Cavity flow over a wall-mounted fence

Ventilated cavity flow over a wall mounted fence is experimentally investigated in a cavitation tunnel. The flow over a 2-D fence, attached to the tunnel test section ceiling, is examined for a range of free-stream conditions. The dependence of cavity topology, cavitation number, upstream wall pressure distribution and drag on several parameters, including ventilation rate, fence height based Froude number (Fr), vapour pressure based cavitation number (σv ) and degree of fence immersion in the oncoming wall boundary layer, is investigated. Three different flow regimes are identified throughout the range of cavitation numbers for a particular set of free-stream conditions: shear layer cavitation, fully developed cavity and ‘blocked’ flow. The cavity exhibits a typical re-entrant jet closure and the re-entrant jet intensity is found to be a function of Fr. The high intensity re-entrant jet, present at high Fr, leads to an increase in drag. Drag decreases significantly with an increase in fence immersion in the oncoming boundary layer. Complementary measurements for a naturally cavitating flow are obtained for comparison. A more detailed examination of the topology and unsteady behaviour of ventilated and natural cavity flows over a 2-D wall-mounted fence was undertaken for fixed length cavities with varying free-stream velocity using high-speed and still imaging, X-ray densitometry and dynamic surface pressure measurements in two experimental facilities. Two main unsteady features are observed, the irregular small-scale shedding of structures at the cavity closure and a larger-scale re-entrant jet oscillation. Small-scale cavity break-up was associated with a high-frequency broad-band peak in the wall pressure spectra, found to be governed by the overlying turbulent boundary layer characteristics, similar to observations from single-phase flow over a forward-facing step. A low-frequency peak reflecting the oscillations in size of re-entrant jet, analogous to the ‘flapping’ motion in single-phase flow, was found to be modulated by gravity effects (i.e. a Froude number dependency). Likewise, a significant change in cavity behaviour was observed as the flow underwent transition analogous to the transition from sub- to super- critical regime in open-channel flow. A companion numerical study is undertaken to provide additional insight into particular flow features such as the separated flow region upstream of the fence and to assess the influence of blockage. An implicit unsteady compressible solver is used with a RANS k − ω SST turbulence model and VOF approach to capture the cavity interface. The numerical results are found to compare reasonably with the experimental data, additionally showing a significant influence of blockage on the studied flow. Along with the 2-D fence, a 3-D wall mounted fence, spanning nominally a quarter of the tunnel test section, is investigated. The impact that 3-D effects have on the cavity topology and the relations between the parameters characterizing the flow is observed. The most notable effect of 3-D flow is a change in the closure mechanism observed for low Fr. Following a decrease in Fr the closure topology transforms from a well defined single re-entrant jet regime, through a phase of gradual re-entrant jet widening to a completely split re-entrant jet separated into two branches. Generally, the 2-D and 3-D flows exhibited similar trends with any significant difference attributable to differing levels of flow confinement due to lesser width of 3-D fence

Chemical nature and structure of organic coating of quantum dots is crucial for their application in imaging diagnostics

Rumiana Bakalova1, Zhivko Zhelev1, Daisuke Kokuryo1, Lubomir Spasov2, Ichio Aoki1, Tsuneo Saga11Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan; 2Medical Faculty, Sofia University, Sofia, BulgariaBackground: One of the most attractive properties of quantum dots is their potential to extend the opportunities for fluorescent and multimodal imaging in vivo. The aim of the present study was to clarify whether the composition and structure of organic coating of nanoparticles are crucial for their application in vivo.Methods: We compared quantum dots coated with non-crosslinked amino-functionalized polyamidoamine (PAMAM) dendrimers, quantum dots encapsulated in crosslinked carboxyl-functionalized PAMAM dendrimers, and silica-shelled amino-functionalized quantum dots. A multimodal fluorescent and paramagnetic quantum dot probe was also developed and analyzed. The probes were applied intravenously in anesthetized animals for visualization of brain vasculature using two-photon excited fluorescent microscopy and visualization of tumors using fluorescent IVIS® imaging (Caliper Life Sciences, Hopkinton, MA) and magnetic resonance imaging.Results: Quantum dots coated with non-crosslinked dendrimers were cytotoxic. They induced side effects in vivo, including vasodilatation with a decrease in mean arterial blood pressure and heart rate. The quantum dots penetrated the vessels, which caused the quality of fluorescent imaging to deteriorate. Quantum dots encapsulated in crosslinked dendrimers had low cytotoxicity and were biocompatible. In concentrations <0.3 nmol quantum dots/kg bodyweight, these nanoparticles did not affect blood pressure and heart rate, and did not induce vasodilatation or vasoconstriction. PEGylation (PEG [polyethylene glycol]) was an indispensable step in development of a quantum dot probe for in vivo imaging, based on silica-shelled quantum dots. The non-PEGylated silica-shelled quantum dots possessed low colloidal stability in high-salt physiological fluids, accompanied by rapid aggregation in vivo. The conjugation of silica-shelled quantum dots with PEG1100 increased their stability and half-life in the circulation without significant enhancement of their size. In concentrations <2.5 nmol/kg bodyweight, these quantum dots did not affect the main physiological variables. It was possible to visualize capillaries, which makes this quantum dot probe appropriate for investigation of mediators of vasoconstriction, vasodilatation, and brain circulation in intact animals in vivo. The multimodal silica-shelled quantum dots allowed visualization of tumor tissue in an early stage of its development, using magnetic resonance imaging.Conclusion: The present study shows that the type and structure of organic/bioorganic shells of quantum dots determine their biocompatibility and are crucial for their application in imaging in vivo, due to the effects of the shell on the following properties: colloidal stability, solubility in physiological fluids, influence of the basic physiological parameters, and cytotoxicity.Keywords: quantum dot, organic shell, biocompatibility, in vivo imaging, two-photon excited fluorescent microscopy, magnetic resonance imagin

MRマイクロイメージングとガドリニウム-デンドロン修飾ナノリポソーム造影剤を用いた3D微小血管およびナノ粒子分布の腫瘍内評価

The enhanced permeability and retention (EPR) effect is variable depending on nanoparticle properties and tumor/vessel conditions. Thus, intratumoral evaluations of the vasculature and nanoparticle distribution are important for predicting the therapeutic efficacy and the intractability of tumors. We aimed to develop a tumor vasculature evaluation method and high-resolution nanoparticle delivery imaging using magnetic resonance (MR) micro-imaging technology with a gadolinium (Gd)-dendron assembled liposomal contrast agent. Using the Gd-liposome and a cryogenic receiving coil, we achieved 50-μm isotropic MR angiography with clear visualization of tumor micro-vessel structure. The Gd-liposome-enhanced MR micro-imaging revealed differences in the vascular structures between Colon26- and SU-DHL6-grafted mice models. The vessel volumes and diameters measured for both tumors were significantly correlated with histological observations. The MR micro-imaging methods facilitate the evaluation of intratumoral vascularization patterns, the quantitative assessment of vascular-properties that alter tumor malignancy, particle retentivity, and the effects of treatment

Optimization of Liposomal Theragnosis :Quantitative T1 Measurement of Drug Distribution and Release in Deep-seated Tumor using Multimodal Thermo-sensitive Polymer-modified Liposome

ISMRM-ESMRMB 2010（ISMRM 18th Scientific Meeting & Exhibition

Application of Thermo-sensitive Polymer-modified Liposome Containing Fluorescence Dye,MR contrast Agent and Anticancer Drug to Deep-seated Tumor

The 13th Conference of Peace　through Mind Brain Scienc

Multimodal Thermo-Sensitive Polymer-Modified Liposome for Visualization and Treatment of Disseminated Cancer

A drug delivery system using a multimodal thermo-sensitive \u27polymer-modified\u27 liposome (MTPL) would be a powerful imaging tool to help avoid the side-effects of chemotherapy on the intact organ. In this study, an accumulation of and thermo-triggered drug release from MTPL were evaluated for disseminated-cancer using MRI and optical imaging. In the ex vivo optical images, the MTPL accumulation in the tumor area increased over 8 hours after the administration. In the T1-weighted MRI, the signal intensities in the bowel and the kidney changed after thermo-triggering.ISMRM 17th Scientific Meeting & Exhibitio

Evaluation of Vessel-based Focal Point Tracking for Focused Ultrasound Surgery of Liver under Free Breathing

The 8th Interventional MRI Symposiu

Hot Spot Tracking for Focused Ultrasound Surgery of Liver using Filtered Venograpy

A target tracking technique using relative displacements of gravity points of cross sectional images of blood vessels was proposed to guide the ultrasound focus in the liver which moves with respiration. Experiments with healthy volunteer livers demonstrated that the average error of the target position estimation was within 3mm. The error was less than 4mm even with a position prediction process for considering time delay between the time points of position estimation and transducer setup. These results suggested that the proposed technique was sufficient for guiding the focus and hence the imaging slab position and orientation for the "self-reference" thermometry.ISMRM 16th Scientific Meeting & Exhibitio

A study on multi-supplier collaborative logistics network with resource sharing under demand uncertainty (Second report, a comparative analysis of shared freight transport and a proposal of cost allocation method)

Due to the shortage of truck drivers, the challenge of improving transportation efficiency through collaboration has been receiving increased attention by both government and private sector. We propose a new methodology to introduce a two-stage stochastic program and cooperative game theory to design a transport network that incorporates truck sharing and Less-Than-Truckload (LTL) shipping under demand uncertainty. The method is focused on the number of suppliers’ own trucks in the first stage, and the flow of parts and trucks from suppliers to manufacturers and in the second stage. We analyze the value of collaboration on three different sets of demand scenarios with two manufacturers and four collaborating suppliers. Our analysis suggests that LTL shipping can reduce the number of trucks more than FTL (Full TruckLoad) shipping when the demand is expected to increase. It is also observed that LTL shipping can be more beneficial than 3PL even for long-distance transportation and reduces the total cost about twice as much as FTL shipping does, which is more than 5% of that of the non-collaborative scenario. Further, LTL shipping cost is allocated to each supplier according to the Shapley value. The results show that LTL shipping is a more cost-effective transportation mode for suppliers with high freight volumes and trucks, and all suppliers acquire cost reduction at almost the same rate

Evaluation of Gd-DTPA Contrast Enhancement of Lung and Metastatic Tumor with Ultra-Short Echo-Time Imaging

In a previous study, we administered nanoparticles containing a MR contrast agent, a fluorescence dye and an anticancer drug to successfully detect and visualize subcutaneous and deep-seated tumor in the back muscle of a mouse cancer model [1, 2]. The tumor appeared as a signal enhancement in T1-weighted MRI. As the next step, it is desired to apply the nanoparticle to lung tumors and other pulmonary disease. Imaging of the lungs is difficult because of the low proton density, short T2* and respiratory motion. However, ultra-short echo-time (UTE) imaging [3, 4] has recently been utilized to evaluate signal changes in lung parenchyma for various animal disease models [5, 6]. Moreover, quantitative assessment of pulmonary perfusion with dynamic contrast-enhanced MRI has been performed for pulmonary embolism and tumor in humans [7, 8]. As a preliminary step toward visible disease therapeutics using nanoparticles, the present study evaluated changes to the signal intensity in lung parenchyma and me tastatic tumor using a positive contrast agent (Gd-DTPA) and UTE imaging