2,924 research outputs found
A macroscopic model for sessile droplet evaporation on a flat surface
The evaporation of sessile droplets on a flat surface involves a complex
interplay between phase change, diffusion, advection and surface forces. In an
attempt to significantly reduce the complexity of the problem and to make it
manageable, we propose a simple model hinged on a surface free energy-based
relaxation dynamics of the droplet shape, a diffusive evaporation model and a
contact line pinning mechanism governed by a yield stress. Our model reproduces
the known dynamics of droplet shape relaxation and of droplet evaporation, both
in the absence and in the presence of contact line pinning. We show that shape
relaxation during evaporation significantly affects the lifetime of a drop. We
find that the dependence of the evaporation time on the initial contact angle
is a function of the competition between the shape relaxation and evaporation,
and is strongly affected by any contact line pinning.Comment: 13 pages, 8 figure
Compound redistribution due to droplet evaporation on a thin polymeric film: theory
A thin polymeric film in contact with a fluid body may leach
low-molecular-weight compounds into the fluid. If this fluid is a small
droplet, the compound concentration within the liquid increases due to ongoing
leaching in combination with the evaporation of the droplet. This may
eventually lead to an inversion of the transport process and a redistribution
of the compounds within the thin film. In order to gain an understanding of the
compound redistribution, we apply a macroscopic model for the evaporation of a
droplet and combine that with a diffusion model for the compound transport. In
the model, material deposition and the resulting contact line pinning are
associated with the precipitation of a fraction of the dissolved material. We
find three power law regimes for the size of the deposit area as a function of
the initial droplet size, dictated by the competition between evaporation,
diffusion and the initial compound concentrations in the droplet and the thin
film. The strength of the contact line pinning determines the deposition
profile of the precipitate, characterised by a pronounced edge and a linearly
decaying profile towards the centre of the stain. Our predictions for the
concentration profile within the solid substrate resemble patterns found
experimentally.Comment: 12 pages, 10 figure
On estimating the size of overcoverage with the latent class model. A critique of the paper "Population Size Estimation Using Multiple Incomplete Lists with Overcoverage" by di Cecco, di Zio, Filipponi and Rocchetti (2018, JOS 34 557-572)
We read with interest the article by di Cecco et al. (2018), but have
reservations about the usefulness of the latent class model specifically for
estimating overcoverage. In particular, we question the interpretation of the
parameters of the fitted latent class model.Comment: 5 page
Organic management and soil health promote nutrient use efficiency
Introduction: Nitrogen is a key nutrient for plants. Often less than 50% of the applied nitrogen fertilisers is acquired by crops and nitrogen can be easily lost into the environment causing environmental pollution. Thus, to make agriculture more sustainable, it is important to investigate which factors determine nitrogen use efficiency (NUE). We investigated whether NUE was higher in organically managed soils compared to conventionally managed soils.
Materials and Methods: To test this, we carried out a pot experiment in a greenhouse using soils from 16 fields. The soils were collected from conventionally (eight fields) or organically managed fields (eight fields). In addition, plants received two different 15N enriched N sources (mineral 15N or an organic fertiliser source, namely 15N enriched plant litter). Plants were harvested at three time points, and growth and nitrogen uptake were assessed at each time point.
Results: NUE depended on management type and harvest time and the higher NUE of organically managed soils became more evident towards the second and third harvest. The average NUE at the end of the experiment was 93% and 55% for mineral fertiliser and litter application, respectively. This indicated that mineral fertilisers were immediately acquired by the plants, while nutrients in organic amendments had a lower availability and probably would be supplied later but steadier. Further, NUE was positively linked to microbial biomass, soil organic carbon content, and aggregate size, indicating that enhanced soil quality and soil health leads to a more efficient use of fertilisers.
Conclusion: Our results indicate that organic management and soil health promote a more efficient use of nutrients and contribute to a more sustainable agriculture
Enumerating soil biodiversity
Soil is an immense habitat for diverse organisms across the tree of life, but just how many organisms live in soil is surprisingly unknown. Previous efforts to enumerate soil biodiversity consider only certain types of organisms (e.g., animals) or report values for diverse groups without partitioning species that live in soil versus other habitats. Here, we reviewed the biodiversity literature to show that soil is likely home to 59 ± 15% of the species on Earth. We therefore estimate an approximately two times greater soil biodiversity than previous estimates, and we include representatives from the simplest (microbial) to most complex (mammals) organisms. Enchytraeidae have the greatest percentage of species in soil (98.6%), followed by fungi (90%), Plantae (85.5%), and Isoptera (84.2%). Our results demonstrate that soil is the most biodiverse singular habitat. By using this estimate of soil biodiversity, we can more accurately and quantitatively advocate for soil organismal conservation and restoration as a central goal of the Anthropocene
Detection of the tulip breaking virus (TBV) in tulips using optical sensors
The tulip breaking virus (TBV) causes severe economic losses for countries that export tulips such as the Netherlands. Infected plants have to be removed from the field as soon as possible. There is an urgent need for a rapid and objective method of screening. In this study, four proximal optical sensing techniques for the detection of TBV in tulip plants were evaluated and compared with a visual assessment by crop experts as well as with an ELISA (enzyme immunoassay) analysis of the same plants. The optical sensor techniques used were an RGB color camera, a spectrophotometer measuring from 350 to 2500 nm, a spectral imaging camera covering a spectral range from 400 to 900 nm and a chlorophyll fluorescence imaging system that measures the photosynthetic activity. Linear discriminant classification was used to compare the results of these optical techniques and the visual assessment with the ELISA score. The spectral imaging system was the best optical technique and its error was only slightly larger than the visual assessment error. The experimental results appear to be promising, and they have led to further research to develop an autonomous robot for the detection and removal of diseased tulip plants in the open field. The application of this robot system will reduce the amount of insecticides and the considerable pressure on labor for selecting diseased plants by the crop expert. © 2010 The Author(s
The influence of thermo-chemotherapy on bladder tumours: an immunohistochemical analysis
To study the influence of microwave induced thermo-chemotherapy on high-grade urothelial cell carcinomas. Five groups of each three patients were formed of whom initial biopsies and cystectomy samples were collected. Patients were treated 2 days prior to cystectomy with mitomycin-C (group 1), hyperthermia (group 2) or thermo-chemotherapy (group 3). Group 4 patients had been treated with a cycle of six thermo-chemotherapy treatments prior to cystectomy and group 5 patients served as control (no treatment). Tumour samples were stained with Haematoxylin and Eosin, monoclonal antibody Ki-67 and the monoclonal antibody p53. In six out of the nine patients treated with hyperthermia a decrease in proliferation activity in the tumour was found. Seven out of nine patients treated with hyperthermia showed a decrease in p53 activity. A decrease in proliferation activity and p53 activity illustrate the potential role of thermo-chemotherapy as a promising intravesical treatment
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