Hospital preparedness during epidemics using simulation: the case of COVID-19

Central European Journal of Operations Research - This paper presents a discrete event simulation model to support decision-making for the short-term planning of hospital resource needs, especially...     

Electronic Structure Modulation in an Exceptionally Stable Non‐Heme Nitrosyl Iron(II) Spin‐Crossover Complex

The highly stable nitrosyl iron(II) mononuclear complex [Fe(bztpen)(NO)](PF₆)₂ (bztpen=N‐benzyl‐N,N′,N′‐tris(2‐pyridylmethyl)ethylenediamine) displays an S=1/2?S=3/2 spin crossover (SCO) behavior (T_1/2=370 K, ΔH=12.48 kJ mol^?1, ΔS=33 J K^?1 mol^?1) stemming from strong magnetic coupling between the NO radical (S=1/2) and thermally interconverted (S=0?S=2) ferrous spin states. The crystal structure of this robust complex has been investigated in the temperature range 120–420 K affording a detailed picture of how the electronic distribution of the t_2g–e_g orbitals modulates the structure of the {FeNO}⁷ bond, providing valuable magneto–structural and spectroscopic correlations and DFT analysis.     

Scaffold Effects on Osteogenic Differentiation of Equine Mesenchymal Stem Cells: An In Vitro Comparative Study

The in vitro viability, osteogenic differentiation, and mineralization of four different equine mesenchymal stem cells (MSCs) from bone marrow, periosteum, muscle, and adipose tissue are compared, when they are cultured with different collagen‐based scaffolds or with fibrin glue. The results indicate that bone marrow cells are the best source of MSCs for osteogenic differentiation, and that an electrochemically aggregated collagen gives the highest cell viability and best osteogenic differentiation among the four kinds of scaffolds studied.

     

Statistical Inference for Partially Observed Markov-Modulated Diffusion Risk Model

We propose a method for obtaining the maximum likelihood estimators of the parameters of the Markov-Modulated Diffusion Risk Model in which the inter-claim times, the claim sizes, and the volatility diffusion process are influenced by an underlying Markov jump process. We consider cases when this process has been observed in two scenarios: first, only observing the inter-claim times and the claim sizes in an interval time, and second, considering the number of claims and the underlying Markov jump process at discrete times. In both cases, the data can be viewed as incomplete observations of a model with a tractable likelihood function, so we propose to use algorithms based on stochastic Expectation-Maximization algorithms to do the statistical inference. For the second scenario, we present a simulation study to estimate the ruin probability. Moreover, we apply the Markov-Modulated Diffusion Risk Model to fit a real dataset of motor insurance.

     

Catalytic and antibacterial evaluation of silver nanoparticles synthesized by a green approach

In this work, silver nanoparticles were synthesized using Salvia microphylla Kunth leaves extract as reducing agent and stabilizing agent. The effect of reaction time and plant extract amount on the biosynthesized nanoparticles were studied. The UV–Vis spectrum indicated that silver nanoparticles show a characteristic surface plasmon resonance at 427 nm. X-ray diffraction experiments show that the silver nanoparticles have a face-centered cubic crystal structure. The density of nanoparticles increases with increasing extract concentration and reaction time. TEM and SEM observations showed well-dispersed quasi-spherical nanoparticles sized in the range of 15–45 nm. The FT-IR analysis suggested the involvement of phenolic compounds in the reduction and stabilization of silver nanoparticles. Synthesized silver nanoparticles showed good antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Finally, the catalytic properties of silver nanoparticles were demonstrated through the degradation of congo red and methyl orange.     

Playing with models and optimization to overcome the tragedy of the commons in groundwater

Groundwater is the natural resource most extracted in the world. It supplies 50% of the total potable water requirements, 40% of the industry take, and 20% of agriculture groundwater is a strategic resource for every country. That common‐pool resources are highly susceptible to lead to a tragedy of the commons is a well‐known fact. We claim that a combination of groundwater modeling, optimization, and a game theoretical analysis may in fact avoid the tragedy. A groundwater model in MODFLOW from Zamora aquifer in Mexico was used as input of a basic but instructive, optimization problem: extract the greatest possible volume of water, but at the same time minimizing the drawdown and drawdown velocity. The solutions of the optimization problem were used to construct the payoffs of a hypothetical game among the aquifer users, the resource's administrator, and a resource protector entity. We show that the success of the optimal management program depends heavily on the information that the users have about the resource. Therefore, better decision‐making processes are a consequence of sustainability literacy. Particularly, water literacy could lead to the usage of water considering it as a part of an ecosystem and not only as a natural resource. Additionally, a new non‐classical equation for underground flow was derived, that may be specially important to understand and predict the groundwater flow in highly heterogeneous conditions as in karstic aquifers or fractured media. © 2013 Wiley Periodicals, Inc. Complexity 19: 9–21, 2013     

Hydrogen embrittlement assisted by ball-milling to obtain AlCuFe nanoparticles

In this work, we show that the synthesis of AlCuFe nanoparticles can be achieved by a wet ball-milling process. The AlCuFe intermetallic system is highly sensitive to the environmental embrittlement mechanism. Taking advantage of this, the wet ball-milling was used to increase the rate of grinding and accelerate the characteristic cleavage fracture of these phases. This research was carried out by subjecting Al₆₄Cu₂₄Fe₁₂ pre-alloyed ribbons to high-energy ball-milling under different powder–humidity relationships. The pre-alloyed and milled powders were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and scanning transmission electron microscopy (STEM). High resolution electron microscopy (HREM) measurements and energy-dispersive X-ray spectroscopy (EDXS) elemental chemical mapping confirm that the nanoparticles have a BCC structure with Al–Cu–Fe chemical composition. During the wet ball-milling, the aluminum content in the ψ-phase diminishes due to embrittlement mechanism which provokes its aperiodic disarrangement. This aluminum loss could be related with a ψ–β transformation.     

Mathematical help-seeking: observing how undergraduate students use the Internet to cope with a mathematical task

ZDM – Mathematics Education - We report on a study focused on identifying how undergraduate students make use of the Internet as a source of help to solve their mathematical queries. In...     

Holo- and hemidirected lead(II) in the polymeric [Pb(4)(mu-3,4-TDTA)2(H2O)2]*4H2O complex. N,N,N',N'-tetraacetate ligands derived from o-phenylenediamines as sequestering agents for lead(II)

The coordinating ability of the ligands 3,4-toluenediamine-N,N,N',N'-tetraacetate (3,4-TDTA), o-phenylenediamine-N,N,N',N'-tetraacetate (o-PhDTA), and 4-chloro-1,2-phenylenediamine-N,N,N',N'-tetraacetate (4-Cl-o-PhDTA) (H4L acids) toward lead(II) is studied by potentiometry (25 degrees C, I = 0.5 mol x dm(-3) in NaClO4), UV-vis spectrophotometry, and 207Pb NMR spectrometry. The stability constants of the complex species formed were determined. X-ray diffraction structural analysis of the complex [Pb4(mu-3,4-TDTA)4(H2O)2]*4H2O (1) revealed that 1 has a 2-D structure. The layers are built up by the polymerization of centrosymmetric [Pb4L2(H2O)2] tetranuclear units. The neutral layers have the aromatic rings of the ligands pointing to the periphery, whereas the metallic ions are located in the central part of the layers. In compound 1, two types of six-coordinate lead(II) environments are produced. The Pb(1) is coordinated to two nitrogen atoms and four carboxylate oxygens from the ligand, whereas Pb(2) has an O6 trigonally distorted octahedral surrounding. The lead(II) ion is surrounded by five carboxylate oxygens and a water molecule. The carboxylate oxygens belong to four different ligands that are also joined to four other Pb(1) ions. The selective uptake of lead(II) was analyzed by means of chemical speciation diagrams as well as the so-called conditional or effective formation constants K(Pb)eff. The results indicate that, in competition with other ligands that are strong complexing agents for lead(II), our ligands are better sequestering agents in acidic media.