Chromatophores and color revelation in the blue variant of the Siamese fighting fish (Betta splendens)

Our light and electron microscopy observations have revealed that the chromatic unit for the caudal fin in the blue variant of the Siamese fighting fish consists exclusively of dermal chromatophores comprised of compact and overlapping light-reflecting motile iridophores underlined by a layer of light absorbing melanophores. The 2 subtypes that make up about 70% of the skin tissue are located just below the basal layer of the considerably thin epidermis. The administration of K-rich saline or norepinephrine induced prompt, but gradual and reversible, changes in the color of the skin from blue to a brown-yellowish color. The induced color change is attributable either to the neurotransmitter releasing effects of the K-rich saline or to the direct effects of norepinephrine on the postsynaptic alpha adrenergic receptors. Both of these agents induced aggregation of the melanosomes within the melanophores and apparently shifted the wavelength of the light reflected by the iridophores towards the shorter (blue) end of the spectrum. Based on the distribution and architectural arrangement of the iridophores and melanophores as well as their physiological responses, we conclude that the generation of the blue coloration in this fish predominantly occurs through motile iridophores via a multilayered thin-film interference phenomenon of the non-ideal type. The presence of the underlying melanophores provides a black sheet of melanin that enhances the chroma and purity of the color.     

Ab initio study of molecular oxygen adsorption on Pu (111) surface

Using the generalized gradient approximation to density functional theory (DFT), molecular and dissociative oxygen adsorptions on a Pu (111) surface has been studied in detail. Dissociative adsorption with a layer‐by‐layer alternate spin arrangement of the plutonium layer is found to be energetically more favorable, and adsorption of oxygen does not change this feature. Hor1 (O₂ is parallel to the surface and lattice vectors) approach on the center2 (center of the unit cell, where there is a Pu atom directly below on the third layer) site, both without and with spin polarization, was found to be the preferred chemisorbed site among all cases studied with chemisorption energies of 8.365 and 7.897 eV, respectively. The second‐highest chemisorption energy occurs at the Ver (O₂ is vertical to the surface) approach of the bridge site with chemisorption energies of 8.294 eV (non‐spin‐polarized) and 7.859 eV (spin‐polarized), respectively. We find that 5f electrons are more localized in the spin‐polarized case than the non‐spin‐polarized counterparts. Localization of the 5f electrons is higher in the oxygen‐adsorbed plutonium layers compared with the bare layers. The ionic part of O? Pu bonding plays a significant role in the chemisorption process, along with Pu 5f? O 2p hybridization. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

A correlation study of small silver clusters

The formalisms of many body perturbation theory and coupled cluster theory have been used to study the electronic and geometric structures of neutral, cationic, and anionic small silver clusters. Hay-Wadt relativistic effective core potentials replacing the twenty-eight core electrons and a Gaussian basis set have been used. Topologically different clusters and clusters belonging to different symmetry groups have been identified and studied in detail. Full geometry optimizations have been carried out at four different correlated levels of theories. Ionization potentials, electron affinities, and fragmentation energies of the optimized clusters have been compared with other experimental and theoretical results available in the literature. No convergence problems are encountered at the various levels of correlated theories. This is noteworthy since it has been claimed in the literature that for d elements the MP series does not converge very well. Received 16 April 2002 / Received in final form 12 September 2002 Published online 21 January 2003 RID="a" ID="a"e-mail: akr@uta.edu     

A density functional study of molecular oxygen adsorption and reaction barrier on Pu (100) surface

Oxygen molecule adsorptions on a Pu(100) surface have been studied in detail, using the generalized gradient approximation to density functional theory. Dissociative adsorption with a layer by layer alternate spin arrangement of the plutonium layer is found to be energetically more favorable compared to molecular adsorption. Hor2 approach on a bridge site without spin polarization was found to the highest chemisorbed site with an energy of 8.787 eV among all the cases studied. The second highest chemisorption energy of 8.236 eV, is the spin-polarized Hor2 or Ver approach at center site. Inclusion of spin polarization affects the chemisorption processes significantly, non-spin-polarized chemisorption energies being typically higher than the spin-polarized energies. We also find that the 5f electrons to be more localized in spin-polarized cases compared to the non-spin-polarized counterparts. The ionic part of O-Pu bonding plays a significant role, while the Pu 5f-O 2p hybridization was found to be rather week. Also, adsorptions of oxygen push the top of 5f band deeper away from the Fermi level, indicating further bonding by the 5f orbitals might be less probable. Except for the interstitial sites, the work functions increase due to adsorptions of oxygen.     

Kinematic design of 3-URU pure rotational parallel mechanism to perform precise motion within a large workspace

We present an optimum design of lower-dof parallel mechanism, a 3-URU pure rotational parallel mechanism that reflects issues of workspace and the position error of the center of rotation of the platform. The uncompensatable error determined by position error of center of rotation was used as an evaluation index for the design. The uncompensatable error index, an index used in the optimum design, was proposed taking into account four sources of errors, representing errors between adjacent joints. Based on the application of the mechanism and the error index, the effect of the redundant platform orientation parameter was numerically investigated and the design flow of the mechanism was proposed. We made a kinematic design of a mechanism with a large workspace subject to minimization of platform’s position error of the center of rotation. A prototype of mechanism with a large inclination angle of the platform up to 1.3 rad was shown, and its characteristics are also discussed.     

Synthesis and fabrication of (1 − x)ZnAl2O4–xSiO2 thin films to be applied as patch antennas

Zinc aluminate compounds have been dispersed in silica matrix prepared by sol-gel method with different compositions for (1 ? x)ZnAl₂O₄–xSiO₂. Continuous stirring of ethylene glycol solution contained zinc nitrate, aluminium nitrate and silicon dioxide to produces gel precursor. Structural and morphological studies of (1 ? x)ZnAl₂O₄–xSiO₂ thin films were examined by field emission scanning electron microscopy (FESEM) and X-ray diffractometer (XRD) analysis. The FESEM images showed the spherical structures with porosity for (1 ? x)ZnAl₂O₄–xSiO₂ thin films. XRD analysis indicated that the crystallite size for (1 ? x)ZnAl₂O₄–xSiO₂ increased from 39.79 to 44.34 nm. Fourier transform infra-red analysis showed that the existence of H₂O molecules and the presence of nitrate group within the samples. Dielectric permittivity (ε _r ) of (1 ? x)ZnAl₂O₄–xSiO₂ samples were measured within frequency range from 1 Hz to 1 MHz. The dielectric permittivity, ε _r decreased as frequency was applied to the sample. The performance of the patch antenna can be measured using return loss analysis. The highest result shows that the patch antenna resonated at frequency 3.46 GHz and gives ?14.25 dB return loss bandwidth.     

Controlled self-assembly of quantum dots and block copolymers in a microfluidic device

The controlled self-assembly of polymer-stabilized quantum dots (QDs) into mesoscale aqueous spherical assemblies using microfluidics is described. In a flow-focusing configuration, self-assembly is initiated by the addition of water to a blended solution of polystyrene-coated QDs and amphiphilic polystyrene-block-poly(acrylic acid) stabilizing chains and terminated in a downstream quench step. The on-chip evolution of assemblies is monitored through fluorescence microscopy, and particle size distributions are determined off-chip by transmission electron microscopy. On-chip size control of the assemblies is demonstrated via both the average water concentration in the channel and the flow rate.     

Cation‐Controlled Formation and Interconversion of the fac/fac and mer/mer Stereoisomers of a Triple‐Stranded Helicate

Two biscatecholester ligands with oligoether spacers were used to prepare dinuclear titanium(IV) triscatecholate based helicates. In the case of Li₄[( 1 / 2 )₃Ti₂], “classical” helicates with three internally bound Li⁺ ions and syn‐oriented ligands in the complex units (fac/fac isomer) were obtained. In the case of the sodium salt Na₄[( 2 )₃Ti₂], a different homochiral dinuclear triple‐stranded helicate with two internally bound Na⁺ ions was formed. The complex units are anti‐configured, and two of the ligand spacers are connecting internal with external positions of the helicate (mer/mer isomer). Removal of the sodium ions and addition of lithium ions leads to the switching from one topology to the other with an expanded helicate [( 2 )₃Ti₂]^4? as an intermediate. Switching back to the “non‐classical” helicate cannot be observed because severe structural rearrangements would be required.     

Density functional study of O2 adsorption on (100) surface of γ‐uranium

Chemisorption of the oxygen molecule on the (100) surface of γ‐uranium was investigated using the generalized gradient approximation to Density Functional Theory. Dissociative adsorptions of O₂ are found to be significantly favored compared to molecular adsorptions. Interstitial adsorptions of molecular oxygen are less probable, as no bound states are found in this case. Only after dissociation of O₂ is atomic oxygen diffusion through the surface possible. The O 2p orbitals are found to hybridize with U 5f bands, and some of the U 5f electrons become more localized. A significant charge transfer from the first layer of the uranium surface to the oxygen atoms is found to occur, making the bonding partly ionic. For the most favored site, the dissociative chemisorption energy is ～9.5 eV, which indicates a strong reaction of uranium surface with oxygen. Spin polarization does not have a significant effect on the chemisorption process. For most of the sites and approaches, chemisorption configurations are almost same for both spin‐polarized and non‐spin‐polarized cases. For the most favored chemisorption sites of oxygen on uranium, paramagnetic adsorption is slightly stronger, by 0.304 eV, compared to magnetic adsorption. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

An efficient and facile synthesis of new tetracyclic fused pyrazolo[4,3-<Emphasis Type="Italic">c</Emphasis>][1,2,4]triazino[4,5-<Emphasis Type="Italic">a</Emphasis>]quinolin-4(5<Emphasis Type="Italic">H</Emphasis>)-ones

Reaction of amidrazones 1a–1i with (1,5-dihydro-3-methyl-5-oxo-1-phenyl-4H-pyrazol-4-ylidene)propanedinitrile (2) in ethyl acetate solution in one-step reaction led to the formation of unprecedented pyrazolo[4,3-c][1,2,4]triazino[4,5-a]quinolin-4(5H)-ones 3a–3g along with pyrazolo[4,3-c][1,2,4]triazino[4,5-a]quinolin-12b-oles 3h–3m in moderate to excellent yields. These novel heterocycles were formed via a Michael addition reaction followed by intramolecular cyclization via a dearomatization process.