OBSERVER-BASED STABILIZATION OF SYSTEMS WITH MONOTONIC NONLINEARITIES

We design an observer-based control law for a class of systems that include monotonic nonlinearities of the unmeasured states. Our observer results in nonlinear error dynamics which can be represented as the feedback interconnection of a linear system and a time-verying multivariable sector nonlinearity. The convergence of the estimation error is guaranteed by an observer matrix that renders the linear part passive, and is computable with LMI software. The feedback design is completed by combining the observer with a control law that renders the plant input-to-state stable with respect to the state estimation error.     

Effects of xanthan gum on physicochemical properties and stability of corn oil-in-water emulsions stabilized by polyoxyethylene (20) sorbitan monooleate

The influence of added xanthan gum on rheological and dispersion characteristics and stability of concentrated (50% w/w) corn oil-in-water emulsions, stabilized with 5% (percentage on oil amount) polyoxyethylene (20) sorbitan monooleate (Tween 80), have been investigated. Emulsion with no xanthan indicated coalescence and poor creaming stability. All emulsions, with and without xanthan, showed shear-thinning flow behavior. Addition of xanthan protected emulsions from coalescence during 15 days of storage. Increase in xanthan concentration led to decrease in droplet average radius and creaming index, and increase in elastic properties of emulsions. Decrease in the emulsions flow behavior indexes, which suggested the extent of non-Newtonian behavior of emulsions, was influenced by increase in xanthan concentration. Above 0.04% of xanthan concentration, G′ and G″ values indicated formation of weak gels. Gel structure existence arises from droplet network association, due to depletion flocculation. Standard deviation of emulsions droplet size mean diameter decreased while concentration of added xanthan increased.     

Synthetic Biology and Tissue Engineering: Toward Fabrication of Complex and Smart Cellular Constructs

Tissue engineering approaches, with the goals of replacing or recovering damaged or diseased tissues, or of reconstituting tissues in vitro for disease modeling and drug development, have the potential to make significant contributions to medicine. Advances in stem cell biology, biomaterial synthesis and characterization, and microscale technologies have made engineered tissues a reality. However, the classic tools used to build tissues in the lab do not allow for complete control of cell behaviors. More recently, synthetic biology principles have developed robust and versatile approaches to program cells with artificial genetic circuits, where cell behavior and function can be manipulated. At the interface between synthetic biology and tissue engineering, there is space for a new area of investigation where material engineering and cellular engineering complement and sustain each other. In this progress report, synthetic biology principles and how they have been used to engineer cells with potential to dictate cell behavior and function in tissue constructs of the future are briefly described. It is believed that this research area still needs further exploration to fully exploit synthetic biology to make smart and functional cellular constructs for therapeutic and in vitro applications.     

Characterization of the Rate-Limiting Steps in the Dark-To-Light Transitions of Closed Photosystem II: Temperature Dependence and Invariance of Waiting Times during Multiple Light Reactions

Rate-limiting steps in the dark-to-light transition of Photosystem II (PSII) were discovered by measuring the variable chlorophyll-a fluorescence transients elicited by single-turnover saturating flashes (STSFs). It was shown that in diuron-treated samples: (i) the first STSF, despite fully reducing the Q_A quinone acceptor molecule, generated only an F₁(<F_m) fluorescence level; (ii) to produce the maximum (F_m) level, additional excitations were required, which, however, (iii) were effective only with sufficiently long Δτ waiting times between consecutive STSFs. Detailed studies revealed the gradual formation of the light-adapted charge-separated state, PSII_L. The data presented here substantiate this assignment: (i) the Δτ_1/2 half-increment rise (or half-waiting) times of the diuron-treated isolated PSII core complexes (CCs) of Thermostichus vulcanus and spinach thylakoid membranes displayed similar temperature dependences between 5 and –80 °C, with substantially increased values at low temperatures; (ii) the Δτ_1/2 values in PSII CC were essentially invariant on the F_k−to-F_k+1 (k = 1–4) increments both at 5 and at −80 °C, indicating the involvement of the same physical mechanism during the light-adaptation process of PSII_L. These data are in harmony with the earlier proposed role of dielectric relaxation processes in the formation of the light-adapted charge-separated state and in the variable chlorophyll-a fluorescence of PSII.     

Toward persistent autonomous intervention in a subsea panel

Intervention autonomous underwater vehicles (I-AUVs) have the potential to open new avenues for the maintenance and monitoring of offshore subsea facilities in a cost-effective way. However, this requires challenging intervention operations to be carried out persistently, thus minimizing human supervision and ensuring a reliable vehicle behaviour under unexpected perturbances and failures. This paper describes a system to perform autonomous intervention—in particular valve-turning—using the concept of persistent autonomy. To achieve this goal, we build a framework that integrates different disciplines, involving mechatronics, localization, control, machine learning and planning techniques, bearing in mind robustness in the implementation of all of them. We present experiments in a water tank, conducted with Girona 500 I-AUV in the context of a multiple intervention mission. Results show how the vehicle sets several valve panel configurations throughout the experiment while handling different errors, either spontaneous or induced. Finally, we report the insights gained from our experience and we discuss the main aspects that must be matured and refined in order to promote the future development of intervention autonomous vehicles that can operate, persistently, in subsea facilities.     

Improvement of the impact strength of ethylene‐propylene random copolymers by nucleation

Five ethylene‐propylene random copolymers were nucleated with two soluble nucleating agents. Ethylene content changed between 1.7 and 5.3 wt %, while nucleating agent content was adjusted according to the solubility of the additive. It changed from 0 to 5000 ppm for the sorbitol (1,2,3‐tridesoxy‐4,6:5,7‐bis‐O‐[(4‐propylphenyl) methylene]‐nonitol) and from 0 to 500 ppm for the trisamide compound (1,3,5‐benzene‐trisamide) used. Crystalline structure was analyzed in detail by various methods (DSC, XRD, and SEM). Mechanical properties were characterized by tensile and instrumented impact measurements. The results showed that most properties changed moderately upon nucleation, but impact resistance increased considerably. Spherulitic structure was not detected, but instead in the presence of the soluble nucleating agents used a microcrystalline structure formed. The large increase of impact resistance could not be related directly to changes in crystalline morphology. On the other hand, local rearrangement of morphology was detected by XRD and SEM analysis including an increase of lamella thickness, crystal orientation, and the formation of shish‐kebab structures in the core of the injection molded specimens. A small increase in the γ‐phase content of PP was also observed. These changes increased crack propagation energy considerably leading to the large improvement observed in impact resistance. Although the phenomenon could be related to ethylene content, differences in molecular weight also helped to explain the changes observed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43823.     

Modeling of liver metastatic disease with applied drug therapy

Colorectal carcinoma is acknowledged as the second leading cause of total cancer-related death in the European Region. The majority of deaths related to colorectal carcinoma are connected with liver metastatic disease. Approximately, in 25% of all patients, liver metastatic disease is diagnosed at the same time as the primary diagnosis, while up to a quarter of others would develop liver metastases in the course of the illness. In this study, we developed reaction-diffusion model and analyzed the effect of drug therapy on liver metastatic disease for a specific patient. Tumor volumes in specific time points were obtained using CT scan images. The nonlinear function for cell proliferation rate as well as data about clinically applied drug therapy was included in the model. Fitting procedure was used for parameter estimation. Good agreement of numerical and experimental results shows the feasibility and efficacy of the proposed system.     

Strategies to enhance dry reforming of methane: Synthesis of ceria-zirconia/nickel–cobalt catalysts by freeze-drying and NO calcination

To improve the activity of nickel–cobalt (NiCo) catalyst supported on ceria-zirconia (CeZr) in the dry reforming of methane (DRM) with carbon dioxide, and to lower the coking rate in this process, 1.5 wt.% and 2.5 wt.% NiCo catalysts were prepared using two approaches, i.e. freeze-drying (FD) and NO calcination for comparison against oven-drying (OD) and air calcination (air), respectively. Their impact was studied for 20 h of DRM at 750 ^°C and 1.2 bar, with undiluted CH₄–CO₂ feed simulating the real conditions. NO-calcined samples show, on average, more pronounced improvement through increased conversion of CH₄ (90%), followed by FD samples (85%) from the air and OD-prepared samples (both 82%). Coking content varied between 0.67 and 0.82 wt.%. The observed slow catalyst deactivation might be caused by sintering of the catalysts. Higher quantity of CO than H₂ for syngas production was obtained, owing to concurrent reverse water-gas shift side reaction, and high redox properties of the defective CeZr lattice that enabled surface carbon gasification by continuous replenishment of oxygen from the support to produce CO, of which the latter phenomenon also explains the low carbon deposition. H₂/CO ratio between 0.42 and 0.85 was achieved, with FD and NO samples fared better (0.83–0.85) over the ones prepared by conventional methods (0.73–0.82) for 2.5%NiCo loaded catalysts.     

Evaluation of in vitro activity of ofloxacin against 73 strains of Chlamydia trachomatis isolated from gynecologic infections

Perfluorocarbon liquids have gained wide acceptance as intraoperative tools that can simplify vitreoretinal surgical maneuvers. These low-viscosity liquids facilitate injection into the eye and removal from the eye during surgery. Tolerance to perfluoroperhydrophenanthrene and the development of proliferative vitreoretinopathy with its extended use are not clear. The authors present the clinical and histologic findings of a patient, previously lost to follow-up, who was examined after several weeks of intraocular tamponade with perfluoroperhydrophenanthrene. Damage to the retina was seen in response to the long-term postoperative use of perfluoroperhydrophenanthrene.