Standardisation of Parameters during Endovenous Laser Therapy of Truncal Varicose Veins - Experimental Ex-vivo Study

BackgroundVein shrinkage is a surrogate marker for successful laser treatment of varicose veins. However, many controversies still remain concerning the best laser parameters to use. The aim of this study was standardisation of intraoperative energy dosages and pull-back rates to achieve optimal clinical results.DesignEx-vivo study in surgically removed saphenous trunks.Material and methodsGreat saphenous veins were removed by Babcock stripping and irradiated with laser energy delivered by a laser diode emitting at 980nm. In total, 279 vein segments (5cm long) were treated using powers from 5–15W. Vein segments were opened longitudinally and the circumference measured in the treated and untreated regions to assess thermal shrinkage.ResultsThe greatest shrinkage and minimum number of perforations was achieved using lower or medium power (8 to 12W) with longer exposure to administer laser energy. The median percentage vein shrinkage was 50% (power 5W), 45% (8W), 40% (10W), 45% (12W) and 59% (15W). When a higher power was used (15W), the perforations were more frequent and carbonisation was marked.ConclusionsOur data suggests that similar efficacy with fewer vein perforations may be obtained with low or medium power settings and increased exposure when undertaking laser obliteration of saphenous trunks. This may result in fewer adverse events such as ecchymosis following treatment in patients

Magnetic interaction of Co ions near the {10\bar{1}0} ZnO surface

Co-doped ZnO is the prototypical dilute magnetic oxide showing many of the characteristics of ferromagnetism. The microscopic origin of the long range order however remains elusive, since the conventional mechanisms for the magnetic interaction, such as super-exchange and double exchange, fail either at the fundamental or at a quantitative level. Intriguingly, there is a growing evidence that defects both in point-like or extended form play a fundamental role in driving the magnetic order. Here we explore one of such possibilities by performing {\it ab initio} density functional theory calculations for the magnetic interaction of Co ions at or near a ZnO \{10$\bar{1}$0\} surface. We find that extended surface states can hybridize with the $e$-levels of Co and efficiently mediate the magnetic order, although such a mechanism is effective only for ions placed in the first few atomic planes near the surface. We also find that the magnetic anisotropy changes at the surface from an hard-axis easy-plane to an easy axis, with an associated increase of its magnitude. We then conclude that clusters with high densities of surfacial Co ions may display blocking temperatures much higher than in the bulk

Carbon Dioxide Dynamics During a Growing Season in Midwestern Cropping Systems

Daily and seasonal CO2-exchange dynamics between the boundary layer and biosphere is important to understanding Net Ecosystem Exchange of terrestrial ecosystems. Spatial and temporal variations of CO2 fluxes across midwestern cropping systems have not been well documented. This study was designed to monitor and evaluate spatial and temporal dynamics of CO2 exchange across a watershed region for typical production fields of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] in the Midwest by quantifying the above-canopy, within-canopy, and soil components of C balance for this cropping system. An energy-balance approach using eddy covariance was utilized across different fields making year-around measurements in both corn and soybean fields to quantify the exchange of CO2 and H2O between the crop canopy and the atmospheric boundary layer. Within-canopy concentrations of CO2 and H2O vapor were measured with an eight-port CO2/H2O infrared analyzer. Soil respiration was quantified using soil chambers at various landscape positions throughout the growing season. Fluxes of CO2 and H2O vapor throughout the day were dependent on net radiation and the stage of canopy development. Diurnal variations in CO2 and H2O vapor fluxes revealed that the magnitude of the fluxes is large and the variation of the fluxes among fields was consistent throughout the season. Integration of the daily fluxes into seasonal totals showed large differences among crops and fields. Flux differences were the result of the effect of varying soil types on water-holding capacity. Seasonal integrated values were lower than estimates derived from biomass samples collected within the fields and the measurement of the C content of the biomass. Within-canopy recycling of soil CO2 may provide insight to this discrepancy. The techniques are available to quantify the CO2 and H2O vapor fluxes across different management systems and landscapes to help refine our understanding of the magnitude of the CO2 and H2O dynamics in cropping systems

Subsurface Flow Barriers to Reduce Nitrate Leaching

Groundwater is a very important natural resource which directly affects many human lives. In the United States, groundwater is the source of about 22 percent of the freshwater used. About 53 percent of the total population and 97 percent of the rural population use groundwater supplies for their drinking water (Moody, 1990). Although contamination of groundwater can occur naturally, agriculture is considered to be one of the most widespread nonprofit sources of groundwater contamination. Among agricultural chemicals, nitrogen-fertilizer has been used most extensively, especially by com producers. About one million tons of nitrogen-fertilizer are used annually in Iowa. In some studies, more than 50 percent of the applied fertilizer nitrogen is not removed by the crop or stored in the soil, and leaching as a form of nitrate is thought to be a major reason for the losses (Blackmer, 1987). Leached nitrate may enter groundwater supplies. Nitrate-nitrogen concentrations found in unsaturated soil below the rootzone of agricultural fields are in the range of 5 to 100 mg!L (Bouwer, 1990). Nitrate-nitrogen concentrations in tile drainage below row crops often exceed 10 mg/L, the U.S.A. drinking water standard (Gast et al., 1978; Baker and Johnson, 1981; Timmons and Dylla, 1981; Baker et al., 1985)

Localized compaction and doming to increase N-use efficiency and reduce leaching

Nitrate-nitrogen leaching from agricultural lands results in inefficient use of nitrogen-fertilizer as well as degradation of groundwater or surface water if leachate returns to the surf ace through artificial drainage or baseflow. Subsurface barriers placed above a fertilizer band have been shown to reduce anion leaching. Laboratory data suggest that compacted soil works well as a subsurface water-flow barrier (Kiuchi et al., 1992; Kiuchi et al., 1994). A field-scale implement has been designed and constructed to inject nitrate-nitrogen fertilizer below the soil surface and create a thin compacted strip of soil above the fertilizer band covered by a small dome of soil. Data from a field study indicate that nitrate-nitrogen placed beneath such a domed, compacted strip is less susceptible to leaching than nitrate-nitrogen placed below the soil surface without such a cover. In 1993, nitrate-nitrogen remaining in the upper soil profile (32 inches deep) after three months of the growing season was 56% of the total amount applied compared with 37% remaining where there was only the typical knife injection band. Grain weight and plant weight at black layer development were not significantly different between the two application methods. Overall grain yields at harvest were different, the conventional knife application technique yielding slightly more than the localized compaction and doming application technique

Kepler Observations of the Three Pre-Launch Exoplanet Candidates: Discover of Two Eclipsing Binaries and a New Exoplanet

Three transiting exoplanet candidate stars were discovered in a ground-based photometric survey prior to the launch of NASA's Kepler mission. Kepler observations of them were obtained during Quarter 1 of the Kepler mission. All three stars are faint by radial velocity follow-up standards, so we have examined these candidates with regard to eliminating false positives and providing high confidence exoplanet selection. We present a first attempt to exclude false positives for this set of faint stars without high-resolution radial velocity analysis. This method of exoplanet confirmation will form a large part of the Kepler mission follow-up for Jupiter-sized exoplanet candidates orbiting faint stars. Using the Kepler light curves and pixel data, as well as medium-resolution reconnaissance spectroscopy and speckle imaging, we find that two of our candidates are binary stars. One consists of a late-F star with an early M companion, while the other is a K0 star plus a late M-dwarf/brown dwarf in a 19 day elliptical orbit. The third candidate (BOKS-1) is an r = 15 G8V star hosting a newly discovered exoplanet with a radius of 1.12 R_(Jupiter) in a 3.9 day orbit

Dispersion strengthening in vanadium microalloyed steels processed by simulated thin slab casting and direct charging. Part 2 - chemical characterisation of dispersion strengthening precipitates

The composition of the sub-15 nm particles in six related vanadium high strength low alloy steels, made by simulated thin slab direct charged casting, has been determined using electron energy loss spectroscopy (EELS). Such particles are considered to be responsible for dispersion hardening. For the first time, particles down to 4 nm in size have had their composition fully determined. In all the steels, the particles were nitrogen and vanadium rich and possibly slightly sub-stoichiometric carbonitrides. Equilibrium thermodynamics predicted much higher carbon to metal atomic ratios than observed in all cases so that kinetics and mechanical deformation clearly control the precipitation process. Thus it is important to formulate the steel with this in mind

Do cover crops increase or decrease nitrous oxide emissions? A meta-analysis

There are many environmental benefits to incorporating cover crops into crop rotations, such as their potential to decrease soil erosion, reduce nitrate (NO3) leaching, and increase soil organic matter. Some of these benefits impact other agroecosystem processes, such as greenhouse gas emissions. In particular, there is not a consensus in the literature regarding the effect of cover crops on nitrous oxide (N2O) emissions. Compared to site-specific studies, meta-analysis can provide a more general investigation into these effects. Twenty-six peer-reviewed articles including 106 observations of cover crop effects on N2O emissions from the soil surface were analyzed according to their response ratio, the natural log of the N2O flux with a cover crop divided by the N2O flux without a cover crop (LRR). Forty percent of the observations had negative LRRs, indicating a cover crop treatment which decreased N2O, while 60% had positive LRRs indicating a cover crop treatment which increased N2O. There was a significant interaction between N rate and the type of cover crop where legumes had higher LRRs at lower N rates than nonlegume species. When cover crop residues were incorporated into the soil, LRRs were significantly higher than those where residue was not incorporated. Geographies with higher total precipitation and variability in precipitation tended to produce higher LRRs. Finally, data points measured during cover crop decomposition had large positive LRRs and were larger than those measured when the cover crop was alive. In contrast, those data points measuring for a full year had LRRs close to zero, indicating that there was a balance between periods when cover crops increased N2O and periods when cover crops decreased emissions. Therefore, N2O measurements over the entire year may be needed to determine the net effect of cover crops on N2O. The data included in this meta-analysis indicate some overarching crop management practices that reduce direct N2O emissions from the soil surface, such as no soil incorporation of residues and use of nonlegume cover crop species. However, our results demonstrate that cover crops do not always reduce direct N2O emissions from the soil surface in the short term and that more work is needed to understand the full global warming potential of cover crop management