bluuebunny/crossref_metadata_2025 huggingface dataset:
Not a slow snail: Rapid rise of environmental awareness and ecological insights regarding invasive island apple snails (Pomacea insularum)
Authors: Burks Romi , Van Dyke Jess
Published: October 2009

Background/Question/Methods

Exotic invaders routinely move faster than scientific publication processes. Lacking aerial dispersal stages, snails generally match descriptions of slow colonizers. However, reminiscent of the pace with which zebra mussels gained notoriety, a growing sense of urgency has emerged from management communities regarding established populations of exotic, invasive island apple snails (Pomacea insularum). Recently separated by mitochondrial markers as a related, yet distinct, species, P. insularum sits poised to follow along the invasive trajectory of its better known relative, the golden apple snail (P. canaliculata). Literature studies examining mechanisms that promote invasiveness suggest family history of invasion serves as a sufficient enough warning sign. Furthermore, a paucity of natural history information exists on this larger (max wet weight 166-g), more fecund (2000 eggs as average clutch size) aquatic plant consumer. Without insights into basic life history, actions within management agencies often stall. In just the past five years, multiple introductions gave rise to established reproductive populations across the entire Gulf Coast, from Texas to Florida and even northward to South Carolina. Using a combination of empirical results from multiple experiments and recently compiled insights from researchers studying invasive apple snails (encapsulated as a blog: http://snailbusters.wordpress.com/), we explore three questions. First, what patterns in life history emerge for P. insularum? Second, what natural history aspects appear missing? And third, how can dissemination of new findings shape future studies?

Results/Conclusions

Synthesis of experiments and observations from Texas provide compelling (i.e. statistically significant) evidence that P. insularum preferentially chooses to deposit clutches on emergent plants. Snails favor plants with strong circular stems, particularly wild taro (Colocasia esculenta). Unfortunately, easy to measure clutch characteristics (e.g. length, width, depth, volume) fail to predict hatching success. Female P. insularum snails tend to oviposit clutches substantially higher on plant stems than smaller female P. canaliculata. Permanent inundation of newly laid clutches completely prevents hatching, although the impact of water stress on clutch hatching efficiency varies with stress intensity and frequency. Complimentary research also notes differences depending in clutch developmental stage. Among managers and researchers, agreement clearly exists that the egg stage represents our best chance at slowing down the invasion. Relatively few studies focus on interactions (i.e. competition, predation) with native organisms. In conclusion, because clear time-pressure exists to protect native biodiversity, rise in popularity of non-traditional formats (i.e. blogs) to speed research along and increase networking has started in the case of invasive apple snails.
Chloroplast HCF101 is a scaffold protein for [4Fe-4S] cluster assembly
Authors: Schwenkert Serena , Netz Daili J. A. , Frazzon Jeverson , Pierik Antonio J. , Bill Eckhard , Gross Jeferson , Lill Roland , Meurer Jörg
Published: October 2009

Oxygen-evolving chloroplasts possess their own iron-sulfur cluster assembly proteins including members of the SUF (sulfur mobilization) and the NFU family. Recently, the chloroplast protein HCF101 (high chlorophyll fluorescence 101) has been shown to be essential for the accumulation of the membrane complex Photosystem I and the soluble ferredoxin-thioredoxin reductases, both containing [4Fe-4S] clusters. The protein belongs to the FSC-NTPase ([4Fe-4S]-cluster-containing P-loop NTPase) superfamily, several members of which play a crucial role in Fe/S cluster biosynthesis. Although the C-terminal ISC-binding site, conserved in other members of the FSC-NTPase family, is not present in chloroplast HCF101 homologues using Mössbauer and EPR spectroscopy, we provide evidence that HCF101 binds a [4Fe-4S] cluster. 55Fe incorporation studies of mitochondrially targeted HCF101 in Saccharomyces cerevisiae confirmed the assembly of an Fe/S cluster in HCF101 in an Nfs1-dependent manner. Site-directed mutagenesis identified three HCF101-specific cysteine residues required for assembly and/or stability of the cluster. We further demonstrate that the reconstituted cluster is transiently bound and can be transferred from HCF101 to a [4Fe-4S] apoprotein. Together, our findings suggest that HCF101 may serve as a chloroplast scaffold protein that specifically assembles [4Fe-4S] clusters and transfers them to the chloroplast membrane and soluble target proteins.
Complement activation and disease: protective effects of hyperbilirubinaemia
Authors: BASIGLIO Cecilia L. , ARRIAGA Sandra M. , PELUSA Fabián , ALMARÁ Adriana M. , KAPITULNIK Jaime , MOTTINO Aldo D.
Published: October 2009

Complement, an important effector mechanism of the immune system, is an enzymatic cascade of approx. 30 serum proteins leading to the amplification of a specific humoral response. It can be activated through the classical or alternative pathways, or through the mannose-binding lectin pathway. The activation of the classical pathway is initiated by the binding of the C1 component to antigen-bound antibodies, known as immunocomplexes. C1 is a complex of one molecule of C1q, two molecules of C1r and two molecules of C1s. C1q contains three copies of a Y-shaped fundamental unit with globular heads included in its structure, which play a major role in the interaction with the Fc portion of immunoglobulins. Deficient or exacerbated activation of the complement system leads to diseases of variable severity, and pharmacological inhibition of the complement system is considered as a therapeutic strategy to ameliorate the inflammatory effects of exacerbated complement activation. Bilirubin is a product of haem degradation by the concerted action of haem oxygenase, which converts haem into biliverdin, and biliverdin reductase, which reduces biliverdin to UCB (unconjugated bilirubin). UCB exerts both cytoprotective and cytotoxic effects in a variety of tissues and cells, acting either as an antioxidant at low concentrations or as an oxidant at high concentrations. In the present review, we describe in detail the anti-complement properties of bilirubin, occurring at levels above the UCB concentrations found in normal human serum, as a beneficial effect of potential clinical relevance. We provide evidence that UCB interferes with the interaction between C1q and immunoglobulins, thus inhibiting the initial step in the activation of complement through the classical pathway. A molecular model is proposed for the interaction between UCB and C1q.
Are stem cells a cure for diabetes?
Authors: McCall Michael D. , Toso Christian , Baetge Emmanuel E. , Shapiro A. M. James
Published: October 2009

With the already heightened demand placed on organ donation, stem cell therapy has become a tantalizing idea to provide glucose-responsive insulin-producing cells to Type 1 diabetic patients as an alternative to islet transplantation. Multiple groups have developed varied approaches to create a population of cells with the appropriate characteristics. Both adult and embryonic stem cells have received an enormous amount of attention as possible sources of insulin-producing cells. Although adult stem cells lack the pluripotent nature of their embryonic counterparts, they appear to avoid the ethical debate that has centred around the latter. This may limit the eventual application of embryonic stem cells, which have already shown promise in early mouse models. One must also consider the potential of stem cells to form teratomas, a complication which would prove devastating in an immunologically compromised transplant recipient. The present review looks at the progress to date in both the adult and embryonic stem cells fields as potential treatments for diabetes. We also consider some of the limitations of stem cell therapy and the potential complications that may develop with their use.
On the origin of threading dislocations in GaN films
Authors: Moram M. A. , Ghedia C. S. , Rao D. V. S. , Barnard J. S. , Zhang Y. , Kappers M. J. , Humphreys C. J.
Published: October 2009

A series of GaN films were grown by metalorganic vapor phase epitaxy on nitrided sapphire using an initial annealed low-temperature nucleation layer (LT-NL), without employing any conventional threading dislocation (TD) reduction methods. Film thicknesses ranging from the LT-NL to 500 nm were used. The island network morphology was investigated at each growth stage using atomic force microscopy. Data from cathodoluminescence studies showed initially uniform luminescence, followed by the gradual development of bright (low TD) regions which had lateral sizes different from the island sizes at all times and which continued to increase in size after coalescence. The formation of low-energy arrays of a-type TDs also continued after island coalescence. X-ray diffraction, transmission electron microscopy (TEM) and AFM data indicated that the highest (a+c)-type TD densities were found in the LT-NL, but subsequently decreased due to TD loop formation (promoted by island facets) and reaction to produce a-type TDs. a-type TD densities were also high in the LT-NL but subsequently increased slightly, due to the reaction of (a+c)-type TDs. A very sharp dynamical ‘correlation’ peak was also observed in XRD of the LT-NL, related to TDs with an a-component. Furthermore, defect formation was observed within the LT-NL using high-resolution TEM. These data are consistent with TD formation predominantly in the LT-NL, followed by TD movement at elevated growth temperatures. Initially, coalesced films had a high TD density with a spatially random TD arrangement, but progressively altered into a lower TD density, spatially clustered arrangement during growth. This type of microstructure may mistakenly be interpreted as arising from island coalescence.
The effect of confinement on the stability of field induced states and on supercooling in antiferro-ferroelectric phase transitions in chiral smectic liquid crystals
Authors: Song Jang-Kun , Vij J. K.
Published: October 2009

We investigate both the supercooling and the hysteresis phenomena of the phase transitions between the smectic C* and the smectic CA* phases driven by temperature and electric field, respectively. These two phenomena show similar characteristics for the dependence of transmittance on both the cell thickness and the applied field. The mechanisms for large supercooling and large hysteresis in thin cells are shown to correspond to the suppression of the propagation of solitary wave by the surfaces. Furthermore, these two phenomena are shown to be controlled by a moderate ac field applied across the cell. We present a clear evidence for the existence of at least two field induced subphases (called states here) between the antiferroelectric and the ferroelectric phases. These are found to correspond to the field induced three-layered and four-layered structures through a comparison of experimental results on the tilt angle and its simulation as well as by discrete changes in the texture by increasing the electric field. The correspondence between the thermotropic phases and the field induced states is demonstrated through measurements of the supercooling/superheating and of the hysteresis as a function of the cell thickness. The instability in the field induced states depends strongly on the cell thickness, and the various states are not observed in a cell of 1.6 μm thickness.
Yield strength of tantalum for shockless compression to 18 GPa
Authors: Asay J. R. , Ao T. , Vogler T. J. , Davis J.-P. , Gray G. T.
Published: October 2009

A magnetic loading technique was used to study the strength of pure, annealed, and cold-rolled polycrystalline tantalum under planar ramp loading at strain rates of ∼106/s. Both the initial yield strength and the flow strength after compression to peak loading stresses of 18 GPa were determined. For sample thicknesses ranging from 0.5–6.0 mm, it was found that the elastic limit of ∼3.2 GPa, corresponding to a yield strength of 1.6 GPa, for annealed Ta was sharply defined and essentially independent of sample thickness. After elastic yielding, relaxation of the longitudinal stress occurred for sample thicknesses greater than ∼0.5 mm, approaching an asymptotic value of ∼1.6 GPa. Two different purities of annealed Ta showed no difference in initial yield strength. Cold-rolling annealed Ta to 26% plastic strain resulted in a more dispersed elastic precursor with an amplitude of about 1.6 GPa and with no stress relaxation after yielding. Analysis of unloading wave profiles from the peak loading states allowed determination of the flow stress, which increased to about 0.9 GPa for annealed Ta and 1.3 GPa for cold-rolled Ta at peak stresses of 17–18 GPa.
Probing royal demolition explosive (1,3,5-trinitro-1,3,5-triazocyclohexane) by low-energy electrons: Strong dissociative electron attachment near 0 eV
Authors: Sulzer P. , Mauracher A. , Ferreira da Silva F. , Denifl S. , Märk T. D. , Probst M. , Limão-Vieira P. , Scheier P.
Published: October 2009

Low energy electron attachment to gas phase royal demolition explosive (RDX) (and RDX-A3) has been performed by means of a crossed electron-molecular beam experiment in an electron energy range from 0 to 14 eV with an energy resolution of ∼70 meV. The most intense signals are observed at 102 and 46 amu and assigned to C2H4N3O2− and NO2−, respectively. Anion efficiency curves of 16 anions have been measured. Product ions are observed mainly in the low energy region, near 0 eV arising from surprisingly complex reactions associated with multiple bond cleavages and structural and electronic rearrangement. The remarkable instability of RDX to electron attachment with virtually thermal electrons reflects the highly explosive nature of this compound. The present results are compared to other explosive aromatic nitrocompounds studied in our laboratory recently.
Effect of 100 MeV swift heavy ions [silver (Ag8+)] on morphological and electrical properties of polypyrrole
Authors: Kaur Amarjeet , Dhillon Anju , Avasthi D. K.
Published: October 2009

Polypyrrole (PPY) films were prepared by the electrochemical polymerization technique. The fully undoped samples were irradiated with different fluences ranging from 1010 to 1012 ions/cm2 of 100 MeV silver (Ag8+) ions. In order to explain the effect of these radiations, a comparative study of samples before and after irradiation was performed by using various techniques such as surface electron microscopy, atomic force microscopy, and X-ray diffraction. With an increase in fluence, the surface structure of PPY films becomes smoother, and the conductivity increases by two orders, which has been explained in light of reordering of polymer chains. The temperature dependence of the dc conductivity of irradiated as well as unirradiated samples has been investigated at 77–300 K. The charge transport properties before and after irradiation are retained although conductivity increases. It has been proposed that swift heavy ion irradiation affects the interchain conductivity. The conductivity of irradiated samples is stable under atmospheric conditions for more than 9 months. The present investigations open up the scope for the applicability of irradiated conducting polymers as microstructures with defined conductivity for sensor applications.
Influence of temperature and excitation procedure on the athermal behavior of Nd3+-doped phosphate glass: Thermal lens, interferometric, and calorimetric measurements
Authors: Astrath N. G. C. , Barboza M. J. , Medina A. N. , Bento A. C. , Baesso M. L. , Silva W. F. , Jacinto C. , Catunda T.
Published: October 2009

In this work, thermal and optical properties of the commercial Q-98 neodymium-doped phosphate glass have been measured at low temperature, from 50 to 300 K. The time-resolved thermal lens spectrometry together with the optical interferometry and the thermal relaxation calorimetry methods were used to investigate the glass athermal characteristics described by the temperature coefficient of the optical path length change, ds/dT. The thermal diffusivity was also determined, and the temperature coefficients of electronic polarizability, linear thermal expansion, and refractive index were calculated and used to explain ds/dT behavior. ds/dT measured via thermal lens method was found to be zero at 225 K. The results provided a complete characterization of the thermo-optical properties of the Q-98 glass, which may be useful for those using this material for diode-pumped solid-state lasers.
Production of hydrogen in a conventional microwave oven
Authors: Nomura Shinfuku , Toyota Hiromichi , Mukasa Shinobu , Yamashita Hiroshi , Maehara Tsunehiro , Kawashima Ayato
Published: October 2009

Hydrogen is produced by generating in-liquid plasma in a conventional microwave oven. A receiving antenna unit consisting of seven copper rods is placed at the bottom of the reactor furnace in the microwave oven. 2.45 GHz microwave in-liquid plasma can be generated at the tips of the electrodes in the microwave oven. When the n-dodecane is decomposed by plasma, 74% pure hydrogen gas can be achieved with this device. The hydrogen generation efficiency for a 750 W magnetron output is estimated to be approximately 56% of that of the electrolysis of water. Also, in this process up to 4 mg/s of solid carbon can be produced at the same time. The present process enables simultaneous production of hydrogen gas and the carbide in the hydrocarbon liquid.
Temperature dependence of current-voltage characteristics in highly doped Ag/p-GaN/In Schottky diodes
Authors: Çınar K. , Yıldırım N. , Coşkun C. , Turut A.
Published: October 2009

To obtain detailed information about the conduction process of the Ag/p-GaN Schottky diodes (SDs) fabricated by us, we measured the I-V characteristics over the temperature range of 80–360 K by the steps of 20 K. The slope of the linear portion of the forward bias I-V plot and nkT=E0 of the device remained almost unchanged as independent of temperature with an average of 25.71±0.90 V−1 and 41.44±1.38 meV, respectively. Therefore, it can be said that the experimental I-V data quite well obey the field emission model rather than the thermionic emission or thermionic field emission model. The study is a very good experimental example for the FE model. Furthermore, the reverse bias saturation current ranges from 8.34×10−8 A at 80 K to 2.10×10−7 A at 360 K, indicating that the charge transport mechanism in the Ag/p-GaN SD is tunneling due to the weak temperature dependence of the saturation current. The possible origin of high experimental characteristic tunneling energy of E00=39 meV, which is ten times larger than possible theoretical value of 3.89 meV, is attributed to the accumulation of a large amount of defect states near the GaN surface or to the deep level defect band induced by high doping or to any mechanism which enhances the electric field and the state density at the semiconductor surface.
Investigation on oblique shock wave control by arc discharge plasma in supersonic airflow
Authors: Wang Jian , Li Yinghong , Xing Fei
Published: October 2009

Wedge oblique shock wave control by arc discharge plasma in supersonic airflow was investigated theoretically, experimentally, and numerically in this paper. Using thermal choking model, the change in oblique shock wave was deduced, which refer that the start point of shock wave shifts upstream, the shock wave angle decreases, and its intensity weakens. Then the theoretical results were validated experimentally in a Mach 2.2 wind tunnel. On the test conditions of arc discharge power of ∼1 kW and arc plasma temperature of ∼3000 K, schlieren photography and gas pressure measurements indicated that the start point of shock wave shifted upstream of ∼4 mm, the shock wave angle decreased 8.6%, and its intensity weakened 8.8%. The deduced theoretical results match the test results qualitatively, so thermal mechanism and thermal choking model are rational to explain the problem of oblique shock wave control by arc discharge plasma. Finally, numerical simulation was developed. Based on thermal mechanism, the arc discharge plasma was simplified as a thermal source term that added to the Navier–Stokes equations. The simulation results of the change in oblique shock wave were consistent with the test results, so the thermal mechanism indeed dominates the oblique shock wave control process.
Near-field wire-based passive probe antenna for the selective detection of the longitudinal electric field at terahertz frequencies
Authors: Adam Ronan , Chusseau Laurent , Grosjean Thierry , Penarier Annick , Guillet Jean-Paul , Charraut Daniel
Published: October 2009

A passive probe antenna for cw near-field microscopy at millimeter and submillimeter wavelengths is defined. It is based on the coupling between a free-space linearly polarized propagating beam to a wire mode. This is obtained efficiently owing to a discontinuous phase plate. This passive “optical” structure allows either the generation of a subwavelength confinement of the longitudinal electric field (polarized along the wire antenna) or, due to reciprocity, the collection of the longitudinal component of the electric field (along the wire antenna) with subwavelength resolution. The emission and collection properties of the proposed antenna have been demonstrated experimentally using a preliminary realization designed to work at 0.1 THz. Experimental results are well supported by calculations.
Efficient, high rep rate, large-bore kinetically enhanced copper vapor laser with low (<1 kW/l) specific input power using new thermal assembly
Authors: Singh Bijendra , Subramaniam V. V. , Daultabad S. R. , Chakraborty Ashim
Published: October 2009

Large-bore kinetically enhanced copper vapor laser (CVL) based on new thermal assembly consisting of different density zones of insulation material (alumina fiber) around the discharge tube is demonstrated for the first time with efficiency η≥1% at extremely low specific input power (SIP) of ≤1 kW/l. As a result of this longitudinal profiling of the insulation material, efficiency of ∼1.2% was achieved at lowest SIP of ∼0.75 kW/l. Net reduction in the input power of ∼1 kW was observed on using this thermal assembly as compared to nonprofiled thermal assembly. These results show significant improvement (25%–30%) at low input requirements of the laser on using new thermal assembly around the discharge tube with overall electro-optical efficiency η≥1%. Maximum laser power achieved from the laser was ∼78 W at ∼9.8 kHz rep rate with efficiency of ∼1.4%. This large-bore CVL is also capable of operating efficiently (η∼1%) at high rep rate of −17 kHz with maximum laser power of ∼50 W. Performance of the laser under various operating conditions is also presented in this short paper.
Numerical simulation of laser-generated Lamb waves in viscoelastic materials by finite element method
Authors: Sun Hongxiang , Xu Baiqiang , Qian Rongzu
Published: October 2009

The effect of material viscoelasticity on the propagation of Lamb wave in a viscoelastic thin plate has been investigated quantitatively. Based on the plane strain theory, a numerical model of the laser-generated Lamb wave is developed in the frequency domain by using the finite element (FE) method. To verify the correctness of the FE model in the frequency domain, a classical FE model in the time domain is established for an elastic plate. The transient waveforms calculated in the frequency domain are in very good agreement with those obtained in the time domain. And then, the laser-generated Lamb waves in the elastic and viscoelastic thin plates are calculated, respectively. By comparing the waveforms of Lamb wave in the two plates, the influence of the material viscoelasticity on the propagation of Lamb waves is studied. Moreover, the effect of the material viscoelastic rate on Lamb waves is analyzed in detail.
On the frequency dispersion of the capacitance-voltage behavior of epitaxial Ge on Si p+-n junctions
Authors: Yang R. , Eneman G. , Wang G. , Claeys C. , Simoen E.
Published: October 2009

The electrically active defects in epitaxial germanium layers grown selectively on silicon-shallow trench isolation (STI) wafers have been investigated by means of p+-n junction characterization. The main focus is on the capacitance-voltage (C-V) analysis in reverse operation. A pronounced frequency dispersion in the C-V characteristics has been found for Ge Si-STI layers, while this is not the case for thick epitaxial Ge on Si layers, which contain a significantly lower density of threading dislocations. It is shown that the apparent free carrier density profile derived from the C-V plot at high frequency exhibits a pronounced overshoot in the vicinity of the Ge–Si heterointerface. However, this feature is not only determined by the band offset between the Ge and Si conduction band edges but also by the high density of extended defects and associated deep levels present near the interface. Finally, the impact of a postgrowth high-temperature annealing on the electrical properties of Ge Si-STI epitaxial layers will be discussed in view of the resulting change in extended defect density and profile.
Bandwidth limit of an ultrathin metamaterial screen
Authors: Huang Ruifeng , Kong Ling Bing , Matitsine Serguei
Published: October 2009

This paper analyzed the bandwidth limit of a class of ultrathin metamaterial screens for reducing reflectivity. The screens consist of arrays of conducting strips or square patches on top of a planar lossy dielectric or magnetic substrate backed by a conducting ground plane. An accurate analytical model has been derived to calculate the reflection coefficients of the screens, which take into account accurately the high order modes between the array and the ground plane. Based on the analytical model, the maximum bandwidth of the screens was explained. The factors determining the maximum bandwidth of the screens were revealed, which can serve as guidelines for the design of the ultrathin metamaterial screens.
Structural colors from Morpho peleides butterfly wing scales
Authors: Ding Yong , Xu Sheng , Wang Zhong Lin
Published: October 2009

A male Morpho peleides butterfly wing is decorated by two types of scales, cover and ground scales. We have studied the optical properties of each type of scales in conjunction with the structural information provided by cross-sectional transmission electron microscopy and computer simulation. The shining blue color is mainly from the Bragg reflection of the one-dimensional photonic structure, e.g., the shelf structure packed regularly in each ridges on cover scales. A thin-film-like interference effect from the base plate of the cover scale enhances such blue color and further gives extra reflection peaks in the infrared and ultraviolet regions. The analogy in the spectra acquired from the original wing and that from the cover scales suggests that the cover scales take a dominant role in its structural color. This study provides insight of using the biotemplates for fabricating smart photonic structures.
Water reactivity with tungsten oxides: H2 production and kinetic traps
Authors: Mayhall Nicholas J. , Rothgeb David W. , Hossain Ekram , Jarrold Caroline Chick , Raghavachari Krishnan
Published: October 2009

In a recent mass spectrometry/photoelectron spectroscopy study on the reactions between W2Oy− (y=2–6) and water, Jarrold and co-workers [J. Chem. Phys. 130, 124314 (2009)] observed interesting differences in the reactivity of the different cluster ions. Particularly noteworthy is the observation that the only product with the incorporation of hydrogens is a single peak corresponding to W2O6H2−. As reactions between metal oxide clusters and small molecules such as water have high potential for catalytic applications, we carried out a careful study to obtain a mechanistic understanding of this observed reactivity. Using electronic structure calculations, we identified and characterized multiple modes of reactivity between unsaturated tungsten oxide clusters [W2Oy− (y=4–6)] and water. By calculating the free energy corrected reaction profiles, our results provide an explanation for the formation of W2O6H2−. We propose a mechanism in which water reacts with a metal oxide cluster and eliminates H2. The results from our calculations show that this is nearly a barrierless process for all suboxide clusters with the exception of W2O5−.
Study on surface properties of PDMS microfluidic chips treated with albumin
Authors: Schrott Walter , Slouka Zdeněk , Červenka Petr , Ston Jiří , Nebyla Marek , Přibyl Michal , Šnita Dalimil
Published: October 2009

Electrokinetic properties and morphology of PDMS microfluidic chips intended for bioassays are studied. The chips are fabricated by a casting method followed by polymerization bonding. Microchannels are coated with 1% solution of bovine serum albumin (BSA) in Tris buffer. Albumin passively adsorbs on the PDMS surface. Electrokinetic characteristics (electro-osmotic velocity, electro-osmotic mobility, and zeta potential) of the coated PDMS channels are experimentally determined as functions of the electric field strength and the characteristic electrolyte concentration. Atomic force microscopy (AFM) analysis of the surface reveals a “peak and ridge” structure of the protein layer and an imperfect substrate coating. On the basis of the AFM observation, several topologies of the BSA-PDMS surface are proposed. A nonslip mathematical model of the electro-osmotic flow is then numerically analyzed. It is found that the electrokinetic characteristics computed for a channel with the homogeneous distribution of a fixed electric charge do not fit the experimental data. Heterogeneous distribution of the fixed electric charge and the surface roughness is thus taken into account. When a flat PDMS surface with electric charge heterogeneities is considered, the numerical results are in very good agreement with our experimental data. An optimization analysis finally allowed the determination of the surface concentration of the electric charge and the degree of the PDMS surface coating. The obtained findings can be important for correct prediction and possibly for robust control of behavior of electrically driven PDMS microfluidic chips. The proposed method of the electro-osmotic flow analysis at surfaces with a heterogeneous distribution of the surface electric charge can also be exploited in the interpretation of experimental studies dealing with protein-solid phase interactions or substrate coatings.
Features of two-dimensional to three-dimensional growth mode transition of Ge in SiGe/Si(001) heterostructures with strained layers
Authors: Yurasov D. V. , Drozdov Yu. N. , Shaleev M. V. , Novikov A. V.
Published: October 2009

The results of the study of the effect of strained SiGe layers on the critical thickness of two-dimensional growth of Ge layer in different SiGe/Si(001) structures are presented. A significant influence of buried strained SiGe layer on the growth of Ge has been found out, which remains considerable even for SiGe layers capped by unstrained Si layer of thickness up to 3.5 nm. The experimental results are well described by the proposed model, where obtained features are explained by means of introducing a phenomenological parameter called “effective decay length” of the strain energy accumulated in the structure.
Carrier distribution in InGaN/GaN tricolor multiple quantum well light emitting diodes
Authors: Charash R. , Maaskant P. P. , Lewis L. , McAleese C. , Kappers M. J. , Humphreys C. J. , Corbett B.
Published: October 2009

Carrier transport in InGaN light emitting diodes has been studied by comparing the electroluminescence (EL) from a set of triple quantum well structures with different indium content in each well, leading to multicolor emission. Both the sequence and width of the quantum wells have been varied. Comparison of the EL spectra reveals the current dependent carrier transport between the quantum wells, with a net carrier flow toward the deepest quantum well.
Impact dynamics of water droplets on chemically modified WOx nanowire arrays
Authors: Kwak Geunjae , Lee Mikyung , Senthil Karuppanan , Yong Kijung
Published: October 2009

The effects of surface energy on the wetting transition for impinging water droplets were investigated on the chemically modified WOx nanowire surfaces. We could modify the surface energy of the nanowires through chemisorption of alkyltrichlorosilanes with various carbon chain lengths and also by the ultraviolet-enhanced decomposition of self assembled monolayer molecules. Three surface wetting states could be identified through the balance between antiwetting and wetting pressures. This approach establishes a simple strategy for design of the water-repellent surface to impinging droplets.
Exact and asymptotic conditions on traveling wave solutions of the Navier–Stokes equations
Authors: Li Y. Charles , Viswanath Divakar
Published: October 2009

We derive necessary conditions that traveling wave and other solutions of the Navier–Stokes equations must satisfy in the pipe, Couette, and channel flow geometries. Some conditions are exact and must hold for any traveling wave solution or periodic solution irrespective of the Reynolds number (Re). Other conditions are asymptotic in the limit Re→∞. For the pipe flow geometry, we give computations up to Re=100 000 showing the connection of our asymptotic conditions to critical layers that accompany vortex structures at high Re.
Emission modification of CdSe quantum dots by titanium dioxide visible logpile photonic crystal
Authors: Subramania G. , Lee Y.-J. , Fischer A. J. , Luk T. S. , Brinker C. J. , Dunphy D.
Published: October 2009

Air band modes of three-dimensional photonic crystals (3DPCs) have a higher photonic density of states, potentially enabling greater emission enhancement. However, it is challenging to introduce emitters into the “air” region without significantly disturbing the photonic band structure of the PC. Here, we overcome this difficulty by introducing a low refractive index aerogel matrix containing CdSe quantum dots (625 nm peak emission) into a titanium dioxide logpile PC. We observe that the aerogel infiltration indeed preserves the bandstructure. We measure an emission suppression of ∼0.25 times inside and an enhancement of approximately three times outside the bandgap with only one vertical unit cell.
Quantum control study of multilevel effect on ultrafast isotope-selective vibrational excitations
Authors: Kurosaki Yuzuru , Yokoyama Keiichi , Yokoyama Atsushi
Published: October 2009

Quantum optimal control calculations have been carried out for isotope-selective vibrational excitations of the cesium iodide (CsI) molecule on the ground-state potential energy curve. Considering a gaseous isotopic mixture of C133sI and C135sI, the initial state is set to the condition that both C133sI and C135sI are in the vibrational ground level (v=0) and the target state is that C133sI is in the v=0 level while C135sI in the first-excited level (v=1). We find that, using the density-matrix formalism, perfect isotope-selective excitations for multilevel systems including more than ten lowest vibrational states can be completed in much shorter time scales than those for two-level systems. It is likely that this multilevel effect comes from the large isotope shifts in the vibrational levels of v>1. To check the reliability of the calculation we also carry out optimal control calculations based on the conventional wave-packet formalism, where the wave-function amplitude is temporally propagated on the grid points in real space, and obtain almost the same results as those with the density-matrix formalism.
Low temperature photoelectron spectra of water cluster anions
Authors: Ma Lei , Majer Kiran , Chirot Fabien , von Issendorff Bernd
Published: October 2009

Photoelectron spectra of cold (10 K) size selected water cluster anions (H2O)n− and (D2O)n− have been measured in the size range n=20–120. A new isomer with a higher binding energy than the so-called isomer I has been identified, which appears in the size range n=25–30 and for (H2O)n− becomes dominant at n=46. Magic numbers observed in the mass spectra of the cluster anions provide evidence that this new isomer class consists of clusters with an internal electron.
Photodesorption of excited iodine atoms from KI (100)
Authors: Joly Alan G. , Beck Kenneth M. , Hess Wayne P.
Published: October 2009

Band-to-band photoexcitation of potassium iodide single crystals with UV photons produces thermal and hyperthermal I-atom emission in both the ground I(P23/2) and spin-orbit excited I∗(P21/2) states. Thermal halogen atom emission is preceded by H-center diffusion from bulk to surface and excited atom emission indicates that the excited hole spin state relaxation is incomplete before H-center diffusion to the surface. The hyperthermal I-atom kinetic energy distribution is inverted in the sense that the electronically excited I∗(P21/2) atoms are more energetic than the ground state I(P23/2) atoms. The mechanism for hyperthermal emission of halogen atoms and their kinetic energy distributions are discussed in terms of recent calculations and a simple curve crossing model for the dynamical desorption process.
Grazing incidence fast atom diffraction: An innovative approach to surface structure analysis
Authors: Khemliche H. , Rousseau P. , Roncin P. , Etgens V. H. , Finocchi F.
Published: October 2009

An alternative diffraction technique, based on grazing incidence scattering of high energy atoms, is applied to surface structure determination of crystalline surfaces. This technique, named GIFAD for grazing incidence fast atom diffraction, uses the same geometry as reflection high energy electron diffraction but is less invasive, more surface sensitive, and readily interpretable quantitatively. We present here a demonstration of this approach on a prototypical II–VI compound, ZnSe(001). Besides providing lattice parameter with high accuracy, we show that GIFAD gives straightforward access to the surface valence electron density profile, allowing clear identification of an electron transfer from Zn to Se.
Termination of the W2Oy−+H2O/D2O→W2Oy+1−+H2/D2 sequential oxidation reaction: An exploration of kinetic versus thermodynamic effects
Authors: Rothgeb David W. , Hossain Ekram , Mayhall Nicholas J. , Raghavachari Krishnan , Jarrold Caroline Chick
Published: October 2009

Several mechanisms proposed and calculated for the sequential oxidation of tungsten suboxide clusters by H2O/D2O [Mayhall et al., J. Chem. Phys. 131, 144302 (2009)] are evaluated using anion photoelectron spectroscopy of an apparent intermediate, W2O6D2−. The spectrum of W2O6D2− is consistent with the W2O5−+D2O→W2O6−+D2 intermediate in which the initial water addition involves the interaction of the oxygen from D2O with a tungsten atom, approaching from a direction with the least repulsion from the W2O5− oxygen atoms, coupled with the interaction between a deuterium with a tungsten-tungsten bridging oxygen on the cluster. The presence of W2O6H2− and W2O6D2− suggests that there is insufficient internal energy in the complex to surmount the barrier for rearrangement required for tungsten hydride and hydroxide formation necessary for H2 or D2 evolution, which was calculated to be energetically favorable. The quality of the calculations is verified by direct comparison between experimental photoelectron spectra of W2O5− and W2O6− and spectral simulations generated from the lowest energy structures calculated for W2O5−, W2O6− and their corresponding neutrals. The results shed light on the importance of repulsion on the pathway a reaction follows under room temperature conditions.
Tunneling anisotropic spin polarization in lateral (Ga,Mn)As/GaAs spin Esaki diode devices
Authors: Einwanger A. , Ciorga M. , Wurstbauer U. , Schuh D. , Wegscheider W. , Weiss D.
Published: October 2009

We report here on anisotropy of spin polarization obtained in lateral all-semiconductor, all-electrical spin injection devices employing p+-(Ga,Mn)As/n+-GaAs Esaki diode structures as spin aligning contacts, resulting from the dependence of the efficiency of spin tunneling on the orientation of spins with respect to different crystallographic directions. We observed an in-plane anisotropy of 8% in the case of spins oriented either along [11¯0] or [110] direction and 25% anisotropy between in-plane and perpendicular-to-plane orientations of spins.
Electronic spectra of the linear polyyne cations HC2nH+ (n=2–8): Anab initiostudy
Authors: Zhang Jinglai , Guo Xugeng , Cao Zexing
Published: October 2009

The B3LYP, CAM-B3LYP, and RCCSD(T) calculations have been used to determine the ground-state geometries of the linear polyyne cations HC2nH+ (n=2–8). The CASSCF method has also been used to optimize the ground and first excited states. The present results indicate that these linear cations generally have an acetylenic structure H–C≡C–C≡C⋯C≡C–H+ with the ground state of X Π2g for even-numbered n or X Π2u for odd-numbered n. Moreover, the bond length alternation of HC2nH+ is less pronounced than the corresponding one of the neutral polyyne chains HC2nH. The CASPT2 approach has been employed to estimate the vertical excitation energies for the dipole-allowed (A⋯D) Π2u/g←X Π2g/u transitions in HC2nH+ (n=2–8) clusters. The predicted A Π2u/g←X Π2g/u transition energies in the gas phase are 2.62, 2.14, 1.81, 1.52, 1.35, 1.22, and 1.10 eV, respectively, in excellent agreement with the corresponding observed values of 2.45, 2.07, 1.75, 1.52, 1.35, 1.20, and 1.08 eV. The present calculations show that the absorption wavelengths for the A Π2u/g←X Π2g/u transitions exhibit notably linear size dependence, as shown in previous experimental studies, quite different from the nonlinear λ-n relationship for origin bands in HC2nH.
Pressure-driven flow in parallel-plate nanochannels
Authors: Zhang ZhongQiang , Zhang HongWu , Ye HongFei
Published: October 2009

A “channel moving” pressure-driven model is proposed to generate a constant pressure gradient in fluid flow. Classical molecular dynamics simulations are carried out to explore the pressure-driven flow in parallel-plate nanochannels with the channel width ranging from 2.611 to 5.595 nm. Considering the slip boundary conditions, relationships among the pressure gradient, mean flow velocity, and the channel width are investigated to couple the atomistic regime to continuum. The results indicate that the pressure-driven flows confined in nanochannels modeled in our simulations can be approximately described by the Navier–Stokes equations while the approximate accuracy increases with enlarging the channel width.
Effect of injection current density on electroluminescence in silicon quantum dot light-emitting diodes
Authors: Kim Baek Hyun , Davis Robert F. , Cho Chang-Hee , Park Seong-Ju
Published: October 2009

We report the effect of injection current density on the electroluminescence (EL) from silicon quantum dot (QD) light-emitting diodes. The EL spectra as a function of injection current density were blueshifted and broad. These results are attributed to both the increase in the contribution of small Si QDs in the silicon nitride film due to the increase in the injection current density and the recombination of electron-hole pairs between excited states in the Si QDs due to band bending under high bias.
Waves on a columnar vortex in a strongly stratified fluid
Authors: Billant Paul , Le Dizès Stéphane
Published: October 2009

This paper investigates the discrete bounded waves sustained by a vertical columnar Rankine vortex in a strongly stratified fluid. We show that these waves are very different from their well-known counterpart in homogeneous fluid (Kelvin vortex waves); they exist only for nonzero azimuthal wavenumber m, their frequency lies in the interval [0,mΩ] (Ω is the angular velocity in the vortex core) and they are unstable because of an outward radiation from the vortex. The instability mechanism is explained in terms of an over-reflection phenomenon by means of a Wentzel–Kramers–Brillouin–Jeffreys analysis for large axial wavenumber.
Continuous particle assembly in a capillary cell
Authors: Xu Lin , Neild Adrian , Ng Tuck Wah , Shao Fen Fen
Published: October 2009

Capillary force mechanisms have the advantages of providing the motive force to move groups of particles to locations of interest while holding them in place, offering delicateness, and obviating the use external energy sources. We report a capillary force method that permits particles to remain hydrated, while assembled and harvested in batches using a single setup, furthermore assembly of different sizes/types is possible. The physics behind the process is described and the technique demonstrated with the formation of an ensemble of 6 μm particles.
Orbit-averaged guiding-center Fokker–Planck operator
Authors: Brizard A. J. , Decker J. , Peysson Y. , Duthoit F.-X.
Published: October 2009

A general orbit-averaged guiding-center Fokker–Planck operator suitable for the numerical analysis of transport processes in axisymmetric magnetized plasmas is presented. The orbit-averaged guiding-center operator describes transport processes in a three-dimensional guiding-center invariant space: the orbit-averaged magnetic-flux invariant ψ¯, the minimum-B pitch-angle coordinate ξ0, and the momentum magnitude p.
Beyond Yield: Plant Disease in the Context of Ecosystem Services
Authors: Cheatham M. R. , Rouse M. N. , Esker P. D. , Ignacio S. , Pradel W. , Raymundo R. , Sparks A. H. , Forbes G. A. , Gordon T. R. , Garrett K. A.
Published: October 2009

The ecosystem services concept provides a means to define successful disease management more broadly, beyond short-term crop yield evaluations. Plant disease can affect ecosystem services directly, such as through removal of plants providing services, or indirectly through the effects of disease management activities, including pesticide applications, tillage, and other methods of plant removal. Increased plant biodiversity may reduce disease risk if susceptible host tissue becomes less common, or may increase risk if additional plant species are important in completing pathogen life cycles. Arthropod and microbial biodiversity may play similar roles. Distant ecosystems may provide a disservice as the setting for the evolution of pathogens that later invade a focal ecosystem, where plants have not evolved defenses. Conversely, distant ecosystems may provide a service as sources of genetic resources of great value to agriculture, including disease resistance genes. Good policies are needed to support conservation and optimal use of genetic resources, protect ecosystems from exotic pathogens, and limit the homogeneity of agricultural systems. Research is needed to provide policy makers, farmers, and consumers with the information required for evaluating trade-offs in the pursuit of the full range of ecosystem services desired from managed and native ecosystems.