Dark zone of the Greenland Ice Sheet controlled by distributed biologically-active impurities

Albedo?a primary control on surface melt?varies considerably across the Greenland Ice Sheet yet the specific surface types that comprise its dark zone remain unquantified. Here we use UAV imagery to attribute seven distinct surface types to observed albedo along a 25?km transect dissecting the western, ablating sector of the ice sheet. Our results demonstrate that distributed surface impurities?an admixture of dust, black carbon and pigmented algae?explain 73% of the observed spatial variability in albedo and are responsible for the dark zone itself. Crevassing and supraglacial water also drive albedo reduction but due to their limited extent, explain just 12 and 15% of the observed variability respectively. Cryoconite, concentrated in large holes or fluvial deposits, is the darkest surface type but accounts for <1% of the area and has minimal impact. We propose that the ongoing emergence and dispersal of distributed impurities, amplified by enhanced ablation and biological activity, will drive future expansion of Greenland's dark zone.publishersversionPeer reviewe

Parenting in a warming world: thermoregulatory responses to heat stress in an endangered seabird

This is the final version. Available on open access from Oxford University Press via the DOI in this recordThe frequency of extreme weather events, including heat waves, is increasing with climate change. The thermoregulatory demands resulting from hotter weather can have catastrophic impacts on animals, leading to mass mortalities. Although less dramatic, animals also experience physiological costs below, but approaching, critical temperature thresholds. These costs may be particularly constraining during reproduction, when parents must balance thermoregulation against breeding activities. Such challenges should be acute among seabirds, which often nest in locations exposed to high solar radiation and predation risk. The globally endangered bank cormorant Phalacrocorax neglectus breeds in southern Africa in the winter, giving little scope for poleward or phenological shifts in the face of increasing temperatures. Physiological studies of endangered species sensitive to human disturbance, like the bank cormorant, are challenging, because individuals cannot be captured for experimental research. Using a novel, non-invasive, videographic approach, we investigated the thermoregulatory responses of this seabird across a range of environmental temperatures at three nesting colonies. The time birds spent gular fluttering, a behaviour enhancing evaporative heat loss, increased with temperature. Crouching or standing birds spent considerably less time gular fluttering than birds sitting on nests (ca 30% less at 22°C), showing that postural adjustments mediate exposure to heat stress and enhance water conservation. Crouching or standing, however, increases the vulnerability of eggs and chicks to suboptimal temperatures and/or expose nest contents to predation, suggesting that parents may trade-off thermoregulatory demands against offspring survival. We modelled thermoregulatory responses under future climate scenarios and found that nest-bound bank cormorants will gular flutter almost continuously for several hours a day by 2100. The associated increase in water loss may lead to dehydration, forcing birds to prioritize survival over breeding, a trade-off that would ultimately deteriorate the conservation status of this species.National Research FoundationDST-NRF Centre of Excellence fund at the FitzPatrick Institute of African OrnithologyLeiden Conservation Foundatio

Low-level dissolved organic carbon subsidies drive a trophic upsurge in a boreal stream

1. Energy pathways in stream food webs are often driven by allochthonous basal resources. However, allochthonous dissolved organic carbon (DOC) is generally viewed as a minor if not insignificant basal resource because much of the DOC pool comprises high molecular weight, recalcitrant compounds and is inefficiently incorporated into biomass. Nevertheless, there is increasing evidence that the relatively small, labile fraction of DOC may indeed fuel microbial activity to a level that stimulates productivity across multiple trophic levels, resulting in a trophic upsurge. Here, we tested the trophic upsurge hypothesis by subsidising the labile DOC pool of an Alaskan boreal stream that had relatively high nutrient availability but low levels of naturally occurring DOC. 2. We continuously added ecologically relevant (0.250 mg C/L, c. 10% increase above ambient bulk DOC) concentrations of labile DOC (acetate-C) for 62 days to a treatment reach that was statistically indistinguishable in its channel form and chemistry from an upstream reference reach. We measured responses of pe-riphyton production and biomass, whole reach metabolism and nutrient uptake, benthic invertebrate abundances, and juvenile salmonid (Dolly Varden, Salvelinus malma) abundance and growth. 3. Measurements of basal ecosystem responses collectively indicated increased en-ergy mobilization at the base of the food web in response to labile DOC addition. Periphyton bacterial production in the treatment reach was generally >1.5× refer-ence reach values, and periphyton ash-free dry mass, chlorophyll-a, and chloro-phyll-a:ash-free dry mass were all greater in the treatment reach by the end of the study. Throughout dosing, ecosystem respiration was 1.3× greater in the treat-ment reach and dissolved inorganic nitrogen uptake was greater in the treatment reach on eight out of nine measurements. 4. Benthic invertebrate counts, dominated by Baetis spp. and Chironomidae, were c. 4× greater after 28 dosing days and c. 8× greater after 56 days in the upstream portion of the treatment reach. Abundance generally declined with increasing dis-tance from the dosing station. Dolly Varden fry and parr age classes were nearly 2× more abundant in the upstream portion of the treatment reach than in any section of the reference reach and also declined with increasing distance from the dosing station. Further, Dolly Varden tagged with passive integrated transponders prior to the experiment had significantly higher instantaneous growth rates in the treatment reach than those recaptured in the reference reach. 5. The strong consumer responses to small quantities of labile DOC mirrored sig-nificant treatment reach increases in basal ecosystem function and therefore demonstrated a response consistent with a trophic upsurge. Terrestrial DOC has historically been viewed as contributing little to metazoan consumers, instead modulating the influence of nutrients and being respired out of a disconnected microbial loop. Because we dosed the treatment reach with a relevant concentra-tion of labile DOC, based on measurements in nearby peatland-draining streams, we suggest that terrestrial DOC deserves more attention as a basal resource for whole food webs, akin to nutrients fuelling green (autochthonous) pathways.Alaska Sustainable Salmon Fund, Grant/Award Number: 4470

Generation and Suppression of Decoherence in Artificial Environment for Qubit System

It is known that a quantum system with finite degrees of freedom can simulate a composite of a system and an environment if the state of the hypothetical environment is randomized by external manipulation. We show theoretically that any phase decoherence phenomena of a single qubit can be simulated with a two-qubit system and demonstrate experimentally two examples: one is phase decoherence of a single qubit in a transmission line, and the other is that in a quantum memory. We perform NMR experiments employing a two-spin molecule and clearly measure decoherence for both cases. We also prove experimentally that the bang-bang control efficiently suppresses decoherence.Comment: 25 pages, 7 figures; added reference

Leaf litter identity alters the timing of lotic nutrient dynamics

1. The effects of resource quality on ecosystems can shift through time based on preferential use and elemental needs of biotic consumers. For example, leaf litter decomposition rates are strongly controlled by initial litter quality, where labile litter is processed and depleted more quickly than recalcitrant litters. 2. We examined the effect of this processing continuum on stream nutrient dynamics.We added one of four different litter compositions differing in litter quality (cot ‐tonwood [Populus deltoides], labile; sycamore [Platanus occidentalis], recalcitrant; bur oak [Quercus macrocarpa], recalcitrant; and mixed [equivalent mixture of pre ‐vious three species]) to 12 large (c. 20 m long, with riffle, glide and pool sections) outdoor stream mesocosms to assess the effect of litter species composition on whole‐stream nutrient uptake. Nutrients were dosed once weekly for 8 weeks to measure uptake of NH4–N, NO3–N, and PO4–P. We also measured changes in lit ‐ter C, N, and P content on days 28 and 56 of the study. 3. Nutrient uptake rates were highly variable, but occasionally very different among litter treatments (c. 5× between highest and lowest uptake rates by species). Uptake rates were generally greatest in cottonwood (labile) streams early in the study. However, during the last 4 weeks of the study, bur oak streams (recalci ‐trant) took up more nutrients than cottonwood streams, resulting in more cumu‐lative NO3–N uptake in bur oak than in cottonwood streams. Cumulative NO3–N uptake was greater in mixed streams than expected (non‐additive) on two dates of measurement, but was generally additive. 4. Changes in litter nutrient content largely corroborated nutrient uptake patterns, suggesting strong N immobilisation early in the study and some N mineralisation later in the study. P was strongly retained by most litters, but especially bur oak. Nutrient content of litter also largely changed additively, suggesting minimal evi ‐dence for non‐additive diversity effects on nutrient source/sink status. 5. Our results demonstrate that litter species identity can have whole‐ecosystem effects on stream nutrient dynamics, with important implications for the for fate of nutrients exported downstream. Further, diverse litter assemblages may serve as temporal stabilisers of ecosystem processes, such as nutrient sequestra‐tion, due to microbial nutrient requirements and differential decomposition rates, or the classic litter processing continuum.NSF, Grant/Award Number: DEB‐144259

The Vehicle, Fall 2004

Table of Contents Six-Billion to One AgainstRyan Maneypage 5 May 25th, 2004Megan Rankinpage 6 Summer DeliveryAnthony Shootpage 7 A Young Family, Smithland, Kentucky. October 1935.Clementinepage 8 UntitledJonathan M. Cookpage 9 October 23, 2021Ryan Maneypage 10 Last NightKaty Dwigginspage 11 UntitledMegan Rankinpage 12 Clever DisguiseSarah Johnsonpage 13 conspiracy against grandmaClementinepage 14 ThunderKitty Apodacapage 15 UntitledJonathan M. Cookpage 16 Self PortraitAnnette Carlinpage 17 LeavesAnthony Shootpage 18 UntitledKaty Dwigginspage 19 The Woman I Almost UnderstoodGreg Lyonspage 20 Flesh and SandJonathan M. Cookpage 21 Lunch DateAlisa Habelpage 22 Like and Unlike Everyone ElseC. Alan Doughtypage 23 Thankfully SwayedSarah Johnsonpage 24 A Warm Winter DayJoshua D. Andersonpage 25-26 Oak, Maple, SassafrasClementinepage 27-30https://thekeep.eiu.edu/vehicle/1080/thumbnail.jp

The Statistical Mechanics of Horizons and Black Hole Thermodynamics

Although we know that black holes are characterized by a temperature and an entropy, we do not yet have a satisfactory microscopic ``statistical mechanical'' explanation for black hole thermodynamics. I describe a new approach that attributes the thermodynamic properties to ``would-be gauge'' degrees of freedom that become dynamical on the horizon. For the (2+1)-dimensional black hole, this approach gives the correct entropy. (Talk given at the Pacific Conference on Gravitation and Cosmology, Seoul, February 1996.)Comment: 11 pages, LaTe

Injection versus Decompression for Carpal Tunnel Syndrome-Pilot trial (INDICATE-P)-protocol for a randomised feasibility study

BACKGROUND: Carpal tunnel syndrome (CTS) is the commonest peripheral nerve disorder in the UK, with over 52,996 carpal tunnel decompressions performed in 2011. By 2030, this figure is estimated to double. Whilst evidence supports conservative measures for mild symptoms, and early surgery for severe symptoms, controversy remains over the most appropriate management for patients that present with moderate disease, with regard to early surgery or late surgery following steroid injection. Injection versus Decompression for Carpal Tunnel Syndrome-Pilot trial (INDICATE-P) is a feasibility study for a multicentre, randomised controlled trial (INDICATE) to determine whether patients over the age of 18 with moderate CTS should undergo early surgical decompression of the median nerve or a single steroid injection (followed by later surgery if required). METHODS/DESIGN: INDICATE-P is a feasibility study for an open (non-blinded) randomised controlled pilot trial. Eligible participants will be adults with a clinical diagnosis of moderate CTS. This is defined as symptoms disturbing sleep or restricting activities of daily living or work, despite a 2-week trial of night splints. Participants will be randomised to one of two possible interventions: surgical decompression or a single steroid injection (followed by surgery later if required). Clinical outcome measures will be captured by postal questionnaire at 1, 3, 6 and 12 months post-randomisation. In order to improve the study design for the main INDICATE trial, feasibility data will also be collected to identify difficulties in recruitment and retention, to gain patient feedback on questionnaires and to confirm the suitability of the proposed outcome measures. DISCUSSION: The INDICATE-P feasibility study will contribute to the design and execution of the INDICATE trial, which will seek to assess the safety and effectiveness of two approaches to treatment for patients over 18 years of age with moderate CTS: early carpal tunnel decompression or a single steroid injection (followed by later surgery)