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关键词： Alzheimer's disease   arterial spin-labeled MRI   cerebral blood flow   spatial coefficient of variation   reproducibility   receiver operating characteristic  

摘要： Background The spatial coefficient of variation (sCoV) of arterial spin-labeled (ASL) MRI can index cerebral blood flow spatial heterogeneity. This metric reflects delayed blood delivery-seen as a hyperintense ASL signal juxtaposed by hypointense regions. Purpose To investigate the use of ASL-sCoV in the classification of cognitively unimpaired (CU), mild cognitive impairment (MCI), and Alzheimer's disease (AD) cohorts. Study Type Prospective/cohort. Population Baseline ASL images from AD neuroimaging initiative dataset in three groups of CU, MCI, and AD (N = 258). Field Strength/Sequence Pulsed ASL (PICORE QT2) images were acquired on 3 T Siemens systems (TE/TR = 12/3400 msec, TI1/2 = 700/1900 msec). Assessment ASL-sCoV was calculated in temporal, parietal, occipital, and frontal lobes as well as whole gray matter. Statistical Tests The primary analysis used an analysis of covariance to investigate sCoV and cognitive group (CU, MCI, AD) associations. We also evaluated the repeatability of sCoV by calculating within-subject agreement in a subgroup of CU participants with a repeat ASL. The secondary analyses assessed ventricular volume, amyloid burden, glucose uptake, ASL-sCoV, and regional CBF as cognitive group classifiers using logistic regression models and receiver operating characteristic analyses. Results We found that global and temporal lobe sCoV differed between cognitive groups (P = 0.006). Post-hoc tests showed that temporal lobe sCoV was lower in CU than in MCI (Cohen's d = -0.36) or AD (Cohen's d = -1.36). We found that sCoV was moderately repeatable in CU (intersession intraclass correlation = 0.50;intrasession intraclass correlation = 0.88). Subsequent logistic regression analyses revealed that temporal lobe sCoV and amyloid uptake classified CU vs. MCI (P < 0.01;accuracy = 78%). Temporal lobe sCoV, amyloid, and glucose uptake classified CU vs. AD (P < 0.01;accuracy = 97%);glucose uptake significantly classified MCI vs. AD (P < 0.01;accuracy = 85%). D

关键词： Gut contents   Scraper   Functional feeding group   Periphyton   Diet   Ephemeroptera  

摘要： Macroinvertebrate grazers mainly feed on periphyton comprising of algae and detritus in streams, and sometimes feed on plant detritus or other invertebrates. We determined food habits of 21 grazer species (19 mayflies, 1 caddisfly, and 1 net-winged midge) from their gut contents, and systematically examined whether taxonomic affiliation, flow habitat, or body size are responsible for variations in food habits among or within the grazer species on a forested stream. We obtained some evidence that the food habits of grazer species varied according to family or genus;for example, species of Ephemerellidae ingested more animal materials. Species inhabiting slow-flow areas in riffles ingested fewer diatoms, while those inhabiting rapid-flow areas in riffles ingested less plant detritus. Larger individuals ingested more plant detritus or animal materials within a particular species (five grazer species), whereas we did not find the opposite patterns. Understanding the trophic roles of stream macroinvertebrates and the energy flow in stream food webs requires systematic exploration of the factors responsible for inter- and intraspecific variation.

关键词： Viscoelastic fluid   Non-Newtonian   PTT   Cylinder   Numerical simulation  

摘要： This study numerically investigates a low Reynolds two-dimensional flow of a viscoelastic fluid over a circular cylinder using the finite volume method. The Phan-Thien-Tanner model, as one of the most accurate non-linear models, for the first time, describes the viscoelastic behavior of a high concentration polymer solution in the flow over a cylinder in high elastic regime in Re = 10. To avoid divergence and to stabilize the numerical process in high elastic cases, the log-conformation approach proposed by previous researchers is used. The convective terms of the equations are discretized using a high-resolution scheme. The physical instability, as observed by some researchers in the creeping regime of high De flow, is very weak in the cases of this research. The numerical results of this research show both drag reduction (for the elasticity number El < 0.025) and drag enhancement (for elasticity number El > 0.025). Compared with the dissipative nature of viscoelastic fluid flows, the drag coefficient, resulted from the polymeric portion of stress, in the high elastic flow regime (El > 10), approached to zero due to an increase in the storing nature of viscoelastic fluid. At these elasticity numbers, the drag coefficient remains constant with El, and the material behaves like a Newtonian fluid. Compared with the shear-thinning behavior and unlike the creeping flow, the elasticity is the main cause of drag variation in most cases. Shear stress affects the drag force directly, while normal stress influences the drag force by changing the pressure distribution over the cylinder. The maximum normal stress occurs at the back of the cylinder due to the wake behind it, while in creeping flow it occurs at its half-front. Finally, the effects of elasticity number, retardation ratio and model parameters on the distribution of stress components, drag coefficient, and vortex dimensions are investigated separately, and a physical discussion is presented.

关键词： Circulating fluidized bed   L-valve   Non-mechanical valve   Solids flow   Group B particles  

摘要： An experimental study was conducted in a large scale circulating fluidized bed (0.3 m diameterx15.5 m tall) equipped with nonmechanical L-valve (0.25 m diameterx1.52 m long) varying the riser superficial gas velocity (U-g), bed inventory (m), L-valve aeration velocity (U-Lvalve), and standpipe aeration velocity (U-more). The effects of these operational parameters on pressure drop were investigated in each of the different components in the CFB and on the solid circulation rate with two different Group B particles (180 mu m glass bead and 750 pm phosphorescent polyethylene beads, PPE). Tests were carried out at ambient temperature and pressure conditions using air as the fluidization gas. The operating parameters were shown to significantly affect pressure drops across various sections of the CFB due to redistribution of solids within the system. The pressure drop in the horizontal section of the L-valve was affected by aeration rates in addition to the solid flow rate reported in previous studies of smaller L-valves without aeration. A new dimensionless semi-empirical correlation was able to explain >98% of the variance between pressure drop across the horizontal section of the L-valve and operating parameters for these Group B particles. The results of present study indicated that the nonmechanical L-valve cannot be isolated from the CFB system for performance evaluation. Published by Elsevier B.V.

关键词： heavy metal   fly ash   leaching   hazardous waste   fluidized bed combustion  

摘要： European solid waste incinerator plants still primarily use grate furnace technology, although circulating fluidized bed (CFB) technology is steadily expanding. Therefore, few investigations have reported on the environmental assessment of fly ash from fluidized incinerators. This research project aims to integrate information on fly ash derived from the combustion of municipal solid waste (FA1) and biomass (FA2) in fluidized bed incinerator facilities. Fly ash samples were comparatively analyzed by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES) to study the mineralogy, morphology, total heavy metal content, and leaching behavior, respectively. The analysis revealed that the two types of fly ash differ in their characteristics and leaching behavior. The concentration of most of the heavy metals in both is low compared to the literature values, but higher than the regulatory limits for use as a soil conditioner, whereas the high contents of Fe, Cu, and Al suggest good potential for metal recovery. The leaching ability of most elements is within the inert waste category, except for Hg, which is slightly above the non-hazardous waste limit.

摘要： Although seasonal patterns of ecosystem productivity have been extensively described and analyzed with respect to their primary forcings in terrestrial and marine systems, comparatively little is known about these same processes in rivers. However, it is now possible to perform a large-scale synthesis on the patterns and drivers of river productivity regimes because of the recent sensor advances allowing for near-continuous estimates of river productivity. Here, we explore a dataset of 47 U.S. rivers to examine whether there are characteristic river productivity regimes. We use classification approaches to develop a typology of productivity regimes and then use these regimes to examine differences with respect to potential controls of productivity. We identified two distinct metabolic regimes, which we named Summer Peak and Spring Peak Rivers, within our dataset. These regimes meaningfully differed in both the timing and magnitude of productivity and were robust to different approaches to classification. We also found that several variables, including watershed area and characteristics of water temperature or discharge, were able to predict the class membership of these regimes with modest accuracy. Our results support the presence of characteristic metabolic regimes and suggests that these regimes may have common sets of environmental controls. We present classification as one approach to begin exploring the productivity regimes of rivers. The strength of our approach is that it fully leverages these newly available high-frequency productivity estimates to create classes that can be used to draw inferences about how the controls of river productivity differ between or within systems.

关键词： Schrodinger equation   Klein-Gordon equation   Dirac equation   relativistic approximation   Hamiltonian   momentum  

摘要： In this paper, the energy and momentum operator substitution method derived from the Schrodinger equation is used to list all possible light and matter wave equations, among which the first light wave equation and relativistic approximation equation are proposed for the first time. We expect that we will have some practical application value. The negative sign pairing of energy and momentum operators are important characteristics of this paper. Then the Klein-Gordon equation and Dirac equation are introduced. The process of deriving relativistic energy-momentum relationship by undetermined coefficient method and establishing Dirac equation are mainly introduced. Dirac's idea of treating negative energy in relativity into positrons is also discussed. Finally, the four-dimensional space-time representation of relativistic wave equation is introduced, which is usually the main representation of quantum electrodynamics and quantum field theory.

关键词： HTML5   移动智能终端   函数  

摘要： HTML5移动智能终端是近年来出现的一项新技术。它已被应用于许多领域。他们中的许多人使用这种技术来记录数据。然而,HTML5移动智能终端还不够成熟。网络平台和本地平台的同时运行带来了更多的安全风险。针对上述背景,提出图和势函数边缘计算影响下HTML5移动智能终端的安全评估方法。建立HTML5移动智能终端威胁图,标记智能终端中响应节点,分析威胁图中网络节点,得到威胁准则编码,计算影响边缘参数,以此实现HTML5移动智能终端安全评估。实验数据表明,与常规安全评估方法比较,提出的安全评估方法在权限设置漏洞以及短信病毒检测率上优于传统方法,说明提出方法具备更高的应用价值。

关键词： ISODATA   Morphology classification   Remote sensing   Top-of-atmosphere (TOA)  

摘要： Mapping of lava flows based on remote sensing data of high accuracy has become a common tool for exploring volcanic eruptions in greater detail. Mapping data based on remote sensing data provides information on the location and flow direction of lava flows as well as their areas and enables the localisation of volcanic vents-valuable knowledge for pre- and post-eruption volcanic activity and behaviour estimations. The current research seeks to expand the understanding of the volcanic and tectonic processes in Harrat Lunayyir, Saudi Arabia. In view of this, remote sensing data was classified using iterative self-organising data analysis technique (ISODATA) algorithms. The aim of the classification is to identify spectral top-of-atmosphere (TOA) reflectance values to distinguish layers of old and recent lava flows based on differences. As a result, three distinct basaltic units were identified to have the following ages: 15.1 +/- 6.1 ka (4%), 15.0 +/- 8.4 ka (6%), and 14.6 +/- 23.1 ka (10%). The differences in the calculated areas of the lava flows as mapped based on the remote sensing data and earlier modelling are captured and identified in relation to the local geomorphologic and geologic structures. The differences can be partly explained as being related to a considerable weathering of the observed geological formations at 800-1600 nm, with reflectance of 12%. The limitation of the methodology relates to the lack of accurate geochronological timeline, that is, an inability to identify accurate age of the samples.