Synergistic Model of Cardiac Function with a Heart Assist Device

The breakdown of cardiac self-organization leads to heart diseases and failure, the number one cause of death worldwide. The left ventricular pressure–volume relation plays a key role in the diagnosis and treatment of heart diseases. Lumped-parameter models combined with pressure–volume loop analysis are very effective in simulating clinical scenarios with a view to treatment optimization and outcome prediction. Unfortunately, often invoked in this analysis is the traditional, time-varying elastance concept, in which the ratio of the ventricular pressure to its volume is prescribed by a periodic function of time, instead of being calculated consistently according to the change in feedback mechanisms (e.g., the lack or breakdown of self-organization) in heart diseases. Therefore, the application of the time-varying elastance for the analysis of left ventricular assist device (LVAD)–heart interactions has been questioned. We propose a paradigm shift from the time-varying elastance concept to a synergistic model of cardiac function by integrating the mechanical, electric, and chemical activity on microscale sarcomere and macroscale heart levels and investigating the effect of an axial rotary pump on a failing heart. We show that our synergistic model works better than the time-varying elastance model in reproducing LVAD–heart interactions with sufficient accuracy to describe the left ventricular pressure–volume relation

Analyzing impact of experience curve on ROI in the software product line adoption process

Cataloged from PDF version of article.Context: Experience curve is a well-known concept in management and education science, which explains the phenomenon of increased worker efficiency with repetitive production of a good or service. Objective: We aim to analyze the impact of the experience curve effect on the Return on Investment (ROI) in the software product line engineering (SPLE) process. Method: We first present the results of a systematic literature review (SLR) to explicitly depict the studies that have considered the impact of experience curve effect on software development in general. Subsequently, based on the results of the SLR, the experience curve effect models in the literature, and the SPLE cost models, we define an approach for extending the cost models with the experience curve effect. Finally, we discuss the application of the refined cost models in a real industrial context. Results: The SLR resulted in 15 primary studies which confirm the impact of experience curve effect on software development in general but the experience curve effect in the adoption of SPLE got less attention. The analytical discussion of the cost models and the application of the refined SPLE cost models in the industrial context showed a clear impact of the experience curve effect on the time-to-market, cost of development and ROI in the SPLE adoption process. Conclusions: The proposed analysis with the newly defined cost models for SPLE adoption provides a more precise analysis tool for the management, and as such helps to support a better decision making. © 2014 Elsevier B.V. All rights reserved

The ERASMUS Teaching Staff Mobility: The Perspectives and Experiences of Turkish ELT Academics

The purpose of this study is to investigate the perspectives and experiences of the Turkish ELT academics about joining ERASMUS Teaching Staff Mobility Program. Under the light of former studies and literature, this study attempts to investigate the preferences of the ELT academics for participating in the ERASMUS Teaching Staff Mobility, to examine the contribution of the enrollment in this program to their professional development and home institution, and finally, to learn about the problems they faced during the mobility period(s). Purposive sample method was used to select seventeen Turkish ELT academics to participate in this study. The data were obtained through a triangulated approach, in which questionnaires, semi-structured interviews and reflective essays were administered to the participants. The findings revealed that apart from some problems experienced before and during the program, the Turkish ELT academics preferred to participate in the ERASMUS Teaching Staff Mobility due to its positive impact on their professional development and their home institution

‘Flash Crash’: The first market crash in the era of algorithms and automated trading

How non-designated intraday intermediaries responded in the E-mini S&P 500 futures market crash on 6 May 2010 - by Andrei Kirilenko, Albert Kyle, Mehrdad Samadi, and Tugkan Tuzu

The flash crash: The impact of high frequency trading on an electronic market

The Flash Crash, a brief period of extreme market volatility on May 6, 2010, raised questions about the current structure of the U.S. financial markets. We use audit-trail data to describe the structure of the E-mini S&P 500 stock index futures market on May 6. We ask three questions. How did High Frequency Traders (HFTs) trade on May 6? What may have triggered the Flash Crash? What role did HFTs play in the Flash Crash? We conclude that HFTs did not trigger the Flash Crash, but their responses to the unusually large selling pressure on that day exacerbated market volatility

The correlation between magnetic resonance detected cartilage defects and spiking of tibial tubercles in osteoarthritis of the knee joint.

The aim of the study was to ascertain whether spiking of the tibial tubercle is associated with cartilage defects detected by magnetic resonance imaging (MRI) in patients with osteoarthritis (OA) of the knee joint. Angulation of the tip of the medial and lateral tubercles, and the height of the tubercles above the tibial plateau were measured on a standard anteroposterior radiograph of the knee joint. Cartilage defects in the tibiofemoral joint (TFJ) were determined by MRI examination. The lengthening and sharpening of the angles of the tubercles were significantly more prominent in the patients than controls. A strong association was found between angulation (if less than 70 degrees) and especially the height (if more than 0.16) of the medial tibial spike and MRI-detected cartilage defects in the medial tibiofemoral compartment. The predictive value of the spiking of tibial tubercles for MRI-detected cartilage defects in TFJ is related to the degree and size of the spiking. The presence of tibial spiking itself may not be a reliable sign of early OA

An efficient heuristic for the multi-vehicle one-to-one pickup and delivery problem with split loads

In this study, we consider the Multi-vehicle One-to-one Pickup and Delivery Problem with Split Loads (MPDPSL). This problem is a generalization of the one-to-one Pickup and Delivery Problem (PDP) where each load can be served by multiple vehicles as well as multiple stops by the same vehicle. In practice, split deliveries is a viable option in many settings where the load can be physically split, such as courier services of third party logistics operators. We propose an efficient heuristic that combines the strengths of Tabu Search and Simulated Annealing for the solution of MPDPSL. Results from experiments on two problems sets in the literature indicate that the heuristic is capable of producing good quality solutions in reasonable time. The experiments also demonstrate that up to 33\% savings can be obtained by allowing split loads; however, the magnitude of savings is dependent largely on the spatial distribution of the pickup and delivery points

Size Segregation of Granular Matter in Silo Discharges

We present an experimental study of segregation of granular matter in a quasi-two dimensional silo emptying out of an orifice. Size separation is observed when multi-sized particles are used with the larger particles found in the center of the silo in the region of fastest flow. We use imaging to study the flow inside the silo and quantitatively measure the concentration profiles of bi-disperse beads as a function of position and time. The angle of the surface is given by the angle of repose of the particles, and the flow occurs in a few layers only near the top of this inclined surface. The flowing region becomes deeper near the center of the silo and is confined to a parabolic region centered at the orifice which is approximately described by the kinematic model. The experimental evidence suggests that the segregation occurs on the surface and not in the flow deep inside the silo where velocity gradients also are present. We report the time development of the concentrations of the bi-disperse particles as a function of size ratios, flow rate, and the ratio of initial mixture. The qualitative aspects of the observed phenomena may be explained by a void filling model of segregation.Comment: 6 pages, 10 figures (gif format), postscript version at http://physics.clarku.edu/~akudrolli/nls.htm