Effects of process parameters on semi-solid squeeze casting performance of aluminum alloy scrolls for scroll compressors

The aluminum alloy scroll is one of the key parts of the scroll compressors widely used in the air-conditioning,refrigeration,and heat pump systems.In this work,the semi-solid squeeze casting(SSSC)process was used to fabricate the aluminum alloy scroll.The effects of process parameters including the pouring temperature,mold temperature,and squeezing velocity on the filling and solidification behaviors of the alloys were investigated through simulations based on the power law cut-off(PLCO)material model.Results show that there is a significant increase in the flow velocity of the slurry,and the area of the high-speed region enlarges with the increase of the pouring temperature.The homogeneity of the temperature and velocity fields in the slurry is improved with an increase in mold temperature.Both the filling time and its variation rate decrease with an increase in squeezing velocity.The maximum solidification time exhibits a linear variation with the increase in pouring temperature.The shrinkage area is decreased by increasing the mold temperature.The optimal process parameters of the SSSC process were obtained from simulation analysis,which are the pouring temperature of 595°C,mold temperature of 350°C,and squeezing velocity of 0.3 m·s-1.Moreover,the qualified scroll casting was fabricated using the SSSC process under the optimal process parameters.

Direct preparation of semi-solid billets by the semi-solid isothermal heat treatment for commercial cold-rolled ZL104 aluminum alloy

Semi-solid isothermal heat treatment was proposed to directly process cold-rolled ZL104 aluminum alloys and obtain semi-solid bil-lets.The effects of two process parameters,namely,temperature and processing time,on the microstructure and hardness of the resulting bil-lets were also experimentally examined.Average grain size(AGS)increased and the shape factor(SF)of the grain improved as the process temperature increased.The SF of the grain also increased with increasing processing time,and the AGS was augmented when the processing time was prolonged from 5 to 20 min at 570℃.The hardness of the aluminum alloy decreased because of the increase in AGS with increasing temperature and processing time.The optimal temperature and time for the preparation of semi-solid ZL104 aluminum alloys were 570℃and 5 min,respectively.Under optimal process parameters,the AGS,SF,and hardness of the resulting alloy were 35.88μm,0.81,and 55.24 MPa,respectively.The Lifshitz-Slyozov-Wagner relationship was analyzed to determine the coarsening rate constant at 570℃,and a rate constant of 1357.2μm3/s was obtained.

A LysM Receptor Heteromer Mediates Perception of Arbuscular Mycorrhizal Symbiotic Signal in Rice

Symbiotic microorganisms improve nutrient uptake by plants.To initiate mutualistic symbiosis with arbus-cular mycorrhizal(AM)fungi,plants perceive Myc factors,including lipochitooligosaccharides(LCOs)and short-chain chitooligosaccharides(CO4/CO5),secreted by AM fungi.However,the molecular mechanism of Myc factor perception remains elusive.In this study,we identified a heteromer of LysM receptor-like kinases consisting of OsMYR1/OsLYK2 and OsCERK1 that mediates the perception of AM fungi in rice.CO4 directly binds to OsMYR1,promoting the dimerization and phosphorylation of this receptor complex.Compared with control plants,Osmyr1 and Oscerk1 mutant rice plants are less sensitive to Myc factors and show decreased AM colonization.We engineered transgenic rice by expressing chimeric receptors that respectively replaced the ectodomains of OsMYR1 and OsCERK1 with those from the homologous Nod factor receptors MtNFP and MtL YK3 of Medicago truncatula.Transgenic plants displayed increased cal-cium oscillations in response to Nod factors compared with control rice.Our study provides significant mechanistic insights into AM symbiotic signal perception in rice.Expression of chimeric Nod/Myc recep-tors achieves a potentially important step toward generating cereals that host nitrogen-fixing bacteria.

Transcriptional activation and phosphorylation of OsCNGC9 confer enhanced chilling tolerance in rice

Low temperature is a major environmental factor that limits plant growth and productivity.Although transient elevation of cytoplasmic calcium has long been recognized as a critical signal for plant cold tolerance,the calcium channels responsible for this process have remained largely elusive.Here we report that OsCNGC9,a cyclic nucleotide-gated channel,positively regulates chilling tolerance by mediating cytoplasmic calcium elevation in rice(Oryza sativa).We showed that the loss-of-function mutant of OsCNGC9 is defective in cold-induced calcium influx and more sensitive to prolonged cold treatment,whereas OsCNGC9 overexpression confers enhanced cold tolerance.Mechanistically,we demonstrated that in response to chilling stress,OsSAPK8,a homolog of Arabidopsis thaliana OST1,phosphorylates and activates OsCNGC9 to trigger Ca2+influx.Moreover,we found that the transcription of OsCNGC9 is activated by a rice dehydration-responsive element-binding transcription factor,OsDREB1A.Taken together,our results suggest that OsCNGC9 enhances chilling tolerance in rice through regulating cold-induced calcium influx and cytoplasmic calcium elevation.

Application of Keyhole Microneurosurgery in China

INTRODUCTIONMicroneurosurgery made its debut in the early 1960s. It became popular in the medical field and became a primary operation method in neurosurgery since it improved the efficacy of neurosurgery with a less surgery-related injury. Over the past five decades, the accumulation of experience of microsurgery, improvement of microsurgery techniques, refined micro-instruments, and advanced preoperative diagnostic imaging allowed the evolution of microneurosurgery techniques and further reduced surgery-related trauma.

Three CNGC Family Members, CNGC5, CNGC6, and CNGC9, Are Required for Constitutive Growth of Arabidopsis Root Hairs as Ca2+-Permeable Channels

The genetic identities of Ca2+ channels in root hair (RH) tips essential for constitutive RH growth have remained elusive for decades. Here, we report the identification and characterization of three cyclicnucleotide-gated channel (CNGC) family members, CNGC5, CNGC6, and CNGC9, as Ca2+ channels essential for constitutive RH growth in Arabidopsis. We found that the cngc5-1cngc6-2cngc9-1 triple mutant(designated shrh1) showed significantly shorter and branching RH phenotypes as compared with thewild type. The defective RH growth phenotype of shrh1 could be rescued by either the expression ofCNGC5, CNGC6, or CNGC9 single gene or by the supply of high external Ca2+, but could not be rescuedby external K+ supply. Cytosolic Ca2+ imaging and patch-clamp data in HEK293T cells showed that thesethree CNGCs all function as Ca2+-permeable channels. Cytosolic Ca2+ imaging in growing RHs furthershowed that the Ca2+ gradients and their oscillation in RH tips were dramatically attenuated in shrh1compared with those in the wild type. Phenotypic analysis revealed that these three CNGCs are Ca2+ channels essential for constitutive RH growth, with different roles in RHs from the conditional player CNGC14.Moreover, we found that these three CNGCs are involved in auxin signaling in RHs. Taken together, ourstudy identified CNGC5, CNGC6, and CNGC9 as three key Ca2+ channels essential for constitutive RHgrowth and auxin signaling in Arabidopsis.

Demographic Characterization of Patients Enrolled in the China Pituitary Disease Register Network

To the Editor:Pituitary disease is a group of pituitary gland disorders, including pituitary adenoma and other lesions,in the sellar region.[1] Typical endocrine symptoms and mass effects are likely to have harmful results on patients,families,and society.Pituitary databases of various sizes and focuses have been established in the USA and Europe.[2-4]

S-type anion channel SLAC1's homologues inhibit inward potassium channels AKT2 and KAT2 in Arabidopsis

Cations and anions are involved in plant growth,development and signaling responses as essential nutrients,signaling molecules and osmotic components,and the dynamic movement of the diverse ions through biological membrane is mainly mediated and regulated by ion channels and transporters.Potassium(K^+)

Constitutive activation of calcium-dependent protein kinase 3 confers a drought tolerance by inhibiting inward K＋ channel KAT1 and stomatal opening in Arabidopsis

The changes of turgor pressure in guard cells resulted from the massive fluxes of osmotic ions into and out of guard cells through ion channels and transporters are the main driving force for stomatal movement[1].The massive efflux of diverse osmotic anions are mainly mediated by slow and rapid anion channels for stomatal closure,whereas the influx of K^+,the main osmotic cation and