A Small World Perspective on Urban Systems

The theory of small-world networks as initiated by Watts and Strogatz (1998) has drawn new insights in spatial analysis as well as systems theory. The theoryâeuro?s concepts and methods are particularly relevant to geography, where spatial interaction is mainstream and where interactions can be described and studied using large numbers of exchanges or similarity matrices. Networks are organized through direct links or by indirect paths, inducing topological proximities that simultaneously involve spatial, social, cultural or organizational dimensions. Network synergies build over similarities and are fed by complementarities between or inside cities, with the two effects potentially amplifying each other according to the âeurooepreferential attachmentâeuro hypothesis that has been explored in a number of different scientific fields (Barabási, Albert 1999; Barabási A-L 2002; Newman M, Watts D, Barabàsi A-L). In fact, according to Barabási and Albert (1999), the high level of hierarchy observed in âeurooescale-free networksâeuro results from âeurooepreferential attachmentâeuro, which characterizes the development of networks: new connections appear preferentially close to nodes that already have the largest number of connections because in this way, the improvement in the network accessibility of the new connection will likely be greater. However, at the same time, network regions gathering dense and numerous weak links (Granovetter, 1985) or network entities acting as bridges between several components (Burt 2005) offer a higher capacity for urban communities to benefit from opportunities and create future synergies. Several methodologies have been suggested to identify such denser and more coherent regions (also called communities or clusters) in terms of links (Watts, Strogatz 1998; Watts 1999; Barabási, Albert 1999; Barabási 2002; Auber 2003; Newman 2006). These communities not only possess a high level of dependency among their member entities but also show a low level of âeurooevulnerabilityâeuro, allowing for numerous redundancies (Burt 2000; Burt 2005). The SPANGEO project 2005âeuro"2008 (SPAtial Networks in GEOgraphy), gathering a team of geographers and computer scientists, has included empirical studies to survey concepts and measures developed in other related fields, such as physics, sociology and communication science. The relevancy and potential interpretation of weighted or non-weighted measures on edges and nodes were examined and analyzed at different scales (intra-urban, inter-urban or both). New classification and clustering schemes based on the relative local density of subgraphs were developed. The present article describes how these notions and methods contribute on a conceptual level, in terms of measures, delineations, explanatory analyses and visualization of geographical phenomena.

Els bancs de dades de la flora dels Països Catalans

Data banks on the flora of the Catalan Countries. Two data banks on the flora of the Catalan Countries (NE and E of the Iberian Peninsule and Balearic Islands) have been set up by the Secció de Ciències of the Institut d'Estudis Catalans (I.E.C., Institute of Catalan Studies). One is devoted to bibliography and the other to floristics, in this first phase concerned only with vascular plants. The sources are all types of publications containing concrete information on the vascular flora of the Catalan Countries. The information is transcribed on precoded forms so as to standardize the data and thus permit homogeneous input for subsequent storage in the computer. The coding schemes and characteristics of the forms are described for each of the data banks. Only the phytocoenological inventories receive special treatment which is discussed withreference to the floristic data bank. A first issue is annexed: the bibliografy concerning the vascular flora of Catalan Countries (years 1983 and 1984).

¿Cómo los académicos españoles se enfrentan con el cambio? respuesta desde una investigación de historias de vida profesionales

[spa] Este documento forma parte de la investigación, Los efectos de los cambios sociales en el trabajo y la vida profesional de los docentes universitarios, parcialmente financiado por el Ministerio de Ciencia e Innovación (SEJ2006-01876), en el que hemos explorado los cambios en la legislación, la organización, los contextos de la investigación y la docencia, etc., en los últimos treinta años. El principal objetivo de este documento es profundizar en nuestra comprensión sobre el impacto del cambio económico, social, cultural, tecnológico y laboral que están experimentando las universidades españolas en la vida y la identidad profesional del personal docente e investigador, teniendo en cuenta el contexto nacional y europeo. Este trabajo recoge parte de los resultados obtenidos en el proyecto, siendo su principal objetivo contribuir a mejorar el conocimiento basado en la investigación sobre el saber profesional y la experiencia laboral en las universidades españolas, y en consecuencia, favorecer nuestra comprensión sobre cómo los académicos se están enfrentando con los cambios actuales.

Alternate Methods of Bridge Strengthening, HR-302, 1989

The need for upgrading a large number of understrength and obsolete bridges in the United States has been well documented in the literature. Through the performance of several Iowa DOT projects, the concept of strengthening bridges (simple and continuous spans) by post-tensioning has been developed. The purpose of this project was to investigate two additional strengthening alternatives that may be more efficient than post-tensioning in certain situations. The research program for each strengthening scheme included a literature review, laboratory testing of the strengthening scheme, and a finite-element analysis of the scheme. For clarity the two strengthening schemes are presented separately. In Part 1 of this report, the strengthening of existing steel stringers in composite steel beam concrete-deck bridges by providing partial end restraint was shown to be feasible. Part 2 of this report summarizes the research that was undertaken to strengthen the negative moment regions of continuous, composite bridges. Two schemes were investigated: post-compression of stringers and superimposed trusses within the stringers.

Diallel analysis for grain yield and mineral absorption rate of soybeans grown in acid brazilian savannah soil

High available aluminium and low levels of calcium below the ploughed zone of the soil are limiting factors for agricultural sustainability in the Brazilian Cerrados (Savannahs). The mineral stresses compound with dry spells effect by preventing deep root growth of cultivated plants and causes yield instability. The mode of inheritance for grain yield and mineral absorption ratio of a diallel cross in soybeans [Glycine max (L.) Merrill] grown in high and low Al areas was identified. Differences among the genotypes for grain yield were more evident in the high Al, by grouping tolerant and non-tolerant genotypes for their respective arrays in the hybrids. A large proportion of genetic variance was additive for grain yield and mineral absorption ratio in both environments. High heritability values suggest that soybeans can be improved by crosses among Al-tolerant genotypes, using modified pedigree, early generation and recurrent selection schemes.

Full-waveform inversion of cross-hole ground-penetrating radar data to characterize a gravel aquifer close to the Thur River, Switzerland

Cross-hole radar tomography is a useful tool for mapping shallow subsurface electrical properties viz. dielectric permittivity and electrical conductivity. Common practice is to invert cross-hole radar data with ray-based tomographic algorithms using first arrival traveltimes and first cycle amplitudes. However, the resolution of conventional standard ray-based inversion schemes for cross-hole ground-penetrating radar (GPR) is limited because only a fraction of the information contained in the radar data is used. The resolution can be improved significantly by using a full-waveform inversion that considers the entire waveform, or significant parts thereof. A recently developed 2D time-domain vectorial full-waveform crosshole radar inversion code has been modified in the present study by allowing optimized acquisition setups that reduce the acquisition time and computational costs significantly. This is achieved by minimizing the number of transmitter points and maximizing the number of receiver positions. The improved algorithm was employed to invert cross-hole GPR data acquired within a gravel aquifer (4-10 m depth) in the Thur valley, Switzerland. The simulated traces of the final model obtained by the full-waveform inversion fit the observed traces very well in the lower part of the section and reasonably well in the upper part of the section. Compared to the ray-based inversion, the results from the full-waveform inversion show significantly higher resolution images. At either side, 2.5 m distance away from the cross-hole plane, borehole logs were acquired. There is a good correspondence between the conductivity tomograms and the natural gamma logs at the boundary of the gravel layer and the underlying lacustrine clay deposits. Using existing petrophysical models, the inversion results and neutron-neutron logs are converted to porosity. Without any additional calibration, the values obtained for the converted neutron-neutron logs and permittivity results are very close and similar vertical variations can be observed. The full-waveform inversion provides in both cases additional information about the subsurface. Due to the presence of the water table and associated refracted/reflected waves, the upper traces are not well fitted and the upper 2 m in the permittivity and conductivity tomograms are not reliably reconstructed because the unsaturated zone is not incorporated into the inversion domain.

¿Cómo los académicos españoles se enfrentan con el cambio? respuesta desde una investigación de historias de vida profesionales

[spa] Este documento forma parte de la investigación, Los efectos de los cambios sociales en el trabajo y la vida profesional de los docentes universitarios, parcialmente financiado por el Ministerio de Ciencia e Innovación (SEJ2006-01876), en el que hemos explorado los cambios en la legislación, la organización, los contextos de la investigación y la docencia, etc., en los últimos treinta años. El principal objetivo de este documento es profundizar en nuestra comprensión sobre el impacto del cambio económico, social, cultural, tecnológico y laboral que están experimentando las universidades españolas en la vida y la identidad profesional del personal docente e investigador, teniendo en cuenta el contexto nacional y europeo. Este trabajo recoge parte de los resultados obtenidos en el proyecto, siendo su principal objetivo contribuir a mejorar el conocimiento basado en la investigación sobre el saber profesional y la experiencia laboral en las universidades españolas, y en consecuencia, favorecer nuestra comprensión sobre cómo los académicos se están enfrentando con los cambios actuales.

How are Spanish academics coping with changes? Responses from a life histories research.

[eng] This report is part of the research project, The effects of social changes in work and professional life of Spanish academics, partially financed by the Spanish Ministry of Science and Innovation (SEJ2006-01876), that has explored change in legislation, organisation, research schemes and so on, in the last thirty years. The main aim of this project is deepening our understanding of the impact of undergoing economic, social, cultural, technological and labour change in Spanish universities in the life and professional identity of the teaching and research staff, taking into account the national and european context. This paper gathers part of the results gained from the project, being its primary objective to contribute to an improved knowledge-base on professional knowledge and work experience in higher education institutions in Spain and, as a consequence, to understand how Spanish academics are coping with current changes.

Refinement of Rapid PCC Coarse Aggregate Testing Program, HR-1071, 1999

The characterization and categorization of coarse aggregates for use in portland cement concrete (PCC) pavements is a highly refined process at the Iowa Department of Transportation. Over the past 10 to 15 years, much effort has been directed at pursuing direct testing schemes to supplement or replace existing physical testing schemes. Direct testing refers to the process of directly measuring the chemical and mineralogical properties of an aggregate and then attempting to correlate those measured properties to historical performance information (i.e., field service record). This is in contrast to indirect measurement techniques, which generally attempt to extrapolate the performance of laboratory test specimens to expected field performance. The purpose of this research project was to investigate and refine the use of direct testing methods, such as X-ray analysis techniques and thermal analysis techniques, to categorize carbonate aggregates for use in portland cement concrete. The results of this study indicated that the general testing methods that are currently used to obtain data for estimating service life tend to be very reliable and have good to excellent repeatability. Several changes in the current techniques were recommended to enhance the long-term reliability of the carbonate database. These changes can be summarized as follows: (a) Limits that are more stringent need to be set on the maximum particle size in the samples subjected to testing. This should help to improve the reliability of all three of the test methods studied during this project. (b) X-ray diffraction testing needs to be refined to incorporate the use of an internal standard. This will help to minimize the influence of sample positioning errors and it will also allow for the calculation of the concentration of the various minerals present in the samples. (c) Thermal analysis data needs to be corrected for moisture content and clay content prior to calculating the carbonate content of the sample.

A History of Particle-Size Limits, Special Report, HR-99

Soils consist largely of mineral particles in a wide range of sizes. It is advantageous to assign names, such as "sand", etc., to describe particles which lie between certain size limits. These names are convenient to use and give more information than merely stating that the particles fit certain size limitations. Many systems of particle-size limits have been proposed and used, and have many discrepancies. For example, depending on the system used, a term such as "sand" may designate very different materials. Since no clear-cut divisions can be made between members of a continuous series all particle-size limit schemes are arbitrary. The originators of the various systems were influenced by many factors: convenience of investigation, methods and equipment available for analysis, ease of presenting data, convenience for statistical analysis, previous work, and systems in use. The complications were further compounded because of widely varying fields of endeavor with varying background, outlook, and goals. For example, many inconsistencies are found in engineering depending on whether the size limits are used to differentiate soils, or characterize aggregates for concrete. Some of the investigators have tried to place limits to correspond with the various properties of the soil components; others were more interested in the ease and convenience of obtaining and presenting data. The purpose of this paper is to review many of the systems which have been proposed and used, and if possible, to suggest what may have been the reasons for the selection of the particle-size limits.

¿Cómo los académicos españoles se enfrentan con el cambio? respuesta desde una investigación de historias de vida profesionales

[spa] Este documento forma parte de la investigación, Los efectos de los cambios sociales en el trabajo y la vida profesional de los docentes universitarios, parcialmente financiado por el Ministerio de Ciencia e Innovación (SEJ2006-01876), en el que hemos explorado los cambios en la legislación, la organización, los contextos de la investigación y la docencia, etc., en los últimos treinta años. El principal objetivo de este documento es profundizar en nuestra comprensión sobre el impacto del cambio económico, social, cultural, tecnológico y laboral que están experimentando las universidades españolas en la vida y la identidad profesional del personal docente e investigador, teniendo en cuenta el contexto nacional y europeo. Este trabajo recoge parte de los resultados obtenidos en el proyecto, siendo su principal objetivo contribuir a mejorar el conocimiento basado en la investigación sobre el saber profesional y la experiencia laboral en las universidades españolas, y en consecuencia, favorecer nuestra comprensión sobre cómo los académicos se están enfrentando con los cambios actuales.

How are Spanish academics coping with changes? Responses from a life histories research.

[eng] This report is part of the research project, The effects of social changes in work and professional life of Spanish academics, partially financed by the Spanish Ministry of Science and Innovation (SEJ2006-01876), that has explored change in legislation, organisation, research schemes and so on, in the last thirty years. The main aim of this project is deepening our understanding of the impact of undergoing economic, social, cultural, technological and labour change in Spanish universities in the life and professional identity of the teaching and research staff, taking into account the national and european context. This paper gathers part of the results gained from the project, being its primary objective to contribute to an improved knowledge-base on professional knowledge and work experience in higher education institutions in Spain and, as a consequence, to understand how Spanish academics are coping with current changes.

Diffusion tensor echo planar imaging using surface coil transceiver with a semiadiabatic RF pulse sequence at 14.1T.

Diffusion magnetic resonance studies of the brain are typically performed using volume coils. Although in human brain this leads to a near optimal filling factor, studies of rodent brain must contend with the fact that only a fraction of the head volume can be ascribed to the brain. The use of surface coil as transceiver increases Signal-to-Noise Ratio (SNR), reduces radiofrequency power requirements and opens the possibility of parallel transmit schemes, likely to allow efficient acquisition schemes, of critical importance for reducing the long scan times implicated in diffusion tensor imaging. This study demonstrates the implementation of a semiadiabatic echo planar imaging sequence (echo time=40 ms, four interleaves) at 14.1T using a quadrature surface coil as transceiver. It resulted in artifact free images with excellent SNR throughout the brain. Diffusion tensor derived parameters obtained within the rat brain were in excellent agreement with reported values.

Ensemble methods for environmental data modelling with support vector regression

This paper investigates the use of ensemble of predictors in order to improve the performance of spatial prediction methods. Support vector regression (SVR), a popular method from the field of statistical machine learning, is used. Several instances of SVR are combined using different data sampling schemes (bagging and boosting). Bagging shows good performance, and proves to be more computationally efficient than training a single SVR model while reducing error. Boosting, however, does not improve results on this specific problem.

Colorectal cancer metastasis: the DNA repair inhibitor Dbait increases sensitivity to hyperthermia and improves efficacy of radiofrequency ablation.

PURPOSE: To assess the usefulness of combining hyperthermia with a DNA repair inhibitor (double-strand break bait [Dbait]) and its potential application to radiofrequency ablation (RFA) in a preclinical model of human colorectal cancer. MATERIALS AND METHODS: The local ethics committee of animal experimentation approved all investigations. First, the relevance was assessed by studying the survival of four human colorectal adenocarcinoma cell cultures after 1 hour of hyperthermia at 41°C or 43°C with or without Dbait. Human colon adenocarcinoma cells (HT-29) were grafted subcutaneously into nude mice (n = 111). When tumors reached approximately 500 mm(3), mice were treated with Dbait alone (n = 20), sublethal RFA (n = 21), three different Dbait schemes and sublethal RFA (n = 52), or a sham treatment (n = 18). RFA was performed to ablate the tumor center alone. To elucidate antitumor mechanisms, 39 mice were sacrificed for blinded pathologic analysis, including assessment of DNA damage, cell proliferation, and tumor necrosis. Others were monitored for tumor growth and survival. Analyses of variance and log-rank tests were used to evaluate differences. RESULTS: When associated with mild hyperthermia, Dbait induced cytotoxicity in all tested colon cancer cell lines. Sublethal RFA or Dbait treatment alone moderately improved survival (median, 40 days vs 28 days for control; P = .0005) but combination treatment significantly improved survival (median, 84 days vs 40 days for RFA alone, P = .0004), with approximately half of the animals showing complete tumor responses. Pathologic studies showed that the Dbait and RFA combination strongly enhances DNA damage and coagulation areas in tumors. CONCLUSION: Combining Dbait with RFA sensitizes the tumor periphery to mild hyperthermia and increases RFA antitumor efficacy.