•A non-equilibrium model of water transport in the vadose zone is developed.•A non-equilibrium isothermal phase change relation is proposed and characterized.•Soil column experiments are carried out ...and compared to numerical simulations.•In our cases, the local equilibrium assumption is not valid and must be rejected.•The evaporation front is explicitly defined and localized.
The dynamics of water content in the superficial layers of soils is critical in the modelling of land-surface processes. In arid regions, vapour flux contributes significantly to the global water mass balance. To account for it in theoretical descriptions, most of the models proposed in the literature rely on the local equilibrium assumption that constrains the vapour pressure to remain at its equilibrium value. It implicitly amounts to consider an instantaneous phase change. Recent works underlined a retardation time and a decrease in phase change rate as the water content gets lower. Therefore, the objective is to revisit water transport modelling by rejecting the local equilibrium assumption. This requires developing a non-equilibrium model by taking into account the phase change kinetics. To assess the interest of this approach, a natural soil of Burkina-Faso has been experimentally characterized from independent tests and soil column experiments have been carried out. The comparison of experimental drying kinetics and water content profiles with computational predictions confirms the reliability of this description. Liquid/gas non-equilibrium is significant in a limited subsurface zone which defines explicitly the transition from liquid transport in lower layers to vapour transport in upper layers, i.e., the evaporation front. The overall moisture dynamics is governed by the coupling between water transport mechanisms (liquid filtration, vapour diffusion, phase change) that mainly occurs in this transition zone.
In this paper, we present the results of numerical model and simulation of water transfers in soils with low water content. The main objective is to identify the major phenomena which allow to ...adequately describe water transfer in soil between the filtration of liquid phase and the capillary rise. We have shown that in the superficial layer of soil, the ambient atmosphere has less influence on the transfer phenomena at low water content. The bibliographic works realized on water transfer mechanisms do not allow to draw conclusions at very low water contents that is why the present manuscript brings answers to concerns not yet elucidated. The methodological approach is based on the off-center upstream method for the flux convection and the implicit scheme in time for the discretization using the Finite Volumes method. The numerical resolution of the problem is based on the Newton–Raphson method. Water profiles for different sizes of sample (30 cm, 40 cm, 50 cm and 60 cm) and for initial water contents,
w
0
, varying from 2 to 7% were obtained at regular time interval of 85,000 s. All the simulation results highlight two distinct domains for water contents
w
< 4 and three distinct domains for water contents
w
≥ 4%. Indeed the lower limit conditions on the flux of filtration cause an accumulation of water leading to an increase in water contents for initial water contents of 4%, 5%, 6% and 7%. We note the existence of a limiting water content
w
lim
= 2.4% representing the hygroscopic limit of the soil.
New mononuculear complexes of the general formula Ru(trpy)(n,n′-F2-bpy)X m+ n = n′ = 5, X = Cl (3+ ) and H2O (52+ ); n = n′ = 6, X = Cl (4+ ) and H2O (62+ ); trpy is 2,2′:6′:2″-terpyridine have been ...prepared and thoroughly characterized. The 5,5′- and 6,6′-F2-bpy ligands allow one to exert a remote electronic perturbation to the ruthenium metal center, which affects the combination of species involved in the catalytic cycle. Additionally, 6,6′-F2-bpy also allows through-space interaction with the Ru–O moiety of the complex via hydrogen interaction, which also affects the stability of the different species involved in the catalytic cycle. The combination of both effects has a strong impact on the kinetics of the catalytic process, as observed through manometric monitoring.
High-oxidation-state decay of mononuclear complexes RuTB(H2O)2+ (X 2+, where B = 2,2′-bpy or bpy for X = 1; B = 5,5′-F2-bpy for X = 2; B = 6,6′-F2-bpy for X = 3; T = 2,2′:6′,2″-terpyridine) oxidized ...with a large excess of CeIV generates a manifold of polynuclear oxo-bridged complexes. These include the following complexes: (a) dinuclear TB-RuIV-O-RuIV-(T)(O)OH22+ (1-dn 4+), TB-RuIII-O-RuIII-T(MeCN)24+ (1-dn-N 4+), and {RuIII(trpy)(bpy)2(μ-O)}4+ (1-dm 4+); (b) trinuclear {RuIII(trpy)(bpy)(μ-O)2RuIV(trpy)(H2O)}(ClO4)5 6+ (1-tr 6+) and {RuIII(trpy)(bpy)(μ-O)2RuIV(pic)2}(ClO4)4 (1-tr-P 4+, where P is the 2-pyridinecarboxylate anion); and (c) tetranuclear TB-RuIII-O-TRuIV(H2O)-O-TRuIV(H2O)-O-RuIII-TB8+ (1-tn 8+), TB-RuIII-O-TRuIV(AcO)-O-TRuIV(AcO)-O-RuIII-TB6+ (1-tn-Ac 6+), and TB-RuII-O-TRuIV(MeCN)-O-TRuIV(MeCN)-O-RuII-TB6+ (1-tn-N 6+). These complexes have been characterized structurally by single-crystal X-ray diffraction analysis, and their structural properties were correlated with their electronic structures. Dinuclear complex 1-dm 4+ has been further characterized by spectroscopic and electrochemical techniques. Addition of excess CeIV to 1-dm 4+ generates dioxygen in a catalytic manner. However, resonance Raman spectroscopy points to the in situ formation of 1-dn 4+ as the active species.
Unsaturated soil hydraulic properties are key properties in the fields of soil science and civil engineering. Because of their strong dependence on water content, there are considerable experimental ...and numerical difficulties in their determination, specifically in the dry range. This situation is encountered regularly in arid and semi‐arid regions. The models commonly used for predicting the unsaturated hydraulic conductivity function rely on pore bundle concepts that account for capillary flow only and neglect film flow. Furthermore, the assumption of a local equilibrium between liquid water and its vapour is no longer valid at small water contents. Thus, with classical approaches, the experimental identification of hydraulic characteristics can fail at small water contents. To emphasize the weakness of capillary models, soil column experiments have been carried out with two sandy soils from Burkina Faso. Special care was taken to prevent any transport processes that are not directly related to liquid transport. Data from profiles of water content were used in an inverse numerical procedure to identify the coefficients of a new relative hydraulic conductivity function. Our results show that this simple approach is suitable for the analysis of flow processes at small water contents. It provides a simple, robust and inexpensive method to identify the properties of the unsaturated conductivity function that account for capillary and film flows.
Highlights
A new kind of soil column experiment is proposed to focus on the dry range.
A new relative hydraulic conductivity function accounting for film flow is introduced.
The weaknesses of classical relative hydraulic conductivity functions are emphasized.
It provides a simple, cheap and robust method to identify the relative hydraulic conductivity.
Summary
Sperm DNA fragmentation (SDF) is becoming an important test to assess male infertility. Several different tests are available, but no consensus has yet been reached as to which tests are most ...predictive of infertility. Few publications have reported a comprehensive analysis comparing these methods within the same population. The objective of this study was to analyze the differences between the five most common methodologies, to study their correlations and to establish their cut‐off values, sensitivity and specificity in predicting male infertility. We found differences in SDF between fertile donors and infertile patients in TUNEL, SCSA, SCD and alkaline Comet assays, but none with the neutral Comet assay. The alkaline COMET assay was the best in predicting male infertility followed by TUNEL, SCD and SCSA, whereas the neutral COMET assay had no predictive power. For our patient population, threshold values for infertility were 20.05% for TUNEL assay, 18.90% for SCSA, 22.75% for the SCD test, 45.37% for alkaline Comet and 34.37% for neutral Comet. This work establishes in a comprehensive study that the all techniques except neutral Comet are useful to distinguish fertile and infertile men.
Summary
The primary aim of this study was to determine the effect of oral antioxidant treatment (1500 mg of l‐Carnitine; 60 mg of vitamin C; 20 mg of coenzyme Q10; 10 mg of vitamin E; 10 mg of zinc; ...200 μg of vitamin B9; 50 μg of selenium; 1 μg of vitamin B12) during a time period of 3 months upon the dynamics of sperm DNA fragmentation following varying periods of sperm storage (0 h, 2 h, 6 h, 8 h and 24 h) at 37 °C in a cohort of 20 infertile patients diagnosed with asthenoteratozoospermia. A secondary objective was to use the sperm chromatin dispersion test (SCD) to study antioxidant effects upon a specific subpopulation of highly DNA degraded sperm (DDS). Semen parameters and pregnancy rate (PR) were also determined. Results showed a significant improvement of DNA integrity at all incubation points (P < 0.01). The proportion of DDS was also significantly reduced (P < 0.05). Semen analysis data showed a significant increase in concentration, motility, vitality and morphology parameters. Our results suggest that antioxidant treatment improves sperm quality not only in terms of key seminal parameters and basal DNA damage, but also helps to maintain DNA integrity. Prior administration of antioxidants could therefore promote better outcomes following assisted reproductive techniques.
The analysis of sperm DNA fragmentation has become a new marker to predict male infertility, and many techniques have been developed. The sperm Comet assay offers the possibility of differentiating ...single- and double-stranded DNA (ssDNA and dsDNA) breaks, which could have different effects on fertility. The objective of this study was to perform a descriptive characterization of different groups of patients, such as those with asthenoteratozoospermic (ATZ) with or without varicocele, oligoasthenoteratozoospermic (OATZ) or balanced chromosome rearrangements, as compared with fertile donors. The Comet assay was used to investigate sperm samples for ssDNA and dsDNA breaks.
METHODS AND RESULTS
The analysis of alkaline and neutral Comet assays in different groups of patients showed different sperm DNA damage profiles. Most fertile donors presented low values for ssDNA and dsDNA fragmentation (low-equivalent Comet profile), which would be the best prognosis for achieving a pregnancy. OATZ, ATZ and ATZ with varicocele presented high percentages of ssDNA and dsDNA fragmentation (high-equivalent Comet assay profile), ATZ with varicocele being associated with the worst prognosis, due to higher levels of DNA fragmentation. Rearranged chromosome carriers display a very high variability and, interestingly, two different profiles were seen: a high-equivalent Comet assay profile, which could be compatible with a bad prognosis, and a non-equivalent Comet assay profile, which has also been found in three fertile donors.
CONCLUSIONS
Comet assay profiles, applied to different clinical groups, may be useful for determining prognosis in cases of male infertility.
We used a mouse model in which sperm DNA damage was induced to understand the relationship of double-stranded DNA (dsDNA) breaks to sperm chromatin structure and to the Comet assay. Sperm chromatin ...fragmentation (SCF) produces dsDNA breaks located on the matrix attachment regions, between protamine toroids. In this model, epididymal sperm induced to undergo SCF can religate dsDNA breaks while vas deferens sperm cannot. Here, we demonstrated that the conventional neutral Comet assay underestimates the epididymal SCF breaks because the broken DNA ends remain attached to the nuclear matrix, causing the DNA to remain associated with the dispersion halo, and the Comet tails to be weak. Therefore, we term these hidden dsDNA breaks. When the Comet assay was modified to include an additional incubation with sodium dodecyl sulfate (SDS) and dithiothreitol (DTT) after the conventional lysis, thereby solubilizing the nuclear matrix, the broken DNA was released from the matrix, which resulted in a reduction of the sperm head halo and an increase in the Comet tail length, exposing the hidden dsDNA breaks. Conversely, SCF-induced vas deferens sperm had small halos and long tails with the conventional neutral Comet assay, suggesting that the broken DNA ends were not tethered to the nuclear matrix. These results suggest that the attachment to the nuclear matrix is crucial for the religation of SCF-induced DNA breaks in sperm. Our data suggest that the neutral Comet assay identifies only dsDNA breaks that are released from the nuclear matrix and that the addition of an SDS treatment can reveal these hidden dsDNA breaks.
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