Fat and Bone: An Odd Couple

In this review, we will first discuss the concept of bone strength and introduce how fat at different locations, including the bone marrow, directly or indirectly regulates bone turnover. We will then review the current literature supporting the mechanistic relationship between marrow fat and bone and our understanding of the relationship between body fat, body weight and bone with emphasis on its hormonal regulation. Finally, we will briefly discuss the importance and challenges of accurately measuring the fat compartments using non-invasive methods. This review highlights the complex relationship between fat and bone and how these new concepts will impact on our diagnostic and therapeutic approaches in the very near future

Decidability of quantified propositional intuitionistic logic and S4 on trees

Quantified propositional intuitionistic logic is obtained from propositional intuitionistic logic by adding quantifiers \forall p, \exists p over propositions. In the context of Kripke semantics, a proposition is a subset of the worlds in a model structure which is upward closed. Kremer (1997) has shown that the quantified propositional intuitionistic logic H\pi+ based on the class of all partial orders is recursively isomorphic to full second-order logic. He raised the question of whether the logic resulting from restriction to trees is axiomatizable. It is shown that it is, in fact, decidable. The methods used can also be used to establish the decidability of modal S4 with propositional quantification on similar types of Kripke structures.Comment: v2, 9 pages, corrections and additions; v1 8 page

A tale of reviews in two history of science journals

This paper examines the role of book reviews in the discipline of the history of science by comparing their appearance in two periodicals, Isis, the flagship journal of the discipline that was founded in 1913, and the Journal for the History of Astronomy, founded in 1970 to serve a newly emerging, specialized subfield within the broader discipline. Our analysis of the reviews published in selected slices of time finds differing norms and reviewing practices within the two journals. Despite important changes during the past century in the conceptualization of the history of science and its research methods, reviewing practices in Isis remained remarkably consistent over time, with reviewers generally defending a fixed set of norms for “good” scholarship. More change appears in reviews of the Journal for the History of Astronomy, as its audience shifted from a mix of the laity, working astronomers, and historians to a specialized group of professional historians of astronomy. Scholarly norms, reflected in the reviews, shifted with these changes in readership. We conclude that book reviews offer rich sources for analyzing the evolution of scholarly disciplines and norms.Analiza recenzji w dwóch czasopismach z historii nauki W artykule przeanalizowano rolę recenzji książek w dyscyplinie historia nauki, porównując ich występowanie w dwóch czasopismach, Isis, flagowym czasopiśmie dyscypliny założonej w 1913 r., oraz Journal for the History of Astronomy, założonym w 1970 r. służącego nowo powstającej, wyspecjalizowanej poddziedzinie w ramach szerszej dyscypliny. Nasza analiza recenzji opublikowanych w wybranych wycinkach czasu wskazuje na różne normy i praktyki recenzowania w obu czasopismach. Pomimo ważnych zmian, jakie dokonały się w ciągu ostatniego stulecia w konceptualizacji historii nauki i jej metodach badawczych, praktyki recenzowania w Isis pozostawały z biegiem czasu niezwykle spójne, a recenzenci generalnie bronili ustalonego zestawu norm dotyczących „dobrej” nauki. Więcej zmian pojawia się w recenzjach czasopisma Journal for the History of Astronomy, gdy uległa zmianie jego publiczność od mieszanki laików: pracujących astronomów i historyków do wyspecjalizowanej grupy zawodowych historyków astronomii. Wraz z tymi zmianami czytelnictwa zmieniały się normy naukowe, odzwierciedlone w recenzjach. Dochodzimy do wniosku, że recenzje książek stanowią bogate źródła do analizy ewolucji dyscyplin i norm naukowych

Acceleration of Nutrient Uptake by Phytoplankton in a Coastal Upwelling Ecosystem: A Modeling Analysis

Studies of upwelling centers in the eastern Pacific suggest that maximum rates of nitrate uptake (light and nutrient saturated) increase, or shift-up, as newly upwelled water moves downstream. The rate of shift-up appears to be related to irradiance and the ambient concentration of limiting nutrient at the time of upwelling. A mathematical model was developed to evaluate effects of irradiance and initial nitrate concentration on temporal patterns of shift-up and subsequent time scales of nutrient utilization over a range of simulated upwelling conditions. When rates consistent with field studies were used, complete shift-up was possible only under certain conditions, and the time scale was on the order of 7-10 d. These results are consistent with field observations. Increased initial nitrate concentrations resulted in more rapid depletion of the nutrient supply. Making acceleration of V max constant and independent of the nitrate concentration reversed the qualitative pattern of nutrient utilization and predicted longer time scales in the region of optimal growth (12- 15 d) than have been observed in the field. Since changes in nitrogen-specific V max observed in situ may be due to downstream sinking of detrital nitrogen, a third hypothesis was evaluated, in which there was no shift-up in Vmax. This last scenario is untenable, predicting time scales of nutrient utilization two to three times longer than observed in the field

In Situ Growth and Chemical Composition of the Giant Kelp, Macrocystis pyrifera: Response to Temporal Changes in Ambient Nutrient Availability

Temporal variations in growth of the giant kelp Macrocystis pyrifera were examined in relation to ambient nutrient availability and chemical composition of mature blades, the primary site of nutrient and carbohydrate storage in M. pyrifera. The effect of nutrient availability on growth was well approximated by a Monod rectangular hyperbola, with growth saturating at ambient nitrate concentra- tions between 1 and 2 FM. M. pyrlfera was unable to generate nutrient reserves that would last beyond 30 d. Nitrogen reserves were stored as free amino acids, and generally constituted about 10 % of total tissue nitrogen. Total nitrogen content was never more than 2.5% of dry weight. There was no significant correlation between growth and tissue nitrogen. In contrast, carbohydrate levels were negatively correlated with growth rates, tissue nitrogen content, and ambient nutrient availability. Although concentrations of nitrogen and carbohydrate reserves showed familiar variations described for other kelps, the physical environment in southern California is probably not amenable to M. pyrifera making strategic use of these reserves. Nutrient availability appears to be too low to permit accumulation of more than 30 d reserve of nitrogen, and light levels are probably never low enough to make stored carbohydrate reserves necessary for survival

Benthic community metabolism and the role of deposit-feeding callianassid shrimp

In temperate and tropical seas, bioturbation resulting from the burrowing and feeding activities of deposit-feeding callianassid shrimp can have an important impact on the ecosystem. In Gorda Sound, British Virgin Islands, 97 μmol NH4 ˙ m−2 ˙ d−1 and 0.2 μmol PO4 ˙ m−2 ˙ d−1 were released to the water column from burrows of callianassid shrimps (Callianassa rathbunae and Calliax Jonesi). Benthic gross primary production was 288 mg C ˙ m−2 ˙ d−1 and the ratio of gross production to total community 24-hr. respiration was 0.86. The flux of dissolved nutrients released from shrimp burrows could supply less than 5% of the need calculated for benthic primary production, while the net flux from the total benthic community could support 21% of the estimated demand. Stable carbon isotope measurements indicated that these callianassid shrimp derive 100% of their nutritional requirements from benthic microflora

Episodic Nutrient Supply to a Kelp Forest Ecosystem in Southern California

Temporal patterns of nutrient input into a Southern California kelp forest were measured using traditional hydrocast sampling coupled with high frequency temperature profiling. Patterns of nutrient input were related to growth rates of Macrocystis pyrifera located in an adjacent kelp forest. There were 2 distinct components to the pattern of nutrient availability. The long term, or seasonal, component was consistent with large-scale storm-induced mixing and horizontal advection during winter months. In addition, vertical motions of the thermocline, bringing nutrients into the kelp forest, occurred throughout the year with a frequency of about 2 per day and were strongest during the summer months. Weekly hydrocast sampling methods were inadequate for measuring these episodic events, and high frequency sampling was required to resolve the pattern of nutrient input accurately. Although measurable, nutrient input from vertical thermocline motion was inadequate to sustain maximum growth of Macrocystis pyrifera at 10 m depth during the summer months. Thus, the major component of nutrient input came during the winter. These results indicate that nitrate limitation of M. pyrifera is a likely cause of reduced summer growth. Further, high frequency sampling is necessary to predict nutrient availability in nearshore ecosystems dominated by benthic macrophytes where the pattern of nutrient input is dominated by episodic events of short duration

Faculty and Student Perceptions on Shared Teaching Materials for Advanced Manufacturing (STAM): Building Momentum Through Workshops

In this paper, we summarize the outcomes of the two workshops aimed at speeding up the transition of research-based advanced manufacturing knowledge into course curriculum for technology and engineering programs. Advanced manufacturing technologies have opened up the realm for new products that only a decade ago were considered unproducible. For example metals 3D Printing has almost no geometric limitations, which allows engineers to develop mesh–based products. Unfortunately, the educational system that serves to educate the majority of manufacturing technicians and engineers still utilizes many of the same curriculum resources for these emerging areas (textbooks, traditional lectures, etc.), frequently creating an unsuitable or inappropriate learning environment for state-of-the-science technician and engineering training. This is especially true for the development of manufacturing materials and laboratories to maintain currency in advanced manufacturing. With funding from NSF, two workshops were conducted that generated great enthusiasm for the concept of a teaching repository for advanced manufacturing technology. More than 50 advanced manufacturing instructors have attended the workshops, and a community of instructors has been created. Results from faculty and student perceptions on shared teaching materials for advanced manufacturing are also shared

Towards artificial photosynthesis: Promoting microscale photochemistry in science education

In order to simulate basic features of the natural cycle of photosynthesis and respiration, a model experiment called Photo-Blue-Bottle PBB has been developed. According to the title of this paper, the experiment will be presented and interpreted in accordance to basic contents from science education. An extended version of the PBB experiment also enables the evolution of hydrogen. This is a key step towards a prospective technological scenario with solar light driven production of “green fuels”. The concept of electronically excited state, the “heart of all photoprocesses” (N. J. Turro), will be completed by further teaching experiments and concepts concerning the up-to-date topic of photoactive molecular switches