Exact Three Dimensional Casimir Force Amplitude, CC-function and Binder's Cumulant Ratio: Spherical Model Results

The three dimensional mean spherical model on a hypercubic lattice with a film geometry $L\times \infty ^2$ under periodic boundary conditions is considered in the presence of an external magnetic field $H$. The universal Casimir amplitude $\Delta$ and the Binder's cumulant ratio $B$ are calculated exactly and found to be $\Delta =-2\zeta (3)/(5\pi)\approx -0.153051$ and $B=2\pi /(\sqrt{5}\ln ^3[(1+\sqrt{5})/2]).$ A discussion on the relations between the finite temperature $C$-function, usually defined for quantum systems, and the excess free energy (due to the finite-size contributions to the free energy of the system) scaling function is presented. It is demonstrated that the $C$-function of the model equals 4/5 at the bulk critical temperature $T_c$. It is analytically shown that the excess free energy is a monotonically increasing function of the temperature $T$ and of the magnetic field $|H|$ in the vicinity of $T_c.$ This property is supposed to hold for any classical $d$-dimensional $O(n),n>2,$ model with a film geometry under periodic boundary conditions when $d\leq 3$. An analytical evidence is also presented to confirm that the Casimir force in the system is negative both below and in the vicinity of the bulk critical temperature $T_c.$Comment: 12 pages revtex, one eps figure, submitted to Phys. Rev E A set of references added with the text needed to incorporate them. Small changes in the title and in the abstrac

Osmium isotope systematics of the Proterozoic and Phanerozoic ophiolitic chromitites : in situ ion probe analysis of primary Os-rich PGM

Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 245 (2006): 777-791, doi:10.1016/j.epsl.2006.03.021.In-situ 187Os/188Os ratios are determined on Os-rich platinum-group minerals in podiform chromitites both in the Proterozoic ophiolite, Eastern Desert, Egypt, and in the Phanerozoic Oman ophiolite. Because they have very low Re/Os, these primary minerals reflect the initial 187Os/188Os ratios of their parental magmas. The platinum-group minerals (PGM) in the central Eastern Desert chromitites exhibit sub-chondritic to chondritic 187Os/188Os ratios, 0.1226 on average, which is lower than the primitive upper mantle evolution trend of a comparable age. Those of the southern Eastern Desert chromitites have more radiogenic Os, with supra-chondritic 187Os/188Os ratio of about 0.1293 on average, which could be due to crustal contamination. The three chromitite types in the northern part of the Oman ophiolite are almost indistinguishable in terms of their 187Os/188Os ratios; they have overlapping values ranging from sub-chondritic to supra-chondritic ratios. The PGE-rich, mantle chromitite samples have a wide range of 187Os/188Os ratio from 0.1230 up to 0.1376, with an average of 0.1299. The values of the PGE-poor mantle chromitites overlap in their 187Os/188Os ratios with PGE-rich chromites, but are less variable and have a significantly higher average ratio. The Moho transition zone (MTZ) chromitites are highly variable in the 187Os/188Os ratio, ranging from 0.1208 up to 0.1459. The wide range of 187Os/188Os ratios, from 0.1192 to 0.1459, in platinum-group minerals in Egyptian and Oman ophiolites can be attributed to the diversity of origin of their podiform chromitites. The Os-isotope data combined with spinel chemistry indicate that the way involved in podiform chromitite formation was not substantially different between the Proterozoic ophiolite of Egypt and the Phanerozoic ophiolite in northern Oman. The Os-isotope compositions of the mantle chromitites in the Proterozoic ophiolite of Egypt clearly suggest crustal contamination. The heterogeneity of 187Os/188Os ratios combined with the spinel chemistry and high PGE contents of the PGE-rich chromitite in the Oman ophiolite may give reliable evidence for high degree partial melting at a supra-subduction zone setting. Crustal contamination from the subducted slab, and assimilation of previously altered, lower crustal gabbro, may have contributed to the high Cr# spinel and radiogenic Os characteristics in chromitite formed in the mantle section and along the Moho transition zone, respectively.Kelemen and Hanghøj were supported in this project by US National Science Foundation grants OCE-9819666 and OCE-0118572

Genome-wide expression quantitative trait loci (eQTL) analysis in maize

<p>Abstract</p> <p>Background</p> <p>Expression QTL analyses have shed light on transcriptional regulation in numerous species of plants, animals, and yeasts. These microarray-based analyses identify regulators of gene expression as either cis-acting factors that regulate proximal genes, or trans-acting factors that function through a variety of mechanisms to affect transcript abundance of unlinked genes.</p> <p>Results</p> <p>A hydroponics-based genetical genomics study in roots of a <it>Zea mays </it>IBM2 Syn10 double haploid population identified tens of thousands of cis-acting and trans-acting eQTL. Cases of false-positive eQTL, which results from the lack of complete genomic sequences from both parental genomes, were described. A candidate gene for a trans-acting regulatory factor was identified through positional cloning. The unexpected regulatory function of a class I glutamine amidotransferase controls the expression of an ABA 8'-hydroxylase pseudogene.</p> <p>Conclusions</p> <p>Identification of a candidate gene underlying a trans-eQTL demonstrated the feasibility of eQTL cloning in maize and could help to understand the mechanism of gene expression regulation. Lack of complete genome sequences from both parents could cause the identification of false-positive cis- and trans-acting eQTL.</p

The IPBES Conceptual Framework - connecting nature and people

The first public product of the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) is its Conceptual Framework. This conceptual and analytical tool, presented here in detail, will underpin all IPBES functions and provide structure and comparability to the syntheses that IPBES will produce at different spatial scales, on different themes, and in different regions. Salient innovative aspects of the IPBES Conceptual Framework are its transparent and participatory construction process and its explicit consideration of diverse scientific disciplines, stakeholders, and knowledge systems, including indigenous and local knowledge. Because the focus on co-construction of integrative knowledge is shared by an increasing number of initiatives worldwide, this framework should be useful beyond IPBES, for the wider research and knowledge-policy communities working on the links between nature and people, such as natural, social and engineering scientists, policy-makers at different levels, and decision-makers in different sectors of society

Nonoverlap proportion and the representation of point-biserial variation.

We consider the problem of constructing a complete set of parameters that account for all of the degrees of freedom for point-biserial variation. We devise an algorithm where sort as an intrinsic property of both numbers and labels, is used to generate the parameters. Algebraically, point-biserial variation is represented by a Cartesian product of statistical parameters for two sets of [Formula: see text] data, and the difference between mean values (δ) corresponds to the representation of variation in the center of mass coordinates, (δ, μ). The existence of alternative effect size measures is explained by the fact that mathematical considerations alone do not specify a preferred coordinate system for the representation of point-biserial variation. We develop a novel algorithm for estimating the nonoverlap proportion (ρpb) of two sets of [Formula: see text] data. ρpb is obtained by sorting the labeled [Formula: see text] data and analyzing the induced order in the categorical data using a diagonally symmetric 2 × 2 contingency table. We examine the correspondence between ρpb and point-biserial correlation (rpb) for uniform and normal distributions. We identify the [Formula: see text], [Formula: see text], and [Formula: see text] representations for Pearson product-moment correlation, Cohen's d, and rpb. We compare the performance of rpb versus ρpb and the sample size proportion corrected correlation (rpbd), confirm that invariance with respect to the sample size proportion is important in the formulation of the effect size, and give an example where three parameters (rpbd, μ, ρpb) are needed to distinguish different forms of point-biserial variation in CART regression tree analysis. We discuss the importance of providing an assessment of cost-benefit trade-offs between relevant system parameters because 'substantive significance' is specified by mapping functional or engineering requirements into the effect size coordinates. Distributions and confidence intervals for the statistical parameters are obtained using Monte Carlo methods

Factoring a 2 x 2 contingency table.

We show that a two-component proportional representation provides the necessary framework to account for the properties of a 2 × 2 contingency table. This corresponds to the factorization of the table as a product of proportion and diagonal row or column sum matrices. The row and column sum invariant measures for proportional variation are obtained. Geometrically, these correspond to displacements of two point vectors in the standard one-simplex, which are reduced to a center-of-mass coordinate representation, [Formula: see text]. Then, effect size measures, such as the odds ratio and relative risk, correspond to different perspective functions for the mapping of (δ, μ) to [Formula: see text]. Furthermore, variations in δ and μ will be associated with different cost-benefit trade-offs for a given application. Therefore, pure mathematics alone does not provide the specification of a general form for the perspective function. This implies that the question of the merits of the odds ratio versus relative risk cannot be resolved in a general way. Expressions are obtained for the marginal sum dependence and the relations between various effect size measures, including the simple matching coefficient, odds ratio, relative risk, Yule's Q, ϕ, and Goodman and Kruskal's τc|r. We also show that Gini information gain (IGG) is equivalent to ϕ2 in the classification and regression tree (CART) algorithm. Then, IGG can yield misleading results due to the dependence on marginal sums. Monte Carlo methods facilitate the detailed specification of stochastic effects in the data acquisition process and provide a practical way to estimate the confidence interval for an effect size

The role of magnetic field gradients in nuclear magnetic resonance

A high resolution NMR probe was modified with gradient coils (31 mm diameter) for the measurement of translational diffusion and for microscopic imaging, and a larger set of gradient coils (15 cm diameter) was constructed for surface coil diffusion measurements. The magnitudes of the gradients produced by these coils were determined from the linewidths and lineshapes of gradient spectra. In diffusion experiments using the pulsed gradient method of Stejskal and Tanner, induced eddy currents and slow variation of the magnetic field at the sample interfered with measurements at short echo times. For these experiments the known diffusion coefficient of water was used to determine the effective gradient in each experiment. The diffusion coefficient of acrylonitrile was measured from the decay of single, double and triple quantum echoes using a modified pulsed field gradient spin echo pulse sequence. In the second part of this thesis, three examples of living systems were studied. The first involved the application of pulsed gradient spin echo measurements to characterize the motion of water and lipid, in-vivo, in human forearm. Spin echo spectra from human forearm gave a water signal that was attributed to extracellular water because of relatively long spin-spin relaxation time (0.8 s) compared to that of intracellular water (20-30 ms). Comparison of the diffusivity of water, from experiments at two different echo times suggest that the major part of the motion of water, in-vivo, was due to directionally randomized bulk flow rather than molecular diffusion. The second application involved the chemical shift resolved mapping of the proton distribution, in one-dimension, along the anteroposterior direction, of pupae of the Douglas-fir cone moth Barbara colfaxiana. Proton distribution maps showed that the distribution of the aqueous fluid depended upon the vertical orientation, head pointing upward or downward, of the pupae. Finally, two dimensional images of mature caps of the marine alga Acetabularia mediterranea were obtained using the normal spin echo sequence as well as with T₁, T₂ and diffusion contrasting. D₂O—contrasting was obtained by briefly submerging the caps in D₂O. All of these images showed features resembling the radial structure of the caps. The resolution was estimated by comparison with microscopic views of the caps and was found to be 0.1 mm, determined as the smallest distinguishable feature in the image.Science, Faculty ofChemistry, Department ofGraduat

A Continuous-Flow Capillary Mixing Method to Monitor Reactions on the Microsecond Time Scale

A continuous-flow capillary mixing apparatus, based on the original design of Regenfuss et al. (Regenfuss, P., R. M. Clegg, M. J. Fulwyler, F. J. Barrantes, and T. M. Jovin. 1985. Rev. Sci. Instrum. 56:283--290), has been developed with significant advances in mixer design, detection method and data analysis. To overcome the problems associated with the free-flowing jet used for observation in the original design (instability, optical artifacts due to scattering, poor definition of the geometry), the solution emerging from the capillary is injected directly into a flow-cell joined to the tip of the outer capillary via a ground-glass joint. The reaction kinetics are followed by measuring fluorescence versus distance downstream from the mixer, using an Hg(Xe) arc lamp for excitation and a digital camera with a UV-sensitized CCD detector for detection. Test reactions involving fluorescent dyes indicate that mixing is completed within 15 #s of its initiation and that the dead time of the measurement is 45 # 5 #s, which represents a #30-fold improvement in time resolution over conventional stopped-flow instruments. The high sensitivity and linearity of the CCD camera have been instrumental in obtaining artifact-free kinetic data over the time window from #45 #s to a few milliseconds with signal-to-noise levels comparable to those of conventional methods. The scope of the method is discussed and illustrated with an example of a protein folding reaction