Simultaneous dual-region two-photon imaging of biological dynamics spanning over 9 mm in vivo

Biodynamical processes,especially in system biology,that occur far apart in space may be highly correlated.To study such biodynamics,simultaneous imaging over a large span at high spatio-temporal resolutions is highly desired.For example,large-scale recording of neural network activities over various brain regions is indispensable in neuroscience.However,limited by the field-of-view(FoV)of conventional microscopes,simultaneous recording of laterally distant regions at high spatio-temporal resolutions is highly challenging.Here,we propose to extend the distance of simultaneous recording regions with a custom micro-mirror unit,taking advantage of the long working distance of the objective and spatio-temporal multiplexing.We demonstrate simultaneous dual-region two-photon imaging,spanning as large as 9 mm,which is 4 times larger than the nominal FoV of the objective.We verify the system performance in in vivo imaging of neural activities and vascular dilations,simultaneously,at two regions in mouse brains as well as in spinal cords,respectively.The adoption of our proposed scheme will promote the study of systematic biology,such as system neuroscience and system immunology.

丛枝菌根真菌促进外来植物豚草的生长

丛枝菌根真菌(AMF)可以通过其菌丝增加寄主植物对养分的吸收,从而促进植物生长。丛枝菌根真菌一直与大多数外来植物的成功入侵联系在一起。然而,有关丛枝菌根真菌如何影响植物入侵成功的机制仍然有待研究。豚草(Ambrosia artemisiifolia)是一种外来的菌根植物。通过长期田间实验,我们研究了种间竞争对豚草和狗尾草(Setaria viridis)根系丛枝菌根真菌多样性和组成的影响。此外,在温室实验中探究了摩西球囊霉(Funneliformis mosseae)对这两种植物生长的影响。研究结果表明,豚草入侵改变了本地植物狗尾草根系丛枝菌根真菌的多样性。另外,豚草根系中摩西球囊霉的相对多度显著高于狗尾草根系中。在田间和温室实验中均发现外来种豚草的丛枝菌根真菌侵染率高于本地种狗尾草。温室实验结果表明,丛枝菌根真菌通过影响豚草的光合能力以及磷和钾的吸收而促进豚草生长。这些研究结果揭示了丛枝菌根真菌和豚草成功入侵之间的重要关系。

Improved Kalman filter method considering multiple factors and its application in landslide prediction

Landslides,seriously threatening human lives and environmental safety,have become some of the most catastrophic natural disasters in hilly and mountainous areas worldwide.Hence,it is necessary to forecast landslide deformation for landslide risk reduction.This paper presents a method of predicting landslide displacement,i.e.,the improved multi-factor Kalman filter(KF)algorithm.The developed model has two advantages over the traditional KF approach.First,it considers multiple external environmental factors(e.g.,rainfall),which are the main triggering factors that may induce slope failure.Second,the model includes random disturbances of triggers.The proposed model was constructed using a time series which consists of over 16-month of data on landslide movement and precipitation collected from the Miaodian loess landslide monitoring system and nearby meteorological stations in Shaanxi province,China.Model validation was performed by predicting movements for periods of up to 7 months in the future.The performance of the developed model was compared with that of the improved single-factor KF,multi-factor KF,multi-factor radial basis function,and multi-factor support vector regression approaches.The results show that the improved multi-factor KF method outperforms the other models and that the predictive capability can be improved by considering random disturbances of triggers.

Enhanced collection of scattered photons in nonlinear fluorescence microscopy by extended epi-detection with a silicon photomultiplier array

To maximize signal collection in nonlinear optical microscopy,non-descanned epi-detection is generally adopted for in vivo imaging.However,because of severe scattering in biological samples,most of the emitted fluorescence photons go beyond the collection angles of objectives and thus cannot be detected.Here,we propose an extended detection scheme to enhance the collection of scattered photons in nonlinear fluorescence microscopy using a silicon photomultiplier array ahead of the front apertures of objectives.We perform numerical simulations to demonstrate the enhanced fluorescence collection via extended epi-detection in the multi-photon fluorescence imaging of human skin and mouse brain through craniotomy windows and intact skulls.For example,with red fluorescence emission at a depth of 600μm in human skin,the increased collection can be as much as about 150%with a 10×,0.6-NA objective.We show that extended epi-detection is a generally applicable,feasible technique for use in nonlinear fluorescence microscopy to enhance signal detection.

Upconversion-luminescent hydrogel optical probe for in situ dopamine monitoring

Dopamine(DA),as a neurotransmitter in human brain,plays a crucial role in reward motivation and motor control.An improper level of DA can be associated with neurological disorders such as schizophrenia and Parkinson’s disease.To quantify DA,optical DA sensors have emerged as an attractive platform due to their capability of high-precision and label-free measurement,and immunity to electromagnetic interference.However,the lack of selectivity,limited biocompatibility,and complex fabrication processes are challenges that hinder their clinical applications.Here,we report a soft and biocompatible luminescent hydrogel optical sensor capable of recognizing and quantifying DA with a simple and compact interrogation setup.The sensor is made of a hydrogel optical fiber(HOF)incorporated with upconversion nanoparticles(UCNPs).DA molecules are detected through the luminescence energy transfer(LET)between the UCNPs and the oxidation products of DA,while the light-guiding HOF enables both excitation and emission collection of the UCNPs.The hydrogel sensor provides an optical readout that shows a linear response up to 200μmol/L with a detection limit as low as 83.6 nmol/L.Our results show that the UCNP-based hydrogel sensor holds great promise of serving as a soft and biocompatible probe for monitoring DA in situ.

Improving signal-to-background ratio by orders of magnitude in high-speed volumetric imaging in vivo by robust Fourier light field microscopy

Fourier light field microscopy(FLFM)shows great potential in high-speed volumetric imaging of biodynamics.However,due to the inherent disadvantage of wide-field illumination,it suffers from intense background,arising from out of the depth-of-field signal and tissue scattered noise.The background will not only deteriorate the image contrast,making quantitative measurement difficult,but also introduce artifacts,especially in functional imaging of the neuronal network activity in vivo.Here,we propose the robust Fourier light field microscopy(RFLFM),which suppresses the background in FLFM by introducing structured illumination and computational reconstruction based on HiLo.The superior performance of RFLFM is verified by volumetric imaging of biological dynamics in larval zebrafish and mouse in vivo,at a volumetric imaging rate up to 33.3 Hz.The statistical results show that the fluorescence background can be significantly depressed,with the signal-to-background ratio improved by orders of magnitude and the whole image contrast improved by as much as~10.4 times.Moreover,we stress that,in functional imaging of neuronal network activity in turbid brain tissues,our system can avoid artifacts resulting from background fluctuations,while conventional light field microscopy fails.As a simple but powerful tool,we anticipate our technique to be widely adopted in robust,high-contrast,high-speed volumetric imaging.

High-axial-resolution optical stimulation of neurons in vivo via two-photon optogenetics with speckle-free beaded-ring patterns

Two-photon optogenetics has become an indispensable technology in neuroscience,due to its capability in precise and specific manipulation of neural activities.A scanless holographic approach is generally adopted to meet the requirement of stimulating neural ensembles simultaneously.However,the commonly used disk patterns fail in achieving single-neuron resolution,especially in axial dimension,and their inherent speckles decrease stimulation efficiency.Here,we propose a novel speckle-free,beaded-ring pattern for high-axial-resolution optical stimulation of neurons in vivo.Using a dye pool and a fluorescent thin film as samples,we verify that,compared to those with disk patterns,higher axial resolution and better localization ability can be achieved with beaded-ring patterns.Furthermore,we perform two-photon based all-optical physiology with neurons in mouse S1 cortex in vivo,and demonstrate that the axial resolution obtained by beaded-ring patterns can be improved by 24%when stimulating multiple neurons,compared to that of disk patterns.