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Two sensory neurons usually display trial-by-trial spike-count correlations given the repeated representations of a stimulus. The effects of such response correlations on population-level sensory coding have been the focal contention in computational neuroscience over the past few years. In the meantime, multivariate pattern analysis (MVPA) has become the leading analysis approach in functional magnetic resonance imaging (fMRI), but the effects of response correlations among voxel populations remain underexplored. Here, instead of conventional MVPA analysis, we calculate linear Fisher information of population responses in human visual cortex (five males, one female) and hypothetically remove response correlations between voxels. We found that voxelwise response correlations generally enhance stimulus information, a result standing in stark contrast to the detrimental effects of response correlations reported in empirical neurophysiological studies. By voxel-encoding modeling, we further show that these two seemingly opposite effects actually can coexist within the primate visual system. Furthermore, we use principal component analysis to decompose stimulus information in population responses onto different principal dimensions in a high-dimensional representational space. Interestingly, response correlations simultaneously reduce and enhance information on higher- and lower-variance principal dimensions, respectively. The relative strength of the two antagonistic effects within the same computational framework produces the apparent discrepancy in the effects of response correlations in neuronal and voxel populations. Our results suggest that multivariate fMRI data contain rich statistical structures that are directly related to sensory information representation, and the general computational framework to analyze neuronal and voxel population responses can be applied in many types of neural measurements.SIGNIFICANCE STATEMENT Despite the vast research interest in the effect of spike-count noise correlations on population codes in neurophysiology, it remains unclear how the response correlations between voxels influence MVPA in human imaging. We used an information-theoretic approach and showed that unlike the detrimental effects of response correlations reported in neurophysiology, voxelwise response correlations generally improve sensory coding. We conducted a series of in-depth analyses and demonstrated that neuronal and voxel response correlations can coexist within the visual system and share some common computational mechanisms. These results shed new light on how the population codes of sensory information can be evaluated via different neural measurements.
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Neurofisiologia , Neurociências , Masculino , Animais , Humanos , Feminino , Imageamento por Ressonância Magnética/métodos , Neurônios/fisiologia , Neurônios AferentesRESUMO
Coherent anti-Stokes Raman scattering (CARS) microscopy offers label-free chemical contrasts based on molecular vibrations. Hyperspectral CARS (HS-CARS) microscopy enables comprehensive microscale chemical characterization of biological samples. Various HS-CARS methods have been developed with individual advantages and disadvantages. We present what we believe to be a new temporally optimized and spectrally shaped (TOSS) HS-CARS method to overcome the limitations of existing techniques by providing precise control of the spatial and temporal profiles of the excitation beams for efficient and accurate measurements. This method uniquely uses Fourier transform pulse shaping based on a two-dimensional spatial light modulator to control the phase and amplitude of the excitation beams. TOSS-HS-CARS achieves fast, stable, and flexible acquisition, minimizes photodamage, and is highly adaptable to a multimodal multiphoton imaging system.
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Hyperspectral coherent Raman scattering microscopy provides a significant improvement in acquisition time compared to spontaneous Raman scattering yet still suffers from the time required to sweep through individual wavenumbers. To address this, we present the use of a pulse shaper with a 2D spatial light modulator for phase- and amplitude-based shaping of the Stokes beam to create programmable spectrally tailored excitation envelopes. This enables collection of useful spectral information in a more rapid and efficient manner.
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The application of standing surface acoustic wave (SSAW) tweezers based on backpropagation superposition to achieve precise behavior manipulation of microscale cells and even nanoscale bacteria has been widely studied and industrialized. However, the structure requires multiple transducer components or full channel resonance. It is very challenging to design a simple structure for nano-control by complex acoustic field. In this study, a reflector-interdigital transducer (R-IDT) acoustofluidic device based on unilateral coherence enhancement is proposed to achieve SSAW definition features of periodic particle capture positions. The SAW device based on a unilateral transducer can not only generate leaky-SAW in water-filled microchannel, but also have a contribution of spherical waves in the vibration area of the substrate-liquid interface due to the Huygens-Fresnel diffractive principle. Both of them form a robust time-averaged spatial periodicity in the pressure potential gradient, accurately predicting the lateral spacing of these positions through acoustic patterning methods. Furthermore, a reflector based on Bragg-reflection is used to suppress backward transmitted SAW and enhance forward conducted SAW beams. By using a finite element model, R-IDT structure's amplitude enhances 60.78% compared to single IDT structure. The particle manipulation range of the diffractive acoustic field greatly improves, verified by experimental polystyrene microspheres. Besides, biocompatibility is conformed through red blood cells and Bacillus subtilis. We investigate the overall shift of periodic pressure field that can still occur when the phase changes. This work provides a simpler and low-cost solution for the application of acoustic tweezer in biological cell culture and filtering.
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Paclitaxel resistance is associated with a poor prognosis in non-small cell lung cancer (NSCLC) patients, and currently, there is no promising drug for paclitaxel resistance. In this study, we investigated the molecular mechanisms underlying the chemoresistance in human NSCLC-derived cell lines. We constructed paclitaxel-resistant NSCLC cell lines (A549/PR and H460/PR) by long-term exposure to paclitaxel. We found that triptolide, a diterpenoid epoxide isolated from the Chinese medicinal herb Tripterygium wilfordii Hook F, effectively enhanced the sensitivity of paclitaxel-resistant cells to paclitaxel by reducing ABCB1 expression in vivo and in vitro. Through high-throughput sequencing, we identified the SHH-initiated Hedgehog signaling pathway playing an important role in this process. We demonstrated that triptolide directly bound to HNF1A, one of the transcription factors of SHH, and inhibited HNF1A/SHH expression, ensuing in attenuation of Hedgehog signaling. In NSCLC tumor tissue microarrays and cancer network databases, we found a positive correlation between HNF1A and SHH expression. Our results illuminate a novel molecular mechanism through which triptolide targets and inhibits HNF1A, thereby impeding the activation of the Hedgehog signaling pathway and reducing the expression of ABCB1. This study suggests the potential clinical application of triptolide and provides promising prospects in targeting the HNF1A/SHH pathway as a therapeutic strategy for NSCLC patients with paclitaxel resistance. Schematic diagram showing that triptolide overcomes paclitaxel resistance by mediating inhibition of the HNF1A/SHH/ABCB1 axis.
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Carcinoma Pulmonar de Células não Pequenas , Diterpenos , Resistencia a Medicamentos Antineoplásicos , Compostos de Epóxi , Proteínas Hedgehog , Fator 1-alfa Nuclear de Hepatócito , Neoplasias Pulmonares , Paclitaxel , Fenantrenos , Compostos de Epóxi/farmacologia , Compostos de Epóxi/uso terapêutico , Humanos , Fenantrenos/farmacologia , Fenantrenos/uso terapêutico , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Carcinoma Pulmonar de Células não Pequenas/metabolismo , Carcinoma Pulmonar de Células não Pequenas/patologia , Diterpenos/farmacologia , Diterpenos/uso terapêutico , Paclitaxel/farmacologia , Paclitaxel/uso terapêutico , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patologia , Proteínas Hedgehog/metabolismo , Fator 1-alfa Nuclear de Hepatócito/metabolismo , Fator 1-alfa Nuclear de Hepatócito/genética , Animais , Linhagem Celular Tumoral , Transdução de Sinais/efeitos dos fármacos , Camundongos Nus , Subfamília B de Transportador de Cassetes de Ligação de ATP/metabolismo , Subfamília B de Transportador de Cassetes de Ligação de ATP/genética , Camundongos , Camundongos Endogâmicos BALB C , Células A549RESUMO
Objective: To explore the relationship between the expression of plectin and the migration of hepatocellular carcinoma (HCC) cells and to elucidate the molecular mechanisms by which plectin expression affects the migration of HCC cells. Methods: First of all, Western blot was performed to determine the expression of plectin in normal hepatocytes and HCC cells. Secondly, a plectin-downregulated HCC cell strain was established and the control group (shNC group) and shPLEC group were set up. Each group was divided into a vehicle control group (shNC+DMSO group or shPLEC+DMSO group) and a F-actin cytoskeleton polymerization inducer Jasplakinolide group (shNC+Jasp group or shPLEC+Jasp group). Western blot was performed to determine the expression of plectin and epithelial-mesenchymal transition (EMT)-related proteins, including N-cadherin, vimentin, and E-cadherin. HCC cell migration was evaluated by Transwell assay. KEGG (Kyoto Encyclopedia of Genes and Genomes) was used to analyze the signaling pathways related to plectin gene. The polymerization of F-actin was analyzed by immunofluorescence assay. Results: Compared with the normal hepatocytes, HCC cells showed high expression of plectin. Compared with those in the shNC group, the expression of plectin in the shPLEC group was decreased (P<0.05), the migration ability of HCC cells was weakened (P<0.05), and the EMT process was inhibited (with the expression of N-cadherin and vimentin being decreased and the expression of E-cadherin being increased) (P<0.05). KEGG analysis showed that the regulation of cytoskeletal F-actin was most closely associated with plectin and cytoskeletal F-actin depolymerized in the shPLEC group. After treatment with Jasplakinolide, an inducer of F-actin cytoskeleton polymerization, the migration ability of HCC cells in the shPLEC+Jasp group was enhanced compared with that of shPLEC+DMSO group (P<0.05) and the EMT process was restored (with the expression of N-cadherin and vimentin being increased and the expression of E-cadherin being decreased) (P<0.05). In addition, the polymerization of cytoskeletal F-actin in HCC cells was also restored. Conclusion: Plectin is highly expressed in HCC cells. Plectin promotes the migration and the EMT of HCC cells through inducing F-actin polymerization.
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Carcinoma Hepatocelular , Neoplasias Hepáticas , Plectina , Humanos , Citoesqueleto de Actina/metabolismo , Citoesqueleto de Actina/patologia , Actinas/metabolismo , Caderinas/metabolismo , Carcinoma Hepatocelular/metabolismo , Linhagem Celular Tumoral , Movimento Celular , Dimetil Sulfóxido , Transição Epitelial-Mesenquimal/genética , Regulação Neoplásica da Expressão Gênica , Neoplasias Hepáticas/metabolismo , Plectina/genética , Plectina/metabolismo , Polimerização , Vimentina/metabolismoRESUMO
A systematic study of the movement of PAHs (Polycyclic aromatic hydrocarbons) and their derivatives through air, soil, and water is key to understanding the exchange and transport mechanisms of these pollutants in the environment and for ultimately improving environmental quality. PAHs and their derivatives, such as nitrated PAHs (NPAHs), oxygenated PAHs (OPAHs), brominated PAHs (BrPAHs) and chlorinated PAHs (ClPAHs), were analyzed in air, bulk deposition, soil, and water samples collected from urban, rural, field, and background sites on the eastern coast of China. The goal was to investigate and discuss their spatiotemporal variations, exchange fluxes, and transport potential. The concentrations of PAHs and their derivatives in the air and bulk deposition displayed distinct seasonal patterns, with higher concentrations observed during the winter and spring and lower concentrations during the summer and autumn. NPAHs exhibited the opposite trend. Significant urban-rural gradients were observed for most of the PAHs and their derivatives. According to the air-soil fugacity calculations, 2-3 ring PAHs, BrPAHs, and ClPAHs were found to volatilize from the soil into the air, while 4-7 ring PAHs, OPAHs, and NPAHs deposited from the air into the soil. The air-water fugacity of the PAHs and their derivatives indicated that surface water was an important source for the ambient atmosphere in Qingdao. The characteristic travel distances (CTDs) and persistence (Pov) for atmospheric transport were much lower than that for the water samples, which may be due to the longer half-lives of PAHs and their derivatives in water. NPAHs and ClPAHs with long transport distances and strong persistence in water could lead to a significant impact on marine pollution.
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The relationships among the four major embryophyte lineages (mosses, liverworts, hornworts, vascular plants) and the timing of the origin of land plants are enigmatic problems in plant evolution. Here, we resolve the monophyly of bryophytes by improving taxon sampling of hornworts and eliminating the effect of synonymous substitutions. We then estimate the divergence time of crown embryophytes based on three fossil calibration strategies, and reveal that maximum calibration constraints have a major effect on estimating the time of origin of land plants. Moreover, comparison of priors and posteriors provides a guide for evaluating the optimal calibration strategy. By considering the reliability of fossil calibrations and the influences of molecular data, we estimate that land plants originated in the Precambrian (980-682 Ma), much older than widely recognized. Our study highlights the important contribution of molecular data when faced with contentious fossil evidence, and that fossil calibrations used in estimating the timescale of plant evolution require critical scrutiny.
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Anthocerotophyta/genética , Briófitas/genética , Fósseis , Genoma de Planta , FilogeniaRESUMO
Green plants (Viridiplantae) are ancient photosynthetic organisms that thrive both in aquatic and terrestrial ecosystems, greatly contributing to the changes in global climates and ecosystems. Significant progress has been made toward understanding the origin and evolution of green plants, and plant biologists have arrived at the consensus that green plants first originated in marine deep-water environments and later colonized fresh water and dry land. The origin of green plants, colonization of land by plants and rapid radiation of angiosperms are three key evolutionary events during the long history of green plants. However, the comprehensive understanding of evolutionary features and molecular innovations that enabled green plants to adapt to complex and changeable environments are still limited. Here, we review current knowledge of phylogenetic relationships and divergence times of green plants, and discuss key morphological innovations and distinct drivers in the evolution of green plants. Ultimately, we highlight fundamental questions to advance our understanding of the phenotypic novelty, environmental adaptation, and domestication of green plants.
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Ecossistema , Viridiplantae , Evolução Biológica , Evolução Molecular , Filogenia , Plantas/genéticaRESUMO
Fluorescence lifetime imaging microscopy (FLIM) characterizes samples by examining the temporal properties of fluorescence emission, providing useful contrast within samples based on the local physical and biochemical environment of fluorophores. Despite this, FLIM applications have been limited in scope by either poor accuracy or long acquisition times. Here, we present a method for computational single-photon counting of directly sampled time-domain FLIM data that is capable of accurate fluorescence lifetime and intensity measurements while acquiring over 160 Mega-counts-per-second with sub-nanosecond time resolution between consecutive photon counts. We demonstrate that our novel method of Single-photon PEak Event Detection (SPEED) is more accurate than direct pulse sampling and faster than established photon counting FLIM methods. We further show that SPEED can be implemented for imaging and quantifying samples that benefit from higher -throughput and -dynamic range imaging with real-time GPU-accelerated processing and use this capability to examine the NAD(P)H-related metabolic dynamics of apoptosis in human breast cancer cells. Computational methods for photon counting such as SPEED open up more opportunities for fast and accurate FLIM imaging and additionally provide a basis for future innovation into alternative FLIM techniques.
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Fluorescência , Microscopia de Fluorescência/métodos , Fótons , Algoritmos , Animais , Apoptose , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Feminino , Fluoresceína , Corantes Fluorescentes , Humanos , Processamento de Imagem Assistida por Computador/métodos , Microscopia de Fluorescência/instrumentação , Modelos Animais , NADP/metabolismo , Radiometria/instrumentação , Radiometria/métodos , Ratos , Rodaminas , Fatores de TempoRESUMO
Intraoperative imaging in surgical oncology can provide information about the tumor microenvironment as well as information about the tumor margin. Visualizing microstructural features and molecular and functional dynamics may provide important diagnostic and prognostic information, especially when obtained in real-time at the point-of-procedure. A majority of current intraoperative optical techniques are based on the use of the labels, such as fluorescent dyes. However, these exogenous agents disrupt the natural microenvironment, perturb biological processes, and alter the endogenous optical signatures that cells and the microenvironment can provide. Portable nonlinear imaging systems have enabled intraoperative imaging for real-time detection and diagnosis of tissue. We review the development of a label-free multimodal nonlinear optical imaging technique that was adapted into a portable imaging system for intraoperative optical assessment of resected human breast tissue. New developments have applied this technology to assessing needle-biopsy specimens. Needle-biopsy procedures most always precede surgical resection and serve as the first sampling of suspicious masses for diagnosis. We demonstrate the diagnostic feasibility of imaging core needle-biopsy specimens during veterinary cancer surgeries. This intraoperative label-free multimodal nonlinear optical imaging technique can potentially provide a powerful tool to assist in cancer diagnosis at the point-of-procedure.
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OBJECTIVE: To determine the diagnostic accuracy of optical coherence tomography (OCT) to assess surgical margins of canine soft tissue sarcoma (STS) and determine the influence of observer specialty and training. STUDY DESIGN: Blinded clinical prospective study. ANIMALS: Twenty-five dogs undergoing surgical excision of STS. METHODS: In vivo and ex vivo surgical margins were imaged with OCT after tumor resection. Representative images and videos were used to generate a training presentation and data sets. These were completed by 16 observers of four specialties (surgery, radiology, pathology, and OCT researchers). Images and videos from data sets were classified as cancerous or noncancerous. RESULTS: The overall sensitivity and specificity were 88.2% and 92.8%, respectively, for in vivo tissues and 82.5% and 93.3%, respectively, for ex vivo specimens. The overall accurate classification for all specimens was 91.4% in vivo and 89.5% ex vivo. There was no difference in accuracy of interpretation of OCT imaging by observers of different specialties or experience levels. CONCLUSION: Use of OCT to accurately assess surgical margins after STS excision was associated with a high sensitivity and specificity among various specialties. Personnel of all specialties and experience levels could effectively be trained to interpret OCT imaging. CLINICAL SIGNIFICANCE: Optical coherence tomography can be used by personnel of different specialty experience levels and from various specialties to accurately identify canine STS in vivo and ex vivo after a short training session. These encouraging results provide evidence to justify further research to assess the ability of OCT to provide real-time assessments of surgical margins and its applicability to other neoplasms.
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Doenças do Cão/cirurgia , Margens de Excisão , Sarcoma/veterinária , Tomografia de Coerência Óptica/veterinária , Animais , Cães , Feminino , Masculino , Sarcoma/cirurgia , Sensibilidade e Especificidade , Tomografia de Coerência Óptica/métodosRESUMO
Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO2 by NO2 is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH3 neutralization or under cloud conditions. Under polluted environments, this SO2 oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH3 and NO2 control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world.
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Poluentes Atmosféricos/análise , Material Particulado/análise , Sulfatos/efeitos adversos , Aerossóis/análise , Poluição do Ar/análise , China , Clima , Monitoramento Ambiental/métodos , Humanos , Londres , Nitratos , Dióxido de Nitrogênio/efeitos adversos , Dióxido de Nitrogênio/química , Óxidos de Nitrogênio/análise , Tamanho da Partícula , Material Particulado/efeitos adversos , Sulfatos/análise , Óxidos de Enxofre/análise , Tempo (Meteorologia)RESUMO
16 nitrated polycyclic aromatic hydrocarbons (NPAHs) and 5 oxygenated polycyclic aromatic hydrocarbons (OPAHs) in PM2.5 at two locations in Northern China were analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Sampling was conducted at an urban site in Shandong University in Jinan (SDU) and a suburban site in Qixingtai in Jinan (QXT) in March, June, September and December in 2016. Overall, the concentrations of NPAHs and OPAHs were higher at SDU (1.88 and 9.49â¯ng/m3, respectively) than QXT (1.57 and 6.90â¯ng/m3, respectively), and the NPAHs and OPAHs concentrations were significantly higher during the winter than the other seasons at both sites. The incremental lifetime cancer risk (ILCR) values were lower than 10-6 for all sites, seasons and age groups (ranging between 1.85E-08 and 2.56E-07), so there was no risk of carcinogenesis due to exposure to these pollutants. Total cancer risk at SDU was higher than QXT and NPAHs have the highest carcinogenic risk for adults aged from 30 to 70 years. The positive matrix factorization (PMF) results revealed that coal/biomass combustion, diesel vehicle emissions, gasoline vehicle emissions and secondary formation were the main sources of NPAHs and OPAHs at SDU and QXT. Coal/biomass combustion contributed more in spring, autumn and winter; diesel vehicle emission contributed the most in summer; secondary formation made greatest contributions in winter; the contributions of gasoline vehicle emission were similar in summer, autumn and winter. Diagnostic ratios clearly demonstrated that secondary formation is more active in winter than in other seasons, and the reactions of PAHs and OH radical were the dominant secondary formation pathway at both SDU and QXT. In addition, the potential source contribution function (PSCF) identified that the Beijing-Tianjin-Hebei region, Shandong province, Bohai Sea, Yellow Sea, Anhui province and Henan province were the main source regions of NPAHs and OPAHs in Jinan.
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Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Neoplasias/epidemiologia , Material Particulado/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Estações do Ano , Adulto , Idoso , China , Carvão Mineral/análise , Humanos , Pessoa de Meia-Idade , Nitratos/análise , Oxigênio/análise , Material Particulado/química , Hidrocarbonetos Policíclicos Aromáticos/química , Medição de Risco , População Suburbana , População Urbana , Emissões de Veículos/análiseRESUMO
Dispersive pulse-stretching at 2.0 µm has long been hindered by the high intrinsic optical loss from conventional dispersive media. Here a flexible pulse-stretching technique at 2.0 µm is demonstrated over a broad bandwidth with large-scale dispersion and low intrinsic optical loss. The technique employs the newly proposed pulse-stretching scheme, namely, free-space angular-chirp-enhanced delay. Both normal and anomalous temporal dispersion (up to ±500 ps/nm) with low intrinsic loss (<6 dB) over a spectral bandwidth of â¼84 nm at 2.0 µm is obtained with low nonlinear effects. Based on this method, an optical wavelength-swept source at 2.0 µm is realized and applied to spectrally encoded imaging at a line scan rate of â¼19 MHz, proving the potential of this pulse-stretching technique for continuous single-shot measurements at the 2.0 µm wavelength regime, particularly for optical microscopy and spectroscopy.
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To overcome the speed limitation of conventional optical tomography, a temporal imaging technique has been integrated with optical time-domain reflectometry to realize ultrafast temporally magnified (TM) tomography. In this Letter, the sensitivity of TM tomography has been further enhanced using optical parametric amplification and distributed Raman amplification, and this technique is named temporally encoded amplified and magnified (TEAM) tomography. As a result, a 78-dB sensitivity has been realized, comparable to ultrafast optical coherence tomography systems. In addition, an 86.7-µm axial resolution can be realized across a 67.5-mm imaging range. To demonstrate the significance of sensitivity improvement, tomographic imaging of a centimeter-thick phantom is provided at an A-scan rate of 44 MHz.
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Regional ozone (O3) pollution has drawn increasing attention in China over the recent decade, but the contributions from urban pollution and biogenic emissions have not been clearly elucidated. To better understand the formation of the regional O3 problem in the North China Plain (NCP), intensive field measurements of O3 and related parameters were conducted at a rural site downwind of Ji'nan, the capital city of Shandong province, in the summer of 2013. Markedly severe O3 pollution was recorded, with the O3 mixing ratios exceeding the Chinese national ambient air quality standard on 28â¯days (a frequency of 78%) and with a maximum hourly value of 198 ppbv. Extensive regional transport of well-processed urban plumes to the site was identified. An observation-constrained chemical box model was deployed to evaluate in situ photochemical O3 production on two episodes. The results show that the in situ formation accounted for approximately 46% of the observed O3 accumulation, while the remainder (~54%) was contributed by regional transport of the O3-laden urban plumes. The in situ ozone production was in a mixed controlled regime that reducing either NOx or VOCs would lead to a reduction of ozone formation. Biogenic VOCs played an important role in the local ozone formation. This study demonstrates the significant mixed effects of both anthropogenic pollution from urban zones and biogenic emission in rural areas on the regional O3 pollution in the NCP region, and may have general applicability in facilitating the understanding of the formation of secondary pollution over China.
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Poluentes Atmosféricos/análise , Monitoramento Ambiental , Ozônio/análise , Poluição do Ar/estatística & dados numéricos , China , Cidades , Compostos Orgânicos Voláteis/análiseRESUMO
We report a high-speed wavelength-swept source operating at 2.0 µm through advanced time-stretch technology. It sweeps over 30 nm at a speed of 3.3×109 nm/s and a repetition rate of â¼19 MHz. To the best of our knowledge, this is the first time that a megahertz-stable swept source has been implemented at such a long wavelength. A wide bandwidth is enabled by a simple mode-locked fiber laser that covers a wavelength range of â¼60 nm. The all-optical wavelength sweeping is realized by a chirped fiber Bragg grating (CFBG), which shows a superior temporal stability and power efficiency, compared with commonly used dispersive fibers, particularly in the 2.0 µm wavelength window. To showcase its specialties, here we employ it to perform high-speed spectrally-encoded microscopy (i.e., time-stretch imaging) through a scattering medium at a line-scan rate of up to â¼19 MHz. Better image quality is achieved, compared with a conventional imaging window at 1.0 µm. It is believed that the potential applications of this new high-speed swept source will benefit the transient diagnosis that requires deep penetration through a scattering medium.
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Oil extraction leads to environmental pollution from the oilfields and dweller activities, however, knowledge of the concentration distributions, migration, secondary formation and toxicity of nitrated/oxygenated polycyclic aromatic hydrocarbons (N/OPAHs) in oilfield regions is limited. In this research, atmospheric and soil samples in 7 different location types in an important oil industrial base in China were gathered. The ΣNPAHs and ΣOPAHs in the air ranged from 0.05 to 2.47 ng/m3 and 0.14-22.72 ng/m3, respectively, and in soil ranged from 0.22 to 17.81 ng/g and 9.69-66.86 ng/g, respectively. Both NPAHs and OPAHs in the atmosphere exhibited higher concentrations during winter. The atmospheric NPAH concentrations decreased exponentially with distance from urban area especially in the summer, revealing the impact of vehicles on the air in the Yellow River Delta area. High NPAH and OPAH concentrations were found only in soil near oil extraction facilities, indicating that the impact of oil extraction is limited to the soil near the extraction facilities. The air-soil exchanges of N/OPAHs were assessed through fugacity fraction analysis, and NPAHs were in the equilibrium-deposition state and OPAHs were in the net-deposition state in the winter. Higher incremental lifetime cancer risk (ILCR) occurred at the urban, industrial, and oilfield sites in the atmospheric samples, and the soil samples had the largest ILCR values in the oilfield sites. However, ILCR values for both air and soil did not exceed the threshold of 10-6.
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The applications of ultrafast optics to biomedical microscopy have expanded rapidly in recent years, including interferometric techniques like optical coherence tomography and microscopy (OCT/OCM). The advances of ultra-high resolution OCT and the inclusion of OCT/OCM in multimodal systems combined with multiphoton microscopy have marked a transition from using pseudo-continuous broadband sources, such as superluminescent diodes, to ultrafast supercontinuum optical sources. We report anomalies in the dispersion profiles of low-coherence ultrafast pulses through long and non-identical arms of a Michelson interferometer that are well beyond group delay or third-order dispersions. This chromatic anomaly worsens the observed axial resolution and causes fringe artifacts in the reconstructed tomograms in OCT/OCM using traditional algorithms. We present DISpersion COmpensation Techniques for Evident Chromatic Anomalies (DISCOTECA) as a universal solution to address the problem of chromatic dispersion mismatch in interferometry, especially with ultrafast sources. First, we demonstrate the origin of these artifacts through the self-phase modulation of ultrafast pulses due to focusing elements in the beam path. Next, we present three solution paradigms for DISCOTECA: optical, optoelectronic, and computational, along with quantitative comparisons to traditional methods to highlight the improvements to the dynamic range and axial profile. We explain the piecewise reconstruction of the phase mismatch between the arms of the spectral-domain interferometer using a modified short-term Fourier transform algorithm inspired by spectroscopic OCT. Finally, we present a decision-making guide for evaluating the utility of DISCOTECA in interferometry and for the artifact-free reconstruction of OCT images using an ultrafast supercontinuum source for biomedical applications.