ABSTRACT Introduction: Traditional physical training has a good effect on the improvement of strength and quality indicators of the athletes; however, recent pieces of evidence indicate that relating it to high-intensity interval training may reduce the physical problems of its practitioners, besides accelerating the physical skills required by volleyball. Objective: Study the application of high-intensity interval training on the physical ability of volleyball players. Methods: 40 volunteers were recruited, among freshmen and university students, practicing volleyball. They were divided equally into the control and experimental group. The control group used traditional physical training based on aerobic exercise, while the experimental group adopted a high-intensity interval training program. Each session lasted 1.5 hours, twice a week, for 9 weeks. Relevant physical and functional data were individually collected before and after the intervention, compared, and statistically analyzed. Results: There was an increase in the quality of the long-distance throw, horizontal pull force, 800 m run, 30 m run, cross jump, and repeated crossing experiment. Conclusion: The high-intensity interval training protocol raised the fitness level of volleyball players, allowing optimization of performance on the court. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

RESUMEN Introducción: El entrenamiento físico tradicional tiene un buen efecto en la mejora de los indicadores de fuerza y calidad de los atletas; sin embargo, recientes evidencias indican que relacionarlo con el entrenamiento interválico de alta intensidad puede reducir los problemas físicos de sus practicantes, además de acelerar las habilidades físicas requeridas por el voleibol. Objetivo: Estudiar la aplicación del entrenamiento interválico de alta intensidad sobre la capacidad física de los practicantes de voleibol. Métodos: Se reclutaron 40 voluntarios, entre estudiantes de primer año y universitarios, practicantes de voleibol. Se dividieron a partes iguales en grupo de control y grupo experimental. El grupo de control utilizó un entrenamiento físico tradicional basado en ejercicios aeróbicos, mientras que el grupo experimental adoptó un programa de entrenamiento interválico de alta intensidad. Cada sesión duró 1,5 horas, dos veces por semana durante 9 semanas. Se recogieron individualmente datos físicos y funcionales relevantes antes y después de la intervención, se compararon y se analizaron estadísticamente. Resultados: Hubo un aumento en la calidad del lanzamiento de larga distancia, la fuerza de tracción horizontal, la carrera de 800 m, la carrera de 30 m, el salto cruzado y en el experimento de cruce repetido. Conclusión: El protocolo de entrenamiento interválico de alta intensidad elevó el nivel de condición física en jugadores de voleibol, permitiendo una optimización del rendimiento en la cancha. Nivel de evidencia II; Estudios terapéuticos - investigación de los resultados del tratamiento.

RESUMO Introdução: O treinamento físico tradicional apresenta um bom efeito na melhoria da força e dos indicadores de qualidade dos atletas, porém evidências recentes indicam que relaciona-lo ao treinamento intervalado de alta intensidade possa reduzir os problemas físicos de seus praticantes além de acelerar as habilidades físicas requeridas pelo voleibol. Objetivo: Estudar a aplicação do treinamento intervalado de alta intensidade sobre a habilidade física dos praticantes de voleibol. Métodos: Foram recrutados 40 voluntários entre calouros e alunos da universidade, praticantes de voleibol. Eles foram divididos igualmente em grupo controle e experimental. O grupo de controle utilizou o treinamento físico tradicional baseado em exercício aeróbico enquanto o experimental adotou o programa de treinamento intervalado de alta intensidade. Cada sessão durou 1,5 horas, duas vezes por semana, por 9 semanas. Os dados físicos e funcionais relevantes foram individualmente coletados antes e após a intervenção, comparados e analisados estatisticamente. Resultados: Houve um aumento na qualidade do arremesso de longa distância, força de tração horizontal, corrida de 800 m, corrida de 30 m, salto transversal e no experimento de cruzamento repetido. Conclusão: O protocolo de treinamento intervalado de alta intensidade elevou o nível de aptidão física nos jogadores de vôlei, permitindo uma otimização de desempenho na quadra. Nível de evidência II; Estudos terapêuticos - investigação dos resultados do tratamento.

ABSTRACT Objectives: This study aimed to examine the relationship between vertical jumping at forces of specific time phase and sprint performance in teenage sprinters. Methods: Fifteen male teenage sprinters (age: 14±2 years, height: 168±2 cm, weight: 61±1 kg) participated in the study. The subjects performed the following bilateral/unilateral jumps on a force platform: a) squat jump (SJ), b) unilateral SJ (USJ), c) 40cm drop jump (DJ), and d) 20cm unilateral DJ (UDJ). The 60m sprint test was administered on the second day. Brower split timers were positioned to record subjects’ 5m, 10m, 50m and 60m split times. The variables for inclusion were vertical jump height, maximum force, and force output at 120ms in all jumps and sprint time measures. Results: The results of the Pearson Product Moment Correlation analysis showed that SJ120ms was correlated to 5m and USJ120ms was correlated to 10m. UDJ120ms showed a stronger correlation with 50m than DJ120ms. Although significant correlations using maximum force and height were observed, there were inconsistent results between bilateral and unilateral jumps. Conclusion: Our results highlighted that jumps that have similar form with certain force outputs at specific event timing could more precisely predict sprint performance in teenage sprinters. USJ120ms and UDJ120ms could better predict the acceleration (10m) and high-speed phase (50m) in sprint performance, respectively. Moreover, coaches and practitioners should be cautious when using only jump height or maximum force to predict sprint performance, since the results could be inaccurate when specific movement variables are not thoughtfully considered. Level of evidence III.

RESUMEN Objetivos: Este estudio tuvo como objetivo examinar la relación entre el salto vertical y la fuerza en tiempo específico y el desempeño del sprint en velocistas adolescentes. Métodos: Participaron en el estudio quince adolescentes varones velocistas (edades: 14 ± 2 años, estatura: 168 ± 2 cm, peso: 61 ± 1 kg). Los individuos realizaron los siguientes saltos bilaterales y unilaterales en una plataforma de fuerza: a) squat jump (SJ), b) SJ unilateral (USJ), c) drop jump (DJ) de 40 cm e d) DJ unilateral (UDJ) de 20 cm. La prueba de sprint de 60 m se realizó el segundo día. Los cronómetros en el entrenamiento fraccionado se ajustaron para registrar tiempos de 5 m, 10 m, 50 m y 60 m. Las variables que se incluyeron fueron la altura del salto vertical, la fuerza máxima y la salida de fuerza a 120 m en todos los saltos y mediciones del tiempo del sprint. Resultados: Los resultados del análisis de correlación producto-tiempo de Pearson revelaron que el SJ de 120 m estaba correlacionado con 5 m y el USJ de 120 m estaba correlacionado con 10 m. El UDJ de 120 m tuvo una mayor correlación con el DJ de 50 m que con el de 120 m. Aunque se observaron correlaciones significativas con la fuerza y la altura máximas, algunos resultados fueron inconsistentes entre los saltos bilaterales y unilaterales. Conclusiones: Nuestros resultados pusieron de manifiesto que los saltos con una forma similar a determinadas salidas de fuerza en un tiempo específico del evento pueden predecir con mayor precisión el desempeño en el sprint en adolescentes velocistas. El USJ de 120 m y el UDJ de 120 m pueden predecir mejor, respectivamente, la aceleración (10 m) y la fase de alta velocidad (50 m) en el desempeño del sprint. Además, los entrenadores y practicantes deben ser cautelosos a la hora de utilizar únicamente la altura del salto o la fuerza máxima para predecir el desempeño en el sprint, ya que los resultados pueden ser inexactos cuando no se tienen en cuenta con precisión las variables específicas del movimiento. Nivel de evidencia III.

RESUMO Objetivos: Este estudo teve como objetivo examinar a relação entre o salto vertical e a força em tempo específico e o desempenho de sprint em velocistas adolescentes. Métodos: Quinze adolescentes velocistas do sexo masculino (idade: 14 ± 2 anos, estatura: 168 ± 2 cm, peso: 61 ± 1 kg) participaram do estudo. Os indivíduos realizaram os seguintes saltos bilaterais e unilaterais em uma plataforma de força: a) squat jump (SJ), b) SJ unilateral (USJ), c) drop jump (DJ) de 40 cm e d) DJ unilateral (UDJ) de 20cm. O teste de sprint de 60 m foi realizado no segundo dia. Os cronômetros rastreadores para treinos fracionados foram posicionados para registrar os tempos fracionados de 5 m, 10 m, 50 m e 60 m. As variáveis para inclusão foram altura do salto vertical, força máxima e saída de força a 120 m em todos os saltos e medidas de tempo do sprint. Resultados: Os resultados da análise da correlação produto-tempo de Pearson mostraram que o SJ de 120 m foi correlacionado com 5 m e USJ de 120 m foi correlacionado com 10 m. O UDJ de 120 m teve correlação mais forte com DJ de 50 m do que de 120 m. Embora tenham sido observadas correlações significativas com força e altura máximas, alguns resultados foram inconsistentes entre os saltos bilaterais e unilaterais. Conclusões: Nossos resultados destacaram que os saltos com forma semelhante a certas saídas de força no tempo específico do evento podem prever com mais precisão o desempenho no sprint em adolescentes velocistas. O USJ de 120 m e o UDJ de 120 m podem prever melhor, respectivamente, a aceleração (10 m) e a fase de alta velocidade (50 m) no desempenho no sprint. Além disso, treinadores e praticantes devem ser cautelosos ao usar apenas a altura do salto ou a força máxima para prever o desempenho no sprint, uma vez que os resultados podem ser imprecisos quando variáveis específicas do movimento não forem consideradas com precisão. Nível de evidência III.

BACKGROUND. The surgical management of children with bronchiectasis has seldom been reported. OBJECTIVE. To describe the presentation, surgical management and outcomes in children with bronchiectasis presenting for surgery. METHODS. We retrospectively reviewed the electronic records of 0 - 13-year-old children who underwent pulmonary resection for bronchiectasis at Inkosi Albert Luthuli Central Hospital, Durban, South Africa, between January 2004 and December 2014. Clinical, radiological and preoperative bronchoscopic findings, as well as surgical and histological outcomes, were analysed. RESULTS. Eighty-eight patients underwent surgical resection. The female/male ratio was 3:2, with a mean age at surgery of 8.2 (range 2 - 13) years; 39 patients were HIV infected and 39 were HIV uninfected. Tuberculosis (TB) (n=68; 77.2%) was the most common cause of bronchiectasis, and recurrent chest infection (n= 45; 51.1%) was the most common clinical finding. Radiological examination confirmed isolated left-sided disease in 40 children (45.4%), isolated right-sided disease in 28 (31.8%) and bilateral disease in 20 (22.7%). Saccular disease with fibrocavitation (n=35; 39.7%) was the most common morphological disease type. Preoperative bronchoalveolar lavage samples confirmed a bacterial cause in 27 patients (30.6%). The most common operative procedures were primary pneumonectomy in 33 patients (37.0%), lobectomy in 30 (34.0%) and bilobectomy in 13 (14.7%). Seventy-five patients were asymptomatic after the operation and complications occurred in 13. Two children (2.2%), one with sepsis and the other with intraoperative hypoxia, died. Seventy patients underwent complete resection. At 1 month after surgery, 89.2% of patients were asymptomatic, while 77.7% of symptomatic patients were HIV positive. CONCLUSIONS. Complete pulmonary resection in children with advanced-stage bronchiectasis is safe, with a low morbidity and mortality. Surgery in HIV-positive patients was not associated with worse outcomes and is not contraindicated. HIV- and TB-preventive measures could reduce the burden of childhood bronchiectasis.

The bottom drainage roadway plays a crucial role in preventing coal and gas outbursts by using underground gas drainage methods. Therefore, it is essential to select the ideal position of the bottom drainage roadway. In this paper use a combination of geological data and numerical simulation to study the ideal position of the bottom drainage roadway, we taking the gas drainage of the first workface of No. 3 coal seam in the Yuxi coal mine in China as an example. The geological study showed a limestone marker layer at an average vertical distance of 14 m from the first mining face. Using this marker layer, the bottom drainage roadway could be excavated without the risk of accidentally exposing the coal seam, and less crosscutting borehole drilling from the bottom drainage roadway would be required. Based on the needs of gas control, the layout of the bottom drainage roadway was selected as an external stagger type. Combined with the numerical simulation results, when located 20 m outside of the mining workface 'footprint' on the horizontal projection, the bottom drainage roadway was a sufficient distance from the stress concentration area during mining of workface 1301, which facilitated roadway maintenance. Furthermore, the length of the crosscutting boreholes is also relatively short, which reduces the amount and cost of drilling. The results of this study are expected to provide a reference for the selection of an ideal position of the bottom drainage roadway in field engineering.

Abstract Introduction: The objective of this study was to investigate the effect of mivacurium in the application of fast-track anesthesia for transthoracic device closure of ventricular septal defects (VSDs) in children. Methods: The data of 108 children who underwent transthoracic device closure of VSDs from December 2018 to June 2020 were recorded and analyzed. All children were divided into group M (mivacurium group, n=55) and group C (cisatracurium group, n=53) according to the different muscle relaxant drug used. Results: No statistically significant differences in general preoperative data, intraoperative hemodynamic changes, or the incidence of adverse reactions were noted between the two groups (P>0.05). However, the intubation condition rating of children in group M was better than that in group C. The onset time, duration of clinical action and recovery index of the muscle relaxant, postoperative mechanical ventilation duration, and length of intensive care unit stay in group M were significantly lower than those in group C (P<0.05). Conclusion: It is safe and feasible to use mivacurium as a muscle relaxant in children undergoing fast-track cardiac anesthesia during transthoracic device closure of VSDs.

ABSTRACT The study was conducted to investigate the effect of GOX on performance, egg quality, and nutrient digestibility in laying hens. In total, 432, 50-week-old Hy-Line brown breeder hens were assigned into four treatments, and fed a basal diet with GOX at 0, 100, 200 and 300 units for 10 weeks, respectively. A Quadratic decrease in FI in week 3 (p<0.05) and linear increase in egg production in week 6 to 10 and overall experiment period (p<0.05) and Quadratic increase in egg production in week 7 (p<0.05), a linear decrease in broken egg rate in week 6 (p<0.05) a quadratic increase in egg weight on day 14 (p<0.05), alinear increase in egg weight on day 28 (p<0.05), and linear decrease in yolk color on day 7 (p<0.05), a linear increase in yolk color on day 42 and day 70 (p<0.05), and linear increase in haugh unit on day 28 and 70 (p<0.05), a linear increase albumen height on day 28 and day 56 (p<0.05), and linear decrease in shell color on day 14 (p<0.05) and day 28(p<0.05), a linear and quadratic increases in eggshell strength and eggshell thickness on day 56 (p<0.05), and linear increase in eggshell strength and eggshell thickness on day 70 (P0.05) were observed with the addition of GOX the the diet. Conclusion: This study suggested that the supplementation of GOX may have beneficial effects on feed intake and egg quality in laying hens.

Abstract To study the effect of okra aqueous extract on the intestinal flora of diabetic rats. Taking normal SD rats as CK group, diabetic rats induced by 40 mg/(kg•bw) streptozotocin (STZ) intraperitoneally as M group, normal and diabetic rats gavaged with 500 mg/(kg•bw) okra aqueous extract were CKO and MO groups,respectively. The bacterial flora of the cecum contents of rats was analyzed with 16S rRNA V3-V4 sequencing after 8 weeks of the experiment. Compared with CK, M increased Firmicutes 14.00% and decreased Proteobacteria 19.32% (P <0.01). Compared with M, MO down-regulated Lachnospiraceae 2.64% (such as Blautia, Anaerostipes), up-regulated Peptostreptococcaceae 1.20% in Firmicutes, and down-regulated Desulfovibrioceae 3.78% (such as Desulfovibrio) and up-regulated Burkholderia 5.24% (such as Parasutterella) in Proteobacteria. It is worth noting that MO up-regulated Christensenellaceae (LDA>4), which was negatively correlated with body mass index, inflammation, and metabolic syndrome. The okra aqueous extract reverses the changes of the intestinal flora of STZ-induced diabetic rats, which decreased Firmicutes and increased Proteobacteria by down-regulating Lachnospiraceae and Desulfovibrionaceae, up-regulating Burkholderiaceae, Christensenellaceae. The okra aqueous extract has the potential as a functional food with regulating intestinal microecology balance of diabetes.

BACKGROUND: The phenomenon of silent hypoxaemia has been described in patients with COVID-19 pneumonia, which is characterised by low oxygen saturation levels of <90% in those who appear clinically well and do not show signs of significant respiratory distress.OBJECTIVES: To assess the impact on clinical outcomes for high-risk COVID-19 patients using a pulse oximeter to monitor oxygen saturation levels in a home setting.METHODS: We performed a retrospective cohort analysis using data from a large South African insurance administrator. Patients were categorised as high risk, based on age and specific underlying clinical conditions, or from predictive models derived from medical scheme administrative claims data. The impact of pulse oximetry home monitoring on COVID-19 clinical outcomes was investigated by the use of Cox proportional hazard models.RESULTS: Between 2 March 2020 and 31 October 2020, of 38 660 patients analysed, 8 115 were in the intervention group. The 60-day mortality rate for the evaluated high-risk population was 1.35%. After adjusting for age and comorbidity differences, the intervention group was found to have an adjusted hazard ratio of 0.52 (p<0.0001). No statistical significance was found between the intervened and control groups for admission to hospital, admission to intensive care unit (ICU) and use of mechanical ventilation. The intervention group had a lower median C-reactive protein (CRP) level on admission (p=0.03). After adjustment for admission CRP levels, elevated CRP was associated with an increased mortality (p<0.0001), while the statistical significance in mortality between the intervention and the control group was lost.CONCLUSIONS: High-risk COVID-19 patients who used a pulse oximeter to monitor oxygen saturation levels had significantly lower mortality rates compared with other high-risk patients. The mortality benefit may be explained by earlier presentation to hospital, as suggested by lower initial CRP levels.

Abstract: Objective: We examined delays during the search for care and associations with mother, child, or health services characteristics, and with symptoms reported prior to death. Materials and methods: Cross-sectional study comprising household interviews with 252 caregivers of children under-5 who died in the state of Yucatán, Mexico, during 2015-2016. We evaluated the three main delays: 1) time to identify symptoms and start search for care, 2) transport time to health facility, and 3) wait time at health facility. Results: Children faced important delays including a mean time to start the search for care of 4.1 days. The mean transport time to the first facility was longer for children enrolled in Seguro Popular and there were longer wait times at public facilities, especially among children who also experienced longer travel time Conclusions: Providing resources to enable caregivers to access health services in a timely manner may reduce delays in seeking care.

Resumen: Objetivo: Analizar las demoras en la búsqueda de atención y su asociación con características de la madre, del niño y los servicios de salud, así como con los síntomas reportados antes de la defunción. Material y métodos: Diseño transversal con entrevistas a 252 cuidadores que se encargaron de niños menores de cinco años que fallecieron en el estado de Yucatán, México, durante 2015-2016. Se evaluaron tres demoras: 1) tiempo en identificar la complicación e iniciar el proceso de búsqueda; 2) tiempo de transporte; y 3) tiempo de espera en la unidad de salud. Resultados: Los niños enfrentaron demoras importantes en la búsqueda de atención. La media de tiempo para iniciar la búsqueda de atención fue de 4.1 días. La media de tiempo de transporte a la primera unidad de atención fue mayor para niños inscritos en el Seguro Popular y hubo tiempos de espera más largos en unidades de salud del sector público, especialmente entre niños que tuvieron tiempos de transporte largos. Conclusión: Proporcionar recursos que permitan a los cuidadores acceder a los servicios de salud de manera oportuna puede reducir las demoras en la búsqueda de atención.

ABSTRACT Sugarcane (Saccharum L. spp. hybrids) is a globally important crop. While roots contribute to its net primary production, knowledge of sugarcane root growth is incomplete and limited in scope. The objective of this study was to determine cumulative root density (LA), root distribution, effective rooting depth (ERD), and root growth rate for four sugarcane genotypes across three crop cycles (plant cane [PC], first ratoon [FR], and second ratoon [SR]). The experiment was conducted in a rain shelter on four sugarcane genotypes (ROC22, YZ04-241, YZ05-194, and YZ05-51) using minirhizotron tubes to a soil profile depth of 1.08 m. Most roots in were found at 0–0.36 m-depth, and about 85.0% were within a 0–0.72 m depth in PC. In FR and SR, however, > 81.8% of roots were found at 0–0.54 m-depth regardless of genotype. The LA of ROC22 was often significantly higher than that of the other genotypes at depths < 0.54 m regardless of crop cycle. The genotype ROC22 had greater root length and faster root growth rate than YZ05-194 at 0.18–0.36 m in PC and FR, while SR YZ05-194 had slower root growth than the other genotypes at 0–0.18m. Ratooning ability of sugarcane genotypes may be related to these root growth attributes.

Both theoretical and field research have shown that protective layer mining with pressure-relief gas extraction in protected coal seams is an effective and economical way of controlling coal and gas outbursts in underground mines. Given the influences of coal seam angles, layer spacing, pressure-relief angles, coal pillars, and other factors in the protected areas of protected seams, the protection range is often smaller than the area of protective seam mining. This problem can be solved by using a gas drainage method based on coal seam geology and the conditions of coalbed methane (CBM) occurrence during protective layer mining. If a protective layer is prone to outbursts, crossing boreholes and bedding boreholes can be used to eliminate outburst hazards. The crossing boreholes should control the upper side of the roadway contour for at least 20 m and the lower side for at least 10 m. For other coal seams, the boreholes should control both sides of the roadway contour for at least 15 m. Crossing boreholes can not only extract CBM from the protective layer but can also extract from the protected coal seam, thus leading to a larger protection range in the protective layer than that predicted by the pressure-relief boundary, as well as expanding the protection range. The actual protection range of the protected layer was determined using an index of residual gas content. The results of the study indicate that the pressure-relief angle increased from 56° to 69° in the strike direction and from 75° to 90° in the inclination direction. The protection range was approximately equal to the mining area of the working face of the protective layer, thereby extending the protection range. One of the important reasons for protection range expansion was the influence of gas drainage via crossing boreholes. The protection range extension mitigated the outburst danger over a large area of the coal seam, thus enabling high efficiency and safe exploitation.

The power of a compound is enhanced by the direct connection of nitrogen atoms, and its stability can be improved through conjugated structure. So novel high energy density materials N14 (1,6-dihydro-1,2,3,3a,4,5,5a,6,7,8,8a,9,10,10a-tetradecazapyrene) and N18 (1,2,2a,3,4,4a,5,6,6a,7,8,8a,9,10,10a,11,12a-octadecazacoronene) were designed, and their structures, detonation performance, and stabilities were calculated employing density functional theory (DFT). The detonation performance includes detonation pressure (P), detonation velocity (D), and heat of detonation (Q). Furthermore, the stability involves frontier molecular orbitals and impact sensitivity. Calculations reveal that they have an excellent power, detonation performance of N14 (P = 43.6 GPa, D = 10040 m s-1, Q = 2214 cal g-1) and N18 (P = 37.4 GPa, D = 9400 m s-1, Q = 2114 cal g-1) are comparable to CL-20. Besides, their impact sensitivities are slightly better than CL-20, therefore they are promising candidates in energetic materials.

Resumen El macizo de Chirripó en la Cordillera de Talamanca, Costa Rica, es uno de los pocos sitios en América Central que conserva evidencia de glaciación en el pasado. Mapeamos formas de relieve glaciales en esta área usando imágenes de alta resolución de Google Earth y un modelo de elevación digital (DEM) de la Misión Topográfica de Radar Shuttle de 30 m. Observaciones previamentes de campo, notas de campo, fotografías y mapas de formas de relieve se usaron para verificar y refinar los límites del relieve delineados. El mapa compuesto incluye morrenas laterales y terminales, laderas, valles glaciares, lagos glaciales, nunataks, arêtes, y cuernos. Las extensiones glaciales durante tres etapas propuestas se mapearon en el Valle de las Morrenas, un importante valle orientado hacia el norte en el macizo, basado en reconstrucciones previas. Las características glaciales mapeadas cubren aproximadamente 22,1 km2, que representan la extensión mínima de la glaciación máxima durante el período del último glacial máximo (LGM). Este mapa refinado proporciona un importante conjunto de datos para ayudar a reconstruir el cambio climático del Cuaternario en este altiplano tropical.

Abstract The Chirripó massif in the Cordillera de Talamanca, Costa Rica, is one of a few sites in Central America that preserve evidence of past glaciation. We mapped glacial landforms in this area using Google Earth high-resolution imagery and a 30 m Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM). Prior field observations, field notes, photographs, and landform maps were used to check and refine the delineated landform boundaries. The composited map includes lateral and terminal moraines, tills, glacial valleys, glacial lakes, nunataks, arêtes, and horns. Glacial extents during three proposed stages were mapped in the Valle de las Morrenas, a major north-facing valley on the massif, based on previous reconstructions. The mapped glacial features cover roughly 22.1 km2, representing the minimum extent of the rnaximum glaciation during the Last Glacial Maximum (LGM). This refined map provides an important dataset to help reconstruct Quaternary climate change in this tropical highland.

RESUMEN La evaluación de la evolución de los poros es clave para obtener una mejor comprensión de la migración y acumulación de petróleo en la exploración de petróleo para arenas compactas; Para estudiar la diagénesis y la evolución de la porosidad de los reservorios de arenas compactas, se anlizó el octavo componente de la Formación Yanchang a través de la observación de núcleos, la observación de secciones delgadas, análisis de catodoluminiscencia, microscopía electrónica de barrido y análisis de registro de datos. Del presente studio se pueden extraer las siguientes conclusiones (1) En los reservorios característicos de arenas compactas, se desarrollaron numerosos poros secundarios a profundidades de enterriamiento en el rango de 1300 a 1400 m, y de aproximadamente 1500 m a 1600 m. (2) La compactación fue el factor más influyente en la densidad del yacimiento y disminuyó el tamaño promedio de los poros en un 24.8%. La cementación por carbonato disminuyó la porosidad en un 8,2%. Mientras que el proceso diagenético más importante para aumentar la porosidad del yacimiento fue la disolución, que aumentó el tamaño de los poros en un 5,1%. Además, la clorita desempeñó un papel activo en la inhibición del crecimiento secundario del cuarzo y en la conservación de los poros primarios. (3) La invasión temprana de gas puede inhibir la diagénesis, y los ácidos orgánicos producidos posteriormente por el petróleo pueden aumentar la disolución, por lo que el fenómeno de alta saturación de petróleo se hace más significativo.

ABSTRACT Evaluation of the pore evolution is key to gaining a better understanding of oil migration and accumulation in tight oil exploration for tight sandstone; to study the diagenesis and porosity evolution of tight sandstone reservoirs, we analysed the 8th member of the Yanchang Formation by core observation, thin section observation, cathodoluminescence, scanning electron microscopy, and logging data analysis. The following conclusions can be drawn (1) In the typical tight sandstone reservoir, numerous secondary pores developed at burial depths in the range of 1300 m to 1400 m, and approximately 1500 m to 1600 m. (2) Compaction was the most influential factor of reservoir density and decreased the average pore size by 24.8%. Carbonate cementation decreased the porosity by 8.2%. The most important diagenetic process for increasing the reservoir porosity was dissolution, which increased the pore size by 5.1%. In addition, chlorite played an active role in inhibiting secondary quartz growth and preserving primary pores. (3) The early gas invasion can inhibit diagenesis, and the organic acids produced by the later oil can increase dissolution, so that the high oil saturation phenomenon becomes more obvious.