The Principio Project: Procedures for Transcribing Witnesses

Instructions for transcribers making electronic transcription files of Greek manuscripts of the Gospel according to John as part of the AHRB Principio Project. This is the final version, as revised on 13.12.2001. No earlier versions have been archived independently

Strongly Anisotropic Transport in Higher Two-Dimensional Landau Levels

Low-temperature, electronic transport in Landau levels N>1 of a two-dimensional electron system is strongly anisotropic. At half-filling of either spin level of each such Landau level the magnetoresistance either collapses to form a deep minimum or is peaked in a sharp maximum, depending on the in-plane current direction. Such anisotropies are absent in the N=0 and N=1 Landau level, which are dominated by the states of the fractional quantum Hall effect. The transport anisotropies may be indicative of a new many particle state, which forms exclusively in higher Landau levels.Comment: 12 pages, 3 Postscript figure

Pelvis morphology suggests that early Mesozoic birds were too heavy to contact incubate their egg

Numerous new fossils have driven an interest in reproduction of early birds, but direct evidence remains elusive. No Mesozoic avian eggs can be unambiguously assigned to a species, which hampers our understanding of the evolution of contact incubation, which is a defining feature of extant birds. Compared to living species, eggs of Mesozoic birds are relatively small, but whether the eggs of Mesozoic birds could actually have borne the weight of a breeding adult has not yet been investigated. We estimated maximal egg breadth for a range of Mesozoic avian taxa from the width of the pelvic canal defined by the pubic symphysis. Known elongation ratios of Mesozoic bird eggs allowed us to predict egg mass and hence the load mass an egg could endure before cracking. These values were compared to the predicted body masses of the adult birds based on skeletal remains. Based on 21 fossil species, we show that for nonornithothoracine birds body mass was 187% of the load mass of the eggs. For Enantiornithes, body mass was 127% greater than the egg load mass, but some early Cretaceous ornithuromorphs were 179% heavier than their eggs could support. Our indirect approach provides the best evidence yet that early birds could not have sat on their eggs without running the risk of causing damage. We suggest that contact incubation evolved comparatively late in birds

Sulfur Mineralogy at the Mars Phoenix Landing Site

The Mars Phoenix Scout mission landed at the northernmost location (approx.68deg N) of any lander or rover on the martian surface. This paper compares the S mineralogy at the Phoenix landing site with S mineralogy of soils studied by previous Mars landers. S-bearing phases were not directly detected by the payload onboard the Phoenix spacecraft. Our objective is to derive the possible mineralogy of S-bearing phases at the Phoenix landing site based upon Phoenix measurements in combination with orbital measurements, terrestrial analog and Martian meteorite studies, and telescopic observations

Experimental Evidence for a Spin-Polarized Ground State in the \nu=5/2 Fractional Quantum Hall Effect

We study the \nu=5/2 even-denominator fractional quantum Hall effect (FQHE) over a wide range of magnetic (B) field in a heterojunction insulated gate field-effect transistor (HIGFET). The electron density can be tuned from n=0 to 7.6 \times 10^{11} cm^{-2} with a peak mobility \mu = 5.5 \times 10^6 cm^2/Vs. The \nu=5/2 state shows a strong minimum in diagonal resistance and a developing Hall plateau at magnetic fields as high as 12.6T. The strength of the energy gap varies smoothly with B-field. We interpret these observations as strong evidence for a spin-polarized ground state at \nu=5/2.Comment: new references adde

Training data distribution significantly impacts the estimation of tissue microstructure with machine learning

Purpose Supervised machine learning (ML) provides a compelling alternative to traditional model fitting for parameter mapping in quantitative MRI. The aim of this work is to demonstrate and quantify the effect of different training data distributions on the accuracy and precision of parameter estimates when supervised ML is used for fitting. Methods We fit a two- and three-compartment biophysical model to diffusion measurements from in-vivo human brain, as well as simulated diffusion data, using both traditional model fitting and supervised ML. For supervised ML, we train several artificial neural networks, as well as random forest regressors, on different distributions of ground truth parameters. We compare the accuracy and precision of parameter estimates obtained from the different estimation approaches using synthetic test data. Results When the distribution of parameter combinations in the training set matches those observed in healthy human data sets, we observe high precision, but inaccurate estimates for atypical parameter combinations. In contrast, when training data is sampled uniformly from the entire plausible parameter space, estimates tend to be more accurate for atypical parameter combinations but may have lower precision for typical parameter combinations. Conclusion This work highlights that estimation of model parameters using supervised ML depends strongly on the training-set distribution. We show that high precision obtained using ML may mask strong bias, and visual assessment of the parameter maps is not sufficient for evaluating the quality of the estimates

Compactness and existence results in weighted Sobolev spaces of radial functions. Part II: Existence

We prove existence and multiplicity results for finite energy solutions to the nonlinear elliptic equation $$-\triangle u+V\left( \left| x\right| \right) u=g\left( \left| x\right| ,u\right) \quad \textrm{in }\Omega \subseteq \mathbb{R}^{N},\ N\geq 3,$$ where $\Omega$ is a radial domain (bounded or unbounded) and $u$ satisfies $u=0$ on $\partial \Omega$ if $\Omega \neq \mathbb{R}^{N}$ and $u\rightarrow 0$ as $\left| x\right| \rightarrow \infty$ if $\Omega$ is unbounded. The potential $V$ may be vanishing or unbounded at zero or at infinity and the nonlinearity $g$ may be superlinear or sublinear. If $g$ is sublinear, the case with $g\left( \left| \cdot \right| ,0\right) \neq 0$ is also considered.Comment: 29 pages, 8 figure

Hund's Rule for Composite Fermions

We consider the ``fractional quantum Hall atom" in the vanishing Zeeman energy limit, and investigate the validity of Hund's maximum-spin rule for interacting electrons in various Landau levels. While it is not valid for {\em electrons} in the lowest Landau level, there are regions of filling factors where it predicts the ground state spin correctly {\em provided it is applied to composite fermions}. The composite fermion theory also reveals a ``self-similar" structure in the filling factor range $4/3>\nu>2/3$.Comment: 10 pages, revte

Pulsed Magnetic Field Measurements of the Composite Fermion Effective Mass

Magnetotransport measurements of Composite Fermions (CF) are reported in 50 T pulsed magnetic fields. The CF effective mass is found to increase approximately linearly with the effective field $B^*$, in agreement with our earlier work at lower fields. For a $B^*$ of 14 T it reaches $1.6m_e$, over 20 times the band edge electron mass. Data from all fractions are unified by the single parameter $B^*$ for all the samples studied over a wide range of electron densities. The energy gap is found to increase like $\sqrt{B^*}$ at high fields.Comment: Has final table, will LaTeX without error

Fractional Quantum Hall States in Low-Zeeman-Energy Limit

We investigate the spectrum of interacting electrons at arbitrary filling factors in the limit of vanishing Zeeman splitting. The composite fermion theory successfully explains the low-energy spectrum {\em provided the composite fermions are treated as hard-core}.Comment: 12 pages, revte