Electrospinning of poly(methyl methacrylate) nanofibers in a pump-free process

The effects of processing parameters, including solution concentration, viscosity, nozzle diameter, voltage bias and the nozzle to collector distance, on the morpho logy and diameters of poly(methyl methacrylate) (PMMA) fibers have been systematically investigated, using a unique pump-free electrospinning method. For PMMA solution concentrations less than the critical entanglement concentration, c e, prolate spheroidshaped droplets or beads with fibers were formed, whereas at concentrations above c e, good quality beadfree fibers were formed. Quantitative analysis revealed a linear dependence between the solution viscosity and fiber diameter. Larger fiber diameters were achieved by increasing the nozzle diameter and voltage bias. Increasing the bias voltage has the additional effect of broadening the diameter distribution, as a result of splaying and splitting. By contrast, when the strength of the electrical field was reduced by increasing the distance between the nozzle and collector, the overall fiber dia meter was reduced

Radial Growth of Qilian Juniper on the Northeast Tibetan Plateau and Potential Climate Associations

There is controversy regarding the limiting climatic factor for tree radial growth at the alpine treeline on the northeastern Tibetan Plateau. In this study, we collected 594 increment cores from 331 trees, grouped within four altitude belts spanning the range 3550 to 4020 m.a.s.l. on a single hillside. We have developed four equivalent ring-width chronologies and shown that there are no significant differences in their growth-climate responses during 1956 to 2011 or in their longer-term growth patterns during the period AD 1110–2011. The main climate influence on radial growth is shown to be precipitation variability. Missing ring analysis shows that tree radial growth at the uppermost treeline location is more sensitive to climate variation than that at other elevations, and poor tree radial growth is particularly linked to the occurrence of serious drought events. Hence water limitation, rather than temperature stress, plays the pivotal role in controlling the radial growth of Sabina przewalskii Kom. at the treeline in this region. This finding contradicts any generalisation that tree-ring chronologies from high-elevation treeline environments are mostly indicators of temperature changes

Superconductivity in HfTe5 across weak to strong topological insulator transition induced via pressures

Recently, theoretical studies show that layered HfTe5 is at the boundary of weak & strong topological insulator (TI) and might crossover to a Dirac semimetal state by changing lattice parameters. The topological properties of 3D stacked HfTe5 are expected hence to be sensitive to pressures tuning. Here, we report pressure induced phase evolution in both electronic & crystal structures for HfTe5 with a culmination of pressure induced superconductivity. Our experiments indicated that the temperature for anomaly resistance peak (Tp) due to Lifshitz transition decreases first before climbs up to a maximum with pressure while the Tp minimum corresponds to the transition from a weak TI to strong TI. The HfTe5 crystal becomes superconductive above ~5.5 GPa where the Tp reaches maximum. The highest superconducting transition temperature (Tc) around 5 K was achieved at 20 GPa. Crystal structure studies indicate that HfTe5 transforms from a Cmcm phase across a monoclinic C2/m phase then to a P-1 phase with increasing pressure. Based on transport, structure studies a comprehensive phase diagram of HfTe5 is constructed as function of pressure. The work provides valuable experimental insights into the evolution on how to proceed from a weak TI precursor across a strong TI to superconductors

Cyclodextrin/cellulose hydrogel with gallic acid to prevent wound infection

Cyclodextrin-based hydrogels have been described as suitable for the controlled-release of bioactive molecules to be used as wound dressing. These materials have major advantages, since they gather the hydrogel properties (high degree of swelling and easy manipulation) and the encapsulation ability of cyclodextrins. β-cyclodextrin (β) or hydroxypropyl-β-cyclodextrin (HPβ) was cross-linked (1,4-butanediol diglycidyl ether) with hydroxypropyl methylcellulose under mild conditions. The hydrogels were chemically characterized by swelling degree, FTIR, DSC and contact angle. The gallic acid loading and release was also analysed, as well the antibacterial activity and cytotoxicity of the polymeric networks. The hydrogels obtained were firm and transparent, with good swelling ability. The gel-HPβ had a surface more hydrophilic when compared with the gel-β. Nevertheless, both hydrogels were capable to incorporate gallic acid and sustain the release for 48 h. The antibacterial activity of gallic acid was maintained after its adsorption within the polymeric matrix, as well as, gallic acid effect on fibroblast proliferation. Therefore, gel-β and gel-HPβ conjugated with gallic acid were shown to be a viable option for antibacterial wound dressing.The authors thank the FCT Strategic Projects PEst-OE/EQB/LA0023/2013, PEst-C/CTM/UI0264/2011, the Project "BioHealth-Biotechnology and Bioengineering approaches to improve health quality'', Ref. NORTE-07-0124-FEDER-000027, co-funded by the Programa Operacional Regional doNorte (ON.2-ONovoNorte), QREN, FEDER, and E. Pinho grant (SFRH/BD/62665/2009)

Observation of a ppb mass threshoud enhancement in \psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) decay

The decay channel $\psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p})$ is studied using a sample of $1.06\times 10^8$ $\psi^\prime$ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the $p\bar{p}$ invariant mass spectrum. The enhancement can be fit with an $S$-wave Breit-Wigner resonance function with a resulting peak mass of $M=1861^{+6}_{-13} {\rm (stat)}^{+7}_{-26} {\rm (syst)} {\rm MeV/}c^2$ and a narrow width that is $\Gamma<38 {\rm MeV/}c^2$ at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with those of any known meson resonance.Comment: 5 pages, 3 figures, submitted to Chinese Physics

MicroRNA-377 suppresses initiation and progression of esophageal cancer by inhibiting CD133 and VEGF

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Experimental studies of e + e -→ some charmless processes containing K S0 at √s = 3.773 and 3.65 GeV

We measure the observed cross sections for the charmless processes e + e -→K S0 K - K - K + π ++ c.c., K S0 K - π + η+c.c., K S0 K - π + π + π - η+c.c., K S0 K - K - K + π + η+c.c., K S0 K - K - K + π + π 0+c.c., K S0 K - ρ ++c.c. and K S0 K - π + ρ 0+c.c. We also extract upper limits on the branching fractions for ψ(3770) decays into these final states at 90% C.L. Analyzed data samples correspond to 17.3 pb-1 and 6.5 pb-1 integrated luminosities registered, respectively, at √s = 3.773 and 3.65 GeV, with the BES-II detector at the BEPC collider. © 2009 Springer-Verlag / Società Italiana di Fisica.published_or_final_versionSpringer Open Choice, 21 Feb 201

Is Malaysia’s banded langur, Presbytis femoralis femoralis, actually Presbytis neglectus neglectus? Taxonomic revision with new insights on the radiation history of the Presbytis species group in Southeast Asia

The disjunct distribution of Presbytis femoralis subspecies across Sumatra (P. f. percura), southern (P. f. femoralis) and northern (P. f. robinsoni) Peninsular Malaysia marks the unique vicariance events in the Sunda Shelf. However, the taxonomic positions and evolutionary history of P. f. femoralis are unresolved after decades of research. To elucidate this evolutionary history, we analyzed 501 base pairs of the mitochondrial HVSI gene from 25 individuals representing Malaysia’s banded langur, with the addition of 29 sequences of Asian Presbytis from Genbank. Our results revealed closer affinity of P. f. femoralis to P. m. mitrata and P. m. sumatrana while maintaining the monophyletic state of P. f. femoralis as compared to P. f. robinsoni. Two central theses were inferred from the results; (1) P. f. femoralis does not belong in the same species classification as P. f. robinsoni, and (2) P. f. femoralis is the basal lineage of the Presbytis in Peninsular Malaysia. Proving the first hypothesis through genetic analysis, we reassigned P. f. femoralis of Malaysia to Presbytis neglectus (Schlegel’s banded langur) (Schlegel in Revue Methodique, Museum d’Histoire Naturelle des Pays-Bas 7:1, 1876) following the International Code of Zoological Nomenclature (article 23.3). The ancestors of P. neglectus are hypothesized to have reached southern Peninsular Malaysia during the Pleistocene and survived in refugium along the western coast. Consequently, they radiated upward, forming P. f. robinsoni and P. siamensis resulting in the highly allopatric distribution in Peninsular Malaysia. This study has successfully resolved the taxonomic position of P. neglectus in Peninsular Malaysia while providing an alternative biogeographic theory for the Asian Presbytis

Search for ψ(3770)→ charmless final states involving η or π0 mesons

We search for ψ(3770) → π+π-η, K+K-η, pp̄η, ρ0π+π-η, K+K-π+π-η, pp̄π+π-η, pp̄K+K-η and pp̄K+K- π0 using data samples of 17.3 and 6.5 pb-1 integrated luminosities recorded at the center-of-mass energies of 3.773 and 3.65 GeV, respectively, by the BES-II detector operating at the BEPC collider. We obtain cross section measurements at both energies and upper limits on ψ(3770) decay branching fractions to the final states studied. © © Springer-Verlag / Società Italiana di Fisica 2010.published_or_final_versionSpringer Open Choice, 21 Feb 201