On co-isosimple modules and co-isoradical of modules

Abstract

In this paper we study “co-isosimple” modules, that is, those modules which are isomorphic to all of its non-zero quotients modules. This allows us to define and study “isomaximal” submodules, “isomax” modules and the “co-isoradical” of a module. We study some of its basic properties and we give a characterization of left V-ring using these concepts.

Communicated by Alberto Facchini     

Asymmetrical hippocampal connectivity in mesial temporal lobe epilepsy: evidence from resting state fMRI

Background

Recent studies have shown that the human right-hemispheric auditory cortex is particularly sensitive to reduction in sound quality, with an increase in distortion resulting in an amplification of the auditory N1m response measured in the magnetoencephalography (MEG). Here, we examined whether this sensitivity is specific to the processing of acoustic properties of speech or whether it can be observed also in the processing of sounds with a simple spectral structure. We degraded speech stimuli (vowel /a/), complex non-speech stimuli (a composite of five sinusoidals), and sinusoidal tones by decreasing the amplitude resolution of the signal waveform. The amplitude resolution was impoverished by reducing the number of bits to represent the signal samples. Auditory evoked magnetic fields (AEFs) were measured in the left and right hemisphere of sixteen healthy subjects.

Results

We found that the AEF amplitudes increased significantly with stimulus distortion for all stimulus types, which indicates that the right-hemispheric N1m sensitivity is not related exclusively to degradation of acoustic properties of speech. In addition, the P1m and P2m responses were amplified with increasing distortion similarly in both hemispheres. The AEF latencies were not systematically affected by the distortion.

Conclusions

We propose that the increased activity of AEFs reflects cortical processing of acoustic properties common to both speech and non-speech stimuli. More specifically, the enhancement is most likely caused by spectral changes brought about by the decrease of amplitude resolution, in particular the introduction of periodic, signal-dependent distortion to the original sound. Converging evidence suggests that the observed AEF amplification could reflect cortical sensitivity to periodic sounds.     

Mapping the global structure of TSP fitness landscapes

The global structure of combinatorial landscapes is not fully understood, yet it is known to impact the performance of heuristic search methods. We use a so-called local optima network model to characterise and visualise the global structure of travelling salesperson fitness landscapes of different classes, including random and structured real-world instances of realistic size. Our study brings rigour to the characterisation of so-called funnels, and proposes an intensive and effective sampling procedure for extracting the networks. We propose enhanced visualisation techniques, including 3D plots and the incorporation of colour, sizes and widths, to reflect relevant aspects of the search process. This brings an almost tangible new perspective to the landscape and funnel metaphors. Our results reveal a much richer global structure than the suggestion of a ‘big-valley’ structure. Most landscapes of the tested instances have multiple valleys or funnels; and the number, disposition and interaction of these funnels seem to relate to search difficulty on the studied landscapes. We also find that the structured TSP instances feature high levels of neutrality, an observation not previously reported in the literature. We then propose ways of analysing and visualising these neutral landscapes.     

Beau bounds for multicritical circle maps

Let $f:S^1\to S^1$ be a $C^3$ homeomorphism without periodic points having a finite number of critical points of power-law type. In this paper we establish real a-priori bounds, on the geometry of orbits of $f$, which are beau in the sense of Sullivan, i.e. bounds that are asymptotically universal at small scales. The proof of the beau bounds presented here is an adaptation, to the multicritical setting, of the one given by the second author and de Melo in de Faria and de Melo (1999), for the case of a single critical point.     

Solutions for the generalized Loewner differential equation in several complex variables

We generalize a one-variable result of J. Becker to several complex variables. We determine the form of arbitrary solutions of the Loewner differential equation that is satisfied by univalent subordination chains of the form ${f(z, t)=e^{tA}z+\cdots,}We generalize a one-variable result of J. Becker to several complex variables. We determine the form of arbitrary solutions of the Loewner differential equation that is satisfied by univalent subordination chains of the form f(z, t)=e^tAz+?,{f(z, t)=e^{tA}z+\cdots,} where A ? L(\mathbbCⁿ, \mathbbCⁿ){A\in L(\mathbb{C}^n, \mathbb{C}^n)} has the property k ₊(A) < 2m(A). Here k₊(A)=max{?l:l ? s(A)}{k_+(A)=\max\{\Re\lambda:\lambda\in \sigma(A)\}} and m(A)=min{?áA(z), z ?: ||z||=1}{m(A)=\min\{\Re\langle A(z), z \rangle: \|z\|=1\}} . (The notion of parametric representation has a useful generalization under these conditions, so that one has a canonical solution of the Loewner differential equation.) In particular, we determine the form of the univalent solutions. The results are applied to subordination chains generated by spirallike mappings on the unit ball in \mathbbCⁿ{\mathbb{C}^n} . Finally, we determine the form of the solutions in the presence of certain coefficient bounds.     

Global solutions and asymptotic behavior for a parabolic degenerate coupled system arising from biology

In this paper we will focus on a parabolic degenerate system with respect to unknown functions u and w on a bounded domain of the two dimensional Euclidean space. This system appears as a mathematical model for some biological processes. Global existence and uniqueness of a nonnegative classical Hölder continuous solution are proved. The last part of the paper is devoted to the study of the asymptotic behavior of the solutions.     

New hybrid nanostructures based on oxacillin-hydrotalcite-like anionic clays and their textural properties

New hybrid nanostructures based on inorganic matrices of hydrotalcite-like anionic clays (HT) incorporated with oxacillin are obtained by using calcinations-restructure method. XRD and TEM analyses are used to study the structural and textural characteristics of the clay containing hybrids. When nanoparticles of iron oxides are loaded on the layered anionic clay matrix a more effective delivery system of the drug is obtained. The results can be used to reduce the toxic side effects of oxacillin (e.g. upset stomach, diarrhea, cholestastic hepatitis), its aggregation process in aqueous solutions and also can open new perspectives for targeted the drug delivery.     

SEM and EDX studies of bioactive hydroxyapatite coatings on titanium implants

This work presents a study on an alternative coating method based on biomimetic techniques which are designed to form a crystalline hydroxyapatite layer very similar to the process corresponding to the formation of natural bone. The HA formation on the surface of titanium alloy pretreated with NaOH solution is investigated. Two types of solutions such as supersaturated calcification solution (SCS) and modified SCS (M-SCS) were used to investigate bone-like apatite formation on alkali-treated titanium. The hydroxyapatite deposits are investigated by means of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The data suggest that the method utilized in this work can be successfully applied to obtain deposition of uniform coatings of crystalline hydroxyapatite on titanium substrates.     

Determination of cardiovascular drugs in sewage sludge by matrix solid-phase dispersion and ultra-performance liquid chromatography tandem mass spectrometry

Analytical and Bioanalytical Chemistry - The current study presents a single step sample preparation procedure for the simultaneous determination of five antihypertensive (propranolol, losartan,...