Search

In the last years, Model Predictive Control (MPC) proved to be one of the most promising approaches for an Artifcial Pancreas (AP), a device for closed-loop blood glucose control in subjects afected by Type 1 Diabetes (T1D). MPC performance is highly infuenced by the quality of the model used for prediction. Moreover, the inter-patient variability characterising subjects with T1D increases the need of patient-tailored models. Recently, promising results have been obtained in silico using the UVA/Padova simulator in Soru et al. (2012) and Messori et al. (2016) where diferent individualization techniques have been studied and compared to the “average” model of the UVA/Padova adult population showing signifcant improvements in term of prediction ability. The aim of this paper is to verify the applicability of the technique described in Soru et al. (2012) and extend it to be used on free-living data collected without ad hoc clinical protocols. Data were collected during a 1 month trial in free-living conditions (Renard et al. (2016)). In this proof-of-concept case study, individualized models obtained with diferent identifcation parameters are compared with the “average” model that was used to synthetize the MPC controller used during that trial. The individualized models show superior prediction performance and prove robustness to non-optimal algorithm initialization in a selected test-case.

Type 1 diabetes is a disease caused by an autoimmune reaction. The Artificial Pancreas (AP) is an automatic closed-loop system composed of a subcutaneous glucose sensor, a subcutaneous insulin pump and a device on which a control algorithm and a human interface are implemented. The last years have seen an accelerated improvement of these three components that became more reliable and compact, making the system safer, wearable, and usable in real life. An overview on AP and its components is presented together with an introduction on the in-silico tools used to develop and tune the control algorithm and to make pre-clinical tests. Particular attention is devoted to the design of a Model Predictive Control, to the choice of the model and of the constraints, and to the definition of the most relevant performance indices. Most of the choices have been driven by the experience gained by both in-silico and in-vivo trials. In-silico experiments involved thousand of hours of simulations on the Food and Drug Administration accepted simulator equipped with 100 adult virtual patients. In-vivo experiments, of which a complete list is presented, involved about forty thousand hours of trials, first, conducted in a clinical environment and, then, at home.

The identification of patient-tailored linear time invariant glucose-insulin models is investigated for type 1 diabetic patients, that are characterized by a substantial inter-subject variability. The individualized linear models are identified by considering a novel kernel-based nonparametric approach and are compared with a linear time invariant average model in terms of prediction performance by means of the coefficient of determination, fit, positive and negative max errors, and root mean squared error. Model identification and validation are based on in-silico data collected from the adult virtual population of the UVA/Padova simulator. The data generation involves a protocol designed to produce a sufficient input excitation without compromising patient safety, compatible also with real life scenarios. The identified models are exploited to synthesize an individualized Model Predictive Controller (MPC) for each patient, which is used in an Artificial Pancreas to maintain the blood glucose concentration within an euglycemic range. The MPC used in several clinical studies, synthesized on the basis of a non-individualized average linear time invariant model, is also considered as reference. The closed-loop control performance is evaluated in an in-silico study on the adult virtual population of the UVA/Padova simulator in a perturbed scenario, in which the MPC is blind to random variations of insulin sensitivity in each virtual patient.

Summary:The sol‐gel synthesis of organic‐inorganic hybrids based on triethoxysilane‐ terminated poly(ethylene oxide) and tetraethylorthosilicate was monitored in‐situ using three spectroscopic methods (FTIR/ATR, Raman, NIR). These spectroscopic methods allow in‐situ monitoring of the evolution of hybrid materials starting from the modification of the polymer and the early steps of hydrolysis up to the network formation. By application of 29Si solid‐state NMR spectroscopy the assignment and quantification of the Raman bands to different end groups and different cross‐linking states was made. The sol‐gel reaction was also followed by in‐line NIR spectroscopy. A multivariate data analysis was accomplished to obtain a conversion‐time curve. Furthermore, we investigated spin‐coated films on wafers using FTIR transmission spectroscopy.

Hybrid coatings, based on poly(ethylene oxide) (PEO) or polycaprolactone (PCL) and silica (SiO2), at different organic–inorganic compositions have been used to coat PET films employed in the electric industry to produce capacitors. The overall electrical behavior of the coated films has been investigated. The electrical strength of the coated films increases up to 10–15% of the uncoated ones regardless of polymer type (PEO/PCL) and amount of inorganic phase, as far as the thickness of the coating is below 5 μm. A systematic increase of surface electrical conductivity is found in all coated samples which however still behave as insulators. Permittivity and loss factor also increase particularly at low frequencies (< 10 Hz) on account of the presence of ions deriving from the sol–gel process and on the presence of interfacial polarization probably related to the coatings nanostructurated morphology which leads to phase separation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4870–4877, 2006

A complete study of the catalytic activity of lanthanide- and hafnium acetylacetonate catalysts in PBT synthesis was conducted in order to investigate any improvement in the process and/or in the properties of the final polymer with respect to the industrially used titanium tetrabutoxide (TBT) catalyst. Small scale polymerization and subsequent scale up in higher capacity reactors showed that TBT-Hf(acac)4and TBT-La(acac)3mixed catalysts were more active with respect to TBT as single catalyst. Decreases in polymerization time and THF formation were also observed, which in turn can improve the productivity of the whole process. Furthermore, for similar values of molecular weight, a lower melt viscosity (and thus better processability and crystallizability) was obtained by using mixed catalysts, presumably due to weaker interactions of the polymer terminal groups to lanthanum and hafnium metals with respect to titanium.

Poly(ɛ-caprolactone-b-perfluoropolyether-b-ɛcaprolactone) (PCL–PFPE–PCL) block copolymers having different PCL block lengths and end-capped with methacrylate groups were prepared and characterized. Spectroscopic analyses confirmed the expected molecular structure of the products. After UV curing, the films revealed the presence of two amorphous phases, corresponding to fluorinated and hydrogenated moieties, respectively. The material containing long PCL blocks showed also a crystalline phase. Surface properties of the UV-cured films were evaluated: The surfaces have a very high hydrophobic character in spite of the presence of many polar OH groups present in the polymeric network and a high hysteresis in wetting. An enrichment of fluorine at the air-side surface was shown by contact-angle measurements, except when long PCL sequences are present. The θadv angles decreased by increasing the content of PCL, that is, by decreasing the content of fluorine. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 651–659, 2000

Hydroxyl-terminated telechelic poly(fluoroalkylene oxide)s, (PFPE)s, with molecular weights ranging from 1100 to 3400 were employed as transfer agents for the ring-opening polymerization of ε-caprolactone (CL) in the presence of various catalysts/initiators. The highest conversion rate of CL was observed using Ti(OBu)4 and Bu2SnO as catalysts/initiators. The polymerization of CL started only from the hydroxyl groups of PFPE, leading to the formation of ABA triblock copolymers without formation of homopolymer poly(ε-caprolactone) (PCL). The rate of insertion of the first unit of CL is much faster than the insertion of the other CL units, and the average molecular weight of the ABA copolymers was that expected by the CL/PFPE ratio. The polymerization rate of CL in the presence of PFPE using aluminum alkoxides as initiator was very slow, contrary to what is known about the homopolymerization of CL.

The catalytic reactivity of maleic anhydride (MA), succinic anhydride (SA) and their dimethyl esters (dimethyl maleate and dimethyl succinate) in the vapour phase hydrogenation to γ-butyrolacetone (GBL) was investigated. In order to obtain general data, both a multicomponent catalyst (CAT 1: Cu/Zn/Mg/Cr 40 : 5 : 5 : 50, atomic ratio %), obtained by reduction of a nonstoichiometric spinel-type precursor, and a commercial catalyst (CAT 2: Cu/Mn/Ba/Cr = 44 : 8 : 1 : 47, atomic ratio %) were used. The MA/GBL solution exhibited the highest GBL production, while the SA/GBL solution was converted only partially due to a competitive adsorption of GBL on the active sites, as evidenced by the similar reactivities observed with pure anhydrides. The best carbon balances were observed with the esters, probably the result of lowest light hydrocarbon synthesis and tar formation. With all the feedstocks, the activity of CAT 2 is higher than that of CAT 1, which, however, gives the best yield in GBL due its lower activity in the overhydrogenation and hydrogenolysis reaction. It was found that n-butanol (BuOH) and butyric acid (BuA) derived mainly from GBL. On this basis, the reactivities of the main products observed were investigated separately, confirming the stability of tetrahydrofuran (THF), which reacted only at high temperature with low conversions to ethanol. On the other hand, GBL gave rise to overhydrogenation and/or hydrogenolysis, with high conversion (mainly with CAT 2), confirming its key role in both reactions. Furthermore, the formation in the catalytic tests with BuA and BuOH of n-butanal, notwithstanding the high H2/organic ratio, implies that it is the main intermediate in the hydrogenolysis reactions. A new reaction scheme is proposed, pointing out the key role of GBL as the "intersection" of two possible reaction pathways, giving rise to THF or overhydrogenation and hydrogenolysis products, respectively.

Telechelic macromers based on hydroxyterminated perfluoropolyethers (HO-RH-PFPE-RH-OH) with different molecular weights were used for the preparation of fluorine-containing unsaturated polyester resins (FUPR). The products resulting from the reaction of the monomers usually employed for the preparation of unsaturated polyesters with HO-RH-PFPE-RH-OH were in any case milky liquids. The degree of reaction of the hydroxyl terminal groups of HO-RH-PFPE-RH-OH was monitored by ¹H-NMR analysis on the fractions collected after sedimentation experiments; amount and composition of the sediment and sedimentation rate were found dependent on both the molecular weight of fluorinated macromer and the method used for polyesterification. The molecular weight of HO-RH-PFPE-RH-OH and the reaction conditions had also a strong influence on the final morphology of crosslinked polymers. A very poor interphase adhesion was observed when unreacted HO-RH-PFPE-RH-OH was blended with the unsaturated polyester. On the contrary, when the fluorinated macromer was allowed to react during polyesterification, the adhesion of the fluorine-rich dispersed phase to the unsaturated polyester matrix was good for low molecular weight HO-RH-PFPE-RH-OH and when the fluorinated prepolymer had been modified by a previous reaction with chlorendic anhydride, but it was poor, as for unreacted macromers, for high molecular weight HO-RH-PFPE-RH-OHs. FUPRs prepared using a low molecular weight HO-RH-PFPE-RH-OH exhibited a significant improvement of the flexural strength even at very low level of addition (3% by wt). © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1679–1691, 1998

Vanadium is a key element in the formulation of catalysts for the production of anhydrides by selective vapor oxidation with molecular oxygen. A study of the oxidations ofo-xylene,n-butane and benzene on V-P, V-Mo and V-Ti mixed oxides, the commercial catalysts for the synthesis of anhydrides, was carried out. The oxidation ofo-xylene on the three catalysts was the most facile reaction leading to high yields in phthalic anhydride; on the contrary in the oxidation ofn-butane only V-P mixed oxide was active and selective. V-P mixed oxide is active and selective in the oxidation of all the feedstocks and can be identified as the most polyfunctional catalyst. V-Mo is active and selective in botho-xylene and benzene oxidation and V-Ti only ino-xylene oxidation. Moreover the lesser selectivity in phthalic anhydride observed with V-P and V-Mo mixed oxides has been attributed to parallel oxidation reactions to the formation of phthalic anhydride, evidenced by a higher amount of phthalide.