Enrichment and adaptation yield high anammox conversion rates under low temperatures.

This study compared two anammox sequencing batch reactors (SBR) for one year. SBRconstantT was kept at 30 °C while temperature in SBRloweringT was decreased step-wise from 30 °C to 20 °C and 15 °C followed by over 140 days at 12.5 °C and 10 °C. High retention of anammox bacteria (AnAOB) and minimization of competition with AnAOB were key. 5-L anoxic reactors with the same inoculum were fed synthetic influent containing 25.9 mg NH4+-N/L and 34.1 mg NO2--N/L (no COD). Specific ammonium removal rates continuously increased in SBRconstantT, reaching 785 mg NH4+-N/gVSS/d, and were maintained in SBRloweringT, reaching 82.2 and 91.8 mg NH4+-N/gVSS/d at 12.5 and 10 °C respectively. AnAOB enrichment (increasing hzsA and 16S rDNA gene concentrations) and adaptation (shift from Ca. Brocadia to Ca. Kuenenia in SBRloweringT) contributed to these high rates. Rapidly settling granules developed, with average diameters of 1.2 (SBRconstantT) and 1.6 mm (SBRloweringT). Results reinforce the potential of anammox for mainstream applications.

Investigation of the frictional response of osteoarthritic human tibiofemoral joints and the potential beneficial tribological effect of healthy synovial fluid.

OBJECTIVE: This study tests the hypothesis that the natural progression of osteoarthritis (OA) in human joints leads to an increase in the friction coefficient. This hypothesis is based on the expectation that the wear observed in OA may be exacerbated by higher friction coefficients. A corollary hypothesis is that healthy synovial fluid (SF) may help mitigate the increase in the friction coefficient in diseased joints. DESIGN: The friction coefficient of human tibiofemoral joints with varying degrees of OA was measured in healthy bovine SF and physiological buffered saline (PBS). Two testing configurations were adopted, one that promotes sustained cartilage interstitial fluid pressurization to investigate the effectiveness of this mechanism with advancing OA, and another that allows interstitial fluid pressure to subside to investigate the effectiveness of boundary lubrication. RESULTS: Seven specimens were visually staged to be normal or mildly degenerated (stages< or =2 on a scale of 1 to 4) and nine others had progressive degeneration (stages>2 and< or =3). No statistical differences were found in the friction coefficient with increasing OA, whether in migrating or stationary contact area configurations; however, the friction coefficient was significantly lower in SF than PBS in both configurations. CONCLUSIONS: The friction coefficient of human tibiofemoral cartilage does not necessarily increase with naturally increasing OA, for visual stages ranging from 1 to 3. This outcome may be explained by the fact that interstitial fluid pressurization is not necessarily defeated by advancing degeneration. This study also demonstrates that healthy SF decreases the friction coefficient of OA joints relative to PBS.

Effects of sustained interstitial fluid pressurization under migrating contact area, and boundary lubrication by synovial fluid, on cartilage friction.

OBJECTIVE: This experimental study tests two hypotheses which address outstanding questions in cartilage lubrication: can the friction coefficient remain low under sustained physiological loading conditions? How effective is synovial fluid (SF) in the lubrication of articular cartilage? Based on theory, it is hypothesized that migrating contact areas can maintain elevated cartilage interstitial fluid pressurization, thus a low friction coefficient, indefinitely. It is also hypothesized that the beneficial effects of SF stem from boundary lubrication rather than fluid-film lubrication. DESIGN: Five experiments were conducted on immature bovine femoro-tibial joints, to compare the frictional response under migrating vs stationary contact areas; the frictional response in SF vs saline; the role of sliding velocity and the role of congruence on the friction coefficient. RESULTS: Migrating contact area could maintain a low friction coefficient under sustained physiological conditions of loading for at least 1 h. SF reduced the friction coefficient by a factor of approximately 1.5 relative to saline. However, interstitial fluid pressurization was far more effective, reducing the friction coefficient by a factor of approximately 60 relative to equilibrium (zero-pressure) conditions. It was confirmed that SF acts as a boundary lubricant. CONCLUSIONS: These results emphasize the importance of interstitial fluid pressurization on the frictional response of cartilage. They imply that the mechanical integrity of cartilage must be maintained to produce low friction in articular joints. The more limited effectiveness of SF implies that intra-articular injections of lubricants in degenerated joints may have only limited effectiveness on their tribological properties.

Rose Dieback Caused by Trichothecium roseum in Argentina.

Rose (Rosa sp.) is one of the most important ornamentals in Argentina. Since 2002, a severe disease has been observed on crops cultivated for cut flowers and garden plants in Escobar, San Pedro, Río Negro, and the surrounding area of Buenos Aires and La Plata. Symptoms consisted of a stem dieback progressing to plant death. In some cases, stem cankers were observed on the dieback limits. Mean incidence of stem dieback was 8% regardless of location. The disease was associated with pruning or harvest wounds. The objective of this study was to identify the causal agent of the described symptoms. Small pieces of diseased tissues from cvs. Rafaela, Merlise, Confeti, Mini rosal, Exótica, Macarena, and Peckowo were surfaced sterilized with a 2-min immersion in 0.2% NaOCl, washed with sterile distilled water, the tissue blotted dry, placed on 2% potato dextrose agar (PDA), and incubated at 22°C. Pure salmon-colored fungal colonies developed within 72 h. Hyaline, two-celled (the upper cell slightly larger), ovoid to ellipsoid conidia formed in chains at the apex of simple, long, slender, septate conidiophores. These characteristics are consistent with the description of Trichothecium roseum (Pers.) Link ex Gray (1) The pathogenicity tests were carried out on 10 plants of cv. Rafaela and 10 plants of cv. Mini Rosal using a conidial suspension (2.4 × 105 spores/ml). All plants were pruned just before inoculation. Another 10 pruned plants (five from each cultivar) were sprayed with sterile water and served as controls. Inoculated and noninoculated plants were placed in a climatic chamber at 20°C and covered with polyethylene bags for 3 days to achieve a humid environment. Stem dieback was evident 7 days after inoculation on both cultivars and cankers appeared in 14 days. A dense, white mold that turned salmon-pink covered all the stems within 25 days. Inoculated plants died after 40 days. Symptoms did not develop on the control plants. The pathogen was recovered from inoculated stems, thus fulfilling Koch's postulates. To our knowledge, this is the first report of T. roseum causing a disease on rose in Argentina. Reference: (1) K. H. Domsch et al. Compendium of Soil Fungi. Academic Press. London, 1980.

Removal of the superficial zone of bovine articular cartilage does not increase its frictional coefficient.

OBJECTIVE: To investigate the role of the superficial zone in regulating the frictional response of articular cartilage. This zone contains the superficial protein (SZP), a proteoglycan synthesized exclusively by superficial zone chondrocytes and implicated in reducing the friction coefficient of cartilage. DESIGN: Unconfined compression creep tests with sliding of cartilage against glass in saline were carried out on fresh bovine cylindrical plugs (slashed circle Ø6 mm, n=35) obtained from 16 bovine shoulder joints (ages 1-3 months). In the first two experiments, friction tests were carried out before and after removal of the superficial zone ( approximately 100 microm), in a control and treatment group, using two different applied load magnitudes (4.4 N and 22.2 N). In the third experiment, friction tests were conducted on intact surfaces and the corresponding microtomed deep zone of the same specimen. RESULTS: In all tests the friction coefficient exhibited a transient response, increasing from a minimum value (mu(min)) to a near-equilibrium final value (micro(eq)). No statistical change (P>0.5) was found in micro(min) before and after removal of the superficial zone in both experiments 1 and 2. However, micro(eq) was observed to decrease significantly (P<0.001) after removal of the surface zone. Results from the third experiment confirm that micro(eq) is even lower at the deep zone. Surface roughness measurements with atomic force microscopy (AFM) revealed an increase in surface roughness after microtoming. Immunohistochemical staining confirmed the presence of SZP in intact specimens and its removal in microtomed specimens. CONCLUSIONS: The topmost ( approximately 100 microm) superficial zone of articular cartilage does not have special properties which enhances its frictional response.