- Incoherent broadband cavity-enhanced absorption spectroscopy for sensitive measurement of nutrients and microalgae. [Journal Article]Appl Opt. 2022 Apr 20; 61(12):3400-3408.AO
- Incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) can achieve sensitive measurements at trace concentrations for liquid phase marine samples. The IBBCEAS system consists of a cavity-enhancement module (CEM) and a transmission hyperspectral module (THM). The CEM has cavity-enhancement factors up to 78 at 550 nm. Measurements were obtained over a wide wavelength range (420-640 …
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- Multifractal analysis of social media use in financial markets. [Journal Article]
- We analyze the nonlinear properties of social media activity(SMA) using the multifractal detrended fluctuation analysis (MF-DFA) method. Social media data related to the stock market are gathered from social media platforms. Using data on over 2000 firms in the Korean stock market for 2018-2020, we study social media activity and its differences to evaluate associated nonlinear and statistical pr…
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- Multifractal analysis of chest CT images of patients with the 2019 novel coronavirus disease (COVID-19). [Journal Article]
- The present study was done to evaluate chest computed tomography (CT) images of patients with 2019 novel coronavirus disease (COVID-19) by multifractal technique as a new method to find a way for comparing lung infection quantitatively and identifying progression pattern of the disease. The multifractal spectra extracted from analysis of CT images showed that these spectra were correlated with lu…
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- Study of a Mode Separation Due to Polarization Existing in a Cavity-Enhanced Absorption Spectroscopy. [Journal Article]
- A special phenomenon of resonance mode separation is observed during the study of a high sensitivity folded-cavity enhanced absorption spectroscopy for the measurement of trace gases. The phenomenon affects the measurement of gas absorption spectrum in the cavity. This resonant mode separation phenomenon of the resonant cavity is different from the resonant modes previously observed in linear-cav…
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- A Prototype Evanescent Wave-Coupled Cavity Ring-down Spectrometer for Probing Real-Time Aggregation Kinetics of Gold and Silver Nanoparticles. [Journal Article]Anal Chem. 2020 03 03; 92(5):3998-4005.AC
- We report on the development of a simple, linear optical cavity-based system combining evanescent wave (EW) with high-sensitive cavity ring-down spectroscopy (CRDS) technique using a diode laser at 644 nm and a right-angled prism for evanescent field generation on prism surface. We characterized the setup in detail and achieved an optimum ring-down time of 159.4 ns and a minimum absorption coeffi…
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- Evaluations of acoustic damping performances of double-layer in-duct perforated plates at low Mach and Helmholtz number. [Journal Article]J Acoust Soc Am. 2019 Nov; 146(5):3512.JA
- In this work, acoustic damping performances of double-layer in-duct perforated plates are studied at low Mach (Ma) and Helmholtz number (He) to evaluate the effects of (1) Ma, (2) the porosities (i.e., open-area ratio) σ1 and σ2 of the front and back plates, and (3) the axial distance Lc between these two plates. The orifices' damping is characterized by sound absorption coefficient α denoting th…
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- Sensitive detection of HO radicals produced in an atmospheric pressure plasma using Faraday rotation cavity ring-down spectroscopy. [Journal Article]
- Cavity ring-down spectroscopy (CRDS) is a well-established, highly sensitive absorption technique whose sensitivity and selectivity for trace radical sensing can be further enhanced by measuring the polarization rotation of the intracavity light by the paramagnetic samples in the presence of a magnetic field. In this paper, we highlight the use of this Faraday rotation cavity ring-down spectrosco…
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- Application of Near-Infrared Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS) to the Detection of Ammonia in Exhaled Human Breath. [Journal Article]
- The qualitative and quantitative analysis to trace gas in exhaled human breath has become a promising technique in biomedical applications such as disease diagnosis and health status monitoring. This paper describes an application of a high spectral resolution optical feedback cavity enhanced absorption spectroscopy (OF-CEAS) for ammonia detection in exhaled human breath, and the main interferenc…
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- Descriptions of Entropy with Fractal Dynamics and Their Applications to the Flow Pressure of Centrifugal Compressor. [Journal Article]
- In this study, some important intrinsic dynamics have been captured after analyzing the relationships between the dynamic pressure at an outlet of centrifugal compressor and fractal characteristics, which is one of powerful descriptions in entropy to measure the disorder or complexity in the nonlinear dynamic system. In particular, the fractal dynamics of dynamic pressure of the flow is studied, …
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- The effect of dental LED light-curing unit photoactivation mode on 3D surface morphology of dental nanocomposites evaluated by two-dimensional multifractal detrended fluctuation analysis. [Journal Article]Microsc Res Tech. 2018 Oct; 81(10):1223-1230.MR
- The objective of this study was to evaluate the effect of two photoactivation modes of dental LED light-curing unit (LCUs) (conventional and "Soft Start" mode) on surface texture parameters of two dental resin-based nanocomposites. LED LCUs were considered as standard light-curing devices in contemporary dental practice. Atomic force microscopy (AFM) was applied to investigate surface morphology …
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- Analysis of normal human retinal vascular network architecture using multifractal geometry. [Journal Article]
- CONCLUSIONS: The multifractal analysis of fundus photographs may be used as a quantitative parameter for the evaluation of the complex three-dimensional structure of the retinal microvasculature as a potential marker for early detection of topological changes associated with retinal diseases.
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- Supercontinuum high-speed cavity-enhanced absorption spectroscopy for sensitive multispecies detection. [Journal Article]
- Cavity-enhanced absorption spectroscopy is promising for many applications requiring a very high concentration sensitivity but often accompanied by low temporal resolution. In this Letter, we demonstrate a broadband cavity-enhanced absorption spectrometer capable of detection rates of up to 50 kHz, based on a spatially coherent supercontinuum (SC) light source and an in-house-built, high-speed ne…
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- Cavity-Enhanced Immunoassay Measurements in Microtiter Plates Using BBCEAS. [Journal Article]
- We report on the first detailed use of broadband cavity enhanced absorption spectroscopy (BBCEAS) as a detection system for immunoassay. A vertical R ≥ 0.99 optical cavity was integrated with a motorized XY stage, which functioned as a receptacle for 96-well microtiter plates. The custom-built cavity enhanced microplate reader was used to make measurements on a commercially available osteocalcin …
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- The self- and foreign-absorption continua of water vapor by cavity ring-down spectroscopy near 2.35 μm. [Journal Article]Phys Chem Chem Phys. 2015 Jul 21; 17(27):17762-70.PC
- The room temperature self- and foreign-continua of water vapor have been measured near 4250 cm(-1) with a newly developed high sensitivity cavity ring down spectrometer (CRDS). The typical sensitivity of the recordings is αmin≈ 6 × 10(-10) cm(-1) which is two orders of magnitude better than previous Fourier transform spectroscopy (FTS) measurements in the spectral region. The investigated spectra…
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- Multifractal Analysis and Relevance Vector Machine-Based Automatic Seizure Detection in Intracranial EEG. [Journal Article]
- Automatic seizure detection technology is of great significance for long-term electroencephalogram (EEG) monitoring of epilepsy patients. The aim of this work is to develop a seizure detection system with high accuracy. The proposed system was mainly based on multifractal analysis, which describes the local singular behavior of fractal objects and characterizes the multifractal structure using a …
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- THz quartz-enhanced photoacoustic sensor for H₂S trace gas detection. [Journal Article]
- We report on a quartz-enhanced photoacoustic (QEPAS) gas sensing system for hydrogen sulphide (H₂S) detection. The system architecture is based on a custom quartz tuning fork (QTF) optoacoustic transducer with a novel geometry and a quantum cascade laser (QCL) emitting 1.1 mW at a frequency of 2.913 THz. The QTF operated on the first flexion resonance frequency of 2871 Hz, with a quality factor Q…
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- Characteristic times of biased random walks on complex networks. [Journal Article]
- We consider degree-biased random walkers whose probability to move from a node to one of its neighbors of degree k is proportional to k(α), where α is a tuning parameter. We study both numerically and analytically three types of characteristic times, namely (i) the time the walker needs to come back to the starting node, (ii) the time it takes to visit a given node for the first time, and (iii) t…
- High sensitivity liquid phase measurements using broadband cavity enhanced absorption spectroscopy (BBCEAS) featuring a low cost webcam based prism spectrometer. [Journal Article]Analyst. 2013 Nov 07; 138(21):6372-9.A
- Cavity enhanced techniques enable high sensitivity absorption measurements in the liquid phase but are typically more complex, and much more expensive, to perform than conventional absorption methods. The latter attributes have so far prevented a wide spread use of these methods in the analytical sciences. In this study we demonstrate a novel BBCEAS instrument that is sensitive, yet simple and ec…
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- Linear cavity optical-feedback cavity-enhanced absorption spectroscopy with a quantum cascade laser. [Journal Article]
- A cw distributed feedback quantum cascade laser (DFB-QCL) coupled to a two-mirror linear optical cavity has been used to successfully demonstrate optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) at 5.5 μm. The noise-equivalent absorption coefficient, α(min), was 2.4×10(-8) cm(-1) for 1 s averaging, limited by etalon-fringing. The temporal stability of the instrument allows NO de…
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- The accuracy of the Gaussian-and-finite-element-Coulomb (GFC) method for the calculation of Coulomb integrals. [Journal Article]J Chem Phys. 2013 Aug 07; 139(5):054114.JC
- We analyze the accuracy of the Coulomb energy calculated using the Gaussian-and-finite-element-Coulomb (GFC) method. In this approach, the electrostatic potential associated with the molecular electronic density is obtained by solving the Poisson equation and then used to calculate matrix elements of the Coulomb operator. The molecular electrostatic potential is expanded in a mixed Gaussian-finit…
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- Extending high-finesse cavity techniques to the far-infrared. [Journal Article]
- Sensitive spectroscopic techniques involving high-finesse Fabry-Perot resonators are widely used in the microwave and near-infrared spectral regimes, but hardware limitations have hindered their extension to far-infrared wavelengths. While there is no theoretical limit to the frequency region where cavity-enhanced techniques are practical, the sensitivity of these methods does depend explicitly o…
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- Multipass millimeter/submillimeter spectrometer to probe dissociative reaction dynamics. [Journal Article]J Phys Chem A. 2013 Oct 03; 117(39):9548-54.JP
- We present here the instrument design and first experimental results from a multipass millimeter/submillimeter spectrometer designed to probe dissociative reaction dynamics. This work focuses on benchmarking the instrument performance through detection of the CH3O and H2CO products from methanol dissociation induced by a high-voltage plasma discharge. Multiple rotational lines from CH3O and H2CO …
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- The absorption spectrum of D2: ultrasensitive cavity ring down spectroscopy of the (2-0) band near 1.7 μm and accurate ab initio line list up to 24,000 cm(-1). [Journal Article]J Chem Phys. 2012 May 14; 136(18):184309.JC
- Eleven very weak electric quadrupole transitions Q(2), Q(1), S(0)-S(8) of the first overtone band of D(2) have been measured by very high sensitivity CW-cavity ring down spectroscopy (CRDS) between 5850 and 6720 cm(-1). The noise equivalent absorption of the recordings is on the order of α(min) ≈ 3 × 10(-11) cm(-1). By averaging a high number of spectra, the noise level was lowered to α(min) ≈ 4 …
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- The absorption spectrum of H2: CRDS measurements of the (2-0) band, review of the literature data and accurate ab initio line list up to 35000 cm(-1). [Journal Article]
- Five very weak transitions-O(2), O(3), O(4), O(5) and Q(5)-of the first overtone band of H(2) are measured by very high sensitivity CW-Cavity Ring Down Spectroscopy (CRDS) between 6900 and 7920 cm(-1). The noise equivalent absorption of the recordings is on the order of α(min)≈ 5 × 10(-11) cm(-1) allowing for the detection of the O(5) transition with an intensity of 1.1 × 10(-30) cm per molecule,…
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- Broadband cavity-enhanced absorption spectroscopy for real time, in situ spectral analysis of microfluidic droplets. [Journal Article]
- Broadband cavity-enhanced absorption spectroscopy has been used to record, in real time, the absorption spectrum of microlitre volume aqueous phase droplets within a microfluidic chip assembly. Using supercontinuum radiation and broadband coated external mirrors, the full visible spectrum (430 nm < λ < 700 nm) of each passing droplet is acquired in situ at high repetition rates (273 Hz/3.66 ms ac…
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- Effects of molting on the visual acuity of the blue crab, Callinectes sapidus. [Journal Article]
- In crustaceans with compound eyes, the corneal lens of each facet is part of the exoskeleton and thus shed during molting. Here we used an optomotor assay to evaluate the impact of molting on visual acuity (as measured by the minimum resolvable angle, α(min)) in the female blue crab, Callinectes sapidus. We found that visual acuity decreases substantially in the days prior to molting and is gradu…
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- The 1.28 μm transparency window of methane (7541-7919 cm⁻¹): empirical line lists and temperature dependence (80 K-300 K). [Journal Article]Phys Chem Chem Phys. 2011 May 07; 13(17):7985-96.PC
- The high sensitivity absorption spectra of methane at room temperature and 80 K were recorded by CW-Cavity Ring Down Spectroscopy in the 1.28 μm transparency window (7541-7919 cm(-1)). The empirical line parameters of 7690 and 5794 transitions were retrieved at room temperature and at 80 K, respectively. The achieved sensitivity (α(min)≈ 10(-10) cm(-1)) allowed detecting transitions with intensit…
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- Demonstration of cavity enhanced FTIR spectroscopy using a femtosecond laser absorption source. [Journal Article]
- A proof of principle experiment was performed by recording the cavity enhanced absorption spectrum of the weak b-X transition of molecular oxygen in the atmosphere using a Ti:Sa femtosecond laser as an absorption source and a high resolution continuous scan Fourier transform interferometer. The cavity was mode matched and either continuously scanned or stabilized at the so-called magic point. An …
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- Mid-infrared ethene detection using difference frequency generation in a quasi-phase-matched LiNbO3 waveguide. [Journal Article]
- A periodically poled LiNbO3 (PPLN) crystal waveguide has been used to produce up to 200 microW of mid-infrared light around 3081 cm(-1) with a wide tunability range of approximately 35 cm(-1). Two commercial near-infrared diode lasers at 1.064 microm (pump) and 1.583 microm (signal) are mixed in a nonlinear optical crystal to achieve difference frequency generation. The 48 mm long directly-bonded…
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- Liquid-phase broadband cavity enhanced absorption spectroscopy (BBCEAS) studies in a 20 cm cell. [Journal Article]Analyst. 2009 Sep; 134(9):1887-95.A
- Sensitive liquid-phase measurements have been made in a 20 cm cell using broadband cavity enhanced absorption spectroscopy (BBCEAS). The cavity was formed by two high reflectivity mirrors which were in direct contact with the liquid-phase analytes. Careful choice of solvent was required to minimise the effect of background solvent absorptions. Measurements were made on the broad absorber Sudan bl…
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