Self-enforcing coalitions with power accumulation

Agents endowed with power compete for a divisible resource by forming coalitions with other agents. The coalition with the greatest power wins the resource and divides it among its members. The agents’ power increases according to their share of the resource.We study two models of coalition formation where winning agents accumulate power and losing agents may participate in further coalition formation processes. An axiomatic approach is provided by focusing on variations of two main axioms: self-enforcement, which requires that no further deviation happens after a coalition has formed, and rationality, which requires that agents pick the coalition that gives them their highest payoff. For these alternative models, we determine the existence of stable coalitions that are self-enforcing and rational for two traditional sharing rules. The models presented in this paper illustrate how power accumulation, the sharing rule, and whether losing agents participate in future coalition formation processes, shape the way coalitions will be stable throughout time.     

Effect of copassivation of Cl and Cu on CdTe grain boundaries

Using a first-principles method, we investigate the structural and electronic properties of grain boundaries (GBs) in polycrystalline CdTe and the effects of copassivation of elements with far distinct electronegativities. Of the two types of GBs studied in this Letter, we find that the Cd core is less harmful to the carrier transport, but is difficult to passivate with impurities such as Cl and Cu, whereas the Te core creates a high defect density below the conduction band minimum, but all these levels can be removed by copassivation of Cl and Cu. Our analysis indicates that for most polycrystalline systems copassivation or multipassivation is required to passivate the GBs.     

Room-temperature spectral hole burning in an engineered inhomogeneously broadened resonance

We observe spectral hole burning in a room-temperature optical fiber pumped by a spectrally broadened pump beam. This beam drives the stimulated Brillouin process, creating an inhomogeneously broadened resonance in the material whose shape can be engineered by tailoring the beam's spectrum. A monochromatic saturating beam "burns" a narrow spectral hole that is approximately 10(4) times narrower than the inhomogeneous width of the resonance. This research paves the way toward agile optical information processing and storage using standard telecommunication components.     

Magnetic, resistive and magnetoresistive properties of melt spun CoCu alloys

_Co10Cu90${\mathrm{Co}}_{10}{\mathrm{Cu}}_{90}$ alloys were prepared by melt spinning in a twin roller device at 5 m/s and 23 m/s tangential wheel velocities. The low temperature (5–300 K) magnetic and electron transport properties were investigated in as cast alloys and in samples annealed for 1 h at 923 K. Magnetoresistance (MR) measurements were performed between 35 K and 295 K, with applied field up to 0.85 T. For each condition, M–H loops and M(T) curves were measured and analyzed to estimate the mean Co particle size and the blocking temperature distribution, respectively. In the as cast condition, particle sizes between 2.3 nm and 5.7 nm and mean blocking temperatures between 31 K and 247 K are found; these alloys, cooled at these relatively low rates, show appreciable room temperature MR values (0.5–1.5% for 0.85 T). A minimum resistance is found at about 30 K in alloys with compositions up to 15 at% Co.     

Dehalogenation of α -haloketones and vic-dibromides with nickel boride

α-Haloketones and $\text{vic}$-dibromides are converted to the corresponding ketones and alkenes respectively with nickel boride generated $\text{in situ}$ from sodium borohydride and nickel chloride.