Collaboration in Social Networks

The very notion of social network implies that linked individuals interact repeatedly with each other. This allows them not only to learn successful strategies and adapt to them, but also to condition their own behavior on the behavior of others, in a strategic forward looking manner. Game theory of repeated games shows that these circumstances are conducive to the emergence of collaboration in simple games of two players. We investigate the extension of this concept to the case where players are engaged in a local contribution game and show that rationality and credibility of threats identify a class of Nash equilibria -- that we call "collaborative equilibria" -- that have a precise interpretation in terms of sub-graphs of the social network. For large network games, the number of such equilibria is exponentially large in the number of players. When incentives to defect are small, equilibria are supported by local structures whereas when incentives exceed a threshold they acquire a non-local nature, which requires a "critical mass" of more than a given fraction of the players to collaborate. Therefore, when incentives are high, an individual deviation typically causes the collapse of collaboration across the whole system. At the same time, higher incentives to defect typically support equilibria with a higher density of collaborators. The resulting picture conforms with several results in sociology and in the experimental literature on game theory, such as the prevalence of collaboration in denser groups and in the structural hubs of sparse networks

Energy in Agriculture: Energy for Swine Facilities Part II: Alternative Sources of Energy

Recently, there has been some concern about energy utilization in agricultural production. Shortages of natural and LP gas have affected many livestock producers, especially swine producers utilizing LP gas as a supplemental heat source in farrowing facilities. These shortages, coupled with an ever-increasing price for fuel and electricity, have encouraged many producers to begin looking for alternative energy sources

Energy in Agriculture: Energy for Swine Facilities Part I: Energy Conservation

Recently, there has been some concern about energy utilization in agricultural production. Shortages of natural and LP gas have affected many livestock producers, especially swine producers utilizing LP gas as a supplemental heat source in farrowing facilities. These shortages, coupled with an ever*increasing price for fuel and electricity, have encouraged many producers to begin looking for ways to reduce energy consumption

Sertraline Hydrochloride

This poster, presented at the Natural Sciences Poster Session at Parkland College, provides the chemical makeup, dosage, and effects of Sertraline Hydrochloride, trade name Zoloft, used to treat the symptoms of depression, obsessive compulsive disorder, panic disorder, social anxiety disorder, premenstual dysphoric disorder, generalized anxiety, and post-traumatic stress disorder

The Nordic Market: Signs of Stress?

The supply shock that hit the Nordic electricity market in 2002-2003 put the market to a severe test. A sharp reduction in inflow to hydro reservoirs during the normally wet months of late autumn pushed electricity prices to unprecedented levels. We take this event as the starting point for analysing some potential weaknesses of the Nordic market. We conclude that fears regarding supply security and adequacy are likely to be unfounded. Nevertheless, as inherited over-capacity is eroded, and new market-based environmental regulation takes effect, tighter market conditions are to be expected. It is then crucial that retail markets are fully developed so as to allow consumers to adequately protect themselves from occurrences of price spikes.

A Dairy Cow Housing System Featuring Motel Free Stalls

The term motel free stalls describes a milking cow housing system that utilizes roof area which protects only the free stalls. Alleys are only partially protected by the roof overhang. This system provides little protection from extreme temperatures but can provide some summer protection if properly constructed. Motel free stall systems reduce the initial cost of constructing lactating cow housing. Motel free stall system described in this paper should be used with caution in climatic regions colder than Kentucky because of limited protection from extreme cold temperatures. This paper describes the application of motel free stall housing systems and a dairy operation that utilizes them

Quantum authentication and encryption with key recycling

We propose an information-theoretically secure encryption scheme for classical messages with quantum ciphertexts that offers detection of eavesdropping attacks, and re-usability of the key in case no eavesdropping took place: the entire key can be securely re-used for encrypting new messages as long as no attack is detected. This is known to be impossible for fully classical schemes, where there is no way to detect plain eavesdropping attacks. This particular application of quantum techniques to cryptography was originally proposed by Bennett, Brassard and Breidbart in 1982, even before proposing quantum-key-distribution, and a simple candidate scheme was suggested but no rigorous security analysis was given. The idea was picked up again in 2005, when Damgård, Pedersen and Salvail suggested a new scheme for the same task, but now with a rigorous security analysis. However, their scheme is much more demanding in terms of quantum capabilities: it requires the users to have a quantum computer. In contrast, and like the original scheme by Bennett et al., our new scheme requires from the honest users merely to prepare and measure single BB84 qubits. As such, we not only show the first provably-secure scheme that is within reach of current technology, but we also confirm Bennett et al.’s original intuition that a scheme in the spirit of their original construction is indeed secure

Complete Insecurity of Quantum Protocols for Classical Two-Party Computation

A fundamental task in modern cryptography is the joint computation of a function which has two inputs, one from Alice and one from Bob, such that neither of the two can learn more about the other's input than what is implied by the value of the function. In this Letter, we show that any quantum protocol for the computation of a classical deterministic function that outputs the result to both parties (two-sided computation) and that is secure against a cheating Bob can be completely broken by a cheating Alice. Whereas it is known that quantum protocols for this task cannot be completely secure, our result implies that security for one party implies complete insecurity for the other. Our findings stand in stark contrast to recent protocols for weak coin tossing, and highlight the limits of cryptography within quantum mechanics. We remark that our conclusions remain valid, even if security is only required to be approximate and if the function that is computed for Bob is different from that of Alice.Comment: v2: 6 pages, 1 figure, text identical to PRL-version (but reasonably formatted

Monitoring and Pay: An Experiment on Employee Performance under Endogenous Supervision

We present an experimental test of a shirking model where monitoring intensity is endogenous and effort a continuous variable. Wage level, monitoring intensity and consequently the desired enforceable effort level are jointly determined by the maximization problem of the firm. As a result, monitoring and pay should be complements. In our experiment, between and within treatment variation is qualitatively in line with the normative predictions of the model under standard assumptions. Yet, we also find evidence for reciprocal behavior. Our data analysis shows, however, that it does not pay for the employer to solely rely on the reciprocity of employees