On Approximation of the Eigenvalues of Perturbed Periodic Schrodinger Operators

This paper addresses the problem of computing the eigenvalues lying in the gaps of the essential spectrum of a periodic Schrodinger operator perturbed by a fast decreasing potential. We use a recently developed technique, the so called quadratic projection method, in order to achieve convergence free from spectral pollution. We describe the theoretical foundations of the method in detail, and illustrate its effectiveness by several examples.Comment: 17 pages, 2 tables and 2 figure

Self‐consistent modeling of the large‐scale distortions in the geomagnetic field during the 24–27 September 1998 major magnetic storm

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94715/1/jgra17531.pd

Measuring the evolution of contemporary western popular music

Popular music is a key cultural expression that has captured listeners' attention for ages. Many of the structural regularities underlying musical discourse are yet to be discovered and, accordingly, their historical evolution remains formally unknown. Here we unveil a number of patterns and metrics characterizing the generic usage of primary musical facets such as pitch, timbre, and loudness in contemporary western popular music. Many of these patterns and metrics have been consistently stable for a period of more than fifty years, thus pointing towards a great degree of conventionalism. Nonetheless, we prove important changes or trends related to the restriction of pitch transitions, the homogenization of the timbral palette, and the growing loudness levels. This suggests that our perception of the new would be rooted on these changing characteristics. Hence, an old tune could perfectly sound novel and fashionable, provided that it consisted of common harmonic progressions, changed the instrumentation, and increased the average loudness.Comment: Supplementary materials not included. Please see the journal reference or contact the author

Magnetoelectric Effect and Spontaneous Polarization in HoFe3_3(BO3_3)4_4 and Ho0.5_{0.5}Nd0.5_{0.5}Fe3_3(BO3_3)4_4

The thermodynamic, magnetic, dielectric, and magnetoelectric properties of HoFe$_3$(BO$_3$)$_4$ and Ho$_{0.5}$Nd$_{0.5}$Fe$_3$(BO$_3$)$_4$ are investigated. Both compounds show a second order Ne\'{e}l transition above 30 K and a first order spin reorientation transition below 10 K. HoFe$_3$(BO$_3$)$_4$ develops a spontaneous electrical polarization below the Ne\'{e}l temperature (T$_N$) which is diminished in external magnetic fields. No magnetoelectric effect could be observed in HoFe$_3$(BO$_3$)$_4$. In contrast, the solid solution Ho$_{0.5}$Nd$_{0.5}$Fe$_3$(BO$_3$)$_4$ exhibits both, a spontaneous polarization below T$_N$ and a magnetoelectric effect at higher fields that extends to high temperatures. The superposition of spontaneous polarization, induced by the internal magnetic field in the ordered state, and the magnetoelectric polarizations due to the external field results in a complex behavior of the total polarization measured as a function of temperature and field.Comment: 12 pages, 15 figure

Revisiting the exercise heart rate-music tempo preference relationship

In the present study, we investigated a hypothesized quartic relationship (meaning three inflection points) between exercise heart rate (HR) and preferred music tempo. Initial theoretical predictions suggested a positive linear relationship (Iwanaga, 1995a, 1995b); however, recent experimental work has shown that as exercise HR increases, step changes and plateaus that punctuate the profile of music tempo preference may occur (Karageorghis, Jones, & Stuart, 2008). Tempi bands consisted of slow (95–100 bpm), medium (115–120 bpm), fast (135–140 bpm), and very fast (155–160 bpm) music. Twenty-eight active undergraduate students cycled at exercise intensities representing 40, 50, 60, 70, 80, and 90% of their maximal HR reserve while their music preference was assessed using a 10-point scale. The Exercise Intensity x Music Tempo interaction was significant, F(6.16, 160.05) = 7.08, p < .001, ηp 2 =.21, as was the test for both cubic and quartic trajectories in the exercise HR–preferred-music-tempo relationship (p < .001). Whereas slow tempo music was not preferred at any exercise intensity, preference for fast tempo increased, relative to medium and very fast tempo music, as exercise intensity increased. The implications for the prescription of music in exercise and physical activity contexts are discussed

Non-linear operations in quantum information theory

Quantum information theory is used to analize various non-linear operations on quantum states. The universal disentanglement machine is shown to be impossible, and partial (negative) results are obtained in the state-dependent case. The efficiency of the transformation of non-orthogonal states into orthogonal ones is discussed.Comment: 11 pages, LaTeX, 3 figures on separate page

The Parity Bit in Quantum Cryptography

An $n$-bit string is encoded as a sequence of non-orthogonal quantum states. The parity bit of that $n$-bit string is described by one of two density matrices, $\rho_0^{(n)}$ and $\rho_1^{(n)}$, both in a Hilbert space of dimension $2^n$. In order to derive the parity bit the receiver must distinguish between the two density matrices, e.g., in terms of optimal mutual information. In this paper we find the measurement which provides the optimal mutual information about the parity bit and calculate that information. We prove that this information decreases exponentially with the length of the string in the case where the single bit states are almost fully overlapping. We believe this result will be useful in proving the ultimate security of quantum crytography in the presence of noise.Comment: 19 pages, RevTe

Multiple General Anesthesia in Children: A Systematic Review of Its Effect on Neurodevelopment

The effect of multiple general anesthesia (mGA) procedures administered in early life is a critical theme and has led the Food and Drug Administration (FDA) to issue an alert. This systematic review seeks to explore the potential effects on neurodevelopment of mGA on patients under 4 years. The Medline, Embase and Web of Science databases were searched for publications up to 31 March 2021. The databases were searched for publications regarding “children multiple general anesthesia OR pediatric multiple general anesthesia”. Case reports, animal studies and expert opinions were excluded. Systematic reviews were not included, but they were screened to identify any possible additional information. A total of 3156 studies were identified. After removing the duplicates, screening the remaining records and analyzing the systematic reviews’ bibliography, 10 studies were considered suitable for inclusion. Comprehensively, a total cohort of 264.759 unexposed children and 11.027 exposed children were assessed for neurodevelopmental outcomes. Only one paper did not find any statistically significant difference between exposed and unexposed children in terms of neurodevelopmental alterations. Controlled studies on mGA administered before 4 years of age support that there might be a greater risk of neurodevelopmental delay in children receiving mGA, warranting the need for careful risk/benefit considerations

Magnetization and specific heat of TbFe3(BO3)4: Experiment and crystal field calculations

We have studied the thermodynamic properties of single-crystalline TbFe3(BO3)4. Magnetization measurements have been carried out as a function of magnetic field (up to 50 T) and temperature up to 350K with the magnetic field both parallel and perpendicular to the trigonal c-axis of the crystal. The specific heat has been measured in the temperature range 2-300K with a magnetic field up to 9 T applied parallel to the c-axis. The data indicate a structural phase transition at 192 K and antiferromagnetic spin ordering at 40 K. A Schottky anomaly is present in the specific heat data around 20 K, arising due to two low-lying energy levels of the Tb3+ ions being split by f-d coupling. Below TN magnetic fields parallel to the c-axis drive a spin-flop phase transition, which is associated with a large magnetization jump. The highly anisotropic character of the magnetic susceptibility is ascribed mainly to the Ising-like behavior of the Tb3+ ions in the trigonal crystal field. We describe our results in the framework of an unified approach which is based on mean-field approximation and crystal-field calculations.Comment: 10 pages, 10 figures, 20 references, accepted by Phys. Rev.