Influence of Qinghai-Xizang Plateau snow cover on interannual variability of Western North Pacific tropical cyclone tracks

Track density function(TDF)was computed for all Western North Pacific tropical cyclones(WNP TCs)tracks from 1950 to 2018,and the TDFs were further investigated using principal component analysis(PCA)to analyze their inter-annual spatial and temporal variability.Then,the relationships between each empirical orthogonal function(EOF)mode and the typhoon count,typhoon landfall count,track pattern,and the Qinghai-Xizang Plateau snow cover(QXPSC)were examined,and the possible physical mechanisms implied by the statistical relationship were explored.The results show the QXPSC significantly affected the surface-atmosphere heat exchange through snow cover(SC)level,then changed the East Asian summer monsoon regional circulation pattern,influenced the subtropical high-pressure system strength and location,and ultimately affected the WNP TCs track patterns and thus changed their landfall locations.

High power,widely tunable femtosecond MgO:PPLN optical parametric oscillator

We demonstrate a high power,widely tunable femtosecond MgO-doped periodically poled lithium niobate(MgO:PPLN)optical parametric oscillator(OPO)at 151 MHz,pumped by a Kerr-lens mode-locked Yb:KGW laser.With a maximum pump power of 7 W,the OPO is capable of delivering as high as 2.2 W of the signal centered around 1500 nm with tunable signal spectrum ranges of 1377 nm-1730 nm at an extraction efficiency of 31.4%,which exhibits a long-term passive power stability better than 0.71%rms over 4 h.The maximum idler bandwidths of 185 nm at 3613 nm are obtained across the idler tuning ranges of 2539 nm-4191 nm.By compensating intracavity dispersion,the signal has the shortest pulse duration of 170 fs at 1428 nm.

Milli-Joule pulses post-compressed from 14 ps to 475 fs in bulk-material multi-pass cell based on cylindrical vector beam

A cylindrical vector beam is utilized to enhance the energy scale of the pulse post-compressed in a bulk-material Herriott multi-pass cell(MPC).The method proposed here enables,for the first time to the best of our knowledge,pulse compression from 14 ps down to 475 fs with throughput energy beyond 1 mJ,corresponding to a compression ratio of 30,which is the highest pulse energy and compression ratio in single-stage bulk-material MPCs.Furthermore,we demonstrate the characteristic of the vector polarization beam is preserved in the MPC.

中强线性啁啾脉冲激发的共振调制频域双光子吸收过程研究

本文基于二阶微扰理论研究频域中强线性啁啾飞秒脉冲作用下双光子过程。详细分析了频域中啁啾因子、中心波长等参数对双光子跃迁的影响。阐明了弱场产生的双光子跃迁在频域的动态演化过程。进一步利用拓展的四阶微扰理论研究了中强场条件下双光子吸收过程的物理机理。相比复杂而昂贵的脉冲整形而言,本文提出的研究方案具有简单、经济且易操作的优势。

Reversible and irreversible heat generation of NCA/Si–C pouch cell during electrochemical energy-storage process

To meet the requirements of electronic vehicles(EVs) and hybrid electric vehicles(HEVs),the high energy density Li Ni_(0.8) Co_(0.15) Al_(0.05) O_2(NCA) cathode and Si–C anode have attracted more attention.Here we report the thermal behaviors of NCA/Si–C pouch cell during the charge/discharge processes at different current densities.The total heat generations are derived from the surface temperature change during electrochemical Li+insertion/extraction in adiabatic surrounding.The reversible heat is determined by the entropic coefficients,which are related with open-circuit voltage at different temperatures; while the irreversible heat is determined by the internal resistance,which can be obtained via V–I characteristic,electrochemical impedance spectroscopy and hybrid pulse power characterization(HPPC).During the electrochemical process,the reversible heat contributes less than 10% to total heat generation; and the heat generated in charge process is less than that in discharge process.The results of thermal behaviors analyses are conducive to understanding the safety management and paving the way for building a reliable thermal model of high energy density lithium ion battery.

Reversible Al^(3+) storage mechanism in anatase TiO_(2) cathode material for ionic liquid electrolyte-based aluminum-ion batteries

Rechargeable aluminum ion battery(AIB) with high theoretical specific capacity, abundant elements and low cost engages considerable attention as a promising next generation energy storage and conversion system. Nevertheless, to date, one of the major barriers to pursuit better AIB is the limited applicable cathode materials with the ability to store aluminum highly reversibly. Herein, a highly reversible AIB is proposed using mesoporous TiO2 microparticles(M-TiO2) as the cathode material. The improved performance of Ti O2/Al battery is ascribed to the high ionic conductivity and material stability, which is caused by the stable architecture with a mesoporous microstructure and no random aggregation of secondary particles. In addition, we conducted detailed characterization to gain deeper understanding of the Al^(3+) storage mechanism in anatase Ti O2 for AIB. Our findings demonstrate clearly that Al^(3+)can be reversibly stored in anatase TiO2 by intercalation reactions based on ionic liquid electrolyte. Especially, DFT calculations were used to investigate the accurate insertion sites of aluminum ions in M-Ti O2 and the volume changes of M-TiO2 cells during discharging. As for the controversial side reactions in AIBs, in this work, by normalized calculation, we confirm that M-Ti O2 alone participate in the redox reaction. Moreover, cyclic voltammetry(CV) test was performed to investigate the pseudocapacitive behavior.

Femtosecond laser user facility for application research on ultrafast science

The advent of chirped-pulse amplification （CPA） has greatly advanced the field of ultrafast and ultra-intense laser technology. CPA has become an indispensable platform for multidisciplinary research, such as physics, chemistry, life sciences, and precision metrology. The femtosecond laser facility at the Synergic Extreme Condition User Facility （SECUF） is a comprehensive experimental platform with an advanced femtosecond laser source for ultrafast scientific research. It will provide an ultrafast scientific research system having a few-cycle pulse duration, wide spectral range, high energy, and high repetition rate for multipurpose applications.

A 515-nm laser-pumped idler-resonant femtosecond BiB_(3)O_(6) optical parametric oscillator

We report on an idler-resonant femtosecond optical parametrical oscillator(OPO)based on BiB_(3)O_(6)(BiBO)crystal,synchronously pumped by a frequency-doubled,mode-locked Yb:KGW laser at 515 nm.The idler wavelengths of OPO can be tuned from 1100 nm to 1540 nm.At a repetition rate of 75.5 MHz,the OPO generates as much as 400 mW of idler power with 3.1 W of pump power,the corresponding pulse duration is 80 fs,which is 1.04 times of Fourier transform-limited(FTL)pulse duration at 1305 nm.In addition,the OPO exhibits excellent beam quality with M^(2)<1.8 at 1150 nm.To the best of our knowledge,this is the first idler-resonant femtosecond OPO pumped by 515 nm.

Direct utilization of crude and waste H_(2) via CO-tolerant hydrogenation

H_(2) tends to be a crucial medium in the foreseeable future as it is not only a green and renewable energy source for vehicles but also a fundamental feedstock for the chemical industry.For instance,selective hydrogenation,one of the catalytic processes used to produce fine compounds,is of vital importance because it enables the selective and efficient conversionof a variety of functional groups under mild reaction conditions.Catalytic hydrogenation of liquid organic hydrogen carriers(LOHCs;eg,methylbenzene)is a safe and economic approach for H_(2) storage.

Interleukin 17-Producing γδ T Cells Increased in Patients with Active Pulmonary Tuberculosis

Although it has been known that γδ T cells may play an important role in the immune response to infection of Mycobacterium tuberculosis （M. tb）, the mechanisms by which the γδ T cells participate in the innate and/or acquired immunity to tuberculosis （TB） have not been full elucidated. In the present study, 27 patients with active pulmonary TB and 16 healthy donors （HD） were performed. We found that proportion of IL-17-producing cells among lymphocyte was similar between TB patients and HD, whereas the proportions of γδ T cells in IL-17-producing cells （59.2%） and IL-17-producing cells in γδ T cells （19.4%） in peripheral blood were markedly increased in TB patients when compared to those in HD （43.9% and 7.7%, respectively）. In addition, the proportions of IFN-T-producing γδ T cells in TB patients were obviously lower than that in HD. Upon re-stimulated with M. tb heat-treated antigen （M. tb-HAg） in vitro, fewer IL-17-producing γδ T cells were generated from HD and TB patients, whereas IFN-T-producing γδ T cells were increased in TB patients compared to that in HD. Our findings in TB patients and healthy human were consistent with other murine investigation that the IL-17- producing γδ T cells were main source of IL-17 in mouse model of BCG infection, suggesting that γδ T cells might be involved in the formation of tubercular granuloma in pulmonary TB patients, but need further identification.

Diode-pumped 10 W femtosecond Yb:CALGO laser with high beam quality

We demonstrate a diode-pumped femtosecond Yb:CaGdAlO_(4)(Yb:CALGO)laser with a semiconductor saturable absorber mirror(SESAM)for stable mode-locking operation.A perfect beam profile is measured under 10 W output power with M_(x)^(2)=1.017 and M_(y)^(2)=1.016 in the horizontal and vertical directions,respectively.At the repetition rate of 71.66 MHz,the optical pulse duration is 247 fs and the pulse energy is 140 nJ at the central wavelength of 1041 nm,corresponding to a peak power of 0.56 MW.In addition,we also generate continuous wave(CW)power of more than 15 W with TEM00 mode,corresponding to an optical-to-optical efficiency of 44.1%.

Harmonically pump a femtosecond optical parametric oscillator to 1.13 GHz by a femtosecond 515 nm laser

We demonstrate a harmonically pumped femtosecond optical parametric oscillator(OPO)laser using a frequency-doubled mode-locked Yb:KGW laser at a repetition rate of 75.5 MHz as the pump laser.Based on a bismuth borate nonlinear crystal,repetition rates up to 1.13 GHz are realized,which is 15 times that of the pump laser.The signal wavelength is tunable from 700 nm to 887 nm.The maximum power of the signal is 207 m W at the central wavelength of 750 nm and the shortest pulse duration is 117 fs at 780 nm.The beam quality(M^2 factor)in the horizontal and vertical directions of the output beam are 1.077 and 1.141,respectively.

Sub-40-fs high-power Yb:CALYO laser pumped by single-mode fiber laser

We report on the study of single-mode fiber-laser-pumped mode-locked Yb:CALYO lasers via using a passive saturable absorber and Kerr-lens mode-locking technique,respectively.Up to 3.1-W average power with 103-fs pulse duration is obtained from the passive mode-locking,and down to 36-fs pulse duration with more than 2-W average power is achieved by the pure Kerr-lens mode-locking,which is to the best of our knowledge,the highest average power from a reported sub-40-fs Yb-based solid-state oscillator.

Diode-pumped 13 W Yb:KGW femtosecond laser

We report on a high-power diode-pumped Yb∶KG(WO_(4))_(2)(Yb:KGW) mode-locked laser with a semiconductor saturable absorber mirror(SESAM). For 32.7 W of incident pump power, we generate 261 fs pulses with the maximum average output power of up to 13.0 W and spectrum centered around 1039 nm at 68.4 MHz, corresponding to 190 n J of single pulse energy and0.72 MW of peak power. The optical-to-optical conversion efficiency is 39.8%, and the slope efficiency is 64.4%. The Yb:KGW laser exhibits a power stability better than 0.543% of the root-mean-square in 2 h.

Protective effect of tanshinone Ⅱ A on signal transduction system protein kinase B in rats with myocardial hypertrophy

The effects of tanshinone II A on cell signal transduction system protein kinase B in rats with myocardial hypertrophy induced by the abdominal aorta partial coarctation were investigated.Rat models of myocardial hypertrophy were established by using abdom-inal aorta partial coarctation method.Forty-eight rats were randomly divided into sham group(S group),model group(M group),valsartan treatment group(X group),low-dose tanshinone treatment group(LD group),medium-dose tanshinone treatment group(MD group),and high-dose tanshinone treatment group(HD group)(n=8 in each group).Left ventricular mass index(LVMI),left ventri-cular posterior wall(LVPW),and septal thickness(IVS)were detected by high frequency ultrasonography.Myocardialfiber diameter(MFD)was examined by Hematoxylin-Eosin(HE)staining,and the contents of phosphorylated protein kinase B(p-Akt)and p-Gsk3βin myocardium were assayed by Western blot.The results showed that compared with S group,the values of LVMI,LVPW,IVS and MFD were increased in other groups(P<0.05),and the contents of p-Akt,and p-Gsk3βwere also increased in other groups.As compared with MD group,the values of LVMI,LVPW,IVS and MFD were decreased in all treatment groups(P<0.05),and the contents of p-Akt,and p-Gsk3βwere also decreased in all treatment groups.However,there were no significant differences among LD,MD,and HD groups(P>0.05),and there were no significant differences between X group and tanshinone treatment groups(P>0.05).It was suggested that tanshinone II A could prevent myocardial hypertrophy by its action on the Akt signaling pathway.

Generation of 601 fs pulse from an 8 kHz Nd:YVO_(4) picosecond laser by multi-pass-cell spectral broadening

We demonstrate nonlinear pulse compression of an 8 k Hz Nd:YVO4 picosecond laser using the multi-pass-cell(MPC) technique with fused silica as the nonlinear medium. The pulse duration is compressed from 12.5 ps to 601 fs, corresponding to a pulse shortening factor of 20.8. The output pulse energy is 154 μJ with an efficiency of 74.5%. To the best of our knowledge,this is the highest pulse compression ratio achieved in a single-stage MPC with bulk material as the nonlinear medium. The laser power stability and the beam quality(M2) before and after the MPC are also experimentally studied. Both the laser power stability and the beam quality are barely deteriorated by the MPC device.