The budget constrained r-interdiction median problem with capacity expansion

In this article, we elaborate on a budget constrained extension of the r-interdiction median problem with fortification (RIMF). The objective in the RIMF is to find the optimal allocation of protection resources to a given service system consisting of p facilities so that the disruptive effects of r possible attacks to the system are minimized. The defender of the system needs to fortify q facilities of the present system to offset the worst-case loss of r non-fortified facilities due to an interdiction in which the attacker’s objective is to cause the maximum possible disruption in the service level of the system. The defender-attacker relationship fits a bilevel integer programming (BIP) formulation where the defender and attacker take on the respective roles of the leader and the follower. We adopt this BIP formulation and augment it with a budget constraint instead of a predetermined number of facilities to be fortified. In addition, we also assume that each facility has a flexible service capacity, which can be expanded at a unit cost to accommodate the demand of customers who were serviced by some other interdicted facility before the attack. First, we provide a discrete optimization model for this new facility protection planning scenario with a novel set of closest assignment constraints. Then, to tackle this BIP problem we use an implicit enumeration algorithm performed on a binary tree. For each node representing a different fortification scheme, the attacker’s problem is solved to optimality using Cplex 11. We report computational results obtained on a test bed of 96 randomly generated instances. The article concludes with suggestions for future research.     

Sensitive and Accurate Determination of Cobalt at Trace Levels by Slotted Quartz Tube-Flame Atomic Absorption Spectrometry Following Preconcentration with Dispersive Liquid–Liquid Microextraction

Slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS) was used as a sensitive technique for the determination of cobalt, an element has toxic effects on living organisms at high doses. For the preliminary preconcentration of cobalt prior to the analysis, dispersive liquid–liquid microextraction (DLLME) was used. The instrument is equipped with a SQT to further increase the sensitivity by increasing the residence time of cobalt atoms in the light path emitted by a hollow cathode lamp. In the complex formation step, pH, the volume of buffer solution, the concentration of 1,5-diphenylcarbazone, and the volume of ligand were optimized. In addition, all of the system parameters, including the type and volume of the extraction solvent, dispersant type and volume of solvent, type of salt and the volume for the dispersion liquid–liquid microextraction, were optimized to obtain the lowest detection limit. Under the optimum conditions, the detection power of FAAS was improved by a factor of 86.56 fold using DLLME-SQT-FAAS. The limit of detection for the DLLME-SQT-FAAS system was 0.97?µg L^?1. The applicability of the developed method was verified in tap and waste water samples by spiking measurements. The percentage recovery values for these were determined to be 91.7% and 111.0%, respectively.     

Enzymatic Activity of Urokinase Immobilized onto Cu2+-Chelated Cibacron Blue F3GA–Derived Poly (HEMA) Magnetic Nanoparticles

Applied Biochemistry and Biotechnology - In this presented work, magnetic poly(2-hydroxyethyl methacrylate) (p (HEMA)) nanoparticles were synthesized by surfactant-free emulsion polymerization...     

2H NMR and X-ray diffraction studies of methyl rotation in crystals of ortho-methyldibenzocycloalkanones

We have used (2)H NMR lineshape analyses and single crystal X-ray diffraction (XRD) to investigate the effects of molecular structure and crystalline environment on the rotational dynamics of methyl groups in four aromatic cycloalkanones. These include two methyl-substituted anthrones, one anthraquinone and one dibenzosuberone, which are known to undergo excited state H-atom tunneling from the ortho-methyl group to the carbonyl oxygen. With experiments conducted between 100 and 300K, samples 1,4-dimethylanthrone (DMAT) and 1,4-dimethylanthraquinone (DMAQ) were shown to enter the intermediate exchange regime (k(rot) approximately <10(7)s(-1)) at ca. 120K while samples of 1,4,10,10-tetramethylanthrone (TMAT) and 1,4-dimethyldibenzosuberone (DMDBS) remained in the fast exchange regime even at ca. 100K. Single crystal XRD analyses suggest that high intramolecular hindrance is avoided by molecular distortions, and that intermolecular contacts play an important role.     

Artificial intelligence-based inventory management: a Monte Carlo tree search approach

The coordination of order policies constitutes a great challenge in supply chain inventory management as various stochastic factors increase its complexity. Therefore, analytical approaches to determine a policy that minimises overall inventory costs are only suitable to a limited extent. In contrast, we adopt a heuristic approach, from the domain of artificial intelligence (AI), namely, Monte Carlo tree search (MCTS). To the best of our knowledge, MCTS has neither been applied to supply chain inventory management before nor is it yet widely disseminated in other branches of operations research. We develop an offline model as well as an online model which bases decisions on real-time data. For demonstration purposes, we consider a supply chain structure similar to the classical beer game with four actors and both stochastic demand and lead times. We demonstrate that both the offline and the online MCTS models perform better than other previously adopted AI-based approaches. Furthermore, we provide evidence that a dynamic order policy determined by MCTS eliminates the bullwhip effect.

     

Covalent Immobilization and Characterization of a Novel Pullulanase from <Emphasis Type="Italic">Fontibacillus</Emphasis> sp. Strain DSHK 107 onto Florisil® and Nano-silica for Pullulan Hydrolysis

A novel pullulanase partially purified from Fontibacillus sp. was covalently immobilized on Florisil® and nano-silica through both glutaraldehyde and (3-glycidyloxypropyl)trimethoxysilane spacer arms. The pullulanase immobilized on Florisil® and nano-silica through glutaraldehyde spacer arm showed 85 and 190 % activity of its free form, respectively, whereas no activity was observed when it was immobilized on the same supports through (3-glycidyloxypropyl)trimethoxysilane spacer arm. The maximum working pHs of both the immobilized pullulanases on Florisil® and nano-silica through glutaraldehyde spacer arm were determined as 5.0; however, the maximum working pH of the free pullulanase was pH 6.0. The maximum temperatures of all the pullulanase preparations were determined as 35 °C. The apparent K _m values were 1.49, 1.54, and 0.59 mg/mL pullunan, respectively, for the free and immobilized pullulanases on Florisil® and nano-silica. The corresponding apparent V _max values were 0.59, 1.53, and 1.57 U mg prot.^?1?min.^?1. Thermal stability of pullulanases immobilized on Florisil® and nano-silica was enhanced 6.5- and 15.6-folds, respectively at 35 °C and 6.6- and 16.0-folds, respectively, at 50 °C. The pullulanases immobilized on Florisil® and nano-silica protected 71 and 90 % of their initial activities after 10 reuses.     

Two‐Dimensional Crowding Uncovers a Hidden Conformation of α‐Synuclein

The intrinsically disordered protein (IDP), α‐synuclein (αS), is well‐known for phospholipid membrane binding‐coupled folding into tunable helical conformers. Here, using single‐molecule experiments in conjunction with ensemble assays and a theoretical model, we present a unique case demonstrating that the interaction–folding landscape of αS can be tuned by two‐dimensional (2D) crowding through simultaneous binding of a second protein on the bilayer surface. Unexpectedly, the experimental data show a clear deviation from a simple competitive inhibition model, but are consistent with a bimodal inhibition mechanism wherein membrane binding of a second protein (a membrane interacting chaperone, Hsp27, in this case) differentially inhibits two distinct modules of αS–membrane interaction. As a consequence, αS molecules are forced to access a hidden conformational state on the phospholipid bilayer in which only the higher‐affinity module remains membrane‐bound. Our results demonstrate that macromolecular crowding in two dimensions can play a significant role in shaping the conformational landscape of membrane‐binding IDPs with multiple binding modes.     

Monolithic valves for microfluidic chips based on thermoresponsive polymer gels

The direct preparation of thermoresponsive monolithic copolymers by photopatterning of a liquid phase consisting of an aqueous solution of N-isopropylacrylamide, N-ethylacrylamide, N,N'-methylenebisacrylamide, and 4,4'-azobis(4-cyanovaleric acid) has been studied and the products used as valves within the channels of microfluidic devices. The volume change associated with the polymer phase transition at its lower critical solution temperature (LCST) leads to the rapid swelling and the deswelling of the 2.5% cross-linked monolithic gel thus enabling the polymer to close or open the channel and to function as a nonmechanically actuated valve. The LCST at which the valve switches was easily adjusted within a range of 35 degrees C-74 degrees C by varying the proportions of the monovinyl monomers in the polymerization mixture. The closed valve holds pressures of up to 18 MPa without noticeable dislocation, structural damage, or leakage. In contrast, following deswelling by raising the temperature above LCST the valve offers no appreciable flow resistance since its large, micrometer-size pores are open. Laser-triggered photobleaching of a fluorescent dye contained in the liquid phase enabled monitoring of flow through the device and determination of the times required to open and close the valve. The valves are characterized by very fast actuation times in a range of 1-4 s depending on the type of device. No changes in performance were observed even after repeated open-close cycling of the valves.