1,345 research outputs found
Learning from observations of the microwave background at small angular scales
In this paper, we focus our attention on the following question: How well can
we recover the power spectrum of the cosmic microwave background from the maps
of a given experiment?. Each experiment is described by a a pixelization scale,
a beam size, a noise level and a sky coverage. We use accurate numerical
simulations of the microwave sky and a cold dark matter model for structure
formation in the universe. Angular scales smaller than those of previous
simulations are included. The spectrum obtained from the simulated maps is
appropriately compared with the theoretical one. Relative deviations between
these spectra are estimated. Various contributions to these deviations are
analyzed. The method used for spectra comparisons is discussed.Comment: 15 pages (LATEX), 2 postcript figures, accepted in Ap
Non-circular rotating beams and CMB experiments
This paper is concerned with small angular scale experiments for the
observation of cosmic microwave background anisotropies. In the absence of
beam, the effects of partial coverage and pixelisation are disentangled and
analyzed (using simulations). Then, appropriate maps involving the CMB signal
plus the synchrotron and dust emissions from the Milky Way are simulated, and
an asymmetric beam --which turns following different strategies-- is used to
smooth the simulated maps. An associated circular beam is defined to estimate
the deviations in the angular power spectrum produced by beam asymmetry without
rotation and, afterwards, the deviations due to beam rotation are calculated.
For a certain large coverage, the deviations due to pure asymmetry and
asymmetry plus rotation appear to be very systematic (very similar in each
simulation). Possible applications of the main results of this paper to data
analysis in large coverage experiments --as PLANCK-- are outlined.Comment: 13 pages, 9 figures, to appear in A&
Hopfield-Enhanced Deep Neural Networks for Artifact-Resilient Brain State Decoding
The study of brain states, ranging from highly synchronous to asynchronous
neuronal patterns like the sleep-wake cycle, is fundamental for assessing the
brain's spatiotemporal dynamics and their close connection to behavior.
However, the development of new techniques to accurately identify them still
remains a challenge, as these are often compromised by the presence of noise,
artifacts, and suboptimal recording quality. In this study, we propose a
two-stage computational framework combining Hopfield Networks for artifact data
preprocessing with Convolutional Neural Networks (CNNs) for classification of
brain states in rat neural recordings under different levels of anesthesia. To
evaluate the robustness of our framework, we deliberately introduced noise
artifacts into the neural recordings. We evaluated our hybrid Hopfield-CNN
pipeline by benchmarking it against two comparative models: a standalone CNN
handling the same noisy inputs, and another CNN trained and tested on
artifact-free data. Performance across various levels of data compression and
noise intensities showed that our framework can effectively mitigate artifacts,
allowing the model to reach parity with the clean-data CNN at lower noise
levels. Although this study mainly benefits small-scale experiments, the
findings highlight the necessity for advanced deep learning and Hopfield
Network models to improve scalability and robustness in diverse real-world
settings
CMB anisotropy: deviations from Gaussianity due to non-linear gravity
Non-linear evolution of cosmological energy density fluctuations triggers
deviations from Gaussianity in the temperature distribution of the cosmic
microwave background. A method to estimate these deviations is proposed. N-body
simulations -- in a CDM cosmology -- are used to simulate the strongly
non-linear evolution of cosmological structures. It is proved that these
simulations can be combined with the potential approximation to calculate the
statistical moments of the CMB anisotropies produced by non-linear gravity.
Some of these moments are computed and the resulting values are different from
those corresponding to Gaussianity.Comment: 6 latex pages with mn.sty, 3 eps figures. Accepted in MNRA
Role of elastic scattering in electron dynamics at ordered alkali overlayers on Cu(111)
Scanning tunneling spectroscopy of p(2x2) Cs and Na ordered overlayers on
Cu(111) reveals similar line widths of quasi two-dimensional quantum well
states despite largely different binding energies. Detailed calculations show
that 50% of the line widths are due to electron-phonon scattering while
inelastic electron-electron scattering is negligible. A frequently ignored
mechanism for ordered structures, i.e., enhanced elastic scattering due to
Brillouin zone back folding, contributes the remaining width.Comment: 4 pages, 2 figures, 1 tabl
Large-scale Production of Recombinant RNAs on a Circular Scaffold Using a Viroid-derived System in Escherichia coli
[EN] With increasing interest in RNA biology and the use of RNA molecules in sophisticated biotechnological applications, the methods to produce large amounts of recombinant RNAs are limited. Here, we describe a protocol to produce large amounts of recombinant RNA in Escherichia coli based on co-expression of a chimeric molecule that contains the RNA of interest in a viroid scaffold and a plant tRNA ligase. Viroids are relatively small, non-coding, highly base-paired circular RNAs that are infectious to higher plants. The host plant tRNA ligase is an enzyme recruited by viroids that belong to the family Avsunviroidae, such as Eggplant latent viroid (ELVd), to mediate RNA circularization during viroid replication. Although ELVd does not replicate in E. coli, an ELVd precursor is efficiently transcribed by the E. coli RNA polymerase and processed by the embedded hammerhead ribozymes in bacterial cells, and the resulting monomers are circularized by the co-expressed tRNA ligase reaching a remarkable concentration. The insertion of an RNA of interest into the ELVd scaffold enables the production of tens of milligrams of the recombinant RNA per liter of bacterial culture in regular laboratory conditions. A main fraction of the RNA product is circular, a feature that facilitates the purification of the recombinant RNA to virtual homogeneity. In this protocol, a complementary DNA (cDNA) corresponding to the RNA of interest is inserted in a particular position of the ELVd cDNA in an expression plasmid that is used, along the plasmid to coexpress eggplant tRNA ligase, to transform E. coli. Co-expression of both molecules under the control of strong constitutive promoters leads to production of large amounts of the recombinant RNA. The recombinant RNA can be extracted from the bacterial cells and separated from the bulk of bacterial RNAs taking advantage of its circularity.This work was supported by grants BIO2017-83184-R and BIO2017-91865-EXP from the Spanish Ministerio de Ciencia, Innovacion y Universidades (co-financed FEDER funds).Cordero-Cucart, MT.; Aragonés, V.; Daros Arnau, JA. (2018). Large-scale Production of Recombinant RNAs on a Circular Scaffold Using a Viroid-derived System in Escherichia coli. Journal of Visualized Experiments. (141). https://doi.org/10.3791/58472S14
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