytic locus of atomic concurrences.Comment: 4 pages, 2 figure
Model-based spacecraft and mission design for the evaluation of technology
In order to meet the future vision of robotic missions, engineers will face intricate mission concepts, new operational approaches, and technologies that have yet to be developed. The concept of smaller, model driven projects helps this transition by including life-cycle cost as part of the decision making process. For example, since planetary exploration missions have cost ceilings and short development periods, heritage flight hardware is utilized. However, conceptual designs that rely solely on heritage technology will result in estimates that may not be truly representative of the actual mission being designed and built. The Laboratory for Spacecraft and Mission Design (LSMD) at the California Institute of Technology is developing integrated concurrent models for mass and cost estimations. The purpose of this project is to quantify the infusion of specific technologies where the data would be useful in guiding technology developments leading up to a mission. This paper introduces the design-to-cost model to determine the implications of various technologies on the spacecraft system in a collaborative engineering environment. In addition, comparisons of the benefits of new or advanced technologies for future deep space missions are examined
The and decays with the fourth generation
If the fourth generation fermions exist, the new quarks could influence the
branching ratios of the decays of and . We
obtain two solutions of the fourth generation CKM factor
from the decay of . We use these
two solutions to calculate the new contributions of the fourth generation quark
to Wilson coefficients of the decay of . The branching ratio
and the forward-backward asymmetry of the decay of in the two
cases are calculated. Our results are quite different from that of SM in one
case, almost same in another case. If Nature chooses the formmer, the meson
decays could provide a possible test of the forth generation existence.Comment: 10 pages, 5 figure
Sperm repository for a breeding program of the eastern oyster crassostrea virginica: Sample collection, processing, cryopreservation, and data management plan
The Eastern oyster Crassostrea virginica (Family Ostreidae) is one of the most important fishery and aquaculture species in the U.S. and is a keystone species for coastal reefs. A breeding program was initiated in 2019 to support the fastâgrowing aquaculture industry culturing this species in the Gulf of Mexico. Oysters from 17 wild populations in embayment along the U.S. Gulf of Mexico coast from southwest Florida to the Matagorda Bay, Texas were used as broodstock for the program to maximize genetic diversity in the base population. A sperm repository of the broodstock was established to support the breeding project. The goal of this study was to demonstrate the sperm sample collection, processing, cryopreservation, and the data management plan involved in the establishment of a sperm germplasm repository of base populations. The supporting objectives were to: (1) develop a data management plan for the sperm repository; (2) streamline the procedure for sample collection, processing, and cryopreservation; (3) incorporate sperm quality analysis into the procedure, and (4) archive the cryopreserved samples as a repository for future use in the breeding program. This sperm repository included a total of 102 male oysters from the 17 collection sites (six oysters per site). A data management plan was developed with six categories, including sample collection, phenotype, fresh sperm, genotype, cryopreservation, and postâthaw sperm, as guide for data collection. Sperm collection was accomplished by strip spawn, and fresh sperm production, motility, and fertility were recorded for quality analysis. Cryopreserved sperm samples were sorted, labelled, archived, and stored in liquid nitrogen for future use. Postâthaw motility (1â30%) and plasm membrane integrity (15.34â70.36%) were recorded as postâthaw quality parameters. Overall, this study demonstrated a streamlined procedure of oyster sperm collection, processing, and cryopreservation for establishing a sperm repository that can serve as a template for construction of oyster germplasm repositories for breeding programs
The evolution of stellar metallicity gradients of the Milky Way disk from LSS-GAC main sequence turn-off stars: a two-phase disk formation history?
We use 297 042 main sequence turn-off stars selected from the LSS-GAC to
determine the radial and vertical gradients of stellar metallicity of the
Galactic disk in the anti-center direction. We determine ages of those turn-off
stars by isochrone fitting and measure the temporal variations of metallicity
gradients. Our results show that the gradients, both in the radial and vertical
directions, exhibit significant spatial and temporal variations. The radial
gradients yielded by stars of oldest ages (>11 Gyr) are essentially zero at all
heights from the disk midplane, while those given by younger stars are always
negative. The vertical gradients deduced from stars of oldest ages (>11Gyr) are
negative and show only very weak variations with the Galactocentric distance in
the disk plane, , while those yielded by younger stars show strong
variations with . After being essentially flat at the earliest epochs of
disk formation, the radial gradients steepen as age decreases, reaching a
maxima (steepest) at age 7-8 Gyr, and then they flatten again. Similar temporal
trends are also found for the vertical gradients. We infer that the assemblage
of the Milky Way disk may have experienced at least two distinct phases. The
earlier phase is probably related to a slow, pressure-supported collapse of
gas, when the gas settles down to the disk mainly in the vertical direction. In
the later phase, there are significant radial flows of gas in the disk, and the
rate of gas inflow near the solar neighborhood reaches a maximum around a
lookback time of 7-8 Gyr. The transition of the two phases occurs around a
lookback time between 8 and 11 Gyr. The two phases may be responsible for the
formation of the Milky Way thick and thin disks, respectively. And, as a
consequence, we recommend that stellar age is a natural, physical criterion to
distinguish thin and thick disk stars. ... (abridged)Comment: 31 pages, 17 figures, Accepted for publication in a special issue of
Research in Astronomy and Astrophysics on LAMOST science
A cosmic ray super high multicore family event. 1: Experiment and general features
Information on the fragmentation region in super high energy hadronic interactions can be obtained through the observations of gamma-ray families produced by cosmic rays. Gamma-ray families with the sum of E sub gamma or 1000 TeV are receiving increasing interests in emulsion chamber experiments. There exist some complications caused by the superposition of nuclear and electromagnetic cascades and the uncertainty in the nature of the primary particles. These complications usually make the conclusions drawn from various interesting phenomena observed in family events not so definite. An interesting family event KO E19, which is likely to have suffered only very slight disturbances is described. It was found in the Mt. Kambala emulsion chamber experiment. The production height of the event is determined to be H=(70 + or - 30)m and some conclusions are given
Intensities of high-energy cosmic rays at Mount Kanbala
The energy spectra of atmospheric cosmic rays at Mt. Kanbala (520 g/sq cm.) are measured with emulsion chambers. The power indexes of the spectra are values of about 2.0 for both gamma-rays and hadrons. Those fluxes are consistent with the ones expected from the model of primary cosmic rays with heavy nuclei of high content in the energy around 10 to the 15th power eV
Peierls distorted chain as a quantum data bus for quantum state transfer
We systematically study the transfer of quantum state of electron spin as the
flying qubit along a half-filled Peierls distorted tight-binding chain
described by the Su-Schrieffer-Heeger (SSH) model, which behaves as a quantum
data bus. This enables a novel physical mechanism for quantum communication
with always-on interaction: the effective hopping of the spin carrier between
sites and connected to two sites in this SSH chain can be induced by
the quasi-excitations of the SSH model. As we prove, it is the Peierls energy
gap of the SSH quasi-excitations that plays a crucial role to protect the
robustness of the quantum state transfer process. Moreover, our observation
also indicates that such a scheme can also be employed to explore the intrinsic
property of the quantum system.Comment: 10 pages, 6 figure
Ages and Masses of 0.64 million Red Giant Branch stars from the LAMOST Galactic Spectroscopic Survey
We present a catalog of stellar age and mass estimates for a sample of
640\,986 red giant branch (RGB) stars of the Galactic disk from the LAMOST
Galactic Spectroscopic Survey (DR4). The RGB stars are distinguished from the
red clump stars utilizing period spacing derived from the spectra with a
machine learning method based on kernel principal component analysis (KPCA).
Cross-validation suggests our method is capable of distinguishing RC from RGB
stars with only 2 per cent contamination rate for stars with signal-to-noise
ratio (SNR) higher than 50. The age and mass of these RGB stars are determined
from their LAMOST spectra with KPCA method by taking the LAMOST -
giant stars having asteroseismic parameters and the LAMOST-TGAS sub-giant stars
based on isochrones as training sets. Examinations suggest that the age and
mass estimates of our RGB sample stars with SNR 30 have a median error of
30 per cent and 10 per cent, respectively. Stellar ages are found to exhibit
positive vertical and negative radial gradients across the disk, and the age
structure of the disk is strongly flared across the whole disk of
\,kpc. The data set demonstrates good correlations among stellar age,
[Fe/H] and [/Fe]. There are two separate sequences in the [Fe/H] --
[/Fe] plane: a high-- sequence with stars older than
\,8\,Gyr and a low-- sequence composed of stars with ages
covering the whole range of possible ages of stars. We also examine relations
between age and kinematic parameters derived from the Gaia DR2 parallax and
proper motions. Both the median value and dispersion of the orbital
eccentricity are found to increase with age. The vertical angular momentum is
found to fairly smoothly decrease with age from 2 to 12\,Gyr, with a rate of
about 50\,kpc\,km\,s\,Gyr. A full table of the catalog is
public available online.Comment: 16 pages, 22 figures,accepted by MNRA
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