Tubular vs. mini-open lumbar discoidectomy: surgical-clinical outcome.

OBJECTIVE: To evaluate the clinical-surgical results of the tubular vs. mini-open approach in lumbar discoidectomy. The tubular approach promises to reduce the number of rest days and an earlier return to daily activities and work. METHOD: A case-control study of patients operated on for disc herniation using tubular surgery (case) and mini-open (control) was carried out. The variables investigated were as follow: radicular and lumbar pain, sex, age, failure in conservative treatment, single-level lumbar hernia, surgical time, bleeding, length of hospital stay, persistence of symptoms, complications, occupational activity, and reintegration into everyday activities. RESULTS: Through 100 surgeries performed, two groups were created, tubular and mini-open, with 50 patients each, with L4-L5 or L5-S1 disc herniation, respectively. The most affected level was L4-L5 (69%). Of the total cases, a significant improvement was found (p < 0.05) at 15 postoperative days in the VAS and ODI scale in the tubular group with respect to mini-open. Complications such as surgical wound infection, durotomy, and persistent pain occurred. CONCLUSIONS: The tubular approach is a safe and effective option for herniated discs of the lumbar segment, and reduces surgical times, bleeding, and the time of reinsertion to daily activities of the patient.

OBJETIVO: Evaluar los resultados clínico-quirúrgicos del abordaje tipo tubular en comparación con el mini-open en la discoidectomía lumbar. El abordaje tubular promete reducir el número de días de reposo y una reincorporación más temprana a las actividades diarias y laborales. MÉTODO: Se realizó un estudio de casos y controles de pacientes operados por hernia discal mediante cirugía tubular (casos) o mini-open (controles). Las variables investigadas fueron: dolor radicular y lumbar, sexo, edad, falla en el tratamiento conservador, hernia lumbar de un solo nivel, tiempo quirúrgico, sangrado, tiempo de estancia hospitalaria, persistencia de síntomas, complicaciones, tipo de actividad ocupacional y reinserción a las actividades cotidianas. RESULTADOS: Se realizaron 100 cirugías y se crearon dos grupos, tubular y mini-open, con 50 pacientes cada uno, con hernia discal de L4-L5 o L5-S1, respectivamente. El nivel más afectado fue L4-L5 (69%). Del total de los casos, se encontró mejoría significativa (p < 0.05) a los 15 días posquirúrgicos en la escala EVA y ODI en el grupo tubular con respecto al mini-open. Ocurrieron complicaciones como infección de herida quirúrgica, durotomía y dolor persistente. CONCLUSIONES: El abordaje tubular es una opción segura y efectiva para hernias discales del segmento lumbar, y reduce los tiempos quirúrgicos, el sangrado y el tiempo de reinserción a las actividades cotidianas del paciente.

Two-photon absorption spectrometers for near infrared.

We present a Silicon-based Charge-Coupled Device (Si-CCD) sensor applied as a cost-effective spectrometer for femtosecond pulse characterization in the Near Infrared region in two different configurations: two-Fourier and Czerny-Turner setups. To test the spectrometer's performance, a femtosecond Optical Parametric Oscillator with a tuning range between 1100 and 1700 nm and a femtosecond Erbium-Doped Fiber Amplifier at 1582 nm were employed. The nonlinear spectrometer operation is based on the Two-Photon Absorption effect generated in the Si-CCD sensor. The achieved spectrometer resolution was 0.6 ± 0.1 nm with a threshold peak intensity of 2×106Wcm2. An analysis of the nonlinear response as a function of the wavelength, the response saturation, and the criteria to prevent it are also presented.

Nonlinear focal shift due to the Kerr effect for a Gaussian beam focused by a lens.

When a low-power, monochromatic Gaussian beam is focused by a thin lens in air and the waist of the beam is in the plane of the lens, there is a shift of the focus position if the waist of the beam is much smaller than the size of the lens. The point of maximum intensity relative to the geometrical focal point shifts closer to the lens. We show that for ultra-intense light beams, when the Kerr effect is unavoidable, there is a nonlinear focal shift. The nonlinear focus position shifts closer to the lens for laser powers below the critical power. To avoid the nonlinear focal shift below the critical power, the correct combination of Gaussian beam waist and focal system has to be used in the experimental setup. It will be shown that as the Fresnel number N w associated with the Gaussian beam radius increases, the nonlinear focal shift first increases and then begins to decrease.

Effect of oils on the transmission properties of a terahertz photonic crystal.

The transmission properties of a photonic crystal immersed in several different oils have been characterized using terahertz time domain spectroscopy in the spectral range of 0.3-1.5 THz. As in previous works, oil samples can be distinguished using terahertz transmission measurements. When the same oils are introduced into a photonic crystal, we find that the effective refractive index of the photonic crystal is sensitive to the properties of the oils and shows differences not seen in bulk measurements. These effects are described in detail and have potential applications in both the sensing of very small volumes of oils and in the fine control of the refractive indices of photonic crystals.

Assisted dorso-lumbar instrumentation with O-arm neuronavegation and minimally invasive surgery: clinical-surgical outcome.

OBJECTIVE: To evaluate the clinical-surgical outcomes after dorso-lumbar instrumentation using O-arm assisted neuronavigation and minimally invasive surgery. METHOD: In this retrospective cohort, 104 patients who underwent dorso-lumbar instrumentation with the use of O-arm from September 2013 to May 2020 were studied. Variables investigated included: symptoms, number of screws, levels approached, bleeding, surgical time, hospital stay, complications and clinical improvement after the surgical procedure. RESULTS: The most frequent symptoms were: unilateral or bilateral radiculopathy of the pelvic extremities, paresthesia, mechanical low back pain and progressive decrease in strength. A total of 542 screws were placed, with the lumbar spine being the site with the highest prevalence. The average bleeding, surgical time, and hospital stay was: 50 ml, 160 minutes, and 24 hours, respectively. The most frequent complications were: Residual neuropathy, dura mater tear and surgical site infection. Clinical improvement at 24 hours, 4 weeks and 6 months was achieved in: 77.3%, 86.5% y 94.8% of the patients, respectively. CONCLUSIONS: Neuronavigation with the use of O-arm along with mini-open surgery approach results in good clinical-surgical outcomes in the correction of complex disorders of the dorso-lumbar spine.

OBJETIVO: Evaluar los resultados clínico-quirúrgicos de la instrumentación dorso-lumbar mediante neuronavegación asistida con O-arm y cirugía mínimamente invasiva. MÉTODO: En esta cohorte retrospectiva se estudiaron 104 pacientes sometidos a instrumentación dorso-lumbar con uso de O-arm, operados entre septiembre de 2013 y mayo de 2020. Las variables investigadas fueron sintomatología, cantidad de tornillos, niveles abordados, sangrado, tiempo quirúrgico, estancia hospitalaria, complicaciones y mejoría clínica posterior al procedimiento quirúrgico. RESULTADOS: La sintomatología más frecuente fue radiculopatía unilateral o bilateral de extremidades pélvicas, parestesias, lumbalgia mecánica y disminución progresiva de la fuerza. Se utilizaron en total 542 tornillos, siendo la columna lumbar el sitio de mayor prevalencia. Los promedios de sangrado, tiempo quirúrgico y estancia hospitalaria fueron de 50 ml, 160 minutos y 24 horas, respectivamente. Las complicaciones más frecuentes fueron neuropatía residual, rasgadura de la duramadre e infección del sitio quirúrgico. La mejoría clínica a las 24 horas, 4 semanas y 6 meses se logró en el 77.3%, el 86.5% y el 94.8% de los pacientes, respectivamente. CONCLUSIONES: La neuronavegación con O-arm junto con el abordaje quirúrgico de tipo mini-open permite buenos resultados clínico-quirúrgicos en la corrección de los trastornos complejos de la columna dorso-lumbar.

Sub-wavelength continuous THz imaging system based on interferometric detection.

We have developed a continuous wave sub-wavelength terahertz (THz) imaging system that combines two prominent classical optical techniques: solid immersion microscopy and interferometric detection. This combination allows for resolution beyond the diffraction limit at 703 GHz. We experimentally demonstrate sub-wavelength spatial resolution working with a relatively low-cost pyroelectric detector and with both high and low contrast samples.

Algorithm to filter the noise in the spectral intensity of ultrashort laser pulses.

We have developed an algorithm to filter the noise in the spectral intensity of ultrashort laser pulses. The filtering procedure consists of smoothing the noise by using the Savitzky-Golay filter, removing the offset, and using a super-Gaussian window to truncate the frequencies of the spectrum. We have modeled bandwidth-limited ultrashort pulses with Gaussian modulated frequencies to show the estimation of the carrier wavelength, reconstruction of the intensity pulse profile, and pulse duration after applying the algorithm. Theoretical results are presented for pulse durations between 5 fs and 100 fs with a carrier wavelength of 825 nm and three different amounts of signal-to-noise ratio (SNR): 30 dB, 20 dB, and 15 dB, normally found in experiments. The algorithm is also applied to an experimental spectral intensity from a homemade Ti:sapphire laser that produces pulses of about 20 fs at 825 nm at 100 MHz. We will show that using only a low-pass Fourier filter and removing offset is not enough to recover the spectral intensity when a large SNR is present, which may be the case when the ultrashort laser beam has been manipulated to compensate for the group velocity dispersion of an external optical system. In cases like this, the use of the Savitzky-Golay filter prior to the super-Gaussian filter improves the recovery of the carrier wavelength and the spectral intensity. We will also show that the algorithm presented in this paper is suitable for experimental analysis and requires limited user intervention.

Impact of frequency-dependent spherical aberration in the focusing of ultrashort pulses.

In this paper, the temporal and spatial intensity pulse distributions are calculated around the focal region of an optical system using a combination of ray tracing and a wave propagation method. We analyze how to measure the width of the intensity pulse distributions to estimate pulse duration and spot size in order to study the impact of the variation of spherical aberration with frequency in a pulse on the intensity distributions. Two experimental techniques used in the laboratory are also modeled: the knife-edge test to measure spatial distribution and the intensity autocorrelation technique to measure the temporal distribution. We use two measuring criteria, the full-width half-maximum (FWHM) and standard deviation (σ), to compare the spatial and temporal intensity distributions of the calculated diffraction patterns and those obtained from the simulated experimental techniques. We show that the FWHM is not a good criterion, since it gives different results in the measured intensity distributions in time and space when they are measured directly from the theoretical modeling and when they are measured from the modeled experimental techniques used in the laboratory. The standard deviation, however, is a consistent criterion, giving the same results for the calculated intensity distributions and the modeled experiments.

Simultaneous measurement of DC two-photon absorption signal offset and amplitude of the intensity autocorrelation in the focusing of femtosecond pulses.

In this work, the DC two-photon absorption signal offset (${{\rm DC}_{\rm TPA}}$DCTPA) and the amplitude of the autocorrelation (${{\rm A}_{\rm AC}}$AAC) are measured simultaneously around the focal point of an apochromatic microscope objective using the z-scan autocorrelation technique. The ${{\rm A}_{\rm AC}}$AAC is obtained from the nonlinear sensor response given by the two-photon-absorption, generated in a GaAsP photodiode, for femtosecond laser pulses. We verify that the change in the ${{\rm DC}_{\rm TPA}}$DCTPA signal along $z$z is coincident with the amplitude of the intensity autocorrelation, and that the highest amplitude of the AC is reached at the same position as the highest amplitude of the ${{\rm DC}_{\rm TPA}}$DCTPA signal. The ${{\rm DC}_{\rm TPA}}$DCTPA signal is typically used as a reference for the alignment in a collinear intensity autocorrelator, and we show that it can also be used as a practical procedure to estimate the depth of focus. The ${{\rm DC}_{\rm TPA}}$DCTPA signal measurement allows us to locate the optimum spatial-temporal coupling given by the highest amplitude of the intensity autocorrelation. Additionally, we find a variation in the pulse duration within the same region due to the radially varying group delay dispersion.

Interference effects in quantum-optical coherence tomography using spectrally engineered photon pairs.

Optical-coherence tomography (OCT) is a technique that employs light in order to measure the internal structure of semitransparent, e.g. biological, samples. It is based on the interference pattern of low-coherence light. Quantum-OCT (QOCT), instead, employs the correlation properties of entangled photon pairs, for example, generated by the process of spontaneous parametric downconversion (SPDC). The usual QOCT scheme uses photon pairs characterised by a joint-spectral amplitude with strict spectral anti-correlations. It has been shown that, in contrast with its classical counterpart, QOCT provides resolution enhancement and dispersion cancellation. In this paper, we revisit the theory of QOCT and extend the theoretical model so as to include photon pairs with arbitrary spectral correlations. We present experimental results that complement the theory and explain the physical underpinnings appearing in the interference pattern. In our experiment, we utilize a pump for the SPDC process ranging from continuous wave to pulsed in the femtosecond regime, and show that cross-correlation interference effects appearing for each pair of layers may be directly suppressed for a sufficiently large pump bandwidth. Our results provide insights and strategies that could guide practical implementations of QOCT.

Low-energy/pulse response and high-resolution-CMOS camera for spatiotemporal femtosecond laser pulses characterization @ 1.55 µm.

In this work, we present a commercial CMOS (Complementary Metal Oxide Semiconductor) Raspberry Pi camera implemented as a Near-Infrared detector for both spatial and temporal characterization of femtosecond pulses delivered from a femtosecond Erbium Doped Fiber laser (fs-EDFL) @ 1.55 µm, based on the Two Photon Absorption (TPA) process. The capacity of the device was assessed by measuring the spatial beam profile of the fs-EDFL and comparing the experimental results with the theoretical Fresnel diffraction pattern. We also demonstrate the potential of the CMOS Raspberry Pi camera as a wavefront sensor through its a nonlinear response in a Shack-Hartmann array and for the temporal characterization of the femtosecond pulses delivered from the fs-EDFL through TPA Intensity autocorrelation measurements. The direct pulse detection and measurement, through the nonlinear response with a CMOS, is proposed as a novel and affordable high-resolution and high-sensitivity alternative to costly detectors such as CCDs, wavefront sensors and beam profilers @ 1.55 µm. The measured fluence threshold, down to 17.5 µJ/cm2, and pJ/pulse energy response represents the lowest reported values applied as a beam profiler and a TPA Shack-Hartmann wavefront sensor, to our knowledge.

Mode-coupling enhancement by pump astigmatism correction in a Ti:Sapphire femtosecond laser.

To pump a solid-state femtosecond laser cavity, a beam from a CW laser is focused by a single lens into the laser crystal. To increase the output power of the laser, the overlap of the laser mode with the pump mode should be maximized. This is particularly important in the so-called mode coupling and the Kerr-lens mode locking (KLM) operation, where the change in beam waist at the position of the gain medium is exploited to enhance the mode overlap with the pump laser in the crystal. In this paper, the astigmatism in the pump beam is reduced by tilting the pump lens. A Gaussian beam is propagated through the complete focusing system-pump lens, tilted spherical mirror, and crystal cut at Brewster's angle-to show the astigmatism inside the crystal as a function of the tilt of the pump lens. A genetic algorithm is presented to optimize the mode coupling between the pump and laser beam inside the crystal by tilting the pump lens. Experimental results are presented to verify the design, showing an increase in the output power of the laser cavity of about 20%.

Webcam autofocus mechanism used as a delay line for the characterization of femtosecond pulses.

In this work, we present an electromagnetic focusing mechanism (EFM), from a commercial webcam, implemented as a delay line of a femtosecond laser pulse characterization system. The characterization system consists on a second order autocorrelator based on a two-photon-absorption detection. The results presented here were performed for two different home-made femtosecond oscillators: Ti:sapph @ 820 nm and highly chirped pulses generated with an Erbium Doped Fiber @ 1550 nm. The EFM applied as a delay line represents an excellent alternative due its performance in terms of stability, resolution, and long scan range up to 3 ps. Due its low power consumption, the device can be connected through the Universal Serial Bus (USB) port. Details of components, schematics of electronic controls, and detection systems are presented.

Análisis de la vulnerabilidad biofísica a los riesgos por inundación en la zona metropolitana de Toluca, México / Biophysics vulnerability analysis to flooding risk in the metropolitan area of toluca, Mexico

Se realizó el análisis multicriterio de los factores físico-naturales de la Zona Metropolitana de Toluca (ZMT), con la finalidad de definir el índice biofísico de exposición a los riesgos por inundación. Para la elaboración del trabajo se utilizó información institucional e información de campo, la cual fue procesada a través de los métodos estadísticos y multicriterio con el apoyo de los Sistemas de Información Geográfica y de percepción remota. Los resultados obtenidos mostraron que el índice de riesgo alto, con un valor de 52,41% comprende los municipios de Lerma, Toluca, San Mateo Atenco y Metepec y cubre una superficie de 1032,73 km²; el índice bajo cubre el 13,71% del territorio y una superficie 13,71 km²; por último el riesgo biofísico medio abarca 687,20 km² o 33,88% del territorio metropolitano. Se pretende que los resultados de la investigación contribuyan en la toma de decisiones en los campos de la protección civil, el desarrollo regional y la seguridad pública, así como la incorporación en los planes de desarrollo urbano y ordenamiento territorial con una visión de riesgo; y sea de utilidad en los campos de la protección civil, el desarrollo metropolitano, la seguridad pública y el ordenamiento territorial.

A multicriteria analysis of natural physical factors of the Toluca Metropolitan Area (ZMT) was performed in order to define the biophysical index of exposure to flood risk. Institutional information and field information was used for carrying out the work and it was processed through statistical and multi-criteria methods with the support of GIS and remote sensing. The results showed that the rate of high risk, with a 52.41% value includes the municipalities of Lerma, Toluca, San Mateo Atenco and Metepec, and covers an area of 1032.73 km². The low rate covers 13.71 % of the territory and an area of 13.71 km², and finally the average biophysical risk covers 687.20 km² or 33.88% of the metropolitan area. It is intended that the research results contribute to decision making in the fields of civil protection, regional development and public safety, as well as incorporation into urban development plans and land use planning with a view of risk, and be useful in the fields of civil protection, metropolitan development, public safety and land use planning.

Direct inversion methods for spectral amplitude modulation of femtosecond pulses.

In the present work, we applied an amplitude-spatial light modulator to shape the spectral amplitude of femtosecond pulses in a single step, without an iterative algorithm, by using an inversion method defined as the generalized retardance function. Additionally, we also present a single step method to shape the intensity profile defined as the influence matrix. Numerical and experimental results are presented for both methods.

A metal mixture induces transformation upon antioxidant depletion in a hepatic cell line.

INTRODUCTION: Metals are ubiquitous soil, air, and water pollutants. A mixture of arsenic cadmium and lead, in particular, has commonly been found in the vicinity of smelter areas. The mixture of As-Cd-Pb has been shown to be carcinogenic, and transforming potential and oxidative stress have been proposed as principal mechanisms involved in this process. The aim of this work was to explore the role of the antioxidant barrier in the establishment of cell transformation upon chronic exposure to a metal mixture containing 2 µM NaAsO(2), 2 µM. CdCl(2), and 5 µM Pb(C(2)H(3)O(2))(2)∙3H(2)O in WRL-68 cells-a non-transformed human hepatic cell line. MATERIAL AND METHODS: In this study, we used a WRL-68 cell model of human embryonic hepatic origin treated with antioxidant inhibitors (L-Buthionine-sulfoxamine and aminotriazole) to test the role of the antioxidant barrier in the establishment of cell transformation upon chronic exposure to a metal mixture of As-Cd-Pb (2 µM NaAsO(2), 2 µM CdCl(2) and 5 µM Pb(C(2)H(3)O(2))(2)∙3H(2)O). We evaluated oxidative damage markers, including reactive oxygen species, lipid peroxidation, and genotoxicity, as well as antioxidant response markers, including glutathione concentration, catalase activity, and superoxide dismutase activity, which promote morphological transformation, which can be quantified by foci formation. RESULTS: As expected, we found an increase in the intracellular concentration of the metals after treatment with the metal mixture. In addition, treatment with the metal mixture in addition to inhibitors resulted in a large increase in the intracellular concentration of cadmium and lead. Our results describe the generation of reactive oxygen species, cytotoxicity, genotoxicity, and oxidative damage to macromolecules that occurred exclusively in cells that were morphologically transformed upon exposure to a metal mixture and antioxidant barrier inhibition. CONCLUSION: Our results show the importance of the antioxidant barrier role in the protection of cellular integrity and the transformation potential of this metal mixture via free radicals.

Aberration effects on femtosecond pulses generated by nonideal achromatic doublets.

There are three main effects that affect the femtosecond pulse focusing process near the focal plane of a refractive lens: the group velocity dispersion (GVD), the propagation time difference (PTD), and the aberrations of the lens. In this paper we study in detail these effects generated by nonideal achromatic doublets based on a Fourier-optical analysis and Seidel aberration theory considering lens material, wavelength range, lens surface design, and temporally and spatially uniform and Gaussian intensity distributions. We show that the residual chromatic aberration in achromatic lenses, which has been neglected so far, has a considerable effect on the focusing of pulses shorter than 20 fs in the spectral range between the UV and IR, 300 to 1100 nm, and is particularly important in the blue and UV spectral range. We present a general fitted function for an estimation of the pulse stretching parameter, which depends only on the numerical aperture and focal length of the doublet as well as the wavelength of the carrier of the pulse.

General ultrafast pulse measurement using the cross-correlation single-shot sonogram technique.

The cross-correlation single-shot sonogram technique offers exact pulse measurement and real-time pulse monitoring via an intuitive time-frequency trace whose shape and orientation directly indicate the spectral chirp of an ultrashort laser pulse. We demonstrate an algorithm that solves a fundamental limitation of the cross-correlation sonogram method, namely, that the time-gating operation is implemented using a replica of the measured pulse rather than the ideal delta-function-like pulse. Using a modified principal-components generalized projections algorithm, we experimentally show accurate pulse retrieval of an asymmetric double pulse, a case that is prone to systematic error when one is using the original sonogram retrieval algorithm.

DNA damage in blood cells from children exposed to arsenic and lead in a mining area.

In this work, we studied the frequency of DNA damage in children living in Villa de la Paz, Mexico, a mining site contaminated with arsenic and lead. DNA damage in blood cells was assessed using the Comet assay, and the results were compared to those found in children living in a less exposed town (Matehuala). In Villa de la Paz, high concentrations of arsenic and lead in surface soil and household dust were found. All of the soil samples had concentrations above 100 mg/kg of arsenic, and 58% of the samples were higher than 400 mg/kg of lead (these concentrations are used as intervention guidelines by the United States Environmental Protection Agency). In agreement with the environmental results, urinary arsenic in children living in Villa de la Paz (geometric mean 136 microg/g creatinine) was significantly higher than that found in children living in Matehuala (34 microg/g creatinine). Blood lead levels were also significantly higher in children from Villa de la Paz (11.6 microg/dL) than in children from Matehuala (8.3 microg/dL). The results of the Comet assay showed that the tail length and the tail moment in children living in Villa de la Paz were higher than those observed for children in Matehuala (P<0.05). Taking all the data into account, our study has shown increased DNA damage in children exposed to arsenic and lead in the mining site of Villa de la Paz.

Overview of human health and chemical mixtures: problems facing developing countries.

In developing countries, chemical mixtures within the vicinity of small-scale enterprises, smelters, mines, agricultural areas, toxic waste disposal sites, etc., often present a health hazard to the populations within those vicinities. Therefore, in these countries, there is a need to study the toxicological effects of mixtures of metals, pesticides, and organic compounds. However, the study of mixtures containing substances such as DDT (dichlorodiphenyltrichloroethane, an insecticide banned in developed nations), and mixtures containing contaminants such as fluoride (of concern only in developing countries) merit special attention. Although the studies may have to take into account simultaneous exposures to metals and organic compounds, there is also a need to consider the interaction between chemicals and other specific factors such as nutritional conditions, alcoholism, smoking, infectious diseases, and ethnicity.