Showing papers on "Absorption (logic) published in 2021"

MHD hybrid nanofluid flow comprising the medication through a blood artery.

Abstract: The current study focuses on the laminar flow of copper and copper oxide ( $${\text{Cu/blood}}$$ and $${\text{Cu}} + {\text{CuO/blood}}$$ ) hybrid nanoliquid, considering blood as a carrier fluid in a rectangular domain between two permeable channels. This study may manipulate for the purpose such as the drug delivery process, flow dynamic mechanism of the micro-circulatory system. In the proposed model, MHD and heat source/sink on the flow pattern have been studied. Furthermore, the sides of each channel are permeable, allowing the nanoliquid to escape, filter, squeezing and dilating with a fixed velocity. Appropriate transformations are incorporated to convert the governing partial differential equations and the boundary conditions suitable for computation. The elegant homotopy analysis method (HAM) is used to obtain analytic approximations for the resulting system of nonlinear differential equations. The features of flow characteristics such as velocity, and temperature profiles in response to the variations of the emerging parameters are simulated and examined with a physical explanation. The magnetic field plays a vital role in the blood flow and therefore the existing literature has been extending with the addition of magnetic field. Among the many outputs of the study, it is found that the pressure distribution decline with the accumulated values of the magnetic parameter at the center of the flow regime. The augmentation in the temperature distribution estimates the pH values and electric conductivity. Therefore, the $${\text{Cu}}\,\,{\text{and}}\,\,{\text{CuO}}$$ hybrid nanofluids are used in this study for medication purposes. The magnetic field has an important role in the blood flow and therefore the extending study has been extending using the magnetic field. The heat emission/absorption term is added to the energy equation to maintain the homogeneous temperature for the blood flow. We expect that this work will provide efficient outputs for medical purposes such as drug delivery.

The Potential of Refractive Index Nanobiosensing Using a Multi-Band Optically Tuned Perfect Light Metamaterial Absorber

Abstract: An optically tunable perfect light absorber as a refractive index (RI) metamaterial (MM) nanobiosensor (NBS) is designed for sensing chemicals, monitoring the concentration of water-soluble glucose, and detecting viruses. This plasmon induced tunable metasurface works based on multiband super-absorption in the infrared frequency regime. It consists of a metal mirror that facilitates the MM to work as an absorber where the metal pattern at the top layer creates an enhanced evanescent wave that facilitates the metasurface to work as a RI optical sensor. The modelling and numerical analysis are carried out using Finite Difference Time Domain (FDTD) method-based software, CST microwave studio where a genetic algorithm (GA) is used to optimize the geometric parameters. We demonstrate multiband super-absorption spectra having maximum absorption of more than 99%. Furthermore, we show how the multiband super-absorber nanostructure can be used as a RI NBS, where the resonance frequency shifts with the RI of the surrounding medium. The achieved opto-chemical sensitivity is approximately ${65}{\textit {nm}}/{\textit {RIU}}~{\textit {RIU}}$ , the bio-optical sensitivity to detect viruses is approximately 76 nm $/$ RIU; and the optical sensitivity of the water-soluble glucose concentration is about ${300}{\textit {nm}}/ {\textit {RIU}}$ ; all sensitivities are comparable in comparison with the reported values in the literature.

Cosmological implications of the anisotropy of ten galaxy cluster scaling relations

Abstract: The hypothesis that the late Universe is isotropic and homogeneous is adopted by most cosmological studies. The expansion rate $H_0$ is thought to be spatially constant, while bulk flows are often presumed to be negligible compared to the Hubble expansion, even at local scales. Their effects on the redshift-distance conversion are hence usually ignored. Any deviation from this consensus can strongly bias the results of such studies and thus the importance of testing these assumptions cannot be understated. Scaling relations of galaxy clusters can be effectively used for that. In previous works, we observed strong anisotropies in cluster scaling relations, whose origins remain ambiguous. By measuring many different cluster properties, several scaling relations with different sensitivities can be built. Nearly independent tests of cosmic isotropy and bulk flows are then feasible. We make use of up to 570 clusters with measured properties at X-ray, microwave, and infrared wavelengths, to construct 10 different cluster scaling relations (five of them presented for the first time) and test the isotropy of the local Universe. Through rigorous tests, we ensure that our analysis is not prone to generally known systematic biases and X-ray absorption issues. By combining all available information, we detect an apparent $9\%$ spatial variation in the local $H_0$ between $(l,b)\sim ({280^{\circ}}^{+35^{\circ}}_{-35^{\circ}},{-15^{\circ}}^{+20^{\circ}}_{-20^{\circ}})$ and the rest of the sky. The observed anisotropy has a nearly dipole form. Using Monte Carlo simulations, we assess the statistical significance of the anisotropy to be $>5\sigma$. This result could also be attributed to a $\sim 900$ km/s bulk flow which seems to extend out to at least $\sim 500$ Mpc. These two effects are indistinguishable until more high$-z$ clusters are observed by future all-sky surveys, such as eROSITA.

Observation of Coulomb-Assisted Nuclear Bound State of Ξ^{-}-^{14}N System.

Abstract: In an emulsion-counter hybrid experiment performed at J-PARC, a Ξ^{-} absorption event was observed which decayed into twin single-Λ hypernuclei. Kinematic calculations enabled a unique identification of the reaction process as Ξ^{-}+^{14}N→_{Λ}^{10}Be+_{Λ}^{5}He. For the binding energy of the Ξ^{-} hyperon in the Ξ^{-}-^{14}N system a value of 1.27±0.21 MeV was deduced. The energy level of Ξ^{-} is likely a nuclear 1p state which indicates a weak ΞN-ΛΛ coupling.

Sub-femtometer scale color charge fluctuations in a proton made of three quarks and a gluon

Abstract: The light-front wave function of a proton composed of three quarks and a perturbative gluon is computed. This is then used to derive expressions for the color charge density correlator $⟨{\ensuremath{\rho}}^{a}({\stackrel{\ensuremath{\rightarrow}}{q}}_{1}){\ensuremath{\rho}}^{b}({\stackrel{\ensuremath{\rightarrow}}{q}}_{2})⟩$ at $\mathcal{O}({g}^{4})$ due to the emission of a gluon by one of the quarks in the light-cone gauge. The correlator exhibits the soft and collinear singularities. Albeit, we employ exact gluon emission and absorption vertices, and hence the gluon is not required to carry very small light-cone momentum, or to be collinear to the emitting quark. We verify that the correlator satisfies the Ward identity and that it is independent of the renormalization scale, i.e., that ultraviolet divergences cancel. Our expressions provide $x$-dependent initial conditions for Balitsky-Kovchegov evolution of the $C$-even part of the dipole scattering matrix to higher energies. That is, we determine the first nontrivial moment of the color charge fluctuations which act as sources for soft color fields in the proton with wavelengths greater than approximately $1/x\ensuremath{\sim}10--100$.

On the Observational Difference between the Accretion Disk-Corona Connections among Super- and Sub-Eddington Accreting Active Galactic Nuclei

Abstract: We present a systematic X-ray and multiwavelength study of a sample of 47 active galactic nuclei (AGNs) with reverberation-mapping measurements This sample includes 21 super-Eddington accreting AGNs and 26 sub-Eddington accreting AGNs Using high-state observations with simultaneous X-ray and UV/optical measurements, we investigate whether super-Eddington accreting AGNs exhibit different accretion disk-corona connections compared to sub-Eddington accreting AGNs We find tight correlations between the X-ray-to-UV/optical spectral slope parameter ($\alpha_{\rm OX}$) and the monochromatic luminosity at $2500~A$ ($L_{\rm 2500~A}$) for both the super- and sub-Eddington subsamples The best-fit $\alpha_{\rm OX}-L_{\rm 2500~A}$ relations are consistent overall, indicating that super-Eddington accreting AGNs are not particularly X-ray weak in general compared to sub-Eddington accreting AGNs We find dependences of $\alpha_{\rm OX}$ on both the Eddington ratio ($L_{\rm Bol}/L_{\rm Edd}$) and black hole mass ($M_{\rm BH}$) parameters for our full sample A multi-variate linear regression analysis yields $\alpha_{\rm OX}=-013 {\rm log}(L_{\rm Bol}/L_{\rm Edd})-010 {\rm log}M_{\rm BH}-069$, with a scatter similar to that of the $\alpha_{\rm OX}-L_{\rm 2500~A}$ relation The hard (rest-frame $>2\rm ~keV$) X-ray photon index ($\Gamma$) is strongly correlated with $L_{\rm Bol}/L_{\rm Edd}$ for the full sample and the super-Eddington subsample, but these two parameters are not significantly correlated for the sub-Eddington subsample A fraction of super-Eddington accreting AGNs show strong X-ray variability, probably due to small-scale gas absorption, and we highlight the importance of employing high-state (intrinsic) X-ray radiation to study the accretion disk-corona connections in AGNs

Low-energy optical properties of the nonmagnetic kagome metal CsV 3 Sb 5

Abstract: Temperature-dependent reflectivity measurements on the kagome metal ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ in a broad frequency range of $50\ensuremath{-}20\phantom{\rule{0.16em}{0ex}}000\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ down to $T$=10 K are reported. The charge-density wave (CDW) formed below ${T}_{\mathrm{CDW}}$ = 94 K manifests itself in a prominent spectral-weight transfer from low to higher energy regions. The CDW gap of 60--75 meV is observed at the lowest temperature and shows significant deviations from an isotropic BCS-type mean-field behavior. Absorption peaks appear at frequencies as low as 200 ${\mathrm{cm}}^{\ensuremath{-}1}$ and can be identified with interband transitions according to density-functional calculations. The change in the interband absorption compared to ${\mathrm{KV}}_{3}{\mathrm{Sb}}_{5}$ reflects the inversion of band saddle points between the K and Cs compounds. Additionally, a broader and strongly temperature-dependent absorption feature is observed below 1000 ${\mathrm{cm}}^{\ensuremath{-}1}$ and assigned to a displaced Drude peak. It reflects localization effects on charge carriers.

Constraining primordial black holes as dark matter using the global 21-cm signal with X-ray heating and excess radio background

Abstract: Using the global 21-cm signal measurement by the EDGES collaboration, we derive constraints on the fraction of the dark matter that is in the form of primordial black holes (PBHs) with masses in the range $10^{15}$-$10^{17}\,$g. Improving upon previous analyses, we consider the effect of the X-ray heating of the intergalactic medium on these constraints, and also use the full shape of the 21-cm absorption feature in our inference. In order to account for the anomalously deep absorption amplitude, we also consider an excess radio background motivated by LWA1 and ARCADE2 observations. Because the heating rate induced by PBH evaporation evolves slowly, the data favour a scenario in which PBH-induced heating is accompanied by X-ray heating. Also, for the same reason, using the full measurement across the EDGES observation band yields much stronger constraints on PBHs than just the redshift of absorption. We find that 21-cm observations exclude $f_{\mathrm{PBH}} \gtrsim 10^{-9.7}$ at 95% CL for $M_{\mathrm{PBH}}=10^{15}\,$g. This limit weakens approximately as $M_{\mathrm{PBH}}^4$ towards higher masses, thus providing the strongest constraints on ultralight evaporating PBHs as dark matter over the entire mass range $10^{15}$-$10^{17}\,$g. Under the assumption of a simple spherical gravitational collapse based on the Press-Schechter formalism, we also derive bounds on the curvature power spectrum at extremely small scales ($k\sim 10^{15}\,$Mpc$^{-1}$). This highlights the usefulness of global 21-cm measurements, including non-detections, across wide frequency bands for probing exotic physical processes.

Ab initio prediction of semiconductivity in a novel two-dimensional Sb2X3 (X= S, Se, Te) monolayers with orthorhombic structure.

Abstract: $$\hbox {Sb}_2\hbox {S}_3$$ and $$\hbox {Sb}_2\hbox {Se}_3$$ are well-known layered bulk structures with weak van der Waals interactions. In this work we explore the atomic lattice, dynamical stability, electronic and optical properties of $$\hbox {Sb}_2\hbox {S}_3$$ , $$\hbox {Sb}_2\hbox {Se}_3$$ and $$\hbox {Sb}_2\hbox {Te}_3$$ monolayers using the density functional theory simulations. Molecular dynamics and phonon dispersion results show the desirable thermal and dynamical stability of studied nanosheets. On the basis of HSE06 and PBE/GGA functionals, we show that all the considered novel monolayers are semiconductors. Using the HSE06 functional the electronic bandgap of $$\hbox {Sb}_2\hbox {S}_3$$ , $$\hbox {Sb}_2\hbox {Se}_3$$ and $$\hbox {Sb}_2\hbox {Te}_3$$ monolayers are predicted to be 2.15, 1.35 and 1.37 eV, respectively. Optical simulations show that the first absorption coefficient peak for $$\hbox {Sb}_2\hbox {S}_3$$ , $$\hbox {Sb}_2\hbox {Se}_3$$ and $$\hbox {Sb}_2\hbox {Te}_3$$ monolayers along in-plane polarization is suitable for the absorption of the visible and IR range of light. Interestingly, optically anisotropic character along planar directions can be desirable for polarization-sensitive photodetectors. Furthermore, we systematically investigate the electrical transport properties with combined first-principles and Boltzmann transport theory calculations. At optimal doping concentration, we found the considerable larger power factor values of 2.69, 4.91, and 5.45 for hole-doped $$\hbox {Sb}_{{2}}\hbox {S}_{{3}}$$ , $$\hbox {Sb}_{{2}}\hbox {Se}_{{3}}$$ , and $$\hbox {Sb}_{{2}}\hbox {Te}_{{3}}$$ , respectively. This study highlights the bright prospect for the application of $$\hbox {Sb}_2\hbox {S}_3$$ , $$\hbox {Sb}_2\hbox {Se}_3$$ and $$\hbox {Sb}_2\hbox {Te}_3$$ nanosheets in novel electronic, optical and energy conversion systems.

Evaluation of the excited state dynamics, photophysical properties, and the influence of donor substitution in a donor- $$\pi$$ π -acceptor system

Abstract: There have been numerous attempts for the theoretical design of a better donor- $$\pi$$ -acceptor structural framework with improved absorption and emission properties. However, for effective dye designing, it is necessary to understand the electronic and photophysical properties of the dye systems. In this work, we report a detailed density functional theory (DFT) and time-dependent density functional theory (TD-DFT) investigations of the excited state characteristics and the influence of various groups (–HCO, =CH2, (–CH3)2, (HCO)2, and (–OCH3)2) attached to the donor group (–NH2) in a p-nitroaniline D- $$\pi$$ -A system which are symbolized respectively as p-nitroaniline (A), N,N-dimethylnitroaniline (A2), N,N-dicarbonylnitroaniline (A3), N-methylenenitroaniline (A4), and N,N-dimethoxynitroaniline (A5). The first principles DFT and TD-DFT calculations from the ground state (S0) to the first five excited states: (S0→S1), (S0→S2), (S0→S3), (S0→S4), and (S0→S5) were utilized to explore the reactivity of D- $$\pi$$ -A system using the conceptual DFT approach, characterization of electron excitation using the hole-electron analysis, visual study of the various real space functions in the hole-electron framework, density of states (DOS), measurement of charge transfer (CT) length of electron excitation ( $$\Delta r$$ ), measurement of the overlapping degrees of hole and electron of electron excitation ( $$\Lambda$$ ), interfragment charge transfer (IFCT) during electron excitation, and the second-order perturbation energy analysis from the natural bond orbitals (NBO) computation. Results of the excitation studies show that all the studied compounds exhibited an n→ $$\pi$$ * localized type for first excitations (S0→S1) on –NO2 group in A, A2, A4, and A5 and –NCl2 in A3. $$\pi$$ → $$\pi$$ * charge transfer excitations were confirmed for S0→S2/S4/S5 in A and A2, S0→S3/S4/S5 in A3 and A5, and S0→S4/S5 in A4. The NBO second-order perturbation energy analysis suggest that the most significant hyperconjugative interactions were $$\uppi ({C}1-{C}2)\to {LP}* (1){ C}6$$ (54.43kcal/mol), $${\pi C}1-{C}2\to {LP }(1){C}3$$ (40.82kcal/mol), $${\pi N}14-{O}16\to {LP }(3){ O}15$$ (11.67kcal/mol), $$\uppi ({C}1-{C}6)\to\uppi *({N}12-{O}13)$$ (29.52kcal/mol), $$\uppi ({N}12-{O}13)\to {LP }(3){ O}14$$ (11.55kcal/mol), $$\uppi ({C}3-{C}4)\to\uppi *({C}5-{C}6)$$ (23.40kcal/mol), and $$\uppi ({C}5-{C}6)\to\uppi *({N}12-{O}14)$$ (24.88kcal/mol) $$\uppi ({C}3-{C}4)\to\uppi *({C}5-{C}6)$$ (24.64kcal/mol), which respectively corresponds to the A, A2, A3, A4, and A5 D- $$\pi$$ -A systems under investigation, and these strong interactions stabilize the systems.

Oxygenation of Janus group III monochalcogenides: First-principles insights into GaIn X O ( X = S , Se, Te) monolayers

Abstract: In this paper, we design and predict the structural, electronic, transport, and optical properties of two-dimensional Janus $\mathrm{GaIn}X\mathrm{O}$ ($X=\mathrm{S}$, Se, Te) monolayers by using first-principles calculations. The stability of all six possible configurations of $\mathrm{GaIn}X\mathrm{O}$ was examined through the analysis of their phonon spectra. It is found that, except for the OGaInTe monolayer, all the other configurations are dynamically stable. Further, the mechanical stability has been also investigated via calculations for the elastic constants. Depending on the stacking configuration, $\mathrm{GaIn}X\mathrm{O}$ can be either semiconductor (with a direct or indirect band gap) or metallic. Interestingly, the carrier mobilities of the investigated systems are found to be highly directional isotropic; however, the mobility of electrons is much higher than that of holes, suggesting that these monolayers can be potential materials for applications in nanoscale electronics. Finally, strong optical absorption in a wide light region extending from the infrared to the ultraviolet region is also predicted in the Janus $\mathrm{GaIn}X\mathrm{O}$ depending on its stacking configuration. The findings not only get insights into the fundamental properties of the Janus materials based on group III monochalcogenide monolayers but also suggest them as potential candidates for applications in the next-generation optoelectronic nanodevices.

MusE GAs FLOw and Wind (MEGAFLOW) VIII. Discovery of a Mgii emission halo probed by a quasar sightline

Abstract: Using deep (11.2hr) VLT/MUSE data from the MEGAFLOW survey, we report the first detection of extended MgII emission from a galaxy's halo that is probed by a quasar sightline. The MgII $\lambda\lambda$ 2796,2803 emission around the $z = 0.702$ galaxy ($\log(M_*/\mathrm{M_\odot}) = 10.05^{+0.15}_{-0.11}$) is detected out to $\approx$25 kpc from the central galaxy and covers $1.0\times10^3$ kpc$^2$ above a surface brightness of $14\times10^{-19} \mathrm{erg} \mathrm{s}^{-1} \mathrm{cm}^{-2}\,\mathrm{arcsec}^{-2}$ ($2 \sigma$; integrated over 1200 km s$^{-1}$ =19A and averaged over $1.5 \;\mathrm{arcsec}^2$). The MgII emission around this highly inclined galaxy ($\simeq$75 deg) is strongest along the galaxy's projected minor axis, consistent with the MgII gas having been ejected from the galaxy into a bi-conical structure. The quasar sightline, which is aligned with the galaxy's minor axis, shows strong MgII $\lambda$2796 absorption (EW$_0$ = 1.8A) at an impact parameter of 39kpc from the galaxy. Comparing the kinematics of both the emission and the absorption - probed with VLT/UVES -, to the expectation from a simple toy model of a bi-conical outflow, we find good consistency when assuming a relatively slow outflow ($v_\mathrm{out}= 130\;\mathrm{km}\,\mathrm{s}^{-1}$). We investigate potential origins of the extended MgII emission using simple toy models. With continuum scattering models we encounter serious difficulties in explaining the luminosity of the MgII halo and in reconciling density estimates from emission and absorption. Instead, we find that shocks might be a more viable source to power the extended MgII (and non-resonant [OII]) emission.

A Simple Polarization-Insensitive and Wide Angular Stable Circular Ring Based Undeca-Band Absorber for EMI/EMC Applications

Abstract: In this article, a closed ring resonator-based absorber with eleven consecutive absorption peaks is proposed over X and K bands with an average absorption rate of 96.29%. The proposed design consists of circular ring resonators embedded in the circularly slotted square patch printed on the top of the grounded FR-4 substrate. The surface current distributions well illustrates the reason behind the electromagnetic (EM) wave absorption. The design is polarization insensitive for normal incidence and wide angular stable up to 45° for TE (60° for TM) polarization. The structure is fabricated on a single-layered FR-4 dielectric substrate with a periodicity of ${{\boldsymbol{\lambda }}_{\boldsymbol{o}}}$ /2.32 and thickness of ${{\boldsymbol{\lambda }}_{\boldsymbol{o}}}$ /16.74, where ${{\boldsymbol{\lambda }}_{\boldsymbol{o}}}$ is the free-space wavelength at the lowest resonant frequency. A transmission line-based equivalent circuit model has been illustrated and good agreement is observed with full-wave simulations. This article's novelty lies in the absorption mechanism of eleven consecutive absorption peaks, demonstrating the controllability of the absorptivity peaks and resonant frequency. To the best of the authors’ knowledge, the proposed absorber demonstrates the highest number of near-unity successive absorption bands with better angular stability. The proposed structure was checked for radar cross section reduction application with an X -band antenna and results show 19.7-dBsm reduction at normal incidence.

Metastable Helium Reveals an Extended Atmosphere for the Gas Giant HAT-P-18b

Abstract: The metastable helium line at 1083 nm can be used to probe the extended upper atmospheres of close-in exoplanets and thus provide insight into their atmospheric mass loss, which is likely to be significant in sculpting their population. We used an ultranarrowband filter centered on this line to observe two transits of the low-density gas giant HAT-P-18b, using the 200" Hale Telescope at Palomar Observatory, and report the detection of its extended upper atmosphere. We constrain the excess absorption to be $0.46\pm0.12\%$ in our 0.635 nm bandpass, exceeding the transit depth from the Transiting Exoplanet Survey Satellite (TESS) by $3.9\sigma$. If we fit this signal with a 1D Parker wind model, we find that it corresponds to an atmospheric mass loss rate between $8.3^{+2.8}_{-1.9} \times 10^{-5}$ $M_\mathrm{J}$/Gyr and $2.63^{+0.46}_{-0.64} \times 10^{-3}$ $M_\mathrm{J}$/Gyr for thermosphere temperatures ranging from 4000 K to 13000 K, respectively. With a J magnitude of 10.8, this is the faintest system for which such a measurement has been made to date, demonstrating the effectiveness of this approach for surveying mass loss on a diverse sample of close-in gas giant planets.

FDTD-Based Optimization of Geometrical Parameters and Material Properties for GaAs-Truncated Nanopyramid Solar Cells

Abstract: Solar cells (SCs) based on semiconductor nanostructures with the distinctive potential of significant savings in material and effective control over light trapping and scattering processes provide a pathway to low-cost and high-efficiency next-generation SCs. To realize efficient light harvesting and reduced reflection and transmission loss of the nanostructures, the geometrical parameters and material properties must be deliberately optimized. In this article, for SCs based on vertically aligned GaAs-truncated nanopyramids, using the 3-D finite-difference time-domain (FDTD) method, we have examined the optimization study of geometrical and material parameters, including base-width, period, top-surface flatness, carrier mobility and lifetime, doping concentration, and surface recombination, to achieve absorption enhancement and in turn optimum photovoltaic parameters. The optimized structure has exhibited an efficiency of 19.16% despite considering low carrier mobility of 1000 cm $^{2}\,\,\text{V}^{-1}\,\,\text{s}^{-1}$ and lifetime of 3 nanoseconds, with heavily doped core ( $\sim 4\times 10^{17}$ cm−3) and substrate ( $\sim 1\times 10^{19}$ cm−3) and surface recombination velocity of 105cm/s at the contacts.

Gas-rich dwarf galaxies as a new probe of dark matter interactions with ordinary matter

Abstract: We use observations of gas-rich dwarf galaxies to derive constraints on dark matter scattering with ordinary matter. We require that heating/cooling due to dark matter (DM) interacting with gas in the Leo T dwarf galaxy not exceed the ultralow radiative cooling rate of the gas. This enables us to set (i) stronger bounds than all the previous literature on ultralight hidden photon DM for nearly all of the mass range ${10}^{\ensuremath{-}23}\ensuremath{\lesssim}{m}_{\mathrm{DM}}\ensuremath{\lesssim}{10}^{\ensuremath{-}10}\text{ }\text{ }\mathrm{eV}$, (ii) limits on sub-GeV millicharged DM which add to the constraints on the recent EDGES 21 cm absorption anomaly, and (iii) constraints on DM-baryon interactions directly at low relative velocities ${v}_{\mathrm{rel}}\ensuremath{\sim}17\text{ }\text{ }\mathrm{km}/\mathrm{s}$. Our study opens a new direction in using observations of gas-rich dwarf galaxies from previous, current, and upcoming optical and 21 cm surveys to probe physics beyond the standard model.

Light echos and coherent autocorrelations in a black hole spacetime

Abstract: The Event Horizon Telescope recently produced the first images of a black hole. These images were synthesized by measuring the coherent correlation function of the complex electric field measured at telescopes located across the Earth. This correlation function corresponds to the Fourier transform of the image under the assumption that the source emits spatially incoherent radiation. However, black holes differ from standard astrophysical objects: in the absence of absorption and scattering, an observer sees a series of increasingly demagnified echos of each emitting location. These echos correspond to rays that orbit the black hole one or more times before reaching the observer. This multi-path propagation introduces spatial and temporal correlations into the electric field that encode properties of the black hole, irrespective of intrinsic variability. We explore the coherent temporal autocorrelation function measured at a single telescope. Specifically, we study the simplified toy problem of scalar field correlation functions $\langle \Psi(t) \Psi(0) \rangle$ sourced by fluctuating matter located near a Schwarzschild black hole. We find that the correlation function is peaked at times equal to integer multiples of the photon orbit period; the corresponding power spectral density vanishes like $\lambda/r_{\rm g}$ where $r_{\rm g} = G M / c^{2}$ is the gravitational radius of the black hole and $\lambda$ is the wavelength of radiation observed. For supermassive black holes observed at millimeter wavelengths, the power in echos is suppressed relative to direct emission by $\sim 10^{-13} \lambda_{\rm mm}/M_{6}$, where $\lambda_{\rm mm} = \lambda/(1\,{\rm mm})$ and $M_6 = M/(10^6 M_\odot)$. Consequently, detecting multi-path propagation near a black hole using the coherent electric field autocorrelation is infeasible with current technology.

Exceptional Responsivity (>6 kA/W) and Dark Current ( 2 O 3 /p-CuO Quasi-Heterojunction-Based Deep UV Photodetector

Abstract: Reduction of high dark current has been a challenge for high responsivity photodetector (PD). In this context, the present article demonstrates an ultralow dark current of Ga2O3-based deep ultraviolet (UV)-photodetectors (UV-PDs) with enhanced photoresponses by tailoring a p/n heterojunction. An n- Ga2O3/p-CuO quasi-heterostructure-based deep UV-PDs has been fabricated on a sapphire (0001) substrate using an inexpensive electrospraying technique. After Ga2O3 deposition, platinum (Pt) electrodes ( $\sim 50$ nm) are fabricated as a metal–semiconductor–metal (MSM) device using sputtering. The device exhibits a very low dark current in the order of few fA $(6.94\times 10^{-14}$ A) at 5 V because of the enhanced depletion width at p/n heterojunction and Pt/ Ga2O3 metal–semiconductor contacts, which provides a narrow path for free carriers to travel from one metal contact to other under dark condition. The depletion layers get thinner due to the absorption of UV-photons in the UV-illumination condition. Hence, the photogenerated carriers get a wider channel to get collected at Pt-electrodes. Thus, in addition to ultralow dark current, the device exhibits an extraordinary photodetection characteristics, such as a high responsivity ( $\sim 6.33 \times 10^{3} \mathrm{AW}^{-1}$ ), remarkable phototo-dark current ratio ( $\sim 2.99 \times 10^{6}$ ), very high detectivity ( $\sim 4.44 \times 10^{14} \mathrm{mHz}^{0.5} \mathrm{~W}^{-1}$ ), and exceptional external quantum efficiency of $\sim 3.1 \times 10^{6}$ % at 5 V.

A complete census of circumgalactic Mg ii at redshift z ≲ 0.5

Abstract: We present a survey of MgII absorbing gas in the vicinity of 380 random galaxies, using 156 background quasi-stellar objects(QSOs) as absorption-line probes The sample comprises 211 isolated (73 quiescent and 138 star-forming galaxies) and 43 non-isolated galaxies with sensitive constraints for both MgII absorption and Ha emission The projected distances span a range from d=9 to 497 kpc, redshifts of the galaxies range from z=010 to 048, and rest-frame absolute B-band magnitudes range from $M_{\rm B}=-167$ to $-228$ Our analysis shows that the rest-frame equivalent width of MgII, $W_r$(2796), depends on halo radius($R_h$), $B$-band luminosity($L_{\rm B}$) and stellar mass ($M_{\rm star}$) of the host galaxies, and declines steeply with increasing $d$ for isolated, star-forming galaxies $W_r$(2796) exhibits no clear trend for either isolated, quiescent galaxies or non-isolated galaxies The covering fraction of MgII absorbing gas $\langle \kappa \rangle$ is high with $\langle \kappa \rangle\gtrsim 60$% at $<40$ kpc for isolated galaxies and declines rapidly to $\langle \kappa \rangle\approx 0$ at $d\gtrsim100$ kpc Within the gaseous radius, $\langle \kappa \rangle$ depends sensitively on both $M_{\rm star}$ and the specific star formation rate inferred from Ha Different from massive quiescent halos, the observed velocity dispersion of MgII gas around star-forming galaxies is consistent with expectations from virial motion, which constrains individual clump mass to $m_{\rm cl} \gtrsim 10^5 \,\rm M_\odot$ and cool gas accretion rate of $\sim 07-2 \,M_\odot\,\rm yr^{-1}$ We find no strong azimuthal dependence of MgII absorption for either star-forming or quiescent galaxies Our results highlight the need of a homogeneous, absorption-blind sample for establishing a holistic description of chemically-enriched gas in the circumgalactic space

Slowly rotating Einstein-bumblebee black hole solution and its greybody factor in a Lorentz violation model

Abstract: We obtain an exact slowly rotating Einstein-bumblebee black hole solution by solving the corresponding \begin{document}$rr$\end{document} and \begin{document}$t\phi$\end{document} components of the gravitational field equations for both cases: A) \begin{document}$b_\mu=(0,b(r),0,0)$\end{document} and B) \begin{document}$b_\mu= (0,b(r), \mathfrak{b}(\theta),0)$\end{document} . Then, we check the other gravitational field equations and the bumblebee field motion equations using this solution. We find that for case A, there indeed exists a slowly rotating black hole solution for an arbitrary LV (Lorentz violation) coupling constant \begin{document}$\ell$\end{document} ; however, for case B, this slowly rotating solution exists if and only if coupling constant \begin{document}$\ell$\end{document} is as small as or smaller than angular momentum a. Thus far, no full rotating black hole solution has been published; hence, the Newman-Janis algorithm cannot be used to generate a rotating solution in the Einstein-bumblebee theory. This is similar to the Einstein-aether theory, wherein only some slowly rotating black hole solutions exist. To study the effects of this broken Lorentz symmetry, we consider the black hole greybody factor and find that, for angular index \begin{document}$l=0$\end{document} , LV constant \begin{document}$\ell$\end{document} decreases the effective potential and enhances the absorption probability, which is similar to the results for the non-minimal derivative coupling theory.

Sulfur-doped graphene anchoring of ultrafine Au25 nanoclusters for electrocatalysis

Abstract: The biggest challenge of exploring the catalytic properties of under-coordinated nanoclusters is the issue of stability. We demonstrate herein that chemical dopants on sulfur-doped graphene (S-G) can be utilized to stabilize ultrafine (sub-2 nm) Au25(PET)18 clusters to enable stable nitrogen reduction reaction (NRR) without significant structural degradation. The Au25@S-G exhibits an ammonia yield rate of $$27.5\,{\rm{\mu }}{{\rm{g}}_{{\rm{N}}{{\rm{H}}_3}}} \cdot {\rm{m}}{{\rm{g}}_{{\rm{Au}}}}^{ - 1} \cdot {{\rm{h}}^{ - 1}}$$ at −0.5 V with faradic efficiency of 2.3%. More importantly, the anchored clusters preserve ∼ 80% NRR activity after four days of continuous operation, a significant improvement over the 15% remaining ammonia production rate for clusters loaded on undoped graphene tested under the same conditions. Isotope labeling experiments confirmed the ammonia was a direct reaction product of N2 feeding gas instead of other chemical contaminations. Ex-situ X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy of post-reaction catalysts reveal that the sulfur dopant plays a critical role in stabilizing the chemical state and coordination environment of Au atoms in clusters. Further ReaxFF molecular dynamics (RMD) simulation confirmed the strong interaction between Au nanoclusters (NCs) and S-G. This substrate-anchoring process could serve as an effective strategy to study ultrafine nanoclusters’ electrocatalytic behavior while minimizing the destruction of the under-coordinated surface motif under harsh electrochemical reaction conditions.

Generalizing the calculable R -matrix theory and eigenvector continuation to the incoming-wave boundary condition

Abstract: The calculable $R$-matrix theory has been formulated successfully for regular boundary conditions with vanishing radial wave functions at the coordinate origins [P. Descouvemont and D. Baye, Rept. Prog. Phys. 73, 036301 (2010)]. We generalize the calculable $R$-matrix theory to the incoming wave boundary condition (IWBC), which is widely used in theoretical studies of low-energy heavy-ion fusion reactions to simulate the strong absorption of incoming flux inside the Coulomb barriers. The generalized calculable $R$-matrix theory also provides a natural starting point to extend eigenvector continuation (EC) [D. Frame et al., Phys. Rev. Lett. 121, 032501 (2018)] to fusion observables. The ${}^{14}\text{N}+{}^{12}\text{C}$ fusion reaction is taken as an example to validate these new theoretical tools. Both local and nonlocal potentials are considered in numerical calculations. Our generalizations of the calculable $R$-matrix theory and EC are found to work well for IWBC.

Ly α as a tracer of cosmic reionization in the SPHINX radiation-hydrodynamics cosmological simulation

Abstract: The Ly$\alpha$ emission line is one of the most promising probes of cosmic reionisation but isolating the signature of a change in the ionisation state of the IGM is challenging because of intrinsic evolution and internal radiation transfer effects. We present the first study of the evolution of Ly$\alpha$ emitters (LAE) during the epoch of reionisation based on a full radiation-hydrodynamics cosmological simulation that is able to capture both the large-scale process of reionisation and the small-scale properties of galaxies. We predict the Ly$\alpha$ emission of galaxies in the $10^3$ cMpc$^3$ SPHINX simulation at $6\leq z\leq9$ by computing the full Ly$\alpha$ radiation transfer from ISM to IGM scales. SPHINX is able to reproduce many observational constraints such as the UV/Ly$\alpha$ luminosity functions and stellar mass functions at z $\geq$ 6 for the dynamical range probed by our simulation ($M_{\rm 1500}\gtrsim-18$, $L_{\rm Ly\alpha}\lesssim10^{42}$ erg/s, $M_{\star}\lesssim10^9$ M$_{\odot}$). As intrinsic Ly$\alpha$ emission and internal Ly$\alpha$ escape fractions barely evolve from $z=6$ to 9, the observed suppression of Ly$\alpha$ luminosities with increasing redshift is fully attributed to IGM absorption. For most observable galaxies ($M_{\rm 1500}\lesssim-16$), the Ly$\alpha$ line profiles are slightly shifted to the red due to internal radiative transfer effects which mitigates the effect of IGM absorption. Overall, the enhanced Ly$\alpha$ suppression during reionisation traces the IGM neutral fraction $x_{\rm HI}$ well but the predicted amplitude of this reduction is a strong function of the Ly$\alpha$ peak shift, which is set at ISM/CGM scales. We find that a large number of LAEs could be detectable in very deep surveys during reionisation when $x_{\rm HI}$ is still $\approx 50\%$.

GASP XXXIV: Unfolding the thermal side of ram pressure stripping in the jellyfish galaxy JO201

Abstract: X-ray studies of jellyfish galaxies play a crucial role in understanding the interactions between the interstellar medium (ISM) and the intracluster medium (ICM). In this paper, we focused on the jellyfish galaxy JO201. By combining archival Chandra observations, MUSE H$\alpha$ cubes, and maps of the emission fraction of the diffuse ionised gas, we investigated both its high energy spectral properties and the spatial correlation between its X-ray and optical emissions. The X-ray emission of JO201 is provided by both the Compton thick AGN (L$_{\text{X}}^{0.5-10 \text{keV}}$=2.7$\cdot$10$^{41}$ erg s$^{-1}$, not corrected for intrinsic absorption) and an extended component (L$_{\text{X}}^{0.5-10 \, \text{keV}}\approx$1.9-4.5$\cdot$10$^{41}$ erg s$^{-1}$) produced by a warm plasma (kT$\approx$1 keV), whose luminosity is higher than expected from the observed star formation (L$_{\text{X}}\sim$3.8$\cdot10^{40}$ erg s$^{-1}$). The spectral analysis showed that the X-ray emission is consistent with the thermal cooling of hot plasma. These properties are similar to the ones found in other jellyfish galaxies showing extended X-ray emission. A point-to-point analysis revealed that this X-ray emission closely follows the ISM distribution, whereas CLOUDY simulations proved that the ionisation triggered by this warm plasma would be able to reproduce the [OI]/H$\alpha$ excess observed in JO201. We conclude that the galactic X-ray emitting plasma is originated on the surface of the ISM as a result of the ICM-ISM interplay. This process would entail the cooling and accretion of the ICM onto the galaxy, which could additionally fuel the star formation, and the emergence of [OI]/H$\alpha$ excess in the optical spectrum.

Search processes with stochastic resetting and partially absorbing targets

Abstract: We extend the theoretical framework used to study search processes with stochastic resetting to the case of partially absorbing targets. Instead of an absorption event occurring when the search particle reaches the boundary of a target, the particle can diffuse freely in and out of the target region and is absorbed at a rate $\kappa$ when inside the target. In the context of cell biology, the target could represent a chemically reactive substrate within a cell or a region where a particle can be offloaded onto a nearby compartment. We apply this framework to a partially absorbing interval and to spherically symmetric targets in $\R^d$. In each case, we determine how the mean first passage time (MFPT) for absorption depends on $\kappa$, the resetting rate $r$, and the target geometry. For the given examples, we find that the MFPT is a monotonically decreasing function of $\kappa$, whereas it is a unimodal function of $r$ with a unique minimum at an optimal resetting rate $r_{\rm opt}$. The variation of $r_{\rm opt}$ with $\kappa$ depends on the spatial dimension $d$, decreasing in sensitivity as $d$ increases. For finite $\kappa$, $ r_{\rm opt}$ is a non-trivial function of the target size and distance between the target and the reset point. We also show how our results converge to those obtained previously for problems with totally absorbing targets and similar geometries when the absorption rate becomes infinite. Finally, we generalize the theory to take into account an extended chemical reaction scheme within a target.

Time-resolved absorption spectroscopic characterization of ultrafast laser-produced plasmas under varying background pressures.

Abstract: Time-resolved tunable laser absorption spectroscopy is used to characterize the physical properties of ultrafast laser-produced plasmas. The plasmas were produced from an Inconel target, with $\ensuremath{\le}0.4\phantom{\rule{0.16em}{0ex}}\mathrm{wt}\phantom{\rule{0.16em}{0ex}}%$ Al, using $\ensuremath{\sim}35\phantom{\rule{0.16em}{0ex}}\mathrm{fs}$, $\ensuremath{\sim}800\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$, $\ensuremath{\sim}5\phantom{\rule{0.16em}{0ex}}\mathrm{mJ}$ laser pulses at varying Ar background pressures from 1 to 100 Torr. The absorption spectrum of atomic Al is measured with high spectral and temporal resolution when the probe laser is stepped across the selected Al transition at 394.4 nm. Spectral fitting is used to infer linewidths, kinetic temperature, Al column density, and pressure broadening coefficient. The late time physical properties of plasmas are compared for various pressure levels. Our studies highlight that a significant lower state population exists even at early times of ultrafast laser-produced plasma evolution, and lower state population persistence decreases with increasing ambient pressure. We also show that the fundamental optical properties, such as pressure broadening, can be measured using ultrafast laser-produced plasmas combined with laser absorption spectroscopy.

Nuclear de-excitations in low-energy charged-current ν e scattering on Ar 40

Abstract: Background: Large argon-based neutrino detectors, such as those planned for the Deep Underground Neutrino Experiment, have the potential to provide unique sensitivity to low-energy (few to tens of MeV) electron neutrinos produced by core-collapse supernovae. Despite their importance for neutrino energy reconstruction, nuclear de-excitations following charged-current ${\ensuremath{ u}}_{e}$ absorption on $^{40}\mathrm{Ar}$ have never been studied in detail at supernova energies.Purpose: I develop a model of nuclear de-excitations that occur following the $^{40}\mathrm{Ar}({\ensuremath{ u}}_{e},{e}^{\ensuremath{-}})^{40}\mathrm{K}^{*}$ reaction. This model is applied to the calculation of exclusive cross sections.Methods: A simple expression for the inclusive differential cross section is derived under the allowed approximation. Nuclear de-excitations are described using a combination of measured $\ensuremath{\gamma}$-ray decay schemes and the Hauser-Feshbach statistical model. All calculations are carried out using a novel Monte Carlo event generator called MARLEY (Model of Argon Reaction Low Energy Yields).Results: Various total and differential cross sections are presented. Two de-excitation modes, one involving only $\ensuremath{\gamma}$ rays and the other including single neutron emission, are found to be dominant at few tens-of-MeV energies.Conclusions: Nuclear de-excitations have a strong impact on the achievable energy resolution for supernova ${\ensuremath{ u}}_{e}$ detection in liquid argon. Tagging events involving neutron emission, though difficult, could substantially improve energy reconstruction. Given a suitable calculation of the inclusive cross section, the MARLEY nuclear de-excitation model may readily be applied to other scattering processes.

The Eddington ratio-dependent 'changing look' events in NGC 2992

Abstract: We present an analysis of historical multi-wavelength emission of the Changing Look (CL) Active Galactic Nucleus (AGN) in NGC 2992, covering epochs ranging from 1978 to 2021, as well as new X-ray and optical spectra. The galaxy presents multiple Seyfert type transitions from type 2 to intermediate-type, losing and regaining its H$\alpha$ BEL recurrently. In X-rays, the source shows intrinsic variability with the absorption corrected luminosity varying by a factor of $\sim$ 40. We rule out tidal disruption events or variable obscuration as causes of the type transitions and show that the presence and the flux of the broad H$\alpha$ emission line are directly correlated with the 2-10 keV X-ray luminosity (L$_{2-10}$): the component disappears at L$_{2-10} \leq 2.6\times10^{42}$\ergcms, this value translates into an Eddington ratio ($\lambda_{\rm Edd}$) of $\sim$ 1%. The $\lambda_{\rm Edd}$ in which the BEL transitions occur is the same as the critical value at which there should be a state transition between a radiatively inefficient accretion flow (RIAF) and a thin accretion disk, such similarity suggests that the AGN is operating at the threshold mass accretion rate between the two accretion modes. We find a correlation between the narrow Fe K$\alpha$ flux and $\lambda_{\rm Edd}$, and an anti-correlation between full-width at half maximum of H$\alpha$ BEL and $\lambda_{\rm Edd}$, in agreement with theoretical predictions. Two possible scenarios for type transitions are compatible with our results: either the dimming of the AGN continuum, which reduces the supply of ionising photons available to excite the gas in the Broad Line Region (BLR), or the fading of the BLR structure itself occurs as the low accretion rate is not able to sustain the required cloud flow rate in a disk-wind BLR model.

Defect Physics of Ternary Semiconductor Zn Ge P 2 with a High Density of Anion-Cation Antisites: A First-Principles Study

Abstract: Anion-cation antisite defects usually have low density in the group III-V (e.g., $\mathrm{Ga}\mathrm{N}$) and ${\mathrm{II}\ensuremath{-}\mathrm{IV}\ensuremath{-}\mathrm{V}}_{2}$ (${\mathrm{Zn}\mathrm{Ge}\mathrm{N}}_{2}$, ${\mathrm{Zn}\mathrm{Sn}\mathrm{P}}_{2}$) semiconductors, and thus, have not drawn enough attention in defect studies of ${\mathrm{Zn}\mathrm{Ge}\mathrm{P}}_{2}$ since 1976. However, our first-principles calculations based on a hybrid functional show that the anion-cation antisite defects (${\mathrm{Ge}}_{\mathrm{P}}$ and ${\mathrm{P}}_{\mathrm{Ge}}$) can have very high density (${10}^{17}\ensuremath{-}{10}^{18}\phantom{\rule{0.1em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$), making them the dominant defects in ${\mathrm{Zn}\mathrm{Ge}\mathrm{P}}_{2}$. Their calculated photoluminescence (PL) spectra agree well with the 1.4 and 1.6 eV PL peaks observed experimentally, indicating that they may be the origin of defects, which challenges previous assumptions that the $\mathrm{P}$ vacancy ($V_{\rm{P}}$) defect is responsible for the two PL peaks. Although the anion-cation antisites (${\mathrm{Ge}}_{\mathrm{P}}$ and ${\mathrm{P}}_{\mathrm{Ge}}$) and cation-cation antisites (${\mathrm{Ge}}_{\mathrm{Zn}}$ and ${\mathrm{Zn}}_{\mathrm{Ge}}$) both have densities as high as ${10}^{17}\phantom{\rule{0.1em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$, ${\mathrm{Zn}\mathrm{Ge}\mathrm{P}}_{2}$ suffers from serious donor-acceptor compensation, which results in a low carrier density (below ${10}^{10}\phantom{\rule{0.1em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$), and thus, poor electrical conductivity. These results explain the mysterious observation that ${\mathrm{Zn}\mathrm{Ge}\mathrm{P}}_{2}$ crystals grown using different methods have a high defect density, but low carrier density and high resistivity, and also indicate that it is challenging to suppress the defect-induced optical absorption in the development of high-power ${\mathrm{Zn}\mathrm{Ge}\mathrm{P}}_{2}$-based optical devices.

Observation of cyclotron resonance and measurement of the hole mass in optimally doped La 2 − x Sr x CuO 4

Abstract: Using time-domain terahertz spectroscopy in pulsed magnetic fields up to 31 T, we measure the terahertz optical conductivity in an optimally doped thin film of the high-temperature superconducting cuprate ${\mathrm{La}}_{1.84}{\mathrm{Sr}}_{0.16}{\mathrm{CuO}}_{4}$. We observe systematic changes in the circularly polarized complex optical conductivity that are consistent with cyclotron absorption of $p$-type charge carriers characterized by a cyclotron mass of $4.9{m}_{\mathrm{e}}\ifmmode\pm\else\textpm\fi{}0.8{m}_{\mathrm{e}}$ and a scattering rate that increases with magnetic field. These results open the door to studies aimed at characterizing the degree to which electron-electron interactions influence carrier masses in cuprate superconductors.