液相色谱质谱联用法研究红花染纺织品褪色分子机理

以红花染纺织品作为主要研究对象,通过紫外光和LED两种光老化方式,研究不同褪色因素影响下纺织品中显色组分红花苷的降解变化情况,实验发现不同酸化作用对红花苷造成不同的影响。采用液相色谱质谱联用的方法,鉴定出红花苷、芹菜素等多种组分,并首次从红花中鉴定出国外报道的但一直未确定的组分Ct4的分子结构,实际是三香豆酰亚精胺,一种酚酰胺类化合物,可作为一种染色工艺指标对现代染和古代染色工艺进行区分。以故宫院藏两件红花染褪色纺织品文物为例阐述褪色机理,显色组分红花苷的降解,产生不同程度的裂化产物小分子,使原本微量存在的三香豆酰亚精胺相对含量增高,从而造成褪色明显,文物在长期日晒下正面原本红色外观呈现橘色打底。同时强调了博物馆应高度重视相同类型文物保存环境中的挥发性酸性气体监测。     

Extensions to the Hub Location Problem: Formulations and Numerical Examples

Although a tremendous amount of analytical research is being conducted on the hub location problem, few models exist that extend the number of characteristics found in actual hub-and-spoke networks. Four extensions are presented in this paper: (1) a capacitated network model; (2) a minimum threshold model; (3) a model that endogenously determines the number of open hubs for the network; and (4) a model that incorporates a flow-dependent cost function for the spokes as well as the interhub links. Both the capacitated and the minimum threshold models drop the assumption of a completely interconnected network commonly found in hub location models. Numerical results show that total network costs are often minimized by closing a few interhub links. The third extension is the first known hub location model to determine the optimal number of hubs based on the needs of the network. In this model, the number of open hubs depends on the distribution of flows in the network and how cost effectively the flows can be moved across the network. Previous models that endogenously determined the number of open hubs utilized a fixed cost for establishing each hub in order to limit the number of hubs in the network. The final extension recognizes the potential of all links to amalgamate flows and includes a separate flow-dependent cost function for the spokes in addition to the one for the interhub links. Numerical results are shown for all four models.     

Revisiting Kalundu Mound,Zambia: Implications for the Timing of Social and Subsistence Transitions in Iron Age Southern Africa

African Archaeological Review - Novel trajectories of food production, urbanism, and inter-regional trade fueled the emergence of numerous complex Iron Age polities in central and southern Africa....     

Shellfish exploitation in Stone Age Arctic Norway: procurement patterns and household activities

Archaeological evidence for coastal shellfish exploitation in Arctic Norway mostly dates from 5300 to 1500 BC, encompassing the terminal Mesolithic, the Late Stone Age, and the beginning of the Early Metal Period. Shell middens are generally associated with semi-subterranean houses, but may also occur as free-standing deposits. The primary shellfish taxa exploited were Littorina littorea, Arctica islandica and Mytilus edulis. Most of the species utilized were available in the littoral zone and were easily procured in the course of daily household activities, but sub-littoral A. islandica would have required greater investment in procurement technology and time, as well as labor cooperation. Shellfish were an occasional dietary supplement and could also serve as fishing bait. Spatial and temporal variation in shellfish assemblages reflects local marine ecology, sea-level changes, household dynamics, and perhaps field processing. Interpretation of the existing data is constrained by inadequate midden sampling and documentation methods.     

PANEL DATA MODELS WITH SPATIALLY DEPENDENT NESTED RANDOM EFFECTS

This paper focuses on panel data models combining spatial dependence with a nested (hierarchical) structure. We use a generalized moments estimator to estimate the spatial autoregressive parameter and the variance components of the disturbance process. A spatial counterpart of the Cochrane‐Orcutt transformation leads to a feasible generalized least squares procedure to estimate the regression parameters. Monte Carlo simulations show that our estimators perform well in terms of root mean square error compared to the maximum likelihood estimator. The approach is applied to English house price data for districts nested within counties.