978 research outputs found
Hippocampal subfields and limbic white matter jointly predict learning rate in older adults
First published online: 04 December 2019Age-related memory impairments have been linked to differences in structural brain parameters, including cerebral white matter (WM) microstructure and hippocampal (HC) volume, but their combined influences are rarely investigated. In a population-based sample of 337 older participants aged 61-82 years (Mage = 69.66, SDage = 3.92 years), we modeled the independent and joint effects of limbic WM microstructure and HC subfield volumes on verbal learning. Participants completed a verbal learning task of recall over five repeated trials and underwent magnetic resonance imaging (MRI), including structural and diffusion scans. We segmented three HC subregions on high-resolution MRI data and sampled mean fractional anisotropy (FA) from bilateral limbic WM tracts identified via deterministic fiber tractography. Using structural equation modeling, we evaluated the associations between learning rate and latent factors representing FA sampled from limbic WM tracts, and HC subfield volumes, and their latent interaction. Results showed limbic WM and the interaction of HC and WM-but not HC volume alone-predicted verbal learning rates. Model decomposition revealed HC volume is only positively associated with learning rate in individuals with higher WM anisotropy. We conclude that the structural characteristics of limbic WM regions and HC volume jointly contribute to verbal learning in older adults
Modulation of three-dimensional structure and research of folding-analoges of AMB A 6 allergen of Ambrosia artemisiifolia
Amb A 6 allergen of Ambrosia artemisiifolia is a ragweed allergen (a principle cause
of late summer hayfever in North America and Europe) (Hiller et al. 1998). The
weed has recently become spreading as a neophyte in Europe, while climate change
may also affect the growth of the plant and additionally may also influence pollen
allergenicity (Kelish et al. 2014). In Ukraine, the number of diseases caused by
this allergen has recently increases. The three-dimensional structure of Amb A 6
allergen is undescribed.
The aim of our study was to modulate of three-dimensional structure and search
of folding-analoges of AMB A 6 allergen of A. artemisiifolia
Estimation of Fiber Orientations Using Neighborhood Information
Data from diffusion magnetic resonance imaging (dMRI) can be used to
reconstruct fiber tracts, for example, in muscle and white matter. Estimation
of fiber orientations (FOs) is a crucial step in the reconstruction process and
these estimates can be corrupted by noise. In this paper, a new method called
Fiber Orientation Reconstruction using Neighborhood Information (FORNI) is
described and shown to reduce the effects of noise and improve FO estimation
performance by incorporating spatial consistency. FORNI uses a fixed tensor
basis to model the diffusion weighted signals, which has the advantage of
providing an explicit relationship between the basis vectors and the FOs. FO
spatial coherence is encouraged using weighted l1-norm regularization terms,
which contain the interaction of directional information between neighbor
voxels. Data fidelity is encouraged using a squared error between the observed
and reconstructed diffusion weighted signals. After appropriate weighting of
these competing objectives, the resulting objective function is minimized using
a block coordinate descent algorithm, and a straightforward parallelization
strategy is used to speed up processing. Experiments were performed on a
digital crossing phantom, ex vivo tongue dMRI data, and in vivo brain dMRI data
for both qualitative and quantitative evaluation. The results demonstrate that
FORNI improves the quality of FO estimation over other state of the art
algorithms.Comment: Journal paper accepted in Medical Image Analysis. 35 pages and 16
figure
Raman fingerprints of ultrasmall nanodiamonds produced from adamantane
The synthesis of ultrasmall (2-5 nm) nanodiamonds purely from adamantane at
pressure of 12 GPa is reported. Their structural features have been studied by
Raman spectroscopy. The unusual vibration band containing a number of
pronounced maxima at about 1147, 1245, 1344, and 1456 cm-1 was detected in
Raman spectra. The band is confidently identified with the bending vibrational
modes of CHx groups terminating the nanodiamonds surface. Excessively intense
mode at 1344 cm-1 is explained by its coupling with the 1328 cm-1 diamond
phonons. The Raman band found is proposed to be used for express recognition of
ultrasmall nanodiamonds produced from adamantane and other hydrocarbons with a
high hydrogen content. Moreover, polarized CH bonds on a diamond surface are
sensitive to environmental conditions. This opens up opportunities for using
the diamond produced from adamantane as ultrasmall nanosensors in biology,
chemistry, and medicineComment: 12 pages, 6 figure
Donor-acceptor recombination emission in hydrogen-terminated nanodiamond: Novel single-photon source for room-temperature quantum photonics
In fluorescence spectra of nanodiamonds (NDs) synthesized at high pressure
from adamantane and other organic compounds, very narrow (~1 nm) lines of
unknown origin are observed in a wide spectroscopic range from ~500 to 800 nm.
Here, we propose and experimentally substantiate the hypothesis that these
mysterious lines arise from radiative recombination of donor-acceptor pairs
(DAPs). To confirm our hypothesis, we study the fluorescence spectra of undoped
and nitrogen-doped NDs of different sizes, before and after thermal oxidation
of their surface. The results obtained with a high degree of confidence allowed
us to conclude that the DAPs are formed through the interaction of donor-like
substitutional nitrogen present in the diamond lattice, and a 2D layer of
acceptors resulting from the transfer doping effect on the surface of
hydrogen-terminated NDs. A specific behavior of the DAP-induced lines was
discovered in the temperature range of 100-10 K: their energy increases and
most lines are split into 2 or more components with decreasing temperature. It
is shown that the majority of the studied DAP emitters are sources of single
photons, with an emission rate of up to >1 million counts/s at room
temperature, which significantly surpasses that of nitrogen-vacancy and
silicon-vacancy centers under the same detection conditions. Despite an
observed temporal instability in the emission, the DAP emitters of H-terminated
NDs represent a powerful room-temperature single-photon source for quantum
optical technologies
New ecological options for the management of horticultural crop pests in Sudano-Sahelian agroecosystems of west Africa
The agroecological approach to agroecosystem management relies on two
pillars: vegetational diversification and soil biological activity enhancement. Although
crop pests and their natural enemies may be diversely affected by measures derived
from these principles, those generally result in increased agroecosystem resilience visà -
vis both aerial and soil pests. Earlier studies by ICRISAT and CIRAD and their
partners in West Africa showed the potential of the implementation of these principles
for the management of some major pests of both staple food and horticultural crops,
and their limitations for others, notably in the water-saving and income-generating
systems mixing cereals, legumes, and high-value crops currently promoted in the
Sudano-Sahelian zones, such as the drip irrigation-based African Market Garden
(AMG) and the water harvesting-based Bio-Reclamation of Degraded Lands (BDL)
systems. Pigeon-pea showed potential for trap-cropping tomato fruit worm (TFW) on
okra, while Andropogon grass was dismissed for such management of stem-borer on
pearl millet, and mixed results were obtained with castor bean and other potential
trap crops for panicle-feeding bug management on sorghum. The results presented
highlight the potential for mobilizing either aerial or soil-bound biological processes
for managing fruit flies (FF), the main pest of grafted jujube tree, and leaf worm, the
main pest of the Moringa tree, for sustainable production of these two major crops (in
BDL and AMG systems, respectively), without having to rely on synthetic pesticide
sprays. Studies on the social acceptability of the proposed management options (e.g.,
pigeon-pea in okra-based BDL) are also underway. The potential of the Jatropha
shrub grown as a live-fence around these systems, either for its top-down effects or via
the use of its extracts in an assisted push-pull strategy, is discussed. These studies on
targeted pathosystems serve the dual purpose of finding solutions to local problems
and contribute more globally to the design of pest resilient agrosystems
Longitudinal in vivo MRI in a Huntington’s disease mouse model: global atrophy in the absence of white matter microstructural damage
Huntington’s disease (HD) is a genetically-determined neurodegenerative disease. Characterising neuropathology in mouse models of HD is commonly restricted to cross-sectional ex vivo analyses, beset by tissue fixation issues. In vivo longitudinal magnetic resonance imaging (MRI) allows for disease progression to be probed non-invasively. In the HdhQ150 mouse model of HD, in vivo MRI was employed at two time points, before and after the onset of motor signs, to assess brain macrostructure and white matter microstructure. Ex vivo MRI, immunohistochemistry, transmission electron microscopy and behavioural testing were also conducted. Global brain atrophy was found in HdhQ150 mice at both time points, with no neuropathological progression across time and an elective sparing of the cerebellum. In contrast, no white matter abnormalities were detected from the MRI images or electron microscopy images alike. The relationship between motor function and MR-based structural measurements was different for the HdhQ150 and wild-type mice, although there was no relationship between motor deficits and histopathology. Widespread neuropathology prior to symptom onset is consistent with patient studies, whereas the absence of white matter abnormalities conflicts with patient data. The myriad reasons for this inconsistency require further attention to improve the translatability from mouse models of disease
New ecological options for the management of horticultural crop pests in Sudano-Sahelian agroecosystems of west Africa
The agroecological approach to agroecosystem management relies on two
pillars: vegetational diversification and soil biological activity enhancement. Although
crop pests and their natural enemies may be diversely affected by measures derived
from these principles, those generally result in increased agroecosystem resilience visà -
vis both aerial and soil pests. Earlier studies by ICRISAT and CIRAD and their
partners in West Africa showed the potential of the implementation of these principles
for the management of some major pests of both staple food and horticultural crops,
and their limitations for others, notably in the water-saving and income-generating
systems mixing cereals, legumes, and high-value crops currently promoted in the
Sudano-Sahelian zones, such as the drip irrigation-based African Market Garden
(AMG) and the water harvesting-based Bio-Reclamation of Degraded Lands (BDL)
systems. Pigeon-pea showed potential for trap-cropping tomato fruit worm (TFW) on
okra, while Andropogon grass was dismissed for such management of stem-borer on
pearl millet, and mixed results were obtained with castor bean and other potential
trap crops for panicle-feeding bug management on sorghum. The results presented
highlight the potential for mobilizing either aerial or soil-bound biological processes
for managing fruit flies (FF), the main pest of grafted jujube tree, and leaf worm, the
main pest of the Moringa tree, for sustainable production of these two major crops (in
BDL and AMG systems, respectively), without having to rely on synthetic pesticide
sprays. Studies on the social acceptability of the proposed management options (e.g.,
pigeon-pea in okra-based BDL) are also underway. The potential of the Jatropha
shrub grown as a live-fence around these systems, either for its top-down effects or via
the use of its extracts in an assisted push-pull strategy, is discussed. These studies on
targeted pathosystems serve the dual purpose of finding solutions to local problems
and contribute more globally to the design of pest resilient agrosystems
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