bluuebunny/crossref_metadata_2025 huggingface dataset:
Respuesta e interpretación a políticas de rendición de cuentas de formación docente en Chile
Authors:   Universidad de Chile, Fernández Cofré María Beatriz , Fernández Quevedo Loreto ,   Universidad de Chile, Diaz Navarro Mónica ,   Universidad Alberto Hurtado (Chile), Jofré Cáceres Patricia ,   Universidad Alberto Hurtado (Chile)
Published: April 2021

Diferentes países han generado políticas para controlar la formación docente mediante regulaciones y rendición de cuentas desde los años 90. Sin embargo, existe escasa y contradictoria evidencia sobre los efectos de estas políticas. En Chile, la rendición de cuentas y la desregulación operan simultáneamente en la formación docente. En 2016 se aprobó la política de Sistema de Desarrollo Profesional Docente, que incluye la acreditación obligatoria de programas, el aumento gradual de la selectividad, la renovación de los estándares, y la implementación de pruebas diagnósticas para estudiantes de pedagogía. Este estudio cualitativo exploratorio analiza, a través de entrevistas semiestructuradas, cómo 40 directores de programas de pedagogía de 10 universidades chilenas ponen en práctica —interpretan y responden a— esta política. Utilizando un análisis de contenido cualitativo, se identificaron cuatro grupos de interpretaciones y respuestas, cuyas diferencias pueden entenderse con base en dimensiones contextuales que median las concepciones de profesionalismo, justicia y relaciones de poder expresadas por los participantes. Este estudio contribuye a comprender los elementos que influyen en la puesta en práctica de políticas de formación docente, a expandir la escasa literatura empírica en esta área, y a informar a quienes toman decisiones de política y forman docentes.
Relación de la variabilidad climática con el crecimiento diamétrico de ocho especies arbóreas de bosque seco en Costa Rica
Authors: Valverde Juan Carlos , Arias Dagoberto , Castillo Marvin , Torres Danilo
Published: April 2021

El crecimiento de árboles en el bosque seco tropical tiene una relación significativa con el clima el crecimiento se desarrolla en la época lluviosa y en época seca el crecimiento se estanca. Sin embargo, son pocas las especies con las que se cuenta de estudios de crecimiento. Por tanto, el estudio caracterizó los efectos de la variación climática en el crecimiento diamétrico (Cd) de las ocho especies arbóreas de mayor importancia en un bosque seco tropical en Costa Rica. Se seleccionaron 12 árboles por especie, en los cuales se midió el Cd entre el 2015 y el 2018, complementado con mediciones climáticas (temperatura, precipitación, humedad relativa y horas luz) y determinación de la densidad de la madera (Dm). Se desarrollaron ecuaciones de Cd con variables climáticas y se evaluaron relaciones de Dm con Cd. Los resultados mostraron que el Cd anual es de 3.04 mm en Albizia niopoides; 2.83 mm en Bursera simaruba, 2.07 mm en Cordia alliodora, 1.92 mm en Cordia panamensis, 0.68 mm en Hymenaea courbaril; 3.82 mm en Luehea speciosa; 1,63 mm en Machaerium biovulatum y 0,30 mm en Handroanthus impetiginosus; se encontró una fase de crecimiento en la estación lluviosa y leves contracciones diamétricas en la estación seca. Con la correlación significativa de Cd con precipitación y temperatura media anual se determinó una relación positiva entre Dc y precipitación y negativa entre Cd y temperatura promedio, lo cual permitió desarrollar ecuaciones lineales de predicción de crecimiento con R2 superiores a 0,61 y errores menores a 1,00. Finalmente, se determinaron relaciones entre Cd y Dm; conforme Dm fue menor se obtuvieron mayores Cd.
Heterogeneidad espacial a pequeña escala y diversidad de interacciones planta-visitante floral en alta montaña
Authors: Santamaría Bueno Silvia , Méndez Iglesias Marcos
Published: April 2021

La homogeneización antrópica de los hábitats reduce la biodiversidad, pero se desconoce su efecto sobre la ocurrencia y frecuencia de interacciones planta-visitante floral. Aquí exploramos cómo la heterogeneidad ambiental a pequeña escala (decenas de metros) contribuye a la diversidad de interacciones planta-visitante floral en dos ecosistemas alpinos. Para ello, obtuvimos redes de interacciones planta-visitante floral en mosaicos de hábitat de ambos ecosistemas y calculamos la importancia de dos fuentes de reemplazo de interacciones entre hábitats: cambios de identidad de especies (reemplazo de especies); y diferencias en las interacciones entre las especies compartidas por los hábitats, i.e. las especies interaccionan solo en un subconjunto de los hábitats en los que coexisten. La heterogeneidad aumentó la diversidad de interacciones, las diferencias en las interacciones entre especies compartidas contribuyeron considerablemente a la diversidad de interacciones y las plantas interaccionaron con más visitantes florales donde eran más abundantes. Las interacciones variaron más de lo predicho por la variación de especies, así que el reemplazo de especies no predice bien el reemplazo de interacciones. Nuestros resultados apoyan el importante papel de la heterogeneidad espacial para mantener una elevada diversidad de interacciones planta-visitante floral.
Estrés fisiológico en urogallos cantábricos (Tetrao urogallus cantabricus) silvestres y en cautividad: variaciones temporales e implicaciones metodológicas
Authors: Martínez Padilla Jesús , Estrada Acedo Alba
Published: April 2021

El estudio de los factores ambientales que pueden explicar los niveles de estrés fisiológico en poblaciones naturales es de vital importancia para especies vulnerables, ya que puede influir en la mortalidad de los individuos y, por tanto, en la viabilidad poblacional. En este trabajo se exploran los condicionantes ambientales que pueden explicar las variaciones de estrés fisiológico medido a través de niveles de corticosterona en plumas de urogallo cantábrico (Tetrao urogallus cantabricus). Se emplearon muestras recogidas de individuos en cautividad y de individuos silvestres. Las muestras recogidas de los individuos silvestres se recopilaron desde 1998 hasta 2017 y se consideraron 35 variables climáticas de temperatura y precipitación. Los análisis de repetibilidad sugirieron que los niveles de corticosterona en la combinación de plumas corporales y secundarias fueron repetibles dentro de individuos, mientras que en la combinación de plumas corporales y primarias no lo fueron, por lo que se consideraron sólo las medidas de las plumas corporales y secundarias. Los resultados indicaron que los individuos en cautividad tuvieron un menor estrés fisiológico y que, en individuos silvestres, hubo un incremento de los niveles de estrés hasta estabilizarse en los últimos años de estudio. Ninguna variable climática estuvo relacionada con los niveles de estrés fisiológico. Especulamos que la tendencia temporal en los niveles de estrés podría estar reflejando limitaciones alimenticias, quizá asociadas a cambios en la estructura o composición del hábitat o interacciones con otras especies silvestres o ganado doméstico, lo que podría explicar el menor estrés fisiológico de los individuos en cautividad. Desde el punto de vista metodológico, las plumas secundarias o corporales, independientemente del sexo, serían las preferibles para establecer un monitoreo del estrés fisiológico del urogallo en condiciones naturales o de cautividad.
Efectos del cambio global sobre la dinámica poblacional de la fauna de montaña
Authors: Gutiérrez David
Published: April 2021

Las montañas ocupan el 27% de la superficie terrestre y están presentes en casi todos sus biomas. Son sistemas que albergan una elevada proporción de especies endémicas y de climas fríos y aportan diversos servicios ecosistémicos. Sin embargo, a pesar de su topografía abrupta, las montañas no están exentas de los impactos del cambio global que, entre otras cosas, han afectado a la dinámica de las poblaciones de fauna, suponiendo en algunos casos retracciones que han incrementado su riesgo de extinción regional. Además, el rango de respuestas observado es amplio debido a los efectos de diversos factores extrínsecos (ambientales) e intrínsecos sobre las poblaciones. Este trabajo revisa las evidencias existentes de los impactos del cambio climático y las alteraciones en los usos del suelo sobre las poblaciones animales de montaña. Para ello, (1) se presenta una síntesis de las tendencias temporales de la climatología y de los usos del suelo, atendiendo a su variación a lo largo del gradiente altitudinal; (2) se describen los tipos de datos disponibles; (3) se sintetizan los patrones encontrados según el tipo de información analizada, así como los posibles mecanismos que explican su variabilidad; y (4) se proponen algunas posibles mejoras para la toma y la interpretación de los datos utilizados en el estudio del impacto del cambio global en poblaciones de montaña.
Conventional and Improved Inclusion-Exclusion Derivations of Symbolic Expressions for the Reliability of a Multi-State Network
Authors: Rushdi Ali Muhammad Ali , Amashah Motaz Hussain
Published: April 2021

This paper deals with an emergent variant of the classical problem of computing the probability of the union of n events, or equivalently the expectation of the disjunction (ORing) of n indicator variables for these events, i.e., the probability of this disjunction being equal to one. The variant considered herein deals with multi-valued variables, in which the required probability stands for the reliability of a multi-state delivery network (MSDN), whose binary system success is a two-valued function expressed in terms of multi-valued component successes. The paper discusses a simple method for handling the afore-mentioned problem in terms of a standard example MSDN, whose success is known in minimal form as the disjunction of prime implicants or minimal paths of the pertinent network. This method utilizes the multi-state inclusion-exclusion (MS-IE) principle associated with a multi-state generalization of the idempotency property of the ANDing operation. The method discussed is illustrated with a detailed symbolic example of a real-case study, and it produces a more precise version of the same numerical value that was obtained earlier. The example demonstrates the notorious shortcomings and the extreme inefficiency that the MS-IE method suffers, but, on the positive side, it reveals the way to alternative methods, in which such a shortcoming is (partially) mitigated. A prominent and well known example of these methods is the construction of a multi-state probability-ready expression (MS-PRE). Another candidate method would be to apply the MS-IE principle to the union of fewer (factored or composite) paths that is converted (at minimal cost) to PRE form. A third candidate method, employed herein, is a novel method for combining the MS-PRE and MS-IE concepts together. It confines the use of MS-PRE to ‘shellable’ disjointing of ORed terms, and then applies MS-IE to the resulting partially orthogonalized disjunctive form. This new method makes the most of both MS-PRE and MS-IE, and bypasses the troubles caused by either of them. The method is illustrated successfully in terms of the same real-case problem used with the conventional MS-IE.
Evaluation of the Renal Safety of Direct Acting Antivirals in Chronic Hepatitis C Patients
Authors: Ashram Islam , Saleh Mohammad
Published: April 2021

Objective:Direct acting antivirals (DAA) is a class of antivirals that hasbeen extensively used in chronic hepatitis C virus (HCV) patients over the past 6 years.Despite the excellent therapeutic benefits of DAA, there is a knowledge gap regardingthe safety of this class. Several reports of possible renal toxicity associated with DAAadministration can be found in the literature. The aims of this study are: to assess therenal safety of DAA used for the treatment of chronic HCV infection and to quantify the odds ofdeveloping renaltoxicityin patients withchronicHCV viralinfection.

Study Design: Disproportionalityanalysiswasusedtodetectsignalsofpotentialsideeffects.

Place andDuration: Amman –Jordan,One year study since September 2017 to march 2018.

Methods: The method that was applied in the current study is obtaining the data from United States (US) food and drug administration(FDA)adverseeventreportingsystem(FAERS).DatabetweenJuly,2014andSeptember,2017werecombinedandexplored.Disproportionalityanalysiswasconducted to reports from chronic HCV patients to explore possible association betweenDAA administrationand renalsideeffects.

Results: This study showed that a total of 3,837,418 safety reports were available in the period between July,2014 and September, 2017. Patients with chronic HCV infection represent 22,022 cases.When considering all DAA as drug of interest, the use of DAA alone or in combinationwith interferon and/or ribavirin did not increase the risk of having renal side effects.Exploring individual DAA demonstrated a significant association between the incidenceofrenalsideeffectsandtheadministrationoftelapreviranddasabuvir.ConsideringrenalsideeffectsindividuallyshowedasignificantassociationbetweenDAAadministrationand chronickidney disease.

Conclusions: In this study, we reported a significant association between DAA administration andchronic kidney disease and between telaprevir or dasabuvir and renal side effect. Thesefindings are used for hypothesis generation rather than testing.
Successful Management of Sickle Cell Disease Patient with Covid-19 Infection in a Low Resource Setting: Case Study
Authors: Kingsley Akaba , Betta Edu C. , Edakabasi Akaba , Ofonime Essien , Philemon Bibia Glory
Published: April 2021

Background: Sickle cell disease (SCD) patients have greater susceptibility to infections, they are reckoned to be vulnerable patients during the current COVID-19 pandemic. SCD patients are commonly affected by pulmonary complications such as acute chest syndrome (ACS), pulmonary embolism (PE) and pneumonia that contribute significantly to mortality risks.

Aim: The study was aimed at showing the impact of SARS-COV viral pandemic on SCD patients.

Presentation of Case: A 42-year-old male known sickle cell disease patient, who presented with a 5 days’ history of chest pain and difficulty in breathing with a pain score of 8/10. Pain was said to be localized and, subside on the ingestion of analgesics (Tab DF118/60mg and PCM 1000mg) with no known aggravating factor, but there was associated history of difficulty in breathing. The patient was being managed as a case of vaso-occlusive crises R/O acute chest syndrome, and was commenced on adequate hydration, oxygen saturation was between 95-85%. On examination, respiratory rate was 20 cycles per minute, pulse rate – 96 beats/minute, BP and chest examination were essentially normal. CBC showed the Packed Cell Volume of 31%, White Blood Cells 15.04 x 109/L, Neutrophils 7.51x103/µL Lymphocyte 6.50 x103/µL, Monocyte 0.76 x103/µL Eosinophils 0.20x103/µL, Basophils 0.05x103/µL, Platelet 358. The electrolytes (Na-135 mmol/L, K 3.5mmol/L, HCO3-20), urea -10 mmol/L and creatinine (88mmol/L) were normal, the chest x-ray showed cardiomegaly but the lung fields were clear. The patient was administered ceftriaxone (prophylactic antibiotics – 1 g daily).  The patient tested positive to COVID-19 and was immediately transferred to the isolation centre for proper management. He was commenced on oral medication, azithromycin, dexamethasone, ivermectine, amoxicillin/clavulanic acid, vitamin C, clexane and the analgesic was changed to paracetamol and dihydrocodeine to alternate 3 hourly with accordance to the national guidelines. In addition, he was administered subcutaneous enoxaparin due to the hypercoagulability state of SCD. The patient’s health status improved within 24hours of commencement of the above medications and remained stable all through the period of isolation and a repeat covid-19 test was done 15 days of admission using and reverse transcriptase PCR and was discharged home according to the National protocol.

Conclusion: Studies and clinical trials are essential to evaluate effective diagnostic and management options for SCD patients and other high-risk conditions like diabetes hypertension, cancer patients and so on that are associated with fatal complications when infected with COVID-19 and similar diseases.
Peripheral venipuncture practices performed by nursing professionals in a university hospital / Práticas de venopunção periférica dos profissionais de enfermagem em um hospital universitário
Authors: Silva Monik , Schuelter Patricia Ilha , Tourinho Francis Solange Vieira , Da Silva Paola Finkler , Santos Viviane Euzébia Pereira , Misiak Marciele
Published: April 2021

Objetivo: caracterizar as práticas de punção venosa periférica executadas pelos profissionais de enfermagem no cuidado aos pacientes pediátricos e geriátricos em um hospital universitário do sul do país. Método: quantitativo, observacional descritivo. Realizado em um hospital universitário da região sul do país, de dezembro de 2015 a junho de 2016, com 14 profissionais da equipe de enfermagem durante a realização da prática de punção venosa periférica em crianças e idosos. Resultados: Realizou-se 20 observações para o grupo de idosos e 5 para o grupo pediátrico, e em todas as observações houveram alguma divergência com a orientação teórica que poderia resultar em um dano ao paciente e/ou profissional. Conclusão: ao realizar esse estudo, percebeu-se uma variação da técnica e divergências entre as ações praticadas, destacando a importância da padronização e desenvolvimento de técnicas a partir de fundamentação científica para promoção da segurança do paciente.
Characteristics of the service provided by the mobile urgency service in different brazilian regions / Características do atendimento prestado pelo serviço de atendimento móvel de urgência em diferentes regiões brasileiras
Authors: Buchs Zucatti Paula , Dias da Silva Lima Maria Alice , Dal Pai Daiane , Melo de Souza Luccas , Cezimbra Hoffmann Caroline
Published: April 2021

Objetivo: Caracterizar o atendimento do Serviço de Atendimento Móvel de Urgência às demandas dos usuários em diferentes municípios brasileiros. Método: Pesquisa transversal, que utilizou observação sistemática de 49 atendimentos realizados pelo Serviço de Atendimento Móvel de Urgência em diferentes regiões brasileiras, entre julho e agosto de 2015. Aplicou-se estatística descritiva e inferencial. Resultados: Predominaram demandas clínicas (42,9%) e atendimentos de Suporte Básico de Vida despachado (65,3%) às residências (40,8%); 71,4% dos usuários foram transportados e 51% encaminhados a unidades de emergência, com registro de 89,8% dos atendimentos. O tempo resposta foi de 12 minutos, sem diferenças entre as regiões, mas menor nas transferências para Unidades de Pronto Atendimento (p < 0,05). A higienização das mãos pelos profissionais foi inexistente em 54,3% atendimentos.  Conclusão: A análise dos atendimentos às demandas dos usuários suscita planejamento da assistência para reorientação da atenção e melhoria da qualidade e segurança.
Mapping the use of the child health handbook by parents and professionals: a descriptive study / Mapeamento do uso da caderneta de saúde da criança por pais e profissionais: um estudo descritivo
Authors: Coelho Isadora Íris de Almeida , Silva Laura Johanson da , Santos Emanuel Pereira dos , Bustamante Isabela de Oliveira , Silva Luan Cláudio de Oliveira , Maciel Maria José Pessanha
Published: April 2021

Objetivos: identificar o conhecimento dos pais acerca da Caderneta de Saúde da Criança, mapear o preenchimento da Caderneta pelos profissionais e correlacionar o preenchimento da caderneta com a orientação dos pais pelos profissionais de saúde. Métodos: pesquisa quantitativa descritiva, realizada num hospital universitário, através da aplicação de formulário com 22 pais ou responsáveis e análise através de tabelas, gráficos, estatística descritiva e inferencial. Resultados: 77,3% dos entrevistados alegaram não ter recebido orientação sobre a Caderneta, a maioria das cadernetas não apresentava registro no item de Índice de Massa Corporal tanto como a maioria apresentava preenchimento completo no item de registro de vacinas do calendário básico e as correlações não foram significativas, apresentando independência na maioria. Conclusão: evidenciou-se uma necessidade de orientação dos familiares tanto como capacitação dos profissionais que trabalham com a população infantil e não se verificou dependência entre a maioria das variáveis correlacionadas neste estudo.
Scientific production of patient nursing care spinal cord injury: a bibliometric analysis / Produção científica dos cuidados de enfermagem ao paciente com traumatismo da medula espinhal: uma análise bibliométrica
Authors: Albuquerque Geyslane Pereira Melo de , Coura Alexsandro Silva , Fernandes Marta Regina Chaves Camilo , França Inácia Sátiro Xavier de , Baptista Rosilene Santos , Nascimento Monique Oliveira do
Published: April 2021

Objetivo: descrever a distribuição da produção científica dos cuidados de enfermagem ao paciente com traumatismo da medula espinhal e verificar quais as temáticas mais abordadas. Método: análise bibliométrica através da Lei de Bradford, Lei de Zipf e estatística textual realizada com publicações em português, inglês e espanhol, disponibilizadas em bases de dados nacionais e internacionais, no período de 1978 a 2018. Resultados: a amostra foi composta por 33 artigos distribuídos em 13 periódicos, sendo a maioria originais e de abordagem quantitativa. O Brasil foi o país com maior número de publicações, apresentando a terceira colocação dos periódicos no núcleo de Bradford. Foi identificado um valor médio do multiplicador de Bradford (XmB) = 2,1. Os termos com maior semântica foram: lesão medular, paciente, enfermagem, enfermeiro e cuidado. Conclusão: os indicadores bibliométricos demonstraram uma produção científica com pouca produtividade, porém com tendência a crescimento nas últimas décadas. Faz-se necessário realizar novos estudos acerca da temática para aprimorar o cuidado ofertado ao paciente com lesão medular.
Breast cancer diagnosis: implications for the behavioral changes in the social support network / Diagnóstico do câncer de mama: implicações na mudança de comportamento da rede de suporte social
Authors: Ambrosim Mariana Zoboli , Almeida Barbosa Bruna Ligia Ferreira , Oliveira Andreia Gomes , Maciel Paulete Maria Ambrosio , Lima Eliane de Fátima Almeida , Leite Franciele Marabotti Costa
Published: April 2021

Objetivo:Desvelar as mudanças de comportamento dos diferentes suportes sociais a partir do diagnóstico de câncer de mama. Metodologia:Estudo descritivo, qualitativo, realizado em um Programa de Reabilitação para Mulheres Mastectomizadas em Vitória, Espírito Santo. Participaram do estudo 16 mulheres com diagnóstico de câncer de mama, submetidas à mastectomia. As falas foram analisadas segundo a técnica de análise de conteúdo. Resultados:Houveram mudanças de comportamento das redes de apoio social após o diagnóstico de câncer de mama, as maiores mudanças comportamentais aconteceram na família (43,5%), seguido do parceiro íntimo (30,4%) e entre os amigos (26,1%). Nas relações de amizade e familiares houve uma melhora no oferecimento de cuidado, já na relação com o parceiro também se verificou afastamento do mesmo. Conclusão:O diagnóstico de câncer de mama acarreta mudanças de comportamentos nos relacionamentos familiares, de amigos e do parceiro íntimo. Recomenda-se a atuação de profissionais de saúde nesse processo.
The quality of life of intensive nurses through instrument sf36 / A qualidade de vida de enfermeiros intensivistas através do instrumento sf36
Authors: De Carvalho Aymê Christina Rosa , Martins Rayane Ferreira , Gama Julyana Cardoso , Marta Cristiano Bertolossi , E Lemos Goulart Maithe de Carvalho , Nassar Pedro Ruiz Barbosa
Published: April 2021

Objetivos: Investigar a qualidade de vida dos enfermeiros na Unidade de Terapia Intensiva e apresentar as dificuldades classificadas como prioritárias por esses enfermeiros. Métodos: Trata-se de um estudo descritivo de delineamento transversal, com abordagem quantitativa. A pesquisa contou com 33 enfermeiros selecionados nas Unidades de Terapia Intensiva (UTI) de um hospital estadual de médio porte do Rio de Janeiro. A análise estatística de conteúdo foi realizada pelo programa SPSS. Resultados: Indicaram que h acentuado comprometimento físico e psicológico no estado geral da saúde e na vitalidade dos profissionais e que a má qualidade de vida deles tem influência direta e extrema na qualidade do serviço prestado. Conclusão: É indispensável que os gestores tenham conhecimento do comprometimento dos scores de qualidade de vida dos profissionais, das dificuldades enfrentadas e de que é preciso estratégias gerencias para o aperfeiçoamento do processo de trabalho.
Temporal aids tendency among young people in northeastern Brazil / Tendência temporal da aids entre jovens no nordeste do Brasil
Authors: De Oliveira Layze Braz , Rodrigues Antônio Filho Alves , Carvalho Herica Emilia Félix de , Sousa Karinna Alves Amorim de , Araújo Telma Maria Evangelista de , Fernandes Ana Paula Morais
Published: April 2021

Objetivo: Caracterizar o perfil epidemiológico da infecção pela Aids em jovens entre 15 a 34 anos, notificados com Aids e o panorama dos óbitos no período de 2007 a 2017 em um estado do nordeste do Brasil. Método: Estudo descritivo realizado por meio de levantamento na base de dados Sistema de Informação de Agravos de Notificação. A coleta ocorreu julho de 2018. Resultados: O sexo masculino obteve 69% das notificações, com um aumento homogêneo no número de notificação com um pico nos anos de 2010 (6,82%), 2014 e 2015 (12,41%) e 2017 (16,11%).  A capital obteve os maiores percentuais de casos (66,41%) e o número de óbito diminuiu ao longo dos anos. Conclusão: À exemplo do acontece nos demais estados do Brasil, o perfil da Aids em jovens experimenta uma mudança ao longo dos anos bem como um considerável aumento do número de casos notificados e declínio dos óbitos.
Rapid and Electronic Identification and Quantification of Age‐Specific Circulating Exosomes via Biologically Activated Graphene Transistors
Authors: Hajian Reza , DeCastro Jonalyn , Parkinson Jonathan , Kane Alex , Camelo Andres Felipe Romero , Chou Peichi Peggy , Yang Jielin , Wong Nathan , Hernandez Ecson Daniel Obando , Goldsmith Brett , Conboy Irina , Aran Kiana
Published: April 2021

Increasing access to modern clinical practices concomitantly extends lifespan, ironically revealing new classes of degenerative and inflammatory diseases of later years. Here, an electronic graphene field‐effect transistor (gFET) is reported, termed EV‐chip, for label‐free, rapid identification and quantification of exosomes (EV) associated with aging through specific surface markers, CD63 and CD151. Studies suggest that blood‐derived exosomes carry specific biomolecules that can be used toward diagnostic applications of age and health. However, to observe improvements in patient outcomes, earlier detection at the point‐of‐care (POC) is required. Unfortunately, conventional techniques and other electronic‐based platforms for exosome sensing are burdensome and inept for the POC distinction of aged blood factors. It is shown that EV‐chip can quantitatively detect purified exosomes from plasma, with a limit of detection (LOD) of 2 × 104 particles mL−1 and a limit of quantification (LOQ) of 6 × 104 particles mL−1. The sensitivity and compact electronics of the EV‐chip improves upon previously published electronic biosensors, making it ideal for a physician's office or a simple biological laboratory. The sensitivity, selectivity, and portability of the EV‐chip demonstrate the potential of the biosensor as a powerful point‐of‐care diagnostic and prognostic tool for age‐related diseases.
Bioprinting of Regenerative Photosynthetic Living Materials
Authors: Balasubramanian Srikkanth , Yu Kui , Meyer Anne S. , Karana Elvin , Aubin‐Tam Marie‐Eve
Published: April 2021

Living materials, which are fabricated by encapsulating living biological cells within a non‐living matrix, have gained increasing attention in recent years. Their fabrication in spatially defined patterns that are mechanically robust is essential for their optimal functional performance but is difficult to achieve. Here, a bioprinting technique employing environmentally friendly chemistry to encapsulate microalgae within an alginate hydrogel matrix is reported. The bioprinted photosynthetic structures adopt pre‐designed geometries at millimeter‐scale resolution. A bacterial cellulose substrate confers exceptional advantages to this living material, including strength, toughness, flexibility, robustness, and retention of physical integrity against extreme physical distortions. The bioprinted materials possess sufficient mechanical strength to be self‐standing, and can be detached and reattached onto different surfaces. Bioprinted materials can survive stably for a period of at least 3 days without nutrients, and their life can be further extended by transferring them to a fresh source of nutrients within this timeframe. These bioprints are regenerative, that is, they can be reused and expanded to print additional living materials. The fabrication of the bioprinted living materials can be readily up‐scaled (up to ≥70 cm × 20 cm), highlighting their potential product applications including artificial leaves, photosynthetic bio‐garments, and adhesive labels.
Nanowire Based Mechanostimulating Platform for Tunable Activation of Natural Killer Cells
Authors: Bhingardive Viraj , Edri Avishay , Kossover Anna , Saux Guillaume Le , Khand Bishnu , Radinsky Olga , Iraqi Muhammed , Porgador Angel , Schvartzman Mark
Published: April 2021

The understanding of the activation mechanism of natural killer (NK) cells has been traditionally based on the biochemical interaction of NK cell receptors with the ligands presenting on target cells. Yet, how physical features of the NK cell environment, such as stiffness and nanoscale topography, regulate the activity of NK cells, is unknown. An artificial microenvironment is developed for NK cell stimulation based on variably elongated nanowires functionalized with activating antigens and used it as a tunable model system to study the separate and cumulative effects of elasticity and nanotopography on NK cell activation. It is found that late signaling, degranulation, and cytokine production in NK cells consistently vary with nanowire length, and it is maximized for the longest nanowires, measuring ≈20 µm in length. Intriguingly, a similar trend is observed for nanowires lacking antigens, albeit with a lower activation magnitude overall, indicating that chemical and mechanical stimuli independently determine the activation of NK cells. The demonstrated tuning of the activation of NK cells by nanoscale physical features of their environment not only provides an important insight into the regulation mechanism of these lymphocytes, but also paves the way to rationally designed nanomaterials for controlled ex vivo activation of NK cells in immunotherapy.
Squaramide‐Based Supramolecular Materials Drive HepG2 Spheroid Differentiation
Authors: Liu Tingxian , van den Berk Linda , Wondergem Joeri A. J. , Tong Ciqing , Kwakernaak Markus C. , Braak Bas ter , Heinrich Doris , van de Water Bob , Kieltyka Roxanne E.
Published: April 2021

A major challenge in the use of HepG2 cell culture models for drug toxicity screening is their lack of maturity in 2D culture. 3D culture in Matrigel promotes the formation of spheroids that express liver‐relevant markers, yet they still lack various primary hepatocyte functions. Therefore, alternative matrices where chemical composition and materials properties are controlled to steer maturation of HepG2 spheroids remain desired. Herein, a modular approach is taken based on a fully synthetic and minimalistic supramolecular matrix based on squaramide synthons outfitted with a cell‐adhesive peptide, RGD for 3D HepG2 spheroid culture. Co‐assemblies of RGD‐functionalized squaramide‐based and native monomers resulted in soft and self‐recovering supramolecular hydrogels with a tunable RGD concentration. HepG2 spheroids are self‐assembled and grown (≈150 µm) within the supramolecular hydrogels with high cell viability and differentiation over 21 days of culture. Importantly, significantly higher mRNA and protein expression levels of phase I and II metabolic enzymes, drug transporters, and liver markers are found for the squaramide hydrogels in comparison to Matrigel. Overall, the fully synthetic squaramide hydrogels are proven to be synthetically accessible and effective for HepG2 differentiation showcasing the potential of this supramolecular matrix to rival and replace naturally‐derived materials classically used in high‐throughput toxicity screening.
Engineering Hydrogel‐Based Biomedical Photonics: Design, Fabrication, and Applications
Authors: Guimarães Carlos F. , Ahmed Rajib , Marques Alexandra P. , Reis Rui L. , Demirci Utkan
Published: April 2021

Light guiding and manipulation in photonics have become ubiquitous in events ranging from everyday communications to complex robotics and nanomedicine. The speed and sensitivity of light–matter interactions offer unprecedented advantages in biomedical optics, data transmission, photomedicine, and detection of multi‐scale phenomena. Recently, hydrogels have emerged as a promising candidate for interfacing photonics and bioengineering by combining their light‐guiding properties with live tissue compatibility in optical, chemical, physiological, and mechanical dimensions. Herein, the latest progress over hydrogel photonics and its applications in guidance and manipulation of light is reviewed. Physics of guiding light through hydrogels and living tissues, and existing technical challenges in translating these tools into biomedical settings are discussed. A comprehensive and thorough overview of materials, fabrication protocols, and design architectures used in hydrogel photonics is provided. Finally, recent examples of applying structures such as hydrogel optical fibers, living photonic constructs, and their use as light‐driven hydrogel robots, photomedicine tools, and organ‐on‐a‐chip models are described. By providing a critical and selective evaluation of the field's status, this work sets a foundation for the next generation of hydrogel photonic research.
Protein Labeling and Crosslinking by Covalent Aptamers
Authors: Tivon Yaniv , Falcone Gianna , Deiters Alexander
Published: April 2021

We developed a new approach to selectively modify native proteins in their biological environment using electrophilic covalent aptamers. These aptamers are generated through introduction of a proximity‐driven electrophile at specific nucleotide sites. Using thrombin as a proof‐of‐concept, we demonstrate that covalent aptamers can selectively transfer a variety of functional handles and/or irreversibly crosslink to the target protein. This approach offers broad programmability and high target specificity. Furthermore, it addresses issues common to aptamers such as instability towards endogenous nucleases and residence times during target engagement. Covalent aptamers are new tools that enable specific protein modification and sensitive protein detection. Moreover, they provide prolonged, nuclease‐resistant enzyme inhibition.
Einsatz photolatenter Basen zur lokalen Kontrolle dynamischer Austauschreaktionen in thermisch aktivierbaren Vitrimeren
Authors: Reisinger David , Kaiser Simon , Rossegger Elisabeth , Alabiso Walter , Rieger Bernhard , Schlögl Sandra
Published: April 2021

Vitrimere sind kovalent vernetzte Polymere, die ihre Netzwerktopologie durch aktivierbaren assoziativen Bindungsaustausch neu organisieren können, wenn die Topologie‐Einfriertemperatur (Tv) überschritten wird. Trotz zahlreicher entwickelter Vitrimersysteme besteht ein gravierender Mangel an Methoden für eine kontrollierte und ortsaufgelöste Aktivierung des Bindungsaustauschs oberhalb der Tv. Hier präsentieren wir ein Konzept, das die lokale Freisetzung des effizienten Umesterungskatalysators 1,5,7‐Triazabicyclo[4.4.0]dec‐5‐en (TBD) durch UV‐induzierte Spaltung einer photolatenten Base in einem kovalent vernetzten Thiol‐Epoxid‐Polymer ermöglicht. Mittels Spannungsrelaxationsmessungen, die weit über der Tv des Netzwerks durchgeführt wurden, konnte gezeigt werden, dass nur die kontrollierte Freisetzung von TBD Umesterungen und die damit verbundene Relaxation der Netzwerkspannung ermöglicht. Zudem konnte durch lokal induzierte permanente Formänderungen im Material eine ortsaufgelöste UV‐vermittelte Photoaktivierung der vitrimeren Eigenschaften demonstriert werden.
Enantioselective Total Synthesis of the Archaeal Lipid Parallel GDGT‐0 (Isocaldarchaeol)**
Authors: Falk Isaac D. , Gál Bálint , Bhattacharya Ahanjit , Wei Jeremy H. , Welander Paula V. , Boxer Steven G. , Burns Noah Z.
Published: April 2021

Archaeal glycerol dibiphytanyl glycerol tetraethers (GDGT) are some of the most unusual membrane lipids identified in nature. These amphiphiles are the major constituents of the membranes of numerous Archaea, some of which are extremophilic organisms. Due to their unique structures, there has been significant interest in studying both the biophysical properties and the biosynthesis of these molecules. However, these studies have thus far been hampered by limited access to chemically pure samples. Herein, we report a concise and stereoselective synthesis of the archaeal tetraether lipid parallel GDGT‐0 and the synthesis and self‐assembly of derivatives bearing different polar groups.
Investigations on performance of PEDOT:PSS/V2O5 hybrid symmetric supercapacitor with redox electrolyte
Authors: Kanth Supriya , Narayanan Padma , Betty C.A. , Rao Rekha , Kumar Sanjay
Published: April 2021

Nanocomposites of PEDOT:PSS with V2O5 nanoparticles are synthesized by simple physical mixing of the two with different weight percentages of the latter and their performance as supercapacitor electrode materials is verified. Best performance is obtained for an optimum weight percent of 16.8% of V2O5. The specific capacitance and specific energy of the composite with 16.8% V2O5 increases by more than two fold, with increase in specific power, as compared to that of pristine PEDOT:PSS device. This is attributed to increase in conductivity brought about by the presence of V2O5 nanoparticles, easier transportation and intimate contact of electrolyte ions with the nanolayers of V2O5 due to the intercalation of PEDOT:PSS between the layers, and additional redox reactions due to various oxidation states of vanadium element, besides redox electrolyte effects. This is further confirmed by the reduced ESR of the composite device as compared to that of pristine PEDOT:PSS device.
Strain rate‐dependent deformation behaviors of multi‐layer carbon fiber reinforced polymer laminates
Authors: Ma Zhichao , Li Weizhi , Yang Siguo , Huang Bin , Tong Shuai , Li Chaofan , Zhao Hongwei , Ren Luquan
Published: April 2021

This paper focuses on the contributions of diversities of strain rate and orientations for aggravating the diversities of micro failure behaviors on carbon fiber reinforced polymer (CFRP) laminates. A miniature horizontal type tensile tester is employed to conduct experiments with strain rate ranging from 2.6 × 10−6 s−1 to 2.6 × 10−3 s−1. The CFRP laminates are obtained based upon a thermoset toughened epoxy matrix (termed CF/Epoxy) with ply orientations of (0°/0°) and (0°/90°). Significant differences in deformation behaviors of CFRP laminates are determined through tests. The study clearly reveals the strain rate‐dependent deformation modes of CFRP laminates, involving pure fiber fracture, epoxy crack with stepped surface and interface failure with residual voids, determines the “low‐high‐low” variation tendency of Young's modulus and strength as a function of strain rate. Ply orientation‐dependent differences in deformation behaviors are also investigated via severe interfacial shearing effect. A unified model consisted of four deformation modes to is clarified to analyze the complexity of CFRP laminates failure mechanism.
Preparation of the organic–inorganic double‐shell microencapsulated aluminum hypophosphite and its improved flame retardancy and mechanical properties of epoxy resin composites
Authors: Chen Zhiquan , Li Yang , Ni Lei , Jiang Juncheng , Yu Yuan , Chen Qiang
Published: April 2021

To develop the functional particles with better flame‐retardant and compatibility with epoxy resin (EP) matrix, organic–inorganic double‐shell microencapsulated aluminum hypophosphite (MSiAHP) was prepared by situ polymerization. The water contact angles of MSiAHP (62.4°) is significantly larger than that of aluminum hypophosphite (34.4°), which shows that the organic shell material of MSiAHP endows excellent hydrophobicity and water resistance. With the incorporation of MSiAHP, EP/30%MSiAHP composite exhibits limiting oxygen index value of 27.3% and V‐0 rating. Furthermore, the cone calorimetry test reveals that MSiAHP reduces the peak heat release rate, total heat release and total smoke release of EP matrix by 33.3%, 24.4% and 56.6%, respectively. Besides, due to the unique organic–inorganic double‐shell structure of MSiAHP particles, EP/30%MSiAHP composite achieves greater thermal stability and higher char yields than pure EP. The investigation of the products in the gas and condensed phase demonstrates that MSiAHP is beneficial to the generation of a high‐density and compact carbon layer structure with a high graphitization degree, and delay the generation time of pyrolysis products in the gas phase, which can improve the fire safety of EP composites effectively. Furthermore, preeminent dispersion and compatibility of MSiAHP lead to EP/MSiAHP composites with excellent mechanical properties.
A Solid‐State Electrochemiluminescence Sensor Based on Novel Two‐Dimensional Ti3C2 MXene
Authors: Xing Huanhuan , Xia Hongyin , Fan Yongchao , Xue Yuan , Peng Chao , Ren Jiangtao , Li Jing , Wang Erkang
Published: April 2021

Herein, highly conductive MXene‐Ti3C2 was employed as effective nanocarriers for anchoring electrochemiluminescence (ECL) luminophore of Ru(bpy)32+ (Ti3C2−Ru). Different from the previous work, the Ti3C2−Ru composite was achieved in several seconds due to the electrostatic interaction between positively charged Ru(bpy)32+ and negatively charged Ti3C2. A series of characterizations indicated the successful formation of Ti3C2−Ru. Then, the solid‐state ECL platform was constructed with the assistance of membrane material, Nafion. The introduction of Ti3C2 with large surface area provided a rapid strategy for capturing luminophore of Ru(bpy)32+ and endowed the solid‐state platform with good electron transfer capacity owing to the super conductivity. Based on the stable loading of Ru(bpy)32+, the as‐designed platform was successfully used for the analysis of lidocaine and the satisfied analytical results were obtained in human plasma. More importantly, the proposed approach not only enriched the application of Ti3C2 in the sensing field, but also shed light on the label‐free ECL bioanalysis.
Co(OH)2 Nanosheets Array Doped by Cu2+ Ions with Optimal Electronic Structure for Urea‐Assisted Electrolytic Hydrogen Generation
Authors: Wang Xiangyu , Zhang Wuzhengzhi , Zhang Junliang , Zhang Jing , Wu Zhengcui
Published: April 2021

Urea electrolysis supplies a great potential in energy‐saving hydrogen generation accompanied by simultaneous urea‐containing wastewater remediation. Herein, the Co(OH)2 nanosheets arrays doped by different amount of Cu2+ ions were prepared via a one‐step solution‐phase method for urea‐assisted electrolytic hydrogen generation. The Cu integration can regulate electronic structure, activate Co active sites at low potential, and optimize the charge transfer properties and adsorption states of the catalyst. Moreover, the partially distorted cobalt surroundings caused by Cu dopant in the catalyst is conductive to favor the adsorption of urea and water molecules to the active sites. The optimal Cu6.2%‐Co(OH)2 nanosheets array exhibited superior urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) performances. Assembling an overall urea electrolyzer using two Cu6.2%‐Co(OH)2 electrodes gave rise to very small voltages of 1.389 V for 10 mA cm−2 and 1.781 V for a high current density of 500 mA cm−2 with remarkable operational stability. The Cu2+ ions doping strategy can be extended to a series of Ni‐based compounds with adjustable electronic structures for boosting the activities of UOR and HER.
Proton‐Transfer Dynamics of Photoacidic Merocyanines in Aqueous Solution
Authors: Kaiser Christoph , Halbritter Thomas , Heckel Alexander , Wachtveitl Josef
Published: April 2021

Photoacids attract increasing scientific attention, as they are valuable tools to spatiotemporally control proton‐release reactions and pH values of solutions. We present the first time‐resolved spectroscopic study of the excited state and proton‐release dynamics of prominent merocyanine representatives. Femtosecond transient absorption measurements of a pyridine merocyanine with two distinct protonation sites revealed dissimilar proton‐release mechanisms: one site acts as a photoacid generator as its pKa value is modulated in the ground state after photoisomerization, while the other functions as an excited state photoacid which releases its proton within 1.1 ps. With a pKa drop of 8.7 units to −5.5 upon excitation, the latter phenolic site is regarded a super‐photoacid. The 6‐nitro derivative exhibits only a phenolic site with similar, yet slightly less photoacidic characteristics and both compounds transfer their proton to methanol and ethanol. In contrast, for the related 6,8‐dinitro compound an intramolecular proton transfer to the ortho‐nitro group is suggested that is involved in a rapid relaxation into the ground state.
Synthesis of Difluoroglycine Derivatives from Amines, Difluorocarbene, and CO2: Computational Design, Scope, and Applications
Authors: Hayashi Hiroki , Takano Hideaki , Katsuyama Hitomi , Harabuchi Yu , Maeda Satoshi , Mita Tsuyoshi
Published: April 2021

A three‐component reaction (3CR) for the synthesis of difluoroglycine derivatives has been achieved by using amines, difluorocarbene (generated in situ), and the abundant, inexpensive, and nontoxic C1 source CO2. Various tert‐amines and pyridine, (iso)quinoline, imidazole, thiazole, and pyrazole derivatives were incorporated, and the corresponding products were isolated in solid form without purification by column chromatography on silica gel. Detailed reaction profiles of the 3CR were obtained from computational analysis using DFT calculations, and the results critically suggest that simple ammonia is not applicable to this reaction. In addition, as strongly supported by computational predictions, a new reagent that can generate difluorocarbene at 0 °C without any additives was discovered. Finally, radical substitution reactions of the obtained difluoroglycine derivatives under photoredox conditions, as well as a synthetic application as an N‐heterocyclic carbene ligand are shown.
Synthesis of Stannylated Aryl Imines and Amines via Aryne Insertion Reactions into Sn−N Bonds
Authors: Kran Eva , Mück‐Lichtenfeld Christian , Daniliuc Constantin G. , Studer Armido
Published: April 2021

The reaction of in situ generated arynes with stannylated imines to provide ortho‐stannyl‐aniline derivatives is reported. The readily prepared trimethylstannyl benzophenone imine is introduced as an efficient reagent to realize the aryne σ‐insertion reaction. The imine functionality is an established N‐protecting group and insertions proceed with good yields and good to excellent regioselectivities. The product anilines are valuable starting materials for follow‐up chemistry thanks to the rich chemistry offered by the trimethylstannyl moiety.