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排序方式: 共有305条查询结果,搜索用时 15 毫秒
1.
Wyatt L. Brown Douglas A. Day Harald Stark Demetrios Pagonis Jordan E. Krechmer Xiaoxi Liu Derek J. Price Erin F. Katz Peter F. DeCarlo Catherine G. Masoud Dongyu S. Wang Lea Hildebrandt Ruiz Caleb Arata David M. Lunderberg Allen H. Goldstein Delphine K. Farmer Marina E. Vance Jose L. Jimenez 《Indoor air》2021,31(1):141-155
Understanding the sources and composition of organic aerosol (OA) in indoor environments requires rapid measurements, since many emissions and processes have short timescales. However, real-time molecular-level OA measurements have not been reported indoors. Here, we present quantitative measurements, at a time resolution of five seconds, of molecular ions corresponding to diverse aerosol-phase species, by applying extractive electrospray ionization mass spectrometry (EESI-MS) to indoor air analysis for the first time, as part of the highly instrumented HOMEChem field study. We demonstrate how the complex spectra of EESI-MS are screened in order to extract chemical information and investigate the possibility of interference from gas-phase semivolatile species. During experiments that simulated the Thanksgiving US holiday meal preparation, EESI-MS quantified multiple species, including fatty acids, carbohydrates, siloxanes, and phthalates. Intercomparisons with Aerosol Mass Spectrometer (AMS) and Scanning Mobility Particle Sizer suggest that EESI-MS quantified a large fraction of OA. Comparisons with FIGAERO-CIMS shows similar signal levels and good correlation, with a range of 100 for the relative sensitivities. Comparisons with SV-TAG for phthalates and with SV-TAG and AMS for total siloxanes also show strong correlation. EESI-MS observations can be used with gas-phase measurements to identify co-emitted gas- and aerosol-phase species, and this is demonstrated using complementary gas-phase PTR-MS observations. 相似文献
2.
Conflicting results have been reported in literature about the influence of beta-adrenergic stimulation on the fast cardiac sodium current (INa+). To elucidate these mechanisms in multicellular preparations we used the loose-patch-clamp technique to evaluate the effect of the beta-adrenergic agonist isoproterenol 1-1000 nmol/l. Isoproterenol enhanced INa+ at all membrane potentials by elevation of the maximal available INa+ . Only at the high concentration of 1 micromol/l was INa+ slightly depressed after depolarizing conditioning clamps. The most marked increase of the maximal available INa+ was 30+/-9% after application of 100 nmol/l isoproterenol. To learn about the mechanisms in view of sodium channel modulation we combined isoproterenol with the sodium channel blocker lidocaine (47 micromol/l). Under these circumstances the effects of both drugs were completely independent. This investigation shows clearly that low concentrations of isoproterenol increase INa+ in multicellular preparations by a gating-independent mechanism. 相似文献
3.
Arata L.K. Dhawan A.P. Broderick J.P. Gaskil-Shipley M.F. Levy A.V. Volkow N.D. 《IEEE transactions on bio-medical engineering》1995,42(11):1069-1078
Model-based segmentation and analysis of brain images depends on anatomical knowledge which may be derived from conventional atlases. Classical anatomical atlases are based on the rigid spatial distribution provided by a single cadaver. Their use to segment internal anatomical brain structures in a high-resolution MR brain image does not provide any knowledge about the subject variability, and therefore they are not very efficient in analysis. The authors present a method to develop three-dimensional computerized composite models of brain structures to build a computerized anatomical atlas. The composite models are developed using the real MR brain images of human subjects which are registered through the principal axes transformation. The composite models provide probabilistic spatial distributions, which represent the variability of brain structures and can be easily updated for additional subjects. The authors demonstrate the use of such a composite model of ventricular structure to help segmentation of the ventricles and cerebrospinal fluid of MR brain images. Here, a composite model of ventricles using a set of 22 human subjects is developed and used in a model-based segmentation of ventricles, sulci, and white matter lesions. To illustrate the clinical usefulness, automatic volumetric measurements on ventricular size and cortical atrophy for an additional eight alcoholics and 10 normal subjects were made. The volumetric quantitative results indicated regional brain atrophy in chronic alcoholics 相似文献
4.
Bonding of ceramics to metals was carried out by using thermal sprayed coatings as interlayer materials. This bonding method is referred as the thermal spray bonding. In the present study, Si3N4 and Al2O3 ceramics were bonded to SS41 mild steel using activated Ti-Cu multilayer coatings plasma-sprayed on the steel in a low pressure atmosphere. The bondability was estimated by SEM/EDX analysis and shear tests of the joints. The results were compared to those obtained using Ti-Cu multilayer foils as interlayers. When using Ti-Cu foils as interlayers, brittle Fe-Ti compound layers were formed in the joint area after long time heating at a bonding temperature of 900°C, which deteriorated the joint strength. In contrast with the activated interlayers made by plasma spraying, the Ti-Cu eutectic reaction took place uniformly at the joint immediately after heating to the bonding temperature. This improved the bondabilrty, and the resultant joints exhibited shear strengths of about 180 MPa. 相似文献
5.
6.
Kazunori Sakurama Kazushi Nakano 《International Journal of Control, Automation and Systems》2012,10(1):50-60
This paper addresses a path tracking problem with obstacle avoidance for Lagrange systems. The proposed method is based on
field potential methods in combination with navigation functions for obstacle avoidance. First, it is shown that a simple
combination of the navigation function with the conventional path tracking controller does not work. Therefore, in order to
cope with this problem, a new feedback law is proposed for a path parameter which characterizes the reference path. It is
proved that the proposed controller achieves both path following and collision avoidance. Moreover, since the method adopts
bounded navigation functions, the proposed controllers generate bounded input signals even when target systems approach obstacles.
Finally, an experimental evaluation is performed with a two-link manipulator to illustrate the effectiveness of the proposed
method. 相似文献
7.
A highly active superacid of 2 wt% Fe-supported ZrO2 for the skeletal isomerization of butane to isobutane was obtained by sfexposing Fe2O3/ZrO2 to 1 N H2SO4 followed by calcining in air at 700°C for more than 24 h; the Fe2O3/ZrO2 was prepared by impregnating zirconia gel with a solution of Fe(NO3)3 followed by drying at 300°C (2 wt% Fe). A much lower activity was observed with the opposite procedure, where the first impregnation was sulfation of the gel, followed by a second impregnation with the iron compound. It was proved from analysis of the sulfur content in the catalysts that residual sulfur species were not related with generation of the superacidic sites. XPS showed the catalyst to be Fe2O3 supported on ZrO2.Superacids by metal oxides, VIII. For previous publications VI and VII in this series see refs. [10,11]. 相似文献
8.
9.
Keisuke Fujita Kohji Higuchi Kazushi Nakano Koji Matsushita Tatsuyoshi Kajikawa Fumiho Chino 《Artificial Life and Robotics》2009,14(3):433-439
There is a need for robust current control of a pulse width modulation (PWM) power amplifier whose transient response characteristics
do not deteriorate with extensive load changes and/or direct-current power supply voltage changes. In this article, we propose
a digital robust controller with bumpless mode switching to control the current of a PWM power amplifier to satisfy the demands
and extend the range of an inductive load width. It is necessary to measure the value of the load in order to implement this
bumpless mode switching automatically depending on the load range. Therefore, a method of estimating the inductive load is
shown. The bumpless mode switching is automatically performed by estimating an inductive value without specifying the value
of the inductive load beforehand. That is, the value of the inductive load is estimated during the DDC execution, and the
control mode is automatically switched bumplessly according to this estimated value. A digital controller equipped with inductance
estimation and bumpless mode switching is realized by a DSP. Some experiments show that the digital controller with the proposed
bumpless mode switching can satisfy larger specifications. 相似文献