Comprehensive evaluations of heat transfer performance with conjugate heat dissipation effect in high-speed rotating free-disk modeling of aero-engines

Thermal boundary conditions of the turbine disk cavity system are of great importance in the design of secondary air systems in aero-engines.This study aims to investigate the complex heat transfer mechanisms of a rotating turbine disk under high-speed conditions.A high-speed rotating free-disk model with Dorfman empirical solutions is developed to evaluate the heat transfer performance considering various factors.Specifically,the influence of compressibility,variable properties,and heat dissipation is determined using theoretical and numerical analyses.In particular,a novel combined solution method is proposed to simplify the complex heat transfer problem.The results indicate that the heat transfer performance of a free disk is primarily influenced by the rotating Mach number,rotating Reynolds number,Rossby number,and wall temperature ratio.The heat transfer temperature and Nusselt number of the free disk are strongly correlated with the rotating Mach number and rotating Reynolds number.Analysis reveals that heat dissipation is a critical factor affecting the accurate evaluation of the heat transfer performance of the turbine disk.Thus,the combined solution method can serve as a reference for future investigations of flow and heat transfer in high-speed rotating turbine disk cavity systems in aero-engines.

Long noncoding RNA XIST:Mechanisms for X chromosome inactivation,roles in sex-biased diseases,and therapeutic opportunities

Sexual dimorphism has been reported in various human diseases including autoimmune diseases,neurological diseases,pulmonary arterial hypertension,and some types of cancers,although the underlying mechanisms remain poorly understood.The long noncoding RNA(lncRNA)X-inactive specific transcript(XIST)is involved in X chromosome inactivation(XCI)in female placental mammals,a process that ensures the balanced expression dosage of X-linked genes between sexes.XIST is abnormally expressed in many sex-biased diseases.In addition,escape from XIST-mediated XCI and skewed XCI also contribute to sex-biased diseases.Therefore,its expression or modification can be regarded as a biomarker for the diagnosis and prognosis of many sex-biased diseases.Genetic manipulation of XIST expression can inhibit the progression of some of these diseases in animal models,and therefore XIST has been proposed as a potential therapeutic target.In this manuscript,we summarize the current knowledge about the mechanisms for XIST-mediated XCI and the roles of XIST in sex-biased diseases,and discuss potential therapeutic strategies targeting XIST.

Pure aromatic hydrocarbons with meta-linked phenyl-core and perihedral fluorene substitutions with/without inert groups of tert-butyl： bipolar hosts for blue phosphorescence

Two pure hydrocarbon molecules of l,3,5-tris(9-phenyl-9H-fluoren-9-yl)benzene(mTPFB)and l,3,5-tris(2-tert-butyl-9-phenyl-9H-fluoren-9-yl)benzene(tBu-mTPFB)were synthesized.Due to the conjugation blocked connection mode and rigid/bulky substitutions,these two materials possess high triplet energy,enabling them as good hosts for blue phosphor in PhOLEDs.By studying their thermal,electrochemical,electronic absorption and photoluminescent properties,it was found that the influence of the inert tert-butyl group on material photoelectrical properties is negligible.For instance,mTPFB and tBu-mTPFB showed very similar absorption and emission profiles,with almost the same bandgap,triplet energy and energy levels.However,the encapsulation of tert-butyl on the 2-position of 9-phenylfluorene enhanced material thermal stability.Most importantly,carrier transport properties were improved dramatically,as proved by the mono carrier device.Blue phosphorescent OLEDs hosted by tBu-mTPFB showed external quantum efficiency of 15.2%and current efficiency of 23.0 cd/A,which were much higher than that of the OLEDs based on mTPFB with the analogous structure.