Optimization and analysis of the profitability of tariff structures with two-part tariffs

Service providers often offer tariff structures with several two-part tariffs that consist of a fixed fee and a usage price, such that consumers may pick the tariff they prefer. Prices of tariffs have significant impacts on service providers’ profit, because they simultaneously influence consumers’ tariff choices and their usage. The number of tariffs also plays an important role, because more tariffs segment the market better but also increase the administrative burden and require more marketing effort. This article presents a mixed-integer nonlinear programming optimization problem to determine profit-maximizing tariffs; compares several heuristic search methods, in particular, the gradient method, stochastic search, and simulated annealing, to solve this problem; analyses the profitability of different tariff structures; and outlines the factors that drive differences in profitability across various tariff structures. The results show that especially for large samples of more than 100 consumers, simulated annealing performs best and deviates only 0.2% from the optimum. Structures with fewer two-part tariffs are generally sufficient, because additional two-part tariffs only negligibly increase service providers’ profit.     

Using genetic programming to evolve action selection rules in traversal-based automated software testing: results obtained with the TESTAR tool

Traversal-based automated software testing involves testing an application via its graphical user interface (GUI) and thereby taking the user’s point of view and executing actions in a human-like manner. These actions are decided on the fly, as the software under test (SUT) is being run, as opposed to being set up in the form of a sequence prior to the testing, a sequence that is then used to exercise the SUT. In practice, random choice is commonly used to decide which action to execute at each state (a procedure commonly referred to as monkey testing), but a number of alternative mechanisms have also been proposed in the literature. Here we propose using genetic programming (GP) to evolve such an action selection strategy, defined as a list of IF-THEN rules. Genetic programming has proved to be suited for evolving all sorts of programs, and rules in particular, provided adequate primitives (functions and terminals) are defined. These primitives must aim to extract the most relevant information from the SUT and the dynamics of the testing process. We introduce a number of such primitives suited to the problem at hand and evaluate their usefulness based on various metrics. We carry out experiments and compare the results with those obtained by random selection and also by Q-learning, a reinforcement learning technique. Three applications are used as Software Under Test (SUT) in the experiments. The analysis shows the potential of GP to evolve action selection strategies.     

An example of an SL2-Hilbert scheme with multiplicities

In [AB05], Alexeev and Brion have introduced the notion of invariant Hilbert schemes. We determine the invariant Hilbert scheme of the zero fibre of the moment map of an action of SL₂ on ( mathbbC² ) ^?6 {left( {{mathbb{C}^2}} right)^{ oplus 6}} as one of the first examples of invariant Hilbert schemes with multiplicities. While doing this, we present a general procedure for realizing these calculations. We also consider questions of smoothness and connectedness and thereby show that our Hilbert scheme gives a resolution of singularities of the symplectic reduction of the action.     

Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods

The self‐assembled structures of atomically precise, ligand‐protected noble metal nanoclusters leading to encapsulation of plasmonic gold nanorods (GNRs) is presented. Unlike highly sophisticated DNA nanotechnology, this strategically simple hydrogen bonding‐directed self‐assembly of nanoclusters leads to octahedral nanocrystals encapsulating GNRs. Specifically, the p‐mercaptobenzoic acid (pMBA)‐protected atomically precise silver nanocluster, Na₄[Ag₄₄(pMBA)₃₀], and pMBA‐functionalized GNRs were used. High‐resolution transmission and scanning transmission electron tomographic reconstructions suggest that the geometry of the GNR surface is responsible for directing the assembly of silver nanoclusters via H‐bonding, leading to octahedral symmetry. The use of water‐dispersible gold nanoclusters, Au_≈250(pMBA)_n and Au₁₀₂(pMBA)₄₄, also formed layered shells encapsulating GNRs. Such cluster assemblies on colloidal particles are a new category of precision hybrids with diverse possibilities.     

A simple adsorptive chronopotentiometric stripping method for determination of vitamin B 1 in pharmaceutical products

A new electroanalytical method for vitamin B1 determination, based on adsorptive chronopotentiometric stripping analysis and non-specific adsorption onto mercury film electrode, was developed and validated. Stripping chronopotentiograms showed a single well-defined oxidation wave corresponding to vitamin B1 at about − 0.43 V in citrate buffer pH 6.0. The most important experimental factors affecting the monitored electroanalytical response of vitamin B1 were investigated and optimised. Under the optimal experimental conditions, linear response of vitamin B1 was obtained in the concentration range of 5–50 mg dm−3, with the achieved limit of detection of 1.64 mg dm−3, and the limit of quantitation of 4.97 mg dm−3. A mean recovery of 97.1% and relative standard deviations of 3.75% were achieved. The developed electrochemical procedure was successfully applied for the determination of vitamin B1 in pharmaceutical products. The results of the proposed method were in good agreement with those obtained by parallel HPLC analyses, confirming an accuracy of the developed method.     

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The novel heteronuclear complexes [{cis-PtCl (NH₃)(μ-pyrazine)ZnCl (terpy)}](ClO₄)₂ (Pt-L1-Zn) and [{cis-PtCl (NH₃)(μ-4,4′-bipyridyl)ZnCl (terpy)}](ClO₄)₂ (Pt-L2-Zn) (where terpy = 2,2′:6′,2′′-terpyridine, L1 = pyrazine, L2 = 4,4′-bipyridyl) were synthesized and characterized. The pK_a values were determined, and based on them it was established that the π-acceptor ability of the pyrazine bridging ligand is more affective on lower pK_a values. The kinetic measurements of the substitution reactions with biologically relevant ligands, such as guanosine-5′-monophosphate (5′-GMP), inosine-5′-monophosphate (5′-IMP) and glutathione (GSH), were studied at pH 7.4. The reactions were followed under pseudo-first-order conditions by UV–Vis spectrophotometry. The order of reactivity of the investigated biomolecules for the first reaction is 5′-GMP > 5′-IMP > GSH, while for the second is 5′-IMP > GSH. Pt-L1-Zn complex is more reactive than Pt-L2-Zn. The cytotoxic activity of heteronuclear Pt-L1-Zn and Pt-L2-Zn complexes was determined on human colorectal cancer cell line (HCT-116) and human breast cancer cell line (MDA-MB-231). Both complexes significantly reduced cell viability on tested cell lines and exerted significant cytotoxic effects, with better effect on HCT-116 cells than cisplatin, especially after 72 hr (IC₅₀ < 0.52 μM). The Pt-L2-Zn complex showed higher activity against human breast cancer cells (MDA-MB-231) than cisplatin after 72 hr. The higher reactivity toward DNA constituent and significant cytotoxic activity may be attributed to the different geometry, Lewis acidity of different metal centers, as well as, to choice of bridging ligands.     

Analytical Uncertainty in Modern Quantitative TLC

JPC – Journal of Planar Chromatography – Modern TLC - Experiments and calculations show the importance of analytical management to reliable analytical results. A method with a...     

Calculation of vibrational spectra of linear tetrapyrroles. 3. Hydrogen-bonded hexamethylpyrromethene dimers

The structure and vibrational spectra of hexamethylpyrromethene (HMPM) have been investigated by X-ray crystallography, IR and Raman spectroscopies, and density functional theory calculations. HMPM crystallizes in the form of dimers, which are held together by bifurcated N-H(...N)(2) hydrogen bonds, involving one intramolecular and one intermolecular N-H...N interaction. The monomers are essentially planar, and the mean planes of the monomers lie approximately perpendicular to one another, so that the four N atoms in the dimer form a distorted tetrahedron. The structure of the HMPM dimer is well-reproduced by B3LYP/6-31G calculations. A comparison of the calculated geometry of the dimer with that of the monomer reveals only small changes in the N-H...N entity and the methine bridge angles upon dimerization. These are a result of weakening of the intramolecular N-H...N hydrogen bond and the formation of a more linear N-H...N intermolecular hydrogen bond. Using an empirical relation between the shift of the N-H stretching frequency of pyrrole and the enthalpy of adduct formation with bases [Nozari, M. S.; Drago, R. S. J. Am. Chem. Soc. 1970, 92, 7086-7090], estimates of the strength of the intra- and intermolecular hydrogen bonds are obtained. IR and Raman spectroscopies of HMPM and its isotopomers deuterated at the pyrrolic nitrogen atom and at the methine bridge reveal that the molecule is monomeric in nonpolar organic solvents but dimeric in a solid Ar matrix and in KBr pellets. The matrix IR spectra show a splitting of vibrational modes for the dimer, particularly those involving the N-H coordinates. Due to intrinsic deficiencies of the B3LYP/6-31G approximation, a satisfactory reproduction of these modes of the monomeric and dimeric HMPM requires specific adjustments of the NH scaling factors for the calculated force constants and, in the case of the NH out-of-plane modes of HMPM dimers, also of intra- and intermolecular coupling constants. This parametrization does not significantly affect the other calculated modes, which in general reveal a very good agreement with the experimental data.