Accurate modelling for the analysis and design of liquid-crystal-based microwave devices

Liquid crystal substrates have been shown to provide the means to develop low-cost, reconfigurable, adaptive and tuneable microwave and MM-wave devices for mobile and wireless communication systems. However, techniques for the characterisation of materials, device fabrication and design are necessary in order to take maximum advantage of the possibilities that these materials offer. This includes appropriate modelling methods to simulate accurately the switching behaviour of the liquid crystal and the characteristics of the wave propagation through the devices, taking full consideration of the point-by-point variation of the material tensor permittivity. We describe these techniques here and show their application in the design of a meander-line phase shifter

Thin-Film Composite Forward-Osmosis Membranes Reinforced on Woven Mesh and Nonwoven Backing Fabric Supports

Thin-film composite (TFC) forward-osmosis (FO) membranes were developed on different woven and nonwoven backing fabrics as support. Embedded backing fabrics have a significant effect on the membrane film sublayer by imparting porosity, membrane mechanical strength, and thickness. Woven and nonwoven backing fabric supports have been used for FO membranes cast on the commercial scale. There are also a few studies on the laboratory scale, but repeating them seems to be a challenge. The results herein show that TFC membranes with nonwoven incorporated substrates gain a higher water flux while keeping the specific reverse salt flux low

Development of 60 GHz Phased Antenna Arrays Using Liquid Crystal Phase-shifters

Liquid crystal based antenna arrays with beam steering capability in one dimension for 60 GHz band is presented. Two array designs are discussed. First design uses slotted patch antenna as an array element. For this array a compact, planar, liquid crystal based meander line phase shifter is designed which have a maximum differential phase shift of 47°. The array comprises of a 4×1 slotted patch array, which is able to scan up to 14° in the E-plane. Second design uses patch antenna as an array element. In this array the phase shifters are liquid crystal based meander lines, each providing a maximum differential phase shift of 38°. The array elements (the patch antennas) are coupled to the microstrip feed line through coupling gaps. These gaps are adjusted in order to uniformly excite the antenna patches. The designed array comprises of a 4 × 1 patch array, which is able to scan up to 9° in the E-plane as the bias on the liquid crystal changes from zero to saturation voltage

Accurate Modelling of Liquid Crystal-Based Microwave Devices

Liquid crystal substrates have been shown to provide the means to develop low-cost, reconfigurable, adaptive and tuneable microwave devices for mobile and wireless communication systems. In order to take maximum advantage of the possibilities that these materials offer and to design LC-based devices appropriately, techniques for the characterisation of the liquid crystal dielectric properties are needed. Similarly, appropriate modelling methods are required to simulate accurately the switching behaviour of the liquid crystal and the characteristics of the wave propagation through the devices, taking full consideration of the point-by-point variation of the material tensor permittivity

p57Kip2 regulates embryonic blood stem cells by controlling sympathoadrenal progenitor expansion

Hematopoietic stem cells (HSCs) are of major clinical importance, and finding methods for their in vitro generation is a prime research focus. We show here that the cell cycle inhibitor p57Kip2/Cdkn1c limits the number of emerging HSCs by restricting the size of the sympathetic nervous system (SNS) and the amount of HSC-supportive catecholamines secreted by these cells. This regulation occurs at the SNS progenitor level and is in contrast to the cell-intrinsic function of p57Kip2 in maintaining adult HSCs, highlighting profound differences in cell cycle requirements of adult HSCs compared with their embryonic counterparts. Furthermore, this effect is specific to the aorta-gonad-mesonephros (AGM) region and shows that the AGM is the main contributor to early fetal liver colonization, as early fetal liver HSC numbers are equally affected. Using a range of antagonists in vivo, we show a requirement for intact β2-adrenergic signaling for SNS-dependent HSC expansion. To gain further molecular insights, we have generated a single-cell RNA-sequencing data set of all Ngfr+ sympathoadrenal cells around the dorsal aorta to dissect their differentiation pathway. Importantly, this not only defined the relevant p57Kip2-expressing SNS progenitor stage but also revealed that some neural crest cells, upon arrival at the aorta, are able to take an alternative differentiation pathway, giving rise to a subset of ventrally restricted mesenchymal cells that express important HSC-supportive factors. Neural crest cells thus appear to contribute to the AGM HSC niche via 2 different mechanisms: SNS-mediated catecholamine secretion and HSC-supportive mesenchymal cell production.Chrysa Kapeni, Leslie Nitsche, Alastair M. Kilpatrick, Nicola K. Wilson, Kankan Xia, Bahar Mirshekar-Syahkal, Vashe Chandrakanthan, Camille Malouf, John E. Pimanda, Berthold Gottgens, Kristina Kirschner, Simon R. Tomlinson, and Katrin Ottersbac