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Sudden Shift (sudden + shift)
Selected AbstractsHigh Density Endocardial Mapping of Shifts in the Site of Earliest Depolarization During Sinus Rhythm and Sinus TachycardiaPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4p1 2003TIM R. BETTS BETTS, T.R., et al.: High Density Endocardial Mapping of Shifts in the Site of Earliest Depolarization During Sinus Rhythm and Sinus Tachycardia.Previous mapping studies of sinus rhythm suggest faster rates arise from more cranial sites within the lateral right atrium. In the intact, beating heart, mapping has been limited to epicardial plaques or single endocardial catheters. The present study was designed to examine shifts in the site of the earliest endocardial depolarization during sinus rhythm and sinus tachycardia using high density activation mapping. Noncontact mapping of the right atrium during sinus rhythm was performed on ten anesthetized swine. Recordings were made during sinus rhythm, phenylephrine infusion, and isoproterenol infusion. The hearts were then excised and the histological sinus node identified. The mean minimum and maximum cycle lengths recorded were355 ± 43and717 ± 108 ms. A median of three (range two to five) sites of earliest endocardial depolarization were documented in each animal. With increasing heart rate the site of earliest endocardial depolarization remained stationary until a sudden shift in a cranial or caudal direction, often to sites beyond the histological sinoatrial node. The endocardial shift was unpredictable with considerable variation between animals; however, faster rates arose from more cranial sites(r = 0.46, P = 0.023). There was no difference in the mean cycle length of sinus rhythm originating from specific positions on the terminal crest(r = 0.44, P = 0.17). Cranial sites displayed a more diffuse pattern of early depolarization than caudal sites. In the porcine heart the relationship between heart rate and site of earliest endocardial depolarization shows considerable variation between individual animals. These findings may have implications for clinical mapping and ablation procedures. (PACE 2003; 26[Pt. I]:874,882) [source] NSAID switching and short-term gastrointestinal outcome rates after the withdrawal of rofecoxibPHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 12 2009Sebastian Schneeweiss MD Abstract Objective The consequences of the rofecoxib withdrawal on upper GI toxicity are largely unknown. We sought to estimate the effect of switching from selective Cox-2 inhibitors to non-selective non-steroidal anti-inflammatory drugs (nsNSAIDs) on the incidence of upper GI adverse events following the withdrawal of rofecoxib on 30 September 2004. Methods We identified a cohort of 33,045 patients with arthritis and chronic use of any selective Cox-2 inhibitor during the 6 months before the withdrawal of rofecoxib in claims data from several US health plans. We calculated monthly rates of hospitalization for upper GI adverse events or upper GI endoscopy for the 6 months before and 3 months after the switching and compared the time trends in outcomes. Results In the subgroup of 15,916 patients using rofecoxib immediately before its withdrawal, 2626 (17%) switched to nsNSAIDs without co-prescribing of a gastroprotective drug, 146 (1%) with a gastroprotective drug, and 5246 (33%) switched to either celecoxib or valdecoxib. Among those switching to nsNSAID without gastroprotection, time trends of upper GI hospitalization rates and endoscopies did not significantly increase compared with those switching to celecoxib or valdecoxib (+0.3 per 1000 per month; 95%CI ,3.0 to 3.5). The visit rate for peptic ulcer disease (PUD) increased more in the group switching to nsNSAIDs without gastroprotection (+5.2 visits per 1000 per month; 1.2,9.2) compared with the group switching to another coxib. Conclusions Short-term follow-up data suggest that the sudden shift from rofecoxib to nsNSAIDs without gastroprotection did not increase the rate of hospitalization for GI complications but increased outpatient visits for PUD. Copyright © 2009 John Wiley & Sons, Ltd. [source] Visual guidance of the human foot during a stepTHE JOURNAL OF PHYSIOLOGY, Issue 2 2005Raymond F. Reynolds When the intended foot placement changes during a step, either due to an obstacle appearing in our path or the sudden shift of a target, visual input can rapidly alter foot trajectory. However, previous studies suggest that when intended foot placement does not change, the path of the foot is fixed after it leaves the floor and vision has no further influence. Here we ask whether visual feedback can be used to improve the accuracy of foot placement during a normal, unperturbed step. To investigate this we measured foot trajectory when subjects made accurate steps, at fast and slow speeds, to stationary floor-mounted targets. Vision was randomly occluded in 50% of trials at the point of foot-off. This caused an increase in foot placement error, reflecting lower accuracy and higher variability. This effect was greatest for slow steps. Trajectory heading analysis revealed that visually guided corrections occurred as the foot neared the target (on average 64 mm away). They occurred closer to the target for the faster movements thus allowing less time and space to execute corrections. However, allowing for a fixed reaction time of 120 ms, movement errors were detected when the foot was approximately halfway to the target. These results suggest that visual information can be used to adjust foot trajectory during the swing phase of a step when stepping onto a stationary target, even for fast movements. Such fine control would be advantageous when environmental constraints place limitations on foot placement, for example when hiking over rough terrain. [source] The Estimation of a Cusp Model to Describe the Adoption of Word for Windows,THE JOURNAL OF PRODUCT INNOVATION MANAGEMENT, Issue 1 2004Rense Lange This article revisits earlier work in this journal by Paul Herbig (1991) that proposed a catastrophe model of industrial product adoption under certain conditions. Catastrophe models are useful for modeling situations where organizations can exhibit both smooth and abrupt adoption behavior. It extends Herbig's work by focusing on organizations' adoption of new products when network externalities are an important part of the decision process, and it presents an empirical estimation of the model. Network externalities occur when firms do not want to adopt a new innovation or product unless other firms do. The reason is that they do not want to end up with an innovation that ends up not being a standard of some sort. Mistakes of this nature can be costly as the firm must invest twice and loses time relative to competitors who have not made such a mistake. However, when such externalities exist, for example with regard to technological adoptions, then normal diffusion gives way to sudden discontinuous shifts as all firms seemingly act together an move to a new technology. Since, technology is an area where the authors expect network externalities to exist, that is the focus of this article. The specific application is developed from two sets of panel data on the organizational adoptions of Microsoft's (MS) Word for Windows software by organizations that previously were using either Word for DOS or Word for Macintosh (Mac). The theoretical framework for the analysis is based on work in the economics literature on network externalities. However, the organization and new product development catastrophe model comes primarily from Herbig (1991). The article focuses on an area of organizational adoption where relatively little empirical research has been done, namely organizational adoption "for use." Longitudinal data provided by Techtel Corporation is used to develop the estimations. Results of the empirical analysis are consistent with the theoretical framework suggested in Herbig's article and in those found in economics and catastrophe theory literatures. This lends clear support to the idea that organizations will adopt a bandwagon-type behavior when network externalities are present. It further suggests that in such markets, the standard S-shaped diffusion curve is not an appropriate model for examining organizational behavior. From a managerial perspective, it means that buyers and sellers may face nonstandard diffusion curves. Instead of S-shaped curves, the actual curves have a break or rift where sales end, and there is a sudden shift to a new product that is relatively high very early on. Clearly, for new product development (NPD), it suggest that organizations' "for-use" purchases may be similar to regular consumers and may change rapidly from one product to another almost instantly, as in the case of the switch from vinyl records to compact discs (CDs). From an old product seller's viewpoint, the market is here today and gone tomorrow, while for the new seller it is a sudden deluge of sales requests. To put it in more everyday terms, sudden changes in adoption behavior are a September 11-type experience for the market. It is the day the world changes. [source] | ||||||||||