Constraints on non-minimal coupling from quantum cosmology

Quantum cosmology is investigated in a de Sitter minisuperspace model with a quantized scalar field non-minimally coupled to curvature. Quantum states of the scalar field must satisfy the regularity condition, which requires that the probability of field fluctuations should not increase with their amplitude. We show that this condition imposes constraints on the allowed values of the curvature coupling parameter $\xi$. This is a surprising result, since the field dynamics depends only on the combination $m^2+\xi R$, where $m$ is the field mass and $R = \mathrm{const}$ is the curvature, and does not depend on $\xi$ separately.Comment: v1, 15 pages, 2 figures; v2, 19 pages, 5 figures, version accepted for publication in JCAP, discussion added to incorporate with a hilltop potentia

Method for creating polynucleotide and polypeptide sequences

The invention provides methods for evolving a polynucleotide toward acquisition of a desired property. Such methods entail incubating a population of parental polynucleotide variants under conditions to generate annealed polynucleotides comprising heteroduplexes. The heteroduplexes are then exposed to a cellular DNA repair system to convert the heteroduplexes to parental polynucleotide variants or recombined polynucleotide variants. The resulting polynucleotides are then screened or selected for the desired property

Adaptive context tree weighting

We describe an adaptive context tree weighting (ACTW) algorithm, as an extension to the standard context tree weighting (CTW) algorithm. Unlike the standard CTW algorithm, which weights all observations equally regardless of the depth, ACTW gives increasing weight to more recent observations, aiming to improve performance in cases where the input sequence is from a non-stationary distribution. Data compression results show ACTW variants improving over CTW on merged files from standard compression benchmark tests while never being significantly worse on any individual file

Pseudodoping of Metallic Two-Dimensional Materials by The Supporting Substrates

We demonstrate how hybridization between a two-dimensional material and its substrate can lead to an apparent heavy doping, using the example of monolayer TaS$_2$ grown on Au(111). Combining $\textit{ab-initio}$ calculations, scanning tunneling spectroscopy experiments and a generic model, we show that strong changes in Fermi areas can arise with much smaller actual charge transfer. This mechanism, which we refer to as pseudodoping, is a generic effect for metallic two-dimensional materials which are either adsorbed to metallic substrates or embedded in vertical heterostructures. It explains the apparent heavy doping of TaS$_2$ on Au(111) observed in photoemission spectroscopy and spectroscopic signatures in scanning tunneling spectroscopy. Pseudodoping is associated with non-linear energy-dependent shifts of electronic spectra, which our scanning tunneling spectroscopy experiments reveal for clean and defective TaS$_2$ monolayer on Au(111). The influence of pseudodoping on the formation of charge ordered, magnetic, or superconducting states is analyzed.Comment: arXiv admin note: substantial text overlap with arXiv:1609.0022

Photon Gas Thermodynamics in Doubly Special Relativity

Doubly special relativity (DSR), with both an invariant velocity and an invariant length scale, elegantly preserves the principle of relativity between moving observers, and appears as a promising candidate of the quantum theory of gravity. We study the modifications of photon gas thermodynamics in the framework of DSR with an invariant length $|\lambda|$, after properly taking into account the effects of modified dispersion relation, upper bounded energy-momentum space, and deformed integration measure. We show that with a positive $\lambda$, the grand partition function, the energy density, the specific heat, the entropy, and the pressure are smaller than those of special relativity (SR), while the velocity of photons and the ratio of pressure to energy are larger. In contrast, with a negative $\lambda$, the quantum gravity effects show up in the opposite direction. However, these effects only manifest themselves significantly when the temperature is larger than $10^{-3} E_{\rm P}$. Thus, DSR can have considerable influence on the early universe in cosmological study.Comment: 17 pages, 7 figures, final version for publication in AP

Large Leptonic Dirac CP Phase from Broken Democracy with Random Perturbations

A large value of the leptonic Dirac CP phase can arise from broken democracy, where the mass matrices are democratic up to small random perturbations. Such perturbations are a natural consequence of broken residual $\mathbb S_3$ symmetries that dictate the democratic mass matrices at leading order. With random perturbations, the leptonic Dirac CP phase has a higher probability to attain a value around $\pm \pi/2$. Comparing with the anarchy model, broken democracy can benefit from residual $\mathbb S_3$ symmetries, and it can produce much better, realistic predictions for the mass hierarchy, mixing angles, and Dirac CP phase in both quark and lepton sectors. Our approach provides a general framework for a class of models in which a residual symmetry determines the general features at leading order, and where, in the absence of other fundamental principles, the symmetry breaking appears in the form of random perturbations.Comment: 14 pages, 5 figures; references added; match the PLB versio

SWIFT J164449.3+573451: a plunging event with the Poynting-flux dominated outflow

Swift J164449+573451 is a peculiar outburst which is most likely powered by the tidal disruption of a star by a massive black hole. Within the tidal disruption scenario, we show that the periastron distance is considerably smaller than the disruption radius and the outflow should be launched mainly via magnetic activities (e.g., Blandford-Znajek process) otherwise the observed long-lasting X-ray afterglow emission satisfying the relation $L_{X}\propto\dot{M}$ can not be reproduced, where $L_{X}$ is the X-ray luminosity and $\dot{M}$ is the accretion rate. We also suggest that $L_{X}\propto\dot{M}$ may hold in the quick decline phase of Gamma-ray Bursts.Comment: 11 pages, to appear in Ap

CryoEM structure of the human SLC4A4 sodium-coupled acid-base transporter NBCe1.

Na+-coupled acid-base transporters play essential roles in human biology. Their dysfunction has been linked to cancer, heart, and brain disease. High-resolution structures of mammalian Na+-coupled acid-base transporters are not available. The sodium-bicarbonate cotransporter NBCe1 functions in multiple organs and its mutations cause blindness, abnormal growth and blood chemistry, migraines, and impaired cognitive function. Here, we have determined the structure of the membrane domain dimer of human NBCe1 at 3.9 Å resolution by cryo electron microscopy. Our atomic model and functional mutagenesis revealed the ion accessibility pathway and the ion coordination site, the latter containing residues involved in human disease-causing mutations. We identified a small number of residues within the ion coordination site whose modification transformed NBCe1 into an anion exchanger. Our data suggest that symporters and exchangers utilize comparable transport machinery and that subtle differences in their substrate-binding regions have very significant effects on their transport mode

Simulation-Based Identification of Operating Point Range for a Novel Laser-Sintering Machine for Additive Manufacturing of Continuous Carbon-Fibre-Reinforced Polymer Parts

Additive manufacturing using continuous carbon-fibre-reinforced polymer (CCFRP) presents an opportunity to create high-strength parts suitable for aerospace, engineering, and other industries. Continuous fibres reinforce the load-bearing path, enhancing the mechanical properties of these parts. However, the existing additive manufacturing processes for CCFRP parts have numerous disadvantages. Resin- and extrusion-based processes require time-consuming and costly post-processing to remove the support structures, severely restricting the design flexibility. Additionally, the production of small batches demands considerable effort. In contrast, laser sintering has emerged as a promising alternative in industry. It enables the creation of robust parts without needing support structures, offering efficiency and cost-effectiveness in producing single units or small batches. Utilising an innovative laser-sintering machine equipped with automated continuous fibre integration, this study aims to merge the benefits of laser-sintering technology with the advantages of continuous fibres. The paper provides an outline, using a finite element model in COMSOL Multiphysics, for simulating and identifying an optimised operating point range for the automated integration of continuous fibres. The results demonstrate a remarkable reduction in processing time of 233% for the fibre integration and a reduction of 56% for the width and 44% for the depth of the heat-affected zone compared to the initial setup