854 research outputs found
Probing the nebular thermal structure using the he i recombination spectrum and evidence against temperature fluctuations and density inhomogeneities
No full textA long-standing problem in nebular astrophysics has been that heavy element abundances derived from collisionally excited lines (CELs) are systematically lower than those derived from optical recombination lines (ORLs). A chemically homogeneous nebula with temperature and density variations fails to account for the discrepancy (c.f. [3]). Instead detailed multi-waveband analyses of a large sample point to the presence of H-deficient condensations embedded in diffuse nebulae [2,8,9]. The 2-abundance model, first proposed by Liu et al. [4], predicts that 2006 Springer.link_to_subscribed_fulltex
High performance latent dirichlet allocation for text mining
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Latent Dirichlet Allocation (LDA), a total probability generative model, is a three-tier Bayesian model. LDA computes the latent topic structure of the data and obtains the significant information of documents. However, traditional LDA has several limitations in practical applications. LDA cannot be directly used in classification because it is a non-supervised learning model. It needs to be embedded into appropriate classification algorithms. LDA is a generative model as it normally generates the latent topics in the categories where the target documents do not belong to, producing the deviation in computation and reducing the classification accuracy. The number of topics in LDA influences the learning process of model parameters greatly. Noise samples in the training data also affect the final text classification result. And, the quality of LDA based classifiers depends on the quality of the training samples to a great extent. Although parallel LDA algorithms are proposed to deal with huge amounts of data, balancing computing loads in a computer cluster poses another challenge. This thesis presents a text classification method which combines the LDA model and Support Vector Machine (SVM) classification algorithm for an improved accuracy in classification when reducing the dimension of datasets. Based on Density-Based Spatial Clustering of Applications with Noise (DBSCAN), the algorithm automatically optimizes the number of topics to be selected which reduces the number of iterations in computation. Furthermore, this thesis presents a noise data reduction scheme to process noise data. When the noise ratio is large in the training data set, the noise reduction scheme can always produce a high level of accuracy in classification. Finally, the thesis parallelizes LDA using the MapReduce model which is the de facto computing standard in supporting data intensive applications. A genetic algorithm based load balancing algorithm is designed to balance the workloads among computers in a heterogeneous MapReduce cluster where the computers have a variety of computing resources in terms of CPU speed, memory space and hard disk space
Sinopoda liui Zhong, Cao & Liu 2017
No full textSinopoda liui Zhong, Cao & Liu, 2017 Figs 31–33, 62 urn:lsid:zoobank.org:act: 75A2498B-12B3-4028-9AAF-777077 B23711 Sinopoda liui Zhong et al., 2017: 160, figs 5C–D, 6C–D, 15C–D (♀, holotype, China: Fujian Province, Longxishan National Nature Reserve, 26.40°N, 117.22°E, 985 m, native forest, 18 July 2013, Y. Zhong & X.W. Cao, deposited in CBEE, examined; 10 ♀, paratypes, same date, in CBEE, examined). Additional material examined. 4 males and 6 females (CBEE), 1 male and 1 female (SMF), same locality as holotype, 28 July 2018, Y. Zhong leg. Diagnosis. Males of this species resemble those of S. tengchongensis Fu & Zhu, 2008 (Fu & Zhu 2008: figs 2–5) in having the embolus tip distinctly shorter than the embolic apophysis and the spermophor distinctly curved in ventral view, but are distinguished from the latter by the following characters: 1. Inner margin of dRTA distinctly curved in ventral view (almost straight in S. tengchongensis); 2. RTA extending moderately to the retrolateral side (extending and bulging strongly to the retrolateral side in S. tengchongensis); 3. Tegulum covering proximal part of embolus (not in S. tengchongensis); 4. Embolus distally leaf-shaped in ventral view (slender in S. tengchongensis). Females of S. liui are similar to those of S. aequalis sp. nov. (Figs 4 D–E, 6A–B) in having sutured lateral lobes with two slight humps posteriorly and a moderately wide lobal septum anteriorly, but can be separated by: vulva with glandular appendages wider than posterior parts of spermathecae, with distal ends slightly curved (as wide as, not curved in S. aequalis). Description. Male: Measurements: PL 5.8, PW 5.2; AW 2.6; OL 6.0, OW 3.3. Eyes: AME 0.22, ALE 0.34, PME 0.24, PLE 0.41, AME–AME 0.21, AME–ALE 0.10, PME–PME 0.32, PME–PLE 0.56, AME–PME 0.40, ALE–PLE 0.43, CH AME 0.15, CH ALE 0.21. Spination: Palp: 131, 101, 1021; Fe: I–III 323, IV 331; Pa: I–IV 101; Ti: I–IV 2326; Mt: I–II 2024, III–IV 3036. Measurements of palp and legs: Palp 10.2 (3.7, 1.6, 1.6, –, 3.3); I 27.0 (7.0, 2.4, 7.5, 7.7, 2.4); II 30.2 (8.3, 2.5, 8.3, 8.4, 2.7); III 21.3 (6.0, 2.1, 5.7, 5.7, 1.8); IV 23.9 (6.6, 2.0, 6.4, 6.9, 2.0). Leg formula: II-I-IV-III. Cheliceral furrow with 3 anterior, 4 posterior teeth and ca. 21 denticles. Palp as in diagnosis. Cymbium distinctly longer than tibia. Embolus arising from tegulum at 7:30 to 8-o’clockposition, with embolic tip distinctly shorter than embolic apophysis. Tegulum partly covering proximal part of embolus. RTA originating medially to proximally from tibia (Figs 31 A–C, 32A–D). Colouration in ethanol. Dorsal prosoma yellowish-brown, with two dark lateral bands with serrated inner and outer margin, lateral margins dark, with yellow submarginal transversal light band posteriorly. Labium and gnathocoxae yellowish-brown, both with distal parts brighter. Sternum yellowish-brown, with margin brown. Chelicerae deep reddish-brown. Legs yellowish-brown with dark spots. Dorsal opisthosoma reddish-brown, covered by gray hairs, lateral field of opisthosoma with three pairs of black patches. Ventral opisthosoma brown with irregular pattern (Figs 32 E–F). Redescription: Female: epigynal field wider than long, with short anterior bands and one slit sensillum on each side close to the epigynal field. Glandular appendages with swollen ends. Posterior parts of spermathecae small, fertilization ducts arising posterio-laterally (Figs 33 A–B). Further details and measurements see Zhong et al. (2017). Distribution. China (Fujian) (Fig. 62).Published as part of Zhong, Yang, Jäger, Peter, Chen, Jian & Liu, Jie, 2019, Taxonomic study of Sinopoda spiders from China (Araneae: Sparassidae), pp. 1-81 in Zootaxa 4607 (1) on pages 41-45, DOI: 10.11646/zootaxa.4607.1.1, http://zenodo.org/record/286084
Hahnia subcorticicola Liu, Huang & Zhang, 2015, sp. nov.
No full textHahnia subcorticicola sp. nov. Figs 1 A–E, 2 A–I, 4 Type material. Holotype male, CHINA: Chongqing: Mt. Jinyun, 29 ° 50.1 ′ N, 106 ° 23.7 ′ E, Guankou, 5 April 2010, Z.S. Zhang, Z.X. Li, K.Y. Xu & L.Y. Wang leg. (SWUC). Paratypes: 12 males, 72 females (SWUC), with same data as holotype; 15 males, 69 females, with same location as holotype, 28 March 2010, Z.X. Li, K.Y. Xu & L.Y. Wang leg. (SWUC); 6 males, 93 females, with same location as holotype, 28 April 2010, Z.X. Li, K.Y. Xu & L.Y. Wang leg. (SWUC); 4 males, 9 females, with same location as holotype, 26 October 2011, Z.X. Li, Z. Li & L.Y. Wang leg. (SWUC); 7 males, 5 females, with same location as holotype, 12 November 2011, M.X. Liu & D. Wang leg. (SWUC); 11 males, 13 females, with same location as holotype, 29 November 2011, M.X. Liu & D. Wang leg. (SWUC); 15 males, 13 females, with same location as holotype, 27 November 2010, L.Y. Wang leg. (SWUC); 12 males, 19 females, Mt. Jinyun, Banzigou, 4 December 2010, Z. Li & Z.X. Li leg. (SWUC); 16 males, 23 females, Mt. Jinyun, Caijiagou, 12 December 2010, Z.S. Zhang leg. (SWUC); 71 males, 206 females, with same location as holotype, 30 March 2011, Z.X. Li, Z. Li & L.Y. Wang leg. (SWUC); 1 male, 6 females, with same location as holotype, 24 October 2011, L.Y. Wang, D. Wang & M.X. Liu leg. (SWUC); 3 females, with same location as holotype, 1 December 2010, Z.X. Li, Z. Li & L.Y. Wang leg. (SWUC); 3 females, with same location as holotype, 25 May 2011, Z. Li & L.Y. Wang leg. (SWUC); 1 female, Mt. Jinyun, Yunhe Village, 15 June 2010, L.Y. Wang leg. (SWUC); 1 female, Mt. Jinyun, Yunhe Village, 15 November 2010 (SWUC); 1 male, 15 females, Mt. Jinyun, Caijiagou, 10 April 2013, X.K. Jiang, X.W. Meng, T. Lu & J. Yang leg. (SWUC); 2 females, Mt. Jinyun, Caijiagou, 29 October 2011, L.Y. Wang, D. Wang & M.X. Liu leg. (SWUC); 1 male, 1 female, Mt. Jinyun, Fuxin Temple, 17 April, 2012, Z. Li & L.Y. Wang leg. (SWUC); 1 male, Mt. Jinyun, Beiwenquan, 9 December 2012, X.K. Jiang & M.X. Liu leg. (SWUC); Hubei: 9 females, Luotian County, Tiantangzhai, 30 ° 5.9 ′ N, 115 °44.0′ E, 25–28 September 2009 (HUBU); 2 females, Tiantangzhai, 20–26 July 2009 (HUBU); 2 males, 5 males, Badong County, Yeshanguan Town, 30 ° 36.8 ′ N, 110 ° 19.8 ′ E, hillside behind the Sanxia wine factory, 24 March 2014, L.Y. Wang leg. (SWUC); Anhui: 123 males, 186 females, Xiuning County, Huangshan City, Mt. Qiyun, 29 ° 48.9 ′ N, 118 ° 2.7 ′ E, from Yuehua Street to the highest point within Qiyun, 19 April 2011, Z.X. Li & L.Y. Wang leg. (SWUC); 17 males, 49 females, Mt. Qiyun, Fanglazhai, 19 April 2011, Z.X. Li & L.Y. Wang leg. (SWUC); 1 female, Mt. Qiyun, 6 September 2011, L.Y. Wang & M.X. Liu leg. (SWUC); 10 males, 12 females, 18 April 2011, Z.X. Li & L.Y. Wang leg. (SWUC); 1 male, 2 females, Mt. Qiyun, 26 September 2011, L.Y. Wang & M.X. Liu leg. (SWUC); 3 males, 5 females, Mt. Qiyun, 27 September 2011, L.Y. Wang & M.X. Liu leg. (SWUC); 4 males, 14 females, Huangshan scenic area, 20 April 2011, Z.X. Li & L.Y. Wang leg. (SWUC). Material examined for comparison. Hahnia corticicola: 16 females, 17 males, CHINA: Sichuan: Jiuzhaigou County, Longkang Town (SWUC); 1 female, 1 male, Shaanxi: Zhouzhi County, Houzhenzi (SWUC). Etymology. The specific epithet refers to the species’ similarity to H. corticicola Bösenberg & Strand 1906. Diagnosis. The new species is similar to H. corticicola (Figs 3 A–I) in having similarly shaped patellar apophysis, RTA, median apophysis, tegulum, and long and deep cymbial furrow as well as a similarly positioned copulatory opening, but it can be distinguished by the pointed apex of the male palpal cymbium, the equally long cymbium and cymbial furrow, the presence of a small tegular apophysis near the base of the embolus, the extremely slender embolus with its tip embedded in a pocket (Figs 1 A–C, 2 E–G), the protruding median part of the posterior margin of the copulatory opening, the long, multi-coiled copulatory ducts and the distinct subspermathecae of the epigyne (1 D–E, 2 H–I). Description. Male holotype (Figs 2 A, C–D) total length 1.77. Prosoma 0.78 long, 0.68 wide; opisthosoma 1.09 long, 0.81 wide. Carapace pear-shaped with dark markings in radial furrows and cervical groove. Fovea longitudinal, brown. Cephalic area elevated. Eight eyes with distinct black rims. Eye sizes and interdistances: AME 0.03, ALE 0.06, PME 0.05, PLE 0.05; AME–AME 0.03, AME–ALE 0.01, PME–PME 0.05, PME–PLE 0.02, ALE–PLE 0.01. MOA 0.12 long, front width 0.09, back width 0.14. Clypeus height 0.12. Chelicerae yellowish with three promarginal and three retromarginal teeth. Gnathocoxae of equal length and width. Labium wider than long. Sternum cordiform with dark marginal markings. Legs yellow with some spines. Leg measurements: I 2.25 (0.66, 0.75, 0.48, 0.36); II 2.11 (0.63, 0.68, 0.44, 0.36); III 1.95 (0.55, 0.62, 0.44, 0.34); IV 2.41 (0.67, 0.79, 0.56, 0.39). Leg formula: 4123. Opisthosoma oval, greyish black with a light quadrate and five light chevrons dorsally. Tracheal spiracle equidistant between the epigastric furrow and the base of spinnerets. Male palp (Figs 1 A–C, 2 E–G) with a hook-like, relatively thin and long patellar apophysis. Distal part of RTA filiform extending dorsally and then proximally. Cymbium with a very deep, long and semi-transparent retrolateral furrow. Embolus originating retrolaterally, clockwise curved along the cymbial margin, then anticlockwise curved inside the cymbial furrow. End of embolus embedded in a transparent pocket. Median apophysis membranous, located near the base of embolus. One female paratype (collected with holotype, Fig. 2 B) total length 2.03. Prosoma 0.81 long, 0.59 wide; opisthosoma 1.26 long, 0.95 wide. Eye sizes and interdistances: AME 0.04, ALE 0.05, PME 0.05, PLE 0.05; AME– AME 0.02, AME–ALE 0.01, PME–PME 0.05, PME–PLE 0.03, ALE–PLE 0.01. MOA 0.13 long, front width 0.09, back width 0.13. Clypeus height 0.09. Leg measurements: I 1.96 (0.59, 0.66, 0.39, 0.32); II 1.83 (0.57, 0.59, 0.37, 0.30); III 1.72 (0.54, 0.54, 0.37, 0.27); IV 2.28 (0.66, 0.75, 0.50, 0.37). Leg formula: 4123. Epigyne (Figs 1 D–E, 2 H–I) with a pair of small copulatory openings medio-posteriorly with posterior margins visible. Copulatory ducts quite long and strongly convoluted as three coils. Subspermathecae located anteriorly, visible in the gap of copulatory duct loops. Spermathecae located centrally in the loops of copulatory ducts. Fertilization ducts extending posteriorly and curving medially. Distribution. China (Chongqing, Hubei, Anhui) (Fig. 4). Remark. The new species was collected in the leaf litter of an old-growth forest area, specifically, along the Yangtze River basin, close to the latitude 30 ° North.Published as part of Liu, Na, Huang, Gui-Qiang & Zhang, Zhi-Sheng, 2015, A new species of the genus Hahnia (Araneae: Hahniidae) from South China, pp. 295-300 in Zootaxa 3994 (2) on pages 295-299, DOI: 10.11646/zootaxa.3994.2.10, http://zenodo.org/record/24032
Sinopoda improcera Zhong & Jäger & Chen & Liu 2019, sp. nov.
No full text<i>Sinopoda improcera</i> sp. nov. <p>Figs 26–28, 62</p> <p>urn:lsid:zoobank.org:act: 7D16F43A-FEE4-48FE-B214-A72F38D08381</p> <p> <b> Type material. Holotype male: CHINA: <i>Yunnan Province</i>:</b> Tengchong County, Ruidian Town, Yunfengshan Scenic Area, 25.38°N, 98.42°E, 1897 m, near road, 10 June 2014, Y. Zhong & X.W. Cao leg. (CBEE) <b>Paratypes:</b> 1 male and 7 females (CBEE), 1 male and 1 female (SMF), with same data as holotype; 7 females, Tengchong County, Houqiao Town, Danzha Village, Langya Mountain, 25.49°N, 98.27°E, 2032 m, near road, 11 June 2014, Y. Zhong & X.W. Cao leg. (CBEE).</p> <p> <b>Etymology.</b> The specific name is derived from the Latin adjective <i>improcerus</i>, - <i>a</i>, - <i>um</i>, meaning among others “nanoid” referring to the internal ducts being very small.</p> <p> <b>Diagnosis.</b> This new species resembles <i>Sinopoda anguina</i> Liu, Li & Jäger, 2008 (Liu <i>et al</i>., 2008: figs 1A–G; Zhong <i>et al</i>., 2017: figs 3A–F, 4A–E) in having the embolus tip shorter than embolic apophysis and straight margins of lobal septum roughly forming a triangle in the median epigyne, but can be distinguished from the latter by the following characters: 1. Embolus tip with small hook-shaped apophysis in this new species, but not in <i>S. anguina</i> (blue arrow in Fig. 26B); 2. Embolic apophysis distally with distinct hook-shaped apophysis in ventral view (smaller in <i>S. anguina)</i>; 3. Female epigyne with lobal septum moderately large, occupying about half epigyne in this new species, but signicantly large, occupying about two thirds of epigyne in <i>S. anguina</i>; 4. Vulva with internal duct system stout, wider than long in this new species, but longer than wide in <i>S. anguina</i>.</p> <p> <b>Description. Male (holotype):</b> Measurements: PL 6.4, PW 5.7; AW 2.7; OL 6.7, OW 3.9. Eyes: AME 0.35, ALE 0.44, PME 0.40, PLE 0.48, AME–AME 0.22, AME–ALE 0.06, PME–PME 0.27, PME–PLE 0.64, AME–PME 0.40, ALE–PLE 0.45, CH AME 0.18, CH ALE 0.25. Spination: Palp: 131, 101, 2121; Fe: I–III 323, IV 321; Pa: I–IV 101; Ti: I–III 2326, IV 2226; Mt: I–II 1014, III–IV 3036. Measurements of palp and legs: Palp 10.8 (3.3, 1.4, 2.1, –, 4.0); I 36.9 (9.5, 3.1, 10.3, 10.9, 3.1); II 40.1 (10.2, 2.9, 11.6, 12.2, 3.2); III 30.5 (8.2, 2.3, 8.7, 8.8, 2.5); IV 33.3 (8.8, 2.2, 9.1, 10.2, 3.0). Leg formula: II-I-IV-III. Cheliceral furrow with 3 anterior, 4 posterior teeth and ca. 16 denticles.</p> <p>Palp as in diagnosis. Cymbium distinctly longer than tibia. Embolus tip slightly shorter than embolic apophysis.</p> <p>Tegulum covering only small part of proximal embolus. Spermophor almost straight in ventral view. RTA arising distally to medially from tibia with distinct brush of stiff hairs, vRTA well developed, blunt in lateral view (Figs 26 A–C, 27A–D).</p> <p>Colouration in ethanol. Dorsal prosoma deep yellowish-brown, lateral margins dark, with yellow submarginal transversal light band posteriorly. Fovea and radial furrows distinctly marked. Labium and gnathocoxae yellowish-brown, both with distal parts brighter. Sternum yellowish-brown, with margin brown. Chelicerae deep reddishbrown. Legs yellowish-brown with dark spots. Dorsal opisthosoma reddish-brown, covered by gray hairs, lateral field of opisthosoma with three pairs of black patches. Ventral opisthosoma yellow-brown with irregular pattern (Figs 27 E–F).</p> <p> <b>Female:</b> Measurements: PL 7.1, PW 6.6;AW 3.8; OL 8.2, OW 4.7. Eyes:AME 0.37, ALE 0.50, PME 0.37, PLE 0.57, AME–AME 0.29, AME–ALE 0.12, PME–PME 0.47, PME–PLE 0.77, AME–PME 0.55, ALE–PLE 0.57, CH AME 0.21, CH ALE 0.28. Spination: Palp: 131, 101, 2121, 1014; Fe: I–III 323, IV 321; Pa: I–IV 101; Ti: I–II 2026, III–IV 2126; Mt: I–II 1014, III 2026, IV 3036. Measurements of palp and legs: Palp 8.0 (2.5, 1.1, 1.7, –, 2.7); I 25.7 (7.0, 2.2, 7.6, 6.5, 2.4); II 28.5 (8.3, 2.9, 8.3, 7.0, 2.0); III 24.4 (7.3, 2.5, 6.7, 5.9, 2.0); IV 25.4 (7.4, 2.2, 7.0, 6.6, 2.2). Leg formula: II-I-IV-III. Cheliceral furrow with 3 anterior, 4 posterior teeth and ca. 18 denticles.</p> <p>Copulatory organ as in diagnosis. Epigynal field wider than long, with short anterior bands. Lateral lobes fused, with median incision. Lobal septum wide. Internal duct system of posterior part strongly diverging. Glandular appendages almost laterad. Fertilization ducts arising posterioly. Membranous sac between fertilization ducts almost rectangular (Figs 26 D–E, 28A–B).</p> <p>Colouration in ethanol. As in males, but dorsal opisthosoma and ventral opisthosoma slightly brighter than in males (Figs 28 C–D).</p> <p> <b>Distribution.</b> China (Yunnan) (Fig. 62).</p>Published as part of <i>Zhong, Yang, Jäger, Peter, Chen, Jian & Liu, Jie, 2019, Taxonomic study of Sinopoda spiders from China (Araneae: Sparassidae), pp. 1-81 in Zootaxa 4607 (1)</i> on pages 35-39, DOI: 10.11646/zootaxa.4607.1.1, <a href="http://zenodo.org/record/2860849">http://zenodo.org/record/2860849</a>
Erratum to:Multidrug efflux pumps: structure, function and regulation (Nature Reviews Microbiology, (2018), 16, 9, (523-539), 10.1038/s41579-018-0048-6)
No full textIn the version of this Review originally published, the author contributions of co-author Arthur Neuberger were incorrectly listed. The author contributions should have appeared as ‘D.D., X.W.-K., A.N., H.W.v.V., K.M.P., L.J.V.P. and B.F.L. researched data for the article, made substantial contributions to discussions of the content, wrote the article, and reviewed and edited the manuscript before submission’. This has now been corrected in all versions of the Review. The authors apologize to readers for this error.</p
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Dislocations in strained-layer semiconductor heterostructures
No full textThe reliability of semiconductor devices depends upon the stability of the constituent materials. Strained-layer semiconductor structures contain a layer whose lattice constant differs from the surrounding layers, resulting in a misfit strain. As dislocations are the main failure mechanism in semiconductor lasers, it is essential to establish whether the stability of these structures is affected by the lattice mismatch and the possibility of relaxation by the formation of misfit dislocations. In this thesis, dislocations in strained-layer semiconductor structures are investigated. Relaxation of strained-layer GaAs/In_xGa_1_-_xAs/GaAs heterostructures through the formation of misfit dislocations is found to occur in stages. Firstly, generation and elongation of misfit dislocations on threading dislocations during molecular beam epitaxy (MBE) growth have been demonstrated with increasing strained-layer thickness. The onset of this stage has been shown to occur at strained-layer thicknesses below those predicted by the Matthews-Blakeslee (M-B) model. The second stage of relaxation is marked by the formation of a network of 60 deg. misfit dislocations. A third stage of relaxation has been discovered, in which pure edge (i.e. 90 deg.) misfit dislocations are formed in addition to the existing network of 60 deg. misfit dislocations. Different mechanisms are found to be responsible for the three stages of relaxation. The M-B model describes the transformation of threading dislocations to generate 60 deg. misfit dislocations. As this affects individual dislocations, it results in only local relaxation. A separate mechanism, which remains unclear but is not dependent on the interactions of dislocations, dominates the formation of a 60 deg. misfit dislocation network. The edge dislocations responsible for further relaxation of the structures are produced by vacancy-producing jogs. These protrude from pre-existing 60 deg. dislocations and trail edge dislocation pairs as they climb. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:DXN030579 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Are oxygen and neon enriched in PNe and is the current solar Ne/O abundance ratio underestimated?
No full textA thorough critical literature survey has been carried out for reliable measurements of oxygen and neon abundances of planetary nebulae (PNe) and H II regions. By contrasting the results of PNe and of H II regions, we aim to address the issues of the evolution of oxygen and neon in the interstellar medium (ISM) and in the late evolutionary phases of low- and intermediate-mass stars (LIMS), as well as the currently hotly disputed solar Ne/O abundance ratio. Through the comparisons, we find that neon abundance and Ne/O ratio increase with increasing oxygen abundance in both types of nebulae, with positive correlation coefficients larger than 0.75. The correlations suggest different enrichment mechanisms for oxygen and neon in the ISM, in the sense that the growth of neon is delayed compared to oxygen. The differences of abundances between PNe and H II regions are mainly attributed to the results of nucleosynthesis and dredge-up processes that occurred in the progenitor stars of PNe. We find that both these alpha-elements are significantly enriched at low metallicity (initial oxygen abundance less than or similar to 8.0) but not at metallicity higher than the Small Magellanic Cloud (SMC). The fact that Ne/O ratios measured in PNe are almost the same as those in H II regions, regardless of the metallicity, suggest a very similar production mechanism of neon and oxygen in intermediate-mass stars (IMS) of low initial metallicities and in more massive stars, a conjecture that requires verification by further theoretical studies. This result also strongly suggests that both the solar neon abundance and the Ne/O ratio should be revised upwards by similar to 0.22 dex from the Asplund, Grevesse & Sauval values or by similar to 0.14 dex from the Grevesse & Sauval values.Astronomy & AstrophysicsSCI(E)13ARTICLE1L33-L3738
A hybrid factorial stepwise-cluster analysis method for streamflow simulation – a case study in northwestern China
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