Long term dynamics for the restricted N-body problem with mean motion resonances and crossing singularities

We consider the long term dynamics of the restricted N -body problem, modeling in a statistical sense the motion of an asteroid in the gravitational field of the Sun and the solar system planets. We deal with the case of a mean motion resonance with one planet and assume that the osculating trajectory of the asteroid crosses the one of some planet, possibly different from the resonant one, during the evolution. Such crossings produce singularities in the differential equations for the motion of the asteroid, obtained by standard perturbation theory. In this work we prove that the vector field of these equations can be extended to two locally Lipschitz-continuous vector fields on both sides of a set of crossing conditions. This allows us to define generalized solutions, continuous but not differentiable, going beyond these singularities. Moreover, we prove that the long term evolution of the ’signed’ orbit distance (Gronchi and Tommei 2007) between the asteroid and the planet is differentiable in a neighborhood of the crossing times. In case of crossings with the resonant planet we recover the known dynamical protection mechanism against collisions. We conclude with a numerical comparison between the long term and the full evolutions in the case of asteroids belonging to the ’Alinda’ and ’Toro’ classes (Milani et al. 1989). This work extends the results in (Gronchi and Tardioli 2013) to the relevant case of asteroids in mean motion resonance with a planet

High Density Polyethylene Composites Containing Alumina-Toughened Zirconia Particles: Mechanical and Tribological Behavior

Alumina-toughened Zirconia (ATZ) was used as filler to endow High Density Polyethylene (HDPE) with enhanced mechanical and wear properties, hence widening the application field of the polyolefin as biomaterial. Composites at different ATZ loadings were produced by melt extrusion followed by compression molding. A good filler dispersion was obtained for all the materials, despite the presence of few voids and agglomerates observed at high ATZ loadings. The combination of high crystallinity and, mainly, lack of voids and agglomerates, appeared responsible for the improvement of Young modulus and mechanical strength. Besides, the filler positively affected the wear resistance of the composites under lubricated conditions

Responding to Vaccine Safety Signals during Pandemic Influenza: A Modeling Study

Background: Managing emerging vaccine safety signals during an influenza pandemic is challenging. Federal regulators must balance vaccine risks against benefits while maintaining public confidence in the public health system. Methods: We developed a multi-criteria decision analysis model to explore regulatory decision-making in the context of emerging vaccine safety signals during a pandemic. We simulated vaccine safety surveillance system capabilities and used an age-structured compartmental model to develop potential pandemic scenarios. We used an expert-derived multi-attribute utility function to evaluate potential regulatory responses by combining four outcome measures into a single measure of interest: 1) expected vaccination benefit from averted influenza; 2) expected vaccination risk from vaccine-associated febrile seizures; 3) expected vaccination risk from vaccine-associated Guillain-Barre Syndrome; and 4) expected change in vaccine-seeking behavior in future influenza seasons. Results: Over multiple scenarios, risk communication, with or without suspension of vaccination of high-risk persons, were the consistently preferred regulatory responses over no action or general suspension when safety signals were detected during a pandemic influenza. On average, the expert panel valued near-term vaccine-related outcomes relative to long-term projected outcomes by 3∶1. However, when decision-makers had minimal ability to influence near-term outcomes, the response was selected primarily by projected impacts on future vaccine-seeking behavior. Conclusions: The selected regulatory response depends on how quickly a vaccine safety signal is identified relative to the peak of the pandemic and the initiation of vaccination. Our analysis suggested two areas for future investment: efforts to improve the size and timeliness of the surveillance system and behavioral research to understand changes in vaccine-seeking behavior

Electron-Beam-Induced Grafting Of Chitosan Onto HDPE/ATZ Composites for Biomedical Applications

HDPE and HDPE/ATZ surfaces were functionalised with chitosan Via electron-beam irradiation technique in order to prepare materials suitable for biomedical purposes. ATR–FTIR and wettability measurements were employed for monitoring the surface changes after both irradiation and chitosan grafting reaction. The presence of ATZ influenced both the EB irradiation process and the surface functionalisation. Mechanical properties of irradiated materials were not remarkably affected by irradiation processing. Biological assays indicated that electrostatic interactions between the negative charges of the surface of cell membranes and the –NH3+ sites on chitosan chains promoted cell adhesion, while some oxidized species produced during the irradiation process were thought to cause a detrimental effect on the cell Viability

Anterior gradient protein 2 promotes survival, migration and invasion of papillary thyroid carcinoma cells

Through a transcriptome microarray analysis, we have isolated Anterior gradient protein 2 (AGR2) as a gene up-regulated in papillary thyroid carcinoma (PTC). AGR2 is a disulfide isomerase over-expressed in several human carcinomas and recently linked to endoplasmic reticulum (ER) stress. Here, we analyzed the expression of AGR2 in PTC and its functional role

Influence of chitosan on the mechanical and biological properties of HDPE for biomedical applications

High density polyethylene (HDPE) is widely used in biomedical field, except when strong cell-material interactions and high mechanical properties are required. To address this pitfall, two kinds of chitosan in different amounts were used as filler in the present research. Composites were prepared by melt extrusion process and their microstructural, thermal and mechanical properties were widely investigated. Also roughness and wettability were studied, as features of paramount importance in dictating cell response. Both types of chitosan endowed HDPE with higher Young modulus and lower elongation at break. Interestingly, fibroblast adhesion and viability were enhanced when a low amount of filler was used. The interaction of HDPE/chitosan composites with biological environment was investigated for the first time in order to assess the feasibility of these composites as materials for biomedical application

The Identification of Sustainability Assessment Indicators for Road Infrastructure Projects in Tanzania

The performance of sustainability in infrastructure projects continues to face challenges in its implementation and attainment in developing countries, one of which is the lack of appraisal tools and indicators for the assessment of sustainability. Studies indicate that there are no formal indicators for sustainability assessment on road infrastructure projects in Tanzania, the lack of which limits the determination of whether projects implemented are sustainable or not. Therefore, this study aimed at determining the key sustainability assessment indicators used for road infrastructure projects in Tanzania. A concurrent mixed research approach was adopted in which the sample was purposively selected. A content analysis and descriptive statistics using the Statistical Package for the Social Sciences (SPSS 20.0) were used to analyze qualitative and quantitative data, respectively. The findings indicate that 24 indicators are applicable to Tanzania. Among the highly ranked include “health and safety training to workers”, “health and safety personnel in the project team”, “site barriers and safety warning signs”, “personal protective equipment (PPE) provision”, and “waste collection”. The qualitative results further support the identified sustainability assessment indicators on road infrastructure projects in Tanzania, with one new indicator of “air quality” emerging. The findings inform the government and other relevant stakeholders in the construction industry including planners, designers, and project managers of the key sustainability assessment indicators for roads, which would influence regulation as well as policies to improve the sustainability performance of road projects in Tanzania

Barriers to the Integration of Building Information Modeling (BIM) in Modular Construction in Sub-Saharan Africa

The construction industry is constantly evolving through government policies, technologies, and innovative processes. BIM and modular construction are innovative concepts aimed at achieving sustainable smart cities by enhancing cost performance, efficiency, and sustainability. Despite growing global interest in their integration, there is a notable knowledge gap in sub-Saharan Africa. As a result, this research aims to explore the barriers to integrating BIM into modular construction in sub-Saharan Africa. The study adopted a non-experimental design, using a four-stage methodological framework. Initially, a literature review was carried out to conceptualize the study. Stage two involves a pilot survey to create an adequate data collection instrument. In the third stage, 81 registered companies were purposely selected, and data was collected through an online survey. Finally, the fourth stage uses descriptive and inferential techniques to make logical and informed conclusions. The top-ranked barriers are high initial costs, insufficient cross-field expertise, stakeholder collaboration problems, limited software interoperability, and skills shortages. Recommendations include early stakeholder collaboration, BIM execution plan development by modular companies, improved staff training, and increasing financial support from the government. Future research should explore country-specific barriers and case studies to aid the integration of the two innovative solutions in the region

Factors Associated with Change in Sexual Transmission Risk Behavior over 3 Years among HIV-Infected Patients in Tanzania.

The reduction of HIV transmission risk behaviors among those infected with HIV remains a major global health priority. Psychosocial characteristics have proven to be important correlates of sexual transmission risk behaviors in high-income countries, but little attention has focused on the influence of psychosocial and psychological factors on sexual transmission risk behaviors in African cohorts. The CHAT Study enrolled a representative sample of 499 HIV-infected patients in established HIV care and 267 newly diagnosed HIV-infected individuals from the Kilimanjaro Region of Tanzania. Participants completed in-person interviews every 6 months for 3 years. Using logistic random effects models to account for repeated observations, we assessed sociodemographic, physical health, and psychosocial predictors of self-reported unprotected sexual intercourse. Among established patients, the proportion reporting any recent unprotected sex was stable, ranging between 6-13% over 3 years. Among newly diagnosed patients, the proportion reporting any unprotected sex dropped from 43% at baseline to 11-21% at 6-36 months. In multivariable models, higher odds of reported unprotected sex was associated with female gender, younger age, being married, better physical health, and greater post-traumatic stress symptoms. In addition, within-individual changes in post-traumatic stress over time coincided with increases in unprotected sex. Changes in post-traumatic stress symptomatology were associated with changes in sexual transmission risk behaviors in this sample of HIV-infected adults in Tanzania, suggesting the importance of investing in appropriate mental health screening and intervention services for HIV-infected patients, both to improve mental health and to support secondary prevention efforts

Polar and non-polar organic binder characterization in Pompeian wall paintings: comparison to a simulated painting mimicking an a secco technique.

The use of Fourier transform infrared spectromicroscopy and mass spectrometry (MS) allowed us to characterize the composition of polar and non-polar binders present in sporadic wall paint fragments taken from Pompeii's archaeological excavation. The analyses of the polar and non-polar binder components extracted from paint powder layer showed the presence of amino acids, sugars, and fatty acids but the absence of proteinaceous material. These results are consistent with a water tempera painting mixture composed of pigments, flours, gums, and oils and are in agreement with those obtained from a simulated wall paint sample made for mimicking an ancient "a secco" technique. Notably, for the first time, we report the capability to discriminate by tandem MS the presence of free amino acids in the paint layer