2,289 research outputs found
Development and Evaluation of the Nebraska Assessment of Computing Knowledge
One way to increase the quality of computing education research is to increase the quality of the measurement tools that are available to researchers, especially measures of students’ knowledge and skills. This paper represents a step toward increasing the number of available thoroughly-evaluated tests that can be used in computing education research by evaluating the psychometric properties of a multiple-choice test designed to differentiate undergraduate students in terms of their mastery of foundational computing concepts. Classical test theory and item response theory analyses are reported and indicate that the test is a reliable, psychometrically-sound instrument suitable for research with undergraduate students. Limitations and the importance of using standardized measures of learning in education research are discussed
Analytic Hypoellipticity in the Presence of Lower Order Terms
We consider a second order operator with analytic coefficients whose
principal symbol vanishes exactly to order two on a symplectic real analytic
manifold. We assume that the first (non degenerate) eigenvalue vanishes on a
symplectic submanifold of the characteristic manifold. In the
framework this situation would mean a loss of 3/2 derivatives. We prove that
this operator is analytic hypoelliptic. The main tool is the FBI transform. A
case in which hypoellipticity fails is also discussed.Comment: 40 page
Perinatal and newborn care in a two years retrospective study in a first level peripheral hospital in Sicily (Italy)
BACKGROUND: Two hundred seventy-five thousand maternal deaths, 2.7 million neonatal deaths, and 2.6 million stillbirths have been estimated in 2015 worldwide, almost all in low-income countries (LICs). Moreover, more than 20 million severe disabilities result from the complications of pregnancy, childbirth or its management each year. A significant decrease of mortality/morbidity rates could be achieved by providing effective perinatal and newborn care also in high-income countries (HICs), especially in peripheral hospitals and/or rural areas, where the number of childbirths per year is often under the minimal threshold recognized by the reference legislation. We report on a 2 years retrospective cohort study, conducted in a first level peripheral hospital in Cefalù, a small city in Sicily (Italy), to evaluate care provided and mortality/morbidity rates. The proposed goal is to improve the quality of care, and the services that peripheral centers can offer. METHODS: We collected data from maternity and neonatal records, over a 2-year period from January 2017 to December 2018. The informations analyzed were related to demographic features (age, ethnicity/origin area, residence, educational level, marital status), diagnosis at admission (attendance of birth training courses, parity, type of pregnancy, gestational age, fetal presentation), mode of delivery, obstetric complications, the weight of the newborns, their feeding and eventual transfer to II level hospitals, also through the Neonatal Emergency Transport Service, if the established criteria were present. RESULTS: Eight hundred sixteen women were included (age 18-48 years). 179 (22%) attended birth training courses. 763 (93%) were Italian, 53 foreign (7%). 175 (21%) came from outside the province of Palermo. Eight hundred ten were single pregnancies, 6 bigeminal; 783 were at term (96%), 33 preterm (4%, GA 30-41 WG); 434 vaginal deliveries (53%), 382 caesarean sections (47%). One maternal death and 28 (3%) obstetric complications occurred during the study period. The total number of children born to these women was 822, 3 of which stillbirths (3.6‰). 787 (96%) were born at term (>37WG), 35 preterm (4%), 31 of which late preterm. Twenty-one newborns (2.5%) were transferred to II level hospitals. Among them, 3 for moderate/severe prematurity, 18 for mild prematurity/other pathology. The outcome was favorable for all women (except 1 hysterectomy) and the newborns transferred, and no neonatal deaths occurred in the biennium under investigation. Of the remaining 798 newborns, 440 were breastfed at discharge (55%), 337 had a mixed feeding (breastfed/formula fed, 42%) and 21 were formula fed (3%). CONCLUSIONS: Although the minimal standard of adequate perinatal care in Italy is >500 childbirths/year, the aims of the Italian legislation concern the rationalization of birth centers as well as the structural, technological and organizational improvement of health facilities. Therefore, specific contexts and critical areas need to be identified and managed. Adequate resources and intervention strategies should be addressed not only to perinatal emergencies, but also to the management of mild prematurity/pathology, especially in vulnerable populations for social or orographic reasons. The increasing availability and spread of health care offers, even in HICs, cannot be separated from the goal of quality of care, which is an ethic and public health imperative
Scaling behavior of jamming fluctuations upon random sequential adsorption
It is shown that the fluctuations of the jamming coverage upon Random
Sequential Adsorption (), decay with the lattice size
according to the power-law , with
, where is the dimension of the substrate and
is the fractal dimension of the set of sites belonging to the
substrate where the RSA process actually takes place. This result is in
excellent agreement with the figure recently reported by Vandewalle {\it et al}
({\it Eur. Phys. J.} B. {\bf 14}, 407 (2000)), namely for the
RSA of needles with and , that gives . Furthermore,
our prediction is in excellent agreement with different previous numerical
results. The derived relationships are also confirmed by means of extensive
numerical simulations applied to the RSA of dimers on both stochastic and
deterministic fractal substrates.Comment: 8 pages, 2 figures. To appear in Eur. Phys. J. B (Rapid note) (2003
Continuous variable quantum teleportation with sculptured and noisy non-Gaussian resources
We investigate continuous variable (CV) quantum teleportation using relevant
classes of non-Gaussian states of the radiation field as entangled resources.
First, we introduce the class two-mode squeezed symmetric superposition of Fock
states, including finite truncations of twin-beam Gaussian states as special
realizations. These states depend on a set of free independent parameters that
can be adjusted for the optimization of teleportation protocols, with an
enhancement of the success probability of teleportation both for coherent and
Fock input states. We show that the optimization procedure reduces the
entangled resources to truncated twin beam states, which thus represents an
optimal class of non-Gaussian resources for quantum teleportation. We then
introduce a further class of two-mode non-Gaussian entangled resources, in the
form of squeezed cat-like states. We analyze the performance and the properties
of such states when optimized for (CV) teleportation, and compare them to the
optimized squeezed Bell-like states introduced in a previous work
\cite{CVTelepNoi}. We discuss how optimal resources for teleportation are
characterized by a suitable balance of entanglement content and squeezed vacuum
affinity. We finally investigate the effects of thermal noise on the efficiency
of quantum teleportation. To this aim, a convenient framework is to describe
noisy entangled resources as linear superpositions of non-Gaussian state and
thermal states. Although the presence of the thermal component strongly reduces
the teleportation fidelity, noisy non-Gaussian states remain preferred
resources when compared to noisy twin-beam Gaussian states.Comment: 11 pages, 8 figures. Largely revised and expanded version. New
material and sections added. To appear in EPJ-ST (Proceedings of the Central
European Workshop on Quantum Optics 2007. 14th Edition, 1-5 June 2007,
Palermo, Italy
Continuous variable quantum teleportation with non-Gaussian resources
We investigate continuous variable quantum teleportation using non-Gaussian
states of the radiation field as entangled resources. We compare the
performance of different classes of degaussified resources, including two-mode
photon-added and two-mode photon-subtracted squeezed states. We then introduce
a class of two-mode squeezed Bell-like states with one-parameter dependence for
optimization. These states interpolate between and include as subcases
different classes of degaussified resources. We show that optimized squeezed
Bell-like resources yield a remarkable improvement in the fidelity of
teleportation both for coherent and nonclassical input states. The
investigation reveals that the optimal non-Gaussian resources for continuous
variable teleportation are those that most closely realize the simultaneous
maximization of the content of entanglement, the degree of affinity with the
two-mode squeezed vacuum and the, suitably measured, amount of non-Gaussianity.Comment: 12 pages, 12 figure
Short time relaxation of a driven elastic string in a random medium
We study numerically the relaxation of a driven elastic string in a two
dimensional pinning landscape. The relaxation of the string, initially flat, is
governed by a growing length separating the short steady-state
equilibrated lengthscales, from the large lengthscales that keep memory of the
initial condition. We find a macroscopic short time regime where relaxation is
universal, both above and below the depinning threshold, different from the one
expected for standard critical phenomena. Below the threshold, the zero
temperature relaxation towards the first pinned configuration provides a novel,
experimentally convenient way to access all the critical exponents of the
depinning transition independently.Comment: 4.2 pages, 3 figure
Caracterização da propagação de vibração através de estruturas de edifícios de betão armado
Este artigo descreve os parâmetros que controlam a propagação da vibração através de estruturas de
edifícios de betão armado para frequências abaixo de 200 Hz. A influência das propriedades dos
materiais e das dimensões dos elementos estruturais foi avaliada com modelos de elementos finitos
validados experimentalmente, considerando cinco tipos de funções de transferência de aceleração: i)
da fundação para o primeiro piso; ii) entre pisos intermédios; iii) do último piso para a cobertura; iv)
entre troços do mesmo piso intermédio; e v) entre troços da cobertura. Os resultados mostram que a
transmissão de vibração depende não tanto do número de pisos mas mais de parâmetros como a
espessura da laje, no caso da transmissão da vibração num pavimento, ou a esbelteza dos pilares, no
caso da propagação de vibração das fundações para o primeiro piso. Observa-se que, apesar da
amplitude de vibração ser maior para elementos estruturais mais flexíveis, os elementos mais rígidos
transmitem efectivamente mais energia devido a um menor efeito dissipativo. Os resultados também
mostram que a atenuação piso-a-piso é aproximadamente constante para todos os pisos excepto a
cobertura, onde a atenuação diminui por via da redução do número de caminhos de dissipação de
energia.info:eu-repo/semantics/publishedVersio
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