It is of great significance in clinical diagnosis and treatment evaluation to accurately identify the lesion tissue and further extract its characteristics and depth location. In this study, we construct tissue phanto...It is of great significance in clinical diagnosis and treatment evaluation to accurately identify the lesion tissue and further extract its characteristics and depth location. In this study, we construct tissue phantoms for three lesion types: fibrosis (FT), organelle proliferation (OPT), and pigmentation (PT). These phantoms allow for the quantitative regulation of mimicked disease depth. The experimental results show that the parameter Kc, combined with MMT parameters, can effectively distinguish the presence of lesions and their abnormal types. Further, the study extracts depth-sensitive polarization feature parameters (DSPFPs) for specific lesion types. Through experiments of tissue phantoms with various depth settings, the established machine learning regression models based on DSPFPs demonstrate their depth retrieval capabilities.展开更多
Non-hydrostatic stress plays a significant role in shaping the properties of materials under compression.High-pressure effects such as yielding deformation,phase transitions,and volume contraction can alter the pressu...Non-hydrostatic stress plays a significant role in shaping the properties of materials under compression.High-pressure effects such as yielding deformation,phase transitions,and volume contraction can alter the pressure distribution within the pressure chamber.However,due to the inherent size limitation of the diamond anvil cell(DAC),in situ high-pressure studies usually assume a hydrostatic environment,equaling the pressure of samples to a pressure calibrator inside the chamber.Accurately imaging pressure distribution within the DAC chamber remains challenging,particularly as the material undergoes phase transitions.Here,we present a method for mapping pressure distribution with high spatial resolution using wide-field optically detected magnetic resonance(ODMR)of nanodiamonds.The pressure gradients during the highpressure transition of zinc oxide(ZnO)were compared using both the multiple rubies technique and wide-field ODMR.The latter technique demonstrated superior spatial resolution,easier operation,and more detailed information.These results highlight the potential of wide-field ODMR as a powerful tool for precise pressure sensing,particularly in studies involving non-hydrostatic pressure conditions.展开更多
Optoacoustic tomography （PAT） is a two-dimensional medical imaging method that has the advantage of optical contrast and resolution of ultrasonic waves. The detection systems with a high sensitivity can be used for ...Optoacoustic tomography （PAT） is a two-dimensional medical imaging method that has the advantage of optical contrast and resolution of ultrasonic waves. The detection systems with a high sensitivity can be used for detecting small tumors, located deeply in human tissues, such as the breast. In this study, the sensitivity of existing ultrasonic detection systems has been compared experimentally with that by using thermoelastic waves as a broadband ultrasonic source. For the comparison, an optical stress transducer （OST）, a polyvinylidene difluoride （PVDF） sheet and a calibrated PVDF needle hydrophone were used. To ensure all of the detection systems interrogated by the same ultrasonic field, a small optical instrument that fixed the generating laser head was constructed. The sensitivity was evaluated by measuring signalto-noise ratios （SNRs） and noise equivalent pressures （NEPs）. The PVDF system, with a 4-kPa NEP has a 22 dB better performance than the OST. The OST showed nearly the same sensitivity as the hydrophone for detecting ultrasound waves at a 1-cm distance in water. PVDF detection system provides a useful tool for imaging of soft tissues because of its high sensitivity and broad detection range.展开更多
Nonlinear optical imaging is a versatile tool that has been proven to be exceptionally useful in various research fields.However,due to the use of photomultiplier tubes(PMTs),the wide application of nonlinear optical ...Nonlinear optical imaging is a versatile tool that has been proven to be exceptionally useful in various research fields.However,due to the use of photomultiplier tubes(PMTs),the wide application of nonlinear optical imaging is limited by the incapability of imaging under am-bient light.In this paper,we propose and demonstrate a new optical imaging detection method based on optical parametric amplification(OPA).As a nonlinear optical process,OPA in-trinsically rejects ambient light photons by coherence gating.Periodical poled lithium niobate(PPLN)crystals are used in this study as the media for OPA.Compared to bulk nonlinear optical crystals,PPLN crystals support the generation of OPA signal with lower pump power.Therefore,this characteristic of PPLN crystals is particularly beneficial when using high-repetition-rate lasers,which facilitate high-speed optical signal detection,such as in spec-troscopy and imaging.A PPLN-based OPA system was built to amplify the emitted imaging signal from second harmonic generation(SHG)and coherent anti-Stokes Raman scattering(CARS)microscopy imaging,and the amplified optical signal was strong enough to be detected by a biased photodiode under ordinary room light conditions.With OPA detection,ambient-light-on SHG and CARS imaging becomes possible,and achieves a similar result as PMT detection under strictly dark environments.These results demonstrate that OPA can be used as a substitute for PMTs in nonlinear optical imaging to adapt it to various applications with complex.light ing conditions.展开更多
History, present situation and importancy of the laser-generated ultrasonic technique are presented. Basic principles and some experimental results of laser ultrasonic generation and optical detection and processing a...History, present situation and importancy of the laser-generated ultrasonic technique are presented. Basic principles and some experimental results of laser ultrasonic generation and optical detection and processing are discussed. Several problems about applying this technique to NDT are also discussed in this paper.展开更多
A distributed optical fiber disturbance detection system consisted of a Sagnac interferometer and a Mach-Zehnder interferometer is demonstrated. Two interferometers outputs are connected to an electric band-pass filte...A distributed optical fiber disturbance detection system consisted of a Sagnac interferometer and a Mach-Zehnder interferometer is demonstrated. Two interferometers outputs are connected to an electric band-pass filter via a detector respectively. The central frequencies of the two filters are selected adaptively according to the disturbance frequency. The disturbance frequency is obtained by either frequency spectrum of the two interferometers outputs. An alarm is given out only when the Sagnac interferometer output is changed. A disturbance position is determined by calculating a time difference with a cross-correlation method between the filter output connected to the Sagnac interferometer and derivative of the filter output connected to the Mach-Zehnder interferometer. The frequency spectrum, derivative and cross-correlation are obtained by a signal processing system. Theory analysis and simulation results are presented. They show that the system structure and location method are effective, accurate, and immune to environmental variations.展开更多
In this paper, we have evaluated a bidirectional wavelength division multiplexing passive optical network(WDM-PON) employing intensity modulated/direct detection optical orthogonal frequency division multiplexing(IM/D...In this paper, we have evaluated a bidirectional wavelength division multiplexing passive optical network(WDM-PON) employing intensity modulated/direct detection optical orthogonal frequency division multiplexing(IM/DD-OFDM). The proposed system employs 100 Gbit/s 16 quadrature amplitude modulation(16-QAM) downstream and 5 Gbit/s on-off keying(OOK) upstream wavelengths, respectively. The proposed system is considered low-cost as non-coherent IM/DD OFDM technology and a simple reflective semiconductor optical amplifier(RSOA) colorless transmitter are employed and no dispersion compensating fiber(DCF) is needed. Based on the bit error rate(BER) results of WDM signals, the proposed WDM-PON system can achieve up to 1.6 Tbit/s(100 Gbit/s/λ × 16 wavelengths) downstream transmission over a 30 km single mode fiber(SMF).展开更多
Singlet oxygen(^(1)O_(2))is the main cytotoxic substance in Type II photodynamic therapy(PDT).The luminescence of ^(1)O_(2) at 1270nm is extremely weak with a low quantum yield,making the direct detection of'O2 at...Singlet oxygen(^(1)O_(2))is the main cytotoxic substance in Type II photodynamic therapy(PDT).The luminescence of ^(1)O_(2) at 1270nm is extremely weak with a low quantum yield,making the direct detection of'O2 at 1270 nm very challenging.In this study,a set of highly sensitive optical fiber detection system is built up to detect the luminescence of photosensitized ^(1)O_(2) We use this system to test the luminescence characteristics of ^(1)O_(2) in pig skin tissue ex vrivo and mouse auricle skin in vivo.The experimental results show that the designed system can quantitatively detect photosensitized ^(1)O_(2) luminescence.The ^(1)O_(2) luminescence signal at 1270 nm is successfully detected in pig skin exr vivo.Compared with RB in an aqueous solution,the lifetime of ^(1)O_(2) increases to 17.4±12pus in pig skin tissue ex vivo.Experiments on living mice suggest that an enhancement of ^(1)O_(2) intensity with the increase of the TMPyP concentration.When the dose is 25 mg/kg,the vasoconstriction can reach more than 80%。The results of this study hold the potential application for clinical PDT dose monitoring using an optical fiber detection system.展开更多
Objective:We conducted a comprehensive physicochemical analysis of one-dimensional ZnO nanowires(1DZnO),incorporating anti-CYFRA 21-1 immobilization to promote fast optical biomarker detection up to 10 ng ml−1.Impact ...Objective:We conducted a comprehensive physicochemical analysis of one-dimensional ZnO nanowires(1DZnO),incorporating anti-CYFRA 21-1 immobilization to promote fast optical biomarker detection up to 10 ng ml−1.Impact Statement:This study highlights the effectiveness of proof-of-concept 1DZnO nanoplatforms for rapid cancer biomarker detection by examining the nanoscale integration of 1DZnO with these bioreceptors to deliver reliable photoluminescent output signals.Introduction:The urgent need for swift and accurate prognoses in healthcare settings drives the rise of sensitive biosensing nanoplatforms for cancer detection,which has benefited from biomarker identification.CYFRA 21-1 is a reliable target for the early prediction of cancer formation that can be perceptible in blood,saliva,and serum.However,1DZnO nanostructures have been barely applied for CYFRA 21-1 detection.Methods:We assessed the nanoscale interaction between 1DZnO and anti-CYFRA 21-1 antibodies to develop rapid CYFRA 21-1 detection in two distinct matrices:PhosphateBuffered Saline(PBS)buffer and artificial saliva.The chemical modifications were tracked utilizing Fourier transform infrared spectroscopy,while transmission electron microscopy and energy dispersive spectroscopy confirmed antigen-antibody interplay over nanostructures.Results:Our results show high antibody immobilization efficiencies,affirming the effectiveness of 1DZnO nanoplatforms for rapid CYFRA 21-1 testing within a 5-min detection window in both PBS and artificial saliva.Photoluminescence measurements also revealed distinct optical responses across biomarker concentrations ranging from 10 to 1,000 ng ml^(−1).Conclusion:Discernible PL signal responses obtained after 5 min affirm the potential of 1DZnO nanoplatforms for further advancement in optical biomarker detection for application in early cancer prognosis.展开更多
Space target imaging simulation technology is an important tool for space target detection and identification,with advantages that include high flexibility and low cost.However,existing space target imaging simulation...Space target imaging simulation technology is an important tool for space target detection and identification,with advantages that include high flexibility and low cost.However,existing space target imaging simulation technologies are mostly based on target magnitudes for simulations,making it difficult to meet image simulation requirements for different signal-to-noise ratio(SNR)needs.Therefore,design of a simulation method that generates target image sequences with various SNRs based on the optical detection system parameters will be important for faint space target detection research.Addressing the SNR calculation issue in optical observation systems,this paper proposes a ground-based detection image SNR calculation method using the optical system parameters.This method calculates the SNR of an observed image precisely using radiative transfer theory,the optical system parameters,and the observation environment parameters.An SNR-based target sequence image simulation method for ground-based detection scenarios is proposed.This method calculates the imaging SNR using the optical system parameters and establishes a model for conversion between the target’s apparent magnitude and image grayscale values,thereby enabling generation of target sequence simulation images with corresponding SNRs for different system parameters.Experiments show that the SNR obtained using this calculation method has an average calculation error of<1 dB when compared with the theoretical SNR of the actual optical system.Additionally,the simulation images generated by the imaging simulation method show high consistency with real images,which meets the requirements of faint space target detection algorithm research and provides reliable data support for development of related technologies.展开更多
We perform a proof-of-principle experiment that uses a single negatively charged nitrogen–vacancy（NV） color center with a nearest neighbor ^13C nuclear spin in diamond to detect the strength and direction（includin...We perform a proof-of-principle experiment that uses a single negatively charged nitrogen–vacancy（NV） color center with a nearest neighbor ^13C nuclear spin in diamond to detect the strength and direction（including both polar and azimuth angles） of a static vector magnetic field by optical detection magnetic resonance（ODMR） technique. With the known hyperfine coupling tensor between an NV center and a nearest neighbor ^13C nuclear spin, we show that the information of static vector magnetic field could be extracted by observing the pulsed continuous wave（CW） spectrum.展开更多
At present,there are no methods that determine the total micro ial load on an abiotic substra tein real time.The utility of such a capability ranges from sterilization and medical diagnostics tothe search for new micr...At present,there are no methods that determine the total micro ial load on an abiotic substra tein real time.The utility of such a capability ranges from sterilization and medical diagnostics tothe search for new microorganisms in the environment and study of their ecological niches.Wereport the development of a hand held,fluorescence detection device and demonstrate its applicability to the field detection of Arctic bacteria,This technology is based on the early pioneering work of Britton Chance which elucidated the intrinsic fiuorescence of a number ofmetabolites and protein cofactors in cels,including reduced pyridine nucleotides,cytochromesand flavins.A PDA controls the device(fluorescence excitation and data collection)and processesthe multiwavelength signals to yield bacterial cell counts,including cstimates of ive cells,deadcells and endospores.Unlike existing methods for cell counting,this method requires no samplecontact or addition of reagents.The use of this technology is demonstrated with in situmea surements of two sub-glacial microbial communities at sites in Palander and colonized surfacerocks in the Bockijord Volcanic Complex during AMASE 2008(Arctic Mars Analog Svalbard Expedition),The total bacterial load on the interrogated sample surfaces ranged from<20 cells/cm to>1o9 cells/cm^(2).展开更多
Optically detected magnetic resonance(ODMR)has emerged as a powerful technique for quantum sensing,enabling high-sensitivity detection of physical quantities even at room temperature.Solid-state defects,such as nitrog...Optically detected magnetic resonance(ODMR)has emerged as a powerful technique for quantum sensing,enabling high-sensitivity detection of physical quantities even at room temperature.Solid-state defects,such as nitrogen-vacancy(NV)centers in diamond,have demonstrated remarkable capabilities in this domain[1–4].However,these systems are limited by their rigid lattice structures and lack tunability.展开更多
AIM：To select the optimal edge detection methods to identify the corneal surface,and compare three fitting curve equations with Matlab software. METHODS：Fifteen subjects were recruited. The corneal images from optic...AIM：To select the optimal edge detection methods to identify the corneal surface,and compare three fitting curve equations with Matlab software. METHODS：Fifteen subjects were recruited. The corneal images from optical coherence tomography（OCT）were imported into Matlab software. Five edge detection methods（Canny,Log,Prewitt,Roberts,Sobel）were used to identify the corneal surface. Then two manual identifying methods（ginput and getpts）were applied to identify the edge coordinates respectively. The differences among these methods were compared. Binomial curve（y=Ax2＋Bx＋C）,Polynomial curve [p（x）=p1xn＋p2x（n-1）＋....＋pnx＋pn＋1] and Conic section（Ax2＋Bxy＋Cy2＋Dx＋Ey＋F=0）were used for curve fitting the corneal surface respectively. The relative merits among three fitting curves were analyzed. Finally,the eccentricity（e）obtained by corneal topography and conic section were compared with paired t-test. RESULTS：Five edge detection algorithms all had continuous coordinates which indicated the edge of the corneal surface. The ordinates of manual identifying were close to the inside of the actual edges. Binomial curve was greatly affected by tilt angle. Polynomial curve was lack of geometrical properties and unstable. Conic section could calculate the tilted symmetry axis,eccentricity,circle center,etc. There were no significant differences between ＇e＇ values by corneal topography and conic section（t=0.9143,P=0.3760 〉0.05）.CONCLUSION：It is feasible to simulate the corneal surface with mathematical curve with Matlab software. Edge detection has better repeatability and higher efficiency. The manual identifying approach is an indispensable complement for detection. Polynomial and conic section are both the alternative methods for corneal curve fitting. Conic curve was the optimal choice based on the specific geometrical properties.展开更多
A fully distributed optical fiber sensor （DOFS） for monitoring long-distance oil pipeline health is proposed based on optical time domain reflectometry （OTDR）. A smart and sensitive optical fiber cable is installe...A fully distributed optical fiber sensor （DOFS） for monitoring long-distance oil pipeline health is proposed based on optical time domain reflectometry （OTDR）. A smart and sensitive optical fiber cable is installed along the pipeline acting as a sensor, The experiments show that the cable swells when exposed to oil and induced additional bending losses inside the fiber, and the optical attenuation of the fiber coated by a thin skin with periodical hardness is sensitive to deformation and vibration caused by oil leakage, tampering, or mechanical impact. The region where the additional attenuation occurred is detected and located by DOFS based on OTDR, the types of pipeline accidents are identified according to the characteristics of transmitted optical power received by an optical power meter, Another prototype of DOFS based on a forward traveling frequency-modulated continuous-wave （FMCW） is also proposed to monitor pipeline. The advantages and disadvantages of DOFSs based on OTDR and FMCW are discussed. The experiments show that DOFSs are capable of detecting and locating distant oil pipeline leakages and damages in real time with an estimated precision of ten meters over tens of kilometers.展开更多
The application of the vector magnetometry based on nitrogen-vacancy(NV)ensembles has been widely investigatedin multiple areas.It has the superiority of high sensitivity and high stability in ambient conditions with ...The application of the vector magnetometry based on nitrogen-vacancy(NV)ensembles has been widely investigatedin multiple areas.It has the superiority of high sensitivity and high stability in ambient conditions with microscale spatialresolution.However,a bias magnetic field is necessary to fully separate the resonance lines of optically detected magneticresonance(ODMR)spectrum of NV ensembles.This brings disturbances in samples being detected and limits the rangeof application.Here,we demonstrate a method of vector magnetometry in zero bias magnetic field using NV ensembles.By utilizing the anisotropy property of fluorescence excited from NV centers,we analyzed the ODMR spectrum of NVensembles under various polarized angles of excitation laser in zero bias magnetic field with a quantitative numerical modeland reconstructed the magnetic field vector.The minimum magnetic field modulus that can be resolved accurately is downto~0.64 G theoretically depending on the ODMR spectral line width(1.8 MHz),and~2 G experimentally due to noisesin fluorescence signals and errors in calibration.By using 13C purified and low nitrogen concentration diamond combinedwith improving calibration of unknown parameters,the ODMR spectral line width can be further decreased below 0.5 MHz,corresponding to~0.18 G minimum resolvable magnetic field modulus.展开更多
Luminescent probes attract increasing attentions for the unique superiorities like visually real-time detecting.However,for optical humidity sensing,it is still quite challenging to attain facile dehydration/activatio...Luminescent probes attract increasing attentions for the unique superiorities like visually real-time detecting.However,for optical humidity sensing,it is still quite challenging to attain facile dehydration/activation in sensing materials,due to the high polarity of water molecules,which limits their applications in real-time detection and energy-conserving applications.Here,we report two fluorescent hydrogen-bonded organic frameworks(HOFs),HPISF-H_(2)O and TPISF.HPISF-H_(2)O achieves water absorption in low humidity,but needs an energy-intensive step(heating to∼92◦C in air)to dehydrate.Conversely,despite only a hydroxyl group being replaced,TPISF cannot bind to H_(2)O at all.In other words,real-time detection is not readily achieved through straightforward molecular design.Therefore,we propose a cocrystallization strategy to adjust their water-binding capacity.As a result,the HOF cocrystals are adjusted to have both good H_(2)O absorptivity and very gentle desorbing operation without heating(dry gas blowing or vacuuming).Benefiting from this strategy,appreciable advantages for an effective humidity sensor are realized,including real-time detection(second-scale response/recovery)and distinguishing fluorescence variation.Efficient sensing across a broad relative humidity(RH)range(10.0%–80.0%)was further achieved.Moreover,the mechanistic insight of fluorescent sensing was ascertained through detailed analyses of structural transformation,spectroscopic data,and theoretical approach.展开更多
Conventional methods for near-field characterization have typically relied on the nanoprobe to point-scan the field,rendering the measurements vulnerable to external environmental influences.Here,we study the direct f...Conventional methods for near-field characterization have typically relied on the nanoprobe to point-scan the field,rendering the measurements vulnerable to external environmental influences.Here,we study the direct far-field imaging of the near-field polarizations based on the four-wave mixing effect.We construct a simulation model to realize the instantaneous extraction of the near-field distributions of a wide range of structured light fields,such as cylindrical vector vortex beams,plasmonic Weber beams,and topological spin textures,including photonic skyrmions and merons.This method is valuable for the studies on manipulation of structured light fields and light-matter interaction at the micro/nano scales.展开更多
CONSPECTUS:Chiral optoelectronics,which utilize the unique interactions between circularly polarized(CP)light and chiral materials,open up exciting possibilities in advanced technologies.These devices can detect,emit,...CONSPECTUS:Chiral optoelectronics,which utilize the unique interactions between circularly polarized(CP)light and chiral materials,open up exciting possibilities in advanced technologies.These devices can detect,emit,or manipulate light with specific polarization,enabling applications in secure communication,sensing,and data processing.A key aspect of chiral optoelectronics is the ability to generate or detect optical and electrical signals by controlling or distinguishing CP light based on its polarization direction.This capability is rooted in the selective interaction of CP light with the stereogenic(non-superimposable)molecular geometry of chiral substances,wherein the polarization of CP light aligns with the intrinsic asymmetry of the material.Among the diverse chiral materials explored for this purpose,π-conjugated molecules offer special advantages due to their tunable optoelectronic properties,efficient light−matter interactions,and cost-effective processability.Recent advancements inπ-conjugated molecule research have demonstrated their ability to generate strong chiroptical responses,thereby paving the way for compact and multifunctional device designs.Building on these unique advantages,π-conjugated molecules have advanced organic electronics into rapidly evolving technological fields.The combination of chiralπ-conjugated molecules with organic electronics is anticipated to simplify the fabrication of chiroptical devices,thereby lowering technical barriers and accelerating progress in chiral optoelectronics.This Account introduces strategies for incorporating chiroptical activity into organic optoelectronic devices,focusing on two main approaches:direct incorporation of chiroptical activity intoπ-conjugated polymer semiconductors and integration of chiral organic nanoarchitectures with conventional organic optoelectronic devices.In the first approach,we especially highlight simple methods to induce chiroptical activity in various achiralπ-conjugated polymers through the transfer of chirality from small chiral molecules.This hybrid approach effectively combines the excellent electrical properties and various optical transition properties of achiral polymers with the strong chiroptical activity of small molecules.Moreover,we address a fundamental challenge in achieving chiroptical transitions in planarπ-conjugated polymers,demonstrating the development of low-bandgapπ-conjugated polymers that exhibit both strong chiroptical activity and excellent electrical performance.Another approach,incorporating chiroptical activity into existing organic optoelectronic devices,which have already achieved significant performance advances,presents an effective strategy for high-performance chiral optoelectronics.For this purpose,we introduce the use of supramolecular assemblies ofπ-conjugated molecules to impart chiroptical responses into high-performance optoelectronic systems,utilizing efficient charge transfer of photoexcited electrons in chiroptical supramolecular nanoarchitectures.Additionally,we explore the integration of organic chiral photonic structure into organic optoelectronic systems,which act as optical filters tailored for CP light.These architectures offer unique advantages,including easy processability and seamless compatibility with existing organic electronic platforms.By bridging concepts from chiral organic optoelectronic materials and advanced organic electronics,this work outlines actionable approaches for advancing chiral optoelectronic technologies.These strategies underscore the versatility ofπ-conjugated molecules while also expanding the framework for next-generation applications.As the field of chiral optoelectronics evolves,integrating chiroptical functionalities into organic devices will facilitate transformative innovations in quantum computing,biosensing,and photonic encryption.展开更多
As a severe environmental pollutant, detection and quantitation of nitrogen dioxide (NO<sub>2</sub>) have been studied for centuries. In this review, recent progress of NO<sub>2</sub> analysis ...As a severe environmental pollutant, detection and quantitation of nitrogen dioxide (NO<sub>2</sub>) have been studied for centuries. In this review, recent progress of NO<sub>2</sub> analysis in the atmosphere will be summarized. Four major types of detection technologies, including traditional chemical detection, optical detection, solid-state field effect transistor detection, and other detection technology are covered. The standard method employed by the US EPA, which is based on luminol, is the most reliable and robust method that is used for fully validated monitoring. In the past two decades, accompanying the fast development of electrical engineering and integrated circuit, micro to nanoscale gas sensors have been gaining more and more attention. Application of novel materials including nano wires and graphene also leads to a new era of research and development of sensors.展开更多
基金supported by the Science and Technology Research Program of Shenzhen(No.JCYJ20200109142820687 and JCYJ20210324120012035)the Cross-research Innovation Fund of In-ternational Graduate School at Shenzhen,Tsinghua University(No.JC2021001)the Russian Sci-ence Foundation(No.23-14-00287)。
文摘It is of great significance in clinical diagnosis and treatment evaluation to accurately identify the lesion tissue and further extract its characteristics and depth location. In this study, we construct tissue phantoms for three lesion types: fibrosis (FT), organelle proliferation (OPT), and pigmentation (PT). These phantoms allow for the quantitative regulation of mimicked disease depth. The experimental results show that the parameter Kc, combined with MMT parameters, can effectively distinguish the presence of lesions and their abnormal types. Further, the study extracts depth-sensitive polarization feature parameters (DSPFPs) for specific lesion types. Through experiments of tissue phantoms with various depth settings, the established machine learning regression models based on DSPFPs demonstrate their depth retrieval capabilities.
基金supported by the National Key R&D Program of China(Grant No.2024YFE0105200)the National Natural Science Foundation of China(Grant Nos.62422408,12374016,12174348,62271450,62027816,12422413,and 62475242).
文摘Non-hydrostatic stress plays a significant role in shaping the properties of materials under compression.High-pressure effects such as yielding deformation,phase transitions,and volume contraction can alter the pressure distribution within the pressure chamber.However,due to the inherent size limitation of the diamond anvil cell(DAC),in situ high-pressure studies usually assume a hydrostatic environment,equaling the pressure of samples to a pressure calibrator inside the chamber.Accurately imaging pressure distribution within the DAC chamber remains challenging,particularly as the material undergoes phase transitions.Here,we present a method for mapping pressure distribution with high spatial resolution using wide-field optically detected magnetic resonance(ODMR)of nanodiamonds.The pressure gradients during the highpressure transition of zinc oxide(ZnO)were compared using both the multiple rubies technique and wide-field ODMR.The latter technique demonstrated superior spatial resolution,easier operation,and more detailed information.These results highlight the potential of wide-field ODMR as a powerful tool for precise pressure sensing,particularly in studies involving non-hydrostatic pressure conditions.
文摘Optoacoustic tomography （PAT） is a two-dimensional medical imaging method that has the advantage of optical contrast and resolution of ultrasonic waves. The detection systems with a high sensitivity can be used for detecting small tumors, located deeply in human tissues, such as the breast. In this study, the sensitivity of existing ultrasonic detection systems has been compared experimentally with that by using thermoelastic waves as a broadband ultrasonic source. For the comparison, an optical stress transducer （OST）, a polyvinylidene difluoride （PVDF） sheet and a calibrated PVDF needle hydrophone were used. To ensure all of the detection systems interrogated by the same ultrasonic field, a small optical instrument that fixed the generating laser head was constructed. The sensitivity was evaluated by measuring signalto-noise ratios （SNRs） and noise equivalent pressures （NEPs）. The PVDF system, with a 4-kPa NEP has a 22 dB better performance than the OST. The OST showed nearly the same sensitivity as the hydrophone for detecting ultrasound waves at a 1-cm distance in water. PVDF detection system provides a useful tool for imaging of soft tissues because of its high sensitivity and broad detection range.
基金supported in part by grants from the National Institutes of Health (R01CA213149,R01CA241618).
文摘Nonlinear optical imaging is a versatile tool that has been proven to be exceptionally useful in various research fields.However,due to the use of photomultiplier tubes(PMTs),the wide application of nonlinear optical imaging is limited by the incapability of imaging under am-bient light.In this paper,we propose and demonstrate a new optical imaging detection method based on optical parametric amplification(OPA).As a nonlinear optical process,OPA in-trinsically rejects ambient light photons by coherence gating.Periodical poled lithium niobate(PPLN)crystals are used in this study as the media for OPA.Compared to bulk nonlinear optical crystals,PPLN crystals support the generation of OPA signal with lower pump power.Therefore,this characteristic of PPLN crystals is particularly beneficial when using high-repetition-rate lasers,which facilitate high-speed optical signal detection,such as in spec-troscopy and imaging.A PPLN-based OPA system was built to amplify the emitted imaging signal from second harmonic generation(SHG)and coherent anti-Stokes Raman scattering(CARS)microscopy imaging,and the amplified optical signal was strong enough to be detected by a biased photodiode under ordinary room light conditions.With OPA detection,ambient-light-on SHG and CARS imaging becomes possible,and achieves a similar result as PMT detection under strictly dark environments.These results demonstrate that OPA can be used as a substitute for PMTs in nonlinear optical imaging to adapt it to various applications with complex.light ing conditions.
文摘History, present situation and importancy of the laser-generated ultrasonic technique are presented. Basic principles and some experimental results of laser ultrasonic generation and optical detection and processing are discussed. Several problems about applying this technique to NDT are also discussed in this paper.
基金Project supported by the Innovation Program of Education Commission of Shanghai Municipality (Grant No.10YZ19)the Shanghai Leading Academic Discipline Project (Grant No.S30108)the Shanghai Key Laboratory of Specialty Fiber Optics and Optical Access Networks (Grant No.SKLSFO200903)
文摘A distributed optical fiber disturbance detection system consisted of a Sagnac interferometer and a Mach-Zehnder interferometer is demonstrated. Two interferometers outputs are connected to an electric band-pass filter via a detector respectively. The central frequencies of the two filters are selected adaptively according to the disturbance frequency. The disturbance frequency is obtained by either frequency spectrum of the two interferometers outputs. An alarm is given out only when the Sagnac interferometer output is changed. A disturbance position is determined by calculating a time difference with a cross-correlation method between the filter output connected to the Sagnac interferometer and derivative of the filter output connected to the Mach-Zehnder interferometer. The frequency spectrum, derivative and cross-correlation are obtained by a signal processing system. Theory analysis and simulation results are presented. They show that the system structure and location method are effective, accurate, and immune to environmental variations.
基金supported by the Erciyes University Scientific Research Projects Coordination Unit (No.FDK-2019-8750)。
文摘In this paper, we have evaluated a bidirectional wavelength division multiplexing passive optical network(WDM-PON) employing intensity modulated/direct detection optical orthogonal frequency division multiplexing(IM/DD-OFDM). The proposed system employs 100 Gbit/s 16 quadrature amplitude modulation(16-QAM) downstream and 5 Gbit/s on-off keying(OOK) upstream wavelengths, respectively. The proposed system is considered low-cost as non-coherent IM/DD OFDM technology and a simple reflective semiconductor optical amplifier(RSOA) colorless transmitter are employed and no dispersion compensating fiber(DCF) is needed. Based on the bit error rate(BER) results of WDM signals, the proposed WDM-PON system can achieve up to 1.6 Tbit/s(100 Gbit/s/λ × 16 wavelengths) downstream transmission over a 30 km single mode fiber(SMF).
基金supported by the National Natural Science Foundation of China(61935004)the Natural Science Foundation of Fujian Province(2020J01155,2022J01171).
文摘Singlet oxygen(^(1)O_(2))is the main cytotoxic substance in Type II photodynamic therapy(PDT).The luminescence of ^(1)O_(2) at 1270nm is extremely weak with a low quantum yield,making the direct detection of'O2 at 1270 nm very challenging.In this study,a set of highly sensitive optical fiber detection system is built up to detect the luminescence of photosensitized ^(1)O_(2) We use this system to test the luminescence characteristics of ^(1)O_(2) in pig skin tissue ex vrivo and mouse auricle skin in vivo.The experimental results show that the designed system can quantitatively detect photosensitized ^(1)O_(2) luminescence.The ^(1)O_(2) luminescence signal at 1270 nm is successfully detected in pig skin exr vivo.Compared with RB in an aqueous solution,the lifetime of ^(1)O_(2) increases to 17.4±12pus in pig skin tissue ex vivo.Experiments on living mice suggest that an enhancement of ^(1)O_(2) intensity with the increase of the TMPyP concentration.When the dose is 25 mg/kg,the vasoconstriction can reach more than 80%。The results of this study hold the potential application for clinical PDT dose monitoring using an optical fiber detection system.
基金R.A.S.(CVU 703153)acknowledges the DGAPA-UNAM postdoctoral grant.S.E.M.T.(CVU 703157)acknowledges the DGAPA-UNAM postdoctoral grantP.G.Z.-B.(CVU 787342)acknowledges the CONAHCyT postdoctoral grant received.A.D.+2 种基金G.S.thank the projects PAPIIT-DGAPA-UNAM IA100123 and IG100123The authors also acknowledge the UIC-UNAM joint collaborative project for the supportThis work was supported by DGAPA PAPIIT funding IA100123.
文摘Objective:We conducted a comprehensive physicochemical analysis of one-dimensional ZnO nanowires(1DZnO),incorporating anti-CYFRA 21-1 immobilization to promote fast optical biomarker detection up to 10 ng ml−1.Impact Statement:This study highlights the effectiveness of proof-of-concept 1DZnO nanoplatforms for rapid cancer biomarker detection by examining the nanoscale integration of 1DZnO with these bioreceptors to deliver reliable photoluminescent output signals.Introduction:The urgent need for swift and accurate prognoses in healthcare settings drives the rise of sensitive biosensing nanoplatforms for cancer detection,which has benefited from biomarker identification.CYFRA 21-1 is a reliable target for the early prediction of cancer formation that can be perceptible in blood,saliva,and serum.However,1DZnO nanostructures have been barely applied for CYFRA 21-1 detection.Methods:We assessed the nanoscale interaction between 1DZnO and anti-CYFRA 21-1 antibodies to develop rapid CYFRA 21-1 detection in two distinct matrices:PhosphateBuffered Saline(PBS)buffer and artificial saliva.The chemical modifications were tracked utilizing Fourier transform infrared spectroscopy,while transmission electron microscopy and energy dispersive spectroscopy confirmed antigen-antibody interplay over nanostructures.Results:Our results show high antibody immobilization efficiencies,affirming the effectiveness of 1DZnO nanoplatforms for rapid CYFRA 21-1 testing within a 5-min detection window in both PBS and artificial saliva.Photoluminescence measurements also revealed distinct optical responses across biomarker concentrations ranging from 10 to 1,000 ng ml^(−1).Conclusion:Discernible PL signal responses obtained after 5 min affirm the potential of 1DZnO nanoplatforms for further advancement in optical biomarker detection for application in early cancer prognosis.
基金supported by Open Fund of National Key Laboratory of Deep Space Exploration(NKDSEL2024014)by Civil Aerospace Pre-research Project of State Administration of Science,Technology and Industry for National Defence,PRC(D040103).
文摘Space target imaging simulation technology is an important tool for space target detection and identification,with advantages that include high flexibility and low cost.However,existing space target imaging simulation technologies are mostly based on target magnitudes for simulations,making it difficult to meet image simulation requirements for different signal-to-noise ratio(SNR)needs.Therefore,design of a simulation method that generates target image sequences with various SNRs based on the optical detection system parameters will be important for faint space target detection research.Addressing the SNR calculation issue in optical observation systems,this paper proposes a ground-based detection image SNR calculation method using the optical system parameters.This method calculates the SNR of an observed image precisely using radiative transfer theory,the optical system parameters,and the observation environment parameters.An SNR-based target sequence image simulation method for ground-based detection scenarios is proposed.This method calculates the imaging SNR using the optical system parameters and establishes a model for conversion between the target’s apparent magnitude and image grayscale values,thereby enabling generation of target sequence simulation images with corresponding SNRs for different system parameters.Experiments show that the SNR obtained using this calculation method has an average calculation error of<1 dB when compared with the theoretical SNR of the actual optical system.Additionally,the simulation images generated by the imaging simulation method show high consistency with real images,which meets the requirements of faint space target detection algorithm research and provides reliable data support for development of related technologies.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11305074,11135002,and 11275083)the Key Program of the Education Department Outstanding Youth Foundation of Anhui Province,China(Grant No.gxyq ZD2017080)the Education Department Natural Science Foundation of Anhui Province,China(Grant No.KJHS2015B09)
文摘We perform a proof-of-principle experiment that uses a single negatively charged nitrogen–vacancy（NV） color center with a nearest neighbor ^13C nuclear spin in diamond to detect the strength and direction（including both polar and azimuth angles） of a static vector magnetic field by optical detection magnetic resonance（ODMR） technique. With the known hyperfine coupling tensor between an NV center and a nearest neighbor ^13C nuclear spin, we show that the information of static vector magnetic field could be extracted by observing the pulsed continuous wave（CW） spectrum.
基金supported by AMASE,under the NASA ASTEP program(A.Stele PI),the Thomas R.Brown Foundation,and the University of Arizona.
文摘At present,there are no methods that determine the total micro ial load on an abiotic substra tein real time.The utility of such a capability ranges from sterilization and medical diagnostics tothe search for new microorganisms in the environment and study of their ecological niches.Wereport the development of a hand held,fluorescence detection device and demonstrate its applicability to the field detection of Arctic bacteria,This technology is based on the early pioneering work of Britton Chance which elucidated the intrinsic fiuorescence of a number ofmetabolites and protein cofactors in cels,including reduced pyridine nucleotides,cytochromesand flavins.A PDA controls the device(fluorescence excitation and data collection)and processesthe multiwavelength signals to yield bacterial cell counts,including cstimates of ive cells,deadcells and endospores.Unlike existing methods for cell counting,this method requires no samplecontact or addition of reagents.The use of this technology is demonstrated with in situmea surements of two sub-glacial microbial communities at sites in Palander and colonized surfacerocks in the Bockijord Volcanic Complex during AMASE 2008(Arctic Mars Analog Svalbard Expedition),The total bacterial load on the interrogated sample surfaces ranged from<20 cells/cm to>1o9 cells/cm^(2).
文摘Optically detected magnetic resonance(ODMR)has emerged as a powerful technique for quantum sensing,enabling high-sensitivity detection of physical quantities even at room temperature.Solid-state defects,such as nitrogen-vacancy(NV)centers in diamond,have demonstrated remarkable capabilities in this domain[1–4].However,these systems are limited by their rigid lattice structures and lack tunability.
基金Supported by the National Natural Science Foundation of China(No.81400428)Science and Technology Commission of Shanghai Municipality(No.134119b1600)
文摘AIM：To select the optimal edge detection methods to identify the corneal surface,and compare three fitting curve equations with Matlab software. METHODS：Fifteen subjects were recruited. The corneal images from optical coherence tomography（OCT）were imported into Matlab software. Five edge detection methods（Canny,Log,Prewitt,Roberts,Sobel）were used to identify the corneal surface. Then two manual identifying methods（ginput and getpts）were applied to identify the edge coordinates respectively. The differences among these methods were compared. Binomial curve（y=Ax2＋Bx＋C）,Polynomial curve [p（x）=p1xn＋p2x（n-1）＋....＋pnx＋pn＋1] and Conic section（Ax2＋Bxy＋Cy2＋Dx＋Ey＋F=0）were used for curve fitting the corneal surface respectively. The relative merits among three fitting curves were analyzed. Finally,the eccentricity（e）obtained by corneal topography and conic section were compared with paired t-test. RESULTS：Five edge detection algorithms all had continuous coordinates which indicated the edge of the corneal surface. The ordinates of manual identifying were close to the inside of the actual edges. Binomial curve was greatly affected by tilt angle. Polynomial curve was lack of geometrical properties and unstable. Conic section could calculate the tilted symmetry axis,eccentricity,circle center,etc. There were no significant differences between ＇e＇ values by corneal topography and conic section（t=0.9143,P=0.3760 〉0.05）.CONCLUSION：It is feasible to simulate the corneal surface with mathematical curve with Matlab software. Edge detection has better repeatability and higher efficiency. The manual identifying approach is an indispensable complement for detection. Polynomial and conic section are both the alternative methods for corneal curve fitting. Conic curve was the optimal choice based on the specific geometrical properties.
基金This project is supported by R&D Foundation of National Petroleum Corporation (CNPC) of China(No.2001411-4).
文摘A fully distributed optical fiber sensor （DOFS） for monitoring long-distance oil pipeline health is proposed based on optical time domain reflectometry （OTDR）. A smart and sensitive optical fiber cable is installed along the pipeline acting as a sensor, The experiments show that the cable swells when exposed to oil and induced additional bending losses inside the fiber, and the optical attenuation of the fiber coated by a thin skin with periodical hardness is sensitive to deformation and vibration caused by oil leakage, tampering, or mechanical impact. The region where the additional attenuation occurred is detected and located by DOFS based on OTDR, the types of pipeline accidents are identified according to the characteristics of transmitted optical power received by an optical power meter, Another prototype of DOFS based on a forward traveling frequency-modulated continuous-wave （FMCW） is also proposed to monitor pipeline. The advantages and disadvantages of DOFSs based on OTDR and FMCW are discussed. The experiments show that DOFSs are capable of detecting and locating distant oil pipeline leakages and damages in real time with an estimated precision of ten meters over tens of kilometers.
基金supported by the National Key R&D Program of China(Grant Nos.2021YFB3202800 and 2023YF0718400)Chinese Academy of Sciences(Grant No.ZDZBGCH2021002)+2 种基金Chinese Academy of Sciences(Grant No.GJJSTD20200001)Innovation Program for Quantum Science and Technology(Grant No.2021ZD0303204)Anhui Initiative in Quantum Information Technologies,USTC Tang Scholar,and the Fundamental Research Funds for the Central Universities.
文摘The application of the vector magnetometry based on nitrogen-vacancy(NV)ensembles has been widely investigatedin multiple areas.It has the superiority of high sensitivity and high stability in ambient conditions with microscale spatialresolution.However,a bias magnetic field is necessary to fully separate the resonance lines of optically detected magneticresonance(ODMR)spectrum of NV ensembles.This brings disturbances in samples being detected and limits the rangeof application.Here,we demonstrate a method of vector magnetometry in zero bias magnetic field using NV ensembles.By utilizing the anisotropy property of fluorescence excited from NV centers,we analyzed the ODMR spectrum of NVensembles under various polarized angles of excitation laser in zero bias magnetic field with a quantitative numerical modeland reconstructed the magnetic field vector.The minimum magnetic field modulus that can be resolved accurately is downto~0.64 G theoretically depending on the ODMR spectral line width(1.8 MHz),and~2 G experimentally due to noisesin fluorescence signals and errors in calibration.By using 13C purified and low nitrogen concentration diamond combinedwith improving calibration of unknown parameters,the ODMR spectral line width can be further decreased below 0.5 MHz,corresponding to~0.18 G minimum resolvable magnetic field modulus.
基金NSFC(21901189 and 22101211)Open Foundation of MOE Key Laboratory of Bioinorganic and Synthetic Chemistry(BISC2022A04)+1 种基金Municipal Science and Technology Bureau(Jiangke 2021-76)Scientific Research Ability Improvement Project of Key Discipline Construction from the Education Department of Guangdong Province(2022ZDJS027).
文摘Luminescent probes attract increasing attentions for the unique superiorities like visually real-time detecting.However,for optical humidity sensing,it is still quite challenging to attain facile dehydration/activation in sensing materials,due to the high polarity of water molecules,which limits their applications in real-time detection and energy-conserving applications.Here,we report two fluorescent hydrogen-bonded organic frameworks(HOFs),HPISF-H_(2)O and TPISF.HPISF-H_(2)O achieves water absorption in low humidity,but needs an energy-intensive step(heating to∼92◦C in air)to dehydrate.Conversely,despite only a hydroxyl group being replaced,TPISF cannot bind to H_(2)O at all.In other words,real-time detection is not readily achieved through straightforward molecular design.Therefore,we propose a cocrystallization strategy to adjust their water-binding capacity.As a result,the HOF cocrystals are adjusted to have both good H_(2)O absorptivity and very gentle desorbing operation without heating(dry gas blowing or vacuuming).Benefiting from this strategy,appreciable advantages for an effective humidity sensor are realized,including real-time detection(second-scale response/recovery)and distinguishing fluorescence variation.Efficient sensing across a broad relative humidity(RH)range(10.0%–80.0%)was further achieved.Moreover,the mechanistic insight of fluorescent sensing was ascertained through detailed analyses of structural transformation,spectroscopic data,and theoretical approach.
基金supported by the Guangdong Major Project of Basic Research(No.2020B0301030009)the National Natural Science Foundation of China(Nos.62075139,61935013,and 12004260)+4 种基金the Natural Science Foundation of Guangdong(No.2024A1515012503)the Innovation Team Project of Ordinary University of Guangdong Provincial Education Bureau(No.2024KCXTD014)the Shenzhen Science and Technology Program(Nos.RCJC20200714114435063 and JCYJ20241202124532024)the Research Team Cultivation Program of Shenzhen University(No.2023QNT012)the Shenzhen University 2035 Initiative(No.2023B004)。
文摘Conventional methods for near-field characterization have typically relied on the nanoprobe to point-scan the field,rendering the measurements vulnerable to external environmental influences.Here,we study the direct far-field imaging of the near-field polarizations based on the four-wave mixing effect.We construct a simulation model to realize the instantaneous extraction of the near-field distributions of a wide range of structured light fields,such as cylindrical vector vortex beams,plasmonic Weber beams,and topological spin textures,including photonic skyrmions and merons.This method is valuable for the studies on manipulation of structured light fields and light-matter interaction at the micro/nano scales.
基金supported by the Air Force Office of Scientific Research under award number FA2386-24-1-4030This study was also part of the Future Resource Research Program of the Korea Institute of Science and Technology(KIST)(2E33853)+1 种基金Ministry of CultureSports and Tourism(MCST)and Korea Creative Content Agency(KOCCA)in the Culture Technology(CT)Research&Development Program 2024(RS-2024-00439361)。
文摘CONSPECTUS:Chiral optoelectronics,which utilize the unique interactions between circularly polarized(CP)light and chiral materials,open up exciting possibilities in advanced technologies.These devices can detect,emit,or manipulate light with specific polarization,enabling applications in secure communication,sensing,and data processing.A key aspect of chiral optoelectronics is the ability to generate or detect optical and electrical signals by controlling or distinguishing CP light based on its polarization direction.This capability is rooted in the selective interaction of CP light with the stereogenic(non-superimposable)molecular geometry of chiral substances,wherein the polarization of CP light aligns with the intrinsic asymmetry of the material.Among the diverse chiral materials explored for this purpose,π-conjugated molecules offer special advantages due to their tunable optoelectronic properties,efficient light−matter interactions,and cost-effective processability.Recent advancements inπ-conjugated molecule research have demonstrated their ability to generate strong chiroptical responses,thereby paving the way for compact and multifunctional device designs.Building on these unique advantages,π-conjugated molecules have advanced organic electronics into rapidly evolving technological fields.The combination of chiralπ-conjugated molecules with organic electronics is anticipated to simplify the fabrication of chiroptical devices,thereby lowering technical barriers and accelerating progress in chiral optoelectronics.This Account introduces strategies for incorporating chiroptical activity into organic optoelectronic devices,focusing on two main approaches:direct incorporation of chiroptical activity intoπ-conjugated polymer semiconductors and integration of chiral organic nanoarchitectures with conventional organic optoelectronic devices.In the first approach,we especially highlight simple methods to induce chiroptical activity in various achiralπ-conjugated polymers through the transfer of chirality from small chiral molecules.This hybrid approach effectively combines the excellent electrical properties and various optical transition properties of achiral polymers with the strong chiroptical activity of small molecules.Moreover,we address a fundamental challenge in achieving chiroptical transitions in planarπ-conjugated polymers,demonstrating the development of low-bandgapπ-conjugated polymers that exhibit both strong chiroptical activity and excellent electrical performance.Another approach,incorporating chiroptical activity into existing organic optoelectronic devices,which have already achieved significant performance advances,presents an effective strategy for high-performance chiral optoelectronics.For this purpose,we introduce the use of supramolecular assemblies ofπ-conjugated molecules to impart chiroptical responses into high-performance optoelectronic systems,utilizing efficient charge transfer of photoexcited electrons in chiroptical supramolecular nanoarchitectures.Additionally,we explore the integration of organic chiral photonic structure into organic optoelectronic systems,which act as optical filters tailored for CP light.These architectures offer unique advantages,including easy processability and seamless compatibility with existing organic electronic platforms.By bridging concepts from chiral organic optoelectronic materials and advanced organic electronics,this work outlines actionable approaches for advancing chiral optoelectronic technologies.These strategies underscore the versatility ofπ-conjugated molecules while also expanding the framework for next-generation applications.As the field of chiral optoelectronics evolves,integrating chiroptical functionalities into organic devices will facilitate transformative innovations in quantum computing,biosensing,and photonic encryption.
文摘As a severe environmental pollutant, detection and quantitation of nitrogen dioxide (NO<sub>2</sub>) have been studied for centuries. In this review, recent progress of NO<sub>2</sub> analysis in the atmosphere will be summarized. Four major types of detection technologies, including traditional chemical detection, optical detection, solid-state field effect transistor detection, and other detection technology are covered. The standard method employed by the US EPA, which is based on luminol, is the most reliable and robust method that is used for fully validated monitoring. In the past two decades, accompanying the fast development of electrical engineering and integrated circuit, micro to nanoscale gas sensors have been gaining more and more attention. Application of novel materials including nano wires and graphene also leads to a new era of research and development of sensors.
