Static and Dynamic Responsive Behavior of Polyelectrolyte Brushes under External Electrical Field

The static and dynamic behaviors of partially charged and end-grafted polyelectrolyte brushes in response to electric fields were investigated by means of molecular dynamics simulation. The results show that the polymer brushes can be partially or fully stretched by applying an external electric field. Moreover, the brushes can switch reversibly from collapsed to stretched states, fully responding to the AC electric stimuli, and the gating response frequency can reach a few hundred MHz. The effects of the grafting density, the charge fraction of the brushes and the strength of the electric field on the average height of the polymer brushes were studied through the simulations. http://dx.doi.org/10.1088/0957-4484/20/19/19570

The Performance of Polymer Solution Added with Viscosity Stabilizer and the Evaluation of Its Oil Displacement Efficiency in Daqing Oilfield

Aiming at the low viscosity of polymer solution, which is compounded with fresh water but diluted with produced water, and at the problems concerning oil displacement efficiency, an onsite test on polymer solution with viscosity stabilizer (PSVS) is carried out. As a result, it has great and guiding significance to the application and popularization of viscosity stabilizer by studying the performance of polymer solution with viscosity stabilizer and its influence on oil displacement efficiency. In this paper, aiming at two different kinds of polymer solutions among which one is compounded with fresh water but diluted with fresh produced water and the other with aerated produced water, two laboratory evaluative tests concerning viscosity stabilization, anti-shear stability, fluidity, and absorbability of polymer solution as well as its oil displacement efficiency are done. The results of onsite application of PSVS are traced and analyzed. The viscosity stabilization of the polymer solution adding with viscosity stabilizer becomes much better than that of the normal polymer solution. The resistance and the residual resistance factors, the static oil sand adsorption rate and the dynamic core adsorption rate of the solution are all increased markedly. The working viscosity and oil displacement efficiency are improved markedly as well. In comparison with the polymer solution diluted with fresh produced water, the polymer solution diluted with aerated produced water is much better in terms of viscosity stabilization. Comparing with the normal polymer solution with viscosity stabilizer before sheared, the polymer solution which is sheared before adding with viscosity stabilizer performs obviously better in terms of viscosity stability. In contrast to the adjacent block injected with normal polymer solution, the block under onsite flooding test with injection of PSVS features that the average injection pressure increases slightly but keeps steady, the recovery speed of the average monthly water cut of production wells slows down, the thickness of the absorptive layers increases, and the periodic recovery rate improves as well.Key words: Polymer solution; Viscosity stabilizer; Daqing oilfiel

Negative Propagation Effects in Two-Dimensional Silicon Photonic Crystals

We demonstrated negative refraction effects of light propagating in two-dimensional square and hexagonal-lattice silicon photonic crystals (PhCs). The plane wave expansion method was used to solve the complex eigenvalue problems, as well as to find dispersion curves and equal-frequency contour (EFC). The finite-difference time-domain (FDTD) method was used to simulate and visualize electromagnetic wave propagation and scattering in the PhCs. Theoretical analyses and numerical simulations are presented. Two different kinds of negative refractions, namely, all-angle negative refraction (AANR) without a negative index and negative refraction with effective negative index, have been verified and compared

A Bandpass Filter Based on Half Mode Substrate Integrated Waveguide-to-Defected Ground Structure Cells

A half mode substrate integrated waveguide-to-defected ground structure (HMSIW-DGS) cell and its embedded form are proposed to miniaturize a bandpass filter. Both cells can purchase wideband frequency response and low insertion loss, as well as simple and easy fabrication. By cascading two of them according to design requirement, an X-band bandpass filter is designed and measured to meet compact size, low insertion loss, good return loss, second harmonic suppression, and linear phase

Efficacy and safety of a NiTi CAR 27 compression ring for end-to-end anastomosis compared with conventional staplers: A real-world analysis in Chinese colorectal cancer patients

OBJECTIVES: This study aimed to evaluate the safety and efficacy of a new nickel-titanium shape memory alloy compression anastomosis ring, NiTi CAR 27, in constructing an anastomosis for colorectal cancer resection compared with conventional staples. METHODS: In total, 234 consecutive patients diagnosed with colorectal cancer receiving sigmoidectomy and anterior resection for end-to-end anastomosis from May 2010 to June 2012 were retrospectively analyzed. The postoperative clinical parameters, postoperative complications and 3-year overall survival in 77 patients using a NiTi CAR 27 compression ring (CAR group) and 157 patients with conventional circular staplers (STA group) were compared. RESULTS: There were no statistically significant differences between the patients in the two groups in terms of general demographics and tumor features. A clinically apparent anastomotic leak occurred in 2 patients (2.6%) in the CAR group and in 5 patients (3.2%) in the STA group (p=0.804). These eight patients received a temporary diverting ileostomy. One patient (1.3%) in the CAR group was diagnosed with anastomotic stricture through an electronic colonoscopy after 3 months postoperatively. The incidence of postoperative intestinal obstruction was comparable between the two groups (p=0.192). With a median follow-up duration of 39.6 months, the 3-year overall survival rate was 83.1% in the CAR group and 89.0% in the STA group (p=0.152). CONCLUSIONS: NiTi CAR 27 is safe and effective for colorectal end-to-end anastomosis. Its use is equivalent to that of the conventional circular staplers. This study suggests that NiTi CAR 27 may be a beneficial alternative in colorectal anastomosis in Chinese colorectal cancer patients

Omnidirectional whispering-gallery-mode lasing in GaN microdisk obtained by selective area growth on sapphire substrate

The optical properties of hexagonal GaN microdisk arrays grown on sapphire substrates by selective area growth (SAG) technique were investigated both experimentally and theoretically. Whispering-gallery-mode (WGM) lasing is observed from various directions of the GaN pyramids collected at room temperature, with the dominant lasing mode being Transverse-Electric (TE) polarized. A relaxation of compressive strain in the lateral overgrown region of the GaN microdisk is illustrated by photoluminescence (PL) mapping and Raman spectroscopy. A strong correlation between the crystalline quality and lasing behavior of the GaN microdisks was also demonstrated