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排序方式: 共有833条查询结果,搜索用时 15 毫秒
1.
OL Lopez RP Brenner JT Becker RF Ulrich F Boller ST DeKosky 《Canadian Metallurgical Quarterly》1997,48(6):1521-1525
We examined whether either psychotic features (e.g., delusions and hallucinations) or EEG abnormalities are associated with more rapid progression of Alzheimer's disease (AD). AD patients with psychosis have exhibited more EEG abnormalities than those without psychosis, and both abnormal EEG and psychosis have been noted to be predictors of functional and cognitive decline in AD. Ninety-five probable AD patients participating in a longitudinal study of dementia had an EEG and a semistructured psychiatric interview at baseline. Using EEG spectral analysis, we classified records as normal/abnormal based on the parasagittal mean frequency. Patients with abnormal EEGs were more functionally (e.g., Blessed Rating Scale for activities of daily living) and cognitively (e.g., Mini-Mental State) impaired than patients with normal EEG. AD patients with psychosis were only more functionally impaired than patients without psychosis. A two-factor analysis showed no interaction between abnormal EEG and psychosis. In addition, using a Cox proportional hazard model adjusted for age and education, the presence of an abnormal EEG or psychotic symptom at study entry was associated with higher risk of reaching severe cognitive and functional impairment during follow-up. Neither abnormal EEG nor the presence of psychosis predicted death. These results indicate that both abnormal EEG and psychosis are independent predictors of disease progression but not of physical survival. 相似文献
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In 4 experiments, chronometric evidence for keypress schemata in typing was sought by presenting stimuli to be typed in positions that were displaced from a central fixation point. Reaction times were shorter when stimulus positions corresponded to keyboard locations of the letters to be typed, suggesting that position was an important part of the internal representation of the response. Experiment 1 presented single letters left and right of fixation. Experiment 2 presented single letters above and below fixation. Experiment 3 presented words left and right of fixation and found evidence of parallel activation of keypress schemata. Experiment 4 found no effect of the eccentricity of the keyboard locations and responding fingers, suggesting that response-location codes are categorical, not metric. The results are consistent with D. E. Rumelhart and D. A. Norman's (1982) theory of typewriting. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
Buried heterostructure lasers with highly strained InGaAs-InGaAsP active regions, emitting at 2 μm have been fabricated and tested. The lasers exhibited threshold current densities of 500 A/cm2 for 1-mm-long cavities, an internal loss of 11 cm-1, and characteristic temperatures as high as 50°C. The gain characteristics were also investigated and a linewidth enhancement factor of 8 was determined 相似文献
5.
Neudorf E.G. Kiguel D.L. Hamoud G.A. Porretta B. Stephenson W.M. Sparks R.W. Logan D.M. Bhavaraju M.P. Billinton R. Garrison D.L. 《Power Systems, IEEE Transactions on》1995,10(3):1667-1675
There is an emerging recognition that utility investments and other decisions that affect electric service reliability should be explicitly evaluated on the basis of their cost and benefit implications. A cost-benefit approach that quantifies the reliability benefits of alternatives in terms of the reduction in costs resulting from unserved energy enables the evaluation of generation and transmission capacity additions on a consistent, economic basis. This approach has been applied to two utility case studies. In a case study for Pacific Gas and Electric Company, it was used to evaluate three options for maintaining reliability in a major load center-two involving local generation, and the third, a new 230 kV transmission connection. In a case study for Duke Power Company, the approach was used to evaluate alternative designs for proposed additions to a transmission station. This paper describes the methodology and presents the two utility studies 相似文献
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Morton P.A. Ackerman D.A. Shtengel G.E. Kazarinov R.F. Hybertsen M.S. Tanbun-Ek T. Logan R.A. Sergent A.M. 《Photonics Technology Letters, IEEE》1995,7(8):833-835
We describe the important characteristics of high-speed p-doped compressively strained MQW lasers obtained from comprehensive below-threshold DC measurements. Results of gain and differential gain versus wavelength and carrier density are verified by above-threshold resonance measurements. Measurement-derived design curves of gain, differential gain, and linewidth enhancement factor allow device optimization for high speed and low chirp 相似文献
9.
M.C. Wu Y.K. Chen T. Tanbun-Ek R.A. Logan M.A. Chin 《Photonics Technology Letters, IEEE》1991,3(10):874-876
The tunabilities of both the wavelength and the pulse-width of monolithic mode-locked semiconductor lasers are demonstrated. Pulses shorter than 1.6 ps, tunable over 8.8 mu m, have been generated by a temperature-tuned monolithic colliding pulse mode-locked (CPM) quantum-well laser. For a fixed wavelength, the pulse-width is independently controlled from 1.2 ps to longer than 3 ps by external bandpass filters. Near transform-limited time-bandwidth products of 0.34 were maintained throughout the tuning processes.<> 相似文献
10.
Katherine A. B. Logan Michael J. S. Floate 《Journal of the science of food and agriculture》1985,36(11):1084-1092
For 30 acid upland and hill soils, with initial pH from 3.5 to 5.8, and loss on ignition from 14% to 94%, cation exchange capacity varied with pH according to the relationship CEC = m pH+C, where m and C are characteristic of each soil. The slope m depended on loss on ignition (LOI), and is given by: m=Δ CEC/Δ=0.22 LOI+1.92. Because of these relationships, CEC measured at the natural pH of the soil (in 0.025 M MgSO4 solution) is more relevant to field conditions than a conventional measurement at pH7. An improved method for estimating lime requirement (LR) of these soils was developed, based on the relationship found between LR and the difference in CEC (ΔCEC) between that at the natural pH of the soil and that at the target pH of 5.5: LR=1.12 ΔCEC+1.48. Lime requirement can therefore also be estimated from loss on ignition using the earlier relationships, and is given by: LR=(0.25 LOI+2.15) Δ+1.48, where Δ is the difference between the natural pH (in 0.025 M MgSO4) and the target pH. Predictions based on this agreed well with results for a further 10 soils. 相似文献