4,117 research outputs found
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
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
Genome-wide interaction study of gene-by-occupational exposures on respiratory symptoms
© 2018 Elsevier Ltd Respiratory symptoms are important indicators of respiratory diseases. Both genetic and environmental factors contribute to respiratory symptoms development but less is known about gene-environment interactions. We aimed to assess interactions between single nucleotide polymorphisms (SNPs) and occupational exposures on respiratory symptoms cough, dyspnea and phlegm. As identification cohort LifeLines I (n = 7976 subjects) was used. Job-specific exposure was estimated using the ALOHA + job exposure matrix. SNP-by-occupational exposure interactions on respiratory symptoms were tested using logistic regression adjusted for gender, age, and current smoking. SNP-by-exposure interactions with a p-value <10 −4 were tested for replication in two independent cohorts: LifeLines II (n = 5260) and the Vlagtwedde-Vlaardingen cohort (n = 1529). The interaction estimates of the replication cohorts were meta-analyzed using PLINK. Replication was achieved when the meta-analysis p-value was <0.05 and the interaction effect had the same direction as in the identification cohort. Additionally, we assessed whether replicated SNPs associated with gene expression by analyzing if they were cis-acting expression quantitative trait loci (eQTL) in lung tissue. In the replication meta-analysis, sixteen out of 477 identified SNP-by-occupational exposure interactions had a p-value <0.05 and 9 of these interactions had the same direction as in the identification cohort. Several identified loci were plausible candidates for respiratory symptoms, such as TMPRSS9, SERPINH1, TOX3, and ARHGAP18. Three replicated SNPs were cis-eQTLs for FCER1A, CHN1, and TIMM13 in lung tissue. Taken together, this genome-wide SNP-by-occupational exposure interaction study in relation to cough, dyspnea, and phlegm identified several suggestive susceptibility genes. Further research should determine if these genes are true susceptibility loci for respiratory symptoms in relation to occupational exposures
Spin Star as Switch for Quantum Networks
Quantum state transfer is an important task in quantum information
processing. It is known that one can engineer the couplings of a
one-dimensional spin chain to achieve the goal of perfect state transfer. To
leverage the value of these spin chains, a spin star is potentially useful for
connecting different parts of a quantum network. In this work, we extend the
spin-chain engineering problem to the problems with a topology of a star
network. We show that a permanently coupled spin star can function as a network
switch for transferring quantum states selectively from one node to another by
varying the local potentials only. Together with one-dimensional chains, this
result allows applications of quantum state transfer be applied to more general
quantum networks.Comment: 10 pages, 2 figur
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