Many important scientific questions in physics, chemistry and biology require effective methodologies to spectroscopically probe ultrafast intra- and inter-atomic/molecular dynamics. However, current methods that extend into the femtosecond regime are capable of only point measurements or single-snapshot visualizations and thus lack the capability to perform ultrafast spectroscopic videography of dynamic single events. Here we present a laser-probe-based method that enables two-dimensional videography at ultrafast timescales (femtosecond and shorter) of single, non-repetitive events. The method is based on superimposing a structural code onto the illumination to encrypt a single event, which is then deciphered in a post-processing step. This coding strategy enables laser probing with arbitrary wavelengths/bandwidths to collect signals with indiscriminate spectral information, thus allowing for ultrafast videography with full spectroscopic capability. To demonstrate the high temporal resolution of our method, we present videography of light propagation with record high 200 femtosecond temporal resolution. The method is widely applicable for studying a multitude of dynamical processes in physics, chemistry and biology over a wide range of time scales. Because the minimum frame separation (temporal resolution) is dictated by only the laser pulse duration, attosecond-laser technology may further increase video rates by several orders of magnitude.
Combustion intermediates in low-pressure premixed laminar
2-methylfuran (MF)/oxygen/argon flames with equivalence ratios of
0.8 and 1.5 were investigated using tunable synchrotron vacuum ultraviolet
photoionization and molecular beam mass spectrometry. MF is a promising
biofuel with great potential of being used in different fields, including
the auto industry. However, the combustion chemistry of MF is not
clear. Photoionization mass spectra of MF/oxygen/argon flames were
recorded as well as the photoionization efficiency curves (PIEs) of
the combustion intermediates. Ionization energies (IEs) were measured
from the PIEs. The combustion intermediates were identified by comparing
the measured IEs to those reported in the literature or calculated
with the method ab initio. Possible reaction pathways
of MF and its primary combustion derivatives were constructed on the
basis of the combustion intermediates identified. H abstraction and
the consecutive reaction products were identified, including furfural,
(Z)-1-oxo-1,3,4-pentatriene, 2-ethylfuran, 2-vinylfuran,
etc. 2-Oxo-2,3-dihydrofuran was also observed, which may originate
from the OH addition products on the furan ring. Furan was not observed
in the low-pressure MF flames. Substituted ketenes, (Z)-1-oxo-1,3,4-pentatriene and (E)-1-oxo-1,3-butadiene,
were both detected in the low-pressure MF flames.
Nerve injury is accompanied by a liberation of diverse nucleotides, some of which act as ‘find/eat-me’ signals in mediating neuron-glial interplay. Intercellular Ca2+ wave (ICW) communication is the main approach by which glial cells interact and coordinate with each other to execute immune defense. However, the detailed mechanisms on how these nucleotides participate in ICW communication remain largely unclear. In the present work, we employed a mechanical stimulus to an individual BV-2 microglia to simulate localized injury. Remarkable ICW propagation was observed no matter whether calcium was in the environment or not. Apyrase (ATP/ADP-hydrolyzing enzyme), suramin (broad-spectrum P2 receptor antagonist), 2-APB (IP3 receptor blocker) and thapsigargin (endoplasmic reticulum calcium pump inhibitor) potently inhibited these ICWs, respectively, indicating the dependence of nucleotide signals and P2Y receptors. Then, we detected the involvement of five naturally occurring nucleotides (ATP, ADP, UTP, UDP and UDP-glucose) by desensitizing receptors. Results showed that desensitization with ATP and ADP could block ICW propagation in a dose-dependent manner, whereas other nucleotides had little effect. Meanwhile, the expression of P2Y receptors in BV-2 microglia was identified and their contributions were analyzed, from which we suggested P2Y12/13 receptors activation mostly contributed to ICWs. Besides, we estimated that extracellular ATP and ADP concentration sensed by BV-2 microglia was about 0.3 μM during ICWs by analyzing calcium dynamic characteristics. Taken together, these results demonstrated that the nucleotides ATP and ADP were predominant signal transmitters in mechanical stimulation-induced ICW communication through acting on P2Y12/13 receptors in BV-2 microglia.
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