bluuebunny/crossref_metadata_2025 huggingface dataset:
METHODS FOR DISPERSION AND ALIGNMENT OF SINGLE-WALLED CARBON NANOTUBES AND EFFECTS ON THEIR STRUCTURAL AND ELECTRONIC PROPERTIES
Authors: JIAO JUN , DONG LIFENG , CHIRAYOS VACHARA , BUSH JOCELYN , HEDBERG JAMES
Published: December 2006

Two effective methods for dispersion and alignment of single-walled carbon nanotubes (SWCNTs) were developed. One is the floating-potential dielectrophoresis (FPD) method, which can achieve the alignment of individual SWCNTs between two electrodes with high yield (more than 30%) and high repeatability. The second is the gas blow method. Using the shear forces associated with a rapidly moving fluid, SWCNTs were positioned in a direction corresponding to the flow vector of the fluid. This technique shows great potential for scaling up the displacement of SWCNTs with controlled orientations. Various dispersion agents including ethanol, dichlorobenzene, sodium dodecyl sulfate (SDS) and DNA were investigated with these two methods. It was found that SDS was the most effective dielectric medium used for FPD dispersion and alignment of SWCNTs. The result of electric measurement for the individual SWCNTs aligned between two electrodes suggests that, using the FPD method, both metallic and semiconducting SWCNTs could be aligned between the electrodes. The individual SWCNT resistances measured range from 20 KΩ to 5 MΩ suggesting a high contact resistance between an aligned SWCNT and metal electrodes. High resolution transmission electron microscopy (TEM) and scanning electron microscopy (SEM) characterization reveal DNA molecules wrapped around the SWNCTs after the dispersion process which may affect the intrinsic properties of SWCNTs.
NOVEL AFM PROBE FOR LOCAL CONDUCTIVITY MEASUREMENT
Authors: JU BING-FENG , JU YANG , SAKA MASUMI
Published: December 2006

A new atomic force microscope (AFM) probe for local conductivity measurement is presented. This silicon nitride based probe with a V-shaped two-dimensional sliced structure tip is patterned by using conventional photolithography method. The probe is then etched to four parallel electrodes that isolated from each other, for the purpose of performing current input and electrical potential drop measurement. The newly developed four-point AFM probe not only inherits the function of AFM surface topography generating but also has the capability of characterizing the local conductivity simultaneously. The nanoresolution position control mechanism of AFM allows the probe scanning across micrometers sized area and creating high spatial resolution map of the in-plane conductivities. Experiments have shown this four-point AFM probe to be mechanically flexible and robust. The repeatable conductivity measurements on the surface of aluminum and indium tin oxide (ITO) thin films indicate this four-point AFM probe technique has potential applications for characterizing devices and materials in microscale.
PLASMA-AIDED NANOFABRICATION: "PLASMA-BUILDING BLOCK" APPROACH
Authors: OSTRIKOV KEN , XU SHUYAN
Published: December 2006

Unique features and benefits of the plasma-aided nanofabrication are considered by using the "plasma-building block" approach, which is based on plasma diagnostics and nanofilm characterization, cross-referenced by numerical simulation of generation and dynamics of building blocks in the gas phase, their interaction with nanostructured surfaces, and ab initio simulation of chemical structure of relevant nanoassemblies. The examples include carbon nanotip microemitter structures, semiconductor quantum dots and nanowires synthesized in the integrated plasma-aided nanofabrication facility.
HIGH PRESSURE EFFECTS ON ELECTRICAL RESISTIVITY AND DIELECTRIC PROPERTIES OF NANOCRYSTALLINE SnO2
Authors: THANGADURAI P. , BOSE A. CHANDRA , RAMASAMY S. , KESAVAMOORTHY R. , RAVINDRAN T. R.
Published: December 2006

Rutile structured nanocrystalline tin oxide (nano- SnO 2) was prepared by chemical precipitation method with different grain sizes. Its electrical and dielectric properties were studied using complex impedance spectroscopy under different hydrostatic pressures. These studies showed a transition in nano- SnO 2 under high-pressure. The transition pressures obtained from both the resistivity and dielectric measurements agree with each other and increase considerably with decrease in grain size. In order to find whether the transition under pressure is structural related or not, in situ high pressure Raman spectroscopy was done up to 3.38 GPa at room temperature. No structural change was observed and the transition may be due to the co-operative phenomenon of the change in band gap and better connectivity between grain boundaries.
SYNTHESIS OF In2O3 NANOWIRES ENHANCED BY ANODIC ALUMINA MEMBRANE
Authors: LAI C. W. , ZHANG X. Y. , ONG H. C. , DAI J. Y. , CHAN H. L. W.
Published: December 2006

Large-scale single crystalline In 2 O 3 nanowires were successfully synthesized on anodic alumina membranes by a simple thermal evaporation method at 570°C. X-ray diffraction, transmission electron microscopy, and scanning electron microscopy studies revealed the formation of single crystalline In 2 O 3 nanowires with diameters of 50–100 nm and lengths of up to a few hundreds of micrometers. Cathodeluminescence study revealed existence of oxygen vacancies evidenced by a strong and broad emission at 470 nm with a shoulder at 400 nm. The growth mechanism of the nanostructures is also discussed.
RF PLASMA PROCESSING OF ULTRAFINESm-LuMIXED OXIDE POWDER
Authors: SUN X. L. , TOK A. I. Y. , BOEY F. Y. C. , HUEBNER R.
Published: December 2006

Ultrafine Sm - Lu mixed oxide powder with an overall composition Sm1.0Lu1.0O3was processed by inductive radio frequency plasma treatment using two different approaches: spraying a mixture of pure Sm2O3and Lu2O3with and without sintering pretreatment. Due to the insufficient reaction time and contact, the mixture sprayed without sintering shows only a marginal reaction between the two materials. Therefore, an alternative approach was adopted. The mixed oxide was first synthesized by solid state reaction at 1600°C. Then, the as-sintered pellets were crushed and ground, followed by plasma treatment. In this way, ultrafine particles of Sm1.0Lu1.0O3mixed oxide were obtained.
FABRICATION OF LSMO SINGLE LAYERS AND LSMO/YBCO DOUBLE LAYERS
Authors: ZHU HONG , OKADA MASANORI , KAMIYA ATSUSHI , SARKAR AJAY KRISHNO , MATSUI MASAHITO , SEIKH MD. MOTIN , ENDO TAMIO
Published: December 2006

( La , Sr ) MnO 3 (LSMO) single-layer and LSMO/YBCO double-layer films have been grown on LAO and MgO substrates using ion beam sputtering. For LSMO single-layer films, the highly epitaxial films can be grown at lower substrate temperatures down to 500°C. The epitaxy of the films, which is degraded with increasing TS, can be restored by supply of plasma oxygen. Smaller lattice mismatch of LSMO on LAO gives two-dimensional step-and-terrace type growth, whereas on MgO grain type growth is observed due to larger mismatch. For the double-layer films, LSMO layer can be grown epitaxially on a-oriented YBCO underlayer, but a part of the underlying a-YBCO is changed into c-YBCO during the deposition of overlayer. For c-YBCO underlayer, a part of the underlying c-YBCO is changed into (110)-oriented phase after the deposition of overlayer. Then it is necessary to deposit the overlayer at lower temperatures.
DIRECT FORMATION OF NANOPORE ARRAY VIA FOCUSED ION BEAM FINE MILLING AND SURFACE COATING TECHNIQUES
Authors: FU YONGQI , NGOI BRYAN KOK ANN , ZHOU WEI , LOH THIAN FATT
Published: December 2006

A nanopore array with diameter of ~30 nm was fabricated by use of focused ion beam (FIB) scanning and thin film coating on Si (100). A thin film of SiO 2 with thickness of 200 nm (used as a sacrificial layer) was coated by physical evaporation deposition (PVD) first. Next, the thin films of poly-silicon with thickness of 50 nm were coated on double side of the substrate. A window with an area of 2 × 2 mm 2 was opened by reactive ion etching from bottom side and reached to the thin film of SiO 2. After that, a fine controlled FIB milling with bitmap function (milling according to a designed pattern in a defined area) was used to scan the area. Signal is obtained by a sensor inside the vacuum chamber collecting secondary electrons emitted from the sputtered material when the beam reach the layer of SiO 2. Stopping the milling process at this moment, the nanopore array was derived after removing the sacrificial layer by wet chemical etching. The nanopore arrays were characterized using transmission electron microscopy (TEM) after the FIB drilling.
STUDY OF DUAL-MATERIAL GATE (DMG) FinFET USING THREE-DIMENSIONAL NUMERICAL SIMULATION
Authors: HAVALDAR DNAYNESH S. , DASGUPTA AMITAVA , DASGUPTA NANDITA
Published: December 2006

In this work, the novel characteristics of a FinFET with dual-material gate (DMG) are explored theoretically using a 3D numerical simulator and compared with those of a single material gate (SMG) FinFET in terms of threshold voltage roll off, drain induced barrier lowering (DIBL) and the ratio of transconductance (gm) to drain conductance (gd). Our studies show that the DMG structure achieves simultaneous suppression of short channel effects (SCEs), enhancement in carrier transport efficiency and transconductance. Also, these features can be controlled by engineering the work function and length of gate material.
STUDY ON NANOMETRIC CUTTING MECHANISM AND BURR FORMATION USING MOLECULAR DYNAMICS SIMULATION
Authors: WU H. , FANG F. Z. , PEI Q. X.
Published: December 2006

Since no physical approach can be employed to study the mechanism in micro cutting, the molecular dynamics simulation is becoming more and more important. In this study, the results of molecular dynamics modeling and analysis on the nanometric machining on silicon surface are presented. According to the simulation, some phenomena in the nanometric cutting process are found. First, surface elastic rebound happens on the cut surface after cutter moving away. The value of the surface elastic rebound is calculated in the simulation. Second, the atoms near the corner of work piece swirl up following the cutter moving direction at the initial stage of removing atoms from the work piece. Third, the simulation results show that no matter how small material removal is, the burr is always formed at the edge of work piece.
CHARGE STORAGE IN CARBON NANOTUBE FIELD-EFFECT TRANSISTORS
Authors: LI HONG , ZHANG QING , LI JINGQI
Published: December 2006

Very significant hysteresis characteristics are found in single wall carbon nanotubes field-effect transistors (CNTFET) fabricated using AC dielectrophoresis method. The CNTFETs show ambipolar characteristics. Two clear hysteresis loops are observed when the gate voltage is forward and backward swept. The hysteresis characteristics are studied from room temperature down to 16 K. It is found that the hysteresis loops become smaller as temperature is decreased. We suggested that the hysteresis is caused by charge trapping in foreign species covering the single wall carbon nanotube. It is more difficult for charges to transfer into and out of the trapping center at a lower temperature; as a result, the hysteresis loops become much smaller at low temperature.
PATTERNING OF TWO-DIMENSIONAL PHOTONIC CRYSTAL STRUCTURES BY NANOIMPRINT LITHOGRAPHY
Authors: CHEN A. , WANG B. Z. , CHUA S. J. , WILHELMI O. , MAHMOOD SHAHRAIN B. , SAW B. T. , KONG J. R. , MOSER H. O.
Published: December 2006

We report on the process parameters of nanoimprint lithography for the fabrication of two-dimensional (2D) photonic crystals. The nickel mold with 2D photonic crystal patterns covering an area up to 20 mm2 is produced by electron-beam lithography and electroplating. Periodic pillars as high as 200 nm to 250 nm are produced on the mold with the diameters ranging from 180 nm to 500 nm. Optimization of process parameters is essential to generate high-quality nanoscale patterns and control the residual stress in the mold. The mold is employed for nanoimprinting on the poly-methyl-methacrylate (PMMA) layer spin-coated on the silicon substrate. Periodic air holes are formed in PMMA above its glass-transition temperature and the patterns on the mold are well transferred. This process can be utilized for commercial applications of photonic crystal devices.
FABRICATION OF SILICON NANOCRYSTALS AND ITS ROOM TEMPERATURE LUMINESCENCE EFFECTS
Authors: CHAN M. Y. , LEE P. S.
Published: December 2006

Silicon ( Si ) nanocrystals have been considered a good candidate for flash memory device and nanophotonic applications. The fabrication of nanocrystal memory is to form uniform, small size and high density quantum dots. In this study, nanometer-scale silicon quantum dots have been fabricated on ultrathin silicon oxide layer using amorphous silicon (a- Si ) deposition followed by various annealing treatments. The a- Si layers were crystallized using furnace annealing, laser annealing and rapid thermal annealing (RTA). After annealing to form nanometer-sized crystallites, silicon wet etch was carried out to isolate the nanocrystals. The size, uniformity and density of the nanocrystals were successfully controlled by different annealing treatments. The mean dot height and mean dot diameter is 1–5 nm and 2–5 nm, respectively. Lateral growth of the silicon dots was further controlled by systemic variations of the annealing conditions. It is found that the annealed a- Si films exhibit room temperature visible photoluminescence (PL) resulting from the formation of nanometer-sized crystallites. Selective wet etch and Secco-etch treatment increased the PL efficiency that is useful for nanophotonics applications. The feasibility of quantum dot formation using ultra thin amorphous Si films is demonstrated in this work.
FABRICATION AND ELECTRON MICROSCOPY CHARACTERIZATION OF METAL-GATED CARBON NANOTUBE EMITTER ARRAYS
Authors: WU JIANFENG , DONG LIFENG , PETTY JEREMY , PAN CHIACHING , JIAO JUN
Published: December 2006

A technique was investigated for the fabrication of triode-type carbon nanotube (CNT) field emitter arrays, where an integrated extraction gate was built between the nanotube cathode and the anode. The gate improves the control capability of emission currents. To fabricate the metal-gated CNT field emitter arrays, well ordered cells were generated by focused ion beam (FIB) milling of platinum ( Pt ) coated silicon ( Si ) substrate and then modified by chemical etching. Two types of catalyst elements iron ( Fe ) and nickel ( Ni ), were used for growing the CNTs inside the cells. The methods for depositing catalysts into the cells include spin coating sol–gel Fe , FIB induced decomposition of ferrocene and sputter coating pure Ni . CNT growth was carried out by a chemical vapor deposition (CVD) process. The results suggest that the CNTs grew from inside the cells where the catalysts were located. In comparison, the CNTs synthesized from the sol–gel Fe catalyst were straighter than those from ferrocene Fe and pure Ni . The density and orientation of the CNTs in each cell are directly related to the type and quantity of the catalysts and are also affected by the size of the cells.
HIGH FREQUENCY RAMAN MODES IN NANOCRYSTALLINE LEAD (II) FLUORIDE
Authors: THANGADURAI P. , RAMASAMY S. , KESAVAMOORTHY R.
Published: December 2006

Nanocrystalline PbF 2 was prepared by inert gas condensation technique. Structural studies using X-ray diffraction showed that as-prepared and annealed samples contained both orthorhombic and cubic phases of PbF 2. The annealed samples contain dominantly the cubic phase. For the first time Raman scattering and PL experiments were carried out on these nano- PbF 2. In addition to regular lattice vibrational modes such as T2g for cubic phase and Ag and B1g for orthorhombic phases, a few new Raman modes have been observed at high frequencies. PL studies confirmed that the new Raman modes are due to the presence of electronic centers. The regular modes agree well with the theoretically calculated values and previously reported experimental values.
PHOTOLUMINESCENCE AND PHOTOACOUSTIC EFFECT OF ERBIUM-DOPED POROUS SILICON NANOSTRUCTURE
Authors: SEKAK K. A. , ABDULLAH S. , PAIMAN S. , YUNUS W. M.
Published: December 2006

We applied photoluminescence (PL) and photoacoustic techniques on erbium-doped porous silicon nanostructured ( Er -doped-PSN) to study the influences of weight percent (%) of erbium-doped in PSN. Erbium-doped PSN has been intensively studied due their potentiality for optical devices such as waveguide and optical amplifier. Electrochemical technique was used to prepare the PSN samples. Polished p-type [100] c- Si was used as based material. Erbium doping process was carried out by electrodeposition technique using Erbium Chloride ( ErCl 3) and ethanol composition as electrolyte. The weight percent of Er concentration is varied to get the optimum effect on PL. The doping process improves PL intensity and changing in peak position. Photoluminescence measurements were performed in the visible light range and excited with the 380 nm line a Xenon ( Xe ) light source. Photoacoustic (PA) measurements is useful to obtain the optical absorption characteristic for strongly scattering media such as PSN and it helps to confirm the possibility of a strong quantum confinement effect.
ELECTRODEPOSITED CoNiFe ALLOY THIN FILMS FOR MAGNETIC RECORDING
Authors: PANDYA DINESH K. , KUMAR YAJVENDRA , KASHYAP SUBHASH C. , CHAUDHARY SUJEET
Published: December 2006

Alloy thin films of ternary system Co – Ni – Fe and binary systems Co – Fe , Co – Ni and Ni – Fe consisting of ~50 nm grains have been deposited by a simple and industrially viable technique of electrodeposition in galvanostatic mode on ITO-coated glass. Bath composition and current density have been varied to prepare films of different compositions and thus, in turn, obtain suitable composition for better magnetic properties. Further, an attempt has been made to deposit films in the presence of Mg 2+ in the bath and to study its linkage with the magnetic properties, i.e., saturation magnetic flux density, BS, and coercivity, HC. Our results clearly demonstrate that addition of Mg 2+ ions in the bath helps in increasing the BS considerably.
CONSTITUTIVE MODELING FOR NANOCERAMIC MATERIALS SINTERING
Authors: XUE F. , MA J.
Published: December 2006

Ultra fine-grained ceramic components, which can be obtained by sintering nanosized ceramic powder, provide excellent mechanical properties for engineering applications. To facilitate the cost efficient fabrication of such components, a full understanding on the sintering of nanosized ceramic materials is most helpful. In this paper, a constitutive model with density and grain size as coupling state variables was developed to study the pressureless sintering of 3Y-TZP nanosized powder. The sintering mechanism and several essential sintering parameters predicted by the model are consistent with our experimental observation. It was found that interface reaction mechanism is dominant during the densification process, and the model was also proved to provide reliable prediction on densification and grain growth.
DC AND AC ANALYSES OF NOVEL SOI MOSFET DEVICES USING 2D AND 3D NUMERICAL SIMULATIONS
Authors: CHUNG TSUNG MING , RASKIN JEAN-PIERRE
Published: December 2006

Novel devices such as Double Gate (DG), Triple Gate (TG) or FinFET, Pi-Gate (PG) and Omega-Gate SOI MOSFETs are potential candidates for achieving the performance predictions of the International Roadmap of the Semiconductor Industry Association. In this paper, we analyzed the DG, TG and PG in comparison with the Single Gate (SG) SOI MOSFET using the commercial 3D numerical simulator SILVACO in the DC and AC regimes from subthreshold region to strong inversion and saturation regions. In the DC regime, multiple gate devices are superior to SG device from micrometer down to nanometer scale lengths. In the AC regime, the advantages of the multiple gate devices over SG devices are significant especially when the channel length reduces below 100 nm. For the first time, we have shown the great interest and potential of these multiple gate devices for high frequency analog applications.
KINETIC STUDIES OF SPHERULITIC CRYSTALLIZATION IN THE GELATION PROCESS OF LOW MOLECULAR-MASS ORGANIC GELATOR
Authors: WANG RONGYAO , LIU XIANG-YANG
Published: December 2006

Spherulite is an important crystal growth form in many organic and inorganic substances. In the sol-to-gel transition of the N -lauroyl-L-glutamic acid di-n-butylamide (GP-1)/propylene glycol (PG) system, the formation of spherulitic fiber network was observed in situ by optical microscopy. The growth mechanism of the spherulite in the gelation process was examined quantitatively. A constant growth rate along the radial direction of the spherulite was ascribed to the surface kinetics controlling mechanism, in which a constant supersaturation throughout the spherulitic growth may be induced by the topological structure of the densely branching morphology in this gel network. Our results also indicate that the engineering of a fiber gel network can be attained via crystallization strategies, since spherulitic growth is a typical example that construction of supramolecular structure occurs as a consequence of the crystallization from dilute solutions.
Nonmodal Stability Theory
Authors: Schmid Peter J.
Published: December 2006

Hydrodynamic stability theory has recently seen a great deal of development. After being dominated by modal (eigenvalue) analysis for many decades, a different perspective has emerged that allows the quantitative description of short-term disturbance behavior. A general formulation based on the linear initial-value problem, thus circumventing the normal-mode approach, yields an efficient framework for stability calculations that is easily extendable to incorporate time-dependent flows, spatially varying configurations, stochastic influences, nonlinear effects, and flows in complex geometries.
The Fluid Dynamics of Taylor Cones
Authors: Fernández de la Mora Juan
Published: December 2006

The formation of cone-jets in charged liquids with electrical conductivities larger than 10−4 S/m is reviewed for steady supported menisci and transient Coulomb fissions in charged drops. Taylor's hydrostatic model does not apply strictly, but it forms the basis for subsequent developments. The jet structure is critically dependent on the model used for charge transport, which has been based mostly on a constant conductivity assumption. Saville's (1997) more general model predicts the formation of rarefaction fronts with wide space charge–dominated regions near the liquid surface, which apparently do arise in polar liquids near the minimum flow rate. Known approximate scaling laws for the jet break down at electrical conductivities of about 1 S/m due to ion evaporation from the meniscus. In molten salts and liquid metals a regime of purely ionic emissions exists without drop or jet formation.
Fragmentation
Authors: Villermaux E.
Published: December 2006

Fragmentation phenomena are reviewed with a particular emphasis on processes that give rise to drops—in the broad sense, the process of atomization. Various observations are brought together to give a unified picture of the overall transition between a compact macroscopic liquid volume and its subsequent dispersion into stable drops. In liquids, primary instabilities always give birth to more or less corrugated ligaments whose breakup determines the shape of the drop-size distribution in the resulting spray. Examples examined here include fragmentation of jets and liquid sheets, formation of spume by the wind blowing over a liquid surface, bursting phenomena upon an impact, and raindrops.
Gravity Current Interaction with Interfaces
Authors: Monaghan J. J.
Published: December 2006

Gravity currents that impact interfaces have a number of features that differ from gravity currents in homogeneous or continuously stratified ambient fluid. The interface can cause sharp changes in the flow and split the current into an undercurrent in the dense layer and a filling intrusion in the upper layer. If the current penetrates the lower layer it can initiate large amplitude waves with a length scale several times larger than the scale of the head of the current. If the current carries particulate matter the change in flow at the interface changes the deposition of particles. Because approximate two-layer systems exist in nature, especially in basins ranging up to the size of the Arctic, and may affect global climate, further experiments are needed to clarify the entrainment and mixing of the ambient fluid with the current. Comprehensive, and accurate, numerical simulations of these flows should now be possible.
Osborne Reynolds and the Publication of His Papers on Turbulent Flow
Authors: Jackson Derek , Launder Brian
Published: December 2006

Following The Royal Society's decision to allow the release of hitherto confidential documents concerning referees' reports and other material relating to the publication of historical manuscripts, the present paper examines the exchanges preceding the publication of the two papers on turbulent flow by Osborne Reynolds that have so greatly influenced the development of Engineering Fluid Mechanics over the past century. The documents cited reveal that, although the earlier experimental paper was warmly welcomed, the referees were critical of the subsequent analytical contribution. It appears that the publication of the latter paper was due mainly to the considerable standing Reynolds had by then acquired, in part from the impact of his experimental paper published 12 years earlier. The paper also provides a summary of Reynolds' career and research prior to his embarking on the research published in the two seminal papers.
Stented Artery Flow Patterns and Their Effects on the Artery Wall
Authors: Duraiswamy Nandini , Schoephoerster Richard T. , Moreno Michael R. , Moore James E.
Published: December 2006

Stent design and geometry influence the fluid mechanical environment in an artery and hence affect clinical outcomes of restenosis. There is clearly a role for biomechanics in improving current stent designs. This review summarizes some of the work that has been done to address the fluid mechanical aspects of stenting. A variety of computational, experimental, and in vivo approaches have been employed, and the results demonstrate a strong dependence on stent design, as well as effects on hemodynamics in locations of the circulatory system quite removed from the stented segment. There are also important solid mechanical aspects that affect clinical failures of stents that are not summarized here.
Turbulence Transition in Pipe Flow
Authors: Eckhardt Bruno , Schneider Tobias M. , Hof Bjorn , Westerweel Jerry
Published: December 2006

Pipe flow is a prominent example among the shear flows that undergo transition to turbulence without mediation by a linear instability of the laminar profile. Experiments on pipe flow, as well as plane Couette and plane Poiseuille flow, show that triggering turbulence depends sensitively on initial conditions, that between the laminar and the turbulent states there exists no intermediate state with simple spatial or temporal characteristics, and that turbulence is not persistent, i.e., it can decay again, if the observation time is long enough. All these features can consistently be explained on the assumption that the turbulent state corresponds to a chaotic saddle in state space. The goal of this review is to explain this concept, summarize the numerical and experimental evidence for pipe flow, and outline the consequences for related flows.
Waterbells and Liquid Sheets
Authors: Clanet Christophe
Published: December 2006

Waterbells result from the impact of a low-viscosity liquid jet (diameter D0, velocity U0) on a solid surface (characteristic length Di) of similar size (Di ∼ D0). Their stationary shape mainly results from the equilibrium between inertia and surface tension. When closed, this shape becomes sensitive to the pressure difference that occurs across the sheet and the bell can become unstable or exhibit stationary cusps. We first review the work done on the shape and stability of waterbells, and then address the case of “special bells,” like swirling bells, polygonal bells, and reverse bells. Finally, we discuss the singular limit of the “flat bell” or liquid sheet.
H. Julian Allen: An Appreciation
Authors: Vincenti Walter G. , Boyd John W. , Bugos Glenn E.
Published: December 2006

Harvey Allen is best known as the genius behind the blunt-body concept, published in 1953, which enables spacecraft to return safely home through Earth's dense atmosphere. He was also an extraordinary research leader, who led a world-class research program in hypersonics at the NACA Ames Aeronautical Laboratory. This paper reviews his career as one of America's leading theorists and experimenters, including his engineering education at Stanford, his work on the inverse problem of calculating the airfoil profile to obtain a desired pressure distribution, his hand in constructing wind tunnels and experimental facilities at Ames, and his pioneering and wide-ranging work on atmospheric re-entry. It concludes with an appreciation of his uniquely inspirational style of research management, and of his magnetic personality.
Long-chain n-3 polyunsaturated fatty acids dissociate phosphorylation of Akt from phosphatidylinositol 3′-kinase activity in rats
Authors: Le Foll Christelle , Corporeau Charlotte , Le Guen Valérie , Gouygou Jean-Paul , Bergé Jean-Pascal , Delarue Jacques
Published: December 2006

We examined whether a low amount of dietary long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) modulated phosphatidylinositol 3′-kinase (PI 3-kinase) activity and downstream Akt phosphorylation differently in normal or insulin-resistant rats. Rats were fed for 28 days with either a control diet containing 14.6% of metabolizable energy (ME) as peanut-rape oil (PR) or an n-3 diet where 4.9% of ME as PR was replaced by fish oil. Over the last 5 days, rats received 9‰ NaCl or dexamethasone (1 mg/kg). Insulin stimulation of both PI 3-kinase activity and Akt serine473phosphorylation and modulation of GLUT4 content were studied in liver, muscle, and adipose tissue (AT). Glucose tolerance and insulin sensitivity were determined by an oral glucose challenge. In muscle and AT, LC n-3 PUFA abolished insulin-stimulated PI 3-kinase activity. These effects were not paralleled by defects in Akt serine473phosphorylation, which was even increased in AT. Dexamethasone abolished insulin-stimulated PI 3-kinase activity in all tissues, whereas Akt serine473phosphorylation was markedly reduced in muscle but unaltered in liver and AT. Such tissue-specific dissociating effects of LC n-3 PUFA on PI 3-kinase/Akt activation took place without alteration of glucose metabolism. Maintenance of a normal glucose metabolism by the n-3 diet despite abolition of PI 3-kinase activation was likely explained by a compensatory downstream Akt serine473phosphorylation. The inability of LC n-3 PUFA to prevent insulin resistance by dexamethasone could result from the lack of such a dissociation.
Overexpression of carnitine palmitoyltransferase I in skeletal muscle in vivo increases fatty acid oxidation and reduces triacylglycerol esterification
Authors: Bruce Clinton R. , Brolin Camilla , Turner Nigel , Cleasby Mark E. , van der Leij Feike R. , Cooney Gregory J. , Kraegen Edward W.
Published: December 2006

A key regulatory point in the control of fatty acid (FA) oxidation is thought to be transport of FAs across the mitochondrial membrane by carnitine palmitoyltransferase I (CPT I). To investigate the role of CPT I in FA metabolism, we used in vivo electrotransfer (IVE) to locally overexpress CPT I in muscle of rodents. A vector expressing the human muscle isoform of CPT I was electrotransferred into the right lateral muscles of the distal hindlimb [tibialis cranialis (TC) and extensor digitorum longus (EDL)] of rats, and a control vector expressing GFP was electrotransferred into the left muscles. Initial studies showed that CPT I protein expression peaked 7 days after IVE (+104%, P < 0.01). This was associated with an increase in maximal CPT I activity (+30%, P < 0.001) and a similar increase in palmitoyl-CoA oxidation (+24%; P < 0.001) in isolated mitochondria from the TC. Importantly, oxidation of the medium-chain FA octanoyl-CoA and CPT I sensitivity to inhibition by malonyl-CoA were not altered by CPT I overexpression. FA oxidation in isolated EDL muscle strips was increased with CPT I overexpression (+28%, P < 0.01), whereas FA incorporation into the muscle triacylglycerol (TAG) pool was reduced (−17%, P < 0.01). As a result, intramyocellular TAG content was decreased with CPT I overexpression in both the TC (−25%, P < 0.05) and the EDL (−45%, P < 0.05). These studies demonstrate that acute overexpression of CPT I in muscle leads to a repartitioning of FAs away from esterification and toward oxidation and highlight the importance of CPT I in regulating muscle FA metabolism.
Laminar Population Analysis: Estimating Firing Rates and Evoked Synaptic Activity From Multielectrode Recordings in Rat Barrel Cortex
Authors: Einevoll Gaute T. , Pettersen Klas H. , Devor Anna , Ulbert Istvan , Halgren Eric , Dale Anders M.
Published: December 2006

We present a new method, laminar population analysis (LPA), for analysis of laminar-electrode (linear multielectrode) data, where physiological constraints are explicitly incorporated in the mathematical model: the high-frequency band [multiunit activity (MUA)] is modeled as a sum over contributions from firing activity of multiple cortical populations, whereas the low-frequency band [local field potential (LFP)] is assumed to reflect the dendritic currents caused by synaptic inputs evoked by this firing. The method is applied to stimulus-averaged laminar-electrode data from barrel cortex of anesthetized rat after single whisker flicks. Two sample data sets, distinguished by stimulus paradigm, type of applied anesthesia, and electrical boundary conditions, are studied in detail. These data sets are well accounted for by a model with four cortical populations: one supragranular, one granular, and two infragranular populations. Population current source densities (CSDs; the CSD signatures after firing in a particular population) provided by LPA are further used to estimate the synaptic connection pattern between the various populations using a new LFP template-fitting technique, where LFP population templates are found by the electrostatic forward solution based on results from compartmental modeling of morphologically reconstructed neurons. Our analysis confirms previous experimental findings regarding the synaptic connections from neurons in the granular layer onto neurons in the supragranular layers and provides predictions about other synaptic connections. Furthermore, the time dependence of the stimulus-evoked population firing activity is predicted, and the temporal ordering of response onset is found to be compatible with earlier findings.
Congenic strains confirm aerobic running capacity quantitative trait loci on rat chromosome 16 and identify possible intermediate phenotypes
Authors: Ways Justin A. , Smith Brian M. , Barbato John C. , Ramdath Ramona S. , Pettee Krista M. , DeRaedt Sarah J. , Allison David C. , Koch Lauren G. , Lee Soon Jin , Cicila George T.
Published: December 2006

We previously identified two inbred rat strains divergent for treadmill aerobic running capacity (ARC), the low-performing Copenhagen (COP) and the high-performing DA rats, and used an F2(COP×DA) population to identify ARC quantitative trait loci (QTLs) on rat chromosome 16 (RNO16) and the proximal portion of rat chromosome 3 (RNO3). Two congenic rat strains were bred to further investigate these ARC QTLs by introgressing RNO16 and the proximal portion of RNO3 from DA rats into the genetic background of COP rats and were named COP.DA(chr 16) and COP.DA(chr 3), respectively. COP.DA(chr 16) rats had significantly greater ARC compared with COP rats (696.7 ± 38.2 m vs. 571.9 ± 27.5 m, P = 0.03). COP.DA(chr 3) rats had increased, although not significant, ARC compared with COP rats (643.6 ± 40.9 m vs. 571.9 ± 27.5 m). COP.DA(chr 16) rats had significantly greater subcutaneous abdominal fat, as well as decreased fasting triglyceride levels, compared with COP rats ( P < 0.05), indicating that genes responsible for strain differences in fat metabolism are also located on RNO16. While this colocalization of QTLs may be coincidental, it is also possible that these differences in energy balance may be associated with the superior running performance of COP.DA(chr 16) consomic rats.
Molecular profile of mouse stromal mesenchymal stem cells
Authors: Chateauvieux Sebastien , Ichanté Jean-Laurent , Delorme Bruno , Frouin Vincent , Piétu Geneviève , Langonné Alain , Gallay Nathalie , Sensebé Luc , Martin Michèle T. , Moore Kateri A. , Charbord Pierre
Published: December 2006

We determined a transcriptional profile specific for clonal stromal mesenchymal stem cells from adult and fetal hematopoietic sites. To identify mesenchymal stem cell-like stromal cell lines, we evaluated the adipocytic, osteoblastic, chondrocytic, and vascular smooth muscle differentiation potential and also the hematopoietic supportive (stromal) capacity of six mouse stromal cell lines from adult bone marrow and day 14.5 fetal liver. We found that two lines were quadripotent and also supported hematopoiesis, BMC9 from bone marrow and AFT024 from fetal liver. We then ascertained the set of genes differentially expressed in the intersection set of AFT024 and BMC9 compared with those expressed in the union set of two negative control lines, 2018 and BFC012 (both from fetal liver); 346 genes were upregulated and 299 downregulated. Using Ingenuity software, we found two major gene networks with highly significant scores. One network contained downregulated genes that are known to be implicated in osteoblastic differentiation, proliferation, or transformation. The other network contained upregulated genes that belonged to two categories, cytoskeletal genes and genes implicated in the transcriptional machinery. The data extend the concept of stromal mesenchymal stem cells to clonal cell populations derived not only from bone marrow but also from fetal liver. The gene networks described should discriminate this cell type from other types of stem cells and help define the stem cell state.
Relativistic and Electron Correlation Effects as a Tool for Explaining Some Trends in Molecular Properties and Interactions
Authors: Urban Miroslav , Kellö Vladimír
Published: December 2006

In this paper we discuss relatively routine Douglas–Kroll–Hess spin–free relativistic calculations as a tool for understanding some trends of molecular properties within the series of related molecules. Electron correlation effects are considered by the Coupled Cluster method with iterative treatment of the single and double excitation operators and perturbative treatment of triples, CCSD(T). For our analysis we use accumulated data on relativistic effects on ionization potentials, electron affinities and polarizabilities of the coinage elements, Cu, Ag, and Au and related series like Ia and IIa group elements. Next we analyze electric properties of diatomic molecules as CuF, AgF, and AuF, and compare electric properties and bonding energies of these molecules with intermetalics CuAl, AgAl, AuAl. Electric dipole moments and dipole polarizabilities of the series of oxides including a heavy atom, GeO, SnO, and PbO in their 1∑ ground states are also analyzed. Particular attention is paid to the dissociation energy of PbO and its electron affinity. The bonding character of the MeL series of complexes (Me=Cu, Ag, Au; L=H2O, NH3, and H2S) is explained by stressing the importance of the charge transfer from the lone pair of the ligand to the metal element. Relativistic effects which affect the Me electron affinity and polarizability facilitate understanding the trends of Me interactions with different ligands. We also mention using of the optimized virtual orbital space (OVOS) as an instrument which allows to circumvent problems with proper contraction needed for a specific approximate relativistic Hamiltonian. OVOS allows to reduce the computer time of correlated relativistic calculation by an order of magnitude.
Structure and Polarizability of Small (GaAs)n Clusters (n= 2, 3, 4, 5, 6, and 8)
Authors: Karamanis P. , Begué D. , Pouchan C.
Published: December 2006

Abstract: We studied the structure and polarizability of small stoichiometric gallium arsenide clusters (GaAs)n (n= 2, 3, 4, 5, 6 and 8) with conventional ab-initio and density functional methods relying on correlation consistent large-core relativistic pseudo potential basis set. Our results show that computations based on those basis sets yield reasonable results compared to all electron basis sets and the polarizability/atom of small gallium arsenide clusters up to the octamer, is predicted to be larger than the Clausius-Mosotti bulk value.
Geometry Optimization of ZnnCdm and (AlTiNi)n Clusters by the Modified Diffusion Monte Carlo Method
Authors: Dugan Nazım , Erkoç Şakir
Published: December 2006

General information about the problem of determining ground-state geometries of atomic clusters has been given. Modified diffusion Monte Carlo (MDMC) method which was recently developed for this problem has been reviewed. A technique, called the rotation operation, has been proposed to escape from local minima. Information about empirical potential energy functions, used in the computations, has been given. Binding energy results for Zn n Cd m and (AlTiNi) n clusters obtained by the combination of the MDMC method and the rotation operation have been presented and these results have been compared with the molecular dynamics (MD) results. Efficiency of the method has been investigated by comparing the results and the computation times with the results of the single walker MDMC method - rotation operation combination.
Rules for Migrating from Entity Relationship (ER) Diagrams to Object Relationship (OR) Diagrams
Authors: Bagui Sikha
Published: December 2006

In this paper, we provide detailed mapping rules (a methodology) to convert an ER schema into an object relationship (OR) schema. The mapping rules are presented in a manner that will keep as much of the semantics of the database intact, in order to smoothen the important step of data migration from an ER schema to an OR schema. This OR schema should also serve as a conceptual design tool for object-oriented data models, very much like the ER diagrams are a conceptual design tool for relational databases. Since we are mainly discussing the conversion from an ER model to an OR model, we are limiting the discussion in this paper to the structural aspects of the OR model.
Exploring Vibrational Optical Activity with PyVib2
Authors: Fedorovsky M.
Published: December 2006

In this work we present a practical example of the automatic correlation of the vibrations of two molecules based on an approach which introduces a new formalism for comparing force fields in cartesian coordinates via the normal modes they entail. We consider two partially deuterated isotopomers of (+)-(R)-1-methylindane, a molecule the absolute configuration of which was successfully verified with vibrational optical activity. The isotopomers are obtained by substituting four hydrogen atoms either in the aromatic or in the aliphatic ring by deuterium atoms. This substitution gives rise to the mixing of the normal modes of the parent system. The automatic correlation of the vibrations will be demostrated with the PyVib2 program.
Block-Structured Adaptive Grids on the Sphere: Advection Experiments
Authors: Jablonowski Christiane , Herzog Michael , Penner Joyce E. , Oehmke Robert C. , Stout Quentin F. , van Leer Bram , Powell Kenneth G.
Published: December 2006

A spherical 2D adaptive mesh refinement (AMR) technique is applied to the so-called Lin–Rood advection algorithm, which is built upon a conservative and oscillation-free finite-volume discretization in flux form. The AMR design is based on two modules: a block-structured data layout and a spherical AMR grid library for parallel computer architectures. The latter defines and manages the adaptive blocks in spherical geometry, provides user interfaces for interpolation routines, and supports the communication and load-balancing aspects for parallel applications. The adaptive grid simulations are guided by user-defined adaptation criteria. Both statically and dynamically adaptive setups that start from a regular block-structured latitude–longitude grid are supported. All blocks are logically rectangular, self-similar, and independent data units that are split into four in the event of refinement requests, thereby doubling the horizontal resolution. Grid coarsenings reverse this refinement principle. Refinement and coarsening levels are constrained so that there is a uniform 2:1 mesh ratio at all fine–coarse-grid interfaces. The adaptive advection model is tested using three standard advection tests with increasing complexity. These include the transport of a cosine bell around the sphere, the advection of a slotted cylinder, and a smooth deformational flow that describes the roll-up of two vortices. The latter two examples exhibit very sharp edges and gradients that challenge not only the numerical scheme but also the AMR approach. The adaptive simulations show that all features of interest are reliably detected and tracked with high-resolution grids. These are steered by either a threshold- or gradient-based adaptation criterion that depends on the characteristics of the advected tracer field. The additional resolution clearly helps preserve the shape and amplitude of the transported tracer while saving computing resources in comparison to uniform-grid model runs.
Frequency Modes of Monsoon Precipitation in Arizona and New Mexico
Authors: Nolin Anne W. , Hall-McKim Eileen A.
Published: December 2006

The interannual and intraseasonal variability of the North American monsoon is of great interest because a large proportion of the annual precipitation for Arizona and New Mexico arrives during the summer monsoon. Forty-one years of daily monsoon season precipitation data for Arizona and New Mexico were studied using wavelet analysis. This time-localized spectral analysis method reveals that periodicities of less than 8 days are positively correlated with mean daily precipitation during the 1 July–15 September monsoon period. Roughly 17% of the years indicate no significant periodicity during the monsoon period for either region and are associated with low monsoon precipitation. High- and low-frequency modes explain an equivalent percentage of the variance in monsoon precipitation in both Arizona and New Mexico, and in many years concurrent multiple periodicities occur. Wavelet analysis was effective in identifying the contribution of high-frequency modes that had not been discerned in previous studies. These results suggest that precipitation processes during the monsoon season are modulated by phenomena operating at synoptic (2–8 days) and longer (>8 days) time scales and point to the need for further studies to better understand the associated atmospheric processes.