From natural environment to artificial system: Chang'an and its water system in the Western Han Dynasty

People around the world have shaped societies and urban spaces around water for millennia. They have transformed natural water structures and patterns to serve their diverse needs. The ways in which historical decisions affect contemporary water systems and influence future planning of urban systems still need to be fully recognized. This paper explores the multiple roles of water systems in Chang'an during the Western Han Dynasty. Chang’an, one of the ancient names for the city of Xi’an, was a typical capital city of China and East Asia in early ancient times. This study explores everyday practices pertaining to water as well as its role in defense, gardening, politics and culture.Drawing upon three historical theories, this study presents findings that water was embedded in the design of traditional Chinese capitals. The siting and construction of capital cities was first based on the Theory of Choosing the Center (3rd century BCE) and the Theory of Conforming to Nature (5th–3rd century BCE). However, the final maturation of this urban morphology, including the water system, was closely related to the Theory of Symbolizing and Modeling Heaven and Earth (4th–3rd century BCE), in a way that manifested the imperial power's organization and control of space and time.Through close analysis of historical documents, archaeological reports and modern investigations, the paper aims to clarify, analyze and summarize the historical context and evolution, functional and structural characteristics, as well as the economic, political, cultural and military connotations of water systems in Chang'an. It argues that the coordination of urban construction and the water environment was a key foundation for capital city development. It proposes that people shaped urban water supply in many ways, including daily life, waterway transportation, agricultural irrigation, aquaculture promotion, military defense and fire prevention.The water system in Chang'an also provided an important place for royalty and nobility to go fishing, to hunt and to engage in leisure and naval training. The landscape with this water system as the core, including Taiye Lake and Kunming Lake, had also inspired Chinese gardening history, and had a profound impact on future generations. More importantly, the capital's urban morphology design was a miniature of the world recognized by the monarch, as well as the symbolic image of the supreme rulers' political and cultural desire to control and possess Tianxia, which essentially means the whole world. In conclusion, the paper calls for a closer study of water-based design as a foundation for urban planning.     

Italian multicentre study on microbial environmental contamination in dental clinics: a pilot study

The dental practice is associated with a high risk of infections, both for patients and healthcare operators, and the environment may play an important role in the transmission of infectious diseases. A microbiological environmental investigation was carried out in six dental clinics as a pilot study for a larger multicentre study that will be performed by the Italian SItI (Society of Hygiene, Preventive Medicine and Public Health) working group "Hygiene in Dentistry". Microbial contamination of water, air and surfaces was assessed in each clinic during the five working days of the week, before and during treatments. Air and surfaces were also examined at the end of the daily activity. A wide variation was found in microbial environmental contamination, both within the participating clinics and relative to the different sampling times. Microbial water contamination in Dental Unit Water Systems (DUWS) reached values of up to 26 × 10⁴ cfu/mL (colony forming units per millilitre). P. aeruginosa was found in 33% of the sampled DUWS and Legionella spp. in 50%. A significant decrease in the Total Viable Count (TVC) was recorded during the activity. Microbial air contamination showed the highest levels during dental treatments and tended to decrease at the end of the working activity (p < 0.05). Microbial buildup on surfaces increased significantly during the working hours. As these findings point out, research on microbial environmental contamination and the related risk factors in dental clinics should be expanded and should also be based on larger collections of data, in order to provide the essential knowledge aimed at targeted preventive interventions.     

Experimental investigation of an industrial scale black liquor gasifier. 1. The effect of reactor operation parameters on product gas composition

A novel technology to mitigate the climate changes and improve energy security is Pressurized Entrained flow High Temperature Black Liquor Gasification (PEHT-BLG) in combination with an efficient fuel synthesis using the resulting syngas. In order to optimise the technology for use in a pulp and paper mill based biorefinery, it is of great importance to understand how the operational parameters of the gasifier affect the product gas composition. The present paper is based on experiments where gas samples were withdrawn from the hot part of a 3 MW entrained flow pressurized black liquor gasifier of semi industrial scale using a high temperature gas sampling system. Specifically, the influence of process conditions on product gas composition (CO₂, CO, H₂, CH₄, H₂S, and COS) were examined by systematically varying the operational parameters: system pressure, oxygen to black liquor equivalence ratio, black liquor flow rate to pressure ratio and black liquor pre-heat temperature. Due to the harsh environment inside the gasification reactor, gas sampling is a challenging task. However, for the purpose of the current study, a specially designed high temperature gas sampling system was successfully developed and used. The results, obtained from two separate experimental campaigns, show that all of the investigated operational parameters have a significant influence on the product gas composition and present valuable information about to the process characteristics.     

Time trends of selected persistent organic pollutants in lake sediments from Greenland

Sediments from seven lakes in West Greenland were used as natural archives to study past and present levels of PCBs (polychlorinated biphenyls, tri- to decachlorinated), tetra-BDE #47 (2,2',4,4'-bromodiphenyl ether), chlordane (cis- and trans-octachlordane) and HxCBz (hexachlorobenzene). The concentrations found are lower than or comparable to concentrations found in sediments from other Arctic regions and one to 2 orders of magnitude lower than concentrations typically found in sediments at lower latitudes. The observed temporal trends (direct and indirect dating) show a decreasing total PCB concentration. Even though local contamination sources exist, the POP deposition in the studied area is most likely a result from long-range transport. The hypothesis about "cold condensation" suggests a latitudinal fractionation to occur between different volatile compounds during the transport toward the pole. In this study a time delay in the deposition for the low-chlorinated PCBs (tri- and tetrachlorinated), compared to their emission histories and compared to higher chlorinated PCBs, was indicated. Although very low tetra-BDE #47 concentrations are observed in this study, there are indications for an increasing concentration in recent sediment layers that may reflect increasing environmental concentrations at lower latitudes. The investigated pesticides are still in use at lower latitudes, however neither chlordane nor HxCBz show any distinct temporal trend of increasing or decreasing concentration toward the sediment surface.     

Observations on the electrical resistivity of steel fibre reinforced concrete

Steel fibre reinforced concrete (SFRC) is in many ways a well-known construction material, and its use has gradually increased over the last decades. The mechanical properties of SFRC are well described based on the theories of fracture mechanics. However, knowledge on other material properties, including the electrical resistivity, is sparse. Among others, the electrical resistivity of concrete has an effect on the corrosion process of possible embedded bar reinforcement and transfer of stray current. The present paper provides experimental results concerning the influence of the fibre volume fraction and the moisture content of the SFRC on its electrical resistivity. The electrical resistivity was measured by alternating current (AC) at 126 Hz. Moreover, an analytical model for the prediction of the electrical resistivity of SFRC is presented. The analytical model is capable of predicting the observed correlation between the fibre volume fraction and the electrical resistivity of the composite (the SFRC) for conductive fibres and moisture saturated concrete. This indicates that the steel fibres were conducting when measuring the electrical resistivity by AC at 126 Hz. For partly saturated concrete the model underestimated the influence of the addition of fibres. The results indicate that the addition of steel fibres reduce the electrical resistivity of concrete if the fibres are conductive. This represents a hypothetical case where all fibres are depassivated (corroding) which was created to obtain a conservative estimate on the influence of fibres on the electrical resistivity of concrete. It was observed that within typical ranges of variation the influence of the moisture content on the electrical resistivity was larger than the effect of addition of conductive steel fibres, but also that the relative impact on the electrical resistivity due to conductive steel fibres increased when the moisture content of the concrete was reduced.     

Tracing waterbird exposure to total mercury and selenium: a case study at the solar saltworks of Thyna (sfax, Tunisia)

Saltworks have emerged as important alternative/complementary feeding habitats for avifauna. However, the consequences of such habitat shifts in terms of changes in exposure to contaminants are poorly understood. We evaluated the exposure of the waterbird community breeding at the saltworks of Thyna (Tunisia) to total Hg (THg) and Se according to their differential use of saltworks dietary resources, as revealed by δ13C and δ1?N values in their eggs (included species [n] -sorted according to increasing reliance on saltworks resources: Yellow-legged Gull Larus michahellis [12], Common Tern Sterna hirundo [12], Slender-billed Gull Larus genei [15], Little Egret Egretta garzetta [20], and Pied Avocet Recurvirostra avosetta [22]). Concentrations of THg and Se were under the threshold points for deleterious effects. Egg THg concentrations significantly decreased as the dietary contribution of saltworks resources increased (mean: 3.23, 1.66, 0.76, 0.4, and 0.27 μg/g dw, respectively). Conversely, egg Se concentrations did not vary according to foraging habitats (2.49, 2.96, 2.61, 3.27, and 1.5 μg/g dw, respectively). Tracing waterbird exposure to THg and Se at saltworks was feasible through the use stable isotopic assays of eggs. Birds using saltworks are not exposed to higher concentrations of THg and Se than in adjacent marine habitats.     

Matching Polyhedral Terrains Using Overlays of Envelopes

For a collection $\F$ of $d$-variate piecewise linear functions of overall combinatorial complexity $n$, the lower envelope $\E(\F)$ of $\F$ is the pointwise minimum of these functions. The minimization diagram $\M(\F)$ is the subdivision of $\reals^d$ obtained by vertically (i.e., in direction $x_{d+1}$) projecting $\E(\F)$. The overlay $\O(\F,\G)$ of two such subdivisions $\M(\F)$ and $\M(\G)$ is their superposition. We extend and improve the analysis of de Berg et al. \cite{bgh-vdt3s-96} by showing that the combinatorial complexity of $\O(\F,\G)$ is $\Omega(n^d \alpha^{2}(n))$ and $O(n^{d+\eps})$ for any $\eps>0$ when $d \ge 2$, and $O(n^2 \alpha(n) \log n)$ when $d=2$. We also describe an algorithm that constructs $\O(\F,\G)$ in this time. We apply these results to obtain efficient general solutions to the problem of matching two polyhedral terrains in higher dimensions under translation. That is, given two piecewise linear terrains of combinatorial complexity $n$ in $\reals^{d+1}$, we wish to find a translation of the first terrain that minimizes its distance to the second, according to some distance measure. For the perpendicular distance measure, which we adopt from functional analysis since it is natural for measuring the similarity of terrains, we present a matching algorithm that runs in time $O(n^{2d+\eps})$ for any $\eps>0$. Sharper running time bounds are shown for $d \le 2$. For the directed and undirected \Hd\ distance measures, we present a matching algorithm that runs in time $O(n^{d^2+d+\eps})$ for any $\eps>0$.     

Synthesis and Functionalization of Fullerenes Encapsulating Atomic Phosphorus

Synthesis, purification, and electron spin properties of the endohedral fullerene P@C₆₀ are reported. Highly enriched material could be obtained for the first time, making this molecule accessible for further experiments. We report the first successful chemical modification of P@C₆₀ via cyclo-propanation to the C_2v symmetric monoadducts P@C₆₁(COOCH₃) and P@C₆₁(COOC₂H₅). X-band electron spin resonance data are presented and discussed. The phosphorus atom shows anisotropic hyperfine coupling in the modified fullerenes, in contrast to the unmodified case, and in contrast to similarly modified N@C₆₀.     

Enterprise-Wide Data Integration and Analysis for Oversize/Overweight Permitting

The automation of oversize/overweight (OS/OW) vehicle permitting can be achieved through GIS-based systems. OS/OW permitting involves network pathfinding given spatial and temporal constraints that are associated with the physical roadway network. This paper presents a data model design that extends and satisfies the consensus functional requirements of OS/OW permitting. Although departments of transportation at the state level invest millions of dollars in development and management of enterprise databases of bridges and highways, many GIS-based OS/OW permitting systems require development of application-specific versions of these databases. Consequently, agency motor carrier service divisions are faced with huge data management problems. The system design in this paper facilitates sustainability by being consistent with the notions of enterprisewide data integration. A robust location-referencing strategy and adherence to the national intelligent transportation systems architecture achieve enterprisewide data integration. This paper presents general system requirements, an OS/OW application design, an enterprisewide database schema, and algorithms for finding OS/OW vehicle routes given spatial and temporal roadway restrictions. The system design accommodates multiple data sources, multiple location-referencing methods, and state-to-state interoperability. Spatial and temporal constraints for OS/OW permitting are represented in a unified modeling language class diagram.