Tracking of mercury ions in living cells with a fluorescent chemodosimeter under single- or two-photon excitation

Tracking of Hg²⁺ in solutions as well as in living cells was conducted with a fluorescent chemodosimeter by measuring the spectral shift of its fluorescence under single- or two-photon excitation. The spectral hypsochromic shifts of this chemodosimeter when reacting with Hg²⁺ were found to be about 50 nm in acetonitrile/water solutions and 32 nm in Euglena gracilis 277 living cells. This chemodosimeter shows high sensitivity and selectivity, and is not influenced by the pH values. It can signal Hg²⁺ in solutions down to the ppb range under either single-photon excitation (SPE) at 405 nm or two-photon excitation (TPE) at 800 nm. However, with low cellular chemodosimeter concentrations, the SPE spectra were disturbed by the auto-fluorescence from the native fluorophore in the cell, while the TPE spectra were still of high quality since the two-photon absorption cross section of this chemodosimeter is much larger than that of the native fluorophores in the cell.     

New Mn12 clusters with tunable oxidation states via the use of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine

Room-temperature reactions of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine with manganese(II) salts yield a novel family of Mn(12) clusters incorporating the same Mn(12)O(4) core and tunable oxidation states of Mn(III)(x)Mn(II)(12-x) (x = 8, 10, and 12). Magnetic susceptibility data indicate that the spin of the ground state increases as the number of Mn(III) ions is increased, leading to increases in the magnitude of the out-of-phase ac susceptibility signal as the number of Mn(III) ions is increased.     

弹性支撑双稳压电悬臂梁振动响应及能量采集研究

在分析了常规刚性支撑非线性能量采集系统的研究基础上,提出外部磁铁弹性支撑的结构设想,保证系统在低强度激励条件下也能处于双稳态振荡,提高机电能量转换效率.研究表明,对于强度变化的随机激励历程,弹性支撑非线性能量采集系统不需要实时调整磁铁间距,能够更好地迎合强度时刻变化的随机激励源,实现高效的机电能量转换.     

Growth and scintillation properties of doped ZnWO4 crystals

A series of ZnWO₄ crystals with different purities of WO₃ and ZnO were grown by conventional Czochralski method and compared with Fe:ZnWO₄, Nb:ZnWO₄, Ag:ZnWO₄ and Ce:ZnWO₄ crystals grown by the same technology. Scintillation experiments revealed that the light yield of undoped ZnWO₄ crystals varied with the purities of raw materials WO₃ and ZnO. Raising the concentration of iron ions in ZnWO₄ crystals resulted in reduction of the light yield from the lighter appearance. On the contrary, the light yield was enhanced by doping Ag₂O, Nb₂O₅ and CeO₂, equivalent to that observed in ZnWO₄ crystals after oxygen-rich annealing at high temperature. The mechanisms of coloration and decolorization in doped ZnWO₄ crystals were analyzed. And the relationship between enhanced scintillation properties and the color center complex of iron impurity and oxygen vacancy in the crystals was discussed.     

High-temporal-quality injector generated by optical parametric amplification with hollow-core-fiber compression

We demonstrate a 100 μJ, <10 fs, high-temporal-contrast injector. The experimental setup is based on an optical parametric amplification system followed by a standard hollow-core-fiber compressor and a frequency-doubling crystal. Pulses near 800 nm with FWHMs of about 160 nm are generated. More than 11 orders of magnitude of the contrast ratio, which is limited by the measurement device, are obtained over a large temporal range extending from <1 ps ahead of the main pulse. The broad spectral bandwidth and the high contrast of this device make it a good front-end injector for a few-cycle, high-power laser system.     

Maintaining maximum signal-to-noise ratio in uncooled vertical-cavity surface-emitting laser-based self-mixing sensors

We demonstrate a method for maintaining the maximum signal-to-noise ratio (SNR) of the signal obtained from the self-mixing sensor based on a vertical-cavity surface-emitting laser (VCSEL). It was found that the locus of the maximum SNR in the current-temperature space can be well approximated by a simple analytical model related to the temperature behavior of the VCSEL threshold current. The optimum sensor performance is achieved by tuning the laser current according to the proposed model, thus enabling the sensor to operate without temperature stabilization in a wide temperature range between -20 °C and +80 °C.     

Few cycle pulse compressor based on hollow-core fiber waveguide results in pulse tails

The hollow-core fiber structure influence of few-cycle pulse compressor on pulse contrast is investigated experimentally. It is found that a periodic structure of pulses at the tail of the main pulse extended hundreds of picoseconds away. It can be due to the fiber structure and could be eliminated by modifying the structure.     

Drug repositioning and pharmacophore identification in the discovery of hookworm MIF inhibitors

The screening of bioactive compound libraries can be an effective approach for repositioning FDA-approved drugs or discovering new pharmacophores. Hookworms are blood-feeding, intestinal nematode parasites that infect up to 600 million people worldwide. Vaccination with recombinant Ancylostoma ceylanicum macrophage migration inhibitory factor (rAceMIF) provided partial protection from disease, thus establishing a "proof-of-concept" for targeting AceMIF to prevent or treat infection. A high-throughput screen (HTS) against rAceMIF identified six AceMIF-specific inhibitors. A?nonsteroidal anti-inflammatory drug (NSAID), sodium meclofenamate, could be tested in an animal model to assess the therapeutic efficacy in treating hookworm disease. Furosemide, an FDA-approved diuretic, exhibited submicromolar inhibition of rAceMIF tautomerase activity. Structure-activity relationships of a pharmacophore based on furosemide included one analog that binds similarly to the active site, yet does not inhibit the Na-K-Cl symporter (NKCC1) responsible for diuretic activity.     

双稳调参高频共振机理

针对双稳系统的高频信号响应,探讨了双稳调参的高频共振机理.研究表明,二次采样频率变换并不改变双稳结构直接在原系统结构上在与高频映射对应的低频处实现共振,而双稳系统参数调节是调参改变双稳结构并直接在高频处实现共振.双稳系统参数调节之所以能够实现高频随机共振,是因为同时调节双稳系统两参数可使Kramers逃逸速率不存在极限值,突破了随机共振信号频率必须在小频率范围内的限制. 关键词： 双稳系统 高频共振 二次采样频率变换 系统参数调节