Cover Crop Effects on Infiltration, Aggregate Stability, and Water Retention on Loessial and Alluvial Soils of the Lower Mississippi River Valley

Cover crops are a widely considered practice to improve soil health in the form of erosion control, organic matter additions, and improving water-holding capacity. Despite the well-documented benefits, little is known about the effect of cover crops on soils in the Lower Mississippi River Valley (LMRV), an area historically dominated by intensive cultivated agriculture, with soils prone to erosion, and unsustainable aquifer withdrawals for irrigation. The main objective of this study was to evaluate the effects of cover crops [with cover crops (CC) and without cover crops (NCC)] on near-surface soil physical/chemical- and infiltration-related properties, aggregate stability, and water retention. The secondary objective of this study was to evaluate the effects of sample/measurement placement [in the bed (B) and in the wheel-track (WT) and non-wheel-track (NWT) furrow] in adjacent CC and NCC treatments on the same soil under wide-row cotton (Gossypium hirsutum L.) production. Soil samples were collected and in-situ measurements were conducted between May 2018 and May 2019 across four locations within the LMRV portion of eastern Arkansas. Using a falling-head, double-ring infiltrometer method for 20 minutes, overall- and steady-state infiltration rates were unaffected (P \u3e 0.05) by cover-crop treatment. Across all locations, extractable soil Na content in the top 10 cm was greater (P ≤ 0.05) with NCC (31.6 kg ha-1) compared with CC (21.6 kg ha-1). Soil pH, electrical conductivity (EC), total C (TC), soil organic matter (SOM), and bulk density (BD) in the top 10 cm were also unaffected (P \u3e 0.05) by cover-crop treatment. However, EC and BD were numerically greater with NCC compared to CC, while TC and SOM were numerically greater with CC compared to NCC. Based on a wet-sieving approach for five minutes, averaged across cover treatment and soil depth (0- to 5- and 5- to 10-cm), water-stable aggregate (WSA) concentration differed (P ≤ 0.05) by aggregate size class. Averaged across treatment and soil depth (0-to 5- and 5- to 10-cm), WSA concentration in the 0.25- to 0.5- (0.101 g g-1) was 1.5 times greater than that in the 1.0- to 2.0-mm size class (0.068 g g-1) and was at least 1.2 times greater than that in the 0.5- to 1.0- (0.079 g g-1) and 2.0- to 4.0-mm (0.084 g g-1) size classes, which were intermediate. Averaged across treatment and soil depth, WSA concentration in the \u3e 4.0- (0.097 g g-1) was at least 1.2 times greater than that in the 0.5- to 1.0- and 1.0- to 2.0-mm size classes, which did not differ, while WSA concentration in the 2.0- to 4.0- was 1.2 times greater than that in the 1.0- to 2.0-mm size class. Extractable soil Na content was greater (P = 0.03) in NCC-WT (26.8 kg ha-1) and CC-WT (26.7 kg ha-1), which did not differ, than NCC-B (19.8 kg ha-1) and NCC-NWT (17.5 kg ha-1), which did not differ. Soil BD in WT was 1.1 times greater than the other two placements, while SOM content was greater in CC-WT (30.7 Mg ha-1) than in all other treatment-placement combinations, except for CC-NWT, which did not differ. Similarly, WSA concentration was 2.3 and 1.6 times greater in the CC-NWT and CC-WT combinations, respectively, which did not differ, compared to their corresponding placements under NCC. Though many soil properties did not significantly differ between CC treatments due to the collective variations in background management practices, CC and cash crop species grown, and CC duration, which ranged from less than one year to greater than 19 years, results of this study clearly demonstrated that CC positively affect physical, chemical, and hydraulic properties across a large area. With continued management using CC, soil property differences that were only numeric will likely continue to deviate from one another into the future, at which time the fuller benefits of long-term CC use may be realized

Random walk on surfaces with hyperbolic cusps

We consider the operator associated to a random walk on finite volume surfaces with hyperbolic cusps. We study the spectral gap (upper and lower bound) associated to this operator and deduce some rate of convergence of the iterated kernel towards its stationary distribution.Comment: 28 page

Predicting Flows of Rarefied Gases

DSMC Analysis Code (DAC) is a flexible, highly automated, easy-to-use computer program for predicting flows of rarefied gases -- especially flows of upper-atmospheric, propulsion, and vented gases impinging on spacecraft surfaces. DAC implements the direct simulation Monte Carlo (DSMC) method, which is widely recognized as standard for simulating flows at densities so low that the continuum-based equations of computational fluid dynamics are invalid. DAC enables users to model complex surface shapes and boundary conditions quickly and easily. The discretization of a flow field into computational grids is automated, thereby relieving the user of a traditionally time-consuming task while ensuring (1) appropriate refinement of grids throughout the computational domain, (2) determination of optimal settings for temporal discretization and other simulation parameters, and (3) satisfaction of the fundamental constraints of the method. In so doing, DAC ensures an accurate and efficient simulation. In addition, DAC can utilize parallel processing to reduce computation time. The domain decomposition needed for parallel processing is completely automated, and the software employs a dynamic load-balancing mechanism to ensure optimal parallel efficiency throughout the simulation

Analysis of Plume Impingement Effects from Orion Crew Service Module Dual Reaction Control System Engine Firings

Plume impingement effects on the Orion Crew Service Module (CSM) were analyzed for various dual Reaction Control System (RCS) engine firings and various configurations of the solar arrays. The study was performed using a decoupled computational fluid dynamics (CFD) and Direct Simulation Monte Carlo (DSMC) approach. This approach included a single jet plume solution for the R1E RCS engine computed with the General Aerodynamic Simulation Program (GASP) CFD code. The CFD solution was used to create an inflow surface for the DSMC solution based on the Bird continuum breakdown parameter. The DSMC solution was then used to model the dual RCS plume impingement effects on the entire CSM geometry with deployed solar arrays. However, because the continuum breakdown parameter of 0.5 could not be achieved due to geometrical constraints and because high resolution in the plume shock interaction region is desired, a focused DSMC simulation modeling only the plumes and the shock interaction region was performed. This high resolution intermediate solution was then used as the inflow to the larger DSMC solution to obtain plume impingement heating, forces, and moments on the CSM and the solar arrays for a total of 21 cases that were analyzed. The results of these simulations were used to populate the Orion CSM Aerothermal Database

Efficacité de la technique d'induction florale d'Ananas comosus (L.) Merr. au moyen de charbon actif enrichi à l'éthylène (TIFBio)

Efficiency of the Ananas comosus (L.) Merr. flower induction treatment based on ethylene enriched activated carbon (TIFBio). Pineapple is an important export crop for tropical countries. The flower induction treatments are essential to the pineapple production for economical and social reasons. For conventional agriculture, many chemicals are available but for organic farming ethylene is the only allowed product. A new flower induction method suited to small organic growers has been developed by the Pesticides Initiative Programme of the Coleacp funded by the European Development Fund. The trials conducted proved that the method reaches more than 80% efficiency at 10 weeks for the different application methods evaluated. The wet application trials show a doses response effect as well as effect of the application replication at 2 days interval. The flowering rate culminates at 100% after 8 weeks for the best results, obtained with the wet treatment at 250 mg per plant applied two times at 2 days interval. The different dry treatments tested gave all 85 – 90% flowering rates at 10 weeks, suggesting the presence of an undetermined limitation factor in the conditions prevailing for the trial. The time of application during the day shows no significant effect. It is concluded that the growers can use the TIFBio technique for production control. It is recommended to evaluate the most suited application technique according to their particular case as environmental effect can affect the efficiency

Analysis of surgical complications after 397 hepatic transplantations

The results of 397 consecutive orthotopic hepatic transplantations in 333 recipients were reviewed. One or more surgical complications developed in 172 of 323 patients (55 per cent), excluding ten intraoperative deaths. The six month mortality rate among the patients with surgical complications (55 of 172; 32 per cent) was statistically higher than that among patients without such complications (16 of 151; 11 per cent) (p < 0.001; chi-square, 58.36). Surgical complications including exploratory laparotomy for bleeding or infection in 74 (22 per cent), reconstruction of the bile duct for biliary obstruction or leakage in 55 (17 per cent), external biliary drainage for biliary leakage in four (1 per cent), tracheostomy in 80 (24 per cent), thoracotomy in 12 (4 per cent) and splenectomy in seven (2 per cent). The incidence of biliary obstruction (16 per cent mortality rate) and leakage (48 per cent mortality rate) was 18 per cent (34 of 193) and 2 per cent (four of 193) each after choledochocholedochostomy, which was 3 per cent (five of 187) and 9 per cent (17 of 187) each choledochojejunostomy. Biliary obstruction (16 per cent mortality rate) was more common after choledochocholedochostomy (p < 0.005; chi-square, 23.01), whereas the incidence of more serious biliary leakage (48 per cent mortality rate) was higher after choledochojejunostomy (p < 0.005; chi-square, 8.97). It is concluded that orthotopic hepatic transplantation remains an unforgiving extensive surgical procedure, in which choledochocholedochostomy remains the first-choice reconstruction of the biliary tract because of its lower mortality

Hemodynamic and biochemical changes during normothermic and hypothermic sanguinous perfusion of the porcine hepatic graft

Using an ex vivo liver sanguinous perfusion system, hemodynamic and biochemical changes of the porcine livers were studied, which were preserved cold (4°C) for 24 hr in University of Wisconsin solution and reperfused with normothermic (37°C) (n=8) or hypothermic (32°C) (n=8) blood for 3 hr. Six more livers were reperfused with normothermic blood (37°C) immediately after procurement as controls. The total hepatic blood flow was adjusted to 1 ml/min/g liver weight, in which hepatic artery and portal vein flows were administered at a 1:2 ratio. In livers stored cold for 24 hr in UW solution and perfused normothermically, a statistically higher hepatic artery resistance was exhibited at 30 an 60 min after reperfusion (P<0.05), and there was lower bile output (P<0.05) at 90 and 120 min as compared to the controls. In livers stored cold for 24 hr in UW solution and perfused hypothermically, as compared to ones perfused normothermically, statistically higher hepatic- artery and portal-vein resistances (P<0.05) were observed throughout the perfusion period and 60 min= after reperfusion, respectively. In addition, bile output and oxygen consumption of these livers were statistically lower than those of ones perfused normothermically (P<O.05). In contrast, chemistries of the perfusat of livers perfused hypothermically were comparable to ones perfused normothermically. Histologic examination of the liver perfused hypothermically demonstrated hepatic arterial and/or portal venous congestion and mild-to-moderate hemorrhage in the portal triads. This study suggests that livers preserved for a prolonged period of time demonstrate a high hepatic arterial resistance shortly after revascularization, and that recipient hypothermia after revascularization may be a risk factor for the development of hepatic arterial thrombosis following liver transplantation. © 1990 by Williams & Wilkins

Nucleation of Stable Superconductivity in YBCO-Films

By means of the linear dynamic conductivity, inductively measured on epitaxial films between 30mHz and 30 MHz, the transition line $T_g (B)$ to generic superconductivity is studied in fields between B=0 and 19T. It follows closely the melting line $T_m (B)$ described recently in terms of a blowout of thermal vortex loops in clean materials. The critical exponents of the correlation length and time near $T_g (B)$, however, seem to be dominated by some intrinsic disorder. Columnar defects produced by heavy-ion irradiation up to field-equivalent-doses of $B_{\phi} = 10T$ lead to a disappointing reduction of $T_g (B \to 0)$ while for $B>B_{\phi}$ the generic line of the pristine film is recovered. These novel results are also discussed in terms of a loop-driven destruction of generic superconductivity.Comment: 11 pages including 7 EPS figures, accepted for publication in the Proceedings of the Spring Meeting of the German Physical Society, Muenster 1999,Festkoerperprobleme/Advances in Solid State Physics 199

Dorsal vs. ventral differences in fast Up-state-associated oscillations in the medial prefrontal cortex of the urethane-anesthetized rat.

Cortical slow oscillations (0.1–1 Hz), which may play a role in memory consolidation, are a hallmark of non-rapid eye movement (NREM) sleep and also occur under anesthesia. During slow oscillations the neuronal network generates faster oscillations on the active Up-states and these nested oscillations are particularly prominent in the PFC. In rodents the medial prefrontal cortex (mPFC) consists of several subregions: anterior cingulate cortex (ACC), prelimbic (PrL), infralimbic (IL), and dorsal peduncular cortices (DP). Although each region has a distinct anatomy and function, it is not known whether slow or fast network oscillations differ between subregions in vivo. We have simultaneously recorded slow and fast network oscillations in all four subregions of the rodent mPFC under urethane anesthesia. Slow oscillations were synchronous between the mPFC subregions, and across the hemispheres, with no consistent amplitude difference between subregions. Delta (2–4 Hz) activity showed only small differences between subregions. However, oscillations in the spindle (6–15 Hz)-, beta (20–30 Hz), gamma (30–80 Hz)-, and high-gamma (80–150 Hz)-frequency bands were consistently larger in the dorsal regions (ACC and PrL) compared with ventral regions (IL and DP). In dorsal regions the peak power of spindle, beta, and gamma activity occurred early after onset of the Up-state. In the ventral regions, especially the DP, the oscillatory power in the spindle-, beta-, and gamma-frequency ranges peaked later in the Up-state. These results suggest variations in fast network oscillations within the mPFC that may reflect the different functions and connectivity of these subregions. NEW & NOTEWORTHY We demonstrate, in the urethane-anesthetized rat, that within the medial prefrontal cortex (mPFC) there are clear subregional differences in the fast network oscillations associated with the slow oscillation Up-state. These differences, particularly between the dorsal and ventral subregions of the mPFC, may reflect the different functions and connectivity of these subregions