Faster all-pairs shortest paths via circuit complexity

We present a new randomized method for computing the min-plus product (a.k.a., tropical product) of two $n \times n$ matrices, yielding a faster algorithm for solving the all-pairs shortest path problem (APSP) in dense $n$-node directed graphs with arbitrary edge weights. On the real RAM, where additions and comparisons of reals are unit cost (but all other operations have typical logarithmic cost), the algorithm runs in time $$\frac{n^3}{2^{\Omega(\log n)^{1/2}}}$$ and is correct with high probability. On the word RAM, the algorithm runs in $n^3/2^{\Omega(\log n)^{1/2}} + n^{2+o(1)}\log M$ time for edge weights in $([0,M] \cap {\mathbb Z})\cup\{\infty\}$. Prior algorithms used either $n^3/(\log^c n)$ time for various $c \leq 2$, or $O(M^{\alpha}n^{\beta})$ time for various $\alpha > 0$ and $\beta > 2$. The new algorithm applies a tool from circuit complexity, namely the Razborov-Smolensky polynomials for approximately representing ${\sf AC}^0[p]$ circuits, to efficiently reduce a matrix product over the $(\min,+)$ algebra to a relatively small number of rectangular matrix products over ${\mathbb F}_2$, each of which are computable using a particularly efficient method due to Coppersmith. We also give a deterministic version of the algorithm running in $n^3/2^{\log^{\delta} n}$ time for some $\delta > 0$, which utilizes the Yao-Beigel-Tarui translation of ${\sf AC}^0[m]$ circuits into "nice" depth-two circuits.Comment: 24 pages. Updated version now has slightly faster running time. To appear in ACM Symposium on Theory of Computing (STOC), 201

Una aproximación al paradigma dominante de la psicología social en una muestra de los manuales publicados desde el año 2000

Esta investigación se propuso determinar cuáles son algunas de las características de los textos y autores de los libros que sirven para introducción a la especialidad y, del mismo modo, los tópicos y autores que resultan definitivos en el estado actual del Paradigma Dominante de la Psicología Social a la luz de dichos manuales. Se seleccionaron 11 títulos que fueron publicados a partir del año 2000 y se consideraron las siguientes categorías de análisis título de la obra, número de la edición, número de autores, número de autoras,número total de páginas, número de capítulos, ejes temáticos, número de páginas dedicadas dichos tópicos y peso relativo de cada uno de ellos en las obras. Los resultados del estudio revelan que existen 11 grandes ejes temáticos sobre los que se desarrolla actualmente el Paradigma Dominante de la Psicología Social y, del mismo modo, que son cerca de 100 los autores que pueden ser considerados como líderes de ésta particular perspectiva.The goal of this investigation was to establish the characteristics of texts and authors of thehandbooks that are used for to introduce social psychology, and the topics and authorswho are definitive ones in the current status of the dominant paradigm of social psycholo-gy according to these handbooks. Eleven titles were selected, those that were publishedsince 2000, and the following categories of analysis were considered: title of the work,number of the edition, number of authors (men and women), total number of pages, numberof chapters, thematic axes, number of pages dedicated to these topics, and relative weightof each one of them in the handbooks. The results of the study reveal that eleven greatthematic axes exist at this moment, based on the dominant paradigm of social psychology,and, in the same way, there are near 100 authors who can be considered like leaders of thisparticular perspective

Living with family: perceptions of health and subjective well-being of adults with an intellectual disability

Background: Little is known about the role of living circumstances to the perception of subjective well‐being (SWB) and health of adults with intellectual disability (ID). The aim of the present study was to examine whether living circumstances impact differently on the perception of health and SWB and whether potential differences persist after accounting for other variables (e.g. level of support needs and reporting method). Methods: Secondary data analysis was undertaken of a large national survey of adults with an ID in England, aged 16 years and over. Participants were identified as living with family (N = 1528) or living out of home (N = 874). Results: The results of t‐test and chi‐square revealed that levels of health and SWB were perceived as being higher for people living with family than those living in out‐of‐home settings. Multiple linear regression analyses fitted to explore factors associated with these reported differences revealed that, when controlling for other variables, living with family was highly associated with reports of better SWB. Multiple logistic regression revealed that whilst the health status of people living with families were perceived as better, this was only true when their support needs were low. Poorest health outcomes were found for people with highest support needs who lived with family. Conclusions: On the whole, the health and well‐being of adults living with family were perceived more positively than those living out of home. However, potential health disparities exist for those with high support needs who live with family. Further longitudinal research is needed to explore causes and potential solution to these inequalities

Good Bye, Soldier Boy

https://digitalcommons.library.umaine.edu/mmb-vp/1530/thumbnail.jp

Ring current effects: Factors affecting the NMR chemical shift of molecules adsorbed on porous carbons

Nuclear magnetic resonance (NMR) spectroscopy is increasingly being used to study the adsorption of molecules in porous carbons, a process which underpins applications ranging from electrochemical energy storage to water purification. Here we present density functional theory (DFT) calculations of the nucleus-independent chemical shift (NICS) near various sp2-hybridized carbon fragments to explore the structural factors that may affect the resonance frequencies observed for adsorbed species. The domain size of the delocalized electron system affects the calculated NICSs, with larger domains giving rise to larger chemical shieldings. In slit pores, overlap of the ring current effects from the pore walls is shown to increase the chemical shielding. Finally, curvature in the carbon sheets is shown to have a significant effect on the NICS. The trends observed are consistent with existing NMR results as well as new spectra presented for an electrolyte adsorbed on carbide-derived carbons prepared at different temperatures.A.C.F., J.M.G., and C.P.G. acknowledge the Sims Scholarship (A.C.F.), EPSRC (via the Supergen consortium; J.M.G.), and the EU ERC (via an Advanced Fellowship to C.P.G.) for funding. CDC synthesis at Drexel University was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award #ER46473. V.P. acknowledges funding from the German Federal Ministry for Research and Education (BMBF) in support of the nanoEES3D project (Award 03EK3013) as part of the strategic funding initiative energy storage framework and thanks Prof. Eduard Arzt (INM) for his continuing support. Mohamed Shamma and Boris Dyatkin (Drexel University) are thanked for their support in the synthesis of CDC material. DFT calculations were performed using the Darwin Supercomputer of the University of Cambridge High Performance Computing Service, provided by Dell Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council.This is the author accepted manuscript. The final version is available from the American Chemical Society via http://dx.doi.org/10.1021/jp502387

Noninvasive In Situ NMR Study of "Dead Lithium" Formation and Lithium Corrosion in Full-Cell Lithium Metal Batteries.

Capacity retention in lithium metal batteries needs to be improved if they are to be commercially viable, the low cycling stability and Li corrosion during storage of lithium metal batteries being even more problematic when there is no excess lithium in the cell. Herein, we develop in situ NMR metrology to study "anode-free" lithium metal batteries where lithium is plated directly onto a bare copper current collector from a LiFePO4 cathode. The methodology allows inactive or "dead lithium" formation during plating and stripping of lithium in a full-cell lithium metal battery to be tracked: dead lithium and SEI formation can be quantified by NMR and their relative rates of formation are here compared in carbonate and ether-electrolytes. Little-to-no dead Li was observed when FEC is used as an additive. The bulk magnetic susceptibility effects arising from the paramagnetic lithium metal were used to distinguish between different surface coverages of lithium deposits. The amount of lithium metal was monitored during rest periods, and lithium metal dissolution (corrosion) was observed in all electrolytes, even during the periods when the battery is not in use, i.e., when no current is flowing, demonstrating that dissolution of lithium remains a critical issue for lithium metal batteries. The high rate of corrosion is attributed to SEI formation on both lithium metal and copper (and Cu+, Cu2+ reduction). Strategies to mitigate the corrosion are explored, the work demonstrating that both polymer coatings and the modification of the copper surface chemistry help to stabilize the lithium metal surface.A.B.G acknowledges the support from the Royal Society (RP/R1/180147) and EPSRC-EP/M009521/1. C.V.A acknowledges financial support from the TomKat Center Postdoctoral Fellowship in Sustainable Energy at Stanford, and a Visiting Fellowship from Corpus Christi College at the University of Cambridge. S.M thanks the Blavatnik Cambridge Fellowships. C.P.G thanks the EU/ERC for an Advanced Fellowship. A.B.G thanks the NanoDTC Cambridge for travel funding

Long-term persistence of rituximab in patients with rheumatoid arthritis: an evaluation of the UCL cohort from 1998 to 2020

OBJECTIVES: B cell depletion therapy based on rituximab in patients with RA was pioneered at University College London Hospitals/University College London in 1998. The objective of this study was to evaluate long-term persistence of rituximab and identify factors associated with discontinuation of treatment. METHODS: Retrospective review of medical records from all rituximab-treated RA patients followed up in a dedicated clinic (1998–2020). Data collected included gender, disease duration, previous DMARDs, autoantibody status, age and concomitant therapy at first cycle, length of follow-up, and number of cycles. Drug survival and factors associated with drug discontinuation were analysed using Kaplan–Meier survival curves, log-rank test and Cox regression analysis. RESULTS: A total of 404 patients were included. Median disease duration and age at time of first rituximab cycle were 10 and 57 years, respectively. Median total follow-up was 55 months and median number of cycles five. 93.1% of patients were seropositive. Overall, 31.2% of patients stopped rituximab, with the largest reason for discontinuing being primary inefficacy (42.1%). Comparison of Kaplan–Meier curves showed that rituximab drug survival was lower in seronegative patients and in patients who had previously failed at least one biologic DMARD (bDMARD). Cox regression analysis revealed that rituximab discontinuation was associated with a greater number of previous bDMARDs. CONCLUSION: Many patients with RA achieve good control of their disease with repeated cycles of rituximab treatment. The most common reasons for treatment discontinuation were either primary or secondary inefficacy. Patients who were seronegative and who had previously failed other bDMARDs were more at risk of drug discontinuation

Transient, unsettling and creative space: Experiences of liminality through the accounts of Chinese students on a UK-based MBA

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ The Author(s) 2009.This article explores the experiences of liminality through the accounts of Chinese students on a UK-based MBA programme. The transient nature of the MBA experience, as well as the international status of the Chinese student, is resonant with conceptualizations of liminality as ‘in between’ space. Based on semi-structured interviews with 20 MBA graduates who had subsequently returned to China with their qualification, we explored their perceptions of outcomes from the course and their experiences as international students on a programme imbued with western norms and values. Results support the unsettling yet creative implications of liminality, as well as the fragmented insecure nature of identities, as individuals pass through the MBA ‘rite of passage’ in terms of ‘becoming’ a manager and entering a new phase of career. Accounts suggest the creation of hierarchical structures within liminal space whereby Chinese students, through their positioning at the margin, have uncomfortable yet illuminating encounters with alterity. At the same time, they experience levels of ambiguity and uncertainty in the post-liminal phase of China-located employments, as new western-based managerial identities collide with dominant discourses of Chinese organization