Optimal control of a revenue management system with dynamic pricing facing linear demand

This paper considers a dynamic pricing problem over a finite horizon where demand for a product is a time‐varying linear function of price. It is assumed that at the start of the horizon there is a fixed amount of the product available. The decision problem is to determine the optimal price at each time period in order to maximize the total revenue generated from the sale of the product. In order to obtain structural results we formulate the decision problem as an optimal control problem and solve it using Pontryagin's principle. For those problems which are not easily solvable when formulated as an optimal control problem, we present a simple convergent algorithm based on Pontryagin's principle that involves solving a sequence of very small quadratic programming (QP) problems. We also consider the case where the initial inventory of the product is a decision variable. We then analyse the two‐product version of the problem where the linear demand functions are defined in the sense of Bertrand and we again solve the problem using Pontryagin's principle. A special case of the optimal control problem is solved by transforming it into a linear complementarity problem. For the two‐product problem we again present a simple algorithm that involves solving a sequence of small QP problems and also consider the case where the initial inventory levels are decision variables. Copyright © 2006 John Wiley & Sons, Ltd.     

输卵管积水造口术对体外受精与胚胎移植的影响

【目的】探讨在体外受精与胚胎移植 (IVF ET)之前输卵管积水患者行输卵管造口术对IVF ET治疗效果的影响。【方法】回顾分析 1999年 2月至 2 0 0 1年 1月因女性输卵管因素不孕行IVF ET治疗的 90 8个周期的资料。按输卵管积水患者在IVF ET前是否治疗分 3组 ,A组 :输卵管积水未手术治疗行IVF ET 2 3个周期 ,B组 :在IVF ET之前行输卵管积水造口术 (腹腔镜下或开腹 ) 2 2个周期 ,C组 :对照组 (输卵管阻塞 ,未发现输卵管积水 ) 86 3个周期。【结果】A组、B组、C组的IVF ET的种植率分别为 9 7%、17 9%、16 7% ,临床妊娠率分别为 2 1 7%、4 0 9%、39 2 %。A组的种植率及临床妊娠率比其它组低 ,经 χ2 检验 ,有统计学意义。【结论】输卵管积水未治疗行IVF ET的种植率及临床妊娠率较低 ,但在IVF ET之前行输卵管造口术可改善IVF ET的种植率及临床妊娠率     

Clinical and epidemiologic evaluation of pressure ulcers in patients at a university hospital in Turkey.

OBJECTIVE: We sought to measure the incidence of pressure ulcer development at a university health center in Turkey, and to determine whether the Waterlow Pressure Sore Risk (PSR) Scale score predicted pressure ulcer development, stage, or number of ulcers. DESIGN: We prospectively evaluated patients who were hospitalized at our university-based medical center. SETTING AND SUBJECTS: We analyzed data from 22,834 patients hospitalized at the Baskent University Adana Teaching and Medical Research Center in Ankara, Turkey from January 1, 2004 to December 31, 2004, including 360 patients who developed pressure ulcers. INSTRUMENTS: The Waterlow PSR Scale was used to assess pressure ulcer risk. In addition, age, sex, the ward or unit in which the patient was hospitalized, reason for hospitalization, and location and stage of ulcers were collected on a data form designed specifically for this study. METHODS: A single nurse physiotherapist assessed all patients daily during their hospitalization. When a pressure ulcer was diagnosed by the nurse physiotherapist, a physician staged the pressure ulcers based on the US National Pressure Ulcer Advisory Panel (NPUAP) staging system. RESULTS: Three hundred sixty out of 22,834 patients developed 1 or more pressure ulcers, resulting in an incidence rate of 1.6%. Most ulcers (59.2%) occurred in patients hospitalized in the intensive care unit (n = 213). A positive correlation between the Waterlow PSR Scale score and number of ulcers per patient (r: 0.178, P < .01) was identified. No significant correlation was found linking Waterlow PSR Scale score and ulcer stage or the development of a single ulcer. CONCLUSION: We found significantly lower pressure ulcer incidence rates than those commonly reported in the literature, which we believe is principally attributable to short hospital stays and a strong emphasis on preventive nursing care. While high Waterlow PSR scale Scores correlated positively with development of multiple ulcers, this did not predict ulcer stage or the presence of a single pressure ulcer.     

Resetting of the arterial baroreflex increases orthostatic sympathetic activation and prevents postural hypotension in rabbits

Since humans are under ceaseless orthostatic stress, the mechanism to maintain arterial pressure (AP) under orthostatic stress against gravitational fluid shift is of great importance. We hypothesized that (1) orthostatic stress resets the arterial baroreflex control of sympathetic nerve activity (SNA) to a higher SNA, and (2) resetting of the arterial baroreflex contributes to preventing postural hypotension. Renal SNA and AP were recorded in eight anaesthetized, vagotomized and aortic-denervated rabbits. Isolated intracarotid sinus pressure (CSP) was increased stepwise from 40 to 160 mmHg with increments of 20 mmHg (60 s for each CSP level) while the animal was placed supine and at 60 deg upright tilt. Upright tilt shifted the CSP–SNA relationship (the baroreflex neural arc) to a higher SNA, shifted the SNA–AP relationship (the baroreflex peripheral arc) to a lower AP, and consequently moved the operating point to marked high SNA while maintaining AP. A simulation study suggests that resetting in the neural arc would double the orthostatic activation of SNA and increase the operating AP in upright tilt by 10 mmHg, compared with the absence of resetting. In addition, upright tilt did not change the CSP–AP relationship (the baroreflex total arc). A simulation study suggests that although a downward shift of the peripheral arc could shift the total arc downward, resetting in the neural arc would compensate this fall and prevent the total arc from shifting downward to a lower AP. In conclusion, upright tilt increases SNA by resetting the baroreflex neural arc. This resetting may compensate for the reduced pressor responses to SNA in the peripheral cardiovascular system and contribute to preventing postural hypotension.     

Goldenhar 综合征家系的临床表型和遗传学分析

目的分析1组Goldenhar综合征家系的临床表现及遗传学特征。方法我们随访到1组4代33人的Goldenhar综合征家系，对目前存活的29人进行了临床表型和遗传学的初步分析。结果家系内有Goldenhaar综合征患者5人．临床表现具高度多样性，累及眼、耳、脊柱、颜面、口腔等多个器官和系统的发育不良，在遗传方式上属于常染色体显性遗传。从细胞遗传学水平对家系中成员进行染色体检查，未发现核型异常。结论该Goldenhar综合征家系属常染色体显性遗传，染色体检查未发现核型异常。     

额叶内侧面损伤的临床特点及救治

目的 总结17例额叶内侧面损伤的临床特点及救治经验。方法 对我科1999年7月至2003年4月收治的额叶内侧面损伤患者进行回顾性分析。结果 手术治疗1例，恢复良好，保守治疗16例，其中恢复良好12例，中残2例，死亡2例，全组死亡率11．77％。结论 额叶内侧面损伤一般意识障碍较轻，但易直接发生枕骨大孔疝，严密观察病情及动态CT检查，颅内压监测，不拘泥传统手术指征，及时抓住手术时机，可有效降低致残率及死亡率。     

Synovial chondromatosis of four compartments of the knee: medial and lateral tibiofemoral spaces,patellofemoral joint and proximal tibiofibular joint

A case of synovial chondromatosis of the proximal tibiofibular joint in addition to lateral and medial tibiofemoral spaces and patellofemoral joint has been presented.     

Pten基因敲除对过氧化物酶家族表达和活性氧水平的影响

目的:探讨Pten基因敲除后对过氧化物酶家族(Peroxiredoxins,Prdxs)水平和活性氧水平的影响.方法:采用Western印迹和化学/荧光发光分析法分别检测了在Pten / MEF和Pten-/-MEF细胞中PRDXs的表达和细胞内活性氧水平.结果:Western印迹结果显示,与Pten / MEF细胞相比,Pten-/-MEF细胞PRDX Ⅰ,Ⅱ,Ⅴ,Ⅵ蛋白水平下调,PRDX Ⅲ不变,PRDX Ⅳ上调.DCFH探针标记后流式结果显示Pten-/-MEF 细胞活性氧荧光值显著高于对照Pten / MEF细胞(P＜0.05).结论:Pten基因敲除引起数种PRDXs表达下调,细胞内活性氧水平增高.