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Publicado 2020
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Quantitative ultrasound has shown potential of improving medical diagnosis. In this work, a regularized power law (RPL) for the joint estimation of backscatter coefficient (BSC) and attenuation coefficient (AC) parameters was derived and tested with simulated phantoms and in vivo. For the RPL method, a total variation regularization term regarding the BSC and AC parameters were used. The results were compared with ground truth simulated values. An improvement of precision can be appreciated without compromising the accuracy by factor of 80% and 54% according to bias and coefficient of variation, respectively. The in vivo experiments showed comparable results of the algorithm with the literature (i.e. fibroadenoma:1.90 ± 0.31dB.cm-1.MHz-1, normal tissue: 0.62 ± 0.20dB.cm-1.MHz-1). The results suggest the RPL method has the potential to accurately and precisely estimating BSCs and ACs. ...
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Publicado 2021
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I read with great interest a recent study by Poterico and Mestanza who described mutations in 30 SARS‐CoV‐2 genomes from South American countries (Argentina, Brazil, Chile, Colombia, Ecuador, and Peru). Next‐generation sequencing (NGS) technologies have accelerated genomic and metagenomic studies providing affordable tools to obtain pathogen genomes and improving diagnosis and surveillance efforts. However, many downstream analyses after assembling the genomes are impacted by low‐quality sequences and sequence contamination, which could lead to wrong conclusion.
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Publicado 2016
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This work was supported by the German funding program “LOEWE − Landes-Offensive zur Entwicklung Wissenschaftlich-ökonomischer Exzellenz” of the Hesse’s Ministry of Higher Education, Research and the Arts, and by JSPS KAKENHI (No. 26291077). P.R. also received a PhD scholarship from CONCYTEC - Peru. We would like to thank Benôit Dayrat, Antonio de Frias Martins, Adrienne Jochum and Alexander Weigand for providing samples or suggestions for this work, and to Claudia Nesselhauf for her support in the laboratory. We also thank the editor and reviewers for their comments on the manuscript. This is Contribution #234, Bermuda Biodiversity Project (BBP), Bermuda Aquarium, Natural History Museum and Zoo, Department of Conservation Services.
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Publicado 2021
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Este trabajo fue financiado por el Fondo Nacional de Desarrollo Cient?fico y Tecnol?gico y de Innovaci?n Tecnol?gica (Fondecyt-Per?) en el marco del ?Proyecto de Mejoramiento y Ampliaci?n de los Servicios del Sistema Nacional de Ciencia, Tecnolog?a e Innovaci?n Tecnol?gica? [N?mero de contrato 34?2019-FONDECYT-BM-INC. INV.], y por el CONCYTEC-FONDECYT en el marco del concurso ?Proyectos Especiales: Respuesta al COVID-19 2020-01? [n?mero de contrato 046-2020-FONDECYT].
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Publicado 2021
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The Rimac river is the main source of water for Lima, Peru's capital megacity. The river is constantly affected by different types of contamination including mine tailings in the Andes and urban sewage in the metropolitan area. In this work, we aim to produce the first characterization of aquatic bacterial communities in the Rimac river using a 16S rRNA metabarcoding approach which would be useful to identify bacterial diversity and potential understudied pathogens. We report a lower diversity in bacterial communities from the Lower Rimac (Metropolitan zone) in comparison to other sub-basins. Samples were generally grouped according to their geographical location. Bacterial classes Alphaproteobacteria, Bacteroidia, Campylobacteria, Fusobacteriia, and Gammaproteobacteria were the most frequent along the river. Arcobacter cryaerophilus (Campylobacteria) was the most frequent species in the...
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Publicado 2021
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Genetic diversity is an important component of biodiversity, and it is crucial for current efforts to protect and sustainably manage several organisms and habitats. As far as we know, there is only one work describing Peruvian genetic information stored in public databases. We aimed to update this previous work searching in four public databases that stored digital sequence information: Nucleotide, BioProject, PATRIC, BOLD. With this information, we comment on the contribution of Peruvian institutions during recent years. In Nucleotide, the largest database, Bacteria are the most sequenced organisms by Peruvian institutions (70.60%), pathogenic bacteria such as Pasteurella multocida, Neisseria meningitidis, and Vibrio parahaemolyticus were the most abundant. We found no sequence records from the Archaea domain. In BioProject, the most common sequence belongs to Salmonella enterica subsp....
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artículo
Publicado 2019
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Imaging of musculoskeletal tissue dynamics is currently an exploratory field with the goal of aiding rehabilitation and performance evaluation of pathological or asymptomatic patients. In this pilot study, initial elasticity assessments of the biceps brachii were conducted in a novel crawling wave sonoelastography (CWS) system implemented on a research ultrasound instrument with graphical processing unit capabilities, displaying quantitative elasticity values at 4 frames per second. The CWS system computes the tissue stiffness with the generation of an interference pattern from external vibrators, which can overcome depth limitations of imaging systems with internal excitation sources. Validation on gelatin-based phantoms reported low bias of elasticity values (4.7%) at low excitation frequencies. Preliminary results on in vivo muscle characterization are in accordance with average elast...
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Publicado 2020
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Quantifying the local stiffness of muscular tissue can be a useful tool for the improvement of diagnosis, treatment or monitoring of muscle abnormality-related diseases. Shear wave elastography techniques provide information about tissue stiffness by measuring the shear wave speed (SWS). Recently, a new framework involving the generation of a reverberant shear wave field that propagates in all directions within the medium was proposed. The aim of this study is to evaluate the feasibility of Reverberant Shear Wave Elastography (R-SWE) for the in vivo assessment of the viscoelastic properties of skeletal muscle, using the biceps brachii. Four experiments were performed at a vibration frequency range between 200-300 Hz in steps of 50 Hz, with the ultrasound transducer placed along the muscle fibers in both relaxed and contracted (MVC) states. The estimation of the SWS and a dispersion analy...
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artículo
Publicado 2020
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Crawling Waves Sonoelastography (CWS) is an elastography technique based on an interference pattern produced by the application of two external vibration sources. In this study, a 3D printed holder was designed to overcome the compatibility limitations of normal excitation modules for different ultrasound systems, previously developed in the literature. This holder was assembled with a transducer and two voice coil actuators, and its performance was tested in homogeneous and inclusion tissue-mimicking phantom. A phase derivative estimator was used to reconstruct the shear wave speed (SWS) map. The coefficient of variation (CV), bias and contrast-to-noise ratio (CNR) were used as quantitative metrics for comparison. These metrics have shown a comparable SWS estimation in the background (SWSb) of the homogeneous phantom with previous studies (e.g. SWSb = 3.58± 0.42 m/s). In the same way, ...
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Skin diseases cause changes in the elasticity of the skin. Recently, a new ultrasound method which combines crawling waves elastography with a high-frequency ultrasound (HF-US) system was reported for the estimation of skin elasticity. This study applies crawling waves method with an HF-US system in homogeneous and heterogeneous phantoms with similar shear wave speeds found in the literature to validate this technique. In addition, estimation performance was compared between the Phase Derivative (PD) estimator and the Regularized Wave-length Average Velocity Estimator (R-WAVE). Results corroborate the feasibility of this method. Additionally, it suggests that R-WAVE estimator can provide better measurements than PD with a lower coefficient of variation and fewer artifacts. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
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artículo
Publicado 2020
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In this work, we study the conditions in which a reverberant field is created by varying the number and locations of multiple mechanical sources, and then fitting axial and lateral autocorrelation profiles to theoretical models. Numerical simulation showed that at least 60 incident plane waves were necessary to generate a R-SWF. The general trend is that by applying more incident waves, the coefficient of determination improves and the error decreases. We report a bias error lower than 6% in the mean shear wave speed (pmb{C}{s}). Phantom experiments showed a similar tendency. Moreover, we demonstrated that the creation of a R-SWF based on the superposition of incident plane waves was possible. At least three vibration sources located at the top of the phantom surface were necessary to measure an average pmb{C}{s} with an error less than 9%. © 2020 IEEE.
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This study aimed to evaluate the efficacy of anthelmintic used in an equine ranch in Cuba. The faecal egg count reduction test of Strongyles (FECRT) was used to evaluate albendazole and ivermectin. Thirty-three horses were selected (18 treated with albendazole, 15 treated with ivermectin). The egg count reduction for albendazole was 38% for micronized albendazole and 33% for albendazole sulfoxide. Ivermectin effectiveness was 100%. Subsequently, four horses that showed high counts of eggs after the albendazole treatment were treated with ivermectin on day 17 after the initial deworming to collect resistant nematodes in the faeces. These nematodes were morphologically identified. It was possible to identified 493 specimens: Cylicocyclus nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, Cylicostephanus goldi and Cylicostephanus minutus which represented 78.5, 7.7, 6.5, 3.9 a...
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This study aimed to evaluate the efficacy of anthelmintic used in an equine ranch in Cuba. The faecal egg count reduction test of Strongyles (FECRT) was used to evaluate albendazole and ivermectin. Thirty-three horses were selected (18 treated with albendazole, 15 treated with ivermectin). The egg count reduction for albendazole was 38% for micronized albendazole and 33% for albendazole sulfoxide. Ivermectin effectiveness was 100%. Subsequently, four horses that showed high counts of eggs after the albendazole treatment were treated with ivermectin on day 17 after the initial deworming to collect resistant nematodes in the faeces. These nematodes were morphologically identified. It was possible to identified 493 specimens: Cylicocyclus nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, Cylicostephanus goldi and Cylicostephanus minutus which represented 78.5, 7.7, 6.5, 3.9 a...
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artículo
Publicado 2021
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This research has been supported by the JPI-Belmont project PACMEDY (via grant ANR-15-JCLI-0003-01 for MC, PB, ME, OM, TC, and BT). MC, JC, DO, RSG, AP, and PR acknowledge funding from Concejo Nacional de Ciencia y Tecnologia de Peru (grant n° 007-2017-FONDECYT , grant n° 034-2019-FONDECYT-BM ). SPH acknowledges funding from the ERC-funded project GC2.0 Global Change 2.0: Unlocking the past for a clearer future, grant number 694481 and from the JPI-Belmont project PACMEDY (via NERC ). The distribution and analyses of the transient Holocene simulations with the IPSL model benefit from the Institut Pierre Simon Laplace Climate Modeling Centre Infrastructure supported by ANR “Investissements d'avenir” program ANR-11-IDEX-0004-17-EURE-0006 .
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artículo
Publicado 2020
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Western South America was one of the worldwide cradles of civilization. The well-known Inca Empire was the tip of the iceberg of an evolutionary process that started 11,000 to 14,000 years ago. Genetic data from 18 Peruvian populations reveal the following: 1) The between-population homogenization of the central southern Andes and its differentiation with respect to Amazonian populations of similar latitudes do not extend northward. Instead, longitudinal gene flow between the northern coast of Peru, Andes, and Amazonia accompanied cultural and socioeconomic interactions revealed by archeology. This pattern recapitulates the environmental and cultural differentiation between the fertile north, where altitudes are lower, and the arid south, where the Andes are higher, acting as a genetic barrier between the sharply different environments of the Andes and Amazonia. 2) The genetic homogeniza...
