Biodegradabilidad de lixiviados procedentes de un relleno sanitario utilizando un sistema de lodos activados flujo pistón / The biodegradability of leachates from a landfill using an activated sludge processes plug flow reactor system / Biodegradabilidade de lixiviados de um aterro usando um sistema de lodos ativados de fluxo de pistão

Resumen En esta investigación se desarrolló un Reactor Flujo Pistón (RFP) de lodos activados, que fue empleado para determinar el Tiempo de Retención Celular (TRC) óptimo para tratar cargas altas de lixiviado y estimar el comportamiento cinético del sistema con el fin que sirva de base para proyecciones de escalamiento y diseño de reactor de este tipo a escala real. Para ello se realizó el diseño, la construcción y puesta en marcha del RFP a nivel de laboratorio (capacidad de 50L) en condiciones de operación continua con recirculación de lodo y se utilizó como sustrato lixiviado procedente del relleno sanitario El Guayabal de la ciudad de Cúcuta. Se determinó como parámetros de control cuatro TRC diferentes entre 5 y 20 días diferenciada por etapas. Se evaluaron las variables de pH, Temperatura, Oxígeno disuelto y Sólidos Suspendidos Volátiles en el Licor Mixto (SSVLM). En cuanto al control y monitoreo de la eficiencia de remoción se escogió la Demanda Química de Oxígeno (DQO) como parámetro para medir la degradación de materia orgánica, dado que este parámetro a diferencia de la Demanda Bioquímica de Oxígeno (DBO5) puede ser calculado en un menor tiempo. El sistema biológico RFP alcanzó estabilizarse en un período de operación entre 20 y 25 días con remociones promedio mayores a 92% para TRC de 15 y 20 días mientras que TRC menores reportaron remociones promedio por debajo del 86%. Así mismo TRC de 15 permitió un Factor de carga (F/M) óptima promedio de 1.1 KgDQO/KgSSV.d. Las constantes cinéticas obtenidas en esta investigación, representativas para un sistema de RFP operado a escala laboratorio para remoción de materia orgánica carbonacea en lixiviados fueron: KS= 836.5 mg/L DQO, k=4.8123 d1, Y= 0.089 mg SSVLM/mg DQO y kd= 0.018 d-1, ajustados por regresión al modelo matemático de Lawrence y McCarty al poseer una correlación de 0.97 entre los datos experimentales obtenidos y el modelo y amplia aplicación en el campo de diseño de reactores de lodos activados.

Abstract An activated sludge processes (ASP) plug flow reactor (PFR) was developed in this research and used for determining optimal cell residence time (CRT) for treating high leachate loads and estimating the system's kinetic behaviour as a basis for scaling projections and this type of reactor design at full-scale. The RFP was designed, built and put into operation in the laboratory (50L capacity) involving continuous operation conditions with sludge recirculation; leached substrate from the city of Cúcuta's El Guayabal landfill was used. Four 5-day CRTs (ranging from 5 to 20 days) were used as control parameters. Variables were evaluated regarding pH, temperature, dissolved oxygen and mixed liquor volatile suspended solids (MLVSS). Regarding removal efficiency control and monitoring, chemical oxygen demand (COD) was chosen as a parameter for measuring organic matter degradation since COD (unlike biochemical oxygen demand (BOD5)) can be calculated in a shorter time. The RFP biological system became stabilised in a 20- to 25-day operating period, having greater than 92% average removal for 15- and 20-day CRTs, whilst lower CRTs reported lower than 86% average removal. A 15-day TRC gave an average 0.26 kgDQO/kgSSV.d optimal load factor (F/M). The representative kinetic constants obtained in this research for a laboratory-scale PFR system for the removal of carbonaceous organic matter in leachates were KS = 836mg COD / l, k = 4.8123 d1, Y = 0.089 mg SSVLM / mg COD and kd = 0.018 d-1, adjusted by regression using Lawrence and McCarty's mathematical model (having 0.97 correlation between the experimental data and the model). Such model should have broad application in the field of ASP-type PFRs.

Resumo Nesta pesquisa, um Reator de lodo ativado de Fluxo de Pistão (RFP) foi desenvolvido para determinar o Tempo de Retenção Celular (CRT) ideal para tratar altas cargas de lixiviado e estimar o comportamento cinético do sistema, a fim de servir de base para projetar o reator em escala real. Para isso, foram realizados RFP em nível de laboratório (capacidade de 50L) em condições de operação contínua com recirculação de lodo e foi utilizada como substrato lixiviado do aterro El Guayabal na cidade de Cúcuta. Usando quatro diferentes CRTs entre 5 e 20 dias como fatores de bloqueio. Foram avaliadas as variáveis ​​pH, Temperatura, Oxigênio Dissolvido e Sólidos Suspensos Voláteis no Licor Misto (SSVLM). Em relação ao controle e monitoramento da eficiência de remoção, a Demanda Química de Oxigênio (DQO) foi escolhida como parâmetro para medir a degradação da matéria orgânica, uma vez que este parâmetro, ao contrário da Demanda Bioquímica de Oxigênio (DBO5), pode ser calculado em um tempo mais curto. O sistema biológico da RFP se estabilizou em um período de operação entre 20 e 25 dias com remoções médias superiores a 92% para TRC de 15 e 20 dias, enquanto TRC menores mostraram remoções médias abaixo de 86%. Da mesma forma, TRC de 15 dias permitiu um fator de carga ideal médio (F / M) de 0,26 KgDQO / d. As constantes cinéticas obtidas nesta pesquisa, representativas de um sistema RFP operado em escala de laboratório para remoção de matéria orgânica carbonácea em lixiviados foram: KS = 836mg COD / l, k = 4,8123 d1, Y = 0,089 mg SSVLM / mg COD e kd = 0,018 d-1, ajustado por regressão ao modelo matemático de Lawrence e McCarty, tendo uma correlação de 0,97 entre os dados experimentais obtidos e o modelo e ampla aplicação na área de projeto de reatores de lodo ativado.

Comparison of gait characteristics between young and elderly people under dual tasks using three-dimensional gait analysis / 中国组织工程研究

BACKGROUND: Dual-task walking is more common in daily life, and more challenging than single-task walking. It is more conducive to find potential gait abnormalities in daily life activities. It is widely used to evaluate the changes in motor performance and gait control when attention is distracted. OBJECTIVE: The three-dimensional gait analysis system was applied to compare the difference of gait characteristics under dual-task walking between healthy young people and elderly people so as to provide reference for preventing the elderly people from falling. METHODS: In the youth group, there were 21 cases aged (24.57±2.27) years old and with the height of (1.64±0.08) m. In the elderly group, there were 25 cases aged (62.72±2.39) years old and with the height of (1.60±0.07) m. The two groups of subjects performed the calculation task of “minus 1 (reciprocal) starting from any number within 100” during level walking. Motion Analysis system and Visual 3D software were applied to collect and analyze the gait data. The differences of gait spatiotemporal and kinetic parameters between the two groups were compared when performing dual-task walking. RESULTS AND CONCLUSION: (1) Spatiotemporal parameters: Compared with youth group, both stride length [(1.14±0.09) m vs. (1.20±0.07) m, P < 0.05] and right step length [(0.57±0.04) m vs. (0.60±0.04) m, P < 0.01] were smaller in the elderly group. (2) Kinetic parameters: Compared with the youth group, the left second peak hip abduction moment was higher [(0.94±0.1) Nm/kg vs. (0.86±0.16) Nm/kg, P < 0.01]; the left ankle plantar flexor moment was lower [(1.27±0.11) Nm/kg vs. (1.35±0.15) Nm/kg, P < 0.05]; and bilateral ankle valgus muscle moments were lower [(0.31±0.14) Nm/kg vs. (0.45±0.16) Nm/kg, P < 0.01; (0.38±0.15) Nm/kg vs. (0.51±0.14) Nm/kg, P < 0.01] in the elderly group. (3) These results suggest that the walking automation ability of the elderly group was lower than youth group during dual-task walking. Dual-task walking mainly affects the hip and ankle joints of the elderly, which may be related to the challenge of dual-task walking to the elderly so that they could adapt the corresponding compensatory mode to maintain stability. The characteristics of gait changes in the elderly under dual tasks can be considered as a reference for the prevention of falls.

The research of the hepatotoxicity of polygonum multiflorum on the basic of the inhibition of the UGT1A1 enzyme in vivo and in vitro / 中国药学杂志

OBJECTIVE: To study the hepatotoxicity of Polygonum multiflorum on the basic of the bilirubin metabolism mediated by glucuronidation of UGT1A1 enzyme. METHODS: Inspected the enzyme kinetic parameters after giving the rats Polygonum multiflorum extract orally(in vivo), and added the Polygonum multiflorum extract into the human liver microsome(rat liver microsome; human recombinant UGT1A1 enzyme) to test the hepatotoxicity using the bilirubin as UGT1A1 enzyme substrate, investigating the inhibition of the UGT1A1 enzyme(in vitro). Apparent inhibition constant Ki and enzyme kinetic parameters were used to evaluate the hepatotoxicity. RESULTS: Polygonum multiflorum extract has a strong inhibiton to the UGT1A1 enzyme in all the three systems in vitro. All the type of inhibition is the competitive inhibition. While Polygonum multiflorum extract has a strong inhibiton to the UGT1A1 enzyme in vivo, but the type of inhibition is the uncompetitive inhibition. CONCLUSION: The method we had established in our study provides a new idea and a new method to evaluate the hepatotoxicity and the safety of Chinese herbs.

Kinematic and Kinetic Characteristics of Gait in Unilateral Below-Knee Amputees

OBJECTIVE: To quantify characteristic gait pattern in below-knee amputees using kinematic and kinetic parameters and to compare those with sound limbs and control group. METHOD: Three dimensional gait analysis was performed in 19 unilateral below-knee amputees and 20 controls. Measured gait parameters were temporal parameters and kinematic and kinetic parameters at hip, knee and ankle joints. Gait parameters obtained from amputated limbs were compared with those of sound limbs and control group. RESULTS: There were no significant differences in temporal parameters among 3 limbs. In amputated limbs, degree of knee flexion and knee extension moment in stance phasewere less than sound limbs and control group. In addition, timing of peak knee extension moment occurred later. Also, timing of ankle plantar flexion in loading response and preswing phase occured later, and degree of ankle plantar flexion in preswing phase were less in amputated limbs compared to other limbs. Peak plantar flexion moment in amputated limbs were less than sound limbs, but not than control group. CONCLUSION: This study suggested that most significant gait abnormalities in unilateral below-knee amputees were observed at the knee and ankle joint in amputated limbs.

Breath-by-breath differences between exercise gas exchange kinetics measured at the mouth and those estimated at the alveolar level / 体力科学

In order to study respiratory transients during exercise, we examined breath-by-breath differences between gas exchange kinetics measured at the mouth and those estimated at the alveolar level. The gas exchange data at the mouth were obtained by measurement of expired gases only (expiratory flow method) . Correction for breath-by-breath changes in lung gas stores was applied to the total gas exchange, which was obtained by subtracting expired from inspired gas volume (alveolar gas exchange method) . Constant work loads (150, 200, 250 W) and a ramp work load (30 W/min) preceded and followed by a 50 W load were generated by a computerized cycle ergometer. Best-fit first- or second-order model values for gas exchange kinetic parameters were found by the non-linear least-squares method.<BR>1. Regardless of work intensity and forcing function, the breath-by-breath variation in gas exchange measured at the mouth was larger than the gas exchange estimated at the alveolar level, in both a non-steady state and a steady state. The variation was caused by the invalidity of assuming zero N<SUB>2</SUB> exchange at the mouth, which was attributed to changes in lung volume.<BR>2. Vo<SUB>2</SUB> kinetics at the alveolar level were faster than those at the mouth, while the converse held for Vco<SUB>2</SUB> at the onset of constant load work, due to the effects of fluctuations in lung gas stores on the kinetics of gas exchange at the mouth. During ramp load work, Vo<SUB>2</SUB> and Vco<SUB>2</SUB> kinetics at the alveolar level were faster than those at the mouth.<BR>3. Steady state gas exchange values at the alveolar level and at the mouth were the same during constant load work, since the lung gas stores corrections added up to small fractions of the total gas exchange when summed over the long term.<BR>4. Consideration of both the proper end-expiratory lung volume and ventilationperfusion inhomogeneity was required in order to estimate the true alveolar gas exchange.