Efficient Semantic-based Content Search in P2P Network

Most existing Peer-to-Peer (P2P) systems support only title-based searches and are limited in functionality when compared to today’s search engines. In this paper, we present the design of a distributed P2P information sharing system that supports semantic-based content searches of relevant documents. First, we propose a general and extensible framework for searching similar documents in P2P network. The framework is based on the novel concept of Hierarchical Summary Structure. Second, based on the framework, we develop our efficient document searching system, by effectively summarizing and maintaining all documents within the network with different granularity. Finally, an experimental study is conducted on a real P2P prototype, and a large-scale network is further simulated. The results show the effectiveness, efficiency and scalability of the proposed system.Singapore-MIT Alliance (SMA

The Incentive Guarantees Behind Nash Welfare in Divisible Resources Allocation

We study the problem of allocating divisible resources among $n$ agents, hopefully in a fair and efficient manner. With the presence of strategic agents, additional incentive guarantees are also necessary, and the problem of designing fair and efficient mechanisms becomes much less tractable. While the maximum Nash welfare (MNW) mechanism has been proven to be prominent by providing desirable fairness and efficiency guarantees as well as other intuitive properties, no incentive property is known for it. We show a surprising result that, when agents have piecewise constant value density functions, the incentive ratio of the MNW mechanism is $2$ for cake cutting, where the incentive ratio of a mechanism is defined as the ratio between the largest possible utility that an agent can gain by manipulation and his utility in honest behavior. Remarkably, this result holds even without the free disposal assumption, which is hard to get rid of in the design of truthful cake cutting mechanisms. We also show that the MNW mechanism is group strategyproof when agents have piecewise uniform value density functions. Moreover, we show that, for cake cutting, the Partial Allocation (PA) mechanism proposed by Cole et al., which is truthful and $1/e$-MNW for homogeneous divisible items, has an incentive ratio between $[e^{1 / e}, e]$ and when randomization is allowed, can be turned to be truthful in expectation. Given two alternatives for a trade-off between incentive ratio and Nash welfare provided by the MNW and PA mechanisms, we establish an interpolation between them for both cake cutting and homogeneous divisible items. Finally, we study the existence of fair mechanisms with a low incentive ratio in the connected pieces setting. We show that any envy-free cake cutting mechanism with the connected pieces constraint has an incentive ratio of at least $\Omega(n)$

Effects of intratracheal administration of nuclear factor-kappaB decoy oligodeoxynucleotides on long-term cigarette smoke-induced lung inflammation and pathology in mice

To determine if nuclear factor-κB (NF-κB) activation may be a key factor in lung inflammation and respiratory dysfunction, we investigated whether NF-κB can be blocked by intratracheal administration of NF-κB decoy oligodeoxynucleotides (ODNs), and whether decoy ODN-mediated NF-κB inhibition can prevent smoke-induced lung inflammation, respiratory dysfunction, and improve pathological alteration in the small airways and lung parenchyma in the long-term smoke-induced mouse model system. We also detected changes in transcriptional factors. In vivo, the transfection efficiency of NF-κB decoy ODNs to alveolar macrophages in BALF was measured by fluorescein isothiocyanate (FITC)-labeled NF-κB decoy ODNs and flow cytometry post intratracheal ODN administration. Pulmonary function was measured by pressure sensors, and pathological changes were assessed using histology and the pathological Mias software. NF-κB and activator protein 1(AP-1) activity was detected by the electrophoretic motility shift assay (EMSA). Mouse cytokine and chemokine pulmonary expression profiles were investigated by enzyme-linked immunosorbent assay (ELISA) in bronchoalveolar lavage fluid (BALF) and lung tissue homogenates, respectively, after repeated exposure to cigarette smoke. After 24 h, the percentage of transfected alveolar macrophages was 30.00 ± 3.30%. Analysis of respiratory function indicated that transfection of NF-κB decoy ODNs significantly impacted peak expiratory flow (PEF), and bronchoalveolar lavage cytology displayed evidence of decreased macrophage infiltration in airways compared to normal saline-treated or scramble NF-κB decoy ODNs smoke exposed mice. NF-κB decoy ODNs inhibited significantly level of macrophage inflammatory protein (MIP) 1α and monocyte chemoattractant protein 1(MCP-1) in lung homogenates compared to normal saline-treated smoke exposed mice. In contrast, these NF-κB decoy ODNs-treated mice showed significant increase in the level of tumor necrosis factor-α(TNF-α) and pro-MMP-9(pro-matrix metalloproteinase-9) in mice BALF. Further measurement revealed administration of NF-κB decoy ODNs did not prevent pathological changes. These findings indicate that NF-κB activation play an important role on the recruitment of macrophages and pulmonary dysfunction in smoke-induced chronic lung inflammation, and with the exception of NF-κB pathway, there might be complex mechanism governing molecular dynamics of pro-inflammatory cytokines expression and structural changes in small airways and pulmonary parenchyma in vivo

Efficient display of active lipase LipB52 with a Pichia pastoris cell surface display system and comparison with the LipB52 displayed on Saccharomyces cerevisiae cell surface

<p>Abstract</p> <p>Background</p> <p>For industrial bioconversion processes, the utilization of surface-displayed lipase in the form of whole-cell biocatalysts is more advantageous, because the enzymes are displayed on the cell surface spontaneously, regarded as immobilized enzymes.</p> <p>Results</p> <p>Two <it>Pichia pastoris </it>cell surface display vectors based on the flocculation functional domain of FLO with its own secretion signal sequence or the α-factor secretion signal sequence were constructed respectively. The lipase gene <it>lipB52 </it>fused with the <it>FLO </it>gene was successfully transformed into <it>Pichia pastoris </it>KM71. The lipase LipB52 was expressed under the control of the <it>AOX1 </it>promoter and displayed on <it>Pichia pastoris </it>KM71 cell surface with the two <it>Pichia pastoris </it>cell surface display vectors. Localization of the displayed LipB52 on the cell surface was confirmed by the confocal laser scanning microscopy (CLSM). The LipB52 displayed on the <it>Pichia pastoris </it>cell surface exhibited activity toward <it>p</it>-nitrophenol ester with carbon chain length ranging from C₁₀to C₁₈, and the optimum substrate was <it>p</it>-nitrophenol-caprate (C₁₀), which was consistent with it displayed on the <it>Saccharomyces cerevisiae </it>EBY100 cell surface. The hydrolysis activity of lipase LipB52 displayed on <it>Pichia pastoris </it>KM71-pLHJ047 and KM71-pLHJ048 cell surface reached 94 and 91 U/g dry cell, respectively. The optimum temperature of the displayed lipases was 40°C at pH8.0, they retained over 90% activity after incubation at 60°C for 2 hours at pH 7.0, and still retained 85% activity after incubation for 3 hours.</p> <p>Conclusion</p> <p>The LipB52 displayed on the <it>Pichia pastoris </it>cell surface exhibited better stability than the lipase LipB52 displayed on <it>Saccharomyces cerevisiae </it>cell surface. The displayed lipases exhibited similar transesterification activity. But the <it>Pichia pastoris </it>dry cell weight per liter (DCW/L) ferment culture was about 5 times than <it>Saccharomyces cerevisiae</it>, the lipase displayed on <it>Pichia pastoris </it>are more suitable for whole-cell biocatalysts than that displayed on <it>Saccharomyces cerevisiae </it>cell surface.</p

Prevalence and molecular typing of the antiseptic resistance genes qacA/B among Staphylococcus aureus strains isolated in a teaching hospital

The qacA/B genes are found in Staphylococcus aureus and confer resistance to various antiseptics and disinfectants. Herein, the prevalence of the qacA/B genes in methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) was investigated. Molecular typing systems were used to analyse the relatedness of these qacA/B-positive strains. 176 six strains of clinically isolated S. aureus were collected between July, 2008 and June, 2010. The strains carrying the qacA/B genes were characterised by pulse-field gel electrophoresis (PFGE) typing, Staphylococcus protein A (spa) typing, Panton-Valentine leucocidin (pvl) polymerase chain reaction (PCR) detection, staphylococcal chromosomal cassette (SCC) mec typing, and antimicrobial resistance profiles. Strains carrying the qacA/B genes composed 9.1% of the strains isolated, but the incidence of qacA/B genes in MRSA strains was significantly higher than that in MSSA strains (14.6 versus 4.3%, p &lt; 0.05). Additionally, two predominant PFGE (B and A) and spa types (t037 and t042) were identified along with two major antimicrobial resistance profiles. All of these qacA/B-positive strains strains were pvl-negative by PCR. The qacA/B-positive MRSA strains all contained the group III SCCmec element. These strains were obtained mainly from patients in surgical wards; therefore, the neurosurgical ward and ICU may be considered as a source of MRSA strains carrying the qacA/B genes. Finally, the strain identified as spa type t037 is likely to be an epidemiological clone. The presence of the antiseptic resistance genes qacA/B by MRSA could potentially lead to MRSA strain prevalence. Thus, the optimal usage of antiseptics and disinfectants is warranted. A policy of molecular typing needs to be implemented to track the possible dissemination of these resistance genes.Key words: Staphylococcus aureus, mecA, qacA/B and pvl genes, methicillin-resistant,  Staphylococcus aureus (MRSA), methicillin-sensitive Staphylococcus aureus (MSSA)