[en] We investigated the dependence of laser-induced breakdown spectral intensity on the focusing position of a lens at different sample temperatures (room temperature to 300 °C) in atmosphere. A Q-switched Nd:YAG nanosecond pulsed laser with 1064 nm wavelength and 10 ns pulse width was used to ablate silicon to produce plasma. It was confirmed that the increase in the sample’s initial temperature could improve spectral line intensity. In addition, when the distance from the target surface to the focal point increased, the intensity firstly rose, and then dropped. The trend of change with distance was more obvious at higher sample temperatures. By observing the distribution of the normalized ratio of Si atomic spectral line intensity and Si ionic spectral line intensity as functions of distance and temperature, the maximum value of normalized ratio appeared at the longer distance as the initial temperature was higher, while the maximum ratio appeared at the shorter distance as the sample temperature was lower. (paper)

[en] In double-pulse laser-induced breakdown spectroscopy (DP-LIBS), the collinear femtosecond double-pulse laser configuration is experimentally investigated with different initial sample temperatures using a Ti:sapphire laser. The glass sample is ablated to produce the plasma spectroscopy. During the experiment, the detected spectral lines include two Na (I) lines (589.0 nm and 589.6 nm) and one Ca (I) line at the wavelength of 585.7 nm. The emission lines are measured at room temperature (22 °C) and three higher initial sample temperatures (T _s = 100 °C, 200 °C, and 250 °C). The inter-pulse delay time ranges from −250 ps to 250 ps. The inter-pulse delay time and the sample temperature strongly influence the spectral intensity, and the spectral intensity can be significantly enhanced by increasing the sample temperature and selecting the optimized inter-pulse time. For the same inter-pulse time of 0 ps (single-pulse LIBS), the enhancement ratio is approximately 2.5 at T _s = 200 °C compared with that obtained at T _s = 22 °C. For the same inter-pulse time of 150 ps, the enhancement ratio can be up to 4 at T _s = 200 °C compared with that obtained at T _s = 22 °C. The combined enhancement effects of the different initial sample temperatures and the double-pulse configuration in femtosecond LIBS are much stronger than that of the different initial sample temperatures or the double-pulse configuration only. (paper)

[en] The combination of spark discharge and laser-induced breakdown spectroscopy (LIBS) is called spark discharge assisted LIBS. It works under laser-plasma triggered spark discharge mode, and shows its ability to enhance spectral emission intensity. This work uses a femtosecond laser as the light source, since femtosecond laser has many advantages in laser-induced plasma compared with nanosecond laser, meanwhile, the study on femtosecond LIBS with spark discharge is rare. Time-resolved spectroscopy of spark discharge assisted femtosecond LIBS was investigated under different discharge voltages and laser energies. The results showed that the spectral intensity was significantly enhanced by using spark discharge compared with LIBS alone. And, the spectral emission intensity using spark discharge assisted LIBS increased with the increase in the laser energy. In addition, at low laser energy, there was an obvious delay on the discharge time compared with high laser energy, and the discharge time with positive voltage was different from that with negative voltage. (paper)

[en] The study on the light hydrocarbons generated by radiation degradation of N,N-diethylhydroxylamine (DEHA) is reported. The results show that when the concentration of DEHA is 0.1-0.5 mol/L and the dose is 10-1000 kGy, the volume fraction of methane, ethane, propane and n-butane increases with the increasing of dose, but decreases with the increasing of the concentration of DEHA. The volume fraction of ethene and propene increases with the increasing of the concentration of DEHA. The relationship of the volume fraction of ethene and propene with dose has something to do with the concentration of DEHA. (authors)

[en] Highlights: • Increasing the target temperature can enhance the spectral intensity of the Cu plasmas. • Spectral intensities firstly increased, and then dropped with an increase in the DFTT. • Spectral maximum in fs moved away from focusing-lens as the target temperature increased. • Spectral maximum in ns moved close to focusing-lens as the target temperature increased. In this study, the influence of distance from focusing-lens to target-surface (DFTT) on the spectral characteristics of femtosecond and nanosecond laser-ablated Cu plasmas for different target temperatures was compared in air. The results showed that the spectral intensities were dependent on the DFTT and the target temperature. The spectral intensities increased with an up-regulation in the target temperature. In addition, as the target temperature increased, the maximum spectral emission and electron temperature moved away from the focusing-lens in the case of the femtosecond laser, while the maximum spectral emission and electron temperature moved closer to the focusing-lens in the case of the nanosecond laser. These phenomena were mainly based on the different pulse widths between femtosecond and nanosecond laser-ablated mechanisms.

[en] Highlights: • MALAT1 was up-regulated in CPCs in hypoxia conditions. • MALAT1 suppression inhibited CPCs proliferation and migration after hypoxia-inducing stimuli. • MALAT1 modulated CPCs proliferation and migration through MALAT1/miR-125/JMJD6 axis under hypoxia conditions. The death of cardiomyocytes after myocardial infarction (MI) often leads to ventricular remodeling as well as heart failure (HF). The cardiac progenitor cells (CPCs) have the ability to regenerate functional heart muscle in patients after MI, which provides a promising method for MI-induced HF therapy. However, to date, CPCs can easily lose their proliferation ability in the infarcted myocardium. Therefore, exploring the mechanism for CPC proliferation is essential for CPC-based therapy in MI-induced HF. A previous study indicated that a hypoxic environment is essential for CPC proliferation, but the mechanism is not yet clear. In this work, we discovered that CoCl₂-induced hypoxia can promote CPC proliferation and migration. Additionally, long non-coding RNA MALAT1 expression was significantly up-regulated in the CoCl₂-induced hypoxia CPC model. MALAT1 suppression inhibited CPC proliferation and migration under hypoxic conditions. In addition, MALAT1 acted as a sponge for miR-125. The miR-125 inhibitor restored the proliferation and migration potentials of CPCs after a MALAT1 knockdown in hypoxia. A further study demonstrated that JMJD6 was a target of miR-125 whose expression was negatively regulated by miR-125. JMJD6 knockdown blocked miR-125 inhibitor's protective effect on CPC function in hypoxia. Ultimately, our finding demonstrated that MALAT1 can modulate CPC proliferation and migration potential through the miR-125/JMJD6 axis in hypoxia. Our finding provided a new regulatory mechanism for CPC proliferation in hypoxia, which provided a new target for MI-induced HF therapy.

[en] Spectral intensity, electron temperature and density of laser-induced plasma (LIP) are important parameters for affecting sensitivity of laser-induced breakdown spectroscopy (LIBS). Increasing target temperature is an easy and feasible method to improve the sensitivity. In this paper, a brass target in a temperature range from 25 °C to 200 °C was ablated to generate the LIP using femtosecond pulse. Time-resolved spectral emission of the femtosecond LIBS was measured under different target temperatures. The results showed that, compared with the experimental condition of 25 °C, the spectral intensity of the femtosecond LIP was enhanced with more temperature target. In addition, the electron temperature and density were calculated by Boltzmann equation and Stark broadening, indicating that the changes in the electron temperature and density of femtosecond LIP with the increase of the target temperature were different from each other. By increasing the target temperature, the electron temperature increased while the electron density decreased. Therefore, in femtosecond LIBS, a high-temperature and low-density plasma with high emission can be generated by increasing the target temperature. The increase in the target temperature can improve the resolution and sensitivity of femtosecond LIBS. (paper)

[en] This study investigates the effect of the intra-seasonal Indo-western Pacific convection oscillation (IPCO) on tropical cyclone (TC) tracks over the western North Pacific (WNP) during the boreal extended summer (May−October). The number of west- and northwest-moving TC tracks is found to sharply increase over the WNP in the positive intra-seasonal IPCO phase. Recurving tracks have greater weight in the negative intra-seasonal IPCO phase. Possible physical mechanisms are further examined in terms of steering flow, energy conversion, and energy propagation. When the intra-seasonal IPCO phase is positive, the first-order moment term of perturbation potential energy (PPE₁) converts into perturbation kinetic energy (PKE) at lower latitudes. The pressure trough spreads farther to the east. Meanwhile, Rossby waves emanating from the convective centers of the intra-seasonal IPCO over the WNP (Wave_WNP) and EEIO (Wave_EEIO) travel into the trough region, thereby deepening the trough. These features enhance the westward and northwestward steering flow between 20°N and about 30°N, sharply increasing the number of straight west- and northwest-moving TC tracks over the WNP. When the intra-seasonal IPCO is in a negative phase, conversion from PPE₁ to PKE at lower latitudes is suppressed and the trough weakens. More PPE₁ converts to PKE in the climatological western Pacific subtropical high (WPSH) region and the WPSH is intensified. Moreover, Wave_EEIO intensifies the north–south ridge of the WPSH over the southern Indian Peninsula. Meanwhile, part Wave_WNP propagate northeastward. These features favor northeastward motion of TCs over the WNP.

[en] The global mean surface air temperature (GMST) shows multidecadal variability over the period of 1910–2013, with an increasing trend. This study quantifies the contribution of hemispheric surface air temperature (SAT) variations and individual ocean sea surface temperature (SST) changes to the GMST multidecadal variability for 1910–2013. At the hemispheric scale, both the Goddard Institute for Space Studies (GISS) observations and the Community Earth System Model (CESM) Community Atmosphere Model 5.3 (CAM5.3) simulation indicate that the Northern Hemisphere (NH) favors the GMST multidecadal trend during periods of accelerated warming (1910–1945, 1975–1998) and cooling (1940–1975, 2001–2013), whereas the Southern Hemisphere (SH) slows the intensity of both warming and cooling processes. The contribution of the NH SAT variation to the GMST multidecadal trend is higher than that of the SH. We conduct six experiments with different ocean SST forcing, and find that all the oceans make positive contributions to the GMST multidecadal trend during rapid warming periods. However, only the Indian, North Atlantic, and western Pacific oceans make positive contributions to the GMST multidecadal trend between 1940 and 1975, whereas only the tropical Pacific and the North Pacific SSTs contribute to the GMST multidecadal trend between 2001 and 2013. The North Atlantic and western Pacific oceans have important impacts on modulating the GMST multidecadal trend across the entire 20th century. Each ocean makes different contributions to the SAT multidecadal trend of different continents during different periods.