Charge-ice dynamics in the negative thermal expansion material Cd(CN)2_2

We use variable-temperature (150--300\,K) single-crystal X-ray diffraction to re-examine the interplay between structure and dynamics in the ambient phase of the isotropic negative thermal expansion (NTE) material Cd(CN)$_2$. We find strong experimental evidence for the existence of low-energy vibrational modes that involve off-centering of Cd$^{2+}$ ions. These modes have the effect of increasing network packing density---suggesting a mechanism for NTE that is different to the generally-accepted picture of correlated Cd(C/N)$_4$ rotation modes. Strong local correlations in the displacement directions of neighbouring cadmium centres are evident in the existence of highly-structured diffuse scattering in the experimental X-ray diffraction patterns. Monte Carlo simulations suggest these patterns might be interpreted in terms of a basic set of `ice-rules' that establish a mapping between the dynamics of Cd(CN)$_2$ and proton ordering in cubic ice VII.Comment: 5 pages, 5 figures, submitted to PR

The application of inelastic neutron scattering to investigate the interaction of methyl propanoate with silica

A modern industrial route for the manufacture of methyl methacrylate involves the reaction of methyl propanoate and formaldehyde over a silica-supported Cs catalyst. Although the process has been successfully commercialised, little is known about the surface interactions responsible for the forward chemistry. This work concentrates upon the interaction of methyl propanoate over a representative silica. A combination of infrared spectroscopy, inelastic neutron scattering, DFT calculations, X-ray diffraction and temperature-programmed desorption is used to deduce how the ester interacts with the silica surface

Mirror Maps in Chern-Simons Gauge Theory

We describe mirror symmetry in N=2 superconformal field theories in terms of a dynamical topology changing process of the principal fiber bundle associated with a topological membrane. We show that the topological symmetries of Calabi-Yau sigma-models can be obtained from discrete geometric transformations of compact Chern-Simons gauge theory coupled to charged matter fields. We demonstrate that the appearence of magnetic monopole-instantons, which interpolate between topologically inequivalent vacua of the gauge theory, implies that the discrete symmetry group of the worldsheet theory is realized kinematically in three dimensions as the magnetic flux symmetry group. From this we construct the mirror map and show that it corresponds to the interchange of topologically non-trivial matter field and gauge degrees of freedom. We also apply the mirror transformation to the mean field theory of the quantum Hall effect. We show that it maps the Jain hierarchy into a new hierarchy of states in which the lowest composite fermions have the same filling fractions.Comment: 40 pages LaTeX, 4 postscript files, uses psfig.sty; minor textual changes, typos corrected, references adde

The Assembly History of Field Spheroidals: Evolution of Mass-to-light Ratios and Signatures of Recent Star Formation

We present a comprehensive catalog of high signal-to-noise spectra obtained with the DEIMOS spectrograph on the Keck II telescope for a sample of F850LP<22.43 (AB) field spheroidal (E+S0s; 163) and bulge dominated disk (61) galaxies in the redshift range 0.2<z<1.2. We examine the zero point, tilt and scatter of the Fundamental Plane (FP) as a function of redshift and morphological properties, carefully accounting for luminosity-dependent biases via Montecarlo simulations. The evolution of the overall FP can be represented by a mean change in effective mass-to-light ratio given by <d \log (M/L_{\rm B})/dz>=-0.72^{+0.07}_{-0.05}\pm0.04. However, this evolution depends significantly on the dynamical mass, being slower for larger masses as reported in a previous letter. In addition, we separately show the intrinsic scatter of the FP increases with redshift as d(rms(M/L_{\rm B}))/dz=0.040\pm0.015. Although these trends are consistent with single burst populations which formed at $z_f>2$ for high mass spheroidals and z_{f}~1.2 for lower mass systems, a more realistic picture is that most of the stellar mass formed in all systems at z>2 with subsequent activity continuing to lower redshifts (z<1.2). The fraction of stellar mass formed at recent times depend strongly on galactic mass, ranging from <1% for masses above 10^{11.5} M_{\odot} to 20-40% below 10^{11} M_{\odot}. Independent support for recent activity is provided by spectroscopic ([\ion{O}{2}] emission, H\delta) and photometric (blue cores and broad-band colors) diagnostics. Via the analysis of a large sample with many independent diagnostics, we are able to reconcile previously disparate interpretations of the assembly history of field spheroidals. [Abridged]Comment: 26 pages including 24 figures, submitted to ApJ. Complete and compact version with full resolution images available at http://www.astro.ucla.edu/~ttreu/ms.pd

An international comparative study of blood pressure in populations of European vs. African descent

Background: The consistent finding of higher prevalence of hypertension in US blacks compared to whites has led to speculation that African-origin populations are particularly susceptible to this condition. Large surveys now provide new information on this issue. Methods: Using a standardized analysis strategy we examined prevalence estimates for 8 white and 3 black populations (N = 85,000 participants). Results: The range in hypertension prevalence was from 27 to 55% for whites and 14 to 44% for blacks. Conclusions: These data demonstrate that not only is there a wide variation in hypertension prevalence among both racial groups, the rates among blacks are not unusually high when viewed internationally. These data suggest that the impact of environmental factors among both populations may have been under-appreciated

Cognitive architectures as Lakatosian research programmes: two case studies

Cognitive architectures - task-general theories of the structure and function of the complete cognitive system - are sometimes argued to be more akin to frameworks or belief systems than scientific theories. The argument stems from the apparent non-falsifiability of existing cognitive architectures. Newell was aware of this criticism and argued that architectures should be viewed not as theories subject to Popperian falsification, but rather as Lakatosian research programs based on cumulative growth. Newell's argument is undermined because he failed to demonstrate that the development of Soar, his own candidate architecture, adhered to Lakatosian principles. This paper presents detailed case studies of the development of two cognitive architectures, Soar and ACT-R, from a Lakatosian perspective. It is demonstrated that both are broadly Lakatosian, but that in both cases there have been theoretical progressions that, according to Lakatosian criteria, are pseudo-scientific. Thus, Newell's defense of Soar as a scientific rather than pseudo-scientific theory is not supported in practice. The ACT series of architectures has fewer pseudo-scientific progressions than Soar, but it too is vulnerable to accusations of pseudo-science. From this analysis, it is argued that successive versions of theories of the human cognitive architecture must explicitly address five questions to maintain scientific credibility

A new lysozyme from the eastern oyster, Crassostrea virginica, and a possible evolutionary pathway for i-type lysozymes in bivalves from host defense to digestion

Background. Lysozymes are enzymes that lyse bacterial cell walls, an activity widely used for host defense but also modified in some instances for digestion. The biochemical and evolutionary changes between these different functional forms has been well-studied in the c-type lysozymes of vertebrates, but less so in the i-type lysozymes prevalent in most invertebrate animals. Some bivalve molluscs possess both defensive and digestive lysozymes. Results. We report a third lysozyme from the oyster Crassostrea virginica, cv-lysozyme 3. The chemical properties of cv-lysozyme 3 (including molecular weight, isoelectric point, basic amino acid residue number, and predicted protease cutting sites) suggest it represents a transitional form between lysozymes used for digestion and immunity. The cv-lysozyme 3 protein inhibited the growth of bacteria (consistent with a defensive function), but semi-quantitative RT-PCR suggested the gene was expressed mainly in digestive glands. Purified cv-lysozyme 3 expressed maximum muramidase activity within a range of pH (7.0 and 8.0) and ionic strength (I = 0.005-0.01) unfavorable for either cv-lysozyme 1 or cv-lysozyme 2 activities. The topology of a phylogenetic analysis of cv-lysozyme 3 cDNA (full length 663 bp, encoding an open reading frame of 187 amino acids) is also consistent with a transitional condition, as cv-lysozyme 3 falls at the base of a monophyletic clade of bivalve lysozymes identified from digestive glands. Rates of nonsynonymous substitution are significantly high at the base of this clade, consistent with an episode of positive selection associated with the functional transition from defense to digestion. Conclusion. The pattern of molecular evolution accompanying the shift from defensive to digestive function in the i-type lysozymes of bivalves parallels those seen for c-type lysozymes in mammals and suggests that the lysozyme paralogs that enhance the range of physiological conditions for lysozyme activity may provide stepping stones between defensive and digestive forms. © 2010 Xue et al; licensee BioMed Central Ltd

Development of a stabilized trimer pre-fusion RSV F recombinant viral glycoprotein vaccine

It has been known that the RSV fusion protein F is a target vaccine protein to produce a protective immune response. The VRC has shown (Ngwuta, et.al.) through binding competition assays that the amount of pre-fusion site Ø–specific antibodies correlates with neutralizing (NT) activity, whereas the pre/post-fusion site II mAbs does not correlate with neutralization. Our results indicate that RSV NT activity in human sera is primarily derived from pre-F–specific antibodies, and therefore, inducing or boosting NT activity by vaccination will be facilitated by using pre-F antigens that preserve site Ø. Therefore, the instability of the RSV pre-fusion conformation has limited the potential of this as a vaccine antigen. Therefore, the VRC has designed a structurally stabilized glycoprotein pre-fusion RSV F trimer vaccine antigen and has shown it to be highly immunogenic in preclinical studies. A description of challenges in the development of a high productivity CHO cell line, production process and product quality and antigenic characterization assays for Phase I clinical material will be presented along with comparison of pre-clinical results of research to development material. Please click Additional Files below to see the full abstract

Influence of the i/d polymorphism of the angiotensin-converting enzyme gene on the outcome of microalbuminuria in essential hypertension

The objective of the present study was to analyze the influence of the I/D polymorphism of the ACE gene on the outcome of microalbuminuria in essential hypertensive patients who were receiving antihypertensive treatment. One hundred thirty-six essential hypertensive patients who were <50 years old and had never previously received treatment with antihypertensive drugs were included in the study. During a 3-year period, patients received nonpharmacological treatment consisting of moderate salt restriction and a low-calorie diet they were obese, with or without a regimen of antihypertensive drugs based on ß-blockers or ACE inhibitors. Hydrochlorothiazide was added when necessary to maintain the blood pressure goal of <135/85 mm Hg. At the beginning of the study and at yearly intervals, systolic and diastolic blood pressures (SBP and DBP, respectively), 24-hour urinary albumin excretion (UAE), renal function, and biochemical profile measurements were made. The insertion/deletion (I/D) polymorphism of the ACE gene was determined through the use of polymerase chain reaction. The variables used in the statistical analysis were the measurements at the start of the study and the increase or decrease detected during the follow-up, estimated as individual specific regression line slope values. At baseline, no differences in blood pressure or UAE values were observed among genotypes. Likewise, the genotype or allele frequency was not significantly different between normoalbuminurics and microalbuminurics. After the 3 treatment years, significant reductions in SBP, DBP, and UAE were found (SBP 151.6±17.3 reduced to 137.2±14.3 mm Hg, P<0.001; DBP 96.6±8.9 reduced to 84.5±9.8 mm Hg, P<0.001; UAE 36.7±71.5 reduced to 28.3±78.6 mg/24 h, P<0.05). The slopes of these parameters over time did not differ significantly among genotypes. The slope of SBP was the main factor related to the slope of logUAE (P<0.003). A significant positive correlation coefficient between the SBP and logUAE slopes was observed for the DD patients (r=0.57, P<0.0001) but was absent in patients carrying the I allele (II r=-0.03, P=NS; I/D r=0.01, P=NS). Follow-up studies should be used to achieve a better understanding of the impact of candidate gene polymorphisms on the development of hypertension-induced organ damage. Assessment of the I/D polymorphism of the ACE gene may identify subjects who require a greatly lowered blood pressure to prevent organ damage and to reduce hypertension-associated complications and death.Redon Mas, Josep, [email protected] ; Chaves Martinez, Felipe Javier, [email protected] ; Pascual Izuel, Jose Maria, [email protected]