An experimental investigation of unstable combustion in solid propellant rocket motors

Unstable combustion in solid propellant rocket motors is characterized by high frequency chamber pressure oscillations, often accompanied by changes in the mean burning rate. Experiments with casebonded, cylindrically perforated motors using a polysulfide, ammoniumperchlorate propellant were reproducible as a result of careful manufacturing control and extended propellant curing time. In these motors the oscillations were in the fundamental standing tangential mode and were accompanied by increases in the average burning rate. At sufficiently high pressure levels all firings were stable. Reduction of the operating level led to mild instability. A sufficient further reduction produced a sudden change to maximum instability. Continued reduction in pressure level from this point resulted in a gradual decrease in the degree of instability but it could not be experimentally verified that a low pressure stable region existed. The levels at which these events took place were frequency dependent and generally increased as the tangential frequency was reduced. At a given operating leve1, the instability became less severe when the grain length was reduced below a critical value. Increasing the length above the critical value did not affect the level at which the motors became stable. The pressure levels for stability and for maximum instability moved to lower values with decreases in the propellant grain temperature in a manner not entirely accounted for by the effect of grain temperature on burning rate. Stable, mildly unstable and severely unstable operation was observed throughout the range -80°F to 180°F. The maximum instability decreased with grain temperature

Whole-grain food consumption in Singaporean children aged 6–12 years

Public health bodies in many countries are attempting to increase population-wide habitual consumption of whole grains. Limited data on dietary habits exist in Singaporean children. The present study therefore aimed to assess whole grain consumption patterns in Singaporean children and compare these with dietary intake, physical activity and health parameters. Dietary intake (assessed by duplicate, multipass, 24-h food recalls), physical activity (by questionnaire) and anthropometric measurements were collected from a cross-section of 561 Singaporean children aged 6–12 years. Intake of whole grains was evaluated using estimates of portion size and international food composition data. Only 38·3 % of participants reported consuming whole grains during the dietary data collection days. Median intake of whole grains in consumers was 15·3 (interquartile range 5·4–34·8) g/d. The most commonly consumed whole-grain food groups were rice (29·5 %), wholemeal bread (28·9 %) and ready-to-eat breakfast cereals (18·8 %). A significantly lower proportion of Malay children (seven out of fifty-eight; P < 0·0001) consumed whole grains than children of other ethnicities. Only 6 % of all children consumed the amount of whole grains most commonly associated with improved health outcomes (48 g/d). There was no relationship between whole grain consumption patterns and BMI, waist circumference or physical activity but higher whole grain intake was associated with increased fruit, vegetable and dairy product consumption (P < 0·001). These findings demonstrate that consumption of whole grain foods is low at a population level and infrequent in Singaporean children. Future drives to increase whole-grain food consumption in this population are likely to require input from multiple stakeholders

Patterns of inflammation, microstructural alterations, and sodium accumulation define multiple sclerosis subtypes after 15 years from onset

INTRODUCTION: Conventional MRI is routinely used for the characterization of pathological changes in multiple sclerosis (MS), but due to its lack of specificity is unable to provide accurate prognoses, explain disease heterogeneity and reconcile the gap between observed clinical symptoms and radiological evidence. Quantitative MRI provides measures of physiological abnormalities, otherwise invisible to conventional MRI, that correlate with MS severity. Analyzing quantitative MRI measures through machine learning techniques has been shown to improve the understanding of the underlying disease by better delineating its alteration patterns. METHODS: In this retrospective study, a cohort of healthy controls (HC) and MS patients with different subtypes, followed up 15 years from clinically isolated syndrome (CIS), was analyzed to produce a multi-modal set of quantitative MRI features encompassing relaxometry, microstructure, sodium ion concentration, and tissue volumetry. Random forest classifiers were used to train a model able to discriminate between HC, CIS, relapsing remitting (RR) and secondary progressive (SP) MS patients based on these features and, for each classification task, to identify the relative contribution of each MRI-derived tissue property to the classification task itself. RESULTS AND DISCUSSION: Average classification accuracy scores of 99 and 95% were obtained when discriminating HC and CIS vs. SP, respectively; 82 and 83% for HC and CIS vs. RR; 76% for RR vs. SP, and 79% for HC vs. CIS. Different patterns of alterations were observed for each classification task, offering key insights in the understanding of MS phenotypes pathophysiology: atrophy and relaxometry emerged particularly in the classification of HC and CIS vs. MS, relaxometry within lesions in RR vs. SP, sodium ion concentration in HC vs. CIS, and microstructural alterations were involved across all tasks

A small dose of whey protein co-ingested with mixed-macronutrient breakfast and lunch meals improves postprandial glycemia and suppresses appetite in men with type 2 diabetes: a randomized controlled trial.

Background: Large doses of whey protein consumed as a preload before single high-glycemic load meals has been shown to improve postprandial glycemia in type 2 diabetes. It is unclear if this effect remains with smaller doses of whey co-ingested at consecutive mixed-macronutrient meals. Moreover, whether hydrolyzed whey offers further benefit under these conditions is unclear. Objective: The aim of this study was to investigate postprandial glycemic and appetite responses after small doses of intact and hydrolyzed whey protein co-ingested with mixed-nutrient breakfast and lunch meals in men with type 2 diabetes. Design: In a randomized, single-blind crossover design, 11 men with type 2 diabetes [mean ± SD age: 54.9 ± 2.3 y; glycated hemoglobin: 6.8% ± 0.3% (51.3 ± 3.4 mmol/mol)] attended the laboratory on 3 mornings and consumed 1) intact whey protein (15 g), 2) hydrolyzed whey protein (15 g), or 3) placebo (control) immediately before mixed-macronutrient breakfast and lunch meals, separated by 3 h. Blood samples were collected periodically and were processed for insulin, intact glucagon-like peptide 1 (GLP-1), gastric inhibitory polypeptide (GIP), leptin, peptide tyrosine tyrosine (PYY3-36), and amino acid concentrations. Interstitial glucose was measured during and for 24 h after each trial. Subjective appetite was assessed with the use of visual analog scales. Results: Total postprandial glycemia area under the curve was reduced by 13% ± 3% after breakfast following the intact whey protein when compared with control (P  0.05). Conclusions: The consumption of a small 15-g dose of intact whey protein immediately before consecutive mixed-macronutrient meals improves postprandial glycemia, stimulates insulin release, and increases satiety in men with type 2 diabetes. This trial was registered at www.clinicialtrials.gov as NCT02903199

DARIAH Beyond Europe

International audienceDARIAH, the digital humanities infrastructure with origins and an organisational home in Europe, is nearing the completion of its implementation phase. The significant investment from the European Commission and member countries has yielded a robust set of technical and social infrastructures, ranging from working groups, various registries, pedagogical materials, and software to support diverse approaches to digital humanities scholarship. While the funding and leadership of DARIAH to date has come from countries in, or contiguous with, Europe, the needs that drive its technical and social development are widely shared within the international digital humanities community beyond Europe. Scholars on every continent would benefit from well-supported technical tools and platforms, directories for facilitating access to information and resources, and support for working groups.The DARIAH Beyond Europe workshop series, organised and financed under the umbrella of the DESIR project (“DARIAH ERIC Sustainability Refined,” 2017–2019, funded by the European Union’s Horizon 2020 Research and Innovation Program), convened three meetings between September 2018 and March 2019 in the United States and Australia. These workshops served as fora for cross-cultural exchange, and introduced many non-European DH scholars to DARIAH; each of the workshops included a significant delegation from various DARIAH bodies, together with a larger number of local presenters and participants. The local contexts for these workshops were significantly different in their embodiment of research infrastructures: on the one hand, in the U.S., a private research university (Stanford) and the de facto national library (the Library of Congress), both in a country with a history of unsuccessful national-scale infrastructure efforts; and in Australia, a system which has invested substantially more in coordinated national research infrastructure in science and technology, but very little on a national scale in the humanities and arts. Europe is in many respects ahead of both host countries in terms of its research infrastructure ecosystem both at the national and pan-European levels.The Stanford workshop had four main topics of focus: corpus management; text and image analysis; geohumanities; and music, theatre, and sound studies. As the first of the workshops, the Stanford group also took the lead in proposing next steps toward exploring actionable “DARIAH beyond Europe” initiatives, including the beginnings of a blog shared among participants from all the workshops, extra-European use of DARIAH’s DH Course Registry, and non-European participation in DARIAH Working Groups.The overall theme of the Library of Congress workshop was “Collections as Data,” building on a number of U.S.-based initiatives exploring how to enhance researcher engagement with digital collections through computationally-driven research. In Washington, D.C., the knowledge exchange sessions focussed on digitised newspapers and text analysis, infrastructural challenges for public humanities, and the use of web-archives in DH research. As at Stanford, interconnecting with DARIAH Working Groups was of core interest to participants, and a new Working Group was proposed to explore global access and use of digitised historical newspapers. A further important outcome was the agreement to explore collaboration between the U.S.-based “Collections as Data” initiatives and the Heritage Data Reuse Charter in Europe. The third and final workshop in the series took place in March 2019 in Australia, hosted by the National Library of Australia in Canberra. Convened by the Australian Academy of the Humanities (AAH), together with the Australian Research Data Commons (ARDC) and DARIAH, this event was co-located with the Academy’s second annual Humanities, Arts and Culture Data Summit. The first day of the event, targeted at research leadership and policy makers, was intended to explore new horizons for data-driven humanities and arts research, digital cultural collections and research infrastructure. The two subsequent days focused on engaging with a wide variety of communities, including (digital) humanities researchers and cultural heritage professionals. Organised around a series of Knowledge Exchange Sessions, combined with research-led lightning talks, the participants spoke in detail about how big ideas can be implemented practically on the ground. This poster reflects on the key outcomes and future directions arising from these three workshops, and considers what it might look like for DARIAH to be adopted as a fundamental DH infrastructure in a complex variety of international, national, and regional contexts, with diverse funding models, resources, needs, and expectations. One major outcome of all workshops was the shared recognition that, in spite of extensive funding, planning, and goodwill, these workshops were not nearly global enough in their reach: most importantly they were not inclusive of the Global South. Our new DARIAH beyond Europe community has a strong shared commitment to address this gap

Quasichemical Models of Multicomponent Nonlinear Diffusion

Diffusion preserves the positivity of concentrations, therefore, multicomponent diffusion should be nonlinear if there exist non-diagonal terms. The vast variety of nonlinear multicomponent diffusion equations should be ordered and special tools are needed to provide the systematic construction of the nonlinear diffusion equations for multicomponent mixtures with significant interaction between components. We develop an approach to nonlinear multicomponent diffusion based on the idea of the reaction mechanism borrowed from chemical kinetics. Chemical kinetics gave rise to very seminal tools for the modeling of processes. This is the stoichiometric algebra supplemented by the simple kinetic law. The results of this invention are now applied in many areas of science, from particle physics to sociology. In our work we extend the area of applications onto nonlinear multicomponent diffusion. We demonstrate, how the mechanism based approach to multicomponent diffusion can be included into the general thermodynamic framework, and prove the corresponding dissipation inequalities. To satisfy thermodynamic restrictions, the kinetic law of an elementary process cannot have an arbitrary form. For the general kinetic law (the generalized Mass Action Law), additional conditions are proved. The cell--jump formalism gives an intuitively clear representation of the elementary transport processes and, at the same time, produces kinetic finite elements, a tool for numerical simulation.Comment: 81 pages, Bibliography 118 references, a review paper (v4: the final published version

“Dogged” Search of Fresh Nakhla Surfaces Reveals New Alteration Textures

Special Issue: 74th Annual Meeting of the Meteoritical Society, August 8-12, 2011, London, U.K.International audienceCarbonaceous chondrites are considered as amongst the most primitive Solar System samples available. One of their primitive characteristics is their enrichment in volatile elements.This includes hydrogen, which is present in hydrated and hydroxylated minerals. More precisely, the mineralogy is expected to be dominated by phyllosilicates in the case of CM chondrites, and by Montmorillonite type clays in the case of CI. Here, in order to characterize and quantify the abundance of lowtemperature minerals in carbonaceous chondrites, we performed thermogravimetric analysis of matrix fragments of Tagish Lake, Murchison and Orgueil

Coordinated Analyses of Presolar Grains in the Allan Hills 77307 and Queen Elizabeth Range 99177 Meteorites

We report the identification of presolar silicates (~177 ppm), presolar oxides (~11 ppm), and one presolar SiO2 grain in the Allan Hills (ALHA) 77307 chondrite. Three grains having Si isotopic compositions similar to SiC X and Z grains were also identified, though the mineral phases are unconfirmed. Similar abundances of presolar silicates (~152 ppm) and oxides (~8 ppm) were also uncovered in the primitive CR chondrite Queen Elizabeth Range (QUE) 99177, along with 13 presolar SiC grains and one presolar silicon nitride. The O isotopic compositions of the presolar silicates and oxides indicate that most of the grains condensed in low-mass red giant and asymptotic giant branch stars. Interestingly, unlike presolar oxides, few presolar silicate grains have isotopic compositions pointing to low-metallicity, low-mass stars (Group 3). The 18O-rich (Group 4) silicates, along with the few Group 3 silicates that were identified, likely have origins in supernova outflows. This is supported by their O and Si isotopic compositions. Elemental compositions for 74 presolar silicate grains were determined by scanning Auger spectroscopy. Most of the grains have non-stoichiometric elemental compositions inconsistent with pyroxene or olivine, the phases commonly used to fit astronomical spectra, and have comparable Mg and Fe contents. Non-equilibrium condensation and/or secondary alteration could produce the high Fe contents. Transmission electron microscopic analysis of three silicate grains also reveals non-stoichiometric compositions, attributable to non-equilibrium or multistep condensation, and very fine scale elemental heterogeneity, possibly due to subsequent annealing. The mineralogies of presolar silicates identified in meteorites thus far seem to differ from those in interplanetary dust particles.Comment: 23 pages, 16 figure

Prospectus, February 25, 1991

https://spark.parkland.edu/prospectus_1991/1003/thumbnail.jp