Effects of aromatic molecules inside argon clusters on the formation of multiply charged atomic ions in moderately intense nanosecond laser fields.

We report the effect of two molecular species, fluorene (C13H10, Fl) and 1, 3, 5-trichlorobenzene (C6H3Cl3, 3ClB), embedded in atomic argon clusters, on the generation of multiply charged atomic ions (MCAIs) in moderately intense nanosecond laser fields at 532 nm. The near resonant-enhancement of two photon absorption in the two aromatic species produces only a few low charge state (+2) atomic ions in a neat molecular cluster, but the enclosure of the same cluster with layers of Ar can significantly increase the charge state of MCAIs. The yields of singly charged atomic ions from the molecular species, such as H+, C+, and Cl+, are positively correlated with the number of molecules inside the Ar cluster, but the yields of the MCAI and Ar+ demonstrate opposite behaviors. A higher number of aromatic molecules are actually detrimental to the production of Ar+ and MCAIs. The results of exponential fittings of the yields of MCAIs at different laser intensities reveal a systematic change for the exponent of Ar+: with increasing concentrations of 3ClB in Ar clusters, the exponent decreases and eventually reaches the same value as those of MCAIs. These results are consistent with our previous hypothesis that the formation mechanism of MCAIs may be different from that of singly charged species and that the strong resonance of Ar3 + may play an important role in the overall energy absorption. Moreover, the effect of the molecular core seems to change the formation mechanism of Ar+ to that of MCAIs.

Intensity dependence of multiply charged atomic ions from argon clusters in moderate nanosecond laser fields.

We report the laser intensity dependence of multiply charged atomic ions (MCAIs) Arn+ with 2 ≤ n ≤ 8 from argon clusters in focused nanosecond laser fields at 532 nm. The laser field, in the range of 1011-1012 W/cm2, is insufficient for optical field ionization but is adequate for multiphoton ionization. The MCAI sections of the mass spectra for clusters containing 3700 and 26 000 atoms are dominated by Arn+ with 7 ≤ n ≤ 9, extending to Ar14+. While the distributions of the MCAIs remain largely constant throughout the intensity range of the laser, the abundance of Ar+ relative to the abundances of the MCAIs increases dramatically with increasing laser intensity. Consequently, exponential fittings of the yields result in a larger exponent for Ar+ than for MCAIs, and the exponents of MCAIs with 2 ≤ n ≤ 8 are similar, with only slight variations for different charge states. The width of the arrival time and, hence, the corresponding kinetic energy of Ar+ also increases with increasing laser intensities, while the width of the arrival time of MCAIs remains constant throughout the range of measurements. These results call for more detailed theoretical investigations in this regime of laser-matter interactions.

Volume averaging effect in nonlinear processes of focused laser fields.

We report theoretical derivations and experimental results on the volume averaging effect of nonlinear processes in focused laser fields. This effect is considered detrimental in revealing the intensity dependence of a nonlinear process, caused by the intensity variation across the sampled volume of a focused laser. Following the treatment in the literature, we prove that if the signal dependence can be expressed as a simple power function of the laser intensity and if the detection region encompasses effectively the whole volume, volume average does not affect the final conclusion on the derived exponent. However, to reveal the detailed saturation effect of a multi-photon process, intensity selective scans involving spatial filters and displacement of the laser focus (z-scan) are required. Moreover, to fully capture the dependence of the signal on the variation of the laser intensity, the degree of spatial discrimination and the corresponding range of the z-scan need to be modeled carefully. Limitations in the dynamic range of the detector or the laser power, however, can thwart the desired scan range, resulting in erroneous fitting exponents. Using our nanosecond laser with a non-ideal Gaussian beam profile based on multiphoton ionization of argon atoms from a collimated molecular beam and from ambient argon gas, we report experimental measurements of the beam waist and Rayleigh range and compare the experimental intensity dependence of Ar+ with theoretical values. Agreements between theory and experiment are remarkable.

Bimodal velocity and size distributions of pulsed superfluid helium droplet beams.

We report detailed measurements of velocities and sizes of superfluid helium droplets produced from an Even-Lavie pulse valve at stagnation pressures of 20-60 atm and temperatures between 5.7 and 18.0 K. By doping neutral droplets with Rhodamine 6G cations produced from an electrospray ionization source and detecting the positively charged droplets at two different locations along the beam path, we determine the velocities of the different groups of droplets. By subjecting the doped droplet beam to a retardation field, size distributions can then be analyzed. We discover that at stagnation temperatures above 8.0 K, a single group of droplets is observed at both locations, but at 8.0 K and below, two different groups of droplets with different velocities are detectable. The slower group, considered from fragmentation of liquid helium, cannot be deterred by the retardation voltage at 9 kV, implying an exceedingly large size. The faster group, considered from condensation of gaseous helium, has a bimodal distribution when the stagnation temperatures are below 12.3 K at 20 and 40 atm, or 16.1 K at 60 atm. We also report similar size measurements using low energy electrons for impact ionization, and this latter method can be used for facile in situ characterization of pulsed droplet beams. The mechanism of the bimodal size distribution of the condensation group and the reason for the coexistence of both the condensation and fragmentation groups remain elusive.

Effect of Exercise Training on Some Anti-Inflammatory Adipokines, High Sensitivity C-Reactive Protein, and Clinical Outcomes in Sedentary Adults With Metabolic Syndrome.

OBJECTIVE: This study aimed to investigate the effects of aerobic interval training and resistance training on anti-inflammatory adipokines, high sensitivity C-reactive protein, and clinical outcomes in sedentary men with metabolic syndrome. METHODS: A total of 33 sedentary men with metabolic syndrome (age: 46.2 ± 4.6 years; body mass index: 35.4 ± 1.9 kg.m2) were randomly assigned to one of 3 groups: aerobic interval training (n = 12), resistance training (n = 10), or control (n = 11). Participants in the exercise groups completed a 12-week training program, 3 sessions per week, while those in the control group maintained their sedentary lifestyle. The levels of high sensitivity C-reactive protein (hs-CRP), omentin-1, adiponectin, lipid profiles, blood pressure, glucose metabolism, body composition, and peak oxygen uptake (VO2peak) were measured at baseline and after the intervention. RESULTS: Both aerobic interval training and resistance training significantly improved the levels of omentin-1 and adiponectin, as well as reduced inflammation, as indicated by a decrease in hs-CRP levels. Exercise training also led to significant improvements in lipid profiles, blood pressure, glucose metabolism, and body composition. Specifically, the aerobic interval training group had significantly greater increases in high-density lipoprotein cholesterol and VO2peak, as well as greater reductions in low-density lipoprotein cholesterol, triglycerides, and total cholesterol compared to the resistance training group. CONCLUSION: Exercise training, particularly aerobic interval training and resistance training, can be an effective non-pharmacological intervention for managing inflammation and improving cardiovascular health in metabolic syndrome patients.

A Decision-Making System for Low Carbon Manufacturing.

Based on the stochastic market demand of products, this paper studies the low-carbon manufacturing decisions making of manufacturing enterprises considering downward substitution and green technology input under the carbon cap-and-trade policy. The results show that the government's carbon trade policy will have a great impact on the production of manufacturing enterprises. Therefore, manufacturing enterprises must attach importance to the constraints of the government's carbon emission reduction policies. In terms of it, there are strategies for manufacturing enterprises such as adjusting the output, trading the carbon emission right, and so on. On this case, green technology input can increase the expected profit of manufacturing enterprises, especially in the case of downward substitution.

Production of Multiply Charged Argon Ions in Moderate Nanosecond Laser Fields: An Open Question or a Forgone Conclusion?

We reply to the Viewpoint by Vatsa and Mathur on our publication reporting the observation of multiply charged atomic ions from argon clusters doped with aromatic chromophores in a moderate nanosecond laser field. Vatsa and Mathur raised three concerns about the proposed explanation and offered additional ideas for the reported process. We agree with some of their concerns and welcome the addition of information, and we also clarify a few misunderstandings of our intention, perhaps caused by our implicit assumption of contextual relations. While the experimental results are indisputable, the interpretation is still a topic of debate, subject to further experimental investigations and theoretical modeling.

Coulomb Explosion in Nanosecond Laser Fields.

We report experimental observations of Coulomb explosion using a nanosecond laser at 532 nm with intensities less than 1012 W/cm2. We observe multiply charged atomic ions Arn+ (1 ≤ n ≤ 7) and Cn+ (1 ≤ n ≤ 4) from argon clusters doped with molecules containing aromatic chromophores. The yield of Arn+ depends on the size of the cluster, the number density, and the photostability of the dopant. We propose that resonant absorption of ArN+ achieves a high degree of ionization, and the highly positively charged cluster has the capability to strip electrons from the evaporating Ar+ on the surface of the cluster prior to Coulomb explosion, forming Arn+.

Electron Diffraction of Pyrene Nanoclusters Embedded in Superfluid Helium Droplets.

We report electron diffraction of pyrene nanoclusters embedded in superfluid helium droplets. Using a least-squares fitting procedure, we have been able to separate the contribution of helium from those of the pyrene nanoclusters and determine the most likely structures for dimers and trimers. We confirm that pyrene dimers form a parallel double-layer structure with an interlayer distance of 3.5 Šand suggest that pyrene trimers form a sandwich structure but that the molecular planes are not completely parallel. The relative contributions of the dimers and trimers are ∼6:1. This work is an extension of our effort of solving structures of biological molecules using serial single-molecule electron diffraction imaging. The success of electron diffraction from an all-light-atom sample embedded in helium droplets offers reassuring evidence of the feasibility of this approach.