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991.
RA Potyrailo RC Conrad AD Ellington GM Hieftje 《Canadian Metallurgical Quarterly》1998,70(16):3419-3425
A flexible biosensor has been developed that utilizes immobilized nucleic acid aptamers to specifically detect free nonlabeled non-nucleic acid targets such as proteins. In a model system, an anti-thrombin DNA aptamer was fluorescently labeled and covalently attached to a glass support. Thrombin in solution was selectively detected by following changes in the evanescent-wave-induced fluorescence anisotropy of the immobilized aptamer. The new biosensor can detect as little as 0.7 amol of thrombin in a 140-pL interrogated volume, has a dynamic range of 3 orders of magnitude, has an inter-sensing-element measurement precision of better than 4% RSD over the range 0-200 nM, and requires less than 10 min for sample analysis. The aptamer-sensor format is generalizable and should allow sensitive, selective, and fast determination of a wide range of analytes. 相似文献
992.
Estimates of the prevalence of arthritis and selected musculoskeletal disorders in the United States 总被引:3,自引:0,他引:3
RC Lawrence CG Helmick FC Arnett RA Deyo DT Felson EH Giannini SP Heyse R Hirsch MC Hochberg GG Hunder MH Liang SR Pillemer VD Steen F Wolfe 《Canadian Metallurgical Quarterly》1998,41(5):778-799
OBJECTIVE: To provide a single source for the best available estimates of the national prevalence of arthritis in general and of selected musculoskeletal disorders (osteoarthritis, rheumatoid arthritis, juvenile rheumatoid arthritis, the spondylarthropathies, systemic lupus erythematosus, scleroderma, polymyalgia rheumatica/giant cell arteritis, gout, fibromyalgia, and low back pain). METHODS: The National Arthritis Data Workgroup reviewed data from available surveys, such as the National Health and Nutrition Examination Survey series. For overall national estimates, we used surveys based on representative samples. Because data based on national population samples are unavailable for most specific musculoskeletal conditions, we derived data from various smaller survey samples from defined populations. Prevalence estimates from these surveys were linked to 1990 US Bureau of the Census population data to calculate national estimates. We also estimated the expected frequency of arthritis in the year 2020. RESULTS: Current national estimates are provided, with important caveats regarding their interpretation, for self-reported arthritis and selected conditions. An estimated 15% (40 million) of Americans had some form of arthritis in 1995. By the year 2020, an estimated 18.2% (59.4 million) will be affected. CONCLUSION: Given the limitations of the data on which they are based, this report provides the best available prevalence estimates for arthritis and other rheumatic conditions overall, and for selected musculoskeletal disorders, in the US population. 相似文献
993.
B. I. Prenitzer L. A. Giannuzzi K. Newman S. R. Brown R. B. Irwin F. A. Stevie T. L. Shofner 《Metallurgical and Materials Transactions A》1998,29(9):2399-2406
Particles of Zn powder have been studied to show that high-quality scanning electron microscope (SEM) and transmission electron
microscope (TEM) specimens can be rapidly produced from a site-specific region on a chosen particle by the focused ion beam
(FIB) lift-out technique. A TEM specimen approximately 20-μm long by 5-μm wide was milled to electron transparency, extracted from the bulk particle, and micromanipulated onto a carbon coated copper
mesh TEM grid. Using the FIB lift-out method, we were able to prepare a site-specific TEM specimen from a difficult material
in under 3 hours. The TEM analysis of the lift-out specimen revealed a large amount of thin area free from characteristic
signs of damage that may be observed as a result of conventional argon ion milling. The overall microstructure of the specimen
prepared by the FIB lift-out method was consistent with samples prepared by conventional metallographic methods. A grain size
of ∼10 to 20 μm was observed in all specimens by both TEM and SEM analysis. Light optical microscopy revealed the presence of internal voids
in ∼10 to 20 pct of all particles. The SEM analysis showed the voids to extend over ∼70 pct of the particle volume in some
cases. 相似文献
994.
Identification of periodic signals with uncertain frequency 总被引:1,自引:0,他引:1
This paper presents a new algorithm to identify periodic signals with uncertain frequency. The approach is based on the behavior of an internal model in an error feedback system. As such, the signal is fed to a fictitious plant with a feedback controller. The feedback controller is based on a traditional controller in parallel with an internal model which identifies and cancels the periodic disturbances. Under ideal circumstances, the phase plot of the states of the internal model form an ellipse. The speed of rotation about this ellipse can be used to calculate the difference between the nominal frequency of the model and the true frequency of the periodic signal. An integral controller or a least-squares estimator can be used to drive this error to zero. Simulations demonstrate the validity of this approach with time-varying frequency, and the algorithm is then applied to some data collected from a spot welder that has been corrupted by a sinusoidal signal whose frequency is between 1 Hz and 5 KHz. 相似文献
995.
D. G. Narehood N. Grube R. M. Dimeo D. W. Brown P. E. Sokol 《Journal of Low Temperature Physics》2003,132(3-4):223-237
The properties of molecular hydrogen adsorbed in Britesorb were studied through inelastic neutron scattering. We have measured both the rotational energy levels and the momentum distribution at bilayer and nearly full pore fillings. Splitting of the J=1 rotational energy levels is observed for molecular hydrogen adsorbed on the surface, while the rotational properties of the hydrogen adsorbed after monolayer completion is consistent with behavior in the bulk. Additionally, the measurement of the momentum distribution showed that the mean kinetic energy of the molecules in the bilayer is 88 K±7 K. The kinetic energy measured in the nearly full pore was 81 K±6 K, which is consistent with a simple model in which the behavior of the monolayer is dominated by the interaction with the surface of the pore wall but H2 adsorbed after monolayer completion is bulk like. 相似文献
996.
Increased operational autonomy and reduced operating costs have become critical design objectives in next-generation NASA and Department of Defense (DoD) space programs. Our objective is to develop a semiautomated system for intelligent spacecraft operations support. This paper presents the Spacecraft Operations and Anomaly Resolution System (SOARS) as a standardized, model-based architecture for performing High-Level Tasking, Status Monitoring and automated Procedure Execution Control for a variety of spacecraft. The particular focus here is on the Procedure Execution Control module. A hierarchical procedure network is proposed as the fundamental means for specifying and representing arbitrary operational procedures. A separate procedure interpreter controls automatic execution of the procedure, taking into account the current status of the spacecraft as maintained in an object-oriented spacecraft model. 相似文献
997.
S. H. Li C. A. Larsen C. H. Chen G. B. Stringfellow D. W. Brown 《Journal of Electronic Materials》1990,19(4):299-304
The pyrolysis mechanisms of dimethylarsine (DMAsH) have been studied mass spectrometrically in an atmospheric pressure flow
tube reactor. In either the D2 or He ambient, DMAsH will be converted to trimethylarsine (TMAs) at temperatures of 400–500° via a homogeneous CH3 radical chain reaction. Supplemental CH3 radicals, produced from azomethane ((CH3)2N2) pyrolysis, have resulted in a significant increase in the pyrolysis rate for DMAsH. As temperature is increased beyond 500°,
the product TMAs will decompose due to hydrogenolysis in D2 and homolysis in He. At a GaAs surface, DMAsH pyrolyzes heterogeneously. The pyrolysis rate is further accelerated by the
addition of trimethylgallium (TMGa). DMAsH has also been combined with TMGa to grow GaAs layers. The as-grown epilayers, at
1 atm and substrate temperatures of 570–720°, are allp-type with the net hole concentration dependent on the carrier gas. The use of N2 leads to a higher concentration as compared to that in H2. Photoluminescence spectra have indicated the acceptor to be carbon. A mechanism is developed to interpret these results
based on the pyrolysis reactions determined from the kinetic studies. 相似文献
998.
999.
A novel technique is proposed to construct sparse regression models based on the orthogonal least squares method with tunable kernels. The proposed technique tunes the centre vector and diagonal covariance matrix of individual regressors by incrementally minimising the training mean square error using a guided random search algorithm, and it offers a state-of-the-art method for constructing very sparse models that generalise well. 相似文献
1000.
Reports an error in the original article by B. Sheese et al (Health Psychology, 2004[Sep], Vol 23 [5], 457-464). On page 459, Table 1 contained errors in the reported values. The corrected table is provided. (The following abstract of this article originally appeared in record 2004-18051-003.) Research has shown that writing about emotional topics can positively influence physical and mental health. The current study tested the efficacy of an e-mail-based writing treatment and shows how such an implementation can aid in the search for moderators. Participants (N = 546) were randomly assigned to either a long- or short-interval traumatic writing condition or to a nonemotional writing control condition. In contrast to previous disclosure research, participants received and submitted their writing responses via e-mail. Health outcomes were assessed weekly for 5 weeks after treatment and were reported at the conclusion of the study. Results supported the effectiveness of an e-mail-based writing treatment in producing positive health outcomes and successfully identified several moderators of the writing treatment effect. The moderators implicated varied depending on the nature of the health outcome assessment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献