Strain-gradient-induced switching of nanoscale domains in free-standing ultrathin films

We report first-principle atomistic simulations on the effect of local strain gradients on the nanoscale domain morphology of free-standing PbTiO$_3$ ultrathin films. First, the ferroelectric properties of free films at the atomic level are reviewed. For the explored thicknesses (10 to 23 unit cells), we find flux-closure domain structures whose morphology is thickness dependent. A critical value of 20 unit cells is observed: thinner films show structures with 90$^\circ$ domain loops, whereas thicker ones develop, in addition, 180$^\circ$ domain walls, giving rise to structures of the Landau-Lifshitz type. When a local and compressive strain gradient at the top surface is imposed, the gradient is able to switch the polarization of the downward domains, but not to the opposite ones. The evolution of the domain pattern as a function of the strain gradient strength consequently depends on the film thickness. Our simulations indicate that in thinner films, first the 90$^\circ$ domain loops migrate towards the strain-gradient region, and then the polarization in that zone is gradually switched. In thicker films, instead, the switching in the strain-gradient region is progressive, not involving domain-wall motion, which is attributed to less mobile 180$^\circ$ domain walls. The ferroelectric switching is understood based on the knowledge of the local atomic properties, and the results confirm that mechanical flexoelectricity provides a means to control the nanodomain pattern in ferroelectric systems.Comment: 9 pages, 6 figure

Role of floor diaphragms on the seismic response of reinforced concrete frames

In existing Reinforced Concrete (RC) framed buildings, floor structural components (i.e. RC topping and joists) may play a crucial role in the seismic performance of the structure. The interaction between floor diaphragms and seismic-resistant frames can lead to different effects, depending on the relative stiffness and resistance of the elements belonging to the structures and on the adopted construction details. In this work, these aspects are deepened with reference to the institute “A. De Gasperi – R. Battaglia”, located in Norcia, Italy, chosen as case study. The seismic response of the building is investigated through pushover analyses by adopting a multi-layered shell element approach, where the mechanical nonlinearity is evaluated by using the PARC_CL 2.1 crack model, implemented as user subroutine in Abaqus FE package. The obtained results highlight that the modelling of the diaphragm increases the flexural capacity of the beams, so determining an increase of the seismic global response for frames characterized by ductile failure modes. The modelling of diaphragms may also alter beam-column strength hierarchy and stresses’ magnitude in beam-to-column joints, leading to anticipated brittle failures, that cannot be detected through the modelling of the bare fram

Regional assessment of the multi-decadal changes in braided riverscapes following large floods (Example of 12 reaches in South East of France)

Abstract. The district of the France Rhône basin is characterised by several braided reaches, preserved from the widespread disappearing occurred in the 20th century. Even if the overall pattern is evolving through a general river narrowing, some reaches have shown to be still active and have widened. The preliminary results suggest that differences in width pattern could be related to several factors, such as high magnitude and low frequency floods, and geographical position in the catchment which influences bedload delivery conditions and vegetation recruitment related to climate. From an initial set of 53 braided reaches, we selected 12 sites, distributed into four main hydro-geographical regions. Reaches were selected to be representative of the overall study area. We analysed the braiding width pattern and the vegetation pattern dynamic among five observation periods dating from the 1950s to the 2000s. We hypothesised that a comparative analysis of a detailed temporal trajectory (i.e. five dates) of a set of rivers within several hydro-geographical contexts would allow us to better distinguish the relative role of floods (in terms of magnitude and duration) and other controlling factors acting at the regional scale. We showed that active channel width is controlled mainly by Q10 flood and secondarily by bedload availability whereas island pattern is in large part independent of flood series characters. Moreover a clear regional differentiation, constant over time, in terms of riverscape response is observed, mainly opposing south-western and south-eastern reaches. This opposition depends on several concurring factors, i.e. the flood characters, the river activity, the human influence and the climate. Finally, these findings allowed us to highlight those sectors in which the braided pattern could disappear, and those sectors in which the braided pattern is still active, because critical processes responsible of channel dynamic are still present

Understanding the structure and reactivity of NiCu nanoparticles: An atomistic model

The structure of bimetallic NiCu nanoparticles (NP) is investigated as a function of their composition and size by means of Lattice MonteCarlo (LMC) and molecular dynamics (MD) simulations. According to our results, copper segregation takes place at any composition of the particles. We found that this feature is not size-dependent. In contrast, nickel segregation depends on the NP size. When the size increases, Ni atoms tend to remain in the vicinity of the surface and deeper. For smaller NPs, Ni atoms are located at the surface as well. Our results also showed that most of the metal atoms segregated at the surface area were found to decorate edges and/or form islands. Our findings agree qualitatively with the experimental data found in the literature. In addition, we comment on the reactivity of these nanoparticles.Fil: Quaino, Paola Monica. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Belletti, Gustavo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; ArgentinaFil: Shermukhamedov, S. A.. Kazan National Research Technological University; RusiaFil: Glukhov, D. V.. Kazan National Research Technological University; RusiaFil: Santos, Elizabeth del Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Institute of Theoretical Chemistry; Alemania. Universitat Ulm; AlemaniaFil: Schmickler, Wolfgang. Universitat Ulm; Alemania. Institute of Theoretical Chemistry; AlemaniaFil: Nazmutdinov, Renat. Kazan National Research Technological University; Rusi

Janus II: a new generation application-driven computer for spin-system simulations

This paper describes the architecture, the development and the implementation of Janus II, a new generation application-driven number cruncher optimized for Monte Carlo simulations of spin systems (mainly spin glasses). This domain of computational physics is a recognized grand challenge of high-performance computing: the resources necessary to study in detail theoretical models that can make contact with experimental data are by far beyond those available using commodity computer systems. On the other hand, several specific features of the associated algorithms suggest that unconventional computer architectures, which can be implemented with available electronics technologies, may lead to order of magnitude increases in performance, reducing to acceptable values on human scales the time needed to carry out simulation campaigns that would take centuries on commercially available machines. Janus II is one such machine, recently developed and commissioned, that builds upon and improves on the successful JANUS machine, which has been used for physics since 2008 and is still in operation today. This paper describes in detail the motivations behind the project, the computational requirements, the architecture and the implementation of this new machine and compares its expected performances with those of currently available commercial systems.Comment: 28 pages, 6 figure

The Unbearable Lightness of Health Science Reporting: A Week Examining Italian Print Media

BACKGROUND: Although being an important source of science news information to the public, print news media have often been criticized in their credibility. Health-related content of press media articles has been examined by many studies underlining that information about benefits, risks and costs are often incomplete or inadequate and financial conflicts of interest are rarely reported. However, these studies have focused their analysis on very selected science articles. The present research aimed at adopting a wider explorative approach, by analysing all types of health science information appearing on the Italian national press in one-week period. Moreover, we attempted to score the balance of the articles. METHODOLOGY/PRINCIPAL FINDINGS: We collected 146 health science communication articles defined as articles aiming at improving the reader's knowledge on health from a scientific perspective. Articles were evaluated by 3 independent physicians with respect to different divulgation parameters: benefits, costs, risks, sources of information, disclosure of financial conflicts of interest and balance. Balance was evaluated with regard to exaggerated or non correct claims. The selected articles appeared on 41 Italian national daily newspapers and 41 weekly magazines, representing 89% of national circulation copies: 97 articles (66%) covered common medical treatments or basic scientific research and 49 (34%) were about new medical treatments, procedures, tests or products. We found that only 6/49 (12%) articles on new treatments, procedures, tests or products mentioned costs or risks to patients. Moreover, benefits were always maximized and in 16/49 cases (33%) they were presented in relative rather than absolute terms. The majority of stories (133/146, 91%) did not report any financial conflict of interest. Among these, 15 were shown to underreport them (15/146, 9.5%), as we demonstrated that conflicts of interest did actually exist. Unbalanced articles were 27/146 (18%). Specifically, the probability of unbalanced reporting was significantly increased in stories about a new treatment, procedure, test or product (22/49, 45%), compared to stories covering common treatments or basic scientific research (5/97, 5%) (risk ratio, 8.72). CONCLUSIONS/SIGNIFICANCE: Consistent with prior research on health science communication in other countries, we report undisclosed costs and risks, emphasized benefits, unrevealed financial conflicts of interest and exaggerated claims in Italian print media. In addition, we show that the risk for a story about a new medical approach to be unbalanced is almost 9 times higher with respect to stories about any other kind of health science-related topics. These findings raise again the fundamental issue whether popular media is detrimental rather than useful to public health

Host-cell dependent role of phosphorylated keratin 8 during influenza A/NWS/33 virus (H1N1) infection in mammalian cells

In this study, we investigated the involvement of keratin 8 during human influenza A/NWS/33 virus (H1N1) infection in semi-permissive rhesus monkey-kidney (LLC-MK2) and permissive human type II alveolar epithelial (A549) cells. In A549 cells, keratin 8 showed major expression and phosphorylation levels. Influenza A/NWS/33 virus was able to subvert keratin 8 structural organization at late stages of infection in both cell models, promoting keratin 8 phosphorylation in A549 cells at early phases of infection. Accordingly, partial colocalizations of the viral nucleoprotein with keratin 8 and its phosphorylated form were assessed by confocal microscopy at early stages of infection in A549 cells. The employment of chemical activators of phosphorylation resulted in structural changes as well as increased phosphorylation of keratin 8 in both cell models, favoring the influenza A/NWS/33 virus's replicative efficiency in A549 but not in LLC-MK2 cells. In A549 and human larynx epidermoid carcinoma (HEp-2) cells inoculated with respiratory secretions from pediatric patients positive for, respectively, influenza A virus or respiratory syncytial virus, the keratin 8 phosphorylation level had increased only in the case of influenza A virus infection. The results obtained suggest that in A549 cells the influenza virus is able to induce keratin 8 phosphorylation thereby enhancing its replicative efficiency

Simulating spin systems on IANUS, an FPGA-based computer

We describe the hardwired implementation of algorithms for Monte Carlo simulations of a large class of spin models. We have implemented these algorithms as VHDL codes and we have mapped them onto a dedicated processor based on a large FPGA device. The measured performance on one such processor is comparable to O(100) carefully programmed high-end PCs: it turns out to be even better for some selected spin models. We describe here codes that we are currently executing on the IANUS massively parallel FPGA-based system.Comment: 19 pages, 8 figures; submitted to Computer Physics Communication

Catheter ablation in an 80-year-old male with late-onset Wolff-Parkinson-White syndrome

Wolff-Parkinson-White syndrome is a congenital condition involving abnormal conductive cardiac tissue between atria and ventricles, that provides a pathway for a re-entrant tachycardia circuit or rapid repetitive ventricular response during atrial fibrillation. Clinical onset is usually from childhood to middle age, and symptoms vary in severity from palpitations (with or without syncope) to cardiac arrest. Presentation varies depending on the patient\u2019s age and presence of comorbidities, as arrhythmias are less tolerated in case of an associated heart disease. In individuals who do not experience symptoms, the condition may go unnoticed for years. We describe the case of an 80-year-old Caucasian male with late-onset of Wolff-Parkinson-White syndrome. He presented with a regular, hemodynamically unstable wide-complex tachycardia with left bundle branch morphology, successfully treated with medical therapy. After recurrence of tachycardia, he underwent an electrophysiological study that showed an orthodromic atrioventricular re-entrant tachycardia using a posterolateral accessory pathway and with functional left bundle branch block. Transseptal radiofrequency catheter ablation of the accessory pathway was successfully performed. After 15 months of follow-up, there was no tachycardia recurrence or findings of pre-excitation on the electrocardiogram. The treatment of both supraventricular and ventricular arrhythmias may be challenging especially in elderly patients. Catheter ablation of left accessory pathways with transseptal approach is feasible and effective in old patients with late-onset Wolff-Parkinson-White syndrome