RIGIDITY THEOREMS OF COMPLETE K?HLER-EINSTEIN MANIFOLDS AND COMPLEX SPACE FORMS

We concentrate on using the traceless Ricci tensor and the Bochner curvature tensor to study the rigidity problems for complete K?hler manifolds. We derive some elliptic differential inequalities from Weitzenb?ck formulas for the traceless Ricci tensor of K?hler manifolds with constant scalar curvature and the Bochner tensor of K?hler-Einstein manifolds respectively. Using elliptic estimates and maximum principle, several L^p and L~∞ pinching results are established to characterize K?hler-Einstein manifolds among K?hler manifolds with constant scalar curvature and complex space forms among K?hler-Einstein manifolds.Our results can be regarded as a complex analogues to the rigidity results for Riemannian manifolds. Moreover, our main results especially establish the rigidity theorems for complete noncompact K?hler manifolds and noncompact K?hler-Einstein manifolds under some pointwise pinching conditions or global integral pinching conditions. To the best of our knowledge,these kinds of results have not been reported.

In vitro Study on a New High Nitrogen Nickel-free Austenitic Stainless Steel for Coronary Stents

Most commercialized coronary stents are made of 316L stainless steels due to its good combination of properties, and currently some new stents are made of cobalt-based alloy owing to its higher mechanical properties. However, the presence of high quantity of nickel and/or cobalt elements in these materials, which are known to trigger the toxic and allergic responses, has caused many concerns. Nickel-free austenitic stainless steels have been developed in order to solve these problems. In this paper, based on the development of a new Fe- Cr-Mn-Mo-N type high nitrogen nickel-free austenitic stainless steel, properties such as mechanical property, corrosion resistance in Hankls solution, and in vitro blood compatibility including the kinetic clotting time and the platelets adhesion, were investigated in comparison to the above two conventional materials, a 316L stainless steel and a Co-28Cr-6Mo alloy. The results showed that the new high nitrogen steel possessed better combination of mechanical properties, corrosion resistance and blood compatibility than those of 316L steel and the Co-28Cr-OMo alloy, and can be a promising alternative material for manufacture of coronary stents.

Effect of cold deformation on corrosion fatigue behavior of nickel-free high nitrogen austenitic stainless steel for coronary stent application

Due to the excellent mechanical properties, good corrosion resistance, high biocompatibility and nickel- free character, the high nitrogen nickel-free austenitic stainless steel （HNASS） becomes an ideally alternative material for coronary stents. Stent implantation works in harsh blood environment after a balloon dilatation, i.e., the material is used in a corrosive environment with a permanent deforma- tion. The present study attempts to investigate effects of pre-straining on high-cycle fatigue behavior and corrosion fatigue behavior of HNASS in Hank＇s solution and the relevant mechanism for coronary stents application. It is found that higher pre-straining on HNASS results in higher strength and maintains almost same corrosion resistance. Fatigue limit of 0% HNASS is 550 MPa, while corrosion fatigue limit is 475 MPa. And improvement in fatigue limit of 20% and 35% pre-strained HNASS is in comparison with the 0% HNASS, while corrosion would undermine the fatigue behavior of HNASS. In a suitable range, the pre- straining had a beneficial effect on corrosion fatigue strength of HNASS, such as nearly 300 MPa improved with 20% cold deformation. This result provides a good reference for predicting the life of HNASS stent and as well its design.

Analysis of Magnetism in High Nitrogen Austenitic Stainless Steel and Its Elimination by High Temperature Gas Nitriding

Stable austenitic structure in medical stainless steels is basically required for surgical implantation. A weak magnetism was found in a high nitrogen nickel-free austenitic stainless steel for cardiovascular stent application. This magnetic behavior in high nitrogen stainless steel was investigated by optical microscopy, X-ray diffraction （XRD）, electron probe microanalysis （EPMA） and superconducting quantum interference device （SQUID）. The results showed that the magnetism came from the composition segregation of ferrite formation elements such as Cr and Mo in the steel and some 6-ferrites were locally formed during the pressurized electroslag remelting process. The magnetism of high nitrogen stainless steel could be eliminated by a proper high temperature gas nitriding （HTGN）.

Preliminary Study on Porous High-Manganese 316L Stainless Steel Through Physical Vacuum Dealloying

In this study, porous stainless steel was prepared successfully by physical vacuum dealloying method. The based alloy is high-manganese 316L-50Mn alloy. The porous high-manganese 316L stainless steel showed a three-dimensional continuous porous structure with 1-2 ktm pore size. Temperature was the key factor for the physical dealloying process to produce porous stainless steel, and the optimized treatment temperature was between 800 and 850 ~C for the high- manganese 316L-50Mn alloy.

Cytocompatibility of High Nitrogen Nickel-Free Stainless Steel for Orthopedic Implants

Cytocompatibility of high nitrogen nickel-free stainless steel （HNS） with different nitrogen content was evalu- ated and compared with a conventional austenitic stainless steel 317L. The MTT assay （3-（4,5-dimethylthiazol- 2-yl）-2,5-diphenyltetrazolium bromide） was performed on MG63 osteoblasts to assess the cytotoxicity. The expression of selected marker typical of differentiated osteoblasts, such as alkaline phosphatase activity （AKP）, was also monitored in MG63 cells cultured on the tested materials. As a result, HNS had higher cell growth than 317L; meanwhile the cytocompatibility was increased with increasing nitrogen content. Furthermore, HNS enhanced osteoblasts differentiation, as confirmed by AKP activity. Overall these facts indicated that HNS had higher cytocompatibility than 317L and the nitrogen content contributed to the higher cytocompatibility of HNS. The influence of nitrogen on surface energy further explained the cytocompatibility of HNS.

An RNA-RNA crosstalk network involving HMGB1 and RICTOR facilitates hepatocellular carcinoma tumorigenesis by promoting glutamine metabolism and impedes immunotherapy by PD-L1+ exosomes activity

Hepatocellular carcinoma(HCC)is the global leading cause of cancer-related deaths due to the deficiency of targets for precision therapy.A new modality of epigenetic regulation has emerged involving RNA-RNA crosstalk networks where two or more competing endogenous RNAs(ceRNAs)bind to the same microRNAs.However,the contribution of such mechanisms in HCC has not been well studied.Herein,potential HMGB1-driven RNA-RNA crosstalk networks were evaluated at different HCC stages,identifying the mT0RC2 component RICTOR as a potential HMGB1 ceRNA in HBV^(+)early stage HCC.Indeed,elevated HMGB1 mRNA was found to promote the expressio n of RICTOR mRNA through competitively bin ding with the miR-200 family,especially miR-429.Functio nal assays emplo ying overexpressi on or in terference strategies dem on strated that the HMGB1 and RICTOR 3zuntra nslated regions(UTR)epigenetically promoted the malignant proliferation,self-renewal,and tumorigenesis in HCC cells.Intriguingly,in terference agai nst HMGB1 and RICTOR in HCC cells promoted a stron ger an ti-PD-L1 immuno therapy resp on se,which appeared to associate with the production of PD-L1^(+)exosomes.Mechanistically,the HMGB1-driven RNA-RNA crosstalk network facilitated HCC cell glutamine metabolism via dual mechanisms,activating a positive feedback loop involving mT0RC2-AKT-C-MYC to upregulate glutamine synthetase(GS)expression,and inducing mTORCI signaling to derepress SIRT4 on glutamate dehydrogenase(GDH).Meanwhile,this crosstalk network could impede the efficacy of immunotherapy through mTORCI-P70S6K dependent PD-L1 production and PD-L1^(+)exosomes activity.In conclusion,our study highlights the non-coding regulatory role of HMGB1 with implicatio ns for RNA-based therapeutic targeting together with a predictio n of an ti-PD-L1 immuno therapy in HCC.

常拟Hermite数量曲率Sasaki流形的刚性

本文在常拟Hermite数量曲率Sasaki流形中,利用Schrdinger型算子的特征值和曲率的增长性条件,建立了拟Einstein Sasaki流形和Sasaki空间形式的刚性.