数学中的探索研究和发现

本书是一本关于数学“解题术”的论著，其目的是引导中学生和大学低年级学生通过解数学题提高思维能力和解题技巧，着重培养他们数学学习中的探索精神，以研究解题规律和发现新的问题和结果。     

Cross-reactivity of autoantibodies from patients with epidermolysis bullosa acquisita with murine collagen VII

The pathomechanism of antibody-mediated tissue damage in autoimmune diseases can be best studied in experimental models by passively transferring specific autoantibodies into animals. The reproduction of the disease in animals depends on several factors, including the cross-reactivity of patient autoantibodies with the animal tissue. Here, we show that autoantibodies from patients with epidermolysis bullosa acquisita (EBA), a subepidermal autoimmune blistering disease, recognize multiple epitopes on murine collagen VII. Indirect immunofluorescence microscopy revealed that EBA patients’ IgG cross-reacts with mouse skin. Overlapping, recombinant fragments of murine collagen VII were used to characterize the reactivity of EBA sera and to map the epitopes on the murine antigen by ELISA and immunoblotting. The patients’ autoantibody binding to murine collagen VII triggered pathogenic events as demonstrated by a complement fixing and an ex vivo granulocyte-dependent dermal–epidermal separation assay. These findings should greatly facilitate the development of improved disease models and novel therapeutic strategies.     

Mechanical properties of a Gum-type Ti-Nb-Zr-Fe-O alloy

A new Gum-type alloy (Ti-Nb-Zr-Fe-O) in which Fe is used instead of Ta was subjected to a particular thermomechanical processing scheme to assess whether its mechanical characteristics (fine β-grains with high strength and low modulus) render it suitable as a biomedical implant material. After a homogenization treatment followed by cold-rolling with 50% reduction, the specimens were subjected to one of three different recrystallization treatments at 1073, 1173, and 1273 K. The structural and mechanical properties of all of the treated specimens were analyzed. The mechanical characterization included tensile tests, microhardness determinations, and fractography by scanning electron microscopy. The possible deformation mechanisms were discussed using the Bo-Md diagram. By correlating all of the experimental results, we concluded that the most promising processing variant corresponds to recrystallization at 1073 K, which can provide suitable mechanical characteristics for this type of alloys:high yield and ultimate tensile strengths (1038 and 1083 MPa, respectively), a low modulus of elasticity (62 GPa), and fine crystalline grain size (approximately 50 μm).     

Dose-related effects of sericin on preadipocyte behavior within collagen/sericin hybrid scaffolds

This paper aims at demonstrating the biocompatibility of recently developed 3D hydrogel scaffolds containing the same amount of collagen(COLL) and variable concentrations of sericin(SS) in order to find the most suitable formula for adipose tissue engineering(ATE) applications.These scaffolds were obtained by COLL crosslinking with glutaraldehyde followed by freeze-drying and, subsequently, seeded with 3T3-L1 preadipocytes. Scanning electron microscopy studies revealed the scaffolds' architecture and cellular colonization. Also, in vitro biocompatibility of the developed scaffolds was evaluated by LDH and MTT assays and Live/Dead analysis of 3T3-L1 preadipocyte populating these 3D matrices.The best results in terms of cell survival and proliferation status were obtained in the case of the hybrid COLL scaffold containing 40% SS(COLL–SS4). Furthermore, the biological performance of the analyzed COLL-based hydrogels at 5- and 8- days post-seeding was found to decrease as follows: COLL–SS4 4 COLL–SS2 4 COLL 4 COLL–SS6. Consequently, our study highlights that hybrid scaffolds obtained by the addition of variable concentrations of SS to a constant COLL composition positively influences the behavior of 3T3-L1 cells with the exception of the COLL–SS6 matrix(60% SS). Altogether, the data obtained recommend SS as a component of COLL-based hydrogels providing them with features that may be useful in ATE applications.