Molecular dynamics simulations of the rotational and translational diffusion of a Janus rod-shaped nanoparticle

The diffusion of a Janus rod-shaped nanoparticle in a dense Lennard-Jones fluid is studied using molecular dynamics (MD) simulations. The Janus particle is modeled as a rigid cylinder whose atoms on each half-side have different interaction energies with fluid molecules, thus comprising wetting and nonwetting surfaces. We found that both rotational and translational diffusion coefficients are larger for Janus particles with higher wettability contrast, and these values are bound between the two limiting cases of uniformly wetting and nonwetting particles. It was also shown that values of the diffusion coefficients for displacements parallel and perpendicular to the major axis of a uniformly wetting particle agree well with analytical predictions despite a finite slip at the particle surface present in MD simulations. It was further demonstrated that diffusion of Janus particles is markedly different from that of uniform particles; namely, Janus particles preferentially rotate and orient their nonwetting sides along the displacement vector to reduce drag. This correlation between translation and rotation is consistent with the previous results on diffusive dynamics of a spherical Janus particle with two hemispheres of different wettability.Comment: 27 pages, 9 figure

Modelling the Role of University-Industry Collaboration in the Iranian National System of Innovation: Generating Transition Policy Scenarios

In a knowledge-based economy the collaboration between university, industry and government is vital for growth and innovation (Etzkowitz, 2008). A conceptual model of the relevant macro and micro environment was developed using the theoretical constructs from the literature on systems of innovation theories including, National Systems of Innovation, Porter’s ‘Cluster’ or ‘Diamond’ model, and the ‘Triple-Helix Model’ of university–industry-government interactions. The role of culture and trust in different systems of innovation theories was examined, and the role these elements play in UIC activities was found to be particularly important, though vague on the processes. A generic model of university-industry-government interrelations was developed to aid a systemic understanding of the mechanisms (primary barriers and drivers) for productive collaboration. This systems model was used in the formation of policy instruments designed to improve university-industry collaboration (UIC), and thereby the means of regional economic development. These policy experiments are applied to the case of Iran. However, since the future of Iran in this context is highly uncertain due to cultural, political and economic factors there are few assumptions which can be relied upon as a basis for traditional innovation management practice. Instead, it is intended to use the systems model in a series of scenario-based analyses of the effectiveness of policy instruments on the UIC associated with two Iranian cluster industries. A questionnaire survey and a series of semi-structured stakeholder interview methodology were used to build a basis for these scenario techniques. The method of systems modelling to generate policy change scenarios for UIC is a novel feature of this research. Analysis of the causal relationships of UIC activities in Iran found many were biased to create an established behaviour pattern (culture) which is overwhelmingly negative. This negative behaviour is manifest as a significant lack of trust at all interfaces between the primary actors in the system. According to the results of this research, trust is influenced by many factors including government activities, institutional structure, institutional culture, and also national culture of the country. The systems model is a complex interaction of reinforcing loops that emphasizes the scale of challenge policy-makers face in creating effective innovation systems, and may explain why few developing countries have been successful in achieving economic transition. This research shows how a policy development framework was formed using the UIC systems model to understand the structural problems facing Iran. A set of evolved states (exploratory and future-backward scenarios) served to illustrate the effect of these policy choices, and therefore to inform an improvement agenda for UIC activities in Iran

Diffusion of a Janus nanoparticle in an explicit solvent: A molecular dynamics simulation study

Molecular dynamics simulations are carried out to study the translational and rotational diffusion of a single Janus particle immersed in a dense Lennard-Jones fluid. We consider a spherical particle with two hemispheres of different wettability. The analysis of the particle dynamics is based on the time-dependent orientation tensor, particle displacement, as well as the translational and angular velocity autocorrelation functions. It was found that both translational and rotational diffusion coefficients increase with decreasing surface energy at the nonwetting hemisphere, provided that the wettability of the other hemisphere remains unchanged. We also observed that in contrast to homogeneous particles, the nonwetting hemisphere of the Janus particle tends to rotate in the direction of the displacement vector during the rotational relaxation time.Comment: Web reference added for animations:http://www.wright.edu/~nikolai.priezjev/janus/janus.htm

The Fourth Wave of Feminism and the Lack of Social Realism in Cyberspace

Recent years have witnessed a surge in research on the impact of the cyberspace on social movements. The feminist movement has built a vocal platform online which attempts to underscore sexual violence against women. Scholars have begun to suspect that the internet has ushered in a new wave, the fourth wave of feminism. The fourth wave’s main feature is its reliance on social media. The accessibility, reach of a widespread audience, low costs and user-friendly environment have encouraged women to use social media to speak out against various forms of sexual violence directed against women. It is also assumed that going forward; the movement will also tackle issues such as the gender pay gap, neoliberal policies, maternity leave, and cultural sexism. Moreover, the internet-based movement is striving to bring to the fore the topic of intersectionality, that is, the intersection of oppressive institutions, and the attempt to rectify the failings of past waves by representing those oppressed by multiple institutions such as sexism, classism, and racism. This commentary provides an overview of the emerging academic literature on the fourth wave of feminism and critically reflects the lack of social realism in its existing form of knowledge production

Race and Ethnicity-Adjusted Age Recommendation for Initiating Breast Cancer Screening.

IMPORTANCE Breast cancer (BC) is the second leading cause of cancer death in women, and there is a substantial disparity in BC mortality by race, especially for early-onset BC in Black women. Many guidelines recommend starting BC screening from age 50 years; however, the current one-size-fits-all policy to start screening all women from a certain age may not be fair, equitable, or optimal. OBJECTIVE To provide race and ethnicity-adapted starting ages of BC screening based on data on current racial and ethnic disparities in BC mortality. DESIGN, SETTING, AND PARTICIPANTS This nationwide population-based cross-sectional study was conducted using data on BC mortality in female patients in the US who died of BC in 2011 to 2020. EXPOSURES Proxy-reported race and ethnicity information was used. The risk-adapted starting age of BC screening by race and ethnicity was measured based on 10-year cumulative risk of BC-specific death. Age-specific 10-year cumulative risk was calculated based on age group-specific mortality data without modeling or adjustment. MAIN OUTCOMES AND MEASURES Disease-specific mortality due to invasive BC in female patients. RESULTS There were BC-specific deaths among 415 277 female patients (1880 American Indian or Alaska Native [0.5%], 12 086 Asian or Pacific Islander [2.9%], 62 695 Black [15.1%], 28 747 Hispanic [6.9%], and 309 869 White [74.6%]; 115 214 patients died before age 60 years [27.7%]) of any age in the US in 2011 to 2020. BC mortality per 100 000 person-years for ages 40 to 49 years was 27 deaths in Black females, 15 deaths in White females, and 11 deaths in American Indian or Alaska Native, Hispanic, and Asian or Pacific Islander females. When BC screening was recommended to start at age 50 years for all females with a 10-year cumulative risk of BC death of 0.329%, Black females reached this risk threshold level 8 years earlier, at age 42 years, whereas White females reached it at age 51 years, American Indian or Alaska Native and Hispanic females at age 57 years, and Asian or Pacific Islander females 11 years later, at age 61 years. Race and ethnicity-adapted starting ages for Black females were 6 years earlier for mass screening at age 40 years and 7 years earlier for mass screening at age 45 years. CONCLUSIONS AND RELEVANCE This study provides evidence-based race-adapted starting ages for BC screening. These findings suggest that health policy makers may consider a risk-adapted approach to BC screening in which individuals who are at high risk are screened earlier to address mortality due to early-onset BC before the recommended age of mass screening