5,561 research outputs found
A new method for the solution of the Schrodinger equation
We present a new method for the solution of the Schrodinger equation
applicable to problems of non-perturbative nature. The method works by
identifying three different scales in the problem, which then are treated
independently: An asymptotic scale, which depends uniquely on the form of the
potential at large distances; an intermediate scale, still characterized by an
exponential decay of the wave function and, finally, a short distance scale, in
which the wave function is sizable. The key feature of our method is the
introduction of an arbitrary parameter in the last two scales, which is then
used to optimize a perturbative expansion in a suitable parameter. We apply the
method to the quantum anharmonic oscillator and find excellent results.Comment: 4 pages, 4 figures, RevTex
Sap flow of a wild cherry tree plantation growing under Mediterranean conditions: Assessing the role of environmental conditions on canopy conductance and the effect of branch pruning on water productivity
In recent decades, wild cherry has been one of the species most widely used for reforestation in Europe. Studies aiming to select and improve trees to give them the best growth rates and wood properties have increased in response to growers’ demands. However, information relating to key physiological processes such as transpiration or stomatal conductance and to the effect of the common practice of pruning on plant–water relations is scarce. The main objective of this study was to assess the effects of environmental conditions on canopy conductance dynamics. Its secondary objective was to examine the short- and medium-term effects of branch pruning on tree transpiration, growth and derived water productivity. To this end, we measured sap flow in an experimental plantation where trees were subjected to drip irrigation and rain-fed conditions and where variables characterizing climate, soil and tree growth were also monitored. The results demonstrated that the Jarvis–Stewart approach was appropriate for studying the responses of canopy conductance to environmental factors. As well as the role of vapour pressure deficit and net radiation in controlling the daily variations of canopy conductance, the single effects of decreasing soil water content (optimum relative extractable water, REW, higher than 0.4) and increasing air temperature (optimum of 21 °C), as summer conditions approached, were correctly incorporated into the modelling exercise. Soil water content exerted the greatest control on canopy conductance for trees growing under rain-fed conditions, while air temperature did for irrigated trees. Pruning significantly reduced transpiration to about 35% when pre- and post-sub-periods were compared, but also affected annual water productivity regardless of the irrigation treatment. To assess the long-term effects of pruning on water productivity, measurements in both pruned and unpruned trees would be desirable.info:eu-repo/semantics/acceptedVersio
Fundamental care and knowledge interests: implications for nursing science
Aims and objectives: The aim of this discursive paper was to characterize the intra-theoretical interests of knowledge in nursing science as an epistemological framework for fundamental care.
Background: For Jürgen Habermas, theory does not separate knowledge interests from life. All knowledge, understanding and human research is always interested. Habermas formulated the knowledge interests in empirical-analytical, historical hermeneutic and critical social sciences; but said nothing about health sciences and nursing science.
Design: Discursive paper.
Results: The paper is organised into five sections that develop our argument about the implications of the Habermasian intra theoretical interests in nursing science and fundamental care: the persistence of a technical interest, the predominance of a practical interest, the importance of an emancipatory interest, “being there” to understand individuals’ experience and an “existential crisis” that uncovers the individual’s subjectivity.
Conclusions: The nursing discipline can take on practical and emancipatory interests (together with a technical interest) as its fundamental knowledge interests. Nurses’ privileged position in the delivery of fundamental care gives them the opportunity to gain a deep understanding of the patient’s experience and illness process through physical contact and empathic communication.
Relevance to clinical practice and nursing research: In clinical, academic and research environments, nurses should highlight the importance of fundamental care, showcasing the value of practical and emancipatory knowledge. This process could help to improve nursing science’s leadership, social visibility and idiosyncrasy
Consumo de drogas adictivas en alumnos de la UNCuyo, Mendoza, Argentina.
Este trabajo muestra los resultados de una encuesta realizada en 2010 sobre
consumo de drogas adictivas en alumnos de 7 Facultades de la UNCUYO y los
compara con los resultados obtenidos 12 años antes con una encuesta equivalente.
La encuesta fue semiestructurada, con 17 preguntas, autocumplimentada, individual y
anónima, con una muestra de 1108 alumnos de ambos sexos. De esa encuesta se
utilizaron 7 preguntas específicas sobre drogas adictivas y una pregunta sobre
consumo de medicamentos en general, con 46 opciones entre las que figuraban 10
denominaciones comerciales de benzodiacepinas, como drogas adictivas de
prescripción. Para las comparaciones estadísticas se utilizó Chi cuadrado. El ranking
de drogas utilizadas fue relativamente similar en 1998 y 2010 pero, exceptuando
tabaco y “otras drogas" que se mantuvieron estables, el resto aumentó alrededor de 4
veces en el periodo. El 82,8% de los alumnos manifestó consumir alcohol (siempre +
a veces); de 1 a 5 vasos semanales el 79%. En todas las Facultades, cerveza y
Fernet encabezaron el ranquing de preferencias por bebidas alcohólicas. La
prevalencia del consumo de tabaco en el total de la muestra se mantuvo constante en
1998 y 2010 (alrededor del 28%) pero el consumo entre Facultades fue variable y en
Artes fue significativamente más elevado (42%). Siguen en el ranking marihuana con
10% de prevalencia, tranquilizantes con alrededor del 6% y cocaína con poco más del 1%. Finalmente “otras drogas" (Hachis, LSD, extasis, anabólicos, anfetaminas,
“hongos") representaron solamente un 3% de prevalencia. Artes y Ciencias Políticas
mostraron las mayores prevalencias de consumo y Derecho e Ingeniería las menores.
Esto indica implementar acciones preventivas y correctivas particulares para cada
Facultad.This is a research on addictive drugs use by students of 7 schools of the UNCUYO.
The results of an inquire made in 2010 are compared with the results of an equivalent
inquire made 12 years before. The inquire was partially structured and consists of 17
questions, autographic, individual and anonymous, and was applied to a 1108
students sample. The inquire was devoted to ascertain use and knowledge about
prescription drugs use and comprised 7 specific questions on addictive drugs use as
well as a prescription drugs question with 46 options comprising 10 commercial
names of benzodiazepines as addictive prescription drugs. Chi square was used for
statistic comparisons. The ranking of addictive drugs use was quite similar in the 1998 and the 2010 inquires. However, excepting tobacco and “other drugs" which
prevalence remained constant, the rest of consigned drugs prevalence increased
about 4 folds in this period. The prevalence of alcohol users was about 83% (always +
some-times users) and 79% said to drank 1 to 5 glasses a week. Bear and Fernet
headed the ranking of alcoholic drinks preference. The prevalence of tobacco use in
the whole student sample was constant in both inquires (about 28%) but the amongschools use was variable; in Arts was significantly higher than that (42%). Followed in the ranking marihuana with a 10% prevalence, tranquilizers (about 6%) and cocaine with a little more than 1%. Finally, “other drugs" (Hachis, LSD, extasis, anabolics, anfetamines and funguses) represented all together a 3% prevalence. Arts and Politic Sciences Schools showed the highest prevalence in addictive drugs use and Law and Engineery the lowest. The results point to planning particular preventing and corrective actions for each School.Fil: Kaiser, L. D..
Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Farmacología.Fil: Rodríguez, C..
Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Farmacología.Fil: Zapata, M. P..
Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Farmacología.Fil: Sacchi, O. J..
Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Farmacología.Fil: Riestra, E. C..
Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Farmacología.Fil: Aranda, L..
Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Farmacología.Fil: Rodríguez Echandía, Eduardo.
Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Área Farmacología
Orthogonal U(1)'s, Proton Stability and Extra Dimensions
In models with a low quantum gravity scale, one might expect that all
operators consistent with gauge symmetries are present in the low-energy
effective theory. If this is the case, some mechanism must be present to
adequately suppress operators that violate baryon number. Here we explore the
possibility that the desired suppression is a consequence of an additional,
spontaneously-broken, non-anomalous U(1) symmetry that is orthogonal to
hypercharge. We show that successful models can be constructed in which the
additional particle content necessary to cancel anomalies is minimal, and
compatible with the constraints from precision electroweak measurements and
gauge unification. If unification is sacrificed, and only the new U(1) and its
associated Higgs fields live in the bulk, it is possible that the gauge field
zero mode and first few Kaluza-Klein excitations lie within the kinematic reach
of the Tevatron. For gauge couplings not much smaller than that of hypercharge,
we show that these highly leptophobic states could evade detection at Run I,
but be discovered at Run II. Our scenario presents an alternative to the
`cartographic' solution to baryon number violation in which leptons and quarks
are separated in an extra dimension.Comment: 16 pages LaTeX, 4 figure
The prolate-to-oblate shape transition of phospholipid vesicles in response to frequency variation of an AC electric field can be explained by the dielectric anisotropy of a phospholipid bilayer
The external electric field deforms flaccid phospholipid vesicles into
spheroidal bodies, with the rotational axis aligned with its direction.
Deformation is frequency dependent: in the low frequency range (~ 1 kHz), the
deformation is typically prolate, while increasing the frequency to the 10 kHz
range changes the deformation to oblate. We attempt to explain this behaviour
with a theoretical model, based on the minimization of the total free energy of
the vesicle. The energy terms taken into account include the membrane bending
energy and the energy of the electric field. The latter is calculated from the
electric field via the Maxwell stress tensor, where the membrane is modelled as
anisotropic lossy dielectric. Vesicle deformation in response to varying
frequency is calculated numerically. Using a series expansion, we also derive a
simplified expression for the deformation, which retains the frequency
dependence of the exact expression and may provide a better substitute for the
series expansion used by Winterhalter and Helfrich, which was found to be valid
only in the limit of low frequencies. The model with the anisotropic membrane
permittivity imposes two constraints on the values of material constants:
tangential component of dielectric permittivity tensor of the phospholipid
membrane must exceed its radial component by approximately a factor of 3; and
the membrane conductivity has to be relatively high, approximately one tenth of
the conductivity of the external aqueous medium.Comment: 17 pages, 6 figures; accepted for publication in J. Phys.: Condens.
Matte
Transition period between vegetation growth and senescence controls interannual variability of C fluxes in a Mediterranean reed wetland
Wetlands are crucial ecosystems modulating climate change due to their great potential
to capture carbon dioxide (CO2), emit methane (CH4) and regulate local climate through
evapotranspiration (ET). Common reed wetlands are particularly interesting given their
high productivity, abundance and highly efficient internal gas-transport mechanism.
However, little is known about the interannual behavior and dominant controlling
factors of Mediterranean reed wetlands, characterized by seasonal flooding and
remarkable weather variability. After 6 years of ecosystem carbon and ET flux
measurements by eddy covariance (3 years for CH4 fluxes), this study shows the
functional vulnerability of such wetlands to climate variability, switching between
carbon (CO2+CH4) sink (660 g CO2-eeq m-2
y
-1
, in 2014) and source (360 g CO2-eq m-2
y
-1
, in 2016) in short periods of time. According to our analyses, the great interannual
variability appeared to mainly depend on the behavior of reed growth dynamics during
the transition to senescence period, what is confirmed through the Enhanced Vegetation
Index as a proxy of photosynthetic activity. Additionally, a similar behavior of seasonal
and daily patterns of carbon fluxes and ET was found compared with other wetlands
under different climates
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