CONTROLLER REDUCTION FOR NONLINEAR PLANTS—AN L2 APPROACH

This paper extends the H_∞ balanced truncation approach of Mustafa–Glover for linear plants to input affine nonlinear plants. Nonlinear H_∞ balanced truncation is used to obtain a reduced order controller. Conditions which ensure that this controller stabilizes the full order plant are derived. This is done by relating the model reduction problem to a robust stabilization problem with unstructured perturbation. In addition an upper bound on the performance of the closed loop system, with respect to the L₂ gain, is obtained. When specialized to linear plants this bound reduces to Mustafa–Glover's result. © 1997 by John Wiley & Sons, Ltd. Int. J. Robust Nonlinear Control, Vol. 7, 475–505 (1997)     

Preparation and phase behavior of blends of polysulfone‐based polymers with phosphorous‐containing smectic‐A liquid crystals

Preparation and experimental studies on the phase transitions and morphology of novel polymer‐dispersed liquid crystal (PDLC) mixtures of polysulfone UDEL‐3000 (PSU) or its derivatives (chloromethylated polysulfone or polysulfone containing lateral phosphaphenanthrene substituent) and a phosphorus‐containing liquid crystalline polymer (LCC) that exhibit isotropic/nematic/smectic‐A mesophase transition were performed. The mesomorphic properties of PDLC have been investigated by differential scanning calorimetry and polarizing optical microscopy. Mesophases structures were also investigated by X‐ray diffraction measurements, the diffraction pattern being in close dependence on the polysulfone structure and PDLC composition. The effect of the phosphorus content on the thermal properties was evaluated by thermogravimetric analysis. The results reveal that the composites were stable up to 337°C in air showing initial decomposition temperatures in the range of 337–368°C and a 10% weight loss in the range of 357–397°C. The presence of P in the structure of LCC leads to higher char yields at 700°C, for PDLCs composites, increasing with the content of phosphorus‐containing polymer. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Tannic acid incorporation in chitosan-based microparticles and in vitro controlled release

Chitosan, a natural polycationic polysaccharide, was coupled with two polyanionic polymers: Na-alginate and carboxymethylcellulose (CMC) and with tannic acid (TA) obtaining three species of self-assembled complexes: chitosan/alginate/TA (sample 1), chitosan/TA (sample 2) and chitosan/CMC/TA (sample 3). The microparticle formation was achieved by dropwise addition of one solution into other by using a coaxial airflow sprayer. These systems were characterized with regard to particle size distribution, thermal stability, tannic acid entrapment efficiency. Sample 2 showed quite a different behavior compared to the other two samples; the particle diameter is located in the nanometric region, the quantity of incorporated tannic acid is higher than in the other two samples and the material shows better thermal stability. The release of tannic acid from these complexes was studied in water (pH = 5.89), phosphates buffer (pH = 7.04) and acetate buffer (pH = 4.11). These studies revealed two distinct periods in tannic acid delivery process: an initial period, varying between 4 and 10 h, characterized by a high release rate with a delivered tannic acid amount of approximately 80% of the incorporated polyphenol and a second period, which starts after 20 to 30 h of delivery and it ends after approximately 120 h, when the release process takes place with low and constant rate and the kinetic curve is linear—characteristic for a zero order kinetic.     

Protein capture in silica nanotube membrane 3-D microwell arrays

The microarray format has allowed for rapid and sensitive detection of thousands of analyte DNAs in a single sample, and there is considerable interest in extending this technology to protein biosensing. While glass is the most common substrate for microarrays, its binding capacity is limited because the glass surface is flat. One way to overcome this limitation is to develop arrays based on porous materials. Such "3-D" arrays can provide greater sensitivity because both the capture molecules and the analyte species they bind are immobilized throughout the thickness of the porous material. We describe here 3-D protein microarrays based on nanopore alumina membranes that contain silica nanotubes within the pores. These microarrays are prepared via a plasma-etch method using a TEM grid as the etch mask and consist of individual nanotube-containing microwells imbedded in a Ag film that coats the alumina membrane surface. We show that the microwells can be functionalized with antibodies and that these antibodies can capture their antigen proteins, which serve as prototype analytes. The analyte proteins are fluorescently tagged, which allows for fluorescence microscopy-based imaging of the array. The Ag surrounding the microwells shows very low background fluorescence, thus improving the signal-background ratio obtained from these arrays.     

Purification and characterization of Phaseolus vulgaris alpha-D-galactosidase isozymes

A highly purified preparation of alpha-D-galactosidase [E.C. 3.2.1.22] isozymes was obtained from Phaseolus vulgaris (pinto bean) seeds by extraction, salt precipitation, ion exchange, and affinity chromatography. The final preparation was homogeneous by SDS-PAGE but revealed isozymes of relative mass of 38.3 and 39.6 kDa. The N-terminal sequence for both isozymes was identical, LANGLAKT (one letter code for amino acids). Relative native molecular mass was estimated at 149.3 kDa by Sephacryl S-200 chromatography. Activity was unaffected by ionic strength at high enzyme concentrations, and was specific for alpha-D-galactoside conjugates. No protease or hemagglutinin activity was detected, and activity was stable at 4 degrees C. Studies with soluble oligosaccharides demonstrated high activity against the selected straight and branched-chain substrates. The enzyme was active against terminal alpha 1-3 galactosyl residues on human and rabbit erythrocyte membranes. Because of its activity against membrane glycoconjugates, these isozymes may have potential utility for modifying membrane epitopes on native erythrocytes.     

Direct Probing of Polarization Charge at Nanoscale Level

Ferroelectric materials possess spontaneous polarization that can be used for multiple applications. Owing to a long‐term development of reducing the sizes of devices, the preparation of ferroelectric materials and devices is entering the nanometer‐scale regime. Accordingly, to evaluate the ferroelectricity, there is a need to investigate the polarization charge at the nanoscale. Nonetheless, it is generally accepted that the detection of polarization charges using a conventional conductive atomic force microscopy (CAFM) without a top electrode is not feasible because the nanometer‐scale radius of an atomic force microscopy (AFM) tip yields a very low signal‐to‐noise ratio. However, the detection is unrelated to the radius of an AFM tip and, in fact, a matter of the switched area. In this work, the direct probing of the polarization charge at the nanoscale is demonstrated using the positive‐up‐negative‐down method based on the conventional CAFM approach without additional corrections or circuits to reduce the parasitic capacitance. The polarization charge densities of 73.7 and 119.0 µC cm^?2 are successfully probed in ferroelectric nanocapacitors and thin films, respectively. The obtained results show the feasibility of the evaluation of polarization charge at the nanoscale and provide a new guideline for evaluating the ferroelectricity at the nanoscale.     

The Genetic Architecture of the Etiology of Lower Extremity Peripheral Artery Disease: Current Knowledge and Future Challenges in the Era of Genomic Medicine

Lower extremity artery disease (LEAD), caused by atherosclerotic obstruction of the arteries of the lower limb extremities, has exhibited an increase in mortality and morbidity worldwide. The phenotypic variability of LEAD is correlated with its complex, multifactorial etiology. In addition to traditional risk factors, it has been shown that the interaction between genetic factors (epistasis) or between genes and the environment potentially have an independent role in the development and progression of LEAD. In recent years, progress has been made in identifying genetic variants associated with LEAD, by Genome-Wide Association Studies (GWAS), Whole Exome Sequencing (WES) studies, and epigenetic profiling. The aim of this review is to present the current knowledge about the genetic factors involved in the etiopathogenic mechanisms of LEAD, as well as possible directions for future research. We analyzed data from the literature, starting with candidate gene-based association studies, and then continuing with extensive association studies, such as GWAS and WES. The results of these studies showed that the genetic architecture of LEAD is extremely heterogeneous. In the future, the identification of new genetic factors will allow for the development of targeted molecular therapies, and the use of polygenic risk scores (PRS) to identify individuals at an increased risk of LEAD will allow for early prophylactic measures and personalized therapy to improve their prognosis.     

The Genetic Architecture of Vascular Anomalies: Current Data and Future Therapeutic Perspectives Correlated with Molecular Mechanisms

Vascular anomalies (VAs) are morphogenesis defects of the vascular system (arteries, capillaries, veins, lymphatic vessels) singularly or in complex combinations, sometimes with a severe impact on the quality of life. The progress made in recent years with the identification of the key molecular pathways (PI3K/AKT/mTOR and RAS/BRAF/MAPK/ERK) and the gene mutations that lead to the appearance of VAs has allowed the deciphering of their complex genetic architecture. Understanding these mechanisms is critical both for the correct definition of the phenotype and classification of VAs, as well as for the initiation of an optimal therapy and the development of new targeted therapies. The purpose of this review is to present in synthesis the current data related to the genetic factors involved in the etiology of VAs, as well as the possible directions for future research. We analyzed the data from the literature related to VAs, using databases (Google Scholar, PubMed, MEDLINE, OMIM, MedGen, Orphanet) and ClinicalTrials.gov. The obtained results revealed that the phenotypic variability of VAs is correlated with genetic heterogeneity. The identification of new genetic factors and the molecular mechanisms in which they intervene, will allow the development of modern therapies that act targeted as a personalized therapy. We emphasize the importance of the geneticist in the diagnosis and treatment of VAs, as part of a multidisciplinary team involved in the management of VAs.