Coherent anti-Stokes Raman Scattering (CARS) Microscopy Visualizes Pharmaceutical Tablets During Dissolution

Traditional pharmaceutical dissolution tests determine the amount of drug dissolved over time by measuring drug content in the dissolution medium. This method provides little direct information about what is happening on the surface of the dissolving tablet. As the tablet surface composition and structure can change during dissolution, it is essential to monitor it during dissolution testing. In this work coherent anti-Stokes Raman scattering microscopy is used to image the surface of tablets during dissolution while UV absorption spectroscopy is simultaneously providing inline analysis of dissolved drug concentration for tablets containing a 50% mixture of theophylline anhydrate and ethyl cellulose. The measurements showed that in situ CARS microscopy is capable of imaging selectively theophylline in the presence of ethyl cellulose. Additionally, the theophylline anhydrate converted to theophylline monohydrate during dissolution, with needle-shaped crystals growing on the tablet surface during dissolution. The conversion of theophylline anhydrate to monohydrate, combined with reduced exposure of the drug to the flowing dissolution medium resulted in decreased dissolution rates. Our results show that in situ CARS microscopy combined with inline UV absorption spectroscopy is capable of monitoring pharmaceutical tablet dissolution and correlating surface changes with changes in dissolution rate

Controlling kinetic pathways in demixing microgel-micelle mixtures

[Image: see text] We investigate the temperature-dependent phase behavior of mixtures of poly(N-isopropylacrylamide) (pNIPAM) microgel colloids and a triblock copolymer (PEO–PPO–PEO) surfactant. Usually, gelation in these systems results from an increase in temperature. Here we investigate the role of the heating rate, and surprisingly, we find that this causes the mechanism of aggregation to change from one which is driven by depletion of the microgels by the micelles at low temperatures to the association of the two species at high temperatures. We thus reveal two competing mechanisms for attractions between the microgel particles which can be controlled by changing the heating rate. We use this heating-rate-dependent response of the system to access multiple structures for the same system composition. Samples were found to demix into phases rich and poor in microgel particles at temperatures below 33 °C, under conditions where the microgels particles are partially swollen. Under rapid heating full demixing is bypassed, and gel networks are formed instead. The temperature history of the sample, therefore, allows for kinetic selection between different final structures, which may be metastable

Residual Strength of Liquefied Sand: Laboratory vs. Field Measurements

Determining the residual strength of liquefied sand is essential for estimating post-earthquake stability of vulnerable earth structures, or calculating runout of liquefaction flow slides. Current practice is to select values from a database of back-calculated residual strengths from failure case histories, which have been related to representative penetration test resistance numbers in the failed materials. Given the uncertainties involved, it is desirable to compare the field data with laboratory tests under controlled conditions. This paper describes residual strength measurements for a uniform fine sand using two recently-developed tests designed to impose large strains and strain rates: a modified triaxial test in which a metal coupon is dragged through the liquefied sample by an external dead weight, and a ring shear device which can impose constant rates of strain on the liquefied sand. In all cases, a stress-thinning behavior is observed; however, coupon movement through the liquefied sand is basically laminar, representing conditions in the interior of a flowing mass, while the rotating ring creates a well-defined contact shear band and higher resistance, which might be considered more representative of flow at the base of a sliding mass. Comparison with back-calculated field values shows that coupon residual strengths plot at the lower bound, and ring shear results at the upper bound, of backcalculated field values

Airline Pilot Perceptions of Stress and Self-Reported Fatigue: A Cross-Sectional Study

In the air transportation sector, fatigue is a known problem influencing safety. Over the past two decades, fatigue mitigation has gained increased regulatory emphasis. The psychosocial construct of perceived stress, however, has been less studied and emphasized, though decades of research demonstrates stress’s impact on psychosocial and physiological wellbeing and safety performance. This observational, cross-sectional study measured airline pilots’ perceived stress levels alongside selected fatigue factors. Data was gathered from a sample of 144 airline pilots and analyzed using non-parametric statistics to explore the relationship between pilots’ perceptions of their own stress levels over the previous month with their answers to a questionnaire on fatigue factors. The objective here was both assessment of Cohen’s (1983) Perceived Stress Scale (PSS) as a tool for measuring chronic stress among airline pilots, along with classification and juxtaposition of organizational, professional, social and biological fatigue factors that may contribute to chronic stress. This study fills a gap in the literature on reliable, repeatable methodologies for studying chronic occupational stress, and importantly–establishes correlations between two safety-influencing constructs not previously explored side-by-side. Results support the validity of the PSS for subjective assessment of stress among airline pilots, thereby contributing to the body of knowledge on measuring chronic stressors and fatigue factors in the airline industry. This study also highlights the relevance of additional emphasis in this area of study. The implications of qualitatively exploring a relationship between these two related safety-influencing constructs may provide a different angle for future practical solutions and regulatory guidance

Effectiveness of Virtual Reality Simulations for Civilian, Ab Initio Pilot Training

Aviation training in the immersive Virtual Reality (VR) world has the power to overcome physical constraints, presenting cues and stimuli that would not be available in flight, nor in a two-dimensional (2D) environment. This gives VR powerful potential as a simulation tool for learning complex skills and maneuvers in the cockpit. This study evaluated the effectiveness of VR simulations as compared to traditional 2D desktop simulations in teaching maneuvers and skills to ab initio (inexperienced) civilian pilot trainees. This quasi-experimental project involved 17 freshman pilot students in an experimental college course at a private university campus in the fall semester of 2020. The participants were split into two sections: Section 1 completed CBT activities and simulations in 2D only, while Section 2 completed CBT activities in 2D and simulations in VR. Academic performance data was collected in the Canvas Learning Management System, broken down by understanding of a maneuver learned in a given lesson module. Descriptive statistics collected included quizzes, discussion board activity, and simulation completion scores. Paired samples t-tests compared perceived benefits of using the various course materials. Researchers also administered post-semester surveys to gather both qualitative and quantitative data, in which participants shared their perceptions of the course, preference for learning material type, and general feedback. Results indicated that students in both groups found the sims/tutorials and VR to be enjoyable and gratifying; the majority of students indicated that simulations were preferred over other learning materials. Early results indicate that although the students perceived that the simulations were beneficial, there were no significant differences in the final course scores or learning rates between those who utilized 2D sims as opposed to VR sims. The most important finding is that for ab initio pilots, VR simulations do not hinder learning mastery, as compared with traditional 2D desktop simulations

The Union and Médecins Sans Frontières approach to operational research.

Operational research (OR) has become a hot topic at national meetings, international conferences and donor fora. The International Union Against Tuberculosis and Lung Disease (The Union) and Médecins Sans Frontières (MSF) Operational Centre Brussels strongly promote and implement OR with colleagues in low- and middle-income countries. Here we describe how the two organisations define OR, and explain the guiding principles and methodology that underpin the strategy for developing and expanding OR in those countries. We articulate The Union's and MSF's approach to supporting OR, highlighting the main synergies and differences. Then, using the Malawi National Tuberculosis Control Programme as an example, we show how OR can be embedded within tuberculosis control activities, leading to changes in policy and practice at the national level. We discuss the difficult, yet vitally important, issue of capacity building, and share our vision of a new paradigm of product-related training and performance-based OR fellowships as two ways of developing the necessary skills at country level to ensure research is actually performed. Finally, we highlight the need to consider and incorporate into practice the ethical components of OR. This is a key moment to be involved in OR. We are confident that in partnership with interested stakeholders, including the World Health Organization, we can stimulate the implementation of quality, relevant OR as an integral part of health service delivery that in turn will lead to better health for people, particularly for those living in the poorer parts of the world

Grain growth of Pennisetum glaucum (L.) R.Br. under well-watered and drought-stressed conditions

The objective of this study was to investigate the possibility of relationships between grain growth parameters and drought response. Grain growth parameters of more than 70 millet lines were assessed under well-watered and postflowering drought-stress conditions in two field trials at the ICRISAT Sahelian Center, Sadoré, Niger. All the grain growth parameters based on thermal time varied more than two-fold between lines in both moisture environments. Single grain mass of the lines ranged from 4.3–10.9 mg under well-watered conditions and 3.4–9.4 mg under drought stress. When averaged across trials, 51% of the accounted variance of final grain mass could be explained by differences in the grain growth rate under well-watered conditions, while differences in the duration of the linear grain growth phase accounted for 37% of the variation in final grain mass. Drought stress reduced the linear grain growth phase and, as a consequence, reduced final grain mass by up to 25%. Lines with long grain filling periods under well-watered conditions had larger reductions in the grain filling period and in final grain mass under stress. In general, there was little effect of drought stress on the grain growth rate. However, because of the negative correlation of grain growth rate and linear grain growth phase, lines with higher grain growth rates in well-watered conditions had smaller reductions in grain filling period under stress. Grain growth rate accounted with 38% for the major part of the variation in grain mass under stress conditions. Grain growth parameters in well-watered and drought-stress conditions were unrelated to drought tolerance as expressed by a drought response index, and were indicators of neither susceptibility nor tolerance to stress. However final grain mass was highly correlated to yield under stress. A feasible risk-reducing strategy in the likelihood of postflowering stress is to select pearl millet lines for drought escape with a high grain growth rate combined with a relatively short grain filling period