Altitudinal gradient

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Thermal quality along an altitudinal gradient for a lizard community in Sierra del Ajusco and Pedregal de San Ángel, Mexico

Thermal quality along an altitudinal gradient for a lizard community in Sierra del Ajusco and Pedregal de San Ángel, Mexico

Abstract. We evaluated and compared the thermal quality for a lizard community (9 species) in Sierra del Ajusco and Pedregal de San Ángel (central Mexico) along an altitudinal gradient (2 320-3 530 m) to determine whether different thermal environments may be influencing species distribution and thermoregulatory behavior. Six areas that differ in elevation and vegetation type are chosen to survey environmental operative temperatures. Habitat thermal quality is estimated from the mean deviation of operative temperatures from lizards’ selected thermal range. Results indicate 3 key findings: 1) operative temperature and thermal quality are higher at lower elevations (2 320 and 2 540 m), where xeric scrub vegetation was abundant; 2) thermal quality is lowest in closed-canopy pine forest (2 870 and 3 220 m); and 3) intermediate values of operative temperature and thermal quality are observed in open grassland habitat (3 000 and 3 530 m). These results support our hypothesis that elevation and vegetation type affect thermal quality and we conclude that thermal ecology studies should be conducted at multiple spatial scales to gain a better understanding of factors influencing the thermal niche and thermoregulatory profiles.
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Spatial distribution of pollen along an altitudinal gradient in Michoacán, Mexico

Spatial distribution of pollen along an altitudinal gradient in Michoacán, Mexico

El análisis de componentes principales mostró la influencia del gradiente altitudinal en la zona, por lo que ordenó a los taxa encontrados en 3 grupos. Un grupo de elementos tropicales, en donde se encuentran elementos arbóreos tropicales como Bombacaceae, Ericaceae, Anacardiaceae, Ficus, Acacia, Tiliaceae y Myrtaceae. Un grupo de elementos templados con Pinus, Betulaceae y Quercus, y un tercer grupo caracterizado por elementos secundarios como Croton, Gramineae, Euphorbiaceae y Compositae (Fig. 4). El APC (análisis de componentes principales) (Fig. 5) y el análisis de discriminantes (Fig. 6) aplicado a los sitios de colecta encuentra 2 grandes grupos: uno formado por los lugares ubicados en Tzitzio, en donde la selva baja caducifolia es la vegetación dominante y otro grupo, reúne los sitios que se ubican en Ichaqueo y La Escalera, caracterizados por un bosque templado.
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Diversidad arbórea a diferentes niveles de altitud en la región de El Salto, Durango

Diversidad arbórea a diferentes niveles de altitud en la región de El Salto, Durango

The presence of plant species is a function of altitude; therefore, the purpose of this study was to estimate and compare tree diversity on the altitudinal gradient of the El Salto, Durango region. Twelve forest communities were selected from between 1 500 and 3 000 m, which was divided into five intervals of 300 m each. A total of 268 circular sites of 0.1 ha were randomly distributed proportionally for each interval, where species richness (S), proportional diversity indexes of Shannon-Wiener (H’) and Simpson (l), of Pielou’s equity (J’) and dominance of Simpson (E l ) were determined. Comparison of tree diversity between altitudes was made on the Shannon-Wiener index using the Hutcheson t-test. Species richness varied from 14 to 25 taxa, the Shannon-Wiener index from 1.94 to 2.67 and Simpson’s 0.09 to 0.18. Equity and dominance by Pielou and Simpson suggest that species abundance tends to be heterogeneous. The Hutcheson t test showed that there are significant differences in species diversity between altitudinal intervals.
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Diversidad de murciélagos en un gradiente altitudinal en el estado de Nuevo León, México

Diversidad de murciélagos en un gradiente altitudinal en el estado de Nuevo León, México

The bats are the second group of mammals and its ecological funtions makes of them an important component of the ecosystem as hunters of insects, pollinators and seed dispersers. Despite the ecological relevance in Nuevo Leon, there are no studies that compare the species composition at different altitudinal ranges. The aim of this study was to identify how the bat species are distributed at different altitudes and vegetation types. The bats were monitored by three consecutive nights, from January to Agust 2014, at three different altitude ranges and vegetation types: (i) 350 m, with Tamaulipan thorn scrub; (ii) 1600 m, Pine-Oak forest; (iii) 2000 m, creosote bush scrub, which are located in Linares, Iturbide and Galeana respectively. To identifying bats species I used an acoustic detector and a Sony brand recorder was used, a total of 8.640 minutes of bat activity were recorded. Each record was analyzed; by using the BatSound Pro. The voices of the recorded species were identified by comparing the sonograms with a library of sounds, generated by capturing bats in mist nets and sonograms of previous studies. Twenty two bat species belonging to four families, six subfamilies, and 15 genera were identified, representing 16% of the quiropterofauna to Mexico and 61% for Nuevo León. The BPE (1600 m) counted with the highest species richness (16), a Margalef diversity index of 15.82 and with a representation of 89%. The best represented trophic guild was the insectivores (18 species). Seasons analysis showed no significant differences (p = 0.4691), however, the stations with higher richness summer in Iturbide and Galeana in autumn (13 species), while the analysis of rain seasonlaity showed a significant difference (p = <0.05) with higher species rincnesfinding greater bat species richenss during the rainy season, with 19 species, and, seven unique records. Itstated that species richness is influenced by the altitudinal gradient, which is responsible for landscape heterogeneity, also I this study helped to generate the first acoustic data from insectivorous bats for the State of Nuevo León.
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Distribución y correlación espacial de especies arbóreas por gradiente altitudinal en la Selva Lacandona, Chiapas

Distribución y correlación espacial de especies arbóreas por gradiente altitudinal en la Selva Lacandona, Chiapas

In this paper the distribution and spatial correlation patterns of tree species along an altitudinal gradient in the Metzabok Protected Natural Area (PNA) in the Selva Lacandona, Chiapas State was analyzed. A 20 × 50 m sampling unit (SU) was installed in each altitudinal strata (AS), and divided into 10 sampling subunits (SSU) of 10 x 10 m targeting pole-sized trees. Within each SSU, one 5 × 5 m plot was installed to register the saplings, and within this, another two 2 × 2 m plots were established for the sampling of seedlings. The spatial distribution of pole-sized trees, saplings and seedlings was analyzed with the Morisita-Horn index; whereas the distribution and spatial correlation of pole-sized trees by height categories (lower, middle and higher) and AS was evaluated using Ripley’s univariate K(t) and bivariate K 12 (t) functions. The mean spatial
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Last century forest productivity in a managed dry edge Scots pine population: The two sides of climate warming

Last century forest productivity in a managed dry edge Scots pine population: The two sides of climate warming

In this study, we use such a historical long-term data set with 113 yr of forest information recorded at decadal resolution in a continental Mediterranean Scots pine (Pinus sylvestris) forest situated in Central Spain along a 900-m ample altitudinal gradient. We evaluate how climatic drivers and management have influenced forest productivity over the last century. Specifically, we ask (1) What was the effect of known climatic stressors (winter coldness and summer drought) on forest productivity? (2) How does forest productivity response to climate warming across the altitudinal gradient? (3) To what extent did historical management practices modulate these responses and what potential does thus exist for manage- ment to buffer climate change impacts? We considered two components of forest productivity: forest growth, which is estimated as the stand volume of adult trees, and forest ingrowth, corresponding to growth of dominated individu- als reaching the canopy. We hypothesize that (1) warm winter temperatures and cool and wet summer conditions enhance forest productivity; (2) forest responses to climate vary along the altitudinal gradient, with larger temperature sensitivity toward higher elevations and larger drought stress toward lower elevations; and (3) forest responses to climate depend on management, specifically that lower stand volume reduces the vulnerability to drought stress.
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Eventos geomorfológicos e hidrológicos en el extremo noroccidental de la Sierra Nevada de Santa Marta  Diciembre de 1999 :informe técnico

Eventos geomorfológicos e hidrológicos en el extremo noroccidental de la Sierra Nevada de Santa Marta Diciembre de 1999 :informe técnico

En el área de estudio se presentan procesos morfodinámicos influenciados por la litología, la configuración del terreno, las pendientes y el clima, con una variación altitudinal e incrementos marcados de la precipitación, esto hace que la zona presente una alta dinámica de vertientes con movimientos en masa, disección profunda y escurrimiento superficial y concentrado especialmente en las formas de cuchillas de disección de las partes altas de las cuencas de los ríos Gaira, Manzanares, piedras, Mendiguaca, Guachaca y Buritaca, donde dominan esquistos Cretácicos y arenas de desagregación en rocas graníticas del Terciario, con suelos residuales superficiales, alta densidad de cobertura vegetal y baja intervención antrópica.
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Sea breeze in the Colombian Caribbean coast

Sea breeze in the Colombian Caribbean coast

A great number of urban centers are located close to the coastal zones, thus it is necessary to determine how safe these areas are both for the population and tourists. For this reason, it is crucial to know the detailed processes of ocean-atmospheric interaction in such zones. Sea breeze is one of these phenome- na that are present in coastal zones, and it has great importance. Sea breeze circulation is a well-known mesoscale system, boosted by the properties of re- ception and storage of thermal energy between land and sea. It is caused by the pressure gradient gener- ated between land and sea, originated by the uneven warming of these two environments as a result of dif- ferent caloric capacities. The temperature difference between the two surfaces generates a local horizontal pressure gradient that pushes winds of high pressure zones into low pressure zones, creating a sea breeze towards the land during the day, and a breeze from land to sea during the night (Simpson, 1994, 1995). The strength, intensity, and direction of a sea breeze can be modified through different ways due to the local orography. When the sea breeze starts blowing, it moves towards the inner land perpendicular to the shore; therefore, if the coast is straight, a uniform
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Abundancia altitudinal de ratones en la Reserva Biológica Uyuca, Honduras

Abundancia altitudinal de ratones en la Reserva Biológica Uyuca, Honduras

Abstract: The Uyuca Biological Reserve is a very rich habitat of flora and fauna, but with little research in mammals, especially small mammals. The objectives were to determine whether the abundance of rodents captured is related to rainfall patterns and altitudinal gradient and to develop a dichotomous key according to literature. Altitudinal strata of 1,700, 1,800 and 1,900 msnm were sampled in the months of May and July. Placing 40 Sherman traps baited with oats and peanut butter 10 m apart from one other along the path in each stratum. Univariate analysis of variance shows that both factors "month" and "altitude" individually influence in the "catch" dependent variable. The Tukey test reveals that there is significant difference between the strata 1,700 and 1,900 msnm. Although the Management plan lists 16 potential small rodents for the Uyuca Biological Reserve, we were only able to confirm two in the present study.
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Determinación de la relación poblacional de tres especies forestales, Aegiphila erruginea, Oreopanax ecuadorensis, Vallea stipularis; en el bosque Leonan de Llucud, cantón Chambo, provincia de Chimborazo

Determinación de la relación poblacional de tres especies forestales, Aegiphila erruginea, Oreopanax ecuadorensis, Vallea stipularis; en el bosque Leonan de Llucud, cantón Chambo, provincia de Chimborazo

Se observo que en el piso altitudinal B solo encontramos a Vallea stipularis y a Oreopanax ecuadorensis Seem dentro de sus subparcelas sin la presencia de otras especies adultas en sus alrededores lo cual nos indica que estas especies presentan gran afinidad, determinándose entre estas una relación poblacional afín. Se hace necesario mencionar que en este piso altitudinal de encontró dos individuos de Aegiphila ferruginea los mismos que han sido cortados, se los identifico por los rebrotes que estos presentaban; en un inventario práctico realizado por el ingeniero Oscar Guadalupe en 2017 con los estudiantes de la escuela de Ingeniería Forestal de la ESPOCH se identificó un mayor número de individuos adultos de esta especie por lo que se puede emitir que esta especie es sometida a una explotación por parte de las personas que viven en los alrededores logrando casi la pérdida total de esta especie en el bosque en estudio.
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Distribución altitudinal de helechos en el cerro Uyuca, Honduras

Distribución altitudinal de helechos en el cerro Uyuca, Honduras

Resumen. Debido a su ubicación geográfica, Honduras posee una gran diversidad de plantas vasculares, entre ellas los helechos. A pesar de que los helechos son un grupo de plantas muy importante por la cantidad de especies y su alto rango de distribución, no se cuenta con un inventario de helechos como el de Nicaragua, El Salvador, Guatemala y Costa Rica. Tampoco existen inventarios completos para todas las zonas protegidas, un ejemplo de esto es el cerro Uyuca que contaba con dos estudios en los que se enlistaban 31 y 45 especies, pero no cubrían toda la reserva, sino en el núcleo que es la zona más protegida. En vista de esto, se definió como objetivo de este estudio conocer las especies de helechos de toda la reserva, incluyendo zona de amortiguamiento y zona núcleo de los dos municipios San Antonio de Oriente y Tatumbla. La metodología consistió en realizar transectos de 50x2 m en pisos altitudinales ubicados entre los 1,000 y 2,000 msnm de la reserva, para tener una distribución altitudinal, además de giras de colecta que permitieron ver la distribución por especie. Entre los resultados más importantes se tienen: el registro de 77 especies de 18 familias, 5 especies de helechos arborescentes dentro del apéndice II de CITES y especies identificadas de la zona de amortiguamiento y núcleo.
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Diversidad y distribución altitudinal de orquídeas terrestres del cerro Uyuca

Diversidad y distribución altitudinal de orquídeas terrestres del cerro Uyuca

Resumen. Debido a las condiciones climáticas, Honduras está beneficiada por una amplia gama de orquídeas epífitas. Sin embargo, carece de información acerca de orquídeas terrestres, por la falta de investigación, a pesar de sus beneficios como bioindicadores. Se realizó un estudio en la Reserva Biológica Uyuca, el cual tuvo como objetivos: establecer una línea base a través de un inventario de orquídeas terrestres durante los meses de junio, julio y agosto del 2015, conocer la diversidad de especies por cada rango altitudinal e identificar su fenología. La metodología del estudio consistió en la ubicación de 5 transectos distribuidos en cada rango altitudinal, dando un total de 35 transectos por los 7 rangos altitudinales desde los 1300 a los 2000 msnm. Para determinar la diversidad se usaron los índices de Shannon-Wiener (H´) y Simpson (λ). Se utilizó la información del Herbario Paul C. Standley para establecer una base de datos que incluyó la fenología y distribución altitudinal por cada especie. Los resultados para el inventario dieron un total de 26 especies distribuidas en 15 géneros, de las cuales 7 no se encuentran registradas para Uyuca. El índice de biodiversidad de Shannon-Wiener resultó en H´= 2.53 y la dominancia de Simpson en λ= 0.12, demostrando que en el Uyuca hay una diversidad moderada y con tendencia a aumentar a medida que se incrementa el esfuerzo de muestreo. Se observó que algunas especies pueden ser vulnerables ante cambios en el entorno y pueden verse afectados por factores climáticos y antropogénicos.
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Aportes a la cronología de los asentamientos agropastoriles de la Puna de Jujuy

Aportes a la cronología de los asentamientos agropastoriles de la Puna de Jujuy

Este sitio, que fue trabajado por Ottonello de García Reinoso (1973) y también por Alfaro de Lanzone (1988), se emplaza en el piso altitudinal Serrano Inferior sobre fondo de valle. Se trata de un sitio de tipo semiconglomerado ubicado entre altos paredones rocosos que supieron contener gran cantidad de estructuras funerarias de tipo chullpa y comprende diferentes sectores de ediicación. En el extremo oriental se encuentran recintos de planta circular formando un núcleo discreto, en la parte media se ubican amplios recintos de planta cuadrangular y, más hacia el oeste, un sector con recintos de planta rectangular de menor tamaño asociados a espacios pircados algo mayores. En el extremo occidental del asentamiento se ubica una elevación natural sobre la cual se ubica una plataforma y a la cual conduce una escalinata de piedra. Al pie de esta construcción se destaca un gran espacio abierto que separa a la estructura escalonada del área habitacional (tabla 12).
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Numerical Implementation of Gradient Algorithms

Numerical Implementation of Gradient Algorithms

In Figure 1, the implementation of an instance of a Hopfield network of dimension n = 30 is depicted, showing the discretization with the discrete gra- dient method and the conventional Hopfield network. Since the trajectories of the 30 components of the state are not particularly informative, only the values of the target function at each state are presented. The graphs show that both algorithms converge to the same equilibrium, thus the attained value of the target function is the same. However, the discrete gradient method converges significantly faster since, for instance, reaching the value V = −600 requires a 20 percent less in the number of computed iterations, approximately. In Fig- ure 2, the values of the target functions along the simulated trajectories with both methods are shown as the percentage that the discrete gradient method is lower than the value achieved by the conventional method. At some stages of the network evolution, the discrete gradient algorithm provides a value of the target function that is almost 80 percent lower than that of the conventional Hopfield method, using the absolute value of the minimum of both values as a base. Note that faster convergence of a method is a significant finding, since it could mean that a quasi-optimal solution is obtained with reasonable computational cost, where is the computing time of a slower algorithm may be unaffordable.
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Structure and natural regeneration in iberian pine forests: implications for management = Estructura y regeneración de los pinares ibéricos: implicaciones para la gestión

Structure and natural regeneration in iberian pine forests: implications for management = Estructura y regeneración de los pinares ibéricos: implicaciones para la gestión

Part of the unexplained variance detected in the small-scale studies (Fig. 3.6) could be due to factors operating at larger scales. Therefore, Scots pine regeneration was analyzed at the cutblock scale (ca. 40 ha; Chapter 4). In addition to the small-scale clustering observed in Chapters 2 and 3, a tendency towards clustering at larger scales was also observed. A regeneration patch size of 400 m (and repetition of the spatial pattern) was found under a group shelterwood system (Fig. 4.4a) and a spatial gradient of approximately 300 m under a uniform shelterwood system (Fig. 4.4b). Soil properties were the most important factor controlling post-harvest Scots pine regeneration at the cutblock scale under both shelterwood systems (Table 4.4). Regeneration was concentrated where organic materials were removed, indicating that a degree of ground level disturbance to break up the herb or organic layer at the stand level may be required for regeneration establishment, depending upon the shelterwood system used. These results are consistent with previous studies that have found higher densities of pine regeneration in mineral soils in Mediterranean forests (Pinus sylvestris in the northeast and south of Spain; González-Martínez and Bravo, 2001; and Pinus nigra in the east of Spain; del Cerro Barja et al., 2009). The effect of retained trees on regeneration density at the stand scale level, evaluated with a spatially explicit competition index (IPOT), was not very significant (Table 4.4) supporting the results described in most studies of Scots pine regeneration in boreal forests (Ruuska et al., 2006; Siipilehto, 2006). The variation in regeneration density because of competition was found only for the uniform shelterwood, with a higher variation in competition. After including the spatial metrics as explanatory variables in the model, the importance of the interaction between fine-scale and coarse-scale processes on regeneration density was suggested by the large percent of explained deviance for the shared spatial-non-spatial variables (Table 4.5).
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Influencia de los sistemas de producción y pisos altitudinales en la composición bioquímica y rendimiento del pasto nicarión (Setaria sphacelata), Distrito Molinopampa, Amazonas

Influencia de los sistemas de producción y pisos altitudinales en la composición bioquímica y rendimiento del pasto nicarión (Setaria sphacelata), Distrito Molinopampa, Amazonas

En el presente trabajo de investigación tuvo como objetivo evaluar el efecto del sistema de producción y piso altitudinal en la composición bioquímica y rendimiento del pasto nicarión (Setaria sphacelata), en el distrito de Molinopampa, tomando en cuenta dos pisos altitudinales, comprendidos entre los 2000-2400 m.s.n.m. y 2401-2800 m.s.n.m., en cuanto a los sistemas de producción se consideró el sistema silvopastoril y el sistema de pastoreo a campo abierto. En cada piso altitudinal se identificaron tres parcelas con pasto nicarión (Setaria sphacelata) bajo sistema silvopastoril y sistema de pastoreo de campo abierto haciendo un total de 12 parcelas con tres repeticiones. Así mismo se consideró como parámetros de evaluación el rendimiento y el aporte nutricional como, proteína, fibra cruda, almidón, azucares, fibra detergente neutra (FDN) y fibra detergente ácida (FDA). Los datos obtenidos fueron procesados mediante la prueba t-Student al 5% (p<0.05) de significancia, teniendo como resultado que en los sistemas de producción se encontró diferencia significativa en el rendimiento (.000 *), también se encontró diferencia significativa en la proteína (.008 *), en los azucares (.032 *) y en la fibra detergente neutra (.017 *). En cuanto al piso altitudinal se encontró diferencia significativa en la fibra cruda (.019 *), también en los azucares (.008 *) y fibra detergente acida (.000 *).
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Biometria, febrer 2013

Biometria, febrer 2013

A l’hora de deduir l’orientació de les serralades mitjançant el gradient, no sols ens podem centrar en l’angle del gradient en un píxel concret ja que estima- ríem l’orientació a una escala massa fina i seria molt sensible al soroll de la imatge de la ditada i a la mateixa resolució del sensor. Aquest és el motiu pel qual ja hem dit que calcularem el valor de l’orientació donada una finestra local (una zona entorn del píxel que cal analitzar). D’altra banda, no podem simplement calcular la mitjana dels angles dins d’aquesta finestra. L’orientació mitjana de dues serralades amb orientacions 5 i 175° no és 90°, com resultaria de portar a terme una mitjana aritmètica, sinó 0°. A més a més, el concepte de la mitjana de l’orientació no està sempre ben definit. Considerem dues serrala- des amb orientacions 0° i 90°. L’orientació mitjana pot ser de 45° o de 135°. En la figura 15 es mostren dues serralades, el valor de la mitjana d’orientació angular, θ′ xy , i el valor de la mitjana aritmètica, a xy .
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Automated detection and classification of brain injury lesions on structural magnetic resonance imaging

Automated detection and classification of brain injury lesions on structural magnetic resonance imaging

‘Fast retina keypoint’ (FREAK) descriptor (Alahi, Ortiz & Vandergheynst 2012) is similar to BRISK, hence it is based on patterns, and to ORB, since it also uses machine learning techniques. Whereas BRIEF uses random pairs, ORB uses learned pairs and BRISK uses a circular pattern where points are equally spaced on circles concentric. FREAK uses the retinal sampling grid which is also circular with the difference of having higher density of points near the center. Each sampling point is smoothed with a Gaussian kernel where the radius of the circle represents the size of the standard deviation of the kernel. As previously mentioned, this descriptor follows ORB’s approach and it tries to learn the pairs by maximizing variance of the pairs and taking pairs that are not correlated. The first pairs selected mainly compare sampling points in the outer rings of the pattern whilst the last pairs compare mainly points in the inner rings of the pattern. This is similar to the way the human eye operates. With the aim of compensating rotation changes, it measures the orientation of the singular point and rotates the sampling pairs my measure angle, similar to BRISK. But FREAK uses a predefined set of 45 symmetric sampling pairs. ‘Gauge-SURF’ (G-SURF) descriptor (Alcantarilla, Bergasa & Davison 2013) is a variant of SURF based on second-order multi-scale gauge derivatives. G-SURF derivatives are evaluated relative to the gradient direction at every pixel, whereas SURF derivatives are all relative to a single chosen orientation. It describes each pixel in the image in such way that the descriptor is the same even in the image is rotated.
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Optimized Diffusion Weighting Gradient Waveform Design (ODGD) formulation for motion compensation and concomitant gradient nulling

Optimized Diffusion Weighting Gradient Waveform Design (ODGD) formulation for motion compensation and concomitant gradient nulling

Recently, Aliotta et al. (21) proposed a novel algorithm, termed Convex Optimized Diffusion Encoding (CODE), to design gradient waveforms with first- and/or second-order moment-nulling. By formulating the gradient waveform design problem as a constrained nonlinear optimization problem (with constraints including sequence timing, hardware limits, and moment-nulling), CODE enables flexible design of gradient waveforms and seeks to minimize the achievable TE for a desired b-value (or conversely, to maximize the achievable b-value for a given TE). By approximating this constrained optimization formulation as a convex (linear) optimization problem (instead of the original nonlinear, non-convex quadratic problem), CODE results in simplified computation. However, because of this approximation, it is unclear whether CODE results in optimal waveforms, i.e., whether it achieves the minimum TE for a given desired b-value. This optimality is critical for moment-nulled diffusion-weighting waveform design, as it will determine the signal-to-noise ratio (SNR) of the DWI acquisition, particularly for organs with relatively short T 2 relaxation
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