RESUMO
Conventional acute myocardial infarction (AMI) diagnosis is quite accurate and has proved its effectiveness. However, despite this, discovering more operative methods of this disease detection is underway. From this point of view, the application of exhaled air analysis for a similar diagnosis is valuable. The aim of the paper is to research effective machine learning algorithms for the predictive model for AMI diagnosis constructing, using exhaled air spectral data. The target group included 30 patients with primary myocardial infarction. The control group included 42 healthy volunteers. The 'LaserBreeze' laser gas analyzer (Special Technologies Ltd, Russia), based on the dual-channel resonant photoacoustic detector cell and optical parametric oscillator as the laser source, had been used. The pattern recognition approach was applied in the same manner for the set of extracted concentrations of AMI volatile markers and the set of absorption coefficients in a most informative spectral range 2.900 ± 0.125µm. The created predictive model based on the set of absorption coefficients provided 0.86 of the mean values of both the sensitivity and specificity when linear support vector machine (SVM) combined with principal component analysis was used. The created predictive model based on using six volatile AMI markers (C5H12, N2O, NO2, C2H4, CO, CO2) provided 0.82 and 0.93 of the mean values of the sensitivity and specificity, respectively, when linear SVM was used.
Assuntos
Testes Respiratórios , Infarto do Miocárdio , Acústica , Humanos , Lasers , Aprendizado de Máquina , Infarto do Miocárdio/diagnóstico , Análise Espectral , Máquina de Vetores de SuporteRESUMO
We report on efficient midinfrared difference-frequency generation (DFG) in orientation-patterned GaAs by intracavity mixing the signal and idler pulses of a narrowband nanosecond optical parametric oscillator based on periodically poled LiNbO3. The maximum average DFG output power reached 215 mW at 8.15 µm for a repetition rate of 35 kHz. The temperature tuning range spanned over 8026-8710 nm. The maximum overall conversion efficiency from 1 to 8 µm amounted to â¼1.3%.
RESUMO
We report on a narrowband, nonresonant periodically poled lithium niobate (PPLN) optical parametric oscillator using a volume Bragg grating (VBG) as the spectral narrowing element. Pumping by a Nd:YVO4 laser at 1.06 µm, a maximum output power of 4.75 W is achieved at a repetition rate of 20 kHz for a conversion efficiency of 47.5%. Both signal and idler spectra are narrowed to less than 2 nm, at good beam quality and stability.
RESUMO
An overall quantum conversion efficiency of 7.8% is achieved by intracavity mixing the signal and idler of a 1.064 µm pumped Rb:PPKTP optical parametric oscillator in BaGa4Se7. In this way, a pulse energy of â¼0.71 mJ is generated at â¼7 µm for a repetition rate of 100 Hz. Tuning of the mid-IR radiation is demonstrated by heating of the Rb:PPKTP crystal.
RESUMO
A BaGa4Se7 nanosecond optical parametric oscillator (OPO) shows extremely wide idler tunability in the mid-IR (2.7-17 µm) under 1.064 µm pumping. The â¼10 ns pulses at â¼7.2 µm have an energy of 3.7 mJ at 10 Hz. The pump-to-idler conversion efficiency for this wavelength reaches 5.9% with a slope of 6.5% corresponding to a quantum conversion efficiency or pump depletion of 40%.
RESUMO
A 1.064 µm pumped Rb:PPKTP optical parametric oscillator (OPO) generates mid-IR radiation by intracavity mixing the resonant signal and idler waves in AgGaSe2. The â¼6 ns pulses at â¼7 µm have an energy of 670 µJ at 100 Hz, equivalent to an average power of 67 mW. The overall quantum conversion efficiency from 1.064 µm amounts to 8%, and the power conversion efficiency is 1.2%.
RESUMO
A human exhaled air analysis by means of infrared (IR) laser photoacoustic spectroscopy is presented. Eleven healthy nonsmoking volunteers (control group) and seven patients with chronic obstructive pulmonary disease (COPD, target group) were involved in the study. The principal component analysis method was used to select the most informative ranges of the absorption spectra of patients' exhaled air in terms of the separation of the studied groups. It is shown that the data of the profiles of exhaled air absorption spectrum in the informative ranges allow identifying COPD patients in comparison to the control group.
Assuntos
Testes Respiratórios/métodos , Técnicas Fotoacústicas/métodos , Análise de Componente Principal/métodos , Doença Pulmonar Obstrutiva Crônica/diagnóstico , Espectrofotometria Infravermelho/métodos , Adulto , Humanos , Masculino , Pessoa de Meia-Idade , Doença Pulmonar Obstrutiva Crônica/metabolismo , Compostos Orgânicos Voláteis/análise , Compostos Orgânicos Voláteis/química , Adulto JovemRESUMO
A AgGaSe2 nonlinear crystal placed in a coupled cavity is intracavity pumped by the ~1.85-µm signal pulses of a 1.064-µm pumped Rb:PPKTP doubly-resonant optical parametric oscillator (OPO) operating at a repetition rate of 100 Hz. Using two samples cut for type-I and II phase-matching, the overall idler tunability of the singly-resonant AgGeSe2 OPO covers an unprecedented spectral range from 5.8 to ~18 µm in the mid-IR.