Optimal Caching and Routing in Hybrid Networks

Hybrid networks consisting of MANET nodes and cellular infrastructure have been recently proposed to improve the performance of military networks. Prior work has demonstrated the benefits of in-network content caching in a wired, Internet context. We investigate the problem of developing optimal routing and caching policies in a hybrid network supporting in-network caching with the goal of minimizing overall content-access delay. Here, needed content may always be accessed at a back-end server via the cellular infrastructure; alternatively, content may also be accessed via cache-equipped "cluster" nodes within the MANET. To access content, MANET nodes must thus decide whether to route to in-MANET cluster nodes or to back-end servers via the cellular infrastructure; the in-MANET cluster nodes must additionally decide which content to cache. We model the cellular path as either i) a congestion-insensitive fixed-delay path or ii) a congestion-sensitive path modeled as an M/M/1 queue. We demonstrate that under the assumption of stationary, independent requests, it is optimal to adopt static caching (i.e., to keep a cache's content fixed over time) based on content popularity. We also show that it is optimal to route to in-MANET caches for content cached there, but to route requests for remaining content via the cellular infrastructure for the congestion-insensitive case and to split traffic between the in-MANET caches and cellular infrastructure for the congestion-sensitive case. We develop a simple distributed algorithm for the joint routing/caching problem and demonstrate its efficacy via simulation.Comment: submitted to Milcom 201

Biological Routes to Gold Nanoplates

Much effort has been devoted to the synthesis of gold nanoparticles with different shapes, including the zero-dimensional nanospheres, one dimensional nanorods, and two-dimensional nanoplates. Compared to zero or one dimensional nanostructures, the synthesis of two-dimensional nanostructures in high yield has always been more involved, often requiring complex and time-consuming steps such as morphology transformation from the nanospheres, or the seeded growth process. Herein we report a high yield method for gold nanoplate synthesis using the extract of unicellular green alga Chlorella vulgaris, which can be carried out under ambient conditions. More than 90% of the total nanoparticle population is of the platelet morphology, surpassing the previously reported value of 45%. The control of the anisotropic growth of different planes; as well as the lateral size, has also been partially optimized.Singapore-MIT Alliance (SMA

City profile: Ningbo

Ningbo is located in the south-east of Yangtze River Delta by the East China Sea, 220 km south of Shanghai. The city has been an important port in East China for foreign trade since 7th century. Since 1980s, encouraged by China’s economic “open-door” policy, one of the ways the city attracted foreign investment and thus grew its economy was by establishing multi-functional economic development zones near its deep-water port. As a result, Ningbo is now one of the top ten coastal ports in the world (as measured in Twenty-Foot Equivalent Units, TEUs). Similarly, the city’s GDP per capita is approximately three times the national average. The current and historic prosperity of Ningbo is in no small way related to its geographical position, just 20 km inland from the Hangzhou estuary and the gateway to the East China Sea. It is also the approximate centre of a 1000 km2 coastal plain, at the confluence of the Fenghua and Yao Rivers, and from where the Yong River leads to the sea. However, also a result of this geographic location the city is now facing an increasing risk of coastal flooding caused by increase in urban area; climate change (increased rainfall intensity); and predicted sea-level rise. As a result both water management and current flood management practice (and related infrastructure) are under scrutiny. In addition to describing the evolution of the city, this paper focuses on the implication of current planning practices in Ningbo, which aim to ensure the sustainable development of the city both in terms of its natural resources and its expected rate of economic growth

Biological Routes to Gold Nanoplates

Gold nanoplates are promising for optical and electronic applications; but their synthesis is complex, often requiring a seeded growth process or spherical to triangle morphology transformation. We have discovered a biological protocol to promote the anisotropic growth of different crystal planes under ambient conditions. Thin, flat, single-crystalline gold nanoplates were produced when aqueous chloroaurate ions reacted with the mycelia-free spent medium. While the exact mechanism for this shape-controlled synthesis is not clear at this time, the possibility of achieving nanoparticle shape control in a fungal based system is exciting.Singapore-MIT Alliance (SMA

On-the-fly pipeline parallelism

Pipeline parallelism organizes a parallel program as a linear sequence of s stages. Each stage processes elements of a data stream, passing each processed data element to the next stage, and then taking on a new element before the subsequent stages have necessarily completed their processing. Pipeline parallelism is used especially in streaming applications that perform video, audio, and digital signal processing. Three out of 13 benchmarks in PARSEC, a popular software benchmark suite designed for shared-memory multiprocessors, can be expressed as pipeline parallelism. Whereas most concurrency platforms that support pipeline parallelism use a "construct-and-run" approach, this paper investigates "on-the-fly" pipeline parallelism, where the structure of the pipeline emerges as the program executes rather than being specified a priori. On-the-fly pipeline parallelism allows the number of stages to vary from iteration to iteration and dependencies to be data dependent. We propose simple linguistics for specifying on-the-fly pipeline parallelism and describe a provably efficient scheduling algorithm, the Piper algorithm, which integrates pipeline parallelism into a work-stealing scheduler, allowing pipeline and fork-join parallelism to be arbitrarily nested. The Piper algorithm automatically throttles the parallelism, precluding "runaway" pipelines. Given a pipeline computation with T[subscript 1] work and T[subscript ∞] span (critical-path length), Piper executes the computation on P processors in T[subscript P]≤ T[subscript 1]/P + O(T[subscript ∞] + lg P) expected time. Piper also limits stack space, ensuring that it does not grow unboundedly with running time. We have incorporated on-the-fly pipeline parallelism into a Cilk-based work-stealing runtime system. Our prototype Cilk-P implementation exploits optimizations such as lazy enabling and dependency folding. We have ported the three PARSEC benchmarks that exhibit pipeline parallelism to run on Cilk-P. One of these, x264, cannot readily be executed by systems that support only construct-and-run pipeline parallelism. Benchmark results indicate that Cilk-P has low serial overhead and good scalability. On x264, for example, Cilk-P exhibits a speedup of 13.87 over its respective serial counterpart when running on 16 processors.National Science Foundation (U.S.) (Grant CNS-1017058)National Science Foundation (U.S.) (Grant CCF-1162148)National Science Foundation (U.S.). Graduate Research Fellowshi

Mycobacterial Nucleoside Diphosphate Kinase Blocks Phagosome Maturation in Murine Raw 264.7 Macrophages

bacille Calmette-Guérin (BCG), disrupt the normal function of host Rab5 and Rab7, two small GTPases that are instrumental in the control of phagosome fusion with early endosomes and late endosomes/lysosomes respectively. nucleoside diphosphate kinase (Ndk) exhibits GTPase activating protein (GAP) activity towards Rab5 and Rab7. Then, using a model of latex bead phagosomes, we demonstrated that Ndk inhibits phagosome maturation and fusion with lysosomes in murine RAW 264.7 macrophages. Maturation arrest of phagosomes containing Ndk-beads was associated with the inactivation of both Rab5 and Rab7 as evidenced by the lack of recruitment of their respective effectors EEA1 (early endosome antigen 1) and RILP (Rab7-interacting lysosomal protein). Consistent with these findings, macrophage infection with an Ndk knocked-down BCG strain resulted in increased fusion of its phagosome with lysosomes along with decreased survival of the mutant.Our findings provide evidence in support of the hypothesis that mycobacterial Ndk is a putative virulence factor that inhibits phagosome maturation and promotes survival of mycobacteria within the macrophage

Safe Open-Nested Transactions Through Ownership

Researchers in transactional memory (TM) have proposed open nesting asa methodology for increasing the concurrency of a program. The ideais to ignore certain "low-level" memory operations of anopen-nested transaction when detecting conflicts for its parenttransaction, and instead perform abstract concurrency control for the"high-level" operation that nested transaction represents. Tosupport this methodology, TM systems use an open-nested commitmechanism that commits all changes performed by an open-nestedtransaction directly to memory, thereby avoiding low-levelconflicts. Unfortunately, because the TM runtime is unaware of thedifferent levels of memory, an unconstrained use of open-nestedcommits can lead to anomalous program behavior.In this paper, we describe a framework of ownership-awaretransactional memory which incorporates the notion of modules into theTM system and requires that transactions and data be associated withspecific transactional modules or Xmodules. We propose a newownership-aware commit mechanism, a hybrid between anopen-nested and closed-nested commit which commits a piece of datadifferently depending on whether the current Xmodule owns the data ornot. Moreover, we give a set of precise constraints on interactionsand sharing of data among the Xmodules based on familiar notions ofabstraction. We prove that ownership-aware TM has has cleanmemory-level semantics and can guarantee serializability bymodules, which is an adaptation of multilevel serializability fromdatabases to TM. In addition, we describe how a programmer canspecify Xmodules and ownership in a Java-like language. Our typesystem can enforce most of the constraints required by ownership-awareTM statically, and can enforce the remaining constraints dynamically.Finally, we prove that if transactions in the process of aborting obeyrestrictions on their memory footprint, the OAT model is free fromsemantic deadlock