Computing toric degenerations of flag varieties

We compute toric degenerations arising from the tropicalization of the full flag varieties $\mathcal{F}\ell_4$ and $\mathcal{F}\ell_5$ embedded in a product of Grassmannians. For $\mathcal{F}\ell_4$ and $\mathcal{F}\ell_5$ we compare toric degenerations arising from string polytopes and the FFLV polytope with those obtained from the tropicalization of the flag varieties. We also present a general procedure to find toric degenerations in the cases where the initial ideal arising from a cone of the tropicalization of a variety is not prime.Comment: 35 pages, 6 figure

Assigning Intentions when Actions are Unobservable: the Impact of Trembling in the Trust Game

This paper reports laboratory experiments investigating behavior when players may make inferences about the intentions behind others' prior actions based on higher- or lower-accuracy information about those actions. We investigate a trust game with first mover trembling, a game in which nature determines whether the first mover's decision is implemented or reversed. The results indicate that second movers give first movers the benefit of the doubt. However, first movers do not anticipate this response. Ultimately, it appears that subjects are thinking on at least three levels when making decisions: they are concerned with their own material well being, the trustworthiness of their counterpart, and how their own actions will be perceived.

When are Women More Generous than Men?

Previous research on gender differences in behavior has led to seemingly contradictory findings about generosity. From data generated by 290 subject pairs, we find that women are more sensitive than men to the costs of generous actions when deciding whether or not to be generous. The factors that affect the level of generosity observed in our experiments are reciprocal motivation, the level of money payoffs, and the level of social distance in the experimental protocol. The relatively greater sensitivity of women to the costs of generous behavior can explain most of the apparent inconsistencies in previously-reported findings.

Electrochemical method for the determination of phosphate in natural water

The objective of this project was to develop a method for the determination of phosphate in natural water which would be an improvement over the presently accepted spectrophotometric technique in terms of detection limit and freedom from interference. Cathodic stripping chronopotentiometry was found to be an analytically sensitive method for phosphate analysis. The technique is based upon the reversible oxidation of a metallic indicator electrode to an insoluble phosphate salt film. When copper is used as the indicator electrode, the detection limit is 10 ppb. Control of the pH at 6.0 and removal of oxygen from the solution eliminates anticipated interferences in natural water samples. The major drawback of the method is that under the electrolysis conditions employed, salt of mixed stoichiometry is deposited which subsequently results in two separate stripping steps. When mercury is the indicator electrode, the system approaches true Nernstian behavior, so a detection limit considerably below 10 ppb is anticipated. However, an observed interference of chloride ion has, to the present, limited application of the electrode to solutions containing phosphate in excess of 50 ppb.U.S. Department of the InteriorU.S. Geological SurveyOpe

Capsaicin as a Tool for Repelling Southern Flying Squirrels from Red-cockaded Woodpecker Cavities

The southern flying squirrel (Glaucomys volans) is an important kleptoparasite of cavities excavated by the imperiled red-cockaded woodpecker (Dryobates borealis). Flying squirrel usurpation of cavities may affect woodpecker productivity, but current efforts to manage flying squirrels are costly and time consuming. We assessed whether capsaicin could deter flying squirrel use of woodpecker cavities on a site in southwest Georgia, USA. Twenty-nine cavity tree clusters received 4 treatments: capsaicin, water, air, and a control (no treatment). Only capsaicin both removed more flying squirrels from the cavity immediately after its application and decreased the probability of a flying squirrel occupying the cavity the next day. The data presented supports the potential of capsaicin to provide a more efficient way for dealing with this common kleptoparasite

Tracking Cyber Adversaries with Adaptive Indicators of Compromise

A forensics investigation after a breach often uncovers network and host indicators of compromise (IOCs) that can be deployed to sensors to allow early detection of the adversary in the future. Over time, the adversary will change tactics, techniques, and procedures (TTPs), which will also change the data generated. If the IOCs are not kept up-to-date with the adversary's new TTPs, the adversary will no longer be detected once all of the IOCs become invalid. Tracking the Known (TTK) is the problem of keeping IOCs, in this case regular expressions (regexes), up-to-date with a dynamic adversary. Our framework solves the TTK problem in an automated, cyclic fashion to bracket a previously discovered adversary. This tracking is accomplished through a data-driven approach of self-adapting a given model based on its own detection capabilities. In our initial experiments, we found that the true positive rate (TPR) of the adaptive solution degrades much less significantly over time than the naive solution, suggesting that self-updating the model allows the continued detection of positives (i.e., adversaries). The cost for this performance is in the false positive rate (FPR), which increases over time for the adaptive solution, but remains constant for the naive solution. However, the difference in overall detection performance, as measured by the area under the curve (AUC), between the two methods is negligible. This result suggests that self-updating the model over time should be done in practice to continue to detect known, evolving adversaries.Comment: This was presented at the 4th Annual Conf. on Computational Science & Computational Intelligence (CSCI'17) held Dec 14-16, 2017 in Las Vegas, Nevada, US

Relaxation oscillations, stability, and cavity feedback in a superradiant Raman laser

We experimentally study the relaxation oscillations and amplitude stability properties of an optical laser operating deep into the bad-cavity regime using a laser-cooled $^{87}$Rb Raman laser. By combining measurements of the laser light field with nondemolition measurements of the atomic populations, we infer the response of the gain medium represented by a collective atomic Bloch vector. The results are qualitatively explained with a simple model. Measurements and theory are extended to include the effect of intermediate repumping states on the closed-loop stability of the oscillator and the role of cavity feedback on stabilizing or enhancing relaxation oscillations. This experimental study of the stability of an optical laser operating deep into the bad-cavity regime will guide future development of superradiant lasers with ultranarrow linewidths.Comment: 9 pages, 6 figure