Near‐Infrared‐Activated Nanocalorifiers in Microcapsules: Vapor Bubble Generation for In Vivo Enhanced Cancer Therapy

Photothermal therapy based on gold nanostructures has been widely investigated as a state‐of‐the‐art noninvasive therapy approach. Because single nanoparticles cannot harvest sufficient energy, self‐assemblies of small plasmonic particles into large aggregates are required for enhanced photothermal performance. Self‐assembled gold nanorods in lipid bilayer‐modified microcapsules are shown to localize at tumor sites, generate vapor bubbles under near‐infrared light exposure, and subsequently damage tumor tissues. The polyelectrolyte multilayer enables dense packing of gold nanorods during the assembly process, which leads to the formation of vapor bubbles around the excited capsules. The resulting vapor bubbles achieve a high efficiency of suppressing tumor growth compared to single gold nanorods. In vivo experiments demonstrated the ability of soft‐polymer multilayer microcapsules to cross the biological barriers of the body and localize at target tissues.     

Pseudo-potential caculations of positron annihilation rates in bubbles of helium contained in the metals Mg,Ag and Au

Abstract

A pseudo-potential technique has been applied to calculate the annihilation rates for positrons in bubbles of helium gas in gold and silver. The positron pseudo-wavefunction in each case was found to be in a surface state of the metal, the exact form of which displayed a slight dependance on the density of the helium gas. The annihilation rate of the positron was the sum of a nearly constant surface rate and a strongly density dependant annihilation rate with the helium electrons. There is a trend for annihilation with the helium to be greater in metals with low free electron densities, the helium in such metals resting closer to the metal surface thus increasing the overlap of the positron wavefunction with the helium.     

Improvement of Acoustic Doppler Velocimetry in bubbly flow measurements as applied to river characterization for kinetic turbines

Acoustic Doppler Velocimetry (ADV) can measure flow velocities in three directions in experimental facilities and field applications. Based on the Doppler shift effect, ADV can accurately resolve the quasi-instantaneous flow field at frequencies of up to approximately 200 Hz. However, this technique is sensitive to operating conditions that can lead to contaminated signals containing large amplitude spikes, a disadvantage of ADV. Aliasing of the Doppler signal creates these spikes. Such a situation occurs when large particles intersect the sampling volume or acoustic waves. For example during the characterization of river velocities, sediments floating near the riverbed cause aliasing from particles, and more importantly, surface entrained air bubbles contaminate the ADV signal. Spikes due to air bubbles not only increase the standard deviation of the velocity, but also corrupt the autocorrelation and power spectra. As some of these spikes appear like velocity fluctuations, developing accurate despiking procedures is an important requirement during post-processing of ADV velocity measurements in bubbly flow applications. A new hybrid method is introduced which has advantages over conventional despiking methods such as the acceleration thresholding method and the phase-space thresholding method when using ADV in bubbly flow. ADV river velocity measurements near kinetic turbines demonstrate the proposed method. This method is applicable to other bubbly flow applications to characterize the liquid phase using ADV.     

冲击波和气泡作用下舰船结构动态响应的数值模拟

针对水下爆炸载荷、瞬态流固耦合效应在舰船水下爆炸数值模拟中的困难,在现有水下爆炸载荷计算模型(Geers and Hunter)的基础上,结合边界元法,修正水下爆炸气泡载荷计算方法.针对用二阶双渐近法(the second-order doubly-asymptotic approximation,DAA2)在处理低频...     

Numerical simulation of cavitation bubble dynamics induced by ultrasound waves in a high frequency reactor

The use of high frequency ultrasound in chemical systems is of major interest to optimize chemical procedures. Characterization of an open air 477 kHz ultrasound reactor shows that, because of the collapse of transient cavitation bubbles and pulsation of stable cavitation bubbles, chemical reactions are enhanced. Numerical modelling is undertaken to determine the spatio-temporal evolution of cavitation bubbles. The calculus of the emergence of cavitation bubbles due to the acoustic driving (by taking into account interactions between the sound field and bubbles' distribution) gives a cartography of bubbles' emergence within the reactor. Computation of their motion induced by the pressure gradients occurring in the reactor show that they migrate to the pressure nodes. Computed bubbles levitation sites gives a cartography of the chemical activity of ultrasound. Modelling of stable cavitation bubbles' motion induced by the motion of the liquid gives some insight on degassing phenomena.     

舰船尾流气泡后向光学检测方法研究

为探索舰船尾流后向光学检测方法,研究了尾流气泡对水中激光脉冲后向散射特性的影响。首先基于Fournier Forand 体积散射函数,利用蒙特卡罗(Monte-Carlo)方法理论分析了近距离尾流气泡对激光脉冲后向散射特性的影响。然后,采用蓝绿激光脉冲作为光源,实验研究了模拟尾流气泡对激光脉冲后向散射信号的影响。研究表明,尾流气泡的存在会使得激光脉冲后向散射信号前沿位置在时域左移,后沿位置在时域右移,信号时域宽度增加,能量增强,峰值增大且位置在时域左移。最后根据研究结果提出了一种基于激光脉冲后向散射信号特征变化的舰船尾流气泡后向检测方法。     

基于马氏域变的房地产泡沫存在概率研究

借鉴股票市场泡沫的研究方法,采用非齐次马氏域变思想对我国2001年1月到2010年12月的房地产市场泡沫进行了分析.通过Johansen协整检验方法从房价数据中分离出泡沫成份,使用极大似然估计方法估计出房价泡沫在两状态下的方差和转移概率的相关参数,进而求出各时期房价泡沫存在的概率.实证结果表明:第一,样本期间大部分时期内我国房地产价格存在泡沫的概率较小,但2009年4月至12月房价存在泡沫的概率较大;第二,提高贷款利率能够减小从无泡沫到有泡沫的概率,同时增加从有泡沫到无泡沫的概率.     

应用于水下能分辨粒径10 μm～500 μm尾流气泡的成像系统

针对尾流气泡成像存在的难点,采用片光源切片扫描与高速摄影相结合的技术手段,研制了一套水下激光成像系统。该系统采用激光片光照明,避免了尾流区气泡图像层叠;设计了3组倍率可切换镜头,实现了对大动态范围（10 m～500 m）粒径小气泡的成像;将镜头分成前后组,以平行光中继,通过片光与前镜组的同步移动,可实现尾流区一定体积内气泡图像的采样,同时还能保证扫描过程中始终成像清晰。此系统通过在海域进行试验,放置深度为5 m,气泡由目标船产生,产生气泡粒径范围10 m～2 000 m,结果表明,系统成像效果良好,满足项目技术要求。     

On the stability of bubbles trapped at a solid–liquid interface: A thermodynamical approach

In this paper we present a condition for thermodynamic equilibrium of gas bubbles of dimensions larger that a few tens of nanometers trapped at a solid–liquid interface. It is defined an intensive adimensional function that relates bubble stability with wettability and surface corrugation related parameters. From it, we deduce that bubbles can be stable on smooth, highly hydrophobic surfaces and that, on weakly hydrophobic surfaces, bubbles may be stabilized by topographical heterogeneities like pores and grooves.