Calibration and validation of the crop growth model LINTUL for grain amaranth (Amaranthus sp.)

Grain amaranth, a C4 plant, is a promising pseudocereal due to its valuable grain components. Knowledge of crop growth parameters is crucial for the introduction of a new crop, and the use of a crop model can help to understand yield formation and yield limiting processes. The aim of the study was to parameterise and validate the model LINTUL for grain amaranth. Basically, LINTUL estimates dry matter production from daily intercepted radiation and light use efficiency under potential growth conditions, i. e. without occurrence of any other limiting factors. A field experiment with the A. hypochondriacus genotypes „Neuer Typ“ and „Anderer Typ“ was carried out under semiarid conditions in 2004 and 2005. Field data of individual years were used for parameterisation while independent observations of the other year allowed for cross-validation, respectively. The estimated light use efficiency ranged between 2.5 and 2.8 g MJ-1 (total biomass per accumulated PAR). Specific leaf area estimates were lower in observations of 2004 (0.014 m2 g-1) than in observations of 2005 (0.018 m2 g-1). The light extinction coefficient of both genotypes measured before heading was 1.1. The effective sum of temperature (above a given threshold of 8°C) to anthesis was 554°C d for the genotype „Neuer Typ“ and 640°C d for „Anderer Typ“ in both years. The effective sum of temperature to maturity was 1127°C d in 2004, and 1249°C d in 2005 independent of the genotype. Model predictions of total biomass agreed well (RMSE: 92 to 136 g m-2) with the observed biomass throughout the growing cycle including final harvest (between 749 and 1172 g m-2). The estimated grain yield over time (RMSE: 47 to 112 g m-2) matched the field observations including final grain yield (between 220 and 367 g m-2) with less accuracy. The leaf area index was overestimated throughout the growing cycle from heading onwards to seed filling. The sharp initial increase in grain yield was underestimated suggesting that currently produced assimilates could not meet the growth capacity of the young seeds but might be complemented by internal re-translocation of biomass

Finite-size effects in amorphous Fe90Zr10/Al75Zr25 multilayers

The thickness dependence of the magnetic properties of amorphous Fe90Zr10 layers has been explored using Fe90Zr10/Al75Zr25 multilayers. The Al75Zr25 layer thickness is kept at 40 \AA, while the thickness of the Fe90Zr10 layers is varied between 5 and 20 \AA. The thickness of the Al75Zr25 layers is sufficiently large to suppress any significant interlayer coupling. Both the Curie temperature and the spontaneous magnetization decrease non-linearly with decreasing thickness of the Fe90Zr10 layers. No ferromagnetic order is observed in the multilayer with 5 {\AA} Fe90Zr10 layers. The variation of the Curie temperature $T_c$ with the Fe90Zr10 layer thickness $t$ is fitted with a finite-size scaling formula [1-\Tc(t)/\Tc(\infty)]=[(t-t')/t_0]^{-\lambda}, yielding $\lambda=1.2$, and a critical thickness $t'=6.5$ \AA, below which the Curie temperature is zero.Comment: 8 pages, 8 figure

On the Sign Problem in the Hirsch-Fye Algorithm for Impurity Problems

We show that there is no fermion sign problem in the Hirsch and Fye algorithm for the single-impurity Anderson model. Beyond the particle-hole symmetric case for which a simple proof exists, this has been known only empirically. Here we prove the nonexistence of a sign problem for the general case by showing that each spin trace for a given Ising configuration is separately positive. We further use this insight to analyze under what conditions orbitally degenerate Anderson models or the two-impurity Anderson model develop a sign.Comment: 2 pages, no figure; published versio

Static critical exponents of the ferromagnetic transition in spin glass re-entrant systems

The static critical phenomenology near the Curie temperature of the re-entrant metallic alloys Au_0.81Fe_0.19, Ni_0.78Mn_0.22, Ni_0.79Mn_0.21 and amorphous a-Fe_0.98Zr_0.08 is studied using a variety of experimental techniques and methods of analysis. We have generally found that the values for the exponents alpha, beta, gamma and delta depart significantly from the predictions for the 3D Heisenberg model and are intermediate between these expectations and the values characterizing a typical spin glass transition. Comparing the exponents obtained in our work with indices for other re-entrant systems reported in the literature, a weak universality class may be defined where the exponents distribute within a certain range around average values.Comment: 17 pages, 11 figure

Artificial Neural Network-based error compensation procedure for low-cost encoders

An Artificial Neural Network-based error compensation method is proposed for improving the accuracy of resolver-based 16-bit encoders by compensating for their respective systematic error profiles. The error compensation procedure, for a particular encoder, involves obtaining its error profile by calibrating it on a precision rotary table, training the neural network by using a part of this data and then determining the corrected encoder angle by subtracting the ANN-predicted error from the measured value of the encoder angle. Since it is not guaranteed that all the resolvers will have exactly similar error profiles because of the inherent differences in their construction on a micro scale, the ANN has been trained on one error profile at a time and the corresponding weight file is then used only for compensating the systematic error of this particular encoder. The systematic nature of the error profile for each of the encoders has also been validated by repeated calibration of the encoders over a period of time and it was found that the error profiles of a particular encoder recorded at different epochs show near reproducible behavior. The ANN-based error compensation procedure has been implemented for 4 encoders by training the ANN with their respective error profiles and the results indicate that the accuracy of encoders can be improved by nearly an order of magnitude from quoted values of ~6 arc-min to ~0.65 arc-min when their corresponding ANN-generated weight files are used for determining the corrected encoder angle.Comment: 16 pages, 4 figures. Accepted for Publication in Measurement Science and Technology (MST

Vitamin B6 Deficiency and Galactose Induced Alterations in Morphology and Osmotic Fragility of Rat Erythrocytes

Recently, red blood cells have been investigated mainly for alterations in ion transporting capacity, membrane bound enzymes or modifications in the structure of its individual constituents in clinical and experimental urolithiasis. However, the implication of such modifications on the physical state or morphology of cells has not been investigated. Scanning electron microscopic studies performed in vitamin B6 deficient and/or galactose fed rat (established hyperoxaluric models) erythrocytes, showed the presence of large number of stomatocytes, spherocytes and other variously deformed cells as compared to discocytic cells seen in normal control group. These changes in shape were in concurrence with red cell osmotic fragility, which decreased both in vitamin B6 deficient and vitamin B6 deficient + galactose fed group (19% and 33% hemolysis at 4 g/l NaCl, respectively) while it increased in galactose control group (73% hemolysis at 4 g/l NaCl) as compared to normal control group (55 % hemolysis at 4 g/l NaCl). These morphological and physical state alterations could be correlated with red blood cells\u27 membrane cholesterol and phospholipid sub-class distribution. These findings suggest that some structural membrane changes occur due to vitamin B6 deficiency and/or galactose feeding, which may be responsible for the altered membrane functions known to be associated with pathogenesis of urolithiasis

Black Hole Entropy from Spin One Punctures

Recent suggestion, that the emission of a quantum of energy corresponding to the asymptotic value of quasinormal modes of a Schwarzschild black hole should be associated with the loss of spin one punctures from the black hole horizon, fixes the Immirzi parameter to a definite value. We show that saturating the horizon with spin one punctures reproduces the earlier formula for the black hole entropy, including the $ln (area)$ correction with definite coefficient (- 3/2) for large area.Comment: 4 pages. RevTe

Post Quantum Cryptography from Mutant Prime Knots

By resorting to basic features of topological knot theory we propose a (classical) cryptographic protocol based on the `difficulty' of decomposing complex knots generated as connected sums of prime knots and their mutants. The scheme combines an asymmetric public key protocol with symmetric private ones and is intrinsecally secure against quantum eavesdropper attacks.Comment: 14 pages, 5 figure