基于消费者认知的产品线策略

以纵向差异化的多产品构建产品线,是厂商普遍采用的(二级)价格歧视策略。现有研究分别基于完全垄断、寡头垄断、耐用性产品等市场结构或产品特性,分析厂商产品线策略。基于消费者认知的存在,讨论了完全垄断厂商的产品线策略。模型分析表明:若消费者认知实现后厂商利润增加,厂商将采用产品线策略;厂商通过设计一个相同成本的低质量产品帮助消费者实现认知,再而向部分消费者提供高质量产品,并获得较消费者认知前更大的利润水平;消费者认知成为产品线设计的关键因素;厂商利润增加的同时,社会总福利水平也获得提高。研究虽然针对完全垄断厂商进行分析,相关性质在寡头及垄断竞争市场也存在适用性。

黑格尔的“绝对理念”存在于自然界和人类社会之前吗?

本文作者提出黑格尔的“绝对理念”并非存在于自然界和人类社会出现之前的观点,值得讨论,因它涉及到如何评价和理解黑格尔的哲学思想体系问题.弄清这个问题,对于正确宣传、解释和讲授黑格尔的哲学思想是很必要的.为此,本刊拟就这个问题进行一些讨论,欢迎大家投稿.

用人史话

用人问题,于国于民,举足轻重。 毛泽东同志说过:“政治路线确定之后,干部就是决定的因素。”并一再强调:“必须善于识别干部”,“必须善于使用干部”,“必须善于爱护干部”;要“任人唯贤”,反对“任人唯亲”。这些论断,是古今用人得失规律的科学总结。说明了用人问题的重要性。 历史是一面镜子,它常常以丰富生动的材料使人清醒,促人谨慎,催人奋进。我们今天要为实现“四个现代化”进行新的长征,回顾一下历史上用人的经验和教训,是大有裨益的。

Railway tunnel concrete lining damaged by formation of gypsum,thaumasite and sulfate crystallization products in southwest of China

The railway tunnel concrete lining exposed to sulfate-bearing groundwater beyond 40 years in southwest of China was investigated. Field investigation, sulfate ions content and corroded products analysis, macro/microscopic test were carried out. Results show that under the tunnel concrete lining structure and its served environmental conditions, sulfate solutions permeate concrete lining and accumulate on windward-side of concrete lining, resulting in the increase of sulfate ions content on windward-side and the diffusion of sulfate ions from windward-side to waterward-side, which cause the concrete lining of windward-side damaged seriously but the waterward-side of concrete lining is still in perfect condition. It is confirmed that structural characteristic of tunnel and environmental conditions lead to physical attack with the leaching of concrete and sodium sulfate crystallization as well as chemical corrosion with formation of gypsum in high sulfate concentration and formation of thaumasite in proper temperature rather than formation of ettringite. These achievements can provide academic and technical supports for understanding the deterioration mechanism of concrete lining as well as constructing railway tunnel under sulfate attack.

Mechanical properties and energy mechanism of saturated sandstones

The effects of saturation on post-peak mechanical properties and energy features are main focal points for sandstones. To obtain these important attributes, post-peak cyclic loading and unloading tests were conducted on sandstone rock samples under natural and saturated states using the RMT-150B rock mechanics testing system. After successful processing of these tests, comparisons of stress-strain, strength, deformation, damage, and degradation of mechanical properties, wave velocity, and energy features of sandstone were conducted between natural and saturated states. The results show that saturation has evident weakening effects on uniaxial cyclic loading and unloading strength and elastic modulus of post-peak fracture sandstone. With the increase of post-peak loading and unloading period, the increases in amplitude of peak axial, lateral, and volumetric strains are all enhanced at approximately constant speed under the natural state. The increase in amplitude of axial peak strain is also enhanced at approximately constant speed, while the amplitudes of lateral and volumetric peak strains increase significantly under the saturated state. Compared with the natural state, the increase in amplitude of saturated samples＇ peak lateral and volumetric strains, and the post-peak cyclic loading and unloading period all conform to the linearly increasing relationship. Under natural and saturated states, the damage factor （the plastic shear strain） of each rock sample gradually increases with the increase of post-peak cyclic loading and unloading period, and the crack damage stress of each rock sample declines rapidly at first and tends to reach a constant value later with the increase in plastic shear strain. Under natural and saturated states, the wave velocities of rock samples all decrease in the process of post-peak cyclic loading and unloading with the increase in plastic shear strain. The wave velocities of rock samples and plastic shear strain conform to the exponential relationship with a constant. Saturation reduces the total absorption energy, dissipated energy, and elastic strain energy of rock samples.

Sustained Contraction of Isolated Rabbit Thoracic Aortic Rings in Endothelial-dependent Manner Induced by βγ-CAT

In vertebrates, non-lens βγ-crystallins are widely expressed in various tissues and their functions are not well known. The molecular mechanisms of trefoil factors （TFFs）, which involved in mucosal healing and tumorigenesis, have remained elusive. βγ-CAT is a novel multifunctional protein complex of non-lens βγ-crystallin and trefoil factor from frog skin secretions. Here we report that βγ-CAT could induce sustained contraction of isolated rabbit aortic rings in dosage （2-35nmol/L） and endothelium dependent manners （P〈0.01 ）. In addition, in situ immunofluorescence indicated that positive TNF-α signals were mainly detected at the endothelial cell layer of βγ-CAT （25nmol/L） treated rings. Furthermore, βγ-CAT induced primary cultured rabbit thoracic aortic endothelial cells （RAECs） rapidly to release TNF-α. After βγ-CAT （25nmol/L） treated for 10 and 30min, the levels of the endothelial cells released TNF-ct were 34.17±5.10 pg/mL and 98.01±4.67 pg/mL （P〈0.01）, respectively. In conclusion, βγ-CAT could induce sustained contraction of isolated aortic rings, and the contractile effect might be partially explained by the release of TNF-α. These findings will give new insight into understanding the functions and physiological roles of non-lens βγ-crystallins and trefoil factors.

First Oxidation Product of Vitamin C, the Dehydro-L-Ascorbic Acid Dimer： A Study Based on FTIR-Raman and DFT Calculations

We studied the first oxidation product of vitamin C, the dehydro-L-ascorbic acid dimer and characterized it by infrared and Raman spectroscopies in the solid phase. The Density functional theory was used to study its structure and vibrational properties. These calculations gave us a precise knowledge of the normal modes of vibration taking into account that the molecule comprises a system of five fused rings; non planar γ-lactone and furonose rings are attached to a central dioxan ring in the twisted boat conformation. The calculated harmonic vibrational frequencies are consistent with the experimental vibrational spectra. An assignment of the observed spectral features is proposed. The shift of the band located in the infrared spectrum of the ascorbic acid from 3409 cm^-1 to 3299 cml and the remarkable increase in the band intensity at 1784 cm^-1 evidences the acid decomposition into its first product, the dehydro-L-ascorbic acid. The theoretical vibrational calculations allowed us to obtain a set of scaled force constants. The nature of the different -γ-lactone, furanose and dioxan rings and their topological properties were investigated by means of natural bond orbital and Bader＇s atoms in the molecule theory, respectively.

Beasts of the Devil, Perishables, and the Natura Morta

Bugs have long embodied that from which we seek protection. Whether a mild irritant （a ＂fly in the ointment＂）, a costly pest to gardeners （＂bug of W＂）, or a destructive force of Biblical proportions （a swarm of locusts）, bugs are nature＇s warning of approaching death. This paper investigates the natura morta canvas during the Golden Age of Dutch art, focusing on how these symbols of natural evil work to enliven the visual rhetoric of the still-life as they invite spiritual contemplation. In religious-themed art, we intuitively recognize these morbid creatures as symbols of decay encroaching on domestic scenes filled with food and cut flowers. Emphasizing the short life of these perishables, bugs embody a classic tension and its dichotomous variations： the corporeal vs. the spiritual, earth vs. heaven, and sin vs. redemption. Though ostensibly a peripheral feature of the natura morta, bugs are a decidedly central motif that reflects the viewer＇s struggle with sin： Is it repellent, attractive, or repellently attractive？ This study will concern the visual rhetoric of flies, dragonflies, and bees in the works of Osias Beert, Ambrosius Bosschaert, and Georg Flegel, with an emphasis on the beasts of the devil as icons of Dutch art.

A Novel Material for Oil-water Separation

Oil products such as petroleum have greatly benefited the human society.However,they may lead to safety and health problems if not handled properly.For example,the oil spillage in the Gulf of Mexico caused serious ocean contamination and ecosystem damage in 2010.There is an urgent need,therefore,