Structural origin and laser performance of thulium-doped germanate glasses

The structural origin and laser performance of thulium-doped germanate glasses have been studied. The investigation includes two main sections. The first part discusses the Raman spectroscopic and thermal stability of the host glass structure. The low value of the largest phonon energy (850 cm(-1)) reduces the probability of nonradiative relaxation. The large emission cross section of the Tm(3+) : (3)F(4) level (8.69 × 10(-21) cm(2)), the high quantum efficiency of the (3)F(4) level (71%), and the low nonradiative relaxation rate of the (3)F(4) → (3)H(6) transition (0.09 ms(-1)) illustrate good optical properties of the germanate glass. In the second part, the room-temperature laser action from the thulium-doped germanate glass is demonstrated when pumped by a 790 nm laser diode. The maximum output power of 346 mW and slope efficiency of 25.6% are achieved.     

Intense 2.7 μm and broadband 2.0 μm emission from diode-pumped Er3+/Tm3+/Ho(3+)-doped fluorophosphate glass

This Letter reports intense emission at 2.7 μm and broadband emission at 2.0 μm from Er(3+)/Tm(3+)/Ho(3+)-doped fluorophosphate glass. The fluorescence characteristics and energy transfer upon excitation of a conventional 980 nm laser diode are investigated. Based on the fluorescence spectra and lifetime measurement, the effect of Tm(3+) and Ho(3+) ions on intense 2.7 μm emission in fluorophosphate glass is demonstrated. It is also found that the effective bandwidth of 2.0 μm emission due to Tm(3+) and Ho(3+) ions can reach as high as 196 nm. These results indicate that the advantageous spectroscopic characteristics of Er(3+)/Tm(3+)/Ho(3+) triply doped fluorophosphate glass together with the outstanding thermal properties may become an attractive host for the mid-IR solid state lasers.     

Enhanced emission of 2.7 μm pumped by laser diode from Er3+/Pr(3+)-codoped germanate glasses

A novel Er(3+)/Pr(3+) codoped germanate glass was fabricated and analyzed. Efficient emission at 2.7 μm from the glass was observed upon excitation of a conventional 980 nm laser diode. The 2.7 μm emission characteristics and energy transfer (ET) were investigated. Population inversions between ?I(13/2) and ?I(11/2) levels have been achieved, and an enhanced emission from 2550 to 2800 nm was obtained. Large ET efficiency of 95% indicates that the ET process from Er(3+) to Pr(3+) (?I(13/2), 3H?)→(?I(15/2), 3F?) is efficient and that Pr(3+) can enhance the emission of 2.7 μm by quenching the lower laser level of Er(3+) via ET.     

Characterization of the Triplet State of Tanshinone IIA and its Reactivity by Laser Flash Photolysis

Tanshinone IIA (Tan IIA) has the properties of cardiovascular protection, anti‐inflammation, antioxidation and anticancer. Its light‐induced instability has drawn our interests in its photochemistry. Therefore, laser flash photolysis herein was used to investigate the transient photochemistry of Tan IIA. Our results show that direct photoexcitation by 355 nm laser pulses or photosensitization by energy transfer can lead to the formation of the triplet state of Tan IIA (³Tan IIA*). The triplet absorption spectrum and molar absorption coefficient, and ISC quantum yield were determined. Self‐quenching of ³Tan IIA* by its ground state was identified as an autooxidation reaction. ³Tan IIA* was proved to react quickly with N, N‐dimethylaniline, tert‐butylhydroquinone and propyl gallate via electron transfer with the diffusion‐controlled rate constants. One of the products with maximum absorption around 390 nm was assigned to the radical anion of Tan IIA. Our results indicate that ³Tan IIA* is a reactive transient species and can be generated by photosensitization or direct photoexcitation. According to our results, the possible role of Tan IIA as a photosensitizer to induce potential phototoxicity via Type‐II pathway in the presence of O₂ can be predicted.     

纳米羟基磷灰石的制备及其在生物医学方面的应用

简要介绍了羟基磷灰石生物陶瓷的晶体结构和性质,综合论述了纳米羟基磷灰石的制备方法,同时,介绍了纳米羟基磷灰石在生物医学方面的主要应用。文中,还报道了笔者实验室最近取得的一些结果。     

Synthesis and electrochemical properties of nanostructured LiAl x Mn2 − x O4 − y Br y particles

Nanostructured LiAl _x Mn_2 − x O_4 − y Br _y particles were synthesized successfully by annealing the mixed precursors, which were prepared by room-temperature solid-state coordination method using lithium acetate, manganese acetate, lithium bromide, aluminum nitrate, citric acid, and polyethylene glycol 400 as starting materials. X-ray diffractometer patterns indicated that the particles of the as-synthesized samples are well-crystallized pure spinel phase. Transmission electron microscopy images showed that the LiAl _x Mn_2 − x O_4 − y Br _y samples consist of small-sized nanoparticles. The results of galvanostatic cycling tests revealed that the initial discharge capacity of LiAl_0.05Mn_1.95O_3.95Br_0.05 is 119 mAh g⁻¹; after the 100th cycle, its discharge capacity still remains at 92 mAh g⁻¹. The introduction of Al and Br in LiMn₂O₄ bring a synergetic effect and is quite effective in increasing the capacity and elevating cycling performance.     

Study on the interaction between tabersonine and human serum albumin by optical spectroscopy and molecular modeling methods

The mechanism of interaction between tabersonine (TAB) and human serum albumin (HSA) was investigated by the methods of fluorescence spectroscopy, UV–vis absorption spectroscopy and molecular modeling under simulative physiological conditions. Results obtained from analysis of fluorescence spectrum and fluorescence intensity indicated that TAB has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The binding site number n and apparent binding constant K_a, corresponding thermodynamic parameters ΔG, ΔH and ΔS at different temperatures were calculated. The distance r between donor (human serum albumin) and acceptor (tabersonine) was obtained according to the Förster theory of non-radiation energy transfer. The effect of common ions on binding constant was also investigated. The synchronous fluorescence and three-dimensional fluorescence spectra were used to investigate the structural change of HSA molecules with addition of TAB. Furthermore, the study of molecular modeling indicated that TAB could bind to the site I of HSA and hydrophobic interaction was the major acting force, which was in agreement with the binding mode study.     

Diffraction characteristics of chirped femtosecond laser pulse by rectangle reflection grating

The spectral and temporal intensity distribution expression for the chirped femtosecond laser pulse diffracted by a rectangle reflection grating is derived. The effects of the chirped coefficient on the spatiotemporal and spectral characteristics are theoretically investigated in detail, and a criterion for judging whether or not the diffraction pulse is just split into two independent pulses in the temporal domain is obtained. The results show that the envelope curve of spectral intensity on the diffraction axis is more blue-shift, and its full width at e^? 1 maximum is wider for bigger chirped coefficient. The principal maximum on the temporal axis can split into two independent principal maximums for enough height from the upper and the nether reflection surface of the grating. Each principal maximum splits into two smooth pulses, namely one principal pulse and one secondary pulse, and the secondary pulse gradually increases with the increasing of the chirped coefficient; the duration of two principal pulses increases with the increasing of the height of the upper and the nether reflection surface of the grating.     

Research progress on the cleaning and regeneration of PM2.5 filter media

Reusable PM2.5 filter media and their regeneration techniques have attracted widespread attention and shown significant prospect for application in air purifica...     

Polygonatum cyrtonema Hua Polysaccharides Protect BV2 Microglia Relief Oxidative Stress and Ferroptosis by Regulating NRF2/HO-1 Pathway

Neuronal-regulated cell death (RCD) due to the accumulation of ROS within the central nervous system (CNS) is one of the crucial causes of central system diseases. Caspase-dependent apoptosis is the only form of RCD. As research progressed, several nonapoptotic cell death pathway RCDs were identified. Ferroptosis is a nonapoptotic RCD characterized by lipid peroxidation and plasma membrane damage. Polygonatum cyrtonema Hua. Polysaccharides (PCP) are an effective antioxidant. Based on this, the protective effect and mechanism of PCP against H₂O₂-induced microglial injury were investigated. Furthermore, the protective mechanism of PCP against ferroptosis in microglia was explored. Our results indicated that PCP could reduce oxidative stress-induced ROS accumulation by activating the NRF2/HO-1 signaling pathway, thus attenuating RCD in microglia. Subsequent studies have revealed that PCP alleviates ferroptosis in microglia due to protein levels of ERASTIN/RSL3 inhibitor SLC7A11/GPX4 by activating the NRF2/HO-1 signaling pathway. Therefore, we hypothesized that PCP exerts antioxidative and anti-ferroptosis effects by activating the expression of the NRF2/HO-1 pathway. This facilitates new ideas for clinically effective prevention and treatment of diseases due to accumulated reactive oxygen species in the CNS. Simultaneously, PCP has the development potential as a new drug candidate for treating CNS diseases.