10,211 research outputs found
Informal sector, productivity, and tax collection
The informal sector is a prominent characteristic of many developing countries. Most of the literature has focused on understanding the determinants of informality. The connection between the informal sector and economic development is, nonetheless, relatively less understood. One of the most important determinants of informality is the tax enforcement quality of a country which, some authors argue, additionally distorts firms' decisions and creates inefficiency. In this paper, I assess the quantitative importance of the effects of incomplete tax enforcement on aggregate output and productivity. I use a dynamic general equilibrium framework to study effects that have received little attention in the literature. I calibrate the model using data for Mexico, an economy where 31% of the employees work in informal establishments. I then investigate the effects of improving enforcement. My main finding is that under complete enforcement, Mexico's labor productivity and output would be 17% higher.Informal Sector, Productivity, tax enforcement, TFP, Heterogeneous plants
The motion of a deformable drop in a second-order fluid
The cross-stream migration of a deformable drop in a unidirectional shear flow of a second-order fluid is considered. Expressions for the particle velocity due to the separate effects of deformation and viscoelastic rheology are obtained. The direction and magnitude of migration are calculated for the particular cases of Poiseuille flow and simple shear flow and compared with experimental data
Petalite as determinant of maximum lithium content of Variscan pegmatites from NW Portugal – paragenetic and geochemical approach
Estudos petrológicos de aplito-pegmatitos Variscos, de tipo LCT, intrusivos em terrenos Silúricos do NW de
Portugal, mostraram que o intercrescimento de espodumena + quartzo, em proporção modal 1:2, é persistente em
dispositivos texturais circunscritos que podem ser interpretados como agregados miméticos, pseudomórficos após
petalite em subsolvus, os quais depois evoluem sujeitos à deformação, metamorfismo e alteração. Cerca de 6 % dos
corpos aplito-pegmatíticos que afloram naqueles terrenos, apresentam estes intercrescimentos, ou p
etalite primária,
a valores de Li2O situados no intervalo de 0,5 a 2,5 %. Uma sistemática químico
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mineralógica das fácies analisadas
sugere que o valor máximo de 2,5 % de Li2O em rocha total, pode ser considerado uma barreira geoquímica, imposta
por um determinante petalítico primário cuja prevalência é balizada pelo equilíbrio com os feldspatos e pela
magnitude da alteração argílica e correspondente lixiviação de LiPetrologica
l studies of Variscan LCT aplite-pegmatites, hosted in Silurian metamorphic suites in
Northwestern Portugal, revealed that the intergrowths of spodumene+quartz, in modal proportions 1:2, is ubiquitous
in concealed pegmatite intergrowths, which can be interpreted as mimetic aggregates, pseudomorphic after petalite,
that, afterwords, evolve, under changing conditions of metamorphism, deformation and alteration. 6% of the aplite –pegmatite bodies individualized in those Silurian host-
rocks show this kind of intergrowths, or primary petalite, at a
Li2O range between 0.5 % and 2.5 %. A chemical-mineralogical systematics of the composition data suggests that the
maximum value of 2.5 % Li2O, in whole-rock analysis, should be considered a geochemical barrier imposed by a
primary petalitic determinant and framed by the equilibrium with feldspars and by the magnitude of argillic alteration
and corresponding lithium leaching(undefined)info:eu-repo/semantics/publishedVersio
Kinetic modelling of epitaxial film growth with up- and downward step barriers
The formation of three-dimensional structures during the epitaxial growth of
films is associated to the reflection of diffusing particles in descending
terraces due to the presence of the so-called Ehrlich-Schwoebel (ES) barrier.
We generalize this concept in a solid-on-solid growth model, in which a barrier
dependent on the particle coordination (number of lateral bonds) exists
whenever the particle performs an interlayer diffusion. The rules do not
distinguish explicitly if the particle is executing a descending or an
ascending interlayer diffusion. We show that the usual model, with a step
barrier in descending steps, produces spurious, columnar, and highly unstable
morphologies if the growth temperature is varied in a usual range of mound
formation experiments. Our model generates well-behaved mounded morphologies
for the same ES barriers that produce anomalous morphologies in the standard
model. Moreover, mounds are also obtained when the step barrier has an equal
value for all particles independently if they are free or bonded. Kinetic
roughening is observed at long times, when the surface roughness w and the
characteristic length scale as and where
and , independently of the growth
temperature.Comment: 15 pages, 7 figure
Water Quality Study and Plume Behavior Modeling for Lake Pontchartrain at the Mouth of the Tchefuncte River
Over the last several decades, the Lake Pontchartrain Basin has been impacted by the presence of high levels of Fecal Coliform bacteria following periods of rainfall. This is a potential problem for recreational uses of the area. In 2003 a field sampling study was initiated in the north shore area of the Lake at the mouth of the Tchefuncte River. The objectives were to determine the water quality in the area and to simulate the plume patterns from the Tchefuncte River. Twenty eight stations at the mouth of the Tchefuncte River, and a station at the Madisonville Bridge were selected for study on the basis of proximity to the mouth of the River. Fecal coliform counts were found to be “wet†weather-dependent at the mouth of the River and unsuitable for primary contact recreation for at least two to three days following a rain event. A 3-D finite volume hydrodynamics model (A coupled Hydrodynamical-Ecological Model for Regional and Shelf Seas – COHERENS) and the TECPLOT™ equation feature were used for the prediction of contaminant plumes from the Tchefuncte River into the Lake Pontchartrain. The field data were used to validate the model. The upper limits predicted by the model and those measured in the field were in good agreement. The model used river flow and tidal forcing without wind shear. The model verified that that the wet weather effect lasted for two to three-day after a high storm water discharges at the mouth of the river
Structure of the granitic pegmatite field of the Northern coast of Portugal—inner pegmatite structures and mineralogical fabrics
On the coastline of Northern Portugal, metamorphic formations and pegmatites were the subject of structural analysis with the main goal of understanding Variscan kinematics and related pegmatite intrusion. This study also aims to discriminate, select and characterize relevant aspects of the structure and the paragenesis of pegmatites, well exposed as a result of coastal erosion, justifying its inclusion in the geological heritage of the Northern coast of Portugal. The pegmatite bodies show distinctive internal and external structures that are attributable to different modes of emplacement and subsequent deformation. The pegmatitic implantation in the areas of Moledo and Afife occurs in an intragneissic and perigranitic environment, for the first area, and perigneissic and perigranitic environment, for the second. In Pedras Ruivas predominates the implantation into an exo-gneissic to exo-granitic domain. The Moledo veins show evidence of multiphase open/filling, revealing positions, shapes, attitudes, sizes and internal structures that change as a function of the host lithology and host structure, but mainly due to the dilation and the cycles number of local telescoping. The structural analysis of the pegmatite bodies allows the deduction of a local fulcrum of expansion that hypothetically overlaps a hidden stock of parental granite. In Afife and Pedras Ruivas, some pegmatitic lenses are specialized and mineralized in Li, Cs and Ta, with spodumene and tantalite ± cassiterite. Spodumene occurs as giant crystals, centimetric to pluri-decimetric in length, which mark very clearly the structures of in situ or in flow crystallization inside the pegmatites (primary structures) and also the secondary structures resulting from deformation. The geometric analysis of fabrics helps the individualization of well-defined stages of progressive evolution of the deformation of the pegmatites, allowing its correlation with major D2–D3 episodes of regional Variscan deformation
Loop representation of charged particles interacting with Maxwell and Chern-Simons fields
The loop representation formulation of non-relativistic particles coupled
with abelian gauge fields is studied. Both Maxwell and Chern-Simons
interactions are separately considered. It is found that the loop-space
formulations of these models share significant similarities, although in the
Chern-Simons case there exists an unitary transformation that allows to remove
the degrees of freedom associated with the paths. The existence of this
transformation, which allows to make contact with the anyonic interpretation of
the model, is subjected to the fact that the charge of the particles be
quantized. On the other hand, in the Maxwell case, we find that charge
quantization is necessary in order to the geometric representation be
consistent.Comment: 6 pages, improved versio
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