Developing a continental-scale measure of gross primary production by combining MODIS and AmeriFlux data through Support Vector Machine approach

Remote sensing is a potentially powerful technology with which to extrapolate eddy covariance-based gross primary production (GPP) to continental scales. In support of this concept, we used meteorological and flux data from the AmeriFlux network and Support Vector Machine (SVM), an inductive machine learning technique, to develop and apply a predictive GPP model for the conterminous U.S. In the following four-step process, we first trained the SVM to predict flux-based GPP from 33 AmeriFlux sites between 2000 and 2003 using three remotely-sensed variables (land surface temperature, enhanced vegetation index (EVI), and land cover) and one ground-measured variable (incident shortwave radiation). Second, we evaluated model performance by predicting GPP for 24 available AmeriFlux sites in 2004. In this independent evaluation, the SVM predicted GPP with a root mean squared error (RMSE) of 1.87 gC/m²/day and an R² of 0.71. Based on annual total GPP at 15 AmeriFlux sites for which the number of 8-day averages in 2004 was no less than 67% (30 out of a possible 45), annual SVM GPP prediction error was 32.1% for non-forest ecosystems and 22.2% for forest ecosystems, while the standard Moderate Resolution Imaging Spectroradiometer GPP product (MOD17) had an error of 50.3% for non-forest ecosystems and 21.5% for forest ecosystems, suggesting that the regionally tuned SVM performed better than the standard global MOD17 GPP for non-forest ecosystems but had similar performance for forest ecosystems. The most important explanatory factor for GPP prediction was EVI, removal of which increased GPP RMSE by 0.85 gC/m²/day in a cross-validation experiment. Third, using the SVM driven by remote sensing data including incident shortwave radiation, we predicted 2004 conterminous U.S. GPP and found that results were consistent with expected spatial and temporal patterns. Finally, as an illustration of SVM GPP for ecological applications, we estimated maximum light use efficiency (e_max), one of the most important factors for standard light use efficiency models, for the conterminous U.S. by integrating the 2004 SVM GPP with the MOD17 GPP algorithm. We found that e_max varied from ∼ 0.86 gC/MJ in grasslands to ∼ 1.56 gC/MJ in deciduous forests, while MOD17 e_max was 0.68 gC/MJ for grasslands and 1.16 gC/MJ for deciduous forests, suggesting that refinements of MOD17 e_max may be beneficial.     

The influence of deuterium exposures on subsequent outgassing rate of an UHV system

The accuracy of results in experiments where a well-processed UHV system is exposed to hydrogen depends on the hydrogen absorption rate and kinetics of subsequent spontaneous release from the system itself. In experiments to date, the sensitivity required to detect very low rates has been achieved only when tritium has been used as a tracer gas. Unfortunately, tritiated water from the surface prevails among released gas species which is not expected for well-outgassed surfaces. In the present studies, UHV system behaviour at 303 K during three deuterium exposures of duration 92 and 72 h at an initial pressure of 1 mbar was explored. The rate of decrease of pressure was constant during the whole of these periods as monitored by non-ionizing vacuum gauges. It corresponded to an effective sticking probability of the order of 1×10^-12 and resulted in absorption of 5×10¹⁴ D atoms/cm². The release kinetics were observed for several days starting immediately after deuterium had been pumped from the system. Initially, the deuterium release rate exceeded the background hydrogen outgassing by more than three orders of magnitude. These results demonstrate that extremely high sensitivity for deuterium absorption and release can be achieved with a precise pressure measuring technique otherwise attributed exclusively to tritium scintillation methods.     

Ring-shaped field emission patterns from carbon nanotube films

Highly symmetric ring-shaped field emission patterns were observed from broad-area flat cathodes prepared by growing a film of vertically aligned carbon nanotubes (CNTs) on TiN coated Si substrates. The images were obtained utilizing a luminescent screen of a specially designed triode cell composed of parallel electrodes. The emission rings sporadically appeared during voltage scans in which the emission patterns and cathode currents were recorded. The fine structure and stability of the rings suggests that their formation is due to an emission state of an individual CNT. The observed patterns are consistent with models that predict the formation of emission rings produced by the inhomogeneous electron emission from CNTs. The macroscopic value of the electric field when the rings were observed was between 0.7 and 2.5 V/μm, and the emission current corresponding to individual rings was estimated to be in the range of 2–4 μA. Numerical simulation of electron trajectories for sidewall emission from similar shaped metallic structures is in qualitative and quantitative agreement with the experimentally observed ring-shaped field emission patterns. The results also appear consistent with a recent model [Marchand M, Journet C, Adessi C, Purcell ST. Phys Rev B 2009;80:245425] based on thermal-field emission due to Joule heating.     

Melt spinning as a microstructural analogue for aluminide diffusion coating

The feasibility of using melt spinning, of a high alloy nickel aluminide, as a microstructural analogue for aluminide diffusion coated nickel base superalloys is investigated in this paper. Transmission electron microscopy studies are used to characterize the relationship between coating and melt spun analogue microstructures. Attention is focused on three phases that are of principal importance in coating mechanical properties, namely: the B2 type phase coating matrix, L1₂ type precipitates and M ₂₃ X ₆ carbides.The microstructure of the matrix of the melt spun analogue is shown to closely resemble that of the coating. Evidence is presented that the formation of in the melt spun alloy generally occurs in a similar manner to that in the coating. The formation of M ₂₃ X ₆ in close association with in the melt spun materials is compared to similar events in the coatings. Limitations in the ability of the melt spun materials to recreate the microstructures resulting from incorporation of substrate M ₂₃ X ₆ into the coating and formation of M ₂₃ X ₆ within precursor phases are discussed.     

Analysis of leaf area index products from combination of MODIS Terra and Aqua data

A prototype product suite, containing the Terra 8-day, Aqua 8-day, Terra-Aqua combined 8- and 4-day products, was generated as part of testing for the next version (Collection 5) of the MODerate resolution Imaging Spectroradiometer (MODIS) leaf area index (LAI) products. These products were analyzed for consistency between Terra and Aqua retrievals over the following data subsets in North America: single 8-day composite over the whole continent and annual time series over three selected MODIS tiles (1200 × 1200 km). The potential for combining retrievals from the two sensors to derive improved products by reducing the impact of environmental conditions and temporal compositing period was also explored. The results suggest no significant discrepancies between large area (from continent to MODIS tile) averages of the Terra and Aqua 8-day LAI and surface reflectances products. The differences over smaller regions, however, can be large due to the random nature of residual atmospheric effects. High quality retrievals from the radiative transfer based algorithm can be expected in 90-95% of the pixels with mostly herbaceous cover and about 50-75% of the pixels with woody vegetation during the growing season. The quality of retrievals during the growing season is mostly restricted by aerosol contamination of the MODIS data. The Terra-Aqua combined 8-day product helps to minimize this effect and increases the number of high quality retrievals by 10-20% over woody vegetation. The combined 8-day product does not improve the number of high quality retrievals during the winter period because the extent of snow contamination of Terra and Aqua observations is similar. Likewise, cloud contamination in the single-sensor and combined products is also similar. The LAI magnitudes, seasonal profiles and retrieval quality in the combined 4-day product are comparable to those in the single-sensor 8-day products. Thus, the combined 4-day product doubles the temporal resolution of the seasonal cycle, which facilitates phenology monitoring in application studies during vegetation transition periods. Both Terra and Aqua LAI products show anomalous seasonality in boreal needle leaf forests, due to limitations of the radiative transfer algorithm to model seasonal variations of MODIS surface reflectance data with respect to solar zenith angle. Finally, this study suggests that further improvement of the MODIS LAI products is mainly restricted by the accuracy of the MODIS observations.     

Squirrel Search Algorithm Based Support Vector Machine for Congestion Control in WSN-IoT

Wireless Personal Communications - As the Wireless sensor network (WSN) has huge part in Internet of Things (IoT), it is used in different applications, for example, detecting climate and sending...     

The influence of a hot cathode vacuum gauge on the residual gas composition

The residual atmosphere of an UHV chamber is known to be influenced by the hot cathode gauge (HCG) via processes on the hot cathode and by ionisation. In the presence of such a gauge, some gases are pumped while several residuals are generated, depending on the condition of the chamber's inner surface, gauge parameters and gases that are released spontaneously or introduced on purpose.We analysed the influence of the HCG in three different cases of gas accumulation lasting typically for 1 h: (1) in the leak tight vessel, where the background outgassing from the walls was the only inflow Q_backg=1.6×10⁻⁸ mbar l H₂ s⁻¹, (2) during the constant nitrogen inflow in the vessel and (3) during the constant deuterium inflow. Both inflow values were in the order of 1×10⁻⁶ mbar l s⁻¹. The absolute total pressure in the 13 l system was monitored by a capacitance manometer. After the accumulation, the composition of the accumulated gases was analysed by a quadrupole mass spectrometer (QMS), calibrated with the gases of interest. Regarding the operation of the HCG, an obvious difference is noted both in the pressure rise curves and QMS spectra. The generation of carbon-contained residuals by the HCG was evident, but the most unexpected was its pumping action: nitrogen content decreased from 99% (HCG off) to 62% (HCG on) and deuterium content decreased from 65% (HCG off) to only 2% (HCG on).     

Estimation of global leaf area index and absorbed par usingradiative transfer models

A simple method for the estimation of global leaf area index (LAI) and fraction of photosynthetically active radiation absorbed by the vegetation (FAPAR) from atmospherically corrected Normalized Difference Vegetation Index (NDVI) observations is described. Recent improvements to the authors' three dimensional radiative transfer model of a vegetated surface are described. Example simulation results and a validation exercise are discussed. The model was utilized to derive land cover specific NDVI-LAI and NDVI-FAPAR relations. The method therefore requires stratification of global vegetation into cover types that are compatible with the radiative transfer model. Such a classification based on vegetation structure is proposed and a simple method for its derivation is presented. Proof-of-concept results are given to illustrate the feasibility of the proposed method     

The Moderate Resolution Imaging Spectroradiometer (MODIS): landremote sensing for global change research

The first Moderate Resolution Imaging Spectroradiometer (MODIS) instrument is planned for launch by NASA in 1998. This instrument will provide a new and improved capability for terrestrial satellite remote sensing aimed at meeting the needs of global change research. The MODIS standard products will provide new and improved tools for moderate resolution land surface monitoring. These higher order data products have been designed to remove the burden of certain common types of data processing from the user community and meet the more general needs of global-to-regional monitoring, modeling, and assessment. The near-daily coverage of moderate resolution data from MODIS, coupled with the planned increase in high-resolution sampling from Landsat 7, will provide a powerful combination of observations. The full potential of MODIS will be realized once a stable and well-calibrated time-series of multispectral data has been established. In this paper the proposed MODIS standard products for land applications are described along with the current plans for data quality assessment and product validation     

Inhibition of presenilin 1 expression is promoted by p53 and p21WAF-1 and results in apoptosis and tumor suppression

Pain on injection is one of the well-known side effects of propofol. Previous studies have shown several methods to alleviate this discomfort. We employed all these methods together to clarity whether pain-free injection of propofol was possible. Sixty adult patients premedicated with midazolam were studied. Control group patients (n = 20) received an induction dose of propofol via a vein on the dorsum of the hand at a slow injection speed with carrier i.v. fluid. Study group patients (n = 40) received i.v. fentanyl 0.1 mg, followed by bolus injection of cold propofol premixed with lidocaine (final concentration of lidocaine was 0.2%) in a forearm vein without carrier i.v. fluid. Eighteen patients (90%) in the control group experienced injection pain. In the study group, however, no patients complained of pain or discomfort. In conclusion, pain-free injection of propofol was possible when prior-administration of fentanyl, premixing of lidocaine, cooling to 4 degrees C, and rapid injection via a forearm vein without carrier i.v. fluid was the adopted precedure.