Restoration Ecology: Two-Sex Dynamics and Cost Minimization

We model a spatially detailed, two-sex population dynamics, to study the cost of ecological restoration. We assume that cost is proportional to the number of individuals introduced into a large habitat. We treat dispersal as homogeneous diffusion. The local population dynamics depends on sex ratio at birth, and allows mortality rates to differ between sexes. Furthermore, local density dependence induces a strong Allee effect, implying that the initial population must be sufficiently large to avert rapid extinction. We address three different initial spatial distributions for the introduced individuals; for each we minimize the associated cost, constrained by the requirement that the species must be restored throughout the habitat. First, we consider spatially inhomogeneous, unstable stationary solutions of the model's equations as plausible candidates for small restoration cost. Second, we use numerical simulations to find the smallest cluster size, enclosing a spatially homogeneous population density, that minimizes the cost of assured restoration. Finally, by employing simulated annealing, we minimize restoration cost among all possible initial spatial distributions of females and males. For biased sex ratios, or for a significant between-sex difference in mortality, we find that sex-specific spatial distributions minimize the cost. But as long as the sex ratio maximizes the local equilibrium density for given mortality rates, a common homogeneous distribution for both sexes that spans a critical distance yields a similarly low cost

Minimum Dominating Sets in Scale-Free Network Ensembles

We study the scaling behavior of the size of minimum dominating set (MDS) in scale-free networks, with respect to network size $N$ and power-law exponent $\gamma$, while keeping the average degree fixed. We study ensembles generated by three different network construction methods, and we use a greedy algorithm to approximate the MDS. With a structural cutoff imposed on the maximal degree ($k_{\max}=\sqrt{N}$) we find linear scaling of the MDS size with respect to $N$ in all three network classes. Without any cutoff ($k_{\max}=N-1$) two of the network classes display a transition at $\gamma \approx 1.9$, with linear scaling above, and vanishingly weak dependence below, but in the third network class we find linear scaling irrespective of $\gamma$. We find that the partial MDS, which dominates a given $z<1$ fraction of nodes, displays essentially the same scaling behavior as the MDS

Building Damage-Resilient Dominating Sets in Complex Networks against Random and Targeted Attacks

We study the vulnerability of dominating sets against random and targeted node removals in complex networks. While small, cost-efficient dominating sets play a significant role in controllability and observability of these networks, a fixed and intact network structure is always implicitly assumed. We find that cost-efficiency of dominating sets optimized for small size alone comes at a price of being vulnerable to damage; domination in the remaining network can be severely disrupted, even if a small fraction of dominator nodes are lost. We develop two new methods for finding flexible dominating sets, allowing either adjustable overall resilience, or dominating set size, while maximizing the dominated fraction of the remaining network after the attack. We analyze the efficiency of each method on synthetic scale-free networks, as well as real complex networks

Searching for Masculine Capital: Experiences Leading to High Drive for Muscularity in Men

Studies on the drive for muscularity (DFM) have primarily been quantitative, focused on identifying correlates. Currently little is known about men’s experiences leading them to desire high levels of muscle and engage in behaviours to increase their masculine capital. Our purpose was to explore the stories of men with high DFM revealing the socio-cultural and personal factors leading to DFM and their search for masculine capital. In-depth life-history interviews and multiple in-the-field conversations were undertaken with twenty men (Mean age=28.45, SD=6.96, years) scoring ≥ 3 on the Drive for Muscularity Scale (Mean=4.30, SD=0.70). Men’s stories focused on a set of dysfunctional childhood and adolescent socio-cultural interactions, including forms of symbolic violence, between them and significant others. In these interactions men were exposed to dominant social narratives of masculinity, and through comparisons and reinforcement they identified discrepancies between themselves and these narratives. In late adolescence and early adulthood men came to believe that they lacked masculine capital. Men struggled to increase their masculine capital through engagement with other traditional masculine activities (e.g., sport) and driven by activating events, they compensated through DFM desires and behaviours. This study advances knowledge by revealing the socio-cultural and personal processes participants believed led to their high DFM. Findings disclose that men’s search for masculine capital may have led them to develop and maintain high levels of DFM

Numerical Studies of QGP Instabilities and Implications

Because the initial shape of the QGP in a heavy ion collision is anisotropic, the momentum distribution becomes anisotropic after a short time. This leads to plasma instabilities, which may help explain how the plasma isotropizes. We explain the physics of instabilities and give the latest results of numerical simulations into their evolution. Nonabelian interactions cut off the size to which the soft unstable fields grow, and energy in the soft fields subsequently cascades towards more ultraviolet scales. We present first results for the power spectrum of this cascade.Comment: Talk given at workshop on Quark-Gluon Plasma Thermalization, Vienna, 10-12 August 2005. 8 page

R&D results on a CsI-TTGEM based photodetector

The very high momentum particle identification detector proposed for the ALICE upgrade is a focusing RICH using a C4F10 gaseous radiator. For the detection of Cherenkov photons, one of the options currently under investigation is to use a CsI coated Triple-Thick-GEM (CsI-TTGEM) with metallic or resistive electrodes. We will present results from the laboratory studies as well as preliminary results of beam tests of a RICH detector prototype consisting of a CaF2 radiator coupled to a 10x10 cm2 CsI-TTGEM equipped with a pad readout and GASSIPLEX-based front-end electronics. With such a prototype the detection of Cherenkov photons simultaneously with minimum ionizing particles has been achieved for the first time in a stable operation mode