315 research outputs found
An investigation of data compression techniques for hyperspectral core imager data
We investigate algorithms for tractable analysis of real hyperspectral image data from core samples provided by AngloGold Ashanti. In particular, we investigate feature extraction, non-linear dimension reduction using diffusion maps and wavelet approximation methods on our data
Does frenotomy help infants with tongue-tie overcome breastfeeding difficulties?
Q: Does frenotomy help infants with tongue-tie overcome breastfeeding difficulties? Evidence-based answer: Probably not. No evidence exists for improved latching after frenotomy, and evidence concerning improvements in maternal comfort is conflicting. At best, frenotomy improves maternal nipple pain by 10% and maternal subjective sense of improvement over the short term (0 to 2 weeks) (strength of recommendation [SOR]: B, randomized controlled trials [RCTs] with conflicting results for maternal nipple pain and overall feeding). No studies have evaluated outcomes such as infant weight gain following frenotomy. Experts don't recommend frenotomy unless a clear association exists between ankyloglossia (tongue-tie) and breastfeeding problems. Frenotomy should be performed with anesthesia by an experienced clinician to minimize the risk of complications (SOR: C, a practice guideline.
A new model of population dynamics of HIV-1 in vivo
Using a simple model of HIV-1 viral load and infected CD4+ count, with easily measurable
coe cients, valid on time scales of approximately a month, we nd that HIV-1 is understood
by sequential outburst of viral populations with delay between populations. AIDS is
characterised by shorter delays between viral populations and HAART is characterised by
longer delays between viral populations, as evidenced in observed viral blips. Infected CD4+
dynamics is understood by sequential outburst with overlap of CD4+ populations. We argue
that viral load and CD4+ counts must be in phase and present a model in di erential
equations that supports this conclusion and is consistent with decay rates discovered by the
outburst model
Using random matrix theory to determine the intrinsic dimension of a hyperspectral image
Determining the intrinsic dimension of a hyperspectral image is an important step in the
spectral unmixing process, since under- or over- estimation of this number may lead to
incorrect unmixing for unsupervised methods. In this thesis we introduce a new method
for determining the intrinsic dimension, using recent advances in Random Matrix Theory
(RMT). This method is not sensitive to non-i.i.d. and correlated noise, and it is entirely
unsupervised and free from any user-determined parameters. The new RMT method is
mathematically derived, and robustness tests are run on synthetic data to determine how
the results are a ected by: image size; noise levels; noise variability; noise approximation;
spectral characteristics of the endmembers, etc. Success rates are determined for many
di erent synthetic images, and the method is compared to two principal state of the
art methods, Noise Subspace Projection (NSP) and HySime. All three methods are
then tested on twelve real hyperspectral images, including images acquired by satellite,
airborne and land-based sensors. When images that were acquired by di erent sensors
over the same spatial area are evaluated, RMT gives consistent results, showing the
robustness of this method to sensor characterisics
Partial Covering Arrays: Algorithms and Asymptotics
A covering array is an array with entries
in , for which every subarray contains each
-tuple of among its rows. Covering arrays find
application in interaction testing, including software and hardware testing,
advanced materials development, and biological systems. A central question is
to determine or bound , the minimum number of rows of
a . The well known bound
is not too far from being
asymptotically optimal. Sensible relaxations of the covering requirement arise
when (1) the set need only be contained among the rows
of at least of the subarrays and (2) the
rows of every subarray need only contain a (large) subset of . In this paper, using probabilistic methods, significant
improvements on the covering array upper bound are established for both
relaxations, and for the conjunction of the two. In each case, a randomized
algorithm constructs such arrays in expected polynomial time
NASA's surface biology and geology designated observable: A perspective on surface imaging algorithms
The 2017â2027 National Academies' Decadal Survey, Thriving on Our Changing Planet, recommended Surface Biology and Geology (SBG) as a âDesignated Targeted Observableâ (DO). The SBG DO is based on the need for capabilities to acquire global, high spatial resolution, visible to shortwave infrared (VSWIR; 380â2500 nm; ~30 m pixel resolution) hyperspectral (imaging spectroscopy) and multispectral midwave and thermal infrared (MWIR: 3â5 ÎŒm; TIR: 8â12 ÎŒm; ~60 m pixel resolution) measurements with sub-monthly temporal revisits over terrestrial, freshwater, and coastal marine habitats. To address the various mission design needs, an SBG Algorithms Working Group of multidisciplinary researchers has been formed to review and evaluate the algorithms applicable to the SBG DO across a wide range of Earth science disciplines, including terrestrial and aquatic ecology, atmospheric science, geology, and hydrology. Here, we summarize current state-of-the-practice VSWIR and TIR algorithms that use airborne or orbital spectral imaging observations to address the SBG DO priorities identified by the Decadal Survey: (i) terrestrial vegetation physiology, functional traits, and health; (ii) inland and coastal aquatic ecosystems physiology, functional traits, and health; (iii) snow and ice accumulation, melting, and albedo; (iv) active surface composition (eruptions, landslides, evolving landscapes, hazard risks); (v) effects of changing land use on surface energy, water, momentum, and carbon fluxes; and (vi) managing agriculture, natural habitats, water use/quality, and urban development. We review existing algorithms in the following categories: snow/ice, aquatic environments, geology, and terrestrial vegetation, and summarize the community-state-of-practice in each category. This effort synthesizes the findings of more than 130 scientists
Nanostructured rigid polyurethane foams with improved specific thermo-mechanical properties using Bacterial Nanocellulose as a Hard Segment
Bacterial nanocellulose (BNC) was used to synthesize rigid polyurethane foams
(RPUFs) based on its reaction with the isocyanate precursor (ISO route) and
also by using the conventional procedure (POL route). The results indicated
that at only 0.1 wt. % of BNC, drastic improvements of specific elastic
compressive modulus (+244.2 %) and strength (+77.5 %) were found. The reaction
of BNC with the precursor was corroborated through the measurement of
isocyanate number and the BNC caused a significant nucleation effect,
decreasing the cell size up to 39.7%. DSC analysis revealed that the BNC had a
strong effect on post-cure enthalpy, decreasing its value when the ISO route
was implemented. DMA analysis revealed that the RPUFs developed using the ISO
route proved to have an improved damping factor, regardless of BNC
concentration. These results emphasize the importance of using the ISO route to
achieve foamed nanocomposites with improved specific mechanical properties
Historical trends in iodine and selenium in soil and herbage at the Park Grass experiment, Rothamsted Research, UK
Long term trends in iodine and selenium retention in soil, and uptake by herbage, were investigated in archived samples from the Park Grass Experiment, initiated in 1856 at Rothamsted, UK. Soil (0-23 cm) and herbage samples from plots receiving various mineral fertilisers and organic manures, with and without lime, were analysed for Se and iodine (I) to assess the effect of soil amendment, annual rainfall, crop yield and changes in soil chemistry from 1876 to 2008. Comparing soil from limed and un-limed control (unfertilized) plots, TMAH-extractable Se and I concentrations both diverged, with time, with greater retention in un-limed plots; differences in concentration amounted to 92 and 1660 ”g kg-1 for Se and I respectively after 105 yr. These differences were broadly consistent with estimated additions from rainfall and dry deposition. Offtake of both elements in herbage was negligible compared to soil concentrations and annual inputs (<0.003% of total soil I and <0.006% of total soil Se). A positive correlation was observed between I and Se concentrations in herbage, suggesting some common factors controlling bioavailability. A growth-dilution effect for I and Se was suggested by the positive correlation between growing season rainfall (GSR) and herbage yield together with soil-to-plant transfer factors decreasing with yield. Phosphate and sulphate fertilizers reduced I and Se herbage concentrations, both through ion competition and increased herbage yield. Results suggest that in intensive agriculture with soil pH control, the I requirement of grazing animals is not likely to be met by herbage alone
Novel methylotrophic bacteria isolated from the River Thames (London, UK)
Enrichment and elective culture for methylotrophs from sediment of the River Thames in central London yielded a diversity of pure cultures representing several genera of Gram-negative and Gram-positive bacteria, which were mainly of organisms not generally regarded as typically methylotrophic. Substrates leading to successful isolations included methanol, monomethylamine, dimethylamine, trimethylamine, methanesulfonate and dimethylsulfone. Several isolates were studied in detail and shown by their biochemical and morphological properties and 16S rRNA gene sequencing to be Sphingomonas melonis strain ET35, Mycobacterium fluoranthenivorans strain DSQ3, Rhodococcus erythropolis strain DSQ4, Brevibacterium casei strain MSQ5, Klebsiella oxytoca strains MMA/F and MMA/1, Pseudomonas mendocina strain TSQ4, and Flavobacterium sp. strains MSA/1 and MMA/2. The results show that facultative methylotrophy is present across a wide range of Bacteria, suggesting that turnover of diverse C1-compounds is of much greater microbiological and environmental significance than is generally thought. The origins of the genes encoding the enzymes of methylotrophy in diverse heterotrophs need further study, and could further our understanding of the phylogeny and antiquity of methylotrophic systems
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