A perspective on vibration-induced size segregation of granular materials

Segregation of particulate mixtures is a problem of great consequence in industries involved with the handling and processing of granular materials in which homogeneity is generally required. While there are several factors that may be responsible for segregation in bulk solids, it is well accepted that nonuniformity in particle size is a fundamental contributor. When the granular material is exposed to vibrations, the question of whether or not convection is an essential ingredient for size segregation is addressed by distinguishing between the situation where vibrations are not sufficiently energetic to promote a mean flow of the bulk solid, and those cases where a convective flow does occur. Based on experimental and simulation results in the literature, as well as dynamical systems analysis of a recent model of a binary granular mixture, it is proposed that "void-filling" beneath large particles is a universal mechanism promoting segregation, while convection essentially provides a means of mixing enhancement

An exploratory study of the association between online gaming addiction and enjoyment motivations for playing massively multiplayer online role-playing games

Massively multiplayer online role-playing games (MMORPGs) are a popular form of entertainment used by millions of gamers worldwide. Potential problems relating to MMORPG play have emerged, particularly in relation to being addicted to playing in such virtual environments. In the present study, factors relating to online gaming addiction and motivations for playing in MMORPGs were examined to establish whether they were associated with addiction. A sample comprised 1167 gamers who were surveyed about their gaming motivations. Latent Class Analysis revealed seven classes of motivations for playing MMORPGs, which comprised: (1) novelty; (2) highly social and discovery-orientated; (3) aggressive, anti-social and non-curious; (4) highly social, competitive; (5) low intensity enjoyment; (6) discovery-orientated; and (7) social classes. Five classes of gaming addiction-related experiences were extracted including: (1) high risk of addiction, (2) time-affected, (3) intermediate risk of addiction, (4) emotional control, and (5) low risk of addiction classes. Gender was a significant predictor of intermediate risk of addiction and emotional control class membership. Membership of the high risk of addiction class was significantly predicted by belonging to a highly social and competitive class, a novelty class, or an aggressive, anti-social, and non-curious class. Implications of these findings for assessment and treatment of MMORPG addiction are discussed

Activating Transcription Factor 4 Modulates TGFβ-Induced Aggressiveness in Triple-Negative Breast Cancer via SMAD2/3/4 and mTORC2 Signaling

Purpose: On the basis of the identified stress-independent cellular functions of activating transcription factor 4 (ATF4), we reported enhanced ATF4 levels in MCF10A cells treated with TGFβ1. ATF4 is overexpressed in patients with triple-negative breast cancer (TNBC), but its impact on patient survival and the underlying mechanisms remain unknown. We aimed to determine ATF4 effects on patients with breast cancer survival and TNBC aggressiveness, and the relationships between TGFβ and ATF4. Defining the signaling pathways may help us identify a cell signaling-tailored gene signature.Experimental Design: Patient survival data were determined by Kaplan-Meier analysis. Relationship between TGFβ and ATF4, their effects on aggressiveness (tumor proliferation, metastasis, and stemness), and the underlying pathways were analyzed in three TNBC cell lines and in vivo using patient-derived xenografts (PDX).Results: ATF4 overexpression correlated with TNBC patient survival decrease and a SMAD-dependent crosstalk between ATF4 and TGFβ was identified. ATF4 expression inhibition reduced migration, invasiveness, mammosphere-forming efficiency, proliferation, epithelial-mesenchymal transition, and antiapoptotic and stemness marker levels. In PDX models, ATF4 silencing decreased metastases, tumor growth, and relapse after chemotherapy. ATF4 was shown to be active downstream of SMAD2/3/4 and mTORC2, regulating TGFβ/SMAD and mTOR/RAC1-RHOA pathways independently of stress. We defined an eight-gene signature with prognostic potential, altered in 45% of 2,509 patients with breast cancer.Conclusions: ATF4 may represent a valuable prognostic biomarker and therapeutic target in patients with TNBC, and we identified a cell signaling pathway-based gene signature that may contribute to the development of combinatorial targeted therapies for breast cancer

Reaching the poor with health interventions: Programme-incidence analysis of seven randomised trials of women's groups to reduce newborn mortality in Asia and Africa

Background Efforts to end preventable newborn deaths will fail if the poor are not reached with effective interventions. To understand what works to reach vulnerable groups, we describe and explain the uptake of a highly effective community-based newborn health intervention across social strata in Asia and Africa. Methods We conducted a secondary analysis of seven randomised trials of participatory women's groups to reduce newborn mortality in India, Bangladesh, Nepal and Malawi. We analysed data on 70 574 pregnancies. Socioeconomic and sociodemographic differences in group attendance were tested using logistic regression. Qualitative data were collected at each trial site (225 focus groups, 20 interviews) to understand our results. Results Socioeconomic differences in women's group attendance were small, except for occasional lower attendance by elites. Sociodemographic differences were large, with lower attendance by young primigravid women in African as well as in South Asian sites. The intervention was considered relevant and interesting to all socioeconomic groups. Local facilitators ensured inclusion of poorer women. Embarrassment and family constraints on movement outside the home restricted attendance among primigravid women. Reproductive health discussions were perceived as inappropriate for them. Conclusions Community-based women's groups can help to reach every newborn with effective interventions. Equitable intervention uptake is enhanced when facilitators actively encourage all women to attend, organise meetings at the participants' convenience and use approaches that are easily understandable for the less educated. Focused efforts to include primigravid women are necessary, working with families and communities to decrease social taboos

Community mobilisation and health management committee strengthening to increase birth attendance by trained health workers in rural Makwanpur, Nepal: study protocol for a cluster randomised controlled trial

Background: Birth attendance by trained health workers is low in rural Nepal. Local participation in improving health services and increased interaction between health systems and communities may stimulate demand for health services. Significant increases in birth attendance by trained health workers may be affected through community mobilisation by local women's groups and health management committee strengthening. We will test the effect of community mobilisation through women's groups, and health management committee strengthening, on institutional deliveries and home deliveries attended by trained health workers in Makwanpur District. Design: Cluster randomised controlled trial involving 43 village development committee clusters. 21 clusters will receive the intervention and 22 clusters will serve as control areas. In intervention areas, Female Community Health Volunteers are supported in convening monthly women's groups. The groups work through an action research cycle in which they consider barriers to institutional delivery, plan and implement strategies to address these barriers with their communities, and evaluate their progress. Health management committees participate in three-day workshops that use appreciative inquiry methods to explore and plan ways to improve maternal and newborn health services. Follow-up meetings are conducted every three months to review progress. Primary outcomes are institutional deliveries and home deliveries conducted by trained health workers. Secondary outcome measures include uptake of antenatal and postnatal care, neonatal mortality and stillbirth rates, and maternal morbidity

Improving Newborn Survival in Low-Income Countries: Community-Based Approaches and Lessons from South Asia

David Osrin and colleagues discuss the critical importance of reducing global neonatal mortality in developing countries and how community-based approaches can help

Explaining the impact of a women's group led community mobilisation intervention on maternal and newborn health outcomes: the Ekjut trial process evaluation

Background: Few large and rigorous evaluations of participatory interventions systematically describe their context and implementation, or attempt to explain the mechanisms behind their impact. This study reports process evaluation data from the Ekjut cluster-randomised controlled trial of a participatory learning and action cycle with women's groups to improve maternal and newborn health outcomes in Jharkhand and Orissa, eastern India (20052008). The study demonstrated a 45% reduction in neonatal mortality in the last two years of the intervention, largely driven by improvements in safe practices for home deliveries.Methods: A participatory learning and action cycle with 244 women's groups was implemented in 18 intervention clusters covering an estimated population of 114 141. We describe the context, content, and implementation of this intervention, identify potential mechanisms behind its impact, and report challenges experienced in the field. Methods included a review of intervention documents, qualitative structured discussions with group members and non-group members, meeting observations, as well as descriptive statistical analysis of data on meeting attendance, activities, and characteristics of group attendees.Results: Six broad, interrelated factors influenced the intervention's impact: (1) acceptability; (2) a participatory approach to the development of knowledge, skills and 'critical consciousness'; (3) community involvement beyond the groups; (4) a focus on marginalized communities; (5) the active recruitment of newly pregnant women into groups; (6) high population coverage. We hypothesize that these factors were responsible for the increase in safe delivery and care practices that led to the reduction in neonatal mortality demonstrated in the Ekjut trial.Conclusions: Participatory interventions with community groups can influence maternal and child health outcomes if key intervention characteristics are preserved and tailored to local contexts. Scaling-up such interventions requires (1) a detailed understanding of the way in which context affects the acceptability and delivery of the intervention; (2) planned but flexible replication of key content and implementation features; (3) strong support for participatory methods from implementing agencies

Experimental Investigation of Vibration-Induced Bulk Solids Transport and Segregation. Final Technical Report, March 28, 1995--September 26, 1996

We report experiments on the rise time T of a single large sphere within a sinusoidally vibrated bed (amplitude a) of uniform particles (diameter d). At fixed acceleration, three distinct behavioral regimes are identified both from visual observations and from the typical increase of T with frequency f. Two convective regimes separated by a critical frequency are found, and for low a and high f, a {open_quotes}non-convective{close_quotes} regime. In the latter, the bed crystallizes and a size dependent rise is evidenced. The relevance of the non-dimensional parameter a/d is shown and a scaling law is deduced which has the form f {proportional_to} d{sup {minus}1/2

Rise-time regimes of a large sphere in vibrated bulk solids

We report experiments on the rise time T of a single large sphere within a sinusoidally vibrated bed (amplitude a) of uniform particles (diameter d). At fixed acceleration, we identify three distinct behavioral regimes both from visual observations and from the typical increase of T with frequency f. We observe two convective regimes separated by a critical frequency and, for low a and high f, a "nonconvective" regime. In the latter, the bed crystallizes and a size dependent rise is evidenced. We show the relevance of the nondimensional parameter a͞d and deduce a scaling law of the form f~d 21͞2 . [ S0031-9007(97) Over approximately the last ten years, significant attention has been given to the phenomenon of size segregation in granular mixture. This is motivated in part by the fact that size segregation is often an undesirable outcome of handling and/or processing operations of bulk solids In general, a large ball placed at the bottom of a vibrated bed will rise to the surface In this paper we report the influence of the macroscopic behavior of a monodisperse bed on the rise time T of a single large sphere. Three rise regimes are identified from the specific relationship between T and the frequency f. Our results show the distinct features of two convective flows: one where heaping occurs and the other where heaping is not present. For the first time, we observe in a three-dimensional bed a dependence of T on the intruder size. This occurs when the bed becomes so compact that it crystallizes. Finally, we emphasize the relevance of the dimensionless amplitude a͞d which allows us to predict the rapid increase of T with frequency at high accelerations. The experimental system consists of a fixed acrylic cylinder of inner diameter D cyl 11.43 cm and a piston mounted onto a Bruel & Kjar shaking head. The piston motion is controlled using an accelerometer with a feedback loop. We emphasize that the bed is excited only through vibrations of the piston. If the walls were moving, the sides of the granular bed during the flight would still be subjected to the shearing motion of the vibrating walls. If the walls are fixed, one can be sure that energy is provided only when the bed is in contact with the piston. Then the shearing effect of the walls is due only to the bed motion. We note also that heaping can be observed when a bed is continuously pushed upward by a pisto

Final Technical Report: Experiments Using Non-Intrusive Particle Tracing Techniques for Granular Chute Flows.

The objective of this contract was to develop a system capable of non-intrusively tracking the motion of an individual particle for the study of granular flows down inclined chutes. The result of the project is a system capable of following the three-dimensional translational and rotational motion of an individual particle embedded with a flowing granular material. The basic system consists of a sphere embedded with three orthogonal transmitters emitting at different frequencies which induce voltages in an antenna array surrounding the flow regime. Analysis of the induced voltage signals within the framework of a derived model yields both the position and orientation of the sphere. Tests were performed in a small scale model chute as well as in a cylindrical vibrated granular bed, which clearly demonstrates the capability of the system. As a result of discussions at meetings held semi-annually for the Granular Flow Advanced Research Objectives (GFARO) contractors, it was deemed necessary to pursue an additional experimental program as part of this contract related to the measurement of sphere collision properties. The outcome of the work (reported in Appendix C) is the determination of certain properties which are needed for use in computer simulations and theory