4,213 research outputs found
Trade Liberalization and Private Savings: The Spanish Experience, 1960-1995
Get PDFThis paper provides an interpretation of the evolution of Spanish private and national savings over the period 1960-1995. During these 35 years private and national saving rates oscillated widely from a very high level in the 1960s to historical minima in the early and mid-1980s to a strong recovery in the more recent years. At the same time, Spain transformed itself from an autarkic, underdeveloped and dictatorial country into an advanced, open economy with a fully democratic political life. First, we show that the apparent long-run reduction in Spanish saving rates is mostly due to a change in relative prices and to the choice of what, in our view, is the incorrect deflator. When Spanish real private savings are measured by using the deflator for the price of capital they appear to behave as a stationary, albeit highly volatile, time series relative to private disposable income. We find that a stable "saving function" can be derived from first principles and estimated using annual macroeconomic data. We adopt a traditional model of intertemporal optimization by a representative agent, facing a complete set of borrowing/lending opportunities and an exogenous income process. We use a "habit formation" utility function, to explain the crucial feature of the data, i. e. , the strong and positive impact that innovations in the growth rate of income (either national or private) have on saving (either national or private).
Multiple orthogonal polynomials of mixed type: Gauss-Borel factorization and the multi-component 2D Toda hierarchy
Get PDFMultiple orthogonality is considered in the realm of a Gauss--Borel
factorization problem for a semi-infinite moment matrix. Perfect combinations
of weights and a finite Borel measure are constructed in terms of M-Nikishin
systems. These perfect combinations ensure that the problem of mixed multiple
orthogonality has a unique solution, that can be obtained from the solution of
a Gauss--Borel factorization problem for a semi-infinite matrix, which plays
the role of a moment matrix. This leads to sequences of multiple orthogonal
polynomials, their duals and second kind functions. It also gives the
corresponding linear forms that are bi-orthogonal to the dual linear forms.
Expressions for these objects in terms of determinants from the moment matrix
are given, recursion relations are found, which imply a multi-diagonal Jacobi
type matrix with snake shape, and results like the ABC theorem or the
Christoffel--Darboux formula are re-derived in this context (using the
factorization problem and the generalized Hankel symmetry of the moment
matrix). The connection between this description of multiple orthogonality and
the multi-component 2D Toda hierarchy, which can be also understood and studied
through a Gauss--Borel factorization problem, is discussed. Deformations of the
weights, natural for M-Nikishin systems, are considered and the correspondence
with solutions to the integrable hierarchy, represented as a collection of Lax
equations, is explored. Corresponding Lax and Zakharov--Shabat matrices as well
as wave functions and their adjoints are determined. The construction of
discrete flows is discussed in terms of Miwa transformations which involve
Darboux transformations for the multiple orthogonality conditions. The bilinear
equations are derived and the -function representation of the multiple
orthogonality is given.Comment: 53 pages. In this version minor revisions regarding the
Christoffel-Darboux operators are performe
Efecto del biocarbón sobre el crecimiento y producción de un cultivo de trigo en condiciones de campo
Get PDFPremio extraordinario de Trabajo Fin de Máster curso 2012-2013.Peoducción, Protección y Mejora vegetal.Actualmente existe una enorme preocupación por el aumento de la
concentración de CO2 atmosférico, su efecto sobre el cambio climático y su
consecuencia negativa sobre la salud humana, la producción de alimentos y la
biodiversidad. Por otro lado, la pérdida de materia orgánica es uno de los problemas
más importantes del suelo en zonas con clima mediterráneo. En la búsqueda de
soluciones, el sector agrícola se presenta como un entorno crítico y la adición al suelo
de biocarbón puede desempeñar un papel importante, favoreciendo la sostenibilidad de
la agricultura a largo plazo.
El biocarbón es un material obtenido a partir de la descomposición térmica de
biomasa residual a temperaturas relativamente bajas (<700 ºC) y bajo condiciones
limitantes de oxígeno (pirólisis). Cuando se aplica al suelo, su alta resistencia a la
descomposición química y biológica favorece que el carbono permanezca más tiempo
en el suelo, reduciendo las emisiones de CO2. Además, los beneficios de su aplicación
incluyen el aumento de la producción de cultivos y la reducción de las pérdidas de
nutrientes por lixiviación debido a su alta capacidad de retención. Sin embargo, sus
efectos pueden ser variables y no está del todo claro si el entusiasmo que suscita
actualmente puede estar justificado.
El objetivo principal de este trabajo es evaluar en condiciones de campo los
efectos de la adición de un biocarbón procedente de restos de poda de olivo sobre el
crecimiento, producción y rasgos funcionales más importantes de un cultivo de trigo
duro (Triticum durum).
La adición de biocarbón provocó un crecimiento más rápido de la planta y un
mayor desarrollo de la espiga antes de la llegada de los meses secos, lo que pudo
favorecer su rendimiento. Los resultados de la cosecha final corroboraron estos
resultados, el rendimiento de las parcelas tratadas con biocarbón fue superior al de las
parcelas control. Nuestros resultados sugieren que los efectos positivos del biocarbón
sobre el crecimiento y la producción del cultivo estuvieron relacionados con su
capacidad para reducir la compactación y aumentar la capacidad de retención hídrica del
suelo. Sin embargo, los efectos del biocarbón sobre la raíz no fueron tan claros,
encontrando sólo un ligero aumento de la longitud específica y una reducción de la
densidad tisular de la raíz en la zona más superficial del suelo.Nowadays, there is a huge concern about the increasing atmospheric CO2
concentration, its effect on climate change and its negative impact on human health,
food production and biodiversity. On the other hand, the loss of organic matter is one of
the most important soil problems in areas with a Mediterranean climate. Seeking
solutions to it, the agricultural sector is presented as a critical factor and biochar
addition to soil can play an important role in promoting the sustainability of agriculture
in the long term.
Biochar is a carbonaceous material obtained from the thermal decomposition of
biomass at relatively low temperatures (<700 ° C) and under oxygen-limited conditions
(pyrolysis). When biochar is applied to soil, its high resistance to chemical and
biological decomposition favours that carbon remains longer in the soil, reducing CO2
emissions. Moreover, the benefits of its application include an increase in crop
production and a reduction in nutrient leaching due to its high retention capacity.
However, its effects can be variable and is not entirely clear whether the enthusiasm
aroused may be justified.
The main objective of this work is to evaluate under field conditions the effects
of the addition to soil of a biochar produced from olive-tree pruning on the growth,
production and functional traits of durum wheat (Triticum durum).
The biochar addition led to a faster plant growth and a better spike development
before dry season, which could favour wheat yield. The results of final harvest were in
this sense, we found that yield of plots treated with biochar was higher than control
plots. Our results suggest that the positive effects of biochar on growth and crop
production were related to the capacity of biochar to reduce soil compaction and
increase soil water-retention capacity. However, biochar effects on root were not so
clear since we found a reduction in root tissue density and a slight increase of specific
root length in the upper soil layer.
In summary, the results obtained suggest that the addition of biochar is a viable
option to enhance soil physical properties and increase production of durum wheat
under Mediterranean climate conditions
Trois fontes méconnues du XXe siècle : Parade (Enric Crous Vidal, c.1949)
Get PDFDepto. de Diseño e ImagenFac. de Bellas ArtesFALSEpu
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