The Long-Term Effectiveness of Methadone Maintenance Treatment in Prevention of Hepatitis C Virus Among Illicit Drug Users : A Modeling Study

Article Accepted Date: Oct 7, 2013 Acknowledgments: We would like to thank all MMT centers' staff in Shiraz for their cooperation in this study. Funding Support: This study was funded and supported by the Tehran University of Medical Sciences.Peer reviewedPublisher PD

Cost-effectiveness of Methadone Maintenance Treatment in prevention of HIV among drug users in Shiraz, south of Iran

Background: The increase in high-risk injections and unsafe sexual behaviors has led to increased HIV infection prevalence among Intravenous Drug Users (IDUs). The high costs of HIV/AIDS care and low financial resources necessitate an economic evaluation to make the best decision for the control of HIV/AIDS. Objectives: This study was conducted to determine the cost-effectiveness of Methadone Maintenance Treatment (MMT) centers in HIV infection prevention among drug users. Materials and Methods: In this interventional study, we included all the seven MMT centers and the drug users registered there (n = 694). We calculated all the costs imposed on the government, i.e. Provider of case. Mathematical models were used to estimate the number of HIV cases averted from high-risk behaviors. Sensitivity analyses were performed to show the effects of uncertainty in parameters on the number of HIV cases averted and also Incremental Cost-Effectiveness Ratio (ICER). Results: Based on the averted models, the selected MMT centers could prevent 128 HIV cases during 1 year. The total cost was $547423 and that of HIV/AIDS care in the no intervention scenario was estimated$ 14171816. ICER was $106382 per HIV case averted. The results of the sensitivity analysis indicated that MMT intervention was cost-effective even in the worst scenario and ICER varied from$ 39149 to $ 290004 per HIV case averted. Conclusions: With regard to the high prevalence of drug injection among drug users and considering the high effectiveness and cost-effectiveness of MMT centers in preventing HIV infection, establishment of MMT centers in regional and national levels seems reasonable. © 2013, Iranian Red Crescent Medical Journal

Phase-field approach to surface-induced phase transformations and dislocations

Martensitic phase transformations (PTs) play a very important part in material science, being responsible for formation of unique microstructure, mechanical properties, and material phenomena in steels, shape memory alloys and ceramics. In particular, surface-induced PTs and pretransformations, surface energy, surface tension, interface, and scale effect at the nanoscale play essential roles in thermodynamics, kinetics, and nanostructures. In addition, various material phenomena are related to the interaction of martensitic PTs and plastic deformation due to twinning and dislocations and are of fundamental and technological importance. Examples are: heat and thermomechanical treatment of material to obtain desired structure and properties; pseudoelasticity, pseudoplasticity, shape memory effect; transformation-induced plasticity (TRIP); and synthesis of materials under high pressure with large plastic deformations, e.g., during ball milling; and PTs during friction, surface treatment, and projectile penetration. The two main approaches to study martensitic PTs are the sharp interface approach (SIA) and the phase field approach (FPA). In the SIA, the interface between two phases is considered as a single surface across which there is a jump in all thermomechanical properties. In contrast, in the FPA, the interface has a finite width across which properties smoothly vary from one phase to another. Each phase is shown by an order parameter which varies from 0, corresponding to austenite (A), to 1, corresponding to martensite (M). The PFA is broadly used to study the martensitic PTs, however the current FP models cannot describe a lot of basic physics. In our work, we advanced the PFA to martensitic PTs in three important directions: the potential is developed that introduces the surface tension at interfaces; a mixed term in gradient energy is introduced to control the martensite-martensite interface energy independent of that for austenite-martensite; and a noncontradictory expression for variable surface energy is suggested. The problems of surface-induced pretransformation, barrierless multivariant nucleation, and the growth of an embryo in a nanosize sample are solved to elucidate the effect of the above contributions. Also, an in-detail study of M-M interface width, energy, and surface tension, as well as the effect of finite element discretization on the width and the energy, and the formation of martensitic nanostructures in the trasnforming grain is presented. In addition, the external surface layer, as a new key parameter in surface-induced PTs, is introduced in PFA, and the effect of the width of this layer and internal stresses on surface-induced pretransformation and PTs is revealed. In addition to study martensitic PTs using FPA, we used FPA to study dislocations evolution. The current PFA to dislocations, which is based on a formalism similar to the PFA for martensitic PTs, suffers from several main drawbacks. In our work, the PF theory to dislocations is conceptually advanced in the following directions: (a) Large strain formulation is developed. (b) A new local potential is developed to eliminate stress-dependence of the Burgers vector and to reproduce desired local stress-strain curve, as well as the desired, mesh-independent, dislocation height for any dislocation orientation. (c) A new gradient energy is defined to exclude localization of dislocation within height smaller than the prescribed height but does not produce artificial interface energy and dislocation widening. After developing the most advanced PFA to PTs and dislocations, we developed a new PF theory to coupled evolution of PTs and dislocations and the following problems of the interaction of PTs and dislocations are studied: hysteretic behavior and propagation of A-M interface with incoherency dislocations for temperature-induced PT; evolution of phase and dislocation structures for stress-induced PT, and the growth and arrest of martensitic plate for temperature-induced PT

Vibration Control of Bridge Stay Cables Using Negative Stiffness Dampers

Stay cables are one of the main structural elements in a cable-stayed bridge. Due to their high lateral flexibility and low inherent damping, cables are susceptible to large-amplitude vibrations that can adversely affect bridge safety and serviceability. As a practical measure, passive viscous dampers are installed transversely near the cable-deck anchorage. However, such devices can only provide a limited amount of damping. In recent years, the need for an effective yet simple control technique has led to the development of high-performance passive negative stiffness dampers (NSD). The present dissertation aims to study the behaviour of NSDs, enable their design for mitigating excessive bridge stay cable vibrations and evaluate their control effectiveness in comparison with other alternative schemes. To investigate the behaviour of NSDs, an analytical study has been conducted to obtain the in-plane free-vibration response of a shallow-flexural damped cable. The effect of damper stiffness was modeled as a linear spring aligned in parallel with a linear viscous dashpot. As a refinement to the existing damper design formulas, a unified design equation has been developed for the idealized fixed-fixed and hinged-hinged cable boundary conditions. The design procedure is based on an asymptotic solution to the modal damping ratio of the cable-damper system. The mode superposition method (MSM) has been adopted to numerically simulate the dynamic response of a controlled shallow-flexural cable subjected to arbitrary dynamic excitations. The numerical efficiency of the MSM was improved by including the cable static displacement caused by an arbitrary point load at the damper location as a correction term in the shape function vector and modifying the conventional sinusoidal shape functions to satisfy the boundary conditions. Results showed that the refined design formula yielded a slightly conservative estimation and therefore safe damper design. Also, the enhanced MSM-based numerical framework was found to substantially reduce the computational cost for designing cable vibration control schemes. Using the aforementioned analytical and numerical tools, the control performance of a NSD has been evaluated. The superior control effectiveness of a NSD compared to the positive- and zero-stiffness dampers was justified by employing the force generation mechanism of a viscous damper with linear stiffness. Theoretical and practical limits of the negative damper stiffness have been identified to ensure the stability of NSD and avoid unsafe design. An innovative NSD design procedure for mitigating both the single-mode and the multi-mode stay cable vibrations has been proposed. Analytical design relationships have been developed to determine NSD parameters for achieving the desired damping ratio in target mode(s). The impact of damper support flexibility on the NSD control performance has been studied to determine the optimum combination of NSD parameters and damper support stiffness. Results showed that the performance of a NSD designed/optimized based on the proposed methods was comparable to that of an optimal active controller. Furthermore, it has been found that optimizing NSD for a flexible damper support would result in a cost-efficient NSD design and inhibit additional NSD-induced cable displacement. The outcomes yielded from this dissertation extend the current knowledge associated with the dynamic behaviour of NSD-equipped bridge stay cables. The developed analytical/numerical tools and optimization methods contribute to the bridge industry by enabling accurate, efficient and reliable design of cable-NSD systems either in the preliminary design stage or during the rehabilitation process of cable-stayed bridges. The findings of this study will assist infrastructure management and improve the global economy by extending the life-span of cable-stayed bridges

Prevalence and types of rectal douches used for anal intercourse: results from an international survey.

BackgroundRectal products used with anal intercourse (AI) may facilitate transmission of STIs/HIV. However, there is limited data on rectal douching behavior in populations practicing AI. We examined the content, types of products, rectal douching practices and risk behaviors among those reporting AI.MethodsFrom August 2011 to May 2012, 1,725 women and men reporting receptive AI in the past 3 months completed an internet-based survey on rectal douching practices. The survey was available in English, French, German, Mandarin, Portuguese, Russian, Spanish, and Thai and included questions on sexual behaviors associated with AI including rectal douching. Differences by rectal douching practices were evaluated using chi-square methods and associations between reported douching practices and other factors including age and reported STI history were evaluated using logistic regression analysis.ResultsRespondents represented 112 countries, were mostly male (88%), and from North America (55%) or Europe (22%). Among the 1,339 respondents (66%) who reported rectal douching, most (83%) reported always/almost always douching before receptive AI. The majority of rectal douchers reported using non-commercial/homemade products (93%), with water being the most commonly used product (82%). Commercial products were used by 31%, with the most common product being saline-based (56%). Rectal douching varied by demographic and risk behaviors. The prevalence of rectal douching was higher among men (70% vs. 32%; p-value < .01), those reporting substance-use with sex (74% vs. 46%; p-value < .01), and those reporting an STI in the past year (69% vs. 57% p-value < .01) or ever testing HIV-positive (72% vs. 53%; p-value < .01). In multivariable analysis, adjusting for age, gender, region, condom and lubricant use, substance use, and HIV-status, douchers had a 74% increased odds of reporting STI in the past year as compared to non-douchers [adjusted odds ratio (AOR) = 1.74; 95% CI 1.01-3.00].ConclusionGiven that rectal douching before receptive AI is common and because rectal douching was associated with other sexual risk behaviors the contribution of this practice to the transmission and acquisition of STIs including HIV may be important

Phase field approach to interaction of phase transformations and plasticity at large strains

Thermodynamically consistent phase field approach (PFA) for multivariant martensitic phase transformations (PTs) and twinning for large strains is developed [1, 2]. Thermodynamic potential in hyperspherical order parameters is introduced, which allowed us to describe each martensite‑martensite (i.e., twin) interface with a single order parameter [3]. These theories are utilized for finite element simulation of various important problems [1‑4]. Phase field approach to dislocation evolution was developed during the last decade and it is widely used for the simulation of plasticity at the nanoscale. Despite significant success, there are still a number of points for essential improvement. In our study [5], a new PFA to dislocation evolution is developed. It leads to a well-posed formulation and mesh-independent solutions and is based on fully large-strain formulation. Our local potential is designed to eliminate stress-dependence of the Burgers vector and to reproduce desired local stress–strain curve, as well as to obtain the mesh-independent dislocation height H for any dislocation orientation. The gradient energy contains an additional term, which excludes localization of dislocation within height smaller than H but disappears at the boundary of dislocation and the rest of the crystal; thus, it does not produce interface energy and does not lead to a dislocation widening. Problems for nucleation and evolution of multiple dislocations along the multiple slip systems are studied. The interaction between PT and dislocations is the most basic problem in the study of martensite nucleation and growth. Here, a PFA is developed to a coupled evolution of martensitic PTs and dislocations [6], including inheritance of dislocation during direct and reverse PTs. A complete system of equations, including Ginzburg–Landau equations is presented. It is applied to studying the hysteretic behavior and propagation of an austenite‑martensite interface with incoherency dislocations, the growth and arrest of martensitic plate for temperature-induced PTs, the evolution of phase and dislocation structures for stress-induced PTs, and the evolution of dislocations and high pressure phase in a nanograined material under pressure and shear [6, 7]. REFERENCES [1] Levitas, V.I., Levin, V.A., Zingerman, K.M., Freiman, E.I. Phys. Rev. Lett. 2009, 103, 025702. [2] Levitas, V.I. Int. J. Plasticity. 2013, 49, 85‑118. [3] Levitas, V.I., Roy, A.M., Preston, D.L. Phys. Rev. B. 2013, 88, 054113. [4] Levin, V.A., Levitas, V.I., Zingerman, K.M., Freiman, E.I. Int. J. Solids & Struct. 2013, 50, 2914‑2928. [5] Levitas, V.I., Javanbakht, M. Phys. Rev. B., Rapid Commun. 2012, 86, 140101. [6] Levitas, V.I., Javanbakht, M. Appl. Phys. Lett. 2013, 102, 251904. [7] Levitas, V.I., Javanbakht, M. Nanoscale. 2014, 6, 162‑166