One of the key challenges of video game design is teaching new players how to play. Although game developers frequently use tutorials to teach game mechanics, little is known about how tutorials affect game learnability and player engagement. Seeking to estimate this value, we implemented eight tutorial designs in three video games of varying complexity and evaluated their effects on player engagement and retention. The results of our multivariate study of over 45,000 players show that the usefulness of tutorials depends greatly on game complexity. Although tutorials increased play time by as much as 29% in the most complex game, they did not significantly improve player engagement in the two simpler games. Our results suggest that investment in tutorials may not be justified for games with mechanics that can be discovered through experimentation.

BackgroundMany clinicians and insurance providers are reluctant to embrace recent guidelines identifying people who inject drugs (PWID) as a priority population to receive hepatitis C virus (HCV) treatment. The aim of this study was to evaluate the efficacy of direct-acting antiviral (DAA) HCV therapy in a real-world population comprised predominantly of PWID.MethodsA retrospective analysis was performed on all HCV-infected patients who were treated at the Vancouver Infectious Diseases Centre between March 2014 and December 2017. All subjects were enrolled in a multidisciplinary model of care, addressing medical, psychological, social, and addiction-related needs. The primary outcome was achievement of sustained virologic response (undetectable HCV RNA) 12 or more weeks after completion of HCV therapy (SVR-12).ResultsOverall, 291 individuals were enrolled and received interferon-free DAA HCV therapy. The mean age was 54 years, 88% were PWID, and 20% were HCV treatment experienced. At data lock, 62 individuals were still on treatment and 229 were eligible for evaluation of SVR by intent-to-treat (ITT) analysis. Overall, 207 individuals achieved SVR (90%), with 13 losses to follow-up, 7 relapses, and 2 premature treatment discontinuations. ITT SVR analysis show that active PWID and treatment-naïve patients were less likely to achieve SVR (P = .0185 and .0317, respectively). Modified ITT analysis of active PWID showed no difference in achieving SVR (P = .1157) compared with non-PWID.ConclusionWithin a multidisciplinary model of care, the treatment of HCV-infected PWID with all-oral DAA regimens is safe and highly effective. These data justify targeted efforts to enhance access to HCV treatment in this vulnerable and marginalized population.

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Many considerations, involving understanding and selection of multiple experimental parameters, are required to perform MicroPET studies properly. The large number of these parameters/ variables and their complicated interdependence make their optimal choice nontrivial. We have a developed kinetic imaging system (KIS), an integrated software system, to assist the planning, design, and data analysis of MicroPET studies. The system serves multiple functions-education, virtual experimentation, experimental design, and image analysis of simulated/experimental dataand consists of four main functional modules-"Dictionary," "Virtual Experimentation," "Image Analysis," and "Model Fitting." The "Dictionary" module provides didactic information on tracer kinetics, pharmacokinetic, MicroPET imaging, and relevant biological/pharmacological information. The "Virtual Experimentation" module allows users to examine via computer simulations the effect of biochemical/pharmacokinetic parameters on tissue tracer kinetics. It generates dynamic MicroPET images based on the user's assignment of kinetics or kinetic parameters to different tissue organs in a 3-D digital mouse phantom. Experimental parameters can be adjusted to investigate the design options of a MicroPET experiment. The "Image Analysis" module is a full-fledged image display/manipulation program. The "Model Fitting" module provides model-fitting capability for measured/simulated tissue kinetics. The system can be run either through the Web or as a stand-alone process. With KIS, radiotracer characteristics, administration method, dose level, imaging sequence, and image resolution-to-noise tradeoff can be evaluated using virtual experimentation. KIS is designed for biology/pharmaceutical scientists to make learning and applying tracer kinetics fun and easy.

Abstract. The etiologic spectrum of acute encephalitis syndrome (AES) has not been well defined in Vietnam. Cohort and case-control studies were performed on all adult and pediatric AES patients admitted to the Neurology Service of Bach Mai Hospital between June 5 and August 3, 1995. Among pediatric AES patients, 31 (67%) of 46 had acute Japanese encephalitis (JE), compared with only two (6%) of 33 adult AES patients (P Ͻ 0.0001). For confirmed JE cases, serum specimens obtained 15-21 days after symptom onset had the highest mean anti-JE IgM signal-to-noise (P/N) ratios (8.08 ϩ 1.09 SE). A serosurvey of adult household members did not reveal any cases of recent subclinical JE infection, although 26% had evidence of past JE infection. The use of bed netting was nearly universal but did not appear to reduce the risk of AES or JE. Given the high incidence of JE, particularly among children, Vietnam seems well suited for the development of a targeted JE vaccination strategy.Japanese encephalitis (JE) virus, an arthropod-borne pathogen, is the most common documented cause of viral encephalitis in Asia, and potentially ranks only after human immunodeficiency virus as the most common cause of viral encephalitis in the world. 1 The JE virus is a member of the Flaviviridae family, is transmitted chiefly by mosquitoes of the Culex tritaeniorhynchus complex, and causes up to 50,000 cases annually in a broad geographic range extending from Japan and the People's Republic of China in the east to the Indian subcontinent in the West and to Oceania. 2 In Southeast Asia, the incidence of JE appears to be increasing, probably as a result of a steady rise in population density, deforestation, and increasing irrigation of agricultural areas. 3 Province-specific attack rates in northern Thailand are reported to be 10-20 per 100,000, making the incidence of the disease similar to that observed for poliomyelitis in the United States before the use of the Salk and Sabin vaccines. 4 The fatality rate for JE is generally high (5-30%), and approximately one-third of survivors suffer serious neurologic sequelae. [5][6][7] In addition, the social prognosis for handicapped survivors of JE is often poor in developing countries.Though viral encephalitis is a pressing public health problem in Vietnam, identification of the leading agents responsible for the acute encephalitis syndrome (AES) has been difficult. The development of the sandwich IgM ELISA test has greatly simplified the diagnosis of acute JE, but this test is generally not available in Vietnam. 8,9 From a perspective of disease surveillance and control, it is important to differentiate JE from other causes of AES, in part because JE is the only arbovirus encephalitis that can be prevented on a large scale by vaccination. We conducted the present study to determine the proportion of AES cases in children and adults that are due to JE, to investigate risk factors for acquisition of AES, and to assess the efficacy of household mosquito protection measures in the absence of a JE vaccin...