-
Optics Express Mar 2012Semiconductor saturable absorber mirror (SESAM) mode-locked thin disk lasers define the state-of-the-art performance for high average power and high pulse energy... (Review)
Review
Semiconductor saturable absorber mirror (SESAM) mode-locked thin disk lasers define the state-of-the-art performance for high average power and high pulse energy femtosecond laser oscillators. To date pulse energies above 30 µJ and average powers above 140 W have been demonstrated. In this paper we review the achievements of mode-locked thin disk lasers in terms of average power and pulse energy. Stable mode locking requires single transverse mode operation even at the highest average power, which is challenging and therefore addressed in more detail. We then summarize our expectations on the main challenges and limitiations for the next generation of mode-locked thin disk laser oscillators with an average power above 500 W and pulse energies in excess of 100 µJ.
Topics: Amplifiers, Electronic; Equipment Design; Equipment Failure Analysis; Lasers, Semiconductor; Miniaturization; Oscillometry
PubMed: 22453386
DOI: 10.1364/OE.20.007054 -
BMC Pulmonary Medicine Nov 2023Continuous positive airway pressure (CPAP) therapy has profound effects in obesity hypoventilation syndrome (OHS). Current therapy initiation focuses on upper airway...
BACKGROUND
Continuous positive airway pressure (CPAP) therapy has profound effects in obesity hypoventilation syndrome (OHS). Current therapy initiation focuses on upper airway patency rather than the assessment of altered respiratory mechanics due to increased extrapulmonary mechanical load.
METHODS
We aimed to examine the viability of intra-breath oscillometry in optimizing CPAP therapy for OHS. We performed intra-breath oscillometry at 10 Hz in the sitting and supine positions, followed by measurements at increasing CPAP levels (none-5-10-15-20 cmHO) in awake OHS patients. We plotted intra-breath resistance and reactance (Xrs) values against flow (V') and volume (V) to identify tidal expiratory flow limitation (tEFL).
RESULTS
Thirty-five patients (65.7% male) completed the study. We found a characteristic looping of the Xrs vs V' plot in all patients in the supine position revealing tEFL: Xrs fell with decreasing flow at end-expiration. Intra-breath variables representing expiratory decrease of Xrs became more negative in the supine position [end-expiratory Xrs (mean ± SD): -1.9 ± 1.8 cmHO·s·L sitting vs. -4.2 ± 2.2 cmHO·s·L supine; difference between end-expiratory and end-inspiratory Xrs: -1.3 ± 1.7 cmHO·s·L sitting vs. -3.6 ± 2.0 cmHO·s·L supine, p < 0.001]. Increasing CPAP altered expiratory Xrs values and loop areas, suggesting diminished tEFL (p < 0.001). 'Optimal CPAP' value (able to cease tEFL) was 14.8 ± 4.1 cmHO in our cohort, close to the long-term support average of 13.01(± 2.97) cmHO but not correlated. We found no correlation between forced spirometry values, patient characteristics, apnea-hypopnea index and intra-breath oscillometry variables.
CONCLUSIONS
tEFL, worsened by the supine position, can be diminished by stepwise CPAP application in most patients. Intra-breath oscillometry is a viable method to detect tEFL during CPAP initiation in OHS patients and tEFL is a possible target for optimizing therapy in OHS patients.
Topics: Humans; Male; Female; Continuous Positive Airway Pressure; Obesity Hypoventilation Syndrome; Oscillometry; Exhalation; Respiratory Mechanics
PubMed: 38017501
DOI: 10.1186/s12890-023-02777-x -
NeuroImage Feb 2022The goal of this paper is to present a theoretical and practical introduction to generalized eigendecomposition (GED), which is a robust and flexible framework used for...
The goal of this paper is to present a theoretical and practical introduction to generalized eigendecomposition (GED), which is a robust and flexible framework used for dimension reduction and source separation in multichannel signal processing. In cognitive electrophysiology, GED is used to create spatial filters that maximize a researcher-specified contrast. For example, one may wish to exploit an assumption that different sources have different frequency content, or that sources vary in magnitude across experimental conditions. GED is fast and easy to compute, performs well in simulated and real data, and is easily adaptable to a variety of specific research goals. This paper introduces GED in a way that ties together myriad individual publications and applications of GED in electrophysiology, and provides sample MATLAB and Python code that can be tested and adapted. Practical considerations and issues that often arise in applications are discussed.
Topics: Electroencephalography; Electrophysiological Phenomena; Humans; Magnetoencephalography; Multivariate Analysis; Oscillometry; Signal Processing, Computer-Assisted
PubMed: 34906717
DOI: 10.1016/j.neuroimage.2021.118809 -
American Journal of Veterinary Research Jul 2010To determine the intra- and interobserver variability of systolic arterial pressure (SAP) and diastolic arterial pressure (DAP) measurements obtained with 2 indirect... (Comparative Study)
Comparative Study
OBJECTIVE
To determine the intra- and interobserver variability of systolic arterial pressure (SAP) and diastolic arterial pressure (DAP) measurements obtained with 2 indirect methods in awake dogs and percentage of successful measurements.
ANIMALS
6 healthy conscious adult dogs.
PROCEDURES
4 observers with different levels of training measured SAP and DAP on 4 days by use of Doppler ultrasonography (DU) and high-definition oscillometry (HDO). The examinations were randomized. Measurements for each technique were recorded 5 consecutive times, and mean values (total, 720 measurements) were used for statistical analysis.
RESULTS
All within- and between-day coefficients of variation (CVs) for SAP were < 15% irrespective of the observer or method (HDO, 3.6% to 14.1%; DU, 4.1% to 12.4%). Conversely, half the CVs for DAP were > 15% with the highest within- and between-day CVs obtained by the least experienced observer by use of DU (19.5% and 25.9%, respectively). All attempts with HDO were successful, whereas DAP could not be measured by use of DU by the least experienced observer in 17% of attempts.
CONCLUSIONS AND CLINICAL RELEVANCE
SAP may be assessed in healthy dogs by use of DU and HDO with good repeatability and reproducibility after a short period of training. Conversely, the variability of DAP is higher and longer training is required to assess DAP via DU than via HDO.
Topics: Animals; Blood Pressure; Blood Pressure Determination; Consciousness; Dogs; Female; Humans; Observer Variation; Oscillometry; Reference Values; Sensitivity and Specificity; Ultrasonography, Doppler
PubMed: 20594078
DOI: 10.2460/ajvr.71.7.766 -
Pneumologie (Stuttgart, Germany) Aug 2009Impulse oscillometry (IOS) is a computer supported method for the measurement of complex mechanical airway characteristics. Bronchial obstructions can reliably be... (Review)
Review
Impulse oscillometry (IOS) is a computer supported method for the measurement of complex mechanical airway characteristics. Bronchial obstructions can reliably be diagnosed by IOS when more complex parameters such as frequency dependence of resistance (FDR) and lung reactance (X5) are evaluated in cases with more severe obstruction. Parameters of conventional methods like pneumotachography, spirometry, and bodyplethysmography show relatively low correlations due to the different measurement principles, not only in comparison to IOS, but also in between one another. The IOS is a convenient method for patients with a low dependency on cooperation for the evaluation of obstructive airway diseases complementary to the established standard methods. Furthermore, IOS may provide a sensitive screening tool for the early detection of bronchial obstructions not only in paediatrics but also in occupational medicine.
Topics: Algorithms; Diagnosis, Computer-Assisted; Humans; Lung Diseases; Oscillometry; Respiration Disorders; Respiratory Function Tests
PubMed: 19670105
DOI: 10.1055/s-0029-1214938 -
IEEE Transactions on Bio-medical... Jun 2016Most automatic cuff blood pressure (BP) measurement devices are based on oscillometry. These devices estimate BP from the envelopes of the cuff pressure oscillations...
OBJECTIVE
Most automatic cuff blood pressure (BP) measurement devices are based on oscillometry. These devices estimate BP from the envelopes of the cuff pressure oscillations using fixed ratios. The values of the fixed ratios represent population averages, so the devices may only be accurate in subjects with normal BP levels. The objective was to develop and demonstrate the validity of a patient-specific oscillometric BP measurement method.
METHODS
The idea of the developed method was to represent the cuff pressure oscillation envelopes with a physiologic model, and then estimate the patient-specific parameters of the model, which includes BP levels, by optimally fitting it to the envelopes. The method was investigated against gold standard reference BP measurements from 57 patients with widely varying pulse pressures. A portion of the data was used to optimize the patient-specific method and a fixed-ratio method, while the remaining data were used to test these methods and a current office device.
RESULTS
The patient-specific method yielded BP root-mean-square-errors ranging from 6.0 to 9.3 mmHg. On an average, these errors were nearly 40% lower than the errors of each existing method.
CONCLUSION
The patient-specific method may improve automatic cuff BP measurement accuracy.
SIGNIFICANCE
A patient-specific oscillometric BP measurement method was proposed and shown to be more accurate than the conventional method and a current device.
Topics: Aged; Blood Pressure Determination; Female; Humans; Male; Middle Aged; Oscillometry; Patient-Specific Modeling; Vascular Stiffness
PubMed: 26485351
DOI: 10.1109/TBME.2015.2491270 -
American Journal of Veterinary Research Aug 2011To compare the use of a semi-invasive vascular access port (VAP) device or noninvasive oscillometry versus invasive telemetry for blood pressure measurements in cats. (Comparative Study)
Comparative Study
OBJECTIVE
To compare the use of a semi-invasive vascular access port (VAP) device or noninvasive oscillometry versus invasive telemetry for blood pressure measurements in cats.
ANIMALS
6 healthy cats.
PROCEDURES
30 days before the study, all cats received an implanted telemeter and a VAP device. During normotension and experimentally induced hypertension, blood pressure was measured with the implanted devices and with noninvasive oscillometry at 4 time points.
RESULTS
Compared with invasive telemetry, VAP had a correlation coefficient from 0.8487 to 0.9972, and noninvasive oscillometry had a correlation coefficient from 0.7478 to 0.9689.
CONCLUSIONS AND CLINICAL RELEVANCE
Use of the VAP device and noninvasive oscillometry had a high degree of correlation with invasive telemetry as the gold standard for blood pressure measurement. Use of a VAP device resulted in a slightly higher degree of correlation, compared with noninvasive oscillometry.
Topics: Anesthesia; Animals; Blood Pressure; Blood Pressure Determination; Blood Pressure Monitors; Catheterization; Catheters, Indwelling; Cats; Female; Male; Oscillometry; Telemetry
PubMed: 21801057
DOI: 10.2460/ajvr.72.8.1015 -
Biomedical Engineering Online Dec 2005The purpose of this review is to examine the literature that has investigated mechanomyographic (MMG) amplitude and frequency responses during dynamic muscle actions. To... (Review)
Review
The purpose of this review is to examine the literature that has investigated mechanomyographic (MMG) amplitude and frequency responses during dynamic muscle actions. To date, the majority of MMG research has focused on isometric muscle actions. Recent studies, however, have examined the MMG time and/or frequency domain responses during various types of dynamic activities, including dynamic constant external resistance (DCER) and isokinetic muscle actions, as well as cycle ergometry. Despite the potential influences of factors such as changes in muscle length and the thickness of the tissue between the muscle and the MMG sensor, there is convincing evidence that during dynamic muscle actions, the MMG signal provides valid information regarding muscle function. This argument is supported by consistencies in the MMG literature, such as the close relationship between MMG amplitude and power output and a linear increase in MMG amplitude with concentric torque production. There are still many issues, however, that have yet to be resolved, and the literature base for MMG during both dynamic and isometric muscle actions is far from complete. Thus, it is important to investigate the unique applications of MMG amplitude and frequency responses with different experimental designs/methodologies to continually reassess the uses/limitations of MMG.
Topics: Animals; Electromyography; Humans; Muscle Contraction; Muscle Fibers, Skeletal; Muscle, Skeletal; Oscillometry; Stress, Mechanical
PubMed: 16364182
DOI: 10.1186/1475-925X-4-67 -
Respiratory Care Sep 2017The impulse oscillometry system (IOS) measures the impedance (Z) of the respiratory system, but proper interpretation of its results requires adequate reference values....
BACKGROUND
The impulse oscillometry system (IOS) measures the impedance (Z) of the respiratory system, but proper interpretation of its results requires adequate reference values. The objectives of this work were: (1) to validate the reference equations for the IOS published previously by our group and (2) to compare the adjustment of new available reference equations for the IOS from different countries in a sample of healthy children.
METHODS
Subjects were healthy 4-15-y-old children from the metropolitan area of Mexico City, who performed an IOS test. The functional IOS parameters obtained were compared with the predicted values from 12 reference equations determined in studies of different ethnic groups. The validation methods applied were: analysis of the differences between measured and predicted values for each reference equation; correlation and concordance coefficients; adjustment by Z-score values; percentage of predicted value; and the percentage of patients below the lower limit of normality or above the upper limit of normality.
RESULTS
Of the 224 participants, 117 (52.3%) were girls, and the mean age was 8.6 ± 2.3 y. The equations that showed the best adjustment for the different parameters were those from the studies by Nowowiejska et al (2008) and Gochicoa et al (2015). The equations proposed by Frei et al (2005), Hellinckx et al (1998), Kalhoff et al (2011), Klug and Bisgaard (1998), de Assumpção et al (2016), and Dencker et al (2006) overestimated the airway resistance of the children in our sample, whereas the equation of Amra et al (2008) underestimated it. In the analysis of the lower and upper limits of normality, Gochicoa et al equation was the closest, since 5% of subjects were below or above percentiles 5 and 95, respectively. The study found that, in general, all of the equations showed greater error at the extremes of the age distribution.
CONCLUSIONS
Because of the robust adjustment of the present study reference equations for the IOS, it can be recommended for both clinical and research purposes in our population. The differential adjustment of other equations underlines the need to obtain local reference values.
Topics: Adolescent; Airway Resistance; Child; Child, Preschool; Female; Healthy Volunteers; Humans; Lung; Male; Mexico; Oscillometry; Plethysmography, Impedance; Reference Standards; Reference Values; Reproducibility of Results; Respiratory Function Tests
PubMed: 28765495
DOI: 10.4187/respcare.05247 -
Chaos (Woodbury, N.Y.) Sep 2008Synchronization in neuronal systems is a new and intriguing application of dynamical systems theory. Why are neuronal systems different as a subject for synchronization?...
Synchronization in neuronal systems is a new and intriguing application of dynamical systems theory. Why are neuronal systems different as a subject for synchronization? (1) Neurons in themselves are multidimensional nonlinear systems that are able to exhibit a wide variety of different activity patterns. Their "dynamical repertoire" includes regular or chaotic spiking, regular or chaotic bursting, multistability, and complex transient regimes. (2) Usually, neuronal oscillations are the result of the cooperative activity of many synaptically connected neurons (a neuronal circuit). Thus, it is necessary to consider synchronization between different neuronal circuits as well. (3) The synapses that implement the coupling between neurons are also dynamical elements and their intrinsic dynamics influences the process of synchronization or entrainment significantly. In this review we will focus on four new problems: (i) the synchronization in minimal neuronal networks with plastic synapses (synchronization with activity dependent coupling), (ii) synchronization of bursts that are generated by a group of nonsymmetrically coupled inhibitory neurons (heteroclinic synchronization), (iii) the coordination of activities of two coupled neuronal networks (partial synchronization of small composite structures), and (iv) coarse grained synchronization in larger systems (synchronization on a mesoscopic scale).
Topics: Animals; Biological Clocks; Brain; Computer Simulation; Feedback; Humans; Models, Neurological; Nerve Net; Nonlinear Dynamics; Oscillometry; Synaptic Transmission
PubMed: 19045493
DOI: 10.1063/1.2949925