The June 2016 Optical and Gamma-Ray Outburst and Optical Micro-Variability of the Blazar 3C454.3

The quasar 3C454.3 underwent a uniquely-structured multi-frequency outburst in June 2016. The blazar was observed in the optical $R$ band by several ground-based telescopes in photometric and polarimetric modes, at $\gamma$-ray frequencies by the \emph{Fermi}\ Large Area Telescope, and at 43 GHz with the Very Long Baseline Array. The maximum flux density was observed on 2016 June 24 at both optical and $\gamma$-ray frequencies, reaching $S^\mathrm{max}_\mathrm{opt}=18.91\pm0.08$ mJy and $S_\gamma^\mathrm{max} =22.20\pm0.18\times10^{-6}$ ph cm$^{-2}$ s$^{-1}$, respectively. The June 2016 outburst possessed a precipitous decay at both $\gamma$-ray and optical frequencies, with the source decreasing in flux density by a factor of 4 over a 24-hour period in $R$ band. Intraday variability was observed throughout the outburst, with flux density changes between 1 and 5 mJy over the course of a night. The precipitous decay featured statistically significant quasi-periodic micro-variability oscillations with an amplitude of $\sim 2$-$3\%$ about the mean trend and a characteristic period of 36 minutes. The optical degree of polarization jumped from $\sim3\%$ to nearly 20\% during the outburst, while the position angle varied by \sim120\degr. A knot was ejected from the 43 GHz core on 2016 Feb 25, moving at an apparent speed $v_\mathrm{app}=20.3c\pm0.8c$. From the observed minimum timescale of variability $\tau_\mathrm{opt}^\mathrm{min}\approx2$ hr and derived Doppler factor $\delta=22.6$, we find a size of the emission region $r\lesssim2.6\times10^{15}$ cm. If the quasi-periodic micro-variability oscillations are caused by periodic variations of the Doppler factor of emission from a turbulent vortex, we derive a rotational speed of the vortex $\sim0.2c$.Comment: 19 pages, 13 figures, 3 tables, accepted to the Astrophysical Journal 2019 March

Effects of stellar-mass primordial black holes on first star formation

We use cosmological hydrodynamic zoom-in simulations and semi-analytical models to study the effects of primordial black holes (PBHs) on first star formation. Our models self-consistently combine two competing effects: initial (isocurvature) perturbations induced by PBHs and BH accretion feedback. Focusing on PBHs with masses $\sim 30\ \rm M_{\odot}$, we find that the standard picture of first star formation in molecular-cooling minihaloes is not changed by PBHs, as the simulated star-forming gas clouds in the central parsec are very similar to those in the $\rm \Lambda CDM$ case when PBHs make up $f_{\rm PBH}\sim 10^{-4}-0.1$ of dark matter. With a dynamical friction timescale of $\sim 2-10\ \rm Myr$ when the central gas density reaches $10^{5}\ \rm cm^{-3}$, it is also unlikely that PBHs can sink into star-forming discs and affect the evolution of protostars, although they may interact with the stars during the main-sequence stage. At larger scales, PBHs tend to shift star formation to more massive haloes, and accelerate structure formation. The latter effect is stronger in regions with higher initial overdensities. For$f_{\rm PBH}\sim 10^{-4}-0.01$(allowed by observational constraints), the collapsed mass fraction of haloes hosting Population III stars is similar (within a factor of$\sim2$at$z\lesssim 30$) to that in$\rm \Lambda CDM$, implying that the impact of stellar-mass PBHs on the cosmic star formation history at$z\gtrsim 10$ is small. We also find that the Lyman-Werner photons from PBH accretion in atomic-cooling haloes may facilitate the formation of direct-collapse BHs.Comment: 23 pages, 18+3 figures, accepted by MNRAS, recognized Virgo and KAGRA in the LIGO-Virgo-KAGRA Scientific Collaboratio

Molecular targeted approaches to cancer therapy and prevention using chalcones.

There is an emerging paradigm shift in oncology that seeks to emphasize molecularly targeted approaches for cancer prevention and therapy. Chalcones (1,3-diphenyl-2-propen-1-ones), naturally-occurring compounds with widespread distribution in spices, tea, beer, fruits and vegetables, consist of open-chain flavonoids in which the two aromatic rings are joined by a three-carbon α, β-unsaturated carbonyl system. Due to their structural diversity, relative ease of chemical manipulation and reaction of α, β-unsaturated carbonyl moiety with cysteine residues in proteins, some lead chalcones from both natural products and synthesis have been identified in a variety of screening assays for modulating important pathways or molecular targets in cancers. These pathways and targets that are affected by chalcones include MDM2/p53, tubulin, proteasome, NF-kappa B, TRIAL/death receptors and mitochondria mediated apoptotic pathways, cell cycle, STAT3, AP-1, NRF2, AR, ER, PPAR-γ and β-catenin/Wnt. Compared to current cancer targeted therapeutic drugs, chalcones have the advantages of being inexpensive, easily available and less toxic; the ease of synthesis of chalcones from substituted benzaldehydes and acetophenones also makes them an attractive drug scaffold. Therefore, this review is focused on molecular targets of chalcones and their potential implications in cancer prevention and therapy

Annual growth progression, nutrient transformation, and carbon storage in tissues of Cunninghamia lanceolata monoculture in relation to soil quality indicators influenced by intraspecific competition intensity

Purpose: Nutrient distribution among tree tissues influence the growth, yield, and persistence of trees. One of the factors which can affect the nutrient concentrations can be stand density because competition for growth space and below-ground resources play a significant role in the productivity of plantation forests. Methods: This study analyzed the impact of planting density and soil quality indicators on the annual growth process, nutrient uptake, nutrient use efficiency, and carbon storage in mid-aged Chinese fir (Cunninghamia lanceolata) stands established at low, intermediate, and high-density. Stem density was 1450 trees hm2 (2.36 x 2.36 m spacing), 2460 trees hm2 (1.83 x 1.83 m spacing), and 3950 trees hm2 (1.44 x 1.44 m spacing) in low-, intermediate-, and high-density stands, respectively. Results: Stand density (R2 = 0.812) was the primal factor responsible for altering nutrients dynamics in tree components, while soil quality (R2 = 0.572) indicators play a secondary role. Across the years, the diameter and volume annual growth increment were more significant in the low-density, whereas height growth increment was more prominent in the intermediate-density. The highest carbon storage (33.78 t hm−2) was observed in the intermediate-density stand. Plant nutrient concentrations and nutrient use efficiency varied significantly among different densities (p<0.05). Significant associations of soil properties with biomass, height, and diameter were observed in intermediate-density. Conclusions: These patterns were co-regulated by planting density, tree growth rate, and soil nutrient status and reflected the plant tissue’s nutrient status, which could provide valuable information for sustainable nutrient management practices in tree plantations for maximizing productivity, yield, and long-term sustainability

Histone Lysine-Specific Methyltransferases and Demethylases in Carcinogenesis: New Targets for Cancer Therapy and Prevention

Aberrant histone lysine methylation that is controlled by histone lysine methyltransferases (KMTs) and demethylases (KDMs) plays significant roles in carcinogenesis. Infections by tumor viruses or parasites and exposures to chemical carcinogens can modify the process of histone lysine methylation. Many KMTs and KDMs contribute to malignant transformation by regulating the expression of human telomerase reverse transcriptase (hTERT), forming a fused gene, interacting with proto-oncogenes or being up-regulated in cancer cells. In addition, histone lysine methylation participates in tumor suppressor gene inactivation during the early stages of carcinogenesis by regulating DNA methylation and/or by other DNA methylation independent mechanisms. Furthermore, recent genetic discoveries of many mutations in KMTs and KDMs in various types of cancers highlight their numerous roles in carcinogenesis and provide rare opportunities for selective and tumor-specific targeting of these enzymes. The study on global histone lysine methylation levels may also offer specific biomarkers for cancer detection, diagnosis and prognosis, as well as for genotoxic and non-genotoxic carcinogenic exposures and risk assessment. This review summarizes the role of histone lysine methylation in the process of cellular transformation and carcinogenesis, genetic alterations of KMTs and KDMs in different cancers and recent progress in discovery of small molecule inhibitors of these enzymes