Technology of preparing anode films and the effect of co-sensitization in dye-sensitized solar cells

Nanocrystalline N–Zn/TiO₂ anode films were prepared by doping element N and Zn. These element-doped films have a better performance in dye-sensitized solar cell than the non-doped film. The test shows that the best thickness of N–Zn/TiO₂ anode film is 13.5 μm. UV–Visible measurements show that there is a complementarity in ultraviolet–visible absorbance range between P3OT and N719, both are used as dyes in this study, the former is prepared and the latter is commercially available. SEM shows a significant mass increase of anode film after treated with TiCl₄. Solar cells based on N–Zn/TiO₂ anode film with TiCl₄ treatment was firstly co-sensitized by N719/P3OT. A solar-to-electric energy conversion efficiency of 3.54 % was obtained. Compared with the traditional dye-sensitized solar cell, the photoelectric conversion efficiency, V _oc and J _sc have been increased.     

Vectors in a box

For an integer d ≥ 1, let τ(d) be the smallest integer with the following property: if v ₁, v ₂, . . . , v _t is a sequence of t ≥ 2 vectors in [?1, 1] ^d with ${{\bf v}_1+{\bf v}_2+\cdots+{\bf v}_t \in [-1,1]^d}$ , then there is a set ${S\subseteq \{1,2,\ldots,t\}}$ of indices, 2 ≤ |S| ≤ τ(d), such that ${\sum_{i \in S}{\bf v}_i \in [-1,1]^d}$ . The quantity τ(d) was introduced by Dash, Fukasawa, and Günlük, who showed that τ(2)?=?2, τ(3)?=?4, and τ(d)?=?Ω(2 ^d ), and asked whether τ(d) is finite for all d. Using the Steinitz lemma, in a quantitative version due to Grinberg and Sevastyanov, we prove an upper bound of τ(d) ≤ d ^d+o(d), and based on a construction of Alon and V?, whose main idea goes back to H?stad, we obtain a lower bound of τ(d) ≥ d ^d/2-o(d). These results contribute to understanding the master equality polyhedron with multiple rows defined by Dash et?al. which is a “universal” polyhedron encoding valid cutting planes for integer programs (this line of research was started by Gomory in the late 1960s). In particular, the upper bound on τ(d) implies a pseudo-polynomial running time for an algorithm of Dash et?al. for integer programming with a fixed number of constraints. The algorithm consists in solving a linear program, and it provides an alternative to a 1981 dynamic programming algorithm of Papadimitriou.     

Glycerol monooleate-blood interactions

In the present study the initial blood compatibility of glycerol monooleate (GMO)-coated surfaces was evaluated after deposition to surfaces and in bulk. The model surface was silica onto which multiple layers of fibrinogen or human serum albumin (HSA) was immobilized. The protein-coated surfaces were subsequently dip-coated in GMO in ethanol and used for blood plasma and whole blood experiments. The characterization methods included null ellipsometry, scanning electron microscopy, imaging of coagulation, hemolysis test and whole blood coagulation time by free oscillation rheometry. The results showed a GMO film thickness of approximately 350 A (approximately 4 microg/cm(2)) upon dip-coating in ethanolic solution. A major part of the deposited layer detached in aqueous solutions, especially during shear conditions. The coagulation time on GMO was significantly prolonged compared to that on HSA coated silica. Whole blood tests showed that GMO is a very weak hemolytic agent. Deposited GMO detached easily from surfaces upon rinsing or shearing, although a stable layer with undefined phase structure and a thickness of 50-70 A remained on HSA and fibrinogen precoated surfaces. This indicates that GMO has stronger adhesive forces to its substrate compared to the cohesive forces acting within the bulk GMO. The ability of GMO to detach from itself and tentatively form micelles or lipid bilayers when subjected to flowing blood may be of use in extravascular applications. It is concluded that GMO results in weak blood activation, and the material may in spite of this be suitable in selected biomaterial applications, especially as a biosealant and in colloidal dispersions.     

Consistent Digital Line Segments

We introduce a novel and general approach for digitalization of line segments in the plane that satisfies a set of axioms naturally arising from Euclidean axioms. In particular, we show how to derive such a system of digital segments from any total order on the integers. As a consequence, using a well-chosen total order, we manage to define a system of digital segments such that all digital segments are, in Hausdorff metric, optimally close to their corresponding Euclidean segments, thus giving an explicit construction that resolves the main question of Chun et al. (Discrete Comput. Geom. 42(3):359–378, 2009).     

Octants Are Cover-Decomposable

We prove that octants are cover-decomposable; i.e., any 12-fold covering of any subset of the space with a finite number of translates of a given octant can be decomposed into two coverings. As a corollary, we obtain that any 12-fold covering of any subset of the plane with a finite number of homothetic copies of a given triangle can be decomposed into two coverings. We also show that any 12-fold covering of the whole plane with the translates of a given open triangle can be decomposed into two coverings. However, we exhibit an indecomposable 3-fold covering with translates of a given triangle.     

Exploring the possible interlinked structures in single‐wall carbon nanotubes under pressure by Raman spectroscopy

High‐pressure Raman measurements on single‐wall carbon nanotubes (SWNTs) have been carried out in a diamond anvil cell by using two wavelength lasers: 830 and 514.5 nm. Irrespective of using a pressure transmitting medium (PTM) or not, we found that nanotubes undergo similar transformations under pressure. The pressure‐induced changes in Raman signals at around 2 and 5 GPa are attributed to the nanotube cross‐section transitions from circle to ellipse and then to a flattened shape, respectively. Especially with pressure increasing up to 15–17 GPa, we observed that the third transition takes place in both the Raman wavenumber and the linewidth of G‐band. We propose explanations that the interlinked configuration with sp³ bonds forms in the bundles of SWNTs under pressure, which was the cause for the occurrence of those Raman anomalies, similar to the structural‐phase transition of graphite above 14 GPa. Our TEM observations and Raman measurements on the decompressed samples support this transition picture. Copyright © 2012 John Wiley & Sons, Ltd.     

(CoAl)n (1 ≤ n ≤ 6)合金团簇的结构、稳定性和磁性理论研究

采用密度泛函理论中的广义梯度近似 (DFT-GGA)对(CoAl)n (1≤n≤6)合金团簇的几何、电子结构和磁性进行了系统的研究。计算结果表明(CoAl)n (1≤n≤6)合金团簇在基态附近出现许多能量十分接近的低能量态，有能量简并态存在，表现出经典的过渡金属密堆积结构；同时在(CoAl)5和(CoAl)6团簇中，有磁性双稳态存在。合金团簇的结合能随着团簇尺寸的增大而增大。CoAl团簇获得了最大的带隙，表现出强的化学惰性，带隙在n>3之后出现明显的奇偶变化规律，且整体呈下降趋势，这种现象源于团簇中共价键、离子键的相互竞争。(CoAl)n ( 1≤n≤6)的总磁矩随尺寸大小呈半梯形状的变化趋势，其中CoAl团簇的磁矩为2 μB，(CoAl)2，(CoAl)3 磁矩为4μB，(CoAl)4，(CoAl)5，(CoAl)6 为6μB，这种磁性变化规律在文中也从磁序排列、电荷转移以及自旋极化等方面进行了详细讨论。     

Carboxymethylated polyethylenimine modified magnetic nanoparticles specifically for purification of His‐tagged protein

Employing immobilized metal‐ion affinity chromatography and magnetic separation could ideally provide a useful analytical strategy for purifying His‐tagged protein. In the current study, a facile route was designed to prepare CMPEI‐Ni²⁺@SiO₂@Fe₃O₄ (CMPEI=carboxymethylated polyethyleneimine) magnetic nanoparticles composed of a strong magnetic core of Fe₃O₄ and a Ni²⁺‐immobilized carboxymethylated polyethyleneimine coated outside shell, which was formed by electrostatic interactions between polyanionic electrolyte of carboxymethylated polyethyleneimine and positively charged surface of 3‐(trimethoxysilyl)propylamin modified SiO₂@Fe₃O₄. The resulting CMPEI‐Ni²⁺@SiO₂@Fe₃O₄ composite nanoparticles displayed well‐uniform structure and high magnetic responsiveness. Hexa His‐tagged peptides and purified His‐tagged recombinant retinoid X receptor alpha were chosen as the model samples to evaluate the adsorption, capacity, and reusability of the composite nanoparticles. The results demonstrated the CMPEI‐Ni²⁺@SiO₂@Fe₃O₄ nanoparticles possessed rapid adsorption, large capacity, and good recyclability. The obtained nanoparticles were further used to purify His‐tagged protein in practical environment. It was found that the nanoparticles could selectively capture His‐tagged recombinant retinoid X receptor protein from complex cell lysate. Owing to its easy synthesis, large binding capacity, and good reusability, the prepared CMPEI‐Ni²⁺@SiO₂@Fe₃O₄ magnetic nanoparticles have great potential for application in biotechnological fields.     

New problems of particle transfer in ferrocolloids: Magnetic Soret effect and thermoosmosis

The paper deals with critical reviewing of the experiments on thermodiffusion in ferrocolloids. The observed magnetic Soret effect is much stronger than that predicted theoretically. It is shown that the main reason of that is the influence of the magnetic field on mass diffusion. Besides, some measurements are affected by uncontrolled thermal and solutal magnetic convection. In porous media, when macroscopic convection is suppressed, thermodiffusion is accompanied by thermoosmosis as well as by a microconvective mass transfer induced by particle magnetophoresis on filter grains.     

Quantized charge pumping by surface acoustic waves in ballistic quasi-1D channels

Adiabatic pumping of electrons induced by surface acoustic waves (SAWs) in a ballistic quasi-1D quantum channel is considered using an exactly solvable tight-binding model for non-interacting electrons. The single-electron degrees of freedom, responsible for acoustoelectric current quantization, are related to the transmission resonances. We study the influence of experimentally controllable parameters (SAW power, gate voltage, source-drain bias, amplitude and phase of a secondary SAW beam) on the plateau-like structure of the acoustoelectric current. The results are consistent with existing experimental observations.Received: 24 February 2004, Published online: 12 July 2004PACS: 73.23.-b Electronic transport in mesoscopic systems - 73.50.Rb Acoustoelectric - magnetoacoustic effects - 73.40.Ei Rectification