1,317 research outputs found
Decadal water balance of a temperate Scots pine forest (Pinus sylvestris L.) based on measurements and modelling
We examined the water balance components of an 80-year-old Scots pine (Pinus sylvestris L.) forest stand in the Campine region of Belgium over a ten year period using five very different approaches; our methods ranged from data intensive measurements to process model simulations. Specifically, we used the conservative ion method (CI), the Eddy Covariance technique (EC), an empirical model (WATBAL), and two process models that vary greatly in their temporal and spatial scaling, the ORCHIDEE global land-surface model and SECRETS a stand- to ecosystem-scale biogeochemical process model. Herein we used the EC technique as a standard for the evapotranspiration (ET) estimates. Using and evaluating process based models with data is extremely useful as models are the primary method for integration of small-scale, process level phenomena into comprehensive description of forest stand or ecosystem function. Results demonstrated that the two process models corresponded well to the seasonal patterns and yearly totals of ET from the EC approach. However, both WATBAL and CI approaches overestimated ET when compared to the EC estimates. We found significant relationships between several meteorological variables (i.e., vapour pressure deficit [VPD], mean air temperature [Tair], and global radiation [Rg]) and ET on monthly basis for all approaches. In contrast, few relationships were significant on annual basis. Independent of the method examined, ET exhibited low inter-annual variability. Consequently, drainage fluxes were highly correlated with annual precipitation for all approaches examined, except CI
Dust-grain processing in circumbinary discs around evolved binaries. The RV Tauri spectral twins RU Cen and AC Her
Context: We study the structure and evolution of circumstellar discs around
evolved binaries and their impact on the evolution of the central system. Aims:
To study in detail the binary nature of RUCen and ACHer, as well as the
structure and mineralogy of the circumstellar environment. Methods: We combine
multi-wavelength observations with a 2D radiative transfer study. Our radial
velocity program studies the central stars, while our Spitzer spectra and
broad-band SEDs are used to constrain mineralogy, grain sizes and physical
structure of the circumstellar environment. Results: We determine the orbital
elements of RUCen showing that the orbit is highly eccentric with a rather long
period of 1500 days. The infrared spectra of both objects are very similar and
the spectral dust features are dominated by Mg-rich crystalline silicates. The
small peak-to-continuum ratios are interpreted as being due to large grains.
Our model contains two components with a cold midplain dominated by large
grains, and the near- and mid-IR which is dominated by the emission of smaller
silicates. The infrared excess is well modelled assuming a hydrostatic passive
irradiated disc. The profile-fitting of the dust resonances shows that the
grains must be very irregular. Conclusions: These two prototypical RVTauri
pulsators with circumstellar dust are binaries where the dust is trapped in a
stable disc. The mineralogy and grain sizes show that the dust is highly
processed, both in crystallinity and grain size. The cool crystals show that
either radial mixing is very efficient and/or that the thermal history at grain
formation has been very different from that in outflows. The physical processes
governing the structure of these discs are similar to those observed in
protoplanetary discs around young stellar objects.Comment: 11 pages, 12 figures, accepted for publication by A&
Varroamijten tellen: wat kan je daar allemaal van leren?
In het oktobernummer van 2007 is te lezen hoe de gevallen van varroamijten aan de hand van een digitale foto kunnen worden geteld. De vraag rijst nu, kunnen uit de telresultaten misschien ook nog andere bijenzaken geleerd worden dan de varroabesmetting
Varroamijten op de bodemplaat tellen
Een eenvoudige, maar doeltreffende om varroamethoden wordt uiteengezet: aan de hand van een raster op de bodemplaat en een digitale foto kunnen op de computer de varroamijten eenvoudig worden getel
Ultrahigh-throughput-directed enzyme evolution by absorbance-activated droplet sorting (AADS)
Ultrahigh-throughput screening, in which members of enzyme libraries compartmentalized in water-in-oil emulsion droplets are assayed, has emerged as a powerful format for directed evolution and functional metagenomics but is currently limited to fluorescence readouts. Here we describe a highly efficient microfluidic absorbance-activated droplet sorter (AADS) that extends the range of assays amenable to this approach. Using this module, microdroplets can be sorted based on absorbance readout at rates of up to 300 droplets per second (i.e., >1 million droplets per hour). To validate this device, we implemented a miniaturized coupled assay for NAD(+)-dependent amino acid dehydrogenases. The detection limit (10 Ī¼M in a coupled assay producing a formazan dye) enables accurate kinetic readouts sensitive enough to detect a minimum of 1,300 turnovers per enzyme molecule, expressed in a single cell, and released by lysis within a droplet. Sorting experiments showed that the AADS successfully enriched active variants up to 2,800-fold from an overwhelming majority of inactive ones at ā¼100 Hz. To demonstrate the utility of this module for protein engineering, two rounds of directed evolution were performed to improve the activity of phenylalanine dehydrogenase toward its native substrate. Fourteen hits showed increased activity (improved >4.5-fold in lysate; kcat increased >2.7-fold), soluble protein expression levels (up 60%), and thermostability (Tm, 12 Ā°C higher). The AADS module makes the most widely used optical detection format amenable to screens of unprecedented size, paving the way for the implementation of chromogenic assays in droplet microfluidics workflows.This research was funded by the Engineering and Physical Sciences Research Council (studentship to RH and an Impact Acceleration Account Partnership Development Award), the Biological and Biotechnological Research Council (BBSRC) and Johnson Matthey. SE and MF were supported by postdoctoral Marie-Curie fellowships
Ultrahigh-throughput-directed enzyme evolution by absorbance-activated droplet sorting (AADS)
This is the final version. Available from National Academy of Sciences via the DOI in this recordUltrahigh-throughput screening, in which members of enzyme libraries compartmentalized in water-in-oil emulsion droplets are assayed, has emerged as a powerful format for directed evolution and functional metagenomics but is currently limited to fluorescence readouts. Here we describe a highly efficient microfluidic absorbance-activated droplet sorter (AADS) that extends the range of assays amenable to this approach. Using this module, microdroplets can be sorted based on absorbance readout at rates of up to 300 droplets per second (i.e., >1 million droplets per hour). To validate this device, we implemented a miniaturized coupled assay for NAD+-dependent amino acid dehydrogenases. The detection limit (10 Ī¼M in a coupled assay producing a formazan dye) enables accurate kinetic readouts sensitive enough to detect a minimum of 1,300 turnovers per enzyme molecule, expressed in a single cell, and released by lysis within a droplet. Sorting experiments showed that the AADS successfully enriched active variants up to 2,800-fold from an overwhelming majority of inactive ones at ā¼100 Hz. To demonstrate the utility of this module for protein engineering, two rounds of directed evolution were performed to improve the activity of phenylalanine dehydro-genase toward its native substrate. Fourteen hits showed increased activity (improved >4.5-fold in lysate; kcat increased >2.7-fold), soluble protein expression levels (up 60%), and thermostability (Tm, 12Ā°C higher). The AADS module makes the most widely used optical detection format amenable to screens of unprecedented size, paving the way for the implementation of chromogenic assays in droplet microfluidics workflows.Biotechnology and Biological Sciences Research CouncilEuropean Research CouncilEngineering and Physical Sciences Research CouncilEuropean Commissio
The Formation of Crystalline Dust in AGB Winds from Binary Induced Spiral Shocks
As stars evolve along the Asymptotic Giant Branch, strong winds are driven
from the outer envelope. These winds form a shell, which may ultimately become
a planetary nebula. Many planetary nebulae are highly asymmetric, hinting at
the presence of a binary companion. Some post-Asymptotic Giant Branch objects
are surrounded by torii of crystalline dust, but there is no generally accepted
mechanism for annealing the amorphous grains in the wind to crystals. In this
Letter, we show that the shaping of the wind by a binary companion is likely to
lead to the formation of crystalline dust in the orbital plane of the binary.Comment: Submitted to ApJ
Exploring sequence space in search of functional enzymes using microfluidic droplets
Screening of enzyme mutants in monodisperse picoliter compartments, generated at kilohertz speed in microfluidic devices, is coming of age. After a decade of proof-of-principle experiments, workflows have emerged that combine existing microfluidic modules to assay reaction progress quantitatively and yield improved enzymes. Recent examples of the screening of libraries of randomised proteins and from metagenomic sources suggest that this approach is not only faster and cheaper, but solves problems beyond the feasibility scope of current methodologies. The establishment of new assays in this format ā so far covering hydrolases, aldolases, polymerases and dehydrogenases ā will enable the exploration of sequence space for new catalysts of natural and non-natural chemical transformations.This work was funded by the Engineering and Physical Sciences Research Council (EPSRC; studentship in the Centre for Doctoral Training āSensor Technologies and Applicationsā to P.M., EP/L015889/1) and the Biotechnology and Biological Research Council (BBSRC; BB/K013629/1). FH is an ERC Advanced Investigator
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