LED-pumped eye-safe pulse laser with an extracavity optical parametric oscillator.

An LED-side-pumped Nd:YAG/Cr4+:YAG passively Q-switched (PQS) laser containing an extracavity optical parametric oscillator (EOPO) is demonstrated. As far as we know, it is the first LED-pumped eye-safe laser. The Nd:YAG pump module is optimized to increase the PQS pulse energy to 24 mJ at 1064 nm. By using a single-pass EOPO design, the output energy of the signal pulse at 1573 nm is 7.44 mJ with a pulse width of 16 ns, the peak power is 434 kW, and the pump-to-signal conversion efficiency is 31%. For double-pass EOPO operation, the pump-to-signal conversion efficiency increases to 45.8%, the output energy of signal pulse is up to 10.98 mJ with a pulse width of 23.5 ns, and the peak power is 459 kW.

[Determination of methyl isobutyl ketone in urine by headspace coupled with gas chromatography-mass spectrometry].

Objective: To establish a method for the determination of methyl isobutyl ketone (MIBK) in urine samples by headspace-gas chromatography-mass spectrometry. Methods: Automatic headspace sampling technique was adopted to optimize the headspace conditions (headspace bottle heating temperature and equilibration time) and gas chromatographic conditions. A total of 5 ml samples were taken and added with 3.0 g ammonium sulfate into a 20 ml headspace bottle. After heated at 60 ℃ for 30 mins, gas from the upper part of headspace bottle was injected into gas chromatography with an injection volume of 100 µl. The target was separated by HP-5MS UI (30 m×0.25 mm×0.25 µm) capillary column and then detected by mass spectrometry detector. The retention time and external standard method were used for qualitative and quantitative analysis of MIBK in samples, respectively. Results: The standard curve of MIBK showed significant linearity between 20.0-1 000.0 µg/L. The standard curve was y=62.9x-652.5, and the correlation coefficient r=0.9998. The detection limit of MIBK was 5.0 µg/L and the quantification limit of MIBK was 16.0 µg/L. The average recovery rate was 95.3%~100.2% at three spiked concentrations of low (50.0 µg/L) , medium (200.0 µg/L) and high (500.0 µg/L) . The intra-day and inter-day precisions were 1.7%~3.8% (n=6) and 1.2%~4.0% (n=6) respectively. This method was stable for the determination of MIBK, and the urine could be kept 14 d at -20 ℃ without significantly loss. Conclusion: This method is proved to be simple, practical and highly sensitive. It can satisfy the request for the determination of urine samples of workers exposed to MIBK.

[Meta-analysis on the contents of trace elements in workers with occupational exposure to lead].

Objective: To quantitatively evaluate the content differences of trace elements in workers with occupational exposure to lead. Methods: In January 2021, relevant literatures on the contents of trace elements in workers with occupational exposure to lead published from 1990 to 2020 were searched through CNKI, Wanfang, VIP, PubMed, web of science and Embase. Screened and extracted the literatures, and evaluated the quality of the included literatures with Newcastle Ottawa Scale. Meta analysis was performed with Review Manager 5.3 software, and standardized mean difference (SMD) and its 95% confidence interval were used as effect indicators. Results: A total of 20 literatures were included, and the quality scores were 5-7. The results of Meta-analysis showed that compared with the control group, the contents of blood zinc (SMD=-1.01, 95%CI: -1.53, -0.49) , hair zinc (SMD=-0.17, 95%CI: -0.33, -0.01) , hair copper (SMD=-0.50, 95%CI: -1.01, 0) , hair iron (SMD=-3.91, 95%CI: -5.80, -2.03) and hair manganese (SMD=-1.09, 95%CI: -2.02, -0.15) in occupational lead exposure group were significantly lower (P<0.05) . Compared with the control group, the content of cobalt in hair of occupational lead exposure group (SMD=1.41, 95%CI: 0.72, 2.10) was higher, and the difference was statistically significant (P<0.05) . There was no significant difference in the contents of blood chromium, blood copper, blood iron, blood manganese, blood selenium and hair nickel between the two groups (P>0.05) . Conclusion: Workers with occupational exposure to lead have abnormal trace elements.

[Determination of the butanone in urine by gas chromatography with precolumn derivation].

Objective: To establish a method for determination of the butanone in urine by gas chromatography (GC) with pre-column derivation. Methods: For detecting of butanone in urine, potassium iodide and potassium dichromate were added into urine under acidic condition, sample derivatization was undertaken in 50 ℃ water bath for 60 min and the iodine butanone was extracted with n-hexane. After the sodium thiosulfate solution was used to remove excess iodine, urine samples were centrifuged at 10000 r/min for 5 min, then the supernatant was analyzed using temperature rising programming with the Agilent Hp-5 column (30 m×0.32 mm, 0.25 µm) and electron capture detector (ECD) as the detector. The detector temperature was 300 ℃, the inlet temperature was 200 ℃, and the carrier gas was nitrogen. Results: For detecting of butanone in urine, potassium iodide and potassium dichromate were added for derivatization under the acidic condition. After extraction and centrifugation, the supernatant directly put through column and detected by ECD. In present study, the sample pretreatment condition was optimized, the relative standard deviations of intra-day and inner-day, the spiked samples and its recovery were evaluated for analyzing the accuracy of the proposed method. Conclusion: This method has proved to be simple, efficient and highly sensitivity, it can be utilized for butanone detection in occupational population.

A composite of exhaled LTB4 , LXA4 , FeNO, and FEV1 as an "asthma classification ratio" characterizes childhood asthma.

BACKGROUND: Aberrant generation of eicosanoids is associated with asthma, but the evidence remains incomplete and its potential utility as biomarkers is unclear. Major eicosanoids in exhaled breath condensates (EBCs) were assessed as candidate markers for childhood asthma. METHODS: Ten exhaled eicosanoid species was evaluated using ELISA in the discovery phase, followed by prediction model-building and validation phases. RESULTS: Exhaled LTB4 , LTE4 , PGE2, and LXA4 showed significant difference between asthmatics (N = 60) and controls (N = 20). For validation, an expanded study population consisting of 626 subjects with asthma and 161 healthy controls was partitioned into a training subset to establish a prediction model and a test sample subset for validation. Receiver operating characteristic (ROC) analyses of the training subset revealed the level of exhaled LTB4 to be the most discriminative among all parameters, including FeNO, and a composite of exhaled LTB4 , LXA4 , together with FeNO and FEV1 , distinguishing asthma with high sensitivity and specificity. Further, the Youden index (J) indicated the cut point value of 0.598 for this composite of markers as having the strongest discriminatory ability (sensitivity = 85.2% and specificity = 83.6%). The predictive algorithm as "asthma classification ratio" was further validated in an independent test sample with sensitivity and specificity being 84.4% and 84.8%, respectively. CONCLUSIONS: In a pediatric study population in Taiwan, the levels of exhaled LTB4 , LTE4 , LXA4, and PGE2 in asthmatic children were significantly different from those of healthy controls, and the combination of exhaled LTB4 and LXA4 , together with FeNO and FEV1 , best characterized childhood asthma.

Broad expansion of optical frequency combs by self-Raman scattering in coupled-cavity self-mode-locked monolithic lasers.

Broad expansion of optical frequency comb (OFC) by the self-Raman scattering is numerically analyzed and experimentally accomplished in a coupled-cavity self-mode-locked (SML) monolithic Yb:KGW laser. The gain medium is coated to achieve the monolithic SML operation and a partially reflective mirror is further exploited to form the coupled cavity and to multiply the repetition rate up to 128.9 GHz. With a coupled reflectivity of 95%, it is experimentally found that not only the first-order but also second-order stimulated Raman scattering (SRS) can be efficiently generated. The mode-locked OFC can be consequently expanded to reach approximately 8.4 THz, leading the pulse width to be as narrow as 53 fs. At the pump power of 8.7 W, the total output power for the fundamental and the first- and second-Stokes waves can be maintained at 1.6 W. The present exploration provides a promising way to generate the ultrahigh-repetition-rate broadband OFC via the simultaneous SML and SRS processes.

Modelling end-pumped passively Q-switched Nd-doped crystal lasers: manifestation by a Nd:YVO4/Cr4+:YAG system with a concave-convex resonator.

A theoretical model for the passively Q-switched (PQS) operation which includes the spatial overlapping between the pump and lasing modes under the thermal lensing effect is developed to give a transcendental equation that can directly determine the critical parameters such as pulse energy, pulse repetition rate, and pulse width for the PQS performance. More importantly, an analytical function which gives the approximate solution for the transcendental equation as well as a specific critical criterion for good PQS operation are derived for practical analyses and design. A Nd:YVO4/Cr4+:YAG system with a concave-convex resonator which can achieve fairly stable PQS pulse trains even at a high pump level is further exploited to manifest the proposed spatially dependent model. The good agreement between the experimental results and the theoretical predictions is verified to show the feasibility of the proposed model for designing high-power PQS lasers with high accuracy.

Exploring transverse pattern formation in a dual-polarization self-mode-locked monolithic Yb: KGW laser and generating a 25-GHz sub-picosecond vortex beam via gain competition.

Formation of transverse modes in a dual-polarization self-mode-locked monolithic Yb: KGW laser under high-power pumping is thoroughly explored. It is experimentally observed that the polarization-resolved transverse patterns are considerably affected by the pump location in the transverse plane of the gain medium. In contrast, the longitudinal self-mode-locking is nearly undisturbed by the pump position, even under the high-power pumping. Under central pumping, a vortex beam of the Laguerre-Gaussian LGp,l mode with p = 1 and l = 1 can be efficiently generated through the process of the gain competition with a sub-picosecond pulse train at 25.3 GHz and the output power can be up to 1.45 W at a pump power of 10.0 W. Under off-center pumping, the symmetry breaking causes the transverse patterns to be dominated by the high-order Hermite-Gaussian modes. Numerical analyses are further performed to manifest the symmetry breaking induced by the off-center pumping.

Synchronized self-mode-locked 1061-nm and 1064-nm monolithic Nd:YAG laser at cryogenic temperatures with two orthogonally polarized emissions: generation of 670 GHz beating.

A dual-wavelength self-mode-locked monolithic Nd:YAG laser at 1061 and 1064 nm is realized at cryogenic temperatures. At an incident pump power of 5.5 W, the total output power can reach 2.5 W and the mode-locked pulse width is 29 ps at a pulse repetition rate of 7.75 GHz. The synchronization of the dual-wavelength emissions leads to a beat frequency of 670 GHz in the individual mode-locked pulse. It is further discovered that the laser output consists of two orthogonally polarized components with a central frequency difference of 127 MHz. The central frequency difference between two orthogonal polarizations mainly arises from the external mechanical stress introduced by the copper holder for the laser crystal.

Dual-comb self-mode-locked monolithic Yb:KGW laser with orthogonal polarizations.

The dependence of lasing threshold on the output transmission is numerically analyzed to find the condition for the gain-to-loss balance for the orthogonal Np and Nm polarizations with a Ng-cut Yb:KGW laser crystal. With the numerical analysis, an orthogonally polarized dual-comb self-mode-locked operation is experimentally achieved with a coated Yb:KGW crystal to form a monolithic cavity. At a pump power of 5.2 W, the average output power, the pulse repetition rate, and the pulse duration are measured to be 0.24 (0.6) W, 25.8 (25.3) GHz, and 1.06 (1.12) ps for the output along the Np (Nm) polarization.