We present galaxy stellar mass functions (GSMFs) at z = 4-8 from a rest-frame ultraviolet (UV) selected sample of similar to 4500 galaxies, found via photometric redshifts over an area of similar to 280 arcmin(2) in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS)/Great Observatories Origins Deep Survey (GOODS) fields and the Hubble Ultra Deep Field. The deepest Spitzer/IRAC data to date and the relatively large volume allow us to place a better constraint at both the low- and high-mass ends of the GSMFs compared to previous space-based studies from pre-CANDELS observations. Supplemented by a stacking analysis, we find a linear correlation between the rest-frame UV absolute magnitude at 1500 angstrom (M-UV) and logarithmic stellar mass (log M-*) that holds for galaxies with log(M-*/M-circle dot) less than or similar to 10. We use simulations to validate our method of measuring the slope of the log M-*-M-UV relation, finding that the bias is minimized with a hybrid technique combining photometry of individual bright galaxies with stacked photometry for faint galaxies. The resultant measured slopes do not significantly evolve over z = 4-8, while the normalization of the trend exhibits a weak evolution toward lower masses at higher redshift. We combine the log M-*-M-UV distribution with observed rest-frame UV luminosity functions at each redshift to derive the GSMFs, finding that the low-mass-end slope becomes steeper with increasing redshift from alpha = -1.55(-0.07)(+0.08) at z = 4 to alpha = -2.25(-0.35)(+0.72) at z = 8. The inferred stellar mass density, when integrated over M-* = 10(8)-10(13) M-circle dot, increases by a factor of 10(-2)(+30) between z = 7 and z = 4 and is in good agreement with the time integral of the cosmic star formation rate density.

SThorium monocarbide (ThC) as a potential fuel for next generation nuclear reactor has been subjected to its structural stability investigation under high pressure, and so far no one reported the observation of structure phase transition induced by pressure. Here, utilizing the synchrotron X-ray diffraction technique, we for the first time, experimentally revealed the phase transition of ThC from B1 to P4/nmm at pressure of similar to 58 GPaat ambient temperature. A volume collapse of 10.2% was estimated during the phase transition. A modulus of 147 GPa for ThC at ambient pressure was obtained and the stoichiometry was attributed to the discrepancy of this value to the previous reports.

We investigate the environmental quenching of galaxies, especially those with stellar masses (M-*) < 10(9.5) Me-circle dot, beyond the local universe. Essentially all local low-mass quenched galaxies (QGs) are believed to live close to massive central galaxies, which is a demonstration of environmental quenching. We use CANDELS data to test whether or not such a dwarf QG-massive central galaxy connection exists beyond the local universe. For this purpose, we only need a statistically representative, rather than complete, sample of low-mass galaxies, which enables our study to z greater than or similar to 1.5. For each low-mass galaxy, we measure the projected distance (d(proj)) to its nearest massive neighbor (M-* > 10(10.5) M-circle dot) within a redshift range. At a given z and M-*, the environmental quenching effect is considered to be observed if the d(proj) distribution of QGs (d(proj)(Q)) is significantly skewed toward lower values than that of star-forming galaxies (d(proj)(SF)). For galaxies with 10(8) M-circle dot < M-* < 10(10) M-circle dot, such a difference between d(proj)(Q) and d(proj)(SF) is detected up to z similar to 1. Also, about 10% of the quenched galaxies in our sample are located between two and four virial radii (R-Vir) of the massive halos. The median projected distance from low-mass QGs to their massive neighbors, d(proj)(Q)/R-Vir, decreases with satellite M-* at M-* less than or similar to 10(9.5) M-circle dot, but increases with satellite M-* at M-* greater than or similar to 10(9.5) M-circle dot. This trend suggests a smooth, if any, transition of the quenching timescale around M-* similar to 10(9.5) M-circle dot at 0.5 < z < 1.0.

Studying giant star-forming clumps in distant galaxies is important to understand galaxy formation and evolution. At present, however, observers and theorists have not reached a consensus on whether the observed "clumps" in distant galaxies are the same phenomenon that is seen in simulations. In this paper, as a step to establish a benchmark of direct comparisons between observations and theories, we publish a sample of clumps constructed to represent the commonly observed "clumps" in the literature. This sample contains 3193 clumps detected from 1270 galaxies at 0.5 <= z < 3.0. The clumps are detected from rest-frame UV images, as described in our previous paper. Their physical properties (e.g., rest-frame color, stellar mass (M-*), star formation rate (SFR), age, and dust extinction) are measured by fitting the spectral energy distribution (SED) to synthetic stellar population models. We carefully test the procedures of measuring clump properties, especially the method of subtracting background fluxes from the diffuse component of galaxies. With our fiducial background subtraction, we find a radial clump U - V color variation, where clumps close to galactic centers are redder than those in outskirts. The slope of the color gradient (clump color as a function of their galactocentric distance scaled by the semimajor axis of galaxies) changes with redshift and M-* of the host galaxies: at a fixed M-*, the slope becomes steeper toward low redshift, and at a fixed redshift, it becomes slightly steeper with M-*. Based on our SED fitting, this observed color gradient can be explained by a combination of a negative age gradient, a negative E(B - V) gradient, and a positive specific SFR gradient of the clumps. We also find that the color gradients of clumps are steeper than those of intra-clump regions. Correspondingly, the radial gradients of the derived physical properties of clumps are different from those of the diffuse component or intra-clump regions.

We use the deep CANDELS observations in the GOODS North and South fields to revisit the correlations between stellar mass (M-*), star formation rate (SFR) and morphology, and to introduce a fourth dimension, the mass-weighted stellar age, in galaxies at 1.2 < z < 4. We do this by making new measures of M-*, SFR, and stellar age thanks to an improved SED fitting procedure that allows various star formation history for each galaxy. Like others, we find that the slope of the main sequence (MS) of star formation in the (M-*; SFR) plane bends at high mass. We observe clear morphological differences among galaxies across the MS, which also correlate with stellar age. At all redshifts, galaxies that are quenching or quenched, and thus old, have high Sigma(1) (the projected density within the central 1 kpc), while younger, star-forming galaxies span a much broader range of Sigma(1), which includes the high values observed for quenched galaxies, but also extends to much lower values. As galaxies age and quench, the stellar age and the dispersion of Sigma(1) for fixed values of M* shows two different regimes: one at the low-mass end, where quenching might be driven by causes external to the galaxies; the other at the high-mass end, where quenching is driven by internal causes, very likely the mass given the low scatter of Sigma(1) (mass quenching). We suggest that the monotonic increase of central density as galaxies grow is one manifestation of a more general phenomenon of structural transformation that galaxies undergo as they evolve.

Jarosite, a mineral with a kagome lattice, displays magnetic frustration yet orders magnetically below 65 K. As magnetic frustration can engender exotic physical properties, understanding the complex magnetism of jarosite comprises a multidecade interdisciplinary challenge. Unraveling the nature of the disparate magnetic coupling interactions that lead to magnetic order in jarosite remains an open question. Specifically, there is no observed trend in the interlayer spacing with magnetic order. Similarly, the relationship between metal ligand bond distance and magnetic order remains uninvestigated. Here, we use applied pressure to smoothly vary jarosite's structure without manipulating the chemical composition, enabling a chemically invariant structure function study. Using single-crystal and powder X-ray diffraction, we show that high applied pressures alter both the interlayer spacing and the metal ligand bond distances. By harnessing a suite of magnetic techniques under pressure, including SQUID-based magnetometry, time-resolved synchrotron MOssbauer spectroscopy, and X-ray magnetic circular dichroism, we construct the magnetic phase diagram for jarosite up to 40 GPa. Notably, we demonstrate that the magnetic ordering temperature increases dramatically to 240 K at the highest pressures. Additionally, we conduct X-ray emission spectroscopy, Mossbauer spectroscopy, and UV visible absorption spectroscopy experiments to comprehensively map the magnetic and electronic structures of jarosite at high pressure. We use these maps to construct chemically pure magnetostructural correlations which fully explain the nature and role of the disparate magnetic coupling interactions in jarosite.

Giant star-forming clumps are a prominent feature of star-forming galaxies (SFGs) and contain important clues on galaxy formation and evolution. However, the basic demographics of clumps and their host galaxies remain uncertain. Using the Hubble Space Telescope/Wide Field Camera 3 F275W images from the Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we detect and analyze giant starforming clumps in galaxies at 0.5 <= z <= 1, connecting two epochs when clumps are common (at cosmic high noon, z similar to 2) and rare (in the local Universe). We construct a clump sample whose rest-frame 1600 angstrom luminosity is 3 times higher than the most luminous local H II regions (MUV <= -16 AB). In our sample, 35% +/- 3% of low-mass galaxies (log[M-*/M-circle dot] < 10) are clumpy (i.e., containing at least one off-center clump). This fraction changes to 22% +/- 3% and 22% +/- 4% for intermediate (10 <= log[M-*/M-circle dot] <= 10.5) and high-mass (log[M*/M-circle dot] > 10.5) galaxies, in agreement with previous studies. When compared to similar-mass nonclumpy SFGs, low- and intermediate-mass clumpy SFGs tend to have higher star formation rates (SFRs) and bluer rest-frame U - V colors, while high-mass clumpy SFGs tend to be larger than nonclumpy SFGs. However, clumpy and nonclumpy SFGs have similar Sersic index, indicating a similar underlying density profile. Furthermore, we investigate how the UV luminosity of star-forming regions correlates with the physical properties of host galaxies. On average, more luminous star-forming regions reside in more luminous, smaller, and/or higher specific SFR galaxies and are found closer to their hosts' galactic centers.

Ingestion of the cycad toxins β-methylamino-L-alanine (BMAA) and azoxyglycosides is harmful to diverse organisms. However, some insects are specialized to feed on toxin-rich cycads with apparent immunity. Some cycad-feeding insects possess a common set of gut bacteria, which might play a role in detoxifying cycad toxins. Here, we investigated the composition of gut microbiota from a worldwide sample of cycadivorous insects and characterized the biosynthetic potential of bacteria isolated as putative keystone taxa. Cycadivorous insects shared a core gut microbiome consisting of six bacterial taxa, mainly belonging to the Proteobacteria, which we were able to isolate. To further investigate these potential keystone taxa from diverging lineages, we performed shotgun metagenomic sequencing of co-cultured bacterial sub-communities. We postulate and characterize four putative keystone bacteria from Serratia, Pantoea, and two different Stenotrophomonas lineages. The biosynthetic potential of these microorganisms includes a suite of biosynthetic gene clusters notably rich in siderophores and carotenoid-like aryl polyene pathways. Siderophore semi-untargeted metabolomics revealed a broad range of chemically related yet diverse iron-chelating metabolites, indicating a complex evolutionary landscape in which siderophores may have converged within the guts of cycadivorous insects. Among these, we provide evidence of the occurrence of an unprecedent desferrioxamine-like biosynthetic pathway that remains to be identified. These results provide a foundation for future investigations into how cycadivorous insects tolerate diets rich in azoxyglycosides, BMAA, and other cycad toxins, and highlight convergent evolution underlying chemical diversity.

Ingestion of the cycad toxins beta-methylamino-L-alanine (BMAA) and azoxyglycosides is harmful to diverse organisms. However, some insects are specialized to feed on toxin-rich cycads with apparent immunity. Some cycad-feeding insects possess a common set of gut bacteria, which might play a role in detoxifying cycad toxins. Here, we investigated the composition of gut microbiota from a worldwide sample of cycadivorous insects and characterized the biosynthetic potential of selected bacteria. Cycadivorous insects shared a core gut microbiome consisting of six bacterial taxa, mainly belonging to the Proteobacteria, which we were able to isolate. To further investigate selected taxa from diverging lineages, we performed shotgun metagenomic sequencing of co-cultured bacterial sub-communities. We characterized the biosynthetic potential of four bacteria from Serratia, Pantoea, and two different Stenotrophomonas lineages, and discovered a suite of biosynthetic gene clusters notably rich in siderophores. Siderophore semi-untargeted metabolomics revealed a broad range of chemically related yet diverse iron-chelating metabolites, including desferrioxamine B, suggesting the occurrence of an unprecedented desferrioxamine-like biosynthetic pathway that remains to be identified. These results provide a foundation for future investigations into how cycadivorous insects tolerate diets rich in azoxyglycosides, BMAA, and other cycad toxins, including a possible role for bacterial siderophores.

An analysis of the effect on the flow regime caused by reservoir operation is crucial to balancing the exploitation and protection of water resources. The long-term effect of this on the intraday scale and small storage capacity is considerable, but rarely analyzed. This study examines the world's largest dual-cascade hydro-junction, the Three Gorges Dam and Gezhouba Dam junction, as a case study, adopting eight indices to characterize the reservoir's inflow and outflow fluctuation. In doing this, we evaluate the alteration of the flow regime induced by an up-cascade reservoir and its alleviation caused by the down-cascade re-regulation. The results show: (1) an increment of the river flow fluctuation at the Three Gorges Dam, matched with hourly scale alleviation at the Gezhouba Dam; (2) a reduction (25.09 similar to 41.35%) in the quantitative indices of the river flow regime fluctuation; (3) perturbations on the power output. These findings provide references for developing methods to assess the re-regulation mechanisms in systems with upper- and lower-cascades.