Tribological and material properties for cartilage of and throughout the bovine stifle: support for the altered joint kinematics hypothesis of osteoarthritis

SummaryObjectivePrior studies suggest that ligament and meniscus tears cause osteoarthritis (OA) when changes in joint kinematics bring underused and underprepared regions of cartilage into contact. This study aims to test the hypothesis that material and tribological properties vary throughout the joint according to the local mechanical environment.MethodThe local tribological and material properties of bovine stifle cartilage (N = 10 joints with 20 samples per joint) were characterized under physiologically consistent contact stress and fluid pressure conditions.ResultsOverall, cartilage from the bovine stifle had an equilibrium contact modulus of Ec0 = 0.62 ± 0.10 MPa, a tensile modulus of Et = 4.3 ± 0.7 MPa, and a permeability of k = 2.8 ± 0.9 × 10−3 mm4/Ns. During sliding, the cartilage had an effective friction coefficient of μeff = 0.024 ± 0.004, an effective contact modulus of Ec = 3.9 ± 0.7 MPa and a fluid load fraction of F′ = 0.81 ± 0.03. Tibial cartilage exhibited significantly poorer material and tribological properties than femoral cartilage. Statistically significant differences were also detected across the femoral condyle and tibial plateau. The central femoral condyle exhibited the most favorable properties while the uncovered tibial plateau exhibited the least favorable properties.ConclusionsOur findings support a previous hypothesis that altered loading patterns can cause OA by overloading underprepared regions. They also help explain why damage to the tibial plateau often precedes damage to the mating femoral condyle following joint injury in animal models. Because the variations are driven by fundamental biological processes, we anticipate similar variations in the human knee, which could explain the OA risk associated with ligament and meniscus tears

Fall and spring tillage effects on sugarbeet production

The ability to vary primary tillage timing between fall and spring for sugarbeet production could benefit producers by providing flexibility for when field work occurs and may allow earlier planting in the spring. This study was conducted to evaluate the effects of strip and conventional tillage conducted in the spring and fall under various N supply levels on sugarbeet production in the northwest U.S. The treatments included tillage time (fall and spring), tillage system (moldboard plow, chisel plow and strip tillage), and N supply (5 levels including a control). The study was conducted in Kimberly, ID in 2008 and 2009 on a Portneuf silt loam. Within each year and tillage type, estimated recoverable sucrose and root yields were not different between fall and spring tillage timings. These data suggest that sugarbeet growers in the northwest U.S. have flexibility in timing their tillage practices across various tillage systems

Effects of tillage system and nitrogen supply on sugarbeet production

The sugarbeet (Beta vulgaris L.) industry in Idaho is interested in strip tillage (ST) primarily due to the potential savings in tillage costs. This study was conducted to evaluate the use of strip tillage in Idaho compared to conventional tillage practices and to evaluate N requirements of sugarbeet under ST and conventional tillage. The effect of tillage method (strip tillage, moldboard plow system [MP], and chisel plow system [CP]) and N supply (5 levels) on sugarbeet production factors were investigated in Kimberly, ID from 2008 to 2010 on a Portneuf silt loam with barley as the previous crop. Root and estimated recoverable sucrose (ERS) yields were the same under all three tillage practices. However, estimated tillage costs for ST were from 53 percent to 76 percent lower than other tillage systems tested. The CP treatment had significantly lower harvest plant population compared to ST and MP, likely because residue inhibited seed-soil contact. In 2008 and 2010, a significant quadratic relationship was observed between N supply and root and ERS yield. During 2008 and 2010, yields at the economic optimum N supply (EONS) ranged from 73.6 to 79.9 Mg roots per ha and 11,054 to 11,415 kg ERS per ha across N prices ranging from $0.44 to$2.20 per kg N. During 2008 and 2010, nitrogen use efficiency (NUE) at the EONS ranged from 50.1 to 67.9 kg sucrose per kg N supply over all N prices. The N requirements at the EONS ranged from 2.4 to 3.0 kg per Mg in 2008 and 2.5 to 2.8 kg per Mg in 2010 over the range of N prices. Strip tillage can be used to obtain yields comparable to other common tillage practices and decrease tillage costs. Nitrogen requirements could be reduced on heavier textured soils compared to past recommendations in the Pacific Northwest. However, adjusting N requirements based on sugarbeet production and quality history, soil type, and soil residual N should be evaluated

Dynamical Localization: Hydrogen Atoms in Magnetic and Microwave fields

We show that dynamical localization for excited hydrogen atoms in magnetic and microwave fields takes place at quite low microwave frequency much lower than the Kepler frequency. The estimates of localization length are given for different parameter regimes, showing that the quantum delocalization border drops significantly as compared to the case of zero magnetic field. This opens up broad possibilities for laboratory investigations.Comment: revtex, 11 pages, 3 figures, to appear in Phys. Rev. A, Feb (1997

Feasibility study and design concept for an orbiting ice-penetrating radar sounder to characterize in three-dimensions the Europan ice mantle down to (and including) any ice/ocean interface

This report presents a radar sounding model based on the range of current working hypotheses for the nature of Europa's icy shell.Institute for Geophysic

The occurrence and characterization of Campylobacter jejuni and C. coli in organic pigs and their outdoor environment

The occurrence and species distribution of thermophilic Campylobacter was investigated in organic outdoor pigs. An increased exposure of outdoor pigs to C. jejuni from the environment may cause a shift from a normal dominance of C. coli to more C. jejuni, which may imply a concern of reduced food safety. Bacteriological methods for determination of Campylobacter excretion level were combined with colony-blot hybridization and real-time PCR for specific detection of C. jejuni in pigs. Campylobacter was isolated from pigs (n = 47), paddock environment (n = 126) and wildlife (n = 44), identified to species by real-time PCR and sub-typed by serotyping (Penner) and pulse-field gel electrophorsis (PFGE) genotyping. All pigs excreted Campylobacter (103–107 CFU g1 faeces) from the age of 8–13-weeks old. C. jejuni was found in 29% of pigs in three consecutive trials and always in minority to C. coli (0.3–46%). C. jejuni and C. coli were isolated from 10% and 29% of the environmental samples, respectively, while crow-birds and rats harboured C. jejuni. Individual pigs hosted several strains (up to nine serotypes). The paddock environment was contaminated with C. coli serotypes similar to pig isolates, while most of the C. jejuni serotypes differed. C. jejuni isolates of different origin comprised few similar serotypes, just one identical genotype was common between pigs, environment and birds. In conclusion, the occurrence of C. jejuni varied considerably between the three groups of outdoor pigs. Furthermore, transfer of C. jejuni to the outdoor pigs from the nearby environment was not predominant according to the subtype dissimilarities of the obtained isolates

Simple choreographies of the planar Newtonian NN-body Problem

In the $N$-body problem, a simple choreography is a periodic solution, where all masses chase each other on a single loop. In this paper we prove that for the planar Newtonian $N$-body problem with equal masses, $N \ge 3$, there are at least $2^{N-3} + 2^{[(N-3)/2]}$ different main simple choreographies. This confirms a conjecture given by Chenciner and etc. in \cite{CGMS02}.Comment: 31pages, 6 figures. Refinements in notations and proof

A Precious Bequest: Contemporary Research with the WPA-CCC Collections from Moundville, Alabama *

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72459/1/j.1749-6632.1981.tb28184.x.pd

Theoretical Evaluations of the Fission Cross Section of the 77 eV Isomer of 235-U

We have developed models of the fission barrier (barrier heights and transition state spectra) that reproduce reasonably well the measured fission cross section of $^{235}$U from neutron energy of 1 keV to 2 MeV. From these models we have calculated the fission cross section of the 77 eV isomer of $^{235}$U over the same energy range. We find that the ratio of the isomer cross section to that of the ground state lies between about 0.45 and 0.55 at low neutron energies. The cross sections become approximately equal above 1 MeV. The ratio of the neutron capture cross section to the fission cross section for the isomer is predicted to be about a factor of 3 larger for the isomer than for the ground state of $^{235}$U at keV neutron energies. We have also calculated the cross section for the population of the isomer by inelastic neutron scattering form the $^{235}$U ground state. We find that the isomer is strongly populated, and for $E_n = 1 MeV$ the $(n,n'\gamma)$ cross section leading to the population of the isomer is of the order of 0.5 barn. Thus, neutron reaction network calculations involving the uranium isotopes in a high neutron fluence are likely to be affected by the 77 eV isomer of $^{235}$U. With these same models the fission cross sections of $^{233}$U and $^{237}$U can be reproduced approximately using only minor adjustments to the barrier heights. With the significant lowering of the outer barrier that is expected for the outer barrier the general behavior of the fission cross section of $^{239}$Pu can also be reproduced.Comment: 17 pages including 8 figure

Soil organic carbon dynamics in semi-arid irrigated cropping systems

The insufficient characterization of soil organic carbon (SOC) dynamics in semi-arid climates contributes uncertainty to SOC sequestration estimates. The opportunity exists to improve estimates of SOC dynamics in irrigated semi-arid croplands by studying research locations in south-central Idaho. This study intended to estimate changes in SOC (0-30 cm depth) due to variations in manure management, tillage regime, adoption of winter cover, and crop rotation. Empirical data from three research locations was also used to drive denitrification decomposition (DNDC) models in a “default” and calibrated capacity as well as forecast SOC levels until 2050 under “high” and “low” emissions future climate scenarios. Empirical data indicates: (i) increasing C input results in more rapid increases in SOC; (ii) no effect (P = 0.51) of winter triticale on SOC after 3 years; (iii) SOC accumulation (0.6 ± 0.5 Mg ha-1 yr-1) under a dairy forage rotation of corn-barley-alfalfax3 and no change (P = 0.905) in a commercial rotation of wheat-potato-barley-sugarbeet; (iv) manure applied annually at rate 1X is not significantly different (P = 0.75) from biennial application at rate 2X; and (v) no significant effect of manure application timing (P = 0.41, fall vs spring). The DNDC model simulated empirical SOC and biomass C measurements adequately in a default capacity, yet specific issues were encountered. The calibration improved model fit however simulation of soil water contents and actual evapotranspiration remained unacceptable. By 2050, model forecasting suggested: (i) SOC stock was ~ 1 % different between future emissions scenarios; (ii) triticale cover resulted in SOC accrual (0.5 – 0.27 Mg ha-1 yr-1); (iii) when manure is applied, conventional tillage regimes are favored; and (iv) manure applied treatments accrue SOC fitting a quadratic relationship (all R2 > 0.85 and all P < 0.0001), yet extending the simulation to 2100 indicated no equilibrium was realized. It is possible that under very large C inputs that C sequestration is inaccurately favored by DNDC which may influence “NetZero” C initiatives. Our findings improve upon knowledge of SOC dynamics in semi-arid irrigated cropping systems and could aid DNDC model development endeavors