463 research outputs found
Interactive image manipulation for surgical planning
The Australian e-Health Research Centre in collaboration with the Queensland University of Technology's Paediatric Spine Research Group is developing software for visualisation and manipulation of large three-dimensional (3D) medical image data sets. The software allows the extraction of anatomical data from individual patients for use in preoperative planning. State-of-the-art computer technology makes it possible to slice through the image dataset at any angle, or manipulate 3D representations of the data instantly. Although the software was initially developed to support planning for scoliosis surgery, it can be applied to any dataset whether obtained from computed tomography, magnetic resonance imaging or any other imaging modality
Fluxes of Reserve-Derived and Currently Assimilated Carbon and Nitrogen in Perennial Ryegrass Recovering from Defoliation. The Regrowing Tiller and Its Component Functionally Distinct Zones
Effect of the 24 September 2011 solar radio burst on precise point positioning service
An intense solar radio burst occurred on 24 September 2011, which affected the tracking of Global Navigation Satellite Systemsâ (GNSS) signals by receivers located in the sunlit hemisphere of the Earth. This manuscript presents for the first time the impacts of this radio burst on the availability of Fugroâs real-time precise point positioning service for GNSS receivers and on the quality of the L band data link used to broadcast this service. During the peak of the radio burst (12:50â13:20 UT), a reduction in the L band signal-to-noise ratio (SNR) is observed. For some receiver locations, a reset in the position filter is observed, which can be either due to the reduction in the L band SNR or the reduction in the number of tracked GNSS satellites. This reset in the position filter is accompanied by degradation in the positioning accuracy, which is also discussed herein
Combining agro-ecological functions in grass-clover mixtures
Grass-clover mixtures show many benefits for sustainable agriculture. In the Netherlands, organic farmers often work together in a so-called partner farm concept, with the aim to close nutrient cycles on a regional level. In this system, arable farms grow one-year grass-clover leys, as fodder for a livestock farm, in exchange for, e.g., manure. This practice could also be used in the transition of conventional farms towards a more circular regenerative and nature inclusive agriculture. In the current experiment we assessed the effect of a range of grass (Lolium perenne: Lp, Lolium multiflorum: Lm) and clover (Trifolium pratense: Tp and Trifolium repens: Tr) monocultures and mixtures on both below- and aboveground parameters in light of benefits for livestock and arable farms, and biodiversity. The grass monocultures showed good weed suppression, high root density, and especially Lp had a positive effect on soil structure. Clover, on the other hand, showed high herbage dry matter yield (particularly Tp) and Nitrogen (N) yield, and Tr showed high digestibility. Moreover, clover had a positive effect on the soil mineral N, and earthworm abundance tended to be higher in the clover monocultures. When (some of) the four species were combined in grass-clover mixtures, they combined the positive effects of the species and often even outperformed the (best) monocultures. We concluded that grass-clover mixtures increased agro-ecological functions
A Hostâparasite Model Explains Variation in Liana Infestation Among Coâoccurring Tree Species
Lianas are structural parasites of trees that reduce the growth, survival and reproduction of their hosts. Given that coâoccurring tree species differ strongly in the proportion of individuals that are infested by lianas (liana prevalence), lianas could differentially impact tree species and thereby influence tree community composition. Surprisingly, little is known about what governs variation in liana prevalence. Here, we apply an approach inspired by disease ecology to investigate the dynamics of liana prevalence over 11 years on Barro Colorado Island, Panama. We followed the fate of 1,938 individual trees from 21 tree species, recording deaths and change in liana infestation status. With these data, we fit speciesâspecific Markov chain models to estimate four rates: colonization by lianas (analogous to disease transmission), shedding or loss of lianas (analogous to host recovery), baseline mortality of uninfested trees (baseline mortality) and additional mortality of infested trees (parasite lethality). Models explained 58% of variation in liana prevalence among tree species, and revealed that host shedding of lianas and parasite lethality were the most important contributors to interspecific variation in liana prevalence at our site. These rates were also strongly related to shade tolerance, with lightâdemanding species having greater rates of shedding and lethality, and lower rates of liana prevalence. An indirect path analysis with a structural equation model revealed that both greater rates of liana shedding and lianaâinduced lethality contribute to the observed lower rates of liana prevalence for lightâdemanding tree species. Synthesis. Our approach revealed that the prevalence of liana infestation among tree species is driven via indirect pathways operating on the rates of shedding and lethality, which relate to the ability (or inability) of trees to shed and/or tolerate lianas. Shadeâtolerant trees have greater proportions of trees infested by lianas because they are both less able to shed lianas and more able to tolerate infestation
Uptake of triiodothyroacetic acid and its effect on thyrotropin secretion in cultured anterior pituitary cells
The uptake of [125I]triiodothyroacetic acid ([125I]Triac) in anterior
pituitary cells was investigated and compared with that of [125I]T3.
Furthermore, the effects of Triac, T3, and T4 on TSH release were
compared. Cells isolated from adult male Wistar rats were cultured for 3
days in medium with 10% fetal calf serum. Uptake was measured at 37 C with
[125I]Triac (100,000 cpm; 120 pM) or [125I]T3 (50,000 cpm; 50 pM) in
medium with 0.5% BSA. In this medium, the ratio of the free fractions of
Triac, T3, and T4 was 1:8:1. Exposure of cells to 100 nM TRH for 2 h
stimulated TSH release by 80-110% (P < 0.001). Comparing total hormone
levels (1 nM to 1 microM), Triac and T3 were equally effective in reducing
this response, and both were 10-fold more effective than T4. The time
course (15 min to 4 h) of [125I]Triac uptake was similar to that of
[125I]T3, showing equilibrium after 1 h. Unlabeled Triac (1 microM)
reduced the uptake of [125I]Triac and [125I]T3 at all time intervals.
Expressed per pM free hormone, the cellular and nuclear uptake of
[125I]Triac were twice those of [125I]T3. The 15-min uptake of [125I]Triac
was reduced by incubation with 10 nM unlabeled Triac (35%; P < 0.001).
Maximum inhibition (56%; P < 0.001) was found with 10 microM Triac. A
similar effect was seen with 10 microM T3, T4, or
3,3',5,5'-tetraiodothyroacetic acid. Preincubation (30 min) and incubation
(15 min) with 10 microM oligomycin reduced the cellular ATP content by 51%
(P < 0.001), [125I]T3 uptake by 77% (P < 0.001), and [125I]Triac uptake by
only 25% (P < 0.001). The temperature dependence of [125I]Triac and
[125I]T3 uptake was the same. Preincubation and incubation with 10 microM
monensin (reduces the Na+ gradient) or 10 microM monodansylcadaverine
(inhibits receptor-mediated endocytosis) reduced 15-min [125I] Triac
uptake by 15% (P < 0.005) and 19% (P < 0.005), respectively. The data show
that 1) Triac, on the basis of the free hormone concentration, is more
potent than T3 or T4 in suppressing TSH secretion; and 2) the rapid uptake
of [125I]Triac by the anterior pituitary occurs by a carrier-mediated
mechanism that is only partially dependent on ATP or the Na+ gradient
Uptake of 3,3',5,5'-tetraiodothyroacetic acid and 3,3',5'-triiodothyronine in cultured rat anterior pituitary cells and their effects on thyrotropin secretion
We compared the uptake, metabolism, and biological effects of
tetraiodothyroacetic acid (Tetrac) and rT3 in anterior pituitary cells
with those of T4 and T3. Cells were isolated from adult male Wistar rats
and cultured for 3 days in medium with 10% fetal calf serum. Uptake was
measured at 37 C in medium with 0.1% BSA for [125I]Tetrac (200,000 cpm;
240 pM) and [125I]T4 (100,000 cpm; 175 pM) or with 0.5% BSA for [125I]rT3
(100,000 cpm; 250 pM) and [125I]T3 (50,000 cpm; 50 pM). The free fraction
of Tetrac was 1% that of T4 (in medium with 0.1 and with 0.5% BSA), and
the free fraction of rT3 was half that of T3. Uptake of the four tracers
increased sharply up to 1 h of incubation and then leveled off. Expressed
as femtomoles per pM free hormone, uptake at equilibrium was 1.16 +/- 0.16
(n = 6) for Tetrac, 0.15 +/- 0.01 (n = 6) for T4, 0.023 +/- 0.003 (n = 6)
for rT3, and 0.21 +/- 0.02 (n = 6) for T3. Cell-associated radioactivity
after incubation for 24 h with [125I]Tetrac was represented for 15% by
[125I]Triac; after incubation with [125I]T4 for 15-20% by [125I]T3, after
incubation with [125I]rT3 for 6% by [125I]3,3'-T2, while [125I]T3 was
still for 98% [125I]T3. Exposure of cells for 2 h to 100 nM TRH stimulated
TSH release by 90-135%. Tetrac was effective in reducing this response at
a free concentration of 0.05 pM, but rT3 was effective only at a free
concentration of 16 nM. A free Tetrac concentration of 5 pM was equally
effective as 50 pM free T4 in reducing the TSH response to TRH. In human
serum, Tetrac was exclusively bound to T4-binding prealbumin. The free
Tetrac fraction was 0.001% in control subjects and rose 2- to 12-fold in
patients with nonthyroidal illness. As uptake of [125I]Tetrac in the
pituitary was higher than that of T4 and T3, and it was more potent than
T4 in reducing TSH release, Tetrac may be of potential significance for
the regulation of TSH secretion in vivo
Causes and consequences of pronounced variation in the isotope composition of plant xylem water
Stable isotopologues of water are widely used to derive relative root water uptake (RWU) profiles and average RWU depth in lignified plants. Uniform isotope composition of plant xylem water (delta(xyl)) along the stem length of woody plants is a central assumption of the isotope tracing approach which has never been properly evaluated.Here we evaluate whether strong variation in delta(xyl) within woody plants exists using empirical field observations from French Guiana, northwestern China, and Germany. In addition, supported by a mechanistic plant hydraulic model, we test hypotheses on how variation in delta(xyl) can develop through the effects of diurnal variation in RWU, sap flux density, diffusion, and various other soil and plant parameters on the delta(xyl) of woody plants.The hydrogen and oxygen isotope composition of plant xylem water shows strong temporal (i.e., sub-daily) and spatial (i.e., along the stem) variation ranging up to 25.2 parts per thousand and 6.8 parts per thousand for delta H-2 and delta O-18, respectively, greatly exceeding the measurement error range in all evaluated datasets. Model explorations predict that significant delta(xyl) variation could arise from diurnal RWU fluctuations and vertical soil water heterogeneity. Moreover, significant differences in delta(xyl) emerge between individuals that differ only in sap flux densities or are monitored at different times or heights.This work shows a complex pattern of delta(xyl) transport in the soil-root-xylem system which can be related to the dynamics of RWU by plants. These dynamics complicate the assessment of RWU when using stable water isotopologues but also open new opportunities to study drought responses to environmental drivers. We propose including the monitoring of sap flow and soil matric potential for more robust estimates of average RWU depth and expansion of attainable insights in plant drought strategies and responses
- âŠ