Experimental and numerical study of Conoscopic Interferometry sensitivity for optimal acoustic pulse detection in ultrafast acoustics.

Conoscopic interferometry is a promising detection technique for ultrafast acoustics. By focusing a probe beam through a birefringent crystal before passing it through a polarizer, conoscopic interferences sculpt the spatial profile of the beam. The use of these patterns for acoustic wave detection revealed a higher detection sensitivity over existing techniques, such as reflectometry and beam distortion detection. However, the physical origin of the increased sensitivity is unknown. In this work, we present a model, describing the sensitivity behavior of conoscopic interferometry with respect to the quarter-wave plate orientation and the diaphragm aperture, which is validated experimentally. Using the model, we optimize the detection sensitivity of conoscopic interferometry. We obtain a maximal sensitivity of detection when placing the diaphragm edge on the dark fringes of the conoscopic interference patterns. In the configurations studied in this work, conoscopic interferometry can be 18 dB more sensitive to acoustic waves than beam distortion detection.

Self-Sealing Complex Oxide Resonators.

Although 2D materials hold great potential for next-generation pressure sensors, recent studies revealed that gases permeate along the membrane-surface interface, necessitating additional sealing procedures. In this work, we demonstrate the use of free-standing complex oxides as self-sealing membranes that allow the reference cavity beneath to be sealed by a simple anneal. To test the hermeticity, we study the gas permeation time constants in nanomechanical resonators made from SrRuO3 and SrTiO3 membranes suspended over SiO2/Si cavities which show an improvement up to 4 orders of magnitude in the permeation time constant after annealing the devices. Similar devices fabricated on Si3N4/Si do not show such improvements, suggesting that the adhesion increase over SiO2 is mediated by oxygen bonds that are formed at the SiO2/complex oxide interface during the self-sealing anneal. Picosecond ultrasonics measurements confirm the improvement in the adhesion by 70% after annealing.

Metabolic Changes after Radioiodine Correction of Grade 1 and Grade 2 Subclinical Hyperthyroidism.

OBJECTIVE: Endogenous subclinical hyperthyroidism (eSCH) is defined by subnormal serum thyroid-stimulating hormone (TSH) level. There is limited evidence of metabolic changes induced by eSCH. The aim of our work was to evaluate changes in BMI and lipid parameters after radioiodine treatment in patients with grade 1 (TSH: 0.1-0.39 mlU/L) and 2 (TSH <0.1 mlU/L) eSCH. DESIGN: A retrospective study was performed on 74 patients with eSCH caused by benign autonomous nodular goiter which was treated with radioiodine. METHODS: We assessed BMI, lipids parameters, and TSH after radioiodine therapy. The 12-month follow-up time point was used to compare the primary outcome variables. TSH was measured by the electrochemiluminescence method. RESULTS: After radioiodine therapy, the absolute and relative increases in BMI at 12 months were significantly higher in the grade 2 group than in the grade 1 group (1.07 ± 0.27 kg/m2 vs. 0.26 ± 0.15 kg/m2, respectively; p = 0.023 and 4.01 ± 0.98% vs. 1.01 ± 0.56%, respectively; p = 0.026). Compared to baseline, significant increases in the levels of total cholesterol and LDL were observed after treatment in the grade 2 eSCH group (16.7 ± 4.5 mg/dL p < 0.01 and 14.3 ± 4.1 mg/dL p < 0.01, respectively) but not in the grade 1 group. In a multivariate model, a negative correlation was observed between pretreatment TSH levels and absolute BMI gain (p < 0.01). CONCLUSIONS: After correction of eSCH, increases in BMI and LDL levels were observed only in patients with grade 2 eSCH. Pretreatment serum TSH was the main independent factor associated with BMI changes after radioiodine treatment.

A new approach to accelerate readout segmented EPI with compressed sensing.

PURPOSE: High resolution diffusion-weighted imaging is limited by susceptibility-induced distortions and relaxation-induced blurring. Segmented acquisition techniques can address these limitations at the expense of a prolonged scan time. If segmentation is performed along the readout direction, e.g., in RESOLVE (readout segmentation of long and variable echo-trains), scan time can be reduced by readout (RO) partial Fourier methods, or simultaneous multi-slice (SMS) methods. In this paper, we present a new approach to additionally accelerate the image acquisition called variable segment (VASE) RESOLVE. METHODS: To avoid discontinuities at the boundaries of the segments, the phase evolution and therefore the effective echo-spacing needs to be adjusted. To achieve this, we use higher undersampling factors in the outer parts of k-space. Simultaneously we increase the width of the outer segments resulting in an increase of the echo-spacing. Because of this variation, we introduce a kind of randomization to the sampling scheme. This enables the use of compressed sensing reconstruction techniques, which results in improved image quality compared to standard parallel imaging methods. RESULTS: The RMS errors for the VASE RESOLVE acquisitions were lower compared to the standard reconstructions. The VASE RESOLVE in vivo images show a higher apparent signal to noise ratio. CONCLUSION: VASE RESOLVE is a new approach to further decrease the acquisition time of RO segmented acquisitions. Compared to RESOLVE with SMS, VASE RESOLVE additionally reduces the acquisition time by a factor of 2.

Influence of the laser source position on the generation of Rayleigh modes in a layer-substrate structure with varying degrees of adhesion.

Non-Destructive Testing of adhesion using Surface Acoustic Waves (SAW) is an important issue in industrial and academic domains. Indeed, these waves are sensitive to the quality of adhesion at the interface between the substrate and the layer with a thickness comparable to the acoustic wavelength. Furthermore, their propagation distance allows a large majority of the sample to be tested quickly. Numerous studies have used SAW for the Non-Destructive Testing of adhesion. However, some recurrent experimental difficulties may lead to an incorrect interpretation of the results. This is the case when the layer thickness is non-uniform, for example. To provide a quasi-constant thickness, a PolyEthylene Terephthalate (PET) film was placed directly on the substrate surface without any glue and Laser-Ultrasonics was used to investigate this type of structure. As the film was transparent at the optical wavelength used, it was possible to focus the laser source on the substrate surface through the film. To the best of our knowledge, no paper has been published on the influence of the source position on adhesion testing. In this work, two source positions were investigated.

Monitoreo de DDI en Mar del Plata: 2003 / Monitoring of DDI in Mar del Plata (2003)

Un total de 1113 alumnos de escolaridad primaria, de ambos sexos, fue estudiado en este monitoreo de bocio endémico en 3 escuelas de la ciudad de Mar del Plata. La edad de los escolares osciló entre 5 y 13 años. La palpación tiroidea fue hecha por el conjunto de los médicos participantes. Sin embargo, con la finalidad de aunar criterios con lo realizado previamente (1-14), se tomó como única referencia la palpación de H.N., que se llevó a cabo en la totalidad de los niños estudiados. La definición del grado de bocio fue similar a la utilizada en los otros relevamientos (1). Se determinó la yoduria en 262 muestras casuales de orina emitidas por los niños una vez que fueron palpados. Se recolectaron 991 muestras de sal de consumo hogareño para medir su contenido en yodo. El examen palpatorio de los niños reveló la existencia de bocio grado 1, con excepción de 1 niño que tuvo un nódulo tiroideo. La prevalencia promedio de bocio encontrada para Mar del Plata fue de 8,6 %, variando entre 7,8 % y 10,1 %, según la escuela encuestada. Los niveles de yoduria tuvieron una media general de 185 µg/L y una mediana general de 149 µg/L. Cuando se analizaron las escuelas en forma individual, las medianas variaron entre 121 y 176 µg/L, pero no correlacionaron con los porcentajes de bocio encontrados. Tampoco hubo correlación entre el contenido promedio de yodo en sal de cada colegio y la mediana de las yodurias de cada uno de ellos. El contenido de yodo de las sales que aportaron los alumnos mostró una media de 24,3 ± 9,7 mg/Kg para las 3 escuelas tomadas en conjunto, con un rango de 21,8 a 26,7 mg/Kg, al analizar las escuelas en forma separada. Al evaluar el porcentaje de muestras, cuyas concentraciones de yodo fueron <15mg/Kg, se vio que las mismas alcanzaron la cifra del 14,5 %, que está algo por encima del 10 % establecido por la ICCIDD (15). Un dato de sumo interés fue el obtenido de la encuesta sobre el consumo de agua de red en las viviendas de los niños. Si bien al momento de este relevamiento, la gran mayoría de los escolares bebía agua de red en sus hogares, casi todos tuvieron el antecedente de haber ingerido en el pasado agua de pozo. Como ya había sido demostrado previamente (16), dicha agua de pozo contenía bociógenos ambientales. Nuestra encuesta reveló que el tiempo transcurrido desde que los alumnos tuvieron acceso al agua de red fue significativamente diferente entre los escolares con y sin bocio, cuando fueron comparados por sexo y edad. Aquellos sin bocio tuvieron acceso al agua de red, en promedio, 4,94 años antes del presente monitoreo, mientras que los niños con bocio solamente lo lograron 2,46 años antes. Concluimos que en la ciudad de Mar del Plata todavía existía, en el año 2003, el efecto residual del consumo de agua de pozo portadora de bociógenos ambientales. Futuros estudios mostrarán si la endemia observada puede ser finalmente erradicada mediante el uso absoluto y continuo de agua de red.

Respiratory tract secretions in the dying patient: a retrospective study.

Respiratory tract secretions (RTS), the sound created by poorly-cleared mucous in the hypopharynx or bronchial tree, can be alarming for dying patients, relatives and staff. Increased knowledge into the etiology of RTS and its response to treatment is needed to improve future management. We studied retrospectively the data from 202 patients who died on a 30-bed specialist palliative care unit during a one-year period. These patients were observed every four hours during the dying phase. RTS was treated with hyoscine hydrobromide. Ninety-nine patients (49%) developed RTS. The median time from onset of RTS till death was 16 hours. Fifty-nine patients could have their treatment response assessed. Of these, 30.5% responded within four hours, 33.9% after four hours, and 35.5% died with RTS. Increasing the dose for nonresponders had no significant effect. Significant risk factors for developing RTS were found to be prolonged dying phase, primary lung cancer and male gender.