Family Policies in the Context of Low Fertility and Social Structure.

The aim of this paper is to analyse the effectivity of family policies in the context of different assumptions regarding the social structure of a society. We use an agent based simulation model to analyse the impact of family policies on individual fertility decisions and on cohort fertility, intended fertility, and the fertility gap on the aggregate level. The crucial features of our simulation model are the agents' heterogeneity with respect to age, income, parity, and intended fertility, the social network and social influence. Our results indicate that both fixed and income dependent child supports have a positive and significant impact on fertility. However, several network and social influence parameters have the ability not only to influence fertility itself but also the effectivity of family policies. Therefore, policymakers aiming to transfer a certain policy mix that has proved successful from one country to another one ignoring differences in the social structure may fail. Family policies can only be successful if they explicitly take into account the characteristics of the society they are assigned for.Family policies, low fertility, social influence, social networks, social structure.

The "Wedding-Ring"

In this paper we develop an agent-based marriage model based on social interaction. We build an population of interacting agents whose chances of marrying depend on the availability of partners, and whose willingness to marry depends on the share of relevant others in their social network who are already married. We then let the typical aggregate age pattern of marriage emerge from the bottom-up. The results of our simulation show that micro-level hypotheses founded on existing theory and evidence on social interaction can reproduce age-at-marriage patterns with both realistic shape and realistic micro-level dynamics.age at marriage, agent-based computational demography, marriage, micro-macro, models, social interaction

Family policies in the context of low fertility and social structure

Objective: In this paper we investigate the effectiveness of family policies in the context of the social structure of a population. Methods: We use an agent-based model to analyse the impact of policies on individual fertility decisions and on fertility at the aggregate level. The crucial features of our model are the interactions between family policies and social structure, the agents' heterogeneity, and the structure and influence of the social network. This modelling framework allows us to disentangle the direct effect (the alleviation of resource constraints) from the indirect effect (the diffusion of fertility intentions via social ties) of family policies. Results: Our results indicate that family policies have a positive and significant impact on fertility. In addition, the specific characteristics of the social network and social effects do not only relate to fertility, but also influence the effectiveness of family policies. Conclusions: Family policies can only be successful if they are designed to take into account the characteristics of the society in which they are implemented

An agent-based marriage model based on social interaction

In this paper we develop an agent-based marriage model based on social interaction. We build an population of interacting agents whose chances of marrying depend on the availability of partners, and whose willingness to marry depends on the share of relevant others in their social network who are already married. We then let the typical aggregate age pattern of marriage emerge from the bottom-up. The results of our simulation show that micro-level hypotheses founded on existing theory and evidence on social interaction can reproduce age-at-marriage patterns with both realistic shape and realistic micro-level dynamics

User-Adaptive Editing for 360 degree Video Streaming with Deep Reinforcement Learning

International audienceThe development through streaming of 360°videos is persistently hindered by how much bandwidth they require. Adapting spatially the quality of the sphere to the user's Field of View (FoV) lowers the data rate but requires to keep the playback buffer small, to predict the user's motion or to make replacements to keep the buffered qualities up to date with the moving FoV, all three being uncertain and risky. We have previously shown that opportunistically regaining control on the FoV with active attention-driving techniques makes for additional levers to ease streaming and improve Quality of Experience (QoE). Deep neural networks have been recently shown to achieve best performance for video streaming adaptation and head motion prediction. This demo presents a step ahead in the important investigation of deep neural network approaches to obtain user-adaptive and network-adaptive 360°video streaming systems. In this demo, we show how snap-changes, an attention-driving technique, can be automatically modulated by the user's motion to improve the streaming QoE. The control of snap-changes is made with a deep neural network trained on head motion traces with the Deep Reinforcement Learning strategy A3C

The Star Formation History of M32

We use deep HST ACS/HRC observations of a field within M32 (F1) and an M31 background field (F2) to determine the star formation history (SFH) of M32 from its resolved stellar population. We find that 2-5Gyr old stars contribute \som40%+/- 17% of M32's mass, while 55%+/-21% of M32's mass comes from stars older than 5 Gyr. The mass-weighted mean age and metallicity of M32 at F1 are =6.8+/-1.5 Gyr and =-0.01+/-0.08 dex. The SFH additionally indicates the presence of young (<2 Gyr old), metal-poor ([M/H]\sim-0.7) stars, suggesting that blue straggler stars contribute ~2% of the mass at F1; the remaining \sim3% of the mass is in young metal-rich stars. Line-strength indices computed from the SFH imply a light-weighted mean age and metallicity of 4.9 Gyr and [M/H] = -0.12 dex, and single-stellar-population-equivalent parameters of 2.9+/-0.2 Gyr and [M/H]=0.02+/-0.01 dex at F1 (~2.7 re). This contradicts spectroscopic studies that show a steep age gradient from M32's center to 1re. The inferred SFH of the M31 background field F2 reveals that the majority of its stars are old, with \sim95% of its mass already acquired 5-14 Gyr ago. It is composed of two dominant populations; \sim30%+/-7.5% of its mass is in a 5-8 Gyr old population, and \sim65%+/-9% of the mass is in a 8-14 Gyr old population. The mass-weighted mean age and metallicity of F2 are =9.2+/-1.2 Gyr and =-0.10+/-0.10 dex, respectively. Our results suggest that the inner disk and spheroid populations of M31 are indistinguishable from those of the outer disk and spheroid. Assuming the mean age of M31's disk at F2 (\sim1 disk scale length) to be 5-9 Gyr, our results agree with an inside-out disk formation scenario for M31's disk.Comment: Accepted to ApJ. 24 pages, 18 figures. A high-resolution version can be downloaded from http://www.astro.rug.nl/~monachesi/monachesi-sfh.pd

Integrating a next-generation optical access network testbed into a large-scale virtual research testbed

Several experimental research networks have been created in the laboratories of prominent universities and research centres to assess new optical communication technologies. A greater value and research impact can be obtained from these testbeds by making them available to other researchers through research infrastructure federations such as GENI and/or FIRE. This is a challenging task due to the limitations of programmability of resource management and virtualisation software in most experimental optical networks. Fed4FIRE is an EU research project that makes it possible to create complex testbed scenarios that interconnect heterogeneous testbeds distributed physically all over the world. In this paper, we present a practical approach for the federation of a next-generation optical access testbed created at Stanford University called UltraFlow Access. That testbed offers its users both packet-switched and circuit-switched services while remaining compatible with conventional PONs. Our approach facilitates experimentation on the UltraFlow Access testbed in the context of large virtual testbeds using Fed4FIRE protocols.The research of this paper was partially financed by the European Union’s FP7 grant agreement no. 318389 Fed4FIRE Project, the National Science Foundation (grant no. 111174), NSERC, the Spanish projects CRAMnet (grant no. TEC2012-38362-C03- 01) and TIGRE5-CM (grant no. S2013/ICE-2919). The authors would also like to acknowledge the support of the Chair of Excellence of Bank of Santander at UC3M.European Community's Seventh Framework Progra

How old are the stars in the halo of NGC 5128 (Centaurus A)?

NGC 5128 (Centaurus A) is, at the distance of just 3.8 Mpc, the nearest easily observable giant elliptical galaxy. Therefore it is the best target to investigate the early star formation history of an elliptical galaxy. Our aims are to establish when the oldest stars formed in NGC 5128, and whether this galaxy formed stars over a long period. We compare simulated colour-magnitude diagrams with the deep ACS/HST photometry. We find that that the observed colour-magnitude diagram can be reproduced satisfactorily only by simulations that have the bulk of the stars with ages in excess of ~10 Gyr, and that the alpha-enhanced models fit the data much better than the solar scaled ones. Data are not consistent with extended star formation over more than 3-4 Gyr. Two burst models, with 70-80% of the stars formed 12+/-1 Gyr ago and with 20-30% younger contribution with 2-4 Gyr old stars provide the best agreement with the data. The old component spans the whole metallicity range of the models (Z=0.0001-0.04), while for the young component the best fitting models indicate higher minimum metallicity (~1/10 - 1/4 Z_sun). The bulk of the halo stars in NGC5128 must have formed at redshift z>=2 and the chemical enrichment was very fast, reaching solar or even twice-solar metallicity already for the ~11-12 Gyr old population. The minor young component, adding ~20-30% of the stars to the halo, and contributing less than 10% of the mass, may have resulted from a later star formation event ~2-4 Gyr ago. (abridged)Comment: 36 pages, 14 figures, accepted for publication in A&

The First Detection of Blue Straggler Stars in the Milky Way Bulge

We report the first detections of Blue Straggler Stars (BSS) in the bulge of the Milky Way galaxy. Proper motions from extensive space-based observations along a single sight-line allow us to separate a sufficiently clean and well-characterized bulge sample that we are able to detect a small population of bulge objects in the region of the color-magnitude diagram commonly occupied young objects and blue strgglers. However, variability measurements of these objects clearly establish that a fraction of them are blue stragglers. Out of the 42 objects found in this region of the color-magnitude diagram, we estimate that at least 18 are genuine BSS. We normalize the BSS population by our estimate of the number of horizontal branch stars in the bulge in order to compare the bulge to other stellar systems. The BSS fraction is clearly discrepant from that found in stellar clusters. The blue straggler population of dwarf spheroidals remains a subject of debate; some authors claim an anticorrelation between the normalised blue straggler fraction and integrated light. If this trend is real, then the bulge may extend it by three orders of magnitude in mass. Conversely, we find that the genuinely young (~5Gy or younger) population in the bulge, must be at most 3.4% under the most conservative scenario for the BSS population.Comment: ApJ in press; 25 pages, 6 figures, 2 table