Hardy's paradox and violation of a state-independent Bell inequality in time

Tests such as Bell's inequality and Hardy's paradox show that joint probabilities and correlations between distant particles in quantum mechanics are inconsistent with local realistic theories. Here we experimentally demonstrate these concepts in the time domain, using a photonic entangling gate to perform nondestructive measurements on a single photon at different times. We show that Hardy's paradox is much stronger in time and demonstrate the violation of a temporal Bell inequality independent of the quantum state, including for fully mixed states.     

Influence of processing parameters on nanomaterials synthesis efficiency by a carbothermal reduction process

In this work, the influence of synthesis parameters on the synthesis efficiency of tin oxide nanomaterials was studied by using the carbothermal reduction method in a sealed tube furnace. The parameters were the starting material, temperature and time of synthesis as well as the gas flux. The starting material was tin dioxide mixed with carbon black in a molar proportion of 1.5:1 and 1:1. The temperature range was from 950 to 1,125 °C with a step of 25 °C, and the synthesis times used were 15, 30, 45, 60, 75, 90, and 120 min. Using optimum values of the above parameters, the gas flux was changed to verify its influence. After completion of the syntheses, we found a grayish-black material inside the tube which was characterized by X-ray diffraction and scanning electron microscopy. The results showed that the collected material is composed of nanobelts (with width around 60 nm) and disks that grew preferentially in the SnO phase. A model based on the oxide vapor pressure was proposed to evaluate the efficiency of the process, and the results showed good agreement between experimental data and the proposed model. Based on the results obtained, the best conditions to obtain a homogeneous material with 95% efficiency is using a starting material in the molar proportion Sn:C of 1.5:1, a temperature of 1,132 °C for 75 min, and a N₂ gas flux of 80 sccm.     

Synchrotron X‐ray tests of an L‐shaped laterally graded multilayer mirror for the analyzer system of the ultra‐high‐resolution IXS spectrometer at NSLS‐II

Characterization and testing of an L‐shaped laterally graded multilayer mirror are presented. This mirror is designed as a two‐dimensional collimating optics for the analyzer system of the ultra‐high‐resolution inelastic X‐ray scattering (IXS) spectrometer at National Synchrotron Light Source II (NSLS‐II). The characterization includes point‐to‐point reflectivity measurements, lattice parameter determination and mirror metrology (figure, slope error and roughness). The synchrotron X‐ray test of the mirror was carried out reversely as a focusing device. The results show that the L‐shaped laterally graded multilayer mirror is suitable to be used, with high efficiency, for the analyzer system of the IXS spectrometer at NSLS‐II.     

Colonization of cashew plants by Lasiodiplodia theobromae: microscopical features

Lasiodiplodia theobromae is a phytopathogenic fungus causing gummosis, a threatening disease for cashew plants in Brazil. In an attempt to investigate the ultrastructural features of the pathogen colonization and its response to immunofluorescence labeling, light, confocal and electron microscope studies were conducted on different severity scale patterns of diseased plants. Lasiodiplodia-antisera was checked for cross reactivity against common cashew plants fungi. Optical microscopy analysis revealed a longitudinally sectioned hyphae located within the xylem vessels, showing an extensive hyphal development in the secondary xylem tissue. SEM images demonstrated that the fungus was found in some asymptomatic samples, particularly within the xylem vessels as confirmed by the optical images. Symptomatic sample images showed an extensive distribution of the fungus along the secondary xylem, within the vessels, infecting xylem parenchyma. A closer look in the secondary xylem parenchyma reveals a heavy and profuse invasion of the cells with a distinguishable cell wall disintegration and fully hyphae dispersal. There was no reactivity of Lasiodiplodia-antisera against mycelial extracts of Colletotrichum gloeosporioides, Phomopsis anardii and Pestalotiopsis guepinii. Following incubation of sections with the polyclonal antisera, the hyphae were intensely and regularly labeled. Rays, vessels and parenchyma cells were the preferred pathway for L. theobromae colonization. Artificial infection provides the information that the vascular cylinder is undoubtedly employed and used by the fungus for hyphae distribution. Immunofluorescence assay employed in situ was applied and the polyclonal antisera produced was able to recognize the fungus and proved to be a sensitive technique to detect it.     

Spatial distribution of AT- and GC-rich DNA within interphase cell nuclei of Triatoma infestans Klug

Heterochromatin bodies in single- and multichromocentered interphase cell nuclei of Triatoma infestans, a vector of Chagas disease, have been suggested to contain AT-rich DNA, based on their positive response to Q-banding and Hoechst 33248 treatment. No information exists on whether GC-rich DNA is also present in these nuclei and whether it plays a role on chromatin condensation. Considering that methodologies more precise than those previously used to determine DNA base composition in situ are currently available, and that the spatial distribution of chromatin areas differing in composition in interphase cell nuclei of different species is a matter of interest, the localization of AT- and GC-rich DNA in T. infestans nuclei is revisited here. The methodologies used included DAPI/AMD and CMA(3)/Distamycin differential staining, Feulgen-DNA image analysis following Msp I and Hpa II enzymatic digestion, 5-methylcytidine immunodetection, AgNOR response, confocal microscopy, and the 5-aza-2'-deoxycytidine (5-AZA) demethylation assay. The results identified the presence of AT-rich/GC-poor DNA in chromocenters and evenly distributed AT and GC sequences in euchromatin. A GC-rich DNA zone encircling the chromocenters was also found but it could not be associated with NOR regions. To corroborate the DNA AT-richness in T. infestans nuclei, bioinformatic analyses were also performed. Methylated cytosine was evident at some points of the chromocenters' edge in single- and multichromocentered nuclei and at the euchromatin of multichromocentered nuclei and could be transiently affected by the 5-AZA treatment. The present results suggest that in the particular case of chromocenters of the hemipteran T. infestans, cytosine methylation is not a relevant factor involved in chromatin condensation.     

Ultrastructural architecture of colonies of different morphologies produced by phenotypic switching of a clinical strain of Candida tropicalis and biofilm formation by variant phenotypes

Candida tropicalis has been identified as one of the most prevalent pathogenic yeast species of the Candida-non-albicans (CNA) group. Study of switching in C. tropicalis has not been the subject of extensive research. Therefore, we investigated switching event and characterized the ultrastructural architecture of different phenotypes and biofilm produced in a C. tropicalis clinical strain. Cells switched heritably, reversibly, and at a high frequency between four phenotypes readily distinguishable by the shape of colonies formed on agar at 25°C. SEM analysis was used to verify the architecture of whole Candida colonies at ultrastructural level. The smooth phenotype (parental phenotype) colony showed a hemispherical shape character, while the semi-smooth was characterized by the presence of shallow marginal depressions. The ring and rough phenotypes exhibited more complex architecture and were characterized by the presence of deep central and peripheral depressions areas. The biofilm-forming ability varied among the switch phenotypes. After 12h incubation, the smooth phenotype formed less biofilm compared to the other phenotypes (P<0.05). The electron microscopy analysis revealed that filamentation (pseudohyphae) was associated with ring and rough colonies. The ultrastructural analysis allowed the observation of the arrangement of individual cells within the colonies. At the deep central and peripheral depressions areas of the ring and rough colonies extracellular material was seen in different arrangements. The data presented here open new avenues to study a possible role for extracellular material in the formation and maintenance of the architecture of switch phenotypes in C. tropicalis. It is therefore essential that more strains be investigated to determine the biological significance of extracellular material in C. tropicalis phenotypic switching phenomenon.     

Combination of Raman, Infrared, and X-Ray Energy-Dispersion Spectroscopies and X-Ray Diffraction to Study a Fossilization Process

X-ray diffraction was combined with X-ray energy-dispersion, Fourier-transform infrared, and Raman spectroscopies to study the fossilization of a Cretaceous specimen of the plant Brachyphyllum castilhoi, a fossil from the Ipubi Formation, in the Araripe Sedimentary Basin, Northeastern Brazil. Among the possible fossilization processes, which could involve pyrite, silicon oxide, calcium oxide, or other minerals, we were able to single out pyritization as the central mechanism producing the fossil, more than 100 million years ago. In addition to expanding the knowledge of the Ipubi Formation, this study shows that, when combined with other experimental techniques, Raman spectroscopy is a valuable tool at the paleontologist’s disposal.     

Time-periodic perturbation of a Liénard equation with an unbounded homoclinic loop

We consider a quadratic Liénard equation with an unbounded homoclinic loop, which is a solution tending in forward and backward time to a non-hyperbolic equilibrium point located at infinity. Under small time-periodic perturbation, this equilibrium becomes a normally hyperbolic line of singularities at infinity. We show that the perturbed system may present homoclinic bifurcations, leading to the existence of transverse intersections between the stable and unstable manifolds of such a normally hyperbolic line of singularities. The global study concerning the infinity is performed using the Poincaré compactification in polar coordinates, from which we obtain a system defined on a set equivalent to a solid torus in R³, whose boundary plays the role of the infinity. The transversality of the manifolds is proved using the Melnikov method and implies, via the Birkhoff-Smale Theorem, a complex dynamical behaviour of the perturbed system solutions in the finite part of the phase space. Numerical simulations are performed in order to illustrate this behaviour, which could be called “the chaos arising from infinity”, since it depends on the global structure of the Liénard equation, including the points at infinity. Although applied to a particular case, the analysis presented provides a geometrical approach to study periodic perturbations of homoclinic (or heteroclinic) loops to infinity of any planar polynomial vector field.     

Nonlinear perturbations of a ‐Laplacian equation with critical growth in

We prove the existence of solution for a class of ‐Laplacian equations where the nonlinearity has a critical growth. Here, we consider two cases: the first case involves the situation where the variable exponents are periodic functions. The second one involves the case where the variable exponents are nonperiodic perturbations.     

Research on calculus: what do we know and where do we need to go?

In this introductory paper we take partial stock of the current state of field on calculus research, exemplifying both the promise of research advances as well as the limitations. We identify four trends in the calculus research literature, starting with identifying misconceptions to investigations of the processes by which students learn particular concepts, evolving into classroom studies, and, more recently research on teacher knowledge, beliefs, and practices. These trends are related to a model for the cycle of research and development aimed at improving learning and teaching. We then make use of these four trends and the model for the cycle of research and development to highlight the contributions of the papers in this issue. We conclude with some reflections on the gaps in literature and what new areas of calculus research are needed.