496 research outputs found
Electron-Beam Manipulation of Silicon Dopants in Graphene
The direct manipulation of individual atoms in materials using scanning probe
microscopy has been a seminal achievement of nanotechnology. Recent advances in
imaging resolution and sample stability have made scanning transmission
electron microscopy a promising alternative for single-atom manipulation of
covalently bound materials. Pioneering experiments using an atomically focused
electron beam have demonstrated the directed movement of silicon atoms over a
handful of sites within the graphene lattice. Here, we achieve a much greater
degree of control, allowing us to precisely move silicon impurities along an
extended path, circulating a single hexagon, or back and forth between the two
graphene sublattices. Even with manual operation, our manipulation rate is
already comparable to the state-of-the-art in any atomically precise technique.
We further explore the influence of electron energy on the manipulation rate,
supported by improved theoretical modeling taking into account the vibrations
of atoms near the impurities, and implement feedback to detect manipulation
events in real time. In addition to atomic-level engineering of its structure
and properties, graphene also provides an excellent platform for refining the
accuracy of quantitative models and for the development of automated
manipulation.Comment: 5 figures, 4 supporting figure
Survey of Treponemal Infections in Free-Ranging and Captive Macaques, 1999-2012.
Survey results showed treponemal infection among pet macaques in Southeast Asia, a region with a high prevalence of human yaws. This finding, along with studies showing treponemal infection in nonhuman primates in Africa, should encourage a One Health approach to yaws eradication and surveillance activities, possibly including monitoring of nonhuman primates in yaws-endemic regions
The Curse of Online Friends: The Detrimental Effects of Online Social Network Usage on Well-Being
In the pursuit of happiness, it has been conventionally accepted that more friends would bring us a better quality of life. However, with the advent of social networking sites, unprecedented social influence has pervaded our daily lives. Across two studies we show that even though people feel more satisfied with their lives when they view the friends added on Facebook, reading friends’ posts reduces their well-being. This is because the more friends people have on Facebook, the more ostentatious information they see. The resultant drop in life satisfaction occurs because people fail to draw a connection between the number of friends and the amount of ostentatious information. Moreover, this decrease in life satisfaction is mediated by envy. We contribute to the literature on consumer well-being by identifying a novel and ubiquitous phenomenon of making social comparisons with hundreds of people, a phenomenon that arose with the advent of social networking and was previously outside the scope of social comparison literature
Clip readjustment in aneurysm surgery after flow evaluation using the ultrasonic perivascular probe: case report
Genetic diversity and relationship of Indian cattle inferred from microsatellite and mitochondrial DNA markers
Combinatorial Polymer Electrospun Matrices Promote Physiologically-Relevant Cardiomyogenic Stem Cell Differentiation
Myocardial infarction results in extensive cardiomyocyte death which can lead to fatal arrhythmias or congestive heart failure. Delivery of stem cells to repopulate damaged cardiac tissue may be an attractive and innovative solution for repairing the damaged heart. Instructive polymer scaffolds with a wide range of properties have been used extensively to direct the differentiation of stem cells. In this study, we have optimized the chemical and mechanical properties of an electrospun polymer mesh for directed differentiation of embryonic stem cells (ESCs) towards a cardiomyogenic lineage. A combinatorial polymer library was prepared by copolymerizing three distinct subunits at varying molar ratios to tune the physicochemical properties of the resulting polymer: hydrophilic polyethylene glycol (PEG), hydrophobic poly(ε-caprolactone) (PCL), and negatively-charged, carboxylated PCL (CPCL). Murine ESCs were cultured on electrospun polymeric scaffolds and their differentiation to cardiomyocytes was assessed through measurements of viability, intracellular reactive oxygen species (ROS), α-myosin heavy chain expression (α-MHC), and intracellular Ca2+ signaling dynamics. Interestingly, ESCs on the most compliant substrate, 4%PEG-86%PCL-10%CPCL, exhibited the highest α-MHC expression as well as the most mature Ca2+ signaling dynamics. To investigate the role of scaffold modulus in ESC differentiation, the scaffold fiber density was reduced by altering the electrospinning parameters. The reduced modulus was found to enhance α-MHC gene expression, and promote maturation of myocyte Ca2+ handling. These data indicate that ESC-derived cardiomyocyte differentiation and maturation can be promoted by tuning the mechanical and chemical properties of polymer scaffold via copolymerization and electrospinning techniques
Production of fructooligosaccharides and b-fructofuranosidase by batch and repeated batch fermentation with immobilized cells of Penicillium expansum
The production of fructooligosaccharides
(FOS) and b-fructofuranosidase (FFase) by immobilized
cells of Penicillium expansum was evaluated. In an initial
stage, different low-cost materials including synthetic fiber,
polyurethane foam, stainless steel sponge, loofah sponge,
and cork oak were tested as carrier for the fungus immobilization.
Additionally, the influence of the inoculum age
(1 or 3 weeks) on cells immobilization, FOS and FFase
production was also verified. Synthetic fiber and polyurethane
foam were the best materials for P. expansum
immobilization (2.21 and 1.98 g/g carrier, respectively)
and FOS production (120.3 and 104.8 g/l), and gave also
high results of FFase activity (23.01 and 32.42 U/ml).
Then, the production of FOS and FFase by repeated batch
fermentation with P. expansum immobilized on synthetic
fiber was studied, aiming to improve the batch fermentation
results. The results obtained in this stage were very
promising with FOS yields of 87, 72, and 44 %, in the 3
initial cycles (60 h), respectively; the FFase activity was
constant throughout the process (6 cycles, 96 h). Repeated
batch fermentation with immobilized cells of P. expansum
was found as being a technology with great potential for
FOS and FFase production on industrial scaleThe financial support from FCT, the Portuguese Foundation for Science and Technology (research grant SFRH/BPD/38212/2007) is gratefully acknowledged
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