Bars and spirals in tidal interactions with an ensemble of galaxy mass models

We present simulations of the gaseous and stellar material in several different galaxy mass models under the influence of different tidal fly-bys to assess the changes in their bar and spiral morphology. Five different mass models are chosen to represent the variety of rotation curves seen in nature. We find a multitude of different spiral and bar structures can be created, with their properties dependent on the strength of the interaction. We calculate pattern speeds, spiral wind-up rates, bar lengths, and angular momentum exchange to quantify the changes in disc morphology in each scenario. The wind-up rates of the tidal spirals follow the 2:1 resonance very closely for the flat and dark matter dominated rotation curves, whereas the more baryon dominated curves tend to wind-up faster, influenced by their inner bars. Clear spurs are seen in most of the tidal spirals, most noticeable in the flat rotation curve models. Bars formed both in isolation and interactions agree well with those seen in real galaxies, with a mixture of "fast" and "slow" rotators. We find no strong correlation between bar length or pattern speed and the interaction strength. Bar formation is, however, accelerated/induced in four out of five of our models. We close by briefly comparing the morphology of our models to real galaxies, easily finding analogues for nearly all simulations presenter here, showing passages of small companions can easily reproduce an ensemble of observed morphologies.Comment: 30 pages, 29 colour figures, accepted for publication in MNRAS. Videos of simulations can be found at http://www.youtube.com/playlist?list=PLQKy--XcWrIVBc1sS2RNc-ekyfeBsGtD

Gas and stellar spiral structures in tidally perturbed disc galaxies

Tidal interactions between disc galaxies and low mass companions are an established method for generating galactic spiral features. In this work we present a study of the structure and dynamics of spiral arms driven in interactions between disc galaxies and perturbing companions in 3-D N-body/smoothed hydrodynamical numerical simulations. Our specific aims are to characterize any differences between structures formed in the gas and stars from a purely hydrodynamical and gravitational perspective, and to find a limiting case for spiral structure generation. Through analysis of a number of different interacting cases, we find that there is very little difference between arm morphology, pitch angles and pattern speeds between the two media. The main differences are a minor offset between gas and stellar arms, clear spurring features in gaseous arms, and different radial migration of material in the stronger interacting cases. We investigate the minimum mass of a companion required to drive spiral structure in a galactic disc, finding the limiting spiral generation cases with companion masses of the order $1\times10^9M_\odot$, equivalent to only 4% of the stellar disc mass, or 0.5% of the total galactic mass of a Milky Way analogue.Comment: 20 pages, 23 figures, accepted for publication by MNRA

Star formation and ISM morphology in tidally induced spiral structures

Tidal encounters are believed to be one of the key drivers of galactic spiral structure in the Universe. Such spirals are expected to produce different morphological and kinematic features compared to density wave and dynamic spiral arms. In this work we present high resolution simulations of a tidal encounter of a small mass companion with a disc galaxy. Included are the effects of gas cooling and heating, star formation and stellar feedback. The structure of the perturbed disc differs greatly from the isolated galaxy, showing clear spiral features that act as sites of new star formation, and displaying interarm spurs. The two arms of the galaxy, the bridge and tail, appear to behave differently; with different star formation histories and structure. Specific attention is focused on offsets between gas and stellar spiral features which can be directly compared to observations. We find some offsets do exist between different media, with gaseous arms appearing mostly on the convex side of the stellar arms, though the exact locations appear highly time dependent. These results further highlight the differences between tidal spirals and other theories of arm structure.Comment: 17 pages, 19 colour figures, accepted for publication in MNRA

The Effect of Enterprise Bargaining on Downsizing in the Australian Retail Banking Sector 1993-1998: a Union Perspective

This paper assesses the effect of enterprise bargaining on the incidence of downsizing in the Australian retail-banking sector between 1993-1998. It appears that the downsizing negotiations performed by the 'Big 4' banks were undertaken in a conflictual fashion, devoid of co-operation. Moreover it seems that enterprise bargaining neither ensured nor prevented downsizing: the decision to downsize was the sole prerogative of the 'Big 4' banks. Enterprise bargaining gave the 'Big 4' greater flexibility in determining staff numbers, yet also enabled the Finance Sector Union to negotiate processes aimed at restricting the number of retrenched employees

An Upper Palaeolithic Proto-writing System and Phenological Calendar

In at least 400 European caves such as Lascaux, Chauvet and Altamira, Upper Palaeolithic Homo sapiens groups drew, painted and engraved non-figurative signs from at least ~42,000 BP and figurative images (notably animals) from at least 37,000 BP. Since their discovery ~150 years ago, the purpose or meaning of European Upper Palaeolithic non-figurative signs has eluded researchers. Despite this, specialists assume that they were notational in some way. Using a database of images spanning the European Upper Palaeolithic, we suggest how three of the most frequently occurring signs—the line , the dot , and the —functioned as units of communication. We demonstrate that when found in close association with images of animals the line and dot constitute numbers denoting months, and form constituent parts of a local phenological/meteorological calendar beginning in spring and recording time from this point in lunar months. We also demonstrate that the sign, one of the most frequently occurring signs in Palaeolithic non-figurative art, has the meaning . The position of the within a sequence of marks denotes month of parturition, an ordinal representation of number in contrast to the cardinal representation used in tallies. Our data indicate that the purpose of this system of associating animals with calendar information was to record and convey seasonal behavioural information about specific prey taxa in the geographical regions of concern. We suggest a specific way in which the pairing of numbers with animal subjects constituted a complete unit of meaning—a notational system combined with its subject—that provides us with a specific insight into what one set of notational marks means. It gives us our first specific reading of European Upper Palaeolithic communication, the first known writing in the history of Homo sapiens

Just one shot? The contextual effects of matched and unmatched intoxication on perceptions of consent in ambiguous alcohol-fueled sexual encounters

The current research examined how contextual factors—the quantity of alcohol consumed by each partner, and whether this quantity matched—influenced how alcohol-fueled sexual encounters were perceived with regard to consent, coercion, sexual assault, and perceived responsibility of the focal partner for the outcome of the encounter. Across four studies (Ntotal = 535), participants read vignettes in which one person described a sexual encounter they had following a night out drinking. These scenarios differed within studies as a function of quantified alcohol consumed (1 shot; 15 shots) and whether both people in the vignettes consumed the same amount of alcohol (matched; unmatched). They also differed between studies as a function of whether the couples described were mixed gender or same gender. Across all four studies, scenarios in which both people in the scenario consumed different quantities of alcohol (i.e., 15 vs. 1 shot) were seen as less consensual, more coercive, and more likely to be an assault compared to scenarios where consumption was matched, especially at lower levels of intoxication (i.e., 1 shot each vs. 15 shots each). However, focal partners were also seen as less responsible for the outcome of the interaction when levels of intoxication were unmatched compared to matched. This pattern replicated across scenarios depicting same-gender and mixed-gender couples. These findings suggest that people prioritize information regarding whether sexual partners are “matched” or “unmatched” in terms of their intoxication when evaluating whether ambiguous sexual encounters are consensual and perceived individual responsibility

Hubungan Asupan Protein, Seng, Zat Besi, Dan Riwayat Penyakit Infeksi Dengan Z-score Tb/u Pada Balita

Latar Belakang : Masalah gizi yang paling banyak ditemukan pada anak di Indonesia adalah stunting, Indikator untuk menilai stunting berdasarkan pada Indeks Tinggi Badan menurut Umur (TB/U) dengan ambang batas (Z-score) <-2 Standart Deviasi (SD). Several micronutrients are required for adequate growth among children. However, it has been unclear as to which nutrient deficiencies contribute most often to growth faltering in populations at risk for poor nutrition and poor growth. Inadequate intakes of dietary energy and protein and frequent infections are well-known causes of growth retardation (3–5). However, the role of specific micronutrient deficiencies in the etiology of growth retardation has gained attention more recently (6–8). Tujuan : Mengetahui hubungan antara asupan protein, seng, zat besi, dan penyakit infeksi terhadap indeks z-score TB/U pada Balita usia 24-59 bulan.Metode : Penelitian observasional dengan pendekatan cross sectional di Kelurahan Jangli Semarang, jumlah sampel 61 Balita usia 24-59 bulan, dipilih dengan simple random sampling. Data yang dikumpulkan meliputi: identitas sampel, berat badan, tinggi badan, riwayat asupan makan, dan riwayat penyakit infeksi. Berat badan diukur menggunakan timbangan digital dan tinggi badan diukur menggunakan microtoise. Asupan protein, seng, zat besi, dan riwayat penyakit infeksi diperoleh dari food frequency questionairre semi-kuantitatif. Data dianalisis dengan uji analisis depskripsi, analisis bivariate menggunakan uji Chi Square, Pearson, dan Spearman.Hasil : Sebanyak 36,1 subjek mengalami stunting. Rerata z-score TB/U -1,25 ± 1,2. Rerata asupan protein, seng, dan zat besi subjek berturut-turut 34.8 ± 13 g, 5.2 ± 2.5 mg, 8.2 ± 6.5 mg dengan sebagian besar tingkat kecukupan protein, seng, dan zat besi subjek adalah cukup. Sebanyak 29.1% subjek memiliki riwayat infeksi. Terdapat hubungan antara protein dan penyakit infeksi dengan z-score TB/U pada Balita. Tidak terdapat hubungan antara asupan seng, dan zat besi dengan z-score TB/U pada Balita. Simpulan : Terdapat hubungan antara asupan protein dan riwayat penyakit infeksi terhadap indeks z-score TB/U pada Balita