Analytic approximation and an improved method for computing the stress-energy of quantized scalar fields in Robertson-Walker spacetimes

An improved method is given for the computation of the stress-energy tensor of a quantized scalar field using adiabatic regularization. The method works for fields with arbitrary mass and curvature coupling in Robertson-Walker spacetimes and is particularly useful for spacetimes with compact spatial sections. For massless fields it yields an analytic approximation for the stress-energy tensor that is similar in nature to those obtained previously for massless fields in static spacetimes.Comment: RevTeX, 8 pages, no figure

Prediction of RNA-protein sequence and structure binding preferences using deep convolutional and recurrent neural networks

Background: RNA regulation is significantly dependent on its binding protein partner, known as the RNA-binding proteins (RBPs). Unfortunately, the binding preferences for most RBPs are still not well characterized. Interdependencies between sequence and secondary structure specificities is challenging for both predicting RBP binding sites and accurate sequence and structure motifs detection. Results: In this study, we propose a deep learning-based method, iDeepS, to simultaneously identify the binding sequence and structure motifs from RNA sequences using convolutional neural networks (CNNs) and a bidirectional long short term memory network (BLSTM). We first perform one-hot encoding for both the sequence and predicted secondary structure, to enable subsequent convolution operations. To reveal the hidden binding knowledge from the observed sequences, the CNNs are applied to learn the abstract features. Considering the close relationship between sequence and predicted structures, we use the BLSTM to capture possible long range dependencies between binding sequence and structure motifs identified by the CNNs. Finally, the learned weighted representations are fed into a classification layer to predict the RBP binding sites. We evaluated iDeepS on verified RBP binding sites derived from large-scale representative CLIP-seq datasets. The results demonstrate that iDeepS can reliably predict the RBP binding sites on RNAs, and outperforms the state-of-the-art methods. An important advantage compared to other methods is that iDeepS can automatically extract both binding sequence and structure motifs, which will improve our understanding of the mechanisms of binding specificities of RBPs. Conclusion: Our study shows that the iDeepS method identifies the sequence and structure motifs to accurately predict RBP binding sites. iDeepS is available at https://github.com/xypan1232/iDeepS

The ARGO-YBJ Experiment Progresses and Future Extension

Gamma ray source detection above 30TeV is an encouraging approach for finding galactic cosmic ray origins. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100GeV. To target the goals, the ARGO-YBJ experiment has been established. Significant progresses have been made in the experiment. A large air shower detector array in an area of 1km2 is proposed to boost the sensitivity. Hybrid detection with multi-techniques will allow a good discrimination between different types of primary particles, including photons and protons, thus enable an energy spectrum measurement for individual specie. Fluorescence light detector array will extend the spectrum measurement above 100PeV where the second knee is located. An energy scale determined by balloon experiments at 10TeV will be propagated to ultra high energy cosmic ray experiments

High Altitude test of RPCs for the ARGO-YBJ experiment

A 50 m**2 RPC carpet was operated at the YangBaJing Cosmic Ray Laboratory (Tibet) located 4300 m a.s.l. The performance of RPCs in detecting Extensive Air Showers was studied. Efficiency and time resolution measurements at the pressure and temperature conditions typical of high mountain laboratories, are reported.Comment: 16 pages, 10 figures, submitted to Nucl. Instr. Met

A measurement of the tau mass and the first CPT test with tau leptons

We measure the mass of the tau lepton to be 1775.1+-1.6(stat)+-1.0(syst.) MeV using tau pairs from Z0 decays. To test CPT invariance we compare the masses of the positively and negatively charged tau leptons. The relative mass difference is found to be smaller than 3.0 10^-3 at the 90% confidence level.Comment: 10 pages, 4 figures, Submitted to Phys. Letts.

First Measurement of Z/gamma* Production in Compton Scattering of Quasi-real Photons

We report the first observation of Z/gamma* production in Compton scattering of quasi-real photons. This is a subprocess of the reaction e+e- to e+e-Z/gamma*, where one of the final state electrons is undetected. Approximately 55 pb-1 of data collected in the year 1997 at an e+e- centre-of-mass energy of 183 GeV with the OPAL detector at LEP have been analysed. The Z/gamma* from Compton scattering has been detected in the hadronic decay channel. Within well defined kinematic bounds, we measure the product of cross-section and Z/gamma* branching ratio to hadrons to be (0.9+-0.3+-0.1) pb for events with a hadronic mass larger than 60 GeV, dominated by (e)eZ production. In the hadronic mass region between 5 GeV and 60 GeV, dominated by (e)egamma* production, this product is found to be (4.1+-1.6+-0.6) pb. Our results agree with the predictions of two Monte Carlo event generators, grc4f and PYTHIA.Comment: 18 pages, LaTeX, 5 eps figures included, submitted to Physics Letters

Search for Higgs Bosons in e+e- Collisions at 183 GeV

The data collected by the OPAL experiment at sqrts=183 GeV were used to search for Higgs bosons which are predicted by the Standard Model and various extensions, such as general models with two Higgs field doublets and the Minimal Supersymmetric Standard Model (MSSM). The data correspond to an integrated luminosity of approximately 54pb-1. None of the searches for neutral and charged Higgs bosons have revealed an excess of events beyond the expected background. This negative outcome, in combination with similar results from searches at lower energies, leads to new limits for the Higgs boson masses and other model parameters. In particular, the 95% confidence level lower limit for the mass of the Standard Model Higgs boson is 88.3 GeV. Charged Higgs bosons can be excluded for masses up to 59.5 GeV. In the MSSM, mh > 70.5 GeV and mA > 72.0 GeV are obtained for tan{beta}>1, no and maximal scalar top mixing and soft SUSY-breaking masses of 1 TeV. The range 0.8 < tanb < 1.9 is excluded for minimal scalar top mixing and m{top} < 175 GeV. More general scans of the MSSM parameter space are also considered.Comment: 49 pages. LaTeX, including 33 eps figures, submitted to European Physical Journal

A Measurement of the Product Branching Ratio f(b->Lambda_b).BR(Lambda_b->Lambda X) in Z0 Decays

The product branching ratio, f(b->Lambda_b).BR(Lambda_b->Lambda X), where Lambda_b denotes any weakly-decaying b-baryon, has been measured using the OPAL detector at LEP. Lambda_b are selected by the presence of energetic Lambda particles in bottom events tagged by the presence of displaced secondary vertices. A fit to the momenta of the Lambda particles separates signal from B meson and fragmentation backgrounds. The measured product branching ratio is f(b->Lambda_b).BR(Lambda_b->Lambda X) = (2.67+-0.38(stat)+0.67-0.60(sys))% Combined with a previous OPAL measurement, one obtains f(b->Lambda_b).BR(Lambda_b->Lambda X) = (3.50+-0.32(stat)+-0.35(sys))%.Comment: 16 pages, LaTeX, 3 eps figs included, submitted to the European Physical Journal