The Coude Echelle Spectrograph for the Lijiang 1.8 m telescope

The Coude Echelle Spectrograph(CES)was originally mounted on Xinglong 2.16 m telescope in 1994.When the High Resolution Fiber-fed Spectrograph(HRS)was commissioned at Xinglong 2.16 m telescope,the red path of CES was moved to Lijiang 1.8 m telescope,following some redesign and reinstallation.The CES of Lijiang 1.8 m telescope has the spectral resolution(R=λ/?λ)ranging from 20000 to 50000 corresponding to different slit widths.With a 2 k×2 k PI CCD,CES has a wavelength coverage between 570 nm to 1030 nm.In particular,the resolution of 37000 at 0.5 mm slit corresponds to 1.3′′on the sky.The limiting magnitude is V=11.5 with the use of the tip-tilt feedback system,and the S/N is about 40 for 1 hour exposure at 600 nm(R=37000).During the installation of CES,the tip-tilt mirror technology had successfully fulfilled high precision guiding and tracking for high resolution spectral observation and significantly improved the observation efficiency.

A tartrate-EDTA-Fe complex mediates electron transfer and enhances ammonia recovery in a bioelectrochemical-stripping system

Traditional bioelectrochemical systems(BESs)coupled with stripping units for ammonia recovery suffer from an insufficient supply of electron acceptors due to the low solubility of oxygen.In this study,we proposed a novel strategy to efficiently transport the oxidizing equivalent provided at the stripping unit to the cathode by introducing a highly soluble electron mediator(EM)into the catholyte.To validate this strategy,we developed a new kind of iron complex system(tartrate-EDTA-Fe)as the EM.EDTA-Fe contributed to the redox property with a midpoint potential of
0.075 V(vs.standard hydrogen electrode,SHE)at pH 10,whereas tartrate acted as a stabilizer to avoid iron precipitation under alkaline conditions.At a ratio of the catholyte recirculation rate to the anolyte flow rate(RC-A)of 12,the NH4 t-N recovery rate in the system with 50mM tartrate-EDTA-Fe complex reached 6.9±0.2 g Nm^(-2) d^(-1),approximately 3.8 times higher than that in the non-EM control.With the help of the complex,our system showed an NH4 t-N recovery performance comparable to that previously reported but with an extremely low RC-A(0.5 vs.288).The strategy proposed here may guide the future of ammonia recovery BES scale-up because the introduction of an EM allows aeration to be performed only at the stripping unit instead of at every cathode,which is beneficial for the system design due to its simplicity and reliability.