Stochastic network interdiction games

Thesis (Ph.D.)--Boston UniversityNetwork interdiction problems consist of games between an attacker and an intelligent network, where the attacker seeks to degrade network operations while the network adapts its operations to counteract the effects of the attacker. This problem has received significant attention in recent years due to its relevance to military problems and network security. When the attacker's actions achieve uncertain effects, the resulting problems become stochastic network interdiction problems. In this thesis, we develop new algorithms for the solutions of different classes of stochastic network interdiction problems. We first focus on static network interdiction games where the attacker attacks the network once, which will change the network with certain probability. Then the network will maximize the flow from a given source to its destination. The attacker is seeking a strategy which minimizes the expected maximum flow after the attack. For this problem, we develop a new solution algorithm, based on parsimonious integration of branch and bound techniques with increasingly accurate lower bounds. Our method obtains solutions significantly faster than previous approaches in the literature. In the second part, we study a multi-stage interdiction problem where the attacker can attack the network multiple times, and observe the outcomes of its past attacks before selecting a current attack. For this dynamic interdiction game, we use a model-predictive approach based on a lower bound approximation. We develop a new set of performance bounds, which are integrated into a modified branch and bound procedure that extends the single stage approach to multiple stages. We show that our new algorithm is faster than other available methods with simulated experiments. In the last part, we study the nested information game between an intelligent network and an attacker, where the attacker has partial information about the network state, which refers to the availability of arcs. The attacker does not know the exact state, but has a probability distribution over the possible network states. The attacker makes several attempts to attack the network and observes the flows on the network. These observations will update the attacker's knowledge of the network and will be used in selecting the next attack actions. The defender can either send flow on that arc if it survived, or refrain from using it in order to deceive the attacker. For these problems, we develop a faster algorithm, which decomposes this game into a sequence of subgames and solves them to get the equilibrium strategy for the original game. Numerical results show that our method can handle large problems which other available methods fail to solve

Allocating System Resources in Display of Advertisements

Generally, the present disclosure is directed to predicting whether bid data of a present ad query (e.g., the largest cost per thousand impressions provided by a bid responsive to the ad query) will satisfy a threshold (e.g., a threshold cost per thousand impressions) based on bid data from one or more previous ad queries and/or characteristics of the present ad query. In particular, in some implementations, the systems and methods of the present disclosure can include or otherwise leverage one or more machine-learned models to predict whether bid data of an ad query will satisfy a threshold based on bid data from one or more previous ad queries and/or the present ad query

An Overview of Electrically Evoked Otoacoustic Emissions in the Mammalian Cochlea

AbstractAlternating currents injected into the cochlea are able to evoke outer hair cell-mediated basilar membrane motion, thus give rise to production of otoacoustic emissions. This electrically evoked otoacoustic emission(EEOAE) provides a useful tool for the research of out hair cell electromotility in vivo. This article reviews the research work on EEOAEs in mammals. Features of the EEOAEs and theories of their generation are introduced. Methods of EEOAE measurement are also described

Adoptive Transfer of Human Gingiva-derived Mesenchymal Stem Cells Ameliorates Collagen-induced Arthritis via Suppression of Th1 and Th17 Cells and Enhancement of Regulatory T Cell Differentiation

Objective Current approaches offer no cures for rheumatoid arthritis (RA). Accumulating evidence has revealed that manipulation of bone marrow-derived mesenchymal stem cells (BM-MSCs) may have the potential to control or even prevent RA, but BM-MSC-based therapy faces many challenges, such as limited cell availability and reduced clinical feasibility. This study in mice with established collagen-induced arthritis (CIA) was undertaken to determine whether substitution of human gingiva-derived mesenchymal stem cells (G-MSCs) would significantly improve the therapeutic effects. Methods CIA was induced in DBA/1J mice by immunization with type II collagen and Freund\u27s complete adjuvant. G-MSCs were injected intravenously into the mice on day 14 after immunization. In some experiments, intraperitoneal injection of PC61 (anti-CD25 antibody) was used to deplete Treg cells in arthritic mice. Results Infusion of G-MSCs in DBA/1J mice with CIA significantly reduced the severity of arthritis, decreased the histopathology scores, and down-regulated the production of inflammatory cytokines (interferon-γ and interleukin-17A). Infusion of G-MSCs also resulted in increased levels of CD4+CD39+FoxP3+ cells in arthritic mice. These increases were noted early after infusion in the spleens and lymph nodes, and later after infusion in the synovial fluid. The FoxP3+ Treg cells that were increased in frequency mainly consisted of Helios-negative cells. When Treg cells were depleted, infusion of G-MSCs partially interfered with the progression of CIA. Pretreatment of G-MSCs with a CD39 or CD73 inhibitor significantly reversed the protective effect of G-MSCs on CIA. Conclusion The role of G-MSCs in controlling the development and severity of CIA mostly depends on CD39/CD73 signals and partially depends on the induction of CD4+CD39+FoxP3+ Treg cells. G-MSCs provide a promising approach for the treatment of autoimmune diseases. Copyright © 2013 by the American College of Rheumatology

The Sabatier principle for Battery Anodes: Chemical Kinetics and Reversible Electrodeposition at Heterointerfaces

How surface chemistry influences reactions occurring thereupon has been a long-standing question of broad scientific and technological interest for centuries. Recently, it has re-emerged as a critical question in a subdiscipline of chemistry - electrochemistry at heterointerphases, where the answers have implications for both how, and in what forms, humanity stores the rising quantities of renewable electric power generated from solar and wind installations world-wide. Here we consider the relation between the surface chemistry at such interphases and the reversibility of electrochemical transformations at a rechargeable battery electrode. Conventional wisdom holds that stronger chemical interaction between the metal deposits and electrode promotes reversibility. We report instead that a moderate strength of chemical interaction between the deposit and the substrate, neither too weak nor too strong, enables highest reversibility and stability of the plating/stripping redox processes at a battery anode. Analogous to the empirical Sabatier principle for chemical heterogeneous catalysis, our finding arises from the confluence of competing processes - one driven by electrochemistry and the other by chemical alloying. Based on experimental evaluation of metal plating/stripping systems in battery anodes of contemporary interest, we show that such knowledge provides a powerful tool for designing key materials in highly reversible electrochemical energy storage technologies based on earth-abundant, low-cost metals.Comment: 64 pages. Initially submitted on March 16th, 2021; revised version submitted on November 14th, 2021 to the same Journa

The First Case of Ischemia-Free Kidney Transplantation in Humans

Background: Ischemia-reperfusion injury (IRI) has been considered an inevitable event in organ transplantation since the first successful kidney transplant was performed in 1954. To avoid IRI, we have established a novel procedure called ischemia-free organ transplantation. Here, we describe the first case of ischemia-free kidney transplantation (IFKT). Materials and Methods: The kidney graft was donated by a 19-year-old brain-dead donor. The recipient was a 47-year-old man with end-stage diabetic nephropathy. The graft was procured, preserved, and implanted without cessation of blood supply using normothermic machine perfusion. Results: The graft appearance, perfusion flow, and urine production suggested that the kidney was functioning well-during the whole procedure. The creatinine dropped rapidly to normal range within 3 days post-transplantation. The levels of serum renal injury markers were low post-transplantation. No rejection or vascular or infectious complications occurred. The patient had an uneventful recovery. Conclusion: This paper marks the first case of IFKT in humans. This innovation may offer a unique solution to optimizing transplant outcomes in kidney transplantation

Magnetism of two-dimensional chromium tellurides

2D ferromagnets have garnered considerable attention for their potential applications in spintronics, magnonics, and spin-orbitronics. Chromium tellurides (CrxTey), in particular, have drawn interest due to their exceptional magnetic properties and diverse range of chemical stoichiometries, attributed to the phenomenon of chromium self-intercalation. To provide an in-depth understanding of this complex material class, this review first explains the origin of 2D magnetism using two well-known 2D ferromagnets, CrI3 and Fe3GeTe2, and compares the structures of CrTe2, Cr5Te8, Cr2Te3, and CrTe to clarify the self-intercalation phenomenon. In addition, it summarizes the growth conditions of CrxTey using the chemical vapor deposition approach as well as commonly practiced characterization techniques for 2D ferromagnetism. This review also compares ferromagnetic properties while analyzing how Cr intercalants affect the magnetic. Finally, it suggests that more attention should be focused on this material system to unlock its full practical and academic potential, and proposes directions for future research.Agency for Science, Technology and Research (A*STAR)National Research Foundation (NRF)Published versionZ.L. acknowledges the support from National Research Foundation, Singapore, under its Competitive Research Program (CRP) (NRF-CRP22-2019-0007 and NRF-CRP22-2019-0004), under its NRF-ISF joint research program (NRF2020-NRF-ISF004-3520). This research is also supported by A*STAR under its AME IRG Grant (Project No. A2083c0052)

Two-dimensional cobalt ferrite through direct chemical vapor deposition for efficient oxygen evolution reaction

Two-dimensional (2D) transition metal oxides (TMOs) are promising electrocatalysts for the new energy industry, owing to their earth-abundancy, excellent performance, and unique physicochemical properties. However, microscopic electrochemical study for 2D TMOs is still lacking to provide detailed electrocatalytic mechanisms due to the challenges in synthesizing 2D TMOs with high quality and controlled thickness, which is indispensable for the microscopic studies. In this study, we report the direct synthesis of 2D cobalt ferrite (CoFeO) using a chemical vapor deposition (CVD) method. The as-synthesized 2D CoFeO possesses a well-crystallized spinel structure with an ultrathin thickness of 6.8 nm. Its oxygen evolution reaction (OER) properties under alkaline conditions were accurately assessed using an ultra-microelectrode testing platform. The (111) facet of the 2D CoFeO exhibits a low overpotential of 330 mV at a current density of 10 mA cm–2 and a high current density of ~142 mA cm–2 at an overpotential of 570 mV. The OER mechanism of the 2D CoFeO was analyzed using density functional theory (DFT) calculations, which reveal the bimetallic sites on the surface reduce the energy barrier and facilitate the reaction. Moreover, we demonstrate the reduced thickness of 2D CoFeO improves the OER activity by lowering the bulk resistance and improving the utilization of active sites, which was confirmed by the thickness-activity dependency (6.8 to 35 nm) tests using the ultra-microelectrode platform. Furthermore, the practical values of the as-prepared 2D CoFeO was demonstrated by synthesizing a large-area continuous film and collecting high OER activity and superb durability from macro-electrochemical experiments. Our study provides new solutions for the controlled synthesis of 2D TMOs electrocatalysts and uncovers the electrocatalytic mechanisms with the ultra-microelectrode platform, which provides new insights for exploring the inherent properties and applications of 2D materials in electrocatalysis.Ministry of Education (MOE)This work was supported by Singapore Ministry of Education AcRF Tier 2 (MOE2019-T2-2-105), AcRF Tier 1 RG4/17 and RG161/19