175 research outputs found
Formation and structure of calcium carbonate thin films and nanofibers precipitated in the presence of poly(allylamine hydrochloride) and magnesium ions
That the cationic polyelectrolyte poly(allylamine hydrochloride) (PAH) exerts a significant influence on CaCO₃ precipitation challenges the idea that only anionic additives have this effect. Here, we show that in common with anionic polyelectrolytes such as poly(aspartic acid), PAH supports the growth of calcite thin films and abundant nanofibers. While investigating the formation of these structures, we also perform the first detailed structural analysis of the nanofibers by transmission electron microscopy (TEM) and selected area electron diffraction. The nanofibers are shown to be principally single crystal, with isolated domains of polycrystallinity, and the single crystal structure is even preserved in regions where the nanofibers dramatically change direction. The formation mechanism of the fibers, which are often hundreds of micrometers long, has been the subject of intense speculation. Our results suggest that they form by aggregation of amorphous particles, which are incorporated into the fibers uniquely at their tips, before crystallizing. Extrusion of polymer during crystallization may inhibit particle addition at the fiber walls and result in local variations in the fiber nanostructure. Finally, we investigate the influence of Mg²+ on CaCO₃ precipitation in the presence of PAH, which gives thinner and smoother films, together with fibers with more polycrystalline, granular structures
Has the internet fostered inclusive innovation in the developing world?
Based on 50,013 firm observations covering 117 developing and emerging countries, this paper shows knowledge spillover effects from industries' use of the internet boosted the average firm's productivity and innovation performance. We document that industries' "digitization" had heterogeneous impacts: results from quantile regressions indicate that the most productive firms benefited much more than others. Wider Internet adoption rates were also of larger benefit to single-plant establishments, non-exporters and firms in remote locations, particularly to the most productive among these firms. Overall, we document that the internet can play an important role to support inclusive innovation, conditional on firms' "absorptive" capacities
The unequal effect of India's industrial liberalization on firms' decision to innovate: Do business conditions matter?
This paper examines the heterogeneous impact of industrial liberalization policy, the dismantling of the "License Raj" in India, on firms' innovation performance. Our results show that larger and more productive firms in liberalized industries were more likely to take up R&D while the smallest and least efficient firms were less likely to do so. We also show that this inequality of effects was strongest in economically less developed Indian states and where financial development and the knowledge base are weaker. This suggests business conditions shape heterogeneous impacts of liberalization policies to the advantage of initially larger and more efficient firms
Shake-induced order in nanosphere systems
Self-assembled patterns obtained from a drying nanosphere suspension are
investigated by computer simulations and simple experiments. Motivated by the
earlier experimental results of Sasaki and Hane and Schope, we confirm that
more ordered triangular lattice structures can be obtained whenever a moderate
intensity random shaking is applied on the drying system. Computer simulations
are realized on an improved version of a recently elaborated
Burridge-Knopoff-type model. Experiments are made following the setup of Sasaki
and Hane, using ultrasonic radiation as source for controlled shaking.Comment: 7 pages, 10 figure
An environmentally benign antimicrobial nanoparticle based on a silver-infused lignin core
Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles
Direct measurements of the effects of salt and surfactant on interaction forces between colloidal particles at water-oil interfaces
The forces between colloidal particles at a decane-water interface, in the
presence of low concentrations of a monovalent salt (NaCl) and of the
surfactant sodium dodecylsulfate (SDS) in the aqueous subphase, have been
studied using laser tweezers. In the absence of electrolyte and surfactant,
particle interactions exhibit a long-range repulsion, yet the variation of the
interaction for different particle pairs is found to be considerable. Averaging
over several particle pairs was hence found to be necessary to obtain reliable
assessment of the effects of salt and surfactant. It has previously been
suggested that the repulsion is consistent with electrostatic interactions
between a small number of dissociated charges in the oil phase, leading to a
decay with distance to the power -4 and an absence of any effect of electrolyte
concentration. However, the present work demonstrates that increasing the
electrolyte concentration does yield, on average, a reduction of the magnitude
of the interaction force with electrolyte concentration. This implies that
charges on the water side also contribute significantly to the electrostatic
interactions. An increase in the concentration of SDS leads to a similar
decrease of the interaction force. Moreover the repulsion at fixed SDS
concentrations decreases over longer times. Finally, measurements of three-body
interactions provide insight into the anisotropic nature of the interactions.
The unique time-dependent and anisotropic interactions between particles at the
oil-water interface allow tailoring of the aggregation kinetics and structure
of the suspension structure.Comment: Submitted to Langmui
Non-monotonic variation with salt concentration of the second virial coefficient in protein solutions
The osmotic virial coefficient of globular protein solutions is
calculated as a function of added salt concentration at fixed pH by computer
simulations of the ``primitive model''. The salt and counter-ions as well as a
discrete charge pattern on the protein surface are explicitly incorporated. For
parameters roughly corresponding to lysozyme, we find that first
decreases with added salt concentration up to a threshold concentration, then
increases to a maximum, and then decreases again upon further raising the ionic
strength. Our studies demonstrate that the existence of a discrete charge
pattern on the protein surface profoundly influences the effective interactions
and that non-linear Poisson Boltzmann and Derjaguin-Landau-Verwey-Overbeek
(DLVO) theory fail for large ionic strength. The observed non-monotonicity of
is compared to experiments. Implications for protein crystallization are
discussed.Comment: 43 pages, including 17 figure
“A long-term mortality analysis of subsidized firms in rural areas: an empirical study in the Portuguese Alentejo region”
Studies have demonstrated that public policies to support private firms’ investment have the ability to promote entrepreneurship, but the sustainability of subsidized firms has not often been analysed. This paper aims to examine this dimension specifically through evaluating the mortality of subsidized firms in the long-term. The analysis focuses on a case study of the LEADER+ Programme in the Alentejo region of Portugal. With this purpose, the paper examines the activity status (active or not active) of 154 private, rural, for-profit firms in Alentejo that had received a subsidy to support investment between 2002 and 2008 under the LEADER+ Programme. The methodology is based on binary choice models in order to study the probability of these firms still being active. The explanatory variables used are the following: (1) the characteristics of entrepreneurs and managers’ strategic decisions, (2) firm profile and characteristics, (3) regional economic environment. Data assessment showed that the cumulative mortality rate of firms on 31st December 2013 is over 20 %. Interpretation of the regression model revealed that he probability of firms’ survival increases with higher investment, firm age and regional business concentration, whereas the number of applications made by firms has a negative impact on their survival. So it seems that for subsidized firms the amount of investment is as important as its frequency
From harmful Microcystis blooms to multi-functional core-double-shell microsphere bio-hydrochar materials
Harmful algal blooms (HABs) induced by eutrophication is becoming a serious global environmental problem affecting public health and aquatic ecological sustainability. A novel strategy for the utilization of biomass from HABs was developed by converting the algae cells into hollow mesoporous biohydrochar microspheres via hydrothermal carbonization method. The hollow microspheres were used as microreactors and carriers for constructing CaO2 core-mesoporous shell-CaO2 shell microspheres (OCRMs). The CaO2 shells could quickly increase dissolved oxygen to extremely anaerobic water in the initial 40 min until the CaO2 shells were consumed. The mesoporous shells continued to act as regulators restricting the release of oxygen from CaO2 cores. The oxygen-release time using OCRMs was 7 times longer than when directly using CaO2. More interestingly, OCRMs presented a high phosphate removal efficiency (95.6%) and prevented the pH of the solution from rising to high levels in comparison with directly adding CaO2 due to the OH− controlled-release effect of OCRMs. The distinct core-doubleshell micro/nanostructure endowed the OCRMs with triple functions for oxygen controlled-release, phosphorus removal and less impact on water pH. The study is to explore the possibility to prepare smarter bio-hydrochar materials by utilizing algal blooms
The Link between Innovation and Productivity in Estonia’s Service Sectors
The emerging literature on the characteristics of innovation processes in the service sector has paid relatively little attention to the links between innovation and productivity. In this paper we investigate how the innovation-productivity relationship differs across various subbranches of the service sector. For the analysis we use the CDM structural model consisting of equations for innovation expenditures, innovation output, productivity and exports. We use data from the community innovation surveys for Estonia. We show that innovation is associated with increased productivity in the service sector. The results indicate surprisingly that the effect of innovation on productivity is stronger in the less knowledge-intensive service sectors, despite the lower frequency of innovative activities and the results of earlier literature. Non-technological innovation only plays a positive role in some specifications, despite its expected importance especially among the service firms. An additional positive channel of the effects of innovation on productivity may function through increased exports.http://deepblue.lib.umich.edu/bitstream/2027.42/133027/1/wp1012.pd
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