NON DESTRUCTIVE DIELECTRIC CHARACTERIZATION OF THIN FERROELECTRIC FILMS MATERIALS USING COPLANAR LINE STRUCTURE

ABSTRACT

This paper presents a nouvelle and non-destructive Broadband characterization method which uses a coplanar line for the measurement of the complex permittivity of linear dielectric materials and precisely, that of ferroelectric thin films. The method uses the transmission coefficient and the quasi-TEM analysis to find the effective permittivity of the multilayer system, and then the coplanar conformal mapping technique is employed to extract the relative permittivity of the thin layer. Comparing our results to those of cavity resonator method at 12 GHz shows a good agreement. The measurement is done in the microwave frequency band (45 MHz–20 GHz).     

EFFECT OF THIN KNbO3 SEED LAYERS ON PULSED LASER DEPOSITED FERROELECTRIC KTa0.65Nb0.35O3 FILMS FOR MICROWAVE TUNABLE APPLICATION

ABSTRACT

Ferroelectric KTa_0.65Nb_0.35O₃ thin films were grown by pulsed laser deposition on R-plane sapphire substrates. The potassium enriched ceramic targets were used for compensating potassium losses. In order to improve the KTa_0.65Nb_0.35O₃ film growth on sapphire, a thin KNbO₃ layer was introduced as seed layer. The experimental results show that the crystalline quality is lowered when increasing the K-excess. Simultaneously, phase purity, orientation and crystalline quality of perovskite (h00)-oriented KTa_0.65Nb_0.35O₃ are greatly improved by the use of the KNbO₃ seed layer. In particular, the presence of the latter effectively suppresses any pyrochlore secondary phase formation.     

Displacement fields using correlation methods as a tool to investigate cell migration in 3D collagen gels

Living cells embedded in a complex extra-cellular matrix migrate in a sophisticated way thanks to adhesions to matrix fibres and contractility. It is important to know what kind of forces are exerted by the cells. Here, we use reflectance confocal microscopy to locate fibres accurately and determine displacement fields. Correlation techniques are used to this aim, coupled with proper digital image processing. Benchmark tests validate the method in the case of shear and stretching motions. Finally, the method is tested successfully for studying cancer cells migrating in collagen gels of different concentration.     

植物纤维单块土坯抗压试验研究

通过对同尺寸的单块素土坯及掺和麦秸秆的单块土坯的各向抗压试验获得了素土坯和掺和麦秸秆土坯的抗压强度及受力破坏形态,总结了单块土坯抗压试验的试验过程及试验现象。得到荷载—位移曲线后,评估掺和麦秸秆对土坯抗压承载能力的影响及得出了麦秸秆的最优掺量。掺和适量的麦秸秆能提高土坯的抗压强度及应变能力。从本试验研究得出的结果,为土坯砌体试验和土坯墙片试验提供基本力学性能数据。     

SWEETNESS EQUIVALENCE OF DIFFERENT SWEETENERS IN STRAWBERRY‐FLAVORED YOGURT

ABSTRACT

To successfully substitute sucrose for sweeteners, further studies must be carried out based on previous knowledge of sweetener concentration to determine the equivalent sweetness of such compounds. In this work, sweetness equivalence of strawberry‐flavored yogurt with different sweeteners and/or their combinations (aspartame, acesulfame‐K, cyclamate, saccharin, stevia and sucralose) and yogurt sweetened with 11.5% w/w sucrose was measured using the sensory magnitude estimation method. The sweetness concentrations equivalent to strawberry yogurt sweetened with 11.5% w/w sucrose in the tested sweeteners were 0.072% w/w for aspartame, 0.042% w/w for aspartame/acesulfame‐K (2:1), 0.064% w/w for cyclamate/saccharin, 0.043% w/w for cyclamate/saccharin (2:1)/stevia (1.8:1) and 0.30% w/w for sucralose. These results can promote the use of different sweetener combinations in strawberry‐flavored yogurt, specially acesulfame‐K and stevia, once they produce more pleasing in this product.

PRACTICAL APPLICATIONS

This study provides some useful information, since there is no data in the literature about sweetness equivalence of sweeteners in yogurt, but only in simpler matrices such as pure water, juices, coffee and teas. The use of stevia blend presented several advantages such as increased sweetening power, demonstrating the potential of this natural sweetener. The magnitude estimation method has been successful in this study, being an important tool for development of new low‐calorie products. It may be noted that when evaluating different types of food using the same kinds of sweeteners, these promote distinct characteristics and that reflect directly on the sensory quality of the final product. Thus, such studies generate important information for the food industries working with dietetic food.     

A versatile sample holder for single plane illumination microscopy

Single Plane Illumination Microscopy is an emerging and powerful technology for live imaging of whole living organisms. However, sample handling that relies on specimen embedding in agarose or gel is often a key limitation, especially for time‐lapse monitoring. To address this issue, we developed a new concept for a holder device allowing us to prepare a sample container made of hydrogel. The production process of this holder is based on 3D printing of both a frame and casting devices. The simplicity of production and the advantages of this versatile new sample holder are shown with time‐lapse recording of multicellular tumour spheroid growth. More importantly, we also show that cell division is not impaired in contrast to what is observed with gel embedding. The benefit of this new holder for other sample types, applications and experiments remains to be evaluated, but this innovative concept of fully customizable sample holder preparation potentially represents a major step forward to facilitate the large diffusion of single plane illumination microscopy technology.