bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential requirement of Salvador-Warts-Hippo pathway members for organ size control in Drosophila melanogaster
Authors: Milton Claire C. , Zhang Xiaomeng , Albanese Nathaniel O. , Harvey Kieran F.
Published: January 2010

The Salvador-Warts-Hippo (SWH) pathway contains multiple growth-inhibitory proteins that control organ size during development by limiting activity of the Yorkie oncoprotein. Increasing evidence indicates that these growth inhibitors act in a complex network upstream of Yorkie. This complexity is emphasised by the distinct phenotypes of tissue lacking different SWH pathway genes. For example, eye tissue lacking the core SWH pathway components salvador, warts or hippo is highly overgrown and resistant to developmental apoptosis, whereas tissue lacking fat or expanded is not. Here we explore the relative contribution of SWH pathway proteins to organ size control by determining their temporal activity profile throughout Drosophila melanogaster eye development. We show that eye tissue lacking fat, expanded or discs overgrown displays elevated Yorkie activity during the larval growth phase of development, but not in the pupal eye when apoptosis ensues. Fat and Expanded do possess Yorkie-repressive activity in the pupal eye, but loss of fat or expanded at this stage of development can be compensated for by Merlin. Fat appears to repress Yorkie independently of Dachs in the pupal eye, which would contrast with the mode of action of Fat during larval development. Fat is more likely to restrict Yorkie activity in the pupal eye together with Expanded, given that pupal eye tissue lacking both these genes resembles that of tissue lacking either gene. This study highlights the complexity employed by different SWH pathway proteins to control organ size at different stages of development.
Slowdown promotes muscle integrity by modulating integrin-mediated adhesion at the myotendinous junction
Authors: Gilsohn Eliezer , Volk Talila
Published: January 2010

The correct assembly of the myotendinous junction (MTJ) is crucial for proper muscle function. In Drosophila, this junction comprises hemi-adherens junctions that are formed upon arrival of muscles at their corresponding tendon cells. The MTJ mainly comprises muscle-specific αPS2βPS integrin receptors and their tendon-derived extracellular matrix ligand Thrombospondin (Tsp). We report the identification and functional analysis of a novel tendon-derived secreted protein named Slowdown (Slow). Homozygous slow mutant larvae exhibit muscle or tendon rupture, sluggish larval movement, partial lethality, and the surviving adult flies are unable to fly. These defects result from improper assembly of the embryonic MTJ. In slow mutants, Tsp prematurely accumulates at muscle ends, the morphology of the muscle leading edge changes and the MTJ architecture is aberrant. Slow was found to form a protein complex with Tsp. This complex is biologically active and capable of altering the morphology and directionality of muscle ends. Our analysis implicates Slow as an essential component of the MTJ, crucial for ensuring muscle and tendon integrity during larval locomotion.
SIX1 acts synergistically with TBX18 in mediating ureteral smooth muscle formation
Authors: Nie Xuguang , Sun Jianbo , Gordon Ronald E. , Cai Chen-Leng , Xu Pin-Xian
Published: January 2010

Dysfunction of the ureter often leads to urine flow impairment from the kidney to the bladder, causing dilation of the ureter and/or renal pelvis. Six1 is a crucial regulator of renal development: mutations in human SIX1 cause branchio-oto-renal (BOR) syndrome and Six1–/– mice exhibit renal agenesis, although the ureter is present. It remains unclear whether Six1 plays a role in regulating ureter morphogenesis. We demonstrate here that Six1 is differentially expressed during ureter morphogenesis. It was expressed in undifferentiated smooth muscle (SM) progenitors, but was downregulated in differentiating SM cells (SMCs) and had disappeared by E18.5. In Six1–/– mice, the ureteral mesenchymal precursors failed to condense and differentiate into normal SMCs and showed increased cell death, indicating that Six1 is required for the maintenance and normal differentiation of SM progenitors. A delay in SMC differentiation was observed in Six1–/– ureters. A lack of Six1 in the ureter led to hydroureter and hydronephrosis without anatomical obstruction when kidney formation was rescued in Six1–/– embryos by specifically expressing Six1 in the metanephric mesenchyme, but not the ureter, under control of the Eya1 promoter. We show that Six1 and Tbx18 genetically interact to synergistically regulate SMC development and ureter function and that their gene products form a complex in cultured cells and in the developing ureter. Two missense mutations in SIX1 from BOR patients reduced or abolished SIX1-TBX18 complex formation. These findings uncover an essential role for Six1 in establishing a functionally normal ureter and provide new insights into the molecular basis of urinary tract malformations in BOR patients.
Chewing variation in lepidosaurs and primates
Authors: Ross C. F. , Baden A. L. , Georgi J. , Herrel A. , Metzger K. A. , Reed D. A. , Schaerlaeken V. , Wolff M. S.
Published: January 2010

Mammals chew more rhythmically than lepidosaurs. The research presented here evaluated possible reasons for this difference in relation to differences between lepidosaurs and mammals in sensorimotor systems. Variance in the absolute and relative durations of the phases of the gape cycle was calculated from kinematic data from four species of primates and eight species of lepidosaurs. The primates exhibit less variance in the duration of the gape cycle than in the durations of the four phases making up the gape cycle. This suggests that increases in the durations of some gape cycle phases are accompanied by decreases in others. Similar effects are much less pronounced in the lepidosaurs. In addition, the primates show isometric changes in gape cycle phase durations, i.e. the relative durations of the phases of the gape cycle change little with increasing cycle time. In contrast, in the lepidosaurs variance in total gape cycle duration is associated with increases in the proportion of the cycle made up by the slow open phase. We hypothesize that in mammals the central nervous system includes a representation of the optimal chew cycle duration maintained using afferent feedback about the ongoing state of the chew cycle. The differences between lepidosaurs and primates do not lie in the nature of the sensory information collected and its feedback to the feeding system, but rather the processing of that information by the CNS and its use feed-forward for modulating jaw movements and gape cycle phase durations during chewing.
Distinct startle responses are associated with neuroanatomical differences in pufferfishes
Authors: Greenwood A. K. , Peichel C. L. , Zottoli S. J.
Published: January 2010

Despite the key function of the Mauthner cells (M-cells) in initiating escape responses and thereby promoting survival, there are multiple examples of M-cell loss across the teleost phylogeny. Only a few studies have directly considered the behavioral consequences of naturally occurring M-cell variation across species. We chose to examine this issue in pufferfishes, as previous research suggested that there might be variability in M-cell anatomy in this group of fish. We characterized the M-cell anatomy and fast-start responses of two pufferfish species, Tetraodon nigroviridis and Diodon holocanthus. T. nigroviridis showed robust fast-starts to both tactile and acoustic startling stimuli. These fast-starts occurred with a latency typical of M-cell initiation in other fish, and retrograde labeling of spinal-projection neurons revealed that T. nigroviridis does have M-cells. By contrast, D. holocanthus only rarely exhibited fast-start-like behavior, and these responses were at a substantially longer latency and were much less extensive than those of T. nigroviridis. Using three complementary anatomical techniques we were unable to identify obvious M-cell candidates in D. holocanthus. These results provide a clear correlation between M-cell presence or absence and dramatic differences in fast-start behavior. The rich diversity within the pufferfish clade should allow future studies investigating the factors that contribute to this correlated anatomical and behavioral variation.
Making sense of electrical sense in crayfish
Authors: Patullo B. W. , Macmillan D. L.
Published: January 2010

The five sensory modalities of humans are also found in a wide range of invertebrates. Other vertebrates have evolved additional special senses, such as the magnetic sense, which are also found in some invertebrates. However, there remain a few sensory abilities that curiously appear to be found in either vertebrates or invertebrates, but not both. For example, electrosensitivity — the ability to detect electric fields in water — which should benefit vertebrates and invertebrates alike, is apparently only used by vertebrates. However, recent reports suggest that some invertebrates could have an electric sense. Here we examine that possibility further and demonstrate a behavioural threshold to low-level electrical fields in two freshwater invertebrates. The responses are not low enough for them to detect the Earth's magnetic field as some other electroreceptive species can do, but sufficiently low for them to use in navigation or prey and predator detection. This finding challenges the current view of the sensory world of aquatic invertebrates and has implications for the evolution of this ability.
Mounting of erratic histoincompatible responses in hermatypic corals: a multi-year interval comparison
Authors: Amar K.-O. , Rinkevich B.
Published: January 2010

Studies on allorecognition in the phylum Cnidaria have disclosed complex arrays of effector mechanisms, specificity and competency to distinguish precisely between self and non-self attributes, and have revealed the existence of allogeneic maturity. Here we studied allo-responses between young Stylophora pistillata colonies by following 517 allogeneic interactions between naturally settled kin aggregates and by establishing 417 forced allogeneic and autogeneic assays made of solitarily settled spat that were cut into two similar size subclones, of which one had been challenged allogeneically. Fused assays were exposed to a second allorecognition challenge, made of three allogeneic types. Whereas about half of the kin allogeneic interactions led to tissue fusions and chimera formations, none of the 83 non-sibling pair combinations were histocompatible. In contrast to previous results we recorded rejections between siblings at the age of less than two months. More challenging, we documented cases of fusions between interacting siblings at ages older than one-year-old partners, all differing from a previous study made on the same coral population more than a decade ago. Similar erratic histoincompatible responses were recorded in other pocilloporid species. We suggest that these results reflect reduced genetic heterogeneity caused by chronic anthropogenic impacts on shallow water coral populations where planulae originating from the same mother colony or from different mother colonies that are genetically related share increasing parts of their genomes. Offspring born to related parents may also reveal an increase in genomic homozygosity, and altogether impose erratic alloimmunity.
Endovenous treatments for varicose veins – over-taking or over-rated?
Authors: Shepherd A C , Gohel M S , Hamish M , Lim C S , Davies A H
Published: January 2010

Objectives

A variety of endovenous therapies for the treatment of superficial venous incompetence are currently available. The aim of this study was to evaluate the prevalence of endovenous techniques used by consultant vascular surgeons in the United Kingdom.

Methods

An anonymous online survey of 16 multiple choice questions relating to the nature and provision of treatment for varicose veins was devised. Consultant members of the Vascular Society of Great Britain and Ireland were invited to participate by email.

Results

A total of 108/352 (31%) surgeons completed the survey. The majority offered surgery as the first-line treatment for primary great saphenous vein (GSV) and small saphenous vein (SSV) incompetence (69% and 74%, respectively). Endovenous procedures were offered as first-line treatment by 32/108 (29.6%) for GSV reflux, 36/51 (70.6%) surgeons performed these under local anaesthetic and 21/51 (41.2%) were performed as an outpatient procedure. The most important factor influencing treatment decisions was considered to be patient preference by 77/108 (71.3%) surgeons, although 48/61 (78.7%) respondents were restricted by primary care trusts with regard to endovenous treatments, and 33/108 (30.6%) offered different treatments to private patients.

Conclusion

Traditional surgery remains the most commonly offered treatment for patients with varicose veins. The provision of endovenous therapies varies greatly, and there are significant differences in local availability regarding these treatments.
Invest or Exit? Optimal Decisions in the Face of a Declining Profit Stream
Authors: Kwon H. Dharma
Published: January 2010

Even in the face of deteriorating and highly volatile demand, firms often invest in, rather than discard, aging technologies. To study this phenomenon, we model the firm's profit stream as a Brownian motion with negative drift. At each point in time, the firm can continue operations, or it can stop and exit the project. In addition, there is a one-time option to make an investment that boosts the project's profit rate. Using stochastic analysis, we show that the optimal policy always exists and that it is characterized by three thresholds. There are investment and exit thresholds before investment, and there is a threshold for exit after investment. We also effect a comparative statics analysis of the thresholds with respect to the drift and the volatility of the Brownian motion. When the profit boost upon investment is sufficiently large, we find a novel result: the investment threshold decreases in volatility.
Distributionally Robust Optimization Under Moment Uncertainty with Application to Data-Driven Problems
Authors: Delage Erick , Ye Yinyu
Published: January 2010

Stochastic programming can effectively describe many decision-making problems in uncertain environments. Unfortunately, such programs are often computationally demanding to solve. In addition, their solution can be misleading when there is ambiguity in the choice of a distribution for the random parameters. In this paper, we propose a model that describes uncertainty in both the distribution form (discrete, Gaussian, exponential, etc.) and moments (mean and covariance matrix). We demonstrate that for a wide range of cost functions the associated distributionally robust (or min-max) stochastic program can be solved efficiently. Furthermore, by deriving a new confidence region for the mean and the covariance matrix of a random vector, we provide probabilistic arguments for using our model in problems that rely heavily on historical data. These arguments are confirmed in a practical example of portfolio selection, where our framework leads to better-performing policies on the “true” distribution underlying the daily returns of financial assets.
Quantitative Comparison of Approximate Solution Sets for Multicriteria Optimization Problems with Weighted Tchebycheff Preference Function
Authors: Bozkurt Bilge , Fowler John W. , Gel Esma S. , Kim Bosun , Köksalan Murat , Wallenius Jyrki
Published: January 2010

We consider the problem of evaluating the quality of solution sets generated by heuristics for multiple-objective combinatorial optimization problems. We extend previous research on the integrated preference functional (IPF), which assigns a scalar value to a given discrete set of nondominated points so that the weighted Tchebycheff function can be used as the underlying implicit value function. This extension is useful because modeling the decision maker's value function with the weighted Tchebycheff function reflects the impact of unsupported points when evaluating sets of nondominated points. We present an exact calculation method for the IPF measure in this case for an arbitrary number of criteria. We show that every nondominated point has its optimal weight interval for the weighted Tchebycheff function. Accordingly, all nondominated points, and not only the supported points in a set, contribute to the value of the IPF measure when using the weighted Tchebycheff function. Two- and three-criteria numerical examples illustrate the desirable properties of the weighted Tchebycheff function, providing a richer measure than the original IPF based on a convex combination of objectives.
Proportion of general factor variance in a hierarchical multiple‐component measuring instrument: A note on a confidence interval estimation procedure
Authors: Raykov Tenko , Zinbarg Richard E.
Published: January 2010

A confidence interval construction procedure for the proportion of explained variance by a hierarchical, general factor in a multi‐component measuring instrument is outlined. The method provides point and interval estimates for the proportion of total scale score variance that is accounted for by the general factor, which could be viewed as common to all components. The approach may also be used for testing composite (one‐tailed) or simple hypotheses about this proportion, and is illustrated with a pair of examples.
Study on Organic Triplet Exciton Emission and Quenching
Processes by Low-temperature Photo- and Electroluminescence
Spectroscopy
Authors: Kaufmann Nils Asmus Kristian , Jessen Frank , Heuken M. , Boerner Herbert , Kalisch Holger , Jansen R. H.
Published: January 2010

Organic light emitting diodes (OLED) are efficient light sources based on
organic semiconductors. Unlike inorganic LEDs which are more or less point
sources, OLED are planar light sources with up to 1 m2 in area.
By using organic materials, they are cheap to produce and economical to use.
The determination of triplet exciton energy levels is of interest for the
development of efficient OLED, based on the fact that electrical excitation
usually creates three times as many triplets as singlets. Additionally, the
knowledge of these energy levels is crucial for the design and choice of
emitter matrix materials and exciton blocking layers. These values are
normally determined by photoluminescence (PL) measurements in solution for
materials which show intersystem crossing (ISC) between singlet and triplet
states. For some materials, the triplet levels cannot be measured this way
because some materials prohibit ISC. In this work, a method is presented
which allows the determination of the energy levels using low-temperature
electroluminescence (EL) spectroscopy. The dependence on ISC is avoided by
creating triplets directly with electrical excitation and this allows to
measure a large class of organic materials. A low-temperature EL spectrum is
presented for
N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD) in
a 3-phenyl-4-(1‘-naphthyl)-5-phenyl-1,2,4-triazole (TAZ) matrix (TPD/TAZ
1:3) at 77 K. Triplet emission is only observed at very low charge carrier
density (0.5 μA/mm2). Quenching processes are analyzed using
combined EL and PL measurements and unipolar devices. Two factors can be the
cause of the quenching: A strong quenching based on a low concentration of
electrically activated impurities could explain the dependency. The other
explanation points to a quenching based on electrons in the emitting layer.
This might be explained with triplet-polaron quenching (TPQ). TPQ is
proportional to the charge carrier density and contributes the dominant part
to the quenching at low current densities.
Effects of annealing on donor and acceptor concentrations in Ga-doped ZnO thin films
Authors: Look David C. , Ghosh Kartik , Leedy Kevin
Published: January 2010

Temperature-dependent Hall-effect measurements have been performed on three Ga-doped ZnO thin films of various thicknesses (65, 177, and 283 nm), grown by pulsed laser deposition at 400 °C and annealed at 400 °C for 10 min in Ar, N2, or forming-gas (5% H2 in Ar). The donor ND and acceptor NAconcentrations as a function of sample thickness and annealing conditions are determined by a new formalism that involves only ionized-impurity and boundary scattering. Before annealing, the samples are highly compensated, with ND = (2.8 ± 0.3) × 1020 cm-3 and NA = (2.6 ± 0.2) × 1020 cm-3. After annealing in Ar the samples are less compensated, with ND = (3.7 ± 0.1) × 1020 cm-3 and NA = (2.0 ± 0.1) × 1020 cm-3; furthermore, these quantities are nearly independent of thickness. However, after annealing in N2 and forming-gas, ND and NA are thickness dependent, partly due to depth-dependent diffusion of N2 and H, respectively.
Light beam induced current measurements on ZnO Schottky diodes and MESFETs
Authors: von Wenckstern Holger , Zhang Zhipeng P. , Lorenz Michael , Czekalla Christian , Frenzel Heiko , Lajn Alexander , Grundmann Marius
Published: January 2010

The homogeneity of the Schottky barrier potential of reactively sputtered PdOy/ZnO Schottky contacts has been investigated by light beam-induced current measurements on the micrometer scale. It is found that a metallic capping layer, acting as an equipotential surface, is not necessary for PdOy/ZnO Schottky contacts in contrast to AgxO/ZnO Schottky diodes. Further, we probed the generated photocurrent of a ZnO-based metal-semiconductor field-effect transistor for a closed and open channel, respectively. The photocurrent is, in general, one order of magnitude larger for closed channel conditions. The position of maximum photocurrent generation shifts towards the drain for higher source drain voltages for closed channel conditions, whereas it is nearly independent of the source drain potential for an open channel.
Studies of Ni and Co Doped Amorphous AlN for Magneto-optical Applications
Authors: Jadwisienczak Wojciech M. , Tanaka Hiroki , Kordesch Marty E. , Khan Aurangzeb , Kaya Savas , Vuppuluri Venkat
Published: January 2010

Magneto-optical properties of Ni- and Co-doped amorphous AlN thin films were investigated as a function of post grown annealing temperature using magneto-optical Kerr effect (MOKE) spectroscopy. The x-ray diffraction spectra confirmed that the as-grown material is amorphous and retained its morphology after thermal treatment; however the sample morphology strongly depends on the concentration of incorporated transition metals. We observed with help of transmission electron microscopy and atomic force microscopy that the films surface containing TMs with concentrations larger than ∼10 at.% undergo morphological changes suggesting possible Ni and Co atom clustering. Significant enhancement of the polar Kerr rotation signal was observed for Ni- and Co-doped a-AlN materials annealed above 300 °C in nitrogen. The studied materials have shown strong magnetic isotropy in polar geometry whereas the MOKE measurements in longitudinal geometry did not show an explicit signal for the transition metals doped a-AlN studied.
Ion induced formation of Silicon nitride substrate and GaN overlayer growth at room temperature on Si (111) surface
Authors: Kumar Praveen , Kumar Mahesh , Gupta Govind , Mehta Bodh R. , Shivaprasad Sonanda M.
Published: January 2010

GaN and related nitride semiconductors have attracted great attention in view of their wide applications in photonics and high temperature & high power electronic devices. Among other issues, reduction of defect densities by forming these interfaces at lower temperature and on novel substrates has been the motivation for several researchers. In the present study ion-induced conversion of Si (111) surface into silicon nitride at room temperature is optimized and used as substrate for the growth of Ga films. These Ga films are again nitrided by optimal N+ ion bombardment. Experiments have been performed in-situ in an ultra high vacuum chamber equipped with a Ga source and X-ray photoelectron spectrometer (XPS) at base pressure of 2×10-10 torr. The energy dependence of the nitridation is carefully performed at constant flux. The results clearly demonstrate the Si-N bond formation after a energy of 2 keV and the formation of GaN layer after 800eV of ion bombardment on Si (111) 7×7 surface and Ga adsorbed silicon nitride surface, respectively. The FWHM and chemical shifts in the core-level spectra of Si(2p), Ga(2p) and N(1s) have been analyzed to probe the interface reactions. The results demonstrate a possible novel and low temperature approach towards the integration of III-nitride & silicon technologies, since silicon nitride bonds can act as barriers to dislocation propagation.
Growth temperature - phase stability relation in In1-xGaxN epilayers grown by high-pressure CVD
Authors: Durkaya Goksel , Alevli Mustafa , Buegler Max , Atalay Ramazan , Gamage Sampath , Kaiser Martin , Kirste Ronny , Hoffmann Axel , Jamil Muhammad , Ferguson Ian , Dietz Nikolaus
Published: January 2010

The influence of the growth temperature on the phase stability and composition of single-phase In1-xGaxN epilayers has been studied. The In1-xGaxN epilayers were grown by high-pressure Chemical Vapor Deposition with nominally composition of x = 0.6 at a reactor pressure of 15 bar at various growth temperatures. The layers were analyzed by x-ray diffraction, optical transmission spectroscopy, atomic force microscopy, and Raman spectroscopy. The results showed that a growth temperature of 925°C led to the best single phase InGaN layers with the smoothest surface and smallest grain areas
Lattice Parameter Variation in ScGaN Alloy Thin Films on MgO(001) Grown by RF Plasma Molecular Beam Epitaxy
Authors: Constantin Costel , Jeongihm Pak , Wang Kangkang , Chinchore Abhijit , Meng Shi , Smith Arthur R.
Published: January 2010

We present the structural and surface characterization of the alloy formation of scandium gallium nitride ScxGa1-xN(001)/MgO(001) grown by radio-frequency molecular beam epitaxy over the Sc range of x = 0-100%. In-plane diffraction measurements show a clear face-centered cubic surface structure with single-crystalline epitaxial type of growth mode for all x; a diffuse/distinct transition in the surface structure occurs at near x = 0.5. This is consistent with out-of-plane diffraction measurements which show a linear variation of perpendicular lattice constant for x = 0 to 0.5, after which the out-of-plane lattice parameter becomes approximately constant. The x = 0.5 transition is interpreted as being related to the cross-over from zinc-blende to rock-salt structure.
GaN Photonic-Crystal Surface-Emitting Laser
Authors: Yoshimoto Susumu , Matsubara Hideki , Sakai Kyosuke , Noda Susumu
Published: January 2010

We introduce the lasing principle and important characteristics of photonic-crystal surface-emitting laser (PC-SELs). Specifically, we demonstrate two-dimensional coherent lasing oscillation with GaN PC-SELs, using a unique crystal growth technique called “air hole retained overgrowth” (AROG). Above the threshold, we obtained a two-dimensionally distributed near-field pattern, and a distinctive far-field pattern with a divergence angle less than 1°. We also investigate a suitable sample structure for the reduction of the threshold current, where the PC structure is moved from an n-cladding layer to a p-cladding one. This is an important step towards the realization of novel light sources that can be integrated two dimensionally for a variety of new scientific and engineering applications in the blue to ultraviolet wavelengths.
Superlattices from Diamond
Authors: Watanabe Hideyuki , Shikata S.
Published: January 2010

Diamond superlattices were fabricated by producing multilayer structures of isotopically pure carbon-12 (12C) and carbon-13 (13C), which confine electrons by a difference in band-gap energy. Secondary ion mass spectrometry (SIMS) measurements were employed to characterize the isotopic composition of the diamond superlattices. Layers between 2 nm and 350 nm in thickness can be designed and fabricated using a microwave plasma-assisted chemical vapor deposition technique.
Thermodynamically Stable, Size Selective Solubilization of Carbon Nanotubes in Aqueous Media by Self-assembly with Amphiphilic Block Copolymers
Authors: Nagarajan Ramanathan
Published: January 2010

Two molecular modes of amphiphilic block copolymer-carbon nanotube interactions have been suggested in the literature, involving the adsorption of either individual block copolymer molecules or of multimolecular, spherical block copolymer micelles on the carbon nanotube. In both cases, the nature of stability imparted to the dispersion of nanotubes is kinetic, controlled by the steric barrier imposed by the adsorbed individual molecules or micelles. In this study we propose an alternate mode of molecular interaction, wherein the block copolymer molecules self-assemble around the nanotube to generate a thermodynamically stable aqueous dispersion. The possibility of such micellar solubilization of nanotubes is examined by constructing a phenomenological theory of nanotube solubilization. Illustrative calculations performed for polyethylene oxide- polypropylene oxide – polyethylene oxide (PEO-PPO-PEO) triblock copolymers show that they are capable of solubilizing carbon nanotubes in aqueous solutions. While the block copolymer molecules that spontaneously form cylindrical micelles are most likely to solubilize the nanotubes, other copolymers whose natural curvature is spherical or lamellar also are capable of forming cylindrical micelles around the nanotubes. Most interestingly, the solubilization is found to be size specific suggesting that this can be developed into a practical method to fractionate carbon nanotubes by size or chirality.
Standards Development for the Characterization of Quantum Dot Suspensions and Solids
Authors: Davis Lynn , Coe-Sullivan Seth , Shchekin Oleg , Mishra K.C. , Raukas Madis , Modi Rohit , Breen Craig , Leibowitz Mike
Published: January 2010

Luminescent nanoparticles such as quantum dots (QDs) are beginning to appear in SSL devices and other commercial products. The allure of QDs in SSL these applications is the potential to provide enhanced device performance (e.g., improved energy efficiency, better color rendering properties, etc.) than is possible with conventional technologies. When used in SSL and other applications, QDs are typically incorporated into or coated onto a solid organic or inorganic matrix and then are excited using external stimuli (e.g., blue light with a maximum wavelength of 450 nm). This structure is vastly different from the colloidal environment in which QDs are typically synthesized and characterized. Bridging the gap between the measurements typically acquired by QD providers and those needed by potential end-users is currently difficult due to the absence of agreed upon standard test methods. Measurements taken in colloidal QD suspensions often do not translate to solid-phase material characterizations due to a variety of factors including sample preparation methods (e.g., temperature, solvents, etc), QD concentrations, and effects arising from the presence of the solid matrix. Additionally, solid samples are more likely to exhibit diffuse reflectance and/or diffuse transmittance necessitating the use of an integrating sphere and a computer-controlled spectrometer to acquire accurate readings. This paper discusses the development of a standard test method to measure the quantum efficiency of QDs contained in solid organic and inorganic matrices. This standard is being developed under the auspices of the International Electrotechnical Commission, Technical Committee 113 on Nano-electrotechnologies.
Surfactant-free Colloidal Crystal of ZnO Quantum Dots
Authors: Zhang Xi , Sun Dazhi , Sue Hung-Jue
Published: January 2010

Monodisperse ZnO quantum dots (QDs) with a particle size of about 5 nm have been synthesized. Isopropanol together with hexane were utilized to precipitate ZnO nanoparticles to form condensed phases, ranging from white flocculation, to gel-like fluid, and to transparent solid. The morphology and structure in the transparent ZnO solid was characterized by UV-vis, X-ray diffraction, small-angle X-ray scattering, transmission electron microscopy, and scanning electron microscopy. The mechanisms for the formation of transparent ZnO QDs close-packed structure were monitored via UV-vis spectra, and found likely to be a colloidal crystal. The colloidal crystal is transparent and absorbs UV light efficiently. Possible conditions for the formation of the ZnO QDs colloidal crystal are discussed.
Electrical Control of LSPR from Gold Nanoparticles Using Electrochemical Oxidation
Authors: Miyazaki Takashi , Hasegawa Rei , Yamaguchi Hajime , Nagato Hitoshi , Oh-oka Haruhi , Amemiya Isao , Uchikoga Shuichi
Published: January 2010

Large shift of localized surface plasmon resonance (LSPR) spectrum of gold nanoparticles was attained by electrochemical oxidation of the nanoparticle surface. This oxidation occurred in a cell consisting of a pair of indium tin oxide (ITO) electrodes with water medium between the electrodes. On one side of the ITO electrode, the gold nanoparticles were adsorbed. The LSPR spectrum was moved consecutively to the red by increasing the applied positive voltage. By the application of 5 V to the cell, the spectrum shift as large as 55 nm was obtained. Though the spectrum shift has already been observed by changing liquid crystal (LC) orientation surrounding gold nanoparticles, the amount of the shift was not large (11 nm). That was because the variation of the effective refractive index of LC was rather small. Our large shift due to electrochemical oxidation resulted from the large refractive index of Au-O. The upper limit of the LSPR spectrum shift by our method is estimated to be 138 nm.
Grating Coupled Surface Plasmon Resonance Enhanced Fluorescence and Its Application for Cell Observation
Authors: Cui Xiaoqiang , Tawa Keiko , Nishii Junji
Published: January 2010

One-dimensional grating with 400 nm pitch was fabricated on a SiO2 glass surface. The grating was applied for detection of fluorescence excited by the electric field of the grating-coupled surface plasmon resonance and highly sensitive observation of fluorescence image by optical microscope. 40-times of fluorescence enhancement was obtained under optimal condition after our systematically investigating depth and duty ratio dependent behavior.
Surface Plasmon Resonance Responses of Au-SnOxNanocomposite Films
Authors: Yang Dongfang
Published: January 2010

Au-SnOxnanocomposite thin films composed of gold nanoparticles embedded in SnOxmatrix were prepared by pulsed laser deposition technique and their crystal structure, morphology and chemical composition were evaluated by low angle X-ray diffraction, field-emission scanning electron microscopy and x-ray photoelectron spectroscopy, respectively. For the nanocomposite films with high Au percentage, the surfaces of nanocomposite films are very smooth, while for the films with low Au percentage, the films consist of many embedded Au nanoparticles with particle size of 5-20 nm. The XRD results revealed that in the nanocomposite films Au existed in a polycrystalline phase while SnOxin an amorphous phase. Surface plasmon resonance (SPR) responses of the Au-SnOxnanocomposite thin films were investigated as functions of Au percentage and film thickness in the Kretschmann geometry of attenuated total reflection using a polarized light beam at the wavelength of 640 nm. The reflectance minima (SPR dip) of SPR responses of the Au-SnOxnanocomposite films appeared at higher values of incident angle than that of a pure Au film and as the Au percentage decreases the SPR angles shift to higher values and the widths also become broader. The potential use of Au-SnOxnanocomposite films for SPR gas sensing was discussed.
Marni Goldman Tribute: Contributions to Materials Science Education
Authors: Wade Charles , Frank Curtis
Published: January 2010

This symposium is a memorial to Dr. Marni Goldman. Although she never walked and had only limited use of her arms, Marni's academic and professional accomplishments placed her in elite company. She obtained two bachelors degrees from the University of Pennsylvania and a Ph.D. in Materials Science from the University of California at Berkeley. Even with a heavy course load, she was involved in educational outreach during her studies. She started her career as a Research Associate (Education Director) in Stanford's NSF Materials Research Science and Engineering Center on Polymer Interfaces and Macromolecular Assemblies in 2000 and retained those responsibilities until her death in 2007. During this period she rapidly added the responsibilities as Education Director for Stanford's Nanofabrication Facility and was ultimately named Associate Director of Stanford's Office of Science Outreach. Marni was a dynamo whose activities at Stanford included a large summer undergraduate internship program, a Research Experiences for Teachers program (local and national activities), a program to bring community college students (especially minority students) to the campus, public science (San Jose Tech Museum of Innovation, San Francisco Exploratorium), outreach to high schools with high minority populations, and a program with summer internships for students with disabilities. Marni's achievements are thanks in no small part to her extraordinary family, to her own intelligence and tenacity, and to a wide and loving circle of friends, drawn to her by the spirit of her determination and the unmistakable largeness of her heart.
Deaf and Hard of Hearing Undergraduate Interns Investigate Smart Polymeric Materials
Authors: Cebe Peggy , Cherdack Daniel , Guertin Robert , Haas Terry , Huang Wenwen , Ince-Gunduz B. Seyhan , Tobin Roger , Valluzzi Regina
Published: January 2010

Smart Materials are those which can undergo a reversible property change in response to an external influence. An important polymeric Smart Material is poly(vinylidene fluoride), or PVF2, which is piezoelectric. The structure of PVF2 determines which crystal phases will be electrically active. Recent research has shown that the electrically active beta phase of PVF2 grows preferentially in nanocomposites of PVF2 mixed with organically modified silicates (OMS) ‘1-4’. These nanocomposite Smart Materials offer a new processing strategy for PVF2 piezo-films. Using PVF2 nanocomposites as the research focal point, a summer internship program was developed for deaf and hard of hearing (DHH) undergraduate students [5,6]. This paper describes the program and presents research results achieved by the interns. It is written from the perspective of the Principal Investigator, Cebe, on behalf of all the co-authors.
Identification, Development and Implementation of Nanoscience Activities for Alabama K-12
Authors: Bakker Martin , Staggemeier Katrina , Grano Amy , Kuntz Aaron , Gleason Jim , McKenzie Leigh , O'Neal Brenda , Pace Rachel
Published: January 2010

We report on a pair of MSP (Mathematics & Science Partnership) START pilot projects designed to identify nanoscience experiments that will fit within the Alabama course of study for use in Alabama K-12 classrooms. As part of the first project we are testing the development, refinement and evaluation of an activity already partly developed. The form of this activity has had input from a focus group of RETs who were tasked to provide input into the activity and how it can be matched to components of the Alabama Course of Study. This activity consists of using sparks generated by abrasion of misch metal by sand paper of different grit size. Different grit sizes produce metal particles of different sizes, resulting in sparks of different size and length. If done in a dry box no sparks are produced and the powder left is not pyrophoric, demonstrating that high surface area, heat and oxygen are all required to produce sparks. SEM characterization of the powder allows the particle sizes to be determined, giving the correlation between size, grit size and spark track length. The activity was tested on groups of middle school science campers at McWane Science Center, and after evaluation, further modified to increase student interest and impact. The activity was then tested on grades 6-8 in a middle school classroom by a graduate student/undergraduate student team.
Innovative Evaluation of Two Materials Science Education Enrichment Programs
Authors: Steinberg Daniel Jonathan , Greco Shannon L. , Carroll Kimberly
Published: January 2010

The Princeton Center for Complex Materials (PCCM) is an NSF-funded Materials Science and Research Center (MRSEC) at Princeton. PCCM currently has four Interdisciplinary Research Groups (IRGs) and several seed projects. PCCM runs a variety of education outreach programs that include: Research Experience for Undergraduates, Research Experience for Teachers, Materials Camp for Teachers, Middle School Science and Engineering Expo (SEE) for 1200 students, and Princeton University Materials Academy (PUMA), for inner city high school students. In this paper we focus on new evaluation efforts for the PUMA and the Science and Engineering Expo. We will discuss first PUMA the SEE and elaborate on the new evaluation efforts for each program.

Created in 2002 by PCCM, PUMA has an inquiry based materials science curriculum designed to work at the high school level. PUMA's activities are paired with an inquiry based evaluation of scientific ability and attitude change. An evaluation of high school students' ability to formulate scientific questions as a result of their participation in this summer program based was developed based on similar studies of college students questioning ability in inquiry learning environments. Created in 2004 by PCCM and partners in Molecular Biology, SEE is run once per year in the spring. It is a day dedicated to capturing the imaginations of young students through science demonstrations and direct interaction with materials scientists and engineers. 1000 middle school students from local schools come to Princeton University to interact with Princeton scientists and engineers and explore science with the help of demonstrations and hands-on activities. Throughout the day, they explore a wide range research from Princeton that is at the cutting edge of science and engineering to generate excitement about science and engineering. In addition to studying over 5000's student written essays we have constructed a pre and post test for student attitudes administered to over 500 students in 2009 to determine the impact of the SEE on students' attitudes about materials science and STEM fields. This large scale attitude assessment and student written statements help to establish the impact of this one day program.
Research Grade Instrumentation for Nanotechnology and MSE Education
Authors: Broadbridge Christine , Garofano Jacquelynn , Altman Eric , Khalil Yehia , Henrich Victor , Segal Yaron , Padmore Myrtle-Rose , Michael Philip , Walker Fred
Published: January 2010

The Center for Research on Interface Structures and Phenomena (CRISP) is a National Science Foundation (NSF) Materials Research Science and Engineering Center (MRSEC). CRISP is a partnership between Yale University, Southern Connecticut State University (SCSU) and Brookhaven National Laboratory. A main focus of CRISP research is complex oxide interfaces that are prepared using epitaxial techniques, including molecular beam epitaxy (MBE). Complex oxides exhibit a wealth of electronic, magnetic and chemical behaviors, and the surfaces and interfaces of complex oxides can have properties that differ substantially from those of the corresponding bulk materials. CRISP employs this research program in a concerted way to educate students at all levels. CRISP has constructed a robust MBE apparatus specifically designed for safe and productive use by undergraduates. Students can grow their own samples and then characterize them with facilities at both Yale and SCSU, providing a complete research and educational experience. This paper will focus on the implementation of the CRISP Teaching MBE facility and its use in the study of the synthesis and properties of the crystalline oxide-silicon interface.
MRI suites and residual design risk from static magnetic field
Authors: Price T. , Wamuziri S. , Gupta N.
Published: January 2010

Since the inception of the UK Construction (Design and Management) Regulations 1994 through to the 2007 Construction (Design and Management) Regulations a duty has been imposed upon the client of premises where a notifiable project has been carried out, to provide a health and safety file which may be needed during future work. This work includes cleaning, maintenance, alterations, extensions, refurbishment and demolition. The Construction (Design and Management) Regulations 2007 also impose further duties on clients to provide information to those who will use their premises as a workplace. This paper reports the results of a study which assessed whether information relevant to the health and safety file for magnetic resonance imaging (MRI) installations in hospitals having had passive magnetic shielding installed was available from National Health Service trusts in Wales, Scotland and England. Information on both the site-specific design and the actual position of the static magnetic field was lacking, as were the existence of as-built drawings showing the magnetic shielding. Information relevant to the risk management of the static magnetic field of MRI suites in the form of a health and safety file is sparse, incomplete and sometimes irrelevant.
Observations on the Chernobyl Disaster and LNT
Authors: Jaworowski Zbigniew
Published: January 2010

The Chernobyl accident was probably the worst possible catastrophe of a nuclear power station. It was the only such catastrophe since the advent of nuclear power 55 years ago. It resulted in a total meltdown of the reactor core, a vast emission of radionuclides, and early deaths of only 31 persons. Its enormous political, economic, social and psychological impact was mainly due to deeply rooted fear of radiation induced by the linear non-threshold hypothesis (LNT) assumption. It was a historic event that provided invaluable lessons for nuclear industry and risk philosophy. One of them is demonstration that counted per electricity units produced, early Chernobyl fatalities amounted to 0.86 death/GWe-year), and they were 47 times lower than from hydroelectric stations (∼40 deaths/GWe-year). The accident demonstrated that using the LNT assumption as a basis for protection measures and radiation dose limitations was counterproductive, and lead to sufferings and pauperization of millions of inhabitants of contaminated areas. The projections of thousands of late cancer deaths based on LNT, are in conflict with observations that in comparison with general population of Russia, a 15% to 30% deficit of solid cancer mortality was found among the Russian emergency workers, and a 5% deficit solid cancer incidence among the population of most contaminated areas.