695 research outputs found
On a New Weighted Hilbert Inequality
It is shown that a weighted Hilbert inequality for double series can be established by introducing a proper weight function. Thus, a quite sharp result of the classical Hilbert inequality for double series is obtained. And a similar result for the Hilbert integral inequality is also proved. Some applications are considered
Expression of endo-1, 4-beta-xylanase from Trichoderma reesei in Pichia pastoris and functional characterization of the produced enzyme
<p>Abstract</p> <p>Background</p> <p>In recent years, xylanases have attracted considerable research interest because of their potential in various industrial applications. The yeast <it>Pichia pastoris </it>can neither utilize nor degrade xylan, but it possesses many attributes that render it an attractive host for the expression and production of industrial enzymes.</p> <p>Results</p> <p>The Xyn2 gene, which encodes the main <it>Trichoderma reesei </it>Rut C-30 endo-β-1, 4-xylanase was cloned into the pPICZαA vector and expressed in <it>Pichia pastoris</it>. The selected <it>P. pastoris </it>strains produced as 4,350 nkat/ml β-xylanase under the control of the methanol inducible alcohol oxidase 1 (<it>AOX1</it>) promoter. The secreted recombinant Xyn2 was estimated by SDS-PAGE to be 21 kDa. The activity of the recombinant Xyn2 was highest at 60°C and it was active over a broad range of pH (3.0–8.0) with maximal activity at pH 6.0. The enzyme was quite stable at 50°C and retained more than 94% of its activity after 30 mins incubation at this temperature. Using Birchwood xylan, the determined apparent <it>K</it><sub>m </sub>and k<sub>cat </sub>values were 2.1 mg/ml and 219.2 S<sup>-1</sup>, respectively. The enzyme was highly specific towards xylan and analysis of xylan hydrolysis products confirmed as expected that the enzyme functions as endo-xylanase with xylotriose as the main hydrolysis products. The produced xylanase was practically free of cellulolytic activity.</p> <p>Conclusion</p> <p>The <it>P. pastoris </it>expression system allows a high level expression of xylanases. Xylanase was the main protein species in the culture supernatant, and the functional tests indicated that even the non-purified enzyme shows highly specific xylanase activity that is free of cellulolytic side acitivities. Therefore, <it>P pastoris </it>is a very useful expression system when the goal is highly specific and large scale production of glycosyl hydrolases.</p
State Estimation of Wireless Sensor Networks in the Presence of Data Packet Drops and Non-Gaussian Noise
Distributed Kalman filter approaches based on the maximum correntropy
criterion have recently demonstrated superior state estimation performance to
that of conventional distributed Kalman filters for wireless sensor networks in
the presence of non-Gaussian impulsive noise. However, these algorithms
currently fail to take account of data packet drops. The present work addresses
this issue by proposing a distributed maximum correntropy Kalman filter that
accounts for data packet drops (i.e., the DMCKF-DPD algorithm). The
effectiveness and feasibility of the algorithm are verified by simulations
conducted in a wireless sensor network with intermittent observations due to
data packet drops under a non-Gaussian noise environment. Moreover, the
computational complexity of the DMCKF-DPD algorithm is demonstrated to be
moderate compared with that of a conventional distributed Kalman filter, and we
provide a sufficient condition to ensure the convergence of the proposed
algorithm
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The influence of street layouts and viaduct settings on daily carbon monoxide exposure and intake fraction in idealized urban canyons
Environmental concerns have been raised on the adverse health effects of vehicle emissions in micro-scale traffic-crowded street canyons, especially for pedestrians and residents living in near-road buildings. Viaduct design is sometimes used to improve transportation efficiency but possibly affects urban airflow and the resultant exposure risk, which have been rarely investigated so far. The personal intake fraction (P_IF) is defined as the average fraction of total emissions that is inhaled by each person of a population (1ppm=1×10-6), and the daily carbon monoxide (CO ) pollutant exposure (Et) is estimated by multiplying the average concentration of a specific micro-environment within one day. As a novelty, by considering time activity patterns and breathing rates in various micro-environments for three age groups, this paper introduces IF and Et into computational fluid dynamic (CFD) simulation to quantify the impacts of street layouts (street width/ building height W/H=1, 1.5, 2), source location, viaduct settings and noise barriers on the source-exposure correlation when realistic CO sources are defined. Narrower streets experience larger P_IF (1.51-5.21 ppm) and CO exposure, and leeward-side buildings always attain higher vehicular pollutant exposure than windward-side. Cases with a viaduct experience smaller P_IF (3.25-1.46 ppm) than cases without a viaduct (P_IF=5.21-2.23 ppm) if the single ground-level CO source is elevated onto the viaduct. With two CO sources (both ground-level and viaduct-level), daily CO exposure rises 2.80-3.33 times but P_IF only change slightly. Noise barriers above a viaduct raise concentration between barriers, but slightly reduce vehicular exposure in near-road buildings. Because people spend most of their time indoors, vehicular pollutant exposure within near-road buildings can be 6-9 times that at pedestrian level. Although further studies are still required to provide practical guidelines, this paper provides effective methodologies to quantify the impacts of street/viaduct configurations on human exposure for urban design purpose
Development of a Sensitive Phospho-p70 S6 Kinase ELISA to Quantify mTOR Proliferation Signal Inhibition
Background: Drug blood levels can only serve as a surrogate because of the lack of information on the drug's direct pharmacological effects in the individual patient. Measurement of the mammalian target of rapamycin (mTOR) activity dependent on the phosphorylation status of p70 S6 kinase (p70 S6K) offers a practical way for monitoring pharmacodynamic drug activity, with the potential to better assess the state of immunosuppression in individual patients. Material and Methods: Here, we established a novel in vitro model system by treating Jurkat cells and peripheral blood mononuclear cells with different concentrations of sirolimus after stimulation with phorbol 12-myristate 13-acetate. Results: A dose-dependent reduction of the p70 S6K phosphorylation status was demonstrated by Western blot and a newly established enzyme-linked immunosorbent assay (ELISA). Relative phospho-p70 S6K values from ELISA and relative densities from Western blot analysis in peripheral blood mononuclear cells revealed a strong correlation (Spearman correlation coefficient r(s) = 0.7, P = 0.01). Finally, parallel assays confirmed a sirolimus dose-dependent reduction of cytokine production and cell proliferation in the in vitro model. Conclusions: Pharmacodynamic monitoring of mTOR inhibition with a p70 S6K ELISA could guide mTOR inhibitor immunosuppression therapy toward a more individualized therapy. The usage of this technique now has to be evaluated in a clinical series of patients
Distributed fusion filter over lossy wireless sensor networks with the presence of non-Gaussian noise
The information transmission between nodes in a wireless sensor networks
(WSNs) often causes packet loss due to denial-of-service (DoS) attack, energy
limitations, and environmental factors, and the information that is
successfully transmitted can also be contaminated by non-Gaussian noise. The
presence of these two factors poses a challenge for distributed state
estimation (DSE) over WSNs. In this paper, a generalized packet drop model is
proposed to describe the packet loss phenomenon caused by DoS attacks and other
factors. Moreover, a modified maximum correntropy Kalman filter is given, and
it is extended to distributed form (DM-MCKF). In addition, a distributed
modified maximum correntropy Kalman filter incorporating the generalized data
packet drop (DM-MCKF-DPD) algorithm is provided to implement DSE with the
presence of both non-Gaussian noise pollution and packet drop. A sufficient
condition to ensure the convergence of the fixed-point iterative process of the
DM-MCKF-DPD algorithm is presented and the computational complexity of the
DM-MCKF-DPD algorithm is analyzed. Finally, the effectiveness and feasibility
of the proposed algorithms are verified by simulations
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