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Near-infrared spectroscopy for assessing microcirculation during laparoscopic gynaecological surgery under combined spinal-general anaesthesia or general anaesthesia alone: a randomised controlled trial
摘要： While pneumoperitoneum causes negative macrohaemodynamic effects, much less is known about microcirculatory effects of different anaesthetic techniques and laparoscopy. Therefore, we aimed to explore microcirculatory effects of combined spinal–general anaesthesia and laparoscopy, as measured by near-infrared spectroscopy over forearm and calf muscles utilising a 3-min ischemic challenge. Patients (n = 102) undergoing elective laparoscopic gynaecological surgery were randomised to receive general anaesthesia alone or in combination with high-dose or low-dose spinal analgesia (levobupivacaine 7.5 mg or 3.75 mg, respectively, plus sufentanil 2.5 μg). Primary outcomes were near-infrared spectroscopy derived parameters before general anaesthesia induction, 5 min after tracheal intubation, and 15 min after pneumoperitoneum commencement. General anaesthesia resulted in impaired post-ischaemic recovery rate in the forearm (p < 0.001, within all groups), which improved during laparoscopy. For the calf, before general anaesthesia induction, high and low dose spinal analgesia significantly slowed the post-ischaemic recovery compared to control (34 ± 16% min?1 and 36 ± 13% min?1 vs. 52 ± 27% min?1, respectively; p = 0.002 and p = 0.006). General anaesthesia abolished differences between the groups (24 ± 14% min?1 and 25 ± 12% min?1 vs. 27 ± 18% min?1), while during laparoscopy high-dose spinal analgesia further reduced the post-ischaemic recovery compared to low-dose spinal and control groups (p = 0.023 and p = 0.040, respectively). During gynaecological laparoscopy patients show impaired calf but maintain forearm microcirculatory function, regardless of the anaesthetic technique. Reduction in post-ischaemic recovery with high-dose spinal analgesia is explained by its sympatholytic effects: number of perfused capillaries is increased, leading to a haemodynamically more favourable state. Blood pressure is positively correlated with the post-ischaemic recovery rate in vascular beds not affected by spinal analgesia.
关键词： Haemodynamic,Microcirculation,Tissue oxygenation,Near-infrared spectroscopy,Laparoscopic surgery,Combined general spinal anaesthesia
更新于2025-09-19 17:13:59
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Sensitivity-Enhanced Fourier Transform Mid-Infrared Spectroscopy Using a Supercontinuum Laser Source
摘要： Fourier transform infrared (FT-IR) spectrometers have been the dominant technology in the field of mid-infrared (mid-IR) spectroscopy for decades. Supercontinuum laser sources operating in the mid-IR spectral region now offer the potential to enrich the field of FT-IR spectroscopy due to their distinctive properties, such as high-brightness, broadband spectral coverage and enhanced stability. In our contribution, we introduce this advanced light source as a replacement for conventional thermal emitters. Furthermore, an approach to efficient coupling of pulsed mid-IR supercontinuum sources to FT-IR spectrometers is proposed and considered in detail. The experimental part is devoted to pulse-to-pulse energy fluctuations of the applied supercontinuum laser, performance of the system, as well as the noise and long-term stability. Comparative measurements performed with a conventional FT-IR instrument equipped with a thermal emitter illustrate that similar noise levels can be achieved with the supercontinuum-based system. The analytical performance of the supercontinuum-based FT-IR spectrometer was tested for a concentration series of aqueous formaldehyde solutions in a liquid flow cell (500 mm path length) and compared with the conventional FT-IR (130 mm path length). The results show a four-times-enhanced detection limit due to the extended path length enabled by the high brightness of the laser. In conclusion, FT-IR spectrometers equipped with novel broadband mid-IR supercontinuum lasers could outperform traditional systems providing superior performance, e.g., interaction path lengths formerly unattainable, while maintaining low noise levels known from highly stable thermal emitters.
关键词： Mid-infrared spectroscopy,mid-IR,supercontinuum laser source,Fourier transform infrared spectroscopy,FT-IR
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Breath Signatures of Cerebral Palsy Patients Revealed with Mid-Infrared FTIR Spectroscopy
摘要： In the absence of “broadband” objective medical diagnostics, photonics technologies are now considered as a promising way to establish it. For example, being applied to human breath, under right conditions they should allow for unambiguous identification of metabolites circulating in blood and released in lungs alveoli as volatile organic compounds (VOCs). Nowadays, tremendous progress is achieved in developing laser-based mid-infrared spectrometers highly sensitive to VOCs [1,2]. Still, the spectral range covered by the laser spectrometers demonstrated so far, and signal-to-nose ratio (SNR) are not superior to conventional FTIR spectrometers based on thermal source. A significant amount of water vapour in breath is another, though general for all techniques, severe problem for VOCs detection. In addition to the detection, data analysis should be advanced in order to accurately compare healthy and diseased cohorts under study.
关键词： cerebral palsy,FTIR spectroscopy,mid-infrared spectroscopy,breath analysis,VOCs
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Infrared 1000-nm-Supercontinuum by Means of Self-Frequency Shift of Raman Solitons Supported by Four-Wave Mixing
摘要： Infrared spectroscopy is deployed in various fields of science and technology such as organic and inorganic chemistry, monitoring of greenhouse gases, food industry, artwork conservation, and analysis of polymers and semiconductor microelectronics [1]. The supercontinuum generation based on self-frequency shift (SFS) of Raman solitons in various optical fibres is a technology to provide promising spectra for infrared spectroscopy applications. However, these spectra are restricted in range due to the limitations of Raman gain spectrum and optical absorption in silica fibres beyond the C band. Thus, they hardly spread over 300 nm if starting from around 1550 nm [2]. However, as I show here using numerical simulations of the Generalised Nonlinear Schr?dinger Equation, if the SFS of Raman solitons is supported by the effect of four-wave mixing (FWM), the range of such supercontinuum can increase up to 1000 nm counteracting the limits of Raman gain and optical absorption.
关键词： four-wave mixing,Infrared spectroscopy,self-frequency shift,Raman solitons,supercontinuum generation
更新于2025-09-16 10:30:52
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[IEEE 2019 10th Workshop on Hyperspectral Imaging and Signal Processing: Evolution in Remote Sensing (WHISPERS) - Amsterdam, Netherlands (2019.9.24-2019.9.26)] 2019 10th Workshop on Hyperspectral Imaging and Signal Processing: Evolution in Remote Sensing (WHISPERS) - Discrete Wavelengths Screening Method for the Near-Infrared Spectroscopic Analysis of Serum Glucose
摘要： The spectral wavelength model optimisation is a fundamental core technology of near-infrared (NIR) spectroscopic analysis. An integrated optimisation method for wavelength selection of serum glucose analysis was proposed in the present study. A global parameter optimisation platform of Norris derivative filter (NDF) was established to achieve the most suitable equidistant preprocessing. combination-partial least squares (EC-PLS) combined with wavelength step-by-step phase-out-PLS (WSP-PLS) was proposed to achieve large-scale screening of discrete wavelengths model for serum glucose. As a result, the combination of eight wavelengths (1583, 1695, 1733, 1816, 1860, 2125, 2340, 2376 nm) was selected and a good prediction effect was obtained. It can provide a valuable reference for non-invasive blood glucose detection and designing dedicated spectrometers. The proposed WSP-PLS can optimise any wavelength model obtained by certain optimisation strategies, improve the prediction performance and reduce the wavelength model complexity. We believe it will have a wider application.
关键词： Near-infrared spectroscopy analysis,equidistant combination PLS,serum glucose,wavelength step-by-step phase-out-PLS,discrete wavelength screening
更新于2025-09-16 10:30:52
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Electron Population Dynamics in Optically Pumped Asymmetric Coupled Ge/SiGe Quantum Wells: Experiment and Models
摘要： n-type doped Ge quantum wells with SiGe barriers represent a promising heterostructure system for the development of radiation emitters in the terahertz range such as electrically pumped quantum cascade lasers and optically pumped quantum fountain lasers. The nonpolar lattice of Ge and SiGe provides electron–phonon scattering rates that are one order of magnitude lower than polar GaAs. We have developed a self-consistent numerical energy-balance model based on a rate equation approach which includes inelastic and elastic inter- and intra-subband scattering events and takes into account a realistic two-dimensional electron gas distribution in all the subband states of the Ge/SiGe quantum wells by considering subband-dependent electronic temperatures and chemical potentials. This full-subband model is compared here to the standard discrete-energy-level model, in which the material parameters are limited to few input values (scattering rates and radiative cross sections). To provide an experimental case study, we have epitaxially grown samples consisting of two asymmetric coupled quantum wells forming a three-level system, which we optically pump with a free electron laser. The benchmark quantity selected for model testing purposes is the saturation intensity at the 1→3 intersubband transition. The numerical quantum model prediction is in reasonable agreement with the experiments and therefore outperforms the discrete-energy-level analytical model, of which the prediction of the saturation intensity is off by a factor 3.
关键词： silicon–germanium heterostructures,intersubband photoluminescence,optical pumping,intersubband transitions,electron–phonon interaction,infrared spectroscopy,quantum wells,free electron laser,terahertz quantum cascade laser
更新于2025-09-16 10:30:52
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Proton release process during the S2-to-S3 transition of photosynthetic water oxidation as revealed by the pH dependence of kinetics monitored by time-resolved infrared spectroscopy
摘要： Photosynthetic water oxidation takes place at the Mn4CaO5 cluster in photosystem II via light driven cycle of intermediates called S states (S0–S4). Clarifying how electron and proton transfer reactions are coupled with each other in the S2→S3 transition, which occurs just before the O-O bond formation, is crucial to understand the water oxidation mechanism. Here, we investigated the pH dependence of the kinetics of the S2→S3 transition using time-resolved infrared (TRIR) spectroscopy to identify the proton release phase in this transition. TRIR measurements of YD-less PSII core complexes from the D2-Y160F mutant of Thermosynechococcus elongatus showed that the last phase in this transition (τ = ~350 μs at pH 6) was strongly pH dependent, and its time constant at pH 5 was larger than that at pH 8 by a factor of more than three. In contrast, the earlier phase with a ~100 μs time constant was virtually independent of pH. These results strongly support the view that proton release is a rate-limiting step of the proton-coupled electron transfer in the last phase of the S2→S3 transition. This proton release enables electron transfer by removing an excessive positive charge from the catalytic center and hence lowering its redox potential.
关键词： Mn4CaO5 cluster,proton-coupled electron transfer,S2→S3 transition,photosynthetic water oxidation,time-resolved infrared spectroscopy
更新于2025-09-16 10:30:52
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Near-infrared spectroscopy coupled with chemometrics algorithms for the quantitative determination of the germinability of Clostridium perfringens in four different matrices
摘要： Clostridium perfringens (C. perfringens) has the ability to form metabolically-dormant spores that can survive food preservation processes and cause food spoilage and foodborne safety risks upon germination outgrowth. This study was conducted to investigate the effects of different AGFK concentrations (0, 50, 100, 200 mM/mL) on the spore germination of C. perfringens in four matrices, including Tris-HCl, FTG, milk, and chicken soup. C. perfringens spore germinability was investigated using near infrared spectroscopy (NIRS) combined with chemometrics. The spore germination rate (S), the OD600%, and the Ca2+-DPA% were measured using traditional spore germination methods. The results of spore germination assays showed that the optimum germination rate was obtained using 100 mM/L concentrations of AGFK in the FTG medium, and the S, OD600% and Ca2+-DPA% were 98.6%, 59.3% and 95%, respectively. The best prediction models for the S, OD600% and Ca2+-DPA% were obtained using SNV as the preprocessing method for the original spectra, with the competitive adaptive weighted resampling method (CARS) as the characteristic variables related to the selected spore germination methods from NIRS data. The results of the S showed that the optimum model was built by CARS-PLSR (RMSEV = 0.745, Rc = 0.897, RMSEP = 0.769, Rp = 0.883). For the OD600%, interval partial least squares regression (CARS -siPLS) was performed to optimize the models. The calibration yielded acceptable results (RMSEV = 0.218, Rc = 0.879, RMSEP = 0.257, Rp = 0.845). For the Ca2+-DPA%, the optimum model with CARS -siPLS yielded acceptable results (RMSEV = 44.7, Rc = 0.883, RMSEP = 50.2, Rp = 0.872). This indicated that quantitative determinations of the germinability of C. perfringens spores using NIR technology is feasible. A new method based on NIR was provided for rapid, automatic, and non-destructive determination of the germinability of C. perfringens spores.
关键词： Near infrared spectroscopy,Clostridium perfringens,Spore germination,chemometrics,AGFK,different matrices
更新于2025-09-16 10:30:52
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Polarization Dependent Reflectivity and Transmission for Cd1-Xznxte/GaAs(001) Epifilms in the Far-Infrared and Near-Infrared to Ultraviolet Region
摘要： The results of a comprehensive experimental and theoretical study is reported to empathize the optical properties of binary GaAs, ZnTe, CdTe and ternary Cd1-xZnxTe (CZT) alloys in the two energy regions: (i) far-infrared (FIR), and (ii) near-infrared (NIR) to ultraviolet (UV). A high resolution Fourier transform infrared spectrometer is used to assess the FIR response of GaAs, ZnTe, CdTe and CZT alloys in the entire composition 1.0 ≥ x ≥ 0 range. Accurate model dielectric functions are established appositely to extort the optical constants of the binary materials. The simulated dielectric functions are meticulously appraised in the FIR → NIR → UV energy range by comparing them against the existing spectroscopic FTIR and ellipsometry data. These outcomes are expended eloquently for evaluating the polarization dependent reflectivity R(λ) and transmission T(λ) spectra of ultrathin CZT/GaAs (001) epifilms. A reasonably accurate assessment of the CZT film thickness by reflectivity study has offered a credible testimony for characterizing any semiconducting epitaxially grown nanostructured materials of technological importance.
关键词： Dielectric functions,Fourier transform infrared spectroscopy,Transmission,Reflectivity,Ellipsometry,Epilayers
更新于2025-09-16 10:30:52
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Enhanced RDX Detection Studies on Various Types of Substrates via Tunable Quantum Cascade Laser Spectrometer Coupled with Grazing Angle Probe
摘要： Owing to scientific advances in the field of materials sciences and engineering, researchers have developed new energy sources used for spectroscopic applications and measurements of properties resulting from the interaction of matter and electromagnetic radiation in the mid-infrared (MIR) region. MIR lasers, such as quantum cascade lasers (QCLs), used for spectroscopy have quickly found numerous applications in a wide cadre of IR techniques. This provides the opportunity to study properties of highly energetic materials (HEM), among many other applications. MIR laser spectroscopy based detection experiments of HEMs were carried out using a QCL optically coupled to compact grazing angle probe mount (QCL-GAP) enabling reflection-absorption infrared spectroscopy (RAIRS) measurements of thin films of HEMs. A saturated solution of RDX in acetone was prepared, and aliquots of subsequent dilutions of the stock solutions were transferred to test surfaces for QCL-GAP back-reflectance measurements. RDX reflectance signals were monitored as function as the decreasing surface concentration until the signal/noise was ~ 3. Stainless steel (SS) plates were used as reflective substrates, and anodized aluminum (AN-Al), cardboard, and Teflon were used as non-reflective (matte) substrates. Using generated calibration curves a low limit of detection (LOD) of 1.7 ng/cm2 for RDX/SS and 95 μg/cm2 for RDX/AN-Al were found. Based on the area of laser spot (0.3 cm2) we conclude the minimum masses detected were 490 pg (RDX/SS) and 28 μg (RDX/AN-Al).
关键词： Quantum Cascade Laser,RDX detection,Grazing Angle Probe,Highly Energetic Materials,Mid-Infrared Spectroscopy
更新于2025-09-16 10:30:52