¿Por qué el campesino se endeuda? : El significado de la usura medieval (Castilla, s. XV)

El objetivo de este trabajo es realizar una aproximación a las características del endeudamiento campesino en la baja Edad Media castellana. La historiografía actual, dominada por el enfoque smithiano de la comercialización y por el neo-institucionalismo, tiende a ignorar las desigualdades que reproducen las relaciones mercantiles y a enfatizar los efectos positivos de los mercados y el crédito rural. Utilizando documentación del área de los concejos de la meseta central de Castilla, se analiza la naturaleza del préstamo rural y su relación con el ciclo agrario y con la extracción feudal de renta. A partir del registro de deudas presente en los Protocolos Notariales abulenses de mediados del siglo XV, se realiza un análisis cuantitativo de la distribución de las obligaciones en el tiempo y de la repetición de acreedores y deudores. Luego se discute en términos analíticos y cualitativos la forma específica que caracteriza al capital usurario precapitalista.

¿Por qué el campesino se endeuda? : El significado de la usura medieval (Castilla, s. XV)

El objetivo de este trabajo es realizar una aproximación a las características del endeudamiento campesino en la baja Edad Media castellana. La historiografía actual, dominada por el enfoque smithiano de la comercialización y por el neo-institucionalismo, tiende a ignorar las desigualdades que reproducen las relaciones mercantiles y a enfatizar los efectos positivos de los mercados y el crédito rural. Utilizando documentación del área de los concejos de la meseta central de Castilla, se analiza la naturaleza del préstamo rural y su relación con el ciclo agrario y con la extracción feudal de renta. A partir del registro de deudas presente en los Protocolos Notariales abulenses de mediados del siglo XV, se realiza un análisis cuantitativo de la distribución de las obligaciones en el tiempo y de la repetición de acreedores y deudores. Luego se discute en términos analíticos y cualitativos la forma específica que caracteriza al capital usurario precapitalista.

¿Por qué el campesino se endeuda? : El significado de la usura medieval (Castilla, s. XV)

El objetivo de este trabajo es realizar una aproximación a las características del endeudamiento campesino en la baja Edad Media castellana. La historiografía actual, dominada por el enfoque smithiano de la comercialización y por el neo-institucionalismo, tiende a ignorar las desigualdades que reproducen las relaciones mercantiles y a enfatizar los efectos positivos de los mercados y el crédito rural. Utilizando documentación del área de los concejos de la meseta central de Castilla, se analiza la naturaleza del préstamo rural y su relación con el ciclo agrario y con la extracción feudal de renta. A partir del registro de deudas presente en los Protocolos Notariales abulenses de mediados del siglo XV, se realiza un análisis cuantitativo de la distribución de las obligaciones en el tiempo y de la repetición de acreedores y deudores. Luego se discute en términos analíticos y cualitativos la forma específica que caracteriza al capital usurario precapitalista.

Diseño de Anillo Térmico para el Patrón Nacional de Ruido

En ese trabajo se presentan los aspectos fundamentales de una parte fundamental del que será patrón nacional de ruido térmico: el anillo que realiza el contacto térmico entre los conductores interior y exterior en la parte superior de la línea coaxial del patrón de ruido. El objetivo de este dispositivo es mantener la misma temperatura en ambos conductores a la entrada del patrón y, asimismo, minimizar el efecto que pueda tener sobre la temperatura de ruido y el coeficiente de reflexión a la entrada del patrón.

Meier, un nuovo Ulisse

Richard Meier, come un novello Ulisse, ha attraversato lo stretto della fama e del riconoscimento aggiogato all'albero maestro dell'architettura con i lacci della ragione, dell'onestà e della bellezza. Le affascinanti sirene lo hanno tentato con il loro canto ammaliante: il denaro, la fama e il potere. Ma nulla potrà impedirgli di raggiungere la sua Itaca per tornare da Penelope.

Understanding sprint velocity fluctuations for improved project plans with Scrum: a case study

Starting from the documentation of high sprint velocity fluctuations in a Scrum project, this paper presents a thorough approach to identify the sources of issues arising in the context of Scrum implementation. Given that Scrum provides guidance on identifying process issues but not their root causes, various approaches are explored. This is of great relevance because Scrum defines project schedules relying heavily on sprint velocity and because it is the most widely used agile methodology. The findings provide a new approach to evaluate such fluctuations and establish a more realistic project assessment than what is currently defined by Scrum. In this respect, this paper contributes to improve the understanding of the software development process using this agile framework.

Multiresidue Analysis of Insecticides and Other Selected Environmental Contaminants in Poultry Manure by Gas Chromatography/Mass Spectrometry

An analytical method was developed for the simultaneous determination in poultry manure of 41 organic contaminants belonging to different chemical classes: pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and polybrominated diphenyl ethers. Poultry manure was extracted with a modified QuEChERS method, and the extracts were analyzed by isotope dilution GC/MS. Recovery of these contaminants from samples spiked at levels ranging from 25 to 100 ng/g was satisfactory for all the compounds. The developed procedure provided LODs from 0.8 to 9.6 ng/g. The analysis of poultry manure samples collected on different farms confirmed the presence of some of the studied contaminants. Pyrethroids and polycyclic aromatic hydrocarbons were the main contaminants detected.

Occurrence and analysis of selected pharmaceutical compounds in soil from Spanish agricultural fields

This work describes the analysis of 15 pharmaceutical compounds, belonging to different therapeutic classes (anti-inflammatory/analgesics, lipid regulators, antiepileptics, ?-blockers and antidepressants) and with diverse physical?chemical properties, in Spanish soils with different farmland uses. The studied compounds were extracted from soil by ultrasound-assisted extraction (UAE) and determined, after derivatization, by gas chromatography with mass spectrometric detection (GC?MS). The limits of detection (LODs) ranged from 0.14 ng g?1 (naproxen) to 0.65 ng g?1 (amitriptyline). At least two compounds where detected in all samples, being ibuprofen, salicylic acid, and paracetamol, the most frequently detected compounds. The highest levels found in soil were 47 ng g?1 for allopurinol and 37 ng g?1 for salicylic acid. The influence of the type of crop and the sampling area on the levels of pharmaceuticals in soil, as well as their relationship with soil physical?chemical properties, was studied. The frequent and widespread detection of some of these compounds in agricultural soils show a diffuse contamination, although the low levels found do not pose a risk to the environment or the human health.

Determination of selected pharmaceutical compounds in biosolids bysupported liquid extraction and gas chromatography?tandem massspectrometry

In this work, an analytical method was developed for the determination of pharmaceutical drugs inbiosolids. Samples were extracted with an acidic mixture of water and acetone (1:2, v/v) and supportedliquid extraction was used for the clean-up of extracts, eluting with ethyl acetate:methanol (90:10, v/v).The compounds were determined by gas chromatography?tandem mass spectrometry using matrix-match calibration after silylation to form their t-butyldimethylsilyl derivatives. This method presentsvarious advantages, such as a fairly simple operation for the analysis of complex matrices, the use ofinexpensive glassware and low solvent volumes. Satisfactory mean recoveries were obtained with thedeveloped method ranging from 70 to 120% with relative standard deviations (RSDs) ? 13%, and limitsof detection between 0.5 and 3.6 ng g?1. The method was then successfully applied to biosolids samplescollected in Madrid and Catalonia (Spain). Eleven of the sixteen target compounds were detected in thestudied samples, at levels up to 1.1 ?g g?1(salicylic acid). Ibuprofen, caffeine, paracetamol and fenofibratewere detected in all of the samples analyzed.

Simultaneous determination of multiclass emerging contaminants in aquatic plants by ultrasound assisted matrix solid phase dispersion and GC-MS

A multiresidue method was developed for the simultaneous determination of 31 emerging contaminants (pharmaceutical compounds, hormones, personal care products, biocides and flame retardants) in aquatic plants. Analytes were extracted by ultrasound assisted-matrix solid phase dispersion (UA-MSPD) and determined by gas chromatography-mass spectrometry after sylilation. The method was validated for different aquatic plants (Typha angustifolia, Arundo donax and Lemna minor) and a semiaquatic cultivated plant (Oryza sativa) with good recoveries at concentrations of 100 and 25 ng g-1 wet weight, ranging from 70 to 120 %, and low method detection limits (0.3 to 2.2 ng g-1 wet weight). A significant difference of the chromatographic response was observed for some compounds in neat solvent versus matrix extracts and therefore quantification was carried out using matrix-matched standards in order to overcome this matrix effect. Aquatic plants taken from rivers located at three Spanish regions were analyzed and the compounds detected were parabens, bisphenol A, benzophenone-3, cyfluthrin and cypermethrin. The levels found ranged from 6 to 25 ng g-1 wet weight except for cypermethrin that was detected at 235 ng g-1 wet weight in Oryza sativa samples.

Spatio-temporal distribution of pyrethroids in soil in Mediterranean paddy fields

Purpose The demand of rice by the increase in population in many countries has intensified the application of pesticides and the use of poor quality water to irrigate fields. The terrestrial environment is one compartment affected by these situations, where soil is working as a reservoir, retaining organic pollutants. Therefore, it is necessary to develop methods to determine insecticides in soil and monitor susceptible areas to be contaminated, applying adequate techniques to remediate them. Materials and methods This study investigates the occurrence of ten pyrethroid insecticides (PYs) and its spatio-temporal variance in soil at two different depths collected in two periods (before plow and during rice production), in a paddy field area located in the Mediterranean coast. Pyrethroids were quantified using gas chromatography?mass spectrometry (GC?MS) after ultrasound-assisted extraction with ethyl acetate. The results obtained were assessed statistically using non-parametric methods, and significant statistical differences (p < 0.05) in pyrethroids content with soil depth and proximity to wastewater treatment plants were evaluated. Moreover, a geographic information system (GIS) was used to monitor the occurrence of PYs in paddy fields and detect risk areas. Results and discussion Pyrethroids were detected at concentrations ?57.0 ng g?1 before plow and ?62.3 ng g?1 during rice production, being resmethrin and cyfluthrin the compounds found at higher concentrations in soil. Pyrethroids were detected mainly at the top soil, and a GIS program was used to depict the obtained results, showing that effluents from wastewater treatment plants (WWTPs) were the main sources of soil contamination. No toxic effects were expected to soil organisms, but it is of concern that PYs may affect aquatic organisms, which represents the worst case scenario. Conclusions A methodology to determine pyrethroids in soil was developed to monitor a paddy field area. The use of water fromWWTPs to irrigate rice fields is one of the main pollution sources of pyrethroids. It is a matter of concern that PYs may present toxic effects on aquatic organisms, as they can be desorbed from soil. Phytoremediation may play an important role in this area, reducing the possible risk associated to PYs levels in soil.

Experiencias en la realización y evaluación de trabajo colaborativo en asignaturas de la Licenciatura en Química, para su adaptación al nuevo Grado en Química

Póster presentado en las IX Jornadas de Redes de Investigación en Docencia Universitaria, Alicante, 16-17 junio 2011.

Well-defined mesoporosity on lignocellulosic-derived activated carbons

Activated carbons with a highly developed mesoscale cavitation-linked structure have been prepared from natural products (e.g. peach stones) by combining chemical and physical activation processes. Characterization results show that these materials exhibit a large “apparent” surface area (∼1500 m2/g) together with a well-defined mesoporous structure, i.e. large cavities connected to the external surface through narrower mesoporous necks (cavitation effects).