Bouncing solutions in Rastall's theory with a barotropic fluid

Rastall's theory is a modification of Einstein's theory of gravity where the covariant divergence of the stress-energy tensor is no more vanishing, but proportional to the gradient of the Ricci scalar. The motivation of this theory is to investigate a possible non-minimal coupling of the matter fields to geometry which, being proportional to the curvature scalar, may represent an effective description of quantum gravity effects. Non-conservation of the stress-energy tensor, via Bianchi identities, implies new field equations which have been recently used in a cosmological context, leading to some interesting results. In this paper we adopt Rastall's theory to reproduce some features of the effective Friedmann's equation emerging from loop quantum cosmology. We determine a class of bouncing cosmological solutions and comment about the possibility of employing these models as effective descriptions of the full quantum theory.Comment: Latex file, 14 pages, 1 figure in eps format. Typos corrected, one reference added. Published versio

High performance reduced order modeling techniques based on optimal energy quadrature: application to geometrically non-linear multiscale inelastic material modeling

A High-Performance Reduced-Order Model (HPROM) technique, previously presented by the authors in the context of hierarchical multiscale models for non linear-materials undergoing infinitesimal strains, is generalized to deal with large deformation elasto-plastic problems. The proposed HPROM technique uses a Proper Orthogonal Decomposition procedure to build a reduced basis of the primary kinematical variable of the micro-scale problem, defined in terms of the micro-deformation gradient fluctuations. Then a Galerkin-projection, onto this reduced basis, is utilized to reduce the dimensionality of the micro-force balance equation, the stress homogenization equation and the effective macro-constitutive tangent tensor equation. Finally, a reduced goal-oriented quadrature rule is introduced to compute the non-affine terms of these equations. Main importance in this paper is given to the numerical assessment of the developed HPROM technique. The numerical experiments are performed on a micro-cell simulating a randomly distributed set of elastic inclusions embedded into an elasto-plastic matrix. This micro-structure is representative of a typical ductile metallic alloy. The HPROM technique applied to this type of problem displays high computational speed-ups, increasing with the complexity of the finite element model. From these results, we conclude that the proposed HPROM technique is an effective computational tool for modeling, with very large speed-ups and acceptable accuracy levels with respect to the high-fidelity case, the multiscale behavior of heterogeneous materials subjected to large deformations involving two well-separated scales of length.Peer ReviewedPostprint (author's final draft

High linear power amplifier for multicarrier satellite communications

High linearity performance in transmitters is receiving continuously attention due to demands of higher data rates in satellite communication links. This paper presents a GaAs pHEMT MMIC high linear power amplifier intended for multicarrier operation at C-band. Junction temperature prediction methods are considered during the amplifier design to keep the temperature under control and achieve high reliability required for space applications. The design method is focused in high linearity optimizing the loads and using a non-linear transistor model to predict harmonic generation and intermodulation products. The amplifier was characterized in terms of S-parameters, single tone output power and two tone output power. The measured S-parameters shows a flattened gain over 25 dB between 3 and 6 GHz. The 1dB compression point is measured at 26.7 dBm and the output third order intercept point (OIP3) is above 40 dBm in the band reaching a maximum of 41.7 dBm at 4.5 GHz. The power consumption is lower than 2.5 W and the junction temperatures are calculated under 105 \ub0C

Detectability of low-oxygenated regions in human muscle tissue using near-infrared spectroscopy and phantom models

The present work aims to describe the detectability limits of hypoxic regions in human muscle under moderate thicknesses of adipose tissue to serve as a groundwork for the development of a wearable device to prevent pressure injuries. The optimal source-detector distances, detection limits, and the spatial resolution of hypoxic volumes in the human muscle are calculated using finite element method-based computer simulations conducted on 3-layer tissue models. Silicone phantoms matching the simulation geometries were manufactured, and their measurement results were compared to the simulations. The simulations showed good agreement with the performed experiments. Our results show detectability of hypoxic volumes under adipose tissue thicknesses of up to 1.5 cm. The maximum tissue depth, at which hypoxic volumes could be detected was 2.8 cm. The smallest detectable hypoxic volume in our study was 1.2 cm3. We thus show the detectability of hypoxic volumes in sizes consistent with those of early-stage pressure injury formation and, consequently, the feasibility of a device to prevent pressure injuries

Maximal and minimal dynamic Petri net slicing

Context: Petri net slicing is a technique to reduce the size of a Petri net so that it can ease the analysis or understanding of the original Petri net. Objective: Presenting two new Petri net slicing algorithms to isolate those places and transitions of a Petri net (the slice) that may contribute tokens to one or more places given (the slicing criterion). Method: The two algorithms proposed are formalized. The completeness of the first algorithm and the minimality of the second algorithm are formally proven. Both algorithms together with other three state-of-the-art algorithms have been implemented and integrated into a single tool so that we have been able to carry out a fair empirical evaluation. Results: Besides the two new Petri net slicing algorithms, a public, free, and open-source implementation of five algorithms is reported. The results of an empirical evaluation of the new algorithms and the slices that they produce are also presented. Conclusions: The first algorithm collects all places and transitions that may influence (in any computation) the slicing criterion, while the second algorithm collects a minimum set of places and transitions that may influence (in some computation) the slicing criterion. Therefore, the net computed by the first algorithm can reproduce any computation that contributes tokens to any place of interest. In contrast, the second algorithm loses this possibility but it often produces a much more reduced subnet (which still can reproduce some computations that contribute tokens to some places of interest). The first algorithm is proven complete, and the second one is proven minimal

Multi-reference approach to the calculation of photoelectron spectra including spin-orbit coupling

X-ray photoelectron spectra provide a wealth of information on the electronic structure. The extraction of molecular details requires adequate theoretical methods, which in case of transition metal complexes has to account for effects due to the multi-configurational and spin-mixed nature of the many-electron wave function. Here, the Restricted Active Space Self-Consistent Field method including spin-orbit coupling is used to cope with this challenge and to calculate valence and core photoelectron spectra. The intensities are estimated within the frameworks of the Dyson orbital formalism and the sudden approximation. Thereby, we utilize an efficient computational algorithm that is based on a biorthonormal basis transformation. The approach is applied to the valence photoionization of the gas phase water molecule and to the core ionization spectrum of the $\text{[Fe(H}_2\text{O)}_6\text{]}^{2+}$ complex. The results show good agreement with the experimental data obtained in this work, whereas the sudden approximation demonstrates distinct deviations from experiments

Depressivität und Einschätzung der Familienverhältnisse unter Kindern kroatischer Vertriebener

The aim of the study was to estimate the prevalence of depressive symptoms and perceived family functioning in a group of 112 displaced Croatian children who had been exiled from their homes (the eastern part of Slavonia and Baranya) at the beginning of war in Croatia. The children had been living in refugee camps near Osijek for 4 years at the time of the investigation. All the examinees completed the Croatian version of the War Trauma Questionnaire, the Children\u27s Depression Inventory (CDI), and the Hudson\u27s Index of Family Relations (HIFS). According to previously established cut-off scores on the CDI, 20 children (17,9%) scored within the clinical range, and 23 children (20,5%) reported significant problems in their perception of family relationship on HIFS. There was a significant correlation between the number of war traumatic experiences and CDI score, HIFS score and the depression scores on CDI. The findings may be useful in the planning of psychosocial intervention programmes for traumatised children.Cilj istraživanja bio je ustanoviti prevalenciju depresivnih simptoma i doživljaj obiteljskih odnosa u skupini od 112 hrvatske djece prognanika, prognanih početkom rata u Hrvatskoj iz Istočne Slavonije i Baranje. Prosječna dužina boravka u prognaničkom naselju blizu Osijeka u vrijeme provedbe istraživanja iznosila je 4 godine. Svi ispitanici ispunili su hrvatske verzije Upitnika ratnih traumatskih iskustava, Ljestvice za dječju depresiju i Indeksa obiteljskih odnosa. Analiza rezultata pokazala je da 17,9% djece ima značajno povišen ukupni rezultat na Ljestvici za dječju depresiju, a 20,5% djece izvijestilo je o značajnom problemu u doživljaju obiteljskih odnosa na Indeksu obiteljskih odnosa. Nađena je statistički značajna korelacija broja traumatskih iskustava i rezultata na CDI i HIFS s ukupnim rezultatom na Ljestvici za dječju depresivnost. Dobiveni rezultati mogu poslužiti u kreiranju psihosocijalnih programa u radu s traumatiziranom djecom prognanicima.Mit dieser Untersuchung sollte die Prävalenzrate von Depressionssymptomen und die Sicht der Familienverhältnisse in einer Gruppe von 112 Kindern, deren Eltern zu Beginn des Krieges in Kroatien (1991) aus Ostslawonien und der Baranja vertrieben worden waren, ermittelt werden. Die Zeit, die die Vertriebenen im Durchschnitt in einem Flüchtlingslager bei Osijek verbracht hatten, betrug vier Jahre. Alle Untersuchungsteilnehmer erhielten die kroatischen Versionen folgender Fragebögen: Fragebogen zur Ermittlung traumatischer Kriegserlebnisse, Skala zur Ermittlung von Depression bei Kindern und Index der Familienverhältnisse. Die Untersuchung ergab, dass 17,9% der Kinder eine wesentlich höhere Gesamtpunktezahl auf der Skala zur Ermittlung von Depression bei Kindern erzielte; 20,5% der Kinder berichteten von beträchtlichen Schwierigkeiten bei der Verarbeitung familiärer Probleme (Index der Familienverhältnisse). Man entdeckte eine statistisch relevante Korrelation zwischen der Zahl traumatischer Kriegserlebnisse und den Gesamtergebnissen der Skala zur Ermittlung von Depression bei Kindern. Die gewonnenen Ergebnisse können beim Entwurf von psychosozialen Programmen zur Behandlung traumatisierter Flüchtlingskinder dienen

Análisis de la relación nota-posición en el aula de los alumnos en escuelas de ingeniería

A menudo hemos escuchado a docentes universitarios decir que sus mejores alumnos se sientan en las primeras filas del aula y que los menos interesados en la materia suelen ocupar los últimos asientos o los más cercanos a la puerta. También se tiene la percepción de que los malos estudiantes por lo general se sientan juntos en el aula. ¿Es todo esto cierto? ¿Podemos cuantificarlo? Y lo más importante, ¿podemos utilizar esta información en favor de los alumnos? Para poder ratificar o no estas sensaciones, en este artículo tratamos de responder a estas preguntas mediante el análisis estadístico detallado de un experimento que hemos realizado a partir de la recolección y el tratamiento de datos sobre la posición exacta que ocuparon diversos estudiantes durante un curso académico y sus notas en varias asignaturas y en sesiones tanto de teoría como de laboratorio.SUMMARY -- We have often heard from university teachers that their best students are seated in the front rows of the lecture room and those less interested in the subject often sit in the last seats or those close to the door. Moreover, there exists also the perception that the worst students are usually seated together. Are these beliefs objectively true? In order to check the validity of these ideas, in this article we perform a detailed statistical analysis of a large experiment done in engineering schools. The experiment collected and processed data about the exact position occupied by students during one academic year, their position changes along the year and their marks in various degrees, courses and semesters of both theory and laboratory practice.Peer Reviewe

The influence of the mass-ratio on the acceleration of particles by filamentation instabilities

Almost all sources of high energy particles and photons are associated with jet phenomena. Prominent sources of such highly relativistic outflows are pulsar winds and Active Galactic Nuclei. The current understanding of these jets assumes diluted plasmas which are best described as kinetic phenomena. In this kinetic description particle acceleration to ultra-relativistic speeds can occur in completely unmagnetized and neutral plasmas through insetting effects of instabilities. Even though the morphology and nature of particle spectra are understood to a certain extent, the composition of the jets is not known yet. While Poynting-flux dominated jets are certainly composed of electron-positron plasmas, the understanding of the governing physics in AGN jets is mostly unclear. In this article we investigate how the constituting elements of an electron-positron-proton plasma behave differently under the variation of the fundamental mass-ratio m_p/m_e. We studied initially unmagnetized counterstreaming plasmas using fully relativistic three-dimensional particle-in-cell simulations to investigate the influence of the mass-ratio on particle acceleration and magnetic field generation in electron-positron-proton plasmas. We covered a range of mass-ratios m_p/m_e between 1 and 100 with a particle number composition of n_{p^+}/n_{e^+} of 1 in one stream, only protons are injected in the other, whereas electrons are present in both to guarantee charge neutrality in the simulation box. We find that with increasing proton mass the instability takes longer to develop and for mass-ratios > 20 the particles seem to be accelerated in two phases which can be accounted to the individual instabilities of the different species. This means that for high mass ratios the coupling between electrons/positrons and the heavier protons, which occurs in low mass-ratios, disappears.Comment: 15 pages, 6 figure

Annexins as cell-type-specific markers in the developing chicken chorionallantoic membrane

Between day E8 and E12 of embryonic development, the chicken chorioallantoic membrane (CAM) undergoes massive structural rearrangement enabling calcium-uptake from the eggshell to supply the growing embryo. However, the contribution of the various cell types of the chorionic epithelium including the capillary covering (CC) cells, villus cavity (VC) cells, endothelial-like cells, and basal cells to this developmental program is largely unknown. In order to obtain markers for the different cell types in the chorionic epithelium, we determined the expression patterns of various calcium-binding annexins in the developing chicken CAM. By reverse transcription/polymerase chain reaction with primers deduced from nucleotide sequences available in various databases, the presence of annexin (anx)-1, anx-2, anx-5, and anx-6 was demonstrated at days E8 and E12. Quantitative immunoblotting with novel antibodies raised against the recombinant proteins revealed that anx-1 and anx-5 were significantly up-regulated at day E12, whereas anx-2 and anx-6 expression remained almost unchanged in comparison to levels at day E8. Immunohistochemistry of paraffin-embedded sections of E12 CAM revealed anx-1 in CC cells and VC cells. Anx-2 was localized in capillaries in the chorionic epithelium and in basal cells of the allantoic epithelium, whereas anx-6 was detected in basal cells or endothelial-like cells of the chorionic epithelium and in the media of larger vessels in the mesenchyme. A 2-day exposure of the CAM to a tumor cell spheroid resulted in strong proliferation of anx-1-expressing CC cells suggesting that these cells participate in the embryonic response to experimental intervention. Thus, annexins exhibit complementary expression patterns and represent appropriate cell markers for the further characterization of CAM development and the interpretation of results obtained when using CAM as an experimental mode