Spectral Properties and Deactivation Processes of Anionic Porphyrin Coupled with TiO2 Nanostructure

Meso-tetrakis (4-sulphonatophenyl)porphyrin (TSPP) and its complex with TiO₂ were studied by absorption, fluorescence, and steady-state and time-resolved photothermal spectroscopy. A TiO₂–TSPP complex was obtained by covalent bonding of anionic porphyrin with the nanostructural form of TiO₂. The TiO₂ colloidal carriers modifying the thermal energy distribution and considerably influencing the photophysical processes were found to lead to changes in the population of the porphyrin singlet and triplet states, resulting in singlet oxygen generation and/or electron transfer.     

基于CFD-DEM方法的柱状颗粒在弯管中输送过程的数值模拟

针对物料在气力输送过程中特别是弯管部分易破碎的问题,采用计算流体力学(CFD)和离散单元法(DEM)耦合模拟弯管内的柱状颗粒气力输送过程,对弯径比k分别为1、2、3、4、6的90°弯管内柱状颗粒的运动状态、碰撞特性、破碎原因及相关的力学特性进行研究。结果表明:球形颗粒与柱状颗粒在输送过程中遵循基本一致的变化规律,同样外部条件下,柱状颗粒的悬浮速度小于球形颗粒。当k=3时气力输送过程颗粒的破碎率最低。同时,颗粒与管壁的碰撞是造成颗粒破碎的主要原因。     

Nanostructure and Properties of a Shinbone

Scanning electron microscope (SEM) observation shows that a shinbone is composed of large-volume-fraction hydroxyapatite and small-volume-fraction collagen protein materials. The hydroxyapatite is of laminated structure and consists of numberless hydroxyapatite sheets. The observation also shows that the hydroxyapatite sheets are parallel with each other and of nanometer scale. The high fracture toughness and fracture strength of the bone are investigated based on the calculation formula of the dissipation work and Griffith criterion. The investigated results reveal that the large-volume fraction and the nanometer scale of the hydroxyapatite sheets are the important factors to the high mechanical performance of the bone.     

Nanostructure in a Ti alloy processed using a cryomilling technique

A nanocrystalline Ti alloy with a uniform distribution of grains was synthesized using cryogenic mechanical milling. The effects of cryomilling parameters, such as milling time and ball to powder ratio (BPR), on the particle size, grain size, chemistry, and structure of cryomilled Ti powders were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The experimental results show that nanocrystalline Ti powders with a grain size of about 20 nm can be prepared using the cryomilling technique. Compared to SPEX milling at room temperature, cryomilling led to lower contamination levels of oxygen, nitrogen, and iron in the cryomilled Ti powder. The average particle size initially increased from the original 55 μm to a maximum value of 125 μm after 2 h of milling, and then decreased to 44 μm after 8 h of milling. Both the average particle size and the grain size decreased as the BPR increased.     

A Carbon Nanostructure for a Thermoelectric Generator

Technical Physics Letters - We demonstrate that it is technologically possible to obtain graphite-like films which can be used for the creation of a thermoelectric generator. The proposed...     

Switching of Self-Assembly in a Peptide Nanostructure with a Specific Enzyme

Peptide self-assembly has been shown to be a useful tool for the preparation of bioactive nanostructures, and recent work has demonstrated their potential as therapies for regenerative medicine. In principle, one route to make these nanostructures more biomimetic would be to incorporate in their molecular design the capacity for biological sensing. We report here on the use of a reversible enzymatic trigger to control the assembly and disassembly of peptide amphiphile (PA) nanostructures. The PA used in these studies contained a consensus substrate sequence specific to protein kinase A (PKA), a biological enzyme important for intracellular signaling that has also been shown to be an extracellular cancer biomarker. Upon treatment with PKA, this PA molecule becomes phosphorylated causing the high aspect-ratio filamentous PA nanostructures to disassemble. Treatment with an enzyme to cleave the phosphate group results in reformation of the filamentous nanostructures. We also show that disassembly in the presence of PKA allows the enzyme-triggered release of an encapsulated cancer drug. In addition, these drug-loaded nanostructures were found to induce preferential cytotoxicity in a cancer cell line that is known to secrete high levels of PKA. This ability to control nanostructure through an enzymatic switch could allow for the preparation of highly sophisticated and biomimetic materials that incorporate a biological sensing capability to enable therapeutic specificity.     

Unsteady Fully-Developed Flow in a Curved Pipe

It is shown that the boundary layer which develops from rest in a loosely coiled pipe of circular cross-section, following the imposition of a constant pressure gradient, terminates in singular behaviour at the inside bend after a finite time. This singularity of the boundary-layer equations is interpreted as an eruption of boundary-layer fluid into the interior or core flow. This result complements earlier work by Stewartson et al. [1] who consider the steady inlet flow to a curved pipe at high Dean number. In that case a singularity also develops, now at a finite distance from the entrance at the inside bend, which is again interpreted in terms of a boundary-layer collision or eruption.     

纳米材料在涂料中的应用

纳米材料是近年发展起来的一种新型高性能材料，认识这种材料的性能和拓展其应用领域，是许多材料工作者非常感兴趣的课题，着重介绍了年年来国内外有关钠米材料在涂料中的应用和研究开发情况，并对其方向提出了一些建议。     

Measure of Entanglement States of Two Interacting Electrons in Vertically Coupled Quantum Dots Induced by a Time-Dependent Electric Field

We study the dynamics of two electrons located in two vertically tunnel-coupled quantum dots in the presence of an oscillatory electric field. By solving the time-dependent Schrödinger equation, we predict the dynamical generation of entangled electron states, such as the EPR (Einstein, Podolsky, and Rosen) pairs or Bell states. The Schmidt rank and the von Neumann entropy are evaluated to characterize the degree of entanglement of the two electron states.     

Self-Organization of a Hybrid Nanostructure consisting of a Nanoneedle and Nanodot

A special materials system that allows the self-organization of a unique hybrid nanonipple structure is developed. The system consists of a nanoneedle with a small nanodot sitting on top. Such hybrid nanonipples provide building blocks to assemble functional devices with significantly improved performance. The application of the system to high-sensitivity gas sensors is also demonstrated.     

Nanostructure defects in Si3N4

Microstructure defect studies of Si₃N₄ have contributed much to the development of Si₃N₄ ceramics material. In this paper we present some results of nanostructure defects by using high-resolution electron microscopy (HREM), showing new structural phenomena at the atomic level.     

Coupled Thermoelasticity in a Composite Half-Space

The problem of fully coupled thermoelasticity in a composite half-space is considered where the composite has variations in its physical properties in one direction only. The resulting one-dimensional problem thus depends on the so-called microscale of the composite. Homogenization of the fully coupled theory provides the leading-order system of coupled equations (independent of the microscale) together with the effective physical properties of the thermoelastic medium. In particular, the effective coupling parameter δ_* is found and it is shown to exhibit rather interesting properties; for a range of volume fractions in two-phase composites it is shown that δ_* lies below the corresponding coupling parameter for a homogeneous material made up of either phase. Transient boundary-value problems of the homogenized system are then solved and compared with the classical problem of a homogeneous half-space. The magnitude of resulting discontinuities in field variables and their derivatives are found and their dependence on the effective coupling parameter is exhibited.     

Nanostructure Formation on a Film Surface Vacuum-Deposited from Laser-Erosion Plasma

We have investigated the crystallographic nature of the nanophase structure on the surface of amorphous carbon diamond-like film vacuum-deposited on a hot glass substrate by exposing a graphite target to a pulsed neodymium laser radiation of nanosecond duration with an energy density of 1.18·10⁴ J/m².     

Curved flow of a viscous liquid in an axiradial channel

The motion of a viscous liquid is an axiradial channel with curving of the flow is investigated with the aid of the implicit method of splitting according to spatial variables. The effect of the Reynolds number and of the intensity of the curving on the formation of regions of reverse flows is established.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 2, pp. 280–285, August, 1984.     

具有曲线轮槽的槽轮机构设计

通过对槽轮机构轮槽曲线方程的推导,借用凸轮曲线的设计思想,提出了一个曲线轮槽理论设计的方法,从而避免了普通槽轮机构高速运动时的柔性冲击。     

Nanostructure of Clusters in Nafion Studied by DSC

The nanostructure that consists of clusters and channels between the clusters in Nafion with absorbed water is studied by Differential Scanning Calorimeter (DSC) measurements with stepwise temperature programs. A cluster size distribution (CSD) is fitted reasonably by a log normal distribution function. The fitted CSD has a peak of approximately 4nm in diameter. In comparison of the water content from gravimetry with that from the fitted CSD, at least three kinds of water states are found, two of which are freezable and non-freezable water in a cluster and another is the non-freezable water in a channel between the clusters. From the assumption of a simple cubic lattice model, the channel length L _ch between the clusters and the cross section S _ch of the channel can be estimated. Also, the degree of desulfonation in the terminal of the side chain by thermal degradation depends on the nanostructure consisting of the clusters and channels in Nafion with absorbed water. The channel length L _ch decreases monotonically with increasing water content. Essentially the channel cross sectionS _ch increases with increasing water content.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Ferromagnetism in Mn-implanted Ge/Si Nanostructure Material

Multistacked Ge quantum dots (QDs) with Si spacers of different thicknesses have been grown on (100) Si substrates by rapid thermal chemical vapor deposition followed by Mn ion implantation and post-annealing. The presence of ferromagnetic structure was confirmed in the insulating (Si_0.45Ge_0.55)Mn_0.03 diluted magnetic quantum dots (DMQD) and semiconducting (Si_0.45Ge_0.55)Mn_0.05 DMQD. The DMQD materials were found to be homogeneous and to exhibit p-type conductivity and ferromagnetic ordering with a Curie temperature of T _C=350 and 160 K. The x-ray diffraction (XRD) data show that there is a phase separation of Mn₅Ge₃ from the MnGe nanostructure. The temperature-dependent electrical resistivity in semiconducting DMQD material indicates that manganese introduces two acceptor levels in germanium, at 0.14 eV from the valence band and 0.41 eV from the conduction band implying Mn substituting Ge. Therefore, it is likely that the ferromagnetic exchange coupling of DMQD material with T _C=160 K is hole mediated due to formation of bound magnetic polarons and the ferromagnetism in a sample with T _C>300 K is due to Mn₅Ge₃ phase.