We demonstrate a versatile single‐laser platform for single‐beam dual‐color two‐photon spectroscopy that combines a short‐pulse laser source with a tunable broadband wavelength converter based on a ...highly nonlinear photonic‐crystal fiber (PCF). We show that the short‐pulse PCF output can be tailored, via dispersion and nonlinearity management, to deliver a broadband optical driver whose spectral structure is ideally suited for a single‐beam two‐photon absorption (2PA) spectroscopy of the next‐generation genetically encodable fluorescent‐protein (FP) sensors of pH and redox‐responsive contrast agents. As a promising spectroscopic resource for redox biology, the short‐pulse PCF output can be finely sculpted to alternately drive an FP system via a one of its two 2PA‐allowed quantum pathways, yielding a high‐contrast fluorescence readout for a highly sensitive detection of redox reactions and signaling, pH sensing, and oxidative‐stress diagnosis.
We demonstrate a versatile single‐laser platform for single‐beam dual‐color two‐photon spectroscopy that combines a short‐pulse laser source with a tunable broadband wavelength converter based on a highly nonlinear photonic‐crystal fiber. This approach suggests a promising spectroscopic resource for a highly sensitive detection of redox reactions and signaling, pH sensing, and oxidative‐stress diagnosis.
Fish as model objects have found wide applications in biology and fundamental medicine and allow studies of behavioral and physiological responses to various environmental factors. Representatives of ...the genus
are one of the most convenient objects for such studies. Male fish belonging to the family
are characterized by extremely diverse coloration, which constantly changes, depending on the age of the fish, environmental factors, and social hierarchical status. These fish species are characterized by a short life cycle, which allows changes in coloration, an indicator of the ontogenesis stage, to be estimated. Existing methods of fish color assessments do not allow the intensity of coloration of particular body zones to be clearly differentiated. In the present study, we suggest a method of two-factor assessment of specific fish body zones using modified methods of photofixation and image processing software. We describe the protocol of the method and the results of its application to different-aged groups of male
. The coloration of selected areas (i.e., red spot on the gill cover (RSGC), black border on the caudal fin (BBCF), and white border on the dorsal fin (WBDF)) differed significantly according to the size and age of the fish (
< 0.05). The data obtained suggest that
can be a model for studying aging by the intensity of body coloration in males.
We demonstrate single‐beam optogenetic multimodal nonlinear‐optical microscopy that combines third‐harmonic generation (THG) and three‐photon‐excited fluorescence (3PEF) – two nonlinear‐optical ...processes related to the third‐ and fifth‐order susceptibilities, χ(3) and χ(5). A carefully tailored unamplified short‐pulse output of mode‐locked solid‐state lasers is shown to provide an ample parameter space for the optimization of such a single‐beam multimodal microscopy, enabling subcellular‐resolution, cell‐specific imaging using genetically encoded fluorescent‐protein‐based reporters in a vast variety of biological systems and settings, ranging from HeLa to brain cells. Experiments on brain slices and cell cultures presented in this paper demonstrate the potential of short‐pulse 3PEF/THG microscopy for a subcellular‐resolution, high‐contrast imaging of HeLa‐line cancer‐cell derivatives, as well as mitochondrial and somatic intracellular structures within deep‐brain neurons and astrocytes. As a step beyond the state of the art in optical brain imaging, single‐beam subcellular‐resolution, cell‐specific optogenetic 3PEF/THG imaging of fundamental functional brain units is experimentally demonstrated. One fundamental question that this work brings up for the future nonlinear absorption and Raman/hyper‐Raman studies is whether the Herzberg–Teller corrections, needed for an accurate description of two‐photon absorption in fluorescent proteins (FPs), would be also sufficient for an adequate treatment of higher‐n n‐photon absorption in FP‐based systems or models that include other quantum pathways would be necessary for the analysis of FP agents for higher‐n nonlinear microscopy.
We demonstrate single‐beam optogenetic multimodal nonlinear‐optical microscopy that combines third‐harmonic generation and three‐photon‐excited fluorescence—two nonlinear‐optical processes related to the third‐ and fifth‐order susceptibilities, χ(3) and χ(5).
Abstract
Magma mixing is a widespread magmagenic process. However, its significance in the formation of ultrapotassic magmas has been largely overlooked so far as they are commonly thought to ...originate directly from the mantle and ascend rapidly through the crust. The Hezhong ultrapotassic lavas in Western Yunnan (SW China) are (basaltic) trachy-andesitic in composition. These rocks display porphyritic textures with olivine, clinopyroxene (Cpx), spinel, and phlogopite occurring as both phenocryst and glomerocryst. Disequilibrium textures and complex zonation of crystals are commonly observed. Specifically, based on the textural and compositional characteristics, olivines can be classified into three different populations: two populations are characterized by highly to moderately magnesian olivines with normal chemical core-rim zonation (Fo~94–86 to Fo~89–79 and Fo~91–89 to Fo~86–84, respectively). The third population lacks obvious crystal zonation, but individual crystals exhibit some compositional variety at lower Fo contents (Fo83–76). Similarly, four populations of Cpx and two populations of spinel phenocrysts are recognized in terms of texture and composition. Notably, Cpx with reverse zoning contains a ‘green-core’ surrounded by a colourless mantle and rim. Hence, based on the variations of mineral assemblage, types of inclusions, and chemical compositions, all phenocryst/glomerocryst minerals can be divided into three groups. Mineral Group I (MG I) consists of high Fo cores of olivine, cores of the zoned spinel, and phlogopite. MG II only includes the green cores of reversed zoned Cpx (green-core Cpx), and MG III is composed of micro phenocrysts without obvious zoning and rims of large phenocrysts. Comparing these mineral groups with relevant minerals occurring in typical temporally and spatially associated igneous rocks, we suggest that the MG I and II could have been derived from magmas with compositions resembling an olivine lamproite and a trachyte, respectively. The overall bulk-rock geochemical and isotopic features of Hezhong lavas also agree with a mixing process between these two endmembers. Hence, we infer that mixing between these two magmas played a key role in the petrogenesis of the ultrapotassic Hezhong lavas and that the MG III crystallized from the mixed magmas. Our study highlights the complex formation of ultrapotassic magmas inferring that caution must be taken when using bulk chemical magma compositions are to deduce source signatures.
Hydrogen peroxide (H2O2) has been identified recently as a meaningful signaling molecule. The ability to perform imaging of H2O2 in complex biological organisms with a high spatio-temporal resolution ...requires advancements in both biosensors and in vivo visualization methods. In this work, we investigated the potential of fluorescent protein HyPer7, a bright and sensitive indicator of hydrogen peroxide, for multiphoton visualization in cell cultures, acute brain slices and neocortical neurons of anesthetized mice. Employing an alternating interrogation of the reduced and oxidized forms of HyPer7 enables the recording of H2O2 dynamics at a rate of one frame per second. Taking advantage of two-photon ratiometric readout of HyPer7, we monitored the intracellular H2O2 concentration growth in hippocampal neurons under chemogenetics tools handling in acute brain slices. At the final step, we visualized the HyPer7-expressed neurons at depths up to 600 µm below the brain surface of the mouse under anesthesia by two- and three-photon excitation microscopy. Autofluorescence, light scattering and out-of-focus background signal reduce the depth limit for HyPer7-imaging by two-photon microscopy, however, these challenges may be overcome by means of three-photon excitation fluorescence by the pulses of the short-wavelength infrared region.
•The H2O2-indicator HyPer7 is bright and pH-stable under two-photon excitation.•Ratiometric two-photon readout allows H2O2-dynamics recording in acute brain slices.•Cell-resolved recording of oxidative stress in brain of alive mouse is feasible.
Centrality metrics play a crucial role in network analysis, while the choice of specific measures significantly influences the accuracy of conclusions as each measure represents a unique concept of ...node importance. Among over 400 proposed indices, selecting the most suitable ones for specific applications remains a challenge. Existing approaches -- model-based, data-driven, and axiomatic -- have limitations, requiring association with models, training datasets, or restrictive axioms for each specific application. To address this, we introduce the culling method, which relies on the expert concept of centrality behavior on simple graphs. The culling method involves forming a set of candidate measures, generating a list of as small graphs as possible needed to distinguish the measures from each other, constructing a decision-tree survey, and identifying the measure consistent with the expert's concept. We apply this approach to a diverse set of 40 centralities, including novel kernel-based indices, and combine it with the axiomatic approach. Remarkably, only 13 small 1-trees are sufficient to separate all 40 measures, even for pairs of closely related ones. By adopting simple ordinal axioms like Self-consistency or Bridge axiom, the set of measures can be drastically reduced making the culling survey short. Applying the culling method provides insightful findings on some centrality indices, such as PageRank, Bridging, and dissimilarity-based Eigencentrality measures, among others. The proposed approach offers a cost-effective solution in terms of labor and time, complementing existing methods for measure selection, and providing deeper insights into the underlying mechanisms of centrality measures.
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