Crackling Noise in Fractional Percolation -- Randomly distributed discontinuous jumps in explosive percolation

Crackling noise is a common feature in many systems that are pushed slowly, the most familiar instance of which is the sound made by a sheet of paper when crumpled. In percolation and regular aggregation clusters of any size merge until a giant component dominates the entire system. Here we establish `fractional percolation' where the coalescence of clusters that substantially differ in size are systematically suppressed. We identify and study percolation models that exhibit multiple jumps in the order parameter where the position and magnitude of the jumps are randomly distributed - characteristic of crackling noise. This enables us to express crackling noise as a result of the simple concept of fractional percolation. In particular, the framework allows us to link percolation with phenomena exhibiting non-self-averaging and power law fluctuations such as Barkhausen noise in ferromagnets.Comment: non-final version, for final see Nature Communications homepag

Arrest stress of uniformly sheared wet granular matter

We conduct extensive independent numerical experiments considering frictionless disks without internal degrees of freedom (rotation etc.) in two dimensions. We report here that for a large range of the packing fractions below random-close packing, all components of the stress tensor of wet granular materials remain finite in the limit of zero shear rate. This is direct evidence for a fluid-to-solid arrest transition. The offset value of the shear stress characterizes plastic deformation of the arrested state {which corresponds to {\em dynamic yield stress} of the system}. {Based on an analytical line of argument, we propose that the mean number of capillary bridges per particle, $\nu$, follows a non-trivial dependence on the packing fraction, $\phi$, and the capillary energy, \vareps. Most noticeably, we show that $\nu$ is a generic and universal quantity which does not depend on the driving protocol.} Using this universal quantity, we calculate the arrest stress, $\sigma_a$, analytically based on a balance of the energy injection rate due to the external force driving the flow and the dissipation rate accounting for the rupture of capillary bridges. The resulting prediction of $\sigma_a$ is a non-linear function of the packing fraction $\phi$, and the capillary energy \vareps. This formula provides an excellent, parameter-free prediction of the numerical data. Corrections to the theory for small and large packing fractions are connected to the emergence of shear bands and of contributions to the stress from repulsive particle interactions, respectively.Comment: 7 pages, g figure

Biopathologic Characterization of Three Mixed Poultry Eimeria spp. Isolates

Background: Coccidiosis of domestic fowl, caused by species of the Genus Eimeria, is responsi­ble for important economic losses in poultry production. Because different species and/or strains can vary in pathogenicity and other biological parameters, their precise characteriza­tion is important for epizootiological studies.Methods: Fifty samples from litter, whole intestinal tract and feces were collected from poul­try houses located in different provinces of Iran. One hundred twenty male day-old broi­ler chicks were challenged with three selected isolates. Data on weight gain, Food Conversion Ratio (FCR), food intake, lesion scoring and shedding of oocysts per gram of feces were rec­orded and analyzed by the Duncan's test.Results: In all treatments, the challenged groups had statistically significant lower weight gain than that of unchallenged control group. Isolate three caused the lowest weight gain and food intake and the worst lesion score as well as FCR. Despite originating from close geographi­cal regions for isolates 1 and 2, the difference in biopathologic factors may be either due to different proportion of identified species or the different pathogenicity of the species present in the isolates.Conclusion: The results highlight the importance of considering various species of Eimeria in designing the preventive, control and treatment strategies to prevent coccidiosis in different regions of Iran. Further characterization of each isolate would be the next step to provide a basis for coccidiosis research with well-characterized local isolates

Attracted Diffusion-Limited Aggregation

In this paper, we present results of extensive Monte Carlo simulations of diffusion-limited aggregation (DLA) with a seed placed on an attractive plane as a simple model in connection with the electrical double layers. We compute the fractal dimension of the aggregated patterns as a function of the attraction strength \alpha. For the patterns grown in both two and three dimensions, the fractal dimension shows a significant dependence on the attraction strength for small values of \alpha, and approaches to that of the ordinary two-dimensional (2D) DLA in the limit of large \alpha. For non-attracting case with \alpha=1, our results in three dimensions reproduce the patterns of 3D ordinary DLA, while in two dimensions our model leads to formation of a compact cluster with dimension two. For intermediate \alpha, the 3D clusters have quasi-2D structure with a fractal dimension very close to that of the ordinary 2D-DLA. This allows one to control morphology of a growing cluster by tuning a single external parameter \alpha.Comment: 6 pages, 6 figures, to appear in Phys. Rev. E (2012

Molecular and Biomorphometrical Identification of Ovine Babesiosis in Iran

Background: Ovine babesiosis is the most important haemoparasitic tick-borne disease of small ruminants in Iran caused by Babesia ovis, B. motasi, and B. crassa. The aim of this study was to characterize the species of ovine Babesia species isolated from different geographical region of Iran.Methods: One hundred fifty four blood samples collected from animals, which demonstrated the pale mucous membranes or hyperthermia. The specimens were transferred to the laboratory and the blood smears stained with Geimsa, the morphological and biometrical data of parasite in any infected erythrocyte have been considered. Extracted DNA from each blood samples were used in PCR and semi nested- PCR in order to confirm the presence of the species.Results: The results of the PCR assays showed nine (5.85%), 81 (53%) and 18 (11.7%) were distinguished as Babesia, Theileria and mixed infection, respectively. Semi nested- PCR did not confirm the presence of B. motasi.Conclusion: The causative organism of many cases of haemoprotozoal diseases, which recorded in previous studies, could be B. ovis or Theileria lestoquardi. The result confirmed that B. ovis was only species which causes babesiosis in the study areas. It seems that the biometrical polymor­phisms could exist in B. ovis in Iran. This polymorphism could be a main problem in differen­tiation between B. ovis and B. motasi and it could be dissolved by specific PCR analysis

Serological survey and comparison of two polymerase chain reaction (PCR) assays with enzyme-linked immunosorbent assay (ELISA) for the diagnosis of canine visceral leishmaniasis in dogs

Visceral leishmaniasis (VL) is systemic zoonotic parasitic infection that is a health problem in some tropical and subtropical countries. The purpose of our study is to determine the seroprevalence of canine visceral leishmaniasis (CVL) in owned dogs of the Sarab area and to identify the species of Leishmania isolated from these dogs. We also compared the sensitivities and specificities of two polymerase chain reaction (PCR) assays (kDNA and ITS1) used for Leishmania infantum identification with culture, microscopic detection and enzyme-linked immunosorbent assay (ELISA) methods as well as validate the PCR techniques for the molecular diagnosis of CVL. Sera from 384 dogs of 30 villages around Sarab, were tested by ELISA and buffy coat blood fractions after sampling tested with PCR by specific primers (kDNA, ITS-18sRNA). Thirty-five dogs were seropositive by ELISA. The seroprevalence rate (SPR) of CVL was 9.1% (CI, 95% 6.6 -12.4). The most important serological result was a high proportion of seropositivity for leishmaniasis. Out of 361 (94%) asymptomatic dogs, 31 (8.6%) were seropositive, and out of 23 (6%) symptomatic dogs, 4 (17.4%) were seropositive. Agreement betweenthe ELISA test and clinical signs was 86.7%. Each assay was performed on 60 blood samples. PCR of kDNA (7/60 positives, 11.8%) was the most sensitive of the assays examined, followed by ELISA (3/60, 5%) and ITS1-PCR (2/60, 3.4 %). All diagnostic assays were highly specific (100 %) and had positive predictive values (PPV) >90% and negative predictive values (NPV) >88% for CVL. As expected, kDNAPCR proved to be the most sensitive (87.5 %) assay for leishmanial DNA in peripheral blood. This study shows that kDNA-PCR is significantly more sensitive than the other parasitological and serological methods, allowing the identification of infected dogs even before the appearance of serum L. infantum antibodies. Because kDNA-PCR is the most reliable, sensitive, and also a rapid diagnostic assay for CVL, it should be employed as the new standard for routine diagnosis.Key words: Leishmania infantum, polymerase chain reaction, kinetoplast DNA, enzyme-linked immunosorbent assay, Visceral leishmaniasis, dogs, prevalence

Study on hybrid combustion of aero-suspensions of boron-aluminum powders in a quiescent reaction medium

© 2017. The present research deals with a hybrid combustion of aluminum/boron dust particles in a heterogeneous quiescent reaction medium with spatially discrete heat sources. A developed thermal model is employed to estimate flame propagation speed in a reaction medium. The burning velocity and minimum ignition energy are studied parametrically as a function of dust concentration and particle diameter for different percentages of boron powder in a hybrid mixture of aluminum/boron dust cloud. The model shows that the addition of boron powder as a component of the mixture decreases the burning rate and causes a higher amount of minimum ignition energy needed for ignition, owing to the role of boron as a heat sink. Comparison of the simulation results with the available experimental data shows that the model captures the flame propagation speed as a function of particle concentration, except at very low concentrations