Investigation of canopy interception characteristics in slope protection grasses: A laboratory experiment.

Canopy interception significantly affects hydrological processes such as infiltration, runoff and evapotranspiration. Research on grass canopy interception remains limited, and the experimental methods employed differ substantially. To thoroughly investigate the canopy interception characteristics of grass and clarify the methodological differences, five commonly utilized slope protection grass species in temperate regions were cultivated in a laboratory setting, and their canopy interception characteristics were experimentally investigated using the water-balance method (WBM), the water-wiping method (WWM) and the water-immersion method (WIM), respectively. The results showed that the WBM is more accurate for measuring canopy interception in grass, whereas both the WWM and the WIM underestimate grass canopy interception capacity. The canopy interception capacity measured by the WBM was 1.61-2.09 times higher than that of the WWM and 1.93-3.47 times higher than that of the WIM. Grey correlation analysis of the eight evaluated factors indicated that leaf area is the most influential factor affecting canopy interception in grass, followed by rainfall amount, dry mass, rainfall intensity, canopy projection area, leaf contact angle, fresh weight, and average height. There is a negative power function relationship between the interception ratio and the rainfall amount. With increasing rainfall intensity, the canopy interception capacity initially increases and then decreases, peaking at rainfall intensities of 15 to 20 mm/h. Leaf contact angle is a key quantifiable parameter that explains the differences in canopy interception among different grass species, and the canopy interception per unit leaf area decreases as the leaf contact angle increases. This study demonstrates that the WBM provides the most accurate measurements of grass canopy interception compared to the WWM and WIM, and highlights the leaf contact angle as a key factor in explaining interspecies differences. These findings could enhance the understanding of grass canopy interception and guide the selection of experimental methods.

Empirical Examination on the Drivers of the U.S. Equity Returns in the During the COVID-19 Crisis.

This study investigates the drivers of the Standard & Poor's (S&P) 500 equity returns during the COVID-19 crisis era. The paper considers various determinants of the equity returns from December 31, 2019, to February 19, 2021. It is observed that the United States Dollar (USD) and the volatility indices (VIX) negatively affect the S&P 500 equity returns. However, the newspaper-based infectious disease "equity market volatility tracker" is positively associated with the stock market returns. These results are robust to consider both the ordinary least squares (OLS) and the least angle regression (LARS) estimators.

Relevance of nonfunctional linear polyacrylic acid for the biodegradation of superabsorbent polymer in soils.

Biodegradability is a desired characteristic for synthetic soil amendments. Cross-linked polyacrylic acid (PAA) is a synthetic superabsorbent used to increase the water availability for plant growth in soils. About 4% within products of cross-linked PAA remains as linear polyacrylic acid (PAAlinear). PAAlinear has no superabsorbent function but may contribute to the apparent biodegradation of the overall product. This is the first study that shows specifically the biodegradation of PAAlinear in agricultural soil. Two (13)C-labeled PAAlinear of the average molecular weights of 530, 400, and 219,500 g mol(-1) were incubated in soil. Mineralization of PAAlinear was measured directly as the (13)CO2 efflux from incubation vessels using an automatic system, which is based on (13)C-sensitive wavelength-scanned cavity ring-down spectroscopy. After 149 days, the PAAlinear with the larger average molecular weight and chain length showed about half of the degradation (0.91% of the initial weight) of the smaller PAAlinear (1.85%). The difference in biodegradation was confirmed by the δ(13)C signature of the microbial biomass (δ(13)Cmic), which was significantly enriched in the samples with short PAAlinear (-13‰ against reference Vienna Pee Dee Belemnite,VPDB) as compared to those with long PAAlinear (-16‰ VPDB). In agreement with other polymer studies, the results suggest that the biodegradation of PAAlinear in soil is determined by the average molecular weight and occurs mainly at terminal sites. Most importantly, the study outlines that the size of PAA that escapes cross-linking can have a significant impact on the overall biodegradability of a PAA-based superabsorbent.

Biodegradability of a polyacrylate superabsorbent in agricultural soil.

Superabsorbent polymers (SAP) are used, inter alia, as soil amendment to increase the water holding capacity of soils. Biodegradability of soil conditioners has become a desired key characteristic to protect soil and groundwater resources. The present study characterized the biodegradability of one acrylate based SAP in four agricultural soils and at three temperatures. Mineralisation was measured as the (13)CO2 efflux from (13)C-labelled SAP in soil incubations. The SAP was either single-labelled in the carboxyl C-atom or triple-labelled including additionally the two C-atoms interlinked in the SAP backbone. The dual labelling allowed estimating the degradation of the polyacrylate main chain. The (13)CO2 efflux from samples was measured using an automated system including wavelength-scanned cavity ring-down spectroscopy. Based on single-labelled SAP, the mean degradation after 24 weeks varied between 0.45% in loamy sand and 0.82% in loam. However, the differences between degradation rates in different soils were not significant due to a large intra-replicate variability. Similarly, mean degradation did not differ significantly between effective temperature regimes of 20° and 30 °C after 12 weeks. Results from the triple-labelled SAP were lower as compared to their single-labelled variant. Detailed results suggest that the polyacrylate main chain degraded in the soils, if at all, at rates of 0.12-0.24 % per 6 months.

Microrheology of highly crosslinked microtubule networks is dominated by force-induced crosslinker unbinding.

We determine the time- and force-dependent viscoelastic responses of reconstituted networks of microtubules that have been strongly crosslinked by biotin-streptavidin bonds. To measure the microscale viscoelasticity of such networks, we use a magnetic tweezers device to apply localized forces. At short time scales, the networks respond nonlinearly to applied force, with stiffening at small forces, followed by a reduction in the stiffening response at high forces, which we attribute to the force-induced unbinding of crosslinks. At long time scales, force-induced bond unbinding leads to local network rearrangement and significant bead creep. Interestingly, the network retains its elastic modulus even under conditions of significant plastic flow, suggesting that crosslinker breakage is balanced by the formation of new bonds. To better understand this effect, we developed a finite element model of such a stiff filament network with labile crosslinkers obeying force-dependent Bell model unbinding dynamics. The coexistence of dissipation, due to bond breakage, and the elastic recovery of the network is possible because each filament has many crosslinkers. Recovery can occur as long as a sufficient number of the original crosslinkers are preserved under the loading period. When these remaining original crosslinkers are broken, plastic flow results.

Biodegradability screening of soil amendments through coupling of wavelength-scanned cavity ring-down spectroscopy to multiple dynamic chambers.

A system was developed for the automatic measurements of ¹³CO2 efflux to determine biodegradation of extra carbon amendments to soils. The system combines wavelength-scanned cavity ring down laser spectroscopy (WS-CRDS) with the open-dynamic chamber (ODC) method. The WS-CRDS instrument and a batch of 24 ODC are coupled via microprocessor-controlled valves. Determination of the biodegradation requires a known δ¹³C value and the applied mass of the carbon compounds, and the biodegradation is calculated based on the ¹³CO2 mixing ratio (ppm) sampled from the headspace of the chambers. The WS-CRDS system provided accurate detection based on parallel samples of three standard gases (¹³CO2 of 2, 11 and 22 ppm) that were measured simultaneously by isotope ratio mass spectrometry (linear regression R² = 0.99). Repeated checking with the same standards showed that the WS-CRDS system showed no drift over seven months.The applicability of the ODC was checked against the closed static chamber (CSC) method using the rapid biodegradation of cane sugar-δ¹³C-labeled through C4 photosynthesis. There was no significant difference between the results from 7-min ODC and 120-min CSC measurements. Further, a test using samples of either cane sugar (C4) or beetroot sugar (C3) mixed into standard soil proved the target functionality of the system, which is to identify the biodegradation of carbon sources with significantly different isotopic signatures.

On the role of the filament length distribution in the mechanics of semiflexible networks.

This paper explores the effects of filament length polydispersity on the mechanical properties of semiflexible crosslinked polymer networks. Extending previous studies on monodisperse networks, we compute numerically the response of crosslinked networks of elastic filaments of bimodal and exponential length distributions. These polydisperse networks are subject to the same affine to nonaffine (A/NA) transition observed previously for monodisperse networks, wherein the decreases in either crosslink density or bending stiffness lead to a shift from affine, stretching-dominated deformations to nonaffine, bending-dominated deformations. We find that the onset of this transition is generally more sensitive to changes in the density of longer filaments than shorter filaments, meaning that longer filaments have greater mechanical efficiency. Moreover, in polydisperse networks, mixtures of long and short filaments interact cooperatively to generally produce a nonaffine mechanical response closer to the affine prediction than comparable monodisperse networks of either long or short filaments. Accordingly, the mechanical affinity of polydisperse networks is dependent on the filament length composition. Overall, length polydispersity has the effect of sharpening and shifting the A/NA transition to lower network densities. We discuss the implications of these results on experimental observation of the A/NA transition, and on the design of advanced materials.

Simultaneous pancreas-kidney transplantation in a single center: 10-year retrospective analysis / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Simultaneous pancreas-kidney transplantation (SPKT) is the best treatment option for diabetic patients with advanced chronic renal failure. The current study aimed to analyze the surgical indications, treatments and prognosis of SPKT.</p><p><b>METHODS</b>We retrospectively analyzed 40 cases of SPKT performed between December 1999 and January 2010 in our center, including the survival rate, complications and the reasons of reoperation.</p><p><b>RESULTS</b>Of all the 40 SPKT cases, the one-year survival rates of the recipients, kidney and pancreas transplant graft were 97.6%, 97.6% and 92.7%, while 97.6%, 91.1%, 92.7% at 3 years and 83.6%, 78.0%, 79.4% at 5 years, respectively. After SPKT, 10 patients need reoperation because of surgical complications (14 operations). The reoperation rate was 25%, including 2 patients (4 operations) with hematuria, 4 patients with abdominal hemorrhage, 2 patients (3 operations) with abdominal infection, 1 patient with pancreatic venous thrombosis, 1 patient with anastomotic leakage, and 1 patient with fistula.</p><p><b>CONCLUSION</b>Although SPKT provides a successful and effective treatment for diabetics with end-stage renal disease, how to reduce the complications of this treatment still need further effort.</p>

Affine-nonaffine transition in networks of nematically ordered semiflexible polymers.

We study the mechanics of nematically ordered semiflexible networks showing that they, like isotropic networks, undergo an affine to nonaffine crossover controlled by the ratio of the filament length to the nonaffinity length. Deep in the nonaffine regime, however, these anisotropic networks exhibit a much more complex mechanical response characterized by a vanishing linear-response regime for highly ordered networks and a dependence of the shear modulus on shear direction at both small (linear) and finite (nonlinear) strains that is different from the affine prediction of orthotropic continuum linear elasticity. We show that these features can be understood in terms of a generalized floppy modes analysis of the nonaffine mechanics and a type of cooperative Euler buckling.

The effect of the different immunosuppression therapy on CD4(+)Foxp3(+) Treg cells in kidney recipients / 中华外科杂志

<p><b>OBJECTIVE</b>To investigate the effect of the different immunosuppression therapy on CD4(+)Foxp3(+)regulatory T cells (CD4(+)Foxp3(+)Treg cells) in the peripheral blood monocytes of kidney transplantation recipients.</p><p><b>METHODS</b>A Closed Cohort study was conducted in 50 primary living kidney transplant recipients between January 2006 and January 2008, who had been followed up for 1 year. The recipients divided into calcineurin inhibitors group (CNI + MMF + Pred) (19 recipients, including cyclosporin group 10 recipients and tacrolimus group 9 recipients), rapamycin group (RAPA + MMF + Pred) (31 recipients). Twenty end-stage renal disease patients were in control group. The frequency of CD4(+)Foxp3(+)Treg cells in total CD4(+)T cells was analyzed by flow cytometry in peripheral blood from three groups, results were compared.</p><p><b>RESULTS</b>The clinical variables of recipients such as age, sex, cold ischemia time, human leucocyte antigen mismatch, panel reaction antibody, rejection episode were no significant difference. The percentage of CD4(+)Foxp3(+)Treg cells in total CD4(+) cells was significantly higher in rapamycin group and end-stage renal disease group than calcineurin inhibitors group (P < 0.01). The level of CD4(+)Foxp3(+)Treg cells between cyclosporin group and tacrolimus group was no significant difference (P > 0.05).</p><p><b>CONCLUSION</b>The level of CD4(+)Foxp3(+)Treg was significantly higher in patients receiving RAPA + MMF + Pred than the patients receiving CNI + MMF + Pred, which suggested that RAPA may be play a more important role in immune tolerance induction.</p>