Blow up solutions to a viscoelastic fluid system and a coupled Navier-Stokes/Phase-Field system in R^2

We find explicit solutions to both the Oldroyd-B model with infinite Weissenberg number and the coupled Navier-Stokes/Phase-Field system. The solutions blow up in finite time.Comment: 5 page

Monitoring fine and ultrafine particles in the atmosphere of a Southeast Chinese city

There have been few studies on submicron particles in the atmosphere reported from developing countries. With rapid economic development, the size of the road vehicle fleet has increased dramatically in China. The increase in vehicle emissions has raised concerns about air quality, especially in the urban areas of this developing country. A model study was conducted in Hangzhou, a city in Southeast China, with the aim of characterizing the emission patterns of submicron particles ≤1.0 micron from on-road vehicles and the impact of vehicle density and speed on the concentrations of submicron particles in the atmosphere. Results showed that the average ultrafine particle (UFP) number concentration was 45805 particles cm−3 and the average mass concentration of particulate matter 1.0 (PM1.0) was 217 μg m−3 during the survey period. Autoregressive Integrated Moving Average modelling results indicated that an increase of vehicle density and driving speed were positively correlated with the increase of UFP and PM1.0 concentrations (p < 0.05) in the atmosphere. Results from this study suggest that vehicle density and driving speed are significant predictors of submicron particle emissions. This study provides first hand information for future investigations on the submicron particle emissions in Hangzhou, a city with rapidly increasing vehicle numbers and for further investigations into a possible causal relationship between submicron particles and health effects on local residents

The mechanism of the polarization dependence of the optical transmission in subwavelength metal hole arrays

We investigate the mechanism of extraordinary optical transmission in subwave-length metal hole arrays. Experimental results for the arrays consisting of square or rectangle holes are well explained about the dependence of transmission strength on the polarization direction of the incident light. This polarization dependence occurs in each single-hole. For a hole array, there is in addition an interplay between the adjacent holes which is caused by the transverse magnetic field of surface plasmon polariton on the metal film surfaces. Based on the detailed study of a single-hole and two-hole structures, a simple method to calculate the total tranmissivity of hole arrays is proposed.Comment: 34 pages, 7 figure

Molecular cloning and characterization of a group 3 LEA gene from Agropyron mongolicum Keng

Late embryogenesis-abundant (LEA) protein is one of the components involved in desiccation tolerance (DT) by maintaining cellular structures in the dry state. In this study, a member of the group 3 LEA, MwLEA1, was cloned from Mongolian wheatgrass (Agropyron mongolium Keng) based on a homologous sequence from wheat (Triticum aestivum L.). Its full-length cDNA sequence was 705 bp, encoding a protein of 187 amino acids. The amino acid sequence comparison revealed its high homology with LEA proteins from other plant species. The deduced MwLEA1 protein had five repeat 11- amino-acid motifs, with a molecular weight of 19.4 kDa and a theoretical isoelectric point of 8.8. Subcellular localization indicated that the MwLEA1 was localized in the nucleus of the onion epithelial cell. Under water stress conditions, MwLEA1 exhibited different expression levels, which was higher in root and shoot but lowest in leaf. The expression profiling under different stresses indicated that MwLEA1 played roles in responses to water, salt stresses as well as abscisic acid (ABA) regulation. The gene of MwLEA1 was transformed into tobaccos by Agrobacterium tumefaciens-mediated method. Eleven regenerated plants were analyzed by polymerase chain reaction (PCR) and southern blotting, and 6 of them were proved to be transgenic plants.Key words: Agropyron mongolium Keng, cloning, late embryogenesis abundant, subcellular localization, expression, transformation

APOBEC3G-UBA2 fusion as a potential strategy for stable expression of APOBEC3G and inhibition of HIV-1 replication

<p>Abstract</p> <p>Background</p> <p>Although APOBEC3G protein is a potent and innate anti-HIV-1 cellular factor, HIV-1 Vif counteracts the effect of APOBEC3G by promoting its degradation through proteasome-mediated proteolysis. Thus, any means that could prevent APOBEC3G degradation could potentially enhance its anti-viral effect. The UBA2 domain has been identified as an intrinsic stabilization signal that protects protein from proteasomal degradation. In this pilot study, we tested whether APOBEC3G, when it is fused with UBA2, can resist Vif-mediated proteasomal degradation and further inhibit HIV-1 infection.</p> <p>Results</p> <p>APOBEC3G-UBA2 fusion protein is indeed more resistant to Vif-mediated degradation than APOBEC3G. The ability of UBA2 domain to stabilize APOBEC3G was diminished when polyubiquitin was over-expressed and the APOBEC3G-UBA2 fusion protein was found to bind less polyubiquitin than APOBEC3G, suggesting that UBA2 stabilizes APOBEC3G by preventing ubiquitin chain elongation and proteasome-mediated proteolysis. Consistently, treatment of cells with a proteasome inhibitor MG132 alleviated protein degradation of APOBEC3G and APOBEC3G-UBA2 fusion proteins. Analysis of the effect of APOBEC3G-UBA2 fusion protein on viral infectivity indicated that infection of virus packaged from HEK293 cells expressing APOBEC3G-UBA2 fusion protein is significantly lower than those packaged from HEK293 cells over-producing APOBEC3G or APOBEC3G-UBA2 mutant fusion proteins.</p> <p>Conclusion</p> <p>Fusion of UBA2 to APOBEC3G can make it more difficult to be degraded by proteasome. Thus, UBA2 could potentially be used to antagonize Vif-mediated APOBEC3G degradation by preventing polyubiquitination. The stabilized APOBEC3G-UBA2 fusion protein gives stronger inhibitory effect on viral infectivity than APOBEC3G without UBA2.</p

Observable Optimal State Points of Sub-additive Potentials

For a sequence of sub-additive potentials, Dai [Optimal state points of the sub-additive ergodic theorem, Nonlinearity, 24 (2011), 1565-1573] gave a method of choosing state points with negative growth rates for an ergodic dynamical system. This paper generalizes Dai's result to the non-ergodic case, and proves that under some mild additional hypothesis, one can choose points with negative growth rates from a positive Lebesgue measure set, even if the system does not preserve any measure that is absolutely continuous with respect to Lebesgue measure.Comment: 16 pages. This work was reported in the summer school in Nanjing University. In this second version we have included some changes suggested by the referee. The final version will appear in Discrete and Continuous Dynamical Systems- Series A - A.I.M. Sciences and will be available at http://aimsciences.org/journals/homeAllIssue.jsp?journalID=

Melting behavior of ultrathin titanium nanowires

The thermal stability and melting behavior of ultrathin titanium nanowires with multi-shell cylindrical structures are studied using molecular dynamic simulation. The melting temperatures of titanium nanowires show remarkable dependence on wire sizes and structures. For the nanowire thinner than 1.2 nm, there is no clear characteristic of first-order phase transition during the melting, implying a coexistence of solid and liquid phases due to finite size effect. An interesting structural transformation from helical multi-shell cylindrical to bulk-like rectangular is observed in the melting process of a thicker hexagonal nanowire with 1.7 nm diameter.Comment: 4 pages, 4 figure

Atom chip based generation of entanglement for quantum metrology

Atom chips provide a versatile `quantum laboratory on a microchip' for experiments with ultracold atomic gases. They have been used in experiments on diverse topics such as low-dimensional quantum gases, cavity quantum electrodynamics, atom-surface interactions, and chip-based atomic clocks and interferometers. A severe limitation of atom chips, however, is that techniques to control atomic interactions and to generate entanglement have not been experimentally available so far. Such techniques enable chip-based studies of entangled many-body systems and are a key prerequisite for atom chip applications in quantum simulations, quantum information processing, and quantum metrology. Here we report experiments where we generate multi-particle entanglement on an atom chip by controlling elastic collisional interactions with a state-dependent potential. We employ this technique to generate spin-squeezed states of a two-component Bose-Einstein condensate and show that they are useful for quantum metrology. The observed 3.7 dB reduction in spin noise combined with the spin coherence imply four-partite entanglement between the condensate atoms and could be used to improve an interferometric measurement by 2.5 dB over the standard quantum limit. Our data show good agreement with a dynamical multi-mode simulation and allow us to reconstruct the Wigner function of the spin-squeezed condensate. The techniques demonstrated here could be directly applied in chip-based atomic clocks which are currently being set up

Observational constraint on dynamical evolution of dark energy

We use the Constitution supernova, the baryon acoustic oscillation, the cosmic microwave background, and the Hubble parameter data to analyze the evolution property of dark energy. We obtain different results when we fit different baryon acoustic oscillation data combined with the Constitution supernova data to the Chevallier-Polarski-Linder model. We find that the difference stems from the different values of $\Omega_{m0}$. We also fit the observational data to the model independent piecewise constant parametrization. Four redshift bins with boundaries at $z=0.22$, 0.53, 0.85 and 1.8 were chosen for the piecewise constant parametrization of the equation of state parameter $w(z)$ of dark energy. We find no significant evidence for evolving $w(z)$. With the addition of the Hubble parameter, the constraint on the equation of state parameter at high redshift isimproved by 70%. The marginalization of the nuisance parameter connected to the supernova distance modulus is discussed.Comment: revtex, 16 pages, 5 figures, V2: published versio