Numerical Algorithms - Iterative algorithms based on thresholding, feedback, and null space tuning (NST+HT+FB) for sparse signal recovery are exceedingly effective and efficient, particularly for... 相似文献
A novel, sensitive electrochemical DNA hybridization detection assay, using silver nanoparticles as the oligonucleotide labeling tag, is described. The assay relies on the hybridization of the target DNA with the silver nanoparticle-oligonucleotide DNA probe, followed by the release of the silver metal atoms anchored on the hybrids by oxidative metal dissolution and the indirect determination of the solubilized Ag(I) ions by anodic stripping voltammetry (ASV) at a carbon fiber ultramicroelectrode. The influence of the relevant experimental variables, including the surface coverage of the target oligonucleotide, the duration of the silver dissolution steps and the parameters of the electrochemical stripping measurement of the silver(I) ions, is examined and optimized. The combination of the remarkable sensitivity of the stripping metal analysis at the microelectrode with the large number of silver(I) ions released from each DNA hybrid allows detection at levels as low as 0.5 pmol L(-1) of the target oligonucleotides. 相似文献
A novel sulfur-bearing secondary antioxidant with a high molecular weight of 2252 (OS-POSS), successfully synthesized via photoinitiated thiol-ene click reaction, was compared with two commercial sulfur-bearing secondary antioxidants on the stabilization of polypropylene (PP). The results of their oxidation induction time (OIT) via differential scanning calorimeter measurement (DSC) showed that the higher the molecular weight of secondary antioxidant is, the longer the OIT value, whether such sulfur-bearing antioxidant is used singly or in combination with primary antioxidant. The study of their long-term accelerated thermal aging in the air oven at 150 °C displayed that the molecular structure of sulfur-bearing secondary antioxidant, besides molecular weight, is another highly important factor determining the antioxidant efficiency, i.e., physical loss of antioxidants with the relatively low molecular weight may determine antioxidant efficiency, whereas thioether groups having neighboring ester carbonyl moieties may decompose more hydroperoxides with quicker rate. 相似文献
Hydrogen peroxide and hydroxyl radical, both important members of the reactive oxygen species (ROS) family, can cause serious oxidative damages in biological systems. In order to proclaim and prevent oxidation stress, researches on the biomolecule oxidation induced by H2O2 or OH. are in crucial need. However, due to the high reactivity of ROS, traditional methods are difficult to achieve the in situ quantitative investigations on those reactions involving ROS. In this work, using scanning electrochemical microscopy technique (SECM) in a tip generation‐substrate collection mode (TG‐SC), the controllable release and the high‐efficiency collection of electrogenerated H2O2 were achieved. Compared to ex situ fluorescence method, SECM improved the collection efficiency approximately two times larger. Based on it, SECM combined with surface plasmon resonance (SPR) was employed to in situ monitor the protein oxidation (taking Cu12+? MT as a model) induced by H2O2. OH., which was generated from the interaction between H2O2 and Cu12+? MT, can attack the peptide chain and induced the unrepairable protein oxidation damage. The whole process was quantitatively characterized by SPR, and the linear relationship between SPR dip shift and the amounts of released H2O2 was successfully built. Our work proves that the combined SECM‐SPR technique can realize the in situ quantitative determinations of the biomolecule oxidation induced by ROS, which affords an avenue for further elucidation on the mechanisms of oxidation stress in organisms. 相似文献
34,354,966 active cases and 460,787 deaths because of COVID-19 pandemic were recorded on November 06, 2021, in India. To end this ongoing global COVID-19 pandemic, there is an urgent need to implement multiple population-wide policies like social distancing, testing more people and contact tracing. To predict the course of the pandemic and come up with a strategy to control it effectively, a compartmental model has been established. The following six stages of infection are taken into consideration: susceptible (S), asymptomatic infected (A), clinically ill or symptomatic infected (I), quarantine (Q), isolation (J) and recovered (R), collectively termed as SAIQJR. The qualitative behavior of the model and the stability of biologically realistic equilibrium points are investigated in terms of the basic reproduction number. We performed sensitivity analysis with respect to the basic reproduction number and obtained that the disease transmission rate has an impact in mitigating the spread of diseases. Moreover, considering the non-pharmaceutical and pharmaceutical intervention strategies as control functions, an optimal control problem is implemented to mitigate the disease fatality. To reduce the infected individuals and to minimize the cost of the controls, an objective functional has been constructed and solved with the aid of Pontryagin’s maximum principle. The implementation of optimal control strategy at the start of a pandemic tends to decrease the intensity of epidemic peaks, spreading the maximal impact of an epidemic over an extended time period. Extensive numerical simulations show that the implementation of intervention strategy has an impact in controlling the transmission dynamics of COVID-19 epidemic. Further, our numerical solutions exhibit that the combination of three controls are more influential when compared with the combination of two controls as well as single control. Therefore, the implementation of all the three control strategies may help to mitigate novel coronavirus disease transmission at this present epidemic scenario.
Summary. In this paper, we derive a posteriori error estimates for the finite element approximation of quadratic optimal control problem
governed by linear parabolic equation. We obtain a posteriori error estimates for both the state and the control approximation.
Such estimates, which are apparently not available in the literature, are an important step towards developing reliable adaptive
finite element approximation schemes for the control problem.
Received July 7, 2000 / Revised version received January 22, 2001 / Published online January 30, 2002
RID="*"
ID="*" Supported by EPSRC research grant GR/R31980 相似文献
In this paper, adaptive finite element method is developed for the estimation of distributed parameter in elliptic equation.
Both upper and lower error bound are derived and used to improve the accuracy by appropriate mesh refinement. An efficient
preconditioned project gradient algorithm is employed to solve the nonlinear least-squares problem arising in the context
of parameter identification problem. The efficiency of our error estimators is demonstrated by some numerical experiments.
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