Strong Ramsey Games in Unbounded Time

For two graphs $B$ and $H$ the strong Ramsey game $\mathcal{R}(B,H)$ on the board $B$ and with target $H$ is played as follows. Two players alternately claim edges of $B$. The first player to build a copy of $H$ wins. If none of the players win, the game is declared a draw. A notorious open question of Beck asks whether the first player has a winning strategy in $\mathcal{R}(K_n,K_k)$ in bounded time as $n\rightarrow\infty$. Surprisingly, in a recent paper Hefetz et al. constructed a $5$-uniform hypergraph $\mathcal{H}$ for which they proved that the first player does not have a winning strategy in $\mathcal{R}(K_n^{(5)},\mathcal{H})$ in bounded time. They naturally ask whether the same result holds for graphs. In this paper we make further progress in decreasing the rank. In our first result, we construct a graph $G$ (in fact $G=K_6\setminus K_4$) and prove that the first player does not have a winning strategy in $\mathcal{R}(K_n \sqcup K_n,G)$ in bounded time. As an application of this result we deduce our second result in which we construct a $4$-uniform hypergraph $G'$ and prove that the first player does not have a winning strategy in $\mathcal{R}(K_n^{(4)},G')$ in bounded time. This improves the result in the paper above. An equivalent formulation of our first result is that the game $\mathcal{R}(K_\omega\sqcup K_\omega,G)$ is a draw. Another reason for interest on the board $K_\omega\sqcup K_\omega$ is a folklore result that the disjoint union of two finite positional games both of which are first player wins is also a first player win. An amusing corollary of our first result is that at least one of the following two natural statements is false: (1) for every graph $H$, $\mathcal{R}(K_\omega,H)$ is a first player win; (2) for every graph $H$ if $\mathcal{R}(K_\omega,H)$ is a first player win, then $\mathcal{R}(K_\omega\sqcup K_\omega,H)$ is also a first player win.Comment: 18 pages, 46 figures; changes: fully reworked presentatio

Willingness to Pay for Improved Milk Sensory Characteristics and Assurances in Northern Kenya Using Experimental Auctions

Pastoralists in northern Kenya may be able to diversify income by selling milk in nearby towns and cities. However, milk sold in open-air markets in communities in northern Kenya is often of low quality in terms of its sensory characteristics. The milk is also often adulterated before sale. These markets are characterized by poor consumers who need to make choices about milk quality with virtually no information other than their own sensory perceptions. These conditions are similar in many parts of the world for many different commodities and products. An examination was undertaken using experimental auctions to determine if consumers in the border town of Moyale, Kenya are willing to pay for enhanced milk sensory characteristics and assurances. The results suggest that even poor consumers are willing to pay for enhanced sensory characteristics and assurances if these can be communicated in a trusted manner. Older, relatively well-informed women are the group most willing to pay the highest prices for milk quality.willingness-to-pay, milk, Kenya, Agribusiness, Agricultural Finance, Q10, Q14,

The Hurricane Exposure, Adversity, and Recovery Tool (HEART): Developing and Validating a Risk Screening Instrument for Youth Exposed to Hurricane Harvey

Given the increasing regularity with which severe (named) hurricanes arise, there is a need for valid, practically useful measures that facilitate child-centered post-hurricane situation analysis and needs assessment. Measures that accurately assess the most potent hurricane-related risk factors are essential to identifying youth at risk for developing posttraumatic stress reactions and providing them with effective post-disaster support. With feedback from community stakeholders (e.g., school personnel, physicians and hospital staff, community clinicians), we developed the Hurricane Exposure, Adversity, and Recovery Tool (HEART), a 29-item self-report measure of hurricane risk factors. Test development procedures included: (1) Reviewing the literature regarding hurricane exposure-related risk factors in youth; (2) Generating a developmentally-informed test item pool; (3) Conducting interviews with clinicians, as well as youth impacted by Hurricane Harvey, to evaluate the comprehensibility and acceptability of candidate items; and (4) evaluating endorsement rates for hurricane exposure-related risk factors among (N = 107) youth in an outpatient clinic specializing in the treatment of childhood trauma and loss. Disaster-related exposure, pre-existing indicators of risk, and ongoing post-disaster adversities were correlated with posttraumatic stress and depressive symptoms. These results provide support for an integrative approach to post-hurricane screening for both hurricane-specific (e.g., witnessing injuries) and non-specific (e.g., prior trauma) factors

A Geometric Problem in Simplicial Cones with Applications to Linear Complementarity Problems

We consider the following geometric question: suppose we are given a simplicial cone K in R^n. Can we find a point @) in the interior of K satisfying the property that the orthogonal projection of @) onto the linear hull of every face of K is in the relative interior of that fence? This question plays an important role in determining whether a certain class of linear complementarity problems (LCP 's) can be solved efficiently by a pivotal algorithm. The answer to this question is always in the affirmative if n=2, but not so for n=3. We establish some conditions for the answer to this question to be yes, and relate them to other well known properties of square matrices. e.g., world: simplicial cones, orthogonal projections, faces, linear complementarity problem, LCP, pivotal algorithms, P-matrices, symmetric positive definite matrices, 2-matrices, M-matrices

Extraordinary movements of the Denali caribou herd following the perfect storm

Although historic literature is replete with anecdotes about atypical and far-reaching movements of caribou (Rangifer tarandus granti) herds in Alaska, very few such events have been described since the late 1970s proliferation of radiotelemetry studies in the region. In September 1992, several herds in Alaska made unusual movements away from their typical year-round ranges as a result of highly unusual weather conditions that affected a broad swath of the state. We describe the movements of 113 radiocollared caribou from the Denali caribou herd during this phenomenon and the subsequent year. The majority of caribou in the Denali Herd left their typical range during 26—28 September 1992, traveling distances up to 221 km and remained out of the area through much of the winter. While the outmigration was highly consolidated and easily noticed, the return was protracted with caribou drifting back to their typical range from October 1992 to early September 1993. All radiocollared caribou that survived the 1992—93 winter ultimately returned to their typical year-round range

Simulation of the Internal Conditions During The Hot-Pressing Process

The development of a two-dimensional mathematical model to describe the internal conditions during the hot-compression of wood-based composite panels is discussed. Five primary variables were considered during the model development: air content, vapor content, bound water content, and temperature within the mat, and the extent of the cure of the adhesive system characterized by the cure index. Different heat and mass transfer processes were identified for the transport of the heat and of the moisture phases. The heat was transported by conduction and convection due to a temperature gradient, while the water phases were transported by bulk flow and diffusion due to total pressure and partial pressure gradients. The resulting differential-algebraic equation system was solved by the method of lines. The spatial derivatives of the conduction terms were discretized by central differences, while the spatial derivatives of the convection terms were discretized according to an upwind scheme. The resulting ordinary differential equations in the time variable were solved by a freely available differential-algebraic system solver (DDASSL). The mathematical model predicted temperature, moisture content, partial air and vapor pressures, total pressure, relative humidity, and extent of adhesive cure within the mat structure under a typical hot-compression process. A set of three-dimensional profiles describes the evolution of these variables with time, in the thickness and width dimensions of the mat. The model results allow a better understanding of the interacting mechanisms involved in a complex production process. The model also supports optimization of the hot-pressing parameters for improved quality of wood-based panel products, while reducing pressing time

Sensitivity Analysis of Internal Mat Environment during Hot-Pressing

The effect of several hot-pressing parameters on the internal mat environment was investigated by using a hot-pressing simulation model. The results were compared to experimental data from laboratory-produced flakeboard. The pressing parameters included initial mat moisture content, final panel density, press platen temperature, and press closing time. The variation of temperature and total gas pressure during the press cycle at six points in the vertical mid-plane of a single layer, random mat structure was predicted with the heat and mass transfer model using the different pressing conditions. Twenty-four boards were manufactured according to the same specifications, and the temperature and internal gas pressure were measured with thermocouples and gas pressure probes at the same six locations. The model consistently predicted the major trends during the hot-pressing operation.The hot-pressing simulation model used in this study was developed based on fundamental engineering principles. The material physical and transport properties were the best available values from the literature or best estimates based on engineering judgment. A sensitivity study assessed the relative importance of the different transport properties during the hot-pressing process. The sensitivity analysis of the model parameters revealed that the thermal conductivity and gas permeability of the mat have the greatest influence on model results. The assessment of these transport properties experimentally, as a function of mat structure, is highly desirable and can considerably improve future model predictions