Towards a Dual-Tip STM Application in Mesoscopic Electron Transport

A new design for a dual-tip scanning tunneling microscope (STM) is presented. The design is a variation on the mechanically controllable break-junction with two electron beam-induced deposition nano-tips. The new design enables one to scan surfaces simultaneously with two probes having a nano-gap separation. By collecting the lateral current flowing between the tips, the transconductance map can then be compared with the STM images for local characterizations of the electron transport. Since the lateral beam carries the property of the density of states of the surface at momentum space, the dispersion of the electronic structure should give an orientation and position dependence of the local transconductance current. In addition, the reduced terminal separation, on the order of the characteristic mesoscopic length scales, is likely to be sensitive to a variety of typically observed interactions and interference effects.     

Almost k-wise independence versus k-wise independence

We say that a distribution over {0,1}ⁿ is (ε,k)-wise independent if its restriction to every k coordinates results in a distribution that is ε-close to the uniform distribution. A natural question regarding (ε,k)-wise independent distributions is how close they are to some k-wise independent distribution. We show that there exist (ε,k)-wise independent distributions whose statistical distance is at least n^O(k)·ε from any k-wise independent distribution. In addition, we show that for any (ε,k)-wise independent distribution there exists some k-wise independent distribution, whose statistical distance is n^O(k)·ε.     

Repeated Budgeted Second Price Ad Auction

Our main goal is to abstract existing repeated sponsored search ad auction mechanisms which incorporate budgets, and study their equilibrium and dynamics. Our abstraction has multiple agents bidding repeatedly for multiple identical items (such as impressions in an ad auction). The agents are budget limited and have a value per item. We abstract this repeated interaction as a one-shot game, which we call budget auction, where agents submit a bid and a budget, and then items are sold by a sequential second price auction. Once an agent exhausts its budget it does not participate in the proceeding auctions. Our main result shows that if agents bid conservatively (never bid above their value) then there always exists a pure Nash equilibrium. We also study simple dynamics of repeated budget auctions, showing their convergence to a Nash equilibrium for two agents and for multiple agents with identical budgets.     

An Experimental and Theoretical Comparison of Model Selection Methods

Machine Learning - We investigate the problem of model selection in the setting of supervised learning of boolean functions from independent random examples. More precisely, we compare methods for...     

Short communication: Effect of pomegranate-residue supplement on Cryptosporidium parvum oocyst shedding in neonatal calves

Cryptosporidium parvum is considered one of the most common enteropathogens, responsible for the high incidence of diarrhea and deleterious implications on immunity and health in neonatal calves. The pomegranate is well known for its health-promoting properties. Two experiments were designed to test the antiparasitical and antidiarrheal effects of concentrated pomegranate extract (CPE) supplement in milk in neonatal Holstein calves. Forty-one calves were randomly divided into control (n = 20) and treatment (n = 21) groups. For the first experiment, the treatment group was supplemented with 3.75% CPE in the daily milk ration, between 3 and 14 d of age, whereas the control group received only milk. Fecal samples were collected between d 5 and 13 to quantify Cryptosporidium oocysts, and the duration and intensity of diarrhea were evaluated. Reduced fecal oocyst count and diarrhea intensity and duration were revealed in the 3.75% CPE calves. No difference was noted in average daily gain between groups. In a second experiment, which was designed to test the effect of a lower CPE concentration (0.6% of daily milk allocation), no effects on fecal oocyst count and average daily gain were observed. However, compared with control, the lower CPE group was characterized by a shorter duration of diarrhea and higher weight gain among males at 14 d of age. These results suggest that the CPE supplement-to-calf milk ratio may potentially alleviate intestinal morbidity caused by Cryptosporidium.     

A Sparse Sampling Algorithm for Near-Optimal Planning in Large Markov Decision Processes

A critical issue for the application of Markov decision processes (MDPs) to realistic problems is how the complexity of planning scales with the size of the MDP. In stochastic environments with very large or infinite state spaces, traditional planning and reinforcement learning algorithms may be inapplicable, since their running time typically grows linearly with the state space size in the worst case. In this paper we present a new algorithm that, given only a generative model (a natural and common type of simulator) for an arbitrary MDP, performs on-line, near-optimal planning with a per-state running time that has no dependence on the number of states. The running time is exponential in the horizon time (which depends only on the discount factor and the desired degree of approximation to the optimal policy). Our algorithm thus provides a different complexity trade-off than classical algorithms such as value iteration—rather than scaling linearly in both horizon time and state space size, our running time trades an exponential dependence on the former in exchange for no dependence on the latter.Our algorithm is based on the idea of sparse sampling. We prove that a randomly sampled look-ahead tree that covers only a vanishing fraction of the full look-ahead tree nevertheless suffices to compute near-optimal actions from any state of an MDP. Practical implementations of the algorithm are discussed, and we draw ties to our related recent results on finding a near-best strategy from a given class of strategies in very large partially observable MDPs (Kearns, Mansour, & Ng. Neural information processing systems 13, to appear).     

Procedural justice, stress appraisal, and athletes' attitudes.

In this study the authors examined a model in which procedural justice may serve as an external-situational resource that improves athletes' appraisals of stress and enhances their attitudes toward their team. Eighty-one Israeli male athletes were questioned on the degree of procedural justice employed on their team, how they appraised stress, and their attitudes toward their team. Results showed that higher procedural justice was associated with more positive appraisals of stress as a challenge and greater team loyalty and commitment and that the relationship of procedural justice to team commitment and loyalty was mediated by how stress is appraised. Findings integrate the cognitive-phenomenological model of stress/coping with the relational factors of the procedural justice approach and extend their validity to the field of sport. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive AIMD Congestion Control

The main objectives of a congestion control algorithm are high bandwidth utilization, fairness and responsiveness in a changing environment. However, these objectives are contradicting in particular situations since the algorithm constantly has to probe available bandwidth, which may affect its stability. This paper proposes a novel congestion control algorithm that achieves high bandwidth utilization providing fairness among competing connections and, on the other hand, is sufficiently responsive to changes of available bandwidth. The main idea of the algorithm is to use adaptive setting for the additive increase/multiplicative decrease (AIMD) congestion control scheme, where parameters may change dynamically, with respect to the current network conditions.     

Improved Competitive Guarantees for QoS Buffering

We consider a network providing Differentiated Services (DiffServ), which allow Internet Service Providers (ISPs) to offer different levels of Quality of Service (QoS) to different traffic streams. We study two types of buffering policies that are used in network switches supporting QoS. In the FIFO type, packets must be transmitted in the order they arrive. In the uniform bounded delay type, there is a maximal delay time associated with the switch and each packet must be transmitted within this time, or otherwise it is dropped. In both models the buffer space is limited, and packets are lost when the buffer overflows. Each packet has an intrinsic value, and the goal is to maximize the total value of transmitted packets. Our main contribution is an algorithm for the FIFO model with arbitrary packet values that for the first time achieves a competitive ratio better than 2, namely 2-ε for a constant ε gt; 0. We also describe an algorithm for the uniform bounded delay model which simulates our algorithm for the FIFO model, and show that it achieves the same competitive ratio.     

Modification of the Redox-Properties of Tetraphenylporphyrin-Complexes by Bases in Methylene-Chloride Solution. The Equilibrium of Different Oxidation-States with Added Base as Measured by Cyclic Voltammetry

The oxidation half-wave potentials of Co²⁺ tetraphenylporphyrin, measured by cyclic voltammetry in methylenechloride solution, are changed by the addition of weak bases like methanol, acetone and dimethylformamide. The wave corresponding to the metal-oxidation Co²⁺ ? Co³⁺ is shifted to lower potential, while the wave, corresponding to the ligand oxidation Co³⁺(TPP) ? Co³⁺(TPP)⁺. is shifted to higher potential. It can be shown, that this is due to a preferential interaction of Co³⁺(TPP) with the bases, which is stronger than that of the Co²⁺(TPP) as well as that of the Co³⁺(TPP)⁺. Because the shifts are proportional to the concentration of added base, they can be followed quantitatively and the equilibrium constants of the interactions between the different oxidation states and the bases can be calculated. The reduction wave of Co²⁺(TPP), corresponding to the Co³⁺ ? Co¹⁺ transition is not changed by the weak bases, but is shifted to lower potential by pyridine and the picolines. The shift is again proportional to the concentration of added base. The reduction wave of Fe^3?(TPP)Cl^? is not changed by the weak bases, but is shifted to lower potential by pyridine. While the reduction wave of the free Fe³⁺(TPP)Cl^? is irreversible, that of the pyridine-adduct is reversible. In this case the shift is not proportional to the amount of added base. The voltammetric curves of the Cu, Ni, and Zn tetraphenyl-porphyrins are not changed by the addition of either the weak or the strong bases.