Possible interpretation of the ZbZ_b(10610) and ZbZ_b(10650) in a chiral quark model

Motivated by the two charged bottomonium-like resonances $Z_b$(10610) and $Z_b$(10650) newly observed by the Belle collaboration, the possible molecular states composed of a pair of heavy mesons, $B\bar{B}, B\bar{B}^*, B^*\bar{B}^*, B_s\bar{B}$, etc (in S-wave), are investigated in the framework of chiral quark models by the Gaussian expansion method. The bound states $B\bar{B}^*$ and $B^*\bar{B}^*$ with quantum numbers $I(J^{PC})=1(1^{+-})$, which are good candidates for the $Z_b(10610)$ and $Z_b(10650)$ respectively, are obtained. Other three bound states $B\bar{B}^*$ with $I(J^{PC})=0(1^{++})$, $B^*\bar{B}^*$ with $I(J^{PC})=1(0^{++}), 0(2^{++})$ are predicted. These states may be observed in open-bottom or hidden-bottom decay channel of highly excited $\Upsilon$. When extending directly the quark model to the hidden color channel of the multi-quark system, more deeply bound states are found. Future experimental search of those states will cast doubt on the validity of applying the chiral constituent quark model to the hidden color channel directly.Comment: 13 pages, 1 figure, title and some arguments in the abstract and section 5 are revised, results unchange

Systematical investigation on the stability of doubly heavy tetraquark states

We systematically investigate the stability of the doubly heavy tetraquark states $[QQ][\bar{q}\bar{q}]$ ($Q=c$ and $b$, $q=u$, $d$ and $s$) within the framework of the color flux-tube model involving a multibody confinement potential, $\sigma$-exchange, one-gluon-exchange and one-Goldstone-boson-exchange interactions. Our numerical analysis indicates that the states $[bb][\bar{u}\bar{d}]$ with $01^+$ and $[bb][\bar{u}\bar{s}]$ with $\frac{1}{2}1^+$ are the most promising stable states against strong interactions. The states $[cc][\bar{u}\bar{d}]$ with $01^+$, $[bc][\bar{u}\bar{d}]$ with $00^+$, $01^+$, and $12^+$, and $[bb][\bar{u}\bar{d}]$ with $01^-$ and $12^+$ as stable states are also predicted in the color flux-tube model. The dynamical mechanism producing those stable doubly heavy tetraquark states are discussed in the color flux-tube model.Comment: 10 pages, 9 table

Do Soil Chemical Changes Contribute to the Dominance of Blady Grass (Imperata cylindrica) in Surface Fire-Affected Forests?

Imperata cylindrica is a perennial grass that often proliferates in fire-affected forests. Recent fire events have been consistently associated with a lowering of soil nitrogen (N) to phosphorus (P) ratios. Thus, I. cylindrica might have a tendency toward P-limited growth and/or tolerance for low soil N availability that confers a competitive advantage post-fire. We contrasted soil and I. cylindrica chemistry between recently burned and unburned areas in eastern Australia. Imperata cylindrica foliar N:P ratios were 21% lower in burned areas than in unburned areas, reflecting an increase in the uptake of P, but not N, post-fire, consistent with P-limitation. We then grew I. cylindrica seedlings in soils with differing fire-exposure histories and subjected them to various resource amendments (including N and P addition). Survival of I. cylindrica seedlings was not affected by the fire-exposure history of soil, but was reduced by 66% through N-addition. Soil fire history did not significantly affect I. cylindrica growth, but addition of P greatly enhanced I. cylindrica growth, particularly on unburned soils. Our results indicate that the association between I. cylindrica and forest fire regime could be facilitated, in part, by the short-term positive effect of fire on soil phosphorus and the long-term positive effect of fire-exclusion on soil nitrogen, particularly on well-weathered soils

Modeling the effects of tree species and incubation temperature on soil's extracellular enzyme activity in 78-year-old tree plantations

Forest plantations have been widely used as an effective measure for increasing soil carbon (C), and nitrogen (N) stocks and soil enzyme activities play a key role in soil C and N losses during decomposition of soil organic matter. However, few studies have been carried out to elucidate the mechanisms behind the differences in soil C and N cycling by different tree species in response to climate warming. Here, we measured the responses of soil's extracellular enzyme activity (EEA) to a gradient of temperatures using incubation methods in 78-year-old forest plantations with different tree species. Based on a soil enzyme kinetics model, we established a new statistical model to investigate the effects of temperature and tree species on soil EEA. In addition, we established a tree species–enzyme–C∕N model to investigate how temperature and tree species influence soil C∕N contents over time without considering plant C inputs. These extracellular enzymes included C acquisition enzymes (β-glucosidase, BG), N acquisition enzymes (N-acetylglucosaminidase, NAG; leucine aminopeptidase, LAP) and phosphorus acquisition enzymes (acid phosphatases). The results showed that incubation temperature and tree species significantly influenced all soil EEA and Eucalyptus had 1.01–2.86 times higher soil EEA than coniferous tree species. Modeling showed that Eucalyptus had larger soil C losses but had 0.99–2.38 times longer soil C residence time than the coniferous tree species over time. The differences in the residual soil C and N contents between Eucalyptus and coniferous tree species, as well as between slash pine (Pinus elliottii Engelm. var. elliottii) and hoop pine (Araucaria cunninghamii Ait.), increase with time. On the other hand, the modeling results help explain why exotic slash pine can grow faster, as it has 1.22–1.38 times longer residual soil N residence time for LAP, which mediate soil N cycling in the long term, than native coniferous tree species like hoop pine and kauri pine (Agathis robusta C. Moore). Our results will be helpful for understanding the mechanisms of soil C and N cycling by different tree species, which will have implications for forest management.Griffith Sciences, Griffith School of EnvironmentFull Tex

Systematic study of pentaquark states: qqq−qqˉqqq-q\bar{q} configuration

Group theoretic method for the systematic study of five-quark states with meson-baryon ($q\bar{q}-q^3$) configuration is developed. The calculation of matrix elements of many body Hamiltonian is simplified by transforming the physical bases (meson-baryon quark cluster bases) to symmetry bases (group chain classified bases), where the fractional parentage expansion method can be used. Three quark models, the naive Glashow-Isgur model, Salamanca chiral quark model and quark delocalization color screening model, are used to show the general applicability of the method and general results of constituent quark models for five-quark states are given. The method can also be useful in the calculation of meson-baryon scattering and the study of the five-quark components effect in baryon structure. The physical contents of different model configurations for the same multi-quark system can also be compared through the transformation between different physical bases to the same set of symmetry bases.Comment: 30 pages, 8 figure

Widespread upper-ocean deoxygenation in the Alpine-Mediterranean Tethys during the Toarcian Oceanic Anoxic Event

The early Toarcian (∼183 Ma) was characterized by pronounced climate warming associated with massive release of 13C-depleted carbon to the exogenic system, as evidenced by globally recognized negative carbon-isotope excursions (N-CIE) in biospheric carbon reservoirs. Global warming during this interval triggered a variety of environmental perturbations, of which large-scale marine deoxygenation (as indicated by the presence of widespread organic carbon-rich deposits) is arguably diagnostic and led to the naming of the interval in question as the Toarcian Oceanic Anoxic Event (T-OAE). Nevertheless, the spatial variability of water-column redox during the T-OAE is unclear because most sedimentological and geochemical methods used to infer marine redox are likely reflective of bottom-water and/or pore-water conditions. Here we report new I/(Ca + Mg) and Cerium (Ce)-anomaly data from two carbonate successions from northern Italy that encompass the T-OAE interval. Both successions were deposited in the Alpine-Mediterranean Tethys; one in a shallow-water platform setting and the other within a pelagic environment. Both successions record an abrupt drop in I/(Ca + Mg) values, coupled with positive excursions in Ce-anomaly records at the onset of the T-OAE N-CIE. The synchronized changes in marine iodate depletion and Ce enrichment suggest widespread and significant upper-ocean deoxygenation in the Alpine-Mediterranean Tethys. This redox pattern is attributed to an expanded oxygen minimum zone (OMZ) formed as a result of sluggish oceanic circulation under climate warming, augmented by enhanced dissolved oxygen consumption due to increased nutrient availability and the consequent eutrophication in both proximal and distal settings. Because reduced seawater dissolved oxygen [O2] would increase the ecological stress and constrict any potentially hospitable habitats, the broad synchroneity between biotic turnovers and upper-ocean deoxygenation in the Alpine-Mediterranean Tethys is compatible with a potential causal link

Cationic Polybutyl Cyanoacrylate Nanoparticles for DNA Delivery

To enhance the intracellular delivery potential of plasmid DNA using nonviral vectors, we used polybutyl cyanoacrylate (PBCA) and chitosan to prepare PBCA nanoparticles (NPs) by emulsion polymerization and prepared NP/DNA complexes through the complex coacervation of nanoparticles with the DNA. The object of our work is to evaluate the characterization and transfection efficiency of PBCA-NPs. The NPs have a zeta potential of 25.53 mV at pH 7.4 and size about 200 nm. Electrophoretic analysis suggested that the NPs with positive charges could protect the DNA from nuclease degradation and cell viability assay showed that the NPs exhibit a low cytotoxicity to human hepatocellular carcinoma (HepG2) cells. Qualitative and quantitative analysis of transfection in HepG2 cells by the nanoparticles carrying plasmid DNA encoding for enhanced green fluorescent protein (EGFP-N1) was done by digital fluorescence imaging microscopy system and fluorescence-activated cell sorting (FACS). Qualitative results showed highly efficient expression of GFP that remained stable for up to 96 hours. Quantitative results from FACS showed that PBCA-NPs were significantly more effective in transfecting HepG2 cells after 72 hours postincubation. The results of this study suggested that PBCA-NPs have favorable properties for nonviral delivery

Modulation effect of sulfated polysaccharide from Sargassum fusiforme on gut microbiota and their metabolites in vitro fermentation

The present study demonstrated the digestion behavior and fermentation characteristics of a sulfated polysaccharide from Sargassum fusiforme (SFSP) in the simulated digestion tract environment. The results showed that the molecular weight of two components in SFSP could not be changed by simulated digestion, and no free monosaccharide was produced. This indicates that most of SFSP can reach the colon as prototypes. During the fermentation with human intestinal flora in vitro, the higher-molecular-weight component of SFSP was utilized, the total sugar content decreased by 16%, the reducing sugar content increased, and the galactose content in monosaccharide composition decreased relatively. This indicates that SFSP can be selectively utilized by human intestinal flora. At the same time, SFSP also changed the structure of intestinal flora. Compared with the blank group, SFSP significantly increased the abundance of Bacteroidetes and decreased the abundance of Firmicutes. At the genus level, the abundances of Bacteroides and Megamonas increased, while the abundances of Shigella, Klebsiella, and Collinsella decreased. Moreover, the concentrations of total short-chain fatty acids (SCFAs), acetic, propionic and n-butyric acids significantly increased compared to the blank group. SFSP could down-regulate the contents of trimethylamine, piperidone and secondary bile acid in fermentation broth. The contents of nicotinic acid, pantothenic acid and other organic acids were increased. Therefore, SFSP shows significant potential to regulate gut microbiota and promote human health