Small Red Shift Research Articles

Boltzmann equations for astrophysical Stochastic Gravitational Wave Backgrounds scattering off of massive objects

The goal of this work is to present a set of coupled Boltzmann equations describing the intensity and polarisation Stokes parameters of the SGWB. Collision terms (as discussed e.g. in ref. [1]) which account for gravitational Compton scattering off of massive objects, are also included. This set resembles that for the CMB Stokes parameters, but the different spin nature of the gravitational radiation and the physics involved in the scattering process determine crucial differences. In the case of gravitational Compton scattering, due to the Rutherford angular dependence of the cross section, all the SGWB intensity multipoles of order ℓ are scattered out, therefore producing outgoing intensity anisotropies of any order ℓ if they are present in the incoming radiation. On the other hand, as already outlined in [1], SGWB linear polarisation modes can be expanded in a basis of spherical harmonics with m = ±4 and ℓ ≥ 4. This means that SGWB polarisation modes can be generated from unpolarised anisotropic radiation only with m = ±4, therefore requiring at least a hexadecapole anisotropy (ℓ ≥ 4) in the incoming intensity. Assuming a simplified toy model where scattering targets are localised in a small redshift range, we solve analytically the set of coupled Boltzmann equations to get explicit expressions for the intensity and polarisation angular power spectra. We confirm the contribution of the gravitational Compton scattering to the SGWB anisoptropies is extremely small for collisions with massive compact objects (BH and SMBH) in the frequency range of current and upcoming surveys. The system of coupled Boltzmann equations presented here provides a way to accurate estimate the total amount of anisotropies generated by multiple SGWB scattering processes off of massive objects, as well as the interplay between polarisation and intensity, during the GW propagation across the LSS of the universe. These results will be useful for the full treatment of the astrophysical SWGB anisotropies in view of upcoming gravitational waves observatories.

Calcium-bound structure of bovine cytochrome c oxidase

The crystal structure of bovine cytochrome c oxidase (CcO) shows a sodium ion (Na+) bound to the surface of subunit I. Changes in the absorption spectrum of heme a caused by calcium ions (Ca2+) are detected as small red shifts, and inhibition of enzymatic activity under low turnover conditions is observed by addition of Ca2+ in a competitive manner with Na+. In this study, we determined the crystal structure of Ca2+-bound bovine CcO in the oxidized and reduced states at 1.7 Å resolution. Although Ca2+ and Na+ bound to the same site of oxidized and reduced CcO, they led to different coordination geometries. Replacement of Na+ with Ca2+ caused a small structural change in the loop segments near the heme a propionate and formyl groups, resulting in spectral changes in heme a. Redox-coupled structural changes observed in the Ca2+-bound form were the same as those previously observed in the Na+-bound form, suggesting that binding of Ca2+ does not severely affect enzymatic function, which depends on these structural changes. The relation between the Ca2+ binding and the inhibitory effect during slow turnover, as well as the possible role of bound Ca2+ are discussed.

The Origin of Cosmic Structures Part 5— Resolution of the Hubble Tension Problem

The two principal contributors to the Hubble tension problem are the predictions of the baryonic acoustic oscillation model and the H0 parameter fit of the “Tip of the Red Giant Branch” collaboration. In this paper, we show that the former is neither necessary nor possible and that the latter yields a value in agreement with the supernovae results when adjustments are made for errors in the peculiar velocity model used to isolate the recession velocities of galaxies. We also make comparisons between the predictions of our new model of cosmology and the curve fits of the standard model. For values of redshift ≤ 1 we find that, with a Hubble constant of H0 = 73, the two agree almost exactly. We resolve the Hubble constant problem and validate the new model predictions for small redshifts.

Exploring the self interacting dark matter properties from low redshift observations

We calculate the shear (eta ) and bulk viscosity (zeta ) of Self Interacting Dark Matter (SIDM) fluid using the kinetic theory formalism. Using the astrophysical constraints on dark matter self-interaction cross section over mass sigma /m , we demonstrate that viscous SIDM fluid violates the lower bound on the ratio of shear viscosity to its entropy density, eta /mathfrak {s}=frac{1}{4pi }. Then, considering the eta /mathfrak {s} bound as universal, we derive a theoretical upper limit on the ratio of velocity average dark matter self interaction cross-section to its mass and also estimate an upper limit on SIDM mass. We report that mass of the SIDM particle should be sub-GeV scale. Furthermore, with the assumption of a power-law form of eta and zeta , we study its evolution in the light of low redshift observations. We show that at the large redshift, the SIDM viscosity is small, but at the small redshift, it becomes sufficiently large and contributes significantly to cosmic dissipation. As a consequence, viscous SIDM can explain the low redshift observations and also consistent with the standard cosmological prediction.

Infrared spectra of the SARS-CoV-2 spike receptor-binding domain: Molecular dynamics simulations

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread around the world rapidly, which seriouslythreatens to human health and safety. The rapid detection of the virus in the early stage is very important to prevent the cross infection and transmission. It is also a key link in the post-treatment examination. This paper has explored the infrared (IR) spectra of spike protein receptor-binding domain (RBD) for SARS-CoV-2 using molecular dynamics simulations, and the absorption bands are assigned. The calculated IR spectra of water and insulin are compared with that measured in the related literatures. The results showed that OH stretching vibration generated a strong absorption band located around 3591 cm−1, the oscillator strength of 310 K is slightly higher than that at 298 K. The absorption peaks have a small red shift or blue shift with the change of temperature. As a theoretical basis for the optical detection of SARS-CoV-2 virus, this work will play a positive role in promoting the development of new virus detection technology.

Gas-phase spectroscopy of photostable PAH ions from the mid- to far-infrared

ABSTRACT We present gas-phase InfraRed Multiple Photon Dissociation (IRMPD) spectroscopy of cationic phenanthrene, pyrene, and perylene over the 100–1700 cm−1 (6–95 μm) spectral range. This range covers both local vibrational modes involving C–C and C–H bonds in the mid-IR, and large-amplitude skeletal modes in the far-IR. The experiments were done using the 7T Fourier-Transform Ion Cyclotron Resonance (FTICR) mass spectrometer integrated in the Free-Electron Laser for Intra-Cavity Experiments (FELICE), and findings were complemented with Density Functional Theory (DFT) calculated harmonic and anharmonic spectra, matching the experimental spectra well. The experimental configuration that enables this sensitive spectroscopy of the strongly bound, photoresistant Polycyclic Aromatic Hydrocarbons (PAHs) over a wide range can provide such high photon densities that even combination modes with calculated intensities as low as 0.01 km mol−1 near 400 cm−1 (25 μm) can be detected. Experimental frequencies from this work and all currently available IRMPD spectra for PAH cations were compared to theoretical frequencies from the NASA Ames PAH IR Spectroscopic Database to verify predicted trends for far-IR vibrational modes depending on PAH shape and size, and only a relatively small redshift (6–11 cm−1) was found between experiment and theory. The absence of spectral congestion and the drastic reduction in bandwidth with respect to the mid-IR make the far-IR fingerprints viable candidates for theoretical benchmarking, which can aid in the search for individual large PAHs in the interstellar medium.

Moderate correlation between the accretion disk and jet power in a large sample of Fermi blazars

We present the results of studying the accretion disk vs jet power for a large fraction of all the blazars detected by the Fermi Gamma-Ray Space Telescope. The disk power is inferred from the emission line luminosities obtained from published results. As indicators of jet power, we use low frequency radio luminosity from the extended jet, maximum speed of radio knots observed in the VLBA monitoring of the pc-scale jets, kinetic energy of electrons in the jet deduced from the best-fit theoretical models of their spectral energy distribution, and $\ensuremath{\gamma}$-ray luminosity with and without beaming correction. We obtain a significant correlation in most of those cases. However, we find that the correlations are often driven by the common redshift dependence of the compared quantities. In order to remove the redshift bias and probe the intrinsic correlation between the disk and jet power, we compute the partial correlation coefficient as well as the correlation in small redshift bins and find that the intrinsic disk-jet correlation is still present but weaker. In the cases, in which the common redshift dependence does not affect the result, we find that blazars do not exhibit high jet power for low disk luminosities while there are both high and low jet power for high disk luminosities. This result indicates that a powerful disk is a necessary but not sufficient condition to produce a powerful jet.

Structure formation in mimetic gravity

We disclose the effects of an extra longitudinal degree of freedom on the evolution of perturbations in the framework of mimetic gravity. We consider a flat Friedmann-Robertson-Walker background and explore the linear perturbations by adopting the spherically symmetric collapse formalism. By suitably choosing the potential of the mimetic field, we are able to solve the perturbed field equations in the linear regime and derive the matter density contrast ${\ensuremath{\delta}}_{m}$ in terms of the redshift parameter $z$. We observe that ${\ensuremath{\delta}}_{m}$ starts growing at the early stages and, as the Universe expands, it grows faster compared to the standard cosmology. This may due to the extra degree of freedom of the gravitational field which affects the growth of perturbations. We observe that in the presence of a mimetic potential, the growth rate function is smaller than the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model in small redshifts. We then consider the effects of this potential on the density abundance, the deceleration parameter and jerk parameter. We find out that mimetic potential can play the role of dark energy (DE) and affects the dynamics of matter perturbations and cosmological parameters. We also investigate the mass function and the number count for the collapsed objects in the mimetic scenario. We find that the mass function of models with potential is smaller than the model without potential. With the decreasing the role of DE, the mass function starts to grow in smaller redshifts; i.e., halo abundance is formed later. It is found that the more massive structures are less abundant and form at later times, as it should be in the hierarchical model of structure formation.

β-Ga2O3 Nanostructures: Chemical Vapor Deposition Growth Using Thermally Dewetted Au Nanoparticles as Catalyst and Characterization.

β-Ga2O3 nanostructures, including nanowires (NWs), nanosheets (NSHs), and nanorods (NRs), were synthesized using thermally dewetted Au nanoparticles as catalyst in a chemical vapor deposition process. The morphology of the as-grown β-Ga2O3 nanostructures depends strongly on the growth temperature and time. Successful growth of β-Ga2O3 NWs with lengths of 7–25 μm, NSHs, and NRs was achieved. It has been demonstrated that the vapor–liquid–solid mechanism governs the NW growth, and the vapor–solid mechanism occurs in the growth of NSHs and NRs. The X-ray diffraction analysis showed that the as-grown nanostructures were highly pure single-phase β-Ga2O3. The bandgap of the β-Ga2O3 nanostructures was determined to lie in the range of 4.68–4.74 eV. Characteristic Raman peaks were observed with a small blue and red shift, both of 1–3 cm−1, as compared with those from the bulk, indicating the presence of internal strain and defects in the as-grown β-Ga2O3 nanostructures. Strong photoluminescence emission in the UV-blue spectral region was obtained in the β-Ga2O3 nanostructures, regardless of their morphology. The UV (374–377 nm) emission is due to the intrinsic radiative recombination of self-trapped excitons present at the band edge. The strong blue (404–490 nm) emissions, consisting of five bands, are attributed to the presence of the complex defect states in the donor (VO) and acceptor (VGa or VGa–O). These β-Ga2O3 nanostructures are expected to have potential applications in optoelectronic devices such as tunable UV–Vis photodetectors.

Photo-oxidative extractive desulfurization of dibenzothiofene over Fe2O3-CeO2 nanocomposites at visible light irradiation

This research represents the role of Fe2O3 loading (10–100%) to ceria on the simultaneous oxidative and extractive photo-desulfurization of dibenzothiophene (DBT) in the visible light range. The catalysts were characterized by several known analyses in photocatalysis. The results revealed the FexCeO1-xOy solid solution fabrication with Fe loading up to 20%. While, Fe2O3 segregation was indicated at the higher loading percent. The Fe15Ce85 catalyst exhibited the highest photocatalytic DBT removal of 94.4%. The optimum conditions of 0.15 g catalyst, 2:1 solvent/oil and 2:1 H2O2/S for 2 h were obtained. The Fe15Ce85 higher activity was attributed to the influenced textural and chemical properties induced by Fe/Ce solid solution fabrication. Also, the small band gap and red shift in visible light absorption assigned to the Fe-Ce nanocomposite are reasons for high activity. The desulfurization mechanism was also proposed.

Probing Cold Gas in a Massive, Compact Star-forming Galaxy at z = 6

Observations of low-order 12C16O transitions represent the most direct way to study galaxies’ cold molecular gas, the fuel of star formation. Here we present the first detection of CO(J = 2 → 1) in a galaxy lying on the main-sequence of star-forming galaxies at z > 6. Our target, G09-83808 at z = 6.03, has a short depletion timescale of τ dep ≈ 50 Myr and a relatively low gas fraction of M gas/M ⋆ ≈ 0.30 that contrasts with those measured for lower-redshift main-sequence galaxies. We conclude that this galaxy is undergoing a starburst episode with a high star formation efficiency that might be the result of gas compression within its compact rotating disk. Its starburst-like nature is further supported by its high star formation rate surface density, thus favoring the use of the Kennicutt–Schmidt relation as a more precise diagnostic diagram. Without further significant gas accretion, this galaxy would become a compact, massive quiescent galaxy at z ∼ 5.5. In addition, we find that the calibration for estimating interstellar medium masses from dust continuum emission satisfactorily reproduces the gas mass derived from the CO(2 → 1) transition (within a factor of ∼2). This is in line with previous studies claiming a small redshift evolution in the gas-to-dust ratio of massive, metal-rich galaxies. In the absence of gravitational amplification, this detection would have required of order 1000 hr of observing time. The detection of cold molecular gas in unlensed star-forming galaxies at high redshifts is thus prohibitive with current facilities and requires a tenfold improvement in sensitivity, such as that envisaged for the Next-Generation Very Large Array .

B and Au doped ZnO and ZnO/Cu(111) bilayer films: A DFT investigation

AbstractsThe structural and electronic properties of B and Au doped graphite‐like ZnO and ZnO/Cu(111) bilayer films have been investigated by using the DFT + U scheme including dispersion correction and compared to that of undoped materials. The differences in electronic properties of the B and Au doped ZnO and ZnO/Cu(111) films compared to undoped materials were probed by CO adsorption. The same oxidation state of B (+3) was observed for B doped ZnO and ZnO/Cu(111) bilayer films. However, an excess electron associated with B doping is delocalized over the conduction band of ZnO, while it transfers to underlying Cu support of ZnO/Cu(111). This is evidenced by a much large redshift of CO frequency on B doped ZnO versus the small redshift of CO frequency on B doped ZnO/Cu(111). At variance, the oxidation state of Au dopant was reduced from +2 (5d9) for Au doped ZnO to +1 (5d10) for Au doped ZnO/Cu(111) films. This is due to the charge transfer from Cu support to doped Au which results in the stronger binding of CO on Au doped ZnO/Cu(111) compared to ZnO bilayer films. However, a slight difference in CO frequency was found for CO bound to Au doped ZnO and ZnO/Cu(111).

106 New Emission-line Galaxies and 29 New Galactic H ii Regions are Identified with Spectra in the Unknown Data Set of LAMOST DR7

This work is to retrieve emission-line spectra from the “Unknown” data set in LAMOST DR7 V1.2, most of which are low signal-to-noise ratios spectra. In the work, we perform emission line search and redshift calculations on the Unknown data set to get possible emission line galaxy spectra. Taking the galaxy spectra released by LAMOST as templates, the Product Quantization (PQ) based approximate nearest neighbor (ANN) search is used to retrieve the nearest neighbors of each spectrum. We keep the spectra for which the calculated redshift and the published redshift of the template meet the threshold, and 16,188 spectra with emission lines are obtained from the LAMOST DR7 Unknown data set. After visual inspection of spectra 10,266 spectra are left, in which 5828 spectra are identified as emission-line galaxies, 1782 spectra show ionization nebula features, and other 2656 are not clearly classified. Among 5828 spectra, 5720 can be found in Strasbourg astronomical Data Center catalog, Sloan Digital Sky Survey catalog, or NASA/IPAC Extragalactic Database catalog. The 108 spectra (corresponding to 106 unique coordinates of R.A. and decl.) which have no record in these three databases are new discoveries; for the 1782 spectra showing ionization nebula features, most of them have radial velocities less than 150 kilometers per second. We check them with the latest version of WISE H ii catalog V2.0 (short for HIICat V2) and 985 out of the 1782 spectra belong to 72 H ii regions. Of these H ii regions, 43 were previously identified while the other 29 are newly identified in this work including 797 newly observed spectra. Besides, there are still 2656 spectra that cannot be clearly classified although they have obvious emission lines and with small redshift. Finally, 106 new emission-line galaxies and 29 new Galactic H ii regions are identified, and we conclude that the ANN method sped up by the PQ algorithm is efficient in solving the problem of pairing spectra with massive data set to figure out their classes. We present our result at the link http://paperdata.china-vo.org/LY_paper/Work2/pressWork2_last.zip.

A highly selective fluorescent sensor for manganese(II) ion detection based on N,S-doped carbon dots triggered by manganese oxide

A highly selective, carbon dots (CDs)-based fluorescent sensor for manganese(II) ions (Mn2+) was proposed. The synthesis of N,S-doped CDs (N,S-CDs) involved simple pyrolysis of a mixture of lactose and l-cysteine in a hot NaOH solution. The as-synthesized codoped CDs exhibited a weak fluorescent emission peak at 510 nm when excited at 430 nm. In the presence of Mn2+, the intensity of the fluorescence signals was effectively increased with a small redshift in the spectrum. Thus, by tracing the degree of fluorescence enhancement, the material could be used as a selective probe for Mn2+ detection. The possible sensing mechanism was based on the oxidation of the N,S-CDs by MnO2, which was generated from mixing Mn2+ with NaOH in the N,S-CDs-containing medium. A linear relationship was established between the extent of the increase in fluorescence and the increasing Mn2+ concentration from 0 to 5.0 μM with a limit of detection (LOD) of 0.12 μM. Remarkably, even in the presence of other cations, the developed sensor remained highly selective toward Mn2+. The feasibility of our developed sensor in real applications was confirmed with environmental samples, showing excellent accuracy and precision.

Supramolecular Nanohelix Fabricated by Pillararene-Based Host–Guest System for Chirality Amplification, Transfer, and Circularly Polarized Luminescence in Water

Supramolecular Nanohelix Fabricated by Pillararene-Based Host–Guest System for Chirality Amplification, Transfer, and Circularly Polarized Luminescence in Water

Molecular Identification of the Transient Species Mediating the Deactivation Dynamics of Solvated Guanosine and Deazaguanosine.

Small structural alterations of the purine/pyrimidine core have been related to important photophysical changes, such as the loss of photostability. Similarly to canonical nucleobases, solute-solvent interactions can lead to a change in the excited state lifetimes and/or to the interplay of different states in the photophysics of these modified nucleobases. To shed light on both effects, we here report a complete picture of the absorption spectra and excited state deactivation of deoxyguanosine and its closely related derivative, deoxydeazaguanosine, in water and methanol through the mapping of the excited state potential energy surfaces and molecular dynamics simulations at the TD-DFT level of theory. We show that the N by CH exchange in the imidazole ring of deoxyguanosine translates into a small red-shift of the bright states and slightly faster dynamics. In contrast, changing solvent from water to methanol implies the opposite, i.e., that the deactivation of both systems to the ground state is significantly hindered.

Numerical optimization of 1D superconductor photonic crystals pressure sensor for low temperatures applications

In this research, reflectance spectra for a one-dimensional (1D) photonic crystal (PC) consists of a high-temperature superconductor Hg-1223 and a semiconductor GaAs have been calculated using the well-known transfer matrix method (TMM) and the two-fluid model. The proposed PC was introduced as an optical pressure sensor at the mid-IR region. The pressure effect is studied on two types of PCs; a defective PC [Air (GaAs/Hg 1223)5 (GaAs) (GaAs/Hg 1223)5 substrate] and periodic PC [Air (GaAs/Hg-1223)10 substrate]. Herein, we have found that the pressure sensitivity reached a high value of 1.7467 nm/GPa at an applied pressure of 6 GPa. However, a small blue shift is noticed for the periodic design. Therefore, the number of periods, thickness, and incident angle were taken after many optimization steps to get the highest-pressure sensitivity for the defective PC. Based on the optimization process, the results reveled higher performance for the other sensitivity parameters such sensor resolution, signal to noise ratio, figure of merit, and quality factor (QF). Finally, we have studied the effect of the operating temperature on the defect mode, which shows a small redshift with increasing the operating temperature. We hope this research may be utilized for applications of tunable filters and hydrostatic pressure sensors.

Strain effect on the intraband absorption coefficient for spherical CdSe/CdS/ZnSe core–shell–shell quantum dots

In this work, we theoretically calculated the intraband absorption coefficient (IAC) between the 1s and 1p conduction band states for a spherical core/shell/shell quantum dot (CSS-QD) as function of inner and outer shells’ sizes with and without the presence of strain effect. The electronic structure for the system is computed in the effective mass approximation framework and the strain effect is considered on the continuum elasticity model. We found out that as we compared the strained and the unstrained system, the former causes that the IAC undergoes a small redshift. A similar behavior occurs as the inner and outer shell size increase. The results show that the strain effect is an important factor that will be considered in these nanostructure type. The incorporation of inner and outer shells allowed us to extend some fractions of eV into the absorption spectrum that could be interesting as a mechanism to control the IAC device design.

Statistical approaches on the apparent horizon entropy and the generalized second law of thermodynamics

In this work we have investigated the effects of three nongaussian entropies, namely, the modified Rényi entropy (MRE), the Sharma-Mittal entropy (SME) and the dual Kaniadakis entropy (DKE) in the investigation of the generalized second law (GSL) of thermodynamics violation. The GSL is an extension of the second law for black holes. Recently, it was concluded that a total entropy is the sum of the entropy enclosed by the apparent horizon plus the entropy of the horizon itself when the apparent horizon is described by the Barrow entropy. It was assumed that the universe is filled with matter and dark energy fluids. Here, the apparent horizon will be described by MRE, SME, and then by DKE proposals. Since GSL holds for usual entropy, but it is conditionally violated in the extended entropies, this implies that the parameter of these entropies should be constrained in small values in order to obey the GSL of thermodynamics. Hence, we have established conditions where the second law of thermodynamics can or cannot be obeyed considering these three statistical concepts just as it was made in Barrow's entropy. Considering the ΛCDM cosmology, we will notice that for MRE, SME and DKE, the GSL of thermodynamics is not obeyed for small redshift values.

The performance of surface enhanced Raman scattering and spatial resolution with triangular plate dimer from ultra-ultraviolet to near-infrared range

The theoretical research on surface enhanced Raman spectroscopy (SERS) of triangular plate dimer (TPD) is of great significance for the design of experimental substrates. In this paper, the SERS properties of the TPD with Au, Ag, Al and Cu have been theoretical investigated in the ultra-ultraviolet, visible and near-infrared region. The influence of the TPD configuration, including the tip radian, the dimer distance and the aspect ratio on the electric field, Raman enhancement and spatial resolution are studied by the finite element method. The results show that there are dipole resonance band and quadruple dipole resonance band in the surface plasmon resonance band of TPD. The tip radian and dimer distance play the dominant role in the electric field enhancement, and the aspect ratio can be mainly used to tune the peak position of the electric field. The smaller tip radian and dimer distance will produce a stronger localized electric field and a small red shift of the peak position. Adjusting the aspect ratio can tune the position of electric field peak from ultraviolet (UV) to near-infrared without changing the peak value of the electric field significantly, especially for Al TPD. The maximum Raman enhancement factor of Au, Ag and Cu all reach 11 orders of magnitude, and 9 orders of magnitude for Al. The spatial resolution changes linearly with the gap distance, and the maximum spatial distributions of Au, Ag, Al and Cu achieve 0.65 nm, 0.67 nm, 0.69 nm and 0.70 nm with the dimer distance of 1 nm. Our results not only provide a better theoretical guidance for the optimization of TPD substrates in the SERS experiment, but also extend its application scope from ultra-UV to near-infrared range.