A comprehensive data set of dissolved organic carbon (DOC) and colored dissolved organic matter (CDOM) absorption measurements is analysed in light of tracing the supply and distribution of dissolved ...organic matter in the Arctic Ocean. Two years of river data from six major Arctic rivers (Kolyma, Lena, Ob, Mackenzie, Yenisei, and Yukon) and measurements from a transect across the Arctic Ocean are presented. The results show that although the Lena River currently dominates the supply of DOC and CDOM, climate change induced increases in base flow discharge will likely increase the contribution of the Yenisei River. Seasonal variations in the spectral characteristics of CDOM in the rivers reflected the shift in the dominant source of organic matter from modern plant litter in the spring freshet to older more degraded material during winter low flow periods. Strong correlations were found between the river loading of CDOM and DOC across the systems studied indicating that in situ CDOM sensors could be used in the future to improve estimates of riverine DOC loading. CDOM in the surface waters of the Eurasian Basin was largely characterised as riverine material although extrapolations to riverine end member concentrations suggested that approximately half the riverine CDOM is removed during its transport across the shelf. In contrast the Canadian Basin surface waters were characterised by a much greater proportion of autochthonous CDOM. These differences in DOM quality in the surface waters of the two basins are hypothesised to also influence the extent to which material is remineralised during its passage through the Arctic Ocean.
► Supply and distribution of dissolved organic matter in the Arctic Ocean is studied. ► Lena River dominates DOM supply but climate change will raise Yenisei's influence. ► River loading of CDOM and DOC was correlated across the systems studied. ► Surface water Eurasian Basin CDOM was largely riverine material. ► Canadian Basin surface water CDOM was characterised as more autochthonous.
The biomarker composition of dissolved organic carbon (DOC) of the six largest Arctic rivers was studied between 2003 and 2007 as part of the PARTNERS Project. Samples were collected over seasonal ...cycles relatively close to the river mouths. Here we report the lignin phenol and p-hydroxybenzene composition of Arctic river DOC in order to identify major sources of carbon. Arctic river DOC represents an important carbon conduit linking the large pools of organic carbon in the Arctic/Subarctic watersheds to the Arctic Ocean. Most of the annual lignin discharge (>75%) occurs during the two month of spring freshet with extremely high lignin concentrations and a lignin phenol composition indicative of fresh vegetation from boreal forests. The three large Siberian rivers, Lena, Yenisei, and Ob, which also have the highest proportion of forests within their watersheds, contribute about 90% of the total lignin discharge to the Arctic Ocean. The composition of river DOC is also characterized by elevated levels of p-hydroxybenzenes, particularly during the low flow season, which indicates a larger contribution from mosses and peat bogs. The lignin composition was strongly related to the average 14C-age of DOC supporting the abundance of young, boreal-vegetation-derived leachates during spring flood, and older, soil-, peat-, and wetland-derived DOC during groundwater dominated low flow conditions, particularly in the Ob and Yukon Rivers. We observed significant differences in DOC concentration and composition between the rivers over the seasonal cycles with the Mackenzie River being the most unique, the Lena River being similar to the Yenisei, and the Yukon being most similar to the Ob. The observed relationship between the lignin phenol composition and watershed characteristics suggests that DOC discharge from these rivers could increase in a warmer climate under otherwise undisturbed conditions.
We report the detection of a transiting planet around π Men (HD 39091), using data from the Transiting Exoplanet Survey Satellite (TESS). The solar-type host star is unusually bright (V = 5.7) and ...was already known to host a Jovian planet on a highly eccentric, 5.7 yr orbit. The newly discovered planet has a size of 2.04 0.05 R⊕ and an orbital period of 6.27 days. Radial-velocity data from the High-Accuracy Radial-velocity Planet Searcher and Anglo-Australian Telescope/University College London Echelle Spectrograph archives also displays a 6.27 day periodicity, confirming the existence of the planet and leading to a mass determination of 4.82 0.85 M⊕. The star's proximity and brightness will facilitate further investigations, such as atmospheric spectroscopy, asteroseismology, the Rossiter-McLaughlin effect, astrometry, and direct imaging.
The hunting-mode–habitat-domain-range framework suggests that the mechanism driving trophic cascades (i.e., trait-mediated indirect interactions TMIIs vs. density-mediated indirect interactions ...DMIIs) should depend upon the functional traits of predators and prey. For example, trophic cascades containing active, broad habitat domain range (BHDR) predators interacting with narrow habitat domain range (NHDR) prey are predicted to arise primarily via TMIIs, because these prey should reduce their conspicuous activity in the presence of these predators. Unfortunately, this hypothesis is difficult to test given the strong bias against studies assessing trophic cascades containing NHDR prey. Furthermore, this hypothesis ignores evidence that (1) active predators can have high consumption rates on prey, (2) continuously responding to active predators foraging across broad areas is energetically costly for prey, and (3) cues from active, BHDR predators may not influence prey density. We examined the TMIIs and total indirect interaction (TII) produced during interactions between an active, BHDR ladybeetle predator (Naemia seriata) and its NHDR prey (scale insects). We exposed scale insects to nonlethal and lethal ladybeetle predators in laboratory mesocosms for 15 weeks. We measured the growth of the scale insect's host plant (cordgrass) and the population density of scale insects. Contrary to theory, nonlethal ladybeetles did not induce TMIIs. However, lethal ladybeetles increased cordgrass total and root dry biomass by 36% and 44%, respectively, suggesting the presence of strong DMIIs. Additionally, both lethal and nonlethal ladybeetles reduced scale insect population density. Our findings suggest that DMIIs, rather than TMIIs, can result from interactions between active BHDR predators and NHDR prey.
Abstract Recent evidence indicates that individuals with Williams syndrome (WS), a rare genetically based neurodevelopmental disorder, show abnormalities of parietal and cerebellar regions of the ...brain that may be involved in the visual control of locomotion. Here we examined whether parietal and cerebellar abnormalities contribute to deficits in spatiotemporal characteristics and foot placement variability during obstacle crossing in adults with WS, when compared with an IQ-matched group of adults with Down syndrome (DS) and typically developing adult controls. We used the GAITRite walkway to examine the spatiotemporal characteristics and foot placement variability relative to a small ground-based obstacle in the travel path. We found that adults with WS showed late adjustments to spatiotemporal gait characteristics alongside an exaggerated and more spatially constrained visual guidance of foot positioning in the final steps prior to stepping over the obstacle. In contrast, the adults with DS showed longer step duration and more variable step length and step duration during the crossing and recovery steps after the obstacle, suggestive of cerebellar dysfunction. Although the controls were able to reduce the variability of foot placement across the obstacle crossing trials, both the WS and DS groups did not become more consistent with practice. These findings indicate a less flexible and overly constrained visuomotor system in WS, which is consistent with more widespread and diffuse abnormalities in parietal and cerebellar regions.
It is commonly assumed that animals should preferentially use habitats that enhance their individual performance. However, there have been few attempts to empirically test the relationship between an ...animals’ habitat use and performance. This is surprising, since knowing about this connection should enhance our ability to predict the local population dynamics of ecologically important species. Here, we used three primary experiments to assess the relationship between habitat use and performance for an important insect consumer (ladybeetles). First, we used field manipulations of resource availability (i.e., scale insects and cordgrass pollen) to examine the habitat use of ladybeetle predators. Second, we conducted a series of no‐choice laboratory assays to compare the performance (fecundity and longevity) of ladybeetles on these different resources. Third, we quantified adult ladybeetle preference for olfactory cues from cordgrass with and without scale insects using a Y‐tube olfactometer. In the field, adult ladybeetles selectively used plots containing scale insects. In the laboratory, diets containing scale insects maximized both adult and larval ladybeetle longevity, and adult fecundity. Adult ladybeetles were attracted to chemical cues associated with scale insects over distances of 10s of centimeters. Overall, our findings suggest that the habitat use and performance of ladybeetles are strongly linked, with ladybeetles preferentially using habitats that maximize their individual performance.
Abstract
We report the discovery and validation of TOI 122b and TOI 237b, two warm planets transiting inactive M dwarfs observed by the Transiting Exoplanet Survey Satellite (TESS). Our analysis ...shows that TOI 122b has a radius of 2.72 ± 0.18
R
⊕
and receives 8.8 ± 1.0 times Earth’s bolometric insolation, and TOI 237b has a radius of 1.44±0.12
R
⊕
and receives 3.7 ± 0.5 times Earth’s insolation, straddling the 6.7 × Earth insolation that Mercury receives from the Sun. This makes these two of the cooler planets yet discovered by TESS, even on their 5.08 and 5.43 day orbits. Together, they span the small-planet radius valley, providing useful laboratories for exploring volatile evolution around M dwarfs. Their relatively nearby distances (62.23 ± 0.21 pc and 38.11 ± 0.23 pc, respectively) make them potentially feasible targets for future radial velocity follow-up and atmospheric characterization, although such observations may require substantial investments of time on large telescopes.
Sustained and complete inhibition of HER3 and its output to PI3K/Akt are required for the optimal antitumor effect of therapeutic inhibitors of the HER2 oncogene. Here, we show that, after inhibition ...of the HER2 tyrosine kinase with lapatinib, there is PI3K/Akt and FoxO3a-dependent up-regulation of HER3 mRNA and protein. Up-regulated HER3 was then phosphorylated by residual HER2 activity, thus partially maintaining P-Akt and limiting the antitumor action of lapatinib. Inhibition of HER3 with siRNA or a neutralizing HER3 antibody sensitized HER2+ breast cancer cells and xenografts to lapatinib both in vitro and in vivo. Combined blockade of HER2 and HER3 inhibited pharmacodynamic biomarkers of PI3K/Akt activity more effectively than each inhibitor alone. These results suggest that because of HER3-mediated compensation, current clinical inhibitors of HER2 and PI3K/Akt will not block the PI3K pathway completely. They also suggest that therapeutic inhibitors of HER3 should be used in combination with HER2 inhibitors and PI3K pathway inhibitors in patients with HER2- and PI3K-dependent cancers.
This study explored the claim that individuals with autism and Asperger's disorder tend to
process locally rather than holistically. Participants observed a large or “global” number
composed of ...smaller or “local” numbers. The response was contingent upon the
identification of either the large stimulus or the small stimuli. Relative to age, sex, and IQ
matched controls, global processing in children and adolescents with autism (N = 12) and
Asperger's disorder (N = 12) was more vulnerable when the local stimuli were incongruent.
The autism group made more global errors than their matched control group, regardless of
whether there was local incongruence. In contrast, the Asperger's disorder group made a
similar number of global errors as their respective control group. These results were
discussed in relation to an “absence of global precedence” notion, “weak central coherence”
theory, and right-hemisphere dysfunction. The neurobiological significance of these findings
were discussed in the context of a fronto-striatal model of dysfunction.
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