Polymeric drugs are a class of drug in which the polymer itself acts as the active ingredient of the drug. Here, we constructed a biodegradable covalent organic porous polymer (COP), denoted as Fc-Ma, composed of clinical drug molecules, i.e., ferrocene (Fc) and D-mannitol (Ma) and pH-responsive acetal bonds. The coexistence of Fc and Ma brought special properties to Fc-Ma, which can be used directly as a polymeric drug integrating the performance of both components. Thus, this special COP features enzyme activity, which can catalyze the conversion of cellular H 2 O 2 to •OH through a Fenton-like reaction. As an artificial enzyme, Fc-Ma may overcome many of the limitations of natural enzymes with more pronounced catalytic activity in weakly acidic environments. Therefore, it enables the sufficient generation of reactive oxygen species (ROS) in tumors and effectively kills tumor cells. Meanwhile, the intrinsic open porous skeleton coupled with the large specific surface areas (393 m 2 g −1 ) makes Fc-Ma an ideal carrier for other drugs. For example, it presents a doxorubicin hydrochloride (DOX) drug loading capacity of 64.4 ± 0.27%, compared with individual drugs; the acetal linkage endowed Fc-Ma with passive targeting, resulting in highly controlled drug delivery with selective and sustained release in acidic media, almost twice as much as that under neutral conditions. Hence, the tumor microenvironment can not only stimulate the generation of multiple ROS but also induce the passive targeted release of DOX, thereby ensuring the accumulation of drugs in the cancer sites, preventing the nonspecific distribution of drugs in the whole body and protecting renal tissues against DOX-induced nephrotoxicity. In summary, Fc-Ma-DOX exhibits significant synergistic actions of enzymatic therapy and chemotherapy, thus significantly improving the overall therapeutic effect.
Whether third-degree price discrimination improves or damages social welfare has always been a hot topic for scholars of economics. At present, research studies on the impact of third-degree price discrimination on welfare have not been carried out under asymmetric price competition. To this end, we studied this problem. In the research process, we divided consumers into two market segments by setting different travel costs based on the Hotelling model; at the same time, we considered three scenarios in which both firms engage in uniform pricing, both engage in price discrimination, and price discrimination vs. uniform pricing, and some intriguing findings and conclusions that differ from the previous studies were obtained through game analysis: (1) compared with two symmetric price games, the total output effect of each firm is unchanged, but the total social welfare is reduced, and as the size of the strong market increases, the reduction effect of total social welfare increases first and then decreases; (2) from local social welfare analysis, although the output of the firm adopting price discrimination remains unchanged, it can produce more producer surplus, consumer surplus and social welfare third-degree; (3) while the firm that uses uniform pricing is at a disadvantage in competition, the local social welfare created by it is decreased, and the reduction effect of social welfare will increase first and then decrease as the increase of the size of the strong market occurs. These conclusions reveal in an oligopoly market why enterprises always choose price discrimination and the government acquiesces in the existence of price discrimination.
The mechanical behavior of single-walled carbon nanotubes (SCWNTs) is one of the basic properties of the nanotube composite and nano machinery. The axial and bending buckling behavior of SWCNTs is systematically investigated by finite element mothod(FEM) in this paper. The results of molecular dynamics and FEM simulations are compared. Simulation results show that the axial buckling loads are dependent strongly on the diameter, and the buckling and postbuckling behavior of SWCNTs under bending depends strongly on the length and radii of the tube. With appropriate choice of Young's modulus and tube thickness, the FEM simulation provides some useful insight into the buckling mechanism of carbon nanotubes. The finite element method turns out to be a new, forthright and precise method for the simulation in solving large-scale nano-mechanics problems.
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