Modelling and stability of FAST TCP

We introduce a discrete-time model of FAST TCP that fully captures the effect of self-clocking and compare it with the traditional continuous-time model. While the continuous-time model predicts instability for homogeneous sources sharing a single link when feedback delay is large, experiments suggest otherwise. Using the discrete-time model, we prove that FAST TCP is locally asymptotically stable in general networks when all sources have a common round-trip feedback delay, no matter how large the delay is. We also prove global stability for a single bottleneck link in the absence of feedback delay. The techniques developed here are new and applicable to other protocols

A Bijection between Atomic Partitions and Unsplitable Partitions

In the study of the algebra $\mathrm{NCSym}$ of symmetric functions in noncommutative variables, Bergeron and Zabrocki found a free generating set consisting of power sum symmetric functions indexed by atomic partitions. On the other hand, Bergeron, Reutenauer, Rosas, and Zabrocki studied another free generating set of $\mathrm{NCSym}$ consisting of monomial symmetric functions indexed by unsplitable partitions. Can and Sagan raised the question of finding a bijection between atomic partitions and unsplitable partitions. In this paper, we provide such a bijection.Comment: 6 page

Quantifying Substitutability

In this thesis, we will tackle the problem of how keyphrase extraction systems can be evaluated to reveal their true efficacy. The aim is to develop a new semantically-oriented approximate string matching criteria, one that is comparable to human judgements, but without the cost and energy associated with manual evaluation. This matching criteria can also be adapted for any information retrieval (IR) system where the evaluation process involves comparing candidate strings (produced by the IR system) to a gold standard (created by humans). Our contributions are threefold. First, we define a new semantic relationship called substitutability – how suitable a phrase is when used in place of another – and then design a generic system which measures/quantifies this relationship by exploiting the interlinking structure of external knowledge sources. Second, we develop two concrete substitutability systems based on our generic design: WordSub, which is backed by WordNet; and WikiSub, which is backed by Wikipedia. Third, we construct a dataset, with the help of human volunteers, that isolates the task of measuring substitutability. This dataset is then used to evaluate the performance of our substitutability systems, along with existing approximate string matching techniques, by comparing them using a set of agreement metrics. Our results clearly demonstrate that WordSub and WikiSub comfortably outperform current approaches to approximate string matching, including both lexical-based methods, such as R-precision; and semantically-oriented techniques, such as METEOR. In fact, WikiSub’s performance comes sensibly close to that of an average human volunteer, when comparing it to the optimistic (best-case) interhuman agreement

Structural and electronic origin of the magnetic structures in hexagonal LuFeO3_3

Using combined theoretical and experimental approaches, we studied the structural and electronic origin of the magnetic structure in hexagonal LuFeO$_3$. Besides showing the strong exchange coupling that is consistent with the high magnetic ordering temperature, the previously observed spin reorientation transition is explained by the theoretically calculated magnetic phase diagram. The structural origin of this spin reorientation that is responsible for the appearance of spontaneous magnetization, is identified by theory and verified by x-ray diffraction and absorption experiments.Comment: 5 pages, 2 tables and 4 figures, Please contact us for the supplementary material. Accepted in Phys. Rev. B, in productio

Elementary solution to the time-independent quantum navigation problem

A quantum navigation problem concerns the identification of a time-optimal Hamiltonian that realizes a required quantum process or task, under the influence of a prevailing ‘background’ Hamiltonian that cannot be manipulated. When the task is to transform one quantum state into another, finding the solution in closed form to the problem is nontrivial even in the case of timeindependent Hamiltonians. An elementary solution, based on trigonometric analysis, is found here when the Hilbert space dimension is two. Difficulties arising from generalizations to higher-dimensional systems are discussed

Exogenous erythropoietin administration attenuates intermittent hypoxia-induced cognitive deficits in a murine model of sleep apnea

Background: In rodents, exposure to intermittent hypoxia (IH), a hallmark of obstructive sleep apnea (OSA), is associated with neurobehavioral impairments, increased apoptosis in the hippocampus and cortex, as well as increased oxidant stress and inflammation. Such findings are markedly attenuated in rodents exposed to sustained hypoxia 9SH) of similar magnitude. The hypoxia-sensitive gene erythropoietin (EPO) has emerged as a major endogenous neuroprotectant, and could be involved in IH-induced neuronal dysfunction. Methods and Results: IH induced only transiently increased expression of EPO mRNA in hippocampus, which was continued in (SH)-exposed mice. IH, but not SH, adversely affected two forms of spatial learning in the water maze, and increased markers of oxidative stress. However, on a standard place training task, mice treated with exogenously administered EPO displayed normal learning, and were protected from the spatial learning deficits observed in vehicle-treated (C) littermates exposed to IH. Moreover, anxiety levels were increased in IH as compared to normoxia, while no changes in anxiety emerged in EPO-treated mice. Additionally, C mice, but not EPO-treated IH-exposed mice had significantly elevated levels of NADPH oxidase expression, as well as increased MDA and 8-OHDG levels in cortical and hippocampal lysates. Conclusions: The oxidative stress responses and neurobehavioral impairments induced by IH during sleep are mediated, at least in part, by imbalances between EPO expression and increased NADPH oxidase activity, and thus pharmacological agents targeting EPO expression in CNS may provide a therapeutic strategy in sleep-disordered breathing

Magnetocaloric effect in GdCoxAl2−x system for (0.15 ≤ x ≤ 1) compositions

Structure and magnetic properties of the GdAl2-GdCo2 system including magnetocaloric effecthave been investigated for various compositions. The as-cast GdCox Al 2-x alloys prepared by arc-melting crystallize in the dual-phase structure of cubic MgCu2-type and hexagonal MgZn2-type phases. All the as-cast dual-phase alloys exhibit only one magnetic phase transition near 77 K even though two ferrimagnetic phases coexist. The magnetic transition was broadened by the continuous transitions of the component phases, which resulted in enhancement of relative cooling power at the expense of the magnetic entropy changes