5,574 research outputs found
Soliton microcomb based spectral domain optical coherence tomography
Spectral domain optical coherence tomography (SD-OCT) is a widely used and
minimally invaive technique for bio-medical imaging [1]. SD-OCT typically
relies on the use of superluminescent diodes (SLD), which provide a low-noise
and broadband optical spectrum. Recent advances in photonic chipscale frequency
combs [2, 3] based on soliton formation in photonic integrated microresonators
provide an chipscale alternative illumination scheme for SD-OCT. Yet to date,
the use of such soliton microcombs in OCT has not yet been analyzed. Here we
explore the use of soliton microcombs in spectral domain OCT and show that, by
using photonic chipscale Si3N4 resonators in conjunction with 1300 nm pump
lasers, spectral bandwidths exceeding those of commercial SLDs are possible. We
demonstrate that the soliton states in microresonators exhibit a noise floor
that is ca. 3 dB lower than for the SLD at identical power, but can exhibit
significantly lower noise performance for powers at the milliWatt level. We
perform SD-OCT imaging on an ex vivo fixed mouse brain tissue using the soliton
microcomb, alongside an SLD for comparison, and demonstrate the principle
viability of soliton based SD-OCT. Importantly, we demonstrate that classical
amplitude noise of all soliton comb teeth are correlated, i.e. common mode, in
contrast to SLD or incoherent microcomb states [4], which should, in theory,
improve the image quality. Moreover, we demonstrate the potential for circular
ranging, i.e. optical sub-sampling [5, 6], due to the high coherence and
temporal periodicity of the soliton state. Taken together, our work indicates
the promising properties of soliton microcombs for SD-OCT
PERCUTANEOUS VASCULAR INTERVENTION MARKET TRENDS: BULLISH ON LEGS, BEARISH ON RENALS- THE BLUE CROSS BLUE SHIELD OF MICHIGAN CARDIOVASCULAR CONSORTIUM EXPERIENCE
Ploidy influences cellular responses to gross chromosomal rearrangements in saccharomyces cerevisiae
<p>Abstract</p> <p>Background</p> <p>Gross chromosomal rearrangements (GCRs) such as aneuploidy are key factors in genome evolution as well as being common features of human cancer. Their role in tumour initiation and progression has not yet been completely elucidated and the effects of additional chromosomes in cancer cells are still unknown. Most previous studies in which <it>Saccharomyces cerevisiae </it>has been used as a model for cancer cells have been carried out in the haploid context. To obtain new insights on the role of ploidy, the cellular effects of GCRs were compared between the haploid and diploid contexts.</p> <p>Results</p> <p>A total number of 21 haploid and diploid <it>S. cerevisiae </it>strains carrying various types of GCRs (aneuploidies, nonreciprocal translocations, segmental duplications and deletions) were studied with a view to determining the effects of ploidy on the cellular responses. Differences in colony and cell morphology as well as in the growth rates were observed between mutant and parental strains. These results suggest that cells are impaired physiologically in both contexts. We also investigated the variation in genomic expression in all the mutants. We observed that gene expression was significantly altered. The data obtained here clearly show that genes involved in energy metabolism, especially in the tricarboxylic acid cycle, are up-regulated in all these mutants. However, the genes involved in the composition of the ribosome or in RNA processing are down-regulated in diploids but up-regulated in haploids. Over-expression of genes involved in the regulation of the proteasome was found to occur only in haploid mutants.</p> <p>Conclusion</p> <p>The present comparisons between the cellular responses of strains carrying GCRs in different ploidy contexts bring to light two main findings. First, GCRs induce a general stress response in all studied mutants, regardless of their ploidy. Secondly, the ploidy context plays a crucial role in maintaining the stoichiometric balance of the proteins: the translation rates decrease in diploid strains, whereas the excess protein synthesized is degraded in haploids by proteasome activity.</p
Towards Structure-Property-Function Relationships for Eumelanin
We discuss recent progress towards the establishment of important
structure-property-function relationships in eumelanins - key functional
bio-macromolecular systems responsible for photo-protection and immune response
in humans, and implicated in the development of melanoma skin cancer. We focus
on the link between eumelanin's secondary structure and optical properties such
as broad band UV-visible absorption and strong non-radiative relaxation; both
key features of the photo-protective function. We emphasise the insights gained
through a holistic approach combining optical spectroscopy with first
principles quantum chemical calculations, and advance the hypothesis that the
robust functionality characteristic of eumelanin is related to extreme chemical
and structural disorder at the secondary level. This inherent disorder is a low
cost natural resource, and it is interesting to speculate as to whether it may
play a role in other functional bio-macromolecular systems.Comment: 19 pages, 8 figures, Invited highlight article for Soft Matte
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Inkjet-Printed Graphene Electronics
We demonstrate inkjet printing as a viable method for large-area fabrication of graphene devices. We produce a graphene-based ink by liquid phase exfoliation of graphite in N-methylpyrrolidone. We use it to print thin-film transistors, with mobilities up to âŒ95 cm2 Vâ1 sâ1, as well as transparent and conductive patterns, with âŒ80% transmittance and âŒ30 kΩ/⥠sheet resistance. This paves the way to all-printed, flexible, and transparent graphene devices on arbitrary substrates
The ESA climate change initiative: Satellite data records for essential climate variables
The ESAâs Climate Change Initiative is reprocessing and reassessing over 40 years of multi-sensor satellite records to generate consistent, traceable, long-term datasets of âessential climate variablesâ for the climate modeling and research communities
Optical High Content Nanoscopy of Epigenetic Marks Decodes Phenotypic Divergence in Stem Cells
While distinct stem cell phenotypes follow global changes in chromatin marks, single-cell chromatin technologies are unable to resolve or predict stem cell fates. We propose the first such use of optical high content nanoscopy of histone epigenetic marks (epi-marks) in stem cells to classify emergent cell states. By combining nanoscopy with epi-mark textural image informatics, we developed a novel approach, termed EDICTS (Epi-mark Descriptor Imaging of Cell Transitional States), to discern chromatin organizational changes, demarcate lineage gradations across a range of stem cell types and robustly track lineage restriction kinetics. We demonstrate the utility of EDICTS by predicting the lineage progression of stem cells cultured on biomaterial substrates with graded nanotopographies and mechanical stiffness, thus parsing the role of specific biophysical cues as sensitive epigenetic drivers. We also demonstrate the unique power of EDICTS to resolve cellular states based on epi-marks that cannot be detected via mass spectrometry based methods for quantifying the abundance of histone posttranslational modifications. Overall, EDICTS represents a powerful new methodology to predict single cell lineage decisions by integrating high content super-resolution nanoscopy and imaging informatics of the nuclear organization of epi-marks.National Institutes of Health (U.S.) (Grant GM110174
Diffusive and Ballistic Transport in Ultra-thin InSb Nanowire Devices Using a Few-layer-Graphene-AlOx Gate
Quantum devices based on InSb nanowires (NWs) are a prime candidate system
for realizing and exploring topologically-protected quantum states and for
electrically-controlled spin-based qubits. The influence of disorder on
achieving reliable topological regimes has been studied theoretically,
highlighting the importance of optimizing both growth and nanofabrication. In
this work we investigate both aspects. We developed InSb nanowires with
ultra-thin diameters, as well as a new gating approach, involving few-layer
graphene (FLG) and Atomic Layer Deposition (ALD)-grown AlOx. Low-temperature
electronic transport measurements of these devices reveal conductance plateaus
and Fabry-P\'erot interference, evidencing phase-coherent transport in the
regime of few quantum modes. The approaches developed in this work could help
mitigate the role of material and fabrication-induced disorder in
semiconductor-based quantum devices.Comment: 14 pages, 5 figure
Examining the growth and stable isotopes of phytoplankton and periphyton communities exposed to oil sands reclamation strategies
The impacts of oil sands processed materials (OSPM) on phytoplankton and periphyton community growth and stable carbon and nitrogen isotopes were examined. Estimates of plankton and periphyton community growth, measured as chl a and dry weight, were low and similar in reference and OSPM reclamation wetlands. The use of stable isotope analyses revealed higher ÎŽ15N of plankton and periphyton in OSPM wetlands than reference wetlands, possibly due to increased TN concentrations in some OSPM wetlands.
In the laboratory, water-soluble fractions (WSF) of two types of OSPM (mature fine tailings, MFT and consolidated tailings, CT) and an amendment material (peat-mineral mixture), potential fill materials in wetland or end pit lake reclamation, were examined for phytoplankton community growth and stable carbon and nitrogen isotopes. All WSF treatments had higher chl a compared to reference water and maximum growth was observed at a 50:50 ratio of peat:CT or peat:MFT. In general, WSFs of peat had the highest concentration of total nitrogen (TN) whereas WSFs of MFT had the highest total phosphorus (TP; 3x higher). The results suggested that the addition of peat as an amendment to OSPM (particularly for MFT), contributing additional TN, could improve phytoplankton community growth in oil sands reclamation. At higher percentages of MFT WSF, there was increased turbidity due to fine clay particles that likely contributed to reduced phytoplankton growth. Turbidity could be an important factor limiting phytoplankton growth and thus reducing dietary resources and biological detritus (via sedimentation) in the initial development of an end pit lake. The WSFs also promoted the unfavourable growth of filamentous algae, highest at intermediate concentrations of peat and CT WSFs and inhibited in MFT WSFs due to light limitation. Stable N isotopes of plankton and filamentous algae suggests that 15N enrichment of algae could be a useful indicator of nutrient inputs, including OSPM seepage into natural aquatic systems, for oil sands regional monitoring programs
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