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
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
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
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
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
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
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
Wavelength modulation technique (WMT) and wavelength sweep technique (WST) are introduced into intra-cavity absorption gas sensors (ICAGS) for low concentration gas detection. The optimized parameters of the sys...Wavelength modulation technique (WMT) and wavelength sweep technique (WST) are introduced into intra-cavity absorption gas sensors (ICAGS) for low concentration gas detection. The optimized parameters of the system maximizing the signal-to-noise ratio (SNR) are found. Calibration of acetylene concentration and gas recognition are both realized.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
To improve the performance of real-time recombinase polymerase amplification(RPA),a microfluidic system with active mixing is developed to optimize the reaction dynamics.Instead of adopting a single typical reaction c...To improve the performance of real-time recombinase polymerase amplification(RPA),a microfluidic system with active mixing is developed to optimize the reaction dynamics.Instead of adopting a single typical reaction chamber,a specific reactor including a relatively large chamber in center with two adjacent zig-zag channels at two sides is integrated into the microfluidic chip.Active mixing is achieved by driving the viscous reagent between the chamber and the channel back and forth periodically with an outside compact peristaltic pump.To avoid reagent evapora-tion,one end of the reactor is sealed with paraffin oil.A hand-held companion device is developed to facilitate real-time RPA amplification within 20 min.The whole area of the reactor is heated with a resistance heater to provide uniform reaction temperature.To achieve real-time monitoring,a compact fluorescence detection module is integrated into the hand-held device.A smartphone with custom application software is adopted to control the hand-held device and display the real-time fluorescence curves.The performances of two cases with and without active on-chip mixing are compared between each other by detecting African swine fever viruses.It has been demonstrated that,with active on-chip mixing,the amplification efficiency and detection sensitivity can be signifi-cantly improved.展开更多
We suggest an experimental scheme that a single nitrogen-vacancy(NV) center coupled to a nearest neighbor ^13C nucleus as a sensor in diamond can be used to detect a static vector magnetic field. By means of optical...We suggest an experimental scheme that a single nitrogen-vacancy(NV) center coupled to a nearest neighbor ^13C nucleus as a sensor in diamond can be used to detect a static vector magnetic field. By means of optical detection magnetic resonance(ODMR) technique, both the strength and the direction of the vector field could be determined by relevant resonance frequencies of continuous wave(CW) and Ramsey spectrums. In addition, we give a method that determines the unique one of eight possible hyperfine tensors for an(NV–^13C) system. Finally, we propose an unambiguous method to exclude the symmetrical solution from eight possible vector fields, which correspond to nearly identical resonance frequencies due to their mirror symmetry about ^14N–Vacancy–^13 C(^14N–V–^13C) plane.展开更多
Axonal tracing is useful for detecting optic nerve injury and regeneration,but many commonly used methods cannot be used to observe axoplasmic flow and synaptic transmission in vivo.Manganese(Mn^2+)-enhanced magnet...Axonal tracing is useful for detecting optic nerve injury and regeneration,but many commonly used methods cannot be used to observe axoplasmic flow and synaptic transmission in vivo.Manganese(Mn^2+)-enhanced magnetic resonance imaging(MEMRI) can be used for in vivo longitudinal tracing of the visual pathway.Here,we explored the dose response and time course of an intravitreal injection of Mn Cl2 for tracing the visual pathway in rabbits in vivo using MEMRI.We found that 2 m M Mn Cl2 enhanced images of the optic nerve but not the lateral geniculate body or superior colliculus,whereas at all other doses tested(5–40 m M),images of the visual pathway from the retina to the contralateral superior colliculus were significantly enhanced.The images were brightest at 24 hours,and then decreased in brightness until the end of the experiment(7 days).No signal enhancement was observed in the visual cortex at any concentration of Mn Cl2.These results suggest that MEMRI is a viable method for temporospatial tracing of the visual pathway in vivo.Signal enhancement in MEMRI depends on the dose of Mn Cl2,and the strongest signals appear 24 hours after intravitreal injection.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
Optical edge detection, a part of image processing, plays an important role in extracting image information used in optical analog computation. In this Letter, we raise a new way to realize optical edge detection. Thi...Optical edge detection, a part of image processing, plays an important role in extracting image information used in optical analog computation. In this Letter, we raise a new way to realize optical edge detection. This design is based on two liquid crystal polarization gratings with a period of 2.2 mm, which function as a spatial differentiator. We experimentally demonstrate broadband optical detection and real-time adjustable resolution.The proposed method takes advantage of the convenience to use, simple fabrication process, and real-time tunable resolution. It may guide more significant applications in the optical field and other practical scenarios like machine vision in computers.展开更多
In underwater optical wireless communication(UOWC),a channel is characterized by abundant scattering/absorption effects and optical turbulence.Most previous studies on UOWC have been limited to scattering/absorption e...In underwater optical wireless communication(UOWC),a channel is characterized by abundant scattering/absorption effects and optical turbulence.Most previous studies on UOWC have been limited to scattering/absorption effects.However,experiments in the literature indicate that underwater optical turbulence(UOT)can cause severe degradation of UOWC performance.In this paper,we characterize an UOWC channel with both scattering/absorption and UOT taken into consideration,and a spatial diversity receiver scheme,say a singleinput–multiple-output(SIMO) scheme,based on a light-emitting-diode(LED) source and multiple detectors is proposed to mitigate deep fading.The Monte Carlo based statistical simulation method is introduced to evaluate the bit-error-rate performance of the system.It is shown that spatial diversity can effectively reduce channel fading and remarkably extend communication range.展开更多
A portable analog lock-in amplifier capable of accurate phase detection is proposed in this paper. The proposed lock-in amplifier, which uses the dual-channel orthometric signals as the references to build the xy coor...A portable analog lock-in amplifier capable of accurate phase detection is proposed in this paper. The proposed lock-in amplifier, which uses the dual-channel orthometric signals as the references to build the xy coordinate system, can detect the relative phase between the input and x-axis based on trigonometric function. The sensitivity of the phase measurement reaches 0.014degree, and a detection precision of 0.1 degree is achieved. At the same time, the performance of the lock-in amplifier is verified in the high precision optical oxygen concentration detection. Experimental results reveal that the portable analog lock-in amplifier is accurate for phase detection applications. In the oxygen sensing experiments, 0.058% oxygen concentration resulted in 0.1 degree phase shift detected by the lock-in amplifier precisely. In addition, the lock-in amplifier is small and economical compared with the commercial lock-in equipments, so it can be easily integrated in many portable devices for industrial applications.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
The application of Golay pulse coding technique in spontaneous Brillouin-based distributed temperature sensor based on self-heterodyne detection of Rayleigh and Brillouin scattering is theoretically and experimentally...The application of Golay pulse coding technique in spontaneous Brillouin-based distributed temperature sensor based on self-heterodyne detection of Rayleigh and Brillouin scattering is theoretically and experimentally analyzed. The enhancement of system signal to noise ratio(SNR) and reduction of temperature measurement error provided by coding are characterized. By using 16-bit Golay coding, SNR can be improved by about 2.77 d B, and temperature measurement error of the 100 m heated fiber is reduced from 1.4 °C to 0.5 °C with a spatial resolution of 13 m. The results are believed to be beneficial for the performance improvement of self-heterodyne detection Brillouin optical time domain reflectometer.展开更多
This paper introduces a new modulation and direct detection scheme of optical phase shift keying (PSK) which is simple and practical in fiber optical communication. A phase modulator is used to modulate a continuous w...This paper introduces a new modulation and direct detection scheme of optical phase shift keying (PSK) which is simple and practical in fiber optical communication. A phase modulator is used to modulate a continuous wave (CW) laser source and return-to-zero (RZ) signal that is changed from the initial transmitting information is used to control a phase modulator to form a optical PSK signal. In the receiver terminal, just add a signal delayed a half of one bit to itself so that the initial information can be restored.展开更多
An optical hydrogen sulfide(H_2S) sensor based on wavelength modulation spectroscopy with the second harmonic(2f) corrected by the first harmonic(1f) signal(WMS-2f/1f) is developed using a distributed feedback(DFB) la...An optical hydrogen sulfide(H_2S) sensor based on wavelength modulation spectroscopy with the second harmonic(2f) corrected by the first harmonic(1f) signal(WMS-2f/1f) is developed using a distributed feedback(DFB) laser emitting at 1.578 μm and a homemade gas cell with 1-m-long optical path length. The novel sensor is constructed by an electrical cabinet and an optical reflecting and receiving end. The DFB laser is employed for targeting a strong H_2S line at 6 336.62 cm^(-1) in the fundamental absorption band of H_2S. The sensor performance, including the minimum detection limit and the stability, can be improved by reducing the laser intensity drift and common mode noise by means of the WMS-2f/1f technique. The experimental results indicate that the linearity and response time of the sensor are 0.999 26 and 6 s(in concentration range of 15.2—45.6 mg/m^3), respectively. The maximum relative deviation for continuous detection(60 min) of 30.4 mg/m^3 H_2S is 0.48% and the minimum detection limit obtained by Allan variance is 79 μg/m^3 with optimal integration time of 32 s. The optical H_2S sensor can be applied to environmental monitoring and industrial production, and it has significance for real-time online detection in many fields.展开更多
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.
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 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 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.
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.
基金supported by the National Natural Science Foundation of China under Grant No. 60577013the New Century Support Program for Talented Young Teachers in Universities, MOE (Ministry of Education of China), China
文摘Wavelength modulation technique (WMT) and wavelength sweep technique (WST) are introduced into intra-cavity absorption gas sensors (ICAGS) for low concentration gas detection. The optimized parameters of the system maximizing the signal-to-noise ratio (SNR) are found. Calibration of acetylene concentration and gas recognition are both realized.
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).
基金supported by the National Natural Science Foundation of China(Nos.81871505,61971026)the Fundamental Research Fund for the Central Universities(No.XK1802-4)+1 种基金the National Science and Technology Major Project(No.2018ZX10732101-001-009)the Research Fund to the Top Scientific and Technological Innovation Team from Beijing University of Chemical Technology(No.buctylkjcx06).
文摘To improve the performance of real-time recombinase polymerase amplification(RPA),a microfluidic system with active mixing is developed to optimize the reaction dynamics.Instead of adopting a single typical reaction chamber,a specific reactor including a relatively large chamber in center with two adjacent zig-zag channels at two sides is integrated into the microfluidic chip.Active mixing is achieved by driving the viscous reagent between the chamber and the channel back and forth periodically with an outside compact peristaltic pump.To avoid reagent evapora-tion,one end of the reactor is sealed with paraffin oil.A hand-held companion device is developed to facilitate real-time RPA amplification within 20 min.The whole area of the reactor is heated with a resistance heater to provide uniform reaction temperature.To achieve real-time monitoring,a compact fluorescence detection module is integrated into the hand-held device.A smartphone with custom application software is adopted to control the hand-held device and display the real-time fluorescence curves.The performances of two cases with and without active on-chip mixing are compared between each other by detecting African swine fever viruses.It has been demonstrated that,with active on-chip mixing,the amplification efficiency and detection sensitivity can be signifi-cantly improved.
基金Protect 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 Natural Science Foundation of Anhui Province,China(Grant No.KJHS2015B09)
文摘We suggest an experimental scheme that a single nitrogen-vacancy(NV) center coupled to a nearest neighbor ^13C nucleus as a sensor in diamond can be used to detect a static vector magnetic field. By means of optical detection magnetic resonance(ODMR) technique, both the strength and the direction of the vector field could be determined by relevant resonance frequencies of continuous wave(CW) and Ramsey spectrums. In addition, we give a method that determines the unique one of eight possible hyperfine tensors for an(NV–^13C) system. Finally, we propose an unambiguous method to exclude the symmetrical solution from eight possible vector fields, which correspond to nearly identical resonance frequencies due to their mirror symmetry about ^14N–Vacancy–^13 C(^14N–V–^13C) plane.
基金supported by a grant from the National Basic Research Program of China(973 Program)No.2011CB707506+1 种基金the Seed Fund from the Peking University Third Hospital of China,No.YZZ08-9-13the Linghu Fund from the Peking University Third Hospital of China,No.64508-01
文摘Axonal tracing is useful for detecting optic nerve injury and regeneration,but many commonly used methods cannot be used to observe axoplasmic flow and synaptic transmission in vivo.Manganese(Mn^2+)-enhanced magnetic resonance imaging(MEMRI) can be used for in vivo longitudinal tracing of the visual pathway.Here,we explored the dose response and time course of an intravitreal injection of Mn Cl2 for tracing the visual pathway in rabbits in vivo using MEMRI.We found that 2 m M Mn Cl2 enhanced images of the optic nerve but not the lateral geniculate body or superior colliculus,whereas at all other doses tested(5–40 m M),images of the visual pathway from the retina to the contralateral superior colliculus were significantly enhanced.The images were brightest at 24 hours,and then decreased in brightness until the end of the experiment(7 days).No signal enhancement was observed in the visual cortex at any concentration of Mn Cl2.These results suggest that MEMRI is a viable method for temporospatial tracing of the visual pathway in vivo.Signal enhancement in MEMRI depends on the dose of Mn Cl2,and the strongest signals appear 24 hours after intravitreal injection.
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 (No. 61704053)the Natural Science Foundation of Hunan Province (No. 2017JJ3032)the Fundamental Research Funds for the Central Universities of China。
文摘Optical edge detection, a part of image processing, plays an important role in extracting image information used in optical analog computation. In this Letter, we raise a new way to realize optical edge detection. This design is based on two liquid crystal polarization gratings with a period of 2.2 mm, which function as a spatial differentiator. We experimentally demonstrate broadband optical detection and real-time adjustable resolution.The proposed method takes advantage of the convenience to use, simple fabrication process, and real-time tunable resolution. It may guide more significant applications in the optical field and other practical scenarios like machine vision in computers.
基金supported by the National Key Basic Research Program of China (Grant No.2013CB329201)the National Natural Science Foundation of China (Grant Nos.61171066 and 61471332)the State Key Laboratory of Robotics
文摘In underwater optical wireless communication(UOWC),a channel is characterized by abundant scattering/absorption effects and optical turbulence.Most previous studies on UOWC have been limited to scattering/absorption effects.However,experiments in the literature indicate that underwater optical turbulence(UOT)can cause severe degradation of UOWC performance.In this paper,we characterize an UOWC channel with both scattering/absorption and UOT taken into consideration,and a spatial diversity receiver scheme,say a singleinput–multiple-output(SIMO) scheme,based on a light-emitting-diode(LED) source and multiple detectors is proposed to mitigate deep fading.The Monte Carlo based statistical simulation method is introduced to evaluate the bit-error-rate performance of the system.It is shown that spatial diversity can effectively reduce channel fading and remarkably extend communication range.
文摘A portable analog lock-in amplifier capable of accurate phase detection is proposed in this paper. The proposed lock-in amplifier, which uses the dual-channel orthometric signals as the references to build the xy coordinate system, can detect the relative phase between the input and x-axis based on trigonometric function. The sensitivity of the phase measurement reaches 0.014degree, and a detection precision of 0.1 degree is achieved. At the same time, the performance of the lock-in amplifier is verified in the high precision optical oxygen concentration detection. Experimental results reveal that the portable analog lock-in amplifier is accurate for phase detection applications. In the oxygen sensing experiments, 0.058% oxygen concentration resulted in 0.1 degree phase shift detected by the lock-in amplifier precisely. In addition, the lock-in amplifier is small and economical compared with the commercial lock-in equipments, so it can be easily integrated in many portable devices for industrial applications.
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 by the National Natural Science Foundation of China(No.61377088)the Natural Science Foundation of Hebei Province of China(Nos.E2015502053 and F2014502098)
文摘The application of Golay pulse coding technique in spontaneous Brillouin-based distributed temperature sensor based on self-heterodyne detection of Rayleigh and Brillouin scattering is theoretically and experimentally analyzed. The enhancement of system signal to noise ratio(SNR) and reduction of temperature measurement error provided by coding are characterized. By using 16-bit Golay coding, SNR can be improved by about 2.77 d B, and temperature measurement error of the 100 m heated fiber is reduced from 1.4 °C to 0.5 °C with a spatial resolution of 13 m. The results are believed to be beneficial for the performance improvement of self-heterodyne detection Brillouin optical time domain reflectometer.
文摘This paper introduces a new modulation and direct detection scheme of optical phase shift keying (PSK) which is simple and practical in fiber optical communication. A phase modulator is used to modulate a continuous wave (CW) laser source and return-to-zero (RZ) signal that is changed from the initial transmitting information is used to control a phase modulator to form a optical PSK signal. In the receiver terminal, just add a signal delayed a half of one bit to itself so that the initial information can be restored.
基金supported by the National Natural Science Foundation of China(Nos.60808020 and 61078041)the Natural Science Foundation of Tianjin(Nos.16JCQNJC02100,15JCYBJC51700 and 16JCYBJC15400)the National Science and Technology Support(No.2014BAH03F01)
文摘An optical hydrogen sulfide(H_2S) sensor based on wavelength modulation spectroscopy with the second harmonic(2f) corrected by the first harmonic(1f) signal(WMS-2f/1f) is developed using a distributed feedback(DFB) laser emitting at 1.578 μm and a homemade gas cell with 1-m-long optical path length. The novel sensor is constructed by an electrical cabinet and an optical reflecting and receiving end. The DFB laser is employed for targeting a strong H_2S line at 6 336.62 cm^(-1) in the fundamental absorption band of H_2S. The sensor performance, including the minimum detection limit and the stability, can be improved by reducing the laser intensity drift and common mode noise by means of the WMS-2f/1f technique. The experimental results indicate that the linearity and response time of the sensor are 0.999 26 and 6 s(in concentration range of 15.2—45.6 mg/m^3), respectively. The maximum relative deviation for continuous detection(60 min) of 30.4 mg/m^3 H_2S is 0.48% and the minimum detection limit obtained by Allan variance is 79 μg/m^3 with optimal integration time of 32 s. The optical H_2S sensor can be applied to environmental monitoring and industrial production, and it has significance for real-time online detection in many fields.