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In this article, we provide guidance for substantive researchers on the use of structural equation modeling in practice for theory testing and development. We present a comprehensive, two-step modeling approach that employs a series of nested models and sequential chi-square difference tests. We discuss the comparative advantages of this approach over a(More)
BACKGROUND AND PURPOSE Different definitions have been proposed to define the ischemic penumbra from perfusion-CT (PCT) data, based on parameters and thresholds tested only in small pilot studies. The purpose of this study was to perform a systematic evaluation of all PCT parameters (cerebral blood flow, volume [CBV], mean transit time [MTT], time-to-peak)(More)
In this paper we examine the use of the key informant methodology by researchers investigating interorganizational relationships. To increase the reliability of informant reports, the use of multiple informants has often been advocated. However, interorganizational research still tends to rely on single informants. Here, we investigate issues having to do(More)
OBJECTIVE MRI at 3 T, which has a higher signal-to-noise ratio than 1.5-T MRI, is potentially more sensitive and specific at delineating epileptogenic lesions and may influence management of refractory epilepsy. The purposes of the current study were to compare image quality of 3-T MRI with that of 1.5-T MRI in the evaluation of epilepsy and, in cases of(More)
This study investigates the adoption of total cost of ownership (TCO) analysis to improve sourcing decisions. TCO can be seen as an application of activity based costing (ABC) that quantifies the costs that are involved in acquiring and using purchased goods or services. TCO supports purchasing decision-makers in focusing on total value received and not(More)
Neurodegenerative disorders with high iron in the basal ganglia encompass an expanding collection of single gene disorders collectively known as neurodegeneration with brain iron accumulation. These disorders can largely be distinguished from one another by their associated clinical and neuroimaging features. The aim of this study was to define the(More)
With few exceptions the genetic codes of all known organisms encode the same 20 amino acids, yet all that is required to add a new building block are a unique tRNA/aminoacyl-tRNA synthetase pair, a source of the amino acid, and a unique codon that specifies the amino acid. For example, the amber nonsense codon, TAG, together with orthogonal Methanococcus(More)