To provide a basis for the selection of suitable emulsifiers in oil-in-water emulsions used as tissue analogs for MRI experiments. Three different emulsifiers were investigated with regard to their ability to stabilize tissue-like oil-in-water emulsions. Furthermore, MR signal properties of the emulsifiers themselves and influences on relaxation times and ADC values of the aqueous phase were investigated.
Materials and methods
Polysorbate 60, sodium dodecyl sulfate (SDS) and soy lecithin were used as emulsifiers. MR characteristics of emulsifiers were assessed in aqueous solutions and their function as a stabilizer was examined in oil-in-water emulsions of varying fat content (10, 20, 30, 40, 50%). Stability and homogeneity of the oil-in-water emulsions were evaluated with a delay of 3 h and 9 h after preparation using T1 mapping and visual control. Signal properties of the emulsifiers were investigated by 1H-MRS in aqueous emulsifier solutions. Relaxometry and diffusion weighted MRI (DWI) were performed to investigate the effect of various emulsifier concentrations on relaxation times (T1 and T2) and ADC values of aqueous solutions.
Results
Emulsions stabilized by polysorbate 60 or soy lecithin were stable and homogeneous across all tested fat fractions. In contrast, emulsions with SDS showed a significantly lower stability and homogeneity. Recorded T1 maps revealed marked creaming of oil droplets in almost all of the emulsions with SDS. The spectral analysis showed several additional signals for polysorbate and SDS. However, lecithin remained invisible in 1H-MRS. Relaxometry and DWI revealed different influences of the emulsifiers on water: Polysorbate and SDS showed only minor effects on relaxation times and ADC values of aqueous solutions, whereas lecithin showed a strong decrease in both relaxation times (r1,lecithin = 0.11 wt.%−1 s−1, r2,lecithin = 0.57 wt.%−1 s−1) and ADC value (Δ(ADC)lecithin = − 0.18 × 10–3 mm2/s⋅wt.%) with increasing concentration.
Conclusion
Lecithin is suggested as the preferred emulsifier of oil-in-water emulsions in MRI as it shows a high stabilizing ability and remains invisible in MRI experiments. In addition, lecithin is suitable as an alternative means of adjusting relaxation times and ADC values of water.
This paper considers the evolution of the velocity and temperature fields within a jet of fluid on a thermally insulated wall. Numerical solutions are obtained for a range of Prandtl numbers and for a class of initial velocity and temperature profiles relevant to intrusion jets observed in certain thermal cavity flows. Numerical results are compared with asymptotic solutions which describe the initial structure of the jet and its subsequent diffusion at large distances downstream. 相似文献
Molecular electronics is an emerging field that seeks to build faster, cheaper, denser computers from nanoscale devices. The nanocell is a molecular electronics design wherein a random, self-assembled array of molecules and metallic nanoparticles is addressed by a relatively small number of input/output pins. The challenge then is to program the nanocell post-fabrication. We have previously demonstrated the ability to program individual simulated nanocells as logic gates. In this paper, we further explore the problem of programming nanocells and consider connecting nanocells into circuits using bistable latches at the interconnects. These latches are critical because they permit signal restoration. Simulated nanocell circuits for logic and memory are presented here. 相似文献
Subjected research on Ivey's (1971) microcounseling program to a comprehensive meta-analytic review. A multistage sampling procedure resulted in the identification of 81 admissible studies. Glass's (1976) effect size (ES) statistic was used to estimate average effects for each study and across all studies, and the relation between ES and the sampling distribution of several important methodological and substantive characteristics was assessed. The most conservative overall ES statistic fell in the large-effect category. ESs were influenced differentially by the populations from which Ss were drawn and by the type of client the Ss interviewed when data for ratings on dependent measures were acquired. There was some evidence that the dependent measures used in microcounseling research are limited, which led to a conclusion that research on the teaching of more complex skills may be delayed. The microcounseling program has made a contribution to counseling training and may have pointed the way to new training models. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
Dobutamine stress echocardiography is a safe method for the evaluation of coronary artery disease, myocardial function, and viability. The potential for cardiac rupture exists. Although clinical and electrocardiographic criteria may be helpful in identifying those patients at risk for cardiac rupture, the criteria are neither sensitive nor specific enough to exclude patients or make recommendations regarding which patients should undergo dobutamine stress echocardiography in the post-infarction period. Physicians must be aware of the possibility and be prepared to treat cardiac rupture when performing dobutamine stress echocardiography. 相似文献
Creating high-quality quad meshes from triangulated surfaces is a highly nontrivial task that necessitates consideration of various application specific metrics of quality. In our work, we follow the premise that automatic reconstruction techniques may not generate outputs meeting all the subjective quality expectations of the user. Instead, we put the user at the center of the process by providing a flexible, interactive approach to quadrangulation design. By combining scalar field topology and combinatorial connectivity techniques, we present a new framework, following a coarse to fine design philosophy, which allows for explicit control of the subjective quality criteria on the output quad mesh, at interactive rates. Our quadrangulation framework uses the new notion of Reeb atlas editing, to define with a small amount of interactions a coarse quadrangulation of the model, capturing the main features of the shape, with user prescribed extraordinary vertices and alignment. Fine grain tuning is easily achieved with the notion of connectivity texturing, which allows for additional extraordinary vertices specification and explicit feature alignment, to capture the high-frequency geometries. Experiments demonstrate the interactivity and flexibility of our approach, as well as its ability to generate quad meshes of arbitrary resolution with high-quality statistics, while meeting the user’s own subjective requirements. 相似文献
Approximately 15 million cars and trucks reach the end of their useful life in the United States each year. More than 75%
of the materials from end-of-life vehicles are profitably recovered and recycled by the private sector; automotive materials
recycling is a success story. To achieve greater fuel efficiency and safety, today’s cars incorporate an increasing share
of innovative light-weight materials. While these materials greatly enhance efficiency during vehicle use, they can present
special challenges for recycling. These challenges will persist as automotive designs and the mix of materials used in vehicles
continue evolving to further improve safety and performance. To meet the challenges of automotive materials recycling, the
U.S. Department of Energy has recently expanded its collaborative research with industry in this area. This article discusses
this collaborative government/industry approach to sustainable end-of-life vehicle recycling.
For more information, contact Edward J. Daniels, Argonne National Laboratory, 9700 S. Cass Avenue, Building 362, Room C393,
Argonne, IL 60439-4815; (630) 252-5279; fax (630) 252-1342; e-mail edaniels@anl.gov. 相似文献
Undergraduate courses in electromechanical energy conversion are typically oriented toward the steady-state analysis of electrical machines. The advent of low-cost computer power and the availability of numerical software tools provide the opportunity to fundamentally reorient the pedagogical approach to the topic. A new approach is consistent with the developing need to emphasize the study of new machine designs and machines employed for control purposes as well as machines for use in more traditional power applications. This paper presents the results obtained from simulations developed as an integral part of an undergraduate electrical machines course at the University of Dayton, USA. Sample simulation files are presented to demonstrate the ease with which the matrix model of the machine is transferred to the program. The matrix models and simulation results of the following machines are included: the single-phase transformer; the variable-reluctance machine; the cylindrical-rotor dual-winding machine; the symmetrical two-phase induction motor; a PWM-controlled DC machine; and an inverter-driven brushless machine. The selected machines provide a systematic framework for analysis and simulation and present problems of increasing complexity to the student 相似文献