bluuebunny/crossref_metadata_2025 huggingface dataset:
Time‐resolved responses to chemoattractant, characteristic of the front and tail of Dictyostelium cells
Authors: Etzrodt Martin , Ishikawa Hellen C.F. , Dalous Jeremie , Müller-Taubenberger Annette , Bretschneider Till , Gerisch Günther
Published: November 2006

In a gradient of chemoattractant, Dictyostelium cells are orientated with their front directed toward the source and their tail pointing into the opposite direction. The front region is specified by the polymerization of actin and the tail by the recruitment of filamentous myosin‐II. We have dissected these front and tail responses by exposing cells to an upshift of cyclic AMP. A sharp rise and fall of polymerized actin within 10 s is accompanied by the recruitment of proteins involved in turning actin polymerization on or off. The cortical accumulation of myosin‐II starts when the front response has declined, supporting the concept of divergent signal transmission and adaptation pathways.
“Black‐box” and “gray‐box” supplier integration in product development: Antecedents, consequences and the moderating role of firm size
Authors: Koufteros Xenophon A. , Edwin Cheng T.C. , Lai Kee‐Hung
Published: November 2006

We investigate here antecedents and consequences of supplier integration (black‐box and gray‐box) in product development activities. Antecedents include embeddedness with suppliers, supply base rationalization, and supplier selection based on product development capabilities. Product innovation and quality are modeled as returns of supplier integration in product development. We also assess the moderating role that firm size may play in the relationships we posit. Our research framework relies primarily on the social network perspective (SNP) and using a sample of 157 firms we found support for many of the posited hypotheses. Specifically, we found that embeddedness with suppliers is positively related to supply base rationalization and supplier selection based on product development capabilities. Supply base rationalization has a significant positive impact on gray‐box integration (i.e., suppliers working along side the customer's engineers for product development) but not black‐box integration (i.e., suppliers carry out on their own the development of components or parts for the customers). On the other hand, selecting suppliers based on their product development capabilities leads to higher levels of both gray‐box and black‐box integration. Only gray‐box integration manifests statistically significant positive effects towards product innovation. The effects of black‐box integration are negligible. Product innovation exhibits strong positive effects on quality. We also found partial support for the moderating impact of firm size. Supply base rationalization practiced by small firms has a statistically significant negative impact on black‐box integration but there is no statistically significant effect for large firms. Supply base rationalization is statistically related to gray‐box integration only for large firms. Finally, the positive effects of product innovation on quality are more potent for large firms.
Foreign participation in local currency bond markets
Authors: Burger John D. , Warnock Francis E.
Published: November 2006

Countries that cannot attract foreigners to invest in their local currency bonds run the risk of currency mismatches that can result in painful crises. We analyze foreign participation in the bond markets of over 40 countries. Bond markets in less developed countries have returns characterized by high variance and negative skewness, factors that we show are eschewed by U.S. investors. While results based on a three‐moment CAPM indicate that it is diversifiable idiosyncratic risk that U.S. investors shun, our analysis suggests that countries can improve foreign participation by reducing macroeconomic instability.
Siliceous microfossil record of late Holocene oceanography and climate along the west coast of Vancouver Island, British Columbia (Canada)
Authors: Hay Murray B. , Dallimore Audrey , Thomson Richard E. , Calvert Stephen E. , Pienitz Reinhard
Published: November 2006

Diatoms, silicoflagellates, and biogenic silica (BSi) were analyzed from two piston cores recovered from Effingham Inlet, British Columbia. Relatively productive marine conditions from 4850 to 4000 cal yr BP were followed by a transition to the modern ocean–climate regime marked by a decreased siliceous microfossil production since 2800 cal yr BP. This change in the northeast Pacific climate was characterized by an apparent cooling associated with higher rainfall and lower light levels. The reduced abundance of most spring–summer bloom diatom taxa (Skeletonema–Thalassiosira–Chaetoceros) was coupled with a decreased abundance of diatoms normally associated with incursions of offshore water into coastal inlets. This pattern reflected a weaker summer upwelling along Vancouver Island associated with the insolation-related increase in the strength of the Aleutian Low and a weakened North Pacific High. After ca. 2800 cal yr BP, diatom assemblages also indicated more frequent periods of relatively low spring–summer surface water salinity and a disruption of the typical bloom sequence, indicative of increased climatic variability. A period of warmer and drier climate conditions and possibly increased coastal upwelling offshore occurred ca. 1450–1050 cal yr BP. The most recent 500 yr are marked by reduced diatom production and the appearance of three distinct diatom biomarkers in the stratigraphic record (Rhizosolenia setigera ca. AD 1940; Minidiscus chilensis ca. AD 1860; Thalassionema nitzschioides morphotype A, ca. AD 1550). The oceanographic changes recorded in Effingham Inlet are correlative with other marine and terrestrial paleoenvironmental records in the northeast Pacific Ocean.
Mechanism of internal waves in the Luzon Strait
Authors: Yuan Yeli , Zheng Quanan , Dai Dejun , Hu Xiaomin , Qiao Fangli , Meng Junmin
Published: November 2006

This study suggests a western boundary current instability generation mechanism for the ocean internal waves. A linear model describing this instability is developed, and an analytical solution is derived from a zero‐order complex frequency–wavenumber relation. The real part of the relation represents a dispersion relation of the generated internal waves, and the imaginary part is an exponential growth rate. The dispersion relation describes the wave propagation characteristics, while the growth rate represents the instability properties. The theoretical results are used for the case of the Kuroshio east of the Luzon Strait. Based on the analysis, it is found that for the westward propagating disturbance, the Kuroshio west wing is unstable and the east wing is stable; while the reverse is true for the eastern propagating disturbance. The results are used to interpret satellite SAR images of the ocean internal waves, which were generated in the Luzon Strait and propagated westward. Reasonable estimates for the growth rate and propagation velocity are derived from a scale analysis of the Kuroshio east of the Luzon Strait.
Interannual variation of the South China Sea circulation and its relation to El Niño, as seen from a variable grid global ocean model
Authors: Wang Yonggang , Fang Guohong , Wei Zexun , Qiao Fangli , Chen Haiying
Published: November 2006

Interannual variation of the South China Sea (SCS) circulation is investigated using variable grid global ocean circulation model results from December 1981 to October 2004 forced by the NCEP Reanalysis wind stress. The upper (0–58 m) Luzon Strait transport (LST) correlates with the local wind stress very well, while the lower (58 m to seabed) LST shows a statistically significant correlation with the integral of wind stress over the tropical Pacific according to Godfrey's “island rule,” with a delay of about 5 months. The Empirical Orthogonal Function (EOF) analysis shows significant correlation between the first wind stress curl EOF mode and El Niño, with a lag of 3 months. The interannual variation of upper layer currents closely correlates with El Niño, with a maximum correlation coefficient of 0.7, lagging by 5 months. The first EOF spatial pattern shows a basin‐scale cyclonic gyre. The interannual variation of subsurface currents marginally correlates with Nino3.4. The model results show that in the winter of 1997/1998, the cyclonic circulation weakens and the associated southward cool water advection is thus reduced. In the summer of 1998, the normal double gyre structure (cyclonic in the south and anticyclonic in the north) of the upper layer currents is replaced by a basin scale anticyclonic gyre, and the offshore current southeast of Vietnam and its associated upwelling vanish. The reduced southward advection in the winter and the disappearance of upwelling in the summer are considered as contributions of the anomalous ocean circulation to the 1998 warm event.
Light and picophytoplankton in the Gulf of Eilat (Aqaba)
Authors: Stambler Noga
Published: November 2006

The underwater light field and phytoplankton abundance in the Gulf of Eilat were studied at station A1 during 1996–2000. In summer, a deep chlorophyll maximum developed at about 80 m, characterized by high concentrations of Prochlorococcus, while during the mixing time, Prochlorococcus, Synechococcus, and eukaryotic algae were found throughout the water column. Chlorophyll concentrations in the euphotic zone were low (0.1–0.6 μg L−1) and as such, the phytoplankton influence on light attenuation was minor. The vertical attenuation coefficient, Kd (PAR) (photosynthetically available radiation), showed seasonal fluctuation, with a summer minimum of ∼0.04 m−1 and a spring maximum of ∼0.065 m−1. The euphotic zone ranged to depths between 80 and 115 m. Phytoplankton absorption spectra were shown to be dependent on depth. During summer stratification, as a response to the exponential decrease of light in the water column, the phytoplankton exhibited photoacclimation, evident as a marked increase in cellular chlorophyll with increasing depth. Light in the Gulf is not a limiting factor even down to more than 100 m, except when combined with stratification, e.g., nutrient limitation, does it affect phytoplankton abundance and composition.
Structure and evolution of the Baikal rift: A synthesis
Authors: Petit Carole , Déverchère Jacques
Published: November 2006

Active continental rifts are spectacular manifestations of the deformation of continents but are not very numerous at the surface of the Earth. Among them, the Baikal rift has been extensively studied during the last decades. Yet no simple scenario explains its origin and development because the style of rifting has changed throughout its ∼30 Myr history. In this paper, we use forward and inverse models of gravity data to map the Moho and lithosphere‐asthenosphere boundary in three dimensions. We then integrate these new results with existing geophysical and geological data on the Baikal rift structure and dynamics, and propose a scenario of its evolution. Earthquake depths, mantle xenoliths, heat flow, and seismic and gravity models advocate for a normal to moderately thinned continental lithosphere and crust, except beneath the Siberian craton, which exhibits a >100‐km‐thick lithosphere. Relatively thin lithosphere (70–80 km) is found east and south of the rift system and is in spatial connection with the Hangai‐Hövsgöl region of anomalous mantle in Mongolia. From top to bottom, the rift structure is asymmetric and appears strongly controlled by the geometry of the suture zone bounding the Siberian craton. Moreover, the mode of topography support changes significantly along the length of the rift: mountain ranges south and north of the rift are underlain by negative Bouguer anomalies, suggesting deep crustal roots and/or anomalous mantle; rift shoulders in the center of the rift seem to result from flexural uplift. The commonly assumed “two‐stage” rift evolution is not corroborated by all stratigraphic and seismic data; however, it seems clear that during the Oligocene, an “early stage,” which might be dominated by strike‐slip tectonics instead of pure extension, created primitive basins much different from the present ones. Most of the “true” rift basins seem to have initiated later, during the Late Miocene or Pliocene. This kinematic change from strike‐slip to extensional tectonics in the Baikal rift is part of a more general kinematic reorganization of Asia and can be associated with the rapid growth of the Tibetan plateau and the end of marginal basins opening along the Pacific boundary.
Gridded isopach maps from the South Pacific and their use in interpreting the sedimentation history of the West Antarctic continental margin
Authors: Scheuer Carsten , Gohl Karsten , Eagles Graeme
Published: November 2006

We model sediment isopach grids for the southern Pacific margin of West Antarctica on the basis of a compilation of more than 10,000 km of single‐channel and multichannel seismic reflection data and correlations with ocean drilling sites. Following recent seismic stratigraphic models, we differentiate two main sequences, the upper of which alone is defined by seismostratigraphic indications for frequent grounded ice advances to the shelf edge off West Antarctica. The subsequent modeling of sediment thickness grids allows us to compare the pre‐glacially dominated and glacially dominated sedimentary development of the study area. On the basis of available age constraints from drilling sites, we assume the onset of accumulation of sediments on the continental rise that were supplied by frequent advances of grounding ice on the continental shelf to have occurred at about 10 Ma. The thickest glacial sediment accumulations occur in front of major glacial drainage outlets, i.e., Marguerite Trough on the western Antarctic Peninsula margin, Belgica Trough in the Bellingshausen Sea, and a depression on the inner and middle shelves off Pine Island Bay in the Amundsen Sea. Glacially dominated sedimentation rates of between 140 and 170 m/m.y. are calculated for these sites.
A comparison of Siberian meimechites and kimberlites: Implications for the source of high‐Mg alkalic magmas and flood basalts
Authors: Carlson Richard W. , Czamanske Gerald , Fedorenko Valeri , Ilupin Iosif
Published: November 2006

Chemical and radiogenic isotope (Sr, Nd, Hf, Os, and Pb) data are presented for a variety of mafic‐alkalic rocks from the Maymecha‐Kotuy section of the Siberian flood‐volcanic province. These data are compared to a similar data set for Siberian kimberlites that were emplaced both before and after the flood‐volcanic event in order to examine the spatial‐temporal evolution of Paleozoic magma sources in the mantle beneath this site of voluminous magmatic activity. As shown in previous studies, the high‐Mg, meimechitic composition rocks extend the range in Sr and Nd isotopic composition seen in the flood basalts in the direction of more “depleted” compositions, i.e., higher 143Nd/144Nd and lower 87Sr/86Sr, overlapping values typically observed in intraplate ocean‐island basalts. Sr, Nd, Hf, and Pb isotopic compositions show little correlation with major‐ and trace‐element compositions in the Maymecha‐Kotuy rocks. Os isotopic compositions, on the other hand, show rough correlations with a number of major‐element characteristics of the magmas. The Os data suggest that the magma sources range from peridotite for the meimechitic magmas to a mixture of peridotite and pyroxenite for the nephelinitic, melilititic, and trachybasaltic compositions. The isotopic overlap of both old and young kimberlites with the Maymecha‐Kotuy rocks is consistent with all these magmas being derived from mantle sources that were present beneath Siberia long before, and long after, the flood‐volcanic event. The isotopic characteristics of the mantle source of these magmas best match the FOZO component observed in ocean‐island basalts, which suggests that this mantle composition may be prevalent in the upper mantle outside of ocean basins. The long‐lived presence of this source beneath Siberia makes it unnecessary to appeal to a mechanism, such as a plume, to bring this type of mantle into play only during the flood‐volcanic episode.
Wind shear with a blowing‐sand boundary layer
Authors: Dong Zhibao , Wang Hongtao , Qian Guangqiang , Luo Wanyin , Zhang Zhengcai
Published: November 2006

In aeolian science, it is thought that the velocity profile of a wind modified by the presence of a cloud of saltating particles bears significant information about the movement of the saltating grains. In this study, we obtained detailed wind‐velocity profiles in the presence of a cloud of saltating particles using a state‐of‐the‐art non‐intrusive measurement technique (particle image velocimetry). The convex‐upward velocity profiles of sand‐laden wind resulted in varying wind shear stress as a function of height. The variation with height in wind‐shear stress was characterized by curves with a maximum shear stress at some height above the surface. The maximum shear stress was well correlated with the sand transport rate and their relationship was close to the Bagnold's transport equation that relates transport rate to shear velocity. Our results suggest that the best estimate of shear velocity during saltation is provided by the maximum shear stress.
Seismogenic structure in a tectonic suture zone: With new constraints from 2006 Mw6.1 Taitung earthquake
Authors: Wu Yih‐Min , Chen Yue‐Gau , Chang Chien‐Hsin , Chung Ling‐Ho , Teng Ta‐Liang , Wu Francis T. , Wu Chien‐Fu
Published: November 2006

A Mw 6.1 earthquake occurred on April 1st, 2006 near Taitung, eastern Taiwan. It produced significant coseismic ground displacements and a large number of aftershocks in the ensuing month. This event provides an opportunity to diagnose the seismogenic structure in the southern Longitudinal Valley (LV) of eastern Taiwan, long viewed as one of the collision sutures between the Philippine Sea and the Eurasian plates. With precisely relocated main‐ and aftershock hypocenters, focal mechanisms for M ≥ 3.8 events, and coseismic ground displacements from strong motion records, we determine a main shock dislocation model. Our results indicate that the main shock occurred on a high angle fault (azimuth 198°, dip 77°). The model comprises a fault with two segments; the main shock and a large number of aftershocks are associated with the northern segment that exhibited predominantly left‐lateral strike‐slip motion, in agreement with P‐wave first motions and waveform (USGS) solutions. The southern segment exhibits a slightly larger thrust component, in agreement with CMT solutions. Tectonically, this event highlights a NNE‐trending fault on the west side of the LV, which is predominantly strike‐slip. The aftershocks clustered to the east of the main shock, which exhibit mainly thrust mechanisms, indicate that shortening is still acting on the sedimentary materials deposited between the Coastal and Central ranges prior to collision. As a result, the southern LV is undergoing slip partitioning along different faults, which has never been specified before.
A first test of climate monitoring with radio occultation instruments: Comparing two processing centers
Authors: von Engeln Axel
Published: November 2006

Two processing centers providing radio occultation (RO) data from the same RO instrument CHAMP have been analyzed in order to estimate the magnitude of structural uncertainty and to test whether different RO data streams or different RO instruments can be combined easily to generate a long term climate monitoring data set. 10,000 CHAMP occultations processed at the centers were selected. The agreement in mean tangent point positions is about 15 km; it is mainly biased at low and mid‐latitudes. Agreement in bending angle, refractivity, and dry temperature profiles is generally not sufficient for climate monitoring and requires further coordination among processing centers. Temperature biases of almost 5 K were found at 35 km altitudes, at lower altitudes biases are smaller but can still be around 1 K. The best bias agreement is found for the product closest to the raw data, bending angle.
Solar induced variations of odd nitrogen: Multiple regression analysis of UARS HALOE data
Authors: Hood L. L. , Soukharev B. E.
Published: November 2006

A linear multiple regression statistical model is applied to estimate the solar induced component of odd nitrogen variability in the stratosphere and lower mesosphere using UARS HALOE data for 1991–2003. Consistent with earlier studies, evidence is obtained for a decadal NOx variation at the highest available latitudes (50° – 70°) that projects positively onto the solar cycle. This variation, which is most statistically significant in the Southern Hemisphere, also correlates positively with the auroral Ap index. It is therefore probably caused by downward transport during the polar night of thermospheric and mesospheric odd nitrogen. In addition, at low latitudes near and above the stratopause, evidence is obtained for an inverse solar cycle NOx variation. It is suggested that this low‐latitude response may be caused primarily by increased photolysis of NO under solar maximum conditions. Throughout most of the rest of the stratosphere, no statistically significant response is obtained.
Influence of Ohio River valley emissions on fine particle sulfate measured from aircraft over large regions of the eastern United States and Canada during INTEX‐NA
Authors: Hennigan Christopher J. , Sandholm Scott , Kim Saewung , Stickel Robert E. , Huey L. Gregory , Weber Rodney J.
Published: November 2006

Aircraft measurements of fine inorganic aerosol composition were made with a particle‐into‐liquid sampler coupled to dual ion chromatographs (PILS‐IC) as part of the NASA INTEX‐NA study. The sampling campaign, which lasted from 1 July to 14 August 2004, centered over the eastern United States and Canada and showed that sulfate was the dominant inorganic species measured. The highest sulfate concentrations were observed at altitudes below 2 km, and back trajectory analyses showed a distinct difference between air masses that had or had not intercepted the Ohio River valley (ORV) region. Air masses encountered below 2 km with a history over the ORV had sulfate concentrations that were higher by a factor of 3.2 and total sulfur (S) concentrations higher by 2.5. The study's highest sulfate concentrations were found in these air masses. The sulfur of the ORV air masses was also more processed with a mean sulfate to total sulfur molar ratio of 0.5 compared to 0.3 in non‐ORV measurements. Results from a second, independent trajectory model agreed well with those from the primary analysis. These ORV‐influenced air masses were encountered on multiple days and were widely spread across the eastern United States and western Atlantic region.
India: A Global Strategic Asset for Developed World Market Businesses
Authors: Tempest Brian
Published: November 2006

This paper is an abridged version of a presentation made by Dr Tempest at the ‘Generics, supergenerics and patent strategies’ conference in London, 15 May 2006. After a steady decline, Asia is now returning to GDP levels it enjoyed in the late 19th century. India, expected to become the world's third largest economy by 2050, offers many advantages, to businesses, investors and partners especially in the pharmaceutical industries in the developed world. India's advantages include projected economic growth at 6–8 per cent, high scientific productivity, a population which is ageing less quickly than other major economies, an attractive environment for research and development investment; a large reservoir of scientifically qualified manpower, a preferred destination for foreign direct investment and an information-driven society. There is great potential for improvement, particularly in infrastructure. The Indian pharmaceutical market, now with intellectual property rights, offers three principal competitive advantages; a very aggressive home market, the relatively low cost of manufacture and most importantly the relatively low cost of innovation. India is well positioned in what looks to be a buoyant future for generics worldwide. While there are potential downsides to consider, India is becoming more pronounced as a global strategic asset for developed world businesses. Foreign companies should be looking to India as a platform for building their European and US markets.
Compact second generation kinetically enhanced copper vapor laser at 10kHz repetition rate
Authors: Singh B. , Subramaniam V. V. , Daultabad S. R. , Chakraborty A.
Published: November 2006

A simple, compact, 60W second generation kinetically enhanced copper vapor laser (KE-CVL) optimized at repetition rate of ∼10kHz is demonstrated using a 25mm bore and a 1m length discharge tube with reduced thermal insulation. Recrystallized alumina tube (45mm bore) is used as an outer enclosure to contain a discharge tube and a thin layer of alumina fibrous thermal insulation for achieving compactness, ruggedness, and reliability in the KE-CVL. Double thyratron pulse modulator has been used for minimizing the switching stresses in the discharge circuit without using snubber circuit and magnetic assist. Specific output power of ∼122W∕liter was achieved with input power of ∼4.5kW and moderate charging voltage of ∼13.5kV (dc supply voltage ∼6.75kV). Specific output energy of ∼12mJ∕cm3 (at 10kHz repetition rate) was achieved as compared to ∼8mJ∕cm3 (at 25kHz) in a 25mm bore KE-CVLs reported previously. The design modifications and KE effects combined are the main reasons for many-fold increase in total output power and energy as compared to standard elemental copper vapor lasers of similar discharge tube and circuitry using pure neon buffer gas at ∼10kHz repetition rate. Warm-up time of about 0.25h was achieved in this compact KE-CVL.
Lattice thermal conductivity of nanoscale AlN∕GaN∕AlN heterostructures: Effects of partial phonon spatial confinement
Authors: Zou Jie , Lange Xavier , Richardson Chris
Published: November 2006

We report a detailed theoretical modeling of lattice thermal conductivity in nanoscale AlN∕GaN∕AlN heterostructures. Thermal conductivity in such heterostructures is derived based on the solution of the phonon Boltzmann equation in the relaxation-time approximation. Phonon dispersion relations are obtained in the elastic continuum approximation using the finite-difference numerical method. Quasi-two-dimensional (2D) phonon density of states is derived using the actual phonon dispersion. To investigate the effects of partial phonon spatial confinement, numerical simulations are performed for both the three-layer heterostructures and the single GaN thin films. The dependence of the thermal conductivity on the core or cladding layer thickness in an AlN∕GaN∕AlN heterostructure is also discussed. We have demonstrated that partial phonon confinement leads to a higher thermal conductivity in an AlN∕GaN∕AlN heterostructure than that in a single GaN thin film with the same total structure thickness. Such thermal conductivity can also be tuned higher or lower by adjusting the core or cladding layer thickness without changing the total thickness of the structure. Obtained results have quantitatively shown that it is possible to improve heat conduction in semiconductor nanostructures through phonon spectrum engineering, in agreement with other recent studies.
Thermopile radiometer signal conditioning for surface atmospheric radiation measurements
Authors: Harrison R. G. , Knight J. R.
Published: November 2006

A highly stable microvolt amplifier for use with atmospheric broadband thermopile radiometers is described. The amplifier has a nominal gain of 500, for bipolar input signals in the range ±10mV from a floating source. The noise level at the input is less than 5μV (at 100kΩ input impedance), permitting instantaneous diffuse solar radiation measurements to 0.5Wm−2 resolution with 12bit analog to digital conversion. The temperature stability of gain is better than 5ppm∕°C (−4to20°C). Averaged over a decade of use, the long term drift of the amplifier gain is less than ∼0.02%∕yr. As well as radiometers measuring solar and terrestrial radiations, the amplifier has also been successfully used with low level signals from thermocouples and ground heat flux plates.
Portable digital microscope apparatus
Authors: Hsu Feng-Chang , Lee Chien-Shing , Huang Kuo-Cheng , Chen Po-Jui , Chen Fong-Zhi , Liao Tai-Shan
Published: November 2006

This article successfully presented the concept of digital camera changing digital microscope using additional adapter with one lens, light emitting diodes, single AAA battery cell, and simple construction without interfering digital camera function. It will be very friendly using general instrument to record miniature target image data in scientific and engineering fields in the future.
Nonconstant piezo velocity in highly dynamic atomic force spectroscopy
Authors: Semin Benoît , Guriyanova Svetlana , Bonaccurso Elmar
Published: November 2006

In this Note we examine six atomic force microscopes or similar instruments for the measurement of surface forces, and we find that they suffer in various degrees from a nonideal performance of the piezo scanner during the acquisition of force curves. This is negligible at low scanning speeds but becomes relevant at higher speeds. In the three most favorable cases the set velocity is attained only after a settling time, which varies among the instruments. In the three least favorable cases, the set velocity is neither attained nor constant. We indicate how to work out the true piezo velocity from experimental force data. We also show that utilizing the wrong velocity leads to misinterpreting the collected data, and we do this on the example of a hydrodynamic drainage force measurement between a colloid and a flat surface in aqueous solution.
Polymer bulk homojunction light-emitting electrochemical cells
Authors: Tracy Corey , Gao Jun
Published: November 2006

We report polymer light-emitting electrochemical cells (LECs) based on the in situ formation of thousands of micrometer-sized light-emitting p-n junctions within the bulk of the device. These “bulk homojunction” LECs, achieved by mixing metallic particles into the LEC film, exhibit dramatically improved electroluminescence (EL) output and response time. This is confirmed by EL intensity and absolute luminance measurements, which reveals an increase in quantum efficiency of more than tenfold, relative to a conventional single junction LEC of similar dimensions. The high performance of a bulk homojunction is attributed to its large specific emitting area. Further, we demonstrate red-, green-, and blue-emitting bulk homojunction LECs by using various combinations of luminescent polymers and metallic particles.
Experimental investigation of the electromagnetic effect on a shock layer around a blunt body in a weakly ionized flow
Authors: Takizawa Yuji , Matsuda Atsushi , Sato Shunichi , Abe Takashi , Konigorski Detlev
Published: November 2006

A reentry vehicle is exposed to a partially ionized flow during the reentry flight. For such a flight, a strong magnet mounted on the vehicle, which generates the magnetic field around the vehicle, is suggested to affect a surrounding ionized flow and make it possible to control the flow. Such an electromagnetic effect on the flow is investigated experimentally by using a small arc-jet wind tunnel. In the experiment, the translational temperature distribution in the shock layer around a magnetized blunt body in a supersonic, weakly ionized, argon flow is determined by applying an absorption spectroscopic technique. For the absorption spectrum affected by the magnetic field, the temperature determination method was newly developed. The temperature distribution thus determined for the shock layer shows that the applied magnetic field significantly affects the shock layer or, specifically, the shock standoff distance and enhances it.
Compositional modulation and optical emission in AlGaN epitaxial films
Authors: Gao Min , Bradley S. T. , Cao Yu , Jena D. , Lin Y. , Ringel S. A. , Hwang J. , Schaff W. J. , Brillson L. J.
Published: November 2006

Compositional, structural, and optical properties of molecular-beam epitaxy grown AlxGa1−xN films were characterized by transmission electron microscopy (TEM), x-ray diffraction, and cathodoluminescence spectroscopy. Spontaneous modulation, phase separation, and band gap reductions were observed to vary systematically with AlN mole fraction across the full alloy series. At low AlN mole fraction (x⩽0.5), AlGaN epilayers display pronounced phase separation. With increasing AlN mole fraction, phase separation is strongly suppressed by the formation of spontaneous modulation which high spatial resolution TEM techniques unambiguously determine to be atomic-scale compositional superlattice. The formation of the spontaneous superlattice is considered responsible for the pronounced reductions in band gaps and emission energies, exceeding several hundred meV for the Al-rich AlGaN, which has been confirmed by band structure calculations.
Energy exchange during stimulated Raman scattering of a relativistic laser in a plasma
Authors: Gupta D. N. , Hur M. S. , Suk H.
Published: November 2006

Energy exchange between pump and daughter waves during the stimulated Raman scattering process in a plasma is investigated, including the effect of a damping coefficient of electron-ion collision at different initial three-wave phases. To obey the energy and momentum conservations, the resonance conditions are satisfied at an optimal initial phase difference between the interacting waves. The amplitudes of the interacting waves exhibit behaviors such as a parametric oscillator. The variations in initial three-wave phase difference generate a phase mismatch, which enhances the rate of the amplitude variations of the interacting waves. The relativistic mass effect modifies the dispersion relations of the interacting waves, and consequently the energy exchange during the stimulated Raman scattering is affected. The collisional damping in the plasma is shown to have an important effect on the evolution of the interacting waves.
Illumination and annealing characteristics of two-dimensional electron gas systems in metal-organic vapor-phase epitaxy grown AlxGa1−xN∕AlN∕GaN heterostructures
Authors: Biyikli N. , Özgür Ü. , Ni X. , Fu Y. , Morkoç H. , Kurdak Ç.
Published: November 2006

We studied the persistent photoconductivity (PPC) effect in AlxGa1−xN∕AlN∕GaN heterostructures with two different Al compositions (x=0.15 and x=0.25). The two-dimensional electron gas formed at the AlN∕GaN heterointerface was characterized by Shubnikov-de Haas and Hall measurements. Using optical illumination, we were able to increase the carrier density of the Al0.15Ga0.85N∕AlN∕GaN sample from 1.6×1012to5.9×1012cm−2, while the electron mobility was enhanced from 9540to21400cm2∕Vs at T=1.6K. The persistent photocurrent in both samples exhibited a strong dependence on illumination wavelength, being highest close to the band gap and decreasing at longer wavelengths. The PPC effect became fairly weak for illumination wavelengths longer than ∼530nm and showed a more complex response with an initial negative photoconductivity in the infrared region of the spectrum (λ>700nm). The maximum PPC efficiency for 390nm illumination was 0.011% and 0.005% for Al0.25Ga0.75N∕AlN∕GaN and Al0.15Ga0.85N∕AlN∕GaN samples, respectively. After illumination, the carrier density could be reduced by annealing the sample. Annealing characteristics of the PPC effect were studied in the 20–280K temperature range. We found that annealing at 280K was not sufficient for full recovery of the carrier density. In fact, the PPC effect occurs in these samples even at room temperature. Comparing the measurement results of two samples, the Al0.25Ga0.75N∕AlN∕GaN sample had a larger response to illumination and displayed a smaller recovery with thermal annealing. This result suggests that the energy scales of the defect configuration-coordinate diagrams for these samples are different, depending on their Al composition.
Magnetic anisotropies and magnetization reversal of the Co2Cr0.6Fe0.4Al Heusler compound
Authors: Hamrle J. , Blomeier S. , Gaier O. , Hillebrands B. , Schäfer R. , Jourdan M.
Published: November 2006

Magnetic anisotropies and magnetization reversal properties of the epitaxial Heusler compound Co2Cr0.6Fe0.4Al deposited on Fe and Cr buffer layers are studied. Both samples exhibit a growth-induced fourfold anisotropy, and magnetization reversal occurs through the formation of stripy domains or 90° domains. During rotational magnetometric scans the sample deposited on Cr exhibits about 2° sharp peaks in the angular dependence of the coercive field, which are oriented along the hard axis directions. These peaks are a consequence of the specific domain structure appearing in this particular measurement geometry. A corresponding feature in the sample deposited on Fe is not observed.
Dielectric, domain, and optical studies in high-Curie-temperature Pb(In1∕2Nb1∕2)1−xTixO3 (x=0.40) single crystal
Authors: Tu C.-S. , Wang F.-T. , Hung C.-M. , Chien R. R. , Luo H.
Published: November 2006

Dielectric permittivity, domain structure, and hysteresis loop have been measured as a function of temperature in a (001)-cut Pb(In1∕2Nb1∕2)0.6Ti0.4O3 (PINT40%) single crystal. A first-order-type tetragonal/monoclinic→cubic phase transition takes place at TC≅486K, below which tetragonal and monoclinic domains coexist. Frequency-dependent maxima in dielectric absorption appear in the region of 180–260K and can be described by the Vogel-Fulcher equation. Optical transmission and refractive indices were obtained as a function of wavelength. The crystal shows a broad transparency (0.4–6.0μm) and no obvious birefringence, indicating that the crystal structure averaged over the optically anisotropic ferroelectric domains is optically isotropic.
Two bonding configurations of acetylene on Si(001)-(2×1): A combined high-resolution electron energy loss spectroscopy and density functional theory study
Authors: Mineva T. , Nathaniel R. , Kostov K. L. , Widdra W.
Published: November 2006

Two coexisting adsorption states of molecularly adsorbed acetylene on the Si(001)-(2×1) surface have been identified by a combined study based on the high-resolution electron energy loss spectroscopy and density functional computations. Seven possible adsorbate-substrate structures are considered theoretically including their full vibrational analysis. Based on a significantly enhanced experimental resolution, the assignment of 15 C2H2- and C2D2-derived vibrational modes identifies a dominant di-σ bonded molecule adsorbed on top of a single Si–Si dimer. Additionally there is clear evidence for a second minority species which is di-σ bonded between two Si–Si dimers within the same dimer row (end-bridge geometry). The possible symmetries of the adsorbate complexes are discussed based on the specular and off-specular vibrational measurements. They suggest lower than ideal C2v and Cs symmetries for on-top and end-bridge species, respectively. At low coverages the symmetry reductions might be lifted.
Study on the vibrational energy relaxation of p-nitroaniline, N,N-dimethyl-p-nitroaniline, and azulene by the transient grating method
Authors: Kimura Y. , Fukuda M. , Kajimoto O. , Terazima M.
Published: November 2006

The vibrational energy dissipation processes of the electronic ground states of p-nitroaniline and N,N-dimethyl-p-nitroaniline have been studied by transient grating spectroscopy with subpicosecond laser pulses. The rise time of the acoustic signal produced by the energy dissipation process of the hot ground state molecule was monitored. The acoustic signal was analyzed by an equation including the acoustic damping. The solvent temperature rise times in various solvents have been determined. The acoustic signals of azulene in previous papers [Y. Kimura et al., J. Chem. Phys. 123, 054512 (2005); 123, 054513 (2005)] were also reanalyzed using this equation. The temperature rise times in all cases are longer than the vibrational energy relaxation times of the solutes determined by the transient absorption measurements. The difference is discussed in terms of the energy transfer pathways from the solute to the solvent. We concluded that both the hydrogen bonding between the solute and the solvent and the lower frequency modes of the solutes play important roles in determining the energy transfer pathway from the solute to the solvent.
Spurious fractional charge on dissociated atoms: Pervasive and resilient self-interaction error of common density functionals
Authors: Ruzsinszky Adrienn , Perdew John P. , Csonka Gábor I. , Vydrov Oleg A. , Scuseria Gustavo E.
Published: November 2006

Semilocal density functional approximations for the exchange-correlation energy can improperly dissociate a neutral molecule XY (Y≠X) to fractionally charged fragments X+q⋯Y−q with an energy significantly lower than X0⋯Y0. For example, NaCl can dissociate to Na+0.4⋯Cl−0.4. Generally, q is positive when the lowest-unoccupied orbital energy of atom Y0 lies below the highest-occupied orbital energy of atom X0. The first 24 open sp-shell atoms of the Periodic Table can form 276 distinct unlike pairs XY, and in the local spin density approximation 174 of these display fractional-charge dissociation. Finding these lowest-energy solutions with standard quantum chemistry codes, however, requires special care. Self-interaction-corrected (SIC) semilocal approximations are exact for one-electron systems and also reduce the spurious fractional charge q. The original SIC of Perdew and Zunger typically reduces q to 0. A scaled-down SIC with better equilibrium properties sometimes fails to reduce q all the way to 0. The desideratum of “many-electron self-interaction freedom” is introduced as a generalization of the one-electron concept.
Nonconvex Hamiltonians in three dimensional level set simulations of the wet etching of silicon
Authors: Radjenović Branislav , Radmilović-Radjenović Marija , Mitrić Miodrag
Published: November 2006

It is shown that profile evolution during anisotropic wet etching of silicon can be described by the nonconvex Hamiltonian arising in the Hamilton-Jacobi equation for the level set function. Etching rate function is determined on the basis of the silicon symmetry properties. An extension of the sparse field method for solving three dimensional level set equations in the case of nonconvex Hamiltonians is presented.
Optimal drive condition for nonlinearity reduction in electrostatic microresonators
Authors: Agarwal Manu , Chandorkar Saurabh A. , Candler Rob N. , Kim Bongsang , Hopcroft Matthew A. , Melamud Renata , Jha Chandra M. , Kenny Thomas W. , Murmann Boris
Published: November 2006

A model for the amplitude-frequency (A-f) effect in electrostatic microresonators is presented. This effect is an undesired nonlinear phenomenon that sets the maximum usable oscillation current and thereby degrades the resonator’s signal-to-noise ratio and performance. The model developed in this letter provides analytical expressions for the A-f effect and derives an optimal bias condition that maximizes the usable current. In addition, the authors present experimental data for a double-ended-tuning-fork resonator. Using the derived bias condition, an improvement of more than two times in the sustainable oscillation current has been achieved.
Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance
Authors: Lee S.-K. , Sauer K. L. , Seltzer S. J. , Alem O. , Romalis M. V.
Published: November 2006

A radio-frequency tunable atomic magnetometer is developed for detection of nuclear quadrupole resonance (NQR) from room temperature solids. It has a field sensitivity 0.24fT∕Hz1∕2 at the 423kHz N14 NQR frequency of ammonium nitrate. A potential application of the magnetometer is detection of nitrogen-containing explosives which is difficult with conventional tuned copper coils due to a poor signal-to-noise ratio (SNR) below a few megahertz. The NQR signal from 22g of powdered ammonium nitrate located 2cm away from the sensor is detected with a SNR of 9 in a 4.4-s-long multiple echo sequence, which represents an estimated order-of-magnitude improvement in sensitivity over the pickup coil detection.
Resonant two-photon ionization spectroscopy of BNB
Authors: Ding Hongbin , Morse Michael D. , Apetrei Cristina , Chacaga Lukasz , Maier John P.
Published: November 2006

Triatomic BNB has been produced by laser ablation of a boron nitride rod in a supersonic expansion of helium carrier gas and has been investigated using resonant two-photon ionization spectroscopy in the visible region. The B̃Πg2−X̃Σu+2 band system has been recorded near 514nm and is dominated by a strong origin band, which has been rotationally resolved and analyzed. Both the B11N14B11 (64% natural abundance) and the B10N14B11 (32% natural abundance) isotopic modifications have been analyzed, leading to the spectroscopic constants (and their 1σ error limits) of B0″(X̃Σu+2)=0.466147(70), B0′(B̃Πg2)=0.467255(75), and A0′(B̃Πg2)=6.1563(38)cm−1 for B10N14B11, corresponding to rB–N″(X̃Σu+2)=1.31247(10)Å and rB–N′(B̃Πg2)=1.31092(11)Å. Very similar values are obtained for the more abundant isotopomer, B11N14B11: B0″(X̃Σu+2)=0.444493(69), B0′(B̃Πg2)=0.445606(70), A0′(B̃Πg2)=6.1455(38)cm−1, corresponding to rB–N″(X̃Σu+2)=1.31241(10)Å and rB–N′(B̃Πg2)=1.31077(10)Å. These results are discussed as they relate to Walsh’s rules and are compared to results for related molecules.
Lasing in GaN microdisks pivoted on Si
Authors: Choi H. W. , Hui K. N. , Lai P. T. , Chen P. , Zhang X. H. , Tripathy S. , Teng J. H. , Chua S. J.
Published: November 2006

Arrays of pivoted GaN microdisks have been fabricated on a GaN∕Si material by a combination of dry and wet etching. The Si material beneath the GaN microdisks is removed by wet etching, leaving behind a fine pillar to support the disks. Raman spectroscopy reveals substantial strain relaxation in these structures. Resonant modes, corresponding to whispering gallery modes, are observed in the photoluminescence spectra. Stimulated emission is achieved at higher optical pumping intensities.
Continuous ultraviolet roll nanoimprinting process for replicating large-scale nano- and micropatterns
Authors: Ahn Suho , Cha Joowon , Myung Ho , Kim Seok-min , Kang Shinill
Published: November 2006

With the increasing demand for large-scale nano- and micropatterns in the field of digital displays, nano- and micropattern replication technology has become a research priority. In this study, a continuous ultraviolet (UV) roll nanoimprinting process using a pattern roll stamper for the replication of large-scale nano- and micropatterns was designed and constructed. Several flexible nano- and micropatterns with large areas were fabricated and analyzed as tests of this continuous UV imprinting process.
Ionization gas sensing in a microelectrode system with carbon nanotubes
Authors: Hou Zhongyu , Xu Dong , Cai Bingchu
Published: November 2006

An efficient technology for manufacturing high-performance ionization gas sensors using carbon nanotubes as electrode materials that identify gases in some short sampling distance is developed in this letter. The microarray with five sensor units of different gap sizes (S≈6, 7, 8, 10, and 12μm) can break down gases at distinct threshold voltages and currents depending on the gap size and gas species. The quite low operation voltage, high accuracy, and chip-based nature may be considered as significant improvements in ionization gas sensors.