This paper presents an approach wherein product design is viewed as a selection process with two main stages: design alternative generation and design alternative evaluation. The focus of this paper is mainly on a design alternative evaluation model in that designer’s preferences, customers’ preferences, and market competition are accounted for in order to select the best possible design. In the model, uncertainties in the product design life, market size and its yearly change, cost and its yearly change, price, and discount rate are considered. Product design selection of a cordless screwdriver is used as a demonstration example. However, the emphasis in the example is on the approach, and not on the details per se. [S1050-0472(00)01504-X]

Despite decades of investigations, the principal mechanisms responsible for the high affinity and specificity of proteins for key physiological cations K+, Na+, and Ca2+ remain a hotly debated topic. At the core of the debate is an apparent need (or lack thereof) for an accurate description of the electrostatic response of the charge distribution in a protein to the binding of an ion. These effects range from partial electronic polarization of the directly ligating atoms to long-range effects related to partial charge transfer and electronic delocalization effects. While accurate modeling of cation recognition by metalloproteins warrants the use of quantum-mechanics (QM) calculations, the most popular approximations used in major biomolecular simulation packages rely on the implicit modeling of electronic polarization effects. That is, high-level QM computations for ion binding to proteins are desirable, but they are often unfeasible, because of the large size of the reactive-site models and the need to sample conformational space exhaustively at finite temperature. Several solutions to this challenge have been proposed in the field, ranging from the recently developed Drude polarizable force-field for simulations of metalloproteins to approximate tight-binding density functional theory (DFTB). To delineate the usefulness of different approximations, we examined the accuracy of three recent and commonly used theoretical models and numerical algorithms, namely, CHARMM C36, the latest developed Drude polarizable force fields, and DFTB3 with the latest 3OB parameters. We performed MD simulations for 30 cation-selective proteins with high-resolution X-ray structures to create ensembles of structures for analysis with different levels of theory, e.g., additive and polarizable force fields, DFTB3, and DFT. The results from DFT computations were used to benchmark CHARMM C36, Drude, and DFTB3 performance. The explicit modeling of quantum effects unveils the key electrostatic properties of the protein sites and the importance of specific ion-protein interactions. One of the most interesting findings is that secondary coordination shells of proteins are noticeably perturbed in a cation-dependent manner, showing significant delocalization and long-range effects of charge transfer and polarization upon binding Ca2+.

4-Methyl-2-nitroacetanilide (1) crystallizes in white (1W), amber (1A), and yellow (1Y) modifications. The isomorphic molecules 4-chloro-2-nitroacetanilide (2) and 2-nitro-4-trifluoromethylacetanilide (3) were synthesized, and their effects on the crystallization of 1 were studied. The percentages of an additive incorporated into the 1W, 1A, and 1Y crystal lattices were determined by HPLC. Compound 2 is incorporated as a solid solution in 1A up to levels of 30% (w/w), whereas the incorporation efficiency of 3 is much lower at the same doping level. From these results it can be assumed that 2 causes less disruption to the host lattices than does 3. At the same doping level of an additive, 1A incorporates the additive at a greater level than 1W or 1Y. As the incorporation level of an additive increases, both the solution and solid-state transformation rate from 1A to either 1W or 1Y decreases. Structural comparison of the 1W, 1A, and 1Y crystal lattices indicates that the additives may be least disruptive to the 1A lattice, therefore explaining the greater incorporation efficiency of an additive in 1A.

Fabricating artificial materials that mimic the structures and properties of tendons is of great significance. Possessing a tensile stress of approximately 10.0 MPa and a water content of around 60%, human tendons exhibit excellent mechanical properties to support daily functions. In contrast to tendons, most synthetic hydrogels with similar water content typically exclude qualified strength, swelling resistance, and biocompatibility. Herein, a facile strategy based on poly­(vinyl alcohol) (PVA) and tannic acid (TA) is demonstrated to tackle this problem via a combination of sequential steps including freezing–thawing PVA aqueous solutions to form crystalline regions, prestretching and air drying in confined conditions to induce anisotropic structures, soaking in TA solutions to form multiple hydrogen bondings between PVA and TA, and finally dialyzing against water for the removal of residual TA molecules and the rearrangements and homogenization of multiple hydrogen bonds. The obtained PVA hydrogels possess hierarchically anisotropic structures, where the alignment of PVA bundles promotes high modulus, while the hydrogen bonding between PVA and TA endows them with an energy dissipation mechanism. Benefitting from the synergy of material composition and structural engineering, the obtained hydrogel displays super-strong mechanics (a tensile stress of 19.3 MPa and a toughness of 32.1 MJ/m3), outperforming most tough hydrogels. Remarkably, this hydrogel demonstrates excellent swelling resistance. It barely expands after immersion in deionized water, phosphate-buffered saline (PBS), and SBF aqueous solutions for 7 days with the strength and volume nearly the same as their initial values. All of the features, combined with excellent cytocompatibility, make it an ideal material for biotechnological and biomedical applications.

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