A fast algorithm to remove proper and homogeneous pairs of cliques (while preserving some graph invariants)

We introduce a family of reductions for removing proper and homogeneous pairs of cliques from a graph G. This family generalizes some routines presented in the literature, mostly in the context of claw-free graphs. These reductions can be embedded in a simple algorithm that in at most |E(G)| steps builds a new graph G^′ without proper and homogeneous pairs of cliques, and such that G and G^′ agree on the value of some relevant invariant (or property).     

Separation routine and extended formulations for the stable set problem in claw-free graphs

Mathematical Programming - The maximum weighted stable set problem in claw-free graphs is a well-known generalization of the maximum weighted matching problem, and a classical problem in...     

Review of Long-Wavelength Optical and NIR Imaging Materials: Contrast Agents, Fluorophores and Multifunctional Nano Carriers

The importance of long wavelength and near infra-red (NIR) imaging has dramatically increased due to the desire to perform whole animal and deep tissue imaging. The adoption of NIR imaging is also growing rapidly due to the availability of targeted biological agents for diagnosis and basic medical research that can be imaged in vivo. The wavelength range of 650-1450 nm falls in the region of the spectrum with the lowest absorption in tissue and therefore enables the deepest tissue penetration. This is the wavelength range we focus on with this review. To operate effectively the imaging agents must both be excited and must emit in this long-wavelength window. We review the agents used both for imaging by absorption, scattering, and excitation (such as fluorescence). Imaging agents comprise both aqueous soluble and insoluble species, both organic and inorganic, and unimolecular and supramolecular constructs. The interest in multi-modal imaging, which involves delivery of actives, targeting, and imaging, requires nanocarriers or supramolecular assemblies. Nanoparticles for diagnostics also have advantages in increasing circulation time and increased imaging brightness relative to single molecule imaging agents. This has led to rapid advances in nanocarriers for long-wavelength, NIR imaging.     

Spectroscopic analyses of an ancient silver fragment of the reliquary bust of St. Leo

A fragment of the silver reliquary bust of St. Leo, made in Messina, Italy, in the last of 1739 and now preserved in the church of SS. Savior of Africo Nuovo, Reggio Calabria, Italy, was investigated with spectroscopic techniques (scanning electron microscopy (SEM)+energy-dispersive X-ray (EDX), X-ray diffraction (XRD)) in order to analyze the composition of the sample in terms of elements and compounds. EDX analysis employs an electron beam that interacts with the sample, leading to the emission of characteristic X-rays as secondary radiation. In the XRD analysis, a Cu Kα X-ray radiation is detected by a Si(Li) solid-state detector after the interaction with the sample. The chemical composition of the bulk allowed to identify the constituting metal alloy, while the detection of surface elements and compounds, closely related to the sample preservation, was useful in order to suggest to restorators the best interventions to minimize the conservation problems that could affect the durability of the precious artefact.     

Impedance measurement technique for high-sensitivity cell detection in microstructures with non-uniform conductivity distribution

Particle detection in microstructures is a key procedure required by modern lab-on-a-chip devices. Unfortunately, state of the art approaches to impedance measuring as applied to cell detection do not perform well in regions characterized by non-homogeneous physical parameters due, for example, to the presence of air-liquid interfaces or when the particle-electrode distance is relatively high. This paper presents a robust impedance measurement technique and a circuit for detecting cells flowing in microstructures such as microchannels and microwells. Our solution makes use of an innovative three-electrode measurement scheme with asymmetric polarization in order to increase cell detection ability in microstructures featuring large electrode distances of up to 100 μm as well as to limit signal loss due to cell position relative to the electrodes. Compared to standard techniques, numerical simulations show that, with the proposed approach, the cell detection sensitivity is increased by more than 40%. In addition, we propose a custom circuit based on division instead of difference between signals, as in standard differential circuits, so as to reduce the baseline signal drift induced by non-homogeneous conductivity. A simplified analytical model shows an increase in the signal-to-noise-ratio comprised in the range 3.9-5.9. Experimental results, carried out using an open-microwell device made with flexible printed circuit board technology, are in agreement with simulations, suggesting a six-fold increase of the signal-to-noise ratio compared to the differential measurement technique. We were thus able to successfully monitor the process of isolating K562 leukemia cells inside open-microwells determining all single-cell events with no false positive detection.     

Balas formulation for the union of polytopes is optimal

Mathematical Programming - A celebrated theorem of Balas gives a linear mixed-integer formulation for the union of two nonempty polytopes whose relaxation gives the convex hull of this union. The...     

New limits of treewidth-based tractability in optimization

Mathematical Programming - Sparse structures are frequently sought when pursuing tractability in optimization problems. They are exploited from both theoretical and computational perspectives to...