533 research outputs found
Using Low-Cost Renewable Energy for Waste Valorization
With renewable electricity costing 2 cents per kwh to even negative in some places during some periods, how to use cheap renewable energy to maximize waste valorization can become an interesting direction. In this talk, I will discuss some recent progress in identifying the synergy between microbial electrochemistry and photoelectrochemistry that led to the development of new materials and systems for spontaneous high rate H2 production from wastewater and sunlight. I will also report some development on functional hydrophobic gas transfer membrane electrodes that enabled specific resource recoveries from wastewater and CO2. While we have been focusing on energy-neutral wastewater treatment, I argue maybe we can start to think broadly on carbon-negative and dollar-positive wastewater treatment beyond energy production
Energy-Efficient Flow Scheduling and Routing with Hard Deadlines in Data Center Networks
The power consumption of enormous network devices in data centers has emerged
as a big concern to data center operators. Despite many
traffic-engineering-based solutions, very little attention has been paid on
performance-guaranteed energy saving schemes. In this paper, we propose a novel
energy-saving model for data center networks by scheduling and routing
"deadline-constrained flows" where the transmission of every flow has to be
accomplished before a rigorous deadline, being the most critical requirement in
production data center networks. Based on speed scaling and power-down energy
saving strategies for network devices, we aim to explore the most energy
efficient way of scheduling and routing flows on the network, as well as
determining the transmission speed for every flow. We consider two general
versions of the problem. For the version of only flow scheduling where routes
of flows are pre-given, we show that it can be solved polynomially and we
develop an optimal combinatorial algorithm for it. For the version of joint
flow scheduling and routing, we prove that it is strongly NP-hard and cannot
have a Fully Polynomial-Time Approximation Scheme (FPTAS) unless P=NP. Based on
a relaxation and randomized rounding technique, we provide an efficient
approximation algorithm which can guarantee a provable performance ratio with
respect to a polynomial of the total number of flows.Comment: 11 pages, accepted by ICDCS'1
Identification et optimisation des propriétés dynamiques des matériaux viscoélastiques
In the automotive, railway and aerospace industries, interior noise is an important consideration in design and operation. Among the available technologies to reduce the structure-borne vibration and noise, the use of Metal-Polymer Sandwich (MPS) panels is attracting more interest from Original Equipment Manufacturers (OEMs). As for constrained-layer damping (CLD) treatments, besides developing more accurate models (theoretical and finite element) to simulate the vibroacoustic performance, it is very important to 'accurately identify the properties of the constituent materials of an MPS. Since the core materials in MPS exhibit viscoelastic properties which vary significantly with temperature and frequency, it is necessary to develop experimental and/or optimization methods to characterize the dynamic properties so that they may be well matched to specific noise and vibration control applications. This is the objective of this thesis.In this thesis, a simple free-free beam based setup, together with an identification algorithm has been developed to identify the dynamic properties of core materials from the measured frequency response functions. The setup involved circumventing some drawbacks of the traditional clamped-free setup.In particular, a new optimization method is brought' forward wherein a four-parameter fractional derivative model plus a three-parameter Williams-Landel-Ferry (WLF) equation are used to describe the temperature and frequency dependent behaviour of core materials. Therefore, few parameters are optimized for the temperature and frequency dependent properties. The objective function in the optimization is based on the so-called amplitude correlation coefficient which can be calculated directly by the frequency response functions. The normal mode superposition method taking the added mass into account, as well as Ross-Kerwin-Ungar (RKU) equations, as a solver, is used to calculate the predicted frequency response functions. The Pattern Search algorithm is used to find the best values of design parameters. This algorithm is a global optimization algorithm and is less sensitive to the initial values of design parameters. Numerical examples and tests on several MPS panels were used to validate the free-free setup and optimization method by systematic comparison with the ASTM E756-04 Standard and with DMA when the latter is possible. However, with some MPS panels, the proposed method failed to provide satisfactory results. It was further postulated that the manufacturing process of these MPS panels may somehow have modified the properties or the constitutive law of the polymer itself
Competitive Exclusion in a DAE Model for Microbial Electrolysis Cells
Microbial electrolysis cells (MECs) employ electroactive bacteria to perform
extracellular electron transfer, enabling hydrogen generation from
biodegradable substrates. In previous work, we developed and analyzed a
differential-algebraic equation (DAE) model for MECs. The model resembles a
chemostat with ordinary differential equations (ODEs) for concentrations of
substrate, microorganisms, and an extracellular mediator involved in electron
transfer. There is also an algebraic constraint for electric current and
hydrogen production. Our goal is to determine the outcome of competition
between methanogenic archaea and electroactive bacteria, because only the
latter contribute to electric current and resulting hydrogen production. We
investigate asymptotic stability in two industrially relevant versions of the
model. An important aspect of chemostats models is the principle of competitive
exclusion -- only microbes which grow at the lowest substrate concentration
will survive as . We show that if methanogens grow at the lowest
substrate concentration, then the equilibrium corresponding to competitive
exclusion by methanogens is globally asymptotically stable. The analogous
result for electroactive bacteria is not necessarily true. We show that local
asymptotic stability of exclusion by electroactive bacteria is not guaranteed,
even in a simplified version of the model. In this case, even if electroactive
bacteria can grow at the lowest substrate concentration, a few additional
conditions are required to guarantee local asymptotic stability. We also
provide numerical simulations supporting these arguments. Our results suggest
operating conditions that are most conducive to success of electroactive
bacteria and the resulting current and hydrogen production in MECs. This will
help identify when methane production or electricity and hydrogen production
are favored
Electrocoagulation: A promising method to treat and reuse mineral processing wastewater with high COD
Mineral processing wastewater contains large amounts of reagents which can lead to severe environmental problems, such as high chemical oxygen demand (COD). Inspired by the wastewater treatment in such industries as those of textiles, food, and petrochemistry, in the present work, electrocoagulation (EC) is applied for the first time to explore its feasibility in the treatment of wastewater with an initial COD of 424.29 mg/L from a Pb/Zn sulfide mineral flotation plant and its effect on water reuse. Typical parameters, such as anode materials, current density, initial pH, and additives, were characterized to evaluate the performance of the EC method. The results showed that, under optimal conditions, i.e., iron anode, pH 7.1, electrolysis time 70 min, 19.23 mA/cm2 current density, and 4.1 g/L activated carbon, the initial COD can be reduced to 72.9 mg/L, corresponding to a removal rate of 82.8%. In addition, compared with the untreated wastewater, EC-treated wastewater was found to benefit the recovery of galena and sphalerite, with galena recovery increasing from 25.01% to 36.06% and sphalerite recovery increasing from 59.99% to 65.33%. This study confirmed that EC is a promising method for the treatment and reuse of high-COD-containing wastewater in the mining industry, and it possesses great potential for wide industrial applications
Meta-analysis of the relationship between interleukin-6 levels and the prognosis and severity of acute coronary syndrome
This study aimed to explore the relationship between plasma interleukin 6 (IL-6) levels, adverse cardiovascular events, and the severity of acute coronary syndrome (ACS). A literature review was performed of studies regarding IL-6 and ACS extracted from databases including EMBASE, Cqvip, MEDLINE, Web of Knowledge, PubMed, Cochrane Library, China National Knowledge Infrastructure, and Wanfang data. The Newcastle-Ottawa scale (NOS) was used to evaluate the quality of the literature. The literature was screened, its quality was evaluated, and relevant data were extracted for performing meta-analysis using RevMan software (version 5.3). A total of 524 studies were included in the initial survey. After several rounds of screening and analysis, six studies met the inclusion criteria and underwent meta-analysis using a fixed-effect model. Patients were divided into non-severe and severe groups based on the concentration of high-sensitivity C-reactive protein. Meta-analysis of the relationship between IL-6 and the severity of ACS showed that the plasma IL-6 level of patients in the severe group was significantly higher than that of patients in the non-severe group (p<0.00001). Additionally, patients with experience of major adverse cardiovascular events had significantly higher plasma IL-6 levels than did patients without experience of such events (p<0.00001). In summary, patients with ACS and high IL-6 levels tended to be in a critical condition, with a higher risk of adverse cardiovascular events and worse prognosis. Thus, IL-6 levels could indicate whether patients with ACS may have adverse cardiovascular events and determine the severity of ACS
Intrinsic chemoresistance to gemcitabine is associated with constitutive and laminin-induced phosphorylation of FAK in pancreatic cancer cell lines
<p>Abstract</p> <p>Background</p> <p>One of the major reasons for poor prognosis of pancreatic cancer is its high resistance to currently available chemotherapeutic agents. In recent years, focal adhesion kinase (FAK), a central molecule in extracellular matrix (ECM)/integrin-mediated signaling, has been thought to be a key determinant of chemoresistance in cancer cells. In this study, we aimed to determine the roles of FAK phosphorylation in the intrinsic chemoresistance of pancreatic cancer cell lines.</p> <p>Results</p> <p>Our results showed that, the level of constitutive phosphorylation of FAK at Tyr397 correlated with the extent of intrinsic resistance to Gemcitabine (Gem) in four pancreatic cancer cell lines. Moreover, in Panc-1 cells, which had high expression of pFAK, specific inhibition of constitutive FAK phosphorylation by either RNAi or FRNK overexpression decreased the phosphorylation of Akt, reduced the levels of survivin expression and Bad phosphorylation at Ser136 and increased Gem-induced cytotoxicity and apoptosis. However, in AsPC-1 cells with a low level of pFAK, neither FAK RNAi nor FRNK overexpression affected Gem-induced cell apoptosis. We further found that laminin (LN) induced FAK and Akt phosphorylation in a time-dependent manner, increased the levels of survivin and pBad (pS136) and decreased Gem-induced cytotoxicity and apoptosis in AsPC-1 cells; Specific inhibition of LN-induced FAK phosphorylation by either FAK RNAi or FRNK overexpression suppressed the effects of LN on AsPC-1 cells. Moreover, inhibition of constitutive FAK phosphorylation in Panc-1 cells and LN-induced FAK phosphorylation in AsPC-1 cells by a novel and more specific FAK phosphorylation inhibitor PF-573,228 showed similar results with those of FAK phosphorylation inhibition by FAK RNAi or FRNK overexpression.</p> <p>Conclusions</p> <p>In conclusion, our research demonstrates for the first time that both constitutive and LN-induced FAK phosphorylation contribute to increased intrinsic chemoresistance to Gem in pancreatic cancer cell lines and these effects are partly due to the regulation of Akt and Bad phosphorylation and survivin expression. Development of selective FAK phosphorylation inhibitors may be a promising way to enhance chemosensitivity in pancreatic cancer.</p
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