bluuebunny/crossref_metadata_2025 huggingface dataset:
ON INDUSTRY MOMENTUM STRATEGIES
Authors: Grobys Klaus , Kolari James
Published: December 2019

In this article, we investigate industry momentum strategies. We find that industry portfolios that outperformed in the previous month generate on average significantly higher returns in the holding period than those that underperformed. Plain and risk‐managed strategies using this short‐run industry momentum are not subject to optionality effects. Also, the tail risks of these strategies are uncorrelated with traditional industry momentum strategies. The spread associated with the risk‐managed strategy both meets necessary conditions as a risk factor and is significantly priced in the cross‐section of U.S. industry portfolios.
Longitudinal Effects of Adolescent Abuse on Relationship Quality and Posttraumatic Stress Symptoms in Mother–Adolescent Dyads
Authors: Fitzgerald Michael , Ledermann Thomas
Published: December 2019

The current study examined dyadic reports of mother–adolescent relationship quality (RQ) as a mechanism by which emotional, physical, and sexual abuse affect posttraumatic stress symptoms (PTSS) over time from a family systems perspective. We used three waves of data from the Longitudinal Studies of Child Abuse and Neglect (LONGSCAN), including 321 mother–adolescent dyads observed when adolescents were approximately 12, 14, and 16 years old. We used an extended version of the actor–partner interdependence mediation model to analyze the effect of emotional, physical, and sexual abuse on adolescents' PTSS through dyadic reports of mother–adolescent RQ. Results yielded significant indirect effects between sexual and emotional abuse, but not physical abuse, and PTSS 4 years later through adolescent perceptions of RQ. Maternal perceptions of RQ were not directly associated with adolescents' PTSS; however, maternal perceptions of RQ positively contributed to future adolescent perceptions of RQ. Clinical implications are discussed.
Desensitization of NMDA channels requires ligand binding to both GluN1 and GluN2 subunits to constrict the pore beside the activation gate
Authors: Chen Yu‐Shian , Tu Ya‐Chi , Lai Yi‐Chen , Liu Erin , Yang Ya‐Chin , Kuo Chung‐Chin
Published: December 2019

N‐methyl‐D‐aspartate (NMDA) receptor channels are activated by glutamate (or NMDA) and glycine. The channels also undergo desensitization, which denotes decreased channel availability, after prolonged exposure to the activating ligands. Glycine apparently has a paradoxical negative effect on desensitization, as the increase in ambient glycine in concentrations required for channel activation would increase sustained NMDA receptor currents. We hypothesized that this classical “glycine‐dependent desensitization” could be glycine‐dependent activation in essence. By performing electrophysiological recordings and biophysical analyses with rat brain NMDA receptors heterogeneously expressed in Xenopus laevis oocytes, we characterized that the channel opened by “only” NMDA (in nominally glycine‐free condition probably with the inevitable nanomolar glycine) would undergo a novel form of deactivation rather than desensitization, and is thus fully available for subsequent activation. Moreover, external tetrapentylammonium ions (TPentA), tetrabutylammonium ions, and tetrapropylammonium ions (TPA, in higher concentrations) block the pore and prohibit channel desensitization with a simple “foot‐in‐the‐door” hindrance effect. TpentA and TPA have the same voltage dependence but show different flow dependence in binding affinity, revealing a common binding site at an electrical distance of ~0.7 from the outside yet differential involvement of the flux‐coupling region in the external pore mouth. The smaller tetraethylammonium ion and the larger tetrahexylammonium and tetraheptylammonium ions may block the channel but could not affect desensitization. We conclude that NMDA receptor desensitization requires concomitant binding of both glycine and glutamate, and thus movement of both GluN1 and GluN2 subunits. Desensitization gate itself embodies a highly restricted pore reduction with a physical distance of ~4 Å from the charged nitrogen atom of bound tetraalkylammonium ions, and is located very close to the activation gate in the bundle‐crossing region in the external pore vestibule.

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Land outsourcing and labour contracting: Labour management in China's capitalist farms
Authors: Yiyuan Chen
Published: December 2019

Difficulty in labour supervision has been considered to be one of the obstacles to the development of capitalist agriculture. This paper presents two distinctive labour management strategies in China's large‐scale agriculture, which contribute to the development of agrarian capitalism in China. As shown in these cases, agribusiness companies engaged in grain crop production retreat from direct labour management by outsourcing crop cultivation, while acquiring profits from upstream and downstream activities. On the other hand, capitalist producers, who are involved in the labour‐intensive and capital‐intensive crop production, tend to mobilize local elites to manage the farmworkers. Although independent labour contracting services have not emerged, a specialized group of labour contractors is being cultivated. Rural social resources are utilized in labour recruitment and supervision to minimize the labour management costs in both strategies. However, the conflicts between capital and labour are covered or replaced instead of being settled.
Longitudinal studies can identify distinct inflammatory cytokines associated with the inhibition or progression of liver cancer
Authors: Mirshahi Faridoddin , Aqbi Hussein F. , Cresswell Kellen , Saneshaw Mulugeta , Coleman Cara , Jacobs Taylor , Idowu Michael O. , Dozmorov Mikhail , Sanyal Arun J. , Manjili Masoud H.
Published: December 2019

Background and Aims

Chronic diseases such as nonalcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma (HCC) are associated with chronic inflammation. However, controversial reports as to the key cytokines involved in the process of chronic inflammation hinder development of targeted therapies for patients. This is because, chronic inflammatory process cannot be fully understood by studying the mechanisms of the disease in a short‐term or isolated fashion. Understanding of the trend of inflammatory cytokines through longitudinal studies could provide a profound insight into the process of disease progression.

Methods

We performed a longitudinal analysis of inflammatory cytokines/chemokines and faecal microbiome dysbiosis associated with the diet‐induced progression of NAFLD to HCC in diet‐induced animal model of NAFLD comparing males and females, since males show a higher incidence of these diseases than females do.

Results

Longitudinal analyses revealed that a transient and timely increase in LIF and TMIP1 was associated with the inhibition of the progression of NAFLD to HCC in females. On the other hand, chronically increasing trends in CCL12, CCL17, CXCL9 and LIX/CXCL5 were associated with the promotion of the progression of NAFLD to HCC in males.

Conclusions

We provided empirical evidence that a methodological shift from snapshot observations to longitudinal data collection and analysis can provide a better understanding of chronic liver diseases.
The interaction between Sporothrix schenckii sensu stricto and Sporothrix brasiliensis with Acanthamoeba castellanii
Authors: Lemos Tavares Priscila , Carvalho Ribeiro Amanda , Kercher Berte Francisco , da Silva Hellwig Alessandra Helena , Machado Pagani Danielle , Tavares de Souza Carine Cristina , Brittes Rott Marilise , Scroferneker Maria Lúcia
Published: December 2019

Background

Sporotrichosis is a group of zoonotic subcutaneous mycoses, found worldwide and caused by fungi belonging to the genus Sporothrix. Protozoans of the genus Acanthamoeba are widely distributed, and some species may be pathogenic and/or opportunistic. These organisms coexist in the same environment and may interact.

Objectives

This study determined the profile of interactions of S schenckii sensu stricto and S brasiliensis with A castellanii, using an in vitro co‐culture model to evaluate the intrinsic characteristics of the two Sporothrix species and A castellanii.

Methods

We compared the rate of phagocytosis of S schenckii sensu stricto and S brasiliensis by A castellanii; the viability of S schenckii sensu stricto and S brasiliensis after contact with A castellanii; the viability of the amoeba after contact with a fungal species; and the influence of S schenckii sensu stricto and S brasiliensis on the encystment process of A castellanii.

Results

The analyses indicated that A castellanii phagocytised both S schenckii and S brasiliensis, with significantly more S schenckii than S brasiliensis in the first two hours of contact. Our results showed a significant increase in conidia and hyphae count after 72 hours of co‐culture of A castellanii with S brasiliensis, and the amoebae lysed after they ingested the fungi, indicating that the fungi probably used the amoebae as a source of nutrition.

Conclusions

Our results were obtained in vitro and these organisms may not behave similarly in vivo; in vivo studies of co‐infections are necessary in order to gain a thorough understanding of this relationship.
Perinatal depressive symptoms among Thai women: A hospital‐based longitudinal study
Authors: Phoosuwan Nitikorn , Manwong Mereerat , Eriksson Leif , Lundberg Pranee C.
Published: December 2019

The authors of this longitudinal study investigated risk factors for postpartum depressive symptoms and differences in depressive symptoms at late pregnancy and at 1 and 3 months postpartum. In Sakhonnakhon Province, in northeastern Thailand, 449 women were recruited during late pregnancy and followed at 1 and 3 months postpartum with the use of psychosocial factors. Depressive symptom scores were measured using the Edinburgh Postnatal Depression Scale (EPDS). The scores were compared using dependent‐samples t‐tests, and multiple linear regression analyses were used to identify risk factors for depressive symptoms at 1 and 3 months postpartum. EPDS scores decreased from late pregnancy to 1 month postpartum and remained on the same level until 3 months postpartum. Low psychological well‐being scores and low personal monthly income were risk factors for increased EPDS scores at 1 and 3 months postpartum. Pregnant women in Thailand who have a low income, have limited social support, and report low psychological well‐being are at increased risk for postpartum depression. Results of this study suggest they should be screened for depressive symptoms during pregnancy, referred for diagnosis, and provided treatment to reduce the risk of ongoing depressive symptoms during the postpartum period.
Investigation of interference from synthetic colloids on the performance of a canine neutrophil gelatinase‐associated lipocalin immunoassay
Authors: Davis Jennifer , Rossi Gabriele , Miller David W. , Shiel Robert E. , Raisis Anthea L.
Published: December 2019

Background

Synthetic colloid solutions, administered by rapid infusion to volume‐depleted dogs, might be present in high concentrations in subsequent urine samples. The potential for these solutions to affect the performance of ELISA measurements due to sample matrix effects when studying kidney injury biomarkers requires investigation.

Objective

We aimed to investigate two different synthetic colloid solutions, 4% succinylated bovine gelatin (GEL) and 6% hydroxyethyl starch (HES), for potential interferences with a commercially available canine neutrophil gelatinase‐associated lipocalin (NGAL) ELISA.

Methods

Assay interference was assessed by measuring the linearity of NGAL concentrations measured using a canine NGAL ELISA after serial dilution of a canine pooled urine sample with an assay diluent, GEL, or HES.

Results

NGAL recovery from urine specimens containing up to 75% HES and up to 62.5% GEL was within acceptable limits (80%‐120%). NGAL recovery from the urine specimen containing 75% GEL was poor (76%). Linear regression analysis demonstrated excellent linearity under dilution when a canine urine sample was diluted with the assay diluent, GEL, or HES.

Conclusions

The presence of large amounts (>62.5%) of GEL in canine urine samples could cause negative interference in the performance of the NGAL ELISA investigated.
Genetic variation in tolerance to defoliation in Cirsium arvense
Authors: Cripps M G , Dowsett C A , Jackman S D , van Koten C , Goeke D F , Houliston G J
Published: December 2019

The perennial weed, Cirsium arvense (creeping, Canada or Californian thistle), is notorious for its ability to tolerate defoliation by mowing, herbivores or herbicides. The tolerance of 36 genotypes of C. arvense was examined by establishing pairs of clonal replicates that were assigned to a clipped or unclipped treatment. Three clippings were applied from spring to early summer to simulate repeated mowing. The average final percentage reduction caused by the repeated clipping was 18%, 72%, 32% and 50% for shoot biomass, root biomass, number of shoots and shoot height respectively. While nearly all genotypes were negatively affected by clipping, some overcompensated, and achieved greater shoot biomass, number of shoots, or increased height than their unclipped counterparts. No genotype was able to overcompensate, or fully tolerate, the lost root biomass due to repeated clipping. Genetic variation for tolerance to defoliation was detected for the number of shoots, maximum shoot height and for relative height growth rate. For relative growth rate, significant genetic variation was not detected until after the third clipping event, indicating that genotypes were equally tolerant to a moderate degree of defoliation, but upon more severe defoliation, genetic differences were evident. Since repeated defoliation is a recommended control technique, selection for more tolerant genotypes is possible and should be considered for the management of this weed.
Regional contributions of nitric oxide synthase to cholinergic cutaneous vasodilatation and sweating in young men
Authors: McGarr Gregory W. , Ghassa Reem , Fujii Naoto , Amano Tatsuro , Kenny Glen P.
Published: December 2019

New Findings

What is the central question of this study?

We evaluated whether regional variations exist in NO‐dependent cutaneous vasodilatation and sweating during cholinergic stimulation.

What is the main finding and its importance?

Peak cutaneous vasodilatation and sweating were greater on the torso than the forearm. Furthermore, we found that NO was an important modulator of cholinergic cutaneous vasodilatation, but not sweating, across body regions, with a greater contribution of NO to cutaneous vasodilatation in the limb compared with the torso. These findings advance our understanding of the mechanisms influencing regional variations in cutaneous vasodilator and sweating responses to pharmacological stimulation.

Regional variations in cutaneous vasodilatation and sweating exist across the body. Nitric oxide (NO) is an important modulator of these heat loss responses in the forearm. However, whether regional differences in NO‐dependent cutaneous vasodilatation and sweating exist remain uncertain. In 14 habitually active young men (23 ± 4 years of age), cutaneous vascular conductance (CVC%max) and local sweat rates were assessed at six skin sites. On each of the dorsal forearm, chest and upper back (trapezius), sites were continuously perfused with either lactated Ringer solution (control) or 10 mm Nω‐nitro‐l‐arginine (l‐NNA; an NO synthase inhibitor) dissolved in Ringer solution, via microdialysis. At all sites, cutaneous vasodilatation and sweating were induced by co‐administration of the cholinergic agonist methacholine (1, 10, 100, 1000 and 2000 mm; 25 min per dose) followed by 50 mm sodium nitroprusside (20–25 min) to induce maximal vasodilatation. The l‐NNA attenuated CVC%max relative to the control conditions for all regions (all P < 0.05), and NO‐dependent vasodilatation was greater at the forearm compared with the back and chest (both P < 0.05). Furthermore, maximal vasodilatation was higher at the back and chest relative to the forearm (both P < 0.05). Conversely, l‐NNA had negligible effects on sweating across the body (all P > 0.05). Peak local sweat rate was higher at the back relative to the forearm (P < 0.05), with a similar trend observed for the chest. In habitually active young men, NO‐dependent cholinergic cutaneous vasodilatation varied across the body, and the contribution to cholinergic sweating was negligible. These findings advance our understanding of the mechanisms influencing regional variations in cutaneous vasodilatation and sweating during pharmacological stimulation.
Accidente por araña Loxosceles spp.: reporte de caso y revisión de literatura
Authors: Aguilar Martínez Leonar , Sarmiento Acuña Karen , Sarmiento Acuña Karen , Salamanca Díaz Natalia , Segura Salguero Juan Camilo , Vargas Guerrero Luis Alejandro
Published: December 2019

La picadura de la araña del género Loxosceles produce dermonecrosis en el sitio de la lesión y complicaciones sistémicas secundarias a reacciones enzimáticas de su veneno, lo que aumenta la tasa de mortalidad. El objetivo es reportar un caso de loxoscelismo en Bogotá a 2600 msnm, donde el paciente tuvo una evolución satisfactoria a pesar de la inexistencia del antiveneno como manejo ideal de la toxicidad.
Estimulación medular en el tratamiento de la angina refractaria
Authors: Rojas Borda Andrés Felipe , Aldana Bitar Jairo Alejandro , Acevedo González Juan Carlos
Published: December 2019

La estimulación medular es considerada una opción eficaz de tratamiento en pacientes con diagnóstico de angina de pecho refractaria. A través del tiempo y con los resultados de los estudios clínicos, se ha posicionado como una alternativa segura que mejora la calidad de vida de los pacientes. En este artículo se revisa su historia, la técnica, su mecanismo de acción, los resultados de estudios clínicos y la utilización como alternativa en los pacientes con diagnóstico de angina refractaria.
Estimulación del nervio hipogloso: una nueva alternativa en el tratamiento de la apnea obstructiva del sueño
Authors: Pérez García Irene Camila , Salcedo Betancourt Juan David , Ríos Rosado Elsa Carolina , Ruiz Morales Álvaro J. , Ospina García Juan Camilo , Hidalgo Martínez Patricia
Published: December 2019

Introducción: la apnea obstructiva del sueño (AOS) es el trastorno respiratorio del sueño más frecuente. La terapia de elección es la presión positiva continua de la vía aérea (CPAP), pero se ha descrito mala adherencia en su uso. La estimulación del nervio hipogloso (ENH) se encuentra entre las nuevas modalidades de tratamiento en estudio.Objetivo: revisar la fisiopatología de este trastorno, así como la efectividad y seguridad de la ENH como terapia de la AOS.Metodología: se realizó una búsqueda en la base de datos de Medline utilizando las palabras clave: Sleep Apnea, Syndrome; Sleep Apnea, Obstructive; Hypoglossal Nerve; Electrodes, Implanted; Implantable Neurostimulators, y Electric Stimulation Therapy.Resultados: se encontraron 267 artículos, de los cuales se seleccionaron 27 según los criterios de inclusión y exclusión. Adicionalmente, se hizo una búsqueda secundaria de estos artículos. La ENH ha mostrado un perfil de efectividad y seguridad favorable con alta adherencia como tratamiento de la AOS. Sin embargo, no se recomienda en pacientes con un índice apnea-hipopnea > 50, ya que produce una reducción parcial, inferior que la que puede producir el CPAP.Conclusiones: la ENH ayuda a corregir, parcialmente, uno de los mecanismos fisiopatológicos de la AOS. Si bien en la revisión se encontraron datos que sugieren efectividad y seguridad aceptables en corto plazo, se necesitan más estudios sobre efectividad y seguridad a largo plazo, sobre comparación directa con CPAP en algunos casos y sobre uso bilateral de esta nueva modalidad terapéutica.
Trabeculectomía, una terapia vigente: estudio observacional descriptivo en el Hospital Universitario San Ignacio en Bogotá
Authors: De Vivero Clemencia , Ruiz Álvaro , Becerra Catalina
Published: December 2019

Introducción: el glaucoma es una enfermedad del nervio óptico de carácter crónico y progresivo que constituye un problema epidemiológico serio, ya que es responsable de la segunda causa de ceguera irreversible en el mundo. Existen diferentes modalidades de tratamiento, entre ellos medicamentos, láseres y cirugías. La trabeculectomía es el procedimiento quirúrgico de elección en el paciente adulto cuando la terapia médica y los procedimientos con láser fracasan en detener esta neuropatía óptica.Objetivo: analizar una serie de pacientes sometidos a trabeculectomía en el Hospital San Ignacio entre el 2005 y el 2011.Conclusión: los resultados, a pesar de ser una serie pequeña de pacientes, nos permiten afirmar que dicha cirugía continúa siendo una buena alternativa en el control de la presión intraocular y, por consiguiente, en la progresión del daño glaucomatoso sobre el nervio óptico.
Competencias, objetivos, habilidades y destrezas: ¿cómo entender las diferencias conceptuales? Una analogía de entendimiento a partir de un bloqueo en el tránsito automotor
Authors: Amaya A. Adalberto
Published: December 2019

Uno de los grandes problemas que enfrentan los docentes, a partir de la revolución educativa curricular centrada en competencias, corresponde a la adaptación del término competencia, que viene del lenguaje laboral, y entenderlo desde el lenguaje académico aplicándolo, además, a las carreras profesionales. Se considera, por lo tanto, necesario aclarar el concepto desde un punto de vista académico y profesional, para analizar los elementos que caracterizan la distinción del término competencia y su diferenciación con las tendencias curriculares precedentes centradas en objetivos y contenidos temáticos. Si bien es cierto que inicialmente se analiza el inconveniente gramatical que ha favorecido la confusión de términos, posteriormente, a través de una estrategia didáctica, se genera un análisis respecto a las diferencias entre competencias, habilidades y destrezas, a partir de una analogía que se hace con un ejemplo de un bloqueo en el tránsito automotor.
Lesiones cutáneas en pacientes con trasplante renal en el Hospital Universitario San Ignacio
Authors: Cuéllar Isabel , Rodríguez Edna , García Paola , Hernández Carolina , Pinto Ramírez Jessica Liliana
Published: December 2019

Introducción: Las enfermedades cutáneas son frecuentes en los pacientes trasplantados renales, por lo cual el monitoreo de la piel es necesario para realizar un diagnóstico precoz e iniciar tratamiento temprano.Objetivo: Determinar la prevalencia de las manifestaciones cutáneas en pacientes con trasplante renal. Materiales y métodos: Se evaluaron en consulta de dermatología 86 pacientes del programa de trasplante renal del Hospital Universitario San Ignacio.Resultados: Las infecciones de piel fueron las manifestaciones más prevalentes, y dentro de estas las más frecuentes fueron las micosis superficiales presentes, en un 48 % de los pacientes; seguidas por las infecciones virales, en un 20 %, y las bacterianas, en un 15 %. Se encontraron dos casos de cáncer de piel: un carcinoma basocelular y un sarcoma de Kaposi. Doce pacientes tuvieron queratosis actínicas consideradas lesiones premalignas.Conclusión: Los resultados del estudio evidencian la necesidad de realizar un examen dermatológico rutinario en los pacientes trasplantados para detectar tempranamente la presencia de lesiones cutáneas y, de esta manera, iniciar un manejo oportuno. Los hallazgos más comunes fueron las micosis superficiales.
Neuromielitis óptica en el embarazo: reporte de un caso
Authors: Laurens Acevedo Michelle , Castañeda C. Camilo , Ruiz de Sánchez Carolina , Rueda María Camila , Zarco M. Luis Alfonso
Published: December 2019

La neuromielitis óptica (NMO) es una enfermedad inflamatoria autoinmune desmielinizante del sistema nervioso central, mediada por autoanticuerpos contra el receptor de acuaporina 4 (Ac IgQ4). Se presenta el caso de una mujer de 23 años de edad con 28 semanas de embarazo y antecedente de neuromielitis óptica, quien consultó por recaída de la enfermedad y pobre respuesta al manejo con corticosteroides, por lo que recibió 5 sesiones de plasmaféresis y tuvo una importante mejoría clínica.
Molecular Dynamics Study on Microscopic Mechanism of Dissolution, Diffusion and Aggregation Process for Waxy Molecules in the Process of Waxy Crude Oil Pipeline Transportation
Authors: Gan Yifan , Cheng Qinglin , Wang Zhihua , Yang Jinwei , Sun Wei , Liu Yang
Published: December 2019

In order to ensure the safe and economic operation of waxy crude oil transportation process, the micro-dynamic mechanism and thermodynamic characteristics of wax precipitation process at nanoscale are necessary to be revealed. Here, we established the molecular dynamics model to characterize the phase transition and precipitation behavior of waxy molecules in multiphase system (including oil, asphaltene and water), the relative error between simulated results and experimental data measured by Dutour et al. (2002) is less than 5%. Under the coupling effect of different operation parameters, the molecular dynamics simulation was employed, the simulated results showed that the spherical paraffin crystals underwent the process of dissolution, diffusion and aggregation, then the waxy cluster crystals with larger amount but smaller volume would form, and it would deposit on the outer wall under the concentration gradient. The influence mechanism of different operating parameters on wax precipitation was analyzed, of which the increase of temperature and water cut will decrease the wax precipitation, while the increase of pressure will enhance the wax precipitation rate, furthermore, by means of the hydrogen bonding and the effect of similar dissolution, the water and asphaltene molecules also affect the wax precipitation process at molecular-scale. The researches of this paper provide the theoretical support for the paraffin removal and control in waxy crude oil pipeline transportation process.
The Comparison and Parameters Optimization for the Mixed Intermediate Fluid of Intermediate Fluid Vaporizer
Authors: Yan Yan , Li Yuxing , Wang Shuo
Published: December 2019

In this paper, an establishment of heat transfer model is performed to study the effects of different types of mixed intermediate fluid on the vaporizer performance. It is found that compared with pure propane, mixed ethane-propane working fluid can bring about a reduction of 10% ∼ 25% for the heat exchange area of intermediate fluid vaporizer IFV. In addition, using mixed butane-propane working medium could stabilize the saturated pressure of intermediate fluid at a relatively low level of 0.2 MPa, while the saturated pressure of pure propane ranges from 0.33 MPa to 0.65 MPa. Thereby, the former one is more reliable than the latter one in an aspect of safe operation. Moreover, after an investigation and selection, the results show that the saturated pressure of intermediate fluid varying from 0.3 MPa to 0.6 MPa and the amount of LNG overloaded over than 130% is beneficial for the improvement of comprehensive heat transfer performance of IFV.
Numerical Simulation of Multi-Phase Flow Distribution in Parallel Pipelines System of Oil Transfer Station
Authors: Wang Yingying , Wang Chunsheng , Sun Qiji , Lv Yuling
Published: December 2019

The mal-distribution of gas-oil-water multi-phase flow in parallel petroleum processing pipelines can directly affect the working condition of the separators. In this paper, the influence of different factors on the flow distribution and the characteristics of gas-oil-water distribution in parallel pipelines was investigated by three-dimensional CFD numerical simulation. Firstly, four different simulation models are established based on different arrangement types of parallel pipelines. The simulation results show that the distribution of gas-oil-water flow in the radial entry symmetrical two-stage pipe-laying simulation model was the most uniform among the four simulation models. Then, four radial entry symmetrical two-stage pipe-laying simulation models with different distance between branch pipes were establish. From the simulated results, it can be found that the distance has no effect on the distribution of gas-oil-water flow in each branch pipe, but great influence on distribution of flow rate in each branch pipe. Finally, the influence of the inlet flow characters on the flow distribution is investigated. It can be found that the “bias flow” phenomenon of the parallel pipelines decreasing with the increase of the inlet flow velocity, the gas content of inlet flow and the water content of inlet liquid.
Analysis on Optimized Operation of Trans-Asia Gas Pipeline
Authors: Jinwei Yang , Qinglin Cheng , Yifan Gan , Yanxin Ma , Yun Feng , Yi Ding
Published: December 2019

In order to ensure efficiency of Trans-Asia Gas Pipeline, engineers in Sino-Petroleum International Company optimized pipeline operation from a whole view through simulated optimization and unit control optimization. The network model of ABC line is established using TGNET, and the error of model is adjusted to the acceptable range by using the practical data. Flow distribution of AB line and C line is optimized to ensure the minimum fuel cost. Principle of gas pack control is built in different working conditions. And the compressor unit is controlled according to the simulation results. Performance of compressor unit is monitored and control mode is regulated to a better way on the basis of data analysis and investigation. After more than one year of exploration and practice, the operation optimization methodology of the Trans-Asia Gas Pipeline has been established. Energy-saving effect is remarkable.
Research on Methods to Solve Emulsion Phenomenon in the Transportation of Diesel Through Pipeline
Authors: Li Wang , Huang Liqiao
Published: December 2019

This paper describes and analyzes the emulsion phenomenon of diesel in commissioning of Products Pipeline by Sinopec and PetroChina in recent years. Studies have shown that the ester anti-wear agent in diesel oil as well as the interface active substance contained in diesel are the emulsifiers of diesel and water, which cause the emulsification of diesel and water under strong shearing in pipeline. On the basis of this background, isentropic simulation experiment is carried out to obtain the emulsion in laboratory by creating a similar shearing stress. The basic properties of diesel, anti-wear properties and emulsion stability are studied, and the rate of water content, surface tension and droplet size are compared and analyzed. Then based on oil-water separation experiment, solutions to diesel emulsification, relevant experience and suggestions for the production of refined oil pipelines are put forward, which may be valuable reference for future commission of Products Pipeline.
Measuring the Losses of Hydrostatic Pumps and Motors: A Critical Review of ISO4409:2007
Authors: Achten Peter , Mommers Robin , Nishiumi Takao , Murrenhoff Hubertus , Sepehri Nariman , Stelson Kim , Palmberg Jan-Ove , Schmitz Katharina
Published: December 2019

ISO 4409 is the most important international standard for measuring the efficiency of hydraulic pumps and motors, the latest edition being 4409:2007. The standard describes methods for determining the steady-state performance in terms of overall efficiency. It also defines equations for calculating the volumetric efficiency of pumps and motors. The hydro-mechanical efficiency is only defined for motors, not for pumps.

This paper analyses the efficiency and losses of pumps and motors in an alternative way. The preference is on loss analysis instead of efficiencies. Especially the effects of the bulk modulus are considered in a different and more inclusive manner. The new methodology results in a higher total loss for motor and a lower total loss for pumps than the current ISO 4409 standard. Furthermore, it results in significant changes of the hydro-mechanical and volumetric losses. The differences between the new methodology and ISO 4409 become larger for high load pressures.

The new methodology demands knowledge about the minimum volume of the displacement chamber. The ratio between this volume and the full displacement of a single displacement chamber strongly influences the hydro-mechanical and volumetric losses of the pump or motor. The new methodology is valid for all positive displacement hydrostatic pumps and motors. The volumetric efficiency, as defined in ISO 4409, can still be used as a flow rate factor, but should not be regarded as an energy conversion efficiency.

The importance of adopting the proposed methodology is further demonstrated by analyzing and comparing the measurement data about a fixed displacement pump and motor, showing the differences in the loss analysis by means of ISO 4409 and the new equations.

The methodology, observations and validation results presented in this paper are significant and can pave the road for improving the current ISO 4409:2007 standard, which would ultimately benefit the industry.
Intelligent Machine Operator Identification to Develop Damage-Reducing Operating Strategies for Mobile Machines
Authors: Brinkschulte Lars , Geimer Marcus
Published: December 2019

Mobile machines are exposed to a multitude of influencing factors, such as the working task, the operator and the environmental conditions. This leads to a broad spectrum of load collectives for the machine components. In many cases it is difficult to influence the working task and the environmental conditions under the objective function of achieving the required work goals optimally while at the same time minimizing the component load. The operation of the machine offers a more evident degree of freedom to minimize the component damage. With control systems adapted to the operator, the external environmental conditions and the working task, which instructs the operator to a less damaging operating behaviour or override the damage-initiating control signals, the loads and damage can be reduced. An explicit operator identification is the basis for such control approaches.

This paper presents a method for machine operator identification (MOI) based on Hidden Markov Models (HMM). Through a parameter influence analysis and a combination with operation state recognition (OSR), a machine operator can be successfully identified among others. To create and validate the method, measurement data from 150 work cycles of seven different operators are analysed. Based on the MOI, a method for an operator-specific damage reduction using adaptive control strategies is developed. The results and limits of this strategy are presented and discussed by means of a complete machine simulation, considering the traction drive and function drives (working hydraulics), a multi-body simulation and the driving dynamics. The conclusion is made by considering predictive operating strategies to avoid damage-intensive operating points.
Novel Pressure Adaptive Piston Cylinder Interface Design for Axial Piston Machines
Authors: Sarode Shanmukh , Shang Lizhi
Published: December 2019

The paper presents a novel concept of a pressure adaptive piston/cylinder interface design for a swashplate type axial piston machine that uses a pressurized groove around the bushing inside the cylinder block. This groove is connected to the pump displacement chamber and it uses pressure deformations of the bushing to improve the sealing function of the piston/cylinder lubricating interface. Such a design concept is based on a groove design that is easy to manufacture, thus resulting in a cost-effective design solution.

The proposed piston/cylinder interface design is simulated using a multi-domain simulation model developed by the authors’ research team. The tool is particularly suitable for the analysis of the internal gap flows, being based on a fully coupled fluid structure thermal interaction model, which calculates the non-isothermal gap fluid behavior considering solid body deformations due to temperature and pressure effects.

The proposed solution is compared in simulation with respect to a standard design of an axial piston pump. The results indicate that the proposed pressure adaptive piston/cylinder interface is able to improve the sealing function of the piston/cylinder interface at different operating conditions. Therefore, the proposed novel design can be seen as a possible method to increase the energy efficiency of the current designs of swash plate units.
Switch-Mode Power Transformer in a Wave-Powered, Reverse Osmosis Desalination Plant
Authors: Simmons Jeremy W. , Van de Ven James D.
Published: December 2019

In the reverse osmosis (RO) desalination process, a salt water solution is pressurized to overcome the osmotic pressure across a semi-permeable membrane. A few groups have proposed that a wave energy converter (WEC) having a seawater based, hydraulic power take-off can could be used to pressurize the feedwater for an RO system. However, coupling the wave energy harvesting process and the RO desalination process imposes unique design constraints on the fluid power system, such as pressure limits of conventional RO system components. In this study, a fluid power circuit with a switch-mode power transformer is used to transfer power while keeping the pressure of the power take-off and RO processes relatively decoupled. The switch-mode power transformer studied herein adds fewer costly components and less significant loss mechanisms to the system than a conventional hydraulic transformer performing the same function. The switch-mode power transformer uses the inertia of a hydraulic motor driven electric generator and switching of the hydraulic motor inlet between high and low-pressure sources to decrease the pressure at which power is being transmitted to the RO process. This process is analogous to DC-DC switching power transformers in the electrical domain. This study seeks to demonstrate this unique switch-mode system as a potential solution for coupling the wave-energy harvesting process with the reverse osmosis process. The system is modeled and studied in the context that the transformer and RO system are onshore, 500 meters from the WEC. Power captured from the WEC is transmitted through a long pipeline to shore. A distributed parameter model is used to model the pipeline dynamics, simultaneously revealing the significance of these dynamics and the robustness with which the switch-mode transformer decouples the pressure dynamics at the RO feed from the pipeline dynamics. The switch-mode power transformer is estimated to be 76% efficient while the system, as a whole, is estimated to be 45% efficient.
Theoretical Modeling, Analysis, and Experimental Results of a Hydraulic Artificial Muscle Prototype
Authors: Slightam Jonathon E. , Nagurka Mark L.
Published: December 2019

Fluidic braided artificial muscles have been studied for close to seventy years. Their high power-to-weight ratio and force-to-weight ratio make them a desirable actuation technology for compact and lightweight mobile manipulation. Use of hydraulics with fluidic artificial muscles has helped realize high actuation forces with new potential applications. To achieve large actuation forces produced from high internal pressure, artificial muscles operate near the limitations of their mechanical strength. Design improvements and future applications in mechanical systems will benefit from detailed theoretical analysis of the fluidic artificial muscle mechanics. This paper presents the theoretical modeling of a hydraulic artificial muscle, analysis of its mechanics, and experimental results that validate the model. A prototype is analyzed that operates at 14 MPa and can generate up to 6.3 kN of force and a displacement of 21.5 mm. This model promises to be useful for mechanical system design and model-based control.
Energetically Passive Bilateral Teleoperation of a Pneumatic Crawling Robot
Authors: Durbha Venkat , Li Perry Y.
Published: December 2019

This paper presents the control methodology and experimental results for the bilateral haptic tele-operation of a pneumatic actuated crawling robot. The two front legs of a robot are teleoperated via a pair of PHANToM haptic interfaces. The system gives the human operator the impression that he/she is physically moving and positioning the robot legs. As the legs hit the ground, the operator would also feel the reaction force via the haptic feedback provided by the PHANToMs. To reduce the physical effort by the operator, kinematic and power scaling factors are applied. For stable tele-operation, the closed loop system is controlled to behave like a common energetically passive mechanical tool interacting with the human operator (on the PHANToM’s end) and the physical environment (on the Crawler’s end). The control design strategy treats the pneumatic actuators as a two-port nonlinear spring. While the mechanical port of the actuator acts on the mechanical structure of the crawler’s leg, the fluid port of the actuator is controlled to mimic the interaction between the pneumatic spring and the PHANToM, and to achieve co-ordination. The control methodology has been tested experimentally. While performing crawling motion, the RMS error of the robot foot placement error was 7mm, well within the crawler’s foot diameter of 25.4mm.
Stirling Thermocompressor: Lumped Parameter Modeling and Experimental Impact of Displacer Motion Profile on Work Output
Authors: Thomas Seth , Barth Eric J.
Published: December 2019

The thermocompressor, a little-known class of Stirling devices that efficiently compresses gas, presents new challenges for modeling and experimental validation. In modeling, traditional analytic assumptions about displacer motion are limiting. In experimental verification, few devices have actually been built and tested. In this paper, the authors test the feasibility of a lumped-parameter approach for predicting the performance of Stirling thermocompressors subject to different displacer motion profiles. Since the displacer of a thermocompressor can be controlled independently, unlike kinematic Stirling engines or dynamic Stirling engines, and has a large influence on output power and efficiency of the device, it is crucial that this is well captured by a system dynamics model for control. Key model parameters are simulated and results are experimentally verified on one of the few, if only, experimental thermocompressor platforms in the world. Conclusions are drawn regarding simplified modeling of the regenerator’s effectiveness and the effects on device work output by varying the displacer piston’s motion profile using different waveforms.
Power Optimization of Series Hydraulic Hybrid Powertrain for Compact Wheel Loader
Authors: Wen Qunya , Wang Feng , Xu Bing , Sun Zongxuan
Published: December 2019

As an effective approach to improving the fuel economy of heavy duty vehicles, hydraulic hybrid has shown great potentials in off-road applications. Although the fuel economy improvement is achieved through different hybrid architectures (parallel, series and power split), the energy management strategy is still the key to hydraulic hybrid powertrain. Different optimization methods provide powerful tools for energy management strategy of hybrid powertrain. In this paper a power optimization method based on equivalent consumption minimization strategy has been proposed for a series hydraulic hybrid wheel loader. To show the fuel saving potential of the proposed strategy, the fuel consumption of the hydraulic hybrid wheel loader with equivalent consumption minimization strategy was investigated and compared with the system with a rule-based strategy. The parameter study of the equivalent consumption minimization strategy has also been conducted.
Vaccine-Specific Immune Responses against Mycobacterium ulcerans Infection in a Low-Dose Murine Challenge Model
Authors: Mangas Kirstie M. , Buultjens Andrew H. , Porter Jessica L. , Baines Sarah L. , Marion Estelle , Marsollier Laurent , Tobias Nicholas J. , Pidot Sacha J. , Quinn Kylie M. , Price David J. , Kedzierska Katherine , Zeng Weiguang , Jackson David C. , Chua Brendon Y. , Stinear Timothy P.
Published: December 2019

The neglected tropical disease Buruli ulcer (BU) is an infection of subcutaneous tissue withMycobacterium ulcerans. There is no effective vaccine. Here, we assessed an experimental prime-boost vaccine in a low-dose murine tail infection model. We used the enoyl reductase (ER) domain of theM. ulceransmycolactone polyketide synthases electrostatically coupled with a previously described Toll-like receptor 2 (TLR-2) agonist-based lipopeptide adjuvant, R4Pam2Cys.
Hypoxanthine-Guanine Phosphoribosyltransferase Is Dispensable for Mycobacterium smegmatis Viability
Authors: Knejzlík Zdeněk , Herkommerová Klára , Hocková Dana , Pichová Iva
Published: December 2019

Purine bases, released by the hydrolytic and phosphorolytic degradation of nucleic acids and nucleotides, can be salvaged and recycled. The hypoxanthine-guanine phosphoribosyltransferase (HGPRT), which catalyzes the formation of guanosine-5′-monophosphate from guanine and inosine-5′-monophosphate from hypoxanthine, represents a potential target for specific inhibitor development. Deletion of the HGPRT gene (
Δhgprt
) in the model organism
Mycobacterium smegmatis
confirmed that this enzyme is not essential for
M. smegmatis
growth. Prodrugs of acyclic nucleoside phosphonates (ANPs), originally designed against HGPRT from
Mycobacterium tuberculosis
, displayed anti-
M. smegmatis
activities comparable to those obtained for
M. tuberculosis
but also inhibited the
Δhgprt
M. smegmatis
strain. These results confirmed that ANPs act in
M. smegmatis
by a mechanism independent of HGPRT.
Apert syndrome: prenatal diagnosis challenge
Authors: Vieira Catarina , Teixeira Neusa , Cadilhe Alexandra , Reis Isabel
Published: December 2019

Apert syndrome is a rare genetic disorder that manifests as craniosynostosis, craniofacial and limb dysmorphic features. Mutations in fibroblast growth factor receptor 2 (FGFR2) gene account for almost all cases. Given the impact it can have throughout life, prenatal management becomes a challenge. A healthy 33-year-old woman, gravida 4, para 0, was referred to routine ultrasound at 22 weeks of gestation. Atypical cranial morphology with prominent forehead, ocular proptosis, hypertelorism and mitten hands were detected. Genetic investigation revealed an FGFR2 gene mutation (c.755C>G(p.Ser252Trp)), confirming the diagnosis. Magnetic resonance showed brachycephaly, turricephaly and cortical malformation. Following counselling, parents requested medical termination of pregnancy. Macroscopic features were consistent with ultrasound findings. This case emphasises the importance of early diagnosis to provide the best family counselling and prenatal management. A multidisciplinary team, consisting of an obstetrician with ultrasonography experience, a medical geneticist and a fetal pathologist, should conduct these cases.