A comparison of emulsifiers for the formation of oil-in-water emulsions: stability of the emulsions within 9 h after production and MR signal properties

Objective

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 (r_1,lecithin = 0.11 wt.%⁻¹ s⁻¹, r_2,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.

     

BiFeO3 Ceramics: Processing,Electrical, and Electromechanical Properties

Bismuth ferrite (BiFeO₃), a perovskite material, rich in properties and with wide functionality, has had a marked impact on the field of multiferroics, as evidenced by the hundreds of articles published annually over the past 10 years. Studies from the very early stages and particularly those on polycrystalline BiFeO₃ ceramics have been faced with difficulties in the preparation of the perovskite free of secondary phases. In this review, we begin by summarizing the major processing issues and clarifying the thermodynamic and kinetic origins of the formation and stabilization of the frequently observed secondary, nonperovskite phases, such as Bi₂₅FeO₃₉ and Bi₂Fe₄O₉. The second part then focuses on the electrical and electromechanical properties of BiFeO₃, including the electrical conductivity, dielectric permittivity, high‐field polarization, and strain response, as well as the weak‐field piezoelectric properties. We attempt to establish a link between these properties and address, in particular, the macroscopic response of the ceramics under an external field in terms of the dynamic interaction between the pinning centers (e.g., charged defects) and the ferroelectric/ferroelastic domain walls.     

Thermal-stability of electric field-induced strain and energy storage density in Nb-doped BNKT-ST piezoceramics

In this work, the relationship between the structural mechanisms and macroscopic electrical properties of the Nb-modified 0.96(Bi_0.5Na_0.84K_0.16TiO₃)–0.04SrTiO₃ (BNKT–ST) system were elucidated by using temperature dependent and in situ synchrotron X-ray diffraction (XRD) techniques. For the composition x?=?0.0175, a large-signal piezoelectric coefficient (S_max/E_max?=?d₃₃*) of 735 pm?V^?1 at 6?kV mm^?1 was observed at room temperature. Interestingly, at a higher temperature of 110?°C, the sample still showed a large d₃₃* of 570 pm V^?1. Furthermore, the temperature-invariant electrostrictive coefficient for this sample was found to be 0.0285?m⁴?C^?2 over the temperature range of 25–170?°C. Moreover, the energy density for x?=?0.030 sample was ～1.0?J?cm^?3 with an energy storage efficiency of ?70% in the temperature range of 25–135?°C. These results suggest that the synthesized Nb-modified BNKT–ST system is promising for the design of ceramic actuators as well as capacitor applications.     

Application of constraint logic programming to asset and liability management in banks

Constraint logic programming is a relatively new and promising paradigm. In this paper it is shown that this approach yields flexible tools to support financial decision making. As an example we present an asset and liability management model implemented in the CHIP language.     

Microwave remote sensing of physically buried objects in the Negev Desert: implications for environmental research

We report remote detections of physically buried specularly reflecting objects using microwave radar at two sites: Ashalim and Tseelim in the northern region of the Negev Desert, Israel. These detections provide confirmation that microwave subsurface remote sensing is a genuine phenomenon. At Ashalim, a scatterometer operating in the P-band (441 MHz, 68 cm) was mounted on a cherry picker truck at a height of 8 m and used to detect two triangular aluminum mesh reflectors (forming a 1-m square area reflector) buried down to a depth of 8 cm in dry sand. At Tseelim, the same scatterometer was mounted on an airplane flying at an altitude of 70 m and used to detect 1-m square aluminum reflectors (each one submerged at a different location along the airplane flight path) buried down to a depth of 20 cm. The experimental results compare favorably with a theoretical model that incorporates radar absorption effects arising in the sandy subsurface layer and radar interference effects arising from phase differences between reflections from the surface and buried reflector. The theoretical modeling also predicts the detection of a subsurface reflector down to a depth of about 4.4 m. This experiment and the associated modeling approach is the first of a series of planned experiments, which we outline for the detection and the theoretical evaluation of buried reflectors using remote microwave and VHF radar. We identify potential subject areas for environmental research.     

Interactive quadrangulation with Reeb atlases and connectivity textures

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.     

Multiple Translational Containment Part I: An Approximate Algorithm

We present an algorithm for finding a solution to the two-dimensional translational approximate multiple containment problem: find translations for k polygons which place them inside a polygonal container so that no point of any polygon is more than 2ε inside of the boundary of any other polygon. The polygons and container may be nonconvex. The value of ε is an input to the algorithm. In industrial applications the containment solution acts as a guide to a machine cutting out polygonal shapes from a sheet of material. If ε is chosen to be a fraction of the cutter's accuracy, then the solution to the approximate containment problem is sufficient for industrial purposes. Given a containment problem, we characterize its solution and create a collection of containment subproblems from this characterization. We solve each subproblem by first restricting certain two-dimensional configuration spaces until a steady state is reached, and then testing for a solution inside the configuration spaces. If necessary, we subdivide the configuration spaces to generate new subproblems. The running time of our algorithm is , where s is the largest number of vertices of any polygon generated by a restriction operation. In the worst case s can be exponential in the size of the input, but, in practice, it is usually not more than quadratic. Received June 24, 1994; revised August 22, 1995.     

如何对付“强制缔约”合同

对于一名为自动化公司提供咨询的律师来说,一件让人很不爽的事情就是有时候摆在我面前的事情是如此之多。下面是一个例子：比方说控制工程有限公司（Control Engineers Limited,CEL）希望让我就一个新项目提供一些法律意见。出现在我的收件箱中的是一份来自于CEL的客户的小礼物．其中包括一份40页的“一般条件说明”．一份5页的“特殊情况说明”．一些令人生畏的规格．以及一份打印精美的采购合同。     

A study of Hogan's model of counselor development and supervision.

The construct validity and developmental structure of R. A. Hogan's (see record 1966-00843-001) model of counselor development and supervision were studied using a sample of 141 counseling psychology graduate student trainees, interns, and professional staff in 20 university counseling centers. Counselor development questionnaire items were developed into 2 arrangements: one based on Hogan's concepts as he organized them into levels, and another derived empirically using factor analysis. The 2 configurations were compared for their ability to predict experience level of Ss using discriminant function analysis. Each empirical factor was also examined for relationship with experience by means of 1-way ANOVA with preplanned comparisons. Results indicate that counselor development is best described by a complex rather than a simple model and that it involves factors of Anxiety/Doubt, Independence, Method/Skills Training, Work Validation, Commitment Ambivalence, and Respectful Confrontation. Developmental profiles of these issues are described, and implications for supervision and training programs are discussed. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)