Evaluating the mineral nutrient status of fresh pasture herbage using laser-induced breakdown spectroscopy

Comprehensive determination of the mineral nutrient status of pasture or horticultural crops currently requires leaf or herbage samples to be harvested and taken to a laboratory for analysis, which is both labour-intensive and time-consuming. This study examined the potential of laser-induced breakdown spectroscopy (LIBS) to provide immediate, in-field assessment of the mineral nutrient status of standing plants. Success would offer the prospects of spatially and temporally improved knowledge of plant status and of real-time remediation of nutrient deficiency. The mineral nutrient status of fresh pasture herbage has been evaluated using an Applied Photonics Ltd？ LIBS-6 system, comprising a Qswitched Nd:YAG laser, a SpectroModule-6 spectrometer (covering wavelengths in the range ~185 – 1064 nm) and an ICE 450 water-cooled Laser power supply. LIBS spectra obtained from the fresh pasture samples were collected with the aim of determining the nutrient status of the herbage. An enclosed Modular Sample Chamber housed the Qswitched Nd:YAG laser, generating energy in the near infrared region at λ = 1064nm. The laser power was set to 100mW per pulse. Samples of approximately 50g of fresh ryegrass and ryegrass/clover mixed pasture were loaded into a sample holder which allowed a flat ‗carpet‘ of individual leaves to be presented at a relatively uniform distance from the laser. The optimum vertical distance between sample and laser was determined by maximising spectra amplitudes. Automated control of the translation stage supporting the sample holder was used to ensure each shot of the laser was acquired from a fresh location. Spectrum sets comprising both 100 individual spectra and 100 shot accumulated spectra were obtained from each sample under both air and under the inert gas, argon. Following the spectral analysis of the fresh pasture, each sample was sent to a commercial laboratory for standard nutrient analysis, providing elementary composition on the most common plant elements (N, P, K, S, Ca, Mg, Na, Fe, Mn, Zn, Cu and B). Once standard nutrient analysis was completed a second set of spectra was taken from tablets formed from compressed dried ground powder remaining after laboratory analysis. To date, initial results from simple chemometric analysis have shown limited success in predicting the nutrient content of fresh pasture with slightly improved results in estimating tablet composition. While initial analyses have concentrated on trends and correlations between actual spectra and laboratory analysis, known emission spectra, have for the meantime, been ignored. Further in-depth analysis using more robust chemometric analysis, utilizing known emission spectra and adjusting for variations in plasma intensity are currently underway and are expected to improve the accuracy of composition measurement

Quantum Gravity and Non-unitarity in Black Hole Evaporation

We discuss the relevance of quantum gravitational corrections to the functional Schr\"odinger equation for the information loss paradox in black hole evaporation. These corrections are found from the Wheeler-DeWitt equation through a semiclassical expansion scheme. The dominant contribution in the final evaporation stage, when the black hole approaches the Planck regime, is a term which explicitly violates unitarity in the non-gravitational sector. While pure states remain pure, there is an increase in the degree of purity for non-pure states in this sector. This result holds irrespective of whether full quantum gravity respects unitarity or not.Comment: 6 pages, Latex, ZU-TH 25/9

The effect of nonmagnetic impurities on the local density of states in s-wave superconductors

We study the effect of nonmagnetic impurities on the local density of states (LDOS) in s-wave superconductors. The quasiclassical equations of superconductivity are solved selfconsistently to show how LDOS evolves with impurity concentration. The spatially averaged zero-energy LDOS is a linear function of magnetic induction in low fields, N(E=0)=cB/H_{c2}, for all impurity concentration. The constant of proportionality "c" depends weakly on the electron mean free path. We present numerical data for differential conductance and spatial profile of zero-energy LDOS which can help in estimating the mean free path through the LDOS measurement.Comment: 7 pages, 7 figures (high quality color figure available on request

Measuring idiosyncratic risks in leveraged buyout transactions

We use a CCA model to calculate implied idiosyncratic risks of LBO transactions. A decisive model feature is the consideration of amortization. From the model, the asset value volatility and the equity value volatility can be derived via a numerical procedure. For a sample of 40 LBO transactions we determine the necessary model parameters and calculate the transactions' implied idiosyncratic risks. We discuss the expected model sensitivities and verify them by variation of the input parameters. With the knowledge of the returns to the equity investors of the LBOs we are able to calculate Sharpe Ratios on individual transaction levels for the first time, thereby fully incorporating the superimposed leverage risks.Idiosyncratic Risk; Private Equity; Benchmarking;

An Introduction to Slice-Based Cohesion and Coupling Metrics

This report provides an overview of slice-based software metrics. It brings together information about the development of the metrics from Weiser’s original idea that program slices may be used in the measurement of program complexity, with alternative slice-based measures proposed by other researchers. In particular, it details two aspects of slice-based metric calculation not covered elsewhere in the literature: output variables and worked examples of the calculations. First, output variables are explained, their use explored and standard reference terms and usage proposed. Calculating slice-based metrics requires a clear understanding of ‘output variables’ because they form the basis for extracting the program slices on which the calculations depend. This report includes a survey of the variation in the definition of output variables used by different research groups and suggests standard terms of reference for these variables. Our study identifies four elements which are combined in the definition of output variables. These are the function return value, modified global variables, modified reference parameters and variables printed or otherwise output by the module. Second, slice-based metric calculations are explained with the aid of worked examples, to assist newcomers to the field. Step-by-step calculations of slice-based cohesion and coupling metrics based on the vertices output by the static analysis tool CodeSurfer (R) are presented and compared with line-based calculations