A new dp-minimal expansion of the integers

We consider the structure $(\mathbb{Z},+,0,|_{p_{1}},\dots,|_{p_{n}})$, where $x|_{p}y$ means $v_{p}(x)\leq v_{p}(y)$ and $v_p$ is the $p$-adic valuation. We prove that its theory has quantifier elimination in the language $\{+,-,0,1,(D_{m})_{m\geq1},|_{p_{1}},\dots,|_{p_{n}}\}$ where $D_m(x)\leftrightarrow \exists y ~ my = x$, and that it has dp-rank $n$. In addition, we prove that a first order structure with universe $\mathbb{Z}$ which is an expansion of $(\mathbb{Z},+,0)$ and a reduct of $(\mathbb{Z},+,0,|_{p})$ must be interdefinable with one of them. We also give an alternative proof for Conant's analogous result about $(\mathbb{Z},+,0,<)$.Comment: 24 page

Structural insights into Clostridium perfringens delta toxin pore formation

Clostridium perfringens Delta toxin is one of the three hemolysin-like proteins produced by C. perfringens type C and possibly type B strains. One of the others, NetB, has been shown to be the major cause of Avian Nectrotic Enteritis, which following the reduction in use of antibiotics as growth promoters, has become an emerging disease of industrial poultry. Delta toxin itself is cytotoxic to the wide range of human and animal macrophages and platelets that present GM2 ganglioside on their membranes. It has sequence similarity with Staphylococcus aureus β-pore forming toxins and is expected to heptamerize and form pores in the lipid bilayer of host cell membranes. Nevertheless, its exact mode of action remains undetermined. Here we report the 2.4 Å crystal structure of monomeric Delta toxin. The superposition of this structure with the structure of the phospholipid-bound F component of S. aureus leucocidin (LukF) revealed that the glycerol molecules bound to Delta toxin and the phospholipids in LukF are accommodated in the same hydrophobic clefts, corresponding to where the toxin is expected to latch onto the membrane, though the binding sites show significant differences. From structure-based sequence alignment with the known structure of staphylococcal α-hemolysin, a model of the Delta toxin pore form has been built. Using electron microscopy, we have validated our model and characterized the Delta toxin pore on liposomes. These results highlight both similarities and differences in the mechanism of Delta toxin (and by extension NetB) cytotoxicity from that of the staphylococcal pore-forming toxins

Reducing Costs and Pollution in Cellular Networks

Cellular wireless networks are expected to provide high-quality audio and video services while enabling fast and low-cost Internet access to mobile users. The need for green cost-efficient networks is twofold: reduce the service price and preserve the environment. In this work, we discuss the various strategies that help reduce infrastructure costs, power costs, and greenhouse gas (GHG) emissions with no impairments on the quality of network services. These strategies range over a wide area from enhancing the electronics, to developing new energy-aware radio access protocols, to deploying enhanced base stations with tunable capacity. To reduce both capital and operational expenditures, and the GHG footprint, manufacturers propose new compact installation with lightweight antenna systems, very efficient power amplifiers, and efficient hardware and software. The resulting economy can be up to 50 percent or more by reducing the electricity bill, sparing the use of air conditioning, and deploying compact sites that would seldom require maintenance. Recent scientific publications confirm that a very high gain could be achieved by optimizing the use of base stations proactively, and huge additional improvements could be obtained by optimizing power saving mechanisms by leveraging traffic statistics.TRUEpu

Analysis of power saving with continuous connectivity

Always-on mobile users need high bandwidth channels with negligible access delay and limited power consumption. Such a continuous connectivity mode requires the management of high-speed channels, which can turn into substantial operational costs (i.e., power consumption rate) even in presence of low traffic, unless a power saving mechanism is enforced. In this paper, we analyze the impact of 3GPP-defined power saving mechanisms on the performance of users with continuous connectivity. We develop a model for packet transmission and operational costs. We model each downlink mobile user’s traffic by means of an M/G/1 queue, and the base station’s downlink traffic as an M/G/1 PS queue with multiple classes and inhomogeneous vacations. The model is validated through packet-level simulations. Our results show that consistent power saving can be achieved in the wireless access network, as high as 75% for mobiles and 55% for base stations.TRUEpu

Power save analysis of cellular networks with continuous connectivity

In this paper, we analyze the power save and its impact on web traffic performance when customers adopt the continuous connectivity paradigm. To this aim, we provide a model for packet transmission and cost. We model each mobile user’s traffic with a realistic web traffic profile, and study the aggregate behavior of the users attached to a base station by means of a processor-shared queueing system. In particular, we evaluate user access delay, download time and expected economy of energy in the cell. The model is validated through packet-level simulations. Our model shows that dramatic energy save can be achieved by both mobile users and base stations, e.g., as much as 70% of the energy cost due to packet transmission at the base station.TRUEpu

On the Minimization of Power Consumption in Base Stations using on/off Power Amplifiers

Using energy generated with fossil fuel causes global warming due to the greenhouse effect, which threatens our environment. One of the challenges for New Generation Networks(NGN) is then the reduction of energy consumption, in particular at the BSs (Base Stations) which use about 85% of the total network energy. We contribute to the research with a mathematical model that calculates the total power consumption of a BS and enlightens the way to minimize it. First, we analyze the power consumed at every different component of the BS. Second, based on the cost incurred in turning off the BS’s power amplifiers, we show how to decide whether it is convenient to keep the BS idle during those intervals in which no traffic has to be sent, or to turn off the amplifiers. Our model is evaluated by means of numerical examples, and shows that interesting power gain can be obtained under a large spectrum of load conditions.TRUEpu

Optimizing Viscous Democracy

Viscous democracy is a generalization of liquid democracy, a social choice framework in which voters may transitively delegate their votes. In viscous democracy, a "viscosity" factor decreases the weight of a delegation the further it travels, reducing the chance of excessive weight flowing between ideologically misaligned voters. We demonstrate that viscous democracy often significantly improves the quality of group decision-making over liquid democracy. We first show that finding optimal delegations within a viscous setting is NP-hard. However, simulations allow us to explore the practical effects of viscosity. Across social network structures, competence distributions, and delegation mechanisms we find high viscosity reduces the chance of "super-voters" attaining large amounts of weight and increases the number of voters that are able to affect the outcome of elections. This, in turn, improves group accuracy as a whole. As a result, we argue that viscosity should be considered a core component of liquid democracy.Comment: To appear at IJCAI 202