Cubic nonlinearity and surface shock waves in soft tissue-like materials.

The cubic nonlinearity of shear wave propagation plays a significant role in brain injury biomechanics. However, soft materials, like the brain, also support the propagation of surface waves, which produce a combination of longitudinal and transverse deformation. The order of the nonlinearity of surface waves in soft materials is still unknown. Here, we directly observe nonlinear Scholte waves propagating in an interface formed by an incompressible gelatin tissue-mimicking phantom and a water layer using ultrasound imaging operated as fast as 16667 frames per second. A two-dimensional correlation-based tracking algorithm was utilized to extract movies of the movement produced by the surface wave. Our results show that the initially nearly monochromatic wave becomes progressively distorted with the propagation due to nonlinearity. The distortion of the wave and its frequency spectrum indicate a high content of odd harmonics when compared with even harmonics. Additionally, by fitting our experimental data to a minimalist one-dimensional model based on the wave speed variation as a function of the perturbation amplitude, we found a cubic nonlinear parameter 46 times larger than the quadratic nonlinear parameter. Overall, the wave distortion, the harmonic development, and the dependence of the wave speed with the amplitude prove that cubic nonlinearity is essential to modeling nonlinear Scholte wave propagation.

The resonant behavior of airborne standing-wave acoustic levitators based on arrays of ultrasonic transducers.

Recently airborne standing-wave acoustic levitation has seen great advances, and its applicability has been broadened due to the development of cavities constructed with arrays of compact ultrasonic sources. Yet, the numerical methods employed to study and predict the pressure distributions inside these cavities do not consider the effect of multiple reflections on the boundaries, hiding their resonant effects. This work presents an analytical, numerical, and experimental study of the effect of multiple reflections inside ultrasonic cavities based on arrays of transducers exhibiting their influence on the pressure amplitudes of focused standing waves. Our numerical results come from a modified version of the Matrix Method to numerically compute the multiple wave reflections of cavities constructed by two opposite arrays of multiple compact sources as boundaries. The correlation between numerical and experimental results reveals that intra-cavity reflections are relevant in focused axisymmetric cavities based on two arrays of multiple ultrasonic sources having a considerable impact on the amplitude of the standing waves and consequently, on the acoustic levitation performance. Thus, intra-cavity reflections must be considered for optimal cavity designs.

Assessment of the effects of heat stress on the production of dairy cows by using two comfort thermal indices in Southern Chile.

Heat stress has been recognized as a serious problem in dairy farms around the world due to the increasing heat waves and higher genetic potential of dairy cows. In Chile, milk production is concentrated in the southern regions of the country, where animals graze all year around, consequently being exposed directly to environmental conditions. Nevertheless, there are few studies conducted in Chile that have evaluated at the commercial level the impact of heat stress on milk production. The aim of this study was to assess the effects of summer conditions, across periods, on the milk production of cows at different stages of lactation in a dairy farm located in Southern Chile. Daily meteorological and milk yield records of three summers from a dairy farm were collected to characterize the relationship between two thermal stress indices and milk yield. The thermal comfort indices used were the comprehensive climate index (CCI), and the adjusted temperature humidity index (THIadj). The average values of CCI and THIadj were dependent on the period (P < 0.0001) with maximum CCI of 40.2 °C, 31.7 °C, and 27.5 °C for the 2012-2013, 2015-2016, and 2016-2017 periods, respectively. A similar response was recorded when THIadj was used (85.5, 78.0, and 73.9, respectively). In the 2012-2013 summer, 44.4% of the days presented conditions of heat stress (CCI ≥23), a value that fell to 26.7% in the summer of 2015-2016 and only 5.6% in the 2016-2017. On the opposite, when the THIadj was used, these values were 50%, 48.9%, and 5.6%, respectively. In conclusion, both comfort thermal indices are good tools to determine the risk of thermal stress in dairy cows, with a large variation between the three summer periods but also between indices. Likewise, cows in the early and mid-lactation periods are more affected in terms of milk yield.

Overnight Electroencephalogram to Forecast Epilepsy Development in Children with Autism Spectrum Disorders.

OBJECTIVE: To establish the utility of long-term electroencephalogram (EEG) in forecasting epilepsy onset in children with autism spectrum disorder (ASD). STUDY DESIGN: A single-institution, retrospective analysis of children with ASD, examining long-term overnight EEG recordings collected over a period of 15 years, was conducted. Clinical EEG findings, patient demographics, medical histories, and additional Autism Diagnostic Observation Schedule data were examined. Predictors for the timing of epilepsy onset were evaluated using survival analysis and Cox regression. RESULTS: Among 151 patients, 17.2% (n = 26) developed unprovoked seizures (Sz group), while 82.8% (n = 125) did not (non-Sz group). The Sz group displayed a higher percentage of interictal epileptiform discharges (IEDs) in their initial EEGs compared with the non-Sz group (46.2% vs 20.0%, P = .01). The Sz group also exhibited a greater frequency of slowing (42.3% vs 13.6%, P < .01). The presence of IEDs or slowing predicted an earlier seizure onset, based on survival analysis. Multivariate Cox proportional hazards regression revealed that the presence of any IEDs (HR 3.83, 95% CI 1.38-10.65, P = .01) or any slowing (HR 2.78, 95% CI 1.02-7.58, P = .046 significantly increased the risk of developing unprovoked seizures. CONCLUSION: Long-term EEGs are valuable for predicting future epilepsy in children with ASD. These findings can guide clinicians in early education and potential interventions for epilepsy prevention.

Impact of heat waves on semen quality: A retrospective study in Argentina between 2005 and 2023.

Heat waves, defined as periods with daily temperatures surpassing the historical average for a specific region, have become more frequent worldwide in recent years. Previous studies have reported a negative association between temperature and semen quality, but the focus has mainly been on Asian and European populations. The study included 54,926 men (18-60 years) undergoing routine semen analysis between 2005 and 2023 at CEUSA-LAEH andrology unit, in Buenos Aires, Argentina. Hourly temperature readings were provided by the Servicio Meteorológico Nacional. R programming (R Studio v2022.07.2) was used to define heat waves, calculate key characteristics, visualize results, and perform statistical tests at the IBYME laboratory. During the period studied, a total of 124 days had heat waves (defined after at least 3 consecutive days with 32.3 °C and 22 °C). Men exposed to heat waves during spermatogenesis exhibited lower sperm number (concentration and count; P < 0.0001) and decreased normal morphology (percentage of normal sperm and normal motile count; P < 0.05) compared to those not exposed. These differences were most pronounced between semen samples from years with several heat waves (2013, 2023) and none (2005, 2007, 2016), displaying 4-5 times higher fold changes (P < 0.05). Further analysis employing multiple regression revealed a significantly negative association between semen quality and heat wave length, suggesting that a prolonged exposure may be more detrimental than an acute exposure. Subsequent analysis focusing on prolonged exposure (≥6-days heat wave) during spermatogenesis revealed a negative (P < 0.05) association between early exposure (spermatocytogenesis: 64-90 days prior semen collection) and semen quality. This study underscores the negative association between early exposure to heat waves during sperm development and semen quality, raising concerns about its possible association with the worldwide declining male fertility. A comprehensive collaborative approach is crucial, involving global governmental policies, sustainable practices, and coordinated efforts across scientific, healthcare, and policy domains.

Relatório Lancet Countdown South America 2023 - saúde e mudanças climáticas: confie na ciência. Agora que sabemos, devemos agir / The 2023 South America report of The Lancet Countdown on health and climate change: trust the science. Now that we know, we must act

O Relatório Lancet Countdown tem feito importantes contribuições ao denunciar os principais agravos à saúde ambiental, graças à ação antropogênica, cada vez mais intensa. O desflorestamento, os incêndios florestais, cada vez mais incontroláveis, a seca, o consumo de combustíveis fósseis, o uso de energia não renovável, propiciam o aparecimento de alterações climáticas caracterizadas por ondas de calor, tempestades cada vez mais intensas, inundações e o consequente comprometimento da saúde dos humanos. A versão Lancet Countdown South America apresenta de forma clara e chocante as alterações no continente e faz chamamento para que essas alterações sejam bloqueadas, pois ainda há tempo.

The Lancet Countdown Report has made significant contributions by exposing the main impacts on environmental health caused primarily by increasingly intense anthropogenic action. Deforestation, increasingly uncontrollable forest fires, drought, fossil fuels, and nonrenewable energy contribute to the onset of climate change. This change is characterized by heat waves, increasingly intense storms, and floods that, consequently, compromise human health. The South America report of The Lancet Countdown highlights the alarming changes occurring in the continent and urges action to stop these changes while there is still time.

Goos-Hänchen shift for coupled vibrational modes in a semiconductor structure.

We present a theoretical investigation of the Goös-Hanchen shift (GHS) experienced by acoustic and optical vibrational modes reflected and transmitted from the surfaces of a semiconductor thin film sandwiched between two semi-infinite media. Our study focuses on the impact of the incident angle on the GHS, considering the coupling between longitudinal and transverse modes. For acoustic vibrations, our findings reveal that the GHS can reach magnitudes up to seven times larger than the thickness of the thin film and up to 20 times larger than the incident wavelength. Besides, it is shown that this significant amplification of the GHS highlights the strong influence of the incident angle and the frequency of the modes involved. In the case of optical vibrations, we observe even more pronounced GHS values, exceeding 30 times the incident wavelength. This demonstrates the potential of GHS in acoustical systems, which opens up possibilities for applications in the design of acoustic devices.

Impact and evolution of risk factors associated with hospitalization and mortality due to COVID-19 during the six epidemic waves in Mexico.

Objectives: This study aims to analyze and compare the main risk factors for hospitalization and deaths due to COVID-19 during the six epidemic waves from February 2020 to June 2023 in Mexico. Methods: First, a descriptive analysis of the risk factors that led to hospitalization and mortality due to COVID-19 was performed. Next, the degree of relationship of each risk factor with hospitalization and death was determined using Cramer's V coefficient. Finally, logistic regression models were applied to estimate the odds ratios of the most statistically significant risk factors for hospitalization and mortality. Results: A direct relationship between age and the possibility of hospitalization and death due to COVID-19 was found. Moreover, the comorbidities most likely to lead to hospitalization and death were pneumonia, hypertension, diabetes, obesity and CKD. It is also remarkable that the second factor of death is endotracheal intubation. Conclusion: The COVID-19 pandemic in Mexico revealed the reality of an epidemiological scenario where infectious diseases and chronic degenerative diseases coexist and interrelate.

Gills de novo assembly reveals oxidative stress, unfolded protein, and immune response on red cusk-eel (Genypterus chilensis) under thermal stress.

The heat waves on the South Pacific coast could lead to thermal stress in native fish. The red cusk-eel (Genypterus chilensis) is relevant for Chilean artisanal fisheries and aquaculture diversification. This study examined the effect of high-temperature stress in the gills of G. chilensis in control (14 °C) and high-temperature stress (19 °C) conditions. High-temperature stress induces a significant increase in gills cortisol levels. Additionally, oxidative damage was observed in gills (protein carbonylation and lipoperoxidation). RNA-seq data was used to build the first transcriptome assembly of gills in this species (23,656 annotated transcripts). A total of 1138 down-regulated and 1531 up-regulated transcripts were observed in response to high-temperature stress in gills. The enrichment analysis showed immune response and replication enriched processes (on down-regulated transcripts), and processes related to the folding of proteins, endoplasmic reticulum, and transporter activity (on up-regulated transcripts). The present study showed how gills could be affected by high-temperature stress.

Coherent Magnons with Giant Nonreciprocity at Nanoscale Wavelengths.

Nonreciprocal wave propagation arises in systems with broken time-reversal symmetry and is key to the functionality of devices, such as isolators or circulators, in microwave, photonic, and acoustic applications. In magnetic systems, collective wave excitations known as magnon quasiparticles have so far yielded moderate nonreciprocities, mainly observed by means of incoherent thermal magnon spectra, while their occurrence as coherent spin waves (magnon ensembles with identical phase) is yet to be demonstrated. Here, we report the direct observation of strongly nonreciprocal propagating coherent spin waves in a patterned element of a ferromagnetic bilayer stack with antiparallel magnetic orientations. We use time-resolved scanning transmission X-ray microscopy (TR-STXM) to directly image the layer-collective dynamics of spin waves with wavelengths ranging from 5 µm down to 100 nm emergent at frequencies between 500 MHz and 5 GHz. The experimentally observed nonreciprocity factor of these counter-propagating waves is greater than 10 with respect to both group velocities and specific wavelengths. Our experimental findings are supported by the results from an analytic theory, and their peculiarities are further discussed in terms of caustic spin-wave focusing.

Effect of superficial adipose tissue mitochondrial and cellular functionality induced by extracorporeal shock wave therapy (ESWT).

Due to its regenerative action, extracorporeal shock wave therapy (ESWT) is applied in treating integumentary and musculoskeletal diseases. However, other potential therapeutic interventions are being investigated. It is essential to fully understand its mitochondrial signaling pathway to achieve this, which plays a fundamental role in elucidating the mechanism of action and possible therapeutic interventions. Thus, this study aimed to analyze the effect of ESWT on mitochondrial pathways through the relationship between lipolysis and adipocyte apoptosis, as well as cellular functionality. This is a non-randomized case-control clinical trial where obese women received ESWT sessions in the abdominal region, after which tissue samples were collected for histological and immunohistochemical analyses of adipose tissue. The data demonstrated positivity in the expression of mitochondrial markers related to cell apoptosis, such as FIS1 (p < 0.0203) and OPA1 (p < 0.0283), in addition to the positivity of anti-MFN1, responsible for regulating mitochondrial cell proliferation (p < 0.0003). In summary, this study demonstrates that ESWT was able to activate specific mitochondrial signaling pathways, which may be associated with its ability to stimulate lipolysis and apoptosis in superficial adipose tissue. However, no significant improvements in cellular functionality were observed.

Changes in lifestyle and physical and mental health related to long-confinement due COVID-19: a study during the first and second pandemic waves in Mexico and Chile.

We investigate changes in lifestyle, physical, and mental health during the confinement period of the first and second waves of COVID-19, as well as their relation to sociodemographic parameters and confinement status. Sociodemographic data and information regarding changes in their lifestyle behavior and changes in body weight and physical activity (PA) were collected. The SF-36 questionnaire was implemented for measuring the domains related to physical health (PH) and mental health (MH). The growth frequency of weight gain in the Mexican (4.8%) and Chilean (10.9%) populations was observed during the second wave. The MH component decreased in the Mexican and the Chilean population (p < 0.05). Moreover, the MH decreased significantly according to the degree of confinement (p < 0.01). Although some sociodemographic factors were related to the presence of a very low score (<50 scores) for the MH component during the first wave, it is perceived as a higher relative risk during the second wave in both populations. The long confinement due to COVID-19 is associated to negative changes in nutritional and physical lifestyle behavior, affecting mainly the MH component.

An appraisal to Hans Berger by the time of his 150th birthday: the human EEG and tales of blood flow, heat and brain waves / Um ensaio sobre o aniversário de 150 anos de Hans Berger: uma história de sangue, calor e ondas cerebrais

Abstract More than 100 years of research have passed by and still the human electroencephalogram (EEG) remains a puzzle to be solved. Starting from his studies on plethysmography until his theories on brain thermodynamics, Hans Berger was able to refine his method of recording cortical signs with the apparatus at his disposal in an ordinary neuropsychiatric yard towards an early account of human EEG. This review is an appraisal of his contribution to the field of modern neurophysiology.

Resumo Mais de 100 anos se passaram e o eletroencefalograma humano (EEG) continua sendo um enigma a ser desvendado. A partir de seus estudos sobre pletismografia até suas teorias sobre termodinâmica cerebral, Hans Berger conseguiu refinar seu método de registro da atividade elétrica cortical com os equipamentos a sua disposição em uma ala psiquiátrica comum produzindo uma descrição acurada do EEG humano. Esta revisão é um breve resumo de sua contribuição para o campo da neurofisiologia moderna.

Risks of Adverse Outcomes for Hospitalized COVID-19 Patients during the Four Waves in Brazil According to SARS-CoV-2 Variants, Age Group, and Vaccine Status.

Brazil was hit with four consecutive waves of COVID-19 until 2022 due to the ancestral SARS-CoV-2 (B.1 lineage), followed by the emergence of variants/subvariants. Relative risks of adverse outcomes for COVID-19 patients hospitalized during the four waves were evaluated. Data were extracted from the largest Brazilian database (SIVEP-Gripe), and COVID-19 patients who were hospitalized during the peak of each of the four waves (15-week intervals) were included in this study. The outcomes of in-hospital death, invasive (IMV) and non-invasive (NIV) ventilation requirements, and intensive care unit (ICU) admission were analyzed to estimate the relative risks. A higher risk of in-hospital death was found during the second wave for all age groups, but a significant reduction was observed in the risk of death for the elderly during the third and fourth waves compared to patients in the first wave. There was an increased risk of IMV requirement and ICU admissions during the second wave for patients aged 18-59 years old compared to the first wave. Relative risk analysis showed that booster-vaccinated individuals have lower risks of in-hospital death and IMV requirement in all age groups compared to unvaccinated/partially vaccinated patients, demonstrating the relevance of full/booster vaccination in reducing adverse outcomes for patients who were hospitalized during the variant prevalence.

[Comparative analysis of clinical characteristics, evolution and mortality of hospitalized patients with COVID-19 during the first and second wave of the pandemic (ECCOVID Study)]. / Análisis comparativo de las características clínicas, evolución y mortalidad de pacientes hospitalizados por COVID-19 durante la primera y segunda ola de la pandemia (Registro ECCOVID).

INTRODUCTION: Clinical features and outcomes of SARSCoV-2 infections may change between different waves of the pandemic. The objective of this study was to compare clinical characteristics and outcomes between two cohorts of patients hospitalized for COVID-19 during the first and second waves in Argentina. METHODS: Multicenter and prospective registry of patients =18 years old with a confirmed diagnosis of COVID-19 admitted to 18 hospitals in Argentina during the first wave (March to October 2020) and second wave (March to July 2021) of the pandemic. Demographics, clinical characteristics, and outcomes of these patients were compared. RESULTS: A total of 1691 patients were included (first wave n = 809, second wave n = 882). Hospitalized patients during the second wave were older (median 53 years vs. 61 years, p < 0.001), had more comorbidities (71% vs. 77%, p=0.007) and required more supplemental oxygen at admission (21% vs 62%, p < 0.001). During hospitalization, patients of the second wave required more supplemental oxygen (49% vs. 85%, p < 0.001), invasive ventilation (12% vs. 22%, p < 0.001) and had higher 30- day mortality (11% vs. 26%, p < 0.001). Comparing only patients who required supplemental oxygen during hospitalization, 30-day mortality was 20% and 30% p < 0.001 for the first and second wave, respectively. CONCLUSION: Compared to patients admitted during the first wave, patients admitted with SARS-CoV2 during the second wave in Argentina were more seriously ill and had a higher mortality.

Introducción: Las características clínicas y evolutivas de los pacientes con diagnóstico de COVID-19 pueden diferir entre las distintas olas de la pandemia. El objetivo de este estudio fue comparar las características clínicas, evolución y mortalidad de pacientes hospitalizados por COVID-19 durante la primera y segunda ola en Argentina. Métodos: Registro multicéntrico y prospectivo de pacientes = 18 años con diagnóstico confirmado de COVID-19 internados en 18 hospitales de Argentina durante la primera (marzo a octubre 2020) y la segunda ola (marzo a julio 2021) de la pandemia. Se compararon variables demográficas, características clínicas, y evolución a 30 días. Resultados: Se incluyeron un total de 1691 pacientes (primera ola n = 809, segunda ola n = 882). Los pacientes hospitalizados durante la segunda ola tenían mayor edad (mediana 53 años vs. 61 años, p < 0.001), comorbilidades (71% vs. 77%, p = 0.007) y requerimiento de oxígeno (21% vs. 62%, p < 0.001). Durante la hospitalización, los pacientes de la segunda ola requirieron más oxigenoterapia (49% vs. 85%, p < 0.001), asistencia mecánica respiratoria (12% vs. 22%, p < 0,001) y presentaron mayor mortalidad (11% vs. 26%, p < 0.001). Comparando únicamente a los que requirieron oxigenoterapia durante la hospitalización, la mortalidad a los 30 días fue de 20% y 30% p < 0.001 en la primera y segunda ola respectivamente. Conclusión: Comparados con los pacientes internados durante la primera ola, los internados durante la segunda ola de SARS-CoV-2 en Argentina presentaron mayor gravedad y mortalidad.

Progesterone circulation and follicular growth in adapted Bos taurus cows.

The creole breed Blanco Orejinegro (Bos taurus adapted) is an important animal genetic resource in Colombia. However, very little is known about the reproductive physiology of the breed. The objective was to determine the dynamics of progesterone circulation and follicular growth in Blanco Orejinegro cows throughout the estrous cycle. Fifteen cyclic Blanco Orejinegro cows were used and subjected to hormonal protocol for estrous and ovulation synchronization. Once the time of ovulation was identified by monitoring the ovarian dynamics with ultrasonography equipment. For description of the results, the mean was used as a measure of central tendency and the standard error of the mean. Statistical analysis was longitudinal descriptive. Blood samples were collected every 24 hr throughout the estrous cycle for serum quantification of progesterone (P4), monitoring of corpus luteum (CL) growth dynamics and follicular dynamics. It was possible to verify that 76.92% of the Blanco Orejinegro cows presented two follicular waves during the estrous cycle and the highest circulating levels of P4 (> 6.00 ng mL-1) were observed on the 14th day of the estrous cycle. It was concluded that the creole cows of the Blanco Orejinegro breed presented two follicular waves per estrous cycle. In addition to, the size of the CL was consistent with the secretion of progesterone presenting higher circulating levels at the end of the luteal phase.

Selective Electron-Phonon Coupling in Dimerized 1T-TaS2 Revealed by Resonance Raman Spectroscopy.

The layered transition-metal dichalcogenide material 1T-TaS2 possesses successive phase transitions upon cooling, resulting in strong electron-electron correlation effects and the formation of charge density waves (CDWs). Recently, a dimerized double-layer stacking configuration was shown to form a Peierls-like instability in the electronic structure. To date, no direct evidence for this double-layer stacking configuration using optical techniques has been reported, in particular through Raman spectroscopy. Here, we employ a multiple excitation and polarized Raman spectroscopy to resolve the behavior of phonons and electron-phonon interactions in the commensurate CDW lattice phase of dimerized 1T-TaS2. We observe a distinct behavior from what is predicted for a single layer and probe a richer number of phonon modes that are compatible with the formation of double-layer units (layer dimerization). The multiple-excitation results show a selective coupling of each Raman-active phonon with specific electronic transitions hidden in the optical spectra of 1T-TaS2, suggesting that selectivity in the electron-phonon coupling must also play a role in the CDW order of 1T-TaS2.

Análisis comparativo de las características clínicas, evolución y mortalidad de pacientes hospitalizados por COVID-19 durante la primera y segunda ola de la pandemia (REGISTRO ECCOVID) / Comparative analysis of clinical characteristics, evolu tion and mortality of hospitalized patients with COVID-19 during the first and second wave of the pandemic (ECCOVID STUDY)

Resumen Introducción : Las características clínicas y evolutivas de los pacientes con diagnóstico de COVID-19 pueden diferir entre las distintas olas de la pandemia. El objetivo de este estudio fue comparar las características clínicas, evolución y mortalidad de pacientes hospitalizados por COVID-19 durante la primera y segunda ola en Argentina. Métodos : Registro multicéntrico y prospectivo de pacientes ≥ 18 años con diagnóstico confirmado de COVID-19 internados en 18 hospitales de Argentina durante la primera (marzo a octubre 2020) y la segunda ola (marzo a julio 2021) de la pandemia. Se compararon variables demográficas, características clínicas, y evolu ción a 30 días. Resultados : Se incluyeron un total de 1691 pacien tes (primera ola n = 809, segunda ola n = 882). Los pa cientes hospitalizados durante la segunda ola tenían mayor edad (mediana 53 años vs. 61 años, p < 0.001), comorbilidades (71% vs. 77%, p = 0.007) y requerimiento de oxígeno (21% vs. 62%, p < 0.001). Durante la hospi talización, los pacientes de la segunda ola requirieron más oxigenoterapia (49% vs. 85%, p < 0.001), asistencia mecánica respiratoria (12% vs. 22%, p <0,001) y presen taron mayor mortalidad (11% vs. 26%, p < 0.001). Compa rando únicamente a los que requirieron oxigenoterapia durante la hospitalización, la mortalidad a los 30 días fue de 20% y 30% p < 0.001 en la primera y segunda ola respectivamente. Conclusión : Comparados con los pacientes interna dos durante la primera ola, los internados durante la segunda ola de SARS-CoV-2 en Argentina presentaron mayor gravedad y mortalidad.

Abstract Introduction : Clinical features and outcomes of SARS-CoV-2 infections may change between different waves of the pandemic. The objective of this study was to compare clinical characteristics and outcomes between two cohorts of patients hospitalized for COVID-19 during the first and second waves in Argentina. Methods : Multicenter and prospective registry of patients ≥18 years old with a confirmed diagnosis of COVID-19 admitted to 18 hospitals in Argentina during the first wave (March to October 2020) and second wave (March to July 2021) of the pandemic. Demographics, clinical characteristics, and outcomes of these patients were compared. Results : A total of 1691 patients were included (first wave n = 809, second wave n = 882). Hospitalized pa tients during the second wave were older (median 53 years vs. 61 years, p < 0.001), had more comorbidities (71% vs. 77%, p=0.007) and required more supplemental oxygen at admission (21% vs 62%, p < 0.001). During hos pitalization, patients of the second wave required more supplemental oxygen (49% vs. 85%, p < 0.001), invasive ventilation (12% vs. 22%, p < 0.001) and had higher 30- day mortality (11% vs. 26%, p < 0.001). Comparing only patients who required supplemental oxygen during hos pitalization, 30-day mortality was 20% and 30% p < 0.001 for the first and second wave, respectively. Conclusion : Compared to patients admitted during the first wave, patients admitted with SARS-CoV2 dur ing the second wave in Argentina were more seriously ill and had a higher mortality.

Effects of Shear Stress Waves on Meat Tenderness: Ultrasonoporation.

Meat is an important part of the food pyramid in Mexico, to such an extent that it is included in the basic food basket. In recent years, there has been great interest in the application of so-called emerging technologies, such as high-intensity ultrasound (HIU), to modify the characteristics of meat and meat products. The advantages of the HIU in meat such as pH, increased water-holding capacity, and antimicrobial activity are well documented and conclusive. However, in terms of meat tenderization, the results are confusing and contradictory, mainly when they focus on three HIU parameters: acoustic intensity, frequency, and application time. This study explores via a texturometer the effect of HIU-generated acoustic cavitation and ultrasonoporation in beef (m. Longissimus dorsi). Loin-steak was ultrasonicated with the following parameters: time tHIU = 30 min/each side; frequency fHIU = 37 kHz; acoustic intensity IHIU = ~6, 7, 16, 28, and 90 W/cm2. The results showed that acoustic cavitation has a chaotic effect on the loin-steak surface and thickness of the rib-eye due to Bjerknes force, generating shear stress waves, and acoustic radiation transmittance via the internal structure of the meat and the modification of the myofibrils, in addition to the collateral effect in which the collagen and pH generated ultrasonoporation. This means that HIU can be beneficial for the tenderization of meat.