Anatomy, biology, physiology and basic pathology of the nail organ

The nail is the largest skin appendage. It grows continuously through life in a non-cyclical manner; its growth is not hormone-dependent. The nail of the middle finger of the dominant hand grows fastest with approximately 0.1 mm/day, whereas the big toe nail grows only 0.03-0.05 mm/d. The nails' size and shape vary characteristically from finger to finger and from toe to toe, for which the size and shape of the bone of the terminal phalanx is responsible. The nail apparatus consists of both epithelial and connective tissue components. The matrix epithelium is responsible for the production of the nail plate whereas the nail bed epithelium mediates firm attachment. The hyponychium is a specialized structure sealing the subungual space and allowing the nail plate to physiologically detach from the nail bed. The proximal nail fold covers most of the matrix. Its free end forms the cuticle which seals the nail pocket or cul-de-sac. The dermis of the matrix and nail bed is specialized with a morphogenetic potency. The proximal and lateral nail folds form a frame on three sides giving the nail stability and allowing it to grow out. The nail protects the distal phalanx, is an extremely versatile tool for defense and dexterity and increases the sensitivity of the tip of the finger. Nail apparatus, finger tip, tendons and ligaments of the distal interphalangeal joint form a functional unit and cannot be seen independently. The nail organ has only a certain number of reaction patterns that differ in many respects from hairy and palmoplantar skin.

Comparative assessment of a canine-specific medium to support colony formation from canine hair follicular keratinocytes.

BACKGROUND Follicular stem cells and their progeny are responsible for the cyclical renewal of hair follicles and maintenance of the hair coat. The understanding of pathways involved in this process is essential to elucidate the pathogenetic mechanisms of primary alopecia. Stem cells and their direct descendants are located in the bulge region of the isthmus of hair follicles. Although these cells have been studied extensively in mice and humans, data for canine isthmic keratinocyte activation and proliferation are not available. HYPOTHESIS/OBJECTIVES The aim was to establish an accurate and reliable in vitro system to study the growth potential of canine isthmic keratinocytes. We assessed the colony-promoting capability of a commercially available canine-specific medium, CELLnTEC (CnT-09), compared with a well-established home-made medium, complete FAD (cFAD). The CnT-09 medium is specific for the growth of canine keratinocytes, while the cFAD medium can support growth and colony formation of keratinocytes from several species. ANIMALS Skin biopsies were obtained from 15 recently euthanized dogs of various breeds with no skin abnormalities. METHODS The isthmic region of compound hair follicles was isolated by microdissection and cell growth monitored using several parameters with colony-forming assays. RESULTS The CnT-09 and cFAD media provided similar growth as measured by the total number and size of colonies, as well as rate of cell differentiation. CONCLUSIONS The commercial canine-specific CnT-09 medium was comparable to the home-made cFAD medium in supporting the growth and proliferation of canine follicular keratinocytes in vitro. The CnT-09 medium should be a viable alternative growth medium for molecular studies of alopecic disorders in dogs.

Comparison of peak cardiopulmonary performance parameters on a robotics-assisted tilt table, a cycle and a treadmill

Robotics-assisted tilt table (RATT) technology provides body support, cyclical stepping movement and physiological loading. This technology can potentially be used to facilitate the estimation of peak cardiopulmonary performance parameters in patients who have neurological or other problems that may preclude testing on a treadmill or cycle ergometer. The aim of the study was to compare the magnitude of peak cardiopulmonary performance parameters including peak oxygen uptake (VO2peak) and peak heart rate (HRpeak) obtained from a robotics-assisted tilt table (RATT), a cycle ergometer and a treadmill. The strength of correlations between the three devices, test-retest reliability and repeatability were also assessed. Eighteen healthy subjects performed six maximal exercise tests, with two tests on each of the three exercise modalities. Data from the second tests were used for the comparative and correlation analyses. For nine subjects, test-retest reliability and repeatability of VO2peak and HRpeak were assessed. Absolute VO2peak from the RATT, the cycle ergometer and the treadmill was (mean (SD)) 2.2 (0.56), 2.8 (0.80) and 3.2 (0.87) L/min, respectively (p < 0.001). HRpeak from the RATT, the cycle ergometer and the treadmill was 168 (9.5), 179 (7.9) and 184 (6.9) beats/min, respectively (p < 0.001). VO2peak and HRpeak from the RATT vs the cycle ergometer and the RATT vs the treadmill showed strong correlations. Test-retest reliability and repeatability were high for VO2peak and HRpeak for all devices. The results demonstrate that the RATT is a valid and reliable device for exercise testing. There is potential for the RATT to be used in severely impaired subjects who cannot use the standard modalities.

Submaximal cardiopulmonary thresholds on a robotics-assisted tilt table, a cycle and a treadmill: a comparative analysis

BACKGROUND: The robotics-assisted tilt table (RATT), including actuators for tilting and cyclical leg movement, is used for rehabilitation of severely disabled neurological patients. Following further engineering development of the system, i.e. the addition of force sensors and visual bio-feedback, patients can actively participate in exercise testing and training on the device. Peak cardiopulmonary performance parameters were previously investigated, but it also important to compare submaximal parameters with standard devices. The aim of this study was to evaluate the feasibility of the RATT for estimation of submaximal exercise thresholds by comparison with a cycle ergometer and a treadmill. METHODS: 17 healthy subjects randomly performed six maximal individualized incremental exercise tests, with two tests on each of the three exercise modalities. The ventilatory anaerobic threshold (VAT) and respiratory compensation point (RCP) were determined from breath-by-breath data. RESULTS: VAT and RCP on the RATT were lower than the cycle ergometer and the treadmill: oxygen uptake (V'O2) at VAT was [mean (SD)] 1.2 (0.3), 1.5 (0.4) and 1.6 (0.5) L/min, respectively (p < 0.001); V'O2 at RCP was 1.7 (0.4), 2.3 (0.8) and 2.6 (0.9) L/min, respectively (p = 0.001). High correlations for VAT and RCP were found between the RATT vs the cycle ergometer and RATT vs the treadmill (R on the range 0.69-0.80). VAT and RCP demonstrated excellent test-retest reliability for all three devices (ICC from 0.81 to 0.98). Mean differences between the test and retest values on each device were close to zero. The ventilatory equivalent for O2 at VAT for the RATT and cycle ergometer were similar and both were higher than the treadmill. The ventilatory equivalent for CO2 at RCP was similar for all devices. Ventilatory equivalent parameters demonstrated fair-to-excellent reliability and repeatability. CONCLUSIONS: It is feasible to use the RATT for estimation of submaximal exercise thresholds: VAT and RCP on the RATT were lower than the cycle ergometer and the treadmill, but there were high correlations between the RATT vs the cycle ergometer and vs the treadmill. Repeatability and test-retest reliability of all submaximal threshold parameters from the RATT were comparable to those of standard devices.

The Aggregate Demand for Private Health Insurance Coverage in the U.S.

This paper estimates the aggregate demand for private health insurance coverage in the U.S. using an error-correction model and by recognizing that people are without private health insurance for voluntary, structural, frictional, and cyclical reasons and because of public alternatives. Insurance coverage is measured both by the percentage of the population enrolled in private health insurance plans and the completeness of the insurance coverage. Annual data for the period 1966-1999 are used and both short and long run price and income elasticities of demand are estimated. The empirical findings indicate that both private insurance enrollment and completeness are relatively inelastic with respect to changes in price and income in the short and long run. Moreover, private health insurance enrollment is found to be inversely related to the poverty rate, particularly in the short-run. Finally, our results suggest that an increase in the number cyclically uninsured generates less of a welfare loss than an increase in the structurally uninsured.

Last Hired, First Fired? Black-White Unemployment and the Business Cycle

Past studies have tested the claim that blacks are the last hired during periods of economic growth and the first fired in recessions by examining the movement of relative unemployment rates over the business cycle. Any conclusion drawn from this type of analysis must be viewed as tentative because the cyclical movements in the underlying transitions into and out of unemployment are not examined. Using Current Population Survey data matched across adjacent months from 1989 to 2004, this paper examines labor market transitions for prime age males to test this hypothesis. Considerable evidence is presented that blacks are the first fired as the business cycle weakens. However, no evidence is found that blacks are the last hired. Instead, blacks are initially hired from the ranks of the unemployed early in the business cycle and later are drawn from non-participation. Narrowing of the racial unemployment gap near the peak of the business cycle is driven by a reduction in the rate of job loss for blacks rather than increases in hiring. There is also evidence that residual differences in the racial unemployment gap vary systematically over the business cycle in a manner consistent with discrimination being more evident in the economy at times when its cost is lower.

Regulation of T cell function by complement C5A in mice during mycobacterial infection

Tuberculosis is the leading cause of death in the world due to a single infectious agent, making it critical to investigate all aspects of the immune response mounted against the causative agent, Mycobacterium tuberculosis , in order to better treat and prevent disease. Previous observations show a disparity in the ability to control mycobacterial growth between mouse strains sufficient in C5, such as C57BL/6 and B10.D2/nSnJ, and those naturally deficient in C5, such as A/J and B10.D2/nSnJ, with C5 deficient mice being more susceptible. It has been shown that during M. tuberculosis infection, C5 deficient macrophages have a defect in production of interleukin (IL)-12, a cytokine involved in the cyclical activation between infected macrophages and effector T cells. T cells stimulated by IL-12 produce interferon (IFN)-γ, the signature cytokine of T helper type 1 (Th1) cells. It is known that a cell-mediated Th1 response is crucial for control of M. tuberculosis in the lungs of humans and mice. This study demonstrates that murine T cells express detectable levels of CD88, a receptor for C5a (C5aR), following antigen presentation by macrophages infected with mycobacteria. T cells from C5 deficient mice infected with M. tuberculosis were found to secrete less IFN-γ and had a reduced Th1 phenotype associated with fewer cells expressing the transcription factor, T-box expressed in T cells (T-bet). The altered Th1 phenotype in M. tuberculosis infected C5 deficient mice coincided with a rise in IL-4 and IL-10 secretion from Th2 cells and inducible regulatory T cells, respectively. It was found that the ineffective T cell response to mycobacteria in C5 deficient mice was due indirectly to a lack of C5a via poor priming by infected macrophages and possibly by a direct interaction between T cells and C5a peptide. Therefore, these studies show a link between the cells of the innate and adaptive arms of the immune system, macrophages and T cells respectively, that was mediated by C5a using a mouse model of M. tuberculosis infection. ^

A STUDY OF ILLNESS AND RESERVOIRS ASSOCIATED WITH GIARDIA LAMBLIA IN RURAL EGYPT

A longitudinal investigation of the health effects and reservoirs of Giardia lamblia was undertaken in forty households located in a rural Nile Delta region of Egypt. Stool specimens obtained once weekly for six months from two to four year old children were cyst or trophozoite-positive in 42 percent of the 724 examined. The mean duration of excretion in all but one Giardia-negative child was seven and one-half weeks with a range of one to 17 weeks. Clinical symptoms of illness were frequently observed within a month before or after Giardia excretion in stool of children, but a statistical inference of association was not demonstrated.^ Seventeen percent of 697 specimens obtained from their mothers was Giardia-positive for a mean duration of four weeks and a range of one to 18 weeks. Mothers were observed to excrete Giardia in stool less frequently during pregnancy than during lactation.^ Nine hundred sixty-two specimens were collected from 13 species of household livestock. Giardia was detected in a total of 22 specimens from cows, goats, sheep and one duck. Giardia cysts were detected in three of 899 samples of household drinking water.^ An ELISA technique of Giardia detection in human and animal stool was field tested under variable environmental conditions. The overall sensitivity of the assay of human specimens was 74 percent and specificity was 97 percent. These values for assay of animal specimens were 82 percent and 98 percent, respectively.^ Surface antigen studies reported from the NIH Laboratory of Parasitic Diseases show that antigens of three Egyptian human isolates are different from each other and from most other isolates against which they were tested.^ The ubiquity of human and animal fecal contamination combined with estimates of ill days per child per year in this setting are substantial arguments for the introduction of a suggested mass parasite control program to intervene in the cyclical transmission of agents of enteric disease. ^

Facies investigations on sediment core CRP-3 from the Ross Sea, Antarctica

The Cenozoic Victoria Land Basin (VLB) stratigraphic section penetrated by CRP-3 is mostly of Early Oligocene age. It contains an array of lithofacies comprising fine-grained mudrocks, interlaminated and interbedded mudrocks/sandstones, mud-rich and mud-poor sandstones, conglomerates and diamctites that are together interpreted as the products of shallow marine to possibly non-marine environments of deposition, affected by the periodic advance and retreat of tidewater glaciers. This lithofacies assemblage can be readily rationalised using the facies scheme designed originally for CRP-2/2A, and published previously. The uppermost 330 metres below sea floor (mbsf) shows a cyclical arrangement of lithofacies also similar to that recognised throughout CRP-2/2A, and interpreted to reflect cyclical variations in relative sea-level driven by ice volume fluctuations ('Motif A'). Between 330 and 480 mbsf, a series of less clearly cyclical units, generally fining-upward but nonetheless incorporating a significant subset of the facies assemblage, has been identified and noted in the Initial Report as 'Motif B' Below 480 mbsf, the section is arranged into a repetitive succession of fining-upward units, each of which comprises dolerite clast conglomerate at the base passing upward into relatively thick intervals of sandstones. The cycles present down 480 mbsf are defined as sequences, each interpreted to record cyclical variation of relative sea-level. The thickness distribution of sequences in CRP-3 provides some insights into the geological variables controlling sediment accumulation in the Early Oligocene section. The uppermost part of the section in CRP-3 comprises two or three thick, complete sequences that show a broadly symmetrical arrangement of lithofacies (similar to Sequences 9-11 in CRP-2/2A). This suggests a period of relatively rapid tectonic subsidence, which allowed preservation of the complete facies cycle. Below Sequence 3, however, is a considerable interval of thin, incomplete and erosionally truncated sequences (4-23), which incorporates both the remainder of Motif A sequences and all Motif B sequences recognised. The thinner and more truncated sequences suggest sediment accumulation under conditions of reduced accommodation, and given the lack of evidence for glacial conditions (see Powell et al., this volume) tends to argue for a period of reduced tectonic subsidence. The section below 480 mbsf consists of a series of fining-upward, conglomerate to sandstone intervals which cannot be readily interpreted in terms of relative sea-level change. A relatively mudrock-rich interval above the basal conglomerate/breccia (782-762 mbsf) may record initial flooding of the basin during early rift subsidence. The lithostratigraphy summarised above has been linked to seismic reflection data using depth conversion techniques (Henrys et al., this volume). The three uppermost reflectors ('o', 'p' and 'q') correlate to the package of thick sequences 1-3, and several deeper reflectors can also be correlated to sequence boundaries. The package of thick Sequences 1-3 shows a sheet-like cross-sectional geometry on seismic reflection lines, unlike the similar package recognised in CRP-2/2A.

Grain size analysis on CRP sediment cores from the Ross Sea, Antarctica

The upper 1200 m of pre-Pliocene sediment recovered by Cape Roberts Project (CRP) drilling off the Victoria Land coast of Antarctica between 1997-1999 has been subdivided into 54 unconformity-bound stratigraphic sequences, spanning the period c. 32 to 17 Ma. The sequences are recognised on the basis of the cyclical vertical stacking of their constituent lithofacies, which are enclosed by erosion surfaces produced during the grounding of the advancing ice margin onto the sea floor. Each sequence represents deposition in a range of offshore shelf to coastal glacimarine sedimentary environments during oscillations in the ice margin across the Western Ross Sea shelf, and coeval fluctuations in water depth. This paper applies spectral analysis techniques to depth- and time-series of sediment grain size (500 samples) for intervals of the core with adequate chronological data. Time series analysis of 0.5-l.0m-spaced grainsize data spanning sequences 9-11 (CRP-2/2A) and sequences 1-7 (CRP-3) suggests that the length of individual sequences correspond to Milankovitch frequencies, probably 41 k.y., but possibly as low as 100 k.y. Higher frequency periodic components at 23 k.y. (orbital precession) and 15-10 k.y. (sub-orbital) are recognised at the intrasequence-scale, and may represent climatic cycles akin to the ice rafting episodes described in the North Atlantic Ocean during the Quaternary. The cyclicity recorded by glacimarine sequences in CRP core provides direct evidence from the periphery of Antarctica for orbital oscillations in the size of the Oligocene-Early Miocene East Antarctic Ice Sheet.

Economía e ideología en el franquismo : tensiones entre utopía y pragmatismo 1945 -1970

El presente trabajo enfoca desde una perspectiva comparativa y analítica algunos aspectos de la economía y la sociedad españolas durante años especialmente interesantes de la dictadura franquista. Se efectúa una revisión de la ideología con la que el régimen pretendió encarar, a través de un proyecto autárquico, inicialmente muy marcado por el modelo fascista, el despegue económico de España y los virajes posteriores originados en las tensiones surgidas en el seno de la sociedad y de los paradigmas externos que marcaban el rumbo hacia una integración de bloques. Como fecha límite de este estudio se presentan los últimos años de la década del '60, puesto que parecen constituir el cierre de un ciclo. En cuestiones ideológico-políticas ese cierre estuvo signado por el ascenso del almirante Carrero Blanco a una posición clave y la sustitución de los viejos falangistas por un grupo más homogéneo de "tecnócratas" del capitalismo moderno. En materia económica también se completó entonces un período de crecimiento sin precedentes en la economía española que hacia 1973/74 entró en una meseta, parte de la crisis cíclica compartida por la economía mundial.

Estado, sociedad y medios de comunicación : contribuciones para pensar la política

El trabajo tiene el propósito de indagar, en la teoría social latinoamericana, la relación entre Estado, sociedad y medios de comunicación. Aunque esta intención expresa un carácter eminentemente teórico se sustenta en la intrincada e ineludible relación entre teoría y realidad social. Relación que nos lleva a preguntarnos por la concreción de las prácticas políticas hoy vigentes. Esto implica re-pensar no solamente los modelos de Estado en pugna, que van desde la intervención pro-cíclica y distributiva a los que lo definen como mero reproductor de la explotación y la desigualdad, sino también por las distintas concepciones de individuo-sociedad que trasvasan dichos modelos y el rol que dichos modelos le asignan a los medios de comunicación. Se trata, entonces, de rescatar los aportes que se construyeron desde los enfoques del desarrollismo y la dependencia, por entenderlos válidos y pertinentes para analizar la realidad actual de nuestro continente. Ciertamente, muchos de los problemas estructurales actuales de las sociedades capitalistas latinoamericanas se pueden pensar a la luz de esos aportes que comenzaron a construirse en la década de los ´60. La noción de desarrollo, con distintas variantes, no sólo es una constante en el pensamiento latinoamericano sino que atraviesa la política contemporánea.

Concepciones de un grupo de profesores de inglés de Venezuela sobre la expansión, uso y enseñanza del inglés como idioma internacional

Esta investigación, orientada bajo un enfoque cualitativo-interpretativo, describe las concepciones de un grupo de setenta y ocho profesores de inglés de los niveles de Educación Media General y Educación Universitaria de la ciudad de San Cristóbal, Venezuela, sobre la expansión, uso y enseñanza del inglés como idioma internacional. Desde una perspectiva crítica y posestructuralista en la que se concibe al inglés como un fenómeno social cargado de ideologías y valores culturales, este estudio pretende dar cuenta de las conexiones existentes entre el inglés y las fuerzas económicas, políticas, sociales e ideológicas que subyacen detrás de su expansión, uso y enseñanza en el mundo (Holliday, 2005, 2006, 2013; Pennycook, 1994; Phillipson, 1992, 2010), y la forma en como estas conexiones son percibidas por los profesores de inglés de un contexto específico de la periferia (Canagarajah, 1999a). Para la exploración en profundidad del fenómeno se adopta en este estudio el método fenomenológico (Colás, 1998b) como propuesta metodológica para descubrir la forma en que los profesores de inglés de este contexto específico comprenden el fenómeno y conciben la expansión, uso y enseñanza del inglés como idioma internacional. Como instrumentos para la recolección de los datos se utilizan dos cuestionarios con preguntas abiertas y cerradas administrados por internet a los participantes, y entrevistas semi-estructuradas cara a cara en profundidad con nueve profesores seleccionados como informantes clave. Para el análisis de los datos se toma el proceso analítico de Strauss y Corbin (2002), proceso que apunta hacia la generación inductiva de teoría a través de la comparación constante de los datos para formar categorías. En este estudio, el análisis de los datos comprende un proceso integral y cíclico que toma en cuenta los datos provenientes de todos los participantes y de todos los instrumentos de recolección. También se hace uso técnico del software Atlas.ti versión 6.0 para el almacenamiento y xivmanipulación sistemática de las entrevistas semi-estructuradas en profundidad. Entre los hallazgos se devela una complejidad enmarcada en el estudio de las concepciones de los profesores de este contexto sociocultural específico que resultan ser fluidas y en oportunidades simultáneamente contradictorias entre sí sobre la expansión, uso y enseñanza del inglés como idioma internacional. En tal sentido, los resultados reflejan poca conciencia crítica de los participantes sobre la hegemonía del inglés en el mundo y su percepción del idioma como un asunto necesario y beneficioso para la comunicación internacional, de allí que consideren su enseñanza y aprendizaje como necesarios en todos los contextos del mundo. Este estudio también expresa una concientización de los participantes en algunos aspectos específicos como su sentido de propiedad del idioma y su percepción como hablantes y docentes competentes del inglés en un contexto específico. Asimismo, revela algunos asuntos sociopolíticos enmarcados en la dicotomía 'nativo' - 'no nativo' del inglés fundamentado en el concepto del 'native speakerism'. Al mismo tiempo, muestra la concepción de los participantes sobre la enseñanza del inglés como una actividad apolítica y neutral aunque simultáneamente refleja su inclinación hacia la promoción del pensamiento crítico y reflexivo de los estudiantes a través de sus clases de inglés

Cambios en la estructura económica social y conflictos sociales en el noroeste del Chubut 1990-2005

Buscamos avanzar en el conocimiento sobre cómo se desarrolla el movimiento de la sociedad argentina en su conjunto, analizado desde un caso particular que es el noreste del Chubut en el período que va desde la imposición de la hegemonía del capital financiero en 1989-1990 hasta el año 2005. Se pretende en esta tesis entender y conceptualizar en términos científicos cómo se mueve esa sociedad, de qué son expresión cada uno de sus conflictos, qué expresan los distintos sectores que se movilizan, qué expresan los cambios estructurales que se desarrollan, etc. Desde esta perspectiva nos interesa específicamente poder aportar al debate sobre cuáles son las opciones de plantear un proyecto alternativo de desarrollo para la provincia, la región y el país. Dentro del tema general de buscar comprender el movimiento de la sociedad, realizamos un abordaje de la realidad desde la utilización de un conocimiento acumulado y desde un recorte de esa realidad. Ese recorte lo realizamos a dos niveles. En primer lugar en términos espaciales: tomamos como base una región que denominamos el noreste de Chubut. Recortamos de la provincia del Chubut al área que tuvo el mayor crecimiento vinculado a los programas de polos de desarrollo durante las décadas del '60, '70 y parte del '80. La misma está delimitada por los actuales departamentos de Rawson y Biedma, de acuerdo a la división administrativa que toma la provincia desde 1957. En segundo lugar realizamos un recorte en términos temporales: abordamos como objeto de estudio al movimiento de la sociedad en esa región durante el período que va de 1989-1990 hasta el 2005. Consideramos que tomar este período nos permite observar el proceso de cambios que se generan con la realización de la hegemonía del capital financiero y el proceso de protestas, luchas y conflictos sociales que en el marco de estos cambios se desarrollan en la sociedad. La decisión de estudiar hasta el 2005 parte de considerar relevante comprender cómo continua el proceso después del 2001-2002. En esos años se produce la recuperación de la economía nacional, con un gran impulso para la región, lo cual genera el interés de poder precisar de qué se trata esta 'recuperación' y si estamos ante un movimiento orgánico o coyuntural de la economía. El período también nos permitió profundizar en el debate de las relaciones de fuerzas políticas, al hacer observable el período en que la burguesía logra recuperar la representación institucional como expresión legítima de la sociedad y consigue frenar la protesta social

Sequías en el sudoeste bonaerense : Vulnerabilidad e incertidumbre

Las sequías se caracterizan por tener un comportamiento cíclico, lo que permite prever, en cierto modo, la probabilidad de su ocurrencia. Sin embargo, en el sudoeste bonaerense las medidas preventivas para mitigar sus efectos en la actividad agropecuaria son insuficientes. La Ley de Emergencia Agropecuaria (LEA) considera la sequía como un fenómeno puramente meteorológico, mientras que nuestro enfoque la aborda como producto de la vulnerabilidad social, consecuencia de una gestión deficiente y de la imprevisión por parte de los productores agropecuarios afectados. El recorte espacial de esta presentación abarca los partidos que conforman el Plan de Desarrollo del Sudoeste Bonaerense; y el temporal, el período 2001-2006, por la significativa ocurrencia de sequías. La sequía no necesariamente es un hecho catastrófico, sino que se da como una 'construcción social de riesgos' (García Acosta, 2005; Lavell, 2000), resultado de la falta de previsión y de la incertidumbre.