An economic evaluation of the use of rare earth screens to reduce the radiation dose from diagnostic X-ray procedures in Israel

In Israel the diffusion of rare earth screen technology has been limited. These screens could halve the radiation dose to the patient from diagnostic X-ray radiography, with little managerial effort and without being detrimental to the quality of the diagnostic image. We estimated the total effective dose from diagnostic film radiography capable of reduction by the use of rare earth screens, based on the number of hospital and ambulatory diagnostic X-ray procedures. This number was multiplied by the computed radiation dose per body site for a series of diagnostic procedures. The annual dose was approximately 0.53 mSv per head, approximately half of which could be averted by the introduction of rare earth screen technology. Based on a fatality risk of 3% Sv-1, it is estimated that the adoption of rare earth screen technology might reduce the annual incidence of cancer by some 93 cases, half of which would be fatal after an average latency period of 18.4 years. The cost of purchasing rare earth screens on a nationwide basis is approximately $3.0 million. This cost is outweighed by a saving of $9.6 million in X-ray tube replacement costs over the period 1997-2006. Government legislation enforcing the use of rare earth screens is essential, because of the lack of prestige associated with acquiring rare earth technology, as well as institutional reluctance to accept the external benefits of reduced morbidity and mortality and/or to extend budgetary time horizons.     

Mass transfer in an electrochemical reactor with two interacting jets

An electrochemical reactor operated with two identical solution streams injected in opposite directions on the same axis, and leaving it at a normal direction was studied by measuring local and global mass transfer coefficients and visualization of solution flow patterns. This flow configuration was compared to a case where a single stream enters the reactor and leaves it on the same axis. It was found that only the data obtained for the single stream mode can be correlated by the Chilton-Colburn relation, indicating a near laminar boundary layer flow. Global mass transfer coefficients for the single stream mode were found to be slightly higher than those for the interacting jets mode. However, when comparing the two modes by taking into account the dimensionless ratio of the mass transfer coefficient (Sh) to the energy consumption (Eu), it was found that the interacting jets (IJ) mode exhibits a better performance as compared to the single stream mode. The superiority of the IJ mode increases with increasing Reynold's number (Re).Nomenclature A, B adjustable parameters - b half width of channel - C electrolyte ion concentration - d inlet pipe diameter - d microelectrode diameter - D diffusion coefficient - maximum value of mean deviation - E pumping energy - Eu Euler number - F Faraday number - i current to a single microelectrode on an active wall - i current to a single microelectrode in an inert wall - I global diffusion current - k mass transfer coefficient to a single microelectrode in an active wall - k mass transfer coefficient to a single microelectrode in an inert wall - K global mass transfer coefficient - Q volumetric flow rate - Q _T total volumetric flow rate - R radius of the electrochemical reactor - Re Reynolds number - s surface area of a microelectrode - S surface area of the working electrode - Sc Schmidt number - Sh Sherwood number - V _x axial flow velocity alongx-axis - V flow velocity at large distance from the leading edge - V mean flow velocity - x axis tangential to the surface - y axis normal to the surface - z number of electrons transferred in the reaction (z=1 in the present case) Greek letters viscosity - specific gravity - kinematic viscosity (/) - P pressure drop across the reactor - V voltage drop across the reactor Abbreviations ST single stream - IJ interacting jets     

Water desalting by means of electrochemical parametric pumping. II. Separation properties of a multistage column

Multistage electrochemical parametric pumping has been successfully carried out for water desalination. Separation was effected by electroadsorption-desorption cycles of the ions into and from the electrical double layer of high surface carbon electrodes. At steady state and total reflux, the concentration ratio between the upper and lower heads of the electrochemical column was as high as 150. Two models for the build up of the concentration profile within the column are presented. The first is based on a solution of the two-phase mass transport equation using the proper boundary and initial conditions. The second treatment is based on the mixed cells assumptions. In both treatments, interphase equilibrium is assumed using the isopotentiograms as the specific equilibrium curves. Use is also made of a fast computer for the simulation of the electrochemical paramatric pumping cycles. The two models are in good agreement with the experimental results particularly in the cases where the initial concentration is high and interphase equilibrium is maintained.     

Infrared study of salt free and salt treated cellulose pyrolysis under nitrogen atmosphere

The pyrolysis under nitrogen of salt free and salt treated cellulose was studied by infrared spectroscopy. The results confirm the unzipping mechanism suggested by DTA and TGA studies, and show this mechanism to apply to the untreated and salt treated samples. The results also show the unzipping to stop at the stage of char formation. The onset of this stage was found to occur after the volatilization of only 45–50% of the initial sample of the borax treated cellulose, compared with 65–70% of the KCl treated cellulose and 80–85% of the untreated cellulose.     

Deconstructing gamification: evaluating the effectiveness of continuous measurement,virtual rewards,and social comparison for promoting physical activity

Game design elements are often implemented in persuasive systems aimed to promote physical activity, a process called “gamification.” Gamification is believed to motivate users to become more active, and is commonly implemented in commercial products. However, relatively few studies rigorously evaluated the effectiveness of gamification, and they yielded contradicting findings. We set out to evaluate the effectiveness of virtual rewards and social comparison—two game elements prevalent in persuasive systems. We developed a research prototype, called “StepByStep,” aimed to promote routine walking. We created different versions of StepByStep, implemented as an application on Android-based mobile devices, and compared their effectiveness in two field studies. Study 1 showed that a quantified version of the application—offering continuous measurement of walking time, a daily goal, and real-time feedback on progress toward this goal—facilitated reflection on activity and significantly increased walking time over baseline level. Study 2 showed that gamified versions offering virtual rewards and social comparison were only as effective as the quantified version. Thus, we advise designers to facilitate reflection on meaningful aspects of physical activity by developing novel ubiquitous measures. Furthermore, our findings highlight the importance of systematic comparisons between quantified and gamified elements for better understanding their motivational affordances.     

Covalent surface functionalization of nonwoven fabrics with controlled hydrophobicity,water absorption,and pH regulation properties

A modular method for functionalization of nonwoven fabrics was developed using a two-step process. In the first step, the fabrics were grafted with a linker molecule, 10-undecenoyl chloride, via esterification, followed by attachment of a functional material under UV irradiation. Perfluorodecanethiol and 3-mercaptopropionic acid (MPA) were connected to the linker-modified fabrics using thiol-ene click chemistry. Perfluorodecanethiol modified fabrics exhibited hydrophobicity with water contact angle of about 140° while MPA-modified fabrics were able to lower the pH of a solution by about 1.6. We additionally demonstrated the possibility to connect functional polymers to the linker-modified fabrics by radical graft polymerization of acrylic acid; this produced a thin layer of the polymer on the surface of the fabric. Fabrics modified with poly(acrylic acid) exhibited increased hydrophilicity with water contact angle of 0° for both cotton and viscose-polyester fabrics, while the water absorption capability for polypropylene fabrics increased from about 50 to 1200%.     

Speeding Up HMM Decoding and Training by Exploiting Sequence Repetitions

We present a method to speed up the dynamic program algorithms used for solving the HMM decoding and training problems for discrete time-independent HMMs. We discuss the application of our method to Viterbi’s decoding and training algorithms (IEEE Trans. Inform. Theory IT-13:260–269, 1967), as well as to the forward-backward and Baum-Welch (Inequalities 3:1–8, 1972) algorithms. Our approach is based on identifying repeated substrings in the observed input sequence. Initially, we show how to exploit repetitions of all sufficiently small substrings (this is similar to the Four Russians method). Then, we describe four algorithms based alternatively on run length encoding (RLE), Lempel-Ziv (LZ78) parsing, grammar-based compression (SLP), and byte pair encoding (BPE). Compared to Viterbi’s algorithm, we achieve speedups of Θ(log n) using the Four Russians method, using RLE, using LZ78, using SLP, and Ω(r) using BPE, where k is the number of hidden states, n is the length of the observed sequence and r is its compression ratio (under each compression scheme). Our experimental results demonstrate that our new algorithms are indeed faster in practice. We also discuss a parallel implementation of our algorithms. A preliminary version of this paper appeared in Proc. 18th Annual Symposium on Combinatorial Pattern Matching (CPM), pp. 4–15, 2007. Y. Lifshits’ research was supported by the Center for the Mathematics of Information and the Lee Center for Advanced Networking. S. Mozes’ work conducted while visiting MIT.     

Back to the Future: An Historical Perspective on the Pendulum-Like Changes in Literacy

This article focuses on the pendulum-like change in the way people read and use text, which was triggered by the introduction of new reading and writing technologies in human history. The paper argues that textual features, which characterized the ancient pre-print writing culture, disappeared with the establishment of the modern-day print culture and has been “revived” in the digital post-modern era. This claim is based on the analysis of four cases which demonstrate this textual-pendulum swing: (1) The swing from concrete iconic-graphic representation of letters and words in the ancient alphabet to abstract phonetic representation of text in modern eras, and from written abstract computer commands “back” to the concrete iconic representation in graphic user interfaces of the digital era; (2) The swing from scroll reading in the pre-print era to page or book reading in the print era and “back” to scroll reading in the digital era; (3) The swing from a low level of authorship in the pre-print era to a strong authorship perception in the print era, and “back” to a low degree of authorship in the digital era; (4) The swing from synchronic representation of text in both visual and audio formats during the pre-print era to a visual representation only in print, and “back” to a synchronic representation in many environments of the digital era. We suggest that the print culture, which is usually considered the natural and preferred textual environment, should be regarded as the exception.     

Lower bounds for testing Euclidean Minimum Spanning Trees

The Euclidean Minimum Spanning Tree problem is to decide whether a given graph G=(P,E) on a set of points in the two-dimensional plane is a minimum spanning tree with respect to the Euclidean distance. Czumaj et al. [A. Czumaj, C. Sohler, M. Ziegler, Testing Euclidean Minimum Spanning Trees in the plane, Unpublished, Part II of ESA 2000 paper, downloaded from http://web.njit.edu/~czumaj/] gave a 1-sided-error non-adaptive property-tester for this task of query complexity . We show that every non-adaptive (not necessarily 1-sided-error) property-tester for this task has a query complexity of , implying that the test in [A. Czumaj, C. Sohler, M. Ziegler, Testing Euclidean Minimum Spanning Trees in the plane, Unpublished, Part II of ESA 2000 paper, downloaded from http://web.njit.edu/~czumaj/] is of asymptotically optimal complexity. We further prove that every adaptive property-tester has query complexity of Ω(n1/3). Those lower bounds hold even when the input graph is promised to be a bounded degree tree.