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Blue LED phototherapy in preterm infants: effects on an oxidative marker of DNA damage
摘要： background Phototherapy is used on the majority of preterm infants with unconjugated hyperbilirubinaemia. The use of fluorescent tube phototherapy is known to induce oxidative DNA damage in infants and has largely been replaced by blue light- emitting diode phototherapy (BLP). To date, it is unknown whether BLP also induces oxidative DNA damage in preterm infants. Objective To determine whether BLP in preterm infants induces oxidative DNA damage as indicated by 8- hydroxy-2′deoxyguanosine (8- OHdG). Design Observational cohort study. Methods Urine samples (n=481) were collected in a cohort of 40 preterm infants (24–32 weeks’ gestational age) during the first week after birth. Urine was analysed for the oxidative marker of DNA damage 8- OHdG and for creatinine, and the 8- OHdG/creatinine ratio was calculated. Durations of phototherapy and levels of irradiance were monitored as well as total serum bilirubin concentrations. results BLP did not alter urinary 8- OHdG/creatinine ratios (B=0.2, 95% CI ?6.2 to 6.6) at either low (10–30 μW/cm2/nm) or high (>30 μW/cm2/nm) irradiance: (B=2.3, 95% CI ?5.7 to 10.2 and B=?3.0, 95% CI ?11.7 to 5.6, respectively). Also, the 8- OHdG/creatinine ratios were independent on phototherapy duration (B=?0.1, 95% CI ?0.3 to 0.1). Conclusions BLP at irradiances up to 35 μW/cm2/nm given to preterm infants ≤32 weeks’ gestation does not affect 8- OHdG, an oxidative marker of DNA damage.
关键词： preterm infants,phototherapy,8-hydroxy-2′deoxyguanosine,blue light-emitting diode phototherapy,oxidative DNA damage
更新于2025-09-23 15:21:01
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Investigation of laser damage of grating waveguide structures submitted to sub-picosecond pulses
摘要： Grating waveguide structures (GWS) are reflective diffractive optical elements that operate based on the combination of sub-wavelength gratings (periodic microstructures) integrated with planar waveguides. They can be used for high-power laser applications for pulse compression, spectral stabilization, wavelength multiplexing, as well as polarization shaping. In this work, we investigate the laser-damage resistance of GWS based on Ta2O5/SiO2 multilayers at pulse durations of 500 fs and wavelength of 1030 nm. We particularly study the influence of the material of the multilayer sequence, the designed grating structure, and the operational conditions (angle of incidence and polarization of the laser beam) on the laser-damage resistance of the GWS. Comparison of measurements to simulation of the electric-field distribution in the structure reveals a good correlation between laser-induced damage threshold (LIDT) values and electric-field enhancement in the structure. Based on this work, an optimized design has been defined to increase the LIDT of the GWS. An improvement of the LIDT of a factor 2 has been obtained.
关键词： Ta2O5/SiO2 multilayers,Grating waveguide structures,Electric-field distribution,Sub-picosecond pulses,Laser-damage resistance
更新于2025-09-23 15:21:01
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Long-Term Systemic Treatment With Methamphetamine Causes Retinal Damage in CD1 Mice
摘要： As a powerful psychostimulant with high potential for abuse, methamphetamine (Meth) could cause long-lasting abnormalities in retinas. The purpose of this study was to investigate the effects of systemic administration of Meth at low dose on retinal damage and understand the underlying mechanisms of pathology. CD1 mice were treated with 0.5 mg/kg or 1 mg/kg Meth by intra-peritoneal injection daily for 2 months, mice treated with saline were used as negative control. Electroretinography (ERG) reflects the mass response of photoreceptor cells and was used to test the outer retinal function after Meth treatment. Toluidine blue staining was used to show the retinal morphology and evaluate the photoreceptor cell loss. Inflammatory factors were measured by enzyme-linked immunosorbent assay to show the inflammatory response. Terminal deoxynucleotidyl transferase dUTP Nick end labeling assay was used to detect the apoptosis-positive cells. Real-time polymerase chain reaction and Western blot were applied to measure the gene and protein change to explore the underlying mechanisms. Results demonstrated that retinal damage was caused by Meth treatment after 2 months, evidenced by loss of rod photoreceptor cells; decreased ERG amplitude; increased apoptotic photoreceptor cells, cytochrome-c release, caspase-3 activity, caspase-9 activity, and apoptosis-related protein expression; increased malondialdehyde level as well as nicotinamide adenine dinucleotide phosphate oxidase 4 protein expression; decreased anti-oxidative agents glutathione as well as superoxide dismutase levels; and increased production and gene expression of inflammatory factors. Our study indicated that systemic administration of Meth caused neurotoxic effects on CD1 mouse retinas, providing the potential mechanisms for the retina damage caused by Meth abuse.
关键词： CD1 mice,retina damage,methamphetamine,inflammatory response
更新于2025-09-23 15:21:01
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Morphology study and threshold measurement of laser induced damage of nano-porous antireflective silica thin films in nano- and femtosecond pulse regimes
摘要： Laser induced damage threshold (LIDT) of nano-porous antire?ective silica thin ?lms is measured using 10 ns laser pulses at k = 532 nm. The thin ?lms are prepared by dip-coating of BK7 substrates and then drying them by three different heating methods, to see how their LIDT and transmission are affected. Furthermore, using SEM imaging, the morphology of the laser induced damages is inspected and compared to those of similar samples, previously irradiated by femtosecond laser pulses at k = 800 nm. The images evidently show that in the regions damaged by nanosecond pulses, the silica nanoparticles are melted and fused to each other, while in the samples irradiated by femtosecond pulses, the silica nanoparticles are sputtered and dispersed around, in the damaged area. The SEM images clearly demonstrate the different damage mechanisms involved in the nanosecond and femtosecond regimes of interaction.
关键词： Optical thin ?lms,Silica thin ?lms,Nano-porous thin ?lms,Laser damage
更新于2025-09-23 15:21:01
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Fatigue behaviors of foreign object damaged Ti-6Al-4V alloys under laser shock peening
摘要： Two-sided and simultaneous laser shock peening (TSLSP) was used to strengthen the Ti-6Al-4V titanium alloy. The fatigue crack growth rate of the specimens was investigated by fatigue test. The results show that both direct TSLSP (TSLSP-D) and indirect TSLSP (TSLSP-I) can reduce the fatigue crack growth rate by producing high magnitude compressive residual stress. The maximum fatigue life increases by 94% (TSLSP-D) and 169% (TSLSP-I) compared with the original specimens. Moreover, the TSLSP-D results show decreased resistance to foreign object damage because of decreased plasticity while the TSLSP-I simultaneously achieves superior foreign object damage resistance and fatigue performance.
关键词： Fatigue performance,Foreign object damage,Two-sided and simultaneous laser shock peening,Titanium alloy
更新于2025-09-23 15:21:01
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Optical characteristics of the undamaged and laser damaged K9 glass in terahertz band
摘要： K9 glass is an important optical element of the high energy laser system. In an attempt to investigate the variation of optical properties of K9 glass before and after laser induced damage, based on the transmission terahertz time-domain spectral system, the undamaged and the damaged K9 glasses induced by laser were tested to obtain the terahertz time-domain and frequency-domain spectra and the refractive index and absorption coef?cient of the samples were calculated in terahertz band for further analysis. Results show that with the increase of laser energy, from the undamaged to the damaged K9 glasses to different extent, the peak to peak value in time domain and the amplitude value in frequency domain present a decreasing trend in varying degrees, and in the 0.4～0.5 THz band, the absorption coef?cient increases continuously with a slight change of refractive index, which indicates that K9 glass not only appears the melting and fracture in the macroscopic morphology after laser-induced damage, but also forms non-bridged oxygen atoms in its microstructure with more ion bonds and free electrons and the change of ion polarization. In this regard, this paper provides a technical basis for exploring the micro characteristics of K9 glass after laser-induced damage, and lays a good foundation for the application of terahertz time-domain spectroscopy to laser-induced damage analysis.
关键词： terahertz time-domain spectrum,K9 glass,laser-induced damage,refractive index,absorption coef?cient
更新于2025-09-23 15:21:01
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Defect generation by nitrogen during pulsed sputter deposition of GaN
摘要： Pulsed sputter deposition has been demonstrated to be a viable process for the growth of high quality GaN and InGaN/GaN LEDs. It enables the fabrication of nitride LEDs with a red emission wavelength at large areas. In this study, we explore details on the epitaxial sputter deposition of GaN with a particular emphasis on ion damage. By changing the argon to nitrogen ratio, we adjust the growth mode from island to layer growth. TEM revealed speckles in the epitaxial GaN, which could be identi?ed as isolated basal stacking faults, acting as non-radiative recombination centers. Using Monte Carlo methods, we modeled the energies of backscattered and sputtered atoms in order to get information on the ion damage mechanisms. Considering the collisions on the way from the target to the substrate, we found energetic nitrogen to induce the speckles. A shielding mechanism based on metallic gallium has been identi?ed, leading to the strongly increased luminescence quality in comparison to the non-shielded material.
关键词： GaN,pulsed sputter deposition,stacking faults,luminescence,ion damage
更新于2025-09-23 15:21:01
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HIFU-induced changes in optical scattering and absorption of tissue over nine orders of thermal dose
摘要： The optical properties of tissue change during thermal ablation. Multi-modal methods such as acousto-optic (AO) and photo-acoustic (PA) imaging may provide a real-time, direct measure of lesion formation. Baseline changes in optical properties have been previously measured over limited ranges of thermal dose for tissues exposed to a temperature-controlled water bath, however, there is scant data for optical properties of lesions created by HIFU. In this work, the optical scattering and absorption coefficients from 400–1300 nm of excised chicken breast exposed to HIFU were measured using an integrating sphere spectrophotometric technique. HIFU-induced spatiotemporal temperature elevations were measured using an infrared camera and used to calculate the thermal dose delivered to a localized region of tissue. Results obtained over a range of thermal dose spanning 9 orders of magnitude show that the reduced scattering coefficient increases for HIFU exposures exceeding a thermal dose of CEM43 = 600 ± 81 cumulative equivalent minutes. HIFU-induced thermal damage results in changes in scattering over all optical wavelengths, with a 2.5-fold increase for thermal lesions exceeding 70 °C. The tissue absorption coefficient was also found to increase for thermally lesioned tissue, however, the magnitude was strongly dependent on the optical wavelength and there was substantial sample-to-sample variability, such that the existence of a threshold thermal dose could not be determined. Therapeutic windows, where the optical penetration depth is expected to be greatest, were identified in the near infrared regime centered near 900 nm and 1100 nm. These data motivate further research to improve the real-time AO and PA sensing of lesion formation during HIFU therapy as an alternative to thermometry.
关键词： thermal damage,optical properties,thermal dose,lesion,high-intensity focused ultrasound
更新于2025-09-23 15:21:01
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reveals remarkable optical linewidths and fine structure for well-known damage centers
摘要： Luminescence and optical absorption due to radiation damage centers in silicon have been studied exhaustively for decades, but are receiving new interest for applications as emitters for integrated silicon photonic technologies. While a variety of other optical transitions have been found to be much sharper in enriched 28Si than in natural Si, due to the elimination of inhomogeneous isotopic broadening, this has not yet been investigated for radiation damage centers. We report results for the well-known G, W, and C damage centers in highly enriched 28Si, with optical linewidth improvements in some cases of over two orders of magnitude, revealing previously hidden ?ne structure in the G-center emission and absorption. These results have direct implications for the linewidths to be expected from single-center emission, even in natural Si, and for models for the G-center structure. The advantages of 28Si can be readily extended to the study of other radiation damage centers in Si.
关键词： 28Si,silicon,fine structure,optical linewidths,radiation damage centers
更新于2025-09-23 15:21:01
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Estimation of damage thickness in fibre-reinforced composites using pulsed thermography
摘要： Non-destructive-testing (NDT), including active thermography, has become an inevitable part of composite process and product verification, post-manufacturing. However, there is no reliable NDT technique available to ensure the interlaminar bond integrity during laminates integration, bonding or repair where the presence of thin airgaps in the interface of dissimilar polymer composite materials would be detrimental to structural integrity. This paper introduces a novel approach attempting to quantify the damage thickness of composites (the thickness of air gaps inside composites) through a single-side inspection of pulsed thermography. The potential of this method is demonstrated by testing on three specimens with different types of defect, where the Pearson Correlation Coefficients of the thickness estimation for block defects and flat-bottom holes are 0.75 and 0.85, respectively. This approach will considerably enhance the degradation assessment performance of active thermography by extending damage measurement from currently two dimensions to three dimensions, and become an enabling technology on quality assurance of structural integrity.
关键词： Active thermography,system identification,bonded repair,nonlinear correlation analysis,composite damage detection
更新于2025-09-23 15:21:01