Robust state estimation for a class of uncertain time-delay systems

This paper considers a robust state estimation problem for a class of uncertain time-delay systems. In this problem, the noise and uncertainty are modelled deterministically via an integral quadratic constraint. The robust state estimation problem involves constructing the set of all possible states at the current time consistent with given output measurements and the integral quadratic constraint. This set is found to be an ellipsoid which is constructed via a linear state estimator.     

Ratiometric Nanoparticle Probe Based on FRET‐Amplified Phosphorescence for Oxygen Sensing with Minimal Phototoxicity

Luminescent oxygen probes enable direct imaging of hypoxic conditions in cells and tissues, which are associated with a variety of diseases, including cancer. Here, a nanoparticle probe that addresses key challenges in the field is developed, it: i) strongly amplifies room temperature phosphorescence of encapsulated oxygen‐sensitive dyes; ii) provides ratiometric response to oxygen; and iii) solves the fundamental problem of phototoxicity of phosphorescent sensors. The nanoprobe is based on 40 nm polymeric nanoparticles, encapsulating ≈2000 blue‐emitting cyanine dyes with fluorinated tetraphenylborate counterions, which are as bright as 70 quantum dots (QD525). It functions as a light‐harvesting nanoantenna that undergoes efficient Förster resonance energy transfer to ≈20 phosphorescent oxygen‐sensitive platinum octaethylporphyrin (PtOEP) acceptor dyes. The obtained nanoprobe emits stable blue fluorescence and oxygen‐sensitive red phosphorescence, providing ratiometric response to dissolved oxygen. The light harvesting leads to ≈60‐fold phosphorescence amplification and makes the single nanoprobe particle as bright as ≈1200 PtOEP dyes. This high brightness enables oxygen detection at a single‐particle level and in cells at ultra‐low nanoprobe concentration with no sign of phototoxicity, in contrast to PtOEP dye. The developed nanoprobe is successfully applied to the imaging of a microfluidics‐generated oxygen gradient in cancer cells. It constitutes a promising tool for bioimaging of hypoxia.     

Edge States and Topological Phase Transitions in Chains of Dielectric Nanoparticles

Recently introduced field of topological photonics aims to explore the concepts of topological insulators for novel phenomena in optics. Here polymeric chains of subwavelength silicon nanodisks are studied and it is demonstrated that these chains can support two types of topological edge modes based on magnetic and electric Mie resonances, and their topological properties are fully dictated by the spatial arrangement of the nanoparticles in the chain. It is observed experimentally and described how theoretically topological phase transitions at the nanoscale define a change from trivial to nontrivial topological states when the edge mode is excited.     

Photoaligned Nanorod Enhancement Films with Polarized Emission for Liquid‐Crystal‐Display Applications

Semiconductor nanorods (NR) emit polarized light, which is expected to bring manifold benefits, in terms of brightness and color enhancement, for modern liquid‐crystal displays (LCD). In this regard, photoaligned nanorod enhancement films (NREF) for color and polarization conversion for LCD backlights are introduced here. The photoinduced anchoring forces, by the photoalignment layer, stimulate well‐ordered self‐assembly of NR in the thin polymer films. Green and red emitting NR with a quantum yield of ≈80% are aligned unidirectionally and in‐plane, showing a polarization ratio of >7:1 and a degree of polarization of >0.81. The photoalignment technique facilitates the fabrication of mixed and multiple stacked NREF for LCDs, which improves the color gamut and polarization efficiency, and is thus expected to increase the optical efficiency of conventional LCDs by ≈60%.     

Fe–As Bond Fluctuations in a Double-Well Potential in LaFeAsO

While for a long time, iron-based superconductors have been investigated looking at the average crystalline structure, there is now growing interest on the divergence of local from the average structure. Here, we use advanced data analysis of EXAFS, a fast and local probe, which has key advantages compared to crystallographic measurements, in unveiling the dynamics of the local structure. The results show that the Fe–As pair oscillates in the double-well potential both in undoped and in cobalt-doped LaFeAsO crystals. The parameters and the characteristics of the double-well potential are determined by curve fits of the polarized EXAFS data. Temperature-dependent Fe–As pair distribution and tunneling frequency are derived from selected model of two potential wells. We observe the softening of the Fe–As oscillations at the tetragonal to orthorhombic structural phase transition at 150 K in LaFeAsO. A weak broad softening is observed while decreasing the temperature from 70 to 40 K in superconducting LaFe_0.89Co_0.11AsO which could be correlated with the onset of short-range charge density wave order.     

Characterization of the nonlinear fracture resistance parameters for an aviation GTE turbine disc

The effects of crack growth rate model formulation, based on the elastic‐plastic and undamaged/damaged creep crack tip fields on the behaviour of low‐cycle fatigue and creep fracture resistance parameter behaviour, are represented by numerical calculations. The crack growth rate models include the fracture process zone size and damage parameters. An aviation gas turbine engine (GTE) rotating turbine disc is the focus of this innovative application of basic analytical and numerical solutions. For the GTE turbine disc, the constraint parameters, local fracture process zone sizes, and nonlinear plastic (K_p) and creep (K_cr) stress intensity factors are calculated by finite element analysis to characterize the fracture resistance along the semielliptical crack front as a function of the flaw aspect ratio, operation temperature, and disc rotation speed. Predictions of the creep‐fatigue crack growth rate and residual lifetime are given for different combinations of operation loading conditions and damage of the GTE turbine disc.     

Residual stress/strain evolution due to low‐cycle fatigue by removing local material volume and optical interferometric data

Three experimental methods, based on optical interferometric measurements of deformation response to local material removing, have been implemented for residual stresses determination. Two first techniques are employed to characterize initial residual stress values and their evolution near welded joints of aluminium plates under low‐cycle fatigue. The hole‐drilling method gives high‐accurate dependencies between residual stress components and number of cycles. The second approach comprises cracks modelling by narrow notches to describe residual stress distributions in more wide spatial range near the weld. The results demonstrate residual stress evolution is of complex character and cannot be uniquely qualified as a gradual relaxation. Besides, the secondary hole drilling method is developed and used as a fast and reliable tool to quantify the redistribution of residual strains near cold‐expanded holes due to low‐cycle fatigue. Dependencies of circumferential residual strains along the secondary hole edge versus number of cycles are constructed.     

Early morphological changes in tissues when replacing abdominal wall defects by bacterial nanocellulose in experimental trials

Experimental trials were done on five dogs to explore if an anterior abdominal wall defect could be repaired using wet (99.9%), compact BNC membranes produced by the Мedusomyces gisevii Sa-12 symbiotic culture. The abdominal wall defect was simulated by middle-midline laparotomy, and a BNC membrane was then fixed to open aponeurotic edges with blanket suture (Prolene 4-0, Ethicon). A comparative study was also done to reinforce the aponeurotic defect with both the BNC membrane and polypropylene mesh (PPM) (Ultrapro, Ethicon). The materials were harvested at 14 and 60 days postoperative to visually evaluate their location in the abdominal tissues and evaluate the presence of BNC and PPM adhesions to the intestinal loops, followed by histologic examination of the tissue response to these prosthetics. The BNC exhibited good fixation to the anterior abdominal wall to form on the 14th day a capsule of loose fibrin around the BNC. Active reparative processes were observed at the BNC site at 60 days post-surgery to generate new, stable connective-tissue elements (macrophages, giant cells, fibroblasts, fibrin) and neocapillaries. Negligible intraperitoneal adhesions were detected between the BNC and the intestinal loops as compared to the case of PPM. There were no suppurative complications throughout the postsurgical period. We noticed on the 60^th day after the BNC placement that collagenous elements and new capillary vessels were actively formed in the abdominal wall tissues, generating a dense postoperative cicatrix whose intraperitoneal adhesions to the intestinal loops were insignificant compared to the PPM graft.

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