Introducing dynamic diversity into a discrete particle swarm optimization

Particle swarm optimization (PSO) is an evolutionary metaheuristic inspired by the flocking behaviour of birds, which has successfully been used to solve several kinds of problems, although there are few studies aimed at solving discrete optimization problems. One disadvantage of PSO is the risk of a premature search convergence. To prevent this, we propose to introduce diversity into a discrete PSO by adding a random velocity. The degree of the introduced diversity is not static (i.e. preset before running PSO) but instead changes dynamically according to the heterogeneity of the population (i.e. if the search has converged or not). We solve the response time variability problem (RTVP) to test these two new ideas. The RTVP is an NP-hard combinatorial scheduling problem that has recently appeared in the literature. It occurs whenever products, clients or jobs need to be sequenced in such a way that the variability in the time between the instants at which they receive the necessary resources is minimized. The most efficient algorithm for solving non-small instances of the RTVP published to date is a classical PSO algorithm, referred to by the authors as PSO-M1F. In this paper, we propose 10 discrete PSO algorithms for solving the RTVP: one based on the ideas described above (PSO  -_c3dyn$c_3\text{<italic>dyn</italic>}$) and nine based on strategies proposed in the literature and adapted for solving a discrete optimization problem such as the RTVP. We compare all 11 PSO algorithms and the computational experiment shows that, on average, the best results obtained are due to our proposal of dynamic control mechanism for introducing diversity.     

Convex Relaxation of a Class of Vertex Penalizing Functionals

We investigate a class of variational problems that incorporate in some sense curvature information of the level lines. The functionals we consider incorporate metrics defined on the orientations of pairs of line segments that meet in the vertices of the level lines. We discuss two particular instances: One instance that minimizes the total number of vertices of the level lines and another instance that minimizes the total sum of the absolute exterior angles between the line segments. In case of smooth level lines, the latter corresponds to the total absolute curvature. We show that these problems can be solved approximately by means of a tractable convex relaxation in higher dimensions. In our numerical experiments we present preliminary results for image segmentation, image denoising and image inpainting.     

Infrared-transparent glasses derived from the fluorides of zirconium,thorium, and barium

Glasses consisting solely of high-purity ZrF₄, ThF₄, and BaF₂ have been synthesized using reactive atmosphere processing (RAP) techniques. RAP of the individual components and the molten material with anhydrous HF and CCl₄ is described. The glass molds easily at 312°C and 1920 psi with a high-fidelity replication of the die surface. The glass is water insoluble, unusually hard and strong, and continuously transparent from 0.3 to 7 μm.     

Formula for two-carrier intermodulation distortion in wavelengthconverted subcarrier multiplexed signals via cross gain modulation

We present, for the first time to our knowledge, closed expression for the computation of the harmonic and intermodulation distortions that appear on a wavelength converted two-tone subcarrier modulation (SCM) signal via cross gain modulation     

Systematic Investigation of Metabolic Oligosaccharide Engineering Efficiency in Intestinal Cells Using a Dibenzocyclooctyne-Monosaccharide Conjugate

Metabolic oligosaccharide engineering (MOE) of cells with synthetic monosaccharides can introduce functionality to the glycans of cell membranes. Unnatural sugars (e. g., peracetylated mannose-azide) can be expressed on the cell surface with the azide group in place. After MOE, the azide group can participate in a copper-free click reaction with an alkyne (e. g., dibenzocyclooctyne, DBCO) probe. This allows the metabolic fate of monosaccharides in cells to be understood. However, in a drug delivery context it is desirable to have azide groups on the probe (e. g. a drug delivery particle) and the alkyne (e. g. DBCO) on the cell surface. Consequently, the labelling efficiency of intestinal cell lines (Caco-2 and HT29-MTX-E12) treated with N-dibenzocyclooctyne-tetra-acetylmannosamine, and the concentration- and time-dependent labelling were determined. Furthermore, the labelling of mucus in HT29-MTX-E12 cells with DBCO was shown. This study highlights the potential for using MOE to target azide-functionalised probes to intestinal tissues for drug delivery applications.     

New Insights to Clathrin and Adaptor Protein 2 for the Design and Development of Therapeutic Strategies

The Amyloid Precursor Protein (APP) has been extensively studied for its role as the precursor of the β-amyloid protein (Aβ) in Alzheimer’s disease (AD). However, our understanding of the normal function of APP is still patchy. Emerging evidence indicates that a dysfunction in APP trafficking and degradation can be responsible for neuronal deficits and progressive degeneration in humans. We recently reported that the Y₆₈₂ mutation in the ₆₈₂YENPTY₆₈₇ domain of APP affects its binding to specific adaptor proteins and leads to its anomalous trafficking, to defects in the autophagy machinery and to neuronal degeneration. In order to identify adaptors that influence APP function, we performed pull-down experiments followed by quantitative mass spectrometry (MS) on hippocampal tissue extracts of three month-old mice incubated with either the ₆₈₂YENPTY₆₈₇ peptide, its mutated form, ₆₈₂GENPTY₆₈₇ or its phosphorylated form, ₆₈₂pYENPTY₆₈₇. Our experiments resulted in the identification of two proteins involved in APP internalization and trafficking: Clathrin heavy chain (hc) and its Adaptor Protein 2 (AP-2). Overall our results consolidate and refine the importance of Y₆₈₂ in APP normal functions from an animal model of premature aging and dementia. Additionally, they open the perspective to consider Clathrin hc and AP-2 as potential targets for the design and development of new therapeutic strategies.     

Electrothermal atomic absorption spectrometric diagnosis of familial hypercholesterolemia

We have developed a new nonradioactive assay to identify human low-density lipoprotein receptor defects. It is based on the incubation of cultured cells with colloidal gold-LDL conjugates and quantitation of the gold associated with the cells by electrothermal atomic absorption spectrometry. After an oxidative treatment with nitric and hydrochloric acids, the biological matrix interferes neither with the gold recovery nor with the gold measurements, which are linear, at least from 0.15 to 3 ng of gold. When cells expressing a functional LDL receptor are incubated with increasing amounts of colloidal-gold LDL conjugates, the obtained saturation curve parallels that described when [125I]LDL is used as ligand. Moreover, this new assay allows us to clearly distinguish among fibroblasts from normal subjects or from heterozygous or homozygous patients of familial hypercholesterolemia, a very common autosomal disease. The assay is easy to perform, is sensitive, and avoids the use of radioactive compounds. Therefore, it could be successfully employed in the clinical diagnosis of this disease. Furthermore, since the methodology developed here can be applied to quantify the association of other gold-conjugated ligands to cells, it could have a widespread use in a variety of clinical and basic research studies.     

Gravity drainage of activated sludge: new experimental method and considerations of settling velocity, specific cake resistance and cake compressibility

A laboratory scale setup was used for characterization of gravitational drainage of waste activated sludge. The aim of the study was to assess how time of drainage and cake dry matter depended on volumetric load, SS content and sludge floc properties. It was demonstrated that activated sludge forms compressible cakes, even at the low pressures found in gravitational drainage. The values of specific cake resistance were two to three orders of magnitude lower than those obtained in pressure filtration. Despite the compressible nature of sludge, key macroscopic parameters such as time of drainage and cake solid content showed simple functional dependency of the volumetric load and SS of a given sludge. This suggests that the proposed method may be applied for design purposes without the use of extensive numerical modeling. The possibilities for application of this new technique are, among others, the estimation of sludge drainability prior to mechanical dewatering on a belt filter, or the application of surplus sludge on reed beds, as well as adjustments of sludge loading, concentration or sludge pre-treatment in order to optimize the drainage process.