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Helicobacter pylori, the most common cause of chronic gastritis, peptic ulcers, and gastric cancers, infects around half of the world's population. Although the drawbacks of antibiotic-based combination therapy are emerging, no effective vaccine is available to prevent H. pylori infections. Here, we describe the total synthesis of the unique α-(1→3)-linked tri-d-glycero-d-manno-heptose antigen from the lipopolysaccharide of H. pylori serogroups O3 and O6 and strains MO19, D2, D4, and D5 based on de novo synthesis of the differentially protected d-glycero-d-manno-heptosyl building blocks. Immunization of mice with the semisynthetic glycoconjugate elicited a very robust T-cell-dependent antigen-specific immune response, resulting in very high titers of IgG1 and IgG2b protective antibody isotypes. The postimmune sera recognized H. pylori NCTC 11637 and bound strongly to the surface of the intact bacteria.

Synthesis of bacterial cell surface l-glycero-d-manno-heptose (l,d-Hep)- and d-glycero-d-manno-heptose (d,d-Hep)-containing higher carbon sugars is a challenging task. Here, we report a convenient and efficient approach for the synthesis of the l,d-Hep and d,d-Hep building blocks. Using l-lyxose and d-ribose as starting materials, this approach features diastereoselective Mukaiyama-type aldol reactions as the key steps. On the basis of the synthetic l,d-Hep and d,d-Hep building blocks, we achieved the first stereoselective synthesis of the unique α-l,d-Hep-(1→3)-α-d,d-Hep-(1→5)-α-Kdo core trisaccharide of the lipopolysaccharide of Vibrio parahemolyticus O2.

In recent years, the number of CPU cores in a multi-core processor keeps increasing. To leverage the increasing hardware resource, programmers need to develop parallelized software programs. One promising approach to parallelizing high-performance applications is pipeline parallelism, which divides a task into a serial of subtasks and then maps these subtasks to a group of CPU cores, making the communication scheme between the subtasks running on different cores a critical component for the parallelized programs. One widely-used implementation of the communication scheme is software-based, lock-free first-in-first-out queues that move data between different subtasks. The primary design goal of the prior lock-free queues was higher throughput, such that the technique of batching data was heavily used in their enqueue and dequeue operations. Unfortunately, a lock-free queue with batching heavily depends on the assumption that data arrive at a constant rate, and the queue is in an equilibrium state. Experimentally we found that the equilibrium state of a queue rarely happens in real, high-performance use cases (e.g., 10Gbps+ network applications) because data arriving rate fluctuates sharply. As a result, existing queues suffer from performance degradation when used in real applications on multi-core processors. In this paper, we present EQueue, a lock-free queue to handle this robustness issue in existing queues. EQueue is lock-free, efficient, and robust. EQueue can adaptively (1) shrink its queue size when data arriving rate is low to keep its memory footprint small to utilize CPU cache better, and (2) enlarge its queue size to avoid overflow when data arriving rate is in burstiness. Experimental results show that when used in high-performance applications, EQueue can always perform an enqueue/dequeue operation in less than 50 CPU cycles, which outperforms FastForward and MCRingBuffer, two state-of-the-art queues, by factors 3 and 2, respectively.

A de novo approach utilizing the d-proline-catalyzed and LDA-promoted aldol reactions as key steps for the preparation of differentiated-protected 6-deoxy-d-manno-heptose building blocks was developed. PPh3AuBAr4F-catalyzed glycosylation with the 6-deoxy-d-manno-heptosyl o-hexynylbenzoate as donor was demonstrated as a direct and practical method for the stereoselective synthesis of the β-linked 6-deoxy-d-manno-heptoside as the major product. Coupling of the 6-deoxy-α-d-manno-heptosyl H-phosphonate with the 3-hydroxyl disaccharide acceptor based on H-phosphonate chemistry was described for the construction of the trisaccharide skeleton with the acid-labile phosphodiester linkage. Finally, first total synthesis of the unique trisaccharide antigen of the capsular polysaccharide of Campylobacter jejuni RM1221 that belongs to HS:53 serotype complex was accomplished for further evaluation as vaccine candidate against C. jejuni RM1221 infection.

Parallelizing performance-critical applications are of critical importance for harnessing the power of multicore processors, which are now ubiquitous. Even though wait-free algorithms offer the appeal of completing each operation of a parallelized application in a finite number of steps, high-performance wait-free algorithms at high levels of concurrency are still rare. In this paper, we demonstrate one primary reason for this inefficiency: existing wait-free algorithms are not optimized for processors’ caches and write buffers, two key components in modern hardware to accelerate memory accesses. As an example, a wait-free multi-producer-single-consumer queue algorithm, which faces common performance problems of wait-free algorithms, is studied in this paper. We accelerate the queue algorithm by (1) allowing producers to buffer enqueue requests in their local buffers and to write them into the shared queue in batch, to exhibit the spatial locality of the program, and (2) eliminating expensive atomic operations, by giving up some degree of internal consistency to avoid write buffers being drained frequently. The outcome is a write-buffer and cache-friendly queue algorithm which is wait-free and efficient on off-the-shelf multicore processors. The experiments show that the optimized queue algorithm outperforms prior queue algorithms on three different architectures ( $\times $ 86, Power8, and ARMv8). On $\times $ 86, it outperforms WFQueue, the state-of-the-art solution, by 2–3 $\times$ , and outperforms CCQueue, the representative of combining solution, by 4–12 $\times $ . Applying the techniques presented in this paper to other wait-free algorithms is straightforward; our queue example demonstrates that these techniques can be applied to other wait-free algorithms while maintaining the control flow of the original algorithms without dramatic changes.

Ulvan is a sulfated polysaccharide from green algae with potent antitumor, antiviral, and immunomodulatory activities. However, no chemical synthesis of ulvan saccharides has been reported to date. In this paper, we performed the first efficient synthesis of the unique sulfated tetrasaccharide motif of type B ulvanobiuronic acid 3-sulfate. Based on the gold(i)-catalyzed glycosylation with glycosyl ynenoates as donors, efficient construction of the challenging α-(1 → 4)-glycosidic bonds between iduronic acid and rhamnose building blocks was achieved to afford the tetrasaccharide skeleton in a stereospecific manner. The synthetic sulfated tetrasaccharide was found to significantly improve the phagocytic activity of macrophage RAW264.7 cells.

Synthesis of bacterial cell surface l

In recent years, high energy consumption has gradually become a prominent problem in a data center. With the advent of cloud computing, computing and storage resources are bringing greater challenges to energy consumption. Virtual machine (VM) initial placement plays an important role in affecting the size of energy consumption. In this paper, we use binary particle swarm optimization (BPSO) algorithm to design a VM placement strategy for low energy consumption measured by proposed energy efficiency fitness, and this strategy needs multiple iterations and updates for VM placement. Finally, the strategy proposed in this paper is compared with other four strategies through simulation experiments. The results show that our strategy for VM placement has better performance in reducing energy consumption than the other four strategies, and it can use less active hosts than others.

Due to the increasing sizes of cloud data centers, the number of virtual machines (VMs) and applications rises quickly. The rapid growth of large scale Internet services results in unbalanced load of network resource. The bandwidth utilization rate of some physical hosts is too high, and this causes network congestion. This paper presents a layered VM migration algorithm (LVMM). At first, the algorithm will divide the cloud data center into several regions according to the bandwidth utilization rate of the hosts. Then we balance the load of network resource of each region by VM migrations, and ultimately achieve the load balance of network resource in the cloud data center. Through simulation experiments in different environments, it is proved that the LVMMalgorithm can effectively balance the load of network resource in cloud computing.

A [4 + 3] synthesis of D-manno-heptulose is described. The cascade aldol/hemiketalization reaction of a C4 aldehyde with a C3 ketone provides the differentially protected ketoheptose building block, which can be further reacted to furnish target D-manno-heptulose.

A practical and efficient synthesis of chloro(organophosphine) gold(I) complexes is reported. Employment of 4,4′-dihydroxydiphenyl sulfide as a safe and non-irritating reductant is highlighted for the generation of Au(I)–S intermediates, which could be trapped by mono- and bidentate phosphine ligands to provide organophosphine gold(I) complexes. The utility of the present method is further demonstrated by the synthesis of the antiarthritic drug auranofin.

Data replication technology has been widely used in cloud storage system. How to select the appropriate data center to place data replication to effectively improve the access performance of cloud storage system became a problem which is worthy of study. To solve this problem we presented a replica placement algorithm based on load balance in this paper. According to the capital value of the data center, the algorithm selects a new replica node and can ensure load balance between the data centers. Related simulation experiments show that the algorithm can quickly and effectively respond to user requests and it is reliable and efficient.

High-level programming is one of the critical building blocks of the effective use of software-defined networking (SDN). Existing solutions, however, either (1) cannot utilize the state-of-the-art switches with flow table pipelining, a key technique to prevent flow rule set explosion or (2) force programmers to manually organize and manage hardware flow table pipelines, which is time-consuming and error-prone. This paper presents a high-level SDN programming framework to address these issues. The framework can automatically (1) generate rule sets for heterogeneous switches with different flow table pipelining designs and (2) update installed rules when the network state changes. As a result, the framework can not only generate efficient rule sets for switches but also provide programmers a centralized, intuitive, and hence easy-to-use programming API. Experiments show that the framework can generate compact rule sets that are 29–116 times smaller than those generated by other open-source SDN controllers. Besides, the framework is 5 times faster to recover from network link failures in comparison to other controllers.

Nowadays, 10Gbps and higher speed network devices have become ubiquitous. These devices typically exploit multiple CPU cores to process packets to avoid overwhelming a single CPU core. The involving of multiple cores, however, brings tricky parallel programming issues. One of them is the miscount in statistical counter, which is the algorithm that has been widely used in high-speed network devices to track fundamental information such as the number of packets received and transmitted. As a result, modern high-speed network devices merely provides weak consistency guarantee on the counting results it returns; that is, the returned results may be inaccurate. This paper first analyses the miscount issue in modern high-speed network devices. Then we present ECCount, a novel counting algorithm which (1) is competitive to the best known solutions in performance, and (2) provides strong consistency guarantee in counting results returned. Experiments show that it takes ECCount 10ns and 1,500ns to perform an update operation and a read operation, respectively. And the counting results returned are accurate.

A [4 + 3] synthesis of D-manno-heptulose is described. The cascade aldol/hemiketalization reaction of a C4 aldehyde with a C3 ketone provides the differentially protected ketoheptose building block, which can be further reacted to furnish target D-manno-heptulose.

Haskell threads provide a key, lightweight concurrency abstraction to simplify the programming of important network applications such as web servers and software-defined network (SDN) controllers. The flagship Glasgow Haskell Compiler (GHC) introduces a run-time system (RTS) to achieve a high-performance multicore implementation of Haskell threads, by introducing effective components such as a multicore scheduler, a parallel garbage collector, an IO manager, and efficient multicore memory allocation. Evaluations of the GHC RTS, however, show that it does not scale well on multicore processors, leading to poor performance of many network applications that try to use lightweight Haskell threads. In this paper, we show that the GHC IO manager, which is a crucial component of the GHC RTS, is the scaling bottleneck. Through a series of experiments, we identify key data structure, scheduling, and dispatching bottlenecks of the GHC IO manager. We then design a new multicore IO manager named Mio that eliminates all these bottlenecks. Our evaluations show that the new Mio manager improves realistic web server throughput by 6.5x and reduces expected web server response time by 5.7x. We also show that with Mio, McNettle (an SDN controller written in Haskell) can scale effectively to 40+ cores, reach a throughput of over 20 million new requests per second on a single machine, and hence become the fastest of all existing SDN controllers.

Software-Defined Networking offers the appeal of a simple, centralized programming model for managing complex networks. However, challenges in managing low-level details, such as setting up and maintaining correct and efficient forwarding tables on distributed switches, often compromise this conceptual simplicity. In this pa- per, we present Maple, a system that simplifies SDN programming by (1) allowing a programmer to use a standard programming language to design an arbitrary, centralized algorithm, which we call an algorithmic policy , to decide the behaviors of an entire network, and (2) providing an abstraction that the programmer-defined, centralized policy runs, conceptually, "afresh" on every packet entering a network, and hence is oblivious to the challenge of translating a high-level policy into sets of rules on distributed individual switches. To implement algorithmic policies efficiently, Maple includes not only a highly-efficient multicore scheduler that can scale efficiently to controllers with 40+ cores, but more importantly a novel tracing runtime optimizer that can automatically record reusable policy decisions, offload work to switches when possible, and keep switch flow tables up-to-date by dynamically tracing the dependency of policy decisions on packet contents as well as the environment (system state). Evaluations using real HP switches show that Maple optimizer reduces HTTP connection time by a factor of 100 at high load. During simulated benchmarking, Maple scheduler, when not running the optimizer, achieves a throughput of over 20 million new flow requests per second on a single machine, with 95-percentile latency under 10 ms.

Objective: This meta-analysis examined the relationship between excess body weight or body mass index (BMI) and risk of thyroid cancer. METHODS: PubMed®, MEDLINE®, EMBASE™ and Academic Search™ Premier databases were searched to identify cohort studies examining the effect of being overweight or obese on the risk of thyroid cancer. RESULTS: The inclusion criteria were met by seven cohort studies (total number of thyroid cancer cases, 5154). The pooled relative risk (RR) of thyroid cancer was 1.13 (95% confidence interval [CI] 1.04, 1.22) for overweight. Obesity was also linked with increased thyroid cancer risk in males and females, the strength of the association increasing with increasing BMI. The combined RR of thyroid cancer was 1.18 (95% CI 1.11, 1.25) for excess body weight (overweight and obesity combined). Being overweight was associated with a significant increase in thyroid cancer risk among non-Asians, but not among Asians. Overweight, obesity and excess body weight were all associated with papillary thyroid carcinoma risk. CONCLUSIONS: The association between overweight/ obesity/excess body weight and thyroid cancer risk was confirmed.

Core-to-core communication is critical to the effective use of multi-core processors. A number of software based concurrent lock-free queues have been proposed to address this problem. Existing solutions, however, suffer from performance degradation in real testbeds, or rely on auxiliary hardware or software timers to handle the deadlock problem when batching is used, making those solutions good in theory but difficult to use in practice. This paper describes the pros and cons of existing concurrent lock-free queues in both dummy and real testbeds and proposes B-Queue, an efficient and practical single-producer-single-consumer concurrent lock-free queue that solves the deadlock problem gracefully by introducing a self-adaptive backtracking mechanism. Experiments show that in real massively-parallel applications, B-Queue is faster than FastForward and MCRingBuffer, the two state-of-the-art concurrent lock-free queues, by up to 10x and 5x, respectively. Moreover, B-Queue outperforms FastForward and MCRingBuffer in terms of stability and scalability, making it a good candidate for fast core-to-core communication on multi-core architectures.

A uniform approach to cyclotomic extensions of diagram algebras is given, focussing on cellular structures. Cyclotomic Temperley–Lieb algebras, cyclotomic Brauer algebras and cyclotomic walled Brauer algebras are discussed as examples.

A typical hash based TCP lookup algorithm is hard to make a trade-off between speed and space. This paper presents DHash, a high-efficient TCP lookup algorithm that aims at supporting large number of sessions in high speed networks. DHash achieves this goal by designing a compact and cache-friendly lookup data structure that well fits the modern computer architectures. To show the power of DHash, we implement it in a user-space TCP/IP stack, and then parallelize the stack on the Intel multicore processors. Experiments show that DHash is able to achieve 16.3Mpps while handling one million concurrent sessions on our parallel platform.

Software defined networking (SDN) introduces centralized controllers to dramatically increase network programmability. The simplicity of a logical centralized controller, however, can come at the cost of control-plane scalability. In this demo, we present McNettle, an extensible SDN control system whose control event processing throughput scales with the number of system CPU cores and which supports control algorithms requiring globally visible state changes occurring at flow arrival rates. Programmers extend McNettle by writing event handlers and background programs in a high-level functional programming language extended with shared state and memory transactions. We implement our framework in Haskell and leverage the multicore facilities of the Glasgow Haskell Compiler (GHC) and runtime system. Our implementation schedules event handlers, allocates memory, optimizes message parsing and serialization, and reduces system calls in order to optimize cache usage, OS processing, and runtime system overhead. Our experiments show that McNettle can serve up to 5000 switches using a single controller with 46 cores, achieving throughput of over 14 million flows per second, near-linear scaling up to 46 cores, and latency under 200 μs for light loads and 10 ms with loads consisting of up to 5000 switches.

Parsing packet payloads according to the syntax and semantics of an application protocol is a key step in analyzing network traffic. However, it is still a challenge to fulfill this task with high speed(10Gbps+) because parsing packets through deep-content analysis to build a corresponding syntax tree requires tremendous computing resources. Multi-core architectures provide a viable solution for building high-performance parsers for application protocols. Existing sequential application protocol parsers are hard to be reused, and building a new protocol parser from scratch is error-prone and time-consuming. This paper proposes a general and efficient approach to building high-performance parallel application protocol parsers on multi-core platforms. First, the open-source lexical analyzer FLEX is used to describe a protocol and generate a sequential parser. Then a source-to-source translation is performed to transform the sequential parser into a parallel one. Finally, an efficient parallel run-time system is built by employing lock-free design principles from top to bottom to support multi-threaded execution on multi-core processors. Experimental results show that our parsers achieve nearly 20Gbps for average HTTP packets and 5Gbps for the challenging smaller FIX packets.

By employing a generalized Riccati technique and an integral averaging technique, some new oscillation criteria are established for the second-order matrix differential systemU′=A(x)U+B(t)V,V′=C(x)U−A∗(t)V, whereA(t),B(t), andC(t)are(n×n)-matrices, andB,Care Hermitian. These results are sharper than some previous results.

Designing of sliding mode variable structure controller for linear discrete uncertain time-delay singular system is studied. Firstly, a new restricted system equivalent form is developed and the system is decomposed into two low dimensional subsystems: one is a difference system without input; the other is a difference system with input. Secondly, under assumption that structural perturbation matrices are bounded, switching function with difference compensator is designed, which guarantee the system is asymptotically stable in quasi-switching manifold. Thirdly, sliding mode variable structure controller is designed, which can force solution trajectory of the system to enter into a small neighborhood of the quasi-switching manifold in finite steps and to converge to a small chattering in the neighborhood ultimately. Finally, a numerical example is given to demonstrate feasibility and simplicity of the design method.