290 research outputs found
Carlos Rojas: su primera obra narrativa (1957-1962)
En las obras narrativas de este primer período de Carlos Rojas se encuentran ya algunos de los elementos básicos de su novelística posterior, como la temática sobre la condición humana, Europa y sus valores, el carácter destructivo del poder y el mal. Igualmente hallamos los componentes de la actitud de Rojas ante la novela: la independencia y autocrítica, el criterio personal en la manera de concebir la novela, el ensayo constante de nuevas formas, la fusión de lo cerebral y lo vital, la conjugación de los elementos de la realidad visible y de la invisible en un «realismo total» y la búsqueda de la transcendencia que apunta a niveles metafísicos y religiosos.In Carlos Rojas' first period narrative works were already some of the basic elements of his later personality, as the theme of the human condition, Europe and its values, the destructive nature of power and evil. Equally, we find the components of Rojas' attitude before the novel: the independence and self-criticism, the personal discretion in the way of conceiving the novel, the constant test of new forms, the merger of the cerebral and vital, the combination of the elements of visible reality and invisible in a "total realism" and the search for the transcendence that aims at metaphysical and religious levels
Retrospective study of the prevalence of postanesthetic hypothermia in cats
A retrospective study of 275 anaesthetic records of cats was undertaken to examine the prevalence of postanaesthetic hypothermia, its clinical predictors and consequences. Temperature was recorded throughout anaesthesia. The temperature reached at the end was classified as hyperthermia (>39.50 °C), normothermia (38.50 to 39.50 °C), slight hypothermia (38.49 to 36.50 °C), moderate hypothermia (36.49 to 34.00 °C) or severe hypothermia (<34.00 °C). Statistical analysis consisted of multiple regression to identify the factors that affect the temperature at the end of the procedure. Before premedication, the mean (sd) temperature was 38.2 (1.0) °C. At 60, 120 and 180 minutes from induction, the temperature was 35.4 (1.4) °C, 35.0 (1.5) °C and 34.6 (1.5) °C, respectively. The prevalence of hypothermia was slight 26.5 per cent (95 per cent CI 21.7 to 32.0 per cent), moderate 60.4 per cent (95 per cent CI 54.5 to 66.0 per cent) and severe 10.5 per cent (95 per cent CI 7.4 to 14.7 per cent). The variables associated with a decrease in the temperature recorded at the end of anaesthesia were the duration of anaesthesia, the reason for anaesthesia (abdominal and orthopaedic surgeries significantly reduced the temperature when compared with minor procedures) and the anaesthetic risk (high-risk cats showed lower temperatures than low-risk cats). The temperature before premedication was associated with an increase in the final temperature.Ciencias Experimentale
Systematic generation of finite-range atomic basis sets for linear-scaling calculations
Basis sets of atomic orbitals are very efficient for density functional
calculations but lack a systematic variational convergence.
We present a variational method to optimize numerical atomic orbitals using a
single parameter to control their range.
The efficiency of the basis generation scheme is tested and compared with
other schemes for multiple zeta basis sets.
The scheme shows to be comparable in quality to other widely used schemes
albeit offering better performance for linear-scaling computations
Electrons in Dry DNA from Density Functional Calculations
The electronic structure of an infinite poly-guanine - poly-cytosine DNA
molecule in its dry A-helix structure is studied by means of density-functional
calculations. An extensive study of 30 nucleic base pairs is performed to
validate the method. The electronic energy bands of DNA close to the Fermi
level are then analyzed in order to clarify the electron transport properties
in this particularly simple DNA realization, probably the best suited candidate
for conduction. The energy scale found for the relevant band widths, as
compared with the energy fluctuations of vibrational or genetic-sequence
origin, makes highly implausible the coherent transport of electrons in this
system. The possibility of diffusive transport with sub-nanometer mean free
paths is, however, still open. Information for model Hamiltonians for
conduction is provided.Comment: 8 pages, 4 figure
Retrospective study of the prevalence of postanesthtic hypotermia in dogs
The anaesthetic records of 1525 dogs were examined to determine the prevalence of
postanaesthetic hypothermia, its clinical predictors and consequences. Temperature was
recorded throughout the anaesthesia. At the end of the procedure, details coded in were:
hyperthermia (>39.50°C), normothermia (38.50°C–39.50°C), slight (38.49°C–36.50°C),
moderate (36.49°C–34.00°C) and severe hypothermia (<34.00°C). Statistical analysis
consisted of multiple regression to identify the factors that are associated with the
temperature at the end of the procedure. Before premedication, the temperature was
38.7±0.6°C (mean±sd). At 60, 120 and 180 minutes from induction, the temperature was
36.7±1.3°C, 36.1±1.4°C and 35.8±1.5°C, respectively. The prevalence of hypothermia
was: slight, 51.5 per cent (95 per cent CI 49.0 to 54.0 per cent); moderate, 29.3 per cent
(27.1–31.7 per cent) and severe: 2.8% (2.0–3.7%). The variables that associated with a
decrease in the temperature recorded at the end of the anaesthesia were: duration of the
preanesthetic time, duration of the anaesthesia, physical condition (ASA III and ASA IV dogs
showed lower temperatures than ASA I dogs), the reason for anaesthesia (anaesthesia
for diagnostic procedures or thoracic surgery reduce the temperature when compared
with minor procedures), and the recumbency during the procedure (sternal and dorsal
recumbencies showed lower temperatures than lateral recumbency). The temperature before
premedication and the body surface (BS) were associated with a higher temperature at the
end of the anaesthesia, and would be considered as protective factors.Ciencias Experimentale
Variational finite-difference representation of the kinetic energy operator
A potential disadvantage of real-space-grid electronic structure methods is
the lack of a variational principle and the concomitant increase of total
energy with grid refinement. We show that the origin of this feature is the
systematic underestimation of the kinetic energy by the finite difference
representation of the Laplacian operator. We present an alternative
representation that provides a rigorous upper bound estimate of the true
kinetic energy and we illustrate its properties with a harmonic oscillator
potential. For a more realistic application, we study the convergence of the
total energy of bulk silicon using a real-space-grid density-functional code
and employing both the conventional and the alternative representations of the
kinetic energy operator.Comment: 3 pages, 3 figures, 1 table. To appear in Phys. Rev. B. Contribution
for the 10th anniversary of the eprint serve
Refractive error study in young subjects: results from a rural area in Paraguay
AIM: To evaluate the distribution of refractive error in young subjects in a rural area of Paraguay in the context of an international cooperation campaign for the prevention of blindness. METHODS: A sample of 1466 young subjects (ranging from 3 to 22 years old), with a mean age of 11.21±3.63 years old, were examined to assess their distance visual acuity (VA) and refractive error. The first screening examination performed by trained volunteers, included visual acuity testing, autokeratometry and non-cycloplegic autorefraction. Inclusion criteria for a second complete cycloplegic eye examination by an optometrist were VA <20/25 (0.10 logMAR or 0.8 decimal) and/or corneal astigmatism ≥1.50 D. RESULTS: An uncorrected distance VA of 0 logMAR (1.0 decimal) was found in 89.2% of children. VA <20/25 and/or corneal astigmatism ≥1.50 D was found in 3.9% of children (n=57), with a prevalence of hyperopia of 5.2% (0.2% of the total) in this specific group. Furthermore, myopia (spherical equivalent ≤-0.5 D) was found in 37.7% of the refracted children (0.5% of the total). The prevalence of refractive astigmatism (cylinder ≤-1.50 D) was 15.8% (0.6% of the total). Visual impairment (VI) (0.05≤VA≤0.3) was found in 12/114 (0.4%) of the refracted eyes. Main causes for VI were refractive error (58%), retinal problems (17%, 2/12), albinism (17%, 2/12) and unknown (8%, 1/12). CONCLUSION: A low prevalence of refractive error has been found in this rural area of Paraguay, with higher prevalence of myopia than of hyperopia
Exchange and correlation as a functional of the local density of states
A functional is presented, in which the exchange
and correlation energy of an electron gas depends on the local density of
occupied states. A simple local parametrization scheme is proposed, entirely
from first principles, based on the decomposition of the exchange-correlation
hole in scattering states of different relative energies. In its practical
Kohn-Sham-like form, the single-electron orbitals become the independent
variables, and an explicit formula for the functional derivative is obtained.Comment: 5 pages. Expanded version. Will appear in Phys. Rev.
Cardiac tamponade associated with a peripheral vein central venous catheter
We present a case of cardiac tamponade associated with placement of a central venous catheter (CVC) via a peripheral vein in a 14-year-old girl with idiopathic scoliosis undergoing corrective surgery. A number of complications have been described in association with CVC misplacement. Sporadic cases of cardiac tamponade from this have been reported, but the actual incidence is unknown. Death from cardiac tamponade attributed to CVCs ranges from 65 to 100%. In our patient, cannulation of the pericardiophrenic vein was probably the cause of cardiac tamponade, based on radiological evidence that the initial location of the catheter was near the right atrium and possibly at the outlet of the pericardiophrenic vein. The catheter could have advanced into the vein and then to the pericardial sac with postural changes. The acute clinical course of cardiac tamponade in our patient had potentially lethal hemodynamic repercussions. The main diagnostic test for this condition is echocardiography and the only effective treatment is drainage of the pericardial effusion. Echocardiography should be performed before pericardiocentesis except in life-threatening situations or high clinical suspicion. Although they are rare, it is important to be aware of the potential for CVC complications
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