Differential cross sections for muonic atom scattering from hydrogenic molecules

The differential cross sections for low-energy muonic hydrogen atom scattering from hydrogenic molecules are directly expressed by the corresponding amplitudes for muonic atom scattering from hydrogen-isotope nuclei. The energy and angular dependence of these three-body amplitudes is thus taken naturally into account in scattering from molecules, without involving any pseudopotentials. Effects of the internal motion of nuclei inside the target molecules are included for every initial rotational-vibrational state. These effects are very significant as the considered three-body amplitudes often vary strongly within the energy interval $\lesssim{}0.1$ eV. The differential cross sections, calculated using the presented method, have been successfully used for planning and interpreting many experiments in low-energy muon physics. Studies of $\mu^{-}$ nuclear capture in $p\mu$ and the measurement of the Lamb shift in $p\mu$ atoms created in H$_2$ gaseous targets are recent examples.Comment: 21 pages, 13 figures, submitted to Phys. Rev.

Discrete-time quantum walks on one-dimensional lattices

In this paper, we study discrete-time quantum walks on one-dimensional lattices. We find that the coherent dynamics depends on the initial states and coin parameters. For infinite size of lattice, we derive an explicit expression for the return probability, which shows scaling behavior $P(0,t)\sim t^{-1}$ and does not depends on the initial states of the walk. In the long-time limit, the probability distribution shows various patterns, depending on the initial states, coin parameters and the lattice size. The average mixing time $M_{\epsilon}$ closes to the limiting probability in linear $N$ (size of the lattice) for large values of thresholds $\epsilon$. Finally, we introduce another kind of quantum walk on infinite or even-numbered size of lattices, and show that the walk is equivalent to the traditional quantum walk with symmetrical initial state and coin parameter.Comment: 17 pages research not

Differential cross sections for muonic atom scattering in solid hydrogenic targets

The differential cross sections for low-energy muonic hydrogen atom scattering in solid molecular H$_2$, D$_2$ and T$_2$ targets under low pressure have been calculated for various temperatures. The polycrystalline fcc and hcp structure of the solid hydrogenic targets are considered. The Bragg and phonon scattering processes are described using the Debye model of a solid. The calculated cross sections are used for Monte Carlo simulations of the muonic atom slowing down in these targets. They have been successfully applied for a description of the production of the muonic atom beams in the multilayer hydrogenic crystals.Comment: 23 pages, 19 figures, 2 table

Chandra grating spectroscopy of three hot white dwarfs

High-resolution soft X-ray spectroscopic observations of single hot white dwarfs are scarce. With the Chandra Low-Energy Transmission Grating, we have observed two white dwarfs, one is of spectral type DA (LB 1919) and the other is a non-DA of spectral type PG1159 (PG 1520+525). The spectra of both stars are analyzed, together with an archival Chandra spectrum of another DA white dwarf (GD 246). The soft X-ray spectra of the two DA white dwarfs are investigated in order to study the effect of gravitational settling and radiative levitation of metals in their photospheres. LB 1919 is of interest because it has a significantly lower metallicity than DAs with otherwise similar atmospheric parameters. GD 246 is the only white dwarf known that shows identifiable individual iron lines in the soft X-ray range. For the PG1159 star, a precise effective temperature determination is performed in order to confine the position of the blue edge of the GW Vir instability region in the HRD. (abridged)Comment: A&A, in pres

Resonant Formation of dμtd\mu t Molecules in Deuterium: An Atomic Beam Measurement of Muon Catalyzed dt Fusion

Resonant formation of $d\mu t$ molecules in collisions of muonic tritium ($\mu t$) on D$_2$ was investigated using a beam of $\mu t$ atoms, demonstrating a new direct approach in muon catalyzed fusion studies. Strong epithermal resonances in $d\mu t$ formation were directly revealed for the first time. From the time-of-flight analysis of $2036\pm 116$ $dt$ fusion events, a formation rate consistent with $0.73\pm (0.16)_{meas} \pm (0.09)_{model}$ times the theoretical prediction was obtained. For the largest peak at a resonance energy of $0.423 \pm 0.037$ eV, this corresponds to a rate of $(7.1 \pm 1.8) \times 10^9$ s$^{-1}$, more than an order of magnitude larger than those at low energies.Comment: To appear in Phys. Rev. Let

Proton Zemach radius from measurements of the hyperfine splitting of hydrogen and muonic hydrogen

While measurements of the hyperfine structure of hydrogen-like atoms are traditionally regarded as test of bound-state QED, we assume that theoretical QED predictions are accurate and discuss the information about the electromagnetic structure of protons that could be extracted from the experimental values of the ground state hyperfine splitting in hydrogen and muonic hydrogen. Using recent theoretical results on the proton polarizability effects and the experimental hydrogen hyperfine splitting we obtain for the Zemach radius of the proton the value 1.040(16) fm. We compare it to the various theoretical estimates the uncertainty of which is shown to be larger that 0.016 fm. This point of view gives quite convincing arguments in support of projects to measure the hyperfine splitting of muonic hydrogen.Comment: Submitted to Phys. Rev.

Back to the Eneolithic: Exploring the Rudki-type ornaments from Poland

For a long time, the Eneolithic attribution of the Rudki-type double spiral ornaments was contested by a wide academic audience, and therefore, this new and extraordinary category of the copper metalwork seemed to have fallen into scientific oblivion. In this paper, we contribute to the debate about cultural attribution of the Rudki-type double spiral ornaments considering their chemical and isotope characteristics (using ED XRF and MC-ICP-MS) and the manufacturing technology (OM, X-ray, CT). Noticeably, this study represents the first documented implementation of the lead isotope analysis (LIA) for the Eneolithic metalwork from Poland. The new scientific analyses give ground to the hypothesis that the Rudki-type double spiral ornaments were produced by the Baden culture metalworker(s) who practiced somewhere in the Carpathian Basin and who have used copper ore mined in the Slovak Ore Mountains (Spania Dolina-Banska Bystrica-Kremnica mine complex). These ornaments were redistributed towards the northern ecumene of the Baden culture complex. The new owners, the Funnel Beaker (TRB) culture communities from the region of modern Poland, deposited the ornaments in hoards (Kaldus, Przeuszyn and Rudki) during the mid-4th millennium BC. The results, furthermore, indicate that the so-called Baden spiral metalwork package must be now complemented by the Rudki-type double spiral ornaments. Remarkably, this package also found an echo in pottery decoration, as documented by a narrative scene incised on an amphora from Kaldus, which could be also interpreted as one of the earliest known proofs for the wagon transport in Europe, alongside the famous ones reported from Bronocice or Flintbek.Material Culture Studie

Continuous-Time Classical and Quantum Random Walk on Direct Product of Cayley Graphs

In this paper we define direct product of graphs and give a recipe for obtained probability of observing particle on vertices in the continuous-time classical and quantum random walk. In the recipe, the probability of observing particle on direct product of graph obtain by multiplication of probability on the corresponding to sub-graphs, where this method is useful to determine probability of walk on complicated graphs. Using this method, we calculate the probability of continuous-time classical and quantum random walks on many of finite direct product cayley graphs (complete cycle, complete $K_n$, charter and $n$-cube). Also, we inquire that the classical state the stationary uniform distribution is reached as $t\longrightarrow \infty$ but for quantum state is not always satisfy.Comment: 21, page. Accepted for publication on CT

EL_PSSM-RT:DNA-binding residue prediction by integrating ensemble learning with PSSM Relation Transformation

Background: Prediction of DNA-binding residue is important for understanding the protein-DNA recognition mechanism. Many computational methods have been proposed for the prediction, but most of them do not consider the relationships of evolutionary information between residues. Results: In this paper, we first propose a novel residue encoding method, referred to as the Position Specific Score Matrix (PSSM) Relation Transformation (PSSM-RT), to encode residues by utilizing the relationships of evolutionary information between residues. PDNA-62 and PDNA-224 are used to evaluate PSSM-RT and two existing PSSM encoding methods by five-fold cross-validation. Performance evaluations indicate that PSSM-RT is more effective than previous methods. This validates the point that the relationship of evolutionary information between residues is indeed useful in DNA-binding residue prediction. An ensemble learning classifier (EL_PSSM-RT) is also proposed by combining ensemble learning model and PSSM-RT to better handle the imbalance between binding and non-binding residues in datasets. EL_PSSM-RT is evaluated by five-fold cross-validation using PDNA-62 and PDNA-224 as well as two independent datasets TS-72 and TS-61. Performance comparisons with existing predictors on the four datasets demonstrate that EL_PSSM-RT is the best-performing method among all the predicting methods with improvement between 0.02-0.07 for MCC, 4.18-21.47% for ST and 0.013-0.131 for AUC. Furthermore, we analyze the importance of the pair-relationships extracted by PSSM-RT and the results validates the usefulness of PSSM-RT for encoding DNA-binding residues. Conclusions: We propose a novel prediction method for the prediction of DNA-binding residue with the inclusion of relationship of evolutionary information and ensemble learning. Performance evaluation shows that the relationship of evolutionary information between residues is indeed useful in DNA-binding residue prediction and ensemble learning can be used to address the data imbalance issue between binding and non-binding residues. A web service of EL_PSSM-RT ( http://hlt.hitsz.edu.cn:8080/PSSM-RT_SVM/ ) is provided for free access to the biological research community