Decomposition of coarse woody debris in a long-term litter manipulation experiment: A focus on nutrient availability

The majority of above-ground carbon in tropical forests is stored in wood, which is returned to the atmosphere during decomposition of coarse woody debris. However, the factors controlling wood decomposition have not been experimentally manipulated over time scales comparable to the length of this process.We hypothesized that wood decomposition is limited by nutrient availability and tested this hypothesis in a long-term litter addition and removal experiment in a lowland tropical forest in Panama. Specifically, we quantified decomposition using a 15-year chronosequence of decaying boles, and measured respiration rates and nutrient limitation of wood decomposer communities.The long-term probability that a dead tree completely decomposed was decreased in plots where litter was removed, but did not differ between litter addition and control treatments. Similarly, respiration rates of wood decomposer communities were greater in control treatments relative to litter removal plots; litter addition treatments did not differ from either of the other treatments. Respiration rates increased in response to nutrient addition (nitrogen, phosphorus, and potassium) in the litter removal and addition treatments, but not in the controls.Established decreases in concentrations of soil nutrients in litter removal plots and increased respiration rates in response to nutrient addition suggest that reduced rates of wood decomposition after litter removal were caused by decreased nutrient availability. The effects of litter manipulations differed directionally from a previous short-term decomposition study in the same plots, and reduced rates of bole decomposition in litter removal plots did not emerge until after more than 6 years of decomposition. These differences suggest that litter-mediated effects on nutrient dynamics have complex interactions with decomposition over time

Direct evidence of lack of colocalisation of fluorescently labelled gold labels used in correlative light electron microscopy

Fluorescently labelled nanoparticles are routinely used in Correlative Light Electron Microscopy (CLEM) to combine the capabilities of two separate microscope platforms: fluorescent light microscopy (LM) and electron microscopy (EM). The inherent assumption is that the fluorescent label observed under LM colocalises well with the electron dense nanoparticle observed in EM. Herein we show, by combining single molecule fluorescent imaging with optical detection of the scattering from single gold nanoparticles, that for a commercially produced sample of 10 nm gold nanoparticles tagged to Alexa-633 there is in fact no colocalisation between the fluorescent signatures of Alexa-633 and the scattering associated with the gold nanoparticle. This shows that the attached gold nanoparticle quenches the fluorescent signal by ~95%, or less likely that the complex has dissociated. In either scenario, the observed fluorescent signal in fact arises from a large population of untagged fluorophores; rendering these labels potentially ineffective and misleading to the field

High-vacuum-compatible high-power Faraday isolators for gravitational-wave interferometers

Faraday isolators play a key role in the operation of large-scale gravitational-wave detectors. Second-generation gravitational-wave interferometers such as the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo will use high-average-power cw lasers (up to 200 W) requiring specially designed Faraday isolators that are immune to the effects resulting from the laser beam absorption–degraded isolation ratio, thermal lensing, and thermally induced beam steering. In this paper, we present a comprehensive study of Faraday isolators designed specifically for high-performance operation in high-power gravitational-wave interferometers

The Anisotropic Spatial Distribution of Hypervelocity Stars

We study the distribution of angular positions and angular separations of unbound hypervelocity stars (HVSs). HVSs are spatially anisotropic at the 3-sigma level. The spatial anisotropy is significant in Galactic longitude, not in latitude, and the inclusion of lower velocity, possibly bound HVSs reduces the significance of the anisotropy. We discuss how the observed distribution of HVSs may be linked to their origin. In the future, measuring the distribution of HVSs in the southern sky will provide additional constraints on the spatial anisotropy and the origin of HVSs.Comment: 4 pages, accepted to ApJ Letter

Tunnelivadelman kirvatorjunnan tehostaminen Anthocoris nemoralis -petoluteen avulla

Tunneli suojaa vadelmakasvustoa monilta kasvitaudeilta ja tuholaisilta, mutta tunneliin päästessään esimerkiksi kirvat lisääntyvät nopeasti, eivätkä biologiset torjuntaeliöt aina torju kirvoja riittävän tehokkaasti. Tunnelivadelmalla esiintyy isovattukirvaa sekä pikkuvattukirvaa. Kirvatorjun-nan tehostamiseen lähdettiin hakemaan apua kenttäkokeella, jossa kirvatorjuntaan käytettiin tyrninokkaludetta (Anthocoris nemoralis). Toimeksiantajana opinnäytetyössä oli biologinen torjuntafirma Biotus Oy. Koe suoritettiin uusimaalaisella tilalla kahdessa vadelmatunnelissa kesän 2017 aikana. Tunneleihin levitettiin kolmen viikon välein hyötyeliöitä. Hyötyeliöinä kokeessa käytettiin vainokaisia, kirvasääskiä sekä tyrninokkaluteita. Kirvojen määrä tunneleista laskettiin joka viikko ja samalla havainnoitiin hyötyeliöiden sekä tuhoeliöiden esiintyvyyttä tunneleissa. Ensimmäiset kirvahavainnot tunneleissa tehtiin heinäkuussa. Suurin osa havaituista kirvoista oli pikkuvattukirvan siivetöntä muotoa. BerryProtect -putkilo oli toimiva ennakkotorjunnassa. Kirvasääski torjui tehokkaammin toisessa tunnelissa, kun taas toisessa tyrninokkalude oli tehokkaampi. Näillä levitysstrategioilla saatiin kuitenkin Wennborgin tilan kannalta toimiva lopputulos

Lithic Analysis of Chipped Stone Artifacts Recovered From Quebrada Jaguay, Peru

Quebrada Jaguay, a Terminal Pleistocene to Early Holocene archaeological site in Southern Peru, is recognized as one of the few sites in the Americas that features evidence of a Paleoindian maritime adaptation. Faunal remains from this multicomponent shell midden include shellfish, fish, crustaceans, and shorebirds. Lithic remains recovered from the site over the course of two field seasons (1996 and 1999) provide information about the technology of the site\u27s inhabitants and afford comparisons with other contemporary sites. These lithic materials provide answers to questions dealing with lithic procurement and production strategies and questions about relationships with other groups along the coast. A systematic survey of several potential quarry sites conducted in 2000 offers useful information about source locations and compliments the lithic analysis. Methods used in the analysis provide a framework for future researchers in the area to use. At Quebrada Jaguay, there is a strong preference for finer-grained materials during the earliest occupation, with a wider variety of materials present later on. In general, as distance from the quarry increases, waste-flake size decreases. Obsidian, with its source in Aka, 130 krn distant from Quebrada Jaguay, demonstrates that the inhabitants of the site had some contact with the highlands. Lithic materials from the various components indicate later stage reduction, with primary production focused on the manufacture of use flakes from prepared cores, as well as the maintenance of bifacial and unifacial tools. In the Early Holocene component from the site, there is a shift from late-stage reduction to initial reduction. Quantification of debitage attributes permits the comparison of Quebrada Jaguay lithic materials to materials from Quebrada Tacahuay, another late Pleistocene maritime site. Because so few maritime Paleoindian sites have been discovered, Quebrada Jaguay provides a unique opportunity to study alternative Paleoindian lifeways (those not related to big-game hunting). The methodology used and analysis of the lithic materials recovered from the site provide a useful groundwork for future researchers to build on. When future work aimed at locating additional sites in the highlands is completed, we will understand much more about Paleoindian migration patterns and will potentially understand more about the initial settlement of the New World

C3/C4 Variations in High Salt Marsh Sediments: An Application of Compound Specific Isotopic Analysis of Lipid Biomarkers to Late Holocene Paleoclimatic Research

Chapter 1 Bulk carbon isotopes were previously used as a tool to differentiate between C3 and C4 plant communities in ancient salt-marsh deposits (Chmura and Aharon 1995). However, the bulk carbon values reflect organic matter contributions not only from salt-marsh plants, but also from algal bacterial inputs, as well as allochtonous terrestrial organic matter. The introduction of gas chromatography-isotope ratio mass spectrometery (GC-IRMS) allows for the separation of algal vs. higher plant contributions to the sediment pool. In the present study, this technique is applied to a core and modern plant samples collected from two Maine salt-marshes. We sampled 10 plant species common to Maine marshes including Spartina alterniflora, Spartina patens, Juncus Gerardi, Solidago sempervirens, Salicornia europa, Potentilla anserina, Atriplex patula, Plantago maritima, Suaeda maritima, and Limonium nashii. Isolation of two n-alkanes (C-27 and C-29) present in marsh plant samples allows for the reconstruction of past plant communities present in a Machiasport, Maine salt-marsh core. Observed δ13C values for the C-27 and C-29 homologues are ~ 10‰ more negative than what would be expected using bulk isotopic analysis. For the C-27 and C-29 homologues there is a 3-10‰ separation in carbon isotopic composition between C3 and C4 species. Carbon isotopic values down core show a transition from a C4 dominated planted community to a C3 dominated community, attributable to the migration of lower marsh zones onto higher marsh zones due to documented late Holocene sea-level rise (Gehrels et al., 1996). The two homologues used have the potential to provide paleoenvironmental information in future core work, where the sea-level variable will be controlled. Chapter 2 Sources of sedimentary organic matter to a Morse River, Maine (USA) salt marsh over the last 3390+/-60 RCYBP are determined using distribution patterns of n-alkanes, bulk carbon isotopic analysis, and compound-specific carbon isotopic analysis. Marsh foraminiferal counts suggest a ubiquitous presence of zone 1B deposits, implying that the deposits were laid down ~0.2m to 0.5m above mean high water. Distributions of n-alkanes show a primary contribution from higher plants, confirmed by an average ACL value of 27.5 for the core sediments, and CPI values all \u3e3. Many sample depths have a maximum abundance at the C25 alkane. The ACL value for the average of 10 common marsh species is 29.1. Salicornia europa has a similar n-alkane distribution to many of the salt marsh sediments, and we suggest that it is either an important source to the biomass of the marsh through time, or that another unidentified higher plant source is contributing heavily to the sediment pool. Bacterial degradation or algal inputs to the marsh sediments appear to be minor. Compound specific carbon isotopic analyses of the C27 alkane are on average 7.2‰ depleted relative to bulk values, but the two records are strongly correlated (R2 = 0.87), suggesting that marsh plants are “swamping” the bulk carbon isotopic signal. Our study underscores the importance of using caution when applying mixing models of plant species to salt marsh sediments, especially when relatively few plants are included in the model. Chapter 3 A record of late Holocene sediment, foraminiferal, compound specific carbon isotope, and organic geochemical stratigraphy is presented for a series of radiocarbon-dated cores from four Maine, USA salt marsh sites. Though we present some evidence for correspondence between foraminiferal records, that indicate mean high water, and carbon isotope values, that record plant community fluctuations (p\u3c0. 05), there are also significant excursions in isotope values within specific foraminiferal zones. These excursions are not predictable, do not correspond between field sites, and cannot be related with any confidence to environmental variables. We suggest that salt marshes in Maine undergo a major change in water level, photosynthetic plant community, or sediment influx on average at least once every 288 years, and probably much more frequently. We question the recent use of salt marshes as recorders of ancient climate change and urge caution in the interpretation of marsh pant community records. Chapter 4 Average fractal dimensions (D) are calculated for Maine’s four coastal compartments using a GIS approach and digitized USGS 7.5 minute series topographic quadrangle maps. The D values indicate relatively little complexity for the southwest coastal compartment (Avg. D=1.11), higher complexity for the south-central compartment (Avg. D=1.35), and intermediate complexity for the north-central compartment (Avg. D=1.23). Our analysis suggests that the northeastern compartment should be further divided into two sub-compartments (Cobscook Bay and Non-Cobscook Bay), which have Average D values of 1.37 and 1.18 respectively. Subdivision of the northeast coastal compartment is also supported by the geologic makeup of the region. Statistical tests show that all of the geologically-different coastal compartments can be discriminated in terms of D at the 95% confidence level, while the geologically similar compartments (south-central compartment and Cobscook Bay sub-compartment) cannot be statistically distinguished. Further research along previously glaciated shorelines should be carried out to build upon our results

Inverse lift: a signature of the elasticity of complex fluids?

To understand the mechanics of a complex fluid such as a foam we propose a model experiment (a bidimensional flow around an obstacle) for which an external sollicitation is applied, and a local response is measured, simultaneously. We observe that an asymmetric obstacle (cambered airfoil profile) experiences a downards lift, opposite to the lift usually known (in a different context) in aerodynamics. Correlations of velocity, deformations and pressure fields yield a clear explanation of this inverse lift, involving the elasticity of the foam. We argue that such an inverse lift is likely common to complex fluids with elasticity.Comment: 4 pages, 4 figures, revised version, submitted to PR

So rare we need to hunt for them: reframing the ethical debate on incidental findings

Incidental findings are the subject of intense ethical debate in medical genomic research. Every human genome contains a number of potentially disease-causing alterations that may be detected during comprehensive genetic analyses to investigate a specific condition. Yet available evidence shows that the frequency of incidental findings in research is much lower than expected. In this Opinion, we argue that the reason for the low level of incidental findings is that the filtering techniques and methods that are applied during the routine handling of genomic data remove these alterations. As incidental findings are systematically filtered out, it is now time to evaluate whether the ethical debate is focused on the right issues. We conclude that the key question is whether to deliberately target and search for disease-causing variations outside the indication that has originally led to the genetic analysis, for instance by using positive lists and algorithms