Diversification and hybridization in firm knowledge bases in nanotechnologies

The paper investigates the linkages between the characteristics of technologies and the structure of a firms' knowledge base. Nanotechnologies have been defined as converging technologies that operate at the nanoscale, and which require integration to fulfill their economic promises. Based on a worldwide database of nanofirms, the paper analyses the degree of convergence and the convergence mechanisms within firms. It argues that the degree of convergence in a firm's nano-knowledge base is relatively independent from the size of the firm's nano-knowledge base. However, while firms with small nano-knowledge bases tend to exploit convergence in each of their patents/publications, firms with large nano-knowledge bases tend to separate their nano-R&D activities in the different established fields and achieve diversity through the juxtaposition of the output of these independent activitie

Organic Waste Management at WPI

Waste is a growing environmental problem worldwide. A typical wasted management process is not conscious of the different types of materials it receives - a mix of organic and inorganic waste. The objective of this research project is to create and efficient organic waste management plan at WPI which will reuse the organic waste thrown away to produce methane and mulch. Our plan proposes anaerobic digestion of food and yard waste to produce methane for power production and rich soil and mulch for campus beds. To get data on the waste that could potentially be reused, we contacted Morgan Commons personnel, the GPS: Feed the World, WPI Grounds Services director, Greek organizations on campus and nearby restaurants such as the Boynton and the Sole Proprietor. For digester and reactor design, we carried out an intense literature survey. Our findings focused on developing a reactor that could be feasibly implemented at WPI(tackling issues such as size, space and cost). In addition we developed an effective mulch production system by recycling leaves. The proposed plan is easily implementable with a payback in 3-4 years. WPI\u27s sustainability initiative can be furthered by implementation of this proposal.https://digitalcommons.wpi.edu/gps-posters/1349/thumbnail.jp

Reconciling observed and simulated stellar halo masses

We use cosmological hydrodynamical simulations of Milky-Way-mass galaxies from the FIRE project to evaluate various strategies for estimating the mass of a galaxy's stellar halo from deep, integrated-light images. We find good agreement with integrated-light observations if we mimic observational methods to measure the mass of the stellar halo by selecting regions of an image via projected radius relative to the disk scale length or by their surface density in stellar mass . However, these observational methods systematically underestimate the accreted stellar component, defined in our (and most) simulations as the mass of stars formed outside of the host galaxy, by up to a factor of ten, since the accreted component is centrally concentrated and therefore substantially obscured by the galactic disk. Furthermore, these observational methods introduce spurious dependencies of the estimated accreted stellar component on the stellar mass and size of galaxies that can obscure the trends in accreted stellar mass predicted by cosmological simulations, since we find that in our simulations the size and shape of the central galaxy is not strongly correlated with the assembly history of the accreted stellar halo. This effect persists whether galaxies are viewed edge-on or face-on. We show that metallicity or color information may provide a way to more cleanly delineate in observations the regions dominated by accreted stars. Absent additional data, we caution that estimates of the mass of the accreted stellar component from single-band images alone should be taken as lower limits.Comment: Version accepted by Ap

Simulating galaxies in the reionization era with FIRE-2: morphologies and sizes

We study the morphologies and sizes of galaxies at z>5 using high-resolution cosmological zoom-in simulations from the Feedback In Realistic Environments project. The galaxies show a variety of morphologies, from compact to clumpy to irregular. The simulated galaxies have more extended morphologies and larger sizes when measured using rest-frame optical B-band light than rest-frame UV light; sizes measured from stellar mass surface density are even larger. The UV morphologies are usually dominated by several small, bright young stellar clumps that are not always associated with significant stellar mass. The B-band light traces stellar mass better than the UV, but it can also be biased by the bright clumps. At all redshifts, galaxy size correlates with stellar mass/luminosity with large scatter. The half-light radii range from 0.01 to 0.2 arcsec (0.05-1 kpc physical) at fixed magnitude. At z>5, the size of galaxies at fixed stellar mass/luminosity evolves as (1+z)^{-m}, with m~1-2. For galaxies less massive than M_star~10^8 M_sun, the ratio of the half-mass radius to the halo virial radius is ~10% and does not evolve significantly at z=5-10; this ratio is typically 1-5% for more massive galaxies. A galaxy's "observed" size decreases dramatically at shallower surface brightness limits. This effect may account for the extremely small sizes of z>5 galaxies measured in the Hubble Frontier Fields. We provide predictions for the cumulative light distribution as a function of surface brightness for typical galaxies at z=6.Comment: 11 pages, 11 figures, resubmitted to MNRAS after revision for referee's comment

Formation of Globular Cluster Candidates in Merging Proto-galaxies at High Redshift: A View from the FIRE Cosmological Simulations

Using a state-of-the-art cosmological simulation of merging proto-galaxies at high redshift from the FIRE project, with explicit treatments of star formation and stellar feedback in the interstellar medium, we investigate the formation of star clusters and examine one of the formation hypothesis of present-day metal-poor globular clusters. We find that frequent mergers in high-redshift proto-galaxies could provide a fertile environment to produce long-lasting bound star clusters. The violent merger event disturbs the gravitational potential and pushes a large gas mass of ~> 1e5-6 Msun collectively to high density, at which point it rapidly turns into stars before stellar feedback can stop star formation. The high dynamic range of the reported simulation is critical in realizing such dense star-forming clouds with a small dynamical timescale, t_ff <~ 3 Myr, shorter than most stellar feedback timescales. Our simulation then allows us to trace how clusters could become virialized and tightly-bound to survive for up to ~420 Myr till the end of the simulation. Because the cluster's tightly-bound core was formed in one short burst, and the nearby older stars originally grouped with the cluster tend to be preferentially removed, at the end of the simulation the cluster has a small age spread.Comment: 14 pages, 14 figures, Accepted for publication in the Monthly Notices of the Royal Astronomical Society, High-resolution version of this article also available at http://www.jihoonkim.org/index/research.html#g

The methodological and reporting quality of systematic reviews from China and the USA are similar

Objective: To compare the methodological and reporting quality of systematic reviews by authors from China and those from the United States (the USA). Study Design: From systematic reviews of randomised trials published in 2014 in English, we randomly selected 100 from China and 100 from the USA. The methodological quality was assessed using the AMSTAR tool, and reporting quality assessed using the PRISMA tool. Results: Compared with systematic reviews from the USA, those from China were more likely to be a meta-analysis, published in low impact journals, and a non-Cochrane review. The mean summary AMSTAR score was 6.7 (95% confidence interval: 6.5 to 7.0) for reviews from China and 6.6 (6.1 to 7.1) for reviews from the USA, and the mean summary PRISMA score was 21.2 (20.7 to 21.6) for reviews from China and 20.6 (19.9 to 21.3) for reviews from the USA. The differences in summary quality scores between China and the USA were statistically non-significant after adjusting for multiple review factors. Conclusions: The overall methodological and reporting quality of systematic reviews by authors from China are similar to those from the USA, although the quality of systematic reviews from both countries could be further improved

Saturated fat in the diet of Spanish children: relationship with anthropometric, alimentary, nutritional and lipid profiles

OBJECTIVE: To compare the anthropometric, alimentary, nutritional and lipid profiles and global diet quality of Spanish children according to saturated fat intake. DESIGN: This was a cross-sectional study. Food data were collected using a food-frequency questionnaire. SUBJECTS AND METHODS: The sample included 1112 children of both sexes, aged between 6 and 7 years, selected by means of random cluster sampling in schools. The plasma lipid profile included measurements of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides, apolipoprotein A1 (apoA1) and apolipoprotein B (apoB). Global diet quality was evaluated by the Dietary Variety Index (DVI) and the Healthy Eating Index (HEI). RESULTS: Energy intake, DVI and HEI of children from the lower quartile of saturated fat intake (LL) were higher (P<001) than in the remaining children (UL). However, there were no significant differences in average height or weight between groups. The UL children had lower intakes of meat, fish, vegetables, fruits and olive oil and a higher intake of dairy products (P<0.001). The intakes of fibre, vitamins C, D, B6, E and folic acid were higher in the LL children, who had lower intakes of vitamin A and calcium. The ratios LDL-C/HDL-C and apoB/apoA1 were lower (P=0.04) in the LL children (1.87 and 0.52, respectively) than in the UL children (2.02 and 0.54, respectively). CONCLUSIONS: The growth rate of children does not seem to be affected by the level of saturated fat intake. Furthermore, at the levels of intake observed in this study, diets with less saturated fat are associated with better alimentary, nutritional and plasma lipid profiles.This study was partly funded by grants from the Fondo deInvestigacio ́n Sanitaria (FIS 020994, FIS02/3104) and theMinisterio Agricultura Pesca y Alimentacio ́n. We thankAlexander G Borun for manuscript revisionS