Failure mechanisms of roadways with non-coplanar axial direction and stress space:True triaxial test and mechanical analysis

The axial direction of a roadway often forms a certain spatial angle with the in-situ stress field.Variations in the spatial angles can lead to differences in the stress environment in which the roadway is exposed.Different forms of failure characteristics occur in the roadway.In order to study the failure mechanism with different spatial characteristics,rock-like material specimens with holes in 9 different horizontal and vertical angles were designed.The true triaxial test system was used to carry out the test with the same loading path.The results show that the horizontal angle a and vertical angle β have a significant effect on the specimen strength,specimen rupture angle,and the form of spalling failure in the hole.The spatial angle leads to the formation of asymmetric heterotype V-notches in both sides within the hole.The asymmetry is evident in both the depth and extent of spalling.The strength of the specimen increases and then decreases with increasing vertical angle β.The rupture angle increases and then decreases with increasing horizontal angle a and increases with the increase of the vertical angle β.The stress analytical model of the specimen under three-dimensional compression was established.The distribution of principal stresses around the holes was theoretically analyzed.It is found that the presence of spatial angle changes the distribution of principal stresses around the hole from symmetric to asymmetric distribution.The shift of the principal stresses is responsible for the change from a V-notch to a heterotype V-notch.

NO REVERSE ERROR BALL TRANSMISSION AND FORCE ANALYSIS ON HETERO TYPE SINGLE CYCLOID

The construction kinematics and no reverse error property of heterotype single cycloid steel ball transmission are studied and its engagement pairs structure as well as foree analysis are al- so presented. It provides a kind of high property driver of large transmission ratio and compact con- struction and has theoretical and practical significance for application of the steel ball transmission.

Pollination characteristics of the ephemeroid plant Eremurus anisopterus

This study was conducted to examine the pol-lination characteristics of Eremurus anisopterus,an ephe-meroid plant in the Gurbantunggut Desert in Xinjiang,China.An integrative approach combining field studies with lab analysis was adopted.Pollen traps were used to measure air-borne pollen loads and artificial isolation experiments were applied to test the potentiality of cross-pollination or apomixes.Results show that the duration of the flowering of Eremurus anisopterus varied from late April to mid-May.Anthesis of a single flower often lasted for 1 d.However,if the daily maximum air temperature was under 20℃,the anthesis of a single flower could be prolonged up to 2 d.The pollen dispersion period of the single flower could last for 4 to 5 h,from 10:30 to 15:00 local time,with the duration of pollen dispersion for a single anther lasting approximately 40 min.The heterotypical maturation of the stigma could significantly prolong the pollen dispersion period of the single flower suggesting an adaptation to the habitat of E.anisopterus in the desert where the pollinators were not reliable.The timing of the blossoms of the ephemeroid plant show close correlations with the wind velocity and the habit and characteristics of the pollinators in the desert.Plant pollens may be spread to over 70 m by wind with approximately 60%of the pollens falling within 20 m away from the plant.Insects,especially bees,hover flies,flesh flies,mason bees and Halictus sp.were very important pollinators.Bees and hover flies usually landed on the yellowish green spot on the tepal and then entered the flower along the purple vein on the pink tepals.The yellowish green spot might be a mimetic structure of nectar that could attract insects to visit.This was also an adaptation of the plant to the sandy desert environment.A higher visiting frequency was reached between 10:30 and 13:30.The pollen-ovule ratio(P/O)of E.anisopterus(6164)suggested that the species was from cross-pollination according to Cruden’s criterion.However,the arti-ficial isolation experiment shows that E.anisopterus is self-compatible which might act as a compensation mechanism for the inadequate opportunities for breeding in the desert environment.Since there was no seed set in the bagged emasculated flowers,apomixes did not occur.In conclusion,E.anisopterus might adapt to the unreliable pollinator habits by self-pollination and by lengthening the pollen dispersion period of a single flower.

Heterotypic signaling of cancer-associated fibroblasts in shaping the cancer cell drug resistance

The context-dependent reciprocal interaction between the cancer cells and surrounding fibroblasts is imperative for regulating malignant potential,metabolic reprogramming,immunosuppression,and ECM deposition.However,recent evidence also suggests that cancer-associated fibroblasts induce chemoresistance in cancer cells to various anticancer regimens.Because of the protumorigenic function of cancer-associated fibroblasts,these stromal cell types have emerged as fascinating therapeutic targets for cancer.However,this notion was recently challenged by studies that targeted cancer-associated fibroblasts and highlighted the underlying heterogeneity by identifying a subset of these cells with tumor-restricting functions.Hence,it is imperative to understand the heterogeneity and heterotypic signaling of cancer-associated fibroblasts to target tumor-promoting signaling processes by sparing tumor-restricting ones.In this review,we discuss the heterogeneity and heterotypic signaling of cancer-associated fibroblasts in shaping drug resistance and also list the cancer-associated fibroblast-targeting therapeutics.