bluuebunny/crossref_metadata_2025 huggingface dataset:
Telehealth Use by Age and Race at a Single Academic Medical Center During the COVID-19 Pandemic: Retrospective Cohort Study
Authors: Stevens Jennifer P , Mechanic Oren , Markson Lawrence , O'Donoghue Ashley , Kimball Alexa B
Published: May 2021

Background

During the COVID-19 pandemic, many ambulatory clinics transitioned to telehealth, but it remains unknown how this may have exacerbated inequitable access to care.

Objective

Given the potential barriers faced by different populations, we investigated whether telehealth use is consistent and equitable across age, race, and gender.

Methods

Our retrospective cohort study of outpatient visits was conducted between March 2 and June 10, 2020, compared with the same time period in 2019, at a single academic health center in Boston, Massachusetts. Visits were divided into in-person visits and telehealth visits and then compared by racial designation, gender, and age.

Results

At our academic medical center, using a retrospective cohort analysis of ambulatory care delivered between March 2 and June 10, 2020, we found that over half (57.6%) of all visits were telehealth visits, and both Black and White patients accessed telehealth more than Asian patients.

Conclusions

Our findings indicate that the rapid implementation of telehealth does not follow prior patterns of health care disparities.
Automated Generation of Personalized Shock Wave Lithotripsy Protocols: Treatment Planning Using Deep Learning
Authors: Chen Zhipeng , Zeng Daniel D , Seltzer Ryan G N , Hamilton Blake D
Published: May 2021

Background

Though shock wave lithotripsy (SWL) has developed to be one of the most common treatment approaches for nephrolithiasis in recent decades, its treatment planning is often a trial-and-error process based on physicians’ subjective judgement. Physicians’ inexperience with this modality can lead to low-quality treatment and unnecessary risks to patients.

Objective

To improve the quality and consistency of shock wave lithotripsy treatment, we aimed to develop a deep learning model for generating the next treatment step by previous steps and preoperative patient characteristics and to produce personalized SWL treatment plans in a step-by-step protocol based on the deep learning model.

Methods

We developed a deep learning model to generate the optimal power level, shock rate, and number of shocks in the next step, given previous treatment steps encoded by long short-term memory neural networks and preoperative patient characteristics. We constructed a next-step data set (N=8583) from top practices of renal SWL treatments recorded in the International Stone Registry. Then, we trained the deep learning model and baseline models (linear regression, logistic regression, random forest, and support vector machine) with 90% of the samples and validated them with the remaining samples.

Results

The deep learning models for generating the next treatment steps outperformed the baseline models (accuracy = 98.8%, F1 = 98.0% for power levels; accuracy = 98.1%, F1 = 96.0% for shock rates; root mean squared error = 207, mean absolute error = 121 for numbers of shocks). The hypothesis testing showed no significant difference between steps generated by our model and the top practices (P=.480 for power levels; P=.782 for shock rates; P=.727 for numbers of shocks).

Conclusions

The high performance of our deep learning approach shows its treatment planning capability on par with top physicians. To the best of our knowledge, our framework is the first effort to implement automated planning of SWL treatment via deep learning. It is a promising technique in assisting treatment planning and physician training at low cost.
A Global Overview of COVID-19 Research in the Pediatric Field: Bibliometric Review
Authors: Monzani Alice , Tagliaferri Francesco , Bellone Simonetta , Genoni Giulia , Rabbone Ivana
Published: May 2021

Background

Since the beginning of the COVID-19 pandemic, a great number of papers have been published in the pediatric field.

Objective

We aimed to assess research around the globe on COVID-19 in the pediatric field by bibliometric analysis, identifying publication trends and topic dissemination and showing the relevance of publishing authors, institutions, and countries.

Methods

The Scopus database was comprehensively searched for all indexed documents published between January 1, 2020, and June 11, 2020, dealing with COVID-19 in the pediatric population (0-18 years). A machine learning bibliometric methodology was applied to evaluate the total number of papers and citations, journal and publication types, the top productive institutions and countries and their scientific collaboration, and core keywords.

Results

A total of 2301 papers were retrieved, with an average of 4.8 citations per article. Of this, 1078 (46.9%) were research articles, 436 (18.9%) were reviews, 363 (15.8%) were letters, 186 (8.1%) were editorials, 7 (0.3%) were conference papers, and 231 (10%) were categorized as others. The studies were published in 969 different journals, headed by The Lancet. The retrieved papers were published by a total of 12,657 authors from 114 countries. The most productive countries were the United States, China, and Italy. The four main clusters of keywords were pathogenesis and clinical characteristics (keyword occurrences: n=2240), public health issues (n=352), mental health (n=82), and therapeutic aspects (n=70).

Conclusions

In the pediatric field, a large number of articles were published within a limited period on COVID-19, testifying to the rush to spread new findings on the topic in a timely manner. The leading authors, countries, and institutions evidently belonged to the most impacted geographical areas. A focus on the pediatric population was often included in general articles, and pediatric research about COVID-19 mainly focused on the clinical features, public health issues, and psychological impact of the disease.
A Virtual Reality–Based App to Educate Health Care Professionals and Medical Students About Inflammatory Arthritis: Feasibility Study (Preprint)
Authors: Klemm Philipp , Kleyer Arnd , Tascilar Koray , Schuster Louis , Meinderink Timo , Steiger Florian , Lange Uwe , Müller-Ladner Ulf , Knitza Johannes , Sewerin Philipp , Mucke Johanna , Hueber Axel J , Schett Georg , Hartmann Fabian , Hueber Axel J , Simon David
Published: May 2021

BACKGROUND

Inflammatory arthritides (IA) such as rheumatoid arthritis or psoriatic arthritis are disorders that can be difficult to comprehend for health professionals and students in terms of the heterogeneity of clinical symptoms and pathologies. New didactic approaches using innovative technologies such as virtual reality (VR) apps could be helpful to demonstrate disease manifestations as well as joint pathologies in a more comprehensive manner. However, the potential of using a VR education concept in IA has not yet been evaluated.

OBJECTIVE

We evaluated the feasibility of a VR app to educate health care professionals and medical students about IA.

METHODS

We developed a VR app using data from IA patients as well as 2D and 3D-visualized pathological joints from X-ray and computed tomography–generated images. This VR app (Rheumality) allows the user to interact with representative arthritic joint and bone pathologies of patients with IA. In a consensus meeting, an online questionnaire was designed to collect basic demographic data (age, sex); profession of the participants; and their feedback on the general impression, knowledge gain, and potential areas of application of the VR app. The VR app was subsequently tested and evaluated by health care professionals (physicians, researchers, and other professionals) and medical students at predefined events (two annual rheumatology conferences and academic teaching seminars at two sites in Germany). To explore associations between categorical variables, the χ2 or Fisher test was used as appropriate. Two-sided P values ≤.05 were regarded as significant.

RESULTS

A total of 125 individuals participated in this study. Among them, 56% of the participants identified as female, 43% identified as male, and 1% identified as nonbinary; 59% of the participants were 18-30 years of age, 18% were 31-40 years old, 10% were 41-50 years old, 8% were 51-60 years old, and 5% were 61-70 years old. The participants (N=125) rated the VR app as excellent, with a mean rating of 9.0 (SD 1.2) out of 10, and many participants would recommend use of the app, with a mean recommendation score of 3.2 (SD 1.1) out of 4. A large majority (120/125, 96.0%) stated that the presentation of pathological bone formation improves understanding of the disease. We did not find any association between participant characteristics and evaluation of the VR experience or recommendation scores.

CONCLUSIONS

The data show that IA-targeting innovative teaching approaches based on VR technology are feasible.
Experiences of Patients Undergoing Chemotherapy With Virtual Reality: Mixed Methods Feasibility Study (Preprint)
Authors: Janssen Anna , Fletcher Jennifer , Keep Melanie , Ahmadpour Naseem , Rouf Anika , Marthick Michael , Booth Rebecca
Published: May 2021

BACKGROUND

Current research into virtual reality (VR) use during chemotherapy shows that it can be an effective distraction intervention. However, there is limited research in adult patients and to investigate how VR can be sustainably implemented in health care organizations.

OBJECTIVE

The aim of this study was to explore the feasibility and acceptability of using VR for adult patients undergoing chemotherapy, and to identify the factors that would enable the sustained use of VR during chemotherapy in health care organizations.

METHODS

Patients undergoing chemotherapy were recruited to participate in a VR intervention during chemotherapy infusion. Participants were observed during the session and completed a postintervention survey. Each participant was invited to participate in a semistructured interview about their experience.

RESULTS

A total of 18 patients participated in the study, 5 of whom participated in semistructured interviews. Findings indicated that the use of VR was acceptable for patients undergoing chemotherapy and the intervention was also feasible. Some participants felt that the VR was an effective distraction during chemotherapy infusion, although most still seemed to be aware of how long their treatment was taking. Although VR was acceptable and feasible to patients, interviews identified several barriers to sustained implementation, including access to a reliable app library and impact on staff workloads.

CONCLUSIONS

VR was acceptable to patients with a diagnosis of cancer undergoing chemotherapy treatment. Patients found VR beneficial for breaking up the monotony of treatment, to provide an additional choice of activity in addition to other recreation, and in some instances as a distraction from the treatment itself. However, there are challenges to address if VR is to be implemented in practice for this patient group.
Explanatory Model of Mental Illness from the Perspective of Traditional Chinese Medicine (Preprint)
Authors: Lin Wan-Ling , Liang Yu-Chi , Chung Kuo-Hsuan , Chen Ping-Ho , Chang Yung-Chun
Published: May 2021

UNSTRUCTURED

The improvement of accurate management of mental illness has become an increasing concern in recent decades. Efforts to understand mental illness have progressed from treating the mind as an isolated system to involving both mind and body as an interactive response. This study attempts to express and ontologize the relationships between different mental illnesses and physical organ systems from the perspective of Traditional Chinese Medicine. In this paper, Natural Language Processing method was introduced to quantify the importance of different mental illness descriptions relative to the five Viscera and two bowels, Stomach and gallbladder through the classical medical text Huangdi Neijing and construct a mental illness network based on the TCM classic text.
The results demonstrate that our proposed framework which integrates natural language processing and data visualization can enable clinicians to arrive at more comprehensive insights into mental health. According to the results of the correlation analysis for mental illnesses, viscera, and symptoms, the organs most affected by mental illness is the Heart, and the most two important factors to cause mental illness are Anger and Worry &Think. Moreover, the current findings promote the present comprehension of the association between the mind and body from the view of Traditional Chinese Medicine. We found the mental illness described in Traditional Chinese Medicine is always related to more than one organ.
Ethnocultural origin of the Word са́ра (“pike”) in the Old Ukrainian language
Authors:   Kharkiv Humanitarian-Pedagogical Academy, Minyailo Roman
Published: May 2021

The article studies the motivational processes of the emergence of the old Ukrainian fishing professionalism са́ра, used to denote pike in the language of Zaporozhian Cossacks. The relevance of the research is determined by the importance of analysing names that reflect ethno-cultural stereotypes, the original semantics of which dates back to the Indo-European period. To identify the mechanisms of formation of the semantic model, according to which the word “са́ра” “pike” is formed, the diachronic method of research (according to the principle of relative chronology) was used together with the linguo-cultural analysis, which proved that: ichthyonymic metaphorization (creation of the figurative name of a fish) was most likely preceded by paronymic attraction (phonetic and semantic convergence of a name of a colour with a female name of ancient Jewish origin) with subsequent metaphorization of the stereotyped name of a Jew as an ichthyonym. Undoubtedly, the paronymic attraction was also facilitated by the mutilation of the noun component of the attributive phrase са́ра (шара) fish, since fishing nouns as derivatives of two-lexemic analytical nouns can be traced in temporal and spatial dimensions in various lexical-semantic groups of fishing names: варовый [tax], свôйска [marine], сьвітова́ [tonya], ка́мбалові [fish], лососе́ві [fish], etc. Thus, the archaic fishing professionalism of са́ра “pike” is connected with the old Ukrainian names of achromatic grey colour сѣрый and шарый, fitting into the motivational model «the name of the animal by the colour of its fur, feathers, scales». The colour name itself as a basis for metaphorical transference reaches the common Indo-European lexical fund and in the historical dimension combines the meaning of «dark» and «light», realising in the ancient and old Ukrainian ideology the idea of darkness and light, where the «dark side» is the image of a person of a different religion with his or her social and ethno-confessional differences, in particular, the colour of clothing. The researched material encourages further study of the Old Ukrainian lexicon in the aspect of the formation of ethno-ideological bases.
THE IMPORTANCE OF MARKETING COMMUNICATION FOR ATTRACTING AND RETAINING INSURANCE SERVICE USERS
Authors: Popović Slavica , Avramović Mira
Published: May 2021

The assumption of successful marketing communication within the service sector is the establishment of two-way interactive communication between service users and service companies. The aim of the strategy of marketing communication is attracting new users, but also retaining the existing users of services and establishing long-term relations with them. A successful achievement of the aim of marketing communication requires that the marketing message is created according to the characteristics and preferences of the target audience. The role of marketing communication differs depending on the stage of the selling process. During the pre-purchase stage, the aim of marketing communication is to inform potential users so that they could create preferences towards the company’s offer. By applying the adequate forms of marketing communication during the stage of using the service, the company tends to explain to and introduce users to the process of servicing and to provide support in solving the occurring problems. The confirmation of users’ positive impressions and the resolution of possible problems which can occur during the process of service provision represent the aim of marketing communication during the post-purchase stage.
Análisis del Sistema Nacional Anticorrupción. Una propuesta legal y organizacional para su fortalecimiento
Authors: Escobar Hernández Luis Enrique
Published: May 2021

La corrupción es uno de los asuntos públicos que debe ocupar a las autoridades y ciudadanía en México, porque constituye un dique para la consolidación de la democracia y para el desarrollo y crecimiento en todos los órdenes, por ello es que se vuelve fundamental indagar los instrumentos legales y organizacionales que se emplean para prevenirla, combatirla y en su caso sancionarla, permitiendo así, detectar propuestas de mejora que coadyuven en el cumplimiento de los objetivos que persiguen dichos intrumentos.
Gobierno Electrónico y Economía Digital en la Sociedad de la Información y el Conocimiento: una revisión conceptual
Authors: García Santiago Jesús , Valencia López Oscar David , Fernández Tapia Joselito , Rentería Gaeta Rafael
Published: May 2021

Las Tecnologías de la Información y Comunicación (TIC) han impactado en el sector gubernamental, dando lugar al Gobierno Electrónico. Asimismo, ha habido repercusiones en la economía,  propiciando una Economía Digital. En ese contexto, de la Sociedad de la Información y el Conocimiento las TIC son esenciales en las actividades sociales.Este artículo aborda aspectos teóricos del Gobierno Electrónico, la Economía Digital y la Sociedad de la Información y el Conocimiento, a partir de distintos enfoques derivados de la investigación documental, esto con el fin de desarrollar un debate teórico a partir de la postura de diversos autores y posteriormente presentar un concepto propio, planteando como pregunta de investigación: ¿qué papel desempeña el Estado ante la ED?.De tal manera, la metodología de la investigación es de carácter documental mediante la obtención de datos secundarios para profundizar en el tema de estudio, subrayando los desafíos y oportunidades que implica la ED para el Estado mexicano.
Multifrequency electromagnetic response of a shielded conductor
Authors: Negi J. G. , Saraf P. D.
Published: May 2021

Se ha obtenido la respuesta electromagnética de frecuencia múltiple de un sistema compuesto mena-roca encajonante, el cual se representa teóricamente por un modelo de dos superficies esféricas concéntricas (que no están en contacto galvánico). Se han investigado comparaciones cualitativas y cuantitativas entre la respuesta electromagnética total del sistema compuesto y las respuestas aisladas del cuerpo de mena (superficie interior) y del cuerpo de roca encajonante (superficie exterior), para combinaciones de parámetros diferentes. Las contribuciones relativas y/o diferenciales de la mena y de la roca encajonante se reflejan predominantemente en la representación de Argand y las curvas de variación de frecuencia contra gradiente. Los diagramas de Argand se han utilizado también para identificar las zonas de frecuencia que resultan en un encubrimiento completo de la mena y las que resultan en poco efecto de la roca encajonante. Los resultados pueden resultar de utilidad en:(i) entender el efecto de encubrimiento de las formaciones corticales superiores {en particular para delinear depósitos de sulfuros en los fondos oceánicos; explorar la distribución y alteración de menas de pórfidos cupríferos y proveer información útil para una selección adecuada de la perforación, minado y excavación, etc.).(ii) interpretación de datos obtenidos por sistemas de inducción electromagnéticos de espectro múltiple (ejemplo 'Geoprobe EMR-14').
Determinación de parámetros focales del temblor de Huajuapan de León, Oaxaca, del 24 de octubre de 1980, usando sismogramas sintéticos de ondas compresionales y un método de inversión linealizada
Authors: Lesage P. D.
Published: May 2021

Utilizando un algoritmo basado en la aproximación WKBJ, para calcular sismogramas sintéticos y un método de inversión linealizada para ajustar parámetros focales, se modelan ondas compresionales de períodos largos, del temblor de Huajuapan de León, Oaxaca, México, del 24 de oct\ lbre de 1980 (mb = 6.6, Ms = 7 .0). Este método resulta eficiente y estable para la determinación de los parámetros físicos del modelo. El mecanismo focal resultante (cp 1 = 279°, ó 1 = 22°, 71.1 = -89°, </J2 = 100°, ó2 = 68°, 71.2 = -89°) representa un afallamiento normal y es poco diferente del obtenido por Jiménez et al. (1982). Además, se obtiene una profundidad de 60 km, coherente con la localización de las réplicas, un momento sísmico de 1.2 1027dina.cm y un tiempo de ruptura de 13.5 seg. Una función de tiempo. triangular en velocidad es suficiente para conseguir este ajuste, lo que indica una historia de ruptura simple para períodos superiores a unos 10 seg.
Monitoring El Chichon aerosol distribution using NOAA-7 satellite AVHRR sea surface temperature observations
Authors: Strong A. E.
Published: May 2021

El velo de polvo de la erupción volcánica de El Chichón en abril de 1982 ha tenido un notable efecto sobre la capacidad del AVHRR del satélite NOAA-7 para registrar la temperatura de la superficie del mar (SST). Las pequeñas partículas de ácido sulfúrico de una micra o aún menos de tamaño en la estratosfera atenúan la radiación de la Tierra causando un desplazamiento.(sesgo) negativo en los SSTs producidos operacionalmente por NOAA. Hemos utilizado este desplazamiento para observar mensualmente la evolución y dispersión de la nube de aerosol a medida que se esparcía rápidamente hacia el norte durante los meses de noviembre y diciembre de 1982 y hasta la primavera de 1983.
Balloonborne particle counter observations of the El Chichón aerosol layers in the 0.01 - 1.8 µm radius range
Authors: Hofmann D. J. , Rosen J. M.
Published: May 2021

Mediante el uso de contadores de partículas ópticas adheridos a los globos meteorológicos se obtuvieron las conclusiones siguientes, concernientes a los efectos de la erupción de El Chichón sobre el aerosol estratosférico. Inicialmente se formaron dos capas de aerosol, la mayor de ellas constituida por gotitas muy grandes (radio modal principal de 0.3mμ) a 25 km de altura, y otra capa de casi la misma concentración, pero con gotitas de menor tamaño (radio modal principal ~0.15mμ a alrededor de 18 km de altura. Ambas capas eran volátiles en ≥98% a 130°C, lo que indica una composición predominante de ácido sulfúrico. La distribución de partículas por tamaños a 25 km era al inicio marcadamente bi-modal, con modos cerca de 0.02mμ y 0.7mμ, sugiriendo la condensación de nuevas gotitas a partir de la fase gaseosa y un aumento excesivo de la distribución anterior a la erupción. La nueva condensación de aerosol pareció cesar después de unos tres meses, pero el crecimiento de las gotitas siguió ocurriendo todavía después de nueve meses. Para diciembre, las capas de aerosol se habían extendido ampliamente hasta la latitud de Laramie. Las características del crecimiento del aerosol sugieren una concentración de vapor de ácido sulfúrico de ~ 10 moléculas cm-3, alrededor de 40 días después de la erupción, y una persistencia del vapor de 22-45 días. La masa total de aerosol de ácido sulfúrico se estima en alrededor de 10 Tg unos nueve meses después de la erupción y hasta de 20 Tg al inicio del fenómeno. En enero de 1983 se descubrió una nueva y extensa nube de gotitas de ácido sulfúrico muy pequeñas (r ~0.02mμ) sobre Laramie, en la región de 30-35 km de altitud. Estas nuevas gotitas parecen haberse condensado termalmente en las regiones polares derivándose probablemente de los vapores de El Chichón y/o de vapores que emanaban de la evaporación del aerosol de ácido sulfúrico del volcán durante los episodios de calentamiento estratosférico polar.
Lidar measurements of stratospheric aerosol content and depolarization ratios after the eruption of El Chichón volcano: measurements at Nagoya, Japan
Authors: Hayashida S. , Kobayashi A. , Iwasaka Y.
Published: May 2021

Después de la erupción de "El Chichón", se observó un enorme aumento en la dispersión de fondo de la luz desde la capa de aerosol estratosférico, utilizando un lidar de rubí en Nagoya, Japón (35ºN, 137ºW).En la parte inferior de la capa principal de aerosol se observó también un aumento aparente en la tasa de despolarización. El aumento en la tasa de despolarización indica la existencia de partículas no esféricas, tales como las de silicatos. La tasa de despolarización disminuyó a solo un porcentaje bajo, lo que sugiere que casi todas las partículas eran esféricas, después de fines de septiembre. Aún varios meses después de la erupción, los aerosoles en la región de los vientos orientales por encima de los 20 km de altitud estaban todavía distribuidos heterogéneamente. Después del cambio del sistema de vientos al de tipo invernal, la capa de aerosol mostraba solamente un ancho pico y parece que los aerosoles estaban distribuidos por zonas, de manera homogénea. Con base en los datos obtenidos después de septiembre3 se calculó un coeficiente efectivo de difusión vertical, y el resultado fue de alrededor de 3 x l O cm 2 / s.
Preliminary estimate of the radiative and climatic effects of the El Chichon eruption
Authors: McCracken M. C. , Luther F.M.
Published: May 2021

Se hizo una estimación preliminar del efecto climático de la mayor erupción volcánica de El Chichón en abril de 1982, utilizando una versión estacional de un modelo zonal de clima, considerando una capa oceánica de 70 m . El aerosol volcánico se introdujo en el modelo de estratosfera a una altitud de 23 - 29 km, donde el aerosol perturba ambos flujos, el solar y el infrarrojo. Se consideró una composición de aerosol de 75°k, de H2SO4 con una distribución logarítmica de tamaños de orden cero. Se utilizó el patrón de opacidad latitudinal y variación temporal desarrollado por Robock (1983), con el pico de opacidad alcanzando 0.3 en junio de 1982. En este cálculo, el caso de perturbación volcánica se corrió desde el lo. de abril de 1982 hasta el lo. de enero de 1983. La temperatura del hemisferio norte se proyectó a decrecimiento gradual durante este período, siendo alrededor de 0.2 K más fresca que lo normal a fines de 1982. El modelo predice también anomalías en la precipitación, incluyendo una reducción de cinco a más de diez por ciento en la tasa de precipitación exactamente al norte del ITCZ.
Las zonas más activas en el Cinturón Volcánico Mexicano (entre Michoacán y Tlaxcala)
Authors: Lugo Hubp J. , Ortiz P. M. A. , Palacio P. J. L. , Bocco V. G.
Published: May 2021

Por medio de una cuantificación de volcanes cuaternarios en áreas de 100 km2 , se establecen zonas de cinco grados de actividad para la porción central del Cinturón Volcánico Mexicano. Las de mayor actividad corresponden a concentraciones de 9, 12 y más volcanes en 100 km2 Estas son seis y ocupan superficies relativamente pequeñas de relieves montañosos en desarrollo.Hay zonas de baja concentración de volcanes muy jóvenes, testigos de una actividad naciente, otras son estables, con relieve montañoso pliocénico. Todo esto permite apoyar la consideración de que el volcanismo en el Cinturón Volcánico Mexicano se presenta con mayor intensidad en algunas áreas durante períodos determinados, "migrando" posteriormente a otras zonas.
ZONEAMIENT0 COMPOSICIONAL Y MINERALOGIC O EN LOS PRODUCTOS ERUPTIVOS DEL CENTRO VOLCANICO DE LOS HUMEROS, PUEBLA, MEXICO
Authors: Ferriz. H.
Published: May 2021

El centro volcánico de Los Humeros, localizado 180 km a1 este de la ciudad de México, es uno de varios centros volcánicos silícicos localizados por "detrás" del frente definido por los volcanes andesíticos activos del Eje Neovolcánico Mexicano. Durante los últimos 460 000 años tres grandes erupciones plinianas y dos períodos de emplazamiento de derrames de lava periódicamente "muestrearon" la cámara magmática de Los Humeros. Los productos de cada una de estas erupciones varían en composición, e indican que la cámara magmática estaba zonada desde niveles superiores de composición riolítica hasta niveles inferiores andesfticos, o tal vez inclusive hasta niveles basálticos. Este fuerte zoneamiento composicional persistió prácticamente durante toda la vida activa del sistema magmático.En general, los productos más silícicos de cada erupción pliniana son afíricos o están caracterizados por un contenido bajo de fenocristales y por las asociaciones minerales más simples (plagioclasa, óxidos de Fe y, Ti, y biotita u ortopiroxeno). Clinopiroxeno y olivino hacen su aparición en productos progresivamente más máï¬cos de cada erupción. Los cocientes Ca/Na en plagioclasa y Mg/ Fe en minerales ferromagnesianos aumentan a medida que la maficidad de las rocas aumenta. El contenido de fenocristales también aumenta progresivamente, alcanza su máximo en productos riodacíticos y andesiticos, y luego disminuye en productos de composición correspondiente a andesita basáltica. Los cambios en las asociaciones de fenocristales y en sus abundancias son probablemente consecuencia de la superposición del zoneamiento composicional de la cámara magmática con gradientes en la temperatura y contenido de volátiles del magma. Temperaturas calculadas por medio de óxidos coexistentes de Fe y Ti varían de 800 a 875° para los niveles riolíticos superiores de la cámara, 860 a 940°C para las porciones riódacíticas, y 920 a 1000°C para los niveles andesíticos.
The Tecpan regional fault: evidence for major ne lineaments
Authors: Sandoval O. J. H.
Published: May 2021

Con base en una revisión de algunos trabajos publicados acerca de estudios sobre la margen continental en el sur de México, se encontró una posible asociación de rasgos morfotectónicos tanto del subfondo marino como del continente. Son doce los rasgos geológicos locales aparentemente independientes que cuando se correlacionan en un panorama regional sugieren la existencia de la Falla Regional de Tecpan que aquí se propone. Esta falla sería un miembro representativo de un sistema de fallas conjugadas del sistema de fallas o rift asociado a la Faja Volcánica Mexicana y del cual muchos otros han sospechado. La falla interpretativa va desde el talud interior de la Trinchera Mesoamericana hasta la Faja Volcánica Mexicana con un rumbo general N 17º E.
Effects of El Niño on Panama rainfall
Authors: Estoque M. A. , Luque J. , Chandeck-Monteza M. , García J.
Published: May 2021

El efecto de "El Niño" en la lluvia sobre Panamá ha sido estudiado, utilizando trece episodios de "El Niño" durante el período de 1920 a 1983. Los resultados muestran que "El Niño" induce precipitación bajo lo normal en casi todas las regiones de Panamá. El promedio anual de la anomalía de precipitación durante todas las ocurrencias de "El Niño" es del 8ºh por debajo de Jo normal. Para el caso de episodios de "El Niño" intensos de los años 1976 y 1982, las anomalías fueron de 28 y 24°1o por debajo de Jo nonnal, respectivamente. El mes más seco del año 1982 (diciembre) tuvo una anomalía de precipitación del 60°1o por debajo de lo normal. Además, los resultados del estudio mostraron que hay una variación geográfica considerable en las anomalías de precipitación. En el caso de "El Niño" de 1976, las mayores anomalías negativas estaban localizadas en el suroeste de Panamá, en el vertiente Pacífico de la cordillera central.Por otro lado, "El Niño" produjo efectos opuestos (anomalías positivas) en el vertiente Atlántico. Se estudió la relación entre las variaciones temporales de la anomalía de precipitación anual y las anomalías de la temperatura superficial del Océano Pacífico Oriental. Se encontró una alta correlación negativa entre las anomalías de precipitación y la temperatura oceánica de los meses anteriores. Esta alta correlación ha sido usada para desarrollar un método de pronóstico de precipitación a largo plazo.
The climate of ten thousand years ago: a numerical simulation
Authors: Adem J.
Published: May 2021

Para simular el clima de hace 10 000 años se aplica un modelo termodinámico que incluye el ciclo anual, una capa oceánica mezclada y una capa de hielo y nieve variable.Se demuestra que en latitudes bajas las anomalías de insolación debidas a las variaciones orbitales fueron el factor principal que produjo las diferencias con respecto al clima presente. Sin embargo, además de las anomalías de insolación, las capas permanentes de hielo también afectaron el clima de hace 1 O 000 años en latitudes medias y altas.En el verano, el promedio de la temperatura calculada en la superficie de los continentes del Hemisferio Norte es 1.9°C más caliente que en la actualidad y en las otras estaciones más frío, con una diferencia de -2.1 °c en invierno. El promedio anual de la diferencia es de -0.7°C. La temperatura de la superficie del océano permanece abajo de los valores actuales durante todo el año, con valores promedio de -0.8 en invierno, -0.2 en verano y -0.5ºC para todo el año. Se demuestra que cuando se prescriben los valores actuales de la temperatura de la superficie del océano, se obtiene un clima más caliente, con una anomalía de temperatura promedio de la superficie del continente igual a 2.2, -1.6 y -0.3ºC para verano, invierno y promedio anual respectivamente. Se lleva a cabo un estudio sobre la importancia de la incorporación en el modelo del ciclo anual, una capa oceánica mezclada y una capa de hielo y nieve variable.
Post-paleozoic tectonics of northeast mexico and its role in the evolution of the Gulf of Mexico
Authors: Padilla y Sánchez R.J.
Published: May 2021

Se muestra la evolución sedimentaria mesozoica del noreste de México a través de varios mapas paleogeográficos regionales. También, con base en diferentes estilos de plegamiento, se propone un modelo alternativo para la deformación del Terciario Temprano del noreste de México, así como una serie de paleorreconstrucciones de tectónica de placas, basados principalmente en la existencia de varias fallas sinistrales de transcurrencia, orientadas al noroeste y una falla dextral transcurrente (Falla Tamaulipas-Oaxaca) orientada al nor-noroeste, a lo largo de la cual el bloque de Yucatán se movió hacia el Sur (Jurásico Tardío) desde su antigua posición en el sitio que hoy ocupa el Golfo de México.
Estudio del factor anelástico Q de la coda de los terremotos correspondientes a las regiones central y oriental del Eje Volcánico de México
Authors: Canas J. A.
Published: May 2021

Del estudio de la coda de diversos terremotos ocurridos en las porciones Central y Oriental del Eje Volcánico de México y registrados en la estación del Servicio Sismológico Nacional, OXM, se han obtenido los siguientes resultados: a) El valor de Q es fuertemente dependiente de la frecuencia en la forma Q = Q0 (f/f0)v. Para la parte Central v= 0.4 y para la parte Oriental v= 0.6 donde 0.6 <f<1-0 (Hz). b) Los valores de Q correspondientes a una frecuencia de referencia f0 = l Hz son 322 para la porción Central y 129 para la porción Oriental. e) Los valores de los coeficientes de atenuación de las ondas S obtenidos son 0.0023 km- para la porción Central y 0.0102 km-1 para la porción Oriental. d) Los coeficientes de excitación de la coda obtenidos son 3.56·x 10-25cm s/dyne cm para la parte Central y 1.85 x 10-24cm s/dyne cm para la parte Oriental. Los resultados anteriores podrían indicar un mayor fallamiento de la parte Oriental y/o una mayor concentración de cámaras magmáticas bajo dicho eje.
Estudio del mecanismo de reajuste litostático posterior al evento de Oaxaca (ms = 7.8) del 29 de noviembre de 1978
Authors: Ruiz Kitcher R. E.
Published: May 2021

Se analizó la actividad sísmica (ML>3.0) del 1 al12 de diciembre de 1978, posterior al terremoto de Oaxaca del 29 de noviembre de 1978. Las soluciones de mecanismo focal para 9 réplicas mayores (ML>4.0) asociadas al terremoto principal, así como las soluciones de mecanismos compuestos para 13 eventos de magnitud menor, muestran un predominio de fallamiento normal y rumbo paralelo a la trinchera mesoamericana. Estos resultados sugieren un reajuste tensional que provoca un rompimiento en bloques en forma escalonada a lo largo de la zona de Benioff en el área. Esta situación puede ser común a los terremotos principales asociados a la zona de subducción de la costa central de Oaxaca.
Effect of cooling condition on the performance of thermoelectric power generation system coupling with PCM module
Authors: Zou Jiapu , Wu Zihua , Liu Anbang , Feng Shi , Xie Huaqing
Published: May 2021

In this study, a thermoelectric power generation (TEG) system coupling with PCM module for thermal control and storage has been fabricated. Bismuth Telluride (Bi2Te3) TEG devices were applied to convert heat into electricity and Sn- Ag-In alloy PCM was employed for heat storage. A cooling channel with pure water and graphene nanofluids as heat exchange media was attached tightly with the cold-sides of the TEG devices. The effects of the flow rate of cooling water and the mass fraction of graphene nanofluids on the heat transfer process and the performance of the as fabricated TEG-PCM coupling system have been investigated. It is found that increasing the heat exchange capability of the cooling channel would help the PCM module to enhance the heat absorption and utilization of thermal energy from heat source, which in turn brings about the improvement of efficiency of TEG system. The output voltage of TEG system by using pure water for cooling is improved by 6.6%-13.1% with the acceleration of flow rate. Using graphene nanofluids as heat exchange media, the TEG system could achieve 7.2%-18.5% enhancement in output voltage with an increase in the mass fraction of the used nanofluid.
Passive control of magneto-nanomaterials transient flow subject to non-linear thermal radiation
Authors: Ullah Ikram , Shah Sayed , Zaman Gul , Muhammad Taseer , Hussain Zakir
Published: May 2021

Present investigation is concerned with mixed convection flow of Williamson nanoliquid over an unsteady slandering stretching sheet. Aspects of non-linear thermal radiation, Brownian diffusion, and thermophoresis effects are addressed. Non-linear stretching surface of varying thickness induce the flow. Novel features of combined zero mass flux and convective conditions are accounted. Use of appropriate transformations results into the non-linear ODE. Computations for the convergent solutions are provided. Graphs are designed for interpretations to quantities. Nusselt number and surface drag are computationally inspected. Our computed results indicate that attributes of nanoparticles and non-linear thermal radiation enhance the temperature distribution.
Thermal-mechanical characteristics of stationary and pulsating gas-flows in a gas-dynamic system: In relation the exhaust system of an engine
Authors: Plotnikov Leonid
Published: May 2021

It is a relevant objective in thermal physics and in building reciprocating internal combustion engines (RICE) to obtain new information about the thermal-mechanical characteristics of both stationary and pulsating gas-flows in a complex gas-dynamic system. The article discusses the physical features of the gas dynamics and heat transfer of flows along the length of a gas-dynamic system typical for RICE exhaust systems. Both an experimental set-up and experimental techniques are described. An indirect method for determining the local heat transfer coefficient of gas-flows in pipe-lines with a constant temperature hot-wire anemometer is proposed. The regularities of changes in the instantaneous values of the flow rate and the local heat transfer coefficient in time for stationary and pulsating gas-flows in different elements of the gas-dynamic system are obtained. The regularities of the change in the turbulence number of stationary and pulsating gas-flows along the length of reciprocating internal combustion engines gas-dynamic systems are established (it is shown that the turbulence number for a pulsating gas-flow is 1.3-2.1 times higher than for a stationary flow). The regularities of changes in the heat transfer coefficient along the length of the engine?s gas-dynamic system for stationary and pulsating gas-flows were identified (it was established that the heat transfer coefficient for a stationary flow is 1.05-1.4 times higher than for a pulsating flow). Empirical equations are obtained to determine the turbulence number and heat transfer coefficient along the length of the gas-dynamic system.
Evaluation of heating efficiency and thermal comfort in special purpose vehicle cabins
Authors: Micovic Aleksandar , Komatina Mirko , Brkljac Nenko , Sarkocevic Zivce , Camagic Ivica , Golubovic Zoran
Published: May 2021

The paper presents the integrated application of two methods during testing HVAC system efficiency in the cabins of HUMMER ?1151A1 and OAR 1RL-128D off-road vehicles. Spatial measurements of change in air temperature per time have been performed at three vertical levels (head, knees, and feet) of the driver and passengers, which totals to 15 measuring points per vehicle. The main goal of testing was to evaluate accurately the efficiency of heating and cooling in relation time interval required to attain a designed temperature of comfort in the vehicle cabin, on condition that the difference in ambient temperature levels does not exceed 10?C. With a view to more efficient evaluation of thermal comfort in vehicle cabins, the testing was performed also of predicted mean vote and predicted percentage of dissatisfied indices. Standard thermal comfort surveys ask subjects about their thermal sensation on a seven-point scale from cold (?3) to hot (+3). This research is carried out according to the methods based on ISO 7730, ASHRAE 55, and SORS 8419 standards.
Risk evaluation in road tunnels based on CFD results
Authors: Vidmar Peter
Published: May 2021

Approaches to risk assessment in tunnelling and underground spaces were introduced in 2004 as a result of several serious accidents in tunnels such as Mont Blanc and Tauern Tunnel in 1999. The EU has published the minimum safety requirements for tunnels over 500 m on Trans-European Road Network. The risk assessment is mandatory and should cover all components of the system, i.e. infrastructure, operation, users and vehicles. The professional community has started using the quantitative risk assessment approach, where the crucial issue is the consequence analysis of fire scenarios in a tunnel. Fire development is a complex physical phenomenon and its calculation is time consuming, therefore, complex models have rarely been used in quantitative risk assessment approaches. This paper presents the methodology of integrating fast-processing risk assessment methods with time-consuming CFD methods for fire consequence analysis in the process of tunnel safety assessment. The main variables are soot density and temperature, which are analyzed in one-minute time steps during the fire. Human behavior is considered with the evacuation model, which is needed to evaluate fatalities during the fire process. The application of the methodology is presented based on the evaluation of the national tolerable risk for tunnel transport and compared with referenced EU risk criteria. Furthermore, the presented methodology links CFD simulation results and the quantitative risk assessment approach, still representing the collective risk with F-N curves.
Numerical investigation of heat and flow characteristics in a laminar flow past two tandem cylinders
Authors: Aydin Neslihan , Ozalp Alper , Karagoz Irfan
Published: May 2021

Heat and flow characteristics were investigated numerically for a laminar stream past two tandem circular cylinders placed in a channel. The blockage ratios (? = D/H) were chosen to be 0.6, 0.7, and 0.8, respectively, and the gap between the cylinders was varied proportionally to the cylinder diameter as g = 0.2D, 0.7D, 1.5D, and 4D at a low Reynolds number (Re = 40). The effects of the blockage ratio, as well as the gap between two cylinders on heat and flow features were examined in detail. Shear stresses, dimensionless static pressure, heat transfer coefficient, and separation points from the cylinders were determined from the velocity and temperature fields in the flow domain. The results showed that the separation angle decreases with both the blockage ratio and the gap size on the downstream cylinder, whereas heat transfer increases with both the block-age ratio and the gap size on the upstream cylinder.
Detailed comparison of the performance between a simple and a modified mono-block-layer-built type solid oxide fuel cell
Authors: Ramirez-Minguela Jose , Alfaro-Ayala Jorge , Uribe-Ramirez Agustín , Minchaca-Mojica Jesus , Ruiz-Camacho Beatriz , Mendoza-Miranda Juan , Alvarado-Rodríguez Carlos
Published: May 2021

A detailed comparison of the performance between a simple mono-block-layer-build type solid oxide fuel cell geometry and a mono-block-layer-build type solid oxide fuel cell with an embedded porous pipe in the air supply channel is carried out. The study considers constant and variable porosities along the porous pipe, fed with an air-flow in a counter-flow arrangement. Four cases are analyzed: without the porous pipe, with a pipe of constant porosity, with two different porosities, and with four variable porosities. This work is based in a 3-D CFD model that considers the phenomena of mass transfer, heat transfer, species transport, and electrochemical reactions. Detailed comparisons of the voltage, temperature, and species concentration are illustrated. The electrode-electrolyte interface contours of species concentration, temperature, and electric fields are compared. The results show that there is approximately twice the current density in the geometry that considers the two different porosities compared to the simple geometry. The consumption of hydrogen has the same behavior for the entire tested current density, while the availability of oxygen at the cathode-electrolyte interface is improved in cases with porous pipe compared to the simple mono-block-layer-build type geometry. The use of a porous pipe embedded in the air channel showed that it is possible to have a wider operating range of a mono-block-layer-build type solid oxide fuel cell, and allowed to obtain a more homogeneous temperature distribution on the electrode-electrolyte interface of the solid oxide fuel cell, consequently, there is the possibility of reducing the thermal stress in the solid oxide fuel cell.
Performance improvement of an industrial control enclosure cooling system
Authors: Chiang Wei-Ming , Wang Fu-Jen , Kusnandar K
Published: May 2021

Following the trend of high accuracy machining, thermal management of industrial control enclosures become a critical issue. Therefore, a well-designed enclosure cooling system is essential to manage the heat generation inside the enclosure. In this study, to improve the performance of cooling system and the air-flow distribution inside the enclosure, CFD simulation has been used to evaluate the application of using the auxiliary circulation fan and air baffler. Furthermore, this study also investigates the lay-out design for both supply air vent and return air vent arrangement by two types of commercialized cooling systems through field measurements. The simulation results show the short circulation of air-flow is improved when the air baffler is installed. It also shows that the auxiliary circulation fan is suggested. Besides, air baffler is used to enhance the temperature distribution. The experimental results reveal the upper supply vent arrangement will cause the short circulation of air-flow slightly. The auxiliary circulation fans can improve the heat dissipation of cooling systems. There is no short circulation of air-flow for the lower supply vent arrangement, but the supply air cannot be distributed smoothly by the auxiliary circulation fans because the shape of the air baffler is not properly designed.