3,154 research outputs found
Surpassing the Standard Quantum Limit in an Atom Interferometer with Four-mode Entanglement Produced from Four-Wave Mixing
We theoretically investigate a scheme for atom interferometry that surpasses
the standard quantum limit. A four-wave mixing scheme similar to the recent
experiment performed by Pertot et al. \cite{pertot} is used to generate
sub-shot noise correlations between two modes. These two modes are then
interfered with the remaining two modes in such a way as to surpass the
standard quantum limit, whilst utilising all of the available atoms. Our scheme
can be viewed as using two correlated interferometers. That is, the signal from
each interferometer when looked at individually is classical, but there are
correlations between the two interferometers that allow for the standard
quantum limit to be surpassed.Comment: 7 pages, 5 figure
A biophysical model of prokaryotic diversity in geothermal hot springs
Recent field investigations of photosynthetic bacteria living in geothermal
hot spring environments have revealed surprisingly complex ecosystems, with an
unexpected level of genetic diversity. One case of particular interest involves
the distribution along hot spring thermal gradients of genetically distinct
bacterial strains that differ in their preferred temperatures for reproduction
and photosynthesis. In such systems, a single variable, temperature, defines
the relevant environmental variation. In spite of this, each region along the
thermal gradient exhibits multiple strains of photosynthetic bacteria adapted
to several distinct thermal optima, rather than the expected single thermal
strain adapted to the local environmental temperature. Here we analyze
microbiology data from several ecological studies to show that the thermal
distribution field data exhibit several universal features independent of
location and specific bacterial strain. These include the distribution of
optimal temperatures of different thermal strains and the functional dependence
of the net population density on temperature. Further, we present a simple
population dynamics model of these systems that is highly constrained by
biophysical data and by physical features of the environment. This model can
explain in detail the observed diversity of different strains of the
photosynthetic bacteria. It also reproduces the observed thermal population
distributions, as well as certain features of population dynamics observed in
laboratory studies of the same organisms
Reduced tillage, but not organic matter input, increased nematode diversity and food web stability in European longâterm field experiments
Soil nematode communities and food web indices can inform about the complexity, nutrient flows and decomposition pathways of soil food webs, reflecting soil quality. Relative abundance of nematode feeding and lifeâhistory groups are used for calculating food web indices, i.e., maturity index (MI), enrichment index (EI), structure index (SI) and channel index (CI). Molecular methods to study nematode communities potentially offer advantages compared to traditional methods in terms of resolution, throughput, cost and time. In spite of such advantages, molecular data have not often been adopted so far to assess the effects of soil management on nematode communities and to calculate these food web indices. Here, we used highâthroughput amplicon sequencing to investigate the effects of tillage (conventional vs. reduced) and organic matter addition (low vs. high) on nematode communities and food web indices in 10 European longâterm field experiments and we assessed the relationship between nematode communities and soil parameters. We found that nematode communities were more strongly affected by tillage than by organic matter addition. Compared to conventional tillage, reduced tillage increased nematode diversity (23% higher Shannon diversity index), nematode community stability (12% higher MI), structure (24% higher SI), and the fungal decomposition channel (59% higher CI), and also the number of herbivorous nematodes (70% higher). Total and labile organic carbon, available K and microbial parameters explained nematode community structure. Our findings show that nematode communities are sensitive indicators of soil quality and that molecular profiling of nematode communities has the potential to reveal the effects of soil management on soil quality
Use of MMG signals for the control of powered orthotic devices: Development of a rectus femoris measurement protocol
Copyright © 2009 Rehabilitation Engineering and Assistive Technology Society (RESNA). This is an Author's Accepted Manuscript of an article published in Assistive Technology, 21(1), 1 - 12, 2009, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/10400430902945678.A test protocol is defined for the purpose of measuring rectus femoris mechanomyographic (MMG) signals. The protocol is specified in terms of the following: measurement equipment, signal processing requirements, human postural requirements, test rig, sensor placement, sensor dermal fixation, and test procedure. Preliminary tests of the statistical nature of rectus femoris MMG signals were performed, and Gaussianity was evaluated by means of a two-sided Kolmogorov-Smirnov test. For all 100 MMG data sets obtained from the testing of two volunteers, the null hypothesis of Gaussianity was rejected at the 1%, 5%, and 10%âsignificance levels. Most skewness values were found to be greater than 0.0, while all kurtosis values were found to be greater than 3.0. A statistical convergence analysis also performed on the same 100 MMG data sets suggested that 25 MMG acquisitions should prove sufficient to statistically characterize rectus femoris MMG. This conclusion is supported by the qualitative characteristics of the mean rectus femoris MMG power spectral densities obtained using 25 averages
Effect of self-assembling peptide, chondrogenic factors, and bone marrow-derived stromal cells on osteochondral repair
Objective
The goal of this study was to test the ability of an injectable self-assembling peptide (KLD) hydrogel with or without chondrogenic factors (CF) and allogeneic bone marrow stromal cells (BMSCs) to stimulate cartilage regeneration in a full-thickness, critically-sized, rabbit cartilage defect model in vivo. We used CF treatments to test the hypotheses that CF would stimulate chondrogenesis and matrix production by cells migrating into acellular KLD (KLD + CF) or by BMSCs delivered in KLD (KLD + CF + BMSCs).
Design
Three groups were tested against contralateral untreated controls: KLD, KLD + CF, and KLD + CF +BMSCs, n = 6â7. Transforming growth factor-ÎČ1 (TGF-ÎČ1), dexamethasone, and insulin-like growth factor-1 (IGF-1) were used as CF pre-mixed with KLD and BMSCs before injection. Evaluations included gross, histological, immunohistochemical and radiographic analyses.
Results
KLD without CF or BMSCs showed the greatest repair after 12 weeks with significantly higher Safranin-O, collagen II immunostaining, and cumulative histology scores than untreated contralateral controls. KLD + CF resulted in significantly higher aggrecan immunostaining than untreated contralateral controls. Including allogeneic BMSCs + CF markedly reduced the quality of repair and increased osteophyte formation compared to KLD-alone.
Conclusions
These data show that KLD can fill full-thickness osteochondral defects in situ and improve cartilage repair as shown by Safranin-O, collagen II immunostaining, and cumulative histology. In this small animal model, the full-thickness critically-sized defect provided access to the marrow, similar in concept to abrasion arthroplasty or spongialization in large animal models, and suggests that combining KLD with these techniques may improve current practice.National Institutes of Health (U.S.) (National Institute for Biomedical Imaging and Bioengineering (U.S.) Grant EB003805)American Society for Engineering Education. National Defense Science and Engineering Graduate FellowshipNational Science Foundation (U.S.). Graduate Research FellowshipNational Institutes of Health (U.S.) (Grant EB003805)National Institutes of Health (U.S.) (Grant AR33236)Arthritis Foundation (Postdoctoral Fellowship
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