Mid Tail Research Articles

Data Mining Reconstruction of Magnetotail Reconnection and Implications for Its First-Principle Modeling

Magnetic reconnection is a fundamental process providing topological changes of the magnetic field, reconfiguration of space plasmas and release of energy in key space weather phenomena, solar flares, coronal mass ejections and magnetospheric substorms. Its multiscale nature is difficult to study in observations because of their sparsity. Here we show how the lazy learning method, known as K nearest neighbors, helps mine data in historical space magnetometer records to provide empirical reconstructions of reconnection in the Earth’s magnetotail where the energy of solar wind-magnetosphere interaction is stored and released during substorms. Data mining reveals two reconnection regions (X-lines) with different properties. In the mid tail (∼30RE from Earth, where RE is the Earth’s radius) reconnection is steady, whereas closer to Earth (∼20RE) it is transient. It is found that a similar combination of the steady and transient reconnection processes can be reproduced in kinetic particle-in-cell simulations of the magnetotail current sheet.

Morphological Sex Determination in Black-Faced Cormorants (Phalacrocorax fuscescens)

Abstract. Black-faced Cormorants (Phalacrocorax fuscescens) are endemic to marine environments in southern Australia and little is known of their biology. Development of a reliable and practical method for sexing adult birds in the field is necessary to aid research into their behavior and life-history. Eleven measurements from museum specimens (27 male; 31 female) were used to document sexual dimorphism in Black-faced Cormorants using discriminant function analyses (DFA). A simultaneous DFA correctly sexed 81% of birds, while a stepwise DFA correctly sexed 85% of birds based on two measurements (bill length and mid tail length). However, terminal wear of the retrices make this measurement unreliable. A logistic regression using bill length correctly predicted the sex of 78% of individuals. Black-faced Cormorants with a bill ≤ 76 mm long are likely female and ≥ 77 mm long are likely male, therefore providing a reliable method for assigning sex in the field. Black-faced Cormorants exhibit the same pattern ...

Focus on Authors

Focus on Authors

Firm Strategies in the 'Mid Tail' of Platform-Based Retailing

While millions of products are sold on its retail platform, Amazon.com itself stocks and sells only a small fraction of them. Most of these products are sold by third-party sellers, who pay Amazon a fee for each unit sold. Empirical evidence clearly suggests that Amazon tends to sell high-demand products and leave long-tail products for independent sellers to offer. We investigate how a platform owner such as Amazon, facing ex ante demand uncertainty, may strategically learn from these sellers’ early sales which of the “mid-tail” products are worthwhile for its direct selling and which are best left for others to sell. The platform owner’s “cherry-picking” of the successful products, however, gives an independent seller the incentive to mask any high demand by lowering his sales with a reduced service level (unobserved by the platform owner). We analyze this strategic interaction between the platform owner and the independent seller using a game-theoretic model with two types of sellers — one with high demand and one with low demand. We show that it may not always be optimal for the platform owner to identify the seller’s demand. Interestingly, the platform owner may be worse off by retaining its option to sell the independent seller’s product whereas both types of sellers may benefit from the platform owner’s threat of entry. The platform owner’s entry option may reduce the consumer surplus in the early period though it increases the consumer surplus in the later period. We also investigate how consumer reviews influence the market outcome.

Firm Strategies in the “Mid Tail” of Platform-Based Retailing

While millions of products are sold on its retail platform, Amazon.com itself stocks and sells only a very small fraction of them. Most of these products are sold by third-party sellers who pay Amazon a fee for each unit sold. Empirical evidence clearly suggests that Amazon tends to sell high-demand products and leave long-tail products for independent sellers to offer. We investigate how a platform owner such as Amazon, facing ex ante demand uncertainty, may strategically learn from these sellers' early sales which of the “mid-tail” products are worthwhile for its direct selling and which are best left for others to sell. The platform owner's “cherry-picking” of the successful products, however, gives an independent seller the incentive to mask any high demand by lowering his sales with a reduced service level (unobserved by the platform owner). We analyze this strategic interaction between a platform owner and an independent seller using a game-theoretic model with two types of sellers—one with high demand and one with low demand. We show that it may not always be optimal for the platform owner to identify the seller's demand. Interestingly, the platform owner may be worse off by retaining its option to sell the independent seller's product, whereas both types of sellers may benefit from the platform owner's threat of entry. The platform owner's entry option may reduce consumer surplus in the early period, although it increases consumer surplus in the later period. We also investigate how consumer reviews influence the market outcome.

Gyrinicola chabadamsoni n. sp. and G. tba (Dinnik 1933) (Nematoda, Oxyuroidea) from tadpoles of the hybridogenetic complex Rana lessonae-esculenta (Amphibia, Ranoidea)

Two morphological types of the viviparous oxyurid nematode Gyrinicola were recovered from waterfrog tadpoles in France (Ain department, Rhône-Alpes region) and assigned to two species: G. tba (Dinnik 1930), redescribed, and G. chabadamsoni n. sp. Gyrinicola tba is close to G. batrachiensis (Walton 1929) and G. chabaudi Araujo and Artigas 1982 in that the female possesses a long tail and few cuticular buccal flaps. The new species, type host Rana kl. esculenta, is distinct by several characters: in females, by the 12 cuticular buccal flaps with internal crests, short caudal filament, short ovary producing embryonated eggs and large uterine pouch containing males and embryos, like in G. japonica Yamaguti 1938, and narrower thick-shelled eggs with subapical elongated operculum; in males, by the round genital cone, the third caudal pair of papillae at mid tail, length of the body and caudal part. Gyrinicola tba and the new species were found in R. lessonae and in the hybrid R. kl. esculenta but each with different seasonal infection rates. Comparative analyses of the data from the five Gyrinicola species were done. All females have one genital tract producing thick-shelled female eggs. The second genital tract is one of four types corresponding to different reproductive patterns: i) it forms a uterine pouch containing males in G. chabadamsoni and G. japonica; ii) it forms a slender uterus containing numerous autoinfective larval stages in G. batrachiensis from R. clamitans; iii) it forms a slender uterus containing only a few embryos in G. tba and G. chabaudi; and iv) it has regressed in G. batrachiensis from Bufo americanus. Haplodiploidy is expected or proved for types i) and ii) and thelytoky for types iii) and iv).

Radopholus arabocoffeae sp. n. (Nematoda: Pratylenchidae), a nematode pathogenic to Coffea arabica in Vietnam, and additional data on R. duriophilus

AbstractRadopholus arabocoffeae sp. n., a new nematode pathogenic on Coffea arabica cv. Catimor, is described from Vietnam. Females of R. arabocoffeae sp. n. are characterised by the broad amphidial apertures with prominent margins. Males are characterised by the bursa extending to one third, rarely middle, of the tail. The new species belongs to the group of species with a long tail in the female. Radopholus arabocoffeae sp. n. is easily distinguished from R. similis by the bursa reaching to only one third of the tail vs extending to the tail terminus. Radopholus arabocoffeae sp. n. is differentiated from R. bridgei by the lateral field having three bands of equal width (vs middle one narrower than others), lateral field completely areolated over whole body vs not areolated except irregularly in neck and tail, hemizonid distinct vs indistinct, four lateral field incisures terminating far behind phasmid vs three incisures terminating at or just behind phasmid, lateral lines fusing at two thirds of tail vs fusing at one third of tail, longer spicule length (18-21 vs 15.5-18.0 μm), and male bursa usually extending to only one third of tail vs mid tail. Radopholus arabocoffeae sp. n. differs from R. colbrani by the rod-like vs round sperm, spicule length (18-21 vs 13-16 μm), tail length to stylet ratio (4.1-4.9 vs more than 5.1) and presence vs absence of a bursa. Radopholus arabocoffeae sp. n. differs from R. duriophilus by the rod-like vs kidney-shaped sperm. Males further differ from R. duriophilus by shorter stylet length (8.2-11.6 vs 11.5-15 μm), smaller distance between dorsal pharyngeal gland orifice and stylet base (1.7-3.4 vs 4-9.5 μm), shorter hyaline tail (2.6-3.4 vs 4-9.5 μm), and bursa extending to one third of tail vs mid-tail. Female R. arabocoffeae sp. n. differ from R. duriophilus by the broad amphidial aperture with prominent margin present vs absent. Males of R. arabocoffeae sp. n. differ from R. musicola by the rudimentary and amalgamated stylet base (vs with knobs), and inner lateral lines fusing at two thirds of the tail vs just posterior to the phasmid. The high level of ITS-rDNA sequence divergence of R. arabocoffeae sp. n. from other Radopholus spp. and the presence of nucleotide autapomorphies support a separate specific status of this new species. On carrot disks, the two species reproduced from 15-30°C; optimum reproduction occurring at 28°C. The reproductive capacity of R. duriophilus was higher than that of R. arabocoffeae sp. n. Radopholus duriophilus reproduced from single juveniles; R. arabocoffeae sp. n. did not. The correlation between initial densities of Pratylenchus coffeae, R. duriophilus and R. arabocoffeae sp. n. and the weight of C. arabica cv. Catimor fitted the Seinhorst model Y = ym for Pi ≥ T, and Y = ym ˙ m + ym(1–m)z(Pi–T). Coffea arabica cv. Catimor was very susceptible for to all three nematode species tested, but especially so to R. arabocoffeae sp. n. The reproductive capacity of R. arabocoffeae sp. n. on C. arabica cv. Catimor was higher than P. coffeae or R. duriophilus.

Simulation of the March 9, 1995, substorm: Auroral brightening and the onset of lobe reconnection

A global MHD simulation of an isolated substorm that occurred on March 9, 1995 is presented. The simulation, driven with solar wind data provided by the Wind satellite, reproduced to a surprising degree the evolution of substorm activity. The onset of the expansion phase was coincident with the penetration of an electric field spike into the near‐Earth region. This impulse launched a tailward propagating signal (rarefaction wave) that enhanced reconnection in the mid tail. Substorm intensification was correlated with the enhancement of the reconnection rate at the preexisting reconnection region located at 30 RE. The importance of the electric field spike in correlating ionospheric and magnetospheric aspects of the substorm is emphasized.

Paraorientatractis semiannulata n. g., n. sp. (Cosmocercoidea: Atractidae) from the Large Intestine of the SideNecked Turtle, Podocnemis unifilis Troschel, 1848 (Testudines: Pelomedusidae) in Brazil

Specimens collected from the large intestine of the side-necked turtle Podocnemis unifilis Troschel, 1848 in the region of Cuminá and Trombetas rivers near Pará, Brazil are assigned to a new genus and new species of the nematode superfamily Cosmocercoidea and family Atractidae and named Paraorientatractis semiannulata. The new genus is separated from the nearest genus Orientatractis by the funnel-shaped mouth opening, the presence of 4 distinct lips, 4 papillae in the internal cycle, one on each lip margin, 2 lateral amphids with large amphidial pores and absence of submedian papillae. It is also separated from Orientatractis and Proatractis by the presence of striated lateral alae which curve dorsally extending from mid oesophagus to mid tail, the difference in size of the vulvar opening and the presence of large transverse ridges or semiannules on the dorsal surface. The new species can be separated from the species of the genera Orientatractis and Proatractis by the characters that distinguish the genera and the arrangement of the caudal papillae on the male. A host/parasite list for Podocnemis spp. is included.

A new stem-chordate solute fromthe Middle Ordovician of Estonia

The solute Maennilia estonica nov. gen. et nov. sp. (Maenniliidae, nov. fam.) from the middle Caradoc Keila Horizon of the village of Vasalemma, near the town of Keila, near Tallin, Estonia is reconstructed and described. Remarkable features include: the hydropore developed as a madreporite and penetrated by the gonopore; ringshaped major plates in the fore tail, visibly formed by the fusion of smaller plates; a symmetrical mid tail, with dorsal and ventral series of ossicles extending forwards to meet the fore-tail rings in the mid line; an anterior lobe projecting leftwards and better developed in large than small individuals; and large size. Maennilia estonica may have lived with the ventral face up. The presence of a branchial pore could not be established. Ontogenetic changes in the anterior lobe suggest that the gonad was anteriorly located in the head, as in other solutes. Maenniliidae nov. fam. comprising M. estonica and Heckericystis kuckersiana ( Hecker ) 1940 , and with Maennilia estonica as the type species, is proposed with three autapomorphies: the gonopore penetrates the hydropore, the mid tail has a peculiar symmetrical structure and the head skeleton is relatively rigid. The Maeniliidae have rings in the fore tail visibly formed by the fusion of smaller plates. Among other solutes, only Dendrocystites sedgwicki Barrande , 1887 seems to share this feature which should therefore probably be seen as a synapomorphy of the Maenniliidae with that species. Within the chordate stem group, the Maenniliidae with Dendrocystites sedgwicki probably represent a plesion crownward of the Iowacystidae and anti-crownward of Dendrocystoides scoticus ( Bather ) 1913 . Hecker's reconstruction of H. kuckersiana is partly mistaken. Isolated hind-tail ossicles of ”Dendrocystites” rossicus Jaekel , 1901 , from the Llanvirn near Pavlovsk in the St. Petersburg area of Russia, suggest a solute of very great size i.e. with a guessed total length of perhaps 300 mm, making it by far the largest known solute. Le Soluta Maennilia estonica nov. gen. et nov. sp., du Caradocien moyen de l'horizon de Keila du village de Vasalemma, près de la ville de Keila dans la région de Tallin, Estonie, est reconstitué et décrit. Les traits remarquables en sont les suivants: un hydropore développé en madréporite et traversé par le gonopore; des plaques majeures de la partie antérieure de la queue en forme d'anneau et visiblement formées par la fusion de plaques plus petites; une partie moyenne de la queue symétrique avec des séries de grandes plaques dorsales et ventrales qui se prolongent dans la ligne médiane jusqu'à l'extrémité postérieure des plaques majeures de la partie antérieure de la queue; un lobe antérieur de la tête qui s'étend vers la gauche et qui est plus developpé chez les individus de grande taille que chez les petits; la taille importante de l'espèce. Il est possible que Maennilia estonica vivait avec la face ventrale vers le côté supérieur. Aucun pore branchial n'a pu être identifié. Des changements ontogénétiques de la forme du lobe antérieur indiquent que la gonade était située antérieurement dans la tête, comme chez les autres Soluta. La nouvelle famille des Maenniliidae, constituée par Maennilia estonica et Heckericystis kuckersiana ( Hecker ) 1940 , avec Maennillia estonica comme espèce type, est proposée avec trois autapomorphies: un gonopore qui traverse le madréporite, la condition relativement rigide du squelette de la tête et une structure symétrique et particulière de la partie moyenne de la queue. Les Maenniliidés ont des anneaux majeurs dans la partie antérieure de la queue qui sont visiblement formés par la fusion de plaques plus petites. Parmi les autres Soluta ce caractèrene ne semble être partagé qu'avec l'espèce Dendrocystites sedgwicki Barrande , 1887 et représente, selon toute probabilité, une synapomorphie avec elle. Les Maenniliidés et Dendrocystites sedgwicki représentent, dans le groupe souche des chordés, un plésion plus proche du groupe cime que les Iowacystidés et moins proche que le plésion de Dendrocystoides scoticus ( Bather ) 1913 . La reconstitution par Hecker de Heckericystis kuckersiana contient des erreurs. Des plaques isolées massives de la queue postérieure de “Dendrocystites” rossicus Jaekel , 1901 , du Llanvirnien des environs de la ville de Pavlovsk dans la région de St.-Pétersbourg, indiquent un Soluta de très grande taille (une longueur totale estimée d'environ 300 mm) qui en fait donc le plus grand des Soluta connus.

A novel way to assess murine delayed type hypersensitivity: Elicitation of response in the tail

Abstract Mice were sensitized with sheep red blood cells (SRBC) and challenged 3–7 days later with a mid tail subcutaneous injection of SRBC. Delayed type hypersensitivity (DTH) was assessed by the amount of tail swelling elicited by antigen challenge and was reflected in a histological pattern of an accumulation of lymphocytes and monocytes-macrophages. The swelling response was specific to the antigen used. The amount of swelling was dependent on the numbers of SRBC used during both sensitization and challenge. The route of administration for sensitization had a variable effect on the DTH response and had significant effects on the amount of hemagglutinating antibody to SRBC. This method of assessing delayed type hypersensitivity in the mouse is rapid, reproducible, and can be done by one individual. We have found the measurement of tail swelling to be a convenient alternative to measuring tissue swelling in a footpad or ear.