Elliptical Spots Research Articles

A study on the effect of surface topography on the actuation performance of stacked-rolled dielectric electro active polymer actuator

Dielectric electro active polymer (DEAP) is a suitable actuator material that finds wide applications in the field of robotics and medical areas. This material is highly controllable, flexible, and capable of developing large strain. The influence of geometrical behavior becomes critical when the material is used as miniaturized actuation devices in robotic applications. The present work focuses on the effect of surface topography on the performance of flat (single sheet) and stacked-rolled DEAP actuators. The non-active areas in the form of elliptical spots that affect the performance of the actuator are identified using scanning electron microscope (SEM) and energy dissipated X-ray (EDX) experiments. Performance of DEAP actuation is critically evaluated, compared, and presented with analytical and experimental results.

Waveform model of a laser altimeter for an elliptical Gaussian beam.

The current waveform model of a laser altimeter is based on the Gaussian laser beam of the fundamental mode, whose cross section is a circular spot, whereas some of the cross sections of Geoscience Laser Altimeter System lasers are closer to elliptical spots. Based on the expression of the elliptical Gaussian beam and the waveform theory of laser altimeters, the primary parameters of an echo waveform were derived. In order to examine the deduced expressions, a laser altimetry waveform simulator and waveform processing software were programmed and improved under the circumstance of an elliptical Gaussian beam. The result shows that all the biases between the theoretical and simulated waveforms were less than 0.5%, and the derived model of an elliptical spot is universal and can also be used for the conventional circular spot. The shape of the waveforms is influenced by the ellipticity of the laser spot, the target slope, and the "azimuth angle" between the major axis and the slope direction. This article provides the waveform theoretical basis of a laser altimeter under an elliptical Gaussian beam.

Experimental observations on the crystalline structures of YAlO3 single crystal at high temperatures

To understand the effects of thermal annealing on a high-permittivity gate insulating material YAlO3, its single crystal was annealed at various high temperatures ranging from 900 to 1300 °C and was examined by various instrumental analyses such as X-ray diffraction, infrared absorption spectroscopy, laser confocal microscopy, and atomic force microscopy. As a result, it was clarified that the crystalline YAlO3 takes at least three structures in a temperature range up to 1300 °C. Namely, it is perovskite below 1160 °C, at which the garnet structure starts to appear, while an unknown structure appears at 1250 °C. On the other hand, the sample surface also shows drastic changes if the temperature exceeds 1160 °C. Furthermore, many elliptical spots are induced after the annealing at 1200 or 1250 °C. Moreover, hydroxyl groups are generated at 1300 °C. It is desirable to take these structural changes into account in determining the annealing temperature of YAlO3 for various industrial purposes such as the manufacture of semiconductor devices.

Heightened Condition Dependence of a Sexually Selected Signal in MalePolistes dominulusPaper Wasps

AbstractSexually selected signals are theoretically expected to exhibit heightened condition dependence compared to non‐signaling traits. This link to condition enables sexual signals to provide information regarding individual quality and also provides a mechanism that allows animals to develop signals that accurately reflect their abilities. Most previous work on sexual signal condition dependence has focused on signals that have clear developmental costs, while less is known about the development of other types of quality signals. MalePolistes dominuluspaper wasps have yellow‐on‐black abdominal spots that are important signals during female choice and male–male competition. These signals lack obvious production costs, as males are covered in yellow and black patterns composed of the same pigments. Here, we assess signal condition dependence by testing whether larval diet has a stronger influence on the development of male spots than on the development of control traits composed of the same pigments. Males reared onad libitumdiets developed elliptical spots similar to those seen on dominant, attractive males, while males reared on restricted diets developed irregularly shaped spots similar to those seen on subordinate, unattractive males. Remarkably, the development of a control trait composed of the same yellow and black pigments was not influenced by larval diet. Therefore, sexually selected signals can be developmentally decoupled from traits comprised of the same pigments. Condition dependence of sexually selected signals is likely to be a widespread solution to the challenge of developing sexually selected signals that accurately convey information about individual quality.

The effect of laser spot shapes on polar-direct-drive implosions on the National Ignition Facility

Ongoing polar-direct-drive (PDD) implosions on the National Ignition Facility (NIF) [J. D. Lindl and E. I. Moses, Phys. Plasmas 18, 050901 (2011)] use existing NIF hardware, including indirect-drive phase plates. This limits the performance achievable in these implosions. Spot shapes are identified that significantly improve the uniformity of PDD NIF implosions; outer surface deviation is reduced by a factor of 7 at the end of the laser pulse and hot-spot distortion is reduced by a factor of 2 when the shell has converged by a factor of ∼10. As a result, the neutron yield increases by approximately a factor of 2. This set of laser spot shapes is a combination of circular and elliptical spots, along with elliptical spot shapes modulated by an additional higher-intensity ellipse offset from the center of the beam. This combination is motivated in this paper. It is also found that this improved implosion uniformity is obtained independent of the heat conduction model. This work indicates that significant improvement in performance can be obtained robustly with the proposed spot shapes.

First Report of Corynespora Leaf Spot Caused by Corynespora cassiicola on Gynura in China.

Gynura (Gynura bicolor DC.) is a perennial herbaceous plant in the family Compositae. It is an important Chinese vegetable, and is commonly used as a Chinese herbal medicine. In 2010, a severe leaf spot disease was observed on gynura grown in the main production areas in Tong Nan County, Chongqing City, China. Some farms experienced 60% disease incidence. Symptoms usually began on the lower leaves, as circular to elliptical or irregular spots with concentric rings. Individual spots were dark brown with grayish centers, sometimes coalescing and leading to extensive necrosis. The fungus associated with lesions was characterized as follows: Conidiophores were single or in clusters, straight or flexuous, unbranched, percurrent, cylindrical, pale to dark brown, 87.5 to 375.0 μm long and 5.0 to 10.5 μm wide. Conidia were solitary or catenate, straight to slightly curved, obclavate to cylindrical, 3 to 14 pseudoseptate, 82.8 to 237.5 μm long and 7.0 to 7.8 μm wide, and pale brown. The morphological characteristics of the conidia and conidiophores agreed with the descriptions for Corynespora cassiicola (1). To isolate the causal pathogen, surface-sterilized tissue at the margin of lesions was immersed in 75% ethanol for 30 s, rinsed in sterile water, dried in a laminar flow bench, transferred to PDA, and incubated at 28°C. Four single-spore cultures of the isolates were obtained and named from ZBTK10110637 to ZBTK10110640. All strains were identified as C. cassiicola. The isolate ZBTK10110637 was selected as representative for molecular identification. Genomic DNA was extracted by CTAB (2). The internal transcribed spacer (ITS) region of the rDNA was amplified using primers with ITS1 (5'-TCCGATGGTGAACCTGCGG-3') and ITS4 (5'-TCCTCCGCTTATTGATATGC-3'). Amplicons were 433 bp (GenBank Accession No. JX867272) and shared 100% similarity with that of C. cassiicola (NRC2-1 No. AB539285.1). To confirm pathogenicity, four isolates were used to inoculate 12 gynura plants (6 weeks old) by mist spray-inoculation with 108 spores/ml suspension in sterile distilled water on the leaves. Control plants were misted with sterile distilled water. After inoculation, all plants were incubated in a greenhouse maintained at 20 to 28°C with relative humidity of 80 to 85%. Five days after inoculation, dark brown spots with a grayish center typical of field symptoms were observed on all inoculated plants. No symptoms were seen on water-treated control plants. The fungus was re-isolated from inoculated plants. The morphological characteristics of isolates were identical with the pathogen recovered originally. This is the first report of C. cassiicola on gynura.

SU‐E‐T‐459: Dosimetric Consequences of Rotated Elliptical Proton Spots in Modeling In‐Air Proton Fluence for Calculating Doses in Water of Proton Pencil Beams

Purpose:We present a study of dosimetric consequences on doses in water in modeling in‐air proton fluence independently along principle axes for rotated elliptical spots.Methods:Phase‐space parameters for modeling in‐air fluence are the position sigma for the spatial distribution, the angle sigma for the angular distribution, and the correlation between position and angle distributions. Proton spots of the McLaren proton therapy system were measured at five locations near the isocenter for the energies of 180 MeV and 250 MeV. An elongated elliptical spot rotated with respect to the principle axes was observed for the 180 MeV, while a circular‐like spot was observed for the 250 MeV. In the first approach, the phase‐space parameters were derived in the principle axes without rotation. In the second approach, the phase space parameters were derived in the reference frame with axes rotated to coincide with the major axes of the elliptical spot. Monte‐Carlo simulations with derived phase‐space parameters using both approaches to tally doses in water were performed and analyzed.Results:For the rotated elliptical 180 MeV spots, the position sigmas were 3.6 mm and 3.2 mm in principle axes, but were 4.3 mm and 2.0 mm when the reference frame was rotated. Measured spots fitted poorly the uncorrelated 2D Gaussian, but the quality of fit was significantly improved after the reference frame was rotated. As a Result, phase space parameters in the rotated frame were more appropriate for modeling in‐air proton fluence of 180 MeV protons. Considerable differences were observed in Monte Carlo simulated dose distributions in water with phase‐space parameters obtained with the two approaches.Conclusion:For rotated elliptical proton spots, phase‐space parameters obtained in the rotated reference frame are better for modeling in‐air proton fluence, and can be introduced into treatment planning systems.

First Report of Pestalotiopsis Species Causing Leaf Spot of Cowpea (Vigna unguiculata) in India.

Cowpea (Vigna unguiculata (L.) Walp) is an important legume crop cultivated in arid and semi-arid regions in underdeveloped and developing countries. India is a leading cowpea producer. In addition to India, Nigeria and Niger are the predominant producers of cowpea in the world. Brazil, Haiti, Myanmar, Sri Lanka, and the United States are also significant producers of cowpea. This is a drought-tolerant annual crop that thrives in warm weather (3), and is more well-adapted to the drier regions of the tropics than any other legume. Cowpea fields (190 ha) surveyed in Mysore district (Karnataka State) from 2010 to 2012 were found affected by a new leaf spot disease. Over 60% of surveyed fields were affected by this disease, with individual fields ranging from 30 to 75% disease incidence. Individual fields experienced an estimated 10 to 15% yield loss. Initially, leaf spot symptoms appeared as small, dark, necrotic lesions that increased to a diameter of 0.5 to 1.0 cm. These spots later enlarged to form brown, circular, elliptical, and irregular spots with halo margins. Symptoms persisted throughout the cropping season. Under severe infection, defoliation occurred. Black, sessile, discoid conidiomata were observed in lesions and exuded a pink spore mass that later turned brown. The fungus was isolated from affected leaf tissues that were surface sterilized with 2% NaOCl2 solution, washed thrice with sterile water, blotter dried, and inoculated onto potato dextrose agar (PDA). White mycelia produced black globular acervuli with conidia on PDA after 7 days of incubation at 28 ± 2°C with a 12-h alternate light and dark period. Conidia had 5-celled (21.37 to 24.89 × 6.3 to 6.9 μm) segmentation with darker median cells and hyaline end cells. The apical cell typically had three appendages (sometimes 2 to 4) measuring 22.0 to 27.3 μm long and the basal appendage was 3.47 to 6.2 μm long. Based on these morphological features, the fungal pathogen was identified as Pestalotiopsis species. The isolated fungus was tested for pathogenecity on 30-day-old healthy cowpea plants grown under greenhouse conditions. A conidial suspension was prepared from 7-day-old culture by flooding with 2 to 4 ml of sterile distilled water. Spores were collected with a sterile micropipette and spore concentration was adjusted to 3 × 106 conidia/ml and applied as foliar spray onto 15 plants each in three replicates. Non-inoculated control plants were sprayed with sterile water. The plants were kept under high humidity (80%) for 5 days and at ambient temperature (28 ± 2°C). After 10 to 12 days post-inoculation, leaf spot symptoms appeared on inoculated plants, and the fungal pathogen was re-isolated and no such symptoms were found on control plants. The pathogen was confirmed by micro-morphological features. The ITS region of the ribosomal RNA gene was amplified using primers ITS1 and ITS4 (2). The amplified PCR product was purified and sequenced. nBLAST search comparison of sequences revealed 99% homology to Pestalotiopsis photiniae (AY682946.1). A representative sequence was deposited in GenBank (KC568288.1). Pestalotiopsis is an important pathogen on many crop plants and has been recorded on a wide variety of hosts, primarily on leaves, fruits, and in the rhizosphere. In recent times, cowpea is susceptible to a wide range of fungal pathogens causing severe yield loss at all stages of growth and development (1). Leaf spot caused by Pestalotiopsis species are becoming a major constraint for cowpea production in India. No previous reports are available on Pestalotiopsis species causing leaf spot of cowpea in India.

Description of a new species of Microglanis (Siluriformes: Pseudopimelodidae) from the Amazon basin, Amazonas State, Brazil

The first species of Microglanis from the rio Amazonas, Amazonas State, Brazil is described. This species differs from all congeners by the forked caudal fin, and color pattern of the supraoccipital region consisting of two elliptical and juxtaposed pale spots, besides a combination of morphometrics characters.

HSTSPECTRAL MAPPING OF L/T TRANSITION BROWN DWARFS REVEALS CLOUD THICKNESS VARIATIONS

Most directly imaged giant exoplanets are fainter than brown dwarfs with similar spectra. To explain their relative underluminosity unusually cloudy atmospheres have been proposed. However, with multiple parameters varying between any two objects, it remained difficult to observationally test this idea. We present a new method, sensitive time-resolved Hubble Space Telescope near-infrared spectroscopy, to study two rotating L/T transition brown dwarfs (2M2139 and SIMP0136). The observations provide spatially and spectrally resolved mapping of the cloud decks of the brown dwarfs. The data allow the study of cloud structure variations while other parameters are unchanged. We find that both brown dwarfs display variations of identical nature: J- and H-band brightness variations with minimal color and spectral changes. Our light curve models show that even the simplest surface brightness distributions require at least three elliptical spots. We show that for each source the spectral changes can be reproduced with a linear combination of only two different spectra, i.e. the entire surface is covered by two distinct types of regions. Modeling the color changes and spectral variations together reveal patchy cloud covers consisting of a spatially heterogenous mix of low-brightness, low-temperature thick clouds and brighter, thin and warm clouds. We show that the same thick cloud patches seen in our varying brown dwarf targets, if extended to the entire photosphere, predict near-infrared colors/magnitudes matching the range occupied by the directly imaged exoplanets that are cooler and less luminous than brown dwarfs with similar spectral types. This supports the models in which thick clouds are responsible for the near infrared properties of these underluminous exoplanets.

Monte Carlo simulation of single-plane magnetically focused narrow proton beams

We present Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet. Such beams are narrowly focused in one longitudinal plane but fan out in the perpendicular plane producing elongated elliptical beam spots (a ‘screwdriver’ shape). The focused beams were compared to passively collimated beams (the current standard of delivery for small radiosurgery beams). Beam energies considered were relevant to functional radiosurgery and standard radiosurgery clinical applications. Three monoenergetic beams (100, 125, and 150 MeV) and a modulated beam were simulated. Monoenergetic magnetically focused beams demonstrated 28 to 32% lower entrance doses, 31 to 47% larger central peak to entrance depth dose ratios, 26 to 35% smaller integral dose, 25 to 32% smaller estimated therapeutic ratios, 19 to 37% smaller penumbra volumes, and 38 to 65% smaller vertical profile lateral penumbras at Bragg depth, compared to the collimated beams. Focused modulated beams showed 31% larger central peak to entrance dose ratio, and 62 to 65% smaller vertical lateral penumbras over the plateau of the spread out Bragg peak. These advantages can be attributed to the directional acceleration of protons in the transverse plane due to the magnetic field. Such beams can be produced using commercially available assemblies of permanent rare earth magnets that do not require electric power or cryrogenic cooling. Our simulations suggest that these magnets can be inexpensively incorporated into the beam line to deliver reduced dose to normal tissue, and enhanced dose to elongated elliptical targets with major and minor axes on the order of a few centimeters and millimeters, respectively. Such beams may find application in novel proton functional and standard radiosurgery treatments in and around critical structures.

A New Rice Disease, Black Sheath Spot, Caused by Curvularia fallax in China

In July 2011, we observed a new rice disease, black sheath spot, on tillering rice plants in Huayuan County, Hunan Province, China. Field surveys indicated that this disease covered a ~1,000-ha paddy field, mainly on Y series 2-line hybrid rice cultivars, especially Y Liangyou 7 and Y Liangyou 302, in hills of which 10 to 70% infection was observed (average of 45%), causing estimated damages up to $1.2 million (US). The diseased rice plants were cultivated with standard practices. Weather, flooding, herbicide damage, and fertilizer application did not appear to account for the symptoms. Typical symptoms of the disease included elliptical spots, about 10 × 5 mm, dark brown to black and with a diffuse yellow-brown margin. The leaf blades with diseased sheaths became yellow and blighted. After 7 days of growth on PDA, groups of cylindrical and branched stromata scattered over dark green colony. Conidia averaged 30.4 × l2.5 μm and contained five cells with three dark central cells. The morphology of spores was consistent with that of C. fallax (1). We inoculated 8-cm healthy rice sheath segments with culture disk of an isolate HNAH001. Sheath segments were divided into four groups: I) disks on wounded sheath surfaces; II) disks on non-wounded sheath surfaces; III) disks between the leaf sheath and stem, and IV) a sterilized water control. The segments were maintained in moist, covered plates in a 25°C incubator after inoculation. After another 24 h, circular brown lesions, less than 10 mm long, appeared on all inoculated segments in treatments I,II, and III. Treatment I induced the most serious symptoms. No lesions developed on control segments. For further verification of pathogenicity, we sprayed a spore suspension of HNHY001 on healthy rice plants at the boot stage. Black spots reappeared on the sheaths after 5 days. No lesions appeared on the stems or the leaf blades of inoculated rice plants. We recovered HNHY001 from the spots on inoculated plants and completed all steps of Koch's postulates. For molecular identification of the fungus, DNA was extracted from mycelia and used as a template for PCR with a primer pair of ITS 5 and ITS 4 targeting the rDNA-ITS. The sequence of the PCR product (Accession No. JQ360963) had 100% identity with rDNA-ITS of Cochliobolus geniculatus (teleomorphic state of C. geniculata) and C. affinis in GenBank after a BLAST search and clustered with them after a phylogenetic analysis. There was no sequence of C. fallax on the BLAST list because ITS sequence of C. fallax had not yet been submitted to any nucleotide databank. Hosokawa et al. concluded that C. fallax and C. affinis are synonyms for C. geniculata (2), which is supported by our results from BLAST and phylogenetic analysis. In view of its relative straight conidia and branching stromata, we suggest that the causal agent of black sheath spot of rice be C. fallax. Although Curvularia spp. were reported as pathogens responsible for black kernel of rice, there is no report of sheath spot of rice caused by Curvularia (3). To our knowledge, this is the first report of a rice sheath disease caused by C. fallax. It seems likely the disease exists in areas beyond Huayuan County. Further field inspection and molecular identification are necessary.

A New Species of Cascudinho of the Genus Hisonotus (Siluriformes: Loricariidae: Hypoptopomatinae) from the Upper Rio Tapajós Basin, Brazil

Hisonotus bockmanni, new species, is described based on specimens collected in a sandbank in the Rio Cururu, a tributary to the Rio Teles Pires, one of the rivers forming the Rio Tapajós in the Amazon Basin. The new taxon is distinguished from its congeners by a unique color pattern, whose most striking features are: two elliptical white spots, anterior to nostrils; predorsal region darkly pigmented with five unpigmented spots arranged as anteriorly pointed chevron; and a rostrocaudally elongate cross along most of the caudal peduncle. The placement of the new species in Hisonotus as well as its possible affinities within that genus are discussed in light of the current knowledge of the phylogenetic relationships among the Hypoptopomatinae.Hisonotus bockmanni, nova espécie, é descrita com base em espécimes coletados em um banco de areia no Rio Cururu, afluente do Rio Teles Pires, um dos formadores do Rio Tapajós na Bacia Amazônica. O novo táxon é distinguido de seus congêneres por possuir um padrão de coloração único cujas características mais marcantes são: duas manchas elípticas brancas, anteriores às narinas; região pré-dorsal escura com cinco pontos não pigmentados dispostos como uma bifurcação apontada anteriormente; e uma cruz alongada rostrocaudalmente ao longo da maior parte do pedúnculo caudal. O posicionamento da nova espécie em Hisonotus, assim como suas possíveis relações dentro do gênero, é discutido com base no conhecimento atual das relações filogenéticas entre os Hypoptopomatinae.

Observation of unconventional optical diffraction in α-Fe2O3/Si two-dimensional photonic crystal slab fabricated by sol-gel method

The α-Fe2O3/Si two-dimensional (2D) photonic crystal (PC) with hexagonal honeycomb structure was fabricated by self-assembly and solution-dipping method based on colloidal monolayer template with 780 and 470 nm diameter polystyrene (PS) spheres. Optical diffraction measurement was carried out under wavelengths of 800, 532 and 400 nm. An interesting dispersion phenomenon with a hexagonal diffraction pattern composed of six elliptical spots is observed under specific wavelengths. Both theoretical and experimental calculations reveal that the diffraction can only occur when the incident wavelength is smaller than \(\sqrt{3}/2\) of lattice constant, and both the shape and distribution of these spots can be modified by the PC lattice constant and the incident wavelength. All these results reveal that optical properties of these 2D PC slabs are different from conventional diffractive devices.

Tight focusing of partially polarized vortex beams by binary phase Fresnel zone plates

Based on vectorial Debye theory, the focusing properties of partially polarized vortex beam by high numerical aperture Fresnel zone plate are investigated. The effects of the numerical apertures of and the phase difference of binary phase Fresnel zone plates, the topological charge of vortex beam and the degree of polarization of incident beam on the intensity distribution and degree of coherence in the focal plane are investigated in detail. It is shown that elliptical light spots and the flat top beam can be obtained by selecting certain parameters. Studies of degree of coherence reveal that the degree of coherence between x and y components of the electric field, which is zero in the source plane, is improved in the focal plane for vortex beam, but it is hardly changed for the nonvortex beam. It is also proved that any two of the three electric field components Ex, Ey and Ez are completely coherent everywhere in the focal region if the incident light beam is linearly polarized.

First Report of Botrytis hyacinthi on Pineapple Lily in California.

Pineapple lily (Eucomis vandermerwei) is grown for its exotic-looking flower spike that looks like a small pineapple. It is used as an accent plant in the garden or for its long-lasting cut flowers. In late November 2007, plant foliage was submitted to the California State Diagnostic Laboratory by a commercial grower for phytosanitary inspection before shipment of bulbs to Europe. Leaves had wet, brown, elliptical spots of 1 to 2 cm long, some with yellow halos. The interior of the older spots was pale brown and papery. Conidiophores typical of Botrytis spp. were observed on the abaxial side of the leaf in the interior of the older spots. Isolations on half-strength acidified potato dextrose agar (APDA) yielded a grayish mycelium with conidiophores developing on the plant tissue only. The agar was grayish yellow, especially when viewed from the underside. Conidiophores measured 275 to 650 μm × 15 to 20 μm (411.2 × 15.5 μm average). Conidia were light brown, subglobose to broadly ellipsoidal, and measuring 10 to 15 × 13 to 20 μm (11.8 × 16.2 μm average). Scattered, black sclerotia measuring 335 to 1,007 × 518 to 1,079 μm (668.9 × 743.9 μm average) formed on the medium after approximately 7 days. Pathogenicity was confirmed by inoculating four Eucomis spp. plants with one inoculation per leaf, four leaves per plant. Each leaf was wounded with a sterile pushpin and three agar plugs from 4-day-old cultures were placed in a plastic screw-cap lid filled with sterile water and clipped onto each wound. Plants were misted with water, covered with a plastic bag, and placed in a growth chamber at 16°C (12-h photoperiod) for 48 h after which the agar plugs and caps were removed. An equal number of plants were wounded and mock inoculated with APDA. Pathogenicity experiments were repeated. After 14 days, all inoculated leaves had lesions and the fungus was reisolated. No Botrytis spp. were isolated from the mock-inoculated plants. Our sequence of the intergenic spacer regions of one isolate, GenBank FJ10809, matched Botrytis hyacinthi sequence AJ716297 with 99.8% identity. Using molecular (3) and morphological characters (1,4), the pathogen was identified as B. hyacinthi, the cause of fire disease in hyacinths. This pathogen was described previously on hyacinths in Washington State (2), the Netherlands (4), and the United Kingdom (2). The importance and economic impact of this disease appears to be limited because it has only been observed on mature or senescing foliage and not bulbs. To our knowledge, this is the first report of B. hyacinthi causing a leaf spot on pineapple lily.

Simulation, analysis and validation of residual stresses on LY2 aluminium alloy by laser shock processing with elliptical spot

The effects of laser shock processing on the residual stresses of the LY2 aluminium alloy samples with elliptical spot (long axis length, 12 mm; short axis length, 3 mm) were experimentally investigated, and the effects of the overlapping rate on the residual stresses were simulated using the Abaqus software. The simulated residual stresses were basically in agreement with the measured data, and the relationship between the magnitude and uniformity of residual stress and the overlapping rate was also addressed. Results show that the largest stress magnitudes are located on the top surface of the sample, and the greatest uniformity is achieved by the overlapping of elliptical laser spots. The overlapping rate is critical for the uniformity of the residual stress across the surface. Within a certain impact number range of one to four times, increasing the shocked number can increase the magnitude of residual stress near the surface but not effectively increase the plastically affected depth.

Focusing of elliptically polarized Gaussian beams through an annular high numerical aperture

Based on the vectorial Debye theory, the focusing properties of the Gaussian beam through an annular high numerical aperture are studied numerically, including the intensity, the phase and the orbital angular momentum properties. Then the influence of certain parameters on the focusing properties is also investigated. It is shown that sub-wavelength elliptical light spots can be obtained. And there exists a vortex in the longitudinal component of the focused field even though the incident beam is Gaussian beam, indicating that the spin angular momentum of the elliptically polarized Gaussian beam is converted into the orbital angular momentum by the focusing.

First Report of Cercospora beticola as a Pathogen of German Statice (Goniolimon tataricum) in Bulgaria.

German statice (Goniolimon tataricum) is a protected, herbaceous, perennial plant species that occurs sporadically throughout Bulgaria. Some varieties, however, are cultivated outdoors because of their dry flowers, which are widely utilized by florists. For the past 3 years, a severe leaf disease has been observed on the lower and middle leaves of German statice plants growing in fields in the region of Plovdiv, Bulgaria. Symptoms consisted of brown, round to elliptical leaf spots (as much as 15 mm in diameter) that led to leaf yellowing and death. Similar sunken lesions were also observed on leaf petioles and flower bases. A cercosporoid fungus was consistently associated with disease symptoms. Conidiophores were fasciculate, unbranched, brown, and smooth. Conidiogenous cells were predominantly terminal, but also lateral, and had darkened, thickened, refractive scars. Conidia were solitary, hyaline, smooth, acicular, slightly curved, multiseptate, with subtruncate bases and acutely rounded apices, 30 to 105 × 2.5 to 4 (average 64.5 × 3.5) μm, in vivo (n = 30), with thickened, darkened, refractive hila. Colonies derived from single conidial isolates were established on potato dextrose agar (PDA). To confirm Koch's postulates, colonized mycelial plugs (5 mm in diameter) from 10-day-old PDA cultures were used to inoculate 3-month-old German statice pot plants (three replicates per treatment, three leaves per plant). Control plants were inoculated with uncolonized agar plugs. Healthy leaves were surface disinfested with 70% ethanol, wounded with a sterile needle, and covered with an agar plug. Inoculated plants were incubated at 20°C in a humidified chamber with a 12-h day/night light cycle. Eight to ten days after inoculation, small necrotic lesions developed around the points of inoculation, leading to necrosis and lesions (8 to 10 mm in diameter). The pathogen was successfully reisolated from all inoculated leaves, while control plants remained healthy. Five isolates (CPC 14616-14620) were subjected to multilocus sequence typing as described by Groenewald et al. (1) and the ITS, translation elongation factor 1-alpha, actin, calmodulin, and histone H3 gene sequences (GenBank Accession Nos. FJ473422-FJ473446) were found to be identical to that of the ex-type strain of Cercospora beticola Sacc. (GenBank Accession Nos. AY840527, AY840494, AY840458, AY840425 and AY840392, respectively). Two strains from Goniolimon were deposited in the CBS Fungal Biodiversity Centre in the Netherlands (CBS 123907 and 123908). To our knowledge, this is the first report of C. beticola occurring on and being destructive to Goniolimon tataricum under field conditions. Reference: (1) M. Groenewald et al. Phytopathology 95:951, 2005.

Tight focusing of elliptically polarized vortex beams

We study the focusing properties of elliptically polarized vortex beams. Based on vectorial Debye theory, some numerical calculations are given to illustrate the intensity and phase distribution properties of tightly focused vortex beams. It is found that the spin angular momentum of the elliptically polarized vortex beam will convert to orbital angular momentum by the focusing. The influence of corresponding parameters on focusing properties is also investigated in great detail. It is shown that elliptical light spots can be obtained in the focal plane. Moreover the elliptical spot may rotate and the spot shape may change with the change of certain parameters. These properties are quite important for application of this kind of elliptically polarized vortex beam.