Diffuse Edge Research Articles

A nonlocal optical potential with a Gaussian nonlocality for proton elastic scattering off light 1p-shell nuclei

In a recent work we used the nonlocal optical model of Perey and Buck (Nucl Phys A 32:353, 1962) to fit the angular distribution data corresponding to neutron elastic scattering off light nuclei from $$^6\hbox {Li}$$ to $$^{18}\hbox {O}$$ over the 9–35 MeV energy range. Although such nuclei posses diffuse edges that complicate the scattering process, the model resulted in improved angular distribution fits compared to those obtained using local optical models. In this work we extend the treatment to the case of proton elastic scattering off light 1p-shell nuclei, but consider the wider 10–70 MeV energy range. No single global set of nonlocal parameters adequately described the measured data across the entire energy range. Instead, we obtained two global sets of fixed nonlocal parameters; one corresponds to the 10–39 MeV range, the other is for the higher 40–70 MeV incident energies. Each set resulted in angular distribution fits which are in very good agreement with experimental data even in the large-angle scattering region, which is usually endowed by nonlocal effects. The fits were improved even further by expressing the imaginary volume and imaginary surface depths as linear functions of energy and the $$(N-Z)/A$$ asymmetry term. This indicates that there is still need for energy-dependent parameters even when nonlocality is explicitly included in the potential. We also used the model to predict elastic angular distributions for proton scattering off nuclei not included in the fitting procedure. The theoretical predictions showed very good agreement with experiment. As a further test of the nonlocal model, we calculated total reaction cross sections for proton scattering off light 1p-shell nuclei. Our predictions are in fair overall agreements with the experimental data.

Defect Structure Determination of GaN Films in GaN/AlN/Si Heterostructures by HR-TEM, XRD, and Slow Positrons Experiments

The present article evaluates, in qualitative and quantitative manners, the characteristics (i.e., thickness of layers, crystal structures, growth orientation, elemental diffusion depths, edge, and screw dislocation densities), within two GaN/AlN/Si heterostructures, that alter their efficiencies as positron moderators. The structure of the GaN film, AlN buffer layer, substrate, and their growth relationships were determined through high-resolution transmission electron microscopy (HR-TEM). Data resulting from high-resolution X-ray diffraction (HR-XRD) was mathematically modeled to extract dislocation densities and correlation lengths in the GaN film. Positron depth profiling was evaluated through an experimental Doppler broadening spectroscopy (DBS) study, in order to quantify the effective positron diffusion length. The differences in values for both edge and screw dislocation densities, and correlation lengths (Le, Ls) found in the 690 nm GaN film, were associated with the better effective positron diffusion length (Leff) of = 43 ± 6 nm.

Band engineering via grain boundary defect states for large scale tuning of photoconductivity in Bi1−xCaxFe1−yTiyO3−δ

Spark plasma sintered Bi1−xCaxFe1−yTiyO3−δ (BCFTO) (x = y = 0.05 and 0.1) nanoparticle ceramics are studied for photoconductivity properties. As-prepared (AP) BCFTO hosts a large concentration of grain boundary (GB) oxygen vacancies (OV), whereas air annealed (AA) BCFTO have significantly suppressed GB OV. X-ray absorption near edge spectroscopy study confirms that Fe and Ti remain in 3+ and 4+ oxidation states, respectively. Thus, lattice OV created when only Ca2+ is substituted in BiFeO3 are charge compensated in Ca and Ti codoped BiFeO3. This ascertains that BCFTO is devoid of lattice OV. Photoconductivity studies show four orders of more photocurrent arising from GB OV contributions in BCFTO-AP compared to that in BCFTO-AA samples. A large increase in the activation energy for the AA samples (0.4 eV to 1.6 eV) compared to that for the AP samples (0.06 eV to 0.5 eV) is obtained from ln ω vs 1/T Arrhenius plots. This further substantiates the suppression of GB OV resulting in poor photoconductivity. Diffuse band edges observed in Kubelka-Munk plots of BCFTO-AP samples are a consequence of OV defect states occupying the bulk bandgap. In the absence of OV defect states, band edge becomes sharper. Density functional theory (DFT) calculations further support the experimental observations. DFT study shows that the presence of Ca and Ti does not enhance the photocurrent as these codopants do not produce mid-bandgap states. The mid-bandgap defect states are attributed only to the unsaturated bonds and OV at the GB in BCFTO. These studies manifest a critical role of OV residing at the GB in tuning the photoconductivity and, hence, the photoresponse of BCFTO.

Properties and performance of photocatalytic CeO2, TiO2, and CeO2–TiO2 layered thin films

CeO2, TiO2, and CeO2–TiO2 layered thin films of different compositions were deposited on polished fused silica glass substrates using spin coating and then annealed at 550 °C for 1 h. Poorly crystalline fluorite-type CeO2 and anatase-type TiO2 were the only phases detected. The valence effects for Ce are attributed to intervalence charge transfer (IVCT) while those for TiO2 are attributed to simultaneous Ti4+ → Ti3+ redox and IVCT. Contamination of the grain boundaries by Si from the substrate is likely to have contributed to blockage of surface-active sites. While the roughnesses of the former thin films exhibited the expected direct correlation with the grain size, those of the latter two types of thin films showed a converse relation, suggesting that the grain boundaries of the layered TiO2 thin films included a recrystallized CeO2–TiO2 invariant point liquid and/or a CeO2–TiO2–SiO2 glass. These would have derived from the other sources of grain boundary contamination, which are Si contamination from the substrate and/or exsolved CeO2 beyond the solubility limit of TiO2. The UV–Vis spectra demonstrated two principal types of curves, with the CeO2 and higher TiO2 concentration giving typical spectra with sharp absorption edges while those of the lower TiO2 concentration indicated highly defective nanostructures with diffuse absorption edges. These data support the conclusion that CeO2 initially decreases the Eg by enhancing nucleation and recrystallization through defect formation but subsequently increases the Eg through supersaturation and consequent lattice distortion. The CeO2 thin films exhibited much worse photocatalytic performances than those of the TiO2 thin films, although no significant differences between the TiO2 thin films and the CeO2–TiO2 layered thin films were apparent, which probably resulted from the competing effects of blockage of the active sites on the grain boundaries and the extent of recrystallization of the thin film phases, the latter of which is more significant.

Semimicroscopic optical model with coupled-channel analysis for neutron scattering off nuclei with mass numbers 12≤A≤208

Background: The phenomenological optical model has been extensively used to study the nucleon-nucleus scattering process. However, its use in describing the observables for nucleon scattering off light $1p$-shell nuclei has been somewhat limited and less successful. This is a result of their diffuse edges and deformations that complicate fitting the experimental data. Therefore, global optical models usually exclude light nuclei and only consider intermediate and heavy nuclei with mass number $A\ensuremath{\ge}24$.Purpose: We test the effectiveness of a semimicroscopic optical model with channel coupling in describing observables for neutron scattering off nuclei covering a wide mass range from $^{12}\mathrm{C}$ to $^{208}\mathrm{Pb}$ corresponding to neutron incident energies in the range $E=10--30\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$.Method: The real central part of the optical model is constructed by single folding the density-independent M3Y-Paris bare nucleon-nucleon interaction over the density of the target nucleus. The rest of the potential terms are of Woods-Saxon form or its derivative. The potential parameters are determined by fitting the elastic and inelastic angular distributions in addition to polarization data for neutron scattering from $^{12}\mathrm{C}, ^{16}\mathrm{O}, ^{54}\mathrm{Fe}, ^{58}\mathrm{Ni}, ^{120}\mathrm{Sn}$, and $^{208}\mathrm{Pb}$. In doing so the ground state is coupled to few, low-lying rotational and vibrational excitation channels.Results: Despite considering a wide mass range of nuclei, the model resulted in good descriptions for the elastic data and, at least, the overall features of the inelastic angular distributions and polarization data are reproduced. Our potential depths are expressed as linear functions of energy while, for each target nucleus, the geometric parameters are fixed. This is unlike purely phenomenological optical models which, in many cases, resulted in best-fit parameters that show unclear energy-dependence trends. In addition, the total cross sections predicted using our parameters are in good overall agreement with experiment.Conclusions: The semimicroscopic model based on the M3Y-Paris bare $NN$ interaction succeeded in, at least, reproducing the overall features of the inelastic experimental data. However, the predicted elastic angular distributions are in good agreement with experiment and progressively improved with increasing mass number of the target. Furthermore, the weak energy dependence, introduced into the M3Y-Paris interaction via the knock-on exchange term, led to improving our data fits. Finally, other density-dependent bare $NN$ interactions resulted in potential parameters that showed less systematic behaviors with energy.

Graphene transistor based on tunable Dirac fermion optics

We present a quantum switch based on analogous Dirac fermion optics (DFO), in which the angle dependence of Klein tunneling is explicitly utilized to build tunable collimators and reflectors for the quantum wave function of Dirac fermions. We employ a dual-source design with a single flat reflector, which minimizes diffusive edge scattering and suppresses the background incoherent transmission. Our gate-tunable collimator-reflector device design enables the quantitative measurement of the net DFO contribution in the switching device operation. We obtain a full set of transmission coefficients between multiple leads of the device, separating the classical contribution from the coherent transport contribution. The DFO behavior demonstrated in this work requires no explicit energy gap. We demonstrate its robustness against thermal fluctuations up to 230 K and large bias current density up to 102 A/m, over a wide range of carrier densities. The characterizable and tunable optical components (collimator-reflector) coupled with the conjugated source electrodes developed in this work provide essential building blocks toward more advanced DFO circuits such as quantum interferometers. The capability of building optical circuit analogies at a microscopic scale with highly tunable electron wavelength paves a path toward highly integrated and electrically tunable electron-optical components and circuits.

Theoretical study of scattering in graphene ribbons in the presence of structural and atomistic edge roughness

We investigate the diffusive electron-transport properties of charge-doped graphene ribbons and nanoribbons with imperfect edges. We consider different regimes of edge scattering, ranging from wide graphene ribbons with (partially) diffusive edge scattering to ribbons with large width variations and nanoribbons with atomistic edge roughness. For the latter, we introduce an approach based on pseudopotentials, allowing for an atomistic treatment of the band structure and the scattering potential, on the self-consistent solution of the Boltzmann transport equation within the relaxation-time approximation and taking into account the edge-roughness properties and statistics. The resulting resistivity depends strongly on the ribbon orientation, with zigzag (armchair) ribbons showing the smallest (largest) resistivity and intermediate ribbon orientations exhibiting intermediate resistivity values. The results also show clear resistivity peaks, corresponding to peaks in the density of states due to the confinement-induced subband quantization, except for armchair-edge ribbons that show a very strong width dependence because of their claromatic behavior. Furthermore, we identify a strong interplay between the relative position of the two valleys of graphene along the transport direction, the correlation profile of the atomistic edge roughness, and the chiral valley modes, leading to a peculiar strongly suppressed resistivity regime, most pronounced for the zigzag orientation.

Field validation and benchmarking of a cloud shadow speed sensor

With ramp rate regulations for photovoltaic plants being discussed in many countries, the speed of clouds has gained significant importance lately. Besides, measuring cloud velocities and directions is of interest for validations of numerical weather predictions and solar nowcasting systems. Recently, the Cloud Shadow Speed Sensor (CSS) was developed and validated in San Diego for low cumulus clouds. In this publication, the CSS is studied under different weather and cloud conditions in the desert of Tabernas in southern Spain. Furthermore, a novel shadow camera based low-cost, low-maintenance approach to determine cloud shadow motion vectors is presented and used as a reference to benchmark the CSS. In comparison, the absolute velocities derived from the CSS and the shadow camera on 59 days for ±5 min temporal medians show deviations of RMSD 2.1 m/s (28.0%), MAD 1.2 m/s (15.7%) and a bias of −0.2 m/s (2.8%). Deviations of the cloud shadow direction are RMSD 47.9° (26.6%), MAD 25.3° (14.0%) and bias 3.7° (2.0%). An adaption of the CSS software yields 91% more measurements on 59 days in comparison to the previously used algorithms at the expense of reduced accuracies, both for the measured velocities and for the measured directions.The CSS and the novel shadow camera based reference system enable long-time, low-maintenance ground measurements of cloud shadow speeds, which were previously not available. The distinct advantages and limitations of the two systems are discussed. In addition to the comparisons between the shadow camera system and the CSS on 59 days, the detection rates of the CSS are classified and measured on 223 days by analyzing CSS radiometer signals. Depending on the shading strength and shading durations, detection rates vary between 3.7% and 21.6%. Furthermore, the basic assumption as well as possible correction approaches of the linear cloud edge – curve fitting method are studied.The CSS was found to be a robust tool with great potential. However, optically thin clouds with diffuse edges pose a challenge and the detection rate leaves room for improvements. The newly developed shadow camera system provides more measurements which scatter less but needs certain geographical requirements. The shadow camera is found to be a feasible validation tool for cloud (shadow) motion vectors.

Two stage image de-noising by SVD on large scale heterogeneous anisotropic diffused image data

De-noising of images along with the edge enhancement has always been a challenging task in large scale heterogeneous image data. This paper presents a two stage image de-noising as well as edge enhancement method where in the first stage two copies of input noisy image are created through diffusion. The first copy is got by using anisotropic diffusion method which employ optimal diffusion function while the second copy is generated to improve the sharp edges by applying the combination of inverse heat diffusion and Canny edge detector. In the next stage, the singular value decomposition is applied on the two copies achieved in first stage to reduce the noise and improve the quality of detected edges. The optimal number of significant singular values have been estimated by the analysis of signal to noise ratio of singular value decomposed images of first copy. The singular values extracted from the second copy of the diffused image are superimposed with non decreasing weights from linear weighting function. Finally the sharp edged and noise reduced output image is generated by taking the linear combination of two singular value decomposed images. The performance of the proposed method has been compared with existing methods based on singular value decomposition as well as anisotropic diffusion. The experimental results exhibit that the proposed method efficiently enhances the edges by reducing the noisy significantly.

Comparative study on machinability improvement in hard turning using coated and uncoated carbide inserts: part II modeling, multi-response optimization, tool life, and economic aspects

The present study focused on mathematical modeling, multi response optimization, tool life, and economical analysis in finish hard turning of AISI D2 steel ((55 ± 1) HRC) using CVD-coated carbide (TiN/TiCN/Al2O3) and uncoated carbide inserts under dry environmental conditions. Regression methodology and the grey relational approach were implemented for modeling and multi-response optimization, respectively. Comparative economic statistics were carried out for both inserts, and the adequacy of the correlation model was verified. The experimental and predicted values for all responses were very close to each other, implying the significance of the model and indicating that the correlation coefficients were close to unity. The optimal parametric combinations for Al2O3 coated carbide were d1–f1–v2 (depth of cut = 0.1 mm, feed = 0.04 mm/r and cutting speed = 108 m/min), and those for the uncoated tool were d1–(0.1 mm)–f1 (0.04 mm/r)–v1 (63 m/min). The observed tool life for the coated carbide insert was 15 times higher than that for the uncoated carbide insert, considering flank wear criteria of 0.3 mm. The chip volume after machining for the coated carbide insert was 26.14 times higher than that of the uncoated carbide insert and could be better utilized for higher material removal rate. Abrasion, diffusion, notching, chipping, and built-up edge have been observed to be the principal wear mechanisms for tool life estimation. Use of the coated carbide tool reduced machining costs by about 3.55 times compared to the use of the uncoated carbide insert, and provided economic benefits in hard turning.

Dynamic hardness of wood – measurements with an automated portable hardness tester

Abstract A research group on forest products from School of Agriculture – Sao Paulo State University. Brazil developed a portable hardness tester for wood, which is based on a displacement transducer and an embedded electronic processor for dynamic evaluation of hardness. This paper presents the results of calibration tests of the equipment, carried out on seven species of Eucalyptus. A new methodology for dynamic hardness calculation has been introduced, which relays on the reaction force of the indentation, while the measurements of indentation depth are performed under load. A moderate to strong linear correlation to Janka hardness and its variations were found. This new approach avoids the classical problems of Brinell hardness test in terms of “sinking-in” (causing diffuse edges) and elastic recovery of the indentation.

A novel field method to distinguish between cryptic carcharhinid sharks, Australian blacktip shark Carcharhinus tilstoni and common blacktip shark C. limbatus, despite the presence of hybrids.

Multivariate and machine-learning methods were used to develop field identification techniques for two species of cryptic blacktip shark. From 112 specimens, precaudal vertebrae (PCV) counts and molecular analysis identified 95 Australian blacktip sharks Carcharhinus tilstoni and 17 common blacktip sharks Carcharhinus limbatus. Molecular analysis also revealed 27 of the 112 were C. tilstoni × C. limbatus hybrids, of which 23 had C. tilstoni PCV counts and four had C. limbatus PCV counts. In the absence of further information about hybrid phenotypes, hybrids were assigned as either C. limbatus or C. tilstoni based on PCV counts. Discriminant analysis achieved 80% successful identification, but machine-learning models were better, achieving 100% successful identification, using six key measurements (fork length, caudal-fin peduncle height, interdorsal space, second dorsal-fin height, pelvic-fin length and pelvic-fin midpoint to first dorsal-fin insertion). Furthermore, pelvic-fin markings could be used for identification: C. limbatus has a distinct black mark >3% of the total pelvic-fin area, while C. tilstoni has markings with diffuse edges, or has smaller or no markings. Machine learning and pelvic-fin marking identification methods were field tested achieving 87 and 90% successful identification, respectively. With further refinement, the techniques developed here will form an important part of a multi-faceted approach to identification of C. tilstoni and C. limbatus and have a clear management and conservation application to these commercially important sharks. The methods developed here are broadly applicable and can be used to resolve species identities in many fisheries where cryptic species exist.

Boundary scattering effects on magnetotransport of narrow metallic wires and films

Electron transport in thin metallic wires and films is strongly influenced by the quality of their surface. Weak localization and magnetoconductivity are also sensitive to the electron scattering at the edges of the sample. We study weak localization effects in a two-dimensional electron gas patterned in the form of a narrow quasi-one-dimensional channel in transverse magnetic field. The most general boundary conditions interpolating between the limits of mirror and diffuse edge scattering are assumed. We calculate magnetoconductivity for an arbitrary width of the sample including the cases of diffusive and ballistic lateral transport as well as the crossover between them. We find that in a broad range of parameters, the electron mobility is limited by the boundary roughness while the magnetotransport is only weakly influenced by the quality of the edges. In addition, we calculate magnetoconductivity for a metallic cylinder in the transverse field and a quasi-two-dimensional metallic film in the parallel field.

Length divergence of the lattice thermal conductivity in suspended graphene nanoribbons

Thermal properties of graphene have attracted much attention, culminating in a recent measurement of its length dependence in ribbons up to 9 $\ensuremath{\mu}\mathrm{m}$ long. In this paper, we use the improved Callaway model to solve the phonon Boltzmann transport equation while capturing both the resistive (umklapp, isotope, and edge roughness) and nonresistive (normal) contributions. We show that for lengths smaller than 100 $\ensuremath{\mu}\mathrm{m}$, scaling the ribbon length while keeping the width constant leads to a logarithmic divergence of thermal conductivity. The length dependence is driven primarily by a ballistic-to-diffusive transition in the in-plane (LA and TA) branches, while in the hydrodynamic regime when $10\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}lLl100$ $\ensuremath{\mu}\mathrm{m}$, the contribution from the in-plane branches saturates and the out-of-plane (ZA) branch shows a clear logarithmic trend, driven by the nonresistive normal contribution. We find that thermal conductivity converges beyond $Lg100$ $\ensuremath{\mu}\mathrm{m}$ due to the coupling between in-plane and flexural modes. This coupling leads to renormalization of ZA phonon dispersion in the long-wavelength range, preventing further divergence of thermal conductivity. We also uncover a strong dependence on sample width, which we attribute to the interplay between nonresistive normal and diffusive edge scattering in the Poisseuille flow regime. We conclude that normal processes play a crucial role in the length and width dependence of thermal transport in graphene in the hydrodynamic regime and dictate the relative in-plane (LA+TA) to out-of-plane (ZA) contribution to transport.

An Investigation on Morphology and Fractal Dimension of Diesel and Diesel‑Biodiesel Soot Agglomerates

In this study, it is reported the fractal dimension and morphology of ultrafine particles emitted by a diesel engine run with B4, B50, and B100. Transmission electron micrographs evidenced two main groups of particles with characteristic and distinct morphological behaviors: (i) particle agglomerate structures self-organized within a fractal-like geometry, and (ii) amorphous and irregular particles with diffuse edges in a liquid-like particle appearance, mainly associated with some sub-fractions of samples collected from B50 and B100 combustion. Particles from (i) showed typical diesel soot morphology and fractal dimension. Primary particle diameter (Dpp) was 24 ± 4 nm, 23 ± 4 nm, and 20 ± 4 nm for B4, B50, and B100, respectively. Mean aggregate gyration diameters (Dg) ranged from 242 ± 140 nm for B4, 210 ± 135 nm for B50, and to 232 ± 140 nm for B100. In turn, fractal dimensions (Df) were 1.94, 1.89, and 1.99 for B4, B50, and B100, respectively. On the other hand, particle from (ii) had their morphology impaired from the addition of biodiesel to petrodiesel in a way it did not follow a fractal geometry.

A new species of Allobates (Anura: Aromobatidae) from Parque Nacional da Amazônia, Pará State, Brazil.

We describe the fourth species of nurse-frog genus Allobates occurring in the southeastern Brazilian Amazonia. The new species is sympatric with Allobates femoralis, Allobates masniger and Allobates magnussoni, and inhabits the margins of streams in forested areas within Parque Nacional da Amazônia, on the western bank of the Tapajós River. Snout-to-vent length ranges between 14.9-16.1 mm among males and 15.6-16.5 mm among females. The species is distinguished by the light brown background color of dorsum, with irregular dark brown blotches appearing from eye level to the urostyle region. In life, ventral surfaces of males are golden yellow on throat and chest, and white to yellow on abdomen. Ventral surfaces of females are predominantly white, except for light yellow on chin. The dark brown lateral band has a diffuse lower edge ventrolaterally. Dorsal surface of thigh is cream, with a longitudinal dark brown band extending dorsally from vent to knee. Tail musculature of tadpoles is robust, bifurcating dorsally over the body and reaching about two-thirds of the body length. Advertisement calls consist predominantly of continuous pairs of notes, but other note arrangements are also emitted. Notes have ascending frequency modulation and average peak frequency ranging between 5.3-5.9 kHz. First and second notes of the same note pair are similar in amplitude, duration and frequency spectrum. Successive note pairs are split by approximately regular silent intervals (0.30-0.49 s). The species lays its eggs inside rolled or folded dead leaves on the leaf litter. Egg capsules and jelly nests are opaque.

Prostate contours delineation using interactive directional active contours model and parametric shape prior model.

Prostate contours delineation on Magnetic Resonance (MR) images is a challenging and important task in medical imaging with applications of guiding biopsy, surgery and therapy. While a fully automated method is highly desired for this application, it can be a very difficult task due to the structure and surrounding tissues of the prostate gland. Traditional active contours-based delineation algorithms are typically quite successful for piecewise constant images. Nevertheless, when MR images have diffuse edges or multiple similar objects (e.g. bladder close to prostate) within close proximity, such approaches have proven to be unsuccessful. In order to mitigate these problems, we proposed a new framework for bi-stage contours delineation algorithm based on directional active contours (DAC) incorporating prior knowledge of the prostate shape. We first explicitly addressed the prostate contour delineation problem based on fast globally DAC that incorporates both statistical and parametric shape prior model. In doing so, we were able to exploit the global aspects of contour delineation problem by incorporating a user feedback in contours delineation process where it is shown that only a small amount of user input can sometimes resolve ambiguous scenarios raised by DAC. In addition, once the prostate contours have been delineated, a cost functional is designed to incorporate both user feedback interaction and the parametric shape prior model. Using data from publicly available prostate MR datasets, which includes several challenging clinical datasets, we highlighted the effectiveness and the capability of the proposed algorithm. Besides, the algorithm has been compared with several state-of-the-art methods.

Overview of recent pedestal studies at ASDEX Upgrade

New or upgraded diagnostics of the edge transport barrier allow investigations of the dominant transport mechanisms in the pedestal. The density build-up after the L–H transition can be explained with a mainly diffusive edge transport barrier. A small inward convection term improves the agreement between modelling and experiment, but its existence cannot be confirmed due to the uncertainty in the neutral sources. Measurements of the impurity ion flow asymmetry as well as the edge current density are in agreement with neoclassical modelling. The inter-ELM pedestal recovery was traced with ideal peeling–ballooning modelling, which shows that the stability boundary moves closer to the operational point as the pedestal becomes wider. Gyrokinetic modelling of the different phases reveal that density gradient driven trapped electron modes are dominant during the early recovery, while electron temperature gradient modes or kinetic ballooning modes determine the temperature gradient in the final phase. Microtearing modes are modelled and also experimentally determined at the top of the pedestal. Non-linear coupling between modes could explain the failure of ideal linear MHD modelling.

Signaling molecules from Lactuca sativa L. induced quorum sensing phenotypes in bacteria

Abstract The outcome of the present investigation revealed that lettuce (Lactuca sativa L.) extract strongly interferes with acyl homoserine lactone (AHL) regulated physiological functions in the bioreporter strain, Chromobacterium violaceum CV026. Extracts of L. sativa also promoted production of virulence factors in plant pathogen, Pectobacterium carotovorum, and significantly increased tissue maceration on potato tubers when there was a low concentration (103 cfu · ml−1) of the bacterium was used. The thin layer chromatogram which visualised with AHL bioreporter strain, CV026, showed that L. sativa extract produced a circular spot with a diffuse edge tail and migrated with the same mobility as standard N-hexanoyl-L-homoserine lactone (C6-HSL). Gas Chromatography Mass Spectroscopy (GC-MS) analysis of the lettuce extract resulted in the identification of 19 compounds of which homoserine was identified for the first time in plants. Homoserine accounted for 2.37% of the total constituents. It is a new finding that lettuce contains AHL like substances (homoserine) which excite AHL related quorum sensing (QS) in bacteria.

Upregulation of integrin β4 promotes epithelial–mesenchymal transition and is a novel prognostic marker in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is a highly aggressive and often lethal malignant tumor. Several studies have shown that epithelial–mesenchymal transition (EMT) is frequently observed in clinical samples of PDA and is related to high metastatic rates and poor outcomes. To identify candidate molecules regulating EMT in PDA, we previously used cDNA microarray analysis and identified integrin β4 (ITGB4) as one of the genes upregulated in high-EMT xenografts derived from PDA patients. The aim of the current study was to clarify the clinicopathological and functional significance of ITGB4 overexpression in PDA. ITGB4 upregulation in high-EMT xenografts was confirmed by immunohistochemistry. Immunohistochemical analyses of 134 surgically resected PDA cases revealed intratumoral heterogeneity with respect to ITGB4 expression and showed that cancer cells undergoing EMT often display strong diffuse ITGB4 expression. High levels of ITGB4 expression were significantly correlated with the hallmarks of EMT (solitary cell infiltration, reduced E-cadherin expression, and increased vimentin expression), with high tumor grade, and with the presence of lymph node metastasis, and showed an independent prognostic effect. Immunocytochemical analyses of PDA cell lines revealed that localization of ITGB4 changed from regions of cell–cell contact to diffuse cytoplasm and cell edges with occasional localization in filopodia during EMT. Knockdown of ITGB4 reduced the migratory and invasive ability of PDA cells. Overexpression of ITGB4 promoted cell scattering and cell motility in combination with downregulation of E-cadherin and upregulation of vimentin expression. In conclusion, we elucidated the prognostic and clinicopathological significance of ITGB4 overexpression in PDA and also the potential role for ITGB4 in the regulation of cancer invasion and EMT.