Changing soil and surface conditions during rainfall: Single rainstorm/subsequent rainstorms

During rainstorms, physical properties of the soil surface change significantly. As a result of surface sealing, variations in infiltration rate, water content, water suction, bulk density and surface roughness can be observed and quantified. Dynamic processes taking place on the soil surface were investigated in laboratory and field experiments on a typical loess-derived soil in Germany. This study focused on the effects of continuous and subsequent rainfall treatments. Furthermore, all laboratory experiments were carried out in two different initial moisture regimes. In the laboratory experiments, a capillary rainfall simulator was used. Water suction was measured with microtensiometers 2 cm below the sealed surface in a 30 s time interval. The water content was determined with TDR probes in a variable time step, depending on the movement of the infiltration front. Compared to the continuous rainfall treatment, the decline of infiltration rate was much steeper in the subsequent rainfall events. After 2 h of continuous rainfall, a ‘drying effect' could be observed underneath the surface sealing at a depth of 2 cm. This was not the case in the intermittent treatment. Saturated conditions 10 cm below the surface sealing were reached in none of the treatments. The variation of bulk density within the first centimeter of the soil was determined via computed tomography and also with two simple methods using micro soil cores [Fohrer, N., 1995. Auswirkungen von Bodenfeuchte, Bodenart und Oberflächenbeschaffenheit auf Prozesse der Flächenerosion durch Wasser. PhD Thesis, Technical University Berlin, Bodenökologie und Bodengenese, No. 19, 183 pp.] and immersion as described by Roth [Roth, C.H., 1997. Bulk density of surface crusts: depth functions and relationships to texture. Catena 29 (3–4) 223–237.]. Under continuous rainfall conditions, the initially dry plots showed a higher compaction than the initially moist treatments. In the case of subsequent rainstorms, it was shown that the bulk density–depth function is not constant with time. The alteration of surface roughness was measured using a laser relief meter. The levelling effect of the intermittent rainfall regime proved to be much stronger in comparison to the continuous event.     

The percolation phase transition in sea Ice

Sea ice exhibits a marked transition in its fluid transport properties at a critical brine volume fraction pc of about 5 percent, or temperature Tc of about -5 degreesC for salinity of 5 parts per thousand. For temperatures warmer than Tc, brine carrying heat and nutrients can move through the ice, whereas for colder temperatures the ice is impermeable. This transition plays a key role in the geophysics, biology, and remote sensing of sea ice. Percolation theory can be used to understand this critical behavior of transport in sea ice. The similarity of sea ice microstructure to compressed powders is used to theoretically predict pc of about 5 percent.     

Multiple forms of alkaline phosphatase in horse bone,liver, kidney,duodenum, caecum and serum separated by agarose gel electrophoresis with and without neuraminidase pretreatment

Horse bone, liver, duodenum, caecum and kidney alkaline phosphatases were separated by a commercial agarose gel electrophoresis method with and without neuraminidase pretreatment, following the manufacturer's directions. Tissue extracts were obtained in saline solution and ALP extracted from cell membranes by the butanol method. Electrophoresis was performed using a TRIS/barbital/sodium barbital buffer with detergent, pH 8.6 to 9.0, at 250 V for 30 minutes. Bone, liver and kidney untreated extracts showed two ALP bands each, but with different relative migration (compared to albumin migration). When they were preincubated with neuraminidase, the two bone bands showed a marked decrease in their migration, followed by the kidney ALP bands and the most anodic band of liver Both intestinal untreated extracts showed three bands but with different mobilities. After preincubation with neuraminidase, the three bands of caecum mucosa decreased in their migration, and the most anodic duodenum band disappeared, overlapping the second one. When tissue extracts were incubated with wheat germ-lectin (WGL), 74.5% of bone extract ALP and 67.2% of caecum extract ALP precipitated, which demonstrated that the ALP band of both tissues have similar groups in the carbohydrate side chains. Horse serum showed two electrophoretic bands, which increased to three bands when treated with neuraminidase. ALP from hepatocytes was the dominant isoform, followed by a caecum band. Because the electrophoretic mobilities of some of the tissue bands studied were identical, the neuraminidase agarose electrophoretic method appeared to be a satisfactory alternative to separate them.     

Metabolic Diversity of Xanthomonas axonopodis pv. vignicola, Causal Agent of Cowpea Bacterial Blight and Pustule

Fifty-five strains of Xanthomonas axonopodis pv. vignicola, isolated from blight and pustule symptoms of cowpea leaves, originating from 11 countries, were characterized for their carbon-source metabolization pattern using the Biolog GN microplate system. Great variation was found between strains according to origin. Dextrin, glycogen and succinamic acid were not used by strains from Benin, Uganda or Thailand, but by all the other strains (excluding two strains from Mozambique), whereas N-acetyl-D-glucosamine and malonic acid were used by the strains from Benin, Uganda and Thailand, but generally not by the other strains. The strains from Benin, Uganda and Thailand, as well as strains from Venezuela, Brazil and Mozambique, clustered separately from the others in multivariate analysis. Nineteen substrates were used by all the strains, 47 not by any strain and 29 only by some strains. No considerable differences were found between strains isolated from blight symptoms and from pustules. Virulence of strains was not related to the metabolic pattern. The Biolog database was not representative of the diversity of X. axonopodis pv. vignicola, since all strains were identified as Xanthomonas campestris, although belonging to eight pathovars, while only eight of nine strains from Benin and both strains from Thailand were identified as X. campestris pv. vignicola. The Biolog system appeared to be useful for characterizing the diversity of X. axonopodis pv. vignicola strains. A set of representative strains based on metabolic and molecular diversity, virulence and geographic origin is suggested for screening for resistant cowpea cultivars.     

Transient elevation of carbon dioxide modifies the microbial community composition in a semi-arid grassland

Using open-top chambers (OTC) on the shortgrass steppe in northern Colorado, changes of microbial community composition were followed over the latter 3 years of a 5-year study of elevated atmospheric CO₂ as well as during 12 months after CO₂ amendment ended. The experiment was composed of nine experimental plots: three chambered plots maintained at ambient CO₂ levels of 360±20 μmol mol^?1 (ambient treatment), three chambered plots maintained at 720±20 μmol mol^?1 CO₂ (elevated treatment) and three unchambered plots. The abundance of fungal phospholipid fatty acids (PLFAs) shifted in the shortgrass steppe under the influence of elevation of CO₂ over the period of 3 years. Whereas the content of the fungal signature molecule (18:2ω6) was similar in soils of the ambient and elevated treatments in the third year of the experiment, CO₂ treatment increased the content of 18:2ω6 by around 60% during the two subsequent years. The shift of microbial community composition towards a more fungal dominated community was likely due to slowly changing substrate quality; plant community forage quality declined under elevated CO₂ because of a decline of N in all tested species as well as shift in species composition towards greater abundance of the low forage quality species (Stipa comata). In the year after which CO₂ enrichment had ceased, abundances of fungal and bacterial PLFAs in the post-CO₂ treatment plots shifted slowly back towards the control plots. Therefore, quantity and quality of available substrates had not changed sufficiently to shift the microbial community permanently to a fungal dominated community. We conclude from PLFA composition of soil microorganisms during the CO₂ elevation experiment and during the subsequent year after cessation of CO₂ treatment that a shift towards a fungal dominated system under higher CO₂ concentrations may slow down C cycling in soils and therefore enhance C sequestration in the shortgrass steppe in future CO₂-enriched atmospheres.     

Quality Parameters for Alpaca (Vicugna pacos) Semen are Affected by Semen Collection Procedure

Artificial insemination (AI) is poorly developed in camelids owing to the difficulty in collecting high quality semen and the highly viscous nature of the semen. Semen collected by artificial vagina (AV) is often of low quality and must be improved before any further development of AI technology can occur. The present study investigated the effects of adding a cervix‐like stricture to the AV, presence of females, collecting semen into Androhep^®, skim‐milk or Tris diluents, and catalase supplementation (0, 100, 200 or 600 units/ml) of Tris diluent on alpaca semen quality parameters. The addition of a cervix‐like stricture increased mating length (p < 0.05), whilst the presence of females during semen collection did not improve semen quality parameters (p > 0.05). Collection of semen into Tris diluent improved sperm motility (58.0 ± 11.9%) compared with the control (34.0 ± 10.8%; p < 0.05), Androhep^® (33.5 ± 10.7%) and skim‐milk diluents (28.2 ± 10.4%). Semen viscosity was reduced by collection into Androhep^® (4.6 ± 1.7 mm) and skim‐milk diluents (3.6 ± 1.3 mm) compared with Tris diluent (5.7 ± 2.1 mm) and no collection medium (9.3 ± 3.5 mm; p < 0.05). Tris diluent supplemented with 100, 200 or 600 units/ml catalase increased semen viscosity (5.0 ± 3.2 and 4.9 ± 3.2 mm). Collection of alpaca semen by AV into Tris diluent increased semen quality facilitating further development of AI technology in alpacas.     

Estimation of body composition of neonatal pigs via deuterium oxide dilution: validation of technique

Five studies were conducted to determine 1) the time period required for the equilibration of deuterium oxide (D2O) in body water in neonatal pigs following the intravenous (iv), intramuscular (im) or intraperitoneal (ip) injection of D2O and 2) the accuracy and precision of estimating body water, protein, fat and ash in neonatal pigs from the body D2O pool space. Deuterium oxide administered by iv and im injection equilibrated with body water by 40 and 20 min postinjection, respectively. Body D2O space determined from individual samples of blood fluids drawn at 40, 80 or 120 min postinjection accurately reflected body water determined by desiccation. The difference between D2O pool space determined at 120 min postinjection and body water in 4-kg pigs injected iv averaged - .050 kg, and the magnitude of the difference was relatively constant (standard deviation [SD] = .121 kg). The D2O pool space determined from im injection overestimated body water slightly (.163 kg), but the precision of the estimate was good (SD = .019 kg). Deuterium oxide injected ip did not consistently equilibrate by 200 min postinjection, and the estimated D2O pool space was not indicative of body water. The 90% confidence limits for estimating body water, protein, fat and ash in 4-kg pigs as determined by im and iv injection of D2O were .020 and .092 kg, .014 and .021 kg, .030 and .043 kg and .007 and .047 kg, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

A modification of the ABC method (avidin-biotin-peroxidase complex) for the detection of viral antigens in coronavirus infections in cats (FIP) and parvovirus type 2 infections in dogs

A modified ABC-method (avidin-biotin-peroxidase complex) is established to demonstrate viral antigens in paraffin sections of tissues of coronavirus (FIP) infected cats and parvovirus type 2 infected dogs using monoclonal antibodies. The pros and cons and potential sources of error are described and discussed.