Measurement of sucrose concentration using Imbibition length on paper: A device for equipment-free and environmentally-friendly detection

The Lucas-Washburn equation is commonly used to predict the distance (L) that a liquid travels through paper. This equation establishes that L2 is linear with time and inversely proportional to the viscosity of the liquid. However, there is currently no theoretical equation connecting the viscosity of a solution to its concentration. In this study, the imbibition flow of a sucrose solution was measured along the length of a horizontal strip of filter paper, featuring a printed, thermometer-shaped hydrophobic boundary. A sample (38 μL) was dispensed onto the bulb area, and the solution's flow was visually tracked using a red dye added to the sample. The imbibition length (L) was measured by a vernier caliper at 10.0 min after the sample addition. An empirical equation, based on literature values of the viscosity (η) and concentration (C) of sucrose solutions, was proposed. By integrating this empirical equation with the Lucas-Washburn equation, the following equation was derived: L = a⋅exp{-(bC + cC2)}, where 'a', 'b' and 'c' are parameters. This equation was fitted to the dataset of L and C, covering C values from 0 to 60 % w/w standard sucrose solutions, resulting in a coefficient of determination of 0.9987. The plot of L against C was observed to closely follow a linear line, with a fitting providing a coefficient of determination of 0.9986. The sucrose contents in samples, such as soft drinks, syrups, and sugarcanes, determined using the imbibition length method and conventional refractometry, were in statistical agreement via the paired t-test at the 95 % confidence level. This method is simple, instrument-free, requiring only a small amount of safe red food dye, and can be conducted on-site.

Exploring water-absorbing capacity: a digital image analysis of seeds from 120 wheat varieties

Wheat is a staple food crop that provides a significant portion of the world's daily caloric intake, serving as a vital source of carbohydrates and dietary fiber for billions of people. Seed shape studies of wheat typically involve the use of digital image analysis software to quantify various seed shape parameters such as length, width, area, aspect ratio, roundness, and symmetry. This study presents a comprehensive investigation into the water-absorbing capacity of seeds from 120 distinct wheat lines, leveraging digital image analysis techniques facilitated by SmartGrain software. Water absorption is a pivotal process in the early stages of seed germination, directly influencing plant growth and crop yield. SmartGrain, a powerful image analysis tool, was employed to extract precise quantitative data from digital images of wheat seeds, enabling the assessment of various seed traits in relation to their water-absorbing capacity. The analysis revealed significant transformations in seed characteristics as they absorbed water, including changes in size, weight, shape, and more. Through statistical analysis and correlation assessments, we identified robust relationships between these seed traits, both before and after water treatment. Principal Component Analysis (PCA) and Agglomerative Hierarchical Clustering (AHC) were employed to categorize genotypes with similar trait patterns, providing insights valuable for crop breeding and genetic research. Multiple linear regression analysis further elucidated the influence of specific seed traits, such as weight, width, and distance, on water-absorbing capacity. Our study contributes to a deeper understanding of seed development, imbibition, and the crucial role of water absorption in wheat. These insights have practical implications in agriculture, offering opportunities to optimize breeding programs for improved water absorption in wheat genotypes. The integration of SmartGrain software with advanced statistical methods enhances the reliability and significance of our findings, paving the way for more efficient and resilient wheat crop production. Significant changes in wheat seed shape parameters were observed after imbibition, with notable increases in area, perimeter, length, width, and weight. The length-to-width ratio (LWR) and circularity displayed opposite trends, with higher values before imbibition and lower values after imbibition.

Dynamic monitoring of dielectric properties during two phase immiscible displacements in sand packs using frequency domain electromagnetic sweeps

Electromagnetic heating is a promising soil remediation method especially in thin formations. The lack of a wide-spread adoption of this method stems from insufficient knowledge of how the complex dielectric properties, that govern propagation of the electromagnetic waves through porous media, change with changing frequency, water saturation, displacement types and flow regimes. To breach these gaps several sets of spontaneous deionized (DI) water imbibition experiments, followed by the primary drainage floods, that were followed by the secondary DI water imbibition floods in confined uniform sand packs were performed. The frequency domain relative dielectric constant and conductivities were extracted from the two-port complex S-parameter measurements taken with the vector network analyzer during these immiscible displacements at various water saturation levels at ambient conditions. A novel coaxial transmission line core holder was designed and commissioned, and a modified version of a plane-invariant dielectric extraction algorithm was developed for this purpose. Series, parallel and semi-disperse mixing models were applied to fit the water saturation dependent relative dielectric constant and conductivity values sampled at 500 MHz from the extracted frequency domain spectra. The Maxwell-Garnett parallel model was proved to be the most flexible because it could capture the sampled conductivity values in all secondary imbibition floods before and after the breakthroughs, where the inflection points were observed. These inflection points were attributed to silica production and a potential shear-stripping flow. This observation was further confirmed by conducting a single-phase Darcy's law analysis of two DI water imbibition floods.

Super-enhanced evaporation of droplets from porous coatings

HYPOTHESIS

The addition of a thin, hydrophilic, porous, coating to an impermeable solid will lead to more rapid evaporation of liquid droplets that impinge on the solid. The droplet will imbibe quickly, but the progress normal to the interface will be limited to the thickness of the coating, and therefore the liquid will spread laterally into a broad disk to expose a large liquid-vapor interface for evaporation.

EXPERIMENTS

Liquid droplets of volume 2.5-25 µL were placed on solids and then both the mass and area of each droplet were monitored over time. We compared data for smooth, impermeable hydrophilic glass to the same glass that was coated in thin (35-109 µm) porous, hydrophilic-glass layer fabricated from glass beads.

FINDINGS

The droplet was imbibed (wicked) into the coating within seconds, and the liquid spread laterally to form a thin, broad, disk. Critically, evaporation of a droplet was enhanced by a factor of 7-8 on the thin coating. The evaporation rate was not proportional to the reciprocal thickness of the coating. The ability to enhance evaporation of small droplets on a solid may have practical applications, for example, in speeding the death of microbes.

Revisiting the pericarp as a barrier restricting water entry/loss from cotyledons and embryonic axis of temperate desiccation-sensitive Quercus acorns

Fully mature acorns of Quercus variabilis, Q. aliena, Q. mongolica, and Q. glandulifera are desiccation-sensitive. X-ray computer tomography showed that cotyledons shrink during drying, but embryos are protected. Information available on recalcitrant acorns of tropical and sub-tropical species of Quercus suggests that an impermeable pericarp, which limits the entry and loss of water only through the hilum (scar), is the underlying mechanism that prevents drying of the embryo axis following dispersal until the germination season. However, there is a lack of consensus supporting this proposition across species, and it is not well understood if such mechanisms occur in temperate Quercus species. This study investigated the significance of the acorn pericarp for temperate oak species and presents an ecological framework based on the post-dispersal climatic conditions. Using Quercus variabilis, Q. aliena, Q. mongolica, and Q. glandulifera acorns, the relationship between moisture content (MC) and germination was established, and X-ray computed tomography (X-ray CT) was used to understand the internal structural changes of cotyledons and embryonic axis occurring during desiccation. Water entry and exit routes through the scar, pericarp and apex were determined by imbibition and drying experiments. Climatic data and acorn morphological characteristics and germination were subjected to a principal component analysis (PCA). Freshly dispersed acorns of all species had a moisture content (MC) above 35% fresh weight (FW) basis, but drying to 15-10% MC resulted in complete loss of viability, implying recalcitrance behaviour. X-ray CT images suggested that the pericarp offers some protection to cotyledons and embryonic axis during desiccation, but it is contingent on MC. Extensive drying to a low MC with the scar and apex covered with vaseline resulted in internal tissues shrinkage, corresponding with viability loss. Water could enter or exit through the pericarp, albeit at a much slower rate than through the scar. A combination of factors including acorn anatomy, moisture content at the time of dispersal, microhabitat, the position of acorns in the soil prevent embryo desiccation below the critical MC and thus promotes survival of acorns on/in the soil during winter in temperate regions. Pericarp anatomy, to some extent, prevents excessive drying of the embryonic axis by slowing water movement, but prolonged drying or predatory pressure could result in pericarp cracks, favouring the absorption of water during sporadic rain. In the latter case, the survival of acorns possibly depends extensively on the continuous erratic rainfall, i.e. continuous wet-dry cycle, but in-situ experiments are yet to be performed to test this hypothesis.

Effect of incubation period on the glycosylated protein content in germinated and ungerminated seeds of mung bean (Vigna radiata (L.) Wilczek)

The effects of different incubation periods on the contents of amino acids, proteins, glycosylated proteins and metabolites in germinated and ungerminated mung bean seeds were investigated in this study. The study employs soaking of mung bean seeds in water under laboratory conditions at 28 °C for 3, 6, and 9 h, followed by germination for 12, 24, 36, and 48 h. Seeds collected from different period of imbibition and germination were subjected to total protein extraction for phytochemical analysis. Germination of the seeds was found to be most successful after 6 h of soaking (rather than 9 h of incubation). Hence, seeds imbibed for 6 h were further investigated for germination at 28 °C for 12, 24, 36, and 48 h. Total protein was extracted from both imbibed and germinated seeds, followed by trypsin digestion. Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based peptide mass fingerprinting revealed 38 proteins in 6 h water-imbibed seeds and 50 proteins in 24 h germinated seeds. Among these, 16 were identified as glycosylated proteins and the maximum number of glycosylated proteins were detected in 6 h water-imbibed seeds and 24 h germinated seeds. Moreover, High Performance Liquid Chromatography (HPLC) was used to quantify amino acids from the extracted proteins. A total of 15 amino acids were detected, of which eight were essential and the remaining were non-essential; amino acid concentrations increased following 3, 6, and 9 h of imbibition when compared to the control. It was concluded from the study that seeds with 6 h of imbibition and 24 h of germination can be used as potential nutritional source of different amino acids, proteins, glycosylated proteins, and other bioactive metabolites in human diet.

Kinetics of low radioactive wastewater imbibition and radionuclides sorption in partially saturated ternary-binder mortar

This study seeks to assess the imbibition kinetics of low radioactive wastewater (from the DayaBay nuclear power plant) into a partially saturated ternary-binder mortar, as well as the sorption kinetics of ⁶⁰Co and ¹³⁷Cs from the water. Mortar samples with the initial saturation degrees of 0, 0.4, 0.6, 0.8 and 1.0 were prepared for the wastewater treatment. Pore structure of the mortar was characterized using water vapor sorption isotherm and mercury intrusion porosimetry tests interpreted by the Guggenheim-Anderson-de Boer isothermal equilibrium, and volume- and energy-based fractal models. Results show that the mortar has consistent fractal pore structure between the models, and the liquid imbibitions follow the fractal imbibition kinetics, in which the parameters are non-linearly impacted by the initial saturation degrees. The sorption rate and retention capacity of ¹³⁷Cs are much lower than those of ⁶⁰Co, and both follow the Brouers-Sotolongo fractional kinetics. The findings uncover the complex liquid imbibition and radionuclides sorption kinetics in cement-based porous materials, and the in-situ data would contribute to the material designs and sorption controls for large scale in-situ treatments of wastewater from nuclear power plant.

New type of pore-snap-off and displacement correlations in imbibition

HYPOTHESIS

Imbibition of a fluid into a porous material involves the invasion of a wetting fluid in the pore space through piston-like displacement, film and corner flow, snap-off and pore bypassing. These processes have been studied extensively in two-dimensional (2D) porous systems; however, their relevance to three-dimensional (3D) natural porous media is poorly understood. Here, we investigate these pore-scale processes in a natural rock sample using time-resolved 3D (i.e., four-dimensional or 4D) X-ray imaging.

EXPERIMENTS

We performed a capillary-controlled drainage-imbibition experiment on an initially brine-saturated carbonate rock sample. The sample was imaged continuously during imbibition using 4D X-ray imaging to visualize and analyze fluid displacement and snap-off processes at the pore-scale.

FINDINGS

We discover a new type of snap-off that occurs in pores, resulting in the entrapment of a small portion of the non-wetting phase in pore corners. This contrasts with previously-observed snap-off in throats which traps the non-wetting phase in pore centers. We relate the new type of pore-snap-off to the pinning of fluid-fluid interfaces at rough surfaces, creating contact angles close to 90°. Subsequently, we provide correlations for displacement events as a function of pore-throat geometry. Our findings indicate that having a small throat does not necessarily favor snap-off: the key criterion is the throat radius in relation to the pore radius involved in a displacement event, captured by the aspect ratio.

In-situ capillary pressure and wettability in natural porous media: Multi-scale experimentation and automated characterization using X-ray images

HYPOTHESIS

Geometrical analyses of pore-scale fluid-fluid-rock interfaces have recently been used for in-situ characterization of capillary pressure and wettability in natural porous media. Nevertheless, more robust techniques and multi-scale, well-characterized experimental data are needed to rigorously validate these techniques and enhance their efficacy when applied to saturated porous media.

EXPERIMENTS AND IMAGE ANALYSIS

We present two new techniques for automated measurements of in-situ capillary pressure and contact angle, which offer several advancements over previous methodologies. These approaches are methodically validated using synthetic data and X-ray images of capillary rise experiments, and subsequently, applied on pore-scale fluid occupancy maps of a miniature Berea sandstone sample obtained during steady-state drainage and imbibition flow experiments.

FINDINGS

The results show encouraging agreement between the image-based capillary pressure-saturation function and its macroscopic counterpart obtained from a porous membrane experiment. However, unlike the macroscopic behavior, the micro-scale measurements demonstrate a nonmonotonic increase with saturation due to the intermittency of the pore-scale displacement events controlling the overall flow behavior. This is further explained using the pertinent micro-scale mechanisms such as Haines jumps. The new methods also enable one to generate in-situ contact angle distributions and distinguish between the advancing and receding values while automatically excluding invalid measurements.

Less is more: Unstable foams clean better than stable foams

HYPOTHESIS

Foamed surfactant solutions can clean surfaces! We hypothesise that the cleaning efficiency depends on the liquid fraction and on the stability of the foam. We also hypothesise that the cleaning efficiency is the better the smaller the average bubble size is.

EXPERIMENTS

The double syringe technique was used to generate foams with varying liquid fractions but the same, very small bubble sizes with and without perfluorohexane in the gas phase. We performed cleaning tests in which the foams were applied to glass substrates contaminated with a fluorescent oil.

FINDINGS

We found that unstable foams clean better than stable foams. Three cleaning mechanisms were identified: (1) imbibition at low liquid fractions, (2) wiping, i.e., shifting of the contact line between oil, foam and glass, at all liquid fractions, and (3) drainage at high liquid fractions. The change of the liquid fraction and of the foam stability lead to different combinations of these mechanisms and thus to different cleaning results.

The genetics and physiology of seed dormancy, a crucial trait in common bean domestication

BACKGROUND

Physical seed dormancy is an important trait in legume domestication. Although seed dormancy is beneficial in wild ecosystems, it is generally considered to be an undesirable trait in crops due to reduction in yield and / or quality. The physiological mechanism and underlying genetic factor(s) of seed dormancy is largely unknown in several legume species. Here we employed an integrative approach to understand the mechanisms controlling physical seed dormancy in common bean (Phaseolus vulgaris L.).

RESULTS

Using an innovative CT scan imaging system, we were able to track water movements inside the seed coat. We found that water uptake initiates from the bean seed lens. Using a scanning electron microscopy (SEM) we further identified several micro-cracks on the lens surface of non-dormant bean genotypes. Bulked segregant analysis (BSA) was conducted on a bi-parental RIL (recombinant inbred line) population, segregating for seed dormancy. This analysis revealed that the seed water uptake is associated with a single major QTL on Pv03. The QTL region was fine-mapped to a 118 Kb interval possessing 11 genes. Coding sequence analysis of candidate genes revealed a 5-bp insertion in an ortholog of pectin acetylesterase 8 that causes a frame shift, loss-of-function mutation in non-dormant genotype. Gene expression analysis of the candidate genes in the seed coat of contrasting genotypes indicated 21-fold lower expression of pectin acetylesterase 8 in non-dormant genotype. An analysis of mutational polymorphism was conducted among wild and domesticated beans. Although all the wild beans possessed the functional allele of pectin acetylesterase 8, the majority (77%) of domesticated beans had the non-functional allele suggesting that this variant was under strong selection pressure through domestication.

CONCLUSIONS

In this study, we identified the physiological mechanism of physical seed dormancy and have identified a candidate allele causing variation in this trait. Our findings suggest that a 5-bp insertion in an ortholog of pectin acetylesterase 8 is likely a major causative mutation underlying the loss of seed dormancy during domestication. Although the results of current study provide strong evidences for the role of pectin acetylesterase 8 in seed dormancy, further confirmations seem necessary by employing transgenic approaches.

Imbibition and structure of silica nanoporous media characterized by neutron imaging

HYPOTHESIS

Colloidal silica dispersions dried under controlled conditions form solid gels that display mechanical properties similar to those observed in several practical processes. An understanding of their structural characteristics and liquid flow properties can therefore help establish these gels as an alternative family of model materials to study practical porous systems.

EXPERIMENTS

Neutron radiography is a non-destructive technique well-adapted to study hydrogen-rich domains in porous materials due to the high attenuation power of hydrogen. We apply this technique to study gels prepared from silica nanoparticles of radii 5-40 nm.

FINDINGS

The water content in the gels have been quantified and different types of porosities have been determined: total porosity, effective porosity that contributes to liquid flow, and residual porosity that contains bound residual water. This residual water increases with decrease in particle size and constitutes an important fraction of the gel. The dynamics of water imbibition follows a √t law, from which the effective pore size and permeability are evaluated. We highlight the role of particle size on water retention, on particle organization and its impact on mechanical resistance. Quantitative analysis of the propagating liquid front shows front broadening that suggests elongated pores with reduced correlated liquid menisci.

Insights into the interplay of wetting and transport in mesoporous silica films

The understanding and design of wetting-transport and wetting-charge-transport interplay in nanometer-sized pores is a still not fully understood key step in improving nanopore transport-related applications. A control of mesopore wettability accompanied by pore filling and ionic mesopore accessibility analysis is expected to deliver major insights into this interplay of nanoscale pore wetting and transport. For a systematic understanding, we demonstrate a gradual adjustment of nanopore ionic accessibility by gradually tuning silica nanopore wettability using chemical vapor phase deposition of 1H,1H,2H,2H-perfluorooctyl dimethylchlorosilane. The mutual influence of wetting on liquid imbibition, condensation, and molecular transport as well as on heat transfer were studied by ellipsometry, cyclic voltammetry and boiling experiments, respectively. A multi-methodical analytic approach was used to directly couple wetting properties of mesoporous silica thin films to ionic mesopore accessibility allowing us to determine two different ion transport mechanisms based on three defined wetting regimes as well as a threshold hydrophobicity suppressing pore accessibility. Furthermore, boiling experiments showed a clear increase in nucleation site density upon changing the wettability of the mesoporous surfaces from hydrophilic to hydrophobic. Hence, these results provide insights into the complex interplay of pore wall functionalization, wetting, and charge-dependent nanopore properties.

Shedding light on the presymbiontic phase of C. arietinum

A complex network of symbiotic events between plants and bacteria allows the biosphere to exploit the atmospheric reservoir of molecular nitrogen. In seeds, a series of presymbiotic steps are already identified during imbibition, while interactions between the host and its symbiont begin in the early stages of germination. In the present study, a detailed analysis of the substances' complex delivered by Cicer arietinum seeds during imbibition showed a relevant presence of proteins and amino acids, which, except for cysteine, occurred with the whole proteinogenic pool. The imbibing solution was found to provide essential probiotic properties able to sustain the growth of the specific chickpea symbiont Mesorhizobium ciceri. Moreover, the imbibing solution, behaving as a complete medium, was found to be critically important for the symbiont's attraction, a fact this that is strictly related to the presence of the amino acids glycine, serine, and threonine. Here, the presence of these amino acids is constantly supported by the presence of the enzymes serine hydroxymethyltransferase and formyltetrahydrofolate deformylase, which are both involved in their biosynthesis. The reported findings are discussed in the light of the pivotal role played by the imbibing solution in attracting and sustaining symbiosis between the host and its symbiont.

Water permeability/impermeability in seeds of 15 species of Caragana (Fabaceae)

Majority legumes in the temperate and arctic zones have water-impermeable seeds (physical dormancy, PY). However, various authors have reported that seeds of some Caragana species are water-permeable and thus non-dormant. We (1) tested seeds of 15 species of Caragana matured in the same site in 2014, 2016 and/or 2017 for presence of PY, (2) determined if dry storage decreased or increased the percentage of seeds with PY and (3) located the site on the seed coat of 11 species where water enters the seed. Sixty-three percent and 45% of the seeds of C. roborovskyi had PY in 2016 and 2017, respectively, but only 0-14% of the seeds of the other 14 species had PY. The palisade layer in the seed coat of water impermeable seeds had no cracks in it, whereas cracks were present in the palisade layer of water-permeable seeds. Year of collection and dry storage had significant effects on imbibition of two species (C. acanthophylla and C. roborovskyi). In two (C. acanthophylla and C. roborovskyi) of the 11 species tested, the hilum was the site of water entry into seeds (control seeds, not any dormant broken treatments), but for the other nine species tested water entered through all parts of the seed coat.

A machine vision platform for measuring imbibition of maize kernels: quantification of genetic effects and correlations with germination

BACKGROUND

Imbibition (uptake of water by a dry seed) initiates the germination process. An automated method for quantifying imbibition would enable research on the genetic elements that influence the underlying hydraulic and biochemical processes. In the case of crop research, a high throughput imbibition assay could be used to investigate seed quality topics or to improve yield by selecting varieties with superior germination characteristics.

RESULTS

An electronic force transducer measured imbibition of single maize kernels with very high resolution but low throughput. An image analysis method was devised to achieve high throughput and sufficient resolution. A transparent fixture held 90 maize kernels in contact with water on the imaging window of a flatbed document scanner that produced an image of the kernels automatically every 10 min for 22 h. Custom image analysis software measured the area A of each indexed kernel in each image to produce imbibition time courses. The ultimate change in area (ΔA) ranged from 19.3 to 23.4% in a population of 72 hybrids derived from 9 inbred parents. Kernel area as a function of time was fit well by A t = A f 1 - e - k t where A _f is the final kernel area. The swelling coefficient, k, ranged from 0.098 to 0.159 h^-1 across the genotypes. The full diallel structure of the population enabled maternal genotype effects to be assessed. In a separate experiment, measurements of kernels of the same 25 inbreds produced in three different years demonstrated that production and storage variables affected imbibition much less than genotype. In a third experiment, measurements of 30 diverse inbred lines showed that k varied inversely with germination time (r = - 0.7) and directly with germination percentage (r = 0.7).

CONCLUSIONS

Nonspecialized imaging hardware and custom analysis software running on public cyber infrastructure form a low-cost platform for measuring seed imbibition with high resolution and throughput. We measured imbibition of thousands of kernels to determine that genotype influenced imbibition of maize kernels much more than seed production and storage environments. In some hybrids, k depended on which inbred parent was maternal. Quantitative relationships between k and germination traits were discovered.

Droplet Imbibition into Paper Coating Layer: Pore-Network Modeling Simulation

Liquid penetration into thin porous media such as paper is often simulated using continuum-scale single-phase Darcy's law. The underlying assumption was that a sharp invasion front percolates through the layer. To explore this ambiguous assumption and to understand the controlling pore-scale mechanisms, we have developed a dynamic pore-network model to simulate imbibition of a wetting phase from a droplet into a paper coating layer. The realistic pore structures are obtained using the FIB-SEM imaging of the coating material with a minimum resolution of 3.5 nm. Pore network was extracted from FIB-SEM images using Avizo software. Data of extracted pore network are used for statistically generating pore network. Droplet sizes are chosen in the range of those applicable in inkjet printing. Our simulations show no sharp invasion front exists and there is the presence of residual non-wetting phase. In addition, penetration of different sizes of droplets of different material properties into the pore network with different pore body and pore throat sizes are performed. We have found an approximately linear decrease in droplet volume with time. This contradicts the expected t -behavior in vertical imbibition that is obtained using macroscopic single-phase Darcy's law. With increase in flow rate, transition of imbibition invasion front from percolation-like pattern to a more sharper one with less trapping of non-wetting phase is also reported. Our simulations suggest that the single-phase Darcy's law does not adequately describe liquid penetration into materials such as paper coating layer. Instead Richards equation would be a better choice.

Biochar physico-chemical properties as affected by environmental exposure

To best use biochar as a sustainable soil management and carbon (C) sequestration technique, we must understand the effect of environmental exposure on its physical and chemical properties because they likely vary with time. These properties play an important role in biochar's environmental behavior and delivery of ecosystem services. We measured biochar before amendment and four years after amendment to a commercial nectarine orchard at rates of 5, 15 and 30tha(-1). We combined two pycnometry techniques to measure skeletal (ρs) and envelope (ρe) density and to estimate the total pore volume of biochar particles. We also examined imbibition, which can provide information about soil hydraulic conductivity. Finally, we investigated the chemical properties, surface, inner layers atomic composition and C1s bonding state of biochar fragments through X-ray photoelectron spectroscopy (XPS). Ageing increased biochar skeletal density and reduced the water imbibition rate within fragments as a consequence of partial pore clogging. However, porosity and the volume of water stored in particles remained unchanged. Exposure reduced biochar pH, EC, and total C, but enhanced total N, nitrate-N, and ammonium-N. X-ray photoelectron spectroscopy analyses showed an increase of O, Si, N, Na, Al, Ca, Mn, and Fe surface (0-5nm) atomic composition (at%) and a reduction of C and K in aged particles, confirming the interactions of biochar with soil inorganic and organic phases. Oxidation of aged biochar fragments occurred mainly in the particle surface, and progressively decreased down to 75nm. Biochar surface chemistry changes included the development of carbonyl and carboxylate functional groups, again mainly on the particle surface. However, changes were noticeable down to 75nm, while no significant changes were measured in the deepest layer, up to 110nm. Results show unequivocal shifts in biochar physical and chemical properties/characteristics over short (~years) timescales.

Water entry for the black locust (Robinia pseudoacacia L.) seeds observed by dedicated micro-magnetic resonance imaging

Water entry at germination for black locust (Robinia pseudoacacia L.) seeds which are known as hard seeds with impermeable seed coat to water, was examined using micro-magnetic resonance imaging (MRI). The MRI apparatus equipped with a low-field (1 T; Tesla) permanent magnet was used, which is open access, easy maintenance, operable and transportable. The excellent point of the apparatus is that T 1-enhancement of water signals absorbed in dry seeds against steeping free water is stronger than the apparatuses with high-field superconducting magnets, which enabled clear detection of water entry. Water hardly penetrated into the seeds for more than 8 h but approximately 60 % of seeds germinated by incubating on wet filter papers for several days. Hot water treatments above 75 °C for 3 min effectively induced water gap; scarification was 70 % at 100 °C and 75 °C, declined to 15 % at 50 °C and decreased further at room temperature. Water entered into the scarified seeds exclusively through the lens, spread along the dorsal side of the seeds and reached the hypocotyl, whereas water migrated slowly through hilum side to radicle within 3 h.

Nectar protein content and attractiveness to Aedes aegypti and Culex pipiens in plants with nectar/insect associations

We chose five easily propagated garden plants previously shown to be attractive to mosquitoes, ants or other insects and tested them for attractiveness to Culex pipiens and Aedes aegypti. Long term imbibition was tested by survival on each plant species. Both mosquito species survived best on Impatiens walleriana, the common garden impatiens, followed by Asclepias curassavica, Campsis radicans and Passiflora edulis, which sponsored survival as well as the 10% sucrose control. Immediate preference for imbibition was tested with nectar dyed in situ on each plant. In addition, competition studies were performed with one dyed plant species in the presence of five undyed plant species to simulate a garden setting. In both preference studies I. walleriana proved superior. Nectar from all plants was then screened for nectar protein content by SDS-PAGE, with great variability being found between species, but with I. walleriana producing the highest levels. The data suggest that I. walleriana may have value as a model plant for subsequent studies exploring nectar delivery of transgenic mosquitocidal proteins.

Impact of protective agents and drying methods on desiccation tolerance of Salix nigra L. seeds

Willow seeds are classified as orthodox, but they show some recalcitrant characteristics, as they lose viability in a few weeks at room temperature. The aim of this work was to improve the desiccation tolerance of willow seeds (Salix nigra L.), as a model of sensitive materials to dehydration, through imbibition in solutions and later vacuum (VD) or freeze-drying (FD). Imbibition was conducted with 45% w/v trehalose or polyethylene glycol 400 -PEG- or water prior to dehydration treatments. Water- and especially trehalose-imbibed seeds subjected to VD showed better germination capability with respect to the freeze-dried ones. Water crystallization was mainly responsible for the great loss of capability germination observed in water- or trehalose-imbibed seeds subjected to FD. PEG behavior was better when seeds were FD instead of VD. DSC thermograms of seeds allowed to identify two thermal transitions corresponding to lipids melting and to proteins denaturation. This last transition reveals information about proteins state/functionality. Dehydration of control and PEG- or water-imbibed seeds affected proteins functionality leading to lower germinability. In the case of trehalose-imbibed seeds subjected to VD, proteins maintained their native state along dehydration, and the seeds showed a great germination capacity for all the water content range. Germinated seeds showed higher luminosity (L*), greenness (a*) and yellowness (b*) values than not-germinated seeds independently of the employed agent. Present work reveals that the presence of adequate protective agents as well the dehydration method were the main critical factors involved in willow seed desiccation tolerance.

The effect of sugar solution type, sugar concentration and viscosity on the imbibition and energy intake rate of bumblebees

Nectar is an essential resource for bumblebees and many other flower-visiting insects. The main constituents of nectar are sugars, which vary in both composition and concentration between plant species. We assessed the influence of sugar concentration, sugar solution viscosity and sugar solution composition on the imbibition and energy intake rate of bumblebees, Bombus impatiens Cresson (Hymenoptera: Apidae). To do this, we measured their rate of solution intake for 49 different sugar solution treatments, which varied in both sugar composition and concentration. In general, the imbibition rates of bumblebees were found to increase with increasing sugar concentration, probably due to their preference for high sugar concentrations, up to a concentration of 27% (w/w), at which point solutions reached a threshold viscosity of approximately 1.5-1.6 mPa.s. Above this threshold, the increasing viscosity of the solutions physically inhibited the imbibition rates of bees, and imbibition rate began to decrease as the concentration increased. Nevertheless, bumblebee energy intake rate increased with increasing concentration up to about 42-56%. Although we found that sugar solution composition had an impact on both imbibition and energy intake rate, its effect was not as straightforward as that of sugar concentration and viscosity.

Transient spreading and swelling behavior of a gel deploying an anti-HIV topical microbicide

Drug delivery of topical microbicidal molecules against HIV offers promise as a modality to prevent sexual transmission of the virus. Success of any microbicide product depends, in an interactive way, upon its drug (the microbicide active pharmaceutical ingredient, API) and its delivery system (e.g. a gel, film or intravaginal ring). There is a widespread agreement that more effective drug delivery vehicles, as well as better APIs, must be developed to improve the efficacy of microbicide products. Non-Newtonian gels are primary microbicide vehicles, but those to date have been created with limited understanding of how their properties govern their spreading and retention in the vagina, which, in turn, govern successful drug delivery. Here, we apply fundamental fluid mechanical and physicochemical transport theory to help better understand how successful microbicide API delivery depends upon properties of a gel and the vaginal environment. We address several critical components of this complex process, including: elastohydrodynamic flow of the bolus of a non-Newtonian fluid; and mass transfer due to inhomogeneous dilution of the gel by vaginal fluid contacting it along a moving boundary (the locally deforming vaginal epithelial surface). Local dilution of gel alters local rheological properties. We evaluated this experimentally, delin-eating the way that constitutive parameters of a shear-thinning gel are modified by dilution. We supplement the Reynolds lubrication equation with a mass conservation equation to model diluting fluid movement across the moving vaginal epithelial surface and into the gel bolus. This is a physicochemically complex phenomenon that is not well understood. We implement a boundary flux model based upon the elevated hydrodynamic pressures in the cells. Results show that this model produces fluxes that lie within the range of mean values that have been reported. Further experimental characterization of the vaginal wall is required for a more precise set of parameters and a more sophisticated theoretical treatment of epithelium.