Step cost functions in a fleet size and mix vehicle routing problem with time windows

Annals of Operations Research - The vehicle routing problem is a traditional combinatorial problem with practical relevance for a wide range of industries. In the literature, several specificities...     

A Carbocationic Triarylmethane-Based Porous Covalent Organic Network

A thermally stable carbocationic covalent organic network (CON), named RIO-70 was prepared from pararosaniline hydrochloride, an inexpensive dye, and triformylphloroglucinol in solvothermal conditions. This nanoporous organic material has shown a specific surface area of 990 m² g⁻¹ and pore size of 10.3 Å. The material has CO₂ uptake of 2.14 mmol g⁻¹ (0.5 bar), 2.7 mmol g⁻¹ (1 bar), and 6.8 mmol g⁻¹ (20 bar), the latter corresponding to 3 CO₂ molecules adsorbed per pore per sheet. It is shown to be a semiconductor, with electrical conductivity (σ) of 3.17×10⁻⁷ S cm⁻¹, which increases to 5.26×10⁻⁴ S cm⁻¹ upon exposure to I₂ vapor. DFT calculations using periodic conditions support the findings.     

Applications of heteronuclear NMR spectroscopy in biological and medicinal inorganic chemistry

There is a wide range of potential applications of inorganic compounds, and metal coordination complexes in particular, in medicine but progress is hampered by a lack of methods to study their speciation. The biological activity of metal complexes is determined by the metal itself, its oxidation state, the types and number of coordinated ligands and their strength of binding, the geometry of the complex, redox potential and ligand exchange rates. For organic drugs a variety of readily observed spin I = 1/2 nuclei can be used (¹H, ¹³C, ¹⁵N, ¹⁹F, ³¹P), but only a few metals fall into this category. Most are quadrupolar nuclei giving rise to broad lines with low detection sensitivity (for biological systems). However we show that, in some cases, heteronuclear NMR studies can provide new insights into the biological and medicinal chemistry of a range of elements and these data will stimulate further advances in this area.     

New heuristics for total tardiness minimization in a flexible flowshop

This paper analyses the total tardiness minimization in a flowshop with multiple processors at each stage. While there is considerable research to minimize the makespan, very little work is reported on minimizing the total tardiness for this problem. This research focuses on heuristic methods that consider this environment as a series of parallel machine problems. New dispatching rules are introduced. One of the proposed rules is able to deal with jobs that will come afterwards and not only the available jobs at the decision time. Dispatching rules are also associated with classical (forward and backward) and new list scheduling algorithms. A special scheduling algorithm able to deal with idle times is proposed. Computational experiments in a set of 4,320 literature instances show that the developed heuristics are competitive and outperforms their classical counterparts.     

Polyviologen dendrimers as hosts and charge-storing devices

Two dendrimers were designed and synthesized that contain a 1,3,5-trisubstituted benzenoid core and incorporate 9 and 21 viologen (4,4'-bipyridinium) units in their branches in addition to hydrophilic (aryloxy) terminal groups. For comparison purposes, model compounds containing one and two viologen units were also studied. These polycationic dendrimers form strong host-guest complexes with the dianionic form of the red dye eosin in dilute CH(2)Cl(2) solutions. Titration experiments, based on fluorescence measurements, showed that each viologen unit in the dendritic structures becomes associated with an eosin dianion. Electrochemical (in MeCN) and photosensitization (in CH(2)Cl(2)) experiments revealed that only a fraction of the viologen units present in the dendritic structures can be reduced. This fraction corresponds to the number of viologen units present in the outer shells of the dendrimers. The reasons for incomplete charge pooling are discussed. Comparison with the behavior of polyviologen dendrimers that are terminated with bulky tetraarylmethane groups and were studied previously enabled the role played by the terminal groups in the redox and hosting properties to be elucidated.     

Lower bounding schemes for flowshops with blocking in-process

While there is a considerable amount of research that deals with a flowshop with no storage constraints, few works have addressed the flowshop with blocking in-process. Scheduling problems with blocking arise in serial manufacturing processes where no intermediate buffer storage is available. This paper proposes a lower bound, which exploits the occurrence of blocking, on the total tardiness of the jobs. Its efficiency is evaluated using a branch-and-bound algorithm on several problems. A lower bound on the makespan is also derived and computational tests are presented.     

A Branch-and-Bound Algorithm to Minimize the Makespan in a Flowshop with Blocking

This work addresses the minimization of the makespan criterion for the flowshop problem with blocking. In this environment there are no buffers between successive machines, and therefore intermediate queues of jobs waiting in the system for their next operations are not allowed. We propose a lower bound which exploits the occurrence of blocking. A branch-and-bound algorithm that uses this lower bound is described and its efficiency is evaluated on several problems. Results of computational experiments are reported.     

Influence of particle size on the SARS-CoV-2 spike protein detection using IgG-capped gold nanoparticles and dynamic light scattering

Due to the unprecedented and ongoing nature of the coronavirus outbreak, the development of rapid immunoassays to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its highly contagious variants is an important and challenging task. Here, we report the development of polyclonal antibody-functionalized spherical gold nanoparticle biosensors as well as the influence of the nanoparticle sizes on the immunoassay response to detect the SARS-CoV-2 spike protein by dynamic light scattering. By monitoring the increment in the hydrodynamic diameter (ΔD_H) by dynamic light scattering measurements in the antigen–antibody interaction, SARS-CoV-2 S-protein can be detected in only 5 min. The larger the nanoparticles, the larger ΔD_H in the presence of spike protein. From adsorption isotherm, the calculated binding constant (K_D) was 83 nM and the estimated limit of detection was 13 ng/mL (30 pM). The biosensor was stable up to 90 days at 4 °C. Therefore, the biosensor developed in this work could be potentially applied as a fast and sensible immunoassay to detect SARS-CoV-2 infection in patient samples.     

Method of sentinels for packing items within arbitrary convex regions

A new method is introduced for packing items in convex regions of the Euclidian n-dimensional space. By means of this approach the packing problem becomes a global finite-dimensional continuous optimization problem. The strategy is based on the new concept of sentinels. Sentinels sets are finite subsets of the items to be packed such that, when two items are superposed, at least one sentinel of one item is in the interior of the other. Minimal sets of sentinels are found in simple two-dimensional cases. Numerical experiments and pictures showing the potentiality of the new technique are presented.