Magnetic field tuning of antiferromagnetic Yb3_{3}Pt4_{4}

We present measurements of the specific heat, magnetization, magnetocaloric effect and magnetic neutron diffraction carried out on single crystals of antiferromagnetic Yb$_{3}$Pt$_{4}$, where highly localized Yb moments order at $T_{\rm N}=2.4$ K in zero field. The antiferromagnetic order was suppressed to $T_{\rm N}\rightarrow 0$ by applying a field of 1.85 T in the $ab$ plane. Magnetocaloric effect measurements show that the antiferromagnetic phase transition is always continuous for $T_{\rm N}>0$, although a pronounced step in the magnetization is observed at the critical field in both neutron diffraction and magnetization measurements. These steps sharpen with decreasing temperature, but the related divergences in the magnetic susceptibility are cut off at the lowest temperatures, where the phase line itself becomes vertical in the field-temperature plane. As $T_{\rm N}\rightarrow0$, the antiferromagnetic transition is increasingly influenced by a quantum critical endpoint, where $T_{\rm N}$ ultimately vanishes in a first order phase transition.Comment: 9 pages, 6 figure

743-2 Superiority of 3D Echo vs 2D Echo for Quantitating Wall Motion Abnormality as an Index of Myocardial Infarction Size

Two-dimensional echo estimations of the fraction of myocardium showing abnormal wall motion (AWM) are often used as an index of infarct size, to establish prognosis and guide therapy. However 2D echo methods rely on image plane and geometric assumptions which may not be valid when infarction affects ventricular shape. 3D echo reconstruction of the endocardial surface can eliminate the need for these assumptions. Purpose; To use 3D echo and 2D echo to quantitate AWM in experimental acute infarction, and to correlate the extent of AWM with the pathologic determination of infarct size.MethodsCoronary ligation was performed in 14 open chest dogs, and echo imaging performed after 6 hours. 3D echo used 7–8 spatially registered short axis cross-sections to measure % of endocardial surface showing AWM. Two 2D echo methods using multiple, non-spatially registered images were evaluated. Both compared summed endocardial length showing AWM to the total of the endocardial circumferences, expressed as %. Method #1 used 7-8 short-axis slices. Method #2 used basal, mid, apical short axis + apical 4-and 2-chamber views. Percent LV mass (% mass) infarcted was determined by a standard technique.Resultsregression of [x = echo %AWM] vs [y = %mass infarcted]Echo Methodr valueStandard Error of the EstimateEquationp value3D0.94±2.6%y =0.71x-1.81%<0.000120-#10.82±4.3%y =0.50x-0.66%0.001520-#2074±5,1%Y =0.47x-1.25%0.0058ConclusionThree-dimensional echocardiography is a more accurate means of non-invasively estimating myocardial infarct size in this animal model, compared to 2D echo methods

Symmetric Versus Nonsymmetric Structure of the Phosphorus Vacancy on InP(110)

The atomic and electronic structure of positively charged P vacancies on InP(110) surfaces is determined by combining scanning tunneling microscopy, photoelectron spectroscopy, and density-functional theory calculations. The vacancy exhibits a nonsymmetric rebonded atomic configuration with a charge transfer level 0.75+-0.1 eV above the valence band maximum. The scanning tunneling microscopy (STM) images show only a time average of two degenerate geometries, due to a thermal flip motion between the mirror configurations. This leads to an apparently symmetric STM image, although the ground state atomic structure is nonsymmetric.Comment: 5 pages including 3 figures. related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

A Field Approach to 3D Gene Expression Pattern Characterization

We present a vector field method for obtaining the spatial organization of 3D patterns of gene expression based on gradients and lines of force obtained by numerical integration. The convergence of these lines of force in local maxima are centers of gene expression, providing a natural and powerful framework to characterize the organization and dynamics of biological structures. We apply this novel methodology to analyze the expression pattern of the Enhanced Green Fluorescent Protein (EGFP) driven by the promoter of light chain myosin II during zebrafish heart formation.Comment: 9 pages, 2 figures, The following article has been submitted to Applied Physics Letters. If it is published, it will be found online at http://apl.aip.or

Equinodermos del Cámbrico de España: situación actual de las investigaciones y perspectivas futuras

This paper reviews all finds of Cambrian echinoderms from Spain since their first discovery in the XIX century. Recent research techniques used for the study of echinoderms are also described, providing a guide for procedure.
 
 Sampling in new fossiliferous localities from the Cambrian of North Spain and the review of classic ones has yielded more than 2,000 echinoderm fossils. These include species belonging to five major classes, Cincta, Eocrinoidea, Edrioasteroidea, Stylophora and Ctenocystoidea, which show the highest diversity reported from Gondwana.
 
 These results suggest that echinoderms underwent major diversification during the middle Cambrian, with many groups more widely distributed than previously thought. These arguments suggest that many classes originated in the lower Cambrian where only a few taxa have been described. Finally, I offer some suggestions about where research efforts need to be focussed for a better knowledge of Cambrian echinoderm faunas in Gondwana.<br><br>En este trabajo se presenta una revisión histórica de todos los equinodermos cámbricos descubier tos en España, desde su primer hallazgo a finales del siglo XIX y las técnicas actuales que se utilizan para su estudio.
 
 El muestreo sistemático de nuevas localidades cámbricas del Norte de España y la revisión de otras ya conocidas, ha proporcionado más de 2.000 ejemplares de equinodermos. En total se han reconocido taxones pertenecientes a cinco clases: Cincta, Eocrinoidea, Edrioasteroidea, Stylophora y Ctenocystoidea, que muestran la mayor diversidad para este periodo en Gondwana.
 
 Estos hallazgos muestran que los equinodermos alcanzaron su primer pico de diversidad durante el Cámbrico medio. Esto, unido a la amplia distribución paleobiogeográfica de algunos clados, nos advierte de un origen para muchos grupos en el Cámbrico inferior, donde sólo unos pocos taxones han sido descritos a nivel mundial. Por último se dan algunas ideas de hacia dónde se podrían dirigir los esfuerzos en este campo de conocimiento

Enclaves in peraluminous allochthonous granites: The case study of Cabeza de Araya Batolith (Cáceres, Spain)

This paper deals with the preliminar study of the petrography and geochemistry of the scarce enclaves of the peraluminous granites of Cabeza de Araya. Three types of enclaves have been distinguished: xenolidc enclaves, leucocratic igneous enclaves and tonalitic igneous enclaves. From geochemical diagrams and mass balance procedures, the different hypothesis have been tested. The main conclusion is that in absence of water-saturated melting processes of crustal rocks (pelites and graywackes metasediments CXC) the most plausible model is the reaction zone in which a contribution of some 25% ofgabbroic rocks should be necessary to account the composition of the most mafic tonalitic enclave