基于“显性”方法 培养学生科学本质观

培养学生的科学本质观是科学教育的重要目标之一,本文通过改变科学史的教学方式、创新多种科学探究方式和优化社会性科学议题的教学方式,探索发展学生科学本质观的有效路径。

Role of calcium in polycystic kidney disease:From signaling to pathology

Autosomal dominant polycystic kidney disease （ADPKD） is the most common inherited monogenic kidney disease. Characterized by the development and growth of cysts that cause progressive kidney enlargement, it ultimately leads to end-stage renal disease. Approximately 85% of ADPKD cases are caused by mutations in the PKD1 gene, while mutations in the PKD2 gene account for the remaining 15% of cases. The PKD1 gene encodes for polycystin-1 （PC1）, a large multi-functional memb-rane receptor protein able to regulate ion channel complexes, whereas polycystin-2 （PC2）, encoded by the PKD2 gene, is an integral membrane protein that functions as a calcium-permeable cation channel, located mainly in the endoplasmic reticulum （ER）. In the primary cilia of the epithelial cells, PC1 interacts with PC2 to form a polycystin complex that acts as a mechanosensor, regulating signaling pathways involved in the differentiation of kidney tubular epithelial cells. Despite progress in understanding the function of these proteins, the molecular mechanisms associated with the pathogenesis of ADPKD remain unclear. In this review we discuss how an imbalance between functional PC1 and PC2 proteins may disrupt calcium channel activities in the cilium, plasma membrane and ER, thereby altering intracellular calcium signaling and leading to the aberrant cell proliferation and apoptosis associated with the development and growth of renal cysts. Research in this feld could lead to the discovery of new molecules able to rebalance intracellular calcium, thereby normalizing cell proliferation and reducing kidney cyst progression.

Estimation of Design Sea Ice Thickness with Maximum Entropy Distribution by Particle Swarm Optimization Method

The maximum entropy distribution, which consists of various recognized theoretical distributions, is a better curve to estimate the design thickness of sea ice. Method of moment and empirical curve fitting method are common-used parameter estimation methods for maximum entropy distribution. In this study, we propose to use the particle swarm optimization method as a new parameter estimation method for the maximum entropy distribution, which has the advantage to avoid deviation introduced by simplifications made in other methods. We conducted a case study to fit the hindcasted thickness of the sea ice in the Liaodong Bay of Bohai Sea using these three parameter-estimation methods for the maximum entropy distribution. All methods implemented in this study pass the K-S tests at 0.05 significant level. In terms of the average sum of deviation squares, the empirical curve fitting method provides the best fit for the original data, while the method of moment provides the worst. Among all three methods, the particle swarm optimization method predicts the largest thickness of the sea ice for a same return period. As a result, we recommend using the particle swarm optimization method for the maximum entropy distribution for offshore structures mainly influenced by the sea ice in winter, but using the empirical curve fitting method to reduce the cost in the design of temporary and economic buildings.

Inverted Meckel's diverticulum as a cause of occult lower gastrointestinal hemorrhage

Meckel's diverticulum is a common asymptomatic congenital gastrointestinal anomaly,but rarely it can present with hemorrhage.Over the last few years inverted Meckel's diverticulum has been reported in the literature with increasing frequency as an occult source of lower gastrointestinal hemorrhage.Here,we report a case of a 54-year-old male,who was referred for surgical evaluation with persistent anemia and occult blood per rectum after a work up which failed to localize the source over 12 mo,including upper and capsule endoscopy,colonoscopy,enteroclysis,Meckel scan,and tagged nuclear red blood cell scan.An abdominal computed tomography scan showed a possible mid-ileal intussusception and intraluminal mass.During the abdominal exploration,inverted Meckel's diverticulum was diagnosed and resected.We review the literature,discuss the forms in which the disease presents,the diagnostic modalities utilized,pathological findings,and treatment.Although less than 40 cases have been reported in the English literature from 1978 to 2005,19 cases have been reported in the last 6 years alone(2006-2012) due to improved diagnostic modalities.Successful diagnosis and treatment of this disease requires a high index of clinical suspicion,which is becoming increasingly relevant to general gastroenterologists.

Simulation analysis of significance and interaction of influencing factors on mixing uniformity of double-drum recycling mixing plant

To examine the influence of the structural parameters and working parameters of a double-drum regeneration mixing station on its mixing uniformity,the influence of the discrete element method and response surface method on the uniformity of the aggregate mixing when the interaction between two different factors was analyzed.A mathematical model of the influence of various factors and interactions on the coefficient of variation of the aggregates was established.The matching of each parameter was optimized with the goal of minimizing the coefficient of variation.The results show that when the aggregate particle size is different,the significance of each parameter affecting its mixing uniformity is also different.Moreover,increasing the speed and reducing the axial installation angle of the blade can reduce the coefficient of variation of the three aggregates.To obtain a good mixing uniformity,the mixing-arm phase angle when the drum inclination angle is large should be smaller than the phase angle when the drum inclination angle is small,and the mixing of large particles should not be arranged with a large mixing-arm phase angle.With a blade radial installation angle of 38°,a blade axial installation angle of 35°,a drum inclination angle of 6°,a drum rotation speed of 10 r/min,and a mixing-arm phase angle of 32°,the aggregate as a whole can exhibit the best mixing uniformity.