► The present work provides field evidence on the effect of biochar on GHG fluxes in Mediterranean wheat crop. ► No significant increase of N
2O and CO
2 emissions observed in char treated plots. ► ...No significant effect of char on CH
4 soil consumption and production. ► Short term stimulating effect of biochar on soil microflora.
Biochar has been recently proposed as a management strategy to improve crop productivity and global warming mitigation. However, the effect of such approach on soil greenhouse gas fluxes is highly uncertain and few data from field experiments are available. In a field trial, cultivated with wheat, biochar was added to the soil (3 or 6
kg
m
−2) in two growing seasons (2008/2009 and 2009/2010) so to monitor the effect of treatments on microbial parameters 3
months and 14
months after char addition. N
2O, CH
4 and CO
2 fluxes were measured in the field during the first year after char addition. Biochar incorporation into the soil increased soil pH (from 5.2 to 6.7) and the rates of net N mineralization, soil microbial respiration and denitrification activity in the first 3
months, but after 14
months treated and control plots did not differ significantly. No changes in total microbial biomass and net nitrification rate were observed. In char treated plots, soil N
2O fluxes were from 26% to 79% lower than N
2O fluxes in control plots, excluding four sampling dates after the last fertilization with urea, when N
2O emissions were higher in char treated plots. However, due to the high spatial variability, the observed differences were rarely significant. No significant differences of CH
4 fluxes and field soil respiration were observed among different treatments, with just few exceptions. Overall the char treatments showed a minimal impact on microbial parameters and GHG fluxes over the first 14
months after biochar incorporation.
We consider the time evolution of a one dimensional
n
-gradient continuum. Our aim is to construct and analyze discrete approximations in terms of physically realizable mechanical systems, referred ...to as microscopic because they are living on a smaller space scale. We validate our construction by proving a convergence theorem of the microscopic system to the given continuum, as the scale parameter goes to zero.
Abstract
Marsh vegetation, a definitive component of delta ecosystems, has a strong effect on sediment retention and land-building, controlling both how much sediment can be delivered to and how much ...is retained by the marsh. An understanding of how vegetation influences these processes would improve the restoration and management of marshes. We use a random displacement model to simulate sediment transport, deposition, and resuspension within a marsh. As vegetation density increases, velocity declines, which reduces sediment supply to the marsh, but also reduces resuspension, which enhances sediment retention within the marsh. The competing trends of supply and retention produce a nonlinear relationship between sedimentation and vegetation density, such that an intermediate density yields the maximum sedimentation. Two patterns of sedimentation spatial distribution emerge in the simulation, and the exponential distribution only occurs when resuspension is absent. With resuspension, sediment is delivered farther into the marsh and in a uniform distribution. The model was validated with field observations of sedimentation response to seasonal variation in vegetation density observed in a marsh within the Mississippi River Delta.
Stationary non equilibrium solutions to the Boltzmann equation, despite their relevance in applications, are much less studied than time dependent solutions, and no general existence theory is yet ...available, due to serious technical difficulties. Here we review some results on the construction of stationary non equilibrium solutions, in a general domain in contact with a slightly non-homogeneous thermal reservoir, both for finite and small Knudsen number. We will describe different approaches and different techniques developed. The main focus will be on stationary solutions close to hydrodynamics. In particular, we will give an answer to the longstanding open problem of the rigorous derivation of the steady incompressible Navier–Stokes–Fourier system from the Boltzmann theory, in the presence of a small external force and diffuse boundary condition with small boundary temperature variations.
Given an obstacle in
R
3
and a non-zero velocity with small amplitude at the infinity, we construct the unique steady Boltzmann solution flowing around such an obstacle with the prescribed velocity ...as
|
x
|
→
∞
, which approaches the corresponding Navier–Stokes steady flow, as the mean-free path goes to zero. Furthermore, we establish the error estimate between the Boltzmann solution and its Navier–Stokes approximation. Our method consists of new
L
6
and
L
3
estimates in the unbounded exterior domain, as well as an iterative scheme preserving the positivity of the distribution function.
In the study of the heat transfer in the Boltzmann theory, the basic problem is to construct solutions to the following steady problem:
v
·
∇
x
F
=
1
K
n
Q
(
F
,
F
)
,
(
x
,
v
)
∈
Ω
×
R
3
,
(
0.1
)
F
...(
x
,
v
)
|
n
(
x
)
·
v
<
0
=
μ
θ
∫
n
(
x
)
·
v
′
>
0
F
(
x
,
v
′
)
(
n
(
x
)
·
v
′
)
d
v
′
,
x
∈
∂
Ω
,
(
0.2
)
where
Ω
is a bounded domain in
R
d
,
1
≤
d
≤
3
, K
n
is the Knudsen number and
μ
θ
=
1
2
π
θ
2
(
x
)
exp
-
|
v
|
2
2
θ
(
x
)
is a Maxwellian with non-constant(non-isothermal) wall temperature
θ
(
x
). Based on new constructive coercivity estimates for both steady and dynamic cases, for
|
θ
-
θ
0
|
≤
δ
≪
1
and any fixed value of K
n
, we construct a unique non-negative solution
F
s
to (0.1) and (0.2), continuous away from the grazing set and exponentially asymptotically stable. This solution is a genuine non-equilibrium stationary solution differing from a local equilibrium Maxwellian. As an application of our results we establish the expansion
F
s
=
μ
θ
0
+
δ
F
1
+
O
(
δ
2
)
and we prove that, if the Fourier law holds, the temperature contribution associated to
F
1
must be linear, in the slab geometry.
•Moisture transport of brick-mortar combination is crucial for bioreceptivity.•The composition of the mortar strongly affects its bioreceptivity.•Lime-trass and, in lower extent, NHL binders show the ...best bioreceptivity.•A compromise is needed between bioreceptivity and mechanical strength.
The effect of mortar and brick properties on the growth of ivy-leaved toadflax (Cymbalaria muralis) and yellow corydalis (Pseudofumaria lutea) has been investigated in laboratory. Different mortar compositions were designed and tested in combination with two different bricks.
Highly porous bricks and mortars showed good bioreceptivity; mortars with lime-trass and, in lower extent, those with natural hydraulic lime binder, gave the best results in terms of bioreceptivity. The addition of vermiculite to the mortar was beneficial for plant growth.
The brick-mortar combinations most favourable for plant growth were those with estimated low compressive and flexural bond strength values. Proposals are advanced for obtaining a compromise between mechanical strength and bioreceptivity.
Liquid biopsy is an alternative to tissue for RAS testing in metastatic colorectal carcinoma (mCRC) patients. Little information is available on the predictive role of liquid biopsy RAS testing in ...patients treated with first-line anti-EGFR monoclonal antibody-based therapy.
In the CAPRI-GOIM trial, 340 KRAS exon-2 wild-type mCRC patients received first-line cetuximab plus FOLFIRI. Tumor samples were retrospectively assessed by next generation sequencing (NGS). Baseline plasma samples were analyzed for KRAS and NRAS mutations using beads, emulsion, amplification, and magnetics digital PCR (BEAMing). Discordant cases were solved by droplet digital PCR (ddPCR) or deep-sequencing.
A subgroup of 92 patients with available both NGS data on tumor samples and baseline plasma samples were included in this study. Both NGS analysis of tumor tissue and plasma testing with BEAMing identified RAS mutations in 33/92 patients (35.9%). However, 10 cases were RAS tissue mutant and plasma wild-type, and additional 10 cases were tissue wild-type and plasma mutant, resulting in a concordance rate of 78.3%. Analysis of plasma samples with ddPCR detected RAS mutations in 2/10 tissue mutant, plasma wild-type patients. In contrast, in all tissue wild-type and plasma mutant cases, ddPCR or deep-sequencing analysis of tumor tissue confirmed the presence of RAS mutations at allelic frequencies ranging between 0.15% and 1.15%. The median progression-free survival of RAS mutant and wild-type patients according to tissue (7.9 versus 12.6 months; P = 0.004) and liquid biopsy testing (7.8 versus 13.8 moths; P < 0.001) were comparable. Similar findings were observed for the median overall survival of RAS mutant and wild-type patients based on tissue (22.1 versus 35.8 months; P = 0.016) and plasma (19.9 versus 35.8 months; P = 0.013) analysis.
This study indicates that RAS testing of liquid biopsy results in a similar outcome when compared with tissue testing in mCRC patients receiving first-line anti-EGFR monoclonal antibodies.
Previous studies have demonstrated that vegetation‐generated turbulence can enhance erosion rate and reduce the velocity threshold for erosion of non‐cohesive sediment. This study considered whether ...vegetation‐generated turbulence had a similar influence on natural cohesive sediment. Cores were collected from a black mangrove forest with aboveground biomass and exposed to stepwise increases in velocity. Erosion was recorded through suspended sediment concentration. For the same velocity, cores with pneumatophores had elevated turbulent kinetic energy compared to bare cores without pneumatophores. However, the vegetation‐generated turbulence did not increase bed stress or the rate of resuspension, relative to bare cores. It was hypothesized that the short time‐scale fluctuations associated with vegetation‐generated turbulence were not of sufficient duration to break cohesion between grains, explaining why elevated levels of turbulence associated with the pneumatophores had no impact on the erosion threshold or rate.
Plain Language Summary
Mangrove habitat grows by retaining sediment. To restore these systems, it is necessary to understand how vegetation influences the transport and retention of sediment. This study used sediment cores collected from the interior of a mangrove forest to study how the aboveground roots, called pneumatophores, influence hydrodynamic conditions and sediment transport, and in particular the onset and rate of sediment erosion. Individual pneumatophores generate eddies that enhance turbulence, compared to conditions without pneumatophores. In sandy soil, vegetation‐generated turbulence can enhance erosion. However, in this study, vegetation‐generated turbulence did not increase the rate of erosion for natural cohesive (muddy) sediment, suggesting that the mangrove forest interior has naturally greater resistance to erosion and sediment loss.
Key Points
For the same velocity, cores with pneumatophores had higher turbulent kinetic energy (TKE) compared to cores without pneumatophores
Unlike sands, the inception of erosion and erosion rates for cohesive sediment were better predicted by bed shear stress than by TKE
Modelers should parameterize erosion within vegetation differently for cohesive and non‐cohesive sediment
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