简介:【摘要】:解数学问题的方法有很多,构造法是其中的一种基本方法,而构造法就是以已知条件为载体,以所求结论为方向构造一种新的数学形式,使问题在这种形式下容易解决,三角函数中的许多问题是求角或三角函数值及最值,巧妙地应用方程、函数、数列等有关知识进行构造,可以在解题过程中避免复杂公式,达到灵活,方便,快捷的目的。
简介:摘要: 函数是数学中的重点和难点,学好函数,基本上数学就学好了一大半。在初中数学中,函数初次出现在学生面前,显得新鲜而又富有挑战性,如何引导学生学好函数,是教师所要积极探索的课题。那么首先,对于函数本质的思考和研究,就是教师所要做的工作,因为只有教师认清楚函数的本质,并从中获得启示,才能在教学生学习函数的时候更为得心应手;更重要的是,教师对于学科中一些问题和知识体系的思索研究,也是对于教师自身专业素养的提升。本文中笔者会从函数对于数学关系的描述作用切入,层层递进以探究函数的本质,从而试图为大家更好地认识函数提供一些思路,以期为教师教好函数、学生学好函数做出微薄贡献。
简介:【摘要】回顾性分析 5例 Madelung’s病病人资料,探讨此病病因、临床表现及治疗方法。该病病因尚不清,常见于中年男性,肿块主要对称分布于头颈部及上躯干部,呈典型“牛颈”或“驼峰”样外观。手术切除为主要治疗方法。该病恶变率低、预后良好。
简介:AbstractObjective:To review indications and techniques for the endoscopic endonasal approach to the craniovertebral junction (CVJ), analyze postoperative outcomes, and discuss important technical considerations.Methods:A retrospective analysis was performed on all patients undergoing endonasal endoscopic approaches to the CVJ from May 2007 to June 2017. Demographic information, presenting symptoms, imaging results, treatment course, postoperative functional status, and follow-up were recorded.Results:There was a total of 30 patients in this series, with a mean follow-up of 11.7 months. The average age was 33.6 years (range, 5-75 years), with 18 females and 12 males. The majority of patients (n = 22, 73.3%) had Chiari malformation type 1 with basilar invagination and symptomatic cervicomedullary compression as the indication for surgery. Intraoperative cerebrospinal fluid leak (CSF) was noted in 3 cases of odontoid resection and a single case of skull base resection. There were no postoperative CSF leaks. Overall, 81% of patients resumed regular diet by post-operative day 2 (range, 0-8 days). Severe postoperative dysphagia occurred in two cases with one requiring gastrostomy tube placement and another utilizing total parenteral nutrition for support prior to eventual gastrostomy. On average, patients were extubated by postoperative day 0.93 (range 0-3 days), with 85% extubated by postoperative day 1. A tracheotomy was required in one patient.Conclusion:The endonasal endoscopic approach is a valuable technique for access to the CVJ with minimal disruption of respiratory and alimentary function.
简介:AbstractPeyronie’s disease (PD) is a benign, progressive fibrotic disorder characterized by scar or plaques within the tunica albuginea (TA) of the penis. This study provides new insights into the pathogenesis of PD based on data from different studies regarding the roles of cytokines, cell signaling pathways, biochemical mechanisms, genetic factors responsible for fibrogenesis. A growing body of literature has shown that PD is a chronically impaired, localized, wound healing process within the TA and the Smith space. It is caused by the influence of different pathological stimuli, most often the effects of mechanical stress during sexual intercourse in genetically sensitive individuals with unusual anatomical TA features, imbalanced matrix metalloproteinase/tissue inhibitor of metalloproteinase (MMP/TIMP), and suppressed antioxidant systems during chronic inflammation. Other intracellular signal cascades are activated during fibrosis along with low expression levels of their negative regulators and transforming growth factor-β1 signaling. The development of multikinase agents with minimal side effects that can block several signal cell pathways would significantly improve fibrosis in PD tissues by acting on common downstream mediators.
简介:【 摘要 】 初中函数作为培养学生逻辑性的重要学科之一 ,在 初中 教学中,具有相当重要的意义,初中函数也是 学习的重难点, 函数也 是高中教学 课堂中最重要 的一环 。近年来,随着新的课程标准的不断深入,思考初中函数学习难点和找出解决办法之间的 内在关联 日益突出。如何找到初中函数学习困难的方法 已慢慢 成为广大教师要解决 的重要教学问题 。在此基础上,本文首先分析了初中函数学习困难的原因 ,重点探讨了解决初中函数学习疑难 的方法策略 。