323,128 research outputs found
Exochella moyanoi Ramalho & Calliari, 2015, sp. nov.
No full textExochella moyanoi sp. nov. (Fig. 6 A–C) Exochella longirostris Marcus, 1937: 82, fig. 43; Marcus, 1941: 22, fig. 16; Marcus, 1949: 1. Material examined. Parcel do Carpinteiro, Rio Grande do Sul, Brazil: MNRJ- 1176, am 28 point 1, 32° 10.086 ’S, 51 ° 28.269 ’W, 28 August 2009; MNRJ- 1211, am09 pc 1, 32° 17.032 ’S, 51 ° 48.754 ’W, 40 meters depth, 28 September 2009; MNRJ- 1212, am 24 station2, 32° 09.406S, 51 ° 28.318 W, 31 July 2009; MNRJ- 1213, am 30 station 0 1, 32° 14.300 ’S, 51 ° 46.630 ’W, 25 meters depth; MNRJ- 1214, am12, 32° 16.724 ’S, 51 ° 47.111 ’W, 25 meters depth; MNRJ- 1215, am05, 32 ° 16.894 ’S, 51 ° 48.454 ’W, 24 meters depth, 28 March 2007; Hermenegildo, Rio Grande do Sul, Brazil: MNRJ- 1216, HS#24, 33° 45.326 ’S, 53 ° 13.991 ’W, 18 meters depth, June 2011, Coll. FURG. Description. Colony encrusting, unilamellar with usually regular growth (Fig. 6 A). Autozooids disposed in quincunx, rectangular (271–443 (341) µm long x 171–243 (197) µm wide); frontal wall smooth, convex with only areolar horizontally elongate (11–15) (Fig. 6 A–B). Secondary orifice D-shaped (86–100 (93) µm long x 86 –100 (95) µm wide) with rounded anter and almost right poster, usually with one central mucro; condyles present almost or just the lateral midline of the orifice; three to five thin distal oral spines, usually shared by oecium (Fig. 6 B–C). One (usually) or two avicularia (86–129 (105) µm long) on the frontal surface located almost middle length of the zooid, near the margin, laterally directed (outwards), on the right or left side (when two avicularia are present, one on each side); triangular mandible; crossbar complete (Fig. 6 B–C). Oecium rounded (157–200 (174) µm long x 186–243 (217) µm wide), immersed on the frontal wall of the next zooid, smooth surface with areolar pores; dependent orifice (Fig. 6 B–C). Etymology. The name moyanoi is in honour to Dr. Hugo Moyano who dedicated his life to Bryozoan studies. Geographic distribution. Rio Grande do Sul States (Parcel do Carpinteiro and Hermenegildo - present study). Remarks. Jullien (1888) described Exochella longirostris from Cap Horn and following authors recorded this species for the Atlantic Ocean (Waters 1889; Rogick 1956; Lagaaij 1963). Marcus also recorded some colonies of this species for São Paulo and Paraná States (Marcus 1937, 1941). However, Hayward (1995) redescribed E. longirostris Jullien, 1888 and mentioned that this species is strictly magellanic (Southern Chile to the Falkland Isles) and Winston et al. (2014) suggested that Marcus’ material (from São Paulo, Marcus 1937) belonged to a distinct species. Despite of E. longirostris being similar to E. moyanoi n. sp., the first one has larger zooids (480– 500 µm long x 300–430 µm wide) with rounded areolar pores, three distal oral spines, avicularia with slender and acuminate rostrum, and oecium coarsely nodular. Winston et al. (2014) described a new species from the Brazilian coasts (Rio de Janeiro State), Exochella frigidula. This species can be distinguished from E. moyanoi as it has two to four distal spines, larger autozooids (396–522 (456) µm long x 324–486 µm wide), longer avicularia (108–180 (156) µm long) with heavy rims and rostrum on a raised camara. Another similar species is E. tropica Winston & Woollacott, 2009, but it has larger autozooids (455–516 (494) µm long x 218–309 (261) µm wide), a thick tubercle below the peristome, larger avicularia (127–218 (170 µm long) with rostrum raised at an angle from downsloping zooid margins and oriented slightly distolaterally. So, we believe that E. moyanoi is a new species.Published as part of Ramalho, Laís V. & Calliari, Lauro, 2015, Bryozoans from Rio Grande do Sul Continental Shelf, Southern Brazil, pp. 569-587 in Zootaxa 3955 (4) on pages 578-580, DOI: 10.11646/zootaxa.3955.4.8, http://zenodo.org/record/23263
Cellaria riograndensis Ramalho & Calliari, 2015, sp. nov.
No full textCellaria riograndensis sp. nov. (Fig. 4 A–D) Material examined. Parcel do Carpinteiro, Rio Grande do Sul, Brazil: Holotype: MNRJ- 1192, am 25 station 2, 32°09.173’S, 51 ° 28.099 ’W, 0 7 Aug 2009; Paratype: MNRJ- 1170, am 25 station 2, 32°09.173’S, 51 ° 28.099 ’W, 0 7 Aug 2009; MNRJ- 1171, am09 lance 6, 32° 17.032 ’S, 51 ° 48.754 ’W, 40 m depth, 28 September 2009; MNRJ- 1172, am 22 pc 1, 32° 13.716 ’S, 51 ° 46.101 ’W, 21 meters depth, 0 2 February 2009; MNRJ- 1169, am 21 P 1 Bento, 32 ° 16.674 ’S, 51 ° 47.330 ’W, 25 meters depth; MNRJ- 1191, am 24 station 2, 32°09.406’S, 51 ° 28.318 ’W, 31 July 2009; MNRJ- 1193, am 26 point 1, 32°08.348’S, 51 ° 27.589 ’W, 14 August 2009; MNRJ- 1194, am 28 point 2, 32°08.402’S, 51 ° 28.045 ’W, 28 August 2009; MNRJ- 1228, am 30 station 1, 32° 14.300 ’S, 51 ° 46.630 ’W, 25 meters depth; MNRJ- 1227, station 113 (Geo Costa I), 32 ° 15.900 ’S, 51 ° 46.970 ’W. Hermenegildo, Rio Grande do Sul, Brazil: MNRJ- 1195, HT#15, 33° 3.321 'S, 53 ° 13.824 'W, 13 meters depth, June 2011, Coll. FURG; MNRJ- 1196, HT#48, 33° 48.453 'S, 53 ° 12.857 'W, 21 meters depth, June 2011, Coll. FURG; MNRJ- 1197, HT# 48 b, 33 ° 48.453 ’S, 53 ° 12.857 ’W, 21 meters depth, June 2011, Coll. FURG; MNRJ- 1198, HT#22, 33° 44.213 ’S, 53 ° 14.414 ’W, 15.4 meters depth, June 2011, Coll. FURG; MNRJ- 1199, HT# 22 b, 33 ° 44.213 ’S, 53 ° 14.414 ’W, 15.4 meters depth, June 2011, Coll. FURG; MNRJ- 1200, HT#27, 33° 44.080 ’S, 53 ° 12.274 ’W, 19 meters depth, June 2011, Coll. FURG; MNRJ- 1258, H#20, 33° 41.254 ’S, 53 ° 10.116 ’W, 17 meters depth, June 2011, Coll. FURG; MNRJ- 1264, H#18, 33° 39.471 ’S, 53 °09.765’W, 14.7 meters depth, June 2011, Coll. FURG. Diagnosis. Colony cylindrical, jointed and branching dichotomously; autozooids rhomboidal to hexagonal, orifice crescent-shaped with distal rim beaded and two prominent condyles rod-shaped, curved to the front. Avicularia replacing the autozooid with triangular mandible; oecium with circular aperture located above the zooidal orifice. Description. Colony erect, cylindrical, branching dichotomously, jointed (Fig. 4 A). Only loose branches were collected. Autozooids rhomboidal to hexagonal (infertile: 337–425 (373) µm long x 200–250 (229) µm wide; fertile: 365–470 (403) µm long x 200–271 (231) µm wide), disposed in series (8-10) around the whole branch (Fig. 4 A–C). Orifice crescent-shaped without size difference between fertile and infertile zooids (59–80 (70) µm long x 100–137 (118) µm wide), proximal rim slightly convex with two prominent condyles rod-shaped, curved and directed to the front; distal rim with small bead. Cryptocyst granular, depressed. Gymnocyst thick, raised, granular like the cryptocyst (Fig. 4 B–D). Avicularia almost the same length of the autozooids, narrower (317–388 (351) µm long x 147–188 (174) µm wide), may replace an autozooid; mandible triangular, palate with a large and shared pore at the proximal region, condiles not observed (Fig. 4 B–D). Oecium immersed, aperture circular (30–71 (49) µm diameter), above the zooidal orifice (Fig. 4 C). Etymology. The name riograndensis refers to the Rio Grande do Sul state, locality of the samples. Geographic distribution. Rio Grande do Sul state (Parcel do Carpinteiro e Hermenegildo–present study). Remarks. Almost 110 fossil and recent Cellaria species are described around the world. For the South Atlantic almost 20 species are recorded, being 17 recent and four fossils, coming mainly from Antarctic waters. Cellaria subtropicalis Vieira et al., 2010 and C. brasiliensis Winston et al., 2014 were the only species described from the Brazilian coast. Cellaria subtropicalis has hexagonal zooids, transversal oecium aperture and a rounded avicularium mandible. Cellaria brasiliensis is very similar to C. riograndensis n. sp. but it has shorter autozooids (324–414 (377) µm long), with different shape and a rounded distal end, slightly shorter orifice (90–126 (106) µm long) with proximal rim more developed and smooth frontal surface, avicularia with the same autozooid size, and rostrum with equilateral triangle-shaped. Another similar species is C. louisorum Winston & Woollacott, 2009 described from West Atlantic (Barbados), but it differs from this species as it has a distinct orifice difference between infertile and fertile zooids (a wider orifice and a concave proximal rim in fertile zooids and a convex proximal rim in infertile ones), condyles of avicularia mandible well demarked, larger avicularia (382–455 (411) µm length), and a small rounded oecium foramen. Other species from South Atlantic have greater differences (larger zooids, series with different quantities of zooids, avicularia with semicircular mandibles, oecium with crescent orifice). Thus, we believe that this Cellaria is a new species.Published as part of Ramalho, Laís V. & Calliari, Lauro, 2015, Bryozoans from Rio Grande do Sul Continental Shelf, Southern Brazil, pp. 569-587 in Zootaxa 3955 (4) on pages 574-576, DOI: 10.11646/zootaxa.3955.4.8, http://zenodo.org/record/23263
Chaperia taylori Ramalho & Calliari, 2015, sp. nov.
No full textChaperia taylori sp. nov. (Fig. 2 A–B) Material examined. Parcel do Carpinteiro, Holotype: MNRJ- 1163, am 25 station 2, 32°09.173’S, 51 ° 28.099 ’W, 0 7 Aug 2009; Paratype: MNRJ- 1164, am 25 station 1, 32°09.513’S, 51 ° 28.013 ’W, 0 7 Aug 2009; MNRJ- 1165, MNRJ- 1185, am09 pc3, 32° 14.605 ’S, 51 ° 43.991 ’W, 22 meters depth, 28 September 2009; MNRJ- 1186, am 22 parcel 1, 32° 13.716 ’S, 51 ° 46.101 ’W, 21 meters depth, 0 2 April 2009; MNRJ- 1187, am 20, 32° 30.086 ’S, 51 ° 34.000 ’W, 40 meters depth; MNRJ- 1188, am 28 point 1, 32° 10.086 ’S, 51 ° 28.269 ’W, 28 August 2009; MNRJ- 1189, am 30 station 0 1, 32° 14.300 ’S, 51 ° 46.630 ’W, 25 meters depth; MNRJ- 1190, am12, 32° 16.724 ’S, 51 ° 47.111 ’W, 25 meters depth; MNRJ- 1229, Am 24 station 2, 32°09.406’S, 51 ° 28.318 ’W, 31 July 2009. Diagnosis. Colony growing around organic substrata; autozooids hexagonal with six distal spines, opesia longer than wide, occlusor laminae near the opesial border; frontal wall short, smooth and flat; distal wall with several spread pores not in the rosette plates. Description. Colony fragments well calcified which grow around organic substrata (Fig. 2 A). Autozooids hexagonal (484–625 (567) µm long x 453–625 (512) µm wide) with rounded distal region, disposed in quincunx (Fig. 2 A). Frontal cryptocystal wall short, smooth to lightly crenulated, and flat. Opesia oval, longer than wide (281–344 (317) µm long x 250–297 (277) µm wide), occupying more than half of the frontal surface (Fig. 2 B). On the distal border there are usually six spines, rarely seven, disposed in line. Only spine scars are present and they suggest that the most distal spines are narrower and the most proximal spines do not reach the midline of the opesia border (Fig. 2 A–B). Distal wall (inner) with numerous spread pores not included in the rosette plates (Fig. 2 B). Two occlusor laminae developed, obliquely located on each side inside and very near the opesia border (Fig. 2 A–B). Avicularia not observed. Oecium not observed. Etymology. The name taylori is in homage to Dr. Paul D. Taylor from the Natural History Museum (London) who has contributed to studies about the Brazilian bryozoan fauna. Geographic distribution. Rio Grande do Sul state - Parcel do Carpinteiro (present study). Remarks. Almost twenty species of this genus are known, seven of them are recorded in the South Atlantic: Chaperia acanthina (Lamouroux, 1824), Chaperia brasiliensis Vieira et al., 2010, C. capensis (Busk, 1884), C. familiaris Hayward & Cook, 1983, C. laticella Canu, 1908, C. polygonia (Kluge, 1914), and C. septispina Florence et al., 2007. All of these species have opesia that are wider than long, differing from Chaperia taylori sp. nov., which has opesia longer than wide. Besides this C. acanthina has four or five distal spines, a longer cryptocyst, shorter and wider opesia (220–260 µm long x 280–300 µm wide); C. brasiliensis has more distal spines (7–11), shorter opesia (236 µm long x 265 µm wide); C. capensis has only two distal spines, opesia occupying more than 60 % of the total front length; in C. familiaris the two most proximal distolateral spines and the occlusor lamina are nearer the distal region; C. laticella has smaller opesia (210 µm long x 250 µm wide), a convex, granulose and more developed cryptocyst; C. septispina has 5–7 distal spines, a shorter cryptocyst, occlusor laminae farther away from the opesium border, originating distally and reaching the proximal edge of the opesium. Chaperia polygonia is the species most similar to Chaperia taylori, but besides the longer than wide opesium, it has a shorter and more crenulated frontal cryptocystal wall, occlusor laminae that are more robust and farther away of the opesium border, and two distal multiporous rosette plates. Based on these observations we believe that Chaperia taylori is a new species. López Gappa & Lichtschein (1988) recorded C. acanthina (var. polygonia Kluge, 1914) for northern Argentina. These specimens may prove to be conspecific with C. taylori sp. nov.Published as part of Ramalho, Laís V. & Calliari, Lauro, 2015, Bryozoans from Rio Grande do Sul Continental Shelf, Southern Brazil, pp. 569-587 in Zootaxa 3955 (4) on pages 571-572, DOI: 10.11646/zootaxa.3955.4.8, http://zenodo.org/record/23263
Momentum transfer effects in near surface Electron Energy Loss
No full textWe examine two formulations for the differential surface excitation parameter (DSEP): one provided by Tung et al. and the other given by the Chen–Kwei position-dependent differential inverse inelastic mean free path integrated over the electron trajectory. We demonstrate that the latter converges to the former provided that the dielectric function of the solid does not depend on the momentum transfer or it depends on just the momentum transfer component parallel to the surface. Tung's DSEP represents therefore an approximation to the Chen–Kwei DSEP calculated for a dielectric function with no restrictions on the momentum dependence. The approximation is shown to work in the limit of small momentum transfer and to imply an error of 4%–5% for electrons traveling through the solid with energy E = 1 keV
The spatial extent of surface effects on electron inelastic scattering
No full textWe calculate the thickness of the surface scattering layer, defined as the region where electron inelastic scattering is affected by the surface, using the semi-classical treatment of electron energy loss provided by the Chen–Kwei theory. To this end, we consider the depth-dependent, surface-related contributions to the inverse inelastic mean free path, namely, the excitation of surface plasmons and the reduction in bulk plasmon excitation (Begrenzung effect). We find that surface effects extend further after electrons cross the surface than before they cross it. The ‘pre-surface thickness’ is given by the ratio of the electron velocity to the plasma frequency, the characteristic decay length for surface effects. All thickness estimates increase linearly with the electron velocity and decrease as (cosα)x with the angle α between the electron trajectory and the surface normal
Reflection electron energy loss spectroscopy: role of the Bethe–Born factor
No full textThe article deals with two issues concerning reflection electron energy loss spectroscopy (REELS), namely, which angular cutoff
should be used to properly define the phase space of energy loss into plasmon excitations and how approximate evaluations of
the surface component of the momentum transfer can affect the surface excitation parameter. With regard to the first point, we
demonstrate the crucial role of plasmon energy dispersion in determining the angular range for inelastic scattering. As for the
second point, we show that an exact evaluation of the surface component of the momentum transfer is needed if the surface
excitation parameter has to be determined in a reliable way over the entire range of angles of surface crossing
Caratterizzazione, tecnologia di fabbricazione e provenienza dei mattoni dei monumenti veneziani
No full textMicrostructural characterization of official and imitative nummi of Vth century A.D
No full textMetallography is an important tool that provides useful data on the fabrication technology, thermo-mechanical history of the object and on the nature of alloy employed. This research is part of a project aimed at reinforcing numismatic classification and description with chemical and microstrustural investigations. In this paper the attention has been focused on three bronze coins: Two Roman nummi struck under Arcadius/Honorius/Theodosius II in Rome (RIC, X, nn. 1271-1283, sample C9) and under Majorian in Ravenna (RIC, X, n. 2621,sample C26); the results of analyses on an italic imitation issued during the second half of V century AD are also presented, in order to evaluate possible connections between official and unofficial coins. The composition has been determined by XRF (Kevex 770) equipped whit a secondary target of Gd. The spectrometer operated at the following conditions: 55 kV, 1.00 mA. The microstructure of coins were investigated on metallographic cross-sections by light microscopy (Leica DM 100) and by SEM (Leica Cambridge Stereoscan 440) and analysed using the X-ray micro-analysis EDS (EDAX Philips) coupled to SEM. The EDS compositional profile is also obtained on the same coins to determine the element distribution and the concentration profile from the surface to the bulk. For EDS compositional profile the SEM operated at 25 kV. The semi-quantitative determination of element concentration was carried out standarless with the ZAF correction. In Tab.1 the bulk (b) and the surface (s) compositions (Wt%), determined whit EDS and XRF, are reported. The disagreement between XRF and SEM results are due to the different surface and bulk composition [2]. The high amount of Pb on the surface layer can be attributed to its preferential migration on the surface. The thickness and morphology of corrosion depend on chemical and physical properties of environment where coin was buried ; then the values obtained by SEM on the bulk (reported in tab 1) are reliable and show that specimens consist of a bronze alloy Cu-Sn with high rates of Pb. The content of Sn, shown in fig. 3, higher of 5%, identifies a western production [1, 10, 11], in contrast with what happens in the eastern mints. The micrographs show large grains flattened, evidence of the original cast microstructure with dendritic segregation; some slip lines were detected, confirming the plastic deformation (Fig 4, Fig 6, Fig 8). In Fig 5, 7, 9 BSE images show the directional preference of Pb. These characteristics can be attributed to identical production technologies for all the samples: The hypothesis is that the flans were obtained for solidification in the mold and then hammered to the desired thickness. Next, the plastic deformation could not be too strong because the Cu-Sn alloy whit an high amount of Pb is too brittle for further deformation. After being reduced in thickness, the flan was heated and coined. The process of hammering is evidenced by the shape of the grains that are not defined and polygonal but reflect a previous dendritic phase, which shows a fusion process. The presence of microsegregation zones shows the low working on metal surface after the melting process. XRF technique, instead, has not delivered the expected results in this work; in fact, the obtained data do not reflect the true composition of the sample but only the surface's layer composition of material
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