Aeolian removal of dust from radiator surfaces on Mars

Simulated radiator surfaces made of arc-textured Cu and Nb-1 percent-Zr and ion beam textured graphite and C-C composite were fabricated and their integrated spectral emittance characterized from 300 to 3000 K. A thin layer of aluminum oxide, basalt, or iron (III) oxide dust was then deposited on them, and they were subjected to low pressure winds in the Martian Surface Wind Tunnel. It was found that dust deposited on simulated radiator surfaces may or may not seriously lower their integrated spectral emittance, depending upon the characteristics of the dust. With Al2O3 there is no appreciable degradation of emittance on a dusted sample, with basaltic dust there is a 10 to 20 percent degradation, and with Fe2O3 a 20 to 40 percent degradation. It was also found that very high winds on dusted highly textured surfaces can result in their abrasion. Degradation in emittance due to abrasion was found to vary with radiator material. Arc-textured Cu and Nb-1 percent Zr was found to be more susceptible to emittance degradation than graphite or C-C composite. The most abrasion occurred at low angles, peaking at the 22.5 deg test samples

Degradation of radiator performance on Mars due to dust

An artificial mineral of the approximate elemental composition of Martian soil was manufactured, crushed, and sorted into four different size ranges. Dust particles from three of these size ranges were applied to arc-textured Nb-1 percent Zr and Cu radiator surfaces to assess their effect on radiator performance. Particles larger than 75 microns did not have sufficient adhesive forces to adhere to the samples at angles greater than about 27 deg. Pre-deposited dust layers were largely removed by clear wind velocities greater than 40 m/s, or by dust-laden wind velocities as low as 25 m/s. Smaller dust grains were more difficult to remove. Abrasion was found to be significant only in high velocity winds (89 m/s or greater). Dust-laden winds were found to be more abrasive than clear wind. Initially dusted samples abraded less than initially clear samples in dust laden wind. Smaller dust particles of the simulant proved to be more abrasive than large. This probably indicates that the larger particles were in fact agglomerates

Minnesota 4-H Science of Agriculture Challenge: Infusing Agricultural Science and Engineering Concepts into 4-H Youth Development

Youth involved in 4-H projects have been engaged in science-related endeavors for years. Since 2006, 4-H has invested considerable resources in the advancement of science learning. The new Minnesota 4-H Science of Agriculture Challenge program challenges 4-H youth to work together to identify agriculture-related issues in their communities and to work with local experts, using scientific and engineering principles, to devise real solutions for those issues. The Minnesota 4-H Science of Agriculture Challenge program has the potential to change the way scientific and engineering principles are integrated into 4-H youth development programming

Exploring cation distribution in ion-exchanged Al,Ga-containing metal-organic frameworks using 17O NMR spectroscopy

The authors would like to thank the ERC (Advanced Grant 787073 ADOR) for support. The UK High-Field Solid-State NMR Facility used in this research was funded by EPSRC and BBSRC (EP/T015063/1), in addition to (for results at 850 MHz) he University of Warwick including via part funding through Birmingham Science City Advanced Materials Projects 1 and 2 supported by Advantage West Midlands (AWM) and the European Regional Development Fund (ERDF), and for the 1 GHz instrument, (EP/R029946/1). Collaborative assistance from the Facility Manager Team (Dr Trent Franks, University of Warwick) is acknowledged. The Jeol JSM-IT200 SEM used in this research was supported by the EPSRC Light Element Analysis Facility Grant (EP/T019298/1) and the EPSRC Strategic Equipment Resource Grant (EP/R023751/1). Collaborative assistance from Dr David Miller (University of St Andrews) is acknowledged.A mixed-metal metal–organic framework, (Al,Ga)-MIL-53, synthesised by post-synthetic ion exchange has been investigated using solid-state nuclear magnetic resonance (NMR) spectroscopy, microscopy and energy dispersive X-ray (EDX) spectroscopy. 17O enrichment during the ion-exchange process enables site specific information on the metal distribution to be obtained. Within this work two ion-exchange processes have been explored. In the first approach (exchange of metals in the framework with dissolved metal salts), 17O NMR spectroscopy reveals the formation of crystallites with a core–shell structure, where the cation exchange takes place on the surface of these materials forming a shell with a roughly equal ratio of Al3+ and Ga3+. For the second approach (exchange of metals between two frameworks), no core–shell structure is observed, and instead crystallites containing a majority of Al3+ are obtained with lower levels of Ga3+. Noticeably, these particles show little variation in the metal cation distribution between crystallites, a result not previously observed for bulk (Al,Ga)-MIL-53 materials. In all cases where ion exchange has taken place NMR spectroscopy reveals a slight preference for clustering of like cations.Publisher PDFPeer reviewe

Effects of dust accumulation and removal on radiators surfaces on Mars

Tests were carried out to assess the impact of wind blown dust accumulation and abrasion on radiator surfaces on Mars. High emittance arc-textured copper and niobium-1 percent-zirconium samples were subjected to basaltic dust laden wind at Martian pressure (1000 Pa) at speeds varying from 19 to 97 m/s in the Martian Surface Wind Tunnel. The effect of accumulated dust was also observed by pre-dusting some of the samples before the test. Radiator degradation was determined by measuring the change in the emittance after dust was deposited and/or removed. The principle mode of degradation was abrasion. Arc textured Nb-1 percent-Zr proved to be more susceptible to degradation than Cu, and pre-dusting appeared to have lessened the abrasion

Computational NMR investigation of mixed-metal (Al,Sc)-MIL-53 and its phase transitions

Funding: The authors would like to thank the ERC (Advanced Grant 787073 ADOR) and the Allan Handsel Postgraduate Research Scholarship for Chemistry for studentship funding for ZHD and EALB, respectively. We also acknowledge support from the Collaborative Computational Project on NMR Crystallography (CCP-NC) funded by EPSRC (EP/T026642/1) and from the UK Materials and Molecular Modelling Hub (Young), which is partially funded by EPSRC (EP/T022213/1, EP/W032260/1 and EP/P020194/1) for which access was obtained via the UKCP consortium and funded by EPSRC (EP/P022561/1).Compositionally complex metal-organic frameworks (MOFs) have properties that depend on local structure that is often difficult to characterise. In this paper a density functional theory (DFT) computational study of mixed-metal (Al,Sc)-MIL-53, a flexible MOF with several different forms, was used to calculate the relative energetics of these forms and to predict NMR parameters that can be used to evaluate whether solid-state NMR spectroscopy can be used to differentiate, identify and characterise the forms adopted by mixed-metal MOFs of different composition. The NMR parameters can also be correlated with structural features in the different forms, giving fundamental insight into the nature and origin of the interactions that affect nuclear spins. Given the complexity of advanced NMR experiments required, and the potential need for expensive and difficult isotopic enrichment, the computational work is invaluable in predicting which experiments and approaches are likely to give the most information on the disorder, local structure and pore forms of these mixed-metal MOFs.Publisher PDFPeer reviewe

Evaluating Medical Student Communication/Professionalism Skills from a Patient’s Perspective

Objective: Evaluate medical students’ communication and professionalism skills from the perspective of the ambulatory patient and later compare these skills in their first year of residency. Methods: Students in third year neurology clerkship clinics see patients alone followed by a revisit with an attending neurologist. The patient is then asked to complete a voluntary, anonymous, Likert scale questionnaire rating the student on friendliness, listening to the patient, respecting the patient, using understandable language, and grooming. For students who had completed 1 year of residency these professionalism ratings were compared with those from their residency director. Results: Seven hundred forty-two questionnaires for 165 clerkship students from 2007 to 2009 were analyzed. Eighty-three percent of forms were returned with an average of 5 per student. In 64% of questionnaires, patients rated students very good in all five categories; in 35% patients selected either very good or good ratings; and <1% rated any student fair. No students were rated poor or very poor. Sixty-two percent of patients wrote complimentary comments about the students. From the Class of 2008, 52% of students received “better than their peers” professionalism ratings from their PGY1 residency directors and only one student was rated “below their peers.” Conclusion: This questionnaire allowed patient perceptions of their students’ communication/professionalism skills to be evaluated in a systematic manner. Residency director ratings of professionalism of the same students at the end of their first year of residency confirms continued professional behavior

The Impact of Peer Mentoring on Marketing Content Mastery

This article describes and assesses a course design that uses peer mentors to facilitate a collaborative, hands-on learning experience in an introductory marketing course. Results demonstrate that peer mentoring increased content mastery and had a positive effect on students’ perceptions of the learning experience. Peer marketing mentors, along with the faculty team, achieved success in providing a demanding and engaging learning environment that meets the needs of learners and equips them with content knowledge required of career-ready professionals. A step-by-step guide is provided to enable others to develop a similar experience for students in their institutions

Factors Influencing African American Youths\u27 Decisions to Stay in School

Little attention has been given to the non-problematic development and positive life decisions of African American youth. This paper reports findings of 231 African American students. The goal of the study was to assess factors which contribute to their academic grade point averages and intentions to stay in school. The conceptual model employed in this study was the Theory of Planned Behavior (TPB) which contends that intentions to carryout a behavior is a function of Attitude towards the behavior, Social Normative support for undertaking the behavior, and the Perceived Control of being able to carry out the behavior. In addition to the TPB components, the contributions of self-esteem and racial self-esteem were also examined for their influence on academic strivings. The TPB model did predict well student’s intentions to stay in school, but predicted less well student grade point averages. Self-esteem was also a significant predictor of intentions to stay in school, but was not a significant predictor of gpa. Racial self-esteem was observed to be only marginally significant, but as predicted, was negatively associated with student Intentions to stay in school. However racial self esteem was not observed to be a significant predictor of student gpa. Hence students with positive self-esteem, who have favorable attitudes towards school and perceive fewer barriers to completing school are most likely to do so. But, the negative association between racial self-esteem and academic intentions suggests that some African American youths may need be convinced that academic success is not an act of racial betrayal

Preconception Maternal Posttraumatic Stress and Child Negative Affectivity: Prospectively Evaluating the Intergenerational Impact of Trauma

The developmental origins of psychopathology begin before birth and perhaps even prior to conception. Understanding the intergenerational transmission of psychopathological risk is critical to identify sensitive windows for prevention and early intervention. Prior research demonstrates that maternal trauma history, typically assessed retrospectively, has adverse consequences for child socioemotional development. However, very few prospective studies of preconception trauma exist, and the role of preconception symptoms of posttraumatic stress disorder (PTSD) remains unknown. The current study prospectively evaluates whether maternal preconception PTSD symptoms predict early childhood negative affectivity, a key dimension of temperament and predictor of later psychopathology. One hundred and eighteen women were recruited following a birth and prior to conception of the study child and were followed until the study child was 3–5 years old. Higher maternal PTSD symptoms prior to conception predicted greater child negative affectivity, adjusting for concurrent maternal depressive symptoms and sociodemographic covariates. In exploratory analyses, we found that neither maternal prenatal nor postpartum depressive symptoms or perceived stress mediated this association. These findings add to a limited prospective literature, highlighting the importance of assessing the mental health of women prior to conception and providing interventions that can disrupt the intergenerational sequelae of trauma