Practical Open-Loop Optimistic Planning

We consider the problem of online planning in a Markov Decision Process when given only access to a generative model, restricted to open-loop policies - i.e. sequences of actions - and under budget constraint. In this setting, the Open-Loop Optimistic Planning (OLOP) algorithm enjoys good theoretical guarantees but is overly conservative in practice, as we show in numerical experiments. We propose a modified version of the algorithm with tighter upper-confidence bounds, KLOLOP, that leads to better practical performances while retaining the sample complexity bound. Finally, we propose an efficient implementation that significantly improves the time complexity of both algorithms

Terrestrial microbialites provide constraints on the mesoproterozoic atmosphere

Palaeoclimate data indicate that Earth surface temperatures have remained largely temperate for the past 3.5 Byr despite significantly lower solar luminosity over this time relative to the present day. There is evidence for episodic early and late Proterozoic glaciation, but little evidence of glaciation in the intervening billion years. A prolonged equable Mesoproterozoic Earth requires elevated greenhouse gas concentrations. Two endmember scenarios have been proposed for maintaining global warmth. These include extremely high pCO2 or more modest pCO2 with higher methane concentrations. This paper reports on the δ13C of organic matter in 1.1 Ga stromatolites from the Copper Harbor Conglomerate (CHC) of the Mesoproterozoic Midcontinent Rift (North America) and δ18O and Δ47 temperatures of inorganic stromatolite carbonate to constrain formation and burial conditions and the magnitude of ancient carbon isotope discrimination. CHC sediments have never been heated above ~125–155°C, providing a novel geochemical archive of the ancient environment. Stromatolite Δ47 data record moderate alteration, and therefore, the occluded organic matter was unlikely to have experienced significant thermal alteration after deposition. The δ13C values of ancient mat organic matter and inorganic carbonate show isotope discrimination (εp) values ~15.5–18.5‰, similar to modern microbial mats formed in equilibrium with low concentrations of dissolved inorganic carbon. In combination, these data are consistent with a temperate climate Mesoproterozoic biosphere supported by relatively modest pCO2. This result agrees with Atmosphere‐Ocean Global Circulation Model reconstructions for Mesoproterozoic climate using 5–10 times present atmospheric levels pCO2 and pCH4 of >28 ppmv. However, given marine modelling constraints of CH4 production that suggest pCH4 was below 10 ppm, this creates a methane paradox. Either an additional source of CH4 (e.g. from terrestrial ecosystems) or another greenhouse gas, such as N2O, would have been necessary to maintain equable conditions in the Mesoproterozoic.This paper, entitled ‘Terrestrial Microbialites Provide Constraints on the Mesoproterozoic Atmosphere’ offers a new look at 1.1 billion‐year‐old stromatolites in the Mesoproterozoic Midcontinent Rift in Michigan to provide new constraints on pCO2 during the long period of earth’s history that is colloquially known as the ‘boring billion’. New clumped isotope temperature measurements are provided to constrain upper temperature bounds for microbial carbonate formation temperature and post‐depositional thermal alteration, as well as organic and inorganic carbon isotope data that are used to constrain carbon isotope discrimination that is regulated by atmospheric carbon dioxide concentrations.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154283/1/dep279_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154283/2/dep279.pd

Knowledge and attitudes about health research amongst a group of Pakistani medical students

Background Health research training is an important part of medical education. This study was conducted to assess the level of knowledge and attitudes regarding health research in a group of Pakistani medical students at Aga Khan University, Karachi. Methods It was a cross-sectional pilot study conducted among a group of Pakistani medical students. Through stratified random sampling, a pre-tested, structured and validated questionnaire was administered to 220 medical students. Knowledge and attitudes were recorded on a scale (graduated in percentages). Results Mean scores of students were 49.0% on knowledge scale and 53.7% on attitude scale. Both knowledge and attitudes improved significantly with increasing years of study in medical college [Regression coefficient 4.10 (p-value; 0.019) and 6.67 (p-value; \u3c 0.001) for knowledge and attitudes, respectively]. Conclusion Medical students demonstrate moderate level of knowledge and attitude towards health research. Intensive training in this regard is associated with significant improvement in knowledge and attitudes of students towards health research

A Simplified Model for Distortional Buckling of Channels and Zees in Flexure

Certain cold-formed sections like channels and zees, when subjected to bending in the plane of the web, often fail in laboratory tests at a load less than that predicted by standard specification equations. The mode of failure is an upward movement of the compression flange and lip relative to the web, which may remain fairly plane. When bends which were right angles change dramatically under load, the section changes shape, or distorts, resulting in a reduction of the section stiffness followed by buckling of the flange. Such a failure is referred to as distortional buckling . An analytical solution to the distortional buckling problem has been proposed by Hancock of the University of Sydney. This method was used to calculate distortional buckling capacities of around 200 shapes and a curve was fit to the results. Finally, a simplified expression was developed to check this limit state with minimal effort. Several full-scale tests were performed on channels and zees of various thicknesses and bracing conditions to verify the Hancock method

A cross-sectional bibliometric study showed suboptimal journal endorsement rates of STROBE and its extensions

OBJECTIVE: The STrengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement provides guidance on reporting observational studies. Many extensions have been created for specialized methods or fields. We determined endorsement prevalence and typology by journals in extension-related fields. STUDY DESIGN AND SETTING: A published protocol defined search strategies to identify journals publishing observational studies (2007 - 2017) across seven fields relating to STROBE extensions. We extracted text regarding STROBE, 7 STROBE extensions, reporting guidelines CONSORT and PRISMA, and transparent reporting documents/groups: ICMJE, COPE, and the EQUATOR Network. Relationships between endorsing STROBE, endorsing other guidelines and journal impact factor were tested using Chi-square and Mann-Whitney. RESULTS: Of 257 unique journals, 12 (5%) required STROBE on submission, 22 (9%) suggested use, 12 (5%) recommended a "relevant guideline", 72 (28%) mentioned it indirectly (via editorial policies or ICMJE Recommendations), and 139 (54%) did not mention STROBE. The relevant extension was required by 2 (<1%) journals; 4 (1%) suggested use. STROBE endorsement was not associated with journal impact indices but was with CONSORT and PRISMA endorsement. CONCLUSION: Reporting guideline endorsement rates are low; information is vague and scattered. Unambiguous language is needed to improve adherence to reporting guidelines and increase the quality of reporting

Individual characteristics and student's engagement in scientific research : a cross-sectional study

Background: In light of the increasing recognition of the importance of physician scientists, and given the association between undergraduate research experiences with future scientific activity, it is important to identify and understand variables related to undergraduate student’s decision to engage in scientific research activities. The present study assessed the influence of individual characteristics, including personality traits and socio-demographic characteristics, on voluntary engagement in scientific research of undergraduate medical students. Methods: For this study, all undergraduate students and alumni of the School of Health Sciences in Minho, Portugal were invited to participate in a survey about voluntary engagement in scientific research activities. Data were available on socio-demographic, personality and university admission variables, as part of an ongoing longitudinal study. A regression model was used to compare (1) engaged with (2) not engaged students. A classification and regression tree model was used to compare students engaged in (3) elective curricular research (4) and extra-curricular research. Results: A total of 466 students (88%) answered the survey. A complete set of data was available for 435 students (83%).Higher scores in admission grade point average and the personality dimensions of “openness to experience” and “conscientiousness” increased chances of engagement. Higher “extraversion” scores had the opposite effect. Male undergraduate students were two times more likely than females to engage in curricular elective scientific research and were also more likely to engage in extra-curricular research activities. Conclusions: This study demonstrated that student’s grade point average and individual characteristics, like gender, openness and consciousness have a unique and statistically significant contribution to student’s involvement in undergraduate scientific research activities.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/ESC/65116/200

Terrestrial cooling in northern Europe during the Eocene-Oligocene transition

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148597/1/Hren_et_al_2013_PNAS-EOT_Cooling.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148597/2/Hren_et_al_2013_PNAS-supplemental_data.pd

Less Work, Less Respect: Authors' Perceived Importance of Research Contributions and Their Declared Contributions to Research Articles

BACKGROUND: Attitudes towards authorship are connected with authors' research experience and with knowledge of authorship criteria of International Committee of Medical Journal Editors (ICMJE). The objective of this study was to assess association between authors' perceived importance of contributions for authorship qualification and their participation in manuscripts submitted to a journal. METHODS: Authors (n = 1181) of 265 manuscripts submitted to the Croatian Medical Journal were asked to identify and rate their contribution in the preparation of the submitted manuscript (0-none to 4-full for 11 listed contributions) and the importance of these contributions as authorship qualifications (0-none to 4-full). They were randomly allocated into 3 groups: the first (n = 90 manuscripts, n = 404 authors) first received the contribution disclosure form and then contribution importance-rating questionnaire; the second (n = 88 manuscripts, n = 382 authors) first received the rating questionnaire and then the contribution disclosure form, and the third group (n = 87 manuscripts, n = 395 authors) received both questionnaires at the same time. We compared authors' perception of importance of contribution categories. RESULTS: 1014 (85.9%) authors of 235 manuscripts responded. Authors who declared contribution to a specific category rated it as more important for authorship than those authors who did not contribute to the same category (P>0.005 for all contribution categories, Mann-Withney test). Authors qualifying for ICMJE authorship rated all contribution categories higher than non-qualifying authors. For all contributions, associations between perceived importance of contribution and actual author's contribution were statistically significant. CONCLUSIONS: Authorship seems to be not a normative issue subjective to categorization into criteria, but also a very personal view of the importance and value of one's contributions