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We predict the 21-cm global signal and power spectra during the Epoch of Reionisation using the MERAXES semi-analytic galaxy formation and reionisation model, updated to include X-ray heating and thermal evolution of the intergalactic medium. Studying the formation and evolution of galaxies together with the reionisation of cosmic hydrogen using semi-analytic models (such as MERAXES) requires N-body simulations within large volumes and high mass resolutions. For this, we use a simulation of side-length $210~h^{-1}$ Mpc with $4320^3$ particles resolving dark matter haloes to masses of $5\times10^8~h^{-1}~M_\odot$. To reach the mass resolution of atomically cooled galaxies, thought to be the dominant population contributing to reionisation, at $z=20$ of $\sim 2\times10^7~h^{-1}~M_\odot$, we augment this simulation using the DARKFOREST Monte-Carlo merger tree algorithm (achieving an effective particle count of $\sim10^{12}$). Using this augmented simulation we explore the impact of mass resolution on the predicted reionisation history as well as the impact of X-ray heating on the 21-cm global signal and the 21-cm power spectra. We also explore the cosmic variance of 21-cm statistics within $70^{3}$ $h^{-3}$ Mpc$^3$ sub-volumes. We find that the midpoint of reionisation varies by $\Delta z\sim0.8$ and that the cosmic variance on the power spectrum is underestimated by a factor of $2-4$ at $k\sim 0.1-0.4$ Mpc$^{-1}$ due to the non-Gaussian nature of the 21-cm signal. To our knowledge, this work represents the first model of both reionisation and galaxy formation which resolves low-mass atomically cooled galaxies while simultaneously sampling sufficiently large scales necessary for exploring the effects of X-rays in the early Universe., Comment: 17 pages, 13 figures, revised and MNRAS accepted version

The transmission of Lyman-{\alpha} (Ly{\alpha}) in the spectra of distant quasars depends on the density, temperature, and ionization state of the intergalactic medium (IGM). Therefore, high-redshift (z > 5) Ly{\alpha} forests could be invaluable in studying the late stages of the epoch of reionization (EoR), as well as properties of the sources that drive it. Indeed, high-quality quasar spectra have now firmly established the existence of large-scale opacity fluctuations at z > 5, whose physical origins are still debated. Here we introduce a Bayesian framework capable of constraining the EoR and galaxy properties by forward-modelling the high-z Ly{\alpha} forest. Using priors from galaxy and CMB observations, we demonstrate that the final overlap stages of the EoR (when >95% of the volume was ionized) should occur at z < 5.6, in order to reproduce the large-scale opacity fluctuations seen in forest spectra. However, it is the combination of patchy reionization and the inhomogeneous UV background that produces the longest Gunn-Peterson troughs. Ly{\alpha} forest observations tighten existing constraints on the characteristic ionizing escape fraction of galaxies, with the combined observations suggesting f_{\rm esc} \approx 7^4_3%, and disfavoring a strong evolution with the galaxy's halo (or stellar) mass., Comment: 19 pages, 11 figures, submitted to MNRAS, comments are welcome

In order to enhance the sensing performance of isopropanol (IPA) vapor at room temperature (RT), a conducting polymer of polypyrrole (PPy) was employed to modify the ordered silicon nanowires (SiNWs). The loose structure of SiNWs which has the advantage of forming the structure of SiNWs uniformly coated by PPy was obtained via a dual-metal-assisted chemical etching (MACE) process. Vapor chemical polymerization of the pyrrole monomer (Py) was employed to prepare ultrathin PPy film uniformly functionalized SiNWs array, i.e., PPy@SiNWs. The results exhibit that an ultrathin PPy shell with thickness of 10 nm is wrapped on the surface of a loose SiNWs array forming perfect core-shell structure. Comparative investigations on the IPA-sensing properties of the PPy@SiNWs, SiNWs and PPy were carried out at RT. It shows that the as-formed PPy@SiNW sensor exhibits about a sevenfold response enhancement to 100 ppm IPA gas compared to the bare SiNWs. Moreover, the PPy@SiNW shows an acceptable stability, with a response attenuation of 8.9% observed within 33 days. The gas sensing results confirm that the PPy decoration can improve the sensing response and stability of the SiNW-based sensor.

Silicon nanowires (SiNWs) array is a promising gas sensitive material featured as room-temperature response and compatibility of modern semiconductor technology. Towards breath diagnosis applications, a dual-functionalized SiNWs-based sensor (APTES&Ag@SiNWs) capable of rarefied acetone detection at high humidity level was developed based on the co-modification of 3-aminopropyl-triethoxylsilane (APTES) and nanoparticles of Ag. The SiNWs array was fabricated via metal assistant chemical etching (MACE) process and Ag nanoparticles modification was one-step achieved conveniently from MACE-produced Ag dendrites during SiNWs etching. In the APTES&Ag@SiNWs sensor, molecular functionalization of APTES could achieve obvious response promotion due to the active terminal amino groups of APTES for acetone molecule adsorption, while the modified Ag nanoparticles serve as wet centers to gather the adsorbed water molecules and then weaken the adverse effect of water adsorption on gas adsorption and response at high humidity. Resultantly, the on-chip sensor based on the dual-functionalized APTES&Ag@SiNWs array is revealed highly effective for acetone-sensing at room temperature and high humidity ambient (up to 85%RH). In particular, the as-developed APTES&Ag@SiNWs sensor shows linear response with the acetone concentration increasing from 1 to 4 ppm at 80%RH. The unique sensing characteristic makes the co-modified sensor promising in noninvasive diagnosis of diabetes via breath sensing. Finally, the moisture resistance analysis of the modified Ag is preformed based on first-principles calculations and meanwhile the contribution of APTES molecular functionalization on response enhancement is clarified.

Correlations between black holes and their host galaxies provide insight into what drives black hole-host co-evolution. We use the Meraxes semi-analytic model to investigate the growth of black holes and their host galaxies from high redshift to the present day. Our modelling finds no significant evolution in the black hole-bulge and black hole-total stellar mass relations out to a redshift of 8. The black hole-total stellar mass relation has similar but slightly larger scatter than the black hole-bulge relation, with the scatter in both decreasing with increasing redshift. In our modelling the growth of galaxies, bulges and black holes are all tightly related, even at the highest redshifts. We find that black hole growth is dominated by instability-driven or secular quasar-mode growth and not by merger-driven growth at all redshifts. Our model also predicts that disc-dominated galaxies lie on the black hole-total stellar mass relation, but lie offset from the black hole-bulge mass relation, in agreement with recent observations and hydrodynamical simulations., Comment: 14 pages, 11 figures. Accepted for publication in MNRAS

X-rays from High-Mass X-ray Binaries (HMXBs) are likely the main source of heating of the intergalactic medium (IGM) during Cosmic Dawn (CD), before the completion of reionization. This Epoch of Heating (EoH; $z\sim 10-15$) should soon be detected via the redshifted 21-cm line from neutral hydrogen, allowing us to indirectly study the properties of HMXBs in the unseen, first galaxies. Low-redshift observations, as well as theoretical models, imply that the integrated X-ray luminosity to star formation rate of HMXBs ($L_{\rm X}/{\rm SFR}$) should increase in metal-poor environments, typical of early galaxies. Here we study the impact of the metallicity ($Z$) dependence of $L_{\rm X}/{\rm SFR}$ during the EoH. For our fiducial models, galaxies with star formation rates of order $10^{-3} - 10^{-1}$ $M_\odot$ yr$^{-1}$ and metallicities of order $10^{-3} - 10^{-2}$ $Z_\odot$ are the dominant contributors to the X-ray background (XRB) during this period. Different $L_{\rm X}/{\rm SFR}$-$Z$ relations result in factors of $\sim$ 3 differences in these ranges, as well as in the mean IGM temperature and the large-scale 21-cm power, at a given redshift. We compute mock 21-cm observations adopting as a baseline a 1000h integration with the upcoming Square Kilometer Array (SKA), for two different $L_{\rm X}/{\rm SFR}$-$Z$ relations. We perform inference on these mock observations using the common simplification of a constant $L_{\rm X}/{\rm SFR}$, finding that constant $L_{\rm X}/{\rm SFR}$ models can recover the IGM evolution of the more complicated $L_{\rm X}/{\rm SFR}$-$Z$ simulations only during the EoH. At $z

We present a new investigation of the intergalactic medium (IGM) near reionization using dark gaps in the Lyman-$\beta$ (Ly$\beta$) forest. With its lower optical depth, Ly$\beta$ offers a potentially more sensitive probe to any remaining neutral gas compared to commonly used Ly$\alpha$ line. We identify dark gaps in the Ly$\beta$ forest using spectra of 42 QSOs at $z_{\rm em}>5.5$, including new data from the XQR-30 VLT Large Programme. Approximately $40\%$ of these QSO spectra exhibit dark gaps longer than $10h^{-1}{\rm Mpc}$ at $z\simeq5.8$. By comparing the results to predictions from simulations, we find that the data are broadly consistent both with models where fluctuations in the Ly$\alpha$ forest are caused solely by ionizing ultraviolet background (UVB) fluctuations and with models that include large neutral hydrogen patches at $z, Comment: 17 pages, 13 figures, accepted for publication in ApJ. The Figure set and machine readable table are available at https://ydzhuastro.github.io/lyb.html

The presence of excess scatter in the Ly-$\alpha$ forest at $z\sim 5.5$, together with the existence of sporadic extended opaque Gunn-Peterson troughs, has started to provide robust evidence for a late end of hydrogen reionisation. However, low data quality and systematic uncertainties complicate the use of Ly-$\alpha$ transmission as a precision probe of reionisation's end stages. In this paper, we assemble a sample of 67 quasar sightlines at $z>5.5$ with high signal-to-noise ratios of $>10$ per $\leq 15$ km s$^{-1}$ spectral pixel, relying largely on the new XQR-30 quasar sample. XQR-30 is a large program on VLT/X-Shooter which obtained deep (SNR $>20$ per pixel) spectra of 30 quasars at $z>5.7$. We carefully account for systematics in continuum reconstruction, instrumentation, and contamination by damped Ly-$\alpha$ systems. We present improved measurements of the mean Ly-$\alpha$ transmission over $4.93.5 \sigma$). Our results indicate that reionisation-related fluctuations, whether in the UVB, residual neutral hydrogen fraction, and/or IGM temperature, persist in the intergalactic medium until at least $z=5.3$ ($t=1.1$ Gyr after the Big Bang). This is further evidence for a late end to reionisation., Comment: Accepted for publication in MNRAS. Full measurement datasets are available on the first author's website

Layered double hydroxides (LDHs) have been acknowledged as potential gas sensing materials owing to their large specific surface area and compositional flexibility. In this work, highly sensitive LDHs-based nanocomposite of In(OH)3/ZnAlIn-LDHs was synthesized via hydrothermal growth of hierarchical ZnAlIn-LDHs and synchronous modification of single-crystalline nanoparticles of In(OH)3. The achieved In(OH)3/ZnAlIn-LDHs shows three-dimensional (3D) hierarchical architecture, with discrete In(OH)3 nanoparticles attachment on the nanosheet surface. The hierarchical ZnAlIn-LDHs forms loose 3D sensitive skeleton facilitating easy gas diffusion; additional In(OH)3 nanoparticles modification on LDHs nanosheets induces heterojunction effect capable of further enhancement of gas-sensing response. The gas-sensing measurements reveal that the achieved In(OH)3/ZnAlIn-LDHs nanocomposite is more sensitive to NO2 with rapid dynamic characteristic in comparison to the single components. At room temperature, the In(OH)3 modified ZnAlIn-LDHs can response ultra rarefied NO2 of 2.5 ppb with response of 35.4%. The significantly enhanced sensing response for the nanocomposite of In(OH)3/ZnAlIn-LDHs could attribute to the co-modulation of unique hierarchical microstructure, In-doping in LDHs layers and heterojunction effect between LDHs and the modified In(OH)3 nanoparticles.

Surface modification and core–shell heterostructure are all proved effective in improving gas-response performance of a semiconductor sensor. Here Ag nanoparticles (Ag NPs) modified W18O49@PPy core–shell nanorods (Ag/CSNRs) prepared by a cost-effective process are investigated for enhanced NH3-sensing response. In present process, surface modification by Ag NPs is achieved in parallel to the PPy-shell formation via chemical polymerization of Py on W18O49 nanorods with AgNO3 as an oxidant. The distribution (partial or total embedding in PPy-shell) and amount of the modified Ag NPs are revealed to be decided by Py polymerization duration, and affect the gas response of corresponding Ag/CSNRs sensor. The sensor based on Ag/CSNRs exhibits significantly enhanced response. The sample modified with partially embedded Ag NPs is capable of detection to rarefied NH3 as low as 100 ppb at room temperature. However, long duration of polymerization induces a full coverage of Ag NPs by PPy film and thus seriously weakens the modification effect to gas response. A sensing mechanism model was proposed and the response feature of Ag/CSNRs was analyzed with the perspective of co-contribution of chemical sensitization and electronic sensitization, which is further correlated to the distribution of attached Ag NPs.

ObjectiveThe aim of this study is to develop a model using Deep Neural Network (DNN) to diagnose thyroid nodules in patients with Hashimoto’s Thyroiditis.MethodsIn this retrospective study, we included 2,932 patients with thyroid nodules who underwent thyroid ultrasonogram in our hospital from January 2017 to August 2019. 80% of them were included as training set and 20% as test set. Nodules suspected for malignancy underwent FNA or surgery for pathological results. Two DNN models were trained to diagnose thyroid nodules, and we chose the one with better performance. The features of nodules as well as parenchyma around nodules will be learned by the model to achieve better performance under diffused parenchyma. 10-fold cross-validation and an independent test set were used to evaluate the performance of the algorithm. The performance of the model was compared with that of the three groups of radiologists with clinical experience of 10 years respectively.ResultsIn total, 9,127 images were collected from 2,932 patients with 7,301 images for the training set and 1,806 for the test set. 56% of the patients enrolled had Hashimoto’s Thyroiditis. The model achieved an AUC of 0.924 for distinguishing malignant and benign nodules in the test set. It showed similar performance under diffused thyroid parenchyma and normal parenchyma with sensitivity of 0.881 versus 0.871 (p = 0.938) and specificity of 0.846 versus 0.822 (p = 0.178). In patients with HT, the model achieved an AUC of 0.924 to differentiate malignant and benign nodules which was significantly higher than that of the three groups of radiologists (AUC = 0.824, 0.857, 0.863 respectively, p < 0.05).ConclusionThe model showed high performance in diagnosing thyroid nodules under both normal and diffused parenchyma. In patients with Hashimoto’s Thyroiditis, the model showed a better performance compared to radiologists with various years of experience.

Salinity is one of the limiting factors of wheat production worldwide. A total of 334 internationally derived wheat genotypes were employed to identify new germplasm resources for salt tolerance breeding. Salt stress caused 39, 49, 58, 55, 21 and 39% reductions in shoot dry weight (SDW), root dry weight (RDW), shoot fresh weight (SFW), root fresh weight (RFW), shoot height (SH) and root length (RL) of wheat, respectively, compared with the control condition at the seedling stage. The wheat genotypes showed a wide genetic and tissue diversity for the determined characteristics in response to salt stress. Finally, 12 wheat genotypes were identified as salt-tolerant through a combination of one-factor (more emphasis on the biomass yield) and multifactor analysis. In general, greater accumulation of osmotic substances, efficient use of soluble sugars, lower Na+/K+ and a higher-efficiency antioxidative system contribute to better growth in the tolerant genotypes under salt stress. In other words, the tolerant genotypes are capable of maintaining stable osmotic potential and ion and redox homeostasis and providing more energy and materials for root growth. The identified genotypes with higher salt tolerance could be useful for developing new salt-tolerant wheat cultivars as well as in further studies to underline the genetic mechanisms of salt tolerance in wheat.

The highly neutral inter-galactic medium (IGM) during the Epoch of Reionization (EoR) is expected to suppress Ly$\alpha$ emission with damping-wing absorption, causing nearly no Ly$\alpha$ detection from star-forming galaxies at $z{\sim}8$. However, spectroscopic observations of the 4 brightest galaxies (${\rm H}_{160}{\sim}25$ mag) at these redshifts do reveal prominent Ly$\alpha$ line, suggesting locally ionised IGM. In this paper, we explore the Ly$\alpha$ IGM transmission and environment of bright galaxies during the EoR using the Meraxes semi-analytic model. We find brighter galaxies to be less affected by damping-wing absorption as they are effective at ionizing surrounding neutral hydrogen. Specifically, the brightest sources (${\rm H}_{160}{\lesssim}25.5$ mag) lie in the largest ionized regions in our simulation, and have low attenuation of their Ly$\alpha$ from the IGM (optical depth ${, Comment: 10 pages, 3 figures, submitted to MNRAS, comments are welcome

The formation of the first galaxies during cosmic dawn and reionization (at redshifts $z=5-30$), triggered the last major phase transition of our universe, as hydrogen evolved from cold and neutral to hot and ionized. The 21-cm line of neutral hydrogen will soon allow us to map these cosmic milestones and study the galaxies that drove them. To aid in interpreting these observations, we upgrade the publicly available code {\tt 21cmFAST}. We introduce a new, flexible parametrization of the additive feedback from: an inhomogeneous, $H_2$-dissociating (Lyman-Werner; LW) background; and dark matter -- baryon relative velocities; which recovers results from recent, small-scale hydrodynamical simulations with both effects. We perform a large, "best-guess" simulation as the 2021 installment of the Evolution of 21-cm Structure (EOS) project. This improves the previous release with a galaxy model that reproduces the observed UV luminosity functions (UVLFs), and by including a population of molecular-cooling galaxies. The resulting 21-cm global signal and power spectrum are significantly weaker, primarily due to a more rapid evolution of the star-formation rate density required to match the UVLFs. Nevertheless, we forecast high signal-to-noise detections for both HERA and the SKA. We demonstrate how the stellar-to-halo mass relation of the unseen, first galaxies can be inferred from the 21-cm evolution. Finally, we show that the spatial modulation of X-ray heating due to relative velocities provides a unique acoustic signature that is detectable at $z \approx 10-15$ in our fiducial model. Ours are the first public simulations with joint inhomogeneous LW and relative-velocity feedback across the entire cosmic dawn and reionization., Comment: 23+3 pages, 23+3 figures. Matches accepted version. Simulation output available at https://www.dropbox.com/sh/dqh9r6wb0s68jfo/AACc9ZCqsN0SQ_JJN7GRVuqDa?dl=0

The first generation of galaxies is expected to form in minihalos, accreting gas through ${\rm H}_2$ cooling, and possessing unique properties. Although unlikely to be directly detected in UV/infrared surveys, the radiation from these molecular-cooling galaxies (MCGs) could leave an imprint in the 21-cm signal from the Cosmic Dawn. Here we quantify their detectability with upcoming radio interferometers. We generate mock 21-cm power spectra using a model for both MCGs as well as more massive, atomic-cooling galaxies (AGCs), allowing both populations to have different properties and scaling relations. The galaxy parameters are chosen so as to be consistent with: (i) high-redshift UV luminosity functions; (ii) the upper limit on the neutral fraction from QSO spectra; (iii) the Thomson scattering optical depth to the CMB; and (iv) the timing of the recent putative EDGES detection. The latter implies a significant contribution of MCGs to the Cosmic Dawn, if confirmed to be cosmological. We then perform Bayesian inference on two models including and ignoring MCG contributions. Comparing their Bayesian evidences, we find a strong preference for the model including MCGs, despite the fact that it has more free parameters. This suggests that if MCGs indeed play a significant role in the Cosmic Dawn, it should be possible to infer their properties from upcoming 21-cm power spectra. Our study illustrates how these observations can discriminate among uncertain galaxy formation models with varying complexities, by maximizing the Bayesian evidence., 12 pages, 3 figures, submitted to MNRAS, comments are welcome

The very first galaxies that started the cosmic dawn likely resided in so-called "minihaloes", with masses of $\sim10^5$-$10^8\mathrm{M}_\odot$, accreting their gas from the intergalactic medium through H$_2$ cooling. Such molecularly cooled galaxies (MCGs) mostly formed in pristine environments, hosted massive, metal-free stars, and were eventually sterilized by the build-up of a disassociating (Lyman-Werner; LW) background. Therefore, their properties might be very different from the galaxies we see in the later Universe. Although MCGs are probably too faint to be observed directly, we could nevertheless infer their properties from the imprint they leave in the cosmic 21-cm signal. Here we quantify this imprint by extending the public simulation code 21cmFAST to allow for a distinct population of MCGs. We allow MCGs to have different properties from other galaxies, including unique scaling relations for their stellar-to-halo mass ratios, ionizing escape fractions, and spectral energy distributions. We track inhomogeneous recombinations, disassociative LW feedback, and photoheating from reionization. After demonstrating how MCGs can shape the 21-cm signal, we explore to what extent current observations can already place constraints on their properties. The cosmic microwave background optical depth from Planck sets an upper limit on the product of the ionizing escape fraction and the stellar mass in MCGs. When including also the timing of the putative EDGES absorption signal, we find an additional strong degeneracy between the stellar mass and the X-ray luminosity of MCGs. If proven to be of cosmic origin, the timing of the EDGES signal would have been set by MCGs., 19 pages, 8 figures, 1 table; Updated to match the published version. Only minor changes

The Epoch of Reionization (EoR) depends on the complex astrophysics governing the birth and evolution of the first galaxies and structures in the intergalactic medium. EoR models rely on cosmic microwave background (CMB) observations, and in particular the large-scale E-mode polarization power spectra (EE PS), to help constrain their highly uncertain parameters. However, rather than directly forward-modelling the EE PS, most EoR models are constrained using a summary statistic -- the Thompson scattering optical depth, $\tau_e$. Compressing CMB observations to $\tau_e$ requires adopting a basis set for the EoR history. The common choice is the unphysical, redshift-symmetric hyperbolic tangent (Tanh) function, which differs in shape from physical EoR models based on hierarchical structure formation. Combining public EoR and CMB codes, 21cmFAST and CLASS, here we quantify how inference using the $\tau_e$ summary statistic impacts the resulting constraints on galaxy properties and EoR histories. Using the last Planck 2018 data release, we show that the marginalized constraints on the EoR history are more sensitive to the choice of the basis set (Tanh vs physical model) than to the CMB likelihood statistic ($\tau_e$ vs PS). For example, EoR histories implied by the growth of structure show a small tail of partial reionization extending to higher redshifts. However, biases in inference using $\tau_e$ are negligible for the Planck 2018 data. Using EoR constraints from high-redshift observations including the quasar dark fraction, galaxy UV luminosity functions and CMB EE PS, our physical model recovers $\tau_e=0.0569^{+0.0081}_{-0.0066}$., Comment: 11 pages, 5 figures, Updated to match the published version. Added Gamma evolution; Only minor changes

This brief code paper presents a new Python-wrapped version of the popular 21cm cosmology simulator, 21cmFAST. The new version, v3+, maintains the same core functionality of previous versions of 21cmFAST, but features a simple and intuitive interface, and a great deal more flexibility. This evolution represents the work of a formalized collaboration, and the new version, available publicly on GitHub, provides a single point-of-reference for all future upgrades and community-added features. In this paper, we describe simple usage of 21cmFAST, some of its new features, and provide a simple performance benchmark., Comment: 6 pages, 3 figures, published in JOSS

Bismuth molybdate is a multi-elemental metal oxide of the molybdate series, which could show great potentials for the application of gas sensors with outstanding sensitivity. Oxygen vacancy is a ubiquitous defect in this class of materials, and their introduction may be an effective strategy to regulate gas sensing performance. In this work, coupling investigations of experiment and first-principles calculations were performed to gain insight into the effect of oxygen deficiency on the gas-sensitive properties of Bi2MoO6. The oxygen vacancies existed in surface lattice changes the adsorption reaction pathway of the gas by modifying the coordination state and geometry of lattice oxygens, which is more favorable for the adsorption or dissociation of target gas and oxygen molecule. Further, the oxygen-deficient Bi2MoO6 was synthesized experimentally by a one-step solvothermal method. The gas sensor based on the oxygen-deficient Bi2MoO6 could respond to NH3 gas sensitively and selectively, with a high response value of 53.97 to 5 ppm NH3 at the optimal temperature of 75 °C. Combining the clarifications by first-principles calculations, the satisfactory sensing performance exhibited experimentally could be understood based on the promotion of adsorption activity and adsorption capability.

In this work, a combined experimental and theoretical study on ultrathin nanobelts of vanadium pentoxide (V2O5) for ethanol-sensing applications is preformed. The ultrathin V2O5 nanobelts were experimentally prepared by an ethylenediaminetetraacetic acid (EDTA)-medicated hydrothermal method followed by a mild annealing at 350 °C in air. The chelating and capping effect of EDTA facilitate the one-dimensional (1D) preferential growth of ultrathin nanobelts. Gas-sensing measurement reveals that the as-synthesized ultrathin V2O5 nanobelts are highly sensitive to ethanol gas with several ppm level at operating temperature of 250 °C. Based on the structural characterization of experimental sample, the nanobelt model was constructed and the surface adsorption of ethanol molecule was investigated by density functional theory (DFT) calculation. It is found that surface adsorption of ethanol tunes the electronic structure of V2O5 nanobelt considerably and cause an n-doping effect. Further atomic Mulliken charge population analysis reveals quantitatively the donation of electrons from the adsorbed ethanol to the surface. The calculated electronic properties are correlated to the experimental measurement of sensing response. Meanwhile the possible adsorption reaction of ethanol on V2O5 nanobelt is proposed based on the geometrical calculation for adsorption configuration.

We present a new investigation of the intergalactic medium (IGM) near the end of reionization using “dark gaps” in the Lyα forest. Using spectra of 55 QSOs at z em > 5.5, including new data from the XQR-30 VLT Large Programme, we identify gaps in the Lyα forest where the transmission averaged over 1 comoving h −1 Mpc bins falls below 5%. Nine ultralong (L > 80 h −1 Mpc) dark gaps are identified at z < 6. In addition, we quantify the fraction of QSO spectra exhibiting gaps longer than 30 h −1 Mpc, F 30, as a function of redshift. We measure F 30 ≃ 0.9, 0.6, and 0.15 at z = 6.0, 5.8, and 5.6, respectively, with the last of these long dark gaps persisting down to z ≃5.3. Comparing our results with predictions from hydrodynamical simulations, we find that the data are consistent with models wherein reionization extends significantly below redshift six. Models wherein the IGM is essentially fully reionized that retain large-scale fluctuations in the ionizing UV background at z ≲6 are also potentially consistent with the data. Overall, our results suggest that signatures of reionization in the form of islands of neutral hydrogen and/or large-scale fluctuations in the ionizing background remain present in the IGM until at least z ≃ 5.3.

Surface functionalization is an effective approach for improving the gas-sensing capabilities of one-dimensional (1D) metal oxides. In this work, tellurium dioxide nanoparticles–decorated tungsten oxide nanorods (TeO2 NPs@W18O49 nanorods) were prepared via a facile two-step process, i.e. solvothermal synthesis of W18O49 nanorods followed by hydrolysis deposition of TeO2 NPs, for gas-sensing applications. In the TeO2 decoration process, sodium dodecyl benzene sulfonic acid was introduced as surfactant to assure formation and attachment of highly discrete, tiny TeO2 NPs on whole surface of nanorods. The microstructures of the decorated nanorods were characterized, and the effect of TeO2 decoration on the gas-sensing characteristics of W18O49 nanorods was investigated. It is found that TeO2 decoration reduces the optimal operating temperature of W18O49 nanorods-based sensor from 200 to 150 °C. The W18O49 nanorods decorated with discrete TeO2 NPs display about four-fold enhancement in gas response to 0.1–1 ppm NO2 at 150 °C compared to pure W18O49 nanorods. The underlying mechanism for the enhanced response of the decorated sensor was demonstrated based on an electronic sensitization-related conductance effect model.

Massive quiescent galaxies (MQGs) are thought to have formed stars rapidly at early times followed by a long period of quiescence. The recent discovery of a MQG, ZF-COSMOS-20115 at $z\sim4$, only 1.5 Gyr after the big bang, places new constraints on galaxy growth and the role of feedback in early star formation. Spectroscopic follow-up confirmed ZF-COSMOS-20115 as a MQG at $z=3.717$ with an estimated stellar mass of ${\sim}10^{11}\mathrm{M}_\odot$, showing no evidence of recent star formation. We use the Meraxes semi-analytic model to investigate how ZF-COSMOS-20115 analogues build stellar mass, and why they become quiescent. We identify three analogue galaxies with similar properties to ZF-COSMOS-20115. We find that ZF-COSMOS-20115 is likely hosted by a massive halo with virial mass of ${\sim}10^{13}\mathrm{M}_\odot$, having been through significant mergers at early times. These merger events drove intense growth of the nucleus, which later prevented cooling and quenched star formation. ZF-COSMOS-20115 likely remained quiescent at $z, 11 pages, 7 figures; Updated to match the published version. All results and conclusions remain unchanged

We present an exploration of the expected detection of the earliest Active Galactic Nuclei (AGN) in the Universe from state-of-art galaxy formation and evolution semi-analytic models and hydro-dynamical simulations. We estimate the number and radiative characteristics of Super Massive Black Holes (SMBHs) at $z\geq 6$, a redshift range that will be intensively explored by the next generation of telescopes, in particular in the radio through the Square Kilometre Array (SKA) and at high energies with ESA's Athena X-ray Observatory. We find that Athena will be able to observe over 5000 AGN/$\rm deg^2$ at the Epoch of Re-ionization (EoR), $6\leq z \leq 10$. Similarly, for the same redshift range the models/simulations suggest that SKA will detect at least 400 AGN/$\rm deg^2$. Additionally, we stress the importance of the volume of the simulation box as well as the initial physical conditions of the models/simulations on their effect on the luminosity functions (LFs) and the creation of the most massive SMBHs that we currently observe at the EoR. Furthermore, following the evolution of the accretion mode of the SMBHs in each model/simulation, we show that, while the quasar dominates over the radio mode at the EoR, detection at radio wavelengths still reaches significant numbers even at the highest redshifts. Finally, we present the effect that the radiative efficiency has on the LFs by comparing results produced with a constant value for the radiative efficiency and more complex calculations based on the spin of each SMBH., Comment: Accepted for publication in MNRAS, 17 pages, 8 figures, 2 tables

We study the sizes, angular momenta and morphologies of high-redshift galaxies using an update of the Meraxes semi-analytic galaxy evolution model. Our model successfully reproduces a range of observations from redshifts $z=0$-$10$. We find that the effective radius of a galaxy disc scales with UV luminosity as $R_e\propto L_{\textrm{UV}}^{0.33}$ at $z=5$-$10$, and with stellar mass as $R_e\propto M_\ast^{0.24}$ at $z=5$ but with a slope that increases at higher redshifts. Our model predicts that the median galaxy size scales with redshift as $R_e \propto (1+z)^{-m}$, where $m=1.98\pm0.07$ for galaxies with $(0.3$-$1)L^\ast_{z=3}$ and $m=2.15\pm0.05$ for galaxies with $(0.12$-$0.3)L^\ast_{z=3}$. We find that the ratio between stellar and halo specific angular momentum is typically less than one and decreases with halo and stellar mass. This relation shows no redshift dependence, while the relation between specific angular momentum and stellar mass decreases by $\sim0.5$ dex from $z=7$ to $z=2$. Our model reproduces the distribution of local galaxy morphologies, with bulges formed predominantly through galaxy mergers for low-mass galaxies, disc-instabilities for galaxies with $M_\ast\simeq10^{10}$-$10^{11.5}M_\odot$, and major mergers for the most massive galaxies. At high redshifts, we find galaxy morphologies that are predominantly bulge-dominated., 21 pages, 12 figures. Accepted for publication in MNRAS

We directly compare predictions of dwarf galaxy properties in a semi-analytic model (SAM) with those extracted from a high-resolution hydrodynamic simulation. We focus on galaxies with halo masses of 1e910$), with the relevant time-scale becoming significantly longer towards lower redshifts. This indicates efficient accretion in cold mode in these low-mass objects at high redshift. Note that the improved SAM, which has been calibrated against hydrodynamic simulations, can provide more accurate predictions of high-redshift dwarf galaxy properties that are essential for reionization study., Comment: 18 pages, 9 figures; submitted to MNRAS, comments are welcome

Intergalactic medium temperature is a powerful probe of the epoch of reionisation, as information is retained long after reionisation itself. However, mean temperatures are highly degenerate with the timing of reionisation, with the amount heat injected during the epoch, and with the subsequent cooling rates. We post-process a suite of semi-analytic galaxy formation models to characterise how different thermal statistics of the intergalactic medium can be used to constrain reionisation. Temperature is highly correlated with redshift of reionisation for a period of time after the gas is heated. However as the gas cools, thermal memory of reionisation is lost, and a power-law temperature-density relation is formed, $T = T_0(1+\delta)^{1-\gamma}$ with $\gamma \approx 1.5$. Constraining our model against observations of electron optical depth and temperature at mean density, we find that reionisation likely finished at $z_{\rm{reion}} = 6.8 ^{+ 0.5} _{-0.8}$ with a soft spectral slope of $\alpha = 2.8 ^{+ 1.2} _{-1.0}$. By restricting spectral slope to the range $[0.5,2.5]$ motivated by population II synthesis models, reionisation timing is further constrained to $z_{\rm{reion}} = 6.9 ^{+ 0.4} _{-0.5}$. We find that, in the future, the degeneracies between reionisation timing and background spectrum can be broken using the scatter in temperatures and integrated thermal history., Comment: 17 pages, 17 figures, Accepted for publication in MNRAS

A new type NO 2 gas sensor constructed with CuO/p-porous silicon(PS) heterojunction was prepared in this paper. The sensor was fabricated by sputtering Cu films on PS substrate and then heating in the furnace tube. The morphology and crystallographic structrue of sensors were investigated by using field emission scanning electron microscope (FESEM) and X-ray diffractometer (XRD). The sensing properties of the sensors were investigated from 25 °C to 100 °C toward 125 ppb–1000 ppb NO 2 . The sensor showed high sensitivity and good selectivity of NO 2 at room temperature(25 °C). The sensing mechanism was also discussed in the paper, in which the effect of heterojunction of CuO and PS was introduced.

In the present work, the tungsten oxide (WO3) nanowires functionalized silicon nanowires (SiNWs) with cactus-like structure has been successfully synthesized for room-temperature NO2 detection. The novel nanocomposite was fabricated by metal-assisted chemical etching (MACE) and thermal annealing of tungsten film. The WO3 nanowires were evenly distributed from the upper to the lower part of the SiNWs, indicating excellent uniformity which is conducive to adsorption and desorption of gas molecules. The gas-sensing properties have been examined by measuring the resistance change towards 0.25–5 ppm NO2 gas. At room temperature, which is the optimum working temperature, the SiNWs/WO3 nanowires composite showed two-times higher NO2 response than that of the bare SiNWs at 2 ppm NO2. On the contrary, the responses of composite sensors to high concentrations of other reducing gases were very low, indicating excellent selectivity. Simultaneously, the composite sensors exhibited good sensing repeatability and stability. The enhancement in gas sensing properties may be attributed to the change in width of the space charge region, which is similar to the behavior of p-n junctions under forward bias, in the high-density p-n heterojunction structure formed between SiNWs and WO3 nanowires.

Vertically aligned array of silicon nanowires (SiNWs) with rough surface was demonstrated to be a promising material for high performance gas sensor applications. A two-step etching process, i.e. metal-induced chemical etching followed by the back-etching of KOH was developed to prepare the rough SiNWs array. The roughness of SiNWs effectively increases the active surface area as evidence that the measured BET specific area is ten times larger than that of the smooth nanowires without KOH etching. Meanwhile, the nanowire diameter and distribution density are also decrease due to KOH etching. The high active surface area and loose configuration of the rough SiNWs array are favorable for gas adsorption and rapid gas diffusion. As a result, the sensor based on the rough SiNWs array exhibits high response, good stability and satisfying response–recovery characteristics in detection of NO2 in ppb–ppm level at room temperature.

Highly ordered geometrical configuration and uniform shell layer are desirable for applications of one-dimensional (1D) core–shell heterostructures in gas sensors. In this work, we put forward a novel preparation of W 18 O 49 /CuO core–shell nanorods array with high alignment and uniform shell layer through the induction of shell film sputtering to roughly aligned W 18 O 49 –core nanorods. The W 18 O 49 -core nanorods with diameter of ∼20 nm were first grown via in-situ thermal oxidation of sputtered W film. Further sputtering-depositon of polycrystalline shell layer of CuO harvests a uniform W 18 O 49 /CuO core–shell nanorods array with improved alignment. Thicker shell results in better alignment. The NO 2 -sensing properties of W 18 O 49 /CuO core–shell nanorods array were investigated at room temperature up to 200 °C. It is found that the formation of core–shell heterostructure lowers the optimal operating temperature of W 18 O 49 nanorods sensor from 150 °C to near-room temperature of 50 °C. The presented heteroarray of W 18 O 49 /CuO core–shell nanorods is responsive to diluted NO 2 gas at ppb level. At 50 °C, it shows satisfactory sensing response to 0.1–1 ppm NO 2 gas with excellent dynamic response-recovery characteristics. These results are associated with the unique aligned configuration and the dual modulations of both heterojunction potential barrier at core–shell interface and the conductive carrier-accumulation channel.

We investigate the dependence of galaxy clustering at $z \sim 4 - 7$ on UV-luminosity and stellar mass. Our sample consists of $\sim$ 10,000 Lyman-break galaxies (LBGs) in the XDF and CANDELS fields. As part of our analysis, the $M_\star - M_{\rm UV}$ relation is estimated for the sample, which is found to have a nearly linear slope of $d\log_{10} M_\star / d M_{\rm UV} \sim 0.44$. We subsequently measure the angular correlation function and bias in different stellar mass and luminosity bins. We focus on comparing the clustering dependence on these two properties. While UV-luminosity is only related to recent starbursts of a galaxy, stellar mass reflects the integrated build-up of the whole star formation history, which should make it more tightly correlated with halo mass. Hence, the clustering segregation with stellar mass is expected to be larger than with luminosity. However, our measurements suggest that the segregation with luminosity is larger with $\simeq 90\%$ confidence (neglecting contributions from systematic errors). We compare this unexpected result with predictions from the \textsc{Meraxes} semi-analytic galaxy formation model. Interestingly, the model reproduces the observed angular correlation functions, and also suggests stronger clustering segregation with luminosity. The comparison between our observations and the model provides evidence of multiple halo occupation in the small scale clustering., Comment: 10 pages, 6 figures, 2 tables, accepted for publication in MNRAS

One-dimensional single crystalline WO 3 nanorods have been successfully synthesized onto the porous silicon substrates by a seed-induced hydrothermal method. The controlled morphology of porous silicon/tungsten oxide nanorods composite was obtained by using oxalic acid as an organic inducer. The reaction was carried out at 180 °C for 2 h. The influence of oxalic acid (pH value) on the morphology of porous silicon/tungsten oxide nanorods composite was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The NO 2 -sensing properties of the sensor based on porous silicon/tungsten oxide nanorods composite were investigated at different temperatures ranging from room temperature (∼25 °C) to 300 °C. At room temperature, the sensor behaved as a typical p-type semiconductor and exhibited high gas response, good repeatability and excellent selectivity characteristics toward NO 2 gas due to its high specific surface area, special structure, and large amounts of oxygen vacancies.

Novel WO 3 hierarchical structure film demonstrates to be a promising material for building highly sensitive and ultrafast responding gas sensors. The individual hierarchical WO 3 structure was constructed hydrothermally through double-sided inductive growth of WO 3 nanowire (or nanorod) arrays from the central nanosheet. The nanosheet was performed on the substrate via spin-coating and thermal annealing. Composed of well-aligned ultrathin nanowires (nanorods) as building blocks, the as-synthesized hierarchical WO 3 shows high active surface area and loose microstructure favorable for gas adsorption and rapid gas diffusion. The NO 2 -sensing properties of the hierarchical WO 3 film-based sensors were evaluated at room temperature over NO 2 concentration ranging from 15 ppb to 5 ppm. At room temperature, the WO 3 hierarchical structure behaves as an abnormal p-type semiconductor and exhibits unique gas-sensing performances including excellent sensitivity and excellent response characteristics towards NO 2 gas. It is found that the sensors based on hierarchical WO 3 responses to NO 2 gas as low as 15 ppb with an ultrashort response time of short than 5 s at room temperature, highlighting the capability of the material for rapid detection of dilute NO 2 at ppb level.

Motivated by recent measurements of the number density of faint AGN at high redshift, we investigate the contribution of quasars to reionization by tracking the growth of central supermassive black holes in an update of the Meraxes semi-analytic model. The model is calibrated against the observed stellar mass function at $z\sim0.6-7$, the black hole mass function at $z\lesssim0.5$, the global ionizing emissivity at $z\sim2-5$ and the Thomson scattering optical depth. The model reproduces a Magorrian relation in agreement with observations at $z, 21 pages, 12 figures; Updated to match the published version. All results and conclusions remain unchanged

The effect of NO2 adsorption on the electronic structure, density of states and electron population of W18O49 nanowires were investigated by using the first principles calculation based on density functional theory (DFT). Two nanowire models, including largely cations W5+ and cations W6+ respectively, were first constructed, and then the most energetically favorable adsorption site was determined through the analysis of adsorption energy. NO2 adsorption introduced new electronic states in the valence band, and as a consequence, the Fermi level shifts toward the energy gap reducing the charge carrier concentration of electrons in adsorbed nanowire. Atomic Mulliken population analysis indicated that NO2 adsorption on W18O49 nanowire can cause more electrons transferred from nanowire to NO2 molecule compared with the case on WO3 nanowire, suggesting an even more potential of W18O49 nanowire in high sensitive NO2 gas sensor application.

Mesoporous three-dimensional (3D) network of crystalline WO 3 nanowires was prepared by nanocasting method using 3D SBA-15 silica with hexagonally ordered mesopores as hard template. After impregnation, mineralization and template removal, a mesoporous 3D framework of ordered crystalline WO 3 nanowires with high specific surface area and stable mesopore channels was formed through the randomly distributed bridging between the neighboring nanowires. The mesostructure of the product was confirmed by low-angle X-ray diffraction (XRD) and nitrogen physisorption measurements. High resolution transmission electron microscopy (HRTEM) images indicate the single crystal structure with different crystal orientation for mesoporous particles. The gas sensing properties of the mesoporous 3D WO 3 nanowires replica were investigated at 50 °C up to 200 °C over NO 2 concentration ranging from 15 to 500 ppb. The results indicate that the mesoporous 3D WO 3 nanowires exhibits high response, good selectivity and fast response–recovery characteristics in the detection of sub-ppm and ppb level NO 2 at the optimal operating temperature of 125 °C due to the stable mesopore channels, large surface area and perfect single-crystal structure.

BaTiO3 ceramics for positive temperature coefficient resistance (PTCR) were fabricated via tape casting technique and reduction/reoxidation process. A novel method was used to regulate the density of the ceramics via changing binder amount in tape casting green bodies. The influences of different amounts of the binder on density, electrical properties, and microstructure of ceramics were investigated. The BaTiO3 ceramic monolith without internal electrodes with an addition of binder of 0.84 wt% was sintered in reducing atmosphere at 1150 °C and reoxidized at 800 °C for 1 h showed a resistivity of 56 Ω·cm and a PTCR jump about 3.2 orders of magnitude. The green and sintered density of the samples decreased with the increasing binder amount. The room temperature resistivity increased monotonically with the binder amount. However, the correlation of the PTCR jump with binder amount showed a contrary tendency. These electrical properties can be explained by the Jonker model. The influences of sintering temperature on the density of BaTiO3 ceramics with different binder amount were also discussed. In addition to the ceramic monoliths without internal electrodes, multilayer elements with internal electrodes were also prepared.