522 research outputs found
Spatial variability of soil properties and soil erodibility in the Alqueva reservoir watershed
The aim of this work is to investigate how the spatial variability of soil properties and soil erodibility (K factor) were affected by the changes in land use allowed by irrigation with water from a reservoir in a semiarid area. To this end, three areas representative of different land uses (agroforestry grassland, lucerne crop and olive orchard) were studied within a 900 ha farm. The interrelationships between variables were analyzed by multivariate techniques and extrapolated using geostatistics. The results confirmed differences between land uses for all properties analyzed, which was explained mainly by the existence of diverse management practices (tillage, fertilization and irrigation), vegetation cover and local soil characteristics. Soil organic matter, clay and nitrogen content decreased significantly, while the K factor increased with intensive cultivation. The HJ-Biplot methodology was used to represent the variation of soil erodibility properties grouped in land uses. Native grassland was the least correlated with the other land uses. The K factor demonstrated high correlation mainly with very fine sand and silt. The maps produced with geostatistics were crucial to understand the current spatial variability in the Alqueva region. Facing the intensification of land-use conversion, a sustainable management is needed to introduce protective measures to control soil erosion
Effects of doping on thermally excited quasiparticles in the high- superconducting state
The physical properties of low energy superconducting quasiparticles in high-
superconductors are examined using magnetic penetration depth and
specific heat experimental data. We find that the low energy density of states
of quasiparticles of LaSrCuO scales with to the
leading order approximation, where is the critical doping concentration
below which . The linear temperature term of the superfluid density is
renormalized by quasiparticle interactions and the renormalization factor times
the Fermi velocity is found to be doping independent.Comment: 3 pages, 3 figures, minor change to the content, fig1 is reploted, to
appear in Phys Rev
Strain-induced interface reconstruction in epitaxial heterostructures
We investigate in the framework of Landau theory the distortion of the strain
fields at the interface of two dissimilar ferroelastic oxides that undergo a
structural cubic-to-tetragonal phase transition. Simple analytical solutions
are derived for the dilatational and the order parameter strains that are
globally valid over the whole of the heterostructure. The solutions reveal that
the dilatational strain exhibits compression close to the interface which may
in turn affect the electronic properties in that region.Comment: 7 pages, 5 figures, to be published in Physical Review
Perturbative and non-perturbative renormalization results of the Chromomagnetic Operator on the Lattice
The Chromomagnetic operator (CMO) mixes with a large number of operators
under renormalization. We identify which operators can mix with the CMO, at the
quantum level. Even in dimensional regularization (DR), which has the simplest
mixing pattern, the CMO mixes with a total of 9 other operators, forming a
basis of dimension-five, Lorentz scalar operators with the same flavor content
as the CMO. Among them, there are also gauge noninvariant operators; these are
BRST invariant and vanish by the equations of motion, as required by
renormalization theory. On the other hand using a lattice regularization
further operators with will mix; choosing the lattice action in a
manner as to preserve certain discrete symmetries, a minimul set of 3
additional operators (all with ) will appear. In order to compute all
relevant mixing coefficients, we calculate the quark-antiquark (2-pt) and the
quark-antiquark-gluon (3-pt) Green's functions of the CMO at nonzero quark
masses. These calculations were performed in the continuum (dimensional
regularization) and on the lattice using the maximally twisted mass fermion
action and the Symanzik improved gluon action. In parallel, non-perturbative
measurements of the matrix element are being performed in simulations
with 4 dynamical () twisted mass fermions and the Iwasaki improved
gluon action.Comment: 7 pages, 1 figure, 3 tables, LATTICE2014 proceeding
matrix elements of the chromomagnetic operator on the lattice
We present the results of the first lattice QCD calculation of the matrix elements of the chromomagnetic operator , which appears in the effective Hamiltonian
describing transitions in and beyond the Standard Model. Having
dimension 5, the chromomagnetic operator is characterized by a rich pattern of
mixing with operators of equal and lower dimensionality. The multiplicative
renormalization factor as well as the mixing coefficients with the operators of
equal dimension have been computed at one loop in perturbation theory. The
power divergent coefficients controlling the mixing with operators of lower
dimension have been determined non-perturbatively, by imposing suitable
subtraction conditions. The numerical simulations have been carried out using
the gauge field configurations produced by the European Twisted Mass
Collaboration with dynamical quarks at three values of the
lattice spacing. Our result for the B-parameter of the chromomagnetic operator
at the physical pion and kaon point is , while
in the SU(3) chiral limit we obtain . Our findings are
significantly smaller than the model-dependent estimate ,
currently used in phenomenological analyses, and improve the uncertainty on
this important phenomenological quantity.Comment: 20 pages, 4 figures, 2 table. Refined SU(3) ChPT analysis with no
changes in the final result. Version to appear in PR
The chromomagnetic operator on the lattice
We study matrix elements of the "chromomagnetic" operator on the lattice.
This operator is contained in the strangeness-changing effective Hamiltonian
which describes electroweak effects in the Standard Model and beyond.
Having dimension 5, the chromomagnetic operator is characterized by a rich
pattern of mixing with other operators of equal and lower dimensionality,
including also non gauge invariant quantities; it is thus quite a challenge to
extract from lattice simulations a clear signal for the hadronic matrix
elements of this operator.
We compute all relevant mixing coefficients to one loop in lattice
perturbation theory; this necessitates calculating both 2-point
(quark-antiquark) and 3-point (gluon-quark-antiquark) Green's functions at
nonzero quark masses. We use the twisted mass lattice formulation, with
Symanzik improved gluon action.
For a comprehensive presentation of our results, along with detailed
explanations and a more complete list of references, we refer to our
forthcoming publication [1].Comment: 7 pages, 1 figure. Talk presented at the 31st International Symposium
on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz,
German
Influence of infection on the distribution patterns of NIH-Chronic Prostatitis Symptom Index scores in patients with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS)
Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a complex condition for which the etiological determinants are still poorly defined. To better characterize the diagnostic and therapeutic profile of patients, an algorithm known as UPOINT was created, addressing six major phenotypic domains of CP/CPPS, specifically the urinary (U), psycho-social (P), organ-specific (O), infection (I), neurological/systemic (N) and muscular tenderness (T) domains. An additional sexual dysfunction domain may be included in the UPOINT(S) system. The impact of the infection domain on the severity of CP/CPPS symptoms is a controversial issue, due to the contradictory results of different trials. The aim of the present retrospective study was to further analyze the extent to which a positive infection domain of UPOINTS may modify the pattern of CP/CPPS symptom scores, assessed with the National Institutes of Health-Chronic Prostatitis Symptom Index (NIH-CPSI). In a cohort of 935 patients that was divided on the basis of the presence or absence of prostatic infection, more severe clinical symptoms were shown by the patients with infection (median NIH total score: 24 versus 20 points in uninfected patients; P<0.001). Moreover, NIH-CPSI score distribution curves were shifted towards more severe symptoms in patients with a positive infection domain. Division of the patients into the six most prominent phenotypic clusters of UPOINTS revealed that the 'prostate infection-related sexual dysfunction' cluster, including the highest proportion of patients with evidence of infection (80%), scored the highest number of NIH-CPSI points among all the clusters. To assess the influence of the infection domain on the severity of patients' symptoms, all subjects with evidence of infection were withdrawn from the 'prostate infection-related sexual dysfunction' cluster. This modified cluster showed symptom scores significantly less severe than the original cluster, and the CPSI values became comparable to the scores of the five other clusters, which were virtually devoid of patients with evidence of infection. These results suggest that the presence of pathogens in the prostate gland may significantly affect the clinical presentation of patients affected by CP/CPPS, and that the infection domain may be a determinant of the severity of CP/CPPS symptoms in clusters of patients phenotyped with the UPOINTS system. This evidence may convey considerable therapeutic implications
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