Dependence of the Critical Adsorption Point on Surface and Sequence Disorders for Self-Avoiding Walks Interacting with a Planar Surface

The critical adsorption point (CAP) of self-avoiding walks (SAW) interacting with a planar surface with surface disorder or sequence disorder has been studied. We present theoretical equations, based on ones previously developed by Soteros and Whittington (J. Phys. A.: Math. Gen. 2004, 37, R279-R325), that describe the dependence of CAP on the disorders along with Monte Carlo simulation data that are in agreement with the equations. We also show simulation results that deviate from the equations when the approximations used in the theory break down. Such knowledge is the first step toward understanding the correlation of surface disorder and sequence disorder during polymer adsorption.Comment: 29 pages, 8 figure

Density functional theory for freezing transition of vortex-line liquid with periodic layer pinning

By the density functional theory for crystallization, it is shown that for vortex lines in an underlying layered structure a smectic phase with period m=2 can be stabilized by strong layer pinning. The freezing of vortex liquid is then two-step, a second-order liquid-smectic transition and a first-order smectic-lattice transition. DFT also indicates that a direct, first-order liquid-lattice transition preempts the smectic order with m>2 irrespectively of the pinning strength. Possible H-T phase diagrams are mapped out. Implications of the DFT results to the interlayer Josephson vortex system in high-Tc cuprates are given.Comment: 4 pages, 5 figures, references adde

Auxin response factor 6A regulates photosynthesis, sugar accumulation, and fruit development in tomato.

Auxin response factors (ARFs) are involved in auxin-mediated transcriptional regulation in plants. In this study, we performed functional characterization of SlARF6A in tomato. SlARF6A is located in the nucleus and exhibits transcriptional activator activity. Overexpression of SlARF6A increased chlorophyll contents in the fruits and leaves of tomato plants, whereas downregulation of SlARF6A decreased chlorophyll contents compared with those of wild-type (WT) plants. Analysis of chloroplasts using transmission electron microscopy indicated increased sizes of chloroplasts in SlARF6A-overexpressing plants and decreased numbers of chloroplasts in SlARF6A-downregulated plants. Overexpression of SlARF6A increased the photosynthesis rate and accumulation of starch and soluble sugars, whereas knockdown of SlARF6A resulted in opposite phenotypes in tomato leaves and fruits. RNA-sequence analysis showed that regulation of SlARF6A expression altered the expression of genes involved in chlorophyll metabolism, photosynthesis and sugar metabolism. SlARF6A directly bound to the promoters of SlGLK1, CAB, and RbcS genes and positively regulated the expression of these genes. Overexpression of SlARF6A also inhibited fruit ripening and ethylene production, whereas downregulation of SlARF6A increased fruit ripening and ethylene production. SlARF6A directly bound to the SAMS1 promoter and negatively regulated SAMS1 expression. Taken together, these results expand our understanding of ARFs with regard to photosynthesis, sugar accumulation and fruit development and provide a potential target for genetic engineering to improve fruit nutrition in horticulture crops

Dissipative particle dynamics simulation on a ternary system with nanoparticles, double-hydrophilic block copolymers, and solvent

Dissipative particle dynamics (DPD) simulations are performed to study the aggregation of hydrophobic nanoparticles in the presence of double-hydrophilic block copolymer (DHBC). A single compact spherical nanoparticle aggregate is formed in the absence of DHBC. The response of the aggregate to a continuous increase in the concentration of DHBC has been investigated in detail. We observe the evolvement from single spherical aggregate, through single ellipsoidal aggregate, single platelike aggregate, single long and curly rod, dispersed aggregates, then to hexagonally packed cylinders, and ultimately to ordered lamellar structures upon slow addition of DHBC chains. However, when nanoparticles and DHBCs are added into the system simultaneously at the beginning of simulation, we only obtain single spherical aggregate, dispersed aggregates, hexagonally packed cylinders, and ordered lamellar structures at different concentrations of DHBC. Phase diagrams of structures against concentration of DHBC are presented for these two methods, and the stabilities of structures obtained with the two methods are compared. © 2008 American Chemical Society

The contact erosion characteristics of SF6 circuit breaker based on dynamic resistance measurement method

For the purpose of investigating the contact erosion characteristics in breaking process of SF6 breaker, an erosion experiment was conducted on the tested SF6 circuit breaker. As a result, the relationship between the dynamic resistance and contact travel in various levels of degradation was acquired. The SF6 contact state parameters were obtained from the experimental results. Considering the parameters change, the follow-up conclusions can be sum up: (1) The contact travel’s minimum value is deduced to be 14.2 mm; (2) The numerical value of contact resistance has an acceptable range, which is 50∼150μΩ for main contact and 200∼400μΩ for arcing contact, respectively. (3) The measured value of arcing contact attenuate length is 0.318 mm, which remains unchanged in each erosion test. Taking all the mentioned above into consideration, we research on the contact material erosion process during the opening operation and the effect on the circuit breaker property. In the meantime, the theoretical calculation formula of length decrement in arcing contact is deduced. Based on the formula, the calculated value is 0.268 mm for each trial, which is close to the measured value of 0.318 mm. At last, the prediction methods for the SF6 circuit breaker’s electrical life is summarized

An AC active power regulation method for MMC by employing the internal energy

Similar to the onshore wind power integrated through AC transmission, the offshore wind power integrated through the modular multilevel converter (MMC) based HVDC also lays remarkable impacts on the stability of the power system. According to grid codes, offshore wind power should be capable of adjusting its active power fast. This paper proposes a fast regulation method at the onshore point of common coupling for offshore wind power by utilizing the energy stored in the distributed capacitors in the MMC. By carefully designing the curve of capacitor energy, the active power can vary expectedly. Meanwhile, no disturbance is placed on the DC-side active power or DC voltage. The effectiveness of the proposed method is verified by electromagnetic simulation

Sensitive Detection of a Modified Base in Single-Stranded DNA by a Single-Walled Carbon Nanotube

In this work, we use molecular dynamics simulations to study the responses of the configuration of single-strand DNA (ssDNA) within a carbon nanotube (CNT) and the concomitant ion flow to a single modified base, i.e., benzoimidazole (Bzim)-modified 5-hydroxymethyl cytosine (5hmC). Our simulation results show the Bzim-modified 5hmC can considerably increase the ion flow through a single-walled carbon nanotube (SWCNT), despite its larger size, which is consistent with prior experimental results. This phenomenon is attributed to enhanced adsorption of DNA to the interior wall of the CNT driven by the Bzim-modified 5hmC, leading to a reduced steric effect on ion transport through the CNT. As revealed in this work, the distribution of ssDNA can be affected by limited change in the interactions with the CNT surface. Such behavior of ssDNA within small-sized CNTs can be exploited to further improve the sensitivity of nanopore detection

R2R3 MYB‐dependent auxin signalling regulates trichome formation, and increased trichome density confers spider mite tolerance on tomato

Unicellular and multicellular tomato trichomes function as mechanical and chemical barriers against herbivores. Auxin treatment increased the formation of II, V and VI type trichomes in tomato leaves. The auxin response factor gene SlARF4, which was highly expressed in II, V and VI type trichomes, positively regulated the auxin-induced formation of II, V and VI type trichomes in the tomato leaves. SlARF4 overexpression plants with high densities of these trichomes exhibited tolerance to spider mites. Two R2R3 MYB genes, SlTHM1 and SlMYB52, were directly targeted and inhibited by SlARF4. SlTHM1 was specifically expressed in II and VI type trichomes and negatively regulated the auxin-induced formation of II and VI type trichomes in the tomato leaves. SlTHM1 down-regulation plants with high densities of II and VI type trichomes also showed tolerance to spider mites. SlMYB52 was specifically expressed in V type trichomes and negatively regulated the auxin-induced formation of V type trichome in the tomato leaves. The regulation of SlARF4 on the formation of II, V and VI type trichomes depended on SlTHM1 and SlMYB52, which directly targeted cyclin gene SlCycB2 and increased its expression. In conclusion, our data indicates that the R2R3 MYB-dependent auxin signalling pathway regulates the formation of II, V and VI type trichomes in tomato leaves. Our study provides an effective method for improving the tolerance of tomato to spider mites