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Interpreting intramuscular electromyography (iEMG) signals for diagnosing and quantifying the severity of lumbosacral radiculopathy is challenging due to the subjective evaluation of signals. To address this limitation, a clinical decision support system (CDSS) was developed for the diagnosis and quantification of the severity of lumbosacral radiculopathy based on intramuscular electromyography (iEMG) signals. The CDSS uses the EMG interference pattern method (QEMG IP) to directly extract features from the iEMG signal and provide a quantitative expression of injury severity for each muscle and overall radiculopathy severity. From 126 time and frequency domain features, a set of five features, including the crest factor, mean absolute value, peak frequency, zero crossing count, and intensity, were selected. These features were derived from raw iEMG signals, empirical mode decomposition, and discrete wavelet transform, and the wrapper method was utilized to determine the most significant features. The CDSS was trained and tested on a dataset of 75 patients, achieving an accuracy of 93.3%, sensitivity of 93.3%, and specificity of 96.6%. The system shows promise in assisting physicians in diagnosing lumbosacral radiculopathy with high accuracy and consistency using iEMG data. The CDSS's objective and standardized diagnostic process, along with its potential to reduce the time and effort required by physicians to interpret EMG signals, makes it a potentially valuable tool for clinicians in the diagnosis and management of lumbosacral radiculopathy. Future work should focus on validating the system's performance in diverse clinical settings and patient populations.

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INTRODUCTION: The EMG filling factor is an index to quantify the degree to which an EMG signal has been filled. Here, we tested the validity of such index to analyse the EMG filling process as contraction force was slowly increased. METHODS: Surface EMG signals were recorded from the quadriceps muscles of healthy subjects as force was gradually increased from 0 to 40% MVC. The sEMG filling process was analyzed by measuring the EMG filling factor (calculated from the non-central moments of the rectified sEMG). RESULTS: (1) As force was gradually increased, one or two prominent abrupt jumps in sEMG amplitude appeared between 0 and 10% of MVC force in all the vastus lateralis and medialis. (2) The jumps in amplitude were originated when a few large-amplitude MUPs, clearly standing out from previous activity, appeared in the sEMG signal. (3) Every time an abrupt jump in sEMG amplitude occurred, a new stage of sEMG filling was initiated. (4) The sEMG was almost completely filled at 2-12% MVC. (5) The filling factor decreased significantly upon the occurrence of an sEMG amplitude jump, and increased as additional MUPs were added to the sEMG signal. (6) The filling factor curve was highly repeatable across repetitions. CONCLUSIONS: It has been validated that the filling factor is a useful, reliable tool to analyse the sEMG filling process. As force was gradually increased in the vastus muscles, the sEMG filling process occurred in one or two stages due to the presence of abrupt jumps in sEMG amplitude.

Asunto(s)

Músculo Esquelético , Músculo Cuádriceps , Humanos , Electromiografía , Voluntarios Sanos

RESUMEN

Josephson junctions (JJs) in the presence of a magnetic field exhibit qualitatively different interference patterns depending on the spatial distribution of the supercurrent through the junction. In JJs based on two-dimensional topological insulators (2DTIs), the electrons/holes forming a Cooper pair (CP) can either propagate along the same edge or be split into the two edges. The former leads to a SQUID-like interference pattern, with the superconducting flux quantum ϕ0 (where ϕ0=h/2e) as a fundamental period. If CPs' splitting is additionally included, the resultant periodicity doubles. Since the edge states are typically considered to be strongly localized, the critical current does not decay as a function of the magnetic field. The present paper goes beyond this approach and inspects a topological JJ in the tunneling regime featuring extended edge states. It is here considered the possibility that the two electrons of a CP propagate and explore the junction independently over length scales comparable to the superconducting coherence length. As a consequence of the spatial extension, a decaying pattern with different possible periods is obtained. In particular, it is shown that, if crossed Andreev reflections (CARs) are dominant and the edge states overlap, the resulting interference pattern features oscillations whose periodicity approaches 2ϕ0.

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Introduction: It has been shown that, for male subjects, the sEMG activity at low contraction forces is normally "pulsatile", i.e., formed by a few large-amplitude MUPs, coming from the most superficial motor units. The subcutaneous layer thickness, known to be greater in females than males, influences the electrode detection volume. Here, we investigated the influence of the subcutaneous layer thickness on the type of sEMG activity (pulsatile vs. continuous) at low contraction forces. Methods: Voluntary surface EMG signals were recorded from the quadriceps muscles of healthy males and females as force was gradually increased from 0% to 40% MVC. The sEMG filling process was examined by measuring the EMG filling factor, computed from the non-central moments of the rectified sEMG signal. Results: 1) The sEMG activity at low contraction forces was "continuous" in the VL, VM and RF of females, whereas this sEMG activity was "pulsatile" in the VL and VM of males. 2) The filling factor at low contraction forces was lower in males than females for the VL (p = 0.003) and VM (p = 0.002), but not for the RF (p = 0.54). 3) The subcutaneous layer was significantly thicker in females than males for the VL (p = 0.001), VM (p = 0.001), and RF (p = 0.003). 4) A significant correlation was found in the vastus muscles between the subcutaneous layer thickness and the filling factor (p < 0.05). Discussion: The present results indicate that the sEMG activity at low contraction forces in the female quadriceps muscles is "continuous" due to the thick subcutaneous layer of these muscles, which impedes an accurate assessment of the sEMG filling process.

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Structurally colored sexual signals are a conspicuous and widespread class of ornament used in mate choice, though the extent to which they encode information on the quality of their bearers is not fully resolved. Theory predicts that signaling traits under strong sexual selection as honest indicators should evolve to be more developmentally integrated and exaggerated than nonsexual traits, thereby leading to heightened condition dependence. Here, we test this prediction through examination of the sexually dimorphic faces and wings of the cursorial fly Lispe cana. Males and females possess structural UV-white and golden faces, respectively, and males present their faces and wings to females during close-range, ground-based courtship displays, thereby creating the opportunity for mutual inspection. Across a field-collected sample of individuals, we found that the appearance of the faces of both sexes scaled positively with individual condition, though along separate axes. Males in better condition expressed brighter faces as modeled according to conspecific flies, whereas condition scaled with facial saturation in females. We found no such relationships for their wing interference pattern nor abdomens, with the latter included as a nonsexual control. Our results suggest that the structurally colored faces, but not the iridescent wings, of male and female L. cana are reliable guides to individual quality and support the broader potential for structural colors as honest signals. They also highlight the potential for mutual mate choice in this system, while arguing for 1 of several alternate signaling roles for wing interferences patterns among the myriad taxa which bear them.

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For two decades, the formalism of quantum mechanics has been successfully used to describe human decision processes, situations of heuristic reasoning, and the contextuality of concepts and their combinations. The phenomenon of 'categorical perception' has put us on track to find a possible deeper cause of the presence of this quantum structure in human cognition. Thus, we show that in an archetype of human perception consisting of the reconciliation of a bottom up stimulus with a top down cognitive expectation pattern, there arises the typical warping of categorical perception, where groups of stimuli clump together to form quanta, which move away from each other and lead to a discretization of a dimension. The individual concepts, which are these quanta, can be modeled by a quantum prototype theory with the square of the absolute value of a corresponding Schrödinger wave function as the fuzzy prototype structure, and the superposition of two such wave functions accounts for the interference pattern that occurs when these concepts are combined. Using a simple quantum measurement model, we analyze this archetype of human perception, provide an overview of the experimental evidence base for categorical perception with the phenomenon of warping leading to quantization, and illustrate our analyses with two examples worked out in detail.

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Terahertz (THz) imaging techniques are attractive for a wide range of applications, such as non-destructive testing, biological sensing, and security imaging. We investigate practical issues in THz imaging systems based on a solid immersion lens (SIL). The system stability in terms of longitudinal misalignment of the SIL is experimentally verified by showing that the diffraction-limited sub-wavelength beam size (0.7 λ) is maintained as long as the SIL is axially located within the depth-of-focus (~13 λ) of the objective lens. The origin of the fringe patterns, which are undesirable but inevitable in THz imaging systems that use continuous waves, is analytically studied, and a method for minimizing the interference patterns is proposed. By combining two THz images obtained at different axial positions of the object and separated by λ/4, the interference patterns are significantly reduced, and the information hidden under the interference patterns is unveiled. The broad applicability of the proposed method is demonstrated by imaging objects with different surface profiles. Our work proves that the resolution of conventional THz imaging systems can easily be enhanced by simply inserting a SIL in front of the object with high tolerance in the longitudinal misalignment and provides a method enabling THz imaging for objects with different surface profiles.

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OBJECTIVE: To explore the relationship between axon loss and measured cross-sectional areas of the median nerve (MN) in severe carpal tunnel syndrome (CTS). METHODS: In this retrospective study of 158 examined wrists, we compared axon loss to the ultrasound parameters MN cross-sectional area at the wrist (wCSA), MN cross-sectional area at the forearm (fCSA) and wrist-to-forearm ratio (WFR), in patients with moderate to extreme CTS. Axon loss was evaluated by needle electromyography (EMG) of the abductor pollicis brevis muscle (spontaneous activity and reduction of interference pattern). RESULTS: Both the spontaneous activity and interference pattern reduction correlated negatively to fCSA (r = -0.189, p = 0.035; r = -0.210, p = 0.019; respectively). In moderate CTS, both the spontaneous activity and interference pattern reduction correlated positively to WFR (r = 0.231, p = 0.048; r = 0.232, p = 0.047; respectively). The WFR was highest when slight spontaneous activity was detected. Neither wCSA nor WFR correlated with axon loss in severe and extreme CTS. CONCLUSIONS: The fCSA is smaller when axon loss in CTS is more prominent. The WFR is highest when CTS is associated with slight axon loss of the MN. SIGNIFICANCE: CTS might cause retrograde axonal atrophy detected as small fCSA. Prominent axon loss in CTS may reduce the diagnostic value of WFR.

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INTRODUCTION: Turns-amplitude, number of small segments (NSS)-activity, and envelope-activity clouds are three methods of electromyography (EMG) interference pattern analysis. Our objective was to evaluate the sensitivity and specificity of each individual cloud analysis and combined clouds analysis to compare with that of quantitative motor unit potential (QMUP) analysis. METHODS: A total of 379 muscles from 100 patients were analyzed by both QMUP and clouds analyses. Calculation of sensitivity and specificity was based on the clinical diagnosis as the "gold standard." RESULTS: For discrimination of abnormal vs normal and neuropathic vs non-neuropathic, combined clouds analysis had greater sensitivity than QMUP analysis and any single cloud analysis, but there were no differences in specificity. For discrimination of myopathic vs non-myopathic, combined clouds analysis and single cloud analysis had greater sensitivity than QMUP analysis, but there were no differences in specificity. DISCUSSION: Combined clouds analysis was superior to QMUP and each single cloud analysis for distinguishing normal, myopathic, and neuropathic muscles.

Asunto(s)

Electromiografía/métodos , Enfermedad de la Neurona Motora/diagnóstico , Músculo Esquelético/fisiopatología , Enfermedades Musculares/diagnóstico , Enfermedades del Sistema Nervioso Periférico/diagnóstico , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Esclerosis Amiotrófica Lateral/diagnóstico , Esclerosis Amiotrófica Lateral/fisiopatología , Dermatomiositis/diagnóstico , Dermatomiositis/fisiopatología , Diagnóstico Diferencial , Electrodiagnóstico , Femenino , Humanos , Masculino , Persona de Mediana Edad , Mononeuropatías/diagnóstico , Mononeuropatías/fisiopatología , Enfermedad de la Neurona Motora/fisiopatología , Atrofia Muscular Espinal/diagnóstico , Atrofia Muscular Espinal/fisiopatología , Enfermedades Musculares/fisiopatología , Distrofias Musculares/diagnóstico , Distrofias Musculares/fisiopatología , Miositis/diagnóstico , Miositis/fisiopatología , Enfermedades del Sistema Nervioso Periférico/fisiopatología , Polineuropatías/diagnóstico , Polineuropatías/fisiopatología , Radiculopatía/diagnóstico , Radiculopatía/fisiopatología , Reclutamiento Neurofisiológico , Sensibilidad y Especificidad , Procesamiento de Señales Asistido por Computador , Atrofias Musculares Espinales de la Infancia/diagnóstico , Atrofias Musculares Espinales de la Infancia/fisiopatología , Adulto Joven

RESUMEN

INTRODUCTION: In contrast to needle electromyography (EMG), surface EMG recordings are painless. It is of interest to develop methods to analyze surface EMG for diagnostic purposes. METHODS: Surface EMG interference pattern (SIP) recordings from the abductor pollicis brevis muscle of healthy subjects and subjects with amyotrophic lateral sclerosis (ALS) were analyzed by measuring root-mean-square (RMS) voltage, mean rectified voltage, form factor (FF), and the clustering index (CI). The FF vs SIP area plot was used for analysis. RESULTS: The SIP FF was increased and abnormal in ALS subjects, especially when SIP area was less than 200 mVms. Power regression showed a faster FF decline with SIP area in ALS patients than in healthy subjects. The CI and FF showed a strong correlation. DISCUSSION: FF is easy to calculate and demonstrates abnormalities in ALS patients.

Asunto(s)

Potenciales de Acción/fisiología , Esclerosis Amiotrófica Lateral/fisiopatología , Electromiografía/métodos , Contracción Muscular/fisiología , Músculo Esquelético/fisiopatología , Adulto , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Electrodiagnóstico/métodos , Femenino , Mano/fisiopatología , Humanos , Masculino , Persona de Mediana Edad

RESUMEN

In infrared weak target detection systems, high-frequency vibrating mirrors (VMs) are a core component. The dynamic surface shape of the VM has a direct impact on imaging quality and the optical modulation effect, so its measurement is necessary but also very difficult. Measurement of the dynamic surface shape of VMs requires a transiently acquired image series, but traditional methods cannot perform this task, as, when the VM is vibrating at a frequency of 3033 Hz, using high-speed cameras to acquire the images would result in frame rates exceeding 1.34 MFPS, which is currently technically impossible. In this paper, we propose the long exposure short pulse synchronous phase lock (LSPL) method, which can capture the dynamic surface shape using a camera working at 10 FPS. In addition, our proposed approach uses a single laser pulse and can achieve the dynamic surface shape measurement on a single frame image.

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We demonstrate that the interference pattern of the plasmonic and photonic modes can be controlled by changing the slit width of a square slit structure. Based on the analyses of the plasmonic and photonic modes of slits with different widths, we theoretically derived the expressions of wavefield generated by a square slit. A far-field scattered imaging system is utilized to collect the intensity distribution experimentally. Various interference patterns, including stripes, square-like lattice array, and diamond-like lattice array, have been observed by adjusting the slit widths. In addition, the results were validated by performing finite-difference time-domain simulations, which are consistent with the theoretical and experimental results.

RESUMEN

BACKGROUND: Number of small segments (NSS) and activity analysis is a mature method for electromyographic automatic interference pattern analysis (IPA), but there are few reports on the application of this technique. Our objective was to establish normal reference values of NSS-activity clouds. METHODS: The NSS and activity data of the sternocleidomastoid, deltoid, biceps brachii (long head), extensor digitorum communis, abductor digiti minimi, vastus medialis, tibialis anterior, and gastrocnemius (lateral head) muscles were obtained from 34 men and 25 women, aged 15-80 years, using concentric needle electrodes. A linear regression of log(NSS) vs log(activity) was performed and the slope, intercept and standard deviation were calculated for each muscle. These variables were transformed back to the original parameters to yield clouds. RESULTS: Normal NSS-activity clouds for the above eight muscles were obtained. CONCLUSIONS: Normal reference values of NSS-activity may facilitate detection of early and mild neurogenic and myogenic abnormalities.

Asunto(s)

Electromiografía/métodos , Músculo Esquelético/fisiología , Procesamiento de Señales Asistido por Computador , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Valores de Referencia , Adulto Joven

RESUMEN

Objective: An electrophysiological technique was established to determine Motor Unit Number Index (MUNIX), and to investigate the stability of MUNIX. Methods: Fifty healthy subjects (25 males and 25 females) from the Outpatient Service of Peking University Third Hospital between December 2017 and September 2018 were included and divided into 5 groups according to age. The relevant parameters were detected in bilateral deltoid muscle (axillary nerve), double little finger abductor muscle (ulnar nerve), double quadriceps muscle (femoral nerve), double tibialis anterior muscle (peroneal nerve). The same muscle and the same healthy subjects were tested again three months later. Three-step detection were conducted: first, the surface electrode was attached to the muscle belly of each muscle, and the reference electrode was placed 2-3 cm away from the muscle belly. At the same time, the maximum compound muscle action potential (CMAP) of corresponding nerve was obtained, and the negative peak amplitude was measured. The second step was to collect the interference phase of the surface electromyography (SIP). There were 10 levels in total. And the measurement was repeated for three times, and the whole interference phase range was measured in the end. In the third step, the negative peak amplitude and SIP value of CMAP were substituted into the Excel table, and the MUNIX and motor unit number size (MUSIX) values were automatically calculated by the instrument through mathematical functions. Results: The mean MUNIX values of deltoid, extensor little finger, quadriceps femoris and tibial anterior were 193.2, 189.0, 159.7, 147.2, MUSIX were 46.9, 54.3, 49.6, 48.1 µV, respectively. The detection rates of MUNIX and MUSIX in the four muscles were 100%, respectively. With the increase of age, it could be seen that MUNIX declined, with statistically significant difference (P<0.05), but there was no significant change in MUSIX. There was no statistically significant difference in MUNIX and MUSIX between different gender, lateral sides and baseline and 3-month's reexamination results (P>0.05). Conclusions: MUNIX technology can improve the motor unit count of proximal upper limb and lower limb muscles. Its parameters are monitored using a mathematical model based on the composite muscle action potential and the interference phase of surface electromyography. Result is stable and reliable.

Asunto(s)

Neuronas Motoras , Músculo Esquelético , Electromiografía , Femenino , Voluntarios Sanos , Humanos , Masculino , Nervio Peroneo

RESUMEN

Metallic nanoparticles are important building blocks for plasmonic applications. The spatially defined arrangement of these nanoparticles in a stable glass matrix is obtained here by nanosecond excimer laser irradiation at 193 nm. Two approaches are addressed: (1) Laser induced formation of particles from a dopant material pre-incorporated in the glass, (2) Particle formation and implantation by irradiation of material pre-coated on top of the glass. Silver nanoparticles are formed inside Ag⁺ doped glass (method 1). Gold nanoparticles are implanted by irradiation of gold coated glass (method 2). In the latter case, with a few laser pulses the original gold film disintegrates into particles which are then embedded in the softened glass matrix. A micron sized spatial resolution (periodic arrangements with 2 µm period) is obtained in both cases by irradiating the samples with an interference beam pattern generated by a phase mask. The plasmonic absorption of the nanoparticles leads to a contrast of the optical density between irradiated and non-irradiated lines of up to 0.6.

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INTRODUCTION: This study proposes guidelines for motor unit number index (MUNIX) recording and analysis. METHODS: MUNIX was measured in control participants and in patients with amyotrophic lateral sclerosis. Changes in MUNIX values due to E1 electrode position, number of surface electromyography interference pattern (SIP) epochs, SIP epoch duration, force of contraction, and outlier data points were investigated. RESULTS: MUNIX depends on optimized compound muscle action potential (CMAP) amplitude. Individual muscles showed variations when the number of epochs was low or when the SIP duration was short. Longer SIP duration allowed better recognition of artifacts. MUNIX results were affected by SIP values at all force levels but was more affected when SIP area was low. DISCUSSION: We recommend changing the E1 electrode position to maximize CMAP amplitude. Twenty or more SIP signals of 500-ms duration should be recorded by using force levels ranging from slight to maximum. Traces should be reviewed to identify and exclude signals with tremor or solitary spikes. Muscle Nerve 58: 374-380, 2018.

Asunto(s)

Potenciales de Acción/fisiología , Electromiografía/normas , Neuronas Motoras/fisiología , Reclutamiento Neurofisiológico/fisiología , Adulto , Anciano , Electromiografía/métodos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Factores de Tiempo

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A successful nerve transfer surgery can provide a wealth of benefits to a patient with cervical spinal cord injury. The process of surgical decision making ideally uses all pertinent information to produce the best functional outcome. Reliance on clinical examination and imaging studies alone can miss valuable information on the state of spinal cord health. In this regard, neurophysiological evaluation has the potential to effectively gauge the neurological status of even select pools of anterior horn cells and their axons to small nerve branches in question to determine the potential efficacy of their use in a transfer. If available preoperatively, knowledge gained from such an evaluation could significantly alter the reconstructive surgical plan and avoid poor results. The authors describe their institution's approach to the assessment of patients with cervical spinal cord injury who are being considered for nerve transfer surgery in both the acute and chronic setting and broadly review the neurophysiological techniques used.

Asunto(s)

Médula Cervical/cirugía , Transferencia de Nervios , Traumatismos de la Médula Espinal/cirugía , Extremidad Superior/cirugía , Animales , Médula Cervical/fisiopatología , Humanos , Transferencia de Nervios/métodos , Procedimientos Neuroquirúrgicos/métodos , Médula Espinal/fisiopatología , Médula Espinal/cirugía , Extremidad Superior/fisiopatología

RESUMEN

We show that the chemical inhomogeneity in ternary three-dimensional topological insulators preserves the topological spin texture of their surface states against a net surface magnetization. The spin texture is that of a Dirac cone with helical spin structure in the reciprocal space, which gives rise to spin-polarized and dissipation-less charge currents. Thanks to the nontrivial topology of the bulk electronic structure, this spin texture is robust against most types of surface defects. However, magnetic perturbations break the time-reversal symmetry, enabling magnetic scattering and loss of spin coherence of the charge carriers. This intrinsic incompatibility precludes the design of magnetoelectronic devices based on the coupling between magnetic materials and topological surface states. We demonstrate that the magnetization coming from individual Co atoms deposited on the surface can disrupt the spin coherence of the carriers in the archetypal topological insulator Bi2Te3, while in Bi2Se2Te the spin texture remains unperturbed. This is concluded from the observation of elastic backscattering events in quasiparticle interference patterns obtained by scanning tunneling spectroscopy. The mechanism responsible for the protection is investigated by energy resolved spectroscopy and ab initio calculations, and it is ascribed to the distorted adsorption geometry of localized magnetic moments due to Se-Te disorder, which suppresses the Co hybridization with the surface states.

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The use of the reflected Global Navigation Satellite Systems' (GNSS) signals in Earth observation applications, referred to as GNSS reflectometry (GNSS-R), has been already studied for more than two decades. However, the estimation precision that can be achieved by GNSS-R sensors in some particular scenarios is still not fully understood yet. In an effort to partially fill this gap, in this paper, we compute the Cramér-Rao bound (CRB) for the specific case of static ground-based GNSS-R receivers and scenarios where the coherent component of the reflected signal is dominant. We compute the CRB for GNSS signals with different modulations, GPS L1 C/A and GPS L5 I/Q, which use binary phase-shift keying, and Galileo E1 B/C and E5, using the binary offset carrier. The CRB for these signals is evaluated as a function of the receiver bandwidth and different scenario parameters, such as the height of the receiver or the properties of the reflection surface. The CRB computation presented considers observation times of up to several tens of seconds, in which the satellite elevation angle observed changes significantly. Finally, the results obtained show the theoretical benefit of using modern GNSS signals with GNSS-R techniques using long observation times, such as the interference pattern technique.

RESUMEN

Laser-induced grating spectroscopy (LIGS) is an experimental method in which two pulsed laser beams and a continuous-wave laser beam have to be superimposed under well-defined angles to generate a coherent signal beam. In this Note, the possible effects of different forms of misalignment are examined. This includes the overlap of the pump lasers as well as the influence of the probe laser alignment on the temporal profile of the signal.