Combination of neutron imaging (NI) and digital image correlation (DIC) to determine intra-ring moisture variation in Norway spruce

The hygroscopic behavior of wood has a strong influence on its mechanical performance, yet the moisture gradients within the growth ring structure have not been sufficiently investigated. The main challenge is that moisture variations are coupled with strong sample deformation, which complicates the spatial referencing of moist and dry states. In this work, neutron imaging (NI) for the detection of water and digital image correlation (DIC) for the detection of local deformation were combined to calculate the local gravimetric moisture content (MCgrav) and the volumetric moisture content (MCvol) within single growth rings. Specimens of Norway spruce [Picea abies (L.) Karst.] were exposed to an adsorption-desorption cycle, with relative humidity (RH) steps varying from 0% (oven dry) up to 95% RH. After each acclimatization step, neutron transmission and DIC images were acquired. The local deformations determined by DIC were used to assign the corresponding dry density in the undeformed state to the compartment in a moist state and thus to calculate its MC by NI. No significant MC gradients could be found between earlywood (EW) and latewood (LW) within ±0.5% accuracy. However, strong density gradients between EW and LW can be directly correlated with MCvol. It appears that the MC in the cell wall is constant regardless of the particular growth ring positio

Air-coupled ultrasound inspection of glued laminated timber

A novel air-coupled ultrasound (ACU) 120kHz normal transmission system enabled successful imaging of bonding and saw cut defects in multilayered glulam beams up to 280mm in height with a signal-to-noise ratio (SNR) of 40dB. The main wave propagation paths were modeled; quasi-longitudinal and quasi-transverse modes were coupled in each lamella and the sound field was found to be shifted from the insonification axis as a function of the ring angle, leading to interference of wave paths in the receiver and to 15dB amplitude variability in defect-free glulam. The assessment was improved with spatial processing algorithms that profited from the arbitrary scanning resolution and high reproducibility of ACU. Overlapped averaging reduced in-band noise by 15dB, amplitude tracking captured only the first incoming oscillation, thus minimizing diffraction around defect regions, and image normalization compensated 6dB of systematic amplitude variability across the fiber direction. The application of ACU to in situ defect monitoring was demonstrated by using multiparameter difference imaging of measurements of the same sample with and without saw cut defects. The segmentation of the defect geometry was improved significantly and the amplitude variability was reduced by 10dB. Further work is planned to model additional insonification setups and grain and density heterogeneitie

Delamination detection in a 90-year-old glulam block with scanning dry point-contact ultrasound

Glued laminated timber (glulam) is known in timber constructions since more than 100 years. Glulam members can delaminate due to aging and excessive changes of temperature and humidity. This results in significantly reduced load bearing capability of the affected structural members. This contribution focuses on the ultrasonic point-contact inspection of gluing plane delamination as a nondestructive method. Ultrasonic measurements on a section of a 90-year-old roofing glulam member are presented. The results are compared with manual detection and evaluation of delamination with a feeler gauge, with X-ray computed tomography analyses, and with numerical simulations. Appropriate data evaluation of the mechanized ultrasonic results allows the determination of material separation that are deeper than 20 mm in the signature of the surface wave and large-scale delamination (>80% of the complete bonding width) in the back-wall echo. Numerical simulations based on the finite-difference time-domain method shed light into the details of the wave propagation and support the experimental finding

Breast Cancer Assessment With Pulse-Echo Speed of Sound Ultrasound From Intrinsic Tissue Reflections: Proof-of-Concept

PURPOSE The aim of this study was to differentiate malignant and benign solid breast lesions with a novel ultrasound (US) technique, which measures speed of sound (SoS) using standard US transducers and intrinsic tissue reflections and scattering (speckles) as internal reference. MATERIALS AND METHODS This prospective, institutional review board-approved, Health Insurance Portability and Accountability Act-compliant prospective comparison study was performed with prior written informed consent from 20 women. Ten women with histological proven breast cancer and 10 with fibroadenoma were measured. A conventional US system with a linear probe was used for SoS-US (SonixTouch; Ultrasonix, Richmond, British Columbia, Canada). Tissue speckle reflections served as a timing reference for the US signals transmitted through the breasts. Relative phase inconsistencies were detected using plane wave measurements from different angular directions, and SoS images with 0.5-mm resolution were generated using a spatial domain reconstruction algorithm. The SoS of tumors were compared with the breast density of a larger cohort of 106 healthy women. RESULTS Breast lesions show focal increments ΔSoS (meters per second) with respect to the tissue background. Peak ΔSoS values were evaluated. Breast carcinoma showed significantly higher ΔSoS than fibroadenomas ([INCREMENT]SoS > 41.64 m/s: sensitivity, 90%; specificity, 80%; area under curve, 0.910) and healthy breast tissue of different densities (area under curve, 0.938; sensitivity, 90%; specificity, 96.5%). The lesion localization in SoS-US images was consistent with B-mode imaging and repeated SoS-US measurements were reproducible. CONCLUSIONS Using SoS-US, based on conventional US and tissue speckles as timing reference, breast carcinoma showed significantly higher SoS values than fibroadenoma and healthy breast tissue of different densities. The SoS presents a promising technique for differentiating solid breast lesions

Damage evolution in wood: synchrotron radiation micro-computed tomography (SRμCT) as a complementary tool for interpreting acoustic emission (AE) behavior

Tensile tests of miniature spruce wood specimens have been performed to investigate the damage evolution in wood at the microscopic scale. For this purpose, the samples were stepwise tensile loaded in the longitudinal (L) and radial (R) directions and the damage evolution was monitored in real-time by acoustic emission (AE) and synchrotron radiation micro-computed tomography (SRμCT). This combination is of outstanding benefit as SRμCT monitoring provides an insight on the crack evolution and the final fracture at microscopic scale, whereas AE permits the detection of the associated accumulation and interaction of single damage events on all length scales with high time resolution. A significant drawback of the AE testing of wood has been overcome by means of calibrating the AE amplitudes with the underlying crack length development. Thus, a setup-dependent and wood species-dependent calibration value was estimated, which associates 1 μm2 crack area generating of 0.0038 mV in the detected AE amplitude. Furthermore, for both L and R specimens, AE signals were classified into two clusters by using a frequency-based approach of unsupervised pattern recognition. The shares of AE signals of both clusters correlate with the ratio of the relative crack area of the interwall and transwall cracks gained from the fractographic analysis of SRμCT scans

Influence of incubation time on the vibration and mechanic properties of mycowood

The goal of the current study was to investigate the physical and mechanical properties of mycowood as a high quality tone-wood, obtained from Norway spruce by treatment of the white rot fungus Physisporinus vitreus as a function of the treatment time. In focus was the stiffness to weight ratio, which is often considered a main criterion for tone-wood selection. The vibro-mechanical properties were tested by non-destructive methods. The change of color and density were also measured after 4-12 months of fungal incubation. Density decreased up to 5% after 12 months of fungal treatment. Sound velocity was measured in small size specimens by means of the free-free vibration approach, while in large specimens the air-coupled ultrasound method was applied. The two techniques gave similar results and indicated that the sound velocity decreased in mycowood. Internal damping was increased in mycowood to a higher extent than the reduction in the specific modulus of elasticity (E/ρ) and thus the sound velocity in the material. The sound velocity was decreasing with increasing incubation times and scattering of data with this regard was larger in the transversal than in the longitudinal direction. The sound radiation coefficient and the characteristic impedance were enhanced in mycowood and its color was more brownish and richer in tone

1 - Introducción

At the end of 2019, a new zoonotic coronavirus originated in China, which was called the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the coronavirus disease 2019 (COVID-19). This virus first generated the denomination by the World Health Organization (WHO) of a Public Health Emergency of International Concern (PHEIC), and later of pandemic. The impact of this COVID-19 pandemic has affected the entire world. Latin America has not been the exception, and with this this Consensus, which brings together the work of experts from different countries in the region, gathered in the Pan American Association of Infectious Diseases (API), seeks to serve as a guide, especially for those countries in which to date have not developed clear guidelines, especially in the diagnosis and treatment of the disease, but also in other epidemiological and preventive aspects. This consensus is divided into parts. This one, corresponds to the first, Introduction.A finales del año 2019 se originó en China un nuevo coronavirus, zoonótico, que fue denominado como el coronavirus del síndrome agudo respiratorio severo 2 (SARS-CoV-2), causante de la enfermedad por coronavirus 2019 (COVID-19). Este virus generó inicialmente la denominación por parte de la Organización Mundial de la Salud (OMS) de Emergencia Sanitaria de Preocupación Internacional (ESPI), y posteriormente de pandemia. El impacto de esta pandemia por COVID-19 ha afectado todo el mundo. América Latina no ha sido la excepción, y con ello el presente Consenso, que reúne el trabajo de expertos de diferentes países de la región, congregados en la Asociación Panamericana de Infectología (API), busca servir de guía, especialmente para aquellos países en los cuales no se han desarrollado a la fecha lineamientos claros, especialmente en el diagnóstico y tratamiento de la enfermedad, pero también en otros aspectos epidemiológicos y preventivos. El presente consenso está dividido en partes. Esta, corresponde a la primera, Introducción

1 - Introducción

At the end of 2019, a new zoonotic coronavirus originated in China, which was called the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the coronavirus disease 2019 (COVID-19). This virus first generated the denomination by the World Health Organization (WHO) of a Public Health Emergency of International Concern (PHEIC), and later of pandemic. The impact of this COVID-19 pandemic has affected the entire world. Latin America has not been the exception, and with this this Consensus, which brings together the work of experts from different countries in the region, gathered in the Pan American Association of Infectious Diseases (API), seeks to serve as a guide, especially for those countries in which to date have not developed clear guidelines, especially in the diagnosis and treatment of the disease, but also in other epidemiological and preventive aspects. This consensus is divided into parts. This one, corresponds to the first, Introduction.A finales del año 2019 se originó en China un nuevo coronavirus, zoonótico, que fue denominado como el coronavirus del síndrome agudo respiratorio severo 2 (SARS-CoV-2), causante de la enfermedad por coronavirus 2019 (COVID-19). Este virus generó inicialmente la denominación por parte de la Organización Mundial de la Salud (OMS) de Emergencia Sanitaria de Preocupación Internacional (ESPI), y posteriormente de pandemia. El impacto de esta pandemia por COVID-19 ha afectado todo el mundo. América Latina no ha sido la excepción, y con ello el presente Consenso, que reúne el trabajo de expertos de diferentes países de la región, congregados en la Asociación Panamericana de Infectología (API), busca servir de guía, especialmente para aquellos países en los cuales no se han desarrollado a la fecha lineamientos claros, especialmente en el diagnóstico y tratamiento de la enfermedad, pero también en otros aspectos epidemiológicos y preventivos. El presente consenso está dividido en partes. Esta, corresponde a la primera, Introducción

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO