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In this work we give an asymptotic lower bound for the Hilbert number for real planar polynomial differential systems. This lower bound equals, up to leading order, to the best existing one, but the method we provide is new and involves slow-fast systems. The construction strongly relies on generalized Liénard systems. [ABSTRACT FROM AUTHOR]

Given trigonometric monomials A 1 , A 2 , A 3 , A 4 , such that A 1 , A 3 have the same signs as sin ⁡ t , and A 2 , A 4 the same signs as cos ⁡ t , and natural numbers n , m > 1 , we study the family of Abel equations x ′ = ( a 1 A 1 ( t ) + a 2 A 2 ( t ) ) x m + ( a 3 A 3 ( t ) + a 4 A 4 ( t ) ) x n , a 1 , a 2 , a 3 , a 4 ∈ R . The center variety is the set of values a 1 , a 2 , a 3 , a 4 such that the Abel equation has a center (every bounded solution is periodic). We prove that the codimension of the center variety is one or two. Moreover, it is one if and only if A 1 = A 3 and A 2 = A 4 and it is two if and only if the family has non-trivial limit cycles (different from x ( t ) ≡ 0 ) for some values of the parameters. [ABSTRACT FROM AUTHOR]

We study the global behaviour of the period function on the period annulus of degenerate centres for two families of planar polynomial vector fields. These families are the quasi-homogeneous vector fields and the vector fields given by the sum of two quasi-homogeneous Hamiltonian ones. In the first case we prove that the period function is globally decreasing, extending previous results that deal either with the Hamiltonian quasi-homogeneous case or with the general homogeneous situation. In the second family, and after adding some more additional hypotheses, we show that the period function of the origin is either decreasing or has at most one critical period and that both possibilities may happen. This result also extends some previous results that deal with the situation where both vector fields are homogeneous and the origin is a non-degenerate centre. [ABSTRACT FROM AUTHOR]

A letter to the editor for an article "Topical anticholinergic drugs in the treatment of multiple hidrocystomas: a cross-over, randomized, double-blind, placebo-controlled study" published in the previous issue is presented.

Abstract: We study the periodic solutions of the generalized Abel equation , where are distinct integers, , and are -periodic analytic functions such that are -periodic positive even functions. When we prove that the equation has no non-trivial (different from zero) limit cycle for any value of the parameters . When we obtain under additional conditions the existence of non-trivial limit cycles. In particular, we obtain limit cycles not detected by Abelian integrals. [Copyright &y& Elsevier]

Abstract: In this paper we study the number of limit cycles of two families of cubic systems introduced in previous papers to model real phenomena. The first one is motivated by a model of star formation histories in giant spiral galaxies and the second one comes from a model of Volterra type. To prove our results we develop a new criterion on the non-existence of periodic orbits and we extend a well-known criterion on the uniqueness of limit cycles due to Kuang and Freedman. Both results allow to reduce the problem to the control of the sign of certain functions that are treated by algebraic tools. Moreover, in both cases, we prove that when the limit cycles exist they are non-algebraic. [Copyright &y& Elsevier]

Abstract: For the family of scalar Abel-like equations , where , , , , , and , we characterize the existence of non-trivial limit cycles (periodic solutions that are isolated in the set of periodic solutions different from the trivial ) in terms of . [Copyright &y& Elsevier]

Abstract: We study the uniqueness of limit cycles (periodic solutions that are isolated in the set of periodic solutions) in the scalar ODE in terms of , , . Our main result characterizes, under some additional hypotheses, the exponents , , , such that for any choice of the equation has at most one limit cycle. The obtained results have direct application to rigid planar vector fields, thus, planar systems of the form , , where . Concretely, when the set has at least three elements (or exactly one) and another technical condition is satisfied, we characterize the exponents , such that the origin of the rigid system is a center for any choice of and also when there are no limit cycles surrounding the origin for any choice of . [Copyright &y& Elsevier]

Abstract: In this work we focus on the configuration (location and stability) of simple critical points of polynomial differential equations of the form , . The case where all the critical points are of center type is studied in more detail finding several new center configurations. One of the main tools in our approach is the 1-dimensional Euler–Jacobi formula. [Copyright &y& Elsevier]

Abstract: We consider the Abel equation , where and are trigonometric polynomials of degree n and m, respectively, and we give lower bounds for its number of isolated periodic orbits for some values of n and m. These lower bounds are obtained by two different methods: the study of the perturbations of some Abel equations having a continuum of periodic orbits and the Hopf-type bifurcation of periodic orbits from the solution . [Copyright &y& Elsevier]

Abstract: In this article we give two criteria for bounding the number of non-contractible limit cycles of a family of differential systems on the cylinder. This family includes Abel equations as well as the polar expression of several types of planar polynomial systems given by the sum of three homogeneous vector fields. [Copyright &y& Elsevier]

Abstract: A solution of the Abel equation such that is called a periodic orbit of the equation. Our main result proves that if there exist two real numbers a and b such that the function is not identically zero, and does not change sign in then the Abel differential equation has at most one non-zero periodic orbit. Furthermore, when this periodic orbit exists, it is hyperbolic. This result extends the known criteria about the Abel equation that only refer to the cases where either or does not change sign. We apply this new criterion to study the number of periodic solutions of two simple cases of Abel equations: the one where the functions and are 1-periodic trigonometric polynomials of degree one and the case where these two functions are polynomials with three monomials. Finally, we give an upper bound for the number of isolated periodic orbits of the general Abel equation , when , and satisfy adequate conditions. [Copyright &y& Elsevier]

Abstract: It is well known that the normal form theory can be applied to solve the center–focus problem for monodromic planar nilpotent singularities. In this paper we see how this theory can also be applied to generate limit cycles from this type of singularities. [Copyright &y& Elsevier]

The rotation of uniaxial ellipsoidal particles has provided the base for many studies of shape preferred orientations of mineral grains in a large variety of rock types. In this paper we present reports of a study of the evolution of a multiparticle system as a function of the elongation ratio of the particles and of the initial particle distribution. Our model reveals that both factors are important in controlling the acquisition of a stable orientation upon deformation. The more elongated particles (r=short axis/long axis≤0.5) will define a stable fabric in almost any situation of geologic interest (γ=shear deformation<10), but less elongated particles (r>0.5) can also be considered to have achieved a stable orientation depending on the total amount of shear experienced by the rock. However, in systems with the less elongated particles (r≥0.8) it is possible to find mean orientations that are perpendicular to the direction of shear, although the occurrence of such behavior constitutes only a minor fraction of the studied examples. In any case, it is suggested that a systematic study of mineral fabrics in samples from the same rock can yield enough information to evaluate whether the mean shape preferred orientation of the minerals is parallel to flow direction. [Copyright &y& Elsevier]

The aim of this paper is to study the existence of limit cycles for a family of generalized Abel equations x ′ = A (t) x m + B (t) x n , m , n ≥ 2. Under certain assumptions, it is proved that there exists a non-trivial limit cycle. This limit cycle has the characteristic that it arises from neither a Hopf bifurcation nor a perturbation of periodic orbits in a period annulus around the centre at the origin. [ABSTRACT FROM AUTHOR]

Background As future health educators, nursing and physiotherapy students will play an essential role in the prevention of smoking. Aim To determine the prevalence of smoking among students and to analyse their knowledge of and attitudes towards smoking. Method This was a descriptive cross-sectional study using an anonymous questionnaire and conducted in a Spanish Faculty of Health Sciences in 2013. Findings 247 nursing and physiotherapy students (82.33%) participated in the study. The global prevalence of smoking (18.2%) was lower compare with the general population group of the same age. We have observed statistical significance in relation to previous studies. Nursing and physiotherapy students showed a low nicotine dependence. We found a lack of knowledge about the harmful effects of cigarette consumption on health. Statistically significant results were also found in relation to degree courses (p < 0.01) as regards students' opinions about their knowledge of strategies and methods to help patients stop smoking. Conclusion Most students started smoking before commencing their university studies; consequently, interventions should focus on cessation programmes. An analysis of university curricula leading to the award of a degree in the health sciences could serve to identify educational deficiencies in order to implement the necessary modifications. Implications for nursing and health policy This paper presents an update in tobacco use characteristics amongst nursing and physiotherapy students. Those results have showed a need to improve the curricula in order to develop specific programmes to improve knowledge, attitudes and beliefs. Measures to prevent smoking must be taken at school. [ABSTRACT FROM AUTHOR]

Abstract: One of the most important challenges that confronts less-than-truckload carriers serving many-to-many distribution networks consists of determining how to consolidate flows of small shipments. The objective is to determine a route for each origin–destination pair that minimizes the cost while still guaranteeing a certain level of service. This research studies different aspects of the problem and provides a metaheuristic algorithm (based on Ant Colony Optimization techniques) capable of solving real-life problems in a reasonable computational time. The viability of the approach has been tested with a real case in Spain and encouraging results have been obtained. [Copyright &y& Elsevier]

Abstract: One of the main problems dealing with iterative methods for solving polynomial systemsis the initialization of the iteration. This paper provides an algorithm to initialize the search of solutions of polynomial systems. [Copyright &y& Elsevier]

Current research on the circular economy (CE) reveals that, while the concept and its application have been extensively explored as shown in several case studies, the definition of tools and criteria measuring "circularity" of products, companies or regions are not well-defined. Therefore, indicators for measuring the different levels of a CE (micro, meso, and macro) should be a high priority for stakeholders (governments, companies, NGOs, civil society, etc.) in order to track progress on CE initiatives. However, the increasing interest on CE has caused a still open debate on the conceptualization of CE which hampers the creation of indicators based on a common conceptual framework. As a result, the absence of standard indicators to track progress on circularity is leading to contradiction and misunderstanding, which represents a challenge to the implementation of CE strategies. Thus, this study tries to address this gap by advancing a set of indicators adapted from existing indicators that guarantees simplicity and effectiveness, closely based on indicators proposed by government bodies. This research carried out an exploratory study to formulate the indicators requirements based on literature, refined through experts' opinion and then they were tested in Spanish companies located in the Basque Country region through an empirical work to assess this theory. A mix of research methods (e.g. semi-structured interviews and surveys) were used to seek applicability of CE indicators for organisations. The study showed that the proposed indicators currently used for assessing the CE at the macro level were applicable at the micro level based on companies' responses. This fact demonstrated that the indicators serve the purpose of being applicable to companies regardless of the type of economic activity they were in. Also, it shows that indicators used to monitor progress on CE at the macro level can be translated to the micro level. Consequently, it is recommended that the set of CE indicators focused on the methodology proposed in this study should be used across different industrial sectors in order to observe performance in companies to facilitate the transition to a CE model. • The main objective of this study was to advance the indicators currently available. • The indicators were tested in companies to prove their suitability for circular economy assessment. • The proposed indicators collected the data in already existing statistics records. • These indicators might help companies to track their actions and strategies in circular economy. [ABSTRACT FROM AUTHOR]

Current PET detectors have a very low sensitivity, of the order of a few percent. One of the reasons is the fact that Compton interactions are rejected. If an event involves multiple Compton scattering and the total deposited energy lays within the photoelectric peak, then an energy-weighted centroid is the given output for the coordinates of the reconstructed interaction point. This introduces distortion in the final reconstructed image. The aim of our work is to prove that Compton events are a very rich source of additional information as one can improve the resolution of the detector and implicitly the final reconstructed image. This could be a real breakthrough for PET detector technology as one should be able to obtain better results with less patient radiation. Using a PET as a double Compton camera , by means of Compton cone matching i.e., Compton cones coming from the same event should be compatible, is applied to discard randoms, patient scattered events and also, to perform a correct matching among events with multiple coincidences. In order to fully benefit experimentally from Compton events using monolithic scintillators a multi-layer configuration is needed and a good time-of-flight resolution. [ABSTRACT FROM AUTHOR]

Streptococcus bovis group and Enterococcus spp. share phenotypic characteristics and intestinal habitat. Both have been associated with endocarditis and colorectal neoplasm (CRN). We studied all cases of endocarditis diagnosed between 1988 and 2014 in our centre and caused by S. bovis (109, 48.8 % of the bacteremia) and by Enterococcus spp. (36, 3.4 % of the bacteremia). Patients were seen until death or during a long-term follow-up, in order to rule out a concomitant CRN. The 109 cases of S. bovis endocarditis (SbIE) compared with the 36 caused by enterococci showed: a higher proportion of males (91 % vs. 72 %, p=0.005), more multivalvular involvement (28 % vs. 6 %, p=0.004), embolic complications (44 vs. 22 %, p=0.02) and colorectal neoplasm (64 % vs. 25 %, p=0.001). SbIE showed fewer co-morbidities (32 vs. 58 %, p=0.005), and less frequently urinary infection source (0 vs. 25 %, p=0.001) and healthcare-related infection (2 vs. 44 %, p=0.001). A total of 123 patients were followed up for an extended period (mean: 65.9 ± 57.5 months). During the follow-up, 6 of 28 (21 %) cases with enterococcal endocarditis and 43 of 95 (45.2 %, p=0.01) cases with SbIE developed a new CRN. These neoplasiae appeared a mean of 60.4 months later (range 12-181 months). Among the 43 cases with SbIE and CRN, 12 had had a previously normal colonoscopy and 31 had had a previous CRN and developed a second neoplasm. Cases of SbIE present important differences with those caused by Enterococcus spp. Colonoscopy must be mandatory both in the initial evaluation of SbIE, as during the follow-up period. [ABSTRACT FROM AUTHOR]

We have developed a detector block composed by a monolithic LYSO scintillator coupled to a custom made 12×12 SiPMs array. The design is mainly focused to applications such as Positron Emission Tomography. The readout electronics is based on 3 identical and scalable Application Specific Integrated Circuits (ASIC). We have determined the main performance of the detector block namely spatial, energy, and time resolution but also the system capability to determine the photon depth of interaction, for different crystal surface treatments. Intrinsic detector spatial resolution values as good as 1.7 mm FWHM and energies of 15% for black painted crystals were measured. [ABSTRACT FROM AUTHOR]

Abstract: In this work we present the energy and spatial resolutions we have obtained for a detector based on a monolithic LYSO crystal coupled to an array of 256 SiPMs. Two crystal configurations of the same trapezoidal shape have been tried. In one approach all surfaces were black painted but the exit one facing the photosensor array which was polished. The other approach included a retroreflector (RR) layer coupled to the entrance face of the crystal powering the amount of transmitted light to the photosensors. Two coupling media between the scintillator and the SiPM array were used, namely direct coupling by means of optical grease and coupling through an array of light guides. Since the same operational voltage was supplied to the entire array, it was needed to equalize their gains before feeding their signals to the Data Acquisition system. Such a job was performed by means of 4 scalable Application Specific Circuits (ASICs). An energy resolution of about 24.4% has been achieved for the direct coupling with the RR layer together with a spatial resolution of approximately 2.9mm at the detector center. With the light guides coupling the effects of image compression at the edges are significantly minimized, but worsening the energy resolution to about 33.1% with a spatial resolution nearing 4mm at the detector center. [Copyright &y& Elsevier]

Abstract: In this work we present a method to efficiently collect scintillation light when using monolithic scintillator crystals. The acceptance angle of the scintillation light has been reduced by means of optical devices reducing the border effect which typically affects continuous crystals. We have applied this procedure on gamma detectors for PET systems using both position sensitive PMTs and arrays of SiPMs. In the case of using SiPMs, this approach also helps to reduce the photosensor active area. We evaluated the method using PMTs with a variety of different crystals with thicknesses ranging from 10 to 24mm. We found that our design allows the use of crystal blocks with a thickness of up to 18mm without degrading the spatial resolution caused by edge effects and without a significant detriment to the energy resolution. These results were compared with simulated data. The first results of monolithic LYSO crystals coupled to an array of 256 SiPMs by means of individual optical light guides are also presented. [Copyright &y& Elsevier]

Abstract: In this work we present an innovative algorithm for the reconstruction of PET images based on the List-Mode (LM) technique which improves their spatial resolution compared to results obtained with current MLEM algorithms. This study appears as a part of a large project with the aim of improving diagnosis in early Alzheimer disease stages by means of a newly developed hybrid PET-MR insert. At the present, Alzheimer is the most relevant neurodegenerative disease and the best way to apply an effective treatment is its early diagnosis. The PET device will consist of several monolithic LYSO crystals coupled to SiPM detectors. Monolithic crystals can reduce scanner costs with the advantage to enable implementation of very small virtual pixels in their geometry. This is especially useful for LM reconstruction algorithms, since they do not need a pre-calculated system matrix. We have developed an LM algorithm which has been initially tested with a large aperture (186mm) breast PET system. Such an algorithm instead of using the common lines of response, incorporates a novel calculation of tubes of response. The new approach improves the volumetric spatial resolution about a factor 2 at the border of the field of view when compared with traditionally used MLEM algorithm. Moreover, it has also shown to decrease the image noise, thus increasing the image quality. [Copyright &y& Elsevier]

Abstract: In this paper we describe the overall design of a PET–MR system for head imaging within the framework of the DREAM Project as well as the first detector module tests. The PET system design consists of 4 rings of 16 detector modules each and it is expected to be integrated in a head dedicated radio frequency coil of an MR scanner. The PET modules are based on monolithic LYSO crystals coupled by means of optical devices to an array of 256 Silicon Photomultipliers. These types of crystals allow to preserve the scintillation light distribution and, thus, to recover the exact photon impact position with the proper characterization of such a distribution. Every module contains 4 Application Specific Integrated Circuits (ASICs) which return detailed information of several light statistical momenta. The preliminary tests carried out on this design and controlled by means of ASICs have shown promising results towards the suitability of hybrid PET–MR systems. [Copyright &y& Elsevier]

Background Obesity is a global epidemic that continues to increase in a great number of countries, and it has become a major public health problem in Spain. Unfortunately, the impact of obesity on survival in liver transplantation (LT) recipients is underestimated and controversial. The aim of this study was to determine if obesity is a risk factor for morbidity and mortality after LT. Methods In a retrospective cohort study of the records of 180 consecutive patients who had undergone to LT from 2007 to 2013, 11 obese patients with body mass index (BMI) >35 kg/m 2 were identified. Their data have been compared with recipients with BMI 20–25 kg/m 2 . Results There were no differences in demographic data, Child-Pugh score, Model for End-Stage Liver Disease score, or cause of liver failure. BMI >35 kg/m 2 recipients had a significantly higher rate of portal vein thrombosis before LT, compared with the BMI 20–25 kg/m 2 group (36.5% vs 13.9%; P = .041). There were also no differences in development of post-reperfusion syndrome. The groups were also comparable concerning morbidity rate after LT, stay in the intensive care unit, and global hospital stay. However, the mortality rate was significantly higher in the obese group compared with the nonobese group (72.7% vs 38.9%; P = .032). Conclusions The results of the study clearly demonstrate higher mortality rates in obese patients undergoing LT; thus, it is fair to consider obesity as a poor prognosis predictive factor concerning mortality rate. [ABSTRACT FROM AUTHOR]

The development of dedicated positron emission tomography scanners is an active area of research, especially aiming at the improvement of lesion detection and in support of cancer treatment and management. Recently, dedicated Positron Emission Tomography (PET) systems with different configurations for specific organs have been developed for improving detection effectiveness. Open geometries are always subject to distortion and artifacts in the reconstructed images. Therefore, the aim of this work is to determine the optimal geometry for a novel cardiac PET system that will be developed by our team, and determine the time resolution needed to achieve reasonable image quality for the chosen geometry. The proposed geometries consist of 36 modules. These modules are arranged in two sets of two plates, each one with different configurations. We performed Monte Carlo simulations with different TOF resolutions, in order to test the image quality improvement in each case. Our results show, as expected, that increasing TOF resolution reduces distortion and artifact effects. We can conclude that a TOF resolution of the order of 200 ps is needed to reduce the artifacts, to acceptable levels, generated in the simulated cardiac-PET open geometries. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Rapamycin (RAPA) is a powerful immunosuppressant that also acts as an antiproliferative, which, therefore, could be useful in the treatment and prevention of bronchiolitis obliterans (BOS) in lung transplant recipients. We sought to report our experiences with RAPA in lung transplant patients with BOS that has not responded to the administration of other drugs. Materials and methods: We performed a retrospective analysis of the clinical characteristics, pulmonary function, and complications among patients with BOS who received RAPA. Results: RAPA was administered to 11 patients, three single-lung transplant and eight bilateral lung transplant recipients, of whom five were women and six men, of mean age 48 years (26 to 65). The median posttransplant time to the initiation of RAPA for progressive BOS was 32 months (4 to 69) with a posttreatment follow-up of 15 months (3 to 34). RAPA was administered to all patients in association with a calcineurin inhibitor (tacrolimus in seven cases, and cyclosporine in four and steroids. Eight of the 11 patients (72%) with progressive deterioration of pulmonary function showed improved and/or stabilized FEV1 figures after introduction of RAPA. Eight patients developed adverse effects, which were possibly related to RAPA, leading to treatment withdrawal in two cases. The most frequent adverse effects were infections among 6 of the 12 cases, and myelosuppression in three. Conclusions: RAPA may be useful to stabilize or improve pulmonary function in patients with BOS. Nevertheless, it was necessary for patients to be closely monitored so that possible adverse effects, and especially infections, may be detected early. [Copyright &y& Elsevier]