Photoluminescence and ratiometric thermo-response of Eu^(2+)and Eu^(3+)in BaAl_(2)B_(2)O_(7):Eu^(2+),Eu^(3+)phosphor materials

A novel Eu^(2+)-Eu^(3+)co-activated ratiometric thermo-sensitive phosphor was developed and synthesized by solid-state reaction.The valence state of Eu,photoluminescence and thermo-sensitive performance of the phosphor prepared either in ambient air or carbothermally were investigated and discussed.The phosphor shows high sensitivity(Sa=0.0173 K^(-1),S_(r)=0.461%/K)and superior signal discriminability(Δν∼10380 cm^(−1)).The thermo-sensitive performance is subject to the dual effects of different thermo-responses by Eu^(2+)versus Eu^(3+)combined with energy transfer from Eu^(2+)to Eu^(3+),so that the sensitivity of the phosphor in the temperature range presents a non-monotonic trend.The development of the BaAl_(2)B_(2)O_(7):Eu^(2+),Eu^(3+)phosphor is not only expected to be relevant for application in the field of temperature sensing,but also of reference significance for improving the sensitivity by means of energy transfer between co-activator ions over a wider temperature range of Eu^(2+)-Eu^(3+)co-activated ratiometric thermo-sensitive phosphors.

A mild iodocyclohexane demethylation for highly enhancing antioxidant activity of lignin

Lignin,as a natural antioxidant,shows great potential in food engineering and medicine.How-ever,the inherent macromolecular structure,high polydispersity,and few phenolic hydroxy seri-ously limit its antioxidant activity.In this work,a mild iodocyclohexane demethylation for highly improving the antioxidant activity of lignin was proposed.The results showed-OCH 3 content exhibited an almost linear decrease as a function of treating time,and the demethylation and cleavage of𝛽-aryl ether bonds prompt an obvious increase in phenolic hydroxyl content(4.01 mmol/g)and a significant decline in aliphatic hydroxyl(∼0.03 mmol/g).Meanwhile,attributing to the fragmentation of𝛽β-O-4,β-β,and𝛽β-5 substructures,the polydispersity of lignin molecular weight decreases from 2.7 to 2.2.As a result,the formed catechol-typed lignin showed an out-standing antioxidant activity,with the radical(DPPH·)scavenging index(inverse of concentration for 50%of maximal effect(EC 50)value)over 2000 mL/mg,much superior to the commercial antioxidants(<500 mL/mg).Further structure-activity relationship analysis implied that the Ph-OH/-OCH 3 ratio might act as a key factor influencing the antioxidant activity of lignin.This mild demethylation demonstrates a facile and effective method for highly enhancing the antioxidant activity of lignin and makes the catechol-typed lignin a green and promising product for practical use in food,medicine,and pharmacy.

Haemodynamic analysis of adult patients with moyamoya disease: CT perfusion and DSA gradings

Object Moyamoya disease(MMD)is a common and chronic progressive stenotic-occlusive cerebrovascular disease in Eastern Asia.To evaluate the hemispheric haemodynamic status of adult patients with MMD,we explored the potential risk factors of hemispheric perfusion alterations with CT perfusion(CTP)and DSA.Methods We retrospectively reviewed 44 male and 44 female(176 hemispheres)adult patients with MMD who had both DSA and CTP.Data on cerebral blood perfusion(CBF),cerebral blood volume(CBV),mean transmit time(MTT),time to peak(TTP)of cerebral hemisphere and cerebellum were gathered and difference of relative haemodynamic parameters between different subgroups were assessed with independent sample t analysis,one-way analysis of variance and general linear regression analysis.Results Parameters in regional CBF(rCBF)of frontal,temporal lobe and basal ganglia in female was more superior than male.rCBF,regional MTT(rMTT)and regional TTP(rTTP)in adult MMD patients with haemorrhage were superior than the ischaemic.With the increase of age,significant difference could be seen in rCBF and rCBV of thalamus.However,with progress of arterial stenosis,significant difference could only be obsevrved in rCBV,rMTT and rTTP,whereas rCBF had no significant difference.For increase of moyamoya vessels,significant decrease of rCBF could be seen in temporal and parietal lobe.With the increase of compensatory artery numbers,no significant difference could be seen in rCBF parameters(p>0.05).Conclusions In adult MMD patients,age,gender and clinical type were potential risk factors for the change of cerebral perfusion.When arterial stenosis is worsened,moyamoya vessels could alter perfusion of temporal and parietal lobe,but not frontal lobe.Extracranial/intracranial compensatory arteries could maintain microcirculation stability in frontal lobe and basal ganglia,indicating that the protection from extracranial compensatory arteries,a theoretic base for surgery treatment if necessary.

Hole quality in longitudinal–torsional coupled ultrasonic vibration assisted drilling of carbon fiber reinforced plastics

Carbon fiber reinforced plastic (CFRP) composites are extremely attractive in the manufacturing of structural and functional components in the aircraft manufacturing field due to their outstanding properties, such as good fatigue resistance, high specific stiffness/strength, and good shock absorption. However, because of their inherent anisotropy, low interlamination strength, and abrasive characteristics, CFRP composites are considered difficult-to-cut materials and are prone to generating serious hole defects, such as delamination, tearing, and burrs. The advanced longitudinal–torsional coupled ultrasonic vibration assisted drilling (LTC-UAD) method has a potential application for drilling CFRP composites. At present, LTC-UAD is mainly adopted for drilling metal materials and rarely for CFRP. Therefore, this study analyzes the kinematic characteristics and the influence of feed rate on the drilling performance of LTC-UAD. Experimental results indicate that LTC-UAD can reduce the thrust force by 39% compared to conventional drilling. Furthermore, LTC-UAD can decrease the delamination and burr factors and improve the surface quality of the hole wall. Thus, LTC-UAD is an applicable process method for drilling components made with CFRP composites.