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排序方式: 共有595条查询结果,搜索用时 125 毫秒
91.
Widarto HT Van Der Meijden E Lefeber AW Erkelens C Kim HK Choi YH Verpoorte R 《Journal of chemical ecology》2006,32(11):2417-2428
The metabolic alterations of Brassica rapa (L.) leaves attacked by larvae of the specialist Plutella xylostella L. (Lepidoptera: Yponomeutidae) and the generalist Spodoptera exigua Hubner (Lepidoptera: Noctuidae) were investigated with nuclear magnetic resonance (NMR) spectroscopy, followed by a multivariate data analysis. The principal component analysis (PCA) of 1H NMR spectra showed that metabolic changes in B. rapa leaves induced by the 2nd and the 4th instars were different from each other. However, the congestion of the one-dimensional 1H NMR spectrum made it difficult to identify discriminating metabolites. To overcome the spectral complexity, several two-dimensional NMR techniques were applied. Of those evaluated, J-resolved spectroscopy, which affords an additional coupling constant, provided a wide range of structure information on differentiating the metabolites. Based on the J-resolved spectra combined with PCA, the major signals contributing to the discrimination were alanine, threonine, glucose, sucrose, feruloyl malate, sinapoyl malate, and gluconapin. 相似文献
92.
Gary E. Bulman Ed Siivola Ryan Wiitala Rama Venkatasubramanian Michael Acree Nathan Ritz 《Journal of Electronic Materials》2009,38(7):1510-1515
Thin-film Bi2Te3- and Sb2Te3-based superlattice (SL) thermoelectric (TE) devices are an enabling technology for high-power and low-temperature applications,
which include low-noise amplifier cooling, electronics hot-spot cooling, radio frequency (RF) amplifier thermal management,
and direct sensor cooling. Bulk TE devices, which can pump heat loads on the order of 10 W/cm2, are not suitable in these applications due to their large size and low heat pumping capacity. Recently, we have demonstrated
an external maximum temperature difference, ΔT
max, as high as 58 K in an SL thin-film p–n couple. This state-of-the-art couple exhibited a cold-side minimum temperature, T
cmin, of −30.9°C. We regularly attain ΔT
max values in excess of 53 K, in spite of the many significant electrical and thermal parasitics that are unique to thin-film
devices. These measurements do not use any complex thermal management at the heat sink to remove the heat flux from the TE
device’s hot side. We describe here multistage SL cooling technologies currently being developed at RTI that can provide useful
microcooling cold-side temperatures of 200 K. This effort includes a three-stage module employing independently powered stages
which produced a ΔT
max of 101.6 K with a T
cmin of −75°C, as well as a novel two-wire three-stage SL cascade which demonstrated a T
cmin of −46°C and a ΔT
max of nearly 74 K. These RTI modules are only 2.5 mm thick, significantly thinner than a similar commercial three-stage module
(5.3 mm thick) that produces a ΔT
max of 96 K. In addition, TE coolers fabricated from these thin-film SL materials perform significantly better than the extrapolated
performance of similar thickness bulk alloy materials. 相似文献
93.
Monique van Scherpenzeel Ed E. Moret Dr. Lluis Ballell Dr. Rob M. J. Liskamp Prof. Dr. Ulf J. Nilsson Dr. Hakon Leffler Dr. Roland J. Pieters Dr. 《Chembiochem : a European journal of chemical biology》2009,10(10):1724-1733
Light up galectin: Photoprobes based on thiodigalactoside were prepared for galectin‐3, a lectin linked to cancer. The probes contained either benzophenone or acetophenone moieties as the photolabel for covalent attachment to the protein. One particular probe labeled galectin‐3 selectively, even in the presence of cell lysate.
94.
《城市公用事业》编辑部 《城市公用事业》2009,23(5):I0001-I0001
节能减排是指节约能源和减少环境有害物排放。中国“十一五”规划纲要提出,“十一五”期间单位国内生产总值能耗降低20%左右,主要污染物排放总量减少10%。这是贯彻落实科学发展观、构建社会主义和谐社会的重大举措;是建设资源节约型、环境友好型社会,推进经济结构调整,转变增长方式的必由之路。节能减排工作也渗透于城市公用事业发展的各个方面。 相似文献
95.
Marcelo Fernandes Cipreste Michele Rocha de Rezende Marlon Luiz Hneda Anderson Maia Peres Alexandre Alberto Chaves Cotta Verônica de Carvalho Teixeira Waldemar Augusto de Almeida Macedo Edésia Martins Barros de Sousa 《Ceramics International》2018,44(15):17800-17811
Hydroxyapatite (HA) nanoparticles (NPs) doped with different radioisotopes for use as theranostic systems play an important role in scientific research nowadays due to their ability to simultaneously act in the treatment and diagnosis of various types of cancers. In this work, we describe the synthesis and characterization of a hydroxyapatite/tenorite nanocomposite functionalized with folic acid, representing a nanotheranostic material with potential for application as an agent in positron emission tomography imaging systems and to act specifically in the treatment and diagnosis of osteosarcoma. 64Cu and 32P were produced by nuclear activation in the TRIGA reactor at CDTN. The obtained samples were characterized by XRD with Rietveld refinement, XAFS, SEM, BET, TGA, FTIR, CHN, ICP-AES, XPS and gamma spectroscopy. We investigated how CuO grows in HA NPs, the stability of the interactions between CuO and HA constituents and the interactions between folic acid and the surface of the HA NPs. The results indicate the formation of a second phase (tenorite) besides hydroxyapatite, and that the interactions between the two phases are stable, resulting in a nanocomposite. Furthermore, the activation of 64Cu and 32P inside the HA matrix, through the exposition to a neutron flux, produces a theranostic material of interest for biological tests. 相似文献
96.
Giovanna Gomes Lara Gracielle Ferreira Andrade Marcelo Fernandes Cipreste Wellington Marcos da Silva Pedro Lana Gastelois Dawidson Assis Gomes Marcelo Coutinho de Miranda Waldemar Augusto de Almeida Macedo Maria Jose Neves Edésia Martins Barros de Sousa 《Journal of materials science. Materials in medicine》2018,29(8):130
The development of a myriad of nanoparticles types has opened new possibilities for the diagnostics and treatment of many diseases, especially for cancer. However, most of the researches done so far do not focus on the protection of normal cells surrounding a tumor from irradiation bystander effects that might lead to cancer recurrence. Gap-junctions are known to be involved in this process, which leads to genomic instability of neighboring normal cells, and flufenamic acid (FFA) is included in a new group of gap-junction blockers recently discovered. The present work explores the use of mesoporous silica nanoparticles MCM-41 functionalized with 3-Aminopropyltriethoxysilane (APTES) for anchoring the flufenamic acid for its prolonged and controlled release and protection from radiation bystander effects. MCM-41 and functionalized samples were structurally and chemically characterized with multiple techniques. The biocompatibility of all samples was tested in a live/dead assay performed in cultured MRC-5 and HeLa cells. HeLa cells cultured were exposed to 50?Gy of gamma-rays and the media transferred to fibroblast cells cultured separately. Our results show that MCM-41 and functionalized samples have high biocompatibility with MCR-5 and HeLa cells, and most importantly, the FFA delivered by these NPs was able to halt apoptosis, one of main bystander effects. 相似文献
97.
A Bayesian framework for accelerated reliability growth testing with multiple sources of uncertainty
Cesar Ruiz Ed Pohl Haitao Liao Kelly M. Sullivan 《Quality and Reliability Engineering International》2019,35(3):837-853
Reliability growth tests are often used for achieving a target reliability for complex systems via multiple test‐fix stages with limited testing resources. Such tests can be sped up via accelerated life testing (ALT) where test units are exposed to harsher‐than‐normal conditions. In this paper, a Bayesian framework is proposed to analyze ALT data in reliability growth. In particular, a complex system with components that have multiple competing failure modes is considered, and the time to failure of each failure mode is assumed to follow a Weibull distribution. We also assume that the accelerated condition has a fixed time scaling effect on each of the failure modes. In addition, a corrective action with fixed ineffectiveness can be performed at the end of each stage to reduce the occurrence of each failure mode. Under the Bayesian framework, a general model is developed to handle uncertainty on all model parameters, and several special cases with some parameters being known are also studied. A simulation study is conducted to assess the performance of the proposed models in estimating the final reliability of the system and to study the effects of unbiased and biased prior knowledge on the system‐level reliability estimates. 相似文献
98.
de Paco P Menendez O Corrales E 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2008,55(9):2030-2037
Using the stacked crystal filter (SCF) concept, a coupled resonator filter (CRF) can be interpreted as a device in which 2 piezoresonators are stacked on top of each other in such a way that a certain degree of acoustic interaction occurs. The work presented in this paper reports a novel all-electrical model for the CRF. The model associates acoustical coupling with an equivalent electrical coupling between resonators. The resulting equivalent circuit makes it possible to apply classical filter synthesis techniques directly based on the coupling control between resonators. It complements with a synthesis approach the analysis approach of the Mason model. 相似文献
99.
Tuytten R Lemière F Esmans EL Herrebout WA van der Veken BJ Maes BU Witters E Newton RP Dudley E 《Analytical chemistry》2007,79(17):6662-6669
Urinary modified nucleosides have a potential role as cancer biomarkers, and most of the methods used in their study have utilized low-pressure phenylboronate affinity chromatography materials for the purification of the cis-diol-containing nucleosides. In this study, a boronate HPLC column was surprisingly shown not to trap the nucleosides as would be expected from experience with the classic Affigel 601 resin but showed only partial selectivity toward cis-diol groups while other groups exhibited better retention. In aprotic conditions, trapping of nucleosides was possible; however, the selectivity toward cis-diol-containing compounds was lost with the Lewis basicity of available nitrogens being the main determinant of retention. The experimental findings are compared to and confirmed by DFT calculations. 相似文献
100.
We present a simple and consistent technique for fabricating slow light structures in dye-doped polymer waveguides using the process of irreversible photobleaching. The slow light structures are moiré gratings. The gratings are holographically written into channel waveguides photobleached in side-chained PMMA/DR1 films. The films are annealed during the photobleaching process in order to remove stresses in the films generated during the photobleaching process. These stresses have been observed to cause distortion and cracking of the film surface. The slowing factor for the moiré gratings is calculated from the reflectance spectrum of the waveguides using the Hilbert transform. Moiré gratings with slowing factors between 1.6 and 2.6 are demonstrated. 相似文献