身份之场所

城市是人类创造的适于居住的区域性的人工生态系统,其主干结构是公共空间系统。公共空间,亦即如是所说的公共城市空间,为所有公民所有,因此,它必须毫无例外地面向每个人,其所有权、领域及使用必须是公共的。这种公共空间是文化与社会的支撑,赋予公民团体以身份。它是同存共生的景致,是集会社交的场所,调控个中的私密功能以维系此般公共空间的权益尤显必要。因为代表了公民团体的身份,公共空间成为一种象征性的场所,其身份的表现为人所知并被传承。     

Subcontracting in commercial and residential construction: an empirical investigation

Some twenty years ago Robert Eccles argued for the theoretical existence of the quasifirm, a semi-integrated form of production in the construction industry, following a field study of home building firms in the USA. The study was aimed at substantiating some aspects of Williamson's transaction cost theory. The present work has similar intents, and illustrates the results of two recent field studies of homebuilders and commercial contractors, and the specific features of their subcontracting practice. Given the difficulty of an effective measurement of transaction costs in construction, Williamson's concept of atmosphere is suggested to explain the different approaches observed in subcontracting.     

One or infinite optimal city sizes? In search of an equilibrium size for cities

In this paper, the stylized assumption that one single “optimal” city size exists for all cities—achieved when marginal location costs equal marginal location benefits—is abandoned, as well as the opposite view that each city operates on its own cost and production curves, defining a specific optimal size. Instead, this work maintains the comparability among cities and demonstrates that urban specificities in functions performed, quality of life, industrial diversity and social conflicts shift up and down the benefits and costs linked to pure physical size, leading to different “equilibrium” sizes for cities. In order to achieve this result, a model of equilibrium urban size is set up, based on urban costs and urban benefits, merging elements suggested both by the traditional urban economics literature as well as by updated approaches considering also environmental quality, urban form and inter-urban cooperation networks. The model is then estimated on a sample of 59 European cities with data at FUA level. Empirical results allow the identification of city-specific “equilibrium” sizes. The error term, that is, the difference between actual urban population and the “equilibrium” one predicted by the model can be explained, beyond a measure of our ignorance, by good or bad governance, thereby suggesting future strategies for more efficient urban planning.     

Removal of heavy metals from wastewater using magnetic nanocomposites: Analysis of the experimental conditions

This contribution provides insight on the elimination of heavy metals from water resources using magnetic separation. Nanocomposites based on magnetite and chitosan were prepared. An exhaustive characterization of the magnetic adsorbents was developed. Adsorption assays were performed in batch using Cu, Zn, Cd, and Cr as model heavy metals. The efficiency of magnetic adsorbents followed the order: Cu > Cd > Zn > Cr, with maximum values of 188, 159, 72, and 46 mg of Me/g of nanocomposite, respectively. Kinetics and mechanistic issues were studied. The magnetic materials were efficient for five to eight cycles using Cu(II),Cd(II), and Cr(VI).     

The Sterol and Erythrodiol + Uvaol Content of Virgin Olive Oils Produced in Five Olive-Growing Zones of Extremadura (Spain)

The content of sterols and erythrodiol + uvaol was studied in 273 virgin olive oil samples from 40 mills in five olive‐growing zones of Extremadura (Spain). An analysis of variance showed significant differences at a confidence level of 95 % between the different zones in each of the main sterols and in the sum of erythrodiol + uvaol. The results of a linear discriminant analysis, considering the different olive‐growing areas as categorical dependent variables and the different sterols as independent variables, explained 78.2 % of the variance with the first two discriminant functions. The resulting model correctly classified 86.9 % of the samples analysed. A validation study was conducted to verify the goodness of the discriminant analysis, resulting in 79.3 % of the new samples used for validation being correctly classified. In the graphical representation of the different groups studied considering the proposed model's first two discriminant functions, the centroids of the Sierra Norte de Cáceres, Vegas del Guadiana and Tierra de Barros olive‐growing zones were clearly separated, but this was not the case for the other two zones—La Serena and La Siberia.     

Shape memory crosslinked polyurethanes containing thermoreversible Diels‐Alder couplings

Crosslinked polyurethanes (PUs) containing irreversible (allophanate) and reversible Diels‐Alder chemical bonds were synthesized using various diisocyanates (methylene diphenyl diisocyanate MDI, 1,6‐hexamethylenediisocyanate HDI) and poly(?‐caprolactone) ((PCL) with different molecular weights (M_n = 10 kg/mol, 25 kg/mol, 50 kg/mol) as diol component. The melting/crystallization of PCL and the reversible DA bonds acted as temperature‐activated switches for shape memory performances, while allophanate network provided the permanent crosslinks for these PUs. The reversible DA bonds were obtained by the reaction of diisocyanate‐ended prepolymers with furfurylamine (FA) followed by the addition of bismaleimide (BMI). The permanent crosslinks between the linear chains containing DA bonds were achieved using additional amounts of diisocyanates (MDI or HDI). The above reaction path was supported by infrared spectroscopic results and swelling experiments. Tensile mechanical and shape memory properties in tension of the PUs were determined and discussed as a function of composition and crosslink densities deduced from swelling and dynamic mechanical analysis. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44145.     

Sustained release of potassium diclofenac from a pH‐responsive hydrogel based on gum arabic conjugates into simulated intestinal fluid

This work describes the preparation, the swelling properties and the potassium diclofenac (KDF) release profile of hydrogels of gum arabic (GA), N′,N′‐dimethylacrylamide, and methacrylic acid. In order to convert GA into a hydrogel, the polysaccharide was vinyl‐modified with glycidyl methacrylate. The hydrogels showed pH‐responsive swelling changes, which were more expressive in the basic environment. Release data of KDF were adjusted to a diffusion‐based kinetic model that provides an important insight on affinity of the drug for hydrogel and solvent, which may be the leading parameter for release of guest molecules from polymers. The KDF release from the hydrogels into simulated intestinal fluid decreases when the amount of modified GA increases. This was demonstrated to be due to the higher affinity of KDF for GA‐richer hydrogel, which makes the anti‐inflammatory release less favorable. The analysis of released drug half‐time (t_1/2 = 16.10 and 21.51 h) indicated sustained release characteristics. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43319.     

Utilization of ramon seeds (Brosimum alicastrum swarts) as a new source material for thermoplastic starch production

The development and characterization of biodegradable polymers deriving from renewable natural sources has attracted much attention. The aim of this work was to partially characterize a thermoplastic starch obtained from the starch of seeds from the ramon tree (TPS‐RS) as an option to substitute thermoplastic starch from corn (TPS‐CS), in some of its applications. At 55% of relative humidity (RH), TPS‐RS had higher tensile strength and deformation than TPS‐CS. X‐ray diffraction analysis showed similar values in residual crystallinity (percentage of crystallinity that remains after plasticization process) in both TPS. The SEM micrographs showed a few remnant granular structures in the TPS‐RS. The FTIR showed a greater intensity in band at 1016 cm^?1 in the TPS‐CS and TPS‐RS in comparison with their corresponding native starch, indicating an increase in the amorphous region after plasticization. The TGA analysis showed greater thermal stability in TPS‐CS (340 °C) compared with TPS‐RS (327 °C). In addition, the glass transition temperature in both TPS was 24 °C. The results obtained represent a starting point to potentialize the use of TPS‐RS instead of TPS‐CS for the development of new biodegradable materials for practical applications in different areas. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44235.     

Increased HDL Size and Enhanced Apo A-I Catabolic Rates Are Associated With Doxorubicin-Induced Proteinuria in New Zealand White Rabbits

The catabolism and structure of high‐density lipoproteins (HDL) may be the determining factor of their atheroprotective properties. To better understand the role of the kidney in HDL catabolism, here we characterized HDL subclasses and the catabolic rates of apo A‐I in a rabbit model of proteinuria. Proteinuria was induced by intravenous administration of doxorubicin in New Zealand white rabbits (n = 10). HDL size and HDL subclass lipids were assessed by electrophoresis of the isolated lipoproteins. The catabolic rate of HDL‐apo A‐I was evaluated by exogenous radiolabelling with iodine‐131. Doxorubicin induced significant proteinuria after 4 weeks (4.47 ± 0.55 vs. 0.30 ± 0.02 g/L of protein in urine, P < 0.001) associated with increased uremia, creatininemia, and cardiotoxicity. Large HDL2b augmented significantly during proteinuria, whereas small HDL3b and HDL3c decreased compared to basal conditions. HDL2b, HDL2a, and HDL3a subclasses were enriched with triacylglycerols in proteinuric animals as determined by the triacylglycerol‐to‐phospholipid ratio; the cholesterol content in HDL subclasses remained unchanged. The fractional catabolic rate (FCR) of [¹³¹I]‐apo A‐I in the proteinuric rabbits was faster (FCR = 0.036 h^?1) compared to control rabbits group (FCR = 0.026 h^?1, P < 0.05). Apo E increased and apo A‐I decreased in HDL, whereas PON‐1 activity increased in proteinuric rabbits. Proteinuria was associated with an increased number of large HDL2b particles and a decreased number of small HDL3b and 3c. Proteinuria was also connected to an alteration in HDL subclass lipids, apolipoprotein content of HDL, high paraoxonase‐1 activity, and a rise in the fractional catabolic rate of the [¹³¹I]‐apo A‐I.     

Toward the prediction of porous membrane permeability from morphological data

One of the challenges in membrane technology is predicting permeability in porous membranes for liquid applications in an easy and inexpensive way. This is the aim of this work. To achieve this objective, several techniques can be considered. In this study, a morphological approach from two‐dimensional scanning electron micrographs is proposed. First, numerical membrane morphological parameters have been determined from micrographs by using the QUANTS tool, which applies a texture recognition process. Second, the obtained data have been fit to the Darcy's and Hagen–Poiseuille models to calculate permeations. The QUANTS results have also been compared with the ones obtained through a mercury porosimeter, which is a classic and well‐known methodology. Each parameter of the Hagen–Poiseuille model has been analyzed. A comparison between experimentally measured permeations and calculated ones has been performed. An even easier approach is proposed to predict flow rate with the only knowledge of membrane surface mean pore size. This method is based on cross‐section pore size interpolation by using function fits from surface mean pore sizes. The obtained results show a reasonable agreement between measured and computed results, making this technique a valid approach for predicting membrane permeability. POLYM. ENG. SCI., 56:118–124, 2016. © 2015 Society of Plastics Engineers