Assessing the contribution of R&;D to total factor productivity—a Bayesian approach to account for heterogeneity and heteroskedasticity

This paper proposes a hierarchical Bayes estimator for a panel data random coefficient model with heteroskedasticity to assess the contribution of R&D capital to total factor productivity. Based on Hall (1993) data for 323 US firms over 1976–1990, we find that there appear to have substantial unobserved heterogeneity and heteroskedasticity across firms and industries that support the use of our Bayes inference procedure. We find much higher returns to R&D capital and a more pronounced downswing for the 1981–1985 period, followed by a more pronounced upswing than those yielded by the conventional feasible generalized least squares estimators or other estimates. The estimated elasticities of R&D capital are 0.062 for 1976–1980, 0.036 for 1981–1985 and 0.081 for 1986–1990, while the estimated elasticities of ordinary capital are much more stable over these periods.     

Quantitative complexity analysis in multi-channel intracranial EEG recordings form epilepsy brains

Epilepsy is a brain disorder characterized clinically by temporary but recurrent disturbances of brain function that may or may not be associated with destruction or loss of consciousness and abnormal behavior. Human brain is composed of more than 10 to the power 10 neurons, each of which receives electrical impulses known as action potentials from others neurons via synapses and sends electrical impulses via a sing output line to a similar (the axon) number of neurons. When neuronal networks are active, they produced a change in voltage potential, which can be captured by an electroencephalogram (EEG). The EEG recordings represent the time series that match up to neurological activity as a function of time. By analyzing the EEG recordings, we sought to evaluate the degree of underlining dynamical complexity prior to progression of seizure onset. Through the utilization of the dynamical measurements, it is possible to classify the state of the brain according to the underlying dynamical properties of EEG recordings. The results from two patients with temporal lobe epilepsy (TLE), the degree of complexity start converging to lower value prior to the epileptic seizures was observed from epileptic regions as well as non-epileptic regions. The dynamical measurements appear to reflect the changes of EEG’s dynamical structure. We suggest that the nonlinear dynamical analysis can provide a useful information for detecting relative changes in brain dynamics, which cannot be detected by conventional linear analysis.     

Population-level adult mortality following the expansion of antiretroviral therapy in Rakai,Uganda

There are limited data on the impact of antiretroviral therapy (ART) on population-level adult mortality in sub-Saharan Africa. We analysed data for 2000–14 from the Rakai Community Cohort Study (RCCS) in Uganda, where free ART was scaled up after 2004. Using non-parametric and parametric (Weibull) survival analysis, we estimated trends in average person-years lived between exact ages 15 and 50, per capita life-years lost to HIV, and the mortality hazards of people living with HIV (PLHIV). Between 2000 and 2014, average adult life-years lived before age 50 increased significantly, from 26.4 to 33.5?years for all women and from 28.6 to 33.8?years for all men. As of 2014, life-years lost to HIV had declined significantly, to 1.3?years among women and 0.4?years among men. Following the roll-out of ART, mortality reductions among PLHIV were initially larger in women than men, but this is no longer the case.     

Marital strategies for regulating exposure to HIV

In a setting where the transmission of HIV occurs primarily through heterosexual contact and where no cure or vaccine is available, behavioral change is imperative for containing the epidemic. Abstinence, faithfulness, and condom use most often receive attention in this regard. In contrast, this article treats marriage as a resource for HIV risk management via mechanisms of positive selection (partner choice) and negative selection (divorce of an adulterous spouse). Retrospective marriage histories and panel data provide the evidence for this study and results indicate that men and women in Malawi increasingly turned to union-based risk-avoidance strategies during the period that the threat of HIV/AIDS materialized. Although both sexes strategize in a similar fashion, men are better equipped than women to deploy these strategies to their advantage. The article concludes with reflections on the long-term and population-level implications of these coping mechanisms.     

On zero-sum $$\mathbb {Z}_{2j}^k$$-magic graphs

Let \(G = (V,E)\) be a finite graph and let \((\mathbb {A},+)\) be an abelian group with identity 0. Then G is \(\mathbb {A}\)-magic if and only if there exists a function \(\phi \) from E into \(\mathbb {A} - \{0\}\) such that for some \(c \in \mathbb {A}, \sum _{e \in E(v)} \phi (e) = c\) for every \(v \in V\), where E(v) is the set of edges incident to v. Additionally, G is zero-sum \(\mathbb {A}\)-magic if and only if \(\phi \) exists such that \(c = 0\). We consider zero-sum \(\mathbb {A}\)-magic labelings of graphs, with particular attention given to \(\mathbb {A} = \mathbb {Z}_{2j}^k\). For \(j \ge 1\), let \(\zeta _{2j}(G)\) be the smallest positive integer c such that G is zero-sum \(\mathbb {Z}_{2j}^c\)-magic if c exists; infinity otherwise. We establish upper bounds on \(\zeta _{2j}(G)\) when \(\zeta _{2j}(G)\) is finite, and show that \(\zeta _{2j}(G)\) is finite for all r-regular \(G, r \ge 2\). Appealing to classical results on the factors of cubic graphs, we prove that \(\zeta _4(G) \le 2\) for a cubic graph G, with equality if and only if G has no 1-factor. We discuss the problem of classifying cubic graphs according to the collection of finite abelian groups for which they are zero-sum group-magic.     

Voices of Children from Around the Globe; An International Analysis of Children's Issues at Child Helplines

Child helplines around the world are an important mental health resource for many children. In this study, an international database was analysed with a total of 25 million registered calls at a total of 111 helplines affiliated with Child Helpline International. The research was aimed at discovering if there are differences between the reasons for calling of children from different parts of the world, and if shifts in the studied 10‐year period can be observed. The data show that all child helplines are contacted by young people seek support with questions concerning abuse, sexual matters and school issues. The results from a mixed model also show significant differences in the reasons for calling between Africa, Asia, Europe, Latin America, North America, the Pacific region and the region Middle East and North Africa. Child helplines in Africa and other developing parts of the world received many calls related to safety and health (e.g. HIV/AIDS, commercial exploitation), whereas children and young people from Europe, North America and the Pacific more often discussed social and psychosocial issues with the helpline (e.g. mental health, peer and family relations). The reasons for calling were relatively stable for the studied period.     

Developing a Human‐centred and Science‐based Approach to Design: The Knowledge Management Platform Project

The gap between theory and practice is a persistent problem in management and organization research. In this respect, several scholars have suggested that ‘design’ is an ideal‐typical form of mode 2 knowledge production. Design research develops knowledge in the service of action and problem solving in organizational settings. In this paper, we connect two perspectives on design that can be considered to be largely complementary but have hardly been combined and integrated in practice: science‐based design drawing on design propositions grounded in research and human‐centred design emphasizing an active and systematic participation by users and other stakeholders. An integrated approach that builds on both perspectives is developed and subsequently applied to designing and developing a portal for mapping competencies in an information technology cluster. This project involves creating problem awareness and articulating design propositions as well as developing scenarios of use, experimenting with prototypes, and organizational transformation. As such, this methodology addresses the dual challenge of rigour and relevance by producing both scientific and practical knowledge.     

When Should a Firm Open its Source Code: A Strategic Analysis

Deciding to open the source code of a software product has advantages and disadvantages. The disadvantage is that the firm loses the revenue from the software. The advantage is that the users' network can contribute to the quality of the software code, which increases the demand for the software and for a complementary product. Demand for the complementary product also goes up, because demand for a product increases when the price of its complement decreases, and under open source, the price of the software product drops down to zero. This paper examines the strategic interactions at work here, within a duopoly framework, and tries to determine the circumstances under which it is optimal for a firm to open its code. We find that firms open the source code when there is a competitive software‐product market, a less competitive complementary‐product market, and when the complementary product is of high quality. Furthermore, it is more profitable for the firm to open the source code if its competitor also does so. When this happens the incentive to open the code can even be higher than in a monopoly situation. More intense competition induces symmetric equilibria in which both firms choose the same strategy.     

Attitudes toward abortion among catholic Mexican-American women: The effects of religiosity and education

Contrary to observed trends in religious fertility and contraceptive use differentials, Catholic/non-Catholic differentials in attitudes toward abortion have not been converging. This study suggests that this may be due to an interaction between religiosity and education. In a sample of Catholic Mexican-American women in Los Angeles County, the authors found that among respondents brought up in Mexico, education had a liberalizing effect on their attitudes. With the exception of the most devout, the same trend was observed among U.S.-reared respondents. Among the most religious group, however, education had the opposite effect, suggesting that convergence will be delayed.     

A measure of aliasing and applications to two-level fractional factorials

This paper examines some properties of a measure of aliasing proposed by Hedayat, Raktoe, and Federer (1974). It is shown that in the case of balanced orthogonal designs with no repeated treatments, minimizing the alias measure is equivalent to minimizing tr Yar(ψ). Lower bounds are found for fixed eigenvalues of the design matrix. These results are applied to two-level fractional factorials to show that in certain cases classical fractional-factorial designs yield minimal solutions for the alias measure.