Evaluation of Tear Malate Dehydrogenase 2 in Mild Dry Eye Disease

Purpose: To evaluate the effect of tear malate dehydrogenase2 on monitoring ocular surface injury in mild dry eye(DE)disease.Methods: A total of 15 DE patients(30 eyes) with mild subjective symptoms but no ocular surface fluorescein staining signs were enrolled in this study.(DE group)..The control group was 15 healthy age- and sex-matched volunteers(30eyes)..All subjects were asked to fill out a DE symptoms questionnaire and take different tests including tear MDH and MDH2 activities evaluation,..tear breakup time.(TBUT),Schirmer I,.and slit-lamp examination of the ocular surface.We investigated different changes in tear MDH and MDH2 activities in the DE group and control group,.discussed the association between tear MDH2 activity and DE symptoms, and the relationship between tear MDH2 activity and diagnostic tests(Schirmer I and TBUT). We also analyzed the changes in tear MDH2 activities after the treatment with artificial tears.Results:.Tear MDH activities in the DE group and control group were 288 ±102 U / L and 259 ±112 U / L,.respectively,and this difference was not statistically significant(P >0.05).The tear MDH2 activities in DE group were significantly increased compared with control group. Tear MDH2 was significantly and negatively correlated with the Schirmer's value(r=-0.733,P<0.01) and the TBUT value(r=-0.841,P<0.01)..MDH2 also had a significant positive correlation with soreness symptoms(r=0.687, P < 0.01). Treatment with artificial tears relieved or eliminated all discomfort symptoms, together with a considerable decrease in MDH2 activities(P <0.01),.but no significant changes in the Schirmer and the TBUT tests were observed.Conclusion: Tear MDH2 activity can indicate ocular surfaceinjury in mild DE patients and may be used to monitor the response to therapy.

D-Shaped Tellurite Photonic Crystal Fiber Hydrogen and Methane Sensor Based on Four-Wave Mixing With SPR Effect

A new D-shaped tellurite photonic crystal fiber sensor based on the four-wave mixing(FWM)effect with the surface plasmon resonance(SPR)effect is designed and optimized.The substrate of the D-shaped photonic crystal fiber(D-PCF)is tellurite glass,and the polished surface is plated with the gold film and hydrogen gas-sensitive film.An air hole of the inner cladding,which is plated with the gold film and methane gas-sensitive film,is selected as the second sensing channel to simultaneously measure the concentration of hydrogen and methane.Based on the four-wave mixing,the wavelength shifts of the Stokes and anti-Stokes spectra resulting from the variation of the gas concentration can be used to accurately detect the concentrations of methane and hydrogen.Meanwhile,it is found that the SPR effect can increase the wavelength shifts,which means the sensitivity of methane and hydrogen augment.After parameter optimization,the maximum sensitivities of methane and hydrogen are 4.03 nm/%and-14.19 nm/%,respectively.Both the linearities are up to 99.9%.The resolution of methane is 1.25×10^(-2)%and hydrogen is 7.14×10^(-3)%.Moreover,the fiber length of this sensor is only 20mm,which is conducive to the construction of a compact or ultra-compact embedded FWM fiber sensor.

High-Sensitive Numerical Gas Detection Using LSPR Effect and Fano Resonance in a Slotted MDM Structure

A high-sensitive numerical measurement of methane based on the combined use of the localized surface plasmon resonance(LSPR)and Fano resonance in a slotted metal-dielectric-metal(MDM)periodic structure is numerically investigated.A groove is etched in an original MDM structure to excite the diploe mode at both sides of the groove,and the coherent coupling of two dipole modes is enhanced to realize a fast response,which is beneficial to gas-sensing.The influence of geometric parameters on the reflection spectra and methane sensitivity are analyzed to obtain optimal geometry.Moreover,an etching ring is introduced on the top metal to further raise the coupling area and coupling strength.The Fano resonance is subtly integrated into the optimized structure with asymmetry to achieve greater gas sensitivity.After the introduction of the Fano resonance,the field enhancement caused by the LSPR effect becomes greater and the methane sensitivity can reach up to 8.421 nm/%in numerical calculations,which increases 56.8%more than that of the original one.The combined use of the LSPR and Fano resonance in an optimized MDM structure provides an effective method for high-sensitive gas detection.