The Two Phases of Galaxy Formation

Cosmological simulations of galaxy formation appear to show a two-phase character with a rapid early phase at z>2 during which in-situ stars are formed within the galaxy from infalling cold gas followed by an extended phase since z<3 during which ex-situ stars are primarily accreted. In the latter phase massive systems grow considerably in mass and radius by accretion of smaller satellite stellar systems formed at quite early times (z>3) outside of the virial radius of the forming central galaxy. These tentative conclusions are obtained from high resolution re-simulations of 39 individual galaxies in a full cosmological context with present-day virial halo masses ranging from 7e11 M_sun h^-1 < M_vir < 2.7e13 M_sun h^-1 and central galaxy masses between 4.5e10 M_sun h^-1 < M_* < 3.6e11 M_sun h^-1. The simulations include the effects of a uniform UV background, radiative cooling, star formation and energetic feedback from SNII. The importance of stellar accretion increases with galaxy mass and towards lower redshift. In our simulations lower mass galaxies ($M_* < 9e10 M_sun h^-1) accrete about 60 per cent of their present-day stellar mass. High mass galaxy ($M_* > 1.7e11 M_sun h^-1) assembly is dominated by accretion and merging with about 80 per cent of the stars added by the present-day. In general the simulated galaxies approximately double their mass since z=1. For massive systems this mass growth is not accompanied by significant star formation. The majority of the in-situ created stars is formed at z>2, primarily out of cold gas flows. We recover the observational result of archaeological downsizing, where the most massive galaxies harbor the oldest stars. We find that this is not in contradiction with hierarchical structure formation. Most stars in the massive galaxies are formed early on in smaller structures, the galaxies themselves are assembled late.Comment: 13 pages, 13 figures, accepted for publication in Ap

The bulge luminosity functions in the MSX infrared bands

We use an inversion technique to derive the luminosity functions of the Galactic bulge from point source counts extracted from the Midcourse Space Experiment's Point Source Catalog (version 1.2).Comment: 5 pages, 2 figures, to be published in A&

A yellowwood by any other name: molecular systematics and the taxonomy of Podocarpus and the Podocarpaceae in southern Africa

We briefly review the taxonomic history of the Podocarpaceae, with an emphasis on the recognition of numerous segregate genera out of Podocarpus sensu lato. Despite some controversy over the recognition of these genera, molecular data (DNA sequences) provide evidence that supports this taxonomy. The implications for African Podocarpaceae are discussed. In particular, molecular data support the recognition of Afrocarpus as distinct from Podocarpus. Additional taxonomic problems concerning the possible segregation of Podocarpus milanjianus from P. latifolius are addressed using DNA sequence data from the nuclear internal transcribed spacer 2 (ITS2) region. Results of this are inconclusive, and suggest that alternative DNA-based evidence, such as from AFLPs or microsatellites, may be more informative in resolving such species complexes in African Podocarpus

Compactifiable classes of compacta

We introduce the notion of compactifiable classes -- these are classes of metrizable compact spaces that can be up to homeomorphic copies ``disjointly combined'' into one metrizable compact space. This is witnessed by so-called compact composition of the class. Analogously, we consider Polishable classes and Polish compositions. The question of compactifiability or Polishability of a class is related to hyperspaces. Strongly compactifiable and strongly Polishable classes may be characterized by the existence of a corresponding family in the hyperspace of all metrizable compacta. We systematically study the introduced notions -- we give several characterizations, consider preservation under various constructions, and raise several questions.Comment: 32 pages, 1 figure, revised versio

Magnetic excitations in a new anisotropic Kagom\'{e} antiferromagnet

The Nd-langasite compound contains planes of magnetic Nd3+ ions on a lattice topologically equivalent to a kagom\'{e} net. The magnetic susceptibility does not reveal any signature of long-range ordering down to 2 K but rather a correlated paramagnetism with significant antiferromagnetic interactions between the Nd and a single-ion anisotropy due to crystal field effect. Inelastic neutron scattering on Nd-langasite powder and single-crystal allowed to probe its very peculiar low temperature dynamical magnetic correlations. They present unusual dispersive features and are broadly localized in wave-vector Q revealing a structure factor associated to characteristics short range-correlations between the magnetic atoms. From comparison with theoretical calculations, these results are interpreted as a possible experimental observation of a spin liquid state in an anisotropic kagom\'{e} antiferromagnet.Comment: to appear in Physica

Prenatal maternal immune activation causes epigenetic differences in adolescent mouse brain

Epigenetic processes such as DNA methylation have been implicated in the pathophysiology of neurodevelopmental disorders including schizophrenia and autism. Epigenetic changes can be induced by environmental exposures such as inflammation. Here we tested the hypothesis that prenatal inflammation, a recognized risk factor for schizophrenia and related neurodevelopmental conditions, alters DNA methylation in key brain regions linked to schizophrenia, namely the dopamine rich striatum and endocrine regulatory centre, the hypothalamus. DNA methylation across highly repetitive elements (long interspersed element 1 (LINE1) and intracisternal A-particles (IAPs)) were used to proxy global DNA methylation. We also investigated the Mecp2 gene because it regulates transcription of LINE1 and has a known association with neurodevelopmental disorders. Brain tissue was harvested from 6 week old offspring of mice exposed to the viral analog PolyI:C or saline on gestation day 9. We used Sequenom EpiTYPER assay to quantitatively analyze differences in DNA methylation at IAPs, LINE1 elements and the promoter region of Mecp2. In the hypothalamus, prenatal exposure to PolyI:C caused significant global DNA hypomethylation (t=2.44, P=0.019, PolyI:C mean 69.67%, saline mean 70.19%), especially in females, and significant hypomethylation of the promoter region of Mecp2, (t=3.32, P=0.002; PolyI:C mean 26.57%, saline mean 34.63%). IAP methylation was unaltered. DNA methylation in the striatum was not significantly altered. This study provides the first experimental evidence that exposure to inflammation during prenatal life is associated with epigenetic changes, including Mecp2 promoter hypomethylation. This suggests that environmental and genetic risk factors associated with neurodevelopmental disorders may act upon similar pathways. This is important because epigenetic changes are potentially modifiable and their investigation may open new avenues for treatment

Like trainer, like bot? Inheritance of bias in algorithmic content moderation

The internet has become a central medium through which `networked publics' express their opinions and engage in debate. Offensive comments and personal attacks can inhibit participation in these spaces. Automated content moderation aims to overcome this problem using machine learning classifiers trained on large corpora of texts manually annotated for offence. While such systems could help encourage more civil debate, they must navigate inherently normatively contestable boundaries, and are subject to the idiosyncratic norms of the human raters who provide the training data. An important objective for platforms implementing such measures might be to ensure that they are not unduly biased towards or against particular norms of offence. This paper provides some exploratory methods by which the normative biases of algorithmic content moderation systems can be measured, by way of a case study using an existing dataset of comments labelled for offence. We train classifiers on comments labelled by different demographic subsets (men and women) to understand how differences in conceptions of offence between these groups might affect the performance of the resulting models on various test sets. We conclude by discussing some of the ethical choices facing the implementers of algorithmic moderation systems, given various desired levels of diversity of viewpoints amongst discussion participants.Comment: 12 pages, 3 figures, 9th International Conference on Social Informatics (SocInfo 2017), Oxford, UK, 13--15 September 2017 (forthcoming in Springer Lecture Notes in Computer Science

ANALISIS STRUKTUR FISIK DAN STRUKTUR BATIN PUISI ANAK DALAM MAJALAH POTRET ANAK CERDAS

ABSTRAK Sri Wahyuni Y. 2017. Analisis Struktur Fisik dan Struktur Batin Puisi Anak dalamMajalah Potret Anak Cerdas. Tesis, Program Studi MagisterPendidikan Bahasa dan Sastra Indonesia, Fakultas Keguruan danIlmu Pendidikan Universitas Syiah Kuala. Pembimbing (1) Dr.Mohd. Harun, M.Pd., Pembimbing (2) Dr. Rajab Bahry, M.Pd. Kata Kunci: Struktur Fisik, Struktur Batin, Puisi Anak Penelitian ini bertujuan mendeskripsikan struktur fisik dan struktur batin puisi anakdalam majalah Potret Anak Cerdas meliputi (1) bunyi, (2) pilihan kata, (3) saranaretorika, (4) tema, dan (5) amanat. Pendekatan yang digunakan dalam penelitian iniadalah pendekatan kualitatif dan jenis penelitian ini adalah penelitian struktural.Sumber data dalam penelitian ini adalah puisi anak dalam majalah Potret AnakCerdas edisi 14, 15, 16, 17, 18, dan 19. Data dalam penelitian ini adalah bunyi, kata,sarana retorika, tema dan amanat dalam puisi anak majalah Potret Anak Cerdas.Teknik pengumpulan data adalah studi kepustakaan. Teknik analisis data terbagidalam tiga tahap, yaitu (1) tahap reduksi data, (2) tahap penyajian data, dan (3) tahappenarikan simpulan. Hasil yang ditemukan sebagai berikut. Pertama, dari segi aspekbunyi berupa rima ditemukan ada 11 jenis rima yang digunakan, yaitu (1) rimaaliterasi (2) rima mutlak, (3) rima awal, (4) rima tengah, (5) rima akhir, (6) rimadatar, (7) rima berpeluk, (8) rima bersilang, (9) rima rangkai, (10) rima kembar, dan(11) rima patah. Rima secara menyeluruh ditemukan yang paling menonjol adalahrima mutlak dan rima patah. Irama yang ditemukan ada 2 jenis irama, yaitu (1)repetisi, dan (2) paralelisme. Irama secara menyeluruh ditemukan yang palingmenonjol adalah bentuk repetisi. Kedua, dari aspek pilihan kata ditemukan ada 4penggunaan kata sifat hakiki puisi, yaitu (1) emotif, (2) objektif, (3) imitatif ataureferensial, dan (4) konotatif. Diksi secara menyeluruh ditemukan yang palingmenonjol adalah kata yang bersifat emotif. Ketiga, dari segi sarana retorika berupagaya bahasa ditemukan ada 4 jenis gaya bahasa, yaitu (1) gaya bahasa personifikasi,(2) gaya bahasa hiperbola, (3) gaya bahasa simile, dan (4) gaya bahasa sinekdoce.Gaya bahasa secara menyeluruh ditemukan yang paling menonjol adalah gayabahasa personifikasi. Citraan yang ditemukan ada 5 jenis citraan, yaitu (1) citraanpenglihatan, (2) citraan pendengaran, (3) citraan perabaan, (4) citraan pencecapan,dan (5) citraan gerak. Citraan secara menyeluruh ditemukan yang paling menonjoladalah citraan gerak. Keempat, tema yang ditemukan dalam puisi anak majalahPotret Anak Cerdas ada 5 tema, yaitu (1) tema orang tua, (2) tema guru, (3) temateman sepermainan, (4) tema religius, dan (5) tema lingkungan alam. Tema secaramenyeluruh ditemukan yang paling menonjol adalah tema orang tua. Kelima, amanatyang ditemukan dalam puisi anak majalah Potret Anak Cerdas, yaitu (1) mengajakpembaca untuk menghargai dan menghormati indahnya kasih sayang yang diberikanoleh orang tua dan guru serta mematuhi segala perintahnya, (2) mengajak pembacauntuk selalu menjaga persahabatan, (3) mengajak pembaca untuk sering berselawatkepada Nabi, (4) mengajak pembaca untuk bersabar, berusaha, semangat, rajinbelajar, dan berakhlak mulia serta tidak cepat cemburu terhadap segala sesuatu, (5)mengajak pembaca untuk selalu menjaga kebersihan dan melestarikan lingkunganalam.Banda Ace