A new, simple parameterization scheme for scalar (heat and moisture) exchange over sea ice and the marginal ice zone is tested in a numerical weather and climate prediction model. This new “Blended ...A87” scheme accounts for the influence of aerodynamic roughness on the relationship between momentum and scalar exchange over consolidated sea ice, in line with long‐standing theory and recent field observations, and in contrast to the crude schemes currently operational in most models. Using aircraft observations and Met Office Unified Model simulations of cold‐air outbreak (CAO) conditions over aerodynamically rough sea ice, we demonstrate striking improvements in model performance when the Blended A87 scheme replaces the model's operational treatment for surface scalar exchange, provided that the aerodynamic roughness over consolidated ice is appropriately prescribed. The mean biases in surface sensible heat flux, surface latent heat flux, near‐surface air temperature, and surface temperature reduce from 25 to 11 W m−2, 22 to 12 W m−2, 0.8 to 0.0 K, and 1.4 to 0.8 K, respectively. We demonstrate that such impacts on surface exchange over sea ice can have a marked impact on the evolution of the atmospheric boundary layer across hundreds of kilometres downwind of the sea ice during CAO conditions in the model. Our results highlight the importance of spatiotemporal variability in the topography of consolidated sea ice for both momentum and scalar exchange over sea ice; accounting for which remains a key challenge for modeling polar weather and climate.
Plain Language Summary
A new algorithm for the turbulent exchange of heat and moisture between the atmosphere and the ice‐covered oceans of the polar regions is tested in a state‐of‐the‐art weather and climate model. The algorithm is applicable both over consolidated sea ice and in regions characterized by a mixture of open seawater and ice. It accounts for the influence of aerodynamic roughness (a function of wind speed and the fine‐scale topographic roughness of the surface), in line with long‐standing theory and recent field observations, and in contrast to the crude schemes currently operational in most models. Using low‐altitude aircraft observations from over the Arctic Ocean and Nordic Seas, we demonstrate striking improvements in model performance when the new algorithm replaces the model's operational treatment for surface scalar exchange, provided that the aerodynamic roughness over consolidated ice is appropriately prescribed. The mean biases in surface sensible heat flux, surface latent heat flux, near‐surface air temperature and surface temperature reduce from 25 to 11 W m−2, 22 to 12 W m−2, 0.8 to 0.0 K, and 1.4 to 0.8 K, respectively. We demonstrate that such impacts on surface exchange over sea ice can have a significant impact on model prediction of high‐latitude weather.
Key Points
The model reproduction of scalar fluxes over sea ice is improved with a new parameterization that accounts for aerodynamic roughness
The properties and structure of the polar atmospheric boundary layer are sensitive to the implementation of this new parameterization
The benefit of the parameterization accounting for aerodynamic roughness hinges on the appropriate prescription of sea‐ice topography
Full text
Available for:
DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Two innovative hot cell Laser-Induced Breakdown Spectroscopy (LIBS) instruments, designed and built by Applied Photonics Limited, are set to be deployed for the purpose of material characterisation ...in a high radiation environment. One LIBS instrument uses a ‘through-wall’ optical periscope, where the laser and optical spectrograph are located outside of the hot cell. The second instrument uses a remote probe located within the hot cell, containing a compact Nd:YAG (neodymium-doped yttrium aluminium garnet) passively Q-switched laser and plasma light collection optics.
The design of both LIBS instruments means that some optical components (e.g. prisms, lenses, fibre optic cables and, in the case of the in-cell remote probe, a Nd:YAG laser head custom-designed and manufactured by Applied Photonics Ltd) will be exposed to high levels of gamma radiation. This entails that these components must be suitably reliable and gamma radiation resistant to last the duration of the planned work. In this article, we report on the results of a limited study on the effect of gamma irradiation (5 kGy, 25 kGy and 50 kGy absorbed dose using a cobalt-60 gamma source) on the optical properties of BK7 (Crown glass) and Ultra-Violet Fused Silica (UVFS) lenses, both with and without high-energy V-coat anti-reflection coating, and UVFS fibre optic cables. The effect of gamma irradiation on the pulsed laser beam energy output of three passively Q-switched Nd:YAG laser heads was also evaluated. The performance of each of the laser heads was tested before and after gamma irradiation by using an energy meter to measure the laser energy output of each of the three laser heads. The optical transmission properties of the components used for plasma light collection and transmission (i.e. lenses, fibre-optics) were tested using a deuterium-halogen lamp in combination with an optical spectrometer. In this limited study, we found that the BK7 lenses were clearly affected by the gamma radiation in that they became light to dark brown in appearance with increasing gamma irradiation whereas the UVFS optics (coated and uncoated) appeared visually, at least, to be unaffected. The optical transmission tests showed that the BK7 lenses became increasingly opaque to UV-VIS wavelengths with increasing gamma irradiation whereas the UVFS lenses and prisms were not so affected. The high-energy V-coat anti-reflection coatings appeared also to be unaffected by the gamma irradiation levels used in this study, at least within the limits of this investigation. However, the UVFS fibre-optic cables did show a reduction in transmission of UV light with increasing gamma irradiation.
Display omitted
•Two bespoke innovative hot cell LIBS instruments designed and built.•Fused Silica (UVFS) components showed no browning when exposed to gamma radiation.•Optical aspects of UVFS lenses and fibres generally unaffected by gamma radiation.•Performance of anti-reflection lens coatings are unaffected by gamma radiation.•Performance of passively Q-switched Nd:YAG laser is unaffected by gamma radiation.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Purpose: Green tea and green tea polyphenols have been shown to possess cancer preventive activities in preclinical model systems.
In preparation for future green tea intervention trials, we have ...conducted a clinical study to determine the safety and pharmacokinetics
of green tea polyphenols after 4 weeks of daily p.o. administration of epigallocatechin gallate (EGCG) or Polyphenon E (a
defined, decaffeinated green tea polyphenol mixture). In an exploratory fashion, we have also determined the effect of chronic
green tea polyphenol administration on UV-induced erythema response.
Experimental Design: Healthy participants with Fitzpatric skin type II or III underwent a 2-week run-in period and were randomly assigned to receive
one of the five treatments for 4 weeks: 800 mg EGCG once/day, 400 mg EGCG twice/day, 800 mg EGCG as Polyphenon E once/day,
400 mg EGCG as Polyphenon E twice/day, or a placebo once/day (8 subjects/group). Samples were collected and measurements performed
before and after the 4-week treatment period for determination of safety, pharmacokinetics, and biological activity of green
tea polyphenol treatment.
Results: Adverse events reported during the 4-week treatment period include excess gas, upset stomach, nausea, heartburn, stomach
ache, abdominal pain, dizziness, headache, and muscle pain. All of the reported events were rated as mild events. For most
events, the incidence reported in the polyphenol-treated groups was not more than that reported in the placebo group. No significant
changes were observed in blood counts and blood chemistry profiles after repeated administration of green tea polyphenol products.
There was a >60% increase in the area under the plasma EGCG concentration-time curve after 4 weeks of green tea polyphenol
treatment at a dosing schedule of 800 mg once daily. No significant changes were observed in the pharmacokinetics of EGCG
after repeated green tea polyphenol treatment at a regimen of 400 mg twice daily. The pharmacokinetics of the conjugated metabolites
of epigallocatechin and epicatechin were not affected by repeated green tea polyphenol treatment. Four weeks of green tea
polyphenol treatment at the selected dose and dosing schedule did not provide protection against UV-induced erythema.
Conclusions: We conclude that it is safe for healthy individuals to take green tea polyphenol products in amounts equivalent to the EGCG
content in 8–16 cups of green tea once a day or in divided doses twice a day for 4 weeks. There is a >60% increase in the
systemic availability of free EGCG after chronic green tea polyphenol administration at a high daily bolus dose (800 mg EGCG
or Polyphenon E once daily).
Bicontinuous cubic structures offer enormous potential in applications ranging from protein crystallisation to drug delivery systems and have been observed in cellular membrane structures. One of the ...current bottlenecks in understanding and exploiting these structures is that cubic scaffolds produced in vitro are considerably smaller in size than those observed in biological systems, differing by almost an order of magnitude in some cases. We have addressed this technological bottleneck and developed a methodology capable of manufacturing highly swollen bicontinuous cubic membranes with length scales approaching those seen in vivo. Crucially, these cubic systems do not require the presence of proteins. We have generated highly swollen Im3m symmetry bicontinuous cubic phases with lattice parameters of up to 480 Å, composed of ternary mixtures of monoolein, cholesterol and negatively charged lipid (DOPS or DOPG) and we have been able to tune their lattice parameters. The swollen cubic phases are highly sensitive to both temperature and pressure; these structural changes are likely to be controlled by a fine balance between lipid headgroup repulsions and lateral pressure in the hydrocarbon chain region.
Stream‐subsurface exchange provides the opportunity for stream‐borne substances to interact with streambed sediments in the subsurface hyporheic mixing zone. The downstream transport of both solutes ...and colloids can be substantially affected by this exchange, with significant implications for contaminant transport and stream ecology. Several previous studies have demonstrated that bed form–induced advective flows (pumping) and scour/deposition of bed sediments (turnover) will often be the dominant processes controlling local exchange with the streambed. A new model is presented for combined turnover and pumping exchange due to relatively fast‐moving bed forms, i.e., when turnover dominates the exchange in the upper part of the bed where active bed sediment transport occurs. While turnover rapidly mixes the upper layer of the bed, advective pumping produces exchange with the deeper, unsecured region of the subsurface. The net exchange due to these processes was analyzed using fundamental hydraulic principles: the initial exchange was calculated using an existing geometric model for turnover, and then the later exchange was determined by analyzing the advective flow induced under the moving bed form field. The exchange of colloidal particles due to moving bed forms was also modeled by considering the further effects of particle settling and filtration in the subsurface. Experiments were conducted in a recirculating flume to evaluate solute (conservative Li+) and colloid (kaolinite) exchange with a sand bed. The solute and colloid exchange models performed well for fast‐moving bed forms, but underpredicted the colloid exchanges observed with lower rates of bed sediment transport. For very slowly moving bed forms it was found that turnover could be completely neglected, and observed colloid exchanges were represented well by a pure pumping model. In the intermediate case where turnover and pumping rates are similar, water carried into the bed by turnover is immediately released by pumping, and vice versa. Thus, while this work further elucidated the basic processes controlling solute and colloid exchange with a bed covered by bed forms and provided a fundamental model for exchange due to fast‐moving bed forms, exchange in the intermediate case where turnover and pumping tend to compete can only be bounded by current models.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We describe Global Atmosphere 4.0 (GA4.0) and Global Land 4.0 (GL4.0): configurations of the Met Office Unified Model and JULES (Joint UK Land Environment Simulator) community land surface model ...developed for use in global and regional climate research and weather prediction activities. GA4.0 and GL4.0 are based on the previous GA3.0 and GL3.0 configurations, with the inclusion of developments made by the Met Office and its collaborators during its annual development cycle. This paper provides a comprehensive technical and scientific description of GA4.0 and GL4.0 as well as details of how these differ from their predecessors. We also present the results of some initial evaluations of their performance. Overall, performance is comparable with that of GA3.0/GL3.0; the updated configurations include improvements to the science of several parametrisation schemes, however, and will form a baseline for further ongoing development.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Neutrinos exist in one of three types or 'flavours'-electron, muon and tau neutrinos-and oscillate from one flavour to another when propagating through space. This phenomena is one of the few that ...cannot be described using the standard model of particle physics (reviewed in ref.
), and so its experimental study can provide new insight into the nature of our Universe (reviewed in ref.
). Neutrinos oscillate as a function of their propagation distance (L) divided by their energy (E). Therefore, experiments extract oscillation parameters by measuring their energy distribution at different locations. As accelerator-based oscillation experiments cannot directly measure E, the interpretation of these experiments relies heavily on phenomenological models of neutrino-nucleus interactions to infer E. Here we exploit the similarity of electron-nucleus and neutrino-nucleus interactions, and use electron scattering data with known beam energies to test energy reconstruction methods and interaction models. We find that even in simple interactions where no pions are detected, only a small fraction of events reconstruct to the correct incident energy. More importantly, widely used interaction models reproduce the reconstructed energy distribution only qualitatively and the quality of the reproduction varies strongly with beam energy. This shows both the need and the pathway to improve current models to meet the requirements of next-generation, high-precision experiments such as Hyper-Kamiokande (Japan)
and DUNE (USA)
.
Full text
Available for:
GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
Neurovascular dysfunction substantially contributes to Alzheimer disease. Here, we show that transcriptional profiling of human brain endothelial cells (BECs) defines a subset of genes whose ...expression is age-independent but is considerably altered in Alzheimer disease, including the homeobox gene MEOX2 (also known as GAX), a regulator of vascular differentiation, whose expression is low in Alzheimer disease. By using viral-mediated MEOX2 gene silencing and transfer, we show that restoring expression of the protein it encodes, GAX, in BECs from individuals with Alzheimer disease stimulates angiogenesis, transcriptionally suppresses AFX1 forkhead transcription factor-mediated apoptosis and increases the levels of a major amyloid-beta peptide (Abeta) clearance receptor, the low-density lipoprotein receptor-related protein 1 (LRP), at the blood-brain barrier. In mice, deletion of Meox2 (also known as Gax) results in reductions in brain capillary density and resting cerebral blood flow, loss of the angiogenic response to hypoxia in the brain and an impaired Abeta efflux from brain caused by reduced LRP levels. The link of MEOX2 to neurovascular dysfunction in Alzheimer disease provides new mechanistic and therapeutic insights into this illness.
Full text
Available for:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Genomes of men and women differ in only a limited number of genes located on the sex chromosomes, whereas the transcriptome is far more sex-specific. Identification of sex-biased gene expression will ...contribute to understanding the molecular basis of sex-differences in complex traits and common diseases.
Sex differences in the human peripheral blood transcriptome were characterized using microarrays in 5,241 subjects, accounting for menopause status and hormonal contraceptive use. Sex-specific expression was observed for 582 autosomal genes, of which 57.7% was upregulated in women (female-biased genes). Female-biased genes were enriched for several immune system GO categories, genes linked to rheumatoid arthritis (16%) and genes regulated by estrogen (18%). Male-biased genes were enriched for genes linked to renal cancer (9%). Sex-differences in gene expression were smaller in postmenopausal women, larger in women using hormonal contraceptives and not caused by sex-specific eQTLs, confirming the role of estrogen in regulating sex-biased genes.
This study indicates that sex-bias in gene expression is extensive and may underlie sex-differences in the prevalence of common diseases.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
