Distribution of residual autocorrelations for multiplicative seasonal ARMA models with uncorrelated but nonindependent error terms

In this paper, we consider portmanteau tests for testing the adequacy of multiplicative seasonal autoregressive moving‐average models under the assumption that the errors are uncorrelated but not necessarily independent. We relax the standard independence assumption on the error terms in order to extend the range of applications of the seasonal autoregressive moving‐average models. We study the asymptotic distributions of residual and normalized residual empirical autocovariances and autocorrelations under weak assumptions on noise. We establish the asymptotic behavior of the proposed statistics. A set of Monte Carlo experiments and an application to monthly mean total sunspot number are presented.     

瑞替普酶治疗急性心肌梗死患者的临床疗效

目的探讨瑞替普酶治疗急性心肌梗死患者的临床疗效。方法收集2013年1月至2014年2月收治的66例急性心肌梗死患者资料,按患者入院治疗时间顺序分为两组,对照组33例患者予以尿激酶治疗,瑞替普酶组33例患者予以瑞替普酶治疗。比较两组患者溶栓后临床再通率、病死率以及并发出血率。结果瑞替普酶组患者临床再通率明显高于对照组(P<0.05);且该组患者并发出血率、病死率均明显低于对照组(均P<0.05)。结论采用瑞替普酶治疗急性心肌梗死具有较高理想的临床治疗效果,且安全性高。     

Economic evaluation of nivolumab for the treatment of second-line advanced squamous NSCLC in Canada: a comparison of modeling approaches to estimate and extrapolate survival outcomes

Background Lung cancer is the most common type of cancer in the world and is associated with significant mortality. Nivolumab demonstrated statistically significant improvements in progression-free survival (PFS) and overall survival (OS) for patients with advanced squamous non-small cell lung cancer (NSCLC) who were previously treated. The cost-effectiveness of nivolumab has not been assessed in Canada. A contentious component of projecting long-term cost and outcomes in cancer relates to the modeling approach adopted, with the two most common approaches being partitioned survival (PS) and Markov models. The objectives of this analysis were to estimate the cost-utility of nivolumab and to compare the results using these alternative modeling approaches.

Methods Both PS and Markov models were developed using docetaxel and erlotinib as comparators. A three-health state model was used consisting of progression-free, progressed disease, and death. Disease progression and time to progression were estimated by identifying best-fitting survival curves from the clinical trial data for PFS and OS. Expected costs and health outcomes were calculated by combining health-state occupancy with medical resource use and quality-of-life assigned to each of the three health states. The health outcomes included in the model were survival and quality-adjusted-life-years (QALYs).

Results Nivolumab was found to have the highest expected per-patient cost, but also improved per-patient life years (LYs) and QALYs. Nivolumab cost an additional $151,560 and $140,601 per QALY gained compared to docetaxel and erlotinib, respectively, using a PS model approach. The cost-utility estimates using a Markov model were very similar ($152,229 and $141,838, respectively, per QALY gained).

Conclusions Nivolumab was found to involve a trade-off between improved patient survival and QALYs, and increased cost. It was found that the use of a PS or Markov model produced very similar estimates of expected cost, outcomes, and incremental cost-utility.     

Cooperation vs. competition in R&D: The role of stability of equilibrium

We consider a model in which firms first choose process R&D expenditures and then compete in an output market. We show the symmetric equilibrium under R&D competition is sometimes unstable, in which case two asymmetric equilibria must also exist. For the latter, we find, in contrast to the literature that total profits are sometimes higher with R&D competition than with research joint venture cartelization (due to the cost asymmetry of the resulting duopoly in the noncooperative case). Furthermore, these equilibria provide another instance of R&D-induced firm heterogeneity.     

Where are the airlines headed? Implications of airline industry structure and change for consumers

The airline industry is undergoing unprecedented change. This paper explores the consumer impacts of recent airline industry change, in the context of its oligopoly market structure and current industry environment. Economic and noneconomic events, increasing competition from low‐fare carriers, technological developments, and changes in industry practices are transforming consumer travel and interaction with airlines. Consumers can anticipate more direct flights, increased price transparency, and increased fees and time cost of security.     

Dynamic lot sizing problem with continuous-time Markovian production cost

This paper develops a polynomial algorithm for obtaining dynamic economic lot sizes in a single product multiperiod production system with the objective of minimizing total production and inventory costs over T periods. It is assumed that production costs are linear, inventory costs are concave, setup costs are zero and backlogging is not permitted in all periods. Moreover, the unit production cost is a stochastic variable, which is evolved according to a continuous-time Markov process over the planning horizon. The model is formulated as a stochastic dynamic programming (DP) optimization with the state variable being unit production cost. Then, it is solved using the backward dynamic programming approach. To justify the application of the proposed model, two practical cases are presented.     

Testing the impact of a promotional video on destination image change: application of China as a tourism destination

This study empirically examines the potential effects of a promotional video on the image change of China as a travel destination. The analysis is based on an experimental study conducted among young, international short‐term employees in the USA. Despite positive changes in almost all the destination attributes as a result of watching the promotional video, the structure of the image constructs remains fairly stable, providing critical insights on the potential role of publicity campaigns in affecting destination images. Results of the study reveal that China's image consists of mixed and often contrasting representations, especially the polarity of modernisation and progress versus nature and history. It was found that the dominant factor affecting the respondents' behavioural intentions was the cultural and nature tourism dimension. Although other image dimensions exhibit influence as well, findings of this study suggest that perceived value should be a strategic focus in promoting China as a desirable travel destination, in addition to culture and nature tourism. This paper ends with conclusions and implications for both research on destination image and destination marketing in China. Copyright © 2009 John Wiley & Sons, Ltd.     

On Environmental Regulation of Oligopoly Markets: Emission versus Performance Standards

By specializing Montero’s (J Environ Econ Manag 44:23–44, 2002) model of environmental regulation under Cournot competition to an oligopoly with linear demand and quadratic abatement costs, we extend his comparison of firms incentives to invest in R&D under emission and performance standards by solving for a closed form solution of the underlying two-stage game. This allows for a full comparison of the two instruments in terms of their resulting propensity for R&D and equilibrium industry output. In addition, we incorporate an equilibrium welfare analysis. Finally, we investigate a three-stage game wherein a welfare-maximizing regulator sets a socially optimal emission cap under each policy instrument. For the latter game, while closed-form solutions for the subgame-perfect equilibrium are not possible, we establish numerically that the resulting welfare is always larger under a performance standard.