Chemical propulsion research at MSFC

Chemical propulsion research reviews at Marshall Space Flight Cente

Elasticity of Stiff Polymer Networks

We study the elasticity of a two-dimensional random network of rigid rods (``Mikado model''). The essential features incorporated into the model are the anisotropic elasticity of the rods and the random geometry of the network. We show that there are three distinct scaling regimes, characterized by two distinct length scales on the elastic backbone. In addition to a critical rigidiy percolation region and a homogeneously elastic regime we find a novel intermediate scaling regime, where elasticity is dominated by bending deformations.Comment: 4 pages, 4 figure

Comparing research investment to United Kingdom institutions and published outputs for tuberculosis, HIV and malaria: A systematic analysis across 1997-2013

Background: The "Unfinished Agenda" of infectious diseases is of great importance to policymakers and research funding agencies that require ongoing research evidence on their effective management. Journal publications help effectively share and disseminate research results to inform policy and practice. We assess research investments to United Kingdom institutions in HIV, tuberculosis and malaria, and analyse these by numbers of publications and citations and by disease and type of science. Methods: Information on infection-related research investments awarded to United Kingdom institutions across 1997-2010 were sourced from funding agencies and individually categorised by disease and type of science. Publications were sourced from the Scopus database via keyword searches and filtered to include only publications relating to human disease and containing a United Kingdom-based first and/or last author. Data were matched by disease and type of science categories. Investment (United Kingdom pounds) and publications were compared to generate an 'investment per publication' metric; similarly, an 'investment per citation' metric was also developed as a measure of the usefulness of research. Results: Total research investment for all three diseases was £1.4 billion, and was greatest for HIV (£651.4 million), followed by malaria (£518.7 million) and tuberculosis (£239.1 million). There were 17,271 included publications, with 9,322 for HIV, 4,451 for malaria, and 3,498 for tuberculosis. HIV publications received the most citations (254,949), followed by malaria (148,559) and tuberculosis (100,244). According to UK pound per publication, tuberculosis (£50,691) appeared the most productive for investment, compared to HIV (£61,971) and malaria (£94,483). By type of science, public health research was most productive for HIV (£27,296) and tuberculosis (£22,273), while phase I-III trials were most productive for malaria (£60,491). According to UK pound per citation, tuberculosis (£1,797) was the most productive area for investment, compared to HIV (£2,265) and malaria (£2,834). Public health research was the most productive type of science for HIV (£2,265) and tuberculosis (£1,797), whereas phase I-III trials were most productive for malaria (£1,713). Conclusions: When comparing total publications and citations with research investment to United Kingdom institutions, tuberculosis research appears to perform best in terms of efficiency. There were more public health-related publications and citations for HIV and tuberculosis than other types of science. These findings demonstrate the diversity of research funding and outputs, and provide new evidence to inform research investment strategies for policymakers, funders, academic institutions, and healthcare organizations.Infectious Disease Research Networ

Differences in research funding for women scientists: a systematic comparison of UK investments in global infectious disease research during 1997–2010

Objectives: There has not previously been a systematic comparison of awards for research funding in infectious diseases by sex. We investigated funding awards to UK institutions for all infectious disease research from 1997 to 2010, across disease categories and along the research and development continuum. Design: Systematic comparison. Methods: Data were obtained from several sources for awards from the period 1997 to 2010 and each study assigned to—disease categories; type of science (preclinical, phases I–III trials, product development, implementation research); categories of funding organisation. Fold differences and statistical analysis were used to compare total investment, study numbers, mean grant and median grant between men and women. Results: 6052 studies were included in the final analysis, comprising 4357 grants (72%) awarded to men and 1695 grants (28%) awarded to women, totalling £2.274 billion. Of this, men received £1.786 billion (78.5%) and women £488 million (21.5%). The median value of award was greater for men (£179 389; IQR £59 146–£371 977) than women (£125 556; IQR £30 982–£261 834). Awards were greater for male principal investigators (PIs) across all infectious disease systems, excepting neurological infections and sexually transmitted infections. The proportion of total funding awarded to women ranged from 14.3% in 1998 to 26.8% in 2009 (mean 21.4%), and was lowest for preclinical research at 18.2% (£285.5 million of £1.573 billion) and highest for operational research at 30.9% (£151.4 million of £489.7 million). Conclusions: There are consistent differences in funding received by men and women PIs: women have fewer funded studies and receive less funding in absolute and in relative terms; the median funding awarded to women is lower across most infectious disease areas, by funder, and type of science. These differences remain broadly unchanged over the 14-year study period

On "the complete basis set limit" and plane-wave methods in first-principles simulations of water

Water structure, measured by the height of the first peak in oxygen-oxygen radial distributions, is converged with respect to plane-wave basis energy cutoffs for ab initio molecular dynamics simulations, confirming the reliability of plane-wave methods.Comment: 9 pages, 3 figure

Funding Infectious Disease Research: A Systematic Analysis of UK Research Investments by Funders 1997–2010

Background: Research investments are essential to address the burden of disease, however allocation of limited resources is poorly documented. We systematically reviewed the investments awarded by funding organisations to UK institutions and their global partners for infectious disease research. Methodology/Principal Findings Public and philanthropic investments for the period 1997 to 2010 were included. We categorised studies by infectious disease, cross-cutting theme, and by research and development value chain, reflecting the type of science. We identified 6165 funded studies, with a total research investment of UK £2.6 billion. Public organisations provided £1.4 billion (54.0%) of investments compared with £1.1 billion (42.4%) by philanthropic organisations. Global health studies represented an investment of £928 million (35.7%). The Wellcome Trust was the leading investor with £688 million (26.5%), closely followed by the UK Medical Research Council (MRC) with £673 million (25.9%). Funding over time was volatile, ranging from ∼£40 million to ∼£160 million per year for philanthropic organisations and ∼£30 million to ∼£230 million for public funders. Conclusions/Significance: Infectious disease research funding requires global coordination and strategic long-term vision. Our analysis demonstrates the diversity and inconsistent patterns in investment, with volatility in annual funding amounts and limited investment for product development and clinical trials

Ab Initio Study of Screw Dislocations in Mo and Ta: A new picture of plasticity in bcc transition metals

We report the first ab initio density-functional study of screw dislocations cores in the bcc transition metals Mo and Ta. Our results suggest a new picture of bcc plasticity with symmetric and compact dislocation cores, contrary to the presently accepted picture based on continuum and interatomic potentials. Core energy scales in this new picture are in much better agreement with the Peierls energy barriers to dislocation motion suggested by experiments.Comment: 3 figures, 3 table

Investments in respiratory infectious disease research 1997–2010: a systematic analysis of UK funding

Objectives: Respiratory infections are responsible for a large global burden of disease. We assessed the public and philanthropic investments awarded to UK institutions for respiratory infectious disease research to identify areas of underinvestment. We aimed to identify projects and categorise them by pathogen, disease and position along the research and development value chain. Setting: The UK. Participants: Institutions that host and carry out infectious disease research. Primary and secondary outcome measures The total amount spent and number of studies with a focus on several different respiratory pathogens or diseases, and to correlate these against the global burden of disease; also the total amount spent and number of studies relating to the type of science, the predominant funder in each category and the mean and median award size. Results: We identified 6165 infectious disease studies with a total investment of £2·6 billion. Respiratory research received £419 million (16.1%) across 1192 (19.3%) studies. The Wellcome Trust provided greatest investment (£135.2 million; 32.3%). Tuberculosis received £155 million (37.1%), influenza £80 million (19.1%) and pneumonia £27.8 million (6.6%). Despite high burden, there was relatively little investment in vaccine-preventable diseases including diphtheria (£0.1 million, 0.03%), measles (£5.0 million, 1.2%) and drug-resistant tuberculosis. There were 802 preclinical studies (67.3%) receiving £273 million (65.2%), while implementation research received £81 million (19.3%) across 274 studies (23%). There were comparatively few phase I–IV trials or product development studies. Global health research received £68.3 million (16.3%). Relative investment was strongly correlated with 2010 disease burden. Conclusions: The UK predominantly funds preclinical science. Tuberculosis is the most studied respiratory disease. The high global burden of pneumonia-related disease warrants greater investment than it has historically received. Other priority areas include antimicrobial resistance (particularly within tuberculosis), economics and proactive investments for emerging infectious threats

Universal features in the growth dynamics of complex organizations

We analyze the fluctuations in the gross domestic product (GDP) of 152 countries for the period 1950--1992. We find that (i) the distribution of annual growth rates for countries of a given GDP decays with ``fatter'' tails than for a Gaussian, and (ii) the width of the distribution scales as a power law of GDP with a scaling exponent $\beta \approx 0.15$. Both findings are in surprising agreement with results on firm growth. These results are consistent with the hypothesis that the evolution of organizations with complex structure is governed by similar growth mechanisms.Comment: 4 pages, 7 ps figures, using Latex2e with epsf rotate and multicol style files. Submitted to PR