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 $C^\infty$ 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 $C^\infty$ 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 ($\sigma_{\theta_J}$), decay with the lattice size according to the power-law $\sigma_{\theta_J} \propto L^{-1 / \nu_J}$, with $\nu_{J} = 2 / (2D - d_f)$, where $D$ is the dimension of the substrate and $d_{\rm f}$ 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 $\nu_J = 1.0 (1)$ for the RSA of needles with $D = 2$ and $d_f = 2$, that gives $\nu_J = 1$. 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

An unified timing and spectral model for the Anomalous X-ray Pulsars XTE J1810-197 and CXOU J164710.2-455216

Anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs) are two small classes of X-ray sources strongly suspected to host a magnetar, i.e. an ultra-magnetized neutron star with $B\approx 10^14-10^15 G. Many SGRs/AXPs are known to be variable, and recently the existence of genuinely "transient" magnetars was discovered. Here we present a comprehensive study of the pulse profile and spectral evolution of the two transient AXPs (TAXPs) XTE J1810-197 and CXOU J164710.2-455216. Our analysis was carried out in the framework of the twisted magnetosphere model for magnetar emission. Starting from 3D Monte Carlo simulations of the emerging spectrum, we produced a large database of synthetic pulse profiles which was fitted to observed lightcurves in different spectral bands and at different epochs. This allowed us to derive the physical parameters of the model and their evolution with time, together with the geometry of the two sources, i.e. the inclination of the line-of-sight and of the magnetic axis with respect to the rotation axis. We then fitted the (phase-averaged) spectra of the two TAXPs at different epochs using a model similar to that used to calculate the pulse profiles ntzang in XSPEC) freezing all parameters to the values obtained from the timing analysis, and leaving only the normalization free to vary. This provided acceptable fits to XMM-Newton data in all the observations we analyzed. Our results support a picture in which a limited portion of the star surface close to one of the magnetic poles is heated at the outburst onset. The subsequent evolution is driven both by the cooling/varying size of the heated cap and by a progressive untwisting of the magnetosphere.Comment: 15 pages, 12 figures, accepted for publication in Ap

Contribution of a time-dependent metric on the dynamics of an interface between two immiscible electro-magnetically controllable Fluids

We consider the case of a deformable material interface between two immiscible moving media, both of them being magnetiable. The time dependence of the metric at the interface introduces a non linear term, proportional to the mean curvature, in the surface dynamical equations of mass momentum and angular momentum. We take into account the effects of that term also in the singular magnetic and electric fields inside the interface which lead to the existence of currents and charges densities through the interface, from the derivation of the Maxwell equations inside both bulks and the interface. Also, we give the expression for the entropy production and of the different thermo-dynamical fluxes. Our results enlarge previous results from other theories where the specific role of the time dependent surface metric was insufficiently stressed.Comment: 25 page

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 $L(t)$ 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